# Millett "Starving Student" hybrid amp



## pmillett

I just posted the design details of the Millett "Starving Student" hybrid amp on my website:

Starving Student hybrid

 Think "Millett Max" for the financially impaired... or maybe "Millett Min"?

 The idea was to design the simplest, lowest cost hybrid headphone amp possible. It still had to perform well and sound good, of course. I think I suceeded... it sounds very good.

 If you're coming to CanJam, you can listen to it. I think Nate M will also have his version there.

 Pete


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## n_maher

Ha, Millett Min!

 As Pete said I've already built and been using one of these for a while (month or so) for my amp at work. To say that it's a bargain would be an understatement. The build, even for non-ptp folks like myself, is easy and straightforward if you can follow a schematic. Here are a few choice shots of mine, I'll upload a picture with the knob mounted some time soon. 
	

	
	
		
		

		
		
	


	















 Big thanks to Pete for another great project for both new and old DIY'ers!


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## Lil' Knight

Look interesting 
	

	
	
		
		

		
		
	


	



 How much do its parts cost?


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## n_maher

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Look interesting 
	

	
	
		
		

		
		
	


	



 How much do its parts cost?_

 

I believe that there's a BOM on Pete's page that includes pricing information. In my build the parts order from Mouser was ~$40 shipped ($11 chassis included) and I think tubes and sockets set me back another $10 shipped. If you have anything in the way of parts laying around (like I do) you can build one of these for under $50 including everything without breaking a sweat.


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## Lil' Knight

Ah yes 
	

	
	
		
		

		
		
	


	




 Just see the parts 
	

	
	
		
		

		
		
	


	



 I wonder where can I get the tubes? And all the other parts can get from Mouser?
 Thanks


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## Uncle Erik

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Ah yes 
	

	
	
		
		

		
		
	


	




 Just see the parts 
	

	
	
		
		

		
		
	


	



 I wonder where can I get the tubes? And all the other parts can get from Mouser?
 Thanks_

 

You can find the 19J6 here:

Antique Electronic Supply

 They're $1.10 each. Pete is loading us down with those pricey NOS tubes again. 
	

	
	
		
		

		
		
	


	




 Nice design! Might have to put one of those on my shelf shortly.


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## Lil' Knight

Quote:


  Originally Posted by *Uncle Erik* /img/forum/go_quote.gif 
_You can find the 19J6 here:

Antique Electronic Supply

 They're $1.10 each. Pete is loading us down with those pricey NOS tubes again. 
	

	
	
		
		

		
		
	


	




 Nice design! Might have to put one of those on my shelf shortly._

 

Thanks Uncle 
	

	
	
		
		

		
		
	


	




 I've just taken a look at eBay but couldn't find one


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## tomb

Pete's given us another great one! This thing looks cool - I've already started ordering parts. I had a bit of trouble finding the power supply, but this link should help you guys:

Cisco 34-1977-03 48V 0.38A PSA18U Power Supply NEW - eBay (item 360035479615 end time May-20-08 14:46:30 PDT)

 The guy is down to 92 from 100 in the last hour, so they may be going fast!

 I'm guessing the ingenious method of loading the MOSFETs with the tube heaters means they're already biased at 150ma. Sounds like a neat trick all the way around.


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## malldian

Think this is a good beginner project?


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## cronic

Wow, thats an awesome budget project. Thanks again for your continued commitment to the diy community.


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## malldian

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I believe that there's a BOM on Pete's page that includes pricing information. In my build the parts order from Mouser was ~$40 shipped ($11 chassis included) and I think tubes and sockets set me back another $10 shipped. If you have anything in the way of parts laying around (like I do) you can build one of these for under $50 including everything without breaking a sweat._

 

What chastise did you use? I don't have any metal boxes lying around...


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## n_maher

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_Think this is a good beginner project?_

 

Reasonably good, yes. You do have to be prepared to do some thinking on your own as there aren't step by step instructions and the layout is entirely up to you. But it's safe enough (48VDC, no exposure to 120VAC) and doesn't require that many parts and there will be folks around here who can help if you have trouble.


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## malldian

I think I am going to try it... just bought the power cord!


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## n_maher

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_What chastise did you use? I don't have any metal boxes lying around..._

 

It's a Hammond Steel enclosure - Mouser part no: 546-1441-12BK3 but I'd encourage you to try something different. There's really no limit to what you can use.


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## malldian

I am wondering about what size to use for the enclosure... I guess the smaller it is the harder to do.


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## LuckyKarma

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_I think I am going to try it... just bought the power cord!_

 

Same here! I'm going to be needing an amp soon, and this sounds like an enjoyable (and affordable) way to get one. I'm going to wait until after finals are over when I've got a little more time and money, but this should be a fun project


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## n_maher

Just one thing to bear in mind for newer folks who might be considering this project as their first: I like to tell people that the wiring or pcb stuffing is generally only half the battle in any given project. The casework and fabrication can often be the more challenging aspect of a build and shouldn't be overlooked. 

 For this particular project you'll need to be able to drill a few larger holes whether you want to mount the tube sockets from below (as I did) or from above (as Pete did). If you choose to do it like I did you have be very careful about how you drill the hole and even if you top-mount the sockets you'll be needing to drill a 3/4" hole. That's not a size commonly found in most drill sets and really the best way to do it is to use a stepped bit. I did all of the chassis fabrication for my amp with just a cordless drill and two stepped bits to prove that it can be done but it does take some planning and tools. Of course you'll want all these tools for the inevitable "next project" so that's hardly a deterrent.


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## G-man

cool, found my amp number 2 to build. first cmoy then this. now just have to wait for stupid exams to be over.


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## manaox2

Definately going to build about two of these I figure, one for me, one for my father whom I've been wanting to do something for. Ordered two of the adapters, they really are going fast.

 If you really are a starving student, perhaps there is a woodshop or metal shop nearby to do your case work at for free. 
	

	
	
		
		

		
		
	


	




 Spent all day in one today, its a good feeling.


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## dBel84

simplicity at it's best 
	

	
	
		
		

		
		
	


	




 ..dB


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## J.D.N

Brilliant. Looks like i finally found a mini project for the summer to run along side my speaker build. The price is great. No doubt it will go up a bit being in england and all... but ho hum.


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## thrice

Neat, looks like a fun little build. This build screams for a crazy whacky case, like mint/cookie/cracker tins or something similarly neato.


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## J.D.N

Quick thought, pmillett ... you say yours is in a wallet tin, what are the dimensions? Im not sure i get the scale of how small this might be...


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## manaox2

I just thought, being low distortion and about noiseless, put a 1/8th jack on it... anyone think it could be alright with IEMS (IE. UE11)?


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## amphead

It can drive K1000s, so IEMs may be borderline(Keep the volume down). But the price is right to give it a try.

 Thanks Pete for another fun design! Its next on my list, and the tubes should be around for a while before becoming scarce.


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## manaox2

Good lord! Someone bought the last 85 of the AC Adapters! Looks like someone is looking to cash in if you ask me... 
	

	
	
		
		

		
		
	


	




 It was bought by Andover Network Liquidators at Computer Liquidators - Network Liquidation - Asset Recovery, so I think they might show up again there.


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## asuka10456

i'm gonna attempt this but don't think i will pull it off lol


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## n_maher

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Quick thought, pmillett ... you say yours is in a wallet tin, what are the dimensions? Im not sure i get the scale of how small this might be..._

 

Mine is 7x5x2 to give you some perspective, clearly it could be a lot smaller and still be easily workable.


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## n_maher

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I just thought, being low distortion and about noiseless, put a 1/8th jack on it... anyone think it could be alright with IEMS (IE. UE11)?_

 

I would entirely depend on your source. If your source has a fixed output at a minimum you'd probably want to choose a better pot than the one in the BOM to ensure that you don't have channel matching issues. But really, I'm not sure I'd recommend it for IEMs given that they need such little amplification anyway. Just my 2¢.


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## amphead

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Good lord! Someone bought the last 85 of the AC Adapters! Looks like someone is looking to cash in if you ask me... 
	

	
	
		
		

		
		
	


	




 It was bought by Andover Network Liquidators at Computer Liquidators - Network Liquidation - Asset Recovery, so I think they might show up again there._

 

Don't worry, if they don't come up again. The power supply is an easy project


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## pmillett

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Quick thought, pmillett ... you say yours is in a wallet tin, what are the dimensions? Im not sure i get the scale of how small this might be..._

 

Mine's 4.5" x 5" x 1.3" or so...

 A jumbo Altoids tin would be cool?

 Pete


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## pmillett

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Good lord! Someone bought the last 85 of the AC Adapters! Looks like someone is looking to cash in if you ask me... 
	

	
	
		
		

		
			



_

 

No worries, there are tons of them on eBay from many different sellers. Do a search for "Cisco PSA18U"...

 Pete


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## manaox2

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_No worries, there are tons of them on eBay from many different sellers. Do a search for "Cisco PSA18U"...

 Pete_

 

Thanks, thats good news for everyone. I'm looking for some good deals on the tubes now.


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## MusicallySilent

Ill have to look into this as a summer Idea, I might upgrade some components especially the Pot and maybe the caps and resistors. I like that a powersupply can just be bought and used for it.

 How does it sound, as compared to cmoy and other budget builds (mini3, soha etc.)


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## synaesthetic

I'm curious to know how this stands up against the SOHA, and whether or not it has a DC offset issue when powering up and down like the SOHA does (necessitating a protection circuit for forgetful folk such as myself).


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## bhjazz

King Pete! 

 Many thanks, Pete, for continuing to feed our obsession. We owe you! And thanks to Nate as well for jumping in and building one up. 
 I'll be digging through the parts bin here and might sneak this one in while I wait for parts for other projects. 

 Very cool!


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## J.D.N

Quote:


  Originally Posted by *amphead* /img/forum/go_quote.gif 
_Don't worry, if they don't come up again. The power supply is an easy project_

 

 Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_No worries, there are tons of them on eBay from many different sellers. Do a search for "Cisco PSA18U"...

 Pete_

 

Looks like im having no luck locating one for the UK. If the supply were an easy project, would someone be able to put up a schematic? Id have no idea even where to start to design a PS.


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## fault151

How does it sound compered to the millet max?


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## tomb

Quote:


  Originally Posted by *synaesthetic* /img/forum/go_quote.gif 
_I'm curious to know how this stands up against the SOHA, and whether or not it has a DC offset issue when powering up and down like the SOHA does (necessitating a protection circuit for forgetful folk such as myself)._

 

If you look at the schematic, the outputs sit at ~19V. So yes, until the coupling cap charges, I would think that your headphones will see that voltage.

 That said, IMHO, the spirit of the design would dictate simply being careful to wait before plugging in, not applying a sophisticated delay/offset protection circuit.
	

	
	
		
		

		
		
	


	




 The same precaution was traditional for a long time with the SOHA and a couple of iterations of the Millett Hybrid before that. 

  Quote:


  Originally Posted by *fault151* 
_How does it sound compered to the millet max?_

 

Gosh - please don't get us into a "this is better than that, etc." by asking a question like that. 
	

	
	
		
		

		
		
	


	










 There's probably nothing that can compete with this as a tube amp and low cost. I'm excited about it - it looks like great fun, but I don't think it takes anything away from the Millett MAX.

 Pete himself suggested about the Starving Student, "This is a fairly tubey sounding amplifier, similar in character to the original hybrid tube headphone amp design I published in audioXpress waaay back in 2002." He is referring to the _famous original_ Millett Hybrid that used monolithic BUF634 buffers and an off-the-shelf DC power supply.

 I would imagine that it's very competitive, but the MAX's power supply and diamond buffer is as sophisticated as many top-level solid-state amps (besides including an on-board delay circuit). However, AFAIK, none of us besides Pete and Nate have tried the 19J6 tubes, yet. So, build them both. That's what I'm going to do - several of each, even. 
	

	
	
		
		

		
		
	


	







 Again - thanks, Pete!!


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## fault151

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Gosh - please don't get us into a "this is better than that, etc." by asking a question like that. 
	

	
	
		
		

		
		
	


	










 There's probably nothing that can compete with this as a tube amp and low cost. I'm excited about it - it looks like great fun, but I don't think it takes anything away from the Millett MAX._

 

I just wondered what the differences were, not which is best. I bet it sounds great and id love to build one. Especially if its pretty small.


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## n_maher

I'm with Tom, there are certain compromises that go along with a sub-$50 amp and if one of those is remebering to unplug your headphones before applying or removing power that shouldn't be too much to ask, should it? 
	

	
	
		
		

		
		
	


	




 And I haven't heard a MAX for months now so you won't see me making any critical comparison between the two.


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## pmillett

Quote:


  Originally Posted by *synaesthetic* /img/forum/go_quote.gif 
_I'm curious to know how this stands up against the SOHA, and whether or not it has a DC offset issue when powering up and down like the SOHA does (necessitating a protection circuit for forgetful folk such as myself)._

 

Pretty much all single-ended amps with an output cap have a bit of a turn-on thump... but since the bias on the FET comes up somewhat slowly (2k resistor and 150uF) it's not too bad. Audible but not enough to damage anything.

 That said, it's still not a bad idea to unplug the headphones.

 Pete


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## holland

.


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## fault151

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm with Tom, there are certain compromises that go along with a sub-$50 amp and if one of those is remebering to unplug your headphones before applying or removing power that shouldn't be too much to ask, should it? 
	

	
	
		
		

		
		
	


	


_

 

Huh, how will i ever live with the ball ache of having to unplug my headphones before turning the power off?


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## holland

.


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## bsakel

Hello I am new here... I saw this thread and I want to try! Probably I will order the parts now... 

 I was wondering is this power adapter the one you propose?


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## iPatcH

This looks tempting. I'm thinking about moving a step up from my PA2v2, would this be a kick in the right direction? It would make for a fun summer project.


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## kipman725

im quite impresed with the performance of this for the price


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## synaesthetic

I don't know about you guys but I have little problem spending 35 dollars on an Epsilon-12 protection circuit as opposed to spending hundreds or more replacing fried headphones for the one time you forget to unplug them first.


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## holland

.


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## tomb

Quote:


  Originally Posted by *synaesthetic* /img/forum/go_quote.gif 
_I don't know about you guys but I have little problem spending 35 dollars on an Epsilon-12 protection circuit as opposed to spending hundreds or more replacing fried headphones for the one time you forget to unplug them first._

 

Well - I didn't think about it, but Pete brings up a great point: apparently, it takes awhile for the MOSFET to start conducting anyway.

 Holland has a good point, too - you may have to come up with a separate power supply just to use the e12.


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## synaesthetic

Oh I am intending to use the circuit in my SOHA build, not in this particular design.


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## bperboy

I've got an old electronics box that had tube sockets in it already.. not the right kind though. I've discarded all the old stuff, but the tube holes are too big for the new sockets 1 5/32 inches vs the necessary 5/8 inches. How would you suggest mounting the sockets in such a way as to avoid drilling new holes?


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## synaesthetic

Quote:


  Originally Posted by *fault151* /img/forum/go_quote.gif 
_Huh, how will i ever live with the ball ache of having to unplug my headphones before turning the power off? 
	

	
	
		
		

		
		
	


	


_

 

It's not that it's a bother to unplug them, but if you forget even once it's bye-bye headphones. =/


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## malldian

Any way to make that not happen?


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## Mr. Tadashi

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_Any way to make that not happen?_

 

Something like this would have to be implemented The &epsilon;12 Muting / Protect Circuit


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## pmillett

Quote:


  Originally Posted by *synaesthetic* /img/forum/go_quote.gif 
_It's not that it's a bother to unplug them, but if you forget even once it's bye-bye headphones. =/_

 

Have you ever actually killed a pair of headphones? It's pretty hard to do. 

 I've done a lot of very bad things to many pairs, and so far only fried one pair of Grados. 

 I can say for certain that they won't stand 300VDC. 

 Pete


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## bhjazz

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_but the tube holes are too big for the new sockets 1 5/32 inches vs the necessary 5/8 inches. How would you suggest mounting the sockets in such a way as to avoid drilling new holes?_

 

There are "hole shrinkers" available, often at places that sell tubes and tube sockets. They look like trim rings but fit a specific size (and the result is a smaller specific size.) haven't seen any for a while, but then I haven't been looking!


 EDIT: Gah. Tried to go look for some but only came up with one good reference at v4tc in China:

Audio Catalog

 Admittedly, though, these are tres sexy! I've dealt with him before and things do arrive...no worries!


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## PhaedrusX

this is so cool.

 does anyone know of any places to source these parts in Asia, or is overseas shipping from Mouser still the best bet?


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## bhjazz

Regarding the Cisco power supply: specs on it look like 48V @ 0.38A. Should that PS be difficult to source (well, just in case...) would a 48V supply be okay @ 1A? 2A? 

 And, just to be sure: the Cisco is an AC/DC supply, is that correct? Pete's webpage describes the tubes as running on 19VDC.

 Thanks!


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## n_maher

48VDC is what you want.


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## malldian

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_Have you ever actually killed a pair of headphones? It's pretty hard to do. 

 I've done a lot of very bad things to many pairs, and so far only fried one pair of Grados. 

 I can say for certain that they won't stand 300VDC. 

 Pete_

 

So the e22 circut isnt needed?


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## FallenAngel

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_So the e22 circut isnt needed?_

 

Kind of goes against the idea of "super cheap" amp to spend almost the same amount of e12 
	

	
	
		
		

		
			





 It's still not recommended to send large amounts of DC to your headphones, even for a short amount of time. It might not "burn" them, but it definitely isn't anything that would be good. I've blown a couple of KSC75 while testing, it's not particularly easy, they don't like 12V DC sent through them for a second during startup, but they absolutely hate getting it for 30 seconds. That's how I burned one of the drivers.

 You can always add on a time delay as per the scraped down version of e12 used by the Millet MAX, that only costs a couple of dollars, I built one for my integrated amp, mostly for peace of mind.


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## dsavitsk

For those of you looking for a more balanced diet, here is a balanced version of the starving student. This is totally untested, and is just a suggestion of where to start if you are so inclined.






 It adds a small input transformer ($10 each, available from http://www.edcorusa.com/products/tra...sm15k-15k.html) and does away with the output caps (note that you may need a small trimmer in line with one of the heaters to eliminate DC offset --- depends how consistent these tubes are). It also draws double the current, which means you'll either need two of the recommended Cisco power supplies (dual mono) or you'll need a beefier supply. The cathode bias resistor value is half to maintain the same bias on the tube, but otherwise parts values don't change much.

 Also, please note that the output sits up about 19V above ground, so the output cannot be referenced to ground, and it will not play well as a preamp without taking some precautions.


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## J.D.N

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_You can always add on a time delay as per the scraped down version of e12 used by the Millet MAX, that only costs a couple of dollars, I built one for my integrated amp, mostly for peace of mind._

 


 Is there some kind of schematic available for just that part of the circuit?


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## FallenAngel

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Is there some kind of schematic available for just that part of the circuit?_

 

Of course, check out the e12 Delay under the Tweak section of the Millet MAX site

Millett Hybrid MAX e12 Delay

 Total cost is about $4


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## tomb

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Of course, check out the e12 Delay under the Tweak section of the Millet MAX site

Millett Hybrid MAX e12 Delay

 Total cost is about $4_

 






 $3.50 of that $4 is for the dadgum relay.
	

	
	
		
		

		
		
	


	







 EDIT: There's still a power supply issue - somebody's got to burn off 24V(!) somewhere or change a lot of that circuit. I already offered an opinion on using it, though, so I won't repeat it.


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## FallenAngel

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_





 $3.50 of that $4 is for the dadgum relay.
	

	
	
		
		

		
		
	


	







 EDIT: There's still a power supply issue - somebody's got to burn off 24V(!) somewhere or change a lot of that circuit. I already offered an opinion on using it, though, so I won't repeat it.
	

	
	
		
		

		
		
	


	


_

 

Come on, a master tinkerer like you can find a way around it 
	

	
	
		
		

		
		
	


	




 Damn, LM317 is out of the question because it only handles up to 37V, but an LM317HV can do up to 57V - how about we use that to drop 12V, then we use a cheapie LM317T to drop another 12V and we have our 24V e12 PSU costing about $3 
	

	
	
		
		

		
		
	


	




 Shouldn't be a big problem without overheating, the e12 eats basically no current, TO220 regulators shouldn't get too hot.


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## tomb

Yes, well - maybe. The thing is, Colin's implemenation of the circuit is already regulated from 24-27VDC down to 10-12VDC. That burned enough Watts at the current use of the relay (16.7ma) that he had to substitute the TO-220 BD-139 instead of a TO-92. With the Starving Student we'd need to go a total about three times that heat dissipation.

 However, there are 48V Omron relays in the very same series - that might be the answer.
	

	
	
		
		

		
		
	


	




 I wonder if Pete or Nate could actually measure the voltage spike from turn-on to cap charge/MOSFET bias. That might calm some concerns.


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## holland

.


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## manaox2

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_Regarding the Cisco power supply: specs on it look like 48V @ 0.38A. Should that PS be difficult to source (well, just in case...) would a 48V supply be okay @ 1A? 2A? 

 And, just to be sure: the Cisco is an AC/DC supply, is that correct? Pete's webpage describes the tubes as running on 19VDC.

 Thanks!_

 

I think that those amperages will be find, the amp will only use/take what it needs.


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## bhjazz

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_For those of you looking for a more balanced diet, here is a balanced version of the starving student. This is totally untested, and is just a suggestion of where to start if you are so inclined._

 

You read my mind! I was thinking 'starving student under $100 balanced amp' and boom...here's a starting design. 

 This place rocks! Thanks dsavitsk!


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## n_maher

Well jazz, if you're not too starving Pete and I have been working on something a little bigger for the past couple of months.
 It's not a hybrid, in fact it's all tubes and it's not for the feint of heart or wallet. 
	

	
	
		
		

		
		
	


	




 Anyone who wants to see or listen to it should swing by CanJam table 13. I'll be publishing the design when I get back and can polish the documents.


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## bhjazz

Ouch! I'd be shouting SWEET, but alas, I won't be able to make the cross-coutry trek to Florida. Damn. Damn. Damn. I suppose I should complete the basic premise of this one plus the other few I've started so I can clear my plate for your all tube surprise. Cool.


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## manaox2

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well jazz, if you're not too starving Pete and I have been working on something a little bigger for the past couple of months.
 It's not a hybrid, in fact it's all tubes and it's not for the feint of heart or wallet. 
	

	
	
		
		

		
		
	


	




 Anyone who wants to see or listen to it should swing by CanJam table 13. I'll be publishing the design when I get back and can polish the documents._

 

Now that this is the second bombshell in less then two weeks, CanJam sounds like its going to be the blast.


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## n_maher

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Now that this is the second bombshell in less then two weeks, CanJam sounds like its going to be the blast._

 

Indeed, I'm sure it will be.


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## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well jazz, if you're not too starving Pete and I have been working on something a little bigger for the past couple of months.
 It's not a hybrid, in fact it's all tubes and it's not for the feint of heart or wallet. 
	

	
	
		
		

		
		
	


	




 Anyone who wants to see or listen to it should swing by CanJam table 13. I'll be publishing the design when I get back and can polish the documents._

 

Are you talkin' 'bout this?


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## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Are you talkin' 'bout this?_

 

Nope, that's a commercial design, the one I'm talking about is DIY. 
	

	
	
		
		

		
		
	


	




 Just to be a wicked tease, here are a couple pictures of the project I lovingly call, The Menace.

 The Power Supply (~50lbs of tube rectified goodness)





 The Amplification Section (6SN7 input, [2] 6AS7/6080/5998/7236/6528 output)





 I fired it up for the first time two nights ago, redid a bunch of the ground wiring last night and got about an hour with it before packing it up and shipping it to Florida this morning.


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## bhjazz

Wicked tease? I have another name for you, but it would likely get covered in asterisks!

 It's a beauty, Nate. *Very *high drool factor in so many ways. I'm sorry I won't be able to hear it first hand. 

 Guess I'll just...get back to...being a Starving Student!

 Pete, I'm sticking to the starving theme as much as possible. I need to order some caps from Handmade and Soniccraft for another project, but I promise not to drop more than a dollar or so towards caps for the SS! (Handmade does have a closeout page so I'll have to dig through it for SS-worthy components.)


----------



## JadeEast

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_



_

 

All that iron makes me wonder how they ever coined the term solid state.


----------



## pabbi1

Damnit nate, at least you could start a new thread - 'Wicked Tease'...

 Estimate on BOM cost?

 BTW, me hate you long time.


----------



## n_maher

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Damnit nate, at least you could start a new thread - 'Wicked Tease'..._

 

I'll do that this weekend at some point and sketch out the basic details. I have schematics but I'd like to polish them up a bit before releasing them to the public. 

  Quote:


 Estimate on BOM cost? 
 

I refuse to keep track of things like that, lest my wife some day discover how much this stuff actually costs! 
	

	
	
		
		

		
		
	


	




 Also, there's no reason that you'd have to use the power supply design that I did, you could save an awful lot of $$ doing a SS power supply. And I had a specific goal when I started this project that precluded using anything solid state.

  Quote:


 BTW, me hate you long time.  
 

Aw come on, where's the love!


----------



## holland

.


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'll do that this weekend at some point and sketch out the basic details. I have schematics but I'd like to polish them up a bit before releasing them to the public. 

 I refuse to keep track of things like that, lest my wife some day discover how much this stuff actually costs! 
	

	
	
		
		

		
		
	


	




 Also, there's no reason that you'd have to use the power supply design that I did, you could save an awful lot of $$ doing a SS power supply. And I had a specific goal when I started this project that precluded using anything solid state.


 Aw come on, where's the love!_

 

You know you MY man - but, needs me some BALANCE(d).


----------



## n_maher

Before we derail this thread entirely, let's move the Menace discussion here.


----------



## sejarzo

Found a 48 VDC, 0.625A supply here:

Jameco Electronics Power Supplies & Wall Adapters: PHIHONG: PSA31U-480


----------



## holland

.


----------



## n_maher

Guys, there are still a ton of these power supplies on Ebay. Try searching using the string "34-1977" which is a part of the part number and I'd bet you'll come up with a whole host of inexpensive options.


----------



## holland

.


----------



## bperboy

I got mine from a buy it now seller for 7.99... shipping was also 7.99, but it was still pretty cheap.


----------



## pmillett

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Hmm, that's a switcher. They do have a linear @ 0.5 for $11.00, but it's not regulated (if it matters at all)._

 

I'll buy one of the linear unregulated ones and try it out. If it doesn't have too much ripple it might be better than the Cisco power supply, which hiccups a few times starting up.

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_True. Keep in mind, if the total goes over $17 or $18 (including shipping), it's probably cheaper to get the Jameco linear.

Jameco Electronics Power Supplies & Wall Adapters: JAMECO RELIAPRO: MW48-4800500
Jameco Electronics Power Supplies & Wall Adapters: JAMECO RELIAPRO: MW48-4800500-R

 Is the Cisco one regulated? If it is, then it's a total bargain._

 

The Cisco supply is a regulated switcher.

 Pete


----------



## MusicallySilent

Ill probably consider this or a mini3 (high or low depends on headphones) over the summer as a amp build once i get headphones, depends if my headphones have better synergy with SS or Tube


----------



## sejarzo

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Hmm, that's a switcher. They do have a linear @ 0.5 for $11.00, but it's not regulated (if it matters at all)._

 

I posted that one from Jameco as the Cisco is also a switcher, and the Jameco would likely have enough oomph to drive that potental balanced variant (I think?)


----------



## n_maher

Come on, if you're going to do a balanced version you have to at least consider a tube rectified PS.


----------



## pmillett

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Come on, if you're going to do a balanced version you have to at least consider a tube rectified PS.
	

	
	
		
		

		
		
	


	





_

 

Tungars are nice for low voltages. You just have to replace them every 1000 hours or so.


----------



## bhjazz

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_I'll buy one of the linear unregulated ones and try it out. If it doesn't have too much ripple it might be better than the Cisco power supply, which hiccups a few times starting up.
 Pete_

 

 Quote:


  Originally Posted by *sejarzo* /img/forum/go_quote.gif 
_I posted that one from Jameco as the Cisco is also a switcher_

 

I've had good luck with Jameco-branded transfomers. Pretty tough little monsters, they are. 

 So would the Jameco switcher be a good replacement? Pete, did you get a chance to check one out?


----------



## amphead

Quote:


 Tungars are nice for low voltages. You just have to replace them every 1000 hours or so. 
 

I use those to light my driveway.


----------



## holland

.


----------



## malldian

Ok I am not really sure about what I am reading here - can I make the amp as I with out worrying about busting my headphones if I turn it off by accident with them plugged in?


----------



## pmillett

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_Ok I am not really sure about what I am reading here - can I make the amp as I with out worrying about busting my headphones if I turn it off by accident with them plugged in?_

 

This amp is no different than any other amp with an output cap (like the original Millett hybrid design, or any number of others).

 Has anybody blown up their headphones with a Millett hybrid (sans delay circuit)? Build errors don't count 
	

	
	
		
		

		
		
	


	




 Yes, it makes a thump when you turn it on or off. 

 I have yet to fry any headphones this way, but I can't gurantee there aren't some particulary sensitive headphones that wouldn't like it. 

 By the way, on first look the simple delay circuit used on the Millett Max should work fine here. As-is, the first transistor (QM1) might get warm enough to ned a heatsink. You could also change the zener (DM1) to 24V and use a 24V relay to lower the heat.

 Pete


----------



## malldian

Alright thanks a lot.


----------



## Gross

Antique Electronic Supply is all out of the 19J6 tubes, and I just bought the last 4 from tubedepot.com for 3.95 a peice.


----------



## malldian

Whats the shipping time from Antique Electronic Supply?


----------



## tomb

Try Dale and Roy Rogalski at Radio Electric Supply - otherwise known as vacuumtubes.net:

Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!


----------



## Gross

Vacuumtubes.net is half the price of tubedepot.com. oh well.


----------



## bhjazz

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Vacuumtubes.net is half the price of tubedepot.com. oh well._

 

Nice! I'd never heard of them before. I've had good luck ordering form tubedepot as well (understanding, of course, that they are out now...heh...don'tcha wonder what they think when they get runs on tubes like this all at once from us DIY monkeys...haha...)


----------



## srserl

I ordered my tubes from RadioDaze.com and received my order very quickly. I placed the order on Wed, it shipped on Thurs (from NY), and I received it in Calif. on Monday. 

 Excellent service!

 Scott


----------



## bperboy

Quote:


  Originally Posted by *srserl* /img/forum/go_quote.gif 
_I ordered my tubes from RadioDaze.com and received my order very quickly. I placed the order on Wed, it shipped on Thurs (from NY), and I received it in Calif. on Monday. 

 Excellent service!

 Scott_

 

Ditto on that!


----------



## John E Woven

I've read all 8 pages of the thread and I'm not understanding; Is it that if you accidentally leave your headphones plugged in and you turn off the amp, it could potentially damage them?


----------



## kvant

Quote:


  Originally Posted by *John E Woven* /img/forum/go_quote.gif 
_I've read all 8 pages of the thread and I'm not understanding; Is it that if you accidentally leave your headphones plugged in and you turn off the amp, it could potentially damage them?_

 

And what part of the following you don't understand? 

  Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_Pretty much all single-ended amps with an output cap have a bit of a turn-on thump... but since the bias on the FET comes up somewhat slowly (2k resistor and 150uF) it's not too bad. *Audible but not enough to damage anything.*_

 

The strength of the turn-on thump is proportional to the size of the output capacitor. With the 150uF specified in the Pete's schematic, the dangers of damaging the headphones are really virtually zero. You can calculate the energies involved, if you are so inclined, and see for yourself. If your phones are low impedance, you might want to increase the output capacitor for deeper bass response. That's OK too, as long as you don't get crazy about it. Putting there 22000uF is not advisable.

 Of course, there is no such thing as 100% guaranty and it is your responsibility what you do with your headphones. That is the reason, why responsible people provide careful statements (note the explicit mention of 150uF in the quote above). Especially since this is DIY and DIYers are known to tinker with "approved" designs, often without really understanding them.

  Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_I have yet to fry any headphones this way, but I can't gurantee there aren't some particulary sensitive headphones that wouldn't like it. _

 

BTW, if you buy a commercial amp, would you first measure its turn on/off transient behavior, or would you just trust the designer/manufacturer? Maybe you shouldn't since there are designs out there that are potentially more dangerous to your phones than this AC coupled "Starving Student".


----------



## pinkfloyd4ever

hey nate what are those little tiny whiskey barrel shaped resistors you used? 

 Also, anyone know if the all parts are available at digikey (well just those listed as coming from Mouser on the bom)? I usually prefer mouser for their site's "project manager", but I was gonna try to use Panny FMs rather than Nichicons for the electrolytics


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_hey nate what are those little tiny whiskey barrel shaped resistors you used? 

 Also, anyone know if the all parts are available at digikey (well just those listed as coming from Mouser on the bom)? I usually prefer mouser for their site's "project manager", but I was gonna try to use Panny FMs rather than Nichicons for the electrolytics_

 

FYI - 50V is as high as Panny FM's go.
	

	
	
		
		

		
		
	


	




 You'll have to use FC's if you want Panasonic.


----------



## n_maher

I'm pretty sure that I stuck darn close to the BOM that Pete posted and I don't have access to the parts that I ordered right now. I'll try to double check and post back in a day or so.


----------



## pinkfloyd4ever

a couple more BOM Qs...

 the film caps apparently are obsolete?

 the link for the heatsinks goes to some that are 1.5" tall, but the notes say they should be 2". It looks to me like pete and nate both used the 1.5 inchers, or am I mistaken? And what's the N at the end of the part number mean, besides an extra dollar?

 What's the advantage to using that big piece of pcb material for a ground plane? Could you just ground everything to the case if you're using a metal one, or would that be susceptible to interference? What exactly did you do, nate?


----------



## n_maher

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_a couple more BOM Qs...
 the film caps apparently are obsolete?_

 

It's possible, look and see if it's just an ROHS thing, perhaps an alternate part is already listed. I'll have a look later.

  Quote:


 the link for the heatsinks goes to some that are 1.5" tall, but the notes say they should be 2". It looks to me like pete and nate both used the 1.5 inchers, or am I mistaken? And what's the N at the end of the part number mean, besides an extra dollar? 
 

Without looking no idea what the N means. And yes, I'm using the 1-1/2 tall version and things seem fine. I'll try and ask Pete if they should have been 2".

  Quote:


 What's the advantage to using that big piece of pcb material for a ground plane? Could you just ground everything to the case if you're using a metal one, or would that be susceptible to interference? What exactly did you do, nate? 
 

I wouldn't use the chassis as the ground plane, I think it'll open up the possibility of noise. I used a terminal strip at the rear of the amp as a star ground which I then tied to the chassis in one location. Using the PCB material just means less wiring, but more drilling.


----------



## kipman725

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_My point with the Jameco switcher is that it is awfully expensive for what it is.

 You could get a toroid that puts out 1A or more @ 48V and build your own with cheap regulation for about that much and get more current to boot. You can cheap out on the filter caps for some higher ripple or use a whole bunch of small caps in parallel.

 If using the LM317 is too hard or costly, you can use the LM7824 and LM7924 and don't use the ground but the + and - rails for the entire 48V differential. A rectifier can be made from 4 diodes and some small caps.

 Another note, Jameco has a 24V AC parallel 0.8A split-bobbin for $4. In series it will put out 48VCT AC @ 0.4A.
 The wallwart case is a couple of dollars. Add a fuse, wiring, diodes, caps, LM7824 and LM7924 and you'll have a bare bones linear DC supply for less than the Jameco switcher.

 Just something else to think about, instead of jumping straight to a $30 PS._

 


 be carefull with not overdoing the capcitance as some regulators are not stable with very large capacitor banks even though they are thought to be (one of those never verified asumptions). EG the 317T has had simulations run on it showing problems >1000uF capacitance.
 Second the thoughts on using a lienar regulator though, they are almost always much lower nosie than switchers.


----------



## tomb

Quote:


  Originally Posted by *kipman725* /img/forum/go_quote.gif 
_be carefull with not overdoing the capcitance as some regulators are not stable with very large capacitor banks even though they are thought to be (one of those never verified asumptions). EG the 317T has had simulations run on it showing problems >1000uF capacitance.
 Second the thoughts on using a lienar regulator though, they are almost always much lower nosie than switchers._

 

Are you sure that's with a LM317? This is well-documented with LDO's, but not the LM317, AFAIK. The LM317 isn't really an LDO. 

 For instance, Tangent's well-established, quiet and stable STEPS PS (LM317-based) uses a bank total of 4000uf after the rectifiers.


----------



## n_maher

Guys, all this discussion surrounding LM317's is making me nervous. Isn't Vout on the LM317 limited to 37V therefore rendering it worthless with regards to this amp?


----------



## holland

.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Guys, all this discussion surrounding LM317's is making me nervous. Isn't Vout on the LM317 limited to 37V therefore rendering it worthless with regards to this amp?_

 

Good point - it looks to me the differential has to remain between 3V and 40V, so I think you're right: 37V limit.

 I assume all this discussion means the power supplies have dried up on ebay? That would still be the preferrable source.


----------



## holland

.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good point - it looks to me the differential has to remain between 3V and 40V, so I think you're right: 37V limit._

 

No, you just have to float it and keep the differential between in and out low enough and it can be used as a high voltage reg. You can also use it as a floating CCS with a shunting resistor to ground and it will work as a shunting V-reg.







 Holland's suggestion will work, too, though it wouldn't be my first choice.


----------



## holland

.


----------



## n_maher

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_No. The differential between in and out is between 3V and 40V.

 I may be wrong, but I didn't get the impression that there is a 37V output voltage limit from the datasheet._

 

This surely won't go down as the last time I read a data sheet wrong. I'd swear I found one reference that specifically called the Vout (not differential) limit 37V, although now that I think about it I see nothing that would preclude it's use provided appropriate steps are taken.

 dsavitsk, is there a way in which something like a TREAD could be used while floating the LM317? I don't fully understand the floating concept.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_This surely won't go down as the last time I read a data sheet wrong. I'd swear I found one reference that specifically called the Vout (not differential) limit 37V, although now that I think about it I see nothing that would preclude it's use provided appropriate steps are taken.

 dsavitsk, is there a way in which something like a TREAD could be used while floating the LM317? I don't fully understand the floating concept._

 

Me, too. I think if it's referencing ground at zero, then it will see 48V. On the other hand, even a TREAD or STEPS only uses a differential of 5-10V (going on memory, here, so don't shoot me), whereas the supply voltage is much larger.

 On a different subject - sort of - it appears that many of the Cisco PS's are still available on ebay:

eBay Stores â€“ Cisco PSA18U, Networking Communications, Desktop Laptop Accessories, PC Components â€“ Original items at low prices.

 You get zip if you do a simple search on regular ebay, but if you click on "Sellers", you get that list of 23 above right now. Several of those sellers have multiples - up to 25 for the few I checked. Most seem to be less than $20-$25 total, with shipping, too.

 One thing not mentioned is that these don't come with a power cord. I got two from that first big seller and was surprised to find the AC cords weren't included. I guess many of us have those laying around - but just in case some of you were expecting a complete product ...


----------



## holland

.


----------



## pmillett

It can certainly be made to work, but you must take care using an LM317 at voltages over 37V. Consider what happens when power is off and input and output are both at zero volts. Now flip the power switch, applying 48V to the input pin almost instantaneously. Until the output cap charges up, there is 48V across the regulator.

 Also consider what happens when you slip with a scope probe and accidently short the output to ground 
	

	
	
		
		

		
		
	


	




.

 Those issues are why the NS app note has transistors and zeners in it...

 There's really no need for good regulation. I think a power transistor/zener regulator would be plenty good. 

 A decently stiff unregulated supply may sound even better. Often people don't realize that the gain in a voltage regulator is very active at audio frequencies, and unless you have very large output caps, you're actually listening to the voltage regulator as much as your amplifier.

 Pete


----------



## holland

.


----------



## fran

You can do this - I use a LM317 regulated supply for the screens in my EL84 amp - in the range 270-310V.

 I don't have the schematic to hand but I'll try to dig it out.

 Fran


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_It's possible, look and see if it's just an ROHS thing, perhaps an alternate part is already listed. I'll have a look later._

 

duh, yeah that's it...somehow i missed the "click here for substitute" link. But I was wondering, would some Wimas be a good upgrade? Hah, gotta love upgrades that mean spending an extra 30 cents.
	

	
	
		
		

		
		
	


	




 Would the metalized polyester film or the polypropylene be preferable? I know they'd be a bit of a hassle using them in p-to-p construction with their short leads, but nothing a little bit of perfboard & some wire can't handle

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Without looking no idea what the N means. And yes, I'm using the 1-1/2 tall version and things seem fine. I'll try and ask Pete if they should have been 2"._

 

ahhh the ones with the N at the end of the p/n have are notched in the middle below where the transistor mates with the sink...not sure what the point of that is, but they're not worth an extra $2 to me on a sub-$40 amp

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I wouldn't use the chassis as the ground plane, I think it'll open up the possibility of noise. I used a terminal strip at the rear of the amp as a star ground which I then tied to the chassis in one location._

 

what's the difference? Isn't the ground still in electrical contact with the whole chassis?


----------



## n_maher

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_duh, yeah that's it...somehow i missed the "click here for substitute" link._

 






  Quote:


 But I was wondering, would some Wimas be a good upgrade? 
 

I think that's going to have to fall to the Y in DIY.
  Quote:


 ahhh the ones with the N at the end of the p/n have are notched in the middle below where the transistor mates with the sink...not sure what the point of that is, but they're not worth an extra $2 to me on a sub-$40 amp 
 

For me it made it much easier to mount the sinks with a hole grommet so they were worth it. 

  Quote:


 what's the difference? Isn't the ground still in electrical contact with the whole chassis? 
 

As far as I understand it it's a bad idea because then you're using the chassis as a conductor rather than a single point. The latter setup doesn't require the chassis to flow any current and lets it act like a shield. At least that's the way it was once explained to me. And all I can tell you is that with my Menace build it made a huge difference in the noise floor of the amp.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I think that's going to have to fall to the Y in DIY._

 

ya, they're actually out of stock on those ROHS compliant versions of the ones pete has listed on the BOM anyway

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_As far as I understand it it's a bad idea because then you're using the chassis as a conductor rather than a single point. The latter setup doesn't require the chassis to flow any current and lets it act like a shield._

 

ahhh that makes sense

 edit: u ever figure out what those little resistors are that you used? I remember seeing them somewhere else but I can't recall where and for some reason it's really bugging me


----------



## dsavitsk

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_u ever figure out what those little resistors are that you used? I remember seeing them somewhere else but I can't recall where and for some reason it's really bugging me_

 

Those little tiny ones are Yageo Carbon Films. At Digikey, use the value+EBK to find the part, i.e., 22EBK, 1.5KEBK, etc.


----------



## malldian

Anyone e,lse do this yet?


----------



## Gross

I have my tubes and powersupply, just waiting for a few things from mouser to show up(with the rest of my parts for my mosfet max)


----------



## -=Germania=-

OK, 

 I am thinking of making one of these and I want to enable two modes. 
 -Pre-amp
 -Headphone amp

 Does anyone know of a switch that will do two channels from Mouser? (I am not very familiar with the site). 

 Thanks ahead of time!


----------



## thrice

Any DPDT (double pole, double throw) toggle switch will do the job. NKK makes some nice ones.

 EDIT; sometimes you see 2P2T or 2PDT or DP2T...etc. Same thing.


----------



## n_maher

I'd just use a switched 1/4" jack, that way you ensure that you can never get confused about which mode the amp is in. It's also one less thing to wire, which I'm always a fan of.


----------



## -=Germania=-

what is part number for said jack? 
	

	
	
		
		

		
			





 Seriously, I think that this woud make a great pre-amp and add a bit o tube to analytical equipment.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_what is part number for said jack? 
	

	
	
		
		

		
		
	


	


_

 

There are too many to list. Just have a look around Neutrik's site and find something you like the look of.


----------



## Gross

just need to solder up my input and output jacks and mine will be done...


----------



## Gross

Finished! Only been listening for 5 mins or so, but so far I like. I is kinda the CMOY of tubes, as far as being simple to build. The longer it is on, the lower my DC offset gets on the output. When I first fired it up it was around 60-70mv per channel, and right now I am around 20mv. I will get some pictures up ( actually, it will be my first build pics I have posted, I havent shown you all my pint, soha, millet-max, aliens, blah blah blah). 

 I pretty much stuck with the original BOM, just upped the 150uf caps to 270uf since they were out of stock. 

 I mounted my tube sockets backwards too, which is purely cosmetic, but I suppose with just the few hours I have invested, I can rebuild this one with the sockets the right way. Who needs LED indicators when you have tubes to light the way. Oh yeah, this is quite the little space heater. I have 1.5" heatsinks, but bigger surely wouldnt hurt.


----------



## J.D.N

Excellent! Really looking forward to hearing what you think. 

 Pic's would also be excellent...


----------



## n_maher

Gross, you should be getting 0 DC offset with the coupling capacitors, not quite sure how you'd be reading anything unless you're using a crappy meter that just isn't accurate at that level of DC.


----------



## Gross

It must have just been the initial charge up of the caps or something, cuz I read practically nothing now. I thought the caps should charge up faster than that. I am using a Fluke 8050A Bench meter, which hasn't failed me yet. 

 On another note, I flipped and resoldered my sockets, so that the silver coating of the tubes is facing backwards, and letting the 'user' look into the tube better. That makes the wiring look a bit messier, since I did not want to rewire everything, but I did have to extend a few wires.

 Since I will primarily be using these with my Grados, and the fact that these tubes have a gain of 38, I am going to throw some resistors on the output, otherwise I sit so low on the pot, the tracking is off a bit.


----------



## n_maher

It shouldn't take very long for the output caps to charge, but it's certainly something that can be measured. I'd be shocked if it took more than a minute or so to fully charge though, even with your 220uF cap (assuming that's what you used). I'm sure your meter is more than up to the task. 
	

	
	
		
		

		
		
	


	




 As far as tracking error goes, yeah, my amp does that as well if I'm right in the bottom of the range. But for me it's not a big deal since the amp is in my work rig (computer as source) and I just attenuate the source material a bit so that I've got more usable range.

 And please, post up some pictures, messy wiring and all. The wiring in my amp is nothing to write home about.


----------



## Gross

Ok, here we go. I stuck with the starving student theme and used a lot of parts I already had, and tried not to spend much money on the rest. The case was about $8 from mouser.


----------



## -=Germania=-

Tehe, I just realized that I can just take a lot of this stuff from the lab (cylindrical caps and resistors) + I have the wire. 

 looks like I would just need the sockets for everything and a power supply.....I have an entire drawer of power supplies and none that would work 
	

	
	
		
		

		
		
	


	





 Question: 

 I am wondering if using different, higher quality parts will make much of a difference? 
 Namely, which parts will make the most. 
 I am assuming POT and Caps. 
 Also, what tubes would be a good choice?


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I am wondering if using different, higher quality parts will make much of a difference?_

 

I'd try near stock to start and see what you think of it's sound. Modifications are pretty easy to a ptp amp, especially this one. For now only three or so of these exist so there's not much of a knowledge pool to pull from.

  Quote:


 I am assuming POT and Caps. 
 

You could use a different pot and perhaps use different output coupling capacitors, but again the aim of this project was to see how cheaply good sound could be found. Rather than fret over parts selections with this amp I decided that I'd just build it and see how it sounded. But there's nothing stopping you from experimenting with it. 
  Quote:


 Also, what tubes would be a good choice? 
 

I don't know how many producers of the 19J6 there were so just get what you can, I just asked for brand-matched pairs when I got mine and ended up with a bunch of RCA tubes. 

 And nice work Gross. There's one tweak that you might want to make. The resistor that attaches to MOSFETs (pin 1 IIRC) really should be directly attached to the mosfet. If not you may experience some instability (this is what Pete tells me, maybe he can explain it more).


----------



## Gross

I will see about moving that resistor when I add my output resistors. 

 Ok, this is what people are waiting for, how it sounds. It has a clean sound to it, and almost no background noise to it. My first thoughts were actually that it is almost kinda bright sounding, nice clean highs to it(I am using RS-1s though, so take that with a grain of salt). I thought the bass was 'O.K.' and didn't put a whole lot more thought into it until I went back to my uncased SOHA with a JRC 4556AD on the output (I bought a bunch of them while working on my RA-1 Clone, and Grados do like that OpAmp) and there was tons more bass. When I get home tonight from visiting my Mother for Mother's Day I am going to put in larger caps for C1 anc C6, cuz if I am reading this right, they are the power reserve caps. Also on the output with 150uf caps and 32 Ohm drivers, isn't that essentially a 33hz hi-pass x-over? I have 270uf in there which brings it down to 18hz, but I am thinking by adding 100 ohm resistors after the cap, in series with the headphones that should bring the x-over point to 4hz, as well as drop the output so I can use more of the pot. 

 Hopefully that all made sense, and I wasn't reading something wrong.

 And don't take any of this as thinking this is a bad amp design, it is deliciously simple for some nice sounds. Besides, who here can actually leave something alone?


----------



## n_maher

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Ok, I will see about moving that resistor when I add my output resistors. Think I will have any problem with 100 ohms or so?_

 

Not sure I'd go as high as 100ohm, but you can try and see how it goes. Maybe one of the members with a bit more of a technical mind can give a better opinion.


----------



## -=Germania=-

hmmmm...


 Ok - so the chasiss and tubes together shipped is $49. 
 $32 from mouser
 $17 from tube depot 

 The power supply is $17 shipped. 

 That bring the total to $66 shipped. 

 unless someone has some extra tubes + sockets they would be willing to sell me....

 I was hoping to keeping it lower... but am I doing something wrong? 

 Mine is also having the switched 1/4 jack and extra RCA out.


----------



## pinkfloyd4ever

my mouser total is only $18.35 (w/o shipping) although I already have a spst switch and the film caps, so maybe call it $21. I'm gonna find something free to use as the chassis. I got my PS for $8 shipped off ebay. And I'm still trying to decide where to get my tubes from. A switched jack and extra RCA outs will add maybe $5?

 tube depot probably has the most expensive prices out there. I'd try 
Vacuum Tubes, Inc. New Tubes, 8JU8A to 50FK5 
https://www.tubeworld.com/index_high.htm 
Radio Daze 
N9TEW TUBE SALES 
Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes! or 
Vacuum Tubes, Electron Tubes, Tubes, Tube Testers and Electronic Parts


----------



## -=Germania=-

where can I get the $8 PS?

 Please tell me!


----------



## holland

.


----------



## -=Germania=-

That includes all the parts from mouser. 

 It looks lie the tubes, tube sockets and power supply will cost more than everything else. lame.....


 *just put in bid for PSU*


----------



## pinkfloyd4ever

eBay Stores â€“ PSA18U, Networking Communications, Desktop Laptop Accessories, PC Components â€“ Original items at low prices.

 it looks like we head-fiers have driven up the prices (or just bought most of the cheap ones)


----------



## holland

.


----------



## holland

.


----------



## pinkfloyd4ever

ya I looked in my yellow pages under electronics...you'd be suprised what you have around you. I found this place that has TONS of used, NOS, and new electronics stuff (power supplies, CRTs, canare starquad, heatshrink, rotary switches) including tubes. This one isn't the most organized place ever tho, so you might spend several hours going thru their tubes to find a pair. That's just the one by me tho, I would think most similar places are more organized

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I bid on one the first day of the thread, with the contingency that if I win, I'll build this amp._

 

 I did the same thing, luckily, no one bid above my 99 cents. I however AM a starving student
  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Now, if there's a starving homeowner amp...._

 

http://www.head-fi.org/forums/f6/pet...menace-320365/


----------



## -=Germania=-

Well, I think tha t this may just be one killer pre-amp for the money and can be used as a headphone amp with the way I am doing it. 

 I wanted just a cheap amp for my workplace over the summer. If this outperforms my XP....situation may change....


----------



## Gross

Just an FYI, I ordered 6 tubes from tubedepot last week, and he only had 4 in stock, so I took them. I got 4 different tubes, 3 similar, and the GE was quite a bit different.




 In the second image I have the tubes facing the same direction according to their pins, but you can see how the getter is positioned way different on the GE compared to the other 3 tubes I got. It leaves the silver deposit on the front of the tube, compared the back on the other 3. I don't know how different these will sound from each other, but obviously they look different.


----------



## -=Germania=-

bought my tubes and sockets - bid on PSU - currently paying mouser for parts.


----------



## n_maher

$17 for tubes? For how many? I think I bought 10 for a couple bucks more than that... 

 There are lots and lots of tube dealers out there and prices vary wildly, if you're paying more than a couple bucks a tube for this amp I don't think you're getting a particularly good deal. 

 And Germania, I'm not sure how it'll do as a preamp. It has a lot of gain (as noted earlier in the thread) which generally isn't what you want out of a preamp and you may have to work on your wiring and grounding scheme to get it really quiet.


----------



## -=Germania=-

^That is the plan. 

 I have some parts around here and I am going to see what works best and post it. 

 I ended up getting a set of tubes for $10 and ceramic sockets for $5 - total of $15 shipped. 

 Also, anyone know any other compatible dual triode tubes? I was thinking that I might be able to make a multi-way switch to roll out some different ones. * 5

 I should probably only focus on the pre-amp for now.....


----------



## dsavitsk

I agree with Nate that mu on this tube is way to high for this to be a reasonable preamp. This is best used with high Z phones.

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Also, anyone know any other compatible dual triode tubes?._

 

Unlikely. There are a 5V (5J6) and 6V (6J6) version, and lots of variations on the 6V version, but none of these can be used here without circuit modification which will destroy the elegance of the heater supply/biasing mechanism. 

 You could use the triode section of a 19CL8 here (other section is a tetrode). It will still make a lousy preamp (mu=40), and it might make a lousy headphone amp too, but the heater will work the same, and the triode section might work. Same for the 19EA8 (same triode as the 19CL8, but has a pentode instead of a tetrode for the other half.) Neither will like the low voltage. I'd get the thing built before you start thinking about swapping tubes in and out.


----------



## scompton

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I agree with Nate that mu on this tube is way to high for this to be a reasonable preamp. This is best used with high Z phones._

 

I've seen this mentioned a few times and I have no idea what Z is. Can someone enlighten me.


----------



## synaesthetic

Z is impedance.


----------



## -=Germania=-

I dont know how much diy I am going to be doing... just pinched a nerve in my pinky. pain to type right now - using only 6/10 fingers.


 EDIT: With be making originally as a high power output on the RCA's - want to try out possibilities as a speaker amp or pre-enegizer stax amp (need stax though).


----------



## trains are bad

The recommended film caps on mouser are obsolete, and the mouser-linked alternatives are back ordered. What exactly is it i'm looking for in finding a replacement; do I just need to find some .1uF 100V 'film' capacitors? Are there different kinds of 'film'? The low-ESR electrolytics are backordered on Mouser too.


----------



## -=Germania=-

These should work. 

HERE

 The only difference is termination style of axial versus radial.


----------



## trains are bad

before you edited your post, you recommended a different cap that appears to me, would have worked equally well. What is it I'm not seeing about choosing caps like this, is there some difference in the data sheet? Is it just reputation? What do you go on when recommending a cap? What's the difference between these two?
MKT1818410015
160104K100C-F

 Plus, what about the electrolytics? I don't even get any hits when filtering for 100V 220uF aluminum electrolytics. And the BOM for the Starving student lists 150uF electrolytics but the part number is for 220uF ones.


----------



## -=Germania=-

UPS1J221MPD


----------



## Snicewicz

I think Ill give this thing a shot. Anyone have any experience with this amp with K701s or 650s?


----------



## trains are bad

Thanks for the cap recommendations! I have K701s too.


----------



## pukka

Another killer project from Pete!! I can't wait to test it out! plus it makes an ideal amp to have at work (sp. if you're an IT guy 
	

	
	
		
		

		
			





 I can plug it anywhere I have POE!!

 For those looking for the power supply, don't agonize over ebay, these PSUs are pretty comon nowadays and you may get a better deal locally, just look for POE (Power Over Ethernet) power supplies; they're used to "inject" 48V through CAT5 cabling, and are widely used in VoIP and Wireless Setups to either power phones with the same cable used to network them, or power WiFI access points/repeaters/bridges w/o having to run an extra DC cable when you have them on top of a mast or building, etc.

 Popular VoIP Phones are Cisco, Grandstream, Thomson, Polycom, Sipura etc. Cisco are easily the most outrageously expensive. But beware not all VoIP POE phones bring a 48V switched adapter. Thomsons for example have 9V linear unregulated ones though they work fine with std. 48V POE.

 There's a lot of chance if you have a WiFi centric shop near you they'll have those PSUs.


----------



## n_maher

And here I was thinking that you were talking about this POE.


----------



## HypnoLobster

Very cool. I just ordered some tubes and all the rest off of Mouser. 

 Any recommendations on a power supply project to compliment it?


----------



## n_maher

Quote:


  Originally Posted by *HypnoLobster* /img/forum/go_quote.gif 
_Any recommendations on a power supply project to compliment it?_

 

You mean other than the supply already discussed at length in this thread?


----------



## HypnoLobster

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_You mean other than the supply already discussed at length in this thread? 
	

	
	
		
		

		
		
	


	


_

 

This will be my first real project, all this talk of LM317's and such just zooms straight over my head.

 Let me rephrase that; anyone have a suggestion for a nicely predetermined power supply project


----------



## tomb

Quote:


  Originally Posted by *HypnoLobster* /img/forum/go_quote.gif 
_This will be my first real project, all this talk of LM317's and such just zooms straight over my head.

 Let me rephrase that; anyone have a suggestion for a nicely predetermined power supply project
	

	
	
		
		

		
			



_

 

No? Not sure that was re-phrased, but I gave a link just a few posts back that had a number of the recommended power supplies on e-bay. Pukka also gave several references and ideas, stating that this type of POI power supply is cheaply available at a number of places.

 If for some reason you don't want one of the ones on ebay, then reference Pete's specs - 48VDC switcher supply at ~0.38A, if memory serves. Pick one out and then come back and ask in this thread. I'm sure Nate or Pete can confirm it as suitable or not.

 Note that even the original $6.99 versions didn't count shipping ($7?) and a power cord, so $20 total from a current ebay seller listing is not that far off.


----------



## holland

.


----------



## Snicewicz

Can someone help me out with parts list? Some of them are backordered and I wanted to make sure my alternatives are acceptable

 Thanks, please shoot me a PM if you are willing to help


----------



## n_maher

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_Can someone help me out with parts list? Some of them are backordered and I wanted to make sure my alternatives are acceptable

 Thanks, please shoot me a PM if you are willing to help_

 

Why don't you just post your parts list.


----------



## Snicewicz

Because its long. Im tired I should have just posted what was out of stock and what I replaced it with:

 Anyways I replaced the following: (mouser part #s) 

 replaced 539-150104K100AA with 539-168104K100H-F

 and replaced 647-UHE1J221MPD with 647-UPW1J221MPD6

 Also I cant find the tubes anywhere. 

 Sorry this is what happens to me when I have little sleep


----------



## tomb

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_Because its long. Im tired I should have just posted what was out of stock and what I replaced it with:

 Anyways I replaced the following: (mouser part #s) 

 replaced 539-150104K100AA with 539-168104K100H-F

 and replaced 647-UHE1J221MPD with 647-UPW1J221MPD6

 Also I cant find the tubes anywhere. 

 Sorry this is what happens to me when I have little sleep_

 

Just MHO, but you can probably do better with the 0.1uf film cap. Polypropylene is better than polyester. A Wima MKP10 might be better if you are going with a box cap. However, there are many to choose from. Perhaps the one you've picked out may still be appropriate for the Starving Student, though. We'll see what Nate says. 
	

	
	
		
		

		
		
	


	




 The UPW electrolytic should be fine.

 The 19J6 is available in quantity at vacuumtubes.net the last time I checked - very cheap, too.


----------



## bhjazz

Wow, stuff out of stock. The bane of our DIY world...


----------



## -=Germania=-

TEHE - just picked up the PS on ebay for.........$8.99 SWEET!


----------



## peter.star

Hello Headfiers!

 This is my first post, I was just lurking here before.
 Starting with a question:
 in my country, it is difficult to get 19j6 tubes. (Don't ask me why, because I've seen Tungsram ones also on the internet.)
 So, I was thinking, would it hurt to divide that 19V down to 6V using a 38K resistor. Would this enable the usage of 6j6 tubes?
 They are dirt cheap, and easy to get.

 Regards
 Peter


----------



## peter.star

Err I mean a 75 ohm resistor. Pff, don't know where the 38k came from.


----------



## Snicewicz

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_TEHE - just picked up the PS on ebay for.........$8.99 SWEET!_

 

Plus 9 dollars shipping? That was the one I was going to buy =[ haha

 And thank you tomb for the information on the tubes


----------



## tomb

Quote:


  Originally Posted by *peter.star* /img/forum/go_quote.gif 
_Hello Headfiers!

 This is my first post, I was just lurking here before.
 Starting with a question:
 in my country, it is difficult to get 19j6 tubes. (Don't ask me why, because I've seen Tungsram ones also on the internet.)
 So, I was thinking, would it hurt to divide that 19V down to 6V using a 38K resistor. Would this enable the usage of 6j6 tubes?
 They are dirt cheap, and easy to get.

 Regards
 Peter_

 

This wouldn't be a good idea, IMHO. The 6J6 has a heater current of 450ma. In the Starving Student, the MOSFETs and their bias are tied into the heaters. That would mean - even if you knocked down the voltage - the MOSFETs would be running at 450ma bias (not to mention the resistor would have to dissipate 13V * 0.45A = ~6 Watts).


----------



## Zigis

Very interesting design !

 Just one thing, I reed all treed and no one ask this - 150 mf otput cap, are this enough for 32 ohm? Maybe something like 470 mf, usually used in OTLs, is better.
 Maybe this is reason why Gross reported about not enough bass ?

 Anyway, I want to try it one day!
 Zigis.


----------



## HypnoLobster

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No? Not sure that was re-phrased, but I gave a link just a few posts back that had a number of the recommended power supplies on e-bay. Pukka also gave several references and ideas, stating that this type of POI power supply is cheaply available at a number of places.

 If for some reason you don't want one of the ones on ebay, then reference Pete's specs - 48VDC switcher supply at ~0.38A, if memory serves. Pick one out and then come back and ask in this thread. I'm sure Nate or Pete can confirm it as suitable or not.

 Note that even the original $6.99 versions didn't count shipping ($7?) and a power cord, so $20 total from a current ebay seller listing is not that far off._

 

I think I'm just generally bad at making any sort of point on the internet.
 What I meant was I was looking for a *project *power supply to build that would work with the Starving Student amp. That way I could keep everything inside the case, just something to help the learning process (and how much wall-power hurts!).
 I see people talking about the TREAD, but it seems it can't supply the required voltage.


----------



## Snicewicz

THe only thing I am having trouble with now is obtaining a PSU. I need to have this build by next thursday for a school project .

 Does anyone know where i can buy one and get 2nd or 3rd day shipping?

 Also does anyone have any extra 7-pin miniature tube socket, top chassis mounts? I am willing to buy them. Just dont have any need to get anything off radiodaze to make my order more than 10 and its faster processing this way seeing time as an issue.


----------



## tomb

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Very interesting design !

 Just one thing, I reed all treed and no one ask this - 150 mf otput cap, are this enough for 32 ohm? Maybe something like 470 mf, usually used in OTLs, is better.
 Maybe this is reason why Gross reported about not enough bass ?

 Anyway, I want to try it one day!
 Zigis._

 

Well, to tell the truth - for resistors, I went for some Stackpoles from Handmade - very cheap and they sure do sound good. That made an easy excuse to get some 470uf 100V Nichicon Muse FG's for the output couplers. That's probably not in the spirit of the Starving Student, but I couldn't resist - still only a couple of dollars each.

 I figure my Goodwill-purchased Spiderman lunch box and/or my Crayola crayons tin will make up for it. Or, maybe I'll mount the caps on the top with some clamps and pretend it's Nate's Menace.


----------



## holland

.


----------



## Gross

Zigis, I am assuming it is a capacitor thing with my amp. I haven't been able to do any changes or give any updates since I have been out of town this week. I will report in this weekend.


----------



## n_maher

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_THe only thing I am having trouble with now is obtaining a PSU. I need to have this build by next thursday for a school project .

 Also does anyone have any extra 7-pin miniature tube socket, top chassis mounts?_

 

Yikes man, didn't leave yourself much wiggle room there did ya? I'll have a look in the parts bin and see what I can find. I'm not itching to sell my spare PS but in the name of you not failing a project I might be coaxed out of it.


----------



## Snicewicz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Yikes man, didn't leave yourself much wiggle room there did ya? I'll have a look in the parts bin and see what I can find. I'm not itching to sell my spare PS but in the name of you not failing a project I might be coaxed out of it._

 

That would be nice but no need to do that. I would not fail. The project is just an alternative to taking a final in that class. 

 Its my AP Physics course so I would obviously like to do something I like and not have to take a final. Now that I think about it. If i order tonight 3-5 days shipping it will be here before next thursday.

 That was very generous of you to offer thank you


----------



## n_maher

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_That would be nice but no need to do that. I would not fail. The project is just an alternative to taking a final in that class. 

 Its my AP Physics course so I would obviously like to do something I like and not have to take a final. Now that I think about it. If i order tonight 3-5 days shipping it will be here before next thursday.

 That was very generous of you to offer thank you_

 

Well, if you get stuck let me know.


----------



## Snicewicz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, if you get stuck let me know._

 

Thanks I appreciate it, but there is no worry. Worst comes to worst I explain and show it with out the power supply.

 Does anyone else know where I can get the 7 pin tube mounts so I dont have to buy 10?


----------



## tomb

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_Thanks I appreciate it, but there is no worry. Worst comes to worst I explain and show it with out the power supply.

 Does anyone else know where I can get the 7 pin tube mounts so I dont have to buy 10?_

 

7-pin Ceramic Mini Tube Socket - eBay (item 330211432830 end time Jun-10-08 16:13:14 PDT)


----------



## Snicewicz

Thanks tomb but the quantity is 0 and I cant wait 2 days for auctions to end. 

 Thanks for the help though 
	

	
	
		
		

		
		
	


	




 i bought the gold plated ones however


----------



## tomb

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_Thanks tomb but the quantity is 0 and I cant wait 2 days for auctions to end. 

 Thanks for the help though 
	

	
	
		
		

		
		
	


	




 i bought the gold plated ones however_

 

You waited too long. It was 2 when I posted it.
	

	
	
		
		

		
		
	


	




 Besides, there are many more listings under that seller. He even runs a separate store where you can buy them directly - cascadesurplus.com:

Cascade Surplus Electronics: 7-pin Ceramic Mini Tube Socket

 He has other ones, too - plastic, phenolic, and gold - take your pick.


----------



## J.D.N

Is it possible to put an LED in somewhere?


----------



## Ferrari

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Is it possible to put an LED in somewhere?_

 

This amp uses 48V DC PS, so you can tap this 48V PS and add a 15KΩ - 20KΩ resistor in the path, then connect a LED on this path (+48V -> (15KΩ - 20KΩ) resistor -> LED -> Ground).
 This is a P-P build, so it's not too difficult to find an appropriate point to connect 2 additional components. Good luck !


----------



## J.D.N

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_This amp uses 48V DC PS, so you can tap this 48V PS and add a 15KΩ - 20KΩ resistor in the path, then connect a LED on this path (+48V -> (15KΩ - 20KΩ) resistor -> LED -> Ground).
 This is a P-P build, so it's not too difficult to find an appropriate point to connect 2 additional components. Good luck ! 
	

	
	
		
		

		
		
	


	


_

 

Sweet. Im thinking of getting a little creative with this. I know its supposed to be the 'Starving Student' but id quite like it to look the part too. Its going to be my post exams project, so going to tincker with it as well. 

 How difficult would it be to put 6-8 LED's in there? I have an idea... might be rubbish, might not. Will just have to wait and see!


----------



## n_maher

Careful adding that many LED's. You'll need to account for their current draw (which you can vary via the resistor) and the existing PS may not be up to the task, or at least struggle even more at startup.


----------



## rds

You should be able to use ferrari's method for n leds.
 Just put resistor (R) between the ps and and the LEDs (which will be in parallel). Then for n LEDs calculate R as 20k/n (for bright LEDs) and 15k/n for dimmer LEDs.
 Each LED will take about 2.4 mA and the PS is rated for 380mA. It probably will be fine unless you're going for like 50 LEDs.


----------



## Ferrari

Yes, pay attention to the total current draw when you planning to use 6-8 LEDs in parallel and check that against the current ability of the used PS.

 Assuming you are using LED as indicator on the front pannel and if you use super bright LED (at least 3000 mcd), then ~2mA per LED is more than sufficient, that is what I usual do with my builds. 6-8 indicator LEDs would draw 12 - 16mA totally. But when you use a LED to light up the tube, then you need more current, 8-10mA is what I usual do (don't go up to 20mA -even that's on the LED's spec- that will shorten the life of the LED). For the later purpose, you can also look at much brighter LEDs @ 12.000 mcd or higher, but these are also more expensive.


----------



## rds

Someone asked earlier about the LPF. Increasing the capacitance will actually lower the cutoff frequency. 
 Since your headphones are in parallel with the output resistor, the R is the RC equation is pretty much set by the headphones being used.
 In the original design 32 ohm headphones will cause a cutoff frequency of about 66 Hz, and 600 ohm headphones will make it about 2.3 Hz. 
 So if you're using low Z headphones use a bigger cap for sure. 1000 uF or higher would be best (probably best in general). I think the reason Pete chose 150 uF is because they're cheaper.

 I think I'll go with 1500 uF Nichicon PW unless someone can give me a good reason not to, other than that I'll have to steal my lunch from the cafeteria.

 I can't think of a good reason to use a bigger C1 and C6, can anyone else?


----------



## J.D.N

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Yes, pay attention to the total current draw when you planning to use 6-8 LEDs in parallel and check that against the current ability of the used PS.

 Assuming you are using LED as indicator on the front pannel and if you use super bright LED (at least 3000 mcd), then ~2mA per LED is more than sufficient, that is what I usual do with my builds. 6-8 indicator LEDs would draw 12 - 16mA totally. But when you use a LED to light up the tube, then you need more current, 8-10mA is what I usual do (don't go up to 20mA -even that's on the LED's spec- that will shorten the life of the LED). For the later purpose, you can also look at much brighter LEDs @ 12.000 mcd or higher, but these are also more expensive._

 

Wonderful. Your help is much appreciated. Im only looking at about 3000-4000mcd and might limit it to 6. It's just an idea i've got. Going to do a bit of planning and then get the ball rolling on a BOM.

 Quick resistor question: Is there anything wrong with using 2w 5% Carbon Film resistors?


----------



## n_maher

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Someone asked earlier about the LPF. Increasing the capacitance will actually lower the cutoff frequency. 
 Since your headphones are in parallel with the output resistor, the R is the RC equation is pretty much set by the headphones being used.
 In the original design 32 ohm headphones will cause a cutoff frequency of about 66 Hz, and 600 ohm headphones will make it about 2.3 Hz. 
 So if you're using low Z headphones use a bigger cap for sure. 1000 uF or higher would be best (probably best in general). I think the reason Pete chose 150 uF is because they're cheaper._

 

It's worth noting that a fair number of headphones start to roll off beyond -3db below 40 or 50 Hz, so it's not like you're losing much information that you'd hear normally anyway. Also, there are a lot of headphones that don't have linear impedance characteristics (although Grados do) which means that the equation is more complex than just assuming half the stated impedance. Have a poke around Headroom's graphs, of note is the fact that the HD650 are actually 400ohm at 40Hz and rise to a peak of nearly 500ohm at ~80Hz. That may be an extreme example but it just goes to show you that there are other factors in play.

  Quote:


 I think I'll go with 1500 uF Nichicon PW unless someone can give me a good reason not to, other than that I'll have to steal my lunch from the cafeteria. 
 

That might be a bit extreme and it will take that cap quite a while to charge, enough so that I personally wouldn't leave headphones connected when you turn the amp on. Moving to a 470uF coupling capacitor will take the -3db point down to a reasonable ~21Hz. I'm not one of those folks who thinks that you need your -3db to be in the basement to get good frequency response so bear that in mind.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_<snip>That might be a bit extreme and it will take that cap quite a while to charge, enough so that I personally wouldn't leave headphones connected when you turn the amp on. Moving to a 470uF coupling capacitor will take the -3db point down to a reasonable ~21Hz. I'm not one of those folks who thinks that you need your -3db to be in the basement to get good frequency response so bear that in mind. 
	

	
	
		
		

		
		
	


	


_

 

I apologize if I started something by suggesting 470uf output caps. It's a common size for many headphone amps and has been traditionally used on the output of Milletts for years. No one has every complained from lack of bass with Grados on Milletts, either.

 That said, Pete has made several references to the PS sort of hiccuping as it starts up on the Starving Student as designed. So, increasing inrush current is probably not something to take lightly. 470uf might be a reasonable increase - it might not. We'll have to wait until one of us tests it first and reports back.

 Under that scenario, Nate is correct: 1500uf would be extreme. It might trip the safeties on the PS and never start - for very little benefit in return.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I apologize if I started something by suggesting 470uf output caps. It's a common size for many headphone amps and has been traditionally used on the output of Milletts for years. No one has every complained from lack of bass with Grados on Milletts, either._

 

Bah, it's a healthy debate to have - I agree that moving to 470uF is not a bad idea. I just ran some test tones through my SSH (starving student hybrid) and there's definitely a drop off below 70Hz. Of course my listening levels in the office are such that I don't even notice it.
  Quote:


 That said, Pete has made several references to the PS sort of hiccuping as it starts up on the Starving Student as designed. So, increasing inrush current is probably not something to take lightly. 470uf might be a reasonable increase - it might not. We'll have to wait until one of us tests it first and reports back. 
 

I can certainly confirm that the PS struggles with the cold heaters. I think there's a solution, but I'll let Pete comment on that when he gets a chance.

 As more of these get built I'm sure folks will tweak it. It's not like the BOM is a set of rules you have to follow, just one example of a working concept.


----------



## rds

Larger caps won't increase the inrush current, they will simply make the time that current is sustained for longer. 

 I'd like to hear more details about the ps struggling. What exactly happens?


----------



## rds

Also, I'm wondering if some people would appreciate a parts kit?
 I'm in the process of placing orders and have some extra cash (a scholarship cheque appropriately). 
 Since people are having trouble getting certain things and have to make 3 orders it seems to be a good candidate.
 I'm using pretty much pete's list with some minor changes (slightly better things here and there), with one major change being a hammond 1455. With the case and 4 tubes (2 extras) the cost for a kit would be about $60.
 Let me know, I'm ordering today.


----------



## n_maher

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I'd like to hear more details about the ps struggling. What exactly happens?_

 

Basically on startup the PS starts, stops, starts, stops and then finally lights the heaters. As soon as the heaters come online the PS is fine but there are some hiccups at startup. According to Pete it's nothing worth worrying about and I've been power cycling my amp every day for the past couple months with no ill effects.


----------



## bhjazz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Moving to a 470uF coupling capacitor will take the -3db point down to a reasonable ~21Hz._

 

470, eh? Interesting. I have 220's (210, 220...Don't rememeber. Need more coffee right now) on my parts list, but had not considered going higher. I'll definitely look into them, though. For the simplicity of the design, it would be pretty easy to swap parts in and out, so maybe I'll get both.


----------



## trains are bad

I pretty much followed the BOM when I ordered my parts; now I'm thinking I should have sprung for some more betterer caps. I didn't realize that the electrolytic caps (I got 220uF) were to be used for the output coupling caps. Electrolytics aren't usually used for audio, right?


----------



## holland

.


----------



## holland

.


----------



## n_maher

Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_Electrolytics aren't usually used for audio, right?_

 

In my experience they are used all the time. A fair number of tube amps have electrolytics on the output, mostly because high-value, high-voltage film caps tend to be huge. For example, the Menace only has 200uF on each output in the form of 2x 100uF motor-run oil caps, each one of those is 2-1/2" in diameter by 4-1/2" long. Not at all practical for most applications.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Larger caps won't increase the inrush current, they will simply make the time that current is sustained for longer. 

 I'd like to hear more details about the ps struggling. What exactly happens?_

 

I'd like to hear more details of that statement up there.
	

	
	
		
		

		
		
	


	




 Maybe I'm missing something, but any number of equations show that peak inrush current is proportional to capacitance:

 I = C * dV/dT


----------



## bhjazz

Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_I pretty much followed the BOM when I ordered my parts; now I'm thinking I should have sprung for some more betterer caps._

 

No worries. The design is simple enough that you can start with the standard bom and swap parts in and out whenever you want to. 

 Also, this brings up Nate's mention a few weeks ago in this very thread where he said, "That's the Y in DIY." YOU can do whatever you want with your own build. I say, stick with the caps you have, build it, enjoy it, then when you are ready to get back under the hood do so and have fun.


----------



## rds

tomb -
 The power source is dc in this case. Here's a good explanation of what happens when you flip the switch. Notice that Imax is V/R.
Charging a Capacitor
 You may be thinking of the instantaneous inrush when the voltage is actually changing from 0 to 48. Yes here the inrush will be very large. Regardless of whether the capacitor is 150 uF or 1 F it will be much greater than 380mA and therefore the current limiting mechanism of the ps will kick in momentarily.


----------



## trains are bad

You know I ordered two different kinds of film caps for the .1uF application, just to have on hand. Whichever ones I don't use, I'll probably put in parallel with the electrolytics.

 Since I've ordered my parts, I came up with a cool circuit that doesn't let you turn the amp on or off, unless the headphones are unplugged. This way you actually couldn't turn the amp on or off if you forgot to unplug the headphones first. The parts are a dollar, but a special order from mouser would be another 6 dollars in shipping. Why o why can't they ship little parts out in envelopes for the price of a stamp?


----------



## MisterX

Quote:


 Why o why can't they ship little parts out in envelopes for the price of a stamp? 
 

I think it has something to do with them having to pay for the packing material, the envelope, the shipping label, the printer that prints the label, the person that picks and packs the order and all of the other expenses involved in operating the web site that you ordered the parts from. 
	

	
	
		
		

		
			





 (given all of that I don't see how they make any money on small orders, especially since they don't have a small order surcharge like Digi-key does)


----------



## bhjazz

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_(given all of that I don't see how they make any money on small orders, especially since they don't have a small order surcharge like Digi-key does)_

 

I avoided a small-order surcharge due to an item being out of stock when I needed it. HOWEVER, I had to pay $5.25 to ship my tiny $1.25 Panny caps...and they put them in a standard-sized box! GAH!


----------



## Gross

I fingered it out! First of all I put some 100 Ohm Kiwame resistors on the output after C3 & C5( I am not a starving student anymore, so I can splurge a bit right?) to first and foremost make the pot much more usable, which it did for my HD-600s and RS-1s. I was also hoping it would bring up the Z of the headphones and lower the F3, but it did not make any difference in that respect. Second I replaced C3 and C5 with some 470uf Nichicon Muse ES, I would like to think it made a difference, but I only tried that config with my HD600s, and not the Grados, So I cannot be sure it fixed a little something, but I could tell even with my Senns, the lower bass was still missing. I thought to myself, hmm, it is still as if there is a HPF in place...what other caps do I have? I did not order anything for C2 and C4, as I have plenty of film caps in stock. Well it turns out I put in some .022uf caps in instead of .22uf. As soon as I replaced them, all that tubby tubey bass that I was expecting sprung to life. I would like to point out that it still sounds very crisp on the high end, however it has the lowend to balance it out now. Also, for those of you ordering parts do not be afraid to go a little crazy with the heatsinks. I have 1.5" sinks and they get pretty toasty, so I would say bigger is better. 

 I think I may put the original 270uf caps back in the output, and see how it compare to the 470uf Muse, since those are supposed to go in my MOSFET-MAX. I am going to completely rewire this guy too, after all these mods, it is a bit messy inside.


----------



## MisterX

Quote:


 GAH! 
 

I have the same response to backorders.


----------



## n_maher

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_I have the same response to backorders._

 

I have the same response to Newark!


----------



## MisterX

lol, I think we all have that responce to Newark.


----------



## FallenAngel

Quote:


  Originally Posted by *MisterX* /img/forum/go_quote.gif 
_lol, I think we all do._

 

Yep, but just wait until you've dealt with moving, then it's even more creative.

 I was in Canada and had a Newark.ca account (where they have kept an exact 50% chance of screwing up my order), then I moved over to San Francisco and opened a Newark.com account (because I couldn't change the country on the account, nor could I create an account with the same name because their database is shared stupidly). Now, I placed an order with Newark.com and they sent me an email with my Canadian billing info! 
	

	
	
		
		

		
		
	


	




 Oh the joys of Newark. At least I got free shipping.


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_<snip>
 You may be thinking of the instantaneous inrush when the voltage is actually changing from 0 to 48. Yes here the inrush will be very large. Regardless of whether the capacitor is 150 uF or 1 F it will be much greater than 380mA and therefore the current limiting mechanism of the ps will kick in momentarily._

 

That's exactly where I was talking about and that was the context. Also, momentarily may be an assumption. Sometimes there's an automatic reset, sometimes a manual one - sometimes, it's permanent.


----------



## rds

Before I place my order I'm interested to hear why *Pete* chose 150 uF and what he or anyone else thinks the disadvantages might be in using a 1000 uF cap.


----------



## pmillett

Hey everybody -

 Sorry I haven't been able to keep up with this thread and answer everybody's questions. I'm busy as heck with the "day job", plus various commercial headphone projects on the side, and have been travelling a lot, and will be travelling more...

 Feel free to send me an email or PM if you have a specific question. I try to answer reasonably quickly, though it can take a few days.

 A few comments:

 The switching power supply has a hard time starting up into the cold filaments, which have a pretty low resistance. So it "hiccups" - turns on and then current limits, and turns off - several times at about a 1Hz rate, until the heaters are warm enough that they don't draw too much current for the supply. You can avoid this by increasing the second filter cap (C6 on my schematic) from 150uF to something like 470uF. Bigger here will not hurt anything - 1000uF or more is fine, no worries. What this does is make the bias on the FETs rise more slowly, causing the filaments to heat gradually, and the power supply is happier.

 As for the output cap size - 150uF is OK for most headphones (even 32 ohms, IMO), 470uF is OK as well. Why did I use 150uF? 'cause I had them 
	

	
	
		
		

		
		
	


	




 I think there's no benefit in going as high as 1000uF. Don't assume that having flat frequency response to 20Hz is necessarily a _good _thing; most headphones only produce distortion at that low of a frequency, and if the amp reproduces it you tend to increase IMD generated in the headphones. Just for kicks, try listening to test tones at these frequencies - what you hear is usually either nasty, or non-existant.

 I usually like to set a -3dB point of 20Hz - 50Hz for the "chosen" headphones. YMMV, IMHO, and lots of other TLA's and FLA's apply here. Another downside to going big (no, I'm not talking about "male enhancement") is that you will get a bigger thump (get your mind out of the gutter) when you turn the power on. You can mitigate this somewhat by lowering the value of the output load resistors (R6 and R12), but you will be stealing current that could otherwise be delivered to the headphones. 

 I still haven't had time to try the Jameco linear supply, but it should not have the hiccup issue. Has anybody used it? Is there any hum? Many of the linear wall warts have pretty small filter caps. You can always add more capacitance (C1 in the schematic) if there is hum, even 10,000uF with a linear supply will probbaly work (but most switchers won't start up into a big capacitance like that).

 You can't really substitute a 6J6 tube for the 19J6, since it requires 600mA to heat it up. I don't think 19J6's are too hard to find - there are lots of tube dealers out there. The beauty of this particular tube is that it has high enough Gm that you can get reasonable gain and distortion from it on 48V B+, and it's heater voltage and current just happen to make a good load for a class-A MOSFET source follower to drive 32 ohms. 

 If you want to try other tubes you need to find something with a filament voltage of (ideally) 10-25V and a current requirement of 100-200mA. 100mA into 32 ohm headphones is 3.2V peak, which is plenty loud. FWIW, for the engineering-inclined, you could design a similar amp using 12V car radio tubes (12AE6A, etc.) that need 12-14V at 150mA. You would bias the gates of the FETs at about 16-17V (Vgs of IRF510 is around 4V at this current). I picked the 19J6 partly because it is cheap and useless 
	

	
	
		
		

		
		
	


	




 I wouldn't be obsessive about the coupling caps - sure, polypropylene is a tad better than PE to most people, but any film cap will do. I'd be more concerned about making sure you have decent electrolytics. Black gates are not necessary - good low ESR caps (Nichicon UHE's, UPL's, or similar low-Z parts from Panasonic of Chemicon) are fine.

 Did I read that right, that somebody gets to build this instead of taking an AP phyics final? That's waaaaay cool.

 Well, that's all that comes to mind for now... have fun!

 Pete


----------



## bhjazz

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_A few comments:_

 

Golden, golden information. Thanks, Pete. Much appreciated! This kind of info allows me some great insight into the design and gives some elbow room to experiment. Coolness! Thanks!


----------



## tomb

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_Golden, golden information. Thanks, Pete. Much appreciated! This kind of info allows me some great insight into the design and gives some elbow room to experiment. Coolness! Thanks!_

 

x2 - as in chiseling every word into memory. 
	

	
	
		
		

		
		
	


	







 What sounds really neat is that slightly upping the size of C6 is enough to overcome the short-term PS current limit in starting the heaters. I was afraid to mention it after all the rest of the talk of upping the cap sizes (had visions of my PS croaking), but had selected 470uf (63V UPW's) for those, too. It didn't seem natural to have smaller caps on the input than on the output.


----------



## rds

Pete - Thanks for the detailed information. That's just what I needed to know before placing my order.


----------



## J.D.N

x3 Thats excellent info. 

 Due to living in England it's hard to get access to the range of capacitors that you guys do in the US. Could someone please run their eye over my choices bellow and OK them? They are partly chosen by what i can get hold of, and partly due to price (what i could get cheap-ish). Surprisingly they dont seem that expensive at all, but then ive never bought that many caps so i cant really compare. 

 C1: 150uF 63v: MUNDORF TYPE - br63 - Bipolar electrolytic 

 C2/C4: 0.1uF 63v [630v]: Clarity Cap - metallized polypropylene

 C3/C5/C6: 470uF 63v: MUNDORF TYPE - br63 - Bipolar electrolytic 

 Also, is it possible to use 2W resistors instead of 1/4W?


----------



## Ferrari

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_x3 Thats excellent info. 

 Due to living in England it's hard to get access to the range of capacitors that you guys do in the US. Could someone please run their eye over my choices bellow and OK them? They are partly chosen by what i can get hold of, and partly due to price (what i could get cheap-ish). Surprisingly they dont seem that expensive at all, but then ive never bought that many caps so i cant really compare. 

 C1: 150uF 63v: MUNDORF TYPE - br63 - Bipolar electrolytic 

 C2/C4: 0.1uF 63v [630v]: Clarity Cap - metallized polypropylene

 C3/C5/C6: 470uF 63v: MUNDORF TYPE - br63 - Bipolar electrolytic 

 Also, is it possible to use 2W resistors instead of 1/4W?_

 

The Mundorf BR63 bipolar electrolytic are developed for speakers manufacturing/industry.
 It's generally larger than generic (polar) electrolitics of the same value and can be considered as a step up from generic (polar) electrolitics. So, you can use these BR63 bipolar electrolytics in this build, the size should not be an issue here.

 Regarding the resistors, 2W power resistors can be used, however power resistors are very often 5% tolerance resistors (check this for sure)! It's better to use 1% tolerance resistors instead of 5%, so try to buy 1/4W 1% tolerance resitors if the 2W type is indeed 5%. Resistors are not so expensive, though. The MKP for C2/C4 is OK !


----------



## J.D.N

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The Mundorf BR63 bipolar electrolytic are developed for speakers manufacturing/industry.
 It's generally larger than generic (polar) electrolitics of the same value and can be considered as a step up from generic (polar) electrolitics. So, you can use these BR63 bipolar electrolytics in this build, the size should not be an issue here.

 Regarding the resistors, 2W power resistors can be used, however power resistors are very often 5% tolerance resistors (check this for sure)! It's better to use 1% tolerance resistors instead of 5%, so try to buy 1/4W 1% tolerance resitors if the 2W type is indeed 5%. Resistors are not so expensive, though. The MKP for C2/C4 is OK !_

 

Cheers Ferrari, the 2w resistors are indeed 5%. Found a few places selling 1/4W but they are all 5%. The BOM says 5%, am i missing something?


----------



## Ferrari

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Cheers Ferrari, the 2w resistors are indeed 5%. Found a few places selling 1/4W but they are all 5%. The BOM says 5%, am i missing something?_

 

Have no time to look at the BOM yet, but 5% resistors can be used and it will work as I posted earlier.
 Metal film resistors 1/4W are usually 1%, it's hard to find wider tolerance (> 1%) metal film resistors 1/4W nowadays, at least in the Nethelands.

 Generally, 1% metal film resistors are prefered in audio applications and ... personally I have never used resistors with 5% tolerance in my amps, unless there are no other choices for small values (< 1Ω) power resistors.

 Edit: Just looked at the BOM, Pete listed *carbon film* resistors in the BOM (these are cheaper), that explains 5% resistors!
 The good man tried to keep the bill as low as possible for starving students, probably.


----------



## rds

How close you want the resistors to be depends on how obsessive you want to be. In my opinion 1% is generally plenty good. Although you'll be ordering 5%, since they'll be from the same batch they'll probably be less than 1% (that's my experience). Remember the rating is the absolute max deviation over all batches. 
 With these large values you can hand match resistors with a multimeter easily.


----------



## HypnoLobster

How did you more successful people mount the heatsinks? The ones I have (the right part number, I swear!) only have little metal lugs protruding from the bottom. Nothing to screw or bolt to.


----------



## Gross

Quote:


  Originally Posted by *HypnoLobster* /img/forum/go_quote.gif 
_How did you more successful people mount the heatsinks? The ones I have (the right part number, I swear!) only have little metal lugs protruding from the bottom. Nothing to screw or bolt to._

 


 I ordered those too... I pulled the pins out with a pair of pliers and then tapped the holes with a 4-40 tap, and used screws to mount them. It would have been easier to buy heatsinks without pins, but oh well.


----------



## HypnoLobster

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_I ordered those too... I pulled the pins out with a pair of pliers and then tapped the holes with a 4-40 tap, and used screws to mount them. It would have been easier to buy heatsinks without pins, but oh well._

 

That was my plan as well. 
 What are the pins intended for? All I can think of is soldering the heatsink to a board or something as such.


----------



## Ech0

Quote:


  Originally Posted by *HypnoLobster* /img/forum/go_quote.gif 
_What are the pins intended for? All I can think of is soldering the heatsink to a board or something as such._

 

Yep, that's it. Which makes it a little hard to remove if you need to.


----------



## tomb

If you look closely, Pete soldered his to the copper board that's in his BOM. This sandwiches the tin between the bottom of the heat sink and the copper board. This is probably a convenient and easy way to do it.

 On the other hand - if you look at Nate's pics, he used screws. Unfortunately, I think we're stuck with pulling the pins out if you go that route. I didn't see any "no pin" options for the size heat sinks we need at Mouser or DigiKey.

 BTW, heat sinks are soldered to PCB's on a regular basis (almost all of the MAX's are built that way). The only reason you might want to remove them is if you decide to use a different size.


----------



## bhjazz

I found a few old-school smoke shops in Seattle, and was considering using a cigar box. If the heatsinks are screwed to the box, though, how much heat would get transferred? Would the whole thing go up in flames on a particularly loud passage?








 Edit: okay, maybe that's a bit extreme....but still....


----------



## Gross

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_I found a few old-school smoke shops in Seattle, and was considering using a cigar box. If the heatsinks are screwed to the box, though, how much heat would get transferred? Would the whole thing go up in flames on a particularly loud passage?_

 

I used a plastic enclosure for mine, and while the sinks get toasty, and I have had it on for several hours at a time, It hasn't done anything to the plastic.

 So, I think you'll be ok


----------



## bhjazz

Thanks, Gross. 

 BTW: I got a good chuckle out of your post yesterday about dropping the .022uf cap into the build. Glad you figured it out!


----------



## trains are bad

I used an aluminum box, with holes drilled for the pins. I just dabbed a bit of JB weld on the pins and stuck it on top till it cured.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_On the other hand - if you look at Nate's pics, he used screws. Unfortunately, I think we're stuck with pulling the pins out if you go that route. I didn't see any "no pin" options for the size heat sinks we need at Mouser or DigiKey._

 

Just a word of warning, I've never successfully pulled a pin from a heatsink. I've tried, not all that hard, but it seemed like it would be a recipe for bad things to happen.

 Someone should have a closer look at 707-411626B25 from Mouser, I don't see any pins and I think that this part would be sufficient. Actually, 707-411621B25 might be fine as well.


----------



## bhjazz

I'll look into that one later today, Nate. Nice catch...I was seconds from clicking CheckOut at Mouser! 

 I tried to find those heatsinks at the Comair Rotron website, but Mouser seems to have fudged the part numbers. There are some similar ones there, but not the matching ones. Still, the idea of the mfr having tapped holes seems a lot better than me flailing around with a running drill in my hand. 

 Off to Costco. Sure wish they had a DIY aisle...

 "Teach a man to DIY, and he'll sit and wow at his creations. Teach a man to shop at Costco, and he'll eat like a king."


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Just a word of warning, I've never successfully pulled a pin from a heatsink. I've tried, not all that hard, but it seemed like it would be a recipe for bad things to happen.

 Someone should have a closer look at 707-411626B25 from Mouser, I don't see any pins and I think that this part would be sufficient. Actually, 707-411621B25 might be fine as well._

 

Thanks for those links - guess I wasn't looking at this "Comair Rotron" brand. (I never tried pulling a pin, either.
	

	
	
		
		

		
			





 )


----------



## trains are bad

I had to use 215kOhm resistors because I didn't have any 220s. I don't suppose this will be a problem, will it?


----------



## Gross

Yeah, as far as pulling pins on those heatsinks, it sucks. They do not come easily, at all. If you can find pre-tapped, or even just holes, go for it. Tapping holes is easy enough, and I've never liked the idea of tapping with a drill, I always do it by hand.


----------



## rds

In my experience standard hardware store washers (I think they're silver-nickel plated) accept solder pretty easily.
 Just get a coating solder on the washer first, then put it in place and it should be the same as soldering to a pcb.


----------



## rds

I've made a thread where you can post your impressions of this amp
http://www.head-fi.org/forums/f5/mil...ssions-326577/


----------



## malldian

If you guys think this is big enough, I found my case:

Newegg.com - Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!


----------



## bhjazz

Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_I had to use 215kOhm resistors because I didn't have any 220s. I don't suppose this will be a problem, will it?_

 

I don't think it will. At the very least all four (R2, R4, R8, R10) should all be the same, which you've covered. My only question would be the voltage change now going to the tube on pin 1 (and across C2).


----------



## Gross

Quote:


  Originally Posted by *malldian* /img/forum/go_quote.gif 
_If you guys think this is big enough, I found my case:

Newegg.com - Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!_

 

I don't think that case will work very good in this application. It is just too small. The capacitors will hardly fit in there, let alone having to wire everying and then slide it in from the side. That would be a damn slick case for an AlienDAC or something those.


----------



## bhjazz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Someone should have a closer look at 707-411626B25 from Mouser, I don't see any pins and I think that this part would be sufficient. Actually, 707-411621B25 might be fine as well._

 

In the end (and the end is at about 11:30 this evening) I chose the 707-411626B25. The thermal properties looked better than the one that is on the BOM, and if I need to switch out of my proposed wood box to accommodate these, then so be it. 

 Onward! (Hey, I got some Alien DAC parts while at Mouser, too! W00t!)


----------



## dominion

AWESOME. someone sell me one o.o.


----------



## trains are bad

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_I don't think it will. At the very least all four (R2, R4, R8, R10) should all be the same, which you've covered. My only question would be the voltage change now going to the tube on pin 1 (and across C2)._

 

Well 220 * .05 is 11, and 220 - 215 = 5, so given that 5% resistors were spec'd in the original starving student design, I reasoned I would be fine. That was my justification anyway.


----------



## royewest

OK, I just finished ordering the parts for this, except for the:

 150uF 63V low-ESR electrolytic capacitor

 Which are backordered at Mouser. I'll try my local shop, but any suggestions for alternate parts for C1,C3,C5,C6?

 Thanks,

 __Roy


----------



## synaesthetic

Try checking a different manufacturer for a similar part?


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_OK, I just finished ordering the parts for this, except for the:

 150uF 63V low-ESR electrolytic capacitor

 Which are backordered at Mouser. I'll try my local shop, but any suggestions for alternate parts for C1,C3,C5,C6?

 Thanks,

 __Roy_

 

Absolutely. If you read Pete's latest post, he suggests 470uf for the electrolytics on the power side anyway. Meanwhile, 470uf's have been a traditional output cap for Milletts for a long time, anyway. So, get yourself four 470uf 63V Nichicon UPW's. Mouser Part#647-UPW1J471MHD3 - $1.23 each.


----------



## royewest

Thanks -- I thought that was what he meant but I was not certain. I included a handful of extra 470uFs in my Mouser order hoping they would work as you describe.


----------



## rds

c3 and c5 can be pretty much any value you want as long as they're greater or equal to 150 uF. So you could get a few different ones and see what you like the sound of the most.


----------



## bhjazz

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_I found a few old-school smoke shops in Seattle, and was considering a cigar box._

 

Not that quoting myself is a good thing, but I did figure something out. Funny how the human brain can digest ideas and come up with a good solution. 

 If a wood or wood cigar box needs to be used (to try to stay within the starving student idiom) consider mounting a piece of sheet metal to the inside of the box. This would create a simple RF shield, plus the heatsinks could be mounted to, and soldered to, the metal.


----------



## J.D.N

Got my BOM pretty much sorted now. Slightly more expensive than the MSSH was supposed to be i think, but then that a consequence of living in England and some of the parts i chose. 

 Im also going to incorporate an alien DAC i've had lying around for about 7 months and an input selector. Figure i might as well get maximum functionality out of it. Just got to hope i still have some cash come end of June for all this!


----------



## royewest

Just FYI, I called around a bit today looking for matched tubes. One of the vendors I called was in the process of making up an order for 40 tubes from someone. All the folks I spoke with asked what the sudden rush was on these tubes. I wonder how long this project will be viable if all the tubes are getting bought up -- I have no idea what the backstock of these tubes is.


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Just FYI, I called around a bit today looking for matched tubes. One of the vendors I called was in the process of making up an order for 40 tubes from someone. All the folks I spoke with asked what the sudden rush was on these tubes. I wonder how long this project will be viable if all the tubes are getting bought up -- I have no idea what the backstock of these tubes is._

 

Could be Jeff is making kits? From the checking I've done, though, it will take a lot more than 40 tubes to make a dent in the 19J6's out there.


----------



## bhjazz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, get yourself four 470uf 63V Nichicon UPW's. Mouser Part#647-UPW1J471MHD3 - $1.23 each._

 

I was trying to be all slick and headed out to Handmade Electronics, hoping to order some Nichicon Muse ES caps in 470uF. Joke's on me. None there. I thought I had seen that value there just last week.... Ah well. I'll go with the UPWs and wait for some ESs to show up in the future, although I'm not sure that they are available at anything over 50V. 


  Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_All the folks I spoke with asked what the sudden rush was on these tubes._

 

SAY NOTHING!!!!!!!!!!!

 DIY Club = Fight Club


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you look closely, Pete soldered his to the copper board that's in his BOM. This sandwiches the tin between the bottom of the heat sink and the copper board. This is probably a convenient and easy way to do it.

 On the other hand - if you look at Nate's pics, he used screws. Unfortunately, I think we're stuck with pulling the pins out if you go that route. I didn't see any "no pin" options for the size heat sinks we need at Mouser or DigiKey.

 BTW, heat sinks are soldered to PCB's on a regular basis (almost all of the MAX's are built that way). The only reason you might want to remove them is if you decide to use a different size._

 

good luck getting the pins out. Just turn it upside down and tap the other ends of the heat sink and drill out a new hole to attach the device to.


----------



## pinkfloyd4ever

hey I accidentally (sort of, it was like half the price of the regular stuff) bought Arctic Silver Ceramique at this local store. Will it work with an Aavid Therma*film* pad?


----------



## rds

That's probably a bad idea. The pad is meant to work on its own. Adding more stuff between the metal surfaces will only reduce heat transfer.
 But arctic silver is really good stuff. I've used that many times for heatsinks. Just use one or the other


----------



## rds

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Just FYI, I called around a bit today looking for matched tubes. One of the vendors I called was in the process of making up an order for 40 tubes from someone. All the folks I spoke with asked what the sudden rush was on these tubes. I wonder how long this project will be viable if all the tubes are getting bought up -- I have no idea what the backstock of these tubes is._

 





 I think that was me... Radio Daze right?

 I've got something up my sleeve 
	

	
	
		
		

		
		
	


	



 It's strictly not-for-profit.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_That's probably a bad idea. The pad is meant to work on its own. Adding more stuff between the metal surfaces will only reduce heat transfer.......Just use one or the other 
	

	
	
		
		

		
		
	


	


_

 

umm are you sure? quoting the Millett Max site: "The choice of pad almost becomes one of convenience. Mica is the cheapest by far, but needs grease. Thermafilm has better heat transfer than Mica, but costs more and still need grease. Thermasil is the one that does not need grease, and often comes with an adhesive back, making it very convenient. " 

MAX Heat Sink Mounting check the 4th paragraph. I wanted to get Therma*film* for this reason but I didn't wanna wait for mouser to get them back in stock


----------



## -=Germania=-

I mangaed to get two identical RCA tubes - sweet!


----------



## rds

I'm sorry, yes, with Thermafilm you will need grease as they say. I would imagine any thermal compound will be fine, but I'm no expert on that.
 Keep in mind that the thermafilm itself is meant to electrically isolate Q1 and Q2 from the heatsink. If the heatsink itself is isolated from the circuit then the thermafilm is not required.
 ...hope that makes sense.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I mangaed to get two identical RCA tubes - sweet!_

 

on an order of only 2?


----------



## dsavitsk

still work to be done, but here's a first draft.


----------



## malldian

Wait what is this?


----------



## pinkfloyd4ever

WWHHHHAAAA?!?!?!


----------



## trains are bad

I ordered 4 tubes from radiodaze and got 4 Tung-sol tubes.


----------



## n_maher

I think in the near future there will be PCBs available for this project. I'm not inclined to say more at this point since I don't want to provide false hope since nothing is guaranteed. Whether they end up being from dsavitsk's layout or someone else's is yet to be determined. But I'd also encourage folks to have a go at PTP'ing the amp, it really is pretty simple and half the challenge/fun is figuring out how you want to layout your amp.


----------



## royewest

Jeff, if you're planning to make kits available, more power to you. I rather hoped that that was the 40-tube order they were working on.


----------



## -=Germania=-

well - I have all of the parts here. 
 Just some questions: 

 How to mount the Mosfets? (like which pin is which)

 Which pin is which on the tube sockets?


 Also, I am building mine into a hammond ABS housing and was wondering what would be better to make the holes. Hot knife or drill? 
 I am worried that the drill might crack the case.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_How to mount the Mosfets? (like which pin is which)_

 

And on the 8th day (insert favorite deity here) created data sheets. 
	

	
	
		
		

		
		
	


	




  Quote:


 Which pin is which on the tube sockets? 
 

Look at the bottom of the socket, many have the numbers printed there. Otherwise the tradition is that when looking at the bottom the numbers increase in a clockwise fashion and pin 1 is the first pin to the right of the notch/gap/etc. A quick google search will probably yield a better explanation.

  Quote:


 Also, I am building mine into a hammond ABS housing and was wondering what would be better to make the holes. Hot knife or drill? 
 

Hot knife = fail. Drilling will take patience and care but should yield much better results. It may mean drilling small pilot holes, but that's the way I'd do it.


----------



## -=Germania=-

I tell you I am so very sick of data sheets right now. 

 I am in a microprocessor system design class and to figure out how to make your stuff, you have to read the 30 page data sheets of each chip to see how it will work and how to program the memory to get it to function. Build+program = frustration, but a great feeling when you finish and have something that works!


----------



## trains are bad

with a bit of googling the TO-220 mosfet, I was able to find short one page datasheets with pinout diagrams saying which one was the gate, drain, source, along with the circuit symbol.


----------



## holland

.


----------



## Zigis

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I think in the near future there will be PCBs available for this project._

 

Hei ! Please, don't distort this marvel tube design with PCB !!!


----------



## n_maher

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Hei ! Please, don't distort this marvel tube design with PCB !!!_

 

Whether or not pcb's end up getting made will have absolutely no impact on how great this design is. It's a gift to the community and the more people the build it (via pcb or ptp) the greater that gift becomes in my opinion. I have zero tolerance for people who want to profess that the only real DIY is ptp so if that's the message you're preaching it's falling on deaf ears my friend.


----------



## fortney

In regard to the matter of drilling a plastic case--

 I use a cone (pencil) shaped solder tip, that I could never use successfully to solder, to melt a dimple in the selected and twice measured location on the case that I want to drill. This will let the drill tip bite right into the plastic and you won't have problems with the drill tip walking (scratching) on the surface of your box.

 Start with a small diameter drill tip and work up. Be sure to safely immobilize your box so it won't rotate with the drill. 

 Ordinarily I find that the 1/4 inch bit will bind in the plastic and so at that point I go to a hand held reamer that I rotate in the hole a few times then measure with the part to be placed for fit. Go slow here so you don't make the hole a little too big. 

 Carefully clean the attached shavings from the perimeter of your hole with a large drill tip or other conical cutting tool turned by hand.

 I use hand drills. Electric drills will require a little different technique.

 Good luck

 F


----------



## -=Germania=-

Yeah, this sounds like a weekend project. 

 I have access to a machine shop and there are always people in there working on projects who could help. 

 Worst comes to worst, its Dremel Time!


----------



## Zigis

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_ I have zero tolerance for people who want to profess that the only real DIY is ptp so if that's the message you're preaching it's falling on deaf ears my friend._

 

I absolutely don't think only real DIY is ptp, I think only real tube amps is ptp 
	

	
	
		
		

		
			




 This design is so easy - only few parts.
 Maybe it is good idea if someone make kits - instead PCB, made predrilled 1.5 - 2 mm aluminum plate ?

 Zigis


----------



## tomb

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_I absolutely don't think only real DIY is ptp, I think only real tube amps is ptp 
	

	
	
		
		

		
		
	


	



 This design is so easy - only few parts.
 Maybe it is good idea if someone make kits - instead PCB, made predrilled 1.5 - 2 mm aluminum plate ?

 Zigis_

 

Easy for you to say.
	

	
	
		
		

		
		
	


	







 IMHO, a person couldn't sell pre-drilled plates for 1/10 the cost and time it would take to make them.

 Don't get me wrong - I know this is mostly a tongue-in-cheek back and forth, but it's hard to make up the labor just in picking out and packing boards and parts, much less something as you mention. I'm not complaining about selling parts, but don't hold your breath for anyone offering something like pre-drilled plates. It's one of the reasons FPE charges what they do.

 Besides, this is a Hybrid, remember.


----------



## n_maher

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_I absolutely don't think only real DIY is ptp, I think only real tube amps is ptp 
	

	
	
		
		

		
		
	


	


_

 

Well, I have to be honest then and say that what you think is going to have no effect on how I conduct myself. If you want to be a PTP elitist that's fine by me. 

  Quote:


 This design is so easy - only few parts. 
 

Agreed, it's pretty simple. But I'm not going to force someone to build it one way or the other. But you can bet I'll give them options. 
	

	
	
		
		

		
		
	


	



  Quote:


 Maybe it is good idea if someone make kits - instead PCB, made predrilled 1.5 - 2 mm aluminum plate ? 
 

How is that any different than a PCB? Both are designed to make things easier for the builder.


----------



## joneeboi

n_maher, I'm wondering what kind of screws you used to drill in the heat sinks. Did you remove the supplied soldering pins? I tried twisting it out with a few different pliers, but no dice so far. Any advice?


----------



## luvdunhill

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_n_maher, I'm wondering what kind of screws you used to drill in the heat sinks. Did you remove the supplied soldering pins? I tried twisting it out with a few different pliers, but no dice so far. Any advice?_

 

stick 'em in the oven for a while. The pins are steel and the heat sinks are aluminum, and as a result have different coefficients of expansion.


----------



## Gross

I grabbed ahold of the pins with a channel-lock pliers, and then with the heatsink resting against the edge of the table yank em out. I didn't pull em straight out, kinda used the head of the pliers as a fulcrum.


----------



## Zigis

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_How is that any different than a PCB? Both are designed to make things easier for the builder. 
	

	
	
		
		

		
		
	


	


_

 

I am not against make things easier for builders, just my IMHO - PCBs is not for tubes, for solid states.

 However, as tomb say - this is Hybrid, than OK, we can do it both ways 
	

	
	
		
		

		
		
	


	




 Peace


----------



## rds

What does the pcb do exactly? What part of it is so incompatible with tubes?


----------



## holland

.


----------



## holland

.


----------



## n_maher

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_n_maher, I'm wondering what kind of screws you used to drill in the heat sinks. Did you remove the supplied soldering pins? I tried twisting it out with a few different pliers, but no dice so far. Any advice?_

 

I used pin-less heat sinks from amb's shop. I've never had any luck getting the pins out although luvdunhill's suggestion sounds interesting. I can only imagine what my wife would say. "Honey, I just need to put these heat sinks in the oven for a while..."

 Zigis, 
 You're welcome to your opinion, I just happen to think that your opinion is pretty unfounded. There are plenty of wonderful examples of tube projects built on pcbs so this is the last time I'll address your opinion on the subject. Either find a way to meaningfully contribute to the thread or find somewhere else to spread the gospel of PTP only.


----------



## holland

.


----------



## trains are bad

I would like to thank the designer of this amp. I've been listening it for a while now and it sounds amazing. Truly an audio bargain. Thanks again.


----------



## n_maher

Very cool layout! And I'm right there with you on your bang-for-buck analysis, it's very good.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Very cool layout! And I'm right there with you on your bang-for-buck analysis, it's very good._

 

x2 - that's very cool!


----------



## trains are bad

I added a 3.5mm input jack on the back, to allow an ipod or whatever to be plugged in with a mini-to-mini cable. I'm also thinking about gluing a bit of steel plate or something into the box to make it feel heavier, because we all know that heavy things are better! I already taped my spare tubes inside. LOL.

 I'm using this to drive K701s. I'm really impressed with how quiet it is.


----------



## dgbiker1

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_It just makes it easier to stuff parts and not route wires.

 I've decided to build this and I don't think I'm going to air wire all the parts. I'll use breadboard with tacked down bare/unsheathed wire, or an unetched PCB (like pmillett). It's the same idea, except someone does the layout work for you when you buy a PCB._

 

Since this isn't a circuit operating in the MHz range I don't know how it applies here, but isn't breadboarding notorious for being noisy?


----------



## fault151

This thing looks like it is off Doctor Who!






 Well done on the build!


----------



## srserl

Haven't built an electronics DIY project in over 10 years, so I'm just trying to remember the simple stuff.
 I finished this amp yesterday, but am having a problem with too much volume. I have the pot wired for maximum resistance at counter clockwise of the volume knob. Resistance varies from 54.8kohm at off to 0 at max between the inputs and the tube. I checked all resistor values this morning to make sure I put them in the correct places. Test voltages are correct (19V & 48V) at the points indicated on the schematic. What stupid mistake have I made?
 Sorry for the poor photos...I know you can't see everything.

 Source was CAL IKON MkII cd player and phones were HD555 (50ohm).
 I like this project on the cheap theme, but ptp is a pita...I think I would spring for a pcb to do another.

 Scott


----------



## n_maher

Scott,

 Can you elaborate on "too much volume"? Are you getting a variable signal as you turn the pot? Is it just that you don't get much for a usable range of attenuation before it gets too loud?


----------



## trains are bad

Make sure you grounded the other side of the pot. I did that at first. Since the line it's in is so high impedence, you can't just treat it like a resistor; nothing will happen, one side needs to be signal, the other side goes to ground through the whole 50kohm, and the wiper goes to the amp.


----------



## utilisateur

I want to incorporate a crossfeed in my MilletSSHybrid , has anyone measured/calculated the Input impedance yet?


----------



## holland

.


----------



## trains are bad

Quote:


 Routing wires everywhere without some attempt at isolation is just as bad as a breadboard with long wire loops sticking out. Besides, tubes aren't the most distortion free devices, so I'm not sure how important the construction methodology really is. You're not really dealing with devices that have issues with wire capacitance or resistance from traces more than a mm in length between components, or having timing violations due to uneven traces and/or signal degredation, so...YMMV 
 

I pretty much just routed wires everywhere without any attempt at isolation, I also had to parallel and series a bunch of resistors to get the right values, and my amp looks like a horrible rat's nest. Perhaps I got lucky, but it sounds wonderful. So let's not overthink this too much, this isn't a phased array radar transceiver or anything.

  Quote:


 I want to incorporate a crossfeed in my MilletSSHybrid , has anyone measured/calculated the Input impedance yet? 
 

What xfeed are you going to use? I built a tangentsoft xfeed kit, and I wasn't happy at all with how it sounded. It affected the sound rather drastically; I'm not sure what I could have done wrong either, what with buying the premade board and parts kit. I had just about given up on analog xfeed, and resigned myself to DSP only.


----------



## utilisateur

Quote:


 What xfeed are you going to use? I built a tangentsoft xfeed kit, and I wasn't happy at all with how it sounded. It affected the sound rather drastically; I'm not sure what I could have done wrong either, what with buying the premade board and parts kit. I had just about given up on analog xfeed, and resigned myself to DSP only. 
 

I'm not realy sure here but i think it's going to be jan Meiers circuit, i'm sure it's not the end of all 3d problems but hopefully an interesting experiment.I'll wire in a bypass switch of course
 I just [size=xx-small](ab?)[/size]used EloyDarks Thread here to hopefuly get a little discussion going maybe we should discuss it there or even in a new thread ..

 So to avoid the grossest problems with the crossfeed i'd need to aproximate the amps Z[size=xx-small]in[/size]


----------



## srserl

Good call Trains. I traced the fault to the solder joint where the pot is grounded to the terminal. I couldn't notice any looseness at the joint, but there was no signal between there and the pot. Works great now...just need some new phones so I can listen to it while building the Millet Max. That makes 2 bad solder joints I had on this small project, but I think it was the cheap 40W iron with a large conical tip that I was using the first night of building. The next day I ordered a soldering station from circuit specialists, and I don't know why I didn't do so before. What a pleasure to use; it heats up in just a few seconds, and keeps up to temp (75 watt model so I can still solder my rc airplane electric motors).

 Scott


----------



## holland

.


----------



## rds

I'd like to see some actual measurements of this so called significant effect in headphone amplifiers.


----------



## holland

.


----------



## rds

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_






 How about you show me some measurements that there is no effect?_

 

No claims require no proof. If you're going to tell people this is causing distortion in their amps then back it up.
 The reason I twist wires is to reduce the EMI being picked up. Perhaps you should read this:
Twisted Pair
  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_If you're an EE, you'll learn about the importance of layout eventually. But, if you don't, go into an interview and spout how it is not important and see if you get the job. You may be lucky and even see the effects in your first electronics lab at school._

 

I don't think there's any need to be so condescending. You are clearly not an EE.


----------



## holland

deleted


----------



## n_maher

Guys, 

 How about you step back a bit and calm down before you derail the thread to the point of requiring moderation? 

 Layout absolutely matters, at the very least the ground path wiring can make a rather large difference. Look no further than my Menace thread for "proof", albeit with my ears used as the instruments of measurement. So as I said, chill, some parts of the wiring are less critical, others absolutely matter. If you want to wire it haphazardly (and my SSH certainly is no gem) go for it.


----------



## dgbiker1

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Besides, tubes aren't the most distortion free devices, so I'm not sure how important the construction methodology really is. You're not really dealing with devices that have issues with wire capacitance or resistance from traces more than a mm in length between components, or having timing violations due to uneven traces and/or signal degredation, so...YMMV._

 

Yea, I was just thinking about the stray capacitance and the inconsistent, relatively high contact resistance at each point. I know it can be a big deal in high frequency applications, I just wasn't sure how it would affect this kind of setup. A few pF ain't much, but I never know what a golden ear can pick up


----------



## rds

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Guys, 

 How about you step back a bit and calm down before you derail the thread to the point of requiring moderation? _

 

Yeah, I should have left this alone. I know wiring layout has an effect. I guess I just take issue with telling people that they need to follow these rules. In some cases the effect of messy wiring will add noise. I think with respect to this amp that is unlikely, unless intentionally done. Especially if you are using a metal case.


----------



## trains are bad

FWIW, while not an EE proper, I am a graduate EE student, and I assembled this amp in the graduate 'open' lab at the intense interest of three different uber-EE nerds, complete with flannel shirts and glasses, who seem to perk up when vacuum tubes are spotted. None of them mentioned the messy PTP wiring, and when I asked one of them if it was going to be a problem, only one of them suggested I keep the case closed so that none of the components got bent some direction and shorted. The issue of effect on the circuit was never considered worthy of attention.


----------



## trains are bad

For those of us that have completed an amp, I have a question

 Should I measure the currents going into the tubes? It's my understanding that usually you have to 'bias' amps after the tubes have burned in, by tweaking resistors in order to match the tubes or put them in their linear range, or to make sure too much current isn't going through the heaters. 

 But I just basically bunged the amp together according to the schematic. This might be in the spirit of the design, but does the designer or someone with more understanding of the design have any advice for 'tuning' the amp? Or is this just not needed?


----------



## dsavitsk

Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_None of them mentioned the messy PTP wiring,_

 

It is likely less of an issue here as the PS is in another box, the voltages are lower than in most tube amps, and the Gm on the tubes is low due to the lower operating point, but wiring and lead dress in tube amps can and does make a huge difference. These are high impedance circuits with a propensity to pick up noise from lots of places, especially poor grounding. Take a visit to a dedicated tube amp forum and look through the daily posts of people trying to eliminate hum if you don't believe me. It can come from a lot of places and can take a lot of experience before building hum free amps happens regularly.

  Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_Should I measure the currents going into the tubes? It's my understanding that usually you have to 'bias' amps after the tubes have burned in, by tweaking resistors in order to match the tubes or put them in their linear range, or to make sure too much current isn't going through the heaters. 

 But I just basically bunged the amp together according to the schematic. This might be in the spirit of the design, but does the designer or someone with more understanding of the design have any advice for 'tuning' the amp? Or is this just not needed?_

 

It is probably not needed, but is never a bad idea to at least have a sense of what is going on. I think the things you are most concerned with are the voltage across the cathode bias resistor, and the voltage across the heaters. It is possible that really imbalanced tubes will draw lots more current through one side, but that's really only something to worry about if you are operating tubes near their plate dissipation max where this would threaten the tube's life. But here, it probably doesn't really matter as there is nothing you can do about it, it would only cause you to pull the tube which would end it's effective life anyway, and you are nowhere near the max dissipation anyway, so it won't do any harm. If you have access to a distortion analyzer and or a scope, then you can adjust the voltage across the bias resistor to try to hit the lowest distortion level. I doubt you'll hear much difference, though.


----------



## bhjazz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Someone should have a closer look at 707-411626B25 from Mouser, I don't see any pins and I think that this part would be sufficient._

 

One word: PINS! 






 No worries. Just posting the answer to the question. I do have my eye on a particular metal case anyway, so this will work out just coolio.


----------



## pinkfloyd4ever

wait so those are the Comair Rotron ones?


----------



## utilisateur

Part Number says they are the Comair rotron ones 
 They look identical to the FischerElektronik ones to me, maybe Fischer is Europe only though


----------



## bhjazz

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_wait so those are the Comair Rotron ones?_

 

Yes, sir. 

Comair Rotron Heatsinks

 The Mouser drawings are at an angle that doesn't effectively show the bottom.

 Edit: Just saw utlisateur's answer...oops. Ah well.

 Have a great day, all.


----------



## Gross

Hmm, I rebuilt mine to do a few changes and clean things up a bit, but now I have a problem...

 I accidentally had pin 1 on my mosfets (with R3/9 in place)wired directly to 48v and when I turned on the amp the tubes looked like light bulbs with 48v to the heaters. ( and you thought the PSU has a hard time starting up running the heaters at default voltage, LOL) Well, I discovered my problem and have reconnected the correct way on both tubes, at least it seems like that the 8 different times I have checked it out. However one tube still will light up the room upon power up. Is it possible to blow a mosfet in a way so it is always 'open'? Leaving everything else connected and just disconnecting the gate, or pin 1 of the mosfet, I get 45v on the side that isnt working properly, and 0v on the mosfet which is good. I suppose I have my answer, and upon reading up on mosfets it appears I have exceeded the gate to source voltage. I guess I am lucky I only blew one. Maybe once I replace it, i will realize the other one sounds like ass.

 That is my story. Moral, hook stuff up right.( If this post reads weird, it is due to the fact I discovered my problem halfway through typing it.)


----------



## pmillett

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_I suppose I have my answer, and upon reading up on mosfets it appears I have exceeded the gate to source voltage. I guess I am lucky I only blew one. Maybe once I replace it, i will realize the other one sounds like ass._

 

You are correct, sir - no doubt popped a hole throuigh the gate oxide. Just think of it as a learning experience.

 For the 50 cents or so that IRF510's cost, I'd replace them both.

 Pete


----------



## Gross

Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_
 For the 50 cents or so that IRF510's cost, I'd replace them both.

 Pete_

 

Good thing I ordered enough parts for 3 amps, although I only plan on building 2.

 Here is an idea I am going to try, unless you guys think I should not. At this point I have a 100ohm resistor on the outputs, but obviously that can change how the amps sounds and damping and blah blah. I am still trying to reduce the output though, so how about throwing a resistor from pin 5 of each tube to ground to create a voltage divider on the input. I was thinking starting with a 10k or even 20k resistor on there, just to make the pot usable.

 ***Update***

 Well, I found a 100k pot I got from Jeff with Glassjar that I didn't use on my SOHA. I put that guy in, took out my 100 Ohm resistors on my output, and now I am a happy camper.


----------



## royewest

My parts arrived. I've been starting to sketch out a wiring diagram. I've downloaded some data sheets. 

 Why on earth doesn't the IRF510 data sheet include a key to the pin numbers? I assume that when looking at a T0-220 chip from the printed side, they are 1,2,3. Sigh. I am clearly a bit further over my head than I'd hoped.


----------



## n_maher

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Why on earth doesn't the IRF510 data sheet include a key to the pin numbers? I assume that when looking at a T0-220 chip from the printed side, they are 1,2,3. Sigh. I am clearly a bit further over my head than I'd hoped._

 

Nah, you're not over your head. Good rule of thumb for this stuff is "if you don't succeed, try, try again." I always check the data sheets from multiple suppliers if I don't find what I want clearly in the first sheet. Try this one from Fairchild. 
	

	
	
		
		

		
			





 I compared that one and Intersil's and they both have the same layout (which I'm sure is standard for all of them).


----------



## royewest

Thank you! And there I was thinking I'd been persistent : )


----------



## m0b1liz3

Hello Pete and everyone else here. I am interested in building this amp for myself. The tricky thing is that I am in Australia so sourcing parts from multiple places would be difficult. Is there any way to order most of the parts from one source? Are PCBs still available or do you recommend PTP? 

 I have limited electronics experience. I have rewired some guitars and toyed with pedals etc but I have always wanted to make a tube amp. I wanted to start with the simplest possible project for the least amount of money so it sounds like your design is ideal. 

 If anyone on Head-fi has built one of these in Australia, your input would be much appreciated on how to go about sourcing the parts needed. (and building with 240v power supply)


----------



## bhjazz

I haven't checked today, but Mouser was out of C2 and C4, the .1 uF/63V film caps. I found some elsewhere, but they are .15uF instead. 

 How much is that going to change the amp? It looks like it would change the relationship between pin 1 of the tube and Q1, but what that is I do not know...

 @royewest: when I built a CK2III, I did the same thing. I checked way too many spec sheets and even consulted many photos of completed builds so I would KNOW that I had those babies in right. No worries. Once you get it laid out, you will succeed!


----------



## rds

Quote:


 Is there any way to order most of the parts from one source? 
 

I'm in the process of building a few of these to sell not-for-profit. Maybe I could send a kit of parts. I'm not sure right now. Anyways the version I'm building is using higher end stuff than the bom.

  Quote:


 how to go about sourcing the parts needed. (and building with 240v power supply) 
 

I'm pretty sure the recommended power supply works with 240v - you just need a different cord (~$3)


----------



## rds

Quote:


 Mouser was out of C2 and C4, the .1 uF/63V film caps. I found some elsewhere, but the deal is for a pair of .15uF. 
 

Pete recommends 0.1 - 0.22 uF caps for that spot. These are a good choice: MKP2-.22/100/5


----------



## Postal_Blue

OK, I am having some difficulties getting this little bugger to work. I have looked over my joints and all look good. Basically nothing is happening when I throw the switch, the power supply starts ticking at me (~twice a second). 

 I noticed that in Nate and Pete's builds the fet bodies/heat sinks do not seem to be insulated from ground which neither are mine, but upon looking at a data sheet, I read you must do so. Could this be my problem? I will post some pics late if there are no ideas based on my description.


----------



## bhjazz

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Pete recommends 0.1 - 0.22 uF caps for that spot._

 

Thanks. I didn't see that!

  Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_I noticed that in Nate and Pete's builds the fet bodies/heat sinks do not seem to be insulated from ground which neither are mine, but upon looking at a data sheet, I read you must do so. Could this be my problem?_

 

Very likely. The BOM does have a listing for Transistor mounting hardware which includes an insulator. It is listed to be at mouser under part 532-4880.


----------



## Gross

Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_I noticed that in Nate and Pete's builds the fet bodies/heat sinks do not seem to be insulated from ground which neither are mine, ._

 

Yeah, checking the datasheet the tab of the mosfet is connected to the drain, which is pin 2. That is where you are feeding +48v into, so you have a dead short from +48v to Gnd.


----------



## Postal_Blue

We have Music!

 This little sucker is sweet. I can't believe how quiet it is. I'm talking no hum even at max volume (no input of course). I used 470 Nichicons at c1,3,5,6; Wima .1's @ c2,4 and 1% metal film resistors from Radio Daze. I ordered my pot from Radio daze as well to get over the minimum order amount. 

 I am very pleased with the sound thus far. I feel like it extends very nicely on both ends of the spectrum, and It lacks for nothing in dynamics. The only "tell" that this is a budget amp is a very small loss of inner detail. Thanks a ton to Pete, your ongoing contributions to the DIY community are priceless. You've got my first ballot vote for DIY Hall of Fame.

 Eye Candy: (I still need to trim the pot shaft to accommodate a nob)


----------



## CountChoculaBot

How'd it compare to your CKKIII and Zhaolu Discrete?


----------



## bperboy

WOW!!!! That case is awesome!!!


----------



## n_maher

My MOSFETs are certainly isolated, or else I'd be having big problems. I used an insulating washer similar to the one called for in the BOM.


----------



## Postal_Blue

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_WOW!!!! That case is awesome!!! 
	

	
	
		
		

		
		
	


	




















_

 

Thank you. It was a small three piece plier kit. Needle Nose, Diagonals and Flush cutters. I must say I am quite pround of the way it turned out.

  Quote:


  Originally Posted by *n_maher* 
_My MOSFETs are certainly isolated, or else I'd be having big problems. I used an insulating washer similar to the one called for in the BOM._

 

Yeah I figured that out. Luckily this particular screwup was relatively harmless.

  Quote:


  Originally Posted by *CountChoculaBot* 
_How'd it compare to your CKKIII and Zhaolu Discrete?_

 

Let me listen to it for a week or two and I will post a comparison.


----------



## n_maher

postal, 

 I meant to say this before as well, heck of a nice build you did there. I love the creative case work.


----------



## rds

Postal_Blue - That's awesome!


----------



## pinkfloyd4ever

Do the input and output jacks need to be isolated from the case too?


----------



## rds

Quote:


 Do the input and output jacks need to be isolated from the case too? 
 

all of those should be connected to ground


----------



## pinkfloyd4ever

Ya I was planning on using a star ground (tied to my metal chassis in one spot), but they're already going to be in contact with the case since they're not insulated or anything...is this going to cause problems?


----------



## holland

.


----------



## n_maher

I would start with the inputs and outputs isolated and have signal ground connected directly to the star ground via a wire.


----------



## bhjazz

Make it three of us, although my post is coming in a bit late. The amounf of control you get when wiring your ground vs. an unknown path on a case can make a difference. 

 In the car audio world (in the 90s), I built a probe which had a little Radio Shack amp+speaker in the middle of the circuit. With the car running, and the little amp on in one hand and the connected probe in the other, one could search for a quiet ground spot on the chassis. For instance, if you wanted your amps in the trunk (like a normal car audio nut) you could usually find that that easy-to-use bolt had far more noise than some weird spot six inches away. Sand away some paint, drill a hole, and an excellent quiet star ground location was yours.

 Geez, to think I used to go through similar hassles...and had to mess with the weather as well. Head-Fi is so much better!


----------



## trains are bad

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Ya I was planning on using a star ground (tied to my metal chassis in one spot), but they're already going to be in contact with the case since they're not insulated or anything...is this going to cause problems?_

 

If you look back a few pages to my case, it's pure aluminum, and I didn't star ground, because I didn't have isolating RCA jacks or headphone jacks. ground for the tubes is achieved by smashing a terminal strip under one of the tube socket mounting nuts. Mine is very quiet, but if I had used a different case I'm not so sure it would be.


----------



## bhjazz

Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_If you look back a few pages to my case, it's pure aluminum, and I didn't star ground, because I didn't have isolating RCA jacks or headphone jacks._

 

Sweetness. This is all good information!


----------



## manaox2

I needed to order some stuff from mouser, so I said what the hey. I am going to build one or two of these.


----------



## bhjazz

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I am going to build one or two of these._

 

Excellent. If you've never built point-to-point this will be a great place to start. 

 BTW: manaox2: one more post to supremus for you! Congrats!


 1100 for me!


----------



## rds

got one done: http://www.head-fi.org/forums/f5/min...be-amp-330777/ 
 It was really hard to squeeze everything in this case. I included screw terminals for gain resistors and output caps. I'm using 680 uF power filter caps and 470 uF output caps.


----------



## malldian

looks great!


----------



## bhjazz

Nice job, rds. I like your built-in ability to swap caps and resistors. Good idea!


----------



## -=Germania=-

Manaox - ur almost headphoneus supremous


----------



## rds

wow, I've tried everything I can think of and can't get rid of this background hum. Do you guys have this humming with your amps? ...really annoying.

 EDIT: 
 I had 680 uF on C1 and I removed that replaced it with 180 uF ( I was doing this to allow space on my board , not to fix the buzzing) and now it's dead silent. Really weird...

 Sounds awesome 
	

	
	
		
		

		
			





 I can't believe how quiet it is. I can turn the volume all the way up with kcs75s and I have to strain to hear anything. 
 Thanks Pete!


----------



## utilisateur

Does anyone know of a tube dealer in Europe (preferably not UK) that might have them? 
 Or any European Tube Dealer while we're at it ?
 Most of the parts are here but i can't seem to find any 19J6 tubes...


----------



## rds

Listening to this amp I've noticed that vocals seem to gain a little detail relative to ss amps. I think what it is is that the midrange is accentuated a little. The high range details seem a little attenuated too. 
 Is this just another example of transference, where I feel that that an amp that glows orange and generates a lot of heat has a nice warm sound?


----------



## rds

Raytheon Tubes Suck
 Just wanted to give a heads up that at least the Raytheon I got totally suck in that they hum in the background.
 Sylvania tubes on the other hand are totally silent. YMMV, but based on my experience I would avoid the Raytheons.

 I'm not used to using tubes and I thought my earlier buzzing problem had come back, but no, it's just those damn Raytheons.

*Edit: It appears these tubes are very good at picking up electrical noise. In this case they were picking up noise from my touch on lamp. When I unplugged it, the noise went away.*


----------



## m0b1liz3

I was trying to figure out how to build one of these at the lowest possible cost. I already have to pay shipping to get the power supply but I can't get the other parts from multiple sources like everyone does in the US (I am in Australia). Can all of this stuff be bought directly from mouser so it is just one order and one shipping bill??


----------



## JamesL

Mouser doesn't distribute tubes afaik.
 If you look at Pete's BOM on the site, all necessary parts asides from the tube(and socket) can be bought from Mouser.


----------



## m0b1liz3

See above post where I don't want multiple sources... Since Glassjar audio does a kit for the Millet Max, wouldn't they do something comprehensive for the Starving Student model? (ie. only one shipping bill!)

 My only other option is seeing if I can get everything through local stores and order the power supply on ebay.


----------



## JamesL

Glass jar audio is a one-man operated service, who puts together kits for projects with a decent amount of demand, which means he needs to buy in bulk to keep costs minimal.
 Also keep in mind that his kits don't include parts such as rca/headphone jacks, potentiometers, knobs, dc jack, etc.

 Maybe you can ask someone here who plans to build one to get extra parts to ship your way?


----------



## m0b1liz3

yeah, no rush on it. i just thought it looked like a cool project. i always wanted to do something PTP. i think my next project will be the Jisbos for a SOHA or an Alien DAC.


----------



## ludoo

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I was trying to figure out how to build one of these at the lowest possible cost. I already have to pay shipping to get the power supply but I can't get the other parts from multiple sources like everyone does in the US (I am in Australia). Can all of this stuff be bought directly from mouser so it is just one order and one shipping bill??_

 

I too would like to build one, but I don't know where to begin sourcing parts as I live in Italy (so US distributors are out of the question) and I don't have much experience at audio DIY apart from the odd recable or cable build. Any help would be much appreciated.


----------



## Luminette

I would like to have a few (2-4) of these built for a head-fi give-away. I'll fund parts cost for whoever builds it. Looking for somebody who has already completed one and has an attractive case solution, as well as a solution to easily acquiring all the parts (ac adapter / power supply too.) PM me if you want to team up and give something back to the community


----------



## utilisateur

Hi Ludoo .
 I couldnt name an italian Seller for the parts but i'm sure there are plenty, there is nothing realy special about the parts required.
 If you realy cant get them in Italy it's no problem to get the parts in Europe.
 PM if you have problems sourcing parts in EU
tnt-audio is the only Italian DIY website that comes to my mind, maybe you can find someting on there though

 I dont know where to get the tubes though


----------



## n_maher

Quote:


  Originally Posted by *Luminette* /img/forum/go_quote.gif 
_I would like to have a few (2-4) of these built for a head-fi give-away. I'll fund parts cost for whoever builds it. Looking for somebody who has already completed one and has an attractive case solution, as well as a solution to easily acquiring all the parts (ac adapter / power supply too.) PM me if you want to team up and give something back to the community 
	

	
	
		
		

		
		
	


	


_

 

While that gesture certainly sounds nice you're asking an awful lot of someone. Start to finish I'd wager that these amps take a good 8 to 10 hours to build, each amp that is. Donating a week's worth of time is a pretty serious donation.


----------



## rds

Raytheon Tubes update:

 Well it looks like the tubes are not really the problem, but they were picking up hum from my touch on lamp. I unplugged the lamp and the hum disappeared. This problem doesn't exist with the sylvanias (with metalized tops).


----------



## m0b1liz3

Has anyone compared the SQ of the MAX to the Student version???


----------



## bperboy

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Has anyone compared the SQ of the MAX to the Student version???_

 

In a couple weeks when I get around to building my Student, I'll compare it to my Mosfet MAX.


----------



## pinkfloyd4ever

with thermafilm pads does the grease go between the transistor and the pad or between the pad and the heatsink? or both?

 also, is it ok to route the wires for my pot ground and output ground thru pin 4 of the tubes? (pot thru one channel's pin 4, output thru the other's) The reason I want to do this is because the tube sockets are right in the path of the output and the pot to ground, and I'm running out of space on my star ground's solder tabs


----------



## rds

Quote:


 with thermafilm pads does the grease go between the transistor and the pad or between the pad and the heatsink? or both? 
 

both

  Quote:


 also, is it ok to route the wires for my pot ground and output ground thru pin 4 of the tubes? (pot thru one channel's pin 4, output thru the other's) The reason I want to do this is because the tube sockets are right in the path of the output and the pot to ground, and I'm running out of space on my star ground's solder tabs 
 

Yeah, why not? Any point in the ground is fine.


----------



## trains are bad

Quote:


 Start to finish I'd wager that these amps take a good 8 to 10 hours to build, each amp that is. 
 

I made mine in about 3, including drilling the case and waiting for the heatsink glue to set. Starving graduate students are also busy!


----------



## tomb

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_with thermafilm pads does the grease go between the transistor and the pad or between the pad and the heatsink? or both?_

 

If it's truly "thermafilm" (Avid trademark), those require grease. If it's a "thermasil" (another Avid trademark) or "sil-pad", don't use grease, period. It will actually interfere with the sil-pad's heat transfer effectiveness. You might as well not use them if you use grease.


----------



## pinkfloyd4ever

it is thermafilm. It actually looks & feels like camera film (if any of you kids know what that is). I got the Aavid mounting kits from mouser. I would've preferred thermasil but I didn't feel like waiting for the Thermasil kits to come back in stock

  Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_I made mine in about 3, including drilling the case and waiting for the heatsink glue to set. Starving graduate students are also busy!
	

	
	
		
		

		
		
	


	


_

 

*WOW* that's really fast. It's taking me FOREVER. It's my first real ptp project and it really makes you appreciate the work that goes into having PCBs made


----------



## bhjazz

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_it is thermafilm. It actually looks & feels like camera film (if any of you kids know what that is)._

 

Sad, but true. Hey, I shot a roll of Ilford Delta in my Holga a few months back....! Real film!!!


----------



## holland

.


----------



## fierce_freak

Thanks for the nice impressions, holland!

 For some time now, I've been considering conducting a little experiment: build a proper "Starving Student" with the great Mr. Millett's BOM and also a "Stupid/Silly/Sorry Student" version with boutique parts (dumb student is starving and can't buy books now due to overspending). I would love to have the two side by side to compare, so I think this will be a fun project.

 Anyone have any suggestions on what I should sub in for the boutique version? I was thinking PRP resistors (maybe some bulk metal foil vishays for the cathode resistors), Blackgate WK caps, Spraque VitQ's. Any suggestions on different boutique parts or possible replacements for the IRF510?


----------



## jarpy

This looks so sweet. I just ordered some tubes from RadioDaze (amazingly fast service).

 It's actually proving harder to locate a 48v power supply. eBay is full of promising offerings but it's surprising how many people only ship to the U.S.A. 

 Did anyone buy a bulk lot of 48v supplies and if so, would you be interested in selling one to an Australian?

 Thanks,
 Jarpy.


----------



## holland

.


----------



## fierce_freak

Thanks for the update. I've been considering K271 for the office. How did you think it paired with your sextett?


----------



## holland

.


----------



## trains are bad

Quote:


 The ripple is about 210mV, but after the 1000uF C1 cap, it's about 30mV. I didn't measure after the C6 filter. 
 

How did you measure this? Just use the AC setting on a voltmeter, or do you have a scope?


----------



## fierce_freak

Thanks again holland. I have the feeling that the Starving Student would go well with cans like W5000, K701 (maybe I'd actually like them on this amp), and even the K1000.


----------



## Postal_Blue

Just wanted to sound off again on the sound of this little amp. I am absolutely floored. This is such a sweet sounding amp. I would love to see it blind tested with some high end tube amps. As it has burned in a bit the inner details have really started to come through which was the only weakness at first listen. It is an incredible match with my 580's.

 No amount of thanks is enough for Pete's contributions to DIY. If you are considering building this amp DO IT. I have < 45 dollars tied up in this project and I could not be happier.


----------



## holland

.


----------



## rds

Postal_Blue

 Are you using bypass caps? I think they're really worth an extra few bucks for more high range detail. Wima mkp or BC components/Vishay 416s are good choices. Personally I like the 416s more, though I'm not sure I can actually hear any difference.
 Also, if you do use bypass caps it's best to use the same kind you are using for coupling.


----------



## fierce_freak

Postal_Blue:

 Just for kicks, have you tried your IEM's with it?


----------



## pinkfloyd4ever

Finally got mine done, and amazingly, no smoke, sparks, or explosions on turn-on, but it does sound pretty damn good. I'll get pics up here soon, tho it's not exactly pretty. Is it ok if the mosfets are too hot too touch? I mean the black plastic (or whatever it's made of) body, not the metal tab. I'm wondering if you're not supposed to tighten down the heatsink mounting screw as tight when using grease and thermafilm as you would using just a thermasil pad?

 oh also, what's the gain of this amp? I'm sure it's been mentioned but I searched and couldn't find it


----------



## Gross

Gain of 38.


----------



## kilgoretrout

Radiodaze has a minimum order of $10, but the two tubes and the socket cost less than that. I've found the same tubes on some of the other sites mentioned in this thread but I couldn't find the same socket on any of them.

 What other sockets can I use for this amp?

 Also, what is the lifespan of the these tubes? Do you guys leave the amp on 24/7 or turn it on only during use?


----------



## pmillett

Quote:


  Originally Posted by *Gross* /img/forum/go_quote.gif 
_Gain of 38._

 

That's the mu of the tube. The votage gain of the circuit is much lower owing to degeneration caused by the unbypassed cathode bias resistor.

 I don't remember what the gain of the amp is - around 15, if I remember right.

 Pete


----------



## procalli2007

I have going to be using this as my first tube amp. Just waiting on farnell.

 My second project will be an original millet hybrid and I have received the tubes for it along with a set for this. Problem is I cant seem to find any pcbs. How easy would it be for me to make my own given that the pcb of the original millet had 3 layers?

 Also would it sound better if this amp was made using a pcb?

 thanks


----------



## jarpy

RadioDaze are currently out of 19J6s. Damn.

 I guess the folks in this thread cleaned 'em out


----------



## rds

$5 +$7 (shipping) cisco 34-1977-03:
Cisco Aironet 48V .38A Power Supply ADP-18PB/34-1977-03 - eBay (item 200227806395 end time Jun-28-08 07:53:51 PDT)

 As for the 19j6 - look for old tv/radio repair shops in your local area. Most places have a small quantity of these that they'll sell for a few dollars each.
 Also, Radiodaze is going to source some more.


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_I have going to be using this as my first tube amp. Just waiting on farnell.

 My second project will be an original millet hybrid and I have received the tubes for it along with a set for this. Problem is I cant seem to find any pcbs. How easy would it be for me to make my own given that the pcb of the original millet had 3 layers?

 Also would it sound better if this amp was made using a pcb?

 thanks_

 

To my knowledge, the original Millett Hybrid PCB's are no longer available. They were sold for a time at DIYCable.com, then at Euphonia Audio, I believe, but are not at either place anymore (not sure Euphonia is around anymore, period). However, Pete Millett has Gerber files, top, and bottom TIFF images of the original board here: Low-voltage Hybrid headphone amp

 The second version Millett Hybrid, the revMH Millett Hybrid by Drew Dunn and Nate Maher, also has Gerbers available at DIYForums.org here:
http://www.diyforums.org/hybrid8a.zip. However, there are some errors on that board. You need to refer to the Forums section for details on fixing those if you have a board made.

 Of course, Colin Toole's version of the Millett MAX is available anytime at beezar.com welcome page with complete building details at The Millett Hybrid MAXed

 Pete's great work continues to multiply.


----------



## jarpy

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_$5 +$7 (shipping) cisco 34-1977-03:
Cisco Aironet 48V .38A Power Supply ADP-18PB/34-1977-03 - eBay (item 200227806395 end time Jun-28-08 07:53:51 PDT)

 As for the 19j6 - look for old tv/radio repair shops in your local area. Most places have a small quantity of these that they'll sell for a few dollars each.
 Also, Radiodaze is going to source some more._

 

Thanks rds. Unfortunately that power supply only ships to the United States, but I'm sure I can find/build something if I'm patient.

 Good call on the valves, I can already think of a shop in my area I should ask.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_not sure Euphonia is around anymore, period)_

 

Alive and well. I just got some parts form them a few weeks ago.

Euphonia Audio Index


----------



## procalli2007

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_To my knowledge, the original Millett Hybrid PCB's are no longer available. They were sold for a time at DIYCable.com, then at Euphonia Audio, I believe, but are not at either place anymore (not sure Euphonia is around anymore, period). However, Pete Millett has Gerber files, top, and bottom TIFF images of the original board here: Low-voltage Hybrid headphone amp

 The second version Millett Hybrid, the revMH Millett Hybrid by Drew Dunn and Nate Maher, also has Gerbers available at DIYForums.org here:
http://www.diyforums.org/hybrid8a.zip. However, there are some errors on that board. You need to refer to the Forums section for details on fixing those if you have a board made.

 Of course, Colin Toole's version of the Millett MAX is available anytime at beezar.com welcome page with complete building details at The Millett Hybrid MAXed

 Pete's great work continues to multiply.
	

	
	
		
		

		
			






_

 

Thanks for that. To make a pcb for the millet hybrid would is it possible to make two boards and glue them back to back as Ive never made a pcb before? 

 I have tried to get to beezar.com but it times out? Are they still in business and would I be able to use my 12AE6?

 Thanks for your help.


 edit: after reading the site above about the max I see it can be used with the tubes I already bought for the hybrid. Also if I read the details correctly it has the power supply built in which makes it a lot easier than the millet hybrid. 

 Any other way of getting a pcb as whatever I try the site is timing out.


----------



## m0b1liz3

With the starving student amp a few people have commented the low bass is a little weak. Would it be possible to add a bass extender/bass boost to the circuit? Will this just end up adding more distortion?


----------



## Snicewicz

I dont know if I can post it here but I thought it might help. I have all the mouser parts and the golden tube holders/rings already and I am opting out of this build right now so if anyone is interested PM me. All the mouser stuff is still in a box xD

 Going to just build a max and a Mini^3. Im not starving any more, schools out its summer


----------



## rds

^ That's pretty cool. I think it was M0n1liz3 who was having problems getting stuff to Australia. 
 Maybe try to send it to someone overseas, cause they really pay through the nose for this stuff in shipping.


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Thanks for that. To make a pcb for the millet hybrid would is it possible to make two boards and glue them back to back as Ive never made a pcb before? 

 I have tried to get to beezar.com but it times out? Are they still in business and would I be able to use my 12AE6?

 Thanks for your help.


 edit: after reading the site above about the max I see it can be used with the tubes I already bought for the hybrid. Also if I read the details correctly it has the power supply built in which makes it a lot easier than the millet hybrid. 

 Any other way of getting a pcb as whatever I try the site is timing out._

 

I am not aware of any issues with the Beezar.com website. I am filling orders as we speak. I also checked the web stats and nothing appears amiss. That said, the traffic is well within the parameters of my service's contract. I hesitate to suggest that it's on your end, but if anyone else notices an issue with connectivity to beezar, please let me know.


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I am not aware of any issues with the Beezar.com website. I am filling orders as we speak. I also checked the web stats and nothing appears amiss. That said, the traffic is well within the parameters of my service's contract. I hesitate to suggest that it's on your end, but if anyone else notices an issue with connectivity to beezar, please let me know._

 

I can access Beezar.com.. maybe make sure the address is typed correctly?


----------



## procalli2007

Tried a few times but it just times out.
 im on aol in the UK.

 I remember trying a while ago and getting the same result. What would be the cost + shipping of the pcb to the uk.

 maybe Ill try and see if I can use a proxy.


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Tried a few times but it just times out.
 im on aol in the UK.

 I remember trying a while ago and getting the same result. What would be the cost + shipping of the pcb to the uk.

 maybe Ill try and see if I can use a proxy._

 

I've had a number of customers in the UK. I suspect it's your AOL and perhaps a dial-up line that's to blame. Beezar is based on the open-source e-commerce software known as "oscommerce." It's in use worldwide on probably thousands of web-based stores.

 Try this direct and specific link and see if it works better for you:

Beezar.com


----------



## procalli2007

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've had a number of customers in the UK. I suspect it's your AOL and perhaps a dial-up line that's to blame. Beezar is based on the open-source e-commerce software known as "oscommerce." It's in use worldwide on probably thousands of web-based stores.

 Try this direct and specific link and see if it works better for you:

Beezar.com_

 

Tried through a proxy and it worked but wouldnt want to purchase through it. Do you supply all parts for the max and what would you estimate shipping for the pcb would be?

 edit: finally sorted it out. problem is I have to connect to the site through the aol software (which is rubbish).


----------



## kilgoretrout

I'd like to fully enclose the tubes inside the case for safe transport. What should the dimensions of the case be so I can successfully do this?

 Since I know nothing about tubes, could someone kindly refer me to the correct tube socket available on TubeDeport?
Tube Sockets


----------



## tomb

Dimensions for a 19J6 tube can be found in the datasheet here: 19J6.

 For your convenience, though, here's the drawing:





 I'm not sure TubeDepot has a good selection for a lugged, 7-pin miniature ceramic tube socket. It looks like the only one they sell has all that shield junk on it. 'Course, if you're going to hide them inside a case it won't make much difference. Nevertheless, Ebay or Cascade Surplus Electronics is probably a better choice, I think:
7-pin Ceramic Mini Tube Socket - Qty 7 - eBay (item 330244042520 end time Jun-19-08 15:05:11 PDT)


----------



## Snicewicz

For anyone inquiring I am giving my parts away already to a fellow head-fier in Italy. 

 Thanks for all the interest.


----------



## bhjazz

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_With the starving student amp a few people have commented the low bass is a little weak. Would it be possible to add a bass extender/bass boost to the circuit? Will this just end up adding more distortion?_

 

It might be easier to explore using larger output caps. You are right in thinking that a circuit like that would add distortion. I think it would. But keep in mind the beauty of this circuit: simple, effective, and very inexpensive to build. Mine is not done yet, but for the money it seems like it's going to be hard to beat. There are always a few tradeoffs! But the tradeoffs could be headphone/system/cable specific. 

 Stay tuned!


----------



## holland

.


----------



## Uncle Bob

Quite fancy building one of these but 19J6's seem to be in short supply at the moment. Anyone know where I can find them? Or if there's any alternatives?

 thanks


----------



## pmillett

It seems that some tube dealers are running low on 19J6 tubes.

 I just talked with Radio Electric Supply (Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!), one of my favorite tube dealers. They have a few hundred 19J6's in stock, and are getting more. 

 There appear to be plenty of them at wholesale suppliers, so even though the "usual sources" may run out, I think they will get more into stock. It historically is a very low demand tube.

 Pete


----------



## royewest

I just finished building one of these. It sounds just delightful. I'm looking forward to spending more time with it.

 I used a wooden 6"x6" "frame" box from an art store and a copper clad board for the top. I followed the photos of Pete's wallet box layout with little shame.

 I would welcome advice on capacitors. Due to outages at Mouser last month when I ordered the parts I have 470uF 63V capacitors everywhere except C2 and C4, where I have 220uF caps. All Nichicon aluminum electrolytics.

 Sorry for the poor photo -- I'm a poor photographer. When I dig out the cable for the camera I'll use that - in the mean time a cell phone camera shot.

 Thanks sincerely to Pete and Nate for offering up this design and all the details around building it and for the kind advice and encouragement on this forum -- I have derived the greatest pleasure building this amp.


----------



## holland

.


----------



## royewest

Not sure if this link will work, but it's the 6x6 wood finish version of this item from Blick art supplies: Ampersand Gessobord Shadow Boxes - BLICK art materials

 Looks like I paid about $8 (I've had the box for a while -- it had something else in it for a while).


----------



## holland

.


----------



## rds

They recommend placing candles inside it... Do they sell home insurance as well?


----------



## gz76

Quote:


  Originally Posted by *Snicewicz* /img/forum/go_quote.gif 
_I dont know if I can post it here but I thought it might help. I have all the mouser parts and the golden tube holders/rings already and I am opting out of this build right now so if anyone is interested PM me. All the mouser stuff is still in a box xD_

 

If anyone else has assembled the BOM on this project and is looking to bail out, please let me know. I wouldn't mind building one of these for fun... its been about 15 years since I built my last amp!


----------



## holland

.


----------



## andrew jc

Not to beat a dead horse but no one intends to make a PCB for this project right? Thanks...


----------



## tomb

Quote:


  Originally Posted by *andrew jc* /img/forum/go_quote.gif 
_Not to beat a dead horse but no one intends to make a PCB for this project right? Thanks..._

 

I believe the focus is on encouraging the P2P version for the time being, but who knows what the future may hold?
	

	
	
		
		

		
			





 I second Pete's recommendation on using vacuumtubes.net (Radio Electric Supply). Roy and Dale are great guys to work with - very knowledgeable, too.


----------



## royewest

I'd really appreciate any advice folks can offer on capacitors - I think this question got buried in my last post:

 I would welcome advice on capacitors. Due to outages at Mouser last month when I ordered the parts I have 470uF 63V capacitors everywhere except C2 and C4, where I have 220uF caps. All Nichicon aluminum electrolytics.

 Thanks in advance.

 __Roy


----------



## bhjazz

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I just finished building one of these. It sounds just delightful. I'm looking forward to spending more time with it._

 

Nice build, royewest. I spy some Bottlehead gear just behind it. THAT is the place that got me into this DIY mess! 
 Building is such a great adventure.


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I'd really appreciate any advice folks can offer on capacitors - I think this question got buried in my last post:

 I would welcome advice on capacitors. Due to outages at Mouser last month when I ordered the parts I have 470uF 63V capacitors everywhere except C2 and C4, where I have 220uF caps. All Nichicon aluminum electrolytics.

 Thanks in advance.

 __Roy_

 

They're not axial, which would make them easier to use in P2P, but some 0.1uf - 0.22uf Wima MKP10's would be ideal, I think. Mouser should have plenty and they don't cost too much.


----------



## rds

Quote:


 ...some 0.1uf - 0.22uf Wima MKP10's would be ideal, I think 
 

I had very good results with .22 uF MKP10s both for coupling and for bypassing the output electrolytics.
 I also had very good results using .12 uF BC Components 416s (Digikey) in the same way.
 I actually prefer the BC Components.


----------



## holland

.


----------



## rds

Quote:


 MKP for output coupling bypass (not in schematic, and not really necessary from a functional perspective). 
 

That really depends on what you mean by functional. It will amplify the sound either way.
 Don't assume that the simplicity of the circuit means it can't produce really good sound. In fact there are many people (myself included) who would argue that there are definite benefits to simplicity. The most obvious one in this case is that using high quality components doesn't add a lot of expense.
 Using good quality larger capacitors, bypassing the output, and adding a mkt filter cap in parallel with c1 adds about $8 in cost. Or in starving student terms, one meal on campus.


----------



## royewest

rds,

 would you be willing to be a little more explicit about what you are suggesting? I'm not an ee -- I'm a writer. Can you describe a bit more completely how to try what you are proposing?

 Thanks.


----------



## rds

When I get home tonight I can add those modifications to Pete's schematic and link it from this post.
 I hope this isn't considered heresy. I'm pretty sure Pete is OK with us trying different things with the circuit.


----------



## holland

.


----------



## rds

Quote:


 I'd really appreciate any advice folks can offer on capacitors -royewest 
 

 Quote:


 I had very good results with .22 uF MKP10s both for coupling and for bypassing the output electrolytics. -rds 
 

 Quote:


 You are imposing a requirement onto others which was not part of the original design. -holland 
 

~


----------



## holland

.


----------



## rds

Quote:


 Though my build is not 1:1 with pmillett's, in my experience the tweaks do not define the amp. 
 

I agree completely. This is Pete's amp, bypass caps or not. I really admire his design.

  Quote:


 “Simplicity is the ultimate sophistication.” - Leonardo da Vinci


----------



## bhjazz

I didn't find the C1, C3, C5, and C6 at Mouser a few weeks ago. If you did the same thing, check again as the Nichicon UPW 470uF 63V caps are back in stock. 

 If this is old news, just know that my job is eating me alive!


----------



## rds

These are the capacitor values I used to build the starving student:

http://i93.photobucket.com/albums/l5.../7170004-1.jpg


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I agree completely. This is Pete's amp, bypass caps or not. I really admire his design._

 

Yes, but like the great benefactor that Pete is, he often leaves his creations to us to do with as we wish.
	

	
	
		
		

		
			





 I can see both sides of this argument. Bypassing with a couple of little Wima's is in the "Millett tradition." rds has done nothing that hasn't been done on every Millett Hybrid that's ever been built, including the MAX - which happens to use 0.22uf Wima's bypasses on every cap as standard.

 That said, there's a principle of simplicity that we're all trying to adhere to with the SSMH. It's true that a bit of bypassing might have some effect, but so would implementing a CCS for the tubes, a push-pull for the MOSFET output, JFET-signal input, linearizing the power supply, adding a relay-delay, etc. ... Pretty soon you'd have a full-blown Millett MAX - not to mention using VitQ's instead of those Wima's, Black Gates for the electrolytics, etc. Then we'd all be arguing which of those changes would have a better effect on the sound.

 If there's a line to be drawn, it might be in _promoting_ a change, rather than simply making one (it's still DIY, after all). Better to leave as is, perhaps - for the majority of users - marveling at the simplicity.


----------



## pmillett

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, but like the great benefactor that Pete is, he often leaves his creations to us to do with as we wish.
	

	
	
		
		

		
		
	


	


_

 

Well said 
	

	
	
		
		

		
		
	


	




 I'll throw in my two cents:

 You can certainly bypass the electrolytics with film caps if you want. I do not believe it can hurt anything. Whether it heps or not depends on the electrolytic caps you use, your headphones, your ears, and your psychoacoustic predujidices 
	

	
	
		
		

		
		
	


	




 Don't understimate the "goodness" of modern electrolytic caps. Just in the last couple of years, affordable "non-audiophile" electrolytic caps have shown up that are really quite good. Caps like the Nichicon UHE family. And there are old standbys like the Muse parts that are not really very expensive.

 On the other hand, if you use generic electrolytic caps from Radio Shack, putting even a cheap film cap across it is probably a good idea.

 If I were building one of these for myself, what would I use? Probably Nichicon UHE or Muse, or Black Gates (the smaller ones aren't horribly expensive) and not bypass them. But my intent was to make the design as simple and cheap as possible. 

 With reasonable quality electrolytics (UPW, etc.) and generic resistors and film caps it still sounds surprisingly good.

 Have fun, and don't be afraid to try your hand at modifications. At least with 48V and limited current you won't electrocute yourself or burn the house down!

 Pete


----------



## pmillett

Oh, one additional comment:

 Don't believe everything you read. I think it's always good to be a skeptic. So just beacuse somebody posts that "this sounds much better" or "you really have to do this" does not mean it's true.

 What matters is how it (whatever "it" is) sounds to YOU.

 That's the beauty of DIY (as opposed to commercial products - don't get me started!). If you build something, and you like it, you have suceeded. If you want, you can try tweaks to see if you can make it sound better TO YOU.

 Trust your ears, not the opinions posted in the forums.

 Kinda oxymoronic, eh?

 Pete


----------



## holland

.


----------



## darkfury18

I just put the amp together and I'm getting significant hums in the right channel and a quieter hum in the left channel. Is there anything I can do to fix this?


----------



## royewest

Hm. (er, no pun intended). Mine is silent at all POT levels.


----------



## rds

Quote:


 I just put the amp together and I'm getting significant hums in the right channel and a quieter hum in the left channel. Is there anything I can do to fix this? 
 

Try holding the amp case with one hand (assuming it is metal and grounded) and cupping your other hand around the right tube. If the hum goes away your tube is probably picking up interference from something close by. Something closer to the right tube.


----------



## holland

.


----------



## bhjazz

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Feel free to use what you feel comfortable with._

 

holland: great information. Thanks for posting! I think I ended up with some 100V caps, and somewhere around here I think I have some values larger than the 470uF as well. This project seems like a great place to tweak and enjoy.


----------



## darkfury18

Thanks for the help. I'm using a plastic case right now, but I will try cupping my hand around the tube and see if it does anything. Would using a metal case help? I'm pretty sure I don't have and cold joints since I was very careful when I was soldering. I'll report back later.


----------



## holland

.


----------



## darkfury18

I tried shielding it, but the hum was still there. I will try using it in a different location tomorrow. 

 I replaced the tube on the side that was humming more, and that reduced the humming. I can listen to it now. The humming is not noticeable when there is music, but is present when there's no music playing.


----------



## MrMajestic2

FIY, the Cisco power adapter is available from two Amazon sellers here:
Amazon.com: CISCO PSA18U-480C /34-1977-03 Power Supply for Aironet Access Point or VOIP Phone: Electronics

 Just $4.50 plus shipping. I wasnt even going to build the Starving Student Millet, but I couldnt resist ordering the PSU


----------



## m0b1liz3

This may be crazy but is there a way to modify this design to use 5963 tubes? I wondered why people hadn't made modifications to this design with different tubes? I am not experienced/wise enough to do this but would appreciate if someone else had some suggestions.


----------



## tomb

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_This may be crazy but is there a way to modify this design to use 5963 tubes? I wondered why people hadn't made modifications to this design with different tubes? I am not experienced/wise enough to do this but would appreciate if someone else had some suggestions._

 

Although not specific to the 5963, this was answered by Dsavitsk in Post #116.


----------



## darkfury18

So I couldn't get rid of the hum, but I don't hear it at all when a song's on. I'm adjusting to the tube sound (coming from a Mini3, so it sounds quite different), but I like it.

 The MOSFETs were getting too hot for my liking so I switched out the heatsinks for these guys GPU heatsink. The MOSFETs barely get warm with them on. Not sure if it'll cause any interference, but it was already humming anyways so it couldn't hurt


----------



## J.D.N

Quote:


  Originally Posted by *darkfury18* /img/forum/go_quote.gif 
_So I couldn't get rid of the hum, but I don't hear it at all when a song's on. I'm adjusting to the tube sound (coming from a Mini3, so it sounds quite different), but I like it.

 The MOSFETs were getting too hot for my liking so I switched out the heatsinks for these guys GPU heatsink. The MOSFETs barely get warm with them on. Not sure if it'll cause any interference, but it was already humming anyways so it couldn't hurt 
	

	
	
		
		

		
		
	


	


_

 

Pictures?! That's gotta look kinda funky...


----------



## darkfury18

I doesn't look too bad, here's with one heatsink on.

 This amp pairs really well with my AD700, but I gotta say it doesn't sound so good with my iM716


----------



## tomb

Quote:


  Originally Posted by *darkfury18* /img/forum/go_quote.gif 
_I doesn't look too bad, here's with one heatsink on.

 This amp pairs really well with my AD700, but I gotta say it doesn't sound so good with my iM716 
	

	
	
		
		

		
		
	


	




 <IMG]http://i140.photobucket.com/albums/r2/darkfury18/ipodmod.jpg[/IMG>_

 

A couple of things might help, but one of them may not be very easy to do:

 1. There's a reason why Pete spec'd a copper PCB even for a Point-to-Point Bill Of Materials. The bare copper provides a ground sink for the circuit that minimizes hum. This might be very important with an all-plastic case.

 2. Do you have R3 and R9 tied directly to the gate legs of the MOSFETs? Pete and Nate both have mentioned a couple of times that might induce oscillation if that isn't done. It's hard to say if that attributes to the hum, but my guess is that it will definitely cause more noise.

 3. One reason the heat sinks might run too hot is that they're upside down. The center-notch in the heat sink is meant to provide better cooling by allowing induced air circulation underneath the sink, through the legs of the MOSFET, and up vertically along the entire height of the sink.

 #2 and #3 are fairly easy to do. #1 is not so easy. One suggestion might be to find a large copper rod - you might find them at Home Depot. Either an electrical panel grounding rod or a small section of copper tubing might work. Cut it to fit the length of your case (the more metal the better). Nestle it at the back of the case top and run all ground wires to that rod. Just a guess - I'm not sure if it will work, though.


----------



## n_maher

One other comment, it doesn't look like that build uses the BOM heat sinks. The one on the left looks a lot thinner than mine, that's for sure, which would certainly contribute to higher temps.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_One other comment, it doesn't look like that build uses the BOM heat sinks. The one on the left looks a lot thinner than mine, that's for sure, which would certainly contribute to higher temps._

 

Good call, Nate!
	

	
	
		
		

		
		
	


	




 That's definitely a half-inch thick sink - not nearly enough at this voltage and current.


----------



## darkfury18

Thanks for the help! I'll see what I can do. Taking it apart shouldn't be too bad if I can get rid of the hum.

 I didn't use the heatsink from the BOM since people were complaining about the pins.


----------



## n_maher

Quote:


  Originally Posted by *darkfury18* /img/forum/go_quote.gif 
_I didn't use the heatsink from the BOM since people were complaining about the pins._

 

Well, then I would respectfully suggest that if you're going to use an alternate sink that you choose appropriately. Be a shame to get something built only to have it cook itself the first time you use it, trust me.


----------



## comrade_boris

Hi there! My first post at head-fi.
 I've been lurking for a while, and decided to build one of these. I'm quite satisfied with how it turned out.

 Pictures are at
www.tc.umn.edu/~hern0163/millet1.jpg
www.tc.umn.edu/~hern0163/millet2.jpg

 I didn't use the BOM heatsinks, either. I went with some 2.5" ones. 
 The chassis is from radioshack--$2.99. It's a tight fit, but it works. I forgot to take a picture of the insides last night, but perhaps today.
 The whole thing worked out to about $60, including power supply, chassis, tubes, mouser stuff, etc. An excellent value, I think. Thanks Pete!


----------



## ludoo

Quote:


  Originally Posted by *comrade_boris* /img/forum/go_quote.gif 
_Hi there! My first post at head-fi.
 I've been lurking for a while, and decided to build one of these. I'm quite satisfied with how it turned out._

 

It looks really really nice. I guess the usual first post greeting does not apply here...


----------



## n_maher

Well done, boris!


----------



## keiths

Basking in the glory of getting my cMoy working 
	

	
	
		
		

		
		
	


	




, my attention now turns to my second project - Millett "Starving Student". Have just bought the power supply on eBay. 

 (If any other UK DIY'ers are interested, the guy I bought the PSU off has 5 more available Buy-it-now for GBP3.99 plus 1.75 shipping withing the UK:

Cisco 34-1977-03 7960 7940 7912 VoIP Phone Power Supply on eBay, also, VoIP Internet Telephones, Networking, Computing (end time 23-Sep-08 16:00:13 BST) 

 )

 Has anyone a UK source for the 19J6 valves (sorry, "toobs" 
	

	
	
		
		

		
		
	


	




) and sockets? Or reliable overseas suppliers that will ship to the UK for sensible shipping costs?

 Thanks in advance,

 Keith


----------



## adamus

If you orde them form ths us will you pm me, i'm in the uk too, would make sense to combine shipping.


----------



## ~n00beR

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Basking in the glory of getting my cMoy working 
	

	
	
		
		

		
		
	


	




, my attention now turns to my second project - Millett "Starving Student". Have just bought the power supply on eBay. 

 (If any other UK DIY'ers are interested, the guy I bought the PSU off has 5 more available Buy-it-now for GBP3.99 plus 1.75 shipping withing the UK:

Cisco 34-1977-03 7960 7940 7912 VoIP Phone Power Supply on eBay, also, VoIP Internet Telephones, Networking, Computing (end time 23-Sep-08 16:00:13 BST) 

 )

 Has anyone a UK source for the 19J6 valves (sorry, "toobs" 
	

	
	
		
		

		
		
	


	




) and sockets? Or reliable overseas suppliers that will ship to the UK for sensible shipping costs?

 Thanks in advance,

 Keith_

 

Let me know how this goes, i may be interested in buying some parts also.

 Depends on the state of other projects as usual 
	

	
	
		
		

		
		
	


	




 As a side note does anyone know an drop in replacment/alternative for the 16j9?


----------



## MrMajestic2

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Has anyone a UK source for the 19J6 valves (sorry, "toobs" 
	

	
	
		
		

		
		
	


	




) and sockets? Or reliable overseas suppliers that will ship to the UK for sensible shipping costs?

 Thanks in advance,

 Keith_

 

I think both Radio Daze and Welcome to TubeDepot.com! har reasonable shipping rates to europe. I have used tubedepot before.


----------



## jarpy

Calling all Aussies:

 I'm going to order this BOM from mouser. Shipping costs more than the parts but I'm doing it anyway 
	

	
	
		
		

		
		
	


	




 It contains everything but valves, sockets, chassis and power supply.

 If you want to get the same order, tell me and I'll re-mail it to you for the cost of parts, plus basic Australia Post. If you live in Melbourne, we could do prisoner exchange over a beer 
	

	
	
		
		

		
		
	


	




 Note that I have specified 470μF electrolytics. If you want a different size (like 150μF) tell me.

 ps.
 Radio Daze and Radio Electric Supply both have 19J6 in stock and ship by USPS, so they're both good for Aussies. I recommend Radio Daze for their excellent service. Sorry I didn't think of group purchase sooner.

 EDIT: Thread split to here: http://www.head-fi.org/forums/f6/aus...tudent-339003/


----------



## rjad

Quote:


  Originally Posted by *jarpy* /img/forum/go_quote.gif 
_Calling all Aussies:

 I'm going to order this BOM from mouser. Shipping costs more than the parts but I'm doing it anyway 
	

	
	
		
		

		
		
	


	




 It contains everything but valves, sockets, chassis and power supply.

 If you want to get the same order, tell me and I'll re-mail it to you for the cost of parts, plus basic Australia Post. If you live in Melbourne, we could do prisoner exchange over a beer 
	

	
	
		
		

		
		
	


	



_

 

Hi Jarpy, I'll jump on that order with you, I'll pm you.


----------



## vixr

Woo Hoo!!! got 4 tubes and 2 PSUs on the way. This looks awesome...now, what enclosure can I put it all in...


----------



## bperboy

Uh oh.. I sense balanced Starving student....


----------



## jarpy

I've split the Aussie group buy thread here:

Aussie group buy for Starving Student - Head-Fi: Covering Headphones, Earphones and Portable Audio


----------



## m0b1liz3

Does anyone know the dimensions of the case that is used to build the mini millet? Or alternatively, how small should I make a case if I am building this for the first time and want it to be relatively small?


----------



## rds

Quote:


 Does anyone know the dimensions of the case that is used to build the mini millet? 
 

This is it:

Mini Millet Case

 It's a pretty tight space to work with. The 2" tall version will make things much easier:

546-1455N1201BK


----------



## m0b1liz3

Would making a case 4' instead of 4.7' deep make a big difference?

 I was thinking 4x4x2


----------



## royewest

I suppose this is a general DIY question, but I'm thinking of it in terms of building a SSMH into a readymade case, so I'll see if someone here can answer this question:

 Where to I need to be careful about distances between components in P-P wiring for an amp like the SSMH? I'm not talking yards here, but are there any connections where, say a foot or two of 22ga wire would be a huge mistake compared to the inch or two for a standard build?

 For example, what if I mounted the FET/Heatsinks and the tube sockets a foot or two away from the rest of the components with a bundle of wires leading back to the board?

 Thanks,

 __Roy


----------



## bhjazz

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_For example, what if I mounted the FET/Heatsinks and the tube sockets a foot or two away from the rest of the components with a bundle of wires leading back to the board?_

 

I think long bundles of wires can pick up noise more easily than short bundles. They can act as antennae. However, twisting or loosely braiding can make that bundle less likely to pick up that same noise. You might search the DIY forum here for similar discussions. Also, search for Litz (a braiding style that is pretty popular).


----------



## fuzzypinkunicorns666

I decided to build one of these last week and I got finished with the build earlier today. I'm new here, but I've been an occasional lurker for a while. I figured it was about time I made an account here since I've built 3 amps so far (cmoy, mini^3, and now a starving student).
	

	
	
		
		

		
			





 The schematic seemed quite intimidating at first since this is the first time I've done an amp without a pcb and/or step-by-step instructions. But I somehow managed to get everything working after a few hours.

 So here's some pictures:




 I picked up the box at jo anne fabric's for $1, keeping with the el cheapo spirit of the amp. Just don't make fun of me for the pink!
	

	
	
		
		

		
		
	


	



 I really didn't need a 1/4 jack there since I don't even have any 1/4 headphones... I reterminated my HD555s for portable use.





 It's not _that_ bad.





 I'm really digging the look of the tubes, especially in the dark. 

 As for the sound... this amp ROCKS! That's all I have to say about it.

 And thank you Pete, for designing a kickass tube amp that even I could afford to build!


----------



## Postal_Blue

Nice looking build. You could slap some hello-kitty stickers on it


----------



## bhjazz

Quote:


  Originally Posted by *fuzzypinkunicorns666* /img/forum/go_quote.gif 
_I'm really digging the look of the tubes, especially in the dark. 

 As for the sound... this amp ROCKS! That's all I have to say about it._

 

Excellent. Cool build! Welcome to the world of tubes as well! Stay tuned. I'm sure some sweet tweaks will come out of this forum.


----------



## m0b1liz3

Hello fuzzypinkunicorns666... ? So this amp sounds better than your mini3??


----------



## royewest

Go pink! Congrats on the great build.


----------



## fuzzypinkunicorns666

Thanks for all the greetings and compliments!

  Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_Nice looking build. You could slap some hello-kitty stickers on it 
	

	
	
		
		

		
		
	


	


_

 

good idea!
	

	
	
		
		

		
		
	


	








  Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hello fuzzypinkunicorns666... ? So this amp sounds better than your mini3??_

 

I like it better. Just doing a quick a/b, it seems to be more detailed with a better soundstage. And just... more musical, basically.


----------



## amphead

Pete, you hit that ball out of the park! I just listened to your Starving Millett at the NorCal meet and it sounds tremendous! I have to recommend this build to everyone. It has much better sound than most would imagine, considering the simplicity of the build. Kudos again Pete!


----------



## pmillett

I'd like to steal some of the pics posted here and start a "starving student" photo gallery on my web site.

 Think anybody would mind my stealing their photos from their posts?

 I'm so impressed with the clever implementations. Way cool.

 Pete


----------



## fuzzypinkunicorns666

Hey Pete, I sure wouldn't mind you stealing my photos. And I doubt anyone else would, either. It's certainly a fair trade for you giving us this wonderful design.

 I'd personally feel quite honored to have my amp posted on your site.


----------



## Gross

If my pics are worthy, go for it. I have plans for another one too.


----------



## rds

A starving student gallery sounds like a great idea.


----------



## m0b1liz3

I remember an initial comparison of this amp with the SOHA said that the student MH seemed to lack bass. Has anyone else found this? I think this hp amp is very cool based on the small form factor and simplicity.


----------



## Gross

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I remember an initial comparison of this amp with the SOHA said that the student MH seemed to lack bass. Has anyone else found this? I think this hp amp is very cool based on the small form factor and simplicity._

 


 That was me that said that, and It was due to the wrong size capacitors. After I found and fixed my mistake, all the bass was there. As long as you build it correct to the schematic, you will have a rocking amp with plenty of bass.


----------



## tomb




----------



## andrew jc

When are you accepting orders?


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_

















_

 

Holy shiznit Batman! Sexy!


----------



## pabbi1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_









_

 

Oh, no, you didn't?!?

 God save the tube supply.

 A $60, one hour build? That should just about corner the low end amp market.


----------



## tomb

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, no, you didn't?!?

 God save the tube supply.

 A $60, one hour build? That should just about corner the low end amp market._

 

Actually, no - I didn't. Dsavitsk did (design the board) - with Pete and Nate's blessing. I'm hoping to be head cheerleader again, though.
	

	
	
		
		

		
		
	


	




 You're close with that estimate, though - it took me about 3 hours today, but I was making mistakes the whole time.


----------



## pabbi1

You will always be the head cheerleader... oh, and I know you ran more than a couple of boards...


----------



## holland

.


----------



## n_maher

holland, 

 we're not adding anything to the design, this is a simple, basic amp and we're keeping it that way for now. If you want features and flexibility either PTP it and add whatever your heart desires or go with something more integrated like the MAX. The reason for this is simple - this is meant to be an introduction and seriously cheap to build, hence the name. 
	

	
	
		
		

		
		
	


	




 Also, right now there aren't any boards (only 4 were made) so folks are just going to have to be patient or PTP it.


----------



## holland

.


----------



## tomb

I am opposed to adding a simplified e12 to the Starving Student. Build a MAX if you want those kind of accessories on the board. There were literally hundreds of Millett Hybrids built without e12 circuits - without incident. It adds at least 10 parts that are totally unrelated and not common to any other part of the amp - and an extra $5. That may sound trivial, but it all adds up. The hassle of parts selection and constructing the e12 is a totally unrelated, complicated exercise. The relay itself would become the single most-expensive part on the board, too.

 1000uf output caps are not necessary, either. There is a long history of the Millett with 470uf output caps and no complaints from lack of bass. Right now as the board stands, 1000uf 63V caps are impossible to fit, anyway. I've got 470uf 63V Panasonic FC caps and the bass almost rivals a full-blown MAX. I'm embarrassed to admit how good this thing sounds with 1/4W carbon-film resistors, four Pana FC caps, two stock Mouser Wima coupling film caps, and a Panasonic EVJ pot.

 Simple is good.


----------



## tomb

OK - the whole issue of a delay-relay is a non-starter. (I think Pete said the same thing earlier.)

 I've got a Fluke tied to the headphone jack with a 32ohm set of headphones connected into the jack. From power up, the biggest spike I've seen is 0.32VDC - most of the time, it's below 0.2VDC (inaudible). On cutoff, the biggest one I've seen is about 0.60VDC, but a relay-delay won't protect against that, anyway. In the end, both of those are trivial. As a matter of fact, the MAX with its relay will send out over 1VDC with high-impedance loads on cutoff. That's also trivial for a high-impedance phone.

 I could hear nothing in the headphones on startup and just a tiny thump on shutdown. Bottom line, it's not an issue - I've got PIMETAs that make more of a pop on startup/shutdown.


----------



## holland

.


----------



## gz76

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_

_

 

Mmm, naked goodness.


----------



## royewest

This looks wonderful and convenient and congrats to tomb - I hope you make a kit of this on beezer.com and introduce a new set of folks to this design - but to echo a few other folks, please don't forget that the original design and P-to-P is really not that challenging (shucks -- I built one!) and sounds fantastic.


----------



## jonjon0nline

Whoa... will there be a GB for this board? I'm about to start my Millett Max but it'd be nice to have something better than a cMoy at work =D


----------



## rds

This is DIY, the responsibility lies with the builder.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_













_

 

That is really awesome. Gimme gimme gimme.


----------



## tomb

Quote:


  Originally Posted by *jonjon0nline* /img/forum/go_quote.gif 
_Whoa... will there be a GB for this board? I'm about to start my Millett Max but it'd be nice to have something better than a cMoy at work =D_

 

There's still development work to be done, yet. There are a few tweaks* that I'm hoping Dsavitsk will incorporate. So, no promises for now.
	

	
	
		
		

		
		
	


	




 Yes, along with everyone who's built a P2P version, we can absolutely confirm that it sounds better than a CMoy. That said, it would be pretty neat if Pete's design and Dsavitsk's board become as popular as the ubiquitous CMoy.
	

	
	
		
		

		
		
	


	





 * As in layout changes, not additions.


----------



## vixr

uh...never mind, I guess.


----------



## n_maher

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I would put notices of limited liability and cap advisories in bold once you start selling these things. I know you said it was never a problem in the past, and I don't know your business arrangements. Just keep in mind, the USA is a litigious society._

 

Holland, please, I understand your concern but I think you're taking the point way too far. Implying that someone might sue over something like this is beyond my comprehension. All of these projects are "at your own risk".

 The pcb is being offered as an alternate to the point to point to try and make the design more accessible. The intent of the pcb is to be exactly what the schematic shows (with one minor exception so far) and that's it. The main goal of the original project, and Pete can correct me if I'm wrong, was to offer an extremely inexpensive, simple build to try and entice new folks to DIY. Adding things like e12's and so on significantly increase the complexity.


----------



## m0b1liz3

Anyways, back to the discussion.... When will those pcbs be available? (Too late for me since I am going to forge ahead and do a PTP one as a project) That PCB would have saved a fair amount of time though!


----------



## n_maher

I would guess that it'll be a good month or so still before the pcb's will be available. The development team (tomb, Dsavitsk, Pete, myself) are working on the prototypes and there's discussion of another round being done to tweak a few things. Note, I said tweak, no wholesale changes are expected. It is also undecided exactly how the boards will be distributed so until all of that is worked out I think we'll probably be pretty mum's the word about the whole thing. Think end of summer and you probably won't end up disappointed. 
	

	
	
		
		

		
		
	


	




 All that said it's really not all that difficult to PTP it and the pcb doesn't save that much time. If you've built a CMoy you can build one of these PTP too without any trouble. If I can do it, you can.


----------



## m0b1liz3

Oh, I don't know about that... My amp6 doesn't seem to be working! But it could just be a bad tripath chip.


----------



## Postal_Blue

My pics are fair game as well.


----------



## comrade_boris

Mine also. I'll post a shot of the insides once I remember to take one, too.


----------



## royewest

Mostly for Pete, here are some more shots of my SSMH after I finished the chassis: Verathane on the wood and acrylic on the top plate. 

 The top is a 1-sided copper-clad board, 6" x 6". 

 Clearly I should have painted before assembling the top -- the paint turned out pretty sloppy, but perhaps it doesn't show so much in these photos, because I'm a worse photographer than I am a painter, if that's possible!


----------



## TimJo

^ Wow! Vitamin Q's - sweet...


----------



## pabbi1

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_All that said it's really not all that difficult to PTP it and the pcb doesn't save that much time. If you've built a CMoy you can build one of these PTP too without any trouble. If I can do it, you can. 
	

	
	
		
		

		
		
	


	


_

 

Yeah, there is the trouble - I never could get that cmoy working... honest.

 Sad, and yet, not really.

 But since I already have all the darn parts, except the tubes and sockets, I guess I'll give it a shot. Finally a place to use that 48v 4a Piltron toroid...


----------



## royewest

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_^ Wow! Vitamin Q's - sweet..._

 

Even a starving student could afford $5 for a pair of vitamins from beezar.com : )

Beezar.com


----------



## fordgtlover

Does anyobody have a recommendation as a replacement for the IRF510. They are a PITA to find locally here.

 I can source the IRF540 quite easily - any thoughts on this as a replacement.

 What should I be looking for in the spec sheets?


----------



## TimJo

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Even a starving student could afford $5 for a pair of vitamins from beezar.com : )

Beezar.com_

 

That's true. But I suppose if you want to save some extra money for beer, you could settle on the Russian PIO caps for $2. 
	

	
	
		
		

		
			





Russian K42Y-2 PIO 0.10uf, 160V


----------



## jarpy

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Does anyobody have a recommendation as a replacement for the IRF510. They are a PITA to find locally here.

 I can source the IRF540 quite easily - any thoughts on this as a replacement.

 What should I be looking for in the spec sheets?_

 

I have a box of IRF610 heading my way. I _think_ they will serve (experts?).

 I think your valves and power supply will now be coming through me, so I can chuck a pair of IRF610 in the package if you like.


----------



## n_maher

A quick look at the data sheets makes me think that the 610 and 510 are *not* interchangeable. It'd be wise to get more knowledgeable feedback from someone before using them.


----------



## pmillett

IRF610 will work fine. Vgs(th) is the same, gm is a bit lower so will result in a little more distortion than a IRF510. But the distortion from the FET is miniscule compared to that of the tube stage, so I don't think you could hear it (and maybe not even measure it).

 The IRF540 is quite a different animal, so I wouldn't recommend it without testing. It will certainly work (almost any MOSFET will work as long as it's good for 50V or more), I'm just not sure how well compared to the 510 or 610.

 Pete


----------



## scompton

I don't know if it's been asked, but is this a good first time DIY project? It looks fairly simple? Also is there a good book on building circuits? I'm currently reading Teach Yourself Electricity and Electronics, which was recommended in another thread, but it doesn't talk about actually putting something together.


----------



## andrew jc

Scompton have you seen these videos? Tangent Tutorials


----------



## scompton

I've gone though all of them and I've done a minimal amount of soldering, mostly reterminating headphone cables. Building a CMoy doesn't interest me to much because I don't have much interest in a portable amp. If need be, I can build a CMoy first and give it away, but I thought this amp didn't look hard to build.

 If you're point out the tutorials in response to my request for a book, they don't deal with tubes and heat sinks and such. For example, I know I saw a post on this thread about how to tell which pin is which in an unlabeled tube socket. I thought it would be nice to have a book that has this type of information in it, if such a thing exists.


----------



## royewest

I am very new to this, too. I have no engineering background. I'm a writer.

 Here are the things I did not know, when I started:

 * How to figure out which pin is which on the tubes and, particularly, the MOSFET -- I think that was answered in this thread (for MOSFET, from the front (the side without the metal plate), 1,2,3 left to right. One thing I found helpful (though not, oddly, in this situation), is that for every part on Mouser, you can get a link to the manufacturer's data sheet for that part.

 * How to convert a circuit diagram into an efficient point-to-point layout. For this and for the tube orientation, I found the high-resolution images of the original builds and some other folks' builds made it possible to "borrow" how they did it. OK, a shameless copy. But heck...

 * Thermafilm MOSFET mounting kits require thermal goo on the MOSFET and heat sink sides. Thermasil kits don't.

 * As other folks have pointed out, but I had to learn for myself, the casework can be harder than the circuitry. I have no skills in this regard, either, but managed to make a tidy-looking amp (until I tried to paint the top after it was assembled, that is : )

 I built a bottlehead.com S.E.X. amp as my first tube amp. It's a bit more complicated (for fitting things together as well as the circuit), but it's a stunningly nice-sounding amp and has meticulously illustrated instructions designed so anyone can build it, comes with all the required parts, down to shoulder washers, and has a good support forum. I think that was a good prep for the SSMH.

 I've said this before and I'll say it again about this design: If I can do it, you can do it! And it's really worth it!


----------



## fuzzypinkunicorns666

As others have said, this is a pretty easy build. I pretty much learned how to read schematics while building this, and didn't have any problems (other than the tube/mosfet numbering, which I figured out from the pictures of other people's builds). You'll probably be fine with this as a first build.

 And on another note, I went to a local surplus store today and picked up 3 different pairs of replacement tubes, all different brands. And 2 of the pairs got rid of a slight humming problem I was having. The other pair just made it really bad. So now I have some replacements if/when my tubes fail.


----------



## procalli2007

I have a couple of questions regarding heatsinks.

 I cant find any mounting kits and wondered if it was possible to just bolt the ir510 directly to the sink. I have some white compound left over from my dual core processor which I could smear on the heatsink if this would help.

 Also will there be a problem if my heatsinks arent on show, ie I put them inside the case (hammond 1455 or similar)


----------



## bperboy

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_I have a couple of questions regarding heatsinks.

 I cant find any mounting kits and wondered if it was possible to just bolt the ir510 directly to the sink. I have some white compound left over from my dual core processor which I could smear on the heatsink if this would help.

 Also will there be a problem if my heatsinks arent on show, ie I put them inside the case (hammond 1455 or similar)_

 

If you don't use mounting kits, then the center pin of the mosfet will be tied to the heatsink... which isn't a problem, as long as the heatsink doesn't have continuity with something it's not supposed to...


----------



## rds

Quote:


 as long as the heatsink doesn't have continuity with something it's not supposed to... 
 

Like anything, including ground


----------



## holland

.


----------



## royewest

I just ordered a handful of these Thermasil kits from Mouser:

4880SG

 Less than a dollar each. They charge over $7 for shipping, so I waited until I had a few other things to group in an order.


----------



## procalli2007

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I just ordered a handful of these Thermasil kits from Mouser:

4880SG

 Less than a dollar each. They charge over $7 for shipping, so I waited until I had a few other things to group in an order._

 

Thanks for the replies. Problem is Im in the uk and cant seem to find suppliers of the kits.


----------



## J.D.N

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Thanks for the replies. Problem is Im in the uk and cant seem to find suppliers of the kits._

 

Have you checked Farnell?

IXYS SEMICONDUCTOR | IXFH26N50 | Transistors | Semiconductors - Discretes | Farnell IE 

 Scroll to the bottom of that page and have a look. I've not looked around for my BOM for a while, but im sure i found kits somewhere in the UK.

 [Edit]

 Maybe...

To-220 Mounting Hardware by Radioshack from T2Online. UK based retailer.

Rapid Electronics - T0-220 Kits

 This is an american site, but they will ship to UK, and it you only want very little might do it standard post. 
TO-220 Heatsink Mounting Kit - Jameco's RobotStore

 Not sure about this place, but worth a try...
Standard Products - Mounting Kits




 good luck!


----------



## fordgtlover

Quote:


  Originally Posted by *jarpy* /img/forum/go_quote.gif 
_I have a box of IRF610 heading my way. I _think_ they will serve (experts?).

 I think your valves and power supply will now be coming through me, so I can chuck a pair of IRF610 in the package if you like._

 

 Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_IRF610 will work fine. Vgs(th) is the same, gm is a bit lower so will result in a little more distortion than a IRF510. But the distortion from the FET is miniscule compared to that of the tube stage, so I don't think you could hear it (and maybe not even measure it).

 The IRF540 is quite a different animal, so I wouldn't recommend it without testing. It will certainly work (almost any MOSFET will work as long as it's good for 50V or more), I'm just not sure how well compared to the 510 or 610.

 Pete_

 

Thanks for the response. I need to do a Mouser order anyway, so I'll just pick up a few 510s with that order (and a few spares).

 Cheers


----------



## scompton

Just a couple of questions

 In the BOM, the part number for the heat sink and the description doesn't match. The description says 2" tall heat sink, but the description on Mouser for 567-657-15ABP says 1.5". I'm ordering 567-657-20ABP which is 2" tall.

 I've read that Cat5 wire works for hook up wire. I have a lot of it, so I'm not ordering any.


----------



## procalli2007

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Have you checked Farnell?

IXYS SEMICONDUCTOR | IXFH26N50 | Transistors | Semiconductors - Discretes | Farnell IE 

 Scroll to the bottom of that page and have a look. I've not looked around for my BOM for a while, but im sure i found kits somewhere in the UK.

 [Edit]

 Maybe...

To-220 Mounting Hardware by Radioshack from T2Online. UK based retailer.

Rapid Electronics - T0-220 Kits

 This is an american site, but they will ship to UK, and it you only want very little might do it standard post. 
TO-220 Heatsink Mounting Kit - Jameco's RobotStore

 Not sure about this place, but worth a try...
Standard Products - Mounting Kits




 good luck!_

 

Thanks, I decided to put an order through beezar.com instead. Worked out cheaper as I needed a pot.


----------



## fuzzypinkunicorns666

Wow, this amp is amazing with grados. (just got a pair of SR-60s today)


----------



## rds

Quote:


 Wow, this amp is amazing with grados 
 

That's what I keep saying


----------



## scompton

Does it work with higher impedance/lower sensitivity phones as well? Almost all of my headphones are harder to drive than Grados.


----------



## J.D.N

People in the UK might want to check out bluebell audio for bits a bobs, great site and good prices.


----------



## procalli2007

Whats the difference between log and linear in regards pots and which one should I buy.

 Also what is the best method of cutting square holes in the hammond alu cases?

 thanks

 jdn, thanks for the link as Im looking for some valve sockets with surrounds.


----------



## ~n00beR

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_People in the UK might want to check out bluebell audio for bits a bobs, great site and good prices._

 

OMG!!! thats like 40mins drive from my house and I didn't even know it was there :O
 I was at uni in dundee too!

 Well I now have a new favourite shop 
	

	
	
		
		

		
		
	


	




 Thanks for the tip J.D.N


----------



## n_maher

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Whats the difference between log and linear in regards pots and which one should I buy._

 

You want a log taper pot, linear (oddly enough) will not give you linear volume adjustment.

  Quote:


 Also what is the best method of cutting square holes in the hammond alu cases? 
 

I find that marking the hole I want to make and then drilling near the perimeter with a small diameter bit works best. You then would have to file down the half rounded shapes to get a straight line but that's the only way I've had good luck doing it. Things like nibblers have never worked for me.

 Also, someone asked me a question via PM about how large a hole was required for bottom mounting the tube sockets and I figured I'd answer it here. This is, unfortunately, impossible to say with any certainty since whatever sockets people buy may or may not resemble the ones that I used. IIRC I was able to use a 3/4" hole for mine and get good results, YMMV and the best method is to just measure the sockets that you get and adjust accordingly. 

 And scompton, yes, the amp works well with high impedance/low sensitivity cans as well.


----------



## tomb

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Does it work with higher impedance/lower sensitivity phones as well? Almost all of my headphones are harder to drive than Grados._

 

Yes, of course! This thing will probably drive a small pair of speakers without too much trouble. It dissipates almost 4-1/2 Watts per channel. It won't deliver all of that to a load and a lot of it goes to the tube heaters, but still ...

  Quote:


  Originally Posted by *procalli2007* 
_Whats the difference between log and linear in regards pots and which one should I buy.

 Also what is the best method of cutting square holes in the hammond alu cases?

 thanks</snip>_

 

Log is what you should purchase, but even then, there's a specific taper known as "audio" that you should look for. Some log pots may go both directions for adjusting balance or tone, etc. Stick with the familiar ones that are labeled as "volume" pots and are "stereo". There's actually a pretty limited selection to pick from when you start looking for those two things.

 You can also cheat by referring to our familiar DIYer sites such as Pete Millett's, Tangent's, AMB's, DIYforums.org, Headwize, Beezar, Cavalli Audio, etc. Check the BOM's for their various designs and you can get some part numbers for volume pots. You can also look at places such as Handmade Electronics, Parts Connexion, Welborne Labs, Michael Percy, etc. Look at the pots that they advertise as stereo-volume pots and see if you can find those in your area or from the vendor you've selected. Mouser and DigiKey have only a couple each - Mouser has the Alpha that Pete has spec'd for the Starving Student, and DigiKey has the Panasonic EVJ. Radio Shack has a large, open-style ALPS. I'm not sure what Allied Elec and Newark have, but it's probably only one or two, as well.

 EDIT: Geez, that was bad timing - posting the same time as Nate. Oh well - hope this helps.


----------



## n_maher

Great minds, Tom, great minds...


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Great minds, Tom, great minds... 
	

	
	
		
		

		
			



_

 

Well, OK - I won't argue with that.


----------



## royewest

beezer.com has a sweet Alps pot for about $16...

 ...hey, I think I just figured out why our student can't afford to eat...


----------



## n_maher

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_beezer.com has a sweet Alps pot for about $16...

 ...hey, I think I just figured out why our student can't afford to eat..._

 

The BOM recommended pot seems to work pretty well and costs a lot less. Not saying the alps isn't a huge step up but if you're working on a budget you've got options.


----------



## procalli2007

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_beezer.com has a sweet Alps pot for about $16...

 ...hey, I think I just figured out why our student can't afford to eat..._

 

thats what ill be putting on it along with the 2 of the russian 0.1 capcitors.


----------



## MoxMonkey

Just curious if anyone has a BOM sourced from Digikey for us Canadians since Mouser wants an arm and a leg to ship stuff here.


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_Just curious if anyone has a BOM sourced from Digikey for us Canadians since Mouser wants an arm and a leg to ship stuff here._

 

Get the Stackpole "SEI CF1/4" resistors. You'll have to type "Stackpole" in and search, they're not in the general catalog. You could start with "CF1/42K5%RCT-ND" - that's the part number for a 2K resistor of those kind. They're excellent resistors for audio and tubes - the same ones sold by Handmade Electronics at a larger wattage. Also, the Panasonic FC's at 470uf 63V seem to sound very good in my Dsavitsk-PCB version.
	

	
	
		
		

		
		
	


	




 DigiKey already has the IRF510's. As for the pot, you may have to pick a Panasonic EVJ if you want one from DigiKey. The P2U4503-ND is a good part number for that. As for film caps at DigiKey, Dsavitsk sort of likes the light blue Vishay/BC box caps - the MMKP 383. There's one at 0.1uf: BC1849-ND.

 The rest is hardware, I believe, and you should be able to figure out.


----------



## amphead

Bravo TomB! Now our Canadian members can build the Starving Millett on a budget.


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Get the Stackpole "SEI CF1/4" resistors. You'll have to type "Stackpole" in and search, they're not in the general catalog. You could start with "CF1/42K5%RCT-ND" - that's the part number for a 2K resistor of those kind. They're excellent resistors for audio and tubes - the same ones sold by Handmade Electronics at a larger wattage. Also, the Panasonic FC's at 470uf 63V seem to sound very good in my Dsavitsk-PCB version.
	

	
	
		
		

		
		
	


	




 DigiKey already has the IRF510's. As for the pot, you may have to pick a Panasonic EVJ if you want one from DigiKey. The P2U4503-ND is a good part number for that. As for film caps at DigiKey, Dsavitsk sort of likes the light blue Vishay/BC box caps - the MMKP 383. There's one at 0.1uf: BC1849-ND.

 The rest is hardware, I believe, and you should be able to figure out._

 

Cool thanks, I'm thinking Starving Student and then a Max in terms of progression of builds and with parts being sourced from DigiKey this is much cheaper


----------



## pabbi1

Per recommendation, I'm asking a couple of questions here - yes, I am _*attempting*_ p2p. 


 Quote:
 Originally Posted by rds (recommendations)
 Put a film cap in the 0.5 uF range in parallel with C1
 Use around 500 - 800 uF for C6 /Quote

 I'm thinking about using a 470uF (or 680uF) on C1 and C6 (mainly because that is all I have laying around, but also have some .47 VitQ - how would the parallel look p2p with C1, and why not also with C6? Does this help if I am using Panasonics (very low ESR)?

 Secondly, I am a visual builder, and follow Pete's build with the schematic OK, except where R3 & R9 tie to pin 1 on the MOSFET - just not in the photo? I follow Nate's ok (edit: now that I look better). So, I am obviously missing R3 & R9 OR is it R6 & R12 - is there some slight of hand here?


----------



## rds

Don't take my advice too seriously. Those are just values that I used and was happy with. 
 There are lots of ways to do this and my way is not necessarily better than any other way.


----------



## procalli2007

A question while I wait for some more parts to arrive.

 Can I add another headphone socket and would this amp drive two headphones. Would this affect the sound.

 The headphones Im looking at are hd 595 or hd600.

 Is there a limit on ohms driven?


----------



## m0b1liz3

I have a somewhat related question that may have been asked already. I was thinking of putting a switch and rca outputs on my build to use the starving mh as a preamp. Any reason why it wouldn't be appropriate for this use?


----------



## holland

.


----------



## fjc

hi guys, I´ve a couple of question about this amp, wich is going to be more tham likely my 2nd DIY build.

 ok first question, can I use this as a preamp, I was thinking of making this my preamp/headphone amp and then building a pair of gainclones (monoblocks) as a power amp, I´ve been told in another thread that the amp has a high gain so maybe using it with a gain control switch(well more like an attenuation switch).

 2nd I know the spirit of the build was to be be a great amp at a great price but lets say that our starving student (that´s me) dosn´t have acces to one of the power supply units used in the original build what PS would you recommend making for the SS.

 would it be possible to add a class a output buffer like the one on headwize, or is the output stage in the amp working near class a 

 Thank you all for your time 

 Francisco


----------



## m0b1liz3

I was wondering the same thing about the gain. Can the gain be dropped in a simple manner to allow for RCA outs?

 I had wanted to use this with a small form factor chip amp to make a sort of mini system for listening to music on my computer since that is where I seem to spend the most time.


----------



## m0b1liz3

"The genious of Pete Millett's design is that he tied the MOSFET output stage to the heaters of the tubes. So as long as the tubes are fired up, the MOSFETs are both Class A-biased to 150ma each. Considering the almost 30V difference (~48V - 19V) at that current, it adds up to almost 4-1/2 Watts per channel of Class A power!"

 Tomb you posted this in RDS's build thread and also mentioned to ask technical questions in the original thread. I am appropriately asking this question here as requested. 

 Is this amp really pushing out that much power? 4.5W of tube power is pretty impressive in such a small design. If it is really pumping out that kind of power couldn't it be used to run small speakers? I have small 6ohm speakers on my desktop by my computer. If I could directly power them with this amp and flip a switch for headphone listening it would be the ideal solution for me right now. I am sure that others would find this idea amazing as well if it is possible. Is there any reason why it couldn't be used to directly power speakers?


----------



## tomb

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_"The genious of Pete Millett's design is that he tied the MOSFET output stage to the heaters of the tubes. So as long as the tubes are fired up, the MOSFETs are both Class A-biased to 150ma each. Considering the almost 30V difference (~48V - 19V) at that current, it adds up to almost 4-1/2 Watts per channel of Class A power!"

 Tomb you posted this in RDS's build thread and also mentioned to ask technical questions in the original thread. I am appropriately asking this question here as requested. 

 Is this amp really pushing out that much power? 4.5W of tube power is pretty impressive in such a small design. If it is really pumping out that kind of power couldn't it be used to run small speakers? I have small 6ohm speakers on my desktop by my computer. If I could directly power them with this amp and flip a switch for headphone listening it would be the ideal solution for me right now. I am sure that others would find this idea amazing as well if it is possible. Is there any reason why it couldn't be used to directly power speakers?_

 

No, it's not pumping out that much power. I just used the hyperbole to illustrate that it's about as far away from NON-Class A as you can get in an amp this small. That was sort of the basis of the original question. So, that's dissipated power, not output power.

 Pete's measurements say 7V RMS into 100ohms at 5% distortion. That's 490 mW, according to my calcs. He also says 3V into 32 ohms. That would be 280 mW. That's more than adequate to drive almost any headphone, I think. It's probably OK for a couple of flea speakers, too.


----------



## tomb

Quote:


  Originally Posted by *fjc* /img/forum/go_quote.gif 
_hi guys, I´ve a couple of question about this amp, wich is going to be more tham likely my 2nd DIY build.

 ok first question, can I use this as a preamp, I was thinking of making this my preamp/headphone amp and then building a pair of gainclones (monoblocks) as a power amp, I´ve been told in another thread that the amp has a high gain so maybe using it with a gain control switch(well more like an attenuation switch)._

 

Sounds like a Pete question. I agree that the voltage swing is probably too great to be used as a preamp. I don't know how the gain could be adjusted, though. rds' implementation of a gain switch is more of an attenuation at the pot. I don't know if that could be used to set it up for a preamp. Maybe someone else has some better suggestions.
  Quote:


 2nd I know the spirit of the build was to be be a great amp at a great price but lets say that our starving student (that´s me) dosn´t have acces to one of the power supply units used in the original build what PS would you recommend making for the SS. 
 

Check for some of the earlier posts - Jameco has linear, regulated walwarts that I think holland used in his build.
  Quote:


 would it be possible to add a class a output buffer like the one on headwize, or is the output stage in the amp working near class a 
 

See the post above and read the rest of the response I made that caused you to post in this thread.


----------



## m0b1liz3

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No, it's not pumping out that much power. I just used the hyperbole to illustrate that it's about as far away from NON-Class A as you can get in an amp this small. That was sort of the basis of the original question. So, that's dissipated power, not output power.

 Pete's measurements say 7V RMS into 100ohms at 5% distortion. That's 490 mW, according to my calcs. He also says 3V into 32 ohms. That would be 280 mW. That's more than adequate to drive almost any headphone, I think. It's probably OK for a couple of flea speakers, too._

 


 So at 6ohms, there is no way it would drive them properly. 1/2W of tube power would have been ok I would imagine but I am sure it is less than that based on what you said above. Too bad. I got really excited for a second over the idea of having an all in one desktop amp. I am looking into building a gainclone too and might want to use the SSMH as a preamp if it is simple enough to lower the gain to proper levels for a line out.


----------



## n_maher

If one really wanted to use the SSMH as a speaker amp it'd probably be worth looking into if it would be possible to trafo-couple the output rather than cap coupled as it is now.


----------



## m0b1liz3

Trafo-couple? Can you explain further? Do you mean a transformer on the output? 

 I don't want it to be solely used as a speaker amp but to add something to the circuit with a switch to allow for both. It would be a great concept as a desktop amp allowing for the best of both worlds if it could be pulled off.


----------



## trains are bad

output transformers are used on class A speaker amps to impedence match them to low (compared to headphone) impedence speakers.


----------



## rds

Quote:


 Can the gain be dropped in a simple manner to allow for RCA outs? 
 

You can effectively lower the gain as much as you want by adding series resistors before the pot. 
 If you wanted a preamp with something around unity gain then you could have 100k resistors in series with a 10k pot.
 If you want a gain of 2 to 3 so this can be used as a headphone amp as well , then you could put 50k resistors in series with a 10k pot.
 This is just a voltage divided concept which allows you to attenuate the source.

 This mod does not change the turn on and turn off thump. So keep that in mind. I use this amp as a pre-amp sometimes and it gives a nice low bass boom from my speakers if I turn it off when the amp is on. This could blow your speakers (see my post on the next page).


----------



## m0b1liz3

Quote:


  Originally Posted by *trains are bad* /img/forum/go_quote.gif 
_output transformers are used on class A speaker amps to impedence match them to low (compared to headphone) impedence speakers._

 

So the output transformer doesn't deliver more watts neccessarily? It just allows for the same power to be delivered to low impedence speakers? 

 In the case of this amp wouldn't it need a bigger power supply in order to have the amps to deliver decent sound through an OPT??

 I quickly scanned this so my understanding is fairly limited:

output-trans-theory
Output Transformer Impedance

 If we have a certain voltage (around 500mw with the SS) then the voltage will drop and the amps will increase in order to drive low ohm speakers. Do I have this right? Does anyone have any numbers that would show what sort of power the SS could deliver? (Running out of time to look right now). 

 Does this make sense to do this with this amp? Could I have a switch before the output that allows to go between a cap for the headphone output and an OPT for speaker output. 

 And on the practical side, don't OPTs themselves cost a fair amount?


----------



## fjc

yes i was thinking about a switch to modify the attenuation of the input signal, good to hear that it works 
	

	
	
		
		

		
		
	


	




 also thanks for the jameco suggestion, but just in case what diy choices would i have that could provide a clean 50 v output


 thanks

 Francisco


----------



## rds

Quote:


 thanks for the jameco suggestion 
 

I never suggested the Jameco. I have no experience with it. 

  Quote:


 but just in case what diy choices would i have that could provide a clean 50 v output 
 

Don`t take this the wrong way, but if you have to ask you probably should avoid building your own power supply. It is dangerous.

 Why not use the recommended Cisco power supply? It works well, is cheap and is readily available.


----------



## n_maher

One quick comment, if your goal is to attenuate the signal before the pot I would use a voltage divider and not series resistance. A voltage divider would essentially be one step of a stepped attenuator and you can control both the input and output impedance of the divider so that you don't cause adverse affects on the signal.


----------



## holland

.


----------



## dsavitsk

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_So the output transformer doesn't deliver more watts neccessarily?_

 

Well, of course not. A transformer is a passive device with no capability to create power.

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_One quick comment, if your goal is to attenuate the signal before the pot I would use a voltage divider and not series resistance._

 

I'll agree with rds here. This method will end up with a lower Zin in most cases. The relationship of the voltage divider and pot will need to be 10x which will leave either the input Z too low for some sources, or the second attenuation stage will be potentially large which can be noisy. Either way, it is two attenuators when you only need one. OTOH, putting a resistor in series with the pot essentially lengthens the resistive element of the pot and just keeps the wiper from traveling over the whole thing.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_<snip>I'll agree with rds here. This method will end up with a lower Zin in most cases. The relationship of the voltage divider and pot will need to be 10x which will leave either the input Z too low for some sources, or the second attenuation stage will be potentially large which can be noisy. Either way, it is two attenuators when you only need one. OTOH, putting a resistor in series with the pot essentially lengthens the resistive element of the pot and just keeps the wiper from traveling over the whole thing._

 

Considering the gain involved, it works pretty well on your SSMH PCB. I went conservative and just added ~50K resistors in line with the 50K pot, but it's a much better adjustment than I expected.


----------



## fjc

thanks holland for the info I ask cause I´ve tried to build a power supply for my YAHA and eventough I got rid of most of the noise there´s still a very little hum. I´ll also look around here and diyaudio for some PS schematics. 

 RDS, I have a couple of reassons to not use the cisco PS unit , one is that me and my familly have a couple of bad experiences with ebay and paypal so I try to use only when theres no way around it. also I live in mexico and the shipping will be more expensive than the actual unit. to make things worse , is that it is really stressful to try to track down a package once it enters costums and the Mexican post service gets in charge ( last time i needed like 20 phone calls and 5 days just to figure if the package had already left customs). so when I order something I make sure its an ammount that has to pay taxes ( belive me it's safer ) and make sure to get a tracking number and insurance.

 As for building the ps I do have some experience around power electronics, the problem is that I don´t have experience around audio electronics. 

 well thank you all for your time 

 Francisco


----------



## fjc

-


----------



## rds

fjc - I could post one to you, but I guess that won`t solve your customs problems.
 If it will send me a pm.


----------



## m0b1liz3

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Considering the gain involved, it works pretty well on your SSMH PCB. I went conservative and just added ~50K resistors in line with the 50K pot, but it's a much better adjustment than I expected._

 

You mean to add 50k resistors to the existing pot right not a separate one for the preamp stage? How many resistors did you use? After you add the resistors is a simple switch between rca outs and hp out is all that is needed?


----------



## rds

I should say:
*The preamp can be deadly to your speakers*
 As you are sending that turn on/off thump to your speaker amp, if your amp is powerful enough it may blow your speakers. I think to be safe you should have a relay if you`re going to do a preamp.


----------



## m0b1liz3

Or I can just always turn the amp off first... Current speakers are el cheapos anyways. I was trying to figure out if there would be any way to use an OPT to drive speakers since someone suggested that but I don't think it could work.


----------



## rds

I just want to make sure someone doesn`t put a hit out on me after they blow their B&W Nautilus or something.


----------



## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I'll agree with rds here. This method will end up with a lower Zin in most cases. The relationship of the voltage divider and pot will need to be 10x which will leave either the input Z too low for some sources, or the second attenuation stage will be potentially large which can be noisy. Either way, it is two attenuators when you only need one. OTOH, putting a resistor in series with the pot essentially lengthens the resistive element of the pot and just keeps the wiper from traveling over the whole thing._

 

Fair enough, I've just always been cautioned against doing that on the input of an amp.


----------



## rex0x0

I started following this thread in the beginning then was away for a month now boom it's 61 pages--which I just finished reading.

 I'm looking to build and I've noted some updates, I'm wondering if this is right or have I missed something in this monster thread?

 Start with Pete's BOM/schematic 
 Change c6 to 470uf as per http://www.head-fi.org/forums/4220313-post238.html
 Maybe change the output to a 470uf as well.

 Is this the "optimum" configuration? There's has been a lot of advice, and since my parts drawer is pretty much empty I'm ordering everything likely using the digikey parts list from tom--mouser's Canadian shipping is absurd.


 Thanks!


----------



## rds

Quote:


 ...I've just always been cautioned against doing that (adding series resistance to a pot) on the input of an amp. 
 

Probably the reason people have cautioned against that is because it is not a good idea to have a huge input impedance. Large input impedances make the amp more susceptible to noise.
 The solution is to use a lower impedance pot if you want to reduce the gain a lot. 
 That is why I recommended a 100k resistor in series with a 10k pot.
 I've also found using 220k in series with a 50k pot to be perfectly acceptable.


----------



## n_maher

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Probably the reason people have cautioned against that is because it is not a good idea to have a huge input impedance. Large input impedances make the amp more susceptible to noise.
 The solution is to use a lower impedance pot if you want to reduce the gain a lot. 
 That is why I recommended a 100k resistor in series with a 10k pot.
 I've also found using 220k in series with a 50k pot to be perfectly acceptable._

 

Thanks for the explanation!


----------



## rds

No problem.
 Just to complete that explanation the noise problem comes from the source feeding the amp. Any source is going to have a superimposed noise in its output current. A higher impedance means the source outputs less current, and therefore the noise to signal ratio increases. At some point with an extremely high impedance the signal will be completely lost in the noise.
 On the other hand if the input impedance is too low the source will have to output a very large current. Too low an impedance will require the source to output more current than it is capable of and therefore will distort.
 So like everything there is some point in the middle that is 'just right'.


----------



## V-DiV

I've just finished my summer commuting and will have some time for a project in the near term. I can't wait any longer for the SOHA II so I'm going to build a Starving Student. I watched this thread when it first started but haven't followed it for a while and I don't necessarily want to read all 600+ posts. Are there any consensus good-bang-for-the-buck upgrades/replacements to the standard BOM listed on Pete Millett's website?

 Thanks,
 Vic


----------



## royewest

I just built an Alien DAC.

 The Alien DAC assembly page says about a pair of caps on the output end: "If your amp (or any other device you are going to connect your DAC to) has some input DC protection, do not populate CL and CR. This way you avoid all sorts of problems with coupling capacitors selection and mounting."

 So here's the beginner's question: Does the SSMH have "input DC protection"?

 Thanks in advance.


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I just built an Alien DAC.

 The Alien DAC assembly page says about a pair of caps on the output end: "If your amp (or any other device you are going to connect your DAC to) has some input DC protection, do not populate CL and CR. This way you avoid all sorts of problems with coupling capacitors selection and mounting."

 So here's the beginner's question: Does the SSMH have "input DC protection"?

 Thanks in advance._

 

NO, not in the sense that the Alien documentation means, anyway.

 For what it's worth, those output caps on the Alien are essentially the only protection afforded to the PCM chip, too. I won't digress into relating the entire sordid story, but suffice to say that I've blown out a couple of PCM chips from messing around with different connections when those output caps were not in the circuit.


----------



## tomb

Quote:


  Originally Posted by *V-DiV* /img/forum/go_quote.gif 
_I've just finished my summer commuting and will have some time for a project in the near term. I can't wait any longer for the SOHA II so I'm going to build a Starving Student. I watched this thread when it first started but haven't followed it for a while and I don't necessarily want to read all 600+ posts. Are there any consensus good-bang-for-the-buck upgrades/replacements to the standard BOM listed on Pete Millett's website?

 Thanks,
 Vic_

 

Change the size of the electrolytic caps to 470uf. 470uf for the caps in the back help tame the startup stutter of the VOIP power supply, while 470uf up front shoves the bass filtering down to ~10Hz for low impedance cans (Grados).


----------



## dsavitsk

For those of you waiting for PCBs, the next stage has been completed. Still no real ETA, but it is getting closer. The basic holdup right now is trying to figure out a decent heatsink strategy. In mine, I connected the mosfets to the case and added a largish sink. This barely even gets warm, so it is probably a little bit of overkill. This sort of construction might require a little more work for some, but it does allow just using a metal sheet as the top with a sink bolted on -- I used the Hammond case as it was sitting in a box of junk on the floor, but it is not a necessary expense. This style of construction also keeps the voltages inside the chassis, which is a good thing. 48V is probably not particularly dangerous, but it is enough to remind you that you are playing with electricity.


----------



## tomb

Very nice! This looks like a great solution if we can source the heat sinks. Where did you get it?


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Where did you get it?_

 

In the drawer of heatsinks I have ... I think it probably came from Nebraska Surplus. They seem to have more and anything on that page would be fine. I think CPU sinks would work, too, for those that have old computers sitting around that they can strip parts from. I'll also try just removing the sink and see how well the case works on it's own.

 One other thing worth noting, I used the cheapest caps that were 470u/63V/105 degrees I could find, and the cheapest resistors. I also used IRF610's as I have a drawer full of them. These things made little difference. Cheap is good for this project.


----------



## V-DiV

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Change the size of the electrolytic caps to 470uf. 470uf for the caps in the back help tame the startup stutter of the VOIP power supply, while 470uf up front shoves the bass filtering down to ~10Hz for low impedance cans (Grados)._

 

Thanks TomB. I gathered that much from the Aussie group buy thread. I had wondered if there were any easy swaps for an upscale part that would make a big difference, but I'll follow dsavitsk's advice that "cheap is good" for this project.

 Cheers,
 Vic


----------



## -=Germania=-

Hey Guys, Here are some early pics. 
 I do have a problem because it doesn't work. If anyone can look at the pics and help me, I would appreciate it! The left seems to be grounded (even at the pot), so please help me!
















 Thank You in advance!


----------



## n_maher

We need more info. Does it do anything? Tubes light up? Smoke? Fire? 

 Did you use insulating washers on the FETs? I can't tell from the pictures, but that'd be an easy thing to go wrong that I think would muck up the works. Heck, even if you did I'd check continuity with a DMM to be sure.

 And another one to check make sure that you have the power supply jack wired correctly, I've certainly been known to use the wrong tab on those switched jacks. 

 Also, I'd swear from looking at those pictures that you have the headphone jack wired wrong. Again, it's a little hard to see in the blurry pics but I just compared it to one of my amps that's sitting here and it sure doesn't look right.

 Otherwise, have you retraced the circuit with the schematic near by. It took me 5 times through mine to find the mistake that I made when I built mine.


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Hey Guys, Here are some early pics. 
 I do have a problem because it doesn't work._

 

It's hard to tell from the pics. But, a first step might be to work on the grounding. Pick a point and connect all the ground leads (input, output, pot, Rk, bottom of the heater, ps caps, power input, etc.) to that point. Beside the fact that this will cut down on noise once you get it going, it will also let us see a little better that things that should be grounded are, and things that shouldn't be, aren't.


----------



## Postal_Blue

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_
 Also, I'd swear from looking at those pictures that you have the headphone jack wired wrong. Again, it's a little hard to see in the blurry pics but I just compared it to one of my amps that's sitting here and it sure doesn't look right.._

 

X2 That was my first thought. Looks like you wired the switched side of the jack thus breaking the circuit when you plug the headphones in.


----------



## vixr

got mine on the run...tubes should be here this week.


----------



## pabbi1

Ok, time to fess up... caveat: I am NOT a machinist, and did all this with my Dremel, drill press and hand drill (stepped drill bit). The front panel was material left over from a Pars Metal case.

Parts
Case
Ground Plane
Front
Guts
Guts 2
Top

 Yes, balanced. I finished late last night, and decided to delay power up until tonight, since I wouldn't sleep otherwise - successful or not. The fancy parts were left over (Neutriks, Vampire XLR, ALPS stepped, Kimber RCA). Everything else was ~$100.


----------



## n_maher

Nice work guys!


----------



## vixr

pabbi1, outstanding work...


----------



## -=Germania=-

Well, if the inside pin is the power and the outside is ground, then the jack is wired correctly. 

 I think that the problem is that the plastic washer is on the wrong side and I used the metal one where the plastic should be. That would be a reason for it to have no power to the tubes. I realized the headphone jack issue as soon as I posted the pics. I just need to fix those problems and test again, going through the whole thing with a multimeter. 

 I am sorry for the low quality of the pics and how bad it looks in the pics. In person it is a very shiny gold and I am going to paint it up more once I get it built (crackle finish? or some other design. I promise that it will look very interesting and the two headphones stands I made also match the AMP (check out in the headphone stand thread).


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Well, if the inside pin is the power and the outside is ground, then the jack is wired correctly._

 

Which jack? The DC power jack? I'd hope that if you didn't know whether or not you had it wired correctly you'd just pull out your DMM and check it with power applied (but not attached to the circuit). I inherently don't trust wallwarts so I always check their polarity, it's just good practice. 
  Quote:


 I think that the problem is that the plastic washer is on the wrong side and I used the metal one where the plastic should be. 
 

You need to explain things better, or at least more completely. I'm pretty sure here that you're talking about the FETs and the isolating washers but I'm guessing and guessing makes me not want to help for fear of just wasting my time.


----------



## -=Germania=-

No - the fet washers - I have the metal one attached to the top of the screw instead of the plastic one. I will be back tonight and will try and mess around with it. I also plan to nix the copper plate to figure out the issue. 

 Thanks guys!


----------



## n_maher

Before making wholesale changes like the removal of the copper plate you might want to undertake some simple troubleshooting. Otherwise you're fighting a fire by burning down the house first.


----------



## -=Germania=-

I was going to connect all the grounds together because I know that something is getting grounded that shouldn't and it will result in a better sounding amp in the end (with a cleaner ground line). I need to fix other things, granted. We will see if those other things fix it - and then the tweeking will begin. Besides, I have some parts around and wanted to see the results of a bit of tweeking (within all ranges given). 

 But, I need to get it up and working first. The tubes are not getting power ATM and nothing seems broken. I will be working on this from 7:30 til about 10PM tonight - I will update then! 

 I do really love building stuff and it gives you the greatest feeling in the end.


----------



## n_maher

Assuming you've rechecked your layout against the schematic I'll say the following - before any of us give any more advice we need some information:

 Step 1: Check the wallwart. Report the results of measuring the unloaded voltage. If you blew the wallwart no amount of troubleshooting of the amp is going to make a bit of difference.

 Step 2: Check the power supply jack wiring. Measure and report the voltage at the dc inlet. If power isn't making it inside the chassis clearly that's problem #1 to solve.

 Step 3: Report the results of measuring voltage across C1.

 Then we can go forward. 

 However, if you insist on ripping the whole thing apart I'm going to throw my hands up in defeat. There's nothing wrong with the ground plane approach and assuming it's done correctly I'd question whether or not you'll get a "better sounding amp" using a star ground. I can guarantee that Pete's amp sounds better than mine and he used the copper plane.


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_There's nothing wrong with the ground plane approach and assuming it's done correctly I'd question whether or not you'll get a "better sounding amp" using a star ground._

 

I suggested a star ground because there were wires everywhere. I figured it would make -=Germania=- think about layout a little more, and it would make things easier to look at. But, either method is probably fine in this case.


----------



## m0b1liz3

This may be a silly question. I was wondering if you can use the case itself as a heatsink instead of the 2 black ones that most people are using for this build. I have a 2-3mm thick aluminum top I am going to use for the case and wondered if I could get away with using it directly as the heatsink.


----------



## n_maher

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_This may be a silly question. I was wondering if you can use the case itself as a heatsink instead of the 2 black ones that most people are using for this build. I have a 2-3mm thick aluminum top I am going to use for the case and wondered if I could get away with using it directly as the heatsink._

 

That's sort of hard to say with any certainty and at a minimum it would be safe to say that the case would get very hot. I wouldn't do it without some additional heat sinking or heat management.


----------



## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I suggested a star ground because there were wires everywhere. I figured it would make -=Germania=- think about layout a little more, and it would make things easier to look at. But, either method is probably fine in this case._

 

Agreed, it's not bad advice, but I think she's got a mountain to climb before she worries about the wires running everywhere. In theory (at least in my brain) the ground plane allows for a simpler layout and therefor one that should be easier to trouble shoot. Of course, it has its share of challenges, but a star ground would as well and would require that she rewire a large portion of the amp.


----------



## shortkidsrus

I just finished my build and I'm having a few issues.

 Upon initial power up, both tubes glowed, but audio only came through the left channel. All I could hear from the right was humming. In the process of testing voltages to try to narrow down the source of the problem, I accidently shorted my circuit somewhere.

 Now, nothing but humming comes out of both channels, and I no longer get 48V in. I tested the wall wart and it outputs 48V with no load. Only one of the tubes attempts to fire up, and it just pulses. The input voltage oscillates at the same frequency from 0 to approximately 10V. Any suggestions on how to figure out what I broke? Ha


----------



## shortkidsrus

Oh yeah, I swapped out the tubes with another set and nothing changed.


----------



## Pars

Quote:


  Originally Posted by *shortkidsrus* /img/forum/go_quote.gif 
_I just finished my build and I'm having a few issues.

 Upon initial power up, both tubes glowed, but audio only came through the left channel. All I could hear from the right was humming. In the process of testing voltages to try to narrow down the source of the problem, I accidently shorted my circuit somewhere.

 Now, nothing but humming comes out of both channels, and I no longer get 48V in. I tested the wall wart and it outputs 48V with no load. Only one of the tubes attempts to fire up, and it just pulses. The input voltage oscillates at the same frequency from 0 to approximately 10V. Any suggestions on how to figure out what I broke? Ha_

 

I haven't built one of these, but at first glance, I would disconnect the PSU and with your meter on ohms, check the power input to ground. If it is pulling the input power down to 0V, I would suspect a short or component fried to a short? Q1 is a possibility.


----------



## shortkidsrus

Yeah I was thinking that I had cooked one or both of the FETs. 

 I checked the power input to ground and it is not shorted.

 The symptoms have changed a bit:
 -Left channel tube lights up just fine
 -Input voltage is a steady 48V
 -Right channel tube remains dark, but voltage is zero across all right channel components except FET drain, which is 48V

 Is there a way to test a FET without switching it out?


----------



## tomb

Quote:


  Originally Posted by *shortkidsrus* /img/forum/go_quote.gif 
_Yeah I was thinking that I had cooked one or both of the FETs. 

 I checked the power input to ground and it is not shorted.

 The symptoms have changed a bit:
 -Left channel tube lights up just fine
 -Input voltage is a steady 48V
 -Right channel tube remains dark, but voltage is zero across all right channel components except FET drain, which is 48V

 Is there a way to test a FET without switching it out?_

 

Testing a MosFet, Testing
 The handheld simple test with a DMM seems to work pretty well when I've done it, but you'll need to remove the MOSFET, first. Note that use of a solder-sucker is contraindicated according to that article.


----------



## -=Germania=-

I am a supreme idiot!

 I seriously wired the pins on the socket in reverse!
 It was a relatively simple fix and this thing has some of the lowest hum I have ever heard in a tube amp. 

 I also got the HD580's in today and they sounded aweful with my solid state....They sound great, even stock, with this amp. 
 Sennheisers and tubes have always made a great mix! Thanks Pete for a great amp. 

 One thing is that I barely turn the pot at all and its loud. I think that you could power some low wattage speakers off of this thing easily.


----------



## -=Germania=-

BTW - sounds great with all of my headphones. 

 The SS is more analytical - but the tube sounds better. 
 Yeah, I am drinking a beer to celebrate now. My tubes have a golden glow which looks awesome reflecting off of the gold surface.


----------



## -=Germania=-

Pics:


----------



## fordgtlover

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I am a supreme idiot!

 I seriously wired the pins on the socket in reverse!_

 

Yep - it's worth paying attention to the responses 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_snip

 Also, I'd swear from looking at those pictures that you have the headphone jack wired wrong. Again, it's a little hard to see in the blurry pics but I just compared it to one of my amps that's sitting here and it sure doesn't look right.

 snip_

 

 Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_X2 That was my first thought. Looks like you wired the switched side of the jack thus breaking the circuit when you plug the headphones in._


----------



## keiths

I've finally got all the parts together and will start my Starving Student in a day or two. As a total newbie, I suspect I'll be posting a fair few questions here over the coming days 
	

	
	
		
		

		
		
	


	




 First off - I don't intend to go the "ground plate" way. I'm using a metal case and think I'll wire the grounds back to a tag. Do I have to isolate ALL the input and output sockets from the chasis? The rca input sockets and power jack have chasis-insulating washers, but the 6.35mm output jack and 3.5mm input jack don't. Am I going to get ground-loop hum if these components are grounded by the chasis AND wired to ground?


----------



## vixr

here is the latest on mine... It sounds really good.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I seriously wired the pins on the socket in reverse!It was a relatively simple fix and this thing has some of the lowest hum I have ever heard in a tube amp._

 

You shouldn't be getting any hum. Was the headphone jack the only issue? It would be good if you could share your trouble shooting experience so that if someone else has a similar issue the potential fix is already here in the thread.

  Quote:


 One thing is that I barely turn the pot at all and its loud. I think that you could power some low wattage speakers off of this thing easily. 
 

The gain is very high compared to other headphone amps but as previously discussed this amp's power into 8ohm would probably not be sufficient to drive even efficient speakers. Unless you're talking tiny desktop computer types.


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_here is the latest on mine... It sounds really good.
 <IMG]http://www1.picfront.org/picture/EUE3xH29/img/inside1.JPG[/IMG>

 <IMG]http://www1.picfront.org/picture/UKHw2mu31OR/img/outside1.JPG[/IMG>

 <IMG]http://www1.picfront.org/picture/2Fgh5AXU7QS/img/tube1.JPG[/IMG][/URL]_

 

Pretty cool, Vixr! I like the Lansing case - we don't see many of those around here. That may change soon, I hope, but it's not a topic for this thread.


----------



## vixr

thanks Tom, This was a really cool learning project for me...P2P is not nearly as hard as I once thought. I had most of the parts and getting the tubes was easy too.


----------



## -=Germania=-

^ The noise floor is virtually non-existant....but I can hear a bit of it. I have to admit that its is noisier with even relatively clean sources. 

 I was able to fix the problem by simply going over data sheets again and realized that I had wired the tube socket in reverse and it was grounding out the tube. 

 I have to admit that having the ground starred did help me trace things better and figure out the issue. Once that happened, it was darn simple to fix. 

 I should also mention that I just used some cheap hook-up wire like the kind that you can get at radio shack (stranded) and it worked just fine. I can imagine that this amp might scale well with upgrades on the capacitors (I used 220's on mine - Nicho) in terms of quality and then using better hookup wire (minimizing the length of the tinned copper components). Now that I have one built, I am almost thinking of doing a balanced version! 

 I have to say that these sound really great. Also, where have you gotten your tubes that glow purple and gold. Mine is a nice gold color, but I might want to try a few different tube brands and see difference. 


 About using as an amp for speakers. I would say that anything that can be powered by the S.E.X. Bottlehead Amp would run just fine off of this amp. Also, mini monitors or computer monitors would sound really great with this small amp. I have some around somewhere, I will test and get back.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_^ The noise floor is virtually non-existant....but I can hear a bit of it. I have to admit that its is noisier with even relatively clean sources._

 

It has some noise floor sure, but if you're hearing humming, buzzing or otherwise there's an issue that is not intrinsic to the design. More than likely it's with the grounding but impossible to say for sure not knowing what type of noise you're talking about.

  Quote:


 I was able to fix the problem by simply going over data sheets again and realized that I had wired the tube socket in reverse and it was grounding out the tube. 
 

Glad you got it working. A small hint for others: some, but not all tube sockets have their pins numbered on the bottom. 


  Quote:


 About using as an amp for speakers. I would say that anything that can be powered by the S.E.X. Bottlehead Amp would run just fine off of this amp. 
 

Say what? 
	

	
	
		
		

		
		
	


	







 The Bottlehead is a trafo-coupled design and capable of about 2W output into 8ohms in stock form. The SSMH puts about 1/2W into 100ohms and .25W into 32ohms so you can see where this is going when you move to an 8ohm load. And there are other factors that make this a pretty poor (if not awful) speaker amp, the first of which is the cap coupled output stage. But as you've demonstrated you don't have much use for my advice so I'll just stop.


----------



## -=Germania=-

^ I only say that because I hooked up some cheap bookshelfs to it and they did fine powering it. 

 It would likely be fine for those computer speakers if you don't want to have two amps (use a switched jack for output to some speaker posts). However many of those computer speakers have a mini input, so there would likely be no need. 

 I trust your opinion more than my own, but I am just going by experience. 

 I have yet to hook these up to a set of really nice speakers, but it could make a really good desktop solution to have a switched system and are using those speakers I was talking about (maybe like the ones Travegan sells?).


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_^ I only say that because I hooked up some cheap bookshelfs to it and they did fine powering it._

 

Define "fine". Made noise, sure, but with those 220uF output coupling caps you said you used you have a -3db point nearing 100Hz (assuming 8ohm speakers). That's pretty non-ideal and if they're closer to four you can double that rolloff point. You'd need to triple the cap value to get a more acceptable number and then you're probably going to start having issues with on/off thump if you don't already. And odds are the amp was clipping even if you weren't hearing it.

  Quote:


 I have yet to hook these up to a set of really nice speakers, 
 

I would suggest never doing that.


----------



## vixr

Nate, I used the 220uF caps because I had em laying around. I haven't noticed any problem driving my HD-600s...are the 220uF caps too small?


----------



## Pars

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_Nate, I used the 220uF caps because I had em laying around. I haven't noticed any problem driving my HD-600s...are the 220uF caps too small?_

 

Not for headphones... for 4-8 ohm speakers they are unless you hate bass...

 -3dB point:

 1/(2 * Pi * R * C) where C is in farads


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_Nate, I used the 220uF caps because I had em laying around. I haven't noticed any problem driving my HD-600s...are the 220uF caps too small?_

 

For your Senns and even Grados, they're just fine. 

 The equation for the cutoff frequency of a high pass filter (which is what the cap coupled output forms with your headphones) is 1 / [2 * pi * R * C] where R is the impedance of your headphone and C is the value of the cap used in Farrads (note that 1uF = 1 x 10^-6F)

 In your example R = 300 and C = 220 x 10^-6 so we get a -3db point of 2.41Hz which I think is plenty low. 
	

	
	
		
		

		
		
	


	







 [edit]Pars is clearly faster, but I provide better examples.


----------



## ingwe

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_
 I trust your opinion more than my own, but I am just going by experience. 
_

 

Please, please, please, please...get a clue. They're all over the place, jumping up and down, waving their hands, making incredibly patient efforts to be polite and helpful.


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_It has some noise floor sure, but if you're hearing humming, buzzing or otherwise there's an issue that is not intrinsic to the design. More than likely it's with the grounding but impossible to say for sure not knowing what type of noise you're talking about._

 

It may also just be the PS. Tube amps can be mode quiet enough that you can't tell they are on, but the PS filtering here is pretty minimal which will likely lead to a little bit of hiss. Probably not worth worrying about for this project.

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_A small hint for others: some, but not all tube sockets have their pins numbered on the bottom._

 

Another small hint is that tubes pins are numbered in the opposite direction from transistors.



  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_The Bottlehead is a trafo-coupled design and capable of about 2W output into 8ohms in stock form._

 

The transformer reduces Zout which is not necessary here. Also, I think the 2W rating might be a little generous there.

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Define "fine". Made noise, sure, but with those 220uF output coupling caps you said you used you have a -3db point nearing 100Hz (assuming 8ohm speakers). That's pretty non-ideal_

 

Actually, while it is never going to be loud or thumping, that seems fine to me for making a little noise on a desktop. I doubt the speakers go below 120Hz on their own anyway. I think it is worth the try, and it is doubtful that anything will be damaged by the experiment. At worst, it sounds too quiet and distorted. Also, you may eek out a tiny bit more volume by putting a small capacitor (100uF/16V is plenty big) across R5 and R11.


----------



## pabbi1

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_ Now that I have one built, I am almost thinking of doing a balanced version!_

 

Unless you really want to drive small speakers, I'd recommend against this from first hand experience. The gain is 4x, and my smallest setting you can hear from across the room on my Senns, at least on the channel(s) that works. 

 The other channel(s) is loud static - scortched Mosfet? I'll look more tonight, but it is amazing how many joints I missed on p2p initially. Didn't test to see if the static got louder with the pot, as it was either my HD600 or 650 to test on... and, of course, I used the 650.

 Vixr, beautiful work. Seriously. Very, very nice.

 Since the gain is so high (4X x 15 = 60?) or so, at least that is how loud it sounds (and, no, it was not for extended periods), is there a way to tame the balanced gain? I'm using 50k stepped pots, and 470uF everywhere except c1 @ 150uF.


----------



## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_It may also just be the PS. <snip> Probably not worth worrying about for this project._

 

It may be the PS, but my amp is built with about as non-ideal an layout as can be done and has no hum or buzz. It also sits on my desktop in about as noisy a place as can be found (computers, monitors, fluorescent lights, etc.) and the only noise is a slight hiss at max volume. Her amp may be fine, but buzzing makes me think it's not.

  Quote:


 Actually, while it is never going to be loud or thumping, that seems fine to me for making a little noise on a desktop. I doubt the speakers go below 120Hz on their own anyway. I think it is worth the try, and it is doubtful that anything will be damaged by the experiment. At worst, it sounds too quiet and distorted. Also, you may eek out a tiny bit more volume by putting a small capacitor (100uF/16V is plenty big) across R5 and R11. 
 

I'm just trying to through a little caution in here before the inevitable "can this thing power my floorstander" questions start in once one person reads that it was used with any speaker. Bottom line if all you need is an 1/8th of a watt or so then yes, you can probably run some very small, efficient speakers with it if you size the output coupling cap properly. But I wouldn't expect great things out of it even when modified as much as possible. There are other ways to build cheap speaker amps that won't cost a lot more and will put out 1000x more power (gainclone).


----------



## holland

.


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm just trying to through a little caution in here before the inevitable "can this thing power my floorstander" questions start in once one person reads that it was used with any speaker._

 

Caution and DIY shouldn't mix 
	

	
	
		
		

		
			





 The whole point is to experiment and learn something.

  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_There are other ways to build cheap speaker amps that won't cost a lot more and will put out 1000x more power (gainclone)._

 

The amount of power that people need is generally overestimated. I have been living with 8W amps in my main system (with fairly inefficient speakers) for years, and I never use even a fraction of that. If you are pushing 100W amps to their max, your hearing is most likely damaged from it.

 Anyway, I have some little computer speakers that my neighbor threw out when he moved. I hooked them up, and this amp could make them much louder than I'd ever want for background music. For a desktop, I think this would work fine.






 These reached volumes I would define as "loud" long before any audible clipping set in. Sound quality was crappy, and bass was non-existent, but for background, it was fine.


----------



## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Caution and DIY shouldn't mix 
	

	
	
		
		

		
		
	


	




 The whole point is to experiment and learn something._

 

Fair enough, in the future I shall revise my stock answer to be "please ask dsavitsk". 
	

	
	
		
		

		
		
	


	




  Quote:


 The amount of power that people need is generally overestimated. 
 

I agree, wholeheartedly. 

  Quote:


 For a desktop, I think this would work fine. 
 

All depends on your desktop. Mine uses a pair of Ascend Acoustics CBM-170s which probably won't perform as well as your speakers did and I don't think I'd try it either.


----------



## J.D.N

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_
 These reached volumes I would define as "loud" long before any audible clipping set in. Sound quality was crappy, and bass was non-existent, but for background, it was fine._

 

Surely such a statement should never be uttered in an 'audiophile' forum?


----------



## -=Germania=-

BTW - my choice on the caps was purposeful. 

 I am much more of a treble and mids person, I like only a little bass and not the traditional thump that comes with tubes. 

 My preference in the past has been for SS amps that are on the lean side. I most certainly will play around with even more caps and parts and such, but it sounds really good now. 

 I do agree that anyone expecting to power something beyond small speakers or very efficient bookshelves will be disappointed. 

 However, if you are looking to have an all-in-one system for the office or desktop.... I think that putting a switched jack with speaker posts wouldn't be a bad idea or even just a mini jack (like what many computer speakers use). 

 If you want to make this as purely a speaker amp, look elsewhere, but if you just need a simple solution..What is wrong with this one?


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_BTW - my choice on the caps was purposeful._

 

How so? I'm going assume for a second that you mean the value, not the brand or sonic signature of the cap.

  Quote:


 I am much more of a treble and mids person, I like only a little bass and not the traditional thump that comes with tubes. 
 

You know, the more you post the more confused I get. From what I read your can of choice is the AKG K400 which have a nominal impedance of 120ohms. Given your purposeful choice of 220uF caps your -3db point was 6Hz. What, exactly, do you think you were intentionally filtering out of the signal? And I don't even know what to say about the "traditional thump" comment. You might as well have said that you chose the gold enclosure hoping for a bright sounding amp. I know I chose a black chassis hoping for a blacker background. 





  Quote:


 I do agree that anyone expecting to power something beyond small speakers or very efficient bookshelves will be disappointed. 
 

Woot! I think you just said what I said about 30 posts ago when you were telling me that this would perform as good as the Bottlehead...


  Quote:


 If you want to make this as purely a speaker amp, look elsewhere, but if you just need a simple solution..What is wrong with this one? 
 

:timewarp:


----------



## vixr

@ holland, it is a steel case with some sort of plastic paint on it, inside and out. LOL at Nate...I thought a light colored case would use less power? All my black Hammond cases run down batteries like crazy...


----------



## rds

Quote:


  Quote:


 Originally Posted by -=Germania=- View Post


 I trust your opinion more than my own, but I am just going by experience. 
 

Please, please, please, please...get a clue. They're all over the place, jumping up and down, waving their hands, making incredibly patient efforts to be polite and helpful. 
 

That's kind of surreal. I have no idea what that is supposed to mean.


----------



## ingwe

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_That's kind of surreal. I have no idea what that is supposed to mean._

 

Don't concern yourself. It wasn't addressed to you.


----------



## -=Germania=-

There is a lot of hate in this DIY thread and its not just directed at me. Where is the love?

 BTW - I would not expect the S.E.X. to work well powering big speakers either. I am sure that there are people doing it....and I am sure that it plays them at listen-able levels. I have seen some small horns in large casings where this works fine. I have been able to power speaker to loud levels even on my Headsix and it sounded pretty decent!

 If you are on this forum I can almost guarantee that you are not coming here to learn how to make a speaker amp. 

 Nate....

 It might be unreasonable to say that because it sounds good with headphones that it wouldn't with speakers. After all, headphones are just tiny speakers that have a specific purpose. 





 The capacitors were a purposely chosen VALUE, not brand specifically. 

 I have heard a fair amount of tube amps with headphones and all of them have had very thumpy low bass which was easily heard. That is not my style and that is the whole purpose of DIY, to get exactly what you want out of it.


----------



## lynxkcg

Look what came in my mail today! 





 The rest of the parts should be here by monday. I gotta admit, I've only been reading up on headphone amps for a week, but I had to do something about the noise problem on my current setup. What really got me motivated to build this amp is the fact that tubedepot.com is about 15 minutes from my house. Can't wait to get this thing built so I can hear what I've been missing!


----------



## tomb

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_@ holland, it is a steel case with some sort of plastic paint on it, inside and out. LOL at Nate...I thought a light colored case would use less power? All my black Hammond cases run down batteries like crazy..._

 

If I'm not mistaken, it's actually a vinyl covering over steel. The endplates can be aluminum like a Hammond, while the bottom is a thick piece of extruded aluminum. There are plastic bezels on both ends like the Hammond. At least, that's how the one is made that I used for the MiniMAX.

 They have other models that don't use the vinyl-covered steel, but I kind've like it.


----------



## rds

Quote:


 Where is the love? 
 

The internet killed off all the love back in 98


----------



## -=Germania=-

^Nice!

 Now I want more tube sets! - awww this hobby never ends does it?


----------



## holland

.


----------



## -=Germania=-

I totally want to see how the Mini Millet come on this forum!


----------



## bperboy

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I totally want to see how the Mini Millet come on this forum!_

 

Heh heh, I wanna see the Mosfet Max website! 
	

	
	
		
		

		
			





*
 [size=small]Coming Soon!
 [/size][size=x-small]Mid-March, 2008[/size]*






 Tee-hee Tom, I guess July is the new March! 
	

	
	
		
		

		
		
	


	




 Haha, no hurries though; we all are really appreciative of all the work you've done on these projects!


----------



## tomb

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_Heh heh, I wanna see the Mosfet Max website! 
	

	
	
		
		

		
		
	


	




*
 [size=small]Coming Soon!
 [/size][size=x-small]Mid-March, 2008[/size]*
 <IMG]http://www.diyforums.org/MOSFET-MAX/MOSFET-MAX.gif[/IMG>


 Tee-hee Tom, I guess July is the new March! 
	

	
	
		
		

		
		
	


	




 Haha, no hurries though; we all are really appreciative of all the work you've done on these projects!_

 

Yeah, we're behind - that's true. However, we're trying to get the power supply as clean as we can make it. I've got a lot of work to do this weekend concerning that. Bottom line, cetoole and I are perhaps within a week or two of ordering prototype MiniMAX boards. The MOSFET-MAX may be closer than that.

 But I digress ... and discussing this is a thread-jack - even if it's still "all things Millett." So, please accept my apologies, Pete/Nate. You all know where to look to find the updates on this other stuff, though.


----------



## Chipp

Ugh, these darned things arrived in the mail today. Looks like I have to build an amplifier now.


----------



## keiths

Somewhere in this thread it says that "R3 and R9 should be directly connected to the gate legs of the MOSFETs" - how important is the "directly" bit of this. Would an inch or so of wire make any difference?

 Also, would it be OK if I connected C3 and C5 to pin 3 of the valve bases (and then run a wire from pin 3 to the source leg of the FET) rather than directly to the source legs of the MOSFETs (for neatness reasons as the valves are closer to the output jack than the FETs are in my layout)?

 Sorry if these are stupid questions - I've never worked a layout out from a schematic before.


----------



## -=Germania=-

It is a good idea if you can, but I definitely believe that you can have a small piece of coated and/or tinned wire between the two. 

 My case is thicker than any I have seen on the forum and that made me have to use a small piece of wire to extend the pins, that one included. The whole thing is to be reasonable and try to keep it as close as you can. Make sure that you have very secure and clean solder joints as this always translates to a better overall product.


----------



## Pars

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Somewhere in this thread it says that "R3 and R9 should be directly connected to the gate legs of the MOSFETs" - how important is the "directly" bit of this. Would an inch or so of wire make any difference?_

 

 Quote:


  Originally Posted by *tomb* 
_2. Do you have R3 and R9 tied directly to the gate legs of the MOSFETs? Pete and Nate both have mentioned a couple of times that *might induce oscillation* if that isn't done. It's hard to say if that attributes to the hum, but my guess is that it will definitely cause more noise._

 

The reason for this is the additional inductance of either long leads or wire. I'm guessing that additional wire/lead length on the other side of R3/R9 is not critical, but that is just a guess.


----------



## keiths

Thanks -=Germainia=- and Pars - I'll take that advice onboard. Regarding the C3 and C5 question, I've just looked at the photos of vixr's build a few pages back, and it looks like he's connected those the same way as I was intending.

 Thanks again!


----------



## scompton

I'm just about to start my build and I have a few questions.

 I was print out the data sheets in preparation of drilling the holes in the case and I noticed the power jack in the BOM is only rated for 12V. Don't I need one rated for over 48V such as this?

 Most of the data sheets don't say how to wire up the component. That's fine for the jacks, but are there instructions somewhere for how to wire up a pot?

 Edit: I found this post on wiring a pot. So I'll go with it.

  Quote:


 Three terminals for each section of the pot. The middle terminal is the wiper and is the output of the pot, that goes to the amp circuits. The input feeds to the one one the right side of the pot, when the shaft of the pot is facing you. The left terminal goes to ground. The second section of the pot is the same, only it gets used for the other channel. If that doesn't clear it up, let me know, as I know sometimes written explinations are tough to make sense of.


----------



## royewest

WRT layout, I figured out a lot by poring over the build photos on this thread....


----------



## scompton

Looking at the pictures, I can see how the power jack is wired, but in Pete's picture, it looks completely different than what I ordered. His has a square of brown material under the pins, mine doesn't. Also mine didn't come with nuts to hold them in. Do they usually come with nuts, or do you have to order them separately.

 I went to Radio Shack and bought a power jack. However, no where is there an indication of how many volts it can handle.


----------



## pmillett

A little underwhelming for a desktop amp, but this thing can deliver about 150mW into an 8 ohm speaker. You probably want some 1000uF or bigger output caps, though.

 Then there's always something like what I use...
	

	
	
		
		

		
		
	


	




Hybrid amp with adjustable damping

 Pete


----------



## pmillett

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_However, no where is there an indication of how many volts it can handle._

 

Don't worry about it, 48V is fine with any of these things. Just make sure the center pin is +48V and the outer contact is ground...

 Pete


----------



## TimJo

So I finally got around to building one of these yesterday, and it is sounding really great. I am totally impressed with the quality of the sound considering the cost of the build. Thanks Pete for creating another brilliant design and giving it to the world to build. So far I have only used RCA's, but look forward to rolling others over the coming days. I find (at least with these RCA's) that I like listening with my AKG 701's better than my Beyer's. I'll see if that changes with other tubes.

 This was my first time trying point-to-point, so it was good practice before delving into building my Bottlehead Seduction. Not really knowing much about it, I set out with the goal of trying to keep signal paths as short as possible, and for the most part I think I did okay on that. After doing this first one, I might do things a bit differently next time, but that's what this all about, right? 

 I decided to use a star ground layout, although in some ways it seemed redundant with an aluminum case. The only thing about this was it did create a spiderweb of ground wires, so what seemed like a pretty clean layout on paper ended up looking quite messy in the end, but oh well. I can say this, it is dead quiet. With the volume cranked to max, I can barely even hear a hiss on my 701's.

 I also decided to build three little sub-assemblies on the bench first, and then wire them into the chassis as a unit. That worked out quite nicely, especially if I decide to play around with a different power supply configuration down the road. I can just swap out that assembly without much work at all.

 I never found a "salvaged" case to use, so I went with the style that _trains are bad_ used. I liked the look of it. I took some pictures, but realized I forgot to put on the volume knob when I took them, so use your imagination for that.


----------



## V-DiV

I'm waiting for my parts to arrive from Mouser. In the meantime, my power supply arrived from an eBay seller and my tubes from Radio Daze. The tubes were made by Hytron. I don't remember seeing that manufacturer's name in this thread. Does anybody know about these?


----------



## tomb

Quote:


  Originally Posted by *V-DiV* /img/forum/go_quote.gif 
_I'm waiting for my parts to arrive from Mouser. In the meantime, my power supply arrived from an eBay seller and my tubes from Radio Daze. The tubes were made by Hytron. I don't remember seeing that manufacturer's name in this thread. Does anybody know about these?_

 

CBS-Hytron was a fairly common brand for many tubes. I haven't studied these tubes, yet, but it's quite possible that many of them are another case of wide subcontracting and re-branding. It might be more fruitful to note the construction details rather than the painted-on brand for distinguishing tube differences.

 There are some distinguishing features that are consistent for almost any tube, though - acid-etched tube designators and white dots are certain to be of GE manufacture. An etched "squished" octagon with the tube designation inside is almost certainly an RCA.


----------



## V-DiV

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_An etched "squished" octagon with the tube designation inside is almost certainly an RCA._

 

These must be RCA. The 19J6 designation is inside a rectangle with diagonal corners (making it a quasi octagon).


----------



## tomb

Quote:


  Originally Posted by *V-DiV* /img/forum/go_quote.gif 
_These must be RCA. The 19J6 designation is inside a rectangle with diagonal corners (making it a quasi octagon)._

 

Yep - that's a sure tell-tale for RCA manufacture.


----------



## shortkidsrus

So I determined that the FETS were cooked. I replaced them and now my left channel runs perfectly.

 The right channel on the other hand...I get nothing but static/humming. I checked the voltage coming from the third pin on the tube and it reads around 40V, which is much higher than the desired 19V. This seems to correlate with the fact that the right channel tube burns significantly brighter than the left channel. I did read that MOSFETs tend to take out surrounding components when they go bad, so I checked all the of the right channel resistors and replaced the caps. The issue remained the same, so I'm thinking that it must be a wiring issue. Any other ideas? Thanks for all the help so far...this is my first DIY project, so I have a lot to learn!


----------



## TimJo

^ Any chance that you could post some photos of your wiring?


----------



## scompton

I have a question about the grommets. I assume they're to keep the pins of the mosfet from grounding. Is this correct? The problem I have is when I put them in the holes, the pins for the heat sink just barely touch to top of the case. There's no way I can solder it. I can't find a good picture of the grommets and heat sink in this thread. Am I doing something wrong?

 Edit: I see that some people have a notch in the bottom of their heat sinks. Mine doesn't have that even though the picture on the data sheet shows one. Could this be my problem?


----------



## srserl

I didn't use grommets, but I used heat shrink on the legs of the mosfets instead.

 Scott


----------



## Zigis

Nice looking amp, TimJo!

 This is something in the air, yesterday i purchase tubes and today morning, before turning in PC I thinking about building amp in retro stile with sloping front panel and all inputs, outputs on it.
 And than I turn on PC and see your design, very close shape to what I thinking about!


----------



## TimJo

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Nice looking amp, TimJo!_

 

Thanks! 

 This case came from Mouser. MDC-642-PLAIN-ALUM It looks like they sold out, but they have more on order. Although, since you are in Latvia, you'll likely not be using Mouser.

  Quote:


  Originally Posted by *srserl* /img/forum/go_quote.gif 
_I didn't use grommets, but I used heat shrink on the legs of the mosfets instead.

 Scott_

 

scompton, that's what I did as well. As long as the leads are covered, and not touching the edge of the hole so the metal doesn't wear thruogh the heat shrink over time, you'll be fine.


----------



## shortkidsrus

Quote:


  Originally Posted by *shortkidsrus* /img/forum/go_quote.gif 
_So I determined that the FETS were cooked. I replaced them and now my left channel runs perfectly.

 The right channel on the other hand...I get nothing but static/humming. I checked the voltage coming from the third pin on the tube and it reads around 40V, which is much higher than the desired 19V. This seems to correlate with the fact that the right channel tube burns significantly brighter than the left channel. I did read that MOSFETs tend to take out surrounding components when they go bad, so I checked all the of the right channel resistors and replaced the caps. The issue remained the same, so I'm thinking that it must be a wiring issue. Any other ideas? Thanks for all the help so far...this is my first DIY project, so I have a lot to learn!_

 

 Quote:


  Originally Posted by *TimJo* 
_^ Any chance that you could post some photos of your wiring?_

 

Here are some pics of the wiring. The wires going into space are attached to the MOSFETs.

 Entire board:





 Lower Section (plugs, etc.)










 Various angles of the right channel:










 Left Channel:


----------



## m0b1liz3

Thanks for the wiring pics. That will hopefully help when I build mine in a week or so. Which leads me to my first silly question:

 For the on/off switch, does it need to be rated to a certain voltage? I thought about using this:

Ring Illuminated - Red (12v), 16mm, SS, 2mm terminals (On/Off) [ASS162FARR12] - $9.85 : GAM Mods, PC Modding Products

 Does it matter if it is only rated to 12v? I am guessing it could work for my amp 6 but not for the millett ss. 

 Anyone know of a similar switch to the vandals?


----------



## JamesL

Only the LED is rated for 12v, the switch is rated for 240VAC, which is plenty.


----------



## m0b1liz3

yeah, i was just looking at it closer because it made no sense at all to have it rated for 12v! i feel silly now!

 so time for the second silly question:

 how do i wire up the led so it gets 12v delivered to it? if the power supply is 48v then i would need to put a few resistors in series right? what values?


----------



## adamus

use the current rating for the led, then work it out with ohms law.


----------



## m0b1liz3

"Rated Voltage* 12v 
 Lamp Life Approx. 40,000 hours 
 * Lamp contains a current limiting resistor to achieve the specified voltage."

 It didn't really rate the mA specification for the LED. Does the above statement mean I don't need to add anything? 

 I was also wondering at what point in the wiring schematic it would be best to add the wires to power the LED.


----------



## holland

.


----------



## lynxkcg

I got a little too excited yesterday and dove into this without any plan at all..... It wasn't pretty; however it did work.






 Then I took it apart and built this.


----------



## HeadphoneAddict

What was wrong with the first attempt?


----------



## keiths

Where's the best place in the curcuit to insert an LED power indicator?


----------



## rds

Quote:


 Where's the best place in the curcuit to insert an LED power indicator? 
 

Off the 48V power supply.


----------



## keiths

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Off the 48V power supply._

 

Is this OK? When I used the LED resistor calculator at LED center to calculate the current-limiting resistor it warned me that a supply voltage >24v would dissipate excessive heat through the resistor (LED forward Voltage = 2.5v, Forward Current = 20mA, Supply Voltage = 48v. Resistor value = 2k7 2W)


----------



## tomb

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Is this OK? When I used the LED resistor calculator at LED center to calculate the current-limiting resistor it warned me that a supply voltage >24v would dissipate excessive heat through the resistor (LED forward Voltage = 2.5v, Forward Current = 20mA, Supply Voltage = 48v. Resistor value = 2k7 2W)_

 

It's OK as far as it goes, but you don't need 20ma - especially just for a power indicator. The chances are much higher that the LED will burn out over a short time. Plus, as you note - the power rating of the resistor becomes an issue.

 You could pick a common-size resistor such as a 5K, then plug it into the Ohm's Law equations:

 I = 48V/5000ohms = 9.6ma. P= (0.0096^2) * 5000 = 0.46W,
 You'd want to have a 2X safety factor for heat, so a 1W resistor would do fine.

 Or, you could go all the way to 10K:
 I = 48V/10000ohms = 4.8ma. P= (0.0048^2) * 10000 = 0.23W,
 a fairly typical 1/2W resistor would do fine in that case.

 4.8ma for a panel-mounted power indicator LED is not at all unusual. For instance, amps such as the PIMETA or Mini3 use power indicator LED's that are down in the ~1-3ma range.


----------



## keiths

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Or, you could go all the way to 10K:
 I = 48V/10000ohms = 4.8ma. P= (0.0048^2) * 10000 = 0.23W,
 a fairly typical 1/2W resistor would do fine in that case._

 

Thanks TomB. I don't have a 10K 0.5W resistor, but I have two 22K 0.25W ones - I'll be OK using those in parallel, won't I?


----------



## vixr

At the risk of sounding like a wise guy, The tubes on mine light up pretty bright...I think you could almost leave out the LED.


----------



## n_maher

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_At the risk of sounding like a wise guy, The tubes on mine light up pretty bright...I think you could almost leave out the LED._

 

I was going to post something like that, so it's not just you. Even if they don't glow brightly it's pretty quickly obvious if you've got power or not.


----------



## keiths

Yeah, I guess I'd not have too much trouble telling if it's on or not without the LED 
	

	
	
		
		

		
		
	


	




 I'm using a knob on the volume pot that's numbered (not up to 11, unfortunately) and want something colourful to use as the index marker. A led seems to fit the bill nicely.


----------



## tomb

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Thanks TomB. I don't have a 10K 0.5W resistor, but I have two 22K 0.25W ones - I'll be OK using those in parallel, won't I?_

 

Well, I'm not a wise guy
	

	
	
		
		

		
		
	


	










, so I would suggest just using the single 22K resistor, period. That would work out to 2.2ma and 0.1W, so a 1/4W resistor would be fine. If that doesn't work to suit you, you can always replace the resistor later.

 The wise guys make a good point 
	

	
	
		
		

		
		
	


	




, but an LED taken close to the power switch can provide an indication of a hot circuit when the tubes aren't in there. They take awhile to light up, too - which can cause some uncertainty for a few seconds, anyway.


----------



## vixr

this lighted rocker is kinda attractive...around 2 dollars at Mouser.


----------



## Mazuki

Quote:


 They take awhile to light up, too - which can cause some uncertainty for a few seconds, anyway. 
 

Those few seconds of uncertainty can give you a heart attack


----------



## vixr

Quote:


  Originally Posted by *Mazuki* /img/forum/go_quote.gif 
_Those few seconds of uncertainty can give you a heart attack_

 

yes...my first power up was ugly...it took forever


----------



## holland

.


----------



## lynxkcg

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_What was wrong with the first attempt? 
	

	
	
		
		

		
			



_

 

Right channel had picked up quite a hum and I couldn't close the box 
	

	
	
		
		

		
		
	


	



 My soldering isn't up to par yet and it hissed and popped at the slightest movement. I'm much happier with second build and already planning on what to change for a third one.


----------



## -=Germania=-

Yeah, the first power up is a pain and I think that it really needs 5 min to be truly rearing to go anyways. That isn't different from most tube amps I have seen.


----------



## Mazuki

I've gotten started on my Staving Student Hybrid, I should have everything done by the weekend.


----------



## bperboy

^^^ 

 Those are some pretty sweet 'sinks! Lookin good so far!


----------



## vixr

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_^^^ 

 Those are some pretty sweet 'sinks! Lookin good so far!_

 


 I thought the same thing... I would have had to mount the tube sockets in the center of them though...


----------



## Mazuki

Quote:


 I would have had to mount the tube sockets in the center of them though 
 

But the the mosfets wouldn't have been heatsinked properly


----------



## vixr

Quote:


  Originally Posted by *Mazuki* /img/forum/go_quote.gif 
_But the the mosfets wouldn't have been heatsinked properly_

 

I type faster than I think sometimes...but mine dont really get hot. I think mounted off center would be OK.


----------



## amphead

Quote:


  Originally Posted by *Mazuki* /img/forum/go_quote.gif 
_I've gotten started on my Staving Student Hybrid, I should have everything done by the weekend.









_

 

Certainly a beautiful case! Good job man!


----------



## joe_seattle

Hi everyone. I've ordered and received all the parts to build this amp and am ready to get started soon. This will be my very first DIY project...which is exciting.

 A few questions...can anyone recommend a good order for the assembly - meaning an order where I can test things along the way with a minimal amount of risk of damage? Also, will the length of wires I use greatly impact the sound quality? What I really mean: if it looks like a rat's nest, but all the connections are fine, am I still ok? Is there a big difference in using an all-metal enclosure vs the copper plate attached to a wooden enclosure like a cigar box?

 Thanks!


----------



## holland

.


----------



## MisterX

Hammond Mfg. - Diecast Aluminum Enclosures (1590 Series) ?? 

 To bad Steve at Small Bear doesn't offer larger cases with powder coated finishes like he does for the "Taiwanese 'BB' Size" cases because that would be wicked. 

Enclosures


----------



## bhjazz

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_Hi everyone. I've ordered and received all the parts to build this amp and am ready to get started soon. This will be my very first DIY project...which is exciting.

 A few questions...can anyone recommend a good order for the assembly - meaning an order where I can test things along the way with a minimal amount of risk of damage? Also, will the length of wires I use greatly impact the sound quality? What I really mean: if it looks like a rat's nest, but all the connections are fine, am I still ok? Is there a big difference in using an all-metal enclosure vs the copper plate attached to a wooden enclosure like a cigar box?

 Thanks!_

 

Hey Joe! Welcome!
 I haven't seen any official "order of build" for this amp, but you might search the thread to see if anyone has tried a 9 volt battery prior to pluggint it in. I would imagine that nobody has done this because the cost is pretty low for the amp. 

 Rat's nest: try not to. If you stay organized while building, your amp will be that much easier to troubleshoot if you have problems later. There is a small chance that you could minimize some induced noise, but let's just get the basic build working for you first.

 Have fun.


----------



## holland

.


----------



## n_maher

PTP doesn't really lend itself to a build order simply because how you go about it is completely layout dependent. I'd suggest figuring out where you want the major components to go first and then do a rough wiring diagram.


----------



## Mazuki

Quote:


 Mazuki,

 What case is that? It looks nice and thick for a small case of that size. 
 

It's a Bud Industries case. The only reason I chose it over the Hammond was because it's cheaper. 

  Quote:


 Hammond Mfg. - Diecast Aluminum Enclosures (1590 Series) ?? 

 To bad Steve at Small Bear doesn't offer larger cases with powder coated finishes like he does for the "Taiwanese 'BB' Size" cases because that would be wicked. 

Enclosures 
 

Oh man, had I seen that, I wouldn't have spent the hours polishing that nasty Bud case!


----------



## bhjazz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_PTP doesn't really lend itself to a build order simply because how you go about it is completely layout dependent. I'd suggest figuring out where you want the major components to go first and then do a rough wiring diagram._

 

/golf claps

 Nice. Good answer! Yes, I think getting item locations set up first is a great start.


----------



## royewest

As I may have mentioned before (heh), the many high-resolution photos on this and related threads are an enormous help to a beginner, when trying to steal^h^h^h design a layout.


----------



## scompton

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_PTP doesn't really lend itself to a build order simply because how you go about it is completely layout dependent. I'd suggest figuring out where you want the major components to go first and then do a rough wiring diagram._

 

This makes me feel good since I spent a good bit of time just doing it. I don't know how a beginner like me could approach this without doing a diagram.


----------



## TimJo

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'd suggest figuring out where you want the major components to go first and then do a rough wiring diagram._

 

I'd concur with this. I know I spent a good deal of time thinking about alternative positions for the heatsinks, tubes, connectors, etc. and then once I settled on a layout, I drew a picture of it as it would be seen from inside the case. This meant the left channel was on the right, right on the left, and the pinouts for the tube socket's and MOSFET's reversed. Having a picture helped from getting this confused in my mind. 

 With that in hand, then it was a matter of transferring the schematic to the physical layout of the sketch. Again, I just drew a new diagram with the resistors and capacitors (with their values) in the actual locations within the chassis. By the time I was ready to start assembling this thing, it was a piece of cake because I could just follow the diagram and concentrate on soldering instead of the schematic. All of the thinking was done ahead of time. 
	

	
	
		
		

		
			





 One other tip is once I got the layout drawn on the masking tape prior to drilling the case, I set all of the large components on top to make sure that the terminal strips would fit comfortably in terms of soldering. I was cramming mine into a small space, so this helped choose the optimum locations before drilling the holes for the terminal strips.

 Maybe this will help somebody starting out. I know this was my first experience with a 'free-form' point-to-point assembly, and I was glad I put so much effort into the planning before plugging in the soldering iron. It paid off because the amp fired up first try.

 BTW, it is a great sounding amp. I am blown away at how good it really sounds. I'll be building another one soon for my brother.


----------



## keiths

And it works 
	

	
	
		
		

		
		
	


	
























 Sounds great too. Absolutely NO audible hum or hiss even with the volume turned right up and the sound quality is fine - well balanced tonally and nice lively dynamics.

 It's a bit messier inside than I'd hoped, but not too bad considering I'm so new to this.






 Took my time - guess I spent 12+ hours on it. Getting the case done was the hardest bit as I was hampered by a severe lack of tools and facilities (one old power drill and the kitchen table). I had to make all the large holes by drilling small ones and then making them bigger with a file. Have since bought a step bit and a Dremmel-type tool - so the next build should be a lot easier.

 I've got nearly enough parts left over to build a second one (partly because I ordered extra in case of me messing up and partly due to Farnell's order multiples for some components) which I'll use on my work desk. I'll need some way of protecting the valves for that one. Also I might include an iPod dock and multiple input switching.

 Thanks Pete for coming up with such a great design and thanks to all posters in this thread without whom I wouldn't have had a prayer of tackling this.


----------



## Postal_Blue

^ very nice build. I really like that case.


----------



## dgbiker1

Wait... it doesn't go up to eleven? 
	

	
	
		
		

		
		
	


	




 Nice build, very classy.
  Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_And it works 
	

	
	
		
		

		
		
	


	







_


----------



## m0b1liz3

Hello Keiths, at what point in the diagram did you take off the wires for your LED? 

 I was also wondering if mounting the heatsinks inside the case is a bad idea. I am not even sure if I can fit mine but I thought it could be a good idea if travelling. Would just have to unplug the tubes and put the box in a bag.


----------



## Chipp

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hello Keiths, at what point in the diagram did you take off the wires for your LED? 

 I was also wondering if mounting the heatsinks inside the case is a bad idea. I am not even sure if I can fit mine but I thought it could be a good idea if travelling. Would just have to unplug the tubes and put the box in a bag._

 

It would not be a problem, so long as the case has proper ventilation. Hestsinks rely on air to dissipate heat, so about the worst thing you could do is close them off from the outside.


----------



## JamesL

Do the mosfets get particularly hot?
 I have some smaller heatsinks lying around and maybe I could recycle those.


----------



## m0b1liz3

I would only have some ventilation at the back. But I suppose I could drill some holes at the top too. It will be very cramped inside if I do this but I like the idea if I can pull it off. The dimensions of my case inside will only be around 12x10x4.5cm so it may be a stretch.


----------



## lynxkcg

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Do the mosfets get particularly hot?
 I have some smaller heatsinks lying around and maybe I could recycle those._

 

My thermomoter that I have only goes up to 120 deg. F and it was well on it's way higher. I'm using 2 inch heatsinks but they're on top of a wood case, so it can't dissipate like a metal case would.

 Off topic: when everyone mentions "bypassing" an electrolytic cap, is that just hooking up a film or PIO cap like a vitamin q in parallel with the electrolytic? (sry I'm still new to all this
	

	
	
		
		

		
			





).


----------



## JamesL

Quote:


  Originally Posted by *lynxkcg* /img/forum/go_quote.gif 
_My thermomoter that I have only goes up to 120 deg. F and it was well on it's way higher. I'm using 2 inch heatsinks but they're on top of a wood case, so it can't dissipate like a metal case would.

 Off topic: when everyone mentions "bypassing" an electrolytic cap, is that just hooking up a film or PIO cap like a vitamin q in parallel with the electrolytic? (sry I'm still new to all this
	

	
	
		
		

		
		
	


	




)._

 

Thanks, guess I'll be looking to use the bigger heatsinks...

 And yup. some info here too


----------



## keiths

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hello Keiths, at what point in the diagram did you take off the wires for your LED?_

 

Here:






 I'm using a 20k resistor which gives a current of 2.4mA. This seems to make the LED bright enough. The resistor dissipates 0.11W at that current, so a 0.25W resistor is fine.

  Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I was also wondering if mounting the heatsinks inside the case is a bad idea. I am not even sure if I can fit mine but I thought it could be a good idea if travelling. Would just have to unplug the tubes and put the box in a bag._

 

I don't know. I was thinking the same for the next one I'm to build. The heatsinks on mine don't seem to get particularly warm. (I'm using 2" x 1" sinks with a thermal resistance of 3.6°C/W). I might try mounting them with 1/2 the heatsinks sticking out of the back of the case.


----------



## Ferrari

keiths, an LED is usually working in a forward-bias condition with current flowing from anode to cathode (the LED is much happier if you rotate it 180 degrees).


----------



## nsx_23

Shame that I suck at electronics at the moment....


----------



## keiths

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_keiths, an LED is usually working in a forward-bias condition with current flowing from anode to cathode (the LED is much happier if you rotate it 180 degrees). 
	

	
	
		
		

		
		
	


	


_

 

Opps
	

	
	
		
		

		
		
	


	




 I've fixed the schematic. (I'd wired the LED the right way round)

 Thanks.


----------



## scompton

Finished my build. I'll post pics later. The only problem I have it that the volume is backwards. I wired it according to a post in another thread.

 With the shaft facing me

Right pins are connected to the RCA jacks
Middle pins are connected to pin 5 of the tube socket
Left pins are grounded

 What have I done wrong?


----------



## TimJo

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_The only problem I have it that the volume is backwards. I wired it according to a post in another thread.

 With the shaft facing me

Right pins are connected to the RCA jacks
Middle pins are connected to pin 5 of the tube socket
Left pins are grounded

 What have I done wrong?_

 

Sounds correct provided the solder lugs are pointing down (5, 6, 7 o'clock if you will). If they are pointing up as described, then they are backwards.


----------



## scompton

Quote:


 Sounds correct provided the solder lugs are pointing down (5, 6, 7 o'clock if you will). If they are pointing up as described, then they are backwards. 
 

They're pointing up so they were backwards. Works great now. Thanks. Pics later. Right now I have a honey-do list.


----------



## joe_seattle

Can anyone recommend a good-looking and not too expensive enclosure that will fit this amp well?

 I saw those fantastic BB size cases on smallbear, but they seem to be tiny. Are they for sure too small? I'd like a nice looking aluminum case ideally or some metal case that could be easily painted.

 Oh...and does anyone know of a place that does the drilling for you? I found frontpanelexpress, but it would be about $80 for what I want - which I guess isn't too bad since it was anodized gold aluminum with all the holes cut. GOLD!


----------



## pmillett

Hello everybody -

 I finally got around to making a "Starving Student" photo gallery on my web site. Nothing fancy, basically I just stole all the pictures out of this thread.

Starving Student Headphone Amp photo gallery

 Hopefully I'll have time to keep it updated. I've been in Japan for half of the month of July.

 On the upside, I gathered lots of info to update my Akihabara info...

Parts in Asia

 Pete


----------



## scompton

I have one tube glowing very bright and the other not so bright. What can cause this? Where do I need to test?

 The channel with the bright tube has a loud buzz, music doesn't play though it.

 Edit: I just realized that the tube started glowing bright after I closed up the box. I assume something shorted or a solder joint broke.


----------



## elliot42

I finished machining my case yesterday. It's aluminium from an old hard drive with the guts ripped out. Machining it was really easy with a stepped drill bit (which I got yesterday, wonderful tool). The case is black but is a bit scratched (it's pretty old) and I may give it some paint later on, but for now it looks fine. 

 I might post some progress pics, but will definitely post pics when it's done, hopefully by the weekend. I'm also using the heatsink from a Pentium 3 Slot 1 card; it's a decent size and should keep the mosfets (which I'm still waiting for in the post) nice and cool (you'll all see the size of it soon, it does look good though).


----------



## n_maher

Pete's gallery reminded me that I'd never posted a picture of my amp after mounting the knob, d'oh! As luck would have it I had the amp home with me this weekend for a little tweaking so I busted out the camera and here it is.











 And just to be a tease I decided to take a couple of photos of my amp with the starving pcb prototype that I've got ~90% populated.











 I should have it done and maybe even cased up by next weekend. I know it's been a while since anyone posted updates on where this is at. Just know that we're still working on it and simply don't want to put something out there that isn't well and completely thought out.


----------



## scott_fx

i built one chan of the amp so far, powered it up and it sounds really great; though, it's not very loud. at full volume it's not as loud as my ipod's internal amp. also, the volume control tops out at about half way. i'm not sure if these are related or not, could it be as simple as not having wired the pot correctly?

 any advice guidance would be great. i can't wait to have this finished, i may build another one learning from my mistakes!


----------



## elliot42

Quote:


  Originally Posted by *scott_fx* /img/forum/go_quote.gif 
_i built one chan of the amp so far, powered it up and it sounds really great; though, it's not very loud. at full volume it's not as loud as my ipod's internal amp. also, the volume control tops out at about half way. i'm not sure if these are related or not, could it be as simple as not having wired the pot correctly?

 any advice guidance would be great. i can't wait to have this finished, i may build another one learning from my mistakes!_

 

Not sure about the volume not being very loud, but I'd double check the wiring on the pot for the other problem and also make sure that it is an audio or logarithmic pot and not a linear pot (usually labeled 'audio' or the rating has a suffix of 'A'; linear has 'B' << I think that's correct, someone correct me if I'm wrong). I had a similar problem with a previous project where I had used a linear pot and the volume increased exponentially and topped at about 1/3 of the pot.


----------



## scott_fx

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_Not sure about the volume not being very loud, but I'd double check the wiring on the pot for the other problem and also make sure that it is an audio or logarithmic pot and not a linear pot (usually labeled 'audio' or the rating has a suffix of 'A'; linear has 'B' << I think that's correct, someone correct me if I'm wrong). I had a similar problem with a previous project where I had used a linear pot and the volume increased exponentially and topped at about 1/3 of the pot._

 


 i did have the pot wired incorrectly and i did check that it was an audio pot. the volume is still lacking. I've tried the amp with cheapo low impedance earbuds as well and still had low volume issues


----------



## scompton

Would a blown mosfet cause the tube to burn bright and only a hum in that channel? Is there a way to test a mosfet short of replacing it?


----------



## n_maher

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Would a blown mosfet cause the tube to burn bright and only a hum in that channel? Is there a way to test a mosfet short of replacing it?_

 

tomb posted a link on how to test mosfets a few pages back. But more to the point, no I don't think that a blown fet would cause that behavior. 

 You might try posting some pictures of the wiring (clear, non-blurry pictures please) so that we can have a look at what might be wrong.


----------



## scompton

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_tomb posted a link on how to test mosfets a few pages back. But more to the point, no I don't think that a blown fet would cause that behavior. 

 You might try posting some pictures of the wiring (clear, non-blurry pictures please) so that we can have a look at what might be wrong._

 

OK here's where I've been and where I am now with my build. As a total noob at DIY, I need help. I've made things worse just trying to take measurements
	

	
	
		
		

		
			





 I finished wiring everything up yesterday and it turned it on with some cheap headphones plugged in. Everything worked fine except the pot was wired backwards. Fixed that and everything was fine. Here's a pic of what the whole thing looks like






 I decided to close it up. Powered it up and at first had a very bad channel imbalance. The right channel was low volume and had a loud hum. The hum was not effected by the pot. It was the same volume no matter what the pot was set at. The tube for the right channel was also glowing a lot brighter than the left. 

 In a PM, it was suggested I measure the voltage at the + side of C3 and C5. C5 was a little under 19V and C3 was over 30V. 

 Then I did something stupid. I tried to measure the input voltage at the power jack. The probe slipped and shorted between the pins on the power jack. 

 After doing that, the voltage at the power jack was fluctuation wildly. So fast that I couldn't read the numbers. I measured the PS and it measured 47.6V. I desoldered the power jack and plugged the PS into it. It measured 47.6V at the pins. I soldered the wires back on and the voltage again fluctuates wildly when I try to measure it.

 Here's a picture of the jack wired.






 Here's some pics of the right channel. I also have pics of the left channel if you want to see them
















 Any suggestions will be greatly appreciated. I was stoked when everything worked the first time. But I figure I'm going to learn more by screwing up like I have.


----------



## -=Germania=-

Added purple LED's and edging see here:








 The pic makes it look like one LED is brighter than the other - that is just my crappy camera!


----------



## Chipp

Good afternoon guys;

 I got going with my build yesterday and after a few hours of casework and a few more hours of building I finished all the inputs and the right channel of the amp. I checked things one last time, plugged in, and flipped the switch to get nothing (not even smoke or flames, which I suppose is a good thing 
	

	
	
		
		

		
		
	


	




).

 I went back to the schematic and figured out that I had not grounded the center pin on the 1/4" out. I made note of that and called it a night. This morning I fix that and while I compared my build to the schematic yet again I noticed I had not grounded R5 so I took care of that, as well. Upon firing it up again, still nothing. I confirmed that I do have 48vdc between the switch and the ground plane; however, I'm not seeing the err of my ways this time. Could anybody be bothered to take a look at what I've got and see if there is somewhere obvious I've gone wrong?

 Pardon the mess (sorry) - I ignorantly designed the layout based on saving the logo on the top of the cigar case, rather than how it might be remotely practical to lay things out. On the mosfet yellow is pin 1, red is pin 2, etc. 

http://rigshowcase.com/album.php?u_id=54UCagi


----------



## tomb

Quote:


  Originally Posted by *Chipp* /img/forum/go_quote.gif 
_Good afternoon guys;

 I got going with my build yesterday and after a few hours of casework and a few more hours of building I finished all the inputs and the right channel of the amp. I checked things one last time, plugged in, and flipped the switch to get nothing (not even smoke or flames, which I suppose is a good thing 
	

	
	
		
		

		
		
	


	




).

 I went back to the schematic and figured out that I had not grounded the center pin on the 1/4" out. I made note of that and called it a night. This morning I fix that and while I compared my build to the schematic yet again I noticed I had not grounded R5 so I took care of that, as well. Upon firing it up again, still nothing. I confirmed that I do have 48vdc between the switch and the ground plane; however, I'm not seeing the err of my ways this time. Could anybody be bothered to take a look at what I've got and see if there is somewhere obvious I've gone wrong?

 Pardon the mess (sorry) - I ignorantly designed the layout based on saving the logo on the top of the cigar case, rather than how it might be remotely practical to lay things out. On the mosfet yellow is pin 1, red is pin 2, etc. 

Seth Hochberg's Online Photo Album -_

 

I'll take a closer look if I have time, but for right now:

 * I think you need to ground the pot. I don't see any ground wires coming off from it.
 * I'm not exactly sure, but you may still have the headphone jack wired wrong. I believe the two spring tabs make contact with L and R, while the Ground is probably one of those small tabs that's in contact with the sleeve and panel button.
 * Pin 4 on the tube should be run to ground - I believe that's the one with the unconnected lead poking out near your "R" mark in the last pic (P1010018.jpg). If that's not run to ground, then a complete connection isn't made to the heaters. I don't think the tube will light.


----------



## TimJo

The headphone jack looks okay to me from image P1010015.jpg, although it is hard to tell for sure. 

 One thing I noticed is the wiring on the tube socket. In P1010017.jpg it looks like you have the cathode (pin 7) tied to ground, with a resistor across the cathode and one side of the heater (pins 7 & 4). The return on the heater (pin 4) needs to go to ground, and you need a 2k resistor between the cathode and the ground plane. 

 Take a look since the photos are sometimes hard to tell for sure, but this may be your problem.


----------



## Chipp

Thanks for the tips guys. I made the aformentioned corrections regarding pin 4's grounding and the resistor between pins 7 and 4 in addition to doublechecking the 1/4" out and wiring ground for the pot. Still a lifeless amplifier though. I do not see any visibly fried components, but I may just go ahead and build the second half keeping my mistakes in mind and see if perhaps that can shine some light on whats wrong.


----------



## TimJo

Quote:


  Originally Posted by *Chipp* /img/forum/go_quote.gif 
_Thanks for the tips guys. I made the aformentioned corrections regarding pin 4's grounding and the resistor between pins 7 and 4 in addition to doublechecking the 1/4" out and wiring ground for the pot. Still a lifeless amplifier though. I do not see any visibly fried components, but I may just go ahead and build the second half keeping my mistakes in mind and see if perhaps that can shine some light on whats wrong._

 

Did you remember to add a ground wire to the third pin on the pot? If not, you'll need that for things to work.

 I'd say that the tube may have seen some damage. I'm not sure what effect there is if the cathode becomes part of the heater circuit. 
	

	
	
		
		

		
		
	


	




 Before you try another tube though, I'd recommend slowly reviewing your wiring component by component until you are pretty sure that the rest of that channel is wired correctly.

 Keep us posted.


----------



## Chipp

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Did you remember to add a ground wire to the third pin on the pot? If not, you'll need that for things to work.

 I'd say that the tube may have seen some damage. I'm not sure what effect there is if the cathode becomes part of the heater circuit. 
	

	
	
		
		

		
		
	


	




 Before you try another tube though, I'd recommend slowly reviewing your wiring component by component until you are pretty sure that the rest of that channel is wired correctly.

 Keep us posted._

 

Yes, I did make sure to ground the pot. 

 I'll give things another go-over and try one of the other tubes.

 EDIT: This is probably a dumb time to ask this, but I was just thinking about the mosfet wiring. I did check the datasheets but could not find exactly what I'm looking for. The pinout for most TO-220 package devices is 1-2-3 from left to right if you are looking at the front (labeled) side of the chip. When I could not find a definitive answer either way as to the pinout of these specific devices I assumed they were the same. Are they not?


----------



## royewest

I was wondering if you'd wired the mosfet in the right order -- there's a post in this thread where I discuss the difficulty I had in verifying the pin numbers. They are 1-2-3 left-to-right when looking at the mosfet on the side that is plastic, not metal. In other words, I think your assumption about pin numbering is correct.


----------



## scompton

The pin outs were pretty clear to me from the data sheet on page 7. http://www.vishay.com/docs/91015/91015irf.pdf


 Well I got mine working again. Both mosfets were fried. I think I fried the first when something shorted when I put tried to close the lid. I fried the other when I shorted the power jack. I removed both to test and they were shorted between pins 1 and 3. Fortunately, 

 I'm not really a starving student and, since this is my first build, I figured I'd screw something up, so I double ordered every thing except the PS. I figure I'll build something else in the future so it's not a total waste, plus I have spare tubes. I remember what a PITA tubes were when I was a kid and you could get them everywhere. Can't make a quick run to the 5 and 10 to buy tubes these days
	

	
	
		
		

		
		
	


	




 I replaced the mosfets and rewired the electrolytic caps so I could put them in the bottom of the case before trying to close. I also put heat shrink on any lead that I thought might short. Powered it up and it sounds great. My only complaint is it's too loud, but that's my complaint with every amp I've tried.


----------



## rds

An amp built for lefties - looks good!


----------



## scompton

I put no thought into the layout like that, at least consciously. I probably did unconsciously. Not because I'm a lefty, I'm not, but because of the way my listening area is set up, both at home and work, the only place for my equipment is to the right of my computer. At home, it's a long reach to the volume knob on my NAD 3155.

 It's going to work after I get back from vacation next week. The reach isn't as bad, but the way I picture fitting it in with my other equipment, it'll be sideways on a pile of other equipment.

 It's going to replace a portable amp at work. Now all I need for my work setup is a preamp.


----------



## TimJo

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_
 Well I got mine working again. Both mosfets were fried. 

 I also put heat shrink on any lead that I thought might short. 
_

 

Glad to see that you got your amp up and running. Looks good!

 I think it is a good idea to add the heatshrink. With the point-to-point wiring, it easy to get a short if things are a bit tight in the case.


----------



## scompton

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Glad to see that you got your amp up and running. Looks good!

 I think it is a good idea to add the heatshrink. With the point-to-point wiring, it easy to get a short if things are a bit tight in the case._

 

If I did it again, I'd also cut the leads shorter. The leads for all of the caps are uncut. The resistor leads are all about as long as you can make them without undoing the tape.


----------



## adamus

will i get away with 240k resistors for r2, r4 etc. thats all i have in the parts bag.


----------



## Chipp

Well, I went ahead and build the second (left) half of amp today completely ignoring how I built the first section and going solely by the schematic. It ended up looking the same and, unfortunately, functioning the same as well. I tried my "tester" Hytron and RCA tubes first, but when they didn't work I dropped one of my matched Sylvania's into the "new" side and still got nothing. Tested both mosfets with the DMM and they are functioning correctly. I also dropped a 1/4" to 1/8" adapter into the 1/4" socket just to see if that would change things. No dice.


----------



## rds

Chipp - post some high res pictures of the wiring


----------



## Chipp

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Chipp - post some high res pictures of the wiring_

 

Sure - just a minute.


----------



## Chipp

Picasa Web Albums - Chipp - Millett Starv...

 You should be able to zoom in quite a ways if the default is not large enough. Thanks for taking a look.

 EDIT: After triple-checking things, it appears I left out 2 of the 2K ohm resistors. However, looking at the schematic, Pete and Nate's builds, and my build I am confused as to where they go. I used 5 2kohm resistors - one between the power switch and C6 (I'm certain it's R13) one between pin 7 on each tube socket and ground (R5 and R11) and one in each channel leading from the 4th terminal post back to the third post (which is grounded). I do not know whether those resistors are R3/R9 or R6/R12. In the pictures Pete and Nate posted I only can count 5 resistors, in the places I currently have them. Looking at the PCB prototype, there clearly are 7 (as on the schematic and BOM). I'm more than just a little confused as to what is going on here.


----------



## rds

See pin 1 of the Mosfets in the schematic. There's not a great angle to see this in your pictures, but it appears pin 1 of the IRF510s is connected together - that's not good.


----------



## Chipp

The mosfet's are correctly wired - each line from pin 1 returns to it's respective lug on the terminal strips, each pin 2 returns to 48v at the power switch, and each pin 3 returns to it's respective pin 3 on the tube sockets. I understand how it would be hard to discern exactly where a wire went in the mess, especially since I didn't color-code.


----------



## m0b1liz3

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I put no thought into the layout like that, at least consciously. I probably did unconsciously. Not because I'm a lefty, I'm not, but because of the way my listening area is set up, both at home and work, the only place for my equipment is to the right of my computer. At home, it's a long reach to the volume knob on my NAD 3155.

 It's going to work after I get back from vacation next week. The reach isn't as bad, but the way I picture fitting it in with my other equipment, it'll be sideways on a pile of other equipment.

 It's going to replace a portable amp at work. Now all I need for my work setup is a preamp._

 

Why not just wire up the Millet SS to have pre outs with a resistor in line and a switch to go from HP amp to pre?


----------



## rds

Quote:


 it appears I left out 2 of the 2K ohm resistors. 
 

There should be a 2k resistor on each pin 1. You didn't mention those, so I figure those are the two you left out.


----------



## rds

Quote:


 Why not just wire up the Millet SS to have pre outs with a resistor in line and a switch to go from HP amp to pre? 
 

Trying to get someone to do your leg work for you?


----------



## Chipp

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_There should be a 2k resistor on each pin 1. You didn't mention those, so I figure those are the two you left out._

 

Well I'll be darned.... Indeed I did.

 Sorry if thats what you were trying to get across earlier, I thought you were saying that it looked like I bridged pin 1 on the mosfets together.

 Update: Well, those resistors weren't whats keeping the tubes from firing.


----------



## adamus

anyone on using 240k resistors? or shall i pop to the electronics shop and buy some 220k?


----------



## dsavitsk

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_anyone on using 240k resistors? or shall i pop to the electronics shop and buy some 220k?_

 

240K is fine


----------



## scompton

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Why not just wire up the Millet SS to have pre outs with a resistor in line and a switch to go from HP amp to pre?_

 

I want a pre because I want tone controls. Some of my vintage cans are a little light on bass but respond well to judicious use of bass boost.


----------



## procalli2007

I have a aluminium hammon case which I will be soldering the heatsings directly to. 

 I also have a pot and dc input which are metal and which ground the case sides.

 Will this be ok? 
 The heatsinks are connected to the mosfets using the beezar heatsink kit.


----------



## scompton

My heat sinks are soldered onto the ground plate. I used the Mouser mounting kits and have no problem. 

 I don't know about the pot and the power jack grounding. The ground pin in the power jack I used is connected to the threaded body, so I'd guess that it wouldn't matter, but that's a guess that I'd want verified, as you do


----------



## tomb

As long as you wire the center pin of the power jack as the "positive" and you use the recommended VOIP power supply, then everything will be negatively grounded - including the metal body of the power jack and the case.

 That's the desired way to do it.
	

	
	
		
		

		
		
	


	





 P.S. I'm not sure you'll have much luck soldering to aluminum.
 I found this excerpt on the Internet:
  Quote:


 Tin the aluminum under oil, then solder as normal.

 Aluminum normally won't accept regular solder. That's because
 of the oxide coating on its surface. By covering the surface with
 oil, you can scrape away the oxide coating while preventing oxygen
 getting to the surface and reforming it. You can then tin the surface
 with an iron, through the oil coating, and get a proper bond. Then
 you can clean the oil off and solder as usual. 
 

I don't know if you want to try that, though.


----------



## TimJo

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_I have a aluminium hammon case which I will be soldering the heatsinks directly to._

 

I know this has been discussed before, with different folks having different results, but I was able to back out the posts on my heatsinks using a pair of vise grips, and then attached them using 4-40 screws. May be worth a try, but I can't guarantee the results for your heatsinks, just saying it worked on mine without a problem.


----------



## scompton

I tried, but not too hard, so I wasn't successful. Considering what a pain it was soldering them to the ground plate with a 15W soldering iron, I wish I'd spent more time trying to do it.


----------



## TimJo

Quote:


  Originally Posted by *Chipp* /img/forum/go_quote.gif 
_Well I'll be darned.... Indeed I did.

 Sorry if thats what you were trying to get across earlier, I thought you were saying that it looked like I bridged pin 1 on the mosfets together.

 Update: Well, those resistors weren't whats keeping the tubes from firing._

 

It's hard to describe things based on the pics, but looking at the close up of the terminal strip with the yellow power wire, it looks like the gate on the Mosfet (pin 1) is not attached in the correct place. It looks like it is attached to the fourth lug on the terminal strip, but it needs to be attached to the second lug, with a 2K resistor between the lug and the gate.


----------



## Chipp

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_It's hard to describe things based on the pics, but looking at the close up of the terminal strip with the yellow power wire, it looks like the gate on the Mosfet (pin 1) is not attached in the correct place. It looks like it is attached to the fourth lug on the terminal strip, but it needs to be attached to the second lug, with a 2K resistor between the lug and the gate._

 

Looks like I seriously need to revisit my schematic reading ability - but, in the meantime the amp is alive. 
	

	
	
		
		

		
		
	


	




 Thanks a ton for the help!


----------



## rds

Quote:


 I have a aluminium hammon case which I will be soldering the heatsings directly to. 
 

More like welding if want to try that 
	

	
	
		
		

		
		
	


	



 But Tomb has a cool suggestion. I've never tried it but it sounds feasible.


----------



## adamus

from parts to sound in 3 hours!

 sounds suprisingly good, not on par with my soha + jisbos but still good.

 I will post pics in a bit


----------



## procalli2007

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As long as you wire the center pin of the power jack as the "positive" and you use the recommended VOIP power supply, then everything will be negatively grounded - including the metal body of the power jack and the case.

 That's the desired way to do it.
	

	
	
		
		

		
		
	


	





 P.S. I'm not sure you'll have much luck soldering to aluminum.
 I found this excerpt on the Internet:


 I don't know if you want to try that, though.
	

	
	
		
		

		
		
	


	


_

 

Could I glue it to the case?


----------



## adamus

Heres my 3 hr mini millet, making lovely sound. I used 470uf pana fc caps, and wima mkp10 330nf film caps. 

 good bass, lovely valvey mids, slightly recessed highs which i expect to develop with a bit of burn in.


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Could I glue it to the case?_

 

Personally, I wouldn't recommend it. If you do, probably JB-Weld would be the way to go.

 However, there's a reason Pete included the copper board in his BOM. The idea is that you're supposed to sandwich the top of the case between the heat sinks and the copper plate. That way, you can solder the heat sink pins to the copper and the case lid is held in place. If you study his very first pic, that's how he attached the whole thing to a wallet tin. 
	

	
	
		
		

		
		
	


	




 P.S. There's always TimJo's suggestion of pulling the pins and using screws, too - but it won't give you the grounding advantage of the copper plate.


----------



## rds

Another method, which is very similar to Pete's is to get #3 or #4 washers and tin them and then solder them to the pins of heatsink with the washers flush against the case.


----------



## jonjon0nline

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_Heres my 3 hr mini millet, making lovely sound. I used 470uf pana fc caps, and wima mkp10 330nf film caps. 

 good bass, lovely valvey mids, slightly recessed highs which i expect to develop with a bit of burn in. 
_

 

Can you post pics of the internals? Thanks =)


----------



## TimJo

Quote:


  Originally Posted by *Chipp* /img/forum/go_quote.gif 
_Looks like I seriously need to revisit my schematic reading ability - but, in the meantime the amp is alive. 
	

	
	
		
		

		
			





 Thanks a ton for the help!_

 

Good to hear that! Enjoy...


----------



## adamus

jojononline- i will post pics of internals tonight (uk). As yo can imagine, there isnt much room in that little case.

 Cheers

 Adam.


----------



## joe_seattle

Sorry if this is redundant. Just curious what tubes folks are using and how the sound signature might vary among the different brands. I ordered some for my build and received both Raytheon and RCA. Are there any in particular to get or to avoid?


----------



## n_maher

I've only been using the RCAs and don't find anything objectionable about them. And being the oddball tube the 19J6 is I'd be willing to bet that there were only a few manufacturers and just lots of rebranding going on.


----------



## scompton

I have Delco tubes. I have no idea who actually made them. I don't know how they compare to any other tubes since this is the first tube amp I've owned.

 I assume since I have Delco tubes that these were originally used in car radios. I would think that would make NOS ones somewhat common. Does anyone know when car radios switched from tubes to chips? I remember going to the hardware store with my father to get tubes for TVs and home radios. I don't remember him changing tubes in the car. Although I don't remember a car radio back then either so we may not have had one.


----------



## Chipp

I have a pair of Sylvanias and an RCA Victor; along with a Hytron that appears to be an RCA rebrand. I can't discern any difference between them from a sound standpoint.


----------



## lynxkcg

I've got a handful of Muse caps here but I can't bring myself to turn off the amp to put em in. It's got UHE caps in there now. It's been running constantly since I built it despite falling off my desk twice. :O


----------



## rds

Quote:


 I've got a handful of Muse caps here but I can't bring myself to turn off the amp to put em in. It's got UHE caps in there now. It's been running constantly since I built it despite falling off my desk twice. :O 
 

I found the Muse were a very nice improvement over the UHE, but they should be bypassed with film caps like the big brother Millets.
 I'm interested to hear your impressions.


----------



## lynxkcg

I have a few WIMA .1uf caps, but would it be worth the wait to order some PIOs? And would silmic IIs sound better bypassed in the same manner? Sorry, I don't have much experience with how this stuff sounds, its hard without some frame of reference.


----------



## rds

I haven't tried Silmics in the signal path, so I can't say. Wima Mkps are work very well with the Muse ES.
 ...I just realized you never said if they were ES (the green ones). So I was just assuming they are.


----------



## lynxkcg

I have a few of both but I was planning on using the KZ. I'm so confused on what to bypass with what


----------



## rds

Try bypassing the Muse ES with the Wima MKP and see if you like it. I've used the KZ by itself in the signal path before. I didn't spend much time listening to it, but it seemed alright.


----------



## scompton

Quote:


  Originally Posted by *lynxkcg* /img/forum/go_quote.gif 
_It's been running constantly since I built it despite falling off my desk twice. :O_

 

Mine has fallen twice too. It's just too light. I need to put lead weights in it or something


----------



## adamus

mine ate a tube last night. I turned it off and about 30 seconds later i hear a ping. The tube has shattered round the base! thats a first!!!


----------



## n_maher

Just another teaser photo of the first prototype of the pcb based version of the amp. Round two in underway so we're making progress.


----------



## elliot42

I've done about half the internals in mine so far, will link to some pics tomorrow.

 But I'm still waiting on the mosfets. I ordered them over 2 weeks ago and they still haven't arrived. I've emailed the supplier and should have a reply on monday, but I'm wondering if anyone here is in Australia and has some extras that they would be willing to sell to me if I don't get my order by very early in the week.

 If you're in Sydney I could drop by, or I'll pay postage. This is the only thing stopping me from finishing the amp tomorrow, otherwise I'll just have to be patient I guess.


----------



## TimJo

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_Sorry if this is redundant. Just curious what tubes folks are using and how the sound signature might vary among the different brands. I ordered some for my build and received both Raytheon and RCA. Are there any in particular to get or to avoid?_

 

I have RCA, Sylvania, and G.E. versions (although the G.E.'s look like RCA's that have been rebranded). Honestly, I can't say I hear a big difference among them. Nothing night and day, that's for sure.

  Quote:


  Originally Posted by *lynxkcg* /img/forum/go_quote.gif 
_I have a few of both but I was planning on using the KZ. I'm so confused on what to bypass with what 
	

	
	
		
		

		
		
	


	


_

 

I've been running the KZ's unbypassed, and it sounds great to me. I have a pair of Vitamin Q's lying around, so I suppose I could do an experiment and bypass one channel, and then do an a/b test listening to each channel while playing a mono lp and see if there is an advantage to bypassing.


----------



## TimJo

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Just another teaser photo of the first prototype of the pcb based version of the amp. Round two in underway so we're making progress.[/IMG]_

 

Looking good. It's nice and compact that's for sure.

 So what are your thoughts on the casework for that style of board?


----------



## Chipp

How warm are everybody's mosfet heatsinks? I used the standard ones from the BOM, but they are _very_ warm to the touch even after just a few minutes on. Is this pretty normal?


----------



## TimJo

Quote:


  Originally Posted by *Chipp* /img/forum/go_quote.gif 
_How warm are everybody's mosfet heatsinks? I used the standard ones from the BOM, but they are very warm to the touch even after just a few minutes on. Is this pretty normal?_

 

I think so. 

 I ended up getting 2" heatsinks so they would be taller than the tubes, and they don't get that warm. Plus they are mounted on an aluminum case, which dissipates even more heat.


----------



## Chipp

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I think so. 

 I ended up getting 2" heatsinks so they would be taller than the tubes, and they don't get that warm. Plus they are mounted on an aluminum case, which dissipates even more heat._

 

Good point - mine are mounted into wood. I may look into grabbing the larger 'sinks just to be on the safe side.


----------



## bhjazz

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I assume since I have Delco tubes that these were originally used in car radios._

 

You are quite correct!


----------



## JamesL

Hey bhjazz, where did you find those black oxidized split aluminum enclosures? I've found the silver one at a few places, but I can't seem to find a distributor for the black oxidized ones. Do you think you could hook me up with a link?


----------



## keiths

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I think so. 

 I ended up getting 2" heatsinks so they would be taller than the tubes, and they don't get that warm. Plus they are mounted on an aluminum case, which dissipates even more heat._

 

Me too - my heatsinks don't get very warm at all. For my second Starving Student build, I've got smaller 1.5" 'sinks, but the datasheet quotes their thermal resistance as 3.9c/W which is the same as the 2" heatsinks I used in my first SS?


----------



## Pandaman

Just built my SS today, but seem to have a problem with the right channel and can't seem to figure out whats wrong. The left channel works, and nothing comes out of the right. Both tubes light up the same. Pic posted below.




 Thanks.


----------



## m0b1liz3

keiths, are those smaller heatsinks commonplace? i am thinking of building mine inside the case so that i can just remove the tubes and not have any parts that can break off while traveling.


----------



## elliot42

Here's a pic of my build. I don't have the fets yet so haven't powered it up. Hopefully my wiring is all correct. It was looking pretty neat as i put it together, then I added ground and other wires and it quickly became messy 
	

	
	
		
		

		
		
	


	




 There are more pics - internals and during the build - here.


----------



## n_maher

Quote:


  Originally Posted by *Pandaman* /img/forum/go_quote.gif 
_Just built my SS today, but seem to have a problem with the right channel and can't seem to figure out whats wrong. The left channel works, and nothing comes out of the right. Both tubes light up the same. Pic posted below.


 Thanks._

 

Could you post a better pic of the headphone jack? I'd swear you have the left wired to one side (the correct side) and the right wired to the switched side. That would explain the outage in only the R channel.


----------



## Pandaman

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Could you post a better pic of the headphone jack? I'd swear you have the left wired to one side (the correct side) and the right wired to the switched side. That would explain the outage in only the R channel._

 

Thanks!
 Yeah, I had the right wired on the other side, didn't know that you could only solder to one side.


----------



## n_maher

That style of jack is designed to be able to act as a switch so that when there aren't any headphones plugged in the signal can pass through the jack (in one side, out the other). When the headphones are plugged in only one side of the jack is "active" since the headphone plug physically breaks the connection between the two sides of the jack. You can observe this phenomenon from the top side of the jack as you plug the your headphones in, try it with a spare jack and you'll see what I'm talking about.


----------



## looser101

Quote:


  Originally Posted by *Pandaman* /img/forum/go_quote.gif 
_Just built my SS today, but seem to have a problem with the right channel and can't seem to figure out whats wrong. The left channel works, and nothing comes out of the right. Both tubes light up the same. Pic posted below.




 Thanks._

 

Usually that kind of headphone jack with solder lugs on both sides has an integral switch. One side are switches which get disconnected when a plug is inserted. The other side is the plug contacts. In your pic I see one channel on one side and the other channel on the other. The quickest, neatest fix is to connect the left side lugs with the right side lugs with a piece of solid wire through the lug eyelets.

 R

 * Nate types faster


----------



## adamus

A couple of mates came round, one of them with some grado RS1's. we had RS1's, MS1's, dt990's and equation rp-21's. 

 After a few hours testing, we found the Starving student has an awesome synergy with the RS1's!! sounded schockingly nice. 

 With my 'better amp' (soha + jisbos + very nice tube) there is obviously more detail, more attack etc etc, but guess which got our feet tapping? the SS (with RS1's). Very involving velvety sound, almost a big hall type sound. 

 With my beyerdynamic dt990's the SS just has a little confusion in the low end, the low mids have a bit too much bloom, its too organic. on the soha + jisbos + nice tubes the dt990's just dissappear and leave you with incredible music. this is still my favourite combination at the moment. 

 Which is the better amp?...... different for different phones and different music. 

 My millet cost £33 in total, the soha plus jisbos more than £100. The millet is a very good perfomer for the size. lovely little thing!


----------



## adamus

couple of internals


----------



## procalli2007

Finally finished and learnt alot. My second one will be better(although I may build the millet max pcb I have first).

 The only problem I have with this one is the volume control works backwards, ie it works anti clockwise to increase volume. Am I right in thinking that my wires just need swopping? Im using a alps blue velvet.

 thanks to p millet for the design.












 Side screws arent in yet as Im looking for black hex ones and I need to open it to fix the pot.


----------



## bhjazz

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Hey bhjazz, where did you find those black oxidized split aluminum enclosures? I've found the silver one at a few places, but I can't seem to find a distributor for the black oxidized ones. Do you think you could hook me up with a link?_

 

Hi James, 
 The cases is from Context Engineering. Search through the DIY forum here to see where they are online, 'cause I think there should be many places. For me, I bought them at Fry's, of all places! So, check there as well...their home page is FRYS.com. The one I used was $17.99 - the 4006H-6B.


----------



## keiths

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_The only problem I have with this one is the volume control works backwards, ie it works anti clockwise to increase volume. Am I right in thinking that my wires just need swopping? Im using a alps blue velvet._

 

With the pot shaft facing TOWARDS you and the pins pointing UP, the wires from the rca sockets should go to the LEFTMOST pair of pins, the wires to pin 5 of the tube sockets connect to the MIDDLE pins whilst the ground connection is to the RIGHTMOST pair of pins. 

 Congratulations on a great looking build by the way.


----------



## keiths

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_keiths, are those smaller heatsinks commonplace? i am thinking of building mine inside the case so that i can just remove the tubes and not have any parts that can break off while traveling._

 

I would imagine so. They are Aavid Thermaloy 6298B

http://www.rapidonline.com/netalogue/specs/36-0180e.pdf


----------



## adamus

I have notice a hum when i use it with my ipod. Its 100% a grounding issue - when i touch the case the hum dissapears. 

 Any ideas on how to get rid of it?


----------



## procalli2007

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I have notice a hum when i use it with my ipod. Its 100% a grounding issue - when i touch the case the hum dissapears. 

 Any ideas on how to get rid of it?_

 

i have no hum but have used the grounding plate that pmillet used in the original.


----------



## Postal_Blue

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I have notice a hum when i use it with my ipod. Its 100% a grounding issue - when i touch the case the hum dissapears. 

 Any ideas on how to get rid of it?_

 

I would try isolating the rca's from the case.


----------



## Pandaman

My amp has a pretty bad channel imbalance, with the left lower than right. Any reasons for this? and how can it be fixed?


----------



## scott_fx

is it considerably lower?


----------



## Pandaman

its lower at lower volume, goes away when I turn it up, but that gets too loud for me.


----------



## -=Germania=-

Guys, I added a 1000uF capacitor across the power and subbed in a 100K pot . Now, I go to halfway on the volume instead of just touching. You might want to try some output resistors as well.


----------



## adamus

Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_I would try isolating the rca's from the case._

 

ok i may try this.

 how about chopping the ground connection from the rca's to the copper ground plane? they would still be grounded through the case, but there would be no loop.


----------



## elliot42

I received a package from rs electronics today and was all excited about finishing my amp, until I discovered that they had messed up my order and sent just one mosfet 
	

	
	
		
		

		
			





 Is it OK to put the one fet in and turn on the amp with just one channel working? Or am I likely to mess something up. The only component missing would be the one fet, there are wires ready for it hanging out the case.


----------



## ruZZ.il

Quote:


  Originally Posted by *Pandaman* /img/forum/go_quote.gif 
_My amp has a pretty bad channel imbalance, with the left lower than right. Any reasons for this? and how can it be fixed?_

 

Switch the tubes around, does the imbalance follow?


----------



## Postal_Blue

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_ok i may try this.

 how about chopping the ground connection from the rca's to the copper ground plane? they would still be grounded through the case, but there would be no loop._

 

You ground plane is gonna be the better one to leave connected. Your hum may be caused by the more resistive path to ground through the case.


----------



## Pandaman

Quote:


  Originally Posted by *ruZZ.il* /img/forum/go_quote.gif 
_Switch the tubes around, does the imbalance follow?_

 

Yes, unfortunately. I even tried another pair of tubes just then, still the same.


----------



## Postal_Blue

Quote:


  Originally Posted by *Pandaman* /img/forum/go_quote.gif 
_Yes, unfortunately. I even tried another pair of tubes just then, still the same._

 

Your response is a bit unclear. When you switch the tube does the imbalance switch channels, or is the left always the lower channel.


----------



## MrMajestic2

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Just another teaser photo of the first prototype of the pcb based version of the amp. Round two in underway so we're making progress.




_

 

Hows the prototyping going on this one? Im too lazy to P2P


----------



## Pandaman

Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_Your response is a bit unclear. When you switch the tube does the imbalance switch channels, or is the left always the lower channel._

 

Sorry bout that, its always the left channel.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Hows the prototyping going on this one? Im too lazy to P2P 
	

	
	
		
		

		
		
	


	


_

 

What Nate said in that post - Dsavitsk is busy working on the 2nd iteration. I think everyone will be quite happy with what he's designed.


----------



## Postal_Blue

Quote:


  Originally Posted by *Pandaman* /img/forum/go_quote.gif 
_Sorry bout that, its always the left channel._

 

It is almost certainly channel imbalance in your pot. You need to get further into the sweep of the pot most/all pots have the most imbalance issues at the lowest volume. A voltage divider on the input may be the best solution, or you could try output resisters as suggested by Germania.


----------



## tomb

Sounds like PostalBlue has your problem diagnosed.

 With the SSMH, Dsavitsk's and rds's method of using input resistors prior to the pot seem very helpful. I can't detect any downside, either - at least on the PCB version.

 They are not a voltage divider, however. A voltage divider channels part of the signal to ground. The input resistors referred to above are only in line with each signal wire to the pot - Left and Right, one resistor each, nothing in the ground lead.

 50K resistors for a 50K pot seem to be a good starting point. You should probably increase by additional 50K resistances from there, if you need it.

 A voltage divider will mess up the input impedance of the amp. On the other hand, output resistors will probably need such a high resistance that dynamics will be lost.

 So, I would suggest trying the input resistors. Dsavitsk is making that a regular feature of the PCB, by the way.


----------



## Chipp

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_I received a package from rs electronics today and was all excited about finishing my amp, until I discovered that they had messed up my order and sent just one mosfet 
	

	
	
		
		

		
		
	


	




 Is it OK to put the one fet in and turn on the amp with just one channel working? Or am I likely to mess something up. The only component missing would be the one fet, there are wires ready for it hanging out the case._

 

No problem at all. I would just make sure to disconnect the incomplete channel from 48v+ to avoid potential issues.


----------



## dsavitsk

Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_It is almost certainly channel imbalance in your pot. You need to get further into the sweep of the pot most/all pots have the most imbalance issues at the lowest volume._

 

That sounds right

  Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_A voltage divider on the input may be the best solution, or you could try output resisters as suggested by Germania._

 

Two poor options

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_With the SSMH, Dsavitsk's and rds's method of using input resistors prior to the pot seem very helpful. I can't detect any downside, either - at least on the PCB version._

 

Here's why and how this works, and why it is a better solution.

 Generally, the load seen by the previous stage is a pot, which is an adjustable resistor divider to ground. At low volumes, the output can be pictorially though of as being closer to ground with the top resistor being larger, and at full volume, it is at the top.






 Putting the resistor in front of the pot essentially elongates the top resistor of the divider pair. If, for instance, you have a 50K pot with a 50K resistor in front of it, you now have a 100K pot where the wiper, which sets the divisor's ratio, can only travel up half the length of the wiper. It also changes the divided ratio such that the same setting on the pot will yield less signal to the first stage of the amplifier. There is also some argument that it improves the quality of the resistor that is in the signal path, so actually sounds better than all but the best pots.






 The full effect is that if you turn the amp all the way up, you have 50/50 divisor that sends, at most, half the signal to the amp when, with a normal pot only you would sent 100%. 50% of the signal is 6dB, which, for most instances is incidental. A 6db difference, especially at high volume, is almost inaudible. If you don't believe this, measure a normal log pot to find the point where it is 6dB down. It will likely be higher than you would ever turn up the amp.


----------



## Postal_Blue

^ Thank you for the better solution and thorough explanation.


----------



## adamus

any other suggestion for my hum? isolated the jacks - no help. Touch the case - blissful darkness.


----------



## -=Germania=-

mm.. I added 100 ohm resistance to the output of each signal to better tune the volume and reduce some of the hiss. 

 We found out that the hiss in my amp that was there - now it is greatly reducde.. but it is due to the power supply. I am building a fully regulated one soo , this bad rectified one makes too much noise.


----------



## adamus

But this seems very much like a grounding issue - its silent if i touch the case. 

 I have isolated the jacks (they were out of the case when i tested it) - noisey. 

 touch the case - silent. it sounds like a 50hz hum.


----------



## adamus

I was just thinking... why didnt i notice this before. Well, because it wasnt there - when plugged into my dac it is silent, completly black. Plug out the interconnect, or plug in the ipod i get the hum back. 

 has to be a grounding issue, but i am stumped as to how to correct it.


----------



## dsavitsk

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_But this seems very much like a grounding issue - its silent if i touch the case. 

 I have isolated the jacks (they were out of the case when i tested it) - noisey. 

 touch the case - silent. it sounds like a 50hz hum._

 

Is this only with the ipod and no other sources? Is the ipod in a dock connected to the wall, or a computer? I've had it happen where a laptop being used as a source induced ground noise in an amp only with unplugged, which was very weird. The fix had nothing to do with the computer. Ground issues can be unpredictable sometimes.

 One thing that can cause noise which seems like ground noise but isn't is proximity to other noisy electronics (monitors, computers, tv's, air conditioners -- I once had an amp that would hum when the neighbor's window ac turned on about 15 feet across the alley). Make sure nothing else is on nearby. Also, you might try making little shields out of aluminum foil and wrapping them around each tube and grounding them to the case.

 If that doesn't work, and my guess is it won't, the usual drill in a tube amp with ground noise is to first make sure it is star grounded. To do this, connect the ground pin of the PS to the negative side of the first PS filter cap (and to nothing else -- make sure the power inlet is isolated from the case). Then, connect that point to a central point, and connect everything else (second ps cap, the ground side of the heaters, the pot, the input jacks, the case, etc.) there, making certain that nothing is grounded twice -- that the pot, jacks, sinks, etc. are all isolated from the case and only grounded at this central point. The copper plane on the pcb material that Pete suggests using can be used a a star point, but be sure that all of your solder connections are really solid which takes a fair bit of heat. The circled ones seem suspect to me.


----------



## n_maher

[edit] what he said ^.


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_mm.. I added 100 ohm resistance to the output of each signal to better tune the volume and reduce some of the hiss._

 

This works with high Z phones, but with Low Z, at least with the high end Grados, where the damping factor matters, it isn't a very good option.


----------



## adamus

dsavitsk - thanks for the reply. its not any interference etc, tried it in different areas. Must be grounding. 

 the hum is when either nothing is connect (open), or with any source that is not mains (ipod, phone, etc). with cd player / dac / pc its fine. 

 Just checked the suspect joints, no continuity problems and seem solid, i will reflow though just in case.


----------



## -=Germania=-

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_This works with high Z phones, but with Low Z, at least with the high end Grados, where the damping factor matters, it isn't a very good option._

 

Yeah, all the ones I use the tube amp wth are very High Z by most people's standards. - the vintage cans are beastly! They love it though. 

 I am building a MUCH better power supply that will produce a solid, steady 48V. That is where hum can be reducde IMO.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Yeah, all the ones I use the tube amp wth are very High Z by most people's standards. - the vintage cans are beastly! They love it though._

 

You should do some reading about damping factor so you can better understand how your output resistors are affecting performance.

  Quote:


 I am building a MUCH better power supply that will produce a solid, steady 48V. That is where hum can be reducde IMO. 
 

Again, as I said before, if you've got hum in your build there's something wrong and probably not just the fault of the PS. What, specifically are you currently using for a power supply? Is it the one Pete recommended or are you using some other 48V ps that you found? In both my builds with the "stock" power supply I get zero hum.


----------



## Listen2this1

Two quick questions. How hot do the mosfets get. Can they share a heatsink if the heat sink was larger? I am going to try to make a smaller possible portable desktop amp. It will be pretty small, so of course I am worried about heat.


----------



## n_maher

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_ How hot do the mosfets get._

 

I believe that mine showed ~110F w/ 1-1/2" heat sinks.

  Quote:


 Can they share a heatsink if the heat sink was larger? 
 

I don't see why not, I'd just make sure that you use isolation material so that you aren't connecting the two FETs together where they might not be supposed to be connected. Just make sure that the heat sink is adequately sized and that you orient it for effective heat dissipation.


----------



## elliot42

Well, I put my one mosfet into my build and powered it on to test it and it works, kinda... The circuitry is fine and I get sound out, but I have some NASTY grounding issues and interference.

 I will try some of the tips posted just a few posts up to fix the hum, but it seems I have built not a headphone amp but a radio 
	

	
	
		
		

		
		
	


	



 There is really bad interference when the pot is in the lowest quarter where there is a lot of hiss and bits of radio stations and almost no music coming through. Just above a quarter turn the music suddenly jumps up and the interference reduces, but still with hiss and hum in the background. This was driven from my ipod and listening with ad900s. The problems occurred even with no source and just cans connected.

 The hum reduced somewhat when I held the plug of my cans, so that's a grounding problem that I should be able to have a look into tonight, but where can I start with the radio interference? There was nothing on in my room, computer was off, radio off, just the amp and room light.

 I have used a star ground and all the ground wires are connected to the PS -ve, which I will change to reflect earlier comments and connect them to the PS filter cap -ve instead. The shaft of the pot makes contact with the aluminium case, as do the input RCA jacks. Phone jack and PS jack are isolated. I also have a huge heatsink that contacts the case, don't know if that would be a problem.

 Some pics are here: Picasa Web Albums - elliot42 - Starving Stud...
 You can see the ground point (inch long bare wire with wires attached). There are pics of the finished internals but they're viewed through the perspex base and aren't the clearest. I can put up some clearer pics if needed tonight.

 Some help debugging this would be greatly appreciated.


----------



## Listen2this1

What happens when you touch the heatsink? What happens when you touch the tubes? Just a thought and I could be way off. The tubes can pick up resonances from other sources. I am wondering if the heatsink is just enough to slow the radio waves where the tubes are picking them up. There is a term for that but it is not coming to me at the moment.


----------



## elliot42

Not much happened when touching the heatsink or the tube, the biggest difference was touching the phone plug and I also got a little difference touching the pot knob and sometimes some clicks as I touched it. The heatsink was my first thought in what could be acting as an antenna, so I could try taking it off and using a smaller sink tonight.


----------



## Listen2this1

I am not able to pick out the type of headphone plug you have. Is the casing of the plug all metal? How did you ground it and where does it connect to? If it is all metal take a wire and connect the wire to the back side of the headphone jack, then to the back of the pot, then to the ground of the ps. This is where having some small wires with alligator clips come in handy. Keep with it. Ground issues can be difficult. Learning the tube realm has been a learning expierence for me. Until them I never really had any problems with grounds.


----------



## -=Germania=-

I added 100 ohm resistors to the output, directly on the jack. 
 Sounds better with them than without and that is all I care about. 

 The hum is barely audible at the highest volume setting - but it IS STILL THERE. 

 I aim to fix that and improve by making a new PS. That Cisco one is not a good DC setups with 1 transformer +1 diode +1 capacitor. That does give you DC, but it isn't clean DC that is super linear. I am aiming to fix that. 

 It will cost more, but I have decided to make this my main amp and make it the best it can be. 



  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_You should do some reading about damping factor so you can better understand how your output resistors are affecting performance.


 Again, as I said before, if you've got hum in your build there's something wrong and probably not just the fault of the PS. What, specifically are you currently using for a power supply? Is it the one Pete recommended or are you using some other 48V ps that you found? In both my builds with the "stock" power supply I get zero hum._


----------



## HeadphoneAddict

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I added 100 ohm resistors to the output, directly on the jack. 
 Sounds better with them than without and that is all I care about. 

 The hum is barely audible at the highest volume setting - but it IS STILL THERE. 

 I aim to fix that and improve by making a new PS. That Cisco one is not a good DC setups with 1 transformer +1 diode +1 capacitor. That does give you DC, but it isn't clean DC that is super linear. I am aiming to fix that. 

 It will cost more, but I have decided to make this my main amp and make it the best it can be._

 

Should be interesting to have a Sigma 11 power supply that costs several times more than what the amp cost to build


----------



## -=Germania=-

Aactually - it is about $25-30 in parts and relatively simple design that was put together with Ray's help this weekend. In design anyway. I will let everyone know how it goes.


----------



## elliot42

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_I am not able to pick out the type of headphone plug you have. Is the casing of the plug all metal? How did you ground it and where does it connect to? If it is all metal take a wire and connect the wire to the back side of the headphone jack, then to the back of the pot, then to the ground of the ps. This is where having some small wires with alligator clips come in handy. Keep with it. Ground issues can be difficult. Learning the tube realm has been a learning expierence for me. Until them I never really had any problems with grounds._

 

The headphone jack was salvaged from a broken receiver ages ago, it has a plastic case and doesn't contact the case at all. It is grounded from the one pin that connects to the ground contact inside, using a wire that connects to PS -ve. The plug on my cans has a metal sheath which I assume is connected to ground as the hum improves when I touch this.


----------



## -=Germania=-

Guys, I got a slightly better 50K pot made by the same company and put that in. 

 MUCH BETTER. so - get the one that costs a bit more - the $3.16 one. Maybe my old one was faulty. 

 The people with channel imbalance - you likely have the pot wired incorrectly. 

 BTW - I know that this is weird, but with the 100K pot - the 100 ohm resistors sounded better...then with the 50K pot - using 12ohm resistors worked best. I am seriously perplexed!

 However, I can still hear some noise on the very highest setting. 

 Will post pics later.


----------



## dsavitsk

Quote:


 However, I can still hear some noise on the very highest setting. 
 

Noise that changes with volume indicates noise on the grid, not on the plate. That is, it is likely not PS noise but is rather from the source.

 Also, did you crack open the Cisco supply? Mine looks like it is a switcher.


----------



## elliot42

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Also, did you crack open the Cisco supply? Mine looks like it is a switcher._

 

I've got the Cisco, and while I haven't opened it, I'm pretty sure it's a switcher. It weighs nothing and is pretty tiny. I'd be surprised if someone could fit a linear supply in there 
	

	
	
		
		

		
		
	


	




 ... or even just the transformer required.


----------



## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Noise that changes with volume indicates noise on the grid, not on the plate. That is, it is likely not PS noise but is rather from the source._

 

Yup, volume variable noise is not likely to be PS noise.

  Quote:


 Also, did you crack open the Cisco supply? Mine looks like it is a switcher. 
 

Ditto, I think Pete confirmed that that Cisco supplies are SMPS's earlier in the thread.


----------



## Citizen86

Sorry if this has been posted before, plus I'm a complete noob, but are there any alternative tubes to the 19j6's? I can't seem to find any for sale on-line... well there was one guy selling them on Ebay for $10 each...

 Also, anyone know of an enclosure that could fit something like an Alien DAC and this amp together? I'm thinking of doing this as my first project... sounds a little difficult though for a first-timer, heh.....


----------



## -=Germania=-

^ This is wha I would consider 1 step above a non-pcb cMoy. 

 Most of the time I prefer PCB's, but this is a nice PTP design that allows you to make your own layout. 

 Actually I am thinking of making an Alien Dac into mine as well!


----------



## n_maher

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_Sorry if this has been posted before, plus I'm a complete noob, but are there any alternative tubes to the 19j6's? I can't seem to find any for sale on-line... well there was one guy selling them on Ebay for $10 each..._

 

For this design, no. The 19J6 is the only tube that will work.

  Quote:


 Also, anyone know of an enclosure that could fit something like an Alien DAC and this amp together? 
 

The options are too numerous to list really and this is one of those decisions that will make you understand the Y part of D-I-Y. You'll have to decide for yourself. 
	

	
	
		
		

		
		
	


	




 And it's a fine first project, just be prepared to do a lot of reading and research.


----------



## keiths

Planning my second Starving Student build - this one for my work desk. I need to protect the tubes against accidental damage on a crowded desk, so am considering mounting them inside the case this time round. How much ventilation do i need to provide? I plan to have two large (~35mm) holes filled in with fine mesh (vivarium air vents) directly above the tubes and a bunch of smaller open holes on the side of the case directly next to the tubes. Will this be good enough? I figure that as the original use of these tubes was in car radios, they will be fairly resistant to high temperatures?


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_For this design, no. The 19J6 is the only tube that will work._

 

Actually, you could get a 19CL8 or 19EA8 to work, but you will need to know what you are doing as there will be some redesign involved. I do think they are not as good a choice for a number of reasons, though at $1.35 each it might be fun to find out ...


----------



## dsavitsk

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_I figure that as the original use of these tubes was in car radios, they will be fairly resistant to high temperatures?_

 

Tubes, in general, are resistant to high temperatures. The real reason you see them on top venting heat is less so they stay cool, and more so they don't cook the components around them. Additionally, not being power tubes, and running at a low voltage, these just don't get that hot.


----------



## Citizen86

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_For this design, no. The 19J6 is the only tube that will work.


 The options are too numerous to list really and this is one of those decisions that will make you understand the Y part of D-I-Y. You'll have to decide for yourself. 
	

	
	
		
		

		
		
	


	




 And it's a fine first project, just be prepared to do a lot of reading and research._

 

Yeah, I was planning on doing a LOT of reading beforehand... it's difficult because there are so many great projects to do on the cheap if you're willing to put the time and effort into it 
	

	
	
		
		

		
		
	


	




 My only problem is I live outside the US (Mexico), so I believe I can get everything shipped to me, just that shipping is a killer... although we do have Radioshack, and sometimes they charge the same price as the US... sometimes not.


----------



## error401

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_Sorry if this has been posted before, plus I'm a complete noob, but are there any alternative tubes to the 19j6's? I can't seem to find any for sale on-line... well there was one guy selling them on Ebay for $10 each...

 Also, anyone know of an enclosure that could fit something like an Alien DAC and this amp together? I'm thinking of doing this as my first project... sounds a little difficult though for a first-timer, heh..... 
	

	
	
		
		

		
			



_

 

I just ordered 2 pairs of 19J6 from RadioDaze yesterday at $3.15 per. It was the only place I could find them, and the price didn't seem too bad.


----------



## Citizen86

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_I just ordered 2 pairs of 19J6 from RadioDaze yesterday at $3.15 per. It was the only place I could find them, and the price didn't seem too bad._

 

Ah thanks, yeah with a little more searching I found a couple more places. I also sent an email to The Tube Center, they are $3 there I think... I just need a quote on shipping.

 BTW, where are you from in Vancouver, error? I grew up in Kitsilano area.


----------



## elliot42

Bit of an update after some more investigation on my interference issue. I tried the amp downstairs at home and the problems were greatly reduced, I could only hear a faint radio signal. But I took it upstairs to my room again and it was back. It picked up ABC Classical (92.9FM) really well.

 I took the big sink off and all this really did was change the station being picked up (now it's a faint WSFM (101.7FM)).

 The interference can be heard very faintly at most positions around the pot, but it is suddenly much louder in the bottom 1k of the full turn.

 The interference starts only when the tube has warmed up. I can see the heater start to go orange on top when I first give it power, but it's a few seconds before the radio starts. I guess this means it's the tube that's picking up the signal, which is what someone mentioned could be happening earlier. Does this mean I have to shield the tube somehow? or could there be other explanations?

 As for the hum, I tried removing the case from the ground star and it resulted in a lot of very loud hum. The hum was sometimes improved with an extra ground wire directly touching the case at some points. I guess this will just be a trial and error process, finding the best spots to ground and reduce hum.


----------



## Listen2this1

Is the hum on one tube or both? If it is on one try swapping the tubes and see if the problem follows. If so then try a new tube. It is pretty odd.


----------



## elliot42

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Is the hum on one tube or both? If it is on one try swapping the tubes and see if the problem follows. If so then try a new tube. It is pretty odd._

 

I only have one channel going at the moment, still waiting on a fet after the supplier messed up my order. I'll give another tube a go, didn't think of that. The tube also produces a hum as I move my hand closer to it and more when I touch it, kind of like a theremin. Is that normal? If not, maybe it is a problem tube.


----------



## Listen2this1

Now we are on to something, I think. My MHM did the same thing (the hand thing) until I grounded the aluminum plate at the top. By the way I think you might be having a condition like this. I would wait until you get all of the product and finish the build the re-do the grounds.

Microphonics - Wikipedia, the free encyclopedia


----------



## adamus

hmmm. Seems like a few people are getting silence with touchin the chassis. maybe we need t isolate everything from the case and just ue the copper plane


----------



## joe_seattle

Question for folks - I want to add a small jack for ipod input along with the left and right rca jacks. Can I route the channels of the two inputs together (since I won't ever have input from both at the same time), or will some of the signal go back to the inactive input jack and cause interference? In other words, do I need to use a switch?


----------



## rds

Quote:


 Can I route the channels of the two inputs together (since I won't ever have input from both at the same time), or will some of the signal go back to the inactive input jack and cause interference? In other words, do I need to use a switch? 
 

If you have them both plugged in at the same time you need a switch.


----------



## MisterX

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_Question for folks - I want to add a small jack for ipod input along with the left and right rca jacks. Can I route the channels of the two inputs together (since I won't ever have input from both at the same time), or will some of the signal go back to the inactive input jack and cause interference? In other words, do I need to use a switch?_

 


 No, you do not need a switch but it is a good idea. 
 FWIW if you are short on space you can always use a closed circuit mini jack like those found at Radio Shack

RadioShack.com - Cables, Parts & Connectors: Connectors & connectivity: A/V connectors & adapters: 1/8" Stereo Panel-Mount Phone Jack

 (wire it like the image and the RCA inputs will get disconnected when something is plugged into the mini jack)


----------



## -=Germania=-

Switches are suggested!

 Plus, it will make the grounding better since the signal its not traveling to an uncontacted source. Just a way to eliminate a potential source of noise!


----------



## m0b1liz3

What switch should be used? I have a single throw switch for the power I wont be using but I am guessing it will require a dpdt?


----------



## JamesL

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_What switch should be used? I have a single throw switch for the power I wont be using but I am guessing it will require a dpdt?_

 

yup 
	

	
	
		
		

		
		
	


	



 Personally, I'd go with a normally-closed 3.5mm jack as misterx suggested, but either would work.


----------



## Zigis

I think better way is put 3.5mm jack very close to RCAs (between them or in triangular form) and connect parallel without switch.
 Why you need additional unknown quality contacts in signal path?


----------



## m0b1liz3

it has been said that we need resistors in order to have rca outs. i guess they would have to come before the switching hp jack? i still haven't finished my case so won't be starting the build just yet.

 it was previously said to put resistors on the volume pot but that would be on the input part of the schematic as opposed to after c3 and c5 on the output. is there a reason wiring the resistors to the pot is preferred?

http://www.jaycar.com.au/productView...Max=&SUBCATID=

 Would the above jack be suitable for this purpose?


----------



## -=Germania=-

That would work - if you put the RCA's after the Mini Jack in the input.

 RCA-> Switched Jack -> Pot


----------



## n_maher

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_it has been said that we need resistors in order to have rca outs._

 

What I think has been said is that the gain of the SSH is prohibitively high for it to be used effectively as a preamp. If I was going to use it as a preamp I'd follow the other advice in this thread about attenuating the input via a series resistor at the input. Output resistors should be a method of last resort in my opinion.

  Quote:


 is there a reason wiring the resistors to the pot is preferred? 
 

Yes, and it's been discussed at length earlier in this thread.

  Quote:


 Would the above jack be suitable for this purpose? 
 

It would work as a switched jack, yes.


----------



## keiths

My second Starving Student is coming together and I have a question regarding the best way to implement input and output switching.

 I have a 4 way 4 pole switch for input switching and a 2 way 4 pole switch to select outputs. The output switch will go immediately before the volume pot so that one position will send the signal to the pot for headphone listening, whilst the other postition will send the input signal straight to a pair of rca phono sockets which will use a long cable to connect to a pre-amp. (In this switch position, the Starving Student is just being used as a passive switch box).

 I'm using star grounding and all sockets are isolated from the case. My intention is to switch the grounds as well as the signal, so that when acting as a switch box, there is no connection to the star ground at all. (When in the other position, the first connection to the star ground will be at the volume pot). Is this the best way to go about this? Or should there be a connection to the star ground when used as a switch box (say at from the output phonos)? Or should each input and the output phonos connect to the star ground and I only switch the signal?


----------



## m0b1liz3

How did you isolate the sockets from the case?


----------



## keiths

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_How did you isolate the sockets from the case?_

 

The phonos came with teflon isolating washers that have a 'ridge' that sits in the hole preventing the socket contacting the case within the hole. I had a couple of spare ones which I'm using on the DC power socket. The Neutrik 6.35mm jack socket is plastic bodied and I'm using nylon washers on the 3.5mm jack sockets.


----------



## heatmizer

Would there be any problems with going to 1 uF film for c2,c4 sort of use what you have.


----------



## joe_seattle

Woohoo! I'm almost done with the right channel build, but I'm running out of room quickly in the case. Oops!


----------



## Zigis

My tubes are arrived and I am waiting for MOSFETs.

 Thinking about high gain problem, maybe we could put an other 220K resistor between C2 and R2 R4 split. New resistor with R4 made -6db attenuator. If this work, we lowering tubes noise for -6db too.
 Are there any downside in amp's operation?

 We can tray put in this place passive RC bass boost too.

 Any opinion?
 Zigis.


----------



## Jingo Lingo

Hi guys, I've just finished my amp and it sounds lovely but I'm getting a fair bit of hum in both channels. However, the hum is reduced considerably when I touch the metal casing of the headphone jack OR when I hold the case of my mp3 player which is acting as a source. Even stranger is that when I hold my mp3 player or jack and hold my other hand over the tubes, without touching them, the hum is pretty much gone.

 I've got no idea what's causing it, I used a blank PCB and my layout is very similar to Pete's original design. Only thing is that some things don't go straight to ground, like my RCA jacks, they are connected to each other, then to the ground on the PSU, then to the PCB. This is just for convince sake, Any problems with this? As you can tell, this is my first build. I'll try to get some pics later, Thanks in advance, any advice would be great.


----------



## TzeYang

Hey guys, gain of 15 seems to be too high for my needs (I barely even need a gain of 2 to begin with). Is it possible that i do some modifications to the circuit such as further degeneration or perhaps adding feedback?


----------



## n_maher

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_Hey guys, gain of 15 seems to be too high for my needs (I barely even need a gain of 2 to begin with). Is it possible that i do some modifications to the circuit such as further degeneration or perhaps adding feedback?_

 

I hate to say this but this topic has already been discussed several times in this thread, I suggest you use the wonderful search function or just read the whole thing. It's not _that_ long. 
	

	
	
		
		

		
			





 And Jingo, your description is pretty much textbook ground loop. I would definitely change some of your ground connections to see if it helps, I'd start with the inputs and go from there.


----------



## m0b1liz3

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Probably the reason people have cautioned against that is because it is not a good idea to have a huge input impedance. Large input impedances make the amp more susceptible to noise.
 The solution is to use a lower impedance pot if you want to reduce the gain a lot. 
 That is why I recommended a 100k resistor in series with a 10k pot.
 I've also found using 220k in series with a 50k pot to be perfectly acceptable._

 

Ok, so I am trying to figure out how I am going to lower the gain so that it is acceptable for both the headphones and line out. Previously a 50k resistor was suggested with the normal BOM pot. Is the above suggestion going to be the best combination in terms of noise?

 I guess TzeYang (and me) are wondering what the final consensus is on how to lower the gain while keeping the noise at a minimum. (Hope this isn't flogging a dead horse!)


----------



## manaox2

I'm guessing a 100k pot or the resister method is a great way to lower the gain without introducing too much more noise when listening. Probably what I would do at this point.


----------



## m0b1liz3

I have a 100k pot on hand. Would that mean I don't need any extra resistors? (If so it would simplify things for me!)


----------



## dsavitsk

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_or perhaps adding feedback?_

 

You could, but it will most likely change the amp's character. How much is for you to discover, I suppose.

  Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Previously a 50k resistor was suggested with the normal BOM pot. Is the above suggestion going to be the best combination in terms of noise?_

 

Noise won't be an issue. Look back a few pages for a description of why and how this works.

  Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_I'm guessing a 100k pot ... is a great way to lower the gain without introducing too much more noise when listening._

 

Switching from a 50K to a 100K pot will have zero influence on the overall gain.

  Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I have a 100k pot on hand. Would that mean I don't need any extra resistors? (If so it would simplify things for me!)_

 

No. You'll need a pair of 100K resistors instead of the pair of 50K's.


----------



## TzeYang

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I hate to say this but this topic has already been discussed several times in this thread, I suggest you use the wonderful search function or just read the whole thing. It's not that long. 
	

	
	
		
		

		
			





 And Jingo, your description is pretty much textbook ground loop. I would definitely change some of your ground connections to see if it helps, I'd start with the inputs and go from there._

 

Yeah like how m0b1liz3 described, we just want to know the best solution to the very high gain.

 I did not like the large input resistor method. It's sort of unwise to stick such a huge resistor at the input. Plus, why would I want to purposely attenuate the signal and then amplify it again with unnecessary high gain? 

 dsavitsk, 

 I'm useless when it comes to tubes lol. 

 Is the circuit operation similar to this:
Single-ended triode - Wikipedia, the free encyclopedia 

 I'm not sure about adding feedback. But if I'm not wrong there is some modifications to be done at the output stage too right? Should I use global feedback or just degenerated local feedback? If i use the latter i would probably have to change the CCS because the CCS (33k resistor) also acts as a degenerative resistor right? 

 Well, this circuit is amazingly nice due to it's simplicity, but the gain is too impractical for a lot of us.


----------



## dsavitsk

Quote:


  Originally Posted by *TzeYang* /img/forum/go_quote.gif 
_I did not like the large input resistor method. It's sort of unwise to stick such a huge resistor at the input._

 

That isn't what you are doing. As explained before, you are turning the 50K pot in to a 100K pot with a slightly different taper, and a limit to how far the wiper can move.

  Quote:


 Plus, why would I want to purposely attenuate the signal and then amplify it again with unnecessary high gain? 
 

You'll get no argument from me on this one: ecp.cc

  Quote:


 Is the circuit operation similar to this:
Single-ended triode - Wikipedia, the free encyclopedia 
 

Sort of. The tube portion of the circuit in the Starving Student is known as a Grounded Cathode. Those circuits are based on the GC, but they are transformer coupled which is a slightly different animal. 

  Quote:


 I'm not sure about adding feedback. 
 

I don't think feedback should be used in this sort of circuit as I think it will do more harm that the attenuator, but I am going to leave it alone as this sort of discussion generally degrades into a lot of useless shouting. So, you are on your own here.

  Quote:


 Well, this circuit is amazingly nice due to it's simplicity, but the gain is too impractical for a lot of us. 
	

	
	
		
		

		
		
	


	



 

So design your own.


----------



## Jingo Lingo

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_And Jingo, your description is pretty much textbook ground loop. I would definitely change some of your ground connections to see if it helps, I'd start with the inputs and go from there._

 

Thanks for the advice. I've re-grounded the input connectors and had a look at all the other grounds and they all seem to be OK. The hum is still there however. Anything else in particular I should check?


----------



## m0b1liz3

I think I need to understand this in terms of I=V/R. We have a resistor for each channel right? So what is the current and voltage of the signal on the starting side of the resistor for each channel and what is an acceptable range coming out of the other side for rca outs/headphones?


----------



## Zigis

What do you think, folks about reducing gain with attenuator between stages? (see my post 923)
 Any trouble in amp operation? Can it work?


----------



## heatmizer

Bump, 
 Would there be any problems with going to 1 uF film for c2,c4 sort of use what you have. thanks


----------



## dsavitsk

Quote:


  Originally Posted by *heatmizer* /img/forum/go_quote.gif 
_Would there be any problems with going to 1 uF film for c2,c4 sort of use what you have. thanks_

 

You should be fine.


----------



## dsavitsk

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I think I need to understand this in terms of I=V/R. We have a resistor for each channel right? So what is the current and voltage of the signal on the starting side of the resistor for each channel and what is an acceptable range coming out of the other side for rca outs/headphones?_

 

It really isn't the right way to think about this. Whether you have a 10K or a 100K pot, it works the same as the tube's Zin is very high, and so almost no current flows to it. You have a resistor divider, the voltage of your source is split by it, and you take the voltage from the point of split to wiggle the tube's grid up and down. The tube, however, draws almost zero current (so low, in fact, that if you use a battery to bias the grid, the battery's lifetime won't be diminished from storing it in a drawer.)


----------



## dsavitsk

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_What do you think, folks about reducing gain with attenuator between stages? (see my post 923)
 Any trouble in amp operation? Can it work?_

 

Those resistors set the mosfet bias. Better to attenuate on the input, otherwise you'll probably need another coupling cap thrown in there.


----------



## thunder

I to have built the Max and it sounds very good! My question is when using my 66 ohm HPs the sound is really good, then switching to 600 ohm HPs it seems the band-width shrinks and power levels drop alot why ?


----------



## Zigis

Thanks for explanation, dsavitsk, and how about attenuator between anode and C2 ?


----------



## TimJo

Well before I started on building a MiniMax prototype, I figured I should finish my second Starving Student amp first. The case is an old tin I found at the goodwill for 69¢ but it required some creative design techniques. It ended up kind of being a pain doing the way I did it, but I think it turned out looking pretty good...

 So here it is, the Hershey's Millett Amp. I think it will become my new portable amp since it has wheels.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well before I started on building a MiniMax prototype, I figured I should finish my second Starving Student amp first. The case is an old tin I found at the goodwill for 69¢ but it required a little creative design techniques. It ended up kind of being a pain doing the way I did it, but I think it turned out looking pretty good...

 So here it is, the Hershey's Millett Amp. I think it will become my new portable amp since it has wheels.
	

	
	
		
		

		
		
	


	


_

 

Now that one is sweet. My 10 year old son is begging me to get him one like that now 
	

	
	
		
		

		
		
	


	




 If it's ever for sale, let me know.


----------



## bhjazz

TimJo - 

 AMAZING! Really creative. Wow. Thanks for posting pics!


----------



## adamus

I fixed my ground loop. It wasnt a ground loop, just a dodgey solder point on a ground.


----------



## Jingo Lingo

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I fixed my ground loop. It wasnt a ground loop, just a dodgey solder point on a ground._

 

How did you isolate it? Just re-solder all the grounds?


----------



## adamus

yep, they all checked out fine with a multimeter but obvisouly once wasnt. The groundplane joint need a lot of heat! This is will nothing isolated.


----------



## Jingo Lingo

I re-soldered all the grounds and swaped out the tubes and the hum has greatly reduced, bit it's still there. With it plugged into my soundcard the hum is totally gone, so I'm happy enough to leave it like it is for now.

 Here's my RS-1 with its new friend:


----------



## tomb

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_I to have built the Max and it sounds very good! My question is when using my 66 ohm HPs the sound is really good, then switching to 600 ohm HPs it seems the band-width shrinks and power levels drop alot why ?_

 

I think you posted in the wrong thread ... look for the "New Millett Hybrid MAXed Amp" thread, instead.


----------



## joe_seattle

Help! I finished building the amp, but it's having issues. Ok...the wiring isn't the most pretty - I used a too-small case and didn't think enough about what would bump into what (I can only fit a small headphone jack at the moment. ha!). Anyway, one channel works great, and sounds great. The other channel does what someone else experienced: mosfet doesn't produce the 19 volts (stays at 40) and the tube glows like a fission reaction. Any easy culprit? I tried two different mosfets with the same result. The headphone out on that channel has much higher voltage than it should, so the problem for sure seems that the mosfet isn't doing anything with the current.


----------



## TimJo

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_The other channel does what someone else experienced: mosfet doesn't produce the 19 volts (stays at 40) and the tube glows like a fission reaction. Any easy culprit? I tried two different mosfets with the same result. The headphone out on that channel has much higher voltage than it should, so the problem for sure seems that the mosfet isn't doing anything with the current._

 

Well your best bet is trying to post some clear photos of the wiring on the bad channel and see if anything is obvious to others looking at the pics. 

 In the meantime, you can slowly go through the circuit and the wiring and see if you can determine what is different between the way you wired each side.


----------



## scompton

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_Help! I finished building the amp, but it's having issues. Ok...the wiring isn't the most pretty - I used a too-small case and didn't think enough about what would bump into what (I can only fit a small headphone jack at the moment. ha!). Anyway, one channel works great, and sounds great. The other channel does what someone else experienced: mosfet doesn't produce the 19 volts (stays at 40) and the tube glows like a fission reaction. Any easy culprit? I tried two different mosfets with the same result. The headphone out on that channel has much higher voltage than it should, so the problem for sure seems that the mosfet isn't doing anything with the current._

 

That was the symptom I had. I'm not sure if it was a blown mosfet or not. When trying to diagnose it I shorted the power jack and, if the mosfet wasn't blown before that, it was afterwords.

 Mine worked fine until I closed the case. Something shorted and I got no sound, high voltage, and a very bright tube. This continued even after reopening the case. With the case open there wasn't a short.

 I think I blew a mosfet when I closed the case, but I'm no expert. After definitely blowing them, I took them out and they had continuity across the pins. I put new ones in and rewired some of the resistors that had long, exposed legs, and rewired the caps. I put heat shrink over any exposed wire. I just used some heat shrink I got at Radio Shack.

 Except for the heat shrink, I'd post pictures to get advice from someone who knows more than me before blaming the mosfet. Once everything is wired, changing the mosfets is a pain, at least in my case.


----------



## procalli2007

Im trying to design a pcb using eagle but im having problems finding the right part for the valve. anyone know where i can find the library which contains a part.
 ive also downloaded eb multisim trial but again cant find the parts for the valves.


----------



## rds

Quote:


 Thanks for explanation, dsavitsk, and how about attenuator between anode and C2 ? 
 

The reason dsavitsk and others have said to put the resistor in front of the pot is not because they can't think of other ways to effectively lower the gain. It's because it is the best way in this case.
 You can use a 10k pot, a 40k resistor, and step down the gain by 1/5 while still having a "normal" input impedance of 50k.


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Im trying to design a pcb using eagle but im having problems finding the right part for the valve. anyone know where i can find the library which contains a part.
 ive also downloaded eb multisim trial but again cant find the parts for the valves._

 

There is an Eagle library for the revMH Millett Hybrid at diyforums.org

 Follow the link for the "revMH Millett Hybrid." The reference is a couple of paragraphs down under the rendering of the PCB. That library should contain 7-pin PCB tube sockets.


----------



## procalli2007

great, thanks


----------



## cetoole

Just note that while the socket is the same, the pinout is different. Wont be difficult to modify the library for the 19j6 though.


----------



## procalli2007

Is there a library which has the tube definition for schematic view so that it automatically produces a board layout?


----------



## joe_seattle

Wow! I got it to work. It was just a small drip of solder that was connecting with a ground plug and doing nonsense.

 This this sounds really good. I'm listening to "Stairway to Heaven" and some Erasure. Awesome, unmuddled sound - on my HD600 a slightly wider soundstage with fuller high notes and a crisper/tighter/more controlled bass. Overall the sound is just slightly more exact and clean, with a greater sense of effortlessness that I appreciate.

 The amp isn't so good with my K340 - oh well, I guess they require more power.


----------



## royewest

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_The reason dsavitsk and others have said to put the resistor in front of the pot is not because they can't think of other ways to effectively lower the gain. It's because it is the best way in this case.
 You can use a 10k pot, a 40k resistor, and step down the gain by 1/5 while still having a "normal" input impedance of 50k._

 

I put a 100K ohm resistor in line with the tip of the RCA input and it's a little quieter but still mighty loud.

 I wonder if anyone can suggest a reasonable quality 10K pot to try, to follow rds' advice? 

 I may also try a voltage-divider arrangement, though I confess I do not really know what I am doing. I might try, in addition to the 100K ohm resistor between the tip and the pot, joining the tip and ground with a 50K or 100K resistor -- am I doing something dangerous here?

 I would appreciate help understanding what the affect of increasing the input impedance can be, particularly if I risk harming my source.

 Thanks,

 __Roy


----------



## dsavitsk

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I put a 100K ohm resistor in line with the tip of the RCA input and it's a little quieter but still mighty loud._

 

Maybe this just isn't the amp for you. Can you really not just turn it down? 

 Try leaving out the tube, connecting the input right to the Mosfet, and replacing the tube heater in the circuit with a high power resistor -- basic instructions here. HeadWize - Project: A Class A MOSFET Headphone Driver by Greg J. Szekeres

  Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I may also try a voltage-divider arrangement, though I confess I do not really know what I am doing. I might try, in addition to the 100K ohm resistor between the tip and the pot, joining the tip and ground with a 50K or 100K resistor -- am I doing something dangerous here?_

 

No, but you aren't doing anything useful either. I'd suggest taking a step back and doing a little studying rather than just throwing resistors at the problem.

  Quote:


 I would appreciate help understanding what the affect of increasing the input impedance can be, particularly if I risk harming my source. 
 

The higher the Zin, the easier it is for your source to drive, so higher is better, in a sense. But, also the higher the noise. This noise will be swamped by the tube noise, so it really isn't an issue here. The caveat, is that there is a limit to what the tube will tolerate, which is probably about 1M or so, so don't worry about it.


----------



## royewest

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_No, but you aren't doing anything useful either. I'd suggest taking a step back and doing a little studying rather than just throwing resistors at the problem._

 

I've been having fun for a few months building amps, DACs, and other gear from recipes and kits on line, getting help from folks when I get stuck, and having a lot of fun and achieving some wonderful sound. But of course it's time to actually try to learn how some of this gear works, at least at a basic level.

 I'd welcome a suggestion of a book (or web site, I suppose) that would help me get started.

 Thanks,

 __Roy


----------



## scompton

My max listening volume is just over the point of channel imbalance with the BOM pot. This is with Sextetts and other similar to drive headphones. I can understand why it would be too loud for someone with very easy to drive headphones. If I make another, I'll put a resistor on the input.


----------



## -=Germania=-

Roy, 

 Likely the Pot is wired incorrectly. 

 Switch the positions of the input and output on the pot and see of that helps.


----------



## n_maher

Roy,

 This is one of those cases where a picture would probably help a lot. Give us something where we can see how the input and pot are wired clearly.


----------



## royewest

I've mentioned before that my photo skills are marginal at best.

 Here's a shot of the pot and its connections. I hope it's clear enough to show if I've made a gross error. What may not be clear is that the far right pins on the pot (in the photo) are connected together and down to the ground plane below them.

 If a larger image would be helpful, let me know and I will post a much higher-res image than is allowed here elsewhere and post a URL.

 Thanks again,

 __Roy


----------



## n_maher

Pot looks to be wired correctly to me.


----------



## joe_seattle

Here is something mysterious...listening to my AKG K340 headphones using the amp last night, I noticed that the treble would cut out when I adjusted the volume. It was like muffling all the high frequencies. When I took my hand off the volume stem, the high notes returned. It didn't do this with my HD600 headphones.

 Could this mean I have a small ground issue somewhere in the amp? Or might it mean something about the grounding in my K340? The K340 has both electret and dynamic drivers, with the electret handling the majority of the mids and high notes. My phones are heavily modded by folks before me, and tend to be weak/rolled off in the high notes, though I haven't heard another pair for comparison.

 Anyone have ideas on what is going on?


----------



## joe_seattle

Thank you to everyone who helped with this project. Here are some pics of the outside, which looks much, much better than the inside. But the amp sounds great!
 -Joe


----------



## TzeYang

WTH, THAT LOOKS BEAUTIFUL. Either you take good pictures or your choice of components are really that good!

 I still want to see the insides though lol.


----------



## error401

The wood base is a nice touch. What case is that?


----------



## JamesL

Nice clean work joe! It kinda reminds me of a earmax for some reason =P

  Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_The wood base is a nice touch. What case is that?_

 

It sorta reminds me of one of these transformer covers. I'm curious as well.. perhaps a diecast hammond enclosure?


----------



## Jingo Lingo

Nice work, my enclosure looks ridiculously large by comparison.


----------



## error401

Quote:


 I'm curious as well.. perhaps a diecast hammond enclosure? 
 

Well, that's what I've got for mine, a diecast hammond. Pretty cheap, and I'm too lazy to go find something suitable to repurpose. I'm just hoping it will be big enough, it'll be a tight fit, but I think it will work.

 What're your opinions on finishing these? Sand and buff it to a shine, then clearcoat (will that work?), or paint?


----------



## heatmizer

Oh Its large enough.
	

	
	
		
		

		
		
	


	









 Actually Bud enclosure. 4.5 "x 4.5"x2.5". What a pain to polish.Was not able to all scratches out even with 1200 grit paper. Aside from the tubes and sockets everything was around the house. Heatsinks are cut down cpu heatsink. Don't know if it works, still waiting for power supply.


----------



## Hayduke

Quote:


  Originally Posted by *heatmizer* /img/forum/go_quote.gif 
_Oh Its large enough.
	

	
	
		
		

		
			










 Actually Bud enclosure. 4.5 "x 4.5"x2.5". What a pain to polish.Was not able to all scratches out even with 1200 grit paper. Aside from the tubes and sockets everything was around the house. Heatsinks are cut down cpu heatsink. Don't know if it works, still waiting for power supply._

 

That looks pretty nice. If you want to polish the case, you have to go well beyond 1200 grit. If you hit up your auto parts store, you can find what you need. There is sandpaper that is 3600 grit. It feels smooth, but it really does remove material. After you finish the sandpaper, you move on to the paste type polishes. You can give that aluminum case a mirror shine, but is it worth all the work? That's up to you. 
	

	
	
		
		

		
		
	


	




 Again though, it looks nice now. I prefer black components myself, but we all have different tastes


----------



## JamesL

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Well, that's what I've got for mine, a diecast hammond. Pretty cheap, and I'm too lazy to go find something suitable to repurpose. I'm just hoping it will be big enough, it'll be a tight fit, but I think it will work.

 What're your opinions on finishing these? Sand and buff it to a shine, then clearcoat (will that work?), or paint?_

 

I'm thinking clearcoat or primer+paint would work. 
 I think hammond sells some that are already powder coated, and if the finish
 is anything like the one on joe's case, I think I might use it for a transformer cover.


----------



## bhjazz

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_After you finish the sandpaper, you move on to the paste type polishes. You can give that aluminum case a mirror shine_

 

I found a polishing wheel that works with a drill. Get that and some polishing compond and you'd be good to go. In fact, the poishing compound I bought was for stainless steel as well (left over form a kitchen project). Definitely takes time, but since 'mizers PS isn't in, hey myman: you've got time! 

 BTW: Looks nice, Heatmizer.


----------



## procalli2007

Ive started to get a hum from my ss which goes if I touch the case or rca sockets?

 Im sure it wasnt there when I first built it. It gets louder as I turn up the volume.


----------



## adamus

mine did that. Recheck your joints to ground.


----------



## procalli2007

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_mine did that. Recheck your joints to ground._

 

thanks for that. One question, did you just resolder all the ground connections shown on the schematic?


----------



## 2162

Quote:


  Originally Posted by *joe_seattle* /img/forum/go_quote.gif 
_Thank you to everyone who helped with this project. Here are some pics of the outside, which looks much, much better than the inside. But the amp sounds great!
 -Joe




































_

 


 Looking great, holy moly, that thing is tiny!


----------



## marktd

I just got my tubes from Radiodaze and 1 says oc9, the other 19j6 the first one is Philco, the second Delco. They lookvery similar, but is this right? The is my first project...... Thanks, Mark


----------



## error401

What're you guys using to cut the 5/8" holes for the tubes in metal? I think I want a metal punch, but I haven't seen them at my local hardware stores. Any ideas where I could find something appropriate locally?


----------



## fuzzyt

So I thought I would build this amp to get my feet wet a little. This is the first time I have done anything like this. I have soldered before in the past and am not concerned about that. I have been studying the schematic for the last couple of days while parts show up. I have everything I need except the tube sockets and the power supply (which are both in transit). The first problem I have run into is with the wall thickness of the box I was planning on using. The walls are 3/8" thick and all of the items that need to mound on it are presenting a challenge already. I have some extra copper clad board that I could possibly use to mount these to then find a good way to attach them to the box internally but I thought I would ask around and see if anyone had a better idea? I can post some pictures of the box if necessary but would rather wait until it is at least somewhat complete. 

 Thanks in advance for any tips.


----------



## elliot42

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_What're you guys using to cut the 5/8" holes for the tubes in metal? I think I want a metal punch, but I haven't seen them at my local hardware stores. Any ideas where I could find something appropriate locally?_

 

I got myself some stepped drill bits (came in a pack of three) and they are fantastic for cutting nice, round holes in metal and other sheet materials. I got them from a hardware store (Bunnings warehouse) for AUS$24.

 This is them:





 Get some, they're great for case work.


----------



## Postal_Blue

^ x2 stepped bits are a must for case work.


----------



## keiths

Finished my second Starving Student - this one's for my work desk.
















 Three switchable inputs (back panel rcas, iPod (mini) dock and front panel 3.5mm jack) and output switch to send (unamplified) signal to external (speaker) amp.

 The heatsink is from an old, broken power amp.


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_What're you guys using to cut the 5/8" holes for the tubes in metal? I think I want a metal punch, but I haven't seen them at my local hardware stores. Any ideas where I could find something appropriate locally?_

 

Grainger or McMaster-Carr are good sources for Greenlee punches. You can also find them on e-bay. They're a good buy used, but don't buy another brand that way, if you can help it. Stay away from the Harbor Freight brand, though. You can also find some limited sizes available at Lowes or Home Depot in the electrical department, if you have those stores near you. Finally, Mouser has them in their catalog.

 Be careful to check the actual hole size. Many of these are sold for "conduit sizes," which are sized for the O.D. of the conduit, but labeled for the nominal conduit I.D.

  Quote:


  Originally Posted by *fuzzyt* 
_So I thought I would build this amp to get my feet wet a little. This is the first time I have done anything like this. I have soldered before in the past and am not concerned about that. I have been studying the schematic for the last couple of days while parts show up. I have everything I need except the tube sockets and the power supply (which are both in transit). The first problem I have run into is with the wall thickness of the box I was planning on using. The walls are 3/8" thick and all of the items that need to mound on it are presenting a challenge already. I have some extra copper clad board that I could possibly use to mount these to then find a good way to attach them to the box internally but I thought I would ask around and see if anyone had a better idea? I can post some pictures of the box if necessary but would rather wait until it is at least somewhat complete. 

 Thanks in advance for any tips._

 

There's no magic solution, I'm afraid. 3/8" is pretty thick unless it's wood. If aluminum, you'll probably be better off drilling pilot holes and then going straight to a full-size bit. Most step drills don't even have 3/8" spacing between steps, so using one will make some awfully funny looking holes.
	

	
	
		
		

		
		
	


	




 Try to use some lubricant - that will cut down on scratches and tears around the hole. I find Marvel Mystery Oil to be a good, all-around oil for stuff like that.


----------



## n_maher

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Finished my second Starving Student - this one's for my work desk._

 

Great work man, very cool.


----------



## Exidous

Well after reading all 99 pages all I can say is I look forward to finishing my ee degree. I'm only two years on so the classes are still very generic and the only electronic training I have is from the Air Force. It's still quite good mind you just not at the level required to create projects.

 With that being said I love you guys already. 

 Now to my question(s). You knew it was coming. 

 I ordered all of my parts(hopefully) and want to include the e12 time delay circuit. I did see a quick note on how to do it but was a tad confused. I don't know the current draw of the e12. Obviously I'm aiming for a 36v drop.

 Without the current I'm not sure how to chose a resistor. Help is of course appreciated and hopefully I didn't make myself look like a fool.

 Oh on anothe note... Anyone know of a link to a linear toroidal PS that would give me a steady 48V and maybe even an output for 12V?

 Thank you Pete for this great and overall simple design.


----------



## adamus

I tested mine for offset on startup, its more of a tap than a thump. really wouldnt be bothered with a e12.


----------



## Exidous

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I tested mine for offset on startup, its more of a tap than a thump. really wouldnt be bothered with a e12._

 

I figured as much but I just spent 200.00 on a new set of cans and for the 6$extra I figure why not.


----------



## n_maher

Quote:


  Originally Posted by *Exidous* /img/forum/go_quote.gif 
_I figured as much but I just spent 200.00 on a new set of cans and for the 6$extra I figure why not._

 

$6? I think it'll cost you a bit more to do an e12. Heck, just the pcb is $8. And I'm a member of the "just unplug your headphones" crowd, that's the cheapest option of all.


----------



## adamus

even if forget, as long as you dont go silly large on the output cap (no need to go larger than 470uf) i would put down a large bet to say you wont kill anything.


----------



## holland

.


----------



## tomb

Quote:


  Originally Posted by *Exidous* /img/forum/go_quote.gif 
_<snip>
 I ordered all of my parts(hopefully) and want to include the e12 time delay circuit. I did see a quick note on how to do it but was a tad confused. I don't know the current draw of the e12. Obviously I'm aiming for a 36v drop.

 Without the current I'm not sure how to chose a resistor. Help is of course appreciated and hopefully I didn't make myself look like a fool.

 Oh on anothe note... Anyone know of a link to a linear toroidal PS that would give me a steady 48V and maybe even an output for 12V?

 Thank you Pete for this great and overall simple design._

 

Others have hinted at it, but by the time you start considering a linear-regulated power supply plus an e12 delay, you're really talking a Millett MAX.
	

	
	
		
		

		
			





 Search through the thread. There was a big discussion on a headphone delay relay, along with some measurements on the actual offset at power up that I did awhile back. The consensus is that it's not a necessary requirement for the SSMH.

 As for linear toroids, I'm no expert on toroids, but "linear" and "steady" imply linear regulation - not something you're going to get straight out of a transformer. The SSMH is not set up for that, either. The VOIP switcher power supply is the thing for the SSMH and it seems to work quite well. There is a linear-regulated supply availble from Jameco that I believe Holland may have used. Maybe he'll post his details if you're interested.

 Yes, Pete is a fantastic benefactor for the DIY community.


----------



## holland

.


----------



## Keithpgdrb

I'm not sure how much the moderators read this, but is it possible to split this discussion up? I am interested in this DIY project, but I really cant sit and scroll through 900+ posts. maybe its time to start a new category in this area? maybe even a couple? Its hard to see what info has been updated and such. Just a thought.


----------



## royewest

A thousand posts. My.

 I wish there were a FAQ for the SSMH; this thread could certainly supply the raw materials for one and even though I've been through all or parts of this thread several times, I lose track of info in it. Perhaps Pete would host it on the SSMH page.

 "Can I use a different tube." "How can I lower the volume." "Can I use it as a preamp." "Do I need to worry about the pop on startup and why not (tied to new specs for the caps)." "I have a bad hum that changes when I touch the chassis." Etc., etc.

 I'd work with someone on this (I write docs for a living), but I'd mostly be helping with editing, etc., since I have so little expertise in audio electronics...


----------



## tomb

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_I'm not sure how much the moderators read this, but is it possible to split this discussion up? I am interested in this DIY project, but I really cant sit and scroll through 900+ posts. maybe its time to start a new category in this area? maybe even a couple? Its hard to see what info has been updated and such. Just a thought._

 

One of us may be building a website soon (hint, hint) - at least to support the PCB version. That's the real answer to your request. In the meantime, _Pete's website is still current_ except for perhaps replacing all the electrolytics with 470uf 63V. The two output electrolytics at that size preserve the bass response for low-impedance headphones (Grados). According to Pete, two rail electrolytics at that size cut out the power supply stuttering on startup.

 Dsavitsk also offered a tweak that works quite well: using input resistors at the volume pot. That helps to push the volume travel down to a more usable range with the gain of the tubes. Start with resistors directly in-line with both the R and L signal inputs to the pot (don't do it for Ground), sized at the same impedance of the pot (50K). You can increase in 50K multiples from there until you get the volume travel desired for your headphones.

 So - not much changed - and those are options, actually.


----------



## n_maher

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_I'm not sure how much the moderators read this, but is it possible to split this discussion up? I am interested in this DIY project, but I really cant sit and scroll through 900+ posts. maybe its time to start a new category in this area? maybe even a couple? Its hard to see what info has been updated and such. Just a thought._

 

Pardon my sarcasm but can you be troubled to read the first post? It's DIY, it's open source, it's constantly evolving to a degree, that's just the nature of these things and no amount of moderation would fix or change that for the better.

 The basic required material is contained in a very user-friendly form on Pete's site and clearly linked in his first post. If you want to modify the design from what is shown on his site be prepared to do some research. 

 Just a thought.


----------



## dsavitsk

Just to clear these up:

  Quote:


 "Can I use a different tube." 
 

No

  Quote:


 "How can I lower the volume." 
 

Use a resistor on the input

  Quote:


 "Can I use it as a preamp." 
 

Not really

  Quote:


 "Do I need to worry about the pop on startup and why not." 
 

No, because there really isn't one.

  Quote:


 "I have a bad hum that changes when I touch the chassis." 
 

Resolder your ground connections.

 Does that suffice for a website?


----------



## error401

Someone wanted to set up a wiki for that sort of purpose. Can't say I disagree, but there didn't seem to be much interest.

 tomb - thanks for the advice on punches, I will see what I can find.


----------



## Exidous

I appreciate everyones input. As said above the ripple is mostly eliminated. I'm fine with that. As for the e12 I did forget about the board. So about 13 or so total. I should have mentioned that I'm not really a Starving Student and am more about the project and a challenge than saving as much money as possible. Hence the e12 question. The parts were already ordered so I'm still looking for a little input on the proper voltage drop to run it.

 I checked where the discussion over the e12 was. (around page 51) There isn't any info in there about how to get the right voltage drop for the 12v circuit.


----------



## ludoo

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_I'm not sure how much the moderators read this, but is it possible to split this discussion up? I am interested in this DIY project, but I really cant sit and scroll through 900+ posts. maybe its time to start a new category in this area? maybe even a couple? Its hard to see what info has been updated and such. Just a thought._

 

I built an app to index and search the Ortho thread as it's a huge goldmine of information, and while I was at it added the Stax thread and this one too, as I plan on building a SS as soon as I receive my parts.

 You can use my (experimental) app at Home / Head-Fi Megathreads I update the index from time to time, will probably schedule it as an automated nightly job soon. Jude (the board owner) knows about it, in fact is there's any interest in making it permanent I will give him the code.

  Quote:


  Originally Posted by *Exidous* /img/forum/go_quote.gif 
_I checked where the discussion over the e12 was. (around page 51) There isn't any info in there about how to get the right voltage drop for the 12v circuit._

 

Using the above app, there are 9 posts on the e12
Search for 'e12' in Head-Fi - Millett "Starving Student" hybrid amp / Head-Fi Megathreads


----------



## Keithpgdrb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Pardon my sarcasm but can you be troubled to read the first post? It's DIY, it's open source, it's constantly evolving to a degree, that's just the nature of these things and no amount of moderation would fix or change that for the better._

 


 Your right, how stupid of me. its open source, DIY, no one would EVER be interested in making it easier to navigate. I'm sure the moderators don't care in the least about their members. I guess in reading the first post, I should have been aware of that. in fact, I think we should just bulk together all the amplifier posts as well.. no need to separate them into portable and full size. people should just stop being lazy and do some reading. Pardon my sarcasm as well. I was trying to make a suggestion that would HELP everyone... 
 I should realize by now that you cant post much on the forums without being attacked by someone. I understand now why some people have been members since 2005, and have under 100 posts. I must wonder if you would have made the same comment if I had about 3000 posts.

 I think i've gone on a rant here. sorry everyone. I wont clutter the thread with any more of this. PM me if need be.


----------



## Exidous

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I built an app to index and search the Ortho thread as it's a huge goldmine of information, and while I was at it added the Stax thread and this one too, as I plan on building a SS as soon as I receive my parts.

 You can use my (experimental) app at Home / Head-Fi Megathreads I update the index from time to time, will probably schedule it as an automated nightly job soon. Jude (the board owner) knows about it, in fact is there's any interest in making it permanent I will give him the code.



 Using the above app, there are 9 posts on the e12
Search for 'e12' in Head-Fi - Millett "Starving Student" hybrid amp / Head-Fi Megathreads_

 

I did the search already and came up with little impementation help. I see one post in that about using an adjustable voltage regulator. Which is excessive and not needed. I just want to know how to calculate the proper voltage drop for the e12 timer setup. I should not need anything more than a resistor. It looks like I'm going to have to just wait for the parts to get here(at least a week). If anyone knows the resistance or current draw of the circuit it would be appreciated.


----------



## n_maher

Quote:


  Originally Posted by *Keithpgdrb* /img/forum/go_quote.gif 
_Your right, how stupid of me. its open source, DIY, no one would EVER be interested in making it easier to navigate._

 

Would you have preferred that Pete posted the schematic and then the thread was locked? Would that have served your particular needs better? Point being that while there are a ton of off topic posts in this thread there's also some good information that doesn't need to be filtered into an easily digestible format.

 You're looking for someone to hold your hand throughout the process and to tell you each and every little turn to take. I'm suggesting that Pete gave you a map with all of the big steps outlined and that at the end of that map there were a bunch of different paths that you could take. Some of those paths have been discussed here, many of them haven't. I think life might be a bit more fun if you picked which of them you took rather than having someone paint the whole picture for you. Is that so wrong?

 And why bring up post count? I can assure you that I didn't think about yours before replying. I don't much care for post counts and don't think that the fact that I have more than others gives me any particular rights or privileges. Now the fact that I've built a hundred or so projects might give me some insight but that remains to be seen as well.


----------



## royewest

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Just to clear these up:
 ...
 Does that suffice for a website?_

 

I guess the point of a FAQ someplace other than this thread was to prevent you and others from having to do that again.

 "Hey, why don't you check out the FAQ at URL." seems more in the helpful spirit of Head-Fi than "Why don't you read the 1009 posts before asking this question, [insert perjorative adjective here]."


----------



## Exidous

I don't suppose we could get back to the original purpose of the thread?


----------



## tomb

Some of you noobs need to look before you bite. You're playing with fire by trying to bite the hand that's feeding you.

 Dsavitsk is one of the foremost designers in our community and just happens to be in the midst of designing the SSMH PCB.

 As for Nate (n_maher), he happens to already be a moderator on no less than two other headphone forums and has given back more to this community than anyone I can think of - including organizing/producing/supporting the very first production Millett Hybrid for the DIY community.

 Yes, a few of us get irritated sometimes at answering the very same question ad nausea - but that's because many of you have no idea of the monumental work that goes on behind the scenes of the people you think should be a bit more patient.


----------



## n_maher

Quote:


  Originally Posted by *Exidous* /img/forum/go_quote.gif 
_I don't suppose we could get back to the original purpose of the thread? _

 

Sure, I'm happy to. Regarding your question concerning the e12, I would suggest posting the question at Headwize in the e12 build thread. I'm guessing it would be answered pretty quickly there and then you can post the information in this thread for future use by others.


----------



## Exidous

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Sure, I'm happy to. Regarding your question concerning the e12, I would suggest posting the question at Headwize in the e12 build thread. I'm guessing it would be answered pretty quickly there and then you can post the information in this thread for future use by others. 
	

	
	
		
		

		
		
	


	


_

 


 tyty sir.


----------



## holland

.


----------



## Citizen86

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Some of you noobs need to look before you bite. You're playing with fire by trying to bite the hand that's feeding you._

 


 Some people always must learn the hard way, fortunately for them there are some amazingly friendly people here


----------



## LeBuLLeT

Hello I cannot seem to find a 19j6 tube anywhere. I was about to order my parts until I discovered that there is no more 19j6 tubes. Unless someone knows where I can get these tubes. Thanks.


----------



## elliot42

Radio Daze is where I got mine. They're still listed there, and I got mine probably 2 months ago.


----------



## error401

I just ordered 4 19J6 from RadioDaze a couple weeks ago. I assume they still have some since they're still listed on the site.

 I ended up with 2 Crosley tubes, 1 RCA and 1 Tung-Sol.

 Elliot beat me! ^5.


----------



## FallenAngel

radiodaze and vacuumtubesinc both carry them, I just ordered mine from VacuumTubesInc today


----------



## LeBuLLeT

Thanks everyone. I was using their search tool and nothing would come up, but through their index I was able to find it. I need to look for something else to buy since they have a minimum of 10 dollars per order. Any ideas as what I should purchase?


----------



## error401

I got a couple 0.1uF Orange Drops there too, to bypass the output 'lytics.


----------



## LeBuLLeT

error401 are you saying to buy the 0.1UF orange drops to replace the 0.1uF 63V film capacitor. Since the ones from mouser seem to be sold out. Also did you buy (part# C-OD15.1-600) 0.1uF orange drops from radio daze? Thanks again.


----------



## error401

Quote:


  Originally Posted by *LeBuLLeT* /img/forum/go_quote.gif 
_error401 are you saying to buy the 0.1UF orange drops to replace the 0.1uF 63V film capacitor. Since the ones from mouser seem to be sold out. Also did you buy (part# C-OD15.1-600) 0.1uF orange drops from radio daze? Thanks again._

 

Mostly I just bought them to up my order 
	

	
	
		
		

		
			





. I bought 4 and will use them to replace the specified 0.1uF as well as add two new 0.1uF in parallel with the output caps, which may or may not improve sound quality.

 You can substitute part # 539-150104K250CB instead if you want, it's a bit cheaper.


----------



## LeBuLLeT

Oh ok I think I get what you are trying to do. You are using those orange drops to replace the specified 0.1uF and then doing something optional which is what I don't get. Where exactly are you going to put those at. Is it right before the output of the amp? Anyways I think I will just order these .1uF orange drops, and the 19j6 tubes and the 7-pin miniature tube socket from radio daze which should get me over 10 dollars. Anything else I should order from radio daze?


----------



## error401

That's all I'd get. You're right about what I'm doing.

 Basically the thinking goes that electrolytic caps are bad for sound quality, but necessary for the required large values, the idea is that if you place a small quality cap in the same position as well, it will improve the sound quality. You'd want to put them across the legs of C3 and C5, and don't remove C3 and C5.


----------



## LeBuLLeT

Are you going to put in between the c3 and r6 or before the c3? Then obviously repeat it for the c5 section. Also thanks for that knowledge didn't know a small quality cap would improve sound quality.


----------



## tomb

This all sounds fairly reasonable if you want to bypass the electrolytics. Keep in mind however, that bypassing electrolytics with film caps is ratcheting up the old capacitor-sound-debate to a new level. There's no rhyme or reason to various combinations: some work well, some make no difference at all, and some sound bad.

 If ordering from a tube dealer, you might want to just order an extra pair of tubes - brand, construction quality, and age degradation can vary the sound quality of a tube quite a bit. It's always a good idea to have spares. On the other hand, if you're ordering from Mouser, the Wima MKP film caps have a long successful history of bypassing electrolytics in Millett Hybrids. They'll work great as the interstage couplers, too.

 Just an alternative suggestion ...


----------



## error401

Quote:


  Originally Posted by *LeBuLLeT* /img/forum/go_quote.gif 
_Are you going to put in between the c3 and r6 or before the c3? Then obviously repeat it for the c5 section. Also thanks for that knowledge didn't know a small quality cap would improve sound quality._

 

Not in between anything. In exactly the same position as C3, without moving C3. Piggyback them. I would say that if you're missing my instruction on this one, it's probably better if you try to build the amp as specified first, before making any modifications.

 tomb is right as well. I tossed them in because they were cheap and I haven't used them before. You're probably better off using the WIMA or caps from the BOM and getting an extra set of tubes. Also, expect your order from RadioDaze not to be brand-matched.


----------



## elliot42

I bought extra tubes (4 in total), a pot and some film caps (C-MF.1-630) to up my order. The pot is pretty big and only just fits in my case, but I needed one anyway. I had to cut a window for it, my case is pretty shallow: Picasa Web Albums - elliot42 - Starving Stud...

 The tubes they sent me were all RCA, two look like they're from the a similar batch, one has slightly different packaging, and the fourth is a bit different again and much newer box (looks like 80s style design).


----------



## error401

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_The tubes they sent me were all RCA, two look like they're from the a similar batch, one has slightly different packaging, and the fourth is a bit different again and much newer box (looks like 80s style design)._

 

Geeze, I specifically asked for brand-matched pairs and I got 3 different brands in my order. LOL.


----------



## tomb

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_<snip>Also, expect your order from RadioDaze not to be brand-matched._

 

Yeah, we drove him crazy with the Millett MAX. Phil Hazen sent me an e-mail or two asking for relief from $2-$3 tube brand matching requests. He's a nice guy and a great vendor, but there's only so much we should ask of these vendors or we'll all drive the prices up for these tubes.


----------



## elliot42

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Geeze, I specifically asked for brand-matched pairs and I got 3 different brands in my order. LOL._

 

Hehe.. I didn't ask, I was just lucky, I guess. I was kinda hoping for 2 pairs of different brands as well, to see if they differed in sound


----------



## LeBuLLeT

Well ok I got it. Think I get what everyone is saying. Just that I can't find a replacement for the film caps on the BOM. Should I go with the orange drops from Radio Daze or with something different? Also whats another good option for tubes.


----------



## royewest

I asked for a matched pair and got a matched single -- at $3 or whatever it wasn't worth trying to fix...


----------



## tomb

Vacuumtubes.net (Radio Electric Supply) remains a great source for the 19J6. As mentioned before, though, try not to drive these guys crazy asking for specific matches for $2 tubes. In some cases, it's barely worth it to them just to dig them out of the stacks.
	

	
	
		
		

		
			





 In many cases, they also agree to Pete and other designers not to raise prices once they start selling because of a new, popular design. So, be nice to your tube vendors.


----------



## elliot42

Quote:


  Originally Posted by *LeBuLLeT* /img/forum/go_quote.gif 
_Well ok I got it. Think I get what everyone is saying. Just that I can't find a replacement for the film caps on the BOM. Should I go with the orange drops from Radio Daze or with something different? Also whats another good option for tubes._

 

There's no option for different tubes, gotta use the 19J6. As for the film caps, the ones I got seem fine, I don't think it matters having a higher voltage rating (is that correct, tomb?). And error401 seems happy with the orange drops.

 EDIT - oops, thought you meant alternatives... never mind...


----------



## tomb

Just answered this a minute ago in a PM, but here's the basics of what I said:

 If you are ordering from Mouser, get the Wima MKP10 - 0.1uf or 0.22uf. The voltage rating on those is 250V, but film cap voltage ratings run high. There's no penalty by purchasing a higher voltage rating. In fact, you may be limiting your selections with film caps by trying to find a 63V.

 Electrolytics are different. They get very big and expensive as the voltage rating increases, so you want to limit them to 63V or 100V, at most.

 The Wimas are box caps, which are really more convenient for PCB's. They're not quite so easy with point-to-point, but they still have plenty of exposed leads to make it fairly easy. They're as good as it gets, IMHO, unless you start getting into boutiques. Then things could get expensive, but they are not warranted with the Starving Student.
	

	
	
		
		

		
		
	


	




 You can find Vitamin Q's and/or some Russian film caps that are fairly cheap if you want to go that route, but it's doubtful they'd make that much difference. Some have used them and have been very happy with them, but I'm not sure they had a comparison.

_Again, we need to emphasize:_ the Starving Student sounds great without film bypasses. The interstage couplers are different, but boutiques are not going to make much difference there, either, IMHO.

 P.S. The orange drops may sound great, just saying that it's more of an unknown and an experiment, perhaps.


----------



## error401

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yeah, we drove him crazy with the Millett MAX. Phil Hazen sent me an e-mail or two asking for relief from $2-$3 tube brand matching requests. He's a nice guy and a great vendor, but there's only so much we should ask of these vendors or we'll all drive the prices up for these tubes.
	

	
	
		
		

		
		
	


	


_

 

Yea, I didn't realize until I received the box that it might've been tougher than I thought. I was very surprised by the number of brands represented in my sample, I figured they'd have a crate of 50 from one brand and another crate from another brand, not a random selection from 50 different brands 
	

	
	
		
		

		
		
	


	




. After that, I was happy I got one matched pair. Thanks Phil!


----------



## keiths

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Geeze, I specifically asked for brand-matched pairs and I got 3 different brands in my order. LOL._

 

I must have been lucky - my first order for four 19J6s from Radio Daze resulted in four identical "IEC Servicemaster" Mullard tubes, and in my second order of four, I got four RCAs - two identical older looking ones and two identical newer looking ones.


----------



## LeBuLLeT

To anyone awake, would (Mouser Part# 647-UPW1J471MHD) nichicon upw 470uF 63v. The one recommended earlier was the (647-UPW1J471MHD3) but that one is currently not available right now. This is the last part I need to figure out before I order everything. SOOOOO anxious to build this thing. Want to hear how it sounds with my HD650's.


----------



## rds

Quote:


 To anyone awake, would (Mouser Part# 647-UPW1J471MHD) nichicon upw 470uF 63v. 
 

I think you're asking if that cap is ok for c3 and c5. If so, then the answer is yes 
	

	
	
		
		

		
		
	


	



 Have fun!


----------



## LeBuLLeT

Actually I was wondering if these were ok for all 4 applications. C1, c3, c5, and c6. Also if anyone is willing to sell their millett hybrid amp I am a willing buyer. :-D


----------



## MisterX

The difference between the three 63V 470uF UPW series caps from Mouser is the physical size. 

 647-UPW1J471MHD = 12.5 mm Dia. x 25 mm L "in stock"
 647-UPW1J471MHD6 = 12.5 mm Dia. x 31.5 mm L "on order"
 647-UPW1J471MHD3 = 16 mm Dia. x 20 mm L "on order"


 Or if you prefer....

 UPW1J471MHD3 = Digikey # 493-1949-ND


----------



## JamesL

Yup, they'll work for all positions.
 They're virtually the same capacitor as the one listed in the BOM, just in a different case-size.


----------



## LeBuLLeT

Great! Yea I prefer to order from Mouser Since everything but my Tubes are coming from there. Oh yea I need to find the Power supply but not till later because I think I may have one laying around. Thanks everyone for the help.

 Oh yea what if instead of RCA jacks I want to use Headphone jacks is it complicated to switch or or both? hmm the possibilities.


----------



## JamesL

Quote:


  Originally Posted by *LeBuLLeT* /img/forum/go_quote.gif 
_Oh yea what if instead of RCA jacks I want to use Headphone jacks is it complicated to switch or or both? hmm the possibilities._

 

A 3.5mm jack can easily be added or substituted for the rca jacks.
 A N.C.(normally closed/shorting) jack, or dpdt switch is recommended when switching between sources.


----------



## rds

I have built a few of these over the summer and have some left over parts (power supplies, tubes, etc).
 I will put together a kit with all necessary parts other than the case as well as Muse ES output caps (and wima film caps for decoupling) if there are a few people interested.
 The cost will be whatever my cost works out to. About $45 sounds right.
 If you're interested send me a pm. If I get 4 interested people in the next week I'll go ahead with it. After that it's back to school and goodbye headfi.


----------



## LeBuLLeT

Ok now I think I am getting a little over my head since I don't know what a N.C. or DPDT switch is. By any chance do you know if Mouser carrys these items. Also is it complicated to install one of these.


----------



## MisterX

Quote:


 Ok now I think I am getting a little over my head since I don't know what a N.C. or DPDT switch is. 
 

Nothing a little reading can't fix. 
	

	
	
		
		

		
		
	


	




Switch - Wikipedia, the free encyclopedia


----------



## LeBuLLeT

Ok read most of it. So this will work for what I Am trying to do?
 Trying to put Rcas and Headphone jacks. 
103-7002-EVX


----------



## MisterX

I think a "on none on" or "on on" type of DPDT switch may be a better option. 
 That way there is no middle off position. 

 I would also suggest silver plated contacts and something that will not take a bunch of force to activate (with an external power supply
 this is a pretty lightweight amp and you don't want to have to hold on to it to keep from sliding half way across your desk while you flip the switch )

611-7101-064 ??


----------



## LeBuLLeT

Oh Ok that makes a lot more sense. Yea imagine me just finishing my build and switching sources and pushing it all the way across my desk because of a switch. Thanks MisterX


----------



## bperboy

Is it to be expected that some tubes might glow at different intensities than others? I've got a few different tubes, and it looks like one doesn't glow as bright.. not an issue with the wiring, as it follows the tube.


----------



## royewest

I believe I have conclusively demonstrated that some noobs^h^h^h er, tubes do not glow as brightly as others.


----------



## HeadphoneAddict

Any chance this can be made to work with a 24v Sigma 11 PSU laying around, and if so what changes would need to be made? Thanks from a DIY noob!


----------



## tomb

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Any chance this can be made to work with a 24v Sigma 11 PSU laying around, and if so what changes would need to be made? Thanks from a DIY noob!_

 

First, it's a big mis-application. Second, the 48V from the VoIP is already reduced voltage for the tubes (by one-half, at least), so 24V would be even worse. A 24V Sigma 11 would be more suitable for pairing with a Millett Hybrid, not the SSMH.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_First, it's a big mis-application. Second, the 48V from the VoIP is already reduced voltage for the tubes (by one-half, at least), so 24V would be even worse. A 24V Sigma 11 would be more suitable for pairing with a Millett Hybrid, not the SSMH._

 

Thanks, I got it to pair with my Travagans Red headphone/speaker amp for driving my Stax energizer. Just trying to find out what else it can be used with.


----------



## G-man

hi all, i have a couple of question that hope one of you could answer. currently still reading this thread (100+ pages, it takes a while) so sorry if some have been answered before. i am sourcing from the UK, due to the fact that i live there 
	

	
	
		
		

		
			





, from a shop called maplin, as it is the easiest for me. but, as you can appreciate, there are some problems. Also, sorry if these seem a bit stupid to you, just humour me and answer them anyway. 

 Firstly, for the 150uF63V electrolytic capacitors, do i need axial or radial? Also, i read that for low impudence headphones (40 ohm ATH-W1000 for me) a slightly higher uF should be used. but what is slightly higher? 220, or 470 or 1000uF? also, should i use 63 or 100V? I presume 63 would be the best. 

 Next, for the film capacitors, are mylar ones ok? they are only ones i could find. also, i dont know if these should be changed to suite any changes above, if so, which ones are best, 0.1, 0.15, or 0.22uF?

 For the Phono (RCA) jacks, do they have to be insulated? The only insulated ones i found are teflon insulated, which are 2.50 each, and that seems a bit overpriced. But i dont mind the cost, just wanted to make sure.

 Am i right that the audio taper pots are the volume pots? Which are best for this the "Standard Dual-Gang Potentiometers" or the "Dual Miniature Potentiometers", or is there not difference. also, what is the difference between a 50k pot (for me 47k) and the 100k pot? and also, the difference between linear and logarithmic is just the progression, or is there another meaning?

 would a 0.6W metal film resistor be a suitable replacement for 1/4W carbon film. it (the website) says that it is an "upgrade" but well, that is the only one i can find. also waht does the 5% in "33k 5% 1/4W carbon film resistor" mean mean, i cant really find it any where in the website.

 what is the "Transistor mounting hardware". i cant really find anything of the like at maplin. 

 thanks again for all the help. i really appreciate it.

 G-man


----------



## fuzzyt

Well I thought I would post a few pictures and hopefully get a little help. Initially I had a couple of CAP's backwards (This is my first time). I got those fixed now that I understand the freaking ovals are negative symbols (Doh!). I tried to take a few good MACRO shots as well. It is probably not the cleanest but it was what I was capable of at the time. I am getting 48VDC to the tube sockets. I am not seeing 19VDC from Q1 or Q2 though? I have the center pin going to the tube socket and I thought that should have been 19VDC. Pin 1 is going to the 48VDC from the capped switch. Anyway I tried plugging in a pair of junk headphones and all I get is a slight hum. It does not change with the volume and there is no voltage leaving the Tubes and they appear to not be on. Any thoughts or help would be greatly appreciated. 

 There are some larger photos located on my site. 






 And a sample teaser image.





 Thanks


----------



## tomb

Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_<snip>Firstly, for the 150uF63V electrolytic capacitors, do i need axial or radial? Also, i read that for low impudence headphones (40 ohm ATH-W1000 for me) a slightly higher uF should be used. but what is slightly higher? 220, or 470 or 1000uF? also, should i use 63 or 100V? I presume 63 would be the best._

 

470uf for all of them. That's a common rating and will give good bass all the way down to Grados. Also, Pete says that using the 470uf's on the back side will prevent the VoIP power supply from stuttering on startup.

 63V will be smaller - that's the essential difference if you go up to 100V. Some boutiques may be easier to find at 100V, but UPW's and FC's are available as 63V.

  Quote:


 Next, for the film capacitors, are mylar ones ok? they are only ones i could find. also, i dont know if these should be changed to suite any changes above, if so, which ones are best, 0.1, 0.15, or 0.22uF? 
 

Generally speaking, polypropylene film are the best, but with interstage coupling use as in the SSMH, it may not make that much difference. Going up in rating is OK, but don't go below 0.1uf.

  Quote:


 For the Phono (RCA) jacks, do they have to be insulated? The only insulated ones i found are teflon insulated, which are 2.50 each, and that seems a bit overpriced. But i dont mind the cost, just wanted to make sure. 
 

No. The SSMH is negatively grounded. They should have contact with the case, IMHO. That might prevent some of the random hum issues you may have read about.

  Quote:


 Am i right that the audio taper pots are the volume pots? Which are best for this the "Standard Dual-Gang Potentiometers" or the "Dual Miniature Potentiometers", or is there not difference. also, what is the difference between a 50k pot (for me 47k) and the 100k pot? and also, the difference between linear and logarithmic is just the progression, or is there another meaning? 
 

Audio taper and logarithmic are generally the same, but read the fine print to be sure. Both could be used in tone or balance controls, so it's best if it says "volume". You must have "dual" for stereo.

  Quote:


 would a 0.6W metal film resistor be a suitable replacement for 1/4W carbon film. it (the website) says that it is an "upgrade" but well, that is the only one i can find. also waht does the 5% in "33k 5% 1/4W carbon film resistor" mean mean, i cant really find it any where in the website. 
 

Yes, 0.6W is fine, as is 1/4W, 1/2W, 1W, and 2W, for that matter. The percentage is a measure of the random tolerance of the resistance. 5% on a 100R resistor means it could be 95R or 105R.

  Quote:


 what is the "Transistor mounting hardware". i cant really find anything of the like at maplin. 
 

Look for "TO-220 mounting kits". It's a common item. 

  Quote:


 thanks again for all the help. i really appreciate it.

 G-man


----------



## G-man

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_470uf for all of them. That's a common rating and will give good bass all the way down to Grados. Also, Pete says that using the 470uf's on the back side will prevent the VoIP power supply from stuttering on startup.

 63V will be smaller - that's the essential difference if you go up to 100V. Some boutiques may be easier to find at 100V, but UPW's and FC's are available as 63V._

 

so, 63V, 470uF. Gotcha

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Generally speaking, polypropylene film are the best, but with interstage coupling use as in the SSMH, it may not make that much difference. Going up in rating is OK, but don't go below 0.1uf._

 

well, the search did not result in those, so i didnt look, but i found the polypropylene ones. will use those, thanks. the only ones available are 100V, but that i believe should not matter.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No. The SSMH is negatively grounded. They should have contact with the case, IMHO. That might prevent some of the random hum issues you may have read about._

 

i was thinking of using a PCB for grounding, but thanks, ill use the non insulated. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Audio taper and logarithmic are generally the same, but read the fine print to be sure. Both could be used in tone or balance controls, so it's best if it says "volume". You must have "dual" for stereo._

 

thanks, so ill just go with standard dual

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, 0.6W is fine, as is 1/4W, 1/2W, 1W, and 2W, for that matter. The percentage is a measure of the random tolerance of the resistance. 5% on a 100R resistor means it could be 95R or 105R._

 

thats what i was thinking, the tolerance for these is 1%, so it should be ok.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Look for "TO-220 mounting kits". It's a common item._

 

i cant really find it at maplin, but i will try and find it elsewhere.

 thanks again

 G-man


----------



## keiths

Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_
 i cant really find it at maplin, but i will try and find it elsewhere.

 thanks again

 G-man_

 

I've got some spare MOSFET mounting hardware - send me your address in a personal message and I'll pop them in the post to you


----------



## ludoo

I just finished my SS, and apart from the pot working backwards it fired up at the first try and is working wonderfully.






 It's my first DIY project, so the wiring is a bit messy as I did not plan too much in advance. I did the "case" with a piece from a sheet of plexiglass, and two small pieces of an L-shaped metal bar.

 At maximum volume it's loud but not unlistenable, but I have to say I'm using my Yamaha HP-3 which are pretty hard to drive. Thanks a lot to the author and everybody in this thread for a great design, and to dBel84 who assembled the BOM and shipped it to me.


----------



## tomb

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_I've got some spare MOSFET mounting hardware - send me your address in a personal message and I'll pop them in the post to you_

 

Beezar has some nice ones. Sorry - I couldn't resist the plug.
	

	
	
		
		

		
		
	


	




 G-man, I'm a little concerned at your reply on the pots: "_standard_ dual". You must use a logarithmic or audio taper pot. All I was saying was that often the two terms are interchangeable. However, they can also be used to describe tone and balance pots, so try to get something that's definitely labeled as a "volume" pot.

 Also - I forgot to mention - 50K is optimum, but 100K is probably fine in this instance. We even used 10K pots on some older Millett Hybrids, but that may be pushing it with tubes.


----------



## G-man

Quote:


 G-man, I'm a little concerned at your reply on the pots: "_standard_ dual". You must use a logarithmic or audio taper pot. All I was saying was that often the two terms are interchangeable. However, they can also be used to describe tone and balance pots, so try to get something that's definitely labeled as a "volume" pot.

 Also - I forgot to mention - 50K is optimum, but 100K is probably fine in this instance. We even used 10K pots on some older Millett Hybrids, but that may be pushing it with tubes.
	

	
	
		
		

		
			




 

yea, i didnt really know what they were, so i decided to do a little reading. i have ended up with log 100k dual pots, but do you think 47k would be better (no 50, sos). 22k, and 10 are also available, but i couldnt really find what "xx k" meant. is it just the steps it increases the volume in, or the resistance?


----------



## tomb

Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_yea, i didnt really know what they were, so i decided to do a little reading. i have ended up with log 100k dual pots, but do you think 47k would be better (no 50, sos). 22k, and 10 are also available, but i couldnt really find what "xx k" meant. is it just the steps it increases the volume in, or the resistance?_

 

It probably won't make any difference, but 50K is what Pete spec'd. The story is that 100K is more noisy, but 10K or less can sometimes cause hiss. I think that's why 50K is often considered optimum for headphone amplifier use.


----------



## G-man

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It probably won't make any difference, but 50K is what Pete spec'd. The story is that 100K is more noisy, but 10K or less can sometimes cause hiss. I think that's why 50K is often considered optimum for headphone amplifier use._

 

so 47k it is then. thanks again for all the help. I should order almost all the part tomorrow. just got the power supply, chasis, tubes + sockets, and the mofset mounter left. man, stuff is expensive in the uk. the bill is around £40, not including the stuff above. it should reach £60 easily, and then i need to buy the soldering iron and multimeter. easily £80.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Also - I forgot to mention - 50K is optimum, but 100K is probably fine in this instance. We even used 10K pots on some older Millett Hybrids, but that may be pushing it with tubes.
	

	
	
		
		

		
		
	


	


_

 

From the tube's perspective, lower is better. This resistor (or pot in this case) references the grid to ground. Grid chokes, for instance, have a DCR in the tens of ohms, which is actually close to ideal. You want high, however, for the sake of the driving stage as it makes for an easier load. The input Z of a tube's grid is in the Mohms range, so the pot really sets the input impedance of the stage. Too high can be trouble due to noise, but 100K is still going to be well below the tube's own noise in this case. 250K is still probably fine, and I often use 1M for guitar stages to keep coupling cap size down.


----------



## jERiCOh

There is mine. I'm done with the case work and I'm still working inside. Better pictures will follow when everything will be put together. 
 BTW, I've been looking for the Cisco Wallwart around and I can't find one at less than 40$ shipped to Canada. If someone have an extra one and wants to sell it at a resonable price... let me know.


----------



## bperboy

^^^ 

 Really like that casework!!


----------



## elliot42

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_^^^ 

 Really like that casework!!_

 

+1

 That's really cute, and neat... so tiny.


----------



## Jingo Lingo

+2


----------



## -=Germania=-

I just want to maybe throw something up here. 

 Recently, I received my Zhaolu and am now using it to handle the digital inputs from my computer (Auzen Cinema) and Marantz CD5001). Well, even with the op-amp upgrades to the 2.5C, the millet amp is decidedly better in every way. Granted, my build differs from the schematic a bit 
	

	
	
		
		

		
		
	


	




 The combo of the Marantz CDP, Zhaolu and Millet is really quite good, exceptional even. 

 I am actually going to build another one of these, even more boutique and incorporating some of my modifications in the initial build (instead of as add-ons). The current one is likely to go to a family member (dad or brother) - whomever wants to pay the parts cost (more than the $65 I estimated originally - believe me)

 Yeah, my current one has had a color change to a flat black and a matching knob to the Zhaolu. I question why I had that weird color scheme in the first place......
	

	
	
		
		

		
		
	


	




Look for the new one to be a stacked design in a bamboo enclosure with the power supply in a separate case below the amp. My hope is to take this design to the upper limits of what it is capable of. Then move on to something nicer and more complicated. This one is cheap and easy to mod!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_
 The combo of the Marantz CDP, Zhaolu and Millet is really quite good, exceptional even. _

 

Or, you could just say, "stick a fork in me, I'm done" and enjoy it. 
	

	
	
		
		

		
		
	


	




 I coulda stopped at Macbook>iBasso D1>Darkvoice 336i or CD5001>336i and been done $24,000 ago...

 [Ahhhh - post 4*666* - I'm evil]

 I do have a Millett SS kit coming from rds now... I hope I can figure out the build...


----------



## m0b1liz3

-=Germania=-,

 How did your first build differ from the schematic?
 How did you modify it?


----------



## -=Germania=-

Where would be the fun in that?
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Or, you could just say, "stick a fork in me, I'm done" and enjoy it. 
	

	
	
		
		

		
		
	


	




 I coulda stopped at Macbook>iBasso D1>Darkvoice 336i or CD5001>336i and been done $24,000 ago...

 [Ahhhh - post 4*666* - I'm evil]

 I do have a Millett SS kit coming from rds now... I hope I can figure out the build..._


----------



## G-man

really like the casework, especially the heatsink. those screws must have been a pain to get in, with the heatsink right above it.


----------



## ingwe

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Where would be the fun in that?
	

	
	
		
		

		
		
	


	


_

 

Then why the hell mention it?

 Oh right...


----------



## Hayduke

Quote:


  Originally Posted by *ingwe* /img/forum/go_quote.gif 
_Then why the hell mention it?

 Oh right..._

 

I think she was responding to HA's advice to stop now and just enjoy her gear. 
	

	
	
		
		

		
		
	


	




 As if a DIYer could do that lol


----------



## ingwe

^^^
 i hope so. then perhaps she'll answer _m0b1liz3 question. 
_


----------



## jERiCOh

Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_really like the casework, especially the heatsink. those screws must have been a pain to get in, with the heatsink right above it._

 

Thank you. It took me a couple of minutes to figure out a good way to screw it in place. It's a bolt/nut assembly so I screwed the nut while holding the bolt with the side of a flat screwdriver.


----------



## G-man

Quote:


  Originally Posted by *jERiCOh* /img/forum/go_quote.gif 
_Thank you. It took me a couple of minutes to figure out a good way to screw it in place. It's a bolt/nut assembly so I screwed the nut while holding the bolt with the side of a flat screwdriver. 
	

	
	
		
		

		
		
	


	


_

 

ah, well, whatever gets it done. thats pretty much how i would have done it, as i would want to keep the screw head clean. btw, how "high" is the amp in the case. i was looking at the case, but its is only 1.5 cm high on the inside, and i think that might not be enough. it is pretty long and wide though.


----------



## jERiCOh

I used that case: 1590BBBK
 I know there is not that much room inside compared to many others but everything seems to fit after some planning.


----------



## G-man

I was thinking of:

http://www.hammondmfg.com/pdf/1455B1202.pdf

 but i dont think that will be possible, as it only open from the side. ill probably jus go with a standard hammond one when and if i decide to build the Alien, so that they both can fit inside.


----------



## -=Germania=-

I added a capacitor between the + and ground directly at the connector - a 200V 330uf nicho-chemi. 

 I used lowered cap values on the output of 220uF, rather than the suggested 470uF. 

 Then, at the output, I used some 10 ohm resistors. It just sounded better with my headphones - don't know why. 

 The load of the extra capacitor does take a bit longer to start up, but you can watch the start up easily since I installed LED's under the tubes. 

 There are a few other little things I did to help the switching power supply be more linear, but that would not be part of the amp itself. Right now, I am shopping diodes and other parts to make a regulated power supply in the next build.


----------



## FallenAngel

I'm ordering parts for this and got myself a Cisco 48V PSU - looks like it's unregulated. I'm planning to implement an LM317 (AHV type that accepts up to 57V, not the "regular" 37V variety) and regulate it down to 48V exactly. The main reason behind this is to use 50V output caps.

 It is actually REALLY hard to find a nice elctrolytic output cap at least 50V! I'm looking at Nichicon Muse ES 220uF/50V 3x per channel which seems a little crazy and the alternative is Nichicon KZ 470uF/50V.

 Elna Silmic don't come in those voltages and Black Gates at those voltages are very expensive so I'm a little lost, any suggestions for a "not so starving" amp?


----------



## rds

Quote:


 It is actually REALLY hard to find a nice elctrolytic output cap at least 50V! I'm looking at Nichicon Muse ES 220uF/50V 3x per channel which seems a little crazy and the alternative is Nichicon KZ 470uF/50V. 
 

The Muse ES comes in a 50V 330uF variety - that is what I've been using and haven't had any bass problems with low impedance headphones that would make me want larger caps.

 Also, as far as the PS is concerned, you don't need to regulate. You won't see more than 50V at the output, even if the FETs where to become a sort circuit. You should be able to get away with 25V caps, but I don't condone or recommend that at all.


----------



## tomb

Nichicon Muse FG (Fine Gold) is available in 470uf, 100V. That might be the boutique of choice for the spec'd voltage rating - unless you go with rds's recommendation. In which case, there are ample Muse KZ's to pick from, too - there's nothing crazy about 470uf.


----------



## n_maher

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I'm ordering parts for this and got myself a Cisco 48V PSU - looks like it's unregulated. I'm planning to implement an LM317 (AHV type that accepts up to 57V, not the "regular" 37V variety) and regulate it down to 48V exactly. The main reason behind this is to use 50V output caps._

 

Two points of clarification: one, I believe that the 37V limit on the LM317 is the maximum difference allowed between input and output voltages. It'd be worth more research to see if there's a limit on V-input, I can't find one in the datasheet.. Two, it's still cutting things pretty close to run 50V output caps on a 48V supply, regulated or otherwise.

 I'd have a look at 100V SilmicII's if you're seeking higher voltage boutique output caps.


----------



## -=Germania=-

There are other regulators out there - look at the ones that go from 15-100V. The 317, even boutique, might be cutting it a bit close on the regulation...


----------



## Citizen86

Got my kit also coming from rds... I'm excited since this will be my first DIY project... not counting recabling my KSC75's... but that was with CAT5 wire and I put the stock cable back on because the CAT5 was so damn stiff 
	

	
	
		
		

		
		
	


	




 Anyways, looking forward to it


----------



## FallenAngel

That's for the clarifications Nate, didn't see that part of LM317.

 As for Silmic II (RFS), I wasn't planning to ordering something completely separate - Percy and Soniccraft I have to do so I'll likely stick to Muse FG 470uF/100V.


----------



## Fitz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Two points of clarification: one, I believe that the 37V limit on the LM317 is the maximum difference allowed between input and output voltages. It'd be worth more research to see if there's a limit on V-input, I can't find one in the datasheet.. Two, it's still cutting things pretty close to run 50V output caps on a 48V supply, regulated or otherwise.

 I'd have a look at 100V SilmicII's if you're seeking higher voltage boutique output caps._

 

I've read an article on natsemi's site about that specifically mentioned the LM317 being suitable even up to several hundred volts, as long as the voltage drop is kept below 40V. Since it has no ground reference, all it cares about is the voltage differential between the input and output.


----------



## Zigis

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_I've read an article on natsemi's site about that specifically mentioned the LM317 being suitable even up to several hundred volts, as long as the voltage drop is kept below 40V. Since it has no ground reference, all it cares about is the voltage differential between the input and output._

 

Is it possible to use LM317 for "real" high voltage tube amp, like MJ ?


----------



## tomb

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_Is it possible to use LM317 for "real" high voltage tube amp, like MJ ?_

 

Apparently. As Fitz described up there, it's the voltage difference that's limited to ~40V. That still means you could regulate from 300V down to 260V, for instance - as long as you floated the ground.


----------



## 00940

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_I've read an article on natsemi's site about that specifically mentioned the LM317 being suitable even up to several hundred volts, as long as the voltage drop is kept below 40V. Since it has no ground reference, all it cares about is the voltage differential between the input and output._

 

This note probably ? http://www.national.com/ms/LB/LB-47.pdf

 It becomes quite clear why you can do such thing once you look at the internals of the lm317, as shown here: http://www.national.com/an/AN/AN-178.pdf


----------



## OldKing

I am yet another first timer. I have been reading and researching and re-reading for a few weeks.

 I am looking at all the Nichicon 470uF caps on Mouser, and looking at this Nichicon diagram of audio caps... 




 (diagram is interactive, click on it for data sheets)

 which raises questions...

 FG and KZ are labeled "High Grade" and KW is labeled "High Sound Quality" (KW). What's the difference? KZ vs KW?

 Mouser has these..
647-UKW1J471MHD (KW, 470uF 63V)
647-UKZ1H471MHB (KZ, 470uF, 50V)

 Is the KZ part's 50V rating too low for this project? 

 What gauge of hook up wire (stranded I assume) is best suited for this type of project? I'm thinking of the physical ease of working with the wire, as well as sufficient gauge for the current. It would be nice to find a kit of a few meters of several colors.

 Thanks,
 Brian


----------



## tomb

Quote:


  Originally Posted by *OldKing* /img/forum/go_quote.gif 
_I am yet another first timer. I have been reading and researching and re-reading for a few weeks.

 I am looking at all the Nichicon 470uF caps on Mouser, and looking at this Nichicon diagram of audio caps... 

<IMG]http://www.nichicon.co.jp/english/products/images/mini3-m.gif[/IMG>
 (diagram is interactive, click on it for data sheets)

 which raises questions...

 FG and KZ are labeled "High Grade" and KW is labeled "High Sound Quality" (KW). What's the difference? KZ vs KW?_

 

Notice that KW uses the word "standard" while KZ uses the word "Premium?" Also, the KW path is not labeled "High Sound Quality" but "Improved of the Sound Quality". Sometimes things are lost in translation, but it should be easy to see that the KZ path is superior.

  Quote:


 Mouser has these..
647-UKW1J471MHD (KW, 470uF 63V)
647-UKZ1H471MHB (KZ, 470uF, 50V)

 Is the KZ part's 50V rating too low for this project? 
 

Strictly speaking, yes. There are some who are willing to take the risk, but you won't see it as an "official" recommendation. The UPW's from Mouser are just fine, but it might be interesting to try the KW. I didn't realize Mouser had started carrying some of those Nichicon caps. Anyway, I've used Panasonic FC's which are comparable to the UPW's and it sounds great. If you want to tweak it later with some boutiques you can get them from Handmade Electronics, PartsConnexion, Michael Percy, etc.

  Quote:


 What gauge of hook up wire (stranded I assume) is best suited for this type of project? I'm thinking of the physical ease of working with the wire, as well as sufficient gauge for the current. It would be nice to find a kit of a few meters of several colors. 
 

22ga silver-plated copper with teflon insulation is what I use, but you may get many opinions on this. John Silver Teflon Wire Shop on e-bay (navships) is a good place to look to get different colors in small lengths.
  Quote:


 Thanks,
 Brian


----------



## OldKing

FWIW, it does say "High Sound Quality" on the KW data sheet itself (the graphic showing an improvement as compared to the FW)... but also says "standard"

 I had concluded pretty much the same, but I thought it possible the KW was a new product or something, so worth asking.

 Thanks for the reply and advice!


----------



## Fitz

Quote:


  Originally Posted by *00940* /img/forum/go_quote.gif 
_This note probably ? http://www.national.com/ms/LB/LB-47.pdf

 It becomes quite clear why you can do such thing once you look at the internals of the lm317, as shown here: http://www.national.com/an/AN/AN-178.pdf_

 

Yep, that's the one.


----------



## FallenAngel

One more thing I noticed - that Cisco PSU is actually regulated, put out exactly 48.1V. That won't leave any room for the LM317 so I'll just have to go insane on the PSU caps, likely will add a coupld of 1000uF at the beginning of the circuit.


----------



## -=Germania=-

Does anyone else "Cisco" PSU say completely different values on teh label than what is on the output?


----------



## dsavitsk

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_One more thing I noticed - that Cisco PSU is actually regulated, put out exactly 48.1V. That won't leave any room for the LM317 so I'll just have to go insane on the PSU caps, likely will add a coupld of 1000uF at the beginning of the circuit._

 

Too much capacitance can cause the PSU trouble. Instead, make it pi filter instead. Or, if you really want to regulate this, dropping a few volts is fine -- there is nothing magical about 48V here.


----------



## jERiCOh

Finally mine is all done 
	

	
	
		
		

		
			





 Now I hope I'll find a PSU to give it a try.


----------



## bperboy

^^









 Neat wiring!! wow!! very neat..

 Are your mosfets isolated from the case?? you could very well run into problems if they aren't...


----------



## gurusan

Congrats jericoh that looks great!


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Does anyone else "Cisco" PSU say completely different values on teh label than what is on the output?_

 

No, and I've seen multiple.


----------



## jERiCOh

Quote:


  Originally Posted by *bperboy* /img/forum/go_quote.gif 
_^^









 Neat wiring!! wow!! very neat..

 Are your mosfets isolated from the case?? you could very well run into problems if they aren't..._

 

Ok... so I'm in trouble ... 
 I totally forgot the mica insulator. One more thing on my shopping list


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Notice that KW uses the word "standard" while KZ uses the word "Premium?" Also, the KW path is not labeled "High Sound Quality" but "Improved of the Sound Quality". Sometimes things are lost in translation, but it should be easy to see that the KZ path is superior._

 

KT also says standard and it is above the KZ in that chart. Perhaps this logic is flawed?


----------



## bperboy

Here's my build.. did the entire thing from casework to tunage last friday and saturday! I used the same line of case as Nate (sorry, not feeling real original, but at least the layout is a little different 
	

	
	
		
		

		
			





), and all the parts are pretty much directly off of the BOM on Pete's site. Sounds great!


----------



## -=Germania=-

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_No, and I've seen multiple._

 


+ YouTube Video​ _*ERROR:* If you can see this, then YouTube is down or you don't have Flash installed._


----------



## -=Germania=-

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Too much capacitance can cause the PSU trouble. Instead, make it pi filter instead. Or, if you really want to regulate this, dropping a few volts is fine -- there is nothing magical about 48V here._

 

Agreed - If you use a 1000uF capacitor the power will continue to just pulse and will not start up properly. Couple it with between 220-470uF. Currently, I am using 330uF 200V PSU capacitor and it has no problem with it.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_KT also says standard and it is above the KZ in that chart. Perhaps this logic is flawed?_

 

Note the temperature rating on the KT. That's why it's above everything, but only of "standard" quality.

 One thing that's flawed is over-analyzing the different type of capacitors:

 There's UPW's and UHE's for Nichicon at Mouser - those are quality power caps.
 There's FM's and FC's for Panasonic at DigiKey - those are also quality power caps (FM's are the best, btw).

 After that, go searching at Handmade Electronics, Parts Connexion, Michael Percy, or Soniccraft and look to see what they label as an audio-grade "boutique" electrolytic. If you're lucky, you may find them carried at DigiKey or Mouser, but the selection will be limited.


----------



## pinkfloyd4ever

what's that little circuit board there, bperboy? A tread?


----------



## n_maher

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what's that little circuit board there, bperboy? A tread?_

 

Definitely not a TREAD, just looks like a different type/kind of perfboard. Note that he actually uses two pieces, you just can't see much of the second piece.


----------



## bperboy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Definitely not a TREAD, just looks like a different type/kind of perfboard. Note that he actually uses two pieces, you just can't see much of the second piece._

 

Actually, there's three pieces... it's just a bit of perfboard that i used to connect the ground points... not exactly a ground plane or a star ground. I just connected all the grounds to the perfboard, connected all the perfboards together, and then connected one of them to the power jack ground...


----------



## tomb

Nice job, bperboy!


----------



## bperboy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Nice job, bperboy!_

 

Thanks Tom! It's been awhile since I did some DIY... I've been bitten by the bug again.. need MiniMax, need MiniMax!!


----------



## scott_fx

Quote:


  Originally Posted by *jERiCOh* /img/forum/go_quote.gif 
_Finally mine is all done 
	

	
	
		
		

		
		
	


	




 Now I hope I'll find a PSU to give it a try.









_

 

wow! that is so clean! i'm inspired to build another one!


----------



## rds

Looks like those 510s need to be isolated.


----------



## jERiCOh

Yeah. My bad. You guys saved me a lot trial and error by telling me. Thanks.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_<video>_

 

I can only guess and say that you didn't get a real Cisco supply.


----------



## -=Germania=-

Hey guys, I am doing the separate power supply - what would be an ideal wattage and current? *As in building a separate power supply*

 I am currently looking at 25-50W and 0.5-1.2 Amps.
 The general rule is that higher power and current is better performance, but if there are limitations to watch for - it would be nice to know.

 Thanks!


----------



## adamus

the cisco was just shy of 20 watts and was fine. i would have thought 20 was ample.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Hey guys, I am doing the separate power supply - what would be an ideal wattage and current? *As in building a separate power supply*_

 

Take your existing amp, cut the B+ wire and measure the startup inrush and idle current to get an idea. The Cisco supply is only rated for ~.4A so that paints a pretty clear picture of what you need at idle and during operation.

 And since watts are just volts x amps it's a pretty irrelevant qualification to use. You know you need 48V, the amps are up to you, so the wattage will simply be a function of that. 

 Me, I'd shoot for the 48V, 1A range.


----------



## adamus

1A would be more than ample. go for it.


----------



## -=Germania=-

Yeah - this next build.... I am kind-of going Millet SS Ultimate!

 The Power supply will be in a separate Bamboo enclosure stacked underneath the amp. 

 My only qualms with the current Cisco is that
 -It is not as stable as I would like
 -More Power! (ability to use a bit more demanding parts)


----------



## J.D.N

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Yeah - this next build.... I am kind-of going Millet SS Ultimate!

 The Power supply will be in a separate Bamboo enclosure stacked underneath the amp. 

 My only qualms with the current Cisco is that
 -It is not as stable as I would like
 -More Power! (ability to use a bit more demanding parts)_

 

Well, if you want ultimate, why not go balanced? For both the amp and the PSU...


----------



## -=Germania=-

I am only not going balanced because I really do not want to convert all of my headphones to balanced and then also have to do a balanced output on my Zhaolu. 

 I will go balanced eventually - but it is too much of a hassle outside of the amp right now.


----------



## dBel84

If you are going "all out" and not wanting to deal with gains of 30 in a balanced build, have you considered an active ground channel? I sketched up this configuration as it was always my plan to build the 3 channel szekeres before the SS Miilett came sailing along and it seemed a natural progression. 

 I have yet to build it but as it is not a high priority for me at this time, I am not sure when it will be complete. Just another potential tweak to consider 
	

	
	
		
		

		
			





 ..dB


----------



## MusicallySilent

This is a pure curiosity kills the cat thing so please dont shoot me down right away. And I am not sure if it has been mentioned elsewhere, if it has, my apologies.

 If you put rather large heatsinks on this build, or get a case with good conduction properties. Is there anything stopping you from being able to run a small pair of very sensitive bookshelf speakers (ex like 2-5 watts per channel) off of this amplifier. My guess is the most likely thing to hinder it would be the mosfet cooling, as I remember atleast on the Beta 22 to drive speakers you need a much better cooling system. Also maybe the powersupply but it does put out 18 watts so I was thinking it may be possible... I would like to know this because I thought it would be nice to have a small tube hybrid speaker and headphone amp.

 Sorry for being kind of a novice at DIY electronics.


----------



## dsavitsk

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_run a small pair of very sensitive bookshelf speakers_

 

http://www.head-fi.org/forums/4487693-post665.html


----------



## MusicallySilent

Interesting, do you think the quality was more the fact they are a cheap pair of computer speakers, or is the the amps fault for the poor quality?

 I was thinking of it as more potentially used as an alternate to a T-Amp


----------



## bhjazz

I can't speak for dsavitsk, but my vote would be that the speakers were the problem. Judging by the photo, they look to be all of 3" for the drivers!


----------



## G-man

to the speaker question, how did you connect them to the speakers. just want to try it out, but the only *crappy* speakers i have have cables attached ending with just the wire, that i beleive you hook up to speaker terminals at the back of an amp, so how would you connect these? i was thinking of just directly connecting them to the wires just before the headphone jack, but i dont really know


----------



## MusicallySilent

Trust me those speakers arent 3", that is generous, I would say 2", I have a pair of boston comp speakers with 3" grills and 2" drivers 

 That is good to know they play loud, I can probably find some semi decent old speakers to experiment with 

 Gman, it looks like he just put alligator clips just before the headphone output and then connected those to the speaker wires.


----------



## tomb

Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_to the speaker question, how did you connect them to the speakers. just want to try it out, but the only *crappy* speakers i have have cables attached ending with just the wire, that i beleive you hook up to speaker terminals at the back of an amp, so how would you connect these? i was thinking of just directly connecting them to the wires just before the headphone jack, but i dont really know 
	

	
	
		
		

		
		
	


	


_

 

Just buy yourself some speaker binding posts (Mouser, DigiKey, Allied, etc.). They're panel mounted and even the banana jack type have a hole in the side of the post to run a bare wire through. Run wiring from the switched terminals on the headhpone jack to the speaker binding posts and then the speakers will be ON unless you plug in headphones.

 Cetoole setup one of his MAXes, this way, too.


----------



## G-man

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Gman, it looks like he just put alligator clips just before the headphone output and then connected those to the speaker wires._

 

so about what i was thinking, awesome. will definately try that, even if only for a short time. i was thinking of building a speaker amp for a pair of spare speakers, and i might just use this, is there a cheap way of switching output between say headphones and speaker out?

 edit: nvm, tomb answered my question before i posted. the guy is mind reader i tell you.

 edit#2: tomb, would i need to (well more like should i) disconnect the speakers when i am turning the amp on/off, like with headphones? or will it not matter?


----------



## dsavitsk

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Trust me those speakers arent 3", that is generous, I would say 2"_

 

They are 3"

  Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_would i need to (well more like should i) disconnect the speakers when i am turning the amp on/off, like with headphones? or will it not matter?_

 

No, it won't matter, and you really don't need to disconnect your headphones either.


----------



## G-man

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_No, it won't matter, and you really don't need to disconnect your headphones either._

 

hey i am paranoid, leave me alone. 
	

	
	
		
		

		
			





. you want proof of my paranoia? 
 I actually bought a "key switch" and am going to attach the key to my headphone cable just so that they will have to be unplugged for me to turn the amp on/off. 
 i dare you to beat that paranoia.


----------



## holland

.


----------



## -=Germania=-

I just want to see what the full potential of this thing is as a single ended amp.

 The active ground is a good idea - however - I am using many of teh parts from the rds kit. We will see though...


----------



## MusicallySilent

I think I might consider making this and see if it works halfy well as a t-amp alternative . Plus it will be fun to play with tubes


----------



## n_maher

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_I think I might consider making this and see if it works halfy well as a t-amp alternative . Plus it will be fun to play with tubes 
	

	
	
		
		

		
		
	


	


_

 

I would say that it will be more about the speakers you're trying to drive than the amp. It's good for 1/4W or so into 8ohms, if that's enough for what you're using it should sound decent. If they crave more current or voltage you're SOL.


----------



## MusicallySilent

Obviously this shows my lack of understanding in circuits because I thought it would be able to put out a bit more than that. What part of the amp causes this limitation?


----------



## FallenAngel

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Obviously this shows my lack of understanding in circuits because I thought it would be able to put out a bit more than that. What part of the amp causes this limitation?_

 

_lack of understanding in circuits_ makes you ask this question as well 
	

	
	
		
		

		
		
	


	




 From this design standpoint, that's like asking what part of a Honda Civic causes it's limitation to pull a train. Well... pretty much everything, it's not designed for it. I think it's mainly that the stock PSU needs to be literally 10x bigger.


----------



## procalli2007

Quote:


  Originally Posted by *G-man* /img/forum/go_quote.gif 
_hey i am paranoid, leave me alone. 
	

	
	
		
		

		
		
	


	




. you want proof of my paranoia? 
 I actually bought a "key switch" and am going to attach the key to my headphone cable just so that they will have to be unplugged for me to turn the amp on/off. 
 i dare you to beat that paranoia._

 

I liked this idea until I thought that its going to be ineffective against a power cut.





 edit: forgot smiley


----------



## adamus

eitherway, you wont damage anything with this amp. null point.


----------



## MusicallySilent

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_lack of understanding in circuits makes you ask this question as well 
	

	
	
		
		

		
		
	


	




 From this design standpoint, that's like asking what part of a Honda Civic causes it's limitation to pull a train. Well... pretty much everything, it's not designed for it. I think it's mainly that the stock PSU needs to be literally 10x bigger._

 

Ok, simple enough 

 Any other relatively budget amps that could possibly drive speakers?


----------



## n_maher

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Any other relatively budget amps that could possibly drive speakers?_

 

Google "gainclone".


----------



## jERiCOh

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Ok, simple enough 

 Any other relatively budget amps that could possibly drive speakers?_

 

This one might be interresting : T-Amp Kit
 If you're absolutely looking for an hybrid amp, there is a tube T-amp available from the same place but it's quite expensive compared to the SS.


----------



## procalli2007

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_eitherway, you wont damage anything with this amp. null point._

 

i know. Although I did get quite a few pops once when I connected the phones before switching on the amp. 

 Wont do that again.


 Any news tomb on the pcb as I have the parts to make another.


----------



## dsavitsk

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_Any news tomb on the pcb as I have the parts to make another._

 

The news is that we are about ready to do the second round of prototypes, but the delay has been my fault. They will get ordered first thing after the holiday. More updates to come.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_The news is that we are about ready to do the second round of prototypes, but the delay has been my fault. They will get ordered first thing after the holiday. More updates to come._

 

Yay!!
	

	
	
		
		

		
		
	


	




 You guys will be very happy, I think. Dsavitsk has come up with a board that has a couple of unique wrinkles, but preserves the entire theme of Pete's creation: Simple, inexpensive, and high performance.


----------



## scott_fx

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_The news is that we are about ready to do the second round of prototypes, but the delay has been my fault. They will get ordered first thing after the holiday. More updates to come._

 

can't wait! i am looking forward to building another one of these guys


----------



## n_maher

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_The news is that we are about ready to do the second round of prototypes, but the delay has been my fault. They will get ordered first thing after the holiday. More updates to come._

 

Correction to this, there are no such things as delays with this. Your work is appreciated and whenever you have time to work is the time you have to work.


----------



## MusicallySilent

Hmm, both this and the gainclone are quite enticing. Now I am almost wondering if there is a a way this little amp could be used as a preamp for a gainclone power amp. Ill have to figure this out in a while after I get the time and money to do so.


----------



## m0b1liz3

Quote:


  Originally Posted by *MusicallySilent* /img/forum/go_quote.gif 
_Hmm, both this and the gainclone are quite enticing. Now I am almost wondering if there is a a way this little amp could be used as a preamp for a gainclone power amp. Ill have to figure this out in a while after I get the time and money to do so._

 

That is my current plan. My problem is that I am relying on friends at work to help finish the case first before I build it. It seems like ages ago I decided to build this thing. 
 There have been a few suggestions on how to make this function as a preamp. 

 Basic Summary:
 1.) resistors in line with vol pot
 2.) a switch or switchable jack going to rca outs


----------



## m0b1liz3

Alternative to E12???:

 "add to the audio rails a tranzorb and 1kV, 1000pf (or larger) cap to ground, with low-value (3 to 10 ohm), high-power resistors in series with the audio line. i've done this to catch turn on/off spikes in systems running XLR cables"

 someone suggested this on another site. i am far too much of a newbie to understand if this would work. can someone comment if it could be used as a cheap way to stop the turn on/off spikes?


----------



## -=Germania=-

The active Ground is a GO!
 Ordered the parts for the power supply. 

 As soon as the stuff comes in, I will be at work. 
 I will let you know the results!


----------



## dBel84

looking forward to your thoughts ..dB


----------



## MusicallySilent

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_That is my current plan. My problem is that I am relying on friends at work to help finish the case first before I build it. It seems like ages ago I decided to build this thing. 
 There have been a few suggestions on how to make this function as a preamp. 

 Basic Summary:
 1.) resistors in line with vol pot
 2.) a switch or switchable jack going to rca outs_

 

Cool, thanks for the suggestions, I just need to get some headphones and some other things [laptop, DAC (alien? or bantam?)] on my to buy list first . Speakers help too, and I am thinking about trying to DIY a single driver set


----------



## ludoo

My case was too minimal, so I followed dbel84's suggestion and made some wood sides, and a base. I think my first SS is really finished. I will probably use an HiFi2000 case for the next one, as making your own case is too much work, and costs probably the same.


----------



## jarpy

I have been loving my Mini-Millet. Great fun to build and listen to.

 I really don't need so much voltage gain though. My source is plenty loud (and has a volume control). So today I built this. It's basically the output stage of the SS repacked as a stand-alone mosfet buffer.

 edit: It runs _hot_. I think a bit less current through the mosfets may be in order


----------



## kuroguy

Just got all my parts and the heatsink is only 1.5" tall. the part number in the bill of materials is incorrect. it should be mouser #567-657-20abp instead of 567-657-15abp. Will it be a problem if I use the 1.5" heatsinks or should I order new ones?

 By the way, to remove the pins squeeze the heatsink in a vise just tight enough to releive the pressure from the heatsink on the pin and they can be easily pulled out. without the vise it is pretty much impossible to remove the pins.

 kuroguy


----------



## n_maher

I've been running one with 1-1/2" heat sinks for more than a month now without a problem, I think you'll be fine. And even with a vise I haven't had much (any) luck removing those pins, well done you for finding a way!


----------



## kuroguy

Gotta squeeze the heatsink pretty hard. I thought the aluminum might yield before the pins were loose enough. Use a rubber jaw vise. 

 Squeeze it until it bends and then back off a 1/4 turn. 
	

	
	
		
		

		
		
	


	




 Got the chassis machined and just need to start soldering. should have it done in a week at most.


----------



## Ub3rMario

God you guys are amazing. I need to take physics again, i've forgotten all but how to read a schematic. lol.


----------



## lynxkcg

I used both comair rotron and aavid headsinks, I stuck em in the oven for 10 mins at 450 and the pins pulled right off with vice grips. I used plenty of lube (breakfree CLP) and they tapped nice and smoothly for screws.


----------



## OldKing

532-531202B00 is 2" with no pins


----------



## holland

.


----------



## luvdunhill

Quote:


  Originally Posted by *lynxkcg* /img/forum/go_quote.gif 
_I used both comair rotron and aavid headsinks, I stuck em in the oven for 10 mins at 450 and the pins pulled right off with vice grips. I used plenty of lube (breakfree CLP) and they tapped nice and smoothly for screws._

 

nate:

 you doubted me?


----------



## n_maher

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_nate:

 you doubted me? 
	

	
	
		
		

		
		
	


	


_

 

Never.


----------



## -=Germania=-

That is part of my goal - removing the output caps. 

 Output caps really don' do anything to "help" overal sound quality because even the very best caps don't sound better that good ole' fashion wire. 

 That is part of the reason for the external power supply that is low leakage, higher ampage, and more linear. 

 Actually, I am thinking of making a B1 preamp (a new passive pre-amp design by Pass, can be done pretty cheap too!) into the same style case and have the three compoenent stacked on each other. Tower of power style!


----------



## m0b1liz3

Germania, Did you try using the MMSH as a pre-amp? I would be wanting tube sound coming out of the speakers too if possible.

 Too bad there aren't very many small simple tube speaker amp designs out there.


----------



## tomb

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Germania, Did you try using the MMSH as a pre-amp? I would be wanting tube sound coming out of the speakers too if possible.

 Too bad there aren't very many small simple tube speaker amp designs out there._

 

Have you looked at Pete Millett's website (http://www.pmillett.com)? He has quite a few to pick from. Granted, none of them are as simple as the SSMH, but they drive a lot more than a couple of flea speakers. His Hybrid Amp with Adjustable Damping Factor is particularly interesting. If you can snag a couple of 6GM8's, it might be a great one to try - low voltage and all.


----------



## m0b1liz3

tomb, It was my plan to build a speaker amp later since I already have too much stuff to move as it is! I still don't know if I am staying in Aus permanently. I might move back to Canada or the states if I can get on to a training program. But I will have to take a closer look at Pete's site. 

 In the short term it was my plan to use the Millet ss as a pre-amp to my amp 6 basic. Has anyone done this yet? Were the results acceptable?


----------



## rds

Quote:


 Has anyone done this yet? Were the results acceptable? 
 

Yes, I have and I said a few times now that I think it's a bad idea. But maybe at this point I should just give you the answer you want. Just don't blame me when your woofers get blown


----------



## -=Germania=-

I have it running as a pre-amp as we speak and it sounds quite good actually.

 I was directly comparing the sound from my Zhaolu>Millet> Receiver amp section to the Receiver's dac conversion and the first setup sounds better by a large margin. 

 Granted that right now I am using the Infinity SL-30's which I would consider a Lower Medium-Level speaker set as far as that craziness is concerned. The Tube-ness really gives these speakers a much more solid Bass response. The sound quality is much more realistic and the soundstage is better as well. 

 Now, keep in mind that I am using a Receiver and not a standard power amp. This may be one of the reasons why I am able to use this as a preamp and not have issues like those potential ones discussed earlier. 

 Sorry guys, but the ears do not lie and to me - this setup certainly doesn't suck.


----------



## n_maher

The simple fact remains that this design has got way more gain than most people would ever want in a preamp. That said, no one is going to come to your house and unplug it if you try and use it that way. Just bear in mind that you use it at your own risk and against the advice of more than just a few folks who've been at this for a long time.


----------



## -=Germania=-

Yeah, my setup is probably MUCH different than anyone here. 

 I should note that the knob is set at 10 o'clock. 
 Plus it is being set into a 100W/channel amp going out to speakers that can handle more power than that. 

 I tested this with my planars and it was not pretty. 

 It is a use at your own risk thing. 

 Also, you will want to mod the output to the pre-amp outs if you decide to do it. I added a capacitor to that output. Not a high value at all, but it did make a difference.


----------



## -=Germania=-

As far as the pre-amp output...

 I added a small resistor in the signal path of each channel and a .1uF film capacitor going between the signal out and the ground out of each channel. 
 I found that those mods fixed the general issue I had when I first tried this as a straight pre-amp (speakers were sounding noisy). 

 YMMV!

 Generally though, you will get better results from a piece of equipment that is meant for that purpose being used for that purpose. I really hope that there is no one here who is thinking of making one of these as a pre-amp in their system when there are so many cheap and good pre-amp designs on the net. It is part of the reason why I am looking the the B1 - cheap, easy-ish build and small footprint.


----------



## m0b1liz3

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Yes, I have and I said a few times now that I think it's a bad idea. But maybe at this point I should just give you the answer you want. Just don't blame me when your woofers get blown 
	

	
	
		
		

		
		
	


	


_

 

I know it is not the ideal way to build a pre-amp but I didn't want to build another tube pre-amp for a desktop system when I plan on doing this for my full sized system later. If it sounds horrible or has too much noise I can just go back to how I am using my amp 6 currently with the line out from my sound card controlling the volume. 

 I just thought it made sense to wire it up so that it could be used as a pre-amp since the additional cost is minimal. If I can inject some tube warmth to my desktop speakers then great, if not then I will only loose out on the extra $5 I spent on parts.


----------



## -=Germania=-

Try and do what I did. Works just fine.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Also, you will want to mod the output to the pre-amp outs if you decide to do it. I added a capacitor to that output. Not a high value at all, but it did make a difference._

 

What do mean, that you added a cap to the preamp output? Did you add this in series with the coupling cap that is already on the headphone output? Please elaborate.


----------



## jbloudg20

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_What do mean, that you added a cap to the preamp output? Did you add this in series with the coupling cap that is already on the headphone output? Please elaborate._

 

I think she removed the coupling caps :facepalm:. At least that was her goal, as stated a few times.

 Good thing she'll only ruin those POS cheap speakers


----------



## -=Germania=-

^ Dude - seriously you need to read before you comment. 

 I didn't remove any caps. I simply added stuff to an RCA out from a swicthed headphone jack. 

 It is kind of like so:






 FYI Guys, I am using different output capacitor values than the rest of you. Mine are 220uF on output instead of 470uf


----------



## jbloudg20

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_^ Dude - seriously you need to read before you comment. _

 

^ Dude- seriously you need to not only use quotes, but better explain yourself before you spout off. I was not the only one who was confused as to what you posted. I wouldn't remove the output caps without a servo implemented.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I didn't remove any caps. I simply added stuff to an RCA out from a swicthed headphone jack. 

 It is kind of like so:



_

 

That's a low pass filter, although I'm not quite sure it works as simply as you have it drawn since in reality you have both a high pass and low pass filter on the output when using your preamp outputs.


----------



## -=Germania=-

opps wrong cap value: 
 Corrected:





 Also you are right about it being a low pass filter, but it works a bit differently since it is directly connected at the output where it is also being grounded.


----------



## jbloudg20

So the next logical question in my head, is why are you implementing a bandpass filter for your preamp?


----------



## -=Germania=-

That filter has it cut off well above the audible range, so it does not mess with the audio signals passing through the amp. 
 You dont get a 1db drop until 80,000 Hz even based on calculations. It does work a little differently the way it is situated, but the basic principle applies.

 It does give it a "push" factor and some more impedence to work with, making a better pre-amp out - None of the distortion that you would have if you used the amp as a direct input to your power amp.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_It does give it a "push" factor and some more impedence to work with, making a better pre-amp out - None of the distortion that you would have if you used the amp as a direct input to your power amp._

 

I'd like a bit more explanation of how you figure that adding resistance on the output is going to reduce distortion. It may have quieted the noise floor on your amp but I'm not sure that's the same thing.


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_It does give it a "push" factor_

 

I don't think I want an amp that drives me from my home. What exactly do you mean.

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_and some more impedence to work with, making a better pre-amp out_

 

I don't know what this means, either.


----------



## -=Germania=-

Well, to me it seems that one of the reasons that this amp has trouble being used as a straight pre-amp is because of the output impedence and potential feedback. 

 What this does is bumps up the impedence, reduces feedback, and gets rid of output noise for use as a pre-amp (at least in my current system).

 Having the high pass and the low pass filter in that configuration does something pretty unique as far as a balancing act between the two. I also found out that it only works well if done directly at the plug with very short resistor leads. Using the master ground and not the one sent to the plug makes a difference as well in terms of the noise - one less signal path I suppose!

 I am sure thae there is more than can be done other than this simple circuit that will improve this aspect, but I have the next Millet Build concerning my mind at the moment with some changes I want to make and doing the math to figure it out.

 The "push" word has to do with dynamics. There is greater dynamics, not greater noise. 

 Also, please note that I have the dial set at 10 o'clock and my amp at 5/8 power. That matches the output from the internal D/A converter that I was comparing it against. 

 I should note that using this pre-amp output from the combo previously described sounded better than using the internal D/A converter as well as just using the output of a modified Zhaolu.


----------



## FallenAngel

Just built one of these, sounds very nice, surprisingly nice for the price actually. I made mine a little more extreme in terms of parts

 Alps RK27 POT
 VitaminQ coupling caps
 Muse FG output caps


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Well, to me it seems that one of the reasons that this amp has trouble being used as a straight pre-amp is because of the output impedence and potential feedback. 

 What this does is bumps up the impedence, reduces feedback, and gets rid of output noise for use as a pre-amp (at least in my current system)._

 

Higher output impedance has never been something described to me as a positive and you'll have to clarify for me how your mods reduce feedback, I don't know what you mean there. 

  Quote:


 Using the master ground and not the one sent to the plug makes a difference as well in terms of the noise - one less signal path I suppose! 
 

I'm afraid I need more explanation here to - what "master ground" are you referring to? All grounds in the amp are the same thing. There is no ground sent to the plug.


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Well, to me it seems that one of the reasons that this amp has trouble being used as a straight pre-amp is because of the output impedence and potential feedback. 

 What this does is bumps up the impedence, reduces feedback, and gets rid of output noise for use as a pre-amp (at least in my current system).

 Having the high pass and the low pass filter in that configuration does something pretty unique as far as a balancing act between the two. I also found out that it only works well if done directly at the plug with very short resistor leads. Using the master ground and not the one sent to the plug makes a difference as well in terms of the noise - one less signal path I suppose!

 I am sure thae there is more than can be done other than this simple circuit that will improve this aspect, but I have the next Millet Build concerning my mind at the moment with some changes I want to make and doing the math to figure it out.

 The "push" word has to do with dynamics. There is greater dynamics, not greater noise. 

 Also, please note that I have the dial set at 10 o'clock and my amp at 5/8 power. That matches the output from the internal D/A converter that I was comparing it against. 

 I should note that using this pre-amp output from the combo previously described sounded better than using the internal D/A converter as well as just using the output of a modified Zhaolu._

 

This is 100% nonsense. It isn't even worth a point by point refutation as not one word of it makes any sense.

 And I'm still waiting on your cable measurements.


----------



## -=Germania=-

I will take pictures. 
 If any of you have enough courage to try it - let me know. 
 Unless you actually try it and think it makes stuff sound worse...I don't see the sense in arguing this. 

 "Master Ground" as in directly to the ground plane instead of the ground on the switched 1/4 jack.

 I will get onto the cables once school starts, but we don't start until almost the end of this month.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I will take pictures. 
 If any of you have enough courage to try it - let me know. 
 Unless you actually try it and think it makes stuff sound worse...I don't see the sense in arguing this._

 

I think Doug is taking issue with the liberties you're taking with seemingly technical terms like "feedback". And regardless of your individual impressions of the sonic differences of lowering the performance of the amp (raising the output impedance, for example) you can't honestly expect us to sit idly by while you trumpet them as triumphs, can you?

  Quote:


 "Master Ground" as in directly to the ground plane instead of the ground on the switched 1/4 jack. 
 

So that'd be just ground then.


----------



## joe_seattle

Hi, I asked this a bit ago, but in a different forum (I think) and didn't see a response. With my AKG K340 phones connected (1/2 dynamic, 1/2 electrostatic), it appears that the electrostatic drivers cut-out or turn-off when I touch the volume knob of the amp. Any ideas on what this may indicate about the amp or about the wiring of my modded phones? My very beginner-guess is that it has something to do with grounding...perhaps the ground signal circuit is closed in a not-so-helpful way by me? The amp works flawlessly otherwise, and of course this problem is not present with dyanmic-only phones like the HD600.


----------



## kuroguy

I'm sure you can guess what this is. I added an led pilot light (cause I had one lying around), 220K resistors to reduce the input signal and used 390uF caps instead of the 150uF shown on the schematic. My three year old (and I) had a great time helping me tighten the screws. Sounds great.

 Kuroguy


----------



## HeadphoneAddict

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_I'm sure you can guess what this is. I added an led pilot light (cause I had one lying around), 220K resistors to reduce the input signal and used 390uF caps instead of the 150uF shown on the schematic. My three year old (and I) had a great time helping me tighten the screws. Sounds great.

 Kuroguy






_

 

When do you plan to install the BUG EYED monster tubes?


----------



## kuroguy

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_When do you plan to install the BUG EYED monster tubes?_

 

Built an 832 amp about a year ago. Haven't found funds for the 829 tubes I have yet.


----------



## exphy

could any1 help me get the tubes to the netherlands?


----------



## adamus

vacuumtubes.net will send them at cost - at least he did to the uk.


----------



## holland

.


----------



## ludoo

Is there any interest for a pre-drilled Hifi2000 case? I called them 5 minutes ago and spoke to the owner, if we find 15-20 people the cost will be acceptable (at least in the EU).

 To pre-drill a case they need to set up the machines, and between that and the actual drilling it takes 2-3 hrs, for a max cost of 135 euros. Once they are set up, drilling 1 case or 30 or 50 does not change costs. So if there's 15-20 people interested, we could think about placing an order, and maybe engrave the panels too.

 Better yet would be if someone in the US made full kits for the BOM, so that with the pre-drilled case and the kit people could buy everything they need to build a beautiful SS, and concentrate only on soldering and mounting connectors etc.


----------



## Citizen86

135 euros??? How much more is that than the total BOM of this project?? heh... not very starving student


----------



## scompton

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Is there any interest for a pre-drilled Hifi2000 case? I called them 5 minutes ago and spoke to the owner, if we find 15-20 people the cost will be acceptable (at least in the EU).

 To pre-drill a case they need to set up the machines, and between that and the actual drilling it takes 2-3 hrs, for a max cost of 135 euros. Once they are set up, drilling 1 case or 30 or 50 does not change costs. So if there's 15-20 people interested, we could think about placing an order, and maybe engrave the panels too.

 Better yet would be if someone in the US made full kits for the BOM, so that with the pre-drilled case and the kit people could buy everything they need to build a beautiful SS, and concentrate only on soldering and mounting connectors etc._

 

I'm interested. It wouldn't hurt to have a second one of these. 

  Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_135 euros??? How much more is that than the total BOM of this project?? heh... not very starving student 
	

	
	
		
		

		
		
	


	


_

 

From how I read it, that's the set up cost that covers 30-50 cases. Even if it's 20, that's less than 7 per case, which seems reasonable to me. Especially for people who don't have stepped drill bits. They're not cheap and without them, I'm not sure how you'd drill the holes for the tube sockets.


----------



## Citizen86

Ohhh... I thought it was 135 euros per... hahahhaaaaaaaa.... nevermind me.

 In that case, I may be in for one! My kit from rds was delivered, but I still need a case to put it in.


----------



## ludoo

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_135 euros??? How much more is that than the total BOM of this project?? heh... not very starving student 
	

	
	
		
		

		
		
	


	


_

 

135 euros to punch perfect holes in 30 or 40 cases? It does not seem like much to me... 
	

	
	
		
		

		
		
	


	




 Edit: As usual, I replied before reading later posts. I will open up a new thread soon so that we can sort out who is interested.


----------



## JamesL

huh? 7 euros per case, or 7 euros to punch the cases?

 It costs about $70 for a single one, shipped to the US.


----------



## Chipp

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_...snip...

 Especially for people who don't have stepped drill bits. They're not cheap and without them, I'm not sure how you'd drill the holes for the tube sockets._

 

Personally, I was able to make do with a $12 set of spade bits from Lowes, but my case was wood while it appears most others are using metal (and having a terribly lacking knowledge of tools, I don't know if the spades would be appropriate for that or not). All told I spent $14 on my casing - twelve of it for the bits, the other two on the thrift store cigar box.


----------



## ludoo

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_huh? 7 euros per case, or 7 euros to punch the cases?

 It costs about $70 for a single one, shipped to the US._

 

7 euro to punch the case, maybe a little less. The case itself costs 6.70 euros + 20% vat (about 8 euros). Each one weighs 0.4kg so shipping to the US by registered mail is 11.50 euros for one or two cases, 19.50 4 cases. Regular air mail costs less.


----------



## procalli2007

I had a hum on my ss so I resoldered but this didnt solve it.

 However I swapped the tubes and the hum followed so I changed the tube and now the hum has gone. Why would a tube hum?


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_I had a hum on my ss so I resoldered but this didnt solve it.

 However I swapped the tubes and the hum followed so I changed the tube and now the hum has gone. Why would a tube hum?_

 

Because it's bad.


----------



## rds

I thought bad tubes whistle


----------



## dsavitsk

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I thought bad tubes whistle_

 

Bad tubes can do any number of things as they can be bad in various ways.


----------



## procalli2007

So Id better order some more tubes. 

 It seemed to be ok when I first built the amp and got the hum later on.

 Thought the tubes should last longer.


----------



## tomb

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_So Id better order some more tubes. 

 It seemed to be ok when I first built the amp and got the hum later on.

 Thought the tubes should last longer._

 

Of course they'll last longer - years, perhaps, in some cases. You obviously got a bad one. Stuff happens.
	

	
	
		
		

		
		
	


	




 I'm sure the tube seller will give you another one or your money back.

 P.S. I sell tubes all the time for the Millett MAX and it still amazes me a bit that people will spend $hundreds on building an amp, but then order only 2 tubes. We all have to make purchasing decisions, but just the random variance in sound from one 40 year-old tube to another is enough to warrant purchasing multiples, IMHO. When they're $2-$5 each, it seems a reasonable thing to do.


----------



## ludoo

Quote:


  Originally Posted by *procalli2007* /img/forum/go_quote.gif 
_So Id better order some more tubes. 

 It seemed to be ok when I first built the amp and got the hum later on.

 Thought the tubes should last longer._

 

I'm a total noob so take what I'm saying with a grain of salt. My SS developed a hum in the left channel, and I discovered it went away (or was only intermittent) when I wiggled one of the wires going to the tube socket, sorry can't remember to which pin now. The socket pin had a lot of free movement, and on top of that the tube had bent pins. I straightened the tube pins, pushed the socket pin inside the socket so it had less free movement, and cleaned the tube pins with fine sandpaper. The hum went away.

 As I said, it might be coincidental, as in DIY most of the time I don't know what I'm doing.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I'm a total noob so take what I'm saying with a grain of salt. My SS developed a hum in the left channel, and I discovered it went away (or was only intermittent) when I wiggled one of the wires going to the tube socket, sorry can't remember to which pin now. The socket pin had a lot of free movement, and on top of that the tube had bent pins. I straightened the tube pins, pushed the socket pin inside the socket so it had less free movement, and cleaned the tube pins with fine sandpaper. The hum went away.

 As I said, it might be coincidental, as in DIY most of the time I don't know what I'm doing._

 

One would think that when he switched the tubes from one socket to another and the hum followed the tube, that would discount the situation you describe.

 It's a good suggestion, though, and it never hurts to try cleaning/straightening the pins.


----------



## procalli2007

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_ cleaned the tube pins with fine sandpaper._

 

I may try this although I did buy 4 tubes to start so am ok for now.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_One would think that when he switched the tubes from one socket to another and the hum followed the tube, that would discount the situation you describe._

 

Heh yes, it occurred to me after posting. I was still a bit excited to have solved my hum problems and could not wait to share.


----------



## wualta

This isn't a DIY, it's a BIY, Buy It Yourself. Got it from an eBay seller for a reasonable price. Wonderful sound, uses 220uF blocking caps, runs very hot. The Fostex T50 likes it too.


----------



## Citizen86

Well I have all my parts now for this, even found a case for it hidden away, an old Tommy Hilfiger wallet box... I think I'm going to paint over the top 
	

	
	
		
		

		
		
	


	




 Anyway's, I'm embarrased to ask, because I'm pretty sure it's alright, but my shining green-ness is going to be shown here (this is my first DIY project), but I have an amazing amount of ethernet cord lying around, it would be alright if I used some of that for wiring of this project, right?


----------



## dsavitsk

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_it would be alright if I used some of that for wiring of this project, right?_

 

yes


----------



## m0b1liz3

I finally started wiring up my millet this weekend. I was looking at the IRF 510 and wondered how you determine what positions are 1, 2 and 3. I was about to wire it and assumed it is simply left to right when looking at it face on but then I thought what if I have it wrong so figured I should ask...


----------



## kuroguy

google irf510 datasheet


----------



## royewest

When looking from the front (the plastic side with the printing), pins down, the pins are numbered 1,2,3 left to right.


----------



## m0b1liz3

Thanks royewest. It was as I thought but I would rather double check with people that are more experienced. I may post a pic of it with 1 channel wired up before I do the other as well...

 And now for another potentially dumb question... I have a switched jack but have no idea what tab is what. It came out of a bin with no instructions etc. I probably just don't know the standard for labeling the tabs. 2,3,4, 8 and SC are the 5 tabs that I have to choose from. Any ideas? Here is the link to the jack I bought. 

Jaycar Electronics


----------



## royewest

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Thanks royewest. It was as I thought but I would rather double check with people that are more experienced. I may post a pic of it with 1 channel wired up before I do the other as well...

 And now for another potentially dumb question... I have a switched jack but have no idea what tab is what. It came out of a bin with no instructions etc. I probably just don't know the standard for labeling the tabs. 2,3,4, 8 and SC are the 5 tabs that I have to choose from. Any ideas? Here is the link to the jack I bought. 

Jaycar Electronics_

 

You're welcome for the pinout info on the chip -- the data sheets I looked at when I got mine did not have that info, much to my annoyance! Someone on this forum helped me out at the time.

 Regarding the socket: have you tried asking Jaycar for a data sheet? You might also find the same item on Mouser of Digikey and see if you can find the data sheet for that item there (those online dealers are fabulous about links to the data sheets for their products). Otherwise, you could use your meter on connectivity-beep mode and some alligator clips and a plug to create your own diagram...


----------



## heatmizer

That jack from jaycar.
 Be careful when you tighten it the plastic thread strips easily.
 pin 4 is left, pin 8 is right, one by itself on edge is ground


----------



## m0b1liz3

so the remaining 2 can be used if I decide to add line out rcas later?


----------



## JamesL

Questions. 
 Concerning C3/C5.
 Does it have to be rated for >= 65v? The output shouldn't have anything more than 2vrms on them, right? + additional dc offset (how big is this value normally?)
 Also, does input impedance = value of pot? In which case, I only need 2-5uF at the output, correct?

 Also, would a simple lm317 regulator help to filter out some of the noise from the switching supply? 

 I normally try to stick close to the default parts/values and configurations when building projects since I'm not so confident in my decisions, but I think this would be a good chance for me to tinker around and learn a bit.


----------



## error401

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Questions. 
 Concerning C3/C5.
 Does it have to be rated for >= 65v? The output shouldn't have anything more than 2vrms on them, right? + additional dc offset (how big is this value normally?)_

 

The output has significant DC on it due to the novel heater supply/bias arrangement. Also, it's possible for the whole supply voltage to appear at the cap if the tube is not in its socket or fails. Use the 65V caps.
  Quote:


 Also, does input impedance = value of pot? In which case, I only need 2-5uF at the output, correct? 
 

For practical purposes, yes.
  Quote:


 Also, would a simple lm317 regulator help to filter out some of the noise from the switching supply? 
 

Maybe, but based on accounts in this thread, it's entirely unnecessary. If your intent is to filter HF noise you'd probably be better off with a different regulator anyway, or even a simple pi or LC filter.


----------



## elliot42

I finished my second Starving Student and it has exactly the same hum/buzz as my first build so I'm wondering if it's the SMPS that's producing the noise. I had a look at LC filters but I'm not sure which design and what values I should be using. Will I need to use a scope to see what frequencies are coming out of the SMPS, or is there an LC or other filter that I can build that will filter out all imperfections in the signal?

 The hum increases volume as I increase the volume with the pot. It's audible from about 1/3 turn (1/2 turn with ambient noise) and is a lowish pitch and has a kind of fluttering sound, I'd describe it as a hum though.


----------



## n_maher

Elliot,

 Sounds to me like you must have a problem with the grounding arrangement. Or you've got a really cruddy power supply that is producing a lot more noise than the one that I have.


----------



## rhys h

I have my first SS amplifier on the way! 

 With this board to go with it, atleast it would be better then my p2p wiring.







 ^^ The terribley designed 'interconnecting' pcb. The All parts except resistors and capacitors are mounted off the board.


----------



## tomb

Your board looks good, but a couple of things:

 1. The 2nd round of SSMH prototype boards are shipping right now and some have received them. I would expect to see them built in the next couple of weeks, perhaps, with the production boards coming shortly thereafter.

 2. Pete Millett has warned of MOSFET oscillation if R3 and R9 are not tied directly to the gate leg of the MOSFETs. So, you may not want to put those particular resistors on your board.


----------



## rhys h

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Your board looks good, but a couple of things:

 1. The 2nd round of SSMH prototype boards are shipping right now and some have received them. I would expect to see them built in the next couple of weeks, perhaps, with the production boards coming shortly thereafter.

 2. Pete Millett has warned of MOSFET oscillation if R3 and R9 are not tied directly to the gate leg of the MOSFETs. So, you may not want to put those particular resistors on your board._

 

Thanks for the comments, i was not even aware there was a ssmh board going round 
	

	
	
		
		

		
		
	


	




, but this is more of a learning project, i will probably never finish it 
	

	
	
		
		

		
		
	


	




. Anyway, about the mofests, so you are saying i should take them off the board and solder them directly to pin number 1 on the mofsets?


----------



## tomb

Quote:


  Originally Posted by *rhys h* /img/forum/go_quote.gif 
_<snip>Anyway, about the mofests, so you are saying i should take them off the board and solder them directly to pin number 1 on the mofsets?_

 

Pretty much. 
	

	
	
		
		

		
		
	


	




 The actual trace that's been tested on the SSMH board is about 1/16" - 1/8" between the MOSFET Gates and R3/R9 and it worked fine.


----------



## elliot42

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Elliot,

 Sounds to me like you must have a problem with the grounding arrangement. Or you've got a really cruddy power supply that is producing a lot more noise than the one that I have._

 

I thought it would be a grounding issue, but I also thought it was funny that the hum sounded identical to my first build. The heatsinks aren't grounded so maybe that's where I should start. Otherwise I think the build looks fine, a little cramped, but I think the joints are OK. I used some blank pcb as a ground plane and everything (but heatsinks) is tied to that.

 The SMPS is the recommended Cisco, from eBay. 48V 0.35A.

 Here are some pics, maybe someone can see something wrong?
http://picasaweb.google.com.au/o.cla...ngStudentTake2


----------



## rhys h

Has anyone in the uk successfully managed to source all the parts locally excluding tubes and tube sockets? I dont fancy getting bitten by fedex for import tax again. ($50 inc admin fee for $110 order).


----------



## n_maher

Quote:


  Originally Posted by *rhys h* /img/forum/go_quote.gif 
_Has anyone in the uk successfully managed to source all the parts locally excluding tubes and tube sockets? I dont fancy getting bitten by fedex for import tax again. ($50 inc admin fee for $110 order)._

 

You might ask around and see if folks in your area have had better experiences using USPS shipping. I'd think that the raw cost would be similar to UPS/FedEx and they don't seem to have BS charges like the big guys do.


----------



## rhys h

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_You might ask around and see if folks in your area have had better experiences using USPS shipping. I'd think that the raw cost would be similar to UPS/FedEx and they don't seem to have BS charges like the big guys do._

 

I think it is the way mouser use huge oversized box's, and attach all the invoices to the outside of the box. 
	

	
	
		
		

		
			





. Another thing about ordering from accross the pond is that the overall build cost is increased by quite a lot, to consider i want this built for under $50.


----------



## keiths

Quote:


  Originally Posted by *rhys h* /img/forum/go_quote.gif 
_Has anyone in the uk successfully managed to source all the parts locally excluding tubes and tube sockets? I dont fancy getting bitten by fedex for import tax again. ($50 inc admin fee for $110 order)._

 

I sourced everything from Farnell (Farnell UK | world-leading distributor of electronic and maintenance, repair and operations products.) and Rapid (Electronic components distributor. Electronic equipment and electrical products from Rapid) - with the exception of the valves (which I got from Radio Daze - just under £10 for 4 including delivery), the valve sockets (off ebay) and the psu (again, ebay).

 There's no way you are going to build this for $50 (£28.25) paying UK prices.

 Farnell have a minimum £35 order and you really have to watch their pricing on some things (if I'd bought the MOSFETs from them, I'd have paid £1.50 each as opposed to 28p each from Rapid!) and they have order multiples for some things (I had to buy 5 of each value for the Panasonic low-esr caps for example - but that wasn't a problem as I wanted to build 2 amps anyway).


----------



## MrKazador

Does it matter if I use different a type of resistor? I doubt there would be a huge difference but I want to make sure...

 All Vishay 1%:
 2k - CCF55
 200k - CCF55
 33k - *RN60*


----------



## rhys h

Thanks! I was thinking more like £30 excluding shipping, valves and sockets.

  Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_I sourced everything from Farnell (Farnell UK | world-leading distributor of electronic and maintenance, repair and operations products.) and Rapid (Electronic components distributor. Electronic equipment and electrical products from Rapid) - with the exception of the valves (which I got from Radio Daze - just under £10 for 4 including delivery), the valve sockets (off ebay) and the psu (again, ebay).

 There's no way you are going to build this for $50 (£28.25) paying UK prices.

 Farnell have a minimum £35 order and you really have to watch their pricing on some things (if I'd bought the MOSFETs from them, I'd have paid £1.50 each as opposed to 28p each from Rapid!) and they have order multiples for some things (I had to buy 5 of each value for the Panasonic low-esr caps for example - but that wasn't a problem as I wanted to build 2 amps anyway)._


----------



## elliot42

Quote:


  Originally Posted by *MrKazador* /img/forum/go_quote.gif 
_Does it matter if I use different a type of resistor? I doubt there would be a huge difference but I want to make sure...

 All Vishay 1%:
 2k - CCF55
 200k - CCF55
 33k - *RN60*_

 

It doesn't matter, not sure if it sounds any different, but I used 2k2 1/4W from my pats bin, 33k 1/8W and 220k 1/4W. I checked the values were close when choosing them with my DMM.

 A different series shouldn't make much, if any, difference.


----------



## elliot42

On another note, I grounded my heatsinks and the hum is still there. Grounding them did help as they now don't hum or pop it I touch the heatsinks, but the main hum is still there.

 Since the hum increases volume as I turn the pot up, does that mean that the cause has to be behind the pot, i.e. at the input connectors?


----------



## dsavitsk

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_On another note, I grounded my heatsinks and the hum is still there. Grounding them did help as they now don't hum or pop it I touch the heatsinks, but the main hum is still there.

 Since the hum increases volume as I turn the pot up, does that mean that the cause has to be behind the pot, i.e. at the input connectors?_

 


 Couple of things to try:
 1. try disconnecting your source and grounding the input jacks and see if that solves anything

 2. if that doesn't help, connect the pot to the tube grids with a 1K resistor (anything from 470R to 10K is fine, so use what you have) right on the grid. Since there are two grids on each tube, try first connecting the grids together and use a single resistor per tube, then, if that doesn't totally work, but does help some, use a resistor per grid. You may have some oscillation, and this can often help.

 3. Twist the input signal and ground wires to prevent picking up any noise.

 Oh, and be sure that the PS is far away, and that you are not near any other electronics.

 Did you post pics?


----------



## elliot42

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Did you post pics?_

 

I did, but they're not great: http://picasaweb.google.com.au/o.cla...ngStudentTake2

 I'll give your suggestions a go when I get home tonight.


----------



## JamesL

Is there any good way to mount to220's onto a flat-back'ed finned heatsink?
 I've thought about using a L-bracket, or self-tapping machine screws, or some sort of epoxy, but I'm still kind of unsure.


----------



## error401

I would drill and tap holes, if you use self-tappers, there's a good chance some of the swarf from cutting the threads will get lodged behind the package and impede heat transfer. For the same reason, insert and remove the screw a few times and file/sand the freshly tapped hole smooth before you mount the transistor.


----------



## keiths

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_I would drill and tap holes_

 

The MOSFET needs to be insulated from the heatsink, so you need to drill a hole large enough for a TO-220 insulating boss to go through and then use a bolt, washer and nut.


----------



## error401

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_The MOSFET needs to be insulated from the heatsink, so you need to drill a hole large enough for a TO-220 insulating boss to go through and then use a bolt, washer and nut._

 

In this circuit the drains of the FETs are on the same net (V+). As long as the heatsink doesn't contact any other parts of the circuit it should be fine. Though 48V is getting a bit up there for exposed voltage, so your way is probably better.


----------



## JamesL

A insulating boss?

 Anyways, I can't use a hex nut to secure it, since there are fins on the other side. 

 I think error401's method would work, as long as I put the thermafilm and shoulder washers in between.


----------



## error401

Quote:


 I think error401's method would work, as long as I put the thermafilm and shoulder washers in between. 
 

To be safe you need to insulate the tab from the screw somehow. If you have shoulder washers that are the right size and still allow a screw to pass through the tab, you can use those safely. Make sure that any washer you use doesn't interfere with the case being clamped tightly to the sink. You could also use nylon screws.

 Or be careful that any parts that may contact the sink have their tabs connected to the same net.


----------



## JamesL

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_To be safe you need to insulate the tab from the screw somehow. If you have shoulder washers that are the right size and still allow a screw to pass through the tab, you can use those safely. Make sure that any washer you use doesn't interfere with the case being clamped tightly to the sink. You could also use nylon screws.

 Or be careful that any parts that may contact the sink have their tabs connected to the same net._

 

I was looking at the datasheet for the recommended insulator (Mouser part #532-4880), and I was under the impression that it came with shoulder washers.


----------



## keiths

Are you mounting both FETs on the same heatsink? If so, how about drilling and tapping a hole between the two FETS and using a short piece of metal bar and a bolt to clamp the FETS to the heatsink (with thermafilm or whatever in between the FETs and the 'sink). As long as the metal bar only touches the black "plastic" part of the FETs, you woun't need shoulder washers/bosses and the FETs will be insulated from the heatsink.


----------



## error401

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Are you mounting both FETs on the same heatsink? If so, how about drilling and tapping a hole between the two FETS and using a short piece of metal bar and a bolt to clamp the FETS to the heatsink (with thermafilm or whatever in between the FETs and the 'sink). As long as the metal bar only touches the black "plastic" part of the FETs, you woun't need shoulder washers/bosses and the FETs will be insulated from the heatsink._

 

Also improves contact with the sink.


----------



## JamesL

sweet. Sounds like an idea! =]

 Thanks


----------



## error401

Just be careful not to overtighten the bar. Depending on the distance from the screw to the transistor, the leverage can make it surprisingly easy to crack the transistors. I would recommend using a bolt on each side instead of one in the centre, and tighten as uniformly as possible to minimize the risk of damage.


----------



## Stikk

Anyone knows were I can find a couple of these tubes? I live in Australia so somewhere that ships internationally would be good. I can't seem to find them anywhere.


----------



## elliot42

Quote:


  Originally Posted by *Stikk* /img/forum/go_quote.gif 
_Anyone knows were I can find a couple of these tubes? I live in Australia so somewhere that ships internationally would be good. I can't seem to find them anywhere._

 

Radio Daze
 Got mine from there and so have a number of others here. Nice guy to deal with.


----------



## elliot42

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Couple of things to try:
 1. try disconnecting your source and grounding the input jacks and see if that solves anything

 2. if that doesn't help, connect the pot to the tube grids with a 1K resistor (anything from 470R to 10K is fine, so use what you have) right on the grid. Since there are two grids on each tube, try first connecting the grids together and use a single resistor per tube, then, if that doesn't totally work, but does help some, use a resistor per grid. You may have some oscillation, and this can often help.

 3. Twist the input signal and ground wires to prevent picking up any noise.

 Oh, and be sure that the PS is far away, and that you are not near any other electronics.

 Did you post pics?_

 

The inputs were already grounded to the ground plate, if that's what you meant. It's better like that and the hum is pretty much gone with the input shorted to ground (with the pot to 0). I can still barely hear it but only in a silent room. The hum becomes noticable at about 1/3 turn and annoying at 1/2. At normal listening levels (1/3 ish) it's fine with music playing, but the hum's there, so it annoys me 
	

	
	
		
		

		
			





 I have also replaced the wires from the input to the pot with some twisty cat5 copper (ran out of hookup to twist). So the input ground now connects to the pot ground and is twisted with the L and R input.

 Each heater also has a 4k7 resistor on it.

 Hum is still there ... 
	

	
	
		
		

		
		
	


	




 might have improved a little, not sure, but not much.

 Thanks for the tips though, good to know for future projects.

 Do you think it could be a dodgy PS, or is that unlikly?
 I'm sure it could be my build, but it doesn't seem like others have had such trouble with hum. Plus I'm no noob to soldering so I think my joints should generally be ok.


----------



## MrKazador

I sent an email to Radiodaze about 2 days ago and they are out of 19j6 tubes...


----------



## n_maher

There are lots of other tube vendors out there.


----------



## MrKazador

TheTubeCenter.com seems to be the cheapest I could fine, $3 per tube. They also have the sockets(sk-7) for $2 each.


----------



## JamesL

Someone just ninja'd the last couple 19j6's right before I ordered from surplussales. !!
 >=[


----------



## dsavitsk

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_Do you think it could be a dodgy PS, or is that unlikly?
 I'm sure it could be my build, but it doesn't seem like others have had such trouble with hum. Plus I'm no noob to soldering so I think my joints should generally be ok._

 

Your picture link didn't work for me.

 But, no, it doesn't sound like a dodgy PS. If the noise changes with volume, it is likely poor wiring, grounding issues, or tube oscillation (probably from poor wiring). So, a picture would help. Is the body of the pot grounded? That can cause issues like this, too.

 Go over the soldering again anyway. Use a good hot iron, and sit on each joint until it really flows. One bad connection to ground can cause all sorts of noise issues.


----------



## elliot42

The body of the pot is grounded. I have some decent hookup wire on the way and I will re-wire the whole thing with that when it comes. Making sure I get as many twists in as possible 
	

	
	
		
		

		
		
	


	




 I'll get some pics up in a minute. Looking at it now, the wiring does look pretty messy


----------



## ltmon

Hi All,

 My first DIY build, and it all works, so I'm very happy. I do however have a lot of background hiss, more than I expected at any rate. I've been tracking through my circuit for a few hours trying to find the problem without luck.

 It's a constant white noise, does not seem to be affected by the volume control or whether there is currently input plugged in or not. Earthing various points (more or less at random) doesn't seem to affect it either.

 Is this enough information to give any more experienced heads a hint where I should look for my problems? My build is very crowded (picked too small an enclosure for a first timer I think), would that be a possible cause?

 Thanks in advance,

 L.


----------



## pinkfloyd4ever

I've had great experience with Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!


----------



## dsavitsk

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_The body of the pot is grounded. I have some decent hookup wire on the way and I will re-wire the whole thing with that when it comes. Making sure I get as many twists in as possible_

 

The quality of the wire won't matter. Teflon insulated wire is nice as it doesn't melt, and solid core is often easier to work with in PTP wiring. But, the sound quality won't change.

  Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_I'll get some pics up in a minute. Looking at it now, the wiring does look pretty messy_

 

It isn't really that bad -- I've seen messier work just fine.

 That said, there are no grid stoppers in these pics. If you haven't yet, add them -- 1K is a good starting point. Another thing to try is connect the power input ground to the negative lead of C1. Connect that to the negative lead of C6, and connect everything that needs to be grounded to C6. In fact, you can connect the negative lead of C6 to the ground plane, then connect everything else there -- preferably close to where C6 connects. At least make sure all the connections are good.

 Oh, the two PS caps should probably be 470u -- I can't see what yours are.


----------



## elliot42

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Teflon insulated wire is nice as it doesn't melt._

 

That's what's coming, it's tricky trying to re-do joints on the ground plane when I have to carefully dodge meltable wires 
	

	
	
		
		

		
			





 The PS ground is connected to the ground plane and C1 -ve. C1 is bottom left in the pics, with C6 above it. I'll try moving the wire to the ground plane to C6 -ve.

 The PS caps are 220uF, as are the output caps. I have some 470uF caps which I can put in.

 And I have the resistors on the grids, did that last night, 4k7 on each grid (4 total). Pics were taken the day before.


----------



## elliot42

Right, put the 470uF caps in, they're a tight fit. And I put the ground plane connection to C6 and PS ground to C1.

 I think that improved a little, but I heard what I reckon is oscillation for sure. Sometimes the hum sounds like: WOWowOWowOWow, if you get what I mean, the wowow sounds like it's about 5-10Hz oscillation on top of the hum. It seems to do this randomly and then cuts back to the regular hum. I have actually heard this before, so it's not recently introduced. I thought it was just some sort of interference. Also, the hum starts only when the tubes are warmed up, not straight away from a cold turn on. If that makes any difference.

 I have the resistors on the grids, but what exactly is tube oscillation and how are those resistors meant to be helping?

 Sorry for all the questions, I haven't worked with tubes before, and not much with audio circuits so I don't have much knowledge in debugging this type of thing.


----------



## dsavitsk

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_Right, put the 470uF caps in, they're a tight fit. And I put the ground plane connection to C6 and PS ground to C1.

 I think that improved a little, but I heard what I reckon is oscillation for sure. Sometimes the hum sounds like: WOWowOWowOWow, if you get what I mean, the wowow sounds like it's about 5-10Hz oscillation on top of the hum. It seems to do this randomly and then cuts back to the regular hum. I have actually heard this before, so it's not recently introduced. I thought it was just some sort of interference. Also, the hum starts only when the tubes are warmed up, not straight away from a cold turn on. If that makes any difference.

 I have the resistors on the grids, but what exactly is tube oscillation and how are those resistors meant to be helping?

 Sorry for all the questions, I haven't worked with tubes before, and not much with audio circuits so I don't have much knowledge in debugging this type of thing._

 

Tube oscillation is typically a pretty high frequency -- outside of the hearing range. There are, however, often artifacts you can hear -- can sound like hum, or hash, or static, or sometimes just microphonics. Hard to know if that is what is happening without a scope.

 As for why the grid stopper works -- I asked the same question. Read posts 5 and 6, and really the whole thread, for some answers here: diyAudio Forums - Grid Stopper - Page 1

 Any chance you can come up with some 130R/5W resistors? If so, remove the tubes and put the resistors across pin 3 and 4 of each tube socket and see what you hear. This will let you know if this is tube oscillation.

 Other things to try -- this could be a bad PS. The only real ways to tell are to measure it, try a different one, or build something as a stand in. If you can't come up with a transformer in th right range or another of these 48V switchers, try a 24V wall wart. The amp won't run ideally, but it should basically still run giving you some indication of whether this is an issue.

 Also, is there any difference between the sides? Do you have another set of tubes to try?


----------



## -=Germania=-

Hey guys, 

 You should check the power supply for just how linear they are because there seems to some not so good even with the cisco ones (YMMV). They are cheap - so take what you will. The build I am using now (3 channel) is using a modified version of this power supply (better caps + 470uF across output - otherwise the sound was pretty "lean"). This power supply is linear, can be used in any country without changing (universal input), and cheap to boot. One thing to consider is that they only deal with businesses (I was able to order through the university) and perhaps some sort of arrangement can be made as a group? One point to consider is that it is powering 3 channels, not two, and the mosfets get slightly warmer than with the cisco. Maybe a different model?

 Is there a better option than the alps blue for under $20-$25? (This standard alps is a bit noisy when turning and not as smooth as I would like).

 Any questions about the sound should be held until a bit later in November and hopefully by other members can answer. Please mind that the overall build cost ended up around $180 and uses premium parts (except the pot) with the output caps bypassed (not floated).

*This thread has been EXTREMELY helpful to everyone and the larger contributors definitely deserve our gratitude.*


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_This standard alps is a bit noisy when turning and not as smooth as I would like)._

 

Noise generally indicates DC on the pot. The only better pot for the money might be some of the cheap eBay steppers.


----------



## -=Germania=-

It is only when turning - otherwise it is fine and it is only occurs in the right channel. Stepped might be the way to go because it isn't always even (only from 9-3 o'clock). The Vishay conductive plastic doesn't look too bad though.

 UPDATE: Have bid going for Stepped Pot


----------



## elliot42

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Any chance you can come up with some 130R/5W resistors? If so, remove the tubes and put the resistors across pin 3 and 4 of each tube socket and see what you hear. This will let you know if this is tube oscillation._

 

110R between pin 3 and 4 instead of plugging in the tubes (had 10 22R 5W, 5 for each socket) = complete and utter silence.

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_If you can't come up with a transformer in th right range or another of these 48V switchers, try a 24V wall wart._

 

I don't have another 48V supply, but I do have a 24VAC brick which I can rectify and see how that goes. But if I'm getting nothing with the resistors instead of the tubes, that should mean the PS is clean, right? As what's then active in the circuit is everything but tubes, pot, R5 and R11.

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Also, is there any difference between the sides? Do you have another set of tubes to try?_

 

Same results with different tubes.

 And thanks so much for the links and help so far. I'm learning a lot.


----------



## holland

.


----------



## rds

You should be able to see oscillation if you set you're multimeter to ac volts and check the output. In the case of oscillation you should see the average value of the oscillating voltage.
 I may be wrong, but that's what I'd expect.


----------



## elliot42

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_You should be able to see oscillation if you set you're multimeter to ac volts and check the output. In the case of oscillation you should see the average value of the oscillating voltage.
 I may be wrong, but that's what I'd expect._

 

I couldn't detect any AC voltage with my DMM, but it only detects down to 0.1VAC, not very accurate.

 Perhaps I should get a better meter, this is a cheap one I've had since I was about 10 (21 now)


----------



## dsavitsk

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_110R between pin 3 and 4 instead of plugging in the tubes (had 10 22R 5W, 5 for each socket) = complete and utter silence._

 

OK, I think that probably means that the PS is fine. It also means the mosfets are fine.

 I'd say the next thing is to test the pot. There are a couple ways to do this, but I think the easiest is to disconnect R1 and R7 from the tube sockets. Then put jumpers from pin 5 to 1 on each socket (pin 5 should already be connected to pin 6, and 1 to 2 -- this only matters inasmuch as C2 is connected to only one of these pins, etc.) You now have a Szekeres buffer. See what you get with this -- there is no gain, so if the pot is the issue, it will be less of an issue now, but you are looking for silence here. The tube amplifies what it gets.


----------



## elliot42

So, I remove R1 and have input from the pot wiper connected to both pins 5/6 and 1/2. And I have the tube in the socket when running? I don't see how that works if I'm shorting out part of the tube. 

 From what I've read, the AC audio on the grid (5/6?) is amplified on the plate (1/2?) and that is passed to the FET. So do I actually have the tube connected, or have it like the schem in the Szekeres buffer page with just a FET?

 I'll do this in the morning though, time to sleep now. I'll read up more on FETs as well; I can see how tubes work, but the FETs' role in the amp still isn't quite clear to me.

 I actually took an Electrical Engineering subject at uni last year, but not much of the theory sank in. I passed with 50%, but probably only because of doing well in the pracs 
	

	
	
		
		

		
		
	


	



 I think I'll re-visit the textbook tomorrow and start from the basics again. Plus it's more fun learning this way while debugging.. better than sitting in a lecture theater and then trying to remember what was said when we had to use that info in the prac later. Just too much math for my liking at the time.


----------



## Zigis

elliot42,
 if you bypath tube as gain stage, you get "Szekeres", however tube's heaters act like R4 in Szekeres schematic, so you still need tube's heaters in place.


----------



## dsavitsk

Quote:


  Originally Posted by *elliot42* /img/forum/go_quote.gif 
_So, I remove R1 and have input from the pot wiper connected to both pins 5/6 and 1/2. And I have the tube in the socket when running? I don't see how that works if I'm shorting out part of the tube. 

 From what I've read, the AC audio on the grid (5/6?) is amplified on the plate (1/2?) and that is passed to the FET. So do I actually have the tube connected, or have it like the schem in the Szekeres buffer page with just a FET?_

 

No, don't add the tube. We are just testing to see where the noise is coming from by adding back one piece at a time. In this case, we are bridging from the input to the buffer, so you'll have about a unity gain amp.

 For a very good introduction to how the tube in this circuit is working, read the first few sections of the NEETS tutorial. It will take you about an hour to get up to speed.


----------



## dsavitsk

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_elliot42,
 if you bypath tube as gain stage, you get "Szekeres", however tube's heaters act like R4 in Szekeres schematic, so you still need tube's heaters in place._

 

That's why he has those big resistors in place -- go back a few posts.


----------



## -=Germania=-

Checked for DC on the pot - doesn't seem to be any. 
 If the issue exists on the new pot, then I may look into it further. It doesn't affect me much at the moment.

 The active ground is done similar to as it is shown on the beta 22 page. Floating or ultra low capacitance is not a good idea as the sound is very "sharp" and "thin". Played around with it and would not recommend.

 Lets allow other people to hear and decide though as my familiarity with high end home amps is primarily through meets and I wouldn't be able to properly compare.


----------



## holland

.


----------



## ltmon

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_Hi All,
 <snip>
 It's a constant white noise, does not seem to be affected by the volume control or whether there is currently input plugged in or not. Earthing various points (more or less at random) doesn't seem to affect it either.
 </snip>_

 

To answer my own question, it turned out to be C1 and C6 were poorly connected to ground. After redoing their connections the amp is almost dead quiet.

 L.


----------



## elliot42

I reconfigured the circuit, and got hum. Then I worked back, removed input jacks, pot, grid stoppers.. still hum. I then put R1 back (now configured how it was when you first told me to put the big resistors in) and it's better, almost silent, but there actually is a very faint hum that I didn't hear before.

 With the Szekeres setup, the hum was less than with the tubes, but I guess that's because there are no tubes to amplify the hum.

 I'll try that 24V supply to make sure I can rule out the PS as the source of the hum.


----------



## m0b1liz3

Well I finally got a day off after working so much lately. Finished my build and it worked right away. I must have gotten dyslexic with the vol pot though since it seems to work in reverse. I guess I just need to mirror image the lugs and re-solder... 











 I previously asked where the best spot was to take a wire off for an LED. The consensus was at the power jack. So I need to drop 48v down to about 2v or so.


----------



## error401

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I previously asked where the best spot was to take a wire off for an LED. The consensus was at the power jack. So I need to drop 48v down to about 2v or so._

 

5-20k would be an appropriate value, tune to taste.


----------



## m0b1liz3

Hmm on one LED calculation site, the claim is that with 48v as the source voltage, too much heat will need to be dissipated from a current limiting resistor.


----------



## ludoo

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hmm on one LED calculation site, the claim is that with 48v as the source voltage, too much heat will need to be dissipated from a current limiting resistor._

 

Answered by Tomb in post #715.


----------



## kuroguy

if you run the LED at 10 mA the power dissipated in the series resistor is .46 watts. use a half watt resistor at least 4.6K and you'll be fine.


----------



## n_maher

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Answered by Tomb in post #715. 
	

	
	
		
		

		
		
	


	


_

 

Just an FYI - given the variable number of posts per page (user-selectable) it's generally better practice to link directly to the post. Your link takes me to a page in the 900's.

 And it could certainly be argued that you don't even need 10mA to achieve sufficient brightness with most LED's. I often run them as low as I can to limited the wasted power draw and avoid the dreaded flashlight syndrome.


----------



## Citizen86

Good job m0b1liz3! What do you think of the amp?

 I'm trying to find a 3/4 drill bit locally, but haven't found anything yet... I think I'm going to have to Ebay something soon


----------



## keiths

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_if you run the LED at 10 mA the power dissipated in the series resistor is .46 watts. use a half watt resistor at least 4.6K and you'll be fine._

 

I settled on a 22K resistor, giving a current of 2.18mA. With my standard-brightness LED, that's plenty bright enough as far as I'm concerned.

 Also, with a 22K resistor, you are only dissipating 0.1W, so a 1/4W resistor is fine.


----------



## kuroguy

In retrospect, I used a 22K resistor too.


----------



## Citizen86

I'm pretty sure this hasn't been posted yet, but has anybody seen the Starving Student for sale? Whiplash audio is selling one with improved parts... at not such a starving student price:

Mini Millet DIY Tube Amplifier - Default Store View


----------



## HeadphoneAddict

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_I'm pretty sure this hasn't been posted yet, but has anybody seen the Starving Student for sale? Whiplash audio is selling one with improved parts... at not such a starving student price:

Mini Millet DIY Tube Amplifier - Default Store View_

 


 It would have been about $200 for a similarly upgraded Millett SS from rds when I was looking for one.


----------



## Citizen86

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_It would have been about $200 for a similarly upgraded Millett SS from rds when I was looking for one._

 

Pretty expensive parts I see.


----------



## holland

.


----------



## n_maher

I sincerely hope who ever that is asked Pete's permission first. I'd also be curious to know who it is since they aren't exactly forthcoming with contact details...


----------



## holland

.


----------



## FallenAngel

Not likely to be over $60 in parts, especially when bought in bulk. 3x markup?


----------



## n_maher

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Not likely to be over $60 in parts, especially when bought in bulk. 3x markup?_

 

3x is pretty typical for professionally built gear but this "product" doesn't quite meet those criteria w/ the generic case and face plates. Looking at some of the other product lists in the DIY section and the associated prices there's a pretty clear profit motive here, not that there's anything wrong with that.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_not worth it, IMO. Way overpriced, considering the amount of parts and the price you can get it for including Muse caps and VD resistors. If they had a custom case, sure.....but, it looks like they ripped off rds's build down to the placement of everything and the parts list. How lame can you get?_

 

That sounds very troll-like to me. So it's not a rip off if they build it like Pete envisioned, with the mouser.com parts list; but to upgrade to parts that many other people here are using then it's a rip off? How much are you charging to source the upgraded parts and build these for others? How much is your time worth?


----------



## HeadphoneAddict

Whiplash Audio is SACD-man, who is also the Qables distributor in the USA, and he is an upstanding head-fi member - I sold him some Stax a while back and bought parts from him too. I figure after $60 in parts upgrades and case for the amp, and paying someone $25/hr to build them, that maybe he makes $20-40 on the sale. I say that is reasonable. 

 rds sold me a DIY kit for $60, but he wanted $200 to build one for me when I PM'd him a while back (including a case and shipping from Canada). I thought both prices were fair, but I didn't have the $200 at the time (money set aside for my Woo GES build) - so I bought the kit. Why can't someone else build them and get paid for their time? I am paying someone to build mine for my son, because I can't do it myself (poor fine motor control now due to illness).


----------



## holland

.


----------



## holland

.


----------



## kuroguy

I have a problem with the description. His page says Mini Millett and Starving Student all over it. I know the two are not the same. Not even close. If it is a SSHH then why would he have "Mini Millett" on the page. All that does is confuse me. I wonder if that is an accident or on purpose. I also wonder how many others are confused about that but only figure it out after the amp arrives?

 Not cool. Not cool at all.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Your words sound like a troll, with due respect. 

 I don't care who it is. The minute you copy somebody else's build *exactly* and profit off of it, it is a rip off. Period. It's a rip off when they copy someone's build down to the letter, identically. Period. There's nothing unique about this build at all, no custom case, nothing. It's an *exact* replica of rds's build. His build, parts, everything was documented on this forum. There's nothing boutique or difficult in this build, standard parts, that's what this build is about.

 My time is worth alot. I don't build for others. There's no need to question me over this. I'm not selling it. I don't know what you are insinuating, but whatever it is, it's nonsensical._

 

Me a troll? You're kidding me.

 BTW, I checked - Whiplash Audio DOES have permission from rds and Pete Millett to build these, and they make $0 on them. So there.

 CHECK YOUR FACTS FIRST - TROLLBOY!


----------



## holland

.


----------



## SACD-Man

Please send me a PM regarding any questions related to this.


----------



## SACD-Man

holland;4836367 said:
			
		

> Your words sound like a troll, with due respect.
> 
> This is insulting and should be noted as such. Please guide questions to me or any of the folks involved with this!!


----------



## holland

.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *SACD-Man* /img/forum/go_quote.gif 
_Please send me a PM regarding any questions related to this._

 

I'm sorry for letting this get out of hand. I don't want my comments to reflect negatively in your regard; but what I read here ticked me off because I know you and you don't rip people off.


----------



## kuroguy

I got a question. if it is a SSHH then why is mini millett pasted all over the page?


----------



## MisterX

This is a DIY thread, not a bash a "Head-fi Sponsor" thread. Can we get back on track here?


----------



## rds

First of all no one's been ripped off, Pete has been consulted, and if you want to point the finger at someone for overcharging it is definitely not Craig. I don't think here is the place to go into the details...


----------



## tomb

Whoa. I agree with MisterX (edit: and rds).

 It seems that Whiplash Audio is offering a good deal for those who want to enjoy the Starving Student (Mini Millett, as rds named his build style) without having to build one. Any of us who've built a DIY amp knows that 2-3 times the cost of parts goes into our time in building. No vendor can offer a fabricated product for sale and expect to make any money - without taking those costs into account.

 As for permissions, one should probably give the vendor the benefit of the doubt before posting accusations on public forum.


----------



## rds

I should leave this now, but since a comment was made about markup I will add that this amp with the power supply and set of tubes is being sold at ~x2 the cost of parts.


----------



## HeadphoneAddict

Yeah, the person building my rds kit is not doing it for profit either, but rather as a favor for my son, and at only the cost of wire and extra tubes and case and screws and such, etc. And I felt the $58 shipped for the spare left over rds kit was more than fair.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for permissions, one should probably give the vendor the benefit of the doubt before posting accusations on public forum.
	

	
	
		
		

		
		
	


	


_

 

From Pete's site:

  Quote:


 I consider all the information that I post here to be in the public domain. So, you can use it however you want, for commercial or non-commercial use. 
 

Pete does ask that you tell him what you are doing if you are using his information commercially, but as Tomb says, some benefit of the doubt is in order.


----------



## looser101

This is a DIY thread in the DIY (Do-It-Yourself) Discussions Forum. Maybe you guys can start your own thread, about an already built product, in another thread?

 Don't bother replying to my post (perpetuating the thread crap) as my next post may not be so kind.

 Renato


----------



## Citizen86

Whoops, didn't realize me asking about that would cause such a commotion. I was just curious because the original BOM was what, $40? That one is being sold for $200.

 Anyways, back on track....


----------



## looser101

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_Good job m0b1liz3! What do you think of the amp?

 I'm trying to find a 3/4 drill bit locally, but haven't found anything yet... I think I'm going to have to Ebay something soon 
	

	
	
		
		

		
		
	


	


_

 

If you can, get yourself a step bit. Much easier to use than a regular drill bit.

 R


----------



## pinkfloyd4ever

harbor freight has sets like that alot cheaper if you don't wanna spend that much. Obviously they're not as good of quality as Irwin, but they're also about $10 for a similar set IIRC, and they work fine for me (without a drill press, just a cordless drill)


----------



## m0b1liz3

I seem to have wired my volume pot strangely (or I have damaged it). it doesn't increase volume, but rather almost acts like a left right balance. Anyone have any idea of what I may have done wrong?


----------



## ltmon

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I seem to have wired my volume pot strangely (or I have damaged it). it doesn't increase volume, but rather almost acts like a left right balance. Anyone have any idea of what I may have done wrong?_

 

Does this help: How to Wire Panel Components (scroll down a bit for the potentiometer section)


----------



## JamesL

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I seem to have wired my volume pot strangely (or I have damaged it). it doesn't increase volume, but rather almost acts like a left right balance. Anyone have any idea of what I may have done wrong?_

 

You made a voltage divider between the two channels.
 Tangent's guide pretty much applies to most stereo pots.
 Just to make sure, put your multimeter between the input and ground. It should read ~50k(given that you're using a 50k pot) at any position on the pot. 
 Input/Output and Ground/output should vary as you turn the pot. (when the volume is maxed, input/output should read 0 ohms)


----------



## m0b1liz3

Hmm, I wired it up as in the pic ALPS RK27. How did I make a voltage divider? The only thing I can think of is that I used too much solder and some got inside the pot? 

 I did have it the reverse of how it should have been previously. It worked but in reverse. So I changed the inputs as per the tangent wiring pic. However, I just realized that I could have mixed up which input was which. If they were reversed and the central tabs stayed the same, that may account for it?


----------



## JamesL

Sorry, I was thinking something else. 
 It's likely you switched the input and ground for one of the channels. (the channel that gets softer as you turn it clockwise)
 Are you using the pot listed in pete's bom?


----------



## m0b1liz3

Pretty sure it is the right one from the BOM. It was a group buy we did here in Aus. I didn't order the pot. It is A50k. I have a B100k pot and a few others I was going to use in my guitar lying around. I am positive it is wired up right on the vol pot. Middle wiper tabs go to the tube socket tabs 5+6 I think. Far right tabs are inputs and far left is ground. It works fine when turned all the way up. Then I just need to use the computer to change vol. But that is only acceptable temporarily.

 I am not superquick with a soldering iron and I had the input tabs/ground tabs reversed on the first go and redid them. So maybe all the heat has damaged the pot?


----------



## JamesL

You said it acted as a left/right channel balance control?
 But if you turn it all the way clockwise, everything is at max volume?


----------



## m0b1liz3

it isn't truly acting like a left right balance. it seems like the left channel is at a certain vol and turning it clockwise kicks in the other channel to a similar volume by the end of the dial. Seems kind of messed up...


----------



## JamesL

That just means that the pot's left channel isn't working.

 You're getting full volume from the left channel, meaning that your input and output are making good contact.. if the ground wire wasn't, then you'd simply have a 0-50k ohm resistor in series with the headphones.

 I'm guessing that the pot is internally shorted (or the wiper is stuck in one position).


----------



## holland

.


----------



## m0b1liz3

Hmm, I took it apart again, looked at the tabs, wiggled them a little, tried it again, and now it works fine. It must have been the cold hard stare that scared it back into proper working order


----------



## -=Germania=-

Where did you get those power buttons?


----------



## J.D.N

Its a vandal switch, usually momentary not latching so you will need some circuitry to get it to stay on. This one might be latching, if it is its great news, looks awesome!


----------



## m0b1liz3

lol, I never knew the difference when I ordered this. i am not using any additional circuit and it works. it must be latching


Ring Illuminated - Red (12v), 16mm, SS, 2mm terminals (On/Off) [ASS162FARR12] - $9.85 : GAM Mods, PC Water Cooling and Modding Supplies


----------



## MoxMonkey

Just wondering if anyone can check my digikey order just to make sure i'm not missing anything or if any of the hardware wont work

 The electrical components are what tomb suggested earlier to me

 tubes, sockets, power supply are all on their way, knob will be salvaged from cmoy 
	

	
	
		
		

		
			





 BOM found here

http://members.shaw.ca/moxmonkey/starving_bom-2.xls

 thanks in advance


----------



## tomb

Looks pretty good. I like the Panasonic FC caps.

 There are a few things you might consider changing, though:
Use the 0.22uf interstage film caps. 0.1uf has been spec'd, but 0.22uf will ensure no loss of frequencies and is very little different in size or price - BC1858-ND
You only need an SPST power switch. CH866-ND is a bit cheaper with fewer lugs to worry about.
You're better off with heat sinks that have 1" wide fins. The ones you have selected are only 1/2". Try HS276-ND (1.5", screw mount), HS374-ND (2" pins), HS347-ND (2" pins). The last one is actually for TO-218, but it may work OK if the others are out-of-stock.

 Finally, I know there aren't any good stereo pot selections from DigiKey except the Panasonic EVJ. Unlike a lot of people around here, I actually like that pot. However, it doesn't track well at low positions on the dial (leakage at zero, channel imbalance, etc.). Also, it's one heckuva difficult pot to air-wire. They're really designed to be snapped into a PCB with those side tabs. That way, the very close and tiny pins are not an issue to wire up. If you do go with it, I suggest using a small piece of perf-board at the pins to help give the pins and wiring some structure and strength.


----------



## MoxMonkey

i knew i had forgotten something, after reading through this entire thread for the up to date tweaks i forgot to update the other caps but you caught that

 power switch makes sense, i missed that searching and could only find the dpst(?) version

 the heatsink i completely missed the fin size but since it was for the to-220 and looked similar (minus the pins) i figured it would work

 as for the pot, air wiring i'm assuming just is wiring it when attached to the chassis alone? if so that shouldn't be a major issue, it's the same pot i used on the cmoy i built and yah it was a bit of a pain but not all that bad


----------



## MrKazador

I was bored and was messing around with Google Spreadsheets.
http://spreadsheets.google.com/pub?k...dvRAS1s3iWXhSw
 That is my Mouser BOM with clickable links shown in Blue. One problem is that I can't make $1.00 show. Instead its $1


----------



## OldKing

(click for more)

 Thanks Pete

 11:41pm ... added BOM


----------



## dd051




----------



## MrKazador

That is really nice OldKing. What heatsink is that?


----------



## olblueyez

OldKing, Puhleeeeeezzzzze post a BOM with all the parts you used to make that beautiful amp.


----------



## rds

Sweet amp OldKing!


----------



## Keno

I don't know if anyone has mentioned it yet, but I received a call from Radiodaze about my order this morning, and apparently they are out of the 19j6 tubes
	

	
	
		
		

		
		
	


	




 Where else would be good to order them from?


----------



## MrKazador

TheTubeCenter.com
 19j6 $3.00 each
 SK-7 socket $2.00 each


----------



## HeadphoneAddict

Has this one been posted yet? A wonderful head-fier built it for my son, from a kit rds sold me, and wouldn't even let me pay her for the work.


----------



## olblueyez

That is cute.


----------



## Keno

Quote:


  Originally Posted by *MrKazador* /img/forum/go_quote.gif 
_TheTubeCenter.com
 19j6 $3.00 each
 SK-7 socket $2.00 each_

 

Thanks, Ordered. They seem to be the cheapest out of sites that still have the tubes in stock. Some were wanting $6-10 per tube


----------



## LeBuLLeT

headphoneaddict who made it for you? I have the same RDS KIT but I just don't have the time to build it myself. School is keeping me busy. Of course I would pay her. Thanks


----------



## HeadphoneAddict

Quote:


  Originally Posted by *LeBuLLeT* /img/forum/go_quote.gif 
_headphoneaddict who made it for you? I have the same RDS KIT but I just don't have the time to build it myself. School is keeping me busy. Of course I would pay her. Thanks_

 

The builder is reading this thread an will contact you if that is doable - but she like many others are wary about accepting any money for the work, and would want approval of Pete Millett first. She did mine as a favor, and I sourced the case from my son's closet. My builder is also a student, so I am fortunate she found time to do this for me as well.


----------



## effcleff

Outstanding build OldKing! I really dig the heatsink/tube configuration. Thanks for posting your BOM too.


----------



## Kabeer

Love the look of that car amp! I will hopefully be building a more modest version toward the end of the month. 
 A complete n00b at DIY amps, so see how it goes


----------



## LeBuLLeT

headphoneaddict thanks. The builder already contacted me. Right now the builder has no time but said that if I needed some technical support they would help. Thanks again.


----------



## m0b1liz3

I have heard of people using chip amps to power guitar amps. I have an LM3875 kit and an extra 2 SSMH and 2 extra SOHA tubes that I haven't used and wondered if anyone here is clever enough to design a pre-amp schematic utilizing either of these tubes.


----------



## -=Germania=-

19j6 info:
19J6, Tube 19J6; Röhre 19J6 (19J6)

 This might give you an ideas for the 12au7 tube. 
DIY 12AU7 - IRF612 MOSFET Hybrid Headphone Amplifier
 (also a cheap/simple build)

 Speaker/guitar amps with different uses of the 12au7 (output and pre-amp)
http://ax84.com/index.php?pg=projects&project=firefly

http://www.harmonicappliances.com/de...ator2_8x14.pdf


----------



## MoxMonkey

tubes have arrived now to order up the rest of the parts


----------



## m0b1liz3

DIY 12AU7 - IRF612 MOSFET Hybrid Headphone Amplifier
 (also a cheap/simple build)

 I had wondered how this one would sound. I do have 2 extra tubes.


 Speaker/guitar amps with different uses of the 12au7 (output and pre-amp)
AX84.com - The Cooperative Tube Guitar Amp Project

 The problem with the firefly is that it needs 3 of those tubes and it is only 1/2 watt. It would break up to early for jazz style playing (trying to get into jazz now). I do like the idea of using a tube preamp to go with my chipamp to give some warmth. I think in the end though tube power is the way to go for guitar amps.


----------



## Zigis

Hi m0b1liz3,
 take AX84 Hi-Octane Tube Guitar Amplifier's schematic, it use 2 tubes (4 triodes) for preamp and is more universal for different distortion modes, than 1 tube preamp.
 You can build whole amp (EL84 and small, not HI End output trafo is not expensive) or only preamp part. Connect chipamp to master volume pot output.


----------



## m0b1liz3

Yeah, I was thinking of building that amp but I am not sure about the fact that is based on a marshall. Marshall's are known more for their distorted sound whereas Fenders are known for their tube clean sounds. I am thinking of building a 5E3 style amp. Just trying to source out the parts. Since this is more for jazz, the AX84 may not be as well suited. If you have built one though and disagree, let me know!


----------



## n_maher

Perhaps you guys could move this line of discussion to a new thread?


----------



## gurusan

got most of my soldering done today. Just need to finish a few things before I go buy a chassis. A bit messy but I think it will be ok once I get it all organized into a chassis.

 This is only my 2nd project (1st was just a desktop cmoy).


----------



## kuroguy

you'll find it is easier to solder point to point if you wait to do the soldering until after you have fixed parts like the tube sockets, pot, switches, etc to the chassis.


----------



## gurusan

thanks for the tip, but I didn't have a chassis and was impatient


----------



## ludoo

I still have to trim the pot shaft, but apart from that my second SS is finished. This time I went a bit overboard and used boutique parts: Elna Cerafine caps (I found them on Italian ebay pretty cheap), Obbligato caps, and a Blue Velvet pot. The case is a Hammond 1591D, plastic as it's easier to drill, and the finished amp is already pretty heavy anyway.

 I planned a lot this build before receving all the parts, as the case is pretty small and the caps big, and I could have saved myself some time: the planned build had a problem (probably a blown Mosfet) and the way I fit everything together made the amp impossible to debug. So I desoldered everything, found an alternative layout, and when I finished reassembling I only got a loud buzz in both channels. I disassembled half of the components before noticing I had forgot to ground the pot...

 A pretty instructive couple of days. 
	

	
	
		
		

		
		
	


	




 At first listen and without burnin it sounds great, with more bass and clearer sound than my previous SS. Pics (click for larger images):


----------



## jERiCOh

Hi everyone, it's been a while since the last time I posted here. It's time to upgrade my SS now. There's something on schematic that gets me confused. There's a note about all caps must be 63v minimum... Does it apply to the output caps as I can read 19v on them? I hope 35v caps will work because there's not much room in my amp for big and tall capacitors.


----------



## JamesL

Quote:


  Originally Posted by *jERiCOh* /img/forum/go_quote.gif 
_Hi everyone, it's been a while since the last time I posted here. It's time to upgrade my SS now. There's something on schematic that gets me confused. There's a note about all caps must be 63v minimum... Does it apply to the output caps as I can read 19v on them? I hope 35v caps will work because there's not much room in my amp for big and tall capacitors. 
	

	
	
		
		

		
		
	


	


_

 

I asked a similar question -

  Quote:


  Originally Posted by *error401* 
_
 The output has significant DC on it due to the novel heater supply/bias arrangement. Also, it's possible for the whole supply voltage to appear at the cap if the tube is not in its socket or fails. Use the 65V caps._


----------



## n_maher

It's a matter of how much of a safety factor you want to maintain along with how comfortable you are risking the consequences of not having enough. 

 If all is going well there _should_ only be 19V on the output to be blocked by the caps so in that case a 35V would be acceptable. But there are probably conditions where something could go wrong (tube or other component failure) and you could end up with as much as the full supply voltage on the output. The temptation there is to say that it would only be 48V and that you'd be ok with 50V caps. However, it's not at all unreasonable for power supplies to overshoot their specs, especially under varying load conditions so we choose to upspec the output caps to 63V which is the next highest common rating. 

 So, if you're confident that there will never be more than 35V on the output of your amp feel free to use 35V caps. But you've been warned, poop happens, plan for rain, etc, etc.


----------



## MoxMonkey

got my digikey order today and started putting together a test run of a 1 channel starving student


 only thing i'm unsure about so far is if the film caps are polarized i'm using digikey part BC1858-ND i'm guessing no as i didn't see any mention of it in the datasheet but figured i'd check here before blowing up some caps


----------



## gurusan

nope not polarized


----------



## ludoo

My build, fully clothed (the volume knob is a Fender original one and it's Kabeer's idea)






 It really sounds very good. Thanks a lot to Pete and all the people in this thread.


----------



## Fitz

But does it go to eleven?


----------



## sandbasser

A little off topic... but, does anyone know of a maker of knobs that actually do go all the way to "11"???


----------



## TzeYang

Since my question was unanswered on another thread,

 Does anyone here know how the "active" ground is connected?

 IMO, it does not make sense since the active ground input is referenced to the...ground? Are we not working with single rail supply here?

 Someone enlighten me please! thanks!


----------



## jERiCOh

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_It's a matter of how much of a safety factor you want to maintain along with how comfortable you are risking the consequences of not having enough. 

 If all is going well there should only be 19V on the output to be blocked by the caps so in that case a 35V would be acceptable. But there are probably conditions where something could go wrong (tube or other component failure) and you could end up with as much as the full supply voltage on the output. The temptation there is to say that it would only be 48V and that you'd be ok with 50V caps. However, it's not at all unreasonable for power supplies to overshoot their specs, especially under varying load conditions so we choose to upspec the output caps to 63V which is the next highest common rating. 

 So, if you're confident that there will never be more than 35V on the output of your amp feel free to use 35V caps. But you've been warned, poop happens, plan for rain, etc, etc._

 

Thanks for the advice. I'll compare the sound of the stock output caps and the silmic 35v. If it really worth it, I'll buy some 50v (or more) and squeeze them inside. 
 I might otherwise try to bypass the Nichicon HE that I call stock caps with some vitamin Q or Wima. Anyone already tried that ?


----------



## -=Germania=-

My Nicho-Chemicon "Negative Black" caps are bypassed with .22uf Wima MKP10. Bypassing the caps with the Wimas did make a very noticeable difference. I believe that D has a long review of many different film caps, check that. 

 Though I like the Obbligato caps for drop in replacements (cheap + high quality); I wouldn't put anything nicer than that in this amp though. Using a higher grade wire (miltary spc, etc.) makes for a nice and cheap upgrade to stock equipment.


----------



## Fitz

"Nicho-Chemicon" = Nippon Chemi-Con?


----------



## -=Germania=-

Yeah - my mind got crossed.


----------



## Fitz

At first it sounded like Nichicon and Nippon Chemi-Con had a love child.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_A little off topic... but, does anyone know of a maker of knobs that actually do go all the way to "11"???_

 

Let's get some made!! YEAHHHH GROUP BUY!!!!! 
	

	
	
		
		

		
		
	


	










 edit: all i could find...for now... http://www.ultimate-guitar.com/forum...d.php?t=535818

 I had a Poli Sci teacher once who had a Spinal Tap song played at his wedding, Rock n Roll Creation I think


----------



## error401

Just make the knob plain and the legend go to 11. Easy


----------



## -=Germania=-

Fitz, 

 I guess we know what to call those fake Nippon-Chemicon caps that come from China (fitted with tiny Nichicon caps inside) now.


----------



## Kabeer

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_My build, fully clothed (the volume knob is a Fender original one and it's Kabeer's idea)






 It really sounds very good. Thanks a lot to Pete and all the people in this thread. 
	

	
	
		
		

		
		
	


	


_

 

Oh and how cool it looks 
	

	
	
		
		

		
		
	


	




. Great build.


----------



## error401

Well, after three months with the parts sitting in their box, I finally got to this project. The case is a Hammond 1590C painted with Rustoleum Hammered - the MOSFET heatsinks just _barely_ fit across the width. Looks pretty slick IMO, but I think I need to find a black knob for it. Since I screwed up my order I substituted 820uF 63V Panasonic FC for all the 'lytics as I had some laying around. I used a star ground and just air wired everything, no terminal blocks, no ground plane. 

 Works great, sounds great. For $50 you'd have a real hard time beating this amp, it's lots of fun. Doesn't seem to play well with my AlienDAC though, not sure why, haven't really cared - been listening 
	

	
	
		
		

		
		
	


	

















 Edit: How microphonic should the tubes be? I find that lightly tapping them results in a tinkling noise from the cans, is that normal? Of the four tubes I purchased, all do this except one that does it only barely.


----------



## HeadphoneAddict

Well, I listened to the rds kit that -=Germania=- assembled for me, and the Nascar 24 amp sounds wonderful. I was not quite expecting it to sound as good as it does with my re-cabled RS-1 and re-cabled Denon D2000. 

 I think I'm gonna have to give my son his "birthday amp" 2 months early, just so I can listen to it every once in a while 
	

	
	
		
		

		
		
	


	




 Everyone needs one of these amps!






 [COOL - POST 5454]


----------



## Citizen86

@error401, So you did you use the case for grounding?


----------



## MoxMonkey

is there any harm running r3/r9 from the leg of the mosfet and then using wire or should it just be using the resistor leg's when connected?


----------



## looser101

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_is there any harm running r3/r9 from the leg of the mosfet and then using wire or should it just be using the resistor leg's when connected?_

 

r3/r9 should be soldered directly to the leg of the mosfet, preferably. Keep the resistors leg reasonably short as well. You can run a wire from the other side of those resistors if you like.


----------



## MoxMonkey

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_r3/r9 should be soldered directly to the leg of the mosfet, preferably. Keep the resistors leg reasonably short as well. You can run a wire from the other side of those resistors if you like._

 

that's what i thought but the search wouldn't let me search for just r3/r9

 i built one channel in a pc board since point to point is a pain now to just figure out a layout for both channels


----------



## error401

Quote:


  Originally Posted by *Citizen86* /img/forum/go_quote.gif 
_@error401, So you did you use the case for grounding?_

 

No, aluminum is a bit tricky to get a good electrical connection with since the oxide is an insulator and it doesn't take solder (or I've never been able to get it to). I thought about drilling and tapping a hole and screwing in a ground wire, but it'd be a bit unsightly and I don't seem to have EMI/RFI issues, so I didn't think it was necessary.

 For ground I just used the negative lead of the main power cap as a star ground and soldered wires to it for each ground connection. Gets a bit messy with a huge, hard to melt solder blob, but it works fine.


----------



## Citizen86

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_For ground I just used the negative lead of the main power cap as a star ground and soldered wires to it for each ground connection. Gets a bit messy with a huge, hard to melt solder blob, but it works fine._

 

Ah okay, great. I'm a big noob at this, but I might try that so that I don't have to try and find any PCB board or something else, because I'm sure it'll be difficult in my area...


----------



## Coreyk78

I just found out about this build last week and I'm really excited to build one of my own. I've got most of my parts in the mail today, just waiting on my tubes and sockets. This will be my first time building a P2P amp, and my first time with tubes, so it should be a fun adventure. And I also really need to learn how to properly read a schematic, hehe.

 I do have a question though, I'm not familiar with bypassing caps, or why it is done. Bypassing would be soldering the film cap in parallel with the electrolytic right? 

 I have a couple of spare .1uF vishay MKPs that I could use to bypass, but I see from reading farther into the thread that people are using .22uF for the bypass caps. Would the .1uF caps be suitable for bypassing? I'm going to be using Panasonic FC 470uF caps for C1, C3, C5 and C6 if that makes any difference. Please help a noobie out!
	

	
	
		
		

		
		
	


	




 Also thank you to Pete and all the contributors to this thread, this seems like a really cool project! I'm building mine in a cool wooden cigar box, so I hope it ends up at least looking neat, hehe.


----------



## -=Germania=-

I think that one of the reasons why people would have used .22uf is because it is used in the main amp section and it is easier buy in bulk. 

 Anyways, film caps have a tendency to sound better than electrolytic. Essentially, you are keeping the overall capacitance, but allowing the signal to pass through a higher quality component. The value of it can mean more or less bass compared to a different value, but not always true. YOU MIGHT WANT TO CHECK OUT THIS THREAD

 As with anything, try it and see if it does anything for you.

 BTW: I had very similar Speaker setup this summer with the SL30's and a powered sub, except I was using a receiver


----------



## gurusan

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Bypassing would be soldering the film cap in parallel with the electrolytic right?_

 

This is correct right? In parallel?


----------



## JamesL

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_This is correct right? In parallel?_

 

yes


----------



## -=Germania=-

The reason why people would have used .22uf is because it is used in the main amp section and it is easier buy in bulk. 

 Anyways, film caps have a tendency to sound better than electrolytic. Essentially, you are keeping the overall capacitance, but allowing the signal to pass through a higher quality component. The value of it can mean more or less bass compared to a different value, but not always true. YOU MIGHT WANT TO CHECK OUT THIS THREAD

 As with anything, try it and see if it does anything for you.


----------



## pinkfloyd4ever

umm i thought starving student meant cheap? mine uses all mouser parts and sounds prob 70-90% as good as the millett max (which cost prob 6x as much to build)...but if you really have to go that route you also have to check out doug's Notes on Coupling Capacitors


----------



## gurusan

Well I heard good things about the Wima MKP10 caps and I bought a huge bag of 100V .33uF off the bay awhile back for cheap. Since I have them around, I'll be using these instead of the .22uF that were included in my SS kit from RDS.

 I would suggest looking for sources like the bay rather than ordering direct from retailers...

 and of course for a project like the Starving student, I don't really see the point in using a 40 dollar audiophile cap.


----------



## Coreyk78

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_The reason why people would have used .22uf is because it is used in the main amp section and it is easier buy in bulk. 
_

 

Well all I have at hand right now are .1uF film caps because I was just using the values on the original BOM. I'm going to build it first using the parts I have for C2 and C4 and leave any bypass caps out of it for now. Do you think there is much of a sound difference between cap sizes at those locations? I'll probably order some wimas or something else like that later and experiment a bit with it.


----------



## pinkfloyd4ever

if you have extras you can just parallel 2 and get .2uf. Otherwise, .1uf is fine, it's what I have in mine. Wimas are great, but I usually order them from mouser since i already have to order stuff from em for just about any project. Ebay is good for stuff like vitQ's (a much more 'starving student' audiophile component than expensive film caps, but if you don't need 20, I know of a website that sells em in quantities down to 1 (cough, cough, beezar)


----------



## JamesL

I'm quite happy with how the price came out for mine.

 Vishay dale resistors, a couple caps including Nichicon muse ES at the output, mosfets, 50k pot, came out to around $7. I shipped it along with my SOHA II parts, so shipping costs were a non-issue.
 Wood/polished sheet aluminum/plexi/leftover hammond faceplate makes for a free case 
	

	
	
		
		

		
			





 I have a few film caps for bypass, and some vitQ's on hand if I should want them, as well as rca/stereo/dc/power jacks/switch leftover from old projects.

 After the tube/socket/heatsink/wallwart + shipping, I think I should still be able to manage something under Pete's original BOM.


----------



## gurusan

Hey everyone. This is my 2nd project (1st was cmoy) and I'm having some problems.

 I wired up 1 channel and the tube is glowing, the mosfet is warm, but I am not getting any sound.

 I accidentally wired the mosfets in wrong the first time, could they be blown? How can I test this?

 Also when I wired the mosfet in wrong, the tube glowed like a nuclear reactor and now the plates of that tube are darker than the other tube......


----------



## n_maher

I'm guessing you cooked the tube during the first "experiment". Can you (carefully) measure and see if you're getting the correct ~19V at the filament? If you are odds are that the mosfet is somehow still ok. Also, triple check your wiring before applying power again.


----------



## kuroguy

considering building one of these into a line preamp I'm building for a headphone output. If I do I'll build a power supply rather than use the linear power supply in the BOM. Anybody done this? can anybody make some recommendations for a starving student power supply of this type? Maybe starting with a center tapped 70 volt transformer?


----------



## -=Germania=-

Power Supplies. 

 HERE

HERE


----------



## gurusan

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm guessing you cooked the tube during the first "experiment". Can you (carefully) measure and see if you're getting the correct ~19V at the filament? If you are odds are that the mosfet is somehow still ok. Also, triple check your wiring before applying power again. 
	

	
	
		
		

		
		
	


	


_

 

I am getting 40-41V at pin 3 of the tube socket!

 I already ordered new mosfets yesterday as I assumed they were blown :/

 On the schematic 1,2 and 3 correspond to gate, drain, and source respectively, right?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Power Supplies. 

 HERE

HERE_

 

Those links didn't work - here is the link I used to order mine: http://www.trcelectronics.com/Meanwell/mps-30-48.shtml

 You must give them a business name to order - I happen to have one, but I don't know how they check up on that.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Those links didn't work - here is the link I used to order mine: MPS-30-48, Mean Well MPS-30-48

 You must give them a business name to order - I happen to have one, but I don't know how they check up on that._

 

It's weird - they called me to let me know the PSU is 1.5 - 2 weeks out, and also to ask what kind of company I run. 

 My company buys things like firearms suppressors and short barreled rifles (and someday maybe a machine gun), which can be passed on to my wife and kids without an additional $200/item transfer tax stamp when I die, so I told them "Investments", which is true.


----------



## Coreyk78

My tubes and sockets came today!
 I found a lot of 7 RCA tubes from a guy in NJ for $3 ea. and figured why not? and bought them all. My sockets are gold pin ceramic ones from cascade surplus.













 pictures aren't that great since they came from my phone...
 If the boxes are correct, from left to right the dates are 5-1956, 9-1960 and the box of 5 are from 4-1970

 first tubes I've ever bought, I didn't expect them to be so tiny, hehe.
 Now I just have to get down to building this little monster


----------



## Coreyk78

I just finished building mine an hour ago, sounds soooooooo good, I'm loving it!
 This is definitely some of the best sound I have ever heard. I haven't installed any bypass caps yet, but I have some russian PIOs on order to try out with this. Just need a knob and it will be done! for now...

 I don't know how to post thumbnail images, but here are a couple pics, I borrowed a decent camera from work, hehe.










 My wiring looks a little tragic but it works! haha 
	

	
	
		
		

		
		
	


	



 This is my first time doing p2p so I might try to straighten it up later or just listen to it. I was a little worried at first, when I tried turning it on for the first time, nothing happened, at all. I checked a bunch of stuff, and then tried changing the mains cable, and it fired right up, weird.

 Hopefully I'm not pissing anyone off posting a lot of pics, I'm just excited!


----------



## gurusan

Well done, that looks great! I'm eager to get mine working when I get the time this weekend. Have to sit through engineering lectures through the rest of the week first


----------



## sandbasser

Does anybody know what became of the PCB for this???... I read about it several pages up but have seen nothing lately. I'm going to try to build a P2P version; but, my confidence level is not particularly high. A PCB would be so much easier for a noob diyer.

 Thanks,


----------



## n_maher

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Does anybody know what became of the PCB for this???... I read about it several pages up but have seen nothing lately. I'm going to try to build a P2P version; but, my confidence level is not particularly high. A PCB would be so much easier for a noob diyer.

 Thanks,_

 

It's still under development. After a largely successful first round of prototyping the team decided to make some improvements to the design which required another round of prototypes. And it's a good thing we did. A small error was found on that second proto pcb which is being corrected and you guessed it, a third round of boards are getting made. Of course we all have stuff going outside of Head-Fi and we try to make this project as much of a priority as time will permit but since the design/prototyping team is all volunteer these things generally just take time. Sorry if that isn't much of an update, but it's the truth about where things are at.


----------



## sacd lover

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_My tubes and sockets came today!
 I found a lot of 7 RCA tubes from a guy in NJ for $3 ea. and figured why not? and bought them all. My sockets are gold pin ceramic ones from cascade surplus.

 first tubes I've ever bought, I didn't expect them to be so tiny, hehe.
 Now I just have to get down to building this little monster 
	

	
	
		
		

		
		
	


	


_

 


 It is a good idea to buy some extra 19J6s .... they are disappearing fast .... and there doesnt seem to be any large stocks anywhere. Antique Electronic Suppy and Radiodaze are sold out. Radio Electric Supply has around 15 total left with no prospects for anymore. Vacuum Tubes Inc. had less than five. The tube sellers I see listing these (sellers I dont usually use or need to use) I have contacted have not returned my emails.


----------



## Coreyk78

Quote:


  Originally Posted by *sacd lover* /img/forum/go_quote.gif 
_It is a good idea to buy some extra 19J6s .... they are disappearing fast .... and there doesnt seem to be any large stocks anywhere. Antique Electronic Suppy and Radiodaze are sold out. Radio Electric Supply has around 15 total left with no prospects for anymore. Vacuum Tubes Inc. had less than five. The tube sellers I see listing these (sellers I dont usually use or need to use) I have contacted have not returned my emails. 
	

	
	
		
		

		
		
	


	


_

 

I was running into the same problem when I was trying to track mine down, I had tried Radiodaze and Antique electronic supply and they had none. I found these on ebid.net which is a site I've never been to before. I was slightly worried about using an unknown auction site, but it worked out just fine. The seller I bought from is selling a lot of NOS tubes on there for pretty decent prices, but he only had 7 19J6 and I wanted spares so I took them all.


----------



## sandbasser

Coreyk78 - how can you determine the dates??? 

 I recently got 8 19J6s from "The Tube Center" (no relationship other than "happy customer"). 

 They're all NOS RCAs... All 8 are physically identical but for a code 'printed' on the tube (*143 *or *152*) and some cryptic markings on the box 'end flap' ( *R-CB 5 / (1-49)* ).

 Thanks,


----------



## Coreyk78

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Coreyk78 - how can you determine the dates??? 

 I recently got 8 19J6s from "The Tube Center" (no relationship other than "happy customer"). 

 They're all NOS RCAs... All 8 are physically identical but for a code 'printed' on the tube (*143 *or *152*) and some cryptic markings on the box 'end flap' ( *R-CB 5 / (1-49)* ).

 Thanks,_

 

Well, to be honest I'm only guessing at it, but it seemed to make sense. 

 The flaps on my boxes had 5-56, 9-60 and 4-70 printed under the other code, and the boxes looked progressively newer and less worn, so my best guess would be that 5-56 = May of 1956 and so on.

 So if thats right then your 1-49 would be January 1949.

 However, I may be totally wrong


----------



## n_maher

Guys, I've got a few friends who are tube dealers who are looking for tubes for me. So far I've tracked down 10 or so and there's the potential for more. Regardless I have what I need for tubes so if I can get a hold of these I'll post them for sale here and put a notice in this thread.


----------



## dd051

By changing the values of the coupling caps to .22, do any of the resistor values change? 

 also, do coupling caps have an effect on quality?


----------



## n_maher

Quote:


  Originally Posted by *dd051* /img/forum/go_quote.gif 
_By changing the values of the coupling caps to .22, do any of the resistor values change?_

 

No.

  Quote:


 also, do coupling caps have an effect on quality? 
 

Some say yes, some say no. I say try it for yourself and see what you think. You may find that in some applications it makes a big difference and in others there is no perceptible difference.


----------



## kuroguy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Guys, I've got a few friends who are tube dealers who are looking for tubes for me. So far I've tracked down 10 or so and there's the potential for more. Regardless I have what I need for tubes so if I can get a hold of these I'll post them for sale here and put a notice in this thread._

 

I'll take 4, please.


----------



## n_maher

I'm not taking orders, reservations or otherwise. When I know what I have I'll post it here and I'll be limiting the number of tubes that each person can buy so that they can be spread out as much as possible.


----------



## J.P.6

Hi there,

 Looking at building this as a first amp. I was going to go with a CMOY, but wanted a tube amplifier instead. How hard will this be for a beginner? I can read the schematic but am a bit confused by some things. 

 Is there a step by step guide out there for this amp?

 Thanks in advance.


----------



## keiths

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_How hard will this be for a beginner? I can read the schematic but am a bit confused by some things. 

 Is there a step by step guide out there for this amp?_

 

FWIW, I did a CMoy first, but can't really say it helped as the builds are pretty different eg. perfboard vs. point to point.

 I found the casework the hardest part (mainly due to a lack of tools and facilities), but took things slowly and it all worked out fine.

 I'd say go for it - people on this forum are EXTREMELY patient and helpful and will be able to sort out any problems - just ask away.


----------



## J.P.6

That's what I was thinking, the perboard was putting me off as i've never used it before.

 However, I'm having trouble finding 19J6 tubes in the UK.


----------



## keiths

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_However, I'm having trouble finding 19J6 tubes in the UK._

 

I couldn't find any for sale in the UK or anywhere else in Europe. I ended up buying them from Radio Daze (Radio Daze) in the States who were very reasonable with their shipping costs. However, I believe they are out of stock at the moment.


----------



## -=Germania=-

A Good rotary tool (Dremel) is the best friend you can ever have when it comes to almost anything DIY (audio or otherwise).

 If you get a high powered one it will make doing a lot of this stuff easier, especially if you are working with materials that might not do well in a traditional drill press.


----------



## J.P.6

Right, got all the bits in the basket at Mouser. However, the 150uF 63V low-ESR electrolytic capacitor (C1, C3, C5, C6) is out of stock, the BOM says 'Any value >= 150uF, voltage >= 63V', so I have replaced it with a 180uF 63V low-ESr capacitor. 

 Just want to make sure this is OK?


----------



## MoxMonkey

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_Right, got all the bits in the basket at Mouser. However, the 150uF 63V low-ESR electrolytic capacitor (C1, C3, C5, C6) is out of stock, the BOM says 'Any value >= 150uF, voltage >= 63V', so I have replaced it with a 180uF 63V low-ESr capacitor. 

 Just want to make sure this is OK?_

 

most people i think are using 470uf nichicon muse's (brand might be different by capacitace is correct)


----------



## J.P.6

UHE1J471MHD That one? What's the benefit of using it?

 Also, does anyone know where I can get some cheap hookup wire, can only find it on 100m reels.


----------



## velogreg

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_UHE1J471MHD That one? What's the benefit of using it?

 Also, does anyone know where I can get some cheap hookup wire, can only find it on 100m reels._

 

Try Navships on Ebay, a lot of diyers use him and he has practically any type of wire you would need. Unless of course you are the 10 guage solid core type of ocp diyer.


----------



## JamesL

Quote:


  Originally Posted by *velogreg* /img/forum/go_quote.gif 
_Try Navships on Ebay, a lot of diyers use him and he has practically any type of wire you would need. Unless of course you are the 10 guage solid core type of ocp diyer. 
	

	
	
		
		

		
		
	


	


_

 

Aka john's wire shop. He's been gone, and will be gone for another month or so..


----------



## tomb

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_UHE1J471MHD That one? What's the benefit of using it?</snip>_

 

Using 470uf does a couple of things:
 1. On the back side, supplying the B+ for the tubes (C1 and C6), 470uf keeps the power supply from stuttering on startup.
 2. On the output (C3 and C5), 470uf helps to create a much lower cutoff frequency, ensuring that no bass is lost with low impedance phones.


----------



## J.P.6

Cheers for that, ordered all the bits now. All I need is a 48V 18W AC/DC adapter, is this the right one? WATT-POWER > 18 Watts PSA18U Desktop Adapter DC Plug 2.1


----------



## ludoo

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_Cheers for that, ordered all the bits now. All I need is a 48V 18W AC/DC adapter, is this the right one? WATT-POWER > 18 Watts PSA18U Desktop Adapter DC Plug 2.1_

 

You need a 48V PS. The Cisco PS for its line of PoE phones are what most everybody is using, there's plenty for cheap on uk ebay. Search for "Cisco power supply" and check that it has 48V 0.38A.


----------



## J.P.6

I did look but some of them don't say if they are 18W or not, is this one correct? CISCO AIR-PWR-A power supply 34-1977-03 NEW IN BOX on eBay, also, Power Cables, Cables Connectors, Computing (end time 22-Nov-08 20:15:51 GMT)


----------



## n_maher

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_I did look but some of them don't say if they are 18W or not, is this one correct?_

 

OUTPUT : 48VDC 0.38A
 Looks to be the right one, or at least an appropriate PS to me.


----------



## gurusan

pretty sure thats the right one


----------



## keiths

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_I did look but some of them don't say if they are 18W or not, is this one correct? CISCO AIR-PWR-A power supply 34-1977-03 NEW IN BOX on eBay, also, Power Cables, Cables Connectors, Computing (end time 22-Nov-08 20:15:51 GMT)_

 

Yep - that's identical to the one I'm using.


----------



## J.P.6

Someone kindly PM'd me a link to one for £4 inc postage 
	

	
	
		
		

		
		
	


	




 Everything is now ordered!


----------



## gurusan

wooooooo! My millet starving student amp works finally! And it sounds great! the bass on my HD 580s has finally come alive, and the sound is so much more full than my CMOY.

 Still have to finish off some casework and straighten up some wiring (it's sort of a nightmare at the moment as you can see)...but it works, this is my first time hearing anything with tubes in it and I love it. 

 Thanks everyone for the help! And a big thanks to RDS for the kit!


----------



## joneeboi

I just finished my amp this morning. I haven't gotten around to listen to it actually since I don't have any 1/8" jacks on me and my 1/8"-to-1/4" adapter resides elsewhere at the moment.






 It wasn't easy deciphering what each wire was. I did some double- and triple-checking before actually firing it up, and everything seems fine. Testing with alligator clips shows a functional amplifier. I can't wait to actually hear it. 
	

	
	
		
		

		
		
	


	




 I have a midterm to study for Monday, but I figured I deserved a little break. Plus, I bought all these parts sometime in June. 
	

	
	
		
		

		
		
	


	








 edit:

 So I finally got around to listening to it. Wow, what a dead quiet amp. Shorting the volume control gave me very little to hear from outer space. I found the overall sound to be surprisingly harsh. I'm getting a spotlight on the HF with a noticeable disregard of the mids. I felt so insecure after listening to this that I ran back to my PIMETA. I get what I paid for, I suppose. Are there any mods to bring a little more balance in my amp? I already upped the output cap to 470 uF. I'll try to read over some more of the thread before I give up on this bad boy. Tip of the hat to Pete Millett for his fine work and dedication to the community.


----------



## HeadphoneAddict

We had a Colorado mini-meet today and all 6 of us at the meet (including my 10yr old son who owns the amp) agreed the Nascar 24 Millett Starving Student amp (built by Germania with an rds kit that I purchased, and a few upgrades for still under $100 total) sounded slightly better than my Dark Voice 336i with $100 worth of tubes in it.


----------



## gurusan

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_So I finally got around to listening to it. Wow, what a dead quiet amp. Shorting the volume control gave me very little to hear from outer space. I found the overall sound to be surprisingly harsh. I'm getting a spotlight on the HF with a noticeable disregard of the mids. I felt so insecure after listening to this that I ran back to my PIMETA. I get what I paid for, I suppose. Are there any mods to bring a little more balance in my amp? I already upped the output cap to 470 uF. I'll try to read over some more of the thread before I give up on this bad boy. Tip of the hat to Pete Millett for his fine work and dedication to the community._

 

Dead quiet? Are you sure you got everything hooked up correctly? 

 Which headphones are you using? I am using 300 ohm HD 580s and this amp drives them to ear splitting volumes....and "harsh" is the last word I would use to describe the sound coming from this amp. 

 More like warm, full, glowing....


----------



## FallenAngel

HeadphoneAddict : That's just awesome 
	

	
	
		
		

		
		
	


	




 joneeboi : Your choice of output and coupling caps may be responsible for this, would you consider switching the coupling to at least a Wima MKP and output to Muse ES?


----------



## gurusan

They might be responsible for the sound signature, but surely not for the volume problems? Wouldn't some odd resistor values cause volume issues?

 And for the record, I am using Nichicon Muse ES output caps, bypassed with Wima MKP10 .33uF


----------



## rds

Quote:


 And a big thanks to RDS for the kit! 
 

My pleasure.
 It's great to see those boxes of parts turn into some really cool amps


----------



## tomb

Joneeboi,

 Although C2 and C4, the midstage film coupling caps, are important - I'm not sure that's your issue. Instead, the R3 and R9 resistors should be soldered directly to the MOSFET gate leads. Pete has noted earlier in the thread that oscillation in the MOSFETs could occur if this was not done.

 At least on the right hand side of your pic, there appears to be no resistor soldered directly to any of the MOSFET leads. It may be that way on the left side, but I can't tell.

 Anyway, this might be the first thing you could try.

 Second, I would look at those mid-stage coupling caps. You might be a lot better off putting those K42's there and just leaving the electrolytics by themselves on the output.


----------



## J.P.6

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_
 http://www.head-fi.org/forums/members/headphoneaddict-albums-headphone-gear-picture963-nascar24meet2008.jpg[/IMG[/i]
 [/td] [/tr] [/table]


That's awesome! [img]http://www.head-fi.org/forums/images/smilies/http://hfimage.head-fi.org/smilies/biggrin.gif_


----------



## joneeboi

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Dead quiet? Are you sure you got everything hooked up correctly? 

 Which headphones are you using? I am using 300 ohm HD 580s and this amp drives them to ear splitting volumes....and "harsh" is the last word I would use to describe the sound coming from this amp. 

 More like warm, full, glowing...._

 

When I said quiet, I meant there was no noise introduced. That's all. =)

  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_joneeboi : Your choice of output and coupling caps may be responsible for this, would you consider switching the coupling to at least a Wima MKP and output to Muse ES?_

 

It's funny you should suggest it because I just happen to have some spares of both sitting around.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Joneeboi,

 Although C2 and C4, the midstage film coupling caps, are important - I'm not sure that's your issue. Instead, the R3 and R9 resistors should be soldered directly to the MOSFET gate leads. Pete has noted earlier in the thread that oscillation in the MOSFETs could occur if this was not done.

 At least on the right hand side of your pic, there appears to be no resistor soldered directly to any of the MOSFET leads. It may be that way on the left side, but I can't tell.

 Anyway, this might be the first thing you could try.

 Second, I would look at those mid-stage coupling caps. You might be a lot better off putting those K42's there and just leaving the electrolytics by themselves on the output.
	

	
	
		
		

		
		
	


	


_

 

I know that picture isn't very clear, but yes, I have R3 and R9 connected. I wasn't aware Pete suggested they be directly connected to the gate, so I'll get on those bad boys. I'm not sure where this issue of the midstage coupling caps comes up, but I'll try switching in the K42Ys like you suggest. Then I'll give Pavel's thing a whirl.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_<snip>I know that picture isn't very clear, but yes, I have R3 and R9 connected. I wasn't aware Pete suggested they be directly connected to the gate, so I'll get on those bad boys. I'm not sure where this issue of the midstage coupling caps comes up, but I'll try switching in the K42Ys like you suggest. Then I'll give Pavel's thing a whirl. 
	

	
	
		
		

		
		
	


	


_

 

Yeah, I figured they were connected or the amp wouldn't work at all. However, the resistor leads themselves must be soldered directly to the MOSFETs' gate leads. Or, as Pete warned - oscillation could result. I'm thinking that may explain all of your problem with harshness, low volume, etc., etc. IOW, the MOSFETs are not amplifying, they're oscillating.

 As for midstage coupling, C2 and C4 are what connect the MOSFETs (output stage) to the tubes (input stage). Those caps should be 0.1uf or larger, or frequency response will suffer. I can't tell what those little yellow caps are, but my suggestion was that the amp might do a lot better with the K42's there instead. Certainly, 100% of the music signal goes through these caps. At least we know the K42's have good sound quality and it looks like they are the 0.22uf size, which would be plenty big enough. That would remove any suspicion that those little yellow things at C2 and C4 are contributing to your issue.

 However, if you have 0.22uf Wima's, you could put those in at C2 and C4, instead. The K42's are fine in either position, but are probably better than the Wimas at the output positions.


----------



## joneeboi

Those little yellow box caps fit the schematic specs, but I'll try swapping them tomorrow; I should really start learning this material for tomorrow's midterm. And I threw in a my bro's iPod nano 3G and tried the beautiful little KSC75 (previously it was playing my SR60s), and the amp seemed to like that combination, so I wonder if it's solely the amp's fault. It didn't completely reject my iPhone 2G on the KSCs, so maybe I'll try different inputs as well as tweaking the layout. Thanks for the help, Tom. Maybe it'll like the BantamDAC once I get it soldered up after I pick up my Hakko 936 Tuesday. 
	

	
	
		
		

		
		
	


	




 It's beautiful. Last midterm tomorrow, free time all Tuesday to build, build, build. And then it's an extra long weekend. Good times for me.


----------



## the_Samurai_chicken

Hi all,

 This is probably a no-brainer question for most of you.
 I have bunch of Nichicon muse FS 63V 2200uf caps and muse FX 63V 220uf caps.

 Of these two which would be the best options to use for a build?
 Also could someone please tell me which is the better quality of the two- I can't find much info on them.

 Thanks.


----------



## n_maher

I would avoid using the 2200uF caps just about everywhere in this build. I think you could safely use the 220's although they are likely to cause the startup hiccup that has already been discussed as well as slightly limit the corner frequency into low impedance loads.


----------



## -=Germania=-

That RDS kit that was put together was very good and it would be nice to see that picked up by one of these suppliers, even as a Non-PCB kit. 

 If I can make one simple part addition that will make a difference, it would be adding a 470uf 90V-100V cap for going across the DC input. Some of these Cisco PS's seem to be noisier than the others and it significantly lowers the noise floor with low impedance headphones (Of the 5 I have come across, 2 were silent and the other 3 varied). Others, like FallenAngel, have suggested doing this previously in the thread.


----------



## rds

On the subject of capacitors, I found that 1000uF for c6, and 470uF for c1 completely eliminated start-up hiccups. I didn't bother to check which cap solved the problem, but I would guess it was c6.

 Also of interest, 180uF for c1, and 680uF for c6 didn't remove hiccups completely.


----------



## -=Germania=-

Yeah, I added to C6 and C1 for my 3 channel build. 

 The C6 was made to 860uf and the C1 was made to 330uf in mine after modification. I have had no hiccups ever, but mine uses a different PS.

 EDIT for clarification: The C1 and C6 values were done in the first day of operation of the 3 channel build. Though, I did it for sound reasons and to stabilize the readings I was getting from my meter.


----------



## pinkfloyd4ever

what are these "hiccups" you guys are referring to? I'm gonna be making Mouser and digikey orders soon, so I figure I'll get some bigger 'lytics since mine has 220uf for all of em. What again are currently the recommended values? Also I think I'm gonna replace my Wimas with some of these crapload of Vitamin Qs I bought 
	

	
	
		
		

		
			





 oh I also just realized that I didn't solder my R3 & 9 resistors directly to the mosfet lead, though they are pretty close. 






 I haven't noticed problems, it sounds great to me as it is now, but is it worth fixing this while I'm in there with the iron? If so I'll prob end up getting a new pair of mosfets while I'm at it, for my peace of mind if nothing else cause I know it's not recommended to repeatedly solder/desolder them


----------



## n_maher

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_what are these "hiccups" you guys are referring to?_

 

At cold startup the tube heaters attempt to draw more current than the power supply can supply so it "hiccups" (starts, stops, starts again) until the heaters get going and the current draw goes down.


----------



## joneeboi

So I inched R3 and R9 right up to the MOSFET gate leads and switched my K42Ys to the C2 and C4 positions. It removed the mess I was getting in the upper spectrum, so chalk another one up for "working MHSS." I also wanted to add that I got some terrifying, truly horrific crackling when testing the sound of the amp. I plug in my SR60s and it made a ginormous pop. It made music quite well, but then I put down my phone onto the table and the crackling just about blew my ears out. Even if I touched the volume knob to turn down the music, it would crackle like those lightning flash sound effects you hear in movies except right next to your ear. After many tests (and taking off my headphones), I bent the tube pins outward a bit and switched them to the other channel. That seemed to remove the crackle, and it withstood just about anything I hit it with. I just figured I'd share that story. I was really scared I had gone deaf, or even worse, that I fried one of the drivers. O_O (!!!!) Yeah, horrible, terrible stuff. I just thought I'd share that gut-wrenching story with you guys.


----------



## tomb

Quote:


  Originally Posted by *joneeboi* /img/forum/go_quote.gif 
_So I inched R3 and R9 right up to the MOSFET gate leads and switched my K42Ys to the C2 and C4 positions. It removed the mess I was getting in the upper spectrum, so chalk another one up for "working MHSS." I also wanted to add that I got some terrifying, truly horrific crackling when testing the sound of the amp. I plug in my SR60s and it made a ginormous pop. It made music quite well, but then I put down my phone onto the table and the crackling just about blew my ears out. Even if I touched the volume knob to turn down the music, it would crackle like those lightning flash sound effects you hear in movies except right next to your ear. After many tests (and taking off my headphones), I bent the tube pins outward a bit and switched them to the other channel. That seemed to remove the crackle, and it withstood just about anything I hit it with. I just figured I'd share that story. I was really scared I had gone deaf, or even worse, that I fried one of the drivers. O_O (!!!!) Yeah, horrible, terrible stuff. I just thought I'd share that gut-wrenching story with you guys. 
	

	
	
		
		

		
		
	


	


_

 

That's great news about the resistors and MOSFETs.

 Yes, crackling would definitely be an indication of a loose connection somewhere - right in the signal path, most likely. It's always a good idea to check the tube pins and use some alcohol swabbing, etc.


----------



## bmwpowere36m3

I've been reading over this thread, and I'm really liking the SSMH. From my understanding, the tubes offer "big" gains in amplification and thus is problematic with easily powered earphones/headphones.

 Currently I'm only using RE2's (32 ohm) and was thinking of upgrading to RE1's (150 ohm). I've been told that both of these or really any earphone will not work with this type of amp. Is this true?

 If so, what type of headphones are you guys using. I've never used headphones really, I've been living my head-fi life in IEM's. I've heard lots of good reviews on Grados, (SR-60, 80, etc...). Any would be nice.


----------



## spanks

I'm really curious about this amp.

 I am looking into getting an amp and new cans soon, and this was suggested to me.

Mini Millet DIY Tube Amplifier - Default Store View

 I am not surprised at its price, but I was curious if there was any differences between it and the $50-$60 version you can build yourself?

 Also, how would an amp like this compare to a $200-$300 tube amp? I was looking at a darkvoice 336se until this was suggested. Amps are hard enough to compare for me as it is, but when you have $60 worth of parts and people are saying it sounds fantastic...I get a bit lost.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *spanks* /img/forum/go_quote.gif 
_I'm really curious about this amp.

 I am looking into getting an amp and new cans soon, and this was suggested to me.

Mini Millet DIY Tube Amplifier - Default Store View

 I am not surprised at its price, but I was curious if there was any differences between it and the $50-$60 version you can build yourself?

 Also, how would an amp like this compare to a $200-$300 tube amp? I was looking at a darkvoice 336se until this was suggested. Amps are hard enough to compare for me as it is, but when you have $60 worth of parts and people are saying it sounds fantastic...I get a bit lost._

 

That amp is based on the build out list put together by rds with upgraded parts, which is a very good sounding collection of parts to build the starving student. I have a starving student based on the rds kit ($58 for most parts plus the cost of case and wire and shipping totalling less than $100) and it sounds better than my dark voice 336i ($300), and very close to my head-direct EF1 hybrid amp which I still like better ($400).

 The sound is well worth the $180-200 for one already built, unless you know how to build one yourself.


----------



## spanks

thanks so much!

 Just the kind of response I was looking for 
	

	
	
		
		

		
		
	


	




 I could build one myself, but not that neat and tidy


----------



## kuroguy

Quote:


  Originally Posted by *spanks* /img/forum/go_quote.gif 
_thanks so much!

 Just the kind of response I was looking for 
	

	
	
		
		

		
		
	


	




 I could build one myself, but not that neat and tidy _

 

From some of the photos I've seen posted here, neatness doesn't count. Get the holes in the chassis correct and it will look good from the outside. nobody will ever see the inside unless you show it to them.

 Forget the kit and get enough parts for 2 amps at the same price. you never know when you're gonna sprout another set of ears and you want to be prepared when it happens.


----------



## the_Samurai_chicken

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_On the subject of capacitors, I found that 1000uF for c6, and 470uF for c1 completely eliminated start-up hiccups. I didn't bother to check which cap solved the problem, but I would guess it was c6.

 Also of interest, 180uF for c1, and 680uF for c6 didn't remove hiccups completely._

 

So 2200uF for c6 and 220uF for c1 would be a overkill/bad combo?

 These 2200 jobbies are burning a hole in my desk at the moment and I want to use them.. somewhere..


----------



## n_maher

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Currently I'm only using RE2's (32 ohm) and was thinking of upgrading to RE1's (150 ohm). I've been told that both of these or really any earphone will not work with this type of amp. Is this true?_

 

Another factor that is just as important (if not moreso) is a headphones sensitivity. I know nothing about the two models you mentioned but as IEMs it's probably a pretty safe bet that they are fairly efficient. So your biggest problem is likely going to be channel matching at low levels with the cheap pot used in the BOM. There have been several methods for reducing the overall amplification factor of this amp already discussed, searching the thread for that is a place to start. If you can't find it post again and we'll re-hash some of the discussion. I think the preferred method is adding a series resistor at the input, but don't hold me to that. Otherwise the amp will work fine with any headphone.

 And folks are using this amp with just about any headphone you can think of so getting recommendations in this thread might prove problematic.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Another factor that is just as important (if not moreso) is a headphones sensitivity. I know nothing about the two models you mentioned but as IEMs it's probably a pretty safe bet that they are fairly efficient. So your biggest problem is likely going to be channel matching at low levels with the cheap pot used in the BOM. There have been several methods for reducing the overall amplification factor of this amp already discussed, searching the thread for that is a place to start. If you can't find it post again and we'll re-hash some of the discussion. I think the preferred method is adding a series resistor at the input, but don't hold me to that. Otherwise the amp will work fine with any headphone.

 And folks are using this amp with just about any headphone you can think of so getting recommendations in this thread might prove problematic._

 

Thanks, I've actually read about using a series resistor with the pot to lower overall gain. At the same time there was a lot of negative feedback to doing that. There were two methods I recall, one using a high resistance pot and two using a low resistance pot plus a high resistance resistor.

 Would using a stepped attenuator help with channel balance at low volumes? I don't really want to build this if I really have to compromise it's quality.


----------



## -=Germania=-

Low impedance/ high sensitivity IEM's are not a good idea with this amp, especially with the original BOM. 
 The modded im716 wasn't bad, but it is neither of those things above. The FreQ, absolutely no. 

 I am only posting because of my own experiences. When testing this amp using the IEM's to check the ground floor works, but it is not something I would listen to. Generally, go with something Solid State designed for IEM's.


----------



## odymmij

I'm really interested in building this amp and I've checked out the schematics, but there are some things about grounding that I'm not so sure about. Where do you connect the grounding wires/caps/resistors? Do you connect them all to the same point/same chunk of metal or do you connect them to separate points?

 I'm a newb when it comes to DIY electrical stuff...


----------



## holland

Been wondering if I should even bother posting this, but what the heck.

 FWIW, I think this goes against pmillett's design philosophy as I don't think any of his amps utilize this. If you're a pmillett purist or other type of purist, then no need to read this at all, and just skip over it.

 I would do something different. I would not do the signal attenuation at all...i.e., resistor in series wired to a switch. That's attenuating the source signal, and with a 15x gain stage, it's not ideal and rather silly, IMO. The ideal would be to reduce the gain by changing tubes. Since that's not really an option (I don't want to scrounge the internet looking for a tube that'll fit and work), I would use negative feedback.

 Remove all that signal attenuation stuff, and build in adjustable NFB to reduce the gain, and should lower the distortion as well. Some people hate that, but I think some NFB is good. Again, pick your poison.

 I haven't measured or done this, but it's a starting point.

 I'm too lazy to draw a diagram for the entire SSMH so I'll describe with words, first, bypass the cathode resistor (R5 and R11) with a 1000uF/16V cap I think even a 10V cap should work, not sure entirely, but 16V is fine. Without R5 and R11 bypassed you will get signal degeneration, so the gain drops some in the default circuit. Bypass it, to avoid some feedback, and the circuit gain should increase. That's right, increase it.

 Put in a 10K grid stopper, that is a 10K resistor between the pot and the tube, but put it right on the tube pins (5 & 6). Also, put another 10K resistor right on pins 5 & 6. Connect this to a pot, and then connect that to the output of the circuit, after the output cap and the 2K resistor to ground.

 The higher the value of the resistance, the less NFB. So, wire the pot in reverse, basically. Shunt the wiper to the input pin and wire the amp output to the input pin. Take the "ground" pin as the output, wire so it connects to the second 10K resistor.

 You can eliminate the adjustable NFB pot, and use a single resistor, once you figure out what you need. I would do some measurements and look for something that gives you about 2:1 for IEMs, or 2x gain. IEMs, ideally, should just use a buffer. Even an IPOD has enough voltage swing for an IEM that can put out 120dB/V. high sensitivity low-Z headphones, I would go for 2x to 4x gain. Higher end Senn dynamics, I can live with 6x to 8x gain. Measure with a 0dbFS file on your computer to a DAC that you know gives 2Vrms output. Feed into the amp, and measure the RMS voltage at the amp output if you really want. Another way is to put a scope on it, but most people don't have one. Measure the pot, add up the resistances and put in the resistor value you want, or leave the NFB adjustable as it'll make the amp more usable for various headphones.

 Again, pick your poison. Some people hate NFB, but I think the extreme amount of series resistance coupled with a 15x gain to utilize an IEM or a high sensitivity low-Z headphone is silly.

 YMMV.

 I hope you find this useful, IMO, it makes the amp more useful for low-Z. With the 150mA Class-A bias, I think this is a good mod for the circuit. You don't need 150mA Class-A bias for high-Z.

 Again, I haven't measured this, but that's what I would do. In theory it should work, but the resistor values may need tweaking. That would require sims, and testing, and measurement, something I'm not going to bother doing.

 You can build in a switch to drop the NFB completely. Break the circuit and change the grid stopper to a lower value, and remove the bypass cap. Since this is right on the tube socket, you can put the switch nearby.


----------



## holland

Quote:


  Originally Posted by *odymmij* /img/forum/go_quote.gif 
_I'm really interested in building this amp and I've checked out the schematics, but there are some things about grounding that I'm not so sure about. Where do you connect the grounding wires/caps/resistors? Do you connect them all to the same point/same chunk of metal or do you connect them to separate points?

 I'm a newb when it comes to DIY electrical stuff..._

 

Google "star ground". This amp is small and simple enough that you don't need local nodes to connect to the star ground. Run them all to the ground strip. You can also use a ground plane. If using the plane, just drop the ground onto the plane from each component, short runs are best. Look at the article on pmillett's web page. 2 implementations. pmillett, ground plane. n_maher, star ground.


----------



## bmwpowere36m3

That's awesome Holland, since I'm still learning this stuff what would be the downside to implementing a NFB. What are the downsides of using it, i.e. upsetting the purists?


----------



## holland

I shouldn't say purists, but there definitely are camps. Some really hate NFB. Just go around and read various forums. But then again, what isn't argued, resistors, capacitors, NFB, etc.

 Part of the argument is that you get phase distortions (but you can also get that from output caps). The other argument is that you can get poor transient behavior, less bandwidth, slew rate impacted, etc.

 But this amp is hardly in opamp territory for bandwidth or gain.

 The mu on this tube, IIRC, is 38 (?) That's not huge for an amp. You should be able to use enough feedback to get what you want. Use your ears to decide.

 Though, for you, I would still reconsider. 
	

	
	
		
		

		
			





 For IEMs, all you really need is a buffer. A JISBOS with a pot, for example, as long as your source can put out 2Vrms. However, adjustable NFB allows you to use your IEMs with the SSMH, till you get some full-sized cans, then you can dial down the NFB and increase the gain for other headphones.


----------



## holland

Audio Power Amplifier Design Handbook - Google Book Search

High-Power Audio Amplifier ... - Google Book Search

 search for negative feedback. I think it gives a good overview.


----------



## rds

Quote:


 Some people hate NFB, but I think the extreme amount of series resistance coupled with a 15x gain to utilize an IEM or a high sensitivity low-Z headphone is silly.. 
 

First off, it's been said many times now that you can use a 10k pot with a 40k resistor in series and have the same input resistance as a standard pot, with effectively 1/5 the gain.
 The type of negative feedback you're suggesting will in most cases cause all sorts of degradations.
 If you're a signals expert you might be able to work something out that is close to distortion free in the audio range... maybe. What you're suggesting is a completely different amp either way.
 What's so silly about using a series resistance as described above?


----------



## holland

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_First off, it's been said many times now that you can use a 10k pot with a 40k resistor in series and have the same input resistance as a standard pot, with effectively 1/5 the gain._

 

Yes, worded improperly. It's not the input resistance, but the ratio. The need to necessitate cutting the input signal by 5 or more. The higher resistance will have more noise if you start with the BOM pot of 50K or a 100K pot, but that's not that big an issue. Nor is the input resistance, in most sources unless it's a portable, which is unlikely in this amp's usage scenario.

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_The type of negative feedback you're suggesting will in most cases cause all sorts of degradations._

 

Disagree, it's a standard feedback loop. There are some that don't do a feedback loop, the SSMH uses local feedback in the VAS. As I had stated in my prior post, the values can be tweaked, but I'm not going to do it. 
	

	
	
		
		

		
		
	


	




 What cases do you refer to?

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_What you're suggesting is a completely different amp either way._

 

Noted, it's why I said purists need not read it, and why I debated posting it. I wouldn't call it completely different though. Completely different would be a different buffer, for example, at least to me. *shrug*

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_What's so silly about using a series resistance as described above?_

 

High signal attenuation followed by high gain vs "normal" attenuation with a more "reasonable" gain for high sensitivity headphones. Using what's appropriate, has been debated for a long time. I won't argue the pros or cons of it here.

 If you want to take an extreme example, an amp with a gain of 150 (10x the SSMH). Is there any detriment in cutting the input signal by 50 (1/5 * 1/10) to then amplify by 150? Same point, different numbers. If that doesn't resonate with you, then it doesn't. Again, I won't argue it here, but think about it. If it doesn't mean anything to you then it doesn't. If it does, it does.

 Hmmm, wonder if head-fi is going to crash, keep getting failures trying to post this.


----------



## rds

Quote:


 Disagree, it's a standard feedback loop. There are some that don't do a feedback loop, the SSMH uses local feedback in the VAS. As I had stated in my prior post, the values can be tweaked, but I'm not going to do it.

 What cases do you refer to? 
 

I'm basing this on my limited knowledge of signals and control systems rather than instances of actual audio amplifiers.
 Of course feedback is generally used to linearize non linear systems. 
 A few problems with this is that feedback increases the system's sensitivity to noise and decreases its stability.
 What you end up with is a control function (which is unknown really) which affects how feedback influences the output. Finding the right balance between transient response, steady state performance, and sensitivity becomes very complicated, and will involve a lot more than just adding a feedback loop.
 Beyond that you are effectively removing the "tube sound" by trying to linearize the amplifier's performance.
 I think a lot of audio people rightly want to minimize the use of feedback in tube amps. It is much better to use stages that are close to linear rather than trying to linearize with feedback, imo.


----------



## holland

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I'm basing this on my limited knowledge of signals and control systems rather than instances of actual audio amplifiers.
 Of course feedback is generally used to linearize non linear systems. 
 A few problems with this is that feedback increases the system's sensitivity to noise and decreases its stability.
 What you end up with is a control function (which is unknown really) which affects how feedback influences the output. Finding the right balance between transient response, steady state performance, and sensitivity becomes very complicated, and will involve a lot more than just adding a feedback loop.
 Beyond that you are effectively removing the "tube sound" by trying to linearize the amplifier's performance.
 I think a lot of audio people rightly want to minimize the use of feedback in tube amps. It is much better to use stages that are close to linear rather than trying to linearize with feedback, imo._

 

Perhaps my memory is lagging, as it's been a long time since I studied linear systems, but I don't really agree with your summation of feedback. IIRC, that doesn't apply to reasonable negative feedback where the feedback signal is an error control and is used to reduce error/distortion. In a positive feedback system, that would be true, but this scheme would use a negative feedback. For there to be issue in a negative feedback system, the amount of feedback will be large I could be wrong though, I admit that freely, it's been a long time. I think you're making it much more complicated than it really is.

 The linearizing, I understand could be an issue for some, and not for others. But, if the argument is that the system is already almost linear, then the feedback shouldn't do much but reduce gain. The end goal is not the linearizing, it's the reduction of gain by the negative voltage feedback factor.

 The open loop gain of the amp isn't enormous, and the amount of feedback will be small, and realistically is only used for high sensitivity low Z headphones (20-30dB drop).

 All that is primarily "different strokes for different folks", and really that's all it is. I'm sure you will find plenty of tube amps with local negative feedback and more than a few with global, be it power amps, or guitar amps. One can also argue that this isn't a tube amp, it's a hybrid. 
	

	
	
		
		

		
		
	


	




 Basically, if you want to try it, try it, if you don't, you don't. You're in the purist camp, but till you get rid of all your SS amps and SS source, I won't really believe it. 
	

	
	
		
		

		
		
	


	




 We can go back and forth, but basically it's going to be the same no matter how you slice it. Your view is yours and mine is mine. There's nothing wrong with that.


----------



## chobint

Hey guys, any idea how the SS would compare to the Bijou in terms of power output?

 The reason I ask is because I am trying to build a makeshift tube radio for my gramps on a strict budget ($100). I showed him a pic of my Bijou and he started reminiscing about listening to ball games on his old radio. So anyway, I'm probably going to rip up an old alarm radio or buy a radio kit and amplify it with the SS through some 107 or 117dB/W speakers. With my Bijou cranked via hd650's(105dB/W) it is plenty loud to be audible a room away. So I just wanted to see if the SS would be able to supply ample power.
 PS: I looked all over for a small speaker tube amp, but all the kits seem to be at least 100$ and I'm not nearly savvy enough to find an unproven schematic and whip one up from scratch :\


----------



## gurusan

just a little update...I was experiencing the coldstart hiccup problems....just swapped out nichicon pw series 180uF (C1) and 680uf (C6).....and replaced them both with Panasonic FC series 1000uF.

 Hiccup cured!


----------



## n_maher

Tube Update

 I've managed to acquire some 19J6's, potentially as many as 20 tubes. They should be arriving mid next week and once I have them I'll sort them into pairs (construction matched, brand might not be possible) and I'll try to list them for sale at the end of the week. I'm posting this hear so that I don't have to reply to any more PM's about this. From here forward anyone who PM's me asking to be put on a list will be removed from eligibility. I'm sorry to be like that, but I'm trying to be as fair as possible with this and I'm not going to try and keep track of "pre-orders". I'll post a link to the FS thread when I have them listed.


----------



## HeadphoneAddict

What would anyone guess to be the approximate number of tubes my son needs for a lifetime of listening with his Nascar 24 MSSH? Assuming he turns it on when he gets home from school or work for 6 hours a day before bedtime, and plays music during at least 2 of those hours? Or, if it is easier, how many years would each pair of tubes last with that kind of use - 5, 7, 10?


----------



## kuroguy

Id guess he'd get about 8000 hours out of a set. that works out to 4 years per set at 6 hours use a day.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Id guess he'd get about 8000 hours out of a set. that works out to 4 years per set at 6 hours use a day._

 

Okay, thanks. We have 4 sets of tubes, and I wasn't sure we needed more. At 2 hours a day (or 4 hours every other day) that would last 48 years!


----------



## gurusan

I just finished the casework finally on my SS millet. Still have to organize the wires a bit but I am done for today


----------



## Hayduke

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_I just finished the casework finally on my SS millet. Still have to organize the wires a bit but I am done for today 
	

	
	
		
		

		
		
	


	




http://img380.imageshack.us/img380/8430/img3690mq3.jpg
http://img380.imageshack.us/img380/3599/img3697uy2.jpg
http://img380.imageshack.us/img380/2313/img3698qj7.jpg_

 

Looks nice, what case is that?


 I'm starting to gather parts to build one of these. I probably shouldn't since I have several other projects with part sitting here 

 I have a question about the power supply. I have one of these I got for free. I think it will work, but wanted to get a second (and maybe third, fourth etc) opinion.

http://www.power-guide.com/pdf/SPU50.pdf

 I have the SPU50-9


----------



## JamesL

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Looks nice, what case is that?


 I'm starting to gather parts to build one of these. I probably shouldn't since I have several other projects with part sitting here 

 I have a question about the power supply. I have one of these I got for free. I think it will work, but wanted to get a second (and maybe third, fourth etc) opinion.

http://www.power-guide.com/pdf/SPU50.pdf

 I have the SPU50-9_

 

The 48VDC is specified at 240VAC input.
 It wouldn't work for a linear psu for sure, but switching psu's work differently.
 I'm not sure myself actually.. =/


----------



## error401

Should be fine, though the noise spec is quite poor. You may want to add some additional filtering.


----------



## johnshade

I just completed a build of the Starving Student. It works beautifully and the sound is excellent. I just wanted to thank pmillet for posting the original design, and all the thread contributors here for sharing their experiences. In the name of sharing information, here are my substitutions for the currently unavailable parts - 

 Mouser parts - 
 540-RRA22H3BBRLN - Rocker Switches SPST ON-OFF 10A RED
 598-150104K100AA1 - DC Film Capacitors .1UF 100V 10% 
 647-TVX1J151MCD - Axial Aluminum Electrolytic Capacitors 150uF 63V 85c 10x21 20% 

 Digi-Key
 8568K - Control Knob

 I purchased the 19J6 Tubes and sockets from Radio Electric Supply, Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes!. ESRC1 Corp also said they had tubes and sockets in stock. They're at Vacuum Tubes @ ESRCVacuumTubes.com - Contact Us Page.

 I used a Radio Shack project box, with the Aluminum lid used as the mounting point for all components. To drill the holes, I used a step bit bought via Amazon (it was chosen based on cost, needed 1/4" shank, would drill through soft metal). It's at -
 Neiko Titanium Step Drill Bit; 1/4" Hex Q/C Shank; 12 Steps; 3/16" - 7/8" at 
Amazon.com: Neiko Titanium Step Drill Bit; 1/4" Hex Q/C Shank; 12 Steps; 3/16" - 7/8": Industrial & Scientific


----------



## n_maher

Guys/Gals,

 I'm going to be listing 9 pairs of RCA 19J6s some time this afternoon (right after I find time to breath 
	

	
	
		
		

		
		
	


	




 ). The cost to acquire these tubes was quite a bit higher than when Pete first launched this product but I don't think it'll put the amp out of the starving student category just yet. Most of the pairs that I'm listing are new old stock RCAs that were taken from a TV service repair man's kit. It took my tube dealer doing quite a bit of leg work to find them and they've all been tested so you should be getting great tubes. 
	

	
	
		
		

		
		
	


	




 Look for the add in the FS forums within the next few hours. Unfortunately this is going to first come first serve type deal.

 Happy building.

 Nate


----------



## n_maher

http://www.head-fi.org/forums/f44/fs...3/#post4971637

 For Sale Add is UP.


----------



## kuroguy

Holy crap, $20.70 for a pair of tubes. I've got 4 tubes and a complete amp that I might consider selling (But it sounds really sweet).

 I'm not one for building amps with pricey tubes, but this one might still be worth building. Even at those prices.


----------



## n_maher

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Holy crap, $20.70 for a pair of tubes. I've got 4 tubes and a complete amp that I might consider selling (But it sounds really sweet).

 I'm not one for building amps with pricey tubes, but this one might still be worth building. Even at those prices._

 

The tubes cost me $7 each. So that's $14 + $5 shipping + PP. As it is I'm sure I'll lose money since I'll have to buy little boxes and packing material for these. So what do you want me to do, give them away and donate the $140 I had to pay to get them to me to the "cause". Some days I wonder if it's worth trying to help.


----------



## kuroguy

No, no. I wasn't commenting on what you are doing. The price certainly looks fair, and I applaud you for helping out in this manner. It is way above and beyond the call of duty. My comment was about how supplies of this tube (which has been around for years) seem to have dried up in a matter of weeks.


----------



## Malanga

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_The tubes cost me $7 each. So that's $14 + $5 shipping + PP. As it is I'm sure I'll lose money since I'll have to buy little boxes and packing material for these. So what do you want me to do, give them away and donate the $140 I had to pay to get them to me to the "cause". Some days I wonder if it's worth trying to help. 
	

	
	
		
		

		
		
	


	


_

 

Strange, I found these tubes with little problem. I ordered mine from this place:
Vacuum Tubes, Inc. New Tubes, 8JU8A to 50FK5
 I believe I paid 3 bucks each, plus a pair of sockets and shipping came out to about 12 dollars shipped. 

 I plan to put mine together later this week. I am using a nice looking cigar box as the case. I hope it works out okay!


----------



## Malanga

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_The tubes cost me $7 each. So that's $14 + $5 shipping + PP. As it is I'm sure I'll lose money since I'll have to buy little boxes and packing material for these. So what do you want me to do, give them away and donate the $140 I had to pay to get them to me to the "cause". Some days I wonder if it's worth trying to help. 
	

	
	
		
		

		
		
	


	


_

 

I believe your efforts are appreciated. Thanks for helping to forward our hobby!


----------



## HeadphoneAddict

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_http://www.head-fi.org/forums/f44/fs...3/#post4971637

 For Sale Add is UP._

 

Great! While I'd like more, I am going to sit back and let the people who have NO tubes buy some, so we aren't hoarding tubes and people can't build new amps.


----------



## Hayduke

OK, I have another power supply question 

 It seems difficult to find specs on Cisco supplies. When I search for PSA18U-480C, that seams to be the model # for Cisco P/N 34-1977-03. I got a hold of a 34-1977-04, but the model number says EADP-18FB. It still says 48V and 0.38A, but I can't find any documentation on the differences between the 2 P/N's.

 Do you guys think this will work OK?


----------



## rds

Quote:


 Do you guys think this will work OK? 
 

Yeah.

 ...man with those 19j6s going into obscurity the "starving student" is really earning its quotations. 
 It's great that Nate's gone to the trouble of making some (of the last few?) available.


----------



## ltmon

How sad the 19J6s are disappearing, the SS is a great first build and I use mine all day every day at work.

 I have two spare 19J6 which I'll gladly pass on for the cost of postage, but I'm pretty sure than one of them is on the fritz. Is there anything you can do about a tube that adds a humming noise into the channel?

 What are the possibilities for this design being updated for some other more easily findable tubes?


----------



## effcleff

A few weeks ago I picked up a pair of NOS Sylvania 19J6s for $12 each at Fistell's here in Denver. At the time I thought it was bit of a rip-off, but grudgingly bought them anyway. Now, I'm glad I did. At the time, I think they had one or two left. 

 The guy at Fistell's thought it was pretty strange that I was interested in this tube.


----------



## n_maher

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_It's great that Nate's gone to the trouble of making some (of the last few?) available._

 

Well, it remains to be seen if I just tossed a ton of money down the toilet considering the feedback I've gotten so far on the pricing. 
	

	
	
		
		

		
			





 I can't believe the backlash over what is essentially $8.


----------



## rds

Quote:


 Well, it remains to be seen if I just tossed a ton of money down the toilet considering the feedback I've gotten so far on the pricing. I can't believe the backlash over what is essentially $8. 
 

Personally I use the 1/3 rule when I do someone a favor, in that 1 out of 3 times I won't regret it.
 However, the people in that 1/3 category are generally great and make it worthwhile. 
 Also, I take names


----------



## Hayduke

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well, it remains to be seen if I just tossed a ton of money down the toilet considering the feedback I've gotten so far on the pricing. 
	

	
	
		
		

		
		
	


	




 I can't believe the backlash over what is essentially $8._

 

I appreciate it 
	

	
	
		
		

		
		
	


	




 Unfortunately I ordered my tubes this weekend 
	

	
	
		
		

		
		
	


	




 I'm hoping to get all my parts in this week and build it this weekend. I know once my buddy hears it, he will want one. If you still have some, I'll probably order from you to make his.

 I just had a thought, if you have trouble selling the tubes, spend (invest?) a little more $$ and build a bunch of amps. I bet there are lots of folks that would want one, but lack the skills or tools to make their own.


----------



## blippster

Quote:


  Originally Posted by *Malanga* /img/forum/go_quote.gif 
_Strange, I found these tubes with little problem. I ordered mine from this place:
Vacuum Tubes, Inc. New Tubes, 8JU8A to 50FK5
 I believe I paid 3 bucks each, plus a pair of sockets and shipping came out to about 12 dollars shipped. 

 I plan to put mine together later this week. I am using a nice looking cigar box as the case. I hope it works out okay! 
	

	
	
		
		

		
		
	


	


_

 

I just wrote in to Jim, and sadly they're now out of the 19J6s.. Still hoping to find a pair to build an SS after term.


----------



## pinkfloyd4ever

Are vacuumtubes.net and vacuumtubes.com both out of em too?


----------



## dsavitsk

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_My comment was about how supplies of this tube (which has been around for years) seem to have dried up in a matter of weeks._

 

Chances are, so long as the dealers know people are after them, a pile of these will turn up from out of a warehouse where they had been forgotten. Or, what would have constituted that pile were all trashed as useless. You would be amazed just how many random warehouses with thousands of random tubes there are. In some cases, the cost of sorting and storing is more than the perceived value of the tubes, so they end up getting trashed.

Here was an old thread about someone selling 1.5 to 2 million tubes on ebay for a quarter million dollars. This wasn't even their large warehouse, which still exists. Nobody is going to sort through all that garbage to find a couple hundred 19J6's.


----------



## FallenAngel

They pop up on eBay quite often; 3 pairs available now.


----------



## blippster

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_They pop up on eBay quite often; 3 pairs available now._

 

I did enquire with them about overseas shipping, but didn't get any reply.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Just built one of these, sounds very nice, surprisingly nice for the price actually. I made mine a little more extreme in terms of parts

 Alps RK27 POT
 VitaminQ coupling caps
 Muse FG output caps_

 

Any pics or more specs on your build, seems similar to what I want?



 Also why are people choosing different values for C1 & C6 (like 680uF and 470uF), why not same? Am I missing something about the circuit.

 Also does putting a cap parallel across the DC input "quiet" down the noisy walwart and provide some "sink", any size recommendations? I'm seeing ~470-680uF

 Also what the general consensus on output caps (C3,C5) 330-470uF? Bypass w/ a film or just leave the films for the Cathode's (C2,C4)?

 I was thinking my setup (maybe):

 C3/C5: 470uF BG's/Muse ES/--- ... possibly bypassed .22 or .47uF VitQ's or K40Y's
 C2/C5: .22uF VitQ's
 C1/C6: 470uF Muse KZ
 C"0"(DC In Cap): 680uF Muse KZ


----------



## J.P.6

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_OK, I have another power supply question 

 It seems difficult to find specs on Cisco supplies. When I search for PSA18U-480C, that seams to be the model # for Cisco P/N 34-1977-03. I got a hold of a 34-1977-04, but the model number says EADP-18FB. It still says 48V and 0.38A, but I can't find any documentation on the differences between the 2 P/N's.

 Do you guys think this will work OK?_

 

Yeah that's fine, it's the one I have.


----------



## n_maher

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I appreciate it 
	

	
	
		
		

		
		
	


	


_

 

Thanks. 
	

	
	
		
		

		
		
	


	




  Quote:


 I just had a thought, if you have trouble selling the tubes, spend (invest?) a little more $$ and build a bunch of amps. I bet there are lots of folks that would want one, but lack the skills or tools to make their own. 
 

me != MOT, and I don't lack for projects to occupy my time. 
	

	
	
		
		

		
		
	


	




 And I'm sure that more will become available from time to time as dealers acquire more stock. There just seemed to be a glut of folks that were having trouble finding them recently.


----------



## Malanga

Quote:


  Originally Posted by *blippster* /img/forum/go_quote.gif 
_I just wrote in to Jim, and sadly they're now out of the 19J6s.. Still hoping to find a pair to build an SS after term._

 

Wow, I guess I got lucky then. One place I called said he used to throw them away because there was no demand for them! Now he has none in stock. Make you wonder, are there any other good tubes out there that are sleepers waiting for the right person to come along and build an equally good amp with? I wish I had the skill to do so...


----------



## holland

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Also why are people choosing different values for C1 & C6 (like 680uF and 470uF), why not same? Am I missing something about the circuit._

 

It's what they have on hand? I use 1000uF. C1 & C6

  Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Also does putting a cap parallel across the DC input "quiet" down the noisy walwart and provide some "sink", any size recommendations? I'm seeing ~470-680uF_

 

Got lucky? I would put a choke on it, if you really want to filter. That is filter out the HF noise from the switching DC adapter.

 Here's what a quick google turned up for a simple explanation. Resonant-choke Power Supply

 You can put more stages to add more filtering. You don't want to put any more R, as it reduces voltage. You can, if you've got voltage to spare.

 C1 & C6 & R13 form a CRC filter, aka "pi" filter. Add an L and another C.

  Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Also what the general consensus on output caps (C3,C5) 330-470uF? Bypass w/ a film or just leave the films for the Cathode's (C2,C4)?_

 

Most people use 470uF. I use 1000uF.

  Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_I was thinking my setup (maybe):

 C3/C5: 470uF BG's/Muse ES/--- ... possibly bypassed .22 or .47uF VitQ's or K40Y's
 C2/C5: .22uF VitQ's
 C1/C6: 470uF Muse KZ
 C"0"(DC In Cap): 680uF Muse KZ_

 

seems fine. If you really want to, bypass C1 and C6 with a film cap to reduce ESR as well, and if your mosfets are "far away" from the PS filter section (pi filter) add another film cap there, near the pins of the mosfet.


----------



## tomb

Just an FYI, but I would hesitate applying a choke to the output of a regulated power supply. Your reference discusses applying the choke directly after rectification. This would be impossible with the SSMH standard PS, unless you broke it open and started modifying the circuit.

 I've run a few tests with small inductors right at the output of a regulated voltage source and the results were not good. It's possible that might be different with a switching supply, but I'd rather not take the chance. On the other hand, placing a capacitor across the output and ground is at least not likely to hurt anything. It's more or less the same as simply adding another rail cap. I still wouldn't consider it unless you seem to have more noise than you want and you've exhausted all other potential sources for the problem - noisy tubes, bad grounding, etc.*

 BTW, the concensus capacitors were reached at 470uf all around. The original design used 220uf, but in the back at the power supply, that caused some hiccups in the PS upon startup. At the output, 220uf is a bit small for low impedance headphones and causes a higher than desired cutoff frequency for the bass. 470uf solved the issue in both places.
	

	
	
		
		

		
			





 *EDIT: What I'm hinting at is that applying either one to the PS output may just as likely cause instability in the PS and cause more noise. Unless someone has actually tested this with the recommended SSMH power supply, I'd look elsewhere to improve the amp.


----------



## bmwpowere36m3

^^^Thanks Tomb. How about the idea of a "THREAD" regulator inside the case. I think you'd need a different LM3xx to handle ~50V, correct?

 On the issue of case grounding, with a metal case do we tie it to ground? If so, do we also tie in the "thru-hole" components (i.e. RCA jacks, DC jack, switch, pot). Or do we need isolated components?


----------



## n_maher

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_^^^Thanks Tomb. How about the idea of a "THREAD" regulator inside the case. I think you'd need a different LM3xx to handle ~50V, correct?_

 

As previously discussed you can operate the LM317 above 50V if you're careful about it. The maximum input/output voltage ratio is what you must not violate. There are other concerns if you want to use something like a TREAD but there are also tools in place to guide you with that as well.


----------



## gurusan

Would heatsinks rated at 5.6C/W be sufficient to cool the FETs?


----------



## ludoo

I also have a question about heatsinks: with the spares from my previous builds I have all that's needed for another SS, except the heatsinks. Getting them from mouser and digikey means paying more than 20 euros of shipping for 2 euros of stuff.

 Unfortunately I did not find any suitable replacements at rsonline, which is very convenient as I can go pick up my orders. Any of you that can help me finding suitable heatsinks there? Or alternatively if someone has a pair to drop in an envelope in exchange for some paypal money.


----------



## n_maher

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Would heatsinks rated at 5.6C/W be sufficient to cool the FETs?_

 

That looks like the right range to me provided they have adequate airflow.


----------



## rds

Each FET consumes about 2.9 Watts.


----------



## looser101

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I also have a question about heatsinks: with the spares from my previous builds I have all that's needed for another SS, except the heatsinks. Getting them from mouser and digikey means paying more than 20 euros of shipping for 2 euros of stuff.

 Unfortunately I did not find any suitable replacements at rsonline, which is very convenient as I can go pick up my orders. Any of you that can help me finding suitable heatsinks there? Or alternatively if someone has a pair to drop in an envelope in exchange for some paypal money._

 

Send me a PM with your address.

 Renato


----------



## holland

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just an FYI, but I would hesitate applying a choke to the output of a regulated power supply. Your reference discusses applying the choke directly after rectification. This would be impossible with the SSMH standard PS, unless you broke it open and started modifying the circuit.

 I've run a few tests with small inductors right at the output of a regulated voltage source and the results were not good._

 

Can you elaborate? I don't understand why it would matter much, and would like to further understand your point.

 A common method of reducing the switching hash is to filter with LC and voltage regulation and more LC filters. Regulation is not enough. This can be used on USB, for instance to completely clean the signal (which utilizes step up, filtering, regulating down to 5V and futher filtering).


----------



## gurusan

ok, thanks guys

  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I also have a question about heatsinks: with the spares from my previous builds I have all that's needed for another SS, except the heatsinks. Getting them from mouser and digikey means paying more than 20 euros of shipping for 2 euros of stuff.

 Unfortunately I did not find any suitable replacements at rsonline, which is very convenient as I can go pick up my orders. Any of you that can help me finding suitable heatsinks there? Or alternatively if someone has a pair to drop in an envelope in exchange for some paypal money._

 

rs-online has these
| Semiconductors | Sockets and Heatsinks | Heat Sinks | Thermal Resistance More Than 1.3Â°C/W

 and i think a few more if you look for t0220 package heatsinks


----------



## ludoo

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_rs-online has these
| Semiconductors | Sockets and Heatsinks | Heat Sinks | Thermal Resistance More Than 1.3Â°C/W

 and i think a few more if you look for t0220 package heatsinks_

 

I saw them, but the "standard" heatsinks on my SS are already running pretty hot, I'm a bit wary of using heatsinks that dissipate even less heat.


----------



## n_maher

FWIW I've been using the heatsinks that amb sells for the beta22.


----------



## Hayduke

OK I think I have all the parts I need on the way. I deliberated far too long over the various parts, and finally just ordered pretty close to the original BOM and will try changes later 
	

	
	
		
		

		
		
	


	




 I do have one more question I didn't see answered. If it was, I'm sorry I missed it. I really did read through the thread!

 What gauge wire are you using for the point to point connections? I have some nice SPC from John's Wire Shop, but it might be too thin compared to the pictures I'm seeing.


----------



## n_maher

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_What gauge wire are you using for the point to point connections?_

 

I'm pretty sure that I used 24ga for everything in my build. It's been running for ~1000hrs or so now without a problem.


----------



## Hayduke

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_I'm pretty sure that I used 24ga for everything in my build. It's been running for ~1000hrs or so now without a problem._

 

hmmm mine is all 26 or smaller. I'm gonna go ahead and use it. If I feel wires getting hot, I'll run 2nd strands


----------



## bhjazz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Some days I wonder if it's worth trying to help. 
	

	
	
		
		

		
		
	


	


_

 

It's worth it...on my end. Nate, I appreciate your work on this. Personally, I had no idea these were getting so difficult to get! I'm in for a pair, and I don't care about the price!


----------



## n_maher

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_It's worth it...on my end. Nate, I appreciate your work on this. Personally, I had no idea these were getting so difficult to get! I'm in for a pair, and I don't care about the price! 




_

 

Thanks man, seems that most folks are in your camp. There's only 1 pair of tubes left at this point.


----------



## kuroguy

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Thanks man, seems that most folks are in your camp. There's only 1 pair of tubes left at this point._

 

Glad to hear that. I have 4 in my personal collection, but if nobody else wants the remaining 2 I'll take them. Gotta support the ones that contribute and I'd put you in the contributing category.


----------



## bhjazz

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_There's only 1 pair of tubes left at this point._

 

Nice! ...my comment about the price seems to go against the whole starving sub-thread, but I'd like to swap tubes for fun, and I already have a pair of Delcos.


----------



## luvdunhill

Nate, it's good to hear that you could move the tubes. For what it's worth, I've had great success with this vendor:

2-TUBES,RADIO,AUDIO,HAM,CB [NOS] 19J6 - eBay (item 360106558695 end time Dec-11-08 13:37:41 PST)

 I bet he has a few pairs squirreled away and he also offers sockets for $2 each.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Nate, it's good to hear that you could move the tubes. For what it's worth, I've had great success with this vendor:

2-TUBES,RADIO,AUDIO,HAM,CB [NOS] 19J6 - eBay (item 360106558695 end time Dec-11-08 13:37:41 PST)

 I bet he has a few pairs squirreled away and he also offers sockets for $2 each._

 

That's good to hear, I just bought up the stock of tubes he was offering on eBay.


----------



## bmwpowere36m3

How does this BOM look:


----------



## effcleff

I plan on using a similar BOM. Question though... What does item 21 (Tube LED) do? Provide a cool lighting effect for the tubes or something?


----------



## FallenAngel

I would assume that 21 does in fact provide a cool lite under the tube.

 Output cap voltage - 35V is too low, go with 50V minimum but recommended at least 63V. Muse FG in PSU performs worse than Nichicon HE.


----------



## -=Germania=-

I would bring up C6 to ~800uf to avoid hiccups.

 Hope you enjoy your SSMH!


----------



## FallenAngel

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I would bring up C6 to ~800uf to avoid hiccups.

 Hope you enjoy your SSMH!_

 

I thought with a low-power PSU like the 350mA stock Cisco, having big caps is the reason for the "hiccups".


----------



## n_maher

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I thought with a low-power PSU like the 350mA stock Cisco, having big caps is the reason for the "hiccups"._

 

I think it's a balancing act, to small a cap and the power supply sees the heaters as the load and can't keep up the cold start current demand, too big a cap and the inrush current to charge the cap exceeds the power supplies abilities. I've got a 680uF cap in my amp at work and definitely still get a little hiccup at the start. I may try backing that down to 470uF to see if that cures it, which is what has been reported to work by lots of other builders.


----------



## gurusan

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I would assume that 21 does in fact provide a cool lite under the tube.

 Output cap voltage - 35V is too low, go with 50V minimum but recommended at least 63V. Muse FG in PSU performs worse than Nichicon HE._

 

Why's this? The output caps only see 19V. 

 Reason I ask is I got a good deal on some 470uf 25V Nichicon Muse FS caps which I was planning on trying on the outputs.

 Also I had a few other questions. How do you properly calculate output cap size vs frequency dropoff? I am using HD 580s so that will be a 300ohm load.

 Also what do I need to consider when choosing bypass film caps? Do I even need them? I have Wima MKP10 .33uF and Audyn-CAP MKP .47uF on hand


----------



## error401

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Why's this? The output caps only see 19V._

 

Under normal conditions yes. However, if the tube or wiring fail, or there's a bit of discontinuity in the tube socket for whatever reason, the cap will see the full supply voltage. It's just good design practice. You can use the 35V cap, but it's not a good idea - always design for fault conditions.

  Quote:


  Originally Posted by *gurusan* 
_Also I had a few other questions. How do you properly calculate output cap size vs frequency dropoff? I am using HD 580s so that will be a 300ohm load._

 

-3dB point will be ~= 1/(2πRC)


----------



## sacd lover

nevermind ...


----------



## bmwpowere36m3

Quote:


  Originally Posted by *effcleff* /img/forum/go_quote.gif 
_I plan on using a similar BOM. Question though... What does item 21 (Tube LED) do? Provide a cool lighting effect for the tubes or something?_

 

Yes, LEd for lighting the tube.

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I would bring up C6 to ~800uf to avoid hiccups.

 Hope you enjoy your SSMH!_

 

From what I read, 470uF seems to be the balancing point. So we'll see, maybe there's something wrong with your PS or your tubes are drawing more than others.

  Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Under normal conditions yes. However, if the tube or wiring fail, or there's a bit of discontinuity in the tube socket for whatever reason, the cap will see the full supply voltage. It's just good design practice. You can use the 35V cap, but it's not a good idea - always design for fault conditions.


 -3dB point will be ~= 1/(2πRC)_

 

I was under the impression that if the mosfet's failed you'd see half the supply voltage on each channel (~25V). I dunno, maybe if you shorted something...? If it's really that important, where's a source for 50+V 470uf Muse ES's?

  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I would assume that 21 does in fact provide a cool lite under the tube.

 Output cap voltage - 35V is too low, go with 50V minimum but recommended at least 63V. Muse FG in PSU performs worse than Nichicon HE._

 

Yup, tube light. I need to find a source for the Muse's now. Oh, I just like to thank *FallenAngel* who's offered me some words of wisdom and helped me secure some build stuff. 
	

	
	
		
		

		
			





 Thanks Pavel.


----------



## error401

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_I was under the impression that if the mosfet's failed you'd see half the supply voltage on each channel (~25V). I dunno, maybe if you shorted something...? If it's really that important, where's a source for 50+V 470uf Muse ES's?_

 

The cap is connected to +48V through the MOSFET, which can conduct that 48V directly across the cap. The cap could then conceivably fail short and apply 48V unimpeded to your cans, hurting your ears and probably causing irreparable damage to the connected headphones. This would require a pretty serious circuit failure and some bad luck, but it would suck to lose your headphones too as a result of using an under-spec part.

 Muse ES is not available in this value, the largest 50V is 330uF. I would put two 1000uF 35V in series if you really must have this capacitor type. You don't need a bipolar here though due to the DC bias so it would make more sense to use Muse KZ or Muse FG here if you want semi-boutique caps. I used 820uF Panasonic FC with no bypass and I still think the amp sounds great, FWIW.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_The cap is connected to +48V through the MOSFET, which can conduct that 48V directly across the cap. The cap could then conceivably fail short and apply 48V unimpeded to your cans, hurting your ears and probably causing irreparable damage to the connected headphones. This would require a pretty serious circuit failure and some bad luck, but it would suck to lose your headphones too as a result of using an under-spec part.

 Muse ES is not available in this value, the largest 50V is 330uF. I would put two 1000uF 35V in series if you really must have this capacitor type. You don't need a bipolar here though due to the DC bias so it would make more sense to use Muse KZ or Muse FG here if you want semi-boutique caps. I used 820uF Panasonic FC with no bypass and I still think the amp sounds great, FWIW._

 

Thanks, how about Cerafine's for output coupling.


----------



## error401

Cerafines would work well and are available in 470uF/63V.


----------



## bmwpowere36m3

nm...


----------



## Hayduke

That switch looks nice. I was looking for a round illuminated switch, but I was trying to stay with the "starving student" philosophy and they were a little too spendy. I'm planning to build a second MHSS with higher end parts after I finish the first one. I might use this switch, but I was hoping to find a black one.

 And yes, AFAIK, that should work just fine.


----------



## JamesL

Has anyone done alright with a 1" tall heat sink(657-10ABP)?
 It's rated 3.7°C/W, whatever that translates to, and it'll be mounted on top of the case. 
 I don't want to mount it all up, just to have to disassemble it again. =/
 Otherwise, I could just make another mouser trip.


----------



## mattcalf

Planning to build this to go along with my Bantam for when I get new headphones..

 I'm rather new to all this so are there any worthy upgrades from the BOM in the opening post. I don't want to spend too much more but if there are some benefits that are to bed had I'd love to know about them.

 Cheers. =]


----------



## Hayduke

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_Planning to build this to go along with my Bantam for when I get new headphones..

 I'm rather new to all this so are there any worthy upgrades from the BOM in the opening post. I don't want to spend too much more but if there are some benefits that are to bed had I'd love to know about them.

 Cheers. =]_

 

I'm not brand new, but I'm no where near an expert. That being said, I would recommend you just build the original BOM to start. Since it's point to point, it won't be hard to make changes later to try upgraded components. About the only thing you will want to consider changing are the capacitors. What changes to make has been the subject of much debate. Read through the thread, and you will get a sense of what has worked for most folks. You can quickly get into considerations of using a film cap and an electrolytic in parallel and changing values etc. The one thing everyone has agreed on is use at least 50V caps, but most are using 63V (myself included).


 I got my tubes yesterday 
	

	
	
		
		

		
		
	


	



 They are all the same brand, so I'm hoping that means they "match". I bought 6 so I can make 2 amps for myself (home and work) and have spares. I have a friend I know is going to ask me to build him one though 
	

	
	
		
		

		
		
	


	



 Unfortunately I won't be getting my order from Mouser until Monday. I was hoping to get this thing built this weekend. 
	

	
	
		
		

		
		
	


	




 Oh well, more time to look around for an interesting case. 
	

	
	
		
		

		
		
	


	




 I have a small tin that a multi tool came in that I think I will use. It is only about 1 in tall though, so I'm not 100% I can make everything fit. I think it will be fine, but I won't know until I get the rest of the parts and can test some layouts.


----------



## -=Germania=-

Hayduke, 

 Good point. 

 The first build was definitely a learning experience and was my first PTP project (previously doing PCB's and some simple CMoys on protoboard). Also, get a nicer potentiometer for about $10 or so (conductive plastic, stepped from china, etc.). My first build used the BOM potentiometer and it was faulty. I ordered 3 more when I had to get some other things from mouser for a class and 1 of the 3 had tracking issues - others were fine. Maybe I had bad luck, but just sharing my experience with the alpha pot. Plus, nicer pot usually means better sound or at least that is my experience. YMMV


----------



## mattcalf

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I'm not brand new, but I'm no where near an expert. That being said, I would recommend you just build the original BOM to start. Since it's point to point, it won't be hard to make changes later to try upgraded components. About the only thing you will want to consider changing are the capacitors. What changes to make has been the subject of much debate. Read through the thread, and you will get a sense of what has worked for most folks. You can quickly get into considerations of using a film cap and an electrolytic in parallel and changing values etc. The one thing everyone has agreed on is use at least 50V caps, but most are using 63V (myself included).


 I got my tubes yesterday 
	

	
	
		
		

		
		
	


	



 They are all the same brand, so I'm hoping that means they "match". I bought 6 so I can make 2 amps for myself (home and work) and have spares. I have a friend I know is going to ask me to build him one though 
	

	
	
		
		

		
		
	


	



 Unfortunately I won't be getting my order from Mouser until Monday. I was hoping to get this thing built this weekend. 
	

	
	
		
		

		
		
	


	




 Oh well, more time to look around for an interesting case. 
	

	
	
		
		

		
		
	


	




 I have a small tin that a multi tool came in that I think I will use. It is only about 1 in tall though, so I'm not 100% I can make everything fit. I think it will be fine, but I won't know until I get the rest of the parts and can test some layouts._

 

Ok thanks. That sounds good. 
 I've been in contact with Radiodaze and they're out of the tubes unfortunately. I'm in no hurry to build though. I'll wait till the holidays and if they don't have any back in stock i'll just look elsewhere.


----------



## Hayduke

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Hayduke, 

 Good point. 

 The first build was definitely a learning experience and was my first PTP project (previously doing PCB's and some simple CMoys on protoboard). Also, get a nicer potentiometer for about $10 or so (conductive plastic, stepped from china, etc.). My first build used the BOM potentiometer and it was faulty. I ordered 3 more when I had to get some other things from mouser for a class and 1 of the 3 had tracking issues - others were fine. Maybe I had bad luck, but just sharing my experience with the alpha pot. Plus, nicer pot usually means better sound or at least that is my experience. YMMV_

 

yep, the pot is definitely a component that could be improved upon. I was going to use an Alps pot, but again, I tried to stay in the starving student" philosophy for the first one. The second will be a "no longer a starving student" version 

  Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_Ok thanks. That sounds good. 
 I've been in contact with Radiodaze and they're out of the tubes unfortunately. I'm in no hurry to build though. I'll wait till the holidays and if they don't have any back in stock i'll just look elsewhere._

 

I got mine here:
Audio Tubes - Vacuum Tubes - ESRC Vacuum Tubes


----------



## -=Germania=-

Premium build of this amp IMO is a fantastic deal. There are not many parts, so going premium is cheap and easy. 

 If you can find one of the Noble Pots for ~$25, grab them immediately! Otherwise I guess that alps blue is fine or one of those stepped ones from china.


----------



## mattcalf

From what I can tell a pot is the volume control?

 Does this look alright?


----------



## Zigis

mattcalf, this is not pot, just knob 
	

	
	
		
		

		
			





 For volume control you need log pot or audio pot.


----------



## -=Germania=-

Premium build of this amp IMO is a fantastic deal. There are not many parts, so going premium is cheap and easy. 

 If you can find one of the Noble Pots for ~$25, grab them immediately! Otherwise I guess that alps blue is fine or one of those stepped ones from china.


----------



## Hayduke

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_From what I can tell a pot is the volume control?

 Does this look alright?_

 

When we talk about a "pot", it's short for potentiometer or another way to think of it is a variable resistor. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Premium build of this amp IMO is a fantastic deal. There are not many parts, so going premium is cheap and easy. 

 If you can find one of the Noble Pots for ~$25, grab them immediately! Otherwise I guess that alps blue is fine or one of those stepped ones from china._

 

Noble pots don't seem to be all that readily available online. Can't find any websites that list a price for one. Some of us don't live near a major urban center and can actually drive somewhere to get parts. If I can't order it, I can't get it. 
	

	
	
		
		

		
		
	


	




 and btw, did something weird happen? You posted that twice


----------



## -=Germania=-

Yeah - I am pretty sure that I only typed that once....its the matrix all over again.


----------



## mattcalf

Ok ill just stick with the OPs BOM. 
	

	
	
		
		

		
		
	


	




 I can get 4 bulbs and 4 connectors for US$30 posted to Australia... Is that a good deal?


----------



## JamesL

4 tubes and 4 sockets?
 I would say so.


----------



## J.P.6

Sounds good, what shop are they from?


----------



## ARwCoco

After reading this entire thread @ ~ 20 pages per night, I decided I needed to build one of these. Went to my local surplus store/joint (LSS) and did manage to snag the following parts. A nice all AL black case ID 7x4-3/8x
 1-5/8", 4 Rubycon 63v 470uf caps, 30k dual pot stamped 6811A1 Japan,
 W30k NOBLE 212-001, pair of used ceramic top and a pair of new cream colored base marked N in a circle 7-pin tube sockets, pair of 3.5mm plastic stereo jacks, panel mount 5-pin 15mmx11mmx7mm. Total spent on the above parts $7.50


----------



## Zigis

Hayduke;4992589 said:
			
		

> When we talk about a "pot", it's short for potentiometer or another way to think of it is a variable resistor.
> 
> 
> 
> ...


----------



## mattcalf

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_Sounds good, what shop are they from?_

 

esrcvacuumtubes.com


----------



## J.P.6

That's weird, same site place as Orlando Vacuum Tubes

 Where I ordered mine from. Anyone had experience with the above guys by the way?


----------



## tomb

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_That's weird, same site place as Orlando Vacuum Tubes

 Where I ordered mine from. Anyone had experience with the above guys by the way?_

 

The Tube Center is definitely legit. Their parent company name is ESRC.


----------



## J.P.6

Good to hear. These tubes are nothing but trouble, have had none turn up from that bloke on eBay after two and a half weeks most other places are sold out or charge over the top for shipping to the UK. 

 The Tube Center have been very helpful and reasonable with their prices. Hopefully these ones will turn up.


----------



## -=Germania=-

If anyone has some spare or is interested in trading these tubes....

 I am very interested in buy or trading for Raytheon and Sylvania Top square getters as well as any RCA Halo Getters. I have most variations on the design and would be interested in trading. They are listed in the Millet SS tube thread. PM me.


----------



## digger945

^Did you see the ones that n_maher had FS a couple of days ago?
 They are gone now, I got two pairs from him(19J6), I will post pics when I get them.
 I don't know square getter, O getter, top getter. I don't even know what a getter is


----------



## -=Germania=-

n-mahler was making those available for people who can't get a hold of these tubes in the first place. I have enough tubes to operate for a while and it would be wrong of me to try and get those. I might have some pairs, but I want to get some more tubes of certain styles before I think of selling them. 

 Currently I have: 
 2 RCA top Square Getter
 2 Sylvania top Square Getter
 2 Sylvania side D-Getter
 5 RCA side D-Getter (2 are being used by my roommate for my first build of the amp)
 2 RCA Top D Getter
 1 RCA Halo Getter (circle) 

 I would like to buy more of the Top Square Getter, 1 more Sylvania side D Getter, and 2 more RCA Halo Getter. I might be willing to trade Sylvania Side D Getter for top getters and Top D-Getter for RCA Halo Getters. My goal is triads of the types. 

 If I can't find triads, I might sell some, but I want to try and make some more sets though. 
 Please PM me if you have some or would be interested in a trade.


----------



## Hayduke

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_n-mahler was making those available for people who can't get a hold of these tubes in the first place. I have enough tubes to operate for a while and it would be wrong of me to try and get those. I might have some pairs, but I want to get some more tubes of certain styles before I think of selling them. 

 Currently I have: 
 2 RCA top Square Getter
 2 Sylvania top Square Getter
 2 Sylvania side D-Getter
 5 RCA side D-Getter (2 are being used by my roommate for my first build of the amp)
 2 RCA Top D Getter
 1 RCA Halo Getter (circle) 

 I would like to buy more of the Top Square Getter, 1 more Sylvania side D Getter, and 2 more RCA Halo Getter. I might be willing to trade Sylvania Side D Getter for top getters and Top D-Getter for RCA Halo Getters. My goal is triads of the types. 

 If I can't find triads, I might sell some, but I want to try and make some more sets though. 
 Please PM me if you have some or would be interested in a trade._

 

hmmmm... Do you notice a difference between different tubes?

 I wouldn't be surprised if you did, and I'm actually concerned that the brand/model of tube will have an impact on the SQ of the amp. The ones I have are "Pro/Comm Industrial Grade Electron Tubes". All the boxes are in remarkably good shape considering these haven't been manufactured in awhile, but my first thought was, "I wonder how these will sound compared to some RCAs?" 
	

	
	
		
		

		
			





 You might make me go on the hunt for other brands. I wish I had bought some of the ones Nate was selling. He posted the sale right after I had bought mine, but before I got them. When I got mine, Nate's were gone 
	

	
	
		
		

		
		
	


	




 Maybe I'll call around this week and see what I can scrounge up.


----------



## n_maher

In all of the tubes that I've seen the general plate structure appears to be the same so I'd be surprised if there are large differences between different getter locations and shapes. I'm not saying there aren't any, but from what I've seen this appears to be one of those situations where different brands aren't very different. And I've got Slyvania, GE, Zenith, RCA and a couple other types of 19J6s and they all appear very similar other than the getter.


----------



## Hayduke

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_In all of the tubes that I've seen the general plate structure appears to be the same so I'd be surprised if there are large differences between different getter locations and shapes. I'm not saying there aren't any, but from what I've seen this appears to be one of those situations where different brands aren't very different. And I've got Slyvania, GE, Zenith, RCA and a couple other types of 19J6s and they all appear very similar other than the getter._

 

Well that's reassuring. Thanks 
	

	
	
		
		

		
		
	


	




 So you can't hear any difference between your different tubes?

 I'll take some macro shots of my tubes and post them. Since I haven't seen any of the others, maybe someone else will tell me if they look significantly different.


----------



## gurusan

Well I have a pair of Sylvanias and a pair of DuMonts. The Dumonts seem to sound a bit more full and warm, while the sylvanias seem to be a bit more accurate...particularly up high.

 Personally, I prefer the DuMonts but I burnt out 1 tube on accident, so am waiting until another comes in.

 Here are some comparison pics. Dumont on the left:


----------



## Kabeer

Just completed my build today! My first (and probably last lol) DIY build.
 Sounds great. Had a bit of a scare when only one channel worked, but it was just a resistor that worked itself loose.
 The knob is a Fender amp knob 
	

	
	
		
		

		
		
	


	




.

 Uses Cerafine caps, Wima film caps and small wima bypass caps. 

 Btw the tubes I have arent exactly the same (even though the box was the same, hope thats not an issue)
 Photos (Click for larger versions):
















 Thanks to Ludo for the help 
	

	
	
		
		

		
		
	


	




.


----------



## Kabeer

Actually, I might need help. Im getting a bit of light humming which stops when I touch the case, or a input jack metal barrel.

 Any ideas what to do?

 EDIT: DUnno if this is relavant but the humming exists when the amp switch is off as well, and the PSU is still plugged in.
 Edit again: lol no it doesnt hapen with the switch off, I think it was just some charge that was retained).

 Humming is mostly only on the left channel, and when i touch the case the humming goes away but a small bit remains. What sould I check exactly for grounding problems?


----------



## rhys h

You have some sort of grounding problem


----------



## n_maher

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_So you can't hear any difference between your different tubes?_

 

I haven't tried and probably won't. It seems somewhat crazy to me (and this, from a crazy person) to endlessly chase better sound through tube rolling on an amp that only permits the use of one kind of tube that appears to be on the rarer side of things. I'd rather enjoy what I have and when those fail throw in the next set and continue to enjoy it. If I saw some sort of significant construction difference I might give it a shot but with just variable getter placement I'm doubtful.

 I fully encourage others to do whatever they want though.


----------



## Hayduke

Thanks again Nate

 I was starting to think the same thing after I posted. My time would probably be better spent making a different amp then looking around for different tubes 
	

	
	
		
		

		
		
	


	




 I got the rest of my parts today, so I'll build mine tonight after work. I have a case I think should work, but it will be a tight fit. Now that I've seen the parts though, I'm convinced I can make them all fit inside.

 I know I asked this earlier, but this question is subtly different 
	

	
	
		
		

		
		
	


	




 Do you think my 26g SPC wire is big enough, or should I just wire up 2 pieces for each connection right from the start? I was originally planning to wire it up and wait to see if they get hot, but if you think 26g is too small, then I'll just double it up on the first go. If I'm going to have to do it later, I don't want to have to do all the work twice 
	

	
	
		
		

		
		
	


	




 I'm so excited to hear a tube amp finally!


----------



## Kabeer

Ok an update on my humming issue, I do still have a grounding problem, but that is so minor I wont bother with it.

 The source of the humming I was hearing is the tubes. How do I know? 
 Well I have 3x tubes, one has no humming, and the other two hum.
 Also tested by switching the good and humming tube around, and like expected the humming noise switched channels too.





 The tube in the middle is the one thats quietest (humming wise). 
 Notice the other two seem to have this 'grey film' on their two metal plates.

 I tried sanding down the legs of one of the humming tubes, but the problem is still there.

 Does anyone have a tube like the one in the middle they are willing to sell me? (ie: shiny metal plates without grey film).

 I think my amp is a bit sensitive and needs the shiny tube.

 Thanks.


----------



## dsavitsk

Quote:


  Originally Posted by *Kabeer* /img/forum/go_quote.gif 
_Ok an update on my humming issue, I do still have a grounding problem, but that is so minor I wont bother with it.

 The source of the humming I was hearing is the tubes._

 

Make a tube out of aluminum foil and wrap the tube in it (it should touch the tube) and make sure it is grounded -- touch it to the socket screw and make sure the screw is grounded under the chassis. See if that doesn't help. If it does, buy some shielded sockets.


----------



## mattcalf

Sorry for the nubby question.

 But what are the advantages of a ground plane and what do you do with them?

 e.g. this vs. this.

 Thanks in advance.


----------



## jduff

In the original BOM I'm curious about the RCA jacks, are they the kind that are insulated from the chassis? I'm guessing that they're not as Pete used a copper plate.

 I'm trying to beat any grounding problems before I order the parts. 

 Thanks.


----------



## -=Germania=-

Signal wires - 26awg is fine. 
 You might want to double up on the power connections though


----------



## Hayduke

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_Sorry for the nubby question.

 But what are the advantages of a ground plane and what do you do with them?

 e.g. this vs. this.

 Thanks in advance._

 

I think the first one was to account for a plastic case perhaps? The second wasn't needed because the case is metal. Just a theory based on the pictures.

  Quote:


  Originally Posted by *jduff* /img/forum/go_quote.gif 
_In the original BOM I'm curious about the RCA jacks, are they the kind that are insulated from the chassis? I'm guessing that they're not as Pete used a copper plate.

 I'm trying to beat any grounding problems before I order the parts. 

 Thanks._

 

I used the BOM jacks and they are definitely grounded to the chassis.

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Signal wires - 26awg is fine. 
 You might want to double up on the power connections though_

 

Thanks. That makes sense. I was thinking if 26 is good enough for the headphones, then it out to be good enough inside the amp, but I agree the circuit near the power supply should be beefier.

 I started with the case work. I got everything mounted (except the caps and resisitors since they don't "mount"), so now I'm ready to wire it all up.

 I got another question though. How did everyone mount the heatsinks? I was considering using the hot glue gun, but they get so hot it might melt. I thought about soldering them to my metal case, but I'm not 100% sure that will work. My heatsinks have pins and I made the holes pretty close fitting. They just aren't tight enough to hold them down with just friction. From everyone's pictures, it looks like most people soldered them. is it OK to have them grounded to the case?


----------



## error401

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I got another question though. How did everyone mount the heatsinks? I was considering using the hot glue gun, but they get so hot it might melt. I thought about soldering them to my metal case, but I'm not 100% sure that will work. My heatsinks have pins and I made the holes pretty close fitting. They just aren't tight enough to hold them down with just friction. From everyone's pictures, it looks like most people soldered them. is it OK to have them grounded to the case?_

 

If you're so equipped, remove the pins (easier said than done) and tap the holes. I used a 4-40 tap and 1/4" machine screws, but I also managed to break a pin off in the channel, so I've only got 3 screws for 2 heatsinks 
	

	
	
		
		

		
			





. There are some suggestions in this thread (and others) for how to remove the pins; I just tried to pry them out with vise grips because I'm lazy.

 If you're going the groundplane route I'd just solder them to the groundplane pressed tight against the case.


----------



## rds

Quote:


 I got another question though. How did everyone mount the heatsinks? I was considering using the hot glue gun, but they get so hot it might melt. I thought about soldering them to my metal case, but I'm not 100% sure that will work. My heatsinks have pins and I made the holes pretty close fitting. 
 

You could get 4 small washers, tin them with solder and then solder them to the pins so they sit against the inside of the case.


----------



## -=Germania=-

rds/Hayduke

 I have the washers way on my case and it works great.
 At any rate, grounding the case is a good idea and if you attach the heatshinks directly to the case, you get instant grounded heatsinks! (you might want a ground break loop though)

 Or you could fix it with some Windex
 'Dere you go!


----------



## Hayduke

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_rds/Hayduke

 I have the washers way on my case and it works great.
 At any rate, grounding the case is a good idea and if you attach the heatshinks directly to the case, you get instant grounded heatsinks! (you might want a ground break loop though)

 Or you could fix it with some Windex
 'Dere you go!



_

 

LOL
 I love that movie 
	

	
	
		
		

		
		
	


	





 I was planning to skip using the PCB--even though I ordered one--since I am using a metal case, but I went ahead and mounted a piece under the heatsinks and sockets. I got the pins to solder to it fine, and I'm kinda glad I did it this way so I can use it as a ground plane. It should make some of the wiring easier.

 I'm still not going to use the terminal blocks though. I don't see any real benefit. Also, my case is pretty small, so I'm not sure I can spare the space.

 Could someone explain what the purpose of C1 and C6? I understand they help to regulate the power being fed into the rest of the circuit, but why are there 2 of them separated by a resistor (R13)?

 Well I got a lot done on my build tonight, but it's way late and I have to work in the AM. I'll finish the wiring tomorrow. I was really hoping to hear the amp tonight 
	

	
	
		
		

		
		
	


	




 I want to say thanks again to Pete and the folks on this thread. This is exactly why I love this community to much


----------



## Coreyk78

With my wood case I just mounted the heatsinks to my case using some liquid nails adhesive. Been working like a charm for me, very secure, I'm pretty sure if I tried removing the sinks they would probably take some wood with them. I just drilled some small holes for the pins and put the adhesive on the pins and the bottom edge of the sinks.
 Some kind of epoxy would probably work well for plastic or metal cases.


----------



## holland

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Could someone explain what the purpose of C1 and C6? I understand they help to regulate the power being fed into the rest of the circuit, but why are there 2 of them separated by a resistor (R13)?_

 

They don't regulate. They filter. It's a CRC filter.

 The first C, C1, smooths the DC coming in to reduce ripple. This is used to feed the mosfets and the valve circuitry. The RC for the valve, form a low-pass filter. The RC in the stock schematic forms a corner frequency of about 0.5Hz. This reduces noise after C1. The reason why it's only on the valve (tube) side is because of the current draw. Putting it on the mosfet side would reduce voltage too much. The tubes draw a handful of mA, so the voltage drop is negligible.

 There is additional functionality as well. C1 filters to smooth the DC, but it also serves as a reservoir for the DC. C6 handles the pulse currents, and the voltage fluctuates across R as the passed ripple from C1 is fed into C6. I don't think there is much for the valve side. In any event, a bypass of C6 with a faster film cap wouldn't be unwise.

 Increasing C6 lowers the corner frequency even further. It also causes the bias on the fets to increase slower, so if you have PS hiccups, C6 is where you can hit it if your stock PS stutters on start. You can go quite large with C6. 1000uF or larger with no adverse effects. I wouldn't go nuts, such as 10,000uF for example.


----------



## Hayduke

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_They don't regulate. They filter. It's a CRC filter.

 The first C, C1, smooths the DC coming in to reduce ripple. This is used to feed the mosfets and the valve circuitry. The RC for the valve, form a low-pass filter. The RC in the stock schematic forms a corner frequency of about 0.5Hz. This reduces noise after C1. The reason why it's only on the valve (tube) side is because of the current draw. Putting it on the mosfet side would reduce voltage too much. The tubes draw a handful of mA, so the voltage drop is negligible.

 There is additional functionality as well. C1 filters to smooth the DC, but it also serves as a reservoir for the DC. C6 handles the pulse currents, and the voltage fluctuates across R as the passed ripple from C1 is fed into C6. I don't think there is much for the valve side. In any event, a bypass of C6 with a faster film cap wouldn't be unwise.

 Increasing C6 lowers the corner frequency even further. It also causes the bias on the fets to increase slower, so if you have PS hiccups, C6 is where you can hit it if your stock PS stutters on start. You can go quite large with C6. 1000uF or larger with no adverse effects. I wouldn't go nuts, such as 10,000uF for example._

 

Thanks Holland

 I knew regulate wasn't the right word. I guess I think of the caps as more like current buffers. I was thinking buffer, but said regulate. It was late 

 OK I understand now why they are arranged that way. It's smoothing out the current for the tubes and the MOSFETS.

 I'm using 470uf 100V caps for C1, C3, C5, and C6. I got 0.22 uf 100V for C2 and C4. In hindsight I might have liked some film caps to bypass the electrolytics, but when I ordered my parts, I had decided to build this first one pretty close to the original design. When I order parts for the second amp (I want one for home and work), I'll probably order some parts to swap out on this one. I'll add some film caps at the very least.

 Thanks again


----------



## Hayduke

It's Alive!!!!!
	

	
	
		
		

		
		
	


	




 Thanks to everyone here and especially Pete for sharing his design. 
	

	
	
		
		

		
		
	


	




 I only made one mistake wiring everything up, but I found it easy enough. This circuit isn't too complex, so it was easy. I had no left channel. I had wired the connection between C3 and pin 3 on the socket to pin 4. Oops! I was pretty pleased with myself that I could find it without referring to the schematic. I saw it and thought, "wait a sec, that shouldn't be going to ground." So THEN I got out the schematic again to look, and I was right.


 I did make an unpleasant discovery though. I ordered 6 tubes, and they aren't all the same. It looks like they just stuck 6 tubes all in the same boxes, so I thought they were all the same. I only pulled out one to look at before tonight. I have 1 RCA and 1 GE for sure. The rest I'm unsure about. They are all pretty similar construction, so I just picked 2 that looked the most alike. They also have a fair amount of oxidation on the pins. I suspect this is normal if they are old. I just hope they aren't used.

 Oh well I'm just gonna enjoy the new amp. It sounds great. Chock full of tubey goodness 
	

	
	
		
		

		
		
	


	




 The next step is to improve my source.


----------



## Hayduke

OK, picture time 
	

	
	
		
		

		
		
	


	




 I used a metal box that a small Gerber multi tool came in. It is really shallow, so I couldn't mount anything on the side. It actually worked out very well. I mounted everything on top.





 Front view





 From the back





 The RCAs aren't connected ATM. My sources use 3.5mm so I didn't want to risk introducing any noise. When I get a source that needs the RCAs, it will be easy enough to wire them in. You will see this in the pic below.

 Inside shot of my messy wiring.


----------



## rds

very nice!


----------



## mattcalf

Loooks awesome!!!

 I bought a soldering iron yesterday and just ordered the power adapters. And I plan to get my hands (virtually) on the tubes in the next day or so.

 I plan on building two amps, hopefully a mate is going to buy the second one. Can't wait to get it done. 
	

	
	
		
		

		
		
	


	




*EDIT*: hayduke, im curious as to how you grounded yours?


----------



## ARwCoco

The Cisco power supply has a plug. 
 Any downside to cutting the plug off and just hard wire to my power switch ?


----------



## Hayduke

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_Loooks awesome!!!

 I bought a soldering iron yesterday and just ordered the power adapters. And I plan to get my hands (virtually) on the tubes in the next day or so.

 I plan on building two amps, hopefully a mate is going to buy the second one. Can't wait to get it done. 
	

	
	
		
		

		
		
	


	




*EDIT*: hayduke, im curious as to how you grounded yours?_

 

Grounded what? I used a piece of copper clad board, per the BOM, as a ground plane. You can see it in the wiring shot. Basically, I soldered the heatsinks to it, then used those solder blobs to attach all my ground connections. Is that what you meant?

  Quote:


  Originally Posted by *ARwCoco* /img/forum/go_quote.gif 
_The Cisco power supply has a plug. 
 Any downside to cutting the plug off and just hard wire to my power switch ?



_

 

I would ask what the benefit of hard wiring it would be?
 The advantage of using the plug would be the ability to swap out the power supply, so I guess the downside to hardwiring it would be the lack of that flexibility.

 These supplies aren't bad. I don't hear anything normally, but at work, I built a little switchbox to switch between my telephone and my music. When I route the signal from the amp through this, I hear noise. It's there if the amp is connected even while turned off. I'm sure it's coming from the power supply. It's a minor issue, but you could surely improve on the Cisco power supplies.


----------



## -=Germania=-

^ Yep. 

 Put a 220-470uf 90V+ capacitor across the power (The higher voltage rating is just as a precaution) and that should calm down quite a bit of noise. Plus, give you a bit more low bass. 

 Cheers!


----------



## Logistic

Quick question, I ordered the therafilm transistor mounting kit. Does that mean I need some thermal grease or can I get away with just attaching the mosfet to the heatsink?

 Thanks.


----------



## Hayduke

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_^ Yep. 

 Put a 220-470uf 90V+ capacitor across the power (The higher voltage rating is just as a precaution) and that should calm down quite a bit of noise. Plus, give you a bit more low bass. 

 Cheers!_

 

Thanks Germania

 I brought this one to work today, and everyone I've let demo it is pretty impressed. Plus I think it looks nice 
	

	
	
		
		

		
			





 I'm already starting to build my BOM for my next amp (need one I can leave at work instead of carting it back and forth). I'll be ordering some extra caps, including some films to wire in parallel to the electrolytics. Do you have any preferences? I'm thinking about ordering some from Soniccraft since I want some blackgates anyway. 

  Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Quick question, I ordered the therafilm transistor mounting kit. Does that mean I need some thermal grease or can I get away with just attaching the mosfet to the heatsink?

 Thanks._

 

Order the item in the BOM and nothing else is needed. I found it worked very very well for mounting the mosfet to the heatsink.


----------



## Gross

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_OK, picture time 
	

	
	
		
		

		
		
	


	




 I used a metal box that a small Gerber multi tool... Blah Blah Blah, Pics, Pics, Pics_

 

Dude, I dig it. That is a real nice Low-Pro enclosure. Shiney too. 
	

	
	
		
		

		
		
	


	






 My next MHSS is in the works. Right now I am working on the power supply, I am planning on putting it in a NABU case.


----------



## kuroguy

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Order the item in the BOM and nothing else is needed. I found it worked very very well for mounting the mosfet to the heatsink._

 

That's just bad advice. Unless the mounting kit is specifically made for use without heatsink compound you should use use heatsink compound. The compound fills voids between the component package and the insulator and the insulator and the heatsink.


----------



## error401

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Order the item in the BOM and nothing else is needed. I found it worked very very well for mounting the mosfet to the heatsink._

 

The BOM part, Mouser 532-4880 includes a Kapton insulator that should be used with thermal grease. Substitute 532-4880_SG_ if you'd like a Thermalsil insulator that doesn't require grease, for a whopping $0.18 more.


----------



## -=Germania=-

Skip the BG's and get Elma Cerafine, cheaper and do a very fine job. From what others have said, Elma is a better choice for equipment which will be turned on and off whereas BG's are better of something is constantly left on. 

 At any rate check out the Obbligato Caps, great deal IMO!


----------



## Hayduke

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_That's just bad advice. Unless the mounting kit is specifically made for use without heatsink compound you should use use heatsink compound. The compound fills voids between the component package and the insulator and the insulator and the heatsink._

 

Excuse me, but do you know what you're talking about? No offense, but I don't think you have ordered the part number on the original BOM (532-4880). It comes with everything you need, and it does work very well. You DON'T want to use any compound with that item, and this has been stated elsewhere in the thread. Please don't criticize my advice unless you're sure I'm mistaken. In this case, I am correct.

  Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_The BOM part, Mouser 532-4880 includes a Kapton insulator that should be used with thermal grease. Substitute 532-4880SG if you'd like a Thermalsil insulator that doesn't require grease, for a whopping $0.18 more._

 

I think you got them confused. The item on the BOM, 532-4880, does not come with grease, nor do you want to use any. I believe the difference between 532-4880 and 532-4880SG is the material the insulator is made out of. The SG one uses mica. I think this is for use in applications involving higher voltages or currents where increased insulation is needed, but I might be mistaken on that part.

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Skip the BG's and get Elma Cerafine, cheaper and do a very fine job. From what others have said, Elma is a better choice for equipment which will be turned on and off whereas BG's are better of something is constantly left on. 

 At any rate check out the Obbligato Caps, great deal IMO!_

 

I want the BGs to build a LOD for a modded iPod. You're the first person I've heared that thought Elmas were better. I'm definitely going to look into getting some of Cerafine now, but I'm still going to order a few BGs before I can't get them anymore 
	

	
	
		
		

		
		
	


	




 Thanks for the recommendations.


----------



## error401

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I think you got them confused. The item on the BOM, 532-4880, does not come with grease, nor do you want to use any. I believe the difference between 532-4880 and 532-4880SG is the material the insulator is made out of. The SG one uses mica. I think this is for use in applications involving higher voltages or currents where increased insulation is needed, but I might be mistaken on that part._

 

Uhm...Thermalfilm is Kapton, a directly replacement for mica which absolutely requires thermal grease. Thermalsil is glass cloth soaked in silicon. 4880MG is the mica part.


----------



## kuroguy

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Excuse me, but do you know what you're talking about? ...._

 

Whatever. It's your amp. you'll know I was right when your MOSFETS overheat and stop working.


----------



## Hayduke

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Uhm...Thermalfilm is Kapton, a directly replacement for mica which absolutely requires thermal grease. Thermalsil is glass cloth soaked in silicon. 4880MG is the mica part._

 

Thanks for clarifying 
	

	
	
		
		

		
		
	


	




 You're saying the mica needs the grease, right? Not the Thermafilm, right?
 I looked at the datasheet you linked, and don't see anything that suggests the need for thermal grease for either though.

 Either way, I didn't use any grease with Mouser PN# 532-4880. It obviously electrically isolated the mosfet from the heatsink (the amp is working) and I think it's transferring heat pretty well. The heatsinks are pretty toasty 
	

	
	
		
		

		
		
	


	




 I guess I'll know for sure after a couple weeks if my mosfets die prematurely hehe

  Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Whatever. It's your amp. you'll know I was right when your MOSFETS overheat and stop working._

 

Could show me where it says I need the thermal grease?


----------



## n_maher

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Could show me where it says I need the thermal grease?_

 

Taken from amb's site, specifically the beta22 parts list.

  Quote:


  Originally Posted by *amb* 
_Heatsink thermal compound
 Not needed if using mounting kits with Thermalsil or Sil-Pad isolators._

 

By exclusion I take that to mean that if you're using either Thermafilm or Mica that it would be advisable to use thermal compound. And I trust Ti's advice. Regardless it's a better safe than sorry scenario, I don't think using it can do any harm regardless of isolation pad material. I sometimes use it just to help hold the pad in place during assembly.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Thanks for clarifying 
	

	
	
		
		

		
		
	


	




 You're saying the mica needs the grease, right? Not the Thermafilm, right?
 I looked at the datasheet you linked, and don't see anything that suggests the need for thermal grease for either though.

 Either way, I didn't use any grease with Mouser PN# 532-4880. It obviously electrically isolated the mosfet from the heatsink (the amp is working) and I think it's transferring heat pretty well. The heatsinks are pretty toasty 
	

	
	
		
		

		
		
	


	




 I guess I'll know for sure after a couple weeks if my mosfets die prematurely hehe



 Could show me where it says I need the thermal grease?_

 

Error401 is absolutely correct about the insulating materials. The thing is, you want the insulator to insulate electrically, but to conduct thermally. There is a big difference between grease with mica and/or Thermafilm vs. not. As he also stated, Thermasil is the only one that does not need it. However, it can be found under other trade names but these names are the ones that Aavid uses.

 This is all explained and referenced on a couple of the Millett MAX websites. This one is on the MOSFET-MAX site:
MOSFET-MAX Heat Sink Mounting
 Scroll down toward the bottom of the page and you will also find a link to Aavid's complete heat sink catalog. The different material insulators and the requirement for grease for mica and Thermafilm are clearly explained.

 Thermasil is a product that actually changes phase when heated - that's why it acts as if it already has grease.
	

	
	
		
		

		
		
	


	




 From Aavid:
 [size=x-small] Quote:


 Thermalsil™ III provides excellent thermal conductivity
 and electrical resistance. It is used as an electrically-isolating
 interface material composed of silicone elastomer
 binder with a thermally conductive filler. It is reinforced
 with glass cloth to resist tearing and cut-through due to
 burrs on transistors or heat sinks.
 Thermalsil™ III eliminates the need for grease application
 and conforms to mounting surfaces under clamping pressure
 for optimum heat conduction.The finely woven glass
 cloth provides the thinnest possible matrix for enhanced
 thermal resistance.Thermalsil™ III is available in any configuration
 with adhesive backing.
 Mica insulators provide high maximum operating temperatures
 (550°C) and excellent electrical properties. 
 

[/size]


----------



## TimJo

Thanks n_maher and tomb for jumping in there...

 I was hoping some long-time posters would weigh in. I'm still feeling like a bit of a newbie to want to get into the middle of that one...


----------



## kuroguy

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Excuse me, but do you know what you're talking about? ....
 You DON'T want to use any compound with that item, and this has been stated elsewhere in the thread. Please don't criticize my advice unless you're sure I'm mistaken. In this case, I am correct._

 


 I apologize. you were right. I stand corrected. Wait. I was right. you stand corrected. Apology accepted.


----------



## tomb

More:
 I use the Bergquist pads in Beezar's heat sink kits. These are also sold at DigiKey (BER167-ND). Bergquist calls their pads "Hi-Flow 115-AC". Real catchy name, huh?
	

	
	
		
		

		
		
	


	




 Here's what they say:
 [size=x-small] Quote:


 Bergquist Hi-Flow 115-AC is a thermally conductive fiber reinforced phase change material. The product consists of a thermally conductive 65deg. C. phase change compound coated on a fiberglass web, and an adhesive coating on one side for attachment to a cold heat sink. There is no need to preheat the heat sink to apply the Hi-Flow 115-AC.
 ...
 Hi-Flow 115-AC handles like a Sil Pad at room temperature and flows like high-quality grease at elevated temperatures. 
 

[/size]

 One might ask, "Why still sell the other kind of pads?" There are advantages and drawbacks for each. I think the sil-pads/Bergquist pads are ideal for the stuff we do with heat sinks - low voltage and relatively low heat: no grease to worry about and a stick-on back. However, Dsavitsk reported that the Bergquist pads in my heat sink kits were not enough for the high-voltage tube stuff he often works with (200-300V!). Something like a Thermafilm pad can offer a higher dielectric strength. Also, mica can stand up to super-hot temperatures (a thousand degrees F.!). So, there are reasons to use each one.


----------



## error401

Yea, thanks for jumping in while I was at work 
	

	
	
		
		

		
			





.

 Kapton and Mica both have significantly lower thermal resistance _and_ usually higher electrical resistance than the silicon-based products - both desirable properties in such an insulator. Thermalsil and similar products are not as good at doing their job, but they're a lot more convenient and can be more reliable since there are less variables involved. They also make products more conducive to automated assembly. I believe the reason grease is required with mica/thermalfilm is that these materials are quite uncompressible, so pressure won't deform them to fill microscopic voids - this can significantly reduce the surface contact area.

 Whenever you're looking at a product like this, the safe assumption to make is that thermal grease is required, not requiring it is a major feature and it'll be mentioned for sure.
  Quote:


  Originally Posted by *n_maher* 
_Regardless it's a better safe than sorry scenario, I don't think using it can do any harm regardless of isolation pad material. I sometimes use it just to help hold the pad in place during assembly._

 

Definitely better to err on the side of using grease if you're unsure, but it will still increase the thermal resistance of the insulator. If the insulator doesn't require it, you're adding an extra interface (two, actually) and thus some thermal resistance - though probably not much, it's not optimal, especially since no-grease insulators are inherently less efficient.

 Most if this is explained in much depth by Rod Elliott in his heatsink guide.


----------



## Kabeer

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Taken from amb's site, specifically the beta22 parts list.

 By exclusion I take that to mean that if you're using either Thermafilm or Mica that it would be advisable to use thermal compound. And I trust Ti's advice. Regardless it's a better safe than sorry scenario, I don't think using it can do any harm regardless of isolation pad material. I sometimes use it just to help hold the pad in place during assembly._

 

Ok, Im using the thermalloy (yellowy orange plastic film).

 Do I need to use special thermal grease? Or can I just use something like Vaseline?


----------



## JamesL

vaseline? really? talk about taking 'starving student' to the max.

 I think thermal compound is like $2 on mouser. You can get some arctic silver $5 shipped off ebay or some stuff from your local radioshack. I wouldn't use vaseline.


----------



## mattcalf

Completely unrelated to the heatsink discussion, but I've made a few decisions today.
 1. In my 'SS' order from mouser I'm going to order parts for 2 basic Cmoys.
 2. I'll build one Cmoy, troubleshot (if needed) until it's right. Build the second one (which'll be a mates bday present).
 3. Then I'll build the SS with the limited experience gained frmo the cmoys.

 [offtopic x2]I've also decided to get the Maudio Q40's instead of the Denon D1001s.[/offtopic x2]

 If anyone has any advice on the 'SS' please post it, if you have any advice on the headphones or Cmoys please PM me as anything will be much appreciated.


----------



## Kabeer

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_vaseline? really? talk about taking 'starving student' to the max.

 I think thermal compound is like $2 on mouser. You can get some arctic silver $5 shipped off ebay or some stuff from your local radioshack. I wouldn't use vaseline._

 

Haha 
	

	
	
		
		

		
		
	


	




 . 
 Well im in London UK, my guess is it would be more here. Ill take a look though. It's just my SS is always needing more and more things, I have spent quite a lot on it (~$120) before counting the tools I bought as well.


----------



## ludoo

Is the grease used for CPUs ok? Something like this





 It's very easy to find around here and pretty cheap.


----------



## JamesL

That'll do fine.
 Grease used for CPU's are probably better than the generic type, considering PC enthusiasts go to long lengths trying to squeeze all the heat from their cpu.


----------



## JamesL

Quote:


  Originally Posted by *Kabeer* /img/forum/go_quote.gif 
_Haha 
	

	
	
		
		

		
		
	


	




 . 
 Well im in London UK, my guess is it would be more here. Ill take a look though. It's just my SS is always needing more and more things, I have spent quite a lot on it (~$120) before counting the tools I bought as well._

 

hehe. That's how it tends to be.
 Those "extra costs" will go down slowly once you get building on your third or fourth project. 
 Are there any local electronics store where you live? I know radioshack, fry's, circuity city, and I think staples carries thermal grease near where I live.


----------



## keiths

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_That'll do fine.
 Grease used for CPU's are probably better than the generic type, considering PC enthusiasts go to long lengths trying to squeeze all the heat from their cpu._

 

Aren't some of the thermal compounds used with CPUs electrically conductive? You wouldn't want that...


----------



## JamesL

Quote:


  Originally Posted by *keiths* /img/forum/go_quote.gif 
_Aren't some of the thermal compounds used with CPUs electrically conductive? You wouldn't want that..._

 

You're using a insulator, yes? Just use a paper thin layer


----------



## n_maher

Quote:


  Originally Posted by *error401* /img/forum/go_quote.gif 
_Definitely better to err on the side of using grease if you're unsure, but it will still increase the thermal resistance of the insulator. If the insulator doesn't require it, you're adding an extra interface (two, actually) and thus some thermal resistance - though probably not much, it's not optimal, especially since no-grease insulators are inherently less efficient.

 Most if this is explained in much depth by Rod Elliott in his heatsink guide._

 

Good point and good link, thanks for cleaning up my mess.


----------



## Kabeer

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_hehe. That's how it tends to be.
 Those "extra costs" will go down slowly once you get building on your third or fourth project. 
 Are there any local electronics store where you live? I know radioshack, fry's, circuity city, and I think staples carries thermal grease near where I live._

 






 Unfortunately this will be my only project for quite a while (I dont need more than one home amp heh, and this is nice and small)! And its a pretty sweet amp so Im happy with that.

 Over here we have a shop called Maplins, I'll check them out, but nothing near me, I have to go past a few towns to get to it.


----------



## kuroguy

Quote:


  Originally Posted by *Kabeer* /img/forum/go_quote.gif 
_Unfortunately this will be my only project for quite a while (I dont need more than one home amp heh._

 

That's what you think.


----------



## J.P.6

Is there any way to test these tubes? 

 One of mine doesn't seem to work.


----------



## tomb

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_Is there any way to test these tubes? 

 One of mine doesn't seem to work._

 

... and when you test it, it still won't work .
	

	
	
		
		

		
		
	


	




 Seriously, testing is only partially indicative of tube status. Even a Hickok and dynamic mutual conductance testing is only as good as the B+ voltage it was done at. Put the tube in an amp running at a different B+ and it may perform just fine. The true test is how it does in the amp. If you can switch the tubes and the problem follows the tube, then the tube is the culprit.


----------



## J.P.6

Yep, that's the problem, definitely a dead tube. Damn, now I have to wait for some more to come from the US! Last ones took over 3 weeks.


----------



## bmwpowere36m3

Well I just finished building my "SS" millet and I'm impressed. It was a lot of work compared to the CMoY I built previously, both in casework and figuring where to put components...

 Of course working most of the day and night led to a couple errors. WHen I first powered it ON all was well and the tubes glowed. When I plugged in my headphones, no sound... crap! I figured I wired it to the wrong side of the jack. Sure enough I did, now I got the headphones working, but I was hearing a loud repeating screeching sound, bad tube? I replaced it and no go, the same sound. I look over the circuit and sure enough I also forgot to wire in the grounds from the pots, silly!

 Once I fixed those problems, I was in musical nirvana. Pics to come.


----------



## mattcalf

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_
 Once I fixed those problems, I was in musical nirvana. Pics to come._

 

Can't wait to see your pics... and build my own.


----------



## RuiCanela

Here is mine


----------



## J.P.6

Some pictures of mine. Sounds fantastic 
	

	
	
		
		

		
		
	


	
























 Compulsory dark shot:


----------



## mattcalf

All those pictures are awesome!!!

 Thanks!


----------



## JamesL

the output jack doesn't have to be insulated, right?


----------



## rds

Quote:


 the output jack doesn't have to be insulated, right? 
 

Nope.


----------



## bmwpowere36m3

teaser...


----------



## mourip

Check out this case. It is made for an external hard drive but would make a really great small amp if set on it's side. 

 I saw it in a thread about a guy who cannibalized a Macbook and put it into this box. It is $40 at NewEgg. Not cheapskate territory but great looking.

My New Mac Pro Ultra Mini


----------



## rds

Quote:


 Check out this case. It is made for an external hard drive but would make a really great small amp if set on it's side. 
 

Considering it has a power button, usb port, and power jack it's a pretty fantastic deal, and means almost no case work to fit something like a pimeta and bantam dac in there.
 ...I think I might have to do that.
 Thanks for pointing this out


----------



## mourip

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Considering it has a power button, usb port, and power jack it's a pretty fantastic deal, and means almost no case work to fit something like a pimeta and bantam dac in there.
 ...I think I might have to do that.
 Thanks for pointing this out 
	

	
	
		
		

		
		
	


	


_

 

Though someone might like it. If you get one do us a favor and post the inside dimensions.

 Thanks...


----------



## bmwpowere36m3

Quote:


  Originally Posted by *mourip* /img/forum/go_quote.gif 
_Check out this case. It is made for an external hard drive but would make a really great small amp if set on it's side. 

 I saw it in a thread about a guy who cannibalized a Macbook and put it into this box. It is $40 at NewEgg. Not cheapskate territory but great looking.

My New Mac Pro Ultra Mini_

 

Nice, I just picked up the same case for my MBP's external HD. I think though it'd be difficult to install the sockets and wiring, since you only have access through the rectagular opening in the back.


----------



## holland

Quote:


  Originally Posted by *mourip* /img/forum/go_quote.gif 
_Though someone might like it. If you get one do us a favor and post the inside dimensions.

 Thanks..._

 

It won't be much larger than a 3.5" hard drive. These types of enclosures are very efficient, as in not wasting space. Actually old SCSI enclosures come in quite handy as well, especially the ones that mount 2 or 3 drives. There are pictures on Amazon.com for this particular enclosure.

Amazon.com: Macally G-S350SUA Hi-Speed eSATA/FireWire/USB2.0 Storage Enclosure for 3.5-Inch SATA HDD: Electronics

 It'll be enough room for some small amps. I would go the y1 route and some p2p amp or something like a Pimeta, as noted. You would be challenged on the height though, as the internal clearances won't be much larger than a 3.5" drive in height and about 1 - 1.5" clearance in the back.


----------



## holland

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Nice, I just picked up the same case for my MBP's external HD. I think though it'd be difficult to install the sockets and wiring, since you only have access through the rectagular opening in the back._

 

Remove the backplate and use a custom FPE plate. More $$$ though.


----------



## bmwpowere36m3

Yay for pics, my completed "SS" Hybrid...




















































 It sounds great and I'm happy I chose to go the boutique route. There is still some fiddling I'll be doing (output resistors & bypass caps), but it good for now. I'm running it with my iModded Mini as a DAC and Senn HD580's. Its the best setup I've had thus far, moving from running RE2's on my CMoY and MBP as the DAC.

 The only thing I'm not happy with is the knob and that is partly my fault for being slightly hasty. The RK27's pot shaft is a lot longer than the knob's 'depth' so the knob kind of sticks out and there's a gap behind it. Nothing a new knob can't fix. I've gone ahead and attached a BOM of my build, though I took cues from 'OldKing' and 'jERiCOh'


----------



## J.P.6

I have a strange 'pitter patter' type of noise on my SS, which goes when I hold my hand over the right tube.. Is this some sort of ground issue?

 And also humming which goes when I touch the input RCA jacks.

 Edit - Never mind, seems to be some interference picked up from my iMac, goes when I move it away.


----------



## error401

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_lots of cool pics_

 

I really like what you've done with the heatsink. Nice casework!


----------



## -=Germania=-

I was thinking of recasing my first build into this: Newegg.com - macally T-S350SU 3.5" USB & eSATA External Enclosure - External Enclosures

 Cheaper!


----------



## sandbasser

-=Germania=-

 Looks interesting... Can't tell if it's plastic or metal. If you do get one, please post details.

 Thanks,


----------



## chobint

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Looks interesting... Can't tell if it's plastic or metal._

 

first review on Newegg.com:
 "Cons: wish there was a firewire port. Construction is what you pay for ... Lots of plastic ... WARNING BE CAREFUL Swapping drives ... you can almost snap off front of enclosure when unloading a drive. It looks better than expected I changed blue led to white"

 @bmw...did you have any trouble drilling thru those heat sinks? looks pretty thick


----------



## bmwpowere36m3

Quote:


  Originally Posted by *chobint* /img/forum/go_quote.gif 
_first review on Newegg.com:
 "Cons: wish there was a firewire port. Construction is what you pay for ... Lots of plastic ... WARNING BE CAREFUL Swapping drives ... you can almost snap off front of enclosure when unloading a drive. It looks better than expected I changed blue led to white"

 @bmw...did you have any trouble drilling thru those heat sinks? looks pretty thick_

 

No, I had a drill press, lots of HSS bits, and a Uni-bit to aid me and a little cutting fluid. I'd say it's about 1/4" thick in that area.


----------



## chobint

cool, looks great.

 I bet a drill press is a man's best friend for case work.


----------



## Logistic

So I built my SS yesterday, and I made a boneheaded move and mixed up the power and ground from the power connector, so it just hiccuped and burned out the switch. Now I've got things sorted out, and the amp works. However, the right channel has some kind of feedback interference which is a quieter version of the signal, but at a different frequency. So I hear the music, and also a quieter version in a different key. Any ideas what could be wrong? Could the mosfet be burned out on that side?

 Thanks.


----------



## MoxMonkey

so i found a small stockpile of tubes and might end up putting some extra amps together for the less diy inclined folks here (minus psu's) 

 can anyone offer suggestions for a cheap quality enclosure to use?


----------



## effcleff

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Yay for pics, my completed "SS" Hybrid...
_

 

Nice! I'm gonna order parts for a build like that any day now.


----------



## espressogeek

Where can I score a pair or two of tubes for this amp right now? Every place I have called always says I just missed them. Ebay has listings for around 20 shipped which seems a bit nuts considering they were 1.10 a pop originally.
 Thanks


----------



## mattcalf

Quote:


  Originally Posted by *espressogeek* /img/forum/go_quote.gif 
_Where can I score a pair or two of tubes for this amp right now? Every place I have called always says I just missed them. Ebay has listings for around 20 shipped which seems a bit nuts considering they were 1.10 a pop originally.
 Thanks_

 

Ditto.
 Let me know if you find anywhere.


----------



## rds

Hang in there, I'm pretty sure a bunch will show up soon - and at very reasonable prices too.


----------



## J.P.6

Tried Orlando Vacuum Tubes ?


----------



## Gross

I threw this together, an Eagle Library for the 19J6 Tube. This was my first real attempt at Eagle, but to the best of my knowledge it should be all correct. I used the template from the original Millet Hybrid, and made the appropriate changes. Maybe this will help someone out. 

 I am just working on a little project for myself, and I am going to etch a few PCBs. 

 Oh yeah, Thanks for the Tutorials Tangent!


----------



## espressogeek

Not this week but I'll call them again in the morning. If someone can PM me when some show up somewhere I would appreciate it.
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_Tried Orlando Vacuum Tubes ?_


----------



## bmwpowere36m3

Quote:


  Originally Posted by *chobint* /img/forum/go_quote.gif 
_cool, looks great.

 I bet a drill press is a man's best friend for case work._

 

It's a great piece equipment for fab work, but so are a lot of other tools. Tools...
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *effcleff* /img/forum/go_quote.gif 
_Nice! I'm gonna order parts for a build like that any day now._

 

Thanks and good luck with the build.


----------



## mattcalf

I just done a beasty mouser order.
 AU$90 for the components to build one starving student and two cmoys.

 I've received the PSUs, I have one extra so might sell that and all I need is some tubes (and mounts).

 Maybe I could trade someone a PSU for a few tubes.


----------



## Hayduke

I've been reluctant to post on this thread after the Thermafilm debate, but I have another question.

 My amp has developed a problem. The right channel's volume is no longer controlled by the pot. Could this be due to the MOSFET dieing?

 It's not a bad tube as I swapped them and the problem didn't change channels.

 I checked the 2 test voltages and I have 48V and 21V. The schematic says ~19V, is 21 close enough?

 I checked the pot and both channels are working correctly. If it matters, I used a 100k pot with the theory that I would be able to use more of the range.

 I have 2 friends that want one of these amps after hearing mine, so I'll be placing another parts order soon. Do I need to add a couple extra MOSFETs? I'm not sure how to test a MOSFET as my meter doesn't have a transistor testing function.

 In regards to the earlier discussion of the need for grease, while I respect everyones opinions, it seemed the position that grease was needed was based on the description of Thermasil not needing it. So the assumption was that the others do need it. I have looked at everything I can find from Aavid. I sent them an email asking about it. We'll see what they say. If my MOSFETs are bad, then I guess I have the proof I need 
	

	
	
		
		

		
		
	


	




 Kuroguy, before you chime in, I want to say that I considered apologizing, but you never offered any support to your labeling of my advice as "bad". Then you had to follow me to another thread to try and rehash the debate there. You're so full of your own self importance, you even quoted yourself in your signature!


----------



## holland

Michael Knowles: Extras

 1) download track #55. Play in a loop.
 2) DMM set to AC mode
 3) Measure voltages at the amp's input (RCA jacks).
 4) Put pot at minimum volume.
 5) Measure voltages going into tube.
 6) Measure voltages coming out of the tube.
 7) Measure voltages at amp output (headphone jack).
 8) Put pot at maximum volume.
 9) Repeat steps 5, 6, and 7.

 Into the tube will be what the pot puts out.

 Out of the tube will be the signal with voltage gain applied.

 Amp output will be after the MOSFET buffer.

 How do they compare to the RCA input?

 That will determine if the problem area is the pot or the tube or the mosfet. After that, it is to determine why there is an issue.


----------



## nikongod

I built a hungry hybrid. 

 Its somewhere between a classic millett hybrid (same gainstage, and direct coupling between gain and power stages) with a mosfet output using the heater as its source resistor like the starving student.






 I got some knobs on my way to work today 
	

	
	
		
		

		
		
	


	




 now I can adjust the stepper without pliers.
  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_My amp has developed a problem. The right channel's volume is no longer controlled by the pot. Could this be due to the MOSFET dieing?_

 

probably not a bad mosfet.

 It sounds like the pot is not wired correctly, I would try hard to figure out how the pot got OUT of the signal path.
  Quote:


 I checked the 2 test voltages and I have 48V and 21V. The schematic says ~19V, is 21 close enough? 
 

Probably close enough. Tube and part inconsistencies will result in small differences.
  Quote:


 I checked the pot and both channels are working correctly. If it matters, I used a 100k pot with the theory that I would be able to use more of the range. 
 

Are you 100% sure its "in" the circuit? With the amp off: Measure resistance from the grid/input of the tube to the center of the RCA. It should change from 100k ohms at "minimum volume" to about 0 ohms at maximum volume. 

 You could also measure the resistance at the RCA plug as you rotated the knob too. It should stay the same as you spin.

 If you twisted signal and ground wires its easy to get them confused somewhere.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I've been reluctant to post on this thread after the Thermafilm debate, but I have another question.

 My amp has developed a problem. The right channel's volume is no longer controlled by the pot. Could this be due to the MOSFET dieing?_

 

That's a possibility, but check this - is the MOSFET hot? If so, then it's probably operating. Quote:


 
 It's not a bad tube as I swapped them and the problem didn't change channels.

 I checked the 2 test voltages and I have 48V and 21V. The schematic says ~19V, is 21 close enough? 
 

Yes. Again, it could be many things.

  Quote:


 I checked the pot and both channels are working correctly. If it matters, I used a 100k pot with the theory that I would be able to use more of the range. 
 

Exactly how did you determine this? My first suspicion would be loss of a signal wire at the pot or the RCA connections - or even at the output headphone jack. Again, if you're splitting the voltages, then the heaters are working and probably the tubes, too. If the MOSFETs are hot (without burning up), then they're probably working, too. Quote:


 
 I have 2 friends that want one of these amps after hearing mine, so I'll be placing another parts order soon. Do I need to add a couple extra MOSFETs? I'm not sure how to test a MOSFET as my meter doesn't have a transistor testing function. 
 

This is easy with a very cheap meter - if the MOSFET is unmounted:

Testing a MosFet, Testing

 Note the following lines in this reference:
_"When MOSFETS fail they often go short-circuit drain-to-gate. This can put the drain voltage back onto the gate where of course it feeds (via the gate resistors) into the drive circuitry, prossibly blowing that section. It will also get to any other paralleled MosFet gates, blowing them also."_

 Now, the SSMH doesn't have a driver stage except the tubes. Nevertheless, methinks you would notice a lot more bad stuff if the MOSFET had blown.

 I'm not sure exactly how to test inside the circuit except the old tried and true - measure like points for voltage from one channel to the other. You should be able to narrow it down in short order if you compare with a schematic and record your readings. The one channel works, so it gives you a perfect basis for comparison.
	

	
	
		
		

		
		
	


	



  Quote:


 In regards to the earlier discussion of the need for grease, while I respect everyones opinions, it seemed the position that grease was needed was based on the description of Thermasil not needing it. So the assumption was that the others do need it. I have looked at everything I can find from Aavid. I sent them an email asking about it. We'll see what they say. If my MOSFETs are bad, then I guess I have the proof I need 
	

	
	
		
		

		
		
	


	



 

You don't need grease with Thermasil and its use is probably detrimental - it could dissolve the Sil pad, etc. Also, grease is not necessarily an insulator, so you have to be careful that the pad is inbetween the greased surfaces. That might be tricky to do with a Thermasil pad that's more or less meant to liquify under heat, but I'm just guessing. We'll see what Aavid tells you.


----------



## JamesL

I haven't assembled my mhss yet, but I did the diode test on my mosfets before hand, and I think one of them may be dead.

 On one of them, the reading on my meter starts off low, at around .1v and rises slowly to about 3v, before the reading cuts off.
 On the other one, it starts off at about .1v, but rises fast to 2.9v, where it lingers.

 I may have overheated one, or both while putting heat-shrink over the pins.. but i'm not sure. =/
 The mosfet isn't soldered onto anything, and power hasn't been applied (except from the dmm)


----------



## ARwCoco

Last week I purchased a pair of old surplus film caps for C2, C3 . The box was labeled 0.15uF 74V . Yesterday I got to looking and the caps are labeled .15K A26 8052. Are these indeed 0.15uF ? How do I check them with my meter ? How do they compare to the WIMA 0.1uF ? Thought I better check here before I make my order to Mouser.
 Thanks


----------



## Bleemv1

hey guys,

 I just signed up today. I have no electronic background or anything but I still want to try this DIY project. 

 Could someone link me to the final schematics and materials list please?

 I was looking through the first few pages and there seemed to be a couple of tweaks/corrections so I don't want to build the wrong thing.

 Thanks 
	

	
	
		
		

		
		
	


	




 I'm from Australia too, so if you guys have any recommendations on where to get the parts from that would be great.


----------



## pinkfloyd4ever

http://www.head-fi.org/forums/f6/mil...1/#post4118757


----------



## Hayduke

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Michael Knowles: Extras
**snip**
 That will determine if the problem area is the pot or the tube or the mosfet. After that, it is to determine why there is an issue._

 

Cool. I'll try this when I get home. Thanks 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_I built a hungry hybrid. 

 Its somewhere between a classic millett hybrid (same gainstage, and direct coupling between gain and power stages) with a mosfet output using the heater as its source resistor like the starving student.

http://img184.imageshack.us/img184/3...000386rqs4.jpg

 I got some knobs on my way to work today 
	

	
	
		
		

		
		
	


	




 now I can adjust the stepper without pliers._

 

That looks cool! I've been sort of waiting for an enclosure to inspire me. That might be it 
	

	
	
		
		

		
		
	


	



  Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_probably not a bad mosfet.

 It sounds like the pot is not wired correctly, I would try hard to figure out how the pot got OUT of the signal path.

 Probably close enough. Tube and part inconsistencies will result in small differences.

 Are you 100% sure its "in" the circuit? With the amp off: Measure resistance from the grid/input of the tube to the center of the RCA. It should change from 100k ohms at "minimum volume" to about 0 ohms at maximum volume. 

 You could also measure the resistance at the RCA plug as you rotated the knob too. It should stay the same as you spin.

 If you twisted signal and ground wires its easy to get them confused somewhere._

 

I think the pot is in the signal path. This amp was working great for awhile, other then a hum when I tried using my BantamDAC. It sounded great when I fed it from the line out of a modded iPod.

 I checked the pot with my meter only at the pot. I'll check it in other places tonight.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's a possibility, but check this - is the MOSFET hot? If so, then it's probably operating.Yes. Again, it could be many things.

 Exactly how did you determine this? My first suspicion would be loss of a signal wire at the pot or the RCA connections - or even at the output headphone jack. Again, if you're splitting the voltages, then the heaters are working and probably the tubes, too. If the MOSFETs are hot (without burning up), then they're probably working, too.This is easy with a very cheap meter - if the MOSFET is unmounted:

Testing a MosFet, Testing

 Note the following lines in this reference:
"When MOSFETS fail they often go short-circuit drain-to-gate. This can put the drain voltage back onto the gate where of course it feeds (via the gate resistors) into the drive circuitry, prossibly blowing that section. It will also get to any other paralleled MosFet gates, blowing them also."

 Now, the SSMH doesn't have a driver stage except the tubes. Nevertheless, methinks you would notice a lot more bad stuff if the MOSFET had blown.

 I'm not sure exactly how to test inside the circuit except the old tried and true - measure like points for voltage from one channel to the other. You should be able to narrow it down in short order if you compare with a schematic and record your readings. The one channel works, so it gives you a perfect basis for comparison.
	

	
	
		
		

		
		
	


	



 You don't need grease with Thermasil and its use is probably detrimental - it could dissolve the Sil pad, etc. Also, grease is not necessarily an insulator, so you have to be careful that the pad is inbetween the greased surfaces. That might be tricky to do with a Thermasil pad that's more or less meant to liquify under heat, but I'm just guessing. We'll see what Aavid tells you. 
	

	
	
		
		

		
		
	


	


_

 

I'll take a look at that link tonight and test the right channel mosfet.

 I checked all my connections last night. I did notice that the area around one of the pins for the right heatsink had melted the solder away from the pin. I used the 4 points where the heatsink pins connect to the copper board as my ground points. So I reflowed this one and added some more solder to fill in the gap. Here is the picture from the build (the gap isn't in this picture, it's to show how I did my grounds)





 I tested the pot just by measuring between ground and the other 2 points and between the 2 point on both channels. It was definitely changing from 0 to 100k ohms (I used a 100k pot as I said above)

 After I posted last night, I did give the amp another listen. The left channel seems to be OK, but it's kinda hard to tell with a wonky right channel. I just used my old iBuds to test as I didn't want to damage my good headphones. I did realize that my previous description was a little inaccurate. The right channel is indeed still affected by the pot. Here the best way I can describe the situation.

 With the volume all the way down, the left channel is silent, but the right channel is moderately loud. Probably a little lower volume then I might listen to when "rocking out", so kind loud. As I turn up the volume, the left channel increases, but so does the right. If I turn it up loud enough, it seems like they eventually catch up and the left channel eventually gets louder then the right. This is hard to tell because it's well beyond a comfortable listening level so I sorta pulled the ibuds halfway out of my ears.

 I'll have to double check when I get home, but I also don't think the right heatsink was getting warm. Of course I don't think the left was either in the couple of minutes I had it on.

 Thanks for all the help everyone. I love this community 
	

	
	
		
		

		
		
	


	



 I'll try the suggestions when I get home. (working a little late tonight)

 -----------------------------------------------------------------------
 I got a response from Aavid, so hopefully we can put this subject to rest once and for all 
	

	
	
		
		

		
		
	


	




*First, here is what I sent them:*
_From: *deleted this part*
 Sent: Wednesday, December 03, 2008 2:42 AM
 To: info
 Subject: product question

 When using part # 4880G, is a thermal grease needed?

 In your description of Thermasil products, you specify as one of its
 features not needing any. Does the imply that the Thermafilm, such as
 the 4880G, products DO need it?_

*Here is their reply:*
_RE: product question
 Wednesday, December 3, 2008 5:41 AM
 From: "Snow, Rick" <snow@aavid.com>
 Add sender to Contacts
 To: *deleted again*
 Good morning,
 It is not necessary to use a thermal grease, however it will increase
 thermal transfer as it fills air gaps between the device and the
 heatsink.

 Rick Snow
 Technical Support Specialist

 Aavid Thermalloy, LLC
 70 Commercial Street, Suite 200
 Concord, NH 03301_

 So it appears it's a case of "can't hurt, might help", but the manufacturer doesn't require it.


----------



## ARwCoco

Come on guys

 holland, hayduke, tomb, n_maher, error401

 Can anybody answer my post #1690 ?

 This is NOT about heatsink grease !


----------



## error401

Quote:


  Originally Posted by *ARwCoco* /img/forum/go_quote.gif 
_Come on guys

 holland, hayduke, tomb, n_maher, error401

 Can anybody answer my post #1690 ?

 This is NOT about heatsink grease !_

 

I didn't have a good answer so I didn't reply, but you can have my answer that doesn't really help you anyway...

 Markings on obsolete components are really going to be best guess if you can't find a datasheet. The value for capacitors is typically given in picofarads in a similar (but numeric) fashion to resistors. 104 for example is 10x10^4 pf, 0.1uF. Yours obviously doesn't match this, but if it says they're 0.15uF, it makes sense to assume that value is correct. The K is probably a tolerance marking. Who knows about the rest of it.

 If you have a meter with capacitance measurement, just, uhm, attach the leads and read the value... If you don't have a capacitance measurement function, you will need to use a more convoluted technique. For example, attach a known R and charge the cap while measuring the time constant (or measure the discharge time constant, which might be easier to set up), but this won't work well with small caps because the timing accuracy gets very bad (or impossible). Or pass a known AC signal through an RC network with the cap and a known R, and measure the attenuation. There are lots of techniques, google turns up this that looks useful: Measuring Capacitance: Methods (fwd)

 How do they compare? Can't comment, I'm not one of those guys that listens to a dozen different caps and takes notes. If it measures well, it sounds good, as far as I'm concerned.


----------



## ARwCoco

Thanks for the reply

 I will take the cap over to our local university and have

 someone check the value using a better meter than I own.

 When I get stubborn I NEED to find an answer


----------



## n_maher

Quote:


  Originally Posted by *ARwCoco* /img/forum/go_quote.gif 
_Last week I purchased a pair of old surplus film caps for C2, C3 . The box was labeled 0.15uF 74V . Yesterday I got to looking and the caps are labeled .15K A26 8052. Are these indeed 0.15uF?_

 

Your guess is as good as mine. I certainly wouldn't trust the box when buying surplus materials.
  Quote:


 How do I check them with my meter ? 
 

error401's advice is solid here. 
  Quote:


 How do they compare to the WIMA 0.1uF ? 
 

How on earth would we be able to tell you that? 
	

	
	
		
		

		
		
	


	



  Quote:


 Thought I better check here before I make my order to Mouser. 
 

I'd just order some known-good (current production) caps and be done with it. What you have may or may not be what it is supposed to be and may or may not sound better. I tend to prefer to go with what I know will work rather than chase infinitesimal gains by rolling bypass caps. YMMV


----------



## tomb

Agree with error401 and Nate. Chances are the caps aren't that good. There are very few old surplus caps that are actually worth something - Vitamin Q's, some orange drops, that's about it. You may hear of others, but it's usually from the guitar community where they're actually looking for _more_ distortion. Sprague Black Beauties come to mind - bad cap, whereas Sprague Vitamin Q's or Sprague Orange Drops might be OK.

 It's impossible to tell without pics, brand name, physical condition of the caps, etc.


----------



## Hayduke

I think I solved my amp problem. I redid the wire from the pot's right channel to the tube socket's pins 5 & 6. I think it is fine now.

 I'm not 100% certain because I realized my LOD was messed up too 
	

	
	
		
		

		
		
	


	




 At first I thought I did something to the amp because everything sounded kind of distant and echoey (a new word I just made up hehe). Then I started wiggling the LOD and it got better sometimes. I tried building a new one, but I melted my plug with the shiny new heat gun I apparently don't know how to use yet 

 Thanks for all the ideas yesterday. I wasn't able to test the mosfet with the instructions Tom linked to. My meter wasn't up to the required spec it asked for. I ran through the instrucitons Holland posted, but I didn't see anything that caught my attention.

 When you guys suggested measuring the same voltages at different locations, it got me thinking I should double check all my wiring. I basically just started tracing out the circuit again to double check that I had everything connected correctly. I didn't really identify that particular connection as bad, but the plan was to redo each connection on the right channel. The wire from the pot to the tube socket was barely long enough, so I started there. I guess I got lucky. The first one I worked on fixed it.


----------



## ltmon

Quote:


  Originally Posted by *Bleemv1* /img/forum/go_quote.gif 
_hey guys,

 I just signed up today. I have no electronic background or anything but I still want to try this DIY project. 

 Could someone link me to the final schematics and materials list please?

 I was looking through the first few pages and there seemed to be a couple of tweaks/corrections so I don't want to build the wrong thing.

 Thanks 
	

	
	
		
		

		
		
	


	




 I'm from Australia too, so if you guys have any recommendations on where to get the parts from that would be great._

 

The final spec and BOM is still as published on PMillett's site: Starving Student hybrid

 A lot of the posts you've seen are just discussing tweaks and small modifications, but you should be fine with the original BOM for a first build. I also found PMillett's post #238 on page 24 useful.

 For parts in Australia: Altronics and Jaycar are the cheapest, but often don't have quite the part you need. In that case go to Farnell AU | Australia.

 For tubes and sockets I don't know of any Australian source. I have two of each spare here in Melbourne however, so PM if you want to get hold of these.

 L.


----------



## bmwpowere36m3

Has anyone experimented with output resistors on "SS" Millet, I got a bunch of Kiwame SPR2 2W resistors that I was thinking of using to lower some of the overall gain of the circuit.

 Are there any downsides to implementing these and any 1st hand accounts? I believe Germania was using 100Ω w/ 100k pot and xxΩ w/ 50k pot. I have a 50k pot in my amp and currently using it with HD580's.


----------



## holland

I really wouldn't consider that as an option, as it affects damping. There are other options. I can tell you what I'm doing, if you're interested.


----------



## rds

Quote:


 I got a bunch of Kiwame SPR2 2W resistors that I was thinking of using to lower some of the overall gain of the circuit. 
 

I wouldn't recommend that. Since headphones are a reactive load it means the resistor would change the frequency response of the headphones. ...I think. 

 EDIT I'm pretty sure on that.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I really wouldn't consider that as an option, as it affects damping. There are other options. I can tell you what I'm doing, if you're interested._

 

Please do!

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I wouldn't recommend that. Since headphones are a reactive load it means the resistor would change the frequency response of the headphones. ...I think. 

 EDIT I'm pretty sure on that._

 

I took the hint from some other members who experimented with it and it's a tweak in the Millet Max build to tame some of the high-end tube noise as well as reduce some gain.


----------



## holland

There are some headphones that recommend an output impedence of 120ohm. For those, I would build an adapter or add a second output with 120 ohm inline. Otherwise they expect as low an output impedance as possible.

 There are 2 things I would do, one is questionable.

 1) Lower the 33K to about 20K or 15K. That'll lower the overall gain of the tube stage, it also reduces the amount of voltage swing possible, but I *think* it'll be OK with 15K. I believe that's what I'm using now.

 2) questionable part and also optional. Add some negative feedback. Put a 10K gridstopper in (right on the tube pins), and then route the output to the input through a 150K resistor. This will give about 4-5dB of negative feedback (I forget exactly how much, it's been a while). It's not a whole lot, but for example, with the plate resistor of 15K and the 150K/10K setup, my gain is about 3.5.

 I would probably skip #2 for the HD580 and a portable source.

 Without the feedback loop (#2) your gain will be higher and some might prefer it. I need it because my headphones don't actually need gain. I'm not sure I would go too low with the plate resistor, mainly because I like a range of options. I have tried 5K, but it was too low for my HD650 while it's actually better for the headphones I am using with it.

 Note, if you're going to use a portable DAC (I don't even at work) that outputs 1Vrms 15K without feedback may be just right.

 I don't know what the imod mini outputs, let alone what it is, but it's up to you to find your gain range.

 BTW, I also changed R13 to 1K, but only because I was going to run it at a higher current and didn't want too much of a voltage drop. I believe stock is about 0.5mA. Anyhow, stock is about 45.5V to the tubes after the pi RC filter and with 1K it's about 46V after the pi RC filter.

 Another note, changing the plate resistor changes the operating point of the tube. It's not major, as the tube is heavily constrained with low voltage and low current so large resistance changes won't move the operating points around too much....if the tube voltage was 300V, that would be very different.

 I hope this helps.


----------



## tomb

Pete Millett has regularly used output resistors in his designs, including the Millett Hybrid and others:
http://www.head-fi.org/forums/f6/que...light=resistor

 The Rickster and I had an unfortunate digression at the end of that thread, but you can get the idea from Pete's first post.
	

	
	
		
		

		
		
	


	




 Likewise, Alex Cavalli used them in the SOHA I - up to 150 ohms on each channel. The Millett started out with 22ohms, but anything from zero up to 100ohms has been used, depending on headphones and other factors.

 There is nothing to fear with using output resistors. However, there are tradeoffs. Higher values dampen the dynamics of the amp, while smaller values may decrease the noise from the tubes. Pete does mention that it affects how some headphones will sound. It's a trial and error/personal preference type of thing, I think.


----------



## holland

good to know. sounds like a battle of religion (haven't read the thread yet).

 ...rickster...now that's a screen name i haven't seen in ages.

 edit: forgot to mention that Jan Meier has, on his site, how a series resistor affects the frequency response. There are some graphical representations with some specific headphones. To my ears, it appears accurate, though I haven't measured it myself.


----------



## bmwpowere36m3

Wow, thanks for that info... Jan Meier site was really informative: Meier-Audio

 It seems like I really want to parallel the outputs instead, since the combo ("SS" Millet & HD580) seems a little dark and not "dampened" as well as I like. Maybe its time just to start on another amp, maybe a SOHA II or BIJOU... synergy w/ HD580's?


----------



## Hayduke

My problem with the right channel resurfaced earlier this tonight. 
	

	
	
		
		

		
		
	


	




 The right channel seemed to have a "base" volume. When the pot was all the way down, the left channel was quiet, but the right channel was somewhat loud. As I turned the volume up, they would balance out at some point, but the left could go a little louder I think (I didn't listen much as this was too loud).

 I started to troubleshoot and came to the conclusion the problem was the pot. I swapped it out with a 10K RK097 I had for another project. I used 8 (4 on each channel) 10k resistors between the input and the pot. The amp is working pretty well, but it has changed the sound noticeably.

 First, it's not as loud. This is OK since full volume is about as loud as I would ever listen. I'm curious though why a 50k net pot would be quieter then the 100k I swapped out.

 Second, it seems like the top end has been affected a bit. I am listening to some Natalie Merchant, and her voice occasionally seems to get a harshness to it. I'll keep listening, but I think I want to replace the pot.

 Any suggestions on what to use? I'm thinking of using a RK27 instead. Is there something else I could consider? Germaina has suggested I look for a Noble pot, but I couldn't find them anywhere. I'd prefer something from Mouser, but I'd like a high quality part. I'm planning to order some boutique caps soon, so maybe something available from someplace like Percy that also sells higher end components?


----------



## royewest

Both beezar.com and the amb.org shop offer the Alps RK27112A 50KΩ pot. 

 I just replaced the stock pot in my S.E.X. amp with one of these (plus metal film resisitors on the input to reduce the volume, but that's another story) and am very happy with the performance.

 The amb.org shop also offers a nifty circuit board you can use to solder the Alps tabs to, and then solder your wire directly to the board (much easier than soldering to the pot tabs) or use snap connectors:

http://www.amb.org/audio/epsilon27/

 P.S. I'd welcome a lead on a Noble pot, too -- couldn't find any, though I did not try all that hard. Amb's board fits those, too, I think, so with the snap-connectors you could swap them in and out to compare....


----------



## Logistic

Hi Everyone,

 Just an update, the strange feedback thing I posted about earlier disappeared. I'm not sure if it was me switching the tubes around and reseating them, or because I had breathed in too many solder fumes that night. However, now I have two issues. The first is the switch. I thought that when I miswired the amp, that burned out the switch, but after wiring it correctly and changing the switch, it worked for a bit, but now once again the switch does not work. I checked the readings with a multimeter. The original switch was a basic SPST, and the resistance was 0 at both positions. I replaced that with a DPDT I had around, and now the resistance is 0 at both positions for the two lugs I soldered to (if it matters I soldered from the power jack to the middle lug, and then from the bottom lug to the amp). The other side of the switch works fine. I'm not sure what's causing these switches to burn out, what should I measure and check?

 Both of the switches are toggle switches and are rated for 5A 120 VAC/28 VDC and 2A 250VAC.

 The second thing is that occasionally the amp would make a pop sound, I'm not sure, but I think it goes away if I turn down the pot or turn down the volume from my computer. It might be coming from my computer sound card. There is also some quiet hissing in the left channel occasionally that is only audible with lower impedance headphones like my KSC75, not my HD 580 (this volume of the hiss can be controlled by the pot). I don't know if this is due to the tube or something else, or if it is related to my switch burning out.

 I measured the voltages, it is 48V across C1 and 19V from socket pin 3 to ground.

 Thanks for all your help.


----------



## -=Germania=-

That was a temp situation. 

 I found other problems in the circuit on that first build which is why certain things sounded really good and shouldn't have. Plus, I had a defective 50K Alpha potentiometer which is why I was using a 100K. 

 The one I currently use has resistors of similar value to the BOM with a few adjustments for my 1A PSU. 

 The HD580's are long gone and in fact I have switched to using a modified and recabled Sony CD1000 almost exclusively. The current build I have has been tuned for use with this headphone.

 The Cisco PSU, IMO, can be pretty noisy and needs capacitance across the leads to fix it. You can adjust the capacitance across the circuit to account for it.



  Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Has anyone experimented with output resistors on "SS" Millet, I got a bunch of Kiwame SPR2 2W resistors that I was thinking of using to lower some of the overall gain of the circuit.

 Are there any downsides to implementing these and any 1st hand accounts? I believe Germania was using 100Ω w/ 100k pot and xxΩ w/ 50k pot. I have a 50k pot in my amp and currently using it with HD580's._


----------



## Coreyk78

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_
 The Cisco PSU, IMO, can be pretty noisy and needs capacitance across the leads to fix it. You can adjust the capacitance across the circuit to account for it._

 

Would you be able to expand on that a little more? What do you mean by capacitance accross the leads? From the switch directly to ground? I'm using the Cisco PSU in my build and I do get some hum at certain times of day, would be nice if I could minimize it.


----------



## rds

Quote:


 What do you mean by capacitance accross the leads? From the switch directly to ground? I'm using the Cisco PSU in my build and I do get some hum at certain times of day, would be nice if I could minimize it. 
 

Yeah, that would be a very good place to put C1. But I'd recommend at least 330uF and a cheap film or ceramic cap in parallel with it.
 It's not going to turn day into night, but it is sensible thing to do.


----------



## Logistic

I took apart one the switches and it turns out that the mechanism inside was probably jammed somehow. I managed to wiggle the other one into place.

 I was looking at the schematic, and I can't figure out the purpose of r3 and r9. Could someone help enlighten me?

 Thanks.


----------



## Fitz

R3/R9 are the gate stopper resistors, their purpose is to keep the MOSFETs from oscillating.


----------



## jduff

Still working out the kinks in this project but very happy so far. 

 Thanks to Monsieur Millett and everyone for posting here. Great stuff. 

 BTW I bought my chassis from Radio Daze and the actual shipping costs wound up being less than what they quoted and they refunded the overage. How cool is that for a DIY audio company? You don't see that too often, believe me. 

 Rock on with your bad self.


----------



## Fuzzy OneThree

I am thinking about building one over the Christmas break and I am wondering how big most of the cases used are. I don't want things to be cramped, but I also want to keep it relatively compact


----------



## Logistic

You can fit it in a pretty small case if you want, mounting the heatsinks and the tube sockets are probably the limiting factors. I fit mine in a pen box. You should be careful in planning the layout of your components, especially with a smaller case. I learned that from making my amp.


----------



## Punnisher

Just ordered all the parts and lots of extras. Will be building sometime in the next couple weeks. Can't wait! It will be my first DIY amp ever.


----------



## zha50

After reading 1720 posts in 2 sittings, I think im ready to start putting together a BOM.

 Valves being the hardest thing to locate in melbourne/australia.

 Also, how well is this amp suited for Audio Technica AD900's? They are rather efficient i think, 35OHM. I could always attenuate the source if the gain is too high i guess(computer as source).


----------



## ltmon

Quote:


  Originally Posted by *zha50* /img/forum/go_quote.gif 
_Valves being the hardest thing to locate in melbourne/australia._

 

Two spare, with sockets, sitting in my office in Camberwell. Will trade for 6-pack 
	

	
	
		
		

		
		
	


	




 PM me if you want them! You can also have a listen to a completed version if you want to come in.


----------



## jon743

---


----------



## tomb

Quote:


  Originally Posted by *jon743* /img/forum/go_quote.gif 
_I've been following this thread for several months, and I'm finally about to make my first Starving Student! (X-mas for my brother. 
	

	
	
		
		

		
		
	


	




 )
 I have one question first though - does the size of the wire matter? I have tons of 12-18 AWG stuff laying around, but it seems like most people are using 24 or so?_

 

18ga is pretty big to try to wire electronic parts together.
	

	
	
		
		

		
		
	


	




 It sounds like you need to pick up some cheap hookup wire, which as you said, runs about 22 to 24 ga. Get the kind that comes in different colors and is stranded (flexible). The best is teflon-insulated. It won't shrink up or melt next to your soldering iron when you're soldering a connection. It's a little pricey to purchase just for what you'd need on an SSMH. It's also not available at your local Radio Shack or Home Depot. So the choice is up to you for which one you want to use.

 If you think you'll do more DIY Projects in the future, check out John's Silver Teflon Wire Shop on ebay (navshipps). He has some good deals on small lengths of teflon wire. It's a little much if all you ever do is this one project, but will serve you well if you do more.


----------



## jon743

---


----------



## jon743

---


----------



## zha50

For thoes who have brought a RK271 pot from AMB or Beezar, are you able to advise me what type they are stocking?

 Slotted or flat shaft and shaft length, looking for a nice aluminum konb. Thanks.


----------



## tomb

Quote:


  Originally Posted by *zha50* /img/forum/go_quote.gif 
_For thoes who have brought a RK271 pot from AMB or Beezar, are you able to advise me what type they are stocking?

 Slotted or flat shaft and shaft length, looking for a nice aluminum konb. Thanks._

 

Tangent also sells the same pot.
	

	
	
		
		

		
			





 The part number is RK27112A-S25-C0-A503. Within that part number, "S25" means "*S*lotted" and "25" means a 25mm long shaft. However, that 25mm also includes 7mm of threads for the pot/shaft mounting nut. Needless to say, there's nothing wrong with trimming the shaft. Just make sure that you tape the rest of the pot up in a baggie or something similar, so that the metal dust doesn't get into the wiper mechanism.


----------



## zha50

I don't remember it being mentioned in this thread, but how much 'better' is the RK271 over the BOM Alpha? 
 I would think a good pot is best in this position as it is the first component the source signal goes though. Just weighing the options, as the RK271 is over 5 times the price + shipping of the Alpha.


----------



## ARwCoco

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_stick 'em in the oven for a while. The pins are steel and the heat sinks are aluminum, and as a result have different coefficients of expansion._

 


 Kudos and a tip-o-the-hat to luvdunhill 
	

	
	
		
		

		
		
	


	




 Used the wife's toaster oven, put my vice grips in the freezer for 5 min and when the "toast" was done, pulled all 4 pins out 1st try. Great tip !


----------



## tomb

Quote:


  Originally Posted by *zha50* /img/forum/go_quote.gif 
_I don't remember it being mentioned in this thread, but how much 'better' is the RK271 over the BOM Alpha? 
 I would think a good pot is best in this position as it is the first component the source signal goes though. Just weighing the options, as the RK271 is over 5 times the price + shipping of the Alpha._

 

Amb uses the RK27 in his B22. If you look at Tangent's tests of pots (http://www.tangentsoft.com/audio/atten.html), the RK27 tests better than at least one stepped attenuator, I believe.

 That said, the little Alpha pot is fine for the SSMH, IMHO.


----------



## Hayduke

What Tom said ^^

 with the caveat that I had a problem with my amp that turned out to be the pot. I used an Alps RK097 that I had on hand to get it working again, but I have an RK27 on the way from Tom 
	

	
	
		
		

		
		
	


	




 btw, thanks for shipping it to be yesterday Tom!


----------



## nsx_23

Is there any place that sells complete kits?


----------



## Hayduke

Quote:


  Originally Posted by *nsx_23* /img/forum/go_quote.gif 
_Is there any place that sells complete kits?_

 

given your location, try this:
http://www.head-fi.org/forums/f6/aus...tudent-339003/


----------



## nsx_23

Hmm, might be a bit late for that one. 

 I wouldn't mind getting one built by someone with more experience.


----------



## blynch1

I'm looking at making one of these for my first DIY projects. 
 I will be using this with denon D2000 and grado sr225, so are there any parts I should switch out to to optimize for either of these cans? I am starting with the stock BOM ordering from mouser. 

 Aside from the mouser BOM order it looks like I will need tubes/sockets, power supply, soldering iron, 63-37 solder(not sure what size), desoldering braid, small tweezers, wirestrippers, small wire cutters. 

 Anything I am missing? Also were is a good place to get all this stuff and if you could list a part number for the items you suggest that would help as well. If mouser sells good options for any of these a part number would help as well, I've browsed around a bit on their website, but it has way too much stuff to wade through. 

 I'd like to just order all of these tools online as there are no specialty electronic stores nearby except radio shack (so that is an option if you can recommend something from there). 

 -I'd also like to get my mouser order in sometime tomorrow, I am anxious to get started!


----------



## Logistic

For the T220 mounting kit, get the thermasil type, 532 - 4880SG, otherwise you need thermal paste.

 Also you might want to order another two film caps to bypass your output electrolytics (if you prefer).

 Also, I've had a lot of trouble with the lead free silver solder from radioshack, I would not recommend it from personal experience.


----------



## nsx_23

Any aussies here interested in building one of these for me?


----------



## mattcalf

Depending on how I go doing mine very, very soon; I'll let you know.


----------



## blynch1

Does mouser sell wire, solder, or desolder braid and if so which one should I get for this project?


----------



## tomb

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_Does mouser sell wire, solder, or desolder braid and if so which one should I get for this project?_

 

This should answer most of your questions:
Getting Started in Audio DIY


----------



## blynch1

I've read quite a bit on tangent's site, but there are so many options on mouser I'd like for someone to just point me to the proper ones for this project.


----------



## n_maher

In order to DIY you must, at some point, do some of it _yourself._


----------



## Bomo.is.ooc

Received almost all of the parts today, will be starting the build in about a week or two. I'm really excited for this.


----------



## MoxMonkey

chassis is 95% done and is pretty snazzy except for one slightly over drilled tube socket hole should have it built be wednesday


----------



## blynch1

Don't see anymore of the cisco ps on ebay. Best price I can find is like 15 used shipped in the US. Anyone know a cheaper place to buy?

 I think I'll go with vacuumtube.net for the tubes they have them in stock for $4+shipping, so if you know a cheaper place for tubes let me know that as well.


----------



## ludoo

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_Don't see anymore of the cisco ps on ebay. Best price I can find is like 15 used shipped in the US. Anyone know a cheaper place to buy?

 I think I'll go with vacuumtube.net for the tubes they have them in stock for $4+shipping, so if you know a cheaper place for tubes let me know that as well._

 

Try Ebay UK, you'll pay a few pounds in shipping but there are some good deals. I bought 3 for 1.50 each.


----------



## blynch1

It looks like all you guys bought every 19J6 tube. radiodaze and vacuumtube.net are out of stock.
 I've got every other part on order, just short tubes. May have to pick them up off ebay, kinda pricey and I don't see sockets either.

 Anyone have a 4 tubes+sockets sitting around they would like to get rid of, I can paypal you a a reasonable offer.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_Don't see anymore of the cisco ps on ebay. Best price I can find is like 15 used shipped in the US. Anyone know a cheaper place to buy?

 I think I'll go with vacuumtube.net for the tubes they have them in stock for $4+shipping, so if you know a cheaper place for tubes let me know that as well._

 

Not sure about used, but for a new PS I paid the same ~$14 shipped which was on par with what others have paid. For tubes it's a little more difficult, but just search tubes on google and probably 10+ tube vendors will appear. I ended up emailing a bunch of them and many said they had stock of them (~4-7/ea.). I haven't found any on eBay minus the occastional one.


----------



## m0b1liz3

Can someone give me some suggestions for troubleshooting? 

 My SSMH has developed a bit of hiss. Sort of like when you put on an LP before the music plays as the needle picks the scratches, debris etc. 

 Could it just be the tubes? Or should I open it up and take a close look at the mess of wires inside?


----------



## Logistic

Is it a consistent hiss, or random? Does it move with the tubes?


----------



## Yaka

Hi guys

 just joined to say after reading this thread over and over again past few days i decided to make one my self. just hope i do ok for my first ever diy amp.

 and im totally impressed by mouser, ordered late Tuesday and it was here this morning not bad considering i live in the UK and shipping was free


----------



## m0b1liz3

Logistic, not sure if it does change with moving the tubes. It seems to come and go. It stays for most of the time though but it isn't just a constant hiss, it fluctuates a little bit. (Sort of like I described previously with the similarity to a record needle)


----------



## Punnisher

I just finished my amp, and I am blown away by it. Needless to say I'll be sticking to tubes for the foreseeable future.

 Thanks to pmillett and everyone who's posts helped me out.

 I was worried about his/hum but there is none as far as I can tell. It has a pitch black background. I used 470uf caps all around and am using a 1.25A power supply from a Cisco device.

 Quick question: Tubes for these are getting rare, and I have two sets. One set is well matched but the other set is not. They are both GE brand but have different internal designs. One is also much brighter than the other. How audible are differences in tube design?


----------



## Mellow Mushroom

cool beans!


----------



## espressogeek

I finally got my hands on tubes. I ordered six but they are all different. Perhaps I can post them online and we can swap to make a set?


----------



## J.P.6

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_Hi guys

 just joined to say after reading this thread over and over again past few days i decided to make one my self. just hope i do ok for my first ever diy amp.

 and im totally impressed by mouser, ordered late Tuesday and it was here this morning not bad considering i live in the UK and shipping was free_

 

It's you from OcUK!


----------



## Logistic

Try switching the tubes and listening carefully to which channel it is coming from to see if it follows the tubes. You can try cleaning the contact pins of the tubes with some contact cleaner or isopropyl alchohol. I had a bad tube that would make faint static noises that sound like what you might have. I changed the tube and it was gone, so it was probably a failing tube or just a fidgety one.

  Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Logistic, not sure if it does change with moving the tubes. It seems to come and go. It stays for most of the time though but it isn't just a constant hiss, it fluctuates a little bit. (Sort of like I described previously with the similarity to a record needle)_


----------



## Yaka

Quote:


  Originally Posted by *J.P.6* /img/forum/go_quote.gif 
_It's you from OcUK!_

 

aye it is me. just hope my tubes arrive before xmas so i can get this done.


----------



## Punnisher

My first diy amp ever! I love it.
 Yeah, the knob is always the last to be added on these types of projects, lol.


----------



## mattcalf

Very nice punisher, I can't wait to get my tubes so I can build it!


----------



## nsx_23

And I can't wait to see how yours turns out


----------



## MoxMonkey

so i completed my build but have one problem

 i have a temp headphone and set of rca jacks hooked to test things and have it hooked to a cd player for testing

 playing back a song is perfect but if i pause, stop, skip tracks i get a really loud popping sound this also happens as things are powering up


 any suggestions?


----------



## royewest

What value caps did you use?


----------



## MoxMonkey

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_What value caps did you use?_

 

470 uf panasonic fc's all around


----------



## blynch1

Anywhere have the tubes+sockets in stock? I've emailed about 8 places with no luck. 

 -Also is there a good beginner guide to point to point soldering, I've watched most of the tutorials on tangent's site but that focuses mainly on pcb stuff.


----------



## Punnisher

You are not supposed to have the headphones plugged in when powering up or powering down. This could damage your phones.

 As for the pausing issue, I have no idea.


----------



## royewest

The issue of leaving your headphones plugged in is pretty thoroughly covered in some earlier segments of this thread. In particular, starting with post 228 from Peter Millett:

http://www.head-fi.org/forums/f6/mil...ml#post4220313

 As originally designed, or with a slightly increased cap value (e.g., "470s all around") there is no risk to your headphones, and with the modified cap values there isn't even much of a "thump" at all.


----------



## MoxMonkey

Quote:


  Originally Posted by *Punnisher* /img/forum/go_quote.gif 
_You are not supposed to have the headphones plugged in when powering up or powering down. This could damage your phones.

 As for the pausing issue, I have no idea._

 

using a cheap pair of headphones to test so i'm not worried about that and i was using it mainly as a comparison to what happens when i pause it


 oddly enough it doesn't happen with my 4th gen ipod as a source, i only get really but popping when i unplug/plug the headphones in


----------



## Logistic

Try tapping the input and output wires, so see if you are stressing a bad connection. Check the connections to the headphone and RCA jacks.

 As for tubes, trying contacting the ebay seller the-radio-tube-supply-company. I got my tubes from him, but he might be out as he doesn't have anymore ebay auctions, but it doesn't hurt to ask.


----------



## krisjan

hiya all - i need some help please regarding parts - it's been so laborious trying to source alternatives and i'm exhausted 
 I live in South Africa and the main supplier i use is rs-components who has a branch here...I could find suitable caps, resistors, pot, switch, etc. the standard parts. What i am unsure about/or can't find is the following:
 1> Heatsink - Is it ok to use any T0220-mount heatsink with similar thermal resistance to the one in pete's bom (6.3 deg C/W)? I suppose the thermal resistance is all that matters? So far I have the following alternatives:
AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W (This one it seems has the standard hole for mounting but TR is slightly higher than the one in the BOM)
AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W (This one looks good in terms of performance but works with a clip (AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor & Heatsink (Accessories)) - no hole for mounting - would this be a problem?)
ABL Components | Semiconductors | Sockets and Heatsinks | Heat Sinks | Thermal Resistance More Than 1.3Â°C/W (This one looks most similar to pete's but i checked the datasheet and it also works with a clip of some sort)
 There is another one which looks quite suitable (AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W) but they only come in packs of ten which would blow my starving student budget 
	

	
	
		
		

		
			




 And then thereafter i will attempt the nightmare at selecting an appropriate heat film material etc.

 The second q is just - I will obviously have to buy the tubes and power supply from ebay/radiodaze etc. Is there anyone who can supply me the tubes, tube sockets, and a power supply in one shipment? Maybe someone who has extra spares from previous builds, or similar - please - i want to try and save on shipping costs...

 k


----------



## MoxMonkey

turns out it doesn't like not having a pot connected


 props to cetoole for the advice


----------



## tomb

Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_hiya all - i need some help please regarding parts - it's been so laborious trying to source alternatives and i'm exhausted 
 I live in South Africa and the main supplier i use is rs-components who has a branch here...I could find suitable caps, resistors, pot, switch, etc. the standard parts. What i am unsure about/or can't find is the following:
 1> Heatsink - Is it ok to use any T0220-mount heatsink with similar thermal resistance to the one in pete's bom (6.3 deg C/W)? I suppose the thermal resistance is all that matters? So far I have the following alternatives:
AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W (This one it seems has the standard hole for mounting but TR is slightly higher than the one in the BOM)
AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W (This one looks good in terms of performance but works with a clip (AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor & Heatsink (Accessories)) - no hole for mounting - would this be a problem?)
ABL Components | Semiconductors | Sockets and Heatsinks | Heat Sinks | Thermal Resistance More Than 1.3Â°C/W (This one looks most similar to pete's but i checked the datasheet and it also works with a clip of some sort)
 There is another one which looks quite suitable (AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W) but they only come in packs of ten which would blow my starving student budget 
	

	
	
		
		

		
		
	


	



 And then thereafter i will attempt the nightmare at selecting an appropriate heat film material etc.

 The second q is just - I will obviously have to buy the tubes and power supply from ebay/radiodaze etc. Is there anyone who can supply me the tubes, tube sockets, and a power supply in one shipment? Maybe someone who has extra spares from previous builds, or similar - please - i want to try and save on shipping costs...

 k_

 

I'm not sure any of those would really work. What you need is this style found on the first page of RS's heat sink listings:
AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W

 Unfortunately, 1-1/2" height should be a minimum even using one of these, but I went through the whole listing and could find nothing like this that was over 1" (25mm) tall. I'm not saying you can't make something in that inventory work, but maybe you should search another supplier. Have you tried calling them personally? It seems a bit hard to believe that they don't have any of these over 1." 2" is best, but 1-1/2" should still be very common (I would've thought).


----------



## ludoo

A quick tip for those whose mosfets get really hot (as in you could cook eggs on them), and who might notice a slightly off sound. I had this problem in one of my SS, with treble appearing to sound a bit weird compared to my other SS, like it was distorted.

 After a few tries, Donald (dBel84) came up with the possible explanation that my mosfets were oscillating, and suggested to put a bypass film cap on the heater pins. Last night I added a 0.1uF cap between pins 3 and 4, and the amp is now running much better: the mosfets are hot but not unbearably so and the sound has cleaned up beautifully.


----------



## Hayduke

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_A quick tip for those whose mosfets get really hot (as in you could cook eggs on them), and who might notice a slightly off sound. I had this problem in one of my SS, with treble appearing to sound a bit weird compared to my other SS, like it was distorted.

 After a few tries, Donald (dBel84) came up with the possible explanation that my mosfets were oscillating, and suggested to put a bypass film cap on the heater pins. Last night I added a 0.1uF cap between pins 3 and 4, and the amp is now running much better: the mosfets are hot but not unbearably so and the sound has cleaned up beautifully._

 

Do you mean pin 3 and 4 of the tube socket? I'm guessing yes since the MOSFETs only have 3 pins


----------



## krisjan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure any of those would really work. What you need is this style found on the first page of RS's heat sink listings:
AAVID THERMALLOY | Semiconductors | Sockets and Heatsinks | Heat Sinks | Transistor Type Packages up to 48Â°C/W

 Unfortunately, 1-1/2" height should be a minimum even using one of these, but I went through the whole listing and could find nothing like this that was over 1" (25mm) tall. I'm not saying you can't make something in that inventory work, but maybe you should search another supplier. Have you tried calling them personally? It seems a bit hard to believe that they don't have any of these over 1." 2" is best, but 1-1/2" should still be very common (I would've thought)._

 

thanks a lot for the reply...As long as the dissipation (indicated by the thermal resistance) is sufficient, would the height matter though - or are you referring to possible space constraints width wise? 
 anyway - the rs-components sometimes mix up their dimensions - this one here is 1.6" high (link to datasheet): http://docs-europe.electrocomponents...6b80031923.pdf - but it looks quite different from the one in the bom - so i'm skeptical...
 the one most similar is this one: http://docs-europe.electrocomponents...6b80029968.pdf (ABL Components | Semiconductors | Sockets and Heatsinks | Heat Sinks | Thermal Resistance More Than 1.3Â°C/W) - it is 50mm high (once again a mix-up in the spec - they refer to it as length), which is over 1.6" - so i guess this one would be best? i suppose the clip should be fine, i could always just drill a hole as well...
 thanks again
 k
 edit: i have looked at some other suppliers but the staff is so clueless and stock so unorganised - rs is really the only way to go here...


----------



## ludoo

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Do you mean pin 3 and 4 of the tube socket? I'm guessing yes since the MOSFETs only have 3 pins 
	

	
	
		
		

		
		
	


	


_

 

Yes, the tube heater pins.


----------



## FallenAngel

So how hot is too hot for the heatsink? I left this thing running for 8 hours straight (overnight), woke up this morning and the heatsink practically burned my fingers!







 Of course I later realized that I used Mica insulators without grease, which I'll probably fix.

 In either case though, I saw the IRF510 can take about 175C, pretty sure it would have burned me pretty bad if it ever got that hot, so I'm curious - how hot is "too hot"? I've ran one with a pair of large heatsinks and they get hot enough that it's unpleasant to hold my finger on them for more than a second or two, but this one gets burning hot after a few hours.


----------



## Punnisher

That's strange. Mine has two standard heatsinks with one layer of thermal tape between them and they don't get too hot. Then again the enclosure is all aluminum so it really soaks up the heat.

 I listened to it in a room that was almost 90 degrees F and it was toasty but not unpleasant to touch. It was on for about 4 hours.


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## scompton

Mine is at work so in on 4-10 hours a day. The heat sinks get warm enough to be uncomfortable to the touch pretty quick, but get no hotter.


----------



## MoxMonkey

and mine is finished 
	

	
	
		
		

		
		
	


	




 now to start rolling the nice selection of 19j6's i have


----------



## krisjan

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_and mine is finished 
	

	
	
		
		

		
		
	


	




 now to start rolling the nice selection of 19j6's i have_

 

lucky you...i've been hunting for tubes - only i could find was for $25 a piece - a little too much if u ask me...so the hunt continues - seems as if all "major" suppliers are out and nothing on ebay - darn, this build is too popular...maybe i should do a pimeta first...
 just out of curiousity, i know it's completely different amps but how does a pimeta (optimized for desktop) compare to a starving student - for those who've heard/built both?


----------



## ludoo

Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_lucky you...i've been hunting for tubes - only i could find was for $25 a piece - a little too much if u ask me...so the hunt continues - seems as if all "major" suppliers are out and nothing on ebay - darn, this build is too popular...maybe i should do a pimeta first...
 just out of curiousity, i know it's completely different amps but how does a pimeta (optimized for desktop) compare to a starving student - for those who've heard/built both?_

 

I may have a couple of extra tubes I got as spares I could sell you. I believe they cost me 6$ each including shipping, I have to check past emails. Shipping to SA should cost little for such a small package. If you don't find anything else drop me a PM.


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## krisjan

(to fallenangel) well if a heatsink gets hot that's usually a good thing because it means that there's decent heatflow/coupling between the chip and the sink...the only way to really tell if theres a problem is too measure the temp on the chip (just coming from building pc's and all the cooling involved on cpu's and gpu's)...I see my multimeter has a temp measurement as well - if yours has one too you could press it against some metal section of the irf510 and measure the temp...
 175 is very hot - instant blister, and possibly more - ie a lot of pain...


----------



## krisjan

one thing i don't get about the starving student are caps c3 and c5 - the output caps - why are they electrolytic? i thought it's best to have a film cap and then ideally polypropylene in the audio signal path?


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## FallenAngel

If you can get film caps big enough not to have serious bass roll-off, by all means, it's a good idea, just goes against the whole "starving student" thing by price.

 I don't have a temp gauge on my dmm, might just use a cooking thermometer though


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## tomb

Ya'll are correct, of course.

 However, try purchasing or installing a 150uf to 470uf polypropylene film cap.


----------



## cetoole

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_turns out it doesn't like not having a pot connected


 props to cetoole for the advice 
	

	
	
		
		

		
		
	


	


_

 

Glad we finally got it working Kefka. 

  Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_So how hot is too hot for the heatsink? I left this thing running for 8 hours straight (overnight), woke up this morning and the heatsink practically burned my fingers!







 Of course I later realized that I used Mica insulators without grease, which I'll probably fix.

 In either case though, I saw the IRF510 can take about 175C, pretty sure it would have burned me pretty bad if it ever got that hot, so I'm curious - how hot is "too hot"? I've ran one with a pair of large heatsinks and they get hot enough that it's unpleasant to hold my finger on them for more than a second or two, but this one gets burning hot after a few hours._

 

Pavel, I love the SSMH inna Linksys concept, but your heatsink is the wrong profile for effect transfer to the air. You are able to get very little natural convection, so even though there is plenty of surface area, it just all heats up and doesnt go anywhere, except by simple radiation and minimal convection from air currents in the room, or at least, this is my guess. Never got too advanced in the relative sciences though, so I could be way off. However, adding grease will only increase heat transfer from the MOSFETs to the heatsinks, so should actually make the heatsinks warmer, not cooler.

  Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_one thing i don't get about the starving student are caps c3 and c5 - the output caps - why are they electrolytic? i thought it's best to have a film cap and then ideally polypropylene in the audio signal path?_

 

Cost, and because Polypropylene caps big enough are huge. Here are some 100uf ones I have, and they are around the size of a 12oz soda can, and most people would still consider the capacitance to be too low for most headphones.
http://img.photobucket.com/albums/v3...rts/1000uf.jpg


----------



## FallenAngel

Thanks 
	

	
	
		
		

		
		
	


	




 I do love the looks and how it just worked together (everything was pretty much perfect size and shape). So I'm curious why a somewhat smaller pair of heatsinks work better at this than this huge monster? More importantly, is there anything I can do to cool this heatsink down? If it doesn't make much more noise, maybe a fan point to the back... ooh, there's an idea, lets make this into a swamp boat/hovercraft


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## holland

You need fins that point up, not sideways. When the heat rises, it'll pull from the surrounding, particularly below the sink. The vertical fins gives it free movement without impedance or turbulence.

 That said, my sinks get hot too, very hot. I can't recall the exact temperature, but could take another measurement soon.


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## cetoole

What Holland said. Ideally, the heatsink would be facing like you had the whole amp on it's side, which might not be a bad test, though I would suspect you could get pretty good improvements from turning it so half of the fins are facing straight up and the other half down. Definitely not perfect, and it wont get a chimney effect at all, but it should do better than now, I think. A fan, even a really slow, tiny one would also make it run much cooler.


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## Captain ?degard

I have an idea for a design for this thing but not sure im willing to put in the cash for both amp and everything I want in this thing









 I was thinking a remote control line out dock for the ipod, sound reactive LEDs in the two tubes on the side and possibly a built in sub with external speakers (PC speaker style) in the bottom part of the jukebox.


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## HeadphoneAddict

Quote:


  Originally Posted by *Captain Ødegård* /img/forum/go_quote.gif 
_I have an idea for a design for this thing but not sure im willing to put in the cash for both amp and everything I want in this thing









 I was thinking a remote control line out dock for the ipod, sound reactive LEDs in the two tubes on the side and possibly a built in sub with external speakers (PC speaker style) in the bottom part of the jukebox._

 

I vote you do it!


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## Logistic

That looks amazing! Please post pics if you decide to make it.


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## Captain ?degard

Ive done something similar some years ago: Captain’s Quarters » Cowon D2 Jukebox Dock
 Compared to the resources and tools I have now its not impossible but still not sure. Living in norway makes getting parts expensive and time consuming


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## krisjan

Quote:


  Originally Posted by *cetoole* /img/forum/go_quote.gif 
_Cost, and because Polypropylene caps big enough are huge. Here are some 100uf ones I have, and they are around the size of a 12oz soda can, and most people would still consider the capacitance to be too low for most headphones.
http://img.photobucket.com/albums/v3...rts/1000uf.jpg_

 

haha - ok - sorry for the dumb questions - i'm still new in this game...but then, why are input caps (on other amps) so low on capacitance (.1-1uf generally from what i can c in the cmoy and pimeta, etc.) - is it because it is a lower level (unamplified) signal? and thus the amplified signal needs a cap with a bigger value?


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## Logistic

Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_haha - ok - sorry for the dumb questions - i'm still new in this game...but then, why are input caps (on other amps) so low on capacitance (.1-1uf generally from what i can c in the cmoy and pimeta, etc.) - is it because it is a lower level (unamplified) signal? and thus the amplified signal needs a cap with a bigger value?_

 

The output capacitors are there to block DC, however, it will also cut off low freq signals. I'm not certain, but I suspect the smaller capacitances used in the inputs are because the impedance of the voltage buffers are very high, and the cutoff freq is proportional to 1/RC. With a high R, you don't need a large C. Whereas at the output, the R is the impedance of your headphones, which isn't as high, so you need a much larger C to avoid a cutoff freq that's too high (in the audible range).

 My understanding of electronics is pretty limited though, so someone else might be able to give a better explanation.


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## Punnisher

Anyone know the secret to making this amp more Grado friendly?

 I am using a 100k potentiometer but the input impedance needs to be much higher due to a large imbalance in the potentiometer. I read about this fix earlier in the thread.

 Also there is a hum present that's only noticeable with grados, not my 880. I assume this is normal with this simple of a design.


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## scompton

This interests me as well because even with my Sextett, I never get the volume past 9 o'clock


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## dsavitsk

Quote:


  Originally Posted by *Punnisher* /img/forum/go_quote.gif 
_Anyone know the secret to making this amp more Grado friendly?

 I am using a 100k potentiometer but the input impedance needs to be much higher due to a large imbalance in the potentiometer. I read about this fix earlier in the thread._

 

The best fix seems to be a resistor inline with the input (before the pot). Something on the same order as your pot will drop the signal 6db.

  Quote:


 Also there is a hum present that's only noticeable with grados, not my 880. I assume this is normal with this simple of a design. 
 

Maybe, maybe not. The last one I made was silent with Grados. What caps did you use in the PS? Upping them to 470u seems to help. Otherwise, if your grounding is less than ideal it can cause some hum. Also, the tubes can pick up noise from nearby components (wrap them in grounded foil to see if shielding them helps). Finally, it is possible that it is amplifying noise in the previous stage that your were previously unaware of.


----------



## dsavitsk

Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_but then, why are input caps (on other amps) so low on capacitance_

 

 Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_My understanding of electronics is pretty limited though, so someone else might be able to give a better explanation._

 

Basically correct. For some more detail, see ecp.cc


----------



## nikongod

Why has nobody else gone out and modified the circuit to use other tubes? The original tube is pretty spiffy with its 18V heaters, but there is no reason that various parts could not be adjusted to use the same ideas with a 12au7 or similar. $25*2 for tubes to put into an amp with $60 in parts?

 I have an alternate schematic, using a tube you may ALREADY have from a previous build, for anyone brave enough to try it.
  Quote:


  Originally Posted by *Punnisher* /img/forum/go_quote.gif 
_Anyone know the secret to making this amp more Grado friendly?_

 

link1
 Works well with REALLY cheap attenuators, especially if you need LOTS of attenuation.
link 2
 Works well with better attenuators, have not tried with cheap parts: I was too happy with the first one.


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## holland

I had done that to use 12au7 (5963) since I've got a few dozen extras. But, then I figured why bother, and B+ shot up to 300V for a plate voltage of around 220V @ 4-8mA with CCS in a few places....and as all things DIY everything else started changing too, with a PS instead of wallwart.

 If you're going to go 9-pin, I would definitely start using some CCS for more tube flexibility. You know that nobody is going to stop with a 12AU7.


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## Yaka

well i have followed the schematics exactly built it ( with the odd mishapp in drilling my case) and nothing. spent past 2 days resoldering and de soldering everything none of my four tubes are lighting up or anything. ive prolly killed small bit or something


----------



## nikongod

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_If you're going to go 9-pin, I would definitely start using some CCS for more tube flexibility. You know that nobody is going to stop with a 12AU7._

 

I agree, a plate-CCS will be mandatory, but its really not that hard to build a simple one. Restricting the design to a B+ of 48V pretty much guarantees that you can use low power transistors with high Hfe.
 There have been a few commercial products through the years that have used 6dj8 and 12au7 (amongst others, but who *needs* more than 30 voltage gain...) with as little as 30V on the plate. I agree that according to the plate curves it should suck hard enough to get a golf-ball through a garden hose... but isnt that the fun of designing with restrictions? The challenge of who can make the "best" compromises to get the most sound out of junk-bin parts on a lunch-money budget.
  Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_well i have followed the schematics exactly built it ( with the odd mishapp in drilling my case) and nothing. spent past 2 days resoldering and de soldering everything none of my four tubes are lighting up or anything. ive prolly killed small bit or something_

 

Is this your first build?
 Tube sockets are numbered as viewed from the bottom.
 got pics?


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## OldKing

I built this one for a friend as a Christmas present.


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## nikongod

Quote:


  Originally Posted by *OldKing* /img/forum/go_quote.gif 
_I built this one for a friend as a Christmas present.

 (photos removed to protect the 56K)_

 

That looks SWEET!
 Where did you get the heat-sinks? I really like the look.


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## OldKing

Heatsink is here

 BOM (more or less) is here  except I changed caps and added the Neutrik jacks.

 The knob and heat sink are black anodized aluminum which I sanded and polished.


----------



## Hayduke

Quote:


  Originally Posted by *OldKing* /img/forum/go_quote.gif 
_Heatsink is here

 BOM (more or less) is here  except I changed caps and added the Neutrik jacks.

 The knob and heat sink are black anodized aluminum which I sanded and polished._

 

Ahhh that's how you got the sink to look like that. Very nice 
	

	
	
		
		

		
			





 Did you use a dremel to polish, or??

 I like the idea of giving a MHSS as a gift! I'm too late for xmas this year, but if I start now, I might have some ready for next year


----------



## holland

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_but isnt that the fun of designing with restrictions? The challenge of who can make the "best" compromises to get the most sound out of junk-bin parts on a lunch-money budget._

 

That's very true. I'm not sure how much can be treaded though, so much has already been done in the <= 48V range. SOHA, SOHA 2, Millett Max, Borbely's hybrid, YAHA, YHHA, MAHA, etc.

 To be honest though, every VAS I come up with, for this simple amp, seems to look like the SOHA, SOHA 2, or Borbely. There's been alot of ground tread already and it's going to be difficult to really differentiate.

 Heatsink: 
641K


----------



## dsavitsk

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_Why has nobody else gone out and modified the circuit to use other tubes? The original tube is pretty spiffy with its 18V heaters, but there is no reason that various parts could not be adjusted to use the same ideas with a 12au7 or similar._

 

12au7, 12sn7, 12j5 all might work, though at the low voltages clipping from overdriving the grid is a real issue.

 Here's the version I drew up a while ago. It is higher voltage, but is the same basic topology as the original with the addition of a plate CCS and a shunt regulator. I've been sitting on it as I have not had a chance to build it to see if it works at all. But, I don't think I will, so this should be considered untested.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *OldKing* /img/forum/go_quote.gif 
_I built this one for a friend as a Christmas present.
_

 

Looks awesome


----------



## holland

interesting, dsavitsk.

 Here's one I put together. I intend to build it, the voltages were chosen based on transformers I have.

 PS will be a 120V->48V (24-0-24) -> 240V using 2 transformers. 240V rectified to about 330V will be filtered with CRCLC. (24-0-24) will be simple 3 pin regs. I intend to put an e12 on the output, hence no cap and trimpot to adjust. e12, in case of thermal drift, will make it super sensitive to DC. startup delay of about 1 minute for PS to settle.

 It's not starving student, and not quite beginner voltages.

 I was sitting on this as well, will likely try a build in a few months. I owe some amps to some relatives, so why not, as I already have most of the parts on hand.


----------



## nikongod

Here is mine:




 EDITED:
 originally posted schematic had an error in the tube! Tube should be 12fk6 as shown now, NOT 12fk7.


----------



## dsavitsk

With the 12V tubes, in many cases you can still use the heater as the mosfet load. That seems to me to be what makes the SS unique and interesting. Indeed, the 18V heater on the 19J6 is hungry in wattage terms and draws about the same current as a lot of 12V heaters.

 12FK7? What's that?


----------



## OldKing

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Ahhh that's how you got the sink to look like that. Very nice 
	

	
	
		
		

		
			





 Did you use a dremel to polish, or??

 I like the idea of giving a MHSS as a gift! I'm too late for xmas this year, but if I start now, I might have some ready for next year 
	

	
	
		
		

		
		
	


	


_

 

For the heat sink, I started with an orbital sander to get the hard anodized layer off.

 Once you get the black off the Al is very soft and goes fast by hand.

 Wet sand with 120 then 320 then 1500 then 2000 in the sink under running water, then metal polish.

 For the knob, I had it in spinning in the drill press and held the papers against the corner to round it off.


----------



## Yaka

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_
 Is this your first build?
 Tube sockets are numbered as viewed from the bottom.
 got pics?_

 

hi yes this is my first build. i have since posting taken everything apart. tho now i think the problem may with the tube sockets. are they meant to hold the tubes firmly in? ans in the ones i have got when placed firmly in using as much force as i dare then i tilt the socket a bit the tubes from both come loose


----------



## nikongod

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_Are they meant to hold the tubes firmly in?_

 

Yes, they should have a pretty decent grip on the pins. The grip on the pins makes the electrical contact.
  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_With the 12V tubes, in many cases you can still use the heater as the mosfet load. That seems to me to be what makes the SS unique and interesting. Indeed, the 18V heater on the 19J6 is hungry in wattage terms and draws about the same current as a lot of 12V heaters._

 

yep, version 1 of the amp I put up did that. I wanted to DC couple the plate to the mosfet though. I dont think the tube I used really liked running at the points that kind of forced on it.
  Quote:


 12FK7? What's that? 
 

I made a mistake on the schematic! It should read 12FK6. will edit.


----------



## holland

Quote:


  Originally Posted by *nikongod* /img/forum/go_quote.gif 
_I wanted to DC couple the plate to the mosfet though._

 

Is there a big difference in dc coupling the plate to the mosfet?


----------



## nikongod

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Is there a big difference in dc coupling the plate to the mosfet?_

 

I never tried to cap couple this design, so I cant say for sure. 

 The general rule of thumb is that "no cap is as good as no cap" but there are exceptions. When you need to isolate DC there are a couple other options but a cap is generally the least expensive and most convenient. 

 I dont know if the SS would suffer the same problems that my amp did trying to DC couple AND force all of the voltages to the right levels. Whats the plate voltage as it sits now, go from there.


----------



## gurusan

Been away awhile, just a small update.

 I have changed the output caps from

 -330uF Nichicon Muse ES
 -bypassed with Wima MKP10 .33uF

 to

 -470uF Muse FS caps
 -bypassed with Audyn-Cap MKP Q4 .47uF

 The effect is that my bass is much more full, stronger and more defined with the HD 580s. Just decided to share my findings....my earpads are extremely worn out so just bit the bullet and bought new ones so hopefully that will give me even more bass.

 I have also noticed that I can now pick out individual sounds in the highs a bit more easily.


----------



## fallen angel

I've been peicing together for this amp.

 So far I have everything, less the tubes. I found the tubes for sale, but haven't received an email back on purchasing a set matched. (site says to inquire about this) 

 Would anyone perhaps know of a site that would match them for me?


----------



## nikongod

Dont worry about tube matching with this amp.


----------



## krisjan

here i have an "international" parts list - twofold purpose - 
 1> to help those outside US access a quick ref to parts numbers of an international supplier (i'm using rs components) 
 2>cross-check - any suggestions to improve the list would be much appreciated - specially if you pick up some fatal errors...

 I know some of the parts are not really "starving", but it's easy to substitute with lower values as needed once you are on the rs-components site.

 I got the tubes and sockets from radioera.com - they are on their way to me - the PSU i am still hunting for, but i found a local company who sells used cisco equipment so hoping to get it from them (awaiting their reply). So apart from that all parts from RS...

 It is quite a bit more expensive to do this if you are not based in the CONUS (main reason would be to get the tubes shipped - easily adds $10 to 20 + if you buy power supply on ebay or sth that has to be shipped seperately), i also think in general rs is a little more expensive than us suppliers...so maybe it should be called "starving US student" amp


----------



## krisjan

Would this power supply work with the SS: Phihong | Power Supplies | Power Supplies, Inverters, DC/DC Converters & Generators | External Power Supplies | Switch Mode - Phihong
 Would the fact that it is switch mode be a problem? Add noise?


----------



## dean0

Im in desperate need of an amp since my darkvoice gave up on me 
	

	
	
		
		

		
		
	


	




 this looks like the perfect 'fill in' amp til i get graham slee solo.

 Ive ordered all the parts i need as listed, expect caps (using better quality ones), and tubes. I cannot find 19j6 tubes anywhere. I live in UK anyone know a good place to find some? or can i use an alternative?
 thanks in advance 
 1st post


----------



## ludoo

Quote:


  Originally Posted by *dean0* /img/forum/go_quote.gif 
_Im in desperate need of an amp since my darkvoice gave up on me 
	

	
	
		
		

		
		
	


	




 this looks like the perfect 'fill in' amp til i get graham slee solo.

 Ive ordered all the parts i need as listed, expect caps (using better quality ones), and tubes. I cannot find 19j6 tubes anywhere. I live in UK anyone know a good place to find some? or can i use an alternative?
 thanks in advance 
 1st post 
	

	
	
		
		

		
		
	


	


_

 

I got my last batch from radioera.com and kris found them there too. If you are desperate I might have a couple to sell, but with added postage etc, radioera would be cheaper.


----------



## krisjan

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I got my last batch from radioera.com and kris found them there too. If you are desperate I might have a couple to sell, but with added postage etc, radioera would be cheaper._

 

bad news - the guy from radioera made a mistake - they don't have any in stock, their records were incorrect or sth, but he's trying to source some from elsewhere for me...i tried thetubecenter as well and they said they might be getting some soon...but yes - it's a big problem - i think the popularity of this build has just wiped out the supply of 19j6's. Anyway - i hope radioera can source me some else i'm gonna go for a pimeta...


----------



## Logistic

There are some 19j6 tubes available on ebid.net. I just checked and there are quite a few available. Just search for 19j6.


----------



## bmwpowere36m3

STRONG ADVICE TO FUTURE "SS" MILLET BUILDERS...

 I would make sure I secure some tubes BEFORE starting this build, it appears that they really are becoming scarce. I would check eBay and google search "vacuum tubes", you'll get tens of "stores" selling tubes. When I set out to do this, I emailed upwards of 10 stores asking if they had the tube. To my surprise, at least 5 or so said they had some.


----------



## dean0

thanks for the info, much appreciated 
	

	
	
		
		

		
			





 Ordered 2 of these NOS 19J6 RCA Vacuum Tube - Valve on eBid.net United Kingdom

 anyone know how this amp will compare with my dead Darkvoice 336i?


----------



## holland

Quote:


  Originally Posted by *dean0* /img/forum/go_quote.gif 
_anyone know how this amp will compare with my *dead Darkvoice 336i*?_

 

Infinitely better...it works.


----------



## Hayduke

Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_bad news - the guy from radioera made a mistake - they don't have any in stock, their records were incorrect or sth, but he's trying to source some from elsewhere for me...i tried thetubecenter as well and they said they might be getting some soon...but yes - it's a big problem - i think the popularity of this build has just wiped out the supply of 19j6's. Anyway - i hope radioera can source me some else i'm gonna go for a pimeta..._

 

When they say they are "sourcing" a new supply, it means that someone is going to start rummaging through old boxes in a dusty warehouse somewhere 
	

	
	
		
		

		
		
	


	




 All these posts about having trouble finding tubes makes me think I should order some more while I still can.

 newb question time...
 Since this is my first tube amp, I'm experiencing something new. I can hear when the tube is tapped or vibrated. For example, I have my amp sitting on my desk here at work, and I can hear myself typing when no music is playing. What can I do to dampen them? I've seen the rubber o-rings for sale. Is that what those are for? Do they work well?


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_When they say they are "sourcing" a new supply, it means that someone is going to start rummaging through old boxes in a dusty warehouse somewhere 
	

	
	
		
		

		
		
	


	




 All these posts about having trouble finding tubes makes me think I should order some more while I still can.

 newb question time...
 Since this is my first tube amp, I'm experiencing something new. I can hear when the tube is tapped or vibrated. For example, I have my amp sitting on my desk here at work, and I can hear myself typing when no music is playing. What can I do to dampen them? I've seen the rubber o-rings for sale. Is that what those are for? Do they work well?_

 

You're experiencing tube microphonics.
	

	
	
		
		

		
		
	


	




 They can range from as slight as ringing when you tap a tube to a crescendo when you just touch the desktop. The defect is in the tube - the mfr installed the getter slap against the plate or some other defect.

 It doesn't mean the tubes are worthless - far from it. Some of the best tubes I've heard have been slightly microphonic. However, if they're badly microphonic, they're almost always useless. Good tube rings can minimize this effect, but they won't entirely eliminate it. They can reduce a strong microphonic tube to one that is less sensitive and listenable. However, there's probably no hope for a badly microphonic tube.

 In defense of tube vendors, though, keep in mind that there's no way to test for this, short of installing the tube in an amp and listening to it.


----------



## dsavitsk

Tube microphonics are not necessarily indicative of a bad tube. They can also be indicative of an oscillating tube which generally means a build issue. Put some stoppers (470R to 1K) right on the grid pins and see if that helps.

 Those O-rings probably won't help.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You're experiencing tube microphonics.
	

	
	
		
		

		
		
	


	




 They can range from as slight as ringing when you tap a tube to a crescendo when you just touch the desktop. The defect is in the tube - the mfr installed the getter slap against the plate or some other defect.

 It doesn't mean the tubes are worthless - far from it. Some of the best tubes I've heard have been slightly microphonic. However, if they're badly microphonic, they're almost always useless. Good tube rings can minimize this effect, but they won't entirely eliminate it. They can reduce a strong microphonic tube to one that is less sensitive and listenable. However, there's probably no hope for a badly microphonic tube.

 In defense of tube vendors, though, keep in mind that there's no way to test for this, short of installing the tube in an amp and listening to it.
	

	
	
		
		

		
		
	


	


_

 

hmmm I have more tubes. I'll try rolling them and see if I notice a difference. It's pretty subtle though, and the amp still sounds good.

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Tube microphonics are not necessarily indicative of a bad tube. They can also be indicative of an oscillating tube which generally means a build issue. Put some stoppers (470R to 1K) right on the grid pins and see if that helps.

 Those O-rings probably won't help._

 

What sort of build issues? Is it something I could fix or do better perhaps?
 I'm not sure I understand what a "stopper" is. So put a resistor between pins 5 and 6 or a resistor on each to ground? Is this something to test with or is it a more permanent solution?

 Sorry for the so many questions. I appreciate everyone's help.


----------



## nikongod

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_What sort of build issues? Is it something I could fix or do better perhaps?
 I'm not sure I understand what a "stopper" is. So put a resistor between pins 5 and 6 or a resistor on each to ground? Is this something to test with or is it a more permanent solution?_

 

A stopper resistor helps to help keep the tube from oscillating or accidentally transmitting RF. 
 5&6 are the grids (inputs) of the tube
 Attach a smallish resistor to EACH pin (with the body of the resistor as close to the pin as practical), then twist the legs together, and solder input to that. signal in now goes to the twisted legs of the resistors, through them to the tube... 

 I agree though, it sounds more like a mechanical issue: I would try to reduce microphonics with tube dampers and other little tricks like that. Don't spend too much on these, they can only do so much. mcmaster carr loves you a lot, go buy some thick high temp silicon o-rings in a size that are a snug fit on your tube.


----------



## krisjan

Quote:


  Originally Posted by *dean0* /img/forum/go_quote.gif 
_thanks for the info, much appreciated 
	

	
	
		
		

		
		
	


	




 Ordered 2 of these NOS 19J6 RCA Vacuum Tube - Valve on eBid.net United Kingdom

 anyone know how this amp will compare with my dead Darkvoice 336i?_

 

yes - tx indeed for the ebid link - they have a za site as well - so just bought 4 tubes off them...radioera couldn't source the tubes - so had to refund me. The store on ebid that sells them is VacuumTubes - i can see 13 19j6 tubes in total there - so if you need some, hurry...
 k


----------



## krisio06

Hi DIY Mates..
 I am very interested in "Starving Student".. It doesn't look very complicated and its very cheap to build.
 I've just build myself GainClone amp using original Peter Daniel's components and I think that it sounds very good but maybe in the future I'll build this amp to..
 There is only one problem. Assembly.
 I like to have the assembly instruction before I start building amplifier..
 Have someone written the assembly instruction to the Starving Student?
 Does it exist?

 CHeers,
 CHarles


----------



## effcleff

I completed my Starving Student a couple of days ago, using OldKing's case design and BOM. What fantastic little amp! It's a shame the tubes are becoming difficult to find, because this little guy is very musical for the money. It seems to be nice match for my late-production sextets.

 A big thank you to Pete for this amplifier, and to OldKing for the BOM!


----------



## scompton

Quote:


  Originally Posted by *krisio06* /img/forum/go_quote.gif 
_Hi DIY Mates..
 I am very interested in "Starving Student".. It doesn't look very complicated and its very cheap to build.
 I've just build myself GainClone amp using original Peter Daniel's components and I think that it sounds very good but maybe in the future I'll build this amp to..
 There is only one problem. Assembly.
 I like to have the assembly instruction before I start building amplifier..
 Have someone written the assembly instruction to the Starving Student?
 Does it exist?

 CHeers,
 CHarles_

 

There aren't any assembly instructions, but it's not hard if you take your time. For many people on this thead, this was their first build, myself included. What I did was take about 5-6 hours and redraw the schematic as a wiring diagram. Once I did that, it was pretty simple.


----------



## omegamajor

Just thought I would drop in and say hello. I've been lurking since I came across the Starving Student design a month ago. I built my own a few weeks ago and have been enjoying it thoroughly. 
	

	
	
		
		

		
		
	


	




 Like many others I departed from the "starving" aspect of the design since I'm no longer a student (and thus not starving). It took me a while to figure out how to lay things out since I wanted to keep wire runs short but straight, especially the incoming signals. The result is interesting and I'm really liking the volume knob on the top.

 Thanks to everyone who has posted here with all the great ideas and information. Particular thanks to bmw & n_maher for design inspiration and tomb for parts.














 Now that I'm hooked I'm trying to decide what to build next.


----------



## digger945

^Welcome to the club omega
	

	
	
		
		

		
		
	


	



 There are many designs to choose from. 
 Are you looking for another PTP build, or just whatever?
 Have you looked at the DIY links and resources thread yet?
 Nice SS amp. I like the layout and design
	

	
	
		
		

		
		
	


	




.


----------



## omegamajor

Thanks digger! For the next possible build I have been thinking about the MiniMAX; not sure though.

 Before I get too ahead of myself though I want to determine how to hear the difference between tubes. I have 6 total (all side D getters and are RCA tubes rebranded as Hytron) for my SS amp and I have swapped them in and out and honestly have not been able to hear a difference, aside from the fact that some of the tubes are slightly more microphonic than others. With all that in mind I'm not sure then if I would be able to appreciate something like a MiniMAX over the SS, though I would enjoy building one.


----------



## vixr

omegamajor, if you like the SS, you will love the MAX...you will be able to hear the difference.


----------



## Fuzzy OneThree

@ omegamajor

 Where did you get that on/off button? I think I have seen a few others use it, and it looks really cool.


----------



## digger945

Quote:


  Originally Posted by *omegamajor* /img/forum/go_quote.gif 
_Thanks digger! For the next possible build I have been thinking about the MiniMAX; not sure though.

 Before I get too ahead of myself though I want to determine how to hear the difference between tubes. I have 6 total (all side D getters and are RCA tubes rebranded as Hytron) for my SS amp and I have swapped them in and out and honestly have not been able to hear a difference, aside from the fact that some of the tubes are slightly more microphonic than others. With all that in mind I'm not sure then if I would be able to appreciate something like a MiniMAX over the SS, though I would enjoy building one._

 

I think I'm gonna sell my miniMAX Lansing case. 
 I don't have time or money to build it now.


----------



## thetelevisi0n

What is that piece? I've seen it in a lot of builds.







 I want to use it for my build but I can't find it since I don't know the name.


----------



## nikongod

Quote:


  Originally Posted by *thetelevisi0n* /img/forum/go_quote.gif 
_I want to use it for my build but I can't find it since I don't know the name._

 

Its a "terminal strip" or "tag board" and a few other names depending on who is describing EXACTLY what. but searching terminal strip will get you the 2 most common uses, one of which is totally not this.


----------



## thetelevisi0n

Thanks nikongod. It was in the BoM all along.


----------



## vixr

Quote:


  Originally Posted by *Fuzzy OneThree* /img/forum/go_quote.gif 
_@ omegamajor

 Where did you get that on/off button? I think I have seen a few others use it, and it looks really cool._

 

you can see the switch HERE

 amb sells a nice set of boards to use it with since its a momentary switch...well mine is. it looks like there is a latching version as well. BTW the switch is kinda pricey...


----------



## omegamajor

Fuzzy: The pushbutton I used is Mouser part # 117-MP0045/1E2RD012. It is a maintained contact, not momentary, so you wouldn't need the boards that vixr was mentioning. I wanted to use this button after I saw it on bmw's amp so I tracked it down. The reason it's expensive is because it's vandal-resistant, meant for installations in publicly used devices. Try looking at the price of the touch-sensitive switches used in elevators sometime. 
	

	
	
		
		

		
		
	


	




 digger: If you are going to sell your lansing case, I may be interested. I assume it's one of the custom run that tomb did? Which color? Let me know and maybe we can work something out. Of course, it's entirely up to you if you want to sell it.


----------



## MoxMonkey

which case is that omega?


----------



## omegamajor

MoxMonkey: It's the Hammond 1590DDBK.


----------



## digger945

^yea I think I wanna sell it. It's silver, Beefy just posted a pic of one onthe miniMAX thread.
 I'll do ya right on the price. I can open it up and take a pic if you want.
 PM me if your interested. No hurry.


----------



## Yaka

well so far i have horrid luck. not sure what i am doing wrong or maybe the components are dead? think i shall try and get some new stuff and try again this week end


----------



## digger945

^Maybe a pic would help to see what you have going on Yaka.


----------



## pistolsnipe

my amp, messy but sounds good. probably should have used thinner wire...


----------



## blynch1

Finished mine tonight. This is my first diy and I am pleasantly surprised with how well it went. Case work was a pita, but it worked perfectly on first power up (minus needing to switch out a dead tube, good thing I ordered an extra). 

 I can only turn the volume knob ~5% to keep it in usable range with a set of SR225. I think I will add a 50K resistor to both inputs right after the rca jacks, correct me if this is the wrong way to fix this.


----------



## royewest

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_I can only turn the volume knob ~5% to keep it in usable range with a set of SR225. I think I will add a 50K resistor to both inputs right after the rca jacks, correct me if this is the wrong way to fix this._

 

This worked well for me. Since you need 2 resistors to do this, even a starving student could spring for high-quality resistors...


----------



## blynch1

Would high-quality resistors have any real world effect at the inputs? If not I'll just pick up whatever radio shack has instead of paying $5 shipping and waiting for a mouser order.


----------



## blynch1

Another question, this was suggested awhile back:
  Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Also you might want to order another two film caps to bypass your output electrolytics (if you prefer)._

 

I have the 2 extra film caps sitting around, what would adding these do and do you just solder them to the junction before and after the output electrolytic caps?


----------



## royewest

My point was just that metal-film 1% resistors are commonly available at my local electronics shop (Al Lasher's -- hardly a high-end boutique but rather the kind of place one's grateful still exists) and worth it to me to match channels. But I have not compared with RS standard issue so I can't claim to hear any difference.


----------



## Hayduke

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_Another question, this was suggested awhile back:

 I have the 2 extra film caps sitting around, what would adding these do and do you just solder them to the junction before and after the output electrolytic caps?_

 

You wire the film caps in parallel with the electrolytics. In other words, the films attach to the same points as the 'lytics.


----------



## blynch1

thanks that makes sense, but how would the film caps effect the sound?


----------



## Hayduke

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_thanks that makes sense, but how would the film caps effect the sound?_

 

Caps act as a sort of reservoir of power. So, for example, when a big bass note hits, there is a larger momentary demand for power. The capacitor is what supplies this. A good analogy is a sink of water. The faucet can only supply a steady amount of water, but what if the size of the drain varied? The sink would be able to buffer the needed water. Does that makes sense?

 OK, now if you understand what the caps are doing, then you can understand what the extra caps do in this circuit. Electrolytics are slow (relatively speaking) to respond to those changes in demand, but they hold a lot of power in them. Film caps respond very quickly, but are very small reservoirs of power. When you put the two in parallel, you have the big capacity of the electrolytic combined with the fast response of the film.

 I'm sure this is an over simplification, but it's the way I think of it. Someone can correct me if I'm wrong


----------



## blynch1

Thanks for the simple explanation. I know how capacitors work so I got the power reserve part. But I did not get how the tiny film cap would make a difference. Nice to know electrolytics are slow and films fast, makes sense now.

 I've put a few hours of listening on this and it sounds good, but not amazing. I was expecting to be able to hear a considerable difference between the SS and the built in amp in my emu0404, yet I can hardly tell the difference between them. Although I am impressed with there being no noticeable hiss or hum, after building it I was half expecting some noise from a poor joint or something.


----------



## Listen2this1

I am having a hard time locating two sets of tubes. Any suggestions?


----------



## -=Germania=-

Try Orlando Vacuum Tubes

 They are very reliable and quick. 

 If you could, try and find some top square getter tubes as I have found them to be the best sounding of any of the tube types with the much more common side D getter style comming in second. The top square getter also have a bit more treble than the other tube types so keep that in mind.


----------



## Listen2this1

Well I checked with Orlando Tubes and they are out. He said that he ordered about a thousand a while back and they went quick. He is expecting some in about a week or two.

 Here is the frustration. I was going to give a SS away at the local meet this weekend and I am not going to have them. If someone can give up 2 pairs I would appreciate it. 

 I guess when they some in I will need to order many pairs.


----------



## Hayduke

Quote:


  Originally Posted by *blynch1* /img/forum/go_quote.gif 
_Thanks for the simple explanation. I know how capacitors work so I got the power reserve part. But I did not get how the tiny film cap would make a difference. Nice to know electrolytics are slow and films fast, makes sense now.

 I've put a few hours of listening on this and it sounds good, but not amazing. I was expecting to be able to hear a considerable difference between the SS and the built in amp in my emu0404, yet I can hardly tell the difference between them. Although I am impressed with there being no noticeable hiss or hum, after building it I was half expecting some noise from a poor joint or something._

 

Someone pointed out to me that my description was accurate for a power coupling cap, but the ones your asking about are DC decoupling caps. I liked the analogy he shared with me, so I'm gonna steal it and take all the credit 
	

	
	
		
		

		
		
	


	




 (just kidding, ruZZ.il deserves the credit for pointing out my error)

 Let's build on the water/sink analogy. We will call the water flow DC current. The AC (the music signal) is represented by changes in the flow or pressure. Now lets put a rubber membrane into the pipe to block the water. So now it won't let the water flow (DC) but the changes in vibration will make the membrane vibrate, so those are transferred down the pipe (ie the AC signal or music). Again, the difference between the caps is a speed issue. Films respond faster, but to smaller vibrations. 'Lytics respond to the larger changes at lower frequencies. It makes sense to me, but I'm not sure I'm explaining it well. 
	

	
	
		
		

		
		
	


	




 Thanks for the PM ruZZ.il
 I'm learning a lot about electronics still, so every little bit helps


----------



## digger945

^I think you explained it very well.
	

	
	
		
		

		
		
	


	



 Cap size(capacitance) would equate to the membrane size and flexibility, or with your film/lytic it is the ability of the membrane to "snap back" or "recover" to it's original position, as the AC signal(music) goes back and forth.


----------



## krisjan

Quote:


  Originally Posted by *krisjan* /img/forum/go_quote.gif 
_yes - tx indeed for the ebid link - they have a za site as well - so just bought 4 tubes off them...radioera couldn't source the tubes - so had to refund me. The store on ebid that sells them is VacuumTubes - i can see 13 19j6 tubes in total there - so if you need some, hurry...
 k_

 

'mazing - all those tubes are gone already...i have a hunch the SS will become an expensive and sought after piece of collectible in the future...i think the design should be modded to accept other tubes to keep it going...pete - how bout the rolling tube SS mod?
 k


----------



## ruZZ.il

no prob. I'm learning a lot too =)


----------



## fallen angel

I just nabbed 2 pair myself. Now to grab the backordered caps, and the sockets for the tubes, then a building I shall go.


----------



## Coreyk78

Well I just finished up my second starving student build, maybe a starving homeowner this time? I used a much smaller case this time around, a Hammond 1455L. I chose to use some 470uf 63v Nichicon KW caps and .22uf K42Y-2 PIOs. The pot is an Alps RK27 100k, I like this pot because it gives more usable volume adjustment than the 50k Alpha in my other build. I also sprang for some Cardas RCA jacks and I used the same Neutrik phono jack as in my first one. I got some 2" tall heatsinks this time, which I recommend, they stay much cooler.

 Sound so far isn't much different than my first one, but its only been operational for a couple hours, so the caps aren't burned in yet, and I'm also burning in a new pair of tubes. I can tell that the Alps pot is better than the Alpha though, better channel balance, and it sounds smoother when adjusting volume.

 And I see someone let the cat out of the bag about the tubes on ebid, haha, thats where I got the 7 I have, and I was going to pick up a few more this weekend because I saw he had other brands than RCA, but they were all gone! 
	

	
	
		
		

		
			





 Anyways, some obligatory pics, I think it turned out nicely.


----------



## Hayduke

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Well I just finished up my second starving student build, maybe a starving homeowner this time? I used a much smaller case this time around, a Hammond 1455L. I chose to use some 470uf 63v Nichicon KW caps and .22uf K42Y-2 PIOs. The pot is an Alps RK27 100k, I like this pot because it gives more usable volume adjustment than the 50k Alpha in my other build. I also sprang for some Cardas RCA jacks and I used the same Neutrik phono jack as in my first one. I got some 2" tall heatsinks this time, which I recommend, they stay much cooler.

 Sound so far isn't much different than my first one, but its only been operational for a couple hours, so the caps aren't burned in yet, and I'm also burning in a new pair of tubes. I can tell that the Alps pot is better than the Alpha though, better channel balance, and it sounds smoother when adjusting volume.

 And I see someone let the cat out of the bag about the tubes on ebid, haha, thats where I got the 7 I have, and I was going to pick up a few more this weekend because I saw he had other brands than RCA, but they were all gone! 
	

	
	
		
		

		
		
	


	




 Anyways, some obligatory pics, I think it turned out nicely.
http://i133.photobucket.com/albums/q...et2cropped.jpg
http://i133.photobucket.com/albums/q...dunski/038.jpg_

 

Looks real nice. I'm planning to build another MHSS too. I'm happy to see your larger heat sinks look nice. I'm going to use larger ones too. I want them to be taller then the tubes 
	

	
	
		
		

		
		
	


	




 What sockets are those? I'd like some that mount under the case. Mine sit on top.


----------



## MoxMonkey

i'm using a pair like this

7 Pin Tube Socket McMurdo British Made Bags of 100 Pcs - (eBay.ca item 380066464762 end time 20-Jan-09 02:56:39 EST)


 and they mount completely flush with the hammond case i used


----------



## Hayduke

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_i'm using a pair like this

7 Pin Tube Socket McMurdo British Made Bags of 100 Pcs - (eBay.ca item 380066464762 end time 20-Jan-09 02:56:39 EST)


 and they mount completely flush with the hammond case i used_

 

Those look similar to the top mount ones I have. I also don't need that many


----------



## Coreyk78

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Looks real nice. I'm planning to build another MHSS too. I'm happy to see your larger heat sinks look nice. I'm going to use larger ones too. I want them to be taller then the tubes 
	

	
	
		
		

		
		
	


	




 What sockets are those? I'd like some that mount under the case. Mine sit on top._

 

Thanks 
	

	
	
		
		

		
		
	


	




 The sockets are from Audiograde on ebay, doesn't look like they have any 7 pins up for sale right now though.


----------



## krisjan

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Someone pointed out to me that my description was accurate for a power coupling cap, but the ones your asking about are DC decoupling caps. I liked the analogy he shared with me, so I'm gonna steal it and take all the credit 
	

	
	
		
		

		
		
	


	




 (just kidding, ruZZ.il deserves the credit for pointing out my error)

 Let's build on the water/sink analogy. We will call the water flow DC current. The AC (the music signal) is represented by changes in the flow or pressure. Now lets put a rubber membrane into the pipe to block the water. So now it won't let the water flow (DC) but the changes in vibration will make the membrane vibrate, so those are transferred down the pipe (ie the AC signal or music). Again, the difference between the caps is a speed issue. Films respond faster, but to smaller vibrations. 'Lytics respond to the larger changes at lower frequencies. It makes sense to me, but I'm not sure I'm explaining it well. 
	

	
	
		
		

		
		
	


	




 Thanks for the PM ruZZ.il
 I'm learning a lot about electronics still, so every little bit helps 
	

	
	
		
		

		
		
	


	


_

 

wow - that's a great analogy - i've heard a few trying to create an analogy between a water reservoir and a cap, but it simply cannot explain the dc blocking aspect as well - the membrane idea works a lot better...thanks for sharing


----------



## krisio06

Hi!
 Where Can I buy some 19J6 tubes from different brands? Like Sylvania or RCa?
 I searched a lot and I didn't find any storees where I can buy them..
 Or if it's possible, are any alternative tubes to the 19J6?


----------



## Punnisher

There aren't many left it seems. I got 4 tubes total but only one matched pair, so I need to get more as well. I still have parts for one more amp.


----------



## -=Germania=-

If anyone has a pair of top Halo Getters I would be interested. 


 BTW: The Raytheon and Sylvania are the same tube. The same construction, printing, print size, and print colors ( yellow brand label and white "19j6"). 

 To anyone who is looking at other brands please consider this.


----------



## Coreyk78

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_If anyone has a pair of top Halo Getters I would be interested. 


 BTW: The Raytheon and Sylvania are the same tube. The same construction, printing, print size, and print colors ( yellow brand label and white "19j6"). 

 To anyone who is looking at other brands please consider this._

 

I have a single RCA top halo getter, but I'd like to try and find a second one for myself.


----------



## scompton

What's a halo getter?


----------



## krisio06

Tube, Tubes 13CW4 - EC-91
 Is that shop still working?
 I wrote them 2 emails and I haven't got any reply.


----------



## Hayduke

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_What's a halo getter?_

 

Tom and Colin have some pics on the Max site
MAX Tubes


----------



## cetoole

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Tom and Colin have some pics on the Max site
MAX Tubes_

 

Actually, that is 100% Tom, I have nothing to do with the development of his excellent webpages.


----------



## scompton

All of my tubes have getters in the top. None of them are in the side like the one in the picture. Some have vertical getters that are U shaped, some have horizontal rectangular ones, and others have horizontal round ones. In all except the round ones, the accompanying splotch of metal on the glass is on the side of the tube. With the round getters, it's the entire top of the tube. I assume the round ones are the only ones considered halos.


----------



## Hayduke

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_All of my tubes have getters in the top. None of them are in the side like the one in the picture. Some have vertical getters that are U shaped, some have horizontal rectangular ones, and others have horizontal round ones. In all except the round ones, the accompanying splotch of metal on the glass is on the side of the tube. With the round getters, it's the entire top of the tube. I assume the round ones are the only ones considered halos._

 

Getters on the top of the tube are referred to as "Halos" because of their resemblance to halos


----------



## ehntoo

Hi. Long time lurker, but this is my first posts.

 I just finished building a Starving Student, and wow, this blows my only other amp (a CMoy I built) way out of the water.

 After a couple of weeks of planning, I found what appear to be the last two 19j6 tubes on the internet from vacuumtubesinc.com. They aren't matched, (one arcturus, one GE), but this is an amazing sounding amp. It makes the low-end on my K271s come alive like I've never heard. It makes me want to listen to some good pipe organ stuff.

 I'll post pictures tomorrow. I built it into a Planters nuts can (starving student, eh?).


----------



## V-DiV

I've had parts for my Starving Student sitting here since the summer and I finally got around to building it. I think my BOM was similar to the Aussie group buy BOM from last summer (so long back I can't remember for sure). Casework took some doing as did figuring how to route everything cleanly in the kind of small space I made for myself. Finished it up about an hour ago, plugged in an old iPod as a source and some Apple buds half expecting to hear nothing, but there it was, beautiful music: Bob James, Diana Krall, Pearl Jam, Dvorak. Wait a minute! Have Pearl Jam and Dvorak ever been mentioned in the same sentence back to back??? Hooked up the good source and my K701s and Wow, not bad!

 The case was confiscated from my son. I haven't decided if I'll let him use the amp or not (Hey, he doesn't need an amp for PX 100s and with tubes being as rare as they are...
	

	
	
		
		

		
		
	


	




)

 I'll probably take some better pictures and post on the Builds thread. I was too lazy to go upstairs and get my tripod and play around with apertures.

 The Dvorak sounded quite good. Zeppelin: Houses of the Holy sounding good...


----------



## gurusan

I'm getting buzzing when I touch the volume knob :/ turning it up to full eliminates this? Some sort of grounding issue?


----------



## adamus

yes 100%. 

 check ground solder points. Consider grounding pot body.

 are the input grounds isolated? if nto then isolate them from the case.


----------



## bearmann

Has anyone tried this amp with efficient headphones? (like Audio Technicas)

  Quote:


  Originally Posted by *pmillett* /img/forum/go_quote.gif 
_I don't remember what the gain of the amp is - around 15, if I remember right._

 

Is there a way to reduce the gain further? Something like 2 ... 4 ... 6 maybe?

 best regards,
 bearmann


----------



## Yaka

well i got down to it and was rushing kinda like got it all done in 20 mins this time i was 100% sure i had done it right. when i powered up i was getting sparks on the right hand side of the heat sink tubes wernt lighting up. whats more onces disconnected from mains it continued to spark for around 2 mins

 heres a pic 






 i am not sure what i am doing wrong here, maybe i killed some parts as its been put together and dismantled sevral times now. ive built a cmoy in the past and thought this was nice step up.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_well i got down to it and was rushing kinda like got it all done in 20 mins this time i was 100% sure i had done it right. when i powered up i was getting sparks on the right hand side of the heat sink tubes wernt lighting up. whats more onces disconnected from mains it continued to spark for around 2 mins

 heres a pic 

 i am not sure what i am doing wrong here, maybe i killed some parts as its been put together and dismantled sevral times now. ive built a cmoy in the past and thought this was nice step up._

 

Nothing personal, but a lot of those joints and wires look terrible. I see a bunch of exposed wire, overstripped, and a bunch of cold solder joints. Try to reflow the joints and go over everything making sure its correct (check the schematic).

 When I built the amp, I took the schematic and turned it into a wiring diagram sort of to help me out...

 ˇˇˇA little messy, but easier to understand component/wire placement


----------



## scompton

Quote:


  Originally Posted by *bearmann* /img/forum/go_quote.gif 
_Has anyone tried this amp with efficient headphones? (like Audio Technicas)



 Is there a way to reduce the gain further? Something like 2 ... 4 ... 6 maybe?

 best regards,
 bearmann_

 

People use Grados with theirs.

  Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Nothing personal, but a lot of those joints and wires look terrible. I see a bunch of exposed wire, overstripped, and a bunch of cold solder joints. Try to reflow the joints and go over everything making sure its correct (check the schematic).

 When I built the amp, I took the schematic and turned it into a wiring diagram sort of to help me out...

 ˇˇˇA little messy, but easier to understand component/wire placement_

 

x2. I took about 5 hours to draw a wiring diagram and I still took 2 days to put it together. Since it was my first build, it was a mess and I left every lead exposed and long. It worked fine until I closed the lid and created a short.


----------



## V-DiV

My Starving Pokemon took most of four days including casework, wiring layout and wiring it up with lots of double-checking that the wiring was correct. I'm sure that mine would have had sparks if I tried to do it in 20 minutes.


----------



## Yaka

thanks for the advice guys, think i'll spend some time after work this evening on it.


----------



## zha50

This is my copy of RDS's Mini Millet, or most of.

 Took most part of the day on case work and the rest of the evening wiring it straight off the schematic.

 I have a weirdish problem. When i don't have any inputs pluged in, i can start to hear noise at about 80% on the pot. But once i plug my sound card in, i get a weird buzzz noise at about 45% which by then is quite loud. Straight from the card to headphones are silent. 

 EDIT. It seems to only buzz when connected to my sound card...i get a plain static noise if i use my iPod which i know is noisy(can hear it unamped through 'fons.)


----------



## gurusan

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_yes 100%. 

 check ground solder points. Consider grounding pot body.

 are the input grounds isolated? if nto then isolate them from the case._

 

thanks, re-did some of the grounding points and grounded the pot body and the buzzing has disappeared.

 The input grounds are connected to the rest of the grounds, the case is made of ABS.

 I am getting a scratchiness as I rotate the pot though....could it be the pot is bad?


----------



## royewest

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_... I am getting a scratchiness as I rotate the pot though....could it be the pot is bad?_

 

Many pots are "scratchy" when you turn them, but silent when you stop turning and are just listening to music.


----------



## V-DiV

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_I am getting a scratchiness as I rotate the pot though....could it be the pot is bad?_

 

Sometimes if you work the pot back and forth you can work out the scratchiness, which is, I presume, some oxidation or dirt. With old pots in particular I've had pretty good luck returning them to health by squirting electrical contact cleaner into them and turning them back and forth.


----------



## jeanba3000

Hello everybody and happy new year !

 I just read all the thread (it took me some time !) and I'm very interested by this Starving Student headphone amp.

 I've already built a preamp (UGS balanced preamp, seems well known in some DIY community), and I'd like to add a small headphone amp after it, maybe in the same box (I have room). The jack socket would command a relay that will switch the signal out from the preamp to the head amp instead of the power amps.

 I also use a Sony MDR-CD1700 which is a 32 ohm AFAIK.

 Do you think the Starving Student would be ok for this purpose ? Or does it require some modifications to accept the output of a preamp instead of the output of a source directly ? 
 I would at start suppress the volume pot because I would use the preamp's control. What else should I think of ?

 Thanks in advance for your advice !


----------



## -=Germania=-

I use a CD1000 with this amp (though a higher current active ground version) and a preamp and have no issues. You could potentially just put a resistor in the signal path to attenuate if you are doing a one box solution (no need for a potentiometer).


----------



## chiefroastbeef

Germania, did you get my pm? Just wondering if you have sent out my cable.

 Thanks


----------



## kellvyn

I'm getting my Mouser order together, and I had a question about the input jacks. Several people have recommended isolating them from the chassis and using a star ground. I'm planning on doing this, but I'm having some trouble figuring out the best way to do this.

 One option is to just buy non-isolated jacks, like the ones in the original BOM, and then buy either a grommet or a shoulder washer and flat washer from the hardware store. But I'm not even sure if it's common to find washers that would be the proper size. Frankly, it's also less convenient than just ordering from Mouser.

 The other option is to order isolated jacks from Mouser. Kobiconn has jacks in black and red that come with "insulating nylon washers" (Mouser P/N 161-2002 & 161-2003). But on the data sheet, the washers are flat. That won't work so well, I think. Switchcraft has a jack (Mouser 502-3501FPX) that can be isolated by purchasing separate shoulder and flat washers (502-S2207 and 502-S1564, respectively). That works out to $2.34 per jack. I'm not too concerned about the money, but I'm wondering if I'm missing out on an obvious solution here. Are isolated jacks so uncommon that Mouser would only carry one, or am I missing something. Any advice?


----------



## n_maher

Quote:


  Originally Posted by *kellvyn* /img/forum/go_quote.gif 
_Any advice?_

 

Mouser just doesn't carry much in the way of RCA jacks, you'll probably want to source them somewhere else if you decide to use isolated jacks.


----------



## V-DiV

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_When I built the amp, I took the schematic and turned it into a wiring diagram sort of to help me out..._

 

I broke down the circuit into major parts and then redrew simplified versions that were easier for me to keep in my head. It made it a lot easier to keep track of what I was connecting and how they related. Maybe somebody else will find it useful, although here it is still in quick and dirty form.


----------



## Dr Evil Dan

I've finally completed mine, so here it is:






 I have yet to get a knob, because I don't want to use a store bought one, and random household objects can't really be converted to knobs with the tools I have... also, I haven't erased the pencil marks yet.






 That is a view of the bottom. I had to attach a fan in order to compensate for the fact that the MOSFETs are on the inside. HOWEVER, when the fan is on, it causes a bastardly buzz in the right channel (and less in the left). It is very noticeable, even at the lowest volumes. My guess is that it is causing the wires to vibrate or some crap like that, but then again I don't see how that could affect sound... If anyone can tell me how to fix it while getting to keep my fan, I would be in your debt 
	

	
	
		
		

		
			





 P.S. the fan is running off of its own power supply.
 P.S.S how hot should the heatsinks be? because when I touch the (un-insulated) screw that holds the plates to the case, it kinda burns 






 internal shot! specs are: dale resistors, Nichicon FG output caps bypassed with WIMAs, Elna Silmic II power supply caps, the film caps are these: Reliable capacitor PPFA series.
 alps rk27 pot (which I accidentally wired backwards), copper point to point wiring (the reason some are insulated and some aren't is because all the wire was cannibalized from random cables, and I switched wire 4 times or something), 1/4" input and output jacks, and a pair of sylvania 19J6 tubes donated by HeadFi-er Dandi. Thank you so much Dandi!






 night shot 
	

	
	
		
		

		
		
	


	



 This thing sounds fantastic! My grados used to be plugged into my computer speakers, because they have an integrated amp, and they sounded pretty lifeless. Now my setup is computer->SS->cans, and the sound is so much warmer and more lively. There was an immediate improvement in soundstage and separation of instruments. The clarity, depth, and power of the bass has improved a lot, although because my cans are grados, I still use Winamp's equalizer for a bass boost. Sibilance seems to be more under control now. Also, this thing is ridiculously loud. I listen to my cans at maybe 20% louder than conversation level, and I can barely move the knob past lowest without becoming uncomfortable with the sound level. Maybe its just the whole low impedance 'phones thing.
 The only drawbacks other than the fan problem is that point to point wiring is such a pain without those little helping hand clips or whatever they're called.


----------



## dandi

congratulations Dr. that last picture is nice the tube glow and the wooden case are fantastic.

 I am no DIY'er but me thinks you might have continued problems with putting a fan in the case. If you haven't maybe put the fan on it's on power supply, perhaps it could be external to the nice case you have?? 
 Enjoy the music!
 Cheers


----------



## Dr Evil Dan

Quote:


  Originally Posted by *dandi* /img/forum/go_quote.gif 
_congratulations Dr. that last picture is nice the tube glow and the wooden case are fantastic.

 I am no DIY'er but me thinks you might have continued problems with putting a fan in the case. If you haven't maybe put the fan on it's on power supply, perhaps it could be external to the nice case you have?? 
 Enjoy the music!
 Cheers_

 

The fan is outside of the case, on the bottom (courtesy of rubber cement). It is on its own power supply, a 3v 500mA wall wart


----------



## ltmon

@Dr Evil Dan

 Nice looking amp, very unique. If you can't find a knob maybe go for one of these wooden ones:

Radio Daze-Reproduction Knobs


----------



## V-DiV

Hey Dr Evil Dan, cool box. What did it used to be? I love off the wall cases.


----------



## Dr Evil Dan

Quote:


  Originally Posted by *V-DiV* /img/forum/go_quote.gif 
_Hey Dr Evil Dan, cool box. What did it used to be? I love off the wall cases._

 

It used to be a box for a doll, which is why it has wallpaper on the inside 
	

	
	
		
		

		
		
	


	



 The part I used is only half of it though, it used to be two identical sections that were connected by a hinge. the bottom covering is from the other half. Upon further consideration, the color of the box in the pictures is all wrong :\ 
 the one below is much better (but I still have to erase those pencil marks!)

  Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_@Dr Evil Dan

 Nice looking amp, very unique. If you can't find a knob maybe go for one of these wooden ones:

Radio Daze-Reproduction Knobs_

 

Hey, thanks. I was thinking about using a wooden knob, and those are really nice. I was also thinking of using a shiny brass knob type thing, to match the color of the headphone jack. Like this one: http://www.minksemporium.com/Brass_Knob_4.jpg
 they only problem is attaching it








 man I hate pictures... The amp looks so much less ugly in real life


----------



## mattcalf

I just received my tubes.
 I need sockets then I'll be good to build when I get back from Sydney.

 Can't wait!!


----------



## Yaka

gonna try and take mine apart again tonite. i am preety much a n00b at this and cant much remeber what i learnt in high school will the capacitors need discharging?


----------



## manaox2

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_gonna try and take mine apart again tonite. i am preety much a n00b at this and cant much remeber what i learnt in high school will the capacitors need discharging?_

 

Anything over 25V is dangerous from what I know (not testing that myself), 48V can possibly be lethal. You would feel it if a cap on this project were to discharge into you as I believe they are all seeing the full voltage at points. You can make a discharge circuit easily though, I need to make one myself.

http://www.repairfaq.org/sam/captest.htm#ctdtk


----------



## omegamajor

Quote:


  Originally Posted by *manaox2* 
_Anything over 25V is dangerous from what I know (not testing that myself), 48V can possibly be lethal. You would feel it if a cap on this project were to discharge into you..._

 

It's the current you need to worry about, not the voltage. About 100mA or less directly through your heart will stop it. Around 10mA will start twitching muscles. A static discharge from shuffling your feet and touching a doorknob is thousands of volts, just a tiny amount of current. Human skin provides a high amount of resistance, on the order of megaohms. If you have a cut on your finger and get a static shock through it the shock feels much more substantial than if you didn't have a cut. If you touch 120VAC power you will feel a little buzz, but it won't harm you (unless you have the aforementioned cut on your skin). I've personally touched a cap that was charged to 400V (on accident of course) and received a little bit of a shock, but mostly it was just a strong tingling sensation.

 Don't worry about the caps in the SS. They will discharge themselves since they are already in the circuit.


----------



## greeny

Hi guys,

 Where else can i find the tubes?
 It seems that they dont have it in my country singapore.


----------



## mattcalf

Quote:


  Originally Posted by *habba* /img/forum/go_quote.gif 
_Hi guys,

 Where else can i find the tubes?
 It seems that they dont have it in my country singapore._

 

 Unfortunatelyit seems the 19J6 tubes are out almost everywhere.

 There are a few that go on eBay but they are mostly overpriced.
 You might want to google search radio tube suppliers and email around to get a pair.


 Good luck!
 Matt.


----------



## greeny

Ahh i think i found them, haha shipping cost more then the tubes!


----------



## jeanba3000

Hello

 I've been informed that tomorrow, The Tube Center will have a small stock of 19J6 tubes ! $4 each.

 I already have ordered my tubes


----------



## Yaka

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Anything over 25V is dangerous from what I know (not testing that myself), 48V can possibly be lethal. You would feel it if a cap on this project were to discharge into you as I believe they are all seeing the full voltage at points. You can make a discharge circuit easily though, I need to make one myself.

http://www.repairfaq.org/sam/captest.htm#ctdtk_

 

 Quote:


 It's the current you need to worry about, not the voltage. About 100mA or less directly through your heart will stop it. Around 10mA will start twitching muscles. A static discharge from shuffling your feet and touching a doorknob is thousands of volts, just a tiny amount of current. Human skin provides a high amount of resistance, on the order of megaohms. If you have a cut on your finger and get a static shock through it the shock feels much more substantial than if you didn't have a cut. If you touch 120VAC power you will feel a little buzz, but it won't harm you (unless you have the aforementioned cut on your skin). I've personally touched a cap that was charged to 400V (on accident of course) and received a little bit of a shock, but mostly it was just a strong tingling sensation.

 Don't worry about the caps in the SS. They will discharge themselves since they are already in the circuit. 
 


 confused, but just to be sure would using a screw driver to discharge be ok? as i dont think i have enough parts to build a tool to discharge


----------



## Fitz

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_confused, but just to be sure would using a screw driver to discharge be ok? as i dont think i have enough parts to build a tool to discharge_

 

Tool to discharge = resistor taped to a stick. Not too terribly expensive.


----------



## pistolsnipe

Quote:


  Originally Posted by *jeanba3000* /img/forum/go_quote.gif 
_Hello

 I've been informed that tomorrow, The Tube Center will have a small stock of 19J6 tubes ! $4 each.

 I already have ordered my tubes 
	

	
	
		
		

		
		
	


	


_

 

thanks for the heads up, just ordered 4, he said they had ~ 50 and is only selling a few to each person to make sure as many people can get them.


----------



## tomb

Quote:


  Originally Posted by *pistolsnipe* /img/forum/go_quote.gif 
_thanks for the heads up, just ordered 4, he said they had ~ 50 and is only selling a few to each person to make sure as many people can get them._

 

I just spoke with Stan at ESRC (The Tube Center, Orlando Tubes, etc. - all the same guy). He says 47 at the moment and is expecting to sell all of them by the end of the weekend.

 So, anyone that wants them - get busy!


----------



## sebrkln

I really hope someone can help me out here, because I've completely exhausted my troubleshooting capabilities. I'm following the schematic correctly as far as I can tell. So here's what I'm getting.

 1) The heatsinks warm up within a minute of turning on the amp, so I at least know the MOSFETs are getting power, right? The tubes however both remain cold (and dark).

 2) I get a quiet thumping from headphones when the amp is turned on, nothing else (as I would expect considering the tubes)

 3) My power supply reads a steady 48V when not plugged into the circuit. When plugged in, the readings are all over the place. Both tubes oscillate from 5.75 or so to 8V, read from the spots labeled 1 and 2 on the diagram. Right before C1, the meter reads from 4 to about 18V.

 Anyone have any ideas as to where I should go from here? They would be much appreciated!

 K


----------



## -=Germania=-

You might have wired the tubes in reverse. Check that pins 1-7 read from the correct direction.


----------



## CaptHowie

1. Are the PCB's any closer to being produced.
 2. A step-by-step tutorial?

 I've built a CMOY already but I used Tangent's excellent tutorial and im scared that I wont be able to read the schematic and stuff it up completely.


----------



## CaptHowie

Ok, forget my previous post... [DISAPPEAR] except for the question on the PCB's... I still want to know when they'll be done!

 I've had a good look over the schematic and it is actually very simple 
	

	
	
		
		

		
		
	


	



 I have still got a few questions though 
	

	
	
		
		

		
		
	


	



 1. With the ground connections, where can I connect them to? In the other amps shown here they used a blank PCB etchboard, and if that is what I have to use, is it a simple matter of hot gluing it to the bottom of the case and soldering ground connections straight to it, or is it a bit harder?
 2. With the connection markings (the black dot connecting wires), there are a few on the same wires (most...). Again, is it a simple case of stripping part of the wire and soldering connections to it, or a bit more?
 3. I know somewhere in this thread there was the tube pinouts, but the head-fi servers were taking a beating and the search wasnt working 
	

	
	
		
		

		
		
	


	



 So what are the pinouts?

 Thanks in advance.


----------



## iareConfusE

I too am looking forward to the PCB's soon.


----------



## ltmon

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_1. With the ground connections, where can I connect them to? In the other amps shown here they used a blank PCB etchboard, and if that is what I have to use, is it a simple matter of hot gluing it to the bottom of the case and soldering ground connections straight to it, or is it a bit harder?_

 

If you use a conductive (i.e. metal) chassis, connect your ground to it. If not, use the blank etchboard. It doesn't need to be connected to anything, it should just unify all the grounds in the circuit together to a single electrical point.

  Quote:


 2. With the connection markings (the black dot connecting wires), there are a few on the same wires (most...). Again, is it a simple case of stripping part of the wire and soldering connections to it, or a bit more? 
 

Close enough. Most people will use some heat shrink tubing in various places to prevent exposed wires shorting on other components etc.

  Quote:


 3. I know somewhere in this thread there was the tube pinouts, but the head-fi servers were taking a beating and the search wasnt working 
	

	
	
		
		

		
		
	


	



 So what are the pinouts? 
 

The tube sockets will have the numbers 1 to 7 marked on them, matching to those numbers on the diagram.


----------



## scompton

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_The tube sockets will have the numbers 1 to 7 marked on them, matching to those numbers on the diagram._

 

Mine didn't have that. Ludoo has written a search engine for this thread, the ortho thread, and the Stax thread. Use it or use google search.


----------



## ludoo

The tube socket pins are numbered clockwise with the bottom of the socket in front of you, with number 1 being the first pin after the larger gap between two pins.

 And yes there's a search engine for this thread (thx Scompton for mentioning it), it's here. I have not updated the SS thread index in a while, if you need the new posts to be indexed drop me a PM.


----------



## mattcalf

Just put two more tubes on order from Stan at ESRC tubes.

 Nice bloke!


----------



## n_maher

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_The tube sockets will have the numbers 1 to 7 marked on them, matching to those numbers on the diagram._

 

Some do, some don't, you can't really count on it. But here's a picture of one that does for future reference. 






 About the PCB's - they are still coming, I swear, your continued patience is appreciated.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_<snip>About the PCB's - they are still coming, I swear, your continued patience is appreciated._

 

Yep - Dsavitsk and I have traded e-mails about it just this morning. I have pricing in hand for both prototype and production boards. We're discussing case options at the moment and should have some concrete info by the end of next week, I hope.

 Also, the tube situation should improve. Again, Stan at ESRC has indicated his strong feeling that there's more in this giant >$1M buy they've made. There are also other provisions in the works to provide the tubes, as well.


----------



## MoxMonkey

looking foward to pcb's being available soon will definately be picking up a few


----------



## CaptHowie

Finding it hard to get parts from the states (Mouser charges $30, DigiKey charges $74!), I've turned to the Annual Jaycar Catalogue and flicked to the Caps page. On the original BOM, the cap used is a 150uF, 63V Low-ESR Electrolyctic Cap. I can't seem to find one in the Jaycar catalogue under Low-ESR Electrolyctic caps! There's 22uF, 47uF, 100uF, 220uF and 470uF. What is the alternative and do I need to change anything else on the BOM to cater for it. I've seen from past posted BOM's that people have been using the 470uF, 63V cap.


----------



## CaptHowie

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_Close enough. Most people will use some heat shrink tubing in various places to prevent exposed wires shorting on other components etc._

 

So can you just strip a little off the side of a wire and solder on to it with another wire then just put heatshrink tubing over it? Simpler than I thought! 
	

	
	
		
		

		
		
	


	




 Thanks for the help there.


----------



## ltmon

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Finding it hard to get parts from the states (Mouser charges $30, DigiKey charges $74!), I've turned to the Annual Jaycar Catalogue and flicked to the Caps page. On the original BOM, the cap used is a 150uF, 63V Low-ESR Electrolyctic Cap. I can't seem to find one in the Jaycar catalogue under Low-ESR Electrolyctic caps! There's 22uF, 47uF, 100uF, 220uF and 470uF. What is the alternative and do I need to change anything else on the BOM to cater for it. I've seen from past posted BOM's that people have been using the 470uF, 63V cap._

 

Better to use Farnell in Australia.

Farnell Australia | Australia

 Should get you over the line easy if you choose components in stock in Australia. There was no way I could get all the right components from Jaycar, their range is just too limited. Although check there first for bargain prices on some components (heatsinks are usually much cheaper).

 Other online outlets in AU are RS-Components and Altronics.

 Cheers,

 L.


----------



## CaptHowie

Has someone got a Farnell-based BOM?


----------



## ltmon

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Has someone got a Farnell-based BOM?_

 

I PM'd you mine from Farnell. Be aware that there are a lot of different brands, cap values etc. you can use... really part of the fun of this build.

 Cheers,

 L.


----------



## mattcalf

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_I PM'd you mine from Farnell. Be aware that there are a lot of different brands, cap values etc. you can use... really part of the fun of this build.

 Cheers,

 L._

 

I'd love to be forwarded this BOM if possible.
 I've already done a mouser order but would be great for future interest.


----------



## CaptHowie

Thank you ltmon you've been a great help. It's just getting very hard to find a few of these 19J6 tubes. Been asking old radio/tv repair shops in Melbourne and emailing a few online ones so hopefully a pair or two turn up. Thanks heaps for the BOM though, great help.


----------



## -=Germania=-

I dunno if anyone is buying from Jaycar, but this might make a cool looking enclosure since it already has the power switches and knobs. Plus the size looks just enough for the build. 

Jaycar Electronics

 I thought it might make a nice enclosure for my dad's one that he hinted at wanting 
	

	
	
		
		

		
		
	


	




, maybe over the summer.


----------



## mattcalf

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I dunno if anyone is buying from Jaycar, but this might make a cool looking enclosure since it already has the power switches and knobs. Plus the size looks just enough for the build. 

Jaycar Electronics

 I thought it might make a nice enclosure for my dad's one that he hinted at wanting 
	

	
	
		
		

		
		
	


	




, maybe over the summer._

 

I'll check it out when I get back home at the Jaycar there.


----------



## CaptHowie

Can someone verify my BOM? It uses a mix of Farnell/Jaycar parts, but i'd rather get them all from somewhere but Farnell because of the delivery costs. Also, any ideas on making it cheaper?
http://www.graphicgraffiti.com.au/st...carfarnell.xls

 Farnell aren't supplying MULTICOMP - MCF 0.25W 2K - RESISTOR, 0.25W 5% 2K anymore... alternatives?


----------



## ltmon

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_I'd love to be forwarded this BOM if possible.
 I've already done a mouser order but would be great for future interest. 
	

	
	
		
		

		
			



_

 

Done.


----------



## mattcalf

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_Done._

 

Awesome, thanks for that. If I do an Aussie build I'll try to edit/update that BOM. I'm sure my bro or a friend will want a SS after they hear mine.


----------



## Hayduke

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_1. With the ground connections, where can I connect them to? In the other amps shown here they used a blank PCB etchboard, and if that is what I have to use, is it a simple matter of hot gluing it to the bottom of the case and soldering ground connections straight to it, or is it a bit harder?_

 

In the original BOM, Pete suggested some terminal blocks. Attach those to the copper clad board then tie all your ground connections to those. Another option, if using the board, Is to let the board be a ground plane and attach all ground connections to it.

  Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_2. With the connection markings (the black dot connecting wires), there are a few on the same wires (most...). Again, is it a simple case of stripping part of the wire and soldering connections to it, or a bit more?_

 

A schematic only shows the circuit. It is NOT intended as a build guide. There are black dots on junctions to differentiate them from places in the schematic where the wires cross but are not attached. (rereading that I'm not sure it's very clear). The black dots mean those circuits are connected. If you see 2 lines crossing each other without a dot, they are not connected.

 That being said, you don't need to strip part of a wire in the middle to attach another wire. When looking at a schematic, you have to keep reminding yourself of the first 2 points above. What I did was take a bunch of different colored highlighters and color coded each section, or "node", of the circuit. Look at the schematic and the areas in between components. These consists of just wires, no resistors, caps etc.

 For example, look at the connection between R1, R2, R13, and C6. The idea to understand from the schematic is that these 4 devices are all attached. They can all be attached to a single point. ie you solder 4 legs together. Or you could solder 2 pairs together and connect them via a wire, or 3 and 1. You get the idea. It doesn't matter where along the circuit you make the connection. All that matters is that the devices all connect to each other correctly.

 Hopefully this helps and others don't mind the lengthy post 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_3. I know somewhere in this thread there was the tube pinouts. So what are the pinouts?_

 

The pinout is easy. There is a gap in the pins. Look at the socket from the bottom (where you are soldering). Count clockwise. Pin 1 is the 1st pin after the gap.

  Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_The tube sockets will have the numbers 1 to 7 marked on them, matching to those numbers on the diagram._

 

My sockets are not numbered. While I haven't seen a lot of them, I have yet to see any that are.


----------



## CaptHowie

Thanks Hayduke. Still having major troubles finding tubes, emailed like 6 places, 2 have replied at the moment with the response 'out of stock'. Hopefully a pair or two shows up somewhere.


----------



## V-DiV

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_The pinout is easy. There is a gap in the pins. Look at the socket from the bottom (where you are soldering). Count clockwise. Pin 1 is the 1st pin after the gap.


 My sockets are not numbered. While I haven't seen a lot of them, I have yet to see any that are._

 

My sockets were numbered. But n_maher shows a picture of the pin numbering (from below) on the previous page of this thread. To sort out the schematic I made a simplified drawing to use a wiring diagram. To simplify it I separated parts of the circuit to make it easier to figure out how to tie it together, and how many nodes/binding points I needed.

 See here.
Millett "Starving Student" hybrid amp - Page 128 - Head-Fi: Covering Headphones, Earphones and Portable Audio


----------



## V-DiV

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Thanks Hayduke. Still having major troubles finding tubes, emailed like 6 places, 2 have replied at the moment with the response 'out of stock'. Hopefully a pair or two shows up somewhere._

 

I just got 2 tubes from The Tube Center yesterday. They still had a few.

Orlando Vacuum Tubes


----------



## thetelevisi0n

Quote:


  Originally Posted by *V-DiV* /img/forum/go_quote.gif 
_I just got 2 tubes from The Tube Center yesterday. They still had a few.

Orlando Vacuum Tubes_

 

How long does it take for them to reply after submitting an order form? I submitted an order form about a month ago and haven't gotten a reply yet. So I sent another one yesterday on Saturday.


----------



## V-DiV

Quote:


  Originally Posted by *thetelevisi0n* /img/forum/go_quote.gif 
_How long does it take for them to reply after submitting an order form? I submitted an order form about a month ago and haven't gotten a reply yet. So I sent another one yesterday on Saturday._

 

I spoke to them on the phone to verify that they actually had the tubes in stock and again to set up payment via Paypal which didn't work automatically from their online order form. I would give a call to see what's up.


----------



## iareConfusE

I submitted an order form a few days ago, and I got the invoice within 1 day. I paid with paypal and that was it. I haven't received a confirmation of payment from them or anything, but they might just not give those out.


----------



## CaptHowie

I got an email from them the other day. They are waiting on a delivery of tubes in around 2 weeks.


----------



## iareConfusE

Has anyone actually received their tubes from the tube center or any of the other stores the guy runs? I placed my order a few days ago, got the invoice, paid through paypal, but haven't received a shipment notice or a payment confirmation letter email from him yet.


----------



## dandi

I received my tubes today from Jack at The Tube Center. Just put them in more later. Jack and Tube Center is a wonderful place to do business with. I have had several transactions over the years always very good.

 The tubes are Delco I got 6 tubes. 5 of them are marked Delco GM and have side getters one does not have the GM printed on it and has a top getter.


----------



## Hayduke

Quote:


  Originally Posted by *dandi* /img/forum/go_quote.gif 
_I received my tubes today from Jack at The Tube Center. Just put them in more later. Jack and Tube Center is a wonderful place to do business with. I have had several transactions over the years always very good.

 The tubes are Delco I got 6 tubes. 5 of them are marked Delco GM and have side getters one does not have the GM printed on it and has a top getter._

 

Nice that you got 5 that matched!


----------



## dandi

yes if anyone gets the same arrangement perhaps we can trade although I doubt very much with this tube that the getter position will matter.


----------



## iareConfusE

Scratch my last post, got my tubes today from Jack. This guy is great, SUPER fast service.

 Now I'm just waiting on that PCB 
	

	
	
		
		

		
			





 Any estimates for when it'll be released?

 Also, will the BOM for the PCB slightly deviate from the BOM posted on the website currently? I ask because on the BOM a tube socket is required, and a terminal strip. Would these be required for the PCB?


----------



## csroc

Got my tubes from The Tube Center today... I'm amazed they got here so quickly (especially with the holiday Monday). I'm expecting the rest of my parts to come in Friday so I might be able to put this together over the weekend.

 Won't have a power supply until Monday unfortunately.


----------



## mattcalf

I'm just waiting on sockets for my tubes! I should end up with 6 tubes and sockets. Which I'll take my pick of and then pass on to any Aussie SS prospective builders. 
	

	
	
		
		

		
		
	


	




 I have my RCA jacks, my power jack, my input 1/4 jack, my LED built into the case and the pot is just setting now. 

 Otherwise have everything ready to go when my sockets get here!


----------



## Hayduke

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Scratch my last post, got my tubes today from Jack. This guy is great, SUPER fast service.

 Now I'm just waiting on that PCB 
	

	
	
		
		

		
		
	


	




 Any estimates for when it'll be released?

 Also, will the BOM for the PCB slightly deviate from the BOM posted on the website currently? I ask because on the BOM a tube socket is required, and a terminal strip. Would these be required for the PCB?_

 

Is someone working on a PCB? I know there was some talk early on, but I didn't think it was being pursued. This circuit is so simple, it really doesn't need it. If you have all your parts, just build it now. It could be weeks or months before someone has PCBs.

 In regards to the socket. You will still need a socket no matter what. Tubes don't plug directly into PCBs. If you soldered them to the board, how would you remove them when they die? 
	

	
	
		
		

		
		
	


	




 The terminal strip isn't "required" even with a PTP build. I didn't use them. They just provide an easy way to tie a lot of connections together.


----------



## n_maher

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Is someone working on a PCB?_

 

Yes.


----------



## csroc

I think I should start by measuring everything that needs a hole (RCA, power, pot, headphone jack, tubes, transistors) and bug someone with a drill press. I really wish I had a drill press of my own... but I have no space for such a fun toy


----------



## iareConfusE

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Yes._

 

Do you think it would really take additional weeks or months? One post Tomb made on one of the previous pages made it seem like it was actually pretty close to being done. I was hoping for just a couple more weeks or less. Of course I don't mean to rush you guys along, I'm just curious. This amp doesn't have to be built immediately.


----------



## dean0

Just finished my first DIY 'SS Headphone Amp', Im very impressed with the music this thing pump out. 
 Putting it together was greatn fun and not that difficult, I can now read electronic diagrams 
	

	
	
		
		

		
		
	


	




 Im realy shocked with sq of this little amp, even prefer it to my darkvoice 336i. Very warm sounding, and decent bass. 

 Hybrid MiniMax on the way..................


----------



## ltmon

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_I think I should start by measuring everything that needs a hole (RCA, power, pot, headphone jack, tubes, transistors) and bug someone with a drill press. I really wish I had a drill press of my own... but I have no space for such a fun toy 
	

	
	
		
		

		
		
	


	


_

 

I had no problem doing this using a stepped drill bit, hand held drill and a couple of vice grips. It was through 1.5mm and 3mm aluminium.

 Use the grips to anchor the aluminium to a scrap piece of wood, then anchor both to something solid. Tap a small indentation with a nail in the center of your cutout then drill a hole with a small drill bit. Now start using the stepped bit to widen the hole to the correct diameter.

 The scrap wood will hold the stepped bit almost perfectly in line, although it gets quite hot doing so, and may even char or smoke. If you've got some scrap aluminium to test this technique first then all the better.


----------



## csroc

Not a bad idea, I don't have a stepped bit but I could use one. I do prefer using a drill press but since I don't have one that's probably my best alternative.

 Thanks for the suggestion!


----------



## Hayduke

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_I think I should start by measuring everything that needs a hole (RCA, power, pot, headphone jack, tubes, transistors) and bug someone with a drill press. I really wish I had a drill press of my own... but I have no space for such a fun toy 
	

	
	
		
		

		
		
	


	


_

 

I did my casework first for this amp. I chose the enclosure (a metal case from a Gerber mini tool), and then figured out how to mount everything on the outside. Made my holes and mounted everything. Then I wired it all up inside.

 I just used a cordless drill and a Dremel tool.

 I started by cutting a piece of cardboard the size of the panel I mounted everything to. Then I rested all the parts (heatsinks, sockets, knobs etc) on it and moved them around until I found a layout I liked. I used a ruler to get everything lined up symmetrically. Once I had the center points for all the holes (everything is round on this amp luckily), I transferred those points to the actual panel. If you are going to try and keep the surface "pretty", I suggest you completely cover the case with painter's tape. When you're done making all your holes, remove the tape and mount everything. The suggestion of having some scrap would around is a good one. I used a chunk of 2x6 
	

	
	
		
		

		
		
	


	




 This amp is a pretty simple circuit. I opened up my Excel spreadsheet that has my BOM in it and I was kinda surprised how small it is (compared to the SOHA II I just ordered parts for).

 In case it helps, here is the link to the pictures I posted on this thread:
http://www.head-fi.org/forums/5013197-post1615.html


----------



## csroc

Thanks, I think it'll be a fun project to put together over the weekend. I think I'm going to go the scrap route as suggested since I have everything but the scrap and the stepped bit. I've been wanting a stepped bit and some countersink bits anyway.


----------



## brandnewgame

I'm thinking this will be my first DIY project and since I'm not starving I'm wondering which components cause the highest gains in SQ.

 First question, the schematic says that all 1/4W resistors are either carbon or metal film. Is there a problem in using a tantalum resistor in this application such as Shinkoh or Audio Note? Also am I correct in assuming the 1/4 wattage is a minimum (I could use 1/2W if I had them)?

 Second question, what is overkill on the capacitors and pot? BlackGate standards? Noble or TKD (high-end pots)? I don't mind paying more if it will improve the sound, though I don't want to waste money if, by the quality of the amplification, the end sound won't be improved.

 My guess is the elements directly in the line from in to out, pot -> tube -> output cap, will have the most significant effect, though I don't plan to skimp on the power related components 
	

	
	
		
		

		
		
	


	




 I'd be interested in any opinions of how to get the best possible out of this simple and tiny design


----------



## csroc

I do think I might want to get a nicer pot, but I haven't exactly decided what that nicer pot would or should be.


----------



## Punnisher

I'd like to get a stepped 100k attenuator with a lot of steps in small increments. That would be a good bet for having channels well balanced at low volume levels.

 Though, they are pricey for sure. Most of them cost more than all the parts of the amp combined.


----------



## Hayduke

Quote:


  Originally Posted by *brandnewgame* /img/forum/go_quote.gif 
_I'm thinking this will be my first DIY project and since I'm not starving I'm wondering which components cause the highest gains in SQ.

 First question, the schematic says that all 1/4W resistors are either carbon or metal film. Is there a problem in using a tantalum resistor in this application such as Shinkoh or Audio Note? Also am I correct in assuming the 1/4 wattage is a minimum (I could use 1/2W if I had them)?

 Second question, what is overkill on the capacitors and pot? BlackGate standards? Noble or TKD (high-end pots)? I don't mind paying more if it will improve the sound, though I don't want to waste money if, by the quality of the amplification, the end sound won't be improved.

 My guess is the elements directly in the line from in to out, pot -> tube -> output cap, will have the most significant effect, though I don't plan to skimp on the power related components 
	

	
	
		
		

		
			





 I'd be interested in any opinions of how to get the best possible out of this simple and tiny design 
	

	
	
		
		

		
		
	


	


_

 

You already nailed the spots that would yield the greatest improvement. Use a nice pot and improve the caps.

 Given the low cost and simplicity of this design. I don't think it's justified to spend a lot on the ultra high end parts, such as a stepped attenuator or some of the expensive boutique caps. A nice Alps RK27 pot and some Nichicon Muse caps though wouldn't be inappropriate IMHO.

 I'm inclined to suggest just building it fairly "stock" to start, and then upgrade the components later. Then you will be able to tell how much of a difference it made.

 I went through this same line of thinking when I built mine. I ended up only changing some cap values, but otherwise using the same parts. The amp sound phenomenal given how inexpensive it is!

 IMHO, you're better off saving the money and putting it towards your next project. If you're at all like me, after hearing this little tubed wonder, you will want another, more sophisticated, tube amp.


----------



## brandnewgame

Quote:


  Originally Posted by *Punnisher* /img/forum/go_quote.gif 
_I'd like to get a stepped 100k attenuator with a lot of steps in small increments. That would be a good bet for having channels well balanced at low volume levels.

 Though, they are pricey for sure. Most of them cost more than all the parts of the amp combined._

 

One of the earlier builders simply added a resister before the output to reduce volume. Since the pot will need to be twiddled further it might provide the same effect.

 By the way, the parts for your low profile LOD tutorial will be arriving soon and I can't wait because other LODs are useless for mobilized portability. Thanks for writing it


----------



## Tritonpad

Hi Everyone !

 First of all, sorry for bad English cause I am a little Frenchy !
 Before asking questions, I would like to congratulate all of you for your contribution in this forum.
 I have the AKG K701 headphone. It is actually drived by the phone output of my yamaha amp, helped with a 2x31 digital berhinger equalizer (because of the lack of presence in LF.)
 I would like to try building the starving student hybrid as a beginning. I've read that it was possible to increase the size of the output cap to increase the frequency response in LF. As you know, AKG K701 is particularly difficult to drive in LF. So my question is : could someone give me a capacity for output caps corresponding to K701 ? I am totally noob in DIY so I have no idea of the range capacity I can choose...
 Thank you for reading.
 Hope someone has an idea about it ^^ 
	

	
	
		
		

		
		
	


	



 By the way, I wish you all a happy neaw year !


----------



## rds

Quote:


 So my question is : could someone give me a capacity for output caps corresponding to K701 ? I am totally noob in DIY so I have no idea of the range capacity I can choose... 
 

K701s don't have a ton of bass to begin with, but what I gather you're asking is what a reasonable value if for the cutoff frequency.
 Here's the Wiki article on high pass filters - that's what the output cap in conjunction with the headphone impedance acts as. The first equation in the article is the one we need to use.
 A reasonable cut-off frequency, imo, is under 10 Hertz. If we put f = 10 into that equation we get C = 265 uF (R ~ 64 ohms - the impedance of k701s). So you want at least that value. Bigger will give a lower cutoff. I chose 330uF. 470uF is another good and readily available value.


----------



## Tritonpad

Thank you for your answer !
 Don't you think 470µF makes a huge difference between the original 150µF, even if we are here dealing with the 701 ? 330 isn't more reasonable ?


----------



## brandnewgame

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_You already nailed the spots that would yield the greatest improvement. Use a nice pot and improve the caps.

 Given the low cost and simplicity of this design. I don't think it's justified to spend a lot on the ultra high end parts, such as a stepped attenuator or some of the expensive boutique caps. A nice Alps RK27 pot and some Nichicon Muse caps though wouldn't be inappropriate IMHO.

 I'm inclined to suggest just building it fairly "stock" to start, and then upgrade the components later. Then you will be able to tell how much of a difference it made.

 I went through this same line of thinking when I built mine. I ended up only changing some cap values, but otherwise using the same parts. The amp sound phenomenal given how inexpensive it is!

 IMHO, you're better off saving the money and putting it towards your next project. If you're at all like me, after hearing this little tubed wonder, you will want another, more sophisticated, tube amp. 
	

	
	
		
		

		
		
	


	


_

 

Very good advice, that's cleared up everything I was thinking about 
	

	
	
		
		

		
		
	


	




 I hadn't thought about swapping components, but surely that's truely in the spirit of DIY. You could blow a grand on Dueland capacitors and they could sound worse than much cheaper ones. I'll try to actually learn which components I like. I can't wait to hear it now


----------



## brandnewgame

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Thank you for your answer !
 Don't you think 470µF makes a huge difference between the original 150µF, even if we are here dealing with the 701 ? 330 isn't more reasonable ?_

 

The higher the capacitance, the flatter the frequency response as you reach 20Hz. It depends on the size and price of the capacitor and your budget/size constraints.

 edit: With your phones, 330uF will do.


----------



## Tritonpad

Ok I understand now...
 Thank you again !

 Er.... We are just talking about increasing the capacity of C3 and C5 only aren't we ??

 I'll get a look at the prices. By the way, noob as I am, I don't know which web shop I should choose... knowing I'm in France...


----------



## ludoo

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Ok I understand now...
 Thank you again !

 Er.... We are just talking about increasing the capacity of C3 and C5 only aren't we ??

 I'll get a look at the prices. By the way, noob as I am, I don't know which web shop I should choose... knowing I'm in France..._

 

I recently found Banzai Effects which are in Germany (so low shipping costs and no import duties) and carry boutique capacitors like the Elna Silmic II at a decent price or the Panasonic FC again at a decent price, good film caps, lots of resistors in all the power ratings you could wish for, the tube sockets you need (7 pin mini), the in/out/ps connectors, the volume pot. Oh, and the Hammond enclosures if you need one. The only thing you won't find there are the tubes, and heatsinks. I have a couple spare sets of tubes, if you find it hard to source them I can send you two tubes at cost.

 Another option is to order from Mouser in the US, for orders above 100$ usually you get free, fast FedEx shipping to the EU. You could team up with someone else, or build two and give one to a friend. The only thing you miss from Mouser are the tubes and (I think, not sure about this) tube sockets.


----------



## Tritonpad

Oh very nice proposition !
 I'll tell you what soon...

 Last point before I leave you all alone ^^ : Increasing the capacity of the outpout caps... We are talking about C3 and C5 aren't we ??

 I think with this answer, I'll be able to start something ^^


----------



## ludoo

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Oh very nice proposition !
 I'll tell you what soon...

 Last point before I leave you all alone ^^ : Increasing the capacity of the outpout caps... We are talking about C3 and C5 aren't we ??

 I think with this answer, I'll be able to start something ^^_

 

The general consensus seems that you can use 470uF (63V) on all four electrolytic caps (C1 C3 C5 C6), and 0.22uF on the film caps (C2 C4). Or at least that's what I used in my Starving Students, and I'm very happy with them.

 Another source of quality reasonably cheap caps, the Obbligato, is Acoustic Dimension, they too are in Europe and also carry the Alps Blue Velvet pots. But you might want to use decent, cheap parts if this is your first build, to keep the costs down. Then either swap in better parts, or build another (or somethign else entirely). You could use the Panasonic FC which cost less than boutique parts, and some Wima MKP (both available from Banzai Effects for little money).

 And get spares for the Mosfets in case you damage them. For the little extra you will spend, it might save you days of waiting for replacements to arrive, and additional shipping costs.


----------



## Tritonpad

All I can say for now is that it is going to be hard to find which part to choose and also where to buy ^^ There is so many choices in the capacitors !! Just look at that : Humble Homemade Hifi
 I did not read the whole 133 pages of this topic, but did someone post a list of detailed parts with corresponding boutiques ?


----------



## mattcalf

I just received my tube sockets today.

 Do the tubes just sit in the sockets or should they be soldered in?

 Sorry if it's a silly question, tis my first project and I want to get everything right.


----------



## ludoo

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_All I can say for now is that it is going to be hard to find which part to choose and also where to buy ^^ There is so many choices in the capacitors !! Just look at that : Humble Homemade Hifi
 I did not read the whole 133 pages of this topic, but did someone post a list of detailed parts with corresponding boutiques ?_

 

If you plan on buying from Banzai Effects, good caps are the Panasonic FC, boutique caps would be the Elna Silmic II. For film caps probably the Wima MKP10, if you want boutique caps they have many but price will increase drastically.


----------



## tomb

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_I just received my tube sockets today.

 Do the tubes just sit in the sockets or should they be soldered in?

 Sorry if it's a silly question, tis my first project and I want to get everything right. 
	

	
	
		
		

		
		
	


	


_

 

No, the tubes are not soldered in. You need to be able to change them from time-to-time. Note, however, that all wiring connections to the sockets should be soldered. Also, the sockets should be securely fastened to a stable structure (the case, etc.). They undergo tremendous stress when plugging/unplugging tubes.


----------



## Tritonpad

I just need one more answer from you guys... Concerning film caps : 0.22µF = 220nF am I right ? (sorry if this question seems ridiculous but it has been a long time since I last did conversions like that ! 
	

	
	
		
		

		
			





)

 630V for this film caps are not too much ? I'm thinking about the WIMA MKP10 220nF 630V...

 Thank you again for all your advices. I feel more capable now ^^


----------



## ludoo

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_I just need one more answer from you guys... Concerning film caps : 0.22µF = 220nF am I right ? (sorry if this question seems ridiculous but it has been a long time since I last did conversions like that ! 
	

	
	
		
		

		
		
	


	




)

 630V for this film caps are not too much ? I'm thinking about the WIMA MKP10 220nF 630V...

 Thank you again for all your advices. I feel more capable now ^^_

 

Capacitor uF - nF - pF Conversion Chart


----------



## Hayduke

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_I just need one more answer from you guys... Concerning film caps : 0.22µF = 220nF am I right ? (sorry if this question seems ridiculous but it has been a long time since I last did conversions like that ! 
	

	
	
		
		

		
		
	


	




)

 630V for this film caps are not too much ? I'm thinking about the WIMA MKP10 220nF 630V...

 Thank you again for all your advices. I feel more capable now ^^_

 

Yes, you got the conversion correct.

 That voltage is pretty large though. I only used 100V components in mine, and that was slightly large. 63V should be OK.

 630V will work fine, but the caps will be much larger then they need to be. If your chosen enclosure has room to spare, then it doesn't matter.

 For C1, C3, C5, C6, I used 470uf 100V Nichicon HE caps (Mouser part 647-UHE2A471MHD). For C2, and C4, I used .22uf 100V film caps from Mallory (Mouser # 539-150224J100CB).


----------



## Tritonpad

Great !

 Thank you ^^


----------



## kansei

I got my parts on Friday and set out to build my first SS amp. I'm about 1/3 done. I strained my brain severely trying to remember what I learned about electronics in high school 25 years ago. My soldering skills are marginal at best, but I watched the Tangent tutorial and learned a few tricks. The next big purchase is a desk lamp with a giant magnifying glass in it... 
	

	
	
		
		

		
		
	


	




*Research*
 I spent countless hours reading this thread. I also brought my laptop to the basement in case I needed a quick answer.

*Inside out or outside in?*
 I started building my SS from the inside out. Drilled the holes for the tube sockets through the copper-clad board, soldered a few things. It occurred to me that this thing will be tough to mount in a box unless I got the copper-clad board situated first. Hunted for an enclosure, bought one from RS, exchanged it for another and finally ended up using what I originally intended to use (an old RS 12v power supply case which looks like a gray brick).

*Casework*
 In general terms, I can't drill to save my life. No matter how well I draw it, or pilot-drill it, the holes never seem to line up nicely. Since I was using bottom-mount sockets, even drilling with the 5/8" drill bit did not work since would need a larger hole on the enclosure to clear the tube glass. Finally, I used my Dremel tool to cut square holes on the enclosure above the tube sockets.

*Tube sockets*
 If I build another SS amp, I'm getting top-mount sockets. They have to be easier than compensating for tube width on the case when mounting them from the bottom.

*Point-to-point wiring*
 I was struggling for a while until I studied the picture on Dave Millett's site which gave me a few clues on how to arrange everything. I wish there was a PCB for this amp, it would make it much easier.

*Caps*
 I ordered 150µF caps but received 220µF ones (c1, c3, c5 and c6). I hope they work.

 I have been messing with this thing since around noon today and need a break. I hope to have it done next weekend. At least most of my case should be easy enough to wire up.


----------



## iareConfusE

Quote:


  Originally Posted by *kansei* /img/forum/go_quote.gif 
_I got my parts on Friday and set out to build my first SS amp. I'm about 1/3 done. I strained my brain severely trying to remember what I learned about electronics in high school 25 years ago. My soldering skills are marginal at best, but I watched the Tangent tutorial and learned a few tricks. The next big purchase is a desk lamp with a giant magnifying glass in it... 
	

	
	
		
		

		
		
	


	




*Research*
 I spent countless hours reading this thread. I also brought my laptop to the basement in case I needed a quick answer.

*Inside out or outside in?*
 I started building my SS from the inside out. Drilled the holes for the tube sockets through the copper-clad board, soldered a few things. It occurred to me that this thing will be tough to mount in a box unless I got the copper-clad board situated first. Hunted for an enclosure, bought one from RS, exchanged it for another and finally ended up using what I originally intended to use (an old RS 12v power supply case which looks like a gray brick).

*Casework*
 In general terms, I can't drill to save my life. No matter how well I draw it, or pilot-drill it, the holes never seem to line up nicely. Since I was using bottom-mount sockets, even drilling with the 5/8" drill bit did not work since would need a larger hole on the enclosure to clear the tube glass. Finally, I used my Dremel tool to cut square holes on the enclosure above the tube sockets.

*Tube sockets*
 If I build another SS amp, I'm getting top-mount sockets. They have to be easier than compensating for tube width on the case when mounting them from the bottom.

*Point-to-point wiring*
 I was struggling for a while until I studied the picture on Dave Millett's site which gave me a few clues on how to arrange everything. I wish there was a PCB for this amp, it would make it much easier.

 I have been messing with this thing since around noon today and need a break. I hope to have it done next weekend. At least most of my case should be easy enough to wire up._

 

The whole point to point wiring confused me quite a bit as well, which is why I'm waiting for the PCB to be released before I order parts. I have a feeling that a few of the parts on the BOM will be changed to work nicely with the PCB. I already have my tubes, all I need now is to order the PSU and the tube sockets off eBay. Hopefully the PCB will be out soon.


----------



## MoxMonkey

Quote:


  Originally Posted by *kansei* /img/forum/go_quote.gif 
_
*Casework*
 In general terms, I can't drill to save my life. No matter how well I draw it, or pilot-drill it, the holes never seem to line up nicely. Since I was using bottom-mount sockets, even drilling with the 5/8" drill bit did not work since would need a larger hole on the enclosure to clear the tube glass. Finally, I used my Dremel tool to cut square holes on the enclosure above the tube sockets.
_

 

use a program like sketchup to make a paper layout and then tape it to the surface of the chassis and drill through it


----------



## kansei

^ great idea, thanks. Perhaps I will be less anxious and can apply this on my second project.


----------



## csroc

Almost done with mine. Did the casework Friday, started soldering yesterday and I have 5 resistors and the 220µF capacitors to connect still. I'll either finish that up tonight or tomorrow sometime since the power supply should be here tomorrow.

 edit: well I just finished the wiring. With my lack of planning ahead enough (I had things laid out nicely but in the end it wound up not being the most ideal configuration) and fitting it in a roughly 4.5" square box it did start to look a little busy at the end but it's done. So if I wired up everything correctly I'll hopefully get to try it tomorrow


----------



## csroc

Well I've stumbled in to a problem. Plugged mine in and turned it on and all I get is a repeated quiet popping/clicking sound which is unaffected by the volume setting. I checked the power supply and it is giving 48V but when connected the voltage at the power connections is fluctuating wildly between around 0 and 30-40V. The voltage at C1 is doing the same.

 Anyone have any ideas? I'm going to set it aside for the moment and look at it again later but I'm not exactly sure what to check next.


----------



## Logistic

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_Well I've stumbled in to a problem. Plugged mine in and turned it on and all I get is a repeated quiet popping/clicking sound which is unaffected by the volume setting. I checked the power supply and it is giving 48V but when connected the voltage at the power connections is fluctuating wildly between around 0 and 30-40V. The voltage at C1 is doing the same.

 Anyone have any ideas? I'm going to set it aside for the moment and look at it again later but I'm not exactly sure what to check next._

 

You might have a short somewhere, check all your connections/soldering.


----------



## csroc

I did a bit of checking for that but haven't been able to track anything down yet (at least where I know what to expect).

 If I put my ear to the power supply I am able to hear the clicking when the amp is turned on. 

 Still a bit stumped but I'll continue to poke around at it and see if anything is amiss (there's only so many connections to worry about a short though).


----------



## scompton

Be careful poking around. Mine was working fine until I tried to close it up which caused a short. When poking around trying to figure out what I did, I created another short with the probe. I fried a mosfet with each short.


----------



## csroc

Yeah I don't want to do that either. I tried testing the MOSFETs based on some instructions I found googling and they seem alright assuming what I was doing was the right thing.

 I'm able to hear the clicking in both channels (it sounds the same in each) and nothing connected to the RCA inputs is heard. There's a short or something somewhere but I've not found it yet.


----------



## Hayduke

I'm sure you've already done this, but go over the entire circuit again and make sure it's all wired correctly. You might find a mistake.

 Are the tubes lighting up? Are the transistors and heatsinks getting hot?


----------



## n_maher

csroc,

 Some nice, clear pictures might help us help.


----------



## csroc

I'm going to check the circuit again in a bit. The tubes are not lighting up but the transistors do start to warm up (I haven't been leaving it on that long).

 I'll see what I can do about a picture in a little while.

 I checked the voltages again with it running and they're not fluctuating as hugely as I thought, they're jumping between almost 0 and 4 or 6 volts. I'm going to look through the circuit in a few minutes.


----------



## n_maher

Did you use all stock values (from the schematic or BOM)?


----------



## csroc

Stock values from the BOM.


----------



## tomb

Dsavitsk and I agreed that perhaps it was a good time to show where we're at with the SSMH PCB. Dsavitsk has designed the PCB, of course, with some comments from n_maher and myself. I've provided the CAD file layouts of the component parts in the second post below.

 The board is designed to be mounted upside down, with the sockets soldered on the bottom of the board and the remainder of the parts hanging down from the other side. This will become clearer with the next post, but suffice to say the ground plane is on top. In order for you to see all of the components of the board, I've included two images, one with the ground plane turned on, and one without:







 With the ground plane layer turned on:





 The MOSFETs are designed to be bolted to the case lid, from the inside. This prevents any exposure to the voltages inside the case.


----------



## tomb

Below are a couple of examples of how the board would fit in the proposed case - either the Hammond 1455L1201 (preferred) or the Hammond 1455N1201 case. The parts clearance in the "L" case is a little more than 20mm. There are several selections of the most used power-type capacitors that will fit - UPW's and FC's, for instance, are available in 470uf 63V at 20mm high.

 If boutiques are desired, which are quite a bit taller (the Nichicon Fine Gold at 470uf 100V comes to mind), then the "N" case provides more than adequate clearance. While the headphone jack and pot shaft line up rather high in that arrangement, one can air-wire both parts if desired.

 Hammond 1455L1201 case:





 Hammond 1455N1201 case:





 Note that the PCB mounting holes are intended for other case choices. The strategy with the Hammonds is to slide the board into the top slot. I don't have them drawn in, but the tube sockets would be soldered into the board on top, and would stick up slightly through the case's top plate.


----------



## iareConfusE

Thanks for the update, looks good.


----------



## Fuzzy OneThree

Anyone else having troubles getting a response from The Tube Center? I filled out the form last Sunday, emailed them earlier today and they still haven't said anything to me.


----------



## MoxMonkey

the pcb looks great guys, i'm sure i can speak for everyone here and say that we appreciate your hard work


 based on the mosfets bolted to the case i'm assuming that the case will act as the heatsink and that the stand alone to-220 ones won't be required?


----------



## wiatrob

I got a message from Tube Center a week ago that they were out of stock (I will assume you were inquiring about 19J6s?) and that they expected more shortly.


----------



## iareConfusE

I've got another question pertaining to the PCBs and the tube sockets. I noticed on every single tube socket that I've seen that the terminals you solder wires to are flat, rather than round like the pins on the bottom of the tube itself. Will the PCB account for this, or will the holes where the socket is to be soldered in still be round?


----------



## Fuzzy OneThree

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I got a message from Tube Center a week ago that they were out of stock (I will assume you were inquiring about 19J6s?) and that they expected more shortly._

 

 Oh well. If they don't reply by midday tomorrow I am going to send another email their way. It is a bad business practice to ignore your customers.


----------



## Sodacose

PCB? I don't need no stinkin' PCB.






 But I'll probably buy one anyways...

 On a side note, I've also had trouble ordering from The Tube Center. Even if they are out of stock, it'd be nice to get an e-mail letting me know that is the case.


----------



## wiatrob

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_...I noticed on every single tube socket that I've seen that the terminals you solder wires to are flat, rather than round like the pins on the bottom of the tube itself. Will the PCB account for this, or will the holes where the socket is to be soldered in still be round?_

 

7 pin ceramic pc board mount sockets should be available...


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_the pcb looks great guys, i'm sure i can speak for everyone here and say that we appreciate your hard work


 based on the mosfets bolted to the case i'm assuming that the case will act as the heatsink and that the stand alone to-220 ones won't be required?_

 

Yes, Dsavitsk says the case itself is enough to dissipate the heat. That was with the "N" case, I believe, which has more metal than the "L" case. In any event, if the "L" case runs hot by itself, we can put one of the half-circle type heat sinks on the top - there's plenty of room. 

  Quote:


  Originally Posted by *iareConfusE* 
_I've got another question pertaining to the PCBs and the tube sockets. I noticed on every single tube socket that I've seen that the terminals you solder wires to are flat, rather than round like the pins on the bottom of the tube itself. Will the PCB account for this, or will the holes where the socket is to be soldered in still be round?_

 

As wiatrob indicated, the sources for PCB-type tube sockets are as numerous as tube dealers:
Beezar.com
SILVER Plated 7 PIN Ceramic Tube Socket PCB - 2PCS - eBay (item 270336166337 end time Jan-28-09 01:33:12 PST)
Cascade Surplus Electronics
7 Pin PC Mount Socket
http://www.partsconnexion.com/catalog/tubesockets.html (scroll down the page)
 etc., etc., etc. ...


----------



## kansei

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Below are a couple of examples of how the board would fit in the proposed case..._

 

That looks incredibly great. Can us mortals hope for a group buy or a store to get the PCB from? You can count me in for at least 5 PCBs.


----------



## tomb

Quote:


  Originally Posted by *kansei* /img/forum/go_quote.gif 
_That looks incredibly great. Can us mortals hope for a group buy or a store to get the PCB from? You can count me in for at least 5 PCBs. 
	

	
	
		
		

		
		
	


	


_

 

I think we're going to want some prototypers to test out the case configurations, first. We'll sell the prototype boards at cost with the option to purchase a couple of tubes and a power supply, too, I think. The prototype boards (there will be 10) are going to run about $15 each. However, production boards should be down in the $5 range. So, you'll have to pay extra for the privilege of being one of the first.
	

	
	
		
		

		
		
	


	




 That's just the way things work with PCB's - you don't want to order in volume until you're sure the board is thoroughly tested. At the same time, it takes volume to get the PCB prices down to something attractive.

 I'll also be building a website for Dsavitsk's SSMH PCB in the days ahead at DIYForums.org, sort of in keeping with all things -Millett-.


----------



## gore.rubicon

OH man, great job on the pcb, cant wait to get my hands on one


----------



## kansei

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The prototype boards (there will be 10) are going to run about $15 each. However, production boards should be down in the $5 range. So, you'll have to pay extra for the privilege of being one of the first.
	

	
	
		
		

		
		
	


	


_

 

You can count me in as a prototyper, I can represent a relative n00b when it comes to building electronics. Send me a PM if you want me to participate and I will send you the $15 for the PCB.


----------



## iareConfusE

I'd be willing to prototype as well. I'd probably make one prototype and one production amp, so I'll probably end up buying the extra tubes, and possibly the power supply if its cheaper than on ebay, which seems to cost a little under $20.

 Also, will somebody be editing the BOM for the PCB, or will we just have to know which ones to omit and which parts to add, because I'm not really good for that kind of stuff


----------



## Bleuburd

What are the chances of someone selling me one of their finished amps?


----------



## iareConfusE

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_What are the chances of someone selling me one of their finished amps?_

 

Once (if) I build the prototype + production one, I'll probably end up selling one of them. Probably the production one, if both perform equally well.


----------



## Bleuburd

Could I be the first in line?


----------



## Logistic

Wow, awesome work Dsavitsk and TomB!

 I noticed you included a spot for bypassing the cathode resister (C7 and C8). Do you recommend using a bypass cap there?


----------



## tomb

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_<snip>
 Also, will somebody be editing the BOM for the PCB, or will we just have to know which ones to omit and which parts to add, because I'm not really good for that kind of stuff 
	

	
	
		
		

		
		
	


	


_

 

From Post #2027:
  Quote:


  Originally Posted by *tomb* 
_I'll also be building a website for Dsavitsk's SSMH PCB in the days ahead at DIYForums.org, sort of in keeping with all things -Millett-._


----------



## tomb

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_<snip>I noticed you included a spot for bypassing the cathode resister (C7 and C8). Do you recommend using a bypass cap there?_

 

Looks like it, but I better let Dsavitsk comment on that.


----------



## Sodacose

Sorry to steer the thread away from the new PCB topic, but does anyone have a lead on tubes? I can't seem to find any anywhere!

 I've even tried the local suppliers and it's no dice.

 Thanks for the help in advance!


----------



## MoxMonkey

i would love to volunteer my time to build one of the prototype pcbs if i didn't have a crazy work load this term with needing to finish my undergrad thesis


----------



## mattcalf

I have all the pieces necessary to complete my build and it's coming along steadily. 

 My one question at the moment is:
 How far do the tubes go into the sockets? When in fully should they be able to rattle around a bit?

 Because when mine go in, they really just sit there and I don't want to force them in fear of breaking a hard to get tube.


----------



## tomb

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_I have all the pieces necessary to complete my build and it's coming along steadily. 

 My one question at the moment is:
 How far do the tubes go into the sockets? When in fully should they be able to rattle around a bit?

 Because when mine go in, they really just sit there and I don't want to force them in fear of breaking a hard to get tube._

 

The bottom of the tube should rest firmly on the top surface of the socket. If that's not the case, you don't have a good connection. Small arcing may take place and eat up the pins on the tube eventually, or worse.

 Sometimes it helps to have an old tube around to force into the sockets. They can be very stiff the first few times they're used.


----------



## csroc

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Did you use all stock values (from the schematic or BOM)?_

 

I'm beginning to wonder, should I not have used stock values from the BOM? I've been busy so I haven't had much time to look in to it or take pictures, but I found out about the Starving Student elsewhere and decided to put it together before reading this thread.


----------



## Punnisher

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_I have all the pieces necessary to complete my build and it's coming along steadily. 

 My one question at the moment is:
 How far do the tubes go into the sockets? When in fully should they be able to rattle around a bit?

 Because when mine go in, they really just sit there and I don't want to force them in fear of breaking a hard to get tube._

 

Mine are all the way down, and they wiggle a bit. This is because the female pins have some wiggle room inside the socket. The connections are good, but the tube can wiggle back and forth a bit if you try.


----------



## n_maher

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_I'm beginning to wonder, should I not have used stock values from the BOM? I've been busy so I haven't had much time to look in to it or take pictures, but I found out about the Starving Student elsewhere and decided to put it together before reading this thread._

 

My stock BOM version ran fine for months. I change a few things, but I don't think parts selection is your issue.


----------



## cegras

I am looking forward to the PCB .. I will be willing to make this my first DIY. If only someone would sell kits, it would be perfect.


----------



## iareConfusE

Quote:


  Originally Posted by *cegras* /img/forum/go_quote.gif 
_I am looking forward to the PCB .. I will be willing to make this my first DIY. If only someone would sell kits, it would be perfect._

 

Its not very hard acquiring your own parts, maybe except for the tubes themselves. Just wait for someone to make a definite BOM for the PCB build, then just oder from mouser or digikey, pretty simple.


----------



## gore.rubicon

where do you get the 19j6 now a days? i couldnt find one at all today


----------



## iareConfusE

I got one from the Tube Center, though I think Jack's out of stock now.


----------



## cegras

I don't mind ordering either. But the PCB will simplify things for me, I think. I have a first year's knowledge of circuits (a lamp, battery, and resistor!), so reading one is challenging. I barely have time now, so I figure by the time summer rolls along I can spend my spare time on this.


----------



## iareConfusE

Quote:


  Originally Posted by *cegras* /img/forum/go_quote.gif 
_I don't mind ordering either. But the PCB will simplify things for me, I think. I have a first year's knowledge of circuits (a lamp, battery, and resistor!), so reading one is challenging. I barely have time now, so I figure by the time summer rolls along I can spend my spare time on this._

 

I'm talking about the components. Even when you buy the PCB, you'll still have to buy the components... Only difference the PCB makes is that you won't have to worry about wiring it point to point flawlessly without a definite layout.


----------



## zkool448

I have the BOM saved project over at Mouser currently ready to be ordered, however I'm not having any luck finding sources for the 19J6 tubes at all. I received a couple of replies this morning from dealers and all are out of stock.

 By the way thought this may be worth a shot. I actually wanted to post this under the classifieds section, however since I have less than 50 post being a new member I'm unable to do so. I'm hoping someone here wouldn't mind parting with they SS hybrid amp and sell me a finished one instead.

 Please send me a PM me if you can help. thanks! : )


----------



## MrMajestic2

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I have the BOM saved project over at Mouser currently ready to be ordered, however I'm not having any luck finding sources for the 19J6 tubes at all. I received a couple of replies this morning from dealers and all are out of stock.

 By the way thought this may be worth a shot. I actually wanted to post this under the classifieds section, however since I have less than 50 post being a new member I'm unable to do so. I'm hoping someone here wouldn't mind parting with they SS hybrid amp and sell me a finished one instead.

 Please send me a PM me if you can help. thanks! : )_

 

Tubedepot.com seems to be in stock. Although they charge $7.75 USD for them


----------



## zkool448

Thanks MrMajestic2, I'll try tubedepot.com and see if they have any left. 

 BTW, in case of anyone looking to sell their finished project, I don't really mind cosmetics, looks, or neatness, etc. as long as the "guts" are all intact and in working order. Thank you.


----------



## mattcalf

Thanks tomb.
 Can't wait for some spare time this weekend.


----------



## zkool448

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Tubedepot.com seems to be in stock. Although they charge $7.75 USD for them 
	

	
	
		
		

		
		
	


	


_

 

Just received confirmation tubedepot is out-of-stock of the 19J6 : (


----------



## Hayduke

Quote:


  Originally Posted by *mattcalf* /img/forum/go_quote.gif 
_I have all the pieces necessary to complete my build and it's coming along steadily. 

 My one question at the moment is:
 How far do the tubes go into the sockets? When in fully should they be able to rattle around a bit?

 Because when mine go in, they really just sit there and I don't want to force them in fear of breaking a hard to get tube._

 

Matt, So can you see the pins? If so, I think I know what happened. When you were building the amp, you probably had the sockets upside down. If you got the pins real hot, solder may have flowed down into the area the pins go because of gravity. I had this happen when I was adding grid stopper resistors. My solution was to turn over the right way and then reheat the pin. Gravity will work again, but this time in your favor. The solder should flow back down to where your wire and/or components are attached.

 You can check if this is the problem. Look into the pin hole. On my sockets, I can see through them. When it was blocked, I couldn't.

 Hope that helps 
	

	
	
		
		

		
		
	


	




 You might have to remove the connections for the blocked pin and use some solder wick to get rid of solder (if you used A LOT). If you aren't sure which pin it is, find something a similar diameter like a needle or a sewing pin, and try sticking it in the hole. Sure it won't be tight like a tube pin, but I suspect your entire plug is blocked.

 Let us know if you figure it out.


----------



## dsavitsk

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_I noticed you included a spot for bypassing the cathode resister (C7 and C8). Do you recommend using a bypass cap there?_

 

No, not necessarilly. That cap is right in the signal path and will thus influence sonics. However, it also lowers rp a little and increases gain, so there are times when one might want it. There was space on the board so I put it in, but I wouldn't worry about it in most cases.


----------



## dsavitsk

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_based on the mosfets bolted to the case i'm assuming that the case will act as the heatsink and that the stand alone to-220 ones won't be required?_

 

An early version based on this premise didn't really get hot at all, just warm. You can, however, bolt a big sink on if you like.


----------



## iareConfusE

^^ Ahaha that looks pretty sweet.


----------



## somestranger26

I found the 19J6 at oldradiotubes.com but dried up their stock of 3 (minimum order of $20 and they were only $2 each!). However, I got some emails today from a few other sellers saying they're in stock.

Richardson Electronics Ltd.: $6.95 each, minimum order of 5 pieces.

http://vacuumtubes.com: $10 each, $30/pair (???)

Vacuum Tubes - Audio Tubes - ESRC Vacuum Tubes - Electron Tubes said they are out of stock but are expecting stock soon, so you could also try there.

 Hope this helps those of you looking for the tubes yet.


----------



## Sodacose

Quote:


  Originally Posted by *somestranger26* /img/forum/go_quote.gif 
_I found the 19J6 at oldradiotubes.com but dried up their stock of 3 (minimum order of $20 and they were only $2 each!). However, I got some emails today from a few other sellers saying they're in stock.

Richardson Electronics Ltd.: $6.95 each, minimum order of 5 pieces.

http://vacuumtubes.com: $10 each, $30/pair (???)

Vacuum Tubes - Audio Tubes - ESRC Vacuum Tubes - Electron Tubes said they are out of stock but are expecting stock soon, so you could also try there.

 Hope this helps those of you looking for the tubes yet._

 


 FYI I believe that last link is the same as The Tube Center. They share the same address. Thanks for the links, though!


----------



## wiatrob

I found a local surplus supplier who is putting the word out to search cobwebbed corners. Will update if i hear anything...


----------



## MoxMonkey

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_An early version based on this premise didn't really get hot at all, just warm. You can, however, bolt a big sink on if you like.
_

 

looks great i've got an old p3 heatsink that would suffice for piece of mind 
	

	
	
		
		

		
		
	


	




 really can't wait for the pcb versions


----------



## zkool448

Quote:


  Originally Posted by *somestranger26* /img/forum/go_quote.gif 
_
Vacuum Tubes, Electron Tubes, Tubes, Tube Testers and Electronic Parts: $10 each, $30/pair (???)

 Hope this helps those of you looking for the tubes yet._

 

Thanks somestranger26. 

 Only the above dealer has stock right now.. $10 ea. might be worthwile but will need 4 pcs. (2 will be used as spare). Total price may end up costing a bit more than expected IMO.

 Thanks again for the lead.


----------



## petterg

Hi all, i finished my starving student today but it doesn't work 
	

	
	
		
		

		
		
	


	




, the MOSFET's are getting warm, i can hear the sound (barely) and the tubes doesn't light up. Anyone here know what might be wrong?


----------



## tomb

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_Hi all, i finished my starving student today but it doesn't work 
	

	
	
		
		

		
		
	


	




, the MOSFET's are getting warm, i can hear the sound (barely) and the tubes doesn't light up. Anyone here know what might be wrong?_

 

Well, if the tubes don't light, that means you don't have the heaters wired up correctly. If you can hear the source, you probably have something else wired incorrectly, too. I'm not sure you would be able to hear any sound if the tubes were dead, assuming it was wired correctly.

 You might post a pic of your SSMH's internals. There's plenty of folks here who would be able to spot a wiring mistake.


----------



## petterg

Ok, as i said in my previous post i've got some problems with my amp and i'm uploading some images, but to warn you: it's a mess!

http://i40.tinypic.com/2wnqnf8.jpg
http://i42.tinypic.com/33z3h5g.jpg
http://i44.tinypic.com/353ayk5.jpg
http://i44.tinypic.com/rr767l.jpg
http://i40.tinypic.com/2mcbo5s.jpg

 Please help me out!


----------



## iareConfusE

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_Ok, as i said in my previous post i've got some problems with my amp and i'm uploading some images, but to warn you: it's a mess!

http://i40.tinypic.com/2wnqnf8.jpg
http://i42.tinypic.com/33z3h5g.jpg
http://i44.tinypic.com/353ayk5.jpg
http://i44.tinypic.com/rr767l.jpg
http://i40.tinypic.com/2mcbo5s.jpg

 Please help me out! 
	

	
	
		
		

		
		
	


	


_

 

Exactly why I'm waiting for the PCB 
	

	
	
		
		

		
		
	


	




 Good luck with it peterrg.


----------



## petterg

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Exactly why I'm waiting for the PCB 
	

	
	
		
		

		
		
	


	




 Good luck with it peterrg._

 

haha yeah, guess that i should have done that too.


----------



## Logistic

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_Ok, as i said in my previous post i've got some problems with my amp and i'm uploading some images, but to warn you: it's a mess!

http://i40.tinypic.com/2wnqnf8.jpg
http://i42.tinypic.com/33z3h5g.jpg
http://i44.tinypic.com/353ayk5.jpg
http://i44.tinypic.com/rr767l.jpg
http://i40.tinypic.com/2mcbo5s.jpg

 Please help me out! 
	

	
	
		
		

		
		
	


	


_

 

Can you take a photo of the tube sockets with the connections in plain view?


----------



## DopeNessMonster

Got mine together last night. Took about 4 or 5 hours. The wiring was a total mess when I got done about 2am and I was sure something would blow, even though I'd traced everything many times. To my total amazement, it not only didn't blow, it actually worked! Score. I really liked Coreyk78's amp, so chose the same enclosure. The volume knob is just something I grabbed from Radio Shack. I'll machine one that fits/suits it better some time later.

 Took half an hour today on my lunch break and shortened up the leads and cleaned stuff up so it'd actually fit in the case. Listening to it now, and it sounds great.

 Don't mind the burnt masking tape holding the heatsinks on, that was a minor heat shrink accident 
	

	
	
		
		

		
		
	


	

































 BTW, name's Brian, I'm new here


----------



## petterg

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Can you take a photo of the tube sockets with the connections in plain view?_

 

Sure, should i take away the shrink tubing too?


----------



## scompton

I don't know if it's the problem, but you made the same mistake I made. You have long exposed leads on the caps and resistors. I did the same thing. It worked fine until I closed the case which caused a short and fried a mosfet.


----------



## petterg

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I don't know if it's the problem, but you made the same mistake I made. You have long exposed leads on the caps and resistors. I did the same thing. It worked fine until I closed the case which caused a short and fried a mosfet._

 

yeah, hope thats not what i did.
 Here is my plans for the amp btw:

http://i43.tinypic.com/oired2.jpg
http://i43.tinypic.com/whd7p1.jpg
http://i43.tinypic.com/2h2qqv6.jpg


----------



## scompton

You don't have the same symptoms I had. I got no sound out of the channel with the dead mosfet and that tube got very bright.


----------



## petterg

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_You don't have the same symptoms I had. I got no sound out of the channel with the dead mosfet and that tube got very bright._

 

Ok, that's a good sign!... i think...
	

	
	
		
		

		
			





, maybe it's just me that's too stupid.


----------



## csroc

As mentioned before, mine seems to be shorting out. I'll get a voltage fluctuation of 0-4V or so as the power supply keeps clicking. The tubes never light but the MOSFETs do start to get a little warm.

http://www.morphien.com/files/MSSH/_T4G5711.jpg
http://www.morphien.com/files/MSSH/_T4G5713.jpg
http://www.morphien.com/files/MSSH/_T4G5715.jpg
http://www.morphien.com/files/MSSH/_T4G5722.jpg
http://www.morphien.com/files/MSSH/_T4G5723.jpg
http://www.morphien.com/files/MSSH/_T4G5725.jpg
http://www.morphien.com/files/MSSH/_T4G5726.jpg

 My soldering started to get rather sloppy towards the end but I haven't identified a problem yet.


----------



## looser101

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_As mentioned before, mine seems to be shorting out. I'll get a voltage fluctuation of 0-4V or so as the power supply keeps clicking. The tubes never light but the MOSFETs do start to get a little warm.

http://www.morphien.com/files/MSSH/_T4G5711.jpg
http://www.morphien.com/files/MSSH/_T4G5713.jpg
http://www.morphien.com/files/MSSH/_T4G5715.jpg
http://www.morphien.com/files/MSSH/_T4G5722.jpg
http://www.morphien.com/files/MSSH/_T4G5723.jpg
http://www.morphien.com/files/MSSH/_T4G5725.jpg
http://www.morphien.com/files/MSSH/_T4G5726.jpg

 My soldering started to get rather sloppy towards the end but I haven't identified a problem yet._

 

To start it looks like your heaters are shorted. Pin 3 is supposed to go to mosfet + output cap, pin 4 to ground.


----------



## csroc

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_To start it looks like your heaters are shorted. Pin 3 is supposed to go to mosfet + output cap, pin 4 to ground._

 

Interesting, I misread the diagram then. Reading a tube diagram is all a bit new to me and it looked to me like 3 and 4 were tied together.


----------



## Hayduke

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_Interesting, I misread the diagram then. Reading a tube diagram is all a bit new to me and it looked to me like 3 and 4 were tied together._

 

3 and 4 are the heater circuit. Current goes into pin 3 and out 4 to ground.
 Your tubes aren't lighting up, right?

 Edit: Looking at the images again, in your last image, the joints to the terminal block look suspect. I would reflow them. Add more solder too. It looks like a lead from one of the components is just wrapped around the terminal block and isn't soldered at all.


----------



## csroc

They are actually soldered, it's just not visible. If it works after this I'll get some more solder on there.

 I've fixed the tube wiring issue, which I must admit makes complete sense and I feel a bit like an idiot, and it's now lighting up and the amp does in fact work now. Thanks for the help


----------



## looser101

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_They are actually soldered, it's just not visible. If it works after this I'll get some more solder on there.

 I've fixed the tube wiring issue, which I must admit makes complete sense and I feel a bit like an idiot, and it's now lighting up and the amp does in fact work now. Thanks for the help 
	

	
	
		
		

		
		
	


	


_

 

If we didn't make mistakes once in a while we wouldn't be human. Consider it a learning opportunity. 

 Enjoy your amp.


----------



## Hayduke

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_They are actually soldered, it's just not visible. If it works after this I'll get some more solder on there.

 I've fixed the tube wiring issue, which I must admit makes complete sense and I feel a bit like an idiot, and it's now lighting up and the amp does in fact work now. Thanks for the help 
	

	
	
		
		

		
		
	


	


_

 

grats!


----------



## csroc

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_If we didn't make mistakes once in a while we wouldn't be human. Consider it a learning opportunity._

 

Indeed! This is my first foray in to tubes and to the best of my understanding of the wiring diagram I got it all right, sadly my understanding came up a bit short 
	

	
	
		
		

		
		
	


	




 For some reason I imagined one of the other pins out of the tubes was the ground for the heater circuit. No harm done


----------



## ThePredator

What is a good replacement for C2 and C4? I can't find any .1uF 63v film caps that would be as easy to wire up as the suggested (and obsolete according to mouser) ones.

 Also, on the power supply, do I want the .38A IP phone one, or the 1A/1.5A one?


----------



## Hayduke

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_What is a good replacement for C2 and C4? I can't find any .1uF 63v film caps that would be as easy to wire up as the suggested (and obsolete according to mouser) ones.

 Also, on the power supply, do I want the .38A IP phone one, or the 1A/1.5A one?_

 

The VoIP injection (.38A) one.

 For C2 and C4, I used 150224J100CB

 Maybe these would be a better choice. I like them in my BantamDAC (different value is all)
http://mouser.com/Search/ProductDeta...2fbVyeg1arI%3d


----------



## ThePredator

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_The VoIP injection (.38A) one.

 For C2 and C4, I used 150224J100CB

 Maybe these would be a better choice. I like them in my BantamDAC (different value is all)
MKT1822422015_

 

Thanks for helping, one last question though. Is this the correct tube socket? (I would rather get it here than tubedaze since they accept paypal)

7 Pin Miniature Socket


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_The VoIP injection (.38A) one.

 For C2 and C4, I used 150224J100CB

 Maybe these would be a better choice. I like them in my BantamDAC (different value is all)
MKT1822422015_

 

Actually, the Bantam has a different set of rules it's operating under for film caps. The input impedance of an amp, while quite high, is still much lower than the impedance seen by interstage couplers such as C2 and C4. That means the cutoff frequency from the resulting RC product of the output couplers' capacitance times the impedance of the amp requires about 0.66uf to 1uf as a minimum rating. Plus, the Bantam is restricted by space, for obvious reasons (it's a very tiny board). For this reason, the smaller metalized polyester caps are used on the Bantam.

 Given a reasonable rating requirement and enough room, metalized _polypropylene_ is the best choice. What you want on the Starving Student is an MKP - type cap. There are series of the Vishay-Roederstein at Mouser that are MKP's, but most of us default to the Wima MKP10's. The 0.22uf size is still not very big and offers a bit more insurance against a too-high cutoff frequency in the interstage coupling.

 There are many axial caps as well - but as mentioned, look for a metalized _polypropylene_.


----------



## ThePredator

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, the Bantam has a different set of rules it's operating under for film caps. The input impedance of an amp, while quite high, is still much lower than the impedance seen by interstage couplers such as C2 and C4. That means the cutoff frequency from the resulting RC product of the output couplers' capacitance times the impedance of the amp requires about 0.66uf to 1uf as a minimum rating. Plus, the Bantam is restricted by space, for obvious reasons (it's a very tiny board). For this reason, the smaller metalized polyester caps are used on the Bantam.

 Given a reasonable rating requirement and enough room, metalized polypropylene is the best choice. What you want on the Starving Student is an MKP - type cap. There are series of the Vishay-Roederstein at Mouser that are MKP's, but most of us default to the Wima MKP10's. The 0.22uf size is still not very big and offers a bit more insurance against a too-high cutoff frequency in the interstage coupling.

 There are many axial caps as well - but as mentioned, look for a metalized polypropylene._

 

So would this one work well?
MKP10-.22/250/10


----------



## tomb

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_So would this one work well?
MKP10-.22/250/10_

 

Yes, it's the Millett MAX standard and rds used the same thing on his Starving Student-MiniMilletts.


----------



## kansei

*Done!*
 Whew! I'm finally done with my Starving Student amp. It took me at least 5 hours of working to get it together, and another 10 hours of scratching my head trying to figure out where to find various bits and how to put things together. 

*The enclosure*
 I used an enclosure from a Radio Shack 12v power supply. I have been meaning to throw it out for about 6 months but could not get myself to do it. Appreciation for technology, I suppose. My goal was to make use of existing holes as much as possible. It still needs a volume knob that doesn't look ridiculous. A cool thing is that this enclosure has a giant heatsink on the inside which I used. The volume knob is where the 12v lighter socket used to be, RCA inputs are in the front, headphone and power jack in the back. I was initially going to install the Cisco power supply inside the case but thought better of it.

*The enclosure, II*
 It took a good amount of time to figure it out and I still hacked it up. As discussed in my previous post, I was either too nervous or of little skill when putting it together. What bothers me the most is not being able to mark and drill so things look even. Most everything is crooked: the pot, the tubes, the inputs, you name it. I hope to improve on my next project. 

*The wiring*
 I cursed point-to-point wiring hundreds of times throughout the project. My wire was also too thick in gauge which made it harder to put together. My brain did not fully wrap around the concept of how this thing had to be wired and I made some mistakes that led to compromises down the road. I had to compensate for my building decisions as I went along. My recommendation to anyone who puts one of these together is to just put together a plain-Jane genuine article like Dave put together, step by step. Look at the giant photo on Dave's website and correlate it to the schematic, the build it. It will save you from having to engineer stuff over and over again until things work out. I may be making too much of this, but my brain still hurts from trying to get it right. The good thing is that my comfort level is much higher now and I am ready to build another.

*The potentiometer*
 The pot from the BOM is OK, but the pads on it are wayyyy too small. Soldering wires to it had to be the worst part of the whole project. It kept shorting and the wires kept falling off and I decided to buy a different pot before I went crazy. Good thing Radio Shack is open late, I went there and picked up 271-1732. Yes, it's 100k but it works now instead of waiting for mail order parts. A nice, new pot will be on my next parts order.

*Shortage of parts*
 I was missing one capacitor and had to improvise for C1. Pulled a 4700uF cap from the power supply PCB that I gutted and installed it. It works, and there's no thump on power-up.

*Failure to read directions*
 I soldered both 4-position terminal strips in reverse (180 degrees backwards). On both channels, C4 and R8 were grounded. It took me 10 minutes of probing around, then examining Dave's photo until I figured out the boneheaded move I pulled. At first I was going to de-solder everything and redo it, then decided to just unsolder the terminal strips from the copper clad board and put some tape under the connectors. Duh. I may need to do the whole thing over again, let's see how my OCD holds up. 
	

	
	
		
		

		
			





*The beautiful music*
 I am utterly amazed at how much better this amp sounds with my Sennheiser HD600s compared to anything else I have in my house. Everything sounds sweeter, especially the bass. The amount of detail is amazing. Forget the EMU 0202, forget the Boa D2, forget the Onkyo receiver and everything else. This is great.

*Thank you*
 I want to thank *digger945 * for helping me with getting some 19j6 tubes. I really appreciate it.

*Pictures*
Millett Starving Student hybrid tube amplifier pictures by kansei13 - Photobucket


----------



## kansei

Quote:


  Originally Posted by *DopeNessMonster* /img/forum/go_quote.gif 
_Got mine together last night. Took about 4 or 5 hours...._

 

Looks very nice.


----------



## csroc

I'm finding I'd rather use more of the volume pot than I currently am. Have any of you made adjustments to lower the gain or do you find just using a 100k potentiometer (I used a 50k) did the trick?


----------



## dsavitsk

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_I'm finding I'd rather use more of the volume pot than I currently am. Have any of you made adjustments to lower the gain or do you find just using a 100k potentiometer (I used a 50k) did the trick?_

 

A 100K vs a 50K pot won't make any difference, but putting a 50K resistor in line before the 50K pot will give you more range, and a higher Z-in.


----------



## csroc

OK, I was actually just looking at this
http://www.wduk.worldomain.net/forum...read.php?t=198

 And it looks like an interesting approach. 

 In reference to my original thought of switching to a 100k pot, I had read discussion earlier in this thread that some were using a 100k pot to at least allow them to turn it up more and get in to the "sweet spot" as it were.


----------



## ThePredator

Is it worth doing the shunt pot mod described here on the stock BOM pot, or would the improvement be negligible?

 [edit]: Seems csroc just posted the same link above me


----------



## csroc

I'm thinking I might do the shunt mod for the reduction in gain if nothing else, although if it improves sound quality then no complaints!

 edit: and a picture of it running


----------



## bidoux

How dangerous is it to work with this starving student ? I mean, because we use tubes the voltage will be a lot higher than in normal SS amp.


----------



## petterg

Hi again, i still having problems with my amp, today i resolder all the ground spots to some "bare PCM material". But still, it's not working, i can hear some sound but it's very low and the tubes doesn't light up.

 I would be more than happy if someone took time to look at the plans i draw for my amp (page 139).

 //Petterg


----------



## Yaka

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_A 100K vs a 50K pot won't make any difference, but putting a 50K resistor in line before the 50K pot will give you more range, and a higher Z-in._

 

sorry to sound newbie but im still on my learning curve. do you mean add the resistors to 1 and 2 points on the pot then atach L/R to other end of the resistor?


----------



## Logistic

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_Hi again, i still having problems with my amp, today i resolder all the ground spots to some "bare PCM material". But still, it's not working, i can hear some sound but it's very low and the tubes doesn't light up.

 I would be more than happy if someone took time to look at the plans i draw for my amp (page 139).

 //Petterg_

 

Recheck all your connections. Your plan seems okay on a cursory glance. However, I can't see all the connections you drew out on the third image, in your amp (on those metal tabs). I assume you soldered some components along the backside?

 Please post a better picture of both sides of the 4 solder tabs and also a picture of the tube socket. You don't have to take off the heatshrink.


----------



## petterg

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Recheck all your connections. Your plan seems okay on a cursory glance. However, I can't see all the connections you drew out on the third image, in your amp (on those metal tabs). I assume you soldered some components along the backside?

 Please post a better picture of both sides of the 4 solder tabs and also a picture of the tube socket. You don't have to take off the heatshrink._

 

I think i've found the problem, i've put C1 facing wrong direction! it's a little buckled now, but can i make it right and then try the amp again without any risk of destroy the other comonents?

 EDIT: Now it's working! and WOW! it sounds amazing.


----------



## sebrkln

Anyone have any tips on wiring the connections to the MOSFETs? It seems like people are using specific connectors from some of the photos -- or are they just soldered?


----------



## csroc

Just soldered for mine. I'm still wondering if that shunt pot mod is a good choice for this. I guess I'll have to get some resistors and try it out.


----------



## looser101

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_Just soldered for mine. I'm still wondering if that shunt pot mod is a good choice for this. I guess I'll have to get some resistors and try it out._

 

Shunt pot won't attenuate the volume. You need the resistors in front (series) of your current volume pot, to attenuate volume and allow more range of adjustment.


----------



## Hayduke

Quote:


  Originally Posted by *sebrkln* /img/forum/go_quote.gif 
_Anyone have any tips on wiring the connections to the MOSFETs? It seems like people are using specific connectors from some of the photos -- or are they just soldered?_

 

I soldered wire leads directly to the MOSFETs, then wrapped them in shrink tubing. There is an advantage in this, you can solder R3 directly to pin 1 of the transistor. You want it as close as possible, so this is as close as you can get


----------



## scompton

Quote:


  Originally Posted by *sebrkln* /img/forum/go_quote.gif 
_Anyone have any tips on wiring the connections to the MOSFETs? It seems like people are using specific connectors from some of the photos -- or are they just soldered?_

 

I think what you're seeing is heat shrink like Hayduke said


----------



## wiatrob

I sorted through about 6 boxes of tubes in Boulder today, with my fingers crossed...found 1 19J6 (now I have one matching pair). Anybody else have any luck obtaining any lately?


----------



## iareConfusE

Does anybody know if there are alternates to the 19J6 tubes that can be used in this amp? Looks like all of the 19J6's of the world are running out ;o

 Is it possible for there to be a substitute for this tube?


----------



## ThePredator

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Does anybody know if there are alternates to the 19J6 tubes that can be used in this amp? Looks like all of the 19J6's of the world are running out ;o

 Is it possible for there to be a substitute for this tube?_

 

No, 19J6 are the only ones that work.

TubeDepot.com has them in stock, a bit expensive though.


----------



## zkool448

As I continue to search high and low for these tubes I got some info from a canuck audio board member and sent me this data sheet.

 I've read this entire thread the last few days and it sounds like a replacement tube cannot be used unless a change to the original design is made. I also realize a PCB is still in the works, however a low probability that many of these SS hybrid will get built any time soon if there is indeed a tube shortage .


----------



## zkool448

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_TubeDepot.com has them in stock, a bit expensive though._

 

I got an email from Brian over at tubedepot.com confirming they were out of stock 2 days ago.. perhaps they're restocked. Thanks will try him again.


----------



## ThePredator

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_As I continue to search high and low for these tubes I got some info from a canuck audio board member and sent me this data sheet.

 I've read this entire thread the last few days and it sounds like a replacement tube cannot be used unless a change to the original design is made. I also realize a PCB is still in the works, however a low probability that many of these SS hybrid will get built any time soon if there is indeed a tube shortage ._

 

Is there actually a tube shortage, or are tube sellers simply not prepared for the demand? From what I have seen the sellers are still able to get them in stock, they simply never kept too many around because of their limited use.


----------



## tomb

The PCB's will be sold with a pair of tubes, each ... and that's all I'm saying about that at this time.

 Prototypes have been ordered. They will ship to me on Feb. 9. So we'll be asking for volunteers: 5 of them. Don't volunteer unless you're going to build one in the next couple of weeks after receiving one. It's not going to help any of us if you volunteer then sock the PCB away for a rainy day. We also would prefer experience and experience with casework and the Hammond 1455 cases. (We're hoping the 1455L1201 will be the preferred choice, but that's one of the reasons for prototyping.) The PCB's will be supplied at cost - $15 ea, plus a pair of tubes for $5 each, and a couple of sockets at a minimal charge. Also, I can supply power supplies for each proto if desired. That should mean that all other parts will be obtainable at Mouser. Note: Production sales will be similar, except the PCB price should be half that.

 Send me an e-mail at tomb@beezar.com with "Starving Student Prototype" in the subject line. Confirm your experience and willingness to build one within a couple of weeks of receiving the proto board. I'll make arrangements in the next few days to get your Paypal account e-mail and send you a Paypal invoice for the components.

 I've been working on a website today, which for me means doing a logo first:
Starving Student Millett Hybrid

 The SSMH PCB support site will be located where we have the rest of all things Millett: diyforums.org.


----------



## zkool448

Thanks Tomb, this is great news!

 As much as I want to get one built today, i think my search for tubes will be put on hold (for now), instead I'll patiently wait and order the production PCB/tubes combo when they become available 
	

	
	
		
		

		
		
	


	




 Can you share any info if there are any mods to the original BOM due to the board design?


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Thanks Tomb, this is great news!

 As much as I want to get one built today, i think my search for tubes will be put on hold (for now), instead I'll patiently wait and order the production PCB/tubes combo when they become available 
	

	
	
		
		

		
		
	


	




 Can you share any info if there are any mods to the original BOM due to the board design?_

 

Yes, there are some extra features - optional, of course. However, Dsavitsk preserved the same circuit that Pete designed. You can build it exactly as Pete's schematic or add a few tweaks - either one.

 I'll have the BOM up in a couple of days.


----------



## iareConfusE

Thanks for your hard work guys, I'm sure everyone in the DIY community appreciates all of it.


----------



## Yaka

great news sent yoiu an email tomb
	

	
	
		
		

		
			






 also 

  Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I think what you're seeing is heat shrink like Hayduke said_

 

there are some pics with a femail 3 pin fan connector being used similar to the one here http://www.maplin.co.uk/Module.aspx?...C=SO&U=strat15


----------



## Hayduke

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_there are some pics with a femail 3 pin fan connector being used similar to the one here 3 Pin Extension Cable > Maplin_

 

Connected to the MOSFETs?
 Can you link one of the posts please?


----------



## tomb

Still need 2 volunteers for the protos ...


----------



## csroc

I would be fun to build one based off the PCB, but having just bought all the parts to build one P2P I'm not sure I want to blow more money


----------



## royewest

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Still need 2 volunteers for the protos ... 
	

	
	
		
		

		
		
	


	


_

 

I just sent you email.


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I just sent you email._

 

Got it and replied! Thanks!


----------



## ludoo

A couple of PCB-related questions.

 On the PCB there are two caps (C7 and C8) that look like bypasses for the cathode bias resistor. I assume they will see little voltage (did not do any calculation though so don't know how little), but will need to be fairly large. Is 470uF 16V ok here? Any suggestions on what to use?

 I think I will drop R16 and R17 as I'm pretty happy with my two SS without them. Anything I should know before deciding to drop them?

 What kind of specs will work for the output caps bypass capacitors (C3A and C5A)? In my builds I used Vishay MKP 1837 0.01uF, but I was even more of a noob than I am now, so I'd like to know if there's anything better to put there. And, are they really bypass caps? I don't really understand how they are wired.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_A couple of PCB-related questions.

 On the PCB there are two caps (C7 and C8) that look like bypasses for the cathode bias resistor. I assume they will see little voltage (did not do any calculation though so don't know how little), but will need to be fairly large. Is 470uF 16V ok here? Any suggestions on what to use?_

 

We'll really need Dsavitsk to chime in here for details. However, a cathode bypass cap has traditionally been anything from 220uf to 1000uf, but 16V is most likely enough for the voltage rating. If you run the calcs on the cutoff frequency, it often ends up with something as small as 220uf, but on the SOHA and the MAX/MiniMAX, we settled at 1000uf as best - bass response suffered otherwise.

 The amp performs quite well without them, but I think using a cathode bypass will create a little -edited-, (EDIT: Oops - looks like I had it backward - positive feedback.). I've probably said more than I'm knowledgeable about, so let's see what Dsavitsk says.

  Quote:


 I think I will drop R16 and R17 as I'm pretty happy with my two SS without them. Anything I should know before deciding to drop them? 
 

Sure - not everyone has your Ortho's. If it works for you without them, that's fine.

  Quote:


 What kind of specs will work for the output caps bypass capacitors (C3A and C5A)? In my builds I used Vishay MKP 1837 0.01uF, but I was even more of a noob than I am now, so I'd like to know if there's anything better to put there. And, are they really bypass caps? I don't really understand how they are wired. 
 

Dsavitsk will have his opinions, too, but 0.01uf is a bit too small. We settled on 0.22uf's for the MAXes and that's what these footprints are for. We use the Wima MKP10 on the MAXes - so did rds on his StarvingStudent-MiniMilletts. You can't go wrong with the Wima's, but the Vishay-Roederstein MKP is a fine bypass cap. It gets great reviews from Humble Homemade Hifi, but I don't know yet from personal experience (I'm trying them on my next MiniMAX, though). The Roederstein MKP1840422254 is probably the one to try. It's the same size and rating as the Wima MKP10, 0.22uf 250V. Anything from about 0.1uf to 0.47uf will work fine, but keep in mind that cap bypassing is a very inexact science.

 If you've got the height (not in the Hammond "L" case), C3a and C5a would be a great spot for VitaminQ's, too - but that's sort of digressing from original principles for the SSMH.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
On the PCB there are two caps (C7 and C8) that look like bypasses for the cathode bias resistor. I assume they will see little voltage (did not do any calculation though so don't know how little), but will need to be fairly large. Is 470uF 16V ok here? Any suggestions on what to use?

 

16V is most likely enough for the voltage rating.

 The amp performs quite well without them, but I think using a cathode bypass will create a little negative feedback, which can't be bad in the SSMH. I've probably said more than I'm knowledgeable about, so let's see what Dsavitsk says._

 

The bias on the grids is less than 2V. So, voltage is not an issue at all -- 6.3V, or even 4V caps should be fine. Size wise, I think I'd start at 470u are work from there.

 Without the caps there is a small amount of degenerative feedback that reduces gain. The caps bypass the AC signal which eliminates this thus increasing gain. Adding the caps also decreases the Z-out of the first stage which may help in pushing the HF signal into the Mosfet's gate capacitance. How much difference any of this makes will need to be found via experimentation.

  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I think I will drop R16 and R17 as I'm pretty happy with my two SS without them. Anything I should know before deciding to drop them?_

 

These increase the Z-in, an also decrease the perceived gain of the amp by 6dB. Useful for sensitive phones to allow more room to move the pot.

 Notice that including R16/17 reduce gain and C7/8 increase gain. By playing around with different combinations, the amp can be constructed so as to be more specific to your phones and or sources. So, there is no right answer.

  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_What kind of specs will work for the output caps bypass capacitors (C3A and C5A)?_

 

Tom probably has more experience here than I do. I'd leave them out 
	

	
	
		
		

		
		
	


	




 The old rule was 1% of the bigger cap, but as electrolytics have gotten better, that rules doesn't seem to always hold anymore. I think anywhere from 100n to 470n is probably reasonable.


----------



## tomb

OK - we have our volunteers. The rest of you will need to wait for the production boards. Hopefully, it won't be too long.


----------



## jeanba3000

Hey hey hey I just received my 19j6s and sockets from TheTubeCenter, now I can enter the next level, finding the other parts…


----------



## ludoo

Thanks tomb and dsavitsk. I will order the cathode bias bypass caps, then wait for the PC to arrive.


----------



## MoxMonkey

will the pcb's be available on their own or simply in combination with tubes?


----------



## Sodacose

alright, it's together and it's making music!

 just a couple questions though:

 one of my tubes is brighter than the other (even when I switch them around it's the same 'channel' that stays bright). It seems like about the same volume coming through them, but it doesn't seem normal to have one brighter. I checked the joints, etc but they all look good. Anyone experience this? Any obvious things I should check?

 Also, considering volume: If I open the pot all the way up and with my iPod at about halfway, this is about the limit of volume I can take through my HD555's. Does this seem to be within normal operating output?

 I am just hesitant to start fixing things if they ain't broke as the sound coming through now is very good. I'm just a little concerned about the difference in tube brightness. Both heatsinks seem to be reaching about the same temperature., though.

 Thanks for the help! And thanks to Millet for the design!


----------



## Logistic

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_alright, it's together and it's making music!

 just a couple questions though:

 one of my tubes is brighter than the other (even when I switch them around it's the same 'channel' that stays bright). It seems like about the same volume coming through them, but it doesn't seem normal to have one brighter. I checked the joints, etc but they all look good. Anyone experience this? Any obvious things I should check?

 Also, considering volume: If I open the pot all the way up and with my iPod at about halfway, this is about the limit of volume I can take through my HD555's. Does this seem to be within normal operating output?

 I am just hesitant to start fixing things if they ain't broke as the sound coming through now is very good. I'm just a little concerned about the difference in tube brightness. Both heatsinks seem to be reaching about the same temperature., though.

 Thanks for the help! And thanks to Millet for the design!_

 

That's normal. Depending on how much of the filament is peeking out the brightness can vary.


----------



## Sodacose

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_That's normal. Depending on how much of the filament is peeking out the brightness can vary._

 

Even if I switch tubes? It seems anything in the one socket isn't quite as bright.

 edit: well the one channel stopped working. I'm going to check the fet wiring tomorrow. i have a feeling I got a bad connection on one of its pins. the heatsink on the dark tube doesn't get hot and the tube itself doesn't light at all. anyone know if there is an easy way to find out if i fried it? i doubt there's a short, but it may be a crappy connection.


----------



## csroc

That seems a bit weird, I have noticed one of my tubes is slightly brighter than the other as well but it's always the same tube and it's not by much.


----------



## dsavitsk

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_one of my tubes is brighter than the other (even when I switch them around it's the same 'channel' that stays bright)._

 

Measure the voltage across the heater.


----------



## ludoo

Would it be possible to have a DXF of the components' placements on the PCB, so that I can check caps diameters etc without bothering you with questions?


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Would it be possible to have a DXF of the components' placements on the PCB, so that I can check caps diameters etc without bothering you with questions?_

 

Yes - of course, but you'll have to wait until I get back home from my day job.
	

	
	
		
		

		
			





 Dsavitsk may have a copy he can send you directly in the meantime, but if not, I'll take care of it about 6PM EST. Would you rather have a DWG?

 By the way, rds and I were discussing the cap fit scenario in the Hammond "L" case. If the board is pressed up against the top side of the slot (the board is slightly less thick than the slot), then there is slightly more than 20mm clearance from the board to the bottom of the case. Remember, we're building upside down with the board at the top. So, 20mm caps will fit, but only if the caps are actually supporting the board. There's quite a bit of stress on the board from the tube sockets when plugging in tubes, meaning those forces will be transmitted to the cap leads, most likely. So it will probably be best to use a 20mm standoff to ensure this fit.

 rds has suggested a minimum of 680uf on the power caps and I think I agree with his assessment. He still experienced some stutter in the power supply at 470uf. Plus, I fried two Alien DACs using 470uf in my early PCB prototype - possibly due to stutter and backwards offset on the RCA jacks. So, larger caps are probably needed. There are 680uf 63V in UPW's and FC's that are only 20mm tall, so that may be the way to go. 470uf on the output caps is still OK.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - of course, but you'll have to wait until I get back home from my day job.
	

	
	
		
		

		
		
	


	




 Dsavitsk may have a copy he can send you directly in the meantime, but if not, I'll take care of it about 6PM EST. Would you rather have a DWG?_

 

Thanks tomb, a DXF would be fine as I'm using an open source CAD that only imports DXF files. Gone are the days of AutoCAD. 
	

	
	
		
		

		
		
	


	




 As for fit, the caps I will use are 18*35.5 so I will definitely need a taller case. And I'm still wondering whether to use an HiFi2000 Galaxy instead of the Hammond, even though it will be larger. On the plus side, I won't have many problems fitting the Obbligatos in the Galaxy, and the aluminum sides should work pretty well as heatsinks for the Mosfets.

 I already have the 470uF, but I could probably get larger power caps. 470uF are working fine in my two SS, *but* I too managed to fry an Alien DAC, and it's something I would not want to repeat.


----------



## rds

20mm Aluminum Standoff at Mouser, and
steel screws for the standoff , also at Mouser


----------



## Logistic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes - of course, but you'll have to wait until I get back home from my day job.
	

	
	
		
		

		
		
	


	




 Dsavitsk may have a copy he can send you directly in the meantime, but if not, I'll take care of it about 6PM EST. Would you rather have a DWG?

 By the way, rds and I were discussing the cap fit scenario in the Hammond "L" case. If the board is pressed up against the top side of the slot (the board is slightly less thick than the slot), then there is slightly more than 20mm clearance from the board to the bottom of the case. Remember, we're building upside down with the board at the top. So, 20mm caps will fit, but only if the caps are actually supporting the board. There's quite a bit of stress on the board from the tube sockets when plugging in tubes, meaning those forces will be transmitted to the cap leads, most likely. So it will probably be best to use a 20mm standoff to ensure this fit.

 rds has suggested a minimum of 680uf on the power caps and I think I agree with his assessment. He still experienced some stutter in the power supply at 470uf. Plus, I fried two Alien DACs using 470uf in my early PCB prototype - possibly due to stutter and backwards offset on the RCA jacks. So, larger caps are probably needed. There are 680uf 63V in UPW's and FC's that are only 20mm tall, so that may be the way to go. 470uf on the output caps is still OK._

 

Just to chime in, I also have some stuttering using 470uf power caps. Have the 680uf been confirmed to stop the stuttering? I might order some new caps then.


----------



## csroc

Are you talking about 470uf causing stuttering on the stock BOM? I'm considering playing around with some upgrades when I have time and was looking at what to do about C1 and C6 as well as C5 and C3.


----------



## tomb

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Just to chime in, I also have some stuttering using 470uf power caps. Have the 680uf been confirmed to stop the stuttering? I might order some new caps then._

 

No, rds confirmed that 1000uf stopped the stuttering on his Starving Student-MiniMilletts. However, there's no 1000uf 63V cap that's 20mm tall - our restriction if we want to use the Hammond "L" case. So, he's suggested 680uf's as something to try on the prototypes. It can't hurt in any event.

 It may be that there's a complex relationship on startup that we'll just have to test. The reason I say that is that Pete mentioned quite awhile back in this thread that 470uf stopped the stuttering, but maybe he was still using 150uf on the output. With 470uf on the output, it may take bigger power caps - such as 680uf - 1000uf to stop the stuttering. We'll see. Even so, if it still stutters at 680uf, I don't think I'm going to change - I'd rather use the "L" case, anyway.


----------



## Sodacose

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Measure the voltage across the heater._

 

Fixed it. Realized after tapping around on the cover that it must have been a loose connection. Sure enough, one of the FET +'s must have been a cold-joint. That's what I get for forgetting to order the mounting hardware and then trimming the leads before it's all assembled.

 Anyone try the RCA's vs. the GE's yet? The GE has a more round top-plate whereas the RCA is foreshortened. Other than that, they seem to have comparable sized plate-grid-cathode structure. I've got five sets of tubes to try and then the dregs are getting dumped here!


----------



## somestranger26

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_Anyone try the RCA's vs. the GE's yet? The GE has a more round top-plate whereas the RCA is foreshortened. Other than that, they seem to have comparable sized plate-grid-cathode structure. I've got five sets of tubes to try and then the dregs are getting dumped here!_

 

Aren't all the 19J6 just rebranded RCAs?


----------



## Swingtops

Does anyone know if you can use a different tube than the 19j6? I am wanting to build this amp just for fun and I am having a terrible time trying to find the 19j6 tubes. If anyone can give me a hand it would be awesome.


----------



## iareConfusE

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_Does anyone know if you can use a different tube than the 19j6? I am wanting to build this amp just for fun and I am having a terrible time trying to find the 19j6 tubes. If anyone can give me a hand it would be awesome._

 

I asked this question above, or maybe a few pages before, but apparently not, the only tubes that work with this amp is the 19J6.


----------



## tomb

Comments:
 1. I'm fairly certain other mfrs besides RCA made the tubes. Not all of them have the etched, "squished" octagon that's a ringer for RCA manufacture - that much is certain.

 2. No, there is not another tube that we know of that will work in the Starving Student circuit as is. This is because of the 19V heaters, which are matched to the VoIP power supplies (~48 - 2X19, minus some minor voltage drop) and the fact that the MOSFETs are Class A-biased by the heater current.


----------



## tomb

Ludoo,

 Here's a direct link to the DXF file for the PCB:
http://www.diyforums.org/SSMH/layout/starving.dxf

 Simply right-click on the link and select, "Save Target As ..." The DXF file is in units of millimeters.

 This is a rather large file, so others of you - if you don't have a CAD program you can use it in, please don't download it. I'll have the important information up on the website soon - including layouts.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Ludoo,

 Here's a direct link to the DXF file for the PCB:
http://www.diyforums.org/SSMH/layout/starving.dxf_

 

Thanks! Really looking forward to building the PCB SS:


----------



## jeanba3000

Hello everyone

 I'm drawing (on Adobe Illustrator) a PCB based on Millet's first schematic as shown on his site. I'd like to make the smallest circuit to insert in my preamp, so I don't need volume pot, headphone jack won't be mounted on the board, and the power for the SS will be integrated in the preamp too, near the preamp's power which is isolated from the preamp boards by a copper shield.

 The actual size of the SS's pcb will be 46 x 59 mm and I've checked the size of all the components. The mounting studs will be plastic studs, so I believe it doesn't matter if some lines touch the screws. The IRF will be mounted horizontaly and screwed to the bottom of my Hifi2000 aluminium case.

 I'd like someone to check the circuit, pointing any newbie mistakes I could have done, before I order it from my PCB maker.

 Thanks






 PS : Tomb, I discover your new pcb, which has some more components. Where can I find details about this evolution of the SS and how it enhances it ? Thanks again


----------



## DopeNessMonster

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Comments:
 1. I'm fairly certain other mfrs besides RCA made the tubes. Not all of them have the etched, "squished" octagon that's a ringer for RCA manufacture - that much is certain.

 2. No, there is not another tube that we know of that will work in the Starving Student circuit as is. This is because of the 19V heaters, which are matched to the VoIP power supplies (~48 - 2X19, minus some minor voltage drop) and the fact that the MOSFETs are Class A-biased by the heater current._

 

I'm a total electronics noob, so the reason may be over my head, but what about dropping the 19v to 6v and using 6J6 tubes? Those seem to be extremely plentiful.


----------



## tomb

Quote:


  Originally Posted by *jeanba3000* /img/forum/go_quote.gif 
_<snip>
 PS : Tomb, I discover your new pcb, which has some more components. Where can I find details about this evolution of the SS and how it enhances it ? Thanks again_

 

It's Dsavitsk's PCB design, I'm just the facilitator.
	

	
	
		
		

		
		
	


	




 Go back about 9 pages in this thread to Post #2015 and a couple of posts after that.

 Also, I'm building a website that will be at DIYForums.org. It'll have all the info you need, but right now there's just a logo for the Starving Student.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *DopeNessMonster* 
_I'm a total electronics noob, so the reason may be over my head, but what about dropping the 19v to 6v and using 6J6 tubes? Those seem to be extremely plentiful._

 

Yep, I've had the same conversation with tube distributors, too. The problem is that we're already rejecting a heck of a lot of heat by biasing the MOSFETs with the tube heaters at 19V and 150ma. However, it you take that 150ma and knock down an additional 13V per tube heater, you get an additional 4 Watts. Plus, that current would be wasted at the resistor you use to cut the voltage - instead of biasing the MOSFET. You'd have to find a separate power supply source. At that point, you're looking at an entirely different design. So, the 6J6 won't work.


----------



## dsavitsk

Quote:


  Originally Posted by *jeanba3000* /img/forum/go_quote.gif 
_I'd like someone to check the circuit, pointing any newbie mistakes I could have done, before I order it from my PCB maker._

 

The only thing that jumps out at me is that the mosfets are facing opposite direction from each other which is going to make screwing them to the case tricky.

 I like the Horst pic 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *DopeNessMonster* /img/forum/go_quote.gif 
_I'm a total electronics noob, so the reason may be over my head, but what about dropping the 19v to 6v and using 6J6 tubes? Those seem to be extremely plentiful. Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
However, it you take that 150ma and knock down an additional 13V per tube heater, you get an additional 4 Watts.

 

_

 

Actually, the 6J6 heater draw is 3x higher. Right now, the fet burns off a little less than 4.5W. With the 6J6, it would burn off about 19W. Plus, as Tom says, you'd need a PS that could supply all of that current to be wasted.

 It is certainly possible to design your own version using different tubes. There have been a few posts aiming to do that, but I don't think anyone has actually tried it. The 19J6 has a nice balance between heater requirement and plate requirement.


----------



## Yaka

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Connected to the MOSFETs?
 Can you link one of the posts please?_

 

oldking used them to build is, i think he posted pics of a few of his builds earlier in the thread

Millett "Starving Student" hybrid headphone amplifier on Flickr - Photo Sharing! he has pics on his flickr page that shows the connector attached to the mosfets


----------



## jeanba3000

Thanks for the infos

 Oops, good eye Dsavitsk, hum it seems I made some other mistakes…

 Still work to do…

 It seems ok now, maybe not very elegant design, but if it does work, I'm fine with it…


----------



## jonjon0nline

I apologize if I missed it, but is there a tentative time frame of when the GB will be on? I only check this site every now and then so I don't want to miss it.


----------



## rds

Quote:


 I apologize if I missed it, but is there a tentative time frame of when the GB will be on? 
 

I haven't heard anything about a group buy. I expect that Beezar will carry the boards and hard to get parts just like the other millet projects.
 Seeing as the prototype boards haven't even arrived yet I wouldn't expect anyone to be able to nail down a time yet.


----------



## ph33lix

Awesome tube project.
 Favorited.


----------



## Kitarist

So how does it sound? or its just popular cause its some tube hybrid and looks cool


----------



## scompton

It sounds great with every headphone I've plugged into it. It's not just popular because it looks cool, but because it sounds great and is cheap and easy to build. You'll be hard pressed to find a better amp for the price IMO.


----------



## ludoo

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_It sounds great with every headphone I've plugged into it. It's not just popular because it looks cool, but because it sounds great and is cheap and easy to build. You'll be hard pressed to find a better amp for the price IMO._

 

x2


----------



## DopeNessMonster

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_x2_

 

Agreed. Listening to my old Porcupine Tree - Signify CD the other day nearly brought a tear to my eye.


----------



## csroc

It sound great with my HD650 and my ATH-AD900s. I'm very happy with it.

 I'll be cracking mine open again to do some things later this week. I want to tweak the output caps to see if that improves bass a bit with my lower impedance phones and I've got some other things I'll be doing.

 From what I've read it seems the suggestions are
 C3 & C5 (output caps): 470uF
 C1 & C6 (power caps): 680uF

 Anyone disagree with that?


----------



## tomb

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_It sound great with my HD650 and my ATH-AD900s. I'm very happy with it.

 I'll be cracking mine open again to do some things later this week. I want to tweak the output caps to see if that improves bass a bit with my lower impedance phones and I've got some other things I'll be doing.

 From what I've read it seems the suggestions are
 C3 & C5 (output caps): 470uF
 C1 & C6 (power caps): 680uF

 Anyone disagree with that?_

 

You tell us - does the power supply stutter on startup with 680uf's on the back side?


----------



## csroc

I can't tell you because I haven't tried it yet. That's why I was asking if that was a recommended configuration. From the discussions I've read it seems like it might be a good choice but I wanted to double check. 

 I'll obviously share my impressions after whatever changes I make.


----------



## tomb

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_I can't tell you because I haven't tried it yet. That's why I was asking if that was a recommended configuration. From the discussions I've read it seems like it might be a good choice but I wanted to double check. 

 I'll obviously share my impressions after whatever changes I make._

 

OK. Well, if you wait, some of us will be trying the 680uf's with the PCB protos. We should be able to confirm something from that.


----------



## csroc

Well I'm not sure if I'll wait or not. I'll definitely be sticking the 470uF in the output to get some more bass out of my low impedance cans.

 I suppose I could do that and just leave my power caps at 220uF for now and wait and see what you guys find out with the PCB builds.


----------



## holland

I used 1000uF power caps with no problems. HTH.


----------



## ludoo

I did some measurements using the PCB DXF, and there are a few axial film caps that can be made to fit without much hassle: the Obbligato 0.15uF (and the 0.22uF but they are longer) can be fit horizontally for C3A and C5A and vertically for C2 and C4. The Solen Fast 0.22uF (nothing special but cheap and I can get them at a store 5 walking minutes from home) are slightly longer but thinner so they can be fit horizontally in all four positions.

 The only problems for both of those (and other caps of course) is the position of R7 which is smack in the way of C4. For the Solens R7 could maybe be placed on the other side, but for other caps which need to be mounted vertically it's right in the way. Any ideas, apart from off-board mounting?


----------



## tomb

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I used 1000uF power caps with no problems. HTH._

 

Yep - this was discussed back in post #2141. The problem is that no one makes a 1000uf small enough to fit in the desired Hammond "L" case. So, some of us are hoping the 680uf's will be enough.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I did some measurements using the PCB DXF, and there are a few axial film caps that can be made to fit without much hassle: the Obbligato 0.15uF (and the 0.22uF but they are longer) can be fit horizontally for C3A and C5A and vertically for C2 and C4. The Solen Fast 0.22uF (nothing special but cheap and I can get them at a store 5 walking minutes from home) are slightly longer but thinner so they can be fit horizontally in all four positions.

 The only problems for both of those (and other caps of course) is the position of R7 which is smack in the way of C4. For the Solens R7 could maybe be placed on the other side, but for other caps which need to be mounted vertically it's right in the way. Any ideas, apart from off-board mounting?_

 

It's awfully close to the case lid lip if you're using a Hammond, but it looks to me that R7 could be placed on the back side in either situation you describe?

 I don't know - maybe the position of R7 is something that Dsavitsk could revise for the production boards. It would be nice to have as much flexibility as possible for the output bypass caps. On the other hand, output bypass caps are a digression from the basic design and considered an optional feature. So, I'm not sure how far we'd want to go with that. The pads are perfectly adequate for Wima's/Roedersteins and others as you've noted.

 Let's see what Dsavitsk says.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's awfully close to the case lid lip if you're using a Hammond, but it looks to me that R7 could be placed on the back side in either situation you describe?_

 

Hmmm yes, but with the vertically mounted caps its legs protrude right where the cap leg is near the board.

  Quote:


 I don't know - maybe the position of R7 is something that Dsavitsk could revise for the production boards. It would be nice to have as much flexibility as possible for the output bypass caps. On the other hand, output bypass caps are a digression from the basic design and considered an optional feature. 
 

R7 is near C2 and C4, not C3A and C5A which are the output bypass caps.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_<snip>R7 is near C2 and C4, not C3A and C5A which are the output bypass caps. 
	

	
	
		
		

		
		
	


	


_

 

OK - expect me to get them mixed up a little longer as we continue through this.
	

	
	
		
		

		
		
	


	




 Again, let's see what Dsavitsk says.


----------



## kuroguy

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_I suppose I could do that and just leave my power caps at 220uF for now and wait and see what you guys find out with the PCB builds._

 

Don't do that. We already know that configuration will have a startup pop.


----------



## csroc

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - this was discussed back in post #2141. The problem is that no one makes a 1000uf small enough to fit in the desired Hammond "L" case. So, some of us are hoping the 680uf's will be enough._

 

Ahh that explains things a bit for me. I was looking for that post since I recall reading it before.

 I'm not building the PCB (although maybe I will in the future) so space isn't as much of an issue for me 
	

	
	
		
		

		
		
	


	




 I'll put the 680uF in with the 470uF (maybe this evening) and let you know how it goes.


----------



## Kitarist

is anyone selling the pcb yet


----------



## holland

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - this was discussed back in post #2141. The problem is that no one makes a 1000uf small enough to fit in the desired Hammond "L" case. So, some of us are hoping the 680uf's will be enough._

 

Oh, I see. Sorry, my bad. I haven't been watching this thread and thought it was a generic question.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's awfully close to the case lid lip if you're using a Hammond, but it looks to me that R7 could be placed on the back side in either situation you describe?_

 

That's probably a good option. This resistor dissipates less than 1/10th of a watt, so a very small resistor will do fine.

 Moving R7 would be a tricky. I'll look some more, but I don't think it is going to happen.

  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Hmmm yes, but with the vertically mounted caps its legs protrude right where the cap leg is near the board._

 

I don't have any idea what that means ...


 Anyhow, don't use a 0.15u or 0.22u cap for C2 or C4. I think you want to keep these as small as possible. Pete used 220K resistors for R2, R4, R8, and R10 which governs the size of the coupling cap, but I don't see any reason that these can't be increased a bit allowing you to reduce the cap size, noth electrically and physically.


----------



## ludoo

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I don't have any idea what that means ..._

 

This (sized for Obbligato copper 0.1uF)







 which admittedly is not much of a problem.


----------



## tomb

I'm afraid I don't understand that, either. Why aren't you showing the Obligatto centered over the film cap pads (C4) - then move R8, R9, and R10 - along with R7 - to the top, if necessary?


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm afraid I don't understand that, either. Why aren't you showing the Obligatto centered over the film cap pads (C4) - then move R8, R9, and R10 - along with R7 - to the top, if necessary?_

 

Oh


----------



## rds

Maybe just go with some options that fit the board better.
 The panasonic ecq-p are very nice polypropylene and foil caps that will fit. I was going to use these myself but for some reason I bought 50v ones.

 EDIT - It seems the reason I got 50V is because only 50V and 400V are available at digikey. 400V won't fit. Too bad.


----------



## dsavitsk

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Maybe just go with some options that fit the board better.
 The panasonic ecq-p are very nice polypropylene and foil caps that will fit. I was going to use these myself but for some reason I bought 50v ones._

 

50V should be fine -- measure the unloaded voltage of the PS. If it is below 50V, you should be fine. Moreover, if the caps did fail, the only thing likely to happen is that the bias on the fets would be changed leading to under or over voltage on the heaters, which might reduce tube life in the long term. 

 Even if the PS voltage is high, one side of the cap is at the tube's plate voltage which is generally going to be in the 20V range. The other side is at the fet's gate voltage, which is also quite close to 20V. So, under normal operating conditions, the voltage across the cap is very low. So, I think you are fine. I would officially recommend 63V caps in case something goes wrong, but 50V is probably enough.


----------



## rds

I'm curious why you don't recommend .22uF for the fets. The only reason I can think of is saving board space. I understand that a lot of people will say it's pointless to have such a low cut off frequency and so .1uF is plenty.
 I can't see any harm in using larger values, assuming that they fit.


----------



## dsavitsk

Because  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_ it's pointless to have such a low cut off frequency_

 

I am not recommending against .22u. What I am saying is that if you want to use boutique caps, and the .22u's of your favorite cap won't fit, then it is OK to adjust some resistors such that the use of a smaller cap that will fit is fine.


----------



## csroc

Just replaced all the 220uF caps in my SS with 470uF output and 680uF power caps and notice no problems upon powering it on.


----------



## tomb

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_Just replaced all the 220uF caps in my SS with 470uF output and 680uF power caps and notice no problems upon powering it on._

 

That's good news so far! Can we ask you to do something else?

 Use your DMM to measure Ground vs. Left or Right at the RCA Jacks when you power up.
	

	
	
		
		

		
		
	


	




 That's where offset has been noted before when the stuttering occurs. You'll need to look quickly - it's probably just a couple of transients. Moreover, the characteristics may be different from a cold start (caps uncharged) vs. a hot start (caps partially charged).


----------



## tomb

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I'm curious why you don't recommend .22uF for the fets. The only reason I can think of is saving board space. I understand that a lot of people will say it's pointless to have such a low cut off frequency and so .1uF is plenty.
 I can't see any harm in using larger values, assuming that they fit._

 

I'll have to take the credit/blame for part of this. Dsavitsk did me a personal favor by making them 0.22uf. It doesn't hurt anything for them to be that size, but more importantly, they're the same size as the bypass caps we use on the MAX/MiniMAX. It's quite possible that many people have these in their parts boxes already - for similar reasons.

 Of course, the 0.22uf Wima MKP10's are readily available at Mouser. Long ago however, international Millett MAX builders asked me to stock the Wima's at Beezar because of Mouser's expensive international shipping charges. They're also widely recognized as excellent, but inexpensive bypass/coupling caps. As mentioned before, the Vishay-Roederstein MKP's are also good candidates, perhaps (also available at Mouser).


----------



## csroc

I just shut mine off so I'll give it a bit for the caps to discharge and get my DMM then I'll test it with both a cold and warm/hot start.

 edit: alright I can't measure any voltage fluctuation on a cold or warm startup. I'll probably check it again tomorrow just to be sure. One thing I noticed is those caps take a fair amount of time to drain.


----------



## rds

Does it seem reasonable to use very low esr caps like the Nichicon hz for cathode bypass? These are available at Mouser in large capacitance and 6.3V. 
 Or would audiophile type capacitors seem like the better choice?


----------



## Swingtops

I don't mean to barge in here, but has anyone considered putting a gain stage or gain control on this amp. My reasoning is that this could be a handy tube preamp for an electric guitar. 
 As I understand the operation of the amp, the input pot would essentially be the gain and the volume on your base amp would control the volume. 
 What I would like to do is have a volume and a gain control right on the amp so that I can use headphones directly from the preamp rather than having to set up the base amp and use the headphone jack. 
 Thanks


----------



## somestranger26

This is my first DIY project, and I just finished connecting everything. Powered it on and instead of pretty tubes I was greeted by burning electrical tape and found a short and need to find why the tubes still aren't lighting/mosfets aren't heating up after fixing it but it's way too late right now to do that.


----------



## Sodacose

Any reason this MOSFET wouldn't work?

 It's rated at 60V, 3.0A and 20W dissipation.

IRF510

 If anyone else is anything like me, they are getting sick of these fragile little things. Everyone make sure you heatshrink the legs on those!


----------



## tomb

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_Any reason this MOSFET wouldn't work?

 It's rated at 60V, 3.0A and 20W dissipation.

IRF510

 If anyone else is anything like me, they are getting sick of these fragile little things. Everyone make sure you heatshrink the legs on those!_

 

That _IS_ the Starving Student MOSFET.


----------



## Sodacose

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That IS the Starving Student MOSFET.
	

	
	
		
		

		
		
	


	


_

 

Really more of an impatient student MOSFET. Thanks!


----------



## Fitz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That IS the Starving Student MOSFET.
	

	
	
		
		

		
		
	


	


_

 

Y'know, I have a bunch of IRF510s, and I think I might have some 19J6s in a box somewhere... I really should build one of these things sometime.


----------



## DopeNessMonster

Quick question; how hot should these things run? I've got the 2 inch tall heatsinks on mine and they almost get too hot to touch. The max. temp on the fets is 175C and it's not even half that. Just wondering if 120-150F is normal.


----------



## csroc

My heatsinks seem to get to around 120-140F right now with it being usually in the mid 70s in my room. I have the 1.5" tall heatsinks on mine. 

 More or less the whole case eventually warms up a bit but not by a great deal, I've seen it get to around 90F on the top near the tubes and heatsinks I think.


----------



## scompton

The heat sinks get pretty warm on mine as does the whole metal lid on the plastic case. The heat sinks are warm enough that I don't like to touch them although not hot enough to burn.


----------



## Fitz

How much heat are they dissipating, around 5 watts or so? That would sound about right if they are.


----------



## DopeNessMonster

Cool, thanks for the quick response guys!


----------



## tomb

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_How much heat are they dissipating, around 5 watts or so? That would sound about right if they are._

 

4.5W, actually, I believe and yes ... 120 to 140 deg.F. should be about right, give or take a bit, depending on the build.


----------



## Sodacose

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_Any reason this MOSFET wouldn't work?

 It's rated at 60V, 3.0A and 20W dissipation.

IRF510

 If anyone else is anything like me, they are getting sick of these fragile little things. Everyone make sure you heatshrink the legs on those!_

 

In case anyone else gets stuck without a MOSFET in the states and doesn't want to wait on shipping, the above is working great.

 Is there a verdict on the use of Grado's with the SS and any needed additional attenuation?


----------



## Hayduke

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_In case anyone else gets stuck without a MOSFET in the states and doesn't want to wait on shipping, the above is working great.

 Is there a verdict on the use of Grado's with the SS and any needed additional attenuation?_

 

Soda, did you miss Tom's reply? That's the standard MOSFET 
	

	
	
		
		

		
		
	


	



 I hope they work great since that's what most of us have used.


----------



## scompton

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_In case anyone else gets stuck without a MOSFET in the states and doesn't want to wait on shipping, the above is working great.

 Is there a verdict on the use of Grado's with the SS and any needed additional attenuation?_

 

I want lower gain for every headphone I've plugged into mine so I can't imagine not wanting it for Grados.


----------



## sachu

A quick question...are people able to source 19J6 tubes anywhere?

 I see that the only place that is selling is asking for about 25$ a pop....


----------



## Sodacose

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Soda, did you miss Tom's reply? That's the standard MOSFET 
	

	
	
		
		

		
			




 I hope they work great since that's what most of us have used._

 

I could have sworn the one listed in the BOM was rated at 100V's? Am I missing something?

 RE: Attenuation
 Was just exchanging with rds in another thread about use of Grado's. He recommends putting resistance in series before the pot. I've been seeing a lot of back and forth on here about that as well. If nothing else it would take just a little bit of fiddling to find a suitable value.


----------



## Sodacose

sachu, have you tried these places?

  Quote:


  Originally Posted by *somestranger26* /img/forum/go_quote.gif 
_I found the 19J6 at oldradiotubes.com but dried up their stock of 3 (minimum order of $20 and they were only $2 each!). However, I got some emails today from a few other sellers saying they're in stock.

Richardson Electronics Ltd.: $6.95 each, minimum order of 5 pieces.

http://vacuumtubes.com: $10 each, $30/pair (???)

Vacuum Tubes - Audio Tubes - ESRC Vacuum Tubes - Electron Tubes said they are out of stock but are expecting stock soon, so you could also try there.

 Hope this helps those of you looking for the tubes yet._


----------



## sachu

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_sachu, have you tried these places?_

 

wow..excellent...thanks..will look it up


----------



## Sodacose

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_wow..excellent...thanks..will look it up_

 

I ordered from the first link a couple weeks ago and they had 50 tubes. Good luck!


----------



## tomb

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_I could have sworn the one listed in the BOM was rated at 100V's? Am I missing something?</snip>_

 

I doubt that there's any difference. It's possible that the Radio Shack version is some cheap knock-off, but every IRF510 in a TO-220 package is rated at 100V Vdss (so far as I can tell). So, I suspect that Radio Shack's data is the one that's wrong.


----------



## Swingtops

Sachu, I talked with the Tube Center just yesterday and the guy said that he has a shipment of 19j6 tubes coming in on Monday the 9th, and my order for four should be to my door by the end of next week. This was the only place I could find the tubes for this amp.


----------



## sachu

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_Sachu, I talked with the Tube Center just yesterday and the guy said that he has a shipment of 19j6 tubes coming in on Monday the 9th, and my order for four should be to my door by the end of next week. This was the only place I could find the tubes for this amp._

 

Thanks for the info Swing tops..i was holding off my BOM order to mouser to sort out the tube availability issue...going to send off the order to Mouser this weekend.


----------



## somestranger26

Well I've spent far too long trying to get my amp working and that it's just not worth what it would cost me to replace some of the parts. If anyone is interested, I have the power supply, 3 19J6 tubes (1 RCA and 2 Sylvania), two of the 2" version of the BOM heatsinks, four 470uf nichicon and two .22uf malory caps, two tube sockets (brown), and all the BOM resistors. PM me and I can give you a better idea of what condition everything is in, etc.


----------



## Kitarist

IS there anyone that would sell me this as a kit and ship to Slovenia

 Thanks!!


----------



## tomb

Quote:


  Originally Posted by *somestranger26* /img/forum/go_quote.gif 
_This is my first DIY project, and I just finished connecting everything. Powered it on and instead of pretty tubes I was greeted by burning electrical tape and found a short and need to find why the tubes still aren't lighting/mosfets aren't heating up after fixing it but it's way too late right now to do that._

 

 Quote:


  Originally Posted by *somestranger26* /img/forum/go_quote.gif 
_Well I've spent far too long trying to get my amp working and that it's just not worth what it would cost me to replace some of the parts. If anyone is interested, I have the power supply, 3 19J6 tubes (1 RCA and 2 Sylvania), two of the 2" version of the BOM heatsinks, four 470uf nichicon and two .22uf malory caps, two tube sockets (brown), and all the BOM resistors. PM me and I can give you a better idea of what condition everything is in, etc._

 

First, let me apologize that no one seemed to offer help after your first post. Second, I'm sorry to hear that you've given up.

 However, you and the rest of the SSMH builders must realize that a post with non-specific symptoms is about like going to the Dr. and saying, "It hurts here, but I don't know why." The first thing the Dr.'s going to want to do is some diagnostic procedures, run tests, and take X-rays.

 It's much worse for us, because we can't see it, we can't touch it, and we can't listen to it. The result is that most often when someone provides a non-specific post with no concrete details, no photo, etc. - it gets ignored. That doesn't mean we don't want to help. It means that there's nothing we can do.
	

	
	
		
		

		
		
	


	




*The single greatest thing any of you can do who desire help is to provide clear photographs of your circuit, period.* There are literally dozens of folks who are looking at this thread constantly and will reply almost immediately if they spot something wrong.

 Again, I'm sorry for your trouble and hope that this doesn't put you off from building things in the future.


----------



## Dr Evil Dan

I redid the woodwork on my amp, and also rewired the insides. It attracts dust like no other, but it looks and sounds much better. 
















 I haven't bothered to attach the bottom plate yet, and STILL no volume knob! :\
 I realize it is kinda dusty - its probably just static or something. For those interested, I used Minwax English Chestnut stain, and two coats of a wipe on satin finish (I think it was polyurethane varnish). This was my first wood working project, so for those who think it was really hard, think again 
	

	
	
		
		

		
		
	


	




 . It just took a hell of a long time to do. Please excuse the picture quality, I am a crappy photographer.


----------



## Kitarist

I'm looking for a pcb of this. Did anyone make it and is willing to sell it


----------



## tomb

Quote:


  Originally Posted by *Kitarist* 
_IS there anyone that would sell me this as a kit and ship to Slovenia

 Thanks!!_

 

 Quote:


  Originally Posted by *Kitarist* /img/forum/go_quote.gif 
_I'm looking for a pcb of this. Did anyone make it and is willing to sell it_

 

Dang, man - keep up! Try reading back a few pages.


----------



## tomb

I've invoiced everyone today for the protoypes. They're supposed to ship from the PCB mfr tomorrow. I'll keep you all updated on the progress.


----------



## zkool448

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I have the BOM saved project over at Mouser currently ready to be ordered, however I'm not having any luck finding sources for the 19J6 tubes at all. I received a couple of replies this morning from dealers and all are out of stock.

 By the way thought this may be worth a shot. I actually wanted to post this under the classifieds section, however since I have less than 50 post being a new member I'm unable to do so. I'm hoping someone here wouldn't mind parting with they SS hybrid amp and sell me a finished one instead.

 Please send me a PM me if you can help. thanks! : )_

 

Quoting myself above, I went ahead and ordered the BOM list through mouser anyway. I'm so glad I didn't give up on this DIY project since I could not find the tubes anywhere. 

 As I searched for 19j6 tubes from every dealer I could find, I had pm conversations with looser101. He felt my frustration and offered to mail me a set of 19j6 spare tubes that he had so I can start my build. He mailed out the tubes the next day and I received it a couple of days later. In return I promise to send him a pair of replacements once they become available at Beezar.com, so Tomb, please *pre*order for me two mssh pcb+tubes combo! : ) 

 I'm so greateful to looser101 for his nice gesture. I don't know too many people who would do what looser101 have done for me (let alone to a complete stranger)... thank You!

 Anyway I finally completed my MSSH over this weekend and wanted to share some pics of my very first DIY. The case is made out of solid maple with a satin varathane finish. This thing sounds awesome and I'm loving it!

 Thanks to Pete for designing a nice quality amp and to all responsible in supporting this DIY community


----------



## sachu

wow..zkool448...that is one mighty fine looking amp you got there..kudos

 where did you source the knob from?


----------



## zkool448

Thanks sachu 
	

	
	
		
		

		
			





 I got the knob from mouser: Metal Knobs ALUM KNURLED 1.25


----------



## CaptHowie

That is one nice looking amp. Great work.


----------



## mattcalf

Awesome build zkool448. 
 I hope I can get mine working soon, my casework will be well below par though. 
	

	
	
		
		

		
		
	


	




 It's all about the sound though.


----------



## looser101

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_



_

 


 Fantastic looking build. Enjoy your new amp.


----------



## ludoo

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Anyway I finally completed my MSSH over this weekend and wanted to share some pics of my very first DIY. The case is made out of solid maple with a satin varathane finish. This thing sounds awesome and I'm loving it!_

 

Splendid case. 
	

	
	
		
		

		
		
	


	




 How did you make those recessed holes, with a stepped bit? They look incredibly neat.


----------



## Hayduke

Wow zkool448! That's a beautiful amp. If my woodworking skills were that good, I would use wood too.


----------



## Kitarist

Yes his build is awesome also how much did he pay for this wood and where did he get it


----------



## kuroguy

looks like Poplar. Inexpensive wood and available at Home Depot and Lowe's. Ages to a nice warm brown.


----------



## Vaughn

Nah, he says in his post it is maple. Insets appear to have been made with a Forstener bit.

 Well, I have ordered all of the parts I need for two SS amps. One will have an Alien DAC built into it for computer use. All I need now is some stinkin' tubes


----------



## scompton

My local home depot has maple, poplar and red oak.


----------



## kuroguy

Actually, Maple is even less expensive than Poplar, and can have some very nice grain patterns. It stays light in color as it ages.


----------



## zkool448

Hi all, thanks a lot for the complements. This amp took many hours to build more so in designing and building the wooden case. I'm pretty sure my next mssh build will only take half the time it took to build this one. The next one should have round-over edges put through a router.

 looser101, I'm already enjoying the amp (with YOUR tubes!) as I type this message -- forever grateful. Many thanks again 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Splendid case. 
	

	
	
		
		

		
		
	


	




 How did you make those recessed holes, with a stepped bit? They look incredibly neat._

 

With wood as opposed to alum/metal, the bit recommended to recessed holes is called a Forstner bit. Luckily I have a set that can do recessed/through holes from 1/4" to 2" in diameter.

  Quote:


  Originally Posted by *Kitarist* /img/forum/go_quote.gif 
_Yes his build is awesome also how much did he pay for this wood and where did he get it_

 

The wood is left over from a previous cabinet project. It's maple and can be purchased anywhere like Home Depot or Lowe lumber section. Very tough hardwood so be sure you have sharp carbide-tipped bits or you'll end up burning. 

 Last night's photos where a tad too dark and doesn't really show the true finish, here are some daylight shots:


----------



## Kitarist

Does anyone know any good seller on ebay that sells wood blanks.

 This really inspired me to do my own enclosure 
	

	
	
		
		

		
		
	


	







 The only thing i would do is to darken the wood with some tint (dark red) or something it would look amazing


----------



## scompton

zkool448,

 What did you use to cut the holes for the heat sinks and the gap between the RCA jacks?


----------



## zkool448

First, I started the holes with 1" forstner bits and used my table router to cut out the heatsink layout. As for the RCA's, same bit but overlapped the drilled holes then I cleaned up the gap between the jacks with a chisel.


----------



## Hayduke

Quote:


  Originally Posted by *Kitarist* /img/forum/go_quote.gif 
_Does anyone know any good seller on ebay that sells wood blanks.

 This really inspired me to do my own enclosure 
	

	
	
		
		

		
			








 The only thing i would do is to darken the wood with some tint (dark red) or something it would look amazing_

 

Where do you live? If you have a lumber store nearby, they should have some. Home Depot by me has it. One board outta be enough. Maybe $10?

 The tools are gonna be the big $$$ 
	

	
	
		
		

		
		
	


	




 If you want red, why not use red oak instead of maple?


----------



## MoxMonkey

i'm curious how you joined the pieces together, i was going to do something similar using box jointed corners but gave up as i couldn't get the fit how i wanted


----------



## zkool448

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_i'm curious how you joined the pieces together, i was going to do something similar using box jointed corners but gave up as i couldn't get the fit how i wanted_

 

Hi MoxMonkey, i thought about a box or even dovetails to get solid joints, however i don't think i would sit or rest anything heavy on top of this amp 
	

	
	
		
		

		
		
	


	




 I took the lazy man's approach and used dowel pins and wood glue to join the pieces together. Conveniently my cellphone was nearby so I took some pics during my dry fit construction as you can see here:


----------



## MoxMonkey

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Hi MoxMonkey, i thought about a box or even dovetails to get solid joints, however i don't think i would sit or rest anything heavy on top of this amp 
	

	
	
		
		

		
		
	


	




 I took the lazy man's approach and used dowel pins and wood glue to join the pieces together. Conveniently my cellphone was nearby so I took some pics during my dry fit construction as you can see here:




_

 

that makes sense i didn't even think of dowels


----------



## Yaka

love the handy work on your case zkool1448


----------



## zkool448

Thanks Yaka -- it was all worth it. The next few will be much easier to build and give them as gifts to families & friends, especially for my dad who enjoys listening to his music.


----------



## Hayduke

zkool, you're making me research drill presses now 
	

	
	
		
		

		
		
	


	




 OK, I already wanted one, but now I have someone else to blame! 
	

	
	
		
		

		
		
	


	




 Again, you are very skilled with wood.


----------



## zkool448

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_OK, I already wanted one, but now I have someone else to blame! 
	

	
	
		
		

		
		
	


	


_

 

hahaha. thanks Hayduke. I highly recommend a drill press, and they are not very expensive. Having more tools in the workshop only gives you more options and an unlimited imagination when designing your case work.


----------



## MoxMonkey

i picked up my 10" mastercraft drill press for $35 used off craigslist


----------



## csroc

A drill press has been long on my wishlist. Once I'm out of an apartment I know I'll be getting one


----------



## Kitarist

You can also get lots of nice stuff on ebay


----------



## nightanole

I hate to ask for some hand holding, but ive noticed alot of bom changes and mods as the 150 pages go on. Does anyone have a bom of the upgraded parts with the thinfilm/electro caps running in parallel and any other upgrades? Its confusing with the caps, runing 2 caps in parallel doubles the value, or so i thought. Sorry this will be my first build and i finally scored some tubes.


----------



## zkool448

nightanole, I stuck with Pete's original bom from his site which I recommend initially if this is your first mssh build. In case something strange happens or doesn't sound quite right, you'll know with certainty it's not because of your mods and it should be less difficult to troubleshoot. The only difference with mine and the original parts list are the heatsinks (2" vs 1.5") and 470uF for C1,C3,C5,C6.

 Once everything works within spec, then you can try some of the suggested tweaks here which I believe help to better suit your cans and/or music taste.


----------



## sachu

guys,

 Is it okay to house the heatsinks inside the case?

 Do they get realy hot. I am planning on using 2" thermalloy heatsinks.


----------



## gurusan

they get quite hot, I wouldn't want them inside anything...


----------



## kansei

My heatsink is inside the case. However, I use a metal power supply case which is meant to operate this way. See my post earlier: http://www.head-fi.org/forums/f6/mil...ml#post5374411


----------



## Kitarist

This threads really makes me wanna build this thing


----------



## nightanole

Well i got most things in order. I have 2 questions though. There are 2 48v cisco power supplies on ebay, one is 1.5 amp and the other is .38 amp. Which one do i get?

 the last question is how to you get this to run lower ohm cans like grado and sony v6's? I dont have any phones over 80 ohms and was planning on getting a 25ohm pair of denon d2000's one day.


----------



## sachu

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well i got most things in order. I have 2 questions though. There are 2 48v cisco power supplies on ebay, one is 1.5 amp and the other is .38 amp. Which one do i get?

 the last question is how to you get this to run lower ohm cans like grado and sony v6's? I dont have any phones over 80 ohms and was planning on getting a 25ohm pair of denon d2000's one day._

 

i just bought 2 of the 1.5 A power supplies. It never hurts to have a PSU capable of higher current. Go for the 1.5A one.


----------



## Dr Evil Dan

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well i got most things in order. I have 2 questions though. There are 2 48v cisco power supplies on ebay, one is 1.5 amp and the other is .38 amp. Which one do i get?

 the last question is how to you get this to run lower ohm cans like grado and sony v6's? I dont have any phones over 80 ohms and was planning on getting a 25ohm pair of denon d2000's one day._

 

the starving student shouldnt have problems driving grados. in fact, i am using a pair of grados now, and they get more than loud enough.


----------



## sgupt

can these handle beyer 880s? (250 ohm)


----------



## Sancho86

Thanks for the info on the tubes, ordered 6 I hope


----------



## sachu

Quote:


  Originally Posted by *Sancho86* /img/forum/go_quote.gif 
_Thanks for the info on the tubes, ordered 6 I hope 
	

	
	
		
		

		
		
	


	


_

 

where did you order from?


----------



## Dr Evil Dan

as it says on the bottom of PMillet's starving student page, these can handle everything from low impedance grados to high impedance sennheisers, to the very difficult-to-drive AKG K1000s.


----------



## sgupt

oh cool didnt see that, thanks


----------



## Sancho86

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_where did you order from?_

 

thetubecenter, I guess they got a shipment yesterday


----------



## Sancho86

Quote:


  Originally Posted by *sgupt* /img/forum/go_quote.gif 
_can these handle beyer 880s? (250 ohm)_

 

It runs fine with my beyer 990's, FWIW


----------



## sachu

Quote:


  Originally Posted by *Sancho86* /img/forum/go_quote.gif 
_thetubecenter, I guess they got a shipment yesterday_

 

yeah..i placed an order at the same place today..they told me they would give me 6 but ended up snding me an invoice for only 4. Still better than none i guess


----------



## scompton

I've driven hard to drive orthos, 600 ohm Sextetts and 125 ohm QP85 with no problem although the volume knob is pretty low. I have had a prblemwith a couple of unmodded orhtos that are pretty easy to drive. I had to turn the volume down so low that I had channel imbalance. I need to bring mine home from work to put resistors on the input. When I do that, I'll probably use a better pot too.


----------



## sgupt

cool! this could be a very viable option for me instead of a zero dac (obv id need a dac too)


----------



## Vaughn

Investigate the Alien DAC, about $50 in kit form or cheaper if you assemble the parts yourself. I plan on building one into my SS.


----------



## tomb

Quote:


  Originally Posted by *Vaughn* /img/forum/go_quote.gif 
_Investigate the Alien DAC, about $50 in kit form or cheaper if you assemble the parts yourself. I plan on building one into my SS._

 

There is _another_ DAC available now, too.
	

	
	
		
		

		
			








 Imagineering invoiced me yesterday, so I expect the proto boards will arrive on my doorstep on Thursday, perhaps, maybe Friday.


----------



## csroc

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There is another DAC available now, too.
	

	
	
		
		

		
		
	


	





_

 

What's that? I might be interested in building a small DAC.


----------



## Forte

Quote:


  Originally Posted by *csroc* /img/forum/go_quote.gif 
_What's that? I might be interested in building a small DAC._

 

I think tomb is referring to the Bantam.

 Thread here http://www.head-fi.org/forums/f6/com...layout-190876/

 Website here BantamDAC Overview

 Have been reading up on this and ordered the boards last night, the small size opens up all sorts of possibilities.


----------



## csroc

Ahh yeah does look to be the Bantam. That would interest me but I need more than USB input. I know there are some other options but they're more involved.


----------



## Swingtops

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah..i placed an order at the same place today..they told me they would give me 6 but ended up snding me an invoice for only 4. Still better than none i guess_

 

I placed my order last week and got no response/invoice just curious if you got a paper copy or email or anything.
 I had called them last week and they told me they were getting a shipment in on Monday but no email, letter, or charge on my account.

 Thanks in advance


----------



## sachu

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_I placed my order last week and got no response/invoice just curious if you got a paper copy or email or anything.
 I had called them last week and they told me they were getting a shipment in on Monday but no email, letter, or charge on my account.

 Thanks in advance_

 

I had them send me an invoice via paypal..


----------



## iareConfusE

How are the prototypes coming along? Has anyone received the boards yet, or are they still being made?


----------



## ludoo

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_How are the prototypes coming along? Has anyone received the boards yet, or are they still being made?_

 

A few posts back:

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Imagineering invoiced me yesterday, so I expect the proto boards will arrive on my doorstep on Thursday, perhaps, maybe Friday.
	

	
	
		
		

		
		
	


	


_


----------



## nightanole

Quote:


  Originally Posted by *Dr Evil Dan* /img/forum/go_quote.gif 
_the starving student shouldnt have problems driving grados. in fact, i am using a pair of grados now, and they get more than loud enough._

 

So your driving grados with stock bom resistors and pot and have usable volume control?


----------



## Dr Evil Dan

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_So your driving grados with stock bom resistors and pot and have usable volume control?_

 

IIRC, the resistors are stock. And I am using an Alps RK27, which is stock value of 50k. I don't have problems with the volume control, but some people might because it gets really loud pretty fast. I would say maybe 20% of the way through the turn is where I have mine. If you have problems with too much gain, you can do this : Shunt Pot Volume Control - World-Designs-Forum


----------



## Sancho86

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_I placed my order last week and got no response/invoice just curious if you got a paper copy or email or anything.
 I had called them last week and they told me they were getting a shipment in on Monday but no email, letter, or charge on my account.

 Thanks in advance_

 

I didn't get one either, but when I called them they told me I'd get 6 on my order of 10. Hopefully they'll show up tommorrow


----------



## Hayduke

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well i got most things in order. I have 2 questions though. There are 2 48v cisco power supplies on ebay, one is 1.5 amp and the other is .38 amp. Which one do i get?

 the last question is how to you get this to run lower ohm cans like grado and sony v6's? I dont have any phones over 80 ohms and was planning on getting a 25ohm pair of denon d2000's one day._

 

The .38amp one is plenty. That's what Pete speced originally and what most of us use. Unless you have another need for a 48V PS and/or the 1.5A one is cheaper, I'm not sure what advantage would be gained. The other poster is right that it won't hurt to have the 1.5A PS, but this project is supposed to be trying to be as inexpensive as possible, so why spend extra on a PS?

  Quote:


  Originally Posted by *sgupt* /img/forum/go_quote.gif 
_can these handle beyer 880s? (250 ohm)_

 

I listen to Sennheiser 580s and 650s with mine and it drives them fine. Those are both 300ohms.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_The .38amp one is plenty. That's what Pete speced originally and what most of us use. Unless you have another need for a 48V PS and/or the 1.5A one is cheaper, I'm not sure what advantage would be gained. The other poster is right that it won't hurt to have the 1.5A PS, but this project is supposed to be trying to be as inexpensive as possible, so why spend extra on a PS? <snip>_

 

Agreed. However, an oversized power supply may actually have trouble producing enough voltage under a very light load. I think this was more of a problem on older switching supplies, but still - there is a greater chance of poor regulation under a very light load than not. That could mean worse sound with a bigger power supply, not better.


----------



## csroc

For the most part I saw a lot of those power supplies with the different outputs all selling for roughly the same price.


----------



## kuroguy

The bigger power supply would allow you to modify the amp to use 6j6 tubes. you would need to rewire the filaments with a voltage regulator and install resistors where the filaments currently act as resistors for the MOSFET. No where near as elegant as the Millett design, but it would be much easier to source 6j6 in lieu of 19j6 tubes. Of course, the trade off is increased power consumption.


----------



## Sancho86

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Agreed. However, an oversized power supply may actually have trouble producing enough voltage under a very light load. I think this was more of a problem on older switching supplies, but still - there is a greater chance of poor regulation under a very light load than not. That could mean worse sound with a bigger power supply, not better._

 

How about an undersized one? I found a 48v .25a supply too small?


----------



## zkool448

Quote:


  Originally Posted by *Sancho86* /img/forum/go_quote.gif 
_How about an undersized one? I found a 48v .25a supply too small?_

 

 Quote:


  Originally Posted by *Sancho86* /img/forum/go_quote.gif 
_How about an undersized one? I found a 48v .25a supply too small?_

 

I'm thinking you should stick with the .38A or higher current ps. If you get a higher one just load your mssh up with a pair of super bright, hi mcd tube LEDs, pwr indicator, enclosure etc. sounds like a good way to spare those extra amps 
	

	
	
		
		

		
			





 By the way, can anyone recommend super bright red LEDs rated at 600-800mcd range? and what resistor value would you recommend to use if I tap to the stock 48v/.38A ps?


----------



## sachu

well,

 I scored 2 more 19J6 tubes.. I will try to mount the heatsinks inside the case and if it gets too warm I will punch some vents on the bottom of the case..

 Now to place that mouser order I have een putting off for so long


----------



## nightanole

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I'm thinking you should stick with the .38A or higher current ps. If you get a higher one just load your mssh up with a pair of super bright, hi mcd tube LEDs, pwr indicator, enclosure etc. sounds like a good way to spare those extra amps 
	

	
	
		
		

		
		
	


	




 By the way, can anyone recommend super bright red LEDs rated at 600-800mcd range? and what resistor value would you recommend to use if I tap to the stock 48v/.38A ps?_

 

The diode is almost impossible. It would have to be anywhere from 10 watts to 40 watts depending on the led. Think about it, a led is basically a short (dropping only 1-3.6v) and the resistor drops the rest, So your just putting a resistor across your powersuppy that has to suck 20-150ma or higher. the 1000mcd ones are 3v 20ma, so thats a 1k 2.5watt resistor.

LED calculator for single LEDs


----------



## rds

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_By the way, can anyone recommend super bright red LEDs rated at 600-800mcd range? and what resistor value would you recommend to use if I tap to the stock 48v/.38A ps?_

 


 I have no idea what the previous poster is talking about, but if you want the LED to be bright you should give it close to its maximum current rating - which is generally 20mA.
 From a 48V supply 2.3K will give you approximately 20mA. That resistor will be burning up 0.92W of power so you're best to use a 2W resistor for safey (ie it is specified to handle 2x the expected power).
 Mouser has very bright red LEDs. They are called "hyper orange" but they're really just red.
 Here's a suitable LED resistor for your application.

 EDIT Here are those LEDs lighting up the tubes on a Starving Student:


----------



## DopeNessMonster

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_EDIT Here are those LEDs lighting up the tubes on a Starving Student:



_

 

Very sharp. I prefer the soft orange glow of the tubes themselves, but it's a nice looking amp. What 1/4" jack is that? I was looking for a black one, but could only find the locking Neutrik which wouldn't fit.


----------



## zkool448

rds, that's one sweet compact ss unit you have there! 

 Thanks for the LED and R source info, I like your tubes look a lot and I will go ahead and grab a couple. As good as they look with a black case I'm however unsure how it'll match with my light maple enclosure though... perhaps blue's?


----------



## tomb

Some of you may not realize (lots of new people), but rds's rendition of the Starving Student is also sold at Whiplash Audio (a Head-Fi sponsor) as the "Mini-Millett":
Mini Millet DIY Tube Amplifier

 They're out of stock right now - maybe they're waiting on the new PCB's.


----------



## Coreyk78

I like the case RDS used, I used the same one for my second SS build in my avatar


----------



## Vaughn

I have ordered all of my parts for a SS and I am starting on the chassis...

 I have a couple of heatsinks which are sufficiently large and I am wondering if
 it is ok to mount them to the chassis so there is no stress on the mosfet legs?
 I don't know if this will create a grounding problem, I ordered the mounting kit which includes an insulator but I wanted to make sure before I start building.


----------



## csroc

Quote:


  Originally Posted by *Vaughn* /img/forum/go_quote.gif 
_I have ordered all of my parts for a SS and I am starting on the chassis...

 I have a couple of heatsinks which are sufficiently large and I am wondering if
 it is ok to mount them to the chassis so there is no stress on the mosfet legs?
 I don't know if this will create a grounding problem, I ordered the mounting kit which includes an insulator but I wanted to make sure before I start building._

 

It's fine, I think that's what basically everyone has been doing if you look at the builds so far. I soldered mine to the enclosure because I couldn't get the damn pins out.


----------



## zkool448

Yes I soldered the pins to the copper clad board also. 

 Regarding the pins, I wonder if it is forged steel (or whichever material they use) that can be filed down with a bench grinder flushed to the heatsink, then tap the other end and use screws for mounting it to the case.


----------



## DopeNessMonster

I pulled the pins out of mine with some vice grips. You just need a really good bite on the pin then twist it out. Then you can either tap it, or use self-tapping #4 size (~3mm) screws. If you're careful, you can use 4-40 machine screws without tapping it first, but I broke a couple screw head off doing that.


----------



## -=Germania=-

You can pick up the switched black plastic Neutrik jacks at partsexpress.com. 

 Cheap and work very well.

 It is nice to not have to worry about the jack being isolated if you are using a metal case.


----------



## tomb

Proto boards have arrived:

 Bottom (remember, we're building the boards upside down with the tube sockets and MOSFETs on the top) -






 Top (the tube sockets and MOSFETs go on this side) -





 Photoshopped overlay -


----------



## J.D.N

Looks good! Might have to get one when the final boards come out...


----------



## Omega17TheTrue

Nice PCB, but i have a little question; do using a PCB produce a (slightly) better sound than from a "point to point wiring" ? (i heard the contrary)

 I guess using PCB made the installation faster but what are the differences between the two ? (pros and cons)

 By the way i'm planning to buy the mini millet from whiplash.


----------



## Coreyk78

The pcbs look very nice, I'll definitely need to pick one up once they are available


----------



## tomb

Quote:


  Originally Posted by *Omega17TheTrue* /img/forum/go_quote.gif 
_Nice PCB, but i have a little question; do using a PCB produce a (slightly) better sound than from a "point to point wiring" ? (i heard the contrary)

 I guess using PCB made the installation faster but what are the differences between the two ? (pros and cons)

 By the way i'm planning to buy the mini millet from whiplash. 
	

	
	
		
		

		
		
	


	


_

 

A _quality_ p2p build compared to a _quality_ through-hole PCB will sound the same, period. Also, I have no doubt that the Whiplash versions are _quality_ builds.

 The same is not true for digital circuits (DACs, SMD, etc.), but that doesn't apply here.


----------



## Yaka

shoulda asked this when i put my order in for the proto board. do the normal tube holders fit the pcbs or will we have to get diffrent ones?

 btw looks great and cant wait to get my hand one it


----------



## tomb

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_shoulda asked this when i put my order in for the proto board. do the normal tube holders fit the pcbs or will we have to get diffrent ones?

 btw looks great and cant wait to get my hand one it
	

	
	
		
		

		
		
	


	


_

 

By tube holders, do you mean the sockets?

 If so, no - you need _PCB_ tube sockets:

Beezar.com 7-pin Gold ceramic Socket
(SET OF 5) 7 PIN CERAMIC PCB VACUUM TUBE SOCKETS - eBay (item 300293030933 end time Feb-17-09 18:38:27 PST)
Parts ConneXion - The authority on hi-fi DIY parts and components (SOCKET- 59028 or 59029)


----------



## Yaka

cool ordering those as well then, thx


----------



## iareConfusE

Awesome, can't wait til production boards are available. Also, is the new BOM up somewhere? I checked diyforums.org and the SS page was still in "coming soon" status.

 Also, silly question(s) but, I'm assuming those two circles above and between C3 and C5 are for LEDs, which way do they go in though? I can't see any marking or symbol for which side positive/neg should go in. Also, can the LED's be wired to run under the tubes for a colored glow? Is that what the hole in the center of the tube is for?

 EDIT: nvm I looked on my PCB tube sockets and noticed that the center hole was plugged. So, how do I go about lighting up these tubes with LEDs? Would I just run the LED's by wire somewhere nearby the underside of the tube? or is there a better approach to this?


----------



## ludoo

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Also, silly question(s) but, I'm assuming those two circles above and between C3 and C5 are for LEDs, which way do they go in though? I can't see any marking or symbol for which side positive/neg should go in. Also, can the LED's be wired to run under the tubes for a colored glow? Is that what the hole in the center of the tube is for?_

 

I assume the LED positive legs go towards RLED.


----------



## zkool448

Quick question regarding the sockets once soldered to the pcb. When the pcb is mounted in the case (upside down) how much clearance is there between the pcb and the top lid of chassis? Will the sockets protrude above or remain below the lid?

 Just wondering for cosmetics purpose when it's time to size the holes on the top side if need to make clearance for the tubes dia or only for the sockets. thanks -zk


----------



## tomb

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Awesome, can't wait til production boards are available. Also, is the new BOM up somewhere? I checked diyforums.org and the SS page was still in "coming soon" status.

 Also, silly question(s) but, I'm assuming those two circles above and between C3 and C5 are for LEDs, which way do they go in though? I can't see any marking or symbol for which side positive/neg should go in. Also, can the LED's be wired to run under the tubes for a colored glow? Is that what the hole in the center of the tube is for?

 EDIT: nvm I looked on my PCB tube sockets and noticed that the center hole was plugged. So, how do I go about lighting up these tubes with LEDs? Would I just run the LED's by wire somewhere nearby the underside of the tube? or is there a better approach to this?_

 

BOM is in work - sorry, it's been a bad week at work.
	

	
	
		
		

		
		
	


	




 As for the tube sockets, this will tell you all you need to know (they're all 7-pin sockets):
Millett Hybrid MiniMAX Tube Lights

  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I assume the LED positive legs go towards RLED. 
	

	
	
		
		

		
		
	


	


_

 

Exactly. The SSMH is negatively grounded, so the side of the LED that has a trace going to it is positive. We'll put "+" signs there for the production boards, though.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *zkool448* 
_Quick question regarding the sockets once soldered to the pcb. When the pcb is mounted in the case (upside down) how much clearance is there between the pcb and the top lid of chassis? Will the sockets protrude above or remain below the lid?

 Just wondering for cosmetics purpose when it's time to size the holes on the top side if need to make clearance for the tubes dia or only for the sockets. thanks -zk_

 

I certainly wouldn't cut it that close. The PCB socket diameter is so close to the diameter of the tubes, the difference is not worth worrying about.

 EDIT2: Never mind about the bushings - there isn't enough clearance - it's a tiny bit more than a 1/4". So, yes - the tube sockets will stick above the holes. It's best to probably still cut the 3/4" hole, though.

 EDIT3: A standard Millett MAX's sockets stick about 0.54" above the surface of the PCB, but this will vary depending on how hard you squish down the socket when you solder it (I squish very hard.) Accounting for the thickness of the plate, about 0.21" of the socket will be above the surface of the top plate (using the Hammond "L" case). Note that the typical PCB 7-pin ceramic socket is 0.725" in diameter. The typical 19J6 tube is about 0.715" in diameter.

 Make the hole 3/4".


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for the tube sockets, this will tell you all you need to know (they're all 7-pin sockets):
Millett Hybrid MiniMAX Tube Lights_

 

I actually prefer these

01 - More Info for item P-ST7-815

 Cheaper, easy to drill holes, and no gold to poison the solder joints. Heat is not an issue with these tubes.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The SSMH is negatively grounded, so the side of the LED that has a trace going to it is positive. We'll put "+" signs there for the production boards, though.
	

	
	
		
		

		
		
	


	


_

 

I guess that's a note to me.


----------



## gurusan

! I want one of those PCBs. Can't wait until they are in production!


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT3: A standard Millett MAX's sockets stick about 0.54" above the surface of the PCB, but this will vary depending on how hard you squish down the socket when you solder it (I squish very hard.) Accounting for the thickness of the plate, about 0.21" of the socket will be above the surface of the top plate (using the Hammond "L" case). Note that the typical PCB 7-pin ceramic socket is 0.725" in diameter. The typical 19J6 tube is about 0.715" in diameter.

 Make the hole 3/4". 
	

	
	
		
		

		
			



_

 

Got it! 
	

	
	
		
		

		
		
	


	




 thanks tomb.

 zk


----------



## Fitz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A quality p2p build compared to a quality through-hole PCB will sound the same, period. Also, I have no doubt that the Whiplash versions are quality builds.

 The same is not true for digital circuits (DACs, SMD, etc.), but that doesn't apply here._

 

Point to point is _so_ much more fun to do though. I don't get anywhere near the same sense of accomplishment from just stuffing a PCB.


----------



## OldKing

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_oldking used them to build is, i think he posted pics of a few of his builds earlier in the thread

Millett "Starving Student" hybrid headphone amplifier on Flickr - Photo Sharing! he has pics on his flickr page that shows the connector attached to the mosfets_

 


 Search for " .100 molex " and you can find them. You also need the pins which insert into the connector. I think I used "k.k." series.

 Or you can just use fan connectors if you have them.

 I wanted to have disconnects at the mosfets to allow me to take the thing apart... they work great.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_<snip>
 I guess that's a note to me._

 

Ha - yes! Consider yourself notified.


----------



## -=Germania=-

Do you guys have any ideas of who will be supplying boards? 

 *I have family members and friends who really want to get their hands on one as their second DIY projects (helped them do a CMoy one saturday and supplied the parts as an Xmas gift).* 

 Boards will be between $15 and 20 I am guessing?


----------



## tomb

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Do you guys have any ideas of who will be supplying boards? 

 *I have family members and friends who really want to get their hands on one as their second DIY projects (helped them do a CMoy one saturday and supplied the parts as an Xmas gift).* 

 Boards will be between $15 and 20 I am guessing?_

 

I haven't discussed it specifically with Nate yet, but Dsavitsk and I agree that beezar.com is the way to handle it. I'm going to set it up so that tubes are sold in tested, matched pairs _only with the PCB_. IOW, if you want tubes, you'll have to purchase the PCB, too. You'll be able to purchase the PCB's separately, but not the tubes. This seems the fairest way to do it and the best way to make certain that most people will get a shot at tubes if they want to build the PCB. Unlike the tubes - if we run out of PCB's, we can always order more.

 As far as pricing, I would expect the boards to be 1/2 what you are guessing.
	

	
	
		
		

		
		
	


	




 It's been $15 for the prototypes, but prototypes are always more expensive.


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Do you guys have any ideas of who will be supplying boards?_

 

beezar.com

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Boards will be between $15 and 20 I am guessing?_

 

Less, I think.


----------



## Sodacose

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_Point to point is so much more fun to do though. I don't get anywhere near the same sense of accomplishment from just stuffing a PCB._

 

+1 

 I don't think I'll ever go back to PCB's! For me, it's the problem solving and interpretation involved that is so much fun.

 Before my SS I was really interested in buying an Aikido kit. Now it's going to have to be bus-bars and bakelite all the way!

 edit: not to crap on anyone's fun! i actually have done a lot of PCB projects before trying PTP.


----------



## V-DiV

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_Point to point is so much more fun to do though. I don't get anywhere near the same sense of accomplishment from just stuffing a PCB._

 

PCBs will be great for the less confident ones who want to explore this nice little amp, but P2P is what made it particularly compelling for me. I learned a lot building mine and had a real sense of accomplishment when I first hit the switch and music came out.


----------



## iareConfusE

But PCB's just look so much neater!


----------



## Omega17TheTrue

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A quality p2p build compared to a quality through-hole PCB will sound the same, period. Also, I have no doubt that the Whiplash versions are quality builds.

 The same is not true for digital circuits (DACs, SMD, etc.), but that doesn't apply here._

 


 Thanks for your response. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_But PCB's just look so much neater!_

 

Yes but its more a matter of personal taste than anything else -IMHO-.


----------



## iareConfusE

Oh one more question, what are the dimensions of the PCB? 
 width x length?


----------



## tomb

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Oh one more question, what are the dimensions of the PCB? 
 width x length?_

 

Board Dimensions: 3.87" wide x 3.14" (98mm wide x 80mm),
 Board Specs: 2oz copper (production version) on an 0.062" (1.6mm) FR4 dielectric


----------



## -=Germania=-

Wow, that is great!

 That is also a really nice service to the community. 

 Is there a specific Hammond or other enclosure that you guys have in mind?

 It would be nice if we could get pre-drilled cases to take care of the other intimidating part - casework. 
 The MiniMax looks fantastic and there could definitly be interest for something like this. 

 PTP can be really intimidating for people, but it is extremely easy to change things or parts if you want to later something harder to do with a PCB. 

 You just made my dad extremely happy!


----------



## sandbasser

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Wow, that is great!

 That is also a really nice service to the community. 

 Is there a specific Hammond or other enclosure that you guys have in mind?

 It would be nice if we could get pre-drilled cases to take care of the other intimidating part - casework. 
 The MiniMax looks fantastic and there could definitly be interest for something like this. 

 PTP can be really intimidating for people, but it is extremely easy to change things or parts if you want to later something harder to do with a PCB. 

 You just made my dad extremely happy!_

 

Have a look at: DIYForums.org &bull; View topic - Starving Student Millett Hybrid PCB - designed by Dsavitsk


----------



## scompton

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Have a look at: DIYForums.org &bull; View topic - Starving Student Millett Hybrid PCB - designed by Dsavitsk_

 

How do you slide the PCB into the case if the sockets protrude from the case?


----------



## sandbasser

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_How do you slide the PCB into the case if the sockets protrude from the case?_

 

My guess would be: the top comes off the case. But, someone with more expertise than I can confirm.


----------



## tomb

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_How do you slide the PCB into the case if the sockets protrude from the case?_

 

Oh my gosh - we never thought about that!
	

	
	
		
		

		
			








 Seriously - the Hammond case lid slides in out, too. The board will be mounted to the case lid with a 20mm standoff. So, the entire assembly willl slide in as one piece.

 EDIT: You can do it without the standoff, too.


----------



## scompton

I knew there was a way, but since the only thing I've built was the SS in a Radio Shack case, I had no idea how they worked.


----------



## tomb

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I knew there was a way, but since the only thing I've built was the SS in a Radio Shack case, I had no idea how they worked._

 

No problem - we'll probably find something else to kick ourselves over. That's why we do prototypes, though.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oh my gosh - we never thought about that!
	

	
	
		
		

		
		
	


	





_

 

I asked Tom the same question


----------



## nightanole

I got my 4 tubes, today. No clue about them. All 4 are rca, 2 types of one, 2 types of another. First type as an all silver top with a horizontal ring inside. The 2nd type has a hald circle ring inside and only silvered by the ring. Uh any feed back on these would be nice. At least i got 2 sets and not 4 diff kinds.


 Also how do i clean the contacts and the tubes? I dont want to use acetone and remove the labels, but i think alcohol leaves a film.


----------



## digger945

^So yer gonna do a SS. I think you will really enjoy it. Are you gonna go PTP or wait for the pcb's?


----------



## Coreyk78

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_I got my 4 tubes, today. No clue about them. All 4 are rca, 2 types of one, 2 types of another. First type as an all silver top with a horizontal ring inside. The 2nd type has a hald circle ring inside and only silvered by the ring. Uh any feed back on these would be nice. At least i got 2 sets and not 4 diff kinds.


 Also how do i clean the contacts and the tubes? I dont want to use acetone and remove the labels, but i think alcohol leaves a film._

 

the rings are the getters. I have tubes with top d-shaped getters, side d getters and top halo getters. Other than having 1 tube thats noisy(static) I honestly can't hear much of a difference between the types, all of them sounded good to me.


----------



## nightanole

So i have side D getters and top halo getters. I learned something today
	

	
	
		
		

		
		
	


	




 Next up is to get my case so i can do a mock ptp setup. Im hoping to find a broke pace soldering station and use it at work. They are all alum with fins and should work for a heatsink. I can use the iron plug for the headphone out, but the tube location might be a problem...


----------



## Hase

So, any current sources for the tubes?


----------



## brashgordon

I have to admit I've skipped through this thread for a couple of hours now and the design and group support seems to be extraordinary. 

 But I haven't been able to find the exact circuit / parts list in a form that I can start building...

 I even went to Pete's site and can't find anything ... I'm afraid I'll die of old age if I start at post one again and go through each posting ... 

 Can anyone bring me up to speed on the stock parts, recommended case, I bought a drill press (for a previous project) in case I go "woodie" ... so I'm inclined to spend money ... even when I have no clue where to go next ... LOL

 That's just like me though ... I've got lots of great solder, a great iron, some nice oak and maple stock, a table saw and a planer ... shucks ... maybe I'll just start building doll houses ... with electric appliances ... 
	

	
	
		
		

		
		
	


	




 LOL


----------



## gurusan

Quote:


  Originally Posted by *brashgordon* /img/forum/go_quote.gif 
_I even went to Pete's site and can't find anything ... I'm afraid I'll die of old age if I start at post one again and go through each posting ..._

 

??? It's all right on his site!!


----------



## brashgordon

Oh.... so that's what those scrolly-slidey things are for ... 

 Geeze, I'm a dweeb ....told you I'd been looking at the thread too long ... \


 Thanks for revealing my some-timers state of mind .... LOL

 OK ...going to start again tomorrow .... maybe with a little coffee...


----------



## nightanole

Quote:


  Originally Posted by *Hase* /img/forum/go_quote.gif 
_So, any current sources for the tubes?_

 

the tube center i got on monday, no waiting.


----------



## Sancho86

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I'm thinking you should stick with the .38A or higher current ps. If you get a higher one just load your mssh up with a pair of super bright, hi mcd tube LEDs, pwr indicator, enclosure etc. sounds like a good way to spare those extra amps 
	

	
	
		
		

		
			





 By the way, can anyone recommend super bright red LEDs rated at 600-800mcd range? and what resistor value would you recommend to use if I tap to the stock 48v/.38A ps?_

 

I ask since I already have a .25a one and dont want to source a higher power one due to cost


----------



## nightanole

Does anyone know how many watts these things suck? 1 watt,10 watt...
 I wonder how much power it can put out too, I dont think its a 1 watt monster, but then again its not using opamps either...


----------



## Hase

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_the tube center i got on monday, no waiting._

 

Can we trust that source? The site seems shady and highly insecure. I'm certainly not going to be putting my CC info into a form that gets sent in cleartext (they need to be slapped for that).

 I'll place an order over the phone with a throw-away card if any can vouch for them.


----------



## Logistic

Just email them. They'll send you a paypal invoice.


----------



## nightanole

OR just call them on the phone like me. I just emailed them if they were instock, they said they are getting a shipment in on monday. I called monday and did a phone order. Less then a week later i had 2 sets of matching tubes.


----------



## tomb

Quote:


  Originally Posted by *Hase* /img/forum/go_quote.gif 
_Can we trust that source? The site seems shady and highly insecure. I'm certainly not going to be putting my CC info into a form that gets sent in cleartext (they need to be slapped for that).

 I'll place an order over the phone with a throw-away card if any can vouch for them._

 

Vouch for Stan at the Tube Center? I'm embarassed to admit I've probably sent him well over $1000 in the last year. Yes, he's trustworthy. He's also big in the Ham radio community and travels to many of the meets, so there may be times when he's a bit hard to get.
	

	
	
		
		

		
		
	


	




 EDIT: Keep in mind that some of these tube vendors have been around since the old days. That doesn't mean they're up on the latest web technology and e-commerce.


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_EDIT: Keep in mind that some of these tube vendors have been around since the old days. That doesn't mean they're up on the latest web technology and e-commerce.
	

	
	
		
		

		
		
	


	


_

 

I'm just glad they have a website. Most tube dealers and tv/radio service shops locally don't even have websites. Can't find them and browse through their catalog easily unless you consult the local yellow pages (what's yellow pages? 
	

	
	
		
		

		
		
	


	




)

 The contact I have is _Jack_ at the tubecenter. Paid through paypal last week and just waiting now for the tubes to arrive this week.

 EDIT: I meant to say Jack, not Jeff... had the names mixed up as I've also inquired at GJA for a soha ii kit : )


----------



## Hase

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I'm just glad they have a website._

 

I agree about the website, NOT the e-commerce part. E-commerce like this is dangerous and makes cyber-crime profitable. They are helping the criminals. If you want to understand how, PM me and I'll send you the research and references, no need to hijack the thread. 

 That said, good to know they themselves are good folks, I just sent an e-mail requesting a paypal invoice.


----------



## tomb

deleted


----------



## ThePredator

How long does The Tube Center usually take to ship out?


----------



## sachu

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_How long does The Tube Center usually take to ship out?_

 

 I sent in my first payment on Monday and the second on tuesday. I haven't received the tubes yet. I expect to have them by tuesday or latest by wednesday. Should be just in time for the mouser order for the rest of the parts to arrive.


----------



## gore.rubicon

Whats the current state of the pcbs? any chance of getting one by the march break?


----------



## tomb

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Whats the current state of the pcbs? any chance of getting one by the march break?_

 

Prototypes will be sent to the prototypers Tuesday morning (the Post Office doesn't open until then). I think all we need is a couple of them to be built and prove out everything. I'm hoping that won't take much longer than 2 weeks, maybe 3. After that, we'll order the production boards. It'll take about 2 weeks for the production boards to be made. Add another week for shipping and for me to get them up for sale on beezar, and then we're off and running.

 Whether that will come in time for your March break, I don't know.


----------



## nightanole

Well im getting my mouser order together. Im going a little high end for the c3,c5, out put cabs and mouser is out of Nichicon KZ 470uF 50V caps till may, and beezer only has 35v caps. What should i do? If i order with mouser, do they auto ship in may for free, or do i have to pay for shipping again? 

 Also do i really need the $16 alps pot if im doing the shunt style approach? To me it looks like the audio isnt going through the pot at all so i was hoping a standard 50k pot from mouser would be fine.


----------



## tomb

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well im getting my mouser order together. Im going a little high end for the c3,c5, out put cabs and mouser is out of Nichicon KZ 470uF 50V caps till may, and beezer only has 35v caps. What should i do? If i order with mouser, do they auto ship in may for free, or do i have to pay for shipping again?_

 

Yes, Mouser will charge you for shipping again. As for Beezar.com - sorry - but officially, I'm only supporting the MAX, MiniMAX, and BantamDAC for the moment. 35V caps are fine on the MAX and MiniMAX, but 50V are not "fine" for the Starving Student. I know what some have said, but you should really use 63V caps, minimum.
  Quote:


 Also do i really need the $16 alps pot if im doing the shunt style approach? To me it looks like the audio isnt going through the pot at all so i was hoping a standard 50k pot from mouser would be fine. 
 

I'm not sure I understand what you mean here by "shunt style." Every bit of the signal goes through the pot unless you're using something like an OptiVol. Even so, I know some people have used the ALPS, but all we're spec'ing for the SSMH PCB is the little Alpha that Pete originally used.


----------



## nightanole

Well im going to try the 100v KW style since the kz no one has above 35v.

UKW2A471MHD


----------



## rds

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ Even so, I know some people have used the ALPS, but all we're spec'ing for the SSMH PCB is the little Alpha that Pete originally used._

 

It works very nicely too. Its weakness is poor channel matching in the first 50 or so degrees of rotation. This problem is easily fixed by adding some resistance in front of the pot.


----------



## Vaughn

If I am using the SS with a component which has variable output(i.e. Oppo or Squeezebox) I assume it would be fine to eliminate the volume control and just put a 50k resistor in line in place of the pot?


----------



## rds

Quote:


  Originally Posted by *Vaughn* /img/forum/go_quote.gif 
_If I am using the SS with a component which has variable output(i.e. Oppo or Squeezebox) I assume it would be fine to eliminate the volume control and just put a 50k resistor in line in place of the pot?_

 

You could, but you will probably find the amp has a lot more gain than you want. I'd use 2 25k resistors as a voltage divider.


----------



## Hayduke

Quote:


  Originally Posted by *Hase* /img/forum/go_quote.gif 
_So, any current sources for the tubes?_

 

 Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_the tube center i got on monday, no waiting._

 

LOL, I'm glad you interpreted this for me. I was thinking, "huh? what's he talking about? We're all using the Cisco PS" 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *Hase* /img/forum/go_quote.gif 
_Can we trust that source? The site seems shady and highly insecure. I'm certainly not going to be putting my CC info into a form that gets sent in cleartext (they need to be slapped for that).

 I'll place an order over the phone with a throw-away card if any can vouch for them._

 

I know it's already been said, but I've ordered from them too. Not only are they legit, they are nice guys 
	

	
	
		
		

		
		
	


	




 Of course, everytime I've ordered tubes (except once on ebay) it's been via the phone.

  Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Also do i really need the $16 alps pot if im doing the shunt style approach? To me it looks like the audio isnt going through the pot at all so i was hoping a standard 50k pot from mouser would be fine._

 

I would think you're correct about this method. That seems to be the whole point.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure I understand what you mean here by "shunt style." Every bit of the signal goes through the pot unless you're using something like an OptiVol._

 

He means this Tom:
Shunt Pot Volume Control - World-Designs-Forum
 I agree though that the standard one works fine 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Well im going to try the 100v KW style since the kz no one has above 35v.

UKW2A471MHD_

 

I used mostly KWs in my SOHA and they sound fine. I'm going to build another MHSS when the production boards are available and plan to use KWs then as well.


----------



## ludoo

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_You could, but you will probably find the amp has a lot more gain than you want. I'd use 2 25k resistors as a voltage divider._

 

Unless you use it with Yamaha orthos, in which case 50k is fine. My SS at 50% volume wiht a 50k pot drives the HP-3 to a quiet listening level. At max volume it's loud but listenable.


----------



## Henmyr

You guys in europe who have done this, where have you bought parts and what was your final cost? I tried to put all the parts together from Swedens largest parts store, but the cost would have been rather high I think. Nothing like the stated $35.80 (pmillet diy site) but over three times that.

 EDIT:
 Secondly, are to tubes so rare that it's not worth it to try to make this? I would not want to end up with a $150 (although shiny) paperweight.


----------



## ludoo

Quote:


  Originally Posted by *Henmyr* /img/forum/go_quote.gif 
_You guys in europe who have done this, where have you bought parts and what was your final cost? I tried to put all the parts together from Swedens largest parts store, but the cost would have been rather high I think. Nothing like the stated $35.80 (pmillet diy site) but over three times that.

 EDIT:
 Secondly, are to tubes so rare that it's not worth it to try to make this? I would not want to end up with a $150 (although shiny) paperweight._

 

Yes, sourcing parts in Europe is much more expensive: tubes have to come from the US (shiping costs), I found the PSU on .uk ebay (very cheap, but again shipping), etc. A good source for parts is Banzai Effects, they carry almost all you need for the SS including Mosfets, tube sockets, cases, and boutique film/electrolytic caps, and ship from Germany. Or you could get parts for 2 SS from Mouser and profit from free shipping (but careful with customs duties).


----------



## jeanba3000

Hello from Paris

 I usually buy my components from Farnell (they have a swedish site), Reichelt (only in german, but I manage to find what I want and order without speaking german) and Radiospares (swedish version too, in France, due to some law, they are restricted to professionnal customers, I don't know for other RS local sites).

 Watch each conditions of sale (minimum amount order, shipping charge…) to see if one is better than another.

 I had a very bad experience with schuro.de, never gonna order to this website again.

 Hope this helps.

 Thanks Ludo for Banzaieffects, I didn't know them.


----------



## Henmyr

Thanks both of you. I will see if I can reduce the cost a bit now.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_<snip>
  Quote:


  Originally Posted by *tomb* 
I'm not sure I understand what you mean here by "shunt style." Every bit of the signal goes through the pot unless you're using something like an OptiVol.

 

He means this Tom:
Shunt Pot Volume Control - World-Designs-Forum
 I agree though that the standard one works fine 
	

	
	
		
		

		
		
	


	


_

 

Thanks for that reminder. Now I remember when you guys were discussing this before.

 However, this is not much different than shunting the signal with a cathode bypass cap on a tube. In that case, a boutique capacitor is used because the signal may pass through from time to time - especially bass frequencies. This case is similar. Even the reference states, _"Any noise at the wiper junction with the track will be isolated/*reduced* by the track resistance between the wiper and signal."_ The author was careful, IMHO, to include the word "reduced." This is because there is a still a signal path through the pot to ground.

 As the author states, this scheme will also permit the input impedance to the amp to vary. That's something we try hard to prevent in headphone amp designs around here, because it will often have an effect on sound. Usually, you want an input-impedance setting resistor (fixed) to ground to prevent this. The SSMH doesn't use one, so perhaps this is not a point to consider.


----------



## tomb

The prototype boards have been shipped to everyone this morning.
	

	
	
		
		

		
		
	


	




 I'll have a link tonight to a BOM.


----------



## MrMajestic2

Quote:


  Originally Posted by *Henmyr* /img/forum/go_quote.gif 
_You guys in europe who have done this, where have you bought parts and what was your final cost? I tried to put all the parts together from Swedens largest parts store, but the cost would have been rather high I think. Nothing like the stated $35.80 (pmillet diy site) but over three times that.

 EDIT:
 Secondly, are to tubes so rare that it's not worth it to try to make this? I would not want to end up with a $150 (although shiny) paperweight._

 

I got my proto parts from Mouser. Free FedEx shipping over €75 Euro so I usually ask friends to order at the same time. Feel free to tag along next time if you want. Elfa makes my wallet scream in agony everytime I go there


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The prototype boards have been shipped to everyone this morning.
	

	
	
		
		

		
		
	


	




 I'll have a link tonight to a BOM._

 

May the lord strike you down if I missed something when I ordered without a BOM


----------



## Yaka

cant wait to get the board. as for peeps wanting to order from mouser they now are in the uk as well so prolly cheaper shipping and less import tax hassles
	

	
	
		
		

		
		
	


	





 also waiting on the bom


----------



## MrMajestic2

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_as for peeps wanting to order from mouser they now are in the uk as well so prolly cheaper shipping and less import tax hassles
	

	
	
		
		

		
			



_

 

They have an office in the UK, but they still ship from the states.


----------



## ThePredator

Just got my tubes from The Tube Center, nice packaging, but the site could definitely use some modern improvements.

 Now if Harbor Freight would hurry and ship my drill bits.


----------



## Bleuburd

Is there any kind of waiting list for the pcb/tube partial kit? If so, I'm definitely in. Really looking forward to doing this as my first diy project.


----------



## iareConfusE

I don't think theres a waiting list. Its probably first come first serve once they get the production boards in.


----------



## Bleuburd

Ok, I'll just keep my eye out then.


----------



## Yaka

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_They have an office in the UK, but they still ship from the states._

 

did not know that.


----------



## tomb

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_I don't think theres a waiting list. Its probably first come first serve once they get the production boards in._

 

There's obviously going to be more demand for this than there are tubes at beezar. (No one call me, please - tubes will only be sold with a PCB, as stated before.)

 I think we'll do it like the Twisted Pear folks. I'll give notice for a specific time - date, hour and minute, for when they'll be available on beezar.

 I'm still working on the website, but as promised - here's a link to the BOM (right click to download):
http://www.diyforums.org/SSMH/bom/SSMH.xls


----------



## zkool448

TomB, thanks for the new PCB bom. 

 Just saw the optional caps/resistors and trying to visualize exactly how they'll be connected, however I'd rather confirm this so if you have a link available to a revised schematic that would be super. thanks.

 zk


----------



## nightanole

also the new plate caps look interesting, dont know what they do yet... Wish i didnt pull the trigger so fast, worse case my hammond case is too small for the pcb if i deside to use it.


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_TomB, thanks for the new PCB bom. 

 Just saw the optional caps/resistors and trying to visualize exactly how they'll be connected, however I'd rather confirm this so if you have a link available to a revised schematic that would be super. thanks.

 zk_

 

http://www.diyforums.org/SSMH/schematic/SSMHsch.gif


----------



## CaptHowie

Hey tomb,
 I'm having trouble understanding the new schematic. I know that schematic is just for the mono channel, but could you please create a stereo schematic like the original with all the labels? I'm a schematic noob so i'm just having a bit of trouble 
	

	
	
		
		

		
		
	


	




 Thanks for all the help you've provided to the SS and i'm looking forward to the PCB's as i'm a bit nervous about point-to-point :|


----------



## ludoo

Tomb, are 16V for C7/C8 really needed? I was thinking of getting some 6.3V os-cons as cathode bypass caps...


----------



## sachu

just received the tubes/sockets and partial parts for the 2 amps I will be building..have the cases and power supplies ready..can't wait


----------



## MrMajestic2

I missed ordering the bypass caps. How important are they and how important is it that they are bipolar?


----------



## MASantos

Tomb, which potentiometer did you choose for this? I can't recognise the footprint in the board.


----------



## ruZZ.il

BOM


----------



## tomb

Quote:


  Originally Posted by *CaptHowie* 
_Hey tomb,
 I'm having trouble understanding the new schematic. I know that schematic is just for the mono channel, but could you please create a stereo schematic like the original with all the labels? I'm a schematic noob so i'm just having a bit of trouble Thanks for all the help you've provided to the SS and i'm looking forward to the PCB's as i'm a bit nervous about point-to-point :|_

 

Sorry, no. Cut and paste to have two schematics, then draw a line from the "+" connection on one to the "+" connection on the other. Dsavitsk did the schematic anyway.
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Tomb, are 16V for C7/C8 really needed? I was thinking of getting some 6.3V os-cons as cathode bypass caps..._

 

It's quite possible that 6.3V os-cons are enough, but maybe not. It think we only have ~4V in the MAXes around the cathode bypass, but the SSMH has a much higher voltage threshold.

 Since the cathode bypass caps are optional, I'd measure the voltage at the pads after you get it built and powered up. It would be easy to install the two caps after that.

  Quote:


  Originally Posted by *MrMajestic2* 
_I missed ordering the bypass caps. How important are they and how important is it that they are bipolar?_

 

I think it's very important that they're bipolar - they meet the primary definition of a bipolar cap: voltage swinging in both directions at all times. However, a regular cap has performed just as well (supposedly) in other amps. In any event, they're optional.

  Quote:


  Originally Posted by *MASantos* 
_Tomb, which potentiometer did you choose for this? I can't recognise the footprint in the board._

 

As ruZZ.il says, check the BOM.
	

	
	
		
		

		
		
	


	




 We are using the same Alpha pot that Pete originally spec'd.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Since the cathode bypass caps are optional, I'd measure the voltage at the pads after you get it built and powered up. It would be easy to install the two caps after that._

 

Good idea. I could also have a look at the 19j6 curves and try to understand what's the cathode/grid voltage.

 Edit: as for them being bipolar, one side (-) is connected to ground and the other side (+) to the cathode which should be positive with respect to ground, why do you say they would see voltage swinging both ways?


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Good idea. I could also have a look at the 19j6 curves and try to understand what's the cathode/grid voltage.

 Edit: as for them being bipolar, one side (-) is connected to ground and the other side (+) to the cathode which should be positive with respect to ground, why do you say they would see voltage swinging both ways?_

 

Dsavitsk will have to give you a better explanation than I can. Suffice to say the signal wave amplitude varies up and down. The bypass cap allows a little extra "room" for the wave to expand on the back side of the tube - both negative and positive portions of the wave. If the cathode bypass cap is not there, the actual bias on the tube alters in response to the wave. This is because the tube reacts in reverse to a negative vs. postive signal. This means the cathode bypass cap increases gain - particularly on the lower frequencies, which often have higher amplitudes. This assumes that the cathode bypass cap is selected for a sufficient size that the RC filter formed by the cap and the resistor do not filter out the bass frequencies.

 In any event, as the music signal passes through the tube, the capacitor is asked to charge and discharge in both directions, keeping the bias difference of the tube at the same value.

 I think that's right, but let's see how much Dsavitsk corrects me.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think it's very important that they're bipolar - they meet the primary definition of a bipolar cap: voltage swinging in both directions at all times. However, a regular cap has performed just as well (supposedly) in other amps. In any event, they're optional._

 

Ah, I see. Hmm, does anyone have a couple of bipolars like in the BOM to sell me


----------



## dsavitsk

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Edit: as for them being bipolar, one side (-) is connected to ground and the other side (+) to the cathode which should be positive with respect to ground, why do you say they would see voltage swinging both ways?_

 

Based on the tube curves (I don't have a working SS in front of me to measure), it looks like the cathodes are biased up about 1 to 1.5V. Under normal circumstances, a polar cap should be fine. As Tom notes, there is signal swing, but it will typically never drive the voltage fully the other way.

 However, that we do usually think of 2V signals in audio. A 3V peak to peak signal will drive the grid just positive which will reverse the voltage on the cap. Now, this would overdrive the amp well past the point of unpleasantness so you wouldn't be listening to it there. Also, most electrolytics are OK with a small reverse voltage for a short period, so again, you are OK. However, OS-CONS may be the exception to that as they are a little more sensitive to voltage than other electrolytics.

 All said, I think polar caps are safe to use, and in fact I think 6.3V is probably plenty. But, do be aware of voltages, and take some measurements to be sure. In the end, if the cap breaks, the worst thing that happens is it leaks a little, and if it shorts completely the amp will lose bias and distort a lot and you'll know what to fix. It won't damage phones, or the other components, or anything like that -- there won't be any tube runaway.

 Also, only use this cap if you need more gain. Otherwise, leave it out.


----------



## ludoo

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Based on the tube curves (I don't have a working SS in front of me to measure), it looks like the cathodes are biased up about 1 to 1.5V. Under normal circumstances, a polar cap should be fine. As Tom notes, there is signal swing, but it will typically never drive the voltage fully the other way.

 <snip...>_

 

Thanks for the really excellent explanation. 
	

	
	
		
		

		
		
	


	




 I was at the office today and had no meter, but I can open up my home SS and measure the grid/cathode voltage if it's of any interest.

 I will probably put in cathode bypass caps as orthos are very hard to drive, and also I'm curious about any sonic differences (if any) with my previous SS that have no cathode bypass caps.

 Edit: I just slightly raised one tube and measured the voltage between cathode and grid, and I get 0.92V.


----------



## dsavitsk

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Edit: I just slightly raised one tube and measured the voltage between cathode and grid, and I get 0.92V._

 

That's about what I figured. With the cathode bypass in place, we may be able to lower the load on the tube (and lower Rk) and increase current through it keeping bias in about the same spot. By doing this, rp will be lowered which might make the proportional load actually higher. Mu, incidentally, will be raised both due to the cap eliminating the degenerative feedback, but also because it increases with current. It will take some experimentation to figure out where these tubes like to run, and for all I know, Pete already did this and settled on where it is. However, the datasheet (look at the bottom graph on the last page) seems to indicate that increasing the current through the tube will be a good thing. So, I think the experiment is worthwhile.


----------



## iareConfusE

Any suggestions for the volume knob? I didn't see it on the BOM and I'm not sure what the dimensions should be. I looked at the manufacturer's page for the potentiometer, and couldn't find any knobs that matched the shaft's dimensions.

 Also, will pre drilled face plates for the Hammond case be sold or are we going to have to drill them ourselves?


----------



## scompton

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Also, only use this cap if you need more gain. Otherwise, leave it out._

 

So if I want less gain, I should skip this cap and add 50K resistors between the input and the pot?


----------



## dsavitsk

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_So if I want less gain, I should skip this cap and add 50K resistors between the input and the pot?_

 

Yes


----------



## zkool448

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_I know that schematic is just for the mono channel, but could you please create a stereo schematic like the original with all the labels? I'm a schematic noob so i'm just having a bit of trouble_

 

CaptHowie, if I add these optional caps/resistors this is exactly how I would connect/add them to Pete's original schematic... *however* before I do I'll need someone here first to kindly verify my diagram! thanks 
	

	
	
		
		

		
		
	


	




 zk


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_CaptHowie, if I add these optional caps/resistors this is exactly how I would connect/add them to Pete's original schematic... *however* before I do I'll need someone here first to kindly verify my diagram! thanks 
	

	
	
		
		

		
		
	


	




 zk



_

 

Looks fine to me! Very good! How about I post that one on the website, too?


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks fine to me! Very good! How about I post that one on the website, too?_

 

Thanks TomB. 

 By all means, please post it on the website if you think it helps.

 zk


----------



## nightanole

I have a question on the bypass caps. I guess i miss read the Bom of one of the early builds. Anyway i have 2 sets of .22uf audio caps coming, the Wima MKP10 .22uF 250V from mouser and the vitamin C's from beezer. I was planning on using the wima as by passcaps on the power supply, and the vitamins on the bypass caps on the outputs. Now i realize i still need another set of .22 coming off the tubes. So which set should i use for c2,c4 and which set for c3a/c5a since i dont have enough caps for the power supply bypass ( and its not really needed anyway)?


----------



## Hayduke

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_CaptHowie, if I add these optional caps/resistors this is exactly how I would connect/add them to Pete's original schematic... *however* before I do I'll need someone here first to kindly verify my diagram! thanks 
	

	
	
		
		

		
			





 zk



_

 

What software did you use to make this? Just paint.net or something?

 Nice job zkool


----------



## tomb

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_I have a question on the bypass caps. I guess i miss read the Bom of one of the early builds. Anyway i have 2 sets of .22uf audio caps coming, the Wima MKP10 .22uF 250V from mouser and the vitamin C's from beezer. I was planning on using the wima as by passcaps on the power supply, and the vitamins on the bypass caps on the outputs. Now i realize i still need another set of .22 coming off the tubes. So which set should i use for c2,c4 and which set for c3a/c5a since *i dont have enough caps for the power supply bypass ( and its not really needed anyway)?*_

 

I think you answered your question.


----------



## Vaughn

Just finished my SS and I'm listening to it now...






 It is built into the cast aluminum enclosure of an old piece of cookware. Easy to service clamshell construction...


----------



## Logistic

Great job Vaughn! That amp has a lot of vintage flair.


----------



## HeadphoneAddict

Nice footwarmer!


----------



## zkool448

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_What software did you use to make this? Just paint.net or something?_

 

Hey Hayduke, just plain 'ol photoshop


----------



## zkool448

Quote:


  Originally Posted by *Vaughn* /img/forum/go_quote.gif 
_



 It is built into the cast aluminum enclosure of an old piece of cookware. <snip>_

 

Wow nice job Vaughn! It's no wonder the students are starving, you take away their cookware


----------



## CaptHowie

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_CaptHowie, if I add these optional caps/resistors this is exactly how I would connect/add them to Pete's original schematic... *however* before I do I'll need someone here first to kindly verify my diagram! thanks 
	

	
	
		
		

		
		
	


	




 zk



_

 

Thanks heaps for that zkool448, should be greatly helpful 
	

	
	
		
		

		
		
	


	




 Edit: Yes! 50th post


----------



## csroc

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Great job Vaughn! That amp has a lot of vintage flair._

 

Agreed, really neat.


----------



## iareConfusE

Any suggestions for the volume knob? I didn't see it on the BOM and I'm not sure what the dimensions should be. I looked at the manufacturer's page for the potentiometer, and couldn't find any knobs that matched the shaft's dimensions.

 Also, will pre drilled face plates for the Hammond case be sold or are we going to have to drill them ourselves?


----------



## MoxMonkey

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Any suggestions for the volume knob? I didn't see it on the BOM and I'm not sure what the dimensions should be. I looked at the manufacturer's page for the potentiometer, and couldn't find any knobs that matched the shaft's dimensions.

 Also, will pre drilled face plates for the Hammond case be sold or are we going to have to drill them ourselves?_

 

most likely will have to do all the casework on our own, although i'm sure someone can whip up some templates


----------



## iareConfusE

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_most likely will have to do all the casework on our own, although i'm sure someone can whip up some templates_

 

Templates would help quite a bit, I also need to buy a drill now D:


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_most likely will have to do all the casework on our own, although i'm sure someone can whip up some templates_

 

Plenty of drawings will be available on the website when it's finished - just as I've done for the MAX and MiniMAX.


----------



## gurusan

Sorry, what's the purpose of the 50k resistors before the pot?


----------



## scompton

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Sorry, what's the purpose of the 50k resistors before the pot?_

 

To reduce gain and allow you to use the middle portion of the pot instead of just the first few degrees


----------



## gurusan

ah got it thanks.


----------



## V-DiV

Vaughn;5438139 said:
			
		

> Just finished my SS and I'm listening to it now...
> 
> It is built into the cast aluminum enclosure of an old piece of cookware. Easy to service clamshell construction...
> /QUOTE]
> ...


----------



## nightanole

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think you answered your question.
	

	
	
		
		

		
			



_

 

So which set of .22uf should i use for c2,c4 and which set for c3a/c5a. I have vitamin c's and mouser ones.


----------



## Vaughn

thanks for the compliments...

 I'm not super impressed with this 100k stepped attenuator I purchased off
 the "Bay". The switching mechanism is not very high quality and causes more of a tracking problem than a typical carbon pot. If I continue to use it as a dedicated unit out of a Squeezebox I might replace it with a resistor.


----------



## tomb

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_So which set of .22uf should i use for c2,c4 and which set for c3a/c5a. I have vitamin c's and mouser ones._

 

If you're asking for a choice, I would use the Wima's as the interstage couplers and the Vitamin Q's as output coupler bypasses (C3a/C5a). (Vitamin c's go in your stomach.
	

	
	
		
		

		
		
	


	




 )


----------



## manaox2

No way I could still PCB mount the RK27 if I wanted on the production PCB is there?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_No way I could still PCB mount the RK27 if I wanted on the production PCB is there?_

 

No. Air-wire, yes - PCB mount, no. It can't be done in the PCB design, either - without putting the RK27 in an entirely different location. Since it violates the 20mm restriction, too, there seemed little point. If you build the SSMH PCB for the larger Hammond "N" case, you would want to air-wire the pot and perhaps the headphone jack, too, just to get them somewhere in the middle of the endplate.


----------



## kellvyn

Quote:


  Originally Posted by *Vaughn* /img/forum/go_quote.gif 
_Just finished my SS and I'm listening to it now..._

 

Vaughn,

 What did you use for terminal strips? Are working with those easier than working with the Keystone strips from the BOM?


----------



## Vaughn

The terminal strips in the BOM appear to be very similar to the type sold at Radio Shack, which I dislike. They have tinned steel lugs, which are magnetic. 
 I like to build up my point to point projects with teflon terminal strips. I had some sheet teflon which I cut into strips and drilled small holes to use as tie down points, which were later soldered. I have also made terminal strips with this material with copper eyelets and a couple of times with sterling silver eyelets. You can buy very high quality terminal strips from various sources, but I don't know if it is really worth the extra cost considering the scope of this project. If you can make your own, though, I highly suggest it.

 There you go, probably more than you wanted to know!


----------



## tomb

Never mind - another post deleted. I need to wake up fully before posting sometimes.


----------



## Bleuburd

How hard will it be to air wire some boutique capacitors? I was thinking about trying to source out some higher end (not too high end to stay starving
	

	
	
		
		

		
		
	


	




) parts and just air wiring them. I'm a first timer, so that probably makes a difference as well.


----------



## Hayduke

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_How hard will it be to air wire some boutique capacitors? I was thinking about trying to source out some higher end (not too high end to stay starving
	

	
	
		
		

		
		
	


	




) parts and just air wiring them. I'm a first timer, so that probably makes a difference as well._

 

Several builders have used boutique parts. You could always air wire the whole amp. That's what everyone has done so far. Has anyone built up a prototype PCB yet?


----------



## royewest

The proto PCB arrived last night but I won't have a all the components until at least Monday. I'll probably have it built within a day or two of having all the pieces. It should be a very quick build to listen to - a little longer to do the case work to finish that part up.


----------



## nightanole

SNiff sniff. Got tubes, got power supplies, hell even got my beezer order. Come on mouser order.


----------



## Vaughn

I bypassed my output caps with some 10uf Solen poly's I had on hand and it definitely improved the sound...

 I am going to build a second SS and have some nice 3.3uf pio caps that I would like to use. Would these be too large for C2 and C4? If so I can just 
 use them as output bypass caps.


----------



## n_maher

Well as far as I can tell the prototype boards are a success. Great work Tom and Doug, I'll provide pictures tomorrow morning. It's late and I need sleep!


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Well as far as I can tell the prototype boards are a success. Great work Tom and Doug, I'll provide pictures tomorrow morning. It's late and I need sleep!_

 

Dang! You never could be beat for speed-building.
	

	
	
		
		

		
			





 I guess the pics will tell, but you cased them up, right? How's the heat and the MOSFETs. Did you use a heat sink?

 Wake up!


----------



## n_maher

Nah, no casework yet, just stock heat sinks hanging off the back of the pcb. I'll be ordering a proper chassis for it this week. Here's what I got done last night.











 It uses a lot of the parts from Pete's original BOM plus some caps that you sent me (thanks!) and some SonicCap GenII's that I had kicking around. The input is just a temporary jack that I use for testing. In fact it's the only use I've ever found for those awful locking jacks.


----------



## tomb

Wow - very nice, Nate! Cool way to test the circuit on an interim basis before casing it up, too. I didn't think about using some spare heat sinks while getting the case ready.

 Yes, those caps are what we're spec'ing as ideal for the SSMH when using the Hammond "L" case, which only allows a 20mm height. The large caps are 680uf 63V Panasonic FC's. The smaller ones are the new Nichicon Muse KW's at 470uf 63V. The KW'S are a slightly lower grade boutique than Muse KZ's - but definitely audio/signal quality grade. With those and the addition of bypass film caps on the output, a very good quality sound should result.

 I'll have plenty of those FC's in stock at Beezar - and DigiKey has a bunch, too. Unfortunately, Mouser does not stock the UPW version, although it is listed (13 week lead time!). The KW's are in short supply, too - Mouser is now out, but I'll have a bit of a stock to last for a little while.

 EDIT: The whole PCB looks ridiculously simple, doesn't it? Dsavitsk has a good layout! I don't think anyone will have trouble assembling the board. Hopefully, casing it up won't be too difficult either.


----------



## zkool448

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Nah, no casework yet, just stock heat sinks hanging off the back of the pcb. I'll be ordering a proper chassis for it this week. Here's what I got done last night.

http://www.pbase.com/n_maher/image/109405113.jpg
http://www.pbase.com/n_maher/image/109405111.jpg_

 

Hey Nate, looks great and I've always admired the neatness and attention to details with your builds. 

 Did you notice any differences (if any) between your original mssh and this one in terms of sq? 

 zk


----------



## nightanole

Any one have any luck opened the stock power supply? Short of dremmeling or chewing it open ive run out of ideas. Popping the sides doesnt work, and there isnt any screws under the label.


----------



## n_maher

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Hey Nate, looks great and I've always admired the neatness and attention to details with your builds._

 

Thanks! But as Tom said, there really isn't much to stuffing this board. I'd say it took me around an hour to do what you see above and I'm not the fastest.

  Quote:


 Did you notice any differences (if any) between your original mssh and this one in terms of sq? 

 zk 
 

I can't say. I used different headphones last night (DT770s) than I do at work (KSC35s). I can say that I thought it sounded quite good fed by my Ipod Touch.


----------



## tomb

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Any one have any luck opened the stock power supply? Short of dremmeling or chewing it open ive run out of ideas. Popping the sides doesnt work, and there isnt any screws under the label._

 

Why would you want to open the power supply? Most likely, it's glued anyway.


----------



## tamasic1

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Any one have any luck opened the stock power supply? Short of dremmeling or chewing it open ive run out of ideas._

 

 Yes, they are epoxied. A dremel works but I've found it just as easy to place these things in a vice and with a couple light strokes of a hacksaw on each side the case falls apart. I'm thinking of doing that also, including the transformer (shielded of course) inside the case. 

 Hi all! Great project, especially for a beginner. A lot of good info on mods and great guidance from experianced members for those of us just getting started. The builds are creative and pics really motivated me to build one. 

 This is going to be a seriously recycled SS project. I found I had all the parts needed for this (except the tubes and sockets) on the PCBs of two UPS and one server PS. I'm going for a p2p build but that SS PCB looks awesome!


----------



## rds

Ha ha, that's cute with the little sonicaps. Looks great!


----------



## gurusan

that looks great! I want one!!


----------



## dsavitsk

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_



_

 

Looks good, Nate. A note to other builders. You might want to mount the mosfets from the other side of the board if you intend to use the top of the case as a heatsink -- bent over backwards as shown here (picture taken from tubelab.com -- if you need a SE power amp, talk to tubelab.) 






 As Nate has them, they may not reach the lid for bolting down.


----------



## nightanole

In other news, jb weld is not electrically conductive, and conducts heat better then aluminum. In theory this could help alot when attaching the mosfets. Back in the water cooling days you could attach a water block to your cpu using just jb weld, and ive encased hot regulators on video cards with no problems.


----------



## nightanole

I think i found the best case yet.

Brand New Aluminum Project Box Electronic DIY #33 - eBay (item 250364921714 end time Feb-27-09 19:48:53 PST)


----------



## Sodacose

Ooh, very nice case! Hard to tell from the pic, but do only the sides open up? That might be a bit difficult to wire in the tight space (my 4x4" box was as small as I'd like to go and the top came off). Of course, with a PCB (vs PTP) it probably wouldn't be as big of a deal.

 I've used one of these for a build:

Aluminum Project Box Enclousure Case Electronic DIY-Mid - eBay (item 250343308549 end time Mar-14-09 21:01:18 PDT)

 My SS is currently in a steel case though. The next one is going in aluminum! That steel was a PITA to work with (but looks oh so industrial when done).


 On another note, I've encountered something strange with my SS. I have a lamp that when plugged in in the same room as the SS creates a hum when off. I've found this before with other things causing hum when on, but not when off! Any ideas as to what might be causing this?


----------



## MoxMonkey

i'm guessing it should be possible to air wire the mosfet as well so long as we solder the correct resistor to the leg and then just wire it right?


----------



## rds

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_Ooh, very nice case! Hard to tell from the pic, but do only the sides open up? That might be a bit difficult to wire in the tight space (my 4x4" box was as small as I'd like to go and the top came off). Of course, with a PCB (vs PTP) it probably wouldn't be as big of a deal.

 I've used one of these for a build:

Aluminum Project Box Enclousure Case Electronic DIY-Mid - eBay (item 250343308549 end time Mar-14-09 21:01:18 PDT)

 My SS is currently in a steel case though. The next one is going in aluminum! That steel was a PITA to work with (but looks oh so industrial when done).


 On another note, I've encountered something strange with my SS. I have a lamp that when plugged in in the same room as the SS creates a hum when off. I've found this before with other things causing hum when on, but not when off! Any ideas as to what might be causing this?_

 

It's probably a touch on lamp


----------



## sachu

well, I just powered up mine with the tubes and found that the voltage on pins 3 of the tubes I am getting 21.1V on one and full 48V on the other..

 Any idea how this could be?


----------



## nightanole

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_well, I just powered up mine with the tubes and found that the voltage on pins 3 of the tubes I am getting 21.1V on one and full 48V on the other..

 Any idea how this could be?_

 

48v is source, the most direct route (and only) is from the transistor. Im guessing your not hooked up to the heaters. There is no way your putting 48v across a 19v heater and it surviving. The whole design is that the output is a ac signal with a 19v dc off set. 

 IN order to get the DC off set (the 19v for heaters) i believe it goes through a voltage divider from the 48v source to set the drain limit. so half the voltage divider is R13 and R2, and the other half is R4. So since r13+R2 is higher then R4 you get 19v out (if they were equal you would get 24v out, half the input). in other news i could be completely wrong. If you saturated the input of the transistor it could send full source (doesnt limit drain at all and "looks" like a short to the source) to the output, which would explain your 48v off set.

 Thinking about it more, check R4.

http://tubes.mkdw.net/sheets/093/6/6J6.pdf


----------



## tamasic1

Most of the caps I've scrounged so far are good quality Nichicon PLs but ran into a problem with the 680uF caps as they're only 35v. I remember Pete posting that C5 could be 1000uF but does that apply to C1 also?


----------



## sachu

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_48v is source, the most direct route (and only) is from the transistor. Im guessing your not hooked up to the heaters. There is no way your putting 48v across a 19v heater and it surviving. The whole design is that the output is a ac signal with a 19v dc off set. 

 IN order to get the DC off set (the 19v for heaters) i believe it goes through a voltage divider from the 48v source to set the drain limit. so half the voltage divider is R13 and R2, and the other half is R4. So since r13+R2 is higher then R4 you get 19v out (if they were equal you would get 24v out, half the input). in other news i could be completely wrong. If you saturated the input of the transistor it could send full source (doesnt limit drain at all and "looks" like a short to the source) to the output, which would explain your 48v off set.

 Thinking about it more, check R4.

http://tubes.mkdw.net/sheets/093/6/6J6.pdf_

 


 IT looks like I might have saturated the transistor..there is almost full 48V on the gate of the transistor which could mean I fried the transistor....but also means the voltage divider is not working..or I have wired something wrong..pin 1 of the transistor could be shorted somewhere to full DC...Going to check it again..

 Also, did a quick check and saw that I had gotten the wiring on the tube socket backwards..wired pin7 as pin 1 and vice versa ..
	

	
	
		
		

		
		
	


	




 I have used the components in the original BOM except for 220uF for the input caps and 1000uF for the output caps.


 Found another stupid mistake..had used 3.3k instead of 33k (really stupid of me..should remember not to do this stuff when I am groggy at 2 in the morning)..I replaced those now..But still the problem persists..

 GOing to redo the network with the 220k/33k resistors again later and see what comes off it...


----------



## nightanole

If i can get some thing backwards, i will get something backwards. I was double checking everything today, and the beezer vitamin q's and the .22 squares from beezer dont appear to have a polarity, but the schematic has them polarized. Are they polarized, and if so which side is what on the caps? Also can you dumb down the pins of the mosfet for me? I have no clue which is pin 1,2,3.


----------



## sachu

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_If i can get some thing backwards, i will get something backwards. I was double checking everything today, and the beezer vitamin q's and the .22 squares from beezer dont appear to have a polarity, but the schematic has them polarized. Are they polarized, and if so which side is what on the caps? Also can you dumb down the pins of the mosfet for me? I have no clue which is pin 1,2,3._

 

HI,

 I assume you are asking about C2 and C4. I am using standard 0.1uF box film capacitors..so they are non polar...

 Pin 1 of the transistor is the Gate...There is something seriously wrong in the input to the ate of the transistors if I have almost VDD on the gate..

 Pin3 is the source and pin 2 is the drain...


----------



## tomb

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_Most of the caps I've scrounged so far are good quality Nichicon PLs but ran into a problem with the 680uF caps as they're only 35v. I remember Pete posting that C5 could be 1000uF but does that apply to C1 also?_

 

Yes. If you are building P2P, you can pretty much put whatever you want in there, assuming you've met the minimums. However, 35V is too low.
  Quote:


  Originally Posted by *nightanole* 
_If i can get some thing backwards, i will get something backwards. I was double checking everything today, and the beezer vitamin q's and the .22 squares from beezer dont appear to have a polarity, but the schematic has them polarized. Are they polarized, and if so which side is what on the caps? Also can you dumb down the pins of the mosfet for me? I have no clue which is pin 1,2,3._

 

Polarity is always shown on a schematic in case someone uses a cap that has polarity.
	

	
	
		
		

		
		
	


	




 The VitaminQ's don't care.

 The first thing you should ever do when having a question about a MOSFET, transistor, opamp, tube, etc. - is to look at the data sheet. These are easily accessible when you order from Mouser or elsewhere. There are also a number of websites that provide data sheet lookup. For most parts, the pin arrangement is one of the first things detailed on the data sheet.

 In the case of MOSFETs, the pins are usually labeled Gate, Drain, and Source. These correspond to pins 1, 2, and 3 on Pete's schematic. Here's a link to a datasheet for the IRF510:
http://www.diyforums.org/SSMH/mosfet/91015.pdf

 EDIT: Oops - Sachu beat me to it.


----------



## sachu

Quickly checked Vgs..it is showing up as 0V..which is right as I seem to have 48V on both the gate and the source terminals..

 BUt having 48V on the source is definitely wrong..and so is having 48V on the gate me thinks..


----------



## tamasic1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes. If you are building P2P, you can pretty much put whatever you want in there, assuming you've met the minimums. However, 35V is too low_

 

Thanks. Forgot to mention the 1000uf were 200v.


----------



## nightanole

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Quickly checked Vgs..it is showing up as 0V..which is right as I seem to have 48V on both the gate and the source terminals..

 BUt having 48V on the source is definitely wrong..and so is having 48V on the gate me thinks.._

 

3 legged piece of wire? pin 2 should be 48v on the mosfet. How you got 48v on the gate seems im possible since its a voltage divider if you simplify it, its only 3 resistors.

 If you are as far as got the tubes wired correctly (not backwards as in 8 hours ago), id dike the lead to pins 1,2 (im assuming its the right channel) and the lead to c3. If you know the heater impedance when its hot, you can pop in a resistor in pins 3-4 and you will have a very simple circuit to trouble shoot without the tube.


----------



## Sodacose

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_It's probably a touch on lamp 
	

	
	
		
		

		
		
	


	


_

 

It has a mechanical switch if that's what you mean?

 It isn't a big deal, I can always unplug the lamp; just seems like a strange problem (and it only occurs in one channel).


----------



## rds

Quote:


  Originally Posted by *Sodacose* /img/forum/go_quote.gif 
_It has a mechanical switch if that's what you mean?

 It isn't a big deal, I can always unplug the lamp; just seems like a strange problem (and it only occurs in one channel)._

 

It is strange, and I don't understand the subtleties, but it should occur in the tube closest to the lamp. Somehow the lamp is acting as an antenna and transmitting the 60 hz hum of the live wire to your tube.


----------



## Sodacose

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_It is strange, and I don't understand the subtleties, but it should occur in the tube closest to the lamp. Somehow the lamp is acting as an antenna and transmitting the 60 hz hum of the live wire to your tube._

 

Yes, it definitely seems to be a 60hz humming. I'll fool around with placement. For a while I was fooling around with the innards, thinking I had some kind of short or bad ground. I couldn't for the life of me figure out what would create the AC hum with the DC PS. Then I happened to turn the light on/off a couple times and noticed this was affecting it.

 I'll have to find a lamp DIY forum.


----------



## royewest

You also might try a temporary, grounded aluminum foil shield around your tubes, to see if that helps -- or even around one tube would be interesting....

 (everything I know I learned on Head-Fi)


----------



## Sodacose

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_You also might try a temporary, grounded aluminum foil shield around your tubes, to see if that helps -- or even around one tube would be interesting....

 (everything I know I learned on Head-Fi)_

 

Actually that reminds me that the tube sockets I bought have spring-shield things included. The collars on the sockets should be grounded through the chasis. I'll pop those shields on and see if that makes a difference.

 EDIT: Worked like a charm! Thanks!


----------



## iareConfusE

Has anyone found a suitable knob for the pot yet?


----------



## nightanole

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Has anyone found a suitable knob for the pot yet?_

 

450-6010


http://www.pmillett.com/images/starving/rds_1.jpg


----------



## iareConfusE

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_450-6010


http://www.pmillett.com/images/starving/rds_1.jpg_

 

Sorry I forgot to specify, does that knob work for the pot provided in the BOM for the PCB Starving Student? I looked at the specs of the pot shaft, but I couldn't seem to find any knobs that matched the dimensions.


----------



## nightanole

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Sorry I forgot to specify, does that knob work for the pot provided in the BOM for the PCB Starving Student? I looked at the specs of the pot shaft, but I couldn't seem to find any knobs that matched the dimensions._

 

It works fine with the orginal bom 50k. The shaft is .24"( i measured it with a caliper) so any .25"( 1/4") knob will work. I just installed it in my case and it works fine.


----------



## nightanole

Where does one find copper foil for cheap? Home depot doesnt have it. I havent tried some stained glass places yet.


----------



## Sodacose

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Where does one find copper foil for cheap? Home depot doesnt have it. I havent tried some stained glass places yet._

 

Hobby stores aka Michael's in the states. Usually comes with adhesive backing as well.


----------



## Yaka

well my lovley proto board arrived today and gotta say you guys did a great job 
 bad news was that i lost my pouch with all my parts inside. stupid bus driver wouldnt stop while i was running after the bus like a lunatic


----------



## -=Germania=-

You can find the copper PCB blank board at Radio shack for ~$6-7 I believe. 

 If you are trying to shield something, steel foil from the grocery store works. If you need it for the ground plane - the above works well. Still, I prefer a star ground. - less confusing and less likely to have a short.


----------



## kellvyn

Quote:


  Originally Posted by *Vaughn* /img/forum/go_quote.gif 
_The terminal strips in the BOM appear to be very similar to the type sold at Radio Shack, which I dislike. They have tinned steel lugs, which are magnetic._

 

Why is it a problem if the lugs are magnetic? (I hope that's not a stupid question!)


----------



## manaox2

Quote:


  Originally Posted by *kellvyn* /img/forum/go_quote.gif 
_Why is it a problem if the lugs are magnetic? (I hope that's not a stupid question!)_

 

Sometimes good to help clean power, magnets may do negative things for analog flow of a signal. Nickel is also ferrous, so I often tend to avoid it also whenever possible.


----------



## Hayduke

Quote:


  Originally Posted by *kellvyn* /img/forum/go_quote.gif 
_Why is it a problem if the lugs are magnetic? (I hope that's not a stupid question!)_

 

Magnetic fields induce current. Technically, if the magnets don't move they don't "create" current, but the magnetic field that is present can also affect existing currents. That's a bad thing since your music signal is a current.


----------



## royewest

I spent this evening building up the prototype SSHM PCB from TomB.

 It took a full evening, but when I connected it up: lovely music!

 I have a few technical nits to pass on to TomB, but the build was completely straightforward. I have not yet tackled the casework -- more on that later.

 But in the mean time, thanks to TomB, DSavitsk, and as always Pete Millett for another wonderful amp.


 P.S. Of course, the heat sinks are temporary (and hot, by the way). And I'm sorry about the photography -- a lifelong handicap.


----------



## cfcubed

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_ < snip >
 P.S. Of course, the heat sinks are temporary (and hot, by the way)._

 

One thing I learned doing my compact hybrid build I'd like to share WRT case-mounting devices as heatsinking... Depending on case size + dissipation, you may not like the result. Haven't followed this, so don't know the dissipation here or whether there is already a full, target-case proto using case-mounting as heat-sinking (or even if that's the plan
	

	
	
		
		

		
		
	


	




 The main heat-producer in the CTH other than the tube is it's LV reg. I measured its apparent dissipation at about 1.5W (not so much). When case-mounted it brought the entire enclosure to about 50C (albeit, a bit smaller enclosure then this PCB build is shooting for)... I'd consider use of a proper heatsink instead, be it internal (w/assoc air holes) or external. When I did this, the case temp dropped nicely.
 It's really personal opinion tho because the components are perfectly happy at such temps even if your hands aren't
	

	
	
		
		

		
		
	


	




 Just something to think about...

 tomb - If you think this post is not applicable here, just let me know.


----------



## tomb

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_One thing I learned doing my compact hybrid build I'd like to share WRT case-mounting devices as heatsinking... Depending on case size + dissipation, you may not like the result. Haven't followed this, so don't know the dissipation here or whether there is already a full, target-case proto using case-mounting as heat-sinking (or even if that's the plan
	

	
	
		
		

		
			





 The main heat-producer in the CTH other than the tube is it's LV reg. I measured its apparent dissipation at about 1.5W (not so much). When case-mounted it brought the entire enclosure to about 50C (albeit, a bit smaller enclosure then this PCB build is shooting for)... I'd consider use of a proper heatsink instead, be it internal (w/assoc air holes) or external. When I did this, the case temp dropped nicely.
 It's really personal opinion tho because the components are perfectly happy at such temps even if your hands aren't
	

	
	
		
		

		
		
	


	




 Just something to think about...

 tomb - If you think this post is not applicable here, just let me know._

 

No problem, cfcubed.
	

	
	
		
		

		
		
	


	




 The Starving Student thread takes input from the whole community.

 I strongly suspect that we will need to slap a heat sink on the top of the case, but have left that conclusion up to real findings. You note the small 1.5W in your CTH, but was it actually mounted to the case metal? There's a big difference in that respect. I know in building several MAXes, just the addition of the handle bars (heavy-weight drawer pulls) on top of the MAX cases brought the case temperature down significantly, regardless of how much was generated inside.

 Again, Dsavitsk has suggested that heat sinks may not be necessary when the MOSFETs are bolted directly to the lid. His findings were based on the Hammond "N" case, though, which has more metal than the "L" case we're attempting to use for the SSMH PCB. So, the question remains whether the "L" case can reject that heat. I'm think the addition of an exposed heat sink - or a couple of drawer pulls - whether they're directly connected to the MOSFET bolts or not, may be all that's necessary to make up the difference in exposed metal from the "N" case to the "L."

 That's the reason we're prototyping, though.


----------



## cfcubed

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ < snip > You note the small 1.5W in your CTH, but was it actually mounted to the case metal? < snip > I'm think the addition of an exposed heat sink - or a couple of drawer pulls - whether they're directly connected to the MOSFET bolts or not, may be all that's necessary to make up the difference in exposed metal from the "N" case to the "L."

 That's the reason we're prototyping, though.
	

	
	
		
		

		
		
	


	


_

 

Thanks for the quick response... Sounds good on all counts... My LV reg was directly mounted to case _bottom_ & case had no extra metal of any kind... So that was probably less than ideal as the heat had too travel to far to be dissipated, etc.

 Didn't think of the handles that way... Thanks! And yes these things are what prototyping is about


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's the reason we're prototyping, though.
	

	
	
		
		

		
		
	


	


_

 

Tom,

 My suspicion is that regardless of case (since the top lid is essentially the heat sink and the same for both cases) is that we may end up using something like I did on the Menace. The three heat sinks in the center of the chassis are just adhesive backed pieces that I got from Mouser.






 I have a couple left from that build so I'll be able to try them on my SSH as soon as the chassis shows up (hopefully today).


----------



## tomb

Agreed, Nate. Those maybe just the ticket. I believe rds is working on a similar tack. The important thing to note for simplicity is that once the MOSFETs are bolted to the case lid, it shouldn't take any sort of elaborate mechanical connection to slap auxuliary heat removing devices on the lid.


----------



## lowendfrequency

Does anyone know of an adequate replacement for the heatsinks (657-15ABP)? Mouser just ran out last night. This one (647-15ABP) seems to be identical other than the fact that it's a touch heavier which changes the thermal characteristics ever so slightly. 

 I'm about to attempt this as my first DIY electrical project in 12 years... so as soon as something doesn't match my BOM or schematics, I start to panic.


----------



## kuroguy

Just make sure the performance is similar on whatever heatsink you use and you'll be fine.


----------



## kuroguy

duplicate post....


----------



## zkool448

Quote:


  Originally Posted by *lowendfrequency* /img/forum/go_quote.gif 
_Does anyone know of an adequate replacement for the heatsinks (657-15ABP)? Mouser just ran out last night. This one (647-15ABP) seems to be identical other than the fact that it's a touch heavier which changes the thermal characteristics ever so slightly. 

 I'm about to attempt this as my first DIY electrical project in 12 years... so as soon as something doesn't match my BOM or schematics, I start to panic._

 

Since the heatsinks do get pretty hot, you can opt for the taller ones (1/2" more) and they're currently in stock. Good luck with your build!

 From the data sheet:
 P/N 
637-15ABP G 1.500 (38.1) 1.375 (34.9) x 0.500 (12.7) 65°C @ 6w 5.5°C/W @ 200 LFM 0.035 (15.88)
637-20ABP G 2.000 (50.8) 1.375 (34.9) x 0.500 (12.7) 55°C @ 6W 4.7°C/W @ 200 LFM 0.050 (22.68)


----------



## n_maher

I have a bunch (12 or so) of the 1-1/2" heatsinks that are already tapped with 4-40 threads that I will probably list for sale in the next few days. They came out of a beta22 but are exactly what I used for my first SSH.


----------



## nightanole

Man mouser is running out of everything. Soon everyone will just have pcbs and tubes, and no caps or heatsinks


----------



## n_maher

Well, my top and front panels are done, time to watch LOST and then I'll either get to the back panel or fire it up as is.


----------



## n_maher

Soup to nuts total is about 4hrs. Apologies for the dirty chassis and lack of internal pics. I'll take care of both tomorrow night but for now you'll just have to imagine.


----------



## n_maher

bitten by the ghost in the machine again


----------



## iareConfusE

Looks clean and neat, good job. Mind making some printable templates for the front pot and output jack, please?


----------



## MoxMonkey

looks great but is it just me or is there no power switch?


----------



## iareConfusE

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_looks great but is it just me or is there no power switch?_

 

Interesting, totally forgot about the power switch. I don't think it could be in the pot, since its the same pot that was in the original P2P BOM.


----------



## rds

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Agreed, Nate. Those maybe just the ticket. I believe rds is working on a similar tack. The important thing to note for simplicity is that once the MOSFETs are bolted to the case lid, it shouldn't take any sort of elaborate mechanical connection to slap auxuliary heat removing devices on the lid._

 

Yes, I think I have just the ticket but since we don't have a dimensional board layout right now I'm not totally sure.
 It would be fairly trivial to attach but would require a pdf template for trouble free assembly.
 ...now I just need to have that pcb show up.


----------



## n_maher

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Looks clean and neat, good job. Mind making some printable templates for the front pot and output jack, please?_

 

Thanks for the compliments. I have to be honest, when it comes to complicated top panels or back panels that are stuffed with components like the MAX I'm all for templates for helping people out. But this is two holes and all you have to do is stick the board in whatever slot you chose, measure the height and distance to the side and you're done. Also, I didn't use the slot that Tom recommended so my build is probably "non standard" and is at best still just a prototype.
  Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_looks great but is it just me or is there no power switch?_

 

No power switch. Didn't have one that I wanted to use so I finished it up without one. It will certainly be added later.


----------



## iareConfusE

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Thanks for the compliments. I have to be honest, when it comes to complicated top panels or back panels that are stuffed with components like the MAX I'm all for templates for helping people out. But this is two holes and all you have to do is stick the board in whatever slot you chose, measure the height and distance to the side and you're done. Also, I didn't use the slot that Tom recommended so my build is probably "non standard" and is at best still just a prototype.
 No power switch. Didn't have one that I wanted to use so I finished it up without one. It will certainly be added later._

 

Alright thanks anyway. Another question though. I've never used anything that utilized the terminal blocks. Obviously, the one labeled IN is for the sound input, but I notice there are two others that seem like 1 block of 4 terminals. I'm guessing one pair of terminals is for the switch, and the other for the DC input jack, but does it matter their hookup orientation apart from pos/neg (which I'm not even sure about since its labeled O1, O2) ? Ex: Can the dc power input be wired to the left block (of 2 terminals) or the right block?

 Is the B+ and G markings supposed to be a label for something other than the switch?


----------



## dsavitsk

Quote:


  Originally Posted by *iareConfusE* /img/forum/go_quote.gif 
_Is the B+ and G markings supposed to be a label for something other than the switch?_

 

B+ is standard terminology for positive voltage. So, you connect the power to B+. G, similarly, is for the ground connection from the power supply. Switch is where you connect the two connectors from a SPST switch. The O1, O2, ... business are pin labels, much like an opamp socket might label pin 1 with no inherent meaning. If you use the terminal blocks, those labels will be covered anyway.


----------



## iareConfusE

Thanks for clearing it up for me Dsavitsk. Hopefully my last question: Is the standoff required? I'm not exactly sure how its used (even after reading the description off of Beezar). I know how its installed, I'm just unsure of its use.

 thanks again.


----------



## n_maher

I did not use a standoff and things seem reasonably secure. Internal pics coming later tonight to show folks how I did things.


----------



## nightanole

Uh i just broke my 50k pot. All i have left is 2 47k resistors and a 27k pot. Whats gonna happen if anything, since im only using it on under 100ohm cans?


----------



## Fitz

The pot only determines input impedance and how much it loads the source, it has nothing to do with the output of the amp (nor does the value of the pot have anything to do with the volume range, a 27k pot at halfway yields the same volume as a 50k pot at halfway, assuming the attenuation curve isn't different between them).

 And @Vince: Needs moar blackgates.


----------



## n_maher

It's just a prototype Fitzy, moar BG's next time.


----------



## grawk

That's an awesome build nate.


----------



## nightanole

I just hooked up my tube to a dc power supply to see if the heater worked (cheap thrill). at 19v the 2 heaters combined sucked 300 ma. That means the poor .38a 48v power supply is going to be working over 50% duty to keep everything going. No wonder it shuts down if you dont have at least 480uf on the ps line while the heaters warmed up.


----------



## n_maher

Thanks Dan! Here are a few internal shots along with a couple of notes:

 1. If you're a beginning builder please do not try the smaller case that Tom has listed. As you can see the working room in side this case from top to bottom is pretty tight. Do yourself a favor, use the larger chassis and some room to breath.

 2. Please note that I had to flip the orientation of the input terminal block. Facing out as it was when I first installed it made it impossible to get the board into the case with wires coming out. 
















 If I have time tonight I'll set the amp up running into a dummy load and take some thermal measurements after a few run time intervals. I had it going for less than a half hour last night but it certainly didn't overheat in that limited window.


----------



## tomb

You're right, Nate - the bigger case might be the way to go. I've been getting a couple of e-mails from another prototyper who's been having a bit of trouble with the other case. It sounds like the tube sockets rise up above the case lid pretty high, which may not look too good. He also mentioned about the input terminal block clearance.

 EDIT: Correct that - he's saying the actual board pads from the input terminal block rub in the slots - also R7 and R10. I'm sure Dsavitsk can correct all of this on the production boards, though.


----------



## tintin47

Do you guys know any good sources for the tubes for this amp? I am looking into building one buy I can't find any tube sources without 4-6 week lead time.


----------



## Swingtops

Quote:


  Originally Posted by *tintin47* /img/forum/go_quote.gif 
_Do you guys know any good sources for the tubes for this amp? I am looking into building one buy I can't find any tube sources without 4-6 week lead time._

 

The Tube Center is probably your best bet. Make SURE you order by phone - I sent my order from their website and got no response for about a week, then after two more weeks of phone calls I did get the tubes all in great shape and working. Orlando Vacuum Tubes 

 And when you call the guy will answer as ESRC so don't be confused - this is the place you are looking for.


----------



## iareConfusE

Apparently the PCB's will be sold with a pair of matched tubes.


----------



## tamasic1

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_The Tube Center is probably your best bet. Make SURE you order by phone - I sent my order from their website and got no response for about a week, then after two more weeks of phone calls I did get the tubes all in great shape and working. Orlando Vacuum Tubes 

 And when you call the guy will answer as ESRC so don't be confused - this is the place you are looking for._

 

Thanks for the info. After a week I've not had a response from them so I'll give them a call.


----------



## n_maher

So after about 40 minutes the case temps are ~110 degrees F and seem to be holding there. This is the surface temperature of the top panel, the sides, front and back are all in the high 80s. I'll try to leave the amp running for a hour or more and see if it goes up any more but so far using the case as the heat sink seems to be working nicely. Sounds pretty darn good too, currently being fed by a Buffalo DAC that's got my Arcam CD73 as a transport.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_So after about 40 minutes the case temps are ~110 degrees F and seem to be holding there. This is the surface temperature of the top panel, the sides, front and back are all in the high 80s. I'll try to leave the amp running for a hour or more and see if it goes up any more but so far using the case as the heat sink seems to be working nicely. Sounds pretty darn good too, currently being fed by a Buffalo DAC that's got my Arcam CD73 as a transport._

 

Well, you know Dsavitsk has been saying that all along - no heat sinks required.

 Let's see if that holds for the smaller case, too - maybe 120 deg. on that one?


----------



## n_maher

After another 45 minutes it was up to almost 120F so this definitely bears watching. If I can I'll bring the amp to work with me next week and let it run for 4hrs or more to see if the gradual escalation continues or if there's a plateau somewhere. 120 is getting to the borderline of what I'd feel comfortable with and makes me start to wonder about the junction temps.


----------



## Fitz

Yeah, one thing I've noticed in other projects using the chassis as a heatsink is that it can take a few hours to stop rising in temperature and reach equilibrium. The more substantial the chassis, the longer it takes to reach that point, which can really give you a false sense of security.


----------



## iareConfusE

It would be possible to just bolt on a heatsink to the outside of the case with some thermal paste, wouldn't it? Would it work well?


----------



## Fitz

Certainly... just look at the link for the Menace in Nate's sig, that's exactly what he did there. The chassis will still rise up in temperature since it's still thermally coupled to the MOSFETs and heatsinks, but the cooling will be more effective than without.


----------



## zkool448

All this prototyping talk is making me more excited and I can't wait to get a hold of a PCB... although to be honest I've also been kinda busy with my own prototyping 
	

	
	
		
		

		
		
	


	




 I had an idea about a certain enclosure design I wanted to build for my next mssh, so off I go and began to model my case:





 Next, I headed over to the workshop and gathered some spare materials but all I had on hand were MDF boards, but that didn't stop me and I went cutting anyway 
	

	
	
		
		

		
		
	


	




 The case came together nicely and I couldn't really wait to get building the internals so I decided why not build another P2P mssh for now, but this time I included ALL of the parts in the BOM (i.e. incl. all the optional parts).





 Lastly, I had it all hooked up and fired it up in it's unfinished shell and wow... it sounds really nice!!! Thanks to Tomb and Dsavitsk for their additional design, and as always of course to Pete


----------



## adamus

I hate seeing perfect builds like that....damn my inadequacy.


----------



## gurusan

That is one awesome build. Very well done!


----------



## rds

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_So after about 40 minutes the case temps are ~110 degrees F and seem to be holding there. This is the surface temperature of the top panel, the sides, front and back are all in the high 80s. I'll try to leave the amp running for a hour or more and see if it goes up any more but so far using the case as the heat sink seems to be working nicely. Sounds pretty darn good too, currently being fed by a Buffalo DAC that's got my Arcam CD73 as a transport._

 

You didn't mention what the room temperate is. I think you'd need to run the amp for several hours in a hot room (25C +) to get a feeling for whether this is a good idea.


----------



## Fuzzy OneThree

For the BOM powerjack, which pin goes to the ground? I was able to use my MM to figure out which pin is which, but I am not sure whether to use the negative or the ground to wire to the ground.


----------



## n_maher

Ambient room temperature is around 65 deg F (18.3 deg C), maybe lower. So basically after an hour and a half the amp is roughly 60 deg F (33 deg C) above ambient. That's not that bad in my book but if it keeps going up in could get to the point where I'm not comfortable any more. As it was you wouldn't have wanted to keep your finger on the chassis for very long.


----------



## n_maher

Quote:


  Originally Posted by *Fuzzy OneThree* /img/forum/go_quote.gif 
_For the BOM powerjack, which pin goes to the ground? I was able to use my MM to figure out which pin is which, but I am not sure whether to use the negative or the ground to wire to the ground._

 

If you're using a DMM to figure out "which pin is which" how are you not able to determine which is the positive one? It's also written right on the power supply.


----------



## zkool448

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_If you're using a DMM to figure out "which pin is which" how are you not able to determine which is the positive one? It's also written right on the power supply. 
	

	
	
		
		

		
		
	


	


_

 

Hey Nate, I think what he's asking is on the dc jack as to which ground pin he should use -- there's the middle positive pin and also 2 potential ground connectors 
	

	
	
		
		

		
		
	


	




 Fuzzy, I use the one close to the jack edge and seems to work fine, not the one close to the middle/positive pin. That one is unswitched when the ps male jack is plugged in.

 zk


----------



## Fuzzy OneThree

I found the positive. I'm not sure whether to put the ground pin to the ground plane or the negative pin to the ground plane.

 EDIT: Thanks zkool. Use the negative pin for the dc jack.


----------



## n_maher

There is no "ground pin" on the DC jack. As zkool said, it's a switched jack and once the plug is inserted you have one positive and one negative "pin". If you don't connect the negative pin to the GND terminal I'd wager you'll be unhappy with the results. GND in this example is zero voltage potential and the power supply's negative pole is the reference that we want to set at 0.


----------



## Fuzzy OneThree

Ok, that makes a little more sense.


----------



## Yaka

i got some of my order delivered today but it seems like they sent me 2k2 resistors instead of 2k ones i ordered. are those ok to use?

 also zcool great work on the case can we have bigger pics with more closeups of your handy work please


----------



## Giuss

Hello,
 I've seen that the 19J6 tube is very hard to find, so I've a question

 Is it possible to use other type of tubes with 12.6v filament like ECC82 or ECC83 ?

 They need 150ma like the 19J6, so if I add a resistor I can use these filaments with a 19V supply

 For the original 19J6 : 19V / 0.15A = 127 ohm

 For the ECC82/83 : 12.6V / 0.15A = 84 ohms

 So a 43 ohm resistor in series to the 12.6V filament can do the job and the mosfet load doesn't change.

 What do you think about that?


----------



## dsavitsk

Sounds like a good solution to me. I have my doubts that the 12AX7 will overcome the fet's gate capacitance, and the gain is likely too high, so I think the 12au7 is the better choice here. AT7, AY7, and AV7 are all worth looking into as well depending on your needs. You'll want to fiddle with the Rk and Rp values most likely. Also, if you have sufficient heatsinking, no reason not to just bias the mosfet at 13 volts and drop the heat across it rather than adding a resistor.

  Quote:


  Originally Posted by *Giuss* /img/forum/go_quote.gif 
_Hello,
 I've seen that the 19J6 tube is very hard to find, so I've a question

 Is it possible to use other type of tubes with 12.6v filament like ECC82 or ECC83 ?

 They need 150ma like the 19J6, so if I add a resistor I can use these filaments with a 19V supply

 For the original 19J6 : 19V / 0.15A = 127 ohm

 For the ECC82/83 : 12.6V / 0.15A = 84 ohms

 So a 43 ohm resistor in series to the 12.6V filament can do the job and the mosfet load doesn't change.

 What do you think about that?_


----------



## ThePredator

Just finished mine and it is quite amazing for the size and price.


 Somehow I even managed to have it working on first startup, a rare situation.


 [EDIT]: The only problem I am having is microphonics, any light touch to even the desk it is on causes a sound. Is there any way to mitigate it?


----------



## Punnisher

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_Just finished mine and it is quite amazing for the size and price.


 Somehow I even managed to have it working on first startup, a rare situation.


 [EDIT]: The only problem I am having is microphonics, any light touch to even the desk it is on causes a sound. Is there any way to mitigate it?_

 

All tubes are different. My Sylvania tubes need a good flick to make a pinging noise. No problem in normal use.


----------



## zkool448

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_also zcool great work on the case can we have bigger pics with more closeups of your handy work please
	

	
	
		
		

		
		
	


	


_

 

Thanks Yaka, sorry about the previous pics I only had my phone cam with me at the time. Anyway, it's not quite ready but I managed to get most of the sanding done today. All it could use now is a fresh coat of paint. I'll try to post some more pics after I decide on a color 
	

	
	
		
		

		
		
	


	




 note: Bottom plate is made of frosted acrylic/plexiglass, the LCDs should make the bottom plate 'glow' in the dark (hopefully). 

 zk


----------



## CaptHowie

Awesome build. Wish I could do that


----------



## nightanole

What would be a good match with this unit for a source for 128kbs mp3's? Right now i have a nano2nd gen (cant imod). Should i get a pcm2702 based usb dac for $40 instead?


----------



## Giuss

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Sounds like a good solution to me. I have my doubts that the 12AX7 will overcome the fet's gate capacitance, and the gain is likely too high, so I think the 12au7 is the better choice here. AT7, AY7, and AV7 are all worth looking into as well depending on your needs. You'll want to fiddle with the Rk and Rp values most likely. Also, if you have sufficient heatsinking, no reason not to just bias the mosfet at 13 volts and drop the heat across it rather than adding a resistor._

 

Yes it is another solution, I think that the results are the same
 I don't know what tube can be a good replacement for the 19J6


----------



## -=Germania=-

Now just some case feet and a bit of tung oil - should look sick!!!!!!


----------



## Hayduke

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_What would be a good match with this unit for a source for 128kbs mp3's? Right now i have a nano2nd gen (cant imod). Should i get a pcm2702 based usb dac for $40 instead?_

 

With 128kbs MP3s, I think you will hear a minimal difference. I assume you're just using the built in soundcard on your PC? If you like to listen from the PC, look into the BantamDAC. It's less then $40, and since you DIYed this amp, the DAC should be doable. Tom makes some recommendations to help protect the DAC from the MHSS when it starts up. Take a look at the posts on the DAC thread here or on Tom's website.

 My recommendation is to build the DAC *AND* get better source files. My friend at work loves to test me to see if I can tell the difference between FLAC and a 320kbs MP3. I'll admit, I can't always tell, and when I do, sometimes I can't tell which is which, just that there is a difference. I *CAN* hear the difference between 192kbs and FLAC every time.

 You don't mention your headphones though. Some are more revealing then others


----------



## Vaughn

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Thanks Yaka, sorry about the previous pics I only had my phone cam with me at the time. Anyway, it's not quite ready but I managed to get most of the sanding done today. All it could use now is a fresh coat of paint. I'll try to post some more pics after I decide on a color 
	

	
	
		
		

		
		
	


	




 note: Bottom plate is made of frosted acrylic/plexiglass, the LCDs should make the bottom plate 'glow' in the dark (hopefully). 

 zk




_

 

I love this...

 I did architectural salvage for years and this looks like a bit of molding with some heatsinks and tubes stuck in it! I mean this in a good way, btw.

 I built two of these SS amps and was very impressed with their sound, and then promptly sold them. I am a little concerned about the availability of the 19J6 tube and as a confirmed member of team "cheap person" would like to stay with tubes on the cheap and available end of the spectrum...

 which is why I am very interested in the possibility of the 12au7 working in this circuit. I will follow developments with interest...

 ADDENDUM; with the way MDF seals up I just see black lacquer as the next logical step on that amp!


----------



## dBel84

I think that amp looks amazing - I would go fire engine red though 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## ThePredator

Has anyone used an AMB ε12 in their Starving Student? Seems like it would be the most elegant way to get rid of the pops/thuds on power on/off.


----------



## royewest

Here are a few sorry snapshots of what I did in my Mom's shop today (well, my Mom's retirement community has a nice shop set up by folks who passed years ago). 

 Obviously, my shop and photography skills are lacking, but I thought folks might be interested in seeing my implementation of the SSMH PCB built into the small Hammond, trying out my idea of mounting the heat sinks horizontally. 

 I cut two 1" wide slots into the top of the case, so I could slip the heat sinks into them, with sightly wider sections at the ends to accommodate the heat sink pins (you can't see it, but the case lid is now a W at that end, not a U). I also notched the tops of the end panel, to allow the pins to rest on them.

 I had to air-wire the MOSFETs with about an inch of wire to get them to reach the heat sinks.

 A few other notes:

 * As I mentioned to TomB by email, all three solder pads from the input connection block and the tips/solder pads for R7 and R10 (all on the tube socket side of the board, of course) are rubbing in the slots on the hammond. At TomB's suggestion, I put electrical tape over them, after filing them down as far as possible. In addition, the input block are very tight against the case when you have wire in them. I hope this can change in the production board.

 * If I do this again, I'll modify the tube sockets to sit lower and leveler, with respect to the PCB board. I think flush the way Nate did it looks best, but it will require some surgery to the socket pins.

 * I had to position the RCAs and the power jack low, to miss the heat sink parts inside the case. The stock switch doesn't fit in there. I just jumpered the switch for now -- probably will leave it like that.

 * I didn't include any LEDs -- the tubes are enuf for me.

 * I left R3 and R9 on the board -- I think wiser heads would have taken them off the board and connected them between the MOSFET 1-pins and the wire that connects the pins to the board.

 * I forgot to get a knob for the pot. Oh well -- I'll get one later.

 * I'll probably try to figure out how to put the heat sink bolt nuts inside the case, rather than leaving them nuts-up.

 * We'll see how the heat dissipation works; there are no vents in the case yet. After about .5 hour, the heat sinks are in the mid 120F degrees; slightly cooler than the tubes. Everything else is well under 100F.

 * Too bad about the scratches on the top of the case -- I realized too late I should have protected it. Perhaps I'll paint it later.

 Best of all, it's tiny and sounds great!

 Thanks again to TomB, cetoole, and Pete Millett. I really needed this kind of project to take my mind off things today, and it did that in spades.


----------



## exphy

Is there someone that could ship me a set of tubes. I'll pay for the tubes and shipping ofcourse(i'm located in the netherlands)


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Here are a few sorry snapshots of what I did in my Mom's shop today (well, my Mom's retirement community has a nice shop set up by folks who passed years ago). 

 Obviously, my shop and photography skills are lacking, but I thought folks might be interested in seeing my implementation of the SSMH PCB built into the small Hammond, trying out my idea of mounting the heat sinks horizontally. 

 I cut two 1" wide slots into the top of the case, so I could slip the heat sinks into them, with sightly wider sections at the ends to accommodate the heat sink pins (you can't see it, but the case lid is now a W at that end, not a U). I also notched the tops of the end panel, to allow the pins to rest on them.
 </snip>_

 

Ooh - looks great, but it sounds like a lot of work.
	

	
	
		
		

		
		
	


	




 There are some flat heat sinks that are available from Aavid, but I believe they have to be specially ordered. Or, the "rainbow" style we've seen a few times in this thread is also available stock from Mouser - ~$4.50, or somewhere thereabouts. Either one might have made this much easier.

 Still, fantastic work - send us more pics! We (me) would like to see other details - how the frontplate works out, a better idea of the socket height, etc., etc.


----------



## tamasic1

Hey, great builds Vaughn, Royewest!

 Anyone with tubes looking for power supplies? Send me a message if so.


----------



## zexnu

Here is my SS,this was my first p2p build,so it's kinda ruff looking on the inside.
	

	
	
		
		

		
		
	


	




[/url][/IMG]


----------



## zexnu

and here is the case


----------



## zkool448

Royewest, Zexnu, both nice looking builds, great job!


----------



## zkool448

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Now just some case feet and a bit of tung oil - should look sick!!!!!!_

 

Thanks for the kind words folks. Germania, mdf is almost construction-like grade and commonly used for cabinetry casing, trims/moldings, etc. and not meant to be oiled/stained : ) As Vaughan said, with it's porous surface it could only be painted to finish. I wanted it to appear like metal so, dbel84 I appreciate the 'fire red engine suggestion' but instead I went with 'textured' metallic right after several layers of primer. To those interested in seeing the final build, pls click the link to the build gallery thread. cheers.

 zk


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Thanks for the kind words folks. Germania, mdf is almost construction-like grade and commonly used for cabinetry casing, trims/moldings, etc. and not meant to be oiled/stained : ) As Vaughan said, with it's porous surface it could only be painted to finish. I wanted it to appear like metal so, dbel84 I appreciate the 'fire red engine suggestion' but instead I went with 'textured' metallic right after several layers of primer. To those interested in seeing the final build, pls click the link to the build gallery thread. cheers.

 zk_

 

Amazing. You even counter-sunk the DC input and RCA jacks again.
	

	
	
		
		

		
		
	


	




 That lighted acrylic bottom plate is just an unbelievable touch.

 We used mdf at Lockheed to test machining programs for some very complicated parts and composite molding fixtures. It's a great material to machine, but it seems you've taken the applicability to an entirely new level. Great work!


----------



## ThePredator

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Thanks for the kind words folks. Germania, mdf is almost construction-like grade and commonly used for cabinetry casing, trims/moldings, etc. and not meant to be oiled/stained : ) As Vaughan said, with it's porous surface it could only be painted to finish. I wanted it to appear like metal so, dbel84 I appreciate the 'fire red engine suggestion' but instead I went with 'textured' metallic right after several layers of primer. To those interested in seeing the final build, pls click the link to the build gallery thread. cheers.

 zk_

 


 It has a very steampunk-ish look, tubes sticking out of a modern finished 40s-reminiscent design. Definitely one of the top starving student cases.


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...That lighted acrylic bottom plate is just an unbelievable touch
 ...We used mdf at Lockheed to test machining programs for some very complicated parts and composite molding fixtures.._

 

Thanks Tomb, thepredator 
	

	
	
		
		

		
		
	


	




 The case work took the entire weekend to complete, a couple of mistakes here and there, made a couple of changes from the original design due to mis-aligned FET's, but I enjoyed every minute of building it. I do like working with MDFs as you already know how machinable they are no matter how dull the blades get they still cut through these boards like butter -- though they're really pain to paint 
	

	
	
		
		

		
		
	


	




 Glow in the dark:


----------



## smeggy

zk, first off, awesome build! Secondly, where do you get your mdf and sinks? Does that mdf have a specific brand/number as I've come across some really crappy stuff. Not all mdf is made equal...


----------



## zkool448

Thanks smeggy, I've been lucky to find decent mdf sheets at my local home depot. To me the batches quality appear to be of same quality also in different sheet sizes with true 3/4" thickness (not 5/8"). 

 In terms of the heatsink, I give full credit to OldKing for sharing his build idea and bom where I got the part no. from (mouser link). cheers.

 zk


----------



## smeggy

Thanks zk, your design has inspired me and now I can get some cool parts too


----------



## ludoo

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Thanks zk, your design has inspired me and now I can get some cool parts too 
	

	
	
		
		

		
		
	


	


_

 

Oh, then you are going to build one at last. 
	

	
	
		
		

		
		
	


	




 Do you still have the Cerafines I sent you ages ago?


----------



## smeggy

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Oh, then you are going to build one at last. 
	

	
	
		
		

		
		
	


	




 Do you still have the Cerafines I sent you ages ago?_

 

Hehe, I do.. still in the bag 
	

	
	
		
		

		
		
	


	




 Yes I am going to build one finally. I love the designs people come up with and I want to do a nice design myself


----------



## Fuzzy OneThree

What type of screws did people use to fasten their heatsinks down? Is there any special technique to get the pins out? 


 I saw that some used solder to hold theirs down, but I personally don't like that.


----------



## Hayduke

Quote:


  Originally Posted by *Fuzzy OneThree* /img/forum/go_quote.gif 
_What type of screws did people use to fasten their heatsinks down? Is there any special technique to get the pins out? 


 I saw that some used solder to hold theirs down, but I personally don't like that._

 

There have been a few techniques described in this thread. Some folks have heated the heatsink, others twist them out, and the one that made sense to me was using a vise. If your build allows the option of soldering them to something metal, why are you reluctant to go that route? You won't be able to see the difference between soldering the pins or using a screw. Actually you might be able to see a difference if you look closely, but I would think the pins would look better. If I was trying to remove the pins, I would wrap the sink in a towel, clamp it in a vise "just tight enough", and then pull the pins out with vise grip pliers.

 Make sure you post pics when you're finished. I think we all enjoy seeing each others' builds


----------



## ThePredator

Quote:


  Originally Posted by *Fuzzy OneThree* /img/forum/go_quote.gif 
_What type of screws did people use to fasten their heatsinks down? Is there any special technique to get the pins out? 


 I saw that some used solder to hold theirs down, but I personally don't like that._

 

I just used gorilla glue after drilling holes for the pins. I was originally worried about heat transfer, but even after 4+ hours they remain only warm to the touch.


----------



## CaptHowie

I'm having a little bit of trouble finding a few of the parts on the revised BOM. The parts are:
 - 50K, 1/4W Resistor;
 - 2.4K, 2W Metal Oxide Resistor;
 - Alpha 50K Audio Taper Stereo Pot [RV122F-20-15F-A50K];
 - Neutrik 3.5mm Stereo Audio Jack [NMJ6HCD2];
 - 20mm M3x0.5, Male-Female Aluminium Hex;
 - TO-220 Heatsink Kit;
 What are alternatives to these parts that are available in Australia. Also, is anybody aware of the price of international shipping to Australia through Beezar? I've heard it's really expensive but I really want to do a PCB build as i'm not too confident of buying AUD$100 worth of parts and stuffing them up on a P2P build. If anyone suggests P2P is better, please tell me... Also, I've developed an Australian version of the Revised BOM. Parts are through Farnell, Jaycar and Beezar, but there are changes to be made... DRAFT PEOPLE! Anyway, if anyone has the time to revise it, and make sure all the parts are correct it would be greatly appreciated. It can be downloaded here. Any help appreciated.


----------



## jeanba3000

Have you tried Farnell ? Looks like they sell in Australia too…


----------



## CaptHowie

Quote:


  Originally Posted by *jeanba3000* /img/forum/go_quote.gif 
_Have you tried Farnell ? Looks like they sell in Australia too…_

 

That's who i'm ordering through...


----------



## rjad

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_I'm having a little bit of trouble finding a few of the parts on the revised BOM._

 

I would consider going halvies in an order from mouser. I think that should cost us around $22 each for the postage.

 pm me if you are interested.


----------



## CaptHowie

Found similar resistors...
 Multicomp [MCMF0W4DF2371A50] Resistor, 2K37, 0.25W (1/4W) 0.5% 50PPM
 Multicomp [MCMF0W4DF4872A50] Resistor, 48K7, 0.25W (1/4W) 0.5% 50PPM
 Would these do to replace the one's I cant find?
 I'll have a think about doing a group buy with Mouser rjad. If anyone can look on Farnell Australia | Australia for me to look for some suitable replacements (if the ones i found dont work) that would be greatly appreciated.


----------



## Forte

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_ Also, is anybody aware of the price of international shipping to Australia through Beezar? I've heard it's really expensive but I really want to do a PCB build_

 

Beezars shipping to OZ is only expensive if you want it in a hurry. Out of three orders I have had shipped from there the most expensive was still less than $10au(USPS First Class).
 Register at Beezar add the parts to your cart and then you can see the various options and cost of shipping at the first step of checkout.


----------



## exphy

Where do you get the 19J6 valves?


----------



## zkool448

exphy, most people sourced their 19J6 online, mine came from thetubecenter.com. If you can wait a couple more weeks when prototyping is successfuly completed, tubes will be available at beezar.com but you must also purchase the mssh pcb.

 zk


----------



## Yaka

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_I'm having a little bit of trouble finding a few of the parts on the revised BOM. The parts are:
 - 50K, 1/4W Resistor;
 - 2.4K, 2W Metal Oxide Resistor;
 - Alpha 50K Audio Taper Stereo Pot [RV122F-20-15F-A50K];
 - Neutrik 3.5mm Stereo Audio Jack [NMJ6HCD2];
 - 20mm M3x0.5, Male-Female Aluminium Hex;
 - TO-220 Heatsink Kit;_

 

i ordered from farnell uk over the phone, instead of 50k resistors they sent me 100k ones, for 2.4k one they sent a led (shipped sepratly from the usa) the alpha pot was wrong and not dual. even tho the person. they did refund me before i even sent them back so i wont lose sleep over it


----------



## Yaka

finaly had time to work on the proto board first pics in its nekid glory















 and i ran into a problem with the pot, one of the legs/lugs was broken. managed to fix it tho






 i am preety much newbie when it comes to this, if anyone spots a mistake let me know. also the L case i got for it is too thin damn caps i got a 1mm to big:/


----------



## Frihed89

Perhaps this question has been asked before, but this is a long thread.

 I am in Denmark: 230VAC/50hz with Schuko plugs. Can anyone give me a part number to an adapter?

 Is there anything tied to the AC frequency?

 Thanks.


----------



## gore.rubicon

ooh man...so beezar is selling a full kit for the mssh?


----------



## smeggy

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_ooh man...so beezar is selling a full kit for the mssh?_

 

Where are you seeing that?


----------



## tomb

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Where are you seeing that?_

 

Yeah, I'd like to know, too.


----------



## Hayduke

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_ooh man...so beezar is selling a full kit for the mssh?_

 

No, Tom is selling the PCB with 2 tubes. You can only get 2 tubes with a PCB, or just a PCB.

 I'm surprised Tom didn't clear htis up himself


----------



## royewest

I finally purchased a knob today and realized there is one other little artifact of mounting the SSMH PCB board "upside down" in the case (as designed). If you mount a typical knob on the shaft and set the knob set-screw on the flat side of the pot shaft, the knob indicator is a little wonky -- it's meant to all work the other way up. Simple enough to back out the set screw and set it into a round section of shaft so 0 is straight down (or up, or whatever), but maybe someone else will come up with a cleverer solution....


----------



## gore.rubicon

gg typed the wrong thing, i wanted to ask if there was gonna be one =D, thanks for clearing it up anyways, but yeah, pcb + 2 tubes is pretty cool for a diy novice


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_No, Tom is selling the PCB with 2 tubes. You can only get 2 tubes with a PCB, or just a PCB.

 I'm surprised Tom didn't clear htis up himself 
	

	
	
		
		

		
		
	


	


_

 

Well for one reason, because I'll have more stuff than just the tubes and PCB. So, clearing it up is a bit more complicated than that.


----------



## Frihed89

Quote:


  Originally Posted by *Frihed89* /img/forum/go_quote.gif 
_Perhaps this question has been asked before, but this is a long thread.

 I am in Denmark: 230VAC/50hz with Schuko plugs. Can anyone give me a part number to an adapter?

 Is there anything tied to the AC frequency?

 Thanks._

 

Wrong amp page ...sorry. This belongs on the MiniMax page.


----------



## J.D.N

Tomb, is there an ETA on the final boards?


----------



## tomb

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Tomb, is there an ETA on the final boards?_

 

We still need some more work done by the prototypers. There's still a few that haven't built their boards (including me) and no one but Nate and Royewest have cased them up. Roy is the only one to use the smaller case so far, but he ran into some issues. So, I'd like to see a few more try it before we finalize some minor changes to the board. I'm hoping to do mine this weekend.
	

	
	
		
		

		
		
	


	




 It should take 2 weeks from the time I order the boards to have them in hand.


----------



## n_maher

Bunch of slackers...


----------



## ludoo

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Bunch of slackers..._

 

You mean our postal system, don't you?


----------



## royewest

Here are some more bad photos of my build. Since my last photos, I added a knob, flipped the heat sink bolts nuts-down, and filed the slots the heat sinks slide into so the case closes up a little better.

 I am delighted with the form factor and appearance of this little amp in person. The scratches and such that the flash reveals are pretty much invisible in normal light and in person.

 The only things I think I might do (but am in no hurry):

 * Get some little rubber feet for the bottom

 * Purchase some nicer end-panel screws and tap the case for them

 EDIT: But how does it _sound_!?

 I've been feeding this build lossless CD rips from a variety of DACs, listening on Senn HD650s. I've listened to baroque organ and viols, 50s and 60s jazz with different size orchestras, and Abby Road, for kicks. I think this little amp sounds fantastic for all of these. My only issues are that the right channel is a little louder than the left -- mostly not a problem. I also find that even with the 50K resistors in (R16/R17) and the cathode bypass caps omitted (C7/C8), I only have a few degrees of volume turn on the pot before it's too loud for me -- I will do some homework and try to adjust the circuit to lower the volume and likely get a more balanced (L/R) sound from this amp (I think folks have mentioned before that this pot has balance issues at low volume). I suspect I prefer to listen to headphones at a lower volume than most folks.


----------



## kuroguy

I used 220K resistors in series with the volume pot on my build and the volume is about right when connected to a USB DAC with supposedly 1V peak to peak output. I keep the volume at about 11 o'clock.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well for one reason, because I'll have more stuff than just the tubes and PCB. So, clearing it up is a bit more complicated than that.
	

	
	
		
		

		
		
	


	


_

 

Sorry Tom. I actually thought about mentioning that you supply lots of other parts too. I just wanted to make it clear your policy of only providing tubes with PCBs.

 Thanks for running Beezar.com for us. I'm sure I'll be placing more orders in the future. I'm thinking about building a MHSS on a PCB at some point, but I'm really waiting for the new Max boards *hint* *hint*


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Sorry Tom. I actually thought about mentioning that you supply lots of other parts too. I just wanted to make it clear your policy of only providing tubes with PCBs.

 Thanks for running Beezar.com for us. I'm sure I'll be placing more orders in the future. I'm thinking about building a MHSS on a PCB at some point, but I'm really waiting for the new Max boards *hint* *hint* 
	

	
	
		
		

		
		
	


	


_

 

Yeah, I've got a bunch of building to do. Besides the SSMH, two MAX V1.2 protoype PCB's have been staring me in the face for a couple of weeks, now. Nate is right - I'm a slacker - NOT!
	

	
	
		
		

		
		
	


	




 Anyway, I have good intentions at the start of every weekend, but things get in the way. Never heard that one, have you?
	

	
	
		
		

		
		
	


	




 Well, anyway - we'll see.
	

	
	
		
		

		
		
	


	





 P.S. Great pics Royewest!


----------



## nightanole

Found this on ebay. The design looks similar.


Valve Headphone Pre Amplifier Class A MP3 ipod Laptop X - eBay (item 260368823526 end time Mar-08-09 15:16:07 PDT)


----------



## Logistic

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Found this on ebay. The design looks similar.


Valve Headphone Pre Amplifier Class A MP3 ipod Laptop X - eBay (item 260368823526 end time Mar-08-09 15:16:07 PDT)_

 

Actually that is a rip of a version of Sijosae's MHHA amps:
http://www.headphoneamp.co.kr/bbs/zb...sijosae&no=247


----------



## royewest

Three More Small Build Notes:

 * Next time I do this I will solder the wires from the MOSFETs to the other side of the board and shorten them a bit. For reasons not worth going into, I've soldered these very tolerant MOSFETs about 4 times already and can't face doing it again.

 * The big caps are tight against the bottom of the case - I have to flex the case slightly to slide the board in. With that support, I don't find the need for a standoff in the middle of the board.

 * The input block did end up getting bent away and back from the board after sliding the board in and out of the case a few times. I used 18G teflon-coated stranded copper for the connections, because it was the best I have on hand for this purpose. I wish I had had 20G or something slightly smaller handy for this, and probably would have had less trouble with the fit. I like teflon-coated here because I was not clever enough to figure out how to keep the wires away from the MOSFETs...


----------



## Yaka

thanks for all the info you have provided roy, i have still not tacklled the L case yet. wish it was tiny little bit bigger


----------



## n_maher

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_* The big caps are tight against the bottom of the case - I have to flex the case slightly to slide the board in. With that support, I don't find the need for a standoff in the middle of the board._

 

In my opinion that is an unacceptable condition. While the cases of the caps may provide some insulation I don't like the idea of the caps either providing support or being in constant contact with the case.


----------



## royewest

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_In my opinion that is an unacceptable condition. While the cases of the caps may provide some insulation I don't like the idea of the caps either providing support or being in constant contact with the case._

 

Hm. Not sure what to say. I could add some more black tape, but I suspect it would not add significantly to your comfort with this. Care to describe your concerns in more detail so I can think if there's any way to address them?

 Don't think I'm disagreeing with you. I'm just reporting what I discovered when trying to fit the PCB in the small case, which has felt like a worthwhile thing to try for me, and even if it fails, I had fun trying. Seems like it barely works in there -- I keep expecting to discover it barely doesn't work -- there are several places where the case anodization is probably providing the only tenuous insulation. But so far....


----------



## royewest

On a separate topic, I added another 110K ohms (so, 160K total) in front of the inputs and got only about another 10 or 15 degrees of tolerable clockwise room on the volume pot. I sure wish I knew what I was doing with this.


----------



## zkool448

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_The big caps are tight against the bottom of the case - I have to flex the case slightly to slide the board in.. </snip>_

 

 Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Hm. Not sure what to say. I could add some more black tape, but I suspect it would not add significantly to your comfort with this</snip>_

 

royewest, nice job and great progress reporting. Since you've already drilled several holes i.e. for the tubes, sinks, jacks, etc., a couple more holes at the bottom plate wouldn't hurt to clear the caps height and prevent them from rubbing against the case, ..then just add some case feet and you're done


----------



## n_maher

zkool,

 While your solution would certainly work I think it's somewhat unreasonable to assume that everyone building the amp would do this. What we're trying to accomplish with the prototyping is what works and what doesn't work in the simplest sense. If the tiny case is just too tiny that's not a loss in my book. If builders wish to pursue that on their own that's the joy of DIY but for what we recommend as the "standard configuration" if you will should be as bullet proof and straight forward as possible. 

 roy,

 It's as you suspect. My fear is that either the cap insulation or anodizing would tend to wear down over time (simple friction) and eventually develop a short.


----------



## tomb

Well, I'm coming around to agreeing that perhaps the "L" case will have to be considered an "advanced" build. There is definitely sufficient clearance when drawing up the details. The problem is that the Hammond cases don't have the best tolerances. Often, the extrusion is bowed in. The rubber plugs on the electrolytics have quite a variance, too. Either or both of those things would explain the contact. One option I did on my PIMETAs a long time ago in a similar scenario was to line the case with a thin sheet of craft foam held in with double-sticky tape. It's worked quite well.

 The other disadvantage is the socket height. We could use the low-profile plastic kind that Dsavitsk recommended, but I've always preferred the ceramics. They never get hot and installed properly, they don't lose contact or break under the strain of tube rolling.


----------



## royewest

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_royewest, nice job and great progress reporting. Since you've already drilled several holes i.e. for the tubes, sinks, jacks, etc., a couple more holes at the bottom plate wouldn't hurt to clear the caps height and prevent them from rubbing against the case, ..then just add some case feet and you're done 
	

	
	
		
		

		
			



_

 

Thanks for the suggestion, zkool448. It would also add a route for air to pass from the bottom to the top of the case, if heat became a problem. (And I stuck feet on this morning.) I might also try to bend the bottom of the case a bit -- we're talking less than a millimeter here. But I'm going to risk things as-is for now.


----------



## nightanole

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_On a separate topic, I added another 110K ohms (so, 160K total) in front of the inputs and got only about another 10 or 15 degrees of tolerable clockwise room on the volume pot. I sure wish I knew what I was doing with this._

 

Do a shunt pot with a 47k resistor and a 10k pot. That should drop you alot more then slowly going to infinity input resistance, and sound alot better too.


Shunt Pot Volume Control - World-Designs-Forum


----------



## royewest

OK, nightanole. I get your point. I just added a 200K resistor in series with a 110K resistor ( in this unshielded and noisy short interconnect I made ) in front of the 50K resistor on the board in front of the 50K pot. If resistors in series work as I understand it, that's 360K in front of the pot. All that adds maybe 40deg of usable turn on the pot (and some hum) when listening to the Mingus Big Band's "Gunslinging Birds." 

 Thankfully the music from Mingus > band > lossless rip > DAC > SSMH amp > headphones > addled brain distracts from the technical issues....


----------



## Fuzzy OneThree

After realizing that a point-to-point soldering job would look horrible to me, I decided to go use a PCB. I am going to use the same blank PCB as the tangent cMoy, found at your local Radioshack. I am going to use one full one for most of the schematic and another half (the half left over from my cMoy 
	

	
	
		
		

		
		
	


	




) to place just the capacitors. Here are some pics:


----------



## kansei

Quote:


  Originally Posted by *Fuzzy OneThree* /img/forum/go_quote.gif 
_After realizing that a point-to-point soldering job would look horrible to me, I decided to go use a PCB..._

 

I just rebuilt my SS using this Radio Shack board. My first attempt was with the copper-clad board and not very pleasing or organized. The rebuild is more elegant and it works great, although I wish I would have planned it better. Right now, wires are sprouting from everyplace on the board (for tubes, input, output). I am going to borrow some layout ideas from your design. Perhaps my 3rd try will be better. 
	

	
	
		
		

		
		
	


	



Universal Component PC Board with 780 Holes - RadioShack.com

 I'm putting it into the enclosure linked below, just had to trim the long side of the PCB by a fraction of an inch. Finishing the fitting is a part of this weekend's festivities.

Aluminum Project Enclosure - RadioShack.com


----------



## nightanole

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_OK, nightanole. I get your point. I just added a 200K resistor in series with a 110K resistor ( in this unshielded and noisy short interconnect I made ) in front of the 50K resistor on the board in front of the 50K pot. If resistors in series work as I understand it, that's 360K in front of the pot. All that adds maybe 40deg of usable turn on the pot (and some hum) when listening to the Mingus Big Band's "Gunslinging Birds." 

 Thankfully the music from Mingus > band > lossless rip > DAC > SSMH amp > headphones > addled brain distracts from the technical issues...._

 

Your going to infinity and its not going to help. You have plenty of parts it seems. Try the shunt pot mod using your 50k pot and a 50k resistor. That should give you alot more movement then just going to infinity. If that doesnt work then replace the 50k pot with a 10k pot and still use the shunt. at that point your signal is attenuated to the point that the amp is more like a buffer that might boost the signal 6-9db if your lucky.

 If you use the 47k stock bom resistor, and a 10k pot, it will give you 10x more degrees of freedom then the stock bom.


----------



## Fuzzy OneThree

Quote:


  Originally Posted by *kansei* /img/forum/go_quote.gif 
_I just rebuilt my SS using this Radio Shack board. My first attempt was with the copper-clad board and not very pleasing or organized. The rebuild is more elegant and it works great, although I wish I would have planned it better. Right now, wires are sprouting from everyplace on the board (for tubes, input, output). I am going to borrow some layout ideas from your design. Perhaps my 3rd try will be better. 
	

	
	
		
		

		
		
	


	



Universal Component PC Board with 780 Holes - RadioShack.com_

 

 Yeah, I saw that board on their website, but sadly, that board was not in my local store. I have a feeling that I could have used the extra space...


----------



## royewest

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_You're going to infinity and its not going to help..._

 

I understand. I will experiment with the air-wired SSMH I built last year. I have notes on various approaches, including the shunt, I took back then and didn't pursue. The PCB and the tight space inside the Hammond make it hard to experiment like this with the PCB proto build.


----------



## tomb

I started building my prototype this morning - finally! The board goes together quickly, but the casing up is something else again. I am now certain that the "L" case _will not work_. In fact, we need to award Royewest a special medal for getting it to fit with his "L" case, period. I honestly don't know how he did it.

 Checking the fit of the board with the capacitors, it became obvious that it wouldn't work. There are two reasons for this. The actual space between the bottom of the case and the surface of the board is 20.11mm, when the board is forced against the top of the slot. (There is some play between the thickness of the PCB and the slot opening.) Here's how that looks:





 First, the Hammond cases are not that precise and the tolerance allowed in the bow of the case extrusion often results in a slight dip. This results in less clearance than one might measure on the mfr's drawings. Secondly, what I feared about the capacitors is also true: a 20mm height spec'd capacitor ends up being 21mm or slightly more. This again is due to wider tolerances allowed in mfg the capacitor - especially with the rubber plug used to seal the cap and leads.

 The result is that there may be up to 2mm less clearance than needed.
	

	
	
		
		

		
		
	


	




 Additionally, Royewest is exactly correct that the outer leads for R7 and R10 strike the edge of the slots. Again, the reason for this is _an undocumented variance in the design _of the Hammond case. The drawing below shows what's going on. At left is shown the design drawing configuration around the top left endplate mounting hole. Next to it is the reality. The metal in the "L" case is carried out in line with the outer edge case thickness of the mounting hole. This carries the effective slot out further on the top side, enough to rub against the outer leads of those two resistors:





 Interestingly, this feature does not seem to be consistent with the deeper cases and the "N" case does not have this type of hole design at top. They probably determined that the extrusion was too weak around that area with a smaller depth, or perhaps the extrusion form was too difficult to construct with the limited depth. In any event, there is no issue with the taller "N" case - the board can easily fit in lower slots, even with the huge caps I've used in the pics at bottom.

 We can only design the best we can with mfr's data until we prove/disprove the scenario with real-world prototyping. That's what's going on here. I wish the news was better with the "L" case, but the "N" case will give us much more flexibility. In fact, I'm going to be discussing with Dsavitsk some other options to try to make the build a bit easier and more straightforward. More on that later, depending on our discussions.
	

	
	
		
		

		
		
	


	




 Knowing that I'll have to use the "N" case, I went ahead and installed some caps I've been wanting try on the SSMH for awhile: the Muse Fine Gold 470uf 100V caps. So, here's what I have so far, but the casework will take the rest of the day, most likely. I'll have to mount it one slot higher than Nate's, but the sockets will only stick out about 1/16" higher than his _(click for bigger pics):_


----------



## bidoux

Really good work ! When will us be able to buy that PCB ?


----------



## jamesbobo007

A little change of pace?
 First thanks to everyone, this is a great place. I hardly ever post but have been meaning to get pictures up of this build for a long time now and finally got around to it. 
 Its kind of the opposite of whats been posted lately. Instead of starving student, think poor husband and father of 4 LOL. 
 This was mostly a scrounged build. I bought the tubes, sockets, a few resistors and the power supply off ebay. Total budget was like $50. $20 for 2 power supplies off Ebay. Then $15 for the tubes and sockets. Another 10 for resistors, the pot and the 510’s. Last, $2 for the handles at HomeDepot. Everything else was scrounged or on hand. The case is an upside down A-B printer switch painted black and the heat sinks are from old CPU’s

 So now my kid wants it and I’d like to build another,,,,but where can a guy find a couple 19J6’s now ????
 Thanks again, hope you enjoy


----------



## MrMajestic2

Got my Prototype up and running now. Sounds great except for the tubes ringing when I touch anything near the amp. Its not cased so touching the pot will make it hum, to be expected. I used Pete Millets original BOM with some additions that were added on the pcb version. I don't have any photos since the battery is dead in my camera.


----------



## tomb

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Got my Prototype up and running now. Sounds great except for the tubes ringing when I touch anything near the amp. Its not cased so touching the pot will make it hum, to be expected. I used Pete Millets original BOM with some additions that were added on the pcb version. I don't have any photos since the battery is dead in my camera._

 

Dang! You and me must be snake-bit. Sounds like even when I sent you the tubes, they've turned out to be microphonic. I test them all, but there's no way to check for microphonics without pluggin them into an amp.


----------



## MrMajestic2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Dang! You and me must be snake-bit. Sounds like even when I sent you the tubes, they've turned out to be microphonic. I test them all, but there's no way to check for microphonics without pluggin them into an amp._

 

Oh no, its the deadly tombsnake 
	

	
	
		
		

		
		
	


	




 Well, I'll give them some time to wake up, they have been dormant for quite some time.


----------



## nightanole

Anyone know a way to get 5vcd out of this thing to power an ipod? 12v regulators stop at 36v so that wont work with the 48v supply. Could i just do a simple voltage divider and calc the current needed to run a ipod?


----------



## Yaka

i too decided to drop the L case and go for the N after measuring and re measuring a few times today which is a shame as i like the small size of the n case better. and why do peeps have the 3 hole terminal block facing inwards? i had it like that first time round till i knocked lose my orignal cap in c7


----------



## tomb

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_i too decided to drop the L case and go for the N after measuring and re measuring a few times today which is a shame as i like the small size of the n case better. and why do peeps have the 3 hole terminal block facing inwards? i had it like that first time round till i knocked lose my orignal cap in c7_

 

There's not enough room to run the wire leads between the terminal block openings and the inside surface of the slots/side of the case.

 Dsavitsk made an excellent point in an e-mail to me earlier: the terminal blocks are probably not needed with the SSMH - it might be better to just solder the leads directly to the board. You only need a small bit of slack with a Hammond case - just enough to swing the backplate up and over so that you can pull the board, lid, and backplate out in one assembly.


----------



## ThePredator

Putting little felt pads (found some extra fluffy ones) under my amp almost completely eliminated the microphonics from touching my desk (and my tubes have some serious microphonics). If I could find some tube dampeners that would fit I think it would be a complete non-issue.



 To decrease startup/poweroff thump I need to put ~1000uF caps on C3 and C5, correct? Or would an ε12 set up for single supply be the best way?


----------



## tomb

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_Putting little felt pads (found some extra fluffy ones) under my amp almost completely eliminated the microphonics from touching my desk (and my tubes have some serious microphonics). If I could find some tube dampeners that would fit I think it would be a complete non-issue._

 

Beezar.com Tube Dampers





  Quote:


 To decrease startup/poweroff thump I need to put ~1000uF caps on C3 and C5, correct? Or would an ε12 set up for single supply be the best way? 
 

680uf's are enough. e12 is a little overboard for this amp, given the "Starving Student" theme.


----------



## kuroguy

Is it possible to install those tall caps horizontally instead of vertically? They look like they would fit above the tube sockets if you use a little double sided foam tape.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I started building my prototype this morning - finally! The board goes together quickly, but the casing up is something else again. I am now certain that the "L" case will not work. In fact, we need to award Royewest a special medal for getting it to fit with his "L" case, period. I honestly don't know how he did it.

 Checking the fit of the board with the capacitors, it became obvious that it wouldn't work. There are two reasons for this. The actual space between the bottom of the case and the surface of the board is 20.11mm, when the board is forced against the top of the slot. (There is some play between the thickness of the PCB and the slot opening.) Here's how that looks:





 First, the Hammond cases are not that precise and the tolerance allowed in the bow of the case extrusion often results in a slight dip. This results in less clearance than one might measure on the mfr's drawings. Secondly, what I feared about the capacitors is also true: a 20mm height spec'd capacitor ends up being 21mm or slightly more. This again is due to wider tolerances allowed in mfg the capacitor - especially with the rubber plug used to seal the cap and leads.

 The result is that there may be up to 2mm less clearance than needed.
	

	
	
		
		

		
		
	


	




 Additionally, Royewest is exactly correct that the outer leads for R7 and R10 strike the edge of the slots. Again, the reason for this is an undocumented variance in the design of the Hammond case. The drawing below shows what's going on. At left is shown the design drawing configuration around the top left endplate mounting hole. Next to it is the reality. The metal in the "L" case is carried out in line with the outer edge case thickness of the mounting hole. This carries the effective slot out further on the top side, enough to rub against the outer leads of those two resistors:





 Interestingly, this feature does not seem to be consistent with the deeper cases and the "N" case does not have this type of hole design at top. They probably determined that the extrusion was too weak around that area with a smaller depth, or perhaps the extrusion form was too difficult to construct with the limited depth. In any event, there is no issue with the taller "N" case - the board can easily fit in lower slots, even with the huge caps I've used in the pics at bottom.

 We can only design the best we can with mfr's data until we prove/disprove the scenario with real-world prototyping. That's what's going on here. I wish the news was better with the "L" case, but the "N" case will give us much more flexibility. In fact, I'm going to be discussing with Dsavitsk some other options to try to make the build a bit easier and more straightforward. More on that later, depending on our discussions.
	

	
	
		
		

		
		
	


	




 Knowing that I'll have to use the "N" case, I went ahead and installed some caps I've been wanting try on the SSMH for awhile: the Muse Fine Gold 470uf 100V caps. So, here's what I have so far, but the casework will take the rest of the day, most likely. I'll have to mount it one slot higher than Nate's, but the sockets will only stick out about 1/16" higher than his (click for bigger pics):






_


----------



## nightanole

Holly crap it works!!!


 Im using a 47k resistors at the input and a 10k pot using the shunt method. That knocks me down 15db or so and is perfect for my 770pro 80's. At 90% its almost too loud 
	

	
	
		
		

		
		
	


	




 It didnt work the first time since i forgot to ground c6 so the heaters were running at 5v and the audio just thumped. Next up is to try to shoe horn in some vitamin Q's into the outputs.

 As for heat. Im using the second smallest hammond encloser with a removable bottom. I also bonded a pentium 3 heatsink to the top uses electronics potting thats thermally more conductive then aluminum. Even with all that it gets very warm, Mr. Fluke says the entire case is 40c with the very hottest point (inbetween the tubes and the mosfets on top) is 45c.


----------



## kansei

Here is my newly (re)built Starving Student. I used a Radio Shack perfboard and enclosure. The perfboard was much easier to put together than the point-to-point (the perfboard just made more sense to my brain). I only wish I spent more time on the component layout because the wires are sprouting from everywhere on the perfboard. I'm building another one with fancy capacitors and better tube sockets, perhaps even nicer heatsinks.

 This iteration is much more compact and it worked out great (except for a few scratches in very visible places).






 More pics of the new and the old version:

Millett Starving Student hybrid tube amplifier pictures by kansei13 - Photobucket


----------



## royewest

What a handsome, tiny build, Kansei. Congratulations!


----------



## CaptHowie

Great build there Kansei, may do a build like you've done. Looks easier that doing P2P. The perfboard is only used as the ground plane if i'm right?


----------



## sachu

I am having some problem with my build.

 I fired it up an hour or two ago and I am getting output from the right channel..nothing from the left.
 I see the tube light up on the right channel..nothing of that sort on the left. I checked to make sure the voltage was right without the tube and it showed around 21.4 volts on both channels, which is spot on. 

 I switched the tubes and the same result. Tried different sets of tubes and same result.

 Any idea what could be the problem?
 Can anyone give me a list of voltages on all pins of each tube? 
 Thanks,
 Sachu


----------



## sachu

I am having some problem with my build.

 I fired it up an hour or two ago and I am getting output from the right channel..nothing from the left.
 I see the tube lights up on the right channel..nothing of that sort on the left. I checked to make sure the voltage was right without the tube and it showed around 21.4 volts on both channels (pin 3 of the tube socket), which is spot on. 

 I switched the tubes and the same result. Tried different sets of tubes and same result.

 Any idea what could be the problem?
 Can anyone give me a list of voltages on all pins of each tube? 
 Thanks,
 Sachu


----------



## tomb

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I am having some problem with my build.

 I fired it up an hour or two ago and I am getting output from the right channel..nothing from the left.
 I see the tube lights up on the right channel..nothing of that sort on the left. I checked to make sure the voltage was right without the tube and it showed around 21.4 volts on both channels (pin 3 of the tube socket), which is spot on. 

 I switched the tubes and the same result. Tried different sets of tubes and same result.

 Any idea what could be the problem?
 Can anyone give me a list of voltages on all pins of each tube? 
 Thanks,
 Sachu_

 

If the left channel fails to light a tube, then the primary issue is the heater circuit. You need to verify that Pin 4 is grounded and that Pin 3 has ~19V on it. Pin 3 for the tube also corresponds to pin 3 on the left MOSFET (the Source pin) and the lead of C5 _away_ from the headphone jack and R12 resistor.

 EDIT: I re-read your post. If Pin 3 has 21.4V, then Pin 4 must've lost its connection to Ground.


----------



## kansei

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Great build there Kansei, may do a build like you've done. Looks easier that doing P2P. The perfboard is only used as the ground plane if i'm right?_

 

If you look at the perfboard, it has "roads", shaped like M and W. Between those "roads" it has "driveways", where each "driveway" has 3 places to put a component. I solder-bridged some of the "driveways" for more complicated layouts, used snipped component leads to reach other locatins in some cases. What I did was to use the M "roads" for +, the W "roads" for -. I figured from the schematic how to interconnect everything else so it was an actual amp. My first layout could have been more organized, I have to rethink how to do this better in the future. The whole amp is built with all the components soldered onto the board except of the FETs.


----------



## kansei

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_What a handsome, tiny build, Kansei. Congratulations!_

 

Thanks!


----------



## sachu

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If the left channel fails to light a tube, then the primary issue is the heater circuit. You need to verify that Pin 4 is grounded and that Pin 3 has ~19V on it. Pin 3 for the tube also corresponds to pin 3 on the left MOSFET (the Source pin) and the lead of C5 away from the headphone jack and R12 resistor.

 EDIT: I re-read your post. If Pin 3 has 21.4V, then Pin 4 must've lost its connection to Ground._

 

Tomb,

 Thanks for the reply. 
 I went back and checked to see for ground..everything seemed alright. Then I checked to make sure the voltage divider was working..sure enough pin1 on the MOSFET was showing close to 0 volts. I re-flowed the connections on the voltage divider for the left channel and fired it up again..and it worked.

 I put it all in a case and again it sopped working. got fed up with it, so not gonna touch it till i calm down else I know I will screw something else up


----------



## tintin47

I am having some issues with my recently completed build. Very very faint music comes out of one channel, in which the drop across the mosfet is 6V, which is extremely wrong. The other channel has just static and the drop is 0V across the mosfet, which again is very wrong. Is it possible to partially damage a mosfet? Possibly by changing the initial voltage of the gate? Is there anything that I should do other than replace the fets? 

 Lastly, is there any way to damage the fets other than static, because I was grounded the whole time while working and it seems unlikely that I could accidentally damage two in the same way.


----------



## v3nom

On the schematic of this amp it shows several nodes headed to 'ground'. Do the grounds mound to the chassis or the ground from the power supply? Or am i completely confused here?

 thanks


----------



## tintin47

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_On the schematic of this amp it shows several nodes headed to 'ground'. Do the grounds mound to the chassis or the ground from the power supply? Or am i completely confused here?

 thanks_

 

Everything has to run through the ground in the outlet eventually, so you can send the grounds into a bolt in the chassis or anything else conductive as long as you connect them in some way to the ground prong of the outlet. What I have used on my amps is a bolt as a star ground for all of the boards and everything and then a wire from the grounding pin to the star ground, which sends everything to the outlet ground.


----------



## v3nom

Quote:


  Originally Posted by *tintin47* /img/forum/go_quote.gif 
_Everything has to run through the ground in the outlet eventually, so you can send the grounds into a bolt in the chassis or anything else conductive as long as you connect them in some way to the ground prong of the outlet. What I have used on my amps is a bolt as a star ground for all of the boards and everything and then a wire from the grounding pin to the star ground, which sends everything to the outlet ground._

 

thanks for the info.

 i am a beginning EE student so i can read schematics like a mad man but dont have a lot of experience in translating it into a real circuit lol. Thanks


----------



## tintin47

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_thanks for the info.

 i am a beginning EE student so i can read schematics like a mad man but dont have a lot of experience in translating it into a real circuit lol. Thanks_

 

Yeah. I am an aspiring EE myself, though in my case it means environmental engineer. 
	

	
	
		
		

		
			





 I don't have much experience with circuit diagrams, though. I just sort of put the amps together. That is funny though. Hopefully in the coming years of school you can actually get a chance to build some stuff.


----------



## royewest

Quote:


  Originally Posted by *tintin47* /img/forum/go_quote.gif 
_...is there any way to damage the fets other than static..._

 

I understand that the MOSFETs are "sensitive," but I must say I tortured mine while soldering and unsoldering them too many times in my SSMH PCB build and they suffered no ill effects. It has been dry, I did not use anti-static measures (and yes, I do know better and do not at all mean to endorse my slothful practice), and I grabbed and dropped and torqued these guys...


----------



## tintin47

Huh. I wonder how they could be damaged. It is obvious that something is wrong, and all resistors and the such are in perfect condition. I guess I am going to go back through the wiring. Maybe theres an issue there.


----------



## ttnl

Recently, I've sold my Starving Studen amp. When I still had the amp, I heard humming noise when volume was turned to max, and no music was playing. However, when music played, I have no problem at all with the amp. I never experienced the screech when it was with me. However, the buyer complains to me about a screech / buzz noise with the amp. That person uses the amp with Cowon D2 or A2. Does anyone know what happens to the amp?


----------



## ThePredator

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I understand that the MOSFETs are "sensitive," but I must say I tortured mine while soldering and unsoldering them too many times in my SSMH PCB build and they suffered no ill effects. It has been dry, I did not use anti-static measures (and yes, I do know better and do not at all mean to endorse my slothful practice), and I grabbed and dropped and torqued these guys..._

 

If the shipping company handled my MOSFETS anywhere near as badly as I handled them myself, they would have received more than an email. I'm nearly convinced that my pair are indestructible.




 If you go back through the schematic and check all the wiring and don't find any problems, check the voltage at the points labeled in the schematic.


----------



## nightanole

Quote:


  Originally Posted by *ttnl* /img/forum/go_quote.gif 
_Recently, I've sold my Starving Studen amp. When I still had the amp, I heard humming noise when volume was turned to max, and no music was playing. However, when music played, I have no problem at all with the amp. I never experienced the screech when it was with me. However, the buyer complains to me about a screech / buzz noise with the amp. That person uses the amp with Cowon D2 or A2. Does anyone know what happens to the amp?_

 

Might not be anything wrong with it. If you are using the original bom with the 150uf power caps then it could happen(and mp3 player/head phone damage if the unit is powered up/down with source/headphone plugged it). If his source doesnt have a series cap then it could happen (the ss doesnt have a cap either for isolation). If your inputs are not isolated from the chassis...

 First id see if it powers up the heaters. I didnt use 1000uf or 680uf caps for power (i used 470uf) and if its really cold i have to turn it on twice to get the power supply to turn on the heaters. Really we should have kept the 1.5 amp cisco supply so we wouldnt need all these bandaids for the power up of the heaters.


----------



## v3nom

I can't remember which amp was it where it was not recommended to have your headphones plugged in while turning the amp on, was it this amp??


----------



## Sodacose

Just finished a second one with larger electrolytics (470's and 680's). I also tried some different techniques with the terminal strips. I must say this is an excellent amp for just $50 and a few nights casual assembly.

 With the larger caps, I am definitely hearing some bass that was not as present with my first build (stock from BOM). I also went with carbon comp in the signal path. I'm not sure what can be attributed to what as I am using other slightly different parts (jack, pot), but this build sounds a little 'thicker' and smoother overall but not as 'light on its feet' as a stock one. All this is in keeping with what I expected from cc and larger caps but I'll have to verify with my other headphones.

 It seems to me that I did notice a change as my first one 'burned in.' I'm going to listen more closely to this second one to see if I can hear differences over time.

 I urge anyone thinking about trying it to give it a shot. This is really a great amp for the money and is not too difficult a build once you get going. For anyone intimidated by PTP directly from a circuit, I found that simply starting at the tube sockets and moving outwards in the schematic makes for a very easy build.

 Thanks for taking it so easy on my wallet for this one head-fi.


----------



## sachu

So the problem seems to be the 0.1mF capacitor in the left channel.

 When I power on the amp, the voltage on pin1 slowly increases all the way to 21 volts.

 Once I put in the tube, the voltage drops all the way down.


----------



## tintin47

nvmd. I made a wiring mistake. Thank god I found it or I would have been going insane.


----------



## sachu

well finally got mine to work..turns out the capacitor was the problem.
 Replaced it and I have all glowy glowy tubes..me like very much...

 the screws for the case got stripped..so taped up the case till I find replacement screws..


----------



## Hayduke

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I put it all in a case and again it sopped working. got fed up with it, so not gonna touch it till i calm down else I know I will screw something else up_

 

I read lots of DIY advice here. This is one is a gem, 
	

	
	
		
		

		
			




 Good decision. I hope you got it figured out once you cooled off a bit.

 You could always try my technique of always soldering with a libation on the desk. 
	

	
	
		
		

		
		
	


	



 Of course it may lead to MORE mistakes, but you won't get upset. Just grab another drink!


----------



## smeggy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_well finally got mine to work..turns out the capacitor was the problem.
 Replaced it and I have all glowy glowy tubes..me like very much...

 the screws for the case got stripped..so taped up the case till I find replacement screws..







[/i]
 [/td] [/tr] [/table]


Congrats Sachu,
 let's hope I can replicate your success! [img]http://www.head-fi.org/forums/images/smilies/smily_headphones1.gif_


----------



## zkool448

Quote:


  Originally Posted by *tintin47* /img/forum/go_quote.gif 
_Huh. I wonder how they could be damaged. It is obvious that something is wrong, and all resistors and the such are in perfect condition. I guess I am going to go back through the wiring. Maybe theres an issue there._

 

tintin47, perhaps you could use an extra pair of eyes so feel free to post a picture of your board wiring so we can take a look?


 EDIT: duh, never mind.. i see that you've fixed it : )


----------



## nightanole

[/url][/IMG]


----------



## smeggy

Woah, thought I was looking at a WooAudio amp for a minute!

 Nice!


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Woah, thought I was looking at a WooAudio amp for a minute!

 Nice!_

 

Same here..very nce...the heatsinks are cool looking..

 Thanks Smeggy. Am sure you will be able to get yours up and running. If you do blow anything up(highly unlikely), PM me, I have some spares..


----------



## lowendfrequency

I'm on the home stretch of assembly here, but I have a quick question. Do the 0.1uF 63V film caps have a polarity or specific orientation? I thought polarity was only an issue with electrolytic caps, but I'd like to be sure so I don't have to go ripping stuff out later. 

 Thanks!


----------



## zkool448

lowendfrequency, correct most (if not all) film caps including those have no polarity.

 zk


----------



## sachu

Quote:


  Originally Posted by *lowendfrequency* /img/forum/go_quote.gif 
_I'm on the home stretch of assembly here, but I have a quick question. Do the 0.1uF 63V film caps have a polarity or specific orientation? I thought polarity was only an issue with electrolytic caps, but I'd like to be sure so I don't have to go ripping stuff out later. 

 Thanks!_

 

tomb had addressed this before..

 The representation in the schematic is for people who have /want to use a polarised capacitor instead..So you could use an electrolytic if you wanted in the schematic and orient the leads as shown.


----------



## lowendfrequency

Thanks for the help guys. I figured it had been discussed here before, but I couldn't find this handy link I had used before to search the thread and was hoping to get an answer while the iron was still hot. Thanks a bunch... time to finish this sucker up.


----------



## ThePredator

1000uF (I already had them ordered, no point in cancelling to get some 680uF) Nichicon's on C3 and C5 only reduced the start up thump to six loud clicks and did nothing for the shut off thump. Is the ε12 my only other choice? (sure it isn't in the spirit, but it is another small project to do now that my Bentam is done)

 [EDIT] Would the ε12 protect the BentamDAC from damage on startup, or does it only delay the output?


----------



## Logistic

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_1000uF (I already had them ordered, no point in cancelling to get some 680uF) Nichicon's on C3 and C5 only reduced the start up thump to six loud clicks and did nothing for the shut off thump. Is the ε12 my only other choice? (sure it isn't in the spirit, but it is another small project to do now that my Bentam is done)

 [EDIT] Would the ε12 protect the BentamDAC from damage on startup, or does it only delay the output?_

 

You want the 1000uFs as the C1 and C6.


----------



## smeggy

Heh, well I'm starting construction of my SS in earnest tomorrow, casework and suchlike first before sticking the bits together and filling it. Found an awesome surplus PC heatsink from work that I just filed the nubs off, perfect for two FETs and some nice wood to house it all.

 Got a PSU coming from ebay, bought a perfboard, wire, heatshrink and the soldering iron is ready. The adventure into my first amp build is about to begin after literally years of procrastination.. 
	

	
	
		
		

		
		
	


	




 This is gonna be fun!


----------



## ludoo

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Heh, well I'm starting construction of my SS in earnest tomorrow, casework and suchlike first before sticking the bits together and filling it. Found an awesome surplus PC heatsink from work that I just filed the nubs off, perfect for two FETs and some nice wood to house it all.

 Got a PSU coming from ebay, bought a perfboard, wire, heatshrink and the soldering iron is ready. The adventure into my first amp build is about to begin after literally years of procrastination.. 
	

	
	
		
		

		
		
	


	




 This is gonna be fun!_

 

I can't wait to see your casework, if it's anything like your custom phones it will be awesome.


----------



## tomb

Quote:


  Originally Posted by *ThePredator* /img/forum/go_quote.gif 
_1000uF (I already had them ordered, no point in cancelling to get some 680uF) Nichicon's on C3 and C5 only reduced the start up thump to six loud clicks and did nothing for the shut off thump._

 

ThePredator covered you on the capacitors - C1 and C6 are the power caps that should effect the startup when upsized to 680uf.

 Your turn-off thump will be louder/longer with the bigger caps on the output (C3, C5), so that's not a surprise. Switch them around with C1 and C6 and you should get the improvement you seek.
  Quote:


 Is the ε12 my only other choice? (sure it isn't in the spirit, but it is another small project to do now that my Bentam is done)

 [EDIT] Would the ε12 protect the BentamDAC from damage on startup, or does it only delay the output? 
 

The e12 is an _output_ delay circuit. It will do nothing for the inputs, which is where you would connect a BantamDAC. If you've switched those caps and still get an offset at the inputs, then the best course of action (short of a procedural change*) would be to add some 100 ohm resistors inline with the L and R channel outputs from the Bantam. Note that these resistors would not be connected to ground - only inline with the respective Left and Right channels.


 * Make certain that your BantamDAC is connected to the USB power for several minutes and before connecting the DAC to the SSMH. This will ensure that the BantamDAC's output caps are fully charged, which should protect the DAC from any offset voltage at the SSMH input's upon turn-on.


----------



## tomb

Just an FYI to everyone - 

 Dsavitsk is working on some final tweaks to the PCB before we order production boards. I think we've fully vetted the board and with the "N" Hammond case (or other cases of your choice), we have plenty of flexibility.

 Some of the changes:
Move the R7 and R8 resistors away from the case slots,
Provide more room for the input terminal block (may be better to just solder the leads in there, actually),
Additional pads on the C1,C3,C5, and C6 capacitor positions for smaller electrolytic caps,
Added ground pad for a volume pot grounding wire,
Mounting holes shrunk slightly to match 4-40 screw size, and
Board width adjusted wider ever so slightly - it's been a little loose in the Hammond slots.
Dsavitsk may or may not have some changes for the LED pads and resistors, too. We haven't been too thrilled with the LED situation if tube lighting is used. The resistor is just too dang big when sized for tube LED's. However, there is no issue at all if you use the RLED as a single, panel LED and size it for 5ma or less. For instance, a 10K resistor would result in 4.8ma and need be only 1/2W for a 2X safety factor power rating.

 Finally, Dsavitsk will have to confirm all of this - he may have different/better solutions. So, there may be some slight differences in what I've listed, but I wanted to let you all know what we've talked about.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_[*]Mounting holes shrunk slightly to match 4-40 screw size, and_

 

Input on this from people would be appreciated. I generally size mounting holes too big (6-32 for 4-40 screws) because I can't drill straight and thus I like the extra wiggle room. But, if others like their holes more precise, then they can be.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_may or may not have some changes for the LED pads and resistors, too. We haven't been too thrilled with the LED situation if tube lighting is used. The resistor is just too dang big when sized for tube LED's. However, there is no issue at all if you use the RLED as a single, panel LED and size it for 5ma or less. For instance, a 10K resistor would result in 4.8ma and need be only 1/2W for a 2X safety factor power rating._

 

The LEDs are tricky. As is, they are somewhat limited in current as the resistor can only be so big. In most amps this is not an issue, but because of the highish voltage, in order to bump up the current a fair amount of watts need to be dissipated. One option is to add pads for a larger resistor (for more wattage) and people would need to mount it on the other side of the board. Thoughts appreciated.


----------



## n_maher

My preference is to stick with the larger holes, not need to be that precise.


----------



## Yaka

i agree nothing wrong with the current sized holes


----------



## Good Times

Noob-to-Millet poster here 
	

	
	
		
		

		
			





. Recently finished a Mini3 and looking to burn some more solder. Zcool, your housing is what inspired me to take on the Millet, phenomenal work. You’ve probably set me up for an horrific first housing build but hey!

 Oh and Howie, cool that you posted the Aussie BOM. Nice. Certainly will save a heap on postage.

 A million questions (well, four);

*1.*Should I read through all 178 pages here, or is it best to start with the basic instructions as per the DIY site and go from there?
*2.*Is P2P version a lot more difficult? I love the concept of this method, and thought it would actually be easier in terms of having less (ie no PCB). (keep in mind my Mini3 was my first project, so still an amateur at diy)
*3.*Is there a quick guide to the different versions available? Ie I hear Millet SS, then MilletMax, Mini etc etc. Or can someone run through it quickly?
*4.*Perhaps this question sums up my others, what would be the best version/method to build, as an amateur wanting to build a hybrid home amp to power some 300ohm Senn HD540s (and HD600s down the track)? 

 If this has all been covered in previous posts then apologies, and will start the read-a-thon from page one!


----------



## smeggy

I have a dumb question, would a SPST 16A 125V Illuminated Round Rocker Switch with Red LED work in the SS? I want an LED but I want it really dim, would this work or is it dumb to use this on a 48V DC circuit? specifically, something like *this*.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I have a dumb question, would a SPST 16A 125V Illuminated Round Rocker Switch with Red LED work in the SS? I want an LED but I want it really dim, would this work or is it dumb to use this on a 48V DC circuit? specifically, something like *this*.



_

 


 yep...that will work


----------



## smeggy

Schweeeeeet. 

 I hate blaringly bright LEDs, subtle and soft, like the glow of tubes is what I want


----------



## n_maher

Pffff, LEDs...


----------



## smeggy

Quiet you! LEDs are sexeh.


----------



## ThePredator

Quote:


  Originally Posted by *Good Times* /img/forum/go_quote.gif 
_Noob-to-Millet poster here 
	

	
	
		
		

		
		
	


	




. Recently finished a Mini3 and looking to burn some more solder. Zcool, your housing is what inspired me to take on the Millet, phenomenal work. You’ve probably set me up for an horrific first housing build but hey!

 Oh and Howie, cool that you posted the Aussie BOM. Nice. Certainly will save a heap on postage.

 A million questions (well, four);

*1.*Should I read through all 178 pages here, or is it best to start with the basic instructions as per the DIY site and go from there?
*2.*Is P2P version a lot more difficult? I love the concept of this method, and thought it would actually be easier in terms of having less (ie no PCB). (keep in mind my Mini3 was my first project, so still an amateur at diy)
*3.*Is there a quick guide to the different versions available? Ie I hear Millet SS, then MilletMax, Mini etc etc. Or can someone run through it quickly?
*4.*Perhaps this question sums up my others, what would be the best version/method to build, as an amateur wanting to build a hybrid home amp to power some 300ohm Senn HD540s (and HD600s down the track)? 

 If this has all been covered in previous posts then apologies, and will start the read-a-thon from page one!_

 

If you do P2P you will get a crash course in translating schematics to their physical representation. It will also help you learn how to organize a build to minimize the work you do (I rebuilt mine after I saw just how much work I was creating for myself by making a bird's nest of wires).

 If you can look at the internal pics on Pete Millet's site and how what corresponds to the schematic you should be able to easily do the build.


----------



## Good Times

Cheers. And I noticed this post from Zcool which sheds light on my other questions:

 "I stuck with Pete's original bom from his site which I recommend initially if this is your first mssh build. In case something strange happens or doesn't sound quite right, you'll know with certainty it's not because of your mods and it should be less difficult to troubleshoot. The only difference with mine and the original parts list are the heatsinks (2" vs 1.5") and 470uF for C1,C3,C5,C6.

 Once everything works within spec, then you can try some of the suggested tweaks here which I believe help to better suit your cans and/or music taste."


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Quiet you! LEDs are sexeh._

 

and how...you should see how excited girls are when they get to make an LED blink..lol..am not kidding..they go gaa gaa over it...at least the hot nerdy ones.
	

	
	
		
		

		
		
	


	




.


----------



## zkool448

Thanks goodtimes. yes follow thepredators advise re: P2P, then stick to the plan with Pete's BOM initially. I suggest you experimant only with the electrolyctics increased to atleast ~470uf + heatsinks. (schematics: official vs incl optional/adjusted values)

 In my case, both my ss milletts are great sounding little amps and don't experience any problems or ps stutter issues some were seeing. IMO there is definitely a subtle difference in sound 'signature' between the two (one has the suggested mods) however I can't honestly say I prefer one over the other.

 p.s. smeggy... no pref here, like 'em either with OR without LEDs 
	

	
	
		
		

		
		
	


	




 zk


----------



## sl_guy

Would anyone show me where to get the 19J6 tubes? I tried beezar.com but they don't have them, can I replace the 19J6 tubes with anything else? Any help would be greatly appreciated.
 Thanks


----------



## v3nom

Quote:


  Originally Posted by *sl_guy* /img/forum/go_quote.gif 
_Would anyone show me where to get the 19J6 tubes? I tried beezar.com but they don't have them, can I replace the 19J6 tubes with anything else? Any help would be greatly appreciated.
 Thanks_

 

pm me, i have some for sale.


----------



## Fuzzy OneThree

IT LIVES! I was a little worried that I would have to wait until the morning to finish it, but I managed to get it working tonight. The pot goes the opposite direction, but I can fix that in the morning. It also seems a tiny bit louder on the right side, so I may just order a better pot (I got the stock one).

 EDIT 2: Pic NOW!







 Fixed the pot going in the wrong direction problem.

 EDIT 3: Could 3k Ohms cause a noticeable imbalance on the pot? Because I have 48.5k vs. 51.5k when I just measured and the channels are clearly unbalanced.


----------



## Bleuburd

So, what's the status on production boards? Like maybe two or three weeks maybe? I really want to give it a try; the PCB looks really easy.


----------



## Fuzzy OneThree

I added 100k resistors before the pot to lower (or raise, i dunno) the gain. The pot is much more balanced in the middle.

 So, right now, everything sounds good!


----------



## tamasic1

I think I see the cause of the imbalance. That tube on the left looks like its enjoying the St Patty's day weekend as much as I am. Give us a few days to straighten up!


----------



## smeggy

Is there a general troubleshooting section somewhere?

 I finished putting mine together and of course it doesn't work... All I'm getting is a pulse on one channel as the tube pulses.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Is there a general troubleshooting section somewhere?

 I finished putting mine together and of course it doesn't work... All I'm getting is a pulse on one channel as the tube pulses._

 

Smeggy,

 Check for voltages on pin 1 and pin 3 of the Mosfets.
 You should be reading 22 volts and 19 volts or thereabouts respectively.

 Make sure your tube socket connections are good. I know the first time I hooked it p I had the pins reversed.

 Oh, and do this without the tubes..don't plug them in just yet. Till you see those voltages on the mosfet don't put in the tubes.


----------



## smeggy

=voltages all over the place, I made a boo-boo.

 I'll try again in the morning.


----------



## smeggy

Yay!






 yeah, messy but working


----------



## nightanole

I have a 1.5v voltage potental between my chassis and earth ground. Any ideas? The only thing touching the chassis i can think of is the pot.


----------



## n_maher

Where are you measuring "earth ground"?


----------



## nightanole

ground on the headphone jack, or ground on the power supply (same thing). If i take a multimeter from the chassis to the starground i get 1.5v. Or if i take chassis to my wire rack at work.


----------



## Kabeer

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yay!
 yeah, messy but working 
	

	
	
		
		

		
		
	


	


_

 

Awesome! You should build a housing from the bones (cups) of the dead fostex youv dismantled.
 Hows it sounding?


----------



## n_maher

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_ground on the headphone jack, or ground on the power supply (same thing). If i take a multimeter from the chassis to the starground i get 1.5v. Or if i take chassis to my wire rack at work._

 

No offense, but that is not "earth". That said I'm not sure I'm understanding you correctly, do you have the PS ground and headphone ground tied to a star ground which is connected to the chassis? If so then it is very odd that you'd see any significant potential difference between the chassis and ground. Your wire rack, I have no clue what you're talking about there.


----------



## nightanole

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_No offense, but that is not "earth". That said I'm not sure I'm understanding you correctly, do you have the PS ground and headphone ground tied to a star ground which is connected to the chassis? If so then it is very odd that you'd see any significant potential difference between the chassis and ground. Your wire rack, I have no clue what you're talking about there._

 

PS ground is connected to a star ground, headphone ground is connected to star ground. Nothing is suppose to connected to chassis. mosfets are connected to chassis but they are isolated with grommets and pads and impedance to chassis is over the limit that the multimeter can measure. However star ground to chassis is 1.5v when the unit is on. star ground to chassis impedance is higher then the multimeter can measure. Zero voltage potential between 3rd prong on wall socket and star ground. 1.5v voltage potental between chassis and 3rd prong of wall socket.


 EDIT: solved it. bad ballast in florescent light.


----------



## smeggy

Cheers Kab, sounds great and I'm listenig to it at the office


----------



## dsavitsk

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_impedance to chassis is over the limit that the multimeter can measure._

 

Unless you have some very fancy measuring equipment, you are measuring resistance, not impedance. They are not the same thing.


----------



## nightanole

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yay!



 yeah, messy but working 
	

	
	
		
		

		
		
	


	


_

 

Paper on carpet with mosfets...

 Guess i dont feel bad about only using a esd wrist strap...


----------



## zkool448

Quote:


  Originally Posted by *Fuzzy OneThree* /img/forum/go_quote.gif 
_I added 100k resistors before the pot to lower (or raise, i dunno) the gain. The pot is much more balanced in the middle.

 So, right now, everything sounds good!_

 

Congrats fuzzy! left tube to me kinda resembles the leaning tower of pisa 
	

	
	
		
		

		
		
	


	




, a tube pin straightener may just straighten it up?


----------



## smeggy

Quote:


  Originally Posted by *nightanole* /img/forum/go_quote.gif 
_Paper on carpet with mosfets...

 Guess i dont feel bad about only using a esd wrist strap..._

 

Hehe, it was only there for switch on and functionality testing. I'm going to house it in a paper mache case for safety 
	

	
	
		
		

		
		
	


	




 I love this little thing!


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Cheers Kab, sounds great and I'm listenig to it at the office 
	

	
	
		
		

		
		
	


	


_

 

good stuff smeggy 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_zk, based on your advise I went to the hardware shop and picked up a MDF stair, 1.5" thick and about 1.5' x 5' very dense and heavy so that should make for quick and easy casings along with some hammered black spray paint. Should make life a lot easier for a lot of things thanks. 
	

	
	
		
		

		
		
	


	


_

 

can't wait to see it!! i'm sure it'll be awesome. pm me if you have any questions -- cheers!


----------



## smeggy

I'm wondering how well the stuff will lathe for turning some small fittings like tube surrounds and such. Guess I'll find out soon enough. But yeah, have my saws and router at the ready.


----------



## kuroguy

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I'm wondering how well the stuff will lathe for turning some small fittings like tube surrounds and such. Guess I'll find out soon enough. But yeah, have my saws and router at the ready._

 

MDF turns pretty easily. You need very sharp chisels and you need to sharpen them before the last pass.


----------



## smeggy

coolies. I'll get honing. Thanks


----------



## Punnisher

A question:

 Is it possible to keep the audio signal completely isolated from the power section?

 I want to remove any source of hum or interference. Right now, all grounds go to the same ground via the power supply. I hear no hum with my 250 ohm 880s, but with my Grados there is very noticeable hum.

 For the record, my wall wart is a Cisco 48v 1.2 amp that has an ac ground conductor.


----------



## nightanole

Well it seems you have a star ground. I also ran a ground wire from headphone ground to input ground for i direct connect. You should also isolate the headphone plug and the input rcas/plug. Also the stock bom power supply has a 3 prong to so thats not the problem. You could also put the 50k input resistors in and make a gain switch for the grados. I dont even know how you would run grados without the input resistors. They are so low you dont need to up the voltage with an amp. line in is 2v,m and at 3v your ears are bleeding with grados


----------



## Bleuburd

How much is it going to matter if the tubes aren't matched? I found some 19J6s, but they aren't going to be paired.


----------



## zkool448

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_How much is it going to matter if the tubes aren't matched? I found some 19J6s, but they aren't going to be paired._

 

Perhaps more information than you need, otherwise very educational 
	

	
	
		
		

		
		
	


	




The Millett Starving Student *Tube* Thread

 zk


----------



## ludoo

I just got my proto PCB, it's tiny and really beautiful. Will start tonight and hopefully finish by this weekend if I manage to get a case.


----------



## ludoo

Uhm, I need your opinion on deciding how to build my SS using the proto PCB. The "problem" is that I want to use (and already have) 4 Elna Cerafine 470uF 63V, and an Alps Blue Velvet. It's the same components I already have in my two other SS amps and they sound great.

 I just measured one Cerafine on the PCB, and the cap + the PCB thickness is 48mm. If I use PCB mount sockets for the tubes on the "correct" side, it's an extra 14mm. Clearly too tall for a Hammond case. If I mount the caps on the same side as the tubes, I then have to slide the PCB in a bottom slot, which causes other problems (the Mosfets should be bolted on the top side, etc.). And the taller case looks pretty ugly imho.

 Another option, and the one I wanted to use, is to get a small Galaxy case from Hifi2000. The second smallest size has more than enough space for everything, and the sides are made of extruded aluminum and would work well as heatsinks. The PCB would be bolted on the bottom. But seeing as Galaxy cases are 40mm tall, I would need to mount the tube sockets on the case top as there's absolutely no space for them. Which I kind of prefer as I find amps look nicer with the tubes completely exposed, and there's less risk of making ugly holes for the tubes. But then I'll have to air wire them, which kind of defeats having a PCB.

 Any other alternatives apart from building a case myself out of wood and aluminum (or brass), which I would prefer not to do as it would take a long time?


----------



## Yaka

when i wanted to build mine in the hammond L case i did strongly think on getting rid of the bottom plate and use plexi to mount mount the pcb. lack of both time and tools made me go for the N case. 

 tbh if you have the time then go for a custom job


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Uhm, I need your opinion on deciding how to build my SS using the proto PCB. The "problem" is that I want to use (and already have) 4 Elna Cerafine 470uF 63V, and an Alps Blue Velvet. It's the same components I already have in my two other SS amps and they sound great.

 I just measured one Cerafine on the PCB, and the cap + the PCB thickness is 48mm. If I use PCB mount sockets for the tubes on the "correct" side, it's an extra 14mm. Clearly too tall for a Hammond case. If I mount the caps on the same side as the tubes, I then have to slide the PCB in a bottom slot, which causes other problems (the Mosfets should be bolted on the top side, etc.). And the taller case looks pretty ugly imho.

 Another option, and the one I wanted to use, is to get a small Galaxy case from Hifi2000. The second smallest size has more than enough space for everything, and the sides are made of extruded aluminum and would work well as heatsinks. The PCB would be bolted on the bottom. But seeing as Galaxy cases are 40mm tall, I would need to mount the tube sockets on the case top as there's absolutely no space for them. Which I kind of prefer as I find amps look nicer with the tubes completely exposed, and there's less risk of making ugly holes for the tubes. But then I'll have to air wire them, which kind of defeats having a PCB.

 Any other alternatives apart from building a case myself out of wood and aluminum (or brass), which I would prefer not to do as it would take a long time?_

 

Well, I'm certain you went to a lot of trouble to get those Cerafines, so my first suggestion would not work (change caps).
	

	
	
		
		

		
			





 One thing to remember, though, is that the SSMH has been a P2P design from day one. So, there would be nothing wrong with laying the caps down horizontally. If you can figure out a way to orient them in a such a way that they don't touch the edges of the board/case that might work. The point of the P2P reference is that I strongly doubt that the extra lead length that occurs by turning radial caps horizontal will have any noticeable effect.


----------



## smeggy

Got mine cased up, almost finished. I just need to make tube flange surrounds to tidy up the top. I put a 1/4 and 1/8" phone sockets cos I keep losing my adapters.

 Anyway, I'm loving this thing


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Got mine cased up, almost finished. I just need to make tube flange surrounds to tidy up the top. I put a 1/4 and 1/8" phone sockets cos I keep losing my adapters.

 Anyway, I'm loving this thing 
	

	
	
		
		

		
		
	


	







_

 

holy smokes!...that is sweeet!!!


----------



## bhjazz

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Got mine cased up, almost finished. 
 Anyway, I'm loving this thing 
	

	
	
		
		

		
		
	


	


_

 

Geez Smeggy, who wouldn't....that's gorgeous! Totally, totally original! 
 Haven't seen you in a while. Hope all is well!


----------



## dBel84

Here here , smashing!! ..dB


----------



## zkool448

whoa smeggy -- It's Awesome and looks rich! (i.e. not starving). I had a feeling it was going to look amazing 
	

	
	
		
		

		
		
	


	




 cheers!

 zk


----------



## smeggy

Thanks guys 
	

	
	
		
		

		
		
	


	




 It's nice having a home amp at last. Believe it or not, my first ever home headphone amp. First tube amp and first DIY amp, so not a bad set of firsts. I usually use power amps for my phones. It was a lot of fun... in a deranged, twisted way


----------



## CaptHowie

@smeggy Good work on the amp... Lovely case, truly unique


----------



## manaox2

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Got mine cased up, almost finished. I just need to make tube flange surrounds to tidy up the top. I put a 1/4 and 1/8" phone sockets cos I keep losing my adapters.

 Anyway, I'm loving this thing 
	

	
	
		
		

		
		
	


	


_

 

I'm really jealous of that thing. 
	

	
	
		
		

		
		
	


	




 Congrats!


----------



## Kabeer

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Got mine cased up, almost finished. I just need to make tube flange surrounds to tidy up the top. I put a 1/4 and 1/8" phone sockets cos I keep losing my adapters.

 Anyway, I'm loving this thing 
	

	
	
		
		

		
		
	


	







_

 






....... ... ... .. ..........
	

	
	
		
		

		
		
	


	




...........*faints*

 (i think with a birds eye view, it would look like a face sticking out its tongue, with an afro! )


----------



## antonyfirst

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Got mine cased up, almost finished. I just need to make tube flange surrounds to tidy up the top. I put a 1/4 and 1/8" phone sockets cos I keep losing my adapters.

 Anyway, I'm loving this thing 
	

	
	
		
		

		
		
	


	







_

 

That's not a Starving Student! That's a Smartass Student!


----------



## Bleuburd

All the builds have been nice, but that is fantastic.


----------



## royewest

Smeggy: That's just gorgeous. Please post more pics!


----------



## Listen2this1

I am un-able to find tubes. 
 Does anybody know where to get them? does someone have any to sell? Has any thought about using a tube that has availability?


----------



## kuroguy

double post


----------



## kuroguy

search google shopping for 19j6. there are several there including what appear to be a matched pair.


----------



## Listen2this1

Everybody only has one. I went ahead and bought a pair from vacuumtubes.net. Even though they are not the same style I hopefully will be able to find more to get a actual pair.


----------



## v3nom

edit


----------



## smeggy

Took more pics after making the small wood tube surrounds for those who wanted more views.


----------



## sachu

hahahha...beautiful..those handles look so cool.. *smiles and then shakes his head amazed *


----------



## Bleuburd

Well, I've decided to try to do this thing p2p with a ground plane, just like Pete's original. I ordered my tubes yesterday, (four zeniths which are probably rebranded rcas) and I'm about to make my other orders from mouser and parts connexion. I decided to go with an alps pot and parts connexion seems to have them for reasonable prices. Is there a definitive guide or section of this thread that deals with mounting the mosfets? I really don't have any idea where to start.

 Edit: How much of a difference in sound quality am I going to hear if I opt for the alps pot instead of a pot from mouser? I'm thinking I want to keep my order down to two places, so it would be nice if I could get everything but the tubes from mouser.


----------



## brashgordon

smeggy 
 Headphoneus Supremus 

 Show-off .... LOL

 Just kidding .... 

 some of the best "ART-WORK" I've ever seen ... 


 GREAT JOB !!!!!


----------



## smeggy




----------



## wiatrob

Truly unique! Great job Smeggy!


----------



## zkool448

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_<snip>...Is there a definitive guide or section of this thread that deals with mounting the mosfets? I really don't have any idea where to start. </snip>_

 

Try to familiarize yourself with the schematic first then think about how you would layout the parts on the copper clad -- use Pete's example as a guide and things should just fall into place. good luck!

 zk


----------



## Bleuburd

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Try to familiarize yourself with the schematic first then think about how you would layout the parts on the copper clad -- use Pete's example as a guide and things should just fall into place. good luck!

 zk_

 

Ok, sounds good. I'll give you guys a shout if I need anything. The schematic makes sense to me, and where I can't totally understand it Pete's photos make up for it. I just made my mouser order, and my tubes are on the way! I'll talk to you guys later.


----------



## zkool448

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Ok, sounds good. I'll give you guys a shout if I need anything. The schematic makes sense to me, and where I can't totally understand it Pete's photos make up for it. I just made my mouser order, and my tubes are on the way! I'll talk to you guys later. 
	

	
	
		
		

		
		
	


	


_

 

great. in terms of mosfets, the T0-220 mounting kit datasheet and diagrams clearly explains how to mount them onto the sinks correctly (with thermalfilm).

 zk


----------



## scompton

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Ok, sounds good. I'll give you guys a shout if I need anything. The schematic makes sense to me, and where I can't totally understand it Pete's photos make up for it. I just made my mouser order, and my tubes are on the way! I'll talk to you guys later. 
	

	
	
		
		

		
		
	


	


_

 

One thing I'd suggest is doing a layout on paper first. It made my build go a lot easier. Basically redraw the schematic with lines for the actual wires


----------



## smeggy

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_One thing I'd suggest is doing a layout on paper first. It made my build go a lot easier. Basically redraw the schematic with lines for the actual wires_

 

x2, that's what I had to do after my first failure and it worked. I laid mine out on perfboard with sticky pads and peeled it off once tested and stuffed it in the case. Of course I had to detach and reattach the tube wires to fit in the case but then I understood it better.


----------



## Bleuburd

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_great. in terms of mosfets, the T0-220 mounting kit datasheet and diagrams clearly explains how to mount them onto the sinks correctly (with thermalfilm).

 zk_

 


 Thanks, zkool! That's exactly what I was looking for. I just got a shipment confirmation from mouser, and my tubes should be here by Monday. I should be able to start by Tuesday at the latest. I just picked up my enclosure from a local shop. I won't say what it is, but it'll be a surprise when I post pics.


----------



## scompton

I'm trying DIY Layout Creator to do a layout on perf board. It's freeware and was mentioned on some thread here. I'm using beta version 2.01 that I can't find on the web right now. I think it's really an alpha version because the creator says the release version won't be able to open files created with the beta. He's currently working on version 3 that will be in open source.






 I think if I ever get to doing a lot of point to point on perf board, I'll buy something like LochMaster


----------



## Forte

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Took more pics after making the small wood tube surrounds for those who wanted more views._

 

Stunning build. Wouldn't look out of place in a Gallery as a piece of sculptural art. Form and Function. 
	

	
	
		
		

		
		
	


	




 How did you make the wood tube surrounds? Turned on a lathe or is there another way?


----------



## smeggy

Thanks Forte, yes, turned on the lathe as a tube then parted down the middle to make two.


----------



## petterg

Hi,
 i've built my amp with the original plans, it worked for a while but now it seems broken, i never hear the music in both ears no matter how i set the volume pot, and i hear a loud humming all the time.
 Anyone have any suggestions how to fix this?

 I'm also intresded in how to improve the sound quality, what parts should i replace/add.

 //Petter


----------



## tomb

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_Hi,
 i've built my amp with the original plans, it worked for a while but now it seems broken, i never hear the music in both ears no matter how i set the volume pot, and i hear a loud humming all the time.
 Anyone have any suggestions how to fix this?

 I'm also intresded in how to improve the sound quality, what parts should i replace/add.

 //Petter_

 

We may need a pic or two. Sounds like some wiring/soldering connections have given way.


----------



## tomb

Here's Dsavitsk's latest PCB design. Resistors and input terminal block have been moved further in, additions are extra pads for smaller caps on the electrolytics (the originals were sized for _very_ large boutiques), an extra pad to accomodate a large resistor on the back side for tube LED's, and the center hole has been grounded to the ground plane. (Again, the ground plane is not shown for clarity.)

 He's probably getting frustrated with me by now - I asked for a few additions to the silkscreen.
	

	
	
		
		

		
		
	


	







 So this may change slightly ... or it may not.


----------



## petterg

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_We may need a pic or two. Sounds like some wiring/soldering connections have given way._

 

It's like when i try to set the volume higher, the right channel gets quiet and vice versa. The amp just "broke" without me changing anything or open it.


----------



## tomb

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_It's like when i try to set the volume higher, the right channel gets quiet and vice versa. The amp just "broke" without me changing anything or open it._

 

Sorry, but that's not helpful. Open it.
	

	
	
		
		

		
		
	


	




 One thing you could do before that - swap the tubes from one channel to the other and see if that changes anything. Otherwise, open it and give us some pics. It may take some measurements, too.


----------



## J.D.N

Quote:


  Originally Posted by *petterg* /img/forum/go_quote.gif 
_It's like when i try to set the volume higher, the right channel gets quiet and vice versa. The amp just "broke" without me changing anything or open it._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry, but that's not helpful. Open it.
	

	
	
		
		

		
		
	


	




 One thing you could do before that - swap the tubes from one channel to the other and see if that changes anything. Otherwise, open it and give us some pics. It may take some measurements, too.
	

	
	
		
		

		
		
	


	


_

 


 I think Tom needs a moto, maybe: 'A picture is worth a thousand words.' 

 I don't have much experience in the department, but from everything read in this thread, pictures really do hold the key.


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Here's Dsavitsk's latest PCB design. Resistors and input terminal block have been moved further in, additions are extra pads for smaller caps on the electrolytics (the originals were sized for very large boutiques), an extra pad to accomodate a large resistor on the back side for tube LED's, and the center hole has been grounded to the ground plane. (Again, the ground plane is not shown for clarity.)

 He's probably getting frustrated with me by now - I asked for a few additions to the silkscreen.
	

	
	
		
		

		
		
	


	







 So this may change slightly ... or it may not.
	

	
	
		
		

		
		
	


	


_

 

tomb, thanks for the update -- will the updated design require a second prototype/test phase before the production board will be released? 

 thanks! -zk


----------



## zkool448

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I'm trying DIY Layout Creator to do a layout on perf board. It's freeware and was mentioned on some thread here. I'm using beta version 2.01 that I can't find on the web right now. I think it's really an alpha version because the creator says the release version won't be able to open files created with the beta. He's currently working on version 3 that will be in open source.






 I think if I ever get to doing a lot of point to point on perf board, I'll buy something like LochMaster_

 

scomptom, I like it but I;ve not tried it yet. Whe you put components on the proto, is it smart enough to show the traces that are connected with each components? (eg. traces change colors).

 zk


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_tomb, thanks for the update -- will the updated design require a second prototype/test phase before the production board will be released? 

 thanks! -zk_

 

*NO!*





 I asked for was a few silkscreen notes -
 * label the ground pad for the pot
 * move the 123 numbers for the MOSFETs to the board (since they're cut off from the edge of the board)
 * put "+" signs in the right places for the tube LED pads, and 
 * label the input terminal block with L, R, G.

 None of those things - whether implemented or not - will create the need for a new prototype run.
	

	
	
		
		

		
		
	


	




 Again I maybe nit-picking, especially for a limited board run (tube availability), but I thought these things might be simple and offer a good benefit. Really, I don't mean to plead my case in public, either. Dsavitsk is busier than I am lately.
	

	
	
		
		

		
		
	


	




 We will be well-served even with the board as it is, quite frankly.


----------



## zkool448

cool thanks 
	

	
	
		
		

		
		
	


	




 apologies for all the questions and completely understand if you can't disclose any info at this time, but how many boards/tube pairs roughly will be available in stock and is there a new release timing date?

 thanks tomb.

 zk


----------



## tomb

I have about 30 power supplies, but not as many as the other things. So my latest thinking is to offer about 30 kits first, then sell the boards with tubes until the tubes run out. I estimate somewhere between 50 - 100 (x2 tubes each) for that, but we'll order 200 boards total. That means some will be left over.

 If more tubes (in qty) show up (we hope that's the case), that strategy may change.


----------



## smeggy

I'm looking forward to getting one of these boards


----------



## dsavitsk

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_tomb, thanks for the update -- will the updated design require a second prototype/test phase before the production board will be released? 

 thanks! -zk_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_*NO!*_

 

Agreed.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I asked for was a few silkscreen notes_

 

These are all added, more or less. I just need to do one last proof read and send the files off to Tom.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Dsavitsk is busier than I am lately._

 

You have no idea. It looks to get a lot worse before it gets better.


----------



## tamasic1

I know the temp of the mosfets were discussed but what about the tubes? How warm to they get while in operation?


----------



## tomb

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_I know the temp of the mosfets were discussed but what about the tubes? How warm to they get while in operation?_

 

Hot enough to burn you if you held on to them for very long, I think.


----------



## smeggy

Thankfully my big-ass heatsink doesn't get extremely hot due to very good heat dissipation and the tubes only get as warm as a 15W bulb, hot but not skin searing if you touch them.


----------



## n_maher

The prototype was setup for ~3hrs yesterday at the NYC meet and by the end of that run it was smoldering pretty good. I didn't get a chance to measure exactly how hot it got but it was hot enough to not pass the finger test and make me shut it down. I'm going to add a heatsink to the top panel as well as ventilating the case a bit and then I'll have another go at letting it run for a good long time driving a load to see how it behaves. I'm leaning more and more towards the case-only heatsink approach not quite cutting it unless you want to make tea on the top panel.


----------



## smeggy

Heh, sounds like a good recipe for meltdown and spontaneous student combustion


----------



## zkool448

nate, that's not good. sounds like heatsinks may be mandatory.

 OT: awesome t-shirt 
	

	
	
		
		

		
		
	


	




 ..source?


----------



## n_maher

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_nate, that's not good. sounds like heatsinks may be mandatory._

 

The heatsinks I plan on using are super easy to install, they use a thermal adhesive so it's just peal and stick. I have the prototype with me at work and I'm going to try using it this afternoon.

  Quote:


 OT: awesome t-shirt 
	

	
	
		
		

		
		
	


	




 ..source? 
 

Thanks. 
	

	
	
		
		

		
		
	


	




 I can't remember where I got it, it was 3 years ago or so. Sorry!


----------



## scompton

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_scomptom, I like it but I;ve not tried it yet. Whe you put components on the proto, is it smart enough to show the traces that are connected with each components? (eg. traces change colors).

 zk_

 

Unfortunately, no. At least if it does, I haven't figured out how to make it work. There is a sticky point option that I haven't used yet.


----------



## vapman

Could anyone share insights on how these are with Etymotics?


----------



## v3nom

whoah wha?? a SS prefab board!?! im sold!


----------



## n_maher

Quote:


  Originally Posted by *mckickflip* /img/forum/go_quote.gif 
_Could anyone share insights on how these are with Etymotics?_

 

My experience, not good, the amp simply has way to much gain for a headphone that barely needs amping at all.


----------



## smeggy

Mind you, the Ety does suck more juice than your normal IEM but I sent mine off as a gift so can't test it.


----------



## vapman

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_My experience, not good, the amp simply has way to much gain for a headphone that barely needs amping at all._

 

even if i was to throw a gain control pot in there?


----------



## nightanole

Quote:


  Originally Posted by *mckickflip* /img/forum/go_quote.gif 
_even if i was to throw a gain control pot in there?_

 

Do what I did for my grado's. a 47k inline resistor with a 10k shunt wired pot. The stock bom model pot comes in 50k and 10k styles. Its still enough to blow the grado's up at 80% volume but at 100% its just enough to make my 80ohm 770 pros distort. At normal levels my grados are at 40% and my 770's at 60%.


----------



## mugdecoffee

I was wondering how hard it would be to add a virtual ground to the amp. I saw a 3 channel amp that Germania made I believe however I was thinking about just adding in a simple solid state buffer that wouldn't require much more space or more case work.

 Earlier a ground channel was discussed but people were worried about DC offset because of the tubes drifting. If you were to use a solid state buffer, would the drifting stop?

 There could also be problems I think if the two tubes had an output at slightly different voltages so they couldn't share a ground channel. Is this correct? If this is true, you'd need a seperate ground buffer for each channel requiring balanced headphones. Would this effectively make the amp balanced?

 Ideally I'd like to use a BUF634 (since they seem to be the standard ground buffers) and use the +19V and 0V for a supply. The caps will remove DC offset even if the ground is raised to a higher potential. I think the 19V on the schematic is just the audio signal and not a supply though.

 I've been reading a lot on this forum and else where but I have no experience designing amps. Am I thinking through this correctly?


----------



## v3nom

Are the huge fin heatsinks necessary? I already have a mosfet heatsink about the same size but without the extra fins, its like a box with 3 sides -> |___| Will it dissipate enough heat?


----------



## smeggy

Depends on size, the mosfets put out quite a bit of heat and I think the standard sinks most use are fine but even they get really hot and I would think they'd be close to minimum size but I don't know the technicalities.


----------



## scompton

I don't know the technicalities either, but those big heat sinks get warm. Smaller ones would probably get too hot to touch. The thought was to use the metal case as the heat sink with the PCB seems to not work according to Nate's test at the NYC meet.


----------



## n_maher

Quote:


  Originally Posted by *mckickflip* /img/forum/go_quote.gif 
_even if i was to throw a gain control pot in there?_

 

Yes, it's still a bad choice in my opinion. You'd be better off building something to act as a current buffer if you use anything at all with the Etys.


----------



## v3nom

I need some help/clarification.

 The pot on the BOM has a 12mm shaft, but all I can find are knobs with the standard 6mm shaft. Do i find a new pot with a 6mm shaft or a knob with 12mm shaft??

 Thanks


----------



## tomb

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_I need some help/clarification.

 The pot on the BOM has a 12mm shaft, but all I can find are knobs with the standard 6mm shaft. Do i find a new pot with a 6mm shaft or a knob with 12mm shaft??

 Thanks_

 

I'm pretty sure the 12mm is the length, not the diameter. If it were, the pot would have a near 1/2" diameter shaft. That might be enough to bolt on a lawnmower blade.


----------



## Fitz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That might be enough to bolt on a lawnmower blade.
	

	
	
		
		

		
		
	


	


_

 

Are you making a challenge?


----------



## v3nom

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm pretty sure the 12mm is the length, not the diameter. If it were, the pot would have a near 1/2" diameter shaft. That might be enough to bolt on a lawnmower blade.
	

	
	
		
		

		
		
	


	


_

 

hmmm, you got me thinking... a nice big shinny blade for a volume knob... 
	

	
	
		
		

		
		
	


	




 jp, thanks for the response, length makes more sense.


----------



## tomb

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_Are you making a challenge? 
	

	
	
		
		

		
		
	


	


_

 

Maybe ... does your Total Eclipse have a volume knob yet?


----------



## nsx_23

Has anybody tried the starving student with a pair of Ultrasone Pro 900s?


----------



## ThePredator

Quote:


  Originally Posted by *nsx_23* /img/forum/go_quote.gif 
_Has anybody tried the starving student with a pair of Ultrasone Pro 900s?_

 

It definitely works well with the Ultrasone sound (using HFI-780), not sure how well that will translate across the lines though.


----------



## tomb

Production PCB's are on order.
	

	
	
		
		

		
		
	


	




 I'll get to work on the website again when I have a chance.


----------



## smeggy

Awesome news Tom. I'm really looking forward to getting one


----------



## v3nom

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Production PCB's are on order.
	

	
	
		
		

		
			





 I'll get to work on the website again when I have a chance._

 

Any way you could list the dimensions of the PCB??


----------



## tomb

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_Any way you could list the dimensions of the PCB??_

 

99mm wide x 80mm.


----------



## cegras

I'm planning to do this as my first DIY over the summer, after exams wind down.


----------



## v3nom

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_99mm wide x 80mm. 
	

	
	
		
		

		
		
	


	


_

 

yes! it will barely fit in my casing. Any idea when it will be ready to purchase?


----------



## tamasic1

Nube question - why are 250v WIMA film caps suggested in the BOM instead of 63 or 100v WIMAs?


----------



## tomb

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_Nube question - why are 250v WIMA film caps suggested in the BOM instead of 63 or 100v WIMAs?_

 

Because we could.
	

	
	
		
		

		
		
	


	




 Seriously, I've explained this before. Those are the same caps used for bypassing on the Millett MAX/MiniMAX. The parts commonality may help many people - including me.
	

	
	
		
		

		
		
	


	




 Other things to consider are that generally speaking, higher voltage caps perform slightly better than the same size lower voltage cap and perhaps most importantly, the more room you can make for larger pads, the more flexible the PCB will be if someone wants to use some boutique film caps.


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Production PCB's are on order.
	

	
	
		
		

		
		
	


	




 I'll get to work on the website again when I have a chance._

 

Awesome, thanks tomb. After seeing Fred's build I have decided that I'm going to redo my p2p builds -- gonna migrate all the components to the new PCB 
	

	
	
		
		

		
		
	


	




 zk


----------



## smeggy

hehe, I hate him!


----------



## zkool448

haha, you and I both


----------



## v3nom

wen will these boards be avail. for purchase??


----------



## n_maher

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_wen will these boards be avail. for purchase??_

 

I'm pretty sure tomb saw your post up higher on this page and would answer if he had an answer. In the interim I'll answer for him, they'll be ready when they're ready and you can be sure that there will be a post in this thread when they're available. No amount of asking is going to speed that along, patience.


----------



## smeggy

Is it done yet? Is it done yet? Is it done yet? Is it done yet? Is it done yet? Is it done yet?
 Is it done yet? Is it done yet? Is it done yet? Is it done yet? Is it done yet? Is it done yet?
 Is it done yet? Is it done yet?
 Is it done yet?


----------



## v3nom

Do you think this heatsink and fan assembly would be as effective as the two recommended heatsinks? I want to have everything in my housing but the big black ones are too big. 





 The 3rd dimension is .5" tall


----------



## cegras

Wouldn't use a fan be detrimental to the tubes, as they need to be hot to work?


----------



## v3nom

the fan will not be blowing on the tubes, or even be in the same compartment. (I have a box with 3 compartments.


----------



## Hayduke

I'd be worried about the fan being noisy


----------



## cegras

Nah .. in the past few years there are excellent fan selections that pop up for computers and are exceptionally quiet. Those sinks look like they would do very well with even a little airflow so you can make it practically inaudible.


----------



## v3nom

i dont mind the noise, it will be next to my gaming computer anyways which isnt really a silent machine anyways. 

 Cegras, when you said "those sinks", were you referring to mine or the black fin sinks everyone uses?


----------



## cegras

I'm not sure how effective airflow will be with it just flowing over a plate, but overall it apparently takes a good amount of hours for it to get 'finger-toasty' hot, so I'm confident you will be able to keep the heat under control.


----------



## v3nom

yea i was thinking the same thing. Its basically the same thing as a CPU heatsink setup. Thanks


----------



## Bleuburd

Hey guys. I've got a quick noob question. How are the pins on the transistors numbered? Left to right? What I'm trying to ask is if I'm looking at the front of the transistor, is the farthest let pin no. 1? Or do they correspond with the schematic, as in middle = no. 1?


----------



## v3nom

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Hey guys. I've got a quick noob question. How are the pins on the transistors numbered? Left to right? What I'm trying to ask is if I'm looking at the front of the transistor, is the farthest let pin no. 1? Or do they correspond with the schematic, as in middle = no. 1?_

 

I dont know if this will help you, but this diagram labels which pin is what





 GL


----------



## tomb

v3nom is faster than me.
	

	
	
		
		

		
		
	


	




 When describing MOSFETs, it's convention to refer to Gate, Drain, and Source - Gate, Drain, & Source ... 1, 2, 3. So if we look at the pic of the IRF510, we have this:





 And if we look at Pete Millett's schematic for the Starving Student, we have this:





 So:
 Gate = 1
 Drain = 2
 Source = 3.


----------



## v3nom

lol, i have great googling skills 
	

	
	
		
		

		
		
	


	




 btw tomb, did u catch my fan and heatsink setup on the previous page? do you think that will suffice for both mosfets on that same panel?


----------



## Bleuburd

Thanks Tomb! That's exactly what I needed. Hoping to finish my starving student by the end of this week. Pics to come!


----------



## tomb

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_lol, i have great googling skills 
	

	
	
		
		

		
		
	


	




 btw tomb, did u catch my fan and heatsink setup on the previous page? do you think that will suffice for both mosfets on that same panel?_

 

To be honest, I don't know. I think most people try to stay away from fans with headphone amps. The signals are so small and amplified so much in some circumstances that noise may become an issue ... and it's not the noise of the fan ... it's motor noise picked up by the amplifier circuit, from what I've heard.

 That said - give it a try and let us know. It may be a good solution.


----------



## v3nom

hmmm, i never though about the motor noise getting into the circuit. I guess i will give it a try, keeping the fan as far away as possible.


----------



## Hayduke

That's the noise I was worried about 
	

	
	
		
		

		
		
	


	




 Not the actual noise of the fan blades moving. I was concerned it would introduce noise into the signal. If you had a separate power supply, it might be fine. I definitely wouldn't try to run it off the same power as the amp.


----------



## v3nom

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_That's the noise I was worried about 
	

	
	
		
		

		
		
	


	




 Not the actual noise of the fan blades moving. I was concerned it would introduce noise into the signal. If you had a separate power supply, it might be fine. I definitely wouldn't try to run it off the same power as the amp._

 

yea, i knew what you meant. I was already planning on running it from a different power supply anyways. I have 2 power buttons that i am using (one for amp one for computer) and they both have 24v leds. I was going to extend a molex power connector from my computer to my housing to power them, so i was also planning to wire the fan to that as well.

 should i also use shielded wires just in case? or would that not even matter.


----------



## smeggy

I'd be more concerned with the fan vibration transmitting to the tubes as they can be very microphonic and a fan may start them ringing in your ears. Using the fan offboard would be more advisable if you don't use tube dampers.


----------



## kuroguy

Not sure if this has been asked, but feel free to eviscerate me if it has. How many sets of 19J6 tubes do you guys have to go with the boards?


----------



## zkool448

Eviscerate? perhaps a bit too extreme 
	

	
	
		
		

		
			





 This is TomB's update from p.184:
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I have about 30 power supplies, but not as many as the other things. So my latest thinking is to offer about 30 kits first, then sell the boards with tubes until the tubes run out. I estimate somewhere between 50 - 100 (x2 tubes each) for that, but we'll order 200 boards total. That means some will be left over.

 If more tubes (in qty) show up (we hope that's the case), that strategy may change.
	

	
	
		
		

		
		
	


	


_


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Eviscerate? perhaps a bit too extreme 
	

	
	
		
		

		
		
	


	




 This is TomB's update from p.184:
  Quote:


  Originally Posted by *tomb* 
I have about 30 power supplies, but not as many as the other things. So my latest thinking is to offer about 30 kits first, then sell the boards with tubes until the tubes run out. I estimate somewhere between 50 - 100 (x2 tubes each) for that, but we'll order 200 boards total. That means some will be left over.

 If more tubes (in qty) show up (we hope that's the case), that strategy may change.
	

	
	
		
		

		
		
	


	




 

_

 

Yes - this is still about right. I was able to make another buy Friday (sorry, it was everything this particular vendor had) so that number may go up to ~130 or so. It's been bothersome because the failure rate on many of the tubes I've purchased has been very high - about 15% or more. These things are so scarce now that I think the vendors are pulling them up from the Great Flood.
	

	
	
		
		

		
		
	


	




 Hence, the failure rate is very bad. I won't know the number exactly until I get through processing all the tubes - that will still take awhile.


----------



## Hayduke

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_yea, i knew what you meant. I was already planning on running it from a different power supply anyways. I have 2 power buttons that i am using (one for amp one for computer) and they both have 24v leds. I was going to extend a molex power connector from my computer to my housing to power them, so i was also planning to wire the fan to that as well.

 should i also use shielded wires just in case? or would that not even matter._

 

You could try it without shielding first if you wanted to, but it might be easier to just shield it from the get go. It's a case of "can't hurt, might help"

  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I'd be more concerned with the fan vibration transmitting to the tubes as they can be very microphonic and a fan may start them ringing in your ears. Using the fan offboard would be more advisable if you don't use tube dampers._

 

Good point. I had not actually thought about that, but some of my tubes are extremely microphonic. 
	

	
	
		
		

		
		
	


	




 I can imagine what a fan vibration would do to some of the "bad" tubes. That would be unlistenable.


----------



## jeanba3000

Hello everybody

 Finaly my first Starving Student is there ! 
	

	
	
		
		

		
		
	


	













 It's based on the last evolution of the SS, with some changes due to the stock I had :

 C1-C6 : 2000 µF 50V
 C2-C4-C3a-C5a : 0.22 µF 100 V
 R14-R16 & R15-R17 : each pair replaced by a 56.2 K
 all resistors are metal 1% 1/4W

 The wiring is P2P with components « legs » (don't know if it's the correct word, excuse my froggy english) and some short isolated wire.

 The sound is very nice but I have a small background noise and hum, and something I believe is microphonics from the tube ? It's my first tube amp so everything is new to me and I'm not sure how to explain things. I hear some tingling like glass bells on the right chanel if I touch the volume pot or any cable.

 What should I check or do to eliminate the tingling and the hum ? Is it possible to reduce the background noise ?


----------



## Hayduke

Quote:


  Originally Posted by *jeanba3000* /img/forum/go_quote.gif 
_The sound is very nice but I have a small background noise and hum, and something I believe is microphonics from the tube ? It's my first tube amp so everything is new to me and I'm not sure how to explain things. I hear some tingling like glass bells on the right chanel if I touch the volume pot or any cable.

 What should I check or do to eliminate the tingling and the hum ? Is it possible to reduce the background noise ?_

 

Hum is usually a grounding issue. I can't really tell how you have grounded the circuit.

 The glass like sound is indeed tube microphonics. That's what it sounds like. There's not a whole lot you can do. You can try dampners, but other then that, I'm not sure what you can do. I have some tubes that are extremely microphonic. So much so that with one set I can hear myself typing. Hitting the keys vibrates the desk enough that the tubes make noise


----------



## jeanba3000

Thanks for the answer.

 I will make photos and post a schematic of my SS.

 OK I wasn't aware that tube microphonics were such a « fatality », even if this tingling sound is beautiful in itself, I could just listen to it as I spent time listening to small bells hanging from budhist temples roof and slowly ringing with the wind, during my last trip to Cambodia 
	

	
	
		
		

		
		
	


	



 (excuse me if I'm too off topic !)

 I'll look for infos about tube dampers, thanks.


----------



## ThePredator

Quote:


  Originally Posted by *jeanba3000* /img/forum/go_quote.gif 
_Thanks for the answer.

 I will make photos and post a schematic of my SS.

 OK I wasn't aware that tube microphonics were such a « fatality », even if this tingling sound is beautiful in itself, I could just listen to it as I spent time listening to small bells hanging from budhist temples roof and slowly ringing with the wind, during my last trip to Cambodia 
	

	
	
		
		

		
		
	


	



 (excuse me if I'm too off topic !)

 I'll look for infos about tube dampers, thanks._

 

Beezar.com
 They fit perfectly and work well. Another thing that helped me was putting soft felt feet on the bottom of the amp.


----------



## v3nom

Are those dampers the same size for the 19j6 tubes?


----------



## tomb

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_Are those dampers the same size for the 19j6 tubes?_

 

Yes.


----------



## -=Germania=-

Having built 4 of these:

 The total gain of the amp might be too high for the headphones you are using. Try adding a 10K resistor on the input. Plus that will give you a better range on the Alps pot. 

 If there is a bunch of hm with the potentiometer turned all the way down, try the stuff below. 

 For grounding:

 - Use wire that is as thick or thicker than signal wire for grounding, it will make sure that you can sink whatever you source. 
 - Star ground or Ground plane. Personally, I like Star Ground just because it is easier to keep track of and less problems with connections touching, etc. Daisy chaining your ground connection might cause extra noise polutions.
 - Ground your case/heatsinks and throw in a ground loop breaker between your case and your headphone ground. Should give you some extra breathing room in case it is a noisy environment.

 You might want to ground that potentiometer as well.
 Plus, a well grounded source like an external DAC will lower this even further.

 You might also notice that if you bring your hand close to the tubes that here will be hum from the affected channel which is completely normal.

 With a bit of tweaking, you can get this amp to be virtually silent with high sensitivity/low impedance headphones. 

 Best of Luck!


----------



## v3nom

Mouser is on back order for the heatsinks on the BOM. Any alternatives from mouser i can get?


----------



## Yaka

try digikey


----------



## tomb

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_Mouser is on back order for the heatsinks on the BOM. Any alternatives from mouser i can get?_

 

Mouser says they're in stock:
567-657-15ABP
 ?

 If that's not suitable, check for similar offerings from Aavid and Comair Rotron. You can easily go 2" as well - just stay with something that has a 1" width (fins), though.


----------



## v3nom

ok, last question lol.

 radiodaze requires a $10 minimum and all i need are 2 tube sockets. Will these work?:
NOS 7 pin 6AV6 size tube bakelite amp sockets $1 each - eBay (item 390040995406 end time Apr-06-09 19:09:50 PDT)

 thanks


----------



## dsavitsk

Those are fine. In fact, I like them better than the new ceramic stuff.


----------



## v3nom

Ok cool, because i wasnt sure if the holes would match the pins. NOW I can buy everything lol

 thanks


----------



## padam

I've got my hands on one today. Sounds nice, only slight issue is that I get some noise with the Aurvana Live! which has a low impedance of 25 ohm (unfortunately no other dynamic headphones at the moment). Would I still get noise with a ESW10JPN which is 45 ohm?


----------



## Logistic

Hi everyone,

 This has been in the works for a while but I finally found some time to put it together. I wanted to modify the starving student amp using an alternative tube to the scarce 19J6's. I finally settled on the 12SR7 and 12SW7 which are only $1 each at vacuumtubes.net. Perfect for the starving student. The caveat is that they are metal tubes and some people may prefer glass tubes. In that case the 12SR7GT is the glass tube version of the 12SR7. It is a few dollars more per tube but still cheap. 


 Here is the result, the metal starving student:


----------



## Logistic

If you want to build this version, you have to make some small changes - 

 R1/R7 - 44k
 R5/R11 - 4K
 R2/R8 - 330K
 R4/R10 - 180K

 You will have to use an octal socket, and here are the conversions from the seven pin socket in the original circuit diagram:

 1,2 -> 6
 5,6 -> 2
 3,4 -> 7,8
 7->3
 Ground pins 4 and 5.

 You will also have to ground pin 1 which is for the metal casing. It is probably a good idea to ground pin 1 with a separate path to ground from the heaters (pins 7,8). That way if the ground connection for the heaters breaks for whatever reason you don't see that voltage on the tubes.

 Using 2" heatsinks is also recommended since the heaters are running at 12V instead of 19V.


----------



## zkool448

Nice job Logistic! I know nil about amp designs but it sounds like you've found a solution for alternate tubes -- not sure if you've built an original 19J6 based before, and now curious how this one sound compare to the original?

 zk


----------



## penneydude

I just ordered all the parts to build one of these off Mouser (I found some 19J6's at a local shop, so I have those already) and I decided to go with the Nichicon Muse KW's - I got 1000uF caps to use as both the power caps and the output caps...I think they will be fine on the power end, but is 1000uF too much for the output caps? Would 470uF be a better choice sound-wise?


----------



## Coreyk78

Quote:


  Originally Posted by *penneydude* /img/forum/go_quote.gif 
_I just ordered all the parts to build one of these off Mouser (I found some 19J6's at a local shop, so I have those already) and I decided to go with the Nichicon Muse KW's - I got 1000uF caps to use as both the power caps and the output caps...I think they will be fine on the power end, but is 1000uF too much for the output caps? Would 470uF be a better choice sound-wise?_

 

I used the KWs in 1 of my SS builds and I really liked them, although I used 470uF all around. The only thing I can think of is that the larger output caps could possibly give a little more of a turn-off pop than smaller caps would.

 Also, to Logistic, that looks like a very interesting build, I do have some octal sockets, extra PSU and chassis so the rest of the parts would be pretty cheap. I'll have to put that one on my to-build list


----------



## penneydude

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_I used the KWs in 1 of my SS builds and I really liked them, although I used 470uF all around. The only thing I can think of is that the larger output caps could possibly give a little more of a turn-off pop than smaller caps would._

 

Do you think the 1000uF caps would make the amp sound muddier than the 470 uF? Or does adding larger caps not really make that much of a difference?

 Good to hear I made a solid choice on the model at least


----------



## sacd lover

I found some nice 19J6s for you guys, if you are interested.

http://www.head-fi.org/forums/f42/at...s-sale-418376/


----------



## smeggy

I like what you've done there logistc, very nicely built and good work on converting for tin tubes. I'm curious as to how it sounds compared to a stock SS.


----------



## Fred_fred2004

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Hi everyone,

 This has been in the works for a while but I finally found some time to put it together. I wanted to modify the starving student amp using an alternative tube to the scarce 19J6's. I finally settled on the 12SR7 and 12SW7 which are only $1 each at vacuumtubes.net. Perfect for the starving student. The caveat is that they are metal tubes and some people may prefer glass tubes. In that case the 12SR7GT is the glass tube version of the 12SR7. It is a few dollars more per tube but still cheap. 


 Here is the result, the metal starving student:_

 

I'm curious, what made you decide on this tube? 

 Cheers
 Fred


----------



## GeckoSlayer

Was thinking about this, I might rip apart my current iphone speaker system and put a millet starving student inside it 
	

	
	
		
		

		
		
	


	




 are there any millet starving students with ipod/iphone docks on them yet?


----------



## GeckoSlayer

Was thinking about this, I might rip apart my current iphone speaker system and put a millet starving student inside it 
	

	
	
		
		

		
		
	


	




 are there any millet starving students with ipod/iphone docks on them yet?


----------



## keiths

Quote:


  Originally Posted by *GeckoSlayer* /img/forum/go_quote.gif 
_are there any millet starving students with ipod/iphone docks on them yet?_

 

Yep


----------



## v3nom

Do I connect all the grounds to the ground from the power supply?

 Like so, but I didnt draw the rest of the grounds but you can still get what I am asking.


----------



## smeggy

Yes, all connected to the same ground. You can buy connector strip things to solder all the grounds to from places like radio shack


----------



## Logistic

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Nice job Logistic! I know nil about amp designs but it sounds like you've found a solution for alternate tubes -- not sure if you've built an original 19J6 based before, and now curious how this one sound compare to the original?

 zk_

 

Thanks, I have built a 19J6 version before. From an initial comparison the 12SR7 seems to have more detailed highs and stronger bass but milder mids. The 19J6 sounds a little more tubey but that may be due to the stronger highs and bass in the 12SR7, I'm not sure. I'll try the 12SW7s (which are almost the same tube) and see if they sound any different.

 Edit: I just tried some 12SW7s and they sound like the 12SR7 but bring out the mids a little more and give a little more "tubebyness" IMO.


----------



## Logistic

Quote:


  Originally Posted by *Fred_fred2004* /img/forum/go_quote.gif 
_I'm curious, what made you decide on this tube? 

 Cheers
 Fred_

 

I chose this tube because it was suitable for adapting to the original design without changing too much and because it was cheap in keep with the starving student theme.


----------



## ThePredator

I think I am going to have to build a 12SR7/12SW7 version now. I am a sucker for the modern look of metal tubes.


----------



## tamasic1

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yes, all connected to the same ground. You can buy connector strip things to solder all the grounds to from places like radio shack_

 

I can see by the SSHA schematics it doesn't show this but in other builds I've done it was recommended that the input's 'star' ground was to be connected to the power ground via a low ohm resistor. Is it that the Cisco PS elimnates the need for this?

 Logistic has created a _Stelth tube amp_ - Very cool! Thanks for the mod.


----------



## zkool448

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Thanks, I have built a 19J6 version before. From an initial comparison the 12SR7 seems to have more detailed highs and stronger bass but milder mids. The 19J6 sounds a little more tubey but that may be due to the stronger highs and bass in the 12SR7, I'm not sure. I'll try the 12SW7s (which are almost the same tube) and see if they sound any different._

 

That's so cool... so in theory, your mods can be applied using the new PCBs (coming soon) as long as some R values are changed, and octel sockets air-wired using the 7 to 8 socket pin conversion... hmmm, interesting.

 zk


----------



## smeggy

I think there's a possibility my next SS may be tintubed 
	

	
	
		
		

		
		
	


	




 BTW, how hot do the tin tubes get compared to the glass variety, pretty similar?


----------



## tomb

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_I can see by the SSHA schematics it doesn't show this but in other builds I've done it was recommended that the input's 'star' ground was to be connected to the power ground via a low ohm resistor. Is it that the Cisco PS elimnates the need for this?</snip>_

 

I don't know of any reason you wouldn't want to connect all grounds (including the power ground) to the common ground with as little resistance (big wires) as possible. While a star ground is certainly acceptable, keep in mind that Pete's original build used a copper board as a common ground plane. This is in effect, the same as a PCB with a ground plane.


----------



## Logistic

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_That's so cool... so in theory, your mods can be applied using the new PCBs (coming soon) as long as some R values are changed, and octel sockets air-wired using the 7 to 8 socket pin conversion... hmmm, interesting.

 zk_

 

Yes, and I would recommend bigger heatsinks to help shed the additional heat from the mosfets.

  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I think there's a possibility my next SS may be tintubed 
	

	
	
		
		

		
		
	


	




 BTW, how hot do the tin tubes get compared to the glass variety, pretty similar?_

 

The tubes actually run cooler than the glass 19J6s. I can actually put my finger on the top of these for a while and they feel warm/hot.


----------



## dsavitsk

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_I can see by the SSHA schematics it doesn't show this but in other builds I've done it was recommended that the input's 'star' ground was to be connected to the power ground via a low ohm resistor._

 

Don't do that, it is a very bad idea.


----------



## Yaka

update on my pcb build. finaly got a chanc eto work on couple of hours before the man utd vs villa football game on sunday















 gonna try file the sockets legs this week end and make em sit more lower and straight as they are both a bit wonky. also i didn't end up soldering the mosfets on to the pcb as i tried a different way to use the case without thinking. nates way is much more faster and simple and easy and had i given more thought i would not have done it the way i have i done was just too much hassle. i am still dreading the fact i am gonna have to drill the flat finned heatsink i got 2 holes both through the fins:/ 

 as peeps will noticed in the close up inner pic that i have leds installed. for some reason they dont work not sue what i have done wrong.


----------



## n_maher

It's not a good idea to mount the FETs that way, it puts potentially too much distance between R3 and R9 and the FET. Pete recommended soldering these resistors direct to the FET to avoid oscillation issues.

 I hope you also have some additional support for that pcb planned as the one rail isn't going to cut it when you insert tubes.


----------



## Yaka

yeah i realised about the resistors on fets i really made a mistake on not thinking it thru. and yes i have added support for the pcb


----------



## v3nom

Ok so I am about 75% done with my build, i just have a few questions.

 1. Is it okay to use solid copper wires for the ground, power, and audio in, as well as 24awg silver wire for all the other hookups including those going/coming from the tubes and mosfets?

 2. Are C2 and C4 polar? What about the coupling caps? 

 That should be it for now 
	

	
	
		
		

		
		
	


	




 thanks


----------



## Fred_fred2004

The wire will be fine,
 C2 & C4 are not polarised
 C1,3,5,6 are polarized

 cheers
 Fred


----------



## CaptHowie

Are the production pcb's available yet? Just need to know as holidays are here, im about to order my BOM from Farnell and i've only got 1 and a half weeks to complete it 
	

	
	
		
		

		
			





 If they're not available yet (which I have a feeling there not) could someone please tell me if it is easy to do a point to point build? I havent built a project using a schematic yet, although I have basic knowledge on all the symbols and how the ground plane works, and I guess it would be handy on future projects.

 Thanks,
 -CaptHowie


----------



## v3nom

I am currently doing the point-to-point build. I'd say it's pretty easy even for my first p2p. All it is, is something like (for example) R2 shares a node with C5 and C2, solder them together... node done... next node...


----------



## CaptHowie

It sounds ok then. Is it just soldering some ends together? Some if 1 resistor was connected to a cap and another resistor, you would just solder all their ends together? Am I right? If that's it i'll happily build p2p.


----------



## v3nom

yep, check out the amp on the first page of this thread, its pure p2p. Also, Pete's design uses a ground plate in combination with a p2p build too.


----------



## Hayduke

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_Ok so I am about 75% done with my build, i just have a few questions.

 1. Is it okay to use solid copper wires for the ground, power, and audio in, as well as 24awg silver wire for all the other hookups including those going/coming from the tubes and mosfets?

 2. Are C2 and C4 polar? What about the coupling caps? 

 That should be it for now 
	

	
	
		
		

		
		
	


	




 thanks_

 

1. I think the gauge is more important then the material or stranded/solid. Since the wiring will be sitting still, solid should be fine. I haven't used silver wire, but isn't it more expensive? I'm not sure what benefit you're hoping to gain. I wired mine with SPC from navships.

 2. I think it depends on the caps you bought. Got part #s? We can look at the datasheet if needed to find out.


----------



## v3nom

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_1. I think the gauge is more important then the material or stranded/solid. Since the wiring will be sitting still, solid should be fine. I haven't used silver wire, but isn't it more expensive? I'm not sure what benefit you're hoping to gain. I wired mine with SPC from navships.

 2. I think it depends on the caps you bought. Got part #s? We can look at the datasheet if needed to find out._

 

My selection of wire wasn't from any hope of benefit gain but it was just what I have currently in my possession. 

 I also got the cap situation all figured out. Thanks guys.


----------



## Hayduke

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_My selection of wire wasn't from any hope of benefit gain but it was just what I have currently in my possession. 

 I also got the cap situation all figured out. Thanks guys._

 

ah, then your wire should be fine 
	

	
	
		
		

		
		
	


	




 glad you figured out the caps. In general, if there isn't a polarity marking on the device, it doesn't matter.


----------



## metal112524

Are there any tubes left for this build out there? I have not been able to find one source. I already have a pair on the way but I don't know if they are matched or not. I don't even know what it means for them to be "matched" exactly.


----------



## Bleuburd

Well, I got mine from thetubecenter.com and was told that they were at least from the same stock. But, they aren't. Two of them look like they're similar, but none of them are "matched".


----------



## Punnisher

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_Are there any tubes left for this build out there? I have not been able to find one source. I already have a pair on the way but I don't know if they are matched or not. I don't even know what it means for them to be "matched" exactly._

 

Matched means the same brand and same design inside the tube.

 Let me know once you get them, as I have an unmatched pair that I could sell if it happened to match yours. RCA or GE I believe.


----------



## tomb

Quote:


  Originally Posted by *Punnisher* /img/forum/go_quote.gif 
_Matched means the same brand and same design inside the tube.

 Let me know once you get them, as I have an unmatched pair that I could sell if it happened to match yours. RCA or GE I believe._

 

Actually, _matched_ means the same output as tested on a tube tester. In the case of the 19J6 tube, it has two triodes (amplifier tube circuits). The Starving Student ties both of these triodes in parallel, a not uncommon way to do it. However, a tube tester measures one triode at a time. I asked Pete Millett if the triodes "average" when they are tied in parallel, but he says they're most often considered "additive." So that means the sum of the tested value for each triode in a tube should be equal to another tube's sum of the triodes' tested values.

 IOW, say we measure one triode in a 19J6 at 110, the second at 95. This is not uncommon - in fact, almost every 19J6 I've tested is slightly different from one triode to another. I suspect that this is the case for most dual-triode tubes. Anyway, the sum of those two triode measurements is 205. So, if I measure another 19J6 with one triode at 100, and another triode at 105, then those two 19J6's will be matched because the sum of both is 205.

 Edit: All of this is at least in the case of the Starving Student where the triodes are in parallel. Another circuit may not tie the triodes in parallel and this premise may not hold true. (One of the reasons tube amp designers tie the triodes together within a dual-triode tube is for this very reason - to minimize the imbalance, or IOW, to increase the chances that two random tubes will work out to be balanced.)


----------



## zkool448

edit: tomb was faster than I am, I was going to post this:
What does Matched Pair mean?

 zk


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_edit: tomb was faster than I am, I was going to post this:
What does Matched Pair mean?

 zk_

 

Yes, good link! However, I wanted to take the opportunity to explain what _matching_ meant specifically for the Starving Student circuit, since that's how I'm going to supply the tubes when we get to that point.


----------



## Punnisher

I see.

 Silly of me to answer a question without knowing the proper answer. My bad!


----------



## metal112524

^Punnisher, I made that same assumption. Tomb, thanks for the info, I doubt ill be getting a matched pair, what are the negatives of having a unmatched pair.


----------



## CaptHowie

Hey Everyone,
 I'm having a bit of trouble obtaining these parts:
 R16/17 50K, 1/4W Resistor
 RLED 2.4K, 2W Metal Oxide Resistor
 3MMAJ Neutrik [NMJ6HCD2] 3.5MM, Stereo Audio Jack
 SNDOF 20MM M3x0.5, Male-Female Aluminium Hex
 TO220 TO-220 Heatsink Kit
 HEATS TO-220 Heatsink, Unspecified (Which one?)
 PWRS Cisco [PSA-18U] 120/240V Input, 48VDC@0.38A Reg. Pwr. Supply

 I need to find these parts in Australia. 
	

	
	
		
		

		
			





 I haven't got much time (i'm in the middle of holidays atm 
	

	
	
		
		

		
		
	


	




 so I have about a week and a half to get all the parts ordered 
	

	
	
		
		

		
		
	


	




) and i'm using Farnell for the majority of my BOM, but I am also using Jaycar for some of the parts that Farnell don't carry.

 Any help would be greatly appreciated. 
	

	
	
		
		

		
		
	


	



 Sorry i'm talking like a lunatic, but i'm in a rush 
	

	
	
		
		

		
		
	


	







 -CaptHowie


----------



## Fred_fred2004

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Hey Everyone,
 I'm having a bit of trouble obtaining these parts:

 R16/17 50K, 1/4W Resistor
*I used Jaycars - RR0614 51K 1% metal film 1/2watt*

 RLED 2.4K, 2W Metal Oxide Resistor
*Jaycars - RR2784 2.7K 1 watt works fine in mine* 
 3MMAJ Neutrik [NMJ6HCD2] 3.5MM, Stereo Audio Jack
*Jaycars - PS0195 *

 SNDOF 20MM M3x0.5, Male-Female Aluminium Hex
*didn't use stand offs*

 TO220 TO-220 Heatsink Kit
*didn't use insulated the heat sink from the case*

 HEATS TO-220 Heatsink, Unspecified (Which one?)
*Jaycars - HH8526 Heavy Duty TO-3P Heatsink (ML97 Type)*

 PWRS Cisco [PSA-18U] 120/240V Input, 48VDC@0.38A Reg. Pwr. Supply
*eBay *


 I need to find these parts in Australia. 
	

	
	
		
		

		
		
	


	




 I haven't got much time (i'm in the middle of holidays atm 
	

	
	
		
		

		
		
	


	




 so I have about a week and a half to get all the parts ordered 
	

	
	
		
		

		
		
	


	




) and i'm using Farnell for the majority of my BOM, but I am also using Jaycar for some of the parts that Farnell don't carry.

 Any help would be greatly appreciated. 
	

	
	
		
		

		
		
	


	



 Sorry i'm talking like a lunatic, but i'm in a rush 
	

	
	
		
		

		
		
	


	







 -CaptHowie_

 

hope that helps
 cheers
 Fred


----------



## CaptHowie

Thanks heaps for that Fred. I've changed a few things in my design like removing the LEDs so that will remove those hard to find resistors. I'm using the Jaycar 3.5mm Stereo Chassis jack as you mentioned above as well. With the standoffs and the heatsink and kit, why didn't you need the standoffs and the kit, and how do you insulate the MOSFETS using the case? I'm trying to minimize the price (i'm a student...) and cutting those things off the list would reduce the price, as would using Jaycar's heatsinks (2x$3.00 something for the Jaycar vs. 2x$12.10 for the Farnell one). Removing the heatsink kit would also save some money as the minimum order quantity on Farnell is 10. Any further tips would be greatly appreciated.

 Thanks,
 -CaptHowie


----------



## CaptHowie

Oops! Head-Fi stuffed up on me and double posted... sorry!


----------



## Fred_fred2004

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Thanks heaps for that Fred. I've changed a few things in my design like removing the LEDs so that will remove those hard to find resistors. I'm using the Jaycar 3.5mm Stereo Chassis jack as you mentioned above as well. With the standoffs and the heatsink and kit, why didn't you need the standoffs and the kit, and how do you insulate the MOSFETS using the case? I'm trying to minimize the price (i'm a student...) and cutting those things off the list would reduce the price, as would using Jaycar's heatsinks (2x$3.00 something for the Jaycar vs. 2x$12.10 for the Farnell one). Removing the heatsink kit would also save some money as the minimum order quantity on Farnell is 10. Any further tips would be greatly appreciated.

 Thanks,
 -CaptHowie_

 

Heres some pics


























 I was using a Jaycars ABS box (HB5970) so the heat sinks were insulated from the circuit, the switch has abuilt in LED ( SP0704) which makes life simple, the home made pcb is sitting flat on the case's base, So I didn't need to stand it clear of any metal. The Mosfets have clear heatshrink on them but its hard to see (because its clear). The amp is great well worth building
 cheers
 Fred


----------



## kuroguy

Anybody know the voltage gain of a starving student with 12sr7 or 12sw7 versus the 19j6 tube?


----------



## tomb

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_^Punnisher, I made that same assumption. Tomb, thanks for the info, I doubt ill be getting a matched pair, what are the negatives of having a unmatched pair._

 

An unmatched pair means the channels will be mis-matched. However, keep in mind that Pete Millett foresaw this to a certain extent, which is one of the reasons he chose to use two tubes with dual triodes tied together - the entire effect is to minimize those differences. That means the chances are less than they might've been, but it's still possible.
	

	
	
		
		

		
		
	


	




 In cases such as the Millett MAX/MiniMAX, there is a bias adjustment that allows you to "center" the Left and Right channels (among other things), but even if biased the same - if one tube has a different output than the other, then one of your headphone cans will seem "dead" compared to the other.

 In the case of the Starving Student the bias adjustment is fixed, so a true tube mis-match is not correctible even for channel centering. One might say that makes tube matching much more critical than not with the SSMH. For example, the 19J6's I've tested run from 70 to 120 (on a Jackson 658A tube tester). I think most tube vendors state tube matching within 10%. So, it might be safe to assume that differences greater than that are noticeable. 70 to 120 is a variance of 25%, so the potential for mis-match exists.


 P.S. Nice work, Fred!


----------



## TimJo

Quote:


  Originally Posted by *Fred_fred2004* /img/forum/go_quote.gif 
_
 I was using a Jaycars ABS box (HB5970) so the heat sinks were insulated from the circuit, the switch has abuilt in LED ( SP0704) which makes life simple, the home made pcb is sitting flat on the case's base, So I didn't need to stand it clear of any metal. The Mosfets have clear heatshrink on them but its hard to see (because its clear). The amp is great well worth building
 cheers
 Fred_

 

Looks good Fred, the only thing I noticed was WRT the FET's. If my memory is correct, I thought Pete said at one point that it was important to attach the 2k resistors connected to the gate of the mosfet as close as possible to prevent oscillation in the buffers. I may be mixing this up with another design, so folks, please correct me if I'm wrong here. 

 Anyway, looking at the photos, it looks like you have a wire going from the gate to the board, with the 2k on the board. Again, it's hard to tell from the photos, but that may be a minor change worth making.

 But on the other hand, if it's working, maybe it's not worth messing with...


----------



## Yaka

nice build fred the braiding was an excellent touch


----------



## cactus friend

Guess I'm a little late to the party...just bought a bunch of parts for this project...only to realize that the tubes are nowhere to be purchased...


----------



## scompton

A few pages back, there's a post on substitute tubes. It also requires different values for some of the resistors. You can also wait a little and buy boards with tubes.


----------



## Logistic

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Anybody know the voltage gain of a starving student with 12sr7 or 12sw7 versus the 19j6 tube?_

 

The gain with the 12sr7 and 12sw7 is around 6.


----------



## Fred_fred2004

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Looks good Fred, the only thing I noticed was WRT the FET's. If my memory is correct, I thought Pete said at one point that it was important to attach the 2k resistors connected to the gate of the mosfet as close as possible to prevent oscillation in the buffers. I may be mixing this up with another design, so folks, please correct me if I'm wrong here. 

 Anyway, looking at the photos, it looks like you have a wire going from the gate to the board, with the 2k on the board. Again, it's hard to tell from the photos, but that may be a minor change worth making.

 But on the other hand, if it's working, maybe it's not worth messing with..._

 

Yes I've just read about the resisters, however its super stable with no hum/hiss or background noise, it drives my AD700's very nicely, so I think I have got away with it, beginners luck 
	

	
	
		
		

		
		
	


	




 cheers
 fred


----------



## zkool448

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_The gain with the 12sr7 and 12sw7 is around 6._

 

Sounds like an ideal recipe for some grados and other low Z cans 
	

	
	
		
		

		
		
	


	




 zk


----------



## CaptHowie

Quote:


  Originally Posted by *Fred_fred2004* /img/forum/go_quote.gif 
_Heres some pics
 I was using a Jaycars ABS box (HB5970) so the heat sinks were insulated from the circuit, the switch has abuilt in LED ( SP0704) which makes life simple, the home made pcb is sitting flat on the case's base, So I didn't need to stand it clear of any metal. The Mosfets have clear heatshrink on them but its hard to see (because its clear). The amp is great well worth building
 cheers
 Fred_

 

Thx Fred for the photos but there are still a few questions I have:
 1. I still don't get how you insulated the MOSFETs as I don't see any heatsinks and the case is ABS (I probably missed them in one of the photos). I know you have heatshrinked the MOSFETs as well.
 2. Where would you connect the LED circuit to?

 You've been heaps of help. Much appreciated.
 -CaptHowie


----------



## v3nom

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Thx Fred for the photos but there are still a few questions I have:
 1. I still don't get how you insulated the MOSFETs as I don't see any heatsinks and the case is ABS (I probably missed them in one of the photos). I know you have heatshrinked the MOSFETs as well.
 2. Where would you connect the LED circuit to?

 You've been heaps of help. Much appreciated.
 -CaptHowie_

 

His FETS are on the heatsinks mounted on the top of his case.


----------



## Fred_fred2004

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Thx Fred for the photos but there are still a few questions I have:
 1. I still don't get how you insulated the MOSFETs as I don't see any heatsinks and the case is ABS (I probably missed them in one of the photos). I know you have heatshrinked the MOSFETs as well.
 2. Where would you connect the LED circuit to?

 You've been heaps of help. Much appreciated.
 -CaptHowie_

 

V3nom is spot on, you don't need to insulate the mosfets from the heatsinks because they are mounted on plastic.

 The LED look at the back of the switch the Rled is in some black heatshrink







 here is the pcb I've tried to show how the led is connected
 cheers
 fred


----------



## penneydude

I'm building this now,can someone double check the way I'm reading the schematic?

 Do R3 and R9 go to pin 1 (gate) of the MOSFETs?


----------



## zkool448

Quote:


  Originally Posted by *penneydude* /img/forum/go_quote.gif 
_I'm building this now,can someone double check the way I'm reading the schematic?

 Do R3 and R9 go to pin 1 (gate) of the MOSFETs?_

 

Yes penneydude, that's correct. Solder the resistor lead directly to pin 1 of the mosfet to keep their distance short.

 zk


----------



## penneydude

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Yes penneydude, that's correct. Solder the resistor lead directly to pin 1 of the mosfet to keep their distance short.

 zk_

 

Thanks! I'm so close...


----------



## cactus friend

One more dumb question - I can't find the exact power supply on ebay, but I do see a similar 48v power supply that offers 1.25amps. Since the original one mentioned only offers .38 amps or so, will this be okay?

*Edit *- oops, I've just found the proper power supply for cheaper on eBay after all. Disregard!


----------



## grendel23

Quote:


  Originally Posted by *cactus friend* /img/forum/go_quote.gif 
_One more dumb question - I can't find the exact power supply on ebay, but I do see a similar 48v power supply that offers 1.25amps. Since the original one mentioned only offers .38 amps or so, will this be okay?_

 

I use the 1.25 amp unit. It works great, without the stuttering the 380ma one can cause.


----------



## metal112524

what is the minimum or recommended wire gauge for running wires to the fets and tube sockets?


----------



## v3nom

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_what is the minimum or recommended wire gauge for running wires to the fets and tube sockets?_

 

I don't think there is a minimum or recommended awg size but if you want to put a size to it i guess the minimum gauge could be equal to the leads on the resistors/capacitors you use.


----------



## metal112524

ok well is 22awg ok? or maybe 2 strands per lead?


----------



## n_maher

22awg is more than fine.


----------



## tomb

PCB's have shipped. It may take a few more days for me after they get here, though - this comes right on top of IRS time.


----------



## tamasic1

Ok, finally got around to building it. 






 True starving student as the tubes were the only things purchased.(thanks v3nom) The rest of the parts came from old ups and computer power supplies. Jacks are from a sound card and the pot is from an old stereo. All wiring was done with Cat5E, p2p so I can upgrade parts as I aquire them. Very, very slight hum when nothing is attached to the input but dead silent when the mp3 was attached. I’ve been listening for 2hrs now and its amazing. Thanks Pete and everyone else for all the info and upgrade ideas.


----------



## TimJo

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_
 True starving student...
_


----------



## Yaka

nice build mate


----------



## cegras

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_PCB's have shipped. It may take a few more days for me after they get here, though - this comes right on top of IRS time.
	

	
	
		
		

		
			



_

 

When everything's ready to go, will beezar be the site where we go to for buying?


----------



## Logistic

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Sounds like an ideal recipe for some grados and other low Z cans 
	

	
	
		
		

		
		
	


	




 zk_

 

I'm very curious how the 12SR7 and 12SW7 sound with low z cans like grados. They sound very good with the HD 580 and the KSC75s. The more detailed highs and slightly increased bass slam really help with rock music while still keeping the tubey mids which fatten the tone.


----------



## tomb

Quote:


  Originally Posted by *cegras* /img/forum/go_quote.gif 
_When everything's ready to go, will beezar be the site where we go to for buying?_

 

According to Head-Fi rules, you should probably send me a PM for such a question, but YES.


----------



## smeggy

General info on where to go for them is appropriate here I think.

 Thanks Tom.


----------



## cegras

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_According to Head-Fi rules, you should probably send me a PM for such a question, but YES._

 

>_< Sorry, I'll keep that in mind next time. Apologies!


----------



## tamasic1

Since I finished my SSHA this morning I've made a couple observations. 

 The mosfet heatsinks are 2"h x 1.25"w x 1.25"L fins. I wouldn't recommend anything less than this. You can put your finger on them but you won't keep it there long (kinda hot). 

 I need a cross filter. To me, it makes a BIG difference in how long I'm able to wear headphones. I've built one cmoy with a static and one with a switchable cross filter. I've gone as long as 6 hrs without tiring. Maybe an hour on any amp without one.
 And when using an MP3 player make sure you ripped your music to it 'CD quality'. If not, this amp will let you know it.


----------



## metal112524

I have this power supply, can someone tell me the polarity of the pin and sleeve. Thanks in advance, its all I need to hook up the amp. lol, idk whats gonna happen when I fire it up though.

Cisco 34-1916-02 A0 PSM60U-480KP Power Supply 48V 1.25A - eBay (item 350177608731 end time Apr-11-09 19:36:38 PDT)


----------



## n_maher

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_I have this power supply, can someone tell me the polarity of the pin and sleeve. Thanks in advance, its all I need to hook up the amp. lol, idk whats gonna happen when I fire it up though.

 ]_

 

You don't need us, use your multimeter.


----------



## metal112524

^ya thanks, i don't have one.


----------



## Fred_fred2004

use a LED and resister in series, the led will only light one way


----------



## metal112524

i dont have a led or resistor


----------



## mb3k

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_i dont have a led or resistor_

 

The listing doesn't indicate the tip/sleeve polarity. You will have to use a multimeter or led/resistor to know for sure. Multimeters can be picked up very cheap and proves to be a must-have in the tool box.


----------



## Fred_fred2004

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_i dont have a led or resistor_

 

what do you have? in the junk box


----------



## n_maher

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_^ya thanks, i don't have one._

 

Then you're going about this 100% the wrong way. Undertaking this, or just about any other DIY electronics project, without the most fundamental tool for the job (short of perhaps a soldering iron) is ridiculous. What's your plan for when something goes wrong with the amp? You plan on keeping a steady supply of tester headphones around so that as you cook pair after pair you can just keep throwing them at the problem? I'm sorry for the sarcasm but what you're basically trying to do is read a book in the dark. On top of that when you noticed the light was out you asked someone to read you the first page but tell you how the story ends.


----------



## v3nom

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_Ok, finally got around to building it. 







 True starving student as the tubes were the only things purchased.(thanks v3nom) The rest of the parts came from old ups and computer power supplies. Jacks are from a sound card and the pot is from an old stereo. All wiring was done with Cat5E, p2p so I can upgrade parts as I aquire them. Very, very slight hum when nothing is attached to the input but dead silent when the mp3 was attached. I’ve been listening for 2hrs now and its amazing. Thanks Pete and everyone else for all the info and upgrade ideas._

 


 Glad you like the tubes. But my build is completely opposite of a "true starving student" lol. All parts together cost me around $80, it's got a lot of extras 
	

	
	
		
		

		
		
	


	




 I was thinking of calling it "Starving Stud" or "Super Student" or something to that effect


----------



## tamasic1

adding more goodies to the circuit or case?


----------



## smeggy

That's a great build Tamasic, very cool look too. What are those huge caps in there and can we get a shot of the underbelly of the beast?


----------



## tamasic1

The big caps are Chemicon rated 200v. I used 1000uF for power decoupling and 330uF for the output as those are what I had. I have Rubycons and Nichicons but none close to the values in this project. The bypass caps are PE 250v. Again I had nice PP spares but only a 50v rating. I'll get a underside pic when i go to work on it again today.


----------



## Earwax

I've built SS amps but never a tube amp. This looks like a good place to start. But if I do it, I'd want to totally encase the tubes. How tall are they and roughly how tall would the case need to be to accomodate tube and socket?


----------



## Yaka

off hand the tubes are smaller than my thumb, any socket you choose will not add much height to the tubes. personally i find the look of the tubes much better sicking out of the case than hidden inside


----------



## metal112524

ground is negative right?


----------



## zkool448

Quote:


  Originally Posted by *metal112524* /img/forum/go_quote.gif 
_ground is negative right?_

 

If you mean the (-/0V) of the 48VDC, yes that will be ground.

  Quote:


  Originally Posted by *Earwax* /img/forum/go_quote.gif 
_How tall are they and roughly how tall would the case need to be to accomodate tube and socket?_

 

19J6 tubes dimensions:


----------



## penneydude

Well I finally got mine built, but I have a few issues.

 There is a pretty terrible hum (60 Hz-ish, but it sounds like more of a chord than a standard 60 Hz buzz) coming out of both channels when I have the amp switched on, regardless of the volume or what I have plugged in. It was just a hum in the left channel and the right sounded fine, so I did some poking around and noticed that on the headphone jack I had switched the tip and the sleeve (right channel audio and ground), so I put those back where they were supposed to be, but now the hum is in both channels instead of just the left. 
	

	
	
		
		

		
		
	


	




 Also, when I first turn the amp on I have to wait a minute and turn the power on and off a few times to get the tubes to heat up and light, with a periodic popping coming out of my headphones - it sounds like once a second, maybe a little faster. I also get a really loud pop from the phones (crappy test phones, fortunately) both when I turn the amp on, and when I turn it off. These things would make sense if I had smaller power caps, but I'm using 1000uF Nichicons for C1 and C6, so I don't really get why this is still happening.

 If anyone could help shed some light on these issues I would really appreciate it. Thank you!


----------



## Fred_fred2004

Quote:


  Originally Posted by *penneydude* /img/forum/go_quote.gif 
_Well I finally got mine built, but I have a few issues.

 There is a pretty terrible hum (60 Hz-ish, but it sounds like more of a chord than a standard 60 Hz buzz) coming out of both channels when I have the amp switched on, regardless of the volume or what I have plugged in. It was just a hum in the left channel and the right sounded fine, so I did some poking around and noticed that on the headphone jack I had switched the tip and the sleeve (right channel audio and ground), so I put those back where they were supposed to be, but now the hum is in both channels instead of just the left. 
	

	
	
		
		

		
		
	


	




 Also, when I first turn the amp on I have to wait a minute and turn the power on and off a few times to get the tubes to heat up and light, with a periodic popping coming out of my headphones - it sounds like once a second, maybe a little faster. I also get a really loud pop from the phones (crappy test phones, fortunately) both when I turn the amp on, and when I turn it off. These things would make sense if I had smaller power caps, but I'm using 1000uF Nichicons for C1 and C6, so I don't really get why this is still happening.

 If anyone could help shed some light on these issues I would really appreciate it. Thank you! 
	

	
	
		
		

		
		
	


	


_

 


 The first thing you must do is check the circuit against your work, be painfully exact about it. This is a tried and proven circuit so the chances are you've made a simple mistake. I know I've done it many times


----------



## zkool448

penneydude, what kind of enclosure are you using? Is the pot grounded or is it isolated from the case? 

 Regarding your power issue, iirc that is the sign of stutter in the ps folks have reported back then, however the larger caps (470uF and higer) supposed to have addressed the problem (?).


----------



## metal112524

Hey guys, just wanted to say thanks for the help, I got a thumpin' headache. I had been listening to my Brand New, Just Completed, Starving Student and after about two hours I took off my headphones and realized that I was probably listening in the way high 90's. Just wow, It sounds awesome, I could never listen to my Fuze straight this loud. AND I DID IT ALL WITHOUT A MULTIMETER!!!!!

 Anyways, I just wanted to give a shout out to the guy that I bought the kit from. Awesome dude, he was the one that finally was able to answer my question about the whole which pin is ground and such. Great guy you can find his kit on ebay for like $60 bucks shipped with tubes and all. Mine got here in two days and he even put a little epistle, which is a nice touch. Thanks extremelighting!


----------



## penneydude

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_penneydude, what kind of enclosure are you using? Is the pot grounded or is it isolated from the case? 

 Regarding your power issue, iirc that is the sign of stutter in the ps folks have reported back then, however the larger caps (470uF and higer) supposed to have addressed the problem (?)._

 

I'm just using a metal box that I had lying around, tea came in it originally. 
	

	
	
		
		

		
		
	


	




 Pins 3 and 6 of the pot go straight to the ground, and the metal shaft is definitely connected to the metal box I have everything in, so I think the pot is ok, but I'll check it again. I might end up running a lead straight from the box to the ground too.

 I'll go back over the whole circuit again tonight and see if I can find this problem. I thought maybe just based on the symptoms someone could point me in the right direction if they had a similar issue, but fortunately I DO have a multimeter. 
	

	
	
		
		

		
		
	


	




 (Congrats on the successful build metal, btw)


----------



## tamasic1

Quote:


  Originally Posted by *penneydude* /img/forum/go_quote.gif 
_I also get a really loud pop from the phones (crappy test phones, fortunately) both when I turn the amp on, and when I turn it off. These things would make sense if I had smaller power caps, but I'm using 1000uF Nichicons for C1 and C6, so I don't really get why this is still happening._

 

I agree with Fred. Carefully go back over your work. I got 1000uf and even with the volume all the way up, when I power on or off there is not the slightest sound. Seriously - dead quiet.


----------



## penneydude

Yep, it was my fault - I forgot to connect the other end of the power caps to the ground, haha.

 Noob mistake, but it's working perfectly now and it sounds GREAT! Thanks for your help guys, and thanks to Pete for the design.


----------



## zkool448

hahaha congrats 
	

	
	
		
		

		
			





 If I may I ask, how the heck did you miss soldering them to ground?


----------



## Fred_fred2004

Quote:


  Originally Posted by *penneydude* /img/forum/go_quote.gif 
_Yep, it was my fault - I forgot to connect the other end of the power caps to the ground, haha.

 Noob mistake, but it's working perfectly now and it sounds GREAT! Thanks for your help guys, and thanks to Pete for the design. 
	

	
	
		
		

		
		
	


	


_

 

Well done, its usually something simple, 
 enjoy the amp


----------



## J.P.6

Guys,

 I've got 4 19J6 tubes available for people looking for some in the UK.

http://www.head-fi.org/forums/f44/fs...bes-uk-419710/

 Thanks.


----------



## penneydude

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_hahaha congrats 
	

	
	
		
		

		
		
	


	




 If I may I ask, how the heck did you miss soldering them to ground? 
	

	
	
		
		

		
		
	


	


_

 

I was working away a couple nights ago and decided to take break, so I walked away and when I came back I guess I just forgot where I left off. After that I printed the schematic off and started crossing stuff out with a pencil to keep track, but I crossed the power caps off because they were on the board already, I assumed I had connected everything to them that had to be. Not the case apparently, haha.

 It was a real "...OHHHH RIGHT" moment.


----------



## zkool448

haha, i've done similar boo-boos before too and yours reminded me of that "ahhhhh, dang it!" moment I had


----------



## Bleuburd

Well, I finished tonight. But, only one tube is lit. I changed the transistor and checked all the power connections coming to the socket. Could it be a bad joint from one of the other pins? (other than power if that makes sense)


----------



## tomb

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Well, I finished tonight. But, only one tube is lit. I changed the transistor and checked all the power connections coming to the socket. Could it be a bad joint from one of the other pins? (other than power if that makes sense)_

 

Focus on the heater circuit. This is the wiring that connects Pins 3 and 4 of each tube to Pin 3 of the respective MOSFET and to C3 or C5, depending on which tube you're looking at.


----------



## Bleuburd

Ok, I'll check it out tomorrow. I thought those joints were good, but I'll double check. Pics tomorrow!


----------



## zkool448

I'm not quite sure if you've already tried swapping the tubes, nevertheless most likely Tomb's suggestion will help you find the problem (you want ~19V at the points tomb mentioned with respect to ground).


----------



## Bleuburd

Yeah, I switched the tubes. I'll go tomorrow and troubleshoot for a while. I've got school to tend to right now.


----------



## penneydude

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_haha, i've done similar boo-boos before too and yours reminded me of that "ahhhhh, dang it!" moment I had 
	

	
	
		
		

		
		
	


	


_

 

Forgetting to put the heat shrink over the wires BEFORE you solder everything together is another good one, which I did quite a few times.


----------



## Bleuburd

Well guys, the connection from the mosfet to the socket is fine. I double checked all the power connections, and still only one tube will light. Any ideas?


----------



## tomb

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Well guys, the connection from the mosfet to the socket is fine. I double checked all the power connections, and still only one tube will light. Any ideas?_

 

Well, I hate to say it, but if the problem is not the tube, then it's a connection somewhere. Look harder.
	

	
	
		
		

		
		
	


	




 Have you actually put a meter to the heater pins and can you read voltage there when the amp is plugged-in/turned-on? How does it compare to the voltage for the same pins on the tube socket that lights?

 EDIT: It might be a blown MOSFET, too. Can you read voltage across the pins (1 and 3 or 1 and 2) of the MOSFET? How does it compare to the operating channel?


----------



## Bleuburd

I'll check the voltage when I get back from my instructor meeting. It's not the mosfet. I switched that already. I thought it could be the cheap socket I got from the tube center, since I checked all the connections, and then double checked them.


----------



## v3nom

which pins on the pot correspond to what?


----------



## v3nom

oops, double post


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *v3nom* /img/forum/go_quote.gif 
_which pins on the pot correspond to what?_

 

I just looked at pete's pic of the inside of his Starving Student hybrid. Click it for a bigger view


----------



## v3nom

cool, thanks


----------



## mattcalf

Any Australian builders/people looking for tubes look here!


----------



## smeggy

Finally got mine back to where it should be after using small caps for the output. Now it has a big pair 
	

	
	
		
		

		
			





 Woo, now it has bass and body!


----------



## smeggy

Ok, got a quick question for the gurus.

 How detremental is it to run a SS at full tilt for extended periods?

 I have some very inefficient phones that are barely reaching listenable even at full volume, so is this damaging to the amp running like this or is it fine


----------



## n_maher

I think you'd be alright if you just watch the heatsink temps and if possible check the junction temperature (where the FET meets the heatsink). Provided you keep both of those within spec I can't see a reason why it'd be a problem.


----------



## smeggy

Cool, mine does have a honking big heatsink as you know and I can rest my hand on it for a good while before it gets uncomfortable.


----------



## Hayduke

I think Nate is advising to make sure that the heat is transfering well from the FET to the heatsink. What did you use in between them? If you're sure there is good thermal transfer and you can leave your hand on the heatsink, then you are probably fine.


----------



## looser101

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ok, got a quick question for the gurus.

 How detremental is it to run a SS at full tilt for extended periods?

 I have some very inefficient phones that are barely reaching listenable even at full volume, so is this damaging to the amp running like this or is it fine 
	

	
	
		
		

		
		
	


	


_

 

Apparently you need to build a balanced SS for those headphones.


----------



## smeggy

hehe, balance SS you say... Hmmm

 yeah the heatsinks have the pad and thermal grease and are well bolted to the sink so it should be fine. If it blows I'll just replace some parts 
	

	
	
		
		

		
		
	


	




 Very nice since I replaced the tiny caps.


----------



## dsavitsk

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_How detremental is it to run a SS at full tilt for extended periods?_

 

Instantaneous current draw varies, but average current draw is constant -- i.e., the amp runs in deep class A -- so signal or no signal, full tilt or no tilt, the "wear" on the amp is the same.

 By the way, add a bypass cap to Rk to increase gain. If you need more, add a CCS load to the tube.


----------



## smeggy

great news, I thought so but wanted to make sure.


----------



## tamasic1

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_How detremental is it to run a SS at full tilt for extended periods?_

 

I'll let you know. That's the only way old rockers like me can listen to anything. 

 Larry the Tube Guy says : Getter Done!


----------



## smeggy

Yeah, I'm blasting my ears off with Rammstein on 30+ year old isodynamics


----------



## -=Germania=-

Hey Smeggy, 

 I did find it pretty useful to add the cathode bypass caps, but something to decide how you want to "tune" the amp is to throw a pot place of the cathode resistor and play with what you like. For my personal amp, I used 470uf Panasonic with 20k ohm resistor because basically I had only 100uf Muse or 470uf Panasonics in resonable voltages and the muse wasn't large enough to get a really nice and full sound. With my PSU, it goves me breathing room. In the others I have built 220uf is plenty, but I bumped the cathode resistor up to 5k or 10k. IMO without upping the value of the cathode resistor the sound can get too bassy. 

 A small gain switch for the input is uber useful. I have mine so that I can choose between 100ohm and 100k ohm with the high gain meant more for extreme case and the 100k as my normal with 32ohm headphones and because I don't listen very loud (even still listening right around of the middle of the pot). 
 In a two channel though, 20-40k is probably more in line depending on user preferences.

 My personal amp is not the same as the BOM and uses a a higher current PSU which is modded and also used much larger power caps on the circuit to account for this, so YMMV and all that. 

 I will say that using a nicer PSU that can supply ample current not results in better sound, but the tubes "burn" less hot and with a bit less light. The fets also heat less. could possibly result in longer tube life, but I don't know.


----------



## rush340

I have been reading up on this for the past couple days, and was disappointed when I found out how hard it is to find the 19j6's now. Are there any places left to purchase them on the 'starving student' budget?


----------



## Logistic

Quote:


  Originally Posted by *rush340* /img/forum/go_quote.gif 
_I have been reading up on this for the past couple days, and was disappointed when I found out how hard it is to find the 19j6's now. Are there any places left to purchase them on the 'starving student' budget?_

 

I think TomB will have some for sale with the PCBs. Also, you can use the 12sr7 or 12sw7 tubes I posted about a few pages back.


----------



## smeggy

I'm gonna enjoy getting a board for the next one


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_Larry the Tube Guy says : Getter Done!_

 

[size=small]*HAH*[/size]
	

	
	
		
		

		
		
	


	




 That's awesome!!!


----------



## bhjazz

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I will say that using a nicer PSU that can supply ample current not results in better sound, but the tubes "burn" less hot and with a bit less light. The fets also heat less. could possibly result in longer tube life, but I don't know._

 

Hi Germania,
 I just searched through this thread to find your link to some power supplies...THANKS!!! I found your post and will probably try one of those since I can't seem to find the "standard" version around town for a decent price. Thanks!

 Oops...just saw the caveat. Well, I'll keep diggin.


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I will say that using a nicer PSU that can supply ample current not results in better sound, but the tubes "burn" less hot and with a bit less light. The fets also heat less. could possibly result in longer tube life, but I don't know._

 

Someone is going to have to provide a more technical explanation of this phenomenon since in my head, unless there's a pant load of ripple or something else I would think that if you measure the same operating points (19V at the heater for example) that the tubes would "burn" exactly the same way regardless of the power supply used. The fets heating less would indicate to me less current flowing through the output stage, would it not? 

 Germania, I'd suggest that you check the various operating points of your amp and see what you get vs. the intended operating points on the original schematic. If the changes you've made have altered them in any way I'd like to see more discussion of the technical side of the changes rather than just hearing you think "they sound good".


----------



## dsavitsk

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I used 470uf Panasonic with 20k ohm resistor because basically I had only 100uf Muse or 470uf Panasonics in resonable voltages and the muse wasn't large enough to get a really nice and full sound. With my PSU, it goves me breathing room. In the others I have built 220uf is plenty, but I bumped the cathode resistor up to 5k or 10k. IMO without upping the value of the cathode resistor the sound can get too bassy._

 

Um, you are severely limiting current across the tube which makes it run in an even less linear place. It also lowers its Gm which in turn reduces its ability to drive the gate capacitance on the mosfet, which rolls off high frequency. That is, you built a tone control to filter out bass and treble.

 Don't you have the 3 channel deal? That design also most likely cuts out bass frequencies.

 Anyhow, voltage for the cathode bypass cap needs to be on the order of 2.5V ... maybe 3V. I doubt you have a lot of 1V caps lying about.

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_My personal amp is not the same as the BOM and uses a a higher current PSU_

 

Current is drawn by the circuit, not pushed by the PS. Thus, the ability of your PS to supply more current shouldn't matter so long as the original PS's Zout is low, and it can supply sufficient current. I have not seen any reason to doubt that this is the case. 

  Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_I will say that using a nicer PSU that can supply ample current not results in better sound, but the tubes "burn" less hot and with a bit less light. The fets also heat less. could possibly result in longer tube life, but I don't know._

 

A different PS may very well change how the amp performs. However, the rest of this makes no sense -- both grammatically, and theoretically. Is that "not" supposed to negate that your PS results in better sound? Assuming you think no, the heaters will draw current based upon the voltage supplied. If they are drawing less current, it is either because you are supplying lower voltage on purpose, or because your power supply is sagging due to inability to supply the current that the circuit is attempting to draw. That is, you are simply running the thing at too low a voltage.

 As to tube life, there are two issues. The first is heater life. There is some indication that running heaters slightly low (like 5% below rated voltage) may result in longer tube life. But, this is not because it keeps the heater filament from burning out. It has to do with cathode emissions. And this brings up the second issue. In fact, running them too low stresses their ability to emit electrons, and may strip the cathodes over time. The second issue is stress on the plate. Running tube very hard does this.

 In the case of this amp, we are barely using these tubes. Cathode stripping is an issue at high currents with cold cathodes above 1000V. Not here. However, we are running these tubes so low that cathode poisoning may be an issue. This happens when you just run the heaters with no voltage on the plates -- the cathodes build up a layer of cruft which keeps them from emitting. Again, it is hardly a danger here, but it is the closest thing to one I can think of.

 As for how hard we are running the tubes, and whether they age, these tubes can dissipate over 3W from their plates. In the stock setup, this amp dissipates around 1/40th of a watt. The tubes are built to drop 100V at 30mA, we are doing 24V at 1mA.


  Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Germania, I'd suggest that you check the various operating points of your amp and see what you get vs. the intended operating points on the original schematic._

 

I agree.


----------



## Bleuburd

Ok, I fixed it. Both tubes light now. I made a stupid mistake I'd rather not explain. But, now there's another problem. Audio is at a whisper. When I turn the pot all the way up, then I can barely hear it. I know others have had this problem. What's most likely the cause?


----------



## smeggy

Cool, glad thats all sorted as it was confusing the hell out of me. Mine's running like a little trooper and even the ridiculous load of the woofdales didn't faze it much aside from the lower volume level and lack of overhead. Is there an easy way to beef the thing up to give it a little more power/gain?


----------



## Bleuburd

No ideas on why volume is so low? The pot is maxed out and I can barely hear a faint sound.


----------



## Swingtops

hey guys 
 I am having a problem with getting my amp to work, nearest I can tell the inputs and outputs are wired correctly, the signal is getting to the tubes but I have no sound whatsoever coming out of the headphones. No buzzing clicking - nothing. I have had a few people look over the schematic and we think that everything is in the right places, I did have a blown mosfet to start out with that is now replaced. All the DC voltages that are listed on the schematic match within about .2 v. The mosfets seem to be getting pretty hot but no sound.


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Is there an easy way to beef the thing up to give it a little more power/gain?_

 

smeggy, what's the value of your pot? My two SS have differents pots, one has 50k the other has 100k. The one with 50k seems to have more gain, as in I can't turn the pot more than past halfway mark since its too loud, but both are ok with my Beyer.


----------



## smeggy

It's a 50k pot but some of my phones are retardedly inefficient. The wharfedale is rated at 3wpc and came with a speaker adapter cable!


----------



## tomb

Smeggy runs a lot of older ortho's. Think K1000-type load.


----------



## smeggy

Heh, it just needs that _teeny _bit more power... 
	

	
	
		
		

		
			





 Honest


----------



## Logistic

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Heh, it just needs that teeny bit more power... 
	

	
	
		
		

		
		
	


	




 Honest 
	

	
	
		
		

		
		
	


	


_

 

Do you have cathode bypass caps in your amp? Adding those will give you more gain.


----------



## Logistic

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_No ideas on why volume is so low? The pot is maxed out and I can barely hear a faint sound._

 

Check your wiring, especially the pot.


----------



## smeggy

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Do you have cathode bypass caps in your amp? Adding those will give you more gain._

 

I have no idea what a cathode bypass cap does or where it goes. I just followed the standard circuit design.

 Looking at the diagram.. I'm thinking maybe the caps would run parallel to R5 and R11, the 2k resistors? I know nothing of electronics so this is a wild guess based on some other diagram I just looked at with bypass caps.


----------



## cswann1

.


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I have no idea what a cathode bypass cap does or where it goes. I just followed the standard circuit design.

 Looking at the diagram.. I'm thinking maybe the caps would run parallel to R5 and R11, the 2k resistors? I know nothing of electronics so this is a wild guess based on some other diagram I just looked at with bypass caps._

 

Yes, I think it's C7 & C8 (new BOM), have a look at this 'revised' schematic I did from a previous post.


----------



## smeggy

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Yes, I think it's C7 & C8 (new BOM), have a look at this 'revised' schematic I did from a previous post._

 

Thanks!
 did this ever get verified by anyone?


----------



## n_maher

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_hey guys 
 I am having a problem with getting my amp to work, nearest I can tell the inputs and outputs are wired correctly, the signal is getting to the tubes but I have no sound whatsoever coming out of the headphones. No buzzing clicking - nothing. I have had a few people look over the schematic and we think that everything is in the right places, I did have a blown mosfet to start out with that is now replaced. All the DC voltages that are listed on the schematic match within about .2 v. The mosfets seem to be getting pretty hot but no sound._

 

Please show us how you have the output jack wired, you wouldn't be the first (or last) who wired one of the switched Neutrik jacks on the wrong side.


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Thanks!
 did this ever get verified by anyone?_

 

yep, tomb gave it the ok.


----------



## smeggy

cool, will go hunting for parts


----------



## scompton

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Thanks!
 did this ever get verified by anyone?_

 

It's on the boards and I assume at least some of the prototypers used it.


----------



## smeggy

hopefully it'll give it the extra push it needs


----------



## Logistic

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I have no idea what a cathode bypass cap does or where it goes. I just followed the standard circuit design.

 Looking at the diagram.. I'm thinking maybe the caps would run parallel to R5 and R11, the 2k resistors? I know nothing of electronics so this is a wild guess based on some other diagram I just looked at with bypass caps._

 

Yes that is correct. It will give you quite a bit more gain, maybe more than you need or want.


----------



## smeggy

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Yes that is correct. It will give you quite a bit more gain, maybe more than you need or want. 
	

	
	
		
		

		
		
	


	


_

 

Heh, maybe some of this stuff is sinking in after all 
	

	
	
		
		

		
		
	


	




 we'll see how it goes. If I decide not to go the full hog re: the new layout, is the 220uF 16V specified there still applicable?


----------



## Logistic

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Heh, maybe some of this stuff is sinking in after all 
	

	
	
		
		

		
		
	


	




 we'll see how it goes. If I decide not to go the full hog re: the new layout, is the 220uF 16V specified there still applicable?_

 

Yes, you can just put in the cathode bypass caps independent of the other changes. In fact, you would not want to put those 50k resisters before the pot, that is meant to reduce the gain.


----------



## smeggy

Ah, don't wanna do that then


----------



## Bleuburd

Ok, when I plug in the headphones, the tubes get way less bright. I'm thinking that's why I'm hearing little to no sound. Even with the pot maxed out. I rewired the pot, so that isn't it. Can someone please help me!?!?


----------



## n_maher

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Ok, when I plug in the headphones, the tubes get way less bright. I'm thinking that's why I'm hearing little to no sound. Even with the pot maxed out. I rewired the pot, so that isn't it. Can someone please help me!?!?_

 

We can't do much without more information - please post some clear pictures and we'll do what we can. You clearly have something wired incorrectly.


----------



## Swingtops

n_maher

 Here are some pics

http://img2.imageshack.us/img2/4138/dscf1889.jpg
http://img2.imageshack.us/img2/2120/dscf1890.jpg
http://img2.imageshack.us/img2/6045/dscf1891.jpg
http://img2.imageshack.us/img2/8100/dscf1892.jpg

 I tried to get the best angles I could but most of the resistors are buried


----------



## tamasic1

I thought the options schematic was the one most people were building. Let me tell you, it screams! IMHO that is the schematic to go with.
	

	
	
		
		

		
		
	


	




 I have the resistors in before the pot and I can't have the headphones on past 3/4 of the way. After I built and tested mine for a couple days I put a very simple crossfilter circuit in before the pot (2 caps + 3 resistors). Only made a miniscule drop in gain. 

 One idea for those who are new at this and plan to build point to point - Sit down with pencil and paper first. Draw out your parts placement then sketch out the wiring. Use different colors if need be to follow input, output, power and ground. Refer to the schematic and see if it makes sense. Reposition components to reduce the wiring as much as possible, within reason of course.

 I don't have a camera with a macro to show the detail but I used Cat5 strands for wiring and color coded each channel, power and gound. This could help if you had diagnose a problem after the build ...and it looks good too.


----------



## tomb

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_n_maher

 Here are some pics

http://img2.imageshack.us/img2/4138/dscf1889.jpg
http://img2.imageshack.us/img2/2120/dscf1890.jpg
http://img2.imageshack.us/img2/6045/dscf1891.jpg
http://img2.imageshack.us/img2/8100/dscf1892.jpg

 I tried to get the best angles I could but most of the resistors are buried_

 

With that much wiring and with many of the joints hidden beneath the perfboard, I'm afraid it's going to be impossible to trouble-shoot. You might look at a few things I saw:

 1. If you can reduce the length of all that wire, or at least tie a piece of tape around the leads that you can trace and label it.
 2. It appears to me that you have several splices in the wiring that are un-insulated and dangerously close to touching the metal case. Wrap those with electrical tape, or unsolder them, slide on some heat shrink, re-solder, then slide the heat shrink back over the joint and shrink.
 3. Likewise, I'm also suspecting that there are un-insulated joints beneath that perfboard. With it slapped up against the case, there may be joints that are touching/shorting out.
 4. It's difficult to tell, but it looks like you have the headphone jack wired up wrong. There are three solder lugs, but you've only run wiring to two. Then it looks like you've soldered directly to one of the contacts. Further, you've run double leads to two of them. The most efficient method would've been to join the leads between the R12-C5 joint (Left) together and join the leads between the R6/C3 joint (right) together on the perfboard, and run single leads only for the Left and Right channel, respectively. The way you have it may result in proper wiring anyway, but it certainly leaves yourself open to error.
 5. Note that the method mentioned in #4 may help reduce the wiring elsewhere. Extra leads and extra length will promote more noise and hum in the amp.


----------



## Bleuburd

Ok, it's not the mosfets and it's not the pot. I fixed some wiring that I fouled up, and now I still have the same problem. I can't hear anything. When the pot is turned all the way up, then I can hear something faint, but it isn't at all listenable. Here are pics as requested. Sorry, they aren't very good, and I didn't really know how to get good shots of the inside. By the way, I housed it in a cigar box. Smokey student hybrid?


----------



## Swingtops

tomb
 Thanks for taking a look at it for me - the case is actually plastic, so I am not too concerned about shorts on the back side of the perf board but the splice I will take care of.
 I began looking over the schematic again and I think I have some serious problems ( perhaps wiring at 4:30 am is not recommended ) one of the .1 uF caps is not even hooked to anything. 
 I also started to put the amp in DIY layout creator and it turned out to be a big CF so I think I might just start over with a new layout that I have thought about for a bit

 thanks again


----------



## tomb

Quote:


  Originally Posted by *Swingtops* /img/forum/go_quote.gif 
_tomb
 Thanks for taking a look at it for me - the case is actually plastic, so I am not too concerned about shorts on the back side of the perf board but the splice I will take care of.
 I began looking over the schematic again and I think I have some serious problems ( perhaps wiring at 4:30 am is not recommended ) one of the .1 uF caps is not even hooked to anything. 
 I also started to put the amp in DIY layout creator and it turned out to be a big CF so I think I might just start over with a new layout that I have thought about for a bit

 thanks again_

 

Sorry I wasn't of more help. If your case is plastic, you're right - no problem with the shorting. Still, a fresh start might be best. Remember that a goal is to minimize the wiring as much as possible. That will always work best. Review Pete's original build photo and also Nate's. That's kind of a key to how the wiring should go. You can copy what's in the photos directly - that's the easiest.


----------



## Logistic

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Ok, it's not the mosfets and it's not the pot. I fixed some wiring that I fouled up, and now I still have the same problem. I can't hear anything. When the pot is turned all the way up, then I can hear something faint, but it isn't at all listenable. Here are pics as requested. Sorry, they aren't very good, and I didn't really know how to get good shots of the inside. By the way, I housed it in a cigar box. Smokey student hybrid?_

 

Can you make your pictures larger?

 Start by tracing the signal path from the inputs to the pot to pins 5 and 6 of the tube sockets.


----------



## Bleuburd

Sure, bigger pics in the next hour.


----------



## Logistic

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Sure, bigger pics in the next hour._

 

Also, take off the masking tape. There are junctions where it is hard to match the wires going under the tape to the ones coming out.


----------



## Bleuburd

Ok, sorry. Masking tape will go too.


----------



## scompton

A similar thing happened to me recently. It was caused by the RCA jacks getting loose because of my lousy case work. Basically the nuts became loose enough that there wasn't a ground. I tightened up the nuts and every thing worked fine.


----------



## Bleuburd

Edit: Well, I rewired the mosfets and mixed up the drain and the source. The resulting current blew the drivers in my hd580s. I'm done. Sorry guys, this is crazy. I've lost money, the amp never worked, and now I have no reason to finish it. This is really upsetting. The hd580s where my only cans. I guess somebody might want them for $50 to replace the drivers. I'm sticking with my ibasso and some IEMs when I get the cash.

 Sincerely,
 ~Bleuburd


----------



## Logistic

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Edit: Well, I rewired the mosfets and mixed up the drain and the source. The resulting current blew the drivers in my hd580s. I'm done. Sorry guys, this is crazy. I've lost money, the amp never worked, and now I have no reason to finish it. This is really upsetting. The hd580s where my only cans. I guess somebody might want them for $50 to replace the drivers. I'm sticking with my ibasso and some IEMs when I get the cash.

 Sincerely,
 ~Bleuburd_

 

Oh no! I'm sorry to hear that, that is terrible. Maybe you can order hd-600 drivers from the sennheiser website?


----------



## Bleuburd

I don't really feel like spending $100 right now. Especially on replacing cans that I thought I'd have for a while. Like I said. Maybe I'll pick up some pfes when I sell back my textbooks. I'm just really bummed out right now. I'll probably save the hd580s and replace the drivers later on, but now I'm taking a break. No more DIY. I'm just not cut out for it. I can do interconnects, LODs, and maybe a cmoy, but anything beyond that is probably asking too much.


----------



## Yaka

that is sad to hear, even tho i myself am not very good at diy audio stuff im slowly making my way up. first from building 3 cmoys to a p2p build of this amp and a beta circuit board. from my first cmoy i got some cheap headphones that cost me £5 rather than risk my grados think i was the first bit of advice given to me on another forum


----------



## manaox2

Sorry to hear. I really do wish you would not give up though because mistakes were made to learn from. 

 Maybe try again with some KSC75?


----------



## Bleuburd

Oh thank God, it's just an encoding snafu. I encoded my entire library in what I thought was V0 with XLD. It actually did VBR at like 30kbps, which obviously would sound like blown drivers. I'm gonna pull the starving student out of the trash, put it in a new enclosure, rewire it, and give this a go!


----------



## Fitz

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Oh thank God, it's just an encoding snafu. I encoded my entire library in what I thought was V0 with XLD. It actually did VBR at like 30kbps, which obviously would sound like blown drivers. I'm gonna pull the starving student out of the trash, put it in a new enclosure, rewire it, and give this a go!_

 

I'll bet that was quite the relief! Reminds me of when I spent hours diagnosing a signal processor that wouldn't sync and was sure it was seriously fubar'ed, only to find out I had the wrong cable plugged into it the whole time. Lesson: Always double-check everything else for silly mistakes before assuming anything is broken.


----------



## tomb

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Oh thank God, it's just an encoding snafu. I encoded my entire library in what I thought was V0 with XLD. It actually did VBR at like 30kbps, which obviously would sound like blown drivers. I'm gonna pull the starving student out of the trash, put it in a new enclosure, rewire it, and give this a go!_

 

Glad to hear it!

 Even so, remember: don't ever plug in a good set of heapdhones the first time out with a newly-built amp. Get some $2 Coby's or something from Big Lots/Goodwill.


----------



## Logistic

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_Oh thank God, it's just an encoding snafu. I encoded my entire library in what I thought was V0 with XLD. It actually did VBR at like 30kbps, which obviously would sound like blown drivers. I'm gonna pull the starving student out of the trash, put it in a new enclosure, rewire it, and give this a go!_

 

That's great news! After a scare like that, make sure you get some cheap headphones to test with though.


----------



## zkool448

thats great news! 
	

	
	
		
		

		
		
	


	




 Follow the schematic very carefully to minimize all the "rewiring" you're doing, checking every p2p connections as fets could blow easily. Watch out for shorts and use colored wires for easier troubleshooting, and *importantly* use a meter to measure voltages and even if values look good then use a pair of cheapie headphones first. good luck!


----------



## tamasic1

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_use colored wires for easier troubleshooting_

 

....I heard that somewhere before. Sounds like good advice.


----------



## -=Germania=-

The cathode caps I am using are just 16V Panasonics I had lying around. 

 I am getting 19.71V on Pin 3 for each of the channels. 
 Right at R1 and R2 I am getting 46.73V. 

 Both seem fine. 

 Here are some readings I just took using my auzen soundcard on my computer. Not the best, but the readings seem pretty darn good.

 No fancy cables, just good ole' Beldens for the readings. 











 Of course, any advice would be apprecated!

 It isn't an Amp I am using right now anyway, so extar tweaking would be fun. 
	

	
	
		
		

		
		
	


	




 Thanks!


  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Um, you are severely limiting current across the tube which makes it run in an even less linear place. It also lowers its Gm which in turn reduces its ability to drive the gate capacitance on the mosfet, which rolls off high frequency. That is, you built a tone control to filter out bass and treble.

 Don't you have the 3 channel deal? That design also most likely cuts out bass frequencies._


----------



## kuroguy

Quote:


  Originally Posted by *Bleuburd* /img/forum/go_quote.gif 
_...I'm gonna pull the starving student out of the trash, put it in a new enclosure, rewire it, and give this a go!_

 

Next time at least offer the carcass up for sale here. 

 By the way, I work with a schematic and a highlighter, coloring in the lines and components as I install them. when the schematic is completely highlighted, you're done.


----------



## BlizzofOZ

Anybody have a BOM parts list from Digi-Key for this amp?


----------



## tomb

Quote:


  Originally Posted by *BlizzofOZ* /img/forum/go_quote.gif 
_Anybody have a BOM parts list from Digi-Key for this amp?_

 

The SSMH PCB BOM has a complete list of Digi-Key parts:
http://www.diyforums.org/SSMH/bom/SSMH.xls
 There are differences with the PCB, but those should be clearly marked.
	

	
	
		
		

		
		
	


	




 P.S. Speaking of which, the PCB's arrived a few days ago. I've been working through the weekend to get one built and cased up. I should be able to report shortly and start sales next week (hopefully) - the production PCB looks great; it's just that we needed to flesh out a few casing and accessory details. I have a heat sink solution, but need a few days to prove it out.


----------



## luiztfc

Guys, I'm trying to build the Starving, but I'm having a hard time to finding these 19J6 tubes. Are missing?


----------



## smeggy

Oooh, good news indeed!

 It'll be nice having a real board


----------



## zkool448

Quote:


  Originally Posted by *luiztfc* /img/forum/go_quote.gif 
_Guys, I'm trying to build the Starving, but I'm having a hard time to finding these 19J6 tubes. Are missing?_

 

Hang in there, luiztfc. It looks like it won't be very long before beezar.com will officially start selling the kits


----------



## n_maher

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Here are some readings I just took using my auzen soundcard on my computer. Not the best, but the readings seem pretty darn good._

 

Loaded, unloaded, output level? Those pictures are pretty worthless without more information.

  Quote:


 No fancy cables, just good ole' Beldens for the readings. 
 

Let me know when you start to be able to measure the difference cables make. If anything other than shielded vs. unshielded shows up you've got big problems.


----------



## -=Germania=-

Unloaded, didn't have any 32 ohm resistors to represent the headphones that I own and actually listen to. 
 Stock opamps. 
 Output level was set for front speakers at 100% as was the line-in used for input. 
 Amp was right at the very middle of the potentiometer, using the lower gain, as this is my normal gain used, though usually I sit at 11 o'clock because I don't listen very loudly for the sake of keeping my hearing. 

 Yeah I know that this isn't a fair indication without putting on an appropriate load, just didn't have 32ohm resistors on hand. Will pick some up for testing purposes. The belden cable combined with connectors on the amp had a bit more than 1.2ohms per channel on the signal line, but I really don't think that would have affected much. Just using beldens because they are what I have left over as spares and it is a standard. Besides, me doing anything about cables would go against MOT, sorry!

 This is connecting to the back of my computer which is a pretty electrically and mechanically noisy place despite using a thick steel/aluminum case, additional damping foam and dynamat, and large fans running at low RPM's. Still has a low level of audible noise that is impossible to be rid of in a tower. 

 Even with a 32 ohm load, I doubt that the overall freq response graph would change drastically in terms of shape. The distortion will likely change a bit, again, I doubt that it would be all that huge. I think the point right now is more along the lines of it not being distorted and the response being pretty even. Again, I will take readings with all of the proper settings and loads, but this was something done spur of the moment. 

 Cheers!


----------



## rds

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Let me know when you start to be able to measure the difference cables make. If anything other than shielded vs. unshielded shows up you've got big problems._

 

First you have to upgrade the wires in your scope


----------



## holland

Quote:


  Originally Posted by *-=Germania=-* /img/forum/go_quote.gif 
_Unloaded, didn't have any 32 ohm resistors to represent the headphones that I own and actually listen to._

 

Personally, I think a 10K to 20K cathode resistor is too much. What you should measure is the voltage on the plate of the triode and the cathode, that is pin 1 and 2, and pin 7. I would bet you're all out of whack, operating in a not so good part of the tube.

 Another personal IMHO. What I did was remove the plate resistor (33K stock) and put a CRD there. I just used what I had, but I think (it's been a while and can't remember what I figured the operating point to be) 0.25mA per triode is the stock configuration. I used a 0.56mA CRD, as that's what I had on hand. Use the stock 2K cathode resistor. If you bypass, I would just use a large value low voltage cap. I have a 1000uF/16V. You need to have the cap be much larger than the cathode resistor or you start to shelve the frequency response....which is what dsavitsk was indicating when you start to bump the cathode resistor up to 20K along with a low value cap (220uF or so). Not to mention, again, that a 20K cathode puts the operating point in a not so great spot.

 If you really, want you can use the stock cathode of 2K, put a 5K 20 turn trimpot in parallel, use a 0.5mA-1mA CRD on the plate and then dial in the trimpot so that you have the plate voltage at 1/2 B+. Watch for thermal drift for a 1 day fully enclosed as if it were the final build, if steady you should be able to remove the interstage cap (0.1uf-0.22uf) and the voltage divider (2 220K resistors) which sets up the gate voltage of the mosfet. The plate will set it up. It just needs to be higher than the heater voltage, and enough to "turn on" the mosfet. The output cap will block the DC, as normal.

 I'm not sure I would do the latter option as there are probably things I don't understand about tube operation, but it wouldn't hurt to try.

 One other thing, which I did. Change R13 to 1K, and make C1 and C6 1000uF. You will need the lower R13, especially if you try to push more current through the tube than the stock configuration. With stock configuration, larger caps and lower R13 you should get about 1V more for B+ and not affect the filter adversely. It's not much, but with such low B+ anything helps when you try to move the operating point.


----------



## luiztfc

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Hang in there, luiztfc. It looks like it won't be very long before beezar.com will officially start selling the kits 
	

	
	
		
		

		
		
	


	


_

 

Ok, but isn't there any other tube that can replace the 19J6?


----------



## tamasic1

if you go back a dozen pages or so there is a few passages about a replacement and the modifications for it. Except for an ebay snag you're pretty much screwed on the 19j6.

 Larry the tube guy says: Getter Done!


----------



## Logistic

Quote:


  Originally Posted by *luiztfc* /img/forum/go_quote.gif 
_Ok, but isn't there any other tube that can replace the 19J6?_

 

I posted a guide to use the 12sr7/12sw7 tubes about 10 pages back. Just search this thread for 12sr7.


----------



## Hayduke

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_I work with a schematic and a highlighter, coloring in the lines and components as I install them. when the schematic is completely highlighted, you're done._

 

I used a printed copy of the schematic and highliters also, but I highlighted first to make it easier for me to see which components were connected together. Basically I wanted to see each "piece" of the circuit. I can't find my color coded schematic now, but I seem to recall I only need 6 colors, so there were only 6 "pieces" of the circuit.

 When I built the amp, I just drew an "X" through each piece or section as I built it.


----------



## luiztfc

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_I posted a guide to use the 12sr7/12sw7 tubes about 10 pages back. Just search this thread for 12sr7._

 


 Thanks, I'll look into it. And just a last question: is there any possibility that the 19J6 model name can differ in different countries?


----------



## tomb

Quote:


  Originally Posted by *luiztfc* /img/forum/go_quote.gif 
_Thanks, I'll look into it. And just a last question: is there any possibility that the 19J6 model name can differ in different countries?_

 

There is a 5J6 and 6J6 in the same series - they even share the same data sheet. However, the "5" and the "6" represent 5V and 6V heater requirements, a far cry from the 19V of the 19J6. IOW, they're useless for the SSMH.


----------



## cactus friend

Just so everyone knows, I was able to order two same brand 19J6s from Jack at thetubecenter.com - not sure how many they have, but it's worth a shot if you're hunting them down.

 Edit - answered my own question again ..


----------



## tomb

Quote:


  Originally Posted by *cactus friend* /img/forum/go_quote.gif 
_Just so everyone knows, I was able to order two same brand 19J6s from Jack at thetubecenter.com - not sure how many they have, but it's worth a shot if you're hunting them down.

 Also, a quick question: Those black o-rings around the holes for the transistors (for instance, in Nate's build), what are those called and where could I find some? Pardon my ignorance - thanks!_

 

Rubber Grommets ...


----------



## cactus friend

Haha, thanks, Tomb. The name slipped my mind for a second until I checked out the BOM to refresh myself.


----------



## rcmc

Beginner here, and I am trying to understand the circuit...

 If I have understood correctly, C2 is an inter-stage cap with R2/R4 paired up as a potential divider for Q1. Then, what is R3 doing there?

 Thanks.


----------



## dsavitsk

Quote:


  Originally Posted by *rcmc* /img/forum/go_quote.gif 
_Then, what is R3 doing there?_

 

It is a gate stopper to keep the mosfet from oscillating.


----------



## Swingtops

As you guys might remember I posted a few pics of my wiring that didn't work four pages ago. 
 Since then I have put the layout into DIY Layout creator and I am just looking for some comments on the new layout.
 Thanks to all in advance.


----------



## Swingtops

sorry - forgot to label the wires at the top and bottom
 top: Green = Power, Black = Ground
 bottom: mosfet 1 = left, mosfet 2 = right, pins on both go 123 from left to right


----------



## Logistic

Looks good, be careful because some of your wires are drawn over junction points where they are not connected so either redraw them or be extra careful not to get confused. Also you might want to streamline the wiring a little more if it makes it easier to build.


----------



## tomb

Looks OK, except for ... don't have any leads between R3 and R9 and the MOSFETs. Otherwise, you may get oscillation. Preferrably, R3 and R9 should be soldered directly to the gate of each MOSFET (pin 1), without any intervening wires - at least for a P2P version of the Starving Student. We've said this many times because it was a warning from Pete Millett himself.


----------



## Baird GoW

Is there anyone in Irvine CA who would be interested in helping me walk through this or would like to team up and make 2 of these and compare for mistakes? Id be more for the 2nd option. I like soldering i find it a fun hobby of mine making cables and what better to do it together with a friend.


----------



## cactus friend

I'm not in the area, but I can guarantee that I'll be posting detailed pictures and needing a few more pairs of eyes on my design for better or for worse...I'd say I'm probably at the same skill level as you, more or less (pretty good at soldering, and I can understand schematic component symbols but can't design my own schematics/circuits yet).

 I'm starting this one from the outside in and I've got everything but the enclosure (it should arrive today). I'll be starting this week and taking pictures all along the way (to post to my blog, which is really just for record-keeping, but might be useful). I'll link to it when I do.


----------



## holland

@Swingtops, what program did you use to generate that? It's handier than pencil and paper (which is what I use).


----------



## tomb

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_@Swingtops, what program did you use to generate that? It's handier than pencil and paper (which is what I use)._

 

You can read the caption at the bottom of the pic:
 "freeware DIY Layout Creator by Storm Software
http://www.storm-software.co.yu/diy"

 EDIT: but then the link doesn't work ... >


----------



## Swingtops

hey, thanks to all. I will try to move the two resistors for a better connection and the program is called DIY layout creator - I just did a google search for it, it's really slick and I wish I had known about it before I started soldering my amp the first time.

 Thanks for all the feedback again.


----------



## holland

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You can read the caption at the bottom of the pic:
 "freeware DIY Layout Creator by Storm Software
http://www.storm-software.co.yu/diy"

 EDIT: but then the link doesn't work ... >
	

	
	
		
		

		
		
	


	


_

 

lol, thanks. i need to start paying attention to fine print.


----------



## ReD.SkY

now for a question:

 how long do the tubes last before they burn out?

 Would it be bad to leave this on continuously or is it something I'd want to turn on and off every time I sat down to the computer?


----------



## tomb

Quote:


  Originally Posted by *ReD.SkY* /img/forum/go_quote.gif 
_now for a question:

 how long do the tubes last before they burn out?

 Would it be bad to leave this on continuously or is it something I'd want to turn on and off every time I sat down to the computer?_

 

Tubes are not light bulbs. I wish the misconception about leaving a tube amp on all the time had never been started. The fact is, a typical tube will last for tens of thousands of hours. Whereas any tube amp, and especially a hybrid, will have many more components that may not last as long - especially when exposed to the long-term heat of an amp that was never turned off.
	

	
	
		
		

		
		
	


	




 Warmup is only ~10-20 seconds before you get sound and perhaps a half-hour to an hour for the best listening (less than that if the tubes are well broken-in). Turn it on when you need it, turn it off when you don't.


----------



## Baird GoW

Quote:


  Originally Posted by *ReD.SkY* /img/forum/go_quote.gif 
_now for a question:

 how long do the tubes last before they burn out?

 Would it be bad to leave this on continuously or is it something I'd want to turn on and off every time I sat down to the computer?_

 

NEVER leave your amp on all the time (HUGE FIRE HAZARD PLUS MOST EVEN TELL YOU NOT TO RUN THEM OVER 6 HOURS STRAIT)! ESPECIALLY if you have pets or a kid for obvious safety reasons.

 Coming from a fire fighter in training.


----------



## ReD.SkY

when the unit is powered off, and the headphones and everything are still plugged in, will you still get unamplified sound, of does this need to be switched on for it to produce sound?


----------



## Baird GoW

Quote:


  Originally Posted by *ReD.SkY* /img/forum/go_quote.gif 
_when the unit is powered off, and the headphones and everything are still plugged in, will you still get unamplified sound, of does this need to be switched on for it to produce sound?_

 

I'm not sure if its always gonna be the same with every amp (I'm pretty sure it is though) but I'm pretty sure it must be turned on.


----------



## kuroguy

Never mind the mosfet stage, current from the signal does not flow from the grid of the 19J6, so without power applied to the tube stage, no sound's gonna come out. I believe the same applies to a transistor stage.


----------



## ReD.SkY

Is there any possible way to build this and have 2 power switches? So it could usually be a solid state, and then when I wanted to, I would flip a switch for some tubier sound.

 maybe have 2 output jacks if thats necessary.


----------



## Baird GoW

does warming up tubes really annoy you THAT much?


----------



## ReD.SkY

its just I want something that I can just set and forget 

 tbh, I really want the exposed tube look, but the sound, ive never heard, so I'm not sure if I'd even like it.


----------



## jageur272

You have nothing to really compare it to. Just build it as is. And it won't work as a solid state, you'd have to build a separate amplifying circuit and maybe have a SPDT toggle switch between the two of them. Entirely inefficient. Just build it as is.


----------



## Baird GoW

Quote:


  Originally Posted by *ReD.SkY* /img/forum/go_quote.gif 
_its just I want something that I can just set and forget 

 tbh, I really want the exposed tube look, but the sound, ive never heard, so I'm not sure if I'd even like it._

 

I say take the Literally the 3 seconds it takes to turn it off and don't forget.
 also don't forget to keep that finger in top shape because if you don't you might get hurt flicking the switch. LOL
 even if you had 2 switches you would still have to flick it on and off every time.


----------



## ReD.SkY

Quote:


  Originally Posted by *Baird GoW* /img/forum/go_quote.gif 
_I say take the Literally the 3 seconds it takes to turn it off and don't forget.
 also don't forget to keep that finger in top shape because if you don't you might get hurt flicking the switch. LOL
 even if you had 2 switches you would still have to flick it on and off every time._

 

I work that finger out daily to prevent freak accidents like those.
 I think I may just go for a solid state since I'm so used to just putting on headphones and listening.


----------



## Baird GoW

Quote:


  Originally Posted by *ReD.SkY* /img/forum/go_quote.gif 
_I work that finger out daily to prevent freak accidents like those.
 I think I may just go for a solid state since I'm so used to just putting on headphones and listening._

 

your being a little ridiculous man your giving up trying something new (that you might really like) because you dont want to have to turn something on and off


----------



## mattcalf

I just got my SS back from Fred_fred2004.

 The sound is amazing!!!!


----------



## ReD.SkY

Quote:


  Originally Posted by *Baird GoW* /img/forum/go_quote.gif 
_your being a little ridiculous man your giving up trying something new (that you might really like) because you dont want to have to turn something on and off_

 

Its not that at all. I'm on an extremely tight budget. I was simply wanting to know a bit more about this to figure out if it is what I need RIGHT NOW.

 I have no doubt in my mind that I will end up building one of these. Just after all my questions were answered, I realized its going to be a bit further down the road now.

 To add to my questions and complete knowledge-ness about this...
 Are tube amps biased towards any certain type of music, or can they produce good results for, say, gaming?


----------



## Baird GoW

Quote:


  Originally Posted by *ReD.SkY* /img/forum/go_quote.gif 
_Its not that at all. I'm on an extremely tight budget. I was simply wanting to know a bit more about this to figure out if it is what I need RIGHT NOW.

 I have no doubt in my mind that I will end up building one of these. Just after all my questions were answered, I realized its going to be a bit further down the road now.

 To add to my questions and complete knowledge-ness about this...
 Are tube amps biased towards any certain type of music, or can they produce good results for, say, gaming?_

 

AHHHHH... ok sorry. lol. I was gonna say a switch is a bad reason not to get it.
 Cool have fun with whatever you get.


----------



## -=Germania=-

I replaced the Panasonic 470uf caps with 100uf Muse ES Bipolar caps. 
 I was able to lower the cathode resistor to be more like 5k ohm, maintaining the same sound sig that I liked and keeping the gain under control. 

 These Muse Bipolars really do sound quite good, more detailed than the larger FM's did while in the same position. That proabablyhas mor eto do with being bipolar and smaller than anything. 

 As we speak, I am using this amp with my 9.4ohm IEM's and the hiss is very small to say the least. I seriosuly need to make an impedance adapter because this amp sounds superb with these IEMs. No noise whatsoever with 32ohm headphones either. I will get around to getting some proper resistors to get graphs, but I have a feeling that it will be pretty similar.


----------



## tamasic1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You can read the caption at the bottom of the pic:
 "freeware DIY Layout Creator by Storm Software
http://www.storm-software.co.yu/diy"

 EDIT: but then the link doesn't work ... >
	

	
	
		
		

		
		
	


	


_

 


 Try this > DIY Layout Creator Download - Softpedia

 Looks like a pretty cool program.


----------



## cactus friend

Okay, well, I finally got the enclosure for my amp...I have no more excuses not to start working on it.

 Here's yet another dumb question - any reason why I can't use the aluminum case as ground? I'm using this case:

Aluminium Case for small projects - 113*70*25 (mm) [STR103C2B] - $7.50 : Seeed Studio Depot, Arsenal for interaction engineering

 My other fear is that it's small, I'll have to mount the heat sinks 'sideways' (compared to many other amps here)...I really hope I can fit everything together in there properly.


----------



## zkool448

That's a real classy looking (and very affordable) alum box. I'm not 100% sure if it will be large enough though, albeit some may have managed to do so with similar size. 

 With SS any conductive material like alum you should be able to use as ground. Btw, is there a reason why you must have the heatsinks 'sideways'? Wouldn't it just sit straight up on top of the enclosure?


----------



## cactus friend

Ah, sorry - I meant sideways as in this one here:

http://www.pmillett.com/images/starving/gross2.jpg 

 I guess it's not technically sideways...


----------



## tomb

OK - I had a little trouble with the panel LED (it's still out), but the production board is a success! So are the heat sinks - horizontal mounting using the same screws that attach the MOSFETs and they're barely warm after about an hour. Plus, these heat sinks are cheap as all get out - about $1.30 ea, if memory serves.

 I went with a 10K pot, using 39K input resistors - works great and gives close to ~40K input impedance, which should be sufficient for most source coupling caps. It certainly doesn't lack any bass fed from a BantamDAC.
	

	
	
		
		

		
			










 EDIT: More pics later ...


----------



## smeggy

cool. 
	

	
	
		
		

		
		
	


	




 Looks good!


----------



## Mr_Nibbles

After buying my parts, most of which are from the original design, I began skimming through this thread. After seeing all of the "improvements" people have made to the amp (different caps, etc...) I am wondering if I should worry about my purchase. Are there any flaws in the original design that I should worry about?

 Also, I have not yet purchased a power supply. Is there a power supply which is readily available that would suit this amp? I am not a huge fan of ebay, but if that is the only source then I will get a PSU there.


----------



## Mr_Nibbles

Oops, sorry for the double post. How do I delete?


----------



## tomb

On for 4 hours and the hottest part of the amp measures 37deg. C. (98.6deg.F.). That's right at the root of the heat sinks. The rest of the case measures no more than 33-34deg.C. (91 to 93 deg.F.) I think we have a winner.


----------



## smeggy

Quote:


  Originally Posted by *Mr_Nibbles* /img/forum/go_quote.gif 
_After buying my parts, most of which are from the original design, I began skimming through this thread. After seeing all of the "improvements" people have made to the amp (different caps, etc...) I am wondering if I should worry about my purchase. Are there any flaws in the original design that I should worry about?

 Also, I have not yet purchased a power supply. Is there a power supply which is readily available that would suit this amp? I am not a huge fan of ebay, but if that is the only source then I will get a PSU there._

 

The original bom sounds very nice, it's what's in mine and I can't really fault it much. I'm not sure how the updated list/layout affect things but I'm very happy with mine as it is.

 The Power brick can probably be bought from a number of sources but I don't think anyone to date has had any problem with getting them from ebay.

  Quote:


  Originally Posted by *tomb* 
_On for 4 hours and the hottest part of the amp measures 37deg. C. (98.6deg.F.). That's right at the root of the heat sinks. The rest of the case measures no more than 33-34deg.C. (91 to 93 deg.F.) I think we have a winner.
	

	
	
		
		

		
		
	


	


_

 

Great news, looks like we have a winner!


----------



## tomb

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Great news, looks like we have a winner!_

 

On for 8hrs now and no hotter - this is it!


----------



## smeggy

Get them in stock soon 
	

	
	
		
		

		
		
	


	




 I just noticed, we have almost the exact post count... must be a sign


----------



## sandbasser

Tom -

 The BOM that I have is dated 2/16/09. When / where will update be available (including the heatsinks)??? And, since I already have all the other components, will you be offering the heat sinks from Beezar???

 Sorry if this is not the appropriate venue to ask this type of question... Mods feel free to delete as you see fit.


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Tom -

 The BOM that I have is dated 2/16/09. When / where will update be available (including the heatsinks)??? And, since I already have all the other components, will you be offering the heat sinks from Beezar???

 Sorry if this is not the appropriate venue to ask this type of question... Mods feel free to delete as you see fit._

 

I'm a one-man band at his point - Dsavitsk has done his work - so give me a chance. I know it's frustrating - I've been sitting on these boards for awhile now, and the tubes longer still.

 The heat sinks will be included in the kits (30). After that, I was not planning on carrying them. They are a standard Mouser-DigiKey item:




569003B00000G

 EDIT: Mouser says $1.23 ea, so definitely in keeping with the Starving Student theme.


----------



## smeggy

As long as I can get a board I'll be happy. Though tubes would be good too.


----------



## tomb

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_As long as I can get a board I'll be happy. Though tubes would be good too._

 

We have over twice the number of boards as tubes, so I think that will be assured.


----------



## smeggy

when do you envision these being in stock?


----------



## bhjazz

I'm working on my PTP version and realized early Sunday one terrrible thing: I'm so out of wire! WTH??? Even the little scraps left from other projects are just not going to be enough. GAH!!! Off to partsconnexion, I guess.


----------



## smeggy

Haha, oh man that's funny 
	

	
	
		
		

		
			





 I got to the stage or stripping starquad.

 How you doing Brian?


----------



## bhjazz

Pretty well. I'm trying to avoid visiting the rat for wire. Maybe I should join the subversive parts of society and start stealing copper from construction sites. I'm sure my SS would look all pimped out with 12 ga bare copper.


----------



## cms5423

Hahaha yeah man, it's what any starving student would do if push comes to shove


----------



## cms5423

Oh and tom, when do you think the kits and boards will be available for sale? I'm probably going to start my build after this week's final exams are over, and I'm debating between p2p and pcb. Plus I'd love to take a look at the BOM you are using


----------



## smeggy

I'll have a board and p2p once they're available. Pretty cool little amps for sure.


----------



## tamasic1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_On for 4 hours and the hottest part of the amp measures 37deg. C. (98.6deg.F.). That's right at the root of the heat sinks. The rest of the case measures no more than 33-34deg.C. (91 to 93 deg.F.) I think we have a winner.
	

	
	
		
		

		
		
	


	


_

 

Is your case between between your mosfets and heatsinks? I just have the fets directly on the sinks and they get seriously hot in 10-15min. Can't leave a finger on them but for a sec or two. (Yes, R3/9 right on the leg of fet pin 1) When I rebuild it I'm going for bigger sinks.


----------



## tomb

Quote:


  Originally Posted by *tamasic1* /img/forum/go_quote.gif 
_Is your case between between your mosfets and heatsinks? I just have the fets directly on the sinks and they get seriously hot in 10-15min. Can't leave a finger on them but for a sec or two. (Yes, R3/9 right on the leg of fet pin 1) When I rebuild it I'm going for bigger sinks._

 

And what heat sinks are you using? These are seriously high heat rejectors - they're actually made for TO-3 power transistors. It's just that they're dang cheap as well, since they're not an extrusion - just bent sheet metal. Since the case is between the MOSFETs and the sinks, you get the added benefit of the case, too. There's no heat issue with the build as photographed - trust me. I've got MAXes and MiniMAXes that run hotter and have used them for a couple of years, now.


----------



## gurusan

I thought these things were rated for 120C or so? Mine are burning hot to the touch...about 55-60C, but I assumed they were well within the safe temp range?


----------



## tomb

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_I thought these things were rated for 120C or so? Mine are burning hot to the touch...about 55-60C, but I assumed they were well within the safe temp range?_

 

Yes, you're correct. If they stay that way, they are well within safe temps.


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_These are seriously high heat rejectors - they're actually made for TO-3 power transistors. <snip>
 Since the case is between the MOSFETs and the sinks, you get the added benefit of the case, too._

 

If the heatsink is efficient enough, then theoretically the FETs can be mounted directly to the heatsink if you cut two small hole on top of case? (keep case panel/internals cool)


----------



## procalli2007

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Warmup is only ~10-20 seconds before you get sound *and perhaps a half-hour to an hour for the best listening* (less than that if the tubes are well broken-in)._

 

Is that why I think it sounds better after its been on a while. More open? 

 Or are you referring to the first time its used?


----------



## JamesL

Hey, I haven't been on head-fi on a while, but I picked up on this project yesterday -
 This was my first P2P, and also my first tube project, so it was a big relief when nothing blew up. I haven't yet hooked up any audio, but the tubes are giving off a nice glow.

 I'm a little worried about the capacitors though. 
 The aluminum case itself gets pretty hot because the heatsinks are cold-welded directly onto it. The capacitors were glued directly onto the case.
 Would this be alright? The Muse KZ and pana PW's I think are both rated at 85 degrees


----------



## tamasic1

tomb;5661804 said:
			
		

> And what heat sinks are you using? QUOTE]
> 
> http://bellsouthpwp2.net/k/a/karlet/MySSHA.jpg


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_If the heatsink is efficient enough, then theoretically the FETs can be mounted directly to the heatsink if you cut two small hole on top of case? (keep case panel/internals cool) 
	

	
	
		
		

		
			



_

 

No, we're specifically avoiding that. Only a small 1/8" hole is required. The MOSFETs are mounted with Bergquist flow pads on the underside of the case lid, then the heat sinks are attached to the same screw with some heat sink grease between the bottom of the sinks and the top of the case lid. Another screw is added through an 1/8" hole to lock the heat sinks in place and keep them from turning. It's really pretty simple and keeps everything inside. I know no one has had an apparent problem, but 48V is enough to pack a good jolt if one comes into contact with it under the right circumstances. The PCB may introduce a lot more people with less experience to the SSMH. After all, building one P2P sort of requires you to think about these things anyway. On the other hand, a PCB is sort of paint-by-numbers and allows people to relax more than they should, perhaps.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *JamesL* 
_Hey, I haven't been on head-fi on a while, but I picked up on this project yesterday -
 This was my first P2P, and also my first tube project, so it was a big relief when nothing blew up. I haven't yet hooked up any audio, but the tubes are giving off a nice glow.

 I'm a little worried about the capacitors though. 
 The aluminum case itself gets pretty hot because the heatsinks are cold-welded directly onto it. The capacitors were glued directly onto the case.
 Would this be alright? The Muse KZ and pana PW's I think are both rated at 85 degrees_

 

This is just my own opinion, but you might want to get them detached from the case if you can. They'll definitely reach a much higher temperature than "free-floating" if the heat sinks are attached to the case. There's basically just liquid in many of these caps, anyway.

  Quote:


  Originally Posted by *tamasic1* 
_ Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
And what heat sinks are you using?

 

http://bellsouthpwp2.net/k/a/karlet/MySSHA.jpg_

 

Well, those look plenty big to me. Again, those temps you measured are not outside of normal for MOSFETs - they can get hotter, for sure. You may even find that things will cool down a bit if you case it up. MOSFETs have a positive temperature coefficient, so they may cool slightly when cased up.


----------



## bhjazz

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_This was my first P2P, and also my first tube project

_

 
 


First P2P, eh? Well that's a sweet looking ladder of resistors. Good work! Very nice!


----------



## smeggy

x2
 very neat indeed.


----------



## gurusan

x3 that is great work, you should be proud.


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This is just my own opinion, but you might want to get them detached from the case if you can. They'll definitely reach a much higher temperature than "free-floating" if the heat sinks are attached to the case. There's basically just liquid in many of these caps, anyway._

 

Well, I'll certainly see what I can do.
 The power caps are small and can hold their own weight, but the output caps are connected to the other components only via the stranded wire, and I'm not sure how to detach it from the case without compromising structural integrity.

 If anybody has got any brilliant ideas, it'd be really appreciated.


 Also, thanks for the compliment x3


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Well, I'll certainly see what I can do.
 The power caps are small and can hold their own weight, but the output caps are connected to the other components only via the stranded wire, and I'm not sure how to detach it from the case without compromising structural integrity.

 If anybody has got any brilliant ideas, it'd be really appreciated.


 Also, thanks for the compliment x3_

 

Well, I just made a general comment based on preference if you had a choice. If it's an issue on how to keep those caps stable (they _are_ big!), then maybe you could just measure the temperature on the cans after the amp has run awhile. They might be fine, assuming heat rises, they're underneath, and perhaps the heat transfer coefficient of the glue is not so good.
	

	
	
		
		

		
		
	


	




 I would not push them toward the 85deg.C. rating, though - you want to be _well_ away from that.


----------



## JamesL

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, I just made a general comment based on preference if you had a choice. If it's an issue on how to keep those caps stable (they are big!), then maybe you could just measure the temperature on the cans after the amp has run awhile. They might be fine, assuming heat rises, they're underneath, and perhaps the heat transfer coefficient of the glue is not so good.
	

	
	
		
		

		
		
	


	




 I would not push them toward the 85deg.C. rating, though - you want to be well away from that._

 

Thanks, but I think you were right. The thermal conductivity of the epoxy I used seems to be fairly high, and I don't know what would happen if the capacitors failed(any dc voltage might go straight through to the headphones)

 I removed the capacitor from the case though, and it doesn't seem to be moving around much at all, contrary to what I thought. 
 The entire amplifier(even the volume knob) seems to be running fairly hot, so I'm trying my best to dissipate heat anywhere I can.


----------



## JamesL

update:
 I wish I could measure the temperature somehow so I know if the temperatures are normal, but subjectively, they're unbearingly hot... and I'm starting to worry that there might be a problem with the FETs.

 With 30 minutes uptime, the heatsink and the case feels like the hood of a car that's been parked outside for hours in 100 degree weather.

 Is this normal? I'm using 1.5" heatsinks, and the case itself is about 4x2.5x1.5"

 I haven't been able to listen to it yet cause I have to order a smaller headphone jack, but if there is something wrong, I might want to order replacement mosfets and maybe the caps as well. 

 The only things I haven't wired so far are the input and the headphone jack.


----------



## tamasic1

Got a meat thermometer? A digital, like you would use for a roast or what I use when grillin' big ol' steaks or a pork loin would work. 
	

	
	
		
		

		
		
	


	




Bed Bath & Beyond - Oneida Digital Probe Thermometer


----------



## gurusan

Well my heatsinks are BURNING hot to the touch..which is about 60C..and that's perfectly fine.

 **edit*** 64C apparently 
	

	
	
		
		

		
		
	


	




 ignore the dusty case, I am lazy. BTW the amp has been on the entire day so it's as hot as it's going to get.


----------



## sandbasser

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - I had a little trouble with the panel LED (it's still out), but the production board is a success! So are the heat sinks - horizontal mounting using the same screws that attach the MOSFETs and they're barely warm after about an hour. Plus, these heat sinks are cheap as all get out - about $1.30 ea, if memory serves.

 I went with a 10K pot, using 39K input resistors - works great and gives close to ~40K input impedance, which should be sufficient for most source coupling caps. It certainly doesn't lack any bass fed from a BantamDAC.
	

	
	
		
		

		
		
	


	









 EDIT: More pics later ..._

 

I'll admit that I'm (mostly) lost when it comes to the electronic theory involved here but I'm wondering about the 10K pot and 39K input resistors you mentioned... Everywhere else I've found in this thread (and the BOM) seems to suggest that the values of the pot and input resistors are the same ... can someone explain???

 Thanks,


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I'll admit that I'm (mostly) lost when it comes to the electronic theory involved here but I'm wondering about the 10K pot and 39K input resistors you mentioned... Everywhere else I've found in this thread (and the BOM) seems to suggest that the values of the pot and input resistors are the same ... can someone explain???

 Thanks,_

 

Well, it has to do with understanding the pot is an attenuator that varies input impedance from 0 to whatever the pot rating is. So a 50K pot has an adjustment from 0 to 50K over it's adjustment travel.

 In the Starving Student, a bit of a problem is created from two things - the amp naturally has a high gain from the tubes (very high compared to SS standards); second, we try to use a cheap pot in the interests of the "starving student" theme. The trouble is, a cheap pot doesn't necessarily track that well at all positions. Typically, at lower position volume settings, you may get quite an imbalance from one channel to the other. This is pretty irritating when the gain is so high that zero to intolerable volume is only 1/4 to 1/3 the total turn of the volume pot.

 So, Dsavitsk came up with the idea of using input resistors. What happens if you use input resistors, the signal sees those as a fixed attenuation first, then sees the adjustable pot. What this means is that if you install a 50K pot and 50K resistors, then the 50K pot adjusts the last 50% of the signal (sort of, but I'm trying to explain in simple terms so I can understand
	

	
	
		
		

		
		
	


	




 ). So instead of having the entire volume range in the first 1/4 turn, now we have the volume range in the first 1/2 turn.

 There are penalties to a certain degree using this arrangement, but they can be overcome with a bit of thought. Ideally, 10K is probably the best for a good headphone amp, because less resistance is in the path of the signal. However, 100K blocks more noise and gives more control. Through empirical knowledge with headphone designs over the last few years, we've all pretty much settled on 50K as a happy medium.

 Now - back to the 50K pot with the adjustment over 1/2 turn. If we introduce 100K resistors at the input, then perhaps we get 1 full turn with the same impedance headphone load, the same source strength, and the same 50K pot. However, now we've introduced a total of 150K that the source sees, perhaps 1/3 more than optimum for the ideal amp.

 So, if we try a 10K pot, we're back to 1/4 turn unless we use the input resistors. We could try 10K or 20K, but now we've introduced a low enough impedance that the coupling caps on typical DIY-DAC sources are not large enough to overcome the RC bass filtering inherent with a 10K pot and coupling caps on the source. If we go ~40K on some input resistors, then we get two-turn control (if the pot would go that far) over the source volume. However, the total impedance seen by the source is at least 40K, very close to the cultural standard of 50K for most headphone amps.


----------



## smeggy

Cool, I almost understood that


----------



## zkool448

hahaha, same here 
	

	
	
		
		

		
		
	


	




 TomB, the pot value/design compensates only for those with sensitive/low Z headphones, yes?


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_hahaha, same here 
	

	
	
		
		

		
		
	


	




 TomB, the pot value/design compensates only for those with sensitive/low Z headphones, yes?_

 

Not really. A reasonable gain for many solid-state amps is about 5 - even for Sennheisers. There are instances where you may see gains as high as 11, which is the standard parts gain for a CMoy, I think. However, the 19J6 tubes on the SSMH have a basic amplification factor of 38.
	

	
	
		
		

		
		
	


	




 Now, the actual gain is probably not nearly that high in the actual circuit, but even at half that value, you can see that there's a basic issue with gain in the SSMH, regardless of headphone impedance/sensitivity. Of course, with low Z/sensitive phones the effect will be much worse. There's a similar issue with 12AE6 tubes in the Millett Hybrid MAX/MiniMAX, but we use an Alps RK27 in that case, so small volume settings still track very well.

 None of this is to say that there's a limitation with the SSMH. The input resistor method works quite well with the little Alpha pot and many successful Starving Students have been built this way, including the Mini Millett sold at Whiplash Audio. As stated before, this method and the use of the inexpensive Alpha pot also preserves the theme of "starving student."


----------



## JamesL

fixed


----------



## smeggy

The one used in the min3 is decent, I have one in my CTH and it works nicely. Bit small and fiddly but works fine.


----------



## gurusan

I found the one in the BOM to be terrible as well. I am using an inexpensive RK09 and it's great.


----------



## JamesL

nvm


----------



## cms5423

I'm sure this has been explained, but really quickly, why are people upping the value of the capacitors to 470uF? What does this do to the audio/circuitry


----------



## JamesL

Of the PS or output?

 It lowers the frequency cutoff at the output, lowers esr, and stabilizes the power supply.


----------



## cms5423

I guess just in general, why are the cap values being tweaked? Like why would the original MSSH use 150uF and then now they are being upped to 470?


----------



## cms5423

and for the PSU, is .38amps enough, or where would i find the PSU that is the cisco 48v one that had a 1.5, or even 1 amp output?


----------



## tomb

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_I guess just in general, why are the cap values being tweaked? Like why would the original MSSH use 150uF and then now they are being upped to 470?_

 

I can't speak for Pete Millett, but perhaps his "regular" headphones are Sennheisers or other high-impedance phones. 150uf provides plenty of bass for a 300ohm load. Cutoff is down into the single digits with 300ohms, but the -3dB response starts as high as 33Hz with 32ohm Grados. 470uf gives you -3dB at 10Hz, so it's well below audibility.

 As for the other two electrolytics, 680uf has been found to prevent startup "stuttering" in every case.

  Quote:


 and for the PSU, is .38amps enough, or where would i find the PSU that is the cisco 48v one that had a 1.5, or even 1 amp output? 
 

0.38A is enough - it only pulls 0.3A in the standard configuration, perhaps 0.32 with a couple of tube LED's. I think someone once said that switching supplies don't like to be lightly loaded, anyway.


----------



## cms5423

thanks a bunch tom. That leads me to my next question: If I want to add some tube LED's, I can just implement them, plus a resistor (RLED) preceding them, anywhere in the circuit right? Is that because adding a resistor+led into the circuit will just pull more energy out of the power supply?

 Also, how big of a volume is a reasonable amount of space to build this in? So that I can narrow down my enclosure options. I'm trying to pick some sort of metal case from mouser to enclose this in, but am not sure how big of one that I need to choose.

 Thanks


----------



## kuroguy

Yes, an LED with a series resistor across power and ground will work fine. 50v=0.01*R. R=5k should be a good starting place.

 I built mine in a 4.5" wide x 3.5" deep x 2" tall hammond enclosure. In retrospect, I could have made it fit in a case that was 1" tall with some squeezing. I could have certainly used a 1.25" tall chassis without a problem.


----------



## cms5423

Great, thanks for the help. And as far as the pot goes for this project: I see people are using many different options, some go 50k, others 100k, and many say the one in the original BOM is awful. What is a good pot that I can purchase through mouser, that I can implement in the original schematic? Thanks again guys


----------



## tomb

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_Great, thanks for the help. And as far as the pot goes for this project: I see people are using many different options, some go 50k, others 100k, and many say the one in the original BOM is awful. What is a good pot that I can purchase through mouser, that I can implement in the original schematic? Thanks again guys_

 

Just remember that suggested 5K resistor will need to be 1W.
	

	
	
		
		

		
		
	


	




 As for the pots, the Alpha is fine if used with the input-resistor-scheme. The production PCB version I just built seems to work fine with a 10K Alpha and ~40K input resistors. That makes the total input impedance ~50K, so it's in the mid-range of things. For typical volume levels and loads, the pot travel is pushed out far enough in its range that the tracking is OK.


----------



## cms5423

Ok, but is there a pot option that mouser sells, that I can use without input resistors? Like just get a 50k pot from alps? But which one?

 Can someone post a mouser part number for a good pot for this project?

 Thanks everyone


----------



## cms5423

Ok, but is there a pot option that mouser sells, that I can use without input resistors? Like just get a 50k pot from alps? But which one?

 Can someone post a mouser part number for a good pot for this project?

 Thanks everyone


----------



## tomb

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_Ok, but is there a pot option that mouser sells, that I can use without input resistors?_

 

No.

  Quote:


 Like just get a 50k pot from alps? But which one?

 Can someone post a mouser part number for a good pot for this project? 
 

... and no.

 Mouser doesn't sell the Alps pot you're thinking about - nobody does but DIY suppliers like Tangent, Amb, or myself. The Alpha is the best compromise if you want to purchase from Mouser. DigiKey sells the Panasonic EVJ, but I think you'd be even less happier with that.


----------



## cms5423

Alright, sounds good to me, See I'd love to buy the pot that you sell on your beezar site, but then with shipping, it's not quite worth it, it pretty much doubles my cost.


----------



## kuroguy

maybe one of those home assemblled ebay stepped attenuators. I got one for $16 shipped. It'll certainly dictate the size of your enclosure, but it works really nice and adds 3 full evenings to the assembly (if you're low on projects and high on spare time).


----------



## cms5423

One more question. Why is this called a hybrid amplifier? I thought hybrids normally had a solidstate output stage, with tubes implemented earlier in the circuit? But from the looks of this project, there is no solid-state component


----------



## smeggy

well the solid state outputs are the MOSFETs attached to those heatsinks.


----------



## cms5423

ah ok. which also on that note (sorry for all the questions, I'm trying to actually learn the ins and outs rather than just put it together). The heatsinks, to work, how do you connect them to the mosfets?


----------



## sachu

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_ah ok. which also on that note (sorry for all the questions, I'm trying to actually learn the ins and outs rather than just put it together). The heatsinks, to work, how do you connect them to the mosfets?_

 

You will need To-220 heatsink mounting kits to insulate the drain of the MOsfet from the heatsink else you can get a nasty shock if you accidentally touched the heatsink.
 .
 Make sure you pick the right type of heatsink, screw type or PCB mount type depending on how you plan to mount the heatsink.

 If you want to go with the beezar PCB kit then go with the PCB mount type, else the screw type heatsink may be easier to deal with.

 Tomb, how much is a PCB kit for the SS going to be sold for? And what doies it include? Can you just buy the PCB and a set of tubes?


----------



## cms5423

Ok, but what exactly will the mounting kit do? Like I guess my question is how does a heatsink work? I understand it gathers the heat and then disperses it through it's large surface area, but how does it gather the heat from the mosfets? Or am I completely wrong?


----------



## sachu

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_Ok, but what exactly will the mounting kit do? Like I guess my question is how does a heatsink work? I understand it gathers the heat and then disperses it through it's large surface area, but how does it gather the heat from the mosfets? Or am I completely wrong?_

 

The Mosfet is basically screwed onto the heatsink so the back of the MOSFET is flush with the heatsink. So through the physics of conduction of heat from the MOSFET package to heatsink (the heatsink acts as an extension of the MOSFET package to dissipate heat), the MOSFET can be in the SOA (safe operating area)


 All that the heatsink mounting kit does is insulate the drain of the MOSFET from the heatsink. most MOSFETs have the tabs shorted to their Drain. The mounitng kit comes with a mica insulator which goes inbetween the MOSFET tab and the heatsink. Then you take the small plastic washer which goes into the mounting hole of the MOSFET through which you wil put the screw. You need this plastic washer without which the screw would short the heatsink and the MOSFET tab.


----------



## cms5423

gotchya. Thanks


----------



## tomb

Sachu is correct. However - to make that happen - there are several things you need:
Bolt
Washer to protect the bolt head
Shoulder washer to insulate the bolt from the hole in the metal tab - preferrably, these are also heat-rated
Thermasil insulating pad or a mica insulator with thermal grease
Washer on the back side to protect the lock washer from cutting into the heat sink
Lock washer
Nut
The surface contact between the MOSFET back and the heat sink is all important. Actually, IMHO, the electrical insulating quality is secondary. The real task of the MOSFET-heat sink interface is to maximize the connection so that as Sachu says, the heat sink simply becomes an extension of the MOSFET.

 Here's another diagram that may help:
MOSFET-MAX Heat Sink Mounting


 EDIT: Looks like Sachu edited his post to include much of what I typed here.
	

	
	
		
		

		
		
	


	




 EDIT2: I'm just repeating what Sachu already said, but note that the purpose of the heat sink is NOT to keep the MOSFET cool - far from it. The real purpose is to keep the MOSFET from exceeding safe operating temperatures. MOSFETs sort of like to run "hot." The heat sinks, when properly sized, provide a "heat inertia" that keeps things from running away and burning up. Improperly sized, a too-small heat sink can be like teetering on a cliff - one slight push and the whole thing crashes and burns. A properly sized heat sink slows this all down, and prevents any runaway temperatures.


----------



## cms5423

lastly, i tried ordering 19j6 tubes from this one site that were 4$, but I haven't heard from them, so does anyone know of any other place to buy them at a reasonable price?


----------



## tomb

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_<snip>

 If you want to go with the beezar PCB kit then go with the PCB mount type, else the screw type heatsink may be easier to deal with.

 Tomb, how much is a PCB kit for the SS going to be sold for? And what does it include? Can you just buy the PCB and a set of tubes?_

 

It will be a fair price.
	

	
	
		
		

		
		
	


	




 I'm not out to gouge anyone. I believe Dsavitsk and I agreed that the PCB itself will be $10. The 19J6 prices will be $5 each plus a $2 charge for matching. There's two triodes in each tube, so it takes awhile to test each tube. They will eventually run out, of course - before the PCB's do. I'm going to make one last call to my tube wholesalers this weekend for any that may remain out there, then we'll call it and start selling. I've also said this before, too, but 30 kits to start, then PCB's + tubes until the tubes run out, then PCB's.

 My real concern is how to guarantee the tubes when the supply is finite. If I sell them all, then someone turns up with a microphonic tube, etc., I won't be able to replace it. You can't test microphonics in a tube tester. So, I guess I will also try out each individual tube in the actuall SSMH, but that's going to take even more time on my part. I think we'll pause for a week or two between selling the kits and the PCB's+tubes just to make sure that those who've invested in the kits have good tubes.

 If any of you have a better idea, let me know.

 P.S. I'm going to conduct a bit of additional testing before we do all of this. Frying another BantamDAC has got me a bit concerned. I'd like to know exactly what the phenomenon is that's causing it before we sell to the masses - and it's not power supply stuttering, because the current parts selection/caps have no stuttering at all. Besides, I blew the Bantam with the SSMH on and running and with the Bantam connected to USB and fully charged.
	

	
	
		
		

		
		
	


	




 EDIT: If this offends a mod, I'm sorry. Because of the limited availability of the 19J6 tubes, this is a one time deal - almost the same as a group buy. Please delete this post if you feel the need.


----------



## sachu

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 P.S. I'm going to conduct a bit of additional testing before we do all of this. Frying another BantamDAC has got me a bit concerned. I'd like to know exactly what the phenomenon is that's causing it before we sell to the masses - and it's not power supply stuttering, because the current parts selection/caps have no stuttering at all. Besides, I blew the Bantam with the SSMH on and running and with the Bantam connected to USB and fully charged.
	

	
	
		
		

		
		
	


	


_

 

Thisis exactly the reason I sold my Starving student amplifier. 

 I really liked the little amp. Punches well above its weight and would love to build another one. Is there a waiting list on the PCB+tubes? Is it possible for you to put me down for a PCB+ tubes set?


----------



## smeggy

me first


----------



## cegras

I've been lurking in silence for forever for the PCB kit. I am so totally in it D:.


----------



## cms5423

I just want the tubes


----------



## jonjon0nline

I've been waiting on the PCB's since they were first announced 
	

	
	
		
		

		
		
	


	




 I'm definitely in when this goes thru. I check the forum everyday just waiting for the GB.


----------



## smeggy

I imagine these will sell out within minutes and I'll miss it


----------



## cactus friend

Hm, so I've finally gotten started on this project (just got back into town). Two short notes:

 1. Wow, Mr Maher, you were correct - setting up the enclosure is at least half the battle!

 2. It looks like I've ordered/received 220uF caps instead of 150uF. Not sure why, maybe the BOM was updated and I'm just reading outdated posts in the thread, or maybe I just intuitively substituted . Theoretically this'll provide a bit less bass cutoff and a slightly easier start for the power suppy? 

 Here's quick phone-cam pics of the small holes I've already drilled and positioning of the external parts on top of the case:










 Tight squeeze! I might actually go with a 1/8" headphone jack on the front panel for this reason alone.


----------



## cms5423

Looks good though 
	

	
	
		
		

		
		
	


	




 Also, has anyone tried this build edit for the 12SR7GT tubes?, or the 12SR7's?
http://www.head-fi.org/forums/f6/mil...ml#post5584504

 How does it sound? And is all that you have to change the tubes and the resistor values? Everything else stays the same?


----------



## Yaka

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_All that the heatsink mounting kit does is insulate the drain of the MOSFET from the heatsink. most MOSFETs have the tabs shorted to their Drain. The mounitng kit comes with a mica insulator which goes inbetween the MOSFET tab and the heatsink. Then you take the small plastic washer which goes into the mounting hole of the MOSFET through which you wil put the screw. You need this plastic washer without which the screw would short the heatsink and the MOSFET tab._

 



 just like to add, if anyone is wondering What happens without the insulator is that you will see you SSH spark up all over the sinks and around the case it keeps going after the power is switched off. you could say my first p2p effort was bit too bright


----------



## cms5423

Looks good though 
	

	
	
		
		

		
		
	


	




 Also, has anyone tried this build edit for the 12SR7GT tubes?, or the 12SR7's?
http://www.head-fi.org/forums/f6/mil...ml#post5584504

 How does it sound? And is all that you have to change the tubes and the resistor values? Everything else stays the same?


----------



## smeggy

I'll be making 12SR7GT version once I get a board but I don't think anyone else has made one yet.


----------



## cms5423

Ugh, because without being able to find 19J6 tubes, I really want to find another option for a hybrid amp to build, but I want to keep it relatively cheap. So i'm thinkin either 12SR7GT, or go for the millett maxed


----------



## cactus friend

Be persistent - you'll find the tubes ... there's lots out there - just spread out all over the place. I just wish I had ordered more than 2 when I had the chance! It may take a while to search more out if I need them.


----------



## cms5423

Haha, I'm trying. I'm emailing everyone out there. Wish me luck


----------



## zkool448

cms5423, I would've waited for the beezar kit.. no guarantees but a good probability you'll get one as tomb *may* let first time builders get first dibs on these kits 
	

	
	
		
		

		
		
	


	




 Tomb, what's your plan when they go on sale... will it be first come first serve?


----------



## Yaka

woulda thought first come first serve makes more sense than anything else


----------



## tomb

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_woulda thought first come first serve makes more sense than anything else_

 

Yes, I don't know how it could work any other way. I'll give plenty of notice, though.


----------



## Fang

Any idea when the kits will be out? I'm really interested in this build.


----------



## smeggy

I'll give it 20 minutes to clear all your stock, Tom


----------



## tomb

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I'll give it 20 minutes to clear all your stock, Tom 
	

	
	
		
		

		
		
	


	


_

 

Promises, promises ... 
	

	
	
		
		

		
		
	


	




 Meanwhile, anyone up for a Group Buy on a pre-drilled Hammond case (same as the one I built)? No guarantees, but I'm going to contact Hammond for pricing tomorrow. Most likely it will be like the MiniMAX case (no cooling slots, though) - we'll probably need 100 to make it worthwhile.

 I'll let you all know if the prices seem feasible.


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I'll give it 20 minutes to clear all your stock, Tom 
	

	
	
		
		

		
		
	


	


_

 

x2, for the first 30 kits that is.


----------



## tomb

Just an FYI, but I have an ROM from a local outfit that would do the holes on a small time basis for $37.50 a case. That's about $55-$60 counting the 1455N1201 case itself. However, the local guy is not prepared to do quantity, but if that's a reasonable going rate for onesie-twosies, Hammond might even be better with a quantity discount.

 This would include:
 Case Lid: 5 - 1/8" holes, 2 - 3/4" holes
 Front Plate: 1 - 7/16" hole, 1 - 5/16" hole
 Rear Plate: 2 - 5/16" hole, 1 - 1/2" hole, 1 - 3/4" hole


----------



## smeggy

yeah, I'm definitely getting one (or two) once they're out.. if I catch them in time.


----------



## cms5423

Just thought that I'd post that I am going to be building the adaptation to this build posted by Logistic. I bought both 12SW7 and 12SR7GT tubes to try. I'll post my BOM, pics, and a brief review once it's build. All the parts should be in the mail.

 I'll still have to layout my p2p design once I get all the parts, so it may be a while still.
 Wish me luck


----------



## smeggy

Cool, looking forward to it, and mine


----------



## cms5423

Sorry everyone for the repost 
 (moderator, please delete if you can)


----------



## cegras

If only you can reserve kits .. I'm working so I can't be refreshing all day D:


----------



## JamesL

i don't plan on buying, but it'd be nice to have maybe a limit 2 per customer on the very first day so everyone can get a shot at building one. 

 After all, no one really needs more than 2 for themselves and maybe a friend.


----------



## smeggy

I promise to limit myself to one board with tubes and one board without


----------



## jonjon0nline

FML if I miss this =P


----------



## gurusan

I just want a PCB


----------



## Arlekiin

is Starving student any good with 600ohm cans?


----------



## JamesL

I've been reading that the turn-on thump was fairly quiet, and hardly noticeable in some people's amplifiers.
 I've been using my ssmh, completed for a couple days and the turn-on/off thump is quite loud. Not enough to damage my headphones, but enough, that it makes me uncomfortable leaving several hundred dollar headphones plugged in.

 I'm using 220uf at the output, and 180uf power caps. Is the fact that the output caps are larger than the power caps a problem? 
 It also seems that it would be near impossible to replace the filter caps without disassembling the entire amp. Could I add another 200uf or so filter cap parallel to c1?
 Currently, I'm getting 4 consecutive thumps at turn-on .. the first and third thump louder than the second and fourth.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I've been reading that the turn-on thump was fairly quiet, and hardly noticeable in some people's amplifiers.
 I've been using my ssmh, completed for a couple days and the turn-on/off thump is quite loud. Not enough to damage my headphones, but enough, that it makes me uncomfortable leaving several hundred dollar headphones plugged in.

 I'm using 220uf at the output, and 180uf power caps. Is the fact that the output caps are larger than the power caps a problem? 
 It also seems that it would be near impossible to replace the filter caps without disassembling the entire amp. Could I add another 200uf or so filter cap parallel to c1?
 Currently, I'm getting 4 consecutive thumps at turn-on .. the first and third thump louder than the second and fourth._

 

There's a couple of things going on here.

 First, turn-on thump is unavoidable - but not 4 consecutive ones. What you're experiencing is the turn-on "stutter" caused by the combination of too-small power caps and the switching power supply. Through trial and error, we've found that at least 680uf for the power caps will stop the stutter.

 Note, however, that you will still get a single, turn-on thump. There are two divergent schools of thought - most of our headphone amps can easily tolerate several volts of offset with no harm ... or never, ever plug your headphones in before the amp is turned on and the tubes are warmed up.
	

	
	
		
		

		
			








 Second, turn-off thump is almost strictly a function of capacitance in the amp and the connected load. The more capacitance, the greater the turn-off thump. Conversely, the higher the connected load, the less the turn-off thump. Note, however, that turn-off thump is much, much less severe in offset voltage than the turn-on thump.

 Finally, yes - you can parallel caps and the capacitance is additive in that case.


----------



## tamasic1

For what it's worth I've never experianced even the slightest thump on power up or down and my primary set of cans are 32 ohm senns. At power on the tubes begin to glow and a just audible hum slowly rises. I followed the bom for the options schematic except I used 1000uF caps for C1, C6 and at 200v they're as tall as the heatsinks. Haven't a clue if this makes the difference or not but it works in my build. I did p2p on perfboard wired with Cat5 cable. 

http://bellsouthpwp2.net/k/a/karlet/BigCaps1.jpg
http://bellsouthpwp2.net/k/a/karlet/BigCaps2.jpg -cased up


 Larry the Tube Guy says: Getter Done


----------



## tomb

Just an FYI, but I have an official RFQ in to Hammond based on the following drawings:









 They promised that they'd have pricing back to me on Monday.


----------



## cms5423

Sweet, would you be able to sell these cases, even if I was going to build my own p2p version?


----------



## tomb

The idea is to sell them to everyone. I think we may do that first - guarantee that everyone who purchases one will get a board and tubes, for instance ... or something like that ... assuming Hammond's price works out.


----------



## andrisll

Hello! I'm beginner in electronics, so here are a few appropriate questions:
 Is there any good pcb layout available?
 I found this one: 
	

	
	
		
		

		
		
	


	



 but as I read it wasn't working very well. And it's made from this "upgraded" schematic: 
	

	
	
		
		

		
		
	


	



 Does it make any difference (good)?

 I have already built working p2p SS but it's a very big mess inside the case, weak wiring isolation and problems with grounding.

 Do I have to connect all the grounding points to one place that connects to chassis?


----------



## smeggy

The upgraded schematic is better in a few ways so it's worth doing as it's an evolution over time from the original as new things were discovered to help the amp in more varied circumstances.

 The ground. You can take the psu input ground as a base to attach all other ground points to, whether it's the case of just a strip. They should all go to one common ground.


----------



## tamasic1

To those of you who have built a GainClone and big speakers, use the Starving Student as its preamp 
	

	
	
		
		

		
		
	


	










 WOW, WOW, WOW


----------



## scompton

Quote:


  Originally Posted by *Arlekiin* /img/forum/go_quote.gif 
_is Starving student any good with 600ohm cans?_

 

Quite a few people have used Sextetts with them, including me.


----------



## cms5423

In case this could help someone with the build:

 So when you were saying put 50k input resistors on my starving student, were you referring to doing that with a 10k pot or a 50k pot?

 Also, I've seen people's upgraded schematics and BOMs that use bypass caps. Are these just caps placed in parallel to the cap that is already there? Like a .22 parallel to c3 and c5, or are they placed befor c3 and c5 and connect to ground? What exactly do these bypass caps do and what capacitors would these be used for?


> _Essentially, the input resistors push the high gain inherent in the SSMH's tubes into the last portion of resistance represented by the pot. Let's say you use a 10K pot and 40K input resistance. The total resistance seen by the source feeding the amp would be 50K. However, all volume control would occur in the last 10K of that 50K. This is acceptable for almost all loads using the SSMH, because the basic gain provided by the tubes is 19, whereas typical headphone amp gains range from a low of about 2 to a maximum of 11, in the case of a basic CMoy used to power a 300ohm Senn.
> 
> Using a 50K pot with a 50K resistor results in a total of 100K seen by the load, but only the last half of the resistance is variable by the pot. Personally - after trying both - I think the 10K and ~40K input resistance is the best combination.
> 
> ...


Also, all my parts get here tomorrow I think!!
 Building starts when UPS arrives 
	

	
	
		
		

		
		
	


	




 --And if someone could elaborate a little bit on the bypass caps, exactly what are they doing in the circuit, like what parts of the signal and why flow into the bypass caps vs the electrolytics, and how do you determine the value of the bypass caps? Thanks


----------



## tomb

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_In case this could help someone with the build:

 So when you were saying put 50k input resistors on my starving student, were you referring to doing that with a 10k pot or a 50k pot?

 Also, I've seen people's upgraded schematics and BOMs that use bypass caps. Are these just caps placed in parallel to the cap that is already there? Like a .22 parallel to c3 and c5, or are they placed befor c3 and c5 and connect to ground? What exactly do these bypass caps do and what capacitors would these be used for?



Essentially, the input resistors push the high gain inherent in the SSMH's tubes into the last portion of resistance represented by the pot. Let's say you use a 10K pot and 40K input resistance. The total resistance seen by the source feeding the amp would be 50K. However, all volume control would occur in the last 10K of that 50K. This is acceptable for almost all loads using the SSMH, because the basic gain provided by the tubes is 19, whereas typical headphone amp gains range from a low of about 2 to a maximum of 11, in the case of a basic CMoy used to power a 300ohm Senn.

 Using a 50K pot with a 50K resistor results in a total of 100K seen by the load, but only the last half of the resistance is variable by the pot. Personally - after trying both - I think the 10K and ~40K input resistance is the best combination.

 As for bypass capacitors - electrolytics are slow, lack detail, and often sound outright bad when used directly in the signal path. Directly in the signal path, the small film bypass may actually reach down to 1K and below in the frequencies, so that the electrolytic is essentially passing mid-bass and bass, only. It's actually more complicated than this really, because the speed, ESR, etc. all roll into the combination. There's very little data regarding cap bypassing - it's mostly an artistic type thing, learned through experience. Some cap combinations sound awful, others surprisingly good. Wima's are kind of traditional and have a great track record of bypassing caps - in the signal path and without. So, think of them of as kind of a booster on the large electrolytics, allowing them to operate through the entire frequency scale, without coloration and with plenty of speed and sparkle in the highs and smooth mids. Of course, the film cap all by itself would be the best choice, but very few are in sizes of the 470uf or 680uf as used in the SSMH. If you can even find film caps in that rating, they'd probably each be bigger than the entire amp. So, there you are.

 P.S. the film bypasses are in parallel - across the leads of the electrolytic, iow.


Click to expand...

Also, all my parts get here tomorrow I think!!
 Building starts when UPS arrives 
	

	
	
		
		

		
		
	


	




 --And if someone could elaborate a little bit on the bypass caps, exactly what are they doing in the circuit, like what parts of the signal and why flow into the bypass caps vs the electrolytics, and how do you determine the value of the bypass caps? Thanks 
	

	
	
		
		

		
		
	


	


_

 

-SIGH- Thanks for posting this, but I would've thought my answer up there was enough.
	

	
	
		
		

		
		
	


	




 As I stated, there is no science regarding how bypass caps work. You can attempt to run the corner frequency equation on the output coupling arrangement, for instance, but it's an exercise in futility:

 Let's say we have a 300ohm Senn as the load -
 0.22uf has a -3dB value at 2411 Hz.
 So, you might say that the film cap will pass most of the music to the Senns until it gets to 2KHz and below, then the electrolytic takes over.

 However, let's say we have a 32ohm Grado as the load -
 0.22uf has a -3dB value at 22,607 Hz.
 So, you might say that the film cap is useless for Grado's because it will never predominate below audible frequencies.

 Unfortunately, we know this is not true. The speed of the film cap comes into play. It may interact with the music signal much more quickly than the electrolytic, regardless of the cutoff frequency for each cap. However, this is highly variable and depends on the specific film cap and the specific electrolytic. Moreover, there's just as much reason to expect the combination of electrolytic and film cap to act as a single 470.22uf, not as separate caps. Yet, you can put a Black Gate in there (assuming voltage ratings are sufficient) and it will seem as if the Wima never adds anything to the equation.

 There is little predictably to any combination except that some bypasses seem to work with more regularity than others. The Wima is one of those. Others may end up sounding lousy. The Wima itself can sound lousy in some scenarios - only trial and error apply.

 The same can be said for sizing the bypass. One rule-of-thumb that's sometimes quoted is 10% of the size of the electrolytic. This doesn't hold in the larger sizes, however, otherwise we'd be talking 47uf film caps on the output coupler and those are impractically large and expensive.

 So how do we know any of this? Trial and error. In the case of the Starving Student, I can assure you that the latest additions by Dsavitsk have made this into a much better amp. I can specifically state that the BOM as it now stands - SSMH Bill Of Materials
 using a combination of the DigiKey and Mouser components sounds better than any other SSMH I've built:

680uf 63V Panasonic FC's (short size)
470uf 63V Nichicon KW's as output couplers,
Wima 0.22uf MKP10's as interstage couplers and output bypasses,
10K Alpha with 39K input resistors,
220uf 16V Muse ES cathode bypass caps
Vishay-Dale resistors throughout.
This combination will be "chiseled in stone" as far as I'm concerned.
	

	
	
		
		

		
		
	


	




 It's far superior to the other prototype built with Muse FG's on the output and Stackpole carbon film resistors, and 50K pot with 50K input resistors. The other prototype, in turn, is far superior to the standard build with no bypasses, no input resistors, etc.


----------



## tomb

BTW, Hammond came back with prices so cheap ... if we only get 50 people to purchase the cases, the total drill and punch price for every hole needed to build this amp will only result in less than $10 over the Mouser cost of the bare case alone (assuming a bit for shipping and Paypal costs). So, we are going to have a Group Buy for the cases if everyone is game. I'll announce the details soon. It will be a one-per person scenario and have a specific cutoff number - so that we can ensure that whoever buys a case gets tubes and a board. There is a 6 week lead time on the cases.

 Buttoning this board up into the Hammond case is somewhat similar to a puzzle box, what with the center standoff of the top plate, and attaching the sinks on top with the MOSFETs underneath. Plus, the tube holes, headphone jack, and pot shaft are totally fixed by the PCB. This makes accurate drilling imperative. With the MOSFETs/heat sink situation critical, it also means that it's impossible to build the amp and have it operate without casing it up - no bare PCB and running it in a cardboard box, iow - it'll burn up. All of this means that the case is integral to building the SSMH PCB. So, if we can make this easier with a pre-punched case, all the better.
	

	
	
		
		

		
		
	


	







 If someone thinks this is objectionable, let me know.


----------



## royewest

Sounds like a great plan, Tomb -- really looking forward to the production version coming together. Thanks for keeping with this.


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Sounds like a great plan, Tomb -- really looking forward to the production version coming together. Thanks for keeping with this._

 

Nice hearing from you again, Roy! Yes, sorry this has gone so slowly, but we're getting very close. The production version I finished recently with that parts spec I listed above is really something special - as good as I've heard anywhere near the price it takes to build one of these. As with most of Pete's stuff - really something special - and Dsavitsk's additions have taken it to a new level.


----------



## JamesL

Quote:


 First, turn-on thump is unavoidable - but not 4 consecutive ones. What you're experiencing is the turn-on "stutter" caused by the combination of too-small power caps and the switching power supply. Through trial and error, we've found that at least 680uf for the power caps will stop the stutter. 
 

Cool. Is that 680uf per cap or total?
 In either case, I'm not making any orders till I get back to Chicago after the summer.. but I have a couple 100uF 50v caps on-hand that I can add after the power switch. Hopefully, that'll alleviate the problem for now.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Cool. Is that 680uf per cap or total?
 In either case, I'm not making any orders till I get back to Chicago after the summer.. but I have a couple 100uF 50v caps on-hand that I can add after the power switch. Hopefully, that'll alleviate the problem for now._

 

That's 680uf per cap (power caps). However, that doesn't mean that parts list applies to a P2P version. I'm just stating that it's the best for the PCB. The power supply on each of mine still stutter - at least once on startup, but it's brief. I think this is variable depending on how much total capacitance is used on the board and also the ratio between the values of the power caps vs. the values of the output coupling caps. Plus, adding tube LEDs complicates the mix. So, I'm not sure we can ever guarantee that stuttering will be prevented. It's best just to take proper precautions and not have a pair of headphones plugged in when you turn the amp on.


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The production version I finished recently with that parts spec I listed above is really something special - as good as I've heard anywhere near the price it takes to build one of these. As with most of Pete's stuff - really something special - and Dsavitsk's additions have taken it to a new level._

 

I admit that I have a soft spot for Pete's SS, to me it is that -- special. The additions is just the icing on the cake.


----------



## smeggy

I'm really looking forward to getting my sticky mits on on of these new board/BoMs to make, sounds like it'll be a sweet amp


----------



## cms5423

Ok, so with the octal socket the conversions were:

 1,2 -> 6
 5,6 -> 2
 3,4 -> 7,8
 7->3

 does that mean that originally we were connecting 5 and 6 together, which went to the pot, but now, we just connect the pot to pin 2 of the octal socket?

 This makes sense, and I know it was stated to connect pin 1 of octal to ground, but what do you connect pins 4 and 5 to of the octal socket?


----------



## cms5423

and if anyone is online on AIM right now that could answer a couple of questions for me, that would be so awesome. my screenname is cmspearman02, thanks soo much


----------



## Logistic

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_Ok, so with the octal socket the conversions were:

 1,2 -> 6
 5,6 -> 2
 3,4 -> 7,8
 7->3

 does that mean that originally we were connecting 5 and 6 together, which went to the pot, but now, we just connect the pot to pin 2 of the octal socket?

 This makes sense, and I know it was stated to connect pin 1 of octal to ground, but what do you connect pins 4 and 5 to of the octal socket?_

 

You want to ground pins 4 and 5.


----------



## Logistic

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Cool. Is that 680uf per cap or total?
 In either case, I'm not making any orders till I get back to Chicago after the summer.. but I have a couple 100uF 50v caps on-hand that I can add after the power switch. Hopefully, that'll alleviate the problem for now._

 

It'll work best to add them to the second cap after the resistor, C6 I believe.


----------



## cms5423

so ground pins 1 4 and 5 from the octal socket? Sounds good. i may have more questions, i'm mapping it all out on paper right now


----------



## cms5423

Also, with the octal socket, 3,4-->7,8: does that mean what was pin 3 on the 7 pin socket is now pin 7 on the octal, and 4 is now pin 8 on the octal?


----------



## Logistic

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_Also, with the octal socket, 3,4-->7,8: does that mean what was pin 3 on the 7 pin socket is now pin 7 on the octal, and 4 is now pin 8 on the octal?_

 

Yes, sorry if that wasn't clear.


----------



## cms5423

I just want to double check then: on the octal: pins 1, 4, 5, and 8 are all grounded, 2 goes to the pot, 3 is grounded with R5/R11, 6 is connected to both C2/C4 and R1/R7, and 7 goes to the mosfets and C3/C5 on to the output?


----------



## Logistic

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_I just want to double check then: on the octal: pins 1, 4, 5, and 8 are all grounded, 2 goes to the pot, 3 is grounded with R5/R11, 6 is connected to both C2/C4 and R1/R7, and 7 goes to the mosfets and C3/C5 on to the output?_

 

Yep looks good to me. I apologize if people feel this conversation should be held over PM. I felt that other people might find this information useful later. If the mods feel this is a problem let me know.


----------



## smeggy

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Yep looks good to me. I apologize if people feel this conversation should be held over PM. I felt that other people might find this information useful later. If the mods feel this is a problem let me know._

 

No, I plan on stealing all your work and claiming it for my own.


----------



## nullstring

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Yep looks good to me. I apologize if people feel this conversation should be held over PM. I felt that other people might find this information useful later. If the mods feel this is a problem let me know._

 

I, for one, also plan on using this information

 So.. don't worry about it.
 I do, however, wonder if it should be put into it's own thread.

 Do you think the optimal capacitor values change with this tube?
 The tube is a different voltage, right? 

 Also, how did you go about choosing this tube for use with the SS?
 I kind of wanted to have traditional looking tubes on my first tube amp. How hard would it be to adapt another tube?


----------



## Logistic

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_I, for one, also plan on using this information

 So.. don't worry about it.
 I do, however, wonder if it should be put into it's own thread.

 Do you think the optimal capacitor values change with this tube?
 The tube is a different voltage, right? 

 Also, how did you go about choosing this tube for use with the millet?
 I kind of wanted to have traditional looking tubes on my first tube amp. How hard would it be to adapt another tube?_

 

You can use the 12SR7GT tubes, which are the glass version of the 12sr7, if you want glass tubes. I chose the 12sr7 because it is very cheap at vaccumtubes.net, in keeping with the starving student theme.

 The capacitor values can stay the same. The voltage of the heaters change, but the resistor changes are all that is necessary. If you want, you can go lighter with the cathode bypass caps, you can probably cut it in half if you want.

 As for creating a new thread, I might consolidate all the info into a new thread sometime in the future.


----------



## zkool448

Logistic, very useful and valuable info indeed IMO – just wait and see once 19J6 tubes aren't anywhere to be found 
	

	
	
		
		

		
			





 I've seen a few attempts (on paper) but I don't think I've yet seen a _fully working _ variation of the MSSH 'in the wild' until you built yours with the 12SR7s/12SW7s -- I do think it deserves it's own thread


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## nullstring

Thanks Logistic.
 Sounds good.

 EDIT:
 You even mentioned the glass tubes in your original post.
 I must've overlooked it before. Sorry about that.


----------



## cms5423

So i have a general question: For the inputs of this amp, most everyone uses RCA inputs. Could I use a 3.5mm input? Or what is the benefit of using RCA jacks? Thanks guys


----------



## whitelabrat

In case anyone is interested ESRC tubes is selling 6J6's for $1 a pop. Same as 19J6 but 6.3v heater.


----------



## zkool448

A quick search through Head-Fi megathreads (luv this search feature 
	

	
	
		
		

		
		
	


	




) suggests the 6J6s have much higher current draw and can't be used without circuit modifications, also won't be as elegant as the existing heater design.


----------



## Llama16

Would placing the reservoir caps before the power switch not eliminate the danger? Like in the Mini^3


----------



## DKJones96

6j6 tubes grow on trees! I know of at least one place in town here that has about 100 of them just sitting there. Nobody ever buys um.

 What if you were to use 3 6j6 tubes per channel so the voltage requirement for the heater circuit remains the same? Current is higher so the Cisco power supply in the original BOM won't work anymore but since it's now more expensive than other, higher capacity, 48v switching units that shouldn't be a problem. You could just not use the other two tubes. They'd be there for aesthetics. 

 Can the FETs take that 450ma current if you can get the heat away from them?


----------



## nullstring

What do you guys think the chances of getting matching 12SR7GT/12SR7/12SW7 from vacuumtubes.net are?

 I plan on buying a pair of each.

 Should I buy more than just a pair?
 If I request the same brand.. do you think they'd oblige?


----------



## Logistic

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_What do you guys think the chances of getting matching 12SR7GT/12SR7/12SW7 from vacuumtubes.net are?

 I plan on buying a pair of each.

 Should I buy more than just a pair?
 If I request the same brand.. do you think they'd oblige?_

 

the 12sr7s and 12sw7s I got from vacuumtubes.net were all military RCAs.


----------



## Hayduke

Quote:


  Originally Posted by *cms5423* /img/forum/go_quote.gif 
_So i have a general question: For the inputs of this amp, most everyone uses RCA inputs. Could I use a 3.5mm input? Or what is the benefit of using RCA jacks? Thanks guys 
	

	
	
		
		

		
		
	


	


_

 

Mine uses a 3.5mm(1/8") input jack. I feed a Bantam cable DAC into it at work.

 I have yet to build anything with RCAs since I don't use them. Even my SOHA has a mini phone input (along with a built in BantamDAC). 


 Tom, I'm bothered to hear you fried another bantam with a MHSS. Mine has been running like a champ. I've adopted the procedure of unplugging the Bantam each night when I leave work and turn off the amp. In the morning, I turn on the amp and give it a couple minutes (sometimes as little as 1 or 2, sometimes several as I get coffee or deal with early AM crisis hehe), then I plug in the bantam. So far, so good, but you have me a little spooked. I know you've recommended modifying the circuit at the input to protect the DAC, but I haven't done anything yet. Of course I am using a 10K pot and 40k in resistors, so maybe I am already blocking some of the problem?


----------



## n_maher

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_What do you guys think the chances of getting matching 12SR7GT/12SR7/12SW7 from vacuumtubes.net are?

 I plan on buying a pair of each.

 Should I buy more than just a pair?
 If I request the same brand.. do you think they'd oblige?_

 

I would bother worrying about matched tubes.


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Mine uses a 3.5mm(1/8") input jack. I feed a Bantam cable DAC into it at work.

 I have yet to build anything with RCAs since I don't use them. Even my SOHA has a mini phone input (along with a built in BantamDAC). 


 Tom, I'm bothered to hear you fried another bantam with a MHSS. Mine has been running like a champ. I've adopted the procedure of unplugging the Bantam each night when I leave work and turn off the amp. In the morning, I turn on the amp and give it a couple minutes (sometimes as little as 1 or 2, sometimes several as I get coffee or deal with early AM crisis hehe), then I plug in the bantam. So far, so good, but you have me a little spooked. I know you've recommended modifying the circuit at the input to protect the DAC, but I haven't done anything yet. Of course I am using a 10K pot and 40k in resistors, so maybe I am already blocking some of the problem?_

 

I had input resistors, too. Although, I think we were suspecting the stuttering on startup as an incorrect diagnosis. This time I fried the Bantam when the SSMH (or MHSS) had been on for quite awhile. I disconnected the RCA jacks from the SSMH and immediately got a lot of hum. I should've known something was wrong at that point, but just thought perhaps the lack of signal ground caused it. In trying to connect the Bantam, I clumsily touched the center pin of the RCA patch cable to the outer surface of the jack on the SSMH. That's all it took - that channel is dead now on the Bantam.

 A few of us suspect that the Cisco's power supply ground "floats" from time-to-time. Unfortunately, it's intermittent and unpredictable. I once measured as much as 0.49V offset between the ground on the SSMH and a capacitively-coupled ground on the Bantam (the dead one, now - OK for testing
	

	
	
		
		

		
		
	


	




 ). Then it went away and I couldn't measure it again. If this is what is happening, that's why an Alien or Bantam DAC would get fried - the grounds/output on those DACs are not isolated from the amp.

 I don't have a scope, but it would be interesting if someone conducted some similar tests on the Cisco power supply ground, just to be sure.
	

	
	
		
		

		
		
	


	




 P.S. One other line of suspicion is a shorted tube. Those can easily be intermittent. I think Nate recently said his PCB prototype had experienced a lot of hum lately - it turned out that one of his tubes developed a short. Knowing that the cathode is directly grounded through the MOSFETs and the rest of the amp, this might make a lot of sense, too. Someone correct me if I'm wrong, but if the tube has an intermittent short, it may sound fine most of the time.


----------



## tomb

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_What do you guys think the chances of getting matching 12SR7GT/12SR7/12SW7 from vacuumtubes.net are?

 I plan on buying a pair of each.

 Should I buy more than just a pair?
 If I request the same brand.. do you think they'd oblige?_

 

Actually, I'd get them matched if you are going this route. Use of this tube series may work fine with the suggested mods, but those are only single-triode tubes. In the 19J6, there are dual triodes that are paralleled together. This tends to average out the differences in tubes and minimizes the need for matching.

 With single triodes, the differences in matching from tube to tube may be quite stark, IMHO. No offense to the excellent work finding a working replacement, but I think this is one of the reasons why Dsavitsk suggested that a 12AU7 modification might work a lot better (with similar mods) for the SSMH than this series of tubes.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I think Nate recently said his PCB prototype had experienced a lot of hum lately - it turned out that one of his tubes developed a short. Knowing that the cathode is directly grounded through the MOSFETs and the rest of the amp, this might make a lot of sense, too. Someone correct me if I'm wrong, but if the tube has an intermittent short, it may sound fine most of the time._

 

Unfortunately replacing the bad tube with a good one has not rectified the grounding issue that I'm having. 
	

	
	
		
		

		
		
	


	




 If I max the pot on my prototype and control the volume with my source I have no noise, anywhere below max volume and I've got bad buzz. Work continues...


----------



## cactus friend

Well, now I've gone and done it. After taking my time and wiring up the power supply/switch/led/pot very nicely, I had a lot of coffee and decided that I should wire up the 'right' channel and give it a whirl.

 I guess I rushed...when I turned it on, there were some loud audible bursts of noise (not through the headphones which weren't plugged in, just audible in general) which coincided with the LED shutting off. I quickly took the bottom of the case off, thinking that maybe something had shorted out and sparked inside of it, and the audible click/bursts stopped, but the tube never 'heated' up. I verified that I still had a solid 48v coming in from the back, but no 19v coming out of pin3.

 I'll post big ugly detailed pictures after work today, but I was wondering if anyone with more experience than me had some intuition regarding what I most likely did...did I destroy the mosfet maybe?


----------



## smeggy

Ack! That's not good


----------



## cactus friend

My plan is to just reverse what I did last night ... I'll probably have to re-buy about $5-10 worth of parts (no big deal, but glad I only did one channel). 

 For now, I still have an untouched, unfinished, hopefully un-broken left channel I can try out. I'll scan in and upload my planned wiring diagram and hopefully someone can slap me upside the head and point out an obvious error


----------



## Logistic

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, I'd get them matched if you are going this route. Use of this tube series may work fine with the suggested mods, but those are only single-triode tubes. In the 19J6, there are dual triodes that are paralleled together. This tends to average out the differences in tubes and minimizes the need for matching.

 With single triodes, the differences in matching from tube to tube may be quite stark, IMHO. No offense to the excellent work finding a working replacement, but I think this is one of the reasons why Dsavitsk suggested that a 12AU7 modification might work a lot better (with similar mods) for the SSMH than this series of tubes.
	

	
	
		
		

		
		
	


	


_

 

A double triode may help with differences in triode sections, but that also depends on the relative tolerances. If the tolerances of one single triode tube is very tight, then it may very well be that two of those tubes are more closely matched than two double triode tubes that have looser tolerances.

 Not knowing the tolerances, matching would be ideal. However, at $1, you can get a few tubes and if two don't sound right, you can try changing them. Tube matching doesn't always guarantee they work the same in an amp anyways.

 I chose this tube because it was very inexpensive. The millet hybrid minimax uses single triodes, and if I recall, beezar used to sell them without matching.


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I had input resistors, too. Although, I think we were suspecting the stuttering on startup as an incorrect diagnosis. This time I fried the Bantam when the SSMH (or MHSS) had been on for quite awhile. I disconnected the RCA jacks from the SSMH and immediately got a lot of hum. I should've known something was wrong at that point, but just thought perhaps the lack of signal ground caused it. In trying to connect the Bantam, I clumsily touched the center pin of the RCA patch cable to the outer surface of the jack on the SSMH. That's all it took - that channel is dead now on the Bantam.

 A few of us suspect that the Cisco's power supply ground "floats" from time-to-time. Unfortunately, it's intermittent and unpredictable. I once measured as much as 0.49V offset between the ground on the SSMH and a capacitively-coupled ground on the Bantam (the dead one, now - OK for testing
	

	
	
		
		

		
		
	


	




 ). Then it went away and I couldn't measure it again. If this is what is happening, that's why an Alien or Bantam DAC would get fried - the grounds/output on those DACs are not isolated from the amp.

 I don't have a scope, but it would be interesting if someone conducted some similar tests on the Cisco power supply ground, just to be sure.
	

	
	
		
		

		
		
	


	




 P.S. One other line of suspicion is a shorted tube. Those can easily be intermittent. I think Nate recently said his PCB prototype had experienced a lot of hum lately - it turned out that one of his tubes developed a short. Knowing that the cathode is directly grounded through the MOSFETs and the rest of the amp, this might make a lot of sense, too. Someone correct me if I'm wrong, but if the tube has an intermittent short, it may sound fine most of the time._

 

interesting... thanks for the response Tom. I'll definitely count my blessings then since my Bantam and MHSS(SSMH? dunno correct acronym hehe) have been operating each weekday flawlessly. Listening to them with the 580s right now 
	

	
	
		
		

		
		
	


	




 One difference though, is my cable BantamDAC uses a mini phone plug (3.5mm 1/8") as the output. It's a cheaper connector, but maybe the TRS design is more resistant then RCAs?

 I'm just gonna continue my practice of unplugging the DAC whenever I turn the amp on. I haven't been doing that when I turn it off. You have me wondering if maybe I should?


----------



## Listen2this1

Ok I give up, 

 I have all of the things that I need to make this amp, and most of all, the time. ( Finally Graduated )

 I have tried to mount one of the heatsinks by removing the pins and inserting some screws. Since it is aluminum it takes steel screws pretty well. Not this heatsink. It ate one of my screws, so I drilled it out and went to re-tap it and the damn thing ate my tap. 

 Now I am at a loss.

 How does you mount your heatsinks to the chassis?

 I am going to run to ratshack to find another one.

 Also a little while back I was able to get two tubes, one a raytheon and the other a tung-sol. Both have the halo's. Will I have any problems?


----------



## Listen2this1

Double post......Seems to happen alot lately?


----------



## tomb

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_<snip>The millet hybrid minimax uses single triodes, and if I recall, beezar used to sell them without matching. 
	

	
	
		
		

		
		
	


	


_

 

The Millett Hybrid/MAX/MiniMAX family of amps have used trimmers to specifically adjust bias on the tubes since day one - all the way back to Pete's original Audio Xpress article in 2001. The adjustable bias allows one to always "center" the stereo signal. It's true that if the tubes aren't perfectly matched that there will be differences in dynamics from one channel to the next, but it usually provided good enough compensation until we refined the MAX to the point that greater precision was needed, and started offering matching. After all, these days - there's a lot of less expensive competition nipping at the MAX's heels.
	

	
	
		
		

		
		
	


	




 P.S. YGPM.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Ok I give up, 

 I have all of the things that I need to make this amp, and most of all, the time. ( Finally Graduated )

 I have tried to mount one of the heatsinks by removing the pins and inserting some screws. Since it is aluminum it takes steel screws pretty well. Not this heatsink. It ate one of my screws, so I drilled it out and went to re-tap it and the damn thing ate my tap. 

 Now I am at a loss.

 How does you mount your heatsinks to the chassis?

 I am going to run to ratshack to find another one._

 

I'm one of those swimming against the stream, I guess - I don't like threaded and tapped heat sinks. Actually, the pins should work quite well if you use a copper ground plate as Pete used in his original. Look carefully at his pics and you'll see he drilled the holes for the pins, pushed the heat sink pins through, and soldered washers on the back side to the pins and to the plate. Looks pretty secure to me.
	

	
	
		
		

		
		
	


	




  Quote:


 Also a little while back I was able to get two tubes, one a raytheon and the other a tung-sol. Both have the halo's. Will I have any problems? 
 

Seeing as how they were both probably made by RCA, I doubt it.


----------



## zkool448

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_<snip>I chose this tube because it was very inexpensive...</snip>_

 

What??? Logistic please don't tell me this is *only* reason you chose these tubes 
	

	
	
		
		

		
		
	


	




 It almost sounds like you could've picked _any_ tube as substitute for 19J6, but you didn't in the spirit of the "starving" theme (?)


----------



## Logistic

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_What??? Logistic please don't tell me this is *only* reason you chose these tubes 
	

	
	
		
		

		
		
	


	




 It almost sounds like you could've picked any tube as substitute for 19J6, but you didn't in the spirit of the "starving" theme (?)_

 

Of course I didn't just pick this tube because it was inexpensive. While there are a number of tubes that would work here, there are a lot that wouldn't. When searching for a tube, the cost was only one of the factors I considered, and only after I made a list of tubes that might work in the amp.

 It is possible to adapt other tubes to the amp, but my primary motivation was to provide an alternative to those would couldn't afford to pay a premium on the scarce 19J6's. Fortunately TomB is providing some 19J6's at beezar, but the supply is limited. This is such a great project that I wanted people to be able to build it that may otherwise have trouble with acquiring tubes.

 Logistic


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm one of those swimming against the stream, I guess - I don't like threaded and tapped heat sinks. Actually, the pins should work quite well if you use a copper ground plate as Pete used in his original. Look carefully at his pics and you'll see he drilled the holes for the pins, pushed the heat sink pins through, and soldered washers on the back side to the pins and to the plate. Looks pretty secure to me.
	

	
	
		
		

		
		
	


	




 Seeing as how they were both probably made by RCA, I doubt it.
	

	
	
		
		

		
		
	


	


_

 

should the heatsinks be grounded or does it really matter?


----------



## zkool448

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_should the heatsinks be grounded or does it really matter?_

 

Not really sure if the recommended practice is to always ground the heatsinks (safety reasons?), but if they are confirm your MOSFETs are electrically isolated so make sure to use TO-220 mounting kits that have some kind of insulators/shoulder washers.


----------



## MoxMonkey

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Not really sure if the recommended practice is to always ground the heatsinks (safety reasons?), but if they are confirm your MOSFETs are electrically isolated so make sure to use TO-220 mounting kits that have some kind of insulators/shoulder washers._

 

Yah they are isolated with shoulder washers already but no idea if grounding the heatsinks would be even safer.


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_Yah they are isolated with shoulder washers already but no idea if grounding the heatsinks would be even safer._

 

The more metal the better when it comes to grounding. I would choose to always ground the heat sinks, but that's me.


----------



## tomb

As promised, here are some detailed pics of both the prototype PCB (silver case) and the production PCB (black case). Click for bigger pics -


----------



## tomb

More ...




 Note that everything is tied to the top plate - the center standoff locks everything in place, but you must choose the correct bend on the MOSFET leads to coordinate this (see below). You should leave enough lead length to the back plate to swing it up and over the body of the case as shown. Then the entire assembly - top plate, PCB, and endplates slide out of the case body.




 For the standard configuration and the pre-punched Hammond case, we'll use the 3rd slot from the top, as shown here.




 Another view showing the entire assembly - front plate, top plate, back plate and PCB. Caps are Panasonic FM 680uf 63V for the power/decoupling caps and the new Nichicon Muse KW's at 480uf 63V for the output coupling caps. 0.22uf 250V Wima MKP10's all around. V-D resistors everywhere with Muse ES at 220uf 16V rounding out Dsavitsk's mods.




 A bit out of focus in part, but this shows the lead-bend required for the pre-punched Hammond case. There's barely enough to solder in the pads, but it results in the tube sockets slightly below the top of the case for the best appearance. Placing the PCB at this level won't fit the larger caps, but the ones shown here have plenty of clearance.
	

	
	
		
		

		
			





 Note the second screws holding each heat sink in place. The sharp bend on the MOSFET leads brings the heat sinks far enough forward that they clear the bezel - unlike with the silver case below.


----------



## tomb

Pics of the silver one using the prototype board. This one uses Stackpole carbon film resistors and Nichicon Muse FG caps for output couplers at 1000uf 63V. Everything else is pretty much the same, but the FG caps required placing the PCB at the 2nd slot. This version sounds much more bassy than the black one. I think the black one is the best combination of parts and sounds scarily good.
	

	
	
		
		

		
		
	


	




 However, as long as you bend the MOSFETs as shown for the black one, you should be able to use the pre-punched Hammond case to build this version, too (placing the PCB in the 2nd slot, iow).




 Note the chunks I had to cut out of the bezel to make room for the heat sinks. This is why we're using the sharp bend for the MOSFET leads as shown above for the black one. It puts the MOSFET mounting holes and thus, the heat sinks, further forward on the top of the case. It's enough to clear the bezel and prevent the need for cutting them as I had to do here.








 Done for now, but I'm going to try to get the Group Buy going for the case before the weekend is out.


----------



## individual6891

Wow, that's incredible! +1 for the GB 
	

	
	
		
		

		
		
	


	




 Looks like you got the dimensions absolutely perfect.

 Will the predrilled endplates come with the hammond case? If so, time to invest in some laser water-slide decal paper!


----------



## tomb

Yes, the endplates will be punched. All that's needed is wiring and assembly once the PCB is populated.


----------



## smeggy

WANT!!

 I must have one... or two


----------



## manaox2

NICE. I want two!


----------



## MoxMonkey

i'd be down for one as well


----------



## jinp6301

Damn thats sexy. In for one!


----------



## royewest

Very elegant solution, Tomb!


----------



## wankski

perfect! very very nice tom... will these be open to orders from down under?
	

	
	
		
		

		
		
	


	




 looks like a great amp!


----------



## tomb

Quote:


  Originally Posted by *wankski* /img/forum/go_quote.gif 
_perfect! very very nice tom... will these be open to orders from down under?
	

	
	
		
		

		
		
	


	




 looks like a great amp!_

 

Of course - I ship everywhere the US Post Office allows.


----------



## tomb

Updated BOM for the PCB SSMH here.

 Friday, 5/29/2009 at 8:00PM EDST, the following will go live:
Pre-orders for SSMH kits, only 1 ea per person (everything in the attached BOM, including the custom-machined Hammond case & guaranteed tubes)
Pre-orders for the custom-machined Hammond case only (tube availability not guaranteed)
PCB sales (tube availability not guaranteed, but will ship immediately)
I hesitated to display something like this up till now, but things are imminent at this point, so I took an inventory. We will definitely have enough tubes for at least 100 SSMH PCB's, with plenty left over to support rejects/losses from shipping or microphonics, etc.:






 Please note that 95% of these tubes were obtained through wholesalers that did not deprive anyone from onesie-twosie purchases. In fact, I had specific conversations with one vendor to make certain that he had a stock remaining for individual purchases after my volume buy. At any rate, building this stock was needed to make the SSMH PCB a possibility.

 I sent a few more questions to Hammond about their custom cases, but am prepared to order as quickly as possible, depending on how brisk the demand from you guys. I'm hoping that we can get at least 100, but remember that there's a 6 week lead time. So, the quicker there's some interest shown, the quicker we'll get them.

 Kits will include everything on the BOM for at least the first 30 kits (Mouser column except for FC caps at C1/C6). I'll be contacting some vendors in the next few days about getting more power supplies. Depending on the results of those conversations, we may or may not include power supplies beyond the first 30.

 It's been a long wait, but hopefully this will be worth it. Thanks for your patience.


----------



## royewest

Heh. Look's like Commons (my college cafeteria) got an upgrade.


----------



## gurusan

That looks great. Excellent work.

 I already have my tubes and components, I just want a PCB and perhaps a chassis.


----------



## Hayduke

/e wonders how well Tom's site is gonna handle the flood of traffic Friday night


----------



## Fitz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Please note that 95% of these tubes were obtained through wholesalers that did not deprive anyone from onesie-twosie purchases. In fact, I had specific conversations with one vendor to make certain that he had a stock remaining for individual purchases after my volume buy._

 

Damn, you pre-emptively killed my joke about cornering the market on those toobses.


----------



## Hayduke

Tom,

 I have a question... I understand the limit on 1 kit per customer, but can we order more then one PCB + Tube kit? I want to get one for myself. A co-worker wants an amp too, but I doubt he is going to build it himself. Will you be letting us order more then one PCB + tube kits?

 Also, do the "full" kits, that include the machined case, ship with the case now? Or will those cases also be a 6 week lead time? I don't mind the lead time, but I'll get one of the big kits if it means I can get the case sooner.

 Thanks for putting all this together. I really like how the project has turned out.


----------



## dsavitsk

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Tom,

 I have a question... I understand the limit on 1 kit per customer, but can we order more then one PCB + Tube kit?_

 

I'll speak for Tom, and he can correct me later. The primary limit here is tubes. We can make as many PCBs as there is a market for. Same goes for cases and the power supplies are readily available on ebay, but Tom wants to make sure that people don't start hording the tubes. Further, being a DIY project, we are interested in allowing everyone who want to to build with tubes, and we are less interested in allowing people to have others build these amps for them. That is, the essence of the project is offering a safe and inexpensive way to put together a first tube amplifier. If one is simply interested in owning an inexpensive tube amp, there are lots of commercial and/or Millett Max-esque options.

 At any rate, my gut still says that somewhere out there is a warehouse with 100,000 of these things in it. Hopefully someone will stumble upon it at some point.


----------



## individual6891

Quote:


 Friday, 5/29/2009 at 8:00PM EDST, the following will go live 
 

Hang on, what's that in GMT London time? I can't find EDST at The World Clock – Time Zone Converter anywhere!

 Then I could only find EST and EDT, not the combination! And it says on ET: Eastern Time (USA & Canada).* What is the time now in EST / EDT? that it's GMT -4 or GMT -5... argh!

 Also, surely loadsa people on a Friday evening will miss out on this just because its a Friday evening. Better to do it on Thursday or even a Sunday? Friday evenings the worst time to catch people


----------



## Yaka

any chance we could put our names down for the full kit rather than waiting till friday?


----------



## individual6891

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_any chance we could put our names down for the full kit rather than waiting till friday?_

 

Surely it would be much better and easier this way. It's still "first come first server", no?

 Better for the following reasons:
 1) People who can't make that time window will be stuck for a few weeks (months?)
 2) Less server load, less chances of a server crash.
 3) Other similarities: still first come first serve, you can still set a max stock level and then if anyone drops out, you'll know exactly who's next in the list making a lot more fairer.

 Albeit, you'd need to collect Paypal and delivery address, but surely that's not difficult? i.e. exactly the same as a GB?


----------



## Fitz

Quote:


  Originally Posted by *individual6891* /img/forum/go_quote.gif 
_Hang on, what's that in GMT London time? I can't find EDST at The World Clock – Time Zone Converter anywhere!

 Then I could only find EST and EDT, not the combination! And it says on ET: Eastern Time (USA & Canada). What is the time now in EST / EDT? that it's GMT -4 or GMT -5... argh!

 Also, surely loadsa people on a Friday evening will miss out on this just because its a Friday evening. Better to do it on Thursday or even a Sunday? Friday evenings the worst time to catch people _

 

I'm pretty sure he means EDT, which is GMT -4.


----------



## tomb

Yeah, I meant EDT. Seems like it was EDST when I was kid, but that was quite awhile ago.

 As for changing days, no. I'm out of town until Thursday and that won't give time to set things up. Sunday would be the worst, because I wouldn't have time between that and Monday work to manage things as orders come in (assumimg they do).

 I think this is plenty of notice,though, and it would be unfair to change it now.

 P.S. This is kind've difficult on a BBerry, but from what read of Dsavitsk's post up there, I agree 100%. The idea is to see how many will want the case, but at the same time, ensure that as many that want one will get one plus tubes.


----------



## n_maher

What people need to realize is that there is no conceivable way that Tom is going to please everyone so while you're welcome to disagree with the way that he chooses to do things you're also welcome to not participate. He's put forth an amazing amount of effort, much of which I'm sure seems thankless when the feedback given by folks around here is "couldn't you do it another way?". So everyone, please calm down, it's only a circuit board and some tubes and remember, no one is getting paid to do any of this. I know I've "volunteered" a couple hundred bucks to help this project along, can any of you outside Tom and Doug say the same?


----------



## individual6891

Calm down? At the end of the day, it was really only a suggestion. Hardly a blasphemous head turner. Just because friday night's usually quite a busy period for many people... maybe you wouldn't understand that, in the same way I'm "seemingly thankless".

 Back to the point, fingers crossed there'll some saturday morning


----------



## dsavitsk

Quote:


  Originally Posted by *individual6891* /img/forum/go_quote.gif 
_Back to the point, fingers crossed there'll some saturday morning 
	

	
	
		
		

		
		
	


	


_

 

I once woke up around 4:30am to bid on a Melos SHA-1 when its ebay auction was ending at an odd time. I won it for about half the then going rate.


----------



## jinp6301

I might have missed it somewhere, but is there a set price for full kit yet?


----------



## manaox2

Quote:


  Originally Posted by *individual6891* /img/forum/go_quote.gif 
_Calm down? At the end of the day, it was really only a suggestion. Hardly a blasphemous head turner. Just because friday night's usually quite a busy period for many people... maybe you wouldn't understand that, in the same way I'm "seemingly thankless".

 Back to the point, fingers crossed there'll some saturday morning 
	

	
	
		
		

		
		
	


	


_

 

I think most, if not all get your point, but also do not think it was anything to worry about. Like many of us, he has his free time focused on the weekend. It was generous of him to donate his Friday night for a project he and a few others spearheaded for practically nothing in return. If you planned something for Friday night, you'll just have to find your tubes and possibly your power supply elsewhere (and it is actually not that hard). I am betting there will be some of everything left anyway. At the end of the day (literally), you'll just have to make time or DIY as that is kind of the point. If not, there is a one buy-it-now kit complete with everything on ebay literally every week and it takes a while to go even though its always priced very fair.

 Meanwhile, your free to do the same as they have and arrange a project the way you think would be best. They aren't doing this as a business, but as a volunteer effort. As n_maher pointed out, he has helped out with the project by donating funds that may not see their way back to him (and even if, it will be without profit). With your last comment, your not only "seemingly thankless" to those who donated time and resources, you are being truly thankless. When your suggestions get turned down and possibly come off as disparaging to those in charge, the correct action is to thank them for considering it; not verbally attack them. I'm kind of upset about your passive aggressive comment aimed at Nate not being understanding, I know how much Nate time and knowledge he goes out of his way to offer for everyone here sometimes without any thank you.


----------



## manaox2

Quote:


  Originally Posted by *jinp6301* /img/forum/go_quote.gif 
_I might have missed it somewhere, but is there a set price for full kit yet?_

 

$112 I estimate from the BOM, though its possible and acceptable that there will be a handling and shipping fee or that the costs change between now and Friday.


----------



## luiztfc

Man, I want a kit please!

 As soon as I'm able, I'll be buying one!

 Thanks, man!


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_$112 I estimate from the BOM, though its possible and acceptable that there will be a handling and shipping fee or that the costs change between now and Friday._

 

The BOM is pretty clear. However, the kit price is slightly less than that.
	

	
	
		
		

		
			





 There is another place where this is spelled out more clearly, but MOT rules prohibit me from being more specific.
	

	
	
		
		

		
		
	


	




 Note that I've tried to include everything in the BOM but wire and solder - seriously.

  Quote:


  Originally Posted by *Hayduke* 
_Tom,

 I have a question... I understand the limit on 1 kit per customer, but can we order more then one PCB + Tube kit? I want to get one for myself. A co-worker wants an amp too, but I doubt he is going to build it himself. Will you be letting us order more then one PCB + tube kits?

 Also, do the "full" kits, that include the machined case, ship with the case now? Or will those cases also be a 6 week lead time? I don't mind the lead time, but I'll get one of the big kits if it means I can get the case sooner.

 Thanks for putting all this together. I really like how the project has turned out._

 

The full kit includes everything on that most recently referenced BOM - including the case and the custom machining. The lead time is 6 weeks from the time I order from Hammond, period. You can order as many cases and as many PCB's as you want. However, only the kit+case's come with tubes and those are one per person, period.

 Here's the deal:

 In the interests of being a "Starving Student" and the very appropriate beginner's attraction to this project, we all felt that a pre-punched, machined case would be ideal - populate the board, screw the connectors into the endplate, solder some wire and you're done. Nothing more than a soldering iron, a wrench and a screwdriver.

 However, there's a price for that and it comes three ways:
 1) The price of machining,
 2) The price of waiting for 6 weeks lead time for the mfg run, and
 3) The up-front price of making a volume mfg run to keep #1 low.
 OK, so we found out that the price of machining is incredibly cheap in this instance. Yay!! Unfortunately, there's still the 6 weeks and the volume required: at least 50 to 100 cases.

 So, how to do this?

 Imagine this scenario: someone decides they want the case, but they'll have to wait 6 weeks. In the meantime, there's many of you that just want PCB's and some want the case and PCB. However, the one scarcity in this whole mix are the tubes. If someone invests over $100 for the case+kit and is willing to wait 6 weeks, then by G*d, I'm going to do everything in my power to ensure they have everything they need to build it when those cases come. That means TUBES.

 That's why we structured it the way we did ... for the time being. Also, one reason I need to have weekend time to monitor the progress is to alter the offerings if we hit 30 (or however many power supplies I end up with), or if we hit 50, 100 and then stop, or whatever ...

 Finally, there is no case that will be available before 6 weeks from the time I order. I'd love nothing more than to have 100 of the kit+case's pre-sold before the weekend is out. If so, I'll order the first thing Monday morning and the 6 wk lead time will start ticking. Most likely, I'll order 100 even if we hit somewhere over 50 by the end of the weekend. However, you never know ... a dozen vocal posters on a forum thread is still just a dozen. 

 Note also that Hammond requires payment up front, not when the cases are ready to ship. One of the additional questions I asked of Hammond was when is the drop dead date that we can add to the numbers after an order has been made? You see, it's an involved process: shop drawing reviews, a single prototype run for final approval, etc. There may be quite awhile that we can continue to revise the order # while keeping the 6 week lead time ticking off.

 So, all of this is in the mix. It's enough that we could keep discussing the options for another month or two. Or, it was time to make a decision and go forward before we burned the summer up.


----------



## Hayduke

Thanks for the replies Doug and Tom 
	

	
	
		
		

		
		
	


	




 I hope I didn't sound like I was trying to be greedy. I do understand your goals, and I agree with them. I was ordering the kit for myself because I like the look of the final product. You're right though that is a great early build, so maybe I'll pass on the "kit". I definitely want a machined case. Casework is always the most difficult part for me. There are two reasons I'm interested in the tubes. First, they are growing scarce. I'm with you in the hope that more will turn up, and that certainly appears to be the case. It seems like the tube dealers keep running out and then, a couple weeks later, they have more. The second, and much more important, reason I was interested in tubes from Beezar is the matching service. Will I hear the difference? Maybe not, but never underestimate cognitive dissonance 
	

	
	
		
		

		
		
	


	




 Since I'm not worried at all about the power supplies, and only interested in the "matched" tubes, I'm willing to wait until Sunday or Monday to see how many orders Tom has received. If there are still plenty to be had, I'll place an order. I understand the reasoning behind limiting each person to 1 set of tubes. I respect that 
	

	
	
		
		

		
		
	


	




 My friend that wants an amp has expressed an interest in building it himself, and I am definitely encouraging it. The _worst_ case would be he asks me to do the soldering since I know he lacks tools, but I've offered to let him sit at my workbench and build it. I know he can assemble the kit in an evening with my guidance. I might make him build a cmoy first though 
	

	
	
		
		

		
		
	


	



 Either way, I'll have him order his own parts/kit/pcb since he's still on the fence about what he wants hehe

 Thanks again to Doug, Tom, Pete, and Nate. Without you guys none of us would have this fun project that yields a great sounding amp!


----------



## smeggy

What's the board dimensions? I need to see if I can squeeze it in somewhere


----------



## Earwax

Looks great! 

 {Edit - nevermind the other question}


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_What's the board dimensions? I need to see if I can squeeze it in somewhere 
	

	
	
		
		

		
		
	


	


_

 

Last I checked they have the proto measuring at about 3.87" wide x 3.14" (98mm wide x 80mm).


----------



## smeggy

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Last I checked they have the proto measuring at about 3.87" wide x 3.14" (98mm wide x 80mm).

_

 

Cool, that'll fit


----------



## Ishcabible

I might be interested in 2 kits without the cases. May I know how much that will be?


----------



## tomb

Quote:


  Originally Posted by *Ishcabible* /img/forum/go_quote.gif 
_I might be interested in 2 kits without the cases. May I know how much that will be?_

 

Sorry, no. First, it would be against MOT rules for me to state a price. Second, we are not now going to offer kits w/o cases. That's because doing so would take tubes away from someone else who might be willing to invest and wait for the cases.

 The PCB's will be on sale for immediate shipment, however. Also, the BOM lists everything you need. There is nothing to stop you from purchasing a PCB and ordering the components yourself, as with any other DIY project.


----------



## Peridot

Just wondering where I go to order a kit 

 Is it on beezar.com ??


----------



## tomb

Quote:


  Originally Posted by *Peridot* /img/forum/go_quote.gif 
_Just wondering where I go to order a kit 

 Is it on beezar.com ??_

 

Yes, but not until 8PM tonight, EDT.


----------



## Peridot

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, but not until 8PM tonight, EDT.
	

	
	
		
		

		
		
	


	


_

 

That's past my bedtime, but I might try to stay awake 

 Been lurking here for a while. Really impressed by the community spirit and looking forward to getting back into a bit of electronics DIY.

 Thanks.


----------



## tomb

It appears that some of you are ordering directly from a product list. However, the detailed product description for the kit clearly states Priority Mail required. This is the minimum service that USPS will allow insurance for international shipments. That's why Priority Mail is a requirement for the kit. Please read the descriptions if you are able.
	

	
	
		
		

		
		
	


	




 Also remember that a 6 week lead time is in effect for the cases (and therefore, the kits), assuming we get enough to order them. If you haven't read the product description, that fact may be missed as well.
	

	
	
		
		

		
		
	


	




 Thanks and mods delete this post if it breaks the rules. I just thought it needed stating in the interests of everyone.


----------



## wankski

legend ! its live on the site now, and i was excited... until i saw shipping... almost half the value. 

 Not a crit, i totally see why. Also timing (6 weeks) is bad for me, since i am leaving the country for a few months. 

 I guess it is the case which is killing the shipping so bad.... If in the future u do put out kit incl tubes minus hammond case i'll probably bite...

 GREAT deal if u're in the US. Applaud the effort. Trying to track down all those things mustn't be easy.


----------



## tomb

Quote:


  Originally Posted by *wankski* /img/forum/go_quote.gif 
_legend ! its live on the site now, and i was excited... until i saw shipping... almost half the value. 

 Not a crit, i totally see why. Also timing (6 weeks) is bad for me, since i am leaving the country for a few months. 

 I guess it is the case which is killing the shipping so bad.... If in the future u do put out kit incl tubes minus hammond case i'll probably bite...

 GREAT deal if u're in the US. Applaud the effort. Trying to track down all those things mustn't be easy._

 

The kit plus case plus power supply weighs approx. 2-1/4 lbs dripping wet (remember the heat sinks, too). The problem is that packing and boxing easily adds another 33%. That means it's closer to 3 lbs. If it's one ounce over 3lbs, then the US Post Office treats it as a 4 lbs charge. That's what is being calculated on Beezar.

 It's true that Priority Mail shipping is high for international shipments, but that's the minimum service that the US Post Office will allow to be insured. Realize that many people won't fool with international shipments at all. I think it's reasonable to require a shipping service that allows insurance. On top of that, Beezar is providing the insurance - I'm not charging for that.

 All that said, I may revise the listings sometime this weekend. We are in danger of not even getting requests for 30 cases, the absolute minimum needed to order from Hammond. I'm open to ideas that are still in the interests of fairness. The first thing I was thinking was to allow multiple orders per person and/or perhaps creating a "case+tubes+PCB" listing.

 Comments are welcome - I'd hate to say we can't get cases and send out refunds.
	

	
	
		
		

		
		
	


	




 P.S. If the packed weight ends up being much less, I'll refund some shipping amounts if necessary. Those of you who participated in the MiniMAX case group buy know that I've done refunds before without an issue. The domestic shipping is only $6.50 - $12, depending on location, though. That's not much for 3-4 lbs. Priority Mail International has a built-in threshold, though, that's where most of the costs are - not in the poundage.


----------



## Earwax

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_All that said, I may revise the listings sometime this weekend. We are in danger of not even getting requests for 30 cases, the absolute minimum needed to order from Hammond. I'm open to ideas that are still in the interests of fairness. The first thing I was thinking was to allow multiple orders per person and/or perhaps creating a "case+tubes+PCB" listing.

 Comments are welcome - I'd hate to say we can't get cases and send out refunds.
	

	
	
		
		

		
			



_

 

Thanks for your efforts TomB!

 I would prefer to buy Case+Tubes+PCB set personally, I might even get two if that were offered. Otherwise, I intend to wait for the first 30 to run out so I can get a kit w/o power supply.


----------



## Juaquin

I went for a full kit. Whatever needs to be done to get this thing going is fine by me. 

 Also, would it be possible at some point to offer a second set of tubes (or even a single tube) to people who bought kits? With the growing scarcity of those tubes, I'd like to have a couple extra on hand should they ever burn out.


----------



## tomb

Right now, the case count stands at 20. That's enough for me to order 30 on Monday. We'll have two weeks to add to that number.

 I'll add some more options tomorrow - PCB's + tubes and other parts.


----------



## royewest

I've recently switched jobs and now work for a company that writes software for cell phones and related devices. This means I'm surrounded by devices that emit RF. The two MSSH amps I tried in that environment (one point-to-point, the other a PCB prototype) were pretty unlistenable with interference.

 I bought some brass screen and am going to see if I can create a Faraday cage with it (while wearing my foil hat). One point about F cages is they must be grounded. I think the MSSH amps are not really grounded (not to earth, that is), because they are using ungrounded power supplies.

 So my question is, is there any reason not to tie the ground of a MSSH amp to real earth ground? For example, bolt a wire from my case (whether or not connected to the star ground) to a banana plug inserted into the grounding hole in a grounded outlet?

 Thanks in advance for any advice that will prevent me from damaging myself or these sweet amps.

 __Roy


----------



## wankski

thanks for your words tomb!

 just so you know, i don't need power supply or case.... just pcb kit and tubes as an alternative would be great down the line when ur sorted with min cases orders. But i understand if you don't wanna.


----------



## rds

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_ One point about F cages is they must be grounded. I think the MSSH amps are not really grounded (not to earth, that is), because they are using ungrounded power supplies.

 So my question is, is there any reason not to tie the ground of a MSSH amp to real earth ground? For example, bolt a wire from my case (whether or not connected to the star ground) to a banana plug inserted into the grounding hole in a grounded outlet?

 __Roy_

 

A Faraday cage does not need to be grounded. Actually, I believe that once you ground it, it's not actually a Faraday cage anymore.

 However, in this _case_ I think what you really want is a shield that is tied to signal ground; and the shield only needs to surround the tubes. Try rolling a piece of tin foil in a cylinder and placing it over the each tube. That should stop the noise (if the tin foil is in contact with something that is tied to signal ground - like the case), but obviously is not a very attractive solution.


----------



## cms5423

Uh you definitely want to ground the F cage, if you don't, then any accumulated charge just sits on the cage, if you do ground it, it will dissipate anything into the earth ground... that's what a faraday cage is supposed to do. otherwise it would just accumulate all the charge/interference and hold it there


----------



## Juaquin

Tying to ground is the idea - any stray interference is picked up by the cage and it has a nice return path to ground. Of course, not tying it to ground is still a faraday cage - think of an airplane being hit by lightning. It's not tied to ground and yet everyone inside is fine.


----------



## Llama16

Hey all

 (I'm sure tomb saw me coming from afar
	

	
	
		
		

		
		
	


	




)
 my first post in the thread 
	

	
	
		
		

		
		
	


	




. I've been trying to read whole the thread for a while now but still am just at page 60. It's pretty interesting and helpful when reading everything, and gives alot better idea of what to do when I'm going to build it and how the starving student actually works, which is really interesting.

 I've already made a seperate thread in which I posted my questions about the order for components I'm planning to make at mouser. And tomb adviced me to post my questions here, and he's completely right about it.

 I'll just copy it, or most of it:

  Quote:


 I was thinking about ordering the components for my first starving student together with my first MINI³, so I'd save alot of shipping (mouser=20euros in europe :S)

 As I always am pretty unsure of what to order and if I'm ordering everything correctly, not missing something. I downloaded the starving students component PDF (which pmillet was so kind to put up for us ) and checked everythings availability.

 I checked everything that was available, I put a small question with those that I was unsure about, and I searched for replacements of one component that wasn't available.
 So my question is: would you guys be so kind to take a quick peek at it and tell me if everything seems ok, or if you would prefer some other components in there that would come out better.

 BTW: I will be primarily using this amp with the HD650, so is there anything that i can replace to make it more suitable for this high impedance headphone? (other caps?)

 HERE's THE LINK TO THE XLS (I'm srry about the crappy upload host, I just picked one quickly)
starving_bom.xls

 Thanks alot in advance
 Dries 
 

Some extra questions that popped up (yet again, they may be very unimportant)
 1) Is it best to buy my tubes and sockets at Beezar, now they're available (are they available seperately?) or should I still go with the, by pmillet, mentioned radiodaze? (I'm in europe)
 2) What powersupply and where to get it, if I live in europe with has plugs of 220/230V? I tried ebay, but they're not available, also mouser doesn't sell PSUs and I didn't immediately found them in some european shops.
 Let me know here you bought it or where you would have better bought it and which one.
 ((((3) This maybe doesnt belong here but o well, while I'm at it... a 9v 325 NIMH mAh for the MINI, where can I find it. preferably in on of the same shops as where i'll be ordering other parts. I don't really like to have alot of orders open, especially when this is the first time ever to order something online 
	

	
	
		
		

		
		
	


	




.

 I also want to apologize for maybe asking questions that may already be answered in this thread, but as I've already said, I'm reading the whole thread post by post already.
 And as it is stalling the order for my MINI³ as well, plz don't blame me for maybe doubleposting this.

 Dries


----------



## Llama16

EDIT: I pushed refresh, so the same post was doubleposted, Srry


----------



## tamasic1

The power supply for this project is the Cisco PSA-18U. Like almost all computer equipment today it runs on either 120 or 240v. It powers Cisco wireless access points (ap) and ip phones. One is included with every wireless ap however its rarely used. Most ap are connected back to a Cisco ethernet switch in the data closet that provides power through the ethernet wiring. The power supplies are abundantly sitting it boxes in network storage closets collecting dust. If you know someone in the computer field ask them if they or a colleague have installed or work with Cisco access points. If so there’s a good chance you’ll score at least one. Techs who work for a large company or school district would be your best contact.


----------



## Llama16

Thanks for the tip,
 I doubt my school uses Cisco, thought it can't hurt asking.
 At least I have something to look forward to and maybe they have one sitting around.

 I'll see if I can find one on the internet. And I'll post it it here to make sure it has the right specs (you never know, and I especially don't, when there are some hidden features that are vital to it)

 Dries


----------



## Llama16

I double posted again!!
 My browser is doing this alot lately. I post and it says 'wait 30 seconds before...' and I wait and then I see my message 2 times. i didn't press refresgh, return,...
 I'll try and figure it out.
 BTW

 this is the one I found: Marktplaats - De plek om Nieuwe en Tweedehands spullen te kopen en verkopen
 I know it's in dutch, I don't know the full specs yet but I sent the seller a PM.

 ALSO: what do you guys think about the rest of my list of questions and BOM? :S

 Dries


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_I double posted again!!
 My browser is doing this alot lately. I post and it says 'wait 30 seconds before...' and I wait and then I see my message 2 times. i didn't press refresgh, return,...
 I'll try and figure it out.
 BTW

 this is the one I found: Marktplaats - De plek om Nieuwe en Tweedehands spullen te kopen en verkopen
 I know it's in dutch, I don't know the full specs yet but I sent the seller a PM.

 ALSO: what do you guys think about the rest of my list of questions and BOM? :S

 Dries_

 

That power supply looks close, but not identical to all the ones I've seen. There's no mention of amperage (0.38A on the genuine), so that throws a little more doubt into it, too. It may be OK, but I bet you can find one that's absolutely identical and has all the right numbers:
Cisco PSA18U-480C AC Power Adapter 20V & Above
Cisco Original PSA18U-480C 34-1977-03 AC Power Supply 48V 0.38A For AP-350 AP-1100 AP-1200 and CP-7960G CP-7914 CP-7940G VOIP Phone [US-Cisco-PSA18U-480C] - $12.99 : Digital Surveillance spy Cameras, spycam, Computer Hardware, crystal, toy
Cisco / Delta Power Supply (48V / .38A) 34-1977-03 A0
CISCO PSA18U-480C 34-1977-03 Power Supply for Aironet Access Point or VOIP Phone (I don't think this website is actually working.)
http://www.norsystems.net/cgi-bin/p?...mno=ciscoAC48v

 RadioDaze has been out of 19J6 tubes for a long time, now.

 As for tube sockets - I'll be putting up some inexpensive silver ones today, along with some other parts and a "tubes+PCB" listing. Also, I'm removing the one-per-customer limit on the kits.

 So far, about 20 cases have been spoken for. That's pretty good so far, so I'm going to order 50 of them tomorrow. Ya'll keep in mind that the PCB was designed for the case and vice-versa. It seems to me that it wll be pretty difficult to come up with a heat sink arrangement without the case. I'll continue work on the website, too - that will make things more clear.


----------



## Llama16

Thanks for the links I'll check them out as soon as I'm finished reading some 40more pages of this thread 
	

	
	
		
		

		
		
	


	




. The guy I asked the specifications to still hasn't responded (he put the offer online yesterday, so I'm quickly at it)

 Congrats with the kits, hope they will keep growing, I think they will. You'll already probably have, but I'm sure other sites would be interested as well. 

 I'm pretty new here so fill me in. of what I read in your post it seems like you made the website, and some posts earlier I think (I REALLY ain't sure 
	

	
	
		
		

		
		
	


	




 it could have been a dream)I read that dsavitsk and millet work together with you about those things? That's awesome, you guys know eachother RL or just by the internet you keep track of things.


----------



## Ajit

I have been out of the country for a few months and had not checked in for a long while. Just noticed that the SSHA kits were being offered. Is it too late to order one? Thank you!

 Ajit


----------



## bmwpowere36m3

Attached is a *P-P* wiring sketch I made a while back for my build, I've been ask many times for it.... so it's easier just to repost it.


----------



## Llama16

Thanks alot for the quick response. I know it would have been a great exercise to try and wire it myself. But it's always alot easier when somebody has already made one. Thanks again.


----------



## tomb

Just an FYI to everyone about the custom Beezar/Hammond cases:

 1. I'm ordering 50 cases tomorrow. Hopefully, the 6wks will start ticking from that point, but I'll let you know for sure.
 2. Based on sales this weekend (and other factors) 30 kits are all I'm going to do. Right now, there are 12 left. A few people ordered just the cases themselves, but we're still quite aways off from 50 cases.
 3. There is no profit for the cases at the price they're at right now - this is essentially the same as a group buy.
 4. However - since Hammond allows us to add to the order, you will still have the next two weeks (till Monday, June 15th) to place a pre-order for a case (or the case+kit) at the _current_ price.


----------



## Llama16

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That power supply looks close, but not identical to all the ones I've seen. There's no mention of amperage (0.38A on the genuine), so that throws a little more doubt into it, too. It may be OK, but I bet you can find one that's absolutely identical and has all the right numbers:_

 

They sent me a PM and it's clearly 48V output and 0.38A. So that's ok. Though is the plug itself ok? (was that what you were doubting about?)
 Here is the plug of the adapter:
Marktplaats - De plek om Nieuwe en Tweedehands spullen te kopen en verkopen

 Thanks
 Dries

 EDIT: NEVER MIND, THE PLUG IS OK: 2.5/5.5 AS IT SCHOULD BE, SORRY FOR POSTING TO FAST
 THANKS


----------



## wankski

hey tomb!

 thanks for making the Millet SS available in pcb + tubes.... i've added all the caps i need, but i can't seem to find the resistors and transistors (q1 + 2) on your site? not there, or am i blind??

 in any case, i'll still order - would be great to get em bundled with the pcb tho, as digi key and mouser charge $$ for shipping making that an uneconomical choice... 

 just thought since you offer full kits, maybe you have these available? if not yet, planning on doing so?

 thanks!

 joe


----------



## tomb

Quote:


  Originally Posted by *wankski* /img/forum/go_quote.gif 
_hey tomb!

 thanks for making the Millet SS available in pcb + tubes.... i've added all the caps i need, but i can't seem to find the resistors and transistors (q1 + 2) on your site? not there, or am i blind??

 in any case, i'll still order - would be great to get em bundled with the pcb tho, as digi key and mouser charge $$ for shipping making that an uneconomical choice... 

 just thought since you offer full kits, maybe you have these available? if not yet, planning on doing so?

 thanks!

 joe_

 


 EDIT: We need to start asking these questions through PM's. Much of this is centered around the case, which we're treating as a Group Buy, figuratively and literally. However, some of the rest of this discussion is on the edge. Mods, please delete if necessary. Thanks.


----------



## Llama16

Hey all

 I replaced the c2 and c4 (539-150104K100AA
 mouser) of the original BOM of pmillet by 2 of these: 598-WMF1P1K-F mouser
 You think those will do?


----------



## rshuck

Hi tomb - I've ordered one of these as well (didn't see this thread at first, just your site). Can't wait for it to come in!

 Thanks for making an easy solution available for this - it'll be my first tube amp aside from a Dynaco Stereo 70 I tried (and failed, horribly) to repair.


----------



## PJPro

Yeap. Me too. Full kit in black.


----------



## zkool448

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Hey all

 I replaced the c2 and c4 (539-150104K100AA
 mouser) of the original BOM of pmillet by 2 of these: 598-WMF1P1K-F mouser
 You think those will do?_

 

Yes they should work fine... however personally I'd use parts from tomb's SSMH BOM as substitutes if you cannot find those obsolete parts.


----------



## Llama16

tomb, I just made an order for the tubes and board (but I ain't gonna use that) of your site. Very easy to order and I was surprised by the low delivery costs for shipment cost to europe. Class A purchase.

 tubedepot asks 72 buck for 3 19J6 tubes!! (and shipment to belgium ofcourse)
 I bought the board, tubes, and sockets for 32 dollars on beezar + shipment!!!

 I don't know if I am allowed to tell this here, so plz delete if inappropriate.

 Dries


----------



## tomb

You're allowed to post what you want, within reason. It's me as an MOT that has restrictions (like when someone posts, "How much?" and I answer.).


----------



## stoned22

Is it possible to replace the mosfet stage with a gainclone to give it enough power to drive speakers? Sorry if its a silly question.


----------



## kvant

Quote:


  Originally Posted by *stoned22* /img/forum/go_quote.gif 
_Is it possible to replace the mosfet stage with a gainclone to give it enough power to drive speakers?_

 

Not directly, since the quiescent current through MOSFET is recycled as heater current for the tube. However, if you provide extra heater power supply, you can certainly hook-up a power opamp ("gainclone") after the tube. Such ideas can be seen at diyaudio.com; Pete Millett also has a project like that, although that one is not the least complex one.

 But what is the purpose of an extra tube gain stage in front of the gainclone? The chip itself can deliver all the gain you need. As a matter of fact, at least some of these chips are not supposed to be used at unity gain (as the MOSFET is in the "starving student")... from LM3886 datasheet: "_LM3886 is designed to be stable when operated at a closed-loop gain of 10 or greater_". So you would have 10 x gain of the tube, I don't know if you need that much. On the other hand, the chip-amp probably performs best if driven from low impedance, so perhaps a cathode follower (instead of common cathode gain stage) would have some benefits. Of course, that would not have anything in common with this "starving student" project to be made out of junk-box parts any more. But then again, the PCBs, custom ordered pre-drilled enclosures etc. discussed here don't either.


----------



## tomb

Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_<snip>Of course, that would not have anything in common with this "starving student" project to be made out of junk-box parts any more. But then again, the PCBs, custom ordered pre-drilled enclosures etc. discussed here don't either._

 

Pete never implied the use of "junk" parts in the Starving Student. Inexpensive doesn't equate to "junk."

 As for the recent refinements, typically a PCB opens a circuit design to many more people, having a bit of the "paint-by-number" aspect of putting together the circuit. That adds $10 to the cost in the case of the Starving Student. The real increase in complexity and cost comes in the case. However, that's less than $10 over the price of a $20 Hammond standard. There again, the purpose is to greatly simplify the skills required compared to a flexible, yet difficult decision and skills process involved in combining heat sink requirements with a free-choice case design.

 The tradeoff for this little bit of extra expense (~$30) is greater ease of construction, allowing even more people than before to build one with minimal variances that could detract from the quality result. I don't think any of that is a divergence from Pete's original theme: a quality, affordable tube-hybrid headphone amp design meant to be easily achievable to the greatest number of possible builders.


----------



## kuroguy

I built my SSMH from scratch and had at least 4 hours in it. That works out to $7.50/hour. My time is worth 10 times that.


----------



## smeggy

Doing P2P is definitely instructive and worth doing if you are interested in gaining a little understanding. If not and just want a very cool little amp up and running quick, the kit is perfect. By no means is it junk in either parts or design.


----------



## gurusan

just ordered 2 pcbs after building a very, very messy p2p starving student. 

 Thanks so much for all the hard work that went into supplying us with these boards tom!


----------



## zkool448

gurusan, I ordered 2 PCBs as well and plan to 'cleanup' both my P2P amps. In case you're not using the same custom beezar hammond mind if I ask how you plan to design your case around the pcb?


----------



## gurusan

I'm just going to throw it in an aluminum project box I got off ebay awhile back...and see if I can fit a bantam or something in there as well.


----------



## Llama16

nice solid case, I like it. You happen to know the partnumber or brand of it?


----------



## gurusan

This is it...very affordable:
Aluminium Project DIY Electronic Box Enclosure Case on eBay, also Other Components Supplies, Components Supplies, Electrical Test Equipment, Business, Office Industrial (end time 08-Jun-09 15:09:52 BST)

 I don't see a black one though, could try emailing him if you didn't want the clear aluminum.


 What I am still trying to figure out is which heatsinks to use.


----------



## Llama16

yeah very nice price.
 How's the quality? any flaws? Paint spots?


----------



## Llama16

... doublepost srry

 I'll just use it for another question then:
http://www.diyforums.org/SSMH/SSMHoverview.php#nogo
 With me most pages won't load, same with you guys. Anyone know when it'll be fixed?

 another question: I ordered the PCB 7pin osckets from beezat, I assume they will work just fine when using thel for P2P right?


----------



## cms5423

Ha, I bought the same enclosure from ebay. I am using it for my p2p starving student build (using the 12SR7GT tubes) but I haven't taken the time to go to the neighbor's yet to use his drill press, so I havent wired everything up, because I'm waiting for the enclosure first.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_... doublepost srry

 I'll just use it for another question then:
SSMH Overview
 With me most pages won't load, same with you guys. Anyone know when it'll be fixed?_

 

Yeah, when I take a week off from work.
	

	
	
		
		

		
		
	


	




 Seriously, that's my next priority. We'll all get to see how that works out.
	

	
	
		
		

		
		
	


	




 Quote:


 
 another question: I ordered the PCB 7pin osckets from beezat, I assume they will work just fine when using thel for P2P right? 
 

Actually, no. The sockets Beezar sells are *PCB* tube sockets. P2P tube sockets are usually considered the type with lugs instead of pins, so that you can loop the wire around it and have it hold in place while you solder it.

 Shoot me an e-mail if you want to revise your order. Then again, I could've already shipped it. Still, let me know and we'll work it out to your satisfaction.


----------



## sandbasser

Got my order in today's mail... beautiful board!!! Thanks,

 MODS if this post is NOT appropriate for this thread feel free to delete it.


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Got my order in today's mail... beautiful board!!! Thanks,

 MODS if this post is NOT appropriate for this thread feel free to delete it._

 

Thanks - and I'm sure Dsavitsk appreciates that as well.

 Sorry I've scared most of you guys about my MOT status. You guys can still post anything, as long as it's civil.
	

	
	
		
		

		
		
	


	




 I'm the one that can't respond with specific details that are business-related or can be construed as advertisements.


----------



## zkool448

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_What I am still trying to figure out is which heatsinks to use._

 

I highly recommend this one. A single sink does the trick for me


----------



## gurusan

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I highly recommend this one. A single sink does the trick for me 
	

	
	
		
		

		
			



_

 

Thanks for that, quite attractive looking as well.


----------



## tomb

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Thanks for that, quite attractive looking as well._

 

Far be it from me to say anything negative about zkool's stuff 
	

	
	
		
		

		
		
	


	




, but we looked at that heat sink for the SSMH PCB. The problem is that it's over $10!
	

	
	
		
		

		
		
	


	




 You may still be faced with drilling it, too, although zkool can confirm that better than me. Anyway, that's why we went with the TO-3 sinks - they're only a buck and change each, besides having one of the highest power rejection ratings, too.


----------



## gurusan

Oh I agree, the heatsink you chose is very, very effective...and inexpensive as well which fits the whole starving student thing.

 Just choosing to do it a bit differently myself.


----------



## tomb

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Oh I agree, the heatsink you chose is very, very effective...and inexpensive as well which fits the whole starving student thing.

 Just choosing to do it a bit differently myself._

 

Sounds good - just wasn't aware of the context.


----------



## Llama16

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The sockets Beezar sells are *PCB* tube sockets. P2P tube sockets are usually considered the type with lugs instead of pins, so that you can loop the wire around it and have it hold in place while you solder it.

 Shoot me an e-mail if you want to revise your order. Then again, I could've already shipped it. Still, let me know and we'll work it out to your satisfaction.
	

	
	
		
		

		
		
	


	


_

 

Thanks for the kind offer for help. I sent you a PM a while ago (half hour maybe) though i just checked my mail in the meanwhile and got an automated mail from beezar that said it was already shipped. I'll try and do it without the lugs, see if it works.

 Dries


----------



## zkool448

I would in no account presume any comments from you as negative Tom 
	

	
	
		
		

		
		
	


	




 I really do like the TO-3 sinks very much and do not imply they're of lesser or inferior in quality versus the one I suggested, far from it.

 Yes the 641K sinks indeed cost more. They don't come predrilled so one would have to drill their own holes, a bit more challenge to get it mounted and lined up precisely with the pcb. In addition, if one decides to use one on the recommended/custom Hammond case being offered here, it would actually extend by about 1.8mm on each side of the top lid (tad wider)… so this is more for the non-starving, custom junkies out here


----------



## Llama16

Yes I prefer those heatsinks as well. But as costs forced me not to buy them, I still find them gorgeous with both tubes in between the fins.


----------



## gurusan

trying to mock up a rough case design and think I have a small problem. It looks like I only have less than 4mm between the top of the PCB and the top of the case. 

 The tube sockets on beezar look to be too thick to squeeze in between there.....

 So I think I will have to mount the PCB in the bottom slot and run wires up to the tube sockets. My question is...will running longer wires to the PCB from the top of the case present any problems in terms of interference or the actual length of the wires? :/

 Also is it bad to have longer mosfet legs?









 **edit*** so I would have to run tube wires from the bottom of the PCB all the way up to the sockets :/ will this cause interference problems? Maybe I will just use standoffs and mount the PCB higher up .


----------



## tomb

No, no problem per se with wiring the tube sockets. It's been done here before and with the revMH Millett Hybrid (Blooze did this). It's just a huge pain - 10 wires leads (two on each socket can be wired together - the plates and the grids), and you may need to leave enough length for your method of diss-assembly as well.

 As for the MOSFETs, you should solder R3 and R9 directly to the MOSFET legs and then wire to R3 and R9.


----------



## komi

That one is also nice:






Wakefield Heatsink TO-3 HORZ MNT BLK


----------



## gurusan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No, no problem per se with wiring the tube sockets. It's been done here before and with the revMH Millett Hybrid (Blooze did this). It's just a huge pain - 10 wires leads (two on each socket can be wired together - the plates and the grids), and you may need to leave enough length for your method of diss-assembly as well.

 As for the MOSFETs, you should solder R3 and R9 directly to the MOSFET legs and then wire to R3 and R9._

 

ok great thanks for the info.


----------



## Llama16

Quote:


  Originally Posted by *komi* /img/forum/go_quote.gif 
_That one is also nice:
Wakefield Heatsink TO-3 HORZ MNT BLK_

 

Yeah they are, but I guess when making a whole for the tubes I can imagine that there won't be enough heatsink left to cool the mosfets properly


----------



## royewest

I think Canjam was the wrong time for me to post a technical question last weekend, so apologies for trying again (this time more simply):

 Is there any reason I should not connect the MMSH star ground, and/or my MMSH chassis, via a dedicated wire, to the third (grounding) pin in an outlet where I have the MMSH power supply (a 2-prong plug) plugged in?

 Thanks!


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_I think Canjam was the wrong time for me to post a technical question last weekend, so apologies for trying again (this time more simply):

 Is there any reason I should not connect the MMSH star ground, and/or my MMSH chassis, via a dedicated wire, to the third (grounding) pin in an outlet where I have the MMSH power supply (a 2-prong plug) plugged in?

 Thanks!_

 

I can't see that it would make any difference. If the power supply is connected via a 2-prong plug, then it's not connected to the house ground anyway.


----------



## Llama16

Wouldn't trying to star ground it to the ground plug of a power supply (if it has one) even be better? As grounding would be optimal then, directly to ground.


----------



## komi

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Yeah they are, but I guess when making a whole for the tubes I can imagine that there won't be enough heatsink left to cool the mosfets properly_

 

What hole for tubes, i was suggestint this hehind tubes ... 

 Just to follow a round tubes round shape ..


----------



## zkool448

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_trying to mock up a rough case design and think I have a small problem. It looks like I only have less than 4mm between the top of the PCB and the top of the case. 

 The tube sockets on beezar look to be too thick to squeeze in between there....._

 

First of all very nice CAD drawings. As moodysteve mentioned in his post it's a real valuable tool to use.

 Not sure if I understand the issue but you may still be able to mount the pcb at top by making the tube hole diameter larger than the sockets? If the sockets do stick out above the top lid perhaps you could just dress them up with tube 'rings' just like what tomb has in his SSMH build photos. Doing it this way you can avoid air-wiring the sockets.


----------



## Llama16

Quote:


  Originally Posted by *komi* /img/forum/go_quote.gif 
_What hole for tubes, i was suggestint this hehind tubes ... 

 Just to follow a round tubes round shape .._

 

Ha yes, I understand. Though then I'd have to say I'd go with the previously mentioned more expensive heatsink. As I would (personal taste ofcourse 
	

	
	
		
		

		
			





) not choose these heatsinks (I think I just dislike the tought of the opening in the middle with just nothing). 

 Though if it were possible to mount the tubes in there, THEY WOULD BE AWESOME!! 
	

	
	
		
		

		
		
	


	




. But yeah then the warmth dissipation capacity would be alot less.
 To bad


----------



## v3nom

My Starving Student has sit on my desk for 2 months because it didnt work p2p. I log onto headfi to find you guys are selling pcb boards!!!!! got the board in the mail and it is a solid piece of work, good job! Now i just need to finish my school work to convert my p2p to pcb.


----------



## Llama16

yeah reminds me to ask something to tomb. Dunno if it has asked before.
 But can i use the parts of the VERY original pmillet design to work with the PCB board? I'm guessing it can't as I saw alot of other caps and extra ones on the BOM


----------



## Yaka

sure you can, the id say the pcb bom over the orignal as they did a ot of testing and is preety much ideal. but i think your free to use stuff from orignal bom if you want to


----------



## tomb

I agree with Yaka. We think the latest version using the PCB is hands down the best sounding SSMH version. However, there are more pieces and better pieces. As many of you have noticed, that made the price go up. I'm convinced that the changes were worth it, having built both versions (in PCB form, anyway), but there's no reason you can't stick with the original.


----------



## Llama16

K thanks, I'll give it a shot then 
	

	
	
		
		

		
		
	


	



 I ordered the tubes so I got the board with them. If I'm lucky enough to find another pair of tubes somewhere else I'll go for it.


----------



## royewest

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Wouldn't trying to star ground it to the ground plug of a power supply (if it has one) even be better? As grounding would be optimal then, directly to ground._

 

First, thanks Tomb for answering my question.

 Second, I assumed (and my meter seems to confirm) that the grounding pin connected to the three-pronged cord is not electrically connected to either + or - on the PS output. Am I missing something?

 Thanks again, folks....


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_First, thanks Tomb for answering my question.

 Second, I assumed (and my meter seems to confirm) that the grounding pin connected to the three-pronged cord is not electrically connected to either + or - on the PS output. Am I missing something?

 Thanks again, folks...._

 

No, you're not missing something. That's why we've been saying that the power supply has a floating ground.


----------



## Llama16

I did some googling about floating ground, but didn't find anything that I really understood.
 Seems like a floating ground is insulated from a real ground and you shouldn't touch it.
 But I don't understand the following, is a floating ground a 'ground' on a certain voltage above the normal ground? I read that when creating a floating ground on 5V, you can create a supply of 7V by using a 12V source with he 5V ground used as a normal ground (uch, I can't follow this myself).

 If so, is the floating ground you mean here at 48V? As this is what the power supply gives. 
 And would you have an idea of what would happen when still connecting the normal ground of the amp to this floating ground? (If we take in account that the ground in the amp stays insulated from the chassis, else probably ***PZZZ***)

 Dries


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_I did some googling about floating ground, but didn't find anything that I really understood.
 Seems like a floating ground is insulated from a real ground and you shouldn't touch it.
 But I don't understand the following, is a floating ground a 'ground' on a certain voltage above the normal ground? I read that when creating a floating ground on 5V, you can create a supply of 7V by using a 12V source with he 5V ground used as a normal ground (uch, I can't follow this myself).

 If so, is the floating ground you mean here at 48V? As this is what the power supply gives. 
 And would you have an idea of what would happen when still connecting the normal ground of the amp to this floating ground? (If we take in account that the ground in the amp stays insulated from the chassis, else probably ***PZZZ***)

 Dries_

 

What you've referenced is actually talking about floating the zero reference relative to creating a + or - voltage for analog signals.
	

	
	
		
		

		
		
	


	




 All sound signals in audio electronics are sine waves, so the signal varies constantly between + and -. The speed at which that wave varies gives you the frequency - in our interests, the value between 20 - 20,000 Hz.

 In the Starving Student, for instance, the supply voltage is set at 48V to the tubes, but the grid (signal ground) is referenced at 19V, i.e., the ground is "floated" to 19V. At the same time, the amplification factor of the 19J6 tube is 38 at 100V. We're running it at 48V, or essentially one-half the rated plate voltage. So, the amplification factor is probably around 19. This means the tube can swing a 1V signal to + or - 19V at the strongest musical peaks. With the reference (or floated ground) set at 19V, the voltage can supply a -19V (down to 0) or a +29V (48V) - but it actually only uses 19V on that high side, too. Actually, it will begin to clip on the low side of the wave, but that clipping will be delayed on the high side until that 29V is reached.

 Anyway, this means the voltage at output is 19V (zero signal or "floated ground"), as soon as you turn it on and the tubes warm up. Hence, we have to use output coupling caps to block that DC voltage level from our headphones. That's a big digression, actually, but what was really being explained in your reference. They were looking at 5V as the reference ground, so that a +7 and -5 would be available to supply analog signals.

 On the other hand, when we talk about the SSMH's power supply as having a floating ground, it's an intermittent error condition. The power supplies should always be referenced back to ground zero in the wall outlet. When you use a BantamDAC, it's referenced that way all the way through the PC back to the wall outlet. Same thing for most other power supplies - even ones that are not plugged into the ground at the wall outlet (they are isolated in that case). However, one would expect that the zero point of the supplied voltage would never change.

 In the case of the SSMH's power supply, I've measured as much as 0.49VDC (1/2 volt) difference between the negative terminal on the Cisco's 2.5mm supply plug and the ground reference measured on a BantamDAC that's connected to a PC's ground. That's 0.49VDC that gets sent back through the BantamDAC's ground. The PCM chip is connected directly to ground in several places, but the output coupling caps in the BantamDAC only sit on the signal lines, not the ground. So, there is no protection from this offset that may potentially develop.

 BTW, that amount of voltage reference difference is trivial to most circuits with output protection, output buffers, opamp buffers, etc., which most sources already have. However, the Alien and BantamDAC are special DIY configurations to obtain the "purest" sound from the DAC chips without any intervening circuitry. (A Swenson mod on a CD player may suffer the same vulnerability.) There's not an issue using an AlienDAC or BantamDAC with any other amp that I'm aware of - but there's not an issue with a power supply moving its zero reference around, either (unless all switching supplies operate this way). That's why the problem is unique with the Starving Student.

 This may also be the same reason that several of us have measured offset on the RCA jacks upon power up with the SSMH. It's the Cisco power supply "moving around" the voltage supply relative to 0VDC ground. We thought perhaps it was a back emf (something in the circuit that was causing a reverse voltage for a time), but it's the power supply itself moving the zero voltage reference around.

 I'm not the best in having theoretical insight to electronic circuits, so you guys correct me if I've stated something wrong.


----------



## Llama16

Wow I completely understand the use of a floating ground now, but I'm still kinda in the dark with it's connection to the SSMH. Plz don't understand me wrong, you're explenation is excellent though I think it is mostly my lack of English that doesn't allow me to really fully understand it.
 SO you are saying that the ground of the SSMH that's being used (the copper clad) is set at 19V(when the amp is turned on), and thus the powersupply offers a voltage of -19 to +29V. And the amp uses just the -19v to +19V. But if the ground of the amp is 19V, shouldn't it (copper clad) be isolated from the case? I don't really recall reading somewhere about it needing to be isolated.
 OR are you meaning that the floating ground of the PSU (cisco) is 0.49VDC, thus different from the 19V ground in the amp --> and when connecting the amps ground to the cisco ground --> you lose the 19V signal of the amps ground as it flows to the PSU ground --> thus losing the wanted -19V and +19V(or +29V usable).

 You guys must have studied enigineering... 
 I really got alot to learn.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Wow I completely understand the use of a floating ground now, but I'm still kinda in the dark with it's connection to the SSMH. Plz don't understand me wrong, you're explenation is excellent though I think it is mostly my lack of English that doesn't allow me to really fully understand it.
 SO you are saying that the ground of the SSMH that's being used (the copper clad) is set at 19V(when the amp is turned on), and thus the powersupply offers a voltage of -19 to +29V. And the amp uses just the -19v to +19V. But if the ground of the amp is 19V, shouldn't it (copper clad) be isolated from the case? I don't really recall reading somewhere about it needing to be isolated._

 

Yes, this is correct, but it doesn't have anything to do with the issue at hand. As for "isolation," none per se, but the output coupling caps are required - otherwise your headphones would see 19VDC, which will burn them out. That's also why you'll read a lot of references in this thread to never having your headphones plugged in until after the amp is powered up - the coupling caps take a few seconds to charge. Before that, they offer no protection whatsoever to that 19V. This is mitigated somewhat by the fact that the tubes don't come up either, so the 19V is not really there, either (but it is a definite voltage a little less than that). It's a race to see whether the tubes transmit that 19V first or whether the caps charge first.
	

	
	
		
		

		
		
	


	




  Quote:


 OR are you meaning that the floating ground of the PSU (cisco) is 0.49VDC, thus different from the 19V ground in the amp --> and when connecting the amps ground to the cisco ground --> you lose the 19V signal of the amps ground as it flows to the PSU ground --> thus losing the wanted -19V and +19V(or +29V usable). 
 

No, this isn't it either. The 0.49 offset will be present everywhere there's a ground - it's just the ground will not be at zero. The 19V is an entirely different situation on the output of the amp and depends on the circuit design. Simple power supplies do not come supplying fixed + and - voltages (many do, but they're not simple or inexpensive), yet an audio amplifier needs to supply continuously variable + and - voltages to produce a music signal (AC). This is one of the ways to do that - by floating the _signal_ ground in order to provide that + or - capability to produce a music signal sine wave.

 The 0.49 offset has to do with an unreferenced _earth_ ground. You can have this happen in commercial/industrial power systems and wiring, for instance, and it can be very dangerous.

  Quote:


 You guys must have studied enigineering... 
 I really got alot to learn. 
 

Well, lots of Mechanical Engineering, anyway - that's my failing around here.


----------



## Llama16

Thank alot tomb that clarifies alot.
 I'm glad I'm correct about the first part, that made me understand alot more about amps.
 Is the floating point a similar method as the virtual ground in the cmoy, or is it practically the same/ completely different.
 Still about the insulation (I found the term
	

	
	
		
		

		
		
	


	




)... wouldn't the 19V ground get lost when connecting it to a real ground? But why does it not have to be insulated then?

 Well, I think I'll be doing engineering myself when I go to uni. Though just one year left to go in high school. Atm I should be studying for latin exam this monday


----------



## royewest

Tomb, thanks a lot for the details. I also really appreciate them. I'd hope to impose further and second LLama16's question: will connecting the star ground to true earth have an effect on the floating ground?


----------



## kuroguy

I believe connecting star ground to earth ground would reference the ground to earth ground (plus the voltage drop in the wire). I believe it would also cause a ground loop. Is that correct?


----------



## tomb

Quote:


  Originally Posted by *royewest* /img/forum/go_quote.gif 
_Tomb, thanks a lot for the details. I also really appreciate them. I'd hope to impose further and second LLama16's question: will connecting the star ground to true earth have an effect on the floating ground?_

 

I believe the Cisco power supply is isolated itself, so this would have no effect. The floating reference occurs in the output of the power supply.

  Quote:


  Originally Posted by *kroguy* 
_I believe connecting star ground to earth ground would reference the ground to earth ground (plus the voltage drop in the wire). I believe it would also cause a ground loop. Is that correct?_

 

If the earth ground was indeed carried all the way back to the wall outlet, then yes - I think this would be the case.

 You guys are testing this ME, though - there are many others who are more knowledgeable than me. (Maybe Dsavitsk will see this and elaborate.)


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Thank alot tomb that clarifies alot.
 I'm glad I'm correct about the first part, that made me understand alot more about amps.
 Is the floating point a similar method as the virtual ground in the cmoy, or is it practically the same/ completely different._

 

The Cmoy creates what's known as a virtual ground. The ground is defined by the middle point of two equal, but opposite polarity voltages. Thus, the virtual ground in the CMoy should always be at zero. That said, one of the ways one troubleshoots a CMoy is to measure voltage offset at the output - the difference of that virtual ground from zero. Quote:


 Still about the insulation (I found the term
	

	
	
		
		

		
			





)... wouldn't the 19V ground get lost when connecting it to a real ground? But why does it not have to be insulated then? 
 

Not really. The way grounds are supposed to work is by providing a reference. You have to have another voltage supplied before it knows there's a difference. IOW, ground is ground untill you reference it to something else (or at least it's supposed to be unless you have offset). Quote:


 
 Well, I think I'll be doing engineering myself when I go to uni. Though just one year left to go in high school. Atm I should be studying for latin exam this monday 
	

	
	
		
		

		
		
	


	



 

Gallia Est Omnis Divisa in Partes Tres?


----------



## Llama16

So the cmoy's virtual ground = floating point of 4.5V + voltage divider. I'm sorry if I keep pushing the cmoy thing 
	

	
	
		
		

		
		
	


	




 k I get the insulation, so as long as no other source that provides a voltage, the grounding won't act up. I just thought that when connecting this floating ground to real ground(case in dirt ground 
	

	
	
		
		

		
		
	


	




), the voltage would 'leak away' and thus making the copper clad a real ground as well.

 'All Gaul (probably not written correctly) is divided in three parts'. One of the first sentences I had to translate for latin 
	

	
	
		
		

		
		
	


	




. Studying is finished, so time to relax.


----------



## kuroguy

Ground is indeed the local reference to zero. It is strictly a datum. Thats why you can string a 5 volt power supply in series with another 5 volt power supply and get 10 volts. You can also call the common point between those two power supplies ground. In that case you have -5, 0, +5 which is still a range of 10 volts, just referenced to a different ground. 

 As a mechanical engineer it helps me to look at the mechanical analogy, a pair of pumps in series. The head of each pump is analogous to the voltage and the flow rate is analagous to the current.


----------



## tomb

Listen guys - just to clarify things ... the description I gave about the power supply and it having a floating ground is strictly conjecture. It may be incorrect or have nothing to do with the situation. The fact remains that the switching power supply is one unique difference between the SSMH and other headphone amps and that blowing Alien and BantamDACs has happened with a number of people in several different scenarios.

 I think the rest of what we were discussing I got correct.


----------



## smeggy

looking forward to getting my bits in the mail. It looks damn spiffy and it it sounds better than the one I built before I'll be very happy.


----------



## Llama16

DAMN!!! Mousere requires a credit card... I have maestro and I hoped to be able to pay by paypal.
 I got like 130EUROs shopping (MINI³, SSMH, 2CMOYs, and lots of extra bits and pieces)
 and now I gotta ask my parents to loan from their visa/master ---> They'll know the price ---> THEY'LL FREAK OUT.
 Ha well, a reason more for me to work hard for exams. I'l try and ask it when I come home with good grades


----------



## tamasic1

Quote:


  Originally Posted by *stoned22* /img/forum/go_quote.gif 
_Is it possible to replace the mosfet stage with a gainclone to give it enough power to drive speakers?_

 

 Quote:


  Originally Posted by *kvant* /img/forum/go_quote.gif 
_Not directly, since the quiescent current through MOSFET is recycled as heater current for the tube. However, if you provide extra heater power supply, you can certainly hook-up a power opamp ("gainclone") after the tube._

 

He, he - try this if you have both. Use the SS as a preamp to your gainclone. 
 I have these large old Kenwood speakers connected to my setup in a very spacious 2+ car garage. Cranked both amps all the way up with no distortion, but it was like being in the first row at an AC/DC concert. - _*the walls were shakin'*_ -literally!


----------



## Llama16

When I use a Star ground (which is prefered right?) for the SSMH, I can just wire EVERY ground wire to a point of the chassis. Inlcuding INPUT, OUTPUT, and POT. Or do I NEED to first take the ground wire of the input to the POT ground and from there to the star ground?

 (Hehe, I thought putting words in CAPS would make things shorter)


----------



## Yaka

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_When I use a Star ground (which is prefered right?) for the SSMH, I can just wire EVERY ground wire to a point of the chassis. Inlcuding INPUT, OUTPUT, and POT. Or do I NEED to first take the ground wire of the input to the POT ground and from there to the star ground?

 (Hehe, I thought putting words in CAPS would make things shorter)_

 

you can do it either way. most i think connect all to the star.


----------



## Llama16

Could it be that pmillet wired the power switch to the tube of one channel in his schematic (dunno if it was left or right) and in his build it was assigned at the tube of the opposite channel?
 I know it doesn't make a difference, but I'm trying to understand the schematic. And compare it to the his wiring. Else I read things wrong.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Could it be that pmillet wired the power switch to the tube of one channel in his schematic (dunno if it was left or right) and in his build it was assigned at the tube of the opposite channel?
 I know it doesn't make a difference, but I'm trying to understand the schematic. And compare it to the his wiring. Else I read things wrong._

 

You read things wrong.
	

	
	
		
		

		
		
	


	




 It's a simple SPST right in the power path from the input socket. After the switch, the circuit branches in three parallel directions - 1) to R13, 2) to the Q1 MOSFET pin 2, and 3) to the Q2 MOSFET pin 2. Further on, the leg through R13 branches off in parallel to the two _tube_ circuits - 1) to R1 and R2 on the Right channel, and 2) to C6, R7 and R8 on the Left channel. (C1 for the Right channel is on the back side of R13.)

 I think that's right. 
	

	
	
		
		

		
		
	


	




 EDIT: Regardless as a beginner, you are better off looking at the circuit in some builds than trying to wire P2P from the schematic. Here's Pete's again:


----------



## zkool448

i don't see any switch wires going to the tubes llama.. I do see two wires going straight to the MOSFETs drain (pin2).

_edit: nevermind 
	

	
	
		
		

		
		
	


	


_


----------



## Llama16

Yes i understand what you mean and thanks for your help. I thought it'd be a good exeraice trying to implement the schematic into wiring and then correcting it by looking at the builds. I didn'T really mean about a wire going straight to the (sorry if i wasn'T clear). I think i pretty much found where i went wrong
	

	
	
		
		

		
			





. (srry for not typing 'i's in caps... Stupid ipod keypad). EDIT: btw zkool, i made a little design about a wooden case for the amp. And I think it's kinda very based one of your amazing designs... I made a sketchup of it which i'll post tomorrow. Just wanted to make sure you would be ok with that or not, let me know. And I know I shouldn't be thinking about a case when i can't even read the schematic properly
	

	
	
		
		

		
		
	


	




... Aah well


----------



## tomb

OK - here's the deal on the custom Hammond cases:
 The 6wk lead time has started today. That means that you will have two weeks to continue ordering cases - until 12 Midnight EDT, Monday, June 22. After that, I can't guarantee anything. That's because the number ordered from Hammond will be set.

 I had hoped to get the clock ticking last week, but Hammond would not take a credit card. I had to send them a check, plus some tax exemption forms. I sent them out via certified mail last Tuesday as soon as I found out their requirements, but I guess this is how long it took Hammond to process everything.

 In any event, cases should ship to me from Hammond 6 wks from today.


----------



## zkool448

Tom, I'm guessing some pcbs have already reached their destinations, very busy builders already populating their boards. I can't wait to hear some impressions on here very soon 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_i made a little design about a wooden case for the amp. And I think it's kinda very based one of your amazing designs... I made a sketchup of it which i'll post tomorrow. Just wanted to make sure you would be ok with that or not, let me know._

 

Llama of course it's OK. truth is I’m constantly flattered when people complement my cases, makes me build more unconventional stuff. They say imitation is the sincerest form of flattery – thanks! 

 Looking forward to seeing your design


----------



## Llama16

I thought so you wouldn't mind 
	

	
	
		
		

		
		
	


	




. I think I'd even like to spread my own designs around instead of copyrighting them (unless they make me rich). Can't wait to see more of your designs coming. (Maybe this has been asked before, but after seeing some pictures of your builds my guess is that you work in 'woodconstruction' )

 But plz don't expect to much, it's just a VERY simple design based on one of the key features of yours (the knob). I can do 'simple' woodwork and I don't really have the acces for alot of tools. So it's very plain. And I think satisfaction-per-difficulty ratio is pretty high 
	

	
	
		
		

		
		
	


	




 Here's a pic (btw, measurements aren't correct yet, It's a design to start from)






 another angle






 EDIT: I'm not sure about the holes of the heatsink, if the wood I'll use wants to cooperate or not. Else I'll probably go with 1 big hole.


----------



## gurusan

Well I received my PCBs today and they are coming along nicely. Got a heatsink coming tomorrow or the day after along with some new mosfets and then it should be all done and I can start thinking about how I am going to do the next build with my 2nd PCB 
	

	
	
		
		

		
		
	


	




 The shaded area on the box is where the heatsink will go. I chose the one below....and it fits perfectly. It's 104.5mm in length and my enclosure is 106mm 
	

	
	
		
		

		
		
	


	




 Will just require a little drilling to secure it to the case and the heatsinks to the case. I am more of a function over form kind of guy, but am hoping it will turn out looking good anyway.


----------



## nullstring

so, I was bored during lunch.. and I was looking through different tubes.

 the 19EZ8 looks similar to the 19J6.. cept it's a triple triode.
 It's available for a $1 from vacuumtubes.net

 You think this could be used as a replacement?

 If so, what changes would need to be done?


----------



## dsavitsk

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_the 19EZ8 looks similar to the 19J6.. cept it's a triple triode._

 

That's a very weird tube. mu is a little high, and biasing it might be tricky with the 48V supply, but perhaps worth playing with. Good find.

 19au4 looks like the same tube.


----------



## Logistic

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_so, I was bored during lunch.. and I was looking through different tubes.

 the 19EZ8 looks similar to the 19J6.. cept it's a triple triode.
 It's available for a $1 from vacuumtubes.net

 You think this could be used as a replacement?

 If so, what changes would need to be done?_

 

I actually got a few to play around with. Like dsavitsk said, it would be tricky to use in the SSMH, it has a high mu and two of the triode sections have their cathodes tied to one end of the heater.


----------



## smeggy

triple triode? That sounds like a 2 channel with active ground to me


----------



## zkool448

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Here's a pic (btw, measurements aren't correct yet, It's a design to start from)
 EDIT: I'm not sure about the holes of the heatsink, if the wood I'll use wants to cooperate or not. Else I'll probably go with 1 big hole._

 

Llama, it's a fine-looking case design you have. My heat sinks and wood get along well – no heat issues for me. Just make sure the heat sinks you order are at least 2” or taller.

 Woodworker? Unfortunately not, it’s only a hobby/stress reliever – I work in IT 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_I am more of a function over form kind of guy, but am hoping it will turn out looking good anyway._

 

gurusan, looking good!


----------



## ezzieyguywuf

For building one of these, can you find the parts at Radio Shack? Saving on shipping would sure increase the starving student factor. Excuse me if its a silly question, I'm a total noob at DIY audio.


----------



## nullstring

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_For building one of these, can you find the parts at Radio Shack? Saving on shipping would sure increase the starving student factor. Excuse me if its a silly question, I'm a total noob at DIY audio._

 

It is a bit silly. 

SSMH Bill Of Materials

 You might be able to find everything at radioshack.. but radioshack is expensive and low quality. It would probably cost more and perform worse


----------



## ezzieyguywuf

oh wow! what a great website I hadn't even seen that one. And I read through the CMOY website and he explained there the same thing about Radio Shack. Sorry!


----------



## gurusan

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_**cool stuff**_

 

Very nice, looks good. I would love to do a wood case but don't have the space for the appropriate tools. Maybe when I move back to the states 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_gurusan, looking good!_

 

thanks


----------



## nullstring

Hey guys,

 I am going through and making my own Build Of Materials, and I remember seeing an alternative BOM for this amp at one point in time.
 I remember cause it has mouser rubber grommets on it.. and I think it had a specific orange LED that I wanted to copy.

 anyone know where that is?
 can't seem to find it..

 EDIT: nevermind, found it
 searching for "xls" did the trick =)


----------



## Llama16

Thanks Zkool.
 I've ordered both the 2" and 1.5" ones, to make sure about heat. I'm really not sure of how I'm gonna do the the heatsink holes as I don't got the tools to cut just half the panel out (dunno the word for the tool). So I'll probably just cut the holes through and then seal it again with a fine piece of wood glued/screwed on the inner side of the top side, where I could then stick the mosfets through.


----------



## rshuck

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Thanks Zkool.
 I've ordered both the 2" and 1.5" ones, to make sure about heat. I'm really not sure of how I'm gonna do the the heatsink holes as I don't got the tools to cut just half the panel out (dunno the word for the tool). So I'll probably just cut the holes through and then seal it again with a fine piece of wood glued/screwed on the inner side of the top side, where I could then stick the mosfets through._

 

Do you mean with the fancy, "intersecting oval" kind of shape you have on the rear part of the top?

 An example for one of the oval openings...
 Use a hole saw or Forstner bit to cut two circles the correct distance apart - say you're using a 1.5" bit, so you'd drill a circle for the left half of the heatsink, and drill another circle for the right half of the heatsink, leaving you with, roughly, the shape of an 8 turned on it's side.

 Then, get a relatively inexpensive Coping Saw and cut the rest out. You can thread the coping saw through the circlular holes and then cut the excess out.

 You could also use a sharp chisel and a very, very steady hand. I'd leave some excess on the inside so you can get a nice even sanded finish.

 Then, repeat for the other heatsink, just overlapping the other oval.


 * oh wait, you mean not drilling all the way through the panel... you'd need a router for that. *


----------



## gurusan

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Hey guys,

 I am going through and making my own Build Of Materials, and I remember seeing an alternative BOM for this amp at one point in time.
 I remember cause it has mouser rubber grommets on it.. and I think it had a specific orange LED that I wanted to copy.

 anyone know where that is?
 can't seem to find it..

 EDIT: nevermind, found it
 searching for "xls" did the trick =)_

 

I just searched and can't find what you found....I'm specifically interested in the rubber grommets? I just drilled the holes for my tubes and am curious if it will look better with some grommets...but can't seem to find any the right size.


----------



## tomb

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_I just searched and can't find what you found....I'm specifically interested in the rubber grommets? I just drilled the holes for my tubes and am curious if it will look better with some grommets...but can't seem to find any the right size.

 <IMG]http://img196.imageshack.us/img196/6784/27067888.jpg[/IMG>_

 

It's not grommets, but hole bushings. I used these on one of the SSMH PCB prototypes (the black one):





 They were used on the Millett MAX (prototype in pic):





 but their use first started way back on the revMH Millett Hybrid:





 n_maher came up with the idea as a way to cover his nasty tube holes.
	

	
	
		
		

		
		
	


	







 Here's the specific info:
 Mouser Part #561-MP10012

 and the catalog diagram:





 You want to cut a 1" hole. These snap in, leaving a 3/4" hole opening for the tubes - just perfect.


----------



## Llama16

Quote:


  Originally Posted by *rshuck* /img/forum/go_quote.gif 
_Do you mean with the fancy, "intersecting oval" kind of shape you have on the rear part of the top?

 An example for one of the oval openings...
 Use a hole saw or Forstner bit to cut two circles the correct distance apart - say you're using a 1.5" bit, so you'd drill a circle for the left half of the heatsink, and drill another circle for the right half of the heatsink, leaving you with, roughly, the shape of an 8 turned on it's side.

 Then, get a relatively inexpensive Coping Saw and cut the rest out. You can thread the coping saw through the circlular holes and then cut the excess out.

 You could also use a sharp chisel and a very, very steady hand. I'd leave some excess on the inside so you can get a nice even sanded finish.

 Then, repeat for the other heatsink, just overlapping the other oval.


 * oh wait, you mean not drilling all the way through the panel... you'd need a router for that. *_

 

Yep, that was what I was planning to do. I thought I will screw up with the frostner bit, so leaving some excess would be the solution when I try this.
 But yeah my problem is that I'll have to go all the way through the case as I don't have that kind of tools to just cut out half (tools like zkool grr).

 So OR I'll just go through the top of the wooden case and close it again from the inside with a very fine board of would (but this wouldn't really make the heatsinks stable, and if I push them down I would probably go through them very easily :S) OR I just put on an extra piece, like on the sides, but then I thought about making those side 'railings' thinner. I already tried drawing it in sketchup, but it just doesn't look good. So perhaps it'll be better if I use thinner railings.


----------



## rshuck

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Yep, that was what I was planning to do. I thought I will screw up with the frostner bit, so leaving some excess would be the solution when I try this.
 But yeah my problem is that I'll have to go all the way through the case as I don't have that kind of tools to just cut out half (tools like zkool grr).

 So OR I'll just go through the top of the wooden case and close it again from the inside with a very fine board of would (but this wouldn't really make the heatsinks stable, and if I push them down I would probably go through them very easily :S) OR I just put on an extra piece, like on the sides, but then I thought about making those side 'railings' thinner. I already tried drawing it in sketchup, but it just doesn't look good. So perhaps it'll be better if I use thinner railings._

 

You could always use a sheet of thin steel for that bit instead of a thin piece of wood. Some places sell carbon fiber sheets that should also hold up to any physical scrutiny you put on it


----------



## Llama16

Hey yeah that's actually a great idea which I'll probably do.
 While I'm at it (the metal 
	

	
	
		
		

		
		
	


	




), I could create some other small metal accents, so that the bottom of those heatsinks don't stand out. Maybe I could buy the feet in the same kind of metal, and also make a wooden knob with the front (or just the pointer) covered by a metal. Lookin' guuud.... Keep the ideas coming 
	

	
	
		
		

		
		
	


	




 as long as it's doable for someone with limited tools and access to resources


----------



## rshuck

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Hey yeah that's actually a great idea which I'll probably do.
 While I'm at it (the metal 
	

	
	
		
		

		
		
	


	




), I could create some other small metal accents, so that the bottom of those heatsinks don't stand out. Maybe I could buy the feet in the same kind of metal, and also make a wooden knob with the front (or just the pointer) covered by a metal. Lookin' guuud.... Keep the ideas coming 
	

	
	
		
		

		
		
	


	




 as long as it's doable for someone with limited tools and access to resources 
	

	
	
		
		

		
		
	


	


_

 

Depending on where you live, the place you buy it from may be able to cut it to size for you. If not, and the piece will not be seen, you could always just bend it back and forth until the metal fatigues enough to break! 
	

	
	
		
		

		
		
	


	




 I actually wouldn't recommend that part. I would just consider other materials besides wood to work with. Plexiglass is easy, and you can get good results cutting that with only a utility knife. I think the melting point should be well above what the heatsinks could put out, but don't quote me on that!


----------



## Llama16

Plexiglass sounds good as well. Floating heatsinks.
 About the metal. The feet I would probably buy then, though shouldn't the round plate fort he know be easy to cut (if I use a good metal) with a metal saw? I'm pretty sure I have one of those lying around.


----------



## kuroguy

tin snips - $5 at the flea market. They'll dull easily, but a pair from Sears with a better steel so it resists dulling is $15 and has a Craftsman lifetime warranty covering anything you might do with them (including burning a hole in the blade from cutting a live wire).


----------



## Llama16

thanks for the tip. I googled those and to be honest, never saw something before. It seems to work because of it's dubbel 'leverage' (dunno the word). Wouldn't like it to be used on me 
	

	
	
		
		

		
		
	


	




.

 I'll keep that in mind and see if I can come across one of those in a local shop. 
 I'm planning to stick with the metal, but if it really wouldn't work I'd go with rschucks other idea of acryl, would be nice as well.


----------



## kuroguy

One more tip. Snips come in 3 flavors. Left cut, right cut, and straight cut. If you can only afford one pair, you want the straight cut (typically yellow handles as opposed to red or green handles).


----------



## Llama16

Yeah I read about that. But I think I'll be glad if I can just fine one of this.
 Little question though, are the r/l cuts necessary (by this I mean, are the necessary for clean curved cuts?) or can it be just as well done with the straight ones and a little more effort.


----------



## nullstring

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's not grommets, but hole bushings. I used these on one of the SSMH PCB prototypes (the black one):_

 

Thanks for that


----------



## gurusan

thanks for the link tomb...

 anyway...
 Well my build was going so nicely..then I managed to get the center pot hole on the faceplate off by about 4mm!! So I temporarily mounted the power switch next to it to try to make it line up better but it looks worse i think lol. Going to have to redo the faceplate i think.

 I had it measured perfectly as well but just don't have the appropriate tools.

 I really need some sort of pillar drill. I'm looking at some smaller ones on the net that mount a hand-drill and use that as a pillar drill. Would one of those suffice for small hobbyist casework kind of jobs?


----------



## Hayduke

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's not grommets, but hole bushings. I used these on one of the SSMH PCB prototypes (the black one):






 They were used on the Millett MAX (prototype in pic):





 but their use first started way back on the revMH Millett Hybrid:





 n_maher came up with the idea as a way to cover his nasty tube holes.
	

	
	
		
		

		
		
	


	







 Here's the specific info:
 Mouser Part #561-MP10012

 and the catalog diagram:





 You want to cut a 1" hole. These snap in, leaving a 3/4" hole opening for the tubes - just perfect.
	

	
	
		
		

		
		
	


	


_

 

FYI...
 This is one of the few items I can get local. My local Ace/Homeco carries these nylon bushing in the hardware isle (where the nuts and bolts are). If you have an Ace nearby, you might wanna check if they have them. Home Depot near me does NOT carry anything like this though


----------



## rshuck

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_thanks for the link tomb...

 anyway...
 Well my build was going so nicely..then I managed to get the center pot hole on the faceplate off by about 4mm!! So I temporarily mounted the power switch next to it to try to make it line up better but it looks worse i think lol. Going to have to redo the faceplate i think.

 I had it measured perfectly as well but just don't have the appropriate tools.

 I really need some sort of pillar drill. I'm looking at some smaller ones on the net that mount a hand-drill and use that as a pillar drill. Would one of those suffice for small hobbyist casework kind of jobs?_

 

You need a spring loaded center punch to get the hole started in the right place.
- Harbor Freight Tools - Quality Tools at the Lowest Prices


----------



## ezzieyguywuf

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_thanks for the link tomb...

 anyway...
 Well my build was going so nicely..then I managed to get the center pot hole on the faceplate off by about 4mm!! So I temporarily mounted the power switch next to it to try to make it line up better but it looks worse i think lol. Going to have to redo the faceplate i think.

 I had it measured perfectly as well but just don't have the appropriate tools.

 I really need some sort of pillar drill. I'm looking at some smaller ones on the net that mount a hand-drill and use that as a pillar drill. Would one of those suffice for small hobbyist casework kind of jobs?
_

 

So what was wrong with the center pot? Looks like its in there all right to me


----------



## balrog

gurusan- I would get a dedicated pillar drill and be done with it. You won't have buyers remorse. 

 Did you use an automatic center punch or centerpunch/hammer to mark your layout points on the faceplate? Should be able to get good results with a hand drill. Check the drill chuck to see if it spinning eccentric.

 Measure and make your layout marks. Then make light dimples by lightly tapping with the centerpunch. Now go back and remeasure all of your layout points with the same ruler that you used for the initial layout- measure from the same edge to the layout point. If the dimples are a little off, you can "massage" the dimple's location. Gently tap the centerpunch at an angle towards the correct location then tap the centerpunch perpendicular to the work surface. This technique works with metal, I would not do this to a plastic faceplate.

 Select a small for a pilot hole and check that you are square to the workpiece. Check the pilot hole for proper location before moving to the next size drill bit.


----------



## kuroguy

$99 gets you a benchtop drill press that will work for pretty much any chassis you make. I'd bet you can get one for $40 at a pawn shop.


----------



## zkool448

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_tin snips - $5 at the flea market. They'll dull easily, but a pair from Sears with a better steel so it resists dulling is $15 and has a Craftsman lifetime warranty covering anything you might do with them (*including burning a hole in the blade from cutting a live wire*)._

 

hahahah funny kuroguy, I have a 'holed' one sitting in my tool chest 
	

	
	
		
		

		
		
	


	




 llama, are you doing a pcb build or p2p? Just want to note that none of my heatsinks touch the wood at all. Many can confim the SSMH sinks do get pretty *hot* when mosfets are mounted to them directly, maybe even hot enough to melt plastic/acrylic.

 gurusan, the heatsink and that black case are a match in heaven - looking good!


----------



## yebisu

Hi, I just built my first P2P SSHA and its not working. I keep going over the wiring, but I can't figure out what's wrong. I'm getting 48v out of the 3rd pin (both sides) instead of 19v. The transistors aren't warming up and the tubes aren't either (not glowing/heating). Can anyone think of why I might be getting 48v instead of 19v? I'll post pictures as soon as i can. Thanks!


----------



## zkool448

Hi yebisu, is it possible that your MOSFET (IRF510s) pins got mixed up?

 See the pic below from the web, check that your:
 Gate = Pin 1
 Drain = Pin 2
 Source = Pin 3


----------



## ezzieyguywuf

Looking at the schematic, the most confusing part for me is the part where you connect the MOSFET to the heatsink. Can anyone provide some explanation here?


----------



## smeggy

The heatsink is attached to the MOSFET with a mounting kit. Basically nut, bolt washers and an insulating pad.

Beezar.com <-see here.


  Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Looking at the schematic, the most confusing part for me is the part where you connect the MOSFET to the heatsink. Can anyone provide some explanation here?_


----------



## smeggy

Buggeration, my ss prts arrived and I underordered the .22uf Wima caps so I need another pair.


----------



## Llama16

Gurusan, very nice build 
	

	
	
		
		

		
		
	


	




 I like the heatsink alot (but I think I've noted that before).
 I don't really see about the pot not centered, on your pictures it looks pretty good perfect even.

 Zkool: I'll exclude acrylic then 
	

	
	
		
		

		
		
	


	




 it. i'll see and measure what the heatsink temps are on both 1.5 and 2" and I'll go from there. I'll probably go with a nice brushed aluminum plate and add some touches of aluminum to the feet and 
 /or knob as well.


----------



## Llama16

Woot, see what I got in the mail 
	

	
	
		
		

		
		
	


	




.
 Now it just got serious.

 I already unwrapped them, they fysically seem to be in perfect shape. Well wrapped in nice big bubbles.
 Great server, faster then I expected. And the shipping cost 5dollars international!!! I thought (as onyu pointed me out) I had to pay alot on customs after arrival. But 5bucks for shipping to belgium is awesome. 
 I'll probably have to pay 40euros on customs for stuff from mouser by fedex... grrr. Free shipping after 75euros... my $ss. Sorry for that 
	

	
	
		
		

		
		
	


	









 Dries


----------



## tomb

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_The heatsink is attached to the MOSFET with a mounting kit. Basically nut, bolt washers and an insulating pad.

Beezar.com <-see here._

 

There's also this pic from the MAX websites that may be helpful:





  Quote:


 Buggeration, my ss prts arrived and I underordered the .22uf Wima caps so I need another pair.
	

	
	
		
		

		
		
	


	



 

Sorry about that, Smeggy. I usually contact people if I think they've shorted something, but peoples' choices in bypass caps can vary quite a bit. Guess I should've said something anyway. Shoot me a PM and we can work something out.


----------



## kuroguy

it is also a good idea to measure the resistance between the heatsink and the tab on the mosfet. Anything other than an open circuit is going to be a problem. Do this before your first powerup and you might just save yourself from needing new mosfets.


----------



## Llama16

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_it is also a good idea to measure the resistance between the heatsink and the tab on the mosfet. Anything other than an open circuit is going to be a problem. Do this before your first powerup and you might just save yourself from needing new mosfets._

 

I can't really follow this one. The MOSFET is insulated from the heatsink right (or needs to be)? And IF you had conductivity between the heastink and mosfet, as long as it doesn't touch anything else of the components that doesn't really matter.


----------



## kuroguy

You are correct since your heatsinks are not tied to ground (of which I was not aware). My point was to make sure the insulator for your mosfet is installed/working properly. I've installed devices and had the insulator not work. In general this is a bad thing. It only takes a few seconds to check and is a good habit in general.


----------



## smeggy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry about that, Smeggy. I usually contact people if I think they've shorted something, but peoples' choices in bypass caps can vary quite a bit. Guess I should've said something anyway. Shoot me a PM and we can work something out.
	

	
	
		
		

		
			



_

 

It's not your fault, just me not looking closely at what I actually needed. Ah well, such is life.


----------



## gurusan

So I've just finished my 2nd millet starving student build, this time using a PCB. Want to thank everyone here for their help, especially for the effort of supplying these pcbs 
	

	
	
		
		

		
		
	


	




 Sounds great and a lot quieter than my messy P2P build...however the balance seems quite a bit off...got to look into that one. Other than that it sounds fantastic and I've graduated from plastic maplin boxes lol.


----------



## royewest

Very clean look, gurusan. Congratulations!

 Do you have any shots showing how you attached the MOSFETs?


----------



## gurusan

Thanks 
	

	
	
		
		

		
		
	


	




 Inside is not as pretty but not too bad either imo. I used arctic silver 5 epoxy that I had laying around to bond the mosfets to the top of the chassis (insulator in between). 

 Also the amp has been playing Metallica, Sonata Arctica, and various electronic music for over an hour now and I just checked the mosfets with a temp probe and they are 46-48C so the heatsink and chassis seem to be doing about 15C better than my old to-220 sinks.


----------



## Llama16

Nice build 
	

	
	
		
		

		
		
	


	




 I think I'm going to make both the PCB and p2p, I've got the board and the tubes. Probably just to make sure I got one working amp (the pcb) when I mess up my p2p hehe

 Tob bad about the imbalance, the other guys will probably find it though


----------



## gurusan

thanks, I think the imbalance thing might be a grounding problem? Or perhaps the ghetto way I hooked up the pot.


----------



## tomb

Looks good!

 My vote is for the pot wiring.
	

	
	
		
		

		
		
	


	




 Although, it's difficult to tell from the pic, but is there a chance that R16 and R17 are different? I think I see a different band on one of the resistors compared to the other one.


----------



## gurusan

Perhaps that's the reason...I did not have any 50k resistors so wired 2 33k in series for 66k. I figured that would just slightly reduce the gain though unless I misunderstood the comment for those parts on the BOM?

 However, I now have 2 51k resistors, though I haven't wired them in yet.


----------



## Llama16

They were probably for a different channel thus the higher gain one was from the channel that had the least sound. I guess...


----------



## tomb

Quote:


  Originally Posted by *gurusan* /img/forum/go_quote.gif 
_Perhaps that's the reason...I did not have any 50k resistors so wired 2 33k in series for 66k. I figured that would just slightly reduce the gain though unless I misunderstood the comment for those parts on the BOM?

 However, I now have 2 51k resistors, though I haven't wired them in yet._

 

With a 50K pot, yes - the 2 x 33K resistors would result in a slight gain reduction. Maybe it's just the wiring, then?

 Have you tried swapping tubes? A channel mis-match is possible. Even though I test them all, I have made mistakes and still do. If the channel mis-match follows the tube swap, then that would be the problem.


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Have you tried swapping tubes? A channel mis-match is possible. Even though I test them all, I have made mistakes and still do. If the channel mis-match follows the tube swap, then that would be the problem._

 

I'd think a tube would have to be failing to cause a channel mismatch that would be perceptible in this amp. 

 I don't particularly like the look of the melted Wima on the output although I'm not sure it's damaged enough to matter.


----------



## gurusan

I've swapped tubes and the problem is still there. Going to double check my pot wiring tomorrow and replace that wima cap. Got tired with the soldering iron and melted it...several times lol.


----------



## zkool448

haha. It really amazes me how the minds work for many of the engineers and gurus that frequent this forum. 

 I see a populated pcb and think to myself "wow, that looks cool" then I move on. The gurus come in and they spot melted caps, backward diodes, inefficient wire gauge, shorted traces, .....


----------



## Llama16

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_haha. It really amazes me how the minds work for many of the engineers and gurus that frequent this forum. 

 I see a populated pcb and think to myself "wow, that looks cool" then I move on. The gurus come in and they spot melted caps, backward diodes, inefficient wire gauge, shorted traces, ..... 
	

	
	
		
		

		
			



_

 

yeah, dubbel that.
 I hope they're wrong one day and screw up one of their own builds....MWUAHAHA, just kidding 
	

	
	
		
		

		
		
	


	




 BTW Zkool, I got some awesome news. The best friend of my sister lives in my street, and her dad is a carpenter. So maybe I could get my courage together, get out of my room and ask her dad if I could use his workshop for a couple of hours. Dunno if it would work


----------



## Hayduke

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_yeah, dubbel that.
 I hope they're wrong one day and screw up one of their own builds....MWUAHAHA, just kidding 
	

	
	
		
		

		
		
	


	


_

 

Why do you think they know what to look for? We all learn by making mistakes. The lucky folks can learn from others' mistakes instead of having to repeat them. 
	

	
	
		
		

		
		
	


	




 btw, I have put in diodes backwards, melted a Wima (2 actually!), and I'm sure I've shorted things.


----------



## Llama16

I'm not critising, I envy them for their knowledge. By reading things on this forum I've learned alot already, and maybe one day I might be able to point those things out as well and help someone


----------



## zkool448

That's awesome llama. He may even cut everything for you as long as you provide the wood -- good luck!


----------



## smeggy

Yeah, I only just found out which way around a diode is supposed to go


----------



## Llama16

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_That's awesome llama. He may even cut everything for you as long as you provide the wood -- good luck! 
	

	
	
		
		

		
		
	


	


_

 

Well I actually want to make it myself 
	

	
	
		
		

		
		
	


	




 that's why I do this all. I know that it would be done hundred times better by him, but then there wouldn't really be any fun about it. I hope to find some nice wood around here, and if I got my plans drawn and scales correct, I'll take them and my wood to him and ask him.
 We'll see.


----------



## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yeah, I only just found out which way around a diode is supposed to go 
	

	
	
		
		

		
		
	


	


_

 

Same here smeggy, if it weren't for the pictures none of my builds would have worked ..But last night though was truly entertaining for me haha 
	

	
	
		
		

		
		
	


	




 The short time I was logged on, digger scoped your backward diodes and then you said "what?? u can see that?" (I was ROFL!!)

 Then a few minutes later, it's adamus' turn: "your diodes are on backwards", and today Nate comes in, "gurusan you're caps are melted" hahaha

 Cheers to these guys...


----------



## tomb

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Why do you think they know what to look for? We all learn by making mistakes. The lucky folks can learn from others' mistakes instead of having to repeat them. 
	

	
	
		
		

		
		
	


	




 btw, I have put in diodes backwards, melted a Wima (2 actually!), and I'm sure I've shorted things. 
	

	
	
		
		

		
		
	


	


_

 

Heck - I saw the melted Wima and never gave it a second thought. I've melted the corner on one or two with every MAX/MiniMAX I've built. I did it on the Starving Student PCB, too, if anyone looks close.

 A secret: the plastic is thick on those things. You can get a file and smooth out any melted dimple you've happened to melt into one and no one will ever know. Unless you confess, that is ... 
	

	
	
		
		

		
		
	


	







 P.S. I've turned the diodes around in the PS and delay-relay on a MAX or MiniMAX more than once or twice, too.


----------



## gurusan

Yup it's great to have such helpful people here, otherwise I'd be lost :/


----------



## zkool448

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Heck - I saw the melted Wima and never gave it a second thought._

 

c'mon tom, you're as guilty as the rest of them (circuit police!) -- aren't you the one who spotted gurusan's R16 and R17 were different?


----------



## tomb

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_c'mon tom, you're as guilty as the rest of them (circuit police!) -- aren't you the one who spotted gurusan's R16 and R17 were different? 
	

	
	
		
		

		
		
	


	


_

 

I saw Smeggy's reversed diodes, too, but it appeared that he had enough help at the time.
	

	
	
		
		

		
		
	


	




 P.S. I'm not sure we've confirmed that his resistors were wrong, though.


----------



## smeggy

My diodes are (in)famous!!! 
	

	
	
		
		

		
		
	


	




 Resistance is futile.. when attached to a Sigma 22!

 Anyway, this is only my second attempt at building an amp so not surprising I don't know what I'm doing and put things in wrong. I am learning.. bit by bit.


----------



## dBel84

what would a dalek be without a death ray 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

Extermicake dalek only give you a sugar spike


----------



## bhjazz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Heck - I saw the melted Wima and never gave it a second thought. I've melted the corner on one or two with every MAX/MiniMAX I've built._

 

When the going gets tough, I often cover tall or obtrusive components like caps with foil. This keeps even the quick tagging of them from looking like hell.


----------



## gurusan

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_P.S. I'm not sure we've confirmed that his resistors were wrong, though.
	

	
	
		
		

		
			



_

 

Both r16 and r17 are each 2 33k in series so it might be a little ghetto but they aren't wrong. Unless I have a bad solder joint :/


----------



## madelvice

So I've finished building my amp and it seems to be a bust.

 I checked for a current at these places:

 -power jack
 -tube connectors (tubes plugged in)
 -rca jacks
 -output jack
 -transistors

 at each point there was a current read. So theoretically it should work, right?

 Well, the tubes aren't lighting up (or even warming at all for that matter). I'm not getting any sound when I plug in my headphones. I'm not sure what's wrong. Any ideas?

 Another point, possibly relevant: I'm reading a current regardless of the position of the switch... is that right? shouldn't there not be any current after the switch in the circuit if it's flipped off? (I tried both settings in case I'd soldered it backwards..)

 Any help would be much appreciated.


----------



## dsavitsk

You need to measure voltage, not current. Pictures would be useful, otherwise nobody has any idea what you might have done.


----------



## tomb

Just an update for those of you who've ordered kits and cases -

 Hammond sent an initial shop drawing for the case to me on Friday. Unfortunately, there were some mistakes. I marked it up and sent it back this weekend. Hopefully they'll make corrections and send me back an updated drawing today.

 This is normal and doesn't really reflect any issues with Hammond. We should be 5 weeks and counting today. I'll continue to keep you updated.
	

	
	
		
		

		
		
	


	






 EDIT: Well, there you go - as soon as I posted this, they hit me with the revised drawing.
	

	
	
		
		

		
		
	


	




 Looks OK so far, but it will be tonight before I can make sure and send it back.


----------



## Juaquin

Awesome, thanks for the continuing updates Tom.


----------



## tomb

Well, another round of corrections on the shop drawings - very minor changes, though. So hopefully, they'll get the final-final back to me today.

 What's happened is that my own drawings are always referenced to the extrusion body because that lines up with the endplate components. Of course, assuming like everyone else around here that all holes/cuts are in the top plate.

 However - Hammond views that plate as the "Belly Plate" and showed all machining to be done on the extrusion. I asked them to transfer all work to the Belly Plate, which we use as a "Top Plate." They did that yesterday, but squished the dimensions around the center line when they did it (the top plate is less wide than the extrusion).

 So, that was corrected on the drawing I sent back to them last night.

 I'll keep you updated. This is still pretty typical, so not to worry.


----------



## tomb

The drawing is approved.


----------



## rshuck

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The drawing is approved._

 

Awesome... one more thing done!


----------



## Tritonpad

Hi everyone ^^

 Tomb, is the deadline for order unchanged ? Still june the 22th ?
 I don't know if I will did it on time...
 Is is possible to consider another "order session" later on ?

 Thank's...


----------



## tomb

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Hi everyone ^^

 Tomb, is the deadline for order unchanged ? Still june the 22th ?
 I don't know if I will did it on time...
 Is is possible to consider another "order session" later on ?

 Thank's..._

 

It's still possible to order at the existing prices by June 22nd. However, Hammond will not let us add to the number after that date. It would not be fair (nor affordable) to give those that come after that date the same price, because the number will have already been fixed - supply will be limited.

 We should still be looking at July 13th for shipping to me, if my calendar calculations are correct. However, once nice thing about Hammond is that they will ship out a prototype to me next to confirm everything for real. I'll post photos when I get it and will go ahead and assemble another amp using it, too.


----------



## bobfig

hay guys! i just finished my starving student it went well but i got one problem. when i play sound through it all the vocals are to the left and all i get to to come out both ears is the background music. they play at the same volume, its not like one plays louder then the other. i tried swapping tubes around but its the same so i don't know. any one know what the problem may be?


----------



## tomb

Quote:


  Originally Posted by *bobfig* /img/forum/go_quote.gif 
_hay guys! i just finished my starving student it went well but i got one problem. when i play sound through it all the vocals are to the left and all i get to to come out both ears is the background music. they play at the same volume, its not like one plays louder then the other. i tried swapping tubes around but its the same so i don't know. any one know what the problem may be?_

 

Typically, the symptoms you describe are most often a wiring issue with the input jacks or the pots - some of the signal wires got crossed or mixed up with ground, etc. Double check the wiring in both of those places.


----------



## bobfig

ok thanx i will. my only real problem with making it was that the pot was not labeled in what wire/pin goes were. ill do a once over


----------



## zkool448

congrats bobfig, 

 For wiring the pot, see pic below from tangent's website (they're all similar). Wiper 1 & 2 are the outputs.


----------



## Hayduke

Quote:


  Originally Posted by *bobfig* /img/forum/go_quote.gif 
_ok thanx i will. my only real problem with making it was that the pot was not labeled in what wire/pin goes were. ill do a once over_

 

That was your only problem area and the most likely cause of the symptoms you're describing. So it looks like you definitely know where to look 
	

	
	
		
		

		
		
	


	




 Where did you get the pot? If you can find the datasheet from the manufacturer, you should be able to figure out what pins to use.


----------



## bobfig

ok guys i figured out what the problem was. it wasn't the pot that was done right. (only wasn't sure when putting it together) the problem was i messed up resisters 14/15. (im using the pcb) i didn't have a single resister for those locations so i used 2 to add the ohms together, SO...... it was different ohm loads there and threw off the balance.

 finished pics i call him "Old Happy Man"


----------



## zkool448

Well done bobfig, i love it! 

 So how does old happy man sound?


----------



## bobfig

gumpy as ever lmao 
 pretty good


----------



## Tritonpad

Is that me or Beezar.com is down ?


----------



## Llama16

I think it's you, I have no problem visiting beezar from belgium.


----------



## Tritonpad

What ??

 Everything is ok except beezar... I checked my Hosts file and no restrictions concerning beezar...
 PC has been cleaned... Always the same...

 Damned ! 
	

	
	
		
		

		
		
	


	




 P.S. : I am from France...


----------



## royewest

This is a handy tool for Tritonpad's situation:

Down for everyone or just me?


----------



## Tritonpad

Thank you for your answer and the tool you propose. It says that beezar is up 
	

	
	
		
		

		
		
	


	



 Seems that it is my ISP that doesn't like beezar ^^ Trying to tell them not to block it anylonger...


----------



## MoxMonkey

the BOM lists a standoff, is it the same as the one listed for the minimax?


----------



## madelvice

Alrighty, so when it was recommended that I take pictures to post to help with trouble shooting I looked at the jumbled mess that was my project and decided I needed to redo. Whatever.

 So having redone the whole thing, it still won't work! This time there are new problems:

 I measured no voltage from the mosfets onward (if you follow the path from power to out put. Well, I didn't get anything from the audio ins either... I think I may have fried the transistors at some point. I'm going to get new ones and see if that helps anything.

 Other issues:
 -Instead of a constant voltage it spikes at regular intervals. In addition, when my phones are plugged in I can hear a clicking, almost like a heartbeat, that matches the voltage spikes. Why is this? 

 -There's a silvery build up on the inside of my tubes near the top (in the same place on both) right where the decal is. If no one's encountered this I'll post a picture, I'm just too tired now. What is that? Is it a problem? 

 I think that's it. I'm hoping new transistors will fix my issues, if they don't I'll post pictures.


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_the BOM lists a standoff, is it the same as the one listed for the minimax?_

 

NO. I've had a little trouble packaging a solution that works in all cases, but I expect to have a SSMH Standoff Kit posted on beezar shortly.

 The issue comes in with the washers. One washer is needed between the PCB and the standoff to provide the final spacing needed. However, all available English washers are too big - they impinge on the back lead and pad of the tube LEDs resistor. Since the standoff makes contact with the PCB ground plane (desired), this will result in a dead short. Instead, I will probably be packaging some metric washers for this use with the standoff - they are much smaller diameter. I should have the kit available tomorrow.

 Likewise, the heat sink kits will be something special for the SSMH. Two extra screws, with corresponding washers, lock washer and nut are needed for the back mounting hole of the TO-3 heat sinks. Also, since the screws used on the MOSFETs go through the MOSFET, the case lid, and the TO-3 heat sink, they have to be longer than the other screws. These will all be socket-head cap screws, stainless washers and lock washers, and genuine polysulfide-filled shoulder washers for the MOSFETs. Bergquist pads will be used to complete the kit. These should be available shortly, too.

 BTW, when using the Hammond case and these TO-3 heat sinks, one should apply heat-transfer grease to the bottoms of the heat sinks where they contact the case lid. I did this on both of the ones I built, but will be detailing it, along with the proper mounting holes and orientation of the heat sinks, on the SSMH website.


----------



## tomb

Quote:


  Originally Posted by *madelvice* /img/forum/go_quote.gif 
_Alrighty, so when it was recommended that I take pictures to post to help with trouble shooting I looked at the jumbled mess that was my project and decided I needed to redo. Whatever.

 So having redone the whole thing, it still won't work! This time there are new problems:

 I measured no voltage from the mosfets onward (if you follow the path from power to out put. Well, I didn't get anything from the audio ins either... I think I may have fried the transistors at some point. I'm going to get new ones and see if that helps anything.

 Other issues:
 -Instead of a constant voltage it spikes at regular intervals. In addition, when my phones are plugged in I can hear a clicking, almost like a heartbeat, that matches the voltage spikes. Why is this?_

 

That voltage is being applied to your headphones through the headphone jack. 
	

	
	
		
		

		
		
	


	




 It could be damaging, so don't let that go on for long. Quote:


 
 -There's a silvery build up on the inside of my tubes near the top (in the same place on both) right where the decal is. If no one's encountered this I'll post a picture, I'm just too tired now. What is that? Is it a problem? 
 

If your tubes didn't have it, it would be a problem.
	

	
	
		
		

		
		
	


	




 That's what's known as the "getter flash" and pretty much every tube everywhere has one. The getter flash is a catalyst chemical designed to react to the gas molecules of air that may have infiltrated into the tube. The getter itself is usually a small loop, square, or D-shaped wire near the getter flash. The getter has voltage applied to its loop, which hopefully ionizes any gas molecules so that they'll react with the shiny chemical "getter flash" painted on the inside of the tube. This is how a tube maintains a clean vacuum over the life of the tube. When you see the getter flash stop being mirror-silver and start to turn white, the tube is worn out or worse - the glass is broken somewhere and the vacuum has been irreparably ruined. Quote:


 
 I think that's it. I'm hoping new transistors will fix my issues, if they don't I'll post pictures.


----------



## madelvice

Replaced Mosfets, no luck.

 Current situation:

 -that same 'heartbeat' spike when the switch is on. Except this time instead of jumping from zero up high it's got a constant voltage and then jumps a little. It's also more frequent.

 -I read no voltage at the output jack, yet I hear the clicking sound (associated with the voltage spikes)

 -Other than that weird clicking there's no sound.

 -Every voltage I measure (with the exception of the power input) is pretty weak. Under 10V usually. 

 There's a picture of the whole thing and here are some links to some closer shots. Picasa Web Albums - Matt - Starving Stud...

 By the way, those two green bundles are connecting the grounds.
 Speaking of which, I'm using a Rat shack chassis and grounding to the metal bottom plate. I can't get anything to solder to it though, any hints?


----------



## Fred_fred2004

You might be better to get a board and start again
 that looks a little scary
 good luck


----------



## Llama16

Yeah I'm sorry to tell you this, but it looks like a bug explode in there.
 I'd say try thing over, check every wire before continueing.


----------



## tomb

Well, it may look a lot worse due to the photo. See if you can get us one without as much glare and maybe we'll be able to tell what's going on.

 As for attaching the ground to the plate - solder your wires to a flat washer, then drill a hole in the plate and use a screw and nut to clamp the washer to the plate. Scrape the metal all around the hole where the washer contacts to ensure that some coating/oxidation doesn't insulate the connection to the washer. Use a couple/several washers if necessary and put them on both sides of the plate.


----------



## madelvice

Well, I think I may be putting this project on hold. At this point my materials have been soldered, re-soldered, and are building up a fluxy residue. I think perhaps the best thing to do is to order the kit. I have a feeling that it will turn out nicer and will be a smoother experience. In the meantime I'll build the bantamDAC from the kit, build up on my skills, and have something to occupy me until the amp kit comes. Thank you, especially to TomB for all your help. I will be back again before the summer's end. Either for more help or with triumphant pictures and happy ears.


----------



## JamesL

I have a question.
 When a capacitor fails due to excessive heat, does it block all current, or does it usually short circuit?

 I'm letting my brother use the one I have right now, but if theres even a small chance that the coupling caps will short circuit, I'd rather just make another one. I made the mistake of thermally-adhering the heatsinks to an small, all-aluminum case, and the case turns into a easy-bake oven.

 Its been working fine up until now (and sounds absolutely wonderful might I add), but better safe than sorry =/


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I have a question.
 When a capacitor fails due to excessive heat, does it block all current, or does it usually short circuit?

 I'm letting my brother use the one I have right now, but if theres even a small chance that the coupling caps will short circuit, I'd rather just make another one. I made the mistake of thermally-adhering the heatsinks to an small, all-aluminum case, and the case turns into a easy-bake oven.

 Its been working fine up until now (and sounds absolutely wonderful might I add), but better safe than sorry =/_

 

Guess I've been lucky to only blow one capacitor so far in my short DIY career.
	

	
	
		
		

		
			





 When it blew, it shorted as best as I can remember, but I think it can go either way. Generally speaking, the electrolyte starts oozing out everywhere and since that's electrically conductive, it causes the short.

 When I blew mine, it was over-voltage. I don't really know what they do when they're exposed to too much heat, except that the performance can no longer be guaranteed. Just a guess, but perhaps they slow bake to a horrible performance level.


----------



## Tritonpad

Hello guys ^^

 Now that my order is ok, I would like to get some informations about the stuff you use to make your DIY amp... Particularly, what do you use to solder ? Is there a suggested power in watts for the "solder tool" (I don't know how to translate it from French ^^ In French it is "Fer à souder")... Also is there a suggested "tin" (Is it well translated ??)

 Thanks a lot in advance !


----------



## rshuck

Tritonpad:
 My guess is that based on this question, you have no DIY experience. In that case, I would suggest an adjustable iron and rosin-core solder. The rosin helps the solder to flow easier, which means you will spend less time with your soldering iron on the joint which is a good idea.

 If you don't want an adjustable soldering iron, I suggest 30 watts at the most to avoid doing damage to components. You may also choose to use silver bearing solder if you want.

 Hope this helps.


----------



## Tritonpad

Thank you for that ^^

 Yes it helps ^^ Even if I am not completely new in soldering... I just want to be sure not to "kill" something... We are dealing with nice sounds around here and I know the soldering is important...


----------



## tomb

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Thank you for that ^^

 Yes it helps ^^ Even if I am not completely new in soldering... I just want to be sure not to "kill" something... We are dealing with nice sounds around here and I know the soldering is important..._

 

I am totally sold on Hakko soldering irons. The Hakko 936 adjustable is a particular favorite around here. It can be purchased for less than $100 at most places. Often, you can find a deal for one that includes several different tips for that price as well. I've seen them as low as $50 at Fry's, where I bought three of them.
	

	
	
		
		

		
		
	


	




 If you don't want to spend that much right now, their Hakko DASH irons are some of the best basic soldering irons I've seen. The 15W (#N452JN-V12) is probably all you'll ever need. I got the 20W (#N453JN-V12) and it's fantastic. The extra power is a little hot for PCB's, but it comes in handy if you're working point-to-point or with perfboards and cases. I think you can get one of these for $30 or less. They are well worth the slight extra expense over the cheap pencil-type soldering iron. The tips are quite special on these irons and seemingly last forever with proper care.

 For solder, get some "Eutectic" - a 63/37 mix of tin/lead with a rosin core. That's the proper ratio to ensure even melting between solid/liquid. Just the use of this solder alone will make your solder joints look professional.
	

	
	
		
		

		
		
	


	




 Something in the 0.30-0.025 in. dia. range is probably best. Thicker just gets in the way of everything and smaller diameters break too often.


----------



## Tritonpad

Once again Tomb, I must say THANK YOU ^^

 Actually I have to say that if you were not around here, I would have passed away without trying building SSMH...
 Now that the SSMH kit is ordered, I can hardly wait !


----------



## tomb

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Once again Tomb, I must say THANK YOU ^^

 Actually I have to say that if you were not around here, I would have passed away without trying building SSMH...
 Now that the SSMH kit is ordered, I can hardly wait ! 
	

	
	
		
		

		
		
	


	


_

 

That's very kind of you to say that! Hopefully, you won't change your opinion once you start building one.


----------



## brucegseidner

It has been a very long time since I have fired up my soldering iron and made anything. If memory serves it was an early 80's Hafler. My knowlege of power supplies is therefore dated. I remember raiding surplus shops and Ham Fests for very large iron - transformers/chokes and enormous blue caps that could power the oven for a half hour after being unplugged.

 Long story short, I think I have goofed up by purchasing a switching power supply in anticipation of building my SSMH. I bought first and am asking questions later. I am learning that these are very sophisticated little buggers and appear not to take kindly to output "filtering" or further regulation. I got a new MEANWELL SR-25-48 48VDC trolling on Ebay and while it is impressively stable in terms of voltage, the max ripple is 200mVp-p.

 I am new to these forums and my searches have been like going down rabbit holes. I have been looking for filtering strategies and loading strategies that would optimize a SMPS for this SSMH amp. I think I have painted myself in a corner having only 48VDC coming out of this power supply.

 It may end up a cute paperweight but if someone could direct me to information or strategies to clean this DC up I would be much obliged.

 Bruce


----------



## tomb

Quote:


  Originally Posted by *brucegseidner* /img/forum/go_quote.gif 
_It has been a very long time since I have fired up my soldering iron and made anything. If memory serves it was an early 80's Hafler. My knowlege of power supplies is therefore dated. I remember raiding surplus shops and Ham Fests for very large iron - transformers/chokes and enormous blue caps that could power the oven for a half hour after being unplugged.

 Long story short, I think I have goofed up by purchasing a switching power supply in anticipation of building my SSMH. I bought first and am asking questions later. I am learning that these are very sophisticated little buggers and appear not to take kindly to output "filtering" or further regulation. I got a new MEANWELL SR-25-48 48VDC trolling on Ebay and while it is impressively stable in terms of voltage, the max ripple is 200mVp-p.

 I am new to these forums and my searches have been like going down rabbit holes. I have been looking for filtering strategies and loading strategies that would optimize a SMPS for this SSMH amp. I think I have painted myself in a corner having only 48VDC coming out of this power supply.

 It may end up a cute paperweight but if someone could direct me to information or strategies to clean this DC up I would be much obliged.

 Bruce_

 

Pete Millett strayed from conventional DIY-headphone-amplifier wisdom with his use of a switching power supply for the Starving Student. It's worked quite well, but there is little data of successful use of switching power supplies for headphone amps beyond that (AFAIK).

 The Cisco PSA18U is the specified power supply for the Starving Student. It's spec'd for 48VDC at 0.38A and performs quite well in the Starving Student. As a VoIP telephone power supply, it's also ubiquitous on ebay and other places, and very inexpensive - sometimes even turning up in surplus and used sales at some outlets.

 Short of that recommendation, you are probably best to pursue a linear-regulated power supply for headphone amps. The simplest of these start with an LM317 (TO-220 style) voltage regulator with a bank of electrolytics for filtering and the parts recommendation as provided in National Semi's datasheet for the LM317. Tangent's TREAD (Tangentsoft) is probably the simplest PCB version of such a circuit and can be powered with a simple AC walwart. You can easily achieve ripple values of less than 1mV with this (~55uV?). Other more sophisticated designs include Tangent's new Young-Jung Power Supply and AMB's Sigma 11 and Sigma 22 and the ripple is in single-digit microvolts with those. Cetoole and I achieved 45uV in the Millett MiniMAX's onboard power supply as well - using the LM317 circuit as a basis.

 However, we often caution everyone in this thread to think twice before expanding on the Starving Student's design. After all, the low cost is a primary design feature. The PCB version increased costs with the addition of the PCB and the custom case from Hammond, but those are mostly structural changes for convenience in building. Dsavitsk applied a couple of new additions to the actual circuit on the SSMH PCB, but these amounted to a couple of pennies's worth of resistors and a couple of dollars for a couple of cathode bypass caps and output bypass film caps. The changes are well worth incorporating and definitely make the amp sound better, but are trivial in cost and added building effort.

 Note that we still recommend the same power supply for the PCB version, however - the Cisco PSA18U.


----------



## yebisu

I've spent a lot of time going over my connections and it looks ok, but I'm not sure why my MHSS still isn't working. I've desoldered and resoldered it to clean it up a little (it's still messy =\), but no luck. Can anyone see what I've done wrong? Thanks!

Flickr: andrewphan86's Photostream


----------



## tomb

Quote:


  Originally Posted by *yebisu* /img/forum/go_quote.gif 
_I've spent a lot of time going over my connections and it looks ok, but I'm not sure why my MHSS still isn't working. I've desoldered and resoldered it to clean it up a little (it's still messy =\), but no luck. Can anyone see what I've done wrong? Thanks!

Flickr: andrewphan86's Photostream_

 

Well, I spent a good while looking at this and you may have the tubes hooked up correctly, but it takes a while trying to trace the wiring in your photos - having the wire all in one color doesn't help, unfortunately.
	

	
	
		
		

		
		
	


	




 I can't find R13, but I'm not sure that means anything other than I can't trace the circuit. One thing - aren't the studs only connected to one tab on each of the terminal strips? If so, then it doesn't look like your star ground is connected to ground. All of your leads go to one tab on the terminal strip, but the other tab is connected to the stud. There doesn't appear to be anything connecting the two tabs, so that would mean the star ground is not grounded?


----------



## yebisu

I accidentally used the wrong stud for the star ground, so I connected that star ground tab to the power jack ground. I also isolated the other tab (with the stud) from the case. R13 is hidden under some heat shrink =\ Thanks for you help! I'll keep going through it to see what I did wrong


----------



## tomb

We're past the date where we can add more cases to the original order to Hammond. We currently have 2 kits (with cases) left and 9 individual cases left. That's it. After we ship, we'll re-assess and see if it's worthwhile to order another round of custom cases.

 Meanwhile, the PCB's and PCB+tubes are still available without restrictions.


----------



## tomb

I've gotten a couple of e-mails about the timeline for delivery. That's a very fair question and you all have a reasonable expectation to be kept up-to-date on the timeline. So, maybe I should post it here to remind everyone and inform the newest to come to this thread.

 The cases cannot ship until they are manufactured and delivered by Hammond Mfg. The cases were "officially" ordered on the 8th (they received my check). Add to that their 6-week lead time. So, I’m expecting shipment from Hammond on July 20th. However, the cases will take a few days to get to me. Plus, I will be out of country that week until the 25th. So, I would expect to ship most of them out during the week of July 27 – 31.


----------



## cegras

I ordered a full kit - I'm guessing the whole thing will ship together by the end of July?


----------



## tomb

Quote:


  Originally Posted by *cegras* /img/forum/go_quote.gif 
_I ordered a full kit - I'm guessing the whole thing will ship together by the end of July?_

 

From the post above yours, "So, I would expect to ship most of them out during the week of July 27 – 31."


----------



## cegras

; ) I figured.


----------



## tomb

Quote:


  Originally Posted by *cegras* /img/forum/go_quote.gif 
_; ) I figured._

 

Yes, everything will be shipped together unless you ordered things separately.


----------



## gore.rubicon

Quick Q how many kits are left, and if a Canadian was to order one in what ballpark can would i need to pay customs?


----------



## rds

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Quick Q how many kits are left, and if a Canadian was to order one in what ballpark can would i need to pay customs?_

 

If you use USPS just taxes. GST and PST.


----------



## tomb

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Quick Q how many kits are left, and if a Canadian was to order one in what ballpark can would i need to pay customs?_

 

Looks like the last of the kits got sold last night.
	

	
	
		
		

		
		
	


	




 As I stated earlier, let's see how this all works out with the custom cases and getting these delivered to everyone. Then I'll compare that with the remaining stock of tubes and see whether it's realistic to go another round.

 The PCB's and the PCB + tubes are still available - as are the custom cases ... just not combined into a kit.


----------



## CaptHowie

I've been browsing on this thread for months now (i think i posted a fair bit between pages 100-210 or something) but school holidays are on and i'm looking at doing a point to point build since the PCB's and stuff are too hard to get ordered down to Australia, plus there's that 6-week lead time on the cases. 
	

	
	
		
		

		
		
	


	




 Anyway, one thing I can never quite get is how to connect up the heatsinks. I'm looking at using a CASE HB5970 [JAYCAR] JAYCAR ABS BOX (jaycar.com.au) or similar with HEATS HH8526 [JAYCAR] JAYCAR HEAVY-DUTY TO-3P HEATSINK (ML97 TYPE) [$X2] heatsinks (search the codes on jaycar.com.au). Do I need these mounting kits? How do I connect the heatsinks to the case, and how do I mount the MOSFET's? I'm finalizing the BOM now, and i'll post it soon if you would like to check it. It would be greatly appreciated.

 Thanks,
 -CaptHowie


----------



## nullstring

So, I am getting ready to order parts from mouser.

 The mounting kit used originally is out of stock. 532-4880
 Does it matter which kit is used? will 532-4880M or 532-4880SG work fine?
 Or should I get one from beezar? (which one?)

 He included bare PCB in his original list.. Should I get this?
 Is it worth the $4 to not have to wire the ground?

 Lastly, anyone have any recommendations for the heatsink used?
 I couldn't really find anything cool on mouser, so I've given up and am using the original one (I think it looks better than tomb's)

 I am gonna upload the list for anyone interested.

 EDIT: adding keyword BOM, so I can find the damn post again next time


----------



## ShinyFalcon

Quote:


 Standard kit contains Thermalfilm insulator. For high maximum operating temperatures (550°C), order a mica insulator by adding suffix letter "M" to the part number. For electrical isolation and excellent thermal resistance, use In-Sil-8 for an insulator by adding suffix letter "S' to the part number. 
 

I think I remember buying 4880 (Thermafilm) for my M³, and this time I bought the SG (Thermasil) for my Beta. The SG seems better and cheaper too. Apparently grease is needed for the Thermafilm, read this article here.

 I never liked point-to-point, so if you're prone to mistakes I think the PCB is worth it.


----------



## nullstring

Sounds good, thanks.

 That article is just what I needed.

 I guess I'll get the PCB. I am trying P2P once to see what it's like.

 EDIT: the 532-4880 is suppose to cost .77 according to their catalog. Must be some sort of backorder pricing.


----------



## ShinyFalcon

I'll probably do some point-to-point myself, but with really small components, which was what my opinion was directed at. If the parts are big like the Starving Student I think point-to-point is fine.


----------



## tomb

Quote:


  Originally Posted by *ShinyFalcon* /img/forum/go_quote.gif 
_I'll probably do some point-to-point myself, but with really small components, which was what my opinion was directed at. If the parts are big like the Starving Student I think point-to-point is fine._

 

There's a case to be made that a PCB-version of a circuit will always perform better than a point-to-point - simply because quality control in the circuit layout is assured. Shorter traces and proper grounding with a ground plane also means that a PCB version will perform better in most instances. If good grounding is used and wiring lengths are organized and run in the optimum way, then a point-to-point should be equivalent. However, the "if" is the key.


----------



## nullstring

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's a case to be made that a PCB-version of a circuit will always perform better than a point-to-point - simply because quality control in the circuit layout is assured. Shorter traces and proper grounding with a ground plane also means that a PCB version will perform better in most instances. If good grounding is used and wiring lengths are organized and run in the optimum way, then a point-to-point should be equivalent. However, the "if" is the key.
	

	
	
		
		

		
			



_

 

sometimes performance isn't everything though.

 maybe it'll be perceived better because someone feels accomplished in making a P2P version instead of taking the easy way out. 
	

	
	
		
		

		
		
	


	




 I don't think anyone is trying to say that P2P is better.


----------



## smeggy

Do both, it's more fun all around


----------



## kuroguy

Yes, and while you're at it build one with the premade chassis and scratch build the chassis for the P2P version.


----------



## Robot

I hope this is a right place to post this, but I have some questions about tomb's pcb's:

 So, this build originally has no panel LED's installed, am I right? And secondly: how are those tube sockets installed? Are they just soldered, or also need some wiring to the board?


----------



## nullstring

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Yes, and while you're at it build one with the premade chassis and scratch build the chassis for the P2P version._

 

I'm using a tin that a fossil wallet came in.


----------



## tomb

Quote:


  Originally Posted by *Robot* /img/forum/go_quote.gif 
_I hope this is a right place to post this, but I have some questions about tomb's pcb's:

 So, this build originally has no panel LED's installed, am I right? And secondly: how are those tube sockets installed? Are they just soldered, or also need some wiring to the board?_

 

We are not recommending a panel LED for the SSMH PCB and custom case. Of course, you are welcome to drill a hole in the front panel and install one on your own, but I didn't feel that the PCB, power supply, etc., was well suited to using a panel LED - especially after using the tube LED's.

 If you look at the pics of my prototypes - they both have panel LEDs, but the one for the black case SSMH doesn't work and isn't wired up. My silver SSMH has a panel LED that works, but it doesn't have tube LEDs. Without going into gory details, I couldn't get things to work when using both - only one or the other. Since the PCB has the positions/holes for the tube LEDs, going with the tube LEDs only - instead of a panel LED - was a better choice for the custom cases. Note that you still have to drill out the center pins in the tube sockets, however. Drilling tube sockets and gluing them back together is described on all of the Millett MAX websites. I'll add it to the SSMH site when I get a chance.

 The tube sockets themselves are "PCB" tube sockets, with pins fashioned to fit into the holes on the PCB. They are simply soldered - no wiring involved. The design of the SSMH PCB requires a bit of wiring for the tube LEDs, though.
	

	
	
		
		

		
		
	


	




 P.S. Just an FYI, but they are "Dsavitsk's PCBs", not mine.


----------



## hislorduberdude

Hello all!

 First post after reading this entire thread and getting the know-how to construct my own Starving Student. 

 I gave up on finding 19J6, and went with the option discussed several pages ago to use 12SR7 tubes instead. Works like a charm, and I honestly can't see why so many people are scrambling to find 19J6 tubes when so many other tubes that run on a more standard 12.6 volts are available. 

 Anyhow, here's my scratch build in a Hammond 1590C...sounds beautiful.


----------



## smeggy

Nice, looks very 'sci-fi film prop' very cool and good to see another 12SR7build.


----------



## smeggy

dbl post


----------



## yebisu

I have another neutrik jack that I want to use with the PCB from tomb. It's this one, NYS230 

 Is it possible to connect this in place of the 6-pin that the PCB is designed for? How would I connect it?


 This is the one in the Beezar build, NMJ6HCD2


----------



## JamesL

Quote:


  Originally Posted by *yebisu* /img/forum/go_quote.gif 
_I have another neutrik jack that I want to use with the PCB from tomb. It's this one, NYS230 

 Is it possible to connect this in place of the 6-pin that the PCB is designed for? How would I connect it?


 This is the one in the Beezar build, NMJ6HCD2_

 

It looks like the PCB-mount one is a switching jack, but its shorted on the PCB anyways.

 Wire the frontmost pair of holes to the ground tab on the jack(not really necessary if the jack isn't isolated), the middle two holes to the right channel tab, and the pair of holes at the back to the left channel tab.
 (use either of the two holes)

 If you can see the mechanism of the jack, plug a TRS plug in and see which of the tab connects to the tip... that one is the left channel. The outermost tab is usually the ground, and the other one is the right channel.


----------



## yebisu

thanks James! I'll try that


----------



## yebisu

I finished my PCB build and it works! at least one channel does...

 The right channel kinda works, but it sounds muted, and there is a loud background hiss. The hiss gets loud when I put my hand near the tube, and I'm hearing microphonics, too, I think. All this is only on the right tube and right channel. Left seems perfect. 

 Should I check my grounds or something? I'm not sure how to troubleshoot with the PCB. Any help would be appreciated. Thanks!


----------



## yebisu

nevermind! it was a loose joint on my pot. now everything's working!


----------



## Logistic

Nice build! It's nice to see another 12sr7 starving student. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *hislorduberdude* /img/forum/go_quote.gif 
_Hello all!

 First post after reading this entire thread and getting the know-how to construct my own Starving Student. 

 I gave up on finding 19J6, and went with the option discussed several pages ago to use 12SR7 tubes instead. Works like a charm, and I honestly can't see why so many people are scrambling to find 19J6 tubes when so many other tubes that run on a more standard 12.6 volts are available. 

 Anyhow, here's my scratch build in a Hammond 1590C...sounds beautiful.









_


----------



## Robot

HELP!

 I've finally built my SSMH, but it isn't working. Nor tubes glow, nor caps emit heat. Does anybody see where the problem might lie?

http://i44.tinypic.com/vcw13l.jpg

http://i43.tinypic.com/2z6w55d.jpg

http://i43.tinypic.com/r9kaxi.jpg


----------



## tomb

Quote:


  Originally Posted by *Robot* /img/forum/go_quote.gif 
_HELP!

 I've finally built my SSMH, but it isn't working. Nor tubes glow, nor caps emit heat. Does anybody see where the problem might lie?

http://i44.tinypic.com/vcw13l.jpg

http://i43.tinypic.com/2z6w55d.jpg

http://i43.tinypic.com/r9kaxi.jpg_

 

It could be a couple of things:
 1. I don't see any insulating pads under those MOSFETs. If they're not there, you've shorted the MOSFET tabs to ground - not a good thing.

 2. There seems to be quite a few tabs on the power input jack. It's possible you haven't connected to the truly "live" terminals. Do you have 48VDC at the terminal block on the board?


----------



## Robot

EDIT: I've got it to work, however it's hissing as a snake and I seem to be getting metallic sound when I'm touching the pot, also some metallic sounds in the background of hiss. hmm.. Any ideas how to fix this?


----------



## tomb

Quote:


  Originally Posted by *Robot* /img/forum/go_quote.gif 
_EDIT: I've got it to work, however it's hissing as a snake and I seem to be getting metallic sound when I'm touching the pot, also some metallic sounds in the background of hiss. hmm.. Any ideas how to fix this?_

 

This is not telling us much - exactly what did you change? Obviously it's not working. The board has been thoroughly vetted, so it must be something in the connections.

 Did you insulate those MOSFETs?
 Did you check those input connectors?

 It looks like you don't have a resistor installed at R16, but you have one at R17 - that will mess things up tremendously with the pot.

 About that center standoff - what's underneath it? There is very little clearance around that center hole. If you used a large nut or washer, it's liable to be shorting against the adjacent traces.


----------



## tomb

Sorry for all the questions, but we need more feedback from you before suggesting a fix.


----------



## Robot

Hmm, it's now working perfectly, no more hiss is present!

 At first, as you suggested, I insulated the mosfets. Then I somehow managed to connect the power input right and all powered up. As might you know, then I experienced hiss, but when I swapped tubes, it started working like a champ!

 Hmm, you're right, R16 doesn't have a resistor installed, but my pot seems allright at the moment - it has some hiss at very high volumes, but is silent at listening levels.
 The standoff has nothing but some free space underneath it. The center hole is fixed with just a bolt and a nut, without any washers.
 By the way, the voltage at socket pins is ~21V, and at mosfet pins it's ~30V, so I guess there are some blemishes, that need fixing.

 At the moment the amp is burning in, and the sounds coming from it are superb, except one flaw: it has pretty shrill highs at the moment, but I hope it will mellow out in time


----------



## tomb

Quote:


  Originally Posted by *Robot* /img/forum/go_quote.gif 
_Hmm, it's now working perfectly, no more hiss is present!

 At first, as you suggested, I insulated the mosfets. Then I somehow managed to connect the power input right and all powered up. As might you know, then I experienced hiss, but when I swapped tubes, it started working like a champ!

 Hmm, you're right, R16 doesn't have a resistor installed, but my pot seems allright at the moment - it has some hiss at very high volumes, but is silent at listening levels.
 The standoff has nothing but some free space underneath it. The center hole is fixed with just a bolt and a nut, without any washers.
 By the way, the voltage at socket pins is ~21V, and at mosfet pins it's ~30V, so I guess there are some blemishes, that need fixing.

 At the moment the amp is burning in, and the sounds coming from it are superb, except one flaw: it has pretty shrill highs at the moment, but I hope it will mellow out in time_

 

Well, it's good news that it seems to be working.

 I'd get that resistor in there at R16. It could have disastrous effects on the sound balance.

 It may sound shrill initially as the caps burn in, but I noticed you used 0.1uf Wima MKP10's. If I'm guessing right and that's what they are - you may lose some bass at the interstage coupling positions - that's where those caps are used to connect the tube stage to the MOSFETs. Less bass may make things sound a little more shrill. 0.1uf at the output bypasses will have negligible effects, but may sound less smooth than it could with 0.22uf's there.

 About the voltages - I'm still confused with your power input socket. I believe that's a three-pole switched socket, in which case one lug should remain disconnected. So, I'm wondering where the black wire is going.

 Glad you got it working, though!


----------



## Ares

I first would like to thank the forum for the wealth of information that allowed me to build this beautiful piece of hardware. However, I have a few questions.

 While my wiring is messy and my parts are budget, (carbon resistors, 610s instead of 510s, generic 180uF capacitors, 24AWG copper wire) the thing seems to function. 

 1) While the amp normally works well, and glows normally, sometimes after i mess around with the MOSFETs, one tube will glow like a 15W lightbulb and the other will stop glowing. This has never happened with headphones in and I always unplug it before it warms up to the full glow. What is going on here? I think i fixed it (rewired the MOSFETS to try to minimize shorts, but i am still curious). 

 2) With headphones pluged in and nothing playing, when i touch the side of the aluminum case that I used, a pinging micro-phonic is transmitted through the headphones. Originally, I had cold solder joints on the ground plate, i believe i fixed it (as the torrent of sound that came through the earpiece when i touched the case has stopped but the ping is still omnipresent). Is the ping still a grounding issue? 

 3) I have installed 2 switches into the case. Both times, I would plug in amp after the switch was installed and the amp would make a click and the switch would no longer work. Did the case (which is wired to ground) short with the 48V? What is going on? Why is my amp frying switches? 

 4) I need a new audio pot (the channels are off by about 15%); what is the cheapest pot that is within about 5% range. I would ideally like to spend less than $5. Many people recommend the ALPS RK27, but i cannot afford that. 

 5) I don't hear an audible click when the amp powers up. Therefore, is it safe to leave my headphones plugged in while turning the amp on? 

 Sorry if any of these were already answered, I tried my best to find answers but the post is so long and has so much information.


----------



## tomb

Quote:


  Originally Posted by *Ares* /img/forum/go_quote.gif 
_I first would like to thank the forum for the wealth of information that allowed me to build this beautiful piece of hardware. However, I have a few questions.

 While my wiring is messy and my parts are budget, (carbon resistors, 610s instead of 510s, generic 180uF capacitors, 24AWG copper wire) the thing seems to function. 

 1) While the amp normally works well, and glows normally, sometimes after i mess around with the MOSFETs, one tube will glow like a 15W lightbulb and the other will stop glowing. This has never happened with headphones in and I always unplug it before it warms up to the full glow. What is going on here? I think i fixed it (rewired the MOSFETS to try to minimize shorts, but i am still curious)._

 

No offense, but what is going on is not good. Having a tube flare up like that is caused by over-voltage applied to the heaters/cathode. It's a good way to burn the tube up. So, somehow messing with the MOSFETs is shorting the circuit to one of the tubes so that they're exposed to the full voltage (the tube heaters are in series, so in a correctly wired amp, they'll split the voltage between them).
  Quote:


 2) With headphones pluged in and nothing playing, when i touch the side of the aluminum case that I used, a pinging micro-phonic is transmitted through the headphones. Originally, I had cold solder joints on the ground plate, i believe i fixed it (as the torrent of sound that came through the earpiece when i touched the case has stopped but the ping is still omnipresent). Is the ping still a grounding issue? 
 

This has nothing to do with the case or cold solder joints. The pinging would not transmit unless the tubes picked it up and amplified it. That means one or both of the tubes is microphonic. Unfortunately, this is not something that can be tested for with a tube tester - only by putting the tubes in an amp can you tell that this condition exists. Any good tube vendor will replace a microphonic tube upon request, however.

 Just to be sure, swap the tubes and see if the pinging travels with one tube more than the other. 
  Quote:


 3) I have installed 2 switches into the case. Both times, I would plug in amp after the switch was installed and the amp would make a click and the switch would no longer work. Did the case (which is wired to ground) short with the 48V? What is going on? Why is my amp frying switches? 
 

The click you hear is in the Cisco power supply. It has an internal circuit breaker that will trip and then automatically reset itself when you unplug it from the shorted device. I doubt seriously that the switch has anything to do with it - most likely your first switch was OK. Reading above about your trouble with the MOSFETs would explain a lot - especially if this is an intermittent issue. Or, you may have a short somewhere else, too.
  Quote:


 4) I need a new audio pot (the channels are off by about 15%); what is the cheapest pot that is within about 5% range. I would ideally like to spend less than $5. Many people recommend the ALPS RK27, but i cannot afford that. 
 

I've not had any trouble with the Alpha pots once you apply the input resistors, but I know people have complained about them. Unfortunately, there's nothing much available under the RK27. The RK097 is a good option, but I've heard just as many complaints about channel mismatching with that one, too.
  Quote:


 5) I don't hear an audible click when the amp powers up. Therefore, is it safe to leave my headphones plugged in while turning the amp on? 
 

Not necessarily. It's possible that the stuttering/slow turn on is enough of a delay by itself to prevent any offset from occurring at the headphone jack.

 However, the best thing for you to do is to measure the voltage relative to ground at the headphone jack connections when you power it up. That'll tell you very quickly if there are voltage levels high enough to damage your headphones.
  Quote:


 Sorry if any of these were already answered, I tried my best to find answers but the post is so long and has so much information. 
 

No problem - hope this helped!


----------



## Ares

Thank you very much. 

 Is it possible that one tube may have glowed extremely hot if the interconnect between the two tubes is loose. Most notably, the wire between R13-R1 and C6? When forcing the MOSFETS up, I placed unnecessary strain on this wire. I think that is what was causing all that falderal. 

 Only my left tube is microphonic; however, my rights as a tube customer are severely mitigated because I purchased the tubes on Ebay. Should I just buy another? (the left one was the one I was heating up anyway)

 The first switch was actually fried (when testing it with a multimeter, outside of the case, the switch always read 0ohms instead of Lo). However, the replacement switch appears to work- today. 

 One last thing. At times, when i unplug the headphone jack, a large amount of sound comes through the jack (no louder than the music playing, but louder than most amps i have used). Is this normal? It has appeared to have stopped, for the most part; nevertheless, I am still curious. 

 I am now cautiously enjoying my new toy. Thanks again.


----------



## tomb

Quote:


  Originally Posted by *Ares* /img/forum/go_quote.gif 
_Thank you very much. 

 Is it possible that one tube may have glowed extremely hot if the interconnect between the two tubes is loose. Most notably, the wire between R13-R1 and C6? When forcing the MOSFETS up, I placed unnecessary strain on this wire. I think that is what was causing all that falderal._

 

Nope - that wouldn't have anything to do with it. Most likely, the wiring going from MOSFET pins 3 to the #3 and #4 pins on the tube sockets - those are the heaters.

  Quote:


 Only my left tube is microphonic; however, my rights as a tube customer are severely mitigated because I purchased the tubes on Ebay. Should I just buy another? (the left one was the one I was heating up anyway) 
 

It depends on how much of a nuisance it is to you. Microphonics rarely effect the sound quality of the tube - as long as you don't rap the amp or the desktop on which it sits. Some microphonics can be so bad that you hear a squeal just looking at the amp, others are so trivial as to become a minor nuisance. You'll have to decide yourself whether it's worth keeping the tube or not.

 You can also try some tube rings - they can generally make a wildly microphonic tube listenable, or a slightly microphonic tube almost normal. However, the results can be inconsistent - YMMV.

  Quote:


 The first switch was actually fried (when testing it with a multimeter, outside of the case, the switch always read 0ohms instead of Lo). However, the replacement switch appears to work- today. 
 

OK. Still, the original "click" you heard was most likely the overload protection in the Cisco power supply. I'm pretty familiar with that sound 
	

	
	
		
		

		
		
	


	







 and it does sound like it's coming right from the amp sometimes.
	

	
	
		
		

		
		
	


	



  Quote:


 One last thing. At times, when i unplug the headphone jack, a large amount of sound comes through the jack (no louder than the music playing, but louder than most amps i have used). Is this normal? It has appeared to have stopped, for the most part; nevertheless, I am still curious. 
 

You got me on this one. What kind of sound? Quote:


 
 I am now cautiously enjoying my new toy. Thanks again.


----------



## dean0

x2 19J6 Valves for sale here;
http://www.head-fi.org/forums/f42/f-...i-more-433620/


----------



## liltehood

is it possible to use this as preamp?


----------



## nullstring

Quote:


  Originally Posted by *liltehood* /img/forum/go_quote.gif 
_is it possible to use this as preamp?_

 

I recommend you try searching the thread.
 I believe a user named -=Germania=- wanted to use it as a preamp at one point.

 Others told her it was a bad idea. I think the gain is too high in this amp for it to be used as a preamp, but you should go look


----------



## liltehood

is it possible to change that?


----------



## tomb

Quote:


  Originally Posted by *liltehood* /img/forum/go_quote.gif 
_is it possible to change that?_

 

Use input resistors around 4 times the pot impedance and that should work. One of the production SSMH's I built uses a 10K pot with 39K input resistors. It's gain/volume travel is similar to a low gain suitable for pre-amping purposes.

 There's another issue that's more of a concern, though, and that's the lack of delay-relay. Since the tubes throw out DC in full whole-number volts before the amp and output caps come up to speed, the result could be some lethal thumps in your speakers if it's connected to a power amplifier during that time.


----------



## liltehood

hm, i just noticed that it is impossible to buy 19j6 tubes in germany, so i have to find something different


----------



## DanielCox

I'd love to build this amp but I don't have a lot of spare time - I work long tiring hours and don't really have the time or will to go through the RS Components website looking for the stuff I need - never mind trying to find the tubes.
 That said is there a website/someone in the UK selling the components needed (and maybe a case) in a bundle. I'd accept a US/EU site for a small shipping fee.


----------



## PJPro

tomb, any update on the progress of the complete kit? Is the end of July still the target date for shipment?


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There's another issue that's more of a concern, though, and that's the lack of delay-relay. Since the tubes throw out DC in full whole-number volts before the amp and output caps come up to speed, the result could be some lethal thumps in your speakers if it's connected to a power amplifier during that time.
	

	
	
		
		

		
		
	


	


_

 

Yes, as a preamp, you need to power off the power amp when turning the Starving Student on, or off. You can damage speakers in addition to the power amp. Also, if it is a preamp only, change the output caps to ~4u film caps.


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_tomb, any update on the progress of the complete kit? Is the end of July still the target date for shipment?_

 

Well, I came back this weekend after being out of town and found the test copy of the Hammond case waiting for me. I measured and re-measured all the holes over the weekend and sent a note to Hammond yesterday that the case is approved.

 So, I think we're still on track - probably shipping to you guys during the week of the 27th unless you hear otherwise.

 One thing a tiny bit disappointing about the Hammond work - and it's only a little bit - the anodizing is before machining. That's probably one reason why the price for the cases is so reasonable. Of course, it has little effect except on the tube holes - all the other holes will be covered by the connectors/volume knob/heat sinks/etc. I suspect that it will go largely un-noticed there, too. Keep in mind that when you build one, there's some variance in how the sockets are soldered to the PCB, so chances are they won't be perfectly centered. Again, just a minor detail in the interests of full disclosure.
	

	
	
		
		

		
		
	


	




 I'll post some pics of the basic machined case tonight.


----------



## Drumonron

I just purchased a starving student millet mini hybrid from whiplash audio...looking forward to my first tube amp...especially interested in how this will work with the Grados!

 oops...sorry, realized now this is the diy forum...sorry for breakin' in.


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, I came back this weekend after being out of town and found the test copy of the Hammond case waiting for me. I measured and re-measured all the holes over the weekend and sent a note to Hammond yesterday that the case is approved.

 So, I think we're still on track - probably shipping to you guys during the week of the 27th unless you hear otherwise.

 One thing a tiny bit disappointing about the Hammond work - and it's only a little bit - the anodizing is before machining. That's probably one reason why the price for the cases is so reasonable. Of course, it has little effect except on the tube holes - all the other holes will be covered by the connectors/volume knob/heat sinks/etc. I suspect that it will go largely un-noticed there, too. Keep in mind that when you build one, there's some variance in how the sockets are soldered to the PCB, so chances are they won't be perfectly centered. Again, just a minor detail in the interests of full disclosure.
	

	
	
		
		

		
		
	


	




 I'll post some pics of the basic machined case tonight._

 

i can't remember if this has been discussed but i'm assuming the tube holes in the hammond cases will fit the plastic ring that the pictures on beezar show? that way it should cover up the anodizing that you mention


----------



## nullstring

so, I ordered the PC mounting sockets from beezar without realizing that these are going to be tough to mount. I am doing a P2P build.
 Does anyone know if I could get the mounting brackets somewhere... or if there is something I could use to replace them?

 If there is a store somewhere with cheap sockets and shipping.. let me know about that too.

 Another thing is.. There is no hole in the center of the tube socket.
 How exactly is the light from the LEDs suppose to shine up to illuminate the tube.


----------



## dsavitsk

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_I am doing a P2P build.
 Does anyone know if I could get the mounting brackets somewhere._

 

I've tried many times with no luck.

  Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_If there is a store somewhere with cheap sockets and shipping.. let me know about that too._

 

Any tube dealer should have them.

  Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Another thing is.. There is no hole in the center of the tube socket. How exactly is the light from the LEDs suppose to shine up to illuminate the tube._

 

I believe Tomb has instruction on his site somewhere.


----------



## nullstring

Which means I have to get new tube sockets.... great..
 Most tube dealers seem to seem to charge high shipping. =(


 I did find the guide about the LEDs


----------



## lynxkcg

I have a bad habit of impulse buys on ebay. I picked up a whole bag of green pcb mount tube sockets last year if anyone's interested. Shouldn't cost too much shipping.


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_i can't remember if this has been discussed but i'm assuming the tube holes in the hammond cases will fit the plastic ring that the pictures on beezar show? that way it should cover up the anodizing that you mention_

 

Nope - the bushings are used for manually-punched holes that don't leave a very clean edge. The tube holes on the custom-Hammond case are 3/4" diameter - they will fit pretty close. I doubt seriously that anyone will notice. The holes that Hammond have made are so clean and the edge is so thin, that it won't make much difference. Note that manual punching stretches the edge of the holes and makes the edge thicker. Besides, one expects a perfectly shaped/finished hole when having the mfr do the the machining, so we don't plan for the need of hole bushings.
	

	
	
		
		

		
		
	


	




 Anyway, I only mentioned the un-anodized edge in the interests of full disclosure.

  Quote:


 If there is a store somewhere with cheap sockets and shipping. let me know about that too. 
 

Ebay is a good place if you're looking for P2P sockets - try Cascade Surplus under ebay sellers. I believe they have a website, too. You'll probably have to order more than two, but they'll still be pretty cheap.

  Quote:


 Another thing is.. There is no hole in the center of the tube socket. How exactly is the light from the LEDs suppose to shine up to illuminate the tube. 
 

Dsavitsk answered this and it appears that you found it. There are pages on each of the Millett MAX websites that detail how to drill the sockets then glue the two halves of the sockets back together. There are some extra wrinkles that must be done on the SSMH because the LED's don't have pads directly under the sockets and require wire leads. I'll try to detail this shortly. Suffice to say that you must go easy on the solder joints and heat shrink to the LED's or they won't fit through the drilled out center holes in the tube sockets.


 P.S. Sorry I don't have pics for the case yet - this is a very busy time for me at work and I've been staying late a lot.


----------



## nullstring

So, I realized that the mounting bracket probably won't help me that much either.. because I don't want to mount them to the top of the case..

 I am thinking of taking a small piece of PVC pipe and glueing it to the bottom of the socket... and then drilling a smallish whole in the side of it for the LED wires to go.
 EDIT: actually, just drilling a whole in the bottom of the copper clad board would make more sense.. I think..

 Does anyone think this will work?


 EDIT: Another idea is to get the new sockets with mounting brackets and use the PVC pipe idea without glue. Mount the brackets to the bottom using nuts and bolts.. having it stand on the PVC pipe.

 This would allow me to service the LEDs much easier.. hmm


----------



## tomb

There's been a cancellation, so there's one SSMH Kit + Case left.


----------



## jon743

---


----------



## tomb

Quote:


  Originally Posted by *jon743* /img/forum/go_quote.gif 
_Has anyone tried this with the 600ohm K240? I'm wondering what pot/resistor values to use - whether 10k or 50k would be better, or even the 10k pot with 40k resistors someone mentioned earlier. (I think it was TomB...) I've tried searching, but the best I found was about the DT-880, which, at 250ohms, has less than half the nominal impedance of the K240._

 

My guess is that the basic gain and voltage swing of the 19J6's in the Starving Student would be sufficient for the K240. Remember, there are some guys around here who've been using the SSMH to power some vintage orthos that probably exceed K1000 amp requirements.

  Quote:


 Also, any advice for values for an amp for ATH-AD700 and one for some Grados? (32 ohms) From what I've read, I think a 100k pot and resistors be best for these? 

 (Note that these are not all the same amp - I'm making one for myself and a couple for my brothers.)

 Oh, and thanks TomB for my pcbs and tubes! 
 

About the pot - try not to think in terms of the impedance of the pot having an affect on the gain. Rather, the impedance of the pot combined with any input resistors you might use represent an overall increase in input impedance seen by your source (more noise, less detail). Dsavitsk may argue with me on this one, but I don't think you'd want the overall input impedance - pot + input resistors - to go much over 100K ohms. That's sort of the limit we put on our headphone pot impedances around here. Now, if it went to 150K or so - that's probably fine. However, if you're looking at controlling gain with low impedance headphones and start out with a 100K pot, then putting input resistors at 2-3 times the pot value would quickly give you a total impedance of 300-400K ohms as seen by your source. That's too much, IMHO.

 So, low impedance/high efficiency phones - you might want a 10K pot and then 40K input resistors. The resulting total input impedance would be only 50K ohms, but you would have attenuated the gain by 4 times.

 Of course, you'd never want any input resistors with a 600K headphone. So, I'd use a 50K or 100K pot, period - nothing else.

 Finally, keep in mind that in my testing (I've lived with these two SSMH's for a couple of months now.), the 50K pot + 50K input resistors is the best balance for Sennheisers to Grado's. If you want something optimum for a single set of headphones, though - by all means try a different combination. 
	

	
	
		
		

		
			






 BTW - some of you have had trouble at Beezar with Paypal recently. I finally researched it today with the help of a customer. Turns out, Paypal changed the address of their payment server over the last few days.
	

	
	
		
		

		
		
	


	




 I confirmed this directly from Paypal and the same stuff was being reported on the OSCommerce support forums. Anyway - I've fixed the problem.


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## jon743

---


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## mugdecoffee

Quote:


  Originally Posted by *jon743* /img/forum/go_quote.gif 
_Has anyone tried this with the 600ohm K240? I'm wondering what pot/resistor values to use - whether 10k or 50k would be better, or even the 10k pot with 40k resistors someone mentioned earlier. (I think it was TomB...) I've tried searching, but the best I found was about the DT-880, which, at 250ohms, has less than half the nominal impedance of the K240.

 Also, any advice for values for an amp for ATH-AD700 and one for some Grados? (32 ohms) From what I've read, I think a 100k pot and resistors be best for these? 

 (Note that these are not all the same amp - I'm making one for myself and a couple for my brothers.)

 Oh, and thanks TomB for my pcbs and tubes!_

 

I have the 600ohm k240s and I used just a 10k pot that I had lying around. It worked perfectly well if I remember though it was a bit much for other headphones.


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## tomb

As promised (but a little late), here's a pic of the custom Beezar/Hammond SSMH case:




_[size=xx-small](Click for a bigger pic)[/size]_


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## tomb

It's getting about that time for the kits soon. I'll be out of the country (more or less) the next week, so I thought it was an appropriate time to post some stuff. This will give you all something to discuss while we're awaiting final shipment on the cases and following that, shipping your kits to you.
	

	
	
		
		

		
		
	


	




 Besides the case pictured in the post above, here's what will constitute a kit:



_[size=xx-small](Click for a very big pic.)[/size]_

 The power supply comes complete with an AC cord, but was too big to photograph here along with the smaller parts. The only thing that won't be included is that the sockets won't be drilled as shown here. You'll have to do that yourself.
	

	
	
		
		

		
		
	


	




 There have been several questions about how to do that - and questions about building the SSMH, in general. So, I'm going to build another one using the kit above and the sample case pictured above in a step-by-step fashion. All of this will be posted on the SSMH website, too.


 P.S. That's a machined aluminum knob, btw, and very hefty. Electroswitch makes some outstanding knobs for Mouser. It's just that they don't fit that well with the typical RK27. We don't have that problem, though, so this one works and looks great.


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## tomb

The first thing I do when building an amp with tube LED's - such as the SSMH, Millett Hybrid, MAX, MiniMAX, etc. is to drill the tube sockets. For one, you can't do that very well once soldered. Even if you could, chances are probably 1 in 4 that you'll break one. If it's already soldered to the board, that's bad.
	

	
	
		
		

		
		
	


	




 Second, it takes awhile for the glue to dry. So drill them out, glue them back together, and let them dry/cure while you start working on the PCB.

 Here's what the tube sockets look like before drilling:




 Some people are able to pull out the center pin from the bottom (there are two halves to the pin - the bottom one has a flange). However, I usually only succeed in tearing up the flange until there's nothing left for my pliers to grip.

 So I drill. Below shows a socket clamped between a couple pieces of pine in a drill vise on my trusty drill press. You don't need a drill press per se, but it's probably best to use some sort of vise to clamp the socket - gently - they are very easy to break.




 Take it slow and *don't push down forcefully!* Let the drill bit do its work. I use a 1/8" bit. Smaller than that and you may just succeed in drilling a very small hole all the way through both pieces of the center pin, but perhaps making them even harder to get out. Larger bits are just too much and will break the socket.




 Lift the bit out of the hole periodically to make sure you're not getting galling - the pins are very cheap pot metal and will easily melt to the bit if you let things get too hot.




 The idea is to let the drill cut through the top half of the pin, allowing the bottom half to fall out/push out, or something similar. If you're lucky, you may end up with what's shown below - the bit will simply grab the top half of the pin and pull it out on one of your periodic bit removals. If so, then you're done drilling!


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## tomb

Here's what we have after drilling two sockets. (I confess, I went through 4 sockets today to get these. I was too distracted taking photos.) You can easily see the two portions of the removed pins:




 OK - now that we've taken the pins out that held the two halves of the sockets together, we need to use something else that will bring the two halves together, but preserve the center hole. Epoxy works best for me. 15-minute is easily available at hobby shops and perhaps some craft stores. The bottles shown here are at least 5 years old. If stored in a cool place away from sunlight, they'll last a good long time. If you can't get the 15-minute kind, then use 5-minute epoxy - but be sure you're organized and work fast.
	

	
	
		
		

		
		
	


	




 Slower epoxies will dry more brittle and also ooze out of the socket until most of the glue is dripped out. It's important to use something that doesn't necessarily depend on soaking in, but cures with some flexibility. Don't use polyurethane glues - they will expand and get into the socket pins, ruining the sockets. Wood glues, on the other hand, will not soak into the grain-less ceramic, so they won't work either.

 To mix up the epoxy, I use a simple sheet of aluminum foil folded over several times to give some thickness. Then I use a toothpick to mix the two parts of the epoxy together. The first step is to squeeze out two same-size blobs next to each other. Be very careful that you don't let the tips of the bottles touch the goo on the aluminum foil, or you won't get anything out of that tip again.
	

	
	
		
		

		
		
	


	







 Next mix up the two parts until it's a single, contigous color and there are no streaks. Again, a toothpick works great for me:




 The clock's ticking on the cure rate now, so start applying the epoxy to the tube sockets. After much trial and error, I've decided that the best way to do this is by applying epoxy only to the bottom half. Use the toothpick to smear a tiny blob between each of the pins - a little more on the socket key. Try not to get any any on the tips of the pins (ruins the tube connections), or near the center hole (you won't be able to fit the LED through). If you happen to get some inside the pins, use another toothpick dipped in rubbing alcohol and push it into the pins a few times. Work fast, because the epoxy is curing all the time.




 Finally, very carefully fit the top half back onto the bottom half of each socket. Do this by lining up the keys that are molded into each half. Gently wiggle the top of the socket until the pins pop into place in each hole. Use rubber bands to clamp the socket halves together until the epoxy is cured. *Let the epoxy cure with the sockets standing up straight!* Otherwise, the epoxy may flow down into the pins, ruining them. Also, if you're in a hurry, this time of year things will speed up if you put the sockets out in the sun to cure.
	

	
	
		
		

		
		
	


	







 Use the epoxy blob left on the aluminum foil to tell you when the epoxy is cured. The blob should feel smooth and slightly oily to the touch when it's fully cured.
	

	
	
		
		

		
		
	


	




 Finally, when cured - do yourself a favor and test out the sockets before you solder them to the PCB:


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## jon743

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## jon743

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## Yaka

tomb would`nt these bits be ideal for removing the pins?


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## zkool448

yaka, though those extractor bits are designed for removing threaded screws with damaged/rusted heads, they _might_ just work. The socket center pins appears to be press-fitted only so maybe once you get the bit's reversed thread in you can simply yank out the pins of the sockets? (sorry I don't have any sockets with center pins therefore I can't try it).


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## jon743

---


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## PJPro

tomb....having seen your pictures, I feel it might be worth ordering a couple of extra tube holders to go with my kit. Can I do this without incurring additional postal charges?


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_tomb....having seen your pictures, I feel it might be worth ordering a couple of extra tube holders to go with my kit. Can I do this without incurring additional postal charges?_

 

Do a couple of tube sockets weigh -0- and have no additional packaging costs?
 No.

 Would a couple of tube sockets added to an existing order cost less to ship than by themselves? 
 Absolutely.

 P.S. Please understand - my purpose of posting the tutorial had nothing to do with trying to sell more tube sockets. On the contrary, it's only to detail everything that's involved. I've had many questions about how to drill tube sockets for LED's. At the same time, whenever someone's asked, I've always recommended buying extras. Some people never break one, some always do - YMMV.


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## PJPro

OK. I'd like to add two to my order, to be shipped with the kit. What's the best way of going about it?


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## n_maher

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_OK. I'd like to add two to my order, to be shipped with the kit. What's the best way of going about it?_

 

Since this issue started at beezar why not use the "contact us" link right on that site?


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## PJPro

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Since this issue started at beezar why not use the "contact us" link right on that site? 
	

	
	
		
		

		
		
	


	


_

 

Oh. I thought this was an issue highlighted as a result of posts on this thread. Others might be interested?

 But yes, I'll go via the beezar site.


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## Listen2this1

Having a little issue. Right after powering up (bumping) I got a snapping sound a little spark. I unhooked the power and seen that there was a little black spot in the mounting hole of the transistor. Apparently it was arcing to the heatsink? I am at a lost I have looked over it a couple of times and found nothing.

 Can the back side of the transistors touch each other or share a common contact? I am attaching them to the heatsink with pressure using a brass tube.

 I am using pads and thermal grease as well.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Having a little issue. Right after powering up (bumping) I got a snapping sound a little spark. I unhooked the power and seen that there was a little black spot in the mounting hole of the transistor. Apparently it was arcing to the heatsink? I am at a lost I have looked over it a couple of times and found nothing.

 Can the back side of the transistors touch each other or share a common contact? I am attaching them to the heatsink with pressure using a brass tube.

 I am using pads and thermal grease as well._

 

I'm pretty sure that if you make contact with ground with the metal tabs on the MOSFETs, you're probably going to get sparks, at a minimum. Be sure they're insulated, in other words.


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## tomb

OK, so the intent was not to show you that the focus of building the SSMH PCB was the tube LEDs - it's not. So, for the next bit of Step-by-Step, we'll focus on the PCB -

*1. Gather Your Tools and Organize Your Workspace -*
 Here's my stuff:




 A board to build the PCB on (1 x 10 high-finish pine), soldering iron, brass wool, light, solder, de-soldering braid, smooth-jaw needle-nose pliers, flush cutters, detail scissors, wire strippers, and a Leatherman to catch everything that the previous tools don't.
	

	
	
		
		

		
		
	


	




 Also note the bending jig - these are very cheap, only a couple of dollars when I bought one - but very valuable in bending the leads on resistors for varying size pads. Also note the BOM. You can essentially build the entire SSMH PCB with only the PCB and the BOM as reference: match the part numbers on the PCB with the part numbers on the BOM - that's it!

*2. Install the Resistors on the PCB -*
 When you populate a PCB, you want to start with the lowest-height parts first, then progress in ever-increasing height to the last parts. You do this because using the wooden board, you're able to turn the board over and mash down with your free hand while holding the soldering iron tip to a solder joint to keep it melted. Remove the soldering iron, let cool - all the while mashing down - and every part will go down flat against the board.

 Anyway, it's a safe bet the V-D resistors are the smallest things on the board, so we'll do those first. Here are a few I've pulled out to determine resistance values -




 With V-D (Vishay-Dale) resistors - at least the mil-spec kind such as sold by Mouser - there is no resistor color code. Instead, V-D uses an 4-digit scientific notation. The first three digits are a whole number, while the last digit is the base-10 exponent. So, in the pic below, we have:
 3302 = 330 x 10^2 or 330 x 100 = 33,000 or 33K ohms
 2203 = 220 x 10^3 or 220 x 1000 = 220,000 or 220K ohms
 5102 = 510 x 10^2 or 510 x 100 = 51,000 or 51K ohms.




 Keep this in mind while interpreting the resistors. Also - MOST IMPORTANT - bend the leads on the resistors so that the exponential rating is facing up when you install them on the PCB. Without the color code, the exponential notation is the only way to determine value on sight. You can use your DMM to determine the resistance of each resistor, but once installed in the PCB, there are many parallel connections and attempting to measure the resistance of a single resistor is somewhat meaningless.

*3. Bend the Resistor Leads and Place Them On the PCB -*
 Here we see me using the bending jig to bend the resistor leads so that they'll fit the pads on the SSMH. All of them fit correctly on slot 4, but there are two exceptions - R16 and R17 (those two are already bent at top in the photo). These are simply bent at the ends of the resistor body - their pads are much shorter and this will allow a perfect fit. Slot 4 works fine for the rest, however. Again, if you don't have a bending jig, then eye ball them as best you can.




*4. Solder One Lead Only with the PCB*
 Here we see the PCB with all of the resistors placed into the pads, and the PCB turned over with the leads sticking straight up. The idea is to solder one of the pads for each resistor, while mashing down on the board with your free hands. (Melt the solder with two hands, but while holding the soldering iron to the joint to keep it melted, use your free hand to apply down-pressure to the board.)


\

 One hint: while masing down on the board to apply pressure with a melted solder joint, shift the PCB slightly up or down, left or right, to keep the leads as nearly vertical on the PCB as possible. This keeps the resistors from twisting in their pads, possibly obscuring the exponential rating.

*4. Ensure Alignment and Complete Resistor Soldering *
 Here we see the silkscreen side of the PCB with one pad per resistor soldered. We do this so that we can check the alignment of the parts on the other side. If some are crooked, we can still slightly adjust their position to correct for the effect.




 When you look at the other side, inspect each pad for a "wicking" solder joint. The solder should travel all the way through to the other side and climb up slightly on the input side to the airline. If they don't, apply a slight bit of solder on the other side around the lead and the pad - just enough to make it look as if the wicking worked:




 In the pic above, note that the right side of leads are not soldered. That's OK - we have more Acts to perform. Note the wicked-through solder on the joints that are acceptable. If you're happy with the resistors's alignment when you get to this point, then flip the board back over and solder all the leads on the other side.

*5. Trim All Leads w/Flush Cutter*
 Here we are with all of the resistor leads trimmed with the flush cutter:




 Here's the PCB with all of the smaller resistors installed correctly:




*6. Next up is the LED resistor -*




 The LED resistor is pretty big. It's sized to handle the two tube LEDs at 10ma a piece and 48VDC. So big, in fact, that it won't fit on the same side as the rest of the parts. This is no problem - it fits fine on the other side. Since it's also much shorter than the tube sockets (they also go on the other side of the PCB), it's best to install it now.

 Bend the leads sharply on each end as shown. That way, it will fit in the longest distance pads on the PCB. Here we see the resistor placed on the other side with the leads sticking out. Just as with the smaller resistors, press down as you solder one lead, then the other:




 Here it is soldered into place. As before, check to make sure you've got wicking, but be very careful about the center hole. We're going to use a standoff there later and it won't take much to come into contact with the lead on the LED resistor from that center hole:


----------



## Mizu

If there's a cancellation, and that a full kit becomes available, i'm a taker !


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## Listen2this1

I did quite of reading about transistor mounting and think the way I have it is OK. So I remounted them and powered it back up and got the same result. I made sure that there was no contact between them.

 Can you use any thermal compound? The stuff I have is from a PC. Could that cause problems? I am at a loss at this point.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_I did quite of reading about transistor mounting and think the way I have it is OK. So I remounted them and powered it back up and got the same result. I made sure that there was no contact between them.

 Can you use any thermal compound? The stuff I have is from a PC. Could that cause problems? I am at a loss at this point._

 

Yes, you should use a thermal compound, but that should also be isolated from touching both the MOSFET back/tab and the metal of the case.

 Pics?


----------



## tomb

Building the PCB (continued) -

*7. Install the tube sockets -*
 After all of our work to drill the tube sockets and populating the PCB so far, hopefully the glue has cured and we're ready to install the tube sockets. As mentioned before, they go on the other side of the PCB which will be mounted up against the top plate of the custom Hammond case. IOW, the tube sockets will poke through the top of the case while the other parts will hang upside down inside the case.

 The tube sockets always come with the pins pretty much mashed into right angles from the sockets. However for proper mounting, they need to be splayed out at an angle. In fact, it works better to make sure the pins are splayed out a little further than the holes in the PCB. This way, you don't have to force the sockets from a "sprung" position to keep them lined up in the holes while soldering them. When the pins are splayed out slightly further than the holes, the act of forcing them into place compresses the socket into place. Shown below is an example of what the sockets may look like without bending the pins, and one with splayed out pins ready to be installed into the board:




 Test fit the sockets/pins into the holes as you bend the pins out. It may take a few trys to get them all OK. Notice the alignment, too. If the top surface of the socket is not parallel to the board when trial fitting, then bend the pins out a little more on the high side.

 What you want to do is place both sockets into position, turn the PCB over, then solder. With both sockets in place, the PCB is actually supported by the sockets and it makes it a lot easier to solder - simply press down slightly on the board while soldering to make certain they're flush. Here are the sockets in position with the PCB ...




 and turned over with the pins sticking out ready to be soldered:




 The tube sockets undergo a lot of stress, so we want these solder joints with the pins to be mechanically sound, in addition to being electrically sound. You should fill the holes completely so that there are no gaps in the solder. At the same time, you want to apply enough heat indirectly (to the solder) that there's wicking along the pins on the other side. A good joint will show the solder completely filled, wicked somewhat along the pins on the other side of the PCB, and will probably show a slight concave surface on the side where you apply the solder. The concave surface is the result of gravity pulling the solder down slightly through the hole. You'll make a mess if you try to get a flush surface with the solder - it will continue to run down the pins on the other side. After a few of them, you'll get the feel however. There's nothing wrong with going back and applying a bit more solder.




 The best way I've found to solder the pins is shown below. Hold the wedge tip on your soldering iron flush against the pin on the outside. Most of the hole opening will be on the other side of the pin surface. Apply solder to the side of the pin opposite of the soldering iron tip and feed the solder until the hole is filled. Keep the heat applied while mashing down slightly on the board. While still mashing down slightly, remove the iron and let the joint cool - it will take longer than you're used to because of the quantity of solder.




 Alternate from the pin on one side of the socket to the other - soldering opposite pins around the circle, so to speak. This is similar to tighteining the bolt pattern on your car's wheel when you change a tire - it keeps the forces symmetrical on the socket and helps to keep it straight. Once you've got two pins soldered on opposite sides of the socket circle, flip the PCB over occasionally to see if the sockets are straight. If the top surface of the socket is crooked (not parallel to the board), apply pressure in the opposite direction while soldering the remaining pins. A slight mis-alignment of the socket will cause the tips of the tubes to be pointing off-centered. Now, some of the glass in the tubes is crooked anyway, but it's still better to start out with a level tube socket surface than not.

 Here we see the sockets soldered in place on the pin side of the board. Note the slightly concave surface of the solder at each position. This is what they should look like to get the best mechanical and electrical connection (Note the clear flux blobs around each pin - we'll need to clean that off.):




 On the other side, you should be able to see the slight wicking along the pins:




 At this point, it's best to clean the PCB on both sides in preparation for installing the rest of the parts. That's because you'll never get all that solder mess cleaned around those socket pins once you solder all the other parts into place.
 (Ask me how I know that!
	

	
	
		
		

		
		
	


	




 )

 I just use rubbing alcohol and an old toothbrush. Walmart sells some 97% pure isopropyl alcohol for about $1 a quart, so it's very cheap. It may take you several rinses to get all the flux off, but keep trying. Use a paper towel to blot up the alcohol - it should turn a dirty yellow where you're picking up the dissolved flux. Rinse, then blot dry, and repeat. When dry, dissolved flux will have a white powder appearance. So, if you still have some of that around the joints - you haven't rinsed enough - do it again.


----------



## tomb

*8. Install the Tube LEDs -*
 Next up is what may be the hardest part of building the SSMH PCB - installing the tube LEDs. Still, it's fairly straightforward and with the help of this tutorial, it should go pretty smooth. I had the most trouble trail-blazing the method of how to do this, so maybe it will become much easier for you guys.

 The trick is to get the LED's soldered to the leads without creating such a blob that you can't get the LED into the tube socket center hole. You also need to thread the leads so that they'll curve around the parts that will go in later. Again, there are a couple of little tricks to do this with the least amount of trouble. Hopefully, this will illustrate and explain those tricks for you.
	

	
	
		
		

		
		
	


	




 Soldering leads together is always a bit difficult, but with a set of Helping Hands, things go a bit easier. The trick is to tin the wire leads, then clamp the leads and the LEDs in place so that the tinned wire touches the LED lead where you want to solder it. Apply heat and it should stick, allowing you to apply a bit more solder for strength. You'll want to ensure that these joints are carefully done, because you'll put the LED under stress when threading it through the tube socket. Once that's done, though, they'll never undergo stress again because they'll be completely protected by the socket.

 Anyway, here's two pairs of leads with the tips stripped and tinned:




 Cheat and look forward to the photo showing the leads soldered into place below. You'll want to cut the leads at least this length, plus another inch or so to account for the vertical length through the socket. Do this by placing the wire along the PCB in the shape shown below, and then add the inch or two of extra and cut. Don't worry about getting them exact - we'll trim them to length once we get them threaded through. Be sure you have more length rather than less, though.

 Here we see both wire leads soldered to the LED leads:




*Important - remember which lead is which!* You'll need to trim the LED's leads as shown here, but once you do that, you'll no longer know which one was the longer lead (positive). I always use either black or green for ground, though. So in these pics, the black wire is negative and was soldered to the shorter lead.

 Another important point - try to solder the leads on the top, bottom, or inside of the LED leads. If you solder the wire leads to the outside, then the overall diameter of the assembly might be too large to fit inside the tube socket hole!

 Here's a closeup of what I mean - soldering the wire leads have not added to the overall outside diameter. This one's slightly out of order because the LED leads have not been trimmed yet. Nip them carefully as close to the solder joint as you can:




 Another trick shown here before threading the assembly through the tube socket hole and the PCB hole. Put heat shrink on one joint, only! This is small stuff, but I suppose a very small bit of electrical tape will work, too:




 Again, nothing is going to come into contact with these leads once they're soldered into place and the LED is inside the socket. However, there's a good chance that they might be squeezed together. You only need to insulate one, though. That way, you haven't created a blob of tape/heat shrink so large that you can't get it into the tube socket hole.

 Here we see the LED's threaded through. You'll want to put the tip of the LED flush with the top surface of the socket. This will provide the best effect for tube lighting. There will be plenty of give in the LED/wire assembly, though, so if the LED sticks up past that a bit, it's OK. If your finger easily pushes them down, then so will the tubes, too.
	

	
	
		
		

		
		
	


	







 Finally, we'll flip the board over and position the leads into the proper pads. Remember, ground is negative and black in this case. So the purple wires have gone into the holes marked "+". Those should also correspond to the longest lead that was on the LEDs, too - way back when you first soldered the leads to the LED. _(NOTE: Use this photo as an illustration of how to measure the lead length for the leads in the first step above.)_




 Trim the leads to length shown here, although a bit of slack is not going to hurt. You've got plenty of room with the taller capacitors and such that will go on later. Once you have them trimmed, slightly tin the leads and bend them down into a 90-degree angle. This makes it easier to fit them into the holes. Be careful, though - those pads are small!. Once you have them in, flip the board over and solder them into place. Once again, you should be able to push down on the board slightly to ensure that the tinned leads are pushed through completely and the insulation is flush with the board.

 NOTE: I use 22ga Navshipps SPC wire for everything. You might cheat here and use 24ga. That could make it a lot easier to thread through and solder the leads into the pads. 22 ga works fine, though, if you're careful not to make a blob when tinning the ends.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I had the most trouble trail-blazing the method of how to do this, so maybe it will become much easier for you guys._

 

That's so clever! 
	

	
	
		
		

		
		
	


	




 Nice tutorial overall, Tom.


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_That's so clever! 
	

	
	
		
		

		
		
	


	




 Nice tutorial overall, Tom._

 

Thanks!

 Let's finish off the PCB!

*9. Check the Relative Heights of the Remaining Parts -*
 Here we see all the rest of the parts, except the MOSFETs, laid out into a row, according to height:




 Note the order - this is how we'll finish the rest of the PCB - shortest to tallest, until they're all done. Things get FUN, now.
	

	
	
		
		

		
		
	


	




*10. Solder the Terminal Blocks in Place -*
 As with all that's gone before, place the parts in the proper pads, turn the board over and press down slightly while soldering the leads. In the case of the terminal blocks, the pins have a lot of slack in the holes. (This is by design - it's critical that the pins make good contact with the board and you have no control over wicking.)




 I like to solder one of the interior pins, first. The blocks seem to rotate better on one of the center pins. I've soldered one of the ends first, found out it was misaligned, but then lacked enough slack to turn the block straight. So - small caveat - but generally easy enough to solder. Some caution is needed because the blocks are plastic. It's possible to apply enough heat that you can melt them.

*Be sure you have the openinings toward the outside of the PCB!*

*11. Solder the WIMA Film Capacitors In Place - *
 There's four of them and they're easy enough to place in position. However, the leads are thick and short - they don't stick the parts in by themselves. If you're using the pine board like me, though, there's a trick:
Hold the PCB with the Wima's in place in one hand.
Pick up the pine board with the other hand, turning it upside down.
Place the pine board over the top of the Wima's and PCB.
While holding the PCB/pine board with both hands like a patty-cake, flip the assembly over so that the pine board is back on the bottom again.
Proceed with your soldering.
You'll find that the Wima's are so square and so evenly placed on the PCB that the entire PCB is supported in a straight and level position while upside down - nothing could be easier!




 Don't forget - like everything else - solder one lead on each Wima while pressing down slightly to ensure that they're flush. Note that there are little tabs on the bottom edge of the Wima's, so "flush" will still mean there's an air gap underneath. Then flip the PCB back over and make sure they're not crooked. Straighten them gently, if necessary. Flip the PCB back over onto the pine board and finish the soldering. Trim the leads when you're done.

_Note: I don't trim the leads on anything else but the capacitors - the terminal blocks, volume pot, and headphone jack are left un-trimmed._

*12. Solder the Headphone Jack in Place -*
 Straightforward, but you'll have to press the PCB down and keep things lined up while you solder the first couple of pins. That's because there's no headphone jack on the other side of the PCB to even things out.




 Use the same method for soldering the headphone jack as you did with the tube sockets:
Alternate pins from side to side while soldering. This has two purposes - 1) It's easier to keep things aligned, and 2) Unlike the ceramic of the tube sockets, the headphone jack is plastic. Too much heat and it can melt, although it takes an awful lot.
	

	
	
		
		

		
		
	


	


The headphone jack also undergoes a lot of stress. Ensure that the pins are completely soldered and pads filled, and try to ensure that there's wicking to the frame on top.
Solder one of middle pins first, ensure that everything's aligned. Solder the ground pins last, because they'll be the hardest to solder (the soldering iron heat will get soaked up by the ground plane a bit).

*13. Solder the Volume Pot Into Place -*




 The pins and pads are small on the volume pot, so it's much easier to keep the pot aligned while soldering. However, it's short from front to back, so it's pretty easy to get the shaft pointing a bit down or up. This will drive you crazy when you try to set the volume knob in position, so do your best to get the pot shaft parallel to the PCB. Solder a couple of the back pins (leave the ground pins for last), then check the alignment. Press down in back or in front, depending on what's needed to keep the shaft aligned. Also check the side-to-side alignment, too. A little care doing all of this will payoff when you go to set the knob in place. Otherwise, the knob may scrape at different positions in volume travel. You may end up with a large gap to keep it from scraping, which may not look aesthetic.
	

	
	
		
		

		
		
	


	




*14. Solder the Electrolytic Capacitors in Place -*
 This one's easy and fun to do! Note from the first pic up there that all of the electrolytic capacitors we've supplied for you in the kit are all the same height! So, we'll want to place everyone of them on the board at the same time, pick up the pine board, turn it upside down while placing it on top of the caps on the PCB that we're holding in our other hand, and do our _reverse patty-cake maneuver_. *Be sure you have them inserted in the proper pads, though. All the long leads go into the holes marked "+".*




 As with the Wima's, the electrolytics completely support the PCB in a straight and level position. Solder the leads - as always, solder one of each for all of them, flip the PCB over and ensure that there's no mis-alignment. Finish all of the soldering and then trim the leads. (I don't trim the leads on anything else except the Wima's. The terminal blocks, headphone jack, and pot all stay untouched.)

 There is one last tweak we'll do to the PCB before we move on to the case assembly, but I haven't done it for real yet. So we'll need to wait until I get more done. It's soldering a small lead from the "G" pad to the metal body on the volume pot. This will remove any ground hum you might hear when grabbing the volume knob to adjust the sound level. I'm not sure that pot hum is an issue with this pot, but it won't hurt anything and will ensure that the issue never comes up.
	

	
	
		
		

		
		
	


	




 We'll do that next and then assemble the case!!


----------



## Llama16

Very nice tomb, This should be a seperate thread in my opinion.
 Don't want to push things :S, but did you get my pmsg? It's just that I'm looking to order another set of tubes (and parts for the pcb version that I can't find at mouser), but I also still need the 'lug' sockets for those tubes of the p2p build. You once (appreciated alot by me) proposed to sell me an extra pair of a spare set of your lug miniature sockets. I was wondering if you still had those, I'll buy them for a reasonable price ofcourse.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Very nice tomb, This should be a seperate thread in my opinion.
 Don't want to push things :S, but did you get my pmsg? It's just that I'm looking to order another set of tubes (and parts for the pcb version that I can't find at mouser), but I also still need the 'lug' sockets for those tubes of the p2p build. You once (appreciated alot by me) proposed to sell me an extra pair of a spare set of your lug miniature sockets. I was wondering if you still had those, I'll buy them for a reasonable price ofcourse._

 

I haven't caught up with all of my PM's, yet, so I'll check and let you know. I've been off the mainland until last night.
	

	
	
		
		

		
		
	


	




 As for a separate thread - no, this is the proper place. I don't believe in creating a bunch of separate threads for the same project. This amp has gotten plenty of publicity and everyone knows where to find it. There's also the search engine within the thread. My next task is to get all of this on the website, anyway. So it'll be easy to find in the future, regardless.


----------



## Listen2this1

I second on having these pics and tutorial on a seperate thread. Great work Tom

 I figured out my problem, some how there was a tiny ball of solder that made it behind the film and the heatsink that must of pushed through and touched the transistor during mounting.

 Sounds good, though too sensitive. I will need to add some resistance to the input for my low ohm cans. I read 10k is good, but what will this do if i plug some Senn's into it? I do not own any right now, but if my wallet stumbles across some money, who knows.


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## hashwood

can someone be kind and tell me if a 54.8 power supply is ok to use with this amplifier? It's all I could find.


----------



## tomb

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_I second on having these pics and tutorial on a seperate thread. Great work Tom

 I figured out my problem, some how there was a tiny ball of solder that made it behind the film and the heatsink that must of pushed through and touched the transistor during mounting.

 Sounds good, though too sensitive. I will need to add some resistance to the input for my low ohm cans. I read 10k is good, but what will this do if i plug some Senn's into it? I do not own any right now, but if my wallet stumbles across some money, who knows._

 

Well, what's the impedance of the pot you're contemplating using that 10K for? It's the combination that dictates the values. 10K with a 10K pot would still be OK for Sennheisers. 10K with a 50K pot is not going to make a difference with any pair of headphones, most likely. I would use 50K with a 50K pot as a minimum. IOW, input resistor = pot impedance at a minimum.

  Quote:


  Originally Posted by *hashwood* 
_can someone be kind and tell me if a 54.8 power supply is ok to use with this amplifier? It's all I could find._

 

No.

 The Cisco VoIP power supply is in plentiful quantity on ebay. Use the search feature for "PSA18U".


----------



## hashwood

thanks for your reply. This one was free, on eBay I'll pay $10-15 just for shipping. I'm in Romania, Europe. Plus I have to wait one week. too bad


----------



## Yaka

very nice guide nice pics tomb
	

	
	
		
		

		
			





 just one question, i have one of the beta boards here and am having trouble removing the tube sockets as i want to have the leds in them. any suggestions?


----------



## tomb

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_very nice guide nice pics tomb
	

	
	
		
		

		
		
	


	




 just one question, i have one of the beta boards here and am having trouble removing the tube sockets as i want to have the leds in them. any suggestions?_

 

Yes, but you won't like the answer. Cut the pins, throw away the sockets and remove the remaining pin tips and solder from the PCB pads. Literally, it might be easier to try and drill the sockets in place. It's worth a try, perhaps.


----------



## hashwood

well the supply is adjustable. I got 48 
	

	
	
		
		

		
		
	


	




)


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## Yaka

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, but you won't like the answer. Cut the pins, throw away the sockets and remove the remaining pin tips and solder from the PCB pads. Literally, it might be easier to try and drill the sockets in place. It's worth a try, perhaps._

 


 ouchie:/ i thought that might be the answer


----------



## tomb

Quote:


  Originally Posted by *hashwood* /img/forum/go_quote.gif 
_well the supply is adjustable. I got 48 
	

	
	
		
		

		
		
	


	




)_

 

That's great! It should work at that, then.

 One caveat, however - the performance of the Starving Student is assured with the Cisco power supply. Other power supplies may be more noisy. They could be less noisy, though. IOW, YMMV.


----------



## hashwood

well this is a power supply taken from a server I think. It has 6 amps 
	

	
	
		
		

		
		
	


	



 Eltek ADC5593/5 , it looks very pro, but it may be noisy. I'll see soon


----------



## hashwood

I finished, but it's not working. Nothing happens. No light, no sound, nothing. 
 I used 220uF 63V capacitors not 150 like in the bill of materials, but a friend of mine said they should be ok. 
 For tube pinout I used: Vacuum Tube Pinouts
 Here are the pics with what I've done: Index of /starving but I don't think they will help.
 It's very strange that the tubes don't glow, can someone tell me what pins should I check for voltage ?


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## Yaka

im a noob my self at this, but same coloured wires make it hard to figure out whats wrong. and mabe a pic without the tubes.

 dont mean to sound rude or anything


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## hashwood

no problem, It works, everything was ok, just the power jack. The inner diameter was different, male-female. Bad seller...
 It works 
	

	
	
		
		

		
		
	


	



 the only problem is the noise, when it receives power. Can it be reduced or stopped ? I have a behringer that makes the same noise...

 Here's a pic: 

www.swooms.com/starving/IMG_3368.JPG

 are the radiators too close from the lamps?


----------



## tomb

Quote:


  Originally Posted by *hashwood* /img/forum/go_quote.gif 
_no problem, It works, everything was ok, just the power jack. The inner diameter was different, male-female. Bad seller...
 It works 
	

	
	
		
		

		
		
	


	



 the only problem is the noise, when it receives power. Can it be reduced or stopped ? I have a behringer that makes the same noise...

 Here's a pic: 

www.swooms.com/starving/IMG_3368.JPG

 are the radiators too close from the lamps?_

 

No offense, but it was mentioned to you that your power supply might end up being more noisy than it should. There's also an issue with proper grounding using a perfboard - that may cause more noise than it should. If you notice on Pete Millett's very first SSMH, there was a solid sheet of copper used for a ground plane beneath the "wallet tin."

 I doubt that the proximity of your heat sinks to the tubes have anything to do with it. That said, those heat sinks look awfully light for the amount of voltage and current that's dissipated by those MOSFETs.

 Sorry to be so negative ... at least you got it working.


----------



## tomb

Just an FYI everyone -

 Hammond requested the final payment from me for the cases and I sent it this weekend (their arrangement was half up front, the other half when they were finished). So, the cases are finished. They will ship them to me when they receive the check, which I sent via Certified Mail. So, I expect a Tuesday or Wednesday shipment to me. Chances are that I'll have them by the end of the week.

 Please give me a week or so to get everything shipped when I receive them, though. It will take a bit of work and time, needless to say.


----------



## n_maher

Tom,
 Outstanding job on the build guide (as usual). Can't wait to see some new build pics in a few weeks.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Tom,
 Outstanding job on the build guide (as usual). Can't wait to see some new build pics in a few weeks._

 

Thanks, Nate! Comments like that from you and Dsavitsk mean a lot, knowing what great builders you guys are.

 More is coming in a couple of hours - I've finished the the "how-to" amp today and will finish up with the pics and posts tonight. The SSMH PCB and case is a rather unique assembly, but you will all find that with a few tricks, it goes together like a no-brainer, with little or no chance for mess-ups.


----------



## Juaquin

Thanks for all the hard work Tom. Just for reference, I was easily able to open the sockets by prying them (carefully) open at the seam until the center pin is a little loose. The best place for this is the little notch used for alignment of the halves. Then once you have a little wiggle on the center pin, pry up the pin itself against the bottom half (no longer working on the seam). A very small flathead screwdriver did the job with no damage. This should be useful for those who don't have drills (or live in an apartment where you can't fit a drillpress, like me), or who are adverse to drilling and possible breaking them.


----------



## tomb

OK - let's finish this thing!
	

	
	
		
		

		
			





*15. Solder the Ground Wire to the Volume Pot -*

 This will essentially complete construction of the PCB except for the MOSFETs, which we'll leave for fitting up with the case lid in a bit.




 Trim a wire so that its length is sufficient to curve over the top of the volume pot from the "G" pad on the PCB. As always, tin the tips of the wire with solder. Strip one end slightly - that one will go into the PCB pad. Strip the other end so that about 1/4" is exposed. That will leave plenty to solder to the metal body of the volume pot.

 The metal body of the volume pot has a finish to it that will inhibit sticking with solder. So, we'll file the top a bit so that the solder will have something to stick to -




 Once we have a patch filed, it's time to solder the ground wire in place -




*16. Clean the PCB of Flux -*
 At this point - as noted earlier - we're basically finished with the PCB. So, let's clean it thoroughly. I'm a cheap-skate on some things and cleaning solder flux is one of them. Basically, I use some 90 cents a quart, Walmart 90% isopropyl alcohol as the rinse. I pour some in an old plastic butter bowl and use an old toothbrush and a paper towel.
	

	
	
		
		

		
		
	


	







 It took me about 5 or 6 rinses, using a paper towel to pat off the alcohol/dissolved flux to get it acceptably clean. There may still be some white spots around the solder joints, but I'm not that picky.


----------



## tomb

Now on to the custom Beezar/Hammond case!

*17. Prepare the Case Lid for Mounting to the PCB -*
 Dsavitsk's SSMH PCB design depends on mounting the PCB to the case lid - everything is keyed off of that. Pictured below is the underside of the case lid. The first thing we want to do is to stick on the Bergquist thermal pads. These will come in the heat sink mounting kits that come with the SSMH kits -




 In this pic, I'm scrapping the anodizing away from the center hole. This hole will be used for a standoff that will be screwed to the center of the PCB. The pad is tied to the ground plane on the PCB, so if we make sure there's good contact with the case lid, that will increase our grounding resource.




 Looks terrible and it feels bad to do this to a brand new, custom-mfg'd case, but it's on the inside and no one will see.
	

	
	
		
		

		
		
	


	




 The benefit is enormous, though, and little touches like these will give us a very quiet amp while many others may have trouble with hum and noise on other P2P tube amps.

 Here is the standoff assembly. This will be provided in the kit with several washers. At least one washer is required for spacing along with the standoff - perhaps two. The only caveat to this you'll see in a moment. There are some smaller washers you can pick from and you'll want to use those next to the PCB, or you may short the standoff against the tube LED resistor - more on that later.




 Essentially, what you see here (I will draw a detail on the SSMH website.) is a 1/4" socket head screw, washer, and lock washer. Those will go on the parts (capacitors, etc.) side of the PCB. The small washer and standoff will go on the tube socket side. We use a lock washer here because the screw on the PCB will be inaccessible from the outside, so we'll want that one to be locked in place. If it came loose, it might turn forever without un-screwing until we took the case apart.
	

	
	
		
		

		
		
	


	




 After that, we'll use just a flat washer and a longer screw from the outside to fasten the case lid to the standoff and thereby, the PCB.

*This is critical!!* Note the spacing between the standoff, washer/spacer and the tube LED resistor lead. Be certain that you have some space here as shown. Otherwise, disaster will ensue. Note also that the flat side of the hex standoff is also facing the resistor lead. This is an additional insurance that a space is maintained. Note that a small washer must be used here - a regular sized flat washer will contact the lead, so don't use one. Nevertheless, the spacing with only the standoff is not sufficient, so some additional spacing is needed and the small washer provides that.




 Here we see the other side of the PCB and the pad and snipped lead side of the tube LED resistor. Note the spacing - *make sure yours is similar or disaster will ensue!*




*18. Screw the Case Lid to the PCB -*
 As mentioned earlier, we use only a screw and a flat washer here - to ensure that if anything comes loose, it's the screw on the outside - the one we can get to! Depending on your build and your Beezar/Hammond custom case, you may need an additional washer/spacer on top of the standoff to make the best fit. I had to use one here, but I didn't on the first two I built. Again, YMMV, and actually - Hammond's MMV - due to extrusion differences, warping, etc.




 You'll want to trial fit a few times to get the spacing just right. When you do, the PCB should fit three slots down from the top of the case as shown here in a couple of views:




 Note the extra washer I had to use on this one.

 Another view from the side:


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Thanks for all the hard work Tom. Just for reference, I was easily able to open the sockets by prying them (carefully) open at the seam until the center pin is a little loose. The best place for this is the little notch used for alignment of the halves. Then once you have a little wiggle on the center pin, pry up the pin itself against the bottom half (no longer working on the seam). A very small flathead screwdriver did the job with no damage. This should be useful for those who don't have drills (or live in an apartment where you can't fit a drillpress, like me), or who are adverse to drilling and possible breaking them._

 

That's great! I marvel at people such as yourself who are able to do this. I have tried for years and can never get those pins loose without drilling. If you can do it this way, though, by all means - do so!!


----------



## tomb

OK, so now we have the case lid attached to the PCB with the center standoff! The next thing we want to do now is to complete the MOSFETs and heat sinks. This is much easier now than attempting to do it before, because the center standoff has determined the proper distance between the PCB, MOSFETs, and case lid.

*19. Insert the MOSFETs into the PCB Pads -*
 With the PCB down to the 3rd slot on the case, there is only one way this will work - you must bend the MOSFET leads at 90 degrees directly at the plastic body. The pic shows the MOSFETs before and after:




 Here we see one MOSFET inserted into the PCB pads, and one in an inbetween position. Work carefully doing this, or you'll scar up the Bergquist pads and perhaps loose heat transfer integrity, or loose insulation capability. Be patient - it may seem like the leads won't fit without a greater clearance between the lid and PCB, but they will. Ensure that the leads on the MOSFETs are straight and equally spaced - that will help things along. Once you get them inserted, it will have seemed so easy that you'll wonder why they didn't go in right away in the first place.
	

	
	
		
		

		
		
	


	







*20. Install the Heat Sinks -*
 Next comes what may be the most frustrating part of building the SSMH PCB - at least it is for me, usually. Before the frustrating part, though, let's review the heat sink solution for the SSMH PCB/case and note how the heat sinks are aligned to the case:




 Note that there are four mounting holes on each heat sink. We will only use two of them - the holes that are the closest to each other. However, note that the two holes perpendicular to those are offset - one is at a greater distance from the closer two holes than the other. Be sure that offset is to the outside on the SSMH case - as shown here. Otherwise, the heat sinks will not fit together on the case lid.

 Once we've established that, our next task is to coat the bottom of the heat sinks with heat transfer goo. You see, the primary contact is between the MOSFETs, the Bergquist pad and the case lid. However, to enable the heat sinks to add their heat dissipation capability to the assembly, we need the best possible contact between the heat sinks and case lid. To do that, we need to use heat transfer goo between the heat sink surfaces and the case lid.

 I should've taken some photos, but I guess I got too frustrated again.
	

	
	
		
		

		
		
	


	




 Anyway, you'll want to use a toothpick or similar to spread - very thinly some heat transfer goo on the bottom surface of the heat sinks. Once you do that, you'll place each one in position - one at a time - until you insert the screw assemblies.

 In the heat sink kits that come with the SSMH kits, there's two longer screws (1/2") and two shorter screws (3/8"). Use the shorter screws on the second hole of the heat sink and use the long screws on the MOSFETs that use the first hole of the heat sinks. When inserting the screws, be sure you take the trouble to "seat" the shoulder washer into the MOSFET tab - it won't do it by itself. Essentially, we have a screw and washer on top of the heat sink and case lid, with a washer, lock washer and nut underneat. The MOSFETs are a bit different in that they present an additional thickness from the tab and also the shoulder washer - that's why the longer screws are used for the MOSFETs.

 I'm sorry I skipped some needed photos, but here's the final assembly shown in detail:




 Now, why do I say this was frustrating? Because - once you put the heat transfer goo on the bottom of the heat sinks, they'll slide like they're on ice. All the while, you're trying to thread a couple of small screws through. When they slide, the goo goes all over the parts of the case that will be visible to everyone once completed. So, it's kind of like they're out to get you.
	

	
	
		
		

		
		
	


	







 Be patient, use a good pair of needlnose pliers to insert the screw assemblies - and be sure to go extra light on that heat transfer goo. If all of this scares you, then don't use the goo, period.

 One thing you should be careful of, though - be sure you don't torque the MOSFETs down so tight that the tabs cut through the Bergquist pads - that would ruin the insulating capability and cause a short. So, tight and secure - but don't torque.

 Oh - by the way:
*21. Solder the MOSFET Leads to the Pads on the PCB -*
 Piece of cake at this point, but don't forget to do it!!
	

	
	
		
		

		
		
	


	




 We're almost finished!! Here's the case lid/PCB assembly completely finished and inserted into the case for a trial fit (and intermediate admiration of our work):




 I used some super-duper heat transfer goo on this one - it's white.


----------



## tomb

Coming down the home stretch!!

 We've finished it all except for the endplates. What's really nice - there's no work at all on the front plates. Once you slide the assemble into the case, that's it - the endplate is already drilled to match the volume pot shaft and the headphone jack.

 The back plate is not as simple, but still not too bad. I get discouraged at this part, though, because to me, wiring is so tedious. What's nice and makes up for that, though, is that you don't have to drill the holes through the back plate and worry about dimensions, hole sizes, or whether it will all fit - it's already done!

 So, given that, the only thing we have to worry about is the connectors on the back plate. These are the Power Input Jack, the Power Switch, and the RCA Input Jacks. These are pictured here in a blowup of our kit parts layout shown way back in the earlier posts:




*22. Install the Power Switch -*
 The power switch, while rated for much higher voltage, is plastic. Thus, it will melt enough that the mechanism may be damaged if you use a soldering iron to connect wire leads to the tabs. Instead, use a couple of fast-on connectors as shown here. These are available in every hardware store. In fact, the ones shown here are for much larger tabs, but they work fine for the power switch, regardless.




 Be sure you crimp them so that the wire is snug. Pull on it and work it back and forth to make sure you have a good connection. I have to crimp it in two places, but maybe that's because I use the cheap tool shown in the photo.

 Before we install the power switch, we'll want to prepare the back plate for the connectors. As with the case lid center hole, we want to scrape the anodizing away from the holes so that the connectors' negative connections will make contact with the case. Negative = Ground in the SSMH, so again, our ground resource will be increased when we do this. Just an FYI, but the RCA jacks fit snuggly enough that the edges of the drilled hole may be sufficient to provide contact. Still, if you're scraping/filing anyway - might as well do them all (except for the power switch - that's all plastic, so it won't do any good).




*Note - be sure you know which side is which!* The outside of the endplates have counter-sunk mounting screw holes. That's the absolute indicator - do your filing/scraping on the other side. The counter-sunk part of the holes are the outside.

*23. Install the Power Input Jack, the RCA Jacks -*
 Similarly, install the power input jack and the RCA jacks. Both require soldered connections, both ground and non-ground (or signal). The pic shows my usual workspace once I start wiring connectors - all h*ll breaks loose and the whole table turns into a mess.
	

	
	
		
		

		
		
	


	







 In the photo, we can see the power input jack already wired and screwed into the back plate (more on that later). The power switch has already been installed on the back plate, and I'm in the process of finishing the wiring connections on the RCA jacks.

 Here's a glamour shot of my soldering one of the ground leads on the RCA jacks. Some use a single ground wire and solder it to both tabs of both RCA jacks. However, I think two ground wires - one soldered to each tab separately works better.




 The backplate finished with all connectors installed and the wire leads soldered. Note that when measuring the length of the wire leads, insure that you have enough slack to move the back plate up and over the main case body - this is the way that dis-assembly will be done. Also, note that the signal wires from the RCA jacks much be much longer to reach the input signal terminal block.




 An outside view:



 Note the insulators on the RCA jacks. Actually, the RCA jacks are best without insulators. As shown in the photo previous, there are no insulators on the inside - this is so the RCA jack grounds can make contact with the case. On the outside, the insulators are purely cosmetic. You'll find that it's almost impossible to plier the jacks down from the outside without scratching a circle into the backplate finish - the insulators will protect the finish and allow easier tightening.

 With the power input jack, the hole is purposely sized larger than needed. This is because Radio Shack makes a similar power input jack that's larger in diameter. I left the hole big enough in case some want to use that jack. The jack in the kits will benefit from an additional finishing washer - simply use one of the washer/spacers that come with the headphone jack - not all of them are needed for the headphone jack.

*24. Install Wiring and Back Plate -*
 Trim the wire leads to length if needed, but remember, there's a huge space behind the PCB - plenty of room to take up slack. The back plate must be able to move up and over the main case extrusion for convenient disassembly, so quite a bit of slack is needed.




 Note also that the input signal terminal block is quite close to the sides of the case when assembled, so bend the wire leads at a 90 degree angle next to the terminal block and trim to fit. This makes it easy to obtain enough clearance for the input wiring. I like to braid mine in a Litz braid or similar, but I'm not sure it means anything over this distance.
	

	
	
		
		

		
		
	


	




*25. Assemble the Amplifier -*
 Hey! We're done!

 Be sure to use the endplate bezels. Don't worry - you can slide the bezel over an endplate even when the wiring is connected. For the front plate, use one spacer on the headphone jack behind the endplate - that should be sufficient for spacing.




 Pictured here, I've assembled it without the screws. If everything works, I'll disassemble it, tap the case holes and use 6-32 machine screws. That's not really necessary, though, the supplied Hammond screws will work fine - but don't use them until you're certain the case and the amp all work fine.

 Back view:




 And we add the volume knob - the idea is to get it as close to the endplate without scraping anywhere in its travel. This may be sometimes more difficult than it sounds - it depends on how well you aligned the volume pot when you soldered it way back when.


----------



## tomb

*Finished!!*

 All fired up and glowing - I used ocean-green LED's for this one.




 Give your Starving Student time to burn in. I'm not an advocate of hundreds of hours like some claim for headphones, etc., but your Starving Student will definitely change tone in the first hour or two. When you first power it up, it will sound bassy, thick and "cloudy." Within an hour or two, the tone will have changed 100% - more detail, more transparency. Things will continue to improve over the next 12 hours, with subtle changes after that as more detail and transparency comes in.

 The electrolytics and Wima caps take time to burn in - not hundreds of hours, but definitely over a day or two - that's a fact!


----------



## gore.rubicon

Very nice writeup, will this also be going onto diyforums?


----------



## ROBSCIX

Very cool.


----------



## smeggy

Excellent work Tom.

 That is truly outstanding, a very good guide indeed. Thanks.


----------



## tomb

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Very nice writeup, will this also be going onto diyforums?_

 

Done.


----------



## shrisha

Thank you Tom for beautiful tutorial. Very inspiring. Is it possible to order whole kit by one click on BEEZAR.COM?


----------



## tomb

Quote:


  Originally Posted by *shrisha* /img/forum/go_quote.gif 
_Thank you Tom for beautiful tutorial. Very inspiring. Is it possible to order whole kit by one click on BEEZAR.COM?_

 

Sorry, no. All the original run of kits were sold. Once the cases come in and I ship out the existing kits, I'll re-evaluate my tube stock and decide whether to offer more kits at that time.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Excellent work Tom.

 That is truly outstanding, a very good guide indeed. Thanks._

 

Thanks, Smeggy!!


----------



## hashwood

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No offense, but it was mentioned to you that your power supply might end up being more noisy than it should. There's also an issue with proper grounding using a perfboard - that may cause more noise than it should. If you notice on Pete Millett's very first SSMH, there was a solid sheet of copper used for a ground plane beneath the "wallet tin."

 I doubt that the proximity of your heat sinks to the tubes have anything to do with it. That said, those heat sinks look awfully light for the amount of voltage and current that's dissipated by those MOSFETs.

 Sorry to be so negative ... at least you got it working.
	

	
	
		
		

		
			



_

 

No problem, but I don't understand what noisy means. If I pause and turn the volume close to max, there is no noise, it's completely silent. I connected one more heat sink in the upper side, so I guess now it's ok. 
 I just was paranoid, not to ruin the tubes, being close to the sinks, but if you're saying it's ok, then Ok it is. 
 Regarding
 Nice job, your amp looks very good. 

 Anyone knows where to find tubes? I need to have some replacements.


----------



## Listen2this1

Almost done. The build is but I am having a friend do some lettering and pin striping. Sounds good. The switch in the front is for a selector switch for the two inputs on the back.

 Will take better pics when the lettering is done.


----------



## crapback

I am having no luck with anything diy lately. Every time I opened up my senn pc 350's for the hero-mod I broke a wire. Now, I've had two of those sweet little rca tubes in my possession for less than 24 hours and as i was setting up the socket alignment, I dropped one. You can guess what happened... 

 This new "hobby" (see addiction) has already cost me way more money than I wanted to spend and now one stupid slip up has cost me my day's sanity.


----------



## nullstring

Quote:


  Originally Posted by *crapback* /img/forum/go_quote.gif 
_I am having no luck with anything diy lately. Every time I opened up my senn pc 350's for the hero-mod I broke a wire. Now, I've had two of those sweet little rca tubes in my possession for less than 24 hours and as i was setting up the socket alignment, I dropped one. You can guess what happened... 

 This new "hobby" (see addiction) has already cost me way more money than I wanted to spend and now one stupid slip up has cost me my day's sanity._

 

yikes, I didn't think they were that fragile.

 You drop it on concrete or ceramic or something?

 I don't think anything would happen if it fell on the vinyl flooring in the basement.


----------



## tomb

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_yikes, I didn't think they were that fragile.

 You drop it on concrete or ceramic or something?

 I don't think anything would happen if it fell on the vinyl flooring in the basement._

 

If it hit on the tip ...


----------



## Llama16

what happens if you try to give them juice when the vacuum is lost (only out of curiousity


----------



## gore.rubicon

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_what happens if you try to give them juice when the vacuum is lost (only out of curiousity_

 

SSMH Tubes 2nd Last photo


----------



## ThePredator

After a number of months without problem, my starving student has started acting up. The problem is that sometimes when starting up the left channel tube will begin pulsating, and through a (cheap) pair of headphones you can hear a popping at about 120-130 bpm (checked with a metronome, not exactly scientific I suppose). I opened it up and I didn't see anything loose or burned (also put in another pair of tubes) but is there anything specific that I can look for?

 [EDIT]: Even with the left channel tube removed the problem persists, but the left tube is the only on that pulsates.

 [EDIT]: I opened it again and traced through the schematic and found that some wire strands had poked through the heatshrink on one of the left mosfet wires and was touching a wire from the other mosfet. Wrapped it in electrical tape and it is working again. I do suppose that is what I get for my rats nest wiring.


----------



## crapback

The floor I dropped the tube on was covered with hard vinyl tile. I'm never handling tubes again without something softer on the floor. That tube was probably as old as I am. I'm still mad at myself for that one. The socket screw holes were the last ones I had to drill in the case too. 

 I sent some business your way tomb so hopefully I can get my first amp project back on track.


----------



## crapback

Weird. I edited this yesterday. Oh well, I made a pretty good funny that I can't quite remember. Something about midgets...


----------



## nullstring

I just finished my amp.
 Seems to be working.. I haven't tried them with anything decent yet though.

 First, when I touch my pot, I get a loud buzzing noise. This doesn't happen with my CMOY. any ideas?

 Second, how bright are the tubes suppose to get? mine get pretty bright. Brighter than I thought they would.
 No where near a light bulb though.

 I'd appreciate any feedback
 thanks


----------



## tomb

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_I just finished my amp.
 Seems to be working.. I haven't tried them with anything decent yet though.

 First, when I touch my pot, I get a loud buzzing noise. This doesn't happen with my CMOY. any ideas?_

 

Grounding issue - although, usually it's more of a hum, not a loud buzzing noise. So, it could be something more serious.
	

	
	
		
		

		
		
	


	




  Quote:


 Second, how bright are the tubes suppose to get? mine get pretty bright. Brighter than I thought they would.
 No where near a light bulb though. 
 

I'd review your wiring. In daylight, you should see a few points of orange tips in the tubes - not really "bright" (assuming you didn't use tube LEDs). The unusual brightness may be caused by an error in wiring that could be letting the full voltage of the power supply to go to each tube's heaters. They should be sharing that voltage in series, along with some drop through the resistors.

 Measure the voltage at pins 3 and 4, referenced to this diagram:
SSMH Tubes
 If you get something a lot higher than 19VDC on each tube, you have a problem! If it's 19VDC, then the brightness is normal. Note that all tube diagrams are referenced from the bottom of the tube! so if you're looking down from the top of the sockets, reverse this numbering. If you're looking at the sockets from underneath, then it's OK.
  Quote:


 I'd appreciate any feedback
 thanks


----------



## Tritonpad

TomB, let me give you a kiss for the job you did on this tuto ^^


----------



## nullstring

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Grounding issue - although, usually it's more of a hum, not a loud buzzing noise. So, it could be something more serious.
	

	
	
		
		

		
		
	


	


_

 

It seems to come and go oddly.
 And it's isolated to the left channel.

 I think that it might have to do with the fact that the Pot is hanging in the air right now, suspended by it's connections.. instead of attached to a metal chassis.


  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd review your wiring. In daylight, you should see a few points of orange tips in the tubes - not really "bright" (assuming you didn't use tube LEDs). The unusual brightness may be caused by an error in wiring that could be letting the full voltage of the power supply to go to each tube's heaters. They should be sharing that voltage in series, along with some drop through the resistors.


 Measure the voltage at pins 3 and 4, referenced to this diagram:
SSMH Tubes
 If you get something a lot higher than 19VDC on each tube, you have a problem! If it's 19VDC, then the brightness is normal. Note that all tube diagrams are referenced from the bottom of the tube! so if you're looking down from the top of the sockets, reverse this numbering. If you're looking at the sockets from underneath, then it's OK._

 

I came up with 19V when checking, so I think it's fine.

 I would, however, like you to explain how exactly they are connected in series. It seems like they are connected in parallel to me...
 Otherwise the ground from one would be connected to the input from the other.

http://www.diyforums.org/SSMH/schema...MH-origPCB.gif
 Is there another schematic that connects them in series or something?


----------



## tomb

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_<snip>
 I came up with 19V when checking, so I think it's fine.

 I would, however, like you to explain how exactly they are connected in series. It seems like they are connected in parallel to me...
 Otherwise the ground from one would be connected to the input from the other.

http://www.diyforums.org/SSMH/schema...MH-origPCB.gif
 Is there another schematic that connects them in series or something?_

 

You're right - I keep getting mixed up with the Millett MAXes. Those heaters are definitely in series.

 In this circuit, there's a voltage divider ahead of the MOSFET, I believe. Drop across the MOSFET takes care of the rest of the voltage drop down to the 19V across the heaters. Dsavitsk will probably have to post a more thorough explanation if you want one, though. I'm just guessing.


----------



## Hi-Po

Is preordering still possible as stated on the beezar site?And how can I do that?
 I'm really interested in building this amazing thing.


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In this circuit, there's a voltage divider ahead of the MOSFET, I believe. Drop across the MOSFET takes care of the rest of the voltage drop down to the 19V across the heaters. Dsavitsk will probably have to post a more thorough explanation if you want one, though. I'm just guessing.
	

	
	
		
		

		
			



_

 

That's basically right. R2 and R4 form a voltage divider, and the mosfet's gate sits at that voltage which is ~24V or so. The fet's source will be a couple of volts lower, ~19V. Then, the heater, which is basically a resistor, will draw a certain current at 19V (V=IR). The mosfet drops the rest of the voltage that is applied to the drain, so, as long as the gate is maintained at ~24V, you could raise the voltage on the drain without changing the voltage across the heater.


----------



## vapman

Would I be able to amp PortaPros well with this? They have a 60ohm impedance. I don't know if I would need to change around the schematic a bit to make up for the low impedance.


----------



## tomb

Quote:


  Originally Posted by *Hi-Po* /img/forum/go_quote.gif 
_Is preordering still possible as stated on the beezar site?And how can I do that?
 I'm really interested in building this amazing thing._

 

Sorry, not for kits. Shipment of the existing kit orders is imminent. That will occupy most of my next week, I think. After that, I'll take stock of the tubes I have left and decide whether to offer more kits.
	

	
	
		
		

		
		
	


	




 Of course, you can always order the PCB and tubes and order the BOM yourself. That seems to be a lost talent around here lately. Everyone wants a kit. I can remember a couple of years ago when we built everything around here without a kit.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *mckickflip* /img/forum/go_quote.gif 
_Would I be able to amp PortaPros well with this? They have a 60ohm impedance. I don't know if I would need to change around the schematic a bit to make up for the low impedance._

 

Of course! I listen to PortaPros on mine all the time - it's a perfect pair of headphones to use with the Starving Student. They work just fine with Input Resistors = Pot Impedance.


----------



## PJPro

Kits tend to work out cheaper. I'm building a pair of dual mono power amps at the moment and they're costing me a fortune! It's the postage from multiple suppliers, getting the wrong stuff, etc


----------



## BikeXCountry

all right. i'm not sure why, but my amp is pretty much silent with no imput, but if i attach an interconnect to the imput jack i get this horrible vibrating noise which with the pot at 30% sounds like a hum, but at full volume sounds like an old turntable microwave right next to your ear. if i poke around with a pin or a nail in the imput jack, i get the same result.

 poking the ground does nothing, but if i touch the left or right signal, i get that noise in the respective channel. if i touch a signal and the ground, the noise dissappears (not really surprising). now, this noise turns to static if i plug my source into the interconnect, but this static popping is still pretty loud (on full volume, virtually silent with volume down), and far noisier than the amp with no imput connected (which sounds like a barely audible, and almost pleasant whoosh at full volume).

 why am i getting this noise, and how come it's totally missing when there's nothing plugged in? is this oscillation? i tried putting a 1k resistor to pins 5-6 on each tube in case it was tube oscillation (the imput goes to pins 5-6 so it seemed likely) but that did absolutely nothing. is it a grounding problem, because i'm pretty sure that i've done a very thorough job of grounding..

 do any of you guys know what the problem could be?


----------



## nullstring

it sounds like a grounding problem to me, in my inexperienced opinion


----------



## Listen2this1

Quote:


  Originally Posted by *BikeXCountry* /img/forum/go_quote.gif 
_all right. i'm not sure why, but my amp is pretty much silent with no imput, but if i attach an interconnect to the imput jack i get this horrible vibrating noise which with the pot at 30% sounds like a hum, but at full volume sounds like an old turntable microwave right next to your ear. if i poke around with a pin or a nail in the imput jack, i get the same result.

 poking the ground does nothing, but if i touch the left or right signal, i get that noise in the respective channel. if i touch a signal and the ground, the noise dissappears (not really surprising). now, this noise turns to static if i plug my source into the interconnect, but this static popping is still pretty loud (on full volume, virtually silent with volume down), and far noisier than the amp with no imput connected (which sounds like a barely audible, and almost pleasant whoosh at full volume).

 why am i getting this noise, and how come it's totally missing when there's nothing plugged in? is this oscillation? i tried putting a 1k resistor to pins 5-6 on each tube in case it was tube oscillation (the imput goes to pins 5-6 so it seemed likely) but that did absolutely nothing. is it a grounding problem, because i'm pretty sure that i've done a very thorough job of grounding..

 do any of you guys know what the problem could be?_

 

So is the ground of the incoming signal attached to the master ground? It should be. If I am thinking right, you saying that the noise is soft with the volume down that is telling you that the noise seems to originate before the volume pot. 

 Read this: http://en.wikipedia.org/wiki/Ground_loop_(electricity)

 Also try searching this thread the same problem has come up a couple of times already.


----------



## the_equalizer

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Almost done. The build is but I am having a friend do some lettering and pin striping. Sounds good. The switch in the front is for a selector switch for the two inputs on the back.

 Will take better pics when the lettering is done.

 <snip>
_

 

Hello there! Nice build! I in turn finished mine late last night (or very early this morning, rather). It's nothing fancy, just a cheap generic plastic enclosure. For the point to point wiring I basically copied the one from Pete Millett's photo. I still have to do some minor stuff (power-on LED, grounding the volume pot's body) but here are three shots from my 3 a.m. first audition session.














 I must say I'm completely astounded at the sound of the amp: clear, punchy, 3-dimensional. My cheap Sony "CD Walkman" sounds gorgeous through it and it absolutely puts my previous two DIY amps to shame (Cmoy style) Thanks Pete! Now I just need a set of REALLY nice cans to go along with it... 

 I also want to thank Tomb for making the tubes available; it's not easy at all to come by those tubes here in MX. Then again I just saw Tomb's tutorial on building the SSH and the Hammond case looks sooo sweet ... I might just have to go and order one! Any still available Tomb?

 A thought for the electronics experts out there. Has anyone tried substituting the 19J6 for some other double triode with 150mA heater current (12AU7 maybe) and a resistor in series? The cathode and plate load resistors would have to be changed too of course, but I'm just checking on the idea's feasibility, since it seems to me that these days 12AU7's are cheaper and easier to come by than the 19J6.

 Cheers!


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_<snip>

 I also want to thank Tomb for making the tubes available; it's not easy at all to come by those tubes here in MX. Then again I just saw Tomb's tutorial on building the SSH and the Hammond case looks sooo sweet ... I might just have to go and order one! Any still available Tomb?_

 

Yes, there are cases available and they'll be shipping soon.
	

	
	
		
		

		
		
	


	



  Quote:


 A thought for the electronics experts out there. Has anyone tried substituting the 19J6 for some other double triode with 150mA heater current (12AU7 maybe) and a resistor in series? The cathode and plate load resistors would have to be changed too of course, but I'm just checking on the idea's feasibility, since it seems to me that these days 12AU7's are cheaper and easier to come by than the 19J6.

 Cheers! 
 

Dsavitsk has already designed a 12AU7 replacement circuit, but that's a ways in the future. We still have a fairly good supply of 19J6's.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, there are cases available and they'll be shipping soon.
	

	
	
		
		

		
		
	


	



 Dsavitsk has already designed a 12AU7 replacement circuit, but that's a ways in the future. We still have a fairly good supply of 19J6's._

 

Do you think there will be an opportunity for those who bought the PCB's when tubes were only offered with a full kit may be able to purchase them before those ship?


----------



## nullstring

Did Dsavitsk publish this replacement circuit anywhere?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Do you think there will be an opportunity for those who bought the PCB's when tubes were only offered with a full kit may be able to purchase them before those ship?_

 

I'm confused - "them" is what - tubes or cases?

  Quote:


  Originally Posted by *nullstring* 
_Did Dsavitsk publish this replacement circuit anywhere?_

 

Probably not. It's not been tested, either and requires a different circuit altogether. As I said, we still have PCB's and tubes for the Starving Student.


----------



## nullstring

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Probably not. It's not been tested, either and requires a different circuit altogether. As I said, we still have PCB's and tubes for the Starving Student._

 

Sometimes it seems like you are more in it for the money...
 don't get me wrong, I appreciate what've you done, and you've been very helpful to many people including myself.

 in any case, is there a problem with publishing a circuit that you won't be selling PCB's of? There are plenty of people who do this project P2P, and obtaining tubes from sources other than you, (who doesn't sell them without the PCB,) is nearing impossible.


----------



## ThePredator

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Sometimes it seems like you are more in it for the money...
 don't get me wrong, I appreciate what've you done, and you've been very helpful to many people including myself.

 in any case, is there a problem with publishing a circuit that you won't be selling PCB's of? There are plenty of people who do this project P2P, and obtaining tubes from sources other than you, (who doesn't sell them without the PCB,) is nearing impossible._

 

Nearly all of the designs that are released have already gone through a testing period.


----------



## dsavitsk

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Sometimes it seems like you are more in it for the money...
 don't get me wrong, I appreciate what've you done, and you've been very helpful to many people including myself._

 

Oh, please. In terms of materials and time, this has cost all of us way more than we'll ever make back. But, more to the point, if you object, design your own stuff.

 Tom did an enormous amount of work gathering tubes from places near and far. Had he not, as someone not in touch with a lot of tube dealers, it is unlikely you, or anyone else here, would have found them. Then, he tested them, and even though he paid for them, he opted not to pass the garbage, which was a large percentage of the tubes, along. Meaning he ate the cost. Then, he sold the rest at a more than reasonable price, all so you could complain that he is in it for the money. Even more, Tom has taken days off work so he can get these kits assembled and shipped out.

 Anyway, a 12AU7 version can be done with literally one resistor change -- I'll leave that change as an exercise for you.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm confused - "them" is what - tubes or cases_

 

Sorry, I was referring to those who had purchased the PCBs without tubes previously possibly being able to purchase tubes. I had placed an order for hammond cases and PCBs in May when the tubes weren't available with anything but the full kit.


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Sorry, I was referring to those who had purchased the PCBs without tubes previously possibly being able to purchase tubes. I had placed an order for hammond cases and PCBs in May when the tubes weren't available with anything but the full kit._

 

OK - that makes sense. Yes - if you've purchased a PCB, I'll definitely sell you a pair of tubes to go with it.


----------



## nullstring

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Oh, please. In terms of materials and time, this has cost all of us way more than we'll ever make back. But, more to the point, if you object, design your own stuff.

 Tom did an enormous amount of work gathering tubes from places near and far. Had he not, as someone not in touch with a lot of tube dealers, it is unlikely you, or anyone else here, would have found them. Then, he tested them, and even though he paid for them, he opted not to pass the garbage, which was a large percentage of the tubes, along. Meaning he ate the cost. Then, he sold the rest at a more than reasonable price, all so you could complain that he is in it for the money. Even more, Tom has taken days off work so he can get these kits assembled and shipped out.

 Anyway, a 12AU7 version can be done with literally one resistor change -- I'll leave that change as an exercise for you._

 

Sorry, I wasn't trying to offend anyone.
 As I said, I'm aware that he, you, and pete have made great efforts, and I appreciate them. None of this would've been possible without you guys.

 I just think that his "As I said, we still have PCB's and tubes for the Starving Student." is poor reasoning, and that the community has demand for other versions.

 I don't want to start an argument. I regret making the comment in the first place.


----------



## tomb

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Sorry, I wasn't trying to offend anyone.
 As I said, I'm aware that he, you, and pete have made great efforts, and I appreciate them. None of this would've been possible without you guys.

 I just think that his "As I said, we still have PCB's and tubes for the Starving Student." is poor reasoning, and that the community has demand for other versions.

 I don't want to start an argument. I regret making the comment in the first place._

 

Let's give you a basis for where that quote is coming from ... since it obviously troubles you so much.

 Since the beginning, Pete and Nate (n_maher) have kept an eye on the Starving Student and how many P2P builds were constructed. At such time as they felt appropriate that enough people who wanted to build a P2P had the chance to build one, then they contacted Dsavitsk and myself about introducing a PCB version. The idea was to expose even more people to the Starving Student than were possible with a P2P version. Surely you can see that a PCB exposes more people to a particular design - it's paint by numbers to a large degree, ensures proper grounding, good trace lengths, and minimizes the casing requirements.

 However, a PCB brings its own issues to the project - namely, volume requirements. In order to get PCB pricing down to "Starving Student standards," enough volume had to be ordered to obtain a reasonable per-PCB price. By the time these discussions were made in earnest, the scarcity of the 19J6 tubes had already occurred. So, what to do - buy PCB's in volume with the prospect that anyone who purchased one would not be able to find the tubes? That's almost throwing money down the toilet. Why purchase $hundreds of dollars worth of boards when no one would buy - knowing that they probably couldn't get tubes?

 So before we made the PCB a reality, I set about purchasing 19J6's from every odd source I could find. As mentioned previously in this thread in a number of places when considering this strategy - no tubes were purchased from vendors who were selling onesie-twosies. In fact, if they wouldn't sell me at least 50 -100 (maybe 30 in one case), I didn't purchase them. In one case, there was a vendor who was selling onesie-twosies, but he assured me that my volume buy would not deprive those customers.

 Once I had a decent stock of tubes, we decided it was OK to go ahead with the PCBs. Even then, I only have stock enough to supply half of the PCB's. So, we all agreed that tubes would only be sold with the purchase of a PCB or a kit. PCB's could be sold separately, because someone might find limited tubes elsewhere, or already have their own. Otherwise, the PCB's would've been a failure.

 So you see, I'm the one who has spent $hundreds for PCB's with not enough tubes available on the market to cover more than half of them. So, you'll have to forgive me when I say again if asked to come up with another option, "we still have PCB's and tubes for the Starving Student."

 P.S. Sorry you didn't have the history on this. Sometimes we forget that stuff that has been an open strategy in this thread for months and months has not been shared with everyone.


----------



## Llama16

I'm pretty darn gratefull for tomb and dsavitsk to put this project on sale for VERY reasonable prices. Not to mention all the organization and searching (just time in general) it must have involved to set all this up.
 This is as much as the only project I could build right now, it's very good to learn from and as I have heard it has alot of quality for it's money. It's a great next step for me in the DIY world.
 I couldn't find the tubes anymore....ANYWHERE, only from some foolish shop that offered them for over 30...EACH! and add about 20 dollars costs for international shipping. That's immense for a student.
 I bought the tubes (matched!), sockets AND the PCB for around 30dollars. SHIPPED!!!!!

 Guess what, I'm about to make a second order. For both a p2p and a pcb version. Because I know that when those tubes are gone from his site, I'll never be able to get my hands on them, certainly when you know I'm from europe.

 Sorry if I came out edgy 
	

	
	
		
		

		
			





, But I'm just glad we have people like them on here.


----------



## PJPro

It an interesting point actually. I hadn't considered the scarcity of the tubes. Are we saying that no other tubes will do? What happens if I accidently break one.....am I going to be unable to purchase a replacement? Should I be buying a couple of spares right now, preparing for the future mishap?


----------



## kuroguy

I've done group buys before and I can attest that there is very little money to be made with them. Generally, they are a way to get a group of people to share the expense. So, what you wind up with is an amp that costs $100 instead of $150 but you also get the hassle of packaging multiple kits. Generally not worth the effort unless you really want to get something done right.

 That said, Just knowing that there are other options out there for tubes is worth something. In fact, I would doubt that the guys doing this group buy should really have a problem with users using their PCB with alternative tubes and a few different resistor values; especially since there is still a huge market for 19J6 tubes. In fact, I would think that anything that helps sell the PCBs would be a plus. 

 Either way, thanks for the effort. It is greatly appreciated. It certainly opens trhe hobby to more people and after all, that's the reason we all meet here in the DIY forum, isn't it?

 Just my $0.02.

 Kuroguy


----------



## procalli2007

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_
 Anyway, a 12AU7 version can be done with literally one resistor change -- I'll leave that change as an exercise for you._

 

Could the pcb be adapted by changing the resistor? Would help me decide on a pcb buy as Im a bit wary as Ive already had 1 19j6 go faulty. Also there doesnt seem to be an option of buying backup valves with the pcbs(ie 3 instead of 2).

 How long do valve usually work for(maximum)?


----------



## Logistic

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_It an interesting point actually. I hadn't considered the scarcity of the tubes. Are we saying that no other tubes will do? What happens if I accidently break one.....am I going to be unable to purchase a replacement? Should I be buying a couple of spares right now, preparing for the future mishap?_

 

I posted a guide a while back on using the 12sr7 or 12sw7 tubes with the starving student. You can use those with the pcb, but will have to mount the tube sockets off the board.


----------



## revolink24

Just a question for the designers/those that have built it, how would using he 50k input resistors (high gain) work on headphones such as Grados? I wish to drive both Grados and potentially higher impedence lower sensitivity headphones, but I dont really want to have to bother about integrating a gain switch.


----------



## Listen2this1

I ended up putting 320k on the inputs and I still get little change in movement on the knob with my Grado's and Denon's. I do not own any Senns so I can not tell you the action on the volume with them, I am guessing that there is little more but not much. I would put in a 320k and live with the little action, just tell any one that is un-experienced with amps to take it easy with the volume.


----------



## revolink24

I just ordered the case and tubes, I would really appreciate someone with experience telling me what Grados sound like on a high-gain SSMH (50k resistors for R16/R17, with pcb work)


----------



## royalflush

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Sometimes it seems like you are more in it for the money...
 don't get me wrong, I appreciate what've you done, and you've been very helpful to many people including myself.

 in any case, is there a problem with publishing a circuit that you won't be selling PCB's of? There are plenty of people who do this project P2P, and obtaining tubes from sources other than you, (who doesn't sell them without the PCB,) is nearing impossible._

 

Comment was not directed at me but I was offended. I think you got off too easy for such blatant disregard for the efforts put forth. Other folks before you asked politely about a kit change and were grilled for even thinking it... I thought with your comment above you'd definitely be in the dog house.

  Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_Sorry, I wasn't trying to offend anyone.
 As I said, I'm aware that he, you, and pete have made great efforts, and I appreciate them. None of this would've been possible without you guys._

 

no sorry I don't think you mean it.

  Quote:


 I just think that his "As I said, we still have PCB's and tubes for the Starving Student." is poor reasoning, and that the community has *demand* for other versions. 
 

demand? you mean "request". There is a difference, you're at the mercy of the designer and owes you nothing. As dsavitsk said why not design it yourself.

 Oh, and give the courtesy by acknowledging the explanation tomb provided (even though I thought you didn't deserve an explanation) at least it might guarantee removal of your name from their ignore list. I've only lurked here a few times and even I knew what the reasoning behind their strategy.

 [/sorry just felt the need to rant]


----------



## Fred_fred2004

I have not been involved with this kit because I prefer to blunder through with my own layouts (and mistakes) but I've been lurking and it staggers me how much work that Tomb has but into this project and how good it looks. 
 The whole community owes a debt of gratitude to members like Tomb who are willing to commit this much time and effort to help others participate in this great hobby
 cheers
 FRED


----------



## yebisu

any word on shipment of the kits? I'm excited 
	

	
	
		
		

		
			





 and i'm also moving across the nation on the 13th, so i really do hope i get mine before then


----------



## amc

Quote:


  Originally Posted by *Fred_fred2004* /img/forum/go_quote.gif 
_The whole community owes a debt of gratitude to members like Tomb who are willing to commit this much time and effort to help others participate in this great hobby_

 

Well said. Couldn't agree more. Thanks a million Tomb and Dsavitsk.


----------



## ThePredator

Quote:


  Originally Posted by *Fred_fred2004* /img/forum/go_quote.gif 
_The whole community owes a debt of gratitude to members like Tomb who are willing to commit this much time and effort to help others participate in this great hobby
 cheers
 FRED_

 

And don't forget amazing designs and resources made available by Pete Millet.


----------



## ethan961

So many people have put so much work into this, they definately deserve a big round of applause.
 TomB, Beezar is a godsend for international people who don't want to pay $8 to get stuff shipped from digikey or $20 to get it shipped from Newark.
 I bought everything but the tubes, tube sockets, and power supply locally. Yes, I did pay more than I needed to, but hey, it's good to do business locally. However, the local electronics shop did not have Wimas afaik so I'll be ordering them from Beezar 
	

	
	
		
		

		
		
	


	




 As well as some nichicon muses for the plate resistance or whatever it is.


----------



## ethan961

Alright I ordered the PSU off eBay and the caps from Beezar (the most painless international transaction I've ever encountered, kudos to TomB 
	

	
	
		
		

		
		
	


	




)
 My case is certainly something original and interesting. Once it's done there will be pics 
	

	
	
		
		

		
		
	


	




 but until then it's a surprise.
 Just need the sinks (local electronics shop actually carries the sinks called for in Pete's BOM but I took them back at first because they weren't 2" tall and I didn't realize there was a misprint. My case should dissipate heat fairly well though 
 I was about to order the tubes from vacuumtubes.net but their secure order form isn't so secure at the moment, so I'll be waiting until that has been clarified. 
 Thanks again to TomB and everyone who made this possible.


----------



## the_equalizer

You can also get a parts kit including PSU, heatsinks (MOSFET's already mounted) and tubes (no enclosure, no terminal strips) from e-bay seller extremelighting 

 Cheers!


----------



## PJPro

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_You can also get a parts kit including PSU, heatsinks (MOSFET's already mounted) and tubes (no enclosure, no terminal strips) from e-bay seller extremelighting 

 Cheers!_

 

I just had a look and he doesn't have anything for sale at the moment.


----------



## the_equalizer

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_I just had a look and he doesn't have anything for sale at the moment._

 

Indeed he sometimes takes his time before posting the next sale. I spent around 3 or 4 days hunting for his post until it finally appeared so... if you're interested, hang on.

 Just to be clear you won't find metal film resistors, Nichicon caps or an ALPS "blue velvet" in his kit; it's quite for the "Starving Student" looking to buy this at a low cost.

 Cheers!


----------



## Listen2this1

Well I have been listening to this amp for about three straight weeks and now I took this amp to my brothers, plugged it in and I am getting some serious distortion. The odd thing is the lower the volume the higher the noise. The louder I go the noise begins to disappear and eventually will disappear completely. In all of my times dealing with gear I have never came across a issue where the noise gets softer when the volume goes up.

 Suggestions?

 James


----------



## the_equalizer

Quote:


  Originally Posted by *Listen2this1* /img/forum/go_quote.gif 
_Well I have been listening to this amp for about three straight weeks and now I took this amp to my brothers, plugged it in and I am getting some serious distortion. The odd thing is the lower the volume the higher the noise. The louder I go the noise begins to disappear and eventually will disappear completely. In all of my times dealing with gear I have never came across a issue where the noise gets softer when the volume goes up.

 Suggestions?

 James_

 

Very strange indeed. Sounds like a grid bias issue, as if the grid circuit were conducting. Is this happening with your usual source? It could be that you're using a different source and this one is putting DC in the tube grid (the original SSHM does not have DC blocking input capacitors).

 If possible check the voltage reading in the tubes cathodes (pin 7, 1.2 volts), grids (pins 5 and 6, 0 volts) and anodes (pins 1 and 2, ~25 volts) with respect to ground. 

 Cheers!


----------



## Zentactics

Just got an email that my order is being processed. Thanks Tom!!!!

 Zen


----------



## Llama16

I wish he had some sort of a complete order of all the parts without the case (*hint!*) Because I hate going through all the backordered stuff on mouser and then still have to pay for it or wait till october (keeping in mind that all the rest stays in stock).

 Naa, just kidding, I understand that it's a pita to still assemble all those packages just with those parts.


----------



## Yaka

prolly not a question for this thread,but gonna ask it none the less
	

	
	
		
		

		
		
	


	




 once my kit will be delivered it will be my 4th SS build, first 2 were messy and horrid p2p builds 3rd was the beta board. so wots the next best project to under take considering im still a newbie?


----------



## Sparhawk

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_I wish he had some sort of a complete order of all the parts without the case (*hint!*) Because I hate going through all the backordered stuff on mouser and then still have to pay for it or wait till october (keeping in mind that all the rest stays in stock).

 Naa, just kidding, I understand that it's a pita to still assemble all those packages just with those parts._

 

He did have kits, but they sold out pretty quick. I just ordered a bunch of individual pieces, amounts to the same thing, but I was sure I checked the list 10 times before I ordered. 
	

	
	
		
		

		
		
	


	




 I just ordered a bunch of the parts from mouser, ships tomorrow. You should be able to find equivalent items that are in stock with a little searching.


----------



## Lamp

I just finished soldering the PCB version tonight, ran some audio through the left channel to make sure it all works (casework still needs finished, so I can't have it all soldered together yet) and C1 swelled and threatened to blow on me.

 I am assuming I put it in backwards? Thing is, when I removing c1, the leads were in fact in the right orientation.
 I am using the Nichicon 680uf (UPW1J681MHD3)....I was under the impression the stripe indicates the negative lead?


----------



## tomb

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_I just finished soldering the PCB version tonight, ran some audio through the left channel to make sure it all works (casework still needs finished, so I can't have it all soldered together yet) and C1 swelled and threatened to blow on me.

 I am assuming I put it in backwards? Thing is, when I removing c1, the leads were in fact in the right orientation.
 I am using the Nichicon 680uf (UPW1J681MHD3)....I was under the impression the stripe indicates the negative lead?_

 

I go by the long lead as positive, but it's the same difference. I would've said take a pic and let us show you where it went wrong, but if you've removed it, it won't matter at this point. However - the PCB has been thoroughly vetted, so sorry to say it must be user error.
	

	
	
		
		

		
			





 Bottom line - if the cap swelled, it's done - throw it out.

 It's pretty easy to see the correct orientation in this pic:


----------



## Lamp

I went by the long lead too, but because they were trimmed I couldn't check my work after. And I remembered the orientation they were in before removing. The stripes were in the same orientation as your pic. I guess I just had a bad cap? Would there be anything else to cause swelling?

 I had left it running for about 5 minutes before I noticed. I wasn't getting any audio and tubes and mosfets were both cold. I was checking my voltages when my hand brushed C1 and I noticed it was extremely hot.


----------



## tomb

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_I went by the long lead too, but because they were trimmed I couldn't check my work after. And I remembered the orientation they were in before removing. The stripes were in the same orientation as your pic. I guess I just had a bad cap? Would there be anything else to cause swelling?

 I had left it running for about 5 minutes before I noticed. I wasn't getting any audio and tubes and mosfets were both cold. I was checking my voltages when my hand brushed C1 and I noticed it was extremely hot._

 

I seriously doubt it. That just does not occur with Nichicon caps (or Panasonics). Obviously, if your memory is correct, then something else is wrong. What power supply were you using?

 NOTE: Just to be clear, the Starving Student is not an amp that you can just "run up" to check audio or other things. Either those MOSFETs have heat sinks on them or they'll burn up in a heartbeat.


----------



## Giuss

Hello, which temperature do you have on your heatsink?

 I'm testing a single heatsink for both mosfets, this heatsink is 9x5x2 cm, so is not small, and I have more than 60°C

 I know that it isn't a dangerous temperature for the mosfet, but I think that it's too high


----------



## tomb

Quote:


  Originally Posted by *Giuss* /img/forum/go_quote.gif 
_Hello, which temperature do you have on your heatsink?

 I'm testing a single heatsink for both mosfets, this heatsink is 9x5x2 cm, so is not small, and I have more than 60°C

 I know that it isn't a dangerous temperature for the mosfet, but I think that it's too high_

 

A lot of factors besides dimensions govern the heat transfer effectiveness of a heat sink. Still, 60°C is not that far off. I wouldn't worry about it unless the heat is re-directed back into the case or your circuit components.


----------



## Lamp

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I seriously doubt it. That just does not occur with Nichicon caps (or Panasonics). Obviously, if your memory is correct, then something else is wrong. What power supply were you using?_

 

48V .38A Cisco.

 Best I can guess, I swapped G and B+ because I had had everything plugged in earlier and no swelling had occurred. And running the circuit backwards could have easily blown C1, as it is grounded. Thats my thinking at least. What an embarrassing goof.

 Anyways, when previously plugged in, I had no response either. LEDs were working (no surprise), but tubes and mosfets were both cold as I mentioned. Mosfets were mounted to the heatsinks btw. I'm making my own case, so everything can be put together before the whole assembly is put in the case. 
 I measured voltages and everything seemed okay. Any tips?


----------



## tomb

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_48V .38A Cisco.

 Best I can guess, I swapped G and B+ because I had had everything plugged in earlier and no swelling had occurred. And running the circuit backwards could have easily blown C1, as it is grounded. Thats my thinking at least. What an embarrassing goof._

 

Not so embarrassing, really - some amps include a diode across the power input to prevent such an occurrence. Such design features are the exception, not the rule, though - just saying that it's not as embarrassing as you think.
	

	
	
		
		

		
		
	


	



  Quote:


 Anyways, when previously plugged in, I had no response either. LEDs were working (no surprise), but tubes and mosfets were both cold as I mentioned. Mosfets were mounted to the heatsinks btw. I'm making my own case, so everything can be put together before the whole assembly is put in the case. 
 I measured voltages and everything seemed okay. Any tips? 
 

The first thing to look at is the heater circuit. If the heaters don't light, the tubes won't operate. In the case of the Starving Student, the MOSFETs are in the heater circuit, too - so it's all the same issue. You might want to supply a pic or two and see if someone can identify what's amiss.


----------



## luvdunhill

Talk about bullet-proof packing 
	

	
	
		
		

		
		
	


	




 Do you have plans in the immediate future to update the "Construction" section of the website at diyforums.org? It's always nice to see what hints and tips Tom B. has to share


----------



## sandbasser

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Talk about bullet-proof packing 
	

	
	
		
		

		
		
	


	




 Do you have plans in the immediate future to update the "Construction" section of the website at diyforums.org? It's always nice to see what hints and tips Tom B. has to share 
	

	
	
		
		

		
		
	


	


_

 

I suspect that TomB will eventually get the SSH doc cleaned up. But, in the mean time he posted a nice thread on his forum. I found it Very, very helpful.


----------



## tomb

Yep - seem to be running behind on everything these days. In the meantime, I've added that Starving Student PCB Build thread to my sig. Maybe that will help everyone get to it fast.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - seem to be running behind on everything these days. In the meantime, I've added that Starving Student PCB Build thread to my sig. Maybe that will help everyone get to it fast.
	

	
	
		
		

		
		
	


	


_

 

just finished steps 1-999 and have the LED sockets ready. Two more steps to go and I'll be listening to music!






 seriously, thanks for the link!


----------



## Lamp

So, just to clarify things.
 If I am reading this circuit correctly, audio has to be coming in before the tubes fire up?


----------



## tomb

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_So, just to clarify things.
 If I am reading this circuit correctly, audio has to be coming in before the tubes fire up?_

 

Nope - didn't say that at all. The tubes will fire, no matter what. Since the MOSFETs are tied into the heaters, that means they have a 150ma Class A current bias. IOW, the amp will sit and cook whether there's any music at all.


----------



## tomb

Shoot!

 After reviewing the Build Thread again, I realized that I forgot to copy in the entire wiring sequence! It's fixed, now.


----------



## revolink24

It would seem I missed out on the custom cases. I got an email from beezar saying Hammond shorted them on the machined cases.... not quite sure what to do now, as it is hard to do precise machining with a drill press/hand drill.... any suggestions?


----------



## Lamp

Okay, got another C1 in there, but the thing is still not warming up.

 Pictures: (I removed heat sinks to take pictures)
http://i589.photobucket.com/albums/s...p/DSC02181.jpg
http://i589.photobucket.com/albums/s...p/DSC02180.jpg
http://i589.photobucket.com/albums/s...p/DSC02179.jpg

 As far as voltages go:
 mosfets: 5.4v on pin 1, 46.1v on pin 2, 35.3v on pin 3
 tubes: 11.7v on pins 1 and 2, 3.7v on pin 3, 0v on the rest.


----------



## dsavitsk

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_Okay, got another C1 in there, but the thing is still not warming up._

 

Your tubes are on the wrong side of the PCB ...


----------



## Lamp

ahhhh hahahahah
 gonna need to fix that.
 Quite an important thing to forget when changing the design.
 My bad.


----------



## the_equalizer

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_ahhhh hahahahah
 gonna need to fix that.
 Quite an important thing to forget when changing the design.
 My bad.
	

	
	
		
		

		
		
	


	


_

 

Also, as someone else pointed out earlier, you need to heatsink the MOSFET's even for you startup test. 150 mA flowing through them without heatsinks will simply destroy them in a few seconds.

 Cheers,


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_It would seem I missed out on the custom cases. I got an email from beezar saying Hammond shorted them on the machined cases.... not quite sure what to do now, as it is hard to do precise machining with a drill press/hand drill.... any suggestions?_

 

Yes, I apologize for this. Hammond sent several cases that weren't machined. I don't know yet whether those are extras or whether they made a mistake or whether I did. I was working very hard at my day job during that time and wasn't able to monitor things as I should, so it could very well be my fault. One thing's certain - there are not enough cases for the last 3 that ordered them - those orders came in only during the last couple of weeks. Please keep in mind that some (most?) people had ordered these all the way back in May, so they got priority. I've contacted Hammond about these extra, un-machined cases and I should know the story by Monday night.

_As always, however, I'll cheerfully refund every penny of your order if no more cases is the end result._

 As for "precise" machining with a drill press and hand drill - no, not at all. It's no harder than drilling any other case for a DIY amp ... actually simpler when it comes to MOSFETs because there's no cooling holes required. I'll post the drawings when I can (they're in this thread if you can find them).


----------



## Lamp

So I got the socket situation solved...kinda.
 Mosfets are nice and toasty now, but tubes are still dark.
 Because of the last minute design change, the sockets are now p2p.
 Could the tubes not be getting enough power due to shoddy p2p soldering?


----------



## tomb

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_So I got the socket situation solved...kinda.
 Mosfets are nice and toasty now, but tubes are still dark.
 Because of the last minute design change, the sockets are now p2p.
 Could the tubes not be getting enough power due to shoddy p2p soldering?_

 

Well, yeah - shoddy soldering could lead to shoddy connections, etc., etc.

 I haven't had good luck in removing tube sockets from a PCB - although some are able to do it. Personally, I would've snipped the pins, thrown away the sockets, and then cleaned up the holes with de-soldering braid. Once that's done, then start fresh with some new sockets - that's only a couple of dollars.


----------



## ludoo

A possibly stupid question since I've finally got around to building my PCB-based SS.

 I'd like to fit the four Cerafine 470uf caps I have, and the only way I can mount them is on top, on the same side as the tube sockets, drilling four holes in the top for them. My question is, since in this position they will be right next to tubes, will the tubes heat damage them, or reduce their performance?

 How hot do the SS tubes run? I could check the one I still have at the office, but I have no way to take a temperature measurement. The Cerafines are rated at 85 degrees.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_A possibly stupid question since I've finally got around to building my PCB-based SS.

 I'd like to fit the four Cerafine 470uf caps I have, and the only way I can mount them is on top, on the same side as the tube sockets, drilling four holes in the top for them. My question is, since in this position they will be right next to tubes, will the tubes heat damage them, or reduce their performance?

 How hot do the SS tubes run? I could check the one I still have at the office, but I have no way to take a temperature measurement. The Cerafines are rated at 85 degrees._

 

I wouldn't worry about it. There will be some radiation, but the air between the spacing is a good insulator.
	

	
	
		
		

		
		
	


	




 Let me ask this, though - have you thought of laying them down horizontally? I haven't looked at it lately, but it's possible that with a bit of creative bending they may fit on the bottom. Lead length in a scenario such is this is trivial, so I wouldn't worry about that.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I wouldn't worry about it. There will be some radiation, but the air between the spacing is a good insulator.
	

	
	
		
		

		
		
	


	




 Let me ask this, though - have you thought of laying them down horizontally? I haven't looked at it lately, but it's possible that with a bit of creative bending they may fit on the bottom. Lead length in a scenario such is this is trivial, so I wouldn't worry about that._

 

Thanks Tom, as usual, for the quick and helpful reply. 
	

	
	
		
		

		
		
	


	




 I thought about laying them horizontally, but the problem is I am also using a couple of copper Obbligato caps, and they take quite a bit of space. A pity the Hammond case isn't half a cm. taller.

 Now I only have to find the right heatsink, I thought I could use the "standard" (i.e. pre-PCB) ones but the mosfets legs aren't tall enough with the PCB mounted in the correct slot.

 I'm pretty good at complicating simple projects. 
	

	
	
		
		

		
		
	


	




 Edit: scrapped my previous edit, I might have found the rs-online equivalent for the standard PCB-build heatsink.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Thanks Tom, as usual, for the quick and helpful reply. 
	

	
	
		
		

		
		
	


	




 I thought about laying them horizontally, but the problem is I am also using a couple of copper Obbligato caps, and they take quite a bit of space. A pity the Hammond case isn't half a cm. taller.

 Now I only have to find the right heatsink, I thought I could use the "standard" (i.e. pre-PCB) ones but the mosfets legs aren't tall enough with the PCB mounted in the correct slot.

 I'm pretty good at complicating simple projects. 
	

	
	
		
		

		
		
	


	




 Edit: scrapped my previous edit, I might have found the rs-online equivalent for the standard PCB-build heatsink._

 

Yep - that's the one!

 About the MOSFETs - it's probably permissable to add some length to the MOSFET legs. Surely enough to cover the distance for an extra slot or two won't be too critical. I used to build the legs up on TO-220 LM317's all the time. Just take a spent resistor lead (one from a quality electrolytic or film cap might be better) and solder to the existing legs. Again, I wouldn't carry this too far, but 1/4" or so might be fine.


----------



## Lamp

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, yeah - shoddy soldering could lead to shoddy connections, etc., etc.

 I haven't had good luck in removing tube sockets from a PCB - although some are able to do it. Personally, I would've snipped the pins, thrown away the sockets, and then cleaned up the holes with de-soldering braid. Once that's done, then start fresh with some new sockets - that's only a couple of dollars.
	

	
	
		
		

		
		
	


	


_

 

Sorry for my persistent failings, but I really am stumped. I checked all the connections and all are sound. 
 Did I allow any harm to the tubes by mounting the sockets upside down?
 I am getting voltages 9.6 on pins 1 and 2 and 1.7 on pin 3, but nothing else.
 According to the layout, pin 3 should be getting ~19v?

 Also, what kind of voltage should I be measuring from the input?
 BantamDac >


----------



## Juaquin

Well I'm not familiar with the 19J6 tube pinout, but if you put the socket on the wrong side of the board all the pins would be switched around, which could cause something bad to happen (applying heater voltage to rest of the tube?).

 I just finished building my kit - I'll post pictures and some further words later. I also have some construction tips. For now I'll just say it's an awesome looking amp and so far the sound quality is very good, which can only improve.


----------



## tomb

Quote:


  Originally Posted by *Lamp* /img/forum/go_quote.gif 
_Sorry for my persistent failings, but I really am stumped. I checked all the connections and all are sound. 
 Did I allow any harm to the tubes by mounting the sockets upside down?
 I am getting voltages 9.6 on pins 1 and 2 and 1.7 on pin 3, but nothing else.
 According to the layout, pin 3 should be getting ~19v?

 Also, what kind of voltage should I be measuring from the input?
 BantamDac >_

 

No offense, but the fact that you installed the sockets backward in the first place and then somehow managed to remove them and air-wire them doesn't give us a very good starting point to try and trouble-shoot from your post. Air-wiring tube sockets from a PCB is a difficult feat even under the best of circumstances.

 One of the advantages of a PCB is to remove the possibility of wiring mistakes, reducing trouble-shooting down to reviewing photos of one's handiwork to confirm correct parts in correct positions. Unless you mis-place a part, there's no way to fail. With your attempt at air-wiring the sockets, you've taken that advantage away and left us with little to do except to ask for another pic. 

 I don't mean to sound discouraging, but maybe I should've been more explicit in my earlier post: _start over with the tube sockets._ There's little you can do to the tubes to damage them short of a physical break ... assuming you don't leave them on for an extended period with bad voltages. However, there's about 14 different ways you can mess up the wiring to tube sockets that were supposed to be soldered to the PCB.


----------



## Lamp

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No offense, but the fact that you installed the sockets backward in the first place and then somehow managed to remove them and air-wire them doesn't give us a very good starting point to try and trouble-shoot from your post. Air-wiring tube sockets from a PCB is a difficult feat even under the best of circumstances.

 One of the advantages of a PCB is to remove the possibility of wiring mistakes, reducing trouble-shooting down to reviewing photos of one's handiwork to confirm correct parts in correct positions. Unless you mis-place a part, there's no way to fail. With your attempt at air-wiring the sockets, you've taken that advantage away and left us with little to do except to ask for another pic. 

 I don't mean to sound discouraging, but maybe I should've been more explicit in my earlier post: start over with the tube sockets. There's little you can do to the tubes to damage them short of a physical break ... assuming you don't leave them on for an extended period with bad voltages. However, there's about 14 different ways you can mess up the wiring to tube sockets that were supposed to be soldered to the PCB._

 

No offense taken at all.
 I am extremely lucky to have any help at all.

 The main reasoning behind "air-wiring" the sockets stems from my sudden lack of a wood shop. The case can't be altered to allow me to mount the pcb upside down to then pcb mount the sockets. I might just find some panel mount sockets to fasten to the inside of the top lid. But if worse comes to worst, I can ditch the case and have the whole thing open-air for a while. 

 The only thing that lead me to believe something other than the wiring was off was the fact that I am getting the same voltages on the same pins for both tubes. I had the tubes reversed and running for a little under 10 minutes, by the way....I was just hoping they were slow on the warmup.

http://i589.photobucket.com/albums/s...H/DSC02185.jpg
http://i589.photobucket.com/albums/s...H/DSC02186.jpg
http://i589.photobucket.com/albums/s...H/DSC02190.jpg

 You can't really see from the pics, but small holes were drilled in the pins to thread the wire through. The thicker wire is the first socket I did. I was frustrated with its stiffness, so tried thinner wire, and then forgot to cover the pins. 

 I have nails (with heatshrink for a tight fit) through the led holes in order to keep the sockets straight and sturdy so they stay on target for the tube holes in the lid. Needless to say, led lighting is lower priority right now, so I just popped some ultra brights in there for at least a little illumination. This whole thing got messy pretty quick.


----------



## luvdunhill

Tom/Doug:

 I like the amount of wiggle room that the board has when inserted into the slots. What percentage of the maximum slot depth did you use when determining the width of the PCB? I'm working on a case/PCB combo and am fairly worried about tolerances preventing the "perfect fit".


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom/Doug:

 I like the amount of wiggle room that the board has when inserted into the slots. What percentage of the maximum slot depth did you use when determining the width of the PCB? I'm working on a case/PCB combo and am fairly worried about tolerances preventing the "perfect fit"._

 

I'll have to check my e-mail files because we went back and forth on it - too loose, too tight, just right. Maybe it was the Goldilocks method.
	

	
	
		
		

		
			





 Alternatively, you can measure it and compare to the published Hammond slot width. I'll do that tonight when I get a chance. I believe it's 1 millimeter of clearance on each side.


----------



## eekimus

So I had just purchased the SSMH PCB, and built my third SSMH.

 I tested it out on a pair of Beyerdynamic DT770, 250ohm. With the 50K pot vol turned up fully, and source volume on full, there's a hum in the background, and barely any sound.

 I have used 30 and 80 ohm headphones on the SSMH with good success, what's up this this one now? P2P wiring from tube sockets to PCB, jacks, plug sockets etc.

 Internal wiring is done with twisted CAT-5 cable pairs. Soldering has all been checked and okay.

 How does teh amp behave with 250ohm loads?


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Tom/Doug:

 I like the amount of wiggle room that the board has when inserted into the slots. What percentage of the maximum slot depth did you use when determining the width of the PCB? I'm working on a case/PCB combo and am fairly worried about tolerances preventing the "perfect fit"._

 

The Hammond 1455N1201 has a slot width of 100mm (3.937").
 The SSMH PCB width is 98.6309mm (3.883").

 If you're looking for a percentage, that's pretty easy to equate with the Hammond millimeter dimension (100) - 98.6309%.

 I think Dsavitsk actually tried for a millimeter and a half clearance - there may be some slight dimensional conversion errors in the DXF file (0.1309).


----------



## tomb

Quote:


  Originally Posted by *eekimus* /img/forum/go_quote.gif 
_So I had just purchased the SSMH PCB, and built my third SSMH.

 I tested it out on a pair of Beyerdynamic DT770, 250ohm. With the 50K pot vol turned up fully, and source volume on full, there's a hum in the background, and barely any sound.

 I have used 30 and 80 ohm headphones on the SSMH with good success, what's up this this one now? P2P wiring from tube sockets to PCB, jacks, plug sockets etc.

 Internal wiring is done with twisted CAT-5 cable pairs. Soldering has all been checked and okay.

 How does teh amp behave with 250ohm loads?_

 

The SSMH has no problems at all with 300 ohm Senns, so 250 ohm Beyers should be a piece of cake.

 Something else is going on ... It sounds like you're saying you've used 30 ohm and 80 ohm headhones, but perhaps not on this particular build. It may have nothing to do with the Beyers. Have you tried other headphones on this one?

 One thing to check is the input wiring. If you've crossed up the grounds with signal, you can get the effect you describe.


----------



## tomb

All kits and cases (except the 2 or 3 who were shorted) have been shipped. I have some extra cases that did not have the top lid machined and will do those myself for the ones who were shorted, if they agree.

 There are quite a few tubes left, so I've asked Hammond for a quote for more cases. So, there will be cases and some partial kits (minus the power supply) available in the future. I'll keep you posted.


----------



## ludoo

I just finished my PCB-based SS (sorry Tom for getting a proto PCB then waiting half a year to build it). As I wrote a few posts above, I top mounted the 4 electrolytic caps as my Cerafines were too tall. This led to an accident while drilling the top holes, and after much head scratching I managed to salvage the case by carving a large space on top with the Dremel. It's not perfect, and I had to move the fastening spacer below the board, but at least it does not look like a bomb went off inside the case.






 On hindsight, I might have just let the tube sockets protrude a little bit more on top, which would have allowed me to mount the board on the second slot, gaining that extra bit of space below for the caps. Or I could have used a slimmer case, with the caps mounted on top as they are now.

 I also had a bit of a scare as when I plugged the amp I had no voltage anywhere, just 3V on the power switch. After some measurements I found out I have a defective switch, what are the chances of that? I bypassed it and the amp powered up fine.

 I tested it with the iGrados and there's a bit of noise at high volume (which curiously is still listenable and not extremely loud) I then switched to the Yamaha HP-3, and the SS is barely able to drive them to listenable volume. My two other SS built using Pete's original BOM are louder, so I guess I'll have to remove something.

*Will it be enough to remove R14/R15 leaving R16/R17 in place?* I had a few accidents with my other SS and a couple Alien DACs, and I seem to remember R16/R17 offer some protection for the source.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_I just finished my PCB-based SS (sorry Tom for getting a proto PCB then waiting half a year to build it). As I wrote a few posts above, I top mounted the 4 electrolytic caps as my Cerafines were too tall. This led to an accident while drilling the top holes, and after much head scratching I managed to salvage the case by carving a large space on top with the Dremel. It's not perfect, and I had to move the fastening spacer below the board, but at least it does not look like a bomb went off inside the case.






 On hindsight, I might have just let the tube sockets protrude a little bit more on top, which would have allowed me to mount the board on the second slot, gaining that extra bit of space below for the caps. Or I could have used a slimmer case, with the caps mounted on top as they are now.

 I also had a bit of a scare as when I plugged the amp I had no voltage anywhere, just 3V on the power switch. After some measurements I found out I have a defective switch, what are the chances of that? I bypassed it and the amp powered up fine.

 I tested it with the iGrados and there's a bit of noise at high volume (which curiously is still listenable and not extremely loud) I then switched to the Yamaha HP-3, and the SS is barely able to drive them to listenable volume. My two other SS built using Pete's original BOM are louder, so I guess I'll have to remove something.

*Will it be enough to remove R14/R15 leaving R16/R17 in place?* I had a few accidents with my other SS and a couple Alien DACs, and I seem to remember R16/R17 offer some protection for the source._

 

The volume/pseudo-gain is entirely dependent on the values of R16/R17 and the impedance of the pot. (Well, to a lesser extent, the cathode bypass, too.) The last of our investigations of the DAC shorting seems to be a tendency of the SSMH to build up a charge on the RCA jacks. I seriously doubt that R16/R17 are going to offer any protection in that scenario. So, I'd remove them (use some jumpers). That should free up the gain issue.

 EDIT: My experience with a wide variety of headphone impedances/efficiencies is that a 1 to 1 relationship with R16/R17 and the pot impedance is about as much as you want to go - probably less in the case of Ortho's - or no R16/R17 resistors at all. I've also not had much complaint about the pot mis-tracking, either. I suspect a lot of the earlier reports had more to do with tube mis-matches than pot issues. That's IMHO, though, I haven't made exhaustive measurements of the pot's tracking.


----------



## ludoo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The volume/pseudo-gain is entirely dependent on the values of R16/R17 and the impedance of the pot. (Well, to a lesser extent, the cathode bypass, too.) The last of our investigations of the DAC shorting seems to be a tendency of the SSMH to build up a charge on the RCA jacks. I seriously doubt that R16/R17 are going to offer any protection in that scenario. So, I'd remove them (use some jumpers). That should free up the gain issue._

 

Thanks Tom!

 And what about R14/R15? BTW my pot is a 50k one. For cathode bypass caps I'm using a pair of OSCONs, I think they are 680uF but I'll have to check.

 Edit: yes I messed up things, I seemed to remeber you saying something about adding input resistors to protect the source, but they were probably connected to ground.


----------



## tomb

Quote:


  Originally Posted by *ludoo* /img/forum/go_quote.gif 
_Thanks Tom!

 And what about R14/R15? BTW my pot is a 50k one. For cathode bypass caps I'm using a pair of OSCONs, I think they are 680uF but I'll have to check._

 

Personally, I don't think R14/R15 have much of an effect - we're talking an entire magnitude of difference in resistance values and volume works exponentially anyway.
  Quote:


 Edit: yes I messed up things, I seemed to remeber you saying something about adding input resistors to protect the source, but they were probably connected to ground. 
 

No - you didn't mess up anything. I'm not sure which would be better for protecting the DAC's output - but it's meaningless if the charge builds up on the RCA jacks. Nothing inside the amp is going to help at that point. Try disconnecting your source from the RCA jacks while the amp is playing music. I don't exactly know why, but you'll probably get a huge hum that won't go away until something touchs the RCA jacks and grounds the charge. That's what's been happening to the DACs. Unfortunately, grounding that charge fries them.


----------



## luvdunhill

Thanks Tom. Those numbers jive with my measurements.

 Now the real question is, can I get you to PM me that rear plate that has a way to attach a Bantam to the rear plate with a pair of small, threaded angle brackets like FPE sells, a square hole for the USB jack, and then on the right side stacked power switch and power inlet? I know you have it


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Thanks Tom. Those numbers jive with my measurements.

 Now the real question is, can I get you to PM me that rear plate that has a way to attach a Bantam to the rear plate with a pair of small, threaded angle brackets like FPE sells, a square hole for the USB jack, and then on the right side stacked power switch and power inlet? I know you have it 
	

	
	
		
		

		
		
	


	


_

 

Hmm ... my guess is that you'd be better off mounting the Bantam to the bottom of the case body, not the backplate - the USB jack has quite a bit of overhang, you know - almost perfect for the bezel distance on the Hammond case.


----------



## ludoo

Removed R16/R17 and everything is back to normal. This one is for my dad, who will also get my second pair of HP-3 and a y1. He is a huge classical fan, has a pretty good (Linn) setup at home and goes to about two concerts a week. His only headphones are a pair of ER4 I gave him a couple of years ago, it will be interesting to know his reactions to one of the great budget setups to come out of HF.


----------



## revolink24

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_All kits and cases (except the 2 or 3 who were shorted) have been shipped. I have some extra cases that did not have the top lid machined and will do those myself for the ones who were shorted, if they agree.

 There are quite a few tubes left, so I've asked Hammond for a quote for more cases. So, there will be cases and some partial kits (minus the power supply) available in the future. I'll keep you posted.
	

	
	
		
		

		
		
	


	


_

 

Wow, that's very kind of you. I will send you an email (probably tomorrow) confirming my order 

 Cheers,

 ~revolink24


----------



## kuroguy

First of all, thanks to the guys who put the kits, cases, and boards together. Group buys are not a way to get rich. Especially when you are machining cases by hand.

 Now, onto my problem. My SSMH has been working flawlessly for the last year. I recently relocated and when I set up my amp at work the left channel had a 60 cycle hum that gets louder when I move my hand near the left tube. if I touch the tube it is the loudest. If I ground my hand to the casewhile it is near the tube the hum goes away. In face, even a paperclip that touches the tip of the tube and a ground point on the case stops the humming. I switched the tubes around and the hum followed the tube. The room it is set up in has an audible 60 cycle hum without the headphones on. Is this a bad tube or a grounding issue? I suspect some aluminum foil around the tube should solve the problem, but that wouldn't be too elegant. 

 Any comments or suggestions?


----------



## tomb

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_First of all, thanks to the guys who put the kits, cases, and boards together. Group buys are not a way to get rich. Especially when you are machining cases by hand.

 Now, onto my problem. My SSMH has been working flawlessly for the last year. I recently relocated and when I set up my amp at work the left channel had a 60 cycle hum that gets louder when I move my hand near the left tube. if I touch the tube it is the loudest. If I ground my hand to the casewhile it is near the tube the hum goes away. In face, even a paperclip that touches the tip of the tube and a ground point on the case stops the humming. I switched the tubes around and the hum followed the tube. The room it is set up in has an audible 60 cycle hum without the headphones on. Is this a bad tube or a grounding issue? I suspect some aluminum foil around the tube should solve the problem, but that wouldn't be too elegant. 

 Any comments or suggestions?_

 

I'd have to say that if the problem followed the tube, that's pretty conclusive. Some of these tubes (not ones I've tested and rejected) have intermittent shorts. I've seen a few that changed with a little shaking.
	

	
	
		
		

		
			





. Just enough metal was flaking off in areas to come into contact with the pins inside - that doesn't mean you'd have to see it for it to be shorted, though.


----------



## Tritonpad

Hi everyone ^^

 Just want to say thank you again : I received my ss pack this morning (considering I am French).

 I hope I'll have time to solder very soon. Off course I'll tell you when it's finished.

 Now I guess I am at the end of the way ^^ Just 1 thing to do : Do It Myself ^^


----------



## revolink24

Just a couple questions for tomb and/or others.

 On the BOM it lists the SSMH Standoff Kit and Heatsink kit as being on Beezar.com. I'm assuming this is the heat sink kit (if not, tell me), but I can't find the standoff kit anywhere.

 Also, what do you think about using the 50K - 1/4W resistors (high gain) on low impedence/high sensitivity headphones (ie Grados). Also, are there any other modifications requited for the use of the 100k (low-gain) resistors?

 Thanks


----------



## revolink24

Just a couple questions for tomb and/or others.

 On the BOM it lists the SSMH Standoff Kit and Heatsink kit as being on Beezar.com. I'm assuming this is the heat sink kit (if not, tell me), and where can I find the standoff kit?

 Also, what do you think about using the 50K - 1/4W resistors (high gain) on low impedence/high sensitivity headphones (ie Grados). Also, are there any other modifications requited for the use of the 100k (low-gain) resistors?

 Thanks

 EDIT: Also, you use "heat transfer goo" on your build thread - is standard heat sink compound (ie Arctic Silver) the type needed?


----------



## kuroguy

Bummer. my spare tubes are in Tampa and won't arrive here for another 2 weeks. Looks like I'll be using some aluminum foil for a couple of weeks. Thanks for the response, Tom. 

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd have to say that if the problem followed the tube, that's pretty conclusive. Some of these tubes (not ones I've tested and rejected) have intermittent shorts. I've seen a few that changed with a little shaking.
	

	
	
		
		

		
		
	


	




. Just enough metal was flaking off in areas to come into contact with the pins inside - that doesn't mean you'd have to see it for it to be shorted, though._


----------



## TeraHz

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_EDIT: Also, you use "heat transfer goo" on your build thread - is standard heat sink compound (ie Arctic Silver) the type needed?_

 

I used Arctic Silver 5 without problems for my build. I'm sure if you have it, you can use it. I believe it is mostly non-conductive (for electricity).


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Just a couple questions for tomb and/or others.

 On the BOM it lists the SSMH Standoff Kit and Heatsink kit as being on Beezar.com. I'm assuming this is the heat sink kit (if not, tell me), and where can I find the standoff kit?_

 

No, it's not the same. Sorry it's not there, but I was overwhelmed for a time. I'll have them both up this weekend.

 The heat sink kit contains 4 times the hardware. Plus, two of the screws are 1/2" long, not 3/8".

 The standoff kit has some metric washers included because they're the only ones with a small enough OD not to short out on the LED resistor.
  Quote:


 Also, what do you think about using the 50K - 1/4W resistors (high gain) on low impedence/high sensitivity headphones (ie Grados). Also, are there any other modifications requited for the use of the 100k (low-gain) resistors? 
 

It depends on whether or not you have a fetish about being <sorry - Blackberry typo> able to turn the volume knob all the way through its travel. I don't and became quite irritated to find myself racking the volume knob with Senns at anything greater than a one-to-one input/pot impedance. IMHO, 50K input resistance is fine for Grados,too. There are those who disagree, however.
  Quote:


 Thanks

 EDIT: Also, you use "heat transfer goo" on your build thread - is standard heat sink compound (ie Arctic Silver) the type needed? 
 

not sure - I wouldn't use anything that dried to a glue-like substance. I don't know if Artic Silver does that or not.


----------



## Juaquin

Artic Silver 5 stays in paste form (although it gels some as it burns in). It's the golden standard for CPU cooling in gaming and watercooled computers. I used it on my SSMH because I have a big syringe full for computer work and it's working great on the amp. But make sure it's AS5 - Artic Silver Ceramique does get hard and glue-like and won't be so great for this amp. You can find AS5 at Fry's or anyone online computer store like Newegg, FrozenCPU, or TigerDirect.

 EDIT: In response to the earlier post about AS5 and conductivity - it IS conductive. There are a lot of silver particles suspended in it. It's not a perfect conductor but it's good enough to fry something in the wrong place, like if you got it on pins of the CPU. Of course, conductivity should not be a problem here because both the base and heatsinks are supposed to be at GND.


----------



## kuroguy

Um, the MOSFETS MUST be isolated from ground or you get to buy new MOSFETs.

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Of course, conductivity should not be a problem here because both the base and heatsinks are supposed to be at GND._


----------



## Juaquin

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Um, the MOSFETS MUST be isolated from ground or you get to buy new MOSFETs._

 

The MOSFETs are isolated from ground by the berguist pads (on the inside of the case). They are not directly attached to the heatsinks.

 The case is purposefully set to ground. And then the heatsinks are attached to the case, thus they too are ok to be at ground. Of course, they're anodized so the connection isn't perfect, but either way conductive or non-conductive doesn't matter when it comes to the paste in this application.


----------



## kuroguy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd have to say that if the problem followed the tube, that's pretty conclusive. Some of these tubes (not ones I've tested and rejected) have intermittent shorts. I've seen a few that changed with a little shaking.
	

	
	
		
		

		
		
	


	




. Just enough metal was flaking off in areas to come into contact with the pins inside - that doesn't mean you'd have to see it for it to be shorted, though._

 

I hear what you are saying. I initially thought that since the problem followed the tube that it had to be a bad tube, and it may still be a bad tube. The thing is, this space has an audible 60 cycle hum coming from either one of the air conditioning units or a bunch of cheap lighting ballasts. I think there is also a pretty good magnetic field that goes along with the humming. Is is possible that my body/hand is acting like an antenna? The reason I ask is that the hum gets louder as my hand gets closer to the tube but if i touch one of the heatsinks (ground) the humming immediately stops. I wedged a paperclip into one of the holes in the top of one of the heatsinks and made a loop around the tip of the tube with the other end and the hum has completely gone regardless of the location of my hand. 

 I'd bet installing a pair of those retainer caps that are held in place with springs would completely solve the problem.


----------



## Juaquin

Also, I wrote a short post on the SSMH kit with a couple pictures here.

 For those constructing the kit, here's a little tip. Bend the very end of the MOSFETs a tiny bit forward, so they slide in a bit easier. Here's a picture of what I mean:


----------



## Juaquin

Double post failure. Keep moving.


----------



## ethan961

Does anyone know of anywhere that does have 19J6 tubes in stock? All the places I have tried are out of stock. I do not need a PCB so buying tubes from Beezar isn't the ideal option for me, as I will just have a PCB that sit in a box unused.


----------



## Juaquin

I've looked around online, and besides places that list them for $15-20 each (I didn't even bother emailing them to check stock), everyone seems to be out of stock. Of course, this is just what I could find using a quick google search. I'm sure they're out there if you dig enough.


----------



## sandbasser

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I've looked around online, and besides places that list them for $15-20 each (I didn't even bother emailing them to check stock), everyone seems to be out of stock. Of course, this is just what I could find using a quick google search. I'm sure they're out there if you dig enough._

 

Juaquin - your website (or the linky in your sig) is great. One of the best I've seen.


----------



## Juaquin

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Juaquin - your website (or the linky in your sig) is great. One of the best I've seen._

 

Not to get off topic, but thank you. If you're referring to the theme, it's a theme for Wordpress called Blog.txt by Scott Wallick (credit where credit's due).

 Back on topic, this amp gets better and better as it burns in. Initially it was a little muddy (most evident in light rock and electronic music) but it's now fairly tight. Doesn't quite beat a solid state amp for electronic music (IMO) but for everything else it's got that great warm tube sound.

 What to build next...


----------



## StephenPM

Finally succumbed to desire and completed my own little Starving Student amp. A huge thanks to Peter for this great design and to all those here, especially tomb and n_maher, who's posts and pics have helped me through this.

 Completed last night, it's been burning in all day with Paul Galbraith's Bach sonatas and partitas. I've been very pleased with it's rich, smooth sound so far and it's quite able to drive the DT880s to high levels. It'll make the perfect little bedside companion.






















 My apologies for the rat's nest, but about five hours into wiring, I remembered why I don't do DIY anymore. I highly encourage fellow builders to follow Pete's example and use the bare circuit board for grounding. I stuffed mine into a cast aluminum Hammond enclosure with a baked, textured black Rust-o-leum finish. I've both gotten the DIY bug out of my system and gained a nice addition to my headphone listening.


----------



## Fishline

I'm almost done with my p2p build (completely follow Pete's original bom, except the psu is the 1.25A one). However, no music so far. I'm hoping some will be able to help me track the problem down.

 I've measure pin 3 on both channels, and I get ~19.6v, so I guess that's good. However, I'm getting 43v on pin 1 in both channels, which were supposed to be 22v, right? Anyone can give me a hint on what can be wrong?

 I can try taking some pics, but it's so messy (my first build of anything) that I don't think I can get very good pics.


----------



## Fishline

Duh... I forgot to connect the input ground to the star ground. Problem solved. It's making music, and very sweet music at that! It's very quiet when not playing music, too!

 If someone can tell me how to post pics, I'd gladly do so. I don't have an external site to put the pictures.


----------



## Juaquin

You can use any picture dumping service, like photobucket, bayimg, etc to upload the picture, then link it in the post using the little image button.


----------



## sandbasser

Got my SSHB Kit working this morning. Sounds nice. A couple of issues:

 1) when I turn the volume pot I hear static in left ear; otherwise no static. Pot is grounded.

 2) any recommendations for burn-in time and method. Just let it sit powered up??? or does it need to be playing with phones connected???

 I'll try to get a few pix posted in the next day or so.

 Regards,


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Got my SSHB Kit working this morning. Sounds nice. A couple of issues:

 1) when I turn the volume pot I hear static in left ear; otherwise no static. Pot is grounded.

 2) any recommendations for burn-in time and method. Just let it sit powered up??? or does it need to be playing with phones connected???

 I'll try to get a few pix posted in the next day or so.

 Regards,_

 

1)This is usually a tube issue. Sometimes the surrounding electronics may be faster than the tube is capable of keeping up when the volume is changed. I've had it happen consistently on the Millett MAX/MiniMAX when using Black Gates. It's a minor irritation we sometimes live with regarding tubes. Maybe askDsavitsk (
	

	
	
		
		

		
		
	


	




 ) will have a specific answer, though.
	

	
	
		
		

		
		
	


	




 2) A signal has to be going through the coupling caps. So - powered, phones connected, music playing.


----------



## sandbasser

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_1)This is usually a tube issue. Sometimes the surrounding electronics may be faster than the tube is capable of keeping up when the volume is changed. I've had it happen consistently on the Millett MAX/MiniMAX when using Black Gates. It's a minor irritation we sometimes live with regarding tubes. Maybe askDsavitsk (
	

	
	
		
		

		
		
	


	




 ) will have a specific answer, though.
	

	
	
		
		

		
		
	


	




 2) A signal has to be going through the coupling caps. So - powered, phones connected, music playing._

 

Thanks TomB -

 The static does not follow the tube when I swap them; so, I'm wondering if I have an issue with the pot... I think I'll the front off the amp and put a tiny drop of ProGold in the pot and see if that makes a difference.

 Thanks for the info on break-in.


----------



## ethan961

Someone was nice enough to offer me some tubes for a good price. Just another example of the great Head-Fi community.
 Now I'm just waiting for my Hakko station to arrive, then let the fumes begin


----------



## revolink24

The following are out of stock at Mouser:

 71-RN55D-F-220K (220k resistor, R2,R8,R4,R10)
 571-2828363 (3 pos terminal block)
 571-2828364 (4 pos terminal block)

 Does anyone know where I can get them, or some alternatives?


----------



## n_maher

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Thanks TomB -

 The static does not follow the tube when I swap them; so, I'm wondering if I have an issue with the pot... I think I'll the front off the amp and put a tiny drop of ProGold in the pot and see if that makes a difference.

 Thanks for the info on break-in.

 - Ray_

 

Ray,

 Definitely try cleaning the pot, that was an issue with one of my prototypes that had a persistent buzz and static. There was something in the pot causing a high resistance short, once it was cleaned the amp worked great and was noise free.


----------



## revolink24

The following are out of stock at Mouser:

 71-RN55D-F-220K (220k resistor, R2,R8,R4,R10)
 571-2828363 (3 pos terminal block)
 571-2828364 (4 pos terminal block)

 Does anyone know where I can get them, or some alternatives?


----------



## dsavitsk

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_The following are out of stock at Mouser:

 71-RN55D-F-220K (220k resistor, R2,R8,R4,R10)
 571-2828363 (3 pos terminal block)
 571-2828364 (4 pos terminal block)

 Does anyone know where I can get them, or some alternatives?_

 

Resistor values are not critical here. Anything from 220K to 500K is fine.

 For terminal blocks, just look for 5mm or 5.08mm blocks -- there are lots of different ones. Or, solder to the board directly.


----------



## tomb

So, where's all the pics of builds from the kits and cases?
	

	
	
		
		

		
		
	


	










 Juaquin's the only one I've seen.


----------



## gore.rubicon

Will be throwing mine up soon, only problem, no light up...is there a delay before it starts up? any prestart checks?

 EDIT: okay first start fears over, lights up, sound coming through, problem now is LEDS dont come on


----------



## bobfig

i see that you forgot the led resister. you have to calculate the resister value in the circle.


----------



## gore.rubicon

Quote:


  Originally Posted by *bobfig* /img/forum/go_quote.gif 
_i see that you forgot the led resister. you have to calculate the resister value in the circle._

 

that resistor i attached to the otherside, pads on both side y'see


----------



## MoxMonkey

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, where's all the pics of builds from the kits and cases?
	

	
	
		
		

		
		
	


	










 Juaquin's the only one I've seen._

 

waiting for payday.....and then mini,SS and a pair of bantams to be built 
	

	
	
		
		

		
		
	


	





 also i've never seen anything nearly as well packed as my recent beezar order


----------



## bobfig

hmm over saw that... could also be that the +'s and the -'s on the led's got mixed up?


----------



## gore.rubicon

Quote:


  Originally Posted by *bobfig* /img/forum/go_quote.gif 
_hmm over saw that... could also be that the +'s and the -'s on the led's got mixed up?_

 

Hmm checked that too, both LEDs do light up, using resistance? mode on multimeter. Initially I thought i got the wrong washer diameter, but fixing that didnt help either. 
	

	
	
		
		

		
		
	


	




, oh well I'm happy atleast the tubes lit up. Thanks TomB, Dsavitsk, and PMillet for making this available. And i gotta agree with MoxMonkey, the packaging is amazing, it looks like I can kick it across a field, without worrying...too much.


----------



## tomb

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Hmm checked that too, both LEDs do light up, using resistance? mode on multimeter. Initially I thought i got the wrong washer diameter, but fixing that didnt help either. 
	

	
	
		
		

		
		
	


	




, oh well I'm happy atleast the tubes lit up. Thanks TomB, Dsavitsk, and PMillet for making this available. And i gotta agree with MoxMonkey, the packaging is amazing, it looks like I can kick it across a field, without worrying...too much._

 

Glad to hear that the rest of it is working.
	

	
	
		
		

		
		
	


	




 Yes, based on what you've said, there are 3 possibilities:
 1. The "+" and "-" got mixed up on the board.
 2. The long LED lead went to the "-" wire connection (backwards).
 3. Maybe you didn't heat shrink one lead on the LEDs and they're shorting out inside the tube sockets.


----------



## revolink24

Another question. Are the LEDs integrated into the basic amplification circuit such that they cannot be omitted? If they are purely cosmetic, then I might omit them and the difficult socket drilling / lead soldering bit. Would any changes have to be made to the rest of the circuit to omit them?


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Another question. Are the LEDs integrated into the basic amplification circuit such that they cannot be omitted? If they are purely cosmetic, then I might omit them and the difficult socket drilling / lead soldering bit. Would any changes have to be made to the rest of the circuit to omit them?_

 

Actually, they're used to switch on the optical decoders in the tube cathode regenerative gateway ... just kidding.
	

	
	
		
		

		
		
	


	




 No - they are purely cosmetic. That also means you can delete the LED resistor, too, of course. Keep in mind that some people have been able to separate the socket center pins with nothing more than a screwdriver.


----------



## gore.rubicon

Will the LEDs power on even if there are no tubes inserted?


----------



## PJPro

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_So, where's all the pics of builds from the kits and cases?
	

	
	
		
		

		
		
	


	










 Juaquin's the only one I've seen._

 

Well, I've added most of the components to the PCB and am unable to progress as I haven't completed the tube socket mods. I managed to remove the centre pin without drama (using my pillar drill) and now need to glue to the two halves together.

 Anyone care to recommend a brand/type of epoxy available in England?


----------



## tomb

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Will the LEDs power on even if there are no tubes inserted?_

 

Yes, I believe so - but they'll take forever to go out without any other load on the capacitors.


----------



## gore.rubicon

oh my, that took too long, and melted the corners of my wimas =[, yup i wired my LEDs backwards, thanks everyone for the tips


----------



## Fitz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_ Keep in mind that some people have been able to separate the socket center pins with nothing more than a screwdriver.
	

	
	
		
		

		
		
	


	


_

 

I heard MacGuyver did it with only some pocket lint and an apple.


----------



## gore.rubicon

Here we are, finished MSSH PCB, blackcase UV LEDs, thanks TomB. 






 too bad my other cameras couldn't capture the purple glow, had to use shoddy blackberry camera


----------



## looser101

Some pics for TomB



























 And before anyone asks... no, I am not using any LEDs.

 Thanks go to tomb, dsavitsk, n_maher, and of course pmillet.


----------



## tomb

It's tough to capture those UV Leds in a photo, but they sure do look nice in person.
	

	
	
		
		

		
		
	


	




 The natural orange glow is very nice, too!

 Nice job, guys! Great pics, too!!


----------



## tomb

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_I heard MacGuyver did it with only some pocket lint and an apple._

 

One day, Pete Millett will make us an amplifier design out of pocket lint and an apple, too. Dsavitsk will improve on it by adding a high-tech shirt-button mod.


----------



## Juaquin

Those UV LEDs look wicked - contemplating taking my amp apart to make the switch, but better not to fix something that isn't broken, knowing my luck.


----------



## PJPro

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Well, I've added most of the components to the PCB and am unable to progress as I haven't completed the tube socket mods. I managed to remove the centre pin without drama (using my pillar drill) and now need to glue to the two halves together.

 Anyone care to recommend a brand/type of epoxy available in England?_

 

I've gone for Araldite. It should be OK. It can cope with heat up to 60degC.


----------



## Tritonpad

Hi there,

 sorry if the question has already been asked, but I am wondering what values i should use for R16/R17 considering my headset is a AKG K701 ??
 (I'm talking about the pcb kit... so that would be 50k or 100k ?)
 I know K701 is 62ohm, but I'm quite new in DIY and it's hard to take a decision...

 Thank you in advance ^^


----------



## tomb

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Hi there,

 sorry if the question has already been asked, but I am wondering what values i should use for R16/R17 considering my headset is a AKG K701 ??
 (I'm talking about the pcb kit... so that would be 50k or 100k ?)
 I know K701 is 62ohm, but I'm quite new in DIY and it's hard to take a decision...

 Thank you in advance ^^_

 

The K701's are not very efficient - at all. I'd use the 50K or even jumpers, perhaps.


----------



## Tritonpad

Ok thank you... That's what I was thinking. I 'll try with 50k first just to see... then I'll go to jumpers if needed...


----------



## sandbasser

I've noticed a very audible hum in the earphones (Grado SR80 or Denon AH-D950) at low volume levels. The hum goes away completely if I touch the tubes, case or standoff screw. The hum is equally bad with an battery player (Sansa Cube or Fuse) or a powered player (my computer).

 I'm suspecting some kind of ground fault. Any suggestions would be greatly appreciated.

 OTOH - it's a little bit cool in a kinda Theremin like way... the hum goes up / down in volume when I pass my hand near the case. Very strange.

 One more query... will the hum actually damage anything in the amp, phones or player???

 Edit: I tried 2 different power adapters - no difference. Right now, I only have one RCA cable - i'm going to try to fab one this weekend, although I doubt it will make a difference.

 Thanks,


----------



## thelast

I'm having the same issue as "sandbasser". I hear a hum when using low impedance earphones but when I use my dt880(250 ohm) i don't hear it anymore. 

 If I put my hand over the tubes and touch the rca's the hum goes away completely. Grounding issue maybe? I don't know. Any help would be appreciated.


----------



## tomb

OK, here's some questions for you guys:

 1. Did you build the SSMH PCB?
 2. If you built the SSMH PCB, did you use the Hammond case?
 3. Did you scrape the anodizing *completely* off around the RCA jack holes and around the center standoff on the case lid?

 The power supply is isolated as best we can tell (switching supply, multiple mfrs, variances, etc.). I've built four of them so far and the only one that's had a hum is the one that I left uncased. Even in that one, if I touched the RCA jacks, the hum went away (which implies a grounding issue).

 If you are careful to make all the grounding contact mentioned above, you should not have a problem. I've never had a hum in any of the others with a wide variety of sources. So, if you get hum but are able to answer YES to those 3 questions, I'd have to suspect either a bad power supply, bad tubes, or both.


----------



## thelast

Tomb, in regards to your questions

 1. Yes, I built the amp using the kit with the custom hammond case
 2. Yes
 3. I just finished disassembling the case and made sure I scraped the anodizing completely.

 But now I have another problem. I assembled the case and now the amp won't turn on. I'm guessing it's the power supply since it was working fine before.


----------



## the_equalizer

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_...
 also i've never seen anything nearly as well packed as my recent beezar order_

 

x2

 Outstanding packing from TomB, simply outstanding

 Cheers!


----------



## TeraHz

Hi, I've been listening to the SSH for a week now and I believe the low freqs. are distorted. My signal follows this path: FLAC -> y2 -> SSH -> Grado SR80. 

 There are not EQs in software. Is anyone experiencing similar results?


----------



## tomb

Quote:


  Originally Posted by *thelast* /img/forum/go_quote.gif 
_Tomb, in regards to your questions

 1. Yes, I built the amp using the kit with the custom hammond case
 2. Yes
 3. I just finished disassembling the case and made sure I scraped the anodizing completely.

 But now I have another problem. I assembled the case and now the amp won't turn on. I'm guessing it's the power supply since it was working fine before._

 

Check that center standoff for a short on the LED resistor trace. The power supply has an automatic cutoff in case of a short. If you can measure 48VDC from the power supply connector when it's not connected, then you've got a short that developed when you re-assembled the case.


----------



## tomb

Quote:


  Originally Posted by *TeraHz* /img/forum/go_quote.gif 
_Hi, I've been listening to the SSH for a week now and I believe the low freqs. are distorted. My signal follows this path: FLAC -> y2 -> SSH -> Grado SR80. 

 There are not EQs in software. Is anyone experiencing similar results?_

 

I can't speak for everyone, but no - I've not heard this except for a bit during initial break-in. The coupling capacitors may sound like they're distorting in the first few hours until they clear up. Other than that, no.


----------



## PJPro

I've almost completed the kit. Progress was halted when I realised that the allen bolts used for the heatsinks are not metric.....and I only have metric keys. Damn! 

 I've also had a bit of difficulty with the LEDs. Why are the holes in the PCB soooo small? They caused the heat shrink to foul. It would seem that they could have been a lot bigger. 

 I also had a fright with glueing the sockets together. I couldn't get the tubes in after glueing! I used the lead from a 5W resistor to free them up. They're still tight but I can get the tubes in now.


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_I've almost completed the kit. Progress was halted when I realised that the allen bolts used for the heatsinks are not metric.....and I only have metric keys. Damn! 

 I've also had a bit of difficulty with the LEDs. Why are the holes in the PCB soooo small? They caused the heat shrink to foul. It would seem that they could have been a lot bigger. 

 I also had a fright with glueing the sockets together. I couldn't get the tubes in after glueing! I used the lead from a 5W resistor to free them up. They're still tight but I can get the tubes in now._

 

Sorry you're having trouble - but except for the 4-40 screws (ironically, the English system), these things were specifically noted in the Build thread.


----------



## PJPro

No real problems, just minor inconveniences. 
	

	
	
		
		

		
		
	


	




 I've not bothered with a allen key. I simply applied some pressure to the bolt with my finger and tightened up the nut. With the locking washer it doesn't need to be that tight and using this approach has made sure that I don't over tighten the MOSFETs.

 I am a little worried with the amount of heat I've had to put into some components to get the solder to flow......I'm assuming this is due to the large ground plane?


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_No real problems, just minor inconveniences. 
	

	
	
		
		

		
		
	


	




 I've not bothered with a allen key. I simply applied some pressure to the bolt with my finger and tightened up the nut. With the locking washer it doesn't need to be that tight and using this approach has made sure that I don't over tighten the MOSFETs.

 I am a little worried with the amount of heat I've had to put into some components to get the solder to flow......I'm assuming this is due to the large ground plane?_

 

Yep. It takes more heat for those pads that are connected to the ground plane.


----------



## Skat

I just stumbled across the SSMH and would like to try and build one. In my research it seems that there are no part kits. All parts need to be bought via the BOM, part by part. I saw it mentioned, around late July, getting them going again but nothing since. Is this due to the scarcity of the tubes? Is there a substitute for the tubes? Is my assessment of the situation correct or do I need to do more research? My apologies if this has been covered over the last 200+ pages.

 Thank You Very Much,
 Steve


----------



## revolink24

Largely, AFAIK, it is mostly due to the scarcity of the tubes. A substitute tube is in the works. The custom case has sold out, you would need to drill the holes yourself. The PCB and several other parts are here. If you want the bill of materials for the PCB SSMH, don't use the Millett original, use the BOM here. Also, I at least recommend reading a good chunk of this thread, there is useful information on issues other people have experienced.

 Cheers.


----------



## revolink24

Sorry, double post.


----------



## Skat

Thanks for the info. Do you have a feeling for when the substitute tubes will be found? I think I'll wait for the substitute, if it is not long in coming (6 months or so?).

 Thanks,
 Steve


----------



## the_equalizer

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Largely, AFAIK, it is mostly due to the scarcity of the tubes. A substitute tube is in the works. 
 ...
 Cheers._

 

Actually there's been a circuit using an alternate tube for some time. Search the thread for 12SR7. 

 Cheers!


----------



## Juaquin

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. It takes more heat for those pads that are connected to the ground plane.
	

	
	
		
		

		
		
	


	


_

 

I can attest to this - I had to heat the ground plane for nearly 10 seconds sometimes to get the solder to flow. It's best to do as many of the grounds at the same time as you can, while the plane is heated. This might also help those having hum issues - if one of your ground connections is not well made it might result in a broken up ground and humming.


----------



## luvdunhill

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I can attest to this - I had to heat the ground plane for nearly 10 seconds sometimes to get the solder to flow. It's best to do as many of the grounds at the same time as you can, while the plane is heated. This might also help those having hum issues - if one of your ground connections is not well made it might result in a broken up ground and humming._

 

Sometimes it can be helpful to heat up the PCB with a heat gun, usually I do this. Otherwise, I have another iron with a fatter tip and a few more watts handy so I don't have to swap tips out of my main iron.


----------



## PJPro

OK. Now finished and listening to the amp. 

 Rig: Vista PC->FLAC->Foobar2K->ASIO4ALL->Xfi Xtreme Gamer->Optical->Modded Beresford TC-7510->SSMH->SR80s. 

 Initial impressions (less than 30 mins) are good. A bit harsh at times, but I'd expect things to mellow over time. No hum to report but I do appear to have some crackle on the pot. 

 Also, the slightest turn of the pot takes the volume to unbearable. I went for the 50K resistors for R16/17. Looks like 100K might have been a better bet? If so, I'll swap them around before finally sealing the box.

 Oh and the LEDs work a treat! I went for blue. I'll post some pictures shortly.


----------



## tomb

I ran out of tested tubes for awhile, but have more available now. There are also a few cases (4) where I manually drilled and punched the case lid, although the endplates were machined by Hammond.

 Still trying to decide whether to offer more kits. If I do, they'll be without power suppies and will probably be limited to 20 or so. Tubes are about 1/3 of what I had and I continue to have a very high rate of rejects - more than I've seen of any other tube. About 3 out of 10 either have dead shorts or are below minimum output on one set of plates.


----------



## PJPro

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Also, the slightest turn of the pot takes the volume to unbearable. I went for the 50K resistors for R16/17. Looks like 100K might have been a better bet? If so, I'll swap them around before finally sealing the box._

 

I've just taken a look at the BOM, which states that 100K should be used for R16/17 when using highly efficient headphones. Are the Grado SR80s regarded as highly efficient? I'd hate to remove the 50K resistors to put in the 100K resistors only to find myself wanting to put the 50K back.

 So, should I go for the lower gain (100K) or stick with the higher gain (50K) and put up with the micro adjustment of the pot?


----------



## looser101

I'm using 100k with Grados and they are very efficient.


----------



## PJPro

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_I'm using 100k with Grados and they are very efficient._

 

OK. Thanks. I'll make the change.


----------



## revolink24

I asked the same question for my Grados earlier. Since I plan to have higher-impedence headphones someday, I stuck with the 50k, and will just deal with the microadjustment on the pot, as you say. Hopefully it won't disappoint me.


----------



## Juaquin

For the record (anyone looking later on), I used the 100k resistors with my Audio Technicas, no problems. It wouldn't be hard to swap resistors later. If you switch headphones with different efficiencies often, you could put some resistors on protoboard and wire up a switch.


----------



## Tritonpad

Hi there !

 Hey it's finished !!! And finally it works perfect ! I say "finally" cause I had some soldering problems due to bad cheap stuff...
 Now, all I can say is "Uhhh"... "Waaaaa"... And then I shut up and listen.
Picasa Albums Web - Olivier - ampli tube

 Those are some pics for the occasion. You 'll even see my big face ^^

 A big big ultimate thank you goes to Pete, TomB and dsavitsk.

 P.S. : for K701, I can validate the use of 50k resistors for r16/r17, as TomB suggested. Gain is ok and no balance pb due to the pot.


----------



## tomb

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Hi there !

 Hey it's finished !!! And finally it works perfect ! I say "finally" cause I had some soldering problems due to bad cheap stuff...
 Now, all I can say is "Uhhh"... "Waaaaa"... And then I shut up and listen.
Picasa Albums Web - Olivier - ampli tube

 Those are some pics for the occasion. You 'll even see my big face ^^

 A big big ultimate thank you goes to Pete, TomB and dsavitsk.

 P.S. : for K701, I can validate the use of 50k resistors for r16/r17, as TomB suggested. Gain is ok and no balance pb due to the pot._

 

Wow! Great pics - very impressive!!


----------



## Juaquin

Quote:


  Originally Posted by *Tritonpad* /img/forum/go_quote.gif 
_Picasa Albums Web - Olivier - ampli tube_

 

The plastic part of the case (gasket kinda thingy?) goes on the case _before_ the faceplate, so it is sandwiched between the metal pieces. It's not necessarily important (I guess you could do it either way) but I did the same thing before realizing my mistake.


----------



## PJPro

Bunged in the 100K for R16/17. Much better. Good range of turn on the pot. Gets too loud before distortion. Absolutely silent.

 It's been running all day (with the 50K in place). And I feel it's already begining to mellow but has a way to go yet.


----------



## Tritonpad

Juaquin : yes you are right, I didn't notice before you say it !

 PJ Pro : 100k resistors for R16/R17 seem definitely to be what Grado's need, but it's not the same for AKG's.


----------



## KeeChoon

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Bunged in the 100K for R16/17. Much better. Good range of turn on the pot. Gets too loud before distortion. Absolutely silent.

 It's been running all day (with the 50K in place). And I feel it's already begining to mellow but has a way to go yet._

 

Hi PJPro, 

 I'm getting parts for the amp and will be running a grado sr-60 with it. I'm wondering if its 100k R16/17 with a 50k pot or 100k pot? Because in the BOM, it was recommended to use 50k R16/17 with 50k pot and 100k R16/17 with 100k pot.


----------



## thelast

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Check that center standoff for a short on the LED resistor trace. The power supply has an automatic cutoff in case of a short. If you can measure 48VDC from the power supply connector when it's not connected, then you've got a short that developed when you re-assembled the case._

 

I checked the center standoff and there is no short. I also checked the power supply connector and I don't get any voltage reading.


----------



## gore.rubicon

Quote:


  Originally Posted by *thelast* /img/forum/go_quote.gif 
_I checked the center standoff and there is no short. I also checked the power supply connector and I don't get any voltage reading._

 

Post pics?

  Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Bunged in the 100K for R16/17. Much better. Good range of turn on the pot. Gets too loud before distortion. Absolutely silent.

 It's been running all day (with the 50K in place). And I feel it's already begining to mellow but has a way to go yet._

 

Can the same effect be had if i used an inline impedance adapter?


----------



## PJPro

Quote:


  Originally Posted by *KeeChoon* /img/forum/go_quote.gif 
_Hi PJPro, 

 I'm getting parts for the amp and will be running a grado sr-60 with it. I'm wondering if its 100k R16/17 with a 50k pot or 100k pot? Because in the BOM, it was recommended to use 50k R16/17 with 50k pot and 100k R16/17 with 100k pot._

 

It's a 50K pot...as supplied with the kit.

 I suspect even higher values for R16/17 would be OK or even better e.g. 150K.....but I think I'll live with the 100K.


----------



## PJPro

I have to say it's been very enjoyable just getting a kit through the post and putting it all together and listening to it. I've been building a couple of mono power amps and it's taken a massive investment in time and money. See here.

 Many thanks to tomb for sorting out the kits. I'm sure it's been very hard work.

 So. What's next?


----------



## tomb

Thanks for the kind comments!

 Keep in mind, guys - the gains you are all searching for have wide variances. 100K resistors for one guy with Grados may not work for the next guy who has Grados and also a pair of Portapros (or Orthos, or Senns, etc., etc.). More important, you all have varying tastes of volume control and you all have different sources. Some sources are weak, some are strong. Some of us are OK with partial volume travel, others want to rack the volume pot just at the point where they are uncomfortable.

 So use the comments as a guide, but - *YMMV*.


----------



## rshuck

Well, I received my kit and assembled it today. I hate to say this... but I am upset. I like this amp more with my K701s than the Heed CanAmp. Why must I change my mind? Now I'm going to have to look at more tube amps!

 Thanks Tom, it's well worth the price!


----------



## sandbasser

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I've noticed a very audible hum in the earphones (Grado SR80 or Denon AH-D950) at low volume levels. The hum goes away completely if I touch the tubes, case or standoff screw. The hum is equally bad with an battery player (Sansa Cube or Fuse) or a powered player (my computer).

 I'm suspecting some kind of ground fault. Any suggestions would be greatly appreciated.

 OTOH - it's a little bit cool in a kinda Theremin like way... the hum goes up / down in volume when I pass my hand near the case. Very strange.

 One more query... will the hum actually damage anything in the amp, phones or player???

 Edit: I tried 2 different power adapters - no difference. Right now, I only have one RCA cable - i'm going to try to fab one this weekend, although I doubt it will make a difference.

 Thanks,_

 

Well, I figured out my mistake... I originally installed 100K resistors instead of 1K at R14 & R15. Just my own stupid carelessness. It's all better now. NO HUM.

 Lesson - double check everything. Then double check it again.

 Question, is there any possiblity that having those resistors in the ckt for a few hours would cause any long term damage???


----------



## dsavitsk

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_Question, is there any possiblity that having those resistors in the ckt for a few hours would cause any long term damage???_

 

No. Those resistors are there to quell any possible tube oscillation. Pete's original didn't use them at all, but we added them just in case. You are probably safe to jumper over them, or to use literally any value. In fact, I am surprised that the 100K's caused problems, and my guess would be that there might actually have been a bad solder joint on one of them. But, at any rate, no chance of hurting anything.


----------



## tomb

Oops! Someone pointed out to me that I forgot to post the actual PDF templates for the case if you want to drill your own. I've posted those files in the last entry of the Build Thread, now, if you want them.


----------



## Daishiknyte

Hey,

 I've been lurking around here for some time. Thanks to you lot, I've already found myself starting down the slippery slope...I love you, my wallet hates you. 
	

	
	
		
		

		
			





 With classes finally starting to move into the hands-on classes (*engineering), I'm looking at small personal projects to get a bit more experience-end the SSA. Unfortunately, it looks like all the kits have been snapped up. 
	

	
	
		
		

		
		
	


	




 Should I hold off for a bit longer and hope that tomb's awesomeness rewards my patience *and the site is restocked? Or am I better off piecing together the parts needed? *Is there another site selling kits?

 Come on guys, it is all your fault I am worked up about this! 
	

	
	
		
		

		
		
	


	




 Help a guy out.


 *-edits


----------



## gore.rubicon

Quote:


  Originally Posted by *Daishiknyte* /img/forum/go_quote.gif 
_Hey,

 I've been lurking around here for some time. Thanks to you lot, I've already found myself starting down the slippery slope...I love you, my wallet hates you. 
	

	
	
		
		

		
		
	


	




 With classes finally starting to move into the hands-on phase (Mech. Eng. Tech), I'm looking at small personal projects to get a bit more experience-end the SSA. Unfortunately, it looks like all the kits have been snapped up. 
	

	
	
		
		

		
		
	


	




 Should I hold off for a bit longer and hope that tomb's awesomeness rewards my patience? Or am I better off piecing together the parts needed?

 Come on guys, it is all your fault I am worked up about this! 
	

	
	
		
		

		
		
	


	




 Help a guy out._

 

You can piece parts together, wait for TomB, or get another kit?


----------



## tomb

Quote:


  Originally Posted by *Daishiknyte* /img/forum/go_quote.gif 
_Hey,

 I've been lurking around here for some time. Thanks to you lot, I've already found myself starting down the slippery slope...I love you, my wallet hates you. 
	

	
	
		
		

		
		
	


	




 With classes finally starting to move into the hands-on classes (*engineering), I'm looking at small personal projects to get a bit more experience-end the SSA. Unfortunately, it looks like all the kits have been snapped up. 
	

	
	
		
		

		
		
	


	




 Should I hold off for a bit longer and hope that tomb's awesomeness rewards my patience *and the site is restocked? Or am I better off piecing together the parts needed? *Is there another site selling kits?

 Come on guys, it is all your fault I am worked up about this! 
	

	
	
		
		

		
		
	


	




 Help a guy out.


 *-edits_

 

From the time I order more cases, it'll be another six weeks at least. I'm not even sure about offering kits again - there's been quite a run on tubes in the last week or so ... Hopefully, I'll have a chance to re-assess again this weekend. As I said, though - it'll be quite awhile from the point of ordering.


----------



## revolink24

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Oops! Someone pointed out to me that I forgot to post the actual PDF templates for the case if you want to drill your own. I've posted those files in the last entry of the Build Thread, now, if you want them._

 

Thanks for doing that, I received my case though and you did a nice job on drilling them yourself, so thanks, I appreciate that


----------



## luvdunhill




----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_<img]http://lh6.ggpht.com/_8RHE4QJC4jI/SqAuxjKTUEI/AAAAAAAAAfM/O5c35kAGnts/s640/PP%20013.jpg[/img>_

 

Very nice! Are those the new Ortho's?


----------



## royewest

Hope it's OK to post here that I have my unbuilt and basically unopened Beezar SSMH kit for sale in the amps-for-sale forum. (I've built 2 and am buried with work so don't have time in the forseeable future to build this one.)

 I made some bravado statement there about "highest offer" by 9 this morning, but really, it will remain for sale until someone wants to pay me what I paid Beezar, so I can recoup my costs.


----------



## luvdunhill

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Very nice! Are those the new Ortho's?_

 

yes they are 
	

	
	
		
		

		
		
	


	




Audez'e


----------



## tomb

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_yes they are 
	

	
	
		
		

		
		
	


	




Audez'e_

 

Cool! That silver looks better than the gold ones.


----------



## ninshin

hi, i just built a starving student, but i had to reopen it up for some maintenance and now there's a high pitched whine that changes when i move my headphones, but it's not the tubes cause i changed them up and it's in one channel. anyone got the same problem and know why?


----------



## tomb

Quote:


  Originally Posted by *ninshin* /img/forum/go_quote.gif 
_hi, i just built a starving student, but i had to reopen it up for some maintenance and now there's a high pitched whine that changes when i move my headphones, but it's not the tubes cause i changed them up and it's in one channel. anyone got the same problem and know why?_

 

This is classic when someone opens up a case and then puts it back together. Check your wiring - leads that are not heat shrunk, exposed ends, wires that got crimped into the case slots, caught by the screws, etc. You've got something contacting the case and causing a short.


----------



## ninshin

tried all the insulating. the headphones start humming when i put my hand near it, and the high pitched whine is only sometimes there depending on where i position my headphones/head. is it feedback?

 edit: it is getting pretty weird, the whine changes volume when i move the headphone cable. can heat transfer gel short the mosfets? i think i checked the connection between the mosfets and the case and there wasn't a short, and music plays fine except for the whine when i turn down the volume, and the whine isn't affected by the pot.


----------



## sandbasser

I just received an order of Navships wire and I'm now going to rewire my SSH (kit from Beezar). I'm wondering (Yes, I've re-read the assembly guide that Tom put together) if I should tin the wires that will be inserted into the terminal blocks, or just insert stripped wire directly??? Also, how hard should I tighten the screws?

 Thanks,


----------



## tomb

Quote:


  Originally Posted by *sandbasser* /img/forum/go_quote.gif 
_I just received an order of Navships wire and I'm now going to rewire my SSH (kit from Beezar). I'm wondering (Yes, I've re-read the assembly guide that Tom put together) if I should tin the wires that will be inserted into the terminal blocks, or just insert stripped wire directly??? Also, how hard should I tighten the screws?

 Thanks,_

 

Same response that I gave in the other thread 
	

	
	
		
		

		
			





 :
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If someone is picky about cabling and wire types, I suppose it may bother them to tin the ends on the signal wiring. When you do that, you're clamping down on the solder with the screws, not the wire. You could use that argument with every soldered joint that's on the PCB, however.
	

	
	
		
		

		
		
	


	




 I've done both and haven't noticed any difference in sound quality. Actually, not tinning may improve the repeatability. It seems that tinning the ends causes them to be more susceptible to breaking over the long haul, but that could just be my imagination. I've tinned both the ground wires and soldered them together before, but it seemed to me that the resulting large lump made worse contact than without soldering them together. Perhaps when you tin, you should keep the wires separate and do it as lightly as you can. That's what I've been doing lately.

 In either event, I screw down the screw as much as I can - using only a small precision screwdriver, though. There might be some of us who could use a large screwdriver and torque the terminal blocks right out of their soldered pads - or worse.
	

	
	
		
		

		
		
	


	





_


----------



## luvdunhill

I always tin wires before inserting them into screw terminals. Afterwards though, I clamp down on them real hard with a pair of smooth jaw pliers to flatten out the end.


----------



## revolink24

Right now I'm using cheap radioshack 6 strand 22ga copper wire, is there really that much of a sound difference between that and high-strand SPC? Im just using what I happened to have lying around at this point.


----------



## royewest

I'll let others respond to the audio characteristics of short runs of different purities of copper, etc. To me, the advantages of decent-quality teflon-coated wire are:
 * Good build quality of the wire that makes it consistent and reliable and easy to work with
 * Teflon doesn't shrink back when you solder the wire, so you can make good connections using short exposed wire ends without the insulation melting back when you solder.


----------



## revolink24

Finished, and not sure if I'll take pics, it looks like everyone else's (especially TomBs, I used some crappy thermal paste that looks like his) now I'm waiting for my PSU to come....


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Finished, and not sure if I'll take pics, it looks like everyone else's (especially TomBs, I used some crappy thermal paste that looks like his) now I'm waiting for my PSU to come...._

 

Hey! I resent that!

 Just kidding!!


----------



## Juaquin

Has anyone NOT used paste? 

 I was contemplating it, but with the toasty temperatures on those MOSFETs I figured it couldn't hurt, although I was worried about it squeezing out and ruining the looks. The key is to go VERY light. The paste is meant to fill in the microscopic areas where the metals do not make full contact and hence there is no conduction - it is not supposed to be a complete layer in between the metals (metal is still a better conductor than the paste). Or at least that's how it works with CPUs and thermal paste; I assume the same applies here.


----------



## revolink24

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hey! I resent that!

 Just kidding!! 
	

	
	
		
		

		
		
	


	








_

 

Actually, I have no idea if its crap. Its whatever came with my Xigmatek HDT-S1283 CPU cooler, and I didn't use it because I used arctic silver. Should be better than arctic silver for this, because its silicone so its not capacitive like AS 5 is. I just hope I didnt scrape enough off the Bergquist pads to cause a short.

 Cheers 
	

	
	
		
		

		
		
	


	




, its a good kit you guys put together


----------



## the_equalizer

Well, I know it'll look just the same as other builds, but still a couple of pics.









 During the building process and particularly at the end, when contemplating the finished amplifier I couldn't help but be truly amazed at the quality of the design, how it all fits together. I can barely believe I assembled the thing! So in short, MAJOR thanks and congratulations to TomB and Dsavitsk on their work.

 On an aside, I assume it's safe to clean the case with isopropyl alcohol, right?

 Cheers!


----------



## Juaquin

Pics are always appreciated. For instance, my tubes are the Raytheon variety and the heating element is covered - it's cool to see the glow in yours.


----------



## PJPro

OK. Here's a couple of mine....


----------



## gore.rubicon

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Has anyone NOT used paste? 

 I was contemplating it, but with the toasty temperatures on those MOSFETs I figured it couldn't hurt, although I was worried about it squeezing out and ruining the looks. The key is to go VERY light. The paste is meant to fill in the microscopic areas where the metals do not make full contact and hence there is no conduction - it is not supposed to be a complete layer in between the metals (metal is still a better conductor than the paste). Or at least that's how it works with CPUs and thermal paste; I assume the same applies here._

 

I didnt use paste, was going to, but was too lazy to trek to my friend's house to borrow some. Building the thing was first priority...I even scavenged heatshrink to insulate the LEDs and used tape as insulation on the inputs to finish it up.


----------



## PJPro

Actually, I may have just identified a problem with my amp. 
	

	
	
		
		

		
		
	


	




 If I turn the sound right down and slowly turn it up, the sound comes out of one headphone while the other is silent. As I turn it up, the other channel gradually gets louder (but always quieter than the other) until it gets to normal listening volume (not that loud) where it appears to have "caught up". I some ways it's like a balance knob being turned from the left to the middle but getting louder at the same time. If I turn it right, right up the sound stays fixed in the middle, rather than continuing on past the middle.

 I haven't noticed this until now because I don't really fiddle with the volume once it's set. The amp had warmed up and had a couple of hours under it's belt that day (50 hrs total) when I discovered the issue. 

 Any ideas or is this normal for valves?


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Actually, I may have just identified a problem with my amp. 
	

	
	
		
		

		
			





 If I turn the sound right down and slowly turn it up, the sound comes out of one headphone while the other is silent. As I turn it up, the other channel gradually gets louder (but always quieter than the other) until it gets to normal listening volume (not that loud) where it appears to have "caught up". I some ways it's like a balance knob being turned from the left to the middle but getting louder at the same time. If I turn it right, right up the sound stays fixed in the middle, rather than continuing on past the middle.

 I haven't noticed this until now because I don't really fiddle with the volume once it's set. The amp had warmed up and had a couple of hours under it's belt that day (50 hrs total) when I discovered the issue. 

 Any ideas or is this normal for valves?_

 

It's the tracking error in the Alpha pot. The Alpha pot is not built for very low-level precision volume adjustment. One of the reasons for using the input resistors is to "level" this trait out, as in the "low volume" progressively extends over a greater range of volume travel. So, you might try higher-value input resistors if this continues to bother you.


----------



## PJPro

Which resistors are the input resistors? Alternatively, do you know of a better pot which will be a straight swap?


----------



## Juaquin

Most pots aren't pin for pin compatible. The input resistors are R16/17.


----------



## dsavitsk

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Alternatively, do you know of a better pot which will be a straight swap?_

 

It would be on the BOM if we did ...


----------



## PJPro

OK Guys. Thanks. 

 I'm using the 100K resistors supplied in the kit. I did try the 50K resistors first but had almost no movement of the pot before it became unbearably loud. So, what to you think might be an appropriate value to try?


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_OK Guys. Thanks. 

 I'm using the 100K resistors supplied in the kit. I did try the 50K resistors first but had almost no movement of the pot before it became unbearably loud. So, what to you think might be an appropriate value to try?_

 

It sounds like you may have a particularly strong source and/or sensitive headphones. I built one SSMH that had 48K resistors with a 10K pot, so that was almost a 5-to-1 ratio. It was fine with efficient phones, but wouldn't drive Sennheisers very well.

 You want as little as you need, so I'd try 150K or 200K ohm resistors (don't worry about being exact - just use a prevalent size that's close). One option might be to take your 50K resistors and 100K resistors and solder them together. It takes a bit of acrobatics, but if you can imagine an "A" frame formed by the two resistors - with their leads soldered together at their tips forming the top, and the bottom of each placed into the pads on the board - /\ .


----------



## llama_egg

After I get my wire in, pick up a Dremel for case work and finish my first CMOY I intend to give this a shot. What's the worst that could happen?


 Any fancy hints that are hidden amongst the 256 pages I should know about?


----------



## Juaquin

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You want as little as you need, so I'd try 150 or 200 ohm resistors (don't worry about being exact - just use a prevalent size that's close)._

 

That's 150k or 200k (I'm sure everyone got that, but just wanted to make sure there were no accidental blind Mouser orders of 200 ohms resistors 
	

	
	
		
		

		
		
	


	




)


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_That's 150k or 200k (I'm sure everyone got that, but just wanted to make sure there were no accidental blind Mouser orders of 200 ohms resistors 
	

	
	
		
		

		
		
	


	




)_

 

Actually, it's been my experience that if you order 220 ohm resistors from Mouser, you get 220K ohm resistors, instead ... but yeah, all the world was lost in that post for the lack of two K's.


----------



## T.IIZUKA

Very it becomes reference.
 I am about the part gathering is done in order DIY to do.


----------



## Nonchalance

What heatsink and mounting combo is the cheapest? Both the ones beezar and the original recommend runs ~$10. And any cheap power supply? 

 The input resisters lead into the L/R ins of the pot right? I'm building the beezar version without a PCB.

 What would be the best way of wiring ground? I'm using a metal case.

 Thanks 
	

	
	
		
		

		
		
	


	




 This is only my second DIY project after the CMOY.


----------



## Nonchalance

Edit: double. Stupid internet...


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_What heatsink and mounting combo is the cheapest? Both the ones beezar and the original recommend runs ~$10._

 

It's true that Mouser and DigiKey have doubled their price on the heat sinks, but doubling $1 and some change still doesn't equal ~$10 (even X2). I'm not sure how you get that.
	

	
	
		
		

		
		
	


	



  Quote:


 And any cheap power supply? 
 

Power supplies are all over the place, including ebay. Google "Cisco PSA18U". 
  Quote:


 The input resisters lead into the L/R ins of the pot right? 
 

Yes, but you're going to have enough problems air-wiring a pot without getting resistors stuck in the muck. Personally, I'd stick the input resistors on the ends of the RCA jacks - much simpler. Quote:


 I'm building the beezar version without a PCB.

 What would be the best way of wiring ground? I'm using a metal case. 
 

Run every negative connection to the case. Quote:


 
 Thanks 
	

	
	
		
		

		
		
	


	




 This is only my second DIY project after the CMOY. 
 

Good luck.


----------



## PJPro

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It sounds like you may have a particularly strong source and/or sensitive headphones. I built one SSMH that had 48K resistors with a 10K pot, so that was almost a 5-to-1 ratio. It was fine with efficient phones, but wouldn't drive Sennheisers very well._

 

Source - Modded Beresford TC-7510; Headphones - Grado SR80.


----------



## Nonchalance

Wow, thanks for the comprehensive reply!

 I think I got the heatsink situation sorted out, this heatsink and this mounting kit. Got the power supply too.

 Just to be absolutely sure, I wire all of 
	

	
	
		
		

		
		
	


	




 into the case right? 

 And I was wondering, is there a way to add both RCA and 3.5mm input without too much hassle?


----------



## dsavitsk

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Just to be absolutely sure, I wire all of 
	

	
	
		
		

		
			





 into the case right?_

 

You can do that, and it is a common way to wire guitar amps, but I think the better option is to use a terminal strip 
	

	
	
		
		

		
		
	


	




 and connect it to the case in one place and connect all of your ground connections to it. Google for "star grounding" for more details. The resistance of the case itself may be a little too high to use it as a ground plane which may lead to some noise.


----------



## Nonchalance

I was wondering what those things were in the SSMH pics! I see now. The article recommends 2 strips and separating certain components, and I actually see 3 terminal strips in the PMillet site that are interconnected. What's the recommended setup? Edit: found on mouser, haha.

 Thanks a lot!


----------



## bpr

I finished building my Starving Student last night, and as this was my first DIY audio project of any kind, I was thrilled when I flipped the switch and heard music instead of silence. Everything seems to have worked as it should - the amp sounds great and I couldn't be happier.

 The only very small problem seems to be a slight channel imbalance. Centered audio material, like vocals I know to be in the dead center of the sound stage, are favoring to the right channel ever so slightly. This happens over a variety of music and three different pairs of headphones.

 I know there could be a number of possible culprits - a problem in the gain stage, or output stage, or the volume pot tracking error mentioned two pages back, etc. What I don't know is where and how to start looking for the error.

 I'm a real beginner here, so any assistance anyone could provide would be immensely helpful. Truthfully, even if I can't find or fix the problem, I'm so happy the amp works and sounds so great that I could live with the imbalance, if I HAD to.

 Thanks.


----------



## dsavitsk

It's most likely a pot imbalance issue. But if it is consistent at all volume settings, then it might be mismatched resistors elsewhere -- most likely the input resistors, possibly the plate loads. It is probably not the tubes, but it is worth swapping them to see if the problem switches sides.


----------



## bpr

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_It is probably not the tubes, but it is worth swapping them to see if the problem switches sides._

 

Thanks for the fast reply. It might actually be the tubes. I swapped them as you recommended, and the channel imbalance switched sides. The difference between channels isn't huge, just enough to be noticeable and mildly annoying. It seems like the soundstage is moved just past center. Everything else about the amp sounds great.

 Aside from looking for more tubes, are there any remedies to this problem that are (easily) performed?


----------



## tomb

Quote:


  Originally Posted by *bpr* /img/forum/go_quote.gif 
_Thanks for the fast reply. It might actually be the tubes. I swapped them as you recommended, and the channel imbalance switched sides. The difference between channels isn't huge, just enough to be noticeable and mildly annoying. It seems like the soundstage is moved just past center. Everything else about the amp sounds great.

 Aside from looking for more tubes, are there any remedies to this problem that are (easily) performed?_

 

I've had a feeling for awhile now that many of the complaints about pot imbalance are actually the tubes. Did you request/pay for tube matching? Tube matching is the answer. If you did and you got them from Beezar, I'll swap them out.


----------



## revolink24

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Check that center standoff for a short on the LED resistor trace. The power supply has an automatic cutoff in case of a short. If you can measure 48VDC from the power supply connector when it's not connected, then you've got a short that developed when you re-assembled the case._

 

Ha, that was my first problem, I was silly enough to use a washer size too big


----------



## PJPro

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've had a feeling for awhile now that many of the complaints about pot imbalance are actually the tubes. Did you request/pay for tube matching? Tube matching is the answer. If you did and you got them from Beezar, I'll swap them out._

 

Was tube matching provided as part of the kit or was it something extra that one had to request?


----------



## bpr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I've had a feeling for awhile now that many of the complaints about pot imbalance are actually the tubes. Did you request/pay for tube matching? Tube matching is the answer. If you did and you got them from Beezar, I'll swap them out._

 

Thanks, Tom. There is an imbalance in my volume pot at very low volumes, as you mentioned a few posts back, but it evens out before the pot is at listening levels. Once at listening levels though, a slight channel imbalance persists, and seems to change channels if I swap the tubes back and forth.

 I did get my tubes from Beezar and I did pay for the tube matching service, so I'll take you up on your swap offer if it's not too much trouble. The tubes I rec'd were both Raytheons, and marked 75/100 and 85/100 on the tops of the boxes respectively. Let me know how best to proceed.


----------



## Nonchalance

Did anyone here follow the wiring diagram posted here a while back? It's probably neater than anything I can come up with, but does it work?


----------



## tomb

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Was tube matching provided as part of the kit or was it something extra that one had to request?_

 

It was definitely included in the kit. Your problem sounded like the pot, though - it varied with the volume knob position.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *bpr* 
_Thanks, Tom. There is an imbalance in my volume pot at very low volumes, as you mentioned a few posts back, but it evens out before the pot is at listening levels. Once at listening levels though, a slight channel imbalance persists, and seems to change channels if I swap the tubes back and forth.

 I did get my tubes from Beezar and I did pay for the tube matching service, so I'll take you up on your swap offer if it's not too much trouble. The tubes I rec'd were both Raytheons, and marked 75/100 and 85/100 on the tops of the boxes respectively. Let me know how best to proceed._

 

Well, heck - those numbers prove that they're imbalanced. Either average those two numbers or add them together - same thing, that's the total output of the tube that must match the other one - so 175 vs. 185. Not much of a difference, but some of you guys are persnickity, I know.
	

	
	
		
		

		
		
	


	




 Anyway, I apologize if I did that and you truly paid for matching. Although, things are getting tough right now for tube matching - there's almost not enough tubes left to assure this anymore. I'm going to remove the matching option on beezar pretty soon.


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Did anyone here follow the wiring diagram posted here a while back? It's probably neater than anything I can come up with, but does it work?_

 

Actually, I think it may look OK - seems like everything matches up.


----------



## n_maher

For what it's worth I have never have volume level differences translate from whatever I measured on my tube tester. One tube would have to be dead (or near dying) to have the gain that it provided be different.


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_For what it's worth I have never have volume level differences translate from whatever I measured on my tube tester. One tube would have to be dead (or near dying) to have the gain that it provided be different._

 

Well ... far be it from me to disagree, but the effect is subtle. It's not a volume level difference, per se - it's more of a feeling that the headphones are less responsive on one side compared to the other. Now, depending on the music with which one's listening, that could translate into a perceived volume difference, too. I find a pretty close correlation between what I measure on the tube tester - at least with the 658 - and whether a pairing ends up with one side of the headphone sounding lively and the other side sounding dead. It took a lot of listening with Milletts before I was able to distinguish this difference - and it pre-dated my experience with tube testers. The testers seem to confirm it, though.

 Obviously, there are circuits that are more susceptible to this than others. Ones with paralleled plates and fixed bias such as the SSMH tend to be less noticeable than with a Millett Hybrid, for instance. There, one might adjust the manual bias to center the volume by ear for the final touch - but if the tubes were mis-matched, then the dead vs. lively headphone can difference would assert itself, regardless. This effect was less for lower gain tubes than the higher ones, however.


----------



## bpr

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It's not a volume level difference, per se - it's more of a feeling that the headphones are less responsive on one side compared to the other._

 

This is the exact problem I'm experiencing. I know we're talking about possibly mismatched tubes, but this IS my first DIY audio build. I'm sure that my inexperience may have contributed to this problem, especially if you guys think that the mismatch in tubes wouldn't contribute to a very noticeable balance difference.

 Before I send the tubes back, are there any measurements or checks I can make on the board and components to determine if I screwed something up?


----------



## tomb

Quote:


  Originally Posted by *bpr* /img/forum/go_quote.gif 
_This is the exact problem I'm experiencing. I know we're talking about possibly mismatched tubes, but this IS my first DIY audio build. I'm sure that my inexperience may have contributed to this problem, especially if you guys think that the mismatch in tubes wouldn't contribute to a very noticeable balance difference.

 Before I send the tubes back, are there any measurements or checks I can make on the board and components to determine if I screwed something up?_

 

Sometimes I don't make myself clear enough while trying to be diplomatic. Nate can take it, however, so let me make it clear:

 I disagree with Nate. You need to swap the tubes.
	

	
	
		
		

		
			








 P.S. If you've already swapped the tubes and the problem seemed to follow them, that's fairly determinate. The tube testing measurements you gave confirmed it for me.


----------



## PJPro

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It was definitely included in the kit. Your problem sounded like the pot, though - it varied with the volume knob position.
	

	
	
		
		

		
		
	


	


_

 

Hmmmmm. My problem sounds a lot like bpr's to me.

  Quote:


  Originally Posted by *bpr* /img/forum/go_quote.gif 
_Thanks, Tom. There is an imbalance in my volume pot at very low volumes, as you mentioned a few posts back, but it evens out before the pot is at listening levels._

 

 Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_If I turn the sound right down and slowly turn it up, the sound comes out of one headphone while the other is silent. As I turn it up, the other channel gradually gets louder (but always quieter than the other) until it gets to normal listening volume (not that loud) where it appears to have "caught up". I some ways it's like a balance knob being turned from the left to the middle but getting louder at the same time. If I turn it right, right up the sound stays fixed in the middle, rather than continuing on past the middle._

 

Perhaps I'm being paranoid.....but the more I listen the more off to one side things sound.


----------



## tomb

Well look - I don't want to create a rash of this sort of thing ... even in the best of circumstances it's tough to get a perfect match. Not to mention that many of these tubes burn off more gas as they break in - that will change the balance some. We do the best we can at the point of sale, but the best I can do is to say that I'll swap them if you think it will help.

 I have said before that I doubt as many people were having trouble with the Alpha pot as it seemed. I just haven't noticed that it tracks that badly - not over the "usual" listening positions, anyway.


----------



## PJPro

OK. I am grateful for your openess and honesty regarding this matter. And I recognise you have done what is reasonably possible to ensure a good match in the vast majority of cases.

 To rule out paranioa, I'll do some blind testing at my usual listening volume (conducted by my good wife) to see if I can consistently identify the louder headphone. I hope to get this done over the weekend and will report back with my findings.


----------



## Nonchalance

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, I think it may look OK - seems like everything matches up._

 

Cool, thanks for checking! Hopefully that'll prevent me from making a total mess of the wiring.


----------



## dsavitsk

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_To rule out paranioa, I'll do some blind testing at my usual listening volume (conducted by my good wife) to see if I can consistently identify the louder headphone._

 

Instead of blind testing, and to prevent a rash of this sort of thing, why not just take a few simple measurements? After all, maybe its your ears that are not the same 
	

	
	
		
		

		
		
	


	




 Here's what to do. First, measure a few pairs of resistors: R1 and R7, R5 and R11, R16 and R17, and R14 and R15. Make sure that there are no incorrect parts.

 Second, power up the amp and measure the DC voltage from pin 7 to ground on both tubes. Next, measure from pin 1 to ground on both tubes. This will give you an idea of the steady state operating point of the tubes.

 Finally, download a 60Hz tone. Play this through the amp at normal listening levels. Then, while it is playing, measure the AC signal (on both sides) at the input, after the pot (at the tube's grid), and at the output. This will tell you if there is imbalance and where it is.

 One other thing, maybe try measuring the resistance across the heaters to see if these are mismatched.


----------



## PJPro

OK. Thanks. I'd prefer something more objective.

 Incidentally, what do you mean by "_measure a few pairs of resistors_"?


----------



## dsavitsk

I mean that R1 and R7 do the same thing and are of the same value -- a pair -- so measure them both and compare them.


----------



## PJPro

OK. I think? I can certainly check pairs are identified as the same value. But if the power isn't switched on at this step, what measurement would you like me to take?


----------



## dsavitsk

I want you to measure the resistance to be sure you didn't put in a 220R on one side and a 220K on the other by mistake, for example. Suppliers (and builders) make mistakes all the time, so if you didn't measure each resistor before you put it in, there could be issues.


----------



## PJPro

Oh. Damn. I didn't check the resistance with a DMM.....I assumed the resistor would be correctly labelled. 

 Measuring the resistance isn't going to be easy now that the resistor is soldered to the board. Don't I have to remove at least one lead to get an accurate reading? Apologies if I'm taking rubbish.


----------



## dsavitsk

No, just measure from one side to the other with the power off. Even if there is influence form other parts, all you care about is that both sides measure the same.


----------



## Juaquin

Quote:


  Originally Posted by *PJPro* /img/forum/go_quote.gif 
_Measuring the resistance isn't going to be easy now that the resistor is soldered to the board. Don't I have to remove at least one lead to get an accurate reading? Apologies if I'm taking rubbish._

 

Yeah, the resistor needs to be removed (at least one leg) to get a correct reading. Perhaps you could cut the leg above the board and then path it with some solder after checking? Not pretty, but easier. [EDIT] Ok, guess not, according to dsavitsk. He's right, since both channels are the same, the total resistance measured at those parts should be the same.


----------



## tomb

Sounds reasonable. Dsavitsk is correct that there are parts in the path that can just as easily cause the issue.


----------



## ethan961

Finally finished my amp. Got about 10 minutes of real use, sounds great so far!
 I built it PTP (mainly for learning purposes) and used a plastic shotgun shell case as a case. It's not pretty, but since it was my learning one I will likely be keeping it anyways. Wiring is a mess, but hey, we all have to start somewhere!
 It drives my Sextetts (600 ohms) easily, and with my LOD, could easily deafen someone. I could even use some 50K resistors on the pot (I thought I wouldn't need them with the Sextetts being 600 ohms) as I only use the first 10% of the pot.

 I had a bit of trouble with solder not sticking to the NOS tube sockets I ordered, causing some issues which burned out the cheap earbuds I used to test somehow at first.
 One thing I will note is that this cost me over $100 in parts, and another $100 in tools.
 The parts cost can be attributed to my failure to see that I could have ordered all my parts from one or two suppliers (and the fact that I am in Canada) and the tools cost can be attributed to the fact that I decided I needed a Hakko 936. It certainly made the job easier but I could have lived without.
 All in all, after a few simple mistakes, I got it working, and working wonderfully.
 Many thanks to TomB and Dsavitsk for their improvements, and of course, pmillet for inventing the thing in the first place and making many cash strapped people happy!

 EDIT: My heatsinks are at 87 degrees celcius.. no damage yet after an hour or so but its not a nice thing to touch accidentally. Is something wrong? I believe I read somewhere that 60 degrees is ideal.. The tubes are generating no heat in comparison.


----------



## PJPro

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Finally, download a 60Hz tone. Play this through the amp at normal listening levels. Then, while it is playing, measure the AC signal (on both sides) at the input, after the pot (at the tube's grid), and at the output. This will tell you if there is imbalance and where it is._

 

No 60Hz available, so I'll go with the 50Hz or the 70Hz


----------



## nullstring

Quote:


  Originally Posted by *ethan961* /img/forum/go_quote.gif 
_
 EDIT: My heatsinks are at 87 degrees celcius.. no damage yet after an hour or so but its not a nice thing to touch accidentally. Is something wrong? I believe I read somewhere that 60 degrees is ideal.. The tubes are generating no heat in comparison._

 


 what heat sinks did you use?

 I've never measured my heat sinks, but I can touch them, and pick them up for a few seconds.
 They are hot, but certainly not 87C.
 (my SSMH is caseless right now >_>)

 I used the original heat sinks the pmillet used.


----------



## the_equalizer

Hi all:

 In the past few weeks I've been working on a Starving Student Hybrid version using 12AU7 tubes. Based on a post by Dsavitsk that a 12AU7 version could be 'done with literally one resistor change', I started by creating a simulation in TINA-TI and had a working virtual 12AU7 SSHM in a short time. Of course, having it work in simulation is one thing; making it work in real life could be quite another. 

 Having first built a P2P SSHM and then the outstanding PCB version by TomB and Dsavitsk I could use my P2P build for experimentation. It wasn't until this weekend that I could sit down and work on the project. Fortunately I can say it worked, as I'm listening to it as I type this. It's been running for almost three hours now, I've tested it with my iPod, my portable CD player and my laptop's headphone out with no problem at all 
	

	
	
		
		

		
			





 no clipping or noise. Unfortunately I don't have any testing equipment other than my DMM so I can't provide you with any distortion or frequency response figures.

 Before the details of the circuit, a disclaimer: I'm not an electrical engineer, merely an electronics aficionado so While I understand some things about electronic circuits very well, I really don't understand others. In short: take what you're about to read with the required grain of salt.

 The required resistor change is R2/R8 = 390 Kohms. This moves the voltage at the MOSFET gate to compensate for the heater voltage dropping from 19 to 12 volts. As with the 12SR7 version by Logistic, you need to have proper heatsinking since the MOSFET's will be running at ~35.4 volts @ 150 mA... let's see that gives us 5.31 watts of disipation! Compare to the 2.85 watts disipated by each MOSFET in the 19J6 version!

 Other structural changes are also required since the 12AU7 is a 9-pin tube, thus requiring a larger socket. Additionaly, the 12AU7 pinout is different to the 19J6's and this requires rewiring of the connections to the tube.

 An important detail to consider when building this version is that the 12AU7 has separate cathodes for each triode (pins 3 and 8), whereas the 19J6 uses a single cathode for both triodes (pin 7). This means you need to connect pins 3 and 8 together with a jumper, along with the 'standard' jumper to tie the two plates together, and the one to tie the two grids together.

 Here's a pinout mapping for the two tubes:

 19J6=> 12AU7
 pin 1=> pin 6
 pin 2=> pin 1
 pin 3=> pin 4
 pin 4=> pin 5
 pin 5=> pin 2
 pin 6=> pin 7
 pin 7=> pin 3, pin 8

 Pin 9 for the 12AU7 is the heater center tap, used when connecting the heater filaments in parallel. In this circuit we want the heaters to be in series so pin 9 must remain unconnected. Here's a not-very-good picture of the socket wiring:





 Still, there's something I'd like some help with. As described, I built the circuit using IRF610 MOSFET's and R2/R8 = 390 Kohms. According to the TINA-TI simulation this should put the gate of the MOSFET's at ~16 volts. But in the real circuit I'm measuring 14.6 volts !! I'm sure someone can explain why this is happening and if it's ok. My guess is it's not ok since the gate should be sitting at around 4 volts higher than the drain, which is sitting at 12.6 volts (the heater voltage). 

 UPDATE 3: Forget the above paragraph. Wrong voltage measurement was caused by a sh%&ty, cheap DMM. Measured with my trusty old Kyoritsu K-200 analog FET VOM, the MOSFET gate sits at 16 volts. So all is well with the circuit 
	

	
	
		
		

		
		
	


	




 I looked at user Logistic's post for his 12SR7 version and he's using R2/R8 = 330K and R4/R10 = 180K. If someone has built that version it'd be nice if he/she posted the voltage at the MOSFET's gate with respect to ground. Still, I think that lowering the value of R4/R10 is not a good idea since it should theoretically increase the bass rolloff in the RC coupling unless, that is, one incremented the value of C2/C4 accordingly. 

 As to the sound, I really don't consider myself and audiophile and thus I don't think I'd really be able to describe in audiophile jargon how does the thing sound; I can merely say it sounds quite good with both my AKG 701's and my Denon AH-D1001K 
	

	
	
		
		

		
		
	


	




 . I haven't compared it to the 19J6 version so I can't comment on that either... sorry !

 About the only bad thing I can say about this version is that the 12AU7 heater glow is very subdued compared to the glow of the 19J6, so the amp doesn't look quite as nice IMHO. Here's a long exposure shot:





 UPDATE: just for kicks I decided to try a couple of old 12AX7 tubes I had lying around. I expected to hear awful noise and distortion but guess what.... it WORKS ! beautiful sound out of the 12AX7 too. This most surely means that one could also plug a 12AT7 into this circuit and it'd work without a hitch.

 UPDATE 2: I whipped out a couple of new production Russian made Mullard 12AX7's I have saved for use in the phono stage of my old tube amp (when I get around to buying a turntable) and plugged them into the SSHM. These tubes are low noise and microphonics and have long plates and enclosed heaters so they DO NOT glow at all; but the sound... I might just be fooling myself (very likely) but it seems to me these lend more depth and space to the sound. Try them!

 cheers!


----------



## Eric1110

the_equalizer,

 Now that was a fantastic post. I love seeing those types of contributions. I sort of got a shiver down my spine while reading it.

 I am just at the "waiting for parts" stage of my Starving Student amp. Great. Now I have to order some 12au7s, new resistors and sockets.

 Cheers to you sir!


----------



## dsavitsk

Nice work!

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Still, there's something I'd like some help with. As described, I built the circuit using IRF610 MOSFET's and R2/R8 = 390 Kohms. According to the TINA-TI simulation this should put the gate of the MOSFET's at ~16 volts. But in the real circuit I'm measuring 14.6 volts !! I'm sure someone can explain why this is happening and if it's ok. My guess is it's not ok since the gate should be sitting at around 4 volts higher than the drain, which is sitting at 12.6 volts (the heater voltage)._

 

390K seems about right to me. My guess is that the PS is running slightly low. To compensate, you can simply lower the R2/R8 value until the heater sits around 12.6V.


----------



## the_equalizer

Quote:


  Originally Posted by *Eric1110* /img/forum/go_quote.gif 
_the_equalizer,

 Now that was a fantastic post. I love seeing those types of contributions. I sort of got a shiver down my spine while reading it.

 I am just at the "waiting for parts" stage of my Starving Student amp. Great. Now I have to order some 12au7s, new resistors and sockets.

 Cheers to you sir!_

 

Thank you very much for your post Eric1110 ! Please post your impressions of this version as soon as you build it; I'd really like to know if it works for you.

 A nice benefit of this version is that you can swap in different tubes for different headphones/earphones (tube rolling !! 
	

	
	
		
		

		
		
	


	




 ). In ascending order of gain you'd have:

 12AU7
 12AT7
 12AX7

 I don't have any 12AT7's in my parts box, so I can't comment on them, though they should work ok. As mentioned in my post, I tried the AU and the AX and the jump in gain is certainly noticeable; not an abismal, hard-to-control gain jump, but a definite increase in volume. 

 Also, I tried a couple of new production Russian made Mullard 12AX7's (that I've been saving for my phono preamp) and they sounded very well (but they DO NOT glow, AT ALL).

 Anyway, I'll be waiting to hear from your build!

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Nice work!

 390K seems about right to me. My guess is that the PS is running slightly low. To compensate, you can simply lower the R2/R8 value until the heater sits around 12.6V._

 

Thank you for your words Dsavitsk; I really appreciate you posting your opinion about this.

 Indeed 390K seemed to work in paper, when calculating the voltage divider biasing, and in the simulator but the real circuit seems to say otherwise.

 Here are some voltage measurements from it (all with respect to ground):

 Power supply: 47.3 V
 Tube plates: 28.5 V
 Tube grids: 0 V
 Tube cathodes: 1 V
 Tube heaters: 12.5 V
 MOSFET gate: 14.5 V

 So, I don't understand very well how MOSFET biasing works, but I thought that since there's no current flowing in the gate-drain circuit, a simple voltage divider should be able to set the gate-to-ground bias without a problem. Maybe I could measure the current flowing through R2/R8.

 Hmm.. it just ocurred to me that I took the measurements using a recently bought cheap DMM, it could be affecting the measurements with it's impedance... Tomorrow after work I'll dig out my old analog FET VOM and measure with it just to confirm. I'll let you know how it goes. Thanks again for your posts.

 cheers!


----------



## the_equalizer

Ok, once I got the idea of the error being in my new cheap DMM I simply couldn't wait until tomorrow. 

 Yeah, I was right. Measured with my analog FET VOM, the MOSFET's gate sits tight at 16 volts 
	

	
	
		
		

		
		
	


	




 so all is well with the circuit. Sorry for the confusion.

 Re-measured with the DMM and it shows 14.43 V. I don't know if it's an impedance problem with the DMM or simply a precision problem but I guess I'll be getting my money back.

 cheers!


----------



## cassegrain

Hi everyone, i've just finished my first diy project a Starving Student.
 Here are some pictures or the "beast"


















 Is there any test i should run before powering up the amp for the first time?


----------



## the_equalizer

Quote:


  Originally Posted by *cassegrain* /img/forum/go_quote.gif 
_Hi everyone, i've just finished my first diy project a Starving Student.
 Here are some pictures or the "beast"
 <snip>
 Is there any test i should run before powering up the amp for the first time?_

 

Congratulations on your build! It looks nice and solid! I'm sure you'll be pleasantly surprised to discover that it also sounds really good 

 As for tests go, here's what I do:

 1.- Switch the amp on with no source or 'phones attached and watch for sparks or smoke. Obviously if there are sparks and/or smoke you must turn the amp off immediately and start debugging.

 2.- Wait for the tube filaments to start glowing (this should take 30 seconds at most). If they don't come up you can start debugging the circuit.

 3.- Use my multimeter and measure DC voltage at the power supply jack (48V) and at the tube filaments (19 v).

 4- Use my multimeter and measure DC voltage at the output jack, both left and right. Repeat the measurement at the RCA jacks. Voltages should be 0 (zero). If they're not zero, you have to debug.

 5.- If the amp passes all the previous tests, I'll turn the volume knob all the way down, plug in some cheap earbuds at the output, my portable CD player at the input and play some music.

 6.- If all went ok, I'll plug in my nice 'phones and enjoy some cool tunes!


 One last tip if you haven't read the rest of the tread. Try not to power the amp on or off while your 'phones are plugged in 
	

	
	
		
		

		
		
	


	



 cheers!


----------



## cassegrain

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Congratulations on your build! It looks nice and solid! I'm sure you'll be pleasantly surprised to discover that it also sounds really good 

 As for tests go, here's what I do:

 1.- Switch the amp on with no source or 'phones attached and watch for sparks or smoke. Obviously if there are sparks and/or smoke you must turn the amp off immediately and start debugging.

 2.- Wait for the tube filaments to start glowing (this should take 30 seconds at most). If they don't come up you can start debugging the circuit.

 3.- Use my multimeter and measure DC voltage at the power supply jack (48V) and at the tube filaments (19 v).

 4- Use my multimeter and measure DC voltage at the output jack, both left and right. Repeat the measurement at the RCA jacks. Voltages should be 0 (zero). If they're not zero, you have to debug.

 5.- If the amp passes all the previous tests, I'll turn the volume knob all the way down, plug in some cheap earbuds at the output, my portable CD player at the input and play some music.

 6.- If all went ok, I'll plug in my nice 'phones and enjoy some cool tunes!


 One last tip if you haven't read the rest of the tread. Try not to power the amp on or off while your 'phones are plugged in 
	

	
	
		
		

		
		
	


	



 cheers!_

 

Thanks for the advice, regarding your last tip, there 's a risk of destroying the hearphone?


----------



## tomb

Quote:


  Originally Posted by *cassegrain* /img/forum/go_quote.gif 
_Thanks for the advice, regarding your last tip, there 's a risk of destroying the hearphone?_

 

"Destroy" is perhaps an extreme term in this case, but the potential for damage is there. It's not so much on the SSMH because of the AC-coupling at the inter-stage capacitors. However, there is the fact that the SSMH will exhibit some DC spikes at the headphone jack while the tubes/output capacitors are charging up. For that reason, you should always plug in your headphones _after_ powering the amp up for 30 seconds or so. The same caution applies for shut off, although there's no waiting required and the chances of offset are less likely and if they occur, are transients that disappear much more quickly.

 That's why you see headphone-delay relays on many tube hybrids such as the MAX/MiniMAX/MOSFET-MAX, SOHA II, CTH, etc. However, it's a simple precaution to follow without one and is in keeping with the "Starving Student" principle.


----------



## scott_fx

Hey guys,

 i have been enjoying my ssha for about 9 months now and I'm going to try my hand at the pcb version. I'm trying to make this one a little more of a 'sleek' version and was wondering if an aluminum case would act as a sufficient heatsink for the mosfets or do they require the finned variety that we've all been using?


 thanks in advance,

 scott


----------



## scott_fx

double post


----------



## dsavitsk

Quote:


  Originally Posted by *scott_fx* /img/forum/go_quote.gif 
_aluminum case would act as a sufficient heatsink for the mosfets_

 

Scott,

 This is what I did in the first one I built and I thought it worked fine. Others tried it and thought that it ran a tad hot. if you want to do it, you probably need a slightly larger case than the small Hammond people are using to provide a little extra metal. But, this is why I put extra mounting holes on the PCB -- so you can still mount it without needing the rails to slide it in to.


----------



## scott_fx

great, that's what i was hoping to hear. now to go find a case.

 Thanks...again.


----------



## n_maher

Quote:


  Originally Posted by *scott_fx* /img/forum/go_quote.gif 
_I'm trying to make this one a little more of a 'sleek' version and was wondering if an aluminum case would act as a sufficient heatsink for the mosfets or do they require the finned variety that we've all been using?_

 

Scott,

 I tried it without the heatsink on one of the PCB prototypes and it ran very hot. Maybe functionally ok, but too hot to touch. I used a different type of heat sink to deal with this. My photo hosting is down right now so I can't post a picture but it was an adhesive backed type which can be found at Mouser and is not all that expensive and is certainly a lower profile than the "stock" sink in Tom's (excellent) BOM.


----------



## scott_fx

oh great, i'd love to see that.


----------



## Juaquin

It's all a question of the mass of the heatsink (and the surface area). These MOSFETs are dissipating a ton of power and need some pretty serious heatsinking. You could probably go with something smaller than the recommended sinks but not too much. A large aluminum case might be ok, although personally I'd stick with heatsinks.


----------



## bhjazz

What's the latest on power supplies for this beast? Any great deals going on for P2P wired version? The last I saw was quite a few months ago, and the power supply from the original BOM was still the one to get. 
 Life has been chaos in the bhjazz house, but I hope to have some time coming up soon!


----------



## the_equalizer

Quote:


  Originally Posted by *bhjazz* /img/forum/go_quote.gif 
_What's the latest on power supplies for this beast? Any great deals going on for P2P wired version? The last I saw was quite a few months ago, and the power supply from the original BOM was still the one to get. 
 Life has been chaos in the bhjazz house, but I hope to have some time coming up soon!_

 

Well, now that you ask... if you (or anyone else) are feeling somewhat adventurous and would like to test an idea... I just finished (in the drawing board) a Millett "Starving Student" Hybrid version using an alternate tube and power supply. The 12AE6 tube is used to substitute for the 19J6 and the power supply unit is an HP 30 volt@400 mA supply from the Deskjet 600 series ( HP C2175A ). A friend of mine in the US told me these supplies are plentiful and cheap, and the 12AE6 is far easier to find than the 19J6 currently.

 Unfortunately I don't yet have neither the tubes nor the supply to actually build this version. I'll order from Beezar and e-bay this weekend but it'll be a good 2 weeks until I get the parts. I haven't been able to find a 12AE6 SPICE model to use in creating a simulation in TINA-TI either. Still, I'm pretty sure (90%) that it'll work. My only worry is how noisy the supply is and/or if it sags badly under load.


 The required changes to Pete Millett's original circuit are:

 R1/R7 = 22 Kohms
 R5/R11 = 2.2 KOhms

 If my calculations are right these should set the operating point of the tube at around 19 volts plate voltage (with respect to the cathode) and 0.42 mA of plate current.


 R2/R8 = 330 Kohms
 R4R10 = 390 Kohms

 These ones should set the MOSFET gate at 16 volts.


 The rest of the circuit components remain unchanged.

 The advantage of using the 12AE6 is that it was designed to run at low plate voltages (rated for 30 volts max) and thus, I think, should be more linear that other tubes which were designed/built for working at 100 volts plate or so. Indeed, as I'm sure most of you know, it's the tube Pete Millett used for the hybrid design he published in Audio Xpress magazine.

 The advantage of using a 30 volt supply with the 12AE6 comes from the fact that we're dealing with a 12 volt heater tube. Thus the MOSFET's would be taking around 17.4 volts @ 150mA which is a little less power than they take in the original 19J6 version. That way you don't have to go nuts over the heatsink requirements for the MOSFET's. 

 Incidentally, a 12A_7 version could be built using this HP supply as well, and the above values for R2/R8 and R4/R10, but I have no way to choose appropriate values for R1/R7 and R5/R11 at such low voltages. It could be that the same values work ok.

 I'm sure there are many in this forum far more experienced than I am in the use of this tube and/or supply so, if you have any comments, suggestions, corrections, chime in!


 cheers!


----------



## Coreyk78

Well I finally got around to finishing a build using 12SR7GT tubes as logistic posted a while back, sounds very nice, quite similar to the 19j6, and the tubes were super cheap, 4 bucks each I think they were. 

 My camera and my picture taking skills both suck so excuse the crappy pic, I redid my original 19j6 build that I put in a cigar box for the 12sr7 since I had built a second 19j6 one in a nice little hammond case. 

 The heatsinks do get pretty warm, but I'm using 2" tall ones and I'm not concerned that they are running too hot, they pass the 5 second finger test.


----------



## hitman47

Hi, I've come here looking for help with my Starving Student build: I just completed it (I used the PCB, but left out some optional resistors and caps, I jumpered where necessary), and nothing seems wrong with it (no short circuits or anything that I could see), but when I turn it on, the tubes start glowing and they kinda pulsate and when I plug in the earphones (using cheap iPod ones) there's a "clack" noise coming out in the same rhythm as the tubes pulsate... Anyone know what I might have done wrong? Any help is greatly appreciated!


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Hi, I've come here looking for help with my Starving Student build: I just completed it (I used the PCB, but left out some optional resistors and caps, I jumpered where necessary), and nothing seems wrong with it (no short circuits or anything that I could see), but when I turn it on, the tubes start glowing and they kinda pulsate and when I plug in the earphones (using cheap iPod ones) there's a "clack" noise coming out in the same rhythm as the tubes pulsate... Anyone know what I might have done wrong? Any help is greatly appreciated!_

 

It sounds like you have something wired wrong. Is it possible you jumpered a cap? That would not be good. Capacitors are only meant to pass AC (the music signal). If you deleted some caps, but put jumpers in instead, that would be bad news. Resistors should be jumpered, on the other hand.

 If this isn't the problem, we need some pics to see what's going on.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It sounds like you have something wired wrong. Is it possible you jumpered a cap? That would not be good. Capacitors are only meant to pass AC (the music signal). If you deleted some caps, but put jumpers in instead, that would be bad news. Resistors should be jumpered, on the other hand.

 If this isn't the problem, we need some pics to see what's going on.
	

	
	
		
		

		
		
	


	


_

 

No, I only jumpered resistors (R14-17)... The periodic clicking makes me think something's wrong with a cap too... I'll take pictures next time I'm at my friend's, cause I'm doing everything there since I don't have a soldering iron.


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_No, I only jumpered resistors (R14-17)... The periodic clicking makes me think something's wrong with a cap too... I'll take pictures next time I'm at my friend's, cause I'm doing everything there since I don't have a soldering iron._

 

OK, we'll wait for the pics. Meanwhile, the only thing I can think of is something that would affect the entire circuit - have you checked the power connection? Remember the center post of the power socket should be positive (B+ on the PCB). Just a guess ...


----------



## hitman47

Yeah I'll just try switching the polarity on the power socket next time I'm there.


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Yeah I'll just try switching the polarity on the power socket next time I'm there._

 

Try measuring it or inspecting it in detail, first. Don't just switch it to try something different.
	

	
	
		
		

		
		
	


	




 I'm only taking a guess - we don't know that reversing the polarity won't blow something up if you happen to have it correctly now.


----------



## scott_fx

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Scott,

 I tried it without the heatsink on one of the PCB prototypes and it ran very hot. Maybe functionally ok, but too hot to touch. I used a different type of heat sink to deal with this. My photo hosting is down right now so I can't post a picture but it was an adhesive backed type which can be found at Mouser and is not all that expensive and is certainly a lower profile than the "stock" sink in Tom's (excellent) BOM._

 

if you want to email me the pic, i can host it for you.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Try measuring it or inspecting it in detail, first. Don't just switch it to try something different.
	

	
	
		
		

		
		
	


	




 I'm only taking a guess - we don't know that reversing the polarity won't blow something up if you happen to have it correctly now.
	

	
	
		
		

		
		
	


	


_

 

Well, I went to my friend's again and switched the wires, and it works now! The only problem left is that on one side, I only hear the music very distantly and it's extremely quiet... I guess something in the other channel isn't soldered properly or something like that...


----------



## bhjazz

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Well, now that you ask... if you (or anyone else) are feeling somewhat adventurous and would like to test an idea... I just finished (in the drawing board) a Millett "Starving Student" Hybrid version using an alternate tube and power supply. The 12AE6 tube is used to substitute for the 19J6 and the power supply unit is an HP 30 volt@400 mA supply from the Deskjet 600..._

 

Good work! Actually, my SS is done, just need to seal up the case and plug it in so I won't be able to make any circuit changes on this one. Please post when you get your updated version working. Its cool to see so many different offshoots from this design.


----------



## hitman47

Alright, I seem to have completely messed it up now: One of the tubes just stopped working 2 minutes ago and now I can't hear anything except a light hum anymore.

 EDIT: Nevermind, I know what happened, one of the wires leading to the transistor snapped.


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Alright, I seem to have completely messed it up now: One of the tubes just stopped working 2 minutes ago and now I can't hear anything except a light hum anymore.

 EDIT: Nevermind, I know what happened, one of the wires leading to the transistor snapped._

 

Glad to hear you found the problem, but I thought you said you used the PCB? Shouldn't have any wires to the MOSFETs with that.


----------



## Logistic

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Well I finally got around to finishing a build using 12SR7GT tubes as logistic posted a while back, sounds very nice, quite similar to the 19j6, and the tubes were super cheap, 4 bucks each I think they were. 

 My camera and my picture taking skills both suck so excuse the crappy pic, I redid my original 19j6 build that I put in a cigar box for the 12sr7 since I had built a second 19j6 one in a nice little hammond case. 

 The heatsinks do get pretty warm, but I'm using 2" tall ones and I'm not concerned that they are running too hot, they pass the 5 second finger test.





_

 

Nice job! I love the enclosure you used. Where did you get your tubes? Through tube rolling I've found that the flat triode plate 12SR7GTs to be the best sounding, especially with my HD-580. How do they sound with your HD-580?


----------



## Juaquin

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad to hear you found the problem, but I thought you said you used the PCB? Shouldn't have any wires to the MOSFETs with that._

 

Well, not if he was using the custom case. If he used his own case he might have had to mount them away from the PCB.


----------



## the_equalizer

Quote:


  Originally Posted by *Coreyk78* /img/forum/go_quote.gif 
_Well I finally got around to finishing a build using 12SR7GT tubes as logistic posted a while back, sounds very nice, quite similar to the 19j6, and the tubes were super cheap, 4 bucks each I think they were. 

 My camera and my picture taking skills both suck so excuse the crappy pic, I redid my original 19j6 build that I put in a cigar box for the 12sr7 since I had built a second 19j6 one in a nice little hammond case. 

 The heatsinks do get pretty warm, but I'm using 2" tall ones and I'm not concerned that they are running too hot, they pass the 5 second finger test.




_

 

Those big round octal tubes sure look nice ! 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## Assasas

Hi!

 My name is Daniel and iam from sweden.
 Iam new here!! 
	

	
	
		
		

		
		
	


	




 I have decided to build the Millets starving student amp, with the cheap 12SR7 tubes and i have some questins regarding that!

 1. My local supplier that have all parts for this project except the mosfet IRF510, so i would like to now if i can replace it with one of these: IRF510A, IRF530N, IRF540, IRF630 or IRF640? 

 2. How important is it to use low-ESR electrolytic capacitors for C1, C3, C5, C6?
 Can i replace them with regular electrolytic capacitors, or is it a bad idea?
 Just trying to go as cheap as possible, Iam really starving 
	

	
	
		
		

		
		
	


	




 3. Would these heat sinks be good enough?? : TO-220 Heatsink, Small Power Aluminum Heat-Sink, x 4pcs - eBay (item 260481603013 end time Oct-23-09 23:26:12 PDT)

 Hope i get some nice answers!

 //Daniel


----------



## dsavitsk

Quote:


  Originally Posted by *Assasas* /img/forum/go_quote.gif 
_replace it with one of these: IRF510A_

 

Looks like the same part.

  Quote:


  Originally Posted by *Assasas* /img/forum/go_quote.gif 
_2. How important is it to use low-ESR electrolytic capacitors for C1, C3, C5, C6?
 Can i replace them with regular electrolytic capacitors, or is it a bad idea?_

 

Not very. Use whatever you can find -- just be sure the voltage rating is high enough.

  Quote:


  Originally Posted by *Assasas* /img/forum/go_quote.gif 
_3. Would these heat sinks be good enough??_

 

They look a little small to me. Keep in mind that on the 12V tube version that the fets need to dissipate an extra watt of heat each beyond what the 19V version does, and these look to small for the original.


----------



## Coreyk78

Quote:


  Originally Posted by *Logistic* /img/forum/go_quote.gif 
_Nice job! I love the enclosure you used. Where did you get your tubes? Through tube rolling I've found that the flat triode plate 12SR7GTs to be the best sounding, especially with my HD-580. How do they sound with your HD-580?_

 

Thank you! I got the tubes from vacuumtubes.net like back in the spring sometime, had a speaker project over the weekend so I never got to it until now. They are Tung Sol JAN tubes, the boxes were stamped 1952, very low microphonics, the heater filament is almost completely covered tho, so not a whole lot of tube glow. 
 I tried them with my HD580s, I was listening to the vinyl reissues of Beastie Boys Paul's Boutique and Check Your Head through it and I like it. C2 and C4 are russian .22uf k42y2, and the output caps are bypassed with those as well. 
 Overall it sounds warm and smooth, even warms up my K702 a bit, sounded good with my JVC RX-700 too, lots of bass with the JVC.

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Those big round octal tubes sure look nice ! 
	

	
	
		
		

		
		
	


	




 cheers!_

 

Hehe, thats probably the biggest reason that I wanted to build one with these tubes, I love the look of big octals.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad to hear you found the problem, but I thought you said you used the PCB? Shouldn't have any wires to the MOSFETs with that._

 

Yeah, I decided not to get the custom hammond case and it's easier to do with wires if you don't have the custom case... I also have the heatsinks from the original BOM so it wouldn't work without wires anyway. That shouldn't make any difference though, right?

 Also, I doubt soldering the wire back on will fix the issue I'd been having before it snapped (left channel is waaaaay too low on the volume and there's some noise on it, too)... I'll just redo all the bad soldering points I see and I'll


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Yeah, I decided not to get the custom hammond case and it's easier to do with wires if you don't have the custom case... I also have the heatsinks from the original BOM so it wouldn't work without wires anyway. That shouldn't make any difference though, right?_

 

Actually - if you remote-wired the MOSFETs, but left R3 and R9 on the board, then you might have oscillating MOSFETs and could cause trouble. Pete Millett warned in his original Starving Student article to keep R3 and R9 close to the MOSFET pins or it would induce MOSFET oscillation.


----------



## n_maher

Quote:


  Originally Posted by *scott_fx* /img/forum/go_quote.gif 
_if you want to email me the pic, i can host it for you._

 

You know what, I can't find it anywhere??!? If you search Mouser for "adhesive heat sink" you'll find a range of products that could be used to assist a chassis mounted FET setup. They look like this when viewed from the bottom.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually - if you remote-wired the MOSFETs, but left R3 and R9 on the board, then you might have oscillating MOSFETs and could cause trouble. Pete Millett warned in his original Starving Student article to keep R3 and R9 close to the MOSFET pins or it would induce MOSFET oscillation._

 

And could that manifest itself as one side being a lot less loud than the other? And if yes, would I have to just take those resistors out and everything would still work?


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_And could that manifest itself as one side being a lot less loud than the other? And if yes, would I have to just take those resistors out and everything would still work?_

 

Don't know - but the amp will not work without those resistors. You can't take them out of the circuit, but you should take them out of the PCB and solder them directly to the MOSFET pins. Then solder your wires to the other end of the resistors.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't know - but the amp will not work without those resistors. You can't take them out of the circuit, but you should take them out of the PCB and solder them directly to the MOSFET pins. Then solder your wires to the other end of the resistors._

 

OK, will do, thanks for the hint! I'll report back after it's done, I hope it'll work now...


----------



## Assasas

Hi guys!

 Iam going to build the the_equalizer's version of this amp so i wounder
 if i can use Sylvania 5963 (12AU7WA) instead of 12AU7?? My guess is that i can!

 //Daniel


----------



## scott_fx

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_You know what, I can't find it anywhere??!? If you search Mouser for "adhesive heat sink" you'll find a range of products that could be used to assist a chassis mounted FET setup. They look like this when viewed from the bottom.





_

 

Thanks,

 thanks, i think i decided with to go with a heatsink mounted to the back of a cigar box. I'm going to try my hand at doing something a little more unique this time around.


----------



## hitman47

Tom, I wanna be sure about mounting these resistors right, could you tell me which pin they have to be soldered to?


----------



## dsavitsk

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Tom, I wanna be sure about mounting these resistors right, could you tell me which pin they have to be soldered to?_

 

You can look on the PCB, or you can look on the datasheet.

http://www.vishay.com/docs/91023/91023.pdf

 I doubt that this is your issue as even if they are oscillating it would not manifest itself as the problem you are having. However, I agree that soldering the resistors directly to the pins is a good idea.


----------



## hitman47

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_You can look on the PCB, or you can look on the datasheet.

http://www.vishay.com/docs/91023/91023.pdf

 I doubt that this is your issue as even if they are oscillating it would not manifest itself as the problem you are having. However, I agree that soldering the resistors directly to the pins is a good idea._

 

Thanks, and yeah I guess I'll just have to redo a couple of contacts to fix the left side... Unless I blew one of the caps by having the voltage supply wired with the wrong polarity, not sure if that could cause one channel to be so quiet though


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Thanks, and yeah I guess I'll just have to redo a couple of contacts to fix the left side... Unless I blew one of the caps by having the voltage supply wired with the wrong polarity, not sure if that could cause one channel to be so quiet though_

 

I'm sure Dsavitsk is correct about your problem now, but in your very first post you described that the tubes were "pulsating." It's possible you may have a couple of different issues. If you can get us some pics, it might help to solve the problem much quicker. There are a lot of eyes around here that will spot just about anything that's out of place.


----------



## Nonchalance

Getting together with a friend on Friday to do this, round of noob questions #2:

 1. I can't for the life of my get the tube into its socket (using the beezar sockets), how much force do I need? I'm pushing until the tube starts to slide in my fingers, but it's still not doing it.

 2. #3 and #4 on tube are connected right?

 3. Does C2 have a positive end and a negative end? I'm using the .22uF VitQs from beezar and it's not marked.

 4. There are 6 connectors on the neutrik phone jack but I only have to connect to one side right?

 5. I keep hearing talk about separating some panel component's ground to reduce noise, I'm not sure what to make of it. It seems I want the RCA jacks and the DC jack to touch both the ground material directly as well as another point on a star ground. Anything else I should watch out for?

 Just like to clear things up so I don't mess up as much. Thanks a lot!


----------



## dsavitsk

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Getting together with a friend on Friday to do this, round of noob questions #2:

 1. I can't for the life of my get the tube into its socket (using the beezar sockets), how much force do I need? I'm pushing until the tube starts to slide in my fingers, but it's still not doing it._

 

Probably not that much - be careful pushing that hard, because when tubes shatter the glass is really sharp. Did you solder them already? Sometimes, if you heat too much and use too much solder, it can creep up and fill in the socket.


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Getting together with a friend on Friday to do this, round of noob questions #2:

 1. I can't for the life of my get the tube into its socket (using the beezar sockets), how much force do I need? I'm pushing until the tube starts to slide in my fingers, but it's still not doing it._

 

First - take Dsavitsk's advice to heart - be careful!

 Second - did you drill out the sockets for tube LEDs and then glue them back together? If so, did you leave them upside down for the glue to cure (not recommended!)? That can more or less ruin the sockets and make it impossible to get a tube plugged in and to make electrical contact. (Glue is in the tube pin holes and in the contacts inside.) If this is the case, then you probably need some new sockets.

 If you can't or don't want to buy new sockets, you can try to get an ice pick, or better yet - some dental-type picks that you can pick up at Harbor Freight. You can carefully spread out the prongs that are inside the tube pin holes for an easier fit. Be careful doing this, however, because you can ruin the sockets by bending the internal prongs so that they never again make good contact with the tubes. It takes a lot to do this, though. Even if you permanently bend them out so that they no longer "grip" the tube pins, you can slightly bend out the tube pins themselves so that they make a positive connection with the contacts inside the socket. A bit of a hassle - you'll need to remember to do this to any tubes from now on that you may use in those sockets. (Assuming my guesses about your situation are valid.)

  Quote:


 2. #3 and #4 on tube are connected right? 
 

Yes, these are the heater filiments and are tied together in series.

  Quote:


 3. Does C2 have a positive end and a negative end? I'm using the .22uF VitQs from beezar and it's not marked. 
 

No. There is no polarity on film caps.

  Quote:


 4. There are 6 connectors on the neutrik phone jack but I only have to connect to one side right? 
 

Yes - only the right side as you're looking from the front. The left side is for switched contacts with a separate output.

  Quote:


 5. I keep hearing talk about separating some panel component's ground to reduce noise, I'm not sure what to make of it. It seems I want the RCA jacks and the DC jack to touch both the ground material directly as well as another point on a star ground. Anything else I should watch out for? 
 

Sounds like a good strategy to me.
	

	
	
		
		

		
		
	


	




  Quote:


 Just like to clear things up so I don't mess up as much. Thanks a lot!


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, these are the heater filiments and are tied together in series._

 

But you don't tie them together. One connects to the mosfet, the other to ground.


----------



## Nonchalance

First of all, thanks for all the detailed answers again! Really appreciated it, I'm kinda OCDing on this project, now I can do work, lol.

 I didn't drill the sockets, just took them straight out and tried to get the tube in. Tried both with a socket that I spread the prongs out a bit with (as recommended in your guide for a better connection) and another that I didn't touch at all. I'm really pushing as hard as I can (then it slides...).

 Edit: well I forced it into the socket, but it's not coming out at all, lol. Gonna have to solder this with the tube attached, oh man...

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_But you don't tie them together. One connects to the mosfet, the other to ground._

 

Ok, so I don't bridge #3 and #4, gotcha.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sure Dsavitsk is correct about your problem now, but in your very first post you described that the tubes were "pulsating." It's possible you may have a couple of different issues. If you can get us some pics, it might help to solve the problem much quicker. There are a lot of eyes around here that will spot just about anything that's out of place.
	

	
	
		
		

		
		
	


	


_

 

No, the pulsating disappeared when I changed the polarity on the DC in... They looked fine until the wire snapped, and I haven't soldered it back on yet but I don't think that's gonna change after it's back on... But thanks for your help!


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_But you don't tie them together. One connects to the mosfet, the other to ground._

 

Yes - thanks for clarifying that. This time, I was looking at the schematic and still said it wrong (because the filaments are combined in the tube). I must have some sort of mental block about this one.


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_First of all, thanks for all the detailed answers again! Really appreciated it, I'm kinda OCDing on this project, now I can do work, lol.

 I didn't drill the sockets, just took them straight out and tried to get the tube in. Tried both with a socket that I spread the prongs out a bit with (as recommended in your guide for a better connection) and another that I didn't touch at all. I'm really pushing as hard as I can (then it slides...).

 Edit: well I forced it into the socket, but it's not coming out at all, lol. Gonna have to solder this with the tube attached, oh man..._

 

I wouldn't do that. If you got it in once, it's only going to get easier each time after that. Some people don't realize that when we say the socket/solder joints undergo a lot of stress that we mean it.
	

	
	
		
		

		
		
	


	




 Practically speaking, the tubes are much easier to push into the sockets once they are soldered into the board, anyway. You're combining two very awkward supporting issues when you're trying to push the tube into the socket without it mounted - trying to hold onto the socket and the tube at the same time. Still, I recommend that you try it in all cases, anyway.

 First, you need to verify that the sockets still work if you drill/glue them for tube LED's. Second - and this doesn't happen often, thank goodness - there are sometimes defects in the sockets themselves. I've had one or two where the ceramic wasn't molded correctly and the holes were missing over a couple of the pin sockets. No amount of drilling was going to fix them, either. At first, I though it possible that you might have had some molding errors on yours (if you hadn't drilled/glued them) - holes too small, or some other obstruction underneath. Still as I said, if you got the tube in once, it's only going to get easier from now on.
	

	
	
		
		

		
		
	


	





  Quote:


 Ok, so I don't bridge #3 and #4, gotcha. 
 

Yeah ... dummy me - glad Dsavitsk is around to correct my mouth ... uh, keyboard fingers.


----------



## Nonchalance

I finally wiggled the little SOAB out... Haha, took me like 10 minutes. I can hear a glass scraping sound, hopefully these things are strong.

 I don't think I'll be doing the LEDs, I like to listen at night in the dark, don't want too much light. I do have the RLED and the LEDs though, and it's tempting 

 Thanks tomb and dsavitsk!


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_I finally wiggled the little SOAB out... Haha, took me like 10 minutes. I can hear a glass scraping sound, hopefully these things are strong.

 I don't think I'll be doing the LEDs, I like to listen at night in the dark, don't want too much light. I do have the RLED and the LEDs though, and it's tempting 

 Thanks tomb and dsavitsk!_

 

A glass scraping sound is normal with a ceramic socket.


----------



## hitman47

Yay, my starving student is working! Thanks for all the help!


----------



## gore.rubicon

On the topic of hard insertion, i used a push pin to loosen up the connector a bit, before putting in the tubes. How much it helped? a bit i guess


----------



## Nonchalance

I have some 18awg single strand copper wire, and I read that 22awg is recommended. Is it ok to use the 18awg?

 Can I use a piece of aluminum for ground? It's about .7-.8mm thick and 14.5mmx7mm.


----------



## tomb

18ga is pretty huge! That's lamp cord, size, I believe. Still, it's OK if you can make it fit, I guess. That ground would be better if it was copper. We often ground to our aluminum cases, but it works well because there's so much there - sounds like you have a pretty small plate.


----------



## tomb

Just a note to let everyone know that I'm suspending sales of the PCB + tubes selection. I've taken inventory and it appears there's enough tubes left for another run of about 25 kits. So, I'm going to save what I have and order more custom cases from Hammond. I'll keep you posted, but expect about one month or so until you hear otherwise.

 Thanks!


----------



## hashwood

I am having a problem with a power supply, cisco adp-18pb, it makes some noise even with the source muted. The noise is only when I am using M-audio 2496 PCI, when using other sources, like a Pioneer receiver, the noise is gone. 
 When using the amp with the Eltek PSU, model ADC 5593/5 there is no noise, on any source. 
 Is the Cisco supply bad?


----------



## Nonchalance

Oh dang, I guess I be getting out to get some 22awg wire from Radioshack.

 Guess I'm getting a copper-clad PC board as well.

 Thanks!


----------



## hashwood

I am having a problem with a power supply, cisco adp-18pb, it makes some noise even with the source muted. The noise is only when I am using M-audio 2496 PCI, when using other sources, like a Pioneer receiver, the noise is gone. 
 When using the amp with the Eltek PSU, model ADC 5593/5 there is no noise, on any source. 
 Is the Cisco supply bad?


----------



## PJPro

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_On the topic of hard insertion, i used a push pin to loosen up the connector a bit, before putting in the tubes. How much it helped? a bit i guess_

 

Yeah. I used a cut lead from a 5w resistor to ease them open a bit.


----------



## tomb

Quote:


  Originally Posted by *hashwood* /img/forum/go_quote.gif 
_I am having a problem with a power supply, cisco adp-18pb, it makes some noise even with the source muted. The noise is only when I am using M-audio 2496 PCI, when using other sources, like a Pioneer receiver, the noise is gone. 
 When using the amp with the Eltek PSU, model ADC 5593/5 there is no noise, on any source. 
 Is the Cisco supply bad?_

 

Well, the only certain thing we can say from your info is that your Cisco supply is noiser than your Eltek.


----------



## PJPro

OK. I've done the tests recommended by dsavitsk and here are the results.

*Resistors*

 R1 = R7 = 33R
 R5 = R11 = 2K
 R16 = R17 = 100K
 R14 = R15 = 1K

 I've rounded these a little but the differences are soooo small they are not worth reporting.

*DC*
 Amp powered on but nothing else attached

 Left Pin 1 = 20.08VDC
 Right Pin 1 = 20.07VDC

 Left Pin 7 = 0.433VDC
 Right Pin 7 = 0.432VDC

 I used the casing of the volume pot as ground.

*AC*
 Played a 50Hz tone at normal listening levels.

Input
 Left = 0.95VAC
 Right = 0.95VAC

Tube Grid (Pin 5) Is Pin 5 the tube grid?
 Left = 5.3mVAC
 Right = 5.6mVAC

Output
 Left = 70.4mVAC
 Right = 73.6mVAC

 Played a 70Hz tone at louder than normal listening levels

Input
 Left = 0.95VAC
 Right = 0.95VAC

Tube Grid (Pin 5)
 Left = 14.1mVAC
 Right = 14.8mVAC

Output
 Left = 188.9mVAC
 Right = 199.8mVAC

 So. What's the verdict? Are the differences at Pin 5 being amplified by the tube and IC....indicating a problem with the pot? 

 There is a further measurement requested by dsavitsk which I haven't taken and that's the resistance across the heaters. Unfortunately, I don't know which pins to use to measure this as I am unable to interpret the tube diagram provided by the schematic. 
	

	
	
		
		

		
		
	


	




 I also had a bit of a nightmare with the LEDs. One of the live wires had snapped at the solder joint on the PCB. I had awful trouble trying to clear the hole and think I may have damaged the board because I was unable to solder the wire back in place. In the end I soldered the wire directly to the positive end of RLED. It's annoying having to resort to a bodge but it was that or ditch the LEDs altogether 
	

	
	
		
		

		
		
	


	




 Grateful for any help / advice offered.


----------



## dsavitsk

I think your tubes are _remarkably_ well matched. Amplification factor is ~13.5 on one, and ~13.4 on the other -- no way you can hear that difference.

 If anything, it looks like the pot is a little out of balance, though really only a little. You can try to correct it by making one of the input resistors slightly larger than the other -- put a 1M rheostat in parallel with R17 and adjust it until the voltage on the outputs match . Then measure across R17 and replace the resistor and a pot with a resistor of the new value. (You could also do a 100K rheostat in series with the input to R16, adjust that, and replace R16 with the value of the resistor + rheostat.) Or you can replace the pot. But, all in all, it really looks pretty good.


----------



## Nonchalance

Got myself some 20awg wire to do this with, doing my best for the most efficient wiring, which is resulting in a lot of wiring by just using the leads off of Rs and Cs:






 Can I wire the film cap bypass by just soldering like this? Also, I hope I have the positive and negative sides matched up (WIMAs weren't marked).






 Now waiting on friend with a drill


----------



## ltmon

Hi all, I need some help troubleshooting:

 I've just finished building my second SSMH, this one built upon TomB's PCB. The first build was over a year ago, and it gave up the ghost after getting 30+ hours a week usage for all that time. Instead of troubleshooting it, I thought I'd start again with the PCB and make it neater this time.

 Unfortunately this one is not powering up. There was a crackle when I first turned it on, so I turned it off again very quickly.

 Upon measuring, the B+ and G (DC input) are shorted together -- not obviously, but they're electrically the same. Pin 2 of each IRF510 seems shorted to the enclosure as well... I'm not sure if this should happen. These measurements are the same without the tubes plugged in.

 I'm not really sure what to measure or test next. Visual inspection shows nothing obvious, and I've thoroughly cleaned a few times as well. I'm working my way through this thread.

 Do these symptoms point towards anything obvious? Any advice on where to look for further problems?

 EDIT: I posted this question, because whenever I post a question on a forum I find the answer myself 5 minutes later 
	

	
	
		
		

		
		
	


	




 It seems the mounting kit for the IRF510's didn't quite work... when I disconnect them from the case, the shorting disappears. I will look into why tomorrow.

 In the meantime, have I damaged the IRF510's by powering up like this? Or should they work still?

 Thanks in advance,

 L.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just a note to let everyone know that I'm suspending sales of the PCB + tubes selection. I've taken inventory and it appears there's enough tubes left for another run of about 25 kits. So, I'm going to save what I have and order more custom cases from Hammond. I'll keep you posted, but expect about one month or so until you hear otherwise._

 

Just after I spend an afternoon trying to do neat and tidy casework -- without much success


----------



## dsavitsk

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_Upon measuring, the B+ and G (DC input) are shorted together -- not obviously, but they're electrically the same. Pin 2 of each IRF510 seems shorted to the enclosure as well... I'm not sure if this should happen. These measurements are the same without the tubes plugged in._

 

Pin 2 is connected to the tab internally. This is the drain which is connected to B+. The chassis should be grounded. So, if the tab is touching the chassis, then this would short B+ to ground.


----------



## ltmon

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Pin 2 is connected to the tab internally. This is the drain which is connected to B+. The chassis should be grounded. So, if the tab is touching the chassis, then this would short B+ to ground._

 

Thanks, see my above edit for more info.

 Have I likely damaged the transistors with this mistake?

 L.


----------



## dsavitsk

Only one way to find out.


----------



## n_maher

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Can I wire the film cap bypass by just soldering like this? Also, I hope I have the positive and negative sides matched up (WIMAs weren't marked).





_

 

You can certainly wire the Wima's like that and they aren't marked because they don't have a polarity.


----------



## Nonchalance

Lol I feel stupid, made same mistake again, haha. Schematics led me to believe they had polarity.

 I'm done for now until I can get a ground plate drilled. I'll post finished pics when I'm done


----------



## PJPro

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_I think your tubes are remarkably well matched. Amplification factor is ~13.5 on one, and ~13.4 on the other -- no way you can hear that difference.

 If anything, it looks like the pot is a little out of balance, though really only a little. You can try to correct it by making one of the input resistors slightly larger than the other -- put a 1M rheostat in parallel with R17 and adjust it until the voltage on the outputs match . Then measure across R17 and replace the resistor and a pot with a resistor of the new value. (You could also do a 100K rheostat in series with the input to R16, adjust that, and replace R16 with the value of the resistor + rheostat.) Or you can replace the pot. But, all in all, it really looks pretty good._

 

OK. Thanks.


----------



## Nonchalance

I plan on screwing the strips onto a copper plate and connecting all the ground connections to one of the lugs on the terminal strip. But I'm actually a bit confused. The lugs don't seem to be connected on the outside. So are they connected somewhere inside or do I have to manually bridge each lug on the strip? 
	

	
	
		
		

		
		
	


	




 I'm using the Keystone strips


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_I plan on screwing the strips onto a copper plate and connecting all the ground connections to one of the lugs on the terminal strip. But I'm actually a bit confused. The lugs don't seem to be connected on the outside. So are they connected somewhere inside or do I have to manually bridge each lug on the strip? 
	

	
	
		
		

		
		
	


	




 I'm using the Keystone strips_

 

According to that data sheet, it's Figure 13. That one has a single lug that's attached to the mounting lug. So, you'll need to bridge all ground connections to that lug.


----------



## ltmon

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_Thanks, see my above edit for more info.

 Have I likely damaged the transistors with this mistake?

 L._

 

I've fixed this. I'm still not sure what was going wrong, but after I while I gave up and wholesale replaced the transistor mounting kits with some mica ones I had lying around and it was fine... no shorts found, and lights on in the pretty glass things!

 Unfortunately when I went to measure DC offset I have found another problem. The right channel is measuring about 2V DC when power is applied, with no source connected and volume at a minimum. This is measured against the ground level of the chassis.

 At that level, I'm afraid to plug in headphones to find out what it sounds like.

 Any idea what would cause such a measurement?

 Thanks again,

 L.


----------



## n_maher

L.

 Something very strange is going on indeed since it should essentially be impossible for you to see DC offset on the output, that's the whole reason the output coupling caps are there. Have you double checked your wiring vs. the schematic?


----------



## tomb

I agree with Nate - you've got something else going on. 

 While that may the true issue with those MOSFETs, let me emphasize a warning that was clearly described in the SSMH PCB Build Thread: Don't torque down to exhaustion on the Bergquist pads in the heat sink mounting kits. The metal tabs on the MOSFETs will cut right through the pads and then into whatever metal is on the heat sink/case underneath, too. It sort of ruins the whole purpose when that happens.
	

	
	
		
		

		
		
	


	




 Firm and tight is just right.


----------



## ltmon

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Firm and tight is just right.
	

	
	
		
		

		
		
	


	


_

 

I was only firm and tight, but, due to my inaccurate casework, on a slight angle. I think the edge of the MOSFET must have bitten down first, and the rest is history.

 I will see if I can check the output caps, as I'm pretty sure I heated one of them more than I intended whilst soldering. I wouldn't have thought enough to turn it to mush, but you never know...

 Thanks for the answers.

 L.


----------



## ltmon

I cleaned up and then reflowed C5 and R12 (which looked a bit dodgy) and the offset dropped down to < 10mv on both sides.

 Sounds really good now, thanks all for the help.


----------



## n_maher

Quote:


  Originally Posted by *ltmon* /img/forum/go_quote.gif 
_I cleaned up and then reflowed C5 and R12 (which looked a bit dodgy) and the offset dropped down to < 10mv on both sides.

 Sounds really good now, thanks all for the help._

 

That may very well be below the threshold of your DMM depending on how good it is. Glad to hear that it was a seemingly easy fix.


----------



## cwboomer

I downloaded this and thought this would save me from my own ignorance. 

 I thought I'd post and show it. 
	

	
	
		
		

		
		
	


	




 Anywho. It looks to me like this diagram has the ground wires from the RCA jacks going to the "ground" of the pot, versus to the chassis. It also looks like the tubes are being bridged between 3 places 1-2, 3-4, & 5-6. Is that correct or am I reading that wrong? I can't tell from the pictures of other wirings that I've seen. Lastly, my silliest question of all. Which lead is which on the headphone jack? I couldn't find a wiring diagram for it. (I can figure out ground). Thanks for you patience with my point-to-point, non-schematical ignorance.

 Admitting dumbness,
 dan
  Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Did anyone here follow the wiring diagram posted here a while back? It's probably neater than anything I can come up with, but does it work?_


----------



## Nonchalance

The grounds of the RCA jacks are connected to the pot grounds then to the actual grounding material on the diagram.

 Apparently 3-4 are NOT bridged. 1-2 and 5-6 are though.

 For the jack, the tip of the jack is left, middle is right, and back part is ground. See Wikipedia's article..

 I ended up not looking at the diagram, more fun to figure stuff out on your own, I'll let you know if it blows up on me


----------



## tomb

I got the quote from Hammond yesterday and put the check in the mail today to Hammond for 25 more cases (for the next batch of kits). I think it will still take a month, though. I'll keep everyone posted on the progress.


----------



## norm2k




----------



## mattcalf

Very nice build, the different heat sinks are very cool and I like the red!


----------



## norm2k

If anyone is wondering, I got the paint from Autozone, glossy red auto paint with no clear coat. The heatsink is from Newegg, part number N82E16835116018. I pulled them from old machines that I was about to chuck. The copper is soft so it was easy to drill. I used the original screws that came with the kit. I also had a hum problem but swapped out the POT for a new one and problem solved!


----------



## manaox2

Are those CPU heatsinks?


----------



## Llama16

OMG, those heastinks are just gorgeous


----------



## norm2k

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_Are those CPU heatsinks?_

 

Nahh, they are North and South bridge chipset heatsinks. Overclocking my P4 required an AM heatsink on the north bridge. I stripped this from an old machine I was throwing out. Search for part number N82E16835116018 on Newegg and you will find them.


----------



## tomb

Wow - looks great. That shows everyone what can be done to spiff up a simple Hammond case. Nice job!


----------



## nullstring

how hot does it get with those heatsinks?

 It gets pretty damn hot with the stock heatsinks..


----------



## tomb

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_how hot does it get with those heatsinks?

 It gets pretty damn hot with the stock heatsinks.._

 

It shouldn't.
	

	
	
		
		

		
		
	


	




 I've got three of them built and use them all the time. The sinks get a little toasty after several hours, but that's about it. We did extensive testing on heat sinks before we chose the method use.

 You should feel one of the MOSFET-MAX heat sinks ... now that's hot.


----------



## nullstring

well, I actually meant the original stock heatsinks from pmillet's BOM.

 Also, my SSMH is not cased right now.. so the heatsinks sit isolated.


----------



## norm2k

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_how hot does it get with those heatsinks?

 It gets pretty damn hot with the stock heatsinks.._

 

It does not get very hot at all but that is probably because it is always cool in the office. BTW, I added those heatsinks purely for aesthetics.


----------



## KeeChoon

On the topic of heat, I'm wondering what's everyone's ambient room temperature? 

 Because in my country, on hot days without the air-con its between 29-33 degrees indoor. With my room's air-con on at around 28 degrees, my SSMH and minimax does get hot too.


----------



## the_equalizer

Quote:


  Originally Posted by *KeeChoon* /img/forum/go_quote.gif 
_On the topic of heat, I'm wondering what's everyone's ambient room temperature? 

 Because in my country, on hot days without the air-con its between 29-33 degrees indoor. With my room's air-con on at around 28 degrees, my SSMH and minimax does get hot too._

 

Gorgeus build norm2k!! 

 I'm in a similar situation, temperatures where I live are usually around 29-33 Celsius too; in May-June it get's up to around 38 Celsius. Still, my beezar SSHM does not get really warm. I can easily lay my hand over the heatsinks with no problem at all.

 On the other hand, my 12AU7 build gets VERY hot, even with bigger heatsinks.

 cheers!


----------



## tomb

Aavid documents imply that for their heat sinks convection is the primary mode of heat transfer. Despite that, other than our attempts to "force" natural convection with all of our cooling holes, without a mechanical source for air movement the primary heat rejection with our heat sinks and amps is probably _radiation_. An example is the MiniMAX first prototype in my avatar - that amp has as many holes or more than any MAX I've built (especially on the bottom) - yet the pebble-vinyl surface is much different than any other case and most likely very low in radiation emissivity (black and smooth are best). In other words, the heat sinks on the PCB inside function perfectly in rejecting the heat to the case, but the case puts on the brakes by being unable to "radiate" the absorbed heat to its surroundings. The result is that amp runs hotter than any MiniMAX with the custom Beezar/Lansing anodized-aluminum case - assuming the convective cooling holes are equal in both cases.

 An analogy that illustrates this is the common misconception that forcibly moving air (a powered attic fan) in a hot attic will reduce the heat load on the interior of a house. Surprisingly, this will only reduce the temperature of the air in the attic. Scientific studies have found that the primary mode of heat transfer is radiation from the underside of the roof to the joists and top surface of the ceiling below. (Sort of like heat sinks boxed up in an amplifier case.) Lowering the temperature of the air in the attic is somewhat mis-directed (ambient does have an effect on space surface temperatures), since the primary mode of heat transfer to the living space below is neither conduction nor convection.

 Convection and conduction transfer heat through a linear gradient - based on the simple temperature difference, along with contact area and heat transfer coeffiicent. However, radiation transfers heat through the temperature difference to the _fourth power_. That's a huge driver and the result is that any lessening of the temperature delta: surface temp of the heat sinks minus ambient air - is immediately impacted if the ambient air (thereby adjacent surfaces) is at a higher temperature.

 So what am I saying? If the ambient air is higher in a room, the amp will run - dis-proportionately - much hotter. This is not just the reduction in temperature difference between the surface temperature of the heat sinks and the ambient air. Rather, the increased surface temperature of surrounding objects (by virtue of the hotter ambient air) reduces the radiation heat transfer _to the fourth power_ of the reduced surface temperature differences.

 P.S. I'm not saying that we shouldn't cut holes in our cases to improve cooling - far from it, convection is still an extremely important mode of heat transfer. I'm only offering an explanation for why only a few degrees of elevated ambient temperatures can result in an amp running dis-proportionately hotter.


----------



## Juaquin

Well that was better (and more concise) than any of my physics professors have ever explained that.


----------



## kuroguy

Tomb,
 that was an extremely accurate description of the physics behind radiant and convective cooling. I haven't heard it put so technically corect since my heat transfer class in college.

 As an air conditioning engineer with an intimate knowledge of the processes involved I whole heartedly agree with your assessment of the situation.

 As usual, thanks for the input.


----------



## Nonchalance

Alright, I finished mine, doesn't work. Nothing lights up or heats up, not even a whisp of smoke to tell me I ****ed up 
	

	
	
		
		

		
			





 What tests should I do to isolate the problem and fix this? Wiring can be seen on one of the previous pages. 

 I'll take pics in the morning when there's better lighting.


----------



## Juaquin

If the LEDs aren't lighting up, that's a major issue. From what I know it could be a few things. The LED resistor could be touching the mounting screw/nut assembly, causing a short. The LED leads could be shorting together in the sockets. There has to be a short somewhere (or the power supply is bad).


----------



## Nonchalance

Hi res pics hosted at Mediafire.

 Thanks a lot. And yes, it's just as messy outside of the case.

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_If the LEDs aren't lighting up, that's a major issue. From what I know it could be a few things. The LED resistor could be touching the mounting screw/nut assembly, causing a short. The LED leads could be shorting together in the sockets. There has to be a short somewhere (or the power supply is bad)._

 

I'm doing a ptp build, hehe. Not using an LED but the tubes aren't lighting up.

 How do I test the power supply? I feel like I did all the wiring correctly, triple checked like everything when I did it.


----------



## nullstring

that sure is messy looking..
 I was gonna try and help, but I'm having a hard time following the wires.

 pmillet gave such a good example of how a clean build could be done. why don't people try and follow that more >_<

 Because nothing is catching on fire, and you think you wired everything correctly, I would say that you probably have a cold solder joint somewhere.

 easy things to do:
 if you look at the schematic, there is a point that says "48V". measure the voltage there, and measure the voltage where it says "19V", which should be pin 3 of the tube sockets.

 because neither sides are working.. I would look more toward the beginning of the circuit... around C1 and C6...
 I specifically can't really "read" your wires for that.

 checking voltages on pin 2 of your FETS might not be a bad idea either.

 Honestly, I have hardly any idea what I am doing, so take my advice with a grain of salt.
 You might want to check your connections to ground too... I soldered my terminal strips..


----------



## Nonchalance

Yea trying this in a small case was a bad idea. I don't have a multimeter at the moment, so can't test anything, I'll grab one soon.

 Meanwhile.

 MOSFETs read 1,2,3 when with the pin side down and metal side down right?

 My wiring for power section:


----------



## nullstring

your diagram is good.

 lol, a multimeter would help =p

 and, yeah, thats how the mosfet pins are.





 EDIT: thats making the relatively safe assumption that the second "C1" is really a "C2"
 EDIT2: put a more relavent (and correct) picture up, didn't realize that mosfets wouldn't all have the same pinout.


----------



## Nonchalance

Yea oops, that should say C2. My bad.

 Going to resolder some points just for right now.


----------



## nullstring

good luck


----------



## tomb

Umm ... thanks for the help, nullstring. Thank goodness you felt like diving into that.
	

	
	
		
		

		
		
	


	




 Just an FYI, but the IRF510 MOSFETs go like this:
 1. Gate
 2. Drain
 3. Source


----------



## Nonchalance

Sorry for my fail organization skills guys, I'll report back with measurements on MOSFET pin, tube pin, and the 48v place.

 Thanks for all the help.


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Sorry for my fail organization skills guys, I'll report back with measurements on MOSFET pin, tube pin, and the 48v place.

 Thanks for all the help._

 

Good luck!

 One thing you might look into - the Cisco power supply has an excellent over-current protection shut-off. If it connects into a dead short, it'll just act like the power supply is dead. No noise, no delay, nothing - it will just fail to produce any voltage. So, if your power-up situation is acting like that ... then look for a short somewhere.


----------



## ethan961

So all was well with my SSMH until recently when I tripped over a cord and the amp went crashing to the ground. It appears nothing was damaged (tubes are both fine) however one of the tubes is now getting 48 volts for some unknown reason. I've checked all the wiring, and I can't for the life of me figure out what happened. Nothing is shorting, all the joints look good... one tube does get 19 volts like it should and is functioning normally. The problem does not follow the tube. I'm sure someone knows off the top of their head where exactly I would need to check, because I am rather lost. I'll admit I am having a hard time following my own wiring, but hey, it was my first electronics build period. (this is PTP btw)
 Anyways, if anyone knows what might be going on, a little help would be greatly appreciated.
 Thanks,
 Ethan


----------



## tomb

Quote:


  Originally Posted by *ethan961* /img/forum/go_quote.gif 
_So all was well with my SSMH until recently when I tripped over a cord and the amp went crashing to the ground. It appears nothing was damaged (tubes are both fine) however one of the tubes is now getting 48 volts for some unknown reason. I've checked all the wiring, and I can't for the life of me figure out what happened. Nothing is shorting, all the joints look good... one tube does get 19 volts like it should and is functioning normally. The problem does not follow the tube. I'm sure someone knows off the top of their head where exactly I would need to check, because I am rather lost. I'll admit I am having a hard time following my own wiring, but hey, it was my first electronics build period. (this is PTP btw)
 Anyways, if anyone knows what might be going on, a little help would be greatly appreciated.
 Thanks,
 Ethan_

 

Actually, it's possible that one of the tubes developed a short. If the plate connections short with the heater connections somewhere inside the tube, then the heaters may see 48V. Just a guess ... but it might explain what you're seeing.


----------



## nullstring

you should try switching the tubes, and see if it switches then.


----------



## kuroguy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, it's possible that one of the tubes developed a short. If the plate connections short with the heater connections somewhere inside the tube, then the heaters may see 48V. Just a guess ... but it might explain what you're seeing._

 

He did say that the problem does not follow the tube. That would usually rule out a bad tube.


----------



## tomb

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_He did say that the problem does not follow the tube. That would usually rule out a bad tube._

 

 Quote:


 The problem does not follow the tube. 
 

Oops! You're right - he did say that..
	

	
	
		
		

		
			





 So, it has to be some of his P2P that's shorting, I guess.


----------



## mlau

Sorry for the dumb question.

 What is the part number for the volume knob on the Beezar kit?

 I really like the minimalist look of the knob, so I'd like to know how much it costs/where to get it.


----------



## tomb

Quote:


  Originally Posted by *mlau* /img/forum/go_quote.gif 
_Sorry for the dumb question.

 What is the part number for the volume knob on the Beezar kit?

 I really like the minimalist look of the knob, so I'd like to know how much it costs/where to get it._

 

Mouser #450-6007


----------



## Nonchalance

I got some measurements.

 48V on MOSFET pin 2 both sides. 48V between R1 and R2, 48V between R7 and R8.

 21.55V on tube pin 3 left, 48V on tube pin 3 right.

 So I guess the right side is messed up, but the tube on left isn't lighting up and I'm not sure how to fix the voltage problem.

 Did I kill the tubes?


----------



## the_equalizer

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_I got some measurements.

 48V on MOSFET pin 2 both sides. 48V between R1 and R2, 48V between R7 and R8.

 21.55V on tube pin 3 left, 48V on tube pin 3 right.

 So I guess the right side is messed up, but the tube on left isn't lighting up and I'm not sure how to fix the voltage problem.

 Did I kill the tubes?_

 

Hmmm... 21.55V on pin 3 and the tube is not lighting up? Maybe an open filament, try measuring resistance between pins 3 and 4 of the tube with the tube out of the circuit; it should give a low resistance value. 

 Now with the right tube 48 volts on pin 3 are sure to kill that filament! Maybe you wired it to the MOSFET's pin 2 instead of pin 3? Another possibility is that the MOSFET's pin 2 and 3 are shorting out?

 cheers!


----------



## Nonchalance

I definitely wired to pin 3. How do I test if the MOSFET is shorting out?

 I can't get a resistance reading on 3-4 on either of the tubes. I guess I blew one and the other was damaged during shipping.

 Well this project failed, haha.

 Is there another way to test the rest of my circuit without the tubes? I want build it right at least.

 Thanks for all the help guys. I really appreciate it


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_I definitely wired to pin 3. How do I test if the MOSFET is shorting out?_

 

Your next line below answers that.
	

	
	
		
		

		
		
	


	




 If you measure zero resistance between the pins. Quote:


 
 I can't get a resistance reading on 3-4 on either of the tubes. I guess I blew one and the other was damaged during shipping.

 Well this project failed, haha.

 Is there another way to test the rest of my circuit without the tubes? I want build it right at least. 
 

You can go through a methodical resistance measurement around each part - or junction measurements referenced to ground, also referenced to the schematic (write down the numbers on a copy of the schematic). In so doing, you can at least compare the readings for the two channels - they should be the same. At points where they're not, chances are that's a problem. Quote:


 
 Thanks for all the help guys. I really appreciate it 
	

	
	
		
		

		
		
	


	



 

One thing I'd try is to put more electrical tape on some of those junctions. It looked like in your pics that there many chances for shorts - especially if the amp got knocked down a few times. It seemed like those Panasonic FC cans were touching part of the power socket, for instance (an electrolytic's wrapper is not sufficient insulation) - but that could've been the camera angle. Good luck.


----------



## Nonchalance

Ok I sorted out a bunch of wires and now I'm getting light and crazy readings. Maybe I'm not as screwed as I thought I was.

 ~44.5 V at pin2 on both MOSFETs and at the 48V marking on the schematic. ~44V at the right tube pin 3, tube lights up a lot. ~18V at left tube pin 3, barely light, mostly in the middle, and I get sound out of this one. I know the tubes are working because both got sound on the left socket, just a buzzing on the right side where the voltage is nuts.


----------



## kuroguy

turn it off before you waste that really bright tube. you are running 44 volts through a 19 volt filament. I bet the tube won't last more than a few minutes at that rate.


----------



## Nonchalance

I know, I took some measurements and put up some music then took the tube out so it doesn't burn out. It was on for ~30 seconds total.


----------



## hitman47

OK, I already managed to screw my amp up again... I finally got the casing more or less done and was running it with my PC as source, so I lifted it onto my desk which has a massive metal frame and there was a huge spark from the casing to the metal frame and now only one tube glows when I turn it on and there's no sound coming out at all. Any ideas as to what might have gone wrong?


----------



## ethan961

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_turn it off before you waste that really bright tube. you are running 44 volts through a 19 volt filament. I bet the tube won't last more than a few minutes at that rate._

 

I believe it is rated for 100V, so there should be no worries. TomB didn't warn me of it (I am having the same problem) and I believe it is on one of his sites at DIYForums.org.
 The tubes normally run at half voltage, so I wouldn't be worried.
 I can't currently check the resistance on my amp but I still cannot see anywhere there might be a short. I might get some pics up when I get home tomorrow evening.


----------



## ethan961

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_OK, I already managed to screw my amp up again... I finally got the casing more or less done and was running it with my PC as source, so I lifted it onto my desk which has a massive metal frame and there was a huge spark from the casing to the metal frame and now only one tube glows when I turn it on and there's no sound coming out at all. Any ideas as to what might have gone wrong?_

 

Something must have shorted to ground, possibly damaging something.


----------



## Fitz

Quote:


  Originally Posted by *ethan961* /img/forum/go_quote.gif 
_I believe it is rated for 100V, so there should be no worries. TomB didn't warn me of it (I am having the same problem) and I believe it is on one of his sites at DIYForums.org.
 The tubes normally run at half voltage, so I wouldn't be worried.
 I can't currently check the resistance on my amp but I still cannot see anywhere there might be a short. I might get some pics up when I get home tomorrow evening._

 

The _plate_ is normally run at around 100V (max 300V), but runs at half that in the SSMH. The _filament_ is absolutely *not* rated to 100V, and running it above 19V is a very good way to damage it. Even going only slightly over the rated filament voltage will rapidly diminish tube life.


----------



## hitman47

Quote:


  Originally Posted by *ethan961* /img/forum/go_quote.gif 
_Something must have shorted to ground, possibly damaging something._

 

Is it possible that it might have come from the back side (the metal part) of one of the caps? Cause those are quite close to the casing in my build, I gotta get a layer of plastic in there


----------



## Nonchalance

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_The plate is normally run at around 100V (max 300V), but runs at half that in the SSMH. The filament is absolutely *not* rated to 100V, and running it above 19V is a very good way to damage it. Even going only slightly over the rated filament voltage will rapidly diminish tube life._

 

Shoot... Oh well I'm lucky that the tube's even alive.

 I still have no idea why it's 48V on the right tube pin 3... I don't think it's the resistors because the circuit wouldn't even go through if a resistor was messed up. Which leaves the MOSFET, but how can a messed up MOSFET change the voltage? 

 I'm not sure what test to do at this point.


----------



## tomb

Quote:


  Originally Posted by *ethan961* /img/forum/go_quote.gif 
_I believe it is rated for 100V, so there should be no worries. TomB didn't warn me of it (I am having the same problem) and I believe it is on one of his sites at DIYForums.org.
 The tubes normally run at half voltage, so I wouldn't be worried.
 I can't currently check the resistance on my amp but I still cannot see anywhere there might be a short. I might get some pics up when I get home tomorrow evening._

 

I'm not sure what it is I didn't warn you about, but I'm absolutely certain I never said that more than 19V was OK for the _heaters_.

 Fitz is absolutely correct - 
 Triode/double triode tubes have two voltage limitations that we are concerned with: the plates and the heaters (filaments). In the 19J6, the plates are rated for 100V and will go much higher (300V) without too much of an issue. As you state, in the Starving Student design - the plates are running at less than half of the smaller voltage spec.

 None of that counts for the heaters, though. Those are on a different circuit - they are used to "turn the tube on" and are what makes a tube glow. In the 19J6, those heaters are run at 19V (spec'd at 18.9V). Most (if not all) tubes have very strict limits when it comes to exceeding heater voltage - like 1 or 2 volts before tube life is _severely_ reduced.


----------



## scompton

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Is it possible that it might have come from the back side (the metal part) of one of the caps? Cause those are quite close to the casing in my build, I gotta get a layer of plastic in there_

 

 Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Shoot... Oh well I'm lucky that the tube's even alive.

 I still have no idea why it's 48V on the right tube pin 3... I don't think it's the resistors because the circuit wouldn't even go through if a resistor was messed up. Which leaves the MOSFET, but how can a messed up MOSFET change the voltage? 

 I'm not sure what test to do at this point._

 

My first build, I had lots of long leads on resistors and caps. First time I powered it up, everything worked fine. When I closed the lid, stuff got pushed together and I had a short. It fried a mosfet which caused the tube to glow very bright.


----------



## Nonchalance

Oh my god that sounds exactly like what I did. Same symptoms too! I'll grab a new MOSFET from Radioshack tomorrow... 

 Have to cut off the nice heat shrink though, haha 

 Thank you so much for the info, cheers


----------



## hitman47

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_My first build, I had lots of long leads on resistors and caps. First time I powered it up, everything worked fine. When I closed the lid, stuff got pushed together and I had a short. It fried a mosfet which caused the tube to glow very bright._

 

I thought of that too, but my tube doesn't glow brighter than usual, the one on the other side just doesn't glow. That's what makes me think it's not one of the FETs, but I can't be sure. I just need to know what I should replace and where I should check voltages and currents to figure it out...


----------



## kuroguy

Regarding the 48 volts at pin 3, I'd bet your mosfet is shorted from pin 2 to 3 and pin 1 is open. Remember Ohm's law: E=IR. for there to be no voltage drop from the node marked 48 volts to pin 3 of the tube there would have to be no current flowing through the mosfet from pin 1 and no drop (resistance) through the mosfets at pins 2 and 3. 

 Of course, this is only a guess, and I am a mechanical engineer as opposed to an electrical engineer.


----------



## Nonchalance

I got my amp to work! Thanks everyone, it was the MOSFET after all. 
	

	
	
		
		

		
		
	


	




 It sounds really good, but there's a slight hum and a really weird noise every 10-20 seconds or so. Wonder if I can fix this. (I have this problem both with the sources connected and disconnected).


----------



## hitman47

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_I got my amp to work! Thanks everyone, it was the MOSFET after all. 
	

	
	
		
		

		
		
	


	




 It sounds really good, but there's a slight hum and a really weird noise every 10-20 seconds or so. Wonder if I can fix this. (I have this problem both with the sources connected and disconnected)._

 

I had that when my amp still worked, I think the problem in my case was that I didn't have enough ground resources, try using an additional copper plate or something like that...

 BTW, anyone have any help for my amp? Should I just assume it's one of the caps and replace them all on that side?


----------



## Llama16

Wow, I lost this thread a while ago 
	

	
	
		
		

		
		
	


	



 I tried reading through all of it but got to p200 and then I gave up 
	

	
	
		
		

		
		
	


	




.

 My mouser order is holding me back, especially the backorder for the p2p build. I just read that the 19j6 tubes got disconnected and saved for and additional 25kits.
 Keep us updated if they'll become available again seperately because I want to do the p2p as well 
	

	
	
		
		

		
		
	


	




 the PCB seems too easy, and it doesn't allow for any basic mistakes that occure in p2p and from which you can learn.

 I'm currently doing the mini3, some cmoys and the pcb SSMH (hopefully the p2p as well someday)
 Any other recommended (useful 
	

	
	
		
		

		
		
	


	




) basic builds that I could order for as well.
 Shipping costs and VAT cost a fortune :S


----------



## Nonchalance

The slight buzzing should be ground, but the regular noise is what's bothering me.


----------



## Nonchalance

I got rid of the buzzing by doing more connections to ground on my panel components, but the slight noise at a regular interval is still there.


----------



## dsavitsk

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_I got rid of the buzzing by doing more connections to ground on my panel components, but the slight noise at a regular interval is still there._

 

It sounds like something is oscillating -- are there stoppers on the pins of the fets and tubes?


----------



## tomb

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_It sounds like something is oscillating -- are there stoppers on the pins of the fets and tubes?_

 

R14 and R15 are the grid stoppers here:




 and R3 and R9 should be attached directly to the Pin 3's on the MOSFETs - right?


----------



## Llama16

Tomb
 Let us know when project '25-more-kits' is a go 
	

	
	
		
		

		
			




 And while you're at it, is there an opening for early pre-orders? hehe

 How is the chance that you will continue to sell the tubes seperately after the kits are sold? I'm guessing the answer is no as they were probably the factor that gave you the chance to make just 25 more kits.

 Dries


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Tomb
 Let us know when project '25-more-kits' is a go 
	

	
	
		
		

		
		
	


	



 And while you're at it, is there an opening for early pre-orders? hehe_

 

Not doing pre-orders this time, thanks.

 I'll ask Hammond how we're doing on the cases and let you all know.
  Quote:


 How is the chance that you will continue to sell the tubes seperately after the kits are sold? I'm guessing the answer is no as they were probably the factor that gave you the chance to make just 25 more kits.

 Dries 
 

If there are tubes left after this round of kits, yes - but we'll have to see. I haven't tested them all yet and those dang 19J6's are still running about 30% bad.
	

	
	
		
		

		
		
	


	




 IOW, there are a bunch more tubes than just 25 kits worth, but how many is unknown for now. I'm working on them - among other things.


----------



## Lou Erickson

I'd love a kit for this, and missed the first ones. The pre-stamped cases sound like a major win.


----------



## Fishline

I'm ready to build my second SSMH, this time following the modified bom, but still p2p. I have a couple of questions that I'm hoping some of you can give me some help on:

 1. C1/C6: The 680uF caps are back-ordered at Mouser. Would this 1000uF (mouser # 647-UPS1J102MHD1AA) work?
UPS1J102MHD1AA Nichicon Aluminum Electrolytic Capacitors - Leaded

 2. For C7/C8, would this one (mouser # 647-UPM1C221MPD) be comparable to the Muse ES, or do I really need the Muse ES? I'd really like to get all the stuff I need from one source to save on shipping if I can help it, and these are the only components I can't find on Mouser.
UPM1C221MPD Nichicon Aluminum Electrolytic Capacitors - Leaded

 3. I have a rocker switch that has LED on it (bought from ratshack). Can someone explain how to wire the LED?

 Thanks y'all in advance!

 fishline


----------



## Nonchalance

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_R14 and R15 are the grid stoppers here:




 and R3 and R9 should be attached directly to the Pin 3's on the MOSFETs - right?_

 

Yea I have R3/9 directly on pin 3, R14 and R15 are in place, though not directly on the tube pins.

 Static has come back on the left channel and left only, persistent. FML... The left happens to be the side where I have all my secondary panel component ground linked to (one on each panel ground went to the copper plate, another went to the terminal strip on the left, where I have my left tube grounded). Would that be the problem?


----------



## hitman47

Do you guys think replacing all caps in my SSMH will fix my problem(described on the previous page)? Cause then I'd head over to Zurich and get everything I need


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I'm ready to build my second SSMH, this time following the modified bom, but still p2p. I have a couple of questions that I'm hoping some of you can give me some help on:

 1. C1/C6: The 680uF caps are back-ordered at Mouser. Would this 1000uF (mouser # 647-UPS1J102MHD1AA) work?
UPS1J102MHD1AA Nichicon Aluminum Electrolytic Capacitors - Leaded_

 

Yeah, those should work - but the Nichicon UPW's are a much better choice:
UPW1J102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded .
  Quote:


 2. For C7/C8, would this one (mouser # 647-UPM1C221MPD) be comparable to the Muse ES, or do I really need the Muse ES? I'd really like to get all the stuff I need from one source to save on shipping if I can help it, and these are the only components I can't find on Mouser.
UPM1C221MPD Nichicon Aluminum Electrolytic Capacitors - Leaded 
 

It's a funny psychology when you see people that will pay $hundreds for parts and not another $5-$7 for shipping. Or, complain when that shipping is $2-$3 higher than they think it should be when the shipper has to deliver them to the Post Office, provide boxes and packing, and or includes delivery confirmation and insurance - there's no logic to it, quite frankly.
	

	
	
		
		

		
		
	


	




 Sorry, but I digress.
	

	
	
		
		

		
		
	


	




 First of all, none of us really recommended the Muse ES. Last time I looked, the highest voltage rating they make is 50V. That's not enough unless you want to push the ratings standards around here. The Muse Fine Gold, on the other hand, comes in 63V sizes. I've built one SSMH PCB using the 1000uf 63V Muse FG's (the silver one pictured on Beezar). They are very nice and available at Handmade Electronics. While you have to do some special things to use them on the PCB (no pre-machined Beezar/Hammond custom case is possible), using them with P2P would be a snap.

 All that said, the one you've picked here is not a good choice. First of all, going to 470uf is an easy, inexpensive choice and will insure no loss of bass with almost all cans. However, since you may end up with 1000uf on the back end (above), might as well go for 1000uf up front, too. Neither is the cap quality you selected as good as it can be. A Nichicon UKW is a much better quality cap in this position and is specifically made for Audio:
UKW1J102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded
 As you can see, it's also available at Mouser.
  Quote:


 3. I have a rocker switch that has LED on it (bought from ratshack). Can someone explain how to wire the LED? 
 

Give us a part number - I'll check. Chances are, it's not worth the trouble. Those things usually have an LED dropping resistor already installed, but set for a voltage that's far different than the SSMH. By the time you added another dropping resistor, chances are you'll exceed the current capacity of the recommended Cisco power supply.
  Quote:


 Thanks y'all in advance!

 fishline


----------



## tomb

Quote:


  Originally Posted by *Nonchalance* /img/forum/go_quote.gif 
_Yea I have R3/9 directly on pin 3, R14 and R15 are in place, though not directly on the tube pins._

 

On the tube pins is not going to make a difference in this case, I think. Quote:


 
 Static has come back on the left channel and left only, persistent. FML... The left happens to be the side where I have all my secondary panel component ground linked to (one on each panel ground went to the copper plate, another went to the terminal strip on the left, where I have my left tube grounded). Would that be the problem? 
 

We've already asked the obvious question, I guess - does it follow the tube if you swap them? Otherwise, then yes, perhaps it's the grounding on that side - but that's only a guess.


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_Do you guys think replacing all caps in my SSMH will fix my problem(described on the previous page)? Cause then I'd head over to Zurich and get everything I need_

 

Hard to say ... if you're looking at what might have the most chance of getting damaged due to a massive short, I'd guess the MOSFETs, not the caps.

 You could inspect the caps - if you see any slight swelling or worse - some liquid oozing from them, then definitely replace them. Otherwise, I'd think a solid-state component is the most likely thing to fry with a short.

 Be careful next time when you case it up. As others have noted, developing shorts when casing something up is a common issue - for noobs and experienced folks alike. It can happen under the best of circumstances.


----------



## hitman47

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Hard to say ... if you're looking at what might have the most chance of getting damaged due to a massive short, I'd guess the MOSFETs, not the caps.

 You could inspect the caps - if you see any slight swelling or worse - some liquid oozing from them, then definitely replace them. Otherwise, I'd think a solid-state component is the most likely thing to fry with a short.

 Be careful next time when you case it up. As others have noted, developing shorts when casing something up is a common issue - for noobs and experienced folks alike. It can happen under the best of circumstances.
	

	
	
		
		

		
		
	


	


_

 

Well, what made me think it's not the MOSFET was that the tube that's still glowing doesn't glow any brighter than normal and when people described a fried transistor in this thread, they usually said that was one of the symptoms...

 What sucks is that I glued the PCB to the spaceholders I installed in the case and now I have to pry it apart again lol


----------



## hitman47

OK, I tried switching the MOSFETS and it turns out one of them's fried after all... I hope the shop near me has IRF510s, else I'll have to make a mouser order and also order the parts for my next project (y1/y2 DAC) as well so I don't have to pay the 40 bucks s+h (it's free to Switzerland from 125 bucks order total upwards)


----------



## tomb

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_OK, I tried switching the MOSFETS and it turns out one of them's fried after all... I hope the shop near me has IRF510s, else I'll have to make a mouser order and also order the parts for my next project (y1/y2 DAC) as well so I don't have to pay the 40 bucks s+h (it's free to Switzerland from 125 bucks order total upwards)_

 

Well, at least you found the problem ... sort of thought it was that, but you never know for sure.


----------



## kuroguy

Quote:


  Originally Posted by *hitman47* /img/forum/go_quote.gif 
_OK, I tried switching the MOSFETS and it turns out one of them's fried after all... I hope the shop near me has IRF510s, else I'll have to make a mouser order and also order the parts for my next project (y1/y2 DAC) as well so I don't have to pay the 40 bucks s+h (it's free to Switzerland from 125 bucks order total upwards)_

 

I believe I told you that it was the MOSFET and how I know it was the MOSFET on the prior page.


----------



## Fishline

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yeah, those should work - but the Nichicon UPW's are a much better choice:
UPW1J102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded_

 

 Quote:


 All that said, the one you've picked here is not a good choice. First of all, going to 470uf is an easy, inexpensive choice and will insure no loss of bass with almost all cans. However, since you may end up with 1000uf on the back end (above), might as well go for 1000uf up front, too. Neither is the cap quality you selected as good as it can be. A Nichicon UKW is a much better quality cap in this position and is specifically made for Audio:
 UKW1J102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded
 As you can see, it's also available at Mouser. 
 

Tom: Thanks very much for sharing your wisdom. However, none of the ones you linked to are in stock at Mouser. All the UPWs are on order, and the only UKW that they have in stock is this 1000uF (UKW2A102MHD):
UKW2A102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded
 It's rather big (18x40mm) and I'm not sure if I can fit four of these guys in the case I'm planning to use. I guess I should consider a different source for caps at least.

  Quote:


 First of all, none of us really recommended the Muse ES. Last time I looked, the highest voltage rating they make is 50V. That's not enough unless you want to push the ratings standards around here. The Muse Fine Gold, on the other hand, comes in 63V sizes. I've built one SSMH PCB using the 1000uf 63V Muse FG's (the silver one pictured on Beezar). They are very nice and available at Handmade Electronics. While you have to do some special things to use them on the PCB (no pre-machined Beezar/Hammond custom case is possible), using them with P2P would be a snap. 
 

I'm confused now: The Muse ES 220uF 16v is what I read in the modified BOM on diyforum, with link to beezar.com, and note in the spreadsheet about also being available from handmade audio. If that's not the correct one to use, perhaps that BOM should be edited?

  Quote:


 Give us a part number - I'll check. Chances are, it's not worth the trouble. Those things usually have an LED dropping resistor already installed, but set for a voltage that's far different than the SSMH. By the time you added another dropping resistor, chances are you'll exceed the current capacity of the recommended Cisco power supply. 
 

Sorry - scratch that. The switch needs a rectangular cutout. I don't think I want that challenge for the SSMH. Will go for the rocker switch on the bom.

  Quote:


 It's a funny psychology when you see people that will pay $hundreds for parts and not another $5-$7 for shipping. Or, complain when that shipping is $2-$3 higher than they think it should be when the shipper has to deliver them to the Post Office, provide boxes and packing, and or includes delivery confirmation and insurance - there's no logic to it, quite frankly. 
 

I completely understand what you're saying, but my POV is, as a consumer, I need to look at the total cost, because all of it come out of my wallet. It's simply that paying $7 S&H for $3 worth of parts seems rather silly, not that the $7 S&H isn't justified, but the fact that the total cost is $10 instead of $3. I think someone had brought this up before: Even with Pete's original BOM, if the parts are obtained from 3 or more sources, the S&H becomes a significant portion of the total cost for this starving student budget amp. 

 My plan for the 2nd SSMH is to push the SQ as far as sensible for this design. I originally was going to get the caps and resistors from ether Michael Percy Audio or Handmade Audio, but after reading one of Tom's post about the SSMH build from the modified BOM being superior to one built from boutique parts, I decided to follow the modified BOM. If I can't get the caps from mouser (within reasonable time, at least), I guess I have to split the order up. If anyone has suggestions on where/what to get for the caps, I'd appreciate it. Also, any recommendation on the wires? I used cat5e cables on my first build, but found the insulation too easily melted when soldering.


----------



## Llama16

Thanks tomb for letting us know 
	

	
	
		
		

		
		
	


	



 You're the man.

 I'll regret the day that your 19j6 tubes will run out, because they're getting really expensive and hard to find.


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Tom: Thanks very much for sharing your wisdom. However, none of the ones you linked to are in stock at Mouser. All the UPWs are on order, and the only UKW that they have in stock is this 1000uF (UKW2A102MHD):
UKW2A102MHD Nichicon Aluminum Electrolytic Capacitors - Leaded
 It's rather big (18x40mm) and I'm not sure if I can fit four of these guys in the case I'm planning to use. I guess I should consider a different source for caps at least._

 

Then pick the 470uf's. Sorry, but you really do have to put a bit of effort in this. There are more caps available than we can shake a stick at.

  Quote:


 I'm confused now: The Muse ES 220uF 16v is what I read in the modified BOM on diyforum, with link to beezar.com, and note in the spreadsheet about also being available from handmade audio. If that's not the correct one to use, perhaps that BOM should be edited? 
 

No, the BOM doesn't need to be edited - only understood.
	

	
	
		
		

		
			





 There are three sets of electrolytic caps used in Dsavitsk's PCB. However, the cathode bypass caps are _optional_. That's why I assumed you were talking about the output caps. In the early renditions of the SSMH, the output caps were the same as the power caps. Fair enough. However, the first choice would be to upgrade the output caps to something of an audio quality. That's where my comments were directed.

 It's true that the Muse ES are recommended for the cathode bypass caps, but that's the third priority in the string of requirements and AFAIK, no one has used them on a P2P design. So, please forgive me if I thought you were talking power caps first, then output caps second.

 If you are wanting to try the cathode caps, but not purchase an audio-quality cap (Nichicon KZ's are available at Mouser and the cathode cap need only be rated for 16V), then any old 220uf 16V cap will do. However, almost all of these will "sound" better if you use some Wima film caps for bypasses (MKP10). Quote:


 If I can't get the caps from mouser (within reasonable time, at least), I guess I have to split the order up. If anyone has suggestions on where/what to get for the caps, I'd appreciate it. 
 

Do some more work. Stick with UPW's or UHE's from Mouser. You need at least a 63V rating for the power caps and output caps. It would help if the power caps are at least 680uf's and the output caps should be at least 470uf. There are a lot of options under those requirements.

  Quote:


 Also, any recommendation on the wires? I used cat5e cables on my first build, but found the insulation too easily melted when soldering. 
 

You won't like this answer, because it requires another source and separate shipping charges, but John's Wire Shop (navshipps) on ebay is an excellent source for SPC teflon-insulated wire (doesn't melt when you solder it). 22ga is the best all-around size, IMHO.


----------



## nullstring

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...and AFAIK, no one has used them on a P2P design_

 

FYI, I did. It's a 90 cent upgrade, why the hell not?

 BTW, I agree with fishline on the shipping stuff, but in this case, beezar ships things really cheaply, and some of their items are cheaper than on mouser. (IIRC).
 finally, if you ever plan on making a bantamDAC, you would need to order from there anyway. so, you might as well just get the PCB for that now, and the shipping loss will be negated.


----------



## Daishiknyte

I finally had a chance to finish the SS kit I bought from royewest (THANKS!). I am unbelievably happy with it. I can't thank you guys enough for the design, pcb, kit, etc. At the same time, I blame you all for assisting my continuing slide down the slippery slope of audio. 
	

	
	
		
		

		
		
	


	




 I did make the mistake of putting the 50k resistors in with the 100k ohm pot. I still am getting good volume, though I might go back in and switch them out. I also left out the socket LED. How can you say no to the tube glow? Toss in the case...mmmmm, tasty.

 I'll have to give the p2p version a shot at some point.


----------



## Nonchalance

Followup to static/noise problem.

 The static indeed follows the tube, so that's probably damage done by the 48V I shot through it. Time to find a replacement tube.

 The noise at a regular interval doesn't follow the tube and stays on the right channel.


----------



## scompton

Sorry posted in the wrong thread.


----------



## Fishline

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Then pick the 470uf's. Sorry, but you really do have to put a bit of effort in this. There are more caps available than we can shake a stick at.

 the first choice would be to upgrade the output caps to something of an audio quality. 

 Do some more work. Stick with UPW's or UHE's from Mouser. You need at least a 63V rating for the power caps and output caps. It would help if the power caps are at least 680uf's and the output caps should be at least 470uf. There are a lot of options under those requirements._

 

Thanks again, Tom. I don't mind doing more work at all, but am just completely ignorant about which ones would pass as "audio quality". I gather from your comments that any UPW or UHE with at least 470uF/680uF and 63v would do. Between the two (UPW vs. UHE) is one better than the other? I've found UPWs for both 470uF/63v (UPW1J471MHD6) and 680uF/100v (UPW2A681MHD). Unless I see more comments about them, I'll go with these.

  Quote:


 If you are wanting to try the cathode caps, but not purchase an audio-quality cap (Nichicon KZ's are available at Mouser and the cathode cap need only be rated for 16V), then any old 220uf 16V cap will do. However, almost all of these will "sound" better if you use some Wima film caps for bypasses (MKP10). 
 

Again, it's not that I don't want to get audio-quality, but that I don't know what's audio quality and what's not, so your guidance is much appreciated. I take it that the cathode caps aren't important to be audio quality, so as long as they are 220uF/16v, they would work. Just to make things as explicit as I can: Do you mean all three pairs (power, output, and cathode) will benefit from addition of film bypass caps such as Wima MKP10? If so then I'll get some extra Wima MKP10s. (I was planning on using them to bypass the output caps, as indicated on the modified schematic/bom.)

  Quote:


 You won't like this answer, because it requires another source and separate shipping charges, but John's Wire Shop (navshipps) on ebay is an excellent source for SPC teflon-insulated wire (doesn't melt when you solder it). 22ga is the best all-around size, IMHO. 
 

No, I don't mind the separate shipping here because I'm not getting just enough wire for SSMH, but plan on getting more for future projects (am thinking of possibly gamma2...). Thanks for the pointer!


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Thanks again, Tom. I don't mind doing more work at all, but am just completely ignorant about which ones would pass as "audio quality". I gather from your comments that any UPW or UHE with at least 470uF/680uF and 63v would do. Between the two (UPW vs. UHE) is one better than the other? I've found UPWs for both 470uF/63v (UPW1J471MHD6) and 680uF/100v (UPW2A681MHD). Unless I see more comments about them, I'll go with these._

 

OK - let's back up. I'll try to explain some of the empirical practices that many of us have learned and discovered. Note that none of this is necessarily prove-able with technical expertise, but is more of an experimental experience about what works and what doesn't.

 There are three types of potential electrolytic capacitor usage in tube and tube hybrid headphone amps:
 1. Power and ground de-coupling
 2. DC-filtering of the audio signal
 3. Cathode bypassing, (audio signal related)

 In the Starving Student, the following caps fit in those categories:
 1. C1 and C6
 2. C3 and C5
 3. C7 and C8.

 In the case of #1, low ESR and high ripple ratings are best. The caps that excel in these specs that are available at Mouser are Nichicon UPW's and UHE's. Generally speaking, the UHE's are better, but this is inconsistent. You'd have to check each size to be sure - sometimes the UPW's are better. Certainly, UPW's are not "bad" in comparison and many builders quite successfully choose UPW's and don't worry about the trouble of making a comparison. IOW, you can't go wrong with either one.

 In the case of #2, every bit of the audio signal passes through these caps. Therefore, the best choice for these caps is to find ones that are audio quality. Note that the power caps that apply to #1 above are not necessarily the best sounding caps. So, two different uses means two different types of caps if you want to optimize things.

 The one exception to this rule is bypassing. It's quite possible through bypassing to make a somewhat bad-sounding power-type cap to sound reasonably good by using bypass caps. Bypass caps usually mean small film caps sized at 0.1 to 0.47uf, but this is highly variable. Many of us have simply settled on 0.22uf out of convenience. Note that bypassing doesn't always work - sometimes the combinations are bad, while others are fantastic. Generally speaking (very generally), bypassing with Wima MKP10's are usually dependable in results. Vitamin Q's make even better bypass caps, but they are nowhere near as convenient.

 If you want greater detail into this practice, study Dsavitsk's excellent reference: Notes on Output Coupling Caps. Also, refer to Humble Homemade Hi-Fi for notes specifically on different bypass caps.

 Finally, case #3 - this cap is used to bypass the cathode on the tube. In simplest terms, I usually think of it as providing extra headroom for the bottom (negative) half of the signal wave. My experience has been that this cap can positively or negatively affect the bass response in a tube/tube hybrid amp. Of all the boutique electrolytic caps available (Black Gates, Nichicon KZ's, FG's, Elna Cerafines, RFS Silmic, etc.), Nichicon Muse ES caps are most known for bass response. At the same time, ES caps are bi-polar, meaning that they should allow the signal to move in both directions just as easily - a perfect application for bypassing the tube's cathode, where the signal wave is fluctuating up and down (positive and negative) on a constant basis.

 This is why we select Muse ES as the first choice cap in that position. Others will work, but again, you may want to bypass them with a good Wima or similar. One thing to remember though, unlike the output coupling caps in #2, not all of the music signal necessarily goes through these caps - only when the signal wave hits a certain amplitude. So, the differences in quality of the caps are not as pronounced in their effect as with #2.

  Quote:


 Again, it's not that I don't want to get audio-quality, but that I don't know what's audio quality and what's not, so your guidance is much appreciated. I take it that the cathode caps aren't important to be audio quality, so as long as they are 220uF/16v, they would work. Just to make things as explicit as I can: Do you mean all three pairs (power, output, and cathode) will benefit from addition of film bypass caps such as Wima MKP10? If so then I'll get some extra Wima MKP10s. (I was planning on using them to bypass the output caps, as indicated on the modified schematic/bom.) 
 

Yes, all three pairs might benefit from bypass caps, but the ones at the output coupling positions will have the most effect. It's questionable whether the difference would be audible in the other two cases (for this amp).
  Quote:


 No, I don't mind the separate shipping here because I'm not getting just enough wire for SSMH, but plan on getting more for future projects (am thinking of possibly gamma2...). Thanks for the pointer! 
 

Good. You won't regret dealing with John's wire shop on ebay. Just check the insulation thickness and get the thinnest kind he has. Don't buy the twisted pair. Also, stay away from the Kapton insulation kind. If he doesn't have what you want (22ga SPC Teflon-coated, single multi-strand wire), send him a message through e-bay. Most likely, he'll make a special listing that you can buy from.


----------



## Fishline

Geez, Tom! Your generosity in sharing your knowledge is just amazing! Can't thank you enough for all the help and the education. Now I feel like I'm seeing more light on the subject, instead of blindly following instructions (which is basically how I built my first SSMH). I will surely read up Dsavik's notes on output caps.

 I will take my time to put everything together. With the first one, I simply used my cordless drill and whatever bits I have to do drill the case, and it is barely passable. With the second one, I ordered a proper case (instead of recycled tin) and plan to use a stepped bit. I don't think I want to go as far as getting a drill press, but the drill guide I found on amazon looks like it should do OK. I've got some used CPU heatsinks that I'm planning to use. Will have to figure out how to fix the MOSFETs to the CPU heatsink.

 It may take a while, but I'll try my best to report my progress (or lack thereof).


----------



## Fishline

double post deleted.


----------



## acvtre

I'm a noob and I wanna build a cheap but good sounding hybrid amp. Do you think is better the SSMH or the millet max?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_I'm a noob and I wanna build a cheap but good sounding hybrid amp. Do you think is better the SSMH or the millet max?_

 

Look - this puts me in a bad position, since I sell both of them and the different designers are all friends. That said, I've built more of both than anyone (4 SSMH's, 4 Millett Hybrids w/DB's, 4 MiniMAXes, 7 Maxes), so I think I can speak with authority on the matter.
	

	
	
		
		

		
		
	


	


_IMHO, the performance of both amps is proportional with the cost._ The proportionality is that the SSMH is half the cost of a MAX/MiniMAX. Some of that price difference exists in a greater feature set on the MAX/MiniMAX, but still - something to consider in the price difference. At the same time, there's probably no tube or tube hybrid amp that is cheaper and simpler with great performance than the SSMH.

 To be more descriptive, while both amps do well with _all_ kinds of phones, you will find that the MM/MiniMAX probably has a greater advantage with mid-to-lower impedance phones, while the SSMH has a greater advantage with high impedance phones, but each has enough current and voltage swing to handle both impedances authoritatively. The SSMH is definitely more "tubey", with emphasized mids, a very dark background but with somewhat rolled off highs and lows, while the MM/MiniMAX has much more of a flat-response, with solid-state-like detail & slam - but with distinctly unique tube flavoring.

 There are those that disagree with my opinions, however. Some people have listened to one or two instances of the above with somewhat esoteric phones and have made sweeping statements in complete contradiction. I make mine based on the phones that I have and use almost constantly: KSC-75, Portapros, PX-100, Grado SR225, HF-1, and HF-2, Sony V6, Sennheiser HD25-1 II, HD580, HD600, AKG 701, and Fostex T50RP. I've also had my hands on a couple of other orthos from time to time (graciously loaned by cetoole). So, please measure my response accordingly in that context. 
	

	
	
		
		

		
		
	


	







 EDIT: Ordinarily, I thoroughly despise requests for amp comparisons, but I seem to be losing that battle around here. Please don't ask me to compare against something I don't sell.


----------



## scompton

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_I'm a noob and I wanna build a cheap but good sounding hybrid amp. Do you think is better the SSMH or the millet max?_

 

Keep in mind that if you can't find the 19J6 tubes, you'll have to do one of the variants posted in the thread. But that means changes to the tube socket and resistor values, so it won't be as straight forward a build.


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Look - this puts me in a bad position, since I sell both of them and the different designers are all friends. That said, I've built more of both than anyone (4 SSMH's, 4 Millett Hybrids w/DB's, 4 MiniMAXes, 7 Maxes), so I think I can speak with authority on the matter.
	

	
	
		
		

		
		
	


	


IMHO, the performance of both amps is proportional with the cost. The proportionality is that the SSMH is half the cost of a MAX/MiniMAX. Some of that price difference exists in a greater feature set on the MAX/MiniMAX, but still - something to consider in the price difference. At the same time, there's probably no tube or tube hybrid amp that is cheaper and simpler with great performance than the SSMH.

 To be more descriptive, while both amps do well with all kinds of phones, you will find that the MM/MiniMAX probably has a greater advantage with mid-to-lower impedance phones, while the SSMH has a greater advantage with high impedance phones, but each has enough current and voltage swing to handle both impedances authoritatively. The SSMH is definitely more "tubey", with emphasized mids, a very dark background but with somewhat rolled off highs and lows, while the MM/MiniMAX has much more of a flat-response, with solid-state-like detail & slam - but with distinctly unique tube flavoring.

 There are those that disagree with my opinions, however. Some people have listened to one or two instances of the above with somewhat esoteric phones and have made sweeping statements in complete contradiction. I make mine based on the phones that I have and use almost constantly: KSC-75, Portapros, PX-100, Grado SR225, HF-1, and HF-2, Sony V6, Sennheiser HD25-1 II, HD580, HD600, AKG 701, and Fostex T50RP. I've also had my hands on a couple of other orthos from time to time (graciously loaned by cetoole). So, please measure my response accordingly in that context. 
	

	
	
		
		

		
		
	


	







 EDIT: Ordinarily, I thoroughly despise requests for amp comparisons, but I seem to be losing that battle around here. Please don't ask me to compare against something I don't sell._

 

Really interesting. Now the questions are, how much do the both kit-amps cost? And which one could be better for me considering that I almost can't read a schematic, so I need a step-by-step guide.
 Can I roll the tubes with the MM? I've also found a pic of the last version of the MM with the space for the Bantam DAC, THAT'S REALLY COOL!

 P.S.: for now I've got a AKG k240 mkII


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Really interesting. Now the questions are, how much do the both kit-amps cost? And which one could be better for me considering that I almost can't read a schematic, so I need a step-by-step guide.
 Can I roll the tubes with the MM? I've also found a pic of the last version of the MM with the space for the Bantam DAC, THAT'S REALLY COOL!

 P.S.: for now I've got a AKG k240 mkII_

 

The Step-by-step guide for the Starving Student is in my signature.

 There are threads for both the MAX and the MiniMAX - we need to keep discussions/questions about those over there.


----------



## the_equalizer

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_<snip>
 Can I roll the tubes with the MM? 
 <snip>_

 

Not exactly. Rather there are three different 'versions' of the circuit, using completely different tubes. This different tubes are not interchangeable, that is, you cannot plug tube A into an amp version built for tube B; this for a variety of reasons that range from the mechanical (e.g. the tubes use different sockets) to the electrical (different pinout, current requirements, etc.)

 Still, given that you mention that you are not very proficient in reading schematics, I strongly recommend you build the Beezar.com version using 19J6 tubes and a printed circuit board (PCB). You'll have to keep an eye on this thread and on Beezar.com for TomB's announcement of kit availability. The kit might be a little more expensive than what you originally could have had in mind for this project but it's an *OUTSTANDING* value: easy to build, beautiful case, good quality components, in a word: great. Just take a look at the step-by-step build thread here.


 If you're still interested in building any of the two alternate tube version, for which no PCB is available, search the thread for 12SR7 and 12AU7.

 cheers!


----------



## TimJo

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_Can I roll the tubes with the MM?_

 

 Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Not exactly. Rather there are three different 'versions' of the circuit, using completely different tubes._

 

Whoops, your referring to the Starving Student equalizer. 

 I think acvtre was asking about the MiniMax. On that one there are three types of tubes, but all within the same family. 

 acvtre, if you go to www.diyforums.org you can read all about the details....


----------



## tomb

Hammond has finished the new run of cases, but I have to send them more money.
	

	
	
		
		

		
			





 They're a bit more expensive this time because of ordering only 25. The one-time tooling charge (paid last time) was fairly trivial in the whole scheme of things.

 The good news is that they should receive the additional check early next week and then ship the cases to me. I'm only waiting now to finish a deal on more power supplies and then we should be ready to start selling the new kits in 1-2 weeks.

 I'll post more progress notes as time goes on and will be sure to give everyone plenty of notice before they go on sale again.


----------



## the_equalizer

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Whoops, your referring to the Starving Student equalizer. 

 I think acvtre was asking about the MiniMax. On that one there are three types of tubes, but all within the same family. 

 acvtre, if you go to www.diyforums.org you can read all about the details...._

 







 oh damn! you're right. _mea culpa_


----------



## acvtre

I'm a noob in audio DIY, so far I've built only a cmoy and a pimeta V2 (not completed), but it seems to me that this amp is not too much difficult to populate, isn't it? Or is it only an impression of mine?

 P.S.:How much does it heat up?


----------



## tomb

Quote:


  Originally Posted by *acvtre* /img/forum/go_quote.gif 
_I'm a noob in audio DIY, so far I've built only a cmoy and a pimeta V2 (not completed), but it seems to me that this amp is not too much difficult to populate, isn't it? Or is it only an impression of mine?

 P.S.:How much does it heat up?_

 

If you've successfully built both of those, you're more than ready for a SSMH PCB. The heat sinks on the PCB design do not get very hot. They definitely get warm, though - you'll know for certain that this thing is different than a CMoy or Pimeta, but it's no big deal if done correctly.


----------



## acvtre

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you've successfully built both of those, you're more than ready for a SSMH PCB. The heat sinks on the PCB design do not get very hot. They definitely get warm, though - you'll know for certain that this thing is different than a CMoy or Pimeta, but it's no big deal if done correctly.
	

	
	
		
		

		
		
	


	


_

 

OOOps wrong thread, last post was for the MM thread.


----------



## devilshell

hi regarding the 19J6 its literally impossible to fine now. isit possible to use other tubes? if yes what are the models. thank you very much. as i am starting this build and just realised i missed out on the tubes.


----------



## Lou Erickson

That's great news about the cases, Tom! I'll be keeping an eye on here so I can get a kit.


----------



## Llama16

hey tom

 Awesome that you'll still be able to offer the kits 
	

	
	
		
		

		
		
	


	



 The price increase is no hickey for the effort you put in it.

 What will be the approximate price for the kit? So I can transfer the cash to my paypal already and thus don't need to wait couple of days and maybe lose my chance for one of the 25 kits.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_hey tom

 Awesome that you'll still be able to offer the kits 
	

	
	
		
		

		
		
	


	



 The price increase is no hickey for the effort you put in it.

 What will be the approximate price for the kit? So I can transfer the cash to my paypal already and thus don't need to wait couple of days and maybe lose my chance for one of the 25 kits._

 

Assuming the power supplies come through, probably $115 - so that's not much of an increase, but don't hold me to it. Things may change at the last minute depending on what I receive and if I have to find more sources for things. Everything looks OK and on-schedule right now, though.


----------



## cwboomer

Besides the Punched Case,....is the kit basically everything you see on Beezar that you see when you click on starving student?

 Can some items be subtracted if we already have them and still be eligible for a punched case. In other words will you accept substitution?

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Assuming the power supplies come through, probably $115 - so that's not much of an increase, but don't hold me to it. Things may change at the last minute depending on what I receive and if I have to find more sources for things. Everything looks OK and on-schedule right now, though._


----------



## tomb

Quote:


  Originally Posted by *cwboomer* /img/forum/go_quote.gif 
_Besides the Punched Case,....is the kit basically everything you see on Beezar that you see when you click on starving student?_

 

Yes. Quote:


 
 Can some items be subtracted if we already have them and still be eligible for a punched case. In other words will you accept substitution? 
 

NO.


----------



## revolink24

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes._

 

Huh? Pardon me if I'm missing something, but none of the resistors, terminal blocks, volume knob, etc are on that particular page.


----------



## akdmx

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Huh? Pardon me if I'm missing something, but none of the resistors, terminal blocks, volume knob, etc are on that particular page._

 

I'm also curious to know what would be needed in addition to the kit in order to complete the amp. Also, I would be interested in pre-ordering a kit if you decide on a price.


----------



## tomb

Quote:


  Originally Posted by *akdmx* /img/forum/go_quote.gif 
_I'm also curious to know what would be needed in addition to the kit in order to complete the amp. Also, I would be interested in pre-ordering a kit if you decide on a price._

 

Sorry. For some reason, I thought you all meant when you click on the website BOM -
SSMH Bill Of Materials

 Everything that's on that BOM is in the kit.


----------



## cwboomer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry. For some reason, I thought you all meant when you click on the website BOM -
SSMH Bill Of Materials

 Everything that's on that BOM is in the kit._

 

Boy that sounds great! I feel dumb for asking for this clarification, but when you say everything on the BOM, do you mean that the kit will contain every part on the BOM, even if the BOM specifies Digi-Key or Mouser as a source? Or just the BEEZAR parts that are listed on the BOM?

 Getting excited for the day of delivery!

 Dan


----------



## tomb

Quote:


  Originally Posted by *cwboomer* /img/forum/go_quote.gif 
_Boy that sounds great! I feel dumb for asking for this clarification, but when you say everything on the BOM, do you mean that the kit will contain every part on the BOM, even if the BOM specifies Digi-Key or Mouser as a source? Or just the BEEZAR parts that are listed on the BOM?

 Getting excited for the day of delivery!

 Dan



_

 

Every part, period. Only wire, heat shrink, and solder are not included.


----------



## akdmx

If there any way we could pre-order these?


----------



## CaptHowie

Nope, you'll have to wait like everyone else.


----------



## Llama16

Tomb, how fast do you recon they'll be sold out? How fast did the first delivery get sold out?

 I don't wanna miss my chance because they're gonna be sold an hour after release 
	

	
	
		
		

		
		
	


	




.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Tomb, how fast do you recon they'll be sold out? How fast did the first delivery get sold out?

 I don't wanna miss my chance because they're gonna be sold an hour after release 
	

	
	
		
		

		
		
	


	




._

 

Just a guess, but if it goes like last time - maybe 10-12 will get sold within the first couple of days, but the remaining dozen or so will drag on for another month or more.
	

	
	
		
		

		
		
	


	




 I don't mean to diminish the enthusiasm in this thread, but I made this same observation many months ago: a half-dozen enthusiastic posters to this thread ... is still just 6 people. Just as an example to that theorem, the last batch of HF-2's that Todd announced recently: people thought they'd be gone in the first half-hour, but it took the better part of the day and into the evening (I think) before they were all gone.

 So, I wouldn't worry too much if you miss by a few days or a week, there's bound to be some left I think.


----------



## Llama16

fiew great to hear that 
	

	
	
		
		

		
		
	


	




 I already got the pcb and tubes for a p2p build. But getting the parts from mouser (I'm across the pond) just keeps on dragging forever.

 I finally decided to get the kit, that way I'm completely sure. And because your service is very quick and trusted, I didn't really reconsider.

 I was thinking that there were maybe alot of people observing the thread twithout posting, and my ability to estimate a number isn't really that great


----------



## Fishline

I have a couple more questions before I get started with my second p2p build:

 - Can anyone tell me what's right size hole for the tube socket, to be mounted from below? I want to make sure I get the bit that can drill the correct size.

 - Volume pot: I'm considering the Alps RK097 pot, to save the space for power switch (as the enclosure I'm planning to use is rather small, and I need all the space I can get). Can anyone tell me how the power switch on this pot works, is it push to turn on/off, or turn all the way to the left to turn off? Also, how does it compare to the alpha, quality-wise? And, it seems like there's only the 10k version (Mouser 688-RK0971221Z05). Do I just add ~40k of resistor(s) in front of it?


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I have a couple more questions before I get started with my second p2p build:

 - Can anyone tell me what's right size hole for the tube socket, to be mounted from below? I want to make sure I get the bit that can drill the correct size._

 

Pretty sure it's 3/4", but I'll check when I get home tonight if someone else doesn't confirm. Quote:


 
 - Volume pot: I'm considering the Alps RK097 pot, to save the space for power switch (as the enclosure I'm planning to use is rather small, and I need all the space I can get). Can anyone tell me how the power switch on this pot works, is it push to turn on/off, or turn all the way to the left to turn off? Also, how does it compare to the alpha, quality-wise? And, it seems like there's only the 10k version (Mouser 688-RK0971221Z05). Do I just add ~40k of resistor(s) in front of it? 
 

It turns to the left to turn off. The general consensus I've seen from most people is that it's on a par with the Alpha (not as good as an RK27, for instance). 

 No, you would not put 40K-worth of resistors in front of it - that would give you 4X attenuation, probably way too much. Start with a 10K resistor(s) and go up in 10K increments from there. One thing to consider is that 10-20K input resistance may filter out some bass with some sources, depending on the output capacitors (if there are any) of the source. That's usually why we go with 50K. A 10K pot works fine for many portables because you're not expecting earth-shattering bass in a portable environment anyway.


----------



## TimJo

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_- Can anyone tell me what's right size hole for the tube socket, to be mounted from below? I want to make sure I get the bit that can drill the correct size._

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Pretty sure it's 3/4", but I'll check when I get home tonight if someone else doesn't confirm._

 

The ceramic ones I use are 3/4" and my guess is that's pretty standard for the miniature 9 pin sockets. 

 Of course, you'll never know for sure sure 'til you have the ones your buying in your hands.


----------



## tomb

I'm sure you meant 7-pin ... 9-pin sockets are bigger in diameter.


----------



## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sure you meant 7-pin ... 9-pin sockets are bigger in diameter.
	

	
	
		
		

		
		
	


	


_

 

No, actually I forgot the 19J6 was a 7-pin. 

 (I've been building more 9-pin stuff lately. 
	

	
	
		
		

		
		
	


	




)

 The 7-pins I used have a 5/8 dia hole. I just measured...

 Sorry for the confusion.


----------



## dsavitsk

Typical 7 pin sockets require 5/8" mounting holes. 9 pin sockets require 7/8". There are exceptions to both.


----------



## tomb

See? We'll get things confirmed for you eventually!
	

	
	
		
		

		
		
	


	




 Thanks, guys!


----------



## kuroguy

Now where did I put that hole shrinker?


----------



## Fishline

You guys are incredibly helpful! If I may ask one more: short of a stepped bit, what kind of bit can work on an aluminum case? It seems like most common power drill bits only go up to 1/2". Do twist bits go up to 5/8"?


----------



## dsavitsk

I use these all the time. I'm sure it's a bad idea, but in aluminum they seem to do just fine.


----------



## cwboomer

The spade bits are technically meant for wood. Generally anything that has a carbide edge will cut aluminum. And wood bits will cut aluminum for a short time, until they dull too quickly. No quicker than really hard tropical woods.

Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies

 here's an individual "twist" drill bit. Probably as cheap as a spade bit. They also have nice hex headed hardware. This is a "jobber" length, meaning much longer than you'd find at a home center. It's for the metalworking trade.

 dan


----------



## cwboomer

Quote:


  Originally Posted by *cwboomer* /img/forum/go_quote.gif 
_The spade bits are technically meant for wood. Generally anything that has a carbide edge will cut aluminum. And wood bits will cut aluminum for a short time, until they dull too quickly. No quicker than really hard tropical woods.

  HTML Code:



		Code:
	

[left]http://www.use-enco.com/CGI/INSRIT?PMAKA=300-0140&PMPXNO=943186&PARTPG=INLMK32[/left]


here's an individual "twist" drill bit. Probably as cheap as a spade bit. They also have nice hex headed hardware. This is a "jobber" length, meaning much longer than you'd find at a home center. It's for the metalworking trade.

 dan_

 

There's also these, but be darn careful and use a drill press:
Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies


----------



## kuroguy

Just make sure to use lots of oil when cutting aluminum and wood bits will last pretty long. I use regular 40 weight in a pump style oil can. So long as you keep the bit cool, the edge will last.


----------



## scompton

Stepped bits don't have to be expensive

Harbor Freight Tools


----------



## Llama16

Does someone happen to know where I can get the European (belgian) version of the powersupply? Byt his I mean the one meant for 230V (220V-240V) network.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Does someone happen to know where I can get the European (belgian) version of the powersupply? Byt his I mean the one meant for 230V (220V-240V) network._

 

The existing supply works on 240V. You'll probably need to get an adapter for the connector, but there are many European folks who use the same power supply as I understand it.


----------



## tomb

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_Stepped bits don't have to be expensive

Harbor Freight Tools_

 

Yep - all I use! Use the 1/4 - 3/4 bit, though. The other two are not so hot, IMHO - especially the big fat one (the long one is ~OK). They go dull fairly easily on the very tip, but heck - they're so cheap that I go buy some more.


----------



## cwboomer

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Just make sure to use lots of oil when cutting aluminum and wood bits will last pretty long. I use regular 40 weight in a pump style oil can. So long as you keep the bit cool, the edge will last._

 

Agreed, and if you can slow down your speed. slow it down.

 Here's a speed guide.
Drill Press Speed Chart


----------



## SaxonFSU

where can you currently get the 19j6 tubes for cheap? and what should you look for when ordering them brand country of manufacture ect

 thanks


----------



## Llama16

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The existing supply works on 240V. You'll probably need to get an adapter for the connector, but there are many European folks who use the same power supply as I understand it._

 

So just a simple socket adapter will do! that's amazing 
	

	
	
		
		

		
		
	


	




 Just made my day. 
 the power supply was my biggest concern. I'm glad I'm rid of it


----------



## SaxonFSU

Quote:


 Hi everyone,

 This has been in the works for a while but I finally found some time to put it together. I wanted to modify the starving student amp using an alternative tube to the scarce 19J6's. I finally settled on the 12SR7 and 12SW7 which are only $1 each at vacuumtubes.net. Perfect for the starving student. The caveat is that they are metal tubes and some people may prefer glass tubes. In that case the 12SR7GT is the glass tube version of the 12SR7. It is a few dollars more per tube but still cheap.


 Here is the result, the metal starving student:


 If you want to build this version, you have to make some small changes -

 R1/R7 - 44k
 R5/R11 - 4K
 R2/R8 - 330K
 R4/R10 - 180K

 You will have to use an octal socket, and here are the conversions from the seven pin socket in the original circuit diagram:

 1,2 -> 6
 5,6 -> 2
 3,4 -> 7,8
 7->3

 You will also have to ground pin 1 which is for the metal casing. It is probably a good idea to ground pin 1 with a separate path to ground from the heaters (pins 7,8). That way if the ground connection for the heaters breaks for whatever reason you don't see that voltage on the tubes.

 Using 2" heatsinks is also recommended since the heaters are running at 12V instead of 19V. 
 

i was looking this over and woundering if anyone has any experience, i want to do this because i am having trouble finding 19j6 tubes. 

 any help would be greatly appreciated because this will be my first tube project. 

 with this setup is there any other modifications that will need to be made?

 thanks in advance


----------



## Lou Erickson

Their website says that vacuumtubes.net has the 19j6 for $4.00 each. They were $1.00 IIRC, so they've gone up a bit, but that's still pretty affordable.

 Mind you, that page might be outdated.

 Google also finds them for $4.00 at thetubecenter.com. A.G. Tannenbaum lists them for $4.00 each. vacuumtubesinc.com says "call" so who knows if they have any, and vacuumtubes.com lists them for $10 each, which seems high.

 Are you hearing from these vendors (particularly vacuumtubes.net who was highly regarded earlier in the thread) that they're out and the web page needs to be updated?

 Maybe I'll order myself a set while I'm thinking about it.


----------



## tomb

The next round of 25 Starving Student Millett Hybrid kits will be available beginning Saturday, 11/14/2009 at 12:01 AM EST (Friday night). 
	

	
	
		
		

		
		
	


	






 EDIT: I haven't talked to them in awhile, but I think both vacuumtubes.net and the Tube Center are out. The only ones that I know have them (besides Beezar) are tube vendors that sell them for $10 or more, such as SND Tube Sales.


----------



## Lou Erickson

I was afraid that was the case.

 That's very good news about when kits will be available! I'll clear my schedule.


----------



## revolink24

I'm guessing there are no plans to sell any more tubes? One of mine started out weak and is now just clinging to life and sputtering


----------



## Juaquin

Any plans for an official revision of the SSMH with a tube that is more obtainable? I've seen all the mod posts for using other tubes, but an official design to circle the wagons around would be nice if a huge warehouse full of 19J6s isn't discovered soon. Or maybe a PCB that somehow allows an easier conversion to the other tubes?


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_I'm guessing there are no plans to sell any more tubes? One of mine started out weak and is now just clinging to life and sputtering 
	

	
	
		
		

		
		
	


	


_

 

If you bought it from Beezar, then I'll replace it if I can. Send me a PM or an e-mail and we can arrange a swap out.


----------



## Lou Erickson

I think Tom's been really fabulous supporting what he's done so far with the kit. The changes for the other tubes were really straightforward. One resistor, and a bigger heat sink. Actually, the other change was more than one resistor. But still pretty straightforward.

 If you wanted to use the PCB, you could get the panel mount versions of the tube sockets and run wires to the PCB. A little fiddly, but it shouldn't be too bad.

 I'm considering building one of each variant. Mouser's stocking is a whole unexpected brand of crazy, though. 
	

	
	
		
		

		
		
	


	




 First, my replacement cable for some Stax, and this cmoy I have sitting as a sad pile of parts. Then tubes in boxes.


----------



## Juaquin

Of course Tom has been great with this. I'm just making suggestions for moving into the future. Pretty soon it will be next to impossible to find the 19J6 for sane prices.

 The point about the PCB was that everyone who has the custom case could make an easy tube switch with a few changed parts directly on the PCB and jumpering to the right pins, without airwiring and other "fiddly" modifications. Panel mounting the tubes would not work well with the way the case is currently designed.

 I'm in no way suggesting that he owes us this, or that he has to do this. Just offering ideas.


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## SaxonFSU

how much were the kits last time they were for sale?


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## cwboomer

I will be selling my 19J6 tubes when I'm able to get a kit in my hands. 

 So maybe 12:02 am on 11/14? 
	

	
	
		
		

		
		
	


	




 Don't know if I can stay up that late the night before an event I have on 11/15, but I will see.

 D


----------



## tomb

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_Their website says that vacuumtubes.net has the 19j6 for $4.00 each. They were $1.00 IIRC, so they've gone up a bit, but that's still pretty affordable.

 Mind you, that page might be outdated.

 Google also finds them for $4.00 at thetubecenter.com. A.G. Tannenbaum lists them for $4.00 each. vacuumtubesinc.com says "call" so who knows if they have any, and vacuumtubes.com lists them for $10 each, which seems high.

 Are you hearing from these vendors (particularly vacuumtubes.net who was highly regarded earlier in the thread) that they're out and the web page needs to be updated?

 Maybe I'll order myself a set while I'm thinking about it._

 

I had actually not heard of A.G. Tannenbaum when you posted this. Just for the heck of it, I decided to contact him directly about 19J6 tubes. Here's his response:

  Quote:


 You must be kidding, we sold out of these 3 years ago . . . I could sell all I could get at $ 20 each these days 
 

It was in red in my e-mail, too.


----------



## Lou Erickson

Bummer! These folks need to keep their websites more current. Being a few weeks, or a quarter behind is one thing, but three years? When does that become false advertising?

 I find it amusing that the tubes for the Starving Student may now cost more than the rest of the amp, possibly in part to the popularity of the amp. 
	

	
	
		
		

		
		
	


	




 I'm trying to reach vacuumtubes.net to get confirmation on the 19j6, and ask some questions about the sockets in their catalog. I'll be ordering some parts to try the variants. The metal tubes seem like a neat idea.

 I did find the power supplies on ebay for $8. Several folks had larger ones (1.5A) that I wish I could find so I could run some other stuff in the box, but those seem to have gotten hard to find.


----------



## SaxonFSU

vacuumtubes.net didnt have them. already called friday


----------



## dsavitsk

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Any plans for an official revision of the SSMH with a tube that is more obtainable? I've seen all the mod posts for using other tubes, but an official design to circle the wagons around would be nice if a huge warehouse full of 19J6s isn't discovered soon. Or maybe a PCB that somehow allows an easier conversion to the other tubes?_

 

We're not necessarilly opposed to a PCB revision based around a tube that's easier to find. The issue is that it isn't clear that there is a market. To make the whole process worthwhile we'd need to be able to sell 100 if not 200 PCBs, and as Tom has said, a couple of vocal people does not necessarilly add up to a lot of sales. 

 Instead, maybe someone could come up with a turret board point to point pattern to share ...


----------



## Juaquin

Sounds like a good plan to me. I understand that there may not be a huge market for them so that's cool.


----------



## Lou Erickson

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_We're not necessarilly opposed to a PCB revision based around a tube that's easier to find. The issue is that it isn't clear that there is a market. To make the whole process worthwhile we'd need to be able to sell 100 if not 200 PCBs, and as Tom has said, a couple of vocal people does not necessarilly add up to a lot of sales. 

 Instead, maybe someone could come up with a turret board point to point pattern to share ..._

 

I have never heard of such a thing before. Digging about on the Internet finds parts at Ampmaker - do you know of any other places to get the turrets?

 If a turret board layout would give people who don't think they can make point to point work the confidence to try, it might be a good idea. If the turret boards are as straightforward as they look, I'd give it a try.

 (Point to point was one of the specific reasons I want to try the SSMH, though! I can try both. Hee.)

 Edit: I found some turrets at Mouser. They're not as uncommon as I expected.


----------



## dsavitsk

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I have never heard of such a thing before._

 

You can get them all over -- Digikey and Mouser both carry them, as do Parts Connexion, AES, etc. You can also just use the terminal strips Pete used in the original in two rows for the same effect. This is point to point how it is really meant to be done. We'd just need a reproducible layout.






 Parts available at Digikey/Mouser

http://www.keyelco.com/pdfs/M55p130.pdf


----------



## SaxonFSU

yes with other tubes, this amp could really be afordable again. and as a starving "collage student" this would be a great help


----------



## TimJo

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Instead, maybe someone could come up with a turret board point to point pattern to share ...





_

 

That's a great old drawing. Not to derail the thread, but where did you find that?


----------



## SaxonFSU

could someone with experience making the version using the other tubes, do a simple draw up schematic using the right resister and cap values? even if its just drawn over the origional

 it doesnt sound like much, but it would be a big help to me.


----------



## tomb

Quote:


  Originally Posted by *SaxonFSU* 
_could someone with experience making the version using the other tubes, do a simple draw up schematic using the right resister and cap values? even if its just drawn over the origional

 it doesnt sound like much, but it would be a big help to me._

 

Why not wait 6 days and decide for yourself if all of this is unaffordable? Seems like you'd have a bit more information then and could make a more intelligent decision. It might even give you time to copy the alternative tube-mod information to the schematics in question yourself, assuming you decide to go that route.
	

	
	
		
		

		
		
	


	




 The schematics are readily available - both Pete Millett's original and the SSMH PCB version:
Pete Millett's DIY Audio pages
SSMH PCB Schematic


----------



## Llama16

I've never stumbled upon that site of pete's, it's a great help 
	

	
	
		
		

		
		
	


	



 As soon as I got my 2* 19J6 SSMH succesfully up and running, and if/when i understand a tad more of how it works, then I won't hesitate to give the other tubes a go, or another project, we'll see.... lovely troubles for later


----------



## cravenz

mm..i notice some people use this setup for the k70x series and I was wondering how that fared or would the canamp or ef1 still be a better choice?


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_I've never stumbled upon that site of pete's, it's a great help 
	

	
	
		
		

		
		
	


	




</snip>_

 

You never read the very first post in this thread? The OP who created this amp in the first place? In that very first post, Pete links directly to his original Starving Student design section on his website.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *cravenz* 
_mm..i notice some people use this setup for the k70x series and I was wondering how that fared or would the canamp or ef1 still be a better choice?_

 

You'll have better luck in the amplifier section here on Head-Fi. Search for comparisons against the "Mini Millett" - that's user rds's version of the Starving Student that's sold at Whiplash Audio.


----------



## Llama16

Yeah I've read it. Tons of times 
	

	
	
		
		

		
		
	


	



 Also did I read the whole link. I just never noticed that the top link on the page from that link leads to his site.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Yeah I've read it. Tons of times 
	

	
	
		
		

		
		
	


	



 Also did I read the whole link. I just never noticed that the top link on the page from that link leads to his site._

 

OK - just making sure.
	

	
	
		
		

		
		
	


	







 Yes, Pete's website is a wealth of information - and that's an understatement, literally! I actually purchased the DVD from the guy on ebay that has Pete's website copied in its entirety - or most of it, anyway. Pete keeps adding to it all the time!.


----------



## Llama16

Yes I really admire you guys.
 It's because of my intrest in this and your knowledge that made me decide to go for civil engineering next year.

 I can't wait to actually learn on how everything works.


----------



## kuroguy

Civil = dirt --> sand --> solid state
 I don't follow your thinking, but good luck. The money's in the sciences and engineering (whatever type) is science.


----------



## Lou Erickson

I just got off the phone with Derek from Radio Electric Supply - they're the company behind the vacuumtubes.net web site - and he's confirmed (again!) at the 19j6's are out.

 He's never seen such a run on a $4 tube.

 He suggested the metal 12SR7 as a possible replacement, which is the alternate that Logistic found. He has them and they're still $1. The glass version is $4.


----------



## swedishhatfaction

I went and visited the guys from Radio Electric Supply in Lacrosse, FL to pick up some 12SR7's (I'm a cheap UF student who lives 30 minutes south of them and didn't want to pay for shipping 
	

	
	
		
		

		
		
	


	




) and they were cool enough to give me a quick tour of their warehouse. Seriously, those are some of the nicest guys I've ever met. They have tons of pallets of tubes still wrapped up in plastic with probably a bunch of 19J6's waiting patiently for stocking. They way they get their tubes is by buying up huge stockpiles when they find them and index, test, and restock them by hand.

 They have the coveted 19J6 in the warehouse -- but just don't quite know where yet...

 I'm using the 12SR7's for the SS as outlined in Logistic's post (http://www.head-fi.org/forums/f6/mil...ml#post5584511) but it is still in the works. I'll post pics when it's done.


----------



## Llama16

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_Civil = dirt --> sand --> solid state
 I don't follow your thinking, but good luck. The money's in the sciences and engineering (whatever type) is science._

 

It's the direction that has it all. Later on in your career/education you'll focus on two expertises.


----------



## cwboomer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_It's the direction that has it all. Later on in your career/education you'll focus on two expertises._

 

Maybe it's different in Belgium. I know when I worked at the Department here, the Civil program here "generally" was directed at those who built bridges, roadways, and public works types of projects, or that's the perception anyway. That might be why Kuroguy was saying Civil=dirt. Electrical, Electrical & Computer (ECE) or Chemical might be what would be an appropriately named Engineering discipline here that would be most applicable for this type of electronics field. Is that claryifying? or am I off base?

 I am not an engineer, by the way. I guess, I'm the opposite!! 
	

	
	
		
		

		
		
	


	




 switched to Art.


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## kuroguy

Exactly. Civil is about roads, grading, etc. I don't say that in a bad way. Whatever floats your boat. I've been a mechanical engineer for almost 20 years and can't imagine doing anything else. I've got friends that are civil engineers (and structural which is a specialized civil) and they're pretty cool too. Personally, I can't imagine being an EE or even a civil engineer, but I'm sure it would be cool for someone that is into that sort of thing. Fact is, I've got friends with Civil degrees doing mechanical, mechanical friends doing EE and others doing all other disciplines then their degrees. In all honesty, the important part is the engineering, regardless of the type. Good luck with it. It is the most rewarding of the things I've done in my entire life aside from growing my family. 

 ... and yes, civil = dirt (silicon) which implies solid state. Engineers (whatever type) are masters of adapting things to do other things. It's what we do. I hope you make it through the curriculum and become a member of the club. Its somewhat exclusive as clubs go, but the company is some of the most interesting you'll ever find. I suspect it is the most popular of careers around here as the degree tends to attract the tinkering type.


----------



## Rain100

I have a problem with my amp. I bought the kit from tomb and built it, but one channel comes through quite a bit louder than the other. What would be the easiest way to fix it?

 P.S. I really like this discussion on engineering, as I've applied to Iowa State for engineering next year.


----------



## Juaquin

Quote:


  Originally Posted by *swedishhatfaction* /img/forum/go_quote.gif 
_They have the coveted 19J6 in the warehouse -- but just don't quite know where yet..._

 

I hope you told them how many people are anxiously awaiting that find


----------



## swedishhatfaction

Quote:


  Originally Posted by *Rain100* /img/forum/go_quote.gif 
_P.S. I really like this discussion on engineering, as I've applied to Iowa State for engineering next year._

 

I'm a freshman in ECE and I'm bummed because I don't get to take any circuit-related classes until at least my sophomore year. Gen eds are lame 
	

	
	
		
		

		
		
	


	




.


----------



## tomb

Quote:


  Originally Posted by *Rain100* /img/forum/go_quote.gif 
_I have a problem with my amp. I bought the kit from tomb and built it, but one channel comes through quite a bit louder than the other. What would be the easiest way to fix it?

 P.S. I really like this discussion on engineering, as I've applied to Iowa State for engineering next year._

 

First, check the resistance of each input resistor to make sure something amiss didn't happen there. Second, if that doesn't reveal a tell-tale mis-match, then try swapping the tubes. If the louder channel follows the tubes, then there's a mis-match. Let us know what you find out and we'll go from there.


----------



## revolink24

Well, I'm having one last odd problem. Occasionally, out of one channel and one channel only, (always the same one) there is a short burst of noise which sounds to me like white noise. It is always a consistent duration, and I have isolated the amplifier as the source; I also swapped tubes to rule them out. Being not terribly knowledgeable about electronics (as the high school student I am), the only things I can think of are intermittent shorts, which I would think would cut the sound completely and be inconsistent, or a problem with one of the capacitors. Anyone else have ideas?

 I'm using the PCB build.

 EDIT: I just thought I would say this before the "It's a DAC problem" posts start. It's happened on my X-Fi, my integrated audio, and my 0404. I thought it must have been something in the D/A conversion, but apparently not.


----------



## Juaquin

I'd try reflowing all the joints in that channel. Easy and a good thing to rule out.


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Well, I'm having one last odd problem. Occasionally, out of one channel and one channel only, (always the same one) there is a short burst of noise which sounds to me like white noise. It is always a consistent duration, and I have isolated the amplifier as the source; I also swapped tubes to rule them out. Being not terribly knowledgeable about electronics (as the high school student I am), the only things I can think of are intermittent shorts, which I would think would cut the sound completely and be inconsistent, or a problem with one of the capacitors. Anyone else have ideas?

 I'm using the PCB build.

 EDIT: I just thought I would say this before the "It's a DAC problem" posts start. It's happened on my X-Fi, my integrated audio, and my 0404. I thought it must have been something in the D/A conversion, but apparently not._

 

 Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I'd try reflowing all the joints in that channel. Easy and a good thing to rule out._

 

Along that line, you might look into the ground connections with the signal wiring. I mention this a lot, but if you somehow get a bad or intermittent ground connection, it can cause a huge blast of static through your headphones. This may be hard to detect, too. Depending on which side of the PCB you solder the terminal block, the ground plane may be invisible to the solder joint. If the through-hole plating is missing (re-soldering, removing the part, etc.), then the ground connection won't be made. I've had this happen on a couple of prototype amps where I played around the the terminal block for various reasons. I ended up soldering a jumper on the bottom of the board to the middle pin of the terminal block.

 Also, be careful of your signal input wiring itself - if that's been removed/replaced a number of times, the wire end can get so compressed that the terminal block screw can't make a connection. All of this can cause that blast of static you describe.


----------



## Llama16

That's what I meant kuroguy 
	

	
	
		
		

		
		
	


	




 You're spot on.
 The engineering-part is most important, and here in belgium, being a civil engineer you can do it all, focussing on the engineering (with the spcializations you choose from there) and we don't focus on the 'civil' part that much, so it doesn't mean 'outdoors/bridges/..' around here. As you said, you have friends that are civil and do mechanical stuff. That's the sole reason I wanna go for civil engineering (here in belgium) because I don't want to narrow down ANYTHING yet. I like it all, as long as it envolves numbers. Though I'm hoping I can go for mechanical.


----------



## kuroguy

On topic: I've gotten that burst of white noise you describe on two of my sound systems. One with the SSMH and another with my 832PP amp. It is not (obviously, in my case) isolated to the SSMH. I suspect it is a buffer underflow and is generated in either the USB DAC (sorry to say) or possibly generated by the Linux boxes I have feeding the DACs. 

 Off Topic:Mechanical and Civil engineering (at least at my ABET accredited school) were almost identical for about the first 3 years and the remaining 1.5 years (before the comments start regarding the extra semester, engineering was 142 credits.) specialized in each particular discipline. In most (if not all) of the united states the PE license is non disciplinary and engineers are permitted to sign any work "in which they are competent". If you know what you are doing, feel free to sign it. it is up to the engineer to know their limitations. Good engineers do, bad ones don't.


----------



## tomb

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_<snip>
 Off Topic:Mechanical and Civil engineering (at least at my ABET accredited school) were almost identical for about the first 3 years and the remaining 1.5 years (before the comments start regarding the extra semester, engineering was 142 credits.) specialized in each particular discipline. In most (if not all) of the united states the PE license is non disciplinary and engineers are permitted to sign any work "in which they are competent". If you know what you are doing, feel free to sign it. it is up to the engineer to know their limitations. Good engineers do, bad ones don't._

 

OK ... I know you mean well, but this goes _against_ the Professional Engineering Code of Ethics, IMHO. The whole intent of the idea of "competence" is intended to mean that you never sign off on drawings in a discipline for which you have not been trained. From the Code of Ethics:
  Quote:


 Engineers shall perform services only in the areas of their competence. 
Engineers shall undertake assignments only when qualified by education or experience in the specific technical fields involved.

Engineers shall not affix their signatures to any plans or documents dealing with subject matter in which they lack competence, nor to any plan or document not prepared under their direction and control.
 
 

Note the emphasis on "qualified by education or experience." The Engineer who gains true discipline experience in an industry that's outside of his specific educational training is very rare. You don't graduate with a Mechanical Engineering degree, then get hired to do electrical engineering. There are instances where it happens, but I submit that experience of that sort is very cursory (on the level of a "designer/draftsman") and not founded in sound engineering principles, unless you've had the educational background, first. There are cases in small firms where some cook-book designs are stamped by a single engineer, but it's usually the firm's principal who takes on that responsibility - and it's almost always a risk.

 Also, it's true that many states (most?) make no distinction on discipline when awarding the PE registration or when stamping and signing drawings, _but the PE exam itself is most definitely discipline-specific_. It's up to you and your individual ethics as a Professional Engineer whether you stretch that loop hole and start stamping/signing drawings outside of your discipline.


----------



## akdmx

I'm really interested in building this amp. It sounds like a really fun first amp to build, and I might have to build it just for the fun factor. The thing is, I'm in to a pretty bright sound with high frequency clarity, and from what I've read, this amp is very warm and tubey. I'm currently between headphones, as I found the hd650's to be a little bit too bassy with not enough clarity and brightness in the higher frequencies. I tried to read through peoples signatures to see what they were using with their ssmh but didn't get much. Do you guys think that this is an amp that I could end up enjoying listening to, or is the sound seriously colored?


----------



## tomb

Quote:


  Originally Posted by *akdmx* /img/forum/go_quote.gif 
_I'm really interested in building this amp. It sounds like a really fun first amp to build, and I might have to build it just for the fun factor. The thing is, I'm in to a pretty bright sound with high frequency clarity, and from what I've read, this amp is very warm and tubey. I'm currently between headphones, as I found the hd650's to be a little bit too bassy with not enough clarity and brightness in the higher frequencies. I tried to read through peoples signatures to see what they were using with their ssmh but didn't get much. Do you guys think that this is an amp that I could end up enjoying listening to, or is the sound seriously colored?_

 

The idea that tubes are "colored" is unjustified. In most cases, it's the capacitors that are colored, not the tubes. There's also an entire camp that believes solid-state is the "colored" alternative, not tubes.
	

	
	
		
		

		
		
	


	




 That said, you will probably never hear a more realistic mid-range than you will with a tube or tube-sounding amp. With Senns IMHO, that combination is lovely. If you're looking for "bright", though, perhaps you should try some Grados. I have both and like each one for certain situations, but I find myself reaching for Grados more often. Some people hate 'em, some love 'em. That argument will go on as long as they keep making them, though.
	

	
	
		
		

		
		
	


	




 The SSMH has enough voltage swing and enough current bias to handle both impedances and type of headphones more than adequately.


----------



## kuroguy

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK ... I know you mean well, but this goes against the Professional Engineering Code of Ethics, IMHO. The whole intent of the idea of "competence" is intended to mean that you never sign off on drawings in a discipline for which you have not been trained. From the Code of Ethics:


 Note the emphasis on "qualified by education or experience." The Engineer who gains true discipline experience in an industry that's outside of his specific educational training is very rare. You don't graduate with a Mechanical Engineering degree, then get hired to do electrical engineering. There are instances where it happens, but I submit that experience of that sort is very cursory (on the level of a "designer/draftsman") and not founded in sound engineering principles, unless you've had the educational background, first. There are cases in small firms where some cook-book designs are stamped by a single engineer, but it's usually the firm's principal who takes on that responsibility - and it's almost always a risk.

 Also, it's true that many states (most?) make no distinction on discipline when awarding the PE registration or when stamping and signing drawings, but the PE exam itself is most definitely discipline-specific. It's up to you and your individual ethics as a Professional Engineer whether you stretch that loop hole and start stamping/signing drawings outside of your discipline._

 

The important word in the rule above is "or". My formal training is in mechanical engineering with a total of 6 credits (all that were offered) in Heating, Ventilation, and Air Conditioning (HVAC). my experience is extensively in HVAC, plumbing, and fire protection. There are exactly 0 credits in the ABET program for fire protection. My experience and knowledge in my field of expertise is vastly greater than what I was taught in college. In fact, most newly graduated engineers know very little about what I do. Engineering school does not teach what I do. It teaches engineers how to think and gives them a basis on which to grow their experience. I am more than competent to design or troubleshoot any HVAC system or problem that you can throw at me. I am exactly what the board of professional engineers considers "Competent" in HVAC design. 

 I have from my curriculum, 6 credits in circuits - exactly the same amount of credits in HVAC. I am by no means competent to sign electrical documents (with the exception that I have on several occasions sealed electrical that was incidental to mechanical such as replacing feeders to a piece of mechanical equipment but only when I was absolutely sure I was cprrect in the work. I would never seal a full electrical drawing. I'm sure I'm not competent to do that. 

 I've done forensic engineering in several cases where I was deemed competent to such an extent where the opposing side withdrew their claim against my clients. Once with respect to damage to a roof. I have exactly 0 credits in roofing. 

 I could go on making the exact same argument regarding fire pumps, fire sprinklers, plumbing (I've taken exactly 0 credits on waste and vent systems and domestic water systems). I am more competent to sign these types of designs than the vast majority of engineers and would easily stand muster should I ever be questioned by any board of engineers. 

 My point here is that the almost all of the experience all engineers (including, I'll guess, you) have is gained in the field, and making a blanket statement such as the one you did is unfair, to say the least.

 I greatly value your advice regarding tube amps. I would say you are competent to design the amps for which you have published designs here. I think I'm correct when I say that you know your limitations. That's the sign of a good engineer.

 As experienced engineers, we are all greater than the sum of just our degrees, and education is a life long thing.

 Respectfully,

 Kuroguy, P.E.


----------



## the_equalizer

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_You can get them all over -- Digikey and Mouser both carry them, as do Parts Connexion, AES, etc. You can also just use the terminal strips Pete used in the original in two rows for the same effect. This is point to point how it is really meant to be done. We'd just need a reproducible layout.
 <snip>_

 

Well maybe I could help here. I used Pete Millett's picture as the pattern to build my first 19J6 P2P "Starving Student".






 This is how mine came out:






 Notice how my terminal strips are aligned just like in Pete's original build. The same goes for R1/R7, C2/C4 and C3/C5.

 When a couple months later I converted that amp to use 12AU7's, all I had to do circuit-wise, besides updating a couple resistors with new value ones, was redo the connections to the tube socket pins; the rest of the amp stayed exactly the same.

 So basically I think Pete Millett's original P2P layout is quite good and maybe with minor improvements could be used to build any of the known variants.

  Quote:


  Originally Posted by *cravenz* /img/forum/go_quote.gif 
_mm..i notice some people use this setup for the k70x series and I was wondering how that fared or would the canamp or ef1 still be a better choice?_

 

Unfortunately I cannot compare since I don't own a canamp or an ef1. But I love the way my K701's sound with the MSSH, warm, punchy, and the amp has more than enough power to drive those hungry cans (more than my WA6 with stock tubes). And of course you can't beat the price of the SS !! 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## tomb

Quote:


  Originally Posted by *kuroguy* /img/forum/go_quote.gif 
_<snip>

 My point here is that the almost all of the experience all engineers (including, I'll guess, you) have is gained in the field, and making a blanket statement such as the one you did is unfair, to say the least.

 I greatly value your advice regarding tube amps. I would say you are competent to design the amps for which you have published designs here. I think I'm correct when I say that you know your limitations. That's the sign of a good engineer.

 As experienced engineers, we are all greater than the sum of just our degrees, and education is a life long thing.

 Respectfully,

 Kuroguy, P.E._

 

I don't think we're that far off in what we're each saying. I agree with exactly what you've stated (except the part about the roof 
	

	
	
		
		

		
			





 ). Other than that however, nothing you listed in your examples would be categorized as anything but mechanical engineering. When you take the mechanical exam for a professional engineer, it's not limited to just HVAC or just mechanical linkage analysis. Yes - experience is an important thing (perhaps more important than the education), but if we are truly talking major disciplines, the instances of competence-worthy experience outside of that _are quite rare_. 

 It sounds as if you're trying to make distinctions in what most would call sub-disciplines. We both agree that you and I would never sign electrical documents. Unfortunately, I've known an electrical engineer (PE) who would sign mechanical documents and civil engineers (also PE's) who would sign off on both mechanical and electrical documents. That's wrong and the implication of "or competent" doesn't apply in those cases, IMHO. It's a violation of the CoE. (I've also known architects who though they could do plumbing and fire protection, but that's a different subject.
	

	
	
		
		

		
		
	


	




 ) 

 Moreover, the context of the discussion was originally about civil engineering and whether that could be applied to other disciplines. This could be interpreted as signing off on mechanical or electrical documents, not whether he does site design, waste treatment, roads and highways, or structural design (all civil). Instead, I thought we should be more careful before implying to a prospective engineering student that he could carry that civil engineering degree into other disciplines based on being "competent." I believe you and I would both agree that there's more to it than that.

 Sorry if you thought I was being unfair. I've just seen a lot of violations in my career and I'm a bit sensitive to that. We work hard to gain professional registration and it's part of the CoE to maintain that trust in competency.


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Well maybe I could help here. I used Pete Millett's picture as the pattern to build my first 19J6 P2P "Starving Student".

 </snip>_

 

Looks good to me!


----------



## Llama16

Tomb and Kuroguy, thanks for your insights. I saw there were points on which I was wrong and got corrected by both of your examples.
 I know that I won't make my choice of specialization before I ended those 3 years of 'standard' education. Hopefully I'll be able to narrow them down once I have to start studying through the night on the different subjects.

 At the moment I think I'll probably go for mechanical or electrical, but as I said I still need to see what I think of the rest because everything that explains how 'things' work fascinates me.


----------



## swedishhatfaction

Please forgive the neophyte question here but I am building my amp into a wooden wine box and just so to make better use of the container's space and decrease external clutter, I was planning on putting the power supply PCB into the same space as the guts of the amp. Will this introduce EMI or have any effect on the sound quality? Why or why not?


----------



## tomb

Quote:


  Originally Posted by *swedishhatfaction* /img/forum/go_quote.gif 
_Please forgive the neophyte question here but I am building my amp into a wooden wine box and just so to make better use of the container's space and decrease external clutter, I was planning on putting the power supply PCB into the same space as the guts of the amp. Will this introduce EMI or have any effect on the sound quality? Why or why not?_

 

I'm not quite sure what you're talking about here. The SSMH does not come with a separate power supply PCB and the recommended Cisco power supply doesn't need one. If you are talking something like a TREAD - where you would use the separate PCB with a AC walwart or a transformer - no, you won't have any issue with the PCB itself. Generally speaking, the issue is if you are building an amp where the power supply is made up of a separate, unshielded transformer. If you locate that transformer within the same box as the rest of the amp circuit, that can sometimes cause noise issues. Usually, you need to enclose the transformer in a ferrous box to obtain any useful shielding - or use something that's supposed to be inherently interference-resistant like a toroid.


----------



## swedishhatfaction

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not quite sure what you're talking about here. The SSMH does not come with a separate power supply PCB and the recommended Cisco power supply doesn't need one. If you are talking something like a TREAD - where you would use the separate PCB with a AC walwart or a transformer - no, you won't have any issue with the PCB itself. Generally speaking, the issue is if you are building an amp where the power supply is made up of a separate, unshielded transformer. If you locate that transformer within the same box as the rest of the amp circuit, that can sometimes cause noise issues. Usually, you need to enclose the transformer in a ferrous box to obtain any useful shielding - or use something that's supposed to be inherently interference-resistant like a toroid._

 

Sorry, let me try to clarify. What I was saying is that since I didn't want the external clutter of a wall wart ( mine is the Mean Well GS18A48-P1J, I was going to put it inside the same space as the amp components. The amp is not using a PCB; it will still be built point-to-point. To get everything to fit properly, I would need to remove the plastic casing on the wall wart and just place the PCB in the wine box; it is a box designed for only one bottle so length and width are sparse. Since the transformer appears to be exposed, I imagine there could be some noise. As far as shielding goes, could I get away with simply placing a sheet of iron between the amp parts and the wall wart or does it have to be enclosed on all sides?


----------



## tomb

Quote:


  Originally Posted by *swedishhatfaction* /img/forum/go_quote.gif 
_Sorry, let me try to clarify. What I was saying is that since I didn't want the external clutter of a wall wart ( mine is the Mean Well GS18A48-P1J, I was going to put it inside the same space as the amp components. The amp is not using a PCB; it will still be built point-to-point. To get everything to fit properly, I would need to remove the plastic casing on the wall wart and just place the PCB in the wine box; it is a box designed for only one bottle so length and width are sparse. Since the transformer appears to be exposed, I imagine there could be some noise. As far as shielding goes, could I get away with simply placing a sheet of iron between the amp parts and the wall wart or does it have to be enclosed on all sides?_

 

Sorry, but I wouldn't recommend taking apart a walwart power supply - at all. There are a lot of safety issues and code violations that are broken by doing that. And yes, you'd get both transformer hum and probably a lot of high-frequency interference as well. High frequency interference is why there's a choke on the end of the DC cord. Further, it looks like your particular power supply has cooling holes, so you'd have a heat issue inside as well. Not a good idea, IMHO.


----------



## swedishhatfaction

Wow... removing that tiny bit of bulk definitely seems like more trouble than it's worth at this point. Thanks for the input, tomb. I will take that advice under heavy consideration.


----------



## Juaquin

I was going to suggest the σ24/σ25 or a transformer/TREAD but the max output voltage of the LM317 (if I'm reading the datasheet right) is 37V and I don't believe they make the LM78XX series in anything larger than 24V. Would the SSMH run on 37V? What would be the preferred method for a linearly regulated 48V supply?


----------



## cobaltmute

LM317HV is good for 60V max.


----------



## tomb

Honestly, I can't find anywhere a maximum voltage is listed for the LM317 - probably just the voltage limit for any piece of silicon, whatever that is. Cobaltmute says 60V, but I would've thought it was higher than that - well over 100V, at least - but I'm just guessing.

 What most mistake for the upper voltage limit on the LM317 (or other regulators) is the maximum voltage differential - that's 37-40V. However, that can mean the voltage coming in is 60V while the regulated output could be down to 20V. There's no issue with using one on an SSMH. I wouldn't do it with the Cisco power supply, though.


----------



## Juaquin

Ah, thanks for the clarification (no wonder I couldn't find anything specifically stating a max output voltage). In that case a transformer and a TREAD might make a good solution.


----------



## TimJo

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_
 What most mistake for the upper voltage limit on the LM317 (or other regulators) is the maximum voltage differential - that's 37-40V. 
_

 

I believe you are right Tom. There are designs for high voltage power supplies using a LM317 as a regulation device, but they are designed to protect the regulator from seeing more than this limit. Morgan Jones has examples of this in his book on amplifier design.


----------



## cobaltmute

The input/output diff allowed for the LM317 and LM317L is 40V but the LM317HV allows 60V. You can see the spec on the datasheet on under the absolute maximum Input/Output differential.

 As tomb says, you can pump alot more voltage into the regulator if you using it floating. to quote the datasheet:

  Quote:


 Besides replacing fixed regulators, the LM117HV is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e. do not short the output to ground. 
 

Tangent's YJPS uses the LM317 in "floating" mode. To my understanding the Tread wouldn't because the adjustment pin is related to ground.


----------



## tomb

Quote:


  Originally Posted by *cobaltmute* /img/forum/go_quote.gif 
_The input/output diff allowed for the LM317 and LM317L is 40V but the LM317HV allows 60V. You can see the spec on the datasheet on under the absolute maximum Input/Output differential.

 As tomb says, you can pump alot more voltage into the regulator if you using it floating. to quote the datasheet:



 Tangent's YJPS uses the LM317 in "floating" mode. To my understanding the Tread wouldn't because the adjustment pin is related to ground._

 

Ah - so that's where the 60V comes from - good info!


----------



## luvdunhill

I have some boards drawn up for a HV regulator that uses a LM317HV and a few people around here have them The board supports a few different versions, including a temperature compensated version, a MOSFET pass, and a Darlington BJT version. It's pretty much good to whatever you want it to be, and I've gone as high as 500V. If there's a wider use for the board, I'd offer them up for general sale if there was a convenient way to do so. It's a very neat way to do a HV supply, and performs amazingly well.


----------



## Juaquin

You can use Seeed Studio's Fusion pcb service. You design it and upload it, they run off a certain number of boards and offer them for sale. I haven't used it myself but the results seem good.


----------



## Lou Erickson

Yay! Kit ordered!

 Now I need to get my act together and get the parts arranged for the other variant's tubes that I bought. 
	

	
	
		
		

		
			





 Maybe later tonight.


----------



## cwboomer

how'd you get to order early!

 I guess I should have checked earlier, but I got one, and that's all that matters.


----------



## Lou Erickson

Midnight, Eastern time is 9:00PM Pacific time. 
	

	
	
		
		

		
		
	


	




 My worry was that I'd still be at work... Tom's reassured us that they won't run out tonight, though, and I believe him.

 Now I'm looking up how to make decals to label the case neatly. 'Cause my handwriting isn't gonna cut it.


----------



## cwboomer

eastern time! news at 11!


----------



## CaptHowie

Ah, the shipping's a killer. Looks like I won't have enough to get one.


----------



## tomb

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_Ah, the shipping's a killer. Looks like I won't have enough to get one. 
	

	
	
		
		

		
		
	


	


_

 

Sorry about that, but I can't ship an entire kit without insurance (I pay for the insurance, though.). Priority Mail International is the minimum service where USPS allows insurance.


----------



## Llama16

Wiii!
 I have ordered the kit (and some other necessary parts for ptp build).
 I'm so excited hehe.

 Tomb, if my order passes your eyes and ANY questions pop up when you read my (in messy english written) commentary, plz don't hesitate to ask, even if it delays my order for days. I'd rather wait and be sure I don't miss a thing then spend extras on shipping costs for 1/2 parts.

 Great service, you guys are the men!


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Wiii!
 I have ordered the kit (and some other necessary parts for ptp build).
 I'm so excited hehe.

 Tomb, if my order passes your eyes and ANY questions pop up when you read my (in messy english written) commentary, plz don't hesitate to ask, even if it delays my order for days. I'd rather wait and be sure I don't miss a thing then spend extras on shipping costs for 1/2 parts.

 Great service, you guys are the men!_

 

Thanks for your note on the invoice. I believe I can meet your needs. If not, I'll let you know.


----------



## Llama16

Thanks alot Tom.
 I understand if you can't, I already thankfull for your effort.
 let me know if some extra costs pop up, I won't mind paying another 2 dollars for the other sockets.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Thanks alot Tom.
 I understand if you can't, I already thankfull for your effort.
 let me know if some extra costs pop up, I won't mind paying another 2 dollars for the other sockets._

 

No - I have what you need - it's not an issue. I'd appreciate you taking a look at the note I gave you, though - there's a slight question I have about something else.


----------



## Llama16

Just saw it 
	

	
	
		
		

		
		
	


	



 Replied.

 yet again, thanks. I can't express my gratitude for your help enough.


----------



## cwboomer

Tom,

 I was wondering if you were aware of the broken links (maybe it's just me??) on the starving student portion of DIY Audio's build? Just wondering (among all your other busy things!!! 
	

	
	
		
		

		
		
	


	




) if it was maybe an easy fix.

 Dan


----------



## Llama16

yeah he knows, it's that way for long.
 I asked as well, and I understand his response completely: lack of time.
 We never have enough of it


----------



## cwboomer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_yeah he knows, it's that way for long.
 I asked as well, and I understand his response completely: lack of time.
 We never have enough of it 
	

	
	
		
		

		
			



_

 

It's not a biggy. I'm sure there are more important things!!! Just didn't see a post about it. Those kits must be gone already. 
	

	
	
		
		

		
		
	


	




 Can't wait to see everyone's shiny black cases! I know that mine is going to get me through the workday.

 D


----------



## tomb

Quote:


  Originally Posted by *cwboomer* /img/forum/go_quote.gif 
_It's not a biggy. I'm sure there are more important things!!! Just didn't see a post about it. Those kits must be gone already. 
	

	
	
		
		

		
		
	


	




 Can't wait to see everyone's shiny black cases! I know that mine is going to get me through the workday.

 D_

 

Actually, no. I had hoped to have the first ones shipped out today, but it will be tomorrow before shipments begin. It took me a little longer than I thought to test the tubes. I'm not sure, but we may have enough left over to consider another run of kits. We'll see ...

 I keep intending to finish the website, but just can't seem to get to it. I'll try again after this round of kits ship. Meanwhile, of course - everything else you need to know is found in the SSMH Build Thread here on Head-Fi - link in my signature below.


----------



## Lou Erickson

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, no. I had hoped to have the first ones shipped out today, but it will be tomorrow before shipments begin._

 

I think he meant, "All the kits are sold", but I could be wrong.

 According to Beezar's front page, there's a few left, though.

  Quote:


 It took me a little longer than I thought to test the tubes. I'm not sure, but we may have enough left over to consider another run of kits. We'll see ... 
 

That'd be cool, as I think kits really make it a lot easier for more people to try things. I would guess that there's a lot of people who'd feel okay building a kit - particularly one with a nice case like this one - that might not be comfortable trying to order a confusing morass of parts and figuring out what to put it in.

 It's a wonderful thing you've done, and I'm happy to have mine coming! Hopefully I'll be able to put it together the Friday after Thanksgiving.


----------



## CaptHowie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure, but we may have enough left over to consider another run of kits. We'll see ..._

 

I hope so. I've been waiting around this thread for months, yet when the kits come out I have no money on me. 
	

	
	
		
		

		
		
	


	




 Anyway, hopefully the people who did get the kits make some nice Starving Students. Can't wait to see some mods!


----------



## the_equalizer

So has any of the experienced headphone gurus here A/B's our beloved MSSH against other amps? I've searched head-fi but I've been unable to find a full fledged review of the "Starving Student" hybrid. I'm particularly interested as to how it fares against comparable amps such as the Little Dot I+

 cheers!


----------



## Juaquin

It's a fairly simple amp but has big sound. I'm not qualified to review it against other amps but I know that it has been reviewed around here with respect to the other Millets, and I'm sure a few other amps as well.


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_So has any of the experienced headphone gurus here A/B's our beloved MSSH against other amps? I've searched head-fi but I've been unable to find a full fledged review of the "Starving Student" hybrid. I'm particularly interested as to how it fares against comparable amps such as the Little Dot I+

 cheers!_

 

Please ... not in this thread. This is the DIY support thread, not a headphone amp comparison thread. I'd rather not get into whose design is better. There are not enough of us in DIY design circles to start shooting bullets at each other. Some may do it in other DIY threads, but I'd rather not do it here.

 The Starving Student has been reviewed extensively. Simply search the Head-Fi amplifier section for "Mini Millett" (rds's version sold at Whiplash Audio) or "Starving Student." There are a number of comparisons with the Little Dot (not sure which one, though).


----------



## Lou Erickson

I'm not swift enough to be able to calculate what the LED resistor size needs to be if you only wanted one LED...

 Tube lights make little sense with metal tubes, and I'd like a power lamp instead. I can move it around, as I'm doing a point-to-point build, but I don't know the voltages there to order parts.

 Can anyone give me any direction?


----------



## Juaquin

V=IR
 In this case V=48V and I should be about 15-20mA depending on the LED used and how bright you want it. Keep in mind that a lot of power will be put across the resistor due to the high voltage so choose a good power rating on the resistor (P=(I^2)*R=IV). For instance, if you shoot for 15mA you need about 3k (3.3k will work), and the power rating would need to be 1W or higher.


----------



## cobaltmute

Tweaks

 Vs is your source voltage (48B in this case). I would target I = 3mA or around there. 15mA for LED current will be very bright. The brightness in part would be determined by the luminousity rating. Some LEDs can be *extremely* bright at very low current


----------



## Juaquin

Yeah, like I said, depends on the LED and how bright you want it. For a power indicator you may want a lower current since it's not supposed to light anything (like the tube lights).

 If you have a pack of resistors of different values (like the radioshack one, or the ones available from eBay) you can try different I_led values (although with lower voltages since those resistors are only rated for 1/4W).


----------



## cobaltmute

I made the mistake of using one of these in my GrubDAC build

VAOL-3LWY4 VCC Standard LED

 Luminous intensity = 2500mcd @ 20ma.

 At 3ma it gives nice room illumination to a dark room

 I used these on my Grub+Carrie build:

TLHP4400 Vishay Semiconductors Standard LED

 Only 1mcd at 10ma. 

 Definitely not as bright.

 The advantage of being dimmer in the first place is that you can always add a resistor in parallel to brighten it up. Harder to go the other way around


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Please ... not in this thread. This is the DIY support thread, not a headphone amp comparison thread. I'd rather not get into whose design is better. There are not enough of us in DIY design circles to start shooting bullets at each other. Some may do it in other DIY threads, but I'd rather not do it here.

 The Starving Student has been reviewed extensively. Simply search the Head-Fi amplifier section for "Mini Millett" (rds's version sold at Whiplash Audio) or "Starving Student." There are a number of comparisons with the Little Dot (not sure which one, though)._

 


 Got it. It was not my intention to "get into whose design is better". Just a description of how it sounds compared to other amps... I'll have to look at the search again then... 
	

	
	
		
		

		
		
	


	




 thanks !


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Got it. It was not my intention to "get into whose design is better". Just a description of how it sounds compared to other amps... I'll have to look at the search again then... 
	

	
	
		
		

		
		
	


	




 thanks !_

 

No problem! And it certainly wasn't meant to single you out. It's just that there are a few individuals who will take advantage of such a conversation.


----------



## tomb

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I'm not swift enough to be able to calculate what the LED resistor size needs to be if you only wanted one LED...

 Tube lights make little sense with metal tubes, and I'd like a power lamp instead. I can move it around, as I'm doing a point-to-point build, but I don't know the voltages there to order parts.

 Can anyone give me any direction?_

 

To actually work through an example, it might go like this:

 Let's assume 3ma as the other guys have suggested - V=IR,
 In this case, V=48VDC, and we'll let I = 0.003A.
 Using a bit of algebra, we have R = V/I, or R = 48/0.003 = 16,000 Ohms.

 * So, you'd need a 16K resistor. *

 We're not done yet, though - we have to check the power rating on the resistor and see if it's enough. For that, we use the equation P = I^2 * R.

 For our 16K resistor and 0.003A, we have P = (0.003^2) * 16000 = 0.144W.
 That's more than a typical RN55 1/8W resistor. Plus, most of us use a 100% safety factor when sizing resistors for power. After all, you're talking about the potential of a small fire if the resistor gets too hot. So, 2 x 0.144 = 0.288. That's more than a 1/4W, so a 1/2W resistor would be truly safe. Since the military rating on Vishay-Dale resistors is 1/2 their commercial rating, an RN60 would be sufficient (1/4W mil-spec, 1/2W commercial).

 What may be more important, though, is that you select a panel LED that's _diffuse_ rather than clear. Even at low levels, it's unsettling to have a panel LED shine a focused beam into your eye - better that it's diffused.


----------



## Lou Erickson

That's one of the fabulous things about this place - not only are people willing to help out and answer simple questions like that, but they explain them so well.

 Thanks, guys! That was perfect!


----------



## kuroguy

Tomb has the basics correct, and since the supply voltage is much bigger than the forward voltage drop of the LED the error introduced by his simplified calculation is insignificant. To be absolutely correct the voltage you would use would be the voltage drop you would like to see, in this case, (V supply - V LED) 48-1.5=46.5

 As you can see, the error introduced in tomb's calculation is on the order of 3%; clearly insignificant, but if V supply was something like 5 volts, the error would be more like 30% which is significant.


----------



## getllamasfast

Hey guys,

 Will either the Electro-Harmonix 12AU7s or the JJ 12AU7s work with the_equalizer's modified version?


----------



## getllamasfast

edit: sorry about the double post


----------



## tomb

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Hey guys,

 Will either the Electro-Harmonix 12AU7s or the JJ 12AU7s work with the_equalizer's modified version?_

 

Equalizer-Dsavitsk's 12AU7 mod should work with any 12AU7 and it only requires changing the resistor to the MOSFET - 390K ohms, I think? (Help me out, guys.)**

 There are a couple of tradeoffs with all of them (including the 19J6!). Logistics's uses some very inexpensive tubes in keeping with the Starving Student tradition, but they only use a single triode (I think - please correct me if I'm wrong, equalizer!). That might make them more sensitive to matching instead of averaging out like parallel triodes. Probably a trivial point, though.

 Dsavitsk had proposed using the 12AU7 and its double triodes in parallel like the 19J6. Equalizer actually built one. While 12AU7's are easily among the most common tubes (even new manufacture!), they tend to be more expensive - probably a $10 range is a more realistic average, but that's just my own SWAG - some can be in the $hundreds if you want a true audiophile 12AU7 (Mullard, Telefunken, Amperex, etc.). There are some that can be found quite cheap - like the 5963's.

 ** Edited per Lou Erickson's and Equalizer's posts. Sorry for getting it mixed up.


----------



## Lou Erickson

Dsavitsk mentioned a single resistor change, but the_equalizer posted it first. Here's the post.

 The post says the change is to change R2/R8 to 390 Kohms, and a different wiring for the socket. (That makes sense, as it's got a different number of pins.)

 I decided not to build this, as the 12AU7's are a bit more expensive, although not hideously.

 I'm going to build a p2p of Logistic's 12SR7 based solution, cause they're cheap. 
	

	
	
		
		

		
		
	


	




 It had a couple more changes, see the post for detals.

 Both of these may also need bigger heat sinks, or may run hotter, too.

 I don't know the differences between the internals of the different tubes, or how closely they may have to be matched. One reason I wanted the cheaper tube was so I wouldn't feel bad about buying extras. I also liked the metal tube, and am considering taking them to work, where they might benefit from being sturdy.

 I ordered some turrets and a turret tool to try and see if I could lay out a turret board like Dsavitsk suggested. Might be fun. Not sure if I'll just push components around on the board or if I'll lay it out in Visio or something yet.


----------



## getllamasfast

Sorry if my question was a little confusing but what I really wanted to know is if all 12AU7 tubes are swappable with eachother; if they all have the same circuit requirements.

 So, if I were to build the SSMH with the modifications that the_equalizer posted, I should be able to use any 12AU7 tube?

 Thanks for the awesome replies guys


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The 12AU7's work on a different circuit modification - that of Dsavitsk's and it only requires changing the resistor to the MOSFET - 340 ohms, I think? (Help me out, guys.)

 The equalizer's mods work with a different tube set. Perhaps he can elaborate with more details. There are tradeoffs with all of them (including the 19J6!). Equalizer's uses some very inexpensive tubes in keeping with the Starving Student tradition, but they only use a single triode (I think - please correct me if I'm wrong, equalizer!). That might make them more sensitive to matching instead of averaging out like parallel triodes. Probably a trivial point, though.

 Dsavitsk has proposed using the 12AU7 and its double triodes in parallel like the 19J6. While 12AU7's are easily among the most common tubes (even new manufacture!), they tend to be more expensive - probably a $10 range is a more realistic average, but that's just my own SWAG - some can be in the $hundreds if you want a true audiophile 12AU7 (Mullard, Telefunken, Amperex, etc.). There are some that can be found quite cheap - like the 5963's._

 

 Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Sorry if my question was a little confusing but what I really wanted to know is if all 12AU7 tubes are swappable with eachother; if they all have the same circuit requirements.

 So, if I were to build the SSMH with the modifications that the_equalizer posted, I should be able to use any 12AU7 tube?

 Thanks for the awesome replies guys 
	

	
	
		
		

		
		
	


	


_

 

Sorry for the delay in replying. I don't have access to the forum from the office. 

 getllamasfast: indeed they are intercheangable and, as a matter of fact, I built my 12AU7 version using new, current production JJ 12AU7 tubes. I also tested with 12AX7 (current production Russian Mullard) and 12AT7 (old GE ones) and they work great too; giving you different levels of gain.

 TomB: actually the modified version I tested and built, based on Dsavitsk's hints, uses the two sections of the triode in parallel, just like the 19J6 version. I wanted to use the 12AU7 precisely because you can get some old ones dirt cheap, some new ones at around $15 USD or some 'boutique' NOS ones at $$$$. So while the current production 12A_7 tubes are not as cheap as the 19J6 was some years ago, at least their price is consistent and they're *very* easy to find.

 Oh! After reading the posts again I see what happened... you were thinking about Logistic's 12SR7 version. 
	

	
	
		
		

		
		
	


	




 That one indeed uses NOS tubes (beautiful octal ones 
	

	
	
		
		

		
		
	


	




 ) that are still VERY cheap. As I remember it those are radio tubes that have a triode and two diodes in the same bulb; so there's no way to use the triodes in parallel. 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Sorry for the delay in replying. I don't have access to the forum from the office. 

 getllamasfast: indeed they are intercheangable and, as a matter of fact, I built my 12AU7 version using new, current production JJ 12AU7 tubes. I also tested with 12AX7 (current production Russian Mullard) and 12AT7 (old GE ones) and they work great too; giving you different levels of gain.

 TomB: actually the modified version I tested and built, based on Dsavitsk's hints, uses the two sections of the triode in parallel, just like the 19J6 version. I wanted to use the 12AU7 precisely because you can get some old ones dirt cheap, some new ones at around $15 USD or some 'boutique' NOS ones at $$$$. So while the current production 12A_7 tubes are not as cheap as the 19J6 was some years ago, at least their price is consistent and they're *very* easy to find.

 Oh! After reading the posts again I see what happened... you were thinking about Logistic's 12SR7 version. 
	

	
	
		
		

		
		
	


	




 That one indeed uses NOS tubes (beautiful octal ones 
	

	
	
		
		

		
		
	


	




 ) that are still VERY cheap. As I remember it those are radio tubes that have a triode and two diodes in the same bulb; so there's no way to use the triodes in parallel. 
	

	
	
		
		

		
		
	


	




 cheers!_

 

Yep - sorry about that. I'll call it the Equalizer-Dsavitsk mod.
	

	
	
		
		

		
		
	


	




 My apologies to Logistics.
	

	
	
		
		

		
		
	


	




 Thanks for correcting me!!

 On a different note, you guys please be patient with me on the kits. Shipping goes slow during the week. I only have a few hours each night. I've sent out 8 so far, but it may go into Saturday before I get them all shipped.


----------



## Lou Erickson

I'm sure we're all excited to get kits, Tom, but we understand. They go out when they go out, and we'll be happy when they arrive.

 It gives us things to look forward to. 
	

	
	
		
		

		
		
	


	




 I didn't realize the 12SR7 version only used one of the parts of the tube, and that could make matching more important. Is it possible to measure tubes to match them without a tube tester? Those are not as common as they once were - I think the guys at Radio Shack would look at me funny if I showed up with tubes and asked to use the tester.

 (Might be fun to go down there and ask, though. Wonder if the high school kid behind the counter has ever SEEN a tube before?)


----------



## dsavitsk

Matching tubes, particularly in this circuit, is really not that important. But, if you must, the easiest way to do it is to use the circuit itself. Drop a tube in and measure the voltage on the cathode and the plate. Then, find another one with matching voltages -- you have a match.

 For the earlier discussion about using 12AU7's, or any tube with a 12.6V heater, you simply need to bias the mosfet's gate differently. The gate needs to be ~4V or 5V higher in voltage than the voltage you want on the heater. In the original, we use an even divider off of B+ to put the gate at a little less than 24V, which in turn leaves the heater at about 19V. So, for the 12AU7, you want the gate to be at about 17V give or take. So, you just need to adjust the resistor divider.

 Several additional things to think about -- 

 1. Once the heater voltage is set, the heaters will draw whatever current they want. A 12AU7 will draw a reasonable current, but put a tube with a high heater current in the circuit and it can cause problems (namely heat and too high a draw on the power supply).

 2. The mosfet is dropping an additional 5V which means an additional 3/4 a watt. Not a ton, but enough that you might need to beef up your heatsinks.

 3. Adjusting the Rp and Rk (the resistors connected directly to the _P_late and _K_athode) would be prudent. To do this, you'll need to get out the datasheet for your chosen tube and draw a load line. This is easy to do, there are tons of web pages with basic instructions, and it will be a good learning experience.

 -d


----------



## Juaquin

The information found on this forum astounds me. I'm not quite finished with school but I never would have learned most of this in the curriculum (especially the tubes, obviously).


----------



## tomb

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_I'm sure we're all excited to get kits, Tom, but we understand. They go out when they go out, and we'll be happy when they arrive.

 It gives us things to look forward to. 
	

	
	
		
		

		
		
	


	


_

 

Yours has shipped, by the way.
	

	
	
		
		

		
		
	


	




 Quote:


 
 I didn't realize the 12SR7 version only used one of the parts of the tube, and that could make matching more important. Is it possible to measure tubes to match them without a tube tester? Those are not as common as they once were - I think the guys at Radio Shack would look at me funny if I showed up with tubes and asked to use the tester.

 (Might be fun to go down there and ask, though. Wonder if the high school kid behind the counter has ever SEEN a tube before?) 
 

Here's the cutting edge these days for tube testers (and perhaps the only consistent source for a tube tester):
tube tester, great deals on Business Industrial, Electronics on eBay!

 There are a couple of companies that make some modern, computerized/digital tube testers. I don't have the links handy, but they run into the $thousands of dollars, unfortunately.

 This guy is an outstanding resource on tube testers and I've learned a lot from studying his website:
Tales From The Tone Lounge; The Idiot's Guide To TubeTesters!

 Just an FYI, but I use the Jackson 658A, sometimes the 648S - he talks about both in the link just above. Of course, there's a bunch of info on Hickoks, B&K's, etc.

 Also, Jim Cross at Vacuum Tubes, Inc., Vacuum Tubes, Electron Tube, Radio Tubes, Audio Tubes, Industrial Tubes, Guitar Tubes, Capacitors, Tube Sockets, Tube Testers is the absolute authority on the Jackson 648 (he re-wrote the manual), another very popular tester. He's quite a resource on testers and tubes as well and is a prominent member of the Tube Collectors Association. The current president of that organization, Ludwell Sibley, has the authoritative book on "Tube Lore."


----------



## the_equalizer

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Matching tubes, particularly in this circuit, is really not that important. But, if you must, the easiest way to do it is to use the circuit itself. Drop a tube in and measure the voltage on the cathode and the plate. Then, find another one with matching voltages -- you have a match.

 For the earlier discussion about using 12AU7's, or any tube with a 12.6V heater, you simply need to bias the mosfet's gate differently. The gate needs to be ~4V or 5V higher in voltage than the voltage you want on the heater. In the original, we use an even divider off of B+ to put the gate at a little less than 24V, which in turn leaves the heater at about 19V. So, for the 12AU7, you want the gate to be at about 17V give or take. So, you just need to adjust the resistor divider.

 Several additional things to think about -- 

 1. Once the heater voltage is set, the heaters will draw whatever current they want. A 12AU7 will draw a reasonable current, but put a tube with a high heater current in the circuit and it can cause problems (namely heat and too high a draw on the power supply).

 2. The mosfet is dropping an additional 5V which means an additional 3/4 a watt. Not a ton, but enough that you might need to beef up your heatsinks.

 3. Adjusting the Rp and Rk (the resistors connected directly to the Plate and Kathode) would be prudent. To do this, you'll need to get out the datasheet for your chosen tube and draw a load line. This is easy to do, there are tons of web pages with basic instructions, and it will be a good learning experience.

 -d_

 

1.- Indeed that was another reason for choosing the 12AU7: it's heater is spec'd to draw the same amount of current as the 19J6 heater. A friend of mine was experimenting with the 6J6 (a 6 volt heater version of the 19J6) and tried dropping the extra voltage with a resistor, but it's just so much extra power because the 6J6 heater draws *450 mA*.

 2.- In my build, with bigger heatsinks, the MOSFETs get so hot you cannot hold your hand on the heatsink for more than a couple of seconds.

 3.- I really wanted to ask you about this Dsavitsk, since I've racked my brain (only in my free time, though) trying to do this but I've been unable to. How can you draw a load line for a 12AU7 using a 48 V B+ when the curves for the tube end with a 50 V B+ ??? I easily did that for the 12AE6 version that I 'designed' on paper (using a 30 volt HP printer supply), because the 12AE6 tube was designed to work at low B+ (I think it's rated for 27V max) and so it's curves include voltages of 50 and lower in 5 volt decrements.. but for a 12AU7 ? In fact I mentioned in my 12AE6 version post that if only I could find a way to choose proper values for Rk and Rp for the 12AU7, a version using the 30 volt HP supply could work too.

 cheers!


----------



## dsavitsk

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_3.- How can you draw a load line for a 12AU7 using a 48 V B+ when the curves for the tube end with a 50 V B+ ???_

 

Well, you should be able to make a reasonable approximation from the 12au7 curves. Even without detailed curves, you can make an educated guess -- for instance, pick an operating current, say 1mA. Then, try to split the voltage between the load and the tube -- thus, 24V/1mA leads to a 24K load. If you look at the curves, ~-2V grid bias is the half way point on this line, so that puts the cathode resistor at 2V/1mA = 2K.

 You may need to adjust from there, but that gets you pretty close. You can also look at the 12U7 curves which are pretty similar at low voltages (12U7 is to the 12AU7 what the 6GM8 is to the 6DJ8).

 Oh, remember that since the tube sides are || that you need to double the current scale on the plate curves.


----------



## randomasdf

Is there a link to a step by step or general overview of the equalizer's mod? I keep seeing it referenced, but not the actual mod itself.


----------



## Lou Erickson

Only the post in this thread. Use the web site and change a few resistors and wire the socket differently.

 It's easy to miss things in this big thread, though.


----------



## bmwpowere36m3

Having built two Millet "starving student" amps, I'll be converting the old one (PnP) to run on SR7GT tubes like Logistic did. I just ordered a couple tubes and sockets off eBay, should be easy enough with a few resistor changes.


----------



## the_equalizer

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Well, you should be able to make a reasonable approximation from the 12au7 curves. Even without detailed curves, you can make an educated guess -- for instance, pick an operating current, say 1mA. Then, try to split the voltage between the load and the tube -- thus, 24V/1mA leads to a 24K load. If you look at the curves, ~-2V grid bias is the half way point on this line, so that puts the cathode resistor at 2V/1mA = 2K.

 You may need to adjust from there, but that gets you pretty close. You can also look at the 12U7 curves which are pretty similar at low voltages (12U7 is to the 12AU7 what the 6GM8 is to the 6DJ8).

 Oh, remember that since the tube sides are || that you need to double the current scale on the plate curves._

 

That post contains so many pieces of useful advise and wisdom that I don't even know where to start. 

 Indeed I printed a nice big plate curve graph for the 12AU7 and I was able to succesfully draw a load line with your indications. The fragment about splitting the voltage between the load and the tube answered a question I had had for a long time about how to set an initial value for Rp.

 Thank you very very much for sharing this knowledge!

 cheers!


----------



## Lou Erickson

That keeps happening around here. Some really smart guys who are happy to share. I'm glad dsavitsk mentioned how to meter tubes in the circuit. It's making it possible for me to stop looking at all the shiny tube testers on eBay... 
	

	
	
		
		

		
			





 I'm probably going to have to buy a new DMM, and that'll use up my tools budget for a bit, at least if I break down and get a good one. I thought I bought a good one last time and it only lasted ten years. Now Sears/Craftsman is giving me a useless run-around trying to figure out if it's covered under warranty. Not happy with them today.

 I am, however, happy with TomB! I got a box from him, full of parts. Beautiful packaging job, and the custom case and board are both very pretty. I wish I could start in on it right now, but that would be silly. It'll probably be next Friday (weekend after Thanksgiving!) before I can build this pretty amp.

 It is smaller than I thought it would be!


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## nkk

So...two stupid questions:

 Tomb: Is there a power supply with this kit? I am thinking not, but wanted to check before I bought one and paid for expedited shipping (this amp is my thanksgiving break project).

 So, any good sources for an acceptable power supply? Amazon.com sources preferred, because I have free 2 day shipping with my amazon prime trial (a rip off IMHO, but for free trial for 3 months, I took it).

 Thanks
 Nkk

 EDIT: There is also no consequence for not wiring in the tube LED, right? If I just want to skip it, I can? I looked for a circuit schematic to make sure it was in parallel and not a vital connection (do not know why you would do it otherwise), but I cannot find one that has them included.


----------



## tomb

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_So...two stupid questions:

 Tomb: Is there a power supply with this kit? I am thinking not, but wanted to check before I bought one and paid for expedited shipping (this amp is my thanksgiving break project).

 So, any good sources for an acceptable power supply? Amazon.com sources preferred, because I have free 2 day shipping with my amazon prime trial (a rip off IMHO, but for free trial for 3 months, I took it).

 Thanks
 Nkk

 EDIT: There is also no consequence for not wiring in the tube LED, right? If I just want to skip it, I can? I looked for a circuit schematic to make sure it was in parallel and not a vital connection (do not know why you would do it otherwise), but I cannot find one that has them included._

 

Yes, each kit included a power supply.

 No, there is no consequence for not wiring in the tube LEDs.

 Yes - the questions are moot because the kits are sold out.


----------



## nkk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, each kit included a power supply.

 No, there is no consequence for not wiring in the tube LEDs.

 Yes - the questions are moot because the kits are sold out._

 

You just saved my life. And no, they are not moot, as I bought a kit and only now thought of the power supply. I am the annoying person who took the chance to ask you about a kit without the case and PCB. I bought a kit anyway 
	

	
	
		
		

		
		
	


	




 I figured I will make another one later, and maybe sell it or give it to my sister depending on how quickly she descends into audiophilia. Really any excuse to make more than one will do.

 -Nkk


----------



## getllamasfast

I have a two questions before I buy my parts. 

 In the 12AU7 version of this amp, R2/R8 ≈ 390Kohms, right? Does it have to be exactly 390Kohms? I'm ordering R2 as a 1.5Kohm and R8 as a 590Kohm which equates to ≈ 393.3Kohms, so is that okay?

 My second question is: Are the heatsinks in this picture are good enough for the extra load the 12AU7 puts on the mosfets?
http://imageups.com/files/131/DSC_1944.jpg

 Thanks.


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## kuroguy

Get within 10%; anything between 350 and 430 ohms should work.


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## tomb

Just an FYI, but all kits have shipped except for two and those will go out on Monday.

 It looks like there are enough tubes to do another run of 25 kits. However, I've sent a note to Hammond asking for a slight mod on the case design. We may try to do something special for this last run.


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## revolink24

If it involves a gain switch, I might just kick myself


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## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_If it involves a gain switch, I might just kick myself 
	

	
	
		
		

		
		
	


	


_

 

No - I just thought we might try Stackpole resistors and Muse Fine Gold caps on the output.

 There's nothing to stop you from adding a gain switch already, though - simply wire a DPDT switch with your resistor choices into the input resistor pads.


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_I have a two questions before I buy my parts. 

 In the 12AU7 version of this amp, R2/R8 ≈ 390Kohms, right? Does it have to be exactly 390Kohms? I'm ordering R2 as a 1.5Kohm and R8 as a 590Kohm which equates to ≈ 393.3Kohms, so is that okay?

 My second question is: Are the heatsinks in this picture are good enough for the extra load the 12AU7 puts on the mosfets?
http://imageups.com/files/131/DSC_1944.jpg

 Thanks. 
	

	
	
		
		

		
		
	


	


_

 

CAUTION!! My writing may have caused this confusion... when writing R2/R8 I did *not mean the ratio* of R2 and R8; rather it was shorthand for meaning *R2 and R8*. Thus you should be ordering two 390Kohms resistors, one for the R2 position and another for the R8 position.

 Now, each individual resistor may indeed be 10% around 390Kohms without a hitch.

 cheers !


----------



## swedishhatfaction

So these are some pictures of my Millett Starving Student Hybrid amp. It's the second amp I've ever built (the first being the Cmoy). The outside looks alright but as you can see the inside is an embarrassing mess. I really need to work on my cable management skills. It works but there is a significant amount of buzzing and hissing in it. It is also very susceptible to stray EMR (on my desk, I can even hear the electrical pulses my keyboard gives off when I type). 
	

	
	
		
		

		
		
	


	

















 I'm thinking that I screwed the nuts too tightly on the MOSFETs and it could have ripped through the thermal pads -- making the back of the FETs touch the heatsinks which aren't grounded. If replacing the thermal pads doesn't fix the issue, I may just redo the internals on perf board to make troubleshooting a bit easier and make it look a great deal cleaner. A larger case may make things easier to work with too.

 Something strange I've noticed is when I touch the right heatsink and the case at the same time, the buzz decreases considerably; touching anywhere on the case (which also isn't grounded) by itself or attempting to do the same with the left heatsink, however, the buzz increases. Also, the noise increases when I move my hand closer to the blue 1uF film caps -- it feels like I'm playing a theramin or something! I don't have any idea what any of that implies. 
	

	
	
		
		

		
		
	


	




 I could definitely use some feedback from a pro.


----------



## dsavitsk

Quote:


  Originally Posted by *swedishhatfaction* /img/forum/go_quote.gif 
_It is also very susceptible to stray EMR (on my desk, I can even hear the electrical pulses my keyboard gives off when I type)._

 

You need to ground pin 1 of the 12SR7.

 As you say, you might want to clean up some wiring, too


----------



## swedishhatfaction

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_You need to ground pin 1 of the 12SR7._

 

Duh! I should have read Logistic's post more thoroughly. Good things happened when I grounded those pins and some of the noise went away. Thanks Dsavitsk.

 I have another question though. Is there any particular reason pin 4 isn't used?


----------



## dsavitsk

Quote:


  Originally Posted by *swedishhatfaction* /img/forum/go_quote.gif 
_I have another question though. Is there any particular reason pin 4 isn't used?_

 

You should probably ground that, too. Ground 5 as well, if you didn't already.


----------



## the_equalizer

Quote:


  Originally Posted by *swedishhatfaction* /img/forum/go_quote.gif 
_Duh! I should have read Logistic's post more thoroughly. Good things happened when I grounded those pins and some of the noise went away. Thanks Dsavitsk.

 I have another question though. Is there any particular reason pin 4 isn't used?_

 

The 12SR7 contains a triode and two diodes in the same bulb. Pins 4 and 5 are the anodes (plates) of the diodes. Since the diodes are not used (only the triode is used in the MSSH circuit) it's better to connect these pins to ground, just as Dsavitsk mentioned.

 You can see the tube's datasheet here.

 cheers !


----------



## lybbert

i just received my kit in the mail and cant wait to start putting it together. Thank you Tomb for all your effort to make this amp so easily accessible.


----------



## tomb

Quote:


  Originally Posted by *lybbert* /img/forum/go_quote.gif 
_i just received my kit in the mail and cant wait to start putting it together. Thank you Tomb for all your effort to make this amp so easily accessible._

 

Glad to hear that some of them are arriving before Thanskgiving! Let us know how the building goes!


----------



## nkk

I have finished the assembly, but my amp does not work. I have checked, and the power and auido are getting to the PCB. The multimeter says there is about 100 kohm between the input signal and output, although I do not know exactly what to make of that given that there is a tube involved. Is there anything else to check before I have to take it apart?

 -NKk

 EDIT: Ok, so I took it apart, and have looked at the bottom closely. Not cold joints or solder bridges as far as I can see. What would be the most likely culprit? Other than my own stupidity, of course.


----------



## Lou Erickson

Mine has arrived - along with the missing part! - and I'm resisting the urge to start putting it together RIGHT NOW. I may stop resisting and assemble it as soon as I get some homework done. 
	

	
	
		
		

		
		
	


	




 I very much hope to have an amp by the end of the long weekend.


----------



## lybbert

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Glad to hear that some of them are arriving before Thanskgiving! Let us know how the building goes! 
	

	
	
		
		

		
		
	


	


_

 

my plan is to build the amp and pack for moving in december. ill be posting pictures when it gets done


----------



## the_equalizer

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_I have finished the assembly, but my amp does not work. I have checked, and the power and auido are getting to the PCB. The multimeter says there is about 100 kohm between the input signal and output, although I do not know exactly what to make of that given that there is a tube involved. Is there anything else to check before I have to take it apart?

 -NKk

 EDIT: Ok, so I took it apart, and have looked at the bottom closely. Not cold joints or solder bridges as far as I can see. What would be the most likely culprit? Other than my own stupidity, of course. 
	

	
	
		
		

		
		
	


	


_

 

Difficult to say... do you hear any sound at all (hum, maybe)? Do the tubes light up ? what are the voltages on the MOSFET pins ? How do you know that the audio is getting to the PCB ?

  Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_Mine has arrived - along with the missing part! - and I'm resisting the urge to start putting it together RIGHT NOW. I may stop resisting and assemble it as soon as I get some homework done. 
	

	
	
		
		

		
		
	


	




 I very much hope to have an amp by the end of the long weekend._

 

The Beezar.com PCB kit is remarkably easy to build, it took me two evenings to get mine ready and, believe me, I'm a *slow* builder (mostly because I triple check everything as I go); most people could get it done in a couple of hours, I bet.

 cheers!


----------



## Lou Erickson

nkk: Can you post a good, clear picture of your work? It's amazing what people have been able to diagnose with pictures in this long thread.

 the_equalizer: I suspect I'll be on the slow side too. I'm way out of practice and was going to build a CMoy to practice on, but seem to be missing a part... I think the SS goes first. 
	

	
	
		
		

		
		
	


	




 TomB has been fantastic to work with, and I am confident that he and Dsavitsk have taken good care of us. I've been looking forward to putting it together since I ordered it.


----------



## tomb

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_I have finished the assembly, but my amp does not work. I have checked, and the power and auido are getting to the PCB. The multimeter says there is about 100 kohm between the input signal and output, although I do not know exactly what to make of that given that there is a tube involved. Is there anything else to check before I have to take it apart?

 -NKk

 EDIT: Ok, so I took it apart, and have looked at the bottom closely. Not cold joints or solder bridges as far as I can see. What would be the most likely culprit? Other than my own stupidity, of course. 
	

	
	
		
		

		
		
	


	


_

 

Lou is correct. It's impossible to tell anything from a "does not work" symptom. So, we need clear pics of the top and bottom.

 One thing I might suggest is to measure between a ground point and the positive connection on the power socket or the B+ position on the terminal block - see if you get zero resistance. This is just a guess, but there may be a short (check the washers on the standoff first and see if they're touching a pad or the LED resistor). The Cisco power supply has a very quick (and silent!) circuit breaker. If there's a short, when you turn on the switch it'll just give the appearance that nothing works - no other symptom. The Cisco will reset immediately when disconnected (again, silently!). So if you measure the power supply by itself, it will still appear as if nothing is wrong.

 Alternately, casing up an amp and finding a short is a common issue in DIY, period. That's another way to cause a short if you went light on heat shrink and have some wiring binding or contacting the case in some way.


----------



## PianistOne111

Hi. I just finished one. It seems that most of the music I listen to is quite loud enough at very low levels on the potentiometer, I'd say about 30 degrees from minimum (using HD600). The problem is that at these levels, the left channel is significantly louder than the right. Would changing R16 and R17 to 100KOhm solve this problem?


----------



## tomb

Quote:


  Originally Posted by *PianistOne111* /img/forum/go_quote.gif 
_Hi. I just finished one. It seems that most of the music I listen to is quite loud enough at very low levels on the potentiometer, I'd say about 30 degrees from minimum (using HD600). The problem is that at these levels, the left channel is significantly louder than the right. Would changing R16 and R17 to 100KOhm solve this problem?_

 

Yes. I believe I supplied 100K resistors in addition to the 50K, too.


----------



## PianistOne111

Done. 
	

	
	
		
		

		
		
	


	




 It was a pain to get the 50K's out, clear the holes, and out the 100K's in though.


----------



## Rhashime

I just wanted to thank Tom for such an awesome little kit! Just finished mine and everything went reasonably smoothly. I did hit a couple small bumps that didn't take long to sort out though: shorted led resistor and didn't install the low gain resistors at first (I feel your pain PianistOne111). Sounds awesome and it isn't even broke in yet.


----------



## Lou Erickson

Where the heck am I going to get epoxy on Thanksgiving?


----------



## tomb

Quote:


  Originally Posted by *Lou Erickson* /img/forum/go_quote.gif 
_Where the heck am I going to get epoxy on Thanksgiving? 
	

	
	
		
		

		
		
	


	


_

 

Got a Kroger's in California? It's quite possible they have little 5-min epoxy dual tube packs in the automotive or hardware section. If not, the largest grocery chain you have open or the local drugstore may have it. I prefer 15 minute, but then I'm usually doing more than 1 or 2 pair when I do them.
	

	
	
		
		

		
		
	


	




 EDIT: Of course, you should have no problem tomorrow.


----------



## Lou Erickson

It was mostly a rhetorical question. It's something I ran into that I didn't prepare for. Tomorrow will be no trouble. Or I could just have skipped the tube lights; I'm dubious about how great an idea that is anyway, but I'm going to give it a try for this kit because I can.

 If I don't break the sockets drilling them out. I do wish I had a drill press. I'll just have to be careful and see how it goes. Worst case, I'll order more. I need to get some tubes for an eXStata anyway.


----------



## PianistOne111

I didn't bother with tube LED's (although I did clear the sockets). Actually I think it looks quite gaudy. To each his own.


----------



## tomb

If that's gaudy, I plead guilty.


----------



## Llama16

I'm also wonndering if I'd take the chance to install them. I ordered green as well and they'd look great here allthough I'd give the tube's own color a chance as well. Luckily I got some of those sockets left from a previous order


----------



## tomb

Here's blue as well:




 (an early production prototype)


----------



## the_equalizer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_I'm also wonndering if I'd take the chance to install them. I ordered green as well and they'd look great here allthough I'd give the tube's own color a chance as well. Luckily I got some of those sockets left from a previous order 
	

	
	
		
		

		
		
	


	


_

 

To each his own, indeed! I chose not to install the LED's, the 19J6 tubes I got glow beautifully on their own. The 12AU7's, on the other hand, could certainly use a nice yellow or red LED... 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## nkk

To those who graciously offered to help when I post pics, here you go:

Starving Student PCB Troubleshooting pictures by nkhosla - Photobucket

 That is the link to the album, as I do not want to post 30 some pics here. Also, please excuse the photos. On top of my poor photo taking skills, the lighting just did nothing to help. 

 Thanks,
 Nkk


----------



## smrtby123

Here is my Beezar SSH kit fresh from this morn. Sounds amazing so far, definitely a step up from my hacked together Cmoy. Kudos to TomB, Dsavitsk and Pete Millett for such a great little amp.


----------



## smrtby123

Here is my Beezar SSH kit fresh from this morn. Sounds amazing so far, definitely a step up from my hacked together Cmoy. Kudos to TomB, Dsavitsk and Pete Millett for such a great little amp.


----------



## Juaquin

My SSMH has the Ratheon tubes that don't have an exposed heater so you don't get that nice glow. The LEDs look great - pictures really don't show how good they look. Maybe some dim orange LEDs to simulate the heater glow?


----------



## nkk

So, quick update, I got it to work, but I have a loud buzzing in the left channel only. I am checking everything again, but any ideas of what may cause it? I am going with a short to ground, but we will see.

 -nkk

 EDIT: Fixed. One of my soldering joints to the RCA jack had broken.


----------



## nkk

Ok, I think I got it. Where would one buy more of the Berquist pads? I think one of mine is shorting. I just put the upper part of the box back on the PCB, and it is not even powering on again. That would make sense if the transistor were shorted to ground, right?

 -Nkk


----------



## tomb

Quote:


  Originally Posted by *smrtby123* /img/forum/go_quote.gif 
_Here is my Beezar SSH kit fresh from this morn. Sounds amazing so far, definitely a step up from my hacked together Cmoy. Kudos to TomB, Dsavitsk and Pete Millett for such a great little amp._

 

Thanks so much!

 Your amp looks great - love those LED's. I sure don't want to be discouraging, but I'm forced to tell you that the endplates/bezels are in the wrong order. The metal plate goes on outside of the bezel. The endplates are supposed to fit on top of the bezel recesses and on top of the bezel screw holes.


----------



## tomb

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_Ok, I think I got it. Where would one buy more of the Berquist pads? I think one of mine is shorting. I just put the upper part of the box back on the PCB, and it is not even powering on again. That would make sense if the transistor were shorted to ground, right?

 -Nkk_

 

Before we jump to conclusions, let's back up and ask some questions, first.
	

	
	
		
		

		
		
	


	




 1. Can you see the Bergquist pad and are you certain that it's cut? Unless you've torqued the MOSFET down so hard that the tab has cut into both the Bergquist pad and the case anodizing, conceivably the case anodizing is enough to insulate the MOSFET.

 2. Did you install the shoulder washer correctly - in the right position and in the correct orientation? I finally finished some more of the SSMH website. Refer to the heat sink mounting diagram here:
SSMH Heat Sink

 Confirm that your assembly is in the same orientation and sequence - especially the shoulder washer. If the shoulder washer is not correctly insulating the MOSFET tab, then it could very well cause a short. This is because the mounting hole is most definitely NOT anodized. However, the shoulder washer provides all the needed insulation from this hole - if installed correctly.

 3. Is it possible that the standoff hardware is contacting the LED resistor and/or pad? If you did not install the lock washer on the PCB side of the standoff kit, it's possible that the hex standoff would turn when assembled to the lid. This might allow a hex corner to contact the resistor lead and/or pad.

 In short, there may be a number of issues going on besides the Bergquist pad. It's not automatic that the MOSFET would short without the Bergquist pad - the case anodizing must be damaged as well.


----------



## Fishline

I've (almost) finished building my second p2p SSMH. The problem is that I can measure 48v at the power jack, but as soon as I turn on the power switch, it drops to basically 0v. Can someone give me some hint on diagnosis?


----------



## Llama16

wrong wiring if the power jack perhaps? Just guessing


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I've (almost) finished building my second p2p SSMH. The problem is that I can measure 48v at the power jack, but as soon as I turn on the power switch, it drops to basically 0v. Can someone give me some hint on diagnosis?_

 

This is classic and has come up at least three times in the last week in this thread and others. You have a short. The Cisco power supply has a VERY good circuit breaker and will instantly cut off the power supply in face of a short. So, it appears everything is fine until you throw the switch - exposing the Cisco to whatever short exists in your circuit - and the voltage instantly drops to zero.

 Go over your build carefully - check for exposed wire, lack of heat shrink, parts that can be binding against the case, and/or a MOSFET that's not isolated.


----------



## Juaquin

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The Cisco power supply has a VERY good circuit breaker and will instantly cut off the power supply in face of a short._

 

Just can't say this enough


----------



## smrtby123

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Thanks so much!

 Your amp looks great - love those LED's. I sure don't want to be discouraging, but I'm forced to tell you that the endplates/bezels are in the wrong order. The metal plate goes on outside of the bezel. The endplates are supposed to fit on top of the bezel recesses and on top of the bezel screw holes.
	

	
	
		
		

		
		
	


	


_

 

Haha wow. That makes a lot more sense than the way I hacked them on there. I think I was so excited that I actually got it to work I didn't even notice.


----------



## nkk

Tomb, you are truly amazing. Thank you. I now have a working SSMH. 
	

	
	
		
		

		
		
	


	




 Although, I get a really loud crack/pop at power up if my phones are plugged in. It also happens sometimes at power down. Is this normal? 

 -Nkk


----------



## tomb

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_Tomb, you are truly amazing. Thank you. I now have a working SSMH. 
	

	
	
		
		

		
		
	


	




 Although, I get a really loud crack/pop at power up if my phones are plugged in. It also happens sometimes at power down. Is this normal? 

 -Nkk_

 

Oops! Never have your headphones plugged in before the amp is already turned on! The Starving Student's music output is referenced at 19VDC. That means "zero" sound is actually 19VDC. (The actual sine wave of music is able to vary from +48VDC down to zero, but 19VDC is the center.) This works because we have the output coupling caps at C3 and C5, which block the DC voltage. However, capacitors take time to charge - perhaps 10 to 20 seconds. While this is happening when you turn the amp on, that 19VDC is gradually reducing down to zero on the headphone jack.

 If you have your headphones connected during those first few seconds, they're exposed to all of that voltage.

 Turn-off is similar, but not as bad. It depends more on how slow the capacitors discharge.

 Best advice to protect your headphones? Keep them unplugged unless the amp is up and running.


----------



## tomb

Quote:


  Originally Posted by *smrtby123* /img/forum/go_quote.gif 
_Haha wow. That makes a lot more sense than the way I hacked them on there. I think I was so excited that I actually got it to work I didn't even notice._

 

's OK - you're not the first one to do it. Looks great, anyway!!


----------



## CaptHowie

tomb, is there still chance of more kits before Christmas?

 -CaptHowie


----------



## nkk

That is what I figured was happening. That would be really helpful as a sort of post build note in your step by step build thread. 

 Anyway, thanks for all the help. I am thinking of building the second PCB I have, although I do not have the time now. Maybe spring break.

 Thanks again,
 Nkk


----------



## tomb

Quote:


  Originally Posted by *CaptHowie* /img/forum/go_quote.gif 
_tomb, is there still chance of more kits before Christmas?

 -CaptHowie_

 

I'm sorry - it will be after the new year. There's just too little time for Hammond to produce the cases again and after talking with them, I felt it was best to wait instead of rushing everything and ruining everyone's holiday.


----------



## CaptHowie

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sorry - it will be after the new year. There's just too little time for Hammond to produce the cases again and after talking with them, I felt it was best to wait instead of rushing everything and ruining everyone's holiday._

 

Understood. Better decision I guess. It's only a few more weeks. 
	

	
	
		
		

		
		
	


	




 -CaptHowie


----------



## GeckoSlayer

I apologize for not wanting to read through all 284 pages of this thread, but a question to someone who has followed this thread, can you use alternate tubes? Namely ones off this page? (And preferably the cheaper ones off that page..?)

 Thanks.


----------



## Fishline

Apparently I can't just paste the flikr link into the image tag... See corrected post on the next page.


----------



## n_maher

Quote:


  Originally Posted by *GeckoSlayer* /img/forum/go_quote.gif 
_I apologize for not wanting to read through all 284 pages of this thread, but a question to someone who has followed this thread, can you use alternate tubes? Namely ones off this page? (And preferably the cheaper ones off that page..?)

 Thanks._

 

Start by reading this.
http://www.head-fi.org/forums/6024902-post3873.html

 Fishline, I'm not seeing a picture?


----------



## Fishline

OK. I've gone through what I have several times and couldn't see anything wrong, so I'm putting a pic of the build and hope some of you will be able to tell me what's wrong with my brain. (Been having a cold lately so progress is s-l-o-w and head couldn't think too straight.)

 I've desoldered the output part for now, and I still get the short as soon as I turn the power on (power drop from 48v down to 0v). Would very much appreciate any pointer.


----------



## n_maher

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I've desoldered the output part for now, and I still get the short as soon as I turn the power on (power drop from 48v down to 0v). Would very much appreciate any pointer._

 

What do you get when you measure resistance between the MOSFET tab and your case? While I can see that you have used isolation pads I've found that those pads tear quite easily (on rough hole edges for example) and it takes next to nothing to create a shorted condition.


----------



## Fishline

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_What do you get when you measure resistance between the MOSFET tab and your case? While I can see that you have used isolation pads I've found that those pads tear quite easily (on rough hole edges for example) and it takes next to nothing to create a shorted condition._

 

I get 0F for both. Sorry for the idiotic question: Does that mean they are shorting?


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I get 0F for both. Sorry for the idiotic question: Does that mean they are shorting?_

 

Hmm ... maybe Nate's distracted, so I'll chime in -

 0.0 resistance = short.

 BTW, it's really hard to tell from your pic, but even if the pads are not torn - if you haven't used an insulating shoulder washer, they'll short for sure.


----------



## n_maher

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I get 0F for both. Sorry for the idiotic question: Does that mean they are shorting?_

 

It depends on your meter and what 0F means, it sounds weird to me. So the real question is what do you get when you touch the two probes of your meter together? I would have expected that if you had a direct short you'd still measure some resistance, the value of which could vary depending on your meter. Example: with the probes shorted together my Fluke 179 reads .1ohm.


----------



## Forte

Quote:


  Originally Posted by *GeckoSlayer* /img/forum/go_quote.gif 
_I apologize for not wanting to read through all 284 pages of this thread, but a question to someone who has followed this thread, can you use alternate tubes? Namely ones off this page? (And preferably the cheaper ones off that page..?)

 Thanks._

 

Try searching for 12SR7 in this thread, there is a version you can build using those. They are available from the store you linked, just not on that page, but it may be cheaper to order from somewhere like Vacuum Tubes Radio Tubes - 5,000 different tubes in stock - Over 10 million tubes! even after shipping.


----------



## Fishline

This is the meter I have:
http://www.radioshack.com/graphics/u...0813_PM_EN.pdf
 Doesn't say what 0F means when measuring resistance.

 I tried the open/close test on the meter. If I test the mosfet tab and the case, I get "open". If I test the mosfet tab and the star ground, I get "close". Does that mean much?


----------



## Fishline

I did have the insulating washers between the nuts and the mosfet tabs.

 The meter starts at 0F, and stay that way when I test between the case and the mosfet tabs. However, I get 0.2ohm when I test between the mosfet tabs and the star ground. Does that mean anything?

 [edit: Apologies for the near double-post. I keep getting the message about can't post within 15 seconds or something like that, and can never be sure if the post made it...]


----------



## n_maher

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_If I test the mosfet tab and the star ground, I get "close". Does that mean much?_

 

That would be bad, yes, but would also be very strange unless your star ground is not connected to the chassis.


----------



## Fishline

You guys are lifesavers! I loosen both mosfets and cleaned the mounting holes, remounted them carefully, and now no short!

 With the output still disconnected, I'm gettting 21.3v on pin 3 of the tube sockets (tubes not installed). Does that sound right? The schematic says 19v there...


----------



## n_maher

I don't think you can get an accurate reading without the tube in there.


----------



## Fishline

It's all done! It played music! Hallelujah!

 Having succeeded with my el cheapo build in a mooncake box and mostly "stock" (and cheap) parts, I tried to make this one as nice as I can manage. The enclosure is actually really tight, and I'm lucky that everything actually fits. There's however, no room for bypass caps. The "upgrades" are really nicer jacks and nichicon kw 470uF output caps and panasonic fc 680uF power caps. The heatsink is an old CPU heatsink that a friend donated.

 I did get the 3-piece set of stepped drill bits from amazon, which made drilling all the holes rather easy. I don't have a drill press, but did inherit a vise, which was really handy for holding the case while I drill the holes.

 Thanks to all the folks for helping with my really newbie questions and wonderful suggestions and recommendations!


----------



## tomb

Looks great! Those are some wild looking heat sinks.


----------



## Fishline

I have a couple of friends with more PCs than people in their household, so I figured they must have some old CPU heatsinks that I can salvage. I got a few, but this is the only one that will fit on the case I used.


----------



## nkk

Mine works, but has a hum. The hum disappears whenever I touch the case, so I am guessing it is ground related. I am not sure how to fix this, as it is not a short or anything. It just seems to want much more grounding resource. Where would I even start?

 thanks,
 Nkk


----------



## Juaquin

Check all your ground solder connections. One is probably a cold joint or bad in some way, especially since it has a large ground plane that takes a lot of heat to get warm and make a good connection.


----------



## Fishline

I second that. I had hum in my first build as well that turned out to be bad solder joints to ground.


----------



## Llama16

Fishline, that's a beautiful build. It looks so tiny 
	

	
	
		
		

		
			




 I love the heatsinks.

 Can't wait to begin on my kit when it arrives, i'm planning on using the case that comes with it, do some inside measurements and then try to go for selfmade woodwork with some badass heatsinks. I've got a carpenter in my street whose daughter is friends of my sis. If I'm lucky i'll try and ask if he wants to get me started/use his tools.


----------



## tomb

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_Mine works, but has a hum. The hum disappears whenever I touch the case, so I am guessing it is ground related. I am not sure how to fix this, as it is not a short or anything. It just seems to want much more grounding resource. Where would I even start?

 thanks,
 Nkk_

 

Based on the prototypes, the PCB may not be big enough to provide a sufficient ground plane by itself. I'd carefully check to make certain that you have the case scraped and full contact is being made between the RCA jacks and the case, and the center standoff and the case. Make sure you use two wires, each connected to the respective RCA jack - for signal ground. You probably don't want to take the shortcut of using a single ground wire simultaneously connected to both jacks for this amp.


----------



## nkk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Based on the prototypes, the PCB may not be big enough to provide a sufficient ground plane by itself. I'd carefully check to make certain that you have the case scraped and full contact is being made between the RCA jacks and the case, and the center standoff and the case. Make sure you use two wires, each connected to the respective RCA jack - for signal ground. You probably don't want to take the shortcut of using a single ground wire simultaneously connected to both jacks for this amp._

 

Will do. I though I was pretty meticulous about that, but it seems perhaps I was mistaken.

 Thanks,
 Nkk


----------



## tomb

Quote:


  Originally Posted by *nkk* /img/forum/go_quote.gif 
_Will do. I though I was pretty meticulous about that, but it seems perhaps I was mistaken.

 Thanks,
 Nkk_

 

Well, it's only a guess after all.
	

	
	
		
		

		
		
	


	




 You might check the pot, too. Did you solder that ground wire to the pot body? That can give hum as well, but it's usually in reverse - hum when you touch, none if you don't.


----------



## choka

I have finished building the amp, and was testing it with my computer as source. There are two things I noticed:
 1. Tonally it is very dark with my k702, compared to other amps I am using. All the voices (midrange) I hear, it is almost like they are singing with a slightly lower frequency. I don't know if this is what you call the "tube sound". I have the Bravo tube amp as well but that one doesn't act like this. However, this works pretty nicely with my darth beyer. Almost feels like the bass is covering up all the details so I don't care anymore.
 2. There seems to be a shielding problem. You know how your computer speakers sometimes make a sequence of low beeping noise before/during your mobile phone rings? I can occassionally hear it on this amp. Is there anything that can be done about this?


----------



## tomb

Quote:


  Originally Posted by *choka* /img/forum/go_quote.gif 
_I have finished building the amp, and was testing it with my computer as source. There are two things I noticed:
 1. Tonally it is very dark with my k702, compared to other amps I am using. All the voices (midrange) I hear, it is almost like they are singing with a slightly lower frequency. I don't know if this is what you call the "tube sound". I have the Bravo tube amp as well but that one doesn't act like this. However, this works pretty nicely with my darth beyer. Almost feels like the bass is covering up all the details so I don't care anymore._

 

This is a perfect symptom of not burning it in enough. (Yes, I know that's a controversial topic - please read the SSMH PCB Build thread!) Both the Nichicon KW's and the Wima's will have a prominent "bass fog" the first few hours that you run the amp. Let it run for a day or so and it will open up enough to surprise you.

  Quote:


 2. There seems to be a shielding problem. You know how your computer speakers sometimes make a sequence of low beeping noise before/during your mobile phone rings? I can occassionally hear it on this amp. Is there anything that can be done about this? 
 

Keep it away from the mobile phone.
	

	
	
		
		

		
		
	


	




 (Translated: "What shielding?")


----------



## choka

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Keep it away from the mobile phone.
	

	
	
		
		

		
		
	


	




 (Translated: "What shielding?")_

 


 Actually my phone is at least 15 feet away from me most of the time and it still happens.

 I've always thought metal cases would be enough of a shield for low energy waves. I am probably wrong.


----------



## Juaquin

Depends on how the case is connected (or not) to the circuit and earth ground. FWIW pretty much all of my audio equipment gets hosed by my iPhone within a couple feet, which extends to 5+ feet when it's actively transmitting.


----------



## choka

the case should be well grounded, i checked with a meter before. let me make sure again tonight.
 i understand it if the phone is right next to it, but i almost always never put the phone close to me.


----------



## tomb

Quote:


  Originally Posted by *choka* /img/forum/go_quote.gif 
_the case should be well grounded, i checked with a meter before. let me make sure again tonight.
 i understand it if the phone is right next to it, but i almost always never put the phone close to me._

 

Unlike magnetic shielding, with RF or microwave shielding, it's possible that additional grounding may help. It may also be in your cables - you can try different pairs that may be shielded. You might try some reflective material in the general vicinity of the amp - try putting up a metal screen between your amp and where you think the source of the radiation might be. Do you have a microwave tower in the general vicinity? Could be that's causing it. Anyway, conductive metal of some sort is best. Aluminum foil may work in a pinch or at least for testing. I'd try the shielded cables, first though - you might even try wrapping the aluminum foil around them.


----------



## choka

i doubt it is the cable because i was using the same cable with another amp. i actually moved the original amp out of the way and put the ssmh in that location and connected with the same cables.

 anyway i'll try some more grounding and other stuff and see what works.


----------



## tomb

Looks like there are enough PCB's for 35 more kits. After that, no more PCB's. There will be some tubes and a few power supplies left over after that. I'm ordering the next batch of Hammond cases this week, so maybe the middle of January for more kits?

 I had also talked about changing up the capacitors a bit for some larger boutique ones, but it's not as many kits as I was hoping for. Best to leave the high-dollar boutique stuff to the P2P versions, I think.

 Also, I'll repeat this when the listing goes on sale, but tube matching will have to be first come first serve, with the following priorities until they run out:
 1. Matched construction, matched transconductance, matched brand *,
 2. Matched construction, matched transconductance, and
 3. Matched construction.

 So, the earliest orders will get #1, later ones #2, and the last kits to be ordered will get #3 until that's no longer possible or the kits are all sold, whichever comes first. I'll give a more specific notice after the holidays - as I did before.

 This will be it for the Starving Student PCB unless more tubes show up in volume.
	

	
	
		
		

		
			






 * Remember, every 19J6 was constructed by RCA anyway.


----------



## the_equalizer

Quote:


  Originally Posted by *choka* /img/forum/go_quote.gif 
_i doubt it is the cable because i was using the same cable with another amp. i actually moved the original amp out of the way and put the ssmh in that location and connected with the same cables.

 anyway i'll try some more grounding and other stuff and see what works._

 

Remember that NOT EVERYTHING in the circuit is within the metal case. In the case of this amp the tubes are unshielded and thus sensitive to picking up noise. 

 cheers!


----------



## coriolis

Not sure if it belongs here, but is anyone willing to make one(or a few?). I'm quite a newbie at DIY stuff, and definitely won't be able to make my own. Shipped to Canada, or locally, would be great.


 Thanks!


----------



## CaptHowie

I would build one for you, but I'm in Australia.


----------



## Juaquin

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This will be it for the Starving Student PCB unless more tubes show up in volume.
	

	
	
		
		

		
		
	


	


_

 

Noooooooooooo! Say it isn't so! 
	

	
	
		
		

		
		
	


	




 That said, any plans on making an (un)official version with the 12AU7 or is that it for the SSMH?


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Noooooooooooo! Say it isn't so! 
	

	
	
		
		

		
		
	


	




 That said, any plans on making an (un)official version with the 12AU7 or is that it for the SSMH?_

 

I don't know. That's definitely it for a 19J6 SSMH PCB. I guess Dsavitsk and I will be discussing the rest.


----------



## Llama16

Yes please do consider it


----------



## smrtby123

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Depends on how the case is connected (or not) to the circuit and earth ground. FWIW pretty much all of my audio equipment gets hosed by my iPhone within a couple feet, which extends to 5+ feet when it's actively transmitting._

 

Yeah if I am not paying attention and have my phone at my PC, I get some great buzzing that is almost 2x the volume my music is at when I am about to get a text.


----------



## choka

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Remember that NOT EVERYTHING in the circuit is within the metal case. In the case of this amp the tubes are unshielded and thus sensitive to picking up noise._

 

The other amp I have is the Bravo tube amp and it is pretty much naked, and I do not pick up noise on that one, which is something I found very strange.


----------



## choka

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This is a perfect symptom of not burning it in enough. (Yes, I know that's a controversial topic - please read the SSMH PCB Build thread!) Both the Nichicon KW's and the Wima's will have a prominent "bass fog" the first few hours that you run the amp. Let it run for a day or so and it will open up enough to surprise you._

 

I now have around 10 hours total on this amp and the muddiness has gone away. I have other amps to A-B it so I can say it is not my ears or brain adapting to the amp. Burn-in is real.


----------



## tomb

Quote:


  Originally Posted by *choka* /img/forum/go_quote.gif 
_I now have around 10 hours total on this amp and the muddiness has gone away. I have other amps to A-B it so I can say it is not my ears or brain adapting to the amp. Burn-in is real._

 

Yep, but when people start talking about something not sounding good until it's had 200 hours or more, I draw the line.
	

	
	
		
		

		
		
	


	




 As you noticed, caps will definitely improve over a 24-hour period (some less, some more), but I don't think it goes much beyond that.

 Glad to hear the sound is rounding up nicely for you!


----------



## the_equalizer

Quote:


  Originally Posted by *choka* /img/forum/go_quote.gif 
_The other amp I have is the Bravo tube amp and it is pretty much naked, and I do not pick up noise on that one, which is something I found very strange._

 

Definitely circuit/tube dependent. I can use a (literally) naked PIMETA v1 in the office without it picking up any noise at all. But when I use my Starving Student it picks up the cell phone signals from people walking by the aisle, around 4 feet away.

 Just try waving your hand real close to the 19J6 
	

	
	
		
		

		
		
	


	




 you'll definitely hear some induced noise there.

 cheers!


----------



## pete15

Hi, Ive been building the ssmh with 12sr7gt tubes, and today I got it done. This is my first build, and this thread has been extremely helpful. 
 It sounds great!


----------



## Fishline

Nice build! Do you get heat issue with the 12SR7GT? I may build yet another one (perhaps modding my first one) with 12SR7GT.


----------



## pete15

Thanks, Fishline. Good question about temps in the 12sr7 version. With the amp running for 90 mins. I measure the temperature at about 48C. I think that'll be o.k.


----------



## Giuss

Hello, this is my starving student, it works great


----------



## Kitarist

Is anyone selling kit for these amps? Or is anyone willing to sell source the parts for me and sell to me as a kit ? (I'm from Europe)

 Thanks!!!


----------



## Kitarist

Is anyone selling kit for these amps? Or is anyone willing to sell source the parts for me and sell to me as a kit ? (I'm from Europe)

 Thanks!!!


----------



## scompton

Looks great. Now you need a LOD for your iPod.

 I use this one, or one just like it, for iPod to RCA Amazon.com: Cables To Go 4-Feet RCA Stereo to Dock Connector Cable for iPod: Electronics

 There's similar cheap ones on Amazon if you need a mini plug.


----------



## Giuss

Do you thin that I can have a better audio quality using this cable instead of the ipod headphone output?

 Using this cable, I can bypass the ipod internal power amplifier?


----------



## tomb

Quote:


  Originally Posted by *Kitarist* /img/forum/go_quote.gif 
_Is anyone selling kit for these amps? Or is anyone willing to sell source the parts for me and sell to me as a kit ? (I'm from Europe)

 Thanks!!!_

 

As of this week, I've ordered a new batch of 35 cases from Hammond. We should have the last round of 35 kits to go on sale in mid-to-late January.


----------



## tomb

Quote:


  Originally Posted by *Giuss* /img/forum/go_quote.gif 
_Do you thin that I can have a better audio quality using this cable instead of the ipod headphone output?

 Using this cable, I can bypass the ipod internal power amplifier?_

 

Yes, that's usually what a "LOD" for an ipod does - as in, "Line Out Device."

 Your build looks very cool. It appears that you essentially used Dsavitsk's PCB method of mounting with a perfboard. Pretty neat!


----------



## the_equalizer

Quote:


  Originally Posted by *Giuss* /img/forum/go_quote.gif 
_Hello, this is my starving student, it works great 
	

	
	
		
		

		
		
	


	


_

 

Cool build ! The wooden box gives it a great 'old tube amp' feel. Congratulations !

 cheers !


----------



## kdris

Guiss, 

 Awesome looking amp!
 Where did you manage to find 19J6 tubes?


----------



## Giuss

Thank you very much to all 
	

	
	
		
		

		
		
	


	




 About the tubes, I found them some time ago on ebay, and I bought 3 pieces of them

 Bye


----------



## getllamasfast

I posted a separate thread about this, but I was told I would get more help if I moved it into this thread, so I'm just going to copy and paste it. BUT! with pictures this time 
	

	
	
		
		

		
		
	


	




 This is the_equalizer's 12AU7 version of the SSMH

 I just finished soldering a starving student and everything looked good, but when I flipped the switch on with no tubes in the mosfets didn't heat up. I thought that maybe it was because I didn't have the tubes in, so I put them in and turned it on, but then the left one flashed a bright orange and I immediately turned off the amp. I've checked all my connections and they seem to be going to the right places. However, I didn't get to check the voltages because in the process of learning how to use my multimeter as a voltmeter, I blew its fuse...

 Anyway, do you guys have any idea on where to start troubleshooting?

 Thanks,
 ~getllamasfast

 EDIT:
 I figured out that the flash was the tube heating up, but only one tube heats up. I let it sit for a while and hope that I could at least get one side working, but then the bottom heaters started flashing and then the power leds started flashing. Now neither tube heats up, nor do the mosfets and the leds blink if the tubes are plugged in. If I leave the tubes out, the leds are fine... 

 Here's a youtube video of what happens when I flip the switch.
YouTube - Broken Starving Student Hybrid

 Pictures: (Sorry about the rats nest of wires and solder... 'twas my first time going p2p and I didn't really have a layout plan... 
	

	
	
		
		

		
		
	


	




)


----------



## dsavitsk

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_BUT! with pictures this time_

 

Take a look at Pete's version






 or Nate's version






 and compare it to yours. I'd start there.


----------



## gurusan

my first millet ss was a horrific ratsnest as well


----------



## tomb

Sorry to say, but it scares me seeing those MOSFETs with bare leads. Could you put some electrical tape around each of those leads? For that matter, some electrical tape around some other bare leads/solder joints may prevent future shorts. I'm not saying you need it on solder lugs or all joints, but some of those resistors have very long leads that could come into contact with a number of other joints if not insulated. Maybe it's the angle of the photos? It's hard to judge depth with 2D photos, unfortunately, so use your own discretion.

 You're correct that it's a ratnest, unfortunately. While the photos are great, I'm afraid it will take a very enterprising user to try and trace that wiring. I've confirmed the input wiring to the pot appears OK, as does the output wiring to the headphone jack. I'm not sure about the rest - I'll keep looking as I get chances.

 What's the plan for that LED?

 Try and get that DMM fixed and refer to a good SSMH schematic. Carefully see if you can trace each part of the circuit and confirm continuity with the meter. You should be able to do this with it turned off. Don't worry about measuring specific resistances, they'll prove indeterminate in a completed circuit with its many parallel connections. You can, however, verify the resistors from the color codes.

 See if that helps and report back. Maybe someone else will spot something in the meantime.


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_I posted a separate thread about this, but I was told I would get more help if I moved it into this thread, so I'm just going to copy and paste it. BUT! with pictures this time 
	

	
	
		
		

		
		
	


	




 This is the_equalizer's 12AU7 version of the SSMH

 I just finished soldering a starving student and everything looked good, but when I flipped the switch on with no tubes in the mosfets didn't heat up. I thought that maybe it was because I didn't have the tubes in, so I put them in and turned it on, but then the left one flashed a bright orange and I immediately turned off the amp. I've checked all my connections and they seem to be going to the right places. However, I didn't get to check the voltages because in the process of learning how to use my multimeter as a voltmeter, I blew its fuse...

 Anyway, do you guys have any idea on where to start troubleshooting?

 Thanks,
 ~getllamasfast

 EDIT:
 I figured out that the flash was the tube heating up, but only one tube heats up. I let it sit for a while and hope that I could at least get one side working, but then the bottom heaters started flashing and then the power leds started flashing. Now neither tube heats up, nor do the mosfets and the leds blink if the tubes are plugged in. If I leave the tubes out, the leds are fine... 

 Here's a youtube video of what happens when I flip the switch.
YouTube - Broken Starving Student Hybrid

 Pictures: (Sorry about the rats nest of wires and solder... 'twas my first time going p2p and I didn't really have a layout plan... 
	

	
	
		
		

		
		
	


	




)_

 

Cool idea that about the internal LED's !! They light up the volume pot quite nicely! 

 Now, from what the video shows... that is indeed a very strange behavior. It _just might_ be a short circuit in your wiring and that pulsing is the power supply protection kicking in and out.

 I tried tracing some of your wiring using the pics, but it proved to much for me (sorry!). I think you can do it much better than any of us can with just the pics. 

 So here are some clear pics of my 12AU7 MSSH wiring. Try following each wiring path in it and compare it with yours. Feel free to PM me if you need some detail about the wiring. 





















 As TomB mentioned, you'll DEFINITELY NEED that VOM to get this to work. As TomB also mentioned, covering the exposed junctions and leads will definitely help avoid any unintentional shorts to the casing. Oh, and I'd start by completely removing the LED's and associated resistors. You can add them back in when you're sure the basic amplifier circuit works.


 cheers !


----------



## nullstring

I'd go as far as to tell you to start over >_<
 It really helps to have a layout plan. I made a little drawing with colored pencils when i made mine. everything is visable and easy to find, and it's easy to tell whats going on.


 anyway, the fact that the LED's blink is because your cisco PSU is detecting current overload and shutting down over and over again. (i think?)
 This means you definately have a short somewhere that you're not suppose to.

 But, yeah, if you make out a drawing, everything goes much smoother..
 And, don't be afraid to use more terminal strips either. I used 4.5 in mine. i needed more cause I used WIMA capacitors, and I didn't want to air wire those


----------



## getllamasfast

Thank you all so much for all the help! 
	

	
	
		
		

		
			





 I'll definitely pickup a fuse for my multimeter.

 @the_equalizer
 I've been looking for pictures of a 12AU7 SSMH to compare mine to. Thanks!

 @nullstring
 I would love to rip this thing apart and put it back together right, but I don't know if I have enough time to do that. This is supposed to be a Christmas present and I don't know if I can plan and solder fast enough to get this ready by tomorrow (I'm leaving to go on vacation). Thanks for the suggestion on the LED problem!


----------



## Llama16

Yes, it's best to take it apart. Make a nice and clean desk, make a drawing and when you're not sure about something then think it over thoroughly, take your time.

 But I see you're having time issues. One day would be rushing it if I'd like to do it my way. you'd probably end up with something similar as you already have. I personally wouldn't do it. But if it was solely meant as a gift and you can't get your hands on another present, and/or you can't use the amp for yourself, then you could always give it a shot 
	

	
	
		
		

		
		
	


	




.


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Thank you all so much for all the help! 
	

	
	
		
		

		
		
	


	




 I'll definitely pickup a fuse for my multimeter.

 @the_equalizer
 I've been looking for pictures of a 12AU7 SSMH to compare mine to. Thanks!

 <snip>_

 

No problem. Actually I don't think there are any other 12AU7 builds aside from yours and mine. 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## kuroguy

I see many cold solder joints. If the solder doesn't completely cover the copper wire at the joint it is a good bet that it is a cold joint. The large ground connections are also cold joints. If the solder doesn't have a smooth finish to it it is likely a cold joint. Thise grounds that have solder with the texture of oatmeal are cold joints too. that texture usually comes from moving the wiring before the solder cools sufficiently.


----------



## getllamasfast

Well, I did end up taking it apart and soldering it back together again.

 Looks much more neat imo, but it still doesn't work. I got my multimeter working again and measured 48v at the mosfet gate with the tubes in.

 I did manage to fix the short! Turned out to be a case of the power plug not being screwed in tight enough 
	

	
	
		
		

		
		
	


	




 I'll post pictures in a second.

 EDIT EDIT:
 I just realized that there were some mis-wired pins on the tube sockets, but I fixed all that and they still don't light up nor do the mosfets heat up 
	

	
	
		
		

		
		
	


	




 EDIT EDIT EDIT: Updated with corrected pictures.

 PICTURES:


----------



## xguntherc

Is there anyone that has a list of the parts I need for this, or should I try to just get a kit from tom. I went to his site and see he sells stuff. I'd like to try this and use it with my soon to be arriving ATH-AD900's

 edit* nevermind, I found the site


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Well, I did end up taking it apart and soldering it back together again.

 Looks much more neat imo, but it still doesn't work. I got my multimeter working again and measured 48v at the mosfet gate with the tubes in.

 I did manage to fix the short! Turned out to be a case of the power plug not being screwed in tight enough 
	

	
	
		
		

		
		
	


	




 I'll post pictures in a second.

 EDIT EDIT:
 I just realized that there were some mis-wired pins on the tube sockets, but I fixed all that and they still don't light up nor do the mosfets heat up 
	

	
	
		
		

		
		
	


	




 EDIT EDIT EDIT: Updated with corrected pictures.

 <snip>_

 

The MOSFETs seem to be wired in reverse; R3/R9 must connect to the first pin FROM THE LEFT. That's the MOSFET gate. Here's a cutout from the IRF 510 datasheet, I rotated it so it'a a bit easier to clearly see which pin is which.






 Here's how the MOSFET wiring in my 12AU7 build looks, you can clearly see R3 connected to pin 1.







 Here's how yours look





 Additionally... are those LED's soldered to the socket's pin 6 !?!? If they are you definitely DO NOT want to do that !! The LED's circuit should go from the 48 V power line to ground, not to the tube plates!! From your pics the LED's seem to be wired from one of the power supply 48 volt junctions through a big metal film resistor then two LED's in series and then pin 6 of a tube socket. Again, I'd leave that out until I'm sure the basic amplifier circuit works, then add it back in.






 cheers !


----------



## tomb

Good eye, equalizer!


----------



## getllamasfast

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_The MOSFETs seem to be wired in reverse; R3/R9 must connect to the first pin FROM THE LEFT. That's the MOSFET gate. Here's a cutout from the IRF 510 datasheet, I rotated it so it'a a bit easier to clearly see which pin is which.

 <snip>
 Here's how the MOSFET wiring in my 12AU7 build looks, you can clearly see R3 connected to pin 1.

 <snip>


 Here's how yours look
 <snip>

*Additionally... are those LED's soldered to the socket's pin 6 !?!?* If they are you definitely DO NOT want to do that !! The LED's circuit should go from the 48 V power line to ground, not to the tube plates!! From your pics the LED's seem to be wired from one of the power supply 48 volt junctions through a big metal film resistor then two LED's in series and then pin 6 of a tube socket. Again, I'd leave that out until I'm sure the basic amplifier circuit works, then add it back in.

 <snip>

 cheers !_

 

I just changed the mosfet pins so that they were correct and the shorting issue came back. I tried using only one tube, and I figured out that one of my tubes was causing the short. I guess I have a dead tube... 
	

	
	
		
		

		
		
	


	




 Also, when the working tube was in, I got ~40v coming out of the mosfet. Could I also have dead mosfets?

 And, I didn't have the led hooked up to the tube pin. That picture is deceiving, and when I look at it, the wire is nowhere close to touching a pin. 
	

	
	
		
		

		
		
	


	




 BTW, thanks for the help again! I can't thank you enough!


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Good eye, equalizer!
	

	
	
		
		

		
		
	


	


_

 

Thanks TomB! 
	

	
	
		
		

		
		
	


	




 I learned the hard way.

  Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_I just changed the mosfet pins so that they were correct and the shorting issue came back. I tried using only one tube, and I figured out that one of my tubes was causing the short. I guess I have a dead tube... 
	

	
	
		
		

		
		
	


	




 Also, when the working tube was in, I got ~40v coming out of the mosfet. Could I also have dead mosfets?

 And, I didn't have the led hooked up to the tube pin. That picture is deceiving, and when I look at it, the wire is nowhere close to touching a pin. 
	

	
	
		
		

		
		
	


	




 BTW, thanks for the help again! I can't thank you enough! 
	

	
	
		
		

		
		
	


	








_

 

Good to know those LED's are not going to the tube plates. There is a chance you have a dead tube but it's very remote. Even more, when tubes 'die' they don't short out (unless you subject it to a GREAT physical shock). 

 Now the chance of dead MOSFET's is much more real. When you say you get 40 volts "out" of the MOSFET do you mean you see 40 V at pin 3? Concentrate in one channel, what voltage reading do you get at the MOSFET pin 3? It should be around 12.6 volts. What's the reading at the MOSFET's pin 1? It should be around 16 volts.

 cheers!


----------



## getllamasfast

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Good to know those LED's are not going to the tube plates. There is a chance you have a dead tube but it's very remote. Even more, when tubes 'die' they don't short out (unless you subject it to a GREAT physical shock). 

 Now the chance of dead MOSFET's is much more real. When you say you get 40 volts "out" of the MOSFET do you mean you see 40 V at pin 3? Concentrate in one channel, what voltage reading do you get at the MOSFET pin 3? It should be around 12.6 volts. What's the reading at the MOSFET's pin 1? It should be around 16 volts.

 cheers!_

 

My multimeter read 40v at pin 1 compared to the ground. I don't know if that's how you use your multimeter as a voltmeter correctly, but it seemed to work...


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_My multimeter read 40v at pin 1 compared to the ground. I don't know if that's how you use your multimeter as a voltmeter correctly, but it seemed to work..._

 

Yes, that is how you use your multimeter as voltmeter 
	

	
	
		
		

		
		
	


	




 Is that the reading in *BOTH* MOSFETs ?? If so, that indicates a bad miswiring. You can see from the original schematic that pin 1 is connected through R3 to the junction of R2, R4. These two form a voltage divider that straps from the power line to ground. So the voltage at these middle junction depends on the ratio of R2 and R4. In the case of the 12AU7 version, the voltage there should be very close to 16 volts. 

 Your reading of 40 volts would seem to indicate that R4 is missing, so no voltage divider and thus you get the full power supply voltage at pin 1.

 What voltage with respect to ground are you reading at the MOSFET pin 3?


 By the way you can find my MSN Messenger address in the Contact Info tab of my user profile. Feel free to add me if you like.

 cheers !


----------



## SteveC89

Ok, so I have been trolling this thread for a while. I have all my parts and my case and I'm ready to start, but I just got an idea. When I build guitars, I line the inside with copper tape to shield the pickups from picking up hum. If I lined the inside of my case with this copper tape, would it help shielding (like from cell phone beeps and stuff)?

 I was also thinking it would be more surface area to ground, in addition to my grounding plane.


----------



## Juaquin

It definitely can't hurt, as long as it doesn't short anything. Let us know how it goes!


----------



## Llama16

Merry christmas everyone, sorry if I'm a bit to late.

 I'm having trouble soldering the ground wire of the left LED tube on the PCB. It stays a blob and won't wick in. I had a bad contact between that ground and another ground on the PCB, so I'm sure that the cire isn't well soldered. 

 would it hurt to just connect that ground wire to the other ground wire from the right LED tube? with perhaps a snip of something.
 I'm guessing it'll be fine, but perhaps it would have a negative effect that I don't know of


----------



## dean0

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Merry christmas everyone, sorry if I'm a bit to late.

 I'm having trouble soldering the ground wire of the left LED tube on the PCB. It stays a blob and won't wick in. I had a bad contact between that ground and another ground on the PCB, so I'm sure that the cire isn't well soldered. 

 would it hurt to just connect that ground wire to the other ground wire from the right LED tube? with perhaps a snip of something.
 I'm guessing it'll be fine, but perhaps it would have a negative effect that I don't know of




_

 

turn up your solder iron, and use plenty of flux, heat the joint for a while before adding solder.


----------



## Yaka

im no expert but judging by the burn marks ( and the well soldered sockets) heat is not the issue lack of flux is. 

 last i say that was when first soldered some thing 9 years ago, back then i use snip first and then solder and it would end up looking just like that


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Merry christmas everyone, sorry if I'm a bit to late.

 I'm having trouble soldering the ground wire of the left LED tube on the PCB. It stays a blob and won't wick in. I had a bad contact between that ground and another ground on the PCB, so I'm sure that the cire isn't well soldered. 

 would it hurt to just connect that ground wire to the other ground wire from the right LED tube? with perhaps a snip of something.
 I'm guessing it'll be fine, but perhaps it would have a negative effect that I don't know of
_

 

Those are some small holes. If you don't get it right the first time, it could be tough going back and trying to get it right.
	

	
	
		
		

		
		
	


	




 Yes, a jumper or similar to the other LED's ground lead will work fine - it's all ground, anyway.


----------



## Llama16

Thanks for the help.

 It's not my pic btw 
	

	
	
		
		

		
		
	


	




 i took the one from tomb's helpfull guide.
 If I don't get a nice solder joint in a few seconds, then I'm quite sure it becomes a blob. it's like the solder 'floats' on the board and just doesn't want to go in, even if I take most of the solder away with a braid. As if it acts like mercury, that's the best description I can give. I use solder wire with flux in it, and i think that when there is to much flux on the pad itself that it becomes a blob.

 After doing a bit of soldering I found that the best way to avoid this is to apply the solder to the iron, and then from the iron to the joint. That way it leaves the excess flux (that keeps coming when applying more of the solder wire) on the tip of the iron. Sadly I only discovered this after trial and error. 

 When desoldering that wire for the 4th time or so, I got a good contact (0.5ohm resistance, and the 0.5 comes from the multimeter itself) so I figured I'd leave it that way. Hoping it'll stay, because the more I touch it, the more it gets worse. The joint doesn't get alot of stress, but if it happens that a ground for 1 of the 2 leds gets loose, what would be the consequence? Double the current for the other LED? And if so, could that LED take it for a short time (because when I see one of the leds don't work, I'll go back and fix it)?

 Thanks for the help everyone


----------



## tomb

I was going to say ... I didn't see any burn marks in that photo.
	

	
	
		
		

		
		
	


	







 Yeah, if you lose the ground wire, the other LED will burn brighter. However, the LED resistor was sized for 10ma, so at the worst, the other LED will just be exposed to 20ma - still OK.

 On the other hand, your soldering problem could just be a cold iron. If the iron tip is not hot enough to _*quickly*_ heat the ground pad, then the reliefs won't do much good and the iron will proceed to try to heat the entire PCB ground plane. That's a losing battle and one result will be solder blobs and no stick.

 If you can't heat the iron up hotter, then different methods to enhance the heat transfer with all you've got is the best strategy. As you've found, if you have a bit of solder melted onto the tip of the iron, it will spread the heat faster to the pad. You can use this trick while never touching the soldering wire to the tip and still adhering to the principle of solder to the joint - not to the iron. Another method is to use extra flux - nothing wrong with doing that. Get yourself some solder paste, dip the tip of the wire into it to get a 1/8"-14" blob of paste and apply it to the joint. The iron should heat the flux, which melts then spreads the heat quickly throughout the joint. The result is that the solder melts easily and sticks. The downside is that it may take you longer to rinse the board and get it clean from all of the extra flux, but that's a small price to pay for the improved soldering.


----------



## Llama16

(Whoops, double post. I thought I deleted this msg... the one below was better anyway)


----------



## Llama16

Thanks, I'm glad to hear that the other LED won't burn out if I'm mistaken. I'll still be able to fix both if the left one doesn't work.

 I really thought that the excess of flux on the solder pad prevented the solder to cover it. I just put my soldering iron to full (was on 4/5 or so), so I don't forget it tomorrow. 

 BTW: I failed to mention that I'm very happy with the kit. Also, thank you for you help with the lug sockets you gave me.

 Dries Fact: The kit got stuck at our famous greedy belgian customs (which btw came with a hefty bill for all sorts of taxes 
	

	
	
		
		

		
		
	


	




). But when I just finished studying for my final exam, the doorbell rang and a happy postman came to deliver it. Now that's timing. Couldn't have been happier.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Thanks, I'm glad to hear that the other LED won't burn out if I'm mistaken. I'll still be able to fix both if the left one doesn't work.

 I really thought that the excess of flux on the solder pad prevented the solder to cover it. I just put my soldering iron to full (was on 4/5 or so), so I don't forget it tomorrow. 

 BTW: I failed to mention that I'm very happy with the kit. Also, thank you for you help with the lug sockets you gave me.

 Dries Fact: The kit got stuck at our famous greedy belgian customs (which btw came with a hefty bill for all sorts of taxes 
	

	
	
		
		

		
		
	


	




). But when I just finished studying for my final exam, the doorbell rang and a happy postman came to deliver it. Now that's timing. Couldn't have been happier._

 

Thanks for the kind comments on the kit.
	

	
	
		
		

		
		
	


	




 No, excess flux is never going to inhibit soldering, IMHO. It will only make things messier (but easier, most likely). There's an outside chance that you may use so much flux that it will cool things off, but again IMHO, that's just more of a sign that your iron heat is marginal. Even solder paste should literally vaporize, bubble and boil when hit with the soldering iron. Meanwhile, all that catalizing reaction with the paste and vaporizing/boiling will burn off any surface sheen/finish and ensures that the melted solder will stick.


----------



## Juaquin

Also, if you have a hot air gun you can heat that area to get solder to flow, especially with that huge ground plane. I just built some speakers at home where I only have a ratshack firestarter 20-30W iron and I had to use a heatgun to get solder to flow on the thick copper traces. A blow dryer might be ok in a pinch. Just don't overheat any components.


----------



## kdris

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Sorry for the delay in replying. I don't have access to the forum from the office. 

 getllamasfast: indeed they are intercheangable and, as a matter of fact, I built my 12AU7 version using new, current production JJ 12AU7 tubes. I also tested with 12AX7 (current production Russian Mullard) and 12AT7 (old GE ones) and they work great too; giving you different levels of gain.

 TomB: actually the modified version I tested and built, based on Dsavitsk's hints, uses the two sections of the triode in parallel, just like the 19J6 version. I wanted to use the 12AU7 precisely because you can get some old ones dirt cheap, some new ones at around $15 USD or some 'boutique' NOS ones at $$$$. So while the current production 12A_7 tubes are not as cheap as the 19J6 was some years ago, at least their price is consistent and they're *very* easy to find.

 Oh! After reading the posts again I see what happened... you were thinking about Logistic's 12SR7 version. 
	

	
	
		
		

		
		
	


	




 That one indeed uses NOS tubes (beautiful octal ones 
	

	
	
		
		

		
		
	


	




 ) that are still VERY cheap. As I remember it those are radio tubes that have a triode and two diodes in the same bulb; so there's no way to use the triodes in parallel. 
	

	
	
		
		

		
		
	


	




 cheers!_

 

Equalizer, 

 If you have a free moment. Is there a link to how exactly the circuit was modified in your 12AU7 version? I've been digging through this thread for a while now and am unable to find it. I know it involves changing resistors R2 and R8 but what are their exact values and how does this affect the circuit as far as pinouts from the original tubes.

 Thanks in advance,

 kdris


----------



## the_equalizer

Quote:


  Originally Posted by *kdris* /img/forum/go_quote.gif 
_Equalizer, 

 If you have a free moment. Is there a link to how exactly the circuit was modified in your 12AU7 version? I've been digging through this thread for a while now and am unable to find it. I know it involves changing resistors R2 and R8 but what are their exact values and how does this affect the circuit as far as pinouts from the original tubes.

 Thanks in advance,

 kdris_

 

Sure. You can find it here. It's (currently) about the 30th post that shows up if you search 12AU7 using the 'Search this thread' feature

 cheers!


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## kdris

thank you so much for the fast reply!


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## Llama16

Little question:
 Does flux conduct? Because I don't got anything to remove it, and I don't think I'll find it somewhere near. So I thought I'd just forget about it.

 I think I'm right when I say it doesn't, allthough I'd definately clean it off if I could (I'm the precision guy... eg: checking for cold joint ABOUT 15 TIMES OR SO, I know I'm a freak.


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## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Little question:
 Does flux conduct?_

 

Over time, ABSOLUTELY.
  Quote:


 Because I don't got anything to remove it, and I don't think I'll find it somewhere near. So I thought I'd just forget about it. 
 

Clean it off. All it takes is an old toothbrush, some paper towels and some 90% or better isopropyl alcohol that you can obtain (very cheaply) at any corner drugstore or Walmart. Use the toothbrush by dipping it into a bowl filled with the alcohol. Scrub the entire board until it's completely coated with alcohol and you've scrubbed down the biggest lumps. Pat up the liquid with paper towels. Repeat as necessary (usually takes 4-6 times). Use several rinses until all of the white powder is gone and your paper towels no longer pick up yellow stains.


----------



## sourced

Woo hoo! I appear to be somewhat successful (finally)! First, here's the money shot (well, it's mirrored but whatever):







 Now, I'm not perfect, so there appear to be a couple issues/notes:
 - It hums very quietly (it's not disturbing, but it is audible when no music is playing). Hum goes up when I put my finger near the tube, but silent when I touch the case. Judging from other posts in the thread, I should check all my grounds. I don't have a pic yet, but I have a ground for all the left channel circuit, and a ground for all the right channel circuit (two star grounds, more or less). Then the two grounds are connected through the case (aluminum). The RCA jacks have their 'cases' touching the case, so I figured that would be ground enough (appears to be similar to how pmillett did his). Should I run wires to the ground lugs?

 - Right channel is louder than left, since my $3 pot isn't very good. I know turned off, resistance reads ~48.5kΩ through right, ~50.4kΩ through left. Would it be ok to solder in a 2kΩ resistor at the right RCA jack? Obviously when right is around ~20kΩ left might be ~21kΩ, and as I turn it up I'd actually have the left channel louder. I'll see if I have a better pot lying around, but what is the general fix? I panned my computer output left but I'm not sure I can pan left with digital out (when I use a DAC).

 - I wired the pot backwards, so the audio taper is all messed up (very sensitive at the low end), which I will fix.

 - The mosfets get _really_ hot, and the whole case warms up (good thing my case is an aluminum heatsink). Awesome.

 - Watching the tubes heat up together just about makes my day

 Regardless, this is pretty amazing. I've been listening for about an hour total (not burned in yet) and it doesn't sound horrid, so... success!


----------



## Llama16

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Over time, ABSOLUTELY.
 Clean it off. All it takes is an old toothbrush, some paper towels and some 90% or better isopropyl alcohol that you can obtain (very cheaply) at any corner drugstore or Walmart. Use the toothbrush by dipping it into a bowl filled with the alcohol. Scrub the entire board until it's completely coated with alcohol and you've scrubbed down the biggest lumps. Pat up the liquid with paper towels. Repeat as necessary (usually takes 4-6 times). Use several rinses until all of the white powder is gone and your paper towels no longer pick up yellow stains._

 

:S, I won't argue with you and I'm sure it's for the best. And I wish I had some of that isopropyl alcohol at hand, allthough my fear of breaking a joint when cleaning the board makes me want to be very sure that I really have to as well.

FELDER GmbH | Solder wires for the electronic | Flux cored soft solder wires ISO-Core® This is the solder I'm using: It's the RA version, 60tin and 40lead with 2.5% flux.

 At the bottom of that info page it says: "The fluxes have a high temperature resistance! The bright, solid flux residues of these solder wires do not result in corrosion on non-iron metals. Therefore, they can remain on the soldering joint"


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_:S, I won't argue with you and I'm sure it's for the best. And I wish I had some of that isopropyl alcohol at hand, allthough my fear of breaking a joint when cleaning the board makes me want to be very sure that I really have to as well.

FELDER GmbH | Solder wires for the electronic | Flux cored soft solder wires ISO-Core® This is the solder I'm using: It's the RA version, 60tin and 40lead with 2.5% flux.

 At the bottom of that info page it says: "The fluxes have a high temperature resistance! The bright, solid flux residues of these solder wires do not result in corrosion on non-iron metals. Therefore, they can remain on the soldering joint"_

 

Yes, well - corrosion is different. You asked if it would conduct - over time, yes.

 Just another note, but if one if your solder joints comes undone from simple scrubbing with a toothbrush and alcohol, then it was too weak to make good electrical contact anyway. You'll be discovering problems that are easier to fix now rather than later.


----------



## Llama16

You're right, I'll stop my search for excuses and see if I can get my hands on some.
 Thanks for letting me see the light 
	

	
	
		
		

		
		
	


	




, I sometimes need a slap so I don't 'stray' off.


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## the_equalizer

Quote:


  Originally Posted by *sourced* /img/forum/go_quote.gif 
_Woo hoo! I appear to be somewhat successful (finally)! First, here's the money shot (well, it's mirrored but whatever):

 <snip>

 Now, I'm not perfect, so there appear to be a couple issues/notes:
 - It hums very quietly (it's not disturbing, but it is audible when no music is playing). Hum goes up when I put my finger near the tube, but silent when I touch the case. Judging from other posts in the thread, I should check all my grounds. I don't have a pic yet, but I have a ground for all the left channel circuit, and a ground for all the right channel circuit (two star grounds, more or less). Then the two grounds are connected through the case (aluminum). The RCA jacks have their 'cases' touching the case, so I figured that would be ground enough (appears to be similar to how pmillett did his). Should I run wires to the ground lugs?

 - Right channel is louder than left, since my $3 pot isn't very good. I know turned off, resistance reads ~48.5kΩ through right, ~50.4kΩ through left. Would it be ok to solder in a 2kΩ resistor at the right RCA jack? Obviously when right is around ~20kΩ left might be ~21kΩ, and as I turn it up I'd actually have the left channel louder. I'll see if I have a better pot lying around, but what is the general fix? I panned my computer output left but I'm not sure I can pan left with digital out (when I use a DAC).

 - I wired the pot backwards, so the audio taper is all messed up (very sensitive at the low end), which I will fix.

 - The mosfets get _really_ hot, and the whole case warms up (good thing my case is an aluminum heatsink). Awesome.

 - Watching the tubes heat up together just about makes my day

 Regardless, this is pretty amazing. I've been listening for about an hour total (not burned in yet) and it doesn't sound horrid, so... success! 
	

	
	
		
		

		
		
	


	


_

 






 Congratulations ! It is indeed a warm fuzzy feeling to watch those tubes light up and hear sweet music coming out of the 'phones!!

 About the hum, I've found some 19J6's to be much more susceptible to hum than others; specially if you use high sensitivity 'phones. Swap the tubes and see if the hum follows the tube. If it does, well: it's the tube that it's at fault.

 On the channel imbalance, indeed, the most 'general' solution would be to use a better pot 
	

	
	
		
		

		
		
	


	




. Short of that you can try adding a couple input resistors as done in the PCB version. Take a look at the schematic. This solution won't make the imbalance dissapear, but it'll make it much less noticeable. 

 cheers !


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## Llama16

Sorry to disrupt again, but I want to be sure before I go on.
 I went to the farmacy, where I bought myself about 100ml of isopropyl alcohol. The farmacist wanted to know what I am gonna use it for (don't blame her ofcourse 
	

	
	
		
		

		
		
	


	




).

 I just cleaned of the back of the board for the first time and yes, I noticed the flux dissolving, allthough the board is now covered with a rather mat, dull residue that sticks a little. I'm guessing that's the dissovled flux.
 What's the best way to get rid of it?

 Also, i'd like to see if I got a connection between the upperside of the RLED and the main ground whole in the middle, I have the caps installed but I get a resistance readin that fluctuates. Is this due to the capacitor that is also connected to the LED?

 Thanks
 Dries


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Sorry to disrupt again, but I want to be sure before I go on.
 I went to the farmacy, where I bought myself about 100ml of isopropyl alcohol. The farmacist wanted to know what I am gonna use it for (don't blame her ofcourse 
	

	
	
		
		

		
		
	


	




).

 I just cleaned of the back of the board for the first time and yes, I noticed the flux dissolving, allthough the board is now covered with a rather mat, dull residue that sticks a little. I'm guessing that's the dissovled flux.
 What's the best way to get rid of it?_

 

Go back to my post where I described the procedure.
	

	
	
		
		

		
		
	


	




 It's going to take 4-6 rinses. As you noted, the alcohol dissolves the flux. What not many people will tell you though, is hitting it with alcohol and a toothbrush again - with no other action - will not accomplish anything but to continue to spread the flux around. What you need to do is dab up the dissolved flux and alcohol with a paper towel while it's still wet. Otherwise, where can it go? the alcohol will dry, but the flux will still be there.* 
	

	
	
		
		

		
		
	


	




 When you dab while the alcohol is still wet and the flux dissolved, you should see the flux on the paper towel as dirty yellow stains. Repeat the rinsing and dabbing up with the paper towel for as many times as it takes, allowing the board to mostly dry inbetween. After 4-6 times, the PCB should be pretty clean.
  Quote:


 Also, i'd like to see if I got a connection between the upperside of the RLED and the main ground whole in the middle, I have the caps installed but I get a resistance readin that fluctuates. Is this due to the capacitor that is also connected to the LED?

 Thanks
 Dries 
 

I can't tell what you're measuring from what you describe. The best way is to put one probe on the wire lead (I'm assuming you can reach the tip.) That's supposed to be ground. Then place the other probe far removed from that area, but on a ground point. You should get no variation and it should measure 0 ohms. Keep in mind that if you're not an awful lot experienced in measuring with a DMM, the process itself is flawed by how you hold the probes and will cause variation. In other words, you may not be able to keep the target centered at all times with your hands. As long as you read zero sometimes and can repeat it with some assurance while you're touching the wire tip and not the surrounding pad, then you have a successful ground connection. 
	

	
	
		
		

		
		
	


	




 Note that you can still leave the amp case dissassembled and turn the power on. As long as the tubes are in and you have the MOSFET heat sinks attached, it should be OK. Certainly, you can tell within a second or less if the LEDs will light. That might be the easier way to do it.
	

	
	
		
		

		
		
	


	





 * One other method is to turn the board on its side as if you're scraping the dissolved flux down off of the edge of the board, allowing it to drip off. This is much more messy and not as positive as the paper towels, IMHO.


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## Llama16

Thanks, I read the procedure (alot!
	

	
	
		
		

		
		
	


	




)and I was just doubting what rinses meant. I went ahead and cleaned it a second, third, forth time or so and yes, you're right now it's alot better 
	

	
	
		
		

		
		
	


	




.

 About the measuring: That's about what I did with all my the connections, I was wrong when mentioning 'connection' I meant more of a 'solder bridge' allthough there isn't any visible solder (just making sure 
	

	
	
		
		

		
		
	


	




)


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## Llama16

Ok guys, bad news :S

 I assembled it and fired it up for the first time.
 I saw the Tube LEds shine rather dim, then they fainted out, the tubes didn't light up...

 I know i'll take some measurements but does anyone maybe already now how this happened? The second time nothing happened.


----------



## the_equalizer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Ok guys, bad news :S

 I assembled it and fired it up for the first time.
 I saw the Tube LEds shine rather dim, then they fainted out, the tubes didn't light up...

 I know i'll take some measurements but does anyone maybe already now how this happened? The second time nothing happened._

 

Sounds like there's a short to ground. The faint light up in the LED's was the power supply just before it shut down due to it's short protection. 

 Check your MOSFET's. See that you mounted them correctly (i.e. there MUST be a plastic shoulder between the MOSFET tab and the nut, there MUST be a thermal pad isolating the MOSFET from the case, etc.)

 cheers!


----------



## Llama16

yeah the mosfets should be fine: shoulder in place abd thermal pads in place, just like tomb instructed I checked the resistance between the MOSFETs iron 'backplate' (dunno the name) and their nuts, not the resistance is higher then 2000k (my meter can't go higher, so I'm guessing there isn't a short.

 I'd also like to say that I'm not sure that it's the short protection of the PSU, as it doesn't cycle. it happened once when I booted it up for the first time, then when I shut it down again (even when I pulled out the plug for a min or two) and then fired ti up again, nothing happened, no fainting of the LEDs, nothing.
 The tubes don't fire up, the LEDS don't light (and there isn't a smell of burning stuff nor do the heatsinks get warm (I don't know how fast they get warm though)).

 Thanks for the help. Really don't know what to do


----------



## the_equalizer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_yeah the mosfets should be fine: shoulder in place abd thermal pads in place, just like tomb instructed I checked the resistance between the MOSFETs iron 'backplate' (dunno the name) and their nuts, not the resistance is higher then 2000k (my meter can't go higher, so I'm guessing there isn't a short.

 I'd also like to say that I'm not sure that it's the short protection of the PSU, as it doesn't cycle. it happened once when I booted it up for the first time, then when I shut it down again (even when I pulled out the plug for a min or two) and then fired ti up again, nothing happened, no fainting of the LEDs, nothing.
 The tubes don't fire up, the LEDS don't light (and there isn't a smell of burning stuff nor do the heatsinks get warm (I don't know how fast they get warm though)).

 Thanks for the help. Really don't know what to do_

 

Voltages please 
	

	
	
		
		

		
		
	


	




 at the power supply connector, at the MOSFET pins. Also measure the voltage at the PSU when it is NOT connected to the amp.

 cheers !


----------



## Llama16

Ok

 You're right I'll be measuring some voltages, I'm quite new at this and I know that those voltages and even pictures are necessary to be able to help. But I first have a little discovery:

 I got the amp back dissassembled (I got it out of the case) and now the leds work fine, they start up in 2 seconds or so and when turned off they darken in abotu 3 seconds.
 I see the tubes lighting up (I didn't expect that they don't light up so bright though, but that's maybe my inexperience) and the heatsinks getting warm.
 I'm not able to test whether it works as an amp or not (I can't find my analog cable and probably have to make one)

 It's really a mistery here :S probably a short but I really can't find it right away (all my cable are insulted, I am 10percent sure there is not single cable left open for even a mm)

 I already checked the voltage of the PSU, and the strange thing is: it's 60V (I'm on the belgian 'european' network) while I think it needs to be 48. This could be my inexperience of using a MM, so i'll quickly explain what I did. I placed the black wire of the MM (which is connected to the 'COM' of the device) on the outer side of the PSU connecter (below the yellow insulater) and put the red wire (which is set on the 1000VDC/750VAC/200mAmax conenctor of the MM) inside of the PSU connector, then I got a positive reading of 60V (the scale I used was 200DCV)

 I got to go catch some sleep, it's been a long day, but I'll see if i can wake up for a sec to see the responses, allthough the measurements need to be for tomorrow.

 Thanks alot equalizer (I think I've added you on MSN, but didn't have the time to say hello yet)


----------



## the_equalizer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Ok

 You're right I'll be measuring some voltages, I'm quite new at this and I know that those voltages and even pictures are necessary to be able to help. But I first have a little discovery:

 I got the amp back dissassembled (I got it out of the case) and now the leds work fine, they start up in 2 seconds or so and when turned off they darken in abotu 3 seconds.
 I see the tubes lighting up (I didn't expect that they don't light up so bright though, but that's maybe my inexperience) and the heatsinks getting warm.
 I'm not able to test whether it works as an amp or not (I can't find my analog cable and probably have to make one)

 It's really a mistery here :S probably a short but I really can't find it right away (all my cable are insulted, I am 10percent sure there is not single cable left open for even a mm)

 I already checked the voltage of the PSU, and the strange thing is: it's 60V (I'm on the belgian 'european' network) while I think it needs to be 48. This could be my inexperience of using a MM, so i'll quickly explain what I did. I placed the black wire of the MM (which is connected to the 'COM' of the device) on the outer side of the PSU connecter (below the yellow insulater) and put the red wire (which is set on the 1000VDC/750VAC/200mAmax conenctor of the MM) inside of the PSU connector, then I got a positive reading of 60V (the scale I used was 200DCV)

 I got to go catch some sleep, it's been a long day, but I'll see if i can wake up for a sec to see the responses, allthough the measurements need to be for tomorrow.

 Thanks alot equalizer (I think I've added you on MSN, but didn't have the time to say hello yet)_

 

Glad it's working ! ... Now you just have to find that short when the circuit is in the case 
	

	
	
		
		

		
		
	


	




 The voltage from the PSU does not seem normal at all; my PSU even gives slightly less than 48 volts. The MOSFETs can take up to 100 volts drain-to-source so, no problem there, but I'm not sure about the gate-to-source.. 

 Anyway, have a good night and let us know the voltage measurements tomorrow. 
	

	
	
		
		

		
		
	


	





 EDIT: BY THE WAY. I think the most common source of shorts when the circuit is in-case, is the standoff and the LED resistor. Check out TomB's step-by-step build thread.

 cheers !


----------



## tomb

Thanks, equalizer!

 Yes, casing an amp up and finding a short is a common problem. However, I'm wondering if you dissassembled it, maybe the center standoff was still connected? If so, it might be an issue with the connectors/wiring on the back plate. Do you have any long leads and when the slack wire is bunched up when you bolt up the case, is there a possibility that some exposed leads can come into contact with something? Could the leads bind, etc., etc.?


----------



## Llama16

Just woke up for a sec 
	

	
	
		
		

		
			





 Equalizer, I'm gonna make work of it tomorrow as soon as I can, leaving something unfinished bugs me tremendously.

 Yes tombs, that's the case, The standoff was indeed left in place. I just 'shove' it out of the case again. I have checked the standoff e couple times, it never moved from it's 'flat side to RLED' position. And as I meantioned before I made very sure that I left no wires exposed. Everyone lead is shrinkwrapped, especially the hot ones (power, RCA jacks signal) I only left he ground wires exposed at the joint itself (which is never over 5mm). Even the terminals I took good care off, The wires are completely pushed in and you cna only see the insulation at the entrance (when assembling I even checked if no wires popped out of the back of the terminals 
	

	
	
		
		

		
		
	


	




). I'm having no clue.

 I must admit though that the wires are a little longer then yours, allthough I crefully bent them so they don't touch to much, even knowing that they are completely insulated.

 What do you say about the PSU tomb? It's rating 60V DC (check in the previous post my way of measuring, I think it was right) when unplugged into the amp. As you stated that the PSU was suitable for 240V, I just took an old powercord wit those uniform 3 pins and plugged it in. Could it be the network? 

 Thanks
 Dries


----------



## tomb

The PSU is supposed to deliver 48VDC, regardless of whether it's 240 or 120V input. Check the label and confirm that this is the case.

 EDIT: You should just check the PSU voltage at the terminal block on the PCB. Sometimes you can get weird readings by trying to measure inside the plug connector on the power supply itself. I suspect that your readings are in error, because it sounds like it works fine when uncased. Keep searching for a bind, someplace where metal is contacting where it shouldn't, etc.

 Could the heat sinks be under tension so that when you slide the case together, the heat sinks are forced up slightly by the case body, thereby forcing additional tension on the MOSFET mounting and perhaps shorting them out? Check for wire bindings in the case slots - especially where the lid slides in. That can be a common source of shorting.

 Maybe you could give us some pics?


----------



## Llama16

Even at the terminals I get 58 Volts and rising (0.1/second or so, I waited for about 5 seconds). The PSU is indeed rated 48V.

 The heatsinks are not torqued as you described in your guide, I can still slide them a little around.

 I'll take a picture with our family's pocket camera. I'm afraid the quality isn't going to help you any further but I'll see what I can do. I'm nto allowed to buy that D5000 I've always wanted 
	

	
	
		
		

		
		
	


	




, though I understand it when my parents say that it's an expensive purchase for someone my age, so I'll have to wait.

 It's an old MM, but I measured a couple of AA (1.5V) duracell batteries to see if it works correctly, it gave a reading of 1.9V, I don't know if that's abnormal or not.

 Could it be the powercord? It's from 95 or even older, but it works perfectly with the projector it came with, so if it was the powercord, that projector shouldn't be working right now.

 I really hope I didn't break anything.

 Could you give a small list of the measurements I should perform, so you'd be a step further? and the MOSFETs, what legs should i measure the voltage of (I read it a couple of times in this thread so a link will suffice.

 Picture: 





 So as you can see, my cables are very well insulated besides the grounds I guess.


----------



## tomb

Ha! If you take your meter's assumed inaccuracy with the 1.5V battery measured at 1.9 (1.267 multiplier) and multiply it times 48 ... you get 60.8!!
	

	
	
		
		

		
		
	


	




 So, I'd forget about making any measurements. They'll just cause you unfounded worries.
	

	
	
		
		

		
		
	


	




 Your workmanship looks great - I can't fault anything that I see. You might try some twist ties on that backplate wiring in a couple of strategic places - just so that you can be sure it all "folds" up nicely when you case it up.

 Remind me - you've confirmed that the amp operates in the uncased condition, including providing music? If so, the only thing I could suggest is to keep searching for a wire binding or a piece of the PCB contacting the case where it shouldn't. Take the case extrusion and slide the PCB back and forth repeatedly while looking edge-on. Try to see if there's anything that's touching. Take another look at that center standoff and see if there's something that's causing it to bind and perhaps contact the LED resistor lead on the PCB - especially the associated washers. Are there any leads on the bottom of the PCB that are untrimmed and could be touching the case lid?

 If the heat sinks are able to move around with your hands, tighten them down securely so that they don't - there's nothing stopping you from torquing down the two mounting screws that aren't attached to the MOSFETs.

 Sorry I don't have anything more specific right now, but your workmanship looks excellent from here and we can dismiss the readings from your meter. I had a MiniMAX that shorted on assembly once and it took me a couple of hours to spot a small bit of insulation that was binding in the very end of a case slot - it was enough to expose the wire underneath and make contact with the case. I couldn't even see the insulation tear until it was bent.


----------



## the_equalizer

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Even at the terminals I get 58 Volts and rising (0.1/second or so, I waited for about 5 seconds). The PSU is indeed rated 48V.

 The heatsinks are not torqued as you described in your guide, I can still slide them a little around.

 I'll take a picture with our family's pocket camera. I'm afraid the quality isn't going to help you any further but I'll see what I can do. I'm nto allowed to buy that D5000 I've always wanted 
	

	
	
		
		

		
		
	


	




, though I understand it when my parents say that it's an expensive purchase for someone my age, so I'll have to wait.

 It's an old MM, but I measured a couple of AA (1.5V) duracell batteries to see if it works correctly, it gave a reading of 1.9V, I don't know if that's abnormal or not.

 Could it be the powercord? It's from 95 or even older, but it works perfectly with the projector it came with, so if it was the powercord, that projector shouldn't be working right now.

 I really hope I didn't break anything.

 Could you give a small list of the measurements I should perform, so you'd be a step further? and the MOSFETs, what legs should i measure the voltage of (I read it a couple of times in this thread so a link will suffice.

 So as you can see, my cables are very well insulated besides the grounds I guess._

 

Nice job! It does look neatly built 
	

	
	
		
		

		
		
	


	




 I can't imagine where that short could be originating. Best I can suggest is to case it "progressively" so to speak. Slide in the PC board and test. If it works then put in the back cover and test, then the front cover and test and so on.

 Fresh alkaline batteries usually test a bit over there rated voltage, specially when tested out of circuit, so that *seems* normal. Still, after some quick calculations, it turns out the deviation from the expected values shown by both measurements is about the same (~25%), so I'm starting to think it's your DMM. 

*PLEASE DO NOT GO testing mains voltage to see if it gives the same error. You're quite inexperienced using a DMM and mains voltage IS LETHAL.
* You can later compare measurements with a friend's DMM or buy a new one in a couple of months.

 Check the label in the PSU brick. Does it say that it can take 220 volts input ? If it does (as I expect it too, since TomB provided it) then you're OK, but you'll need to get a new DMM later 
	

	
	
		
		

		
		
	


	




 After all, you probably won't find it very useful to hunt down that shorting bug when you case the amp.

 So, finally, aside from looking at the circuit light up when out of its case, have you tested playing some music throught it ? Plug in some cheap Sony earbuds and tell us if sweet music comes through !!

 EDIT: I took so much to write my post that TomB beat me to it, and it seems I'm echoing his comments.

 cheers!


----------



## Llama16

K, thanks for the advice. I'm so glad it's the meter. My dad used it alot when laying the wiring of our house and as he learned to do that by himself he admits that he has encountered alot of nasty sparks (I can confirm that from the both pins that are molten on several spots. I mainly used it to check the resistance between joints and see if I got a proper connection or any unwanted solder bridge.

 Yes, I haven't yet tested it out. I lost my mini to analog for my ipod, so I'll have to make that, also I don't like risking my HD650s, so I don't mind taking the time for making a female mini to 1/4 jack for some generic headphones to test on. I have the parts lying around though.

 Thanks for the kind words about the build, my heart jumped a little when the amp (at least the leds and tubes) fired up after all. The MOSFETS heaten up the heatsink nicely, so I think that's a good sign. Allthough I still can't find that short.

 My tubes are making the exact same effect as toms one in his step-by-step guide.

 I have some final questions (hopefully!):

 Is it possible to test the output jack signal (am gonna go to the store for a new MM tomorrow), so I don't have to worry about testing it with a generic headphones first? Also, what are the tests I need to do to see if I haven't messed up those infamous MOSFETs? I read alot around this thread that breaking them is about the most common problem when something is wrong.

 Thank you alot everyone 
	

	
	
		
		

		
		
	


	



 Dries


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## tomb

Great minds think alike, equalizer! 
	

	
	
		
		

		
		
	


	







 Let's hope Mr. Llama finds whatever it is - soon.


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## tomb

We're all posting over ourselves, now. No worry - all the merrier and maybe it'll him get it fixed.

 Llama - I wouldn't measure those MOSFETs if I were you. There's too much chance of shorting them when the power is on. If they're heating up the heat sinks, that sounds like they're working just fine - better leave well enough alone, especially with that meter.

 The meter might be good enough to read offset at the headphone jack, though, and the fact that it reads higher than it should would add to the safety factor. People do this different ways, but I think it's fine to simply put your black (common) probe to the front headphone jack contact, then alternately measure to the other two contacts. You should set your meter to measure DC millivolts. If you measure somewhere around 5mV or less, I'd say it's fine to plug your headphones in and see if you can hear music.

 Alternately, many of us use a cheap headphone that we've gotten from a cheap CD player, kid's toy, throw-away, etc. It's possible your corner drugstore might have one for $5 or less if you don't. You don't need quality to do a gut check on the amplifier - just enough to let you know there's no huge pops or static that could blow out a nicer headphone.

 Let us know what you find - just be careful of that thing while dissassembled. You've done a nice job. I'm sure you'll spot the problem eventually, so it would be tragic to short something out now and do some real damage.


----------



## Llama16

Succes! 
 I powered up the amp, put the mm on 200mVDC, then the black lead on the ground of the headphone jack and the red one on left and then right. i get a reading of 1.8 ish.
 I'm thrilled, Now let's hope that I don't get a short again when assembling because I still can't find where it came from.

 Ok not so succes.
 As Equalizer said, I tried to assemble it, and test it everytime I advance. When sliding it back in, the same short happened.
 I took it out and nothing, wouldn't work. Now (5mins later), it works again... This Thing is instable, and I can't find it.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Great minds think alike, equalizer! 
	

	
	
		
		

		
		
	


	







 Let's hope Mr. Llama finds whatever it is - soon.
	

	
	
		
		

		
		
	


	


_

 









  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>

 Llama - I wouldn't measure those MOSFETs if I were you. There's too much chance of shorting them when the power is on. If they're heating up the heat sinks, that sounds like they're working just fine - better leave well enough alone, especially with that meter.

 <snip>

 Let us know what you find - just be careful of that thing while dissassembled. You've done a nice job. I'm sure you'll spot the problem eventually, so it would be tragic to short something out now and do some real damage._

 

x2 . No need to measure those voltages now that the amp is known to work.

  Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Succes! 
 I powered up the amp, put the mm on 200mVDC, then the black lead on the ground of the headphone jack and the red one on left and then right. i get a reading of 1.8 ish.
 I'm thrilled, Now let's hope that I don't get a short again when assembling because I still can't find where it came from._

 

Congratulations ! Now get some cheap headphones and play some music *before* you case the amp again. That way you'll be sure it works OK and won't have to dissasemble it again in case it does not.

 Again, case it step by step, and test. That'll lead you to the short. Patience is your greatest ally here; the tinyest, most simple bugs are the hardest to hunt down.

 cheers!


----------



## Llama16

you beat me to editing my own reply, equalizer 
	

	
	
		
		

		
		
	


	




. my bad though, I should've made a seperate post.


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_you beat me to editing my own reply, equalizer 
	

	
	
		
		

		
		
	


	




. my bad though, I should've made a seperate post._

 

Just a thought - but you know, we're only assuming it's a short. Maybe you've got a dodgy solder connection and as the wires get folded into the case, it comes loose and the amp loses power. It could even be that the terminal block screws are not screwed down hard enough. Check that and check the bottom of the board - especially those pins on the terminal block to see if there's any solder connection that's loose. Go ahead and wiggle stuff and see if you can see a pin move within a solder joint.

 EDIT: Also check the connections on the power socket - wiggle those and see if the solder connections are tight.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just a thought - but you know, we're only assuming it's a short. Maybe you've got a dodgy solder connection and as the wires get folded into the case, it comes loose and the amp loses power. It could even be that the terminal block screws are not screwed down hard enough. Check that and check the bottom of the board - especially those pins on the terminal block to see if there's any solder connection that's loose. Go ahead and wiggle stuff and see if you can see a pin move within a solder joint.

 EDIT: Also check the connections on the power socket - wiggle those and see if the solder connections are tight._

 

x2

 Less likely but also possible: a cable broken on the inside, making intermittent contact when moved around.

 cheers!


----------



## Llama16

OK, I slid it into place and there's no short, the Tube leds go on as they should. Heatsinks till heat up (not alot, though they're warmer then the rest of the case) and the tubes seem to work.

 But what shoudl I do now? Should I keep looking for what caused it or leave it be and keep testing it while I case it up.
 I actually thought about this for quite some time: What do you guys do when something unexplainable like this happens, and it goes over? Do you keep looking even if it doesn't happen anymore. Or do you stop questioning, be gratefull nothing is broke and hope that when enclosed nothing exterior can cause it anymore.

 And what if it happens again, can it cause harm if it happens while listening to my headphones?

 Dries


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_OK, I slid it into place and there's no short, the Tube leds go on as they should. Heatsinks till heat up (not alot, though they're warmer then the rest of the case) and the tubes seem to work.

 But what shoudl I do now? Should I keep looking for what caused it or leave it be and keep testing it while I case it up.
 I actually thought about this for quite some time: What do you guys do when something unexplainable like this happens, and it goes over? Do you keep looking even if it doesn't happen anymore. Or do you stop questioning, be gratefull nothing is broke and hope that when enclosed nothing exterior can cause it anymore.

 Dries_

 

It can literally be the way you case it up. Get it assembled and it works and the problem may never manifest itself again. I'm sort of stubborn, though, and will continue to look for something until I find it. Maybe take a break and look at it tomorrow? It's up to you. There are no moving parts inside, so if it works when you case it up this time - maybe shake it around gently once it's assembled. If it still works, forget about it. Chances are that it stays that way.


----------



## Llama16

you're right. Tomorrow is a new day.
 I'm already very glad that it hasn't caused any (so it seems at least) non-temporary damage, and that the offset is good.
 I shone a flashlight from the back and I didn't see anything coming close to the case at all.
 I'm just really unsure what would happen if it does happen when listening to headphones. 

 Troubles for tomorrow.
 I'd already like to thank you and equalizer alot for your support and help. You guys are pretty patient with me


----------



## Fishline

Since I have ordered enough parts to build two, I started (and finished) my second Starving Student amp with the caps specified in the modified schematic, this time even with WIMA MKPoutput bypass caps. However, I have a strange problem. The amp powers up fine. The junction between R1/R2 and between R7/R8 both reads around 46v as specified in the schematic. However, pin 3 in the right channel takes a couple of minutes to reach 19v (and the tube in that channel takes about that long to reach full brightness), while the left channel shows 19v right after power up.

 I get no sound in the right channel, while the left channcel works just fine, even after the voltage at pin 3 reached 19v in the right channel.

 Will post pics tomorrow. Any hints/clues? Thanks in advance!

 Fishline


----------



## tomb

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Since I have ordered enough parts to build two, I started (and finished) my second Starving Student amp with the caps specified in the modified schematic, this time even with WIMA MKPoutput bypass caps. However, I have a strange problem. The amp powers up fine. The junction between R1/R2 and between R7/R8 both reads around 46v as specified in the schematic. However, pin 3 in the right channel takes a couple of minutes to reach 19v (and the tube in that channel takes about that long to reach full brightness), while the left channel shows 19v right after power up.

 I get no sound in the right channel, while the left channcel works just fine, even after the voltage at pin 3 reached 19v in the right channel.

 Will post pics tomorrow. Any hints/clues? Thanks in advance!

 Fishline_

 

Try switching the tubes and see if it does the same thing.


----------



## Fishline

I did try swapping tubes, but the problem stays with the right channel, so it's not the tube. One more thing: the DC offset on the left is under 5mV, but the right will start at around 60mV and gradually come down to below 5mV, as the voltage on pin 3 of that channel climb up to 19V.

 Here are some pics.


----------



## Fishline

Clarification: The problematic channel is the one near the top of the pictures in the first two pics, and the one on the left in the 3rd picture.


----------



## Llama16

I feel like interrupting again, but I just couldn't waite sharing my succes 
	

	
	
		
		

		
		
	


	



 I slid the amp back in the case and haven't yet screwed on the front and backplate, but as my DC offset was only 1.2mvolt after half a minute, I plugged in my HD650.
 An amazing little amp 
	

	
	
		
		

		
		
	


	




 I understand it when some say that the caps need a burn in period because when I left it running for about 2 hours or so I recongised quite bit of difference from the first few minutes. 

 Allthough I do recognise that the right channel is significantly louder (not very very much, but you really feel it though, subtle). It becomes really clear when I compare it to my headphone straight from my ipod touch. I have set my rockboxed ipod for 13% more left channel volume to temporary kinda equalize them. Is there any way I can internally fix this? Because I don't really plan on using this solely with rockboxed ipods 
	

	
	
		
		

		
		
	


	




.
 Tomorow I'm gonna try some 'pinknoise' on it 
	

	
	
		
		

		
		
	


	




, so I can get a more accurate idea of how bad the imbalance is. I also read that I should try switching the tubes, or see if the effect is less when the pot is turned up more (signs of an imbalanced pot, I read). I'll be switching the tubes tomorrow (If the channel switches with them, I'll sue my spare set of tubes, so no worries there). Allthough, as far as I improfessionaly tested it, I can't really say that the effect doesn't lessen when I switch from 'low ipod volume, high pot volume' to 'high ipod volume, low pot volume', so I don't think it's an imbalanced pot.
 It's as if, when normally the singer is in the middle of my head, it's like as if he shifted more to the right.

 Is there any other test I could perform before casing up the amp? And is there a way to internally fix this (I heard of adding a resistor to the right channel to balance it, but yet again, I should know the exact grade of imbalance), if so I'll wait before boxing up the amp 
	

	
	
		
		

		
		
	


	




.

 BTW: I forgot to say, could it be the cable? I'll explain why. Right now i'm not having a mini to RCA cable at hand so I'm actually using like 3 crappy cables to comensate: First I got an RCA cable from the television (male on each side) connected to the amp. Then I got a selfmade 'female RCAs to female mini connector' to connect to the first cable. As las I got a mini interconnect (two times male) to make the last step towards my ipod. 
 I was making a (yep even trying to braid it 
	

	
	
		
		

		
		
	


	




) a mini male to RCAmales with some generic parts though, when I came to the genial idea to just use those 3 components for a while, to try the amp out. So maybe it's that.

 Also, are there any 'professional' ways to test the imbalance? I'm gonna try the pinknoise demo, switch the tubes.. but that's about all I can imagine.

 Thanks
 Dries

 AND A HAPPY NEW YEAR EVERYONE (4 hours to go here though 
	

	
	
		
		

		
		
	


	




)!!! You guys made my holiday 
	

	
	
		
		

		
		
	


	




 My best wishes, a good health, lots of luck and have fun the next year!
 *draws a partyhat*


----------



## Juaquin

I'd say 90% of channel imbalance comes from the pot used in this amp (Tom or someone can correct me, if wrong). As such, the way to fix this (short of using a better pot) would be to adjust the input resistors.


----------



## the_equalizer

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Since I have ordered enough parts to build two, I started (and finished) my second Starving Student amp with the caps specified in the modified schematic, this time even with WIMA MKPoutput bypass caps. However, I have a strange problem. The amp powers up fine. The junction between R1/R2 and between R7/R8 both reads around 46v as specified in the schematic. However, pin 3 in the right channel takes a couple of minutes to reach 19v (and the tube in that channel takes about that long to reach full brightness), while the left channel shows 19v right after power up.

 I get no sound in the right channel, while the left channcel works just fine, even after the voltage at pin 3 reached 19v in the right channel.

 Will post pics tomorrow. Any hints/clues? Thanks in advance!

 Fishline_

 

 Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_I did try swapping tubes, but the problem stays with the right channel, so it's not the tube. One more thing: the DC offset on the left is under 5mV, but the right will start at around 60mV and gradually come down to below 5mV, as the voltage on pin 3 of that channel climb up to 19V.

 Here are some pics._

 

Strange behaviour indeed. So if you've swapped the tubes and get sound from the left channel, I think we can discard a bad tube as the cause. 

 So that leaves us with the MOSFET. It's either fried or badly polarized. What's the voltage at the junction of R2 and R4 ? It should be around 23 volts (4 volts higher than the tube heater voltage). If it's not, check the values of the resistors, they should both be the same value. 

 HAPPY NEW YEAR EVERYONE !

 cheers!


----------



## tomb

X2 on what equalizer and Juaquin say. If you've confirmed that swapping the tubes has no effect, then it's in the circuit. You have to decide if you can live with it, or whether you need to make a change. I'd rather boost both input resistors to a higher value so that you can get the pot into a more channel-matched regime. IMHO, trying to assymetrically offset the input resistors is an exercise in futility - the balance will vary with the tracking of the pot.


----------



## SteveC89

Ok, so I am about to start my build, but I just realized I ordered 220uF capacitors instead of the 150uF specified. I noticed in the original BOM notes it says any value > 150uF. I was just wondering how the higher value caps might effect the sound.


----------



## Fishline

My first SS has 220uF caps. If you look at the "modified" schematic, the caps have even higher values (470uF and 680uF). Some had gone as high as 1000uF.

 Anyone has suggestion for my problem with no sound in one channel (posts 4381, 4383 and 4384 above)? I'd really appreciate the help!


----------



## Fishline

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Strange behaviour indeed. So if you've swapped the tubes and get sound from the left channel, I think we can discard a bad tube as the cause. 

 So that leaves us with the MOSFET. It's either fried or badly polarized. What's the voltage at the junction of R2 and R4 ? It should be around 23 volts (4 volts higher than the tube heater voltage). If it's not, check the values of the resistors, they should both be the same value. 

 HAPPY NEW YEAR EVERYONE !

 cheers!_

 

Apologies: Don't know how I could have missed this post. Also, it really should be the left channel in the schematic that's giving me problem. I measured the voltage between R8 and R10, and again, it slowly rose to 22.6v, while between R2 and R4 the voltage is at 22.8v at power on. Both heatsinks get hot, too. If a MOSFET is fried, it wouldn't heat up, would it? Any way to test the mosfet? I do have a couple more spare MOSFETs, but swapping it would be quite a bit of work...

 Happy New Year to everyone, too!!


----------



## Fishline

Found the problem. After looking over the schematic again, I noticed I soldered the positive lead of C6 to the junction between R8 and R10, instead of R7 and R8. After correcting that, bingo!

 Thanks to all for helping!


----------



## Fishline

Found the problem. After looking over the schematic again, I noticed I soldered the positive lead of C6 to the junction between R8 and R10, instead of R7 and R8. After correcting that, bingo!

 Thanks to all for helping!


----------



## the_equalizer

Quote:


  Originally Posted by *Fishline* /img/forum/go_quote.gif 
_Found the problem. After looking over the schematic again, I noticed I soldered the positive lead of C6 to the junction between R8 and R10, instead of R7 and R8. After correcting that, bingo!

 Thanks to all for helping!_

 






 Great news! Enjoy your new amp!

 cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *SteveC89* /img/forum/go_quote.gif 
_Ok, so I am about to start my build, but I just realized I ordered 220uF capacitors instead of the 150uF specified. I noticed in the original BOM notes it says any value > 150uF. I was just wondering how the higher value caps might effect the sound._

 

This is my understanding of what increased cap values does in the MSSH.

 In the C3 and C5 positions higher value caps will extend the lower end frequency response with lower impedance 'phones. As mentioned in another post some have put 1000uF caps here. The only possible downside to this is that this will also increase the strenght of the turn on/off thump.

 Higher values for C1, C6 will improve the power supply filtering/decoupling thus producing a tighter, less sagging sound in loud transients.

 cheers!


----------



## Llama16

Good news and bad news! 
	

	
	
		
		

		
			




 Happy NEW YEAR GUYS!!!

 If you look back at my obnoxious post, I was complaining about a right channel that has an increased volume. I set the left channel to an additional 17 percent volume!!
 When i switched the tubes, the left channel was alot louder (also noticable do to that extra 15 percent). So it's the tubes!!!! The bad news is: it's the tubes... sigh, bummer.
 The good news is, I was so clever enough to order a second pare of tubes also from beezar before the kit (the tubes that are bad are from the kit). So hopefully they're better, else I'm screwed.

 Allthough I'm bummered that I know can't really make a second p2p standalone SSMH without constantly using the tubes of the kit. To bad the tubes are bad :S. A well i'm already glad that it's nothing else.

 Fingers crossed that the other tubes are better 
	

	
	
		
		

		
		
	


	




 I'll keep you posted.
 ATM I'm listening to the bad tubes still, allthough with the left channel increased in volume, it's amazing!! I'm stunned with the sound quality. It's my first experience of tubes... well my first experienced with a desktop amp even!!!

 I'll keep you guys updated.

 EDIT: SUCCES!! the second set of tubes (and actually alot prettier 
	

	
	
		
		

		
		
	


	




) are alot more balanced. I'll have to do with these two.
 For the p2p build, can I still use the 'bad tubes' and just install a resistor (as the balance unbalace is conistent


----------



## SteveC89

Ok, just finished my build and I'm having issues. So, when I turn on the amp with the source running, I can hear it slowly come up to volume, presumably as the tubes warm up. My problem is that full volume is only about unity gain with the original signal. Also, the tubes don't get hot at all, and the heat sink only gets maybe just above room temp. I know you guys like to have pictures of theses things, and I can probably post some soon, but in the meantime, any ideas?


----------



## tomb

Quote:


  Originally Posted by *SteveC89* /img/forum/go_quote.gif 
_Ok, just finished my build and I'm having issues. So, when I turn on the amp with the source running, I can hear it slowly come up to volume, presumably as the tubes warm up. My problem is that full volume is only about unity gain with the original signal. Also, the tubes don't get hot at all, and the heat sink only gets maybe just above room temp. I know you guys like to have pictures of theses things, and I can probably post some soon, but in the meantime, any ideas?_

 

When you say the tubes don't get hot, do they light up?

 The MOSFETs are supposed to be tied to the tube heaters. So if things don't get warm on both ends (tubes and heat sinks), something's wrong with those connections.

 Yeah, pics are needed ... although if it's P2P, you're the best one to find the problem first. Also, measure pin 3 on each MOSFET to Ground and see what you get.


----------



## Juaquin

Also, don't have headphones plugged in when you power up (if you like your headphones). It can damage them because there is a large DC offset until the capacitors charge and everything warms up.


----------



## SteveC89

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_When you say the tubes don't get hot, do they light up?_

 

Yes

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The MOSFETs are supposed to be tied to the tube heaters. So if things don't get warm on both ends (tubes and heat sinks), something's wrong with those connections._

 

Everything seems ok here

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yeah, pics are needed ... although if it's P2P, you're the best one to find the problem first. Also, measure pin 3 on each MOSFET to Ground and see what you get._

 

One thing I forgot to mention, it is a 12sr7 build.
 Ya, its P2P, and I figured to get anywhere I would need some pictures. 

 So I measured pin 3 to ground and only got 5.6v. I believe Logistic said this should be 12v. So, curious, I measured the r13/c6 node that is supposed to have 48v to ground and it was only at 27.7V. I measured the power supply to find that it was only supplying, suprise, 27.7v. 

 I am using the PSA18U prescribed in the original BOM. So, do you all think if I order another power supply that will fix my problem? For some reason, the seller I bought the PS from sent me a second PS. This one is 48v @ .2A. I know this is almost half the current of the other one, but would it be ok if I tested it out with this one, or would that fry something?

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Also, don't have headphones plugged in when you power up (if you like your headphones). It can damage them because there is a large DC offset until the capacitors charge and everything warms up._

 

I did not know that, thanks for the tip. I was sort of working off the idea from guitar tube amps that you could damage the tubes if there is no speaker hooked up. Do you know how this relates here?


----------



## Juaquin

I don't know much about guitar amps so I can't comment on that, but the SSMH website specifically warns against it:

  Quote:


 There are some precautions you should take while enjoying your SSMH:
 1. Wait until the tubes are glowing (the orange cathode, not the tube LED's!) before connecting your headphones.
 2. Disconnect your headphones prior to turning your SSMH off.

 The SSMH output is referenced at 19VDC. The output coupling capacitors prevent this DC from reaching the headphones, but there is a delay when turning on the amp before the caps fully charge. For similar reasons, you may experience a turn-off thump as well. So, #1 and #2 above are prudent precautions.


----------



## the_equalizer

Quote:


  Originally Posted by *SteveC89* /img/forum/go_quote.gif 
_Yes


 Everything seems ok here


 One thing I forgot to mention, it is a 12sr7 build.
 Ya, its P2P, and I figured to get anywhere I would need some pictures. 

 So I measured pin 3 to ground and only got 5.6v. I believe Logistic said this should be 12v. So, curious, I measured the r13/c6 node that is supposed to have 48v to ground and it was only at 27.7V. I measured the power supply to find that it was only supplying, suprise, 27.7v. 

 I am using the PSA18U prescribed in the original BOM. So, do you all think if I order another power supply that will fix my problem? For some reason, the seller I bought the PS from sent me a second PS. This one is 48v @ .2A. I know this is almost half the current of the other one, but would it be ok if I tested it out with this one, or would that fry something?


 I did not know that, thanks for the tip. I was sort of working off the idea from guitar tube amps that you could damage the tubes if there is no speaker hooked up. Do you know how this relates here?_

 

A 0.2 A power supply will not do it. EACH tube filament needs 0.15 Amperes. The current demand will overflow the PSU and it'll shut down. You need at the very least a .35 A PSU.

 It's amplifiers with transformer coupled output sections that get damaged if there's no load connected to their outputs (the transformer secondary winding). This includes not only guitar amps but also some headphone and speaker hi-fi amps. 

 The SSHM does not use a transformer to couple its output MOSFETs to the 'phones and thus it's immune to this kind of damage, as are most (though not all) amplifiers with solid state output sections.

 cheers!


----------



## SteveC89

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_A 0.2 A power supply will not do it. EACH tube filament needs 0.15 Amperes. The current demand will overflow the PSU and it'll shut down. You need at the very least a .35 A PSU.

 It's amplifiers with transformer coupled output sections that get damaged if there's no load connected to their outputs (the transformer secondary winding). This includes not only guitar amps but also some headphone and speaker hi-fi amps. 

 The SSHM does not use a transformer to couple its output MOSFETs to the 'phones and thus it's immune to this kind of damage, as are most (though not all) amplifiers with solid state output sections.

 cheers!_

 

Thanks for the info. That makes sense about the output transformer.

 BTW to all I have a new power supply on its way and I'm crossing my fingers that that will fix it.


----------



## th3bl0b

Hi,

 This is my first post here. I've been reading along and finding this thread really useful! I've been trying to build the SS in a P2P version. For the MOSFETS and heatsinks, am I supposed to connect these with a special adhesive like arctic silver? the MOSFETS came with some special sticker. Should that do the trick?

 Also, are the kits still being sold or have you stopped making those? (I was thinking of using a kit to make another one after I finished making it P2P : p)

 Thanks,
 Ben


----------



## th3bl0b

Hi,

 This is my first post here. I've been reading along and finding this thread really useful! I've been trying to build the SS in a P2P version. For the MOSFETS and heatsinks, am I supposed to connect these with a special adhesive like arctic silver? the MOSFETS came with some special sticker. Should that do the trick?

 Also, are the kits still being sold or have you stopped making those? (I was thinking of using a kit to make another one after I finished making it P2P : p)

 Thanks,
 Ben


----------



## Llama16

Hello

 Yes, Arctic silver should do the job extremely well. I think there are some other thermal compounds that are more suitable for the job in terms of use and finish, but I used some könig compound myself and I feel the case warm up just as much as the heatsinks which means that it has an excellent thermal conductivity.

 I'm not sure about the sticker tomb'll know for sure. I don't know if it's already applied to the mosfet and sticks or it came sperately. It's probably indeed thermal pads, but you should be sure on that. Maybe it's mentioned on some data sheet of the product.

 About the kits, If I recall correctly, I've read that tomb mentioned a final run for the kits. When, how many and if it's still on, you should ask him 
	

	
	
		
		

		
		
	


	




. 

 Welcome to head-fi and the world of DIY, enjoy!

 BTW: To the rest: I owe you guys some pics about my build 
	

	
	
		
		

		
		
	


	




, it's finally completely cased up and all the little buggers are out of it. I know you've seen these same pics over and over again (it's the same kit), but don't you try and mess with my chance of glory 
	

	
	
		
		

		
		
	


	




 hehe. the 'post your builds...' thread will hear from me as well 
	

	
	
		
		

		
		
	


	




.


----------



## tomb

Right now, it looks like there may be 35 kits and perhaps 2-3 partial kits available late-January to early-February time frame. They should be the same price, but I can't guarantee. I'll have to compare the pricing, but everything is ordered or already delivered - I just haven't compared that to the existing BOM. As most of you know, some of the prices on electronic parts are changing as we speak.

 There's another thing that bears repeating - tubes will go by first come, first serve basis. What I mean by that is that there aren't enough tubes to provide matching in all cases. You need about 3X tubes to provide 1X matched pairs. There aren't that many left anymore. So, we'll practice the following order until the stock gets depleted, based on first-come, first-serve:

 1. regular matches first - brand, construction, and testing; 
 2. tube construction and test matching;
 3. just construction matching;
 4. two tubes - pot luck.


----------



## th3bl0b

Thanks for getting back to me so quickly!

 The sticker thing I got was included in this heat sink mounting kit in the BOM. So, will that work? otherwise, i'll have to go out and buy some more stuff...

 I've finally understood how much of a pain it is to go ahead and do the casework yourself especially when you don't have a machine shop.


----------



## tomb

Quote:


  Originally Posted by *th3bl0b* /img/forum/go_quote.gif 
_Thanks for getting back to me so quickly!

 The sticker thing I got was included in this heat sink mounting kit in the BOM. So, will that work? otherwise, i'll have to go out and buy some more stuff...

 I've finally understood how much of a pain it is to go ahead and do the casework yourself especially when you don't have a machine shop._

 

Yes, the "sticker thing" will work. Just don't torque down on the MOSFET so much that the metal tab cuts into the "sticker thing."


----------



## d34dh0r53

Does anyone happen to know which post number host the modified schematics? Is it worth it? I built an original point to point from Pete's site, but I'm going to build one for my dad and I'm wondering whether I should stick to the 'O' or use the modified schematics?

 thx


----------



## dsavitsk

Schematics are at SSMH Overview

 The differences are pretty minor, and on a PTP version can be installed/removed in about 3 minutes.


----------



## Llama16

Hey everyone 
	

	
	
		
		

		
			





 As promised, I'll post a pic of the finished product. As I said before it's rather boring because it looks the same anyway 
	

	
	
		
		

		
		
	


	




. But I'm proud of it. I'd like to thank Tomb and equalizer alot for the help they gave me with this. It's my first real amp I built besides my Cmoy.

 I couldn't wait for taking the pic, I would have liked the afternoon light better in the picture. It's made with some compact camera that's over 5 years old and doesn't like closeups. It'll do.






 I'm glad of the color.
 Dries


----------



## tomb

Hey now - that pic looks great!! It's pretty difficult to get a good pic that shows the details of the amp, but at the same time shows off the LEDs to good effect. Your pic does both!

 I like the green, too. Blue is most popular, but those ocean green LEDs are really nice for a change of pace and not a color that you see very often.
	

	
	
		
		

		
		
	


	




 Good work!!


----------



## Llama16

Thanks for the compliments, I hope I could get myself in a little bit of semi-professional photography someday.

 I just couldn't leave but noticing something amazing about this amp. I was listening to This Was from Jethro Tull and I can't remember the exact song, but I heard the subtle clapping of the valves on the cross flute and his detailed breathing, what a feeling 
	

	
	
		
		

		
		
	


	




 But now I'm already looking for a next build ofcourse 
	

	
	
		
		

		
		
	


	




. I'm learning about the working of tubes (which equalizer recommended me to) and everything is going smoothly. I was suggested the SOHA amp, which I actually have thought about myself. Allthough I haven't got into reading about it thoroughly so I don't know the 'differences in sound'/'advantages' over the SSMH.
 I also considered the PIMETA v2 of Tangent which I have been waiting for, allthough I don't have the courage to get myself into learning about opamps without knowing how the first amplificating component, tubes, work. I also don't feel like a build which just means soldering components on the right pads. Allthough I already have the MINI³ parts partially, because I actually long for a little more advanced portable amp over my Cmoy.

 The chance of making another 'little different' SSMH is very real, as I heard from equalizer that the 12AU7 tubes are almost everywhere available and cheap, and I haven't used any spare parts for this SSMH, so i'll have most of it. I might even 'dare' to get myself in messing around with the capacitor values as I'm reading about them.

 But what are your opinions on this? Any suggestions on a educating/next step amp that isn't yet to complex with maybe an even a little more advanced sound over the SSMH?

 Kind regards,
 Dries


----------



## tomb

Sorry, Dries -

 Many of us have definite opinions and suggestions for other amps, but I'd rather keep it out of the SSMH thread. It's kind of counter-productive and will lead to gobs of comparisons with the SSMH, which I don't think is fair to this thread or the amp.

 It's best to create a new thread in the open DIY space and ask that question. Others will feel more free to offer suggestions that way, anyway.


----------



## th3bl0b

That looks awesome! Good work! I hope that mine will look remotely like that some time in the future...


----------



## Llama16

Thanks alot for the compliment th3bl0b. Enjoy your own build, it's alot of fun to build it, and I wish I could do over mine already 
	

	
	
		
		

		
		
	


	




.

 I'm sorry Tomb, I now recall the same reaction when people asked comparisons before, and I completely agree, the thread would get caught up. I didn't think further then my nose was long, and got a little carried away. My apologies 
	

	
	
		
		

		
		
	


	




.

 I'll be creating the thread as soon as possible, be sure to stop by, I'm curious what you think as well and maybe any suggestions.

 Kind regards, 
 Dries


----------



## tomb

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Thanks alot for the compliment th3bl0b. Enjoy your own build, it's alot of fun to build it, and I wish I could do over mine already 
	

	
	
		
		

		
		
	


	




.

 I'm sorry Tomb, I now recall the same reaction when people asked comparisons before, and I completely agree, the thread would get caught up. I didn't think further then my nose was long, and got a little carried away. My apologies 
	

	
	
		
		

		
		
	


	




.

 I'll be creating the thread as soon as possible, be sure to stop by, I'm curious what you think as well and maybe any suggestions.

 Kind regards, 
 Dries_

 

No problem. There are a lot of good amps out there that you can build. I don't think I will voice opinions in that thread, though - as a MOT, that's not really a good thing to do. You are welcome to PM me, though.


----------



## simwells

Trying to work out what parts I want for my build, heat sink wise how much does size matter?! Also when there is an outline dimension listed on a website is this the footprint?

 Also do you think this could all be fitted into an enclosure that's roughly 100mmx60x50mm?

 And finally! How would you go about wiring in LEDs that would be constantly on whilst the unit is? To illuminate the tubes or similar, my electronics knowledge is very limited fine with the practical side and can read schematics but get a bit lost especially having to alter them.


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Trying to work out what parts I want for my build, heat sink wise how much does size matter?!_

 

It matters a lot - more mass, more exposure to the air, etc.
  Quote:


 Also when there is an outline dimension listed on a website is this the footprint? 
 

I'm not sure what you mean by this, can you give us an example? Actually, I can't think of any reason that an outline dimension wouldn't be the footprint - assuming that's the part you're using for the base (as in "footprint"). I suppose there could be an outline drawing of the side, but then that wouldn't be a footprint.
	

	
	
		
		

		
		
	


	



  Quote:


 Also do you think this could all be fitted into an enclosure that's roughly 100mmx60x50mm? 
 

I'd say that's way tight. Most likely, user rds's version that he builds for Whiplash Audio (MiniMillett) is about as small as you can get, point-to-point. I'm sure people can build them smaller if they're really ingenious, but that varies most likely.
  Quote:


 And finally! How would you go about wiring in LEDs that would be constantly on whilst the unit is? To illuminate the tubes or similar, my electronics knowledge is very limited fine with the practical side and can read schematics but get a bit lost especially having to alter them. 
 

All of the LED wiring that we design and recommend uses the amp power for LED power. I'm not sure how else you'd do it unless you used batteries. Certainly, the LED circuit is independent of the tubes if you wire them using amp power (typical).


----------



## simwells

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_It matters a lot - more mass, more exposure to the air, etc._

 

Well what is the easiest way to work out if a heatsink would be adequate? The thermal resistance?

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not sure what you mean by this, can you give us an example? Actually, I can't think of any reason that an outline dimension wouldn't be the footprint - assuming that's the part you're using for the base (as in "footprint"). I suppose there could be an outline drawing of the side, but then that wouldn't be a footprint.
	

	
	
		
		

		
		
	


	


_

 

I mean I'm looking at heatsinks that fan outwards and so the footprint that it actually sits on is smaller than the fanned out dimensions.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'd say that's way tight. Most likely, user rds's version that he builds for Whiplash Audio (MiniMillett) is about as small as you can get, point-to-point. I'm sure people can build them smaller if they're really ingenious, but that varies most likely._

 

Do you have any idea of what you would consider to be roughly the minimum size to be then?


----------



## SteveC89

I got my new power supply yesterday and everything seems to be working, but I have a few questions for you.

 My question involves mosfet temp. So I did the 12sr7 build and I ordered the 1.5" heatsinks. I know for this build people recommended the 2" but I didn't see that till later. Anyway, the heatsinks get pretty hot. I put a meat thermometer on the heatsink and it reads between 50-55 degrees Celcius (~125-130 Fahrenheit). Could these temperatures harm the mosfets?

 This is probably silly, but how bright should 12sr7gt glow? I am used to guitar tubes and those things can put out some light, but I was a little disappointed with the little dot of light at the top. Is this about what other people have seen? 

 Also, I bought the lighted version of the switch in the original BOM (mouser# 540-RRA32H3BBRLN), but I can't figure out how to make it work. Anyone see what I'm missing here?

 Here are some pics of the finished build (and no, the speaker in there is not hooked up...yet):
http://i72.photobucket.com/albums/i1...0/DSC00435.jpg

http://i72.photobucket.com/albums/i1...0/DSC00434.jpg


----------



## the_equalizer

Quote:


  Originally Posted by *SteveC89* /img/forum/go_quote.gif 
_I got my new power supply yesterday and everything seems to be working, but I have a few questions for you.

 My question involves mosfet temp. So I did the 12sr7 build and I ordered the 1.5" heatsinks. I know for this build people recommended the 2" but I didn't see that till later. Anyway, the heatsinks get pretty hot. I put a meat thermometer on the heatsink and it reads between 50-55 degrees Celcius (~125-130 Fahrenheit). Could these temperatures harm the mosfets?

 This is probably silly, but how bright should 12sr7gt glow? I am used to guitar tubes and those things can put out some light, but I was a little disappointed with the little dot of light at the top. Is this about what other people have seen? 

 Also, I bought the lighted version of the switch in the original BOM (mouser# 540-RRA32H3BBRLN), but I can't figure out how to make it work. Anyone see what I'm missing here?

 Here are some pics of the finished build (and no, the speaker in there is not hooked up...yet):_

 

Good to hear the new power supply got your amp working! Congratulations!

 Different tubes light up differently, even different makes of the same tube do. I think it was user Juaquin who mentioned that the 19J6 tubes he got had enclosed heaters and barely gave out any light. You could try other 12SR7's to see if those shine a bit more. 

 As temperature goes, 55° C won't damage the MOSFETs. I recall reading a post mentioning that 60° C is the maximum temperature that you'd want to have. Remember that with 12 volt heater tube builds (like yours) the MOSFETs get more voltage and thus get hotter than with the 19J6 version. Finally, it is still worth pointing out that the cooler the MOSFETs work the longer they'll live

 cheers !


----------



## tomb

Quote:


  Originally Posted by *SteveC89* /img/forum/go_quote.gif 
_<snip>

 Also, I bought the lighted version of the switch in the original BOM (mouser# 540-RRA32H3BBRLN), but I can't figure out how to make it work. Anyone see what I'm missing here?_

 

Unfortunately, according to the data sheet (http://www.cherrycorp.com/english/ro.../RR_Series.pdf), the "L" designates a lamp rated for 125VAC. There's probably not enough voltage in the 48VDC power supply to light it up.


----------



## Fishline

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Well what is the easiest way to work out if a heatsink would be adequate? The thermal resistance?_

 

If you can find some old PCs, the heatsink for probably anything Pentium or later would be sufficient. In my second p2p build I used one cpu heatsink for both MOSFETS.

  Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_I mean I'm looking at heatsinks that fan outwards and so the footprint that it actually sits on is smaller than the fanned out dimensions.

 Do you have any idea of what you would consider to be roughly the minimum size to be then?_

 

My 2nd and 3rd builds used this case:
small aluminum project case 113x70x25
 (Similar cases can be found on eBay at similar prices, but with free shipping.) It was pretty tight, but manageable if you do careful planning. A month or so ago in the for sale forum someone sold a Starving student that's really small, barely any space left after tube sockets and heatsinks.

 The pictures of my 2nd & 3rd p2p build can be found here:
2nd p2p build with CPU heatsink
3rd SSMH, with corrected wiring mentioned a few posts down

 Good luck!


----------



## Juaquin

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Different tubes light up differently, even different makes of the same tube do. I think it was user Juaquin who mentioned that the 19J6 tubes he got had enclosed heaters and barely gave out any light.!_

 

This is correct - the heating elements are enclosed in my two Raytheon tubes. I have to get my line of sight just right to see the heater elements. If there weren't any LEDS there would be barely any light coming out of them. I also have a pair of the RCAs (I believe) that I'm using for a second build and those heaters are exposed.


----------



## simwells

Think I'm down to one last question!

 It's about heatsinks again, is it possible to glue them directly to the caseing? Otherwise can they just be screwed in place. Is there anything I'd need to be wary of if I did so?


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Think I'm down to one last question!

 It's about heatsinks again, is it possible to glue them directly to the caseing? Otherwise can they just be screwed in place. Is there anything I'd need to be wary of if I did so?_

 

I think screws would be better than glue for longevity. You just need to be concerned that the MOSFETs are fully insulated from the case and the heat sinks - and the wire leads.


----------



## meme

Just thought I'd post some pictures of my effort that I made over the Christmas holidays ~







 This is my first go at any sort of DIY electronics, it's the Beezar kit in my own enclosure. I must say that it sounds pretty good, very impressed.











 So, thanks to tomb & dsavitsk for putting this excellent kit out there!


----------



## scompton

Beautiful


----------



## meme

Cheers scompton ~

 It's amazing what you can do with some old bits of plywood lying about.


----------



## simwells

Last bit of a stupid question but, LED choice if I want blue to light up tubes and as indicators what should the max voltage on them be?


----------



## Llama16

Wow nice job meme, that's a beauty of a case.


----------



## scompton

Quote:


  Originally Posted by *meme* /img/forum/go_quote.gif 
_Cheers scompton ~

 It's amazing what you can do with some old bits of plywood lying about._

 

From the pics of the top it looks like a block of wood. Did you miter the top to the sides?


----------



## meme

Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_Wow nice job meme, that's a beauty of a case._

 

Thanks Llama16, glad you like it!

  Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_From the pics of the top it looks like a block of wood._

 

That was the effect I was after - but I just glued the sides to the bottom of the top piece and covered the sides in the veneer cut from the same plywood, I only mitered the four corner joints.

 Basically I just cut along the length of a piece cut slightly larger than needed, around 1/8 in from the surface - you could use a band saw to do this - then (very) carefully sand down from behind the back of the veneer to remove what's left of the glue/wood and Hey Presto! you have your veneer. 

 It would probably be much easier working with solid wood, but it's what was available to me at the time and the box is quite small, so wasn't much trouble.


----------



## revolink24

Anyone have any ideas as to why tapping one of my tubes sometimes results in an EXTREMELY loud cracking sound?


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Last bit of a stupid question but, LED choice if I want blue to light up tubes and as indicators what should the max voltage on them be?_

 

I had an explanation, but it seems that Head-Fi dropped off line right when I was posting it.

 Suffice to say we've already done the work for you. For two high-brightness LED's, the resistor we've spec'd in the SSMH BOM is the right one for the voltage and about 10ma a piece. The kicker is that it needs to be sized for the right wattage. We normally size resistors for power ratings of 2X (close to the board, no air circulation, etc.) for safety. You'll need a 2W resistor:
SSMH Bill Of Materials


 EDIT: 2 LED's at 10ma each, R = 48/0.02 = 2.4K. P = 48 * 0.02 = 0.96W, or 2W for safety's sake.


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Anyone have any ideas as to why tapping one of my tubes sometimes results in an EXTREMELY loud cracking sound?_

 

There's a loose connection somewhere around the pins and the socket, or the tube is bad. Switching tubes will tell you very quickly if it's the tube.


----------



## UKToecutter

Hello

 My first post on Head-Fi.

 Great Project. I've actually read all 296 pages over the last few days (yeah, sad, I know).

 Looking forward to the release of another batch of kits by Beezar.

 TomB. When I order, can I have Ocean Green LED's please?


----------



## tomb

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Hello

 My first post on Head-Fi.

 Great Project. I've actually read all 296 pages over the last few days (yeah, sad, I know).

 Looking forward to the release of another batch of kits by Beezar.

 TomB. When I order, can I have Ocean Green LED's please?

_

 

Absolutely!! Just remember to note it in the Beezar invoice when the time comes.


----------



## Juaquin

Now I just have to figure out a way to make a socket for the LEDs within the tube socket so I can change them out at will. Gotta see that ocean green in person, given all the fuss everyone's making over them


----------



## the_equalizer

Quote:


  Originally Posted by *meme* /img/forum/go_quote.gif 
_Just thought I'd post some pictures of my effort that I made over the Christmas holidays ~

 This is my first go at any sort of DIY electronics, it's the Beezar kit in my own enclosure. I must say that it sounds pretty good, very impressed.

 So, thanks to tomb & dsavitsk for putting this excellent kit out there!_

 

VERY nice looking! What a clean build! Congratulations !

 cheers!


----------



## meme

Thank you for your compliments equalizer

 I'm very tempted to have a go at a point to point version, should be able to fit it in that spare Hammond case I guess.


----------



## simwells

Would there be any complications with using this as a switch?

BULGIN|MP0045/1E2BL012|SWITCH, FLUSH LATCHING, BLUE ILLUM | Farnell United Kingdom


----------



## duckbutter

How does this amp compare in sound to the Hifiman EF2 form head-direct?
Head-Direct.com | YUIN

 I was originally saving up to by an EF2, but since discovering this thread was wondering if it would be worth it to save a couple bucks and build one for myself.


----------



## the_equalizer

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Would there be any complications with using this as a switch?

BULGIN|MP0045/1E2BL012|SWITCH, FLUSH LATCHING, BLUE ILLUM | Farnell United Kingdom_

 

From looking at the specs it seems it'd work very nicely. It's rated for 250 V @ 3A and the SSMH supply is only 48 V @ ~.35A

 cheers!


----------



## Juaquin

Quote:


  Originally Posted by *duckbutter* /img/forum/go_quote.gif 
_How does this amp compare in sound to the Hifiman EF2 form head-direct?
Head-Direct.com | YUIN_

 

TomB has mentioned several time (most recently, two pages before this one) that he would prefer not to discuss comparisons between the SSMH and any other amps in this thread - mostly because it could appear to be a biased comparison and we don't want to put down any other amps. You would probably have better luck posting in the Amps sub-forum and telling them what you listen to and asking what the best amp would be for your application.


----------



## simwells

Would it be possible to use a Pot similar to the one in the AMB mini^3 to act as a volume control and on/off. If so is there an example of exactly what I'd be looking for, I find pots are surprisingly complex!


----------



## Juaquin

Yes, you can use a pot with an on/off switch. Of course, it wouldn't fit on the PCB, but if you're doing your own P2P build, go for it! I don't know any quality pots offhand that have an on/off switch besides the ALPS RK097 used in the Mini3, but I'm sure someone will have suggestions.


----------



## simwells

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Yes, you can use a pot with an on/off switch. Of course, it wouldn't fit on the PCB, but if you're doing your own P2P build, go for it! I don't know any quality pots offhand that have an on/off switch besides the ALPS RK097 used in the Mini3, but I'm sure someone will have suggestions._

 

Yeah would indeed be for a P2P build so any recommendations would be fantastic!


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_ Quote:


  Originally Posted by *duckbutter* 
How does this amp compare in sound to the Hifiman EF2 form head-direct?
 Head-Direct.com | YUIN

 I was originally saving up to by an EF2, but since discovering this thread was wondering if it would be worth it to save a couple bucks and build one for myself.

 

TomB has mentioned several time (most recently, two pages before this one) that he would prefer not to discuss comparisons between the SSMH and any other amps in this thread - mostly because it could appear to be a biased comparison and we don't want to put down any other amps. You would probably have better luck posting in the Amps sub-forum and telling them what you listen to and asking what the best amp would be for your application._

 

Yes, Juaquin is correct. I'm probably unique in applying this discipline, but sorry - that's the way it is. Too many folk take advantage of Pete Millett's good heartedness in sharing designs and take advantage by discounting them. It's something that gets my blood boiling, so the self-imposed policy is more for my protection than anything else.
	

	
	
		
		

		
		
	


	







 Let me state this extraordinary claim, though (I'm not making specific comparisons): Everything we build over here in the DIY section is worth 2-3 times as much as any commercial amp - at least, the HeadDirect EF2 included.


----------



## amc

Hi everyone

 Looking for some basic advice on bench testing my PCB build Starving Student. Put it together over the holidays and its all cased up. But I get no LED lightup. Tubes dont heat up and it seems just plain old dead. Checked the power supply and it is providing 48.2 VDC. Measuring from pin 3 on the mosfet to lid mounting screw ground point I get just milivolts. Measuring from the B+ screw to the mosfet pin 3 I get 48 VDC. Infact measuring from B+ to any traceable destination when looking at the schematic and board layout I measure between 47.7 and 48.2 VDC. Any ideas what I screwed up? I need some pointers to get going on debugging this...

 Looking back, I did have trouble getting the LED leads through the holes in the PCB and had to pull them through with pliers. I also torqued down the mosfets before reading that I shouldn't as I could damage the burquist pads. I also got a fancy new Hakko 936 and was experimenting with heat settings especially when soldering the ground connections to try and speed up heating the ground plane but I don't think I would have damaged any parts. 

 Any pointers greatly appreciated


----------



## tomb

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_Hi everyone

 Looking for some basic advice on bench testing my PCB build Starving Student. Put it together over the holidays and its all cased up. But I get no LED lightup. Tubes dont heat up and it seems just plain old dead. Checked the power supply and it is providing 48.2 VDC. Measuring from pin 3 on the mosfet to lid mounting screw ground point I get just milivolts. Measuring from the B+ screw to the mosfet pin 3 I get 48 VDC. Infact measuring from B+ to any traceable destination when looking at the schematic and board layout I measure between 47.7 and 48.2 VDC. Any ideas what I screwed up? I need some pointers to get going on debugging this...

 Looking back, I did have trouble getting the LED leads through the holes in the PCB and had to pull them through with pliers. I also torqued down the mosfets before reading that I shouldn't as I could damage the burquist pads. I also got a fancy new Hakko 936 and was experimenting with heat settings especially when soldering the ground connections to try and speed up heating the ground plane but I don't think I would have damaged any parts. 

 Any pointers greatly appreciated_

 

The LED's are more or less independent of the rest of the circuit and as far as torquing down the MOSFETs - if that were the issue you'd short out the amp and your power supply would go to zero.

 We need some clear pics of the PCB.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The LED's are more or less independent of the rest of the circuit and as far as torquing down the MOSFETs - if that were the issue you'd short out the amp and your power supply would go to zero.

 We need some clear pics of the PCB.
	

	
	
		
		

		
		
	


	


_

 

x2. And from several different angles... Are you *sure* you did not reverse the connection from the power supply? Off the top of my head, the tip or center of the PSU connector is positive (B+) and the ring goes to ground.

 cheers!


----------



## kellvyn

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Right now, it looks like there may be 35 kits and perhaps 2-3 partial kits available late-January to early-February time frame._

 

Will there be any PCBs left over, and will they be available for purchase as a separate item? I was ready to buy one but missed my chance.


----------



## amc

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_x2. And from several different angles... Are you *sure* you did not reverse the connection from the power supply? Off the top of my head, the tip or center of the PSU connector is positive (B+) and the ring goes to ground.

 cheers!_

 

Hi Tomb / Equalizer,

 I checked. Tip is the red wire in the following pictures and its going to the B+ pad. I even reversed them and tried again and I get the same measurements just negative instead of positive. Here are a bunch of angles of the top and sides of the board. Did not detach the heatsinks but can if need be for more pictures of the underside and to start removing parts - sigh...

*Rear Panel Connections and wiring:*
Attachment 24610 Attachment 24611

*Board top and side:*
Attachment 24609 Attachment 24613

*Angles from sides and corners:*
Attachment 24614 Attachment 24615 Attachment 24616 Attachment 24617 Attachment 24618 Attachment 24619


----------



## tomb

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_Hi Tomb / Equalizer,

 I checked. Tip is the red wire in the following pictures and its going to the B+ pad. I even reversed them and tried again and I get the same measurements just negative instead of positive. Here are a bunch of angles of the top and sides of the board. Did not detach the heatsinks but can if need be for more pictures of the underside and to start removing parts - sigh..._

 

I can't fault your work from what I see in the pics - you've done a good job!

 However, it looks like maybe R13 is not soldered on one end - that's the resistor up against the power input terminal block. That resistor divides the voltage supply between the two tubes and may cause some of your symptoms if it's not soldered.

 A second suspicion is your tube LEDs. Those leads look awfully fat. I'm not surprised that it took a pair of pliers to get them through those tube socket holes.
	

	
	
		
		

		
			





 You may have an intermittent short if forcing them through did some damage. If R13 or any other resistor doesn't check out (check them all - for value, too), you might try de-soldering those leads, put some electrical tape on tips and see if that makes a difference when you turn the amp on.

 Take a look at those things and let us know.


----------



## gore.rubicon

Is there an easy way to turn off the tube LEDs on the PCB build without desoldering? and what are some boutique modifications i can do with the PCB build?


----------



## luvdunhill

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_Is there an easy way to turn off the tube LEDs on the PCB build without desoldering? and what are some boutique modifications i can do with the PCB build?_

 

does cutting wires count? that will definitely turn the tube LEDs off.

 As for modifications, are you only interested in mods that don't require desoldering?


----------



## dsavitsk

Quote:


  Originally Posted by *gore.rubicon* /img/forum/go_quote.gif 
_and what are some boutique modifications i can do with the PCB build?_

 

The two main ones I can think of are (1) replacing the plate load with a CCS of some sort (a LND150 could probably be made to work), and (2) you can probably DC couple the two stages together. The second one probably requires an adjustable cathode resistor, and a bit (perhaps a lot) of diligence in watching for tube drift. As a third (and fairly advanced -- don't try this unless you really know what you are doing) option, you can likely tie the cathode to the heater and run the heater current through Rk thus eliminating Ck and keeping rp in check. None of this has been tried, so it is definitely in the realm of experimentation.


----------



## the_equalizer

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_Hi Tomb / Equalizer,

 I checked. Tip is the red wire in the following pictures and its going to the B+ pad. I even reversed them and tried again 
 <snip>_

 

Whoa! Don't do that. I was just asking you to make sure 
	

	
	
		
		

		
		
	


	




 . In some circuits reversing the PSU polarity can severely fry stuff so... don't do it. 
	

	
	
		
		

		
		
	


	




 Great pics, thanks! As TomB says, check R13, one of the pads does look as if it weren't soldered. If that doesn't solve it... what's the voltage across R4 (and across R10) ?

 cheers!


----------



## sourced

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_





 Congratulations ! It is indeed a warm fuzzy feeling to watch those tubes light up and hear sweet music coming out of the 'phones!!

 About the hum, I've found some 19J6's to be much more susceptible to hum than others; specially if you use high sensitivity 'phones. Swap the tubes and see if the hum follows the tube. If it does, well: it's the tube that it's at fault.

 On the channel imbalance, indeed, the most 'general' solution would be to use a better pot 
	

	
	
		
		

		
		
	


	




. Short of that you can try adding a couple input resistors as done in the PCB version. Take a look at the schematic. This solution won't make the imbalance dissapear, but it'll make it much less noticeable. 

 cheers !_

 

Man, what a night! I decided to bite the bullet and fix this hum issue. I took your recommendation and soldered in some input resistors (2 33ks in series for each channel). I was putting the tubes back in and heard a spark/pop or something... so I turned it on and the right tube did not warm up! I thought I might have fried the tube (which is really the worst case scenario, as it seems past my extra 2 they are in short supply). I swapped l/r tubes and it wasn't the tube, though. I then went to measure the mosfet voltages (this part's funny), and things didn't seem off. I had left a little bit of lead showing right under the mosfet packaging (above my electrical tape). ~23v at gate, 48 at drain, and ... whoops I let the probe touch the drain and source. The mosfet didn't take too kindly, and the fried voltages were 8v at gate, 31v at source, or so. NOT so good. So I desoldered/resoldered/liberally applied electrical tape.

 The hum is now very minimal! Success. Thank you much, equalizer. I was worried for a second because I was hearing some hiss, but it's actually part of the music (!). 

 This did not magically make my pot better, as expected. Channel imbalance is about the same... I think I may be ordering parts for an M^3 soon (whoa there, I've just burned this in) so I can put an alps pot in there (we shall see). I'm looking on Mouser, is 688-RK27112A00AK the right kind? I realize it's 100kΩ instead of 50kΩ, but I don't see anything else on Mouser. If that's it, any recommendation on knobs? There appear to be thousands...


----------



## bhjazz

I have no idea when I started my P2P build. Obviously it was over a year ago. But then I moved, lost parts, found others...Gah! Anyway, my P2P build fired up on the first try last night. Sweet! The internals look like hell but it sounds great. And it obviously is quite powerful. I had eye-blinking tunes on last night for a very short time. Certainly power to spare which is fantastic. Once I get things cleaned up inside I'll post some pics. Lots of fun, and I had completely forgotten the total rush that is turning a creation on for the first time. Note to self: must get back to the amp backlog!

 I do have a subtle amount of channel imbalance. Not sure if it's tubes yet until I can take some more measurements. I'll swap tubes once I get this right-side up. 

 Thanks for a great design, Pete, and thanks for all the fantastic support I see you doing, tomb!


----------



## revolink24

Does anyone here have any good guides that they know of for handling the different braids of the wires inside the SSMH? I was just revisiting it to fix the rats nest of wires inside it.


----------



## Llama16

I found the litz braid on chimeralabs, allthough i think that the pictures don't correspond with the explenation. But it's still very do-able. It could also be my own fault ofvourse, so plz someone correct me if so


----------



## th3bl0b

I finished putting together my p2p but the tubes don't light up when i turn it on. are they supposed to? i don't have an input or anything going into them yet, cause i can't find a rca to 3.5 mm (i have one in my apartment but i'm somewhere else for christmas break)...


----------



## tomb

Quote:


  Originally Posted by *th3bl0b* /img/forum/go_quote.gif 
_I finished putting together my p2p but the tubes don't light up when i turn it on. are they supposed to? i don't have an input or anything going into them yet, cause i can't find a rca to 3.5 mm (i have one in my apartment but i'm somewhere else for christmas break)..._

 

Yes, the tubes are supposed to lightup. Better post some pics so we can take a look at what's going on.

 Are you able to measure whether there's power coming from the walwart when you turn it on? The Cisco power supply has a very good circuit protector. If you have a short in your amp, it will simply refuse to supply voltage. Measured separately and disconnected, it will appear to function just fine under those circumstances. Try and measure from the wires coming from your power socket on the amp and see if it's supplying voltage.


----------



## simwells

Still no one know of a suitable pot with in built switch?


----------



## tomb

Quote:


  Originally Posted by *simwells* 
_Still no one know of a suitable pot with in built switch?_

 

An RK097 would probably be a realistic option, but most are only available in 10K. You'd have to re-work your input resistor sizing accordingly. If you've used the PCB, the pin spacing is not going to match (there'd be more for the switch, anyway).


----------



## revolink24

Yes! I just managed to score 5 19J6s for $8 a pop on ebay. Should I keep them just to have (lots) of spares, sell them, or build another amp? Building another amp sounds redundant albeit fun. I could always build and sell one.


----------



## Juaquin

Do whatever your heart desires, but if you do decide to sell them be sure to let people know here - I'm sure many are looking for them.


----------



## th3bl0b

Oh, I thought about pictures, but the insides of it looks like spaghetti. 

 After a while, I realized that I had my rocker switch incorrectly wired. Nothing was getting through. There was no voltage between the ground and anything beyond the rocker, but once I took out the rocker. The tubes started to light up. Boy, that felt great when they did. I realized that all my work wasn't for anything!

 I'd put pics up, but my enclosure needs some work. I plan to try again as far as making an enclosure goes.

 Thanks for your help! Let me know when the kits are ready cause I'll definitely have to jump on that.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yes, the tubes are supposed to lightup. Better post some pics so we can take a look at what's going on.

 Are you able to measure whether there's power coming from the walwart when you turn it on? The Cisco power supply has a very good circuit protector. If you have a short in your amp, it will simply refuse to supply voltage. Measured separately and disconnected, it will appear to function just fine under those circumstances. Try and measure from the wires coming from your power socket on the amp and see if it's supplying voltage._


----------



## tomb

Quote:


  Originally Posted by *th3bl0b* /img/forum/go_quote.gif 
_Oh, I thought about pictures, but the insides of it looks like spaghetti. 

 After a while, I realized that I had my rocker switch incorrectly wired. Nothing was getting through. There was no voltage between the ground and anything beyond the rocker, but once I took out the rocker. The tubes started to light up. Boy, that felt great when they did. I realized that all my work wasn't for anything!

 I'd put pics up, but my enclosure needs some work. I plan to try again as far as making an enclosure goes.

 Thanks for your help! Let me know when the kits are ready cause I'll definitely have to jump on that._

 

Glad to hear you found the problem!


----------



## Entropy1

I was reading earlier in this or another thread about removing coupling caps on the source when going into an amp. It's possible I misunderstood this, but is this appropriate? Could I test the DC by having no audio playing, and measuring this directly? If this does turn out to be at least somewhat accurate, what would be a reasonable level that it should be under to do this? Would it be good to change the input pot or anything if I do this? Thanks for the help.


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_I was reading earlier in this or another thread about removing coupling caps on the source when going into an amp. It's possible I misunderstood this, but is this appropriate? Could I test the DC by having no audio playing, and measuring this directly? If this does turn out to be at least somewhat accurate, what would be a reasonable level that it should be under to do this? Would it be good to change the input pot or anything if I do this? Thanks for the help._

 

You may be stating this in the reverse. _Input_ caps on an amp may be deleted if the source is found to have no DC offset. However, the Starving Student uses NO input capacitors.

 As for the source, if the source is using _output_ caps, there is normally a reason - there's too much votage to subject to an amp or a load. There would be no reason to apply capacitors to the output of a source unless there is significant DC present. That certainly doesn't mean that you can remove them, though.

 I have heard of isolated instances where people used output caps just to "flavor" the sound, even if they weren't needed to block DC - but that's usually someone's idea of a mod and the evidence is obvious.


----------



## amc

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_...it looks like maybe R13 is not soldered on one end - that's the resistor up against the power input terminal block. That resistor divides the voltage supply between the two tubes and may cause some of your symptoms if it's not soldered._

 

Thanks tomb. I checked underneath and it does in fact have a solder volcano on the pin but it did not suck up through the hole. I must have been impatient and not heated the pad enough. I managed to get my iron between the cap and terminal block and apply some solder to the pad and lead on the top side. Hopefully thats got it if it was shorting or cold.

Attachment 24743

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_A second suspicion is your tube LEDs....If R13 or any other resistor doesn't check out (check them all - for value, too), you might try de-soldering those leads...Take a look at those things and let us know.
	

	
	
		
		

		
			



_

 


 I checked all the resistors for suspect joints again - everything else looks good with good wicking from the bottom. I checked the resistance of all of them. Here is what I measured:

 R1 33.07K
 R2 110.0K *
 R3 2K
 R4 120.0K *
 R5 2K
 R6 1.998K
 R7 33.01K
 R8 105K *
 R9 2K
 R10 108K *
 R11 2K
 R12 2K
 R13 2K
 R14 0.997K
 R15 0.998K
 R16 99.8K
 R17 99.9K

 Notice the ones with the Astrix (*). For the life of me I can not get an accurate reading of these 4 resistors. As soon as I put the probes down the meter drifts upwards from about 110 at a constant rate - never zeroing in on the expected value of 220K (markings on the resistors are 2203 so thats 220K right?) Its painful. I have left the probes down for close to 10 minutes and only reached 140 or so ohms. any explanation of this behavior?


  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_ Great pics, thanks! As TomB says, check R13, one of the pads does look as if it weren't soldered. If that doesn't solve it... what's the voltage across R4 (and across R10) ?_

 

So already Im weirded by R4 and R10 because of the resistance. Measuring B+ to one side of the resistor measures 48.1v and B+ to the other side of the resistor measures 47.6v consistent for both R4 and R10. So there is a 0.5v drop. Measuring with the probes directly across the leads of each resistor is a bit different. After measuring from B+ to the resistor leads I try and measure between the leads. I get about 4.5mV and it drops consistently so that after a minute I am down to 1.9mV

 So still stuck hopefully this helps in narrowing down the issue... fingers crossed.


----------



## tomb

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_Thanks tomb. I checked underneath and it does in fact have a solder volcano on the pin but it did not suck up through the hole. I must have been impatient and not heated the pad enough. I managed to get my iron between the cap and terminal block and apply some solder to the pad and lead on the top side. Hopefully thats got it if it was shorting or cold.

Attachment 24743




 I checked all the resistors for suspect joints again - everything else looks good with good wicking from the bottom. I checked the resistance of all of them. Here is what I measured:

 R1 33.07K
 R2 110.0K *
 R3 2K
 R4 120.0K *
 R5 2K
 R6 1.998K
 R7 33.01K
 R8 105K *
 R9 2K
 R10 108K *
 R11 2K
 R12 2K
 R13 2K
 R14 0.997K
 R15 0.998K
 R16 99.8K
 R17 99.9K

 Notice the ones with the Astrix (*). For the life of me I can not get an accurate reading of these 4 resistors. As soon as I put the probes down the meter drifts upwards from about 110 at a constant rate - never zeroing in on the expected value of 220K (markings on the resistors are 2203 so thats 220K right?) Its painful. I have left the probes down for close to 10 minutes and only reached 140 or so ohms. any explanation of this behavior?




 So already Im weirded by R4 and R10 because of the resistance. Measuring B+ to one side of the resistor measures 48.1v and B+ to the other side of the resistor measures 47.6v consistent for both R4 and R10. So there is a 0.5v drop. Measuring with the probes directly across the leads of each resistor is a bit different. After measuring from B+ to the resistor leads I try and measure between the leads. I get about 4.5mV and it drops consistently so that after a minute I am down to 1.9mV

 So still stuck hopefully this helps in narrowing down the issue... fingers crossed._

 

You can't measure resistances on a populated PCB. Too many of them are in parallel with other resistors or other items in the circuit, including capacitors that the DMM will charge and discharge as you found out.
	

	
	
		
		

		
		
	


	







 Unfortunately, it can be a meaningless exercise.

 It's best always to read voltages across the resistors on a populated board - or measure voltage at points with one probe at ground. Go back and try again.
	

	
	
		
		

		
		
	


	




 EDIT: Maybe the equalizer can make something of your voltage readings. The ~47.6 - 48V is close enough for my tastes, but it sounds like you're reading across a capacitor again on the other one.

 EDIT #2: I just looked at your pic and while dark, it appears that you may have torqued down the MOSFETs so much that it cut into the insulators. Going against what I just said about measuring resistances, with the amp OFF, try seeing if you get a resistance across the MOSFET tab and an unanodized part of the case. If you don't read infinite resistance or something similar, you may have shorted out the MOSFETs.


----------



## rauschie

Hello guys, I'm quite certain that I'm not the first one asking this, but I don't have time to read 300 pages, so If there is already an answer in the forum, please just link it then ignore me, but now let me have this absolutely lame question:
 I'm planning to build this amp, I already have the tubes and the mosfets (which are the most difficult parts to find in Hungary) so there's not much left to begin.
 The problem:
 At the moment, I'm using Senn HD555's, but as fast as I can afford, i'm going to change to 580's, 600's or 650's, so I want the amp to perform well both with the 300 ohm headphones and as well as the sensitive 555's, therefore I'm supposed to build in a gain-switch.
 The question itself:
 Which components do I have to replace, and what type of components do I have to use?
 As far as I could understand, I'm going to have to change some resistors or capacitors, or rather have two different type of them with a switc with which I can choose which to use.
 I'm quite a newbye at DIY electronics, so please have mercy on me and try to answer in an easy-to-understand way.
 Sorry for my bad english and Thanks for the answer!


----------



## Juaquin

Instead of a gain switch, it would probably be easier to switch the input resistors. Have the switch short across them for a "higher" gain (technically it's not a higher gain, just not reducing the input signal) and then switch over to the 100k resistors for "less" gain (because the resistors are reducing the input signal).


----------



## sourced

Quote:


  Originally Posted by *rauschie* /img/forum/go_quote.gif 
_... gain-switch.
 The question itself:
 Which components do I have to replace, and what type of components do I have to use?
 As far as I could understand, I'm going to have to change some resistors or capacitors, or rather have two different type of them with a switc with which I can choose which to use.
 I'm quite a newbye at DIY electronics, so please have mercy on me and try to answer in an easy-to-understand way.
 Sorry for my bad english and Thanks for the answer!_

 

This I found in a similar thread (so not in the 300 pages, but still on head-fi).

http://www.head-fi.org/forums/f6/mil...-build-332593/

 Scroll past the pictures until you see a hand-drawn diagram. That isn't really a 'gain' switch per se, but it will have a similar effect. Is that what you were trying to figure out?


----------



## RedLeader

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Yes! I just managed to score 5 19J6s for $8 a pop on ebay. Should I keep them just to have (lots) of spares, sell them, or build another amp? Building another amp sounds redundant albeit fun. I could always build and sell one._

 

Some of us want some....


----------



## the_equalizer

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_Thanks tomb. I checked underneath and it does in fact have a solder volcano on the pin but it did not suck up through the hole. I must have been impatient and not heated the pad enough. I managed to get my iron between the cap and terminal block and apply some solder to the pad and lead on the top side. Hopefully thats got it if it was shorting or cold.

 I checked all the resistors for suspect joints again - everything else looks good with good wicking from the bottom. I checked the resistance of all of them. Here is what I measured:

 R1 33.07K
 R2 110.0K *
 R3 2K
 R4 120.0K *
 R5 2K
 R6 1.998K
 R7 33.01K
 R8 105K *
 R9 2K
 R10 108K *
 R11 2K
 R12 2K
 R13 2K
 R14 0.997K
 R15 0.998K
 R16 99.8K
 R17 99.9K

 Notice the ones with the Astrix (*). For the life of me I can not get an accurate reading of these 4 resistors. As soon as I put the probes down the meter drifts upwards from about 110 at a constant rate - never zeroing in on the expected value of 220K (markings on the resistors are 2203 so thats 220K right?) Its painful. I have left the probes down for close to 10 minutes and only reached 140 or so ohms. any explanation of this behavior?_

 

As TomB has said, you can't measure a resistor's resistance value while it's connected to a circuit. Other resistors in the circuit, capacitors, semiconductors, etc. will form a current path and you'll get all kinds of crazy readings.


  Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_So already Im weirded by R4 and R10 because of the resistance. Measuring B+ to one side of the resistor measures 48.1v and B+ to the other side of the resistor measures 47.6v consistent for both R4 and R10. So there is a 0.5v drop. Measuring with the probes directly across the leads of each resistor is a bit different. After measuring from B+ to the resistor leads I try and measure between the leads. I get about 4.5mV and it drops consistently so that after a minute I am down to 1.9mV

 So still stuck hopefully this helps in narrowing down the issue... fingers crossed._

 

The reading of 4.5mV across R4 and R10 shows there's something seriously amiss. The reading should be half the power supply voltage (between 23 and 24 V). So there must be a big short circuit somewhere. 

 As TomB says, check the MOSFETs for shorts to the case (did you install the plastic shoulder washer between the nut and the MOSFET tab? )

 cheers!

 cheers!


----------



## amc

Quote:


  Originally Posted by *the_equalizer* 
_As TomB says, check the MOSFETs for shorts to the case (did you install the plastic shoulder washer between the nut and the MOSFET tab? )_

 

I did install the washers but i really torqued down the heatsinks before reading about damaging the burquist pads.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_you may have torqued down the MOSFETs so much that it cut into the insulators. Going against what I just said about measuring resistances, with the amp OFF, try seeing if you get a resistance across the MOSFET tab and an unanodized part of the case. If you don't read infinite resistance or something similar, you may have shorted out the MOSFETs._

 

Indeed you are right. I read resistance between a scratch i put in the underside of the lid and both mosfet tabs. The mosfets will still be OK right? I just need new insulators?

 I got some at a local electronics store but they are not the same as the burquist pads you supplied but mica sheets. Can I use those? Should I clean off the buquist pads or just leave them in place...

 Will work on it tonight and keep you guys posted. Thanks for your help so far.


----------



## simwells

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_An RK097 would probably be a realistic option, but most are only available in 10K. You'd have to re-work your input resistor sizing accordingly. If you've used the PCB, the pin spacing is not going to match (there'd be more for the switch, anyway)._

 

Wasn't planning on going the PCB route, but my lack of electronics means I think I'll stick with a normal switch! No idea how to recalculate other values.


----------



## tomb

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_I did install the washers but i really torqued down the heatsinks before reading about damaging the burquist pads._

 

Yep. Quote:


 Indeed you are right. I read resistance between a scratch i put in the underside of the lid and both mosfet tabs. 
 

Near zero resistance if they're shorting. Near infinite resistance if they're not. I'm not exactly sure what you mean by "I read resistance ..." Quote:


 The mosfets will still be OK right? I just need new insulators? 
 

Yes. Quote:


 
 I got some at a local electronics store but they are not the same as the burquist pads you supplied but mica sheets. Can I use those? Should I clean off the buquist pads or just leave them in place... 
 

The mica insulators are fine - you just need to use some heat sink grease between the mica and the MOSFET, and between the mica and the case. Quote:


 
 Will work on it tonight and keep you guys posted. Thanks for your help so far.


----------



## simwells

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Wasn't planning on going the PCB route, but my lack of electronics means I think I'll stick with a normal switch! No idea how to recalculate other values._

 

Actually, how straight forward would changeing the resistor values to use a 10k pot be?


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Actually, how straight forward would changeing the resistor values to use a 10k pot be?_

 

If you're talking the input resistors, they're sized at X times the pot impedance. So, if you're using a 10K pot, you'd want to try 10K, 20K, etc. - in those increments to find the volume range you want.


----------



## simwells

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If you're talking the input resistors, they're sized at X times the pot impedance. So, if you're using a 10K pot, you'd want to try 10K, 20K, etc. - in those increments to find the volume range you want._

 

So is it only the resistors shown here http://www.diyforums.org/SSMH/schema...MH-origPCB.gif as R16 and R17 that would have to be changed?


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_So is it only the resistors shown here http://www.diyforums.org/SSMH/schema...MH-origPCB.gif as R16 and R17 that would have to be changed?_

 

Yep.


----------



## simwells

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep.
	

	
	
		
		

		
		
	


	


_

 

Thanks for all your help! Almost there with ordering everything I need! Only thing I'm struggling to find is the power jack on farnell UK, any help with this? Think I must somehow searching wrong.


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Thanks for all your help! Almost there with ordering everything I need! Only thing I'm struggling to find is the power jack on farnell UK, any help with this? Think I must somehow searching wrong._

 

This one looks like it will work:
MULTICOMP|MJ-15SR|CHASSIS SOCKET, PSU, PANEL MOUNT | Farnell United Kingdom


----------



## simwells

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This one looks like it will work:
MULTICOMP|MJ-15SR|CHASSIS SOCKET, PSU, PANEL MOUNT | Farnell United Kingdom_

 

Thankyou very much for the help, think I have everything sorted to order all the parts this week!


----------



## amc

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep.Near zero resistance if they're shorting. Near infinite resistance if they're not. I'm not exactly sure what you mean by "I read resistance. mica insulators are fine - you just need to use some heat sink grease between the mica and the MOSFET, and between the mica and the case._

 

Hi Tomb / the_equalizer:

 Should have been more specific sorry. After detaching the case lid I could see the case anodizing where the pads had been all but squished out close to the case holes. So I scraped off burquist pads and cleaned the lid with alcohol then had to make a trip to the computer store for another tube of heat sink compound. I have been extra careful re-attaching the mosfets to the case with grease on both sided of a mica sheet as an insulator. Here are 2 pictures of my handiwork. With no power to the board I measure 18Mohms on one mosfet and 22Mohms. High enough to be considered nice and isolated? 

*Left mosfet resistance reading 
*Attachment 24915 

*Right mosfet resistance reading
*Attachment 24916

 But alas I still have problems. Tubes dont heat up, and at R4 and R10 I only get ~=145mV across them. Any other ideas on where I should be looking next? Any closeup pictures that could help?


----------



## tomb

Quote:


  Originally Posted by *amc* /img/forum/go_quote.gif 
_Hi Tomb / the_equalizer:

 Should have been more specific sorry. After detaching the case lid I could see the case anodizing where the pads had been all but squished out close to the case holes. So I scraped off burquist pads and cleaned the lid with alcohol then had to make a trip to the computer store for another tube of heat sink compound. I have been extra careful re-attaching the mosfets to the case with grease on both sided of a mica sheet as an insulator. Here are 2 pictures of my handiwork. With no power to the board I measure 18Mohms on one mosfet and 22Mohms. High enough to be considered nice and isolated? 

*Left mosfet resistance reading 
*Attachment 24915 

*Right mosfet resistance reading
*Attachment 24916

 But alas I still have problems. Tubes dont heat up, and at R4 and R10 I only get ~=145mV across them. Any other ideas on where I should be looking next? Any closeup pictures that could help?_

 

Those readings are fine. At this point, we need pics.


----------



## bhjazz

Got my P2P build running in tonight. And all four of my tubes sound a little different. I have two Delcos and two RCAs. One Delco has too-mellow high end, the other is good. The two RCAs are closer. I'll try one Delco and one RCA next to see if I can get these matched up good. 

 (edit: yes, one of each seems to be the trick!)

 I've seen a few posts about people finding spares on eBay. Anyone having luck in other places? I'd sure like to get a few more in case mine are on their way out!


----------



## simwells

What's considered a reasonable/good price for 19J6 tubes now, have found them difficult to get hold of but have been quoted $10 per tube, I know they have gone up in value but is it by this much?


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_What's considered a reasonable/good price for 19J6 tubes now, have found them difficult to get hold of but have been quoted $10 per tube, I know they have gone up in value but is it by this much?_

 

YES.


----------



## Fishline

I got them from ESRC back in last summer, and they were already at $8 per tube, so I wouldn't be surprise if they are $10 or more now.


----------



## UKToecutter

Yeah,

 I got 4. All Tung-Sol and all the same batch number at $10 each.


----------



## bhjazz

I ran into another place that had them for, you guessed it: $10. Now we'll be calling it the Really Starving Student. In spite of that, I think I'll get a spare pair or two. The sound of the amp is great for what I put into it, and I'd like the amp to at least outlast one set of tubes!

 Tube magic!


----------



## tomb

The final round of Starving Student Millett Hybrid PCB kits will go on sale at 11 PM EST, Friday, 1/29/2010!


----------



## UKToecutter

Ooh. Can I order and pay for one now then?


----------



## Juaquin

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Ooh. Can I order and pay for one now then?_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The final round of Starving Student Millett Hybrid PCB kits will go on sale at 11 PM EST, Friday, 1/29/2010!_

 

I don't mean to be rude, but Tom was pretty clear about the exact time they would go on sale. When the first round was being offered, I set the alarm on my phone so I would remember to order one right away. Of course, it took several days to sell out but I wanted to be sure. I'm not sure how long this final round will last, though.


----------



## UKToecutter

Juaquin

 Point taken, however, I'd hate to end up at the back of the queue if he was taking pre-orders.
 I apologise for my haste.

 I'd better google EST and find out how that relates to GMT


----------



## Juaquin

No problem, like I said, I didn't want to be rude, just answer your question. TomB posts the time so that everyone has a fair chance at getting one should there be a huge rush, although so far I don't think any of the kit offerings have sold out quickly enough that you have to have your cursor hovering over the "Buy One" button like I was doing.


----------



## UKToecutter

Just out of interest, how does one order the kit?

 Is it through Tom's website?

 Hmmm... 11PM EST is 4AM for me.
 I think it's gonna be a late one!!!


----------



## Juaquin

Ouch, yeah that's either a late one or an early one. It'll listed on this page when it goes live, I believe: Beezar.com


----------



## Logos

Is there any way to find out about how much one of these bad boys will run?


----------



## UKToecutter

I guess it'll depend on how much Tom has paid for the tubes.
 Also, the case fabrication isn't cheap on small runs.

 We'll find out on Friday.

 I have to say, I'm looking forward to building this.


----------



## tomb

I'll have to review the parts cost before I set price. The first round of kits was $110 each. The last round was $115. However, prices are rising all the time. Just as a for instance, the heat sinks have gone up 2-3 times since we built the first prototypes.

 Pricing will be based on the BOM on the SSMH PCB website:
Starving Student Millett Hybrid .
 I'll be updating the BOM pricing today - if there are any changes.
	

	
	
		
		

		
		
	


	




 EDIT: My price for the tubes is fixed. I purchased the initial stock well over a year ago. However, please let me repeat - since these are the last volume stock of 19J6's left anywhere, matching will be first come, first serve with the kits and in this order:
 1. Fully matched
 2. Triodes and construction matched (not brand)
 3. Construction matched (not triodes and brand)
 4. Two tubes, period.
 Sorry, but there's no other way I can do it. As Dsavitsk has often mentioned, there is very little difference even with matched tubes - the design tends to minimize any differences.


----------



## tomb

OK - the price for this round of kits will be $120.

 As stated, the heat sinks continue to increase and the cases are slightly higher than before. Finally, even though the BOM shows $118, there are a couple of hidden costs for me:

 1. The power caps are Panasonic FC's. Those are $2.65 each at DigiKey.
 (Pricing is based on the Mouser column except for these.)
 2. For this round of kits, I am drilling and gluing the tube sockets so that you can use the tube LED's without any additional work.

 #2 is a significant added feature, but one many of you have requested.


----------



## UKToecutter

Don't keep us in suspense LOL

 I'll bet he's gonna give us all a free pair of HD800's


----------



## revolink24

I've got a puzzle for everyone.

 I said earlier that whenever I tapped one of my tubes, there was a very loud cracking sound coming out of the headphones. I swapped tubes, and lo and behold, the other side began cracking, so I ordered some new tubes. 5 of them, in fact. The problem is, that the problem occurs with ALL 5, and only one tube of the seven I now own seems to not do this. I doubt that all of them are bad, and can only hypothesize that the one is very good and there is another problem somewhere. Anyone have any idea what that might be?

 Oh, and I'm using a pcb build.


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_I've got a puzzle for everyone.

 I said earlier that whenever I tapped one of my tubes, there was a very loud cracking sound coming out of the headphones. I swapped tubes, and lo and behold, the other side began cracking, so I ordered some new tubes. 5 of them, in fact. The problem is, that the problem occurs with ALL 5, and only one tube of the seven I now own seems to not do this. I doubt that all of them are bad, and can only hypothesize that the one is very good and there is another problem somewhere. Anyone have any idea what that might be?

 Oh, and I'm using a pcb build._

 

I think I actually suggested this before, but you may have something wrong with the sockets. Intermittent connections on certain of the pins can cause huge noises in the audio circuit. After all, the tubes are the amplification device, so if the connections aren't good ... it may only take a slight tapping on the tube to reveal the problem. Even if you have good connections - if you happen to torque a tube around in it's socket while the amp is on and you're listening - you'll get some very rude noises - or worse. (Don't try it on purpose!) 

 Look for a bad solder joint, or if you drilled the sockets for tube LED's, maybe there's some glue on the socket pins? Ultimately, if the amp performs well otherwise, why tap on the tubes and cause problems?


----------



## the_equalizer

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_I've got a puzzle for everyone.

 I said earlier that whenever I tapped one of my tubes, there was a very loud cracking sound coming out of the headphones. I swapped tubes, and lo and behold, the other side began cracking, so I ordered some new tubes. 5 of them, in fact. The problem is, that the problem occurs with ALL 5, and only one tube of the seven I now own seems to not do this. I doubt that all of them are bad, and can only hypothesize that the one is very good and there is another problem somewhere. Anyone have any idea what that might be?

 Oh, and I'm using a pcb build._

 

Could be that that particular socket is defective, maybe one of the pins of that socket is very very loose.

 It could also be a cold solder joint for one or more of that socket's pins.

 cheers !


----------



## revolink24

I've been suspecting that for a while, it's just odd that it would happen to both sockets and not affect one of the tubes. The pins must be bent oddly or something. 

 Anyhow, I guess I'll deal with what Ive got for now and worry about getting new sockets later. It just happened once without tapping it and I don't particularly want to damage my ears or headphones.


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_I've been suspecting that for a while, it's just odd that it would happen to both sockets and not affect one of the tubes. The pins must be bent oddly or something. 

 Anyhow, I guess I'll deal with what Ive got for now and worry about getting new sockets later. It just happened once without tapping it and I don't particularly want to damage my ears or headphones._

 

It's tough to tell for sure, but it could still be the tube pins. Vendors are dragging the bottom of the barrel for these tubes now and many of them are in very sorry shape when it comes to the pins. I've tested many of them that registered as bad, but then months later went back after wire-brushing the pins and they tested good. It's something you can try, but do it very carefully - then use some alcohol to clean up so there's no fine metal dust to further exacerbate this issue.
	

	
	
		
		

		
			





 EDIT: Heck, I've had some that had so much corrosion on the pins that the pins wouldn't even fit in the socket holes - ugly, green, foul stuff, too.


----------



## Logos

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_OK - the price for this round of kits will be $120.

 As stated, the heat sinks continue to increase and the cases are slightly higher than before. Finally, even though the BOM shows $118, there are a couple of hidden costs for me:

 1. The power caps are Panasonic FC's. Those are $2.65 each at DigiKey.
 (Pricing is based on the Mouser column except for these.)
 2. For this round of kits, I am drilling and gluing the tube sockets so that you can use the tube LED's without any additional work.

 #2 is a significant added feature, but one many of you have requested. 
	

	
	
		
		

		
		
	


	


_

 

Well, that is more than fair. I'm surprised you're actually justifying the low cost, and doing all this extra work for the kits. You've got a heart of gold man, a heart of gold. 
	

	
	
		
		

		
		
	


	




 ...Now to get me one of these things...


----------



## Llama16

Yeah tomb, 
 I can't stop envying your effort. That you are going to make the sockets yourself, wow!
 It would be more then reasonable to raise the price just for that.

 You're making many happy!


----------



## Dunceiam

I hate to sidetrack the thread with such a meager question, but how else does one learn these things? 
	

	
	
		
		

		
		
	


	




 I'm doing a PtP SSMH, and looking over the schematic, something caught my eye - why are there resistors/capacitors connecting to ground? (ex. R6, R12, R5, C6, R11, C1 - too name a few). This is one of my first non-stick in hole and solder projects, so excuse me for the quick question.


----------



## timmyGCSE

I won't have the money to order the PCB kit, I'll probably look at doing this in a month or so..but from what I read above it sounds like the tubes are in that short supply that I may not be able to?
 I found a place selling the tubes for $4 a piece but haven't enquired about that yet


----------



## tomb

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_I won't have the money to order the PCB kit, I'll probably look at doing this in a month or so..but from what I read above it sounds like the tubes are in that short supply that I may not be able to?
 I found a place selling the tubes for $4 a piece but haven't enquired about that yet_

 

When you do, I bet they tell you they don't have any. If a vendor does have some, they won't be $4 anymore.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Dunceiam* 
_I hate to sidetrack the thread with such a meager question, but how else does one learn these things? 

 I'm doing a PtP SSMH, and looking over the schematic, something caught my eye - why are there resistors/capacitors connecting to ground? (ex. R6, R12, R5, C6, R11, C1 - too name a few). This is one of my first non-stick in hole and solder projects, so excuse me for the quick question._

 

_Every_ electronics design has resistors and capacitors connecting to ground. You might refer to some of the many electronics articles and books that have been talked about often in the DIY section. The Search Tool is your friend.


----------



## timmyGCSE

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_When you do, I bet they tell you they don't have any. If a vendor does have some, they won't be $4 anymore.
	

	
	
		
		

		
		
	


	



_

 

so I have no other option unless I can just be lucky and source some from somewhere?


----------



## Llama16

I don't know if this is possible on the PCB, but equalizer has gone with the very accessible, cheap and new production 12AU7 guitar tubes. 

 Check the link for any help. It could be a very helpfull solution, and they don't sound bad either I've heard 
	

	
	
		
		

		
		
	


	




.
 If you've got any questions contact equalizer, who has showed me as well.
http://www.head-fi.org/forums/6024902-post3873.html


----------



## revolink24

I promised pictures 8 million years ago on this thread, so I've finally made one.







 And about that $120 price on those kits, I can't think of anything but the amazing amount of effort you put into this stuff for such little reward. The care with which you treat every order and customer is amazing. Thanks for all your hard work.


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_so I have no other option unless I can just be lucky and source some from somewhere?_

 

 Quote:


  Originally Posted by *Llama16* /img/forum/go_quote.gif 
_I don't know if this is possible on the PCB, but equalizer has gone with the very accessible, cheap and new production 12AU7 guitar tubes. 

 Check the link for any help. It could be a very helpfull solution, and they don't sound bad either I've heard 
	

	
	
		
		

		
		
	


	




.
 If you've got any questions contact equalizer, who has showed me as well.
http://www.head-fi.org/forums/6024902-post3873.html_

 

Well, if you manage to get an adapter tube socket, then it would be easy to use the 12AU7 tubes in the beezar.com PCB SSMH. The only thing you'd need to do is swap R2 and R8 in the PCB for 390Kohms.

 Unfortunately I don't think such an adapter exists, even though I know there are adapters for some popular audio tubes (like this one, for example); so this 19J6 -> 12AU7 adapter would have to be custom built.

 Then again, as some previous post suggested, there's also the possibility of re-designing the PCB for the 9-pin 12AU7 socket; but that, of course, is not an easy or quick endeavour.

 cheers!


----------



## scompton

This web site claims to make custom adapters, but they're $35 a piece.

Vacuum Tubes, Inc. > Products > Sockets, Adapters & Parts > Adapters and Parts

 While doing more searches, I found a socket that may not need drilling

http://www.alltronics.com/cgi-bin/it...in-Tube-Socket


----------



## the_equalizer

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_I hate to sidetrack the thread with such a meager question, but how else does one learn these things? 
	

	
	
		
		

		
		
	


	




 I'm doing a PtP SSMH, and looking over the schematic, something caught my eye - why are there resistors/capacitors connecting to ground? (ex. R6, R12, R5, C6, R11, C1 - too name a few). This is one of my first non-stick in hole and solder projects, so excuse me for the quick question._

 


 Aside from TomB's recommendation on checking electronics articles and books, you might want to read this carefully. It might help you understand what do R5/R11 (the cathode resistors) do in the "Starving Student" Hybrid circuit.


----------



## tomb

Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_I promised pictures 8 million years ago on this thread, so I've finally made one._

 

Looks great! Quote:


 And about that $120 price on those kits, I can't think of anything but the amazing amount of effort you put into this stuff for such little reward. The care with which you treat every order and customer is amazing. Thanks for all your hard work. 
 

What a nice thing to say! Thank you very much.


----------



## Juaquin

No kidding - for those who are ordering kits, wait 'till you get the package. I'd almost go so far as to say that TomB is obsessive-compulsive the way he packs those things


----------



## burgunder

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Unfortunately I don't think such an adapter exists, even though I know there are adapters for some popular audio tubes (like this one, for example); so this 19J6 -> 12AU7 adapter would have to be custom built._

 

I seem to remember an article about DIY tube adapters, but I'm not able to locate it rigth now.

 Edit. I found what I was looking for http://www.head-fi.org/forums/f5/rev...ifiers-301219/


----------



## the_equalizer

Quote:


  Originally Posted by *burgunder* /img/forum/go_quote.gif 
_I seem to remember an article about DIY tube adapters, but I'm not able to locate it rigth now.

 Edit. I found what I was looking for http://www.head-fi.org/forums/f5/rev...ifiers-301219/_

 


 Very interesting ! I read the whole article and followed the links to leedselect.com. Apparently they have the necesary items in stock


> 7 pin minature plug -fits sockets for 1L6, 6AU6 etc
> good for making tube adapters and test jigs with
> screw on back shell - NOS $7.00


Add a couple of regular ceramic 9-pin tube sockets and copper pipe caps.

 Then use a DPDT mini to switch to a couple of 170Kohms resistors in series with R2/R8 and you'd have a SSMH that could roll with either 19J6 or 12A_7 tubes 
	

	
	
		
		

		
		
	


	




. 

 cheers !


----------



## UKToecutter

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_No kidding - for those who are ordering kits, wait 'till you get the package. I'd almost go so far as to say that TomB is obsessive-compulsive the way he packs those things 
	

	
	
		
		

		
		
	


	


_

 

Great,

 There was me thinking I was the only guy on the forum with OCD!!!!


----------



## Yaka

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_No kidding - for those who are ordering kits, wait 'till you get the package. I'd almost go so far as to say that TomB is obsessive-compulsive the way he packs those things 
	

	
	
		
		

		
		
	


	


_

 

well im glad he takes the time to do that, there have times in the past when ive oardered parts from farnell, mouser etc that they had been dammaged and rendered un usable do to poor packaging. one of many reasons i am about to order a mini max kit as my next proj


----------



## loki993

Om so Ive been thinking about tacking one of these for some time. I have a few questions. First off are there any tweaks? Possibly higher end parts, Id like the get the best sounding Amp I can, within reason. If the headphones I'm using make a difference I would be using it with some AD700s a bit, but it will be used primarily to try and clean up my DT770 pros. Love the phones, love the bass, but as we all know the highs are a bit muddy. 

 Has anyone done any tube rolling or is that not really possible due to the way the tubes are set up?

 Also Ive heard about someone selling kits. What are these running and how would I go about getting one If I wanted?

 Thanks.


----------



## Juaquin

The "tweaks", besides doing obvious replacements (extremely high-end caps in place of the regular ones, etc) is to build one of the other Millet's, like the MiniMax. Similar topology (hybrid) with more bells and whistles.

 Tube rolling is not possible the standard way these are built. It is possible to use 12AU7 tubes, but it requires changing some resistors and a different socket, so it's not so much rolling as it is rebuilding. A couple posts up, Equalizer mentions some socket adapter information that would make switching back and forth easier, although I still wouldn't call it rolling.

 If you read two pages back, you'll see the kits will be going for $120 and they'll be available at Beezar Audio on Friday night.


----------



## the_equalizer

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_The "tweaks", besides doing obvious replacements (extremely high-end caps in place of the regular ones, etc) is to build one of the other Millet's, like the MiniMax. Similar topology (hybrid) with more bells and whistles.

 Tube rolling is not possible the standard way these are built. It is possible to use 12AU7 tubes, but it requires changing some resistors and a different socket, so it's not so much rolling as it is rebuilding. A couple posts up, Equalizer mentions some socket adapter information that would make switching back and forth easier, although I still wouldn't call it rolling.

 If you read two pages back, you'll see the kits will be going for $120 and they'll be available at Beezar Audio on Friday night._

 

Actually you *can* roll tubes with a 12A_7 version. Personally I have tried new production JJ brand 12AU7 tubes, new production Electro-Harmonix 12AX7 tubes and new production 12AX7 Mullard tubes. 

 A friend who also built a 12A_7 version also tried 12AT7 tubes (a pair of old, used ones he found in a scrap shop) and I'm pretty sure he also plugged a couple 12AV7's

 They all work great without needing any further modification to the circuit aside from the "one resistor change" as compared to the 19J6 version. 

 cheers!


----------



## Juaquin

Ah, so you can roll with a resistor change? Good to know. Still not quite plug-and-play, but with creativeness (a DPDT switch mounted to the case, as you suggested) you could make it pretty simple.


----------



## the_equalizer

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Ah, so you can roll with a resistor change? Good to know. Still not quite plug-and-play, but with creativeness (a DPDT switch mounted to the case, as you suggested) you could make it pretty simple._

 

I think I need to clarify what I wrote above 
	

	
	
		
		

		
		
	


	




 If you build a 12A_7 version, you can roll tubes within the 12A_7 family, that is 12AT7, 12AU7, 12AV7 and 12AX7 tubes.

 As you very well mentioned in your previous post, a 12A_7 version differs from the 19J6 version in two ways:

 Electrically: you need to change R2 and R8 to be 390 Khoms
 Mechanically: you need to use 9-pin sockets for the tubes (as opposed to the 7-pin socket used by the 19J6)

 So once you change that socket, plugging in a 19J6 is no longer possible... (unless you use adapter sockets 
	

	
	
		
		

		
		
	


	




 )

 cheers!


----------



## loki993

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_The "tweaks", besides doing obvious replacements (extremely high-end caps in place of the regular ones, etc) is to build one of the other Millet's, like the MiniMax. Similar topology (hybrid) with more bells and whistles.

 Tube rolling is not possible the standard way these are built. It is possible to use 12AU7 tubes, but it requires changing some resistors and a different socket, so it's not so much rolling as it is rebuilding. A couple posts up, Equalizer mentions some socket adapter information that would make switching back and forth easier, although I still wouldn't call it rolling.

 If you read two pages back, you'll see the kits will be going for $120 and they'll be available at Beezar Audio on Friday night._

 

Missed that, was just on here a couple days go and they still didn't know when they were coming. Good to know. 

 Wow, that's a lot more than the original $50 when I first saw this. I suppose the PCB and the Custom enclosure are a bit of the cause of that price though. Is he using better components that the original design? 

 What do the MiniMax kits run? They are out of stock on the website.

 Can the SSMH still be done for under or around $50? I kinda have gravitated towards this particular amp, because it seemed to be simple to build, it would be my first, and was really cheap. Even cheaper, by a fair bit, than a lot of solid state amps I was looking at. Have prices gone up that much?


----------



## loki993

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_I think I need to clarify what I wrote above 
	

	
	
		
		

		
		
	


	




 If you build a 12A_7 version, you can roll tubes within the 12A_7 family, that is 12AT7, 12AU7, 12AV7 and 12AX7 tubes.

 As you very well mentioned in your previous post, a 12A_7 version differs from the 19J6 version in two ways:

 Electrically: you need to change R2 and R8 to be 390 Khoms
 Mechanically: you need to use 9-pin sockets for the tubes (as opposed to the 7-pin socket used by the 19J6)

 So once you change that socket, plugging in a 19J6 is no longer possible... (unless you use adapter sockets 
	

	
	
		
		

		
		
	


	




 )

 cheers!_

 

Is this a recommended setup? How do they sound compared to the 19J6. What little Ive been reading in the past few days, Haven't been on the site in a while, is seems that the 19J6s are getting hard to find. True?


----------



## loki993

Ok Ive been looking around the Minimax Kits seem the be over $200, definitely not an option for me right now.


----------



## the_equalizer

Quote:


  Originally Posted by *loki993* /img/forum/go_quote.gif 
_Is this a recommended setup? How do they sound compared to the 19J6. What little Ive been reading in the past few days, Haven't been on the site in a while, is seems that the 19J6s are getting hard to find. True?_

 

Yup 19J6 are currently scarce, though some recent posts mentioned they're available at some sites at $10 US per tube, which is still cheaper than new current production 12AU/X/T7 tubes.

 I wouldn't call it a 'recommended setup' It's just another option at your disposal to build the amp. The sound is slightly less warm than the 19J6, somewhat more edgy, but that's only my perception.

 If you search the thread for 12SR7 you'll find there's a third option using cheap and easy to find 12SR7 tubes. I haven't built or heard that version so I can't comment, but those who've built it like it.

 You can certainly build this amp for less than $50.00 but you'll obviously have to forego the kit. Get the PSU from e-bay, get the tubes from a tube supplier, be creative for the enclosure, etc..

 Having said that, the Beezar.com kit is *seriously* worth it. An outstanding value in all respects: boutique output capacitors, 1% metal film resistors, WIMA film caps, a pre-drilled extruded aluminum enclosure... Having built one, I can say that the results are so professional looking that I could barely believe I had put the thing together myself.

 cheers!


----------



## loki993

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Yup 19J6 are currently scarce, though some recent posts mentioned they're available at some sites at $10 US per tube, which is still cheaper than new current production 12AU/X/T7 tubes.

 I wouldn't call it a 'recommended setup' It's just another option at your disposal to build the amp. The sound is slightly less warm than the 19J6, somewhat more edgy, but that's only my perception.

 If you search the thread for 12SR7 you'll find there's a third option using cheap and easy to find 12SR7 tubes. I haven't built or heard that version so I can't comment, but those who've built it like it.

 You can certainly build this amp for less than $50.00 but you'll obviously have to forego the kit. Get the PSU from e-bay, get the tubes from a tube supplier, be creative for the enclosure, etc..

 Having said that, the Beezar.com kit is *seriously* worth it. An outstanding value in all respects: boutique output capacitors, 1% metal film resistors, WIMA film caps, a pre-drilled extruded aluminum enclosure... Having built one, I can say that the results are so professional looking that I could barely believe I had put the thing together myself.

 cheers!_

 

Ok so it is High end stuff, that would explain the higher price. Id love to try one, I just don't have that money right now and I doubt they will last very long.


----------



## Juaquin

You can definitely do it cheaper yourself if you're ok with making your own enclosure without a PCB. It is called the Starving Student after all. That also gives you the option of using the 12AU7 (and similar) tubes - while they might be a little more expensive now, they'll still be available in ten years.

 Equalizer, thanks for clarifying, I was a little confused. I didn't think that the 19J6-12AU7 conversion was all that easy (as it turns out it isn't) but it makes sense that you can roll the 12_7 series fairly easily.


----------



## timmyGCSE

ah great that looks awsome, I'll end up most likely building the 12AU7 version since I can get the tubes for £5-£10 each on ebay, I will build p2p so don't have to worry about the PCB and I'll be extra creative over an enclosure 
	

	
	
		
		

		
			





 I will probably cut my teeth (done electronics but not audio electronics) on mini3 to start with then have this as my second project probably in a couple of months time. One of the cisco power supplys for this project finished on ebay UK for £3 with no bidders the other day


----------



## loki993

So here's another thing that confuses me. Like I said I'm basically a total noob. The BOM for the amp says the caps can be anything 150uF and up. So the first thing I think is bigger is better, but to what extent. Thats what I think, but I don't really know what going with a bigger cap does. Also the BOM that TomB put up has 2 different sizes. I'm assuming that 2 are for input and 2 output. What does putting larger ones in one spot or another accomplish?

 Boutique caps. Ive read a bit about them, They're supposed to sound better ok. What are the boutique caps though? I know about the Blackgates, but Ive seen them at $20 a pop so that's out of the questions. Also there's gotta be a point of diminishing returns with this thing right?

 Sorry for all the questions. Feel free to answer or if you want point me somehow where I can read up and learn about all this stuff without having to dig through tons of threads. I search the board a lot trying to find out, but it can be hard getting info that way.


----------



## the_equalizer

Quote:


  Originally Posted by *loki993* /img/forum/go_quote.gif 
_So here's another thing that confuses me. Like I said I'm basically a total noob. The BOM for the amp says the caps can be anything 150uF and up. So the first thing I think is bigger is better, but to what extent. Thats what I think, but I don't really know what going with a bigger cap does. Also the BOM that TomB put up has 2 different sizes. I'm assuming that 2 are for input and 2 output. What does putting larger ones in one spot or another accomplish?
 <snip>_

 

Two electrolytic caps are for the output stage, the other two are for power supply decoupling. Power supply decoupling is an important topic, but the explanation is a bit long and you'd do better to google it and read up 
	

	
	
		
		

		
		
	


	




.

 In general, the answer to what extent bigger is better with these caps can be answered by:

 a) the size of your chosen enclosure.- Capacitor size increases rapidly with increasing capacitance value.
 b) the size of your budget.- Capacitor prices increase rapidly with increasing capacitance value.

 Within these two constraints you want to get the highest value capacitors that you can, so that the bass frequency response doesn't suffer (this is also dependent on the impedance of the phones you're planning to use with the amp, lower impedance 'phones require higher valued output caps to preserve bass frequency response)

 As to 'boutique' caps, these are manufactured with higher quality raw materials and techniques to offer reduced distortion figures for signals crossing them. Read up on 'reactance' and 'phase distortion' to get the details of why/how caps distort.

 cheers!


----------



## simwells

I'm about to build a P2P SSMH, but am wondering if you guys think it'd be worth trying out one of the PCB based ones too or whether thart'd be a bit of a waste and I should think about a larger scale project next? (only audio exp is building a mini^3 if that effects things)


----------



## UKToecutter

I'm going to build a PC based one.
 I don't want any hassle with stray emf (I like to play safe !!)

 If you want to do a more elaborate project you could try the beta 22....

 That'll keep you quiet for about 3 months


----------



## FallenAngel

P2P is more fun


----------



## UKToecutter

yeah, I know.

 I might have a go at a P2P one as well, but only after I've done a PCB version.

 I'll give the PCB one to my son.


----------



## Juaquin

P2P is probably more of a learning experience because you'll probably end up with some issues (oftentimes, hum from a ground loop or insufficient grounding). With the PCB version you're virtually guaranteed to get an awesome working amp as long as your soldering skills are good.


----------



## simwells

Hmm, guess I'm unlikely to have time to wait to see how mine sounds before they'll sell out. I wonder if I could get a partial kit so as not to be buying the parts I already have.


----------



## tomb

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Hmm, guess I'm unlikely to have time to wait to see how mine sounds before they'll sell out. I wonder if I could get a partial kit so as not to be buying the parts I already have._

 

No.


----------



## revolink24

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Hmm, guess I'm unlikely to have time to wait to see how mine sounds before they'll sell out. I wonder if I could get a partial kit so as not to be buying the parts I already have._

 

Why not just order from Mouser or digikey? The BOM on the site is useful enough, thats how I built mine.


----------



## loki993

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Two electrolytic caps are for the output stage, the other two are for power supply decoupling. Power supply decoupling is an important topic, but the explanation is a bit long and you'd do better to google it and read up 
	

	
	
		
		

		
		
	


	




.

 In general, the answer to what extent bigger is better with these caps can be answered by:

 a) the size of your chosen enclosure.- Capacitor size increases rapidly with increasing capacitance value.
 b) the size of your budget.- Capacitor prices increase rapidly with increasing capacitance value.

 Within these two constraints you want to get the highest value capacitors that you can, so that the bass frequency response doesn't suffer (this is also dependent on the impedance of the phones you're planning to use with the amp, lower impedance 'phones require higher valued output caps to preserve bass frequency response)

 As to 'boutique' caps, these are manufactured with higher quality raw materials and techniques to offer reduced distortion figures for signals crossing them. Read up on 'reactance' and 'phase distortion' to get the details of why/how caps distort.

 cheers!_

 

Thanks. 

 So bigger is better than and bigger caps help bass response?

 Ill be running AD700s, not sure what impedance they are, 32 maybe? Also, and honestly what the amp will be for mainly, will be my dt770 pro 80s. Id love to clean up the highs on those. Giving the AD700s a bit more punch in the bass department wouldn't be bad either 
	

	
	
		
		

		
		
	


	




, I have no complaints about the AD700s except the weak bass.


----------



## the_equalizer

Quote:


  Originally Posted by *loki993* /img/forum/go_quote.gif 
_Thanks. 

 So bigger is better than and bigger caps help bass response?

 <snip>_

 

In general, yes, higher capacitance value is better for the supply decoupling and output caps. And for the output positions in the SSMH, it helps bass response. 

 As mentioned, there are other factors and you don't want to end up with a cap so big that it becomes unwieldy.

 You do want to get good quality caps too. A bad quality part will distort your signal in many ways, so it doesn't matter that it's a zillion microfarads and get's you a theoretical bass response down to 2Hz...

 So, short story, order the parts specified in the BOM.

 A good place to get them is Beezar.com, for example these look great for the output caps of a "Starving Student".

 cheers!


----------



## tomb

I can only see this on my BBerry right now, but if that Beezar link goes to the Muse ES 1000uf 16V - remember that we want a 63V rating for the power and output caps in the SSMH. 
	

	
	
		
		

		
		
	


	







 There is a very nice cap that's newly available at Handmade Electronics that would be interesting to try at the output - a Muse Fine Gold (FG) at 470uf, 63V - only 25mm high, too.

 We're still using the Nichicon KW's in the kit, but it might be a decent option if someone is interested. Remember though, that bypassing with the Wima's tends to level things out with many electrolytics. The improvement would be very subtle, if at all noticeable.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I can only see this on my BBerry right now, but if that Beezar link goes to the Muse ES 1000uf 16V - remember that we want a 63V rating for the power and output caps in the SSMH. 
	

	
	
		
		

		
			






_

 

My bad! 
	

	
	
		
		

		
		
	


	




 Indeed, that one looks nice... except that it needs to be rated for 63 V
	

	
	
		
		

		
		
	


	




 cheers!


----------



## loki993

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I can only see this on my BBerry right now, but if that Beezar link goes to the Muse ES 1000uf 16V - remember that we want a 63V rating for the power and output caps in the SSMH. 
	

	
	
		
		

		
		
	


	







 There is a very nice cap that's newly available at Handmade Electronics that would be interesting to try at the output - a Muse Fine Gold (FG) at 470uf, 63V - only 25mm high, too.

 We're still using the Nichicon KW's in the kit, but it might be a decent option if someone is interested. Remember though, that bypassing with the Wima's tends to level things out with many electrolytics. The improvement would be very subtle, if at all noticeable._

 

So Leave the Wimas out if someone was to use them? Or dont worry so much about the caps. Is there another one that can be used that doesn't smooth everything out as much, even though as I would imagine this is probably the primary reason for having a bypass to begin with. I heard early on that people were using the Vitamin Q caps for these, correct? how are they?

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_My bad! 
	

	
	
		
		

		
		
	


	




 Indeed, that one looks nice... except that it needs to be rated for 63 V
	

	
	
		
		

		
		
	


	




 cheers!_

 

Yeah I did a little research and it seems that the Muse ES dont come in 63v, the highest they have are 1000uF 50v oh well. I got a bit excited about them because that said they have excellent bass slam, I'm a bit of basshead, hence the DT770 pros. 

 The description of the ES on the Beezar site of them is very good though. Is there anywhere else that kinda explains how different caps sound and things like that?

 I was in fact looking at the diyforums BOM, I'm also assuming this is the one that TomB is using for the kits also, because he posted it at sometime, and was thinking about following that pretty closely. Probably going with bigger caps, just becasue. Depends on what I decide to do about a case.


----------



## tomb

Quote:


  Originally Posted by *loki993* /img/forum/go_quote.gif 
_So Leave the Wimas out if someone was to use them? Or dont worry so much about the caps. Is there another one that can be used that doesn't smooth everything out as much, even though as I would imagine this is probably the primary reason for having a bypass to begin with. I heard early on that people were using the Vitamin Q caps for these, correct? how are they?_

 

"Smooth" was not the word I used.
	

	
	
		
		

		
		
	


	




 Bypassing electrolytics in the audio signal path is done to provide better high-frequency response. When one concludes that bigger electrolytic caps are better, there is a caveat - the bigger caps are slower. So, you may gain bass but lose detail. This may happen even if you use a minimally-sized electrolytic by itself. Actually, you want a majority of the music signal to go through the film cap, given a choice, but there are diminishing returns there as well. Bypassing in the signal path does not follow prescribed rules - it's all trial and error: some combinations work well, others may not.

 Generally speaking, using 0.1uf or 0.22uf Wima MKP's for bypassing has a long history of successful results in the Millett Hybrid heritage. We tried them for the Starving Student long ago (probably rds who did it first) and they worked well, so they became part of the design for the SSMH PCB. VitaminQ's are probably a better choice, but there are tradeoffs in size, bass response, and a bit of detail. It would be very difficult to get them to fit on the PCB and in the custom Beezer/Hammond case, for instance.

 At any rate, a great deal of the higher audio frequencies - the kind you regularly resolve into details with your ears - go through the film cap bypasses anyway, so the electrolytic only has effect in the lower frequencies. Sort of.
	

	
	
		
		

		
		
	


	




 As I said, when bypassing, strict rules don't always apply. At any rate, "leveling out the differences with electrolytic boutique options" was a very general statement and was _not_ meant at all to mean that it "smoothed everything out."
	

	
	
		
		

		
		
	


	








  Quote:


 Yeah I did a little research and it seems that the Muse ES dont come in 63v, the highest they have are 1000uF 50v oh well. I got a bit excited about them because that said they have excellent bass slam, I'm a bit of basshead, hence the DT770 pros. 

 The description of the ES on the Beezar site of them is very good though. Is there anywhere else that kinda explains how different caps sound and things like that? 
 

Dsavitsk's (the SSMH PCB designer) own website is one of the best sources on the net for this:
Notes on Output Coupling Capacitors
 There is also another that's not quite as good in scoring, etc., but still useful:
Humble Homemade Hifi - Cap Test
  Quote:


 
 I was in fact looking at the diyforums BOM, I'm also assuming this is the one that TomB is using for the kits also, because he posted it at sometime, and was thinking about following that pretty closely. Probably going with bigger caps, just becasue. Depends on what I decide to do about a case. 
 

Yes - Beezar/DIYForums/TomB - we're all the same person.
	

	
	
		
		

		
		
	


	




 The kits are all packaged with a printout of that BOM - that's all you need to populate the PCB, along with the paint-by-numbers silkscreen.


----------



## loki993

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_"Smooth" was not the word I used.
	

	
	
		
		

		
		
	


	




 Bypassing electrolytics in the audio signal path is done to provide better high-frequency response. When one concludes that bigger electrolytic caps are better, there is a caveat - the bigger caps are slower. So, you may gain bass but lose detail. This may happen even if you use a minimally-sized electrolytic by itself. Actually, you want a majority of the music signal to go through the film cap, given a choice, but there are diminishing returns there as well. Bypassing in the signal path does not follow prescribed rules - it's all trial and error: some combinations work well, others may not.

 Generally speaking, using 0.1uf or 0.22uf Wima MKP's for bypassing has a long history of successful results in the Millett Hybrid heritage. We tried them for the Starving Student long ago (probably rds who did it first) and they worked well, so they became part of the design for the SSMH PCB. VitaminQ's are probably a better choice, but there are tradeoffs in size, bass response, and a bit of detail. It would be very difficult to get them to fit on the PCB and in the custom Beezer/Hammond case, for instance.

 At any rate, a great deal of the higher audio frequencies - the kind you regularly resolve into details with your ears - go through the film cap bypasses anyway, so the electrolytic only has effect in the lower frequencies. Sort of.
	

	
	
		
		

		
		
	


	




 As I said, when bypassing, strict rules don't always apply. At any rate, "leveling out the differences with electrolytic boutique options" was a very general statement and was not meant at all to mean that it "smoothed everything out."
	

	
	
		
		

		
		
	


	









 Dsavitsk's (the SSMH PCB designer) own website is one of the best sources on the net for this:
Notes on Output Coupling Capacitors
 There is also another that's not quite as good in scoring, etc., but still useful:
Humble Homemade Hifi - Cap Test_

 

Thanks that all good info. 

 I was just kind of thinking that since you said the difference from using the FGs and the wimas may be very subtle or not anything at all meant that there may not be much point in using them. I guess though a about a dollar more a cap for 2 caps it cant hurt. I was just trying to find a way that could possibly make the cap change more noticeable.

 I don't want to loose any detail or bass response. I'm trying to increase bass and mostly try and gain detail, so if the Vitamin Qs will take some of that away I wouldn't want to use them. 

 I'm thinking that I will follow that BOM you have pretty closely as its gotta be a great sounding amp after all the work you have put into it. Im thinking about using different caps in the output, probably the FGs you recommended and see what its like.


----------



## UKToecutter

Bah !!!!

 Tom. I meant Ocean Green !!!

 Andy


----------



## tomb

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Bah !!!!

 Tom. I meant Ocean Green !!!

 Andy_

 

Thanks - that will save me some work in contacting you. Ocean Blue I did not have.


----------



## tomb

Please guys - it takes time I don't have to straighten this out - READ THE LISTING!

*PRIORITY MAIL SHIPPING, ONLY!*


----------



## UKToecutter

I set my alarm for 3:55am to make sure I got an order in.
 I clicked straight through wihout reading (well, there are only 35 of these kits after all)
 Cocked up the LED colour in the comments, picked the wrong shipping.
 Decided to calculate the difference in shipping and sent the wrong supplementry amount.

 Lesson 1

 Don't wake up 5 minutes before ordering anything at 4am

 Tom
 I apologise


----------



## sam_cat

Ditto.. Alarm went off at 4am, woke up and clicked the alarm off... Woke up an hour later having an 'Oh S***' moment... Got online and ordered it.
 Gone with the default leds, but have some special colours here in 3mm (yellow/white ones, and some dark purple ones, along with all the usual colours).. Ordered a 2nd pair of sockits with it, going to adapt them and test the various led colours I have before commiting to one colour, see what I prefer...






 Tomb - Any idea where in the order stack I am, ie will I be getting fully matched tubes? or ???

 Sam


----------



## sam_cat

Double post, sorry!
 Please delete this one.


----------



## tomb

Quote:


  Originally Posted by *sam_cat* /img/forum/go_quote.gif 
_Ditto.. Alarm went off at 4am, woke up and clicked the alarm off... Woke up an hour later having an 'Oh S***' moment... Got online and ordered it.
 Gone with the default leds, but have some special colours here in 3mm (yellow/white ones, and some dark purple ones, along with all the usual colours).. Ordered a 2nd pair of sockits with it, going to adapt them and test the various led colours I have before commiting to one colour, see what I prefer...






 Tomb - Any idea where in the order stack I am, ie will I be getting fully matched tubes? or ???

 Sam_

 

I can't tell specifically, yet, but my guess is that it will have to get down further than this before you'll have to worry about the tubes. As Dsavitsk has said many times, it takes a huge mis-match to have any effect at all, though.

 Please remember - I'm only providing pin-less and glued tube sockets for the kits. Any other tube sockets you order - you'll have to do them yourself.


----------



## sam_cat

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Please remember - I'm only providing pin-less and glued tube sockets for the kits. Any other tube sockets you order - you'll have to do them yourself.
	

	
	
		
		

		
		
	


	


_

 

Thought that would be the case, and its not an issue. Thanks anyway.


----------



## UKToecutter

Tom,

 After the 35 kits will there be any PCB's left over?

 I have this thought about putting together a balanced SSHA.

 Andy


----------



## tomb

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Tom,

 After the 35 kits will there be any PCB's left over?

 I have this thought about putting together a balanced SSHA.

 Andy_

 

There will be some odds and ends that I'll put up for sale once we know that everyone has their kits and I didn't forget anything. It appears that there may even be some tubes left. Unfortunately, PCB's were actually the limiting item for this final round. To get more at a reasonable price, I'd have to order about 200 and there are not enough tubes for that.


----------



## UKToecutter

Hmmm

 So maybe I'll do a P2P balanced SSHA then.


----------



## sam_cat

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Hmmm

 So maybe I'll do a P2P balanced SSHA then.

_

 

Ditto, would make a great present for my bro, along with the decent headphones I am planning on getting him for his birthday.


----------



## getllamasfast

Hey everyone, just finished building my 12AU7 SSMH.
 It's not entirely finished as I still need to finish the case, but at least it works. 
	

	
	
		
		

		
		
	


	



 I had a rough time getting it to work, (you can see my frustrations documented earlier in this thread) but with the help of the_equalizer, I managed to find my problem and now all is good! Right now, I'm using this with my K702's and they sound great!
 I'll post more details later since I'm busy building second 12AU7 SSMH for my bro at the moment.

 EDIT: forgot to add pictures of it turned on 
	

	
	
		
		

		
		
	


	




 Here are some pictures:


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Hey everyone, just finished building my 12AU7 SSMH.
 It's not entirely finished as I still need to finish the case, but at least it works. 
	

	
	
		
		

		
		
	


	



 I had a rough time getting it to work, (you can see my frustrations documented earlier in this thread) but with the help of the_equalizer, I managed to find my problem and now all is good! Right now, I'm using this with my K702's and they sound great!
 I'll post more details later since I'm busy building second 12AU7 SSMH for my bro at the moment.

 EDIT: forgot to add pictures of it turned on 
	

	
	
		
		

		
		
	


	




 Here are some pictures:
 <snip>_

 


 Great news! Another 12AU7 build 
	

	
	
		
		

		
		
	


	




 I'm really glad that it worked! I also used JJ tubes to build mine. 
	

	
	
		
		

		
		
	


	




 I particularly like the turned-on pic, the illuminated volume control you used for your build looks really great! I'm sure your brother will like his a lot.

 cheers!


----------



## tomb

Just an FYI to ask for a little patience of those who've ordered kits so far. I'm running about a day behind and hope to get the first kits shipped out tomorrow. Doing those tube sockets took a little longer than I'd hoped. Gluing and testing 70 of them was a little daunting. I think I lost some brain cells that will never come back from all of the epoxy fumes.


----------



## sam_cat

Lol! 
 Thanks for the update Tom, and the work is appreciated!

 Have sent you an email about tubes..

 Thanks,
 Sam


----------



## kevenigma

hey tom, i didnt specify a led color when i was ordering, i ordered from my phone at a bar. i don't know if its too late or not but is there any way i can get sea green leds? my order is #1013.

 Thanks,
 Kevin


----------



## Juaquin

Quote:


  Originally Posted by *kevenigma* /img/forum/go_quote.gif 
_i ordered from my phone at a bar._

 

Is there any better place to make an order?


----------



## simwells

Starting to wire mine up now with the tube sockets am I right in thinking that they're numbered in order clockwork with the first one being the first from the gap?

 Also any tips for soldering the earth to the enclosure, other than keying it beforehand?


----------



## sourced

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Starting to wire mine up now with the tube sockets am I right in thinking that they're numbered in order clockwork with the first one being the first from the gap?

 Also any tips for soldering the earth to the enclosure, other than keying it beforehand?_

 

Yes, as you look from the bottom. When I flip mine over, I see (clockwise): gap, 48V, 48V, output cap, ground, pot, pot. EDIT: and lastly the 2k resistor to ground, of course.


----------



## Dunceiam

Hey everyone, halfway done with my P2P amp, when I noticed a problem.

 C1, C2, and C7 all have their correct capacitor in, however, I noticed I don't have the right capacitor (as marked) for C3a, C5a, C8, C7. 

 Capacitors I have: (2) Muse 470uF 35V, (2) 470uF 63V, (3) 0.22uF 35V. 

 Can I still use these, or is it back to Mouser I go? 
	

	
	
		
		

		
		
	


	




.

 Edit-

 On a different note, I forgot to cut the holes for the mosfet to attach directly to the heatsink, so instead I've used Arctic Silver 5 and a little bit of glue to attach the mosfet to the steel chassis wall, and then mounted the heatsink, also with AC5, directly above where the mosfet is, just on the other side of the wall. Would this still work? (I used the same 'sink as in the original BOM)


----------



## tomb

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_Hey everyone, halfway done with my P2P amp, when I noticed a problem.

 C1, C2, and C7 all have their correct capacitor in, however, I noticed I don't have the right capacitor (as marked) for C3a, C5a, C8, C7. 

 Capacitors I have: (2) Muse 470uF 35V, (2) 470uF 63V, (3) 0.22uF 35V. 

 Can I still use these, or is it back to Mouser I go? 
	

	
	
		
		

		
		
	


	




.

 Edit-

 On a different note, I forgot to cut the holes for the mosfet to attach directly to the heatsink, so instead I've used Arctic Silver 5 and a little bit of glue to attach the mosfet to the steel chassis wall, and then mounted the heatsink, also with AC5, directly above where the mosfet is, just on the other side of the wall. Would this still work? (I used the same 'sink as in the original BOM)_

 

Unfortunately, the Muse 470uf 35V has a voltage rating that will only work at C7 and C8. The 470uf 63V caps can be used at C1, C3, C5 or C6. The 0.22uf can't be used at all if it's a truly a 35V rating, but I suspect you're wrong about that - 35V is pretty low for a film cap, which is what I assume a 0.22uf is. If so, those are used at C2, C4, and C3a, C5a.

 As for the MOSFET - the Artic Silver is not the key - the fact that you have no insulator is the problem. I'm afraid you'll have a direct short when you power it up unless you have an insulator in there between the MOSFET and the chassis wall.


----------



## simwells

Last question I should probably already know the answer to!

 The mosfet pins are from left to right when the pins are pointing down right?


----------



## sourced

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Last question I should probably already know the answer to!

 The mosfet pins are from left to right when the pins are pointing down right?_

 

Yes, looking straight at the MOSFET, pins pointing down, black side toward you, heatsink behind the mosfet, 1 2 3 left to right. So the rightmost pins connect to the output caps.


----------



## Dunceiam

Ah, you're right. I mistook '358' on the 0.22uF caps for 35V. 

 However, I've taken a second look and I think I actually have everything I need. The capacitors I still need are C7, C8, C3, C3a, C5, C5a, C4. 

 Would this work?

 C7: Muse 470uF 35V
 C8: Muse 470uF 35V
 C3: Nichicon 470uF 63V
 C3a: 0.22uF 250V
 C5: Nichicon 470uF 63V
 C5a: 0.22uF 250V
 C4: 0.22uF 250V

 And regarding the insulating material, what would you suggest? I was a little rash and put Gorilla glue on the back of the mosfet in the plastic area, and AC5 in the metal area's, then stuck it to the chassis. Doubtful I could get the mosfets off unharmed, but hey, they were cheap anyway.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Unfortunately, the Muse 470uf 35V has a voltage rating that will only work at C7 and C8. The 470uf 63V caps can be used at C1, C3, C5 or C6. The 0.22uf can't be used at all if it's a truly a 35V rating, but I suspect you're wrong about that - 35V is pretty low for a film cap, which is what I assume a 0.22uf is. If so, those are used at C2, C4, and C3a, C5a.

 As for the MOSFET - the Artic Silver is not the key - the fact that you have no insulator is the problem. I'm afraid you'll have a direct short when you power it up unless you have an insulator in there between the MOSFET and the chassis wall.
	

	
	
		
		

		
		
	


	


_


----------



## tomb

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_Ah, you're right. I mistook '358' on the 0.22uF caps for 35V. 

 However, I've taken a second look and I think I actually have everything I need. The capacitors I still need are C7, C8, C3, C3a, C5, C5a, C4. 

 Would this work?

 C7: Muse 470uF 35V
 C8: Muse 470uF 35V
 C3: Nichicon 470uF 63V
 C3a: 0.22uF 250V
 C5: Nichicon 470uF 63V
 C5a: 0.22uF 250V
 C4: 0.22uF 250V

 And regarding the insulating material, what would you suggest? I was a little rash and put Gorilla glue on the back of the mosfet in the plastic area, and AC5 in the metal area's, then stuck it to the chassis. Doubtful I could get the mosfets off unharmed, but hey, they were cheap anyway._

 

If the Gorilla glue is not conductive, then maybe you'll be OK. Use your DMM to measure the resistance between the metal tab of the MOSFET and the case - see if you get near infinite resistance or near zero (very bad).

 The caps look OK as you have them arranged in that list.


----------



## tomb

Everybody - please, I beg your patience. I've had some inquiries about shipping time which is not unexpected, I guess. As with last time, the most I can ship during the week is about 4-5 a day. Because of the tube sockets, I actually didn't start shipping until Tuesday. So far, more than a dozen kits have shipped, but I'm still behind. I'm usually able to catch up on the weekends, so please bear with me awhile longer.

 Thanks!


----------



## simwells

This should actually be the final question now!

 For the pot and switch I am using the alps RK0971221Z05, but I am not entirely sure on wiring it, the back pins are obviously the switch and I'm presuming non directional but I am unsure of the direction of the pot pins, though I guess it's one row per channel.

 Data sheet is here if needed

RK097/RK098 Seriesï½œBasic information


----------



## Juaquin

Yep, one row per channel, middle pin should be wiper.


----------



## simwells

Does it matter whether I go from left to right or vice versa?


----------



## Dunceiam

Not getting any resistance between the metal tab and the case, I take it that's a good thing? 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If the Gorilla glue is not conductive, then maybe you'll be OK. Use your DMM to measure the resistance between the metal tab of the MOSFET and the case - see if you get near infinite resistance or near zero (very bad).

 The caps look OK as you have them arranged in that list._


----------



## Juaquin

NO. That is BAD. There should be a lot of resistance (infinite, or close to it) between the MOSFET tab (which carries voltage) and the case (which should be at ground). Hopefully you mean that you are not getting any _conductance_ between the two? There should be no electrical connection between them. From what you've described earlier I don't think you are isolated properly. Use a Berquist pad, mica, something that's purpose-built for isolation.


----------



## Juaquin

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Does it matter whether I go from left to right or vice versa?_

 

Not terribly, but you probably want to set it up so that when the switch is off, you're at very high resistance (so that when the switch gets turned on, it doesn't start at the highest volume).


----------



## simwells

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Not terribly, but you probably want to set it up so that when the switch is off, you're at very high resistance (so that when the switch gets turned on, it doesn't start at the highest volume)._

 

Hopefully I've got it the right way round then!

 It's all finished just waiting on the tubes arriving! LED's are working at least!


----------



## Dunceiam

By, 'no resistance' I meant the meter was not picking up any signal whatsoever between the two prongs of the meter. By this, I'm led to believe there is no electrical connection between the two, therefore a good thing. (Right?)

 I probably meant the wrong thing when I said, 'not getting any resistance'. When the meter's prongs are not touching (while measuring ohms), I get a flashing '0.00' to indicate no continuity, when I put one prong on the MOSFET's metal, and one on the case, the meter continues to read out the flashing '0.00' without any change. Sorry for any confusion.

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_NO. That is BAD. There should be a lot of resistance (infinite, or close to it) between the MOSFET tab (which carries voltage) and the case (which should be at ground). Hopefully you mean that you are not getting any conductance between the two? There should be no electrical connection between them. From what you've described earlier I don't think you are isolated properly. Use a Berquist pad, mica, something that's purpose-built for isolation._


----------



## UKToecutter

I'm not sure what your meter is saying or how it works, but......

 If you just short the two meter probes together and you get the same flashing 0.00, then this is bad !!!!!

 It means the tabs of the mosfets are directly shorted to the case.


----------



## UKToecutter

bah.

 Scrub that. I just re-read Dunceiam's last message properly......


----------



## Lil' Knight

Ordered the kit 2 days ago. So excited because it'll be my first project ever.

 What's the recommended headphones' impedance for the SSMH? I'm thinking of using it with the AD2000 which is only 40ohm.


----------



## the_equalizer

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Ordered the kit 2 days ago. So excited because it'll be my first project ever.

 What's the recommended headphones' impedance for the SSMH? I'm thinking of using it with the AD2000 which is only 40ohm._

 

In my experience the amp handles both low and high impedance with aplomb. It has both voltage gain (for high impedance 'phones) due to the tube's high gain; and current gain (for low impedance 'phones) due to the power MOSFET output stage.

 Also, according to Pete Millett's page on the amp it's output impedance is around 3 ohms, confirming it's quite adecuate for both kinds.

 cheers!


----------



## kevenigma

got my kit from Beezar today! 

 too bad my right hand is in a cast for the next 8 weeks... won't be building it for a while...


----------



## tomb

Quote:


  Originally Posted by *kevenigma* /img/forum/go_quote.gif 
_got my kit from Beezar today! 

 too bad my right hand is in a cast for the next 8 weeks... won't be building it for a while... 
	

	
	
		
		

		
		
	


	


_

 

It's nice to hear that the kit arrived! I was hoping some people would've received theirs by now.

 Sorry to hear about the cast, though - that's a bummer.


----------



## Dunceiam

Well, finished mine today, however, doesn't work as I had hoped, wishful thinking?

 Plugged everything in, a $10 Sansa MP3 player as source, and stock earbuds. Soon as I turn on the amp, the Sansa makes a loud cracking noise, the screen flickers black, the entire device turns off, and refuses to turn on, and one of the amp's tubes lights up. Despite the bricked Sansa, I left the amp on for a few minutes to make sure nothing's overheating, and noticed how the tube's got too hot to touch for longer than one second, within 2-3 minutes, normal? The tube was also much brighter than I was expecting, I could see the light being emitted from it as a circle on the ceiling. 

 Any idea's towards the now-dead Sansa? I'm afraid to plug in any other source before I have the problem figured out.


----------



## tomb

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_Well, finished mine today, however, doesn't work as I had hoped, wishful thinking?

 Plugged everything in, a $10 Sansa MP3 player as source, and stock earbuds. Soon as I turn on the amp, the Sansa makes a loud cracking noise, the screen flickers black, the entire device turns off, and refuses to turn on, and one of the amp's tubes lights up. Despite the bricked Sansa, I left the amp on for a few minutes to make sure nothing's overheating, and noticed how the tube's got too hot to touch for longer than one second, within 2-3 minutes, normal? The tube was also much brighter than I was expecting, I could see the light being emitted from it as a circle on the ceiling. 

 Any idea's towards the now-dead Sansa? I'm afraid to plug in any other source before I have the problem figured out._

 

Sorry that this advice is too late, but you should always check the inputs/outputs on a DIY-build for voltage offset before you go plugging in your equipment. Obviously, you have something crossed and/or shorted. It sounds like you've over-voltaged one of the tube heaters, too - so that tube may be fried if you left it on too long. Sorry to have such bad news. If we can see your wiring, maybe someone can spot the errors.

 Pics ...


----------



## tomb

OK - as promised, the weekend has let me catch up with shipping.
	

	
	
		
		

		
			





 All purchased kits have now been shipped.
	

	
	
		
		

		
		
	


	


*There are still 8 kits left*, plus some odds and ends. I've also got several extra power supplies and tubes, too, but will wait until I hear that everyone is OK with their kits before putting those up for sale.

 ** Remember that this is it for the Starving Student Millett Hybrid PCB, unless more tubes show up in volume. **

 Thanks for your patience everyone!


----------



## MoxMonkey

i'd likely be interested in an extra psu or two if and when all the kits are gone and the extras remain to be sorted


----------



## tomb

Quote:


  Originally Posted by *MoxMonkey* /img/forum/go_quote.gif 
_i'd likely be interested in an extra psu or two if and when all the kits are gone and the extras remain to be sorted_

 

The way things worked out, I'll almost have more PSU's than anything else, probably - at least a dozen, I think.

 Tubes are probably 2 dozen. I've got about 10 top-halo's that I saved, quite frankly, because they seem to be the most rare. Plus, top-halo's have always been my favorite, regardless of the tube type - always liked them best in the MAX/MiniMAX, too. Most important - I have 6 special 19J6's that have thickly-plated gold pins. I've never seen any others like them anywhere. Branded "International", it appears that company applied the coating post-production.

 There will be some other stuff, too - some of which is available now, including 8 kits still remaining.


----------



## Dunceiam

Alright, here are some photos. Good luck deciphering the maze of wires 
	

	
	
		
		

		
		
	


	




. 

 Oh, and the switch in between the heatsinks is a DPDT. I'm going to have a second 3.5mm jack at the back, for my speakers to plug into. If the switch is on, the audio will bypass the amp and just go straight to the speakers, if the switch is off, the audio will go into the amp, and out the 1/4" to my headphones. Also, should the pot be wired, G-I-O with the shaft pointing away from you? And finally, the tube that lit up was the right (looking down from the top)

 (Large Images)
http://img41.imageshack.us/img41/2061/28932598.jpg
http://img403.imageshack.us/img403/6595/92538694.jpg
http://img341.imageshack.us/img341/6568/12497374.jpg
http://img197.imageshack.us/img197/4425/43789515.jpg
http://img25.imageshack.us/img25/7897/84860904.jpg
http://img15.imageshack.us/img15/5489/17413807.jpg
http://img683.imageshack.us/img683/5882/57829775.jpg
http://img25.imageshack.us/img25/1938/12631784.jpg

 Thanks for all the help!


----------



## Entropy1

I just received and build my SSMH. First off, compliments to tomb for putting everything together so nicely and shipping everything in good time. Unfortunately I am having a couple problems. First is that I have audio only through the left. I have swapped tubes with no effect. Next off is a bit of static with is rather bothersome. Any suggestions before I start probing around comparing the two channels? If not, what would be the best way to do this? Thanks for any help

 edit: Also, both tubes are heating up like they are suppose to and the leds are both working properly.
 edit2: while messing around with stuff, i just picked up my low impedance iems and am actually getting audio of both channels. the right is significantly louder than the other but i'd even say the left side sounds better. it must be some powering issue as i can only get a faint clicking with my hd580's. any ideas?
 edit3: Somehow my x-fi card was broken while testing the amp. I now have no audio except crackling and a vague outline of the music with volume maxed. I am at a loss as to what I should do. Any help is appreciated, thanks.


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_I just received and build my SSMH. First off, compliments to tomb for putting everything together so nicely and shipping everything in good time. Unfortunately I am having a couple problems. First is that I have audio only through the left. I have swapped tubes with no effect. Next off is a bit of static with is rather bothersome. Any suggestions before I start probing around comparing the two channels? If not, what would be the best way to do this? Thanks for any help

 edit: Also, both tubes are heating up like they are suppose to and the leds are both working properly.
 edit2: while messing around with stuff, i just picked up my low impedance iems and am actually getting audio of both channels. the right is significantly louder than the other but i'd even say the left side sounds better. it must be some powering issue as i can only get a faint clicking with my hd580's. any ideas?
 edit3: Somehow my x-fi card was broken while testing the amp. I now have no audio except crackling and a vague outline of the music with volume maxed. I am at a loss as to what I should do. Any help is appreciated, thanks._

 

The PCB has been thoroughly tested and vetted. There are no mistakes or bugs with it. Unfortunately, that leaves the likely prospect that you have some parts in the wrong position, or some other building error has ocurred (MOSFETs not insulated?). Can you get us some pics?

 Meanwhile, check to see if your resistors are in the correct positions. Hopefully, you installed them with the ratings up so that you can read the values - as pointed out in the build instructions in the Head-Fi thread and on the SSMH website.

 Also, check to see if your MOSFETs are insulated and that you didn't torque them down so much that the Bergquist pads were cut. You can check this by measuring the resistance between the MOSFET tabs and an un-anodized place on the case lid.

 Check the LED resistor and whether one of the leads is shorting out with the center standoff.

 Finally, check to see that you didn't mix up the input wiring. Switching a ground wire with one of the signal wires is a common mistake and can cause some of the symptoms you describe.


----------



## Entropy1

Sorry, I did not mean to imply that I thought there was an issue with the PCB. I'll try to get some pictures but as I don't have a camera, that may take a while. The input cables are correct from what i see but I am kind of puzzled as to how the MOSFETs can be grounded. Mine are not insulated like you say as there is a metal screw causing contact between the case and MOSFET. How do I get this grounded? Thanks again.


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Sorry, I did not mean to imply that I thought there was an issue with the PCB. I'll try to get some pictures but as I don't have a camera, that may take a while. The input cables are correct from what i see but I am kind of puzzled as to how the MOSFETs can be grounded. Mine are not insulated like you say as there is a metal screw causing contact between the case and MOSFET. How do I get this grounded? Thanks again._

 

No implication was taken about the PCB. That was just laying out the facts that the only way you can mess one up is by installing the parts in the wrong place or installing some things incorrectly (as in MOSFETs and heatsinks below).
	

	
	
		
		

		
		
	


	




 I'm concerned about your description of the MOSFETs, however. Did you study this page on the SSMH website: SSMH Heat Sink ? The proper heat sink mounting was also described and pictured in detail in the build thread and in the construction instructions on the website.
	

	
	
		
		

		
		
	


	




 If you didn't use the shoulder washer and the Bergquist pads, it will cause a whole heck of a lot of trouble.


----------



## Juaquin

The MOSFET tab and the Case should NEVER come in electrical contact. This will cause a short because the case is at Ground and the MOSFET tabs have quite a bit of voltage on them. 

 The fact that you're getting very low audio in the left channel with loud audio in the right suggests that your right channel is working correctly and that what you're probably hearing in the left channel is crosstalk from the shared ground. 

 Check that there is very high or infinite resistance between the metal MOSFET tab and the case. If there is very little resistance, you have a short and this is a problem. You do not want them grounded, you want them isolated. If you're building the kit, it came with Berquist pads for this purpose. Check that they are placed between the MOSFET and the case as the build guide says to do, and that they have not been cut/torn. Also, do not forget the isolation washer bit that is part of the heatsink mounting kit (it's a little, brown, oddly-shaped washer that is not conductive). This is what allows the screw to clamp down on the MOSFET and case without electrically connecting the two.

 Your dead soundcard is probably a result of this short coming back from the SSMH to your soundcard. Live and learn. In the future try to use a cheap source (handheld radio, walkman, cheap MP3 player, etc) when testing.

 [EDIT] TomB beats me to the punch again.


----------



## Entropy1

Yeah, I must have missed that page on the MOSFETS. That is fixed now but unfortunately there is still the static and the major volume difference present. I suppose the most likely explanation for the volume discrepancy is a swapped resistor so I will double check all of them again. Thanks for the help and hopefully I can at least get the amp working.


----------



## Dunceiam

I've troubleshooted a little, and I found quite a few errors. Firstly, the MOSFETS were indeed shorting to the case. My first measurements didn't show it at first because the chassis' black outer coating is insulating, so no continuity was being shown. But when I tried a spot of bare metal, continuity existed. Also, the ground for the MOSFET (for the tube that was not lighting up) was not soldered properly and became loose. 

 I've ordered new mosfets, along with the insulating pads. Let's do this properly this time 
	

	
	
		
		

		
		
	


	




.


----------



## Juaquin

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Yeah, I must have missed that page on the MOSFETS. That is fixed now but unfortunately there is still the static and the major volume difference present. I suppose the most likely explanation for the volume discrepancy is a swapped resistor so I will double check all of them again. Thanks for the help and hopefully I can at least get the amp working._

 

At this point I'd say that it probably isn't a resistor issue (that could still exist, of course). Most likely you've blown the MOSFET in the quiet channel, and what you're hearing is crosstalk from the good channel. This is all theory, of course. Check the resistors and if they are correct, time to order a new MOSFET.


----------



## simwells

I'm still waiting for my tubes to arrive but before I wire this up to a source and phones when they arrive what other checks do I need to do on my wiring, the earths are all checked and fine anything else to make sure I won't damage anything?


----------



## Juaquin

You've checked that there is no conductance between the MOSFET tabs and the case, right? 
	

	
	
		
		

		
			





 If you're really obsessive compulsive you can check the resistance of various resistors. They won't necessarily be their rated value (because they are now in the circuit), but resistors in the left channel should measure very close to their counterparts in the right channel. This is of course not necessary but it will catch a wrong resistor value or perhaps a bad solder joint.


----------



## simwells

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_You've checked that there is no conductance between the MOSFET tabs and the case, right? 
	

	
	
		
		

		
		
	


	




 If you're really obsessive compulsive you can check the resistance of various resistors. They won't necessarily be their rated value (because they are now in the circuit), but resistors in the left channel should measure very close to their counterparts in the right channel. This is of course not necessary but it will catch a wrong resistor value or perhaps a bad solder joint._

 

Yep that was the first thing I checked and that's fine, think I'll just wait til the tubes turn up and see how it sounds then! As long as there's nothing else to check that could damage the amp, phones or source.

 Just need to respray the volume knob to match the heatsinks and it'll be finished.


----------



## Entropy1

Okay, there is definately channel cross talk as with only one rca jack connected, I can hear audio on both sides. Testing signal on both rca jacks there is no conduction like it should be, but at the 1/4 headphone jack, everything - left, right and even ground- has very little resistance. I have no idea how this is possible as I have double and triple check how everything is put together. If anyone has any ideas, please let me know. Thanks.


----------



## Juaquin

I'm not sure what you mean there - are you saying that when you measure resistance between the left output and ground (and right output and ground), it is near zero? You should be seeing somewhere around 2k (R6/R12) after a few seconds (once the capacitors charge), although I'm not sure how useful that measurement is anyway.

 My guess is still that you've blown the MOSFET in the quiet channel (left, correct?) and it's shorted that signal path to ground internally (even though you have now fixed the isolation issue). Have you replaced the MOSFET(s)? Once you do that, testing will be more conclusive. Pictures would be helpful too.


----------



## Entropy1

Okay, I am getting around those readings for the output jack. I expected those to have infinite resistance. i will try to get hold of a camera to see if we can figure out what's going on.


----------



## Lil' Knight

Got the kit in the mailbox! Awesome packaging. 

 I ordered the Green LED but got the Blue one. Not a big deal though. Can't wait until weekend to start building it.


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Got the kit in the mailbox! Awesome packaging. 

 I ordered the Green LED but got the Blue one. Not a big deal though. Can't wait until weekend to start building it._

 

Uh-oh. I thought I had kept those straight. Send me a PM with your real name and I'll send some green ones out to you.

 EDIT: Never mind. I looked up one of your earlier PM's - I know who you are.
	

	
	
		
		

		
		
	


	




 I'll get those green LED's out to you tomorrow.


----------



## UKToecutter

I'm still waiting for mine, but it's not Tom's fault.

 I just live a long way away and have to wait for 2 delivery companies and a customs check.


----------



## Llama16

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_I'm still waiting for mine, but it's not Tom's fault.

 I just live a long way away and have to wait for 2 delivery companies and a customs check._

 

yeah it does! Trust me on that one. But it's ok, they usually give me a nice and shiny paper when it arrives after all... to pay extra taxes.


----------



## Lil' Knight

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Uh-oh. I thought I had kept those straight. Send me a PM with your real name and I'll send some green ones out to you.

 EDIT: Never mind. I looked up one of your earlier PM's - I know who you are.
	

	
	
		
		

		
		
	


	




 I'll get those green LED's out to you tomorrow._

 

Cool beans. Thanks


----------



## Juaquin

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Okay, I am getting around those readings for the output jack. I expected those to have infinite resistance. i will try to get hold of a camera to see if we can figure out what's going on._

 

I hate to be pushy, but have you replaced the MOSFETs? You haven't said yes or no. If you keep running a (potentially) shorted MOSFET you could (in theory, at least) do further damage.


----------



## Entropy1

No, I need to either order some or go digging around at our EE building. I'd like to look for them first as I'm sure a majority of the cost of ordering will be shipping. Thanks for the help and I'll get back to you as soon as I have other MOSFETs to test with.


----------



## Lil' Knight

So I spent a couple of hours working on the PCB. My first try ever with the PCB!






 The problem is on the back side, there are some solder pads that I messed up and they can't stick solder any more 
	

	
	
		
		

		
		
	


	




 any tips on how to solve this?

 Another question is there is holes next to the caps' legs. Do I have to solder these too?


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_So I spent a couple of hours working on the PCB. My first try ever with the PCB!

 <IMG]http://farm5.static.flickr.com/4065/4342052612_33e39462f1_d.jpg[/IMG>

 The problem is on the back side, there are some solder pads that I messed up and they can't stick solder any more 
	

	
	
		
		

		
		
	


	




 any tips on how to solve this?_

 

Are you sure? The pads on the other side are all tied to the ground plane. You need to turn the temp up on your iron to quickly heat the local area around the pad before it starts heating up the entire ground plane, instead. Otherwise, you'll never get the pad itself hot enough to let the solder "stick."

 If you've truly torn up a pad and it was supposed to be connected to the ground plane, then scrape a small portion of the ground plane next to the pad and solder a jumper using a spent resistor lead. However, if your problem was as above, you'll have even more trouble making the solder "stick."

  Quote:


 Another question is there is holes next to the caps' legs. Do I have to solder these too? 
 

Those are holes for different size caps. Perhaps you noticed that the KW's use different holes than the Panasonic FC's. If there's nothing in them, then don't worry about it.
	

	
	
		
		

		
		
	


	




 How are you going to solder in the green LED's now? Looks like you've finished it.


----------



## Lil' Knight

So far this is the only solder joint I think bad, one of the legs of C8. Looks like I didn't put enough heat when soldering it.






 About the green LED, I think I'm still able to solder the wires. Pretty tight but not impossible


----------



## Dunceiam

I hate to ask such a simple question, but how would one use the LED/LED resistors on a PtP build? I've searched and searched, but couldn't find anything 
	

	
	
		
		

		
			





.


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_So far this is the only solder joint I think bad, one of the legs of C8. Looks like I didn't put enough heat when soldering it.

 <IMG]http://farm3.static.flickr.com/2719/4341454459_d93f9549b9_d.jpg[/IMG>

 About the green LED, I think I'm still able to solder the wires. Pretty tight but not impossible 
	

	
	
		
		

		
		
	


	


_

 

Well, it's hard to tell from the photo - but if that's the other leg of C8, then that pad is definitely tied to the ground plane. So make sure you apply enough heat - use more flux, that will help. If that doesn't work, then you may need to solder a small jumper from a scraped off portion nearby to that leg of C8.


----------



## Lil' Knight

Thanks. I applied a ton of flux but it still didn't stick solder. Will try again later to see if it works.


----------



## simwells

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_I hate to ask such a simple question, but how would one use the LED/LED resistors on a PtP build? I've searched and searched, but couldn't find anything 
	

	
	
		
		

		
		
	


	




._

 

Just tap the 48V (I went straight from the switch) then resistor, LEDs in parallel, ground.


----------



## Juaquin

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Just tap the 48V (I went straight from the switch) then resistor, LEDs in parallel, ground._

 

Don't forget that the resistor needs to be at least 2W power rating because of the 48V. You probably want to set the LEDs for roughly 10mA (up to 20 if you want brighter, down to 5 or so if you want it really dim, this all depend on the LED specs), so solve V=IR for those values to find the resistor you need.


----------



## tomb

There is someone from France who has ordered a SSMH kit and has not paid. That in itself is not an issue. I often send an e-mail back to some people who have trouble with the Paypal procedure, or when the connection to Paypal drops out. It's not an issue because a manual payment is a snap once they know the account for beezar. 

 However, when someone registers and the only means I have of contacting them is an e-mail address that kicks every one of my messages back as spam, the situation becomes difficult. I've tried sending from Beezar, my home account, several different subject lines, etc. - everything is blocked and I receive a nice formatted and lengthy "You've been blocked." e-mail reply to every message I send.

 If you are the person who's ordered the kit from France and sees this, please contact me through some method that allows me to contact you.

 Thanks.

 P.S. It's also not an issue if the order was a mistake and they want to cancel it. That happens every once in awhile, too - and it's not a problem! However, please tell me! There are not many kits left and I'm sure there are others who would like to purchase this one.


----------



## Lil' Knight

Just done the mosfet + heatshink. Does it look right? It's really a PITA to do.


----------



## Juaquin

Looks pretty good to me. I can't see the isolation washer offhand but as long as you followed the build guide it should be in the right place.


----------



## Lil' Knight

I hope it would work fine. 
	

	
	
		
		

		
		
	


	




 About the terminals, I just push the wires in the screw them, right?


----------



## Juaquin

Yep. Just make sure you've got good contact.


----------



## Lil' Knight

How important is the heat transfer goo? I just found out that I don't have it right now


----------



## Juaquin

In the build notes, TomB says it can be skipped. From my experience with the amp that's probably correct, especially if you only run it for an hour or two at a time. I think you'd be fine without it for now - you can always add it later on.


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Just done the mosfet + heatshink. Does it look right? It's really a PITA to do.




_

 

Where's the lock washers?


----------



## Lil' Knight

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Where's the lock washers?
	

	
	
		
		

		
		
	


	


_

 

Yeah, I know they're not there


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Yeah, I know they're not there 
	

	
	
		
		

		
		
	


	


_

 

Well, it might be a good idea to use them. If you're not using the heat transfer grease between the case and the heat sinks, you sure enough don't want the contact between the two to loosen up over time. That will happen as the metal heats and cools, expands and contracts. Just a friendly recommendation.


----------



## Lil' Knight

I'm done, and time for troubleshooting 
	

	
	
		
		

		
			





 LED on. Both tubes look good. However, when I plug my headphones in, there's a huge noise coming out. I guess something wrong with the ground. Any idea on this?


----------



## Jrome

Hey, Just got mine in the mail today! Thanks!

 Question: Are the tubes supposed to fit all the way into the sockets? If so, is there supposed to be some resistance? I mean, I didn't want to force them in before asking.


----------



## Jrome

double.....Sorry!


----------



## tomb

Quote:


  Originally Posted by *Jrome* /img/forum/go_quote.gif 
_Hey, Just got mine in the mail today! Thanks!

 Question: Are the tubes supposed to fit all the way into the sockets? If so, is there supposed to be some resistance? I mean, I didn't want to force them in before asking._

 

Believe it or not, I personally tested every single one of the tube sockets after I glued them. Yes, there will be some resistance. However, I can assure you that all of them allowed me to insert the tube pins all the way until the tube bottom was resting against the ceramic. However, unless you're experienced with this, it's best to wait until you get them anchored into the PCB before fooling with them much. You can break the ceramic in half or rip off a tube pin (did that to a couple), otherwise.


----------



## Lil' Knight

So I got music coming out from both sides but the terrible noise is there 
	

	
	
		
		

		
		
	


	




 is there any step I should check? Also, the tubes are damn hot only after 20 minutes or so, is it normal?


----------



## Juaquin

Tubes should be warm enough that you aren't comfortable holding your finger there for more than a second or two (scientific, I know). Remember that tubes only work when they are hot, hence the tube has heaters (the orange glow in the middle). I'd say you're probably ok.

 The terrible noise is probably a ground loop. Make sure all your ground solder points are 100% flowed and not cold.


----------



## Dunceiam

I'm using a PCB board for ground, should I also make a solder connection to the chassis?


----------



## the_equalizer

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_I'm using a PCB board for ground, should I also make a solder connection to the chassis?_

 

A good, solid connection that grounds the enclosure is usually a good thing to have, as the case will shield the internal circuits from noise.

 This, of course, only applies if the enclosure is made of a material that is a good conductor of electricity (e.g. metal)

 cheers!


----------



## Lil' Knight

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Tubes should be warm enough that you aren't comfortable holding your finger there for more than a second or two (scientific, I know). Remember that tubes only work when they are hot, hence the tube has heaters (the orange glow in the middle). I'd say you're probably ok.

 The terrible noise is probably a ground loop. Make sure all your ground solder points are 100% flowed and not cold._

 

So when I move the volume knob and headphone jack around, the noise disappears for a while but then the problem still the same. Sound still comes out from both sides. Does that mean the problem is in the solder points of the volume and headphone jack?


----------



## Juaquin

It's possible, but my guess is that the noise disappears because you're touching it. I'm not certain what the technical reason for this is, but I've had it happen many time (both with amps that had ground loops / hum, and unstable circuits in labs).


----------



## Lil' Knight

Anything I should do to solve the ground loop?


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_So when I move the volume knob and headphone jack around, the noise disappears for a while but then the problem still the same. Sound still comes out from both sides. Does that mean the problem is in the solder points of the volume and headphone jack?_

 

I'm not so sure it's a ground loop as this phenomenon that you describe above. (Of course, Juaquin and I are both making educated guesses - his thought is as likely as mine.) I thought it was an optical illusion at first, but it appeared in your photo of the PCB that one could see the holes in the pads around the headphone jack - especially the one in front. The front pads on the headphone jack are the ground connections.

 If you are still having issues soldering to grounded pads, you may need another soldering iron. At the least, I'd try to re-flow those joints. You need to have enough wicking that the solder flows up the sides of the metal contacts on the headphone jack - but be careful! It's still just a plastic body!

 If you have intermittent contact or lack of contact around those ground pads on the headphone jack and/or pot, it can cause a lot of noise - same for the RCA jacks, too. Make certain you've got good grounding wires and contact all the way from the RCA jacks to the input terminal block. Again, if you're not getting wicking all the way from the ground plane on the bottom to the part on top, there may be a potential that you're not getting a good connection to ground - with _any_ part.


----------



## tomb

Just a hint to some of you new folks building with tubes for the first time. Yes, there will be resistance plugging a tube into a socket - especially if the sockets have been glued back together. As stated earlier, I personally tested each socket to make sure a tube would plug into it. However, I may have a little better touch on how to do this after doing literally hundreds.
	

	
	
		
		

		
		
	


	




 The proper method to plug in a tube - especially if there's some resistance in the socket - is NOT to jam the tube straight in there. Instead, try a gentle spiral rocking motion while pushing down. In other words, it's almost like pushing one pin in at a time, while turning and pushing the tube at the same time. If this doesn't work or it sounds too difficult, then rock the tube gently back and forth while pushing down. This rotates the pressure around the tube pins, equalizing the stress somewhat - same as alternating the lug nuts on a car wheel.

 After a few times of plugging and unplugging the tubes, the sockets should loosen up some. Meanwhile, hopefully you haven't shattered a tube.


----------



## Lil' Knight

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not so sure it's a ground loop as this phenomenon that you describe above. (Of course, Juaquin and I are both making educated guesses - his thought is as likely as mine.) I thought it was an optical illusion at first, but it appeared in your photo of the PCB that one could see the holes in the pads around the headphone jack - especially the one in front. The front pads on the headphone jack are the ground connections.

 If you are still having issues soldering to grounded pads, you may need another soldering iron. At the least, I'd try to re-flow those joints. You need to have enough wicking that the solder flows up the sides of the metal contacts on the headphone jack - but be careful! It's still just a plastic body!

 If you have intermittent contact or lack of contact around those ground pads on the headphone jack and/or pot, it can cause a lot of noise - same for the RCA jacks, too. Make certain you've got good grounding wires and contact all the way from the RCA jacks to the input terminal block. Again, if you're not getting wicking all the way from the ground plane on the bottom to the part on top, there may be a potential that you're not getting a good connection to ground - with any part._

 

The wiring is pretty good and all have good connections with the terminal blocks.






 I'll check the solder pads on the headphone jack tomorrow. Maybe I'll reflow them on both sides of the PCB.


----------



## Juaquin

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not so sure it's a ground loop as this phenomenon that you describe above. (Of course, Juaquin and I are both making educated guesses - his thought is as likely as mine.)_

 

My guess is probably not as educated as yours. I'm just grasping at straws here 
	

	
	
		
		

		
		
	


	




 This is probably a topic for another thread, but does anyone know why certain unstable circuits become more stable when you touch them? My guess is something to do with capacitance but I have no idea. I've had this happen with the occasional opamp and/or transistor in lab settings.


----------



## Juaquin

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_




_

 

That's some pretty impressive wiring - 4" of techflex wrapped signal wires? Nice touch.


----------



## Jrome

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just a hint to some of you new folks building with tubes for the first time. Yes, there will be resistance plugging a tube into a socket - especially if the sockets have been glued back together. As stated earlier, I personally tested each socket to make sure a tube would plug into it. However, I may have a little better touch on how to do this after doing literally hundreds.
	

	
	
		
		

		
		
	


	




 The proper method to plug in a tube - especially if there's some resistance in the socket - is NOT to jam the tube straight in there. Instead, try a gentle spiral rocking motion while pushing down. In other words, it's almost like pushing one pin in at a time, while turning and pushing the tube at the same time. If this doesn't work or it sounds too difficult, then rock the tube gently back and forth while pushing down. This rotates the pressure around the tube pins, equalizing the stress somewhat - same as alternating the lug nuts on a car wheel.

 After a few times of plugging and unplugging the tubes, the sockets should loosen up some. Meanwhile, hopefully you haven't shattered a tube. 
	

	
	
		
		

		
		
	


	


_

 


 Thanks Tom! 
 (I was the one who shattered one 
	

	
	
		
		

		
		
	


	




)

 This was my first time using tubes, and I just had no idea what I should expect. Thanks for all of your help and being so understanding!


----------



## particleman14

Just wanted to come in here and give a big thanks to tom and everyone else who helped make this kit possible. I just finished ( took me about 8 hours) and i am very pleased with the results. I followed the build guide on the forums here and everything went off without a hitch.!! something i'm not used to. I fired it up and started playing immediately ( and still now too). thanks for making such a great kit and diy experience. now I gotta save up for the minimax!

 I am glad I got in on this last run of starving students. couldn't be happier!

 pics!!


----------



## particleman14

edit double..


----------



## Juaquin

The plastic rings go _between_ the case and the front panels. Of course, you don't have to if you like this look better, but that's how it was designed.


----------



## tomb

Quote:


  Originally Posted by *Jrome* /img/forum/go_quote.gif 
_Thanks Tom! 
 (I was the one who shattered one 
	

	
	
		
		

		
		
	


	




)

 This was my first time using tubes, and I just had no idea what I should expect. Thanks for all of your help and being so understanding!_

 

True confessions? I wasn't going to identify you!


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_The plastic rings go between the case and the front panels. Of course, you don't have to if you like this look better, but that's how it was designed._

 

Yep. It's very easy to slip the plastic bezel over the end plates with a small twist, even with all the wiring attached.


----------



## Juaquin

If you look closely at my avatar (the SSMH), you'll see I took that picture before I had figured it out too. Shhh


----------



## the_equalizer

Quote:


  Originally Posted by *particleman14* /img/forum/go_quote.gif 
_Just wanted to come in here and give a big thanks to tom and everyone else who helped make this kit possible. I just finished ( took me about 8 hours) and i am very pleased with the results. I followed the build guide on the forums here and everything went off without a hitch.!! something i'm not used to. I fired it up and started playing immediately ( and still now too). thanks for making such a great kit and diy experience. now I gotta save up for the minimax!

 I am glad I got in on this last run of starving students. couldn't be happier!

 pics!!_

 

Congratulations on your build! If you liked the DIY experience of the "Starving Student" Hybrid (which I like very much too; I've built three of them, and have a fourth variation in the oven) you'll absolutely *love* the MiniMAX kit. I just built one this last weekend and all I can tell you is: go for it.

 cheers!


----------



## Lil' Knight

Noise issue solved 
	

	
	
		
		

		
		
	


	




 sweet sound coming.











 At first I thought the channel was imbalanced; the left side was a little bit louder than the right one. However, after 15 minutes, the sound is much more balanced now.

 Another point is that when I tested the amp uncased, no noise. But when I attached the front panel into the case, there's noise! Looks like the volume control touches the hole of the panel. Will try to figure this but it's sounding great with my AD2000 right now. What is the values of low and high gain? I'm running high gain but it might be high for my AD2000.

 Thanks tomb for the great project. 3 days of fun building my first ever amp (I even never built the Cmoy before). Will switch to the green LED when it comes.


----------



## Juaquin

Lil' Knight - you too! Plastic rings go _between_ the pieces of case metal, not on the very outside!


----------



## Yaka

which rings are you talking about?


----------



## Lil' Knight

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Lil' Knight - you too! Plastic rings go between the pieces of case metal, not on the very outside! 
	

	
	
		
		

		
		
	


	


_

 

LOL. I didn't notice that. Will change it when I have time.


----------



## the_equalizer

Quote:


  Originally Posted by *Yaka* /img/forum/go_quote.gif 
_which rings are you talking about?_

 

He's talking about the rectangular front and back panel plastic bevels.

 EDIT: I meant *bezels* not bevels 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## tomb

Yeah, it's easier to get the picture when you see the picture.
	

	
	
		
		

		
		
	


	








 It's especially clear on the silver cases, because the plastic bezels are still black.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>
 It's especially clear on the silver cases, because the plastic bezels are still black.
	

	
	
		
		

		
			



_

 

*bezel* : that's the word I was looking for 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## particleman14

hah ic whaT i did wrong. fixed the bezel thing.. I was so excited about the last step i did it wrong
	

	
	
		
		

		
		
	


	



 ALso, is there any possibility to try a little tube rolling with these? any recommendations for comparison sake? 

 Lil knight, thing sounds good with the uDAC huh? 
 for a 1st project that's a pretty good job man..props


----------



## Lil' Knight

Yes, it sounds really nice but I have to lower the volume on the uDAC. The bass distorts when I set it at full volume.

 I will enjoy this little gem for a while before moving to the Mini Maxx. Hopefully I'm capable of building it


----------



## the_equalizer

Quote:


  Originally Posted by *particleman14* /img/forum/go_quote.gif 
_hah ic whaT i did wrong. fixed the bezel thing.. I was so excited about the last step i did it wrong
	

	
	
		
		

		
		
	


	



 ALso, is there any possibility to try a little tube rolling with these? any recommendations for comparison sake? 

 Lil knight, thing sounds good with the uDAC huh? 
 for a 1st project that's a pretty good job man..props_

 

No tube rolling on this amp, unless you refer to trying different brands of the same tube (19J6).

 cheers!


----------



## Juaquin

No tube rolling on the PCB version, at least not easily. Other tubes that are similar use a different pin layout - you'd have to cut pins and re-make solid connections, plus change some resistors on the board.


----------



## Lil' Knight

So I'm looking at the Minimax instruction and see this:






 Looks like the grounds are tied together. Is there any difference between this and separate grounds? I mean the 2 ground tabs on the RCA jacks don't touch together.


----------



## tomb

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_So I'm looking at the Minimax instruction and see this:

 <IMG]http://www.diyforums.org/MiniMAX/construction/wiring/RCA1.jpg[/IMG>

 Looks like the grounds are tied together. Is there any difference between this and separate grounds? I mean the 2 ground tabs on the RCA jacks don't touch together._

 

It's six of one and half-a-dozen of the other, isn't it? The grounds all come together in the terminal block, anyway. The important thing is that both RCA jacks are grounded and that you use two ground wires to lower the resistance of the ground path compared to the signal wiring (IMHO).


----------



## Lil' Knight

Gotcha. Thanks.

 I'm very interested in the minimax but have no idea how to do the tube bias so I guess I have to stay away from it for a while


----------



## the_equalizer

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Gotcha. Thanks.

 I'm very interested in the minimax but have no idea how to do the tube bias so I guess I have to stay away from it for a while 
	

	
	
		
		

		
		
	


	


_

 

Biasing the tubes is the *easiest* part of building the MiniMAX, really. Being able to carefully follow the BOM and the board layout to sort out the sheer number of components, put each one in its correct location in the board and all the soldering you have to do are the hardest parts, IMO. Biasing the output diamond buffers would come in a close second. 

 Sharpen both your soldering and DMM usage skills and you'll be fine building a MiniMAX. Just get a scrap PCB or a RadioShack protoboard (part no. 276-0150) to practice your soldering. In the DMM front read a good tutorial (google: DMM tutorial) and you'll be set.

 You might also want to follow the MiniMAX thread here and read as much as you can before you delve into that build.

 cheers !


----------



## UKToecutter

Damn international mail!!!!!

 Nothing arrived as yet.


----------



## Chipp

Got a bit of a shielding question I didn't see answered - I've recently started using my Starving Student with my ER6i and/or RP-21, as opposed to my 80-ohm DT770s. This combo of lower impedance/higher sensitivity has led me to notice a quite obnoxious rendition of my college's FM radio station in the right channel (as the 1,300w transmitter for the station sits about an 1/8th a mile from my dorm). 

 Is there anything I can do to help reduce this? I'd thought of lining the insides of my wood case with aluminum foil and then tieing that to ground, but then I remembered that the interference is only in one channel, which seems to suggest there is a flaw in my construction somewhere that is allowing for excessive noise. 

 Any hints?


----------



## iPoodz

Alright guys, get ready for a really novice question.

 I noticed that TomB specified what wire he used for the LEDs, but I didn't see any mention of the wires used in the other part of the project. I just bought an obnoxious amount of something called 'hookup wire' {stranded, 22-guage} from RadioShack. I also have some left over, stranded silver cable from earlier projects. 

 Would any of these work for the full project? Or should I return the RadioShack wire, and look elsewhere?


----------



## Juaquin

22awg hookup wire is fine for the power connections. I would use better stuff for the audio signal, like that stranded silver.


----------



## the_equalizer

Quote:


  Originally Posted by *Chipp* /img/forum/go_quote.gif 
_Got a bit of a shielding question I didn't see answered - I've recently started using my Starving Student with my ER6i and/or RP-21, as opposed to my 80-ohm DT770s. This combo of lower impedance/higher sensitivity has led me to notice a quite obnoxious rendition of my college's FM radio station in the right channel (as the 1,300w transmitter for the station sits about an 1/8th a mile from my dorm). 

 Is there anything I can do to help reduce this? I'd thought of lining the insides of my wood case with aluminum foil and then tieing that to ground, but then I remembered that the interference is only in one channel, which seems to suggest there is a flaw in my construction somewhere that is allowing for excessive noise. 

 Any hints?_

 

I'd say shielding will definitely help. Still, I've found some 19J6 tubes to be more susceptible to picking up hum and noise. Maybe swap the tubes and see if the radio follows the tube? If it does, I guess you'll need to shield the tubes.

 My first build using 19J6 tubes hummed like crazy in one channel when using sensitive phones (not only IEM's, it happened with my Denon cans, for example). When I slipped a shield from one of the preamp tubes in my speaker amp over the offending channel tube, and making sure the tube-shield touched the tube-socket screws (which were grounded) the amp was as silent as can be.

 cheers!


----------



## Meliphcient

Just started to test mine after building thisevening. Took a bit more than I expected, maybe 10 hours all told. I'm new to DIY audio stuff and literally had to wipe the dust off my soldering iron from highschool.

 This is my first experience with tubes so I wasn't sure if i'd seated them hard enough or not. Turned on the amp - LEDs lit up nice and green - turned on my old discman (ready to be sacrificed if I'd wired something up wrong) and plugged in some el-cheapo headphones (again incase something went wrong). At first...silence....then a gentle glow from the tubes! ALL WAS NOT LOST! faintly at first, then slowly louder it came - the music!

 I popped the earphones in for a moment to see what sort of volume this beast was going to give me...and I was almost in tears. I have never heard a soundstage like it. My post count and join date are probably very good indicators that I am damn new to this, but what an eye opener. If this is what's on offer from a relatively cheap amp, cheap source and cheap headphones...I know where all my money will be going soon 
	

	
	
		
		

		
		
	


	









 Thanks Tom for making the kit available and getting it all the way out to Australia for me


----------



## Meliphcient

Ok I thought it was in my head....but the left channel is slightly weaker than the right. I pulled my headphones (Senn HD215) off and swapped them around, the difference is very noticeable when you A/B it like that.
 Any suggestions where to look for the fault? I was very careful and inspected every solder along the way - could it be the wires connecting the RCA inputs to the board?


----------



## UKToecutter

I guess you could swap the tubes around and see if the weaker channel appears on the other ear.


----------



## tomb

Quote:


  Originally Posted by *Meliphcient* /img/forum/go_quote.gif 
_Ok I thought it was in my head....but the left channel is slightly weaker than the right. I pulled my headphones (Senn HD215) off and swapped them around, the difference is very noticeable when you A/B it like that.
 Any suggestions where to look for the fault? I was very careful and inspected every solder along the way - could it be the wires connecting the RCA inputs to the board?_

 

UKToecutter's advice is good. However, keep in mind that there are no tubes left to provide matching.
	

	
	
		
		

		
			





 You may be able to adjust the input resistors to a higher rating (I provided two choices in the kit - 50K and 100K). Using higher value resistors would move the typical volume setting to a point higher in the volume pot's travel - where it may be better matched.

 Hopefully, you're experiencing the imbalance in the pot. CD players tend to have fairly high outputs and earphones are pretty efficient. The combination may mean that you're in the very low end of pot travel and the little Alpha is not matched very well between channels at that point.

 P.S. Just a word to the wise - don't ever have your headphones plugged in when you power it up. Power it up first, make sure the tubes are warmed up, then plug in your headphones.

 Strictly speaking, there is 19V on the headphone output until the output coupling caps charge up. The SSMH is a bit forgiving in this regard because the power supply takes a while for the voltage to develop. If you had done that with another OTL tube amp or hybrid without a relay-delay, you might've blown out your headphones.


----------



## the_equalizer

Quote:


  Originally Posted by *Meliphcient* /img/forum/go_quote.gif 
_Just started to test mine after building thisevening. Took a bit more than I expected, maybe 10 hours all told. I'm new to DIY audio stuff and literally had to wipe the dust off my soldering iron from highschool.

 This is my first experience with tubes so I wasn't sure if i'd seated them hard enough or not. Turned on the amp - LEDs lit up nice and green - turned on my old discman (ready to be sacrificed if I'd wired something up wrong) and plugged in some el-cheapo headphones (again incase something went wrong). At first...silence....then a gentle glow from the tubes! ALL WAS NOT LOST! faintly at first, then slowly louder it came - the music!

 I popped the earphones in for a moment to see what sort of volume this beast was going to give me...and I was almost in tears. I have never heard a soundstage like it. My post count and join date are probably very good indicators that I am damn new to this, but what an eye opener. If this is what's on offer from a relatively cheap amp, cheap source and cheap headphones...I know where all my money will be going soon 
	

	
	
		
		

		
		
	


	




 Thanks Tom for making the kit available and getting it all the way out to Australia for me 
	

	
	
		
		

		
		
	


	


_

 

Ah, yes! That sweet moment when you turn the amp on and the tubes soft glow starts coming up.... Congratulations on your build!

 As to the channel-imbalance issue and related to TomB's comment on the output of your portable CD player. Try lowering the volume in your CD player, and turning it up in the amp. Sure, this will worsen the signal-noise ratio a bit, but hopefully not much, and it will allow you to turn up the pot to a point where the channels are better matched.

 If this doesn't work, well then you can try the input resistors or get a better volume pot. Try reading this post and the ensuing discussion.

 cheers!


----------



## tomb

Please note:

*The Starving Student Millett Hybrid PCB kits are all sold out.*


----------



## Yaka

that was quick, your hard work deserves such popularity


----------



## Lil' Knight

Quote:


  Originally Posted by *Meliphcient* /img/forum/go_quote.gif 
_Ok I thought it was in my head....but the left channel is slightly weaker than the right. I pulled my headphones (Senn HD215) off and swapped them around, the difference is very noticeable when you A/B it like that.
 Any suggestions where to look for the fault? I was very careful and inspected every solder along the way - could it be the wires connecting the RCA inputs to the board?_

 

I also noticed this with my SSMH. As mentioned, try swapping the tubes and waiting for the tubes warming-up. The channel would be much more balanced.


----------



## oxymoron08

Hi guys,

 I have been reading up on the cmoy build, a few guys on recommended on another forum. I don't really wanna build a cmoy as I will have no use for it.

 I have never even held a soldering gun before, is this easy enough for someone who's most electrical experience is building his own pc's, and thats just mechano 
	

	
	
		
		

		
		
	


	




 Am I going to be biting of more than i can chew?


----------



## simwells

Quote:


  Originally Posted by *oxymoron08* /img/forum/go_quote.gif 
_Hi guys,

 I have been reading up on the cmoy build, a few guys on recommended on another forum. I don't really wanna build a cmoy as I will have no use for it.

 I have never even held a soldering gun before, is this easy enough for someone who's most electrical experience is building his own pc's, and thats just mechano 
	

	
	
		
		

		
		
	


	




 Am I going to be biting of more than i can chew?_

 

I wouldn't say so no, I'd just practise soldering random wires together and things first, there's nothing at all complex with the soldering needed to do one of these P2P.


----------



## oxymoron08

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_I wouldn't say so no, I'd just practise soldering random wires together and things first, there's nothing at all complex with the soldering needed to do one of these P2P._

 

ok, my Dad is pretty handy and I need to learn these things anyway. My uncle is a sparky so should be able to help out too.

 Where can I source parts in England?


----------



## simwells

Quote:


  Originally Posted by *oxymoron08* /img/forum/go_quote.gif 
_ok, my Dad is pretty handy and I need to learn these things anyway. My uncle is a sparky so should be able to help out too.

 Where can I source parts in England?_

 

Farnell, maplin, RS etc.

 Tubes and PSU will have to come from elsewhere though, PSU's are available through eBay. Tubes may not be so easy to find anymore.


----------



## oxymoron08

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Farnell, maplin, RS etc.

 Tubes and PSU will have to come from elsewhere though, PSU's are available through eBay. Tubes may not be so easy to find anymore._

 

ah thanks man!

 been on the bay and found this psu:
  Quote:


 Original Cisco Systems AC Adapter
 Model: EADP-18FB B
 P/N: 34-1977-05

 INPUT: 100V-240V~ 0.5A, 50-60Hz
 OUTPUT: 48V 0.38A
 Connecter size: Int. Diameter: 2.50mm 
 Ext. Diameter: 5.50mm

 Dimensions: 100 x 54 x 28 mm 
 

It's a tenner, buy it now. Is it the right one?


----------



## UKToecutter

yep, that's the one


----------



## quarzo

Hi people, I've read most of the thread but not all since its imposible. My build is complete and it's working as it should. But the tubes are not lightening too much, the mosfets are ok, the sound it's great but the I can barely see any light coming from them. They are a pair of Hungary made Tungsram. Should I worry about that?


----------



## UKToecutter

Quote:


  Originally Posted by *quarzo* /img/forum/go_quote.gif 
_Hi people, I've read most of the thread but not all since its imposible. My build is complete and it's working as it should. But the tubes are not lightening too much, the mosfets are ok, the sound it's great but the I can barely see any light coming from them. They are a pair of Hungary made Tungsram. Should I worry about that?_

 

And you're sure they are 19J6?


----------



## quarzo

Yes, absolutely shure. They light but don't shine very much. Just a bit on the bottom and on the top


----------



## quarzo

By the way, I had the power source made so it's not bought from a dealer. I get 46v instead of 48 and I' starting to worry about the amper measure but i have no idea how to use the tester to get that value. I'm a beginner sorry


----------



## UKToecutter

You will only see a slight glow from the heaters.

 Most of the people here have put LED's underneath their valves, so don't be fooled by how bright they look.


----------



## quarzo

I know, I've studied a lot of light and have seen many kinds of glow (non led) so just wanted to check on that. Had a lot of truble while building but learnt a lot, and it was my last doubt


----------



## Lou Erickson

Welcome to the world of Head-Fi, Meliphcient. Sorry about your wallet. 
	

	
	
		
		

		
			





 I would urge you not to go too far and too fast with your newfound fun. Enjoy the Starving Student for a while, and the consider moving up carefully and thoughtfully. If you jump straight to the top of the heap, you miss out on a lot of the wonders and wonderful, "Oh, yes, that sounds fantastic!" moments that you get to experience on the way.


----------



## drclaw

I just finished building my kit! It is fantastic! 
 Thanks Tom!!!


----------



## tomb

Quote:


  Originally Posted by *drclaw* /img/forum/go_quote.gif 
_I just finished building my kit! It is fantastic! 
 Thanks Tom!!!_

 

It doesn't count without pics.


----------



## drclaw

Here are some pics!





 With flash..


----------



## iPoodz

Alright, tonight was a fun Saturday night/Sunday morning.

 I was so anxious upon completing the amp, because the only other amp I'd ever built was dead as soon as I turned it on.

 With the SSHA, I hoped it would be different. It wasn't 
	

	
	
		
		

		
		
	


	




 However, I checked this thread, and saw the issues people were having as a result of insufficient insulation of the MOSFETs. I quickly disassembled, and added the extra washers, which I didn't remember, in the guide.

 {quick question: did I irreversibly mess something up, but just don't know it yet?}

 Then, I was only getting volume in one of the ears. I checked around the PCB, and by chance, happened to touch the green electrolytic on the left side, and suddenly: SOUND IN BOTH EARS!!! I was extatic, so I disconnected everything, and fixed the capacitor's leads.

 Now, the only issue was, that only one of the two LEDs was being illuminated {this isn't a result of the cap. only one was being illuminated the whole time}. I remembered that I put the left side LED through some trouble while assembling it {testing out different ways so it would fit properly}, so I cut it out, and replaced it with a amber one I had.

 Rather than try and explain what's going on, I figured a video might be more useful.

 Any thoughts would be appreciated. I'm too tired to do anything right now, but I look forward to your suggestions/solutions, in the morning!


+ YouTube Video​ _*ERROR:* If you can see this, then YouTube is down or you don't have Flash installed._ 




 Btw, thank you, Tom. I would not have made it without your guide, or your beautifully crafted kit. I also feel confident, after following the guide, that I can move onto projects that are a bit more involved, now!

 EDIT: Ok, so my amp just took a fall, beacuse I tripped over the power cord. Thankfully, the tubes were out, but not so thankfully, the case wasn't on. I didn't see any major damage, except for the pot breaking almost completely off. I'll check in the morning for any other damage, but cosmetically, I don't see anything.

 So, my question is: should I get this or this to replace my broken pot? 

 I ask, because on the BOM, the first link is what it has under Dsavitsk's outline, but the description corresponds to the second link.

 I feel so terrible about this, I really want to order it ASAP.


----------



## oxymoron08

I can't seem to find the SSMH PCB anywhere, has it been discontinued?


----------



## UKToecutter

Quote:


  Originally Posted by *oxymoron08* /img/forum/go_quote.gif 
_I can't seem to find the SSMH PCB anywhere, has it been discontinued?_

 

All gone.

 You'll have to do a point to point build I guess.


----------



## oxymoron08

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_All gone.

 You'll have to do a point to point build I guess._

 

ah right i see! I think I may buy some of that holey stuff for a cmoy build and practice soldering first. Then build the cmoy.

 Then when I have read up on what capicitors and resistors actually are I may feel more confident.

 I'm one of those people that must understand what each part does before I wildly start soldering


----------



## Meliphcient

I was too busy today to do more than basic troubleshooting as per everyones suggestions.
 First up the volume pot makes no difference where it is. Max, min, middle, all favour the right channel.
 Secondly swapping the tubes did....nothing!

 I'm guessing bad workmanship on my part, or a bad cable from the source (I only own one mini-to-rca cable) but I bought some connectors and cable when I was out today so I'll knock together another cable and see how that goes.


----------



## UKToecutter

I can't see the cable being the culprit (although it's possible).
 Have you checked that you have the correct value resistors in all positions?

 The volume pot is a possibility. Do you have another you can test?


----------



## tomb

Quote:


  Originally Posted by *iPoodz* /img/forum/go_quote.gif 
_EDIT: Ok, so my amp just took a fall, beacuse I tripped over the power cord. Thankfully, the tubes were out, but not so thankfully, the case wasn't on. I didn't see any major damage, except for the pot breaking almost completely off. I'll check in the morning for any other damage, but cosmetically, I don't see anything.

 So, my question is: should I get this or this to replace my broken pot? 

 I ask, because on the BOM, the first link is what it has under Dsavitsk's outline, but the description corresponds to the second link.

 I feel so terrible about this, I really want to order it ASAP._

 

Get the 50K. We tried both in the prototypes and I couldn't tell a difference. However, it really just ends up being what input resistors you used. Since the input resistors that came with the kit were sized for the 50K pot, you should get that one.
	

	
	
		
		

		
		
	


	




 EDIT: Your LED's definitely are wired badly. You need to work on the connections to the PCB - that's why the other one is going out when you put pressure on the amber one. It's forcing one wire to connect and in turn, forcing the other wire to disconnect. That means shoddy connections on both, unfortunately - at the PCB. Those are pretty small holes on the PCB, so you have to be careful what wire size you use, etc. 22ga will fit, but you have to do everything just right. Maybe you could get some smaller wire - 24ga or even smaller. It's not going to hurt, the LEDs draw very little current.


----------



## the_equalizer

Quote:


  Originally Posted by *quarzo* /img/forum/go_quote.gif 
_Yes, absolutely shure. They light but don't shine very much. Just a bit on the bottom and on the top_

 

 Quote:


  Originally Posted by *quarzo* /img/forum/go_quote.gif 
_By the way, I had the power source made so it's not bought from a dealer. I get 46v instead of 48 and I' starting to worry about the amper measure but i have no idea how to use the tester to get that value. I'm a beginner sorry_

 

 Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_You will only see a slight glow from the heaters.

 Most of the people here have put LED's underneath their valves, so don't be fooled by how bright they look._

 

Actually most 19J6 give out a considerable amount of light. There are some, though, that have _enclosed heaters_ and those will shine a bit on the bottom and on the top. They work just as well in the circuit.

 As to the power supply it's ok if it's a couple of volts off. My Cisco supply puts out 47 volts. The current that the supply puts out is a little bit more important; but I'm guessing if your amp turns on (meaning the tubes light up) your supply is quite probably coping with the current demand ok.

 cheers!


----------



## tomb

Quote:


  Originally Posted by *drclaw* /img/forum/go_quote.gif 
_Here are some pics!






 With flash..







_

 

Those are page links, not image links. Here's what they should look like:




 with flash -





 Good job!
	

	
	
		
		

		
		
	


	




 P.S. I'm not sure, but it looks like you may have the bezels reversed, even though the endplate is on the correct side.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Those are page links, not image links. Here's what they should look like:
 <snip>

 Good job!
	

	
	
		
		

		
		
	


	




 P.S. I'm not sure, but it looks like you may have the bezels reversed, even though the endplate is on the correct side.
	

	
	
		
		

		
		
	


	


_

 

It certainly looks as if it were reversed in the first pic.

 cheers !


----------



## getllamasfast

Hey guys I'm having trouble with finishing my second 12AU7 ssmh. When the tubes aren't plugged in, the voltage at pin 4 on both sockets is ~16v, which is where it should be. When I put the tubes in, the voltage drops to ~.2V at both of them. With the_equalizer's help, I've managed to figure out that it is a miswiring, but I can't seem to find out where I've made my mistake.

 Does anyone know what could possibly be wired up wrong that would cause the big voltage drop?


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Hey guys I'm having trouble with finishing my second 12AU7 ssmh. When the tubes aren't plugged in, the voltage at pin 4 on both sockets is ~16v, which is where it should be. When I put the tubes in, the voltage drops to ~.2V at both of them. With the_equalizer's help, I've managed to figure out that it is a miswiring, but I can't seem to find out where I've made my mistake.

 Does anyone know what could possibly be wired up wrong that would cause the big voltage drop?_

 

Just to add a bit more info. The tubes are known good, since they work perfectly OK when plugged into a working SSMH. 

 Thus, there has to be a miswiring in this other amp, causing a short and the supply to drop.

 As to where that short exactly resides, it is very difficult to say. Getllamasfast has already gone through the tube socket wiring and he tells me it is OK. So, it must be something in the protoboard layout.

 cheers!


----------



## iPoodz

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Get the 50K. We tried both in the prototypes and I couldn't tell a difference. However, it really just ends up being what input resistors you used. Since the input resistors that came with the kit were sized for the 50K pot, you should get that one.
	

	
	
		
		

		
		
	


	




 EDIT: Your LED's definitely are wired badly. You need to work on the connections to the PCB - that's why the other one is going out when you put pressure on the amber one. It's forcing one wire to connect and in turn, forcing the other wire to disconnect. That means shoddy connections on both, unfortunately - at the PCB. Those are pretty small holes on the PCB, so you have to be careful what wire size you use, etc. 22ga will fit, but you have to do everything just right. Maybe you could get some smaller wire - 24ga or even smaller. It's not going to hurt, the LEDs draw very little current.
	

	
	
		
		

		
		
	


	


_

 

Thanks, Tom. I'll order that right away.

 I was on my way to make sure I turned the switch off and disconnected the power supply, when I tripped over the wire, and painfully found the answer to my question.

 I just checked, and both the tubes are getting hot, and I plugged in my headphones for a few seconds, and got sound in both ears 
	

	
	
		
		

		
		
	


	




 {the right side might be a little lower, but I'll deal with that later!}

 I assume that because pretty much everything's working, using the MOFSETs without proper insulation for a few minutes wasn't a killer.

 Also, I cracked the ceramic on the R16 resistor. I had initially soldered the 100KOhm on, but realized that this was for low gain, and in the re-soldering, I cracked the ceramic part. I'm ordering two, from Mouser, but do I really need to replace it?

 Finally, what tool should I use to tighten the knob on the pot? I tried searching online, but I'm blanking on what it's called.


----------



## the_equalizer

Quote:


  Originally Posted by *iPoodz* /img/forum/go_quote.gif 
_
 <snip>
 Finally, what tool should I use to tighten the knob on the pot? I tried searching online, but I'm blanking on what it's called._

 

It's an Allen wrench or hex key. 

Hex key - Wikipedia, the free encyclopedia

 Unfortunately I can't tell you what size you need since I don't own a PCB version of the SSMH anymore.

 EDIT: OK, if my memory serves me well, I'd say it's the key labeled 3''/32 in my set.

 cheers!


----------



## getllamasfast

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Just to add a bit more info. The tubes are known good, since they work perfectly OK when plugged into a working SSMH. 

 Thus, there has to be a miswiring in this other amp, causing a short and the supply to drop.

 As to where that short exactly resides, it is very difficult to say. Getllamasfast has already gone through the tube socket wiring and he tells me it is OK. So, it must be something in the protoboard layout.

 cheers!_

 

Actually I just figured it out!!! I feel so stupid now because the problem was so simple. It was that pin 2 of the mosfets was wired up after r13 when it should have been wired up right before it... 

 I really need to take my time with these things.
	

	
	
		
		

		
		
	


	




 I'll post pics later. 
	

	
	
		
		

		
		
	


	




 PS: I love you equalizer! : 
	

	
	
		
		

		
		
	


	




 EDIT: well, upon testing the amp there is a buzzing noise that gets progressively louder as I turn up the pot. Also, there is this weird issue where the right channel is much louder than the left until I turn the pot about 3/4 it's full rotation. Any ideas?

 EDIT: EDIT: This is the pot I'm using: Digi-Key - P2S2503-ND (Manufacturer - EVJ-CC1F02368)


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Actually I just figured it out!!! I feel so stupid now because the problem was so simple. It was that pin 2 of the mosfets was wired up after r13 when it should have been wired up right before it... 

 I really need to take my time with these things.
	

	
	
		
		

		
		
	


	




 I'll post pics later. 
	

	
	
		
		

		
		
	


	




 PS: I love you equalizer! : 
	

	
	
		
		

		
		
	


	




 EDIT: well, upon testing the amp there is a buzzing noise that gets progressively louder as I turn up the pot. Also, there is this weird issue where the right channel is much louder than the left until I turn the pot about 3/4 it's full rotation. Any ideas?

 EDIT: EDIT: This is the pot I'm using: Digi-Key - P2S2503-ND (Manufacturer - EVJ-CC1F02368)_

 

Good to hear you're making progress! Buzzing almost always means a grounding issue. That the buzzing varies with the volume pot would seem to indicate that your interconnects are bad or that the pot itself is bad, or that it is incorrectly wired (see next paragraph). If the pot's body is metallic, solder a wire from the pot's body to ground.

 About the channel imbalance I'm at a loss. Maybe you wired the pot in reverse ? Make sure it is the pot's *wipers* that are wired to the tubes.

 cheers!


----------



## drclaw

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Those are page links, not image links. Here's what they should look like:

 with flash -

 Good job!
	

	
	
		
		

		
		
	


	




 P.S. I'm not sure, but it looks like you may have the bezels reversed, even though the endplate is on the correct side.
	

	
	
		
		

		
		
	


	


_

 

Silly me, I guess that's what I get for being on a 2 AM
	

	
	
		
		

		
		
	


	




 Opps. They are. Easy fix though!

 It's a great little amp, and a great learning experience! It was my first project, and I couldn't be happier!


----------



## Oberst Oswald

My Beezar Starving Student is done. Couldn't ask for a better amp for the money and a real shame that this is the end of the kits & tubes. Some pictures...?


----------



## iPoodz

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_It's an Allen wrench or hex key. 

Hex key - Wikipedia, the free encyclopedia

 Unfortunately I can't tell you what size you need since I don't own a PCB version of the SSMH anymore.

 EDIT: OK, if my memory serves me well, I'd say it's the key labeled 3''/32 in my set.

 cheers!_

 

Thanks so much, equalizer!


----------



## Logos

Firstly, thanks to Tom for the really great work that went into this kit. It showed down to the immaculate packaging! 

 *Edit* Seem to have found a solution to my problem, was a mistake in the crimping of one of the fast-on connectors. Back to 
	

	
	
		
		

		
		
	


	




 This amp is super awesome and seems to provide a lot of value for the money. It's almost surprising. I've grown quite fond of the little guy...


----------



## tomb

Quote:


  Originally Posted by *Logos* /img/forum/go_quote.gif 
_Firstly, thanks to Tom for the really great work that went into this kit. It showed down to the immaculate packaging! 

 *Edit* Seem to have found a solution to my problem, was a mistake in the crimping of one of the fast-on connectors. Back to 
	

	
	
		
		

		
		
	


	




 This amp is super awesome and seems to provide a lot of value for the money. It's almost surprising. I've grown quite fond of the little guy..._

 

Well, whatever the symptoms - glad you found your problem and that you're enjoying the amp.
	

	
	
		
		

		
		
	


	




 EDIT: Great pics, Oberst!!


----------



## Kitarist

I really need to build one of these to see whats all the hype about


----------



## Logos

Thanks again, Tom! Here are some pics for your enjoyment:

*Ocean Green!*






*Spot the Gamma 1*





*Headphone Love*





 Thanks for looking! 
	

	
	
		
		

		
		
	


	




 P.S. Kitarist: Do it!


----------



## simwells

Finally got my tubes this morning and it does sound really good, letting it burn it atm.

 Here's my little P2P version;


----------



## UKToecutter

Thats a very nice looking and compact build...


----------



## the_equalizer

Quote:


  Originally Posted by *Logos* /img/forum/go_quote.gif 
_Thanks again, Tom! Here are some pics for your enjoyment:

 <snip>

 Thanks for looking! 
	

	
	
		
		

		
		
	


	




 P.S. Kitarist: Do it!_

 

Nice pics! I like the Grado's + SSMH combo a lot.

  Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_Finally got my tubes this morning and it does sound really good, letting it burn it atm.

 Here's my little P2P version;_

 


 Cool build! You even managed to find a couple 19J6 tubes, congratulations! 

 cheers!


----------



## simwells

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Cool build! You even managed to find a couple 19J6 tubes, congratulations! 

 cheers!_

 

I may (debating what to do with them) have a couple spare too.


----------



## UKToecutter

Quote:


  Originally Posted by *simwells* /img/forum/go_quote.gif 
_I may (debating what to do with them) have a couple spare too._

 

I'd keep a hold of them if I were you.

 You never know how long the ones you're using will last !!!!


----------



## Jrome

So I finally got my replacement tube! (Thanks TomB!)


 Everything works and it sounds awesome. One quick question, the tube on the right is glows slightly brighter than the one on the left. Is this a cause for concern?


----------



## tomb

Quote:


  Originally Posted by *Jrome* /img/forum/go_quote.gif 
_So I finally got my replacement tube! (Thanks TomB!)


 Everything works and it sounds awesome. One quick question, the tube on the right is glows slightly brighter than the one on the left. Is this a cause for concern?_

 

No - no cause for concern. Every tube glows somewhat differently. Even if you switched them and noticed that the right side still glow brighter, the circuit itself splits the voltage through resistors. That usually results in one side being slightly brighter than the other s imply because of the minute differences in resistors.


----------



## ethan961

A few months ago I had a problem, it seemed that there was a short and one tube was getting 48v. Well, after months of off and on searching for the short, I discovered that one of the FEts had gone bad and was providing no resistance. Replaced that and everything is working great 
	

	
	
		
		

		
		
	


	




 I'm not sure if this has been posted before but that's just my experience.


----------



## Entropy1

So I just swapped out the MOSFETs (thanks a lot tomb) and am getting the channel bleed. Before the MOSFET swap, it wouldn't even turn on, but that also means I might be in a position to kill this set too. I don't know what is going on. Between the metal on the MOSFETs and ground there is ~4k which I'm hoping is okay as i spent a bit of time making sure they were isolated. It seems to me as if there must still be two issues as the still present significant volume difference and channel bleed are still both present. I've gone over all the soldering and wiring connections several times and have failed to spot a problem. Does anyone have any ideas or what would be some good resistances to check? Thanks for any help.


----------



## Entropy1

I've been checking resistances and for some reason decided to check the resistance directly from the input to the output expecting to get no continuity from each channel. For some reason though, I am getting just over 100k between the left input and left output, right output and ground. The right channel yields infinite resistance between everything as i believe it should. Any ideas on how this could have happened? I don't see any solder bridges and am pretty puzzled by it. Thanks again.

 Edit: there appears to be some resistance between left and ground at the terminal block input. This also exists with the wires connecting the rca jack disconnected.


----------



## the_equalizer

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_I've been checking resistances and for some reason decided to check the resistance directly from the input to the output expecting to get no continuity from each channel. For some reason though, I am getting just over 100k between the left input and left output, right output and ground. The right channel yields infinite resistance between everything as i believe it should. Any ideas on how this could have happened? I don't see any solder bridges and am pretty puzzled by it. Thanks again.

 Edit: there appears to be some resistance between left and ground at the terminal block input. This also exists with the wires connecting the rca jack disconnected._

 

Resistance measurements in circuit do not usually say much. If you look at the schematic, you can see that at the input terminal block, you can expect to see a resistance of 50K (the volume pot) from the live wire to ground.

 Measuring MOSFET isolation could turn out to be somewhat tricky too, but 4K definitely does not seem right; the value should be up in the megohm range. The MOSFET's metal tab is electrically connected to pin 2, if I remember correctly. If you look at the schematic you can see that there's a big decoupling capacitor (C1) strapped from both the MOSFETs' pin 2 to ground, which will affect the measurement.

 Connected between the 48 volt line (which is connected to the MOSFETs' pin 2) and ground you also have the series combination or R13 and the parrallel combination of R2-R4 and R8-R10 which totals 222Kohms; again affecting your measurements of MOSFET tab to case isolation.

 cheers!


----------



## Entropy1

Thanks for the response. I'm aware that the readings don't necessarily mean much but I'm hoping that the discrepancies at the same points of each channel should tell me if any inconsistencies that might exist. Are there any better approaches I should be taking? Thanks again.


----------



## the_equalizer

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Thanks for the response. I'm aware that the readings don't necessarily mean much but I'm hoping that the discrepancies at the same points of each channel should tell me if any inconsistencies that might exist. Are there any better approaches I should be taking? Thanks again._

 

Well, in the case of measuring the MOSFET to case isolation, and if this is a PCB beezar.com build we're talking about, I'd make sure the sliding aluminum panel to which the MOSFET's are bolted is *not grounded* when I take the measurement, so that the capacitor and resistors I mentioned before do not influence the measurement. 

 To this end I would completely remove the panel from the case and I'd temporarily remove the standoff, then I'd measure the resistance from MOSFET tab to aluminum panel, which should be in the megohm range. 

 As to the other circuit problems, it's difficult to imagine what could be causing the channel bleed. The volume difference could be caused by cold solder joints, bad MOSFETs, wrong value resistors, defective volume pot, etc, etc, Maybe you could provide us with some clear pictures of your wiring and of the PCB ?

 cheers!


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Thanks for the response. I'm aware that the readings don't necessarily mean much but I'm hoping that the discrepancies at the same points of each channel should tell me if any inconsistencies that might exist. Are there any better approaches I should be taking? Thanks again._

 

Pics?


----------



## Entropy1

Here are the pictures. I apologize about the poor picture quality but they're all I can get hold of. Not all of the soldering points are pretty, but I'm pretty sure all are okay. I have no idea what else could be wrong.

Imageshack - img00018201002171926.jpg
Imageshack - img00017201002171926.jpg
Imageshack - img00014201002171925.jpg
Imageshack - img00008201002171921.jpg


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Here are the pictures. I apologize about the poor picture quality but they're all I can get hold of. Not all of the soldering points are pretty, but I'm pretty sure all are okay. I have no idea what else could be wrong.

Imageshack - img00018201002171926.jpg
Imageshack - img00017201002171926.jpg
Imageshack - img00014201002171925.jpg
Imageshack - img00008201002171921.jpg_

 

Well, I can't tell anything from the pics - they're too out of focus. Besides, this doesn't tell us anything if you've got an issue when casing it up - momentary short, exposed wire, uninsulated MOSFET touching the case, etc.

 I'm also wondering about the LED resistor - I saw someone else snake that resistor lead around like that - curious. What was wrong with the open pad right there at the end of the resistor?


----------



## Entropy1

Yeah, I guess I didn't see that extra hole for the led resistor. Also, I get the same readings with the case on or off so I'm pretty sure I don't have a short. Any other suggestions?


----------



## iPoodz

I'm going to sidetrack for a second, while I'm waiting for a part to come from Mouser, and ask you all:

 Where do you go, online, to get real basic parts, like wires, RCA cables, solder, flux, etc?

 I'm trying to support my local mom+pop electronics shop, but the parts there suck [really flimsy 1/4" and 1/8" plugs, crappy switches for $8 a pop, and such], are overpriced, and they don't have a lot of variety. I've spent maybe maybe 80$ there over the last few weeks for various projects, and maybe 40$ at RadioShack, and never seem to walk away with the feeling that I got my money's worth.

 Do you have any favorite online vendors for parts/basic supplies?

 I know Harbor Freight is pretty good for helping hands, thanks to TomB's BantamDAC website.


----------



## Lil' Knight

Redco has a great variety of the parts you mentioned. Markertek has larger collection but price is not as good as that of Redco.


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Yeah, I guess I didn't see that extra hole for the led resistor. Also, I get the same readings with the case on or off so I'm pretty sure I don't have a short. Any other suggestions?_

 

Unless you can get us some pics that are in better focus:

Concentrate on those MOSFETs - make absolutely certain that they are isolated from the case.
Check all of your resistors - look at the rating designations and make certain that they're in the right positions. Refer to the Layout and/or PCB pages on the SSMH website. Reference those pics with the part #'s and ratings on the BOM. Make certain that you haven't switched up a resistor somewhere.
Go over your terminal block connections. Make certain you have the correct polarity coming in from the power supply and that you have proper grounding from the RCA jacks to the signal input terminal block at the volume pot.
If you've got any dodgy soldering, go over that again with more heat, more solder, and more flux. Be certain that you get wicking on the part side of the board. If you're unsure about what this is, refer to the Build Thread (link below) or the Construction pages on the SSMH website.
Check for any leads, standoff, etc. that may be touching a pad it shouldn't - especially around the LED resistor. Are the LED's lighting or is there any possibility of a short in the LED leads? Check for solder joints that may intrude into other areas. In one of your pics, it may have been the out-of-focus issue, but it looked like some significant solder blobs around the MOSFET pins. Is it possible those pins are shorting?
I hate to mention this again, but please remember that the PCB was/is thoroughly vetted. Every build has been successful - at least from every one of the kits - so far. So, you either have a part in the wrong place, wires/leads touching somewhere they shouldn't, or the MOSFETs are not properly isolated. That's pretty much all it can be.


----------



## Meliphcient

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_I can't see the cable being the culprit (although it's possible).
 Have you checked that you have the correct value resistors in all positions?

 The volume pot is a possibility. Do you have another you can test?_

 

No, but I do have an old dmm! I opened up my ssmh and took some readings - the volume pot is out on the rear set. I'll have to get another and swap them. If that solves my problem I'll be ecstatic


----------



## iPoodz

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Redco has a great variety of the parts you mentioned. Markertek has larger collection but price is not as good as that of Redco._

 

Thanks, Lil' Knight!

 Btw, I really like your build. Very neat, on the inside.


----------



## amc

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Unless you can get us some pics that are in better focus:

Concentrate on those MOSFETs - make absolutely certain that they are isolated from the case.
Check all of your resistors - look at the rating designations and make certain that they're in the right positions. Refer to the Layout and/or PCB pages on the SSMH website. Reference those pics with the part #'s and ratings on the BOM. Make certain that you haven't switched up a resistor somewhere.
Go over your terminal block connections. Make certain you have the correct polarity coming in from the power supply and that you have proper grounding from the RCA jacks to the signal input terminal block at the volume pot.
If you've got any dodgy soldering, go over that again with more heat, more solder, and more flux. Be certain that you get wicking on the part side of the board. If you're unsure about what this is, refer to the Build Thread (link below) or the Construction pages on the SSMH website.
Check for any leads, standoff, etc. that may be touching a pad it shouldn't - especially around the LED resistor. Are the LED's lighting or is there any possibility of a short in the LED leads? Check for solder joints that may intrude into other areas. In one of your pics, it may have been the out-of-focus issue, but it looked like some significant solder blobs around the MOSFET pins. Is it possible those pins are shorting?
I hate to mention this again, but please remember that the PCB was/is thoroughly vetted. Every build has been successful - at least from every one of the kits - so far. So, you either have a part in the wrong place, wires/leads touching somewhere they shouldn't, or the MOSFETs are not properly isolated. That's pretty much all it can be._

 


 Awesome summary Tomb - I too have a PCB build that has been giving me trouble but has been gathering dust for the last month out of frustration and lack of time for hobbies. This is new inspiration to dust it off again when things calm down around the house (pregnant wife seems more demanding these days of my time - go figure)...


----------



## Entropy1

I'll do my best to get hold of a better camera but in the meantime here are some of the results of what you suggested.

 1. I'm assuming both MOSFETs are isolated as I get the same reading on both MOSFETs with or without the case. Whether or not these readings make sense I don't know. Between ground and pin 1, I get the odd ~120k and between ground and 2 and 3 I get a reading approaching 0 continuity. This goes for both MOSFETs

 2. I've looked through all the resistors several times and haven't noticed anything incorrect.

 3. I've redone terminal connections several times and get the same readings regardless of whether or not they are connected.

 4. I've tried to do what I with the soldering but I have no solder wick or solder sucker to redo anything. I will attempt to get hold of something and redo some connections though.

 5. The LEDs glow fairly brightly as I believe they should. The MOSFETs are rather messy but each time I've resoldered them, I've gotten the same readings. Pins 1 and 2 give the 120k, 1 and 3 give infinite, and 2 and 3 give infinite.

 Thanks for the suggestions. I'll keep working with and and do not mean to sound like I am blaming the kit at all. I too am almost certain it is my own fault although I would like to verify that the volume pot is good. What bothers me most is that I get a continuity between left signal and the output. With that, the only thing I can think of is that the left signal must be touching ground somewhere. I honestly don't mind troubleshooting as it has kind of caused me to learn a bit more and somewhat understand the schematic.


----------



## Entropy1

So I just found the source for the difference in readings although I'm not sure which is correct. I just found that one of the two pins circled was grounded while the other was not. Now each channel is the same so that is a good thing. Should both of these be grounded or should both not be grounded? (I assume they should be the same) I can't quite tell by the pictures of the PCB which is correct.

http://img193.imageshack.us/img193/2...cb2800x650.jpg


----------



## Jrome

So I spoke a bit too soon when i said everything was going well....There's a problem!
 The weird thing is, the amp sounds fine, BUT there's only one channel going through both left and right.
 I only noticed this after listening to a song that i know pans from left to right. Through the amp, the left channel was loud and clear through both sides, but the right was through both as well but ultra quiet.

 Do any of you know what could be causing this?

 thanks


----------



## tomb

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_So I just found the source for the difference in readings although I'm not sure which is correct. I just found that one of the two pins circled was grounded while the other was not. Now each channel is the same so that is a good thing. Should both of these be grounded or should both not be grounded? (I assume they should be the same) I can't quite tell by the pictures of the PCB which is correct.

http://img193.imageshack.us/img193/2...cb2800x650.jpg_

 

Those are both grounded pads (connected to the ground plane). If you don't have good solder contact on those pads, it can cause all sorts of problems.


----------



## tomb

Quote:


  Originally Posted by *Jrome* /img/forum/go_quote.gif 
_So I spoke a bit too soon when i said everything was going well....There's a problem!
 The weird thing is, the amp sounds fine, BUT there's only one channel going through both left and right.
 I only noticed this after listening to a song that i know pans from left to right. Through the amp, the left channel was loud and clear through both sides, but the right was through both as well but ultra quiet.

 Do any of you know what could be causing this?

 thanks_

 

1. You've mis-wired the RCA jacks, or
 2. You've mis-wired the terminal block connections at the volume pot, or
 3. The soldering is messed up on the headphone jack, volume pot, or input terminal block, (worst culprit is bad connection to ground) or
 4. You don't have the headphone plug plugged in all the way in the jack.


----------



## UKToecutter

Another SSMH was born @ 15:30 UK time today.......


----------



## iPoodz

Pics or it didn't happen!

 Congrats.

 Silly question #(I lost count): I read tangent's DIY audio guide and realized that I've been using 60-40 solder for everything. Should I be worried about the longevity of the amp, as a result?


----------



## UKToecutter

I wasn't going to bother as they all look the same built from the kit but anyways. Here you go.............












 By the way...

 Tom, you are the man.

 The kit is beautifully packed and complete.
 Tubes are nicely match and no microphonics.

 And you have the patience of a saint.

 Thank you


----------



## the_equalizer

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_I wasn't going to bother as they all look the same built from the kit but anyways. Here you go.............
 <snip>

 By the way...

 Tom, you are the man.

 The kit is beautifully packed and complete.
 Tubes are nicely match and no microphonics.

 And you have the patience of a saint.

 Thank you_

 

Great pics ! nice looking pair of GE tubes.... man, all these pics make me miss my beezar.com SSMH.... 

 cheers!


----------



## Llama16

Great pics indeed and well done on the amp,
 and it never gets tired to look at some beautiful work.


----------



## tomb

Very nice pics and very nice comments, UKToecutter! Thank you very much!


----------



## skkhai

My contribution.






 Building it went smooth except one of the original 2 LEDs was DOA. Ended up ordering more and just finished switching the bad LED out. (I ordered 10 LEDs for this and another project but was actually sent 11, makes up for original one that was DOA 
	

	
	
		
		

		
		
	


	




)

 Can't wait until the next project... Kudos to Tom for a great kit.


----------



## iPoodz

How pretty! Are those white or blue LEDs?

 Tom, I didn't want to hijack the other thread more than I already did, but I wanted to thank you for your amazing advice. I was a little skeptical of the idea of adding solder to the joint, but I tried it anyway. The results were phenomenal.

 Before (here you can see the cracked ceramic on the gain resistor {I think that's what it is}. Worth replacing?):





 After:





 The pics don't do it justice, but except for the flux everywhere, it looks like there was nothing there before. Anyways, it's off-topic, but I'm just so grateful. This was surprisingly my favorite part of the build.


----------



## UKToecutter

Personally, I would replace the resistor even if it measured correctly.
 It isn't worth taking the chance of a failure later.

 My 2 cents worth (about the same cost as the resistor, nearly)


----------



## tomb

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Personally, I would replace the resistor even if it measured correctly.
 It isn't worth taking the chance of a failure later.

 My 2 cents worth (about the same cost as the resistor, nearly)

_

 

Yep - I agree with that.


----------



## iPoodz

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Personally, I would replace the resistor even if it measured correctly.
 It isn't worth taking the chance of a failure later.

 My 2 cents worth (about the same cost as the resistor, nearly)

_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep - I agree with that._

 

Okay, I definitely will, then. I ordered a few from Mouser, and I'm feeling pretty good about my desoldering skills now, so I'll do it in a few hours


----------



## Narwhalius

Hi all.

 Just finished up my build. Awesome kit by the way.






 This was my first experience with amps and soldering and I had a lot of fun building this. Originally I miswired one of the LED's so I took it apart and got that fixed. The music sounded awesome before I took it apart but when I put it back together I didn't get any sound in the left ear. Took it back apart again and everything looked fine, no wired touching, nothing that I could see that would cause this. So what should I do to fix this and what could be the cause?


----------



## the_equalizer

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_Hi all.

 Just finished up my build. Awesome kit by the way.

 <snip>

 This was my first experience with amps and soldering and I had a lot of fun building this. Originally I miswired one of the LED's so I took it apart and got that fixed. The music sounded awesome before I took it apart but when I put it back together I didn't get any sound in the left ear. Took it back apart again and everything looked fine, no wired touching, nothing that I could see that would cause this. So what should I do to fix this and what could be the cause?_

 

Congratulations! Great pic and a nice, clean build. I'd just point out that you installed the end panels and the bezels reversed. Here's the pic TomB posted a few pages back in the thread.






 As to the no sound issue, if the mute channel tube lights up and the MOSFET heats up, it could be the wiring from the RCA jack to the input block, or some cold solder joint along the way. Good luck debugging !

 cheers!


----------



## Narwhalius

Ah thanks for the pic. Wasn't really sure which way they were supposed to go so I just put em on. Though I gotta say I do like kinda like how it looks now. As far as the tube, yes it does light up and the MOSFET gets warm. I'll take another look at the solder joints. Thanks again.


----------



## iPoodz

I was listening to my amp, and it was sounding nice, then I heard a bit of crackle in the left channel, and suddenly, it sounded like the sound broke through, and was a lot louder/cleaner. It has yet to happen to the right channel. Is this normal/expected? I know that this needs a bit of burn-in time, but I didn't think it would be as pronounced as that.

 EDIT: I left the amp running for an hour or so, and I don't notice it anymore. So, nevermind


----------



## Dunceiam

Still having trouble with the SSMH P2P I'm building, 

 Symptoms: 

 One tube lights up as expected, the other is VERY dim. 
 Zero audio coming out of the amp. Not even crackling. 
 When you flick the switch, the LED flashes three times at the same rate in this video. But then stops, and the tube's begin to glow after it stops. 

 I've been checking and reflowing all the connections, the MOSFET's do indeed heat up now that I've used the Bergquist pads/mounting kit. 

 Any ideas? (Old, but largely the same) photos are here.
http://www.head-fi.org/forums/f6/mil...ml#post6380448

 Thanks!

 Also, is this the correct pin placement for the pot? With the shaft pointing away from you, pins pointing down, the left row is ground, middle row is input, right row is the output?


----------



## Entropy1

Unfortunately I'm still having issues. The pin on the volume pot actually didn't change anything to my surprise. Would it be bad to check voltages to the tubes when it's running? Someone mentioned that one of the tubes wasn't getting the same voltage as the other. Other than that I don't know what could be the problem as I've checked the resistances in both channels everywhere but each yields different results.


----------



## UKToecutter

Quote:


  Originally Posted by *Dunceiam* /img/forum/go_quote.gif 
_Still having trouble with the SSMH P2P I'm building, 

 Symptoms: 

 One tube lights up as expected, the other is VERY dim. 
 Zero audio coming out of the amp. Not even crackling. 
 When you flick the switch, the LED flashes three times at the same rate in this video. But then stops, and the tube's begin to glow after it stops. 

 I've been checking and reflowing all the connections, the MOSFET's do indeed heat up now that I've used the Bergquist pads/mounting kit. 

 Any ideas? (Old, but largely the same) photos are here.
http://www.head-fi.org/forums/f6/mil...ml#post6380448

 Thanks!

 Also, is this the correct pin placement for the pot? With the shaft pointing away from you, pins pointing down, the left row is ground, middle row is input, right row is the output?_

 

Looking from behind the pot the right hand pins are ground.

 The initial flashing is the PS collapsing. That should settle after some seconds.

 There is a mod (mentioned earlier in this thread) that resolves that issue


----------



## UKToecutter

.


----------



## UKToecutter

I think the mod was increasing C1 to 680uF 63V

 Have a look at http://www.diyforums.org/SSMH/schema...origPCB-sm.gif


----------



## Dunceiam

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_I think the mod was increasing C1 to 680uF 63V

 Have a look at http://www.diyforums.org/SSMH/schema...origPCB-sm.gif_

 

C1 already is 680uF 63v 
	

	
	
		
		

		
			





. However, if it's not harmful at all to the PSU, I kind of like it's effect.


----------



## UKToecutter

Dunceiam,

 Sorry if I missed it, but are you using the 'standard' Cisco 48V PS?


----------



## skkhai

Quote:


  Originally Posted by *iPoodz* /img/forum/go_quote.gif 
_How pretty! Are those white or blue LEDs?_

 

Those are white LEDs, guess my camera's white balance was a little off.


----------



## Dunceiam

Using the exact one in the BOM.


----------



## getllamasfast

Pics of my second 12AU7 build:

 I did this one on this radioshack board.
















 ^ the tubes are actually a little brighter than they seem in this pic ^


----------



## Narwhalius

I went back and checked my soldering joints on the inputs and everything looked good. Turned the amp on when it wasn't fully in the case and I was getting sound out of both ears. Then I put the amp back in completely and was back to just the right ear getting sound. Took it completely apart again and touched every joint on the bottom and now I'm getting very little sound out of the left ear and full sound out of the right ear. Any ideas?


----------



## tomb

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_I went back and checked my soldering joints on the inputs and everything looked good. Turned the amp on when it wasn't fully in the case and I was getting sound out of both ears. Then I put the amp back in completely and was back to just the right ear getting sound. Took it completely apart again and touched every joint on the bottom and now I'm getting very little sound out of the left ear and full sound out of the right ear. Any ideas?_

 

These things happen when you assemble a case and then disassemble. It's all because of the wire leads. They get torqued or twisted, which puts stress on the connections or terminal blocks. A dodgey solder joint gives way, or a partially cut lead becomes fully broken.

 First thing I'd look at would the be the terminal blocks. Make certain the screws are all tight and are clamped down on good wire. After repeated tightening, you can compress the wire ends so much that the screw is no longer able to grip them. At the very least, a little wiggling back and forth - which will happen when wire is folded into and out of a case under pressure - and the screws will start to loosen.


----------



## Narwhalius

I tried some configurations with the terminal block. Switched the wire that I had in the right spot with the wire I had in the left spot thinking maybe the left wire is faulty but I got no sound from either channel *EDIT*: I get no sound from the left channel. So the left spot doesn't work even with the wire from the right spot which I know works. So something with my left spot is wrong? Also I'm hearing a beeping noise, very faint, and constant. Idk if its my computer or what.

 EDIT: Made some changes to clarifiy


----------



## the_equalizer

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Pics of my second 12AU7 build:

 I did this one on this radioshack board.
 <snip>

 ^ the tubes are actually a little brighter than they seem in this pic ^_

 

Beautiful pics my friend ! Nice to see another 12AU7 build 
	

	
	
		
		

		
		
	


	




 So, did you solve the noise issue you were having?

 cheers!


----------



## the_equalizer

Hello all,

 Some months ago, I posted in this thread about a 'drawing board' version of the SSMH using a 30 volt HP printer supply and 12AE6 tubes. Today I finally got around to building the circuit and can happily report that it works 
	

	
	
		
		

		
		
	


	




. I'm listening to it as I type and it sounds wonderful. 
	

	
	
		
		

		
		
	


	




 My original idea was to use the C2175A HP printer supply, since a friend in the US told me they were cheap and plentiful (and it uses the same connector as the Cisco 48 V supply). Unfortunately I couldn't manage to get a hold of one where I live and I was forced to use my own HP printer supply which provides 32 volts @ 350 mA and would be good to build the prototype in spite of it's weird proprietary connector.

 Back in october I drew a load line for the 12AE6 with a 22 Kohm plate load and a 2 Kohm cathode resistor. According to my calculations these values would result in a quiescent point of 20 v plate voltage and .42 mA plate current. 

 Considering what Dsavitsk posted about load line drawing (try to choose a plate resistor that halves the supply voltage) today I redid the load line and the calculations resulted in 35 Kohm plate load resistor and 1.6 Kohm cathode resistor. These values would yield a 15 v plate voltage @ .42 mA plate current. Looking in my parts box I only managed to find 33 Kohms and 1.7 Kohms which I figured would do for the purposes of the prototype. 

 This is the first time I've actually 'designed' a common cathode triode amplifier of any kind and so the quiescent current I chose could probably be considered far from optimal for the 12AE6. I kindly ask the help of more experienced electronic designers here to choose a better quiescent current if that is the case.

 The values measured in the actual circuit are 10 volts plate to cathode and -.97 volts grid to ground, which considering a 1784 ohm resistor results in a .54 mA plate current. The value for the plate voltage baffles me a bit... tube variance maybe ?... I guess using a 27 Kohm plate resistor would be a good idea.

 So summarizing the only component changes in my prototype were R5, R11 = 1.7 Kohms, 12AE6 tubes and the HP 30 volts supply!! Incredible how adaptable this elegantly simple circuit is.

 As with the 12AU7 version, please note that the 12AE6 while using the same 7-pin mini tube socket as the 19J6, has a different pinout. You must change the socket wiring accordingly. You can find the 12AE6 pinout in its datasheet.


 Some pics now 
	

	
	
		
		

		
		
	


	




 Going through the parts box






 Proto-board wiring, one channel done, one to go






 First time turn-on. The heaters took about 30 seconds to start glowing... but to me it felt like half an hour!!






 After measuring DC offset at the inputs and outputs, (0 v at the input, 4~5 mV at the outputs); ready to plug the cheap earbuds and listen to Yes' "Drama"





 The weird HP printer supply connector.






 cheers!


----------



## iPoodz

Excellent work, equalizer! I don't understand all the details, but it's great that you are able to adapt the amp to whatever parts are available to you. I jumped on the kit because I don't think I'd be able to do that 
	

	
	
		
		

		
		
	


	




 getllamasfast, what case are you using? Did you get the holes precut?


----------



## getllamasfast

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Beautiful pics my friend ! Nice to see another 12AU7 build 
	

	
	
		
		

		
			





 So, did you solve the noise issue you were having?

 cheers!_

 

Thank you!

 Yeah, I did fix it, although I'm not exactly sure how... 
	

	
	
		
		

		
		
	


	




 I just put it together one last time and it suddenly just worked! 
	

	
	
		
		

		
		
	


	





 Nice job on the 12AE6 amp!


----------



## ezzieyguywuf

Haven't been up here in a while, but I been itchin' to build one of these. I still can't seem to locate these tubes though. Tubedepot has them for 15 bucks a pop, but I'm wondering if you guys could suggest anywhere else I could purchase them more reasonably. I truly am a starving student, soon to be starving newly-wed! lol


----------



## tomb

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Haven't been up here in a while, but I been itchin' to build one of these. I still can't seem to locate these tubes though. Tubedepot has them for 15 bucks a pop, but I'm wondering if you guys could suggest anywhere else I could purchase them more reasonably. I truly am a starving student, soon to be starving newly-wed! lol_

 

Last time I looked, SND Tube Sales (vacuumtubes.com) had them for $10.


----------



## simwells

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Last time I looked, SND Tube Sales (vacuumtubes.com) had them for $10._

 

When I was looking SND didn't have any left, but Radio Tube Supply had some at $10


----------



## the_equalizer

Quote:


  Originally Posted by *iPoodz* /img/forum/go_quote.gif 
_Excellent work, equalizer! I don't understand all the details, but it's great that you are able to adapt the amp to whatever parts are available to you. I jumped on the kit because I don't think I'd be able to do that 
	

	
	
		
		

		
		
	


	




 getllamasfast, what case are you using? Did you get the holes precut?_

 

 Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Thank you!

 Yeah, I did fix it, although I'm not exactly sure how... 
	

	
	
		
		

		
		
	


	




 I just put it together one last time and it suddenly just worked! 
	

	
	
		
		

		
		
	


	





 Nice job on the 12AE6 amp! 
	

	
	
		
		

		
		
	


	


_

 


 Thanks guys! I just tried to work out another option to build this amp despite the growing scarcity of the original 19J6 tubes; 12AE6 can be found easily and for at least half of what 19J6's or 12AU7's cost.

 Also, checkout the power supply in ebay. You can get one for $6.00 to $9.00 USD

 I've been listening to the prototype on and off since yesterday and it really sounds well. For one, even though it's wired in a protoboard, it's very very silent: I'm listening to a CD edition of a 1963 recording, and above the amp's noise floor, you can clearly hear the tape hiss when the music starts. 

 About the bias current I browsed the MiniMAX website and it turns out the current I got in my prototype is very similar to what they chose for the quiescent current of the tubes in the MiniMAX. The problem lies in the fact that they recommend 13.5 volts and upwards for the tube plates and I'm running them at 10! I trust that tomorrow I can go by the electronics store and pickup some resistors to try as plate loads and push the plate voltage up to around 15 volts. That should improve the sound quality.

 So, there it is, another option if you guys want to build this fun little amp.

 cheers!


----------



## Narwhalius

Hey all,

 Still having issues with no sound on my left channel. Got myself a multimeter but I really have no clue on how to use it. Followed the directions that came with it to test for continuity. Touched the backside of each RCA jack, not the wire but the part where you screw on the screw to tighten it to the panel, to the R spot on the block. The meter moved a little bit. Tried the same thing with the L spot and the meter never moved. Are those correct spots to test at? Anywhere else I should be testing?


----------



## timmyGCSE

I was all ready to go ordering parts for a mini3 this morning but the US$ - GB£ exchange rate is poor meaning the PCB etc. from AMB was more expensive, £57 there or thereabouts in total. 
 So I thought hmm price up a SSHA 12AU7 version..
 components, cisco PSU from ebay, Philips 5963 NOS tubes and tube holders £46.10 all in, about a tenner less. I was going to use the mini3 for desktop use anyway so I went for the SSHA instead 
	

	
	
		
		

		
		
	


	




 next jobs are to relearn to read schematics after doing electronics in college and find/make a suitable case for all the biz.

 can't wait 
	

	
	
		
		

		
		
	


	




 edit: oh and if anyone needs some resistors for this build I will have plenty! Rapid electronics sold them in packs of 100 for 50p each! haha


----------



## Entropy1

I've done some more testing and the heaters on both tubes are getting the proper 20v. I don't understand how each channel on the amp has exactly the same resistances but produce different volumes along with the channel bleed. Sorry to keep posting but I really want to get this working.


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_I was all ready to go ordering parts for a mini3 this morning but the US$ - GB£ exchange rate is poor meaning the PCB etc. from AMB was more expensive, £57 there or thereabouts in total. 
 So I thought hmm price up a SSHA 12AU7 version..
 components, cisco PSU from ebay, Philips 5963 NOS tubes and tube holders £46.10 all in, about a tenner less. I was going to use the mini3 for desktop use anyway so I went for the SSHA instead 
	

	
	
		
		

		
		
	


	




 next jobs are to relearn to read schematics after doing electronics in college and find/make a suitable case for all the biz.

 can't wait 
	

	
	
		
		

		
		
	


	




 edit: oh and if anyone needs some resistors for this build I will have plenty! Rapid electronics sold them in packs of 100 for 50p each! haha_

 

Cool! another 12AU7 build in the making! Please post your progress/impressions ! 

  Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_I've done some more testing and the heaters on both tubes are getting the proper 20v. I don't understand how each channel on the amp has exactly the same resistances but produce different volumes along with the channel bleed. Sorry to keep posting but I really want to get this working._

 

As TomB posted before, those problems MUST come from a miswiring of some kind, as the PCB is a proven build. Clear pics would help us help you.

 What you describe as "channel bleed" seems particularly strange. What is your source ? Have you tried different sources ?

 The lower volume in one channel, if not caused by the tube (easily checked by swapping the tubes) can be caused by cold solder joints, incorrect value resistors, or a semi-fried MOSFET; you should check the solder joints of your headphone jack too.

 cheers!


----------



## Juaquin

Have you tried playing an audio track that plays only one channel at a time, to confirm this channel bleed? There is a Left Right track on this page, along with a bunch of other fun test tracks.

 As for mismatched volume, there are a number of potential causes. The volume pot is not tracking well (especially in the low levels), you have bad joints or connections in one (or both) channels that are adding resistance, or the tubes (although I doubt this since TomB is very good about matching them for the kits).


----------



## Entropy1

Thanks for the response equilizer. Yes, the channel bleed is what bother me most also. I've tried different sources along with different rca cables. All of what I test does fine in other systems. I know there is channel bleed because I can disconnect either RCA jack completely, and still hear things in both channels. I can't think of anything other than a bridge causing this problem but I don't know. Perhaps a few more alcohol baths for flux?

 I have also swapped tubes to try and determine which tube was at fault, if either. When doing this I get the same result suggesting both are good and not the cause of the problem. I have also swapped to a new set of MOSFETs with no change. The headphone jack looks to be soldered in well but I will go over it again just to make sure.


----------



## UKToecutter

Post some nice close up pictures of your RCA wiring and the underside of the board


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Cool! another 12AU7 build in the making! Please post your progress/impressions ! 

_

 

yep shall do, still fretting over the case, I want to make it look nice as well as sound good 
	

	
	
		
		

		
		
	


	




 I was pretty pleased with the tube find, £5.50 ($8.50) each, ECC82/12AU7 equivelent, this is a few notes I've found on them:

  Quote:


 very close to ECC802S

 5963 Special Quality ECC82: Different in two points: 1)Longer Stand by function 2) balanced tube by default. * With those two points you have basically the same properties as the Telefunken ECC802S. These are the pearls 
 

 Quote:


 This is a nice industrial type which is nearly identical to the standard 12AU7. RCA made a nice blackplate version of this tube, Sylvania has a gold pin version, and GE has it in their 5-star broadcast line. The plate voltage rating is a little lower than for a 12AU7, but for most applications, it will work fine. It has a rugged cathode and should be long lived, similar to the 5814. Watch this tube, as it is plentiful now and prices are low. As audiophiles discover it, the rush will be on! 
 


 still going on ebay uk:
5963 PHILIPS ECG 12AU7 ECC82 TUBE VALVE 1 PC on eBay (end time 09-Mar-10 12:47:43 GMT)


----------



## Entropy1

When testing for the channel bleed, I noticed that in one channel, I get the same volume regardless of where the volume pot is. To me, this would suggest that there is a problem before even hitting the volume pot, yet I can't seem to find any bad connections. Are there any other inferences I'm missing? How often are volume pots bad? I'm sure it's more likely that I messed something up rather than a component being bad, but I've gone over it so much. Anyways, thanks again and I'll keep looking.


----------



## UKToecutter

The volume pot is the first thing the signal hits after the input resistors (R16/R17)


----------



## Entropy1

Yes, I know that it's the first thing the signal hits. It has to be a problem between the terminal cables and the volume pot. I think I will try remounting the terminal block to see if anything is changed.


----------



## dsavitsk

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_How often are volume pots bad?_

 

Not very, but too much heat while soldering could certainly short it.


----------



## the_equalizer

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_When testing for the channel bleed, I noticed that in one channel, I get the same volume regardless of where the volume pot is. To me, this would suggest that there is a problem before even hitting the volume pot, yet I can't seem to find any bad connections. Are there any other inferences I'm missing? How often are volume pots bad? I'm sure it's more likely that I messed something up rather than a component being bad, but I've gone over it so much. Anyways, thanks again and I'll keep looking._

 

It would be quite the opposite: the problem should be AFTER the volume pot, since it's not affected by it.

 The only part of the circuit where the two channels come together is the 48 V line, and indeed bad supply decoupling causes channel crosstalk. Make sure R13 has the correct value but specially that C1 and C6 are the correct value, are properly installed (check the polarity) and soldered (no cold solder joints).

 I'll test my 12AU7 P2P build for crosstalk when I get home and let you know how it behaves.

 cheers!


----------



## ezzieyguywuf

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Last time I looked, SND Tube Sales (vacuumtubes.com) had them for $10._

 

Just sent them an email, thanks.


----------



## Entropy1

Thanks, that'd be really nice. I assume that the signal must be the same intensity regardless of where the pot is turned to, and assuming the pot is good, it should make a difference but I'm not sure. C1 and C6 are both soldered in well and are oriented properly. R13 reads 2k and measure to around 2.1k which seems within reason. Oddly, the issue of getting ~150k between left signal and ground has come back (I thought I had it fixed at least.) Hope this helps, and thanks for the help.


----------



## sam_cat

Another one lives 
	

	
	
		
		

		
			




 All in, probably about 6 hrs from start to finish including some testing time and hunting for the right sized allan key.

 Left channel sound slightly different to the right, not as much presence. It moves if I swap the tubes over too... Any ideas?

 Should have my shiny new scope tomorrow, so will be able to map out any differences/problems.

 Sam


----------



## Juaquin

If it moves with the tube, it's the tube. Replacing the tubes will fix it (if you can carefully match them), although that's not really an option nowadays with the scarcity of the 19J6. If it's a matter of volume, you can fine-tune the input resistors for one channel or the other to get it louder or softer.


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_If it moves with the tube, it's the tube. Replacing the tubes will fix it (if you can carefully match them), although that's not really an option nowadays with the scarcity of the 19J6. If it's a matter of volume, you can fine-tune the input resistors for one channel or the other to get it louder or softer._

 

Yeah, I hate to be a downer, but I warned everyone up front about this last round of kits. Each customer got the best matched tubes that were available according to his/her time of purchase and the availability at that time. So iow, the tube matching is as good as it's going to get. I still have enough left to replace a few outright failures, but that's all.


----------



## the_equalizer

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Thanks, that'd be really nice. I assume that the signal must be the same intensity regardless of where the pot is turned to, and assuming the pot is good, it should make a difference but I'm not sure. C1 and C6 are both soldered in well and are oriented properly. R13 reads 2k and measure to around 2.1k which seems within reason. Oddly, the issue of getting ~150k between left signal and ground has come back (I thought I had it fixed at least.) Hope this helps, and thanks for the help._

 

So I tested my P2P build and there is indeed audible crosstalk; thought it's only really noticeable with IEMs. I tested by plugging in only the right channel and inserting only the left IEM; then I reversed the setup

 You can start hearing the crosstalk with the volume knob at around 8 o'clock and it's clearly audible with the volume knob at 9 o'clock (a volume level that would melt your eardrums in normal use with IEM's). Now if I understand your previous posts correctly, this is clearly a difference since in my case the crosstalk level *is* affected by the volume knob; as would be normally expected.

 cheers!


----------



## Narwhalius

Is there a list of voltage that I should be getting at certain points on my board? I'm still having the issue of no sound out of the left channel. Picked up a multimeter and I tested the RCA jacks to the terminal blocks. Both moved the meter, though only a little ways so I'm guessing that I have continuity there?


----------



## tomb

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_Is there a list of voltage that I should be getting at certain points on my board? I'm still having the issue of no sound out of the left channel. Picked up a multimeter and I tested the RCA jacks to the terminal blocks. Both moved the meter, though only a little ways so I'm guessing that I have continuity there?_

 

From what I read on your last post, I'm not sure you were testing anything. No, there isn't a list of voltages for certain points on the PCB. Quite frankly, the PCB doesn't rise to the level of complication where that might be required.

 Your best bet is to provide us with some pics. Unless you've blown the tube out on that side, you've got a wire loose somewhere - bad terminal block connection, mixed up ground/signal connection, etc. Since you fail to recognize it yourself (not unusual for most folk, else they wouldn't ask for help
	

	
	
		
		

		
		
	


	




 ), the best bet is to provide a pic or two and see if someone else can spot the issue.


----------



## Entropy1

Thanks equilizer. I did only notice this with my small IEMs. ( <12 ohms impedance I would suspect ) The amp will only be used with my 300 ohm HD580's and I don't notice the crosstalk when using them. I guess this means my only problem is the volume difference which is most likely due to a bad solder joint somewhere. Thanks for the help and I'll do my best to get some pics once I'm up and running.


----------



## the_equalizer

Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_Thanks equilizer. I did only notice this with my small IEMs. ( <12 ohms impedance I would suspect ) The amp will only be used with my 300 ohm HD580's and I don't notice the crosstalk when using them. I guess this means my only problem is the volume difference which is most likely due to a bad solder joint somewhere. Thanks for the help and I'll do my best to get some pics once I'm up and running._

 

Ah yes, then the channel bleed you're hearing is really normal. All multi channel headphone amplifiers exhibit it in varying degrees. IEM's pose a bigger problem because of their high sensitivity and (usually) low impedance (crosstalk levels tend to increase as load impedance goes down).

 So hunt down that volume difference bug and you'll be done ! 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## Lil' Knight

Quote:


  Originally Posted by *sam_cat* /img/forum/go_quote.gif 
_Another one lives 
	

	
	
		
		

		
		
	


	



 All in, probably about 6 hrs from start to finish including some testing time and hunting for the right sized allan key._

 

Did you find out the correct size of the allen?


----------



## the_equalizer

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Did you find out the correct size of the allen?_

 

I'm pretty sure it's the one labeled 3''/32 in my set.

 cheers!


----------



## sam_cat

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Did you find out the correct size of the allen?_

 

Yup... But I have a nicely organised set of about 200 allen keys.. Didnt note what size it was though.

 Sam


----------



## Lil' Knight

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_I'm pretty sure it's the one labeled 3''/32 in my set.

 cheers!_

 

Is that 3"/32 or 3/32"? 3/32" is pretty small, I think.


----------



## Narwhalius

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_From what I read on your last post, I'm not sure you were testing anything. No, there isn't a list of voltages for certain points on the PCB. Quite frankly, the PCB doesn't rise to the level of complication where that might be required.

 Your best bet is to provide us with some pics. Unless you've blown the tube out on that side, you've got a wire loose somewhere - bad terminal block connection, mixed up ground/signal connection, etc. Since you fail to recognize it yourself (not unusual for most folk, else they wouldn't ask for help
	

	
	
		
		

		
			





 ), the best bet is to provide a pic or two and see if someone else can spot the issue.
	

	
	
		
		

		
		
	


	





_

 

Alright. I'll try to get some pics but I can't guarantee they'll be super quality. The camera I have isn't the best for that. Where should I take pics of? Also, last night I was experimenting with the volume knob. While the amp was turned on and no music was playing I turned the volume knob up almost all the way. At a certain point like 95% of the way to the max the left speaker would "click" on, litereally I could hear a click and then it would turn on, and I could hear static in both ears then. Whilist up to that point I couldn't hear anything out of the left ear.


----------



## the_equalizer

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_Is that 3"/32 or 3/32"? 3/32" is pretty small, I think._

 

There, third one from the right (80% sure that's the one)... but it could be the second one from the right...


----------



## Lil' Knight

Ohh, ok. Thanks!


----------



## tomb

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_Alright. I'll try to get some pics but I can't guarantee they'll be super quality. The camera I have isn't the best for that. Where should I take pics of? Also, last night I was experimenting with the volume knob. While the amp was turned on and no music was playing I turned the volume knob up almost all the way. At a certain point like 95% of the way to the max the left speaker would "click" on, litereally I could hear a click and then it would turn on, and I could hear static in both ears then. Whilist up to that point I couldn't hear anything out of the left ear._

 

This almost confirms that you've got bad solder connections at the pot, and that perhaps casing and uncasing it put enough stress on it to loosen some connections. The clicking is where the circuit makes contact through the volume pot when it's shorted (turned all the way up). The signal is partially diverted to ground before that, and as the volume control is adjusted upward, less and less signal is sent to ground. However, if the ground connection is not there, then the circuit is broken until the full-shorting connection is made, hence - no sound.


----------



## Entropy1

I've finally found the source of the volume difference. I installed the tube sockets upside down originally (Yeah, I know that's pretty bad) Anyways, I didn't have a solder sucker or anything at the time so I had to remove the sockets one pin at a time. Once I had done this, I had to drill out the remaining solder any I must have messed up the connection to the PCB then. Between pin 1 and 2 and C4 there was no continuity meaning the tube wasn't getting power from the MOSFET. I know it's a bit sketchy, but I ended up just running a piece of wire there to make the connection.

 The remaining problem is that when I turn the volume low, there is still a bit of audio in the right channel. This volume is proportional only to the volume of the source and not the pot meaning I must have a bridge somewhere. I will keep up the search for this.

 With the volume up on the amp, both channels equilize. My first impressions ( <30 minutes runtime on the amp ) are very good despite how bad I think my mp3 player's DAC sounds. There are still some pops and crackles here and there but that is probably due to the break in and the amp not being inside the case yet. The leak into the right channel is actually from the left input as I've just found out so I will be looking around for the cause of that. Anyways, I'm making progress and if I do okay getting everything working, maybe I'll be up for a gamma 2


----------



## Narwhalius

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_This almost confirms that you've got bad solder connections at the pot, and that perhaps casing and uncasing it put enough stress on it to loosen some connections. The clicking is where the circuit makes contact through the volume pot when it's shorted (turned all the way up). The signal is partially diverted to ground before that, and as the volume control is adjusted upward, less and less signal is sent to ground. However, if the ground connection is not there, then the circuit is broken until the full-shorting connection is made, hence - no sound._

 

I took it apart again and resoldered all the pins on the volume pot. No dice. Looking with the volume knob facing away from me the two on the farthest right dont want the solder to stick very well. What can I do to remedy this? And is there any way to test which pin is causing this problem exactly? Or would it be just one of those two no matter what?


----------



## Entropy1

FINALLY GOT IT WORKING! Turned out being the volume pot. I don't know how I didn't get this earlier as with just a bit of shaking it with music playing I noticed it. Everything is working great and it does sound good. The first thing I notice is the separation. Even with the amp and onboard sound, compared to my (now dead) x-fi card, the separation is much improved. The bass is also great and can really get my Senns moving. I'm not sure whether I'm a bit fatigued because of the volume I'm listening at (I'm splurging a bit on how loud I usually let myself listen) or if it's the onboard sound. I was pretty fond of my modded x-fi and loved it's balance and how smooth it was so there's still a bit to be desired on my end. I can't wait to listen to this thing with a decent DAC or sound card. I may post my results then, but until then, thanks for all the help and kudos to tomb for putting together this kit.


----------



## the_equalizer

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_I took it apart again and resoldered all the pins on the volume pot. No dice. Looking with the volume knob facing away from me the two on the farthest right dont want the solder to stick very well. What can I do to remedy this? And is there any way to test which pin is causing this problem exactly? Or would it be just one of those two no matter what?_

 

Solder doesn't stick very well because the pads where you want to solder those pins are connected to the boards ground plane. The ground plane is a sheet of copper the size of the PCB, thus when you apply your soldering iron to those pads, the big copper surface acts like a heatsink and sucks the heat out of your iron.

 This is my technique to solder to ground planes; I don't claim it's the best, but it works for me. With the part inserted in place, apply your iron to the pad only, not the part pin. Be patient, maybe move your iron a bit around the pad, as if you were trying to spread the heat. Obviously, if your iron has a temperature control, it helps if you set it near its maximum.

 After maybe a couple of minutes you'll notice that the solder in the pad really starts flowing. It is then that you want to apply the iron to the part pin too for maybe 3 to 5 seconds. Then apply a bit of solder. You're done.

  Quote:


  Originally Posted by *Entropy1* /img/forum/go_quote.gif 
_FINALLY GOT IT WORKING! Turned out being the volume pot. I don't know how I didn't get this earlier as with just a bit of shaking it with music playing I noticed it. Everything is working great and it does sound good. The first thing I notice is the separation. Even with the amp and onboard sound, compared to my (now dead) x-fi card, the separation is much improved. The bass is also great and can really get my Senns moving. I'm not sure whether I'm a bit fatigued because of the volume I'm listening at (I'm splurging a bit on how loud I usually let myself listen) or if it's the onboard sound. I was pretty fond of my modded x-fi and loved it's balance and how smooth it was so there's still a bit to be desired on my end. I can't wait to listen to this thing with a decent DAC or sound card. I may post my results then, but until then, thanks for all the help and kudos to tomb for putting together this kit._

 

I'm glad you got it working Entropy1. 
	

	
	
		
		

		
		
	


	




 Congratulations. Persistence does have its rewards, huh? Enjoy!

 cheers!


----------



## Narwhalius

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Solder doesn't stick very well because the pads where you want to solder those pins are connected to the boards ground plane. The ground plane is a sheet of copper the size of the PCB, thus when you apply your soldering iron to those pads, the big copper surface acts like a heatsink and sucks the heat out of your iron.

 This is my technique to solder to ground planes; I don't claim it's the best, but it works for me. With the part inserted in place, apply your iron to the pad only, not the part pin. Be patient, maybe move your iron a bit around the pad, as if you were trying to spread the heat. Obviously, if your iron has a temperature control, it helps if you set it near its maximum.

 After maybe a couple of minutes you'll notice that the solder in the pad really starts flowing. It is then that you want to apply the iron to the part pin too for maybe 3 to 5 seconds. Then apply a bit of solder. You're done.
 cheers!_

 

Man I must have soldered that thing twenty times by now. Did what you said and I'm still not getting any sound out of the left ear. I've check my wires too. Both work in the R block.


----------



## Lil' Knight

Can you take a pic of how you soldered the volume pot? 

 I also had a problem with the pot but a reflow fixed the it perfectly.


----------



## Juaquin

I like to use a heat gun for big ground planes. Warm up the board (not too hot!) and there's less work for the iron to do.


----------



## the_equalizer

Yeah, I think I read somewhere someone used a hot air gun on the PCB to get the ground plane going.

 cheers!


----------



## Narwhalius

Ok here's some pictures of the volume pot pins. Hope these aren't too big.


----------



## Lil' Knight

On the other side, does the solder touch the metal part of the pot?


----------



## Juaquin

The joints look ok, maybe a bit on the "cold" side (especially the ground ones). What kind of solder and iron are you using?


----------



## Narwhalius

Quote:


  Originally Posted by *Lil' Knight* /img/forum/go_quote.gif 
_On the other side, does the solder touch the metal part of the pot?_

 

Its hard to see some of the points but from what I can tell yes there is solder touching all pins on the other side.

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_The joints look ok, maybe a bit on the "cold" side (especially the ground ones). What kind of solder and iron are you using?_

 

I'm using 62/36/2 Rosing-Core Solder from Radio Shack and a basic Radio Shack iron. Tried to keep the budget as tight as I could since its this project is for my Senior Project.


----------



## Juaquin

The solder is good - eutectic, which helps in preventing cold joints. The iron may not have enough power to heat the ground plane (wicks it away and dissipates it before the iron can catch up) - what wattage was the iron?


----------



## Narwhalius

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_The solder is good - eutectic, which helps in preventing cold joints. The iron may not have enough power to heat the ground plane (wicks it away and dissipates it before the iron can catch up) - what wattage was the iron?_

 

I believe it's 30 watts. Though we do have a 100 watt soldering gun in the garage.


----------



## timmyGCSE

equalizer I'm having trouble with the tube pinout mappings from this picture:






 and your description:
  Quote:


 19J6 => 12AU7
 pin 1 => pin 6
 pin 2 => pin 1
 pin 3 => pin 4
 pin 4 => pin 5
 pin 5 => pin 2
 pin 6 => pin 7
 pin 7 => pin 3, pin 8 
 

right, talking about the 12AU7 pinouts here - 
 pin 1 => pin 2 - thats fine, pin 1 connects to pin 6 and they both go off to the 4-terminal, so in effect pins 1&2 on the 19J6 (this is how it looks..or is it going into 5 in which case I'm totally lost)

 pin 2 => pin 5 - also cool, this is in effect joining pin 5&6 from the 19J6 and taking it to the RCA's 

 pin 3/8 => pin 7 - got it, in effect pin 7 from 19J6 with a 2K resistor to ground, clearly visible in pic. But then where's the cap come from that also looks like its soldered to pin 3??

 pin 4 => pin 3 - now we get confused.. as per your pinout mappings, pin four should be pin 3 from the 19J6, which has the 150uF cap then to the 4-terminal ready for the output. but in your picture it shows as pin 4 going to ground!....which brings us to..

 pin 5 => pin 4 - I expected this to go to ground since pin 4 on the 19J6 goes directly to ground.. but from the picture, well I'm not sure where that wire goes to! and then you have the 150uF cap into that pin as well..it looks to me as if that should be pin 3 of the 19J6 but ooh god I'm so confused...


 please help


----------



## Juaquin

30W should be ok, just gotta let it work for a while (while being careful not to overheat the pot)


----------



## Narwhalius

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_30W should be ok, just gotta let it work for a while (while being careful not to overheat the pot)_

 

I'll try again. Say I did successfully get all the joints soldered correctly, would there be any other major point that could cause this? Also, how do you know which component relates to left channel and right channel? So I could go through and make sure each left channel component is correctly soldered.


----------



## tomb

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_I'll try again. Say I did successfully get all the joints soldered correctly, would there be any other major point that could cause this? Also, how do you know which component relates to left channel and right channel? So I could go through and make sure each left channel component is correctly soldered._

 

You took some great pics awhile ago. Can you take a couple that show the entire PCB, top and bottom? Also, it would help to get a view of the wiring to the backplate and the terminal block at the pot.


----------



## getllamasfast

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_equalizer I'm having trouble with the tube pinout mappings from this picture:
 <snip>

 and your description:


 right, talking about the 12AU7 pinouts here - 
 pin 1 => pin 2 - thats fine, pin 1 connects to pin 6 and they both go off to the 4-terminal, so in effect pins 1&2 on the 19J6 (this is how it looks..or is it going into 5 in which case I'm totally lost)

 pin 2 => pin 5 - also cool, this is in effect joining pin 5&6 from the 19J6 and taking it to the RCA's 

 pin 3/8 => pin 7 - got it, in effect pin 7 from 19J6 with a 2K resistor to ground, clearly visible in pic. But then where's the cap come from that also looks like its soldered to pin 3??

 pin 4 => pin 3 - now we get confused.. as per your pinout mappings, pin four should be pin 3 from the 19J6, which has the 150uF cap then to the 4-terminal ready for the output. but in your picture it shows as pin 4 going to ground!....which brings us to..

 pin 5 => pin 4 - I expected this to go to ground since pin 4 on the 19J6 goes directly to ground.. but from the picture, well I'm not sure where that wire goes to! and then you have the 150uF cap into that pin as well..it looks to me as if that should be pin 3 of the 19J6 but ooh god I'm so confused...


 please help 
	

	
	
		
		

		
		
	


	





_

 

Are you following the vanilla ssmh schematic or are you following the one with Dsavitsk's modifications?

 The_equalizer's build is based on the modified schematic which can be found here


----------



## Narwhalius

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_You took some great pics awhile ago. Can you take a couple that show the entire PCB, top and bottom? Also, it would help to get a view of the wiring to the backplate and the terminal block at the pot._

 

Alright, no problem.


----------



## Juaquin

Some of those joints, particularly the ground ones, look cold. For example, in the third pic from the bottom, that joint in the middle. You can tell because it is not a smooth mound and doesn't look like it's all flowed together. If you want to be sure, grab the DMM and check the resistance between a lead that should be connected to ground, and a ground point elsewhere. It should be almost exactly 0 (less than an ohm, preferably lower).


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_equalizer I'm having trouble with the tube pinout mappings from this picture:_

 

Hello timmyGCSE

 Ok, I'll try to address your questions one by one. What we need to do when substituting the tubes is wire the connections to the equivalent pins, that is, if a wire connected to the 19J6's grid, we now need to find the 12AU7 grid pin and run the wire to that instead.

 So here's the pinout mapping again with a description added

 ______________19J6 12AU7
 ------------------------------
 Plate 1 -------- pin 1 = pin 6
 Plate 2 -------- pin 2 = pin 1
 Heater --------- pin 3 = pin 4
 Heater --------- pin 4 = pin 5
 Grid 2 --------- pin 5 = pin 2
 Grid 1 --------- pin 6 = pin 7
 Cathode ------- pin 7 = pin 3, pin 8

 About pins 3 and 8, even though both the 19J6 and the 12AU7 contain two triodes in a single bulb, the 19J6 has only one cathode for both triodes, whereas the 12AU7 has an individual cathode for each triode. 

 Finally, remember that we want to wire the triodes in each 12AU7 in parallel.

  Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_right, talking about the 12AU7 pinouts here - 
 pin 1 => pin 2 - thats fine, pin 1 connects to pin 6 and they both go off to the 4-terminal, so in effect pins 1&2 on the 19J6 (this is how it looks..or is it going into 5 in which case I'm totally lost)_

 

These are the tube plates. I see the confusion, the pic does look unclear on that point. Indeed, pin 1 in the picture connects to pin 6 through the orange wire.


  Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_pin 2 => pin 5 - also cool, this is in effect joining pin 5&6 from the 19J6 and taking it to the RCA's _

 

Pins 2 and 7 in the 12AU7 are the grids. Again this must be wired together. That's what the white wire does.


  Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_pin 3/8 => pin 7 - got it, in effect pin 7 from 19J6 with a 2K resistor to ground, clearly visible in pic. But then where's the cap come from that also looks like its soldered to pin 3??_

 

The cap IS soldered to pin 3. Pins 3 and 8 in the 12AU7 are the cathodes. You need to wire them together, that is done by a gray wire, barely visible in the picture at pin 8. Since the two pins are wired together, the cap and resistor (which is also barely visible behind the cap) can go to ground from either one of them; I chose to do it at pin 3.


  Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_pin 4 => pin 3 - now we get confused.. as per your pinout mappings, pin four should be pin 3 from the 19J6, which has the 150uF cap then to the 4-terminal ready for the output. but in your picture it shows as pin 4 going to ground!....which brings us to..

 pin 5 => pin 4 - I expected this to go to ground since pin 4 on the 19J6 goes directly to ground.. but from the picture, well I'm not sure where that wire goes to! and then you have the 150uF cap into that pin as well..it looks to me as if that should be pin 3 of the 19J6 but ooh god I'm so confused..._

 

Pins 4 and 5 are the tube heater; now the heater has no polarity, so you can wire either pin 4 to ground and pin 5 to the MOSFET or viceversa. I chose the former, indeed.

 I hope this helps with the confusion. Feel free to post or PM me if you have more questions.

 cheers!


----------



## Narwhalius

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Some of those joints, particularly the ground ones, look cold. For example, in the third pic from the bottom, that joint in the middle. You can tell because it is not a smooth mound and doesn't look like it's all flowed together. If you want to be sure, grab the DMM and check the resistance between a lead that should be connected to ground, and a ground point elsewhere. It should be almost exactly 0 (less than an ohm, preferably lower)._

 

Which other ones do you think could be cold? And could this possibly be my volume pot?


----------



## Juaquin

My internet is crap at night so I'm having trouble loading the pictures at the moment, but look for any like that one. Even if they aren't the source of the problem, they may become a problem later on. Also, it looks like the wires going to your LEDs (this picture) have cuts in them that aren't heatshrinked or covered with electrical tape? If those ever touch each other you'll short 48V to GND and have big problems.


----------



## tomb

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_Which other ones do you think could be cold? And could this possibly be my volume pot?_

 

I'm not so sure those solder joints look bad, IMHO. However, the pics are great - but it's tough to get a perspective on your amp when we're only seeing postage-stamp views here and there.

 That said, I'm concerned with the wiring going to the right LED. That wiring is an accident waiting to happen. I'd wrap some black electrical tape around those joints.

 At this point, you may need to test the pot. The channels are the rows of three pins - three pins for left, three pins for right. The signal input are the two pins closet to the terminal block. See if you can measure resistance between that pin and one of the other pins in the same row of three (same channel). Rotate the pot shaft and see if the resistance changes. It's very easy to verify the pot condition this way, because any differences between the two rows of three are the differences between the right and left channels.

 Tell us what you get. Again, perfect values are not necessarily important, but differences in the measurements between pins on on row of three versus the other row of three - before and after rotating the pot shaft.


----------



## timmyGCSE

Quote:


  Originally Posted by *getllamasfast* /img/forum/go_quote.gif 
_Are you following the vanilla ssmh schematic or are you following the one with Dsavitsk's modifications?

 The_equalizer's build is based on the modified schematic which can be found here_

 

ha this is exactly what I've done!! doh! what a wally. Clever chap you are and thankyou for pointing that out

 Now..presumably (or I'm hoping) I can still build it using the original schematic and translate in the different pin mappings? or are the pin mappings specific to the modified design?

 Its just that..I've bought all my components from teh original bill of materials, and sure there aren't that many extras and it would cost me a couple of quid more but I would have to get them from maplins and not rapid where I got my original stuff (otherwise I will be charged another £4.95 delivery) so the caps will be different..does that matter? or as long as I get the correct caps of a decent brand it should be cool?

 what does the modded schematic give extra?

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Hello timmyGCSE

 Ok, I'll try to address your questions one by one. What we need to do when substituting the tubes is wire the connections to the equivalent pins, that is, if a wire connected to the 19J6's grid, we now need to find the 12AU7 grid pin and run the wire to that instead.

 So here's the pinout mapping again with a description added

 ______________19J6 12AU7
 ------------------------------
 Plate 1 -------- pin 1 = pin 6
 Plate 2 -------- pin 2 = pin 1
 Heater --------- pin 3 = pin 4
 Heater --------- pin 4 = pin 5
 Grid 2 --------- pin 5 = pin 2
 Grid 1 --------- pin 6 = pin 7
 Cathode ------- pin 7 = pin 3, pin 8

 About pins 3 and 8, even though both the 19J6 and the 12AU7 contain two triodes in a single bulb, the 19J6 has only one cathode for both triodes, whereas the 12AU7 has an individual cathode for each triode. 

 Finally, remember that we want to wire the triodes in each 12AU7 in parallel.



 These are the tube plates. I see the confusion, the pic does look unclear on that point. Indeed, pin 1 in the picture connects to pin 6 through the orange wire.




 Pins 2 and 7 in the 12AU7 are the grids. Again this must be wired together. That's what the white wire does.




 The cap IS soldered to pin 3. Pins 3 and 8 in the 12AU7 are the cathodes. You need to wire them together, that is done by a gray wire, barely visible in the picture at pin 8. Since the two pins are wired together, the cap and resistor (which is also barely visible behind the cap) can go to ground from either one of them; I chose to do it at pin 3.




 Pins 4 and 5 are the tube heater; now the heater has no polarity, so you can wire either pin 4 to ground and pin 5 to the MOSFET or viceversa. I chose the former, indeed.

 I hope this helps with the confusion. Feel free to post or PM me if you have more questions.

 cheers!_

 

massive help, really I appreciate the explanation so much. As above..do I _need_ to use the modified schematic? or as long as I stick to the modified pin mappings I will be ok?

 edit: I sound very n00bish asking about this I know..I just want to be sure


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_ha this is exactly what I've done!! doh! what a wally. Clever chap you are and thankyou for pointing that out

 Now..presumably (or I'm hoping) I can still build it using the original schematic and translate in the different pin mappings? or are the pin mappings specific to the modified design?

 Its just that..I've bought all my components from teh original bill of materials, and sure there aren't that many extras and it would cost me a couple of quid more but I would have to get them from maplins and not rapid where I got my original stuff (otherwise I will be charged another £4.95 delivery) so the caps will be different..does that matter? or as long as I get the correct caps of a decent brand it should be cool?

 what does the modded schematic give extra?

 massive help, really I appreciate the explanation so much. As above..do I need to use the modified schematic? or as long as I stick to the modified pin mappings I will be ok?_

 

No problem, I'm glad it helped! 
	

	
	
		
		

		
		
	


	




 No, you do not *need* to follow the modified schematic. You can follow whichever you choose 
	

	
	
		
		

		
		
	


	




 as both are essentially the same circuit. But please let's not forget that for the 12AU7 build to work, aside from remapping the tube's pins, you need to make R4, R10 = 390 Kohms

 The modified schematic basically adds bypass capacitors to tube cathode resistors (labeled C7 and C8 in the modified schematic) and film bypass capacitors for the output electrolytics (labeled C3a and C5a in the modified schematic). The effect of bypass cathode caps is a slight (but very noticeable) increase in gain, whereas the film output bypass help improve the amplifier's response to high frequency transients.

 Other modifications are the input and grid stopper resistors (R16, R17 and R15, R16 respectively in the modified schematic). These help you control gain and compensate for some of the volume pot's tracking deficiencies and would be very useful if you plan to use your amp with sensitive IEMs.

 But don't think that if you build a 'vanilla' SSMH you're stuck there, as a matter of fact, my amp started life as a vanilla flavor, and later on I added some features from the modified schematic (the cathode bypass and output bypass caps) while ignoring others (the input and grid stopper resistors).

 Whichever you choose, good luck with your build! Let us know how it goes 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## timmyGCSE

ah great 
	

	
	
		
		

		
		
	


	




 you've outdone yourself in helpfulness! ok I will go vanilla for now, its my first DIY amp ever and I'm not expecting miracles..even if it just works I will be dead chuffed and will spur me on to build bigger and better lol.

 thanks again so much

 edit: oh I forgot to say..I've picked my case now..I'm not going to say what it is yet but provided I can pull it off, its going to be rather unique


----------



## Entropy1

I was wondering if adding some RCA pass through jacks would be okay. This way, I could have speakers attached and turn them on if I want them on, and turn off the amp to stop music from playing in my headphones. Would this degrade the signal at all? I know it shouldn't theoretically, but I don't know in application.


----------



## Entropy1

I was also wondering, is it normal to notice a faint hiss while music is playing? I can pause music and it is completely silent. I don't notice this without the amp. I'm not sure if my bad onboard sound card produces this but I can't hear it as it doesn't have enough power to produce it on my headphones or what could cause this. It may even be in the recordings but I've never heard it before due to my headphones not being powered correctly.


----------



## UKToecutter

Short both inputs to ground and crank it up.
 That'll tell you if the noise is from your source.


----------



## audiophile8706

My internet decided to hang and it never said that the post went through... so this post can be deleted...


----------



## audiophile8706

Hey everyone.. I'm new here so forgive me if this question has been posed. (325 pages is a lot to go through )

 I was searching google for an inexpensive and easy tube amp build and came across the pmillet.com ssmh, and thus followed the links to here and diyforum. I'm just curious where this build stands at the moment. Both pmillet and diyforum seem to have a different list of parts and schematics. Which build is better when it comes to audio quality?

 Also.. I'm rather new to the whole tube thing.. what is the difference between 19J6 and 12AU7 in terms of schematic and tonal qualities?

 Thanks!


----------



## UKToecutter

Quote:


  Originally Posted by *audiophile8706* /img/forum/go_quote.gif 
_Hey everyone.. I'm new here so forgive me if this question has been posed. (325 pages is a lot to go through )

 I was searching google for an inexpensive and easy tube amp build and came across the pmillet.com ssmh, and thus followed the links to here and diyforum. I'm just curious where this build stands at the moment. Both pmillet and diyforum seem to have a different list of parts and schematics. Which build is better when it comes to audio quality?

 Also.. I'm rather new to the whole tube thing.. what is the difference between 19J6 and 12AU7 in terms of schematic and tonal qualities?

 Thanks!_

 

Hi and welcome.
 Yes, there has been a fair amount of modification done since the thread started.

 Have a look at SSMH Overview

 That'll give a good idea of where we are at the moment.

 The bad news is that the 19J6 tubes are in short supply and therefore have become rather expensive. As a result, there are no more kits available.

 So....
 You could do a Point 2 Point build (as described on the earlier posts on this thread).

 As far as the difference in sound between the 12au7 and the 19J6, I personally cannot comment as I have only built the 19J6 version.


----------



## audiophile8706

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_Hi and welcome.
 Yes, there has been a fair amount of modification done since the thread started.

 Have a look at SSMH Overview

 That'll give a good idea of where we are at the moment.

 The bad news is that the 19J6 tubes are in short supply and therefore have become rather expensive. As a result, there are no more kits available.

 So....
 You could do a Point 2 Point build (as described on the earlier posts on this thread).

 As far as the difference in sound between the 12au7 and the 19J6, I personally cannot comment as I have only built the 19J6 version._

 

So the schematic and parts list that's on diyforums is the most up to date version?

 Thanks for the info!


----------



## UKToecutter

Yes,

 Use the schematic with the yellow highlights on it


----------



## Narwhalius

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm not so sure those solder joints look bad, IMHO. However, the pics are great - but it's tough to get a perspective on your amp when we're only seeing postage-stamp views here and there.

 That said, I'm concerned with the wiring going to the right LED. That wiring is an accident waiting to happen. I'd wrap some black electrical tape around those joints.

 At this point, you may need to test the pot. The channels are the rows of three pins - three pins for left, three pins for right. The signal input are the two pins closet to the terminal block. See if you can measure resistance between that pin and one of the other pins in the same row of three (same channel). Rotate the pot shaft and see if the resistance changes. It's very easy to verify the pot condition this way, because any differences between the two rows of three are the differences between the right and left channels.

 Tell us what you get. Again, perfect values are not necessarily important, but differences in the measurements between pins on on row of three versus the other row of three - before and after rotating the pot shaft._

 

Following what you said the row of pins closest to the knob only seem to have continuity when its turned up to about 95% of the way. The other row moves the multimeter no matter where the knob is turned. That would explain why I'm hearing a click and the left speaker comes on at about the same spot? Would you still like some pictures of the whole amp?


----------



## UKToecutter

I think you should change that pot.......


----------



## tomb

Quote:


  Originally Posted by *UKToecutter* /img/forum/go_quote.gif 
_I think you should change that pot......._

 

Unfortunately - agreed.


----------



## Narwhalius

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Unfortunately - agreed._

 

Would this fit?


----------



## tomb

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_Would this fit?_

 

No - you need to order the one that's on the SSMH BOM.


----------



## Narwhalius

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No - you need to order the one that's on the SSMH BOM._

 

Ok its ordered. So any advice on desoldering this thing? This is my first experience with soldering so I don't know much about it.


----------



## Juaquin

If possible, cut off the broken one and then worry about removing the leads from the holes. Heating 6 holes at the same time and trying to pry it out would be near impossible.


----------



## tomb

Or ... add solder on the bottom so that the blob is big enough to cover all 6 pins at once. That way, your soldering iron has a chance to melt all of the solder at once. If you're lucky, the pot will drop right out. If not, tie a string on it and pull while you're holding the iron to keep the solder melted.

 Once it's out, clean up the solder with braid, etc. Use lots of extra flux with the braid. To get the solder out of the holes takes practice and is a bit of an art, but again - add solder. You should have convex surfaces over the holes instead of concave. When you add the solder, the idea is to get the solder and the heat equally mixed, top to bottom through the hole. That way, when you get the braid wicking properly, it will suck all of the solder out of the hole.

 To aid in wicking, use lots of flux, but you can also make certain you have a bit of melted solder on your iron tip - that will "prime" the wick and give it a better chance to suck up all of the solder.

 Good luck.


----------



## Juaquin

That's a pretty big blob of solder, but that's definitely an easy way to get it off 
	

	
	
		
		

		
		
	


	




 Just don't splash any on yourself!


----------



## timmyGCSE

n00b question alert

 how hot does the heatsinks get? i.e....how much heat will get transfered to the surface which the heatsinks are mounted on?

 basically is hard plastic, like the type you would find a..say..umm..games console made out of..a bad idea for case material?

 edit: oh and I'm dead excited now..I have all the components ready to rumble and my tubes came this morning


----------



## Juaquin

If you wanted to you could use plastic for the case, but the MOSFETs themselves _must_ be connected directly to a metal heatsink. Connecting them to plastic is a sure way to fry the MOSFETs (or at least force them into thermal protection mode).


----------



## tomb

Yep. You're looking at each MOSFET dissipating over 2-1/2W each - that's not a small amount. The sinks we chose for the SSMH kit don't look like much, but they're actually sized for large, TO-3 type transistors and are rated quite a bit higher than most extruded sinks.


----------



## the_equalizer

There's also the fact that timmyGCSE is building a 12AU7 version, so the MOSFETs will be taking an extra 7 volts.... 

 So you need good heatsinks timmyGCSE. 
	

	
	
		
		

		
		
	


	




 Ah! and don't forget that if those heatsinks are electrically connected to the circuit's ground, the MOSFET's need to be electrically isolated from the heatsinks (with mica spacers or something like the Beezar MOSFET mounting kits.)

 cheers!


----------



## studwo

wondering where can i buy this tube amp's kit set ? how much is it ?


----------



## tomb

Quote:


  Originally Posted by *studwo* /img/forum/go_quote.gif 
_wondering where can i buy this tube amp's kit set ? how much is it ?_

 

Sorry, they're no longer available. The PCB's ran out and there aren't enough tubes on the market to support another production run.


----------



## UKToecutter

Tom,

 Perhaps you might consider putting together a 12AU7 version of the kit?


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_There's also the fact that timmyGCSE is building a 12AU7 version, so the MOSFETs will be taking an extra 7 volts.... 

 So you need good heatsinks timmyGCSE. 
	

	
	
		
		

		
		
	


	




 Ah! and don't forget that if those heatsinks are electrically connected to the circuit's ground, the MOSFET's need to be electrically isolated from the heatsinks (with mica spacers or something like the Beezar MOSFET mounting kits.)

 cheers!_

 

in the end I decided on a wooden case type thing..I will reveal all hopefully tomorrow..don't expect to be in shock and awe though, it looks aiight but nothing special and I'm not the tidiest wiring person in the world. And yes the heatsinks will already be isolated from ground

 I'm about 75% of the way through..I have the MOSFET's to wire, 5 ground points and erm..ahem, I bought 330K resistors instead of 33K so I need to make a long old trip to Brighton tomorrow to get some 33K's. But my newly bought today soldering iron packed up anyway (What.. :-/ ) so I have to take that back and get another too. ah well

 edit: ah just something..in your original 12AU7 post where you explained the pin mappings you said it needed r2/r8 to change
  Quote:


 The required resistor change is R2/R8 = 390 Kohms. This moves the voltage at the MOSFET gate to compensate for the heater voltage dropping from 19 to 12 volts. 
 

whereas the post a couple of pages back with advice you say R4/R10. Does it matter or can it be either?


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_<snip>

 edit: ah just something..in your original 12AU7 post where you explained the pin mappings you said it needed r2/r8 to change


 whereas the post a couple of pages back with advice you say R4/R10. Does it matter or can it be either?_

 

You're absolutely right, my apologies. Indeed it is R2 and R8 that need to be 390 Kohms.

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_You're absolutely right, my apologies. Indeed it is R2 and R8 that need to be 390 Kohms.

 cheers!_

 







 ...and...its all done 
	

	
	
		
		

		
		
	


	




 it works perfectly too 
	

	
	
		
		

		
		
	


	




 Koss Porta's sound amazing through them, so gonna sit down now and try my JH13's...ahhh 
	

	
	
		
		

		
		
	


	




 I have some other jobs to do today but I will hopefully get around to posting some pictures later, its not too neat but hey whatever it works..in the words of vicki pollard..face..bovvered

 edit: wow..the 13's sound amazing with the SSMH!

 edit2: and here we go:





















 sorry there is no picture of the tube sockets themselves, I didn't have a camera to hand when I screwed the bottom plate on. I did take one on my phone, whether it came out good or not I don't know but I will have a look at that later. Following equalizer's revised pin mapping worked just peachy though.

 As you can see, tidy wires isn't my strong point. I'm not fussed at all..it works perfectly and yea its an open box design but pfft whatever I'm still proud that the damn thing works!!

 some notes:
 - For the wiring I used the wire from a CAT6 ethernet cable, both strands of each colour making up one wire. It worked quite well and is nice and still but I think it contributed to the messyness and my fingers hurt from stripping it! haha

 - the PSU is not a Cisco PSA-18, it is a Cisco EADP-18FB, its from what I can tell exactly from pdf specs exactly the same apart from the label colour and unit shape. The Cisco ADP-18PB is also the same/similar and will work which will make it even easier to find one on ebay, the PSA-18 on ebay UK was about £12, the one I got £4. The EADP-18FB and ADP-18PB both use 2.5mm sockets

 - the tubes are not 12A_x_7 tubes..they are Philips 5963 tubes which are part of the same ECC82 family..this is what Jac Music says:
  Quote:


 Special Quality ECC82. Different in two points: 1)Longer Stand by function 2) balanced tube by default. * With those two points you have basically the same properties as the Telefunken ECC802S 
 

see here for other compatible tubes with this build:
http://www.jacmusic.com/nos/ECC82.htm
 they cost me £5.50 each from ebay, and they are NOS tubes..imo a bargain

 - I used 2.2k resistors instead of 2k..whether this makes a difference or not I don't know but rapid electronics didn't have any 2k in stock and it sounds good regardless.

 so how does it sound? awsome.
 I haven't listened to it fully and properly yet but I had about 15 minutes and I was amazed. I tested with PortaPro's and they sounded fantastic then I listened to my JH13's and I was blown away, the sound is so much richer, fuller and soundstage is more airy. As an example I have a dubstep track that has an extra drum beat that is usually hidden behind the bassline, the only time I've heard this extra beat is using the foobar virtual 5.1 thingy on my RX700's, never just playing it standard even with the 13's. With the SSMH its clear as a bell 
	

	
	
		
		

		
		
	


	



 The 5963 tubes sound brilliant..can't compare them to any others since this is the first tubes I've ever listened to..but I will probably pick some others up, 12A's or generic ECC82's to compare

 I would like to publically thank equalizer for the advice given on this build, and everyone who contributes knowledge because this is a great project...

 now all it needs is for someone get working on a proper schematic for SSMH v2 (i.e 12AU7)..lets not let the SSMH die out through lack of 19J6 tubes!


----------



## hss3

Hey, I'm currently drawing up a 12AU7 version PCB that was described in this thread earlier.

 I'm basically just redrawing the original circuit board that came inthe production run with the 12AU7 modifications

 Probably going to do a toner tranfer etch to make the PBC. I plan to actually etch both sides, then toner transfer on the markings for ease of assembly. I'll post pics when I'm done. 

 I'm still checking over my circuitry at the moment, but I'll post up the .pdf if people are interested.


----------



## hss3

Im actually going to run these as well.

RK27112A-S20-C0-A104 ALPS Potentiometers

 I see nothing wrong with that? Enlighten me if i'm wrong.


----------



## hss3

gah! repost


----------



## timmyGCSE

ha just realised I've made a grave mistake! soldered only point 6 on the pot to ground and not point 3! well ok so its not really bad but the vol was acting as a fader not a volume control..sigh..out comes the iron..

 5 mins later done 
	

	
	
		
		

		
		
	


	




 much better works now


----------



## the_equalizer

@timmyGCSE

 Cool! Another 12AU7 build ! 
	

	
	
		
		

		
		
	


	




 I like the retro "1930s ham radio" look very much, the vintage military tubes add to the vibe. 

 I'm glad it all worked great and that you're enjoying your amp. About tube rolling, you're not confined to ECC82/12AU7. I tried 12AT7 and 12AX7 and they all worked nicely; probably 12AY7 and 12AZ7 would work too. Still, if you'll be using IEMs with the amp I guess 12AU7 will work best, since the other options might have too much gain.

 Anyway, enjoy your music ! Again, just one suggestion in case you haven't read through the whole thread: do not turn the amp on or off with your headphones plugged in.

 cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *hss3* /img/forum/go_quote.gif 
_Im actually going to run these as well.

RK27112A-S20-C0-A104 ALPS Potentiometers

 I see nothing wrong with that? Enlighten me if i'm wrong._

 

That certainly looks like a nice pot. While it'll certainly work with either a PCB or P2P build (even though it's 100K and the BOM usually specifies a 50K pot; just a minor point, really), I'm pretty sure it won't fit into the Beezar.com PCB Hammond case. Then again if that's not what you're aiming for, then it is not a problem!

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_@timmyGCSE

 Cool! Another 12AU7 build ! 
	

	
	
		
		

		
		
	


	




 I like the retro "1930s ham radio" look very much, the vintage military tubes add to the vibe. 

 I'm glad it all worked great and that you're enjoying your amp. About tube rolling, you're not confined to ECC82/12AU7. I tried 12AT7 and 12AX7 and they all worked nicely; probably 12AY7 and 12AZ7 would work too. Still, if you'll be using IEMs with the amp I guess 12AU7 will work best, since the other options might have too much gain.

 Anyway, enjoy your music ! Again, just one suggestion in case you haven't read through the whole thread: do not turn the amp on or off with your headphones plugged in.

 cheers!_

 

well thank you! without your help and original pinout work I wouldn't have this now. Cheers..I mean its not the nicest looking kid on the block but hey it does the job and sounds amazing. And I think I will roll a few tubes over time just to listen to the differences..but seriously these sound great - I let my mum and grandad listen with my RX700's and they haven't got a clue about audio in general and they were blown away. People say RX700's don't benefit from amping..I beg to differ

 and ah yea cheers I knew about turning on but not off so thankyou for that


----------



## blitzpirate

hey guys i just finished the assembly and i have a bit of a problem, the ssmh turns on and everything but when i hook it up to a dac i only get sound through the right channel then i turn the volume up on the Amp, after that i get sound on both channel however the right channel is stronger, and if turn the volume off i still get sound through my right ear.... and suggestions?


----------



## the_equalizer

Quote:


  Originally Posted by *blitzpirate* /img/forum/go_quote.gif 
_hey guys i just finished the assembly and i have a bit of a problem, the ssmh turns on and everything but when i hook it up to a dac i only get sound through the right channel then i turn the volume up on the Amp, after that i get sound on both channel however the right channel is stronger, and if turn the volume off i still get sound through my right ear.... and suggestions?_

 

Sounds like the potentiometer pins that connect to the ground plane are not correctly soldered, particularly the pin corresponding to the right channel.

 Check those solder points. Getting the solder to really flow in those takes quite a bit of heat, you'll need to apply your soldering iron for some 2 or three minutes until the ground plane heats up and the solder flows. 

 Problem is that you don't want to heat the pot pin as much, just the pad. So I'd suggest removing the solder, applying the iron to the pad long enough so that the solder flows, then apply the iron for some seconds to the pot pin too and then feed in the solder.

 cheers!


----------



## timmyGCSE

yea just to add to that, make sure pins 3 and 6 are soldered to ground, I had that and realised I'm not soldered pin 3!


----------



## timmyGCSE

Quote:


  Originally Posted by *hss3* /img/forum/go_quote.gif 
_Hey, I'm currently drawing up a 12AU7 version PCB that was described in this thread earlier.

 I'm basically just redrawing the original circuit board that came inthe production run with the 12AU7 modifications

 Probably going to do a toner tranfer etch to make the PBC. I plan to actually etch both sides, then toner transfer on the markings for ease of assembly. I'll post pics when I'm done. 

 I'm still checking over my circuitry at the moment, but I'll post up the .pdf if people are interested._

 

I'm going to give this a whirl too but with a twist, I aim to make it modular so that the tube sockets and MOSFETs sit on a different PCB and are connected via ribbon cable to the main PCB


----------



## ezzieyguywuf

Any chance of updating the first post or something with updates to this design. I'm guessing this 12AU7 is an alternative tube that can be used, with some modifications to the original design? I'm having a horrible time tracking down some 19J6's


----------



## Juaquin

Yes, the 12AU7 is the popular alternative with some modifications because of the scarcity of the 19J6.

 Chances are the original post will not be updated, considering it was written by Pete Millet himself and was the beginning of the SSMH. It's history. Perhaps someone (paging the_equalizer to the SMMH thread) could start a thread for the 12AU7 variant.


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Yes, the 12AU7 is the popular alternative with some modifications because of the scarcity of the 19J6.

 Chances are the original post will not be updated, considering it was written by Pete Millet himself and was the beginning of the SSMH. It's history. Perhaps someone (paging the_equalizer to the SMMH thread) could start a thread for the 12AU7 variant._

 

If someone can provide me with a writeup, parts list/BOM, schematic, etc., on the variants (would want to include logistics' 12SR7 variant, too) - I can try to post it on the SSMH website. No guarantees as to when, though, it seems I'm staying pretty busy these days.


----------



## UKToecutter

Tom,

 Always better to be busy than idle...........


----------



## m11a1

Hey Tom,

 I purchased the SSMH about 3 weeks ago and recently I have finished the kit. I would like to just thank you to putting together such an awesome sounding kit. Since it is my first DIY project ever, you have made my introduction to DIY very exciting and educational. 

 Also, I'm super happy that I was able to grab one of the last remaining kits. Well, after this one, I'll be looking forward to the MiniMax. 
	

	
	
		
		

		
			















 Thanks again.

 Cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *m11a1* /img/forum/go_quote.gif 
_Hey Tom,

 I purchased the SSMH about 3 weeks ago and recently I have finished the kit. I would like to just thank you to putting together such an awesome sounding kit. Since it is my first DIY project ever, you have made my introduction to DIY very exciting and educational. 

 Also, I'm super happy that I was able to grab one of the last remaining kits. Well, after this one, I'll be looking forward to the MiniMax. 
	

	
	
		
		

		
		
	


	




 <snip>

 Thanks again.

 Cheers!_

 

*Very nice* pics! Congratulations!

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_If someone can provide me with a writeup, parts list/BOM, schematic, etc., on the variants (would want to include logistics' 12SR7 variant, too) - I can try to post it on the SSMH website. No guarantees as to when, though, it seems I'm staying pretty busy these days.
	

	
	
		
		

		
		
	


	


_

 

I'll try my hand at drawing the schematic for the 12A_7 version. Is "Eagle" a good program to do it?

 cheers !


----------



## Juaquin

I'm a big fan of Eagle, mostly 'cus it's free, it works, and there are a lot of part libraries for it. I've designed a couple schematics / PCBs with it, feel free to ask if you have questions.


----------



## the_equalizer

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I'm a big fan of Eagle, mostly 'cus it's free, it works, and there are a lot of part libraries for it. I've designed a couple schematics / PCBs with it, feel free to ask if you have questions._

 

Thanks Juaquin! I certainly will 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_<snip>
 I'll try my hand at drawing the schematic for the 12A_7 version. Is "Eagle" a good program to do it?

 cheers !_

 

Actually, Eagle may not be the best thing to use. What may be more useful is to Photoshop the existing Pete Millett schematic for the necessary changes, just as was done for the PCB differences over the original.


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, Eagle may not be the best thing to use. What may be more useful is to Photoshop the existing Pete Millett schematic for the necessary changes, just as was done for the PCB differences over the original.
	

	
	
		
		

		
		
	


	


_

 

Note taken. I don't have Photoshop, but I'll try doing it with GIMP. 

 cheers!


----------



## ezzieyguywuf

GIMP ftw. Could anyone with the knowledge simply let me know what the necessary changes are? I have the feeling that it's as simple as changing some resistor values. I'm trying to get together a BOM because I want to build this bad boy over spring break, in two weeks. I may even try my hand at an Alien DAC, but I've read that it has issues with the SSMH? Any comments on that? Any alternatives?


----------



## Juaquin

Search the thread, the_equalizer has posted the required changes a few times.


----------



## tomb

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_GIMP ftw. Could anyone with the knowledge simply let me know what the necessary changes are? I have the feeling that it's as simple as changing some resistor values. I'm trying to get together a BOM because I want to build this bad boy over spring break, in two weeks. I may even try my hand at an Alien DAC, but I've read that it has issues with the SSMH? Any comments on that? Any alternatives?_

 

There is a charge issue that sporadically seems to develop on the RCA input jacks of the SSMH. This is enough under the right conditions to blow out the DAC chip on the Alien or BantamDAC. This seems to occur if there's ever an occasion of connecting/disconnecting the DAC from the SSMH while it's on. I've actually seen the static charge jump from the RCA jack (ground connection) to the RCA plug from the DAC (signal connection). The DAC was fried on that channel from then on.

 You can test this yourself while listening to the SSMH - try disconnecting the RCA cables from the SSMH while it's on and playing. Sometimes you'll get a huge hum that won't go away until you touch the RCA jacks and ground them to your body.

 We don't know what causes it, but it seems peculiar only to the SSMH. As for DACs, the ones that are in danger because of this are the type of DACs that have only a filter capacitor separating the DAC chip from the connection on the amp. I don't know if this exists for the GrubDAC, but I would be reluctant to test it out on the SSMH.

 OTOH, I've had an SSMH connected to a PC's sound card for over a year with no ill effect - connect, disconnect, whatever - no issue at all.


----------



## ezzieyguywuf

Hm. I'd like to know if maybe theres a way to mod the Alien DAC to prevent this from happening? I don't know what a "filter capacitor separating the DAC chip from the connection on the amp" is, but I hope my Compass has it! I know it's got separate boards for the amp, dac, a power supply but I don't know how they're connected.

 Juaquin: thanks for that, at least now I know which posts to look for.

 Also, I saw on this thread somewhere that someone said something along the lines of "it sounded great even though I had it on my proto board". I'm planning on building this thing on a bread board, mainly cuz I'm still newb at this and I want it to be neat and easy to enclosure. Are there sound benefits to doing it point-to-point, or rather, are there sound detriments to doing it on a board?


----------



## tomb

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Hm. I'd like to know if maybe theres a way to mod the Alien DAC to prevent this from happening? I don't know what a "filter capacitor separating the DAC chip from the connection on the amp" is, but I hope my Compass has it! I know it's got separate boards for the amp, dac, a power supply but I don't know how they're connected._

 

What's meant by a filter capacitor is that the DAC's output is offset at about 2.5VDC (same as the output in the SSMH - it's at 19VDC.). In order to prevent this DC from damaging your equipment or headphones, blocking or "filter" capacitors are used to block the DC. AC (the music signal) passes through unaffected, assuming the caps are sized correctly.
	

	
	
		
		

		
		
	


	




 In the case of the Alien and BantamDACs, the only thing separating the output directly off of the PCM (DAC) chip from anything it's connected to are those capacitors. Meaning, there's nothing to absorb spikes if/when they occur in the SSMH. Many other DACs use filter/output capacitors too, but there's often a small amplifier circuit, opamp, etc. inbetween. The protective circuitry in those, while coloring the signal even more, tends to protect the sensitive DAC chip from extraneous charges.

 It's been suggested before that some output resistors - probably 100R - on the output of the DAC may protect it from these issues. I'm not aware of anyone who's tried it, though. However, there are users out there who are using the SSMH with the BantamDAC without issue. On the other hand, I've blown two AlienDACs and one BantamDAC myself with the SSMH - but I was prototyping and switching a lot of things around, so who knows? It's safest to give the warning, though.
  Quote:


 Juaquin: thanks for that, at least now I know which posts to look for.

 Also, I saw on this thread somewhere that someone said something along the lines of "it sounded great even though I had it on my proto board". I'm planning on building this thing on a bread board, mainly cuz I'm still newb at this and I want it to be neat and easy to enclosure. Are there sound benefits to doing it point-to-point, or rather, are there sound detriments to doing it on a board? 
 

Either one is fine, as long as you have sufficient material for grounding. You should note that Pete Millett's original contained a hefty copper plate that had everything that was grounded soldered to it. The copper plate was in his original BOM, too.


----------



## hss3

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, Eagle may not be the best thing to use. What may be more useful is to Photoshop the existing Pete Millett schematic for the necessary changes, just as was done for the PCB differences over the original.
	

	
	
		
		

		
		
	


	


_

 

Here is a "flipped" image of the PCB ready for laser printing and toner transfer etching in .pdf form for 12AU7 tubes. It follows the same schematic as the Beezar circuit boards minus the modifications for the 9pin sockets. 

 Someone check the circuitry also...

SSMH 12AU7.pdf

 I screwed up my first PCB etch.. hoping to try again soon.


----------



## ezzieyguywuf

Some more questions. I've heard of "boutique" parts, but I don't know exactly what is being referenced to here. I know that they are more expensive, and that they're _supposed_ to be better, but what kind of difference are we really looking at here? I'm not exactly the most audiophiliphic audiophile, and my ears aren't super sensitive or anything, but I do appreciate some good noise -P) coming out of my D2000's. Also, I'm looking to invest in another set of cans in the (not so near) future. Maybe some Senns or something. Something different from the Denon's. Something that mates good with tubes. Anyways the point I'm getting at is, how much of a price difference will these "boutique" parts make, and will there me a notable audible difference on a range of headphones? Including IEMs actually.


----------



## the_equalizer

Quote:


  Originally Posted by *hss3* /img/forum/go_quote.gif 
_Here is a "flipped" image of the PCB ready for laser printing and toner transfer etching in .pdf form for 12AU7 tubes. It follows the same schematic as the Beezar circuit boards minus the modifications for the 9pin sockets. 

 Someone check the circuitry also...

SSMH 12AU7.pdf

 I screwed up my first PCB etch.. hoping to try again soon._

 

Am I correct in assuming it's a double sided board?

 cheers!


----------



## Juaquin

The current SSMH BOM uses some pretty high-quality parts. You could pay 2-5x the price for "boutique" parts that would only give you maybe a 5% increase in quality. Boutique parts would be things like SoniCaps or Mundorf caps, black gates (no longer available), etc. The resistors used in the SSMH are pretty much top-of-the-line as it is, so nothing to do there. You could switch out the pot for an Alps RK27 - in fact, that is probably worth the extra cost (the pot in the default BOM is good but not amazing). You could even use a stepped attenuator instead of a pot.

 Really, if you're looking to upgrade the SSMH you'd be better off just building a higher-end amp like the Mini-Max. You'll get more for your money that way than you would buying "boutique" parts.


----------



## the_equalizer

So, what do you guys think? This is the first draft schematic for the 12AU7 version of the Millett "Starving Student" Hybrid headphone amplifier.







 cheers!


----------



## hss3

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Am I correct in assuming it's a double sided board?

 cheers!_

 

Yes it is. 

 Wow, everyone on here is so helpful. Thanks for the above schematic... seems right to me.


----------



## Juaquin

Looks good to me. Might want to add a note somewhere that it's a modification so people don't get confused.


----------



## the_equalizer

Quote:


  Originally Posted by *hss3* /img/forum/go_quote.gif 
_Yes it is. 

 Wow, everyone on here is so helpful. Thanks for the above schematic... seems right to me._

 

Well, your PCB drawing is certainly very helpful! So far it looks great!

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Looks good to me. Might want to add a note somewhere that it's a modification so people don't get confused._

 

Good point. I edited the post to add that clarification and I'll add it to the schematic. Thanks !


----------



## blitzpirate

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Sounds like the potentiometer pins that connect to the ground plane are not correctly soldered, particularly the pin corresponding to the right channel.

 Check those solder points. Getting the solder to really flow in those takes quite a bit of heat, you'll need to apply your soldering iron for some 2 or three minutes until the ground plane heats up and the solder flows. 

 Problem is that you don't want to heat the pot pin as much, just the pad. So I'd suggest removing the solder, applying the iron to the pad long enough so that the solder flows, then apply the iron for some seconds to the pot pin too and then feed in the solder.

 cheers!_

 

hey thx for the help, but i did a noobie mistake and put to much solder and it went through the pins and connected on the other side. haha now do you have any tips on how to take the potentiometer off or how to disable the volume part completely because i can just use my dac for changing the volume? and if i cant do it, can anyone fix it for me if i ship it to them and pay for return shipping plus what you want to charge me for fixing it?


----------



## m11a1

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_So, what do you guys think? This is the first draft schematic for the 12AU7 version of the Millett "Starving Student" Hybrid headphone amplifier.
 cheers!_

 

Looks great!

 By the way, I have a question regarding the SSMH. Do you think it's possible to make a balanced SSMH. So it would be 2 boards for each channel? Or am I just crazy here....


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_So, what do you guys think? This is the first draft schematic for the 12AU7 version of the Millett "Starving Student" Hybrid headphone amplifier.
 </snip>_

 

Looks great!


----------



## the_equalizer

Quote:


  Originally Posted by *blitzpirate* /img/forum/go_quote.gif 
_hey thx for the help, but i did a noobie mistake and put to much solder and it went through the pins and connected on the other side. haha now do you have any tips on how to take the potentiometer off or how to disable the volume part completely because i can just use my dac for changing the volume? and if i cant do it, can anyone fix it for me if i ship it to them and pay for return shipping plus what you want to charge me for fixing it?_

 

Well, that's no mistake. That actually means you did a *great job* of soldering. 
	

	
	
		
		

		
		
	


	




 Maybe you could try posting some clear pics of the board underside and topside in the area where the pot is installed? Just to be sure before advancing any definite advice.

  Quote:


  Originally Posted by *m11a1* /img/forum/go_quote.gif 
_Looks great!

 By the way, I have a question regarding the SSMH. Do you think it's possible to make a balanced SSMH. So it would be 2 boards for each channel? Or am I just crazy here...._

 

It would require 1 board per channel, so four tubes, 4 MOSFETs, 2 PSUs (unless you're using a 1 amp PSU already),etc.

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks great!
	

	
	
		
		

		
		
	


	


_

 

Thanks ! I think I'll add the updated value for the electrolytics and the optional parts from the new schematic and that's it!

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_So, what do you guys think? This is the first draft schematic for the 12AU7 version of the Millett "Starving Student" Hybrid headphone amplifier.

 image

 cheers!_

 

nice but am I correct in saying you've used the original design and not this one?
http://www.diyforums.org/SSMH/schema...MH-origPCB.gif


----------



## tomb

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_nice but am I correct in saying you've used the original design and not this one?
http://www.diyforums.org/SSMH/schema...MH-origPCB.gif_

 

That's a good question and one I'm not sure how to answer. I guess it's up to the_equalizer, since the 12AU7 mods are his. The image you reference here is Dsavitsk's mods for the SSMH PCB. These mods definitely made the amp sound better. However, without a PCB, it's back to P2P and maybe it's better to reference the original schematic and let those who investigate further add the PCB mods.


----------



## timmyGCSE

from what I can gather..the schematic above is defo the original and not Dsavitsk's mods. In the original 12AU7 post the_equalizer made with a picture of the P2P wired tube sockets of his 12AU7, it was of the modified version and that threw me when I was comparing it to the original schematic lol, but just then it threw me again because he schematic is back to the original haha.

 Anyway yes I don't want to tread on equalizers toes, I started hand sketching a PCB design for the modded version yesterday, but it will be crap and I will spare my own embarressment by not showing anyone haha! but I want to make it myself and that just to prove to myself I can do it


----------



## ezzieyguywuf

Juaquin: thanks, thats the kind of answer I was looking for. Now that you've mentioned the minimax and I've checked it out, I don't know which direction I want to go  Of course, if I went with the mini it'd have to be sans enclosure, as its way outa my price range as it is.


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_

 It would require 1 board per channel, so four tubes, 4 MOSFETs, 2 PSUs (unless you're using a 1 amp PSU already),etc.
_

 

I was thinking of this! would there be any advantage to doing it?


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_nice but am I correct in saying you've used the original design and not this one?
http://www.diyforums.org/SSMH/schema...MH-origPCB.gif_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_That's a good question and one I'm not sure how to answer. I guess it's up to the_equalizer, since the 12AU7 mods are his. The image you reference here is Dsavitsk's mods for the SSMH PCB. These mods definitely made the amp sound better. However, without a PCB, it's back to P2P and maybe it's better to reference the original schematic and let those who investigate further add the PCB mods._

 

 Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_from what I can gather..the schematic above is defo the original and not Dsavitsk's mods. In the original 12AU7 post the_equalizer made with a picture of the P2P wired tube sockets of his 12AU7, it was of the modified version and that threw me when I was comparing it to the original schematic lol, but just then it threw me again because he schematic is back to the original haha.

 Anyway yes I don't want to tread on equalizers toes, I started hand sketching a PCB design for the modded version yesterday, but it will be crap and I will spare my own embarressment by not showing anyone haha! but I want to make it myself and that just to prove to myself I can do it_

 

Guys, guys! as I said in my previous post: I'll add the higher value for the electrolytics and the optional parts (the highlighted ones) from the new schematic 
	

	
	
		
		

		
		
	


	




 @timmyGCSE: If you read at the top of Dsavitsk's schematic you can see that the highlighted parts are _optional_; they're not essential to the operation of the circuit but, as TomB mentions, improve the way it sounds.

 cheers!


----------



## timmyGCSE

oh I know 
	

	
	
		
		

		
			





 and I realise you're doing the original but 12AU7,
 I just want to build the optional one onto PCB now 
	

	
	
		
		

		
		
	


	




 I've done a really bad rough hand PCB sketch, its terrible and over complex but once I get it in expressPCB I can tweak it better


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_I was thinking of this! would there be any advantage to doing it?_

 

Balanced operation has several advantages over "single ended" among which are: twice the output power, twice the slew rate, decreased otput impedance, decreased noise and zero crosstalk. You can read a bit more here.

 A balanced SSHM seems like an interesting experiment, I'm working on a balanced apheared 47 and recabled Grado SR-60is myself 
	

	
	
		
		

		
		
	


	




. Still it seems to me that you'd need to get closely matched tubes and MOSFETs for it to be effective. Just build one, m11a1.. and let us know how it works ! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_oh I know 
	

	
	
		
		

		
		
	


	




 and I realise you're doing the original but 12AU7,
 I just want to build the optional one onto PCB now 
	

	
	
		
		

		
		
	


	




 I've done a really bad rough hand PCB sketch, its terrible and over complex but once I get it in expressPCB I can tweak it better_

 

I definitely would *love* to try one of those PCB's too. hss3, if you plan on getting a batch of those produced, count me in.

 cheers!


----------



## Juaquin

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Now that you've mentioned the minimax and I've checked it out, I don't know which direction I want to go_

 

Honestly, you'd probably be fine with the SSMH - it's a great place to start. You can always build the minimax sometime in the future if you feel the SSMH isn't enough.


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Guys, guys! as I said in my previous post: I'll add the higher value for the electrolytics and the optional parts (the highlighted ones) from the new schematic 
	

	
	
		
		

		
		
	


	


_

 

Oops.


----------



## timmyGCSE

this amp really does sound crazy good...just using it with my Klipsch S2's, my mere £20 mainstay throw around IEM's, and I'm shocked at the huge openness and massive width and airyness of it all. In fairness I rank the S2's as the best dynamic I've personally heard but still...

 think next step is different tubes


----------



## m11a1

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_A balanced SSHM seems like an interesting experiment, I'm working on a balanced apheared 47 and recabled Grado SR-60is myself 
	

	
	
		
		

		
		
	


	




. Still it seems to me that you'd need to get closely matched tubes and MOSFETs for it to be effective. Just build one, m11a1.. and let us know how it works ! 
	

	
	
		
		

		
		
	


	


_

 

Well, I'm really thinking about a balanced SSMH 12AU7 version. 

 But, before I start anything, I really want to sketch out my ideas to see what you think. 
	

	
	
		
		

		
		
	


	




 I'll start drawing it out soon.


----------



## hss3

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_
 I definitely would *love* to try one of those PCB's too. hss3, if you plan on getting a batch of those produced, count me in.

 cheers!_

 

right now, no batch at the moment. I completed one that looks okay, but i still need a bit more practice.

 I think i can make 2 more? so if i dont screw up on teh next two, i will have 2 great ones and one good one that is missing a mosfet connection.

 If i have good extras, ill offer them out to people


----------



## timmyGCSE

equalizer..would it be worth you starting a new thread to branch the EIA 9A Starving Student off because it will get confusing otherwise, and since the 19J6 tubes look to be so scarce this ought to be the way forward to keep the project alive..


----------



## m11a1

Does anyone know where the PCB for SSMH besides Beezar? They are sold out there...


----------



## tomb

Quote:


  Originally Posted by *m11a1* /img/forum/go_quote.gif 
_Does anyone know where the PCB for SSMH besides Beezar? They are sold out there..._

 

Since the PCB was a Dsavitsk-Beezar proprietary product (with Pete Millett/n_maher's blessing), let me know if you find one somewhere else.
	

	
	
		
		

		
		
	


	







  Quote:


  Originally Posted by *timmyGCSE* 
_equalizer..would it be worth you starting a new thread to branch the EIA 9A Starving Student off because it will get confusing otherwise, and since the 19J6 tubes look to be so scarce this ought to be the way forward to keep the project alive.._

 

Just MHO, but I don't think we'd want to lose the connection to Pete Millett as the original designer. All of this is done with his permission, after all. The fact that his initial post anchors this thread is not unimportant.

 Besides, posting the writeup, schematic, etc. on the SSMH website would address your worries about confusion.


----------



## timmyGCSE

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Just MHO, but I don't think we'd want to lose the connection to Pete Millett as the original designer. All of this is done with his permission, after all. The fact that his initial post anchors this thread is not unimportant

 Besides, posting the writeup, schematic, etc. on the SSMH website would address your worries about confusion._

 

very true, the original design from Pete is as you say the reason for all this, I didn't mean to sound like this is a new design so forget the old one type thing, just meant there will more than likely be quite a bit of interest in the 12AU7 version but yes that'll be nice to have it written up on the website


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_<snip>

 Just MHO, but I don't think we'd want to lose the connection to Pete Millett as the original designer. All of this is done with his permission, after all. The fact that his initial post anchors this thread is not unimportant.

 Besides, posting the writeup, schematic, etc. on the SSMH website would address your worries about confusion._

 

I definitely agree that it should be kept under this thread, also why I did not start a new one when I posted about the mod.

 About the schematics, I'm hoping to integrate the remaining changes to the 12AU7 diagram today. As to other versions, if no one else volunteers (Logistic ? 
	

	
	
		
		

		
		
	


	




 ) I'll tackle the schematic for Logistic's 12SR7 mod too.

 cheers!


----------



## ezzieyguywuf

/me is getting excited about doing this build. I hope I can get organized befor spring break! (week of the 11th)


----------



## Lil' Knight

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_
 A balanced SSHM seems like an interesting experiment..._

 

Color me interested 
	

	
	
		
		

		
		
	


	



 Would be great if you could make a PCB for the balanced SSMH.


----------



## Narwhalius

Got my new pot in today. Took the old one out and put it in as soon as I could. Everything works good now. Even volume in both ears. Thanks for the help everyone.


----------



## the_equalizer

Quote:


  Originally Posted by *Narwhalius* /img/forum/go_quote.gif 
_Got my new pot in today. Took the old one out and put it in as soon as I could. Everything works good now. Even volume in both ears. Thanks for the help everyone._

 

Good to hear it's all going smoothly now 
	

	
	
		
		

		
			





 Enjoy your amp!

 cheers!


----------



## ezzieyguywuf

Ok, I got my BOM all ready for ordering from Digikey. I still need to source the tubes (I'll be building the 12AU7 or w/e the heck it is version), the sockets, and the power supply. I was wondering if anyone wouldn't mind taking a look at my BOM as it stands now? I'm up to $38 right now and was reaaaly trying to keep it under $50. I don't really wanna skimp on anything that might really matter though. So I'm open to any suggestions. For example, did I choose a crappy pot? I don't know! What about the headphone jack, or RCA jacks? I was pretty much just choosing w/e had the best looking picture, or looked about like what is listed in the original BOM. So please help me headfi!

 <edit> Also ,looks like the Mosfets are backordered? Can I get different ones?
 <edit> http://search.digikey.com/scripts/Dk...=IXTP60N10T-ND will that work?


----------



## ezzieyguywuf

Damn coulda swore I attached the file.

 <edit> turns out you can't upload .xls files. I zipped it.


----------



## Fitz

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_<edit> Also ,looks like the Mosfets are backordered? Can I get different ones?_

 

I've got some IRF510s here in my stuff, lemme know your shipping address and I'll drop a couple in the mail to you on Monday.


----------



## ezzieyguywuf

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_I've got some IRF510s here in my stuff, lemme know your shipping address and I'll drop a couple in the mail to you on Monday. 
	

	
	
		
		

		
		
	


	


_

 

Wow that's awesome! YGPM my friend. By the way, did I mention that I'm a soon-to-be-married starving student? 
	

	
	
		
		

		
		
	


	




 the less I spend on this project the happier wifey will be. I just GOTTA experience the tube sound though! Lol.


----------



## m11a1

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Wow that's awesome! YGPM my friend. By the way, did I mention that I'm a soon-to-be-married starving student? 
	

	
	
		
		

		
		
	


	




 the less I spend on this project the happier wifey will be. I just GOTTA experience the tube sound though! Lol._

 

Wow.....uhhhhhh.....um....good luck I guess


----------



## Juaquin

Probably better to wait until after the wedding to tell her about your addiction.


----------



## Llama16

You can still scare her away you know...


----------



## ezzieyguywuf

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Probably better to wait until after the wedding to tell her about your addiction._

 

Lol nah I just had to tell her when I bought the woodied Denon's and the Composs. The whole trust thing you know?

  Quote:


 You can still scare her away you know... 
 

I doubt it. We been dating since high school, for 5 years now. We're pretty solid.

  Quote:


 Wow.....uhhhhhh.....um....good luck I guess 
 

So I guess that was TMI? 
	

	
	
		
		

		
		
	


	




 My bad. I'm pretty proud that I'm getting married and I tell anyone who'll listen.


----------



## the_equalizer

Well, finally it's done. Here's the schematic for the 12AU7 version including the optional parts from the Beezar.com PCB version.

 Dsavitsk agreed to have his name on it; obviously the mod had been in his mind before I came around and built it 
	

	
	
		
		

		
		
	


	









 cheers!


----------



## ezzieyguywuf

Alright I thought I could do it but still I'm epic failing at this. Anywhere I look for tubes (12AU7) they seem to be ~$16. I thought these could be had for cheaper? Or maybe its an alternative that can be had for cheaper? Also, i'm trying to find a tube vendor that will also sell me the sockets I need, as I don't want to have to go to another party, and have to pay shipping a third time, for two small components.


----------



## tomb

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Alright I thought I could do it but still I'm epic failing at this. Anywhere I look for tubes (12AU7) they seem to be ~$16. I thought these could be had for cheaper? Or maybe its an alternative that can be had for cheaper? Also, i'm trying to find a tube vendor that will also sell me the sockets I need, as I don't want to have to go to another party, and have to pay shipping a third time, for two small components._

 

Not really - that's sort of the one disadvantage of using 12AU7's. At least for some types, they can be among the most expensive.

 Try some 5963's and sockets at Antique Electronic Supply - Antique Electronic Supply. There are some places where you can get them cheaper, but probably not with the sockets, too.


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Well, finally it's done. Here's the schematic for the 12AU7 version including the optional parts from the Beezar.com PCB version.

 Dsavitsk agreed to have his name on it; obviously the mod had been in his mind before I came around and built it 
	

	
	
		
		

		
		
	


	




 <IMG]http://img169.imageshack.us/img169/6263/12au7millettstarvingstu.jpg[/IMG>

 cheers!_

 

Looks great! I'll try to post it today!


----------



## ezzieyguywuf

Sweet, it turned out a lot cheaper at the site you linked than at thetubestore.com My total is now under $50!!!! Including tubes! Alls I got left is to think about a chassis. Woot. I think I'll use a breadboard as my common ground, instead of a copper plate. does that defeat the purpose or will it suffice?


----------



## bmwpowere36m3

Success, I've converted my original point-to-point build to use 12SR7GT tubes as per 
Logistic... sounds great.


----------



## tomb

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Sweet, it turned out a lot cheaper at the site you linked than at thetubestore.com My total is now under $50!!!! Including tubes! Alls I got left is to think about a chassis. Woot. I think I'll use a breadboard as my common ground, instead of a copper plate. does that defeat the purpose or will it suffice?_

 

The copper plate would be better, but I guess it depends on your choice of case. If the case you end up using has plenty of metal in it to form a good ground sink, then a breadboard will be fine. This isn't a statement of precise knowledge, but I just have a feeling after building a few of the PCB versions that the SSMH needs a hefty ground to be happy. Those that have hum/noise issues in P2P versions seem to go light on the grounding material. It doesn't matter how many wires you run to ground - if the ground you're running to is insubstantial. A couple of the early PCB protos seemed to have had this issue, especially if they were left uncased.

 Just as example, in the MAX/MiniMAX, a 2 oz. ground plane was worth an additional 5-10 uVAC in ripple reduction (in the PS) over a PCB with a 1 oz. ground plane - with everything else equal. I think the SSMH is more sensitive to good grounding than that, even.


----------



## ezzieyguywuf

Ah. How about running them all to a breadboard (for neatness) and then connecting the breadboard to a nice hunk of copper: or the case (if it ends up being metal?)?


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Alright I thought I could do it but still I'm epic failing at this. Anywhere I look for tubes (12AU7) they seem to be ~$16. I thought these could be had for cheaper? Or maybe its an alternative that can be had for cheaper? Also, i'm trying to find a tube vendor that will also sell me the sockets I need, as I don't want to have to go to another party, and have to pay shipping a third time, for two small components._

 

You could also try e-bay. I just did a quick search for 12AU7 and found a 'Buy it Now' offer for four 12AU7's at $15.00 USD. Maybe not premium vintage 'golden sounding' Amperex or Telefunken, but 12AU7's certainly 
	

	
	
		
		

		
			





. 

 cheers!


----------



## ezzieyguywuf

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_You could also try e-bay. I just did a quick search for 12AU7 and found a 'Buy it Now' offer for four 12AU7's at $15.00 USD. Maybe not premium vintage 'golden sounding' Amperex or Telefunken, but 12AU7's certainly 
	

	
	
		
		

		
		
	


	




. 

 cheers!_

 

Ah I hadn't even thought about using ebay. Will do thanks!


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Looks great! I'll try to post it today!_

 

Thanks Tom! I worked hard at making it look like the Beezar one.

 Now to the 12SR7 and 12AE6 schematics... 

 cheers!


----------



## nullstring

How exactly do you calculate the resistors necessary for different tubes?

 I was bored and was looking through a few lists of tubes, and I couldn't figure out why a 14n7 wouldn't work well.

 After looking through what logistic and the_equalizer decided to use for their resistors, I am thinking that this tube may only need the single resistor change to 390k.
 This is because, 19J6, 12au7, and 14n7 are all twin triodes, and the 14n7 runs at the same voltage as the 12au7... but this is just inductive logic.

 anyway, the tubes are cheaper than 12au7's as far as I can tell... and from they seem to sound quite nice from what I am reading.

 would anyone mind confirming my theory? I really don't have any idea what I'm talking about =p
 would a 14n7 work well?

 How wonder how hard it would be to make an adapter from 14n7 to 19j6.
 I'd need a reverse socket thing... to plug into the 7pin tube socket... the rest should be easy.


----------



## the_equalizer

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_How exactly do you calculate the resistors necessary for different tubes?

 I was bored and was looking through a few lists of tubes, and I couldn't figure out why a 14n7 wouldn't work well.

 After looking through what logistic and the_equalizer decided to use for their resistors, I am thinking that this tube may only need the single resistor change to 390k.
 This is because, 19J6, 12au7, and 14n7 are all twin triodes, and the 14n7 runs at the same voltage as the 12au7... but this is just inductive logic.

 anyway, the tubes are cheaper than 12au7's as far as I can tell... and from they seem to sound quite nice from what I am reading.

 How wonder how hard it would be to make an adapter from 14n7 to 19j6.
 I'd need a reverse socket thing... to plug into the 7pin tube socket... the rest should be easy._

 


 Ok, this is a short description of how I did it. However, as I said before, I'm not an electrical engineer and there are a couple of things I don't (yet) understand about the circuit.

 If you look at the schematic you can clearly see that there are two parts to the circuit:

 a) the tube voltage gain stage (increases the volume of the signal)
 b) the MOSFET output current gain stage (increases the power of the signal)

 For simplicity I'll refer to just the right channel part numbers. Naturally the left channel works in exactly the same way.

 Capacitor C2 isolates the DC bias voltages and currents from these two stages.

 Bias voltages and currents for the tube stage are set by resistors R1 (the plate load resistor) and R5 (the cathode resistor). The way to establish the value of those resistors is by drawing a load line and calculating the values. You can read how it's done here. After reading that, you might want to read this post by Dsavitsk.

 Theoretically any triode (or maybe even any pentode) would do I guess.

 Now the interesting part of making tubes work with the SSMH is the MOSFET output stage. There are two bias voltages and currents you want to provide to the MOSFET

 a) The drain-source voltage and current
 b) The gate-source voltage

 As to the drain-source voltage and current, you can see that the MOSFET drain and source are in a series circuit formed by the power supply, the MOSFET and the tube heater. The current in that circuit will be the tube's heater current, a value you can find in the tube datasheets; whereas the voltage will be the power supply voltage less the tube heater voltage.

 So in the 19J6 version, the MOSFET is biased at 150mA (the 19J6 heater current) and 29 volts (48V - 19V). 

 In order so keep things simple, you want to find a substitute tube that has a heater voltage close to 19V and the *same heater current* as the 19J6. 

 There are several reasons why you want to stick to the same heater current: first, the heatsinking requirements of the MOSFET will grow *enourmously* with increasing heater current. Secondly, the standard PSU used in the SSHM has a current capability of .35 A, which is just enough to power two tube filaments, each drawing 150 mA; if your substitute tube draws more heater current you'll need to scale the PSU (more $$) . Finally, and this is something I haven't checked in the IRF510/610 datasheet, you want to make sure that the MOSFET can withstand your proposed heater current.

 The heater voltage requirements are somewhat less strict, but you want to stay around 19 V. Too high a heater voltage and the voltage across the MOSFET will be too low for it to drive your cans (it wont have enough room to move, enough voltage to swing); whereas too low a heater voltage and you'll have the same problem as a high bias current: you'd be dropping too much power on the MOSFET and you'll need BIG heatsinks.

 So, for example, using a 6J6 (a 6 volt heater equivalent to the 19J6) is almost impossible: it's heater voltage is too low as you'd be dropping 42 volts across the MOSFET (compared to 29 V in the 19J6 version) and it's heater current is *450 mA* (!!!!!). Nor can you easily use 5J6 (4.7 V@600 mA heater) or 6DJ8 (6.3 V @ 365 mA heater) tubes.

 Yes, you could insert a power resistor in series with the MOSFET and the heater to dissipate the extra voltage but the resistor would have to be well ventilated (it'd need to dissipate some 6 to 8 watts) and that still leaves you with the heatsinking required for the MOSFET to operate at 29 volts @ 450 mA !!!

 So, specifically about the 14N7, while the heater voltage is adequate (12.6 V according to my tube manual) it's heater current is too high (300mA). It could be made to work if you check the three points I mentioned above (massive heatsinks, a 1 A power supply and check that the MOSFETs can withstand 300ma drain-source current).

 Last but not least, we just need to talk about the MOSFET gate-source bias voltage. In the SSHM this voltage is set by the tube heater voltage and the voltage divider formed by R2 and R4. You can see that the MOSFET's source pin (the pin tied to the tube heater) voltage to ground is equal to the tube heater voltage. So in the 19J6 version the MOSFET source pin voltage is close to 19 V, as indicated by Pete Millett in the schematic.

 Now, in order to "turn-on" the MOSFET, the gate needs to be a little bit more positive than the source. How much more positive is something I deduced from the schematic. If the PSU voltage is 48 V, then the voltage at the midpoint of the voltage divider formed by R2 and R4 must be half that voltage (since R2 and R4 have the same value) thus the voltage with respect to ground at the MOSFET gate is 24 volts; if the source is at around 19 V, then the gate-source voltage is around 5 volts. Resistor R3 has no influence in this due to the way MOSFETs operate: there's no current flow in the gate-source circuit, so no current flowing through R3 and no voltage drop across it.

 So, I assumed that that voltage had to be preserved. I was aided in this assumption by Dsavitsk's hint that "only one resistor" had to be changed, so I deduced, it had to be one resistor in the gate biasing voltage divider. Then it was a matter of using Ohm's law to calculate the value for such resistor so that if the MOSFET source pin were at around 12 volts, the MOSFET gate pin sat at around 17, thus mantaining the 5 volt difference.

 The math is simple:

 Total resistance in the voltage divider
 390 Kohms + 220 Kohms = 610 Kohms

 Total current in the voltage divider
 48V / 610 Kohms = .08 mA

 Voltage at the junction 
 .08 mA * 220 Kohms = 17.31 V

 You can also see that Logistic got the same result with different resistor values. The possible implications of choosing different values are something that I don't completely understand. I think you'd want to keep R4 the same value or higher, so that there's no bass roll off in the insterstage RC coupling formed by R4 and C2 but this I get from my incomplete understanding of the circuit; I could (very likely) be wrong.

 Another thing I don't yet understand: does the source-gate voltage have to be around 5 volts ? Can it be higher? How much higher? Could the 12AU7 version work with the same voltage divider as the 19J6 version (e.g. with the gate sitting at 24 volts with respect to ground) ? I can see that this voltage (along with the source-drain voltage) determines how much voltage the MOSFET can swing, but I haven't yet sat down to carefully read the datasheet and run some experiments with the amp 
	

	
	
		
		

		
		
	


	




 So, that's pretty much it... it didn't end up as brief as I thought it would be 
	

	
	
		
		

		
		
	


	




. I hope it wasn't too confusing and that I managed to answer your questions. 

 cheers!


----------



## m11a1

Great explanation the_equalizer!!

 Cheers


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## tomb

In fact, that makes for a great writeup to post on the web!


----------



## tomb

Posted!
SSMH Variations


----------



## the_equalizer

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_In fact, that makes for a great writeup to post on the web!
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Posted!
SSMH Variations



_

 

Wow, thanks.! .. 
	

	
	
		
		

		
		
	


	




 it might be a good idea for someone more technically savy than I am to revise it 
	

	
	
		
		

		
		
	


	




 By the way, to those interested, I think a possible good substitute tube would be the 17EW8. It's a double triode with a 17.5 V @ 150 mA heater. It would be a great exercise to draw the load line, determine the values for the plate load and cathode resistors and adjust the MOSFET gate bias voltage divider.

 I already ordered a couple of these tubes from e-bay, they should be in my hands in about a couple of weeks. But please, don't let that stop you! If you have those tubes handy please design and prototype your own variation on the SSMH 
	

	
	
		
		

		
		
	


	




... and obviously post it here, please! If it works, we could call it the "head-fi 17EW8 mod" 
	

	
	
		
		

		
		
	


	





 cheers!


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Wow, thanks.! .. 
	

	
	
		
		

		
		
	


	




 it might be a good idea for someone more technically savy than I am to revise it 
	

	
	
		
		

		
		
	


	




 </snip>_

 

Well, I edited it a bit.
	

	
	
		
		

		
		
	


	




 Still, it's in your own words and in your opinion - and it worked! So, I don't think it will need a lot of revising, per se. We'll get Dsavitsk to look at, though.


----------



## timmyGCSE

wow man, thats a nice writeup indeed.

 I'm torn now..I'm 80ish % of the way through a PCB design for the 12AU7 using the modified Dsavitsk schematic, I think I've got it right. I priced it up this morning using nice parts, kinda spending a bit extra to get some nice bits like full metal TruConnect jack instead of the REAN plastic one, plus the PCB stuff to make the PCB, plus a clear blue hammond case and it all comes to around £50. Which is how much I paid for my original SSMH but that included tubes and PSU, this one wouldn't.

 Or, I can build a mini3 or a SOHA (yes..aware that its obselete but its all pratice on the cheap) for the same cost. I'm tempted by the SOHA actually because I can still make the PCB myself (expressPCB design is already done on headwize) and its different and possibly actually cheaper than the SSMH to make.
 But I dunno, making the modified SSMH seems somewhat appealing bearing in mind how good the SSMH 12AU7 vanilla sounded.


----------



## nullstring

thanks the_equalizer, much appreciated.

 So, it sounds like the better solution, if I really wanted to use the 14N7, would be to use double the mosfets.


----------



## the_equalizer

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_thanks the_equalizer, much appreciated.

 So, it sounds like the better solution, if I really wanted to use the 14N7, would be to use double the mosfets._

 

No problem, glad it helped.

 I'm not sure I quite follow you there with the "double the mosfets" idea. As it is you already have as many MOSFETs as you need: one for the right channel and one for the left channel.

 As I mentioned in my post, the way to get the 14N7 to work would be:
 1.- Draw a load line and determine the value for the plate and cathode resistors.

 2.- Get a PSU that can supply at least 650 mA of current (300 mA for each tube heater + a 50mA safe area)

 3.- Get some REALLY BIG heatsinks for the MOSFETs - You'll be dropping (48 V - 12V) = 36 V @ 300 mA ... let's see that's 10.8 watts per MOSFET (compare to the 4.35 watts per MOSFET in the 19J6 version)

 The gate voltage divider resistors would be the same as for the 12AU7 version, since the 14N7 heater runs at 12.6 V too.

 Finally, I checked the IRF510 datasheet and it can easly work with the 300 mA current (it's rated for a maximum of 5.6 A)

 cheers!


----------



## dsavitsk

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Another thing I don't yet understand: does the source-gate voltage have to be around 5 volts ? Can it be higher? How much higher? Could the 12AU7 version work with the same voltage divider as the 19J6 version (e.g. with the gate sitting at 24 volts with respect to ground) ? I can see that this voltage (along with the source-drain voltage) determines how much voltage the MOSFET can swing, but I haven't yet sat down to carefully read the datasheet and run some experiments with the amp 
	

	
	
		
		

		
			



_

 

Vgs is a property of the Mosfet and changes depending upon how much current is going through it. That is, there is a correlational relationship between Ids and Vgs. This can work in two ways -- first, as here, as the current increases, Vgs also increases, and as the current decreases, Vgs decreases. Vgs is pretty much always close to 4.5V for the IRF510 and IRF610, and just moves up a small amount with different currents -- too small an amount for concern on this amp.

 However, you can use it the other way, too. That is, by carefully controlling Vgs, you can control the amount of current that goes through the mosfet thus making it a constant current source. So, for instance, you can use a resistor divider from + to bias the gate. Then, by varying a resistor between the source and ground, a resistor that drops voltage across it, you can control the voltage between the gate and the source, which controls the amount of current that can flow.

 So, in the Starving Student, why is it not acting like a CCS? The reason is because the mosfet is biased into saturation. The amount of voltage we have between the gate and the source is too high to be able to control the current, so the mosfet will let basically any amount of current flow. Instead, the current is limited by the heater which, at the bias voltage of the mosfet minus Vgs (~19V), can only draw 150mA thus limiting the current across the mosfet. You can think of the heater as the resistor used with an LED -- the LED will pass full current and burn itself up without a current limiting resistor inline with it. Here, the heater acts as as the limit. The mosfet differs from the LED, though, in that it has an extra leg whose voltage with regard to the cathode is set by the current between the anode and the cathode.


----------



## nullstring

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_I'm not sure I quite follow you there with the "double the mosfets" idea._

 

unless I'm wrong, you should be able to run the mosfets in parallel just to dissipate the heat between two mosfets instead of one.


----------



## the_equalizer

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_Vgs is a property of the Mosfet and changes depending upon how much current is going through it. That is, there is a correlational relationship between Ids and Vgs. This can work in two ways -- first, as here, as the current increases, Vgs also increases, and as the current decreases, Vgs decreases. Vgs is pretty much always close to 4.5V for the IRF510 and IRF610, and just moves up a small amount with different currents -- too small an amount for concern on this amp.

 However, you can use it the other way, too. That is, by carefully controlling Vgs, you can control the amount of current that goes through the mosfet thus making it a constant current source. So, for instance, you can use a resistor divider from + to bias the gate. Then, by varying a resistor between the source and ground, a resistor that drops voltage across it, you can control the voltage between the gate and the source, which controls the amount of current that can flow.

 So, in the Starving Student, why is it not acting like a CCS? The reason is because the mosfet is biased into saturation. The amount of voltage we have between the gate and the source is too high to be able to control the current, so the mosfet will let basically any amount of current flow. Instead, the current is limited by the heater which, at the bias voltage of the mosfet minus Vgs (~19V), can only draw 150mA thus limiting the current across the mosfet. You can think of the heater as the resistor used with an LED -- the LED will pass full current and burn itself up without a current limiting resistor inline with it. Here, the heater acts as as the limit. The mosfet differs from the LED, though, in that it has an extra leg whose voltage with regard to the cathode is set by the current between the anode and the cathode._

 

Thanks for that! I'm already reading up on biasing MOSFETs into their saturation region.

 I'd have just one more question, with Vgs sitting at 4.5 volts, does that mean that the maximum input signal amplitude the MOSFET can take without being driven out of saturation (clipping) would be around 9 V p-p ?

 Thanks again!

  Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_unless I'm wrong, you should be able to run the mosfets in parallel just to dissipate the heat between two mosfets instead of one._

 

Ok, I see what you mean. Well, it looks as if it could work, yes, some kind of parallel source follower. You'd also have to include a gate resistor (R3a, let's call it) for the new MOSFET: one end connected directly to the MOSFET's pin 1 and the other end connected to the junction of R2, R4 and R3; this would bias the MOSFET to conduct and input the signal into it's gate.

 Still, it seems to me that the space occupied by the new MOSFET and it's heatsink could as easily be used to harbour a BIG heatsink for a lone MOSFET, plus you wouldn't need another heatsink mounting kit.

 On the other hand the four heatsinked MOSFETs would look cool 
	

	
	
		
		

		
		
	


	




. Time to build a prototype maybe ?

 cheers!


----------



## ezzieyguywuf

For the power supply, is it 48 VDC and >= 0.350 amps? Because some of these powersupplys I'm seeing on ebay seem to be a little different from the one Millett used. Cisco Power Supply PN 34-1977-03 model PSA18U-480C - eBay (item 320483355045 end time Apr-03-10 16:02:27 PDT) 

 theres an example. Says 0.38 amps. I can't get that one cuz it doesn't have the power cable :-/ otherwise it's an awesome deal at $5.


----------



## ezzieyguywuf

double-post


----------



## Juaquin

Yep, 48V and anything over .350A is good. If you're doing one of the mod versions you might want more current though, I seem to remember that's called for but I can't find numbers.


----------



## ezzieyguywuf

I'm doing the 12AU7 Version. According to this schematic, the same source can be used. Is this just an oversight on the_equalizer's part? 

 Also, am I right in thinking that just one of these can be used to cool both mosfets? I'm looking for any means of cutting down the price on this bad boy.

 While I'm asking questions, how do you go about mounting this to a chassis? Seems like it'd be pretty straight-forward but the picture is not all that great.


----------



## nullstring

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_ Cisco Power Supply PN 34-1977-03 model PSA18U-480C - eBay (item 320483355045 end time Apr-03-10 16:02:27 PDT) 

 theres an example. Says 0.38 amps. I can't get that one cuz it doesn't have the power cable :-/ otherwise it's an awesome deal at $5._

 

You know that the cable from main to the power supply is just standard computer cable, right?

 I don't know the proper name for them, but it's just the cable that tends to go from 120VAC to a desktop computer PSU.
 The type that tends to DIY audio, tends to build their own computers, so it wouldn't be uncommon if you already had a few extras.

 Although, now that I look at the link, the shipping is $16.. which kills the deal anyway, making this post useless.. oh well, I already typed it.


----------



## ezzieyguywuf

I'm doing the 12AU7 Version. According to this schematic, the same source can be used. Is this just an oversight on the_equalizer's part? 

 Also, am I right in thinking that just one of these can be used to cool both mosfets? I'm looking for any means of cutting down the price on this bad boy.

 While I'm asking questions, how do you go about mounting this to a chassis? Seems like it'd be pretty straight-forward but the picture is not all that great.

 <edit>
  Quote:


 You know that the cable from main to the power supply is just standard computer cable, right?

 I don't know the proper name for them, but it's just the cable that tends to go from 120VAC to a desktop computer PSU.

 Although, now that I look at the link, the shipping is $16.. which kills the deal anyway, making this post useless.. oh well, I already typed it. 
 

I found this deal, which is $10 shipped, so I'll just get that one. Thanks though.


----------



## Juaquin

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_I'm doing the 12AU7 Version. According to this schematic, the same source can be used. Is this just an oversight on the_equalizer's part?_

 

No, it looks ok, I'm just getting things messed up in my head, that's all. Nice to know the power adapters are still readily available.


----------



## ezzieyguywuf

Ah I still have yet another question actually: when wiring up the mosfets, should I use shrink wrap or something to keep the feet from touching each other? Is there a standard way of doing this? Also, I'm guessing my enclosure will have to have a hold for the mosfet wires to go through?


----------



## tomb

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Ah I still have yet another question actually: when wiring up the mosfets, should I use shrink wrap or something to keep the feet from touching each other? Is there a standard way of doing this?_

 

It depends ... remember that the MOSFETs are going to be bolted down, so there's not much chance of them moving. I'd still do it, but then I'm the cautious type.
	

	
	
		
		

		
		
	


	



  Quote:


 Also, I'm guessing my enclosure will have to have a hold for the mosfet wires to go through? 
 

Most people used rubber grommets to insulate the edges of a hole from contacting the MOSFET leads. Look back at Pete's original, Nate's, and some of the early P2P builds.


----------



## ezzieyguywuf

thanks tomb, I'll look at those earlier builds.

 I'm beginning to think more and more that enclosing this thing is going to be infinitely worse than getting the circuit together. My plan is actually to build the circuit next week, and then maybe wait till the summer to design and build a case for it  darn grad school is sooo time consuming. Only thing is, I have access to a machine shop now (through one of my classes), and I won't later in the summer. *sigh*.


----------



## timmyGCSE

Koss PortaPro + SSMH = match made in heaven


 that is all


----------



## Fitz

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_I'm beginning to think more and more that enclosing this thing is going to be infinitely worse than getting the circuit together._

 

You catch on quick. 
	

	
	
		
		

		
		
	


	




 Casework can very easily make up most of the time and money spent on a DIY project.


----------



## timmyGCSE

seems I have a problem... :-/

 I noticed the left channel was louder and more bassy than the right. Unplug the left phono, and no sound in the left ear, as to be expected. Unplug the right phono..and umm..sound in both ears, much bassier but much more veiled :-/
 I've quadruple checked everything, made sure there is no cross contact between any wires, traced the circuit in both channels to see if I've crosswired something..nope. I must be missing something..there must be a wire touching somewhere but I'll be darned if I can find it...


----------



## tomb

Quote:


  Originally Posted by *Fitz* /img/forum/go_quote.gif 
_You catch on quick. 
	

	
	
		
		

		
			





 Casework can very easily make up most of the time and money spent on a DIY project._

 

Yep. Ditto on the casework.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *timmyGCSE* 
_seems I have a problem... :-/

 I noticed the left channel was louder and more bassy than the right. Unplug the left phono, and no sound in the left ear, as to be expected. Unplug the right phono..and umm..sound in both ears, much bassier but much more veiled :-/
 I've quadruple checked everything, made sure there is no cross contact between any wires, traced the circuit in both channels to see if I've crosswired something..nope. I must be missing something..there must be a wire touching somewhere but I'll be darned if I can find it..._

 

Well, you're correct to assume that the signal wires are crossed somewhere.
	

	
	
		
		

		
		
	


	




 Look carefully over the signal input wires from the RCA jacks to the pot and then look at the output to the headphone jack. Somewhere, you have the ground crossed with the Right channel.


----------



## ezzieyguywuf

I think I'll get a case from Radioshack, drill some holes in it, and then do my build around that. I was originally planning on building the whole thing, and then casing it, but figured it'd be hard to get mosfets through the holes with the wires on them. I dunno though. Oh, and the tube sockets. I think I need to mount them before connecting any wires to them.

 <edit> I can't seem to PM Fitz, so instead, I'll just say on here that I have received the mosfets you sent in the mail today. Once again, thank you very much for your contribution.


----------



## timmyGCSE

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Well, you're correct to assume that the signal wires are crossed somewhere.
	

	
	
		
		

		
		
	


	




 Look carefully over the signal input wires from the RCA jacks to the pot and then look at the output to the headphone jack. Somewhere, you have the ground crossed with the Right channel.
	

	
	
		
		

		
		
	


	


_

 

yea...must be somewhere but I've checked, checked and checked again..its going to be somewhere real awkward and stuff.

 but my PCB is finished for the Dsavitsk 12AU7 version, the BOM comes to £30 from rapid including PCB making materials, so I've got an ebay auction finishing on Saturday and depending how much that goes for I will buy the stuff and make a PCB version. I've got the parts for a mini3 being delivered (today I think!) but I'm a bit scared to make it lol! and I may also order a batamDAC for the mini3 after the SSMH PCB and mini3 are done hmmmm


----------



## m11a1

Does anyone ever had a problem with volume imbalance on the SSMH before? 

 I feel like the right side is always a bit louder so I decided to open it up and check it out and accidentally switched the mosfets and now the higher volume is on the left side. So, is one of the mosfets the true culprit?


----------



## Juaquin

Well, if you switched the MOSFETs and the channel imbalance followed it, then yeah, probably the MOSFET. I don't recall the MOSFETs ever having caused an imbalance, but it seems to be the case here. Maybe one is slightly damaged?

 Also, how do you accidentally switch the MOSFETs? Are they not soldered in?


----------



## m11a1

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Well, if you switched the MOSFETs and the channel imbalance followed it, then yeah, probably the MOSFET. I don't recall the MOSFETs ever having caused an imbalance, but it seems to be the case here. Maybe one is slightly damaged?

 Also, how do you accidentally switch the MOSFETs? Are they not soldered in?_

 

Yea I was testing it out before I soldered it. But now thats its solder it's going to be annoying to remove. Now I have to replace both since I don't know each is the defective one. Also, do you know where I can even buy replacement/high quality mosfets that I can use since Beezar no longer sells them?


----------



## nullstring

while they are extremely expensive, you can get the IRF510's from radio shack..

 cheaper after shipping...

 EDIT:
 also, they look -exactly- the same as the mosfets from mouser, so, they aren't some cheaper version.


----------



## tomb

Give me some time this weekend and I'll put the IRF5150's on the store. I've got about a hundred of them that aren't going anywhere soon.
	

	
	
		
		

		
		
	


	




 Meanwhile, shoot me a PM with your address. m11a1, and I'll send you a pair gratis.


----------



## Entropy1

Hey, so I just came into inheritance of maybe 30 tubes and apparently there's a another chest of around 400 tubes somewhere. My grandfather use to repair TV's and worked at a radio station so there's quite a bit of stuff, including a massive 40lb tube used on one of the radio towers. I'll try to get some pictures taken of them as they are quite impressive. There is also a tube tester and some other supplies that will keep me busy for quite some time. Anyways, I suppose the only relevance to this thread is possibly finding other compatible tubes in the massive stash. Losing my 19JS's is kind of a big concern to me because my amp goes on and off around 5 times a day. I'll post pictures and post if i find anything interesting.


----------



## FallenAngel

Catalog them all, make a big list and you'll be sure to find something of interest (while being able to find them later).


----------



## Juaquin

Awesome, can't wait to see some pictures (especially of that monster 40lb one)


----------



## hss3

so after finishing the build, plugged it in...

 i could hear something from the left side faintly even though it wasnt switched on...

 but when i switched it on, sparks and popping came from the unit underneath the heatsink/tubes. My mosfets sit close to the tubes... and i think i may have accidently grounded the heatsink?

 now i dont hear sound at all from the unit, even when its off. 

 so right now.. despair!


----------



## nullstring

should it matter if you ground the heatsink?

 everything should be isolated from the heatsink..


----------



## n_maher

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_should it matter if you ground the heatsink?

 everything should be isolated from the heatsink.._

 

Everything _should be_ but that doesn't mean everything is. 
	

	
	
		
		

		
		
	


	




 That's where I'd start with the trouble shooting, check continuity between the metal tab of the FET and ground.


----------



## ezzieyguywuf

P2Y7503-ND I orderered this pot off of digikey, but realize now that the shaft doesn't have any threads. Anyone know of a good way of mounting this to my enclosure? I was thinking of making a square hole that fits the flats, and then just putting a piece of tape behind it to hold it in place. Theres gotta be a more elegant way though. Also, CP-009BH-ND that is the connector I got for the power supply. I'm guessing that for this I make a square hole in my case and just shove it in? The material really doesn't seem like it'll give enough to allow that to happen. 

 Thanks for your help guys!

 Ah yes, I also got HS374-ND those as heat sinks. I know some people pull the pin out and tap some threads in it, so that they don't have to solder it down. Now that I got them, though, I see that the hole the pins go in aren't really holes. They're more like a C slot, i.e. one side has no material. Is that what you guys are tapping? I'd think that gap would pose some problems, but maybe I'm wrong.


----------



## Sganzerla

I need some help from you guys. 
	

	
	
		
		

		
			





 Today I build my first amp, this one, with some help from a friend that was guiding me trough MSN (mic + webcam), he got the picture of the layout I was using, and the circuit from official website.

 Everything was installed and then when I got to use this amp, I have some strange behaviour occuring:

 - First when I turn it ON I hear a loud pop and then 5 pop sound (I think it is the power supply causing this). Is everything ok? My worry is about this very loud pop...

 - After turning volume on, I hear more sound on the right side, and after 10 seconds or so, sound begin to turn down and it keeps going until it has almost none. While this occur, the sound imbalance goes from right side to the left. I'm pretty sure something wrong is happening here... 
	

	
	
		
		

		
		
	


	




 - I think my tubes are a little oxized, is there any easy way of cleaning this and my tube socket? I live in a country where some speciality things aren't easy or cheap to get.

 Here is a picture of my build, I think will try to desolder and solder everything back tomorrow, if someone can instruct me on what look/is wrong and/or how to solve this problem, I'd be very thankfull:

LINK TO BIG IMAGE

 While the sound lasts 10 seconds or so, it sounds like it will kill my Compass amp on quality (timbre is different, bass and highs too), hopefully it will begin to work as desired.


----------



## n_maher

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Is that what you guys are tapping? I'd think that gap would pose some problems, but maybe I'm wrong._

 

Yup. There's no issue taping that section of the heat sink.

 As for you other parts problem I don't have much for advice other than to say I don't think either was a good choice and I'd get the "right" parts rather than kludge together the bits that don't want to work.


----------



## the_equalizer

Quote:


  Originally Posted by *Sganzerla* /img/forum/go_quote.gif 
_I need some help from you guys. 
	

	
	
		
		

		
		
	


	




 Today I build my first amp, this one, with some help from a friend that was guiding me trough MSN (mic + webcam), he got the picture of the layout I was using, and the circuit from official website.

 Everything was installed and then when I got to use this amp, I have some strange behaviour occuring:

 - First when I turn it ON I hear a loud pop and then 5 pop sound (I think it is the power supply causing this). Is everything ok? My worry is about this very loud pop...

 - After turning volume on, I hear more sound on the right side, and after 10 seconds or so, sound begin to turn down and it keeps going until it has almost none. While this occur, the sound imbalance goes from right side to the left. I'm pretty sure something wrong is happening here... 
	

	
	
		
		

		
		
	


	




 - I think my tubes are a little oxized, is there any easy way of cleaning this and my tube socket? I live in a country where some speciality things aren't easy or cheap to get.

 Here is a picture of my build, I think will try to desolder and solder everything back tomorrow, if someone can instruct me on what look/is wrong and/or how to solve this problem, I'd be very thankfull:

LINK TO BIG IMAGE

 While the sound lasts 10 seconds or so, it sounds like it will kill my Compass amp on quality (timbre is different, bass and highs too), hopefully it will begin to work as desired._

 

Your wiring looks OK. I'd need to see some other angles of your build, for instance, to have a side look at those terminal strips, and more detail on the volume pot.

 Also, when this 10 second fade-out happens.... do the tubes remain lit up? I'm betting they don't.

 cheers!


----------



## Juaquin

Taking stabs in the dark here, but it sounds like a capacitor is draining (given the slow fading over ~10 seconds). Perhaps one of the output caps is shorting?

 [EDIT] If the LEDs fade through, that indicates the power supply (likely the power caps are draining somehow).


----------



## ezzieyguywuf

So I got my build laid out on the table, with a bunch of alligator clips connecting stuff (just to test it). I noticed that when I power it on, nothing happens. After a bit of troubleshooting, I find that when I make the very first connection after the switch in the schematic, I get a spark. More specifically, when I hook up the resiston/capacitor, which I've got hooked up on a breadboard. I used the breadboard due to all the common nodes at the "48V" on the schematic. Any guess as to why this connection would result in a spark? I've double (though not quite triple, it's getting late) checked all the capacitors to make sure they're lined up right, and I've also checked all the connections on my breadboard, but to no avail. I can post pics tomorrow morning, but just thought I'd go ahead and post this to see if anyone with more experience with this schematic than me might offer a suggestion as to what is causing this spark.

 <edit> couldn't wait . You'll notice that I joined the ground for C6, R4 and R10. Also, the "48V" is that one node in the schematic that is marked as such. The 48V to the top right connects directly to my power supply, and this is what causes the sparks. If I connect just the mosfets, pin 2, I do not get any sparks. I should also note that I'm not getting the "~12V" that is listed in the schematic, though I am getting the "48V".....

 <double edit> Got this far in my post and decided to actually try measuring the "48V" on my breadboard, as I had only been measuring it at the Pin2/Pin2/48V--> . Hooked it up and my tubes are a glowin! I'm getting ~32V where I'm supposed to be getting ~12V though, coming out of pin4 and into the + of C3 and C5. Is this gonna blow up?

 <triple edit> Turns out I had forgotten to connect the "Pin 1/6" L and R as I have it annotated. I now get the appropriate voltages AND sound! Only problem is the right channel is significantly lower volume than the left, and it hummmms. I haven't started troubleshooting it yet, but heck I got sound! time for bed cheers!

 <I really should be in bed right now> Omg... http://tangentsoft.net/audio/bitmaps/annotated-evj.jpg I used that image to wire my pot and just realized I did it looking at it from the front, not the back. Man this sucks. I spent soooo much timing doing a "good" job wiring that thing too. at least I know where the problem is. I'm surprised I got any sound out of it at all......


----------



## Sganzerla

Well, let me first thank you both for your time and attention.
 Here are the links for the 4 images I made:

LINK1
LINK2
LINK3
LINK4

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Your wiring looks OK. I'd need to see some other angles of your build, for instance, to have a side look at those terminal strips, and more detail on the volume pot.

 Also, when this 10 second fade-out happens.... do the tubes remain lit up? I'm betting they don't._

 

 Yes, they do. Looks like they fade a little from the intensity they are at start, but they continue lit up.

  Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Taking stabs in the dark here, but it sounds like a capacitor is draining (given the slow fading over ~10 seconds). Perhaps one of the output caps is shorting?

 [EDIT] If the LEDs fade through, that indicates the power supply (likely the power caps are draining somehow)._

 

 I have problems with terminology of these components, could you point wich value (or the color) are the power caps and the output caps? It is easier for me to understand.

 Thanks again!


----------



## the_equalizer

Quote:


  Originally Posted by *Sganzerla* /img/forum/go_quote.gif 
_Well, let me first thank you both for your time and attention.
 Here are the links for the 4 images I made:

LINK1
LINK2
LINK3
LINK4



 Yes, they do. Looks like they fade a little from the intensity they are at start, but they continue lit up._

 


 Thanks for the pics! I'll review them carefully and comment on them later (gotta go to the office now!). If the tubes remain lit up then it's stranger than I thought; I was aiming at the same thing Juaquin mentioned: power supply shut off and power caps draining causing that slow fade out. The issue still probably has to do with caps slowly discharging but if the tubes remain lit up, the power supply is working. 

 I do have a question already, on the first pic, the terminal strip on the right side, immediately to the right of the solder point connecting the terminal's middle pin to ground there's a small solder blob... is anything connected to it? From the pic _it seems_ as though one teflon cable is connected to it.

 Oh, forgot to mention, those loud thumps at turn on are normal: those are the sound of the output caps charging up through the parallel combination of your 'phones and R6, R12. That's why you do not want to turn the amp on or off with your cans plugged in.

  Quote:


  Originally Posted by *Sganzerla* /img/forum/go_quote.gif 
_ I have problems with terminology of these components, could you point wich value (or the color) are the power caps and the output caps? It is easier for me to understand.

 Thanks again!_

 

Refering to the schematic, power caps are C1 and C6; output caps are C3 and C5.

 cheers!


----------



## Sganzerla

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_I do have a question already, on the first pic, the terminal strip on the right side, immediately to the right of the solder point connecting the terminal's middle pin to ground there's a small solder blob... is anything connected to it? From the pic it seems as though one teflon cable is connected to it._

 

 Thanks again, no, there is nothing connected to that blob, it is there alone - I almost soldered the terminal there, but later moved more to the center.


----------



## Juaquin

I had trouble following your description - which channel is getting quieter and fading away? I would check the output capacitor in that channel for shorts or damage.

 Also, until you nail down the problem, don't plug any good headphones into the amp. It's possible that you're passing DC voltage through the to headphones, which could fry them.


----------



## ezzieyguywuf

alright, "finished"! The only thing I use the alligator clips for now are the ground connections, which I'm running to a huge copper thing I bought at Lowe's. I got everything laid out on the table, and seeing as to how I went over budget, might have to resort to poking some holes in a cardboard box as an enclosure. The problem is, though, that I have humming! When I have the pot really really low, first of all, I only get sound in the right ear. As I turn the pot higher, I eventually get sound in both ears. It doesn't sound uneven though, same volume in both ears. Also, with no source connected, I can adjust the pot until I find a "sweet spot" where there is no hum.

 Finally, with my source set at 0dB volume, I can barely touch the pot on the amp before it is too loud to do anything with. Its like off-off-offf-off-SUPER LOUD. The only reason I mention this is that on my CMOY, I can use the same source at the same volume and have a fair bit of play with the volume knob.

 Any help with any of these issues guys? I realize after searching that ground seems to be the issue for humming, but I wonder if this "sweet spot" business I described might now point to something else?


----------



## nullstring

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_The problem is, though, that I have humming!_

 

This could very well be caused by the alligator clips
  Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_When I have the pot really really low, first of all, I only get sound in the right ear. As I turn the pot higher, I eventually get sound in both ears. It doesn't sound uneven though, same volume in both ears. _

 

pots that are mismatched at low volumes are very common.

  Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Finally, with my source set at 0dB volume, I can barely touch the pot on the amp before it is too loud to do anything with. Its like off-off-offf-off-SUPER LOUD._

 

You don't have any high impedance cans...
 What did you use for your R16/R17? you may need to increase them.
 When you fix this issue, the mismatched pot won't matter.

  Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_ but I wonder if this "sweet spot" business I described might now point to something else?_

 

Might be oscillations in that case. I don't know enough about the circuit to tell you where the problem parts are.


----------



## ezzieyguywuf

Thanks for the response nullstring. I'll try removing the alligator clips and see what happens.

  Quote:


 What did you use for your R16/R17 
 

I did not use an R16/R17 as they are marked "optional". Decided to go with the simplest build possible. (already over budget ya know). I do have some spare resistors though, so what would you suggest?

 FYI I used none of the highlighted parts shown here

  Quote:


 When you fix this issue, the mismatched pot won't matter. 
 

You mean the resistors? I see, so the higher resistance means that a lower sweep of the pot will fix the mismatch. Gotcha.


----------



## nullstring

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_I did not use an R16/R17 as they are marked "optional". Decided to go with the simplest build possible. (already over budget ya know). I do have some spare resistors though, so what would you suggest?_

 

lol, you shoulda done a bit more research.
 Anything from 33k to 150k or so should work fine... just make sure they match.
 [EDIT: you should probably add R14/R15 as well if you have any spare resistors in the 1K area.]

 What pot do you have?

  Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_You mean the resistors? I see, so the higher resistance means that a lower sweep of the pot will fix the mismatch. Gotcha._

 

It won't actually fix the mismatch.. you just won't be using the pot at the very low end anymore.


----------



## Sganzerla

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_I had trouble following your description - which channel is getting quieter and fading away? I would check the output capacitor in that channel for shorts or damage.

 Also, until you nail down the problem, don't plug any good headphones into the amp. It's possible that you're passing DC voltage through the to headphones, which could fry them._

 

 Juaquin,

 First it was the right channel playing stronger, but I noticed I may had made a mistake, so I changed the L/R wire in the phone jack, and now it is stronger on left side. To say the truth I still don't know if these cables are right, here is a link to the image showing how it is wired:

LINK
 (Hope it is not wrong...)

 It plays this way now: I turn on, plug my headphones, level up volume and sound is good, but imbalanced towards left speaker. When the sound begin to fade away, after 10/15 seconds, it happens to both channels, but at the same time sound begin to imbalance toward the right side.


----------



## FallenAngel

That's backwards 
	

	
	
		
		

		
			





 Tip is left, ring is right.


----------



## Sganzerla

Thanks, will go back again... 
	

	
	
		
		

		
		
	


	




 So everything I said about sound stronger on left channel... invert. It will be at the right side, and when fading, it slowly begins to imbalance to the left channel. Back to the first description...


----------



## ezzieyguywuf

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_What pot do you have?_

 

I have this pot. I'll add all those resistors, though I'm loathe to as the easiest way will be to splice all my cables, and the just sucks 
	

	
	
		
		

		
		
	


	




 . 

 What research are you talking about? You mean I shoulda looked up why to do the mods?


----------



## nullstring

yeah, you shoulda looked up why those were put there.

 Resistors are way too cheap to skimp on >_>

 Anyway, I attached my resistors right to the pot. Just unsolder the wire from the pot and put the resistor in between the pot and the wire.


----------



## netsky3

Wich one is the base version of this amp?
 I hope to build one of this in the future, how much is the cost of the pcb and all the components necessary? (without case and other stuff)


----------



## tomb

Quote:


  Originally Posted by *netsky3* /img/forum/go_quote.gif 
_Wich one is the base version of this amp?
 I hope to build one of this in the future, how much is the cost of the pcb and all the components necessary? (without case and other stuff)



_

 

Do some reading in this thread and on the SSMH website - Starving Student Millett Hybrid

 I keep getting inquiries, but the PCB's are gone. If someone tells me where I can buy a hundred or more 19J6's, we'll do another PCB production run - but other than that, no.


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_<snip>

 Finally, with my source set at 0dB volume, I can barely touch the pot on the amp before it is too loud to do anything with. Its like off-off-offf-off-SUPER LOUD. The only reason I mention this is that on my CMOY, I can use the same source at the same volume and have a fair bit of play with the volume knob.

 </snip>_

 

 Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_</snip>
 I did not use an R16/R17 as they are marked "optional". Decided to go with the simplest build possible. (already over budget ya know). I do have some spare resistors though, so what would you suggest?_

 

 Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_lol, you shoulda done a bit more research.
 Anything from 33k to 150k or so should work fine... just make sure they match.
 [EDIT: you should probably add R14/R15 as well if you have any spare resistors in the 1K area.]

 What pot do you have?



 It won't actually fix the mismatch.. you just won't be using the pot at the very low end anymore._

 


 R14, R15, R16 and R17 *are* optional. I can even use my very sensitive ER-6i IEMs with my SSMH (without the input resistors) and strong sources. Your problem sounds exactly like what a miswired pot does. Make sure it's the pot's *wipers* that are connected to the tube's grids. Then one end to ground and the other end to the RCA's

 cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *Sganzerla* /img/forum/go_quote.gif 
_Well, let me first thank you both for your time and attention.
 Here are the links for the 4 images I made:

LINK1
LINK2
LINK3
LINK4



 Yes, they do. Looks like they fade a little from the intensity they are at start, but they continue lit up.



 I have problems with terminology of these components, could you point wich value (or the color) are the power caps and the output caps? It is easier for me to understand.

 Thanks again!_

 

Well, after reviewing your pics, I just can't find any obvious mistake. I just have a suggestion: when soldering to a terminal strip, you want it to look like this






 That is, the solder blob is covering the whole terminal, this insures a solid mechanical and electrical connection and you don't even need to wrap component leads around the terminal as that will make them very difficult to remove if the need ever arises.

 The connections to the leftmost terminal on both terminal strips in this pic look a bit suspicious.


 On other things... the components you used look all so very familiar, I'm betting you bought them as a kit on ebay; my first SSHM I built from that very same kit 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## ezzieyguywuf

Is it pretty? No. Is it messy? Not really actually? Does it work? Sometimes (working on it!). Does it sound good? Actually, I'm holding off on that judgement until I get it working 100%. From what I've heard I think I'll be pleased though. Yes, that is a digi-key box that I put it in. As I've stated earlier in this thread, I've gone over budget on this already and just couldn't justify paying for a case at this point, plastic or otherwise. This enclosure is definitely temporary, and hopefully this summer I'll be able to enclose it properly. The problem I'm having is that I get only some sound on one of the channels (left I think, I haven't bothered to label them yet). I've traced it to what I believe is pin4 on one of my tubes, as when I move it, I get some popping in my earphone. I'm hoping to get around to re-soldering that connection tomorrow. I went and re-did _all_ of the pins on both tubes after tracing a problem to pin 1, but I guess that one didn't take. Yea, and after taking a second look, I'm almost certain it's this pin4 connection. This goes to the output cap (don't know the technical terms, sorry), so I'm fairly confident that when I resolder the connection, it will fix it. Everything was actually working great until I closed up the bottom of the box and moved it to on top of my Compass, so a loose connection seems to make sense. If I sound repetetive, it's cuz I reaaaly hope thats the only problem.

 I did add R16/R17 and R14/R15. We'll see how that helps.

 Oh, and my ground is this huge copper plate thing I found in the plumbing section of Lowe's. Worked out great cuz I was able to bend it to fit in my box, and it already had holes so I didn't have to sodder anything to it, I just bolted it down. Soldering to something that big seemed impossible, as it effectively acts as a heat sink, so the copper never gets hot enough to hold the solder.


----------



## Juaquin

At least with cardboard, you don't have to worry about the MOSFET isolation!


----------



## m11a1

Darn it, I'm so frustrated. I had a problem with volume imbalance on my SSMH. Originally, I had actually thought that the problem was because one of the MOSFETS but after getting new MOSFETS, the problem still exist....arg!

 Now that it isn't the MOSFETS, I have no idea what is causing the volume imbalance anymore....


----------



## tomb

Quote:


  Originally Posted by *m11a1* /img/forum/go_quote.gif 
_Darn it, I'm so frustrated. I had a problem with volume imbalance on my SSMH. Originally, I had actually thought that the problem was because one of the MOSFETS but after getting new MOSFETS, the problem still exist....arg!

 Now that it isn't the MOSFETS, I have no idea what is causing the volume imbalance anymore....




_

 

Sorry about that. I didn't think the MOSFETs could cause a channel imbalance, but it was easier to send them to you rather than argue the point.
	

	
	
		
		

		
		
	


	




 There are potentially three things that can cause the channel imbalance:
 1. Mis-matched tubes,
 2. imprecise volume pot tracking, or
 3. mis-matched resistors somewhere in the signal path.

 Of those three, the tubes and pot have the greatest chance of causing the imbalance (unless you mistakenly used different-sized input resistors, as in one at 100K and the other at 200K). If the volume difference is consistent across the range of volume travel, then most likely it's the tubes. Swapping the tubes is an easy check. If the volume difference is inconsistent and changes with the volume travel, then it's the pot. What you can do there is adjust the input resistors to get the volume range you like within the most consistent portion of the volume pot travel.

 As for the resistors, it would take a huge difference to cause a volume mis-match between channels - something like the example given above - as in incorrect values, period, in one channel.

 Hope that helps.


----------



## ezzieyguywuf

Wow great post tomb. I'll be checking those things if my bad solder joint doesn't turn out to be the culprit.


----------



## nullstring

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Wow great post tomb. I'll be checking those things if my bad solder joint doesn't turn out to be the culprit._

 

did the addition of those resistors and removable the alligator clips not help?


----------



## ezzieyguywuf

Quote:


 did the addition of those resistors and removable the alligator clips not help? 
 

Ah, yea it fixed the hum. There is a very silent "swooooooosh" like a very very distant waterfall, but only when no music is being played. The problem that I'm having now is channel imbalance, and like I said I think I've found the culprit.

 <edit> Turn out it wasn't a bad solder joint. One of the pins fell out of my tube socket at one point, and I couldn't get it to stay in there, so I (stupidly) tried making the hole bigger, i.e. the metal thing the tube pin sits in. I apparently had made it so big that there was minimal contact when the tube was installed. This is fixed now! The only imbalance I have is when my pot is at a low setting.

 The resistors don't seem to help. When I feed the SSMH an analog signal out of my Compass' DAC, which I can't attenuate with the volume knob, I can't turn the pot past the "imbalance point" without bleeding ear syndrome (this is on my Grado SR60s). If I plug in my DAP, I can cut the volume down to where I'm forced to turn the pot on the SSMH past the "imbalance point". So whats the next step, bigger resistors? I'm at 100k for R16/R17 and 1k for R14/R15. My next step up is 330K for what I got laying around.


----------



## nullstring

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_ So whats the next step, bigger resistors? I'm at 100k for R16/R17 and 1k for R14/R15. My next step up is 330K for what I got laying around._

 

The 100k resistors helped, right? You can get farther in the pot before you get to this point?
 If so, you could try the 330k resistors..

 However, I have 50k resistors and a 50k pot and line out from my ipod (which I can't turn down either), and it works.. alright for 32ohm cans..
 It's possible that our compass is louder than the ipod.. /me shrugs?


----------



## ezzieyguywuf

Could be. I probably should have mentioned that I've build a 12AU7 version. And come to think of it, I don't think I can turn the pot much further than before. I could be wrong though, I've been doing this over the course of a few days. Where else can I get a line-out signal to test this? I have a cowon D2, and thats the DAP I mentioned before, but nothing else. I guess for now I'll just run it throught the Compass' amp and attentuate the signal before it gets to the SSMH. Not really optimal though...


----------



## Juaquin

Not many people have had to use more than 100k, but it can't hurt much to go higher if you need to.


----------



## ezzieyguywuf

Could it be something else that is causing this? Maybe my gain is too high for some reason?


----------



## netsky3

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Do some reading in this thread and on the SSMH website - Starving Student Millett Hybrid

 I keep getting inquiries, but the PCB's are gone. If someone tells me where I can buy a hundred or more 19J6's, we'll do another PCB production run - but other than that, no._

 

Is this the PCB for the "basic" version of the millett?

Beezar.com


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Could it be something else that is causing this? Maybe my gain is too high for some reason?_

 

I've already posted in the previous page that your 'off off off *ON*' problem is most surely caused by an incorrectly wired volume pot. Check that it's the pot's wipers that are connected to the tubes.

 The fact that it's a 12AU7 does not make much difference as the 12AU7 and 19J6 versions have more or less the same gain.

 cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *netsky3* /img/forum/go_quote.gif 
_Is this the PCB for the "basic" version of the millett?

Beezar.com




_

 

That's it. But as TomB mentioned, there are no more PCB's and unless someone uncovers a stash of a hundred 19J6 no more of that PCB shall be produced.

 cheers!


----------



## revolink24

Actually, that's the Millett Max, which doesn't use the 19J6 tubes, and isn't nearly as basic as the SSMH, if I'm not mistaken.


----------



## netsky3

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_That's it. But as TomB mentioned, there are no more PCB's and unless someone uncovers a stash of a hundred 19J6 no more of that PCB shall be produced.

 cheers!_

 

 Quote:


  Originally Posted by *revolink24* /img/forum/go_quote.gif 
_Actually, that's the Millett Max, which doesn't use the 19J6 tubes, and isn't nearly as basic as the SSMH, if I'm not mistaken._

 

Thanks =)


----------



## tomb

No offense netsky3, but if you looked at the Starving Student Millett Hybrid PCB website, you would have seen this:





 So, I'm not quite sure how you would mistake it for this:


----------



## netsky3

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_No offense netsky3, but if you looked at the Starving Student Millett Hybrid PCB website, you would have seen this:
http://www.diyforums.org/SSMH/board/...-1-240x195.jpg

 So, I'm not quite sure how you would mistake it for this:
http://www.diyforums.org/MOSFET-MAX/...overlay-sm.jpg










_

 

uhm...true 
	

	
	
		
		

		
		
	


	



 The first is easier to build than the second that is more full of components


----------



## Sganzerla

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Well, after reviewing your pics, I just can't find any obvious mistake. 

 On other things... the components you used look all so very familiar, I'm betting you bought them as a kit on ebay; my first SSHM I built from that very same kit 
	

	
	
		
		

		
		
	


	


_

 

 Thanks for your suggestion! I'll remade those "strange" solders you pointed when I got back home, and hope solves the problems.

 This kit I bought from Alphaphoenix here at HeadFi.


----------



## m11a1

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Sorry about that. I didn't think the MOSFETs could cause a channel imbalance, but it was easier to send them to you rather than argue the point.
	

	
	
		
		

		
		
	


	




 There are potentially three things that can cause the channel imbalance:
 1. Mis-matched tubes,
 2. imprecise volume pot tracking, or
 3. mis-matched resistors somewhere in the signal path.

 Of those three, the tubes and pot have the greatest chance of causing the imbalance (unless you mistakenly used different-sized input resistors, as in one at 100K and the other at 200K). If the volume difference is consistent across the range of volume travel, then most likely it's the tubes. Swapping the tubes is an easy check. If the volume difference is inconsistent and changes with the volume travel, then it's the pot. What you can do there is adjust the input resistors to get the volume range you like within the most consistent portion of the volume pot travel.

 As for the resistors, it would take a huge difference to cause a volume mis-match between channels - something like the example given above - as in incorrect values, period, in one channel.

 Hope that helps.
	

	
	
		
		

		
		
	


	


_

 

I'll start working on it. Thanks for all the help!

 Cheers!


----------



## timmyGCSE

I've bought all the parts for SSMH mk2 
	

	
	
		
		

		
		
	


	



 This time, still using the 12AU7 version but with Dsavitsk's mods, plus I've designed my own PCB that I _think_ is correct lol, I've got the copper board and echant and stuff. I've also bought a nice MB plastic box for it:
MB Plastic Boxes : Plastic Enclosures : Maplin

 plus the heatsinks are much beefier than the last ones I used.

 Hopefully will make the PCB and solder the PCB components this weekend then do the casework next weekend


----------



## ezzieyguywuf

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_I've already posted in the previous page that your 'off off off *ON*' problem is most surely caused by an incorrectly wired volume pot. Check that it's the pot's wipers that are connected to the tubes.

 The fact that it's a 12AU7 does not make much difference as the 12AU7 and 19J6 versions have more or less the same gain.

 cheers!_

 

Oh, sorry. I did see your previous post but disregarded it as I've rewired my pot once already, and triple checked against the datasheet to make sure I wired it correctly. Here is the datasheet I'm talking about. Excuse my screenshot, I couldn't be bothered to GIMP out the image from the pdf. As per that image, I've got pins I2 and II2 going to the pot "grids" (I'm unfamiliar with that term), I got I3 and II3 going to the RCA jacks, and I1 and II1 are my ground. Is this not correct? Looking at my pot from the back, the six pins are wired as follows:

 RCA L, RCA R, GROUND, GROUND (I jumped the two), GRID L, GRID R

 This corresponds to the image I posted, which shows the pins with a "view from mounted part side". My extreme zoom on there blocked out that foot note. 

 Please, tell me if I'm wrong as I'd love to get this thing up to 100%.

 My power switch has a LED, and this thing pulses two or three times when I first power it up. I guess this is normal?


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Oh, sorry. I did see your previous post but disregarded it as I've rewired my pot once already, and triple checked against the datasheet to make sure I wired it correctly. Here is the datasheet I'm talking about. Excuse my screenshot, I couldn't be bothered to GIMP out the image from the pdf. As per that image, I've got pins I2 and II2 going to the pot "grids" (I'm unfamiliar with that term), I got I3 and II3 going to the RCA jacks, and I1 and II1 are my ground. Is this not correct? Looking at my pot from the back, the six pins are wired as follows:

 RCA L, RCA R, GROUND, GROUND (I jumped the two), GRID L, GRID R

 This corresponds to the image I posted, which shows the pins with a "view from mounted part side". My extreme zoom on there blocked out that foot note. 

 Please, tell me if I'm wrong as I'd love to get this thing up to 100%.

 My power switch has a LED, and this thing pulses two or three times when I first power it up. I guess this is normal?_

 

You _almost_ got it right. It seems only one of your channels is wired in reverse 
	

	
	
		
		

		
			





 According to the datasheet pinout here's how it should go:

 RCAL - RCAR - GRIDR - GROUND - GROUND - GRIDL

 I3 - II3 - II2 - II1 - I1 - I2


 Just to clarify it a bit, label "II" corresponds to one 'pot' (for the right channel in your build) and label "I" corresponds to the other pot. Pin 2 on both sections corresponds to the wipers, pin 1 goes to ground, pin 3 to the inputs.

 Also, I couldn't find in the datasheet something that told me if the pinout was looking from the front of the pot or from the back... but I only skimmed over the datasheet

 The pulsing at startup is normal. When cold, the tube heaters (filaments) draw much more current, so much so that they look like a short circuit to the power supply which starts up, shuts down due to the "short", comes up again, etc.. after some such cycles, the heaters have warmed up a bit, and their current demand lowers to the point where the power supply can cope with it. Then the supply stays on (no more pulsing) and the heaters start glowing.

 BTW, nice Linux desktop 
	

	
	
		
		

		
		
	


	




 I'm also a *IX user.

 cheers!


----------



## ezzieyguywuf

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_ </snip>

 BTW, nice Linux desktop 
	

	
	
		
		

		
		
	


	




 I'm also a *IX user.

 cheers!_

 

Lol thanks. Its my first gentoo box, and I love it! I used 'buntu for the longest time, but was ready to have greater control over my linux desktop. 

 I'm playing FFXII right now, so I'll get around to fixing the pot tomorrow. Thank you so much for your help, and for your modified schematic for the 12AU7!


----------



## nullstring

lol, ubuntu has just as much control as gentoo..
 It's just not as required >_>.

 But, anything that you can do in gentoo, you can do in ubuntu minus seemlessly compiling your packages with your own optimization options (but who really wants to do that >_>)

 figures ezzieguywuf would be a ricer =p.


----------



## Volkum

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_lol, ubuntu has just as much control as gentoo..
 It's just not as required >_>.

 But, anything that you can do in gentoo, you can do in ubuntu minus seemlessly compiling your packages with your own optimization options (but who really wants to do that >_>)

 figures ezzieguywuf would be a ricer =p._

 

I much prefer compiling my own stuff so that I can have more control over my dependencies rather than having to pull in a bajillion packages (bloat) I don't need just because someone thought compile a package their way with all possible options. I've also yet to come across a package manager as robust as Portage.

 Not a diss to Ubuntu, but just my preference. I run a Proxmox server and Proxmox is using Debian.


----------



## ezzieyguywuf

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_You almost got it right. It seems only one of your channels is wired in reverse 
	

	
	
		
		

		
		
	


	




 According to the datasheet pinout here's how it should go:

 RCAL - RCAR - GRIDR - GROUND - GROUND - GRIDL

 I3 - II3 - II2 - II1 - I1 - I2


 Just to clarify it a bit, label "II" corresponds to one 'pot' (for the right channel in your build) and label "I" corresponds to the other pot. Pin 2 on both sections corresponds to the wipers, pin 1 goes to ground, pin 3 to the inputs.

 Also, I couldn't find in the datasheet something that told me if the pinout was looking from the front of the pot or from the back... but I only skimmed over the datasheet

 The pulsing at startup is normal. When cold, the tube heaters (filaments) draw much more current, so much so that they look like a short circuit to the power supply which starts up, shuts down due to the "short", comes up again, etc.. after some such cycles, the heaters have warmed up a bit, and their current demand lowers to the point where the power supply can cope with it. Then the supply stays on (no more pulsing) and the heaters start glowing.

 BTW, nice Linux desktop 
	

	
	
		
		

		
		
	


	




 I'm also a *IX user.

 cheers!_

 


 Ok. Here is my pot.





 I was mistaken the first time I posted my pinout. I believe that the way I have it is just as you described it. To explain my wiring, red is one channel, black is the other, and green is ground. That green wire is jumping the 4th and 5th pins. The red/black pair on the left go to RCA jacks, and the pair on the right (separated by ground) goes to the tubes. Sooo, whats the next step in shooting this trouble?

  Quote:


 ol, ubuntu has just as much control as gentoo.. 
 

I suppose you could make that arguement. I just got tired of having to use packages the way someone else decided to compile it. 

 Really, my evolution to gentoo stemmed from my winter break, in which I built an LFS box. It was a lot of fun, and very enlightening. I learned that I could have so much more control over my linux box than I actually had. When I saw how gentoo worked, I realized that, "Hey, this gives me about as much control as an LFS box, but with a super awesome package management system". 

 Ubuntu is great. It was my first distro and I used it for a long time. I really see it as an intro-to-linux distro though. They do everything for you and keep it all hidden behind-the-scenes. Yea, you could theoretically change whatever you want, but it becomes a chore sometimes, especially when you update and something breaks due to your custom configs. On gentoo, you have a make.conf and package.use that specifies your customizations, so that when you emerge --update world, portage takes care of making sure that everything agrees with each other.


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Ok. Here is my pot.

 </snip>

 I was mistaken the first time I posted my pinout. I believe that the way I have it is just as you described it. To explain my wiring, red is one channel, black is the other, and green is ground. That green wire is jumping the 4th and 5th pins. The red/black pair on the left go to RCA jacks, and the pair on the right (separated by ground) goes to the tubes. Sooo, whats the next step in shooting this trouble?

 </snip>_

 

It's difficult to tell from the pic if the wiring is alright. I would just make sure if the pinout from the datasheet is from the front or the back of the pot, this *is* important because if you follow the pinout from the 'wrong' side then *both* your channels end up wired in reverse.

 The practical way would be to get a multimeter and determine which pins are the wipers.

 Oh, and BTW I'm actually a FreeBSD user 
	

	
	
		
		

		
		
	


	




 it wasn't my intention to open that Linux distro can of worms (not in this thread, at least)

 cheers!


----------



## ezzieyguywuf

Quote:


 It's difficult to tell from the pic if the wiring is alright. I would just make sure if the pinout from the datasheet is from the front or the back of the pot, this is important because if you follow the pinout from the 'wrong' side then both your channels end up wired in reverse. 
 

Hm, I thought it was a pretty good picture . Either way, I _know_ that the datasheet says the pinout I posted is from the pront. As a matter of fact, here is the datasheet, so you con see for yourself. Page 5.

 What else could be causing my problems?


----------



## timmyGCSE

now..
 *sigh*
 I've just finished my second SSMH, used the 12AU7 version (as before), but this time I completely designed the PCB from the schematic myself, and used the extra Dsavitsk mods.
 it works, it looks the dogs (pictures will follow I promise), but....

 ...same problem as before on my p2p first attempt - left ear plays louder (this shouldn't happen). When I remove the right RCA I still get sound from both channels (this also shouldn't happen). When I remove the left RCA I only get sound from the right channel (this should happen).

 I've tried multiple headphones, multiple sources, multiple connection cables.
 And sorry but to have exactly the same issue on two builds, especially this one where there is a very slim chance of a wire being accidently grounded, I think it highly unlikely..
 plus I don't believe I am interpreting the schematic wrong...

 so this leads me to the conclusion that I'm either wiring the pot wrong (I really don't think I am, this has been checked so many times), or..I'm wiring my TRS jack wrong.
 This is the jack I have used:
Rapid Electronics - Cables & Connectors
 and this is its datasheet:
http://www.neutrik.com/Secure30/getM...pplication/pdf

 I've used only 3 of the 6 pins on the jack...should I be using all 6? :-/ 

 the jack is definately wired correctly as in ground at the rear, right in the 'middle' and left at the tip. 

 Just can't figure this one out..arggh

 then again.....lets relook at the pot for a second....

 edit...ermm...hold on..

 edit2: idiot!! idiot idiot idiot

 I just said
  Quote:


 the jack is definately wired correctly as in ground at the rear, right in the 'middle' and left at the tip. 
 

no it friggin well was not! in a state of sheer stupidity, I wired the ground to the tip and the left to the sleeve..on both!?! hahahaha. So I now have two working SSMH's, and one working tried and tested 12AU7 PCB design (albeit very messy and scrappy design and its very amatuerish and looks awful tbh but het it works!!) 
	

	
	
		
		

		
		
	


	




 I will upload pictures and stuff tomorrow


----------



## timmyGCSE

right so as I said its all done, I still have a little issue in that the right side is a bit crackly sometimes so I obv have a cold joint somewhere but it works now as to be expected.
 Making a PCB and stuff was, imo, a lot less laborious than P2P, and it was enjoyable to make the PCB too. My PCB design leaves _a lot_ to be desired, but this is my first design since I was studying electronics at school 9 years ago (I made a random number selector..I still have it in the cupboard 
	

	
	
		
		

		
		
	


	




) and it works at the end of the day. But more about that later.

 So here is some pictures for you:





 soaking the PCB to remove the glossy paper 





 PCB all done and drilled, the hardest part was removing the toner after! see the design..poor eh 
	

	
	
		
		

		
		
	


	








 all my bits, ready to start work....and inexplicably a comic with some fishes on it :-/





 all the board components soldered. Notice the wires? yea thats coz I can't design PCBs so I cheat when I can't figure out a way to 'escape' a track. At least there is only 2..my original design had about 5 
	

	
	
		
		

		
		
	


	








 casework done with a pillar drill





 tube sockets wired, note the use of ribbon cable, I though this would be easy because the cables are stuck together making them easier to manage, and it was a good choice (albeit not audio grade stuff but meh)
 Ginger Beer is the best drink going btw 
	

	
	
		
		

		
		
	


	








 tube sockets wired to the PCB





 everything wired in place, of course..the TRS jack at this point was wrong 
	

	
	
		
		

		
		
	


	




 messy? thats my middle name didn't you know? haha





 oh hello there..a finished SSMH 12AU7 
	

	
	
		
		

		
		
	


	








 looking laaavly darling, just laavly





 oo looking sexy, give me fierce, I wanna see some attitude..ooh laavly, you're doing great





 now twirl, show us some of that gorgeous backside, oh you're giving me the chills





 and relax..natural pose. beautiful.

 so ahem..anyway..yes, this is loud..much more than my previous one, because I've used the mods on this one. I left out R14/15 too (by accident I admit). But it sounds great, I haven't had a proper listen because I finished it at 5am and like I say I have a slight crackling issue.

 The PCB design - I will upload it a bit later if anyone is interested, but you have to promise not to laugh. 
 - Its big, I designed it around the case I bought for it to go in. 
 - The pad sizes are wrong in some cases (all the component spacing is right though, designed for the components I had in front of me)
 - the layout is poor, I had to use two wires to join tracks

 blah blah it could be a hellavalot better I know but I'm learning and it works so that's whats important. enjoy


----------



## the_equalizer

Fantastic timmyGCSE, simply fantastic! Your PCB looks nice and clean as does your casework. I really like it! Congratulations, I hope you get some time to enjoy it today!


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Hm, I thought it was a pretty good picture . Either way, I know that the datasheet says the pinout I posted is from the pront. As a matter of fact, here is the datasheet, so you con see for yourself. Page 5.

 What else could be causing my problems?_

 

I didn't mean the pic was bad, it's just that you're familiar with your build while I'm obviously not, so the pic makes perfect sense to you while looking unclear to me 
	

	
	
		
		

		
		
	


	




 Ok, I can see the little note in page 5:
 "3. View from mounted part side"

 I assume that means from the back of the pot, doesn't it? 
	

	
	
		
		

		
		
	


	




 Man that is one confusing datasheet to me...

 EDIT: Oh! I think I understood it: it means from the component side of the PCB; so neither from the front or the back of the pot, rather from the _top_ of the pot.


----------



## Yaka

very nnice work mate


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Fantastic timmyGCSE, simply fantastic! Your PCB looks nice and clean as does your casework. I really like it! Congratulations, I hope you get some time to enjoy it today!_

 

thank you 
	

	
	
		
		

		
		
	


	




 I was pretty proud of my casework but I still think I could have done better on the PCB

 anyway as promised:
4shared.com - online file sharing and storage - download SSMH v3.pcb

 be gentle


----------



## ezzieyguywuf

I think I'll have to attribute my channel imbalance to a bad pot. I've checked the resistances manually and they are never equal, throughout the whole sweep of the wipers. I mean, I payed $2.53 for it. I dunno if that's a lot for a pot or not, but I was seriously trying to keep this thing cheap. And (as I've mentioned twice) I'm already over budget, so I new pot will have to wait. Probably for a while... *sigh*.

 the_equalizer, thanks for all your help. I'm rather certain that its wired up properly. I did all the checks that dsavitsk talks about in post #3861 on page 258 and everything actually measures pretty good. The thing is, though, that my AC Voltmeter doesn't have super high resolution, so even with the pot maxed and the input maxed, the voltages at grid and output are still in the 0.0 to 0.3 range. And I noly get the one decimal, so yea on that. Oh, and I had to use a 70Hz tone, though I'm sure that made no difference...oh gawd, did my headphones just blow up? 

 Anywho, I had lots of fun building this thing, but can't really listen to it as it stands now. I'll have to wait till later in the summer, or maybe closer to august to give a new pot a shot. 

 It does sound good though :-D


----------



## nullstring

did you add the 330k resistors?

 if the pot balances out as it gets louder, then this would be a quick fix..
 It wouldn't be able to get as loud.. but at least it'd be usable right?


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_I think I'll have to attribute my channel imbalance to a bad pot. I've checked the resistances manually and they are never equal, throughout the whole sweep of the wipers. I mean, I payed $2.53 for it. I dunno if that's a lot for a pot or not, but I was seriously trying to keep this thing cheap. And (as I've mentioned twice) I'm already over budget, so I new pot will have to wait. Probably for a while... *sigh*.

 the_equalizer, thanks for all your help. I'm rather certain that its wired up properly. I did all the checks that dsavitsk talks about in post #3861 on page 258 and everything actually measures pretty good. The thing is, though, that my AC Voltmeter doesn't have super high resolution, so even with the pot maxed and the input maxed, the voltages at grid and output are still in the 0.0 to 0.3 range. And I noly get the one decimal, so yea on that. Oh, and I had to use a 70Hz tone, though I'm sure that made no difference...oh gawd, did my headphones just blow up? 

 Anywho, I had lots of fun building this thing, but can't really listen to it as it stands now. I'll have to wait till later in the summer, or maybe closer to august to give a new pot a shot. 

 It does sound good though :-D_

 

I agree, your pot does seem to be correctly wired. Maybe it got damaged while soldering? Difficult to say but in any case, I use the same 'phones you do (Grado SR-60i) with my 12AU7 SSMH and the pot sits at 9 o'clock for my normal listening (and I like listening at low levels).

 Well, the pots I use for prototypes are $2.73 at Mouser, part number RV24BF-10-15R1-A50K. Not a "blue velvet" but robust and functional.

 cheers!


----------



## ezzieyguywuf

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_did you add the 330k resistors?

 if the pot balances out as it gets louder, then this would be a quick fix..
 It wouldn't be able to get as loud.. but at least it'd be usable right?_

 

I did add the resistors. :-/ No help really (surprisingly)


  Quote:


 Maybe it got damaged while soldering? 
 

Could be. I ended up soldering on it like 3 times. *sigh*. It's not real easy to justify paying shipping from mouser or digi-key for just a pot. I wonder if I could get a decent one at radiowhack?

 Both the pot you listed and mine have a tolerance of 20%. Thats rather large if you ask me, but far be it for my ears to distinguish a difference where yours can't. This is most likely probably potentially without a shred of a little bit of what might possibly be doubt a damaged pot. 

 +1 to headfi for helping me figure that out though! And assuming thats the only problem, I'm pretty satisfied that everything else is good. I even sorta like the cardboard enclosure


----------



## nullstring

Digi-Key - P2R1503-ND (Manufacturer - EVJ-C51F02B54)
 I'd use this pot if I were going from digikey.
 It's the 50k variant of the pot that tangent suggests for the CMOY.

 if you choose USPS first class shipping, the shipping will work out to only ~$2.50

 I am sure a radioshack pot will end up being over $5..


----------



## alphaphoenix

Sorry folks if this is already dressed, but search didn't come up to confirm. I have an interested buyer from Australia who is interested in my MSSH, which uses the 48V Cisco power adapter rated input 100-240V. My question is, "can the mate use the amp in Australia as is and only needs to have a power plug converter?" I just want to make sure the amp itself doesn't need any changes with resistors and such for use in the land of down under. 

 Thanks.


----------



## Fred_fred2004

I made a MSSH in Australia its bog standard and uses the 48V Cisco adapter, works fine, I also made one for another Aussie and he had no problems

 cheers
 FRED


----------



## alphaphoenix

Thanks Fred. BTW: Nice work on the CMOY amps.


----------



## hellomoto

Hello,

 First, sorry for my poor english. I come from France. 

 I discovered the Millet Starving Student Hybrid a week ago, and I would like to build one. It's the first amp I build. I would like to drive Grado headphones, and I only listen to Rock Music

 The main problem is the tube. I looked a lot for a 19J6, I found website who could sell them 20$ each, is it worth the price? It's really high, in comparison with Millet's Bill of Material! Is there a replacement for what I need? I tried to look on the board but my English comprehension is poor, so if someone could give me some simple answers. The problem is that I think I'll have to change lot of parts to adjust to the new tube.

 I also would like to have a model of alimentation I could use in France. I couldn't find "Cisco PSA-18".

 I have also seen on "Beezer" that they were plate to soldier on the materials. Is it still possible to buy them?

 Thanks you very much for your attention and your answer, sorry for my bad English!

 Antoine


----------



## tomb

Quote:


  Originally Posted by *hellomoto* /img/forum/go_quote.gif 
_Hello,

 First, sorry for my poor english. I come from France. 

 I discovered the Millet Starving Student Hybrid a week ago, and I would like to build one. It's the first amp I build. I would like to drive Grado headphones, and I only listen to Rock Music

 The main problem is the tube. I looked a lot for a 19J6, I found website who could sell them 20$ each, is it worth the price? It's really high, in comparison with Millet's Bill of Material! Is there a replacement for what I need? I tried to look on the board but my English comprehension is poor, so if someone could give me some simple answers. The problem is that I think I'll have to change lot of parts to adjust to the new tube._

 

The tubes started out at $2 and went up as the scarcity increased. I believe $10-$15 should be the normal going rate from the few tube dealers who still have them. $20 sounds too high.

  Quote:


 I also would like to have a model of alimentation I could use in France. I couldn't find "Cisco PSA-18". 
 

Search for "Cisco PSA18U" on ebay - you'll get almost a couple of dozen hits. The power supply is good for either 110V or 220V wall supplies. Quote:


 
 I have also seen on "Beezer" that they were plate to soldier on the materials. Is it still possible to buy them? 
 

The PCB's are gone. Unfortunately, there's no economic justification to order another manufacturing run when there are so few tubes left. Quote:


 
 Thanks you very much for your attention and your answer, sorry for my bad English!

 Antoine


----------



## Juaquin

Don't forget you can also build the 12AU7 and other versions, if those tubes are easier for you to find.


----------



## hellomoto

@tomb: Thank you very much for your answer! Is there some part from the original Bill Of Material that I should change?
 I've seen that the original film capacitors (150104K100AA Cornell Dubilier Polyester Film Capacitors) were discontinued, I think I can replace them with these one (150104K100BB Cornell Dubilier Polyester Film Capacitors) Am I right?

 @Juaquin: Thanks! Will I have to modify some things if I take 12AU7 tubes or will it be the same?

 Thank you very much! It's really hard to find informations on French forums, Head-Fi is like a Gold Mine!!!


 THanks!

 Antoine


----------



## Juaquin

Quote:


  Originally Posted by *hellomoto* /img/forum/go_quote.gif 
_@Juaquin: Thanks! Will I have to modify some things if I take 12AU7 tubes or will it be the same?_

 

Yes, here is a schematic and some notes on the variant versions: SSMH Variations


----------



## baka1969

I'm purchasing a MSSH from a fellow Head-Fi'er. Sent out payment on Tuesday. I hope that because I didn't build it myself that I can still ask questions. 
	

	
	
		
		

		
			





 This is also my first tube amp. It should be interesting to compare/contrast it with my GLite. I only have another 300 pages to read. LoL

 Pece,


----------



## timmyGCSE

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Search for "Cisco PSA18U" on ebay_

 

they are rare in Europe (well...in the Uk certainly, and they are quite expensive when they do pop up, ~£20/$30
 Cisco ADP-18PB and EADP-18FB-B both are from what I can tell exactly the same (perhaps an EU model? :-/ ) both are 48v, 0.38A and use a standard 2.5mm jack. I'm using this one:
Cisco power supply EADP-18FB-B 48V 0.38A on eBay (end time 06-Mar-10 19:39:48 GMT)

 with my build and it works like a charm

 which as you can see is only £6/$9


----------



## Shayla

Double post, sorry.


----------



## Shayla

I bought a starving student amp a while back, and it does something a bit strange. Sometimes with a fairly low level input, I hear humming that grows in volume until it pops (sounds like an arc) and the humming goes away. It will also 'pop' when I tap the amp with my finger and the humming goes away.

 Any idea what is happening? I don't know much about tube amplifiers.


----------



## tomb

Quote:


  Originally Posted by *Ryuichi* /img/forum/go_quote.gif 
_I bought a starving student amp a while back, and it does something a bit strange. Sometimes with a fairly low level input, I hear humming that grows in volume until it pops (sounds like an arc) and the humming goes away. It will also 'pop' when I tap the amp with my finger and the humming goes away.

 Any idea what is happening? I don't know much about tube amplifiers._

 

The starving student can build up a charge on the signal ground for some reason - we suspect it has something to do with the power supply or the heater-biased mosfets. The problem is worse when the ground "sink" is not very big/good. Whichever it is, the pop is the sound of the charge dissipating - which makes the hum go away.

 You might check all of your connections and the connectors on the case - make sure they're all tight and have good ground connections.


----------



## Shayla

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_The starving student can build up a charge on the signal ground for some reason - we suspect it has something to do with the power supply or the heater-biased mosfets. The problem is worse when the ground "sink" is not very big/good. Whichever it is, the pop is the sound of the charge dissipating - which makes the hum go away.

 You might check all of your connections and the connectors on the case - make sure they're all tight and have good ground connections._

 

Will do, thank you! Sometimes the volume control doesn't do much with the right channel, think this is just a solder joint or bad pot?


----------



## ezzieyguywuf

Anytime my ground plane moves, I hear it in my headphones. Is this normal? Also, I have a distinct hummmmm in the amp. Its not super loud, but definitely noticeable in quite parts of songs and when no music is being played. 

 All of my ground connection are made with a bolt, not solder. Could this be the problem? i.e. I put the wire through a hole, then a bolt through the same hole and clamp it down with a nut.


----------



## the_equalizer

Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_Anytime my ground plane moves, I hear it in my headphones. Is this normal? Also, I have a distinct hummmmm in the amp. Its not super loud, but definitely noticeable in quite parts of songs and when no music is being played. 

 All of my ground connection are made with a bolt, not solder. Could this be the problem? i.e. I put the wire through a hole, then a bolt through the same hole and clamp it down with a nut._

 

Certain level of hum in a P2P build housed within a non-metal, non-grounded enclosure is normal, as the wiring is somewhat exposed.

 Also, the tubes are exposed and that also induces a bit of hum (try holding your hand hear the tubes, and you'll hear the hum grow in intensity).


 cheers!


----------



## bhjazz

Finally got some shots of my P2P MHSS. I've sure been enjoying it. I posted a while back that there seemed to be some channel imbalance, and I found it was very much due to my tubes. No matter. I had fun working on this P2P build. Been a long time since I've done one. Anyway, here are some shots. 

 Here's the completed build. I used a Context Engineering case, and turned it 90 degrees so I could get some space to work with on the inside. And I thought it looked kindof cool this way.

 I had to drill the access holes along the seam of the case, which meant bolting the unit together and dremeling out the excess. This turned out to be far more time consuming than I expected. 

 As for internals, geez, it's, well, P2P. I tricked out the star ground, used Solens on C2/C4,and tucked resistors and parts away where ever I could. 

 There is lots of power to spare, and I like it. The sound, as others have said, belies it's price tag. I have no hum, buzz, or squeals, just great music. I continue to dig through the web searching for backup tubes, which have all increased in price to about $10 each. Charming. 

 This is definitely a keeper!


----------



## hellomoto

Hello,

 I found 2 19J6 tubes on the internet, at a fair price for France.

 They are Raytheon 19J6 tubes. Both are vertical D getters. Will it be ok, and are this tubes good?

 Thanks!

 Antoine


----------



## Juaquin

Should be fine. It's been suggested that RCA was the only real manufacturer of those tubes anyway.


----------



## nullstring

IDK, my CBS tubes look very much different than my RCA tubes.
 CBS tubes have square getters and I prefer them over my RCA tubes.


----------



## tomb

I'm sorry to report that AMB has posted a new update on his Gamma 1 web pages. There are reports of the Starving Student damaging that DAC as well as Aliens and Bantams. So, a word to the wise ... just in case.


----------



## hellomoto

First, thank you for your help.

 I have two last questions.

 First, about the components: will I have to modify some components because of the Raytheon 19J6 tubes with vertical D getters? I also would like to know if they are upgrades I can do using other parts, not to expensives. I tried to read the Beezar page on this, but couldn't understand a word, and so in the topic...

 My second question is about the enclosure. I'd like to buy a nice aluminium case, but I have only basic tools (i have a preety powerful drill) and i'd like to know if it was hard to dril the enclosure to make holes for the tubes and jacks... Maybe is it possible to buy custom enclosures?
 What size would be the best (i'll use by me, so it can be big)

 Thank you very much for your help!!! it is very useful!

 Antoine


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I'm sorry to report that AMB has posted a new update on his Gamma 1 web pages. There are reports of the Starving Student damaging that DAC as well as Aliens and Bantams. So, a word to the wise ... just in case.
	

	
	
		
		

		
		
	


	


_

 

You had some experience with that as well I think I remember. Are there any tips maybe to help prevent this?


----------



## tomb

Quote:


  Originally Posted by *manaox2* /img/forum/go_quote.gif 
_You had some experience with that as well I think I remember. Are there any tips maybe to help prevent this?_

 

Don't ever disconnect/connect the DAC while the Starving Student is on.


----------



## manaox2

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't ever disconnect/connect the DAC while the Starving Student is on.
	

	
	
		
		

		
		
	


	


_

 

Got it.


----------



## tomb

Quote:


  Originally Posted by *hellomoto* /img/forum/go_quote.gif 
_First, thank you for your help.

 I have two last questions.

 First, about the components: will I have to modify some components because of the Raytheon 19J6 tubes with vertical D getters?_

 

Yes the radiation from those particular getters will require some lead lining inside the case and special dark glasses when you are listening. ... NOT!
	

	
	
		
		

		
		
	


	







 Seriously ... of course not! A 19J6 is a 19J6. There are some who profess to tell a difference in sound of one tube vs another, but they all work just the same in the circuit.

  Quote:


 I also would like to know if they are upgrades I can do using other parts, not to expensives. I tried to read the Beezar page on this, but couldn't understand a word, and so in the topic... 
 

You can try different film caps or electrolytics. There are some very nice Nichicon Fine Gold that will fit the bill that you can purchase from Handmade Electronics. I believe Mouser is carrying some now, too, but I'm not exactly sure on that.

 As for the film caps - the sky's the limit. I'm not sure how much difference you're going to notice, though. The parts selection we made on the SSMH PCB website is about as good as it gets.
	

	
	
		
		

		
		
	


	



  Quote:


 My second question is about the enclosure. I'd like to buy a nice aluminium case, but I have only basic tools (i have a preety powerful drill) and i'd like to know if it was hard to dril the enclosure to make holes for the tubes and jacks... Maybe is it possible to buy custom enclosures?
 What size would be the best (i'll use by me, so it can be big) 
 

Check into the Hammond 1455-series cases. They're aluminum, but you can whittle them with a sharp knife. Drilling is not much of a problem. I've found that a Greenlee punch is best for the tube holes. Some people do well with hole saws, but I've never had any luck with them.
  Quote:


 Thank you very much for your help!!! it is very useful!

 Antoine


----------



## n_maher

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Don't ever disconnect/connect the DAC while the Starving Student is on.
	

	
	
		
		

		
		
	


	


_

 

Has anyone explained what exactly is going on that is so unique to the SSMH design that causes the issue? I read both your comments and Ti's and while there is anecdotal evidence to support that _something_ is going on it seems like that something should have a more complete explanation. If you point me in the right direction I'll take it up with Pete.


----------



## hellomoto

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_There are some very nice Nichicon Fine Gold that will fit the bill that you can purchase from Handmade Electronics. I believe Mouser is carrying some now, too, but I'm not exactly sure on that._

 


 Couldn't find anything on Mouser. Is it okay to buy normal ones, and then if I want buy new ones to replace the standard ones?
  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_As for the film caps - the sky's the limit. I'm not sure how much difference you're going to notice, though. The parts selection we made on the SSMH PCB website is about as good as it gets.
	

	
	
		
		

		
			



_

 

The same as the Electrolytics.


 I've seen on your (very well made) build-thread that you added led. If i'm right, I just have to buy standards 3mm leds, and standard wire, and drill the sockets to put them in the AMP Right?

 Thanks you very very much for your help tomb!


----------



## tomb

Quote:


  Originally Posted by *n_maher* /img/forum/go_quote.gif 
_Has anyone explained what exactly is going on that is so unique to the SSMH design that causes the issue? I read both your comments and Ti's and while there is anecdotal evidence to support that something is going on it seems like that something should have a more complete explanation. If you point me in the right direction I'll take it up with Pete._

 

Cetoole actually had me doing several different tests, but to no avail. What happens, and this was first theorized by Dsavitsk (Colin was heading down the same road, too.), is that for some reason a charge builds up on the RCA jacks. This is first evident when the SSMH has been operating and for some reason, you disconnect the RCA jacks (like switching sources). A significant hum will develop until something discharges the jacks. In the case of the DACs frying, the DACs themselves are absorbing that charge, which burns them out.

 I remember distinctly doing this on an Alien DAC. My fumbling fingers accidently touched the signal portion of the RCA plug to the outside ground connection of the RCA jack on the SSMH. The DAC was fried in that channel, instaneously, and never worked again. I fried a couple of Bantams along the way, too. Ludoo fried a couple and there have been others, too. The one SSMH I listen to on a regular basis is plugged into my PC's sound card. There has never been any trouble with one of those. It seems more related to DAC's that have no intervening buffer or I/V circuitry between their outputs and the connections to an amp input.

 For awhile, I suspected the power supply created a ground that was at another potential from true ground, hence - some voltage present on the SSMH RCA jacks' ground. That's what Colin had me testing, but the tests were inconclusive. It's too intermittent, though, and more like Dsavitsk's theory: a charge that develops for some reason and is then grounded.

 It's either the power supply or the heater-biased MOSFETs. There's not much else in the amp that could do it.


----------



## tomb

Quote:


  Originally Posted by *hellomoto* /img/forum/go_quote.gif 
_Couldn't find anything on Mouser. Is it okay to buy normal ones, and then if I want buy new ones to replace the standard ones?


 The same as the Electrolytics._

 

Yes and yes.

  Quote:


 I've seen on your (very well made) build-thread that you added led. If i'm right, I just have to buy standards 3mm leds, and standard wire, and drill the sockets to put them in the AMP Right? 
 

Well, there's the matter of finding the right place to draw power for the LED's and sizing the resistor(s). The one on the SSMH PCB website BOM should suffice if you connect to the 48V portion of the circuit. Quote:


 
 Thanks you very very much for your help tomb! 
 

You're welcome!


----------



## Juaquin

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_IDK, my CBS tubes look very much different than my RCA tubes.
 CBS tubes have square getters and I prefer them over my RCA tubes._

 

Different getters doesn't necessarily mean a different manufacturer. They (CBS, other brands) simply could have wanted their tubes to look different so when (if) they contracted RCA, they asked for a different getter design. I haven't done any research myself so I'm not making any claims, but the SSMH website suggests it and I've seen it repeated many times here. I believe at some point someone posted more specific reasoning behind it but I can't find that post. Hopefully someone else can clarify further, not that it really matters - all that matters is you like the sound of your tubes!


----------



## JamesL

I know this was discussed somewhere in the thread before but I can't seem to find it.

 There are several, albeit small nuisances with the pot that i want to fix.

 I tried putting my brain to use and came up with the following conclusion.. can someone tell me if it would be a good idea, or if its completely wacko?

  Quote:


 Put a series resistor at the input of the pot to:
 1. get better attenuation when completely counterclockwise
 2. better channel balance at normal listening volume
 3. Get more use out of the full rotation
 4. effectively truncate the the right portion of the pot's travel.

 Since the potentiometer follows a logarithmic curve, I would need about 10x the value of the potentiometer to effectively truncate the last 50% of the volume control. 
 I should decrease the value of the pot first to maintain a reasonable input impedance 
 

currently, it doesn't completely mute when I turn down the knob, and i'd rather truncate than adjust the curve since there is quite a bit of noise at the far end of the pot, and I don't want to accidentally blow my ears out.


----------



## tomb

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Different getters doesn't necessarily mean a different manufacturer. They (CBS, other brands) simply could have wanted their tubes to look different so when (if) they contracted RCA, they asked for a different getter design. I haven't done any research myself so I'm not making any claims, but the SSMH website suggests it and I've seen it repeated many times here. I believe at some point someone posted more specific reasoning behind it but I can't find that post. Hopefully someone else can clarify further, not that it really matters - all that matters is you like the sound of your tubes! 
	

	
	
		
		

		
		
	


	


_

 

Yes. Based on my experience, Top Halo, Top Square, Side Square, Top D, Side D - they all appear on the major brands, including CBS. However, the gray-etched squished octagon tube designator - unique to RCA - appears on every tube. In some cases, it's been worn enough that it's almost invisible, but you can usually find evidence of it if you look hard enough.

 I've only gone through 400+ tubes, though, so there may be some different ones out there that I haven't seen yet.


----------



## tomb

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I know this was discussed somewhere in the thread before but I can't seem to find it.

 There are several, albeit small nuisances with the pot that i want to fix.

 I tried putting my brain to use and came up with the following conclusion.. can someone tell me if it would be a good idea, or if its completely wacko?



 currently, it doesn't completely mute when I turn down the knob, and i'd rather truncate than adjust the curve since there is quite a bit of noise at the far end of the pot, and I don't want to accidentally blow my ears out._

 

I agree that attempting to adjust the curve would be an exercise in futility, most likely. However, you should be able to attenuate the input with an optimum choice of resistors to get most music listening levels in a "good" range of the pot travel. Try 2X, 3X, even 4X times the pot impedance, depending on the impedance-sensitivity of your phones.


----------



## hellomoto

Thanks for your help tomb!

 All the stuff is now on the way!!!

 Bye,

 Antoine


----------



## JamesL

I just put in a 470k R in since I had one on hand. It did the trick perfectly. Volume range is perfect with my d1k's, but I'll probably swap it out with ~180k R so I get better range with my hd650's. =)

  Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_I agree that attempting to adjust the curve would be an exercise in futility, most likely. However, you should be able to attenuate the input with an optimum choice of resistors to get most music listening levels in a "good" range of the pot travel. Try 2X, 3X, even 4X times the pot impedance, depending on the impedance-sensitivity of your phones._


----------



## the_equalizer

As I posted a few weeks back, going through my tube manual I found a tube that seemed like a good substitute for the 19J6 in our beloved Millett "Starving Student" Hybrid.

 The tube in question is the 17EW8, a double triode in a 9-pin mini glass envelope with a 17.5 volt @ 150 mA heater; it's pinout the same as the 12A_7 tubes except for pin 9 which is unconnected (in the 12A_7 tubes pin 9 is the heater center tap)

 I went ahead and ordered a couple off of ebay ( USD $3.60 per tube !!) and received my package yesterday. Since the pinout is the same as the 12A_7, I decided to use my 12AU7 SSMH build and adapt it for the new tube. 

 Unfortunately I haven't been able to find plate characteristic curves for the 17EW8 so, I've been unable to work on a load line that helps me choose good working values for the plate load and cathode resistors. 

 Thus basically the only change I made to my 12AU7 circuit was adjusting the MOSFET gate biasing resistors to work with the heater voltage of the new tube. The heater voltage being close to the 19J6, I decided to use the same values as in the original circuit, that is R2, R4, R8, R10 = 220 Kohms. 

 In all, it took about 15 minutes to modify the amp to run the 17EW8 tubes! Just desoldering a couple 390 Kohm resistors and soldering two new 220 Kohm ones. This leaves us with a circuit that is exactly the same as the original 19J6, but with a 9-pin tube socket with the 12A_7 pinout.

 For maximum versatility, a MOSFET gate bias switch could be wired so that the amp could be used with 12 volt and 19 volt heater tubes at the flick of said switch. 






 I can happily report the new version works very well! I've been testing it for 3 straight hours and already I like it better than my 12AU7 version because the MOSFETs don't get as hot and the tubes glow a bit more. 
	

	
	
		
		

		
		
	


	




 Soundwise, it seems to me that it has slightly more detailed treble and punchier mids than my new production JJ 12AU7 tubes.

 Here's the schematic and a couple pics. Good luck with your builds!
















 cheers!


----------



## timmyGCSE

oh yea..thanks man, yet another excuse to do this project all over again!! haha naa just kidding great work! you're doing such a brilliant job in keeping this project alive. Maybe one for the future for me...


----------



## ezzieyguywuf

+1 at the_equalizer for keeping this thing alive! I'm still waiting for a chance to order and install a new pot. :-D


----------



## dsavitsk

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Cetoole actually had me doing several different tests, but to no avail. What happens, and this was first theorized by Dsavitsk (Colin was heading down the same road, too.), is that for some reason a charge builds up on the RCA jacks._

 

To add a little more to this, here's my working theory. There is a measurable capacitance between the Cisco power supply's output ground terminal, and earth -- don't remember what it is, and can't find my Cisco to check right now -- I think it was around 50nF though. That is, there is no continuity between these two things. Something about the Cisco's design allows this capacitance to charge, and it seems to get discharged into a grounded source.

 The simplest fix is to simply stop using the Cisco and build a basic 48V supply instead. This could be done pretty easily and inexpensively. Indeed, one could use a Tread so long as the voltages are watched -- that is, the kit version won't work. Otherwise, some sort of protection network might work -- maybe some back to back zeners, or cap coupling the output and output ground of the dac? I'm not sure what would be most effective and least intrusive. 

 But, the basic Starving Student design, a grounded cathode tube into a mosfet follower, is pretty harmless and is unlikely to be the source of the problem.


----------



## dsavitsk

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_The tube in question is the 17EW8, a double triode in a 9-pin mini glass envelope with a 17.5 volt @ 150 mA heater; it's pinout the same as the 12A_7 tubes except for pin 9 which is unconnected (in the 12A_7 tubes pin 9 is the heater center tap)_

 

It's a little less than ideal though not horrible. At a normal operating point, mu is 50, Gm is 4600 which puts rp at about 11K. With both sides in parallel, this is reduced to 5K5 which certainly works here. However, since we are running very low current through the tube, the reality is that rp is a lot higher, how high is hard to know. Also, mu of 50 is a lot of amplification, too high for many setups I'd think. But, it is a decent find and should be fun to play around with.


----------



## nullstring

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_To add a little more to this, here's my working theory. There is a measurable capacitance between the Cisco power supply's output ground terminal, and earth -- don't remember what it is, and can't find my Cisco to check right now -- I think it was around 50nF though. That is, there is no continuity between these two things. Something about the Cisco's design allows this capacitance to charge, and it seems to get discharged into a grounded source._

 

What if we just attached ground to mains Earth?


----------



## dsavitsk

Quote:


  Originally Posted by *nullstring* /img/forum/go_quote.gif 
_What if we just attached ground to mains Earth?_

 

That should be fine. The only problem is that the Cisco doesn't make it easy to do.


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_oh yea..thanks man, yet another excuse to do this project all over again!! haha naa just kidding great work! you're doing such a brilliant job in keeping this project alive. Maybe one for the future for me..._

 

 Quote:


  Originally Posted by *ezzieyguywuf* /img/forum/go_quote.gif 
_+1 at the_equalizer for keeping this thing alive! I'm still waiting for a chance to order and install a new pot. :-D_

 

Thanks guys ! 
	

	
	
		
		

		
			





 I just like tinkering with this beautifully simple circuit.

 @timmyGCSE - Actually the beauty of it is that you *do not* have to do it all over again. Just make R2, R8 = 220 Kohm and plug a couple 17EW8 tubes into any of your 12AU7 builds

  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_It's a little less than ideal though not horrible. At a normal operating point, mu is 50, Gm is 4600 which puts rp at about 11K. With both sides in parallel, this is reduced to 5K5 which certainly works here. However, since we are running very low current through the tube, the reality is that rp is a lot higher, how high is hard to know. Also, mu of 50 is a lot of amplification, too high for many setups I'd think. But, it is a decent find and should be fun to play around with._

 

Thanks for posting your thoughts Dsavitsk. Actually after doing the mod, and before plugging my headphones I measured the quiescent values, just to check everything was in order. I used my trusty analog Kyoritsu FET VOM for the measurements. Here are the numbers:

 Plate voltage: 29V
 Cathode voltage: 1V
 Current through each triode: 0.25 mA
 gain = 10

 For gain measurement I used test track no. 55 from here. I set the volume in my computer until I measured 1V AC at the grid with the volume control set on full. Then I measured AC voltage at the plate. With 1 volt going in I got 10 volts (11 volts on the left channel) coming out.

 So the gain is about the same as for a standard CMoy. Admittedly I only use my SSMH with relatively low output level sources (iPod, discman, computer headphone out) so the gain does not seem overwhelming or hard to control even with Grados or my ER-6i IEMs.

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_@timmyGCSE - Actually the beauty of it is that you *do not* have to do it all over again. Just make R2, R8 = 220 Kohm and plug a couple 17EW8 tubes into any of your 12AU7 builds_

 

very true! I have my original SSMH that could be modded and of course I have plenty of 220kohm resistors left over from my original build


----------



## iPoodz

Hey guys, I have a quick question.

 I recently noticed that two of my favorite headphones started to develop in the right channel, which was pronounced in low frequency sounds. It first happened to my AKG Sextetts, which I sent off for repair, faulting the the ancient drivers. Then, it happened to my AKG 140s... This could totally be coincidence, because the 140s are equally ancient, but I'm wondering if anyone thinks it could be caused to a faulty build, which either caused, or exacerbated the problem.

 I was advised by a trusted friend to measure the DC offset, as a high DC offset could have been the issue, but I measured 1 mV in both channels, which is very good, if I'm interpreting it correctly.

 Other possibly helpful info: I have the audio and power signals coming through copper wire, with electrical tape on the exposed parts. I never have the headphones plugged in when I turn on the amp. I listen at volumes that are 45 to (maximum) 135 degrees from 0 volume.

 Any advice/thoughts would be greatly appreciated!


----------



## the_equalizer

Quote:


  Originally Posted by *iPoodz* /img/forum/go_quote.gif 
_Hey guys, I have a quick question.

 I recently noticed that two of my favorite headphones started to develop in the right channel, which was pronounced in low frequency sounds. It first happened to my AKG Sextetts, which I sent off for repair, faulting the the ancient drivers. Then, it happened to my AKG 140s... This could totally be coincidence, because the 140s are equally ancient, but I'm wondering if anyone thinks it could be caused to a faulty build, which either caused, or exacerbated the problem.

 I was advised by a trusted friend to measure the DC offset, as a high DC offset could have been the issue, but I measured 1 mV in both channels, which is very good, if I'm interpreting it correctly.

 Other possibly helpful info: I have the audio and power signals coming through copper wire, with electrical tape on the exposed parts. I never have the headphones plugged in when I turn on the amp. I listen at volumes that are 45 to (maximum) 135 degrees from 0 volume.

 Any advice/thoughts would be greatly appreciated!_

 

A 1 mV (milivolt) DC offset is completely inocuous. The "electrical tape on the exposed parts" sounds a bit scary, but I doubt that caused the problem.

 You mention you don't have your 'phones plugged in at power on... but what about power off ? At power on the output caps charge through your cans' coils if they're plugged in; at power off the output caps would _discharge_ through them, also causing a *loud* thump.

 cheers!


----------



## iPoodz

Oh! Is electrical tape bad? Can you recommend an alternative? I thought that's what electrical tape was for.

 I try to have my headphones out of the socket when I power off, but I'll be honest, and say that I have left them in on occasion.

 Thanks for the thoughts, equalizer!


----------



## Juaquin

Electrical tape works but for long-term peace of mind, I'd use heatshrink.


----------



## m11a1

Tomb, 

 Do you remember how I had that volume imbalance problem? Well, I finally had time to work on my SSMH today. The first thing I did was checked all of the resistors and then I removed the 2 LEDs along with LED resistor. I also changed out new MOSFETs that I just brought from Mouser (3rd pair). Anyways, I figured I'll just try it out see if anything change and what do you know....the imbalance is gone! It's completely balanced and it sounds great. So I'm not really sure what fixed it....regardless it works well now.

 However, I have a question for you. As I was checking the resistors, I noticed that 4 of the resistors had very strange measurements. R2/R8 and R4/R10, according to the schematics were supposed to be 220K ohms, but I got 110-120 ohms when I measured them. Despite this, the individual resistors are labeled "2203", which is correct for 220k ohm. Is this a problem that I should be concern about...even though it sounds great at the moment.

 Thanks a lot!


----------



## Juaquin

Did you measure them in the circuit? If they're connected to the rest of the amp then current can flow through those other connections, making the overall resistance between those two points lower.


----------



## m11a1

Quote:


  Originally Posted by *Juaquin* /img/forum/go_quote.gif 
_Did you measure them in the circuit? If they're connected to the rest of the amp then current can flow through those other connections, making the overall resistance between those two points lower._

 

Yes, I read them right off the circuit because they are all soldered in...that's really interesting because the rest of the resistors give me the right reading according to their values...

 ...despite that, you're still right.

 Well either way, I suppose I don't have to worry about it then. My SSMH is done!

 Thanks!


----------



## fogmachine

okay, i've read all the pages of the thread, well done to every one on their builds some great looking amps there.

 got one question to anyone that might be able to help, the 12sr7/gt build where do you connect pins 4 & 5, the diode plate no. 1 & 2 ?

 would like to give them a go but my valve knowledge is minimal so dont want to start pluggin them in anywhere.

 cheers in advance

 fog.


----------



## the_equalizer

Quote:


  Originally Posted by *fogmachine* /img/forum/go_quote.gif 
_okay, i've read all the pages of the thread, 

 </snip>_

 

Man, I admire your patience and will power !

  Quote:


  Originally Posted by *fogmachine* /img/forum/go_quote.gif 
_</snip>
 got one question to anyone that might be able to help, the 12sr7/gt build where do you connect pins 4 & 5, the diode plate no. 1 & 2 ?

 would like to give them a go but my valve knowledge is minimal so dont want to start pluggin them in anywhere.

 cheers in advance

 fog._

 

Pins 4 and 5 of the 12SR7/GT should be grounded. If you have a non-GT variety (with a metal casing) pin 1 should be grounded too.

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Man, I admire your patience and will power !_

 

woah me too..342 pages?! good on you fogmachine 
	

	
	
		
		

		
		
	


	




 my gf came to mine this weekend (she lives by birmingham 
	

	
	
		
		

		
		
	


	




 ) and all too often she berates me for my headphone purchases lol but I think she was quietly impressed with my SSMH and she's ended up stealing my RX700's lol. It was interesting training her to make sure the headphones are not plugged in before turning it on or off though lol


----------



## fogmachine

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_woah me too..342 pages?! good on you fogmachine 
	

	
	
		
		

		
		
	


	


_

 

it just made sense, if your planning on building something like this and there is that much help, suggestions, issues etc all ready documented, make the most of them or at least use the search function and stop asking the same questions over and over again! tbh i'm surprised some of you are still replying to some of the questions that have been asked soo many times already. 

 oh, and i didnt do it in one sitting, about 100 pages at a time 
	

	
	
		
		

		
		
	


	




 right back to the breadboards, got a birdsnest to unpick, looking forward to see how much the 12sr7gt glow, both 12au7 and 12ax7s dont glow nearly as much at the 19j6's, but of couse its not all about how it looks 
	

	
	
		
		

		
		
	


	




 cheers for the help, my initial guess was to ground them, but is always good to check. thank you head-fi'ers


----------



## fogmachine

wicked, works just great


----------



## the_equalizer

Quote:


  Originally Posted by *fogmachine* /img/forum/go_quote.gif 
_it just made sense, if your planning on building something like this and there is that much help, suggestions, issues etc all ready documented, make the most of them or at least use the search function and stop asking the same questions over and over again! tbh i'm surprised some of you are still replying to some of the questions that have been asked soo many times already. 
 </snip>_

 

I agree... but still nearly 350 pages !!


  Quote:


  Originally Posted by *fogmachine* /img/forum/go_quote.gif 
_</snip>
 right back to the breadboards, got a birdsnest to unpick, looking forward to see how much the 12sr7gt glow, both 12au7 and 12ax7s dont glow nearly as much at the 19j6's, but of couse its not all about how it looks 
	

	
	
		
		

		
			





 cheers for the help, my initial guess was to ground them, but is always good to check. thank you head-fi'ers_

 

No problem... so I take it you've already built prototypes with those three other tubes? 

 cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *fogmachine* /img/forum/go_quote.gif 
_wicked, works just great_

 

Nice! hmmm... no tube sockets ?


----------



## fogmachine

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Nice! hmmm... no tube sockets ?_

 

ha, i knew if i started posting pics i'd get some questions about it, trying to keep it as a little surprise as i've put quite alot of work into the chassis so far, and if all goes to plan will be looking very nice. the 12sr7gt's are in sockets but due to their long pins they happily slot in the socket via a piece of acrylic, the socket will be mounted from the underside, the brackets on them are easily prized off and flipped around to make this possible, been running it fairly hot for a couple of hours now and the acrylic isnt even slightly warm either side, so seems safe enough.

 the only down side is that i dont think you can mount a led in the middle of the socket due to the central pin of the valve. correct me if i'm wrong but this central pin is purely for the orientation of the valve, has anyone ever drilled into this? would love to see if you could stick an led in it but dont fancy ruining my valves as they all still work! - anyone got any old dead ones they fancy sticking a drill bit in?

 cheers ears


----------



## c12mech

the equalizer,

 In your 17ew8 mod, are all the caps electrolytics? In the original I thought that c2 and c4 were film. I'm ordering parts this week to start this along with several other projects and just want to make sure I've got it all right. I'm going to try my hand at building the power supply for this also.

 Thanks,
 Bryant


----------



## c12mech

the equalizer,

 In your 17ew8 mod, are all the caps electrolytics? In the original I thought that c2 and c4 were film. I'm ordering parts this week to start this along with several other projects and just want to make sure I've got it all right. I'm going to try my hand at building the power supply for this also.

 Thanks,
 Bryant


----------



## the_equalizer

Quote:


  Originally Posted by *c12mech* /img/forum/go_quote.gif 
_the equalizer,

 In your 17ew8 mod, are all the caps electrolytics? In the original I thought that c2 and c4 were film. I'm ordering parts this week to start this along with several other projects and just want to make sure I've got it all right. I'm going to try my hand at building the power supply for this also.

 Thanks,
 Bryant_

 

Hello Bryant,

 C2 and C4 are film caps indeed. You can either use the original value in Pete Millett's BOM (0.1 uF) or the value set by Dsavitsk's modified BOM ( 0.22 uF ).

 cheers!


----------



## blippster

Finished a 12AU7 version last week in a recycled Hammond case, after missing the old 19J6 version I built and sold enough to give this a second spin. 12AU7s are a lot more widely available, so I won't have to ditch this amp for a fear of lack of tubes again.

 Had a couple of failed attempts along the way until traced the problem to the MOSFETs not working and so preventing the heaters from coming up. One had a failed gate and the drain leg of the other broke off before I could figure out what was wrong. Using Cerafines gave a ~1V DC offset at the output at first, until switching to Nichicon KWs solved the problem.

 The increased 7-volt drop does seem to make the amp run hotter, but manageably so with the Aavids - though the case was heating up much faster that the sinks until the application of thermal paste.

 Have a pair of 17EW8s that should (hopefully) be on the way, so will try those when they arrive. In the meantime though, thank you to the_equalizer for providing the impetus to come back to this.


----------



## tomb

Nice job!


----------



## the_equalizer

*Very* nice job, indeed! 
	

	
	
		
		

		
		
	


	




 Question: if the on/off switch is in the back of the unit, what does that red-tipped switch in the front panel do? 

 Remember that even though you can directly plug 17EW8's in place of the 12AU7's, their higher heater voltage requires to change R2 and R8 = 220 Kohms

 I'd love to read your impressions on both the 12AU7 and 17EW8 versions. 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## Juaquin

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Question: if the on/off switch is in the back of the unit, what does that red-tipped switch in the front panel do?_

 

It looks like there's two inputs on the back, possibly source select.


----------



## blippster

Thank you tomb. Your SSMH site was very useful when deciding how to construct it, and the suggested heatsinks were nice big ones that didn't look ugly.. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Question: if the on/off switch is in the back of the unit, what does that red-tipped switch in the front panel do? 

 Remember that even though you can directly plug 17EW8's in place of the 12AU7's, their higher heater voltage requires to change R2 and R8 = 220 Kohms

 I'd love to read your impressions on both the 12AU7 and 17EW8 versions. 
	

	
	
		
		

		
		
	


	


_

 

The front switch is a DPDT for mute, connected after the output capacitors to the 2K dummy load, so they can charge without needing to the headphones. Wait a bit and flick the switch - no pop! 

 I'll probably wire up an internal DPDT for switching between the 17EW8s and the 12AU7s following your suggestion a bit back, but for now that's a moot point until the postal service brings those tubes over


----------



## the_equalizer

Quote:


  Originally Posted by *blippster* /img/forum/go_quote.gif 
_<snip>
 The front switch is a DPDT for mute, connected after the output capacitors to the 2K dummy load, so they can charge without needing to the headphones. Wait a bit and flick the switch - no pop! 

 I'll probably wire up an internal DPDT for switching between the 17EW8s and the 12AU7s following your suggestion a bit back, but for now that's a moot point until the postal service brings those tubes over 
	

	
	
		
		

		
		
	


	


_

 

Cool, kind of like the 'Standby' switch on old Fender tube amps.

 Enjoy!


----------



## m11a1

Hey Equalizer, 

 You have mentioned many times that you especially love the sound of the K701 coupled with the SSMH. However, have you tried the K701 with the MiniMax? I'm thinking about building a MiniMax but I'm not sure how much of an upgrade it truly is. 

 Thanks


----------



## the_equalizer

Quote:


  Originally Posted by *m11a1* /img/forum/go_quote.gif 
_Hey Equalizer, 

 You have mentioned many times that you especially love the sound of the K701 coupled with the SSMH. However, have you tried the K701 with the MiniMax? I'm thinking about building a MiniMax but I'm not sure how much of an upgrade it truly is. 

 Thanks_

 

Yes, I do own a MiniMAX. I'll respond in PM with my impressions on these two amps.

 cheers!


----------



## c12mech

I'm finally getting all the parts together for this build. I found a power supply on evilbay yesterday. 

 Would there be any issues with mounting the power supply in the enclosure and just wiring in direct instead of using the plug? I'm not sure about heat dissipation of the PS. Just a thought. I'll be making my own enclosure, so size is not a problem.

 the equalizer,
 I would like to here what you have to say about the K701's also since the MilletMax is most likely next on the list. I'm planning on picking up some K701's in the next week or so.


----------



## c12mech

double post deleted


----------



## Juaquin

Quote:


  Originally Posted by *c12mech* /img/forum/go_quote.gif 
_Would there be any issues with mounting the power supply in the enclosure and just wiring in direct instead of using the plug? I'm not sure about heat dissipation of the PS._

 

Heat may not be a big issue depending on the enclosure, but it would be a bad idea to do this. If you put the power supply inside the case that means you are running AC to the case. This can (and probably will) cause noise in your circuit, and could also be a safety issue.

 If you want to build the power supply into the unit, you'd be better off using a transformer and DIY supply that is shielded/isolated to prevent hum, while of course following all safety protocols.


----------



## c12mech

Thanks Juaquin.

 I knew there was a reason I had not seen it done anywhere. I will just stick to the way it was intended to go together.


----------



## Juaquin

No problemo. I don't want to discourage you from trying - you'll learn something new in the process - but it's not as simple as just dropping it in. There _are_ a couple people who have built their own supplies to use with the SSMH, but it greatly increases the complexity and cost, and given the "value" nature of the starving student it's probably better to spend that time/money on a higher quality amp like the MiniMax or otherwise (not to imply that the SSMH is a lower quality amp).


----------



## m11a1

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Yes, I do own a MiniMAX. I'll respond in PM with my impressions on these two amps.

 cheers!_

 

I'm sure there are others who wonder the same question. 
	

	
	
		
		

		
			





 Cheers!


----------



## the_equalizer

Quote:


  Originally Posted by *m11a1* /img/forum/go_quote.gif 
_I'm sure there are others who wonder the same question. 
	

	
	
		
		

		
		
	


	




 Cheers!_

 

I know 
	

	
	
		
		

		
		
	


	




 but this being the build thread, TomB wants to keep it free of sonic impressions/comparisons. Thus my reticence to post them here.

 cheers!


----------



## blippster

The 17EW8s showed up, so popped them in to the amp. Didn't switch the bias resistor though for lack of time.

 Initial impressions are that they are a definite improvement over the 12AU7s previously in there 
	

	
	
		
		

		
		
	


	




, although those were generics just labeled '12AU7 China'. Now those sound at least a bit veiled in comparison, especially in the midrange; there's a better sense of space and dynamics with the 17EW8s.

 Someone please correct me if I'm wrong, but I don't think the tubes would be too affected by running them on 12V heaters, since effectively that's just dissipating less power in the heaters. The extra 7V drop over the MOSFETs is balanced out by a drop in the bias current from 150mA to ~105mA, so the amp still runs much cooler, and I'm not a fan of huge bias currents anyway. Perhaps that may (or not) compromise sonically, but (imo) 105mA is still plenty, especially with comparatively high-Z Sennheisers.


----------



## the_equalizer

Quote:


  Originally Posted by *blippster* /img/forum/go_quote.gif 
_The 17EW8s showed up, so popped them in to the amp. Didn't switch the bias resistor though for lack of time.

 Initial impressions are that they are a definite improvement over the 12AU7s previously in there 
	

	
	
		
		

		
		
	


	




, although those were generics just labeled '12AU7 China'. Now those sound at least a bit veiled in comparison, especially in the midrange; there's a better sense of space and dynamics with the 17EW8s.

 Someone please correct me if I'm wrong, but I don't think the tubes would be too affected by running them on 12V heaters, since effectively that's just dissipating less power in the heaters. The extra 7V drop over the MOSFETs is balanced out by a drop in the bias current from 150mA to ~105mA, so the amp still runs much cooler, and I'm not a fan of huge bias currents anyway. Perhaps that may (or not) compromise sonically, but (imo) 105mA is still plenty, especially with comparatively high-Z Sennheisers._

 

Oh wow... this little circuit doesn't cease to amaze me.... so it works without changing the gate bias resistors!? I'll have to try it myself this evening!

 I don't think the tube suffers any damage by running it's heater with a lower voltage. Did you measure those 12 volts across the tube heaters? 

 cheers!


----------



## blippster

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_Oh wow... this little circuit doesn't cease to amaze me.... so it works without changing the gate bias resistors!? I'll have to try it myself this evening!

 I don't think the tube suffers any damage by running it's heater with a lower voltage. Did you measure those 12 volts across the tube heaters? _

 

Just measured with the DMM. I get a reading of 13.7V across the heater pins with the 17EW8, and ~13V for the 12AU7. Looks like they were being run a bit hard. 
	

	
	
		
		

		
		
	


	




 I think getting the exact voltage shouldn't matter too much in terms of getting the tube to operate, as long as the heaters are burning enough power to get the electrons free of the cathode (and of course, not pushing them hard enough to wear out prematurely).


----------



## timmyGCSE

so does that mean the 17EW8 tubes can be used in place with no change?


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_so does that mean the 17EW8 tubes can be used in place with no change?_

 

That seems to be the case, indeed.

  Quote:


  Originally Posted by *blippster* /img/forum/go_quote.gif 
_Just measured with the DMM. I get a reading of 13.7V across the heater pins with the 17EW8, and ~13V for the 12AU7. Looks like they were being run a bit hard. 
	

	
	
		
		

		
		
	


	




 I think getting the exact voltage shouldn't matter too much in terms of getting the tube to operate, as long as the heaters are burning enough power to get the electrons free of the cathode (and of course, not pushing them hard enough to wear out prematurely)._

 

13 volts at the 12A_7 heater is quite alright. They're nominally rated at 12.6 heater volts. But what seems interesting to me from your post is that it's the MOSFET gate bias (the gate to source voltage) what determines the MOSFET source voltage, and NOT the tube heater voltage setting up a fixed MOSFET source voltage.

 You see, what I'd thought would happen was that the MOSFET source would sit at ~18 volts (the 17EW8 tube heater voltage) and, with R2, R8 = 390 K the MOSFET gate would sit at ~17 volts; so the MOSFET wouldn't turn on.

 But what's happening is that the MOSFET source voltage, sitting over the tube heater, get's 'clampled down' 4 volts below the gate voltage (~17 volts) thus the voltage you read across the 17EW8 heater, and thus the 
 MOSFET turns on and the amp works! Very nice !


----------



## blippster

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_<snip>

 You see, what I'd thought would happen was that the MOSFET source would sit at ~18 volts (the 17EW8 tube heater voltage) and, with R2, R8 = 390 K the MOSFET gate would sit at ~17 volts; so the MOSFET wouldn't turn on.

 But what's happening is that the MOSFET source voltage, sitting over the tube heater, get's 'clampled down' 4 volts below the gate voltage (~17 volts) thus the voltage you read across the 17EW8 heater, and thus the 
 MOSFET turns on and the amp works! Very nice !_

 

That's interesting. I was looking at it as akin to the 4 resistor MOSFET biasing diagram.





 (image from Headwize, modified)

 Here the source resistor Rs is replaced with the tube heater (18.9V/0.15A=125R?) to ground - the elegance of one less resistor per channel while providing the tube heater supply as well.


----------



## the_equalizer

Well, I tested my 17EW8 with R2, R8 = 390 Kohms as blippster did and I can confirm it does work; the tube filaments barely light up, but the amp works alright. 

 My measurement of the heater voltage coincides with blippster's but certainly not the bias current, as I measured 140 mA flowing through each MOSFET (measured with both my analog VOM and my DMM). Considering the internal resistance of the meter, what we're seeing is the usual 150mA current. 

 So now I see that tube heaters do not behave like constant voltage sources, but rather like constant _current_ sources! 
	

	
	
		
		

		
		
	


	




 My measurements, taken with my analog Kyoritsu FET VOM
 PS voltage: ~47 V
 Heater voltage: 12.5 V
 MOSFET voltage: 34 V
 drain-source current: 140mA

 plate voltage: 31 V
 cathode voltage: 0.84 V
 current through each triode: 0.21 mA

 So you can see that the current through the tube is ever so slightly lower than with the heater at 18 V (0.25) mA, which would make sense since the cathode is running cooler and thus emitting fewer electrons.

 cheers!


----------



## timmyGCSE

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_That seems to be the case, indeed._

 

ah ok cool, well I've had to shelve the minimax idea for now (
	

	
	
		
		

		
		
	


	




 import taxes) so I may pick up a set of these. Cheers 
	

	
	
		
		

		
		
	


	




 edit: I get a fair amount of buzz from my SSMH..now, with my first SSMH I got no buzz when I was running it direct from my Sony mp3 but when I plugged it into my computer I got buzzing...any ideas? my interconnect isn't great, maybe I need a shielded one?


----------



## timmyGCSE

would this tube be 'suitable'
http://www.r-type.org/pdfs/6bq7a.pdf
6BQ7A, Tube 6BQ7A; Röhre 6BQ7A (6BQ7A)

 the pinout may be different though


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_would this tube be 'suitable'
http://www.r-type.org/pdfs/6bq7a.pdf
6BQ7A, Tube 6BQ7A; Röhre 6BQ7A (6BQ7A)

 the pinout may be different though 
	

	
	
		
		

		
			



_

 

As I posted here it could be made to work but it'd require *mammoth* size heatsinks for the MOSFETs as the 6BQ5 heater is rated at 6.3 volts (you'd be dropping ~42 volts on the MOSFETs) @ 400mA (more than twice the current for the 19J6, 12A_7, 17EW8).

 cheers!


----------



## timmyGCSE

ah ok well nothing a bit of active cooling wouldn't sort out 
	

	
	
		
		

		
		
	


	



 lol just joking, I just read they are part of the same family as the 17EW8 and they seem be easier to get hold of than the 17EW8's in the UK. But ok thanks for the info.

 Any thoughts on the buzzing? cheers


----------



## tomb

Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_As I posted here it could be made to work but it'd require *mammoth* size heatsinks for the MOSFETs as the 6BQ5 heater is rated at 6.3 volts (you'd be dropping ~42 volts on the MOSFETs) @ 400mA (more than twice the current for the 19J6, 12A_7, 17EW8).

 cheers!_

 

Yep. If a 6.3V heater would work, we'd have gone with 6J6's, but it's an insurmountable problem with the present design, IMHO (Dsavitsk's too).


----------



## dsavitsk

Quote:


  Originally Posted by *blippster* /img/forum/go_quote.gif 
_Someone please correct me if I'm wrong, but I don't think the tubes would be too affected by running them on 12V heaters, since effectively that's just dissipating less power in the heaters. The extra 7V drop over the MOSFETs is balanced out by a drop in the bias current from 150mA to ~105mA, so the amp still runs much cooler, and I'm not a fan of huge bias currents anyway. Perhaps that may (or not) compromise sonically, but (imo) 105mA is still plenty, especially with comparatively high-Z Sennheisers._

 

Well, from a tube life perspective, running heaters too low is probably not ideal, but this circuit runs tubes so gently that it surely does not matter here.

 There is some controversy regarding starving the heaters -- with directly heated tubes (2A3, 300B, etc) it seems to lower the distortion slightly. Some people think this is a good thing to do, others not so much. Other people claim this is the case with indirectly heated tubes, too, though I've not seen any research to back that up. 

 It probably does not matter here because the low voltage and current across the tube likely lead to a high 2nd harmonic component in this amp. However, too low of a heater voltage and the tube won't work properly -- probably can't drive the fet's gate capacitance which could lead to treble roll off.

  Quote:


  Originally Posted by *blippster* /img/forum/go_quote.gif 
_Just measured with the DMM. I get a reading of 13.7V across the heater pins with the 17EW8, and ~13V for the 12AU7. Looks like they were being run a bit hard._

 

The difference in current across the FET would account for the extra .7V on the lower current tube.


  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_But what seems interesting to me from your post is that it's the MOSFET gate bias (the gate to source voltage) what determines the MOSFET source voltage_

 

Yes, 

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_You see, what I'd thought would happen was that the MOSFET source would sit at ~18 volts (the 17EW8 tube heater voltage) and, with R2, R8 = 390 K the MOSFET gate would sit at ~17 volts; so the MOSFET wouldn't turn on._

 

No

 The Mosfet's source will be ~4.5V below the gate. There is a relationship between Vgs and Ids (current from drain to source). This is what allows a mosfet to be used as a CCS -- set that voltage and the fet will only allow the corresponding amount of current to flow across it.

  Quote:


  Originally Posted by *the_equalizer* /img/forum/go_quote.gif 
_So now I see that tube heaters do not behave like constant voltage sources, but rather like constant current sources! 
	

	
	
		
		

		
		
	


	


_

 

No, I think something is wrong with your measurements -- heaters are resistors. Like all resistors, their resistance changes with heat -- happens that they change a lot more than a standard resistor. But, the current is simply determined by V=IR.


  Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_ah ok well nothing a bit of active cooling wouldn't sort out 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Yep. If a 6.3V heater would work, we'd have gone with 6J6's, but it's an insurmountable problem with the present design, IMHO (Dsavitsk's too).
	

	
	
		
		

		
		
	


	


_

 

You can certainly run 500mA through one of these fets, and the more current generally the better. But, I do think that IRF610's perform very well for headphone use at ~100-120mA and any more is unnecessary. And, you will have not only the increased current to deal with, but a much larger voltage drop -- 40V at 350mA or so is not trivial -- ~15W per side. So, not only would you need a really beefed up PS, but you'd need a ton of heatsinking. It could be done, but you could build a better amp for less effort other ways.


----------



## the_equalizer

Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_</snip>
 No, I think something is wrong with your measurements -- heaters are resistors. Like all resistors, their resistance changes with heat -- happens that they change a lot more than a standard resistor. But, the current is simply determined by V=IR._

 

Well, I didn't mean they behave like a ring of two BJTs active constant current source; but that 'change a lot more than a standard resistor' part makes them behave more like a CCS than a standard resistor. 


  Quote:


  Originally Posted by *dsavitsk* /img/forum/go_quote.gif 
_</snip>
 And, you will have not only the increased current to deal with, but a much larger voltage drop -- 40V at 350mA or so is not trivial -- ~15W per side. So, not only would you need a really beefed up PS, but you'd need a ton of heatsinking. It could be done, but you could build a better amp for less effort other ways._

 

Agreed


----------



## timmyGCSE

well I've bought two RCA 17EW8 tubes this morning, the ebay seller says they are matched in emissions and construction so that should keep me happy


----------



## the_equalizer

Quote:


  Originally Posted by *timmyGCSE* /img/forum/go_quote.gif 
_well I've bought two RCA 17EW8 tubes this morning, the ebay seller says they are matched in emissions and construction so that should keep me happy 
	

	
	
		
		

		
		
	


	


_

 

Nice! Try them with the 220Kohm bias resistors too.

 cheers!


----------



## the_equalizer

Oh well, after 5 months I got my Beezar SSMH back. The friend I sold it to put it up for sale and as I told him: 'if that amp is not with a close friend or relative, it must be with me', so I re-bought it.

 I had forgotten what a cool, nifty, fun little amp this is. I had to open it to spray some cleaner into the pot and while taking it apart I again enjoyed so much the clever case/pc board design. Thanks again to Dsavitsk and TomB for such a nice amp! I don't think I'll let it go again!


----------



## Iniamyen

Are PCB's still available or did I miss out? I want to build one of these for a friend. Can't seem to find them on Beezar. I am probably just oblivious.
	

	
	
		
		

		
		
	


	




 Edit: Haha, just read the website. That answers my original question.

 Are there any plans to do another round of PCBs in the future?


----------



## Juaquin

No, because it's next to impossible to find the 19J6 tubes. You can build one of the modified versions with different tubes using point to point construction rather easily - it's a pretty simple amp so a PCB isn't required for anything other than convenience.


----------



## Sganzerla

Some pages ago I wrote about my Millet not working well, now I discovered what the problem was and it is working, but channel imbalance continues. If I invert the tubes the imbalance follows it.
 Should I use more to see if this disappears (they have 12 hours of use) or better begin to look for a new pair?


----------



## the_equalizer

Quote:


  Originally Posted by *Sganzerla* /img/forum/go_quote.gif
_ Some pages ago I wrote about my Millet not working well, now I discovered what the problem was and it is working, but channel imbalance continues. If I invert the tubes the imbalance follows it.
 Should I use more to see if this disappears (they have 12 hours of use) or better begin to look for a new pair? 
	

	
	
		
		

		
		
	


	


_

 

  I don't think tubes age much in the SSMH since they're not driven hard (high plate voltage and current). Still, you can naturally do the experiment, that is, "burn them in" and hear if it makes a difference 
	

	
	
		
		

		
		
	


	




 cheers!


----------



## timmyGCSE

got the 17EW8 tubes, yes..the midrange is noticibly richer and better. I like


----------



## the_equalizer

^^  Great!  Did you try them with the 220K or the 390K biasing resistors?
   
  cheers!


----------



## timmyGCSE

390K. Though I have channel imbalance - this is not tube specific, it was happening with my old ones as well. I plugged my Denons quickly into my mobile and them seemed ok though I was using just one low quality mp3 so I will have to try my mptrois player when I get a chance and root behind my PC and plug my Denons straight into the soundcard see if that makes a difference


----------



## amc

Quote: 





tomb said:


> Quote:
> 
> 
> Originally Posted by *amc* /img/forum/go_quote.gif
> ...


 
   
  So after gathering dust on my bench for the last 5 months while there was a ban on melting lead in the house due to pregnancy, my 2nd daughter Ava has been born.  I pulled out this frustrating project and had a go at it with renewed enthusiasm and it is now working fine and sounds great.  To close the loop on my troubleshooting and resolution here is what I did.  
   
  I followed the advise and painfully dis-assembled the heatsinks yet again to go over the bottom of the board with a fine tooth comb.  I did find solder joint I was not happy with and for good measure reflowed a lot of the ground connections with a larger tip than the last time - this sped up heating the groundplane significantly! I re-did the LEDs with thinner wire and re-attached the heatsinks and still nothing.  Cr*p!  
   
  So I started probing again and found the problem - so simple!  I did not have continuity between the switch wires regardless of the position of the power switch.  Checking closer I determined I did not have a good connection between one of the fast on connectors and the wire connecting the switch to the board.  So I removed the switch and jumpered the switch connection and the LEDs powered up, the tubes started to glow and the amp worked.
   
  Moral of the story - take small steps and eliminate the easy things before you just to conslusions.  I could have saved myself a tonne of pain!  Thanks to Tomb and the_equalizer for helping me out.


----------



## the_equalizer

Well.. what can I say... congratulations, first and foremost, for your new-born child!  and secondly, congratulations on finding that little bug. I hope you enjoy your amp !


----------



## Beftus

I know I'm late to the party, but please bear with me. I want to make one too. I gather that 19j6's are in short supply ATM. There's the 12AU7 mod though, thanks for that! I have a few questions about this 12AU7 mod.
   
  The yellow marked parts are optional but what purpose do the following parts serve?
   

 R14/R15
 R16/R17
 C7/C8
   
  I see the interstage caps C2/C4 are changed from 0.1uF to 0.22uF. Why the change? Or will 0.1uF do too (just like in Peter Millett's original BOM)?


----------



## the_equalizer

Quote: 





beftus said:


> I know I'm late to the party, but please bear with me. I want to make one too. I gather that 19j6's are in short supply ATM. There's the 12AU7 mod though, thanks for that! I have a few questions about this 12AU7 mod.
> 
> The yellow marked parts are optional but what purpose do the following parts serve?
> 
> ...


 

 Hi Beftus,
   
     R14, R15, R16, R17 are "input resistors", they help with two things:
   
  a) By attenuating the input signal a bit, they help pad down the gain of the amp, which can be a bit excesive under some circumstances (sensitive IEMs + full line level input signal, for example).
   
  b) Help compensate for the volume potentiometer channel mismatch at lower volumes.
   
  C7 and C8 are the "cathode bypass" capacitors. These help increase the gain of the amplifier by bypassing the AC audio signal around the cathode resistors R5 and R11
   
  Finally, a 0.1 uF coupling cap will do; the 0.22 uF caps help extend the low frequency -3dB point of the coupling stage down a bit more, thus increasing the low frequency response of the amp. 
   
  I hope I've answered your questions.
   
  cheers!


----------



## Beftus

Quote:
   
   


the_equalizer said:


> Hi Beftus,
> 
> R14, R15, R16, R17 are "input resistors", they help with two things:
> 
> ...


   

 Many thanks!
   
   
  I thought that increasing the output caps (C3,C5) from the original 150uF to 470uF already enhanced low freq. response. 
	

	
	
		
		

		
		
	


	




 What's the -3dB point with the 0.1uF cap?
   
   
   
  I tried to find 19J6's locally this afternoon. No luck however. The 12AU7 (or ECC82 as it's known in Europe) is available new. Asking price for Sovtek 12AU7's is 10 euros a piece. Are Sovtek's any good?


----------



## the_equalizer

Quote: 





beftus said:


> Quote:
> 
> 
> 
> ...


 
   
  You are correct, the output cap interacts with your 'phones impedance to form a high pass filter too.  You want both the interstage coupling and the output coupling to have reasonable -3 db points.
   
  You can calculate the -3 dB point with the formula
   

   

 where R is in Ohms and C in Farads ( http://en.wikipedia.org/wiki/High-pass_filter ).
   
  The formula gives a -3dB point of 7.95 Hz with the 0.1 uF cap and  3.97 Hz with the 0.2uF cap (R = 200,000 ohms, the value of R4).
   
   
  I used JJ new production 12AU7's for my build.I haven't used Sovtek 12AU7, though I have Sovtek 12AX7s in my integrated tube amp and they sound very nice.  I also tested a set of new production 'Mullard'  12AX7s in the "Starving Student" and I thought they sounded stellar, but they costed $17.00 USD each :S
   
  cheers!


----------



## Beftus

Awesome equaliser, many thanks! All the information I needed to help me decide to make one for myself. 
	

	
	
		
		

		
		
	


	



   
  I think I can live with a corner frequency of ~8Hz. I have some 0.1uF MKP1837's I want to use for the interstage caps. Now it's time to go sourcing all the parts my humble parts box doesn't contain.
   
   
  Did I say thank you?


----------



## the_equalizer

Quote: 





beftus said:


> Awesome equaliser, many thanks! All the information I needed to help me decide to make one for myself.
> 
> 
> 
> ...


 
   
  You're welcome, I'm glad I can help.  Good luck with your build and let us know how it went.
   
  cheers!


----------



## Rangiroa

Hey guys,

 I have just commenced building the starving student, I am very excited but I have already made tons of mistakes  Its not my first electronics project but it is the first project in about 10 years, so obviously I need to brush the cobwebs out of that part of my brain.

 I ordered the Hammond case that comes in the BOM. It arrived yesterday and I started drilling out the front and rear panels for mounting. I plan to use 12au7 tubes and I have all the resistors and tube sockets for the change to the schematics. After I had drilled out the front panel I realized that the case was not going to work for me, obviously because the bottom and top do not open, so i will not be able to solder p2p in the box.

 I would just use some junk box lying around but I want this to look nice so the wife approves of it  Anyone have the part number or link to mouser//digikey where i can get a nice looking box that opens from the top? Or maybe a brand or line of jameco or hammond that they have found works well for the p2p?
   
  I tried searching for this topic with no luck, so i apologize if this was discussed somewhere within this 350 page behemoth.


----------



## tomb

Quote: 





rangiroa said:


> Hey guys,
> 
> I have just commenced building the starving student, I am very excited but I have already made tons of mistakes  Its not my first electronics project but it is the first project in about 10 years, so obviously I need to brush the cobwebs out of that part of my brain.
> 
> ...


 
  I'm not sure what's going on here, but Hammond refers to the removable plate on the 1455-series cases as the _belly_ plate.  However, all you have to do is turn the case over to make it a _top_ plate.
	

	
	
		
		

		
		
	


	







  In either situation, the plate is removable.  Which Hammond do you specifically have?  Is it possible that you didn't realize the plate is removable or am I completely off-base and you've purchased something else entirely?


----------



## amc

So,  My kit starving student is happily working away and I am enjoying it quite a bit.  I have one issue though.  I seem to get significant ringing or pinging in my cans if I touch the amp while listening.  Happens if I touch the heat sinks, the tubes, the volume knob, touch my source (Ipod), or even the side table the amp sits on.  I can get it to be really pronounced if I start tapping, even by tapping on my Ipod.  
   
  So are my symptoms what is referred to as Microphonics or is it something else?
  Can it be minimized? (isolation of the amp / some sort of dampening of the tubes / some tweak to the amp)
   
  The problem is that it uses the increasingly difficult to source 19J6 tubes - so I am hoping it is not a problem with the tubes.  Ideas on how to troubleshoot would be greatly appreciated.
   
  Thanks


----------



## Rangiroa

Hammond 1455N1201 - Black
   
  What is going on is that I don't believe I can wire a SSMH amp p2p if I cannot access most of the connections, it would very hard to wire most of it jamming my fat hands into the little case to make connections, etc.

 I was hoping to find a box where the top is removable but it appears this case is solid aluminum except for the endcaps. Maybe I am missing something though, will have to take a look later on this evening.
   
  If all else fails ill go find a cheapo box to start wiring things and go from there.
   
  Any tips on how to drill holes big enough for the power switch or the tube sockets? My drill only goes up to 3/8in. Im thinking about going to the hardware store for some kind of adaptor for larger drill bits.


----------



## tomb

Quote: 





rangiroa said:


> Hammond 1455N1201 - Black
> 
> What is going on is that I don't believe I can wire a SSMH amp p2p if I cannot access most of the connections, it would very hard to wire most of it jamming my fat hands into the little case to make connections, etc.
> 
> ...


 
  You are definitely missing something.  The top plate slides completely out.  When the endplates are off, you have complete unfettered acces to the entire channel that makes up the body.  Alternately, you could build most of it on the top plate itself with maximum access.
   
  Go look in the SSMH build thread at the pics (link in my sig!) and you'll understand right away.


----------



## tomb

Quote: 





amc said:


> So,  My kit starving student is happily working away and I am enjoying it quite a bit.  I have one issue though.  I seem to get significant ringing or pinging in my cans if I touch the amp while listening.  Happens if I touch the heat sinks, the tubes, the volume knob, touch my source (Ipod), or even the side table the amp sits on.  I can get it to be really pronounced if I start tapping, even by tapping on my Ipod.
> 
> So are my symptoms what is referred to as Microphonics or is it something else?
> Can it be minimized? (isolation of the amp / some sort of dampening of the tubes / some tweak to the amp)
> ...


 
  Yes, it's tube microphonics.  It's possible some tube dampers will alleviate some of the symptoms down to a tolerable amount, but it won't remove them completely.
   
  If they're Beezar tubes, contact me through a PM.  There may be something I can do to replace your tubes.
	

	
	
		
		

		
		
	


	




  One thing that will help - try to determine which tube is microphonic.  It's possible that both are, but that would really be an unusual bit of bad luck.  If it's only one, we've got a better chance of getting it replaced.


----------



## Rangiroa

Doh you are right, Tomb.
   
  After i looked at your thread I definately need to look closer at my case, it felt really solid at first glance.

 Thanks for the help, when I get my build close to finish i will post pics, of course


----------



## JamesL

Tube microphonics - I have the same problem on one of my tubes.
  Unfortunately, the 19j6 aren't easy to come by.
   
  I've never had a problem with microphonics traveling up from the desk, but I've used a cloth mousepad under a amplifier before which was very effective at preventing vibrations in my PC-case making its way up to the amp.
   
  Clamping down part of the cable from your ipod to the amplifier to something solid helps to dampen any microphonics going up that way.  
   
  I still experience microphonics when touching any part of the case, but I haven't been bothered enough to do something about it yet.
   
   
  Quote: 





amc said:


> So,  My kit starving student is happily working away and I am enjoying it quite a bit.  I have one issue though.  I seem to get significant ringing or pinging in my cans if I touch the amp while listening.  Happens if I touch the heat sinks, the tubes, the volume knob, touch my source (Ipod), or even the side table the amp sits on.  I can get it to be really pronounced if I start tapping, even by tapping on my Ipod.
> 
> So are my symptoms what is referred to as Microphonics or is it something else?
> Can it be minimized? (isolation of the amp / some sort of dampening of the tubes / some tweak to the amp)
> ...


----------



## Ikarios

Are there any good repositories of info for new builds of the SSMH with replacement tubes and PtP wiring? I've been wanting to build a starving student for so long but the lack of availability of the original 19J6 tubes (and thus, kits) has deterred me. I'm not good with schematics and I don't really trust myself to be able to read one without screwing up a connection and having to redo the whole thing. However, I'm itching to build something, and I just remembered I had some Alien DAC boards down in my basement from way back, so I'm thinking about populating those this summer as well. Does someone want to hold my hand through this process?


----------



## tomb

Quote: 





ikarios said:


> Are there any good repositories of info for new builds of the SSMH with replacement tubes and PtP wiring? I've been wanting to build a starving student for so long but the lack of availability of the original 19J6 tubes (and thus, kits) has deterred me. I'm not good with schematics and I don't really trust myself to be able to read one without screwing up a connection and having to redo the whole thing. However, I'm itching to build something, and I just remembered I had some Alien DAC boards down in my basement from way back, so I'm thinking about populating those this summer as well. Does someone want to hold my hand through this process?


 

 I hate to put a hole in your enthusiasm, but the SSMH will blow an Alien DAC if you're not very, very careful.  Search the thread and read the warnings on the SSMH PCB website.
	

	
	
		
		

		
			




   
  As for P2P designs with replacement tubes, I put a page that was generously donated by the Equalizer on the SSMH website.  He has supported many design changes using other tubes.  Just reading the last couple of dozen pages in this thread can clue you in to the numerous possibilities.


----------



## Ikarios

Okay, so I spent most of my time at work today reading the last 50 pages of this thread (read: slacking off). From the looks of it, I'll probably be making a 17EW8 variant with the modified 220Kohm bias resistors (which, if I'm not mistaken, results in the heaters glowing a little brighter.... right?). I'm not a very adventurous DIYer and I hated physics, so I'm going to stick as closely to the BOM as possible, with exceptions being made if I can buy a bunch of components at the same place, like beezar. I have a couple extra pots sitting around from my first cmoy (a panny evj-c20 that tangent recommended, and an alps RK097). I can just wire these in without modifications, right?
   
  also, the possibility of killing some DACs is a little worrying to me. however, if I'm not mistaken, it most likely happens when you touch connections between the DAC and the amp, right? What if I wired an alien or a bantam/grub directly to the SSMH? In that case the only IC I'd be changing would be the USB. Hmm, but now that I think about it, that might not be the best solution...
   
  is there an inexpensive USB DAC (DIY or otherwise) that will not suffer from this death charge on the SSMH? I have a "hotrodded" X-Fi but I'd rather not connect an amp that is known for killing some DACs to my beloved desktop; I'd also like to keep my speakers connected to the X-Fi and not have to change a bunch of connections every time I want to use the amp.
   
  Anyway, over the next week or so I'll study the 12AU7 variant schematic and draw it out on paper with components and all just to make sure I understand it. I'll report back soon, hopefully


----------



## tomb

There are only a few DACs that the SSMH will potentially kill - those with little to no output protection or buffer.  The AlienDAC, the BantamDAC, and I believe the Gamma 1 apply.  There's not a sound card that I know of that would be vulnerable to the SSMH - neither would almost any DAC that provides a secondary buffer or opamp at its output.
   
  Where you'd need to be careful is with a DAC design that outputs directly to a voltage signal right from the DAC chip and no additional buffer is used inbetween.
   
  EDIT: You are correct that it appears the danger occurs if the DAC is connected when the amp is running.  Due to the SSMH Cisco switching power supply, a charge may develop on the RCA jacks.  If you touch the output of the DAC to the RCA jacks when that charge exists, that's when the damage occurs.  Again, most commercial equipment and high-level DACs use extensive output circuitry that insulates the DAC from this scenario.


----------



## Ikarios

Well, in my case, since this will be my only amp (if I get another one it will most likely be a Carrie amp + grub/bantam combo), I will probably leave the DAC connected 24/7. Since the Alien and the Bantam/Grub are the two DACs I'm most interested in, mostly due to cost and simplicity, I think I'll build one or two anyway and just be careful about connecting it while the amp is running.
   
  EDIT: I'm assuming there's no way to simply "add" the output protection, as the problem lies in the way the circuit is designed, right? If not, is it a simple fix or something?


----------



## Beftus

Fire in the hole! No magic blue smoke. The heatsinks heat up nicely, the 12AU7 tubes too. Uh-oh, I'd better check my work again. I get ~12.5 VDC on the left and right outputs... Aha, forgot to add the last two 2K resistors near the outputs. 
	

	
	
		
		

		
		
	


	



   
   
  With both resistors added I measure ~3mV DC offset left and right. Plugged in my PX-100's... It works! Woohoo! On top of the 2" tall heatsinks I measure ~50°C (122°F), the IRF510 metal tab clocks in at ~63° (145°F). This thing gets bloody HOT! 
	

	
	
		
		

		
		
	


	



   
  It sounds great already. Plenty of punch, lovely highs. Gotta do some burning in but I really like what I'm hearing. No hum. Veeeery slight hiss, hardly worth mentioning. Touching the aluminium volume knob introduces hum. Should I ground the pot casing to get rid of it?
   
  I'm a bit disappointed in the tubes: no tube glow as the heaters are enclosed. I might install orange LEDs to light up the tubes. I did prepare the tube sockets for that.
   
  Specs for the nerds among us (you know what you are):

 4x Panasonic FC 470µF 63V
 2x Panasonic FC 220µF 25V
 6x MKP1837 0.1µF
 2x Electro-Harmonix 12AU7
 Alps 50K pot
 resistors 0.6W metal film
 2"tall heatsinks
 really cheap wood box
   
  Many thanks to:

 Pete Millett for the design
 Dsavitsk & the_equalizer for making the the conversion to 12AU7 tubes
 others who have contributed to the enormous Starving Student thread


----------



## ArtemF

Hi everybody and many thanks to the author of the thread for simple yet effective design.
   
  I tried to reproduce the scheme but it's next to impossible to find the 19J6 tubes nowadays.
  So, I ended up with slight modification of the original circuit diagram to fit it to 6J6 tubes that
  are exactly the same as 19J6 except for the heater voltages.
  (May be somebody has done the same, I just don't have patience to scroll through 300+ pages   )
   
  To do this mod one will need 2 150Ohm resistors (mouser part # 286-150-RC ) that will serve as
  heaters replacements in the MOSFET circuit and two powerful 10W 39 Ohm resistors that
  are connected in series with two heaters (all 4 elements in this circuit are in series - 2 x 39Ohm
  and two heaters).
  An obvious drawback of this approach is more heat that is dissipated due to Ohmic voltage divider
  and two extra resistors that replace the heaters. An advantage is also obvious - 6J6 are easy to find
  and the price is ~$2 a piece.
  I also added diodes protection to the outputs to eliminate the headphones load problem.
  I took 8 blue LEDs (they are said to have higher opening voltage but in reality they open at ~1.2V so
  I put two in series to get ~2.4V threshold). They flash nice when the power is on and they glow a bit
  when it's off.
   
  Now about the sound: it's pleasant, with a good bass and gives good details. I tested it switching from
  the headphones output of Harman Kardon 75  (optical input from the player) to the Millet's amplifier and to
  the headphones output of the player itself. The volume levels were adjusted to get more or less the same
  sound volume. All frequency corrections were turned off. The new amp definitely outperforms the Harman Kardon
  though the latter gives a good sound on the speakers. To my surprise, the internal headphones amp of the
  player gives almost the same quality as the new amp. The frequency response is a bit different and the tube amp
  is a bit softer but these are the peculiarities and one has to make a blind test to identify what is really better.
  Of course, I can make the tube amp sound much louder and it performs great but if one compares apples to apples
  (same volume levels) then they are comparable. Perhaps, the internal one is just very well designed 
   
  Summarizing, it was a nice experience, I recalled my young years when the tube amplifiers were still around (though rare).
   
  Here's the picture. Everything except the tubes sits inside (and is getting hot - I think of changing the design but the box
  is metal and it serves as a big radiator so I'll keep it for a while as is).


----------



## Yaka

very nice build there mate


----------



## Beftus

Thanks, though I know it's nothing special in terms of layout. Seen plenty like this one, but hey it's mine and I made it myself and above all it works bloody well! 
	

	
	
		
		

		
		
	


	



   
  I still gotta do some minor improvements, like hot glueing the large caps to the inside of the case. I did ground the pot casing, no more hum when I touch the volume knob. I must say it sounds absolutely wonderful. Listening to Bob Berg's _Silverado_ now, Mike Stern's guitar never sounded so good.


----------



## vixr

Beftus...that is a very nice build...love the penny idea. Mind if I steal it?


----------



## Beftus

Quote:


vixr said:


> Beftus...that is a very nice build...love the penny idea. Mind if I steal it?


 
 Be my guest! I read that removing the solder pins from these heat sinks is pretty difficult so I had to come up with a solution. And a cheap one too, in true Starving Student spirit. Never had so much fun drilling holes in pennies. 
   
  Don't tell her but I raided my daughters piggy bank for those pennies...


----------



## the_equalizer

Quote: 





beftus said:


> Fire in the hole! No magic blue smoke. The heatsinks heat up nicely, the 12AU7 tubes too. Uh-oh, I'd better check my work again. I get ~12.5 VDC on the left and right outputs... Aha, forgot to add the last two 2K resistors near the outputs.
> 
> 
> 
> ...


 

 Nice build !  Great to hear you're enjoying it. I also like it very much for anything guitar: Stern, Burrell, Metheny, Green, Montgomery; not to mention Gilmour, Hacket, Beck, Page, Clapton, Hendrix...  they all sound great through it!
   
  cheers!


----------



## ArtemF

Hi everybody and many thanks for this thread.
   
  Here’s my build. I modified the circuit a bit to use 6J6 tubes that are still abundant and available at ~$2 a piece. The modification is straightforward: one will need two 39 Ohm 10W resistors (mouser part# 71-CP10-K-39) and two 150 Ohm resistors (286-150-RC). The latter replace the heaters while the former connected  in series with two "real" heaters make them work.
  An obvious drawback of this scheme is extra heat produced by the ohmic voltage divider. But one can live with that taken into account the tubes availability.
  I also added diode protection to the output (2 x 2 x 2 = 8 diodes = forward/reverse 2.4V threshold protection for two channels). I used blue LEDs so they flash nicely when the power is on.
   
  Now about the sound: it's very nice. I made a test using the same source and different outputs: Harman Kardon AVR75 amplifier, new tube amp and internal headphones amp of the player. The new amp definitely outperforms Harman Kardon though this amplifier works very well with the speakers.  The internal amp, though, is very competitive. If one compares apples to apples (same volume level) then it’s difficult to tell what is better. Perhaps, the tube amp is softer (in a good sense) in the mid-frequencies. An obvious advantage of the tube amp is higher volume level. The sound is distortion-free and rich. Overall, I'm very pleased


----------



## wiisus

I'm going to be starting this project soon.  I'm building the 12AU7 version.  I wanted to order almost everything from one place to save on shipping.  Mouser has everything I need except .22uF 250v and .22uF 63v capacitors.  They only have 50v 100v and 200v.  Will any of those work as replacements? Otherwise, where I else should I order from? 
 Thanks


----------



## the_equalizer

Quote: 





artemf said:


> Hi everybody and many thanks for this thread.
> 
> Here’s my build. I modified the circuit a bit to use 6J6 tubes that are still abundant and available at ~$2 a piece. The modification is straightforward: one will need two 39 Ohm 10W resistors (mouser part# 71-CP10-K-39) and two 150 Ohm resistors (286-150-RC). The latter replace the heaters while the former connected  in series with two "real" heaters make them work.
> An obvious drawback of this scheme is extra heat produced by the ohmic voltage divider. But one can live with that taken into account the tubes availability.
> ...


 

 Nice work! Congratulations on getting a 6J6 variant up and running! 

  
  Quote: 





wiisus said:


> I'm going to be starting this project soon.  I'm building the 12AU7 version.  I wanted to order almost everything from one place to save on shipping.  Mouser has everything I need except .22uF 250v and .22uF 63v capacitors.  They only have 50v 100v and 200v.  Will any of those work as replacements? Otherwise, where I else should I order from?
> Thanks


 

 0.22 uF @ 100v will do nicely for C2, C4  and C3a, C5a
   
  EDIT: of course, 0.22 uF @ 200v will also work perfectly.
   
  cheers!


----------



## wiisus

Thanks for the reply!  After reading 100 pages of posts, I'm getting very excited to build this.  Placing parts order tomorrow.


----------



## Rangiroa

Ok guys,
   
  I have finished putting together the amp using the_equalizers 12au7 method. I will post pics but im highly embarrassed of my wiring skills. Its a hot mess.
   
  And thats probably why I am having issues, TBH.

 I did a little search beforehand but because I am using a different tube than 80 percent of the thread talks about I feel more comfortable just asking for help 
   
  Anyway, When i first plugged in the amp the power switched sparked, and sparked a couple more times but once it got turned on the tubes were glowing like they should have. I believe a grounding issue caused the sparks. I am led to believe that everything was connected correctly at first because the tubes appeared to be working as expected.

 I then proceded to try and fit everything into my case and that is when things got screwy. Now, my power switch regardless of whether its on or off allows the tubes to heat up. It could also be that the tubes take a little while to lose its glow. I built the amp with all the sides unscrewed so i had more room to work, instead of building it inside with walls all in place.
   
  After I did some more fiddling to make sure no wires were touching any other part of the circuit, now only one tube is lighting up, and its brighter than normal and sometimes flickers in and out. It appears that all connections on the tube sockets are solid.
   
  I have not hooked a source or phones up yet, just tryign to get these things out of the way.

 I cannot post a pic until later this evening when I get off work, so if you need a pic it will have to be later today.
   
  Could it be possible that a resistor is touching the aluminum case and is grounding out part of the circuit or shorting something?
   
  Could my power switch be causing all these weird problems, and I need to get a new one? Should I insulate all open resistor metal so they don't touch the sides of the case?
   
  Is there a way to use my DMM and find where my problem is? im not exactly comfortable using the DMM, I have only used it for tube biasing.
   
  Its a tight fit for everything in the case and I am sure that is causing my issues.
   
  Any tips, or ideas would be appreciated, I spent a long time last night working through the kinks on this and now im stuck.


----------



## ArtemF

Did you measure the voltages in the key circuit points? What were the results?
  I'd suggest disconnecting everything except the heaters and to make them working properly.
  After that one can move further.


----------



## Rangiroa

Thanks, I will try that, as fun as that doesnt sound 
   
  I don't leave the amp on long enough to check voltages because the tube lighting up seems unnaturally bright and i dont want to burn it out.


----------



## tomb

Quote: 





rangiroa said:


> Ok guys,
> 
> I have finished putting together the amp using the_equalizers 12au7 method. I will post pics but im highly embarrassed of my wiring skills. Its a hot mess.
> 
> ...


 

 I think the answers to all your questions are, "yes."  Because there are so many of them, though, IMHO a pic will do us the most good.


----------



## nightarya

Heya Head-fi
   
  First time poster here, been looking at thist hread for quite some time to make one of these puppies.
   
  But anyway, i made a 12AU7 version of this amp, plugged it in, turned it on. Then....nothing.
   
  I've went through most of the connections with a multimeter, NOTHING. I find no issues with my soldering job but either way, my tubes aren't doing anything. Nothing. They're not heating up, no audio, nothing.
   
  Is there something wrong with the way i soldered this? This is just the 12AU7 schematic (the one with the swapped out pinouts & 390k resistors)
   
  Pictures included to see if you guys can help me at all...i really want to know what i messed up >.<
   

   



   
  Any help you could provide would be greatly appreciated! Thank you guys! Please don't tell me my tubes are fried because i wired them wrong >.< Please.... I'd hate myself if i did.


----------



## wiisus

I don't know gallons about electronics, but it looks like some of your solder joints might be touching the case...I don't think they should be, as your case isn't the ground...

 I'm not sure if I'm fully correct on this, just my guess.


----------



## Ikarios

So I spent most of the day thinking about my AlienDAC -> Millet build, and figuring out all the little bits and pieces I needed to get the whole thing set up in one big shot whenever I'm ready. I drafted up a really basic schematic interpretation; tomorrow I'll refine it and turn it into my draft enclosure layout for a P2P 12AU7 build. First, I need to get these questions out of my head before I forget some.
   
  1) how exactly does a bypassing capacitor work? Do you just run a film cap in parallel with whatever cap (generally electrolytic?) you want to bypass? I notice the schematic shows C3a and C5a as what I think are bypass caps; are the Wima film caps in the BOM good enough for this or should I spring for something like the Beezar VitaminQs?
   
  2) I spent some time wrapping my brain around what the tube looks like in the schematic. If I'm reading this right, pins 2/7, 1/6, and 3/8 are essentially bridged, right?
   
  3) If I want to build a version that switches between RCA and 3.5mm mini inputs, I'd want to use a DPDT toggle, right?
   
  4) The BOM calls for a 50k pot; I have a couple of 10k pots left over from my CMoy build maybe four years ago O), including the Panasonic recommended in Tangent's guide and an Alps RK097. Can I use these pots simply by modifying values of R16/17 to 10k instead of 50k?
  4a) which resistors are the resistors that affect the gain? R16/17? If I wanted a higher gain version for use with 200ohm+ headphones or so, would I use 20-25k values?
  4b) how do most common gain toggles work? a DPST switch, two connections from the input jacks leading to both sides of the switch, one side with one gain resistor set and the other with another? is there any way i can do this with my input switching idea without running a giant mess of connections? gain is more important than input switching (which can be fixed by using the right IC), so I might just use the gain idea...
   
  5) how do most people mount tube sockets in a p2p build without a place for them to sit??
  5a) possibly answering my own question - would I want to use a socket like the third one down on this page (http://www.tubesandmore.com/scripts/foxweb.dll/catalog@d:/dfs/elevclients/cemirror/ELEVATOR.FXP?PAGE=SUBCAT&SEARCH_TREE01=ZCATALOG&SEARCH_TREE02=2009013) and mount those metal tabs at the top to the top of the enclosure?
  5b) what's the difference between the different types of tube sockets? I think I get "chassis mount" vs "pc mount", but I don't know about top or bottom mount... or the differences in socket material, for that matter.
   
  6) do Mouser or Newark carry switch faceplates like these found at handmade? (http://www.hndme.com/productcart/pc/viewPrd.asp?idproduct=702&idcategory=127) I spent a while playing with their search filters but didn't come up with the goods. I think ideally I'd want a blank faceplate, as I have access to a laser cutter/etcher at work. I'd also like to be able to etch directly into the case, but at $20 a pop and without ordering replacement panels, this is probably a no-go seeing as how we'd probably have to use trial-and-error for figuring out the power of the laser.
   
  7) I see most people are using some type of copper sheet as their ground plane. I have some leftover sheets of galvanized steel sheet metal from Home Depot - will this suffice for a ground plane, or are the benefits of copper worth it?
   
  Phew... that's a lot of dumb questions for someone who hasn't even picked out all the parts yet. I'd revise and condense these, but it's getting late and I need to get to work tomorrow morning. Thanks in advance!


----------



## ArtemF

2 nightarya:
  what do you mean by "nothing"? No voltage at either of the points?
  What do you measure when the power supply unit is unplugged?
  (I mean, does it work at all? - it sounds stupid but I faced with many cases including the
  faulty connector that looked absolutely normal and new).
  Can you take a powerful resistor and plug it instead of your circuit to test the power supply?
  May be it simply "refuses" to work with this load.
   
  Can you test the resistance of the heaters? What changes when you plug the tubes to the amp?
  What is the resistance between the "plus" and "ground" wires of the circuit when the DC power
  cord is unplugged?
  If the system withstands these tests then you can go further and check the voltages in the key points.


----------



## Rangiroa

Quote: 





ikarios said:


> So I spent most of the day thinking about my AlienDAC -> Millet build, and figuring out all the little bits and pieces I needed to get the whole thing set up in one big shot whenever I'm ready. I drafted up a really basic schematic interpretation; tomorrow I'll refine it and turn it into my draft enclosure layout for a P2P 12AU7 build. First, I need to get these questions out of my head before I forget some.
> 
> 1) how exactly does a bypassing capacitor work? Do you just run a film cap in parallel with whatever cap (generally electrolytic?) you want to bypass? I notice the schematic shows C3a and C5a as what I think are bypass caps; are the Wima film caps in the BOM good enough for this or should I spring for something like the Beezar VitaminQs?
> 
> ...


 
   To answer #3, I only bridged 3/8 but 1/4 have 2 connections running to them.

 Then again, my tubes light up but i cant confirm anything works just yet 
   
   
  To answer #5, I used chassis mount tube sockets to mount the sockets because they have flanges for a screw. I believe the PC mount tube sockets do not have flanges bc they are for use on a circuit board.


----------



## Rangiroa

Nightarya:
   
  Your soldering job looks similar to mine and I have your problem as well.

 I believe if you shorten some of those wires and snipping excess resistor leads, make sure and seal each connection with heat shrink (i am using electricians tape atm) it should hopefully work. shortening the wires reduces the chance for there to be any connections touching.
   
  I didnt study your actual soldering i just assumed you built it exactly like the schematic.


----------



## Beftus

I couldn't resist....
   
  Here's mine again, this time with tube LEDs. I installed orange LEDs to match normal tube glow instead of going for the popular Cherenkov-look. I'm running both LEDs @ 10mA.
   
  Yesterday I slipped two grease coated Kapton insulation foils between the IRF510's and the heat sinks. Thermal conductivity is much better now, the heat sinks are now ~58°C (136°F). Without thermal compound they were ~50°C. I may install 2.5" tall heat sinks in the future.
   
  I also applied some wood oil to the box to bring out the grain a bit. The more I listen to this puppy the more I love it.


----------



## Ikarios

Nice glow, Beftus! I'm probably going to run orange LEDs to my tubes as well, so thanks for supplying the mA info so I know what to expect. Still need to figure out how to wire up the LEDs, though...
   
  in your pic, your glow seems a little red. is that your camera or the LED?


----------



## Beftus

Read this one and the post following it. That's my source of information. Good luck.
   
  http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/705#post_4510827
   
  Here's why I chose 10 mA:
   
  http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/210#post_4217905


----------



## Rangiroa

Ok, 
   
  A little update to my problems from a few days ago.

 I started prodding around with my DMM and found that pin 4 on one tube socket is receiving 13.9 volts, and one the other one its receiving the full 48.

 What connection is missing that would involve allowing all 48v into that pin?
   
  Also, What is the best way to ground all the ground wires? I attempted to use the Terminals that were for the PCB. I locked down every ground cable into the terminal then ran a wire and soldered it to all of them and screwed that wire to the case.

 Where can i find those things a lot of people are using that look like its a bracket for soldering ground leads too.
   
  is it proper to ground to my case? I think that might be why my screws spark and snap lol
   
  Sorry for these basic questions, I appreciate any help on basic electricity principles


----------



## the_equalizer

Quote: 





rangiroa said:


> Ok,
> 
> A little update to my problems from a few days ago.
> 
> ...


 

 Grounding the metal case is a good practice, as it provides shielding from electromagnetic interference to the the circuit within. Your description of your ground wiring sounds quite alright.
   
  As to your problem of getting 48 v in one of the heaters, I can only imagine that you miswired the tube heater to the MOSFETs pin 2, which is in turn connected to the 48 v line, instead of to the MOSFET's pin 3.
   
  cheers!


----------



## the_equalizer

Quote: 





nightarya said:


> Heya Head-fi
> 
> First time poster here, been looking at thist hread for quite some time to make one of these puppies.
> 
> ...


 
   
  Zero or very little voltage readings in the circuit probably means there's some *big* short circuit that causes the power supply protection to kick in and shut down the power
   
  You need to sit down and carefully and patiently trace down all your connections, step by step, against the schematic.
   
  Remove the tubes, apply power to the circuit and measure the voltage (with respect to ground) at various points in the circuit: positive terminal of the power connector, the junctions of R2,R4 and R8,R10. Reinsert the tubes and measure those voltages again, as well as the voltage of pins 1 and 4 of the tube.
   
  Frying a tube is *really* hard, particularly with the voltages used in the SSMH. One tip: Using different colored wire for each kind of connection might seem like extra work while building but it pays off with great interest if the need to debug arises.
   
  cheers!


----------



## Rangiroa

Thanks for all your help equalizer. 
   
  I would post pics but i tried taking some and my old camera cant really show the detail too well.

 Its probably just easier to not 

 I will check out the mosfet wiring to make sure they are wired correctly.

 the drain on the mosfet was very strange to wire bc the schematic shows both mosfet pin 2's connected, is this correct? What i did was run a wire between both pin 2's and then run 1 wire from there. Should i do this a different way, such as connect both pins to the wima caps and then connect the caps together? 
   
  this may be why im getting one tube to light up and the other to not, because the mosfets being connected incorrectly.

 However, it still doesnt explain why both tubes would light up to normal brightness when i first started up the amp. I must have dislodged a connections. 
   
  Will update tomorrow with hopefully more progress.


----------



## the_equalizer

Quote: 





rangiroa said:


> <snip>
> the drain on the mosfet was very strange to wire bc the schematic shows both mosfet pin 2's connected, is this correct? What i did was run a wire between both pin 2's and then run 1 wire from there. Should i do this a different way, such as connect both pins to the wima caps and then connect the caps together?
> 
> <snip


 
   
   
  No problem, sorry for taking my time to reply but I was away on holidays for 2 weeks.
   
  No, connecting the MOSFET's pins '1' and '2' (actually pins 2 and 3 in the diagram) to one another is *not* correct. The diagram connection you mention between drain and source is just the symbol for the MOSFET and somewhat represents it's *internal* construction/wiring.
  
  cheers!


----------



## Rangiroa

so basically, I do not want to run a connection between mosfet pin 2's on each one i just want to connect them seperately?
   
  This is because each tube is its own channel? Am i correct that the only thing connecting both channels is the Capacitor that is grounded and connects to the 33k resistor?
   
  edit: the volts on the connection between the 390k resistor and the 33k resistor that connects to the grounding 680uf capacitor and the switch are only 13v whereas the schematic says they should be more like 45ish.
   
  My connections on the mosfets are as follows: each 2k resistor is hooked to mosfet gate pins.

 I ran a wire from both mosfet drain pins to the 2k resistor connected to the switch. should i physically connect the 2 wires at the switch instead of at the resistor? maybe a missing connection there is causing problems.
   
  source pin 3 is connected by a wire from tube socket pin 4 as well as a secondary wire off tube socket pin 4 which is running to the + side of the wima caps.
   
  thats how my mosfets are setup.

 I cannot find fault in other places in my wiring aside from it not being as neat as i would have hoped. 
   
  are there any other trouble spots i should check the volts on to help narrow the problem down?


----------



## the_equalizer

Quote: 





rangiroa said:


> so basically, I do not want to run a connection between mosfet pin 2's on each one i just want to connect them seperately?
> 
> This is because each tube is its own channel? Am i correct that the only thing connecting both channels is the Capacitor that is grounded and connects to the 33k resistor?
> 
> ...


 
   
  Oh, got it now. Both MOSFET drains (pin 2) are connected to the 48 v line. Theoretically It's OK if you run a wire between the MOSFETs and then run another to the 48 v line, but I'd run an independent wire for each drain to the power line.
   
  When you say that another wire runs from the tube's pin 4 to the WIMA cap (C3a, I assume)... the electrolytic cap (C3) is also connected there, right ?
  
  13 volts in the junction of R1, R2, R13 and C6... that's certainly not right, and suspiciously close to the tube heater voltage; of course it might be just a coincidence but I'd re-check that I have not wired the MOSFETs drain and source in reverse.
   
  cheers!


----------



## Rangiroa

Ok,
   
  Sorry in advance for the poor quality, but i have an older 6mp camera and I am not quite sure how to take detailed stills with it. I have always had trouble. If anyone can instruct me in basic camera use, id be appreciated. Maybe then i could take better detailed pics. EDIT: in the middle of posting this I have figured out how to use my camera :S

 Anyways, I am desperate to get this thing working. I have a couple pics to attach and hopefully they will be able to describe my problem.
   
  The first pic here is a pic of my tube wiring on the socket which does not light up. The blue and orange cable in the pic refers to wires that are being grounded, or bridging pins 3 and 8. green wires are connection wires and have been used to connect the components.

   
  This next picture show a look at how my power switch is connected. Since quality is bad, I would like to note that pin 1 of the swtich has the blue and orange power, and off of pin 2 are 2 wires that are connected to pin 1 of the mosfets (I switched pin 1 gate and 2 drain of the mosfets since Equalizer suggested the voltages seemed as though they were switched) as well as the 2k resistor and the 680uf capacitor. My power switch sparks sometimes when I turn it on.

   
  These next few are for reference. As i was taking this pics I seemed to have damaged one of the resistors in this next pic so i will be ordering a replacement few. That was fine before just now and not a reason for unworking tube socket i think.
  This next picture is my working tube socket wiring
   

   
  Here are the mosfet connections for the tube that lights up.
   

   
  So besides that one resistor that literally broke as i was taking pictures, do you need to see a photo of anything else?
   
  At this point the only thing I can think of that I may have majorly overlooked is that the wima cap and electrolytic cap are wired together and connected backwords for the nonworking tube, but taht doesnt explain the funny voltages IMO.
   
  Other ideas of mine are that the power switch needs replaced, or I possibly in one of the resistor connections made a connection at the wrong spot on the connector. I didnt think it would matter as long as they were wired in series like the schematic calls for. Thoughts, Ideas? I will place an order tomorrow for some new resistors. I also accidently ordered 1 watt 390k resistors instead of 1/4 watt. But that still doesnt explain one working tube and one nonworking tube. I would just like to get both tubes fired up and then I will be able to handle the rest i think .... lol.
   
  Im racking my brain and I cannot find a connection problem, so maybe someone else can here.

 Thanks in advance.


----------



## ArtemF

it's not clear from the pictures if the the MOSFETs are electrically insulated from the radiator/ground.
  If they are not then you ground the sink that for this MOSFET means short-cutting the power supply.
  May be all the troubles started with that, the MOSFETs were fried and everything got messed up?


----------



## the_equalizer

Quote: 





> Originally Posted by *Rangiroa* /img/forum/go_quote.gif
> 
> SNIP
> 
> ...


 
   
  Indeed your MOSFETs are miswired; the gate is NOT the middle pin, it is the first one from the left. See here for the correct pinout.
   
  ArtemF's observation of MOSFET to case insulation is also very important; it's very likely your MOSFETs are fried 
   
  cheers!


----------



## Rangiroa

Thanks,

 I will just order a new set of mosfets. The way they are hooked in the picture was only because equalizer suggested maybe the gate and drain were hooked backwards, I changed it just for effect.

 I believe I mentioned that before I posted the picture.
   
  Will the heatsink pads sold on beezar do the trick? i was going to order a pair of them anyways for another build.
   
  Thanks for helping me narrow the situation down. Note to self:dont hook the mosfets up to the case.

 That explains why they worked for a min on the first try, because they werent fried yet  
   
  I will order my missing parts and respond back in a few days with results 
   
  Thanks again


----------



## Rangiroa

What is humorous to me and maybe others can laugh with me, but I thought "hey, the idea of this amp is to save money so im going to use the case as a heatsink and screw the mosfets into the case".
   
  Oops. Would have saved me lots of headaches had I known how important insulation was for those mosfets.
   
  Oh well, I have learned alot with this build and provided i hook up the mosfets to my new heatsinks, with the pads and hardware and it works, I will be very pleased with it 
   
  Thanks for all the help in regards to this


----------



## ArtemF

next time when you mount your new MOSFETs, try to "reverse-engineer" your circuit.
  I mean, draw a circuit diagram looking just at your connections. If you get the original scheme,
  congratulations. Then you can take the ohmmeter and check for the shortcuts.
  If you don't find any, power the circuit and check the voltages.
  You might also start with just one channel to avoid the mess with the wires.


----------



## Rangiroa

Thanks I will definately give that a try when I rewire.
  
  I feel like i quadruple checked everything over the weekend, because i was looking for that 1 possible connection that was screwing everything up.
   
  But i will definately try your advice before i power up so i dont fry my mosfets.

 I ordered extras of the mosfets, and heatsink pads too this time lol, that way i dont have to wait on mouser if they blow up.


----------



## Darkraver

Just finished my first DIY amplifier, wanted to show it off here 
   


   
  I never realized how small 4" x 4" really was, until I started to solder everything together. Also, I really should think about buying another colour for wire, staring into a blue mess doesn't help in debugging, though luckily everything worked the first time I turned it on.
   
  -Dark


----------



## the_equalizer

Quote: 





darkraver said:


> Just finished my first DIY amplifier, wanted to show it off here
> 
> 
> SNIP
> ...


 

*Cool* paint job! Congratulations, I hope you enjoy it!  What tubes did you use?
   
  cheers!


----------



## Darkraver

thanks, paint job was done by my sis, kinda gave her free reign over what to do.
   
  As for the tubes, all i know is that they were 12au7's made by Baldwin, found them off of kijiji. No microphonics! Beyond that I have no idea what they are, haha
   
  -Dark


----------



## the_equalizer

Quote: 





darkraver said:


> thanks, paint job was done by my sis, kinda gave her free reign over what to do.
> 
> As for the tubes, all i know is that they were 12au7's made by Baldwin, found them off of kijiji. No microphonics! Beyond that I have no idea what they are, haha
> 
> -Dark


 

 Nice job by both you and your sister!  I hope you find the K701 + SSMH combo as enjoyable as I do 
   
  cheers!


----------



## nightarya

Well I just wanted to say thank you to multiple people for your replies to my issue
  -Wiisus
  -ArtemF
  -Rangiroa
  -the_equalizer
   
  I figured out what i did wrong, and the answer is: I screwed up when i first started.
   
  I bought a METAL case for my build, and used LOTS of parts with open metal connections (doesn't take a genius to figure out there's something that was probably a bad idea) I tried taking off the connections on the terminals touching the case. That didn't work, and that was the only thing i could still do. I assume that was the RCA jacks still hitting the case, because i checked a screw on the case to the positive on the DC in jack. Basically (got 13 ohms resistance, ick!). Tomorrow I'm going to cave in and decide to buy an ABS project box from radio shack (maybe the one thing they still do properly) due to the nonconductance of ABS. So, all in all, it was poor planning that ended up getting me in the end. This wouldn't have happened if i had bought plastic cased jacks, and used a 1/8'' instead of the RCAs. Well, live and learn, it was my first electronics project.
   
  Then this project should hopefully be done...leaving an opening for the next one...a DIY DAC (SMS Oh jeez)
   
  But seriously, guys, thanks for your input, it helped me make my realization!
   
  Lucky the casework should be easier on ABS vs the metal case. I can actually use forstner bits instead of sitting there and trying to circle drill bits haphazardly around the hole to make it 1/2'', that was some serious guesswork.
   
  I ended up having this epiphany whilst running a show for a dance school. I still have "Wake Me up Before You Go-Go" stuck in my head. It was a mixed victory.


----------



## the_equalizer

Quote: 





nightarya said:


> Well I just wanted to say thank you to multiple people for your replies to my issue
> -Wiisus
> -ArtemF
> -Rangiroa
> ...


 
   
  A non-metal case is definitely helpful to avoid such shorting issues. Indeed my first SSMH build was done in an ABS enclosure  .
   
  If you later feel like it, I'd still recommend you try a build in a metal case. You don't need isolated jacks, just isolating pads for the MOSFETs.  Also, I suggest you follow the path opened by Mr. Millett himself and follow his build layout from this pic. I did and it saved me a lot of work, plus it worked at the first try!
   
  I hope you're able to get your amp working after you extricate WHAM! from your mind's ear !
   
  cheers!


----------



## Darkraver

Quote: 





the_equalizer said:


> Nice job by both you and your sister!  I hope you find the K701 + SSMH combo as enjoyable as I do
> 
> cheers!


 
   
  Thanks! Unfortunately there's a buzzing sound whenever I plug it into my laptop, so source will have to be from my sansa clip+ until I build an Alien DAC.
   
  -Dark


----------



## wiisus

This is my first real electronics project and I'm not really sure how I'm suppose to use the terminal strips.  Can someone take a clear picture of theirs for me, please?  Most of them are kind of hard to see.

 And the the mosfet pins are numbered from left to right, correct?

 Thanks


----------



## Ikarios

Quote: 





wiisus said:


> This is my first real electronics project and I'm not really sure how I'm suppose to use the terminal strips.  Can someone take a clear picture of theirs for me, please?  Most of them are kind of hard to see.
> 
> And the the mosfet pins are numbered from left to right, correct?
> 
> Thanks


 

 I think the terminal blocks are for connecting the output wires to the pot/output jack, but I could be wrong. I was going to ask this question myself at some point.
   
  You need to be careful about the mosfets - they're deceptive in the way they're wired up.
  Check this post for more info - http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/4320#post_6258684
  read the schematic/pdf for the mosfet, then compare it to the schematic for the SSMH. That should give you a better idea of how they're wired. Go over the last couple pages, too, the_equalizer and ArtemF posted some useful info.


----------



## the_equalizer

Quote: 





wiisus said:


> This is my first real electronics project and I'm not really sure how I'm suppose to use the terminal strips.  Can someone take a clear picture of theirs for me, please?  Most of them are kind of hard to see.
> 
> And the the mosfet pins are numbered from left to right, correct?
> 
> Thanks


 

 Try Mr. Millett's pic (I just posted it a couple of posts up).
   
   
  cheers!


----------



## wiisus

yeah, that is a good one.  I was hoping for more of a side view or something.  But I think I got it.

 Thanks


----------



## hellomoto

Hello,
   
  Wiisus, here are some informations about the Mofsets: http://www.diyforums.org/SSMH/SSMHmosfet.php
   
  I also have some questions. First, sorry for my bad english, I hope you can understand me! Then, I tried to search the answers to my questions, I wouldn't find anything, maybe I didn't use the apprpriate word, it's hard to speak about technical things in english for me lol
   
  Si, here are my questions. I'm going to use a blank PCB material for my amp. I received all my stuff, I understand how to mount the major part of the components, but I still have question:
  - About the Power jack: there are three pins on it, I don't know how to connect them to the network, I think there must be two wires coming from it, one from the + pin, and one for the ground right? How can I make a difference between the pins (I use the power jack from the BOM)
  - About the Input: I'd like to use a 1/4" Jack input, but I don't understand how to soldier it: the Jack has 6 pins, but I only have to soldier two wires from the Jack to the pot, right? How should I solder them?
  - About the Output: I also would like to use a 1/4" jack (the same as the input), and I have to soldier three wires to the six pins, which one go where???
  - About the LEDs: I would like to put LEDs in my tubes, one in each, they'll be soldered in the same resistor (the one of the BOM), but where should I put the resistor in the network, and how should I solder the LEDs on the resistor?
  - I also have a question about the terminal strips: where should they be mounted on the shematic?
   
  That's all... for the moment lol!
   
  Thank you very much for your help 
	

	
	
		
		

		
			




   
  Antoine


----------



## the_equalizer

Quote: 





wiisus said:


> yeah, that is a good one.  I was hoping for more of a side view or something.  But I think I got it.
> 
> Thanks


 

 A couple sideways views from my 12AU7 build. Hope they help.
   
http://img63.imageshack.us/img63/5757/dscf1904g.jpg
   
http://img683.imageshack.us/img683/7749/dscf1903.jpg
   
  cheers!


----------



## ArtemF

Antoine,
   
  the easiest and safest way to do is to use the multimeter (seriously).
  Take a power jack, plug the power connector, measure the voltages, write them down,
  and so on. I always double-check that even if I know the pinouts.
  Plug the earphones to the output jack and measure the resistance between the contacts.
  The values will be 2R and 2 times R where R is the resistance of one earphone (normally, 32Ohms).
  The points with 2R between them are left and right outputs. The third point will be the ground.
   
  LEDs and resistors - I would put it off till the circuit starts working.
  Generally, you have to connect them in series with the current limiting resistor. Depending on the
  type of LED this resistor will be in 10-30 KOhm range (if you don't know the specs of your LED
  you can experiment starting with high values like 50KOhms and then go down in 5-10Kohm increments
  till the LED opens and the brightness will be reasonable).


----------



## c12mech

I finally finished my 17EW8 version of this amp last week.  It's been working fine and sounds great.  There is one issue though.  When I turn it on the power supply cycles on and off for several seconds.  It seems to be taking longer and longer each time it is turned on.  The first few times it was turned on only took about 3 or 4 cycles. Last night it took about 30 seconds before the tubes lit up and the PS stopped cycling.  All the voltages are correct according to the schematic.  
   
  Is this a big problem and if so what do I do to fix it?  I used the equalizers schematic and parts are exactly as listed.  The PS is a Cisco 48V 380ma version that I got from evilbay.  
   
  It's not in its finished case yet so no pics yet.


----------



## Beftus

Quote: 





artemf said:


> LEDs and resistors - I would put it off till the circuit starts working.
> Generally, you have to connect them in series with the current limiting resistor. Depending on the type of LED this resistor will be in 10-30 KOhm range (if you don't know the specs of your LED you can experiment starting with high values like 50KOhms and then go down in 5-10Kohm increments
> till the LED opens and the brightness will be reasonable).


 
   

  Agreed, first get the amp working then start adding gimmicks.
   
  LEDs and resistor-wise, use the online LED calculator: http://led.linear1.org/1led.wiz
   
  For a power status LED 3-5 mA of current is usually enough. For lighting up a tube: 8-10 mA. Don't go up to the maximum current the LED can handle (usually 20mA), it will shorten LED life and it will put a lot strain on the 380mA PSU, assuming you have one like that.


----------



## hellomoto

Thanks ArtemF and Beftus!
   
  Could you just describe a little bit more how to differenciate the pins of the power jack, using the multimeter?
   
  I also would like to know what would be a good wire setup for the amp: which material, which gauge (inside the amp, not for the link between the amp and the source)? What about that:
  http://cgi.ebay.fr/25-22-AWG-Silver-Teflon-Wire-White-red-19-strands-/380230270671?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item58877d7ecf
   
  or that:
  http://cgi.ebay.fr/50-feet-stranded-28-AWG-Silver-Teflon-Wire-White-Red-/380213369681?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item58867b9b51
   
  About the LED, i already bought the ones describe in the BOM from DIYForums, it show how to put it in the PCB, but not how to put it when you haven't a PCB.

 Thanks!
   
  Antoine


----------



## the_equalizer

Quote: 





c12mech said:


> I finally finished my 17EW8 version of this amp last week.  It's been working fine and sounds great.  There is one issue though.  When I turn it on the power supply cycles on and off for several seconds.  It seems to be taking longer and longer each time it is turned on.  The first few times it was turned on only took about 3 or 4 cycles. Last night it took about 30 seconds before the tubes lit up and the PS stopped cycling.  All the voltages are correct according to the schematic.
> 
> Is this a big problem and if so what do I do to fix it?  I used the equalizers schematic and parts are exactly as listed.  The PS is a Cisco 48V 380ma version that I got from evilbay.
> 
> It's not in its finished case yet so no pics yet.


 

 That's perfectly normal. When cold, the heaters look like a short circuit to the PSU; which then starts, dumps a bit of current into the heaters and shuts down. It then re-starts, dumps some more current into the heaters and shuts down again.  The tube heaters start increasing their temperature with the current dumps until eventually they no longer look like a short circuit to the PSU which is then able to sustain the required current; so the tubes start glowing and the amp comes on normally.
   
  As to the increasing turn on time, I'd monitor it for a few days but 30 seconds is really OK.
   
  cheers!


----------



## c12mech

Thanks for the quick reply.  That's what I thought was going on from reading some of the early posts in this thread.  I just was not sure if it would hurt the PSU. 
   
  As for the amp itself, it has made a huge difference in the way my DT880's sound.  I can hear peoples conversations in the background during one live performance that I listen to regularly.  I think I'm just going to keep listening to this thing for a while before I decide to upgrade.  I'm thinking Bijou or CK²III, I know they are both completely different animals, but isn't that the fun of diying.  Right now though for the money I don't think the SSMH can be beat.


----------



## hellomoto

Double post error, sorry!


----------



## wiisus

Thanks for the pics!  Those are exactly what I needed.


----------



## wiisus

Just wondering, how difficult would it be to add a S/PDIF-in to this?


----------



## FallenAngel

Uhm... it's not a DAC.


----------



## the_equalizer

Quote: 





c12mech said:


> Thanks for the quick reply.  That's what I thought was going on from reading some of the early posts in this thread.  I just was not sure if it would hurt the PSU.
> 
> As for the amp itself, it has made a huge difference in the way my DT880's sound.  I can hear peoples conversations in the background during one live performance that I listen to regularly.  I think I'm just going to keep listening to this thing for a while before I decide to upgrade.  I'm thinking Bijou or CK²III, I know they are both completely different animals, but isn't that the fun of diying.  Right now though for the money I don't think the SSMH can be beat.


 

 Glad to hear you're enjoying it with your Beyers. I agree, for the money, it's a really great little amp.
   
  cheers!


----------



## c12mech

I got home tonight and tried to turn on my amp and it does not seem to want to come on.  The PSU cycled for more than 2 minutes and still the tubes did not light up.  I pulled out my dmm and took some measurements.  The PSU reads 48V at the output.  When I plug it into the amp, where I should get 48V I'm getting 5~6V.  At pin 6 on both tubes I get ~3V.  At pin 4 I get 0V. 
   
  I checked the grounds and they are good.  Nothing is burned and all the other checks with the meter read good.  I'm at a loss here.  Did both mosfets die at the same time?  They are both isolated from the heat sinks and have heat shrink around all the pins.  It worked fine last night and now nothing.  Any help would be appreciated.
   
  Bryant


----------



## ArtemF

It looks like your power supply units do not like the cold heaters. I mean they do not withstand the
  initial current. There are two solutions: 1) buy a more powerful PSU. 2) Install a switch (or two switches)
  that will allow you first to start one channel, then the second one.


----------



## ArtemF

add-on - if the mosfets die they can do it in two ways: always open and completely burnt when there's no conductivity at all.
  In the second case there will be no load so the PSU voltage will not drop. If we're dealing with the first case then they will
  not act as current limiters and the PSU will not be able to feed the heaters with 48V because of high current.
  Put 1K resistor instead of one of the heaters so you'll be able to check if the problem is in the
  weak PSU that doesn't want to feed two cold heaters.


----------



## Beftus

Quote:


hellomoto said:


> About the LED, i already bought the ones describe in the BOM from DIYForums, it show how to put it in the PCB, but not how to put it when you haven't a PCB.
> 
> Thanks!
> 
> Antoine


   
  Connect the LEDs right after the on/off switch like this: 
 http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/705#post_4510827


----------



## c12mech

Quote: 





artemf said:


> add-on - if the mosfets die they can do it in two ways: always open and completely burnt when there's no conductivity at all.
> In the second case there will be no load so the PSU voltage will not drop. If we're dealing with the first case then they will
> not act as current limiters and the PSU will not be able to feed the heaters with 48V because of high current.
> Put 1K resistor instead of one of the heaters so you'll be able to check if the problem is in the
> weak PSU that doesn't want to feed two cold heaters.


 
  I'm thinking it is the PSU.  When I turn it on now it does not cycle.  It still reads 48V with no load but only ~5V with a load.  If I pull out one tube and put in a 1K resistor and it works I'll know that is the problem.  I assume that is what you meant by that.  At that point I'll just add a switch inline to start one and then the other.  If that does not work I may just build a power supply for it that can handle the load.


----------



## ArtemF

that's exactly what I meant. If the PSU can power one channel and if you do the same test for the second channel
  (just to make sure they are identical and there are no surprises to expect) then you know for sure that you need
  either a more powerful PSU or separate power switches for the channels.


----------



## the_equalizer

Quote: 





c12mech said:


> I got home tonight and tried to turn on my amp and it does not seem to want to come on.  The PSU cycled for more than 2 minutes and still the tubes did not light up.  I pulled out my dmm and took some measurements.  The PSU reads 48V at the output.  When I plug it into the amp, where I should get 48V I'm getting 5~6V.  At pin 6 on both tubes I get ~3V.  At pin 4 I get 0V.
> 
> I checked the grounds and they are good.  Nothing is burned and all the other checks with the meter read good.  I'm at a loss here.  Did both mosfets die at the same time?  They are both isolated from the heat sinks and have heat shrink around all the pins.  It worked fine last night and now nothing.  Any help would be appreciated.
> 
> Bryant


 
   
   
  Wow, that's certainly new. I agree with ArtemF's suggestion about inserting a 1K resistor in series with the tube filament. There are 1A Cisco PSU's out there that might help solve your problem, in case it's the PSU.
   
  cheers!


----------



## Beftus

Weird. Mine doesn't cycle at all. I have a 48VDC 380mA Cisco ADP-18PB.


----------



## the_equalizer

Quote: 





beftus said:


> Weird. Mine doesn't cycle at all. I have a 48VDC 380mA Cisco ADP-18PB.


 

 It's noticeable if you have some kind of power indicator (a LED or pilot lamp). Then you see the indicator pulse a few times before the tubes come up.
   
  cheers!


----------



## Ikarios

Considering some of the problems involving the PSU (the power cycling, the capacitance between the PSU ground and true ground = possibility of killing non-protected DAC), are there any possible replacements? Would any 48VDC PSU with a higher current work? Perhaps a modified TREAD? another easy-to-find wall wart PSU?


----------



## Beftus

Quote:


the_equalizer said:


> It's noticeable if you have some kind of power indicator (a LED or pilot lamp). Then you see the indicator pulse a few times before the tubes come up.
> 
> cheers!


 
 Both my tube LEDs do not blink at power up. The voltage doesn't drop at power up either, it remains steady at 48.3 volts. Perhaps the size of C1 and C6 makes a difference? I used 470uF for those caps instead of the specified 680uF in the BOM.


----------



## c12mech

I will work on it some tonight when I get home.  I'll post what I find out later on.  I was thinking the same thing about the size of C1 and C6 since I did use the 680uf caps there.  How big of a difference does it make to use a smaller cap there?


----------



## Rangiroa

Ok everyone,
   
  Update to my project as it was a few days ago since i fried my mosfets (actually i think the mosfets are fine, they are not burnt) But i used new mosfets anyways to be safe.
   
  My first build of this project has spanned over 3 weeks, including casework which i tried to make look as professional as i could with the tools that i had, including making some mistakes.

 I shouldnt have used a 21 dollar case for my first case...but i digress 
   
  I used the original millet BOM and got the heatsinks and protective pads for the mosfets, rewired all that and boom the tubes light up correct, and it gets as hot as people says, and theres no sparks when i turn it on (ALL GOOD THINGS  )
   
  Anyways, now i dont have any sound with a source plugged in. I suspect its either in my potentiometer or my neutrik wiring. I wasnt sure which side of the potentiometer to wire both grounds so maybe i have it backwards, my grounds are on the right side as you look at the pot from the connection side. On my neutrik jack, do i wire the l, r , and ground on the right or left side of the jack? i couldnt figure that out either.


----------



## the_equalizer

Quote: 





beftus said:


> Quote:
> 
> 
> the_equalizer said:
> ...


 
  Quote: 





c12mech said:


> I will work on it some tonight when I get home.  I'll post what I find out later on.  I was thinking the same thing about the size of C1 and C6 since I did use the 680uf caps there.  How big of a difference does it make to use a smaller cap there?


 

 Bigger caps definitely demand more current to chage up.  I just checked my 17EW8 build and I too used 470 uF eletrolytics for C1, C6.  
   
  Could you try a couple of 470 uF electrolytics and let me know if that solved the problem? If that solves it I guess I'll update the 17EW8 schematic setting C1,C6 = 470 uF just to be on the safe side.
   
  cheers!


----------



## c12mech

I played with it some tonight and am pretty sure the PSU is the problem.  I pulled both tubes out and turned it on just to see what would happen.  I kept a meter hooked up and let it sit for a few minutes.  The voltage started coming up very slowly.  It finally got to around 22V and I turned it off and just put one tube in.  Back to ~5.5V.  Pulled the tube back out and again a very slow voltage gain.  Since I don't have another 48V PSU I plugged in a 12V one just to see if there was a big drop.  I got 12V every where I should have.  The big caps charged to 12V almost instantly since I left the tubes out.  I may try to order another PSU with a higher amp rating and see what happens.
   
  If it did not defeat the whole SS theme I would build a 48V power supply in a separate enclosure.  As with most projects the PS would cost more than the amp.


----------



## ArtemF

wait a second - you mean that the voltage was not equal to 48V when BOTH tubes were unplugged?
  And at the same time the unloaded PSU shows 48V? I'm a bit confused. Can you measure the resistance
  of the unpowered circuit without tubes? It might be that the PSU has gone crazy so it can't power any reasonable load.
  What is the power rating of this PSU? 0.15A? Can you take a separate 350Ohm load (40W light bulb?) and test the
  PSU without the circuit?


----------



## the_equalizer

Quote: 





ikarios said:


> Considering some of the problems involving the PSU (the power cycling, the capacitance between the PSU ground and true ground = possibility of killing non-protected DAC), are there any possible replacements? Would any 48VDC PSU with a higher current work? Perhaps a modified TREAD? another easy-to-find wall wart PSU?


 

 Certainly, any 48 VDC with 350 mA or more of current capacity will work. I've used a 30 V HP printer supply to build a version using 12AE6 tubes.
   
  The simple amplifier circuit has very low rejection of power supply noise and ripple, so you'd have to be carfeul about that point. Voltage is not that critical and I'm pretty sure that anything between, say, 45 and 53 volts will work OK.
   
   
  cheers!


----------



## Rangiroa

can anyone explain to me which side of the potentiometer the ground wires are connected to?
   
  Also, The Neutrik Hphone Jack, which side to connect the wires, I wired mine as the original Millett was pictured.
   
  For the potentiometer, I am unsure.

 If i am not receiving sound, which tube pins should i measure resistances etc to?


----------



## nikongod

Quote: 





rangiroa said:


> can anyone explain to me which side of the potentiometer the ground wires are connected to?


 

 I usually just measure it. When the pot is turned to "minimum volume" the resistance from the center pin to the one that is typically grounded should be roughly 0ohms. the resistance from the center pin to the one where signal comes IN should be roughly the nominal value of the pot +/- a few % depending on your luck (czek the datasheet if you really care).


----------



## c12mech

Quote: 





artemf said:


> wait a second - you mean that the voltage was not equal to 48V when BOTH tubes were unplugged?
> And at the same time the unloaded PSU shows 48V? I'm a bit confused. Can you measure the resistance
> of the unpowered circuit without tubes? It might be that the PSU has gone crazy so it can't power any reasonable load.
> What is the power rating of this PSU? 0.15A? Can you take a separate 350Ohm load (40W light bulb?) and test the
> PSU without the circuit?


 

 The answer to your first two questions is yes.  As soon as any load is applied to the PSU it drops its voltage.  It is a 380ma rated PSU.  Everywhere I measure I get ~.3ohm except across the resistors where I get indicated values.  I will try the light bulb tonight when I get home.
   
  I think as you said the PSU has gone crazy.


----------



## ArtemF

I meant the resistance of the whole circuit when you unplug the power jack and put the ohmmeter leads to "+" and "-" of your circuit.


----------



## c12mech

I'll try that tonight as well.  I'll do it with the tubes in and with them out.  I don't really think that is a problem since it worked fine for about a week than decided to quit.  As I said earlier, the PSU does not even cycle when turned on now.  It just drops voltage and sits.


----------



## c12mech

I tried a 60W bulb, it measured 17.1ohms, with the PSU and it did nothing.  Well, it went from 48V to less than 1V as soon as the load was added.  I'm sure that the PSU is my problem now.


----------



## Beftus

What's the risk if I use 50 volt output caps (C3,C5) for a 12AU7 version? In normal operation these caps have ~12.5 volts accross them. Why the high margin?


----------



## wiisus

I built the amp! 

 When I first turned it on, the left side was ridiculously feint.  After spending a while troubleshooting, I realized I had R7 (33k) and R8 (390k) mixed up.  Changed that and it worked amazing!  

 But I turned it off for a bit.  Than I came back and turned it on.  They both started up than suddenly the left one just stopped working...neither the MOSFET nor the left Tube are working now, and there's just a loud hiss in the left channel.

 Any ideas on what the problem may be?

 Thanks. 
   
   

 EDIT:

 I switched the tubes around; It's definitely the tube that went out.


----------



## ArtemF

check the resistance of the heater. The one that is working shines too bright for me - normally they should glow.
  I suspect the heater was burnt. If that's the case, look for the reason. Otherwise you'll fry the second tube.


----------



## the_equalizer

Quote: 





artemf said:


> check the resistance of the heater. The one that is working shines too bright for me - normally they should glow.
> I suspect the heater was burnt. If that's the case, look for the reason. Otherwise you'll fry the second tube.


 
    
  Agreed, seeing the other one shine it looks like your build is hitting the tube heaters with much more voltage than they can take.  I'd revise *all* the wiring *step by step* to catch that bug, particularly the MOSFET and it's associated resistors; it looks as if you had wired the tube heater to the MOSFET drain, which is connected to the PSU 48 v line.
   
  In the meantime, as ArtemF says, do not turn the amp with the tube plugged in, or you risk blowing the second heater.
   
   
  Quote:


beftus said:


> What's the risk if I use 50 volt output caps (C3,C5) for a 12AU7 version? In normal operation these caps have ~12.5 volts accross them. Why the high margin?


 

 When the amp starts up, the heater looks like a short circuit thus there's no voltage drop across it, so, for a while, the DC voltage appearing at the MOSFET source (and the cap's + terminal) is very close to the supply voltage.
   
  cheers!


----------



## Beftus

Quote:


> Originally Posted by *the_equalizer* /img/forum/go_quote.gif
> 
> When the amp starts up, the heater looks like a short circuit thus there's no voltage drop across it, so, for a while, the DC voltage appearing at the MOSFET source (and the cap's + terminal) is very close to the supply voltage.
> 
> cheers!


   

 Cool, thanks! I'm gonna make another one but can only find Elna Silmic's 470uF in 50 volts... Ordering from the "big three" isn't an option, shipping cost is too high for my liking.
   
  I'm gonna try my luck. Besides, the PSU is regulated @ 48 volts, surely a 50 volts rated cap must be able to handle 48 volts for a while.


----------



## Rangiroa

update to my build,

 I have decided that I need to start from scratch for my build, so i will be ordering new caps and resistors.
   
  I was able to get faint noise from both channels, but only if i pushed around some of my wires.

 It seems that I have hooked everything together correctly for about 98-99 percent of the connections and I am missing one thing to just make it work.
   
  I might try and post some pics before giving up, see if someone here can spot my errors. At this point im ready to just give it up.

 I wish my mistake was more blatant because i could have found it by now. But you know how it is, after a long time of looking at something its impossible to see your wrongs.
   
  EDIT: forgot to mention that i ordered heatsinks and thermal protectors for mosfets off the original SS BOM. That has helped immensly, but I think there is a problem in my wima and electrolytic output area.
   
  I will post pics later with my thoughts. I believe the tubes are correct, and i believe the mosfets are correct.

 I am iffy in regards to the Wima output caps that connect to the neutrik jack
   
  (I am just thinking out loud, I will revist this idea with pics when i get off work.)


----------



## Ikarios

Quote: 





beftus said:


> Quote:
> 
> 
> > Originally Posted by *the_equalizer* /img/forum/go_quote.gif
> ...


 

 I wouldn't trust running even theoretical 48v across a 50v cap. Have you looked into ordering from a place like Beezar? Tomb has the caps you probably need, and I don't think it would kill him (or you) to ship out a few.


----------



## wiisus

Found out my issues.  Had the 390k and 33k mixed up in both channels.  Damn it.  Anyone happen to have a spare 12AU7?


----------



## Rangiroa

Ok,
   
  Here are some more pics of my build, As I said earlier the green and white wires are 99 percent connections and the blue and orange wires are ground wires.
   
  I have many problems and I am open to all suggestions at this point. my first problem is how to stabilize my connections. I was thinking about getting some heat shrink and a gun, would that make a large difference here?

 My amp will randomly produce a small, muted sound that sounds like music coming from my source if i press on my connections in random places. There is a 50 percent chance that i put the whole thing together and cram it into the case and it works lol.
   
  I am hoping that someone here can figure out something that I can't I have exhausted all options and I have stared at it for far too long. lol.
   
  This pic is intended to show how my output caps are connected, because since my sound was muted i assumed there is a problem with these cap connections, thoughts?

   
  This next picture is a pic of how my mosfet pin 2 connections are wired. The resistor in the upper part of the screen in front of the panasonic cap is connected to mosfet pin 2 by a wire.
   
  This next pic is a shot at my power area. it has the upper tube (not working) as well as the power jack and the wire running to the switch. the green terminal is used to ground wires. all wires in that connection are solidly screwed down.

  This last pic is the top of my amp. The tubes are actually on and lit up, although the heaters are very dim.its hard to see but the tops of the heaters are a light red and both tubes are lit up.
  Thoughts on why the tubes are so dim?

   
  Thanks for all your patience and help regarding my project. I believed i could do this before I started, and its very frustrating to be stuck and feel so close. Any help or ideas to help clean up my wire mess would be appreciated. Where can I find those connection terminals/braces that lots of people have used in their build? its the one where people usually bolt it down to their tube socket. If i knew what that was called i would definately use those for my next build.


----------



## c12mech

What you are looking for are terminal strips.  Mouser sells them P/N 534-812. 
   
  You said that you had the resistor going to pin two of the mosfet.  If that is the case then it is not right.  The resistor should got to pin one.  Find the data sheet for the mosfets and look carefully at the way they are laid out.  I had to look a couple of times to make sure that I had it right.  That could be why your tubes are not getting any brighter. 
   
  From what I see your output caps are wired correctly although not very pretty.  I cannot say much as mine is not a really pretty job either.
   
  One more suggestion.  Where you have multiple parts tying together, make the lead from one of the parts into a loop, then bend the other leads through the loop and solder.  It makes a much cleaner and stronger joint, IMO.


----------



## Beftus

Quote:


rangiroa said:


> This last pic is the top of my amp. The tubes are actually on and lit up, although the heaters are very dim.its hard to see but the tops of the heaters are a light red and both tubes are lit up.
> Thoughts on why the tubes are so dim?


   

 Perhaps you have bought tubes with enclosed heaters. My Electro-Harmonix 12au7's are like that, no tube glow to be seen. A tube led will light them up nicely though.
   
  BTW a word of warning. Your heatsinks appear to be very small for a 12au7 version IMO. They look like 1.5" tall to me. Correct? They will get *bloody hot* in use, trust me.
  My 2" tall heatsinks reach 60 °C easily on top, that's 140 °F. They get uncomfortable to touch very quickly. 
	

	
	
		
		

		
			





 For my next build I've bought 2.5" tall ones.


----------



## Beftus

Quote:


> Originally Posted by *Aflac* /img/forum/go_quote.gif
> 
> I wouldn't trust running even theoretical 48v across a 50v cap. Have you looked into ordering from a place like Beezar? Tomb has the caps you probably need, and I don't think it would kill him (or you) to ship out a few.


 
 I know of an amp of a respected builder with a 23-25 volt supply that has 25 volt caps in the PSU. Those caps see 25 volts continuously. Apparently it isn't a problem.
   
   
  A check on my 12au7 version shows a slowly rising voltage until it reaches ~12.5 volts and stabilizes. Not 48 volts at start up and decreasing to 12.5 volts.


----------



## the_equalizer

Quote: 





beftus said:


> Quote:
> 
> 
> > Originally Posted by *Aflac* /img/forum/go_quote.gif
> ...


 

 Remember all components have a tolerance rating, so using such closely matched values is a risk, even if it's done by a 'respected builder'.
   
  If you feel comfortable with it, use the 50 volts caps or even 25 or 18 volts caps, since according to your measurements in normal operation there are never more than 12.5 volts in those caps.
   
  Just understand that there could be some failure scenarios where the caps get hit by 48 volts and they'll breakdown, letting all that DC pass through to whatever 'phones are connected to the amplifier's output.
   
  cheers!


----------



## Juaquin

Quote: 





beftus said:


> I know of an amp of a respected builder with a 23-25 volt supply that has 25 volt caps in the PSU. Those caps see 25 volts continuously. Apparently it isn't a problem.


 

 This is never recommended. It may work, but you're risking longevity and cap failure. I'm not sure why a builder would do that, except maybe if a certain boutique cap is only available in that rating (or that rating has better specs).


----------



## the_equalizer

Quote: 





rangiroa said:


> SNIP
> This next pic is a shot at my power area. it has the upper tube (not working) as well as the power jack and the wire running to the switch. the green terminal is used to ground wires. all wires in that connection are solidly screwed down.
> 
> SNIP
> ...


 

 The connection points in a terminal block DO NOT connect to one another. Unless you somehow bridged the different connections together, this defeats your grounding.
   
  Indeed it seems you're very very close, so I'd recommend you do not give up!  Just give it a rest, for a few days, even a week so you come back to the project with a clean state of mind. Rushing it is the best way to mess up an electronics project, particularly when it's your first 
   
  cheers!


----------



## Rangiroa

Thanks all, i will check my mosfet connections. hopefully its a simple mixup of pin 1 and 2. I am hoping that is the case.
   
  If not...ill go back to the drawing board lol. I instantly regretted twisting things together because if i made a mistake its basically impossible to get apart.


----------



## nightarya

Well.
   
  I fixed it. But now somethings broken. Just my luck.
   
  Anyway, if you read my former posts, i found out there was a short, put my amp in a new abs box blah blah.
   
  I lost an RCA jack along the way (silly me)
   
  So i didn't use it when powering up the amp for the first time. So, it ran PERFECT. Played the first track of Fear of a Black Planet through it. But then, i left it on for quite a few hours. I mean, we're talking 4-5 hours, i had to go to my fathers birthday dinner.
   
  So i went back to play another track before bed to celebrate my own personal victory, and well....I put my earbud that worked in (test set of cheap buds, didn't wanna risk my cans!) Well, all i heard was a pulsing BUZZ, over and over. Only on one of my tubes though, it would pulse with my tube heater (you would see the orange flash in unison with the buzz
   
  Other tube wasn't hot, the MOSFETs weren't giving off heat, nothing. Just the one, firing over and over, making a buzz. Turned it off, waited like 10 minutes for it to cool, turned it back on, same thing
   
  What the heck could be wrong? It worked for the first 10 minutes, then left it for a few hours, now it's broken, what happened?? I know this shouldn't happen in that period of time.
   
  Any help you could provide, that would be appreciated, AGAIN. I hope this is the last of the issues.


----------



## Beftus

I just added the optional 1K resistors R14 and R15 to my build. My SSMH is now less noisy than before. Touching the metal casing of my iPod Nano with the music paused doesn't introduce noise anymore. Both resistors are in fact grid stopper resistors and help to filter out high frequency (radio frequency) noise. I soldered them as close as possible to the tube socket.
   
  IMO these "input resistors" as the_equalizer called them aren't optional at all!


----------



## c12mech

I finally got a new PSU yesterday and the amp  is back to working as it should.  It still takes about 15 seconds for the tubes to light up but I think that is because of the 680uf caps for C1 and C6.  I'm going to keep paying attention to the start-up time and if it gets to be to long I'll install a switch to start one side then the other.  When I took one tube out just to see what would happen it came on in about 3 seconds. 
   
  Thanks for all the help on this.
   
  Bryant


----------



## n_maher

For those still looking for 19J6 tubes I listed the last of my collection tonight in the FS forums here.


----------



## Ikarios

If I got four relatively cheap (~$5 each) 12AU7 tubes (or specifically, 5814s, which are the milspec versions, with no manufacturer listed), what are the chances they're going to be mismatched? I'm wondering if I should pay the premium for those 19J6s...


----------



## Beftus

Quote:


ikarios said:


> If I got four relatively cheap (~$5 each) 12AU7 tubes (or specifically, 5814s, which are the milspec versions, with no manufacturer listed), what are the chances they're going to be mismatched? I'm wondering if I should pay the premium for those 19J6s...


 
 If I were you I'd skip the on 19J6's and go for the 12AU7 instead. The 19J6's are increasingly hard to get and will command an ever increasing price. Basic supply and demand. The 12AU7 however is still made today, very common and thus easy to get. Price for a current production 12AU7 is ~$10 each. AFAIK the 19J6 tube is nothing special at all, Pete Millett used them because they were cheap and plentiful. Now that they're very hard to get and expensive IMO it's time to look at other tubes. The 12AU7 or it's family members are a safe bet. If you wanna go cheap, look into the 12SR7 mod. I can get NOS 12SR7 tubes for €2 each at a Dutch webshop.


----------



## nikongod

Why do you need matched tubes for a single ended amp?
  you dont.
  
  Quote: 





beftus said:


> AFAIK the 19J6 tube is nothing special at all...


 

 The 19j6 is actually a fairly special tube. What is neat about it is that it has a single cathode shared between the 2 plates & grids. It would work outstandingly well in a long tail pair.


----------



## hypnoticbob

Fantastic thread. I am enjoying the vast sums of input.


----------



## tomb

Quote: 





nikongod said:


> Why do you need matched tubes for a single ended amp?
> you dont.


 
  With respect nikongod, that could be viewed as an opinion.  Typically, the standard mantra is that power tubes need matching, but not pre-amp tubes.  However, with our sensitive headphones (as compared to guitars or speakers) and the typically high gains in most tubes - a mis-match can be detected.  It manifests itself as an imbalance between channel dynamics.  One headphone driver may sound a little dead compared to the other.  This can happen even with manual bias adjustments that will center the sound between channels.
   
  Granted, it could be that it's peculiar to tube hybrids (the limit of my experience).  It may be that the differences are magnified simply because there's only a singe tube providing all of the gain within a channel.  That's only conjecture, of course, but in my experience with Millletts/Maxes/MiniMAXes and the Starving Student, tube matching can make a difference.  The Starving Student is a bit better in this respect because of the single cathode and paralleled grids/plates tending to level the differences, but some people are still irritated by a tube mis-match.
   
  I agree that the chances are still fairly slim that two random, un-matched tubes will cause a noticeable effect.  It all depends on whether someone wants that assurance, relative to the cost of matching.


----------



## revolink24

[size=medium]Has anyone here done a P2P build with dsavitsk's additions? If so, was it worth it?
   
  Also, I want to put a gain switch on this build that selects between two sets of input resistors, 50k and 100k. And as I see it, there are two ways of doing this, with either a power switch and a DPDT switch, a power switch and a rotary switch, or just a (very special) rotary switch (off, low, high). Does anyone have any input on the best way to do this, or good parts (preferably from mouser) for doing so? I would love to be able to do it with a single rotary switch but I'm not sure how that would be possible since the power would be SPST and the gain DPDT unless I'm mistaken.​[/size]


----------



## Ikarios

Quote: 





revolink24 said:


> [size=medium]Has anyone here done a P2P build with dsavitsk's additions? If so, was it worth it?
> 
> Also, I want to put a gain switch on this build that selects between two sets of input resistors, 50k and 100k. And as I see it, there are two ways of doing this, with either a power switch and a DPDT switch, a power switch and a rotary switch, or just a (very special) rotary switch (off, low, high). Does anyone have any input on the best way to do this, or good parts (preferably from mouser) for doing so? I would love to be able to do it with a single rotary switch but I'm not sure how that would be possible since the power would be SPST and the gain DPDT unless I'm mistaken.​[/size]


 

 I've done some thinking re: implementing a gain switch and I came up with a few ideas. The easy way to do it would be to simply wire two wires, connected to resistors, straight from the input jack, both connected to a pole of a DPDT switch, which would pick between the resistors, i.e. a gain selector switch.
   
  I've toyed with the fancier idea of using a linear sweep pot as the gain selector, but I don't know how efficient this would be seeing as how it'll be difficult to replicate a certain gain setting unless you're using max or min gain every time. Still, might be worth looking into...
   
  if you want to get even fancier, you can use an Alps RK097 as that gain pot, because it has a built-in SPST power switch. This would save you the cost of a power toggle, but it might make a mess of your wiring depending on how you have your case laid out.
   
  In any case I can't think of a decent way to wire up more than two gain selections, as the more gain possibilities you have, you need to add at least two more wires to the switch and inputs, which will get messy quickly. Hopefully someone else has a better idea regarding gain switches...


----------



## revolink24

I found an NKK DPDT rotary at mouser.
   
http://www.mouser.com/search/ProductDetail.aspx?R=MRT23-A-ROvirtualkey63300000virtualkey633-MRT23-A-RO
   
  As far as I can tell though it would only be suitable for selecting gain, not my ultimate rotary switch dream.
   
  Can anyone point me to a rotary switch that can do this? (pardon the poor illustration)
   

   
  EDIT: Would something like this work? http://www.mouser.com/ProductDetail/NKK-Switches/MRF206-RO/?qs=sGAEpiMZZMvNbjZ2WlReYmt/ckRDMbNxDxWhl99ESfc%3d


----------



## hellomoto

Hi,
   
  I've got two small questions about the build of my MSSH!
   
  First, ArtemF told it was possible to differenciate the pins of th power jack using a multimeter to solder the wires in the right way, how can I do that?
  I also wonder how to put the tube sockets. I'm not using the PCB, and I bought a Hammond Case, but I don't know how to put it in the case, so that it won't move, I tried to find some pics of builds, but I couldn't find any help, could someone give me a solution?
  
  Thanks!
   
  Antoine


----------



## Beftus

Quote:


hellomoto said:


> Hi,
> 
> I've got two small questions about the build of my MSSH!
> 
> ...


   

 Take your DMM, set it to measure conductivity or resistance. Touch the center pin with one probe then the probe contact pins of the power jack. When your DMM beeps (conductivity) or reads zero ohms (resistance) then you've found the corresponding contact pin. The center pin is positive, the sleeve is negative.
   
  What kind of sockets did you buy? Sockets come in two flavours: PCB mount and chassis mount. You need chassis mount sockets since you don't use a PCB. Chassis mount sockets usually have solder eyelets.


----------



## hellomoto

Hi!
   
  First, thank you for your reply!
   
  I realized that I had PCB Mount, problem resolved, thanks!
   
  Antoine


----------



## wiisus

So, I have mine all setup and it sounds pretty good!  I have to go through and rewire it with some better wire soon (waiting for solder to come), and some kind of better grounding.  Whateves.  But, one of my tubes is a good deal brighter than my other one.  But there isn't any channel imbalance or anything.  They are different brands, though, could that be the reason?  I've rechecked my wiring multiple times and it looks correct.

 thanks


----------



## c12mech

I had that same issue with the tubes not being the same brightness.  I swapped them from side to side.  One tube is just a little brighter than the other no matter where it is.  It's just the tube itself.  On my amp there is about a half volt difference between sides and I thought that was the reason but I guess not.


----------



## jamesbobo007

I kind of lost track of things here. Was there ever any solution to the DAC issues ? and was it ever determined if it was just the Alien DAC or all DAC's ?
   
  c12mech and wiisus, what tubes did you build with? Adding tube led's might be a nice solution.


----------



## Juaquin

No true solution, but you can build your own power supply since it's thought to be caused by the Cisco PSU. Advice is to leave the DAC connected to the amp at all times to prevent a charge from building up and zapping the DAC when you plug it into the amp. That's been working perfectly with my GrubDAC and SSMH for months now, but it's not a guarantee. The issue was supposed to be confined to the Alien/Bantam but there have been a couple reports of it frying the Gamma1/2 over on the AMB forums. Since the issue is believed to be due to the Cisco supply, has anyone who's built their own supply been able to verify that their amp does not fry an Alien/Bantam?


----------



## Beftus

Grid stopper question.
  I have a built the 12AU7 version that I like very much. It suffered from some noise when I touched the (grounded pot) volume knob and also when I touched my iPod. Did some reading on grid stoppers and installed R14 and R15, both 1K, right before pin 2. No more noise. Good!
   
  I just found this _way back_ in this thread:
   
   
  Quote:


> Originally Posted by *nikongod* /img/forum/go_quote.gif
> 
> 5&6 are the grids (inputs) of the tube
> Attach a smallish resistor to EACH pin (with the body of the resistor as close to the pin as practical), then twist the legs together, and solder input to that. signal in now goes to the twisted legs of the resistors, through them to the tube...


 
 Pin 5 and 6 are the grids of the 19J6 tubes, in the 12AU7 version the grids are pin 2 and 7. For my next 12AU7 build I want to implement two grid stoppers as outlined above. What value should they be? Still 1K each?


----------



## c12mech

Quote: 





jamesbobo007 said:


> c12mech and wiisus, what tubes did you build with? Adding tube led's might be a nice solution.


 

 I used 17EW8 tubes.  No tube LED's for me.  I just don't care for the way they look.  I like the way the tubes look by themselves.  So far since I hooked up the new PSU it is working great.


----------



## wiisus

I used 12AU7. 

 I'm going to be adding LEDs soon.


----------



## nikongod

Quote: 





beftus said:


> Pin 5 and 6 are the grids of the 19J6 tubes, in the 12AU7 version the grids are pin 2 and 7. For my next 12AU7 build I want to implement two grid stoppers as outlined above. What value should they be? Still 1K each?


 

 The best answer is: the smallest value/least resistance that does the job. 
  1K is nice because it almost always works. I would get a bunch of values and try them out.


----------



## Beftus

Quote:


nikongod said:


> The best answer is: the smallest value/least resistance that does the job.
> 1K is nice because it almost always works. I would get a bunch of values and try them out.


   

 Cool, thanks! Gonna start with two 1K's since a single 1K works so well already. Too bad I don't have access to a scope to obtain the optimum value.


----------



## revolink24

Quote: 





revolink24 said:


> I found an NKK DPDT rotary at mouser.
> 
> http://www.mouser.com/search/ProductDetail.aspx?R=MRT23-A-ROvirtualkey63300000virtualkey633-MRT23-A-RO
> 
> ...


 

 In addition to this, I was hoping someone could point me to some heatshrink and wire suitable for a p2p build of the SSMH, since this will be my first P2P build. Mouser part numbers would be great.


----------



## hellomoto

Quote: 





> Originally posted by *Beftus*
> 
> Take your DMM, set it to measure conductivity or resistance. Touch the center pin with one probe then the probe contact pins of the power jack. When your DMM beeps (conductivity) or reads zero ohms (resistance) then you've found the corresponding contact pin. The center pin is positive, the sleeve is negative.


 

 Hello,
   
  The center pin is the biggest pin, who makes an "L" right? When I put one probe on this one, and the other on each of the two other pins, it tells me "1", used in resistivity, so no conductivity I think? It tells me 0 when i put the probes on the contact pin, so conductivity, right?
   
  When I put the plug in the power jack, I haven't any conductivity between any of the pins
   
  Is this normal?
   
  On the site of P.Millet it shows on the picture how to solder it, (the pins are in the same disposition, and i also use a blank PCB board for ground) so can I solder it like on the picture?
   
  Thanks


----------



## ArtemF

First of all, do NOT measure the resistance when the system is powered.
  You can fry your multimeter.
   
  Second, I'd suggested to use multimeter in voltage measuring mode to know for sure
  where is "+" and "-". Naturally, this measurement should be performed when the PSU works.
  Regardless of the internal stuff in the plug you'll have to find two pins with +48V across
  them. The one the red lead of your multimeter is connected to is the "+", the other one is  "-".
  That's it.


----------



## hellomoto

Thanks ArtemF, it works perfectly
   
  I would like to know how to solder the Jack Output. I didn't pay attention and bought a PCB one, so I have 6 pins, two for each of plus, minus ang ground, and I recognized which was which, but how should i solder the pins on the wires?
  http://fr.mouser.com/Search/ProductDetail.aspx?R=NMJ6HCD2virtualkey56810000virtualkey550-22302
   
  For the pot, I have the same problem, I don't know which wire goes were, but It is the same as the one of Pete Millet on his website, so I think I just have to solder the wires like in the picture.
  http://fr.mouser.com/Search/ProductDetail.aspx?R=RV122F-20-15F-A50Kvirtualkey14860000virtualkey313-1240F-50K

 Thanks
   
  Antoine


----------



## Beftus

This is how I wired my pot. Don't forget to ground the metal pot casing too.


----------



## Trower

I just built one of these, found some of the 19j6's in my uncles collection of tubes and he let me have them. Such a nice little amp! Way more detailed and smooth than I expected. Once I get more time I'll have to read through the thread here a build another one with some 17EW8's or 12AU7's.


----------



## Beftus

Quote:


trower said:


> Such a nice little amp!   ...build another one with some 17EW8's or 12AU7's.


 
 Show us some pics! I have a 12AU7 version which sounds absolutely wonderful. I like it better than my Hi-Performance Mini³. That's what I would like to have: a headphone amp with the the sound of my 12AU7 and the portability of the Mini³.


----------



## hellomoto

Thanks Beftus, that perfect, and it matches the pic of P. Millet! All my problems resolved!
   
  Antoine


----------



## Beftus

Quote:


hellomoto said:


> Thanks Beftus, that perfect, and it matches the pic of P. Millet! All my problems resolved!
> 
> Antoine


 
 You're welcome Antoine. Oh and now that your problems are resolved, please show us the amp when you finish it.
   
  For my next 12AU7 I'm slowly gathering parts and assembling small building blocks. Here's the progress so far.
   

  Caps are Elna RJH 470uF and Elna Silmic 470uF output caps with MKP1837 bypass caps. Interstage caps are MKP1837's too. Tube sockets with 1K grid stoppers. IRF510's with gate stoppers. Blue tube LED.


----------



## Trower

Quote: 





beftus said:


> Show us some pics! I have a 12AU7 version which sounds absolutely wonderful. I like it better than my Hi-Performance Mini³. That's what I would like to have: a headphone amp with the the sound of my 12AU7 and the portability of the Mini³.


 

 Well here are a couple crappy cell pix, just built it at a camp and will be staying here for a few weeks and I forgot my camera.....
   


   
   
  I am really diggin this amp! Its much better than I expected. I can forsee this getting alot more use than planned


----------



## Beftus

LOL. Great looking box!


----------



## jamesbobo007

Looks good Trower, I really like the look, its "Starving Student" for sure. How about a peek inside ? How much did you spend on the build?


----------



## Trower

Quote: 





jamesbobo007 said:


> Looks good Trower, I really like the look, its "Starving Student" for sure. How about a peek inside ? How much did you spend on the build?


 

 Thanks, I really like the way the cigar box looks with tubes As far as seeing the inside, she's glued shut now.......plus it was a quick build that I didn't pretty up, so I would kinda be ashamed to show it
  As far as cost, I got the sockets and tubes for free from my uncle who used to have an electronics repair shop for years, and alot of the parts I had lying around, so it kept the cost for parts to about 20 bux I would say. I'll post some better pictures of the next one I build....though that might not be until the fall when I have more time.


----------



## kellvyn

The idea of doing a P2P build of this scares me a little.  The idea of troubleshooting a P2P build scares me a lot.  Since the PCBs aren't available any more, I thought I might try doing a protoboard build using the Radio Shack 276-0150 that tangent's cmoy tutorial uses.  The first step of my plan was to draw a board layout and post it here for comments; I was hoping to get some advice before I started, however.

 Is this an entirely stupid idea?
 Any recommendations for how to draw the layout (besides pen and paper)? The images on Tangent's site (160k pdf) are nice, although I don't think I need them to be so fancy.  I was hoping Eagle would have some protoboard templates, but no luck.
 Are there any parts of the layout were I'd need to allow extra space between components?
  Thanks!


----------



## Beftus

Quote:


kellvyn said:


> The idea of doing a P2P build of this scares me a little.  The idea of troubleshooting a P2P build scares me a lot.


 
 Better make sure you don't make any mistakes then... The Starving Student was my first P2P build. Just take your time and double check everything do. Measure every resistor prior to soldering it. Lay out all the parts needed in front of you, make sure you don't forget to add a single part.
  I forgot to add two resistors, got 12.5 volts on the output, saw my mistake, added the last two resistors and then it worked.


----------



## wiisus

Yeah, and don't mix up a 33k and a 390k...you'll end up with it sounding really quiet for a while...than a tube will go out...


----------



## Juaquin

Quote: 





kellvyn said:


> The idea of doing a P2P build of this scares me a little.  The idea of troubleshooting a P2P build scares me a lot.  Since the PCBs aren't available any more, I thought I might try doing a protoboard build using the Radio Shack 276-0150 that tangent's cmoy tutorial uses.  The first step of my plan was to draw a board layout and post it here for comments; I was hoping to get some advice before I started, however.
> 
> Is this an entirely stupid idea?
> Any recommendations for how to draw the layout (besides pen and paper)? The images on Tangent's site (160k pdf) are nice, although I don't think I need them to be so fancy.  I was hoping Eagle would have some protoboard templates, but no luck.
> ...


 
   
  1) No, not at all, but P2P would probably be a lot easier than coming up for a layout on protoboard IMO. There aren't that many parts in this build, and if you are clean about your wiring (making wires as short as possible) and don't just leave uninsulated leads sticking out all over the place you'll be fine. Troubleshooting P2P is no different than a protoboard - putting something on a board doesn't mean you won't make errors as to which resistor to use where, or what should be connected to what. A PCB fixes this because you can not vary from the design even if you tried (except putting parts in wrong places). A protoboard lets you do whatever you want and thus IMO is the same as P2P, just with a nice board holding everything together. The board might actually be harder because you have less freedom of placement.
   
  2) I don't believe there are any programs that have any sort of protoboard design tools. If you want it to look nice you could use Illustrator, but that's just pen and paper on a screen.
   
  3) Yes. The MOSFETs usually are mounted to heatsinks outside the case. Obviously the tubes don't go to the board. The LED resistor should have some space as it's putting out a lot of heat, if you choose to use LEDs.
   
  So, in summary, don't be afraid of P2P. And either way you go, don't forget to use a star ground - hum has been known to be a problem.


----------



## Zink

Are the 12AU7 like these the cheapest tubes to use? What is the likely hood that within a year one of the tubes will fail? Would it be worth it to get 3 or 4 as spares since the tubes are $5 each and shipping is $8 no matter how many I get?


----------



## tomb

Quote: 





zink said:


> Are the 12AU7 like these the cheapest tubes to use? What is the likely hood that within a year one of the tubes will fail? Would it be worth it to get 3 or 4 as spares since the tubes are $5 each and shipping is $8 no matter how many I get?


 

 The terrible secret is that some 12AU7 tubes are among the most expensive of all tubes.  At the very least, they are not among the "cheapest."  Plentiful, but at the same time in high demand, they occupy something of a middle-level price range in the tube market.  Of the variants available, the 5963 is probably the cheapest, but that still may not be cheap on the Starving Student scale.  If you bought two tubes from the link you gave, you'd spend $18 for two tubes - that's $9 each, not what I would consider cheap.  Better deals can be had from recognized tube vendors.
   
  As for getting spares, I wouldn't worry about whether the tubes will fail.  In the Starving Student, they are running at a much reduced plate voltage and will probably outlast the amp itself.  Rather, if you are buying "pot-luck" ebay, as it were, the goal would be to get as many as you can so that you increase your odds of having a pair that are the better performing out of the group (tube quality is sometimes wildly variable) and that match each other.


----------



## Zink

What are some good recognized tube vendors to check? Is there any way to get a matched pair of tubes for less than $25? Thanks for the help.
   
  Edit: Ok, I found the couple of sites that sell tubes.


----------



## revolink24

Does anyone here have any tips for wiring the ground in the SSMH? On a P2P build, do you just wire all the schematic's grounds into a ground plane? Pardon my noobishness but I'm completely new to P2P. Also, can anyone point me to good wire to use for a P2P build?


----------



## Beftus

Quote: 





revolink24 said:


> On a P2P build, do you just wire all the schematic's grounds into a ground plane?


 

 That's exactly what Pete Millett did in his build. You can also star ground it, running the grounds to a single point.


----------



## kellvyn

Quote: 





> Originally Posted by *Juaquin* /img/forum/go_quote.gif
> 
> So, in summary, don't be afraid of P2P. And either way you go, don't forget to use a star ground - hum has been known to be a problem.


 

 I might give the protoboard a shot, just as a learning exercise.  But I know that grounding is an issue.  If you look at a picture of the protoboard I'm considering, you'll see the strips going down the middle (image from Tangent's site):
   

   
  I had thought about using them for the ground bus.  Would that be considered a star ground?  I'm not sure how literally one must understand "tie all ground paths to a single point."  If I use those strips, my ground paths are tied to a line, not a point.  There's also the ground sink issue:
  
  Quote: 





tomb said:


> There's a reason why Pete spec'd a copper PCB even for a Point-to-Point Bill Of Materials. The bare copper provides a ground sink for the circuit that minimizes hum. This might be very important with an all-plastic case.


 

 Will those strips be enough of a ground sink if I use a plastic case?  Will it be a non-issue if I use a metal case and non-insulated jacks?


----------



## Juaquin

The strips will tie everything together, but I worry that it's not enough metal to act effectively. The PCB/kit from Beezar essentially used the whole case as a ground, with good results for noise rejection. Depending on your application, case, and environment those strips might be ok. In a worse case scenario you could always connect them to your metal case (making sure everything else was isolated, especially the MOSFETs).


----------



## Trower

I found just using a bare copper PCB and using it as a ground plane worked well. I will say its a pain to drill, but easy for grounding purposes.


----------



## Beftus

Quote: 





juaquin said:


> The PCB/kit from Beezar essentially used the whole case as a ground, with good results for noise rejection.


 

 Grounding a metal case is a good thing, using the case as a ground conductor isn't because of the unpredictable path the ground would take. I'm sure I have read that somewhere, either here or on diyaudio.com...


----------



## the_equalizer

Quote: 





zink said:


> Are the 12AU7 like these the cheapest tubes to use? What is the likely hood that within a year one of the tubes will fail? Would it be worth it to get 3 or 4 as spares since the tubes are $5 each and shipping is $8 no matter how many I get?


 

 No, you can get a couple of 17EW8 tubes on e-bay for the cost of one 12AU7.
   
  EDIT:  Oh, and let's not forget you can also build the amp with 12SR7 tubes, which are also cheaper than the 12AU7.
   
  cheers!


----------



## hellomoto

Hi!
   
  I decided to use a ground plane, that was my very first DIY build, took me a lot of time, but it was pretty easy! With an organized work area, a good soldering iron, and time to spend, everything goes right, just take your time, read and be sure to fully understand the scheme, and use the pics of Pete Millet's website (giant pics, great for details), and P2P will be really easy!
   
  I nerlyh finished my amp, I just have to drill the holes for the tubes, and attach the MOFSETs and heatsinks.
   
  I have two small questions: first, i used the case as ground (Hammond black one, like the PCB build). I removed some black anodiing around the holes of the RCA jacks, to have a better ground, but should I connect the backplate to my ground plane using a wire?
   
  I also noticed a small pin on the pot,, going to the outside, under the axle, and over the 6 pins, you can see it on the picture:
  http://fr.mouser.com/images/alphataiwan/images/inhouse_rv122f2015fa50k_1.jpg

 What the point of that thing? It just make the mounting of the pot harder, I had to use spare spacers I had to have it mounted right, was it the right thing to do?
   
  Thanks for all your help guys!


----------



## the_equalizer

Quote: 





hellomoto said:


> Hi!
> 
> I decided to use a ground plane, that was my very first DIY build, took me a lot of time, but it was pretty easy! With an organized work area, a good soldering iron, and time to spend, everything goes right, just take your time, read and be sure to fully understand the scheme, and use the pics of Pete Millet's website (giant pics, great for details), and P2P will be really easy!
> 
> ...


 

 I completely agree about the pics from Pete Millett's site: they're a great guide for those of you who want to build a P2P version.
   
   
  The 'pin' in the pot goes into an auxiliary hole and helps the pot stay in place under 'heavy torsion'. You could try snipping it of with pliers or a dremel.
   
  cheers!


----------



## Juaquin

Quote: 





beftus said:


> Grounding a metal case is a good thing, using the case as a ground conductor isn't because of the unpredictable path the ground would take. I'm sure I have read that somewhere, either here or on diyaudio.com...


 

 Yes, I wasn't suggesting using the case as a conductor. The circuit should only contact the case at one point, hence adding a larger mass of conductive metal to ground (but no real current should be flowing through it). The ideal way to build this is to either use a very large ground plane (like Pete's original SSMH) or to use a star ground, where all ground are connected directly to one point which in turn connects to the case.


----------



## Beftus

Quote:


> Originally Posted by *the_equalizer* /img/forum/go_quote.gif
> 
> No, you can get a couple of 17EW8 tubes on e-bay for the cost of one 12AU7.
> 
> ...


 
 True, 12SR7 tubes can be very cheap ($1 - $2 each) but those metal tubes don't have the appeal of glass tubes IMO.


----------



## the_equalizer

Quote: 





beftus said:


> Quote:
> 
> 
> > Originally Posted by *the_equalizer* /img/forum/go_quote.gif
> ...


 

 You can always get a couple 12SR7*GT*
   
  cheers!


----------



## Beftus

Quote: 





the_equalizer said:


> You can always get a couple 12SR7*GT*
> 
> cheers!


 

 Indeed you can. But those are more expensive IIRC...
   
  When money isn't an issue the 12AU7 is a safe choice. At $10 each for a new production tube I don't think they're expensive at all.


----------



## c12mech

I got my 17EW8 tubes from here:
   
  http://www.vacuumtubes.net/
   
  They cost $3 each and shipping was about $6.  I bought a couple other things from them as well.  They had the lowest price that I found for these tubes and were very easy to deal with.


----------



## the_equalizer

Quote: 





c12mech said:


> I got my 17EW8 tubes from here:
> 
> http://www.vacuumtubes.net/
> 
> They cost $3 each and shipping was about $6.  I bought a couple other things from them as well.  They had the lowest price that I found for these tubes and were very easy to deal with.


 
   
  Yeah, they're one of the good tube vendors IMO. They also have the 12SR7GT listed for $4.00 US each.
   
  cheers!


----------



## wiisus

My amp is 95% finished!  I'm going go through, and redo some of the grounding eventually and maybe give it a new case.  Using the box the parts from mouser came in.  But for now, it's good.  
  
  I kept hearing this weird buzz every once in a while, and it was driving me insane.  I couldn't for the life of me figure it out.  Turns out, it would only happen when my cellphone was near 
	

	
	
		
		

		
			





.
   
  Overall, fun build, and it sounds awesome.
   
   

   
   

   
  Thanks everyone for all the help and info!


----------



## Zink

Quote: 





c12mech said:


> I got my 17EW8 tubes from here:
> 
> http://www.vacuumtubes.net/
> 
> They cost $3 each and shipping was about $6.  I bought a couple other things from them as well.  They had the lowest price that I found for these tubes and were very easy to deal with.


 

 Thanks a lot. I went back and read what the the_equalizer had to say about his 17EW8 version and it seems that I missed that he liked it better than the 12AU7 the first time I read the thread. I ordered three 17EW8 from vacuumtubes.net and I also ordered two "PCP9" which are supposed to be 9 pin chassis mount sockets. Are these the right nine pins for mounting on the top of a case PTP wired or is there a mini variant that I need? Will there be pins in the socket or do I need to buy those as well? I got the rest from Mouser and some at my local shop so now I think I have everything but the power supply ordered.


----------



## the_equalizer

Quote: 





zink said:


> Thanks a lot. I went back and read what the the_equalizer had to say about his 17EW8 version and it seems that I missed that he liked it better than the 12AU7 the first time I read the thread. I ordered three 17EW8 from vacuumtubes.net and I also ordered two "PCP9" which are supposed to be 9 pin chassis mount sockets. Are these the right nine pins for mounting on the top of a case PTP wired or is there a mini variant that I need? Will there be pins in the socket or do I need to buy those as well? I got the rest from Mouser and some at my local shop so now I think I have everything but the power supply ordered.


 

 Well, It's not that the 17EW8 version is superior to the 12AU7 version, just slightly different   I'm sure you'll enjoy any of the two, but since you asked if those 12AU7's were the cheapest tubes one could use I felt compelled to answer.
   
  As to the socket, I'm not sure what you mean by 'Will there be pins in the socket'.
   
  cheers !


----------



## c12mech

Zink,
   
  Those sockets are exactly what you need.  They are the same that I used.  They mount to the top of the enclosure and are pretty easy to work with.  If I had to do it again I would have put a little more thought into what order I soldered things together.  I gets kind of tight around the socket as more connections start to be added.  Altogether it was a pretty straight forward build.
   
  As for the amp, it is starting to sound better each time I turn it on now.  I usually listen at a low volume and am hearing things that I never knew was in some of the recordings I listen to.  This is the best bang for the buck amp out there, IMHO.  
   
  For my next project I'm going to use another of Pete Millett's amps as the base for a tube ipod dock similar to the Bose sound dock.  I know it's not for headphones but I need something for my toolbox at work.


----------



## Juaquin

Quote: 





wiisus said:


> kept hearing this weird buzz every once in a while, and it was driving me insane.  I couldn't for the life of me figure it out.  Turns out, it would only happen when my cellphone was near
> 
> 
> 
> ...


 

 My cellphone can do this. When we moved apartments and I had room to put the amp on my desk, I suddenly noticed more interference. Turns out my wifi router (2.4GHz and 5GHz channels) was causing interference, and only in the tubes (if I blocked the tubes with my hand, all was well). I need to figure out something to shield them. Maybe just some foil wrapped on the outside of a couple 35mm film capsules fitted over the tubes - that would certainly be starving student!


----------



## Beftus

Have you tried adding grid stopper resistors to eliminate interference?
   
  You could also make one with those metal tubes: the 12SR7 mod. Perhaps the metal enclosure can be tied to ground?


----------



## the_equalizer

Quote: 





beftus said:


> Have you tried adding grid stopper resistors to eliminate interference?
> 
> You could also make one with those metal tubes: the 12SR7 mod. Perhaps the metal enclosure can be tied to ground?


 
   
  Indeed, the metal case is connected to a pin which can (and should) be grounded.


----------



## Juaquin

The SSMH kit that I have isn't easily modified into a 12SR7 or similar (given the socket difference), but it's not really a big deal since I don't use the amp on my desk much. As soon as I have time I'll try modding it a bit.


----------



## Ikarios

I just got the 5814a tubes I ordered today, along with some other stuff like sockets, RCA jacks and heatshrink. A couple thoughts and questions...
   
  they're a lot smaller than i thought. for some reason I thought these things would be like at least film canister size. This probably means the whole Hammond case will also be a lot smaller than I thought as well.
   
  there are NINE pins! I thought this thing was supposed to be an 8-pin tube... why are there only eight pins as indicated on the 12AU7 variation schematic? D: do I just ignore pin 9?
   
  also, I'm having a heck of a time getting my tubes to insert into the sockets I ordered. I've tried wiggling the pins around but one socket refuses to have a tube put into it. is this what I get for ordering cheap sockets, or is there a way around it?
   
  I had the bright idea of using a variable resistor/pot (rheostat?) for RLED, but I don't know if it's viable or not. First, what does the resistance rating of a pot refer to, the highest resistance point? Second, I wouldn't even know how to wire up a single pot as RLED... would I run a single supply voltage line, split it to two, connect to the inputs, then wire the LEDs to the outputs? wouldn't that count as resistors running in parallel and require some not-straightforward calculations? I'm looking to vary the RLED current between 5 and 12mA, ideally running all the way down to zero.
   
  Also, I had a question regarding ground for this amp - some people have mentioned using the chassis as ground, but then some people mentioned not using the chassis as a "conductor". does this mean to connect ground to the chassis, but not directly (i.e. run all grounds to, say, a copper plate, then connect the plate to the case)? What about, say, for the pot or RCA jacks, where the ground tab will probably touch the metal case?
   
  I have a lot more questions but since my last question post got ignored for the most part, I'll post them slowly this time...


----------



## Juaquin

For grounding - basically what you want to avoid is actually passing current through the case. Therefore, you want circuit ground to touch the chassis at really only one point (if it connected at two points, there's a possibility some current would flow through the case, which may or may not be a good conductor and hence add noise). So you can either use star ground (run ALL grounds to a single post connected to the chassis) or use a large ground plane (like a copper plate) and connect that plane to the chassis at one point. For the jacks and the pot, you'll probably be fine just letting them touch the case (if they need to and they're not insulated). You'd still run a ground wire to the jacks anyways - electricity takes the path of least resistance, and since the case likely has a higher resistance than the wire you wouldn't be running much current through the case even in a worst-case scenario.
   
  A pot is rated for it's highest resistance (so a 1k pot goes from about 0 ohm to 1000 ohms). To use a pot for RLED, pick a pot that is equal to or higher than the value you would have used for RLED. Hook one of the outer pins (doesn't matter which, except which way you want to turn the pot) to one side of where RLED would go and the wiper (middle pin) to the other side. Keep in mind that RLED on the SSMH needs to be rated for at least 2 watts because of the 48V supply, from what I remember. I'm not sure most pots meet that rating.
   
  So if you had a pot rated for 2W+, and you were shooting for around 10ma through the LED on a 48V supply, you would do 48V/10ma=4800ohm. So I'd go with 10k pot so you could lower the brightness further (48V/10000=5ma). This is all assuming you can find a pot with a suitable power rating.
   
  As far as inserting tubes into sockets - it can be hard sometimes. You can use some force as long as you're careful not to break the tube. You could also stick a screwdriver in there and loosen the socket a bit, but overdoing it could lead to a bad connection.


----------



## Beftus

Quote: 





ikarios said:


> there are NINE pins! I thought this thing was supposed to be an 8-pin tube... why are there only eight pins as indicated on the 12AU7 variation schematic? D: do I just ignore pin 9?
> 
> 
> I had the bright idea of using a variable resistor/pot (rheostat?) for RLED, but I don't know if it's viable or not.


 
   

 Indeed, nine pins, pin 9 isn't used. I even removed pin 9 from the tube socket when I was modifying the socket to accept a tube LED.
   

   
  The LED needs a pot with a high watt rating, as outlined before. I plan to install a on/off/on switch giving me the option to run the LEDs at a low current, a high current or turned off.


----------



## Juaquin

Quote: 





beftus said:


> The LED needs a pot with a high watt rating, as outlined before. I plan to install a on/off/on switch giving me the option to run the LEDs at a low current, a high current or turned off.


 

 Yes, this might be the better idea. Set up a switch to switch between open circuit, one resistor, and a higher resistor. That way you can use any standard 2W+ resistors and still have control over brightness.


----------



## Ikarios

Quote: 





juaquin said:


> For grounding - basically what you want to avoid is actually passing current through the case. Therefore, you want circuit ground to touch the chassis at really only one point (if it connected at two points, there's a possibility some current would flow through the case, which may or may not be a good conductor and hence add noise). So you can either use star ground (run ALL grounds to a single post connected to the chassis) or use a large ground plane (like a copper plate) and connect that plane to the chassis at one point. For the jacks and the pot, you'll probably be fine just letting them touch the case (if they need to and they're not insulated). You'd still run a ground wire to the jacks anyways - electricity takes the path of least resistance, and since the case likely has a higher resistance than the wire you wouldn't be running much current through the case even in a worst-case scenario.
> 
> A pot is rated for it's highest resistance (so a 1k pot goes from about 0 ohm to 1000 ohms). To use a pot for RLED, pick a pot that is equal to or higher than the value you would have used for RLED. Hook one of the outer pins (doesn't matter which, except which way you want to turn the pot) to one side of where RLED would go and the wiper (middle pin) to the other side. Keep in mind that RLED on the SSMH needs to be rated for at least 2 watts because of the 48V supply, from what I remember. I'm not sure most pots meet that rating.
> 
> ...


 

 I think I found a suitable pot for RLED - http://www.mouser.com/ProductDetail/Bourns/3852A-162-503AL/?qs=sGAEpiMZZMtxdMMi52izyhVRLOm6MJTqb9DViJ%252b2ghU%3d
  compared to buying two 2W resistors (about $2 each) and a DPDT switch (~$5-8) it's not a bad deal. 50K ohms for the ability to use more of the pot, and if it goes down to ~0 ohms it won't matter, right?
   
  Since it only has three lugs, do I connect one end of each LED to the wiper pin and the connection from power to the far side pin so it starts at 50k, then goes down? I think I've been confused about the whole 2-LED thing, do most people use one RLED for both LEDs? or two resistors and two connections from power for each LED?
   
  EDIT: I did some more thinking on the matter and I think instead of only using a 50k pot like this, what about using a 10k pot with a ~5k resistor right before the LED, so the LED current will swing from ~3.2mA to ~12mA? This way, there's no possibility of blowing out the LED if someone accidentally turns the pot all the way up. The main disadvantage of this method is that there's no way to turn the LED completely OFF... but I don't know if an LED fed by 3.2mA will be very visible when placed underneath a tube anyway.
   
  As an aside... how do I know if my tubes' heaters are enclosed? One of my main concerns about this whole LED thing is that some people have very bright orange tubes, whereas others have zero tube glow. I plan on using the sea green LEDs from Beezar, which will probably not look good with the standard orange-yellow tube glow...


----------



## Juaquin

Quote: 





ikarios said:


> EDIT: I did some more thinking on the matter and I think instead of only using a 50k pot like this, what about using a 10k pot with a ~5k resistor right before the LED, so the LED current will swing from ~3.2mA to ~12mA? This way, there's no possibility of blowing out the LED if someone accidentally turns the pot all the way up. The main disadvantage of this method is that there's no way to turn the LED completely OFF... but I don't know if an LED fed by 3.2mA will be very visible when placed underneath a tube anyway.


 

 This is a good idea. 3.2ma might be visible but not much, depending on the LED. You can connect both LEDs to one resistor/pot - that's how the SSMH kit did it.
   
  I'm not sure which tubes are enclosed and which aren't, or if you can tell by looking at them. I suppose the easiest way would be simply to hook up the heater and find out. You don't have to build the rest of the circuit just for that.


----------



## Beftus

Quote: 





ikarios said:


> compared to buying two 2W resistors (about $2 each) and a DPDT switch (~$5-8) it's not a bad deal.


 

 I don't know where you do your shopping but those prices are very high. A simple DPDT switch at my supplier is only €0.75 (~USD 0.95).


----------



## Ikarios

Quote: 





beftus said:


> I don't know where you do your shopping but those prices are very high. A simple DPDT switch at my supplier is only €0.75 (~USD 0.95).


 

 Mouser's cheapest DPDT switches are ~$2.50, from what I can find. Switches from tubesandmore were ~$8, too. I was also looking at metal film resistors, which are like $2 for the 2W versions. I did find power resistors which are maybe 20 cents. It actually doesn't matter, because I discovered that we have lots and lots of switches at work, so I borrowed a few. Regardless, I really like the idea of being able to fade the tube LEDs. Now that I think about it, though, I may not have enough room on the panels of the case; it's a lot smaller than I thought. I'll have to rethink this whole thing...
   
  Also, it appears that the DC jack sourced at mouser is OOS until August (http://www.mouser.com/Search/ProductDetail.aspx?R=163-4025virtualkey11180000virtualkey163-4025). I looked for a replacement but couldn't find one with the right jack sizing. Does anyone have a spare lying around that they would sell/donate to me?


----------



## islubio

Are these boards available anywhere?
  checked out beezar and seems like they are sold out 
  would love to build this as my first amp


----------



## Beftus

Quote:


islubio said:


> Are these boards available anywhere?
> checked out beezar and seems like they are sold out
> would love to build this as my first amp


 
 No more boards. The Starving Student became victim of its own success. The supply of cheap 19J6 tubes has dried up. They're now very difficult to find and if you do prepare to pay a premium price. So far the bad news.
   
  The good news is that you can still make a Starving Student with other tube types. There's the 12SR7, the 12AU7 and the 17EW8 modifications. There's no PCB for these mods though. You'll have to do a point-to-point or make your own PCB. I have made the 12AU7 mod and it sounds awesome. Schematic is here. Good luck!


----------



## Ikarios

Anyone know if I can use a 1A/250VDC rated DC power jack as opposed to the spec'ed 2A/100VDC jack?
   
  http://www.mouser.com/ProductDetail/Kobiconn/163-2325-E/?qs=sGAEpiMZZMu2f9RNbWupYlhRViv1JeBB6A17xm18uDs%3d
   
  The one in the BOM is backordered until August 6th and I plan on buying all my crap Friday this week. The PSU is only rated for 0.38A, I just have to not use a different PSU, right?


----------



## nullstring

lol, I am sure the original part was chosen pretty arbitrarily. (or for cheapest price)
   
  If it's rated for more than 48V and .38 amps.. I think you're good.


----------



## the_equalizer

As nullstring mentioned, I'd say you're safe using that part. You could even use the 1A PSU if you so wish it, since the amp's current draw won't go near 1A during operation.
   
  cheers!


----------



## Beftus

A question about the 12AU7 mod. The optional caps C7 and C8 are listed as 220uF 16V. I measured the voltage across those caps in my build and there's only 1.12 and 1.14 volt across them. Why are they specified as 16V? Do they get to handle more than what I measure? Or was their voltage rating chosen arbitrarily?
   
  Edit: Please ignore question. Found the answer here. Gotta learn to use the forum search...


----------



## swedishhatfaction

Quote: 





darkraver said:


> Just finished my first DIY amplifier, wanted to show it off here
> 
> 
> 
> ...





   
 [size=medium] 
  Wow darkraver -- that's a pretty snazzy exterior you got going on there. It kinda reminds me of the crazy abstract art my sister paints. Also, congratulations on having it work the first time. I was not nearly as lucky/skilled and ended up rebuilding mine from scratch.
   
  Edit: Whoops. Didn't realize that post was 10 pages back.​[/size]


----------



## baka1969

Hi,

 Will the SSHT properly drive low impedance headphones like the 25 ohm or 8 ohm Beyer DT48?

 Thanks,

 Ross


----------



## baka1969

Hi,

 Will the SSHT properly drive low impedance headphones like the 25 ohm and 8 ohm Beyer DT48?

 Thanks,

 Ross


----------



## WC Annihilus

Curious, does anyone know how this would pair with the DT990/600?  I'm considering trying to build one as a relatively cheap summer project to burn time and get an intro to amps as well.  Other option I've been looking into is the CK2III.


----------



## nullstring

I just got a PM about that today.
   
  This was my response.
  Quote: 





> I think it sounds good.
> It certainly has enough volume for the vintage DT880/600.
> I don't, however, think it sounds as good as it could.
> 
> I am planning on building a much better amp to replace it soon.


----------



## the_equalizer

Quote: 





baka1969 said:


> Hi,
> 
> Will the SSHT properly drive low impedance headphones like the 25 ohm and 8 ohm Beyer DT48?
> 
> ...


 

 The output stage has enough muscle, so I think it'd do perfectly with the 8 ohms cans. Though the lowest impedance I've tried with the amp has been some 16 ohm earbuds; it had no problems with them.
   
  cheers!


----------



## hellomoto

Hello!
   
  I'm now finished with my build, the tubes are glowing, but I still haven't put my heaphones on it: I found a really nice post from the_equalizer about testing your amp, so It doesn't destroy your whole setup 
	

	
	
		
		

		
		
	


	



   
  Here it is: http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/3870#post_6032606
   
  I've got some questions about it, more precisely about the different voltage test:
  - How do you measure the voltage at the tube filaments
  - How do you measure the voltage in the Output Jack? Do you plug in a Mini to Mini, and measure at the other side?
  - How do you measure the voltage in the Jack Plug?
   
  Thank you very much, I'll post some pics!
   
  Antoine


----------



## Fred_fred2004

I'm too impatient, I just wack in some cheap headphones and listen


----------



## ArtemF

in principle, nothing bad should happen given that you've put the output caps. To be on a safe side
  you can start from the output: measure the DC voltage on the output jack. If there's no DC component,
  switch to AC measurement mode and check if the amp doesn't generate by itself when the volume knob
  is in the left (=min) position. If there's no AC component, you can plug (cheap) headphones and give it a try.
   
  If it doesn't work, check the voltages in key points of the circuit and start investigating the problem.


----------



## revolink24

A couple of questions. Would 63V 220uF Nichicon Electrolytic caps (Mouser number 647-UHE1J221MPD work for C1, C3, C5, and C6? And is there a decent alternative (or maybe Im missing it) to C7/C8 on Mouser?


----------



## baka1969

Quote:
 Originally Posted by the_equalizer  


 " The output stage has enough muscle, so I think it'd do perfectly with the 8 ohms cans. Though the lowest impedance I've tried with the amp has been some 16 ohm earbuds; it had no problems with them.
 cheers!"

 Thanks!


----------



## FallenAngel

C1 and C6, I'd use considerably higher than 220uF, maybe even 1000uF.  For C3 and C5, I would really recommend 470uF Muse ES, not HE.
  
  Quote: 





revolink24 said:


> A couple of questions. Would 63V 220uF Nichicon Electrolytic caps (Mouser number 647-UHE1J221MPD work for C1, C3, C5, and C6? And is there a decent alternative (or maybe Im missing it) to C7/C8 on Mouser?


----------



## revolink24

Thanks for the response. What thermal material do you use for the MOSFETs (if any)? Also, does anyone know of a DPDT switch that could be used as a gain switch?
   
  Also, these would be correct for C7/C8, correct? http://www.mouser.com/ProductDetail/Nichicon/UES1C221MPM/?qs=kArNe9LFxXkkfHBfMYU2Pw%3d%3d
   
  More edit: What do you think of this DPDT switch for a gain selector? http://www.mouser.com/ProductDetail/Mountain-Switch/108-1MD2T2B3M1QE-EVX/?qs=sGAEpiMZZMvudeGI7i40XJQ7caDfyBlLkZYiLn5EiQs=
   
  As far as I know it would go each RCA to 2 and 65, and then 50k resistors or so at 1 and 4 and 100k at 3 and 6. (if you look at the data sheet on Mouser)
   
  I suppose this NKK would be higher quality, but any DPDT ON (ON) toggle should work, correct? http://www.mouser.com/ProductDetail/NKK-Switches/S335T-RO/?qs=V2oqQAr0jIiS08sISfWzXQ%3d%3d
   
  The only difference I can see between the two is 2A vs 15A, but there shouldn't be more than 2A on R16/R17, should there?


----------



## the_equalizer

Quote: 





fred_fred2004 said:


> I'm too impatient, I just wack in some cheap headphones and listen


 


 That's definitely an option  
  
  Quote: 





hellomoto said:


> Hello!
> 
> I'm now finished with my build, the tubes are glowing, but I still haven't put my heaphones on it: I found a really nice post from the_equalizer about testing your amp, so It doesn't destroy your whole setup
> 
> ...


 

  
  - Measure  from ground to the tube's pin 3 or 4 (the one that is NOT grounded, naturally)
  - Measure from the ground lug to the the left, then the right lug (be sure to measure with the volume at min, and at mid or max)
  - Measure from the ground lug to the 'hot' lug.
   
  As always, measuring a 'live' circuit requires care and a steady hand so as not to short out things.
   
  As someone else posted, the risk of DC at the output jack is minimal, due to the capacitors. Still, you could get a defective cap or have some serious miswiring that puts DC at the output, so it's still a good idea to measure and then use some cheapos for the first listen.
   
  cheers!


----------



## the_equalizer

Quote: 





wc annihilus said:


> Curious, does anyone know how this would pair with the DT990/600?  I'm considering trying to build one as a relatively cheap summer project to burn time and get an intro to amps as well.  Other option I've been looking into is the CK2III.


 

 The highest impedance cans I've tried with my SSMH have been Sennheiser HD-600's and I found the volume output by the amp more than enough to drive those cans to nice volume levels.
   
  Still, I've never heard 600 ohm Beyers so it could be different. Anyway, you can easily build a 12AU7 version and, if you find the volume insufficient, just swap the tubes for 12AX7's (drop-in replacement no rewiring needed at all) which have noticeably more gain (I have tried them in my SSMH).
   
  cheers!


----------



## ArtemF

2 revolink24:
   
  thermal material is __necessary__ to insulate your mosfets from the ground.
  Otherwise you'll have to insulate the radiators that might be tricky.
  Check the list of items provided by Peter Millet on the first page.
  I recall there were two mounting sets that included thin insulating pads.


----------



## revolink24

Well some insulator is necessary, although whether these MOSFETs need thermal conductive material seems to be up for debate. But Beezar is still selling the mounting kits! Yay TomB! I totally didn't realize that.


----------



## Beftus

Quote: 





the_equalizer said:


> As someone else posted, the risk of DC at the output jack is minimal, due to the capacitors. Still, you could get a defective cap or have some serious miswiring that puts DC at the output


 

 If you forget to add the 2K resistors right at the output (R6,R12) you get ~12.5 volt DC at the output. Been there, done that...


----------



## the_equalizer

Quote: 





beftus said:


> If you forget to add the 2K resistors right at the output (R6,R12) you get ~12.5 volt DC at the output. Been there, done that...


 

 Yeah. That would qualify as a serious miswiring !    So how is your SSMH doing Beftus? Tried different tubes? Has it burned-in nicely?
   
  cheers!


----------



## Ikarios

two quick questions - if I'm using a gain switch to switch between 50K and 150K ohm resistors (using a 50K ohm pot), is it better to put the resistors on the input of the gain switch (i.e. split the line from the input and connect the resistor leads to the poles of the switch) or is it better to connect the input to the main pole of the switch and connect the resistors to the switching poles (i.e. split the resistors at the "pot side")?
  also, what do I do about input ground in this situation? Do I need to connect it to the switch? In other words, can I use a DPDT switch for gain or do I have to use a 3PDT? I was planning on using a DPDT but I seem to have confused myself with all this wiring and switches (currently have five planned... 
	

	
	
		
		

		
		
	


	




)


----------



## the_equalizer

I'm not sure about the first question. That is, I'm not sure if one way is better than the other. Maybe some others might chime in, or you can simply do both and see which one works better.
   
  About the ground switching, no, you do not need to switch ground lines, as ground is a common reference point to all lines; a DPDT switch should do nicely.
   
  cheers!


----------



## Beftus

Quote:
   
   


> Originally Posted by *the_equalizer* /img/forum/go_quote.gif
> 
> Yeah. That would qualify as a serious miswiring !    So how is your SSMH doing Beftus? Tried different tubes? Has it burned-in nicely?


   

 It's burned in very, very nice. Haven't tried other tubes as it sounds _so schweet_ already!
  I have a second SSMH still in parts (gonna use Elna caps), waiting to be built into a functioning amp. Haven't gotten around to building it yet, I just came back from my holiday in France. Will report back here with the results of the second build.


----------



## livewire

Hello all!
  I'm kind of late to the party, I've been lurking the past few days reading this fine thread.
  So far, I've only digested 175 pages, about half. Whew this is a long read!
  Got all of the parts together to do this build, scrounged an old finned heatpipe cpu cooler
  from the junk parts bin to put up top for the fets. Below is a blurry pic of the mock-up,
  hope to have it wired this weekend. Wish me luck!
   
  BTW as an intro, I love all things audio.
  My hobby is restoring 1920's - 1950's tube radios and 1960's - 1970's stereo receivers.
  Just did a Marantz 2275, at the moment I'm rebuilding a 1963 Sansui 1000.


----------



## Beftus

Nice looking case you got there. Love the CPU cooler. Well done!


----------



## the_equalizer

Quote: 





livewire said:


> SNIP
> My hobby is restoring 1920's - 1950's tube radios
> 
> SNIP


 
   
  I used to do that back in my early twenties!   I still have a (working) 1940's Pilot tube radio in my living room, with a lovely Art Deco bakelite case
  
  Your 'mock-up' looks great !  It seems to me that you managed to get your hands on a couple of the coveted 19J6 tubes? 
   
  Given your background in electronics I'm not sure you need any luck to get this little amp working! And please post pics of your built and working amp !
   
  cheers


----------



## livewire

Quote:Originally Posted by *the_equalizer* /img/forum/go_quote.gif


 Â 
  It seems to me that you managed to get your hands on a couple of the coveted 19J6 tubes? 
  Â 
   
  Funny you mention that!
  What a mixed bag that was. So far, the "hardest part" of this build.
  Let's see, Antique Electronic Supply had one left at the "old" price of $1.10,
  (or maybe they were limiting what one could order?) I snapped that one up.
  The next guy I contacted has them in stock advertised at $10 each.
  So I contacted him and he says that the going price is now $20 each + $10 shipping.
  No thank you. Sheesh! I can find them on fleabay for that price.
  The last guy I contacted only had two left in stock at $10 each, so I bought those as well.
  They all seem like new old stock in the original boxes, mixed bag, no matching.
  Two D-ring getters and one halo. I hope they work, they test good on my B&K tube tester.


----------



## livewire

Quote: 





beftus said:


> Nice looking case you got there. Love the CPU cooler. Well done!


 


 Thank you!
  I'll post more pics next week when it is done. (and hopefuly working) 
  The aluminum case will be painted with a "granite look" finish.


----------



## Beftus

Quote: 





livewire said:


> I hope they work


 

 In the event that they don't work you can modify if and make the 12AU7 version. My 12AU7 version sounds delightful. While 12AU7 tubes aren't the cheapest tubes around, they are very easily sourced. The 12AU7 version also allows you to play with higher gain tubes from the same 12A.7 family. The 19J6 is a bit of a dead end street as finding them becomes difficult and should you have found them prices are very high.


----------



## Ikarios

Quote: 





beftus said:


> In the event that they don't work you can modify if and make the 12AU7 version. My 12AU7 version sounds delightful. While 12AU7 tubes aren't the cheapest tubes around, they are very easily sourced. The 12AU7 version also allows you to play with higher gain tubes from the same 12A.7 family. The 19J6 is a bit of a dead end street as finding them becomes difficult and should you have found them prices are very high.


 

 also apparently, the 12AU7 mod can also swap in 17EW8 tubes (which ARE cheap) with apparently no modification. I plan on trying it at some point down the road when my finances are a little more free and I have a way to get tubes without getting charged for shipping.


----------



## the_equalizer

Quote: 





ikarios said:


> also apparently, the 12AU7 mod can also swap in 17EW8 tubes (which ARE cheap) with apparently no modification. I plan on trying it at some point down the road when my finances are a little more free and I have a way to get tubes without getting charged for shipping.


 
   
  That is correct, another builder tried it and reported it worked. I then tested in my build and indeed it works.
   
  cheers!


----------



## Beftus

For the 17EW8 mod, shouldn't R2 and R8 be around 250K - 260K? In practice this could be a 270K resistor. Correct?


----------



## vrenlos

I just found one hell of a score of NOS tubes buried in my lab at work, does anyone happen to have a list of tube models that have been tried/verified working?  I was trying to look through but 360+ pages is a lot to comb.


----------



## Beftus

19J6
 17EW8
 12AU7
 12AV7
 12AT7
 12AX7
 12SR7


----------



## vrenlos

Excellent, thanks.  I'm going to cart these home over the next few days and I'll try to catalog what I've got.  I'm pretty sure I saw a handful of 12AT7's, but there's probably a total of a few hundred to look through.


----------



## Beftus

Tubes you don't need/want or have in adundance could be sold here...


----------



## vrenlos

Very true...also found two old tube testers - one from circa 1946 and another from probably 60-70's with updated charts for testing.  Both work.
   
  It's probably going to take me a few days to haul most of this stuff home but I'll catalog it all and let everyone know what I've got.  As of now I see plenty of 12AU7's and 12AT7's.


----------



## the_equalizer

Quote: 





beftus said:


> For the 17EW8 mod, shouldn't R2 and R8 be around 250K - 260K? In practice this could be a 270K resistor. Correct?


 

 Technically yes, it should be a ~250K ohm; but the 220K value of the 19J6 version does nicely.  A 270K will work too, after all, it works with the 390K that a 12A_7 version uses.
   
  cheers!


----------



## Beftus

Quote: 





the_equalizer said:


> Technically yes, it should be a ~250K ohm; but the 220K value of the 19J6 version does nicely.  A 270K will work too, after all, it works with the 390K that a 12A_7 version uses.
> 
> cheers!


 
   

 Cool, thanks! It means I understand the math behind the conversion. Never too old to learn something new.


----------



## Beftus

Could the 18AQ8 be used to make a Starving Student? Has an 18 volt heater @ 150mA current draw. The increased heater could be nice to lower the heat dissipated by the heatsinks when compared to a 12A.7 version.
   
  Found a site selling them for €4 a piece.


----------



## the_equalizer

Just looked that tube up in google, a double triode it seems. I'm pretty sure it'll work... but there's *only one* way to know for sure   
   
   
  cheers!


----------



## Ikarios

Quote: 





beftus said:


> 19J6
> 17EW8
> 12AU7
> 12AV7
> ...


 

 Also ArtemF created a 6J6 version using a couple resistors in place of the heater -
  http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/5190#post_6680044


----------



## nullstring

Quote: 





beftus said:


> Tubes you don't need/want or have in adundance could be sold here...


 

 or... given away


----------



## Beftus

Quote: 





ikarios said:


> Also ArtemF created a 6J6 version using a couple resistors in place of the heater -  http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/5190#post_6680044


 
   

 You are generating a hot of heat and need a power supply capable of delivering much more current to make it work though. http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/2145#post_5384865


----------



## Ikarios

okay, I'm too excited - I can't keep it in anymore. here's a quick teaser shot 
	

	
	
		
		

		
		
	


	




 hopefully I should be finished with the rest of the connections later this afternoon and can take real pics tonight.


----------



## the_equalizer

Quote: 





ikarios said:


> okay, I'm too excited - I can't keep it in anymore. here's a quick teaser shot
> 
> 
> 
> ...


 
  Wow !   Looks *really* nice and professional. I'm looking forward to seeing those pics tonight !


----------



## Ikarios

Ah, crap - was all excited to get everything all set up and working, and when I plugged in the power and flipped the switch - nothing. I disconnected everything and poked around with the multimeter. In my haste to case the thing up, I shorted my mosfets to ground. I guess I didn't seat my shoulder washer correctly (I mounted my mosfets the same way TomB did in his PCB build), and the metal tab on the mosfet (drain) must be touching the screw, which is in turn touching the case/ground. Are my mosfets fried, or can I just fix up the short and have everything work magically?
   
  EDIT: did some more exploring regarding my mosfets.
   
  I switched around the nut and the screw head (i.e. screwing UP from the inside) and covered the screw threads with teflon tape, ensuring that it would not cause a short to ground, and that the shoulder washer was in place. upon flipping the power switch, a huge spark emits from somewhere on the back panel. needless to say I didn't want to find out exactly where this spark was coming from.
   
  I unmounted the mosfets and let them hang in midair, and turned on the amp for a few seconds - it appears to work fine, the LEDs light up, the mosfets get hot, and no spark. this ensures that I did not knock another part out of place and cause another short.
   
  So this means that there is a problem with the way I've mounted the mosfets. However, I'm not sure what part of the setup is causing a short. I'm going to leave this alone tonight and hope that I can find 4-40 plastic screws at work tomorrow. in the meantime, does anyone have any ideas?
   
  Thanks for your help!


----------



## nullstring

You should've used your multimeter to see whether or not your mosfets were shorted to ground in the first place..
   
  You don't need to turn it on to figure that out >_>


----------



## the_equalizer

Did you use a thermal Bergquist pad between the MOSFET tab and the case ?


----------



## jamesbobo007

Aflac, I am thinking like Equalizer, that your not using an insulator. The back of the MOSFET can not be grounded ! and if your not using a thermal pad its grounding out thru the heatsink.
  Here is some info that might help ?
http://www.aavidthermalloy.com/products/standard/access/kits.shtml
  If you dont have these, you'll need to get them, Radio Shack has them if your in a hurry.
  Also, if you can make sure the heatsink is not grounded, you can go ahead and test the amp.


----------



## tomb

Just an FYI, but if the shoulder washer is used properly, it completely insulates the screw from the MOSFET's metal tab.  It doesn't matter whether the screw touches the heat sink or not (it will).
   
  We discussed this in a PM, but it bears repeating - there are warnings in the SSMH build thread and on the SSMH website about torquing down too much on the Bergquist pad.  The MOSFET tab can slice right through the Bergquist pad if tightened too much.  You just need to make certain that the assembly is snug and that the lock washer has been compressed.  The Bergquist pad itself will turn to almost a flowable liquid under heat and provides all the thermal contact that's necessary for optimum heat sink conduction with the MOSFET.  Note that if your MOSFET is torqued itself in how it's soldered into the circuit, that could cause the edges of the metal tab to cut into the Bergquist pad, regardless of how gingerly you tighten the assembly.
   
  Despite all the verbiage above, this shouldn't be a difficult task.  Only one or two builders ever had trouble with cutting into the Bergquist pad over scores of builds.  If the pads are already torn up, there's nothing wrong with simply slipping a mica insulating pad right in there and torquing down on it.


----------



## Ikarios

Thanks for the help. I didn't think I had cut through the bergquist pads in the first place, I didn't tighten them any more than I thought it would take to secure the mosfet in place. There must've been something wrong with my mounting methods (both the normal shoulder washer assembly and the teflon-wrapped screw method), because I replaced the whole thing with a plastic screw coming up from the bottom and a metal nut from the top, and I don't see a short anymore.
   
  How hot do the mosfets get during normal operation? maybe 60-70C? I need to ensure that these plastic screws don't melt or something.
   
  Also, are my mosfets okay even after shorting them to ground and turning the amp on? I did get two extras in case this happened, it would just be easier to replace everything at once if the current ones are shot.


----------



## tomb

MOSFETs are pretty tough and they like to run hot.70-80 deg.C. would not be a concern, IMHO - at least from the perspective of the MOSFETs.  I doubt that shorting one out would've caused much damage either, unless it got too hot.
   
  EDIT: I'm still a bit concerned with your use of the shoulder washer.  As I said, used properly, it completely insulates the metal tab from any part of the screw. So, it shouldn't matter if the screw is metal and it touches anything else.
   
  As far as plastic screws, I would definitely be concerned with those at the temps we're talking about.  Most plastic screws are nylon, I believe, and at the very least will experience long-term creep (or even in the short term).  So, it'll be an accident waiting to happen perhaps.  That's one reason I go to an extra effort and expense to get the genuine Aavid glass-filled polysulfide shoulder washers.  Most TO-220 mounting kits have a very cheap nylon shoulder washer that won't stand up very well to heat - kind of cross-purposed, but I guess they try to keep those kits pretty cheap.


----------



## the_equalizer

I agree with TomB. The shoulder washer completely isolates the tab from the case. I think it's time you show us a couple high-res pics from your amp's innards


----------



## Ikarios

Well, there is definitely another issue in my amp aside from my mosfets. even with the plastic screws added, something causing a huge spark as I turn the amp on. The LEDs still light up, so I don't think it's the mosfets that are shorting (initially when the mosfets were shorted, the LEDs didn't turn on). I searched for "spark" in the thread but didn't find anything enlightening.
   
  EDIT 2: I disconnected the mosfets again, let them hang, and turned on the amp - no spark. I guess it really is an issue with my mosfet mounting. I suspect it has something to do with the hole I drilled for the mounting of the mosfet. I sized it for slightly larger than a 4-40 screw, but the mosfet/Bergquist pad hole is larger than that. The holes in my top panel are not the cleanest, and I had a number of burrs with the smaller holes. There might be a small bump at the edge of the hole that is coming up and contacting the mosfet flange. Guess i'll have to run out to Radioshack and pick up some a new thermal pad or two.
   
  I thought I had been meticulous enough in planning the build that I wouldn't have any miswirings. I'm guessing if there is an issue, it is either with one of the panel components or something is shorting as I cram the thing inside the case.
   
  Here are some pics i've taken:
  http://picasaweb.google.com/submergence/SSMHTroubleshooting?authkey=Gv1sRgCPnjg6DLuZLykAE#
  I've taken some pics of my general wiring, as well as pre-casing pics of the real guts of the amp. I've added a lot of crap in the panel components, though, so the wiring gets very confusing very quickly. I also used solid core 22awg wire, so things stay put, but on the flip side are difficult to move.
   
  As for my Ground - I was originally going to use a large copper plate as ground and solder all my ground connections to that, but after I cased everything up it quickly became evident that I wouldn't have much space for the copper, so I opted to use a star ground and just soldered all my ground wires (ALL of them - LEDs, output jack, pot, power, input, etc) together (black).
   
  Red wires are the right channel, white wires are the left channel. blue wires are directly off of power, green wires are either my DAC outputs or LEDs.
   
  The reason my amp is such a snake's nest is due to all the extras i've stuffed in there - DAC power, DAC output, DAC LED, two tube LEDs, input selector from RCAs, and a gain switch. I also left all of my leads a good bit longer than necessary should I have to cut something off and redo a connection. I put heatshrink over just about every exposed joint, so it's unlikely that one part is shorting against another part.
   
  EDIT: okay, I turned on the amp ensuring that no exposed metal was touching another part of exposed metal. The sparking is coming from the back panel itself - generally from the screw holes, or from the nicks in the anodizing of the back panel. I think this points to a grounding issue, as I think the only part that touches the case metal is the ground (outside) connection of my DC jack. Is that right?


----------



## Ikarios

Anyone know where I can get solid thermal pads B&M (read: immediately)? Radioshack's website shows they have some type of thermal pad, but it shows as web-only. I'm hoping a place like Best Buy carries thermal pads for GPU ramsinks, but I doubt it...


----------



## tomb

Quote: 





ikarios said:


> Anyone know where I can get solid thermal pads B&M (read: immediately)? Radioshack's website shows they have some type of thermal pad, but it shows as web-only. I'm hoping a place like Best Buy carries thermal pads for GPU ramsinks, but I doubt it...


 

 Radio Shack should have them in their small parts bins - at least the TO-220 mounting kits.  You'll probably have to buy one of those.  Even if you go to an electronics supplier like Mouser/DigiKey/et al, you'll have to purchase mica insulators in multi-packs.
   
  Best Buy is not going to have anything like this.  Fry's will, if you have one of those nearby.


----------



## jamesbobo007

The radio shack near me has them has them, I think most of them will.
http://www.radioshack.com/product/index.jsp?productId=2102859
   
  Also, if your using a conductive thermal paste, you may want to get some plain-jane paste while your there.


----------



## Ikarios

I had to go to two radioshacks to find the mounting kits. The first radioshack I went to (near work) had no idea what they were, and I couldn't find them in-store. Actually, they told me it was an "online only" item. So I got back to work, checked online, and of course - they did show as available at the very store I went to. So I called the store and asked for the catalog number. the person said "hold on, let me go check", then promptly hung up. I called back again, and a different person answered - I asked for the first one, she said "hold on", then put me on hold for five minutes - and promptly hung up. At this point I just gave up.

 Fortunately the radioshack near my house DID have them - exactly two in stock. I asked them if they could keep them on hold for me and they said sure, asked me my name, and put them behind the counter.

 While at work, I expanded the mounting holes slightly - from 1/8" (.125") to... 1/7? (0.140"), and also made sure to deburr the hole from the inside, as per Tomb's advice. When I got home I used some Arctic Silver Ceramique I had left over from a CPU upgrade (non-conductive). It's messy stuff, and harder to spread than I thought! A thin layer on both sides, and some fine working with tweezers and the shoulder washer... everything is in place. Flip the switch... NO SPARK! whoooo (is it bad I expect a massive spark every time I turn on the amp now?).
  
  For posterity, I was going over the thread again last night and I came across this post . I don't know how I didn't catch it the first time around, but it exactly described my problem.
   
  Some quick thoughts until I can get to my nicer camera and attach my real volume knob.
       - my tube LED switch doesn't really make much of an impact. I use 4.3kohm and 2.4kohm resistors (each one feeding both LEDs) connected to the switch. However, there isn't much of a brightness difference. Next time I open my amp and do some surgery I think I'll try to get the LEDs at 3mA and 10mA.
       - tomb's "sea-green" LEDs are more "green" than "sea"... his picture is deceptive! 
	

	
	
		
		

		
			





 I want my money back.
       - For better or for worse, the tube heaters are very dim; there's only a tiny hint of a glow at the very top of the tube. I can't see it unless I turn out the lights and turn the tube LEDs off.
       - both heatsinks and tubes get nice and toasty, hot enough that I wouldn't really want to hold either for longer than a few seconds. I'll see if I can't find a temp probe somewhere in the lab to get hard numbers. EDIT: after about an hour of on time, the entire amp gets pretty toasty. I think I'll have to put finding that thermo higher up on my priority list. EDIT2: a surface temp probe tells me the temp is around 40-45C, but I don't believe it - I would say it felt closer to 50 or even 60 C. An 80C oven did not feel that much hotter than my case. I'm a little concerned about running this thing for long periods of time...
       - my diode protection LEDs flash nicely when I turn on and off the amp... and with headphones connected, there's still a rather unfriendly thump, but only when turning the amp off. I guess I'll still be taking precautions when turning the amp on and off.
       - my gain switch does not do a whole lot. I have it switching between 50k and 150k input resistors, along with a 50k amp. I'd say at the top end of volume, there's only about a 20% difference between the two. This is with low-impedance headphones, though, so I don't know how it reacts to, say, Sennheisers or Beyers. I hope to find out soon 
	

	
	
		
		

		
		
	


	



       - perhaps related to my gain switch, hiss becomes rather noticeable at about the 3'o'clock position for my 150kohms (low gain?) and maybe 1:30 for my 50k (high gain?). This is too bad, because the whole reason for the gain switch was to use more of the pot... oh well.
       - is it just me, or is the pot really cheap? I didn't think i was putting very much stress on it and when I looked last night, the wiper pin had somehow detached itself from the pot. The whole pin! I thought it was a bad solder job at first, but I noticed the heatshrink was still on, and the end of the wire didn't look like a real wire. I put a large blob of solder here to hopefully prevent it from happening again. Just a note for people in the future, especially if you're using solid core wire - be careful with the panel components!
  I think that's all for now. Back to the music!


----------



## Beftus

Quote: 





ikarios said:


> For posterity, I was going over the thread again last night and I came across this post . I don't know how I didn't catch it the first time around, but it exactly described my problem.


 
   

 Who can blame you? With over 5400 replies in this thread and no sign stopping it's not easy to find these little nuggets.
   
  I wonder how Pete Millett feels about the still growing popularity of his design.


----------



## Ikarios

The rest of the pics (50 decent ones all told) are here:
   
  http://picasaweb.google.com/submergence/StarvingStudentMillettHybridSSMH?feat=directlink
   
  I haven't done a serious critique of the thing (and I probably won't until I get back to my desktop and proper desk at school), but it sounds quite good. I also noticed that my tube LED pics are the same color as TomBs - very deceptive! This must be the LED's version of bait-and-switch. They look okay for now, but I'd really love to swap them out for red ones, and change RLEDs and gain resistors at the same time. But for now - god knows I've spent enough time on this project.
   
  From start to finish, a twinkle in my eye to pushing out Rob Thomas, was about three months total - from reading this thread, to lots and lots of planning, then about a week for construction and casework (which took up most of the time, really - from drawing out exactly where holes would go, measuring inside and outside dimensions of each panel component, lots of pixel nudging in Photoshop until everything fit just perfectly and looked good at the same time, and learning how to use the laser and figuring out how to make the text look like it wasn't spray-painted on). Speaking of the laser, the engraving on the front, back, and bottom panels was done with a VersaLaser engraver we have at work. My boss mentioned it, and I figured if I have access to cool tools, I may as well utilize them. I personally think this finishing touch is what really makes this amp my baby - not the hours and hours of hard and painstaking work, the many schematic interpretations and placement maps I drew, having to carry this thing gingerly in my backpack to and from work every day for two weeks, the hours I spent making sure the holes I drilled with the drill press were EXACTLY where they needed to be, the high I got from the solder fumes, and the stupid MOSFET grounding issue I had. But all of these things is what makes me really proud to be a fath-... er, a DIYer.
   
  I'm still a little concerned about the heat this thing generates, though - I'll have to hit it with an IR gun when I get back to work to find out what the real surface temps are. Until then... I'll be testing to see if this amp can play music 24/7, and how long I can listen to it until my ears start to bleed!


----------



## wiisus

Holy ****!  That looks amazing!  Congrats, sir.


----------



## tomb

Yes, very nice work!  The laser etching adds a professional touch.
   
  About your comments on the "ocean green" LED's - it seems like changing to red is a fairly radical departure from that.
	

	
	
		
		

		
		
	


	




  In any event, the Angstroms are clearly specified (5000):
http://beezar.com/oscommerce2/catalog/product_info.php?cPath=39&products_id=114
  There's no attempt at exaggerating the color description.  It comes straight from the supplier.  Plus, anyone can look up that value of Angstroms on a color chart if there's any doubt.  Generally speaking, blue light is considered as wavelengths from 4500 to 5000 Angstroms, whereas green goes from about 5000 to 5500 Angstroms.  There are differences in those bandwidths, depending on which source you reference - some say blue is 4500 to 4900 Angstroms and green from 4900 to 5600.  In either one, though, it's pretty clear that the LED in question is much closer to the blue side of green, hence "ocean green."


----------



## jdkJake

Color and color names are in the eye of the beholder. If you do not believe that, walk into any paint store.  
   
  I think it looks nice. Certainly more interesting than Red. Red is so overdone.


----------



## livewire

Well here it is.
  I've named it "The Kryptonite Supercharger".
  (It will have green LED's under the base and around the phone jack in the future)
   
  No problems at all with this PTP build, it worked flawlessly from the first time I plugged it in.
  No static hiss, no hum, no microphonics. It also has pretty good channel matching.
  Of course I stand on the shoulders of those who have labored hard through the myriad
  of problems encountered and solved, I was able to avoid them. (after reading 360+ pages!)
   
  I used a variation of the star ground that I call "the bar ground".
  It is basically a 2 inch long piece of 12 gauge copper wire strung between two terminal strips.
  The aluminum case is isolated from all ground points except where the terminal strips are bolted.
  Towards the end of construction I was running out of ground tie points, so it is a little messy
  underneath the chassis with jumper wires running over others. 
   
  Lastly, I want to thank all of the principles who contributed their knowledge and time to this project.
  Thank you Mr. pmillet for giving this elegant design to the world, thank you Mr. tomb,
  thank you Mr. dsavitsk, thank you Mr. n_maher and thank you to the_equalizer who
  became quite the expert towards the end of this thread with his tube rolling mods.


----------



## the_equalizer

@Aflac and @livewire: 
   
     Great job on both your builds, they look fantastic !    I really dig the copper pipe and radiator in livewire's amp and I'm impressed with the  hi-tech look of Aflac's panels and lighted tubes. 
   
  I hope you enjoy using your amps as much as you evidently enjoyed putting them together. Well done gentlemen !


----------



## hellomoto

Hello,
   
  I tried my SSMH today, I first only plugged the Power Jack, with no source or headphone. All was working okay: the two tybes were glowing, with the same brightness, i let it like this for around two minutes, then, I plugged an old walkman, and a cheap per of earphones, I couldn't hear any sound, I then hear and saw a spark who was, I think, coming from the power jack, and the tubes started to unglow, and i shut it down. I opened it, tried to debug but all looked fine, i verified some opened wire, and put some heatshrink on it, just in case, I plugged th power jack, i heard and saw again the spark, and immediatly shut it down, there was no glowing tube.
  
  Do you know what can be my problem? How can I find out by myself what it is? Some tests to do?

 I'm husing a metal Hammond Case, maybe this is part of the problem? I used a blank PCB platform, i don't know if I had to solder a wire between it and the case, so I didn't, indeed, i used a file to remove the black paint, so my RCA jacks are also grounded by the case.
   
  Thanks for your help!
   
  Antoine


----------



## Beftus

Did you insulate the mosfets from the casing? The metal mosfet tab must not be connected to ground! Check if there's continuety between the tabs and the metal casing. Did you use an insulating washer when mounting the mosfets to the heatsinks?
   
   
  Do not use the metal casing as a ground conductor. Use a wire for grounding. Only connect the metal casing to ground at the power input.


----------



## hellomoto

Hi Beftus,
   
  I think you just found out what my problem was... I used a Bergquist pad, from Beezar and thought the metal tab were insulated from the casing...
   
  I used the kit from Beezar, and mounted it as shown here (http://www.diyforums.org/SSMH/SSMHheatsink.php), and I used the kit wo shoulder washer... I now understand the problem... Okay, first DIY project, I learn ^^
   
  Thanks for your help Beftus, I should now be able to make it work! I guess my mofsets are dead now? Is there any way to control them? Are there other parts that could have burnt at the same time, and again a way to control them?

  
  Quote: 





beftus said:


> Do not use the metal casing as a ground conductor. Use a wire for grounding. Only connect the metal casing to ground at the power input.


 

 I just used the metal case as ground for my RCA, should I insolate them? I have the propers plastic rings, so it no big deal: what's the best solution?
   
  About the power input, if I understand right, I just have to solder a second wire to the ground pin, and solder it to the case, using a file to remove a bit of black paint, and solder it there?
   
  Thank you so much for your help, I really appreciate it!
   
  Antoine


----------



## Beftus

Using a metal case as a ground conductor is to be avoided at all times. The ground can take an unpredictable path which can result in hum. The best method is to attach all grounds to a single point (star ground). From the star ground run a single wire to the metal casing (yes, remove some paint first). This way the metal casing acts as a Faraday cage and keeps out noise and interference.
   
  Take a look at this bit. It's from the lower left corner of Pete Millett's original Starving Student. What you see is the single connection from ground to the metal casing. 
   
   
   
  As for the mosfets, I would mount them properly and then fire up the amp again. If the heatsinks get warm first and then too hot to touch for long, they're OK and you turned your Sparkling Student into a Starving Student 
	

	
	
		
		

		
			





. If not replace them with new ones. IRF510's are cheap. I don't think other parts got killed-in-action. Resistors and film caps are likely still OK, if the electrolytics appear normal they should be fine. Tubes are probably fine too.
   
  If all goes well during power-up, check DC-offset @ left and right channel first! Measure between out-gnd & out-left and out-gnd & out-right. A reading of several _milli_volts is OK. Then plugin a cheap set of headphones to check sound. Good luck Antoine!


----------



## Ikarios

hellomoto,
   
  If you go back and reread a couple of my posts from my own troubleshooting you'll see that I had the exact same issue you did. Your mosfets should be fine, as long as the only problem was a short from the drain tab to ground, and not a miswire of the mosfet (which would be much more likely to kill it).
   
  as for ground - it's very difficult to isolate the RCAs from ground, even with the isolation washers - the metal body of the RCA is quite likely to touch the inside of the hole anyway. This is evidently not an issue, because if you go and read TomB's tutorials on assembly, you'll notice he omitted the inside isolation washers, which means that at least two components are touching the back panel - the DC jack and the RCA jacks.
   
  Personally, I'm using a star ground, where I have wires from every ground connection on the entire schematic join together at one point in one big soldered blob. I don't think I have any hum issues - maybe a little higher noise floor than i'd like, but not hum-like...


----------



## hellomoto

Thank you very much Beftus and Aflac (your MSSH looks really amazing!!!),I hope everything will be fixed soon, i'll order insulated washers asap, i'm pretty confident, maybe shoudln't i ^^!
   
  Thanks again!
   
  Bye
   
  Antoine


----------



## Ikarios

Quote: 





hellomoto said:


> Thank you very much Beftus and Aflac (your MSSH looks really amazing!!!),I hope everything will be fixed soon, i'll order insulated washers asap, i'm pretty confident, maybe shoudln't i ^^!
> 
> Thanks again!
> 
> ...


 

 Don't worry about the insulation washers - TomB just uses them for cosmetic reasons (when you tighten the nut on the RCA, it's quite likely to scratch the finish of the back plate. the isolation washer helps stop that, but a regular washer will work just fine too. it also depends on your type of RCA jack. As far as I know it shouldn't make a difference if your RCA grounds touch the back plate.


----------



## hellomoto

Hi,
   
  I was talking about insulation washers for the mofsets lol!
   
  Oh, a last question, should I also solder a second wire from the ground pin of the power jack to the case, or the one going from the pin to the blanck PCB board is enough?
   
  Thanks
   
  Antoine


----------



## Ikarios

Quote: 





hellomoto said:


> Hi,
> 
> I was talking about insulation washers for the mofsets lol!
> 
> ...


 
  Oops! yes, definitely get mosfet insulators. In addition, make sure to deburr the mounting hole you're using - this is probably what caused my problem. You can use mica insulators - which Radioshack carries - and use thermal grease on both sides of the insulator, or if you're ordering online, use a sil-pad or a Bergquist pad.
   
  I would connect your DC power ground to your common ground (in my case, a star ground), just to not cause any complications, unless you plan on connecting your star ground to the back panel - in which case it wouldn't make much of a difference. I'm not too sure of how your case/grounds are set up so it's a little hard to advise here.


----------



## livewire

Dang! I've been listening to my SS for a week now,
  and all I can say is WOW! Best $50 bucks I've ever spent.
  This little tuber has opened up a whole new dimension of sound for me.
  Listening to Lady Gaga "Bad Romance".
  Not exactly audiophile music, I dig her wild climatic ranting and
  the synthesizer's spacial separation and clarity is out of this world on this little amp.
   
  Just a n00b bitten by the bug. Had to go out and buy a DAC and some better cans.
  Maybe a Little Dot MKIII is on the way? Poor wallet....


----------



## Secretninja

Hi all, I've been lurking for a while and had this amp in mind.  Read through all 364 pages over the past few weeks, while waiting for some ebay bids to go through.  Finally won a set of 4 12au7 tubes off ebay today for $15 dollars shipped, so I guess it is time to start sourcing parts. I had 1 question, though.
   
  I plan to use one of the stainless steel pans that you see in kitchens that go into hotboxes, over sternos, etc., (my boss said I could have one for free) and had originally planned to just ground everything to it.  After reading that using a separate ground, then grounding it to the case would provide better shielding, I was wondering if a 3-5 inch section of copper pipe would work for this purpose?


----------



## hellomoto

Hello,
   
  I received two insulators washers from Beezar, I mounted them, as showed on DIYForums, bith a Bergquist pad, but there's still conductivity between the mofset and the case... What is the best way to insolate the mofset completely then?
   
  Thanks for your help!
   
  Antoine


----------



## tomb

Quote: 





hellomoto said:


> Hello,
> 
> I received two insulators washers from Beezar, I mounted them, as showed on DIYForums, bith a Bergquist pad, but there's still conductivity between the mofset and the case... What is the best way to insolate the mofset completely then?
> 
> ...


 

 Is it possible that you torqued down too hard on the Bergquist pad and the MOSFET tab cut through to the case?  Also, is the hole de-burred?  You may need to show us a pic, if you can.


----------



## hellomoto

Hello,
   
  I think the Mofsets are isolated from the case. What confused me is that there are conductivity between the mofsets and the case, but this conductivity is still present when the mofset isn't mounted on the case. Is that normal? My build is with a blank cooper board to use as ground, it isn't linked to the case, I didn't suceed in soldering a wire on the case, but the RCA are both linked to the case and to the board, that may emplain this conductivity?
   
  I tried to make it work again, I plugged it in, but nothing happened, no spark, but the tubes were not lighting. Maybe some components get damaged during the first try. Is there a way to verify if a condensator, a tube and a mofset is working, using a DMM?
   
  Thanks for your help guys!


----------



## Ikarios

Quote: 





hellomoto said:


> Hello,
> 
> I think the Mofsets are isolated from the case. What confused me is that there are conductivity between the mofsets and the case, but this conductivity is still present when the mofset isn't mounted on the case. Is that normal? My build is with a blank cooper board to use as ground, it isn't linked to the case, I didn't suceed in soldering a wire on the case, but the RCA are both linked to the case and to the board, that may emplain this conductivity?
> 
> ...


 
  I would check for a short elsewhere. Follow the drain line to the MOSFET and see if you have any other accidental connections. A good macro picture would do us good here, as we may be able to help you spot a problem.


----------



## tomb

Quote: 





ikarios said:


> I would check for a short elsewhere. Follow the drain line to the MOSFET and see if you have any other accidental connections. A good macro picture would do us good here, as we may be able to help you spot a problem.


 

 Agreed.  If the conductivity between the MOSFETs and case still exist when the MOSFET is not even mounted, then the short to ground lies elsewhere in the circuit.


----------



## the_equalizer

Quote: 





secretninja said:


> Hi all, I've been lurking for a while and had this amp in mind.  Read through all 364 pages over the past few weeks, while waiting for some ebay bids to go through.  Finally won a set of 4 12au7 tubes off ebay today for $15 dollars shipped, so I guess it is time to start sourcing parts. I had 1 question, though.
> 
> I plan to use one of the stainless steel pans that you see in kitchens that go into hotboxes, over sternos, etc., (my boss said I could have one for free) and had originally planned to just ground everything to it.  After reading that using a separate ground, then grounding it to the case would provide better shielding, I was wondering if a 3-5 inch section of copper pipe would work for this purpose?


 

 It would do fine, but it might be challenging to solder to it with a regular soldering iron. A 3 - 5 inch section of 'thick' copper wire would also work well as a ground point (that would be called a 'bus' ground) and would be easier to solder to.
   
  So, are you planning to build two amps or just keep the extra 2 tubes as spares?
   
  cheers!


----------



## Secretninja

Thanks for the input.  How thick of copper wire should I use?  I am guessing about 8-12 ga would be sufficient?
   
  The plan is to build an amp right now in the cheapo pan right now, then an attractive wooden enclosed one over thanksgiving or christmas break when I have access to my dad's workshop.  I plan on trying to emulate the look of an old radio, and might end up trying to incorporate a dac.  But, I should probably focus on getting this amp to work first
	

	
	
		
		

		
			





  I have a few cmoys under my belt, and have done a bit of other soldering work, but nothing ptp.  I'll keep you all updated as I go.


----------



## livewire

I believe that 20 to 24 ga solid is recommended for this build.
   
  EDIT:  Above I was referring to the point to point connection wire.
             If you were referring to the ground bus wire, yes 8 to 12 ga will do fine.
             I used a buss wire 2 inches long, 12 ga for mine. It ended up being kind of short
             to accept all of the ground connections. 3 or 4 inches should do it.
             My 30 watt soldering iron really struggled soldering to this buss wire.
             I recommend something around 75 watts for flowing the solder to these connections.


----------



## Ikarios

Most people use 20-22ga wire. I personally used 22ga solid core, which was a pain to work with in a small enclosure with lots of extra wire (the Beezar Hammond, but with a bunch of extra stuff like my gain switch, DAC, input selector). I would stick with 20-22ga stranded.


----------



## the_equalizer

Quote: 





secretninja said:


> Thanks for the input.  How thick of copper wire should I use?  I am guessing about 8-12 ga would be sufficient?
> 
> The plan is to build an amp right now in the cheapo pan right now, then an attractive wooden enclosed one over thanksgiving or christmas break when I have access to my dad's workshop.  I plan on trying to emulate the look of an old radio, and might end up trying to incorporate a dac.  But, I should probably focus on getting this amp to work first
> 
> ...


 
   
  As both livewire and Aflac have commented on wire gauge to use for the ground bus and general wiring, I'll only add that while doing an 'air-wiring' build is feasible (as demonstrated by many builds in this thread) using terminal strips really helps ease P2P wiring and provides support to circuit elements.
   
  Good luck with your builds and let us know how they go !


----------



## hellomoto

Hello,
   
  Here are a few pics I took. Such a mess, I'll try to remove some wire that is useless when I have enough time, next week i should be able to work on it.
   
  http://antoinemoreau1.free.fr/MSSH/
   
  Thanks!
   
  Antoine


----------



## livewire

Antoine,
   
  How does your amp work? Thanks for posting your pics.
  Dont feel bad, the inside of mine doesnt look much better.


----------



## hellomoto

No, I still haven't find what was wrong, and I'm quite busy these weeks, so I still didn't find time to sit and really debug, I should have enought time today!

 Thanks!
   
  Antoine


----------



## nullstring

Hey guys,
   
  My SSMH got damaged when I moved into my into my new apartment.
  Only one tube lights up.
   
  I did some debugging and came up with the following observations.
   

 If you short pin 1 of each mosfet together, both tubes light up
 Therefore, mosfets and tubes are fine.
 If you bypass C2, the tube lights up like a christmas tree. I reflowed C2, didn't help.
   
  Is is possible that the move damaged C2? Does that make any sense at all?
  You'd think a cap would be the last thing to be damaged..
   
  I don't exactly understand the circuit but.. is it possible that the voltage isn't high enough to charge the cap? but, when you short out the cap, it no longer needs to be charged, so a low voltage current activates the transistor.
   
  Any insight would be helpful..


----------



## nikongod

Is pin 1 the drain or source on the mosfet you used?
   
  If its the drain look for where the power supply wire got screwed up.
  If its the source it could be any number of things 
	

	
	
		
		

		
		
	


	




 Do you have good voltage at the gate of the mosfet?


----------



## the_equalizer

EDIT: After reading nikongod's post I needed to clarify that I'm assuming a regular IRF510 / IRF610 MOSFET in which pin 1 is the gate, pin 2 the drain and pin 3 the source; as mentioned in this post from Dec 09.
   
  Since you're talking about C2, and refering to this schematic, I assume it's V1 which doesn't light up.
   
  By your description of your tests it seems to me that pin 1 of MOSFET Q1 is not at it's intended voltage level, which should be ~17 volts for a 12A_7 build and ~24 V for a 19J6 build. Since bypassing C2 makes the MOSFET turn on (which in turn lights up the tube), we can assume R3 is OK. Thus I can only think of R2 and R4 as the culprits, most likely R2.
   
  Check the values of R2 and R4 (off circuit, of course; you can unsolder one end of each to check their values). Check their solder points. Check that the 'upper' (refering to the schematic) end of R2 does indeed sit at ~48V as the schematics point out. Check that the 'lower' end of R4 (again referring to the schematic) does indeed sit at ground ( 0 volts). If those previous conditions are true then the joint of R2, R4 and R3 must be at ~17 V. If this is true and yet the MOSFET does not turn on, then most likely the MOSFET is faulty.
   
  BTW, about C2, it's purpose is precisely to isolate the MOSFETs pin 1 from the DC voltage and current present at the tube plate. Thus if it had somehow failed and became a "completely open circuit" that wouldn't affect the DC biasing of the MOSFET; you'd see the amp light and warm up correctly but no sound would come out of the Q1 channel, since the audio signal would not be able to cross C2 to get from the tube to the MOSFET.
   
  On the other hand, if C2 had failed in other way and became a short circuit, then you'd see the tube light up 'as a Christmas tree'  
	

	
	
		
		

		
		
	


	




  as you yourself saw in your experiments.  That happens because with a shorted C2 the MOSFET gate sits at the DC voltage of the tube plate, ~27 V  if I remember correctly. Thus it's source pin is then forced to be at around 22 volts, which is the voltage that feeds the tube heater: 10 volts higher than it's intended voltage, making it light up brightly.
   
  Since from your description we know that none of these last two things happen, we can pretty safely assume that C2 is OK.
   
  I hope this helps you in understanding the circuit, but more importantly, to get your amp back up and running. 
	

	
	
		
		

		
		
	


	



   
  cheers!


----------



## nullstring

Quote: 





nikongod said:


> Is pin 1 the drain or source on the mosfet you used?
> 
> If its the drain look for where the power supply wire got screwed up.
> If its the source it could be any number of things
> ...


 

 http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif
  Pin 1 there.
   
  Forgive me, I would look up which one it is, but I'm at work currently.
  I really do need to learn the terminology for transistors.


----------



## the_equalizer

Quote: 





nullstring said:


> http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif
> Pin 1 there.
> 
> Forgive me, I would look up which one it is, but I'm at work currently.
> I really do need to learn the terminology for transistors.


 

 Yeah, that's the MOSFET gate pin, the one connected to R3/R9


----------



## nullstring

Hrm,
   
  Thanks the_equalizer.
   
  I think I understand..
  I'll do a few more experiments when I get back home
  I recall that R4 must be working, but I suppose I am not entirely sure about R2.
  Tha


----------



## Secretninja

Ok, after a somewhat crappy week of quizzes and overly involved homework (god I hate tax laws), I have ordered all the parts.  I'm into this thing $55 dollars all told, so hopefully I can get it working properly.
   
  I had a couple silly questions while waiting for the parts to arrive.  In the schematic here http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif , I was somewhat confused.  I know that dots where lines meet indicate a connection, and I know that the jumps added by dsavistsk for the optional parts indicate no connection, but I was wondering about the points where lines cross but no dot appears.  I am assuming that this is just a different way of indicating a no connection cross in the schematic, but just wanted to make sure.  Also, pin 9 (12au7 build) is missing from the schematic.  Is it simply jumped to ground, along with pin 5?


----------



## the_equalizer

Quote: 





secretninja said:


> Ok, after a somewhat crappy week of quizzes and overly involved homework (god I hate tax laws), I have ordered all the parts.  I'm into this thing $55 dollars all told, so hopefully I can get it working properly.
> 
> I had a couple silly questions while waiting for the parts to arrive.  In the schematic here http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif , I was somewhat confused.  I know that dots where lines meet indicate a connection, and I know that the jumps added by dsavistsk for the optional parts indicate no connection, but I was wondering about the points where lines cross but no dot appears.  I am assuming that this is just a different way of indicating a no connection cross in the schematic, but just wanted to make sure.  Also, pin 9 (12au7 build) is missing from the schematic.  Is it simply jumped to ground, along with pin 5?


 
   
  a) Lines crossing with no dot indeed indicate a no connection cross.
   
  b) Pin 9 is not in the schematic because it must NOT be connected to *anything*. That pin is the heater center tap, used when wiring the 12A_7 heater as two independent 6.3 V parallel heaters. In the SSMH the heaters are used in series to look like a single 12.6V heater. Grounding pin 9 will short out one of the heaters and dump ~12 volts into the other one.... not good 
	

	
	
		
		

		
		
	


	



   
  cheers!


----------



## Beftus

My 12AU7 Mk II is alive. Finished it tonight, finally got around to putting it all together. Worked first time. 
   
  some specs:
  aluminium top panel also doubles as a bit of a heatsink
  each triode now has it's own grid stopper resistor
  no cathode resistor bypass caps as I want to try higher gain tubes
  Elna RJH (C1,C6) and Silmic (C3,C5) caps, Silmic's are 50 volt type
  MKP1837's as bypass and interstage caps
  2.5" tall heatsinks (that still get pretty hot compared to 2" tall ones)
   
  Still to do:
  mount blue tube LEDs and wire up two resistors for bright-off-dimmed settings to be operated with a on-off-on switch (right one)
   
  Nasty surprise: a cheap RCA jack spilled it's guts, a stark reminder to buy better quality parts. My Mk I is now missing one RCA jack...
   
  How does it sound? Schweet! Doesn't play as loud as Mk I because it lacks C7 and C8. A picture to prove it happened. 
   

   
  No pics of the wiring inside. Wanna know what it looks like? Imagine a bowl of spaghetti...


----------



## the_equalizer

Nice job, congratulations! 
   
    BTW, what do you mean about not using cathode resistor bypass caps in order to try higher gain tubes?
   
  cheers!


----------



## Beftus

The cathode bypass increases gain, combined with a higher gain tube the overall gain might become too high. Too much gain will limit the volume control to a small arc right at the beginning of the pot travel where the pot has less than ideal tracking.


----------



## the_equalizer

Quote: 





beftus said:


> The cathode bypass increases gain, combined with a higher gain tube the overall gain might become too high. Too much gain will limit the volume control to a small arc right at the beginning of the pot travel where the pot has less than ideal tracking.


 

 Ah, OK, it's about staying out of the volume pot imbalance zone. So what other tubes are you planning to try?
   
  cheers !


----------



## Beftus

I think I'm gonna buy NOS Philips JAN 12AT7WC tubes.  Not too expensive at €9.25 each.


----------



## Ikarios

Is increasing gain all the cathode bypass caps do? i.e. can I remove them with no ill effects? As it stands I can't really turn my amp below 9 o'clock and regularly get into my pot imbalance.


----------



## Beftus

Quote:


ikarios said:


> Is increasing gain all the cathode bypass caps do? i.e. can I remove them with no ill effects? As it stands I can't really turn my amp below 9 o'clock and regularly get into my pot imbalance.


   
  I am not going to explain this because I can't. I did find this however: http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/2115#post_5379295
   
  This too: http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/2385#post_5436249
   
  Please note that Pete Millett didn't include the cathode bypass caps in the original 19J6 version. I can confirm a 12AU7 will happily play without them, just not that loud as with them. Listening now with volume pot @ 3 o'clock, couldn't do that with my Mk I


----------



## the_equalizer

Quote: 





ikarios said:


> Is increasing gain all the cathode bypass caps do? i.e. can I remove them with no ill effects? As it stands I can't really turn my amp below 9 o'clock and regularly get into my pot imbalance.


 

 Yes, that is basically all they do, you can remove them with no ill effects.
   
  If you want a bit more detail...  some people prefer to have them since they do away with the local negative feedback generated by the cathode resistor (negative feedback is taboo to many audiophiles) and stabilize the quiescent point of each triode; others dislike them for the reason that they are in the signal path (capacitors, particularly electrolytics, in the signal path are taboo to many audiophiles); even further others dislike cathode resistor biasing for these previous reasons and use other means of biasing the tube.   In synthesis, it's pretty much a matter of personal preference if you want them there or not 
	

	
	
		
		

		
		
	


	



   
   
  cheers!


----------



## ArtemF

there are simpler ways to cope with high gain/9o'clock pot problem:
  add a resistor in series with your pot and you'll easily go beyond 9 o'clock


----------



## Ikarios

Quote: 





artemf said:


> there are simpler ways to cope with high gain/9o'clock pot problem:
> add a resistor in series with your pot and you'll easily go beyond 9 o'clock
> 
> 
> ...


 

 actually I do have a gain switch installed (50k/150k resistors in line with a 50k pot). It doesn't help too much, plus I'm afraid I'd be bumping the noise floor. it would be easier to snip off a couple capacitors... I'll have to think about this for a while.


----------



## Beftus

You can make the bypass caps switchable too...


----------



## Ikarios

Quote: 





beftus said:


> You can make the bypass caps switchable too...


 

 have you seen my panels? 
	

	
	
		
		

		
		
	


	




 there's like no space to put anything new, unless I wanted two gain switches on my front... I don't have access to my drill press either currently (nor the laser engraver) so it would just be easier to remove them. but you do make an interesting proposition. I guess I could just stuff it inside... I'm not sure if I have space for that, though.
  I think I found a cathode resistor gain calculator here:
  http://www.pentodepress.com/home/amplifier-calculators/cathode-capacitor/
  plugged in my numbers (220uF for cathode bypass cap, 1k for grid resistor, 33k for plate resistor (what is this? whatever it is it doesn't change the numbers too much), and 2.2k for cathode resistor. It says the gain will be about 5.5dB across the board of frequencies. I have no idea what this means in relation to degrees of "turn" on my pot, though. I don't know anything about gain calculations yet.


----------



## the_equalizer

I wouldn't rely very much in that calculator; it's geared towards guitar amplifiers where the tubes are run at some 150 to 200 volts; with the much smaller voltages and currents in the SSMH the situation changes drastically.
   
  Anyway, I think you're making this a bit more complicated than it is 
	

	
	
		
		

		
		
	


	




;  I think you should simply remove the cathode resistor bypass caps and listen if that works for you in sound and volume pot tracking. If you find that for any reason you prefer the amp with the caps connected, you can always get something like these.
   
  Finally, if you're really curious about what the plate resistor does, you can check this page out.
   
  cheers!


----------



## ArtemF

it's interesting... I wonder how it can be that 150K resistor switched in series with 50K pot doesn't help.
  It's 1:4 attenuation.


----------



## calipilot227

I'm debating whether to build this or the CMOY....screw it, I'm doing both! Can't wait to plug my Sennheiser HD280 pros into one of these bad boys!!!


----------



## nullstring

Quote: 





the_equalizer said:


> EDIT: After reading nikongod's post I needed to clarify that I'm assuming a regular IRF510 / IRF610 MOSFET in which pin 1 is the gate, pin 2 the drain and pin 3 the source; as mentioned in this post from Dec 09.
> 
> Since you're talking about C2, and refering to this schematic, I assume it's V1 which doesn't light up.
> 
> ...


 
   
  As it turns out, the resistor connected to the positive voltage was cold soldered (I never reflowed this one, it was the best looking joint on the terminal strip >_<)
  Thanks again for the help.


----------



## the_equalizer

Quote: 





nullstring said:


> As it turns out, the resistor connected to the positive voltage was cold soldered (I never reflowed this one, it was the best looking joint on the terminal strip >_<)
> Thanks again for the help.


 

 No problem! So it was indeed R2. Great to hear you got it back up and running again!
   
  cheers!


----------



## AudioNoob

Is there anyway to get a kit to build a ~100 millett?


----------



## tomb

What's a "100 millett?"


----------



## FallenAngel

SSMH for $100?  Yes, easily possible, buy parts form Mouser, get tubes/sockets elsewhere.


----------



## marcus76

...


----------



## marcus76

Hi there Head-Fi,
 First post, my name is Marcus and i'm from germany, excuse my bad english.

 After reading most of this thread (which took quite some time),
  I decided to go for a build even though some parts got me confused.
  I have some soldering experience and from the many great builds i've seen so far i thought it could be possible for me to do too.
   
  There's only a problem with sourcing the parts here in germany since i don't want the shipping costs to eat up my budget that much by ordering at like 4 to 5 stores. Another problem would be which bom to use for an 12au7 build?
  (Which of the modifications would be useful for my senn hd650 for example?)
  I already checked some online stores, most of them only had some of the parts needed, were to pricey compared to the orig. bom, some parts not available at all, plus i can't decide which comparable parts would fit.
  I'll make a list/bom at the weekend and post it here, maybe someone could check it and tell me if i chose the right parts,
  before i place an order.
   
  btw, already ordered parts are the power supply and some cheap nos tubes for 8 euro a pair.
  I took a look at www.jacmusic.com/nos/ECC82.htm and got me two jan 6189W sylvania.
  Hopefully these will do for my first try.
   
  Thanks in advance for any help/info ,
  Marcus


----------



## livewire

*@ Beftus *- Nice clean looking build you got there!
  And it works without problems? Good feeling, aint it?
  Ha-Ha! I hear you about the bowl of spagetti inside, mine is like that too.
   
*@ marcus76 *- Your english is perfect! No worries there.
  Beftus and the_equalizer are two of the 12AU7 experts around this thread.
  (I'm not, mine is a 19J6 model, I havent taken the time to study other variants.)
  I'm sure they will check in to help with your B.O.M. Good luck!


----------



## the_equalizer

Quote: 





marcus76 said:


> Hi there Head-Fi,
> First post, my name is Marcus and i'm from germany, excuse my bad english.
> 
> After reading most of this thread (which took quite some time),
> ...


 
   
  Those tubes will certainly do fine for your build; you also need to get 9-pin mini tube sockets (like these ones).
   
  As to which BOM to use, I believe there's no published BOM for P2P builds of a 12AU7 amp with Dsavitsk's improvements. You can either build using Pete Millett's original BOM (omit the tubes and tube sockets, naturally) and skip on Dsavitsk's improvements or use the diyforums.org BOM (again, omitting the tubes and tube sockets) and add three or four terminal strips (part number in Pete Millett's original BOM)
   
  Finally, regarding where to source your parts from, I hope some of the builders in the thread that reside in Europe chime in and help you.
   
  Good luck with your build and let us know how it goes; it's always nice hearing that a new SSMH has come to life.
   
  cheers!


----------



## AudioNoob

beezar doesn't sell pcbs/cases anymore, how would I get those?


----------



## Ikarios

Quote: 





audionoob said:


> beezar doesn't sell pcbs/cases anymore, how would I get those?


 

 If you want the original case, look for the Hammond model number. You'll have to drill holes yourself. You can use whatever case you want, but most likely you'll still have to drill holes yourself.
  PCBs have been gone for a while; most builds since 19J6 stock ran out have been 12AU7, and point-to-point air-wired or done on a perfboard. It definitely takes more work, but you learn some more in the process because you basically have to understand the schematic.


----------



## Beftus

Quote:


marcus76 said:


> There's only a problem with sourcing the parts here in germany since i don't want the shipping costs to eat up my budget that much by ordering at like 4 to 5 stores.


   
  Have you tried Conrad.de? I order from Conrad.nl regularly, IME most of the stuff needed can be found @ Conrad. The parts needed to make one is pretty much bog standard stuff. Since German and Dutch Conrad part numbers are identical I can even help you find stuff that's difficult to locate in their catalog.


----------



## Beftus

Quote:


livewire said:


> *@ marcus76 *- Your english is perfect! No worries there.
> Beftus and the_equalizer are two of the 12AU7 experts around this thread.


   
  Thanks for the praise, but I don't consider myself to be an expert. BTW I really like spaghetti


----------



## Secretninja

Well, I got it finished but it doesn't work. One tube lights up, and produces sound, which I guess is a good thing.  It is however, very quiet.  The other tube fails to light up and the mosfet doesn't generate any heat.  Assuming I can figure out where I screwed up and fix the other channel, would removing the 50k resistors I put in between the rca jacks and the pot give it some more volume?
   
  Thanks for any input.
   
  Well, I tried re-flowing all the joints on the side that doesn't work, but no luck.  I'm hoping it isn't a problem where the mosfet is mounted, because that is epoxied in place.  Tomorrow I am going to pick up a piece of protoboard from radio shack and redo it on there.  I have more experience working with through holes, and I can check everything piece by piece.


----------



## the_equalizer

Low volume in the other channel is most likely an indicator of a miswiring in that channel too, if anything the SSMH is too loud, not too quiet. The only recommendation I can give you is to sit down and calmly trace your build against the schematic, wire by wire, pin by pin.
   
  Good luck!


----------



## Secretninja

It is definitely wired correctly, just a bad connection at some point.  I am going to redo the whole thing probably tomorrow, with a little more thought put into the placement of parts and a better grounding system.  I just got a little fidgety once I got all the inputs, outputs, and tube sockets placed into my box and started soldering.  It resulted in a cluster****, and you can't really tell what is going on at all.  It is aggravating, both channels are wired exactly the same as far as I can tell, and only one is working, and that one is very quiet.
   
  On a side note, my landlord was in the apartment to spray for bugs, and asked me if I was making bombs.


----------



## th3bl0b

Hi guys!
   
  I was really pumped to put together the starving student kit... and I finally have like half a year later. Anyhow, I powered it up, it doesn't seem like anything is running, I'm pretty sure the power is working cause I've been probing around and a few sparks on the board went off... (oops!) However, the mosfets don't seem to be heating up and the leds under the tubes are lighting up so I'm fairly certain nothing is going on there. How would you guys suggest probing around because the top plate is in the way of the probing?
   
  Anyhow, I'll keep probing around, but wanted to see if you guys had any suggestions. I used the kit from beezar (which, by the way, thanks to the guys that put it together!). I can snap a few pics when I get home.
   
  Thanks in advance!


----------



## th3bl0b

Sorry for taking so long. I've attached a picture of what my circuit looks like. I think everything is correct.
   
  Thanks for helping me out!


----------



## th3bl0b

Ah! I realized the problem was something that someone else had gone over here. The MOSFETs were somehow shorted to ground so they wouldn't turn on! However, my LEDs don't turn on is that an indication that I wired them up backwards?


----------



## meme

Thought I'd post some pictures of my recent 12AU7 effort.
   
  All resistors are Ohmite carbon composite, capacitors are Vishay axial 'lytics and TAD mustards. Valves are JJs.
   


   
  I've used the Hammond case supplied with the Beezar kit and embellished it with teak from and old box and fancy gold bits.
   

   
  Chuffed that it worked first time with no problems ~ Cheers!


----------



## Beftus

Posh! Well done.


----------



## cobaltmute

Very nice, meme.


----------



## the_equalizer

Quote: 





meme said:


> Thought I'd post some pictures of my recent 12AU7 effort.
> 
> All resistors are Ohmite carbon composite, capacitors are Vishay axial 'lytics and TAD mustards. Valves are JJs.
> 
> ...


 


  Nice looking build! Congratulations!


----------



## meme

Thanks everybody!


----------



## jdkJake

Beautiful work. You should post that on the "Post pics of your build" thread.


----------



## meme

Quote: 





jdkjake said:


> Beautiful work. You should post that on the "Post pics of your build" thread.


 


  Cheers ~ I shall do just that.


----------



## jamesbobo007

Very very nice. Hope she sounds as good as she looks !


----------



## marcus76

hi there,
  lovely @ meme, the gold and teak/black fits perfectly imo!
   
  I didn't even mess with a possible enclosure yet 
	

	
	
		
		

		
			





 need to source the parts first hehe.
  At first I thought about doing something in engineered stone/marble/granite, but regarding the size... almost impossible for me.
  (I work in a small stonemason business, most of the stuff we do is tombstones... , and as we don't have cnc/waterjet...no chance, even drilling would get difficult.. so I'd go for wood or alu too) 
   
  I hooked up a BoM , first part is from Conrad.de as Beftus suggested, second part is from Banzaimusic.com, german store ..
  Might order most parts there , since they got almost everything. Need to check the total tomorrow.
  Maybe you guys could take a look, I made some notes ...
  Here's the link : http://frickel.dezern.at/
  Thanks for looking,
  Marcus


----------



## th3bl0b

Wow that looks great, meme!
   
  So after debugging and fixing the LEDs up - it was just some loose connection. For some reason the left channel is quite a bit softer than the other. I looked at all the connections, but didn't see any connections that weren't soldered completely. I also noticed that when I only had the RCA cable hooked up only to the right channel, there was a ground hum, but when I hooked up the RCA cable only to the left channel, the sound was pretty clean. I'm fairly certain both channels work as well because when I switch the RCA connections inside the box there is sound coming from both RCA connectors.Also, the left channel - which is softer - also has quite a bit of distortion on it. What would you suggest me doing?
   
  Thanks,
  Ben


----------



## the_equalizer

Hi Ben,
   
    Good to hear your making progress with your amp. About your problem, try first swapping the tubes and see if the problem 'follows the tube'.
   
  If it doesn't then check the connections from the RCA jacks to the board, it sounds like one of them might be inverted (ground connected to signal and signal to ground) or not making good contact at the terminal block or the jack.
   
  Good luck!


----------



## intlplby

I was thinking of building Pete's ECC99 SRPP Headphone Amp to drive my K-1000 but the BOM is outside my current budget. I saw that Pete said that this amp was able to drive the K-1000s. I have two questions:
   
  1) Is it worth building this to drive K-1000? It doesn't have to drive the K-1000s perfectly. It just has to drive them well enough to be delightful
   
  2) What modifications are suggested to the original design to make this amp more appropriate for the K-1000?


----------



## Uncle Erik

intlplby said:


> I was thinking of building Pete's ECC99 SRPP Headphone Amp to drive my K-1000 but the BOM is outside my current budget. I saw that Pete said that this amp was able to drive the K-1000s. I have two questions:
> 
> 
> 
> ...





I haven't built this one yet, but I have the parts for it. The biggest problem is getting the output transformers from Sowter in the UK. Sowter is great, but it took something like four to six weeks to get them over here.

 You shouldn't need to mod the design to work better with the K-1000. Millett designed it specifically for the K-1000. You might want to pick around with the out resistors to make it work better with other headphones, though,


----------



## the_equalizer

Quote: 





> Originally Posted by *intlplby* /img/forum/go_quote.gif
> 
> SNIP
> I saw that Pete said that this amp was able to drive the K-1000s. I have two questions:
> SNIP


 
   
   
  Uncle Erik, I believe when intlbpy said the above he was referring to the "Starving Student"  
	

	
	
		
		

		
			





.
   
  Unfortunately I've never even listened to the K-1000s, much less tried them with my SSMH so... someone else would need to chime in here.


----------



## intlplby

Yeah, I was referring to mods to the Starving Student. Sorry for not being clear. Those transformers are like ~130 each and you need more than one of them so that makes the SRPP much more expensive. 
   
  I saw that Pete said that he tried driving the K-1000 with the Starving Student and that it performed very well. I wanted to see if it is a worthwhile build for the K-1000. 
   
  I currently run my K-1000 off my Consonance Cyber-800 Power Amps, but it's a huge pain to disconnect the speakers to then connect the K-1000s and vice versa. Because of this I use the K-1000s a lot less. I would like a dedicated amp for the K-1000, but I am cash poor right now as I am currently funding my own startup and need to watch my burn rate.


----------



## Secretninja

Well, I just got done redoing my internal wiring, and have the same problem of a dead left channel.  Pretty sure it is the mosfet, so I'm going to buy another one next time I'm near radioshack.  Here are some pics in the meantime.


----------



## th3bl0b

Thanks for helping me out guys and in particular the_equilizer! I checked the RCA jacks and it was fine. Turns out one of the resistors wasn't completely soldered... I don't know how that happened. I probably overlooked it when I was double checking the board before putting the FETS in. At any rate, a little soldering did the trick and it works now!
   
  I'm now enjoying my amp... and looking for another one to build


----------



## the_equalizer

Quote: 





th3bl0b said:


> Thanks for helping me out guys and in particular the_equilizer! I checked the RCA jacks and it was fine. Turns out one of the resistors wasn't completely soldered... I don't know how that happened. I probably overlooked it when I was double checking the board before putting the FETS in. At any rate, a little soldering did the trick and it works now!
> 
> I'm now enjoying my amp... and looking for another one to build


 
   
   
  Great news, glad you squashed that bug !  Good luck with the next build and, if it's another SSMH, post some pics here.


----------



## hellomoto

Hi!
   
  So, I finally managed to find some time to debug my MSSH. (Again, sorry for my bad English!)
   
  Here it was, one month ago
  - When I first tried to plug it in, the tube glowed nicely and equally, but suddenly it began to sparkle, and the tubes shut down.
  - I then checked the circuit, there was conductivity between the Mofset tab and the case/ground, even when not mounted on the case. I used heatshrink and shoulder washer to assure there was no conductivity between the tab and the case, I'm sure the tab and the screw and washers were not in contact with the case, but still, there was conductivity. I was quite busy then, and I didn't find enough time to take more time to debug, and I let it like this.
   
  Today
  - I verified the circuit, and all seems ok.
  - I put some heatshrink on some opened connections that may short
  - There is no more conductivity between the mofset tab and the case and the ground
  - I tried to plug it in, but the tubes didn't start to glow.
   
  Does that mean that the Mofsets are dead?
  Here are some pictures I took of my wiring, not very clear, I can take other pictures of certain spots if necessary!
  http://antoinemoreau1.free.fr/MSSH/
   
  Thanks!
   
  Antoine


----------



## electrovice

Hello, I am a new poster on this forum.
   
  I had  seen a Starving Student amp at a recent Headphone meet here in Seattle. I researched the amp and thought it would make an interesting project but I was also quite became quite concerned about the lack of 19J6 tubes. Fortunately I was able to find enough cheap tubes at a radio swap meet and that auction place to try the amp.
   
  I used a small stainless steel tray from Goodwill for my amp's chassis. I wired  the amp "point to point" using the standard inexpensive parts from Mouser and salvaged tube sockets. I shamelessly copied Pete Millett's original layout and used the 4 by 6 inch copper ground plane.  The base is made from some scraps of maple that I have had for years.
   
  The amp worked perfectly when I fired it up. It sounds great without a trace of hum. I have only listened to it using a portable Sony CD player for my source and  Sennheiser  HD 414 headphones.  I am very pleased with this amp even with the modest source and old school headphones. I will try the amp soon with better sources and upgraded cans when I get some.
   
  This was a fun build. I will probably try a 17EW8 version of this amp too. I have a nice stash of those tubes. I also have a huge stash of 12AU7 tubes.
   
  A few questions:
   
  What sort of life can one expect with these tubes? I have two spare pairs, will that keep me going for a while?
   
  Is this a final amp or is this a gateway to better amps?
   
  What headphones should I ....? Just kidding
   
  John
   
  John


----------



## Beftus

Nice build!


----------



## akgfan

Is there any hiss or hum on this amp? It is something that bothers me because I always wanted to build headamp with tubes. And this headamp looks good and simple that I am "DIY horny". 
	

	
	
		
		

		
		
	


	




 I want it to be deadly quiet. There is probably no high gain but are tubes quiet in this application?


----------



## tomb

Quote: 





akgfan said:


> Is there any hiss or hum on this amp? It is something that bothers me because I always wanted to build headamp with tubes. And this headamp looks good and simple that I am "DIY horny".
> 
> 
> 
> ...


 
  Built correctly, there is no hum ... period.  The key phrase in that sentence, though, is "built correctly."  Those who have had problems with hum have tried to shortcut things by leaving out a decent ground plane (as in, copper plate).  If you case the amp up without enough metal to provide a decent ground sink, or you snake wires that are so long that the signal is exposed to every interference that exists, then you may have an issue.


----------



## akgfan

OK. And what about hiss? Is there any?
   
  Edit: I'm on page 69 and it looks like there is no hiss if everything is OK. So my only problem would be 19J6 tubes but I could use other and do some modification if it would be posible.


----------



## Secretninja

Well, I finally got around to replacing the mosfet I thought was bad.  Turned out to be the case, as both tubes fired up.  I set it down to go get an rca cable and test for audio, and when I got back everything had gone dark.  I opened up the case and a wire to ground had snapped.  Resoldering the wire, everything was still dead.  I had one spare tube, and tried it out.  It lights up and produces sound.  I guess both tubes that were in got blown by whatever the ground hit as it broke.  I don't mind buying another couple tubes, but I am having the same problem of a very quiet amp.  Will removing the resistors that are right before the pot help with the volume issue?  If not, I may as well save my money on the tubes, because the amp is unusable with the volume it currently produces.


----------



## wiisus

How bright were the tubes?  I had a quiet issue when I first built mine, and the tubes were super bright.  I had resistors mixed up.


----------



## Secretninja

I am not really familiar with tubes, but the one working seems to be about the correct brightness.  Tomorrow I am going to pull those resistors and see if that helps.  If not, I am probably going to be done with it and see if anyone wants it on for sale forums as is.  I am not quite a starving student, but I don't eat quite as well as I would like if you know what I mean.


----------



## hellomoto

Quote: 





hellomoto said:


> Hi!
> 
> So, I finally managed to find some time to debug my MSSH. (Again, sorry for my bad English!)
> 
> ...


 


  Hello,
   
  Do you think my mofsets or my tubes are dead? How could I test them?
   
  Thanks for your help!
   
  Antoine


----------



## ArtemF

the correct way to test the circuit is to measure the voltages in key points.
  The cathode voltage should be >0 and less than a couple of volts,
  the grid voltage in this scheme must be equal to zero, and the anode voltage
  should be less than 48 V but greater than 40 (my guess, I don't have a specs
  sheet at the moment so I can't calculate the working I and U, but there should
  be some common sense in the analysis - the filaments must glow,
  the accelerating voltage must be applied, the grid must regulate the flow).


----------



## hellomoto

Thanks for your answer!
   
  When you talk about cathode/anode foltage, it's the voltage between the anode or the cathode of the tube, and the ground? And what's grid voltage?
   
  If my filaments don't glow, I guess I won't have the desired measures. I'll order some mofsets and replace them, to see if it's the problem.
   
  Thanks!
   
  Antoine


----------



## ArtemF

all voltages are measured with respect to the ground.
   
  The grid voltage in this connection should be = 0 (there's no voltage source
  at the potentiometer and the grid current must be negligible).


----------



## ArtemF

if the filaments don't glow that means either burnt filaments (measure them with Ohmmeter when the
  tubes are out of the sockets) or burnt mosfets or closed mosfets.


----------



## hellomoto

Thanks ArtemF for your help, that should help me figure out what the problem is!
   
  Antoine


----------



## tabacaru

Does anyone know if it's possible to use IRF840 mosfets instead of the IRF510? I only have one IRF510 lying around and don't want to order any right at the moment!
   
  Thanks!


----------



## yellowjeep

The IRF510s are actually available at radio shack, at least the one by me. They had 2 of them as of about 10 min ago.


----------



## chew

Hi,
   
  I'm new to this forum, and I've just finished to build my own Starving Student amp.
   
  I now have a problem with the sound level. Even with the potentiometer set to the maximum, the sound coming from my AKG 141 isn't loud at all. Though the AKG is only a 50ohm impedance can. I tried with a Audio Technica ES7 rated at 32ohm and it's a little bit better but not sufficient.
   
  I checked voltages, and some seems quite low. I get only 10V at the heater whereas it is written 12v on the schematics, and 13.5V at R2/R3/R4, but I've read in the thread that I have to get 17V there.
   
  These voltages are the same on both channels.
   
  I can see that the tubes are lightning but it's not as bright as I've seen on some pictures.
   
  Does it mean some values of my components aren't correct ? 
   
  Here's my BOM :
   
  Thanks


----------



## Beftus

Add the cathode bypass capacitors (C7,C8). It will increase gain.


----------



## the_equalizer

Quote: 





chew said:


> Hi,
> 
> I'm new to this forum, and I've just finished to build my own Starving Student amp.
> 
> ...


 

  
  I doubt bypass caps will help, the voltage at the MOSFET gate is too low. The low heater voltage is a consequence of the gate voltage being low. What's the voltage with respect to ground at both ends of R13 ?  it should be ~48 at the end connecting to C1 and ~45 at the other end.
   
  If those voltages are OK, I'd then unsolder one end of R2, R3, R4 each and measure their values. Same thing with the other channel.
   
  cheers!


----------



## ouldsmobile

thinking about trying this project out. would it work good for PC gaming?


----------



## Ikarios

Quote: 





ouldsmobile said:


> thinking about trying this project out. would it work good for PC gaming?


 


  I use mine with K701s for gaming but it mostly depends on what kind of headphones you have. The effect of the amp is miniscule compared to the effect of the headphones.


----------



## marcus76

Hi there...
  Oh well, just finished soldering all the parts together, what a mess!!
  Thought using a Star Ground like this  http://mark.rehorst.com/LM3886_amp/amps_chips_and_star_ground.jpg
  would be a good idea.. It wasn't. Loads of extra wire... 
	

	
	
		
		

		
			




   
  Would it be a bad idea if I used a solid copper plate (1,5mm thick, found that @ work) , connected to the Star Ground
  and this plate to the Case or would a strip of it fit ?
   
  btw, I went a little to generous with the wire lenght which resulted in some nice noodle salad, guess that's ok? 
  But i got spare parts...if anything's not working (and i bet there is) I have plenty of lenght to cut out and resolder 
	

	
	
		
		

		
		
	


	



   
  Cheers


----------



## Ikarios

Quote: 





marcus76 said:


> Hi there...
> Oh well, just finished soldering all the parts together, what a mess!!
> Thought using a Star Ground like this  http://mark.rehorst.com/LM3886_amp/amps_chips_and_star_ground.jpg
> would be a good idea.. It wasn't. Loads of extra wire...
> ...


 

 the more area for ground, the better. you can attach your star ground to a copper plate, then to the case, but try not to make too many paths - things can go bad if ground takes unpredictable paths. just connect at one point, and the plate to the case at one point.
   
  I did the same thing as you and used lots of extra wire; it may cause some extra interference but it shouldn't be a really big problem.


----------



## CaptHowie

I haven't been on this thread in a long while, but I've finally got time to put a Starving Student together, but I've become stuck with a few things in planning. Firstly, I'm building a point-to-point 19J6-based Starving Student. I brought the tubes when I was suppose to build it last year, but hence, as a Year 12 student, I was stuck down with school. My current BOM is here (Excel format). Here are the things I'm having problems with:
   
  1. R16/R17 on the BOM: You can choose between a 50K resistor, and a 100K "low-gain" resistor. If I was to use a 50K pot, which would be the best one to choose when using a pair of Grado SR-60's and Ultimate Ears Triple.Fi 10's (both rated at 32ohms impedance)?
  2. Regarding the pot, heatsink and heatsink mounting kit, I have had trouble finding them. Does Farnell/Element14 stock them, and if so, could someone please supply a catalog code?
  3. Generally, can you use IEM's with the Starving Student? I remember reading early in the thread that someone was advising against using them.
   
  I'm pretty sure the BOM parts are right, but I am still looking for a few specific parts, such as the pot, heatsink and the TO-220 mounting kit which I haven't been able to find. Is there anything else I need to know before I start ordering the parts?


----------



## howc

#1 : I thought you have to match your pot resistance with R16/R17 resistance. so if you were to use 50k ohm pot, you have to use 50k ohm resistor for R16/R17. As for your headphone impedance, i am not really sure about this but low impedance phone needs high gain. I would say 10k ohm pot and 10k R16/R17 would be good. 
   
  #3 : from what i have gathered from this thread, starving student will have some "popping" sound during power up and shut down ( with headphone plug in). headphone can withstand such "popping" but it is not advisable so i would say IEM is not really suitable because IEM might not be able to take the "popping"
   
  i am thinking of build this amp as well and i am sourcing for parts as well. Need some advice on these parts,
   
10k stereo pot will this work? 
   
  is there any difference between metal film resistor and carbon film resistor? can i substitute the resistor with a similar ohm but rated at 1W? 
   
  i am using a D2000 headphone (25 ohm) so should i substitute the nichicon muse es to a 470uf? it helps with bass response right? or is it the other way round. 
   
  Thanks.


----------



## Beftus

Quote: 





howc said:


> #3 : from what i have gathered from this thread, starving student will have some "popping" sound during power up and shut down ( with headphone plug in). headphone can withstand such "popping" but it is not advisable so i would say IEM is not really suitable because IEM might not be able to take the "popping"
> 
> i am thinking of build this amp as well and i am sourcing for parts as well. Need some advice on these parts,
> 
> ...


 


  Plug in after powering up, unplug before powering down.
   
  That pot will work but you will need two (one for left channel, one for right). You can also buy a stereo pot.
   
  Carbon film or metal film will both do. Some people prefer carbon, some metal film. YMMV. Using 1W resistors is not a problem. Output caps of 470uF will do fine, large output caps help with bass response. Build it per spec first, then start tinkering with it or build a second one differently. Enjoy.


----------



## hellomoto

Hello,
   
  I have a question about the MSSH schematic, especially where the red circle is. In my build, I have all the four wires directly connected to the pin of the switch, one to each mofset, one to C1, and one to R13. Is that right? The  schematic makes a differences between the wires, I mean, there are two distinct points, and I was wondering if the right wiring was switch -> wire divided in two, one to C1, the other one to both R13 and the mofsets.
   
  I hope you'll get me, it's hard to find the words!
   
  Thanks you very much for your help!!!
   
  Antoine


----------



## Avro_Arrow

Using separate connecting points in the schematic like that is good drawing
  practice and done to prevent confusion but does not mean those points
  need to be connected separately in reality. What you did was fine.
  
  Quote: 





hellomoto said:


> Hello,
> 
> I have a question about the MSSH schematic, especially where the red circle is. In my build, I have all the four wires directly connected to the pin of the switch, one to each mofset, one to C1, and one to R13. Is that right? The  schematic makes a differences between the wires, I mean, there are two distinct points, and I was wondering if the right wiring was switch -> wire divided in two, one to C1, the other one to both R13 and the mofsets.
> 
> ...


----------



## hellomoto

Thank you very much!
   
  Antoine


----------



## howc

hi, can i replace 2.5mm Metal Socket, 100VDC 2A with this?
   
  If not is there other choice other than mouser? i have search farnell but highest rating is at 16V.
   
  Thanks.


----------



## revolink24

Quote: 





howc said:


> #1 : I thought you have to match your pot resistance with R16/R17 resistance. so if you were to use 50k ohm pot, you have to use 50k ohm resistor for R16/R17. As for your headphone impedance, i am not really sure about this but low impedance phone needs high gain. I would say 10k ohm pot and 10k R16/R17 would be good.
> 
> #3 : from what i have gathered from this thread, starving student will have some "popping" sound during power up and shut down ( with headphone plug in). headphone can withstand such "popping" but it is not advisable so i would say IEM is not really suitable because IEM might not be able to take the "popping"
> 
> ...


 

  
  I don't see why it would be necessary to match them. Can anyone enlighten me on this?


----------



## howc

the BOM which is created from Dsavitsk stated that the ohm for the stereo pot should be adjusted according to R16/R17. 
   
  i am not really sure why as well but maybe this gives a smoother volume control ?


----------



## tomb

There is no need to match the input resistors to the same value as the pot.  What you're trying to do with the input resistors is "push" the active band of the pot into something with a reasonable travel over the volume range.  The gain of the tubes is much too high for most headphones, so that if you build the amp without those input resistors, your total volume range - between not hearing and having your eardrums blown out - is about 1/4 turn or less.
   
  A great many of us used input resistors that are 2X the value of the pot impedance.  It just depends on the sensitivity of your headphones.  There is no hard and fast rule - either 1X the value of the pot impedance, 2X, or there were some builders who went all the way to 3X.  (Note that there were some who used -0- input resistors, because of hard-to-drive vintage orthos.)
   
  Pot impedance, as a general rule, has nothing to do with the gain.  Generally speaking, 100K introduces more noise, while 10K may mean the source will have trouble driving the amp.  It also presents a much lower input impedance to the source, which may necessitate changing output capacitors if the source has any (to prevent a loss of bass).  That's generally why we settle on 50K most often around here - but 10K or 100K will still work OK.
   
  About some other comments from previous posts:

 Low impedance phones do not necessarily need high gain.  Gain is function of voltage and with low impedance phones, they're more interested in current than voltage for a given power output.  So, it's quite possible that high gain with low impedance is the worst combination.  There are always exceptions, but as a general rule, you want gain low if your load is low impedance.
   

 Popping is your headphone being exposed to DC voltage spikes.  Some headphones can tolerate it, some can't.  Why take the chance?  In the case of the Starving Student, learn to plug your headphones in and out only when the amp is on and the tubes are warmed up.
   

 The headphone's impedance combines with the output capacitors on the Starving Student to form a bass cutoff filter.  If you use Denon's at 25 ohms, you'll probably need 680uf or 1000uf at the output or you'll notice a loss of bass.


----------



## revolink24

Quote: 





tomb said:


> There is no need to match the input resistors to the same value as the pot.  What you're trying to do with the input resistors is "push" the active band of the pot into something with a reasonable travel over the volume range.  The gain of the tubes is much too high for most headphones, so that if you build the amp without those input resistors, your total volume range - between not hearing and having your eardrums blown out - is about 1/4 turn or less.
> 
> A great many of us used input resistors that are 2X the value of the pot impedance.  It just depends on the sensitivity of your headphones.  There is no hard and fast rule - either 1X the value of the pot impedance, 2X, or there were some builders who went all the way to 3X.  (Note that there were some who used -0- input resistors, because of hard-to-drive vintage orthos.)
> 
> ...


 

 Thanks. I was confused since I used a 50k Blue Velvet and 100k/50k input resistors with a gain switch. It would make it awfully difficult to adjust gain if we had to change the pot as well!


----------



## howc

Thanks tomb for clearing the mist in my head!


----------



## ArtemF

Quote: 





tomb said:


> Popping is your headphone being exposed to DC voltage spikes.  Some headphones can tolerate it, some can't.  Why take the chance?  In the case of the Starving Student, learn to plug your headphones in and out only when the amp is on and the tubes are warmed up.


 
  There is a simple way to get rid of this problem: diode protection. The diodes should be switched in parallel to earphones and each channel
  will need either 2 of them (to kill both forward and reverse spikes) or 4 of them (to double the threshold above which the spikes/sounds will be cut).
  Assuming that the opening voltage of a regular diode is 0.7-1.5V and that the earphones can tolerate a short-term 3V overload, I would recommend
  using the latter variant (I applied it in my amp since I'm 100% sure that there will be one day when I will forget to unplug the earphones 
	

	
	
		
		

		
		
	


	




 ).
  It softens the spikes dramatically and it doesn't distort the "normal" sound at all.


----------



## marcus76

Oh oh....
  thanks to a pic Aflac has on his picasa acc. I had it working yesterday , had something wired completely wrong before ...after rewiring , both tubes lit up, mosfets got hot, tested as the_equalizer posted @ page 259, seemed fine...
  Today I was double checking the voltages before casing it up and managed to short something ... There's 2 possible things (or both together) : for cleaning up the wire mess I cut one of 'em , leading to a mosfet pin 2.
  I just drilled it by hand yesterday ..Was just about to start measuring @ the tubes , the probe slipped and the tube I was about to check lit up like a christmas tree ...
  Power off ... took a look at the mess and see the hand drilled part i was talking about connecting to the other mosfets heatsink ... the heatsinks are insulated by washer/pad though (at least i thought so, if not would that be a possibility ?) I have no idea on what to check now .. might be the mosfet thats fried ? I have some spare tubes but wanted to ask first .. 
  greets,
  Marcus


----------



## ArtemF

most probably you either short-cut the mosfets or fried them resulting in a complete
  open mosfet. You can check if the filaments are still operable by testing the resistance
  between the corresponding pins (#3 and #4). For the future tests you can first use
  a powerful resistor instead of the tube filament.The working point for mosfet is set
  by R2 and R4 resistors so the circuit will not notice the absence of the tubes.
  When there is no smoke/sparks 
	

	
	
		
		

		
			





 and the voltages in the key points seem to be
  reasonable then you can try it with the tube.


----------



## marcus76

hey thanks for the tip with the resistor,
  the mosfet was fried , swapped both and now its back working, tube seems to be ok 
  Don't have any cheap headphones to try right now, so there's something else to do hehe
  I forgot to install the socket mounting ring ...
  Think it's time declutter some of the wire mess, but not now.. with the amount of beer I already had 
  cheers,
  Marcus


----------



## revolink24

Anyone have any input about using this as a gain selector: http://www.mouser.com/ProductDetail/Mountain-Switch/103-0012-EVX/?qs=sGAEpiMZZMvudeGI7i40XAbTfEi3IR5MNzbsWphK5Lc%3d
   
  Last time I ordered a $13 NKK Switch of the wrong type, a mistake I hope not to repeat.


----------



## AirForceTeacher

OK, I tried to find it with a search, but 350+ pages?  What are the ramifications of changing the heat sink you use?  I know it's supposed to be about sound, not looks, but I want to build a nice wood case for it, something reminiscent of my Yamaha CR-820 or an old Marantz. 
   
  Can I use something like this? Do I need two, or can both MOSFETs use one heat sink (is the tab just a heat conductor, or is it electrical ground as well?)
   
  http://cgi.ebay.com/Heatsink-CPU-MOSFET-HEAT-SINK-16-FIN-DENSITY-102-x-64-/250541753999?pt=LH_DefaultDomain_0&hash=item3a5573c68f


----------



## Fred_fred2004

Both mosfets can share a heatsink
   
  this is what I used

   
  cheers
  FRED


----------



## revolink24

In addition to my previous question (see 2 posts above) what do you guys think of using a potentiometer to adjust gain? And what value potentiometer would be best for this? (I plan on using a blue velvet, since this build is already over budget I'm just going with it.)


----------



## the_equalizer

Quote: 





fred_fred2004 said:


> Both mosfets can share a heatsink
> 
> this is what I used
> 
> ...


 

 Nice build Fred.  Is that a 12AU7 version?
   
  cheers!


----------



## Fred_fred2004

Hi yes 12AU7 the original valves are just too hard to find at a sensible price
   
  cheers
  FRED


----------



## Legis31

Revolink,
   
  I've used similar switches to good effect setting up multiple gain choices for single triode sections on guitar amps before. The switch you're looking at has 1/4" solder lugs and is more than stout enough for what you want. It's not a mini switch, though....
  As far as using a pot to vary gain, I can't advise as I've not used a full sized pot for such. I'd think the switch would be the easier way to go but I leave the resistor values to you.
   
  Legis31


----------



## rauschie

Hy all!
  I am wondering how the SS would compare to a bravo v2? Has anyone tried both? I could get them for roughly about the same price. Actually, the materials for the SS would be a bit more expensive than the bravo completely assembled. The headphones to drive are HD580's, and sometimes my HD555's.
  My other question would be, that is there a significant difference in sound quality using more expensive parts for the SS? I mean, I can get the R's and C's for 1c each and for 1$each, and that is quite a difference given the total price of the amp, but I don't know whether it's worth it.


----------



## howc

Hi, i just did a draft layout of the p2p circuit for 12AU7 SS. can anyone do a check on this and let me know if i did it correctly? 
   
  ignore the placing of the 1/4 jack as it was placed there for easy interpreting of the diagram. 
   
  The brown lines are all ground lines. 
   
  Thanks in advance!


----------



## the_equalizer

Quote: 





rauschie said:


> Hy all!
> I am wondering how the SS would compare to a bravo v2? Has anyone tried both? I could get them for roughly about the same price. Actually, the materials for the SS would be a bit more expensive than the bravo completely assembled. The headphones to drive are HD580's, and sometimes my HD555's.
> My other question would be, that is there a significant difference in sound quality using more expensive parts for the SS? I mean, I can get the R's and C's for 1c each and for 1$each, and that is quite a difference given the total price of the amp, but I don't know whether it's worth it.


 

  
  There's kind of a tacit agreement to keep this thread on the technical aspects of the build and not to post listening comparisons in this thread. Maybe someone who hast listened to both amps can send you a PM with his/her impressions.
   
   
  Quote: 





howc said:


> SNIP
> 
> 
> Hi, i just did a draft layout of the p2p circuit for 12AU7 SS. can anyone do a check on this and let me know if i did it correctly?
> ...


 


  I won't comment on the quality of the layout as my expertise there is null. As to the wiring, the circuit seems to be correct. I'd just do a small change in wiring a jumper for pins 1 and 6 at the tube sockets, as you did for the other pin pairs, instead of independent wires going from each of those pins to the junction of C4/R7 - C2/R1.
   
  cheers!
  Oscar A. Ross


----------



## headfisupporter

check out the new site by Farnell: http://au.element14.com.. stuff are cheap, with technical support provided!


----------



## headfisupporter

another place offers the Alps RK27112A 50KΩ pot  too! http://au.element14.com previously was farnell site.. delivery is fast!


----------



## Fred_fred2004

For $83.56 I don't think its a good choice 
   
http://au.element14.com/alps/rk27111250k/potentiometer-50k/dp/1191723
   
  cheers
  FRED


----------



## Planar_head

Hey guys,
   
  I've been trying to understand some simple amplifier circuits like this and I'm curious what R2, R3, and R4 do.
   
  They look like they relate to biasing the gate of the MOSFET, but I'm not 100% sure how. If someone could give me some direction on what to look for or explain it outright, that would be great.
   
  Thanks.


----------



## the_equalizer

R2 and R4 are a simple voltage divider. R3 is analog to a 'grid stopper' for a tube, it's there to discourage oscillation (which is why it's recommended that it's soldered directly to the gate pin), it plays no role in biasing since no current flows in a MOSFET gate circuit as it is reverse biased (Ok, there is a leak gate current but it's in the order of micro or nano Amperes and not taken into consideration for biasing)
   
  In the SSMH circuit the values for R2 and R4 are chosen with two factors in mind:
   
  1) to set a gate voltage around 5 volts higher than the tube heater voltage. So when you bias the gate the source pin sits at ~ 5 volts under that thus feeding a proper voltage to the tube heater.
   
  2) to set an adequate -3dB point for the RC filter formed by C2 and R4
   
  If you do the math for the voltage divider, you'll see that in the 19J6 version it sets the MOSFET gate to 24V (19 + 5) and in the 12A_7 version it sets it to approximately 17V (12+5)
   
  cheers!


----------



## Planar_head

Very succinct explanation, thanks equalizer!


----------



## AirForceTeacher

OK, I tried to follow that, but I don't have enough background.  Is there a primer on amplication circuitry?


----------



## the_equalizer

Considering that MOSFETs are similar to tubes, this one might help you
   
  http://boozhoundlabs.com/howto/
   
  Aside from that you really need a firm grasp of Ohm's law and some of it's applications (like voltage dividers), this one might help:
   
  http://www.ikalogic.com/beg_1_res_v_c.php
   
  cheers!


----------



## livewire

Quote: 





headfisupporter said:


> another place offers the Alps RK27112A 50KΩ pot  too! http://au.element14.com previously was farnell site.. delivery is fast!


 


  That price of $83+ is horrendous for an ALPS RK27 pot.
  They can be had for $10 to $15 plus shipping.
  Check ebay often.
  At the moment there are no ALPS 50K's on the bay.
  Just keep checking, they'll pop up.


----------



## livewire

Quote: 





the_equalizer said:


> R2 and R4 are a simple voltage divider. R3 is analog to a 'grid stopper' for a tube, it's there to discourage oscillation (which is why it's recommended that it's soldered directly to the gate pin), it plays no role in biasing since no current flows in a MOSFET gate circuit as it is reverse biased (Ok, there is a leak gate current but it's in the order of micro or nano Amperes and not taken into consideration for biasing)
> 
> In the SSMH circuit the values for R2 and R4 are chosen with two factors in mind:
> 
> ...


 

 As usual, well said!


----------



## AirForceTeacher

Thanks, EQ - started reading it and it makes some sense - I love it!  I wanna build an SSMH in a wood case, and I have all these extension ideas, but I need to understand what everything does first.


----------



## the_equalizer

Quote: 





livewire said:


> As usual, well said!


 

 Thanks!
   

  
  Quote: 





airforceteacher said:


> Thanks, EQ - started reading it and it makes some sense - I love it!  I wanna build an SSMH in a wood case, and I have all these extension ideas, but I need to understand what everything does first.


 

  
  Glad to hear you're enjoying that tutorial. The SSMH is a good circuit to experiment with, as it is so simple. I'm definitely interested to see with what ideas you come up!
   
  cheers!


----------



## Amatsu

I'm thinking of trying one of these amps for my Beyers DT770/250 and I wanted to ask something, is it difficult to assemble one of these? I don't have much soldering experience, but I'm able to repair headphones cables and change capacitors.
   
  Also, do you know any stores in Europe selling the parts? Thanks.
   
  By the way, is Pete still selling the parts in his website? I can't find it.


----------



## Ikarios

Quote: 





amatsu said:


> I'm thinking of trying one of these amps for my Beyers DT770/250 and I wanted to ask something, is it difficult to assemble one of these? I don't have much soldering experience, but I'm able to repair headphones cables and change capacitors.
> 
> Also, do you know any stores in Europe selling the parts? Thanks.
> 
> By the way, is Pete still selling the parts in his website? I can't find it.


 
  The part assembly part is very easy, especially if you know your way around a soldering iron. Since there's no PCB it's just figuring out the best way to air-wire components and wires together. Casework, on the other hand, is a bit tougher... you pretty much need access to a drill press and lots of planning to get a case that has holes that are lined up properly.
  
  As for parts availability in Europe, there have been a few vendors mentioned in the past maybe... idk, 20? pages of this thread. I can't remember any off the top of my head though.


----------



## Amatsu

Hey thanks for the info. The case doesn't really worry me because my father is an experienced carpenter and we have lot's of tools in the garage.


----------



## Amatsu

Hey, I finally made an European shopping list for the 17EW8 version from *The_Equalizer*, but it's much expensive to what I anticipated (around 116$), if someone is kind enough to take a look I'll appreciate any feedback:
   
  HTML:
http://dl.dropbox.com/u/1910765/millett.html
   
  OpenOffice:
  http://dl.dropbox.com/u/1910765/millett.ods
   
  Cisco Adapter is from Asia.
   
  I find the tubes a little expensive and I don't know if I can use other types, the 680uF 63V capacitor is also expensive in that shop.
  It's hard to believe that the original BOM from Pete was only 36$.
  I'm just wondering if it's still worth doing for this price.


----------



## AirForceTeacher

Quote:


the_equalizer said:


> Quote:
> 
> 
> 
> ...


 

 Nothing too terribly original - I want to leave space for a DAC and a switch between the DAC and analog sources.  I'm also wondering if I can take a slot load cd drive from a laptop and install it as well, but wondering how to control it.


----------



## Beftus

Quote: 





amatsu said:


> Hey, I finally made an European shopping list for the 17EW8 version from *The_Equalizer*, but it's much expensive to what I anticipated (around 116$)...


 


  Have you tried http://www.conrad.com/ for parts?


----------



## the_equalizer

Quote: 





amatsu said:


> Hey, I finally made an European shopping list for the 17EW8 version from *The_Equalizer*, but it's much expensive to what I anticipated (around 116$), if someone is kind enough to take a look I'll appreciate any feedback:
> 
> HTML:
> http://dl.dropbox.com/u/1910765/millett.html
> ...


 
   
  Aside from Beftus' recommendation to check some other shop for parts, yes: you can use other tubes such as
   
  12AU7
  12AX7
  12AT7
   
  Only modification to the circuit is changing the value of a couple of resistors (R2 and R8), schematic here. Maybe you can find a couple of those tubes cheaper than the 17EW8.
   
  You can also build a version using 12SR7 tubes (which are very very cheap), as posted by user 'Logistic' but that requires another type of tube socket (octal) and different values for several resistors. Check his post here.
   
  Good luck and be sure to post some pics of your amp here when you're done building it.
   
  cheers!


----------



## Beftus

Quote: 





> It's hard to believe that the original BOM from Pete was only 36$.
> 
> ... the 680uF 63V capacitor is also expensive in that shop.


 


  Simple, Pete didn't use boutique parts for his Starving Student...
   
  Why bipolar caps for C1 and C6? Use a polar electrolytic, a 470uF or 680uF Panasonic FC is an excellent choice and doesn't cost a lot.
  Where are C3 and C5 on your BOM?
   
  The heatsink you found is a bit small IMO, a beefier one might be a better choice. Like this one: http://www.banzaimusic.com/Heat-Sink-FHS129-50-8STS.html


----------



## Procession

I've been looking for all the parts to build one of these and it seems that no place stocks everything, or even the tubes for that matter.
  I'm in Australia and this is really annoying me, I'd love one of these amps to death, but honestly, It's getting really daunting trying to find the parts to build one of these.
   
  So in a nutshell I want to know:
   
  1. Is there an Australian retailer from which I can buy most of the parts?
   
  2. Where can I find some tubes for these?
   
  3. Are there PCB sold for this project?
   
  4. How hard is it to wire in a DAC?


----------



## Beftus

Quote: 





procession said:


> 2. Where can I find some tubes for these?
> 
> 3. Are there PCB sold for this project?
> 
> 4. How hard is it to wire in a DAC?


 


  2. The 19J6 tubes from the original Starving Student are very hard to find and if you do find them they're expensive. Easy to find are 12AU7 tubes. Current production tubes aren't very expensive.
   
  3. No, not anymore. You'll have to do a point to point or make your own PCB.
   
  4. The Starving Student has been known to cause damage to DACs. YMMV. Use the search function.


----------



## Fred_fred2004

Quote: 





procession said:


> I've been looking for all the parts to build one of these and it seems that no place stocks everything, or even the tubes for that matter.
> I'm in Australia and this is really annoying me, I'd love one of these amps to death, but honestly, It's getting really daunting trying to find the parts to build one of these.
> 
> So in a nutshell I want to know:
> ...


   
  1. Farnells has virtually all the parts you need, free overnight delivery in Australia
   
  2. Tubes and sockets checkout ebay
   
  cheers
  FRED


----------



## Amatsu

Thanks everyone for the recommendations, I will be buying from *Conrad *probably, I also managed to find the 17EW8 tubes for 3$ each, so the final price is at around 80$ right now (62€) which is certaintly better than before. I'm still going to wait a couple of days before pushing the button, I need to re-check some items I'm not sure about.
   
   
   
  @*Procession*
  Someone made an Australian BOM some pages ago, check it out, maybe you'll find something interesting: http://dl.dropbox.com/u/1910765/BWr9.bom_thoward.xls


----------



## Ikarios

Quote: 





beftus said:


> Quote:
> 
> 
> 
> ...


 


  FWIW I haven't had any problems with my Grub hardwired into the SSMH (using a DPDT input selector switch). I've turned off the amp with the DAC on, vice versa, vice versa, etc etc. I don't think tehre've been any reports of Grubs dying from SSMHs either.


----------



## Procession

Thanks to everyone for the help, I'm going to make this my next project.


----------



## Mr_Nibbles

Hi guys I could really use some help finding a replacement potentiometer for my PCB board Starving Student. The one that I previously had fit right into the PCB that was sold at Beezar. I would love to replace it with another that will fit right it. Thanks


----------



## tomb

Quote: 





mr_nibbles said:


> Hi guys I could really use some help finding a replacement potentiometer for my PCB board Starving Student. The one that I previously had fit right into the PCB that was sold at Beezar. I would love to replace it with another that will fit right it. Thanks


 

 The BOM is still available on the Starving Student website:
http://www.diyforums.org/SSMH
  It lists the proper Alpha pot that you can order from Mouser:
313-1240F-50K


----------



## revolink24

I keep hearing about this "DAC damage" from the SSMH. Can anyone elaborate on what causes it? Is it just the DC offset? If so, would it be helped with an offset protection circuit (like the Epsilon 12)? Sorry, I'm kind of an electronics newb.
  FWIW, I haven't had any issues with my 0404.


----------



## rauschie

Hi everybody!
 If I am looking for help to find out what did i do wrong building my amp (it doesnt work, actually, it doesnt seem to do anything), is this the proper thread?


----------



## Ikarios

Quote: 





revolink24 said:


> I keep hearing about this "DAC damage" from the SSMH. Can anyone elaborate on what causes it? Is it just the DC offset? If so, would it be helped with an offset protection circuit (like the Epsilon 12)? Sorry, I'm kind of an electronics newb.
> FWIW, I haven't had any issues with my 0404.


 


  the SSMH has been known to kill some DIY DACs (Aliens, Bantams, and some Gamma1s). I believe it's basically caused by accidentally touching the signal from the DAC to the ground of the amp, but a cause was never definitively singled out. There's some info within the last 50 pages posted by TomB and some info on DIYforums too.


----------



## tomb

Quote: 





ikarios said:


> Quote:
> 
> 
> 
> ...


 

 The grounding on the Cisco power supply is not the best.  What happens is that a static charge can build up on the RCA jacks under certain scenarios.  That zaps the DAC.  You can test this yourself (without damaging anything) by disconnecting the RCA jacks while the amp is on.  Often, you'll get a huge hum until you ground the charge from the jacks.  (Don't ground them with a DAC. 
	

	
	
		
		

		
			





)


----------



## dsavitsk

To elaborate a little: re the static charge.  The cisco PS is connected to safety earth at the wall.  However, the output ground is not connected to it, and there is a capacitance between them.  This charges, and when it discharges it can damage sensitive parts, like DAC chips.  As Tomb says, you can simply be careful to not let this happen. 
   
  So, the Cisco is the culprit, and you can build a different PS to eliminate the issue.  One way to do this is with a power transformer like the 62065 (at Digikey), a rectifier, a cap, a pass transistor, and a zener to set the voltage.  Or, if you want to use a LM317 based PS, you can run the amp at a lower voltage by adjusting the bias resistors for the mosfet and replacing the tube's plate load with a CRD or other small CCS.


----------



## the_equalizer

Quote: 





rauschie said:


> Hi everybody!
> If I am looking for help to find out what did i do wrong building my amp (it doesnt work, actually, it doesnt seem to do anything), is this the proper thread?


 


  If your amp is a Millett "Starving Student" then yes, this is the proper thread. But please provide us with a bit more detail than "it doesn't work" 
	

	
	
		
		

		
			





   Clear pictures, voltage measurements, etc;  all help to diagnose what might be wrong
   
  cheers!


----------



## Ikarios

Am I mistaken, or is there no real "impressions" thread about this amp? I know TomB has wanted to keep sonic impressions out of this thread, but for 375 pages the popularity of this amp (either that, or the difficulty in building...) can't be mistaken. Has anyone done an in-depth review of the SSMH?
   
  One of the reasons I ask now is I basically just coerced my friend into buying one on the FS/T forums, but honestly I don't know how the SSMH sounds compared to commercial amps in its price range like the LDs or the chinese amps (Bravos, etc). Also it makes me wonder whether or not I'm amp-limited when I look at my near-future upgrade path, but I wouldn't know what to upgrade to.


----------



## Amatsu

I'd also like an impressions thread, there was one 2 years ago but with only 2 pages and no real impressions: http://www.head-fi.org/forum/thread/326577/millett-starving-student-hybrid-amp-impressions


----------



## Dubwicht

I completed a Starving Student on the weekend and had some trouble at first.  Double and tripple check all your wiring with the Schematic. I had the heater wires connected to pin 3 & 4 and as soon as I cut the link it fired up.  Also had a few other misfires in the wiring. 
   
  I still have a bug to work out.  Sound is full in one channel but not in the other.  I may have a cold connection somewhere and must trouble shoot tonight.


----------



## the_equalizer

Show us some pics of your build Dubwicht!


----------



## jwrossie

Hello,
   
  I am going to build two starving student togheter with a friend of mine.
  We are going to build the 12au7 version, because this tubes are easier to find.
   
  So we are using this schematic http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
   
  This is our partslist that we ordered:
  010      4      week 52           120561    Buisvoet Chassismontage                                      3,38       13,52
 020      4      week 52           459845    MKS2-foliecondensator 0,22µF 250V                     0,24        0,96
 030      2      week 52           733954    Inbouwbus 2.5MM                                                       0,87        1,74
 040      2      week 52           736406    STEREO-INBOUWB.6.3MM                                       0,72        1,44
 050      2      week 52           734101    STEREO JACKPLUGBUS 3,5                                   0,99        1,98
 060      4      week 52           162402    IRF 510 HEXFET TO-220  IR                                     0,44        1,76
 070      2      week 52           424196    Precisie potmeter 50K                                                5,48       10,96
 080      1      week 52           404322    Koolfilmweerstand 0,25W 220kOhm 100stuks    1,88        1,88
 090      1      week 52           408344    Metaalfilm weerstand 0,25W 33kOhm 100st         2,28        2,28
 100      1      week 52           409456    Metaalfilm weerstand 0,25W 2,0kOhm 100st        2,28        2,28
 110      1      week 52           408166    Metaalfilm weerstand 0,25W 1,0kOhm 100st        2,28        2,28
 120      4      week 52           189066    Warmtegeleidende folie 70/50 TO-220                   0,20        0,80
 130      1      week 52           409073    Metaalfilm weerstand 0,25W 51kOhm 100st         2,28        2,28
 140      1      week 52           408476    Metaalfilm weerstand 0,25W 390kOhm 100st       2,28        2,28
 150      4      week 52           422068    Elco NHG-R 470µF 63V 20%                                     0,78        3,12
 160      4      week 52           445454    Radiale elcos 63V 680µF                                           0,59        2,36
 170      4      week 52           422030    Elco NHG-R 220µF 16V 105C                                   0,11        0,44
 180      4      week 52           459908    MKS4-foliecondensator 0,22µF 63V                         0,21        0,84
 200      4      week 52           188002    Koellichaam zwart 8337/50/ST 50x42x25mm        2,67       10,68
   
  As you can al read, we are from the Netherlands.
  The 48v adapters are on its way, bought it on ebay.
   
  What do you guys think of our 50k pot?
http://www2.conrad.nl/goto.php?artikel=424196
   
   
  We still need te find the 12au7 tubes, we are trying to find 2 matched pairs.
   
  But when we ordered all the components we came across this post http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/3870#post_6035921:


> Originally Posted by *cassegrain*
> 
> 
> _ Thanks for the advice, regarding your last tip, there 's a risk of destroying the hearphone?_
> "Destroy" is perhaps an extreme term in this case, but the potential for damage is there. It's not so much on the SSMH because of the AC-coupling at the inter-stage capacitors. However, there is the fact that the SSMH will exhibit some DC spikes at the headphone jack while the tubes/output capacitors are charging up. For that reason, you should always plug in your headphones _after_ powering the amp up for 30 seconds or so. The same caution applies for shut off, although there's no waiting required and the chances of offset are less likely and if they occur, are transients that disappear much more quickly.


   
  How many of u destroyed their headphones? And how many of u are taking this precaution?
  I have an Sennheiser HD650 and I am getting a bit anxious with the amp.
  I don't want to damage my HD650 as you can imagine.
   
  Is there also a way to place a PWRon LED somewhere? What is the best location for the LED?
  And what kind of a resistor do I need for a simple 3 mm LED.
   
  The case for my amp is going to be an old media showcenter from pinnacle:

   
   
  Cheers.


----------



## Amatsu

*Jwrossie@*
  If I'm not mistaken I think the pot needs to be stereo or dual, but I'd prefer if someone else confirmed this since I also want to be sure for my order.
  Another forum user (marcus) recommended me this one: http://shop.conrad.nl/componenten/componenten-passief/potentiometers/draaipotmeters/441895.html


----------



## holland

Correct.  A stereo logarithmic potentiometer is necessary.  The gain on the ssmh is very high for most normal headphones.  The more control you have, the better.  I would go further and shunt the pot as well.


----------



## Dubwicht

I finished trouble shooting the amp tonight and it works great.  I had the wrong resistor on one channel and a bad solder joint.  I will post some photos tomorrow.  Cheers,  D


----------



## Beftus

Quote: 





> Originally Posted by *Amatsu* /img/forum/go_quote.gif
> 
> Another forum user (marcus) recommended me this one: http://shop.conrad.nl/componenten/componenten-passief/potentiometers/draaipotmeters/441895.html


 


  An excellent choice if you're on a budget. I used it too.


----------



## dirkpitt45

Just finished mine a few minutes ago using a Beezar kit! 
   
  Looks and sounds awesome with my Ms1s (they finally have some bass). Ironically though, my m50s aren't working. The adapter, 1/8 to 1/4, works great with the Ms1s and DBA-02s, but only the left channel comes through when I use it with the m50s. M50s still work fine out my pc's 3.5 or my zune hd, just using the adapter  seems to be the problem. But then the adapter works fine with other plugs >,<
   
  Just gonna pick up a cheapo one from "the source" probably.


----------



## tomb

Quote: 





dirkpitt45 said:


> Just finished mine a few minutes ago using a Beezar kit!
> 
> </snip>


 
  Glad to hear you have a successful build, but - Geez!  How long had you been holding on to that Beezar kit?  Please let everyone know this wasn't a recent purchase or I'll get overrun with people bugging me for kits again!


----------



## dirkpitt45

Ah yeah picked it up off a fellow forumer who I think got it off someone who just never got around to building it and then had the same thing happen to him. 
   
  I didn't know they were that old lol. Was planning on buying the parts seperetely and it popped up on the FS side and decided to save some time looking around for the everything. 
   
  EDIT: Following up to my earlier problem with pc->Fubar II->MSSH->ATH-M50s, I picked up another 1/8 to 1/4 adapter and I still only get sound to the left cup on my m50s. Even if I change the RCA jacks around it still only plays from the left side. Both adapters work fine with my ms1s and DBA-02s, but not the m50s. Could it have something to do with the small circuit board in the m50s? I remember reading a thread a while ago where it was said not using the board reduced crosstalk (not that I notice any). 
   
  If I just turn up the volume on the amp (with no music playing) the static is much louder in the left ear, it comes through on the right but only barely. I'm gonna try going from headphone out on my onboard to amp and see if it's the fubar II that's causing the problem maybe. 
   
  EDIT #2: Still the same, left channel is loud while the right is very quiet. I can change the balance options just through windows and that seemed to work. Turned what it calls the right channel down to 89 and left the left channel at 100.  
   
  Would WASAPI or something help with this? Though I don't know what it is tbh.


----------



## Yaka

some of take our time building the kits you. still not started that minimax kit i got from you yet
  Quote: 





tomb said:


> Quote:
> 
> 
> 
> ...


----------



## ArtemF

Quote: 





dirkpitt45 said:


> If I just turn up the volume on the amp (with no music playing) the static is much louder in the left ear, it comes through on the right but only barely. I'm gonna try going from headphone out on my onboard to amp and see if it's the fubar II that's causing the problem maybe.
> 
> EDIT #2: Still the same, left channel is loud while the right is very quiet. I can change the balance options just through windows and that seemed to work. Turned what it calls the right channel down to 89 and left the left channel at 100.
> 
> Would WASAPI or something help with this? Though I don't know what it is tbh.


 
   
  Do you have a multimeter? If you don't then I definitely recommend buying one (HarborFreight had them for $3.50).
  With multimeter in hand I'd do the following: since nothing is burning you can test the 
  circuit as is. Draw a table, name the key points of the circuit and compare the voltages in key points, one by one.
  Check the columns of the table for consistency. This might give a clue and in most cases it does.
   
  If the voltages agree within 10-20% then one has to test the individual elements.
  The problem you have might be due to poor contact, burnt caps, burnt pot, burnt filament, and so on.


----------



## ArtemF

add-on: by "comparing voltages"  I meant comparing them in working and non-working channels.


----------



## Amatsu

Hello again, can someone recommend me some colored wires/cables for soldering the amp? I'm trying to find some on Conrad so I can include it with my shopping list but I don't know what name it has or the type to buy.
  Also, is this same wire good to recable headphones? I also need some of those to recable my KSC75. Thanks again.


----------



## dirkpitt45

I think it might be the pot. M50s are easy to drive so I barely have to turn the volume wheel. With the ms1s I have to turn it about same + almost double. Found if I turn down the volume on my pc and turn up the volume on the amp the channels are balanced. Might try installing some larger resisters in 16/17 I think it was.
  
   
   
  Quote: 





artemf said:


> Do you have a multimeter? If you don't then I definitely recommend buying one (HarborFreight had them for $3.50).
> With multimeter in hand I'd do the following: since nothing is burning you can test the
> circuit as is. Draw a table, name the key points of the circuit and compare the voltages in key points, one by one.
> Check the columns of the table for consistency. This might give a clue and in most cases it does.
> ...


 

   
   
    
   
  I just used cat5 for the LED wires, and some cheapo radio shack 22awg stranded for the rest of the stuff. 
   
  Quote:


amatsu said:


> Hello again, can someone recommend me some colored wires/cables for soldering the amp? I'm trying to find some on Conrad so I can include it with my shopping list but I don't know what name it has or the type to buy.
> Also, is this same wire good to recable headphones? I also need some of those to recable my KSC75. Thanks again.


----------



## Dubwicht

My Starving Student is behaving badly.  When I plug it in it makes static in both sides.  The static builds and when goes away when I either touch the nut on the outside of the headphone jack or spin the jack - very odd.  It appears that something is being discharged.   Could this be a grounding issue?  I was also wondering about the 2.5 mm jack for the power.  It has three pins and I have connected only two.  Should I connect the third?  Any help would be greatly appreciated.  I am still working on posting photos.


----------



## the_equalizer

Two things jump to my mind
   
  1.- The volume pot, check carefuly that it is correctly connected; the pot acts as a grid resistor, keeping the grid from acummulating charge.
   
  2.- Are R6 and R12 correctly connected? These ones are required for the output caps to charge/discharge properly.
   
  Happy New Year everyone !    May it be a great year for everyone !


----------



## jwrossie

Hello everybody!
   
  Today I made my Starving Student Headphone amp based on the 12au7 tubes.
  But it's not working as it should.
   
  I used this schematics:

   
  The amp is making this sound (with and without a source playing):
http://www.fysiohoogeveen.nl/images/stories/Spraak001.amr
  on both channels.
   
  The Tubes glow a bit, as you can see on the photo's.
   
  I am not an electronic expert, so here are a few things:
  1. pinout of the tube chassis,  this is how I connected the tubes

   
  2. the IRF510

   

  I used this schedule to figure out how to connect the IRF510, so with the schematic of the_equalizer
  1 = G = Gate
  2 = S = Source
  3 = D = Drain
  This is how I connected the IRF510.
   
   
  3.  The 0.22uF 250v and 0.22uF 63v, I used these:
  http://www2.conrad.nl/goto.php?artikel=459845
  http://www2.conrad.nl/goto.php?artikel=459908
  The legs are the same length, so no obvious + and - , that doesn't matter?
   
  4. The R16 en R17, I couldn't find the 50k 0,25W, so I used 51k 0,25W, Is that ok?
   
   
   
   
   
   
   





   
  Cheers.


----------



## Beftus

As you are using a metal box, you _did_ isolate the mosfet's from the heatsinks? Did you? The metal tab should NOT be in contact with ground (or grounded metal box). There must be a difference of 48 volts between the mosfet metal tab and ground!
   
   
  That said...
  1. tubes pins are numbered clock-wise looking at the bottom (pins side) of the tube
  2. the IRF510 pins in the photo are labelled correctly
  3. it doesn't matter how you connect these film caps, they don't have a polarity.
  4. 50k or 51k doesn't matter. These are optional, I didn't use them. BTW R14 and R15 (grid stoppers) aren't optional IMO.


----------



## Dubwicht

Two things jump to my mind

  

 1.- The volume pot, check carefuly that it is correctly connected; the pot acts as a grid resistor, keeping the grid from acummulating charge.

  

 2.- Are R6 and R12 correctly connected? These ones are required for the output caps to charge/discharge properly.

  

 Happy New Year everyone !    May it be a great year for everyone !

 _____________________________________________________________

  

 Thanks for the advice.  I will have a look at the amp today.  Cheers,  Doug


----------



## kdris

Hi,  I just finished building my 12au7 amp per the instructions above. However I'm having some problems, when both channels are connected the amp sounds tinny and weak. When a single channel is connected sound comes out both sides of my headphones at equal volumes. I believe it might be a faulty RCA jack. Would a faulty RCA jack cause what I described?


----------



## jwrossie

OK my amp is working now! The problem was the IRF510 the Drain en Source were mixed up, so the schedule a few post back isn't true.
   
  Thanks to the foto's of another forummember Fred_fred2004 , I came to this conclusion!
  This build.
   

   
   
  It sounds very good in combination with my HD650. The only thing is the noise that I hear when there is
 no source playing. I think this will be a ground issue.


----------



## Fred_fred2004

Glad to help 
	

	
	
		
		

		
			




   
  cheers
  FRED


----------



## dirkpitt45

Anyone know what would cause occasional static bursts in one channel? Just started today, and only in the right channel. It's a different noise than the popping that was happening for the first few hours after I finished (building and turned it on for the first time) and it's different than the noise caused by my cellphone. Only happened twice so far (about an hour apart). 
   
  I can't seem to find any problems with my soldering, took it apart again just to check on everything the other day. Other than the LED wires which I kinda messed up on but they just aren't as clean looking as the rest of the joints. One tube socket is also slightly off centre, but it's not touching anything. Ran a screw-driver between all the points on the board again to clear any small strands of solder, also added a piece of electrical tape to the centre standoff to make sure the LED resister won't contact it (even though there was lots of space).


----------



## CaptHowie

After a long while, I've hit the final stages of organising the build of my Starving Student. I've been watching this thread for a while, and I purchased some 19J6 tubes around a year and a half ago off a fellow Head-Fi'er, and I haven't had much time up until now to organise and build the thing. I'm fairly sure I've completed the BOM, which I've attached (might be helpful for fellow Australian HeadFi'ers looking to build the amp), and now I need to make sure I'm on the right track to building it. I've been working on a Prototype Board layout all day, which is found below. Hopefully it's all correct, I'm really not too skilled in prototyping; if someone could have a look over it I'd be greatly appreciative. FYI, the codes on the parts on the prototype correlate to the codes found in the BOM. One thing I am a little worried about on the prototype is if I have the MOSFET terminated correctly, e.g. 1, 2, 3 and how they correlate to Drain, etc...
   
  BOM: http://dl.dropbox.com/u/10765/bom_thoward.xls
  Prototype: http://dl.dropbox.com/u/10765/starving_student_19j6.jpg


----------



## tomb

Quote: 





dirkpitt45 said:


> Anyone know what would cause occasional static bursts in one channel? Just started today, and only in the right channel. It's a different noise than the popping that was happening for the first few hours after I finished (building and turned it on for the first time) and it's different than the noise caused by my cellphone. Only happened twice so far (about an hour apart).
> 
> I can't seem to find any problems with my soldering, took it apart again just to check on everything the other day. Other than the LED wires which I kinda messed up on but they just aren't as clean looking as the rest of the joints. One tube socket is also slightly off centre, but it's not touching anything. Ran a screw-driver between all the points on the board again to clear any small strands of solder, also added a piece of electrical tape to the centre standoff to make sure the LED resister won't contact it (even though there was lots of space).


 

 It sounds like the tube is going bad.  Swap them from Right to Left and see if the problem follows to the Left channel.


----------



## Amatsu

Hey, my electronic parts just arrived so I'm going to start mounting this little guy very soon (still awaiting tubes and power supply).
   
  I'm probably going to start working on the case. What would be the best material for the case? Is wood okay? My father's a carpenter so I could get some help there. I'm asking because I don't want to have noise or hum on the amp. Maybe a combination of wood and metal? Thanks.


----------



## tomb

Quote: 





amatsu said:


> Hey, my electronic parts just arrived so I'm going to start mounting this little guy very soon (still awaiting tubes and power supply).
> 
> I'm probably going to start working on the case. What would be the best material for the case? Is wood okay? My father's a carpenter so I could get some help there. I'm asking because I don't want to have noise or hum on the amp. Maybe a combination of wood and metal? Thanks.


 

 While there is nothing wrong with a wood case, more metal is better for grounding and reducing hum.  If you use wood, you should probably add something similar to the copper ground plate that Pete Millett used in the original.


----------



## tomb

Quote: 





kdris said:


> Hi,  I just finished building my 12au7 amp per the instructions above. However I'm having some problems, when both channels are connected the amp sounds tinny and weak. When a single channel is connected sound comes out both sides of my headphones at equal volumes. I believe it might be a faulty RCA jack. Would a faulty RCA jack cause what I described?


 

 It looks like no one responded to this.  If it's not too late, the symptoms you describe are a perfect example of wiring up the jacks or the heapdhone jack incorrectly.  Take a good look at your wiring and make certain that you didn't use an opposite channel's signal wire for the ground on one of the RCA jacks/headphone jack connections.


----------



## Amatsu

Hey, my tubes and sockets just arrived but I can't fit the tubes inside the sockets even though they align perfectly, the tube doesn't enter the metallic part of the socket and doesn't stay still... I'm starting to wonder if the sockets holes are too small or if they are different kind of sockets. I'd appreciate any feedback. These are the sockets I bought (a pack of 4): http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=300462903452&ru=http://shop.ebay.co.uk:80/%3F_from%3DR40%26_trksid%3Dp5197.m570.l1313%26_nkw%3D300462903452%26_sacat%3DSee-All-Categories%26_fvi%3D1&_rdc=1#ht_500wt_922The tubes are 17EW8, both socket and tubes are 9-pin.
   
  Edit:
   
  I tried widening the holes with a small screwdriver and now the tube enters fine.


----------



## Ikarios

So I've suspected that my 12AU7 SSMH has a higher-than-normal noise floor for quite some time. At my normal listening levels (which is generally quiet by most people's standards) I can hear some hiss with low impedance headphones like Grados and most portables. I don't really hear it with my K701 so I didn't really bother with it. I confirmed that my version does have a much higher noise floor than a stock kit 19J6 SSMH (but also has about 2x more volume/gain). Now that I'm beginning to diversify and getting a whole bunch of portables I figure I should tackle this issue sooner rather than later. What's generally the main culprit of a high noise floor?
   
  For the components of my build I stuck to the TomB PCB BOM as closely as possible, only making changes for some of my switch implementations (gain, input, LED) and the 12AU7 version differences given by the_equalizer. I'm also using a GrubDAC wired to the input switch, which is my main input, but I've tried it with other inputs (through RCAs also connected to the input switch) and it's not the input that's the issue. I've considered cutting out C7 and C8 and instead attaching them to the gain switch (which currently switches between 50k and 150k resistors feeding into a 50k pot, but doesn't make a very big impact - only approx. 30-60 degrees of the volume knob). I'm also using a star ground with (I believe) no copper plane. Any ideas?


----------



## holland

1) bad tubes
  2) poor grounding scheme
  3) poor wiring/layout
  4) oscillating mosfets
   
  what kind of noise do you have?


----------



## Ikarios

With low impedance headphones, a low steady hiss that increases steadily as I turn the volume knob. I'm thinking it's a combination of #2 and #3 (lots of extra wire inside, no ground plane) but I haven't spend much time listening to the other set of tubes I have so I guess it *could* be the problem. Should I try adding a copper plate as ground?


----------



## the_equalizer

I seem to remember Beftus mentioned in a post that adding grid-stoppers helped with a similar noise issue. Maybe he can chime in.
   
  cheers!


----------



## walangalam

Are you sure you're not hearing the hiss from your source?
   
  Ground you inputs.  If you still hear hiss its from the amp.


----------



## Beftus

Quote:


the_equalizer said:


> I seem to remember Beftus mentioned in a post that adding grid-stoppers helped with a similar noise issue. Maybe he can chime in.
> 
> cheers!


 

  I don't think we have the same noise issue : http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/5310#post_6733980


----------



## monkeyevil

Any issue using these caps?
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&itemSeq=96055649&uq=634323643171191105
   
   
  EDIT:
  NM, Went with 
http://beezar.com/oscommerce2/catalog/product_info.php?products_id=73


----------



## Ikarios

Quote: 





walangalam said:


> Are you sure you're not hearing the hiss from your source?
> 
> Ground you inputs.  If you still hear hiss its from the amp.


 

 I'm not sure what grounding my inputs means, but I've tried two sources (USB -> GrubDAC -> switch -> SSMH, and X-Fi XtremeMusic -> RCA in -> switch -> SSMH) and the hiss exists. I will have a third source available by next week that I can try, but I doubt it will make a difference.


----------



## walangalam

Grounding the inputs means shorting the ground lug to the signal lug in the RCA jack.  Its like the minimum position of the volume pot, where essentially the wiper of the pot is shorted to ground.  But because of production tolerances, its only "almost" shorted, not completely shorted, so there is some signal still present.
   
  The reason I ask is because of your comment that the hiss increases as you rotate the volume pot.  Since the amp components sit behind the pot, then increasing the volume should not increase the hiss at all.  So I suspect that you are hearing the source hiss.


----------



## Ikarios

Quote: 





walangalam said:


> Grounding the inputs means shorting the ground lug to the signal lug in the RCA jack.  Its like the minimum position of the volume pot, where essentially the wiper of the pot is shorted to ground.  But because of production tolerances, its only "almost" shorted, not completely shorted, so there is some signal still present.
> 
> The reason I ask is because of your comment that the hiss increases as you rotate the volume pot.  Since the amp components sit behind the pot, then increasing the volume should not increase the hiss at all.  So I suspect that you are hearing the source hiss.


 

 Okay. I did some experimenting.
  A couple things:
 1) My RCA inputs are always noisier than the GrubDAC inputs (when off).
  2) If I don't ground the RCA inputs and turn up the volume all the way max, I get a buzzing sound in the left channel (and only really noticeable in the left channel). This is interesting, because I've always thought my pot had a channel imbalance between leftmost turn and ~8-9 o'clock (where the left channel would be louder than the right).
  3) If I ground the RCA inputs and turn up the volume, the hiss will be less evident, but still more than when I have the GrubDAC selected (and off).
  4) With the DAC selected the hiss does increase with the volume, but only slightly. Most of the hiss is still present at zero volume (maybe about twice as loud going from zero volume to max volume).
  5) with the GrubDAC on and volume to max, I definitely hear computer noise, as it gets worse when I move my mouse. This is not something I hear at normal listening levels.
  6) With the RCAs selected and the inputs not grounded, most of the noise/hum (mostly evident in the left channel) (not the background hiss) is attenuated when I put my hand on the metal case of the amp, then completely disappears when I lift the amp off my desk. My case is isolated with little rubber feet, and placing some paper underneath the amp doesn't get rid of the "lift" effect. I suspect my tubes are slightly susceptible to vibration.
   
  So while I can definitely hear some input noise depending on what it's connected to, the "hiss" I hear with Grados is definitely coming from the amp. I don't think it's a ground plane issue, because my star ground is linked to the case, which should be good enough. I have a lot of excess wiring; could that be a major contributor to noise/hiss?


----------



## monkeyevil

Just because I had a hard time figuring out what parts I needed, I'll post this.
   
  For the 9 pin and 17EW8 or similar the only real substitution from the original parts list (besides any of the optional stuff.) is the 390omh resistors in R2 & R8. Correct?
   
  This is the current parts list I have on order for mine.  I subbed 63volts 470uF 20% general caps for the audio ones suggested because they were back orderd.  Not saying it's all correct, but I had a hell of a time figuring out what I needed and what I didn't from the 370 page thread 
   
http://www.evilmonkeymedia.com/dl/SSamp.htm


----------



## holland

Quote: 





ikarios said:


> Okay. I did some experimenting.
> A couple things:
> 1) My RCA inputs are always noisier than the GrubDAC inputs (when off).
> 2) If I don't ground the RCA inputs and turn up the volume all the way max, I get a buzzing sound in the left channel (and only really noticeable in the left channel). This is interesting, because I've always thought my pot had a channel imbalance between leftmost turn and ~8-9 o'clock (where the left channel would be louder than the right).
> ...


 

 Pictures.  You need to ground your case.  It sounds like you may have a ground loop as well.


----------



## Amatsu

I just finished my case but I have a question. The potentiometer doesn't quite stay still due to the case being very wide, can I use some kind of glue to help fix it into the wood case? Maybe some other method instead of glue?
  By the way, what would be the best material to use as a ground plate? Copper? Aluminium? Thanks.


----------



## redsevn

Quote: 





amatsu said:


> I just finished my case but I have a question. The potentiometer doesn't quite stay still due to the case being very wide, can I use some kind of glue to help fix it into the wood case? Maybe some other method instead of glue?
> By the way, what would be the best material to use as a ground plate? Copper? Aluminium? Thanks.


 
   
  What do you mean by the case being "very wide"? Like the hole the potentiometer sits in is too wide for the shaft? To secure the pot you generally want to just screw it in tight enough (but not too tight to warp anything). Glue would work, too, I guess...
  
  Most people use copper, because it's low resistance (I think).


----------



## sandeepk

Hopefully not too much of a threadjack but wondering if anyone knows of online stores selling NOS 19J6 tubes. Just started listening to my SSMH but I'm worried that the tubes are running on their last legs


----------



## Fred_fred2004

There's a few on ebay at the moment
   
  cheers
  FRED


----------



## livewire

Quote: 





sandeepk said:


> Hopefully not too much of a threadjack but wondering if anyone knows of online stores selling NOS 19J6 tubes. Just started listening to my SSMH but I'm worried that the tubes are running on their last legs


 
   
  Not a threadjack at all, well within the subject matter discussed here.

 Fred offers sage advice. Ebay is indeed your friend.
  The days of cheap 19J6 tubes are over.
  Expect to pay about $20 each for NOS tubes.
  Heh, it wasnt too long ago that one could pick them up for $1 to $3 each, I did.
  All of the online tube sellers have been cleaned out with the advent of the MSSH amp.
  Happy hunting and here's hoping you dont get stuck with a couple of duds.<<crosses fingers>>


----------



## sandeepk

Quote: 





livewire said:


> Quote:
> 
> 
> 
> ...


 

 Thanks for the help! I'll keep a lookout for a potential deal and in the meanwhile hold out hope that my current tubes keep chugging along...


----------



## Amatsu

Try vacuumtubes, that's where I bought my 17ew8 tubes, the 19J6 are listed as 10$ each: http://www.vacuumtubes.net/Prices%2012A%20to%2029LE3.htm


----------



## Amatsu

Just finished my first try at building it, but when I turn the amp on, it starts making a constant high-pitched noise, it comes from the amp, there's nothing plugged yet. Any ideas? 
  I'll probably start from scratch some other day because it's a little messy with lots of cables. Is there any way I can check what's good and what's bad with a multimeter/tester? I also did a quick test to see if there was sound but there's nothing as I suspected, although when I turned it off, the headphones did make a static sound. I didn't do any more tests because I'm worried about that high-pitched sound.
  Thanks. I can't upload pics right now sorry.


----------



## the_equalizer

Your amp is most probably oscillating; this could be due to faulty wiring or to all the feedback (due to stray capacitance and electromagnetic fields) that messy wiring can cause.
   
  I don't know if it helps but... from what I've read, a frequent cause for oscillation in the SSMH is to connect R3 and R9 to the MOSFET gate pin with a 'long' wire. This two resistors should be soldered directly to the pin as their purpose is precisely to discourage oscilation.
   
  Good luck with your build and post pics when it's done !
   
  Cheers!


----------



## Amatsu

Hey thanks Equalizer. Those resistors are soldered directly on the mosfets unfortunetly. I'm probably going to desolder everything and start again because I can't even close the case, there's too much wiring.
  By the way, can I use 220uF 16v on the C3 and C5? I forgot to order those two 470uF, I figured it would be okay for a temporary solution, but I don't know.
   
  Oh and just to be safe, I have to ask about the pins on the DC Jack and Switch, I have these two:
http://www.conrad.com/Panel-jack-2.5-mm.htm?websale7=conrad-int&pi=738204
http://www.conrad.com/ROCKER-SWT.-SPST,-ROUND-STECK-4,8-SW/SW.htm?websale7=conrad-int&pi=703040
   
  I'm not completly sure which pin on the DC Jack is the ground, I assume it's the longer one? And on the switch, does it matter which pin is 1 and 2 on the schematic? Thanks again.


----------



## the_equalizer

Quote: 





amatsu said:


> Hey thanks Equalizer. Those resistors are soldered directly on the mosfets unfortunetly. I'm probably going to desolder everything and start again because I can't even close the case, there's too much wiring.
> By the way, can I use 220uF 16v on the C3 and C5? I forgot to order those two 470uF, I figured it would be okay for a temporary solution, but I don't know.
> 
> Oh and just to be safe, I have to ask about the pins on the DC Jack and Switch, I have these two:
> ...


 

 16 volts is too low for those caps, I think. If everything is OK they'll never see more than ~12 volts; but that's a somewhat big if... a miswiring, a shorted MOSFET...  and BAM!!
   
  In my opinion the best way to identify pins in jacks is to use a DMM and measure continuity between the different tabs and pins.
   
  No, in a 1 pole 1 throw switch (that is, a switch with only two pins) it does not matter which pin is 1 and which is 2.
   
  Cheers!


----------



## Speedway

Hey All
  I'd like to try this amp as my first tube build.  Like everyone else, I can't source the 19J6's, so I want to go with the 12SR7 's. I've spent several days reading this thread but have not found an updated schematic with the value changes and BOM for the build.
  Could someone help me out please?
  Thx


----------



## Ikarios

Quote: 





speedway said:


> Hey All
> I'd like to try this amp as my first tube build.  Like everyone else, I can't source the 19J6's, so I want to go with the 12SR7 's. I've spent several days reading this thread but have not found an updated schematic with the value changes and BOM for the build.
> Could someone help me out please?
> Thx


 

 I don't think anyone has posted one. Unless you have a good reason to do a 12SR7 build, why don't you do the 17EW8 or 12AU7 mod? The tubes are just as easy to source and only a tad more expensive.


----------



## Speedway

Aflac
  The only reason I was going with the 12SR7 is because I had bookmarked that post. My eyes must have been crossed when the 17EW8 was tried.
  Anyway, I will search that tube in the thread to see what has to be changed in the circuit, unless it is a direct swap using the original BOM....
  Thx


----------



## Ikarios

Quote: 





speedway said:


> Aflac
> The only reason I was going with the 12SR7 is because I had bookmarked that post. My eyes must have been crossed when the 17EW8 was tried.
> Anyway, I will search that tube in the thread to see what has to be changed in the circuit, unless it is a direct swap using the original BOM....
> Thx


 

 Yes, IIRC the 12AU7 mod is just a change to a couple of resistors. I used the original PCB BOM of the 19J6 kit build when I put together my 12AU7. Since you have to build point-to-point anyway it should be helpful to go through the schematic and double-check all values of capacitors and resistors on your BOM. It's also helpful to label what components are what if you're using Mouser or Digikey to put together your BOM.
   
  The 17EW8 can also be used in the same circuit. I believe the_equalizer came up with the 17EW8 mod first, then detailed the 12AU7, then another user reported that the 17EW8 works great as a drop-in replacement in the 12AU7 version. You should probably search the thread to make sure, but I'm pretty sure this is how it went.


----------



## Forte

Quote: 





speedway said:


> Hey All
> I'd like to try this amp as my first tube build.  Like everyone else, I can't source the 19J6's, so I want to go with the 12SR7 's. I've spent several days reading this thread but have not found an updated schematic with the value changes and BOM for the build.
> Could someone help me out please?
> Thx


 


  The main changes are mentioned in posts #2824 & #2825 of this thread, a few more details may be in the following few pages after that as well.


----------



## Speedway

Thanks guys
   
  I should have my stuff by this weekend and hope to get started.
  Will report back when finished...


----------



## chrisw302

Hi all.
  I have decided to try to build on of these as my first diy project. I have never done anything with tubes before but this looks doable. I am going to use 12au7 tubes but I am wondering if there are any recommended inexpensive brands to use or to stay away from? Or if there is anything specific to look for in tubes? Also it looks like most places charge extra to match tubes, I assume that paying the extra for matched tubes would be a good deal?
  Any advise would be greatly appreciated and I would like to thank Pete and all the other contributors here for a great thread.
  Chris.


----------



## Speedway

I'm no expert on tubes but for this build I wouldn't pay the money for tube matching.  I just built mine yesterday and used a couple of ecc83's that have been rolling around in my desk drawer for years and it sounds great.


----------



## Speedway

Thought I'd throw out a picture of my SS build I did yesterday. I haven't heard music through  anything with a tube in it for many years and must say it rocks!


----------



## Amatsu

Do you have any pics from the inside, Speedway?


----------



## Speedway

Here's some. It's a bit messy but I have some vintage stuff I want to swap into it later.


----------



## Amatsu

Thanks a lot, it's not messy at all. Does your installation have any ground or it doesn't need any? I'm asking becasue I also have a wood case.


----------



## Speedway

It doesn't have a ground. I guess it wouldn't hurt to add one though...


----------



## DarkTiger892

So I'm building this amp, but I ordered regular 470uF 63V electrolytics for the coupling caps by accident (not the low-ESR types).  I think I'm going to wind up spending another $7 for shipping on mouser, but I'd really rather not.  What will the effects be of using regular electrolytics for C3 and C5 as opposed to low-ESR electrolytics?  Rolled off highs?


----------



## rds

In my opinion there's no reason to have low ESR caps for coupling to a 32+ ohm load.  However, using audio grade caps for coupling may be a good idea.


----------



## monkeyevil

Is pin 9 of the tubes on the modified scematics left open?

Also on the optional caps that are tied to ground (c7, c8), do those parallel the resistors or replace them? What is the reason for installing them?

Same questions on the caps c5a and c3a.

Thanks!


----------



## Bombshell

hi all, i've read a decent portion of this and, despite what's been said about the amp not really being able to damage most headphones, i have a question.
  first off, i'm no guru in any of this, i'm just starting out, so please excuse my ignorance 
  would it be at all possible to do something as simple as a switch before the phone jack, like on most tube guitar amps? (DPDT?)
  i play guitar and i'm used to flipping two switches and waiting a couple seconds to get my amp completely up and running as it is.
  would that fix that -potential- issue without having to use a relay/delay?


----------



## Ikarios

Quote: 





monkeyevil said:


> Is pin 9 of the tubes on the modified scematics left open?
> 
> Also on the optional caps that are tied to ground (c7, c8), do those parallel the resistors or replace them? What is the reason for installing them?
> 
> ...


 

 Yes, pin 9 connects to the middle tap of the heaters and is not used in this schematic. If you look at something like the Bravo V2 amp 12AU7 it utilizes each triode of one tube by using the center tap.
   
  I don't know about C7/C8... you can try searching this thread.
   
  Caps c5a and c3a are bypass caps, film caps to bypass the electrolytics. You can also search to get more info on bypass caps.


----------



## Beftus

C7 and C8 go parallel to the resistors. When installed they increase gain.
   
  A copy & paste answer from way back in this thread:
   
  "[size=12.0pt]That cap is right in the signal path and will thus influence sonics. However, it also lowers rp a little and increases gain, so there are times when one might want it.[/size]
   
  [size=12.0pt]Without the caps there is a small amount of degenerative feedback that reduces gain. The caps bypass the AC signal which eliminates this thus increasing gain[/size]
   
  [size=12.0pt]Also, only use this cap if you need more gain. Otherwise, leave it out.[/size]"


----------



## RedLeader

Was cleaning out my desk and had forgotten an almost-finished SSMH.  Took an hour or two to get it all together, and here it is!  Seems I've got about a 20% channel imbalance and some buzzing in the right channel that is pot-independant.  I'll have to do a thorough look through later, it's a p2p job, so a bit of a rats nest.


----------



## monkeyevil

Quote: 





beftus said:


> C7 and C8 go parallel to the resistors. When installed they increase gain.
> 
> A copy & paste answer from way back in this thread:
> 
> ...


 
  Thanks 
   

  
  Quote: 





ikarios said:


> Yes, pin 9 connects to the middle tap of the heaters and is not used in this schematic. If you look at something like the Bravo V2 amp 12AU7 it utilizes each triode of one tube by using the center tap.
> 
> I don't know about C7/C8... you can try searching this thread.
> 
> Caps c5a and c3a are bypass caps, film caps to bypass the electrolytics. You can also search to get more info on bypass caps.


 
  Thanks


----------



## monkeyevil

Done with case work (need to modify the tube socket nuts for clearance) and maybe halfway done with wiring.  Still couldn't resist seeing how it will look finished.


----------



## c12mech

Looks good so far.  It will look even better when the tubes start to glow.


----------



## the_equalizer

@monkeyevil  and @RedLeader:  Cool looking builds!  Congratulations!


----------



## c12mech

Since I've had mine together for almost a year I should probably get around to actually finishing the case work.  I got it working and started listening to it and that was all  needed.  As we say at work, "It may not be pretty but it is effective."


----------



## RedLeader

Alright, I'm a little baffled.  I've swapped out the pot, switched the tubes and double checked the jack and everything else.  I still have a 20% channel imbalance and buzzing in the quieter channel.  Sounds like a grounding issue to me, but I've checked all the ground.  I am, however, just using a piece of copper as the ground.  Do you guys think that running the grounds across other wiring like that is what is causing it?  Should I add another ground plate on the opposite side?
   
  EDIT: I've added a second ground plate (which seemed to increase the noise floor in the normal channel) and replaced both of the mostfets.  Nothing I do makes any difference.  I must be missing something obvious here, because this is really not that complex an amp.


----------



## Danthrax

Quote: 





monkeyevil said:


> Just because I had a hard time figuring out what parts I needed, I'll post this.
> 
> For the 9 pin and 17EW8 or similar the only real substitution from the original parts list (besides any of the optional stuff.) is the 390omh resistors in R2 & R8. Correct?
> 
> ...


 


  I noticed that you have 100Kohm resistors but no 50Kohm resistors is there a reason for this substitution? I was also wondering where the LEDs would be connected
   
  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif <-- that parts list is for this schematic correct?


----------



## Beftus

LED.
   
  Adjust RLED to set current through LED. Maximum current for a standard LED is usually 20mA. Don't run LED @ 20mA though, lower is better for LED life. A power status LED needs a few mA (3- 5 mA). Tube LEDs need more (10 mA or more).
   
  Use LED calc here: http://led.linear1.org/1led.wiz


----------



## Danthrax

Oh ok so do 2 LEDs connect there or just 1? And also the bigger question I still have is the reason for the 100Kohm resistors that I am going to assume replace the 50Kohm in the picture that are connected to the left and right input.


----------



## the_equalizer

Quote: 





redleader said:


> Alright, I'm a little baffled.  I've swapped out the pot, switched the tubes and double checked the jack and everything else.  I still have a 20% channel imbalance and buzzing in the quieter channel.  Sounds like a grounding issue to me, but I've checked all the ground.  I am, however, just using a piece of copper as the ground.  Do you guys think that running the grounds across other wiring like that is what is causing it?  Should I add another ground plate on the opposite side?
> 
> EDIT: I've added a second ground plate (which seemed to increase the noise floor in the normal channel) and replaced both of the mostfets.  Nothing I do makes any difference.  I must be missing something obvious here, because this is really not that complex an amp.


 
  I can only think that maybe some of the resistors are not at their correct values, or maybe the coupling cap is open... . Measuring the voltages at the tube plates and grids, as well as MOSFET gates and drains could point you in the right direction. Both channels' measurements should be the same (or very close). IIRC, for a 12AU7 version, plates sit at ~27 V, grids at ~ -1 volt, MOSFET gates at ~ 17 volts, MOSFET drains at ~48 volts and MOSFET sources at ~ 12 volts.
   
  cheers!


----------



## monkeyevil

It's done! Works great on the first try with no troubleshooting... woot!
   

   

   

   
  In it's new home...


----------



## c12mech

monkeyevil that looks real nice.  Hope you enjoy listening to it as much as I like mine.  This thing cannot be beat for the price or time involved.


----------



## Danthrax

Nice hopefully mine will look somewhat like that except my case will probably not be as good.


----------



## the_equalizer

Very nice work with your amp, monkeyevil !  Enjoy!


----------



## Danthrax

Hey does anyone know the pinout on this pot http://www.mouser.com/Search/ProductDetail.aspx?R=RV122F-20-15F-A50Kvirtualkey14860000virtualkey313-1240F-50K Is 1 the left pin closest to the knob? And I was also wondering what the pinout is on the power it has 3 tabs but I thought it was just positive and ground? http://www.mouser.com/Search/ProductDetail.aspx?R=163-4305virtualkey11180000virtualkey163-4305
   
  Thanks


----------



## c12mech

Quote: 





danthrax said:


> Hey does anyone know the pinout on this pot http://www.mouser.com/Search/ProductDetail.aspx?R=RV122F-20-15F-A50Kvirtualkey14860000virtualkey313-1240F-50K Is 1 the left pin closest to the knob? And I was also wondering what the pinout is on the power it has 3 tabs but I thought it was just positive and ground? http://www.mouser.com/Search/ProductDetail.aspx?R=163-4305virtualkey11180000virtualkey163-4305
> 
> Thanks


 

 There is a good pin out and explanation of the pot on tangent's webpage.  Best thing I can say is if you are looking at the pot from the back, the right pins, front and back, are the inputs, the middle the outputs, and the left are ground.  I hope that makes sense.
   
  http://tangentsoft.net/audio/pancomp.html (Best explanation I've found yet)
   
  As for the power plug, there are 2 ground pins.  The datasheet  shows them as pins 2 and 3.  The easiest way to figure it out is to check your power supply to see if the center is power or ground.  If it is power then the center pin on the plug is where you want to connect the 48v line to.  Use a multimeter to check continuity between the pin in the plug and the pis on the back.  You can use either of the other 2 pins for your ground.
   
  Like I said, I hope all that makes sense.
   
  Bryant


----------



## RedLeader

Yea, I realized I'd have to bust out the meter, I just wasn't sure what the values I should be looking for.  I checked the sources first, got 12.62 on the good channel, 13.37 on the bad.  Both drains held at 47.9, and the good channel gate was 17.2.  However, the voltage on the bad channel gate was "shut off multimeter and make the speakers plugged into the same powerbar buzz".  That's on the MOSFET I already replaced, so I'm continuing to dig.
  Tube measurements - 1.3v(bad) 1.4v(good), 12.85v(bad) 13.61v(good)
   
  Quote: 





the_equalizer said:


> I can only think that maybe some of the resistors are not at their correct values, or maybe the coupling cap is open... . Measuring the voltages at the tube plates and grids, as well as MOSFET gates and drains could point you in the right direction. Both channels' measurements should be the same (or very close). IIRC, for a 12AU7 version, plates sit at ~27 V, grids at ~ -1 volt, MOSFET gates at ~ 17 volts, MOSFET drains at ~48 volts and MOSFET sources at ~ 12 volts.
> 
> cheers!


----------



## Amatsu

I've a question about the tube pins. In a 9-pin tube socket for 17EW8 which one is pin 1? Looking at the schematic http://img338.imageshack.us/img338/2543/17ew8millettstarvingstu.jpg I'm a little confused because they are not in order, 6 is next to 1 for example. Thanks.


----------



## tomb

Quote: 





amatsu said:


> I've a question about the tube pins. In a 9-pin tube socket for 17EW8 which one is pin 1? Looking at the schematic http://img338.imageshack.us/img338/2543/17ew8millettstarvingstu.jpg I'm a little confused because they are not in order, 6 is next to 1 for example. Thanks.


 

 That's because it's a _fully_-schematic representation, but completely accurate for the design.  However, the physical reality is that every 7-pin tube is going to begin on 1 and end on 7.  Likewise, every 9-pin tube is going to start on 1 and end on 9.  Look at the datasheet for the tube to be sure.  I can't help you with the 17EW8, but TDSL or Pete's pages or many other resources can provide a datasheet, I'm certain.
   
  As for the 19J6, just to use as an example:
http://www.diyforums.org/SSMH/SSMHtubes.php
  You can see the physical pin arrangement with a schematic representation of the elements inside the tube - this is typical for all tube datasheets.  Further, the pin orientiation is always shown as if you were looking underneath, up at the bottom of the tube.  So, to reverse that - if you were standing over your amp and looking down at the tubes and sockets that were upright - then Pin 1 will be on the Right and Pin 7 (9) will be on the Left.
   
  Hope that clears it up for you!


----------



## Amatsu

Thanks tomb, that's very helpful.


----------



## Danthrax

I thought someone a few pages back said it was clockwise from the opening for 12au7 So the 1-9 in order starting at the gap in the pins when looking from the bottom.


----------



## chrisw302

My Starving Student. This is my first diy audio project and my first tube amp of any sort. Gotta say that it sounds pretty nice. Thanks to Pete and all who contributed here.This thing is just great.
  Chris.


----------



## Danthrax

Ok so for those with metal cases how did you perfectly isolate the heatsink and mosfets from the ground? No matter what I tried I still got beeps from the multimeter between my mosfets and my metal box... I ended up just using double sided tape and some JB Weld but it seriously looks like crap.


----------



## Danthrax

Quote: 





c12mech said:


> There is a good pin out and explanation of the pot on tangent's webpage.  Best thing I can say is if you are looking at the pot from the back, the right pins, front and back, are the inputs, the middle the outputs, and the left are ground.  I hope that makes sense.
> 
> http://tangentsoft.net/audio/pancomp.html (Best explanation I've found yet)
> 
> ...


 


  Thank you.


----------



## chrisw302

Quote: 





danthrax said:


> Ok so for those with metal cases how did you perfectly isolate the heatsink and mosfets from the ground? No matter what I tried I still got beeps from the multimeter between my mosfets and my metal box... I ended up just using double sided tape and some JB Weld but it seriously looks like crap.


 


  The heat sink does not need to be isolated from ground, only the mosfet. The mounting kit for the mosfet comes with an isolator for the mounting screw to keep the screw from actually touching the mosfet and the therafilm isolates the body of the mosfet from the heat sink. My heat sinks are soldered directly to the metal case.
  Hope this helps.
  Chris.


----------



## the_equalizer

Quote: 





redleader said:


> Yea, I realized I'd have to bust out the meter, I just wasn't sure what the values I should be looking for.  I checked the sources first, got 12.62 on the good channel, 13.37 on the bad.  Both drains held at 47.9, and the good channel gate was 17.2.  However, the voltage on the bad channel gate was "shut off multimeter and make the speakers plugged into the same powerbar buzz".  That's on the MOSFET I already replaced, so I'm continuing to dig.
> Tube measurements - 1.3v(bad) 1.4v(good), 12.85v(bad) 13.61v(good)


 

 I didn't quite get what the problem with the voltage was in the "bad channel" MOSFET gate. But if it's really off from the correct value, I'd check the connections involving (referring to the diagram's upper channel part numbers) R2, R3, R4 and C2 as well as check the resistor values with a multimeter (disconnecting at least one end of each resistor from the circuit).
   
  cheers !


----------



## RedLeader

Resistor values check out fine, but I don't have a meter thats capable of checking capacitance.  What I meant was, the voltages are off by about 0.6v or so, but when I tried to check the voltage on the gate of one MOSFET, the meter shut off, which I assume means some kind of ground fault.


----------



## Danthrax

Ok so i have a problem I get power, leds light up, the tubes have some red showing like its heating up but I have no sound coming out. The heatsinks for the mosfets also get warm. Are there any possibilities for a fix that jump out at you right away? Maybe it is the optional resistors at the audio inp ut? Should I be hearing complete silence when nothing is plugged in I was expecting some form of interference or something.


----------



## nullstring

Quote: 





danthrax said:


> Should I be hearing complete silence when nothing is plugged in I was expecting some form of interference or something.


 

 Wait, are you telling us you have nothing plugged in?
   
  Yes you should be hearing silence with nothing plugged in >_<.


----------



## Danthrax

No I tried a source as well and still nothing... But I was using adapters for both the source and the output so those could very well be the problem... I'm going to look into it more tomorrow. But has anyone heard of this happening before?


----------



## Danthrax

It appears that my right channel is working now but it makes the driver move a lot and sounds almost like an electrical short... So I'm going to do some isolating and troubleshooting tomorrow and the left channel still isn't working, but the tube heats up so I guess I need to focus on the audio circuit and not the power circuit...


----------



## 00940

If you want us to help you, it would be a good idea to post tomorrow some pictures as well as voltage readings at the following points marked in red (for both channels obviously):


----------



## Danthrax

It works!!!!!!!! The solder let loose that connected a wire to pin 4 on the tube and the shorting sound was from the pins some of the excess solder on the tube sockets touching or coming close together so I re-soldered all the pins and taped them up.


----------



## 00940

All good then. Now, for the important bit: how does it sound ?


----------



## Danthrax

Well I listened to it for a little bit and it sounded really good with my AKGs when I hooked it up to my PS2 for testing but I didn't get my RCA plugs in so I can't make any connector from my PC to it so I haven't done much listening yet. But it definitely drives my 600ohm headphones better than my PC lol.


----------



## Amatsu

Quote: 





amatsu said:


> Just finished my first try at building it, but when I turn the amp on, it starts making a constant high-pitched noise, it comes from the amp, there's nothing plugged yet. Any ideas?
> I'll probably start from scratch some other day because it's a little messy with lots of cables. Is there any way I can check what's good and what's bad with a multimeter/tester? I also did a quick test to see if there was sound but there's nothing as I suspected, although when I turned it off, the headphones did make a static sound. I didn't do any more tests because I'm worried about that high-pitched sound.
> Thanks. I can't upload pics right now sorry.


 
   
  Hey guys, me again. After a second failure (oscillation again), I decided to change the whole case because the first one was very small. I was eager to start so I just used a Kodak cardboard case from my old camera, this way I could make the holes more easily.
  Anyway, I've finally managed to make it work but I'm afraid I'll have to change the heatsinks, because they get really really hot in just a few seconds. This is a 17ew8 build and these are the heatsinks I have (they look a little smaller in reality): http://www.conrad.com/Cool+PIN-EL-CTX/409/50-50X45X12,7-MM.htm?websale7=conrad-int&pi=188041
  
  Unless someone tells my it might be a problem with the build, I'll try to use some computer heatsinks I have around here tomorrow because I don't know if it's supposed to be this hot. (I could leave my hand in there but it was like scary hot.)
   
  I don't know if it's important but the cisco adapter gets very hot too.


----------



## the_equalizer

Good to hear you got your build working! Those heatsinks are a bit small indeed. But there's no need to go to computer heatsinks, unless you're going for the aesthetic effect as a couple of cool builds in the thread have demonstrated. The ones in my 17EW8 build are the same style as the ones you're currently using but are half an inch taller and have larger fins.
   
  EDIT: I just read your comment about the CISCO adapter. What is the adapter's rated current output? It should be no less than 350ma.
   
  cheers!


----------



## Amatsu

Thanks. I'm sorry but I don't know how to check that, I have a basic multimeter here though.
  I don't know if this is normal but I'm checking the cisco and it gets hot by just being connected to the current (it's not connected to the amp right now). After around 4-5 minutes it starts getting hot by itself.


----------



## Beftus

Check the label on the Cisco PSU, what does it say after output? The recommended Cisco PSU is 48 volt DC @ 0.38A (= 380mA).
   
  You've got fairly small heatsinks, no wonder they get hot very quickly. These would have been a better choice: http://www.conrad.com/Heatsink-SK129%2f50.8STS.htm?websale7=conrad-int&pi=188018&ci=SHOP_AREA_27805_0205043
   
  It's normal for the heatsinks to get hot (50-60°C), the mosfets can handle it, don't worry.


----------



## Amatsu

Ok thanks, the label says exactly that, I guess it's the right one. I'll replace the heatsinks, summer it's around the corner anyway and it gets extremely hot in this room, that's why I'm so worried. I'll post pics another day, but it's not that pretty.


----------



## Danthrax

Best case ever.


----------



## Amatsu

It looks like mine! It's really handy making the holes with this type of case. I like how you positioned the volume on the "O".


----------



## Amatsu

What could cause the right side to hum? Left is fine, but the right side starts humming in about 5 seconds after I turn on the amp. Volume doesn't affect it, changing tubes doesn't either. I think I still can hear the music playing very very low along with the hum. I remember this happened to me the first time (2-3 days ago), but I don't know how I solved it. It happens even if the RCA are not connected nor soldered.


----------



## c12mech

Most of the hum problems I remember seeing in the past posts were caused by a bad ground.  Some of the others may be able to help you more but I would start by checking all the grounds on the right channel.


----------



## the_equalizer

Maybe you reversed the signal and ground connections for that channel at some point without noticing. Probably when wiring the headphone jack?


----------



## Amatsu

How do you reverse a signal? I also thought it had something to do with the headphone jack because if I disconnect the ground from it, the same hum appears in both channels. But I resoldered it a few times with no luck.


----------



## Danthrax

Quote: 





amatsu said:


> How do you reverse a signal? I also thought it had something to do with the headphone jack because if I disconnect the ground from it, the same hum appears in both channels. But I resoldered it a few times with no luck.


 


  Check all solder points, ALL seriously that was my issue. Also make sure you have the pin outs on the bottom of the tube isolated from each other (wrap them in electrical tape after you check the solder).


----------



## the_equalizer

What I meant is that you could have soldered the "hot" wire to the jack's ground lug and the ground wire to the jack's "hot" tab.  I't also been known to happen at the other end (the RCA input jacks).
   
  cheers!


----------



## Amatsu

Thanks. I'm pretty sure the headphone jack is correct. I tried it again today connecting everything and realized that even with the semi-loud hum, there's music playing in both channels and it sounds very nice. At least I know there is nothing broken, that's a relief. There must be a serious ground issue since I also get pops and noises touching the other parts or the case itself, also putting the hand close to the tubes can cause the hum to get louder.
   
  I'm thinking of starting again in a different case, maybe it wasn't a good idea doing it in a cardbox. I have a cookie case ready just in case, looks like aluminium: http://img.alibaba.com/photo/209300012/Royal_Dansk_Danish_Butter_Cookies.jpg
   
  I also have a question about tube pins 4 and 5. Right now I have pin 5 alone to ground, I was wondering if maybe it was 4 goes through 5, and then to ground. I'll keep you guys updated.


----------



## the_equalizer

I thought you mentioned the loud hum was only in one channel, thus my suggestion of your possible wiring inversion. If the hum is in both channels then it most surely is indeed a grounding issue.
   
  Since most tubes are not magnetically or electrically shielded, they'll hum when you put your hand close by; that is normal.
   
  Metal enclosures definitely work better in my experience. You can't solder to aluminum so I strongly suggest you do as Mr. Millett and use a PCB blank or copper sheet as a ground plane for your circuit; look at the pics of his build on his site or this thread's very first post.
   
  About pins 4 and 5, which are the tube heater: one of them must connect to the MOSFET and the other one to ground, it makes no difference which does what (the heater is not polarized) but when drawing the schematic a choice had to be made. Connecting them together will not only short out the tube heater (the heater won't light up and the tube won't work at all) but will also short the MOSFET source to ground.
   
  cheers!


----------



## Amatsu

Good to know, thanks. The hum is often on the right channel, but sometimes after messing around with the ground wires it goes to center. I'll start on the new case tomorrow


----------



## Beftus

A 3-channel Starving Student. Has anyone built this too?
   
  http://doesitpew.blogspot.com/2011/02/modified-and-refined-ss-tube-hybrid.html


----------



## Danthrax

Ok so today I noticed a volume imbalance between the left and right with left being significantly louder. I turned the volume to off (all the way down on the volume knob) and audio is still playing from the left channel. So I am wondering if there is a pot that is better than the standard 50k alps pot?


----------



## tomb

Quote: 





danthrax said:


> Ok so today I noticed a volume imbalance between the left and right with left being significantly louder. I turned the volume to off (all the way down on the volume knob) and audio is still playing from the left channel. So I am wondering if there is a pot that is better than the standard 50k alps pot?


 

 Let's be certain here before we go casting aspersions on brand names.  I've never had an _*ALPS*_ RK27 do what you describe.  However, the _*Alpha*_ pot originally spec'd for the Starving Student has had some known channel-balance issues, particularly at the bottom end of travel.  Quality control is not as good, either, so you may be able to buy several (they're pretty cheap), test them with a multimeter, and use the best one of the bunch.
   
  One other method that we've recommended many times in this thread: select the input resistors so that most of your volume adjustment is in the middle of the pot's travel.  Even if there is a mis-match near the start of the pot turn, there should be plenty of room to allow for a complete shut-off at low volumes.


----------



## Danthrax

Actually I was using this one http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A50K/?qs=sGAEpiMZZMtxdMMi52izyq1dbvqSIaEoVagiCpW33UU%3d and I don't think that there should be any volume coming from any channel when the knob is fully off that is a defect regardless of if it has bad tracking, it should turn off. But I did manage to find a revision? or at least what looks like a newer model here: http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-B50K/?qs=sGAEpiMZZMtxdMMi52izyq1dbvqSIaEoVMNCqk4w9sE%3d


----------



## DarkTiger892

Finally finished my 12AU7 build up with a lot of help from the_equalizer (thanks so much, you're a very patient and helpful guy).  Just wanted to share a few things I ran into that might help someone building one in the future.  I'm sure some of these things are super obvious to those who have built stuff like this before, but I know I struggled with them when I started building this.
   
  A)
  12AU7 Tube socket = 7/8" hole.  A step bit (even from harbor freight) does a really great in making perfectly sized holes in metal).  
   
  B)
  I had some buzzing issues, that were fixed by doing two things:
  1) Make sure your wiring on the volume pot is correct.  I had my inputs flipped with my outputs and that induced a great deal of 60/120hz hum.
  2) Make your output wires from the volume pot to the 12AU7 as short as possible.  The shorter they are, the less noise they pick up, and the less noise that gets amplified by first stage (tubes).
   
  C) The 6mm knobs that are speced for the volume pot suck and don't fit on very well.  If you can find something better, get them.  They don't push on nearly far enough (even the deeper knob that mouser has in stock).  I had to bore out my knobs a bit, and then glue them to the pot to get them to go on far enough and look nice.
   
  D) My biggest screw up was ordering 390 ohm resistors and not 390K ohm resistors for R2 and R8.  The difference between the incorrect 390 OHM and 220K OHM resistors makes the tube heater voltage very high (thanks the_equializer), the tubes very bright (and unhappy) and will quickly blow out the mosfets due to a higher than speced voltage on the gates.  
   
  E)  I put a double pole switch on my outputs that when off isolates the headphone jack from the output of the amp.  I didn't want to have to keep plugging my headphones in and out, so I put a switch to disconnect.  This way I can turn the amp on, let it warm up, then flip the mute switch.  When I'm done, flip the mute switch off, flip the power switch off.  No thud, no voltage spikes on the output = happy headphones.
   
  Here's some pictures.  Case is a rad shack project box.
   
  http://img18.imageshack.us/i/finisheds.jpg
  http://img145.imageshack.us/i/finisheddark.jpg/
   
  edit:
  F)  To anyone thinking about using these heatsinks: http://www.mouser.com/Search/ProductDetail.aspx?R=657-15ABPvirtualkey56720000virtualkey567-657-15ABP Those pins don't pull out.  They will shear off before they will pull out (speaking from experience).  They're nice heatsinks, but just be aware of this.  If you want to use them though, they must either be soldiered down (if they're on a material you can soldier to) or flip them over, and use the holes on the other side.  Don't even try to pull the pins out, you will just make a mess.


----------



## tomb

Quote: 





danthrax said:


> Actually I was using this one http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A50K/?qs=sGAEpiMZZMtxdMMi52izyq1dbvqSIaEoVagiCpW33UU%3d and I don't think that there should be any volume coming from any channel when the knob is fully off that is a defect regardless of if it has bad tracking, it should turn off. But I did manage to find a revision? or at least what looks like a newer model here: http://www.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-B50K/?qs=sGAEpiMZZMtxdMMi52izyq1dbvqSIaEoVMNCqk4w9sE%3d


 

 That's a linear taper pot and will not work for audio.  Yes, inexpensive pots will leak sound at their lowest setting.  There are probably other limitations you may notice with a Starving Student purchasing philosophy.
	

	
	
		
		

		
			





  I'm sorry about that disappointment, but I gave you some suggestions to help alleviate the issue.  My concern was that you incorrectly blamed ALPS, which has a sterling reputation around here, costs significantly more, and doesn't have the problems you're complaining about.
   
  I have Walkmans and other stereo equipment that leak sound with very efficient buds and the volume racked to zero.  It's not an isolated issue.  You give up certain conveniences, depending on the design constraints of the product.


----------



## Danthrax

Oh no I wasn't blaming alps I was just wondering if there was a better model.


----------



## Amatsu

Hey. I tried rebuilding the amp on my first wood case, the one where I failed twice. This time I managed to build it with fewer cables and better positioning. Well, even though there's still a quiet hum in both channels, I can finally listen to it. There's still something wrong with the ground because there are still some issues. For example, touching the volume pot generates a different kind of hum until I let it go. Also in some circumstances touching the case generates some pops.
   
  I'll try to take some pics tomorrow, maybe you guys can see someting or give me some tips on the ground thing. It's messy though because I'm a newbie at these things and on top of it my soldering iron is kinda big for these projects.
   
  I have spend around 40 mins listening to it, I almost cried when I have finally listened to the Beyer's with an amplifier, I've had these for around 2 years without amplification.


----------



## revolink24

tomb said:


> That's a linear taper pot and will not work for audio.  Yes, inexpensive pots will leak sound at their lowest setting.  There are probably other limitations you may notice with a Starving Student purchasing philosophy.
> 
> 
> 
> ...




My E-MU 0404 does that. Just a cheap pot. It's definitely not an isolated issue.

I just put an Alps RK27 in my SSMH. Not exactly a "starving student" budget decision, but worth it considering my first build was pretty much ruined by that alpha pot.


----------



## DarkTiger892

My amp is doing something strange, and I'm wondering if anyone here has any ideas what may be causing it.  Randomly the amp seems to make pulses of digital sounding noise at 1 second intervals or so.  It will do this even with no input connected and the volume turned all the way down.  I'll hear silence then...ptshhhhh....ptshhhhh......nothing.......ptshhhhh.  It sounds almost like the digital interference you would get from an onboard laptop soundcard's headphone jack...yet there is nothing connected.  The tubes themselves seem susceptible to interference from cell phones, etc, but I took the battery out of my cell phone, moved the amp away from things that could generate interference, even covered the tubes with tin foil and none of that made any difference.  Any thoughts where this could could be coming from?
   
  --Matt


----------



## Ikarios

Quote: 





darktiger892 said:


> My amp is doing something strange, and I'm wondering if anyone here has any ideas what may be causing it.  Randomly the amp seems to make pulses of digital sounding noise at 1 second intervals or so.  It will do this even with no input connected and the volume turned all the way down.  I'll hear silence then...ptshhhhh....ptshhhhh......nothing.......ptshhhhh.  It sounds almost like the digital interference you would get from an onboard laptop soundcard's headphone jack...yet there is nothing connected.  The tubes themselves seem susceptible to interference from cell phones, etc, but I took the battery out of my cell phone, moved the amp away from things that could generate interference, even covered the tubes with tin foil and none of that made any difference.  Any thoughts where this could could be coming from?
> 
> --Matt


 

 What is the power supply plugged into? Try running it on its own circuit like a separate surge protector or direct into the wall and see if that works.


----------



## revolink24

Has anyone tried using a linear potentiometer instead of R16/17 to adjust gain? If so, did you have any success? I'm tempted to find a decent range linear pot for R16/17 and use that instead of a switch between 50k and 100k. (Would a linear pot even work right for what I want?)


----------



## DarkTiger892

Quote: 





ikarios said:


> What is the power supply plugged into? Try running it on its own circuit like a separate surge protector or direct into the wall and see if that works.


 

 It is plugged into an APC UPS (along with my computer).  I'll try plugging it into the wall for a while.


----------



## Amatsu

Here's a photo of my case:
   
   
  I'm happy to report that I've solved all of the hum and buzzing problems, it's pretty much silent.
  Although I don't know why the volume pot isn't working properly now, it has a fixed volume unaffected by the position of the knob, also it appears to be in reverse, I have to turn it clockwise to silence it. Once it gets some volume (a very small knob turn) it just stays that way even if I keep turning the knob. I don't really mind because I control the volume from the computer, I'm just wondering if maybe the pot is broken because I've checked the wires to the pot and they are fine. The main concern I have is if this can affect the power/consume or temperature the amp gets, for example if having the volume turned to maximum the mosferts are getting unnecessary heat. Because in this state, I don't really know which way the amp thinks it's the maximum and minimum.
   
  On another note, I'll replace again the first heatsink, this one is still getting very hot, the bigger one is fine I think. Cheers.


----------



## tomb

Quote: 





amatsu said:


> Here's a photo of my case:
> 
> 
> I'm happy to report that I've solved all of the hum and buzzing problems, it's pretty much silent.
> ...


 

 You need quite a substantial load connected to the jack (speakers?) before the MOSFETs will run with more current than what the heaters are biasing them with already.
   
  As for the volume pot, your description matches that of a backwards-wired pot.
   
  Neat looking case!


----------



## DarkTiger892

Quote: 





amatsu said:


> On another note, I'll replace again the first heatsink, this one is still getting very hot, the bigger one is fine I think. Cheers.


 

 The mosfets say they are rated to operate up to 170*C  As long as they're mounted to some kind of heatsink, I don't think you really have to worry about them getting too hot


----------



## the_equalizer

The cooler the MOSFETs run, the longer they'll live; though there's obviously a point where the cost of a bigger, better heatsink for use in the SSMH stops making sense.
   
  cheers!


----------



## Amatsu

Well that's a relief, I was getting too worried maybe. The thing is I couldn't leave my fingers on the first heatsink, but I also had the amp running for abour 2 hours with no problems. I figured since this amp will be running most of the day it wouldn't hurt to cool it properly.


----------



## c12mech

I've left mine on for a day or so by accident and can still touch the heatsinks.  They are hot but nothing to extreme.  No damage to the amp by the way.


----------



## Ikarios

My 12AU7 SSMH, with the original heatsinks TomB specified for the 19J6 Beezar kit build, gets to a maximum of around 45C (tested with an IR thermometer). It's uncomfortable to touch but much lower than spec'ed tolerances. I've also accidentally left the SSMH on overnight on many occasions, usually when I turn off the tube LEDs and forget that the amp is still on.


----------



## Amatsu

Well I won't worry too much then. I think my amp is finally finished now, so thanks a lot everyone. Let's hope it lasts. This is the first dedicated amp I have, so I don't have much experience, but it's sounding awesome with my DT770, this headphones are supposed to have recessed mids but I think a tube amp might be giving the mids a little push.


----------



## dirkpitt45

Anyone have any ideas as to why a single channel would just stop working? 
   
  I know my fubarII is working fine, and I tried using my zune hd to source the MSSH (beezer kit with 19J6 tubes) and still have the same problem. Actually (after just typing out my problem >.<) the right channel was completely silent, but it started to develop some static after a few minutes. I unplugged the headphones (MS1s), plugged them back in and the static is now gone. But no music comes through the right channel still. I've had headphones plugged in for ~5minutes, and no static has come back, but no music in the right channel either. 
   
  It was working fine this morning, and for about 2-3 months before. I've had no trouble with it at all (surprisingly lol). At first there was some noise, but it eventually disappeared after a few days and I figured it was just the tubes burning in. Maybe one of them died now?


----------



## Beftus

Switch the tubes. Does the problem follow the tubes?


----------



## dirkpitt45

I'm thinking it must be the headphone jack now. If I push the plug in sort of half way, there's music (well sound) in both channels. But then as soon as it's all the way in, only one channel. 
   
   
  I will try to switch the tubes once they cool down.


----------



## Ikarios

Quote: 





dirkpitt45 said:


> I'm thinking it must be the headphone jack now. If I push the plug in sort of half way, there's music (well sound) in both channels. But then as soon as it's all the way in, only one channel.
> 
> 
> I will try to switch the tubes once they cool down.


 

 You might just be bridging the R signal between the ring and the tip of the plug. Your amp's L channel probably still doesn't work.


----------



## dirkpitt45

Well switched the tubes and it made no difference. Tried again with the MS1s and still nothing in the right channel, but then I plugged my hd600s and it started working fine. Must be the headphone jack then right? I'll have to resolder it next time I have some time off. Till then I just won't touch the plug lol. 
   
  Disaster averted! I don't know what I'd do if one of the tubes failed, then I'd be dba-02less and hd600less.


----------



## DarkTiger892

My SS amp works well, but I'm still trying to eliminate ground hum. It's not that audible at the lower end of the pot (with 32 ohm headphones), but if I turn it up past half way with no source playing (but still connected), the hum starts to get to a level where it would interfere with music. I noticed that the potential voltage between the - on the cisco power supply and the AC Mains ground ~18VAC. This is (if I understand correctly) how the SS fries some equipment that doesnt ground its inputs to earth. If I ground the amp to mains ground, 90% of this hum goes away. The 18V can get to ground either by sticking a wire in the ground of a wall outlet and touching the chassis or allowing the amp to ground itself through my soundcard (seems less than ideal). The last 10% of the hum goes away if I touch the metal chassis with my finger. 

I guess I have two questions then. 

1) Is the Cisco power supply's (-) supposed to float 18VAC or so above mains ground? It has a 3 prong plug, so I would assume that the output - and input gnd or netural would be tied together, but apparently not.

2) This is the hard one. How can I knock out the last 10% of the hum? I can't sit there and hold my finger on it all day. Like I said, even when the amp is completely grounded to the source and electrical system, the last little bit of hum seems to persist. Once I ground myself, the amp, and mains ground together, 100% of the hum is gone. I don't understand how when I'm not touching the amp, it has some hum at 100% volume. Any ideas on how I can fix this one? The plastic case doesn't seem to be allowing it to pick up much interference, because when I'm grounded to it, there is none even with the plastic case. I did a point to point build, and all the grounds have good soldering joints. I have the DC ground, signal ground, the chassis, and headphone jack ground all tied together with 2 two terminal strips and wire. I wouldn't call it a star ground because the wires don't all meet at a single point, but they all have a good connection to each other and the longest wire is maybe 4". I even insulated some of the sensitive spots (grid pins, etc.) with electrical tape, but that didn't really do much good.

Any ideas?


----------



## the_equalizer

I haven't measured the voltage between my the amp's ground and AC ground... but somehow 18 volts just doesn't seem right, it seems too much. I've been using my SSMH with my grubDAC for more than 6 months already without a problem (just follow the rule of never connect/disconnet the DAC to the amp's input when the amp is on).
   
  Hum increasing as you turn the volume pot suggests the hum is already present at the amp's input; but that may have to do with that weird voltage measurement you're getting. 
   
  I'll try testing my 17EW8 build later and see how that measures.
   
  cheers!


----------



## DarkTiger892

Thanks, let me know what you come up with. You really don't even need the amp to test it. I get the same ~18VAC measurement with the power supply unplugged from the amp and 1 probe of my meter on mains ground and the other on the outside of the power supply plug (neg).


----------



## the_equalizer

Well, just measured and I get 0V between the AC ground prong and DC ground. Try another AC cord, and/or another AC outlet.


----------



## DarkTiger892

I tried another cord and another outlet, and theres no difference. I wonder if my power supply is screwed up. You did measure between AC ground and DC ground with your meter on AC right?

Here's what I did (in pictures)







If anyone else could check out their power supplies and let me know if yours is the same as mine or different, I would appreciate it. Maybe my power supply is bad 

-Matt


----------



## the_equalizer

Yes, that's how I measured too, I was going to take pics but I got a bit lazy 
	

	
	
		
		

		
			





.   Let's see if someone else posts how much their supply measures.
   
  cheers!


----------



## c12mech

The first power supply that I bought never did seem to work right and finally just died.  I bought another of the same type and rating but different model number and it has benn perfect since.  I'll check the voltages when I get home today.


----------



## DarkTiger892

C12 and the_equalizer, what model power supplies do you guys have?  Mine is the PSA18U-480C.  From looking at ebay, it seems that there are a few other 48V Cisco power supplies.  There is the ADP-18FB, the CP-7941, the CP-7940G, and several others.  I don't want to buy another PSA18U if its just going to do the same thing.


----------



## c12mech

Home now and measured mine.  0v when meter was set to DC and a range of .2v to 3.3v when set to AC.  It changed if I touched a different part of the AC ground socket, weird.  I do have it plugged in to a power strip though and don't know that it makes much difference but it shouldn't.
   
  I'm still guessing power supply.  I still see them going on ebay for about $10.  If I had an extra I would send it to you to try.


----------



## c12mech

Mine is a model PA-48ml.  It looks to be kind of generic.  I had one of the Cisco models that you have listed at first and it did not last that long.


----------



## cactus friend

Wow, it's been years and people are still posting in this thread.  That's reassuring because I haven't touched my in-progress mssh since it kinda 'blew up' all those years ago.  But I think I'd like to try my hand again.  I never even got far enough to bust the tubes so I should have most everything I need.  I'll spend the next week or so digging through the pics in this thread for some nice point-to-point examples 
	

	
	
		
		

		
		
	


	




 (to maybe see why mine flipped out).


----------



## DarkTiger892

I ordered a Cisco EADP-18FB B (p/n 34.1977-04) from fleabay.  The plug is the same size and it's still 48VDC .38A but it seems to be manufactured by a different company (delta electronics) for Cisco.  Also it is made in a different location than my PSA18U (thailand v china).  Hopefully It will work better.  I'll keep you posted.
   
  --Matt


----------



## DarkTiger892

I'm not an expert in electronics or electrical engineering by any means, but I've been thinking a bit about why grounding the grounds of my amp to mains ground makes 90% of the hum on my amplifier power supply go away.  The ground problems aren't internal to the amp, but rather to the power supply.  Like I said in my earlier posts, the entire 48V rail of the power supply is offset by ~+17V AC from the mains ground.  I'm going to try to do my best to explain why I think it has the effect that it does.  I hope that it may help someone else out if for no other reason than to be a critical thinking excercise about how things work.  If I'm wrong about this, someone smarter than myself please feel free to correct me.
   
  Normally when dealing with audio equipment, DC offset is a concern, in a power amplifier for example.  The useful signal is AC, and any DC offset is a shift of the sine wave up or down.  The useful signal in the power supply circuit for the headphone amp is DC, and in this case, the AC is the unwanted voltage.  At first I had trouble understanding how AC and DC power can exist on the same line, but then it hit me.  Unlike a DC offset of AC power which shifts the useful signal up or down by a fixed amount relative to a constant point, an AC offset of DC power fluctuates the steady DC voltage up and down relative to a constant point in accordance with the AC sine wave.  The voltage between the DC -  and DC + will always measure 48V, but this 48V is shifting up and down by 17V relative to earth ground at the mains frequency--60 times a second.  Now, I believe the reason that this 60Hz (or some of its harmonics) comes through in the audio signal chain has to do with the resistance of the circuit.  The ground of the amplifier has almost no resistance on it, while the input side has a resitance in the 10's of kOhms.  So what I think is happening (and correct me if I'm wrong) is that due to the resistance of the input circuit relative to the essentially non-exitant resistance of the ground, a voltage differential is caused by this resistance [ohm's law?] between the signal ground (same as DC ground) and the signal hot.  This voltage differential caused by the resistance is only very slight which I think is why the 60hz hum is relatively quiet.  If the voltage differential between signal and ground was larger (just like with a louder input source) the hum would be more prevalent.  When the chassis (DC -) is grounded to earth, there is no longer any AC offset being induced into the circuit, and the hum goes away.
   
  I hope that made sense.  Please let me know if you have any input on this.
   
  --Matt


----------



## the_equalizer

Quote: 





darktiger892 said:


> C12 and the_equalizer, what model power supplies do you guys have?  Mine is the PSA18U-480C.  From looking at ebay, it seems that there are a few other 48V Cisco power supplies.  There is the ADP-18FB, the CP-7941, the CP-7940G, and several others.  I don't want to buy another PSA18U if its just going to do the same thing.


 

 I have a PSM60U-480KP made in China, which can output 1.25 A, and a PSA18U-480C, also made in China, with a 380 mA output current capability.  Both have worked fine for more than a year and with no ground issues.
   
  cheers!


----------



## juntom10

What kind of tube can i use to build this?
   
  because i tried to find original tubes that were used , but i couldnt find.
   
  Also, where can i get tubes that can be used here in canada? (online stores)
   
  thank you.
   
  Ps. Are there any other parts that are needed to be replaced when using different tubes?


----------



## Beftus

juntom10 said:


> What kind of tube can i use to build this?
> 
> because i tried to find original tubes that were used , but i couldnt find.
> 
> ...




Start reading here: http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/3870#post_6024902


----------



## juntom10

Thank you for the reply.
   
  I just ordered 12AT7x2 and 12AU7x2 from ebay with surface mount sockets 
   
  Now it is time to make a list of other parts....
   
  oh by the way, i'm thinking of order other parts from digikey.... when i was reading the list of parts from pmillet website, it is based on mouser....
   
  i was trying to find similar spec parts from digikey, but there are so many kinds...any suggetions?


----------



## c12mech

The easiest way for me to cross reference parts from Mouser to Digikey is to find the part on one site and copy/paste the mfg. p/n to the other site.  I ordered all my parts from mouser since digikey has a minimum of 10 for some of the smaller parts.  It was cheaper in the long run to get it all from Mouser.  Also, the pmillet bom will be different if you are using the tubes you specified.  I had to make my own list from the schematic that was posted, I did the 17ew8 build.  It is almost the same as the 12ax7 with a couple of resistor changes I believe.  The equalizer is who I got a lot of my information from.  Find some of his posts about this to make sure you are buying the right things.


----------



## eertelppa

Everyone,
   
  I have read for about an hour now but really cannot invest any more time until I get a whole night to read through everything.
  I would like to make an order through mouser and bezzar soon. I was planning on using the BOM from diyforums.com that was poster here a while back. 
   
  Something that I was wanting input in was:
   
  - seems there are multiple tube options and it is not simply changing out tubes for different ones (i guess the term tube rolling would apply)
  - with all the different tubes i assume different tones and sounds go with them?
  - the decision on which tubes to be used seems to change the BOM other than the tubes themselves. seems other parts must be changed in order to handle tubes other than the 19J6. would like to look at different companies and options. would prefer telefunkens if possible. 
  - if i choose based on the different sound qualities how do i know what all needs to change for the BOM in order to build accordingly?
  - not sure if it matters but I listen to rock, harder music, folk, indie, slow stuff, etc so a big variety
   
  Sorry for the questions that are most likely redundant. I just would like to order soon so I can work with a friend in a few weeks on it. The only thing hanging me up from ordering everything is the tubes and what changes to the BOM the tube decision makes...
   
  EDIT: talked with my dad a little kinda busy at work on my end and trying to hurry up and type this out but told him i read about the 12au7 and 19j6 and he said he would go with the 12au7 since tons of companies made them and it was a standard tube for stereo amps. he has two mc225s so he has spent his fair time with tubes. so now to update the BOM to use a 12au7 and go about ordering some parts!
   
  Thanks for any advice and help,
   
  Austin


----------



## DarkTiger892

Even with the new power supply, I don't have the 17V but I'm still fighting a buzz problem. All I can find anywhere is "I have a ground problem". Does anyone have any more specific advice than this? I started off with all the grounds tied together: pot ground, input ground, tube heater grounds, and DC in ground, etc. I've seen it suggested with other amps to isolate the signal ground from the DC ground, but with this amp it seems like the signal/not signal grounds are one in the same in some places. For example, the ground after R4 and R10. Is that a "signal ground" or not? What about R5 and R11? R6 and R12 I think WOULD be a signal ground, but it is also the ground to discharge the output caps, so I don't know. Can someone tell me how to isolate the signal ground from DC ground in this design? I'm not sure which grounds i need to disconnect from the rest of them and soldier together in their own ground. I tried isolating the RCA grounds and the pot ground, but that only made the problem worse.

http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif


----------



## nullstring

Quote: 





eertelppa said:


> EDIT: talked with my dad a little kinda busy at work on my end and trying to hurry up and type this out but told him i read about the 12au7 and 19j6 and he said he would go with the 12au7 since tons of companies made them and it was a standard tube for stereo amps. he has two mc225s so he has spent his fair time with tubes. so now to update the BOM to use a 12au7 and go about ordering some parts!


 

 I am surprised, looks like 12AU7's have a large range in cost..
  Which is a good thing.
   
  Really, IIRC, there is just one resistor change between the 12AU7 and the 17EW8, so you could do either/box
  They use the same sockets (again, IIRC).
   
  One thing to keep in mind is that the power capacitors in the BOM were chosen because of space issues.
  If don't have the same space issues, you can get panasonic FM caps that are longer, etc. for cheaper (I think)


----------



## nullstring

Lately I've been thinking of if there is a way to improve the SSMH.
  It's such a neat simple circuit.
   
  3 channel? Different mosfets? IDK, but the M^3 is also a surprisingly simply design.
  I wonder if there might be some way to combine the two.
   
  I also wonder if one could build an miniaturized M^3 with cheaper parts and similar performance.


----------



## DarkTiger892

Anyone?  Help?


----------



## Beftus

nullstring said:


> Lately I've been thinking of if there is a way to improve the SSMH.
> It's such a neat simple circuit.
> 
> 3 channel? Different mosfets? IDK, but the M^3 is also a surprisingly simply design.
> ...




3-channel Starving Student: http://doesitpew.blogspot.com/2011/02/modified-and-refined-ss-tube-hybrid.html

miniaturized M^3: http://www.amb.org/audio/mini3/


----------



## nullstring

beftus said:


> nullstring said:
> 
> 
> > Lately I've been thinking of if there is a way to improve the SSMH.
> ...




I knew the 3-channel version existed, but had not seen a schematic, thanks.

Also, mini^3 is hardly a miniaturized M^3 (M is for mosfet)
I didn't really mean miniaturized . More like stripped down.


----------



## tomb

Quote: 





nullstring said:


> Quote:
> 
> 
> 
> ...


 

 If you want a tube-powered M3, the MOSFET-MAX may come the closest.  As a matter of fact, I'm not aware of anyone who uses a _diamond buffer _with MOSFETs.
   
  That said, Dsavitsk has some upgrades planned for the SSMH - a regulated supply using something other than the Cisco adapter and different tubes of course, but otherwise very similar.


----------



## c12mech

Quote: 





darktiger892 said:


> Even with the new power supply, I don't have the 17V but I'm still fighting a buzz problem. All I can find anywhere is "I have a ground problem". Does anyone have any more specific advice than this? I started off with all the grounds tied together: pot ground, input ground, tube heater grounds, and DC in ground, etc. I've seen it suggested with other amps to isolate the signal ground from the DC ground, but with this amp it seems like the signal/not signal grounds are one in the same in some places. For example, the ground after R4 and R10. Is that a "signal ground" or not? What about R5 and R11? R6 and R12 I think WOULD be a signal ground, but it is also the ground to discharge the output caps, so I don't know. Can someone tell me how to isolate the signal ground from DC ground in this design? I'm not sure which grounds i need to disconnect from the rest of them and soldier together in their own ground. I tried isolating the RCA grounds and the pot ground, but that only made the problem worse.
> 
> http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif


 
   
  Do you have the input rca jacks isolated or are they grounded to the case.  I just looked at how I did mine and they are not isolated but I also ran a wire to ground.  Output jack is isolated and also has wire to ground also.  I used a kind of bus bar ground.  It is simply a piece of wire that loops around the inside of the case and has all the grounds connected.  Also make sure that the pot is grounded.  I had a slight hum when I first finished mine and it turned out to be the rca ground.  Hope this helps a little.


----------



## DarkTiger892

c12mech said:


> Do you have the input rca jacks isolated or are they grounded to the case.  I just looked at how I did mine and they are not isolated but I also ran a wire to ground.  Output jack is isolated and also has wire to ground also.  I used a kind of bus bar ground.  It is simply a piece of wire that loops around the inside of the case and has all the grounds connected.  Also make sure that the pot is grounded.  I had a slight hum when I first finished mine and it turned out to be the rca ground.  Hope this helps a little.




None of my jacks and switches are grounded to the case because it is plastic (except for the metal top). Here's a picture to help you visualize it. http://mattbarszcz.homedns.org/files/tube%20amp%20so%20far/finished.JPG I did like you and created a ground bus that everything that required a ground got soldiered into (either directly or with a short piece of wire). If I touch the metal top of the amp, the buzz goes away completely. As soon as I let off, it starts up again. What gives? I have everything soldiered together to create a good low resistance path to ground for the components. After looking over the schematic I don't think it is possible to isolate signal ground from DC ground in this circuit (other than the RCA's and the pots, which just made things worse). Too many components are shared between powering/biasing the tubes and carrying audio (anode components, mosfet, output caps + resistor). All the components do have a good ground though. I don't know what to do to make the buzz go away. I can't give anything a BETTER ground, and any grounds I disconnect just make things worse. I'm stuck. Everything is grounded point to point, but the effect should be the same as it would be if it was built on a copper ground plate. Why does the problem go away when I touch the metal? The chassis already has a good path to ground. How can a high resistance ground (my finger) be better than a path than through the power supply?

Surely enough people have built this dumb thing that someone else has run into this problem.

:mad::mad:


----------



## the_equalizer

Are you using a full metal case?  That can help shield the circuit and remove the last traces of buzz.
   
  Buzzing goes down when you touch the circuit's ground because your body is a big mass that can both act as a current sink and as a big antenna tu swamp electromagnetic fields around the amp. That's why single coil (and even some humbucker equipped) guitars are usually sold with a ground cable connected to the strings.
   
  cheers!


----------



## c12mech

Have you got the ground bus connected to the top metal plate?  I remember when I was trying to find what was causing the hum in mine I took a jumper wire and connected it to the case top then touched just the *GROUNDS* of connectors and components until it went away.  At that point I knew where the ground was missing.  Since then it has worked perfectly.


----------



## DarkTiger892

the_equalizer said:


> Are you using a full metal case?  That can help shield the circuit and remove the last traces of buzz.
> 
> Buzzing goes down when you touch the circuit's ground because your body is a big mass that can both act as a current sink and as a big antenna tu swamp electromagnetic fields around the amp. That's why single coil (and even some humbucker equipped) guitars are usually sold with a ground cable connected to the strings.
> 
> cheers!




No I'm not using a full metal case. The only case I could find was a radioshack project box, and unfortunately those aren't all metal. People seem to have built these as bare PCB's, in wooden cases and in cardboard boxes and those people don't seem to have this hum problem. I understand about the current current sink now. Unfortunately, I can't sit and touch the case the whole time though



c12mech said:


> Have you got the ground bus connected to the top metal plate?  I remember when I was trying to find what was causing the hum in mine I took a jumper wire and connected it to the case top then touched just the *GROUNDS* of connectors and components until it went away.  At that point I knew where the ground was missing.  Since then it has worked perfectly.




Yeah I have a wire run from the ground bus tightened down under one of the heatsink mounting screws against the bare metal of the top plate. It's better with the ground bus tied into the top plate but not by much. I keep poking different point with a grounded cable, but they already have a good ground soldiered to them. In case anyone is wondering, my mosfets _are _isolated from the heatsinks as well. Aside from building this in a metal case which I don't have, nor do I have the money to buy (I'm embarrassed to say that I've already spent close to $150 ...ugh should've just bought a little dot....) what else can i do in terms of grounding? I've tried a different power supply that doesn't have a mysterious 17VAC on the output, and even broken the ground pin off of a test AC cord to float the AC ground, but that just made the situation worse. There aren't any more components I can connect to ground, or anymore wires to shorten. There are no AC cables, sources, or other equipment nearby the amp that it could possibly be picking up interference from. I don't know where to go from here.


----------



## Ikarios

Is the SSMH design the equivalent of the Cmoy with tubes, simplicity-wise? I noticed that the 12AU7 Bravo amps (those $60 chinese amps found on ebay) had a somewhat-similar design to the SSMH, but used each triode separately with a center-tapped design.


----------



## the_equalizer

Quote: 





> Originally Posted by *DarkTiger892* /img/forum/go_quote.gif
> 
> [SNIP]
> 
> ...


 

 Actually, the more I think of it, the fact that the hum goes away when you touch the metal plate suggests your issue is not so much with grounding but with shielding, so I'm pretty sure that a conductive enclosure will help.
   
  No need to get a fancy Hammond extruded aluminum case, you can either:
   
  a) use glue and alumminun foil to cover the interior of the radio shack project box, then ground it (with a nut and bolt, since you can't solder to alumminum). I did this for my first build of RJM audio's "Very Simple Phono Stage". It definitely worked in removing some buzzing the circuit was picking up.
   
  b) get a cheap metal box for other product, like Mr Pete Millet's build, done on a wallet box. I've been considering using the tin boxes from some dominoes games I've seen sold at Wal-Mart and Office Depot for around $10.00 USD
   
  cheers!


----------



## DarkTiger892

the_equalizer said:


> Actually, the more I think of it, the fact that the hum goes away when you touch the metal plate suggests your issue is not so much with grounding but with shielding, so I'm pretty sure that a conductive enclosure will help.
> 
> No need to get a fancy Hammond extruded aluminum case, you can either:
> 
> ...




Excellent. The tin foil worked. I cut tin foil and overlapped/taped the edges together on all sides of the box, then grounded it with a nut and bolt to the ground bus you said. To not make a mess with glue, I stuck the foil to the sides with glue dots. In case you're not familiar, they're little sticky blob things of glue. 





They don't have to dry like regular glue (and don't make a mess). You just stick them onto the side, and stick the tin foil to them. They're popular for sticking things in scrapbooks. 

That was the suggestion I was looking for. Thanks equalizer. No more buzz/hum/anything.  I hope someone reading this thread can learn from this. 

--Matt


----------



## c12mech

Glad to here you got it straightened out.  The shielding makes perfect sense and I should have thought of it since I had a similar problem years ago with a bass guitar.  Always had a hum unless you were touching the strings.  Foil in the pot cavity fixed it right up.
   
  On a different note I'm seriously considering doing a three channel 12ax7 version.  I wonder what difference it makes sonically?  And would the stock power supply be up to task for it?


----------



## DarkTiger892

Quote:  





> On a different note I'm seriously considering doing a three channel 12ax7 version.  I wonder what difference it makes sonically?  And would the stock power supply be up to task for it?


 

 3 channel?  Maybe I'm missing something here, but what is the third channel for?


----------



## c12mech

3-channel Starving Student: http://doesitpew.blogspot.com/2011/02/modified-and-refined-ss-tube-hybrid.html
   
  Active ground.


----------



## Ikarios

So I've been thinking about how to manage the gain on my SSMH. On the one hand, Grados and other low impedance headphones are hissy, and get generally too loud beyond 10 o'clock. If I want to listen to Grados at a low level I worry about hitting the channel imbalance on this cheap alpha pot. On the other hand, my K501s (and other inefficient cans, like vintage AKGs or planars) take a lot of voltage swing to get up there in volume, especially for quiet songs. My gain switch does very little (IIRC it switches between 50k and 150k input resistors), maybe an extra two o'clocks in volume at the most.
   
  For a while I've been considering snipping out C7 and C8, since they apparently increase gain (though I never got a figure about how much they increase gain by). Now that I've found the K501s, though, I realize that I want the extra volume that my current configuration provides. What if I snip out C7/C8 and rewire them to my gain switch (so that the "gain switch" switches between having C7/C8 in the path to ground and not having them connected)? Anyone think this is a good idea?
  Thanks!


----------



## Beftus

c12mech said:


> And would the stock power supply be up to task for it?




Most certainly not! In a 2 channel one: 2x 150mA for the heaters plus a few LEDs and you're rapidly reaching the 380mA limit of the Cisco PSU.


----------



## c12mech

That's what I thought.  I was considering building a better power supply anyway.  Now I have a good reason.


----------



## nullstring

beftus said:


> c12mech said:
> 
> 
> > And would the stock power supply be up to task for it?
> ...




Err, you realize that the 150mA is at 19V (or 12V) and the 380mA is at 48V, right?


----------



## the_equalizer

Quote: 





nullstring said:


> Quote:
> 
> 
> 
> ...


 

 Not exactly. You have to realize that the MOSFET and the heater are in series, from the 48 volt supply line to ground. So whatever voltage the heater 'uses' the rest is taken by the MOSFET; they being in series, the same current flows through them. So it's 150ma @ 48 volts per channel, as Beftus pointed out.
   
  cheers!


----------



## Beftus

The Cisco PSU provides a _regulated_ 48 volts DC. At least, mine do (I have two). They do not automagically supply either 12 or 19 volts.


----------



## the_equalizer

Quote: 





darktiger892 said:


> Quote:
> 
> 
> 
> ...


 
  Great!  I'm glad you solved it!  Enjoy your amp!
   
  cheers!


----------



## eertelppa

Quote: 





eertelppa said:


> Everyone,
> 
> I have read for about an hour now but really cannot invest any more time until I get a whole night to read through everything.
> I would like to make an order through mouser and bezzar soon. I was planning on using the BOM from diyforums.com that was poster here a while back.
> ...


 
   
  Quote: 





nullstring said:


> I am surprised, looks like 12AU7's have a large range in cost..
> Which is a good thing.
> 
> Really, IIRC, there is just one resistor change between the 12AU7 and the 17EW8, so you could do either/box
> ...


 
   
  Yeah it seems like you only need to change the resistor(s) and have the appropriate sockets. I had to go further back in my reading then i did initially, i had started reading around page 300. As far as space issues I plan to make my own box out of wood or metal. my dad has a shop and we can fab something real nice. Not sure if wood is ok to use or metal is the standard....
   
  I am going to order all my stuff tonight. I guess I just need the appropriate sockets and resistors.
   
  Thanks for the advice. Any one else is welcome to chime in.
   
  Also as previously stated any differentiation between 12au7, 12ax7, 19j6 tubes would be appreciated. Does it really matter? Do they all sound different / have certain traits? Have some questions about the tubes themselves and pins, plates, etc but my dad knows all that so I will have to get him to explain it all so I know what I am buying. He has like 3 testers as well so should be good on that end.
   
  Austin
   
  EDIT: not sure if i will get a reply to the above but I would like to add....if I am going to buy a few extras what are the things I should for sure order a few backups of?


----------



## nullstring

So, this means that the MOSFET's are dropping 29*150 = 4.350 watts each?
   
  Is there a real benefit to doing this?
  What would happen if you powered the amp using a 26V source?
   
  Or was this done just because a 48V power supply is super cheap?
   
  Quote: 





the_equalizer said:


> Not exactly. You have to realize that the MOSFET and the heater are in series, from the 48 volt supply line to ground. So whatever voltage the heater 'uses' the rest is taken by the MOSFET; they being in series, the same current flows through them. So it's 150ma @ 48 volts per channel, as Beftus pointed out.
> 
> cheers!


----------



## Beftus

nullstring said:


> So, this means that the MOSFET's are dropping 29*150 = 4.350 watts each?
> 
> Is there a real benefit to doing this?
> What would happen if you powered the amp using a 26V source?
> ...




Yup, that's why the heatsinks get so hot. If you take a lower voltage PSU the MOSFETs will dissipate less heat and you will need to turn up the central heating in your home.  The Cisco PSU's are cheap (mine were), hence the name: Starving Student.


----------



## Ikarios

While we're talking about power, has anyone checked specs on the power output capabilities of the SSMH? I'd like to compare it to other commercial amps in this regard so numbers would help.


----------



## DarkTiger892

The 48V PSU is used so that the tubes can have 48V on the plate.


----------



## Beftus

darktiger892 said:


> The 48V PSU is used so that the tubes can have 48V on the plate.




True. Silly me, I forgot that. Less plate voltage in essence means a starved plate which leads to the tube operating in a non-linear area. This will give interesting distortion if you're into that. An area usually only interesting to rock guitar players.


----------



## the_equalizer

Quote: 





nullstring said:


> So, this means that the MOSFET's are dropping 29*150 = 4.350 watts each?
> 
> Is there a real benefit to doing this?
> What would happen if you powered the amp using a 26V source?
> ...


 
  Quote: 





> Originally Posted by *DarkTiger892* /img/forum/go_quote.gif
> 
> The 48V PSU is used so that the tubes can have 48V on the plate.


 
  Quote: 





beftus said:


> [SNIP]
> 
> 
> True. Silly me, I forgot that. Less plate voltage in essence means a starved plate which leads to the tube operating in a non-linear area. This will give interesting distortion if you're into that. An area usually only interesting to rock guitar players.


 

 Yeah, I'd say the choice of PS was a combination of those two factors: reasonably high plate voltage for the tubes *and* drain voltage for the MOSFETs as well as a compact, plentiful and cheap supply brick.
   
  cheers!


----------



## the_equalizer

Quote: 





ikarios said:


> While we're talking about power, has anyone checked specs on the power output capabilities of the SSMH? I'd like to compare it to other commercial amps in this regard so numbers would help.


 


  Well, If I remember correctly, from a simulation in TINA-TI, using a 1 KHz sine wave as input, the amp was putting out 200 mili Watts into a 62 ohm resistor (the impedance of the K701) with .5% harmonic distortion. It's a simulation but it gives you a reference.  Does it seem low compared to the theoretical dissipation?  That's class A operation for you !
   
  You can get some reference measurements in real life: get a 1 KHz tone mp3 file, and use your DVM to measure AC volts at the headphone jack. Then, knowing the impedance of your heaphones (which is usually rated @ 1 KHz) you can calculate the power output by the amp; maybe at the volume knob position you usually listen to.
   
  EDIT: Take a look at http://www.pmillett.com/starving.htm  Almost at the bottom of the page Mr. Millet states that the 5% Total Harmonic Distortion point is 7 volts RMS @ 100 ohms   and  3 volts RMS @ 32 ohms. That means 280 mW and 490 mW respectively.
   
  cheers!


----------



## Surruk

sorry if this has been answered, but i looked through a fair bit of this thread before giving up and deciding just to ask this.
   
  Did anyone ever come up with a simple way to install a "safety" to stop potential damage to headphones during start up / turn off?


----------



## Ikarios

Quote: 





surruk said:


> sorry if this has been answered, but i looked through a fair bit of this thread before giving up and deciding just to ask this.
> 
> Did anyone ever come up with a simple way to install a "safety" to stop potential damage to headphones during start up / turn off?


 

 I only came across one (besides using AMB's epsilon12) - it was briefly detailed by ArtemF in one of his first posts.
   
  http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/5190#post_6680044
  Quote: 





> I also added diode protection to the output (2 x 2 x 2 = 8 diodes = forward/reverse 2.4V threshold protection for two channels). I used blue LEDs so they flash nicely when the power is on.


 
   
  I sent him a PM clarifying how he has it set up, he responded with this:
   
  Quote: 





> Hi Aflac,
> 
> the idea of output diode protection is the following: when the caps are charging (through
> the headphones) we'd like to bypass the headphones. On the other hand, we don't want
> ...


 
   
  I considered doing this protection with zener diodes, but I decided I wasn't strong enough electronically to stray from what Artem did, so I ended up using some LEDs.
   
  Quote: 





> When the caps are charged the upper points of R6 and R12 are at zero potential with respect to ground.
> 
> It's fine to use the diodes you named. One in forward, one in reverse for each channel.
> The scheme for one channel is like that:
> ...


 
   
  I can't say how good of a job they do, and I still get some pop when turning on (and especially turning off) the amp. I'm not sure if it's damaging to my headphones but I've done it a few times early on and my headphones were okay. I unplug my headphones anyway now that the ones I'm using are more expensive.


----------



## Surruk

awesome, thanks for the fast reply, i think i might just copy what ArtemF did, im not that great at DIY so i will play it safe.
  I was mainly looking for a fail safe just in case i forget to unplug before i turn on / off (i can be a real air head at times  ) rather than risk blowing up my headphones. this fits the bill pretty well.
   
  Thanks again.


----------



## DarkTiger892

I just put a double pole switch on the outputs. So when I want to use it, I turn the main power switch on, wait a little while, then turn on the headphone switch (a sort of reverse mute switch).  To turn it off, flip the mute, flip the power.  Works every time, no pop.


----------



## kchapdaily

does anyone know where to get a pair of 19j6 tubes? i want to build this amp but im having a hard time finding the tubes.
  is there a workaround to use a different kind of tube?


----------



## alphaphoenix

Unless you find them in the forums here, ebay is really the other choice.  Search the thread for reconfiguring the MSSH to use other than 19J6 tubes. Good luck.


----------



## Lou Erickson

Yes, there's a change to use a more common tube.  the_equalizer posted it some time ago.  Try searching for posts from that user in this thread.  Or maybe someone has the link.


----------



## tomb

Quote: 





lou erickson said:


> Yes, there's a change to use a more common tube.  the_equalizer posted it some time ago.  Try searching for posts from that user in this thread.  Or maybe someone has the link.


 

http://www.diyforums.org/SSMH/SSMHvariants.php


----------



## revolink24

There's a mod for using 12AU7 tubes, which are quite common. Try searching the thread.


----------



## Veggiel

Can somebody help me with this small problem, I have ordered all the parts for the amp and bought 5 pieces of 5814A (ECC82) tubes. Today I also received the sockets for my tubes but unfortunately they do not fit at all. The sockets I have ordered are these ones: http://cgi.benl.ebay.be/ws/eBayISAPI.dll?ViewItem&item=170496119876&ssPageName=STRK:MEWNX:IT
   
  Can anyone explain what I have done wrong?


----------



## Ikarios

Quote: 





veggiel said:


> Can somebody help me with this small problem, I have ordered all the parts for the amp and bought 5 pieces of 5814A (ECC82) tubes. Today I also received the sockets for my tubes but unfortunately they do not fit at all. The sockets I have ordered are these ones: http://cgi.benl.ebay.be/ws/eBayISAPI.dll?ViewItem&item=170496119876&ssPageName=STRK:MEWNX:IT
> 
> Can anyone explain what I have done wrong?


 

 They should fit. Do all the pins line up? Sometimes you have to use a little bit of force to get the tubes into the socket; just grip it firmly (but not too firmly!) and wiggle the tube in a circle around the socket; it should eventually fit in. If they don't, you might have to get new sockets - I had a faulty socket where one pin socket would not accept a pin, no matter how hard I pushed. I contacted my seller and they sent me a new socket, which has been working great.
   
  On the other hand, if your tubes aren't new or something, they might have bent pins - check for that if the pins don't line up with the socket.


----------



## Veggiel

The problem is that the socket holes and the pins don't have the right dimensions. So the socket holes cicle outer diameter is +/-19mm and the tube pins outer diameter is 12+/-mm.
  So they do not fit at all exept if I would bend the tube pins. Which is not a good idea I think.


----------



## Surruk

to answer an earlier question, 19j6 s are still available if you know where to look. i just ordered some from http://www.vacuumtubes.net/prices.htm
   
  that being said, i am yet to hear back from them so i guess it is possible that they don't despite the fact that their price list says they do >_>


----------



## Ikarios

Quote: 





veggiel said:


> The problem is that the socket holes and the pins don't have the right dimensions. So the socket holes cicle outer diameter is +/-19mm and the tube pins outer diameter is 12+/-mm.
> So they do not fit at all exept if I would bend the tube pins. Which is not a good idea I think.


 

 That's weird. My 5814A/12AU7 tubes have around a 12mm diameter as well so it sounds like you got the wrong sockets. Do you think you can take a picture comparing the two side by side?


----------



## Veggiel

I have taken a quick foto of the socket and tube on top of each other.


----------



## Ikarios

Quote: 





veggiel said:


> I have taken a quick foto of the socket and tube on top of each other.


 

 A quick search shows that you might have gotten magnoval sockets instead of the noval ones you wanted (and the ones the eBay listing advertised). I'd try getting your money back or getting them to send the correct sockets. I'm not a tube buff though so someone may be able to come in here and confirm/correct me.


----------



## Veggiel

Quote: 





ikarios said:


> A quick search shows that you might have gotten magnoval sockets instead of the noval ones you wanted (and the ones the eBay listing advertised). I'd try getting your money back or getting them to send the correct sockets. I'm not a tube buff though so someone may be able to come in here and confirm/correct me.


 
   
   
  Those magnoval sockets seem to be the exact same dimensions as the sockets I received, I will contact the seller. Thanks for the info.


----------



## Surruk

Hi again, hope you all don't mind helping me a little more.
   
  I am currently in the process of purchasing all the bits necisary for this project. but i am not sure about what to do for the mosfet. the B.O.M. says that a TO-220 mosfet at V100 is ok. but when i run a search for that i get many results of mildly different things. is the item in this link suitable? (see link below) if not, what else on that site is?
   
  http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6875377
   
  Thanks in advance for your input.


----------



## Ikarios

Quote: 





surruk said:


> Hi again, hope you all don't mind helping me a little more.
> 
> I am currently in the process of purchasing all the bits necisary for this project. but i am not sure about what to do for the mosfet. the B.O.M. says that a TO-220 mosfet at V100 is ok. but when i run a search for that i get many results of mildly different things. is the item in this link suitable? (see link below) if not, what else on that site is?
> 
> ...


 

 I don't know about MOSFET selection or what you can put in there, but the IRF510/610 is the one specified. I don't know if you can play around with different MOSFETs but I wouldn't recommend it. This is what you want, and it's cheaper too.
  http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=5430046


----------



## Surruk

Brilliant, thanks for the help, i didn't know that the 610 was usable.


----------



## juntom10

What kind of bolts and nuts should i use to mount the heatsink to a chassis?


----------



## Ikarios

Quote: 





juntom10 said:


> What kind of bolts and nuts should i use to mount the heatsink to a chassis?


 

 Anything as long as you don't tie the MOSFET tab to the chassis (ground). You can use Beezar's mounting kit, which includes everything you need and has an insulator and a thermal pad.
   
  http://beezar.com/catalog/product_info.php?cPath=30&products_id=60
   

 4-40 x 3/8" Socket Head Cap Screw - SAE black steel
 #4 Flat Washer (2) - 18-8 Stainless Steel
 Aavid high-temp, rigid polysulfide glass-filled shoulder washer
 #4 Lock Washer, Stainless Steel, split-ring
 4-40 Steel Nut
 Bergquist adhesive-backed thermal pad (no grease required)


----------



## juntom10

Quote: 





ikarios said:


> Anything as long as you don't tie the MOSFET tab to the chassis (ground). You can use Beezar's mounting kit, which includes everything you need and has an insulator and a thermal pad.
> 
> http://beezar.com/catalog/product_info.php?cPath=30&products_id=60
> 
> ...


 

 I was wondering how to put the original heatsink on the case (the one that you have to solder). but i guess i can just use ones that were used for pcb kit (square looking heatsink), and use parts that you listed above... 
  To do that, i need to get a metal panel.
  Hmm actually this project is getting more interesting...
  Everything is new to me (i was building kits before), and kind of excited to make my own version.
  Yesterday, it took me 3 hours to make BOM for 12AU7 version with parts that i want to use...
  Now it is time to order parts, and need to find materials for the casing


----------



## juntom10

I'm attaching the BOM that i made for 12AU7 version.
   
  Of course you can change parts to ones that you like.
   

  (I realized i can not attach the .xls file....so i took a screen shot lol)
   
  By the way, I have some questions.
   
  For capacitors, can i use whatever capacitors that have higher capacitance and voltage stated in the list?
   
  Also, lets say i need 680uF, 63V capacitor, can i use 2 of 680uF 50v capacitors in series?


----------



## nullstring

Quote: 





juntom10 said:


> By the way, I have some questions.
> 
> For capacitors, can i use whatever capacitors that have higher capacitance and voltage stated in the list?
> 
> Also, lets say i need 680uF, 63V capacitor, can i use 2 of 680uF 50v capacitors in series?


 

 You can probably use higher values, but realize that there is more to capacitors than values.
  That doesn't mean that there will be any benefit from it. And different caps sound different.. Power caps should have low ripple, and stuff like that.
   
  When you put two 680uF caps in series, you'll double the voltage capability, but you'll loose half the capacitance.
   
  So, you'd need two 50v 1360uF caps in series to have over 63v


----------



## juntom10

OH! that makes sense!
   
  Thank you for the answer! 
  
  Quote: 





nullstring said:


> You can probably use higher values, but realize that there is more to capacitors than values.
> That doesn't mean that there will be any benefit from it. And different caps sound different.. Power caps should have low ripple, and stuff like that.
> 
> When you put two 680uF caps in series, you'll double the voltage capability, but you'll loose half the capacitance.
> ...


----------



## juntom10

Today, i received the package from digikey.
   
  I was so happy looking at parts haha...
   
  but one sec.
   
  ???????????????????
   
  what is this?
   
  wow....ugh...ugh..
   
  .
  .
  .
   
  I didnt know i ordered this enormous toggle switch...ugh
   
  it looks cool. but bit bigger than i thought lol (i didnt check the size when i was ordering it)
   
  I was bit wondering why this costs 6 bucks....
   
  and now i know lol
   
  haha
   
  After i receive wires and pots that i've ordered, ill start building!
​


----------



## DarkTiger892

So I came across another DIY project that integrated nicely with my starving student amp.  http://www.head-fi.org/forum/thread/198828/the-hissbuster-for-sensitive-headphones  I was looking for a way to tame the gain for sensitive/efficient headphones, and this does the trick.  I used the resistor values for a -20dB attenuator with my Ultrasone HFI-780s.  To give you an idea, that brings the volume control from ~9:00 to 1:00 on the pot at normal listening volume. (minimum with the pot speced out in the BOM is around 7:00.  You just make this up, and put it between your output caps and your headphone jack. 
   
  The parts I used (and their mouser part #'s)
  1x 3PDT switch (108-1M31T1B1M1QE-EVX)
  2x 27 ohm metal film resistors .5W (660-MF1/2LCT52R270J)
  2x 3.32 ohm metal film resistors .5W  (660-MF1/2DCT52R3R32F)
   
  I was looking for a good way to decrease the gain, while still keeping the option for a high gain mode for headphones like my buddy's AKG K240 Studios which require the volume pot to be up half way anyway.  
   
  You can see by the original schematic that the layout is pretty simple, but I incorporated it all onto the back of a switch to keep things tidy inside the amp.  I originally only used a dpdt switch, but that created a 3.3 ohm load in parallel with the headphones when the attenuation circuit wasn't active (and I figured that using up current=less than ideal).  I included a paint drawing in case to help visualize what I did.  I mounted this switch on the back of my amp, and when i want a -20dB attenuation on the volume output, I flip the switch.  If I want full output, I flip it the other way.  This seemed to me like  a better solution than increasing the input resistance well over 100k ohms just to get some attenuation on the output.  (Also this eliminates any trace of hiss (however small) on the output.  I haven't seen this mentioned in this thread before, but I have seen people trying to reduce gain to bring the volume pot out of the poor tracking area and increase volume pot turn usability.  This solution worked very well for me and I hope someone else finds this useful.
   
  .


----------



## revolink24

I just stuck a DPDT switch on R16 and R17 (from the PCB schematic).


----------



## DarkTiger892

With my headphones I had too much gain even with the input going through 50k resistors.


----------



## Ikarios

Is that implemented at the output? I tried using a switch on R16/17 but it doesn't work well. I could use something like this. Can this be used in a breakout box?


----------



## DarkTiger892

Yes, it goes on the output.  On my drawing, the "input" to the attenuator comes from the output capacitors, and the "output" wires go to the headphone jack.
   
  Edit: It could absolutely be implemented in a small box (or even in line possibly without a switch).  I chose to put my inside the amplifier though so it was all self contained.


----------



## nullstring

To clear something up.
  the 50k resistors in series with the pot do *not* attenuate the signal at all
   
  If you need to lower the volume, put a resistor in parallel with the pot.
   
  ignore me
 ignore me


----------



## Ikarios

Quote: 





nullstring said:


> To clear something up.
> the 50k resistors in series with the pot do *not* attenuate the signal at all
> 
> If you need to lower the volume, put a resistor in parallel with the pot.


 

 What? They have some effect on volume, and that's attenuation if I think I'm using the word correctly... I have 50k/150k resistors (R16/R17) hooked up to a switch which I use as a "gain switch", although it's not terribly effective.


----------



## tomb

Quote: 





ikarios said:


> Originally Posted by *nullstring* /img/forum/go_quote.gif
> 
> To clear something up.
> the 50k resistors in series with the pot do *not* attenuate the signal at all
> ...


 

 Yeah, I think something's mixed up here.  Resistance in series with the pot will most definitely attenuate the signal.


----------



## dsavitsk

Quote: 





nullstring said:


> To clear something up.
> the 50k resistors in series with the pot do *not* attenuate the signal at all
> 
> If you need to lower the volume, put a resistor in parallel with the pot.


 

 Maybe a picture will help.  50K input resistors with a 50K pot effectively turns it into a 100K pot where the knob only turns half way.  It also changes the taper a bit allowing you to turn the knob further for the same attenuation, and ensuring 6db of attenuation even when turned all the way up.


----------



## nullstring

Quote: 





dsavitsk said:


> Maybe a picture will help.  50K input resistors with a 50K pot effectively turns it into a 100K pot where the knob only turns half way.  It also changes the taper a bit allowing you to turn the knob further for the same attenuation, and ensuring 6db of attenuation even when turned all the way up.


 

  
  EDIT: I am tired. I am going to reply to this later when I can't make more sense of things, and be sure what I am saying makes sense.
  In either case, putting a 50K resistor in series will do nothing to increase the voltage divider, and therefore will not lower the volume.
   
  Put 50K resistors on there should only increase the impedance.. nothing more..


----------



## the_equalizer

Quote: 





nullstring said:


> EDIT: I am tired. I am going to reply to this later when I can't make more sense of things, and be sure what I am saying makes sense.
> In either case, putting a 50K resistor in series will do nothing to increase the voltage divider, and therefore will not lower the volume.
> 
> Put 50K resistors on there should only increase the impedance.. nothing more..


 
   
  That is, unfortunately, wrong. It will attenuate the signal. The portion of the signal available at the pot's wiper is a fraction proportional to the ratio of R1/R2. Where R1 = The resistance value of the upper leg resistor plus the resistance value of the 'upper half' of the pot (from the first terminal to the wiper); and R2 is the value of the 'lower half' of the pot (from the wiper to ground).
   
  Try a simple experiment and insert a 1Mohm resistor in series before the pot (R16, R17) or take a look here and do the math.
   
  cheers!


----------



## juntom10

I think it will work as a voltage divider...which means it attenuates the signal....
   
  ps. oops. i read the_equalizer's link after i posted it lol


----------



## nullstring

I knew I must've been mistaken to be disagreeing with dsavitsk (and others apparently, I didn't even see those posts till now)
   
  I apologize and Thanks for your patience with me.
   
   
  Apparently the way I had it explained to me was very wrong.


----------



## the_equalizer

I, for one, don't think there's a need to apologize 
	

	
	
		
		

		
			





. Disagreeing with anyone is not wrong... but that's another story for another thread 
	

	
	
		
		

		
		
	


	




.
   
  What you did (putting a resistor in paralel) certainly does attenuate the signal too, but it does it by dividing the current (or "shunting" it). A side effect of it is that it decreases input impedance (just as a side effect of the above pictured voltage divider is to increase the input impedance, as you very well pointed out).
   
  cheers!


----------



## juntom10

Quote: 





the_equalizer said:


> I, for one, don't think there's a need to apologize
> 
> 
> 
> ...


 

 That reminds me of my prof saying...
  "Very high Zin and very low Zout  = the best "


----------



## kellzey

Did they ever come out with a PCB for this available for purchase?


----------



## revolink24

Yes, but unfortunately, it's no longer available.


----------



## Veggiel

Does the heatsink of the mosfet have to be insulated from the chassis if the chassis is being used as ground?


----------



## Ikarios

Quote: 





veggiel said:


> Does the heatsink of the mosfet have to be insulated from the chassis if the chassis is being used as ground?


 

 yes, you to isolate the tab from the case. you can either use a mica insulator with thermal grease and a shoulder washer for the screw you attach it to, or you can pick up a mosfet mounting kit from beezar, which has bergquist pads and all the hardware you need for one mosfet.


----------



## dsavitsk

Quote:


kellzey said:


> Did they ever come out with a PCB for this available for purchase?


 


  I've been cleaning out old boxes and I stumbled upon some (3) of the original prototype PCBs. These are pretty different than what we ultimately settled upon for a design, but they do work OK ... I think.  If anyone wants one you can have one for the price of shipping and a padded envelope, ~$4.
   
  Here's what they look like: http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/510#post_4403745
   
  The FETs can be mounted to the case as with the final version, or, as shown, they can be used with sinks.
   
  I also have my original built prototype that someone can have. Shown here (but no big sink included, but otherwise as shown with no front panel) http://www.head-fi.org/forum/thread/319231/millett-starving-student-hybrid-amp/615#post_4475495
   
  Yours for the shipping + a $5 donation to the Red Cross.
   
  Send me a PM if interested.


----------



## sailorman

PM sent on amp.


----------



## dsavitsk

sorry, all taken.


----------



## revolink24

Wow, too bad I missed this. I'd love to do another PCB build.


----------



## nullstring

Quote: 





revolink24 said:


> Wow, too bad I missed this. I'd love to do another PCB build.


 


  If you haven't done a P2P build, you should try it =)


----------



## revolink24

I'm working on one right now. Still 19J6, since I've got 8 of them left over, and going all out with parts while I'm at it (Sonicaps, RN55Ds, Neutrik/Switchcraft all the way around, etc.) Should be fun.


----------



## Veggiel

I have assembled a starving student amp, but when I was testing the voltage I caused a short circuit.
  Now the voltage on pin 3 of the mosfet is 48v instead of the prior 12v. Is the mosfet burnt or is it something else?
  Also the other channel is ok but the 12v going to the output caps C3 and C5 stops at the caps. So one leg measures 12v and the other 0v. What could be the problem here?


----------



## the_equalizer

Quote: 





veggiel said:


> I have assembled a starving student amp, but when I was testing the voltage I caused a short circuit.
> Now the voltage on pin 3 of the mosfet is 48v instead of the prior 12v. Is the mosfet burnt or is it something else?
> Also the other channel is ok but the 12v going to the output caps C3 and C5 stops at the caps. So one leg measures 12v and the other 0v. What could be the problem here?


 



 48 volts at pin 3 would indicate that there's no current flowing through the MOSFET and/or through the tube heater. Does the tube light up? If it does, then it should be very bright.  I wouldn't be able to confirm if that's how a burnt MOSFET would behave but given your description that you caused a short, it could very well be. Best bet would be to replace it and measure voltages before plugging your cans.
   
  As an added tip, with the relatively low currents and voltages in the amp, you don't need to put your voltmeter probes on the MOSFET pins where it's easy for them to slip and wreak havoc. For example, for measuring the voltage to ground at pin 3 you could put your probe on the terminal of C3 or C3a directly attached to it.
   
  As to the caps, that's EXACTLY what they're there to do: stop those measured 12, or in your amp's other channel case 48, DC volts from getting to your headphones and frying the coils.
   
  Incidentally, your burnt MOSFET channel is a great example of why in the schematic the output caps are  rated @ 63 volts and not only @ 16 or something around 12.
   
  cheers!


----------



## kchapdaily

working on my starving student right now, cant wait to get it finished!


----------



## kchapdaily

finally finished! this amp sounds pretty **** good!
  il post pics once i finish the case. making it out of cherry wood


----------



## revolink24

Has anyone here tried using a SSMH as a preamp? I'm thinking of building one solely on preamp duty, but I'm not sure about its suitability.


----------



## Ikarios

Quote: 





revolink24 said:


> Has anyone here tried using a SSMH as a preamp? I'm thinking of building one solely on preamp duty, but I'm not sure about its suitability.


 

 I recall there was a discussion about modifying an SSMH to use as a preamp, a couple hundred pages ago. I believe Germania had a hand in that discussion.


----------



## .Sup

Lately I'm really enjoying 1k€ headphones and 1k€ DAC with this 100€ amp


----------



## kchapdaily

does anyone have any extra 19j6 tubes? i have rca's right now and i want to try some different ones out


----------



## Veggiel

My amp is working very good but I'm a bit worried about the heat it produces, my heatsink gets really hot. So hot that I can barely touch it.
  My case also starts to warm up after a few minutes.
  I am curently using a heatsink of a intel cpu for the two mosfets. How warm should it normally get?


----------



## Ikarios

Quote: 





veggiel said:


> My amp is working very good but I'm a bit worried about the heat it produces, my heatsink gets really hot. So hot that I can barely touch it.
> My case also starts to warm up after a few minutes.
> I am curently using a heatsink of a intel cpu for the two mosfets. How warm should it normally get?


 

 My heatsinks heat up to 45C tops during the summer, which is uncomfortable to touch but no big deal for the mosfets (which are rated up to at least 80C IIRC). 45C is pretty hot to the touch - very uncomfortable - but not really that hot in the grand scheme of things. Capacitors won't like the increased heat much but under maybe 60C won't be problematic at all.


----------



## Beftus

Remember it's a class A amp. Class A runs hot by design. It's perfectly normal for a Starving Student to run really hot. Don't worry about. Keep your hands of the heatsinks. Play air guitar instead.


----------



## bhjazz

Just what I was looking for!  Thanks, equalizer.  Looks like two resistors, two new sockets, some rewiring and new heatsinks.  Not a bad way to spend an afternoon.
   
  BTW: I didn't find any reference to the actual heatsinks for the 12AU7 build.  Does anyone have a part number?
   
  Thank you!
  
  Quote: 





the_equalizer said:


> So, what do you guys think? This is the first draft schematic for the 12AU7 version of the Millett "Starving Student" Hybrid headphone amplifier.
> 
> 
> 
> ...


----------



## bhjazz

Quote: 





kchapdaily said:


> does anyone have any extra 19j6 tubes? i have rca's right now and i want to try some different ones out


 


 The supply ran out about two years ago.  I've tried most places online and they either say they'll get back to me (which is never) or they tell the truth and say they're out. 
   
  How about a retrofit for 12AU7......


----------



## livewire

*answers for bhjazz*................I forgot to include quotes from previous page.
   
  There are always a few "scraps" on ebay - NOS 19j6 tubes (not matched), if you dont mind paying out the kazoo. ($15 to $30 ea)
   
  As far as heatsinks go, two each - Digikey p/n: HS380-ND or equivalent should work fine. About $1.71 each + S&H.
   
  Linky:  http://search.digikey.com/scripts/DkSearch/dksus.dll?lang=en&site=US&KeyWords=hs380-nd&x=0&y=0


----------



## Beftus

Those 63mm tall heatsinks are a good choice. You can also use cheaper 50mm tall ones but they will get noticeably hotter.


----------



## bhjazz

So the 63mm is what people are using for the 12AU7 builds?  After looking through the thread it's clear that the original ones are too small!
   
  Thanks guys!


----------



## Beftus

A 12AU7 build needs to dissipate more heat than the original 19J6 build. Every bit of extra heatsink surface area helps to keep things from getting too hot to touch.


----------



## digger945

Ohmite makes a similar heatsink, sold at Mouser. About $2 each.
http://www.mouser.com/ProductDetail/Ohmite/FA-T220-64E/?qs=sGAEpiMZZMttgyDkZ5WiumlCfl50RTwzVA%252bY4U4BtvA%3d
   
  The mosfet on the 19j6 amp would be trying to dissipate about 4.35 watts, the 12au7 about 5.31 watts.


----------



## bhjazz

Good deal.  I just wanted to make sure I had the minimum size to work with.  It looks like the dissipation factor isn't a giant leap, but definitely something I'll need to adjust for.
   
  Thanks guys!


----------



## the_equalizer

As already pointed out by Beftus and livewire, the larger heatsinks are more appropriate for 12 volt heater tubes.
   
   Good to see that there are still builders interested in this great little amp!
   
  cheers!


----------



## videoman5

Would a heatsink ripped from an old computer PSU be sufficient? I mean, those are often meant to handle higher heat loads.


----------



## Ikarios

Quote: 





videoman5 said:


> Would a heatsink ripped from an old computer PSU be sufficient? I mean, those are often meant to handle higher heat loads.


 

 as long as you can mount it to the case/mosfets, sure. People have used heatsinks before.


----------



## livewire

Quote: 





videoman5 said:


> Would a heatsink ripped from an old computer PSU be sufficient? I mean, those are often meant to handle higher heat loads.


 


 He is a pic of my MSSH build with a dual heatpipe CPU cooler rated at 30 watts.
  I ripped it from a boat anchor outdated desktop box. Both of the mosfets are bolted to it from below.
  (and electrically insulated, so no direct contact with the grounded metal of the heatsink.)
  IIRC in this circuit, the mosfets each dissipate ~5 or 6 watts, so 12 watts total.
  It runs warm to the touch. You want to avoid using a smallish heatsink that will run really hot.


----------



## videoman5

livewire said:


> He is a pic of my MSSH build with a dual heatpipe CPU cooler rated at 30 watts.
> I ripped it from a boat anchor outdated desktop box. Both of the mosfets are bolted to it from below.
> (and electrically insulated, so no direct contact with the grounded metal of the heatsink.)
> IIRC in this circuit, the mosfets each dissipate ~5 or 6 watts, so 12 watts total.
> It runs warm to the touch. You want to avoid using a smallish heatsink that will run really hot.






ikarios said:


> as long as you can mount it to the case/mosfets, sure. People have used heatsinks before.




Thanks! PSU heatsinks are already mounted to MOSFETS, so I wouldn't have to modify them for them to work, and they come with a mounting kit to boot! 

I am a computer tech, so I have tons of dead PSUs laying around. So this should shave 10 bucks or so off my 2 orders. My friend has a birthday coming up, and he recently got some DT880's. He ordered the 250 Ohm ones, but got the 600 Ohm ones instead. He went to e-mail the dealer about it, and dealer wanted him to ship back the headphones before he refunded him. My friend, not one to fuss, just sucked it up and said that he would just keep the 600 Ohm pair. Since he got me ~$50 of stuff on my birthday last year, I'd thought I'd make it up to him by building him one these amps for his new pair of headphones. Sort of ironic when you consider that I'm the Civil Engineering major, and he's Electrical Engineering major. 

Anywho, I am using the modified 12AU7 design, and as soon as I get around to building them, I'll give back some insights on how it sounds. Hopefully they will drive my MB Quart 805HS's a bit better than my sound card. If it doesn't, well, it's quite the conversation piece!


----------



## SpringHalo

Comparing the schematics for the 17EW8 and the original 19J6, I've noticed everything is exactly the same, except for the pins on the tube. How hard would it be to just edit the PCB to support the new pin-out?
   
  EDIT: Jesus, the pins are rather muxed up on the 17EW8.
   
  EDIT v2: Sketching out a re-wired PCB right now. Might post them later. I'm trying not to move any components, but R1 is probably going to move. You want the least amount of parallel paths though, right?


----------



## the_equalizer

Quote: 





springhalo said:


> Comparing the schematics for the 17EW8 and the original 19J6, I've noticed everything is exactly the same, except for the pins on the tube. How hard would it be to just edit the PCB to support the new pin-out?
> 
> EDIT: Jesus, the pins are rather muxed up on the 17EW8.


 


  'Editing' the PCB layout for a different tube might seem simple but, as you just discovered, it's usually not. You might want to consider building tube socket adapters, which are certainly feasible, and use the same PCB layout.  There was talk about that in the thread some 2 years ago, I think. Search the thread for 'adapter' or some such thing.
   
  cheers!


----------



## Ikarios

The 17EW8 is one of the few tubes that has been used as a replacement for the 19J6 (with some modifications, of course), the others being a 6J6, 12SR7 or 12SN7 (can't remember), and 12AU7. if you search back it should be there. equalizer I thought you built one?
   
  FWIR the 17EW8 tube works as a drop-in replacement for the 12AU7 circuit as well, although I think the resistor change for the 17EW8 was suposed to be around 250k (instead of the 390k for the 12AU7).


----------



## the_equalizer

Quote: 





ikarios said:


> The 17EW8 is one of the few tubes that has been used as a replacement for the 19J6 (with some modifications, of course), the others being a 6J6, 12SR7 or 12SN7 (can't remember), and 12AU7. if you search back it should be there. equalizer I thought you built one?
> 
> FWIR the 17EW8 tube works as a drop-in replacement for the 12AU7 circuit as well, although I think the resistor change for the 17EW8 was suposed to be around 250k (instead of the 390k for the 12AU7).


 

 Indeed I built the prototype 17EW8 version, but it was a point-to-point build, not 'editing' the beezar PCB. As you very well said it has the same pinout as the 12AU7 so it CAN be used as a drop-in replacement for the 12AU7, but the heater voltage will not be optimum. As you pointed out too, some simple modifications (to the MOSFET biasing resistors) can put that voltage around the 17 volts that make the 17EW8 happiest.
   
  Said modifications can be found earlier in the thread (a year ago, I think?? Time flies !)
   
  cheers!


----------



## SpringHalo

Quote: 





the_equalizer said:


> 'Editing' the PCB layout for a different tube might seem simple but, as you just discovered, it's usually not. You might want to consider building tube socket adapters, which are certainly feasible, and use the same PCB layout.  There was talk about that in the thread some 2 years ago, I think. Search the thread for 'adapter' or some such thing.
> 
> cheers!


 


   


  Quote: 





the_equalizer said:


> Indeed I built the prototype 17EW8 version, but it was a point-to-point build, not 'editing' the beezar PCB. As you very well said it has the same pinout as the 12AU7 so it CAN be used as a drop-in replacement for the 12AU7, but the heater voltage will not be optimum. As you pointed out too, some simple modifications (to the MOSFET biasing resistors) can put that voltage around the 17 volts that make the 17EW8 happiest.
> 
> Said modifications can be found earlier in the thread (a year ago, I think?? Time flies !)
> 
> cheers!


 

 I have gone through most of this thread, from page ~150 to present. I must have skimmed over the speak of an adapter for the PCB. I think I've come up with a few edits to the PCB, but right now they're just drawings. I rotated the 9-pin to a certain direction, but I'm worried that the tad bit of clutter around the tubes could cause unnessecary inductance. I've read your post about using the 17EW8, and that's what I'm basing the pinouts on. Much appreciated. I'll upload the sketches in a few minutes.
   
  R1 would probably be moved further up to bridge at a -45 degree angle over the line connecting pin 4 and C3


----------



## videoman5

Not up on my tubes; can I use a 12AU6 instead of a 12AU7?


----------



## livewire

Quote: 





videoman5 said:


> Not up on my tubes; can I use a 12AU6 instead of a 12AU7?


 
  Nope. Different animals.


----------



## the_equalizer

Quote: 





videoman5 said:


> Not up on my tubes; can I use a 12AU6 instead of a 12AU7?


 


  As livewire showed, you can't. But you can use a 12AX7, 12AT7, 12AV7 hence why we like refering to the mod as the 12A_7 mod. I personally have only tried 12AU7 and 12AX7 but know from others who have built the amp that 12AT7 and 12AV7 also work.
   
  The difference between all those tubes? The gain they will provide, as well as differences in distortion, hence a slightly different 'tone'.  Ah, there'll also be a difference in cost. I believe the 12AV7, being more rare, will be more expensive than the very common 12AX7
   
   
   
  cheers!


----------



## videoman5

the_equalizer said:


> As livewire showed, you can't. But you can use a 12AX7, 12AT7, 12AV7 hence why we like refering to the mod as the 12A_7 mod. I personally have only tried 12AU7 and 12AX7 but know from others who have built the amp that 12AT7 and 12AV7 also work.
> 
> The difference between all those tubes? The gain they will provide, as well as differences in distortion, hence a slightly different 'tone'.  Ah, there'll also be a difference in cost. I believe the 12AV7, being more rare, will be more expensive than the very common 12AX7
> 
> ...




Would a 12SR7 work? I can get them super-cheap.


----------



## the_equalizer

Quote: 





videoman5 said:


> Would a 12SR7 work? I can get them super-cheap.


 


  They certainly do. But it's a different type of tube (a single triode), that requires a different socket (octal). Search the thread for '12SR7'. It was user 'Logistic' who developed and built the 12SR7 version.
   

 EDIT:  Ok, took a bit of searching but here's Logistic's original post.
   
  cheers!


----------



## SpringHalo

After doing some searching [Actually looking at the first page in the DIY forums] I found this thread, which I'll probably use for my design. I just asked a friend, and he said he has a few 12AT7s and sockets, as well as etching resources to help, so I'm in business. 
	

	
	
		
		

		
			





 I'll probably post a build thread once I order the parts.


----------



## the_equalizer

Quote: 





springhalo said:


> After doing some searching [Actually looking at the first page in the DIY forums] I found this thread, which I'll probably use for my design. I just asked a friend, and he said he has a few 12AT7s and sockets, as well as etching resources to help, so I'm in business.
> 
> 
> 
> ...


 


  Yes, he's also started a build log thread. He's already populated the PCB and done basic voltage testing. 
   
  In this very thread, someone else has built a PCB 12AU7 SSMH I just can't remember the user name.


----------



## Ikarios

Be careful with using the 12AX/AT7 tubes - they are useable alongside the 12AU7, but the gain is very high and may make the amp unuseable beyond the first few degrees of the pot. With my 12AU7s I could barely use the first third of the volume pot before getting unreasonably loud with most headphones.
   
  Head-Fi user "TestSubject" has done a stripboard version of the 12AU7, it's pretty nice. I don't know what progress he has made and if he has found a fully complete board layout yet, though.


----------



## zammykoo

Quote: 





the_equalizer said:


> Yes, he's also started a build log thread. He's already populated the PCB and done basic voltage testing.
> 
> In this very thread, someone else has built a PCB 12AU7 SSMH I just can't remember the user name.


 


  IIRC, I think it was Fred_fred2004 who built the 12AU7 SSMH based on dsavitsk's pcb design


----------



## SpringHalo

Quote: 





ikarios said:


> Be careful with using the 12AX/AT7 tubes - they are useable alongside the 12AU7, but the gain is very high and may make the amp unuseable beyond the first few degrees of the pot. With my 12AU7s I could barely use the first third of the volume pot before getting unreasonably loud with most headphones.


 


  In attempt to increase the sensitivity of the pot, could I change R16/R17 from 50k to 100k. Or would that still be not enough? I'm using ATH-M50 36ohm (rated for 32ohm, but I recently measured 36.).
   
  The caps that I got from a friend are all rated at 50v, which include C1/C6, which I think 1000uf should be fine (increases the lower frequency response? Or is that C3/C5?) He also has C3/C5 , which are 470uf @50v. Are C2/C4, C3a/C5a able to be substituted by .22uf/50v film caps? Is there a point for them being rated for 250v?


----------



## tomb

Quote: 





springhalo said:


> In attempt to increase the sensitivity of the pot, could I change R16/R17 from 50k to 100k. Or would that still be not enough? I'm using ATH-M50 36ohm (rated for 32ohm, but I recently measured 36.).
> 
> The caps that I got from a friend are all rated at 50v, which include C1/C6, which I think 1000uf should be fine (increases the lower frequency response? Or is that C3/C5?) He also has C3/C5 , which are 470uf @50v. Are C2/C4, C3a/C5a able to be substituted by .22uf/50v film caps? Is there a point for them being rated for 250v?


 

 You could go to 200K - 250K on the input resistors without a problem, IMHO.  There's no reason why you can't experiment with it.  Try it in increments of 50K or 100K as you go up in your resistance.
   
  If you are using the Cisco power supply, the caps should be rated at 63V, minimum, IMHO - 50V is too close with a 48V power supply.
   
  C3 and C5 are the output electrolytic capacitors.  You will notice a bass improvement going to 1000uf if you are using low impedance (32 ohms or less) phones.  Grados and all higher-impedance phones are OK with the 470uf's, though, because while Grados are 32ohms, they tend to peak at 50Hz, not 20Hz.  At least, that's been my experience with several different amp designs.  All of this has to do with the physics of the RC circuit formed by the output caps and the impedance of the phones.  It forms a high-pass frequency filter and unless the cap is big enough (in uf's) compared to the headphones' impedance, bass-filtering will occur.
   
  The only reason the film caps are rated for 250V is because the wonderfully performing Wima MKP10 simply come that way.  The Wima's have more or less been a bypassing standard all the way back to the original Millett Hybrid.  They also matched what I already carry at Beezar for the MAX/MiniMAX/MOSFET-MAX, so it was an easy choice.  They were picked for sound quality, not for the voltage rating.


----------



## SpringHalo

Quote: 





tomb said:


> You could go to 200K - 250K on the input resistors without a problem, IMHO.  There's no reason why you can't experiment with it.  Try it in increments of 50K or 100K as you go up in your resistance.
> 
> If you are using the Cisco power supply, the caps should be rated at 63V, minimum, IMHO - 50V is too close with a 48V power supply.
> 
> ...


 

 So I should just buy all new caps? I'm also planning on getting parts for a grubDAC, so I could grab a couple caps while I'm at it, (though they're also on mouser IIRC.. Probably ordering later today. Should I get a 100K potentiometer or just stick with the 50K?
   
  Thanks!


----------



## Fred_fred2004

Quote: 





zammykoo said:


> IIRC, I think it was Fred_fred2004 who built the 12AU7 SSMH based on dsavitsk's pcb design


 


 No sorry not me I used Dsavitsk's circuit but the layout was a single sided toner transfer effort of my own


----------



## zammykoo

Quote: 





fred_fred2004 said:


> No sorry not me I used Dsavitsk's circuit but the layout was a single sided toner transfer effort of my own


 


  Oops my apologies, now I remember that's your single sided pcb


----------



## liamstrain

This would be great to build into a cigar box... 
   
  Must ponder.


----------



## SpringHalo

The PSU socket is out of stock on mouser, could I get this one that's rated 5A@30v? I'm pretty sure it'll fit.
  http://www.mouser.com/ProductDetail/Switchcraft/L712RAS/?qs=sGAEpiMZZMu2f9RNbWupYqW6S1LL%252bTeZ9lcjPfOr4HQ%3d


----------



## tomb

Quote: 





springhalo said:


> The PSU socket is out of stock on mouser, could I get this one that's rated 5A@30v? I'm pretty sure it'll fit.
> http://www.mouser.com/ProductDetail/Switchcraft/L712RAS/?qs=sGAEpiMZZMu2f9RNbWupYqW6S1LL%252bTeZ9lcjPfOr4HQ%3d


 

 Are you using the Cisco power supply?  You never made that clear after my previous question.  If so, then NO - absolutely NOT.  The Cisco puts out 48V and you've picked something rated for 30V.


----------



## SpringHalo

Quote: 





tomb said:


> Are you using the Cisco power supply?  You never made that clear after my previous question.  If so, then NO - absolutely NOT.  The Cisco puts out 48V and you've picked something rated for 30V.


 


  Ah yes, sorry. I plan to use the Cisco power supply. There don't seem to be any sockets with that size rated for 50+ volts. I've been looking mainly at the mouser side of the BOM, and didn't see that the digikey side had one for radio shack. I checked on the site and it seems they have it in stock.

 Thanks.


----------



## videoman5

Is there any designs that don't call for a 48VDC PSU? I would have to buy one of those, and I would rather just recycle one the few hundred 12v adapters that I have.


EDIT: After toying around with the design of the original I came up with this which would use 6J6's (instead of 19J6's) and a 12VDC PSU:



Critique as you may. I am not a E.Engineering student. This amp will output 120mW @ 300 Ohms, 60mW @ 600 Ohms, 240mW @ 150 Ohms, etc. So, this amp design, AFAIK, should work well. 

EDIT2:

The PSU should be more than 1.5A @ 12v. 500mA won't work. Oh, and the "48v" should obviously read "12v". Whoops!


----------



## the_equalizer

Well, IMO there's only one way to REALLY find out if it works, and that is to build it. I know of at least two persons who have succesfully built 6J6 versions of the amp, but they used the Cisco 48V PSU.

 For one thing, 6 volts across the MOSFETs seems very low to me as it is barely greater than the gate to source threshold. It also seems too low for the tubes, I've seen 12 volts used across tubes to intentionally create distortion for guitar pre-amps.

Another point, in my opinion decreasing the values of R2 and R8 by a factor of 10 is not a good idea: you want a voltage divider to have high resistance so that little current flows through it. Increasing R4 and R10 would be better.

Again, these are only my impressions, I'm not an electrical engineer either, so I say build it and tell us how it went.


----------



## videoman5

the_equalizer said:


> Well, IMO there's only one way to REALLY find out if it works, and that is to build it. I know of at least two persons who have succesfully built 6J6 versions of the amp, but they used the Cisco 48V PSU.
> For one thing, 6 volts across the MOSFETs seems very low to me as it is barely greater than the gate to source threshold. It also seems to low for the tubes, I've seen 12 volts used across tubes to intentionally create distortion for guitar pre-amps.
> Another point, in my opinion decreasing the values of R2 and R8 by a factor of 10 is not a good idea: you want a voltage divider to have high resistance so that little current flows through it. Increasing R4 and R10 would be better.
> Again, these are only my impressions, I'm not an electrical engineer either, so I say build it and tell us how it went.




So like this? I was wonder exactly what goes where; I can't visualize it without a diagram.


----------



## the_equalizer

Quote: 





videoman5 said:


> So like this? I was wonder exactly what goes where; I can't visualize it without a diagram.


 


  Yep, that's one of the succesful 6J6 buils I know of. He made some clever modifications to the circuit to avoid having to use giant heatsinks for the MOSFETs.
   
  To keep the current and voltage through the MOSFETs at the same level of a 19J6 build (and thus the heatsinking requirements), he did not wire the heaters and MOSFETs in series. Instead, he put the heaters on an altogether different circuit consisting of
   
  +48V -> 39 Ohm 10 Watt resistor -> heater -> ground
   
  obviously there are two such circuits as there are two heaters that need to be fed. Those 39 ohm 10 watt resistors must get pretty hot so if you build this version be sure to leave ample room around them so that air can flow. Certainly do not put any electrolytic capacitors near them.
   
  So back to the MOSFET's, he replaced the tube heaters in that series circuit with 150 ohm resistors. He doesn't mention what wattage he used there but considering they must hold 12 volts across @ 150 mA they should be 2 watts at the very least. Double that to have some safety room. So that circuit is now
   
  +48V -> MOSFET -> 150 Ohm resistor -> ground
   
  Your observation about the PSU holds: a 1.5A PSU would still be necessary as the heaters, while not in series with the MOSFETs (they are actually in parallel now), are still fed from the same supply.
   
  cheers!


----------



## c12mech

I've been using my amp for a while now and so far it has been great.  I'm wondering though, how much better it could be with a better power supply.  I know that defeats the purpose of the low cost of this amp but that's not my concern.  Does anyone have a schematic for a standalone 48v power supply that would work with this amp.  I know I've seen a couple of different completed amps but not a published design.  Any help would be appreciated.


----------



## Avro_Arrow

Maybe something based on a 337 regulator?
   
  I would have suggested the O11 buy it does not go up to 48 volts.


----------



## c12mech

As far as I know the 337 only goes to 36-37v.  That would be to easy.  I was thinking more along the lines of a traditional power supply.  Transformer, diodes, capacitors, and resistors like a real amp has.


----------



## Avro_Arrow

Sorry, typo...I meant 338.
   
  But yes, you could also do a traditional unregulated design.
   
  Maybe something like this:

   
  Of course you will have to adjust the values to reflect the voltages you will need.


----------



## Ikarios

Quote: 





tomb said:


> Are you using the Cisco power supply?  You never made that clear after my previous question.  If so, then NO - absolutely NOT.  The Cisco puts out 48V and you've picked something rated for 30V.


 

 Is that how power jacks work? I remember asking something similar and being told that if I needed something for, say, 1A at 5V, a unit rated for 2A at 2.5V would also work. Now that I think about it that might have been for the SPST power switch...


----------



## tomb

Quote: 





ikarios said:


> Is that how power jacks work? I remember asking something similar and being told that if I needed something for, say, 1A at 5V, a unit rated for 2A at 2.5V would also work. Now that I think about it that might have been for the SPST power switch...


 

 I don't think your description works, even for a switch.  You might be thinking about the power rating for resistors - then what you've described is OK, because you're looking at the product (power) of 1A * 5V = 2A * 2.5V.
   
  As for specific ratings for current and voltage, voltage has specific requirements - especially when considering switches and connectors, because underatings could result in arcing or fusing the contacts over time.


----------



## videoman5

Would there be a problem if I used an IRF530 instead of an IRF510? I can get the former locally, and for much cheaper than mouser.


----------



## Ikarios

Quote: 





tomb said:


> I don't think your description works, even for a switch.  You might be thinking about the power rating for resistors - then what you've described is OK, because you're looking at the product (power) of 1A * 5V = 2A * 2.5V.
> 
> As for specific ratings for current and voltage, voltage has specific requirements - especially when considering switches and connectors, because underatings could result in arcing or fusing the contacts over time.


 

 Okay, looks like you are right.
http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/5370#post_6791173
  That was the question I was thinking of. Voltage limits due to the possibility of arcing makes sense.


----------



## the_equalizer

Quote: 





videoman5 said:


> Would there be a problem if I used an IRF530 instead of an IRF510? I can get the former locally, and for much cheaper than mouser.


 


  From looking at their respective datasheets, I'd say an IRF530 would work OK...  I can't guarantee it, though 
   
  cheers!


----------



## davidvanderbilt

I have been searching on the pages in this thread. Can someone tell me what schematic/instructions I can use to build this amp. I am extremely confused, because a few threads i read said that the original tubes and PCB board are very scarce. What can I do, or how are people currently building this amp? Thanks!


----------



## Beftus

You build the 12au7 version of the amp. Start reading here: http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/3870#post_6024902
   
  Schematic: http://diyforums.org/SSMH/variants/SSMH-12AU7.gif


----------



## ericj

Quote: 





davidvanderbilt said:


> I have been searching on the pages in this thread. Can someone tell me what schematic/instructions I can use to build this amp. I am extremely confused, because a few threads i read said that the original tubes and PCB board are very scarce. What can I do, or how are people currently building this amp? Thanks!


 

 PCB? This is an amp to be built point-to-point!


----------



## videoman5

I found my enclosure at a garage sale:
   

   
  The pot will be connected to the turn dial, and the heatsinks and tubes will free float in the bubble. The PCB and other crap will be held in an empty space in the bottom part. The power and input will be mounted on the back, and the output will be in the gumball dispenser part. I've got almost all the parts together; I just need the PSU, tubes, and sockets. I am not too worried about the MOSFETs getting too hot, as they are rated up to 175C, which they won't reach. I also want to mount something in the quarter part. I am thinking about using a Devo button I have. Pretty excited about this.


----------



## SpringHalo

Another friend of mine is giving me some sockets and a pot, but also has two 250uf capacitors that I might be able to use as substitutes for C7/C8. The BOM says it's to increase plate resistance, but also needs a good cap. Would I be better off without it, or will a 250uf cap work?
   
  Just to be sure, the pot can be anywhere from ~10ohms to 200ohms, right? It just changes the sensitivity of the volume?
   
  Thanks
   
  EDIT: I have a socket and two 12AT7 tubes, and am thinking of getting two orange tube LEDs to light up the tube better. First of all, is 320mcd enough, and second of all, can I test out the tube heaters to see how much light they give off by simply attaching 12V (@1.2A) to the heater pins?
   
  Editv2: Tested the tube heaters today with a 12v constant power source. The heaters are mostly covered, so there isn't as much glow as I would have hoped. LEDs are a must now.


----------



## jacobthellamer

Just built the amp with Fujitsu 19R-P11 pentodes(wired as triodes) and a custom 48V power supply.
   
  There is a local electronics store clearing out their tube stock so I picked out 6 of these particular tubes hoping that they would work from the specs. I will be back for more as soon as pay day hits now that I know these work 
   
  The 19R-P11 has a heater voltage of 19V too and a heater current of .2amps and seems to work fine without modifying the circuit.
   
  This thing really makes my grubdac shine 
   
  I still need to get a case sorted and need to repaint the heatsink as it got a little scratched drilling out holes for the tubes.
   
  Here is everything together for testing:


   
  Pin out equivalent for the 19j6 if anyone else wants to try:


----------



## videoman5

I have some insanely large caps I can use. Would it be safe to use .3F caps for the power caps?


----------



## Beftus

Quote: 





videoman5 said:


> I have some insanely large caps I can use. Would it be safe to use .3F caps for the power caps?


 


  A complete waste of capacitance IMO. Perhaps you could use them to make a flux capacitor...


----------



## the_equalizer

Quote: 





jacobthellamer said:


> Just built the amp with Fujitsu 19R-P11 pentodes(wired as triodes) and a custom 48V power supply.
> 
> There is a local electronics store clearing out their tube stock so I picked out 6 of these particular tubes hoping that they would work from the specs. I will be back for more as soon as pay day hits now that I know these work
> 
> ...


 
   
  Well done! Congratulations! It's good to see another version of this design come to life!  Yes, I love mine with my grubdac too 
   
  cheers!


----------



## jacobthellamer

Quote: 





the_equalizer said:


> Well done! Congratulations! It's good to see another version of this design come to life!  Yes, I love mine with my grubdac too
> 
> cheers!


 

  
  Cheers! 
   
  I was surprised how at easy it was to get working.
   
  I think I will make use of the pentode screen for my next build


----------



## capernicus

>


 

 This is incredible work!  Can anyone tell me how to mount heatsinks like these?  Are they screw in from the bottom?  Can anyone recommend a source/part number to get a pair of these?  I'm about to build one for a gift.


----------



## tomb

Quote: 





capernicus said:


> This is incredible work!  Can anyone tell me how to mount heatsinks like these?  Are they screw in from the bottom?  Can anyone recommend a source/part number to get a pair of these?  I'm about to build one for a gift.


 
  I agree it's formidable work.  I can't remember the builder's name off-hand, but he built just about every tube amp available in the DIY section of Head-Fi with just the same techniques.  His magnificent work was based in 3D CAD designs, first, then machined directly from the 3D CAD models, if I remember correctly.  Some of the finest work I've ever seen.
   
  As for the specifics of your question, I'm fairly certain that despite the superlative case design, he still used the SSMH PCB, which means those heat sinks were simply soldered onto the PCB by virtue of the heat sink pins.


----------



## livewire

WOW!
  Very nice build, simple and elegant.


----------



## Forte

Quote: 





capernicus said:


> This is incredible work!  Can anyone tell me how to mount heatsinks like these?  Are they screw in from the bottom?  Can anyone recommend a source/part number to get a pair of these?  I'm about to build one for a gift.


 


  Check out his thread where you can see some more phtos of this amp including internal shots, this was built very similar to Pete Milletts original point to point method - http://www.head-fi.org/t/422110/casework-share-your-diy-enclosures


----------



## tubey1

Need help!!
   
  It has been working great for 4 months but I turned it on today and the right side channel tube was glowing VERY bright like a light bulb and that channel sounded like loud static. I turned it off immediately. All the capacitors(no bulging) and parts look normal with no smoke or any funny smell. I tried another set of 19J6 tubes but got the same thing. I don't understand what is wrong with my amp.
   
  I used this schematic.
http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif


----------



## jacobthellamer

Quote: 





tubey1 said:


> Need help!!
> 
> It has been working great for 4 months but I turned it on today and the right side channel tube was glowing VERY bright like a light bulb and that channel sounded like loud static. I turned it off immediately. All the capacitors(no bulging) and parts look normal with no smoke or any funny smell. I tried another set of 19J6 tubes but got the same thing. I don't understand what is wrong with my amp.
> 
> ...


 

  
  Sounds like either the bias on your mosfet has been tied to the 48V rail (R2+R4) or it has failed causing a drain-source short.
   
  Check the voltage on either side of R3 to ground. Let us know.
   
  With the circuit powered off check the resistance across R1 and R2 - this should be around 28.7Kohms.


----------



## livewire

I think tubey1 is on to something.
   
  I remember the "glows like a light bulb" has been reported before in this thread.
  If memory serves me well, it was due to a shorted mosfet in the same channel.


----------



## jacobthellamer

Check that R4 is not open circuit and is properly connected to ground - that could also cause the problem.


----------



## tubey1

Yes, R4 is still grounded.
   
  Voltage from R3 to ground 46V(yikes). I guess that's the problem. For the R9(left channel) it's 22V. Does everyone get around 22V there or around 19V? Isn't 22V kind of high for 19V heaters?


----------



## jacobthellamer

Check the heater voltage on the heater not the gate as there will be a voltage drop between the gate and source. The IRF510's Gate-Source threashold is between 2V and 4V.


----------



## tubey1

Quote: 





jacobthellamer said:


> Check the heater voltage on the heater not the gate as there will be a voltage drop between the gate and source. The IRF510's Gate-Source threashold is between 2V and 4V.


 

  
  With tubes in sockets, Heater on the (normal) left channel reads 20V while the (malfunctioning) right channel heater reads 46V. Also checked the IRF510 of the channel and all 3 leads are not touching each other.


----------



## livewire

The IRF510 could possibly have an _internal _short.
  Most likely the metal tab (where the mosfet is bolted) is shorting to the heatsink.
  (which I am assuming the metal heatsink is also grounded)
   
  With the power supply unplugged, do a continuity (ohms) test with your ohmeter between
  the heatsink and the mosfet metal tab. If it shows a low resistance, there is your short path to ground.
  The mosfet and the insulator pad / washer will need to be replaced.


----------



## jacobthellamer

Second Amp Built  -
   
  This is hard wired to a grubdac, I have since installed a new heatsink and am waiting for a PSU to arrive.


----------



## Ares

I have just finished building this amplifier, it is the second SSH I have built. The version I built is the 12AU7 modification. It sounds great! Well the left channel does. I haven't had the chance to listen to the right channel yet, but I am working on it. Both tubes light up and both MOSFETs get warm, When I check the heater voltage I get about 13.3V on both left and right heaters. When checking to see if there is audio on pin 2 and 7 of the 12AU7s I find that there is. Switching tubes does not help. I assumed the problem was somewhere between C3 and R6 and output; however, when I crank up the volume enough I can hear the volume of the crosstalk coming through. Likewise, when hooked up to a meter it shows both channels displaying the DC offset 'thump' from 3V to nearly 0V when turning the amp on. making me skeptical that it is one of those and rather a problem with the input. I am hoping to be able to hook it up to a scope to see what is going on, but until then does anyone have any suggestions for debugging it? Additionally, it has been having a nasty habit of burning up IRF510s. I assumed that the output was shorting to ground accidentally but this time I was extra careful in my soldering and as a result I cannot not find the short that killed it this time. I checked the continuity with the heat-sink and with all the other pins before turning it on, everything was alright, turned it on and the one channel worked but after about 20 minutes both tubes turned off and the pins of the MOSFET appear to be conducting between each other. Suggestions? Thank you very much for the help!


----------



## jacobthellamer

What voltage is it at the drain of the fets?


----------



## Ares

It works now! It turns out the problem was, embarrassingly, a broken wire to the output (I think...) that I did not see because of the angle and enclosure. It sounds pretty good, low distortion not much coloration. I was originally using old RCA or another American made clear top 12AU7A that does not sound too good, swapped them out for some British Mullard 12AX7s that I happened to have picked up a few years ago and they sound noticeably better to me. I am pretty pleased with this little thing


----------



## drunkenpoet

Hey guys,

I'd like to build this for my first DIY amp and would like some advice. I ran into two different part lists which contain different parts...one is HERE at the Pmillett site and the other is HERE at the DIYforums site.

I'm looking to build this as cheaply as possible. Is mouser still the cheapest place to buy most of the parts?


----------



## livewire

Quote: 





drunkenpoet said:


> Hey guys,
> I'd like to build this for my first DIY amp and would like some advice. I ran into two different part lists which contain different parts...one is HERE at the Pmillett site and the other is HERE at the DIYforums site.
> I'm looking to build this as cheaply as possible. Is mouser still the cheapest place to buy most of the parts?


 

 You really need to read back about 396 pages to learn everything. (ha-ha, good luck!)
   
  Seriously, the DIYforums BOM is a newer updated version, complete with recommended chassis, hardware and revised components.
  The PMillett is the original el cheapo bare-bones BOM. I dont recommend using it, as component values have morphed somewhat.
  If you want to go cheap, find some junk laying around to fab your chassis. Rape out an old strereo for knobs, heatsinks, jacks, etc.
  That is the original spirit of this build. Good luck finding the 19J6 tubes. They are on ebay, not cheap and may be from dubious sources.
  YMMV, buyer beware, rotz-o-ruck.
  There are other variants of this amp using other, easier to get (& cheaper) 12AU7 or 12AX7  tubes. Some required component values will change though.
  Run a search or do some reading back....really. You will learn a lot.
  That is what I did before I fired up the soldering iron, although it took days.

 BTW, Mouser is a good source although it may not be the cheapest. Shipping cost is rather high.


----------



## hellomoto

Hello,
   
  I just rebuilt my unfinished MSSH that was on its shelf for too long, but I can't get it to work... I've powered it up but there happened to be sparkles at the power jack... Do you have any idea of the problem? I'm wonderg of its not a problem with the power jack itself since I bought the one featured on Pete millet's bom but I looked at the spec sheet and it doesn't look like its suited for 48v (the one of diyforums is), I'm wondering if it can be the problem but still, I assume the original bom is correct !
   
   
  Rthanks for your help!
   
  Antoine


----------



## ictin

Hi,
  Because i wanted a tube amp, i started to build a starving student. I used the 12AU7 version by the_equalizer with the mods by Dsavitsk. I added also the meyer crossfeed and a hiss buster, and i tried also to put the protection diodes. I made also a stripboard design
   
   

  My current problem with this build is that one channel is mixed in both of the headphones, and the other one if very faint, so if i removed the input RCA jack from one channel, i hear music pretty loud in both cans, if i remove the other one i hear only a faint sound in only in one can. Also the pot don't seams to work properly. At 0 a hear a faint sound. If i turn it a few degrees, the sound gets louder, and after that it remains at the same level. Also at the output jack, there is very low resistance between the 2 channels. And i wanted to know where and what to measure to identify the problem, and what should be the normal resistance between the 2 channels at the output.
   
  Now for the other problems encounter that lead to this, maybe it will give you a hint.
   
  For the case i used the standard hammond case that was used in most of the builds. Yesterday i finished soldering all the components. I fired it up, did some measurements and when all seamed ok i tried a pair of cheap headphones. At first everything seamed good and i tried to put everything in the case. After i put everything in the case the problems started. First one tube didn't light and his channel was humming. Turn out that the tube was not properly inserted into his socket (i use some sockets from an old TV). The sockets are attached to the case and the pins of the sockets are are soldered to the strip board by wires. I tried to push the lamp harder in the socket, and i think that the sockets pins have touched the soldered parts of the strip board. After that i started to hear a very loud buzz in both channels without any source and even with the volume at 0. Also the music was distorted. I tried to investigate, and after touching the pins from one socket the loud buzz was gone, and now i had another problem. If i used only one input channel as i heard good sound in both cans, if i used both input channel i heard a scrambled and somehow metallic sound in both of the cans.By messing further with the pins of the socket the scrambling problem was also gone, but i remained with the final problem(with the mixed channels). It can be a problem from the sockets, being old?
   
  During the debugging i removed also the 50K resistors from the pot because at maximum volume the sound wasn't loud enough, and the diodes because i thought that the mixing is because of them. Also i removed the crossfeed completely for a while  to discard it as a source of this extreme channel mixing.


----------



## ictin

Ok, i was able to fix most of the problems (there where some loose connections, i think), but now when i have no input source, i get a loud buzz when a source is connected, even if is on silent, nu buzz or hum is present.
  This being my first amp that i build, there are still some thing that i don't understand. The main problem that i had, was that one channel was louder, and the other one, almost at one third as the first one. The thing was that one of the inputs was loose, and if only one channel input was connected, it leaked to the other one, but if both of them are properly connected there is no leak between channels (if i mute one channel, i hear only the other one, and vice-versa).
   
  Anyhow, i decided to order a new pot (an ALPS this time) to replace the old one (is not working properly,when i turn it i hear loud hum and some times one of channels get interrupted), and together with the pot i wanted to buy 4 Mundorf caps at 0.22, but they had only 2 on stock. In this situation what caps is better to replace C2&C4 or C3a&C5a? (currently i have some DNA caps - never heard of them, but my father had some spares in his old stash of electronic components).


----------



## capernicus

Been busy getting this ready for my build - going to try something a little different - purple heart and maple.  
   
  So far I've laminated and rough cut the block as well as hogged out the inside.  Still had a lot of woodwork to do...
   
  This one will be a 12AU7 build - wish me luck!


----------



## takili

Hi all, I have been lurking for a while after first discovering the amp then making it. This is the 12AU7 version with changes to bias:-
   

   
  Well, it looks very nice, I think anyway, but no ways does it want to work! The tubes don't glow or warm up at all, Neither will the mosfets show any sign of warming, (the heatsinks are different but specs are close to the original). When I check voltage, my PSU shows just below 48V at the socket before switch on. After the switch on the voltage drops and appears to rise and fall at various test points, initially falling further but after a while falling less then settling down to a consistent difference between max and min, say 12v, 8v from 12v, zero initial. After a while, three or four minutes, I noticed that C1 was getting warm. I changed it then from a 680uf bipolar to a 1000uf polarised but this made no difference. 
     I have checked the wiring pin to pin, (photoes below), checked the orientation of the valve pins and Mosfet pins and the continuity of all my solder joints plus reflowing a couple that were dodgy.
     My own opinion is that because I am seeing this rising and falling of voltage, the Cisco PSU, rated at 0.38A is somehow seeing too much current demand and cycling on and off, (this could maybe be the cause of C1 getting warm as it passes this varying supply to ground but I am guessing here).
     If anyone has some thoughts I would be grateful as this is my first build after a long absence from DIY electronics and I am trying to find my feet again.


----------



## takili

After much scratching of head my problem amp, (above post), is now working. Yipee! The cause: yep, human error. I somehow managed to get C1/C6 mixed up with C7/C8. All seems to be working ok despite one 220uf cap rated for 16v being subjeced to 48v potential. (I may do a replacement for new caps anyway for C1/C6 just in-case any damage was suffered).
     So, lesson learned, not only check wiring but also check correct component values.


----------



## Llama16

Hey all,
   
  It's been a long time and I've been enjoying my SSMH for years now 
  Sadly faith has struk and I dropped my SSMH. Luckily no tubes are broken and I don't think anything else broke, but the pot did.
   
  This is the pot (I made the kit from tomb): http://nl.mouser.com/ProductDetail/Alpha-Taiwan/RV122F-20-15F-A50K/?qs=NDtHcshGFph1R5NpjYPgdw%3d%3d.
   
  Now I need something to fit, but here's the catch: I can only order from RS components and Farnell. Yet I can't seem to find the alpha brand, nor anything that would fit.
   
  Maybe I looked over it,
  Someone care to lend me a hand :S
   
  Thanks
  Dries


----------



## tomb

Quote: 





llama16 said:


> Hey all,
> 
> It's been a long time and I've been enjoying my SSMH for years now
> Sadly faith has struk and I dropped my SSMH. Luckily no tubes are broken and I don't think anything else broke, but the pot did.
> ...


 

 Shoot me a PM with your address - I think I have some extras I could send you.


----------



## vixr

Quote: 





tomb said:


> Shoot me a PM with your address - I think I have some extras I could send you.


 


 The most awesome guy on these forums.


----------



## proid

Can i  use 50V capacitors instead of 63V capacitor? I can't get the  63V here.


----------



## tomb

Quote: 





proid said:


> Can i  use 50V capacitors instead of 63V capacitor? I can't get the  63V here.


 

 If you use the Cisco power supply (48VDC), I wouldn't recommend it.  2V is not enough of a safety margin.  There may be many circumstances where the 48V might be exceeded slightly.  There's some overage in the 50V rating of most caps, but it would still be risky.
   
  If you can't get 63V, there's nothing wrong with going even higher - 100V.
   
   
  EDIT: Thanks for that very kind comment, vixr!!


----------



## Llama16

Thanks tomb, PM sent


----------



## proid

Are those caps good enough for the MSSH?
  Philips BC 470uF/63V 
  Nichicon FW 220uF/50V
  Rubycon ZL 820uF/63V instead of 680uf


----------



## tomb

Quote: 





proid said:


> Are those caps good enough for the MSSH?
> Philips BC 470uF/63V
> Nichicon FW 220uF/50V
> Rubycon ZL 820uF/63V instead of 680uf


 

 If you use the Nichicon FW 220uf/50V as the cathode bypass - those are an exception.  For instance, the standard cathode bypass cap (C7 and C8) that we supplied in the old SSMH kits was the Nichicon Muse ES 220uf *16V*.  The voltage around the cathode bypass is very low and the 16V rating was never an issue.
   
  The other caps are fine.  There's no reason you can't go higher on the uf, either.  You didn't specify, but the 820uf would be good in the power positions - C1 and C6.  Also, the 470uf's are fine for output caps - C3 and C5.  However, if you use low impedance phones (32 ohms or lower), you would actually benefit a bit by using 1000uf at C3 and C5.  There's really no limit on C1 and C6, but if you get outrageously high in uf, you may trip the power supply on the startup current surge.
	

	
	
		
		

		
			





  I would keep all other caps except C7 and C8 at that 63V voltage rating or higher.


----------



## capernicus

Ok y'all, I need a little troubleshooting assistance!!!
   
  Left channel works gerat, right channel seems to only get some kind of cross talk - signal comes through but you have to crank it way up - the left channel is ear bleeding just to get audible sound out of right channel.  I don't have any noise to speak of which is nice for a change.
   
  I have indicated the voltages I have measured in red, there are some real differences between L and R.  Notably, Pin 1/6 on the tubes - 47.4V (R) vs 26.8V (L)
   
  I did measure to see if there is a short between the heatsink and the MOSFET but wasn't able to measure anything.  The heatsinks mounts to wood anyway with the heatsinks floating - not attached to ground as of yet.
   
  I suspect I have a blown MOSET but am unsure.  The real kicker is the voltage readings at Pin 1 of the MOSFET - Left (good) side is around 46V while the Right (bad) is not measurable.  The strange thing here is that where R2, R3 and R4 (Right) and R8, R9 and R10 (Left) all meet up I measure 15.4 volts on each side.
   
  Something isn't making sense...
   
  Please help!!!


----------



## capernicus

I replaced the right MOSFET but not change in the observables.
   
  I can't figure out why pin 1 / 6 voltages would be so different between L and R.  I measured the resistances of R1 and R7 and both are reading 33k.  Could my problem be a short in C2? - unfortunately I don't have any spares of those...


----------



## digger945

^ Can you post some pics, with close ups?
   
  Its kinda hard to see 15.4v on one side of R9 and 46v on the other.


----------



## capernicus

Ok, so I have this thing mostly complete.  Its Purple Heart and Maple in a 12AU7 build
   

   
  Unfortunately, as I mentioned in my previous posts I can't seem to get the Right side working correctly...
   
  I took a picture of the internal bird nest below - I'm the first to admit I still have much to learn on how to do clean wiring and am also open for some pointers.
   
  I picked up some nice aerospace grade wire scraps from work (silver tinned copper) and used it throughout except for the black wire which is when I ran out of the good stuff and had to dip into my crummy Depot stock.
   

   
  Please let me know if you have any suggestions for my sick right channel...


----------



## digger945

Check the headphone jack wiring.
  L and R should each be connected directly to the output coupling caps, with each channel having its own 2k resistor parallel and to ground.


----------



## digger945

Also, check for proper wiring of the jack itself. You could have one channel and ground reversed and that channel will still play, the other channel being only the difference between L and R.


----------



## capernicus

just studying the internal picture I see that I do have C8 installed backwards - I wonder if this could be contributing to my problem...


----------



## digger945

Quote: 





capernicus said:


> just studying the internal picture I see that I do have C8 installed backwards - I wonder if this could be contributing to my problem...


 

 It should be fixed, but likely not the problem. 
   
  In post #5970, you have an attachment with some of your operating points. You show 46volts at the gate of Q2, but 15.4volts on the other side of R9? With a good mosfet, you should read the same voltage on both sides of R9. If indeed you do show 46volts at the gate, then most likely you have a cold solder joint or bad connection to ground, at R10.


----------



## CaptHowie

Could anyone tell me where to find a mounting kit for the MOSFET on the heatsink? I live in Australia, so I'll be using Farnell/Element14 to order. At the moment I've found the heatsink, but the accompanying mounting kit is $9.85. Seems a little steep considering the heatsink is around $5.
   
  Edit: Or would even this one work? Link


----------



## Fred_fred2004

I didn't use a kit on mine I insulated the whole heatsink from the circuit by useing an ABS case, if you are not useing a metal case you might not need to worry


----------



## capernicus

yes, i believe your e-bay link should work... you are correct, this should be an inexpensive purchase...
   
  For comparison sake I purchased this one from Mouser: Link  I paid $1.65 US.  I have to think you should be able to get something like this for about the same cost in Australia.


----------



## CaptHowie

Quote: 





fred_fred2004 said:


> I didn't use a kit on mine I insulated the whole heatsink from the circuit by useing an ABS case, if you are not useing a metal case you might not need to worry


 

 I am using an ABS case. How exactly does this work?
   
  Quote: 





capernicus said:


> yes, i believe your e-bay link should work... you are correct, this should be an inexpensive purchase...
> 
> For comparison sake I purchased this one from Mouser: Link  I paid $1.65 US.  I have to think you should be able to get something like this for about the same cost in Australia.


 

 I thought it was a tad expensive, especially for something as basic as a few screws and washers. Thanks for clarifying that.


----------



## Fred_fred2004

Here's some pics of the case I used, Its from Jaycars under $10 (from memory), as you can see the heatsinks are electrically isolated
   
 
   
  cheers
  FRED


----------



## Ikarios

Quote: 





capthowie said:


> I am using an ABS case. How exactly does this work?


 

 The reason that the heatsink mounting kit is used is because on the SSMH PCB version, the metal case was tied to ground, but the heatsinks/mosfets were NOT. Thus it was crucial to isolate the metal heatsink from the metal case, otherwise you would short the mosfet and burn it up. If you're using an ABS case, there's no concern, as long as your heatsinks are electrically connected only to the mosfets and not anything else.


----------



## nikongod

I would insulate the mosfets, and ground the heatsinks no mater what kind of case you used. 
   
  The drain on the mosfet is connected to the mounting tab and accordingly there is +48V on the heat-sink tab of the mosfet. Certainly enough to give you a nasty shock if you touch the heatsinks & something that is grounded. Maybe it requires you to do a couple things at the same time, but they are not uncommon actions so its likely to happen. Its best not to leave things to luck once you have more than a few volts in a circuit.
   
  Measure DC volts from the heatsinks to the ground in the amp. If its more than 0V, and it will almost certainly be, fix it. 
   
  If we are talking about FRED's amp above, it will not be hard to attach a ground wire to the heat-sinks. Much better to blow up a mosfet or even a power supply than give someone a nasty shock.


----------



## Fred_fred2004

You will struggle to get a nasty shock from 48 volts


----------



## nikongod

Quote: 





fred_fred2004 said:


> You will struggle to get a nasty shock from 48 volts


 


  Wikipedia... not exactly the gold standard, but why risk compromising safety to save 3 dollars?
   
  "Voltages over approximately 50 volts can usually cause dangerous amounts of current to flow through a human being touching two points of a circuit, so safety standards, in general, are more restrictive where the chance of contact with such high-voltage circuits exists."
   
http://en.wikipedia.org/wiki/High_voltage
   
  Approximately - 48V is approximately 50V - you would struggle to measure the difference on the 200V scale of an analog meter. 
  dangerous amounts of current - with at least 0.5A on tap there are dangerous ammounts of current in the amp. 
  touching 2 points of the circuit - like the grounded headphone jack and the heatsinks while plugging in/pulling out. 
  Spend the extra $3


----------



## Fred_fred2004

You'd have to be soaking wet in a salt solution to get a shock
   
  I worked for many years for Australian Telstra and its power source was 48 volts derived (believe it or not) from huge lead acid battery banks, and we never took any precautions other than not shorting out the (+) and (-) which fused wires pretty thoroughly 
   
  sorry its just not going to hurt you


----------



## nikongod

Quote: 





fred_fred2004 said:


> You'd have to be soaking wet in a salt solution to get a shock
> 
> I worked for many years for Australian Telstra and its power source was 48 volts derived (believe it or not) from huge lead acid battery banks, and we never took any precautions other than not shorting out the (+) and (-) which fused wires pretty thoroughly
> 
> sorry its just not going to hurt you


 

 I have heard stories of people having limbs blown off by 48V battery banks. 
   
  I would not be so casual with voltages outside of an enclosure. People have zapped themselves mighty good on 12V car batteries. Its not even hard - your out working in the sun, your hands get sweaty, you brush the + terminal with your tummy resting on top of the radiator and zap.
   
  I can see an equally plausible scenario playing out where someone with sweaty hands goes to plug in his headphones, grabs the amp by the top, pushes his headphones in (with a metal plug) and zap. 
   
  Agreed, you would need to be somewhat unlucky to zap yourself. The opposite of that is of course that you need to be somewhat lucky so that someone does not zap themself. So the safety of your design decision is conditional on luck, to save $3.


----------



## Fred_fred2004

It's actually 62,000VND (vietnamese dong)
   
  so well worth saving


----------



## nikongod

Quote: 





fred_fred2004 said:


> It's actually 62,000VND (vietnamese dong)
> 
> so well worth saving


 

 At the current time, not even $3us. 
  Creating an electrocution hazard to save less than $3. That sounds pretty irresponsible to me.


----------



## Fred_fred2004

It would be if it was a hazard
   
  its not


----------



## tomb

Sorry, but I'd have to come down on nikongod's side on this one.  I remember when Dsavitsk was designing the PCB for the Starving Student.  He went to great lengths for added safety - specifically because 48V is high enough to start causing some real pain, under the right circumstances.  The issue as a responsible designer is that you try to limit those "right circumstances" from happening.


----------



## digger945

While the IRF510 output MOSFET here has internal protection devices built in, it could be possible for the drain to remain "hot" even if the device failed, and the entire circuit were inoperable. A problem with the power supply, be it a Cisco or alternate DIY variety, could pose lethal to even an experienced diy'er. More so with the heatsinks isolated from a safety ground.


----------



## livewire

And as a responsible DIY builder, one must employ correct electronic assembly methods.
  Exposed tube equipment is inherently dangerous as it is, why add exposed voltage on the heatsinks to the equation?
  I sure would not want 50 volts at 1/2 amp crossing through my heart.
  I've also been shocked by a car battery. Scared the pee out of me.
  My left arm went flying into the raised hood of the car.
  Might not have killed me, but was still a dangerous wake-up call.


----------



## Fred_fred2004

You are all perfectly correct, if there is any chance of danger it should be protected against
   
  and if by any chance you get 1/2 and amp at 50 volts across your heart dont worry you'll be dead already


----------



## capernicus

that was an interesting dirt road... glad we have that issue resolved...


----------



## proid

So how does the MSSH compare to other amp? Reading this thread, i only know that it's very good for the price but don't know how well is stack to other commercial products?


----------



## capernicus

Quote: 





capernicus said:


> Ok, so I have this thing mostly complete.  Its Purple Heart and Maple in a 12AU7 build
> 
> 
> 
> ...


 

 OK so I've double checked that R10 is properly connected at both ends and reflowed the solder - no change.  Nothing happens when swapping tubes.  headphone jack is wired properly.  Replaced the MOSFET - till no change.  Both tubes glow nicely and voltages at the tube heaters checkout.  It would appear that I'm not getting a healthy current through the tube as Pin 1 is measuring too high of a voltage ~47 volts.  Any thoughts?


----------



## nikongod

Quote: 





capernicus said:


> OK so I've double checked that R10 is properly connected at both ends and reflowed the solder - no change.  Nothing happens when swapping tubes.  headphone jack is wired properly.  Replaced the MOSFET - till no change.  Both tubes glow nicely and voltages at the tube heaters checkout.  It would appear that I'm not getting a healthy current through the tube as Pin 1 is measuring too high of a voltage ~47 volts.  Any thoughts?


 

 Measure resistance to ground at the cathodes of both tubes with the amp off. Should be the same, probably isn't. 
   
   
   
  Its almost certainly not the cause of the problems your having, but the 2Kohm resistors R3/R9 should be soldered directly to the mosfets' gates with the wire going to the middle of the resistor divider. This resistor is a "gate stopper" for the output mosfets. Most of the time these resistors do nothing, but for them to work when necessary they have to be snuggled up close to the mosfets.


----------



## capernicus

That was it!  Thanks!  The cap and resistor tying the cathode to ground are twisted together and connected to a wire that went over to ground which turned out to be in the correct place but not soldered in...
   
  Now I am enjoying the music - sounds terrific!  I look forward to putting it side by side with my SOHA II...
  
   
  Quote: 





nikongod said:


> Its almost certainly not the cause of the problems your having, but the 2Kohm resistors R3/R9 should be soldered directly to the mosfets' gates with the wire going to the middle of the resistor divider. This resistor is a "gate stopper" for the output mosfets. Most of the time these resistors do nothing, but for them to work when necessary they have to be snuggled up close to the mosfets.


 
   
  So I have my 2k resistor at the other end of the wire from the mosfet - not right on it as you suggest.  How critical is it to put the resistor at the mosfet?  My limited understanding of all this would suggest that either way you have a 2k load on the gate and considering the distance we are talking is very small being right on the gate or 2" away shouldn't matter.  I'd like to understand this better - i haven't worked much with MOSFETs...
   
  Thanks again Nikongod for the troubleshooting assistance!


----------



## capernicus

Amp #2 - need help on this one too (unfortunately I'm just not getting a break on these things...)
   
  So I actually built 2 of these amps as Christmas presents...  The first one featured earlier is for the lovely Mrs Capernicus.  Number two is for the bro-in-law.  I had my father in law build the box (another woody) and I wired it all up.
   
   
  Amp #2 Problem:
  Left Channel is there but only about half as loud (maybe less) than the Right but it is certainly there.
   
  Observables:
  -All of the voltages check out - closely match amp #1 across the board.
  -I checked all of the resistances - R17, R15, R12, and from the negative side of C4 to GND - all checks out and measures same as working side.
  -I tried swapping tubes - weak channel did not follow the tubes
  -MOSFET voltages look good...
  -measured resistances through POT and both channels track nicely
  -I checked the CD source - even flop flopped the L vs R and nothing changes.  (I know the source is OK because it works as expected with Amp #1)
   
  I am stumped... what have I missed?


----------



## nikongod

Quote: 





capernicus said:


> So I have my 2k resistor at the other end of the wire from the mosfet - not right on it as you suggest.  How critical is it to put the resistor at the mosfet?  My limited understanding of all this would suggest that either way you have a 2k load on the gate and considering the distance we are talking is very small being right on the gate or 2" away shouldn't matter.  I'd like to understand this better - i haven't worked much with MOSFETs...
> 
> Thanks again Nikongod for the troubleshooting assistance!


 

 I would say the importance is either 0 or 100%. It either makes no difference, or all the difference in the world. 
   
  The idea behind the resistor is that mosfets can osciilate when they have RF on their inputs. By putting the resistor directly on the pin there is no antenna to pick up RF, and thus the likelihood of the mosfet oscillating drops. 
   
  If the wires are very short, it probably doesnt matter.


----------



## proid

I'm planning on using Panasonic FC 1200uf/63V for C1,C6, Wima MKP10 0.47uf/400V for C2, C4, C3a, C5a, will that be fine?


----------



## tomb

Quote: 





proid said:


> I'm planning on using Panasonic FC 1200uf/63V for C1,C6, Wima MKP10 0.47uf/400V for C2, C4, C3a, C5a, will that be fine?


 

 Seems fine if you want to go with _moar_ farads.
	

	
	
		
		

		
			





 
   
  So, what are you proposing for C3 and C5?


----------



## capernicus

Quote: 





nikongod said:


> I would say the importance is either 0 or 100%. It either makes no difference, or all the difference in the world.
> 
> The idea behind the resistor is that mosfets can osciilate when they have RF on their inputs. By putting the resistor directly on the pin there is no antenna to pick up RF, and thus the likelihood of the mosfet oscillating drops.
> 
> If the wires are very short, it probably doesnt matter.


 

 Interesting -  Thanks for the response!


----------



## proid

Quote: 





tomb said:


> Seems fine if you want to go with _moar_ farads.
> 
> 
> 
> ...


 


  Just because i can't get lower farad 63V cap 
	

	
	
		
		

		
		
	


	



  I'll use Philips BC 470uf/63V for C3 and C5


----------



## TestSubject

My Stripboard SSHM amplifier. Layout here LINK


----------



## Starfire

Figured I'd add mine to the thread, though I think I'll sell it.
   
  First time I've really done a full point to point, I almost always use a perfboard, also used some navships teflon wire for all the audio signal.  Sound great though!
   
  Outside:
   
   

  Inside:


----------



## proid

i have just turned on the amp without un-plug my headphone for about 2-3 minute. I think my headphone now sound not different than before but i'm still worry ...


----------



## nikongod

[joke]How do you know its not the amp that sounds different due to different amounts of current going through the caps to allow for the turn on thump?[/joke]
   
  Seriously:
  I would not loose sleep over doing this once, especically if your headphones sound the same as before. I would certainly not make a habit of it, but relax. Damage from turn-on-spikes is pretty obvious.


----------



## proid

Quote: 





nikongod said:


> [joke]How do you know its not the amp that sounds different due to different amounts of current going through the caps to allow for the turn on thump?[/joke]
> 
> Seriously:
> I would not loose sleep over doing this once, especically if your headphones sound the same as before. I would certainly not make a habit of it, but relax. Damage from turn-on-spikes is pretty obvious.


 


  In fact, i have just tried to turn off my amp then turn on and mesure the output and it's only around 5mv DC? Another problem i have is that when i solder the leds to the board, my amp sound very very tiny, even after i turn volume all the way up, i still can't  get comfortable volume. When i desolder leds, problem has gone but i want to use these leds, they look damn good (my amp is the modifed pcb version to use with 12au7)


----------



## capernicus

So how hot is too hot with respect to the heatsink?  After about an hour the heatsink is so hot that I can only touch it for about 1 second before I need to take my hand away...  is this normal?


----------



## nikongod

Quote: 





proid said:


> In fact, i have just tried to turn off my amp then turn on and mesure the output and it's only around 5mv DC? Another problem i have is that when i solder the leds to the board, my amp sound very very tiny, even after i turn volume all the way up, i still can't  get comfortable volume. When i desolder leds, problem has gone but i want to use these leds, they look damn good (my amp is the modifed pcb version to use with 12au7)


 

 It sounds like you soldered the LEDs to the wrong places, or maybe skipped some resistor. Im not too familiar with the 12au7 boards, but that is where I'd start looking. 
   
  Quote: 





capernicus said:


> So how hot is too hot with respect to the heatsink?  After about an hour the heatsink is so hot that I can only touch it for about 1 second before I need to take my hand away...  is this normal?


 

 Mosfets can run hot enough to burn skin for a VERY long time. Cooler is better, but hot isn't necessarily unacceptable. 
  Do you have an IR thermometer, or some other way of getting an accurate temperature measurement? I would strongly advise against touching stuff in a live circuit, but since you already did and it did not burn your skin I'd bet that the mosfet is pretty much OK.


----------



## Ikarios

I believe the MOSFETs are rated for at least 80C continuous, maybe up to 105C. Obviously you would not want them to run at such a high temperature for long periods of time, but that is what they are rated for. I thought my amp ran pretty hot too (uncomfortable to touch but not unbearable), but I decided to check it with an IR thermometer anyway, and got a measy ~38-40C at the heatsinks. I'd say anything under 50C would be just fine, 60C you probably want to look into better heatsinking, vent holes, etc.


----------



## rodneywimberly

I have to brag to someone cause my wife just don't care. It's 2:00 AM and I just got my amp finalized, and tested. It's f_cking AWESOME. I gotta go to work early but I can't quit listening. Thanks to everyone in these posts and Pete Millet.


----------



## CaptHowie

Hi All,
   
  I've ordered all the parts to build my amp, and I've encountered a problem. The heatsinks I ordered, instead of using screws, use two pins. Upon further research, I've discovered that they are PCB-mount TO-220 heatsinks. Problem is, I'm using an ABS case. Is there any way to mount these heatsinks, or will I have to order another set? I've attached a photo in case here http://dl.dropbox.com/u/10765/photo.JPG


----------



## livewire

The pins are pressed into the heatsink and will usually come out without too much trouble.
  A small screw then can be used instead of the pin in the extrusion hole.
   
  I grab the pin tightly with a vice-grip pliers, then twist and pull. 
  A flat blade screwdriver can also be used to pry between the heatsink body and the vice-grip,
  thus prying the pin out upward. Just dont wiggle the pliers side to side, it could break the pin off.
   
  If a pin does break, just use screws on the other end of the heatsink. It has the same holes in the extruded metal.
   
  Since you are using a plastic case, always connect your heatsinks to a ground.
  Use a wire with a ring connector attached to it on one of the screws on each heatsink.


----------



## the_equalizer

Wow, I "leave" for a couple of months and then the thread bursts into activity!  It's great reading all the posts from new builders not to mention some truly beautiful builds (that purple wood case is gorgeous).


----------



## Bombshell

Hi, I've been reading a lot on this thread and I didn't see anyone asking about any kind of protection for their headphones from DC spikes when turning the amp on. Could you just wire in a 3PDT switch at the outs? like a standby switch on a guitar amplifier? I understand it's a simple task to remember to wait before plugging the headphones in, but i have a terrible short-term memory.


----------



## nikongod

Your horrible short term memory wont help you remember to flip the switch if it doesnt remind you to unplug your headphones. 
   
  I have on more than one occasion flipped mute switches (or forgotten source selectors) with the volume way higher than I would like after a few head-scratching moments asking why the stereo isn't making noise? Much better to minimize points of failure.


----------



## the_equalizer

Agreed: a switch to manually flip makes no difference from a plug to manually unplug. That, of course, is no reason not to wire said switch in your amp .  Just don't think it's a failsafe protection for your cans!


----------



## 3nto86

Hi all,
   
   
  I have a problem with my millet starving student..I follow the instructions for build it with the 12AU7 tube (not the 19j6); and I rechecked several times the schematic and circuit, and it is right.
  The problem is that I have a big noise in the output, if i put any resistence between the input jack and the tube (50Kohm R, and 50k alpha pots).
  So if there isn't any resistence the output is very very clear; but when i put the 50Kohm or the trimmer the noise grow up!
  For example if I turn the pot to the max volume, the noise decrease (because decrease the input resistance between jack and input 2 of tube).
  I recable the amp with short cable; but nothing change.
  I don't understand the problem, the circuit is right, the mosfet and tube work fine (i think, because without any resistence the sound is very goood!) so which are the problem?
  I have a plastic case, and if i touch with my hand the heatsink the noise decrease; so it could be a mass problem? but why work fine without input resistance?
   
  Thanks to all, and sorry for my bad english..


----------



## Bombshell

Quote: 





nikongod said:


> Your horrible short term memory wont help you remember to flip the switch if it doesnt remind you to unplug your headphones.
> 
> I have on more than one occasion flipped mute switches (or forgotten source selectors) with the volume way higher than I would like after a few head-scratching moments asking why the stereo isn't making noise? Much better to minimize points of failure.


 
   
  alright, i was just wondering if it would mess with something. i didn't think it'd be an issue but i wanted to ask someone who'd actually know.  Thanks!


----------



## the_equalizer

Quote: 





3nto86 said:


> Hi all,
> 
> 
> I have a problem with my millet starving student..I follow the instructions for build it with the 12AU7 tube (not the 19j6); and I rechecked several times the schematic and circuit, and it is right.
> ...


 


  Most definitely a grounding problem.  That and you might live in an area particularly rich in electromagnetic noise. Tube circuits are high input impedance circuits which, among other things, makes them excellent pickup antennas for whatever signals might be around. Input resistances push the input impedance even slightly higher.
   
  I can suggest two things:
   
  1.- Make ABSOLUTELY sure the pot is wired correctly. The wiper MUST be wired to optional input resistance R14/R15 or the tube grid. Then one end of the resistance path is wired to the input signal and the other one to ground. In this way when you vary the pot's position you vary the tube's input resistance to ground; essentialy shorting out the input to ground (0 volts) at the minimum position and connecting it directly to the input signal at the other end.
   
  It is a very common mistake to miswire it, something we've probably all have done in our first builds. Do not assume that the middle solder lug/pin in your pot is the wiper; check with a multimeter.
   
  The usual mistake is to wire the input signal to the wiper. So when you move the volume to the minimum the tube's input is left 'floating' which makes all kinds of stray signals go into the wire. This is also VERY bad because it means you are shorting out to ground the outputs of whatever you are feeding into the SSMH; some devices might not tolerate this and will die trying to feed a signal into a 0 ohm resistance.
   
  2.- Cover your case's interior with conductive material e.g. aluminum foil, copper tape (as used in musical instrument shielding), graphite paint (used in musical instrument shielding too). Then put a bolt and nut somewhere in the case that makes good contact with your shielding, and connect a wire from this nut and bolt to the circuit's ground. If you search the thread, you'll find a couple of users who did this and were successful in quieting their amps.
   
  From what you mention about touching the heat sinks, it seems as though they are electrically isolated from the MOSFET tabs. If you do shield your case's interior, make ABSOLUTELY sure they are isolated or you'll blow the MOSFETs when you turn the amp on.
   
  I hope this helps. Good luck and let us know how it goes.
   
  cheers!


----------



## proid

What about tube rolling with 12au7? Did anyone try?


----------



## the_equalizer

Sure, you can obviously try different brands and makes of the 12AU7, but you can also try 12AX7, 12AT7 and 12AV7.  As someone else has posted, the 12AU7 are the less wild of all these because as it is, the SSMH has more than enough.gain already and the 12AU7 are the ones with less gain of the above batch. However there's no danger in trying the other ones if you're careful with your volume knob.
   
  Oh, if I remember correctly, you can also drop in a pair of 17EW8 directly and it'll work. Search the thread to confirm this. It's been so long since I last played around with this amp and tubes that my memories about it are a bit vague.
   
  cheers!


----------



## Starfire

Yes the 17EW8 work, also I've seen 12SR7 and 12SW7 which are 8pin octal base metal tubes (I would imagine they pick up less interference)  Pretty much anything that's a triode and within acceptable voltage ranges (Can't really go much lower then 12VDC on the heaters or the Mosfets will run really hot!), also I don't believe the 12SR7/12SW7 are dual triode, but a single triode can be used also.
   
  12AU7, 12AX7, 12AT7, 12AV7 are by far the easiest and cheapest to find though, remember then also have European names too, I believe ecc81, ecc82, ecc83.
   
  Mine with 17ew8's:


----------



## the_equalizer

Absolutely, you can also build the amp using the 17EW8 (I have) or 12SR7 and 12SW7 (I haven't). What I meant was that in a 12AU7 circuit you can directly drop in a pair of 17EW8 or all the other 12A_7 tubes without any modification to the circuit and it'll work; thus enabling you to roll tubes 
   
  The 12SR7 and 12SW7 require some changes in component values as well as a diferent socket, an octal one, as you pointed out.
   
  That's a beautiful looking 17EW8 build you have there, congratulations! I wouldn't mind seeing some more pics of it    Is that third tube driving a ground channel?
   
  cheers!


----------



## 3nto86

Thank you very much ..
 I see that the pot is wired correctly.
  So i will try with cover the case with a conductive material.
  Sure I will let us know how it goes!
   
  Bye!
   
  Quote: 





the_equalizer said:


> Most definitely a grounding problem.  That and you might live in an area particularly rich in electromagnetic noise. Tube circuits are high input impedance circuits which, among other things, makes them excellent pickup antennas for whatever signals might be around. Input resistances push the input impedance even slightly higher.
> 
> I can suggest two things:
> 
> ...


----------



## Starfire

Quote: 





the_equalizer said:


> Absolutely, you can also build the amp using the 17EW8 (I have) or 12SR7 and 12SW7 (I haven't). What I meant was that in a 12AU7 circuit you can directly drop in a pair of 17EW8 or all the other 12A_7 tubes without any modification to the circuit and it'll work; thus enabling you to roll tubes
> 
> The 12SR7 and 12SW7 require some changes in component values as well as a diferent socket, an octal one, as you pointed out.
> 
> ...


 

 It is an active ground, it's not perfect though, with sensitive headphones (My D5000s) the ground will pick up some of the output from the other channels since all the grounds are connected together, but it's pretty minuet you only notice it with a song that will have something with a 100%/0% balance.  It does drop some of the noise and widens the soundstage some, which in some peoples book means it's less accurate but I like, and that's what counts.  I do have a toggle in the back to switch between active and passive on the fly.  
   
  I still have some experimentation to do with values of components also, but here is a picture inside at the moment, nothing fancy just spaghetti!


----------



## the_equalizer

Wonderful! It looks like you did a really clean work in that perfboard. Really nice!


----------



## bengoshi2000

Greetings all,
   
  After years of being frustrated that I can't use my AKG240's with my iPod/iPhone (or really anything else I have), I have decided to quit whining and build something... I think the Starving Student is going to fit the bill acoustically, aesthetically and most important, financially.  I have a couple of questions though...
   
  I'm going to confess up front that I haven't read all 400+ pages of this thread, so please excuse me if the following questions have been previously answered.
   
  1)  I want to use a different type of heatsink for the mosfets... will just about any heatsink work (as long as the mosfet is properly mounted to it) or are there some types to avoid?
   
  2)  I also want to use a rotary on/off switch.  Will any ol' switch do (as long as it meets or exceeds the specs of the switch from the BOM)?  Would someone be willing to suggest an appropriate switch?
   
  This will be my first foray into diy amplifiers so I'm a bit nervous about the project.  Are there any good EE for Dummies type books I could pick up?
   
  Thanks in advance!


----------



## Starfire

Quote: 





bengoshi2000 said:


> Greetings all,
> 
> After years of being frustrated that I can't use my AKG240's with my iPod/iPhone (or really anything else I have), I have decided to quit whining and build something... I think the Starving Student is going to fit the bill acoustically, aesthetically and most important, financially.  I have a couple of questions though...
> 
> ...


 

  
  Yes any heatsink of sufficient size will work, if you want you can mount the mosfets to one large one as I did in my build, be sure to get the mounting kits or I just get the thermalsil (Search that in mouser) pads and some nylon screws and nuts, you want them to be isolated.  Then you can ground the heatsink for extra noise reduction.
   
  Any switch will work as long as it can handle the current, which really isn't much.  I've used the volume pots that have a switch built in to kill two birds with one stone.


----------



## thelostMIDrange

So, just stumbled on this thread....wow is it a big'un.....this starving student is a simpler version of the minmax?  the concensus is that it sounds good and likes low ohm grado type phones too?  thanks for any quick synopsis' of this 400 page thread...


----------



## bengoshi2000

Greetings all,
  I'm looking into building the 12au7 version as an option if I can't find any 19j6 tubes.  I've been reading over the schematic for that mod:  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
   
  My question relates to the highlighted changes... Where the changes are alongside another (i.e. original design component), is the highlighted option to be used _*in addition*_ to the original or _*in place*_ of the original?  I know that's a rank, noobie question but I wanted to be clear before I started putting together a BOM/shopping list.
   
  Also, are there any good basic electronics resources in print (or electronic) that I should take a read of before I warm up the soldering iron?
   
  Thanks again!


----------



## SpringHalo

Quote: 





starfire said:


> Yes any heatsink of sufficient size will work, if you want you can mount the mosfets to one large one as I did in my build, be sure to get the mounting kits or I just get the thermalsil (Search that in mouser) pads and some nylon screws and nuts, you want them to be isolated.  Then you can ground the heatsink for extra noise reduction.
> 
> Any switch will work as long as it can handle the current, which really isn't much.  I've used the volume pots that have a switch built in to kill two birds with one stone.


 

 Would this switch work? I see that it has 2A/250V AC, but only 28V DC. You say you used volume pots with switches in them, and I can't seem to find dual pots with switches (on mouser) could you link me to the one you used?
   
  If I did use a standalone switch (to enable/disable headphones so they don't pop) would I need a DPST (for both channels) or could I just short the ground with it?
   


  Quote: 





bengoshi2000 said:


> Greetings all,
> I'm looking into building the 12au7 version as an option if I can't find any 19j6 tubes.  I've been reading over the schematic for that mod:  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
> 
> My question relates to the highlighted changes... Where the changes are alongside another (i.e. original design component), is the highlighted option to be used _*in addition*_ to the original or _*in place*_ of the original?  I know that's a rank, noobie question but I wanted to be clear before I started putting together a BOM/shopping list.
> ...


 

 The two capacitors that are tacked in parallel to the others are output coupling capacitors. They are to be *added *to the current components. (I'm making a 12A_7 version too) Have fun with your build!
   
   
   
   
   
  Speaking of builds, I messed around in sketchup for a while and produced my case idea! The top and bottom are maple, while the front/back plates, as well as the heatsinks on the sides (going to make them myself) are going to be made of either aluminum or steel. The switch to the right is going to be the headphone-safety switch, but I might end up getting rid of it in favor of starfire's idea, and mounting the potentiometer on the right side of the face.


----------



## the_equalizer

Quote: 





bengoshi2000 said:


> Greetings all,
> I'm looking into building the 12au7 version as an option if I can't find any 19j6 tubes.  I've been reading over the schematic for that mod:  http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
> 
> My question relates to the highlighted changes... Where the changes are alongside another (i.e. original design component), is the highlighted option to be used _*in addition*_ to the original or _*in place*_ of the original?  I know that's a rank, noobie question but I wanted to be clear before I started putting together a BOM/shopping list.
> ...


 
   
  I'm not sure what exactly do you refer to when you say 'alongside another' but if you're talking about, for example, C1 and C6, where there's a value crossed with a line and another value non-crossed value next to that, then they're not to be used in addition to but in place of the original (the crossed number). 
   
  So for C1 and C6 the original schematic specified 150uF electrolitic capactitors where the modified version uses 680uF caps @ 63 volts.
   
  To also clarify another potentially confusing issue, parts highlighted in yellow are optional, you can leave them out if you so wish. If you DO leave them out R14, R15, R16, R17 must be substituted by a wire connection; whereas C3a, C5a, C7 and C8 need nothing of the sort, you just don't connect them.
   
  Oh, and certainly anything you can read on introductory electricity and/or electronics helps. I wish I could give you some URLs but I really don't know any. Google is your friend or maybe others could chime in here.
  
  Hope this helps.


----------



## bengoshi2000

Quote: 





the_equalizer said:


> I'm not sure what exactly do you refer to when you say 'alongside another' but if you're talking about, for example, C1 and C6, where there's a value crossed with a line and another value non-crossed value next to that, then they're not to be used in addition to but in place of the original (the crossed number).
> 
> So for C1 and C6 the original schematic specified 150uF electrolitic capactitors where the modified version uses 680uF caps @ 63 volts.
> 
> ...


 

 Thank you!  That does clarify things for me.  I had been concerned that c7, c8 c3a and c5a  would be used in place of r5, r11, r6 and r12.  Now I understand now that if I use the yellow, highlighted options that they would be used in addition to NOT instead of.
   
  What benefits do the highlighted additions bring to the build?  (...my apologies if this is clearly answered elsewhere and I missed it.)
   
  Looks like I'm going to place some orders today!


----------



## the_equalizer

C7 and C8 have the effect of increasing the net gain of the tube amplification stage by removing a local negative feedback effect produced by using cathode resistors R5 and R11 to bias the tubes. Their intention is more the removal of the local negative feedback than an increase of gain; the amp has more than enough gain as it is.
   
  C3a and C5a have quite a complex effect but in summary they basically improve the high end frequency response of the output stage. They're called 'snubber' caps, if I recall correctly; heavily used in power supplies to suppress noise and transients.
   
  R16 and R17 help control the 'throw' of the volume pot, in theory allowing you to set the pot further ahead in its travel than you would have to set for a similar volume without the resistors (I swear that last sentence makes sense  ). Say, set the pot at 12 o'clock rather than at 8 or 9 for a similar volume level. This is good because the first section of the travel for volume pots is very uneven. I believe both Dsavitsk and TomB have posted much finer and better explanations of how these work elsewhere in the thread (the search function is your friend).
   
  Finally, R14 and R15 are grid stoppers. They have the intention of discouraging oscillations and some other noises in the tube amplification stage. Some builders in the thread report quite dramatic noise reductions when using them.
   
  For more about why these things have the effects they do you'll have to make your way through amplification theory texts 
   
  Good luck with your build!


----------



## bengoshi2000

the_equalizer,
  Thank you for the short explanation.  I do appreciate your considerable time/wisdom on this project (still working my way through this thread, btw).
   
  My last question is what caps would be of equivalent quality to the nichicon muse es 220uf for c7/c8 (that is also available at mouser)...
   
  I.E. what about this Panasonic Cap?
   
http://www.mouser.com/ProductDetail/Panasonic-Electronic-Components/EEU-FM1E221/?qs=sGAEpiMZZMtZ1n0r9vR22ZGaUoI0JcRfFCgLDbfQFjo%3d
   
  Nevermind... found the Nichicon Muse ES at Mouser:
   
http://www.mouser.com/Search/ProductDetail.aspx?R=UES1C221MPMvirtualkey64700000virtualkey647-UES1C221MPM


----------



## bengoshi2000

Ok... where do you wire in the tube illumination leds and resistor?
   
http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif


----------



## Beftus

It's all in this thread: http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/5685#post_7319936
  
  Quote: 





bengoshi2000 said:


> Ok... where do you wire in the tube illumination leds and resistor?
> 
> http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif


----------



## bengoshi2000

Thank you Beftus... I did a search and actually found that post, but it didn't make sense to me last nite.  Amazing what a good night's sleep and a hot morning cup of coffee will do for reading comprehension.


----------



## Beftus

For the sake of tinkering, you can make the tube LEDs switchable. I wired a on-off-on switch between the tube LEDs, I can run them at two different levels of brightness.


----------



## bowei006

Thought about doing this.....ill start wtih a cmoy first..


----------



## loki993

Im just not sure a Cmoy would satisfy my needs. Maybe a Mini3, but I really wanted to try tubes. I will build one of these eventually. 
   
   
  How is this with DT-770 Pro 80s? Anyone know? Would the optional mods make it better with them or worse?


----------



## akiroz

Interesting design, as i am a student myself (high school no less), i've always thought valves costs at least $10USD ea.
 I currently specialize in designing descrete solid-state amps and always wanted to try the "sound of tubes".
 just a quick question: is the tubes' heating element acting as the output resistor?, will that induce thermal noise?


----------



## Starfire

Quote: 





loki993 said:


> Im just not sure a Cmoy would satisfy my needs. Maybe a Mini3, but I really wanted to try tubes. I will build one of these eventually.
> 
> 
> How is this with DT-770 Pro 80s? Anyone know? Would the optional mods make it better with them or worse?


 

 The only parts I would leave out on any build would be the 50K resistors off the pot, they have no effect on the quality of the sound, just the level.  On something like an 80ohm headphone I'd keep them too.  All the other "optional" parts are there to improve sound.  I typically increase the value of the electrolytic capacitors on my builds for better filtering of power noise and a bit of an increase in bass response, but be sure to use decent capacitors such as the Nichicon Muze series.


----------



## bengoshi2000

All the parts are in... build thread to follow soon...


----------



## Starfire

Cool I'll follow along!


----------



## scottwhat12

Hey all!
  I really want to build a starving student, have just started electronics and i have built a cmoy and some other small things with pcb kits. Im just having trouble trying to understand how to ground? on the schematic it shows what needs grounds but where do i connect them to, just the chassis? any helps appreciated. 
  Thanks


----------



## tomb

Quote: 





scottwhat12 said:


> Hey all!
> I really want to build a starving student, have just started electronics and i have built a cmoy and some other small things with pcb kits. Im just having trouble trying to understand how to ground? on the schematic it shows what needs grounds but where do i connect them to, just the chassis? any helps appreciated.
> Thanks


 

 You can do that, assuming the chassis is metal and you make certain that the ground connections are good, electrically speaking.  Many cases that are sold and used for DIY are anodized and you need to be sure that you scrape the anodizing off where you make the ground connections.
   
  OTOH, if you use a non-metal case, then look at Pete Millett's first couple of posts that started this thread.  He used a copper plate (available for purchase from Mouser) and grounded everything to that.


----------



## Oeufdepoire

I have a few (maybe silly) questions. I didn't search through the 400+ pages of this thread for the answers. Here they are :
   
  Why are there two RCA plugs for the signal input ? Why no "standard" female jack ?
  Would I be able to use the amp with my Sansa Clip+ as the source ?
  Would this amp be usable with my Grado SR80i's ?
   
  Thank you


----------



## bengoshi2000

In case anyone is interested, I've started a build thread...
   
http://www.head-fi.org/t/597166/another-millett-starving-student-build#post_8165147


----------



## the_equalizer

1.- Input connector(s) can be whichever you wish. RCA jacks are actually the standard but if you wish to use a female phone jack instead you can.
   
  2.- Certainly
   
  3.- Yes
   
  cheers!
  
  Quote: 





oeufdepoire said:


> I have a few (maybe silly) questions. I didn't search through the 400+ pages of this thread for the answers. Here they are :
> 
> Why are there two RCA plugs for the signal input ? Why no "standard" female jack ?
> Would I be able to use the amp with my Sansa Clip+ as the source ?
> ...


----------



## bengoshi2000

Ok, my first (hopefully only) screw-up so far.  I thought I had ordered a stereo 50k pot with integrated switch... turns out it's mono (i.e. only one pot, not two).  Since I don't want to order another pot from Mouser and wait for it to ship, I found that RatShack has a stereo volume pot, but it's 100k (vs. the 50k spec'd on the BOM).  Could I use the 100k RatShack pot and leave out the 50k pots (R16/17)?


----------



## Starfire

Yeah it'll work in pinch.


----------



## bengoshi2000

Let the troubleshooting begin...
   
  So this weekend I got the ssmh wired up (with the exception of the rca inputs, volume control and the headphone jack).  Before getting things settled into the case, I decided to do a quick and dirty test by hooking it up to the power supply to see if anything would smoke.  Well, nothing smoked... but not much of anything else happened either.  I expected to get _some_ sort of glow at the heaters.  No dice.
   
  I got out my MM and took some measurements.
   
  Cisco PS:  48v
   
  Tube Pin #4 (L and R):  12.5v  
  I'm getting zilch on all other pins.  For 2 and 7 I'm assuming that's ok with no input, and since 5 is the ground I wasn't expecting anything there either.  But I thought I'd get some reading on pins 1 and 6...
   
  I slid the tubes a wee bit out of their sockets and took readings at the pins (thinking maybe a bad socket) but got the same results.
   
  Q1 and Q2:  D = 48v, G = 12.5v, S = 12.5v
   
  Any ideas??
   
*Note*:  I had to do some adaptation at R2/8.  I left the 390k resistor out of my purchase list.  A friend gave me a some 120k and 270k resistors.  I wired those in series and used them in place of the 390k resistors.  I have no idea what wattage they are (though the size makes me think 1/4 watt) and they are carbon film (the rest of the resistors are metal film).
   
*EDIT #1 2/28/12*:
  I've been doing some vigorous reading in this gargantuan thread and I came across a post by Dsavitsk that indicates the FET's should be reading:
   
  Pin 1 (gate) - 4v-5v above heater
  Pin 3 (source) - 12.5v (feeding the heater, tube pin 4).
   
  It wasn't stated specifically in the post, but since the drain connects straight to the power source the 48v reading I noted would be correct.  And my reading on the source of 12.5v. is also correct.  Error must be in R13, R1/7, C2/4, R4/10, R2/8 or the associated wiring/solder joints.
   
  The way I constructed my perfboard/p2p wiring, I worked each junction of the left and right sides at the same time (and they are mirror images of each other on the board).  So if I made one error on the right side, I probably duplicated the error on the left. 
   
  Sorry to put down my thought process here in this post, but maybe another electronics newbie like me will find it helpful...
   
*EDIT #2 2/28/12:*
  More troubleshooting done...
   
  The R13 side of R1/7 reads 42.5v, the Tube #1 pin side of R1/7 reads 0.
  The R13 side of R2/8 also reads 42.5v.
  The junctions at R2 and R4 (and R8 and R10) read 11.5v.
  The Tube #6 pin sides of C2 and C4 are also 0.
   
  I was thinking that my R1 and R7 resistors were bad... I pulled R7 and it tested out to a perfect 33k.  
   
  The fact that I'm getting 0v on the tube side of R1 and R7 makes me think they are shorting straight to ground... I just can't figure out where/how.


----------



## bengoshi2000

Day 3 of trying to work this out and I've gotten nowhere.  The problem seems to be somewhere around R1/7 and C2/4.  I'm desperately in need of some assistance...


----------



## bengoshi2000

Okay... my 2nd Dip$h*t moment:  Both tubes wired backwards.  I had assumed that tube pinouts were drawn as if one was looking down from the top of the tube (as opposed to looking at the tube from the bottom).  Rank newbie mistake...
   
  I did a rewire and the heaters began to glow as expected.
   
  Now I've got to figure out why I'm getting 100+ volts at the gates of both 'FETs...  (don't worry, once I read that voltage I shut it down... the 'fets only saw that voltage for 20 seconds or so).
   
  FETs were reading 48v and 12.5v on the drain and the source, respectively...


----------



## the_equalizer

100 volts at the gates!?!? That seems almost impossible, particularly if the voltages at drain and source are correct.... it's as if you were reading across the + and - lines of a bipolar 48V supply.  Are you absolutely sure you measured between gate and ground? 
   
  cheers!


----------



## Breck

I'm looking at your layout here:
  https://lh4.googleusercontent.com/-qE7XzkVTjsI/T0O4wRY_enI/AAAAAAAAAF4/icJYQ7ZiqUs/s1600/ssmh.jpg
   
  Are you using IRF510s for the MOSFETs?  Because if so, I think the pinout is different than what is shown on your layout.  Looks like the gate is on the far left (what shows as pin 2 on your layout).Here's the datasheet so you can verify:

 http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cts=1330622071782&ved=0CD4QFjAA&url=http%3A%2F%2Fwww.radiotechnika.hu%2Fimages%2FIRF510.pdf&ei=ea5PT728LcSTiQKkirC1Bg&usg=AFQjCNFejssSQlCxYBoBLl33bfN9_70h2Q
   
  Anyway, I may be completely wrong, but its something to look into.  It wouldn't necessarily explain the 100V you're seeing, but it might help it.
   
  Good luck!


----------



## bengoshi2000

Thank you for your replies and advice!!
   
  I'm going to double check everything tonite... the 100+ volts surprised me too (as far as I understand there's nothing in the circuit that could provide that level of voltage amplification... or even potential difference?!).
   
  As for my stripboard layout, the drawing IS incorrect re: the 510 fets.  I ended up building the amp on perfboard (as the piece of stripboard I planned with was too big for my enclosure).  I know that pins 1, 2, and 3 correlate to gate, drain and source respectively. 
   
  I'll post again tonite...


----------



## bengoshi2000

Ok... I desoldered and rewired the tube sockets again to make sure that everything was correct.  When I started it up the tube heaters began to glow after a couple of seconds (right channel heaters lit up a couple of seconds before the left channel).
   
  Readings on both fets were g = 100v+, d = 48v, s = 12.5v.  Tubes began to get warm as did the heatsinks.  
   
  On my old (read cheep) RatShack analogue meter, set on the 125vdc range, the meter was pegged.  For giggles I switched it to the 500vdc range... still pegged.  Somethin' ain't right here...
   
  I decided to just let it sit turned on for 2-3 minutes.  Tubes warm to the touch... heatsinks were very warm (uncomfortable to hold onto for more than 10-15 seconds... but not burning).  I took the readings again and now both gates were reading 12.5v... a few minutes later and it's pegging the meter again.  
   
  Two things to note:  1) I'm using a pair of 12au7a tubes that as I understand them, take longer to warm up.  2) I'm only reading 42.5 volts at the R1 side of R13... schematic says it should be 48v.
   
  Sooo, are the 12au7a's doing something odd due to their longer warm up period OR is my RatShack AMM to blame?
   
  EDIT:
   
  Went back and turned it on and took a couple more measurements.  At the junction R2 and R3 (and R8 and R9), I'm getting 15v... on the fet side of R3 and 9 I'm still getting the crazy high voltage reading.
   
  It's been on for about 15 minutes now and the heatsinks are holding steady around 135*F (according to my laser thermometer).


----------



## the_equalizer

Crazy indeed, I really can't imagine what's producing those extreme voltage readings... I really don't think the tube type has anything to do with it, unless your specific 12AU7s have some kind of weird internal failure or short of some kind...
   
  The analogue meter certainly has a low input impedance that DOES affect voltage readings in high impedance circuits (such as FET gates) but it makes the reading  LOWER not higher (I had a such an experience with a cheap multimeter and the first 12AU7 prototype I built)...
   
  I'm REALLY curious as to what's happening in your circuit..


----------



## bengoshi2000

I think my multimeter lies...

This morning I hooked up all of the inputs and took the amp on a 20 min. test drive. It worked perfectly... clean sound, no hiss, no audible crosstalk, no hum. I got out my old AKG240s and they sounded awesome... better than I remember. Temp reading on the heatsinks was 125*F after 20 min. I ran it as loud as I could stand with some AC/DC, Cee Lo and Daft Punk. I heard things in the soundstage I've NEVER heard before! 

I've got a friend coming by tomorrow with his Fluke DMM... hopefully that will settle the issue of these squirrelly readings.

Any opinions on a good, mid priced DMM ($50 or less)?


----------



## the_equalizer

Ah, nice! That's what all the other voltage readings suggested. Testing with the Fluke should indeed settle the matter of how many volts are you seeing at the FET gates.
   
  As to a multimeter, I got this one with my MiniMAX kit and it works great.
   
  Remember not to turn the amp on or off with your headphones plugged in. Enjoy your music!
   
  cheers!


----------



## Breck

I have one of those as well.  Cheap little buggers ($12 maybe), but they get the job done very well.


----------



## bengoshi2000

Testing with the Fluke revealed 45v on the south end of R13, 16.5v on the gate and 12.5 on the source (for both FETs).  Still don't know why my analogue meter would go nuts on the gate readings but anyhoo...
   
  Now I just have to get everything into the case and put some pics up on the build thread!


----------



## baintronic

hey guys i made it a few hundred pages through this thread, but i wanted to make sure of two things:
   
  does anyone have a current BOM for the 12au7 version with the "optional" BOM stuff?
   
  is this still the correct schematic for the 12au7 version?
   
http://img169.imageshack.us/img169/6263/12au7millettstarvingstu.jpg
   
  thanks for your help!!


----------



## tomb

Quote: 





baintronic said:


> hey guys i made it a few hundred pages through this thread, but i wanted to make sure of two things:
> 
> does anyone have a current BOM for the 12au7 version with the "optional" BOM stuff?
> 
> ...


 

SSMH Variants


----------



## scoopbb

are there no more pcbs for this being sold?


----------



## tomb

Quote: 





scoopbb said:


> are there no more pcbs for this being sold?


 

 Sorry, no.  The PCB's were based on the 19J6 tubes, which have disappeared in quantity from the face of the earth.  There are not enough to justify another manufacturing run in a big enough volume that would result in prices worthy of the Starving Student tradition


----------



## scoopbb

makes sense. thanks for the response 
  
  Quote: 





tomb said:


> Sorry, no.  The PCB's were based on the 19J6 tubes, which have disappeared in quantity from the face of the earth.  There are not enough to justify another manufacturing run in a big enough volume that would result in prices worthy of the Starving Student tradition


----------



## bengoshi2000

Finished!


----------



## the_equalizer

Cool case! Reminds me of the old tube radios I used to restore 15 years ago. How are you liking the amplifier ?
   
  cheers!


----------



## bengoshi2000

Thanks! I picked this case for that exact reason... the retro radio look (even though it's just an old antenna rotor contol box).

I'm REALLY liking the amp. It drives my old AKG240 Monitors ridiculously well. I'd forgotten how much I like those cans!!

I have noticed that the amp *can* reveal some of the deficiencies of lower bitrate mp3's, specifically in the highs. I've ripped my cd's at 192kbps and those sound spectacular... I really think the tubes work well to hide artifacts at higher bitrates. I've got a couple albums from iTunes that I'm now disappointed in as it's painfully obvious that they were ripped at a lower AAC rate. 

The amp really does blow my mind. I can pump any type of music through it and it just shines. Daft Punk sounds like I'm driving their mixing console. I can hear each level of layered synth effects with clarity that makes my eyes water. Classical music sounds like I'm sitting in the concert hall live. Strings have a vibrance and clarity that i dont think ive ever heard before. The soundstage is expansive! AC/DC makes me feel as if I've been possessed by Angus Young!

My only complaint is now I have a new mental health diagnosis... MTAAD (Multiple Tube Amp Acquisition Disorder).

...but I'm not complaining...


----------



## baintronic

im sure its in here somewhere but what is the mouser link for the "star" heat sinks everyone is using?
   
  thanks!


----------



## tomb

Quote: 





baintronic said:


> im sure its in here somewhere but what is the mouser link for the "star" heat sinks everyone is using?
> 
> thanks!


 

 If you're talking about the extruded, finned heat sinks - this one is 1-1/2" tall and is about as big as you can get and still be "standard" for TO-220 devices:
  [size=10pt]647-15ABP[/size]
   
  We use it as the power supply heat sink on the MOSFET-MAX and a 1" tall one is used on the MiniMAX.  It's got pins for PCB's, but if you poke around a bit on the Mouser catalog page link, you should be able to find one without so that you can thread it for a point-to-point build.  Or, you can do like Pete did on the original and solder washers on the bottom of the pins to hold them to the top of your case (see first post in this thread).
   
  The SSMH PCB kit used a different heat sink altogether - a stamped, bent aluminum affair that was actually for use with TO-3 transistors.  That one is in the BOM on the SSMH website if you're interested in that one.


----------



## baintronic

Thanks for the rapid response!
   
  I ordered those up this morning.
   
  Another thing i noticed is that the BOM links to mouser send you to 1/8 resistors .... which i purchased.....
   
  is this going to cause a huge problem?
   
  thanks


----------



## tomb

Quote: 





baintronic said:


> Thanks for the rapid response!
> 
> I ordered those up this morning.
> 
> ...


 

 It's military-spec vs. commercial spec.  Mil-spec is de-rated by one-half.  So an RN-series (mil-spec) V-D resistor is listed as 1/8W, but its commercial rating is 1/4W.


----------



## Starfire

Looks nice, keeping that back open for cooling I hope.

Good job!


----------



## SpringHalo

I've returned from a lul due to lack of freetime with a completeted starving student amp! Shortly after the arrival of my shipment of parts, I got to work assembling and a mere two days later I had a functioning amplifier!

 The front and back panels are made from 1/8" aluminum, and the top and bottom portions are beech. I still have to get a lacquer finish on to tidy up the appearance. I had a very generous friend that let me use his milling machine to make the front and back panels, as well as transform the heatsinks from one large sink to two smaller ones with tapped holes in them for easier assembly. The silver switch on the back is a SPDT brightness switch with Low, high, and off positions for the tube LEDs. I haven't gotten a chance to pick up some RCA plugs for the input, so I've got a temporary 1/8" female plug tethered on to the back.

 Enough of the babble, let's get on to the pictures!
   

   
  Here's a front shot, with LEDs on 'high' brightness. I really wish that 12AT7s had more open heaters so I wouldn't have to use external lighting, but I'm satisfied with the way they turned out.
   

   
  Backside shot, showing a glimpse of my altoids-tinned AlienDAC.
   

   
  And one final shot next to my recently acquired DT880s -- they sound great together!
   
  I'd like to give thanks to my friend for the tubes and milling machine usage, my father for providing some of his precious beech, and everyone who helped me out with any questions I had in this thread. Thanks!
   
  -Spring
   
   
   
  On a side note, there's a hiss that is only apparent when there's no music playing and the volume is at ~75% and higher, I think it might be a grounding issue, and there's not much to do to fix that.


----------



## bengoshi2000

Very nice looking build Spring, very nice indeed!  Did you build as a point2point or use a strip board of some sort?
   
  With regards to the hiss are you sure it's the amp and not the source?


----------



## the_equalizer

Slick looking build, indeed. Congratulations!


----------



## SpringHalo

Quote:


bengoshi2000 said:


> Very nice looking build Spring, very nice indeed!  Did you build as a point2point or use a strip board of some sort?
> 
> With regards to the hiss are you sure it's the amp and not the source?


 
   
  It's a strict point-to-point build with a sticky copper foil ground plane. Another notable feature I forgot to mention earlier is a switch included in the potentiometer that isolates the ground of the headphone output so you can turn the amp on and off while having headphones still plugged in. I'm almost positive that it's not the source, as the source is an alienDAC that when plugged into a cMoyBB has no hiss or static. I also noticed that the hiss was a lot worse when no source was connected, and that the hiss decreased significantly (about half or so) when I touched any ground part of the build. This was only apparent when I had some cheapo low impedance cans plugged in. With my 600 ohm beyers, the hiss is only apparent when the volume is up to ~60%+ when there's a source plugged in. Comfortable listening volume is around 20-50 though, so it shouldn't be much of a problem.
   
   
   




the_equalizer said:


> Slick looking build, indeed. Congratulations!


 

  
  Thanks! I spent a lot of time on it and I'm already planning my next DIY project! There is one other tiny problem that I have -- my original plans called for the tube holes to be 2 inches from the front and 1.5 inches from the sides, but I got them flipped, so now my proposed addition of metal rings around the tubes is messed up. Luckily, I've got an extra bit of beech with the same dimensions, so look forward to version 1.5!


----------



## KimLaroux

I came upon this thread while going trough the DIY forum. I'm really impressed by the simplicity of this design. Using the tube's heaters in place of resistors to bias the output mosfet is just brilliant. 
	

	
	
		
		

		
			




   
  Conveniently enough, my room mate gave me 3 GT-12AX7 marketed for fenders. It was used in his guitar amplifier. I used the search tool for 12ax7 and saw that it can be used with the 12a_7 variant. Not much talk on the final result though. From what I can read in the datasheets, the 12ax7 has an "amplification factor" of 100, while the 12AU7 has one of 20. Does it mean the 12AX7 has 5 times the gain of the 12AU7? If that's so, I doubt the 12AX7 I have could be used for this design. Anyone can explain to me what the "amplification factor" is and if the 12AX7 can be used with the SSMH? 
   
  Quote from http://en.wikipedia.org/wiki/12AX7: 





> Typically a 12AX7 triode is configured with a high-value plate resistor, 100k ohms in most guitar amps and 220k ohms or more in high-fidelity equipment. Grid bias is most often provided by a cathode resistor. If the cathode resistor is unbypassed, negative feedback is introduced and each half of a 12AX7 provides a typical voltage gain of about 30; the amplification factor is basically twice the maximum stage gain, as the plate impedance must be matched. Thus half the voltage is across the tube at rest, half across the load resistor. The cathode resistor can be bypassed to reduce or eliminate AC negative feedback and thereby increase gain; maximum gain is about 60 times.


 
   
  There's a few things here that I'd like to get educated on. First, the plate resistor on the SSMH are 33k, that seems like a long shot from what they say on WP. Is this because the SSMH was designed to drive headphones, or is it that much different for the 12AX7? Then there's the bypassing of the cathode resistor. I read that a few times. What's that exactly? Is it adding a capacitor in parallel to the resistor? If yes, then it seems like it's already added to the 12AU7 variant of the design, is that correct? If yes, then I conclude that removing it will cut the gain in half, making it possible to use 12AX7 on the SSMH. Am I wrong?
   
  Though I'd really like some feedback on the difference between say the 12AX7 and the 12AU7. Does one sound better than the other? Is it worth the trouble to modify the design for my used 12AX7 or should I just order new 12AU7?


----------



## SpringHalo

(in regards to C7 and C8)
  
  Quote: 





> Originally Posted by *the_equalizer* /img/forum/go_quote.gif
> 
> 
> Yes, that is basically all they do, you can remove them with no ill effects.
> ...


 
   
  I used 12AT7 tubes in mine, which have a gain of 60. They run my DT880/600s quite well, but the gain was a bit high (comfortable listening volume at ~90 degree pot turn) so I disconnected C7 and C8 (which were in parallel with the cathode resistor), and now the comfortable listening volume is around half volume. I'm using 100K resistors for R16 and R17 and that seems to work (had 50K but changed that too). If you've got efficient headphones (less than 250ohm I'd assume) I would go ahead and buy the 12AU7s. If not, the only noticeable difference between caps and no caps is a slightly louder buzz when the potentiometer is turned all the way down (which you doesn't really matter). It irks me a little bit, so I might put the Caps back in but you might have a different opinion. Heck, if you get both tubes you can try both and see what you like best.


----------



## the_equalizer

@KimLaroux  This being a build thread, discussion of sonic details is not encouraged, though certainly not forbidden; just to keep things sane and oriented to the 'build the amp' side of things.
   
  I did try a couple of nice Mullard 12AX7 tubes with enclosed heaters when I built the 12AU7 prototype. As expected from their higher amplification factor, they produce quite more gain than the 12AU7. I don't think one sounds better than the other, just different. In any case, you can build the amp with your current tubes and, if you're curious you can order 12AU7s (or 12AT7, 12AV7, etc.) afterwards and tube roll 'till you drop .  Beware that if you're planning to use the amp with very sensitive 'phones, IEMs for instance, the 12AX7 will be problematic as the gain they produce will be hard to control. If you're planning to use "stiffer" headphones, you won't have much trouble. I tested mine with AKG K701's and had no problem controlling the volume.
   
  You don't *need* to modify anything from the 12AU7 schematic to use 12AX7s: just plug them in. As SpringHalo mentioned in his post, he used 12AT7s in the same circuit. I'm sure you can certainly optimize the circuit for these other tubes by changing the plate resistor and/or the cathode resistor but I suggest you first build the amp as is and, once you get it working, play around with component values.
   
  The reason the plate resistor value you're seeing is so different is that that's the value chosen by Mr. Millett for the original design using 19J6 tubes. When I built the 12AU7 version I simply reused my 19J6 with it's 33K plate resistors. I found the 12AU7 did not produce any evident (to my ears) distortion so I did not see a need to find a better value for those resistors.
   
  Remember also that the typical values you found in Wikipedia (and that you'll find in most tube manuals) are for high voltage supplies, like those in guitar amps; usually in the 200 volt range. The SSMH uses a 48 volt supply. At such low voltages, the behavior of the tube changes quite a bit so that typical values for biasing resistors are not very reliable.
   
  RE cathode bypass caps: Indeed, the 12AU7 schematic includes cathode bypass capacitors, marked as optional. Additionaly to what SpringHalo posted above... you are indeed correct, removing the cathode bypass capacitors will reduce the gain of the circuit (though not as much as half IIRC), so it can help tame the high gain that the 12AX7s produce in the circuit.
   
  Finally, the amplification factor of a tube  (simbolyzed with the greek letter 'mu') does not translate plainly to the gain the tube will produce in a given circuit but it does give you an aproximate idea of how much gain a tube will produced compared to others. If I recall correctly from my electronics theory books, it is the voltage gain the tube would yield in a *perfect* circuit, that is, one with no resistive loss, phase shifts, impedance changing with frequency and all those other constraints that real life circuits (as opposed to ideal circuits) have to deal with.
   
  Good luck and be sure to post pics of your build here!
   
  cheers!


----------



## KimLaroux

Thanks for the complete and detailed answers, The_Equalizer. I didn't mean to ask about the difference in tubes as a discussion to find the best options, but simply to know if the one I have is a compatible part I can build the amplifier around.
   
  Good to know the 12AU7 variation circuit can work with the 12AX7 without modifications. I'll do as you recommend then : I'll build the circuit as it is and try it out with the 12AX7. I'll see then how things goes. I have the AKG Q701, so it might be that gain won't be a problem. 
	

	
	
		
		

		
		
	


	



   
  In the spirit of the Starving Student, I'll try to build the amplifier using as many recycled parts as I can. So it might take a while to build it. I'm not in a hurry anyways. I'm thinking about building it inside an old car stereo.. might look nice. And I could probably recycle the knobs and pots.


----------



## bengoshi2000

I've found that 12AX7's will amplify any defect in the circuit.  On my build the higher gain tube, the more pot noise I get (cheapo RatShack pot).  12AT7's strike a good balance on my build.  YMMV.
   
  I'm gearing up to build another SSMH with the add-on of a start-up delay.  Thinking about upping the capacity of the output caps as well in hopes of squeezing a wee bit more bass out of the amp.
   
  This amp building stuff is frighteningly addictive...


----------



## the_equalizer

Quote: 





kimlaroux said:


> Thanks for the complete and detailed answers, The_Equalizer. I didn't mean to ask about the difference in tubes as a discussion to find the best options, but simply to know if the one I have is a compatible part I can build the amplifier around.
> 
> Good to know the 12AU7 variation circuit can work with the 12AX7 without modifications. I'll do as you recommend then : I'll build the circuit as it is and try it out with the 12AX7. I'll see then how things goes. I have the AKG Q701, so it might be that gain won't be a problem.
> 
> ...


 

 Good luck with your build! Don't forget that if you get stuck, this thread is here to help. 
   

  
  Quote: 





bengoshi2000 said:


> I've found that 12AX7's will amplify any defect in the circuit.  On my build the higher gain tube, the more pot noise I get (cheapo RatShack pot).  12AT7's strike a good balance on my build.  YMMV.
> 
> I'm gearing up to build another SSMH with the add-on of a start-up delay.  Thinking about upping the capacity of the output caps as well in hopes of squeezing a wee bit more bass out of the amp.
> 
> This amp building stuff is frighteningly addictive...


 

  
  It most definitely is addictive! I'm really interested in that start-up delay. Please post here if you manage to get it working nicely.  Good luck!
   
  cheers!


----------



## Fred_fred2004

I just spotted this delay circuit, while looking at that crystal cmoy
   
http://runawaybrainz.blogspot.co.uk/2011/11/audio-simple-555-headphone-delayed-on.html
   
  it looks very simple and cheap, it could be adapted


----------



## DudeMyCans

Just pulled the trigger on some 19j6's and all the associated bits to build me a MSSH.  Can't wait....


----------



## Oeufdepoire

I've just retireved some IRF640, and I wonder if they would fit the circuit as some IRF510 (that I don't own)  would. I've just peered at both's characteristics, and nothing, in theory, prevents me from using the 640.
  So, I'd like to know : are the IRF510 the only transistor fitting the circuit, or some IRF640 would comply too ?


----------



## Athur126

Hi was thinking of building it but idk wether I can get the 19j6 Tubes.. Is it possible to use and alternative set of tubes? If so what kind and do I have to do any modification?


----------



## bengoshi2000

Quote: 





dudemycans said:


> Just pulled the trigger on some 19j6's and all the associated bits to build me a MSSH.  Can't wait....


 


  Where did you find the 19j6's?


----------



## DudeMyCans

Quote: 





bengoshi2000 said:


> Where did you find the 19j6's?


 


 Got them off eBay. Try searching for them. They still seem to come up occassionally.


----------



## DudeMyCans

Quote: 





athur126 said:


> Hi was thinking of building it but idk wether I can get the 19j6 Tubes.. Is it possible to use and alternative set of tubes? If so what kind and do I have to do any modification?


 


 When I was researching this, I found that there's a few people built them with 12AU7's which have the benefits of being readily available (you can buy then new from musical instrument shops) and cheap. The schematic is slightly different but all the information you'll ever need is in this thread.


----------



## piratetrips

Hey guys,
   
  I'm building the starving student amp and am about to order some tubes. I was wondering, which models are your favorites out of the 12AU7, 12AX7, and 12AT7?
   
  Out of those models, which are your favorite brands?
   
  Thanks!


----------



## DudeMyCans

Well I now have everything I need to build an amp sat on the desk infront of me  
	

	
	
		
		

		
		
	


	




    ....except I can't find any tube sockets...


----------



## DudeMyCans

Quote: 





dudemycans said:


> Well I now have everything I need to build an amp sat on the desk infront of me
> 
> 
> 
> ...


 
   
  Sorted.
   
  I've ordered the sockets, so should be ready to start next weekend.


----------



## bnk0430

Found a couple of 19j6, I'm going to order the parts and attempt to build it next week.


----------



## KimLaroux

I'm trying to find capacitor on Digikey.ca. I'm either not doing it right, or they carry very little audio quality capacitors... I am very limited to the choices.
   
  For the output capacitor, isn't 63 volts a bit overkill? I mean the mosfets barely have 35v of peak to peak voltage. Would 50v caps be acceptable? Would using 35v caps asking for troubles?
   
  They don't stock Nichicon ES... Is Elna RFS a good replacement? They look like nice caps to me. And they stock all of the sizes and voltages. At this rate I'll be using them for everything.


----------



## Avro_Arrow

Electrolytic capacitors need some DC bias to sound good.
  About 3/4 of their rated voltage is a good target.
  That being said, they also have to survive any voltage that
  may be thrown at them...in this case as much as 48 volts
  or whatever your supply is capable of if it malfunctions.
  50 volts would probably be fine, but 63 volts is not unreasonable.
   
  You may be able to get away with 35 volt caps, but don't be surprised
  if they have a shortened lifespan or just go POP one day if they
  see a unusually large spike.
   
  I use ELNA RFS (Silmac II) on the output of my Bravo amp.
  Power supply is 24 volts and I use 25 volts caps with no problem
  so far.
   
  I use Nichicon VR for the power supply cap. Requirements for audio
  signal caps and power supply caps are quite different...it would be
  a mistake to use the same cap everywhere.


----------



## KimLaroux

Thanks for the info.
   
  I know PSU caps and signal caps have different requirement, but I'm still unsure what the difference is. I read that for power, you need low ESR and high ripple current. But what should I look for in a signal cap?
   
  I just found http://www.partsconnexion.com which is a canadian company. They have all the bootique capacitors listed. And at nice prices too.
   
  So I got Nichicon ES for cathode bypass and Elna RFS (Silmic II) for output caps. What would be recommended for power caps? (C1 and C6)
   
  Edit: What about Nichicon FW for the power caps?


----------



## Avro_Arrow

Here is what I would use for C1 and C6
Panasonic FM
   
  Digi-Key does not stock many values/voltages of the Nichicon FW 
  so it's hard to compare. It should work OK, but I think the Panasonic
  is a better choice.
   
  Edit: Parts ConneXion didn't have many different values either...


----------



## c12mech

I've been using my ssmh for a while now and am thinking of doing something different with it.  I've seen a couple of active ground builds which I think would be cool.  What I really want though is a better power supply.  I ran across a thread in another forum about using a LM317 regulator for high voltages. 
   
  Another thing I've seen is this regulator, TL783CKC, which can go up to 125v. 
   
  Does anyone know of a good power supply circuit I could use for this. 
   
  I know it goes against the whole "starving student" part of the name to do any of this but I'm not a starving student anymore.


----------



## bengoshi2000

Well, I picked up a new set of cans (M-Audio Q40) which run at 64ohm.  Now I'm picking up some noise in my MSSH... primarily hiss.  Definitely independent of source.  Hiss does not get louder by turning up the volume knob.  At this point I'm guessing it's the RatShack 100k stereo pot that I used for the volume control.  On my next Mouser order I plan on getting an appropriate 50k pot and use the 50k resistors.
   
  But let's assume for a minute that the pot is not the culprit... where else would I look to eliminate hiss?
   
  I tried a different pair of 12AU7's... same hiss.
   
  Hmmmmm.....


----------



## HoopsMcCann

Hello to all!  First post after lurking the past few months.
   
  I finally finished building and debugging my 12AU7 starving student.  It sounds great and works as expected despite an issue I have with the MOSFET’s voltage divider (R2/R4 and R8/R10) that  has me stumped.   
   
  I measure 48V between the top of R2 and ground which is the correct value.  However the voltages across R2 and R4 are only 27V and 15V respectively.  That totals 42V across both resistors so somewhere in between I’ve lost 6V.  The V measurements on both L and R channels are identical. 
   
  What am I missing, where did the 6V go? 
   
  I’ve removed the resistors from the circuit and measured them to be the correct values before putting them back in.  I’ve tried disconnecting the voltage divider from C2 and R3 to isolate it and get the same results. I even changed my DMMs battery in case it was low.
   
  Nevertheless, with the voltage at the Gate only 15V instead of the designed 17V the amp still works. 
   
  I measure 13.3V across the heaters but that is probably unrelated to the issue.
   
  At this point I am inclined to leave it as is since the amp has been running without problems and I am already enjoying the music.


----------



## KimLaroux

Hi guys. I'm still salvaging parts for my MSSH. I got two options for the case and I thought i'd ask you guys what would be best suited.
   
  The first option is to use one of those project boxes I've had laying around for a few years. They are about 1.5 X 4.5 X 6 inches. It's a "tube" design, with a main body made of 2mm thick aluminum. It opens on both ends with plastic covers.

   
  The other option is to use the body of an old multimeter. This multimeter was given to me this week end, and since the dial was broken, it couldn't be repaired. The case is about 2 X 5.25 X 7 inches. It's made of thick plastic, with metal screw mounts. The case's faceplate opens up.

   
  So here's what I think. The aluminum case is smaller and might look better once finished. It has a nice mate finish except for the end covers which are shiny. All the walls are square to each others. The problem is it opens only on both ends, making it a pain for P2P if I want to mount the MOSFET and tubes on the top of the case. I'd have to cut the bottom off and then figure tidy a way to mount it back on. The heat sink is also to wide and I'd have to cut the two end walls off... but then as those are used for mounting, cutting them off will just make the eat sink look better.
   
  The multimeter case is heavy duty and made of thick 1/4 inch plastic. It will obviously be able to withstand abuse, but abuse and lamps just don't really go together anyway, so this point is not really relevant. Since the case opens up top-off, it makes P2P easier. It's also larger, with more inside room and place on top to fit the whole heat sink. It's shiny black finish with white engraved lettering. I believe this option fits well in the Starving Student philosophy. 
	

	
	
		
		

		
			





 The problem is the external walls are angled, which would make stuff mounted to them look weird. Internally the walls are square though.
   
  Ah decisions... I hate making them. So what do you think? Is there anything I am unaware of that would make one of those case better suited for this amplifier?


----------



## RanDiesel

Hi, I have been working on a SSMH for a couple weeks now and have finished the case work and starting working on the circuit. But I have never built a circuit like this before and in fact this is the my first time even soldering. I was having a hard time laying out the resistors and capacitors for a point to point circuit so I found these little break apart pcb boards at radio shack and laid out the right side of the circuit and soldered it together. I was able to fit all the components of the right half of the circuit on this little board with the terminal strips, so I should just be able to screw in the wires from the sockets and mosfets. But I am wondering if it is bad to have the power and signal paths so close together? I was also wondering if it is ok to run all the grounds together and then just ground the single wire? So before I build the other half of the circuit I was wondering if anyone could comment on this layout, I don't really want to build the whole amp only to have a hum or distortion because I made a rookie mistake in the layout. Here are the pics, any help is appreciated.


----------



## bengoshi2000

On my MSSH I grounded to one main ground wire with no I'll effects. I didn't worry about where I ran the sound/power wires. The only noise I've ended up with came from the cheap azz ratshack stereo pot I used.


----------



## KimLaroux

It is best to connect all your grounds to one single point. This is called a Star ground. The idea is to avoid having a chained ground line where one wire goes around the circuit connecting all the grounds. The problem with this point to point ground is that the current going trough the ground wire an passing by all the junctions will create hum and other artifacts, like not having a 0v ground. Think of the ground wire acting as a voltage divider. Since it's not 0 ohms, there will be a voltage drop inside the wire. So at each points along the ground wire you have different voltage. This voltage will vary depending on the current passing trough it. Dirty.
   
  Search images for "star ground" if you are of the visual type.
   
  But then, all this might be over kill for this design. It's not like you were building a 50w discreet class A monoblock.


----------



## RanDiesel

Thanks for the info, I am going to go ahead and finish the other channel and put it all together. I will post pics when it is done.
   
  I have seen several posts about putting a delay in the circuit so that you don't have to unplug your headphones before turning it off and on, but I haven't read about anyone implementing one. Anyone have any success with this?


----------



## switch32763

3 years ago, I bought all the parts for a 19J6 Starving Student build. I had a working breadboard prototype, but for some reason I just never saw it through to the end.
   
  Fast forward to now, and I've been working on it again. Unfortunately, the other day I was trying to isolate a hum when I accidentally shorted pins 3 and 4 of the tube with my multimeter. The tube immediately got a lot brighter than the other channel's tube, so I shut off the whole thing. After some testing I realized it was actually the MOSFET that was shot, not the tube. So now I'm back in business as long as I get a new MOSFET, which is obviously really cheap. But I'm having some doubts about using my rare 19J6's at this point, since I already thought I killed a tube. I'm thinking about switching over to a 12A_7 build since this would be the perfect time before I actually wire everything and drill the enclosure I plan to put this in.
   
  So basically, I have a few questions:
   

 Is it worth it to stick with the 19J6s for any reason? The only reason I'm considering switching over to 12A_7s is for when I lose a tube in the future and I have to purchase a new pair. I figured with 19J6s I'd be out of luck, and most likely have to also re-drill a new enclosure to fit the 9 pin socket for 12AU7s.
 Assuming everything goes well, for how many hours of use can NOS 19J6s be expected to last?
 I know for sure that I fried a MOSFET, but is there a chance I did damage to anything else? Specifically the tube, because it doesn't look there's anything else that could be shorted to ground by shorting pins 3 and 4.
 From what I could find online, it seems like 9 pin sockets typically fit through a 7/8" hole for the socket. Can anyone else verify the size of the actual socket part of their socket? The diameter of my (7 pin) socket is 0.610". Also, what's the typical center-center distance of the mounting holes for a 9 pin socket? For my 7 pin, it's only about 0.89".
   
  Thanks so much to anyone taking the time to read this!


----------



## KimLaroux

I just placed an order at Parts Connexion. They had a 20% off special on every electrolytic capacitors, so I went all out and got the best they had to offer.
   
  I finally got my hands on some TL783 by Texas Instruments. The datasheet for this part is very verbose, so I feel comfortable about using it to build a linear regulated PSU for the SSMH. I studied many headphone amp's PSUs and noticed that they are more or less all built the same way. I'll just build mine according to that. I was lucky and found a transformer with the perfect voltage for this chip. Salvaged it from a vintage stereo. I'll let you guys know how my experience goes.
   
  For those who prefer to stay within sight of the beaten path while upgrading their SSMH's PSU, take a look at what I found:
   
TL783 based adjustable 700mA PSU. ~25$ free shipping

   
  It's a nice little unit sold on Ebay. Searching for "TL783" brings up a few listings. The item's description even includes a schematic and some PCB traces. You'd need a transformer with ~60v of secondary voltage. Can go higher, but not really lower. I'd like to listen to this thing paired with the SSMH. At 25$ + a transformer, I think it's expensive for something like the SSMH. It might be worth it though if you can salvage a used transformer... or a switching PSU with at least 60V.
   
  Audio-gd sells discreet PSUs. Obviously these are much higher quality than the unit sold on Ebay, but if this translate directly to better SQ... I don't know. Here are two that could power the SSMH:
   
PSU-L 500mA 12$ + shipping

I'm not sure if this one actually goes to 48v, but I guess it does. I sent an email to Audio-gd asking. Wow! Kingwa answered while I was typing this! This unit can supply up to 60v. This one doesn't have a diode bridge to rectify AC, so you'd have to add this before the input. You'd need at least 50v at the input. Note that you could use this unit with a 50v or more switching PSU. At this price, I think it's a good value to use with the SSMH. And since it has only 2v of dropout, it can be used with a much lower input voltage than the TL783.
   
PSU09 35W 32$ + shipping
   

  This is actually a dual rail power supply. It might be overkill for the SSMH, but it's still an option. You'd actually only need half of it for the SSMH.


----------



## KimLaroux

I have a feeling this thread is dead... has the SSMH fell out of favor for cheap and easy DIY project? 
	

	
	
		
		

		
		
	


	



   
  But anyways, I've spent the lass week working on my amplifier, and I thought I'd take a break to share my progress with whoever follows this thread.
   
  I ended up building a custom enclosure from pieces of clear plastics I had in stock. The top and (yet to come) bottom are from a 5/16" thick clear plastic I salvaged from an LCD monitor. I think it's PMMA (aka plexiglass), but I'm not certain. The sides are 1/8" polycarbonate (aka Lexan). The whole thing was cut and filled by hand. The only power tool I used was a hand drill. The top, front and back panels were frosted using sandpaper. This adds a sens of focus to the build. A completely transparent case is just too transparent, it makes the build look like a mess.
   

   
  It took me a few hours just to mount all the hardware on to the case. After breaking two screws inside the plastic, which I had to drill out without damaging the original hole, I had the brilliant idea of cutting a V into one of the screw and use it to make fillets inside each holes. Yes, I had to break two screws before I finally gave up. All the metal parts are grounded to earth. The electronics are isolated from the heat sinks.
   

   
  Here's a picture of the progress I have made so far. The AC side of the power supply is done. There's a mess of wires in there. I didn't want to cut the wires from the transformer too short, just in case I want to re-use this transformer in another project. It's a 100W transformer with two isolated secondary windings, one of which has 5 poles. The two blue wires are a 6v secondary. I'll use this one to power the LEDs in the tube sockets. 
   

   
  I'll be working from there. I should get the 48v rail up and running tonight. Any input would be greatly appreciated. If you spot a problem with my design, something that could potentially go wrong, I'd really like to know. Thanks.


----------



## KimLaroux

I finished the power supply and started distributing the power across the amplifier. I'm now stuck at a question mark regarding R13.
   
  I use 4 decoupling capacitors instead of 2. I solder them directly to the item it decouples. I also try to separate the channels as much as possible to reduce crosstalk. At this point, dividing R13 into two resistor would make more sens in my design, since I'd just solder a different one from the central power rail (like, physical rail...) to each side of the amplifier. The other option seems dirtier, since I'd have to run a wire from one side back to the next....
   

   
  So I'm wondering, would it be better to use two different resistors instead of just one R13? Is it irrelevant? Or is it a bad idea?
   
  I searched for information regarding R13 and it's role in the design, but couldn't find anything, so I'm asking. My guess is it's used as a CRC filter to isolate the MOSFET power from the rest of the amplifier. Is that correct? If so, then wouldn't using two, one for each channel, also isolate the channels from each others?
   
  Obviously I'd have to find two identical resistors. But that's not a problem, unless a difference of less than a single ohm have adverse effects.


----------



## proid

Quote: 





kimlaroux said:


> I finished the power supply and started distributing the power across the amplifier. I'm now stuck at a question mark regarding R13.
> 
> I use 4 decoupling capacitors instead of 2. I solder them directly to the item it decouples. I also try to separate the channels as much as possible to reduce crosstalk. At this point, dividing R13 into two resistor would make more sens in my design, since I'd just solder a different one from the central power rail (like, physical rail...) to each side of the amplifier. The other option seems dirtier, since I'd have to run a wire from one side back to the next....
> 
> ...


 
   
  What a great build 
	

	
	
		
		

		
		
	


	




. I really enjoy my MHSS and i'm planning to do another one ptp with better part and regulated power supply, your posts are really interested. So which psu board did you use?


----------



## Avro_Arrow

Yes, R13 is part of an RC filter.
  What you wish to do would be a good idea.
  You can use the same value or maybe increase it
  slightly as there will be less current going through
  each R13. Maybe increase to 2k5.


----------



## KimLaroux

Quote: 





proid said:


> What a great build
> 
> 
> 
> ...


 
   
  Thanks! I didn't use any of the pre-built boards I posted. I built a custom PSU using a TL783 linear regulator. All in P2P form. Everything right of the tube sockets in the last picture is part of the power supply, excluding the audio input. I'll probably post a schematic when everything is done and working properly.
   
  Quote: 





avro_arrow said:


> Yes, R13 is part of an RC filter.
> What you wish to do would be a good idea.
> You can use the same value or maybe increase it
> slightly as there will be less current going through
> each R13. Maybe increase to 2k5.


 
   
  Again, thanks for the clear and informative answer. It's exciting all the stuff I'm learning from this simple build.
   
  I don't have any 2k5 in stock, the next value I have over 2k is 4k5. I'll use 2k for now and see if it needs adjustment during testing.


----------



## Avro_Arrow

The exact value for R13 is not that important, 2k will probably work just fine.
  After you have it up and running, try a cap about 100u to 500u across R5/R11.


----------



## KimLaroux

It's done! And it worked the first time I turned it on! 
	

	
	
		
		

		
		
	


	



   

   

   
  Yes I know, I need a better camera.
   
  I tested it a few minutes and I must admit of being very impressed. And I don't even have the bypass capacitors in yet. I noticed a few issues I'll have to work on though.
   
  First was the noisy pot, it makes scratching sounds every time I turn it. Being a salvaged pot, I'll just buy a (new) better one some day. Another thing is I get some humming if I touch the pot. Problem solved with a plastic knob, but still something I wasn't expecting. Any idea why this happens? Is it normal?
   
  I also get very bad humming if no RCA is plugged in. I don't understand the cause of this. My guesses are either a floating input picking up EMI or a bad ground. I thought both of these things were fixed by the way the potentiometer is cabled... As you can see from the picture, the ground from the RCA connector is braided with the input wires all the way to the pot. It then follows the wires to the center of the amplifier where it's soldered on the star ground. Could this be the cause? The Bottlehead Crack uses this technique, so I thought it would be worth something.
   
  And then there's the heat coming from the MOSFETs. it's insane! I didn't expect that much heat. I couldn't find any 390k resistors so I used 330k. After a few minutes the MOSFET bias settled at 17v. Is this the cause of all the heat or is the design that inefficient?


----------



## vixr

wow! Kim, awesome work...is the pot grounded too? put a wire from the metal case of the pot to ground, should clear up the hum...Sometimes input jack wires too close to power wires will cause hum too.


----------



## KimLaroux

Quote: 





vixr said:


> wow! Kim, awesome work...*is the pot grounded too? put a wire from the metal case of the pot to ground, should clear up the hum*...Sometimes input jack wires too close to power wires will cause hum too.


 
   
  Thanks. =)
   
  This is exactly what I thought just a few minutes after I posted my last message last night. I remembered that many amplifiers have a ground wire that mounts on the pot's shaft. I'll have to add one next time I fire my soldering iron. For now, I'm just enjoying the music. 
   
  With the Q701, the background is totally silent and I don't hear the scratching noise from the pot. Again this headphone amazes me... it's like it's filtering which sound to reproduce and which not to. I do get some little static noise with the Shure though. I hoped my PSU would be quieter. Well at least I'll have something to debug. That way I get to learn even more.


----------



## vixr

KimLaroux, would you mind sharing the part number of the transformer you used for your PSU? Also, did you draw a scheme for the PSU? Thank you in advance...


----------



## KimLaroux

Quote: 





vixr said:


> KimLaroux, would you mind sharing the part number of the transformer you used for your PSU? Also, did you draw a scheme for the PSU? Thank you in advance...


 
   
  I salvaged the transformer from a vintage radio. I doubt you could find it in retail. But anyhow, here's the markings on top of it, it case it helps:
   

```
4-2519-23385 JAPAN 67-21
```
   
  And you just reminded me I have to install a program to draw the schematic. Haven't done that in a while. I'll post the schematic of the PSU when I get it done.


----------



## vixr

Thank you...   and again, very nice work.


----------



## qusp

scratching noise on the pot could also be DC on the input signal


----------



## KimLaroux

Quote: 





qusp said:


> scratching noise on the pot could also be DC on the input signal


 
   
  I actually thought about that. The NFB-12 has no feedback, so it might have DC on it's signal. I'll have to verify this. Though the scratch was present even when using my laptop's audio out... I'm not thrilled by the idea of adding yet another capacitor in the signal path.
   
  Edit: Just checked the RCA out of the NFB-12. One channel has -19mV of DC, the other has -7mV.... Think it can be enough of a problem?
   
  Here's the schematic I just finished. I used gEDA on Linux.

   
  This is the current version, it's how it's built right now in my amplifier. I plan on testing different things to quiet down the power supply. It's quiet with my Q701, but not with my SRH440. Any ideas?


----------



## KimLaroux

I just spent a few hours tweaking my MSSH.
   
  Connected the 0V rail to earth with a 100Ω resistor. This eliminated the noise picked from the floating inputs.
   
  Doubled the value of R13 hoping to lower the back ground noise, it didn't change anything.
   
  Added an identical resistor in parallel with the one in the CRC filter of the power supply, because the original 7Ω dropped too many volts and overheated. I thought it would make the noise louder, but it didn't.
   
  Connected the volume pot's metal casing to ground. This eliminated the static noise when touching the pot.
   
  Here's the revised schematic of my PSU.

   

   
  So now the noises I get are scratching from the pot, and background static noises. I tried a few things, but nothing worked. Even tried another 4700µf cap on the power rail, but it didn't change anything. I will try another pot, since I've got a few, but as for the background noise... I just don't know what to try at this point. I really whish I had an oscilloscope right now. Maybe I should bring my MSSH to college and test it in the electronic labs. What I want to know is, is the noise coming from the power supply itself, or is it parasite noise created by the unshielded tubes? I do have the 12AX7 in there, which have a much higher gain than the 12AU7. Getting some 12AU7 might lower the noise or mute it for good. Or would it?
   
  Another thing I learned. The unconnected wires from the transformer can really contaminate the signals. I had the blue ones loose, because I planned on using them to power some LEDs in the tubes. During testing, the wires got close to the tubes and I could hear bad interference. Learning from that, I moved all of the unused wires that were bellow the RCA to the other side of the amplifier, bellow the AC plug and switch. While I was doing that, I noticed that I had the switch connected on the neutral line, instead of the live one. So I fixed that too. I guess I'll just power the LEDs from the DC, or just not use any. I like the unspoiled glow from the tube heaters. =)
   
  While the amp was running, I tried the bypass caps across the tube's cathode resistor and across the output caps. I could honestly cannot hear any difference with or without the 0.22µf film cap bypassing the 470µf electrolytic on the output. What difference is it supposed to bring? The difference with the 220µf across the cathode's resistor was quite obvious, on the other hand. It basically just boosts up the gain. I didn't test it more than that though since the 12AX7 has so much gain already, that adding these caps would just make the thing more troublesome. I will revisit this addition some other day, probably when I get some 12AU7.


----------



## vixr

snip...While the amp was running, I tried the bypass caps across the tube's cathode resistor and across the output caps. I could honestly cannot hear any difference with or without the 0.22µf film cap bypassing the 470µf electrolytic on the output....
   I thought I read that the 0.22 film cap helps lower the ESR of the 470uF electrolytic? Thank you for the schematic of the PSU


----------



## qusp

I doubt thats enough to cause the scratching; its certainly not ideal, but unless your amp is DC coupled I dont think it would be a problem


----------



## qusp

Quote: 





vixr said:


> snip...While the amp was running, I tried the bypass caps across the tube's cathode resistor and across the output caps. I could honestly cannot hear any difference with or without the 0.22µf film cap bypassing the 470µf electrolytic on the output....
> I thought I read that the 0.22 film cap helps lower the ESR of the 470uF electrolytic? Thank you for the schematic of the PSU


 
   
  no, the impedance of the 470uf cap remains the same at most frequencies, but the impedance at higher frequencies that can pass through the 0.22uf film cap is much lower and the path more linear. bypass caps in parallel at the output is very unlikely to improve matters. the frequency able to pass through a 0.22uf film cap into what? what impedance are your headphones? very low anyway; is likely to be up with the bats, so no wonder you didnt hear anything =)


----------



## KimLaroux

Quote: 





qusp said:


> I doubt thats enough to cause the scratching; its certainly not ideal, but unless your amp is DC coupled I dont think it would be a problem


 
   
  I'm still unsure which is "ac coupled" and which is "dc coupled" I know the MSSH has no capacitor on it's input, so that makes it what, dc coupled?
  Quote: 





qusp said:


> no, the impedance of the 470uf cap remains the same (well not really, but i'm not going to do the math
> 
> 
> 
> ...


 
   
  I just calculated. The .22µf cuts off at 17khz with the SRH440 and 11khz with the Q701. It's high, but it should be audible on certain tracks. At least it didn't make things worse, so it can't hurt to bypass I suppose.


----------



## enforcer

I feel like this THREAD needs a sticky! So much information!
   
  Im going to build a SSMH-12AU7 and was wondering if there is a roundup anywhere of some performance/feature modifications before I start ordering parts. Things like adding a DAC, support for multiple inputs, reducing noise and hum, increasing longevity, yada yada yada. I dont know if this information is all in one place somewhere but if anyone can post some links that would be appreciated!


----------



## bengoshi2000

When I put 12AX7s in my MSSH I experienced similar issues (scratchy pot, hiss) SQ was off the chart otherwise. 12AU7s eliminated the noise problems. With my 600 ohm AKG 240M cans the MSSH is dead silent. With my MAudio Q40's I can hear some hiss even with the volume at normal listening levels (and a wee bit of pot noise). The casing of my pot is not grounded though and I'm sure that is contributing to the problem.

It's my opinion that the 12AX7s amplify and exaggerate ANY noise in the amp... just too much gain I suppose. 12AU7s are more forgiving.


----------



## KimLaroux

Quote: 





bengoshi2000 said:


> When I put 12AX7s in my MSSH I experienced similar issues (scratchy pot, hiss) *SQ was off the chart otherwise.* 12AU7s eliminated the noise problems. With my 600 ohm AKG 240M cans the MSSH is dead silent. With my MAudio Q40's I can hear some hiss even with the volume at normal listening levels (and a wee bit of pot noise). The casing of my pot is not grounded though and I'm sure that is contributing to the problem.
> It's my opinion that the 12AX7s amplify and exaggerate ANY noise in the amp... just too much gain I suppose. 12AU7s are more forgiving.


 
   
  I know this is not the place to talk about that, but what did you mean by "SQ was of the chart otherwise"?
   
  I'm just gonna get some NOS 12AU7... tube rolling, here I come! 
	

	
	
		
		

		
		
	


	



   
  Just for kicks, I tried only the .22µf MKP as output caps. There is a lot of audio going trough them, I'd say half of what the 470µf electrolytic pass trough. So I installed the MKP permanently. I had them anyways, so why not? I don't know if it's placebo or what, but once they were soldered in, I could ear the difference. I'm guessing the reason why I didn't hear anything when just touched the wires together was that the ESR of the electrolytic was way lower than the MKP + the two solder-less connections.
   
  I also calculated that my SSMH burns around 25W of power. Less efficient amplifier I've ever seen. 
	

	
	
		
		

		
		
	


	




 I'm actually using the MOSFET's heat sink as cup warmer. Keeps my tea warm for hours.


----------



## bengoshi2000

SQ = sound quality. 

Also with the 12AX7s, I could only use about the first 10-15 degrees of the volume pot before it was just too darn loud. I found that 12AT7s were a reasonable compromise with my AKGs, but still too much gain to use with the Q40s.

The heatsinks do get hot! My laser thermometer shows them running at about 130*F!


----------



## KimLaroux

Quote: 





bengoshi2000 said:


> SQ = sound quality.
> Also with the 12AX7s, I could only use about the first 10-15 degrees of the volume pot before it was just too darn loud. I found that 12AT7s were a reasonable compromise with my AKGs, but still too much gain to use with the Q40s.
> The heatsinks do get hot! My laser thermometer shows them running at about 130*F!


 
   
  Yes, I know that SQ means Sound Quality. But I still don't get what you meant by "Sound quality was off the chart otherwise". Were you saying that the 12AX7 had a much higher SQ than the AU? Or that it was just awful?


----------



## bengoshi2000

Umm... "off the charts" In this context would mean "exceptional" and/or "superior"... clean, crisp, transparent highs; full-bodied mids; tight, deep bass.


----------



## vixr

Well, I gave the 12AU7 version a shot and its pretty nice. I etched myself a board and built it using some old GE tubes...


----------



## KimLaroux

Great job!
   
  The schematic in the first picture shows the LED connected across the tube heater. Is that the way it's connected in the Beezar PCB, or is it your addition? I thought of doing this, but wondered if it would affect the circuit, or if the LED would flash like a VU meter. It's probably more efficient than powering the LED from the 48v and dropping all this voltage trough a resistor, anyways.
   
  Do you have an enclosure for it? Don't forget to post pictures when it's fully assembled.


----------



## vixr

Quote: 





kimlaroux said:


> Great job!
> 
> The schematic in the first picture shows the LED connected across the tube heater. Is that the way it's connected in the Beezar PCB, or is it your addition? I thought of doing this, but wondered if it would affect the circuit, or if the LED would flash like a VU meter. It's probably more efficient than powering the LED from the 48v and dropping all this voltage trough a resistor, anyways.
> 
> Do you have an enclosure for it? Don't forget to post pictures when it's fully assembled.


 
  KimLaroux,
      I dont remember where I got this schematic but the LED addition was already there. The LED isnt very bright and it doesn't flash...I was sorta leaning towards a clear enclosure like the one you used (fabulous) but this amp was a prototype. I am hoping to do some tweaks to the board now that I know the traces are all good. I am really infatuated with this amp right now, I built the 19J6 version when it first came out, but this version is more desirable in my humble opinion. I will put up some pics of the optimized board as soon as I etch one...thank you for the kind comments.
   

   
  I changed a few things...gonna try to etch this soon.


----------



## vixr

I found this aluminum case in my stash along with the heat sink from something I gutted. The board I etched fit perfect inside...I still have to cut the holes in the lid for the tubes but I will do that at work tomorrow...I just need to polish up the outside a little.


----------



## KimLaroux

That's a serious case. It would take quite something to break it. Not like mine...* Though if I were you, I'd drill holes into the fins of the heat sink, from top to bottom. Because heat goes up, and placing the fins horizontally like you did is not very efficient.
   
  *Yesterday I tried to clean the flux from the case with alcohol. Some solvent got into a hole with a screw and it cracked the plastic. I learned that PMMA will crack that way if solvent get on a part that is under stress.
   

   
  You can see the cracks in the plastic right of the tubes. So yeah, building an enclosure out of PMMA is not a good idea. I don't know what I'll do at this point. It's cracked so badly that there's no way I can tighten the screw without shattering the plastic into pieces.
   
  These are the new NOS 12AU7 tubes I received yesterday. I'm still testing them. The gain is indeed lower than the AX, but not as dramatically lower as I expected. I added 100K resistors before the 100K pot, something I omitted originally. At least now the pot has an useful range. I tried a few other pots, and also cleaned them, but I still get pot scratching noise. Though the scratching noise is only audible when the pot is turned to max, which is just too loud anyways.
   
  I still have a low hissing noise in the background, but low enough to be acceptable. I have two new parasitic noises though. One seems to be a ground loop hum. I don't see why I get such a hum though since I took extreme cares with the grounds and used only two star grounds : one for the PSU and one for the amplifier. I guess I'll have to experiment some more, but I honestly don't know what to try next. I connected the 0v/ground to earth using a 100 ohms resistor. Any opinions on this? Should I just connect them directly together, or use a 10 ohms resistor?
   
  The second new noise is interesting, to say the least. I can hear my laptop and my router talking to each others! 
	

	
	
		
		

		
		
	


	




 That's something I really had not expected. I'm blaming it on the plastic enclosure, which cannot shield the amplifier from EMI. I'd really like some clarification here. Anyone else experienced such problem? Was your enclosure metal or something else? I'm starting to regret building an enclosure out of plastic. But then some people used wood... so the problem could be somewhere else.


----------



## vixr

KimLaroux,
      sorry to hear about the cracks in the enclosure...It is one of the coolest I've seen here. If i understand the grounding issue (prolly not), there are two common problems...ground loops and ground imbalances. Look for any turns or partial turns in the transformer wiring and get the signal wires as far away as possible from mains wiring...Long wires act like antennas...Do you have hum before the music source is connected? Is the imbalance caused by your computer being plugged into the same mains circuit as the amp? Seems like two star grounds could cause trouble...I found (using a toroidal transformer) that turning the transformer can reduce hum...if you rebuild the enclosure, you could try setting the transformer on the case, listen, rotate 90 degrees, listen...etc. The noise from the laptop is common. I always use my iphone as source with no hiss, so try running the computer on batteries only? or change sources to a portable type for a test?... My old cell phone would put all kinds of buzzing and clicking on my amps if it were too close to the amp.


----------



## vixr

Finished!!! Now for a good polish... And a better knob.


----------



## KimLaroux

I just did a few tests to isolate the cause of the noises.
   
  I noticed that if I lifted the amplifier in the air, the hum stopped. So I placed it on a metal pan, which made things worse. I then grounded the pan, and all the hum just muted.
   

   
  But I could still loudly hear the interference of my wifi network. So I placed the other part of the pan, which is actually the cover for a box, on top of the amplifier and grounded it. This eliminated this interference.
   

   
  Now there's just a hiss if I crank the volume to max. That's probably just random EMI picked by the open RCA connectors. This isn't an issue when listening to music.
   
  Can I now conclude that building the starving student in a plastic enclosure is an epic failure? I mean the results of this experiment are hard to argue against: enclosed in this grounded shield, the amplifier is dead silent at any listenable level. Still I've seen plenty of such amplifiers built in plastic or wood enclosures, and I haven't heard their owner talking about such noises problems. I'll have to go trough this thread again and see if I can dig up anything related.


----------



## vixr

wow...I just finished etching a board and populating mine for a _plastic_ enclosure... I hope I dont have too many noise issues with it. The amp will be standing up when finished...I took the pictures with it laying down. I hope to finish it in the morning.


----------



## jacobthellamer

Looking good vixr!


----------



## KimLaroux

After a few hours of research, I came to the conclusion that not having at least a ground plane is a bad idea. I also found that the unshielded tubes will pickup the interference from wifi networks.
   
  All this is leaving me very disappointed in my design. I expected the electronics to be more troublesome, but it turned out the casework is the thing that makes me scratch my head the most. 
	

	
	
		
		

		
			




   
  Now I'm thinking just scraping the case and rebuilding the amplifier inside an Hammond 1444 enclosure. Not the sexiest thing, but possibly more functional. Edit: Just found out Hammond 1455 have slide out bottom. I'm _so_ ordering one from my local supplier, today.
   
   
  On a different note, I'm currently testing the NOS Sylvania 12AU7 I spent almost 50$ on. I can barely pick any difference between them and the new Sovtek 12AX7. Just for fun, I'm currently using one of each in different channel. Using software balance, I only have to move the balance by 7% to get the volume equal on both channel. That's far less significant that I was led to believe.
   
  And I honestly could never tell which channel has which tube in a blind test. Which forces me to conclude that, for the SSMH, spending 50$ or more on the tubes alone is probably not a good idea.


----------



## vixr

here are the latest pics of my MHSS.


----------



## KimLaroux

Well, that's a novel chassis. If you aimed for Extravangant, I believe you didn't fall far off. It looks like the type of prop you bring to a science fair. Mind if I dub it "The Unorthodox Millet Hybrid"?
   
  Lemme know if you get humming or interference issues. On my part, I have an hammond 1455 on order. I should receive it this week end. I'll reshell the whole thing into the aluminum enclosure and take the opportunity to change the MOSFET heat sink for something more efficient. I'll then see what I can do to shield the tubes themselves. I'm thinking a cage made of perforated metal.
   
  I learned an important lesson with this build: There is more to an enclosure than just looks. Or at least it is so with these types of audio amplifiers.
   
  The question that haunts me right now is, is this only relevant to P2P wiring? Because from what I have gathered, amplifiers built on PCBs don't seem to mind plastic enclosures.


----------



## vixr

Hahahahaaa!!!   It _is_ unorthodox... I'm using a home made PCB with a ground plane and a wall wart for power, so I have my fingers crossed that there will be no noise. I have some metal braid to put over the volume wires, or where ever its needed, just in case. The other purpose of building it tall like this is it will also be a headphone stand...picture my HD-600s hanging on the amp. I dont know about P2P being more prone to noise, but I used metal cases and a ground plane on both of the others I've built...zero noise. Good luck with the new build.


----------



## KimLaroux

I received the hammond enclosure yesterday. I'm really impressed by this thing. It's made of 2mm thick aluminum and even their largest case (6.5" X 8.66") is impossible to bend with your hands. I was concerned I'd have to reinforce it to support the transformer, but this won't be necessary after all.
   
  I also got a bunch of bigger heat sinks. All I got to do now is figure which one to use.
   
 
   
  Either way I'll cut the excess from the heat sink, so it won't look exactly like that. The one on the left picture is too long, and the one on the right picture has tabs that aren't used in my application.
   
  I ordered a couple of step drill bit from Amazon, so I suppose I have until I receive them to make up my mind. Any inputs?


----------



## vixr

I like the one on the right...


----------



## tamasic1

[size=medium]Cool design Vixr! I really like that. [/size]
   
  [size=medium] Kim, interesting what you said about picking up wifi interference. I built my MHSS quite a while back, when you could still get the 19J6 for a couple dollars. All components are exposed on top of a perfboard, except resistors. They’re inside the enclosure with Cat5 P2P tying everything together. The amp always sits in front of my computer monitor and I listen to it often.[/size]
   
  [size=medium]Pic:  http://bellsouthpwp2.net/k/a/karlet/BigCaps2.jpg[/size]
   
  [size=medium] When I turned it on last night I was getting a clipping noise in both channels. The noise level was independent of the volume control. I swapped the Cisco power supply with another but same issue.  I was about to open the case and test for a bad connection when I noticed moving the amp changed the sound. Moved the amp just a few feet away from the desk and the noise disappeared. Never had interference issues previously.[/size]
   
  [size=medium] It turned out to be the new wireless modem/router sent by my ISP when I upgraded my service this week. Until now I had a modem from the ISP but connected my own Linksys wireless router. It sat about a foot or so to the side of the amp. Never had any issue. [/size]


----------



## KimLaroux

Indeed, we bath a electromagnetic radiation nowadays. In here we have two wireless routers and at least a dozen machines connected to them. On my desk I have my laptop and my phone connected with wifi to the router under the desk. At this point, the only solution is to shield the amplifier. I can't live without wifi, but I can live without the amp. 
	

	
	
		
		

		
		
	


	



   
  Though building a tube amplifier that is shielded from wifi is an interesting challenge. Here's a picture of my progress so far.
   



   
  It's the first time I use stepped drill bits. It's quite a pain to use with a hand drill, and I'd venture to say they would be less so from a press drill.
   
  Machining is done, next step is to paint the enclosure in a piano finish black. 
	

	
	
		
		

		
		
	


	




 I'll then assemble the amp, and see if the tubes still pick up wifi. They probably still will. If they do, I'll build a Faraday cage around them.


----------



## audio snob

I need a new headphone amp and it looks like it would be really fun to build one but I know next to nothing on how to read schematics and most of the knowledge required to build an amp. Is this an easy enough project that I could pick it up on the way or is there an easier one I should look in to?


----------



## KimLaroux

Quote: 





audio snob said:


> I need a new headphone amp and it looks like it would be really fun to build one but I know next to nothing on how to read schematics and most of the knowledge required to build an amp. Is this an easy enough project that I could pick it up on the way or is there an easier one I should look in to?


 
   
  I would not recommend starting with this amplifier if you can't even read a schematic. I'd recommend it only if you can find one of the original kits with the PCB, but from what I know, these are not available anymore. To build this amplifier now, one only has the schematic to work with. You have to acquire all the components and then either construct your own circuit board or build the amplifier with point-to-point wiring. Sure you learn a lot of things along the way, but it might be too steep of a learning curve if you start from nil.
   
  If you search on ebay for "_headphone amp* kit_" you will find hundreds of complete kits ranging from 10$ to 200$. At around 20$ you can buy a RA1/Cmoy kit, which can be built quite easily. If you never assembled electronics, I would recommend you buy such a kit and assemble it just to gain the experience. If you find it enjoyable, then you can get a Project Sunrise II for 200$. Don't forget the enclosure when considering these kits. Some of them come with pre-machined cases, which makes things a lot easier and often allow for a cleaner finish. Buying an enclosure separately add to the final cost and complexity, since you have to machine it yourself. 
   
  Either way, you will need the same tools: a soldering iron, solder, solder paste... a multimeter, pliers, wire cutter, flush cutter... If you don't have the tools, you'll have to acquire them before you start any electronic projects. I also recommend you read forum threads and web pages related to the kit before committing to them. These are good resources that can makes things clearer, or simply conclude that a particular kit is to be avoided.
   
  ###
   
  As for my Starving Student, I started the final assembly today. Here's a picture of what my desk looked like this morning:
   

   
  I think the paint job turned out alright. Sad I don't have a camera good enough to give it justice. Can anyone guess the one thing that's missing in this picture?


----------



## audio snob

Ok ill look through ebay for something like that. Thank you for the advice. I believe I have all the tools that are necessary for this and more. Are there any easy kits that sound very good or is it more for the sake of building than sound?


----------



## shamazo

no chance anyone has a 12au7 version in a schematic file/pcb layout program or in a format I can send to a cnc?


----------



## KimLaroux

I just finished version 2 of my MSSH.
   
  I think it looks cleaner than the first version.


 


   
  The enclosure is shorter than the original, but it's both wider and higher internally. I had to rebuild the whole PSU from the ground up to make up for the lost length, while making use of the extra width. I think the end result is pleasant looking. Of course I learned many thing from the original design, which were lessons applied to the revision.



   
  The new enclosure fits perfectly atop the Audio-gd NFB-12.



   
  I built Faraday cages around each tubes in an effort to shield them from EMI. They are made of steel mesh, which were grounded. I expected this to be the end game for interference, but WiFi still gets trough! I just don't understand how this can be, 2.4Ghz has a wavelenght of about 12cm, while the holes in the mesh are 1mm. They do keep the AC hum out of the tubes though. I tried the amplifier before installing the cages and there was bad magnetic coupling between the transformer and the tubes. It's gone with the cages.
   
  I guess I have to redo my homework...


----------



## Goobley

Having been convinced that this is the right amp for me to build I have been interested in more fancy power supplies for it. I'm not sure I'm able to design and build one myself (I do a lot of logic design and use almost entirely lm7805s!). If someone can supply me with an easy schematic I'd love to take a look, and then build it on stripboard. (I'll build the amp on stripboard too, but keep the pieces separate).
   
  Or I have also been looking at items like Mouser 709-PLP20-48 along with mouser 693-6200.4315. This seems like an easier answer to me whilst being cheaper than the cisco supplies are in europe. Would the meanwell ps work in Europe (230v 60Hz AC, I believe it does) and well with the starving student?
   
  [size=xx-small]EDIT: OR even something inline such as Mouser [/size]709-PLN20-48 ? seems really easy and neat compared to the 30€ people seem to want for the ciscos at the moment.
   
Thanks for any responses and info regarding the subject of powering these amps


----------



## KimLaroux

Using a switching LED power supply for an audio amplifier is a very bad idea. If you look at the datasheet for those PSU, you will see that they have 3.8vpp of ripple noise. That's unacceptable in an audio power supply. You need a "Low noise" power supply.
   
  I designed and built a linear regulated PSU for my starving student. If you read the last few pages you should find all the information. It was possible for me because I already had a transformer with an acceptable secondary voltage. Buying one might be cost prohibitive. Actually buying a whole linear regulated 48v PSU might be cheaper. Though I haven't checked Mouser is they stocked a transformer that could be used... I'll do that after dinner.


----------



## KimLaroux

It's not as bad as I expected. Mouser stocks economical Hammond transformers that can be used in the PSU I designed. Examples include 546-186E56 at 21$ and 546-186F56 at 29$. Both of these are dual Primary so can be wired for either 115 or 230V.
   
  On the other hand, these transformers alone are the price of a complete switching mode power supply. Add the cost of all the other parts to build a linear PSU, and it's about twice as expensive to go that route. It might not fit well into the "Starving Student" philosophy. Though faced with the choice, I'd build a linear supply, just for the fun of it. Linear PSU are easy to build, so why not? The schematic I posted isn't much more complicated than your average 7805 based PSU. Plus going linear just seems proper.
   
  In post #8422704 I listed a few linear PSU that can be bought pre-assembled. Though they still need either a transformer or a switching PSU, as you can't just feed them main's voltage.
   
  If you prefer a complete, plug-and-play solution from Mouser, I'd suggest 967-LS2548 at 19$. The datasheet says it only has 0.2Vpp of noise, which is good for a SMPS. You can probably just mount if inside your amplifier, and add a power socket on the back.


----------



## Goobley

How amazingly brilliantly helpful!
  I'm really glad I posted  I'm currently leaning towards the pre-built switchers as I have a slight aversion to dropping more than a few volts off with a linear (needs a lot of heat sinking I'd imagine). Looking at your schematic (I had previously managed to find the pages before and after it!) you just state power diodes so do you mean something like the 1N4002?
   
  Are there any major advantages to the linear other than it looking and feeling right? As I'm not sure I could build something better than 0.2Vpp, then again I have no experience so maybe that's completely wrong.
   
  I also notcied you resistor value of 3017, how accurate does this 48V want to be?


----------



## KimLaroux

Thanks.
   
  Theoretically, a linear PSU will have a lower noise floor than a switcher. This of course is on paper, and the design and construction of the power supply will have a significant effect on the noise floor. It's possible for a switcher to be quieter than a linear. In my amp, there's obvious noise with my sensitive headphones. The problem is I have no way of verifying if the noise comes from the power supply, or from the tubes themselves. Or if it's just the design of the amplifier that is to blame. Maybe it's too simple?
   
  0.2vpp at 48v is just bellow 0.5%. It might look impressive, but the datasheet of the TL783 states an average noise of 0.003%. That's about 0.0014v at 48v. Now whether the construction of my PSU allows for such a low noise, I'm clueless. I really have to bring my amp to my college's electronic laboratories and try it on an oscilloscope... But as I said, I hear noise on it's output. If it's from the tubes, then 0.5% or 0.003% from the PSU would be irrelevant.
   
  As for efficiency, you are right that it does waste a lot of energy. The TL783 is a old regulator which has a high drop-out voltage, all wasted in heat. I'm estimating the regulator wastes 5W in my amplifier. But if you think this is ugly, maybe this amplifier isn't for you... Each MOSFET drops 5W trough bias current. That's 10W to dissipate from the transistors. It gets very hot.
   
  I did not precise the diodes, as it's not really important. I built it using what I had on hands. I used a 1N400-something as protection diode for the regulator, and a 4A bridge-in-a-cube for the main rectifier bridge. 1N400X diodes are rated for 1A, which is border-line in this application. I feel safer with 4A.


----------



## Goobley

Hi,
  I'm almost ordering my stuff - will get and use the switching psu for now and then see how it goes. I'm going to try and build the whole thing into one enclosure (psu + amp) and therefore have a bit of mains wiring. (I'm careful enough). How ever I just wanted to know if I should use a double pole switch to turn off live and neutral (leave ground connected and live fused) or just a single pole switch to turn on and off fused live?
   
  Many thanks, this is not my area of expertise at all.


----------



## KimLaroux

I don't know how mains are wired in Europe, but here in Canada the Neutral line is actually grounded in the electric panel. This means it's useless to open the Neutral line (N), all you really need is to open the Hot line (L for Live or Line). The problem is, you never know if the main's plug is wired reversed in the wall. It's the first thing I check when I move in a new room/apartment, but that's just me being OCD.
   
  Either way, it's usually not necessary to use a double pole switch to open both lines. In theory, it's safer, but in practice, it's just overkill. I have never seen a media equipment that had a double pole to open both lines. Just use a single pole on the Live line, and place a fuse between the power socket and the switch. Leave Neutral and Ground hard wired.


----------



## Goobley

I went with a socket for a kettle lead that has a fuse and a switch built in. Everything is now ordered and should arrive within a week. I just need to sit down and start drawing some stripboard diagrams and cutting some wood for the case.
  I am thinking of splitting the amp's constituent channels into two seperate boards to give my case a more balanced look, I take it this will not cause any major adverse affects?


----------



## KimLaroux

Great! Don't forget to post pictures, they are always welcome.
   
  Someone else built a MSSH on a perfboard recently. It was supposed to be on a stripboard but the builder decided to go with a smaller perfboard in the end. There's pictures and drawings on the thread, it might be useful: http://www.head-fi.org/t/597166/another-millett-starving-student-build
   
  There's no problems with separating the channels. The two channels on my build are pretty much isolated from each others. You can divide C1 and C6 into smaller capacitors, so that you have one C1 and one C6 per board. Same for R13: you'll need one per board. Another option is to build a small board with C1, R13 and C6 on it, and from it send a pair of wires to each channels. I would recommend the first option, since the later misses the point of these capacitors. They are power decoupling capacitors, and so they have to be as close as possible to the item they decouple. In this case it's the MOSFET for C1, and the tubes for C6.


----------



## Goobley

Would it cause any harm if I didn't change c1 and c6? If I just kept them both at stock values while still splitting to two boards? I did sort of go a bit overboard and buy enough caps and resistors for 2 amps...
   
  EDIT: I have been looking at the power supply I bought, manual is here ( http://us.tdk-lambda.com/lp/ftp/manuals/ls_manual.pdf ) Obviously I connect my circuits inputs to v+ and v-, but do I connect the heatsinks to circuit ground, powersupply ground or v-? I'm inclined to go with circuit ground and therefore logically v-. 
   
  As I am working on some stripboard layouts and would like some advice, should I start my own build log, or keep it contained to this thread?


----------



## KimLaroux

Yeah no problems, you can use two C1 of the same size, for twice the capacity. Same for C6.
   
  As for the power supply, the manual says the V- and Earth are isolated, more or less. What I'd do is connect all the heat sinks and the enclosure to the PSU's Earth. I'd connect all the amplifier "circuit grounds", or 0V, to V-. If you get some static noise, you can add a 100 Ohms resistor between V- and GND.
   
  You may want to start a new thread if you plan on extensively log your project, with pictures and all. You might get more discussion this way.


----------



## tamasic1

Kim, that turned out very well. Very sharp build.
   
  Note about original power supply. These are included with Cisco's wireless access points and some VOIP phones. In a building that uses Cisco ethernet switchs the power for these devices comes through the ethernet cable so the little power supplies are general tossed into a box in a data closet, collecting dust.
   
  If you work in a good size office building, school, etc or know someone who does, contact the computer person there. If they are using Cisco devices you might be able to score one for free.


----------



## Legis31

hello everyone!
   
  Long time reader, first time posting. My question pertains to the 12au7/17ew8 builds.
  Since pins 3 and 8 are jumpered, can the cathode cap and 2K resistor be connected to pin 8 instead of 3?
  Same question for the input grids on pins 2 and 7? Thanks in advance!


----------



## KimLaroux

Quote: 





legis31 said:


> hello everyone!
> 
> Long time reader, first time posting. My question pertains to the 12au7/17ew8 builds.
> Since pins 3 and 8 are jumpered, can the cathode cap and 2K resistor be connected to pin 8 instead of 3?
> Same question for the input grids on pins 2 and 7? Thanks in advance!


 
   
  Yeah no problems! On my build, I actually passed the long resistor's leads trough both solder tabs. Since my build is symmetrical, but the tubes are mounted in parallel, the resistor goes trough 8 to 3 on one side, but from 3 to 8 on the other. I studied a few other builds, and noticed that this is how most people wired this. It doesn't seem to be as important as ground wiring.


----------



## Legis31

Thanks, Kim for the quick reply! I may end up wiring my cathode caps and resistors just like you did although mine was a space issue cuz  I used coupling and bypass caps rated for 600v since i had them on hand and wanted to keep costs down. the 8-3 and 3-8 method u describe will work perfectly!


----------



## bigmac

hey so I'm pretty keen to attempt this just for fun, BUT i have a few questions..
  I know the answers are probably in this thread but its 400 pages long and I dont know where to start looking for them searching turns up hundreds of results and none of em really tell me what I want to know..
   
  1. Is this build still worth it? 400 pages of replys must be pretty popular right but its also 4 years old has it been supersceeded?
  2. how does it compare with say the project horizon? or also a manufacturer amp. eg. fiio e17?
  3. the guide / parts list on the pmillet page, is it still valid? or is there an updated version I should look at? other than changing the tubes to 12au7's (seems to be the go)
  4. How hard is it? I did electronics in year 11/12 and 2 1st year university electrical engineering subjects so I do have an idea. Im confident I can wire it up probably point to point with a negative rail on the side or something. but theres alot of talk about things i have no understanding of ( i never learnt about amplification), is understanding optional and just being able to wire it correctly would be enough? 
  5. seriously can someone just give me a link to a powersupply i should buy? I'm really lost when it comes to this and dont know what to look for (been reading kimlaroux's posts but i think im more confused now than before)
  6. I live in australia, where do i buy these parts?..
   
  I really think building this would be fun mostly and maby one day drive something worthwhile one day..
   
  Thanks so much for anyone who answers! 
   
  ps: I understand that the only answer might be that if have this many questions maby you shouldnt be trying this...
  in the meantime im going to continue serching and reading


----------



## tomb

Quote: 





bigmac said:


> hey so I'm pretty keen to attempt this just for fun, BUT i have a few questions..
> I know the answers are probably in this thread but its 400 pages long and I dont know where to start looking for them searching turns up hundreds of results and none of em really tell me what I want to know..
> 
> 1. Is this build still worth it? 400 pages of replys must be pretty popular right but its also 4 years old has it been supersceeded?
> ...


 
  1. The principles will remain valid for as long as there are tubes, I suspect.  The problem is that the original 19J6 tubes have disappeared from the face of the earth in any kind of quantity to support someone making kits or PCB's and selling them to the masses.
  2. I may get accused of bias, for sure, but in my experience, dual triodes are somewhat of a problem when using a single tube (just 1) for both left and right channels.   The principle of the SSMH and many other tube amps - that use dual triode tubes - tie the triodes together so that you have one tube per channel, regardless of whether the tubes inherently possess two separate circuits or not. Without going into a lengthy discussion that comes from testing literally hundreds of dual-triode tubes, IMHO, it's better if the tubes are used one-per-channel, period.
  3. Yes, Pete Millett's schematic is still valid - for 19J6 tubes.  However, during the course of the SSMH, Dsavitsk designed a PCB with some improvements.  Those improvements seemed to work even with the point-to-point versions as well.  As you mention, however, the 12AU7 seems to be the way to go with the scarcity of the 19J6 tubes.  The newer version with all the tweaks is documented on the SSMH website here:
http://www.diyforums.org/SSMH/SSMHvariants.php
  4. That's a highly subjective question.  Bottom line, if you can/have built a CMoy, you are probably capable of building a SSMH.
  5. The 48V Cisco power supply is still valid, but you need to be careful with the DACs you may plug into it.  The Cisco power supply will fry some DACs that have little output protection, such as the Gamma 1, AlienDAC, BantamDAC or similar.  The Cisco Supply is specified in the BOM here:
http://www.diyforums.org/SSMH/SSMHbom.php
  6. Farnell?


----------



## Fred_fred2004

Parts in Australia:-
   
  Farnells - now Element14 free shipping if you spend over $45 - not hard to do 
  RS Australia - Free shipping
  Jaycars
  Altronics
   
  cheers
  FRED


----------



## lehtinel

One more 12AU7 Starving Student running:
   

   

   
   
  Home made PCB (thanks Fred for the layout!), Panasonic FC electrolytic caps, Icel 1uF on C2/C4, IRF510, EHX tubes, pot knob from a Cambridge Audio amp. Took me about a year to complete, including gathering the parts, making the PCB (twice, as I screwed up the first time) and getting it running.

 Compared to my 6DJ8 Super Simple amp - it seems to sound a bit more detailed and precise. Really nice.


----------



## bigmac

wow thanks heaps tomb! thats exactly the information I was after! and I didnt even know about all that info on DIY ive read most of it now and feeling alot more confident.. ..
  alright looks time to go spend some money.. fortunatly for this build not TOO much..


----------



## KimLaroux

Quote: 





bigmac said:


> wow thanks heaps tomb! thats exactly the information I was after! and I didnt even know about all that info on DIY ive read most of it now and feeling alot more confident.. ..
> *alright looks time to go spend some money.. fortunatly for this build not TOO much..*


 
   
  haha! Good luck with that. I stopped counting at around 300$... and half of the hardware I used was salvaged from used amplifiers. There's really no limit to how much money you can throw into a DIY project. You just have to figure for yourself what will be "good enough". Something that's not easy when you have no experience, and gets worse when you get into boutique parts. Heck you could easily spend 300$ per output capacitor.
   
  I think anyone who goes the boutique road misses the whole "starving student" idea. I know I did. 
	

	
	
		
		

		
			




   
  And yes, many thanks to tomb for answering all the questions, no matter how newb they sound.
   
  As with the different tubes usable with the MSSH, I think I'll try the metal cased ones if ever I build another amp. 12SR7 if I remember correctly... They are really cheap, and I think they'll be more practical. Their metal case shields them from all the EMI in today's digital world.


----------



## shamazo

Can anyone post their BOM for a 12au7 build. Or a link to one

Thanks


----------



## lehtinel

Quote: 





shamazo said:


> Can anyone post their BOM for a 12au7 build. Or a link to one
> Thanks


 
   
This should be correct.


----------



## KimLaroux

Quote: 





lehtinel said:


> This should be correct.


 
   
  Don't forget the two 9 pins tube sockets, if you don't have them already. These are missing from this BOM.
   
  Also, why is this BOM listing C3a and C5a as electrolytic? Usually, people use the same caps as C2 and C4, just buy 4 of them.


----------



## shamazo

Thanks it's very helpful, I'm gonna order my parts in a couple of weeks. 
Can I use any 12a 7 tube such as 12ax7?


----------



## the_equalizer

Quote: 





shamazo said:


> Thanks it's very helpful, I'm gonna order my parts in a couple of weeks.
> Can I use any 12a 7 tube such as 12ax7?


 

 You certainly can but, depending on your headphones, 12AX7's can be hard to control as they have a high amplification factor. 12AU7s are more recommendable.


----------



## shamazo

If i changed the value of the pot or the resistors after it would I be able to use a higher gain tube to have simmiler gain as the 12au7? Just because higher gain 12a 7 tubes are significantly cheaper.


----------



## KimLaroux

Quote: 





shamazo said:


> If i changed the value of the pot or the resistors after it would I be able to use a higher gain tube to have simmiler gain as the 12au7? Just because higher gain 12a 7 tubes are significantly cheaper.


 
   
  I originally built mine because I had 12AX7 in stock. After a few days of testing, I ordered a pair of 12AU7A.
   
  You can lower the total "gain" of the amplifier by using higher values resistors before the pot, but this method doesn't really lower the gain, it just attenuates the input signal. The problem is that the tubes themselves have a fixed gain, and they amplify any noise in the circuit. So if you have a constant background noise, and that you attenuate the input level, you're basically lowering the Signal-To-Noise ratio. In real life, this means you'll have even more background noise with a high-gain tube than you'd have with a mid- or low-gain tube.


----------



## shamazo

kimlaroux said:


> Quote:
> 
> 
> 
> ...




Great explanation, I'll spend more to get the 12au7s then. Rep coming when I get to my computer.


----------



## vixr

Quote: 





kimlaroux said:


> I originally built mine because I had 12AX7 in stock. After a few days of testing, I ordered a pair of 12AU7A.
> 
> You can lower the total "gain" of the amplifier by using higher values resistors before the pot, but this method doesn't really lower the gain, it just attenuates the input signal. The problem is that the tubes themselves have a fixed gain, and they amplify any noise in the circuit. So if you have a constant background noise, and that you attenuate the input level, you're basically lowering the Signal-To-Noise ratio. In real life, this means you'll have even more background noise with a high-gain tube than you'd have with a mid- or low-gain tube.


 
  Kim,
      what phones do you use? I have some HD-600 and the gain is a bit low on my last build. I think I could benefit from a 12AX7...


----------



## the_equalizer

Quote: 





vixr said:


> Kim,
> what phones do you use? I have some HD-600 and the gain is a bit low on my last build. I think I could benefit from a 12AX7...


 

 I did very limited experiments back when I built the 12A_7 but I do remember that HD-600s work well with the 12AX7; Grados, however, already have problems taming them.


----------



## KimLaroux

Ah, yeah. I forgot about this point. I mainly use the Q701 with my MSSH. It has plenty of gain to drive them. I can't use my SRH440 with the MSSH because these cans are too sensitive, the noise level is too high to enjoy the rest of the audio. For some reason, the Q701 is silent on the MSSH, and at normal listening level I can't even hear the noise.
   
  Another factor is the output level of your DAC. The NFB-12 has a very high line out volume level. I guess this helps, but it has more to do with the input resistors of the amp than the gain.
   
  Vixr, are there input resistors in the build you use with the HD600? If the gain is too low, you could simply bypass them, or lower their value. They are optional, after all. I did some test with and without them, and the difference is very significant. Without them, the volume knob was useless with both my headphones. I'm curious how this scales with the HD600.


----------



## vixr

yes...A few years ago there was a version of the SOHA that we used SIP sockets under the input resistors...they could be jumpered or used to tweak the resistor value...thanks for reminding me of this option. I will give it a try. I actually have a few boards left from the GB on that amp. I may have to build one again just for grins, I sold my original.


----------



## shamazo

about to grab some tubes off ebay, couple questions first, how important is it to have matched tubes? and what is the differance between the 12au7a and the 12au7?


----------



## the_equalizer

Quote: 





shamazo said:


> about to grab some tubes off ebay, couple questions first, how important is it to have matched tubes? and what is the differance between the 12au7a and the 12au7?


 

 You don't need matched tubes for the SSMH. Matched tubes are only "needed" in push-pull amplifiers tu minimize distortion (and even there I've read a couple of articles that say there are no real benefits to matched pairs). Unless your couple tubes vary WILDLY (as in one is dying and the other is brand new) it's not likely you'll hear any difference between the channels.
   
  You don't need matched triodes either (each 12A_7 tube contains a couple triodes and some companies will sell tubes with matched triodes) as the parallel connection of the two triodes in the SSMH averages the differences between them.
   
  The 'A' suffix indicates controlled heater startup time. Some say it also indicates a higher amplification factor variant of the tube but my old RCA tube manual lists the same amplification factor (17) for the 12AU7 and the 12AU7A
   
  cheers!


----------



## the_equalizer

It's been a while since I last worked on this little amp, but motivated by a friend of mine who saw my build gathering dust in my closet and asked to try it out I finally decided to implement a modification that's been on my mind for over a year.

 Inspired by the design of the Millett Hybrid, Millett [Mini]Max, SOHA II, a re-reading of Morgan Jones' "Valve amplifiers"  and some posts by Dsavitsk where he mentioned that the best mod you could do to the SSMH was substituting the plate loads for constant current sources, I thought I might try my hand at it.

 The benefits of using a CCS as plate load are many and described in detail in many pages (Google is your friend). I'll just summarize a quick list here:
 Improved distortion figures
 Fantastic power supply ripple rejection (PSRR)
 Reduced crosstalk
 More gain from the tube


 I decided to use the ring of two transistors design, just as in the MiniMAX, since the necessary parts (a couple PNP transistor and a couple resistors) are easily available most anywhere in the world. I settled for the BC327 PNP transistor since that's what was easily available to me where I live.

 Based on some current measurements I did in the 12A_7 version, I went for a plate current of ~0.7 mA per tube which based on the details posted here (http://www.diyforums.org/MiniMAX/MiniMAXccs.php), and after rounding to common resistor values, resulted in one 680 ohm resistor and one 10K resistor for the CCS.

 I decided to also substitute the cathode bias resistors (R5, R11) for 2K trimpots, so as to be able to set the plate voltage; again, just like in the MiniMAX. I did not use bypass caps around the trimpots.

 I put the components in a little perfboard and, after removing the plate load resistors (R1, R7), I ran wires from the junction of R13 and C6 (V+), each tube plate and ground to my CCS "module".

  I must say that it didn't work at first, which was terribly frustrating. After much testing, debugging, rewiring, even swapping out one of the output MOSFET's, I found out that one or both transistors in one of the CCSs were blown. After substituting them... Ah!  voilá! Sweet music!
  
  I proceeded to measure the voltage at the junction of R13 and C6 (V+) and found 42.6 volts. Then I hooked up the meter to each tube plate and, using the trimpot, I set each plate voltage to 21.3 volts. I measured the cathode voltage to ground and found out it was 0.9 volts. Finally, and just to make sure everything was well before pluggin in my beloved Grado 'phones, I measured DC at the output: 0.0 volts.  So all looks good.
  
  Finally, I got set for a listening session using my collection of 320Kpbs MP3 files, Foobar200 and Bantam DAC. What I'm going to say is of course highly subjective without any detailed measurements to back it up, but, given that disclaimer I'll go ahead:  I was absolutely enthralled by the sound coming out from the amplifier. It seemed to have more clarity and definition. It also seemed to me that it had a 'blacker background'. Drums were a delight: listening to Tony Williams' drumming in the second great Miles Davis quintet recordings was a real joy: the transient response, the "air" around the drum sound. Piano was a treat too, whether it was jazz, classical, blues. I just kept listening to album after album and falling in love with my little amp as the added clarity, definition, quieter background and transient response all built up to enhance the 'you are there' sensation.

 Again, I'm perfeclty aware that all the above is highly subjective, but for the price of 4 transistors, 4 resistors, a couple trimpots and 2 or 3 hours of your time (just for the build, don't come to me complaining that you spent your whole weekend sitting by the amp with your headphones on!) it seems to me that the bang for the buck factor of this mod is stratosferical.

 A couple final things. In the first place, the amp is harder to control now with the additional gain; not a  problem with 300 ohm but certainly hard with 32 ohm Grados. It's probably time for me to add those input resistors to attenuate the input signals.

 Second, taking into consideration the great PSRR that the CCS adds to the tube stage, I think those who built your own linear power supply should give it a try.


 I'll post some pictures later today and will try to add the CCS to the 12A_7 schematic.

 cheers!


----------



## the_equalizer

Ok, so here are a couple pictures from my amp with the CCS mod. Since I built it just as a test it's not very neat and I haven't removed the unused parts from the regular build (cathode bias resistor and bypass electrolytic capacitor). Now that it's working I'll split the CCS board in two and fix each little module between the tube socket and the terminal strip. The location will also help with lead length and I could also use a couple connectors for the wiring so the modules are easy to replace or service.
   

   

   
  In the following descriptions I'll refer to the 12A_7 / 17EW8 pins and to right channel parts. The left channel CCS should connect to the homologous points in the left channel; and naturally other tubes (like the 19J6) will have different pinouts.
   
  Black wire is ground, brown wire comes from the tube cathodes (pins 3 and 8), red is power (from the junction of R13 and C6) and orange goes to the tube plates (pins 1 and 6).
   
  The blue 2K ohm trimpots replace the cathode bias resistors and are simply wired as rheostats. You could maybe do without them but it's definitely nicer being able to dial in the plate voltage and hence get the best sound from the tubes.
   

   
   
  Here's the schematic for the CCS. It's just the typical ring of two transistors. The circuit simply replaces the plate load resistor R1.

   
   
  I've been listening to the amplifier constantly and I just keep playing album after album. I'm really enjoying the sound from it with all kinds of music I've tried. I'm really glad I decided to build the CCS mod.
   
  I hope someone else also tries it. It's fun and it works great!
   
  cheers!


----------



## Legis31

After building 4 kits and 2 P2Ps I thought there wasn't anything left to try on this amazing little design and then Bang, Equalizer saves the day again with a great idea!!!
   
  Any chance we can get a pic of the flip side of your new board?
   
  I recently finished a 17ew8 version and must say I am very pleased with the way it sounds! With a Mu factor of 50 it's a little more unforgiving
  of generic mp3s but the mids are right in your face. i found myself adjusting the equalization on my source player a wee bit and everything was just fine!


----------



## the_equalizer

Quote: 





legis31 said:


> After building 4 kits and 2 P2Ps I thought there wasn't anything left to try on this amazing little design and then Bang, Equalizer saves the day again with a great idea!!!
> 
> Any chance we can get a pic of the flip side of your new board?
> 
> ...


 
   
  You certainly have experience building this amp! I've only built two of them, and wired the 12AE6 variant on protoboard.
   
  Here's a pic of the flip side of the board, but there's just nothing special to it, nothing particular about the layout.
   

   
  Good to hear you're enjoying the sound from the 17EW8. One thing I like about that variant is that the MOSFET's don't get as hot as they do with the 12A_7 build.
   
  About the CCS setup, just like TomB mentions in the MiniMAX CCS page, there's nothing special at the current I chose, certainly do try with other currents. I was thinking of setting it to 2mA so each triode gets 1mA.
   
  BUT here's something important you need to keep in mind. If you set the CCS to work at more that 1mA each, you'd do better to hook them up directly to the power line (C1) just like the MOSFETs are. The reason is that the extra current pulled by the CCSs will increase the voltage drop across R13, and since R13 forms part of the voltage divider (R2/R4) that biases the MOSFET gates, that extra voltage drop across R13 can mess up that biasing.
   
  If I get the chance this sunday I'll experiment with that setup. In the meantime I'm going back to my listening session (netbook + Linux Mint + Wine + Foobar2000 + Bauer Stereo-to-binaural -> Bantam DAC -> 12AU7 CCS SSMH -> AKG K701)  
   
  cheers!


----------



## Legis31

Thanks big time for the pic and especially the labels! it'll help more than you know! Your 12au7 pics got me through my 9 pin conversion without a hitch.
   
  Granted I'm using 1 1/2" sinks on my 17ew8 and probably should have used 2", but the temp runs at 130-135F whereas I can hold the 19j6 sinks all day at approx 85F.
   
  Keep up the great work....this thread might have died out a long time ago if not for you! Thanks again!


----------



## the_equalizer

legis31 said:


> Granted I'm using 1 1/2" sinks on my 17ew8 and probably should have used 2", but the temp runs at 130-135F whereas I can hold the 19j6 sinks all day at approx 85F.




Hmmm...did you use R2 and R8 = 220K like in the 19j6 version? Otherwise, if you're using 390K, you're feeding the 17 volt heater in the 17EW8 with 12 volts, which would explain why your MOSFETs are running as hot as in the 12A_7 variant.

I'm glad that the pic(s) helped and thank you for you kind words but it's all of us here, all interested in this rocking little amp, who help keep the thread alive. 

If you plan to add the CCSs to your amp, I'm certainly interested in reading your opinion, impressions.

Cheers!


----------



## Legis31

Equalizer,
  as per your question about which resister i used, I ran a 220K and 33k in series which gave me 17.2V on both heaters.Darn close to what the tube manual says at 17.5v. I did use IRF 610s if that could be the cause?
  I do find it odd that my sinks get that hot just dropping 2 additional volts from the 19j6 version, though. My other measurements are as follws.
   
  Power supply     47.5V
  tube plates        32/32
  tube grids           0/0
  tube cathodes  61.2mv/370.7mv
  mosfet gates     21v/21v
  dc offset            1mv/1mv
   
  Pretty well balanced 'cept for the cathodes.
   
  it may be a while before i can try the CCS rig.... wifey says its fall clean up time around the house but I'll definitely keep you posted!


----------



## the_equalizer

Interesting measurments, thanks. I guess 2 volts is enough to heat up the MOSFETs that much.  Good luck with the clean-up!
   
  cheers!


----------



## kchapdaily

very interesting! i might have to give the ccs mod a try... my starving student is one of the original 19j6 versions, should still work right?


----------



## the_equalizer

Quote: 





kchapdaily said:


> very interesting! i might have to give the ccs mod a try... my starving student is one of the original 19j6 versions, should still work right?


 
   
  Certainly. It's been a looong time since I had a 19J6 build but I seem to remember the current going through each 19J6 is ~0.5 mA; so I'd set the CCS to that value. The default resistor values used in the MiniMAX ( 1.13K and 11.3 K )  will do for that.
   
  cheers!


----------



## kchapdaily

sounds good! if i ever get around to it ill be sure to let you know how it sounds


----------



## doors666

i am a tube newbie, want to build this as a first tube project. whats a good source for these tubes. which tubes are good, I see russian, chinese etc on ebay. any recommendations? dont want to spend too much though. any particular brand i should be looking at.


----------



## the_equalizer

Quote: 





doors666 said:


> i am a tube newbie, want to build this as a first tube project. whats a good source for these tubes. which tubes are good, I see russian, chinese etc on ebay. any recommendations? dont want to spend too much though. any particular brand i should be looking at.


 
   


 I'll asume you're talking about 12AU7 tubes. An ultra quick Google search yielded this. It also gave links to www.tubeworld.com, www.thetubestore.com and www.tubedepot.com.  Remember, Google is your friend.
   
  As to brands, pretty much any 12A_7  you get from those places will do. My own 12AU7 build was done with a couple of JJ tubes from tubedepot.com. I also tried a couple of new 'Mullard' (Russian made) and Sovtek 12AX7 tubes.
   
  Your local musical instrument shop might also carry the Sovtkek 12A_7 tubes as they're popular for guitar amplifiers.
   
  Good luck with your build.
   
  cheers!


----------



## doors666

Quote: 





the_equalizer said:


> I'll asume you're talking about 12AU7 tubes. An ultra quick Google search yielded this. It also gave links to www.tubeworld.com, www.thetubestore.com and www.tubedepot.com.  Remember, Google is your friend.
> 
> As to brands, pretty much any 12A_7  you get from those places will do. My own 12AU7 build was done with a couple of JJ tubes from tubedepot.com. I also tried a couple of new 'Mullard' (Russian made) and Sovtek 12AX7 tubes.
> 
> ...


 

 Actually I am not sure which tube i should go for, as long as its low voltage. I will go with whatever recommendations I get here as I am a total tube newbie. Yes, google is a friend as long as you know what you are looking for
	

	
	
		
		

		
			





.


----------



## the_equalizer

Quote: 





doors666 said:


> Actually I am not sure which tube i should go for, as long as its low voltage. I will go with whatever recommendations I get here as I am a total tube newbie. Yes, google is a friend as long as you know what you are looking for
> 
> 
> 
> ...


 
   
  The amp design is low voltage, and there are several tube options to implement it:
   

 19J6 - (if you can find any) this is the tube used in the original design by Mr Millett
 12SR7 - details posted by user Logistic in this same thread
 12A_7 (usually 12AU7) - details start with this post.
 17EW8 - same pinout as the 12AU7 build, only a couple resistor values change.
   
  Any of them will do nicely, I recommend you pick the one that is the easiest/cheapest for you to get.
   
  cheers!


----------



## doors666

Quote: 





the_equalizer said:


> The amp design is low voltage, and there are several tube options to implement it:
> 
> 
> 19J6 - (if you can find any) this is the tube used in the original design by Mr Millett
> ...


 

 Thank you, that surely helps.


----------



## kchapdaily

19j6 tubes are so hard to find these days. i was hoping to get some different models to compare sound signatures on my ssmh, but the ones i found are pricey. probably just better to go with a 12AU7 build


----------



## shamazo

Just starting my build now, wont be able to finish it for a couple weeks though, as a couples of caps the mosfets are coming from overseas.


----------



## kchapdaily

@the_equalizer: quick question. im putting together my bom for a ccs for my 19j6 ssmh. would a value of 1.2Kohm for RA8 and a value of 12Kohm for RA9 be alright? that should give me a current of about .542mA through the 19j6. also, is it ok to use the same transistor you selected? or will any pnp bjt transistor with the right tolerances be ok? 
   
  also, what value trimmer would be good for adjusting the bias of the tubes? 
   
  i am also concerned that this will constrict the use of my volume pot. with a stock build and my hifiman he-4's, i already have limited use of the volume pot. should i put some additional resistance between the pot and the input for each channel? if so, how would i go about calculating these values?


----------



## the_equalizer

Quote: 





kchapdaily said:


> @the_equalizer: quick question. im putting together my bom for a ccs for my 19j6 ssmh. would a value of 1.2Kohm for RA8 and a value of 12Kohm for RA9 be alright? that should give me a current of about .542mA through the 19j6. also, is it ok to use the same transistor you selected? or will any pnp bjt transistor with the right tolerances be ok?
> 
> also, what value trimmer would be good for adjusting the bias of the tubes?
> 
> i am also concerned that this will constrict the use of my volume pot. with a stock build and my hifiman he-4's, i already have limited use of the volume pot. should i put some additional resistance between the pot and the input for each channel? if so, how would i go about calculating these values?


 
   
  Those resistor values seem quite alright, yes. If you want to be absolutely sure and set the CCS to the idle current in your 19J6 build, simply use your meter to measure the voltage across the cathode bias resistors R5 or R11 (no music playing, volume pot fully down) and use Ohm's law to calculate the current passing through the resistor; that's the current passing through the tube. Oh, while you're at it, get some sockets for your CCS resistors, you'll surely want to experiment with other current values and desoldering gets old quickly 
   
  Your question about the transistors got me thinking. I'd suggest you use BC557 or BC560 at the very least; 2N5087 (same as used in the MiniMAX) should be better and BC556 would be best, I think. The reason is that the BC327 has an emitter to collector voltage (Vceo) of 30V which is low compared to the supply voltage of 48V. I think, the transistor should be OK given the voltages it most likely sees but it's better to play it safe. I'll try measuring the voltage across the BC327 at amp startup if I have some time later today and report back.
   
  According to the datasheets I checked, the BC557 and BC560 have a Vceo of 45V, the 2N5087 has a Vceo of 50V (just adequate) and the value for BC556 is 65V (nice safety margin). All of these transistors (including the BC327) have an Hfe (current gain) greater than 100, which according to my limited understanding is a requirement for constant current sources; with the 2N5087 having a value of 250.
   
  Whichever you choose, be sure to check the datasheets to get the correct pinout for your part.
   
  About the trimmer, I think twice the value of the bias resistors is OK, so go with 4K. Those will still give you fine control if you decide to try higher currents (1 or 2 mA maybe).
   
  Finally, I can't help much with the padding resistors as I have never used them myself. Still, remember they operate as a voltage divider so Ohm's law is again your friend, maybe 100K resistors will do. However, I suggest you try the amplifier without them first just to see how it handles; then add them later if you feel you can't tame the little amp. 
   
  Good luck with your mod.
   
  cheers!


----------



## kchapdaily

thanks for the detailed response! i have an exam tomorrow, so i wont be able to open up my amp and start measuring values until tuesday. value of 4kohm sounds good for the bias pot, and i will be sure to check out the BC556. my microelectronics professor was actually just talking about using 2 transistors to create a constant current source last week, so maybe ill stop by his office hours and see what he thinks. ill be sure to post my results! and thanks again equalizer


----------



## marcus76

hi there,
  nice to see theres still something going on in this thread!!
   
  since my first try on the ssmh 12au7 has been hiding in a box for way over a year or even longer, last week i decided to redo it with some perfboard.
  Mostly because my old build (not working) was just a mess of wires.
  I ordered all parts (around 8 Euro's) and tried again, re-using the already wired pot/sockets/power switch and the rca's.
   
  I fired it up at the weekend and luckily : no sparks and stuff, tubes light up fine, mosfets get warm,
  so i decided to hook up a cheap mp3 player and some old sony headphones.
  And then : NOTHING ... not even a hint of sound, noise or whatever, just pure silence 
   
  Btw, I wired my pot like beftus did in post #5326 (should be the same one) and the switched neutrik jack just to try if this might be the fault, on the other side, too. nothing.....
   
  So i measured :
  48V ---r13--- 44,7V
  Zero V at both inputs and zero V at both outputs at r6 & r12
  48,1 V at both Mosfet Pin 1 after r3 + r9
  1,4 V at both sides of the tubes pin 3 + 8
  21,6 V at the tubes pin 1 + 6 both sides , and 18,7 V at mosfet pin 3 both sides
   
  Whats wrong ?
  Any help is much appreciated


----------



## kchapdaily

so i opened up my amp today to measure the cathode bias resistor current, resistors 5 and 11. one channel reads about 2mA, the other reads 1.21mA. now i am a bit worried that the values are not closer to the .5mA. are there any other values i can measure to check if it is functioning correctly? could this be because i used .22uF caps at C2 and C4 and 220uF caps at C1 C3 and C5?


----------



## nikongod

Quote: 





kchapdaily said:


> so i opened up my amp today to measure the cathode bias resistor current, resistors 5 and 11. one channel reads about 2mA, the other reads 1.21mA. now i am a bit worried that the values are not closer to the .5mA. are there any other values i can measure to check if it is functioning correctly? could this be because i used .22uF caps at C2 and C4 and 220uF caps at C1 C3 and C5?


 
   
  How did you measure the current across the cathode resistor? 
  I must ask because the "obvious" way of setting your meter to current and plugging away is totally wrong. 
   
  The correct way is to measure the DCR of the cathode resistor with the amp off. This is a bad place to say "well I know its a 6Kohm resistor, plug that into the calculator" MEASURE! Measuring verifies what you already know - which is a failsafe if your trying to figure stuff out. 
   
  Then fire up the beast, and measure DCV across the resistor. 
   
  If you just want to verify that the 2 channels work the same just look at the voltages. 
  If you are looking for a specific current do the math for: I=V/R. Respect units. 2Kohms=2000ohms NOT 2ohms...
   
  If you did it right, I got nothing.


----------



## kchapdaily

I measured the current with the amp on, volume pot all the way down, no music and no load. Am I right in assuming that the bias resistor cannot have current without the power on? Also where should I measure voltage to see if each channel performs similarly?


----------



## nikongod

Probably where you measured current... 
  Without unsoldering stuff you cant measure current directly in a running amp. you must measure resistance (with the amp off) and voltage across that resistor (with the amp on) and crunch the numbers.


----------



## kchapdaily

facepalm. i get it. ive got 0.551mA on one channel and 0.5mA on the other. my dmm is kind of crappy, might take it to the lab tomorrow and get the values from one of the nice fluke bench dmm's. everything seems to be in order, had a quick scare though.  thanks guys. when i order parts for the ccs, i will be getting trimmers to replace R5 and R11 as equalizer suggested, so that value of .051mA can be turned down a bit.


----------



## the_equalizer

Quote: 





marcus76 said:


> hi there,
> nice to see theres still something going on in this thread!!
> 
> since my first try on the ssmh 12au7 has been hiding in a box for way over a year or even longer, last week i decided to redo it with some perfboard.
> ...


 
   
  I'm away from home right now and can't compare to my amp, but your readings look quite alright to me. I bet your problem is a simple miswiring. I'd check the pot first. Did you try moving it while music was playing? Check the output caps and resistors (C3, R6; C5 R12). Check also the interstage coupling caps (C2, C4).
   
  cheers!


----------



## the_equalizer

Quote: 





kchapdaily said:


> facepalm. i get it. ive got 0.551mA on one channel and 0.5mA on the other. my dmm is kind of crappy, might take it to the lab tomorrow and get the values from one of the nice fluke bench dmm's. everything seems to be in order, had a quick scare though.  thanks guys. when i order parts for the ccs, i will be getting trimmers to replace R5 and R11 as equalizer suggested, so that value of .051mA can be turned down a bit.


 

  So I'm not getting old and decrepit  ! I did seem to remember that the current in the 19J6 build was ~.5 mA
   
  Careful there, the trimpots will NOT change the current. The current is set by the *Constant* Current Source. For changing the current set by it, you choose different values for the two resistors associated to the transistors. For easy change of those resistors I suggested you use some form of socketing for them.
   
  What the trimpots allow you to do is to change the tubes' cathode bias. As you change the value of the trimmer, the constant current going through it will cause the voltage drop across it to change. This effectively changes the grid to cathode voltage which in turn changes the operating point of the tube.
   
  By measuring the voltage at the tube's plate while turning the trimmer you can set a voltage that is half the supply voltage, allowing the tube to swing voltages symmetrically... at least in theory 
   
  cheers!


----------



## kchapdaily

ok thanks for the advice. will a 10% tolerance trimmer be ok? it feels high for such an important position


----------



## the_equalizer

Quote: 





kchapdaily said:


> ok thanks for the advice. will a 10% tolerance trimmer be ok? it feels high for such an important position


 
   
  10 percent is perfectly fine. You will, after all, be setting the plate voltage by measuring it while setting the trimmer so it doesn't matter if you have to set one of them one or two turns further more than the other one 
   
   
  cheers!


----------



## kchapdaily

thanks! ill be ordering parts soon.


----------



## marcus76

I wired c3 + c5 to the output, but not to the rest ....
  Sweet music is playing for 20 minutes now, i got some 50hz buzz, but i think thats because of my laptop wallwart. Already had that with other equipment.
  Thanks to the_equalizer  
  Next : Casework


----------



## the_equalizer

Quote: 





marcus76 said:


> I wired c3 + c5 to the output, but not to the rest ....
> Sweet music is playing for 20 minutes now, i got some 50hz buzz, but i think thats because of my laptop wallwart. Already had that with other equipment.
> Thanks to the_equalizer
> Next : Casework


 

 Excellent! I'm glad that you're enjoying some music out of your build. It's always thrillilng to see those tubes glow and hear music coming out of the amp.
   
  cheers!


----------



## marcus76

Hi there,
  beginner question again:
  I'd like to put some switchable (dim/bright) tube led's and a power led into the circuit, would this be correct for the wiring (switch wiring lower right) ?
  Or is there a better point to hook up the tube led's?

   
  Need to check for the proper resistor values.
  Thanks


----------



## Goobley

This LED wiring looks sensible to me, however, if you're using the original stock PSU I'd be wary about adding three LEDs, as I know that this may be quite tight on current (I remember people commenting that two LEDs plus the amp was tight). So if your power supply will handle it (what is its rated current?) then great, go for it.
   
  I'm planning on doing something similar as I've almost removed all of the noise from my build now (big update to my thread coming up )
   
  Cheers


----------



## KimLaroux

Quote: 





marcus76 said:


> Hi there,
> beginner question again:
> I'd like to put some switchable (dim/bright) tube led's and a power led into the circuit, would this be correct for the wiring (switch wiring lower right) ?
> Or is there a better point to hook up the tube led's?
> ...


 
   
  What type of switch is that? I've never seen one that works that way. Usually, the middle pins are the common, and the connections are made in the same row, like so:
   

  The red lines correspond to the pins that are connected together internally when the switch is either up or down. Note that this is inverted in the case of a sliding switch. But either way, you should simply use your multimeter and check the continuity between each pins, at each switch positions. You can't go wrong this way. Even people with experience do this as a good practice, just to make sure the switch is working properly.
   
  You don't even need a dual pole switch for your application. A single pole will do just fine:

   
  A more efficient way to power LEDs in the SSMH is to use the voltage across the tube heater. Connect one of them to pin 4 of each tube, or both to just one tube if you want to use a switch. If you have a double pole switch, then you can use it to connect one LED to one tube. Since the voltage of the tube heater is only 14v, you won't have has many volts to drop across a resistor to power the LEDs. This means less wasted power.


----------



## Goobley

Well thought with regards to the switch, I just assumed that marcus had checked it and that was how it was (I believe I may have seen one with this sort of pinout before). It is of course very true that one should check things with a multimeter, particularly if it's just something that you've dug out of your parts bin (the other day I spent several hours changing caps and op amps when i actually had a dodgy contact in the power switch which would have shown had I used my multimeter).
   
  Interesting idea about connecting it to the heater, it certainly sounds like less power loss, but wouldn't the extra current draw across the heaters affect the voltages. Also IIRC the heaters are pins 4 and 5 and in my build are just under 13V, pins 3 and 8 are the cathodes and measure under 1.5V.  I just checked the diyforums PCB build of the original 19J6 build and they definitely dropped from 48V for the LEDs using a large 2.4k 2W metal oxide resistor. Whilst I am not sure of any implications of connecting the leds to these tube pins I'd be very wary of doing so for fear of messing up the biaising or something. I may be talking crap in this last paragraph, so if anyone with more knowledge than myself would care to contradict and correct me I feel that it'd be a useful learning experience for all involved. 
   
  Cheers


----------



## KimLaroux

Oh you're right, it's pin 4! I confused myself there. Thanks for clarifying that, I edited my post to correct this. In my build I actually connected them to the source of each mosfet. It was easier that way.
   
  Many people in this thread built the SSMH with LEDs connected across the tube heaters. I did it myself, without issues. I'm not entirely sure it actually is more efficient, as the additional 20mA used by the LED is an additional 20mA that passes trough the MOSFET. This means that instead of dropping the voltage across a huge resistor, the voltage is dropped trough the MOSFET. But I'm not sure if this is the case, or if it's the heaters that will adjust so that less voltage drops across them... it's confusing. Anyone else can explain what happens when we add an LED across the heater? Else I'll have to add this test to my to-do list, for next time I open my amp.
   
  Many DIY amplifiers connect tube LEDs across the tube heaters. Just take for example the Bijou and the SOHA II. But then these don't use the heaters as current sources to bias a mosfet, like the SSMH does. They actually have dedicated power rails just for the heaters.


----------



## marcus76

Hi,
  I have the stock PSU with 48V 380mA, after moving it to another outlet, away from my laptop PSU, its perfectly quiet. But its not in its case yet...
  For the switch, its a "miyama ms 169" and I found it to be odd that it didnt worked the way I thought it should, like KimLaroux said.
  I tested it for continuity and it seems to work like this... had it in my parts box, so i thought why not...
  Interesting idea to use the voltage across the heaters (which is 18,7V in my build)
  I have to look into that, escpecially for the wiring of the switch, i'm a bit confused about it. Best way seems to use this dual pole switch to connect one LED to each heater.
  I'll wait if someone else chimes in about efficiency, since I really like the idea of using the heaters, but as Goobley pointed out, I dont want to mess up something.
  I'm quite happy right now I got it working, so i might do some casework before 
  Btw. here's what it looks like so far :

   
  The wiring is still quite long and messy, but as I dont know how/if it would fit in my case, I thought having some extra lenght might be a good thing.
  Case is some old metal printer switch box, where the base slides in to the top part..
  cheers


----------



## Beftus

Quote: 





marcus76 said:


> Hi there,
> beginner question again:
> I'd like to put some switchable (dim/bright) tube led's and a power led into the circuit..
> 
> Need to check for the proper resistor values.


 
   
  Consider using an on-off-on switch so you switch of the LEDs with the switch in its central position.
   
  Need LED resitor values? Check this: http://led.linear1.org/1led.wiz


----------



## marcus76

Quote: 





beftus said:


> Consider using an on-off-on switch so you switch of the LEDs with the switch in its central position.
> 
> Need LED resitor values? Check this: http://led.linear1.org/1led.wiz


 
   
  I already have a on/off/on switch with center off, where did you put this in your circuit?
  Values for 48V with 5000mcd red 2V LED :
  3,3K 2W for bright @ 15mA / 4,7K 1W for dimmed @ 10mA and 10K 1/2W @ 5mA for the power LED
  Did your build have a power LED?


----------



## KimLaroux

With all the information I gathered recently both here and there, it was time I open my amp again and try a few things. College have kept me busy, and today's the first day I actually had the time for it. So I spent the whole day on it. (okay, I got out of bed at 12... but I did spend the last 12 hours on this)
   
  Here's what I did:
   

 Shortened the cable from the RCA to the pot by a couple of inches. (the grey cable)
 Connected a ground wire directly to the RCA, so that the shield of the cable is no longer carrying a signal.
 Shortened the cables from the pot to the tubes. (the red cables)
 Bypassed the terminal strip for the input of the tubes: The signal cables are connected directly to R14/R15, which in turn are soldered directly to the tubes. Leads of the resistors are as short as possible.
 Grounded the red signal cables at the pot, with a single ground wire to the star ground. Again, the shield of those cables do not carry signal, there's just shields.
 Shortened the output wires, so that they stay away from the pot.
 Moved the MOSFET gate resistors as close as possible to the MOSFET, and cut the leads of the gates shorter.
 Shortened the LED power wire.
   
  I think that's it... Oh no, forgot. Before I opened the amp, I did a listening test with open RCA, just as a reference. Randomly, I touched both tubes, and noticed that the right tube hummed badly when touched, but not the left one. When I opened the amp, I saw that pin 6 of the bad tube was not connected. I guess I forgot to solder it, as I studied it and found no sign of a broken joint. Funny though that all this time only half the tube was used but I could hear no difference to the other channel.
   
  So after all that, I fired it up for a test. There is no audible difference in noise level. It's just as bad, nothing's changed. Actually it's worse, now I get unstable noise too, as if someone was continuously moving the pot around. I think I damaged the pot with all this soldering. Now it pops to 100% at around 2%, in one channel. I tried to clean it, but it didn't help. I'll buy a new pot for my NFB-12, and transfer the Alps in the NFB-12 to my Starving Student, some day. I took care of keeping space in the enclosure for those big Alps. My current pot is really bad, so I'll place any further tweaks on hold until I can change it.
   
  Could ferrous resistors and terminal strips be the source of the noise? I used a magnet and noticed that all my resistors are ferrous, and so are the tabs of the terminal strips. Since my enclosure is non-ferrous, magnetic fields can get trough and induce a current across the resistors and terminal strips. Possible?
   
  Edit: Oh wow, 500th post. Could not ask better for a 500th post I suppose.


----------



## Beftus

Quote: 





marcus76 said:


> I already have a on/off/on switch with center off, where did you put this in your circuit?
> Values for 48V with 5000mcd red 2V LED :
> 3,3K 2W for bright @ 15mA / 4,7K 1W for dimmed @ 10mA and 10K 1/2W @ 5mA for the power LED
> Did your build have a power LED?


 
   
  My build didn't have a power LED, the tube LEDs double as a pair of power LEDs. I connected the on-off-on switch, LED resistors and both tube LEDs to the 48 volts right after the power switch. For the LED resistors I used two resistors in parallel to distribute the power dissipation load, this way I could get away with using normal size resistors.


----------



## doors666

Quote: 





the_equalizer said:


> The amp design is low voltage, and there are several tube options to implement it:
> 
> 
> 19J6 - (if you can find any) this is the tube used in the original design by Mr Millett
> ...


 
   
  Got hold of RCA 12AU7A on ebay. From the pics, looks like cleartop with black plates. logo says hammond and the number mentioned is 274-6026. Any idea how good or bad are these. Should work with this amp right.[size=medium] [/size]


----------



## KimLaroux

Oh yeah, I wanted to mention. For those looking for tubes, especially Canadians, Parts ConneXion is having a sale on tubes and accessories. The sale lasts all of October. It's a good place to get both your tubes and socket, things Digi-key doesn't carry.
   
  Ah and why not, while I'm posting... I noticed earlier today that the schematic lists a 50K pot. I'm using a 100k pot in my build. Since the background noise actually gets louder as I turn the volume up, I'm wondering if the higher impedance pot would be to blame. I mean, a higher value pot would place a higher resistance between the grid an ground, at the same volume level as a lower value pot. Would this have an effect on noise levels? Since the noise is proportional to the pot's position, something tells me it would. Another thing I'll have to try out. Is there a minimum value for this amp, or is it safe to use even a 10k pot?


----------



## Arkyle

This one looks like a winner. When I have some free time I'll design a PCB to have the circuit printed, although I'm thinking about changing some resistors in order to use more commonly used tubes since these are practically non-existent in Mexico.


----------



## the_equalizer

Quote: 





kimlaroux said:


> Oh yeah, I wanted to mention. For those looking for tubes, especially Canadians, Parts ConneXion is having a sale on tubes and accessories. The sale lasts all of October. It's a good place to get both your tubes and socket, things Digi-key doesn't carry.
> 
> Ah and why not, while I'm posting... I noticed earlier today that the schematic lists a 50K pot. I'm using a 100k pot in my build. Since the background noise actually gets louder as I turn the volume up, I'm wondering if the higher impedance pot would be to blame. I mean, a higher value pot would place a higher resistance between the grid an ground, at the same volume level as a lower value pot. Would this have an effect on noise levels? Since the noise is proportional to the pot's position, something tells me it would. Another thing I'll have to try out. Is there a minimum value for this amp, or is it safe to use even a 10k pot?


 
   
  I've been wondering about that myself lately as I've been meaning to try a larger volume pot to get finer control. However, the pot in the SSHM also acts as the grid resistor, grounding the electric charge that would otherwise build up in the grid and drive the tube to cutoff. Since the 19J6 was designed to operate at low plate voltages I think there should be a considerable (compared to other tubes) grid current and that's probably why the value of the grid resistor could be critical.
   
  I think, however that one might use a higher value pot in parallel with a 50K resistor, hence the grids impedance to ground is always at most 50k, while the input signal flows through a higher value pot. The parallel connection will most definitely affect the response curve of the volume pot but I think it would be usable.
   
  Alas, only trying it out will give a definite yes or no answer.
   
   
  Quote: 





arkyle said:


> This one looks like a winner. When I have some free time I'll design a PCB to have the circuit printed, although I'm thinking about changing some resistors in order to use more commonly used tubes since these are practically non-existent in Mexico.


 
   

 Hey! A fellow country man!   This is a great little amp certainly, and a good platform to try different mods. You would have to be more specific as to which tubes it is you're talking about. I have recently posted all the different tube options available. The 12A_7 and the 12SR7 are certainly easy to get in Mexico.
   
  Feel free to send a private message whenever you like. ¡Saludos!
   
  cheers!


----------



## lehtinel

I have a wierd problem with my build (it's posted some 5 pages back), it refuses to power on after a day or so. I've reflowed the power switch and even chaged it to a different model, with no luck. It works okay after reflowing the solder at the switch but then stops.
   
  Could it be the Cisco PSU? Got it off eBay like the most of us.


----------



## the_equalizer

Quote: 





lehtinel said:


> I have a wierd problem with my build (it's posted some 5 pages back), it refuses to power on after a day or so. I've reflowed the power switch and even chaged it to a different model, with no luck. It works okay after reflowing the solder at the switch but then stops.
> 
> Could it be the Cisco PSU? Got it off eBay like the most of us.


 

 What is the current capability of your PSU? Did you include extras like tube LEDs, power LED, etc?. 
   
  If possible, try measuring the voltage output of the PSU while you turn on the amplifier. Do you see it "cycle"?
   
  cheers!


----------



## nikongod

I would be more concerned with the turn-on currents drawn by the tubes than by anything but the most tasteless of LED displays. 
   
  A power supply rated for at least twice the design idle current of the amp is mandatory - not optional.


----------



## the_equalizer

Yes, though usually the 350 mA  PSU works alright. It does cycle quite a bit at startup but it ends up warming up the filaments and powering up the amp. That said I do use a 1A Cisco PSU 
   
  I guess if you're using the 350 mA PSU and add some 10mA for a LED here and there such a subtle change as the surface resistance of a new vs tarnished solder joint could tip the balance so that the PSU just cycles on and off forever.
   
  It could also be just an über-hungry tube filament maybe?


----------



## KimLaroux

Well an easy way to test that is to try powering it with only one tube in. Try once with only the left tube, and once with only the right tube. If it starts in both configuration, it's a clear sign your PSU is overloaded. If it doesn't start with one or the other, or both, then your problem is probably elsewhere.
   
  I just find it weird that it works after reflowing the switch, even with a different switch. I have a feeling it's not a direct consequence. It's probably some other variable that happens to change when you reflow the switch, like time. What if you switch it on, wait, switch off, wait, and switch back on? Try it without waiting? It could be that your PSU isn't powerful enough to charge the capacitors and power the cold heaters at the same time. Isn't there a power LED on the PSU? The LED on a SMPS will usually flash when the unit cycles trough overload protection.


----------



## kLevkoff

Quote: 





kimlaroux said:


> After a few hours of research, I came to the conclusion that not having at least a ground plane is a bad idea. I also found that the unshielded tubes will pickup the interference from wifi networks.
> 
> All this is leaving me very disappointed in my design. I expected the electronics to be more troublesome, but it turned out the casework is the thing that makes me scratch my head the most.
> 
> ...


 
   
  Just had to chime in here about tubes and "tube rolling". The differences between tube TYPES (12AX7 vs 12AU7) are obviously real - although the effect will depend on the circuit.
  (For example, when you use a cathode resistor with a capacitor across it, there is no cathode feedback; when you remove the capacitor, the resistor value acts as cathode feedback and reduces the gain. The gain reduction will be greater with a higher gain tube, so the net result is to reduce the difference between them in THAT circuit.)
   
  HOWEVER, the differences between different BRANDS (or even plate styles) of the SAME tube number are largely nonexistent. In "the old days", all tubes of a given type were considered interchangeable; nobody expected a certain brand or plate color to sound different, and they all cost the same few dollars. Some vendors claimed that their "special formulation" of cathode coating or plate paint was a bit quieter, but nobody much believed them. There were also sometimes slight differences in things like inter-electrode capacitance between different brands, but it was also accepted that a well designed circuit would NOT be sensitive to those differences. A circuit that sounded best with a certain brand of tube would have been thought of like a car that only worked well with one brand of gas. It is only in recent times that this silliness about certain brands of tubes sounding better has appeared.... The reality is that, other than certain few Russian and Chinese brands actually sometimes having poor production quality and life spans, you are wasting your money paying extra for some specific brand of tube and expecting some significant difference in "sound".)


----------



## marcus76

For the LED's and the stock PSU , I added 3 (switchable) at 7mA and 17mA, and the amp turns on just like before, takes like 2-3 seconds for the tubes to light up.
  I did not do any measurements yet. Seems to work alright. I might look into the voltages before putting it into the case...
   
  Nice info on the tube rolling thing, as i thought about buying some other "cheap" 12au7 to compare to mine but I'll use them for now.. cost:  8$ each. 
  NOS Sylvania 6189w -> bought them because of this article I found before I placed an order  http://www.jacmusic.com/nos/ECC82.htm
  For anyone looking for tubes in europe, take a look at http://www.nostubestore.com , some guy from turkey, the prices/shipping seem reasonable imo, quick delivery.
  @ KimLaroux, what kind of sylvania did you buy?


----------



## KimLaroux

I got parts connexions # NOS-75306 which is described as "Sylvania JAN CHS 12AU7 / ECC82, Gold Logo, Short Black Ladder Plate, Medium-Mu Dual Triode, 9 pin, Original Box, USA". Though they really have green logo and markings. It also says 12AU7A on them. The ribbed black plates do look nice, and match my enclosure well. =P
   
  Today I randomly noticed that I can hear humming from my transformer. If I place my hear directly on it, I can hear the same type of humming I often hear from step-down transformers on power lines. Is this normal, or a sign that it's overloaded? There's also another noise close to the mounts of the transformer, which is not quite the same as the white noise at the output. Wondering now what could be the cause of that. It may be current leaking trough the chassis.


----------



## lehtinel

Quote: 





the_equalizer said:


> What is the current capability of your PSU? Did you include extras like tube LEDs, power LED, etc?.
> 
> If possible, try measuring the voltage output of the PSU while you turn on the amplifier. Do you see it "cycle"?
> 
> cheers!


 
   
  No leds in my build. I'll measure the output and see if it cycles, I'v got the 380mA version of the PSU.


----------



## vixr

I built the 19J6 version with no LEDs and the 12AU7 version with LEDs...the 19J6 cycled for a few seconds, the 12AU7 did not. Both use the 380mA cisco. When I say "cycled" I mean the tube heaters in the 19J6 would come on then go out a few times, then stay on...this event lasted about 3 seconds. I did not use a DMM to actually test it. The 12AU7 version heaters come on and stay on.


----------



## the_equalizer

A year or two ago there was a builder in this thread who had a similar problem. His PSU's performance slooooowly degraded until it wouldn't power the amp at all. He got another one from ebay and that solved the problem.
   
  cheers!


----------



## KimLaroux

I just learned the hard way how to blow a tube in this amplifier: Turn it ON without R4 or R10.
   
  I wanted to try higher bias at the MOSFET, as I thought mine was low. A few pages back it was recommended to add a 33K resistor in series with the 220K one to raise the bias, so I tried that today. I started by unsoldering one side of the 220K resistor on both channels. I then added a 33K on one side, and thought I should compare voltages with the other side. So I turned the amp on, forgetting the 220K resistor was still unconnected in one channel. The MOSFET went fully ON and blew up the tube heater on this side, within a couple of seconds. By the time I realized what was going on, it was too late. YAY!
   





   
  So yeah, this amplifier can blow up tubes, be careful.
   
  On a more positive note, I tried the amp with a 20K Alps RK27 and the noise level was significantly lower. It was so low that the noise at the RCA out of the NFB-12 drowned the noise from the SSMH. I thought the NFB-12 had a 10K pot, but it turned out to be a 20K. I really wanted to try the amp with a 10K, as those are easier to get. I'm debating whether to take a chance and just order a 10K one. There didn't seem to be a problem with 20K, but I'm really concerned 10K would be too low.
   
  (yes I did take the pot out of my NFB-12 to try it in the SSMH.)
   
  This seems to confirm my theory. A higher value pot will have the grid "floating" higher relative to ground, and will therefore be more sensitive to noise. I'd really like if anyone with noise problem give it a try and report back. Note that I originally had a 100K pot, so the difference between 100 and 20 may be more significant than 50 to 20. Anyone can try a 10K pot?


----------



## vixr

Quote: 





kimlaroux said:


> I just learned the hard way how to blow a tube in this amplifier: Turn it ON without R4 or R10....


 
   
  Kim,
      thanks for posting this.


----------



## shamazo

I just started building the 12au7 version of this amp after waiting a  couple weeks to get my hands on some IRF 510s. My question is, what does c6 do? and does it matter if c1 and c6 are 1000 uf?


----------



## the_equalizer

C1 and C6 are power supply decoupling caps. Along with R13 they form a filter whose intent is to minimize the interaction between the input and output stages through their common line to the power supply. Wikipedia has a nice explanation here: http://en.wikipedia.org/wiki/Decoupling_capacitor

As to the value, theoretically speaking a greater value provides more power storage and hence increases the effectiveness of the decoupling. Real world that power must come from your power supply; it'll need to provide enough power at startup to charge those caps (along with lighting up the tube heaters, charging the output caps, providing current to the tube plates and MOSFET drains, etc.)

Will your specific supply be able to cope with the demands? I can't answer that. But, as I mentioned a few posts back, I bought a Cisco 1A supply to do away with all those concerns.

cheers!


----------



## Makiah S

Quote: 





n_maher said:


> If you have anything in the way of parts laying around (like I do) you can build one of these for under $50 including everything without breaking a sweat.


 
  ooh Only read the first page of this but it seems interesting <3 I love getting DIY'r Amps :3


----------



## shamazo

Quote: 





the_equalizer said:


> C1 and C6 are power supply decoupling caps. Along with R13 they form a filter whose intent is to minimize the interaction between the input and output stages through their common line to the power supply. Wikipedia has a nice explanation here: http://en.wikipedia.org/wiki/Decoupling_capacitor
> As to the value, theoretically speaking a greater value provides more power storage and hence increases the effectiveness of the decoupling. Real world that power must come from your power supply; it'll need to provide enough power at startup to charge those caps (along with lighting up the tube heaters, charging the output caps, providing current to the tube plates and MOSFET drains, etc.)
> Will your specific supply be able to cope with the demands? I can't answer that. But, as I mentioned a few posts back, I bought a Cisco 1A supply to do away with all those concerns.
> cheers!


 
  +rep helps alot. I am using a .7A PSU I think this is more than the original one. hopefully I don't have any issues.


----------



## the_equalizer

Quote: 





shamazo said:


> +rep helps alot. I am using a .7A PSU I think this is more than the original one. hopefully I don't have any issues.


 

 Glad I can help. As others have posted they do quite fine with the 350ma or 380ma Cisco PSU so with the 700ma you won't be having any current supply problems. Good luck with your build.
   
  cheers!


----------



## Makiah S

Quote: 





the_equalizer said:


> Glad I can help. As others have posted they do quite fine with the 350ma or 380ma Cisco PSU so with the 700ma you won't be having any current supply problems. Good luck with your build.
> 
> cheers!


 
  So you know any one selling one of these


----------



## the_equalizer

Quote: 





mshenay said:


> So you know any one selling one of these


 
   
  You'll have to go to the "For Sale/Trade" forums for that. From time to time one pops up on e-bay too. Good luck.


----------



## Makiah S

Quote: 





the_equalizer said:


> You'll have to go to the "For Sale/Trade" forums for that. From time to time one pops up on e-bay too. Good luck.


 
  There's some fellow selling a kit on ebay, here's another question
   
  Do these have enough power to drive a 250 ohm can? I'm sure the answer depends on who built it and what the used, but following the CHEAPEST build plana [in case I end up with that <.<] how would they do!


----------



## kchapdaily

it depends on the can. but millet states on the starving page that his hd600's are well powered with a standard starving student and thats a 300ohm can. ive never used anything high impedance with mine because im an ortho type of guy, but my ssmh poweres my hifiman he-4's well and they are usually difficult to power. generally any amp with tubes will have the required voltage to power high impedance voltage hungry cans.


----------



## the_equalizer

Quote: 





mshenay said:


> There's some fellow selling a kit on ebay, here's another question
> 
> Do these have enough power to drive a 250 ohm can? I'm sure the answer depends on who built it and what the used, but following the CHEAPEST build plana [in case I end up with that <.<] how would they do!


 
   
  It doesn't really depend much on who built it, really, as long as it's built and it operates correctly.
   
  Be assured, this amp has power to spare. 250 ohms cans will pose no problem to it. It will also perfectly drive low impedance headphones such as Grado or Denon. I have even used it to drive a couple of small 8 ohm speakers.
   
  cheers!


----------



## the_equalizer

Quote: 





kchapdaily said:


> it depends on the can. but millet states on the starving page that his hd600's are well powered with a standard starving student and thats a 300ohm can. ive never used anything high impedance with mine because im an ortho type of guy, but my ssmh poweres my hifiman he-4's well and they are usually difficult to power. generally any amp with tubes will have the required voltage to power high impedance voltage hungry cans.


 
   
   
  Indeed, the HD-600 work very nicely with the "Starving Student". Mr. Millett also mentions he used it to drive his AKG K1000 and was surprised with how good they sounded.
   
  Ah! I'm so curious about the HE-X + SSMH pairing. I'm sure this little amp can drive the planar magnetic headphones with enough authority and dynamics.


----------



## kchapdaily

it can indeed! my amp is pretty stock, and ive never experienced any clipping or distortion, even at high volumes. the ssmh can get the he-4 to volumes past listenable limits. i think the only hifiman that the ssmh might have difficulty with would be the he-6.


----------



## KimLaroux

AAahh! There was an HE-6 at the last Montreal Meet, but it was way too busy for me to try it on my stuff. Just for kicks, I'll try all the high-end stuff with my SSMH at the next meet. I'm sure I could try the HD800, some Audeze and the HE-6. =D
    
  Quote from Millett's original webpage:


> The 5% THD point is about 7V RMS into 100 ohms, or 3V into 32 ohms.  If you've ever listened to 3V RMS into a pair of Grados... you've probably suffered long term hearing damage.  For comparison, the Millett hybrid design clips at 2-3V RMS into pretty much any load.


 
   
  I think 7V rms should be sufficient to drive just about any headphones, though. And with a MOSFET at the output, current should not be a problem either.
   
  I've actually been curious about building a beefed-up version of the SSMH with 12AX7 tubes and use it to power close-field monitors. Great to see someone else thought about it. I'm not that crazy, after all.


----------



## nikongod

Quote: 





kimlaroux said:


> I've actually been curious about building a beefed-up version of the SSMH with 12AX7 tubes and use it to power close-field monitors. Great to see someone else thought about it. I'm not that crazy, after all.


 
   
   
  Gain is not the problem.
   
  Stick with the 12au7 for speakers. How many vrms do you put into your nearfeield monitors? Like 2vrms? So you still have a decent bit of voltage headroom. Not an awful lot, but at the same time not an awful little  
   
  You can probably find a few more vrms if you go around and realllllly optimize the circuit you have now. Using *just* the heater as the source resistor is a great way to save a few bucks, but not necessarily the best way to get the most voltage swing out the amp. Try to get the source of the mosfet around the middle of the voltage supply +/-a few Vdc. Add a resistor or CCS in series with the heater to make it happen. I would lean towards a resistor if you want absolute maximum voltage swing (despite my love of CCS's) since resistors behave better when you drive them into the rails. CCS's often work better under "ideal" conditions, but if you are really pushing an amp to its absolute limits things quickly become non-ideal. Its something else to experiment with anyways 
   
  You may also want to replace the plate resistors for the tubes with a CCS - this should buy you some basically free gain and improve the linearity of the tube a bit too. 
   
  If your interested in more current (have you hit that limit with your monitors? Yea, um no, but since I'm already here) try folding the heater so its 6.3V@300mA rather than 12V@150mA and adding a resistor or CCS to make up for the voltage difference. Ooh, you will need a PSU good for at least 1A and heatsinks like whoa. 
   
  Is now the right time to say that the 12ax7 is a sucky tube? Perhaps not the best time, but its never really a bad time to call a sucky tube a sucky tube. In the case of the MHSS or a variant thereof the very high plate impedance will not react well to the input capacitance of the mosfet and unless you have a very low output source you will almost certainly not need the gain after you change the plate resistors to CCS. Just stick with the 12au7, or one of its low gain, low Rp cousins.


----------



## the_equalizer

Quote: 





kimlaroux said:


> AAahh! There was an HE-6 at the last Montreal Meet, but it was way too busy for me to try it on my stuff. Just for kicks, I'll try all the high-end stuff with my SSMH at the next meet. I'm sure I could try the HD800, some Audeze and the HE-6. =D
> 
> I think 7V rms should be sufficient to drive just about any headphones, though. And with a MOSFET at the output, current should not be a problem either.
> 
> I've actually been curious about building a beefed-up version of the SSMH with 12AX7 tubes and use it to power close-field monitors. Great to see someone else thought about it. I'm not that crazy, after all.


 
  EDIT: Right after posting I saw Nikongod beat me to it 
   

 I used it to drive a couple of small speakers, like the ones in old transistor radios. Of course the sound wasn't great but it was certainly listenable. While using a 12AX7 will get you more voltage gain from that first stage (even more if you use CCS loads), given the very low plate voltage I don't think it'll get you more _headroom_. From what I have read you need to throw around 200 volts at the plate of a 12AX7 to bias it out of grid current.
   
  Now, of course, I would definitely try it  I think your build uses the 12AU7, so you just need to plug in a couple 12AX7 and hook up a couple monitors to the output; no need to change any biasing resistors.
   
  Another idea is to build a tube gain stage with "proper" plate voltages and the same MOSFET output stage. It would require two power supplies. You could still use the tube heaters as MOSFET loads. Yet from there it should be easy to add another 6.3 volt supply for the heaters and use a current source to load the MOSFETs. Use a couple other more CCS to load the tubes. Or maybe, while you're at it and since we already have plate and heater supplies, throw away the 12A_7 and use a couple 6DJ8, maybe in cascode configuration. Finally make the output stage power supply bipolar and do away with the output cap by using complementary MOSFETs in a class-A push-pull configuration. Something similar to this.  Or maybe take one of Nelson Pass "Zen" output stages, and use a cascoded 6DJ8 as input stage... Now I only need a couple of months and maybe $1,500.00 USD in parts to build my dream  .


----------



## nikongod

I use the low-power headphone amp (there was an optional hi-power version) in a Zhalou to drive my single driver speakers. They fill a medium sized room very nicely.  
   
  Efficient speakers are very fun with powerful headphone amps.


----------



## Makiah S

mmm the more I hear the more I want it  
   
  What's the input options? RCA in would be nice!


----------



## Lou Erickson

You build it yourself.  Lots of people have built it with RCA inputs.


----------



## the_equalizer

Quote: 





mshenay said:


> mmm the more I hear the more I want it
> 
> What's the input options? RCA in would be nice!


 
   
  Quote: 





lou erickson said:


> You build it yourself.  Lots of people have built it with RCA inputs.


 

 Indeed, a builder in this thread even built it with switchable RCA  *and*  USB inputs (a Bantam DAC, if I remember correctly, built into the same enclosure)


----------



## Makiah S

Neat-o, I might want the RCA for simplicity. Seeing as teh Dac I'm gunning for has RCA out and I'm getting some Audio Quest RCA interconnector cables


----------



## shamazo

I just finished my amp and now its onto the debugging stage. 
   
  1 I turned it on, no smoke good sign 
  2 felt heat sinks, only the left channel warmed up, I quickly spotted that I hadn't connected the other mosfet to the power
  3 voltages, I have 16 volts at the source of the mosfets? I should only have 12 any idea what i could have done/mis-wired to make it this high?
   
  EDIT  one is at 14.8 the other is at 15.8 , is this okay or do i need to change something?
  EDIT 2 i went ahead and plugged in some cheapo ear buds, i get sound but alot of hum and a clicking sound about every 2 seconds.


----------



## KimLaroux

The clicking noise is probably wireless interference. Try turning stuff off until you find the source: cellphone, laptop, router... The humming may be internal or external. Try moving the amp around while it's on. Mine stops humming if I move it away from my DAC.
   
  16 volts is normal. Keep in mind that the tube heaters are simply resistive elements. They are rated for 150ma at 12v, but since the mosfet pushes more than 150ma into them, you will see a higher voltage across. This current is set by the bias of the mosfets, R2/R3 and R8/R9. Higher voltage at the mosfet gate means more current trough the tube heater, means higher voltage drop across the heater. Check the voltages between the gate and the source (Vgs) of each mosfet. It should be somewhere around 4v. Since you have more voltage across one tube, this one should have higher Vgs. It's probably unbalanced because you did not match the resistors, and their values are far apart. You could always rebuild the bias networks, so the voltages are closer together. Keep in mind that the mosfet will turn off at 2V, and that you need some headroom. 4v is a safe margin. Too much and you'll blow the tubes, or you'll overload the PSU. Wait a couple of minutes for things to warm up before taking measurements.


----------



## shamazo

Quote: 





kimlaroux said:


> The clicking noise is probably wireless interference. Try turning stuff off until you find the source: cellphone, laptop, router... The humming may be internal or external. Try moving the amp around while it's on. Mine stops humming if I move it away from my DAC.
> 
> 16 volts is normal. Keep in mind that the tube heaters are simply resistive elements. They are rated for 150ma at 12v, but since the mosfet pushes more than 150ma into them, you will see a higher voltage across. This current is set by the bias of the mosfets, R2/R3 and R8/R9. Higher voltage at the mosfet gate means more current trough the tube heater, means higher voltage drop across the heater. Check the voltages between the gate and the source (Vgs) of each mosfet. It should be somewhere around 4v. Since you have more voltage across one tube, this one should have higher Vgs. It's probably unbalanced because you did not match the resistors, and their values are far apart. You could always rebuild the bias networks, so the voltages are closer together. Keep in mind that the mosfet will turn off at 2V, and that you need some headroom. 4v is a safe margin. Too much and you'll blow the tubes, or you'll overload the PSU. Wait a couple of minutes for things to warm up before taking measurements.


 
  thanks, ill do some measurements soon. would the interference just be in the tubes or through the whole circuit? as my tubes are in sockets that cover them in aluminium.
  also roughly how long to let it warm up? is 5 minutes enough?
   
  EDIT i have 3.5 and 3.65 after about two minutes.
  EDIT 2 i get a large increase in hum when i touch the volume pot. it also makes a kind of scratching noise when i move it, but i don't really mind that. I think the interference could be a mixture if internal and external, it increases when i move the power supply closer, but doesn't entirely go away when i move it even further away. even if i surround the entire thing with tinfoil. I'm guessing its a ground loop? any ideas on finding the source/fixing it?
  Probably not a problem, but are the tubes meant to be hot to the touch?


----------



## KimLaroux

Yeah tubes do get hot, it's how they work. 5 minutes is enough to take measurements.
   
  So you're actually using tube shields, but you still get noise? Meh. I too have been fighting with all sort of noises out of this amplifier. I bought a couple of shields for the tubes, but haven't had the chance to try them yet. The Faraday cage I originally built is good to block hum, but not wireless. The tubes themselves will pickup interference and amplify it, but the circuit around the tubes is also sensible to EMI. Make sure that no power wire come close to the tube sockets. Moving wires around may help. The input is a high impedance circuit and is also very sensible to interference. In my build I get hum if I just move a finger or a metal tool close to it. The input wire should be kept as far away as possible to the power wires, and if they need to cross make sure they do it at a right angle.
   
  As for the pot buzz, you have to ground the pot's shaft. This fixed it for me.
   
  Is your enclosure built of metal? My original build was plastic, and it was unusable. It picked up just about every single stray EMI in my room and amplified it. I rebuilt it in aluminum, which helped but isn't perfect. My next one will be in a ferrous enclosure. Though with the number of people these days who build it and give up because it's too noisy, I might think about it twice if I ever use the design again.


----------



## shamazo

Lol, I don't even have an enclosure yet I kind of over looked it, thanks for the tips I'll double check where my wires go. This might be a stupid idea but could I shield the wires with aluminum foil?


----------



## the_equalizer

Silver tube shields will actually make the tubes run hotter since they'll reflect back the heat to the tube. Proper tube shields are coated in matte black paint, but they're really hard to find.
   
  As to noise in your build Kim, I really wouldn't blame it on the design. My own build sits inside an ABS plastic enclosure and the only times it picks up noise are when I lay my cell phone directly next to it (then again my Woo Audio amp will also pick up noise that way) or if I put my netbook (while downloading a big file) right next to it.
   
  Shamazo, the heater voltages in your build are a little strange. What values did you use for R2, R3, R8 and R10. Did you check the resistor value with your meter?
   
  cheers!


----------



## kchapdaily

yesterday i plugged a set of gr06 into mine, and with the volume knob all the way down, i actually picked up what sounded like an fm frequency. some random song i had never heard before was playing quietly, and when i turned the pot up, it would go away. tried it with my he-4 and it wouldnt pick it up. guess it was the high sensitivity of the iems. has anyone ever heard something like this happen?


----------



## shamazo

Quote: 





the_equalizer said:


> Silver tube shields will actually make the tubes run hotter since they'll reflect back the heat to the tube. Proper tube shields are coated in matte black paint, but they're really hard to find.
> 
> As to noise in your build Kim, I really wouldn't blame it on the design. My own build sits inside an ABS plastic enclosure and the only times it picks up noise are when I lay my cell phone directly next to it (then again my Woo Audio amp will also pick up noise that way) or if I put my netbook (while downloading a big file) right next to it.
> 
> ...


 
  The resistor values SHOULD be 33kohm for 1/7 and 390 for 2/8, but i  get the feeling that i mixed up r2/8 with r4/10 which are 220kohms, ill edit this in a second when i check with a meter
   
  EDIT r1/7 are 33 exactly for both, the other ones seem to keep going up as i measure them, do the caps affect my measurements? 
   
  EDIT 2 according to resistor codes i used 390 kohm for r2/8, 220kohm for r4/10 and 2 1kohms in series for r 3/9.


----------



## shamazo

Well now after I double checked everything I am sure is is interference, I had it sounding great when I had all the wire positioned in a certain wire, the bam I moved one and it started humming again. So I need to buy a case pronto to shield it. If it is internal interference how should I shield the wires?
Odd fact, most of the humming goes away if I touch the top of one of the caps.

EDIT remeasered the volts at pin4. It's at 19 volts way way to high. I think I have a short on r2/8 or 1/7 going to scrub it off with some alcohol and recheck it.


----------



## the_equalizer

Your resistor values seem certainly right, yet 19 V at the heater is not. I'll have to take out my meter tonight and check the voltage in my own 12AU7 build after running it for a while.
   
  Indeed, measuring resistances in circuit is not always possible due to parallel current paths and capacitance. You need to unsolder one end and then measure.
   
   
  Quote: 





kchapdaily said:


> yesterday i plugged a set of gr06 into mine, and with the volume knob all the way down, i actually picked up what sounded like an fm frequency. some random song i had never heard before was playing quietly, and when i turned the pot up, it would go away. tried it with my he-4 and it wouldnt pick it up. guess it was the high sensitivity of the iems. has anyone ever heard something like this happen?


 
   
  It hasn't happened to me with the SSMH but it did happen from time to time with my electric guitar rig. Sometimes kicking in the overdrive pedal would make the radio sound really loud!
   
  When I used to have my Etymotic ER-6i I could hear the noise floor of the SSMH. Not hum, but the pink (or is it white?) noise "SSSHHHH" sound coming out of the anp.
   
  cheers!


----------



## Goobley

Whilst I still haven't got my ssmh entirely working, the voltages I measured are on this post:
   
  http://www.head-fi.org/t/624475/yanssmh-yet-another-not-so-starving-student-millett-hybrid/15#post_8753199
   
  They sound right but I still have permanent background noise; I'm putting it down to the power supply, because I'm not going to rebuild it again, I've already built it 3 times...
   
  Hope you get yours sorted,
  Chris


----------



## marcus76

Hi there...
  Next one alive and behaving quite good, no noise and only very very little hum.
   

   
  Things left to do : order some slightly larger knob and add some paint.
  Cheers


----------



## Goobley

Nice one! I've seen people who use those heatsinks sand down the curved edges slightly to make them shiny, if that's the sorta thing that interests you


----------



## marcus76

Yeah, thought about that too. Looks pretty nice.


----------



## the_equalizer

Last night I took out my meter and made some measurements in my SSMH 12AU7 build. I had some problems measuring the gate to ground voltage as it is a very high impedance circuit. My DMM would report only 13.71 and 13.62 volts on the gates with 11.82 and 11.71 volts at the tube heaters. The difference is less than two volts!
   
  I had to bring out my old analog FET VOM with 10Mohm input impedance to get a more reliable measurement of ~16.1 and ~16.2 volts (the "~" is because it's an analog meter). Gate to source voltage was thus ~4.2 volts. Much better.
   
  Shamazo, your measurements are definitely strange since they're not lower but much higher Might it be that you reversed R2 and R4?
   
  I also measured the voltages at Q3 and Q4 in the constant current source plate loads. Q3 being my main concern since I knew it would bare the highest voltage drop of the two After the amp has run for a while I saw a voltage of 1.1 across Q4 while voltages of 23 and 24 volts showed up across each Q3.  I must have gotten really mixed up a few days ago when reviewing the datasheets for the BC327 since now that I recheck them I see Vceo listed as 45 V and Vces = 50 V. Since the only way the transistor would see more than 45 volts in regular operation would be that the tube became a short circuit (highly improbable, though not impossible),  I deem that the BC327 is just adequate for the application. Definitely go with the 2N5087 or BC556 if you want increased peace of mind.
   
  By the way, measuring both the plate to ground voltate and the voltage across Q3 were also affected by my DMM's input impedance. I could only get reliable measurements with my FET VOM.
   
  Finally, I noticed that the heater voltage was lowish so I measured the voltage drop across R13 and noticed it was too high. This was due to the higher current set by the CSS going through it. Since R13 sits at the top of the gate bias voltage divider, it was lowering the gate bias.
   
  So I removed the CCS from that junction and connected them directly to the 48 V line from the power source. Since the CSS do a great job of decoupling the tube circuits from each other and from the output MOSFETs I think this configuration won't be a problem. Naturally, I'd definitely like to hear the opinion of someone with more experience building amplifiers with CCS plate loads. Another option would be to wire independent 'R13a' and 'R13b' for each CCS.
   
  After moving the CCS directly to the 48V line the voltage at the MOSFET gates was now ~17 and the heater voltage went up to ~13.2. A little hot but quite alright. I did some listening tests and the amp worked quite alright. No hum and only by pushing the volume up real high was I able to hear the amp's noise floor through the Grado SR-80i
   
  This showed something that I observed when I originally worked with the 12AU7 and 17EW8: I don't see a way to increase the MOSFET bias, that is to increase the voltage from gate to source in this amp. The voltage of the source seems to be "clamped" some 4.2 volts below the voltage set at the gate as when I increased the gate voltage the source voltage moved up correspondingly. Might this be because some sort of CCS-like behavior from the tube heaters? That by holding the drain-source current at ~150mA the source voltage is "clamped" below the gate voltage?
   
  Shamazo: If you're seeing 19 volts at the heaters, what's the voltage at the MOSFET gates in your build?
   
  Next I'll setup the amp and CCS loads to work with the 17EW8 and see how that measures.
   
  cheers!


----------



## KimLaroux

Quote: 





the_equalizer said:


> Last night I took out my meter and made some measurements in my SSMH 12AU7 build. I had some problems measuring the gate to ground voltage as it is a very high impedance circuit. My DMM would report only 13.71 and 13.62 volts on the gates with 11.82 and 11.71 volts at the tube heaters. The difference is less than two volts!
> 
> I had to bring out my old analog FET VOM with 10Mohm input impedance to get a more reliable measurement of ~16.1 and ~16.2 volts (the "~" is because it's an analog meter). Gate to source voltage was thus ~4.2 volts. Much better.


   
  I also noticed these weird measurements with my cheap DMM. The only reliable way I can measure Vgs is to place my probes directly on the MOSFET pins. One probe at the gate, the other at the source. I didn't think of it as an impedance problem, this is good to know.
   
   


> Shamazo, your measurements are definitely strange since they're not lower but much higher Might it be that you reversed R2 and R4?
> 
> I also measured the voltages at Q3 and Q4 in the constant current source plate loads. Q3 being my main concern since I knew it would bare the highest voltage drop of the two After the amp has run for a while I saw a voltage of 1.1 across Q4 while voltages of 23 and 24 volts showed up across each Q3.  I must have gotten really mixed up a few days ago when reviewing the datasheets for the BC327 since now that I recheck them I see Vceo listed as 45 V and Vces = 50 V. Since the only way the transistor would see more than 45 volts in regular operation would be that the tube became a short circuit (highly improbable, though not impossible),  I deem that the BC327 is just adequate for the application. Definitely go with the 2N5087 or BC556 if you want increased peace of mind.
> 
> By the way, measuring both the plate to ground voltate and the voltage across Q3 were also affected by my DMM's input impedance. I could only get reliable measurements with my FET VOM.


   
  I compared some datasheets, and I concluded that the BC556 family may not be the best choice in an audio application. It's a very noisy transistor compared to both BC560 and 2N5087. Those last two are defined as "low noise", and their datasheet show a max noise of 2dB. In comparison, the BC556 has an typical noise of 2dB and a max of 10db. The 2N5087 is rated for 50V and is the cheaper of the bunch, so this is the one I'll get in my next parts order.
   
   


> Finally, I noticed that the heater voltage was lowish so I measured the voltage drop across R13 and noticed it was too high. This was due to the higher current set by the CSS going through it. Since R13 sits at the top of the gate bias voltage divider, it was lowering the gate bias.
> 
> So I removed the CCS from that junction and connected them directly to the 48 V line from the power source. Since the CSS do a great job of decoupling the tube circuits from each other and from the output MOSFETs I think this configuration won't be a problem. Naturally, I'd definitely like to hear the opinion of someone with more experience building amplifiers with CCS plate loads. Another option would be to wire independent 'R13a' and 'R13b' for each CCS.


   
  How did you connect the bypass capacitor without R13? I've been thinking about replacing R13 with a CCS for each channel, but since there's a decoupling cap in there it would make a CCS pointless, so I just don't see how we can do without R13. My build already has an R13 and a decoupling cap for each channel, so I'll give it a try as you recommend.
   
  On a different note, why not simply lower the source current? Could you lower the amp's gain by lowering the CCS's current? That could potentially be a good idea, considering how troublesome the gain of the amp is. Starving the plates might not be such a good idea though.
   
   


> After moving the CCS directly to the 48V line the voltage at the MOSFET gates was now ~17 and the heater voltage went up to ~13.2. A little hot but quite alright. I did some listening tests and the amp worked quite alright. No hum and only by pushing the volume up real high was I able to hear the amp's noise floor through the Grado SR-80i
> 
> This showed something that I observed when I originally worked with the 12AU7 and 17EW8: I don't see a way to increase the MOSFET bias, that is to increase the voltage from gate to source in this amp. The voltage of the source seems to be "clamped" some 4.2 volts below the voltage set at the gate as when I increased the gate voltage the source voltage moved up correspondingly. Might this be because some sort of CCS-like behavior from the tube heaters? That by holding the drain-source current at ~150mA the source voltage is "clamped" below the gate voltage?


   
  4V is the gate to source threshold voltage. This means at this point the MOSFET already is fully ON. After this point, the source current is directly proportional to the gate voltage. Raising the voltage only raises the current trough the MOSFET, which by design also raise the current trough the tube heater. Since the heater is essentially a resistive load, pushing more current trough it will also raise the voltage drop across it. This is why it looks like the voltage at the gate is "clamped" 4V bellow the gate. The tube is not "holding" the source current at 150mA: The MOSFET is biased to allow only 150mA trough the tube. Then's it's just a question of how this current affects the voltages at different points of the circuit. The heaters of the 12AU7 are rated for 150mA at 12.6V. This can also be read the other way around: They will have 12.6V across them when 150mA goes trough them. If you raise the current, they will have a higher voltage cross them, and vice versa. Too little current, and they won't be hot enough for the tube to work properly: too much, and they'll simply blow up.
   
This is how I blew up a heater last week: I turned the amp ON without R4, so that Vgs was around 46V. This pushed an insane amount of current trough the heater, and since the drain of the MOSFET sits at 48V, the voltage across the heater was close to 48V before it blew.
   
  I was wrong, see equalizer's post for the real explanation.
   
   


> Shamazo: If you're seeing 19 volts at the heaters, what's the voltage at the MOSFET gates in your build?
> 
> Next I'll setup the amp and CCS loads to work with the 17EW8 and see how that measures.
> 
> cheers!


----------



## nikongod

Quote: 





kimlaroux said:


> "On a different note, why not simply lower the source current? Could you lower the amp's gain by lowering the CCS's current? That could potentially be a good idea, considering how troublesome the gain of the amp is. Starving the plates might not be such a good idea though."


 
   
Once you have a CCS as a plate load Av~=mu. 
   
Without lots of mods you need to revert to resistors and load the tube down to waste some gain OR add a voltage divider. Neither is really a great option.
   
The best solution is to use a long tail pair, or redesign the amp around tubes with lower Mu. If your going to use an LTP you may as well just build one of Cavalli's amps that starts off with it as you will save endless headaches setting up the multiple power supplies that doing it well kind of needs. If your going with a lower Mu tube you simply have to redesign the amp around that. 
   
  Quote: 





kimlaroux said:


> 4V is the gate to source threshold voltage. This means at this point the MOSFET already is fully ON. After this point, the source current is directly proportional to the gate voltage. Raising the voltage only raises the current trough the MOSFET, which by design also raise the current trough the tube heater. Since the heater is essentially a resistive load, pushing more current trough it will also raise the voltage drop across it. This is why it looks like the voltage at the gate is "clamped" 4V bellow the gate. The tube is not "holding" the source current at 150mA: The MOSFET is biased to allow only 150mA trough the tube. Then's it's just a question of how this current affects the voltages at different points of the circuit. The heaters of the 12AU7 are rated for 150mA at 12.6V. This can also be read the other way around: They will have 12.6V across them when 150mA goes trough them. If you raise the current, they will have a higher voltage cross them, and vice versa. Too little current, and they won't be hot enough for the tube to work properly: too much, and they'll simply blow up.
> 
> This is how I blew up a heater last week: I turned the amp ON without R4, so that Vgs was around 46V. This pushed an insane amount of current trough the heater, and since the drain of the MOSFET sits at 48V, the voltage across the heater was close to 48V before it blew.


 
   
  The mosfets are configured as simple source followers. The mosfet sets the source voltage and output current is conditional on the load.  
  They are not current-controlled devices (ccs's) and should not be thought of as such. Ever. 
   
  How could Vgs possibly be 46V when you said you put ~48V across the heater? Putting ~48V across the heater requires that the source be at 48V and the gate cant possibly be higher than the 48V rail...
  Indeed, the Vgs curves only go to like 10V for the IRF510, and that sucking down 10A! What do the Vgs curves look like with your mosfet?
  Vgs was still what it normally is, give or take a bit. Vg and Vs were no where near what they normally are which kind of screwed you up a lot. Lots of voltage, then the current came because of the voltage across a resistance... then poof.


----------



## nikongod

Quote: 





nikongod said:


> They are not current-controlled devices (ccs's) and should not be thought of as such. Ever.


 
   
  How about now?


----------



## nikongod

Quote: 





nikongod said:


> How about now?


 
   
  Nope. too soon


----------



## KimLaroux

Quote: 





> Originally Posted by *nikongod* /img/forum/go_quote.gif
> 
> The mosfets are configured as simple source followers. The mosfet sets the source voltage and output current is conditional on the load.
> They are not current-controlled devices (ccs's) and should not be thought of as such. Ever.
> ...


 
   
  I never said the MOSFET were current controlled. I said the source current was dependent on the gate _voltage_ when in saturation mode, which I believe is the case here.
   
  I did not say I put 48v across the heaters. I said the MOSFET went fully ON, so I guessed it was like hooking the heaters directly to the power rails. I forgot about the drop needed for Vgs, and I don't know how much it was. But you're right the heater surely did not see as much voltage.


----------



## nikongod

Quote: 





kimlaroux said:


> I never said the MOSFET were current controlled. I said the source current was dependent on the gate _voltage_ when in saturation mode, which I believe is the case here.


 
   
  Quote: 





kimlaroux said:


> The tube is not "holding" the source current at 150mA: The MOSFET is biased to allow only 150mA trough the tube.


 
   
  This is CCS operation. In fact the whole paragraph I cut this out of makes no mention of the fact that its a source follower and works based on voltage controlled voltages. This paragraph only references voltage controlled currents as in a CCS. 
   
  Sometimes looking at the problem from a different angle helps. sometimes it hurts. Where are you going looking at a voltage problem from a current perspective? 
   
   
   
   
  Quote: 





kimlaroux said:


> I did not say I put 48v across the heaters. I said the MOSFET went fully ON, so I guessed it was like hooking the heaters directly to the power rails. I forgot about the drop needed for Vgs, and I don't know how much it was. But you're right the heater surely did not see as much voltage.


 
   
  Quote: 





kimlaroux said:


> the voltage across the heater was close to 48V before it blew.


 
   
  I actually agree that the heater probably saw fairly close to 48V before it blew. I disagree with your values of Vgs.


----------



## shamazo

Quote: 





the_equalizer said:


> Shamazo, your measurements are definitely strange since they're not lower but much higher Might it be that you reversed R2 and R4?
> 
> 
> 
> ...


 
  I'll measurethis soon and edit this post, knowing myself I probably did reverse them.


----------



## spazmochad

Quote: 





kchapdaily said:


> yesterday i plugged a set of gr06 into mine, and with the volume knob all the way down, i actually picked up what sounded like an fm frequency. some random song i had never heard before was playing quietly, and when i turned the pot up, it would go away. tried it with my he-4 and it wouldnt pick it up. guess it was the high sensitivity of the iems. has anyone ever heard something like this happen?


 
   
  I had this when I forgot to wire in the two 2K R3/R9 resistors. They need to be soldered as close as possible to the mosfets.


----------



## the_equalizer

@KimLaroux and nikongod: Gentlemen, thanks for your replies. After reading them several times carefuly the error of my ways dawned on me. And it was so simple and obvious! I had it in front of my eyes all this time but I refused to see it...  *Of course* the quiescient source voltage rises when you raise the gate bias. It is *supposed* to, the MOSFET is working as a source *follower*. Oh my! it's so simple... increased current through the load tied to the MOSFET source causes an increased voltage drop across it ... how could I be so blind!
   
  @KimLaroux: As nikongod pointed out, decreasing the current set by the CCS plate loads will not really reduce the gain, it'll only change the operating point of the tube. A quick and simple way to sensibly reduce the gain of the tube stage is to remove the cathode bypass electrolytic capacitors. I removed them from my build a long time ago to make it more manageable.
   
  About R13: I did not remove it. It is still there, but basically doing nothing but providing a place to hook the bypass cap and the gate bias voltage divider.
   
  Great observation on the CCS transistors: I concentrated on Vceo and completely disregarded noise values.The 2N5087 is a great choice, it's the same part used in the Millet MiniMAX (which I've built) and it works perfectly
   
  About measuring errors, it is indeed a matter of meter input impedance. Decent meters (e.g. Fluke) have an imput impedance in the order of 10 Megohms for voltage measurements, just like my old Kyoritsu FET VOM. You can read a bit more about the meter input impedance problem here and here.
   
  cheers!


----------



## shamazo

Well I got rid of all of the hum, I forgot to ground the pot. 
Now onto the next issue, I only have sound in one channel, I'll do some more trouble shooting later but ATM, I have roughly equal voltages on both channels but at pin 4 the dead channel has 9 volts vs 13 of the working channel.
 I tried swapping tubes and that made no difference, so any voltages or resistor values I should be checking?


----------



## the_equalizer

Quote: 





shamazo said:


> Well I got rid of all of the hum, I forgot to ground the pot.
> Now onto the next issue, I only have sound in one channel, I'll do some more trouble shooting later but ATM, I have roughly equal voltages on both channels but at pin 4 the dead channel has 9 volts vs 13 of the working channel.
> I tried swapping tubes and that made no difference, so any voltages or resistor values I should be checking?


 

 Whoa! What happened to the 19 volts you had there before ?    Good to hear you zapped that hum.
   
   
  I can think of some things that might be going wrong with that channel:
   
  1.- The MOSFET gate bias voltage divider for that channel has something wrong and it's setting the gate at around 13 volts which causes the source to sit at 9V. Such voltage at the tube heater is maybey too low for the heater to raise the cathode's temperature into thermionic emission and that's why that channel is silent.
   
  EDIT: I remember one builder plugged in a set of 17EW8 tubes (17 volt heater) into his build biased for 12A_7 (12 volt heater) and he reported it worked perfectly So I don't think that channel's silent because of the low heater voltage. Either there is a problem in the gate bias voltage divider and some other miswiring or the MOSFET is bad.
   
  2.- That channel's MOSFET is (somehow) "blown" causing the source to sit at 9V regardless of correct gate bias voltage.
   
  3.- The heater's connection to ground (pin 5 in your build) is 'faulty', offering a large resistance and causing a voltage drop across it, "robbing" 2 volts from the heater.
   
  Good luck with your debugging!


----------



## the_equalizer

Quote: 





> Originally Posted by *KimLaroux* /img/forum/go_quote.gif
> 
> The tube is not "holding" the source current at 150mA: The MOSFET is biased to allow only 150mA trough the tube.


 
   
  Quote: 





nikongod said:


> The mosfets are configured as simple source followers. The mosfet sets the source voltage and output current is conditional on the load.
> They are not current-controlled devices (ccs's) and should not be thought of as such. Ever.


 
   
  Still thinking about the MOSFET source follower configuration I now see what nikongod's point was with the above statement. It is indeed the load resistance that limits the current in that series circuit because the voltage drop across it will raise the source voltage to a certain point of equilibrium with respect to the gate voltage. An interesting situation of dynamic equilibrium of Vgs set by the IR drop across the load.
   
  So let's imagine how this works: At amp startup the heaters are cold, their resistance is low, so the voltage drop across them is very low. For the purpose of this thought experiment let's say it's 2 volts, hence the MOSFET source, tied to the heaters, sees this same voltage. Meanwhile the voltage drop across the voltage divider gate bias network is fixed (at 17 volts for the 12A_7 build) so all the time the MOSFETs gate voltage to ground sits at that level so Vgs is 17 V - 2 V= 15 V which is quite larger than the MOSFET turn on voltage and a large amount of current can pass through the MOSFET drain-source circuit. At amp startup this current is so big that it overloads the Cisco PSU causing it to shut down and restart one or more times.
   
  The heaters start warming up slowly, their resistance increasing with temperature, so the current going through them causes an increased voltage drop which causes the MOSFET source voltage to rise accordingly thus reducing Vgs more and more, as the heater temperature and resistance grow, until it reaches the critical turn on value for the MOSFET.  At this point you can imagine that the IR drop across the load makes the MOSFET source voltage to still rise, Vgs goes under the turn-on value, the MOSFET shuts down, no more current flows, the IR drop through the load drops towards ground, hence Vgs goes over the threshold and lets current through, causing the IR drop across the load to rise, hence reducing Vgs to the critical turn-on value, and so on and so forth...  A very nice dynamic equilibrium at play here keeps the MOSFET source voltage *just* right at the turn on value under the MOSFET gate voltage at all times.  Beautiful!
   
  From that it follows that a load with a _larger_ resistance value would need *less* current to make the MOSFET source voltage reach the Vgs threshold voltage simply because the IR drop across it is _larger_. Obviously the reverse also works, a load with a _lower_ resistance value would need *more* current to make the MOSFET source voltage reach the Vgs threshold voltage due to the IR drop across it being _smaller_.
   
  I finally ran some simulations in TINA-TI, the first one with a load resistor of a value similar to the 12AU7 heaters (R = V/I ,  R = 12.6 V / 0.150A , R = 84 ohms), then one with half that value and a last one with twice that value. The results were just as expected:
   

   

   

   
  So, we can conclude a couple of things from these thought and computer experiments
   

 You can't bias the MOSFET hotter by modifying the gate bias voltage divider, you need to change the MOSFET source load for that.
 _*It is* *the tube heater*_ that's holding the current at 150ma, though not quite in the way I imagined   
   
  cheers!


----------



## KimLaroux

Wow thanks for the clear and informative post. Really clears things up. Source follower topology really confused me, as I'm used to use MOSFET as a switch to power electric motors and such.
   
  That makes a lot of sens now. The gate voltage sets the limit, so that the source will never rise over Vg-Vgs(th). How clever!
   
  The idea in this amp is to adjust the bias so that the source never goes higher than the heater voltage, or not too much higher. Raising the gate voltage will raise the source voltage, which in turn will make the heaters pull more current. So there's really no way to adjust Vgs, since it's a property of the MOSFET itself, and the heater will always "push" the source voltage until Vgs(th) starves it. If I got that right, then there's simply no reason to raise the gate voltage, as it does not give the MOSFET any more headroom. Sure it will allow more current for the output, but I think 150mA is enough for most headphones, right?
   
  When I finally get the time to continue working on my amp, I think I'll just revert the bias to what it was so that the source sits around 15v. Damn, to think that I blew a nice Sylvania tube for no reason. 
	

	
	
		
		

		
			




   
  Again, thanks the_equalizer, really appreciated.


----------



## Goobley

Yeah this is really great, it's helping me learn so much more than I expected from a simple amp project, I'm sure this info will be useful one day (having had no formal training).
   
  Cheers all,


----------



## shamazo

Quote: 





the_equalizer said:


> Whoa! What happened to the 19 volts you had there before ?    Good to hear you zapped that hum.
> 
> 
> I can think of some things that might be going wrong with that channel:
> ...


 
  how can I check if my MOSFET is blown?
  I checked the resistance and it was only about 6 ohms.
   
  for the volatage divider would that be something wrong with r1/2 and c2?
   
  EDIT I measured from the positive terminal of the power to pins 1 and 6, on the wokring channel its 37kohms and on the non working its 3 kohms,


----------



## the_equalizer

shamazo said:


> how can I check if my MOSFET is blown?
> I checked the resistance and it was only about 6 ohms.
> 
> for the volatage divider would that be something wrong with r1/2 and c2?
> ...





I don't know of a way of checking the MOSFET; but just like you seem to be doing, I'd first check the rest of the circuit thoroughly.

3 Kohms is waaay too low. If the value of R13 is correct ( 2 Kohms ) , that would leave only leave only 1 Kohms for the plate load resistor R1 / R7 which, as your other channel mesurements show, should be around 33 Kohms.


----------



## shamazo

Quote: 





the_equalizer said:


> I don't know of a way of checking the MOSFET; but just like you seem to be doing, I'd first check the rest of the circuit thoroughly.
> 3 Kohms is waaay too low. If the value of R13 is correct ( 2 Kohms ) , that would leave only leave only 1 Kohms for the plate load resistor R1 / R7 which, as your other channel mesurements show, should be around 33 Kohms.


 
  R13 is correct, so I am fairly sure I have a short on r7. I'll try and have a look at it and clean it up.
   
  EDIT even if I swap rca inputs it is still only the right channel working, with leads me to believe i have shorted the channels together somewhere.
  now I have 14 kohm resistance from positive in to pin 1/6 
  both channels have similer volts at the source of the irf510,


----------



## the_equalizer

Quote: 





kimlaroux said:


> Wow thanks for the clear and informative post. Really clears things up. Source follower topology really confused me, as I'm used to use MOSFET as a switch to power electric motors and such.
> 
> That makes a lot of sens now. The gate voltage sets the limit, so that the source will never rise over Vg-Vgs(th). How clever!
> 
> ...


 
   
  Quote: 





goobley said:


> Yeah this is really great, it's helping me learn so much more than I expected from a simple amp project, I'm sure this info will be useful one day (having had no formal training).
> 
> Cheers all,


 

 Thank you. I'm glad you found the post clear and informative. This piece of understanding eluded me for so long that I actually have a feeling of relief now. And to think it was so obvious right from the start. For me too, aside from the musical pleasure it has brought me, building it and tweaking the amp has taught me a lot.
   
  I've kept thinking about the source-follower configuration and doing analysis and simulation trying to understand some other aspects of the output stage. For instance, KimLaroux mentions headroom. At first I also thought that the output's stage headroom depended directly and completely on Vgs. I thought that since the drain is sitting at 48V and the source at 13V then the gate voltage should be right in the middle of that range, that is  13 + (48-13)/2 = 30.5V, then that would give a headroom of 17.5V peak-to-peak and set the quiescent point of the MOSFET right in the middle of class A... Oh, how mistaken I was! I was trying to understand a source-follower (or common drain) as if it were a common source amplifier...
   
  However, armed with what we now understand of the behavior of Vgs in the source follower configuration we can more clearly see the limits of voltage swing available to the output MOSFET.
   
  On the negative swing side we have the situation where no voltage is dropped across the source load, 0 volts. All the supply voltage is dropped across the MOSFET. Since the quiescent (no signal) voltage drop across the load is ~13 volts it follows that the input signal at the gate can go to ~ -13 volts. Probably a little more since the source-follower's voltage gain is slightly less than 1.
   
  On the positive side the theoretical limit of positive swing would be when Vg reaches the supply voltage; when it 'hits the positive rail'. Since the quiescent gate voltage is ~17 volts, it follows the maximum positive swing is ~31 volts. Probably somewhat less since as the source voltage rises following the gate voltage, the drain-source voltage decreases dramatically and it'll reach a region of non-linearity or saturation (given the Vds, the MOSFET cannot let more current through to support an increase in Vs, or support it linearly) before the gate gets to 48 V.
   
  As you can see the headroom is assymetrical and if you read the literature on source-followers (or tube cathode followers for that matter) other biasing schemes are required to allow the MOSFET to swing symetrically; such as a negative supply connected to the source load, or a 'bootstrapping' resistor.
   
  Please note that the above discussion assumes the ONLY load is the MOSFET source load, in the SSMH that is the tube heater. The moment you hook up a capacitor to take the AC and apply it to the headphones load, the available headroom alters quite significantly. I've run some simulations with 32 ohm resistive loads and the negative and positive swings are considerably diminished. I don't have the exact numbers handy but it was something like +15 to -5 V !   This is logical since, from the alternating current point of view, the load looks like 23 ohms (84 ohm and 32 ohm in parallel). As expected, higher impedance headphone loads have less noticeable effects.
   
  Being able to swing 'only -5 V' with a 32 ohm headphone load is probably a bit of a moot point given that even Mr. Millett himself mentions that listening to a 3V RMS signal in a pair of Grados will cause permanent hearing damage. But sill, understanding the inner working and limitations of the SSMH output stage will definitely help in understanding how the amp will interact with difficult loads (like planar headphones) and/or to modify it to improve it's performance.
   
  cheers!


----------



## Makiah S

Just to throw this out there again you guys, I'm currently looking at Intro Tube amps and I would LOVE to buy one of these from you guys OR be a tester [for a non explody one lol]   as I so do enjoy trying new gear but ^^ I'm happy to see the pics you guys have of them :3. Still though shoot me a pm if any of you have one you'd like to sell :3


----------



## Goobley

I wondered if any of you clever people would be able to explain some stuff regarding the mosfets to me.
   
  I am aware that the mosfets are operating as source followers and that one biases them to be above their ohmic range. (With the heaters as one of the biasing resitors)
   
  If I understand correctly that would mean that the mosfets would be permanantly fully on, with all the power flowing from drain to source and therefore into the heaters. Now most of us are running 12 or 17v circuits for the tubes and it's pretty clear to anybody that 12 =! 48. Does that mean that the heaters (which are more or less lightbulb filaments as far as I'm aware) are purely current dependant? Do they just need their 12V*0.15A=1.8W? or does the mosfet only provide them with the appropriate power/voltage? If so how does this work? (I've been unable to find much information on this subject despite a fair amount of googling, it's always too simple or too hard for me to understand.)
   
  Another part of my question is once again related to the source follower nautre of the fets. We apply plate voltage + amplified music ac to the fet gate (high impedance therefore low current) and we get a low impedance, high current output from the source. The question is probably the same as the last, how come we just have a fully open transistor but instead get a buffered version of the original?
   
  If somebody could explain this topology or could point me to some decent reference material on the subject I'd be very grateful,
  Cheers,
  Chris


----------



## the_equalizer

No, the MOSFETs are not fully on, they are 'just enough on', that's how the source follower works, as I mentioned in a previous post.
   
  The source resistor, in our case the tube heater, effectively acts like a current sensor, that provides 100% negative feedback to the circuit, self biasing the source in relation to the gate to a point where just the exact amount of current for the particular gate to source voltage to be self-sustained.
   
  As I said in my post, if the gate rises, more current goes through, so the voltage drop across the source resistor rises, so the source voltage terminal rises so the gate to source voltage again decreases to just that point where the current required to sustain the gate-to-source voltage is let through.
   
  The reverse happens when the gate voltage decreases, the gate-to-source voltage decreases, less current goes through, the voltage drop across the source resistor falls, so the source voltage falls. Again to the point where just that current required to sustain it is let through. It can't let more current through because then the voltage drop across the source resistor would rise, thus diminishing the gate-to-source voltage, which will turn off the MOSFET, which shuts down the current, then the voltage drop falls, gate-to-source rises, the MOSFET turns on, ad infinitum.
   
  It's a self-sustained bias, a negative feedback bias.
   
  So you can see that the voltage at the source, tracks the voltage at the gate. And since you have a lot of current going through the MOSFET you can sustain that voltage across low impedance loads too. That's why the signal at the source terminal is a copy of the signal at the gate. That's what a source follower does.
   
  The negative feedback effect created by the source resistor in relation to the gate also helps explain in part the low output impedance and high-linearity of the source follower.
   
  As Kim Laroux mentioned in a previous post, the tube heater is a resistor that, when you put 12.6 volts across it, will have 150ma going through it, or viceversa: push 150ma through it and you'll have 12.6 volts across it. All this once it reaches it's operating temperature.
   
  So knowing this, and the fact that the MOSFET gate-to-source turn on voltage is ~4 volts, you set the gate biasing voltage divider so that when idle, the gate sits at about 4 volts more than the tube heater voltage. Then the rest is done by the self-biasing effect I described above and in my previous post.
   
  So it's not the MOSFET per se that provides just exactly what the heater requires, it's the combination of the heater and the MOSFET in this negative feedback arrangement, the source follower topology, that makes it all work.
   
  cheers!


----------



## KimLaroux

the_equalizer explained all that on the last page.
   
  You can't really "bias" a MOSFET to operate outside of it's ohmic region. This is dependent on the drain-to-source voltage and the drain current. In the MSSH, Vds is ~35 V and Id is ~150 mA. This puts the MOSFET far into it's saturation region.
   
  To understand how source follower works, you have to understand a couple of things:
   

 MOSFET are controlled using voltage, and no current flows trough the gate.
 By design, they are turned on by applying a positive voltage between the gate and the source, Vgs. The voltage needed to fully turn it on, Vgs(th), is around 4 V in this circuit.*
 In the MSSH, the gate is biased at a fixed voltage using a voltage divider between the power rails. This means the gate voltage always stays fixed, regardless of how much current goes trough the MOSFET.*
 The heaters will use as much voltage and, consequently, current as is available to them. This means they will use 10 V if that's all they've got, but if you give them 48 V , they will burn 48 V. They are rated 0.15 A at 13 V, so they'll use 0.3 A at 26 V.
   
  When we switch on the MSSH, there's 0 V across the heater, the source of the MOSFET sits at 0 V, the drain at 48 V* and the gate at, say, 17 V*. Since there's 17 V between the gate and the source of the MOSFET, it turns fully on and conduct as much current as the PSU can supply (#1, 2). The heater starts pulling power, so the voltage drop across it rises (#4). This pushes the source voltage of the MOSFET up. Now if the MOSFET was only a relay, the heater voltage would simply rise until it hit 48 V... or until the heater blows.
   
  But if you remember #2 and #3, it's impossible for the source to rise all the way up to the rail. The gate is biased at 17 V, and stays there. The MOSFET will turn off if Vgs goes bellow Vgs(th). As the heater voltage rises, Vgs falls. When Vgs approaches Vgs(th), the MOSFET starts to turn off, and chokes the heater. An equilibrium state is reached, where Vgs = Vgs(th). If your gate sits at 17 V, the source will never rise over 13 V or so.
   
  Since we use a tube heater as a source follower, we're limited in the source voltage and current.
   
  * For the sake of simplicity, I disregarded audio signal, voltage rise at power on and that Vgs(th) depends on Id...
   
  Edit: Aahh.. You posted while I was typing this.


----------



## the_equalizer

Quote: 





kimlaroux said:


> <snip>
> Edit: Aahh.. You posted while I was typing this.


 
   





   
  So Kim, are you planning to put the CCS plate loads into your amp?


----------



## KimLaroux

Yes, but I don't have the transistors in stock. I don't feel like placing an order at Digi-Key and pay 8$ of shipping for 2$ worth of parts. I'll just wait a couple of months.
   
  Last week end, I had another round of modifications:
   

 Changed the pot for an 50K RK27.
 Removed R16/R17.
 Changed the RCA for better ones, as the cheap ones I had were an insult to the word "RCA". One had the outside too large to plug a connector in, and the other had the inside too loose to make a proper connection.
 Moved the signal ground of the RCA to the star ground in the middle of the amp.
 Rebuilt the whole PSU. Moved the output cap away from AC. Rewired in balanced fashion, i.e. no star ground in the PSU.
 Twisted the wires from the AC in to the transformer.
 Removed cathode bypass caps.
 Added 47K resistor to R2/R8. I originally used 330K as this was all I had in stock. With the latest information, I realized it was useless to have the MOSFET biased so high, so I lowered it. Which makes me think, I should add 390K resistors to my to-buy list...
   
   

   
   
  I tried it using the 12AX7 as I didn't dare turning it on for the first time with my new German NOS tubes. And was it a good idea! There was a cold joint in one pull-down resistor, so the corresponding MOSFET went fully ON. Did you know current production Sovtek tubes can take 40 volts or so on their heaters without flinching? hahaha! The tube glowed purple, it was beautiful. It didn't seem to care much, and it's still working perfectly.




   
  I haven't tried it yet with the new tubes, so I can't comment if the modifications improved the SNR. I tried it with the 12AX7, and noticed that if my NFB-12 has it's volume over 50%, the noise out of the DAC drowns the noise from the MSSH itself. But these were 12AX7... I'll test again with the 12AU7.
   
  I also got some real tube shields, so I'll be trying these too. I'll report back if they are better or worse than my Faraday cages built out of speaker grill mesh.


----------



## the_equalizer

Wow... impressive list of work you did there! I'll keep my fingers crossed that all that work solves your noise woes.
   
  cheers!


----------



## Makiah S

love how invovled you guys are... might build this one day... still intersted in buying Hand Built from Head-fi'r ;3


----------



## the_equalizer

Mshenay, please post your "want to buy" messages in the "sale/trade" forum.


----------



## Goobley

Thanks very much to you both, I'm aware that the equalizer had already explained this and I've read his post several times, however lacking certain pieces of knowledge, I couldn't quite put the whole puzzle together. However thanks to these newer explanations I actually really understand what you're on about and have been able to read those previous posts with new eyes. The comment on tomb's site by Dsatavisk about only needing to change one resistor to change to compatible tubes also makes sense now. These last few posts have been extremely helpful and will help me think whilst I go around diagnosing once again this weekend. I have to say that I'm certainly looking forward to a university setting where I'm going to be able to learn things like this from the people around me 
   
  I should be getting hold of a friends linear regulated bench supply this weekend that is as clean as a whistle and should help my find where to look for noise.
   
  Thanks again for this great help, it's certainly hard to get one's head around when I've only used a transistor as a switch before,
  Cheers,
  Chris


----------



## Goobley

Edit: Deleted as I was talking rubbish and worked it out for myself


----------



## Makiah S

Ahh, have a friend who is looking to help me build it, so I'm STAYING. I'm looking at building one and my questions are, for around $30 what upgrads would you suggest, and as far as changeing the sound, I'd like to have deep detailed bass [+12db would b nice] and transparent highs, and ofc the Tubey Lush mids!


----------



## Goobley

Quote: 





mshenay said:


> Ahh, have a friend who is looking to help me build it, so I'm STAYING. I'm looking at building one and my questions are, for around $30 what upgrads would you suggest, and as far as changeing the sound, I'd like to have deep detailed bass [+12db would b nice] and transparent highs, and ofc the Tubey Lush mids!


 
  Around $30 over what price? This amp has evolved considerably since Mr Millett created the original design, I doubt the tubes you're going to be using will cost you $2 either... Of course I think it's a good project to do, and the standardish build would be this:

  However depending on the tubes you use, you may have the change the voltage divider values, this divider will work for the standard 12v heater tubes (12A_7). With regards to any upgrade beyond this, I'd suggest you get a decent potentiometer (ALPS etc.), and make sure it looks pretty (if that's your sorta thing), this amp works very well as is. As has been discussed a little recently the caps C7/C8 can sometimes be a bit troublesome even if they help give better bass (I removed them from my build today and believe it improved a bit). I'd get these caps and then try with and without them to see how it works in your case.
   
  I find this amp to have a nice rather classic valve sound with a bit of mosfet/SS sheen/polish/sparkle, I like it a lot, I find tubes have fairly emphasised bass anyway (may just be the circuits I'm used to), but if you want a full 12dB you're either gonna have to build some filters or use an eq on your source. (IMHO it shouldn't be the amp that makes such a large difference to sound, subtleties yes, bass control etc. (not emphasis), but over +/- 3dB I'd expect to have to eq).
   
  Hope this helps, I'm sure others will have different suggestions for you too.
   
   
   
  On a different note, does anyone see any reason why a power supply like the one below wouldn't work?

   
  (Ignore the microphone stuff obviously)
  I'd be planning on significantly increasing the capacitance and using a 317HV instead but it looks pretty solid to me (nothing revolutionary obviously). It looks like a fairly decent circuit particularly as there's a place not too far from me that'll custom wind me a 2*20v transformer, which would be almost spot on dropout for the 317HV.
   
  Cheers
  Chris


----------



## scootsit

Quote: 





goobley said:


> Quote:
> 
> 
> 
> ...


 

 A millet hybrid can be built pretty inexpensively, too. I opted to go that route as the zillions of variations on the starving student gave me some pause.


----------



## Makiah S

Quote: 





goobley said:


> Around $30 over what price? This amp has evolved considerably since Mr Millett created the original design, I doubt the tubes you're going to be using will cost you $2 either... Of course I think it's a good project to do, and the standardish build would be this:


 
  Ok so let's start from point A, the Basic Parts needed are what... were talking about building the Simplest version of this Amp following the very old and outdated compents. Now once we have established what BARE minumum is for this project [because I'm sure we can all agree on SOME varition of lowest quality and cheapest build on this amp] so again once we established the CHEAPEST way to build this, let's add +$30 to that budget to make some improvements!
   
  I was told a few times that a basic Millet Hybrid cost around $100, so my question is... do I build a simple Millet hybrid for $100 or maybe $130 OR do I buy a Bravo v2 for $70 and Mod that with around $30 worth of parts and improve on it... because I've heard both options and people are telling me that at the end of the day... wheather you build a Millet amp for around $100 maybe more, OR yoy buy and mod a V2 for around $100 [or more] they both will have about the same Price to Performance Ratio... as far as the skillz in building and modding I have that taken of... just trying to decide the BEST option for a realitive Cheap Intro Hybrid Tube amp
   
  Build a Basic Millet or Mod a Bravo V2


----------



## scootsit

I don't know what a Bravo is. My girlfriend uses a Millett daily and loves it. With the buf634 mounted directly to the chassis, it has gobs of current, and sounds pretty close to my mosfet max. I also customized it to her aesthetic. It sounds like you are asking for a decision that only you can make.

Here's the thread I made with some pictures: http://www.head-fi.org/t/598987/millett-hybrid


----------



## Avro_Arrow

Edit: Deleted


----------



## Makiah S

Quote: 





avro_arrow said:


> This is my somewhat modified Bravo...
> 
> The schematic is similar to this except the Bravo uses
> an LM317 current source instead of the Q2 arrangement.
> ...


 
  Well Why don't I make this a new thread! As I think Modding the Bravo will be the cheapest method [how much did youpay for the parts to mod it]  [although i liked the the guy before us who built the LED lit Millet Hybrid!] Still for a first Tube, I think I'll mod a Bravo that way if I don't like it It should be an easy sell!] 

 So to the Led Lit Guy what was your price


----------



## scootsit

ooh, a bidding war, I like it! No clue.


----------



## Avro_Arrow

Edit: Deleted


----------



## Goobley

I'm interested in setting up a ccs (one the plates) for the tubes in this amp, however after looking at the datasheets the 12au7s seem to be much more current hungry than their 12ax7 counterparts (about an order of magnitude higher). Could anybody hazard a guess as to what value ccs would be a good starting point for the 12au7s? Would measuring the voltage drop of the current plate load resistor be a good place to start?
   
  I would expect that the 12au7s require more current as they have a lower rp, but I don't know if this extra current remains necessary in the ssmh, so ccs advice'd be nice.
   
  Cheers,
  Chris


----------



## the_equalizer

Given the very low currents and voltages involved IMO its very difficult to extract a useful operatng point from the 12AU7 datasheet. So I would say yes: measuring the voltage drop across the plate resistors is a good starting point  If, that is, you like how your amp sounds at its current operating point. If I recall correctly, a 12AU7 build with the default components should be pushing ~0.7mA per tube (0.35 mA per triode)

Another alternative is to simply choose a nice round number, say 1mA, and go for that, which is what I did with my build.

Good luck!


----------



## kidmuffin

Hello everyone, I am wanting to make this amp. I am wanting to make the MSSH to drive my Sennheiser HD595s as they lack power and definition when directly hooked up to my computer. I know these are not the best audiophile cans but they were the best I could afford at the time.
  
  Anyway, I have been unable to find the_equalizer's version of this amp and the BOM for it. I was planning on making it with the 12AX7, any advice on that would be hanndy if these are the right tubes to use. Also, what is the best way to go about making the amp, should I use some sort of strip board or just solder everything together. I am a novice when it comes to actually building from the ground up electronics.
   
  So, any help with this would be greatly appreciated! Thanks!


----------



## Goobley

Quote: 





the_equalizer said:


> Given the very low currents and voltages involved IMO its very difficult to extract a useful operatng point from the 12AU7 datasheet. So I would say yes: measuring the voltage drop across the plate resistors is a good starting point
> 
> 
> 
> ...


 
   
  Your memory is very close to what I measured today. For the 12AU7 I measured a 20.8Vdrop across the 33k resistor so about 0.63mA of current for the tube. The 12AX7 as expected measured quite differently with a Vdrop of 7.8V so 0.23mA of current. I'm going to be running AU7s so I'll start with 0.75 or 1mA for the CCS as it's still well within the safe plate dissipation from the datasheet graphs and it can't be a bad thing pushing it a bit further up its operating range. Another advantage to the CCS would have to be lower voltage drop before the plates (my 12AU7 plate only sees 24V, it'd be nice to get that up a bit. I'm gonna sim some bits and get on to making this after sorting out my power supply.
   
  Quote: 





kidmuffin said:


> Hello everyone, I am wanting to make this amp. I am wanting to make the MSSH to drive my Sennheiser HD595s as they lack power and definition when directly hooked up to my computer. I know these are not the best audiophile cans but they were the best I could afford at the time.
> 
> Anyway, I have been unable to find the_equalizer's version of this amp and the BOM for it. I was planning on making it with the 12AX7, any advice on that would be hanndy if these are the right tubes to use. Also, what is the best way to go about making the amp, should I use some sort of strip board or just solder everything together. I am a novice when it comes to actually building from the ground up electronics.
> 
> So, any help with this would be greatly appreciated! Thanks!


 
  I take it you've found the circuit diagram for this version (if not it's here http://diyforums.org/SSMH/SSMHvariants.php along with a bit of information valid for all the variants) as far as I'm aware I haven't come across a BoM for this version however this amp requires very few components and if you read everything of the diagram then you should have everything. With regards to building it, there is a good stripboard design thread around that couple of people have reported success with. I started with stripboard but ended up with point to point over a ground plane as I feel it's better for this particular amp, due to its noise catching properties. IIRC the HD595s are not overly power hungry, you may not need the extra gain that the AXs provide over the AUs then. Well they use exactly the same build, so you can always try rolling them.


----------



## kidmuffin

Quote: 





goobley said:


> I take it you've found the circuit diagram for this version (if not it's here http://diyforums.org/SSMH/SSMHvariants.php along with a bit of information valid for all the variants) as far as I'm aware I haven't come across a BoM for this version however this amp requires very few components and if you read everything of the diagram then you should have everything. With regards to building it, there is a good stripboard design thread around that couple of people have reported success with. I started with stripboard but ended up with point to point over a ground plane as I feel it's better for this particular amp, due to its noise catching properties. IIRC the HD595s are not overly power hungry, you may not need the extra gain that the AXs provide over the AUs then. Well they use exactly the same build, so you can always try rolling them.


 
  Thanks for the advice. I took a look at the diagram and think I got everything sorted. I am wanting to try out different tube and might just start with the 12AU7s for now and later if I want just buy a pair of 12AX7s or 12AT7s.
   
  I took the time and created a BOM for this build, roughly based on the original one created by Millett. If there are any suggestion on changes to make it cheaper or even just better, let me know.
   
12au7_mod_starving_bom.xls


----------



## KimLaroux

To everyone who helped me build this amplifier, I have good news for you. I am happy to report success. After half a year of debugging, brainstorming and experimenting, the noise level of my starving student is now low enough to be almost inaudible even trough my most sensitive headphones. For the first time since I powered the amplifier for the first time in June, I am currently listening to music trough it and actually enjoying it. And oh my is it great...
   
  I came to the conclusion that this amplifier and my DAC simply hate each others. The MSSH gets very noisy when I place it directly on the DAC, but if I leave it on a shelf half a meter away, it's silent.
   

   
  Last night I debugged the last noise. A mix of flux and dirt got so deep into a tube socket, it allowed current to arc between pins, which made an audible noise. It was a dynamic noise which came and went, cluing me on a possible arcing. By desoldering the interstage coupling cap, then one side of the tube at a time, I managed to narrow down the problem to the socket itself. I already had swapped the tubes and the noise stayed on the same channel, so it wasn't a tube. I soaked the whole sockets in flux cleaner, blew air into the pin holes, and let it dry over night. Today the noise is history.
   
  Now the problem is, I made so many modifications simultaneously during my last round of modifications that I have no way of concluding which modification was responsible for lowering the noise... so I'm just gonna conclude all of them had a positive effect.
   

   
  Currently I don't have the cathode bypass caps in, nor the resistors before the pot. The volume is still usable, but just barely. Since my DAC has a volume control, I use it instead.
   
  I think I learned all that was to learn from this project. My next step will be to divide the PSU in two, raise one rail as high as I can for the tubes and lower the other for the output. I've been studying the SOHA II circuitry, and I'll probably aim for something similar. The transformer already has enough voltage on the secondary to let me build a 60 V supply without voltage multiplier, and has lower taps for a 30 V supply. I mean if I'm gonna build a CCS, I may as well go all out. At this point though, I'll stop referring to this amplifier as a Starving Student and start a new thread just for it.
   
  Thank you all for the support, you made this project a lot more pleasurable than if I was left on my own. You make this community worth being part of.


----------



## Goobley

I'm really glad to hear this Kim, I'm also pleased to report that I am in a very similar position to you. After the measurements that I took allowed me to conclude that my power supply was responsible for the noise, I went all out and built a pair of linear regulated power supplies, one at 24V and one at 48V (but with scope for increase of the latter). I've also entirely rebuilt my amp with new components almost everywhere. I managed to finish in time for Christmas when I was very happy to receive a Beyer DT880. What a superb combination these two make...  
   
  Just after dinner today I implemented a ccd, based on the_equalizers/minimax design but using BC560s as they were the only transistors I could really get. Using a sensing resistor of 620R my tubes are set to 1.05mA constant current. I may also attempt 1mA per triode as has been suggested. I will also reiterate what has already been mentioned with regards to the crazy extra gain the ccs provides. After turning the amp on, setting the plates to have max voltage and plugging in my headphones I was amazed to hear that I had more background noise than before. It wasn't until I connected a source and listened that I realised why... Previously with my srh440s if I listened at night I could just hear some noise with the pot at minimum, now for the 440s the pot turned all the way down is quite a comfortable listening volume I struggle to get the 250R Beyers over 20° :O  With a gain that high I think a bit of background noise further up the pot (in a totally inaccesible region unless you want your ears to bleed) is pretty damn good.
   
  With regards to the cathode bypass caps I would have to say that even though it's something that increases the gain of the amp it does make the bass much creamier, but I'm gonna add some input resistors to try and make the pot usable again, does anyone know what sort of value I can go up to before the sound starts to significantly suffer? (A friend had some 220k input resistors in a different amp and could never get it to sound right 'till he removed them). 
   
  Anyhow, I'm going to revive my thread probably tomorrow with some new pictures schematics and info as to what I've done as well as some questions about raising the B+ a notch 
   
  Really glad to hear about your success, this is certainly a wonderful community
   
  Cheers,
  Chris


----------



## KimLaroux

Hey nice to hear you haven't given up! Can't wait to see pictures and schematics...
   
  Also nice to see you're also using the 440. Those are so sensitive it's amazing. I'll keep them forever just for this, as they are perfect to debug noises. At the last meet, I used them to prove to other head-fi'ers that even the Bryston BHA-1 had noise on it's output. 
	

	
	
		
		

		
		
	


	



   
  Tho mines have the 940's velour pads, which isolate better. Better isolation means you can hear lower levels signal...
   
  As for the resistor before the pot, you have to look at them as an extension to the pot's range. Placing a 50 K resistor before a 50 K pot virtually creates a 100 K resistor where only the first half is usable. Well, not exactly half as they are logarithmic, but you get the idea. It simply extends the resistive strip on which the wiper slides. Using a 250 K resistor before a 50 K pot is like using a 300 K pot limited to only 17% of motion. If I had to add a resistor before a pot, I'd start with a low value. For a 50 K, I'd start with something around 22 K. If that's not enough, I'd try 33...
   
  But honestly, I just don't like the idea. If the input signal has better SNR than the amplifier, why would you attenuate it and then amplify it again with more noise? It's just silly. Since this amplifier is inverting, you can just run a wire from the output to the input trough a 10K resistor... simple negative feedback that you can adjust. This would be a cleaner solution with other benefits.


----------



## the_equalizer

It's great to see that both of you made good progress with your amplifiers and are actually enjoying them now. Congratulations!  It'll be interesting to see how you carry your project further. I believe it has been suggested before (not by me) but I'll reiterate the suggestion here: since you're going with a higher B+, go for another tube. The 12A_7 have never been *really* good for hi-fi audio, the 6DJ8 on the other hand...  A bipolar power supply for a complementary MOSFET output stage would do away with the output cap too.... but, hey! I'm starting to list my wishes here!  
   
  @KimLaroux: That was quite a noise debugging you performed there to diagnose it was a dirty tube socket! 
   
  @Goobley: Good to hear you implemented the CCS in your amp. I just love the punch and transient response the amp got with them, particularly with my Shure SRH840. I think you're liking it too 
   
  @Goobley: About the cathode bypass caps, I think you had also mentioned in a previous post that they were related to the frequency response of the tube stage. It actually has nothing to do with increasing the bass response of the tube stage. What the cathode bypass capacitor does is avoid the gain reduction that results from the local negative feedback effect that using cathode resistor biasing implies. Something quite similar to the negative feedback effect the source resistor works in the MOSFET source follower.  The capacitor detours the audio AC signal away from the cathode resistor, hence the voltage across this resistor does not vary, which in turn means the grid to cathode resistor voltage does not vary; hence no local negative feedback effect to reduce the gain. Also, the dynamic changes in gain in an amplification stage are a major source of distortion so, theoretically, a cathode bypass cap also helps improving the linearity of the stage (if we forget about its phase shifiting effects, that is).
   
  According to the above discussion, using a CCS as plate load makes the cathode bypass caps completely redundant, because the CCS is already making the bias constant (constant current through the tube means constant current through the cathode resistor, which in turn means constant voltage across said resistor) and getting the maximum gain out of the tube. I must, however, ask other more experienced builders/designers to chime in here, as, for example, the original Millet Hybrid and the MiniMax have _*both*_ a CCS plate load *and* cathode bypass caps.
   
  About the input resistors to tame the input down. They're certainly not a technically ideal solution but they're a good practical one so if one really wants to tame the gain of the amp down, well, what else is one to do?
   
  Anyway, congratulations again, and enjoy your amps and cans!
   
  cheers!


----------



## Goobley

Just a quick word of advice as I'm about to go to bed - almost 1am here...  Just spent a good 4 hours debugging a CCS issue, just before dinner I set the CCS to 2mA and everything seemed to be ok possibly a slightly better sound but marginal. Came back later and noticed that there was a horrible crunching noise in the background, I though it was the CCS then touched the power cable (external psu) and the noise changed significantly, I could almost get it quiet. I had been thinking that the DC barrel jacks that I had used had tabs that were a bit flimsy inside, and when I checked they were almost broken inside, so the ps input is replaced with a terminal block. This however did not fix either the crunch or the variation in its volume when the bales where moved. _strange... _the connections were very solid after all that and I had used fresh wire, eventually after checking for dry joints in othe rplaces I came back to the CCS and bumped it down to 1mA, the amp is silent again... 
   
  I'm guessing that 2mA is too high for the voltage that we're running the valves at and this must be saturation/overdrive (although overdrive's voltage based, isn't it?).
   
   
  Second part of this quick note: Kim's idea about NFB from the output of the amp is pretty much genius, (I know it's an old idea but I'd never have thought of implementing it here). With a 20k resistor from the output of the amp to the RCA/pot input I can use around half of the pot with my high impedance cans. As far as I'm aware this should be well below the 20dB level that people say to avoid. To my ears this sounds better than the input resistors that I've played with.
   
  The DC barrel jacks I've been using obviously aren't up to scratch (they also had the disadvantage of being interchangeable 24 and 48V), what'd you guys suggest for carrying +48V/+24V/0V/Gnd/and maybe one or two more future voltages to the amp in one connector (if only one is possible)? Possibly something like a PCI-e 6/8 Pin?
   
  The CCS was set up more or less as per the_equalizers instructions and with the minimax page http://www.diyforums.org/MiniMAX/MiniMAXccs.php  
  Currently I have kept the plate voltage below 50V because I'm using BC560C as my transistors http://www.datasheetcatalog.org/datasheet/motorola/BC560C.pdf  Their V(ce) is -45V max, now the only place where that could be an issue in the ccs would be in QA2 however in my TINA sims and from my scope V(ce) never really seems to go below -10V, since RA9 is not a 'pull-down' resistor as such (I originally assumed it was), would I be ok taking my B+ significantly over 50V (towards 100)?
   
  Cheers, thanks again for all the advice,
  Chris


----------



## KimLaroux

I think you'd have better chances asking about those modifications in another thread... I have a feeling you and I are getting off topic here. In order to respect the original design and keep this thread dedicated to it, I think it would be more appropriate if we continued our discussions in another thread.


----------



## scootsit

Quote: 





kimlaroux said:


> I think you'd have better chances asking about those modifications in another thread... I have a feeling you and I are getting off topic here. In order to respect the original design and keep this thread dedicated to it, I think it would be more appropriate if we continued our discussions in another thread.


 

 I think you're okay, this is the DIY section.


----------



## Oeufdepoire

After a very, very long procrastination that began when I finally gathered all the elements, I eventually started building my MSSHA.
   
  It has been more work than I thought, but also infinitely more pleasure.
   
*Here are the pics of the complete process.*​


----------



## dustinsterk

For anyone who is looking to build this amp, I have updated the BOM (attached) and also created a Mouser one click to buy project:
   
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=de75dcc795
   
  I hope this helps others as it took me a while to go though all the posts and collect all the final parts needed to build the new 12AU7 version.
   
  Thanks!
  Dustin


----------



## Oeufdepoire

Ewww... Two day after testing the amp for the first time, the right channel just ceased working. I'm stuck, because the problem seems particuliar, and I am ignorant at electronics. Thus, I'm asking help from you electronic gurus.
   
Here's the matter :
V1 belongs to the right channel, and V2 to the left channel. The problem doesn't come from the tubes themselves; I have switched them, changed them, nothing works.
When the tubes aren't plugged in their sockets, I have 48 V of voltage between pin 1 and the ground, for both sockets.
But, with tubes plugged, the voltage between pin 1 and ground, for V1 only, progressively goes down from 48 to 24 V, while the voltage for V2 remains good (48 V between pin 1 and ground). And I have no sound in the right channel.
   
Can anyone help me ? Any piece of advice would be very much appreciated.
   
  Stupid me. Unable to figure out the problem, I checked all the solders and made them cleaner. It was just a fraying cable going to the ground that was touching R3's lead to Q1.


----------



## ProTofik

Hi. I am going to build my first tube amp ever. 
  I am planning to build Starving Student amp based on 12SR7 tubes. I've collected all necessary parts however I would like to ask you one thing. Is that correct:
   
   
   


> If you want to build this version, you have to make some small changes -
> 
> R1/R7 - 44k
> R5/R11 - 4K
> ...


 
   
   
  Are these the only changes I need to make to the original project from this website? I want to build it in the simpliest possible way. 
  Sorry for stupid questions but I am not good with electronic (but not bad with soldering iron 
	

	
	
		
		

		
			





 )
  Thanks.


----------



## DudeMyCans

Well I spent a very wet and miserable Irish afternoon yesterday building my MSSH as I want it to drive my DT880/600s. I have the electronics all done, but so far I'm not getting any output.

I went for the 19J6 version built on strip board.

I've not had much chance to troubleshoot, but have checked a few voltages and all seem OK. I'm getting 48v where I expect to, 18v on the sources and around 22v on the gates.

Both valves, oops sorry tubes  , are glowing nicely and the heatsinks get pretty warm.

I get around 22v on pins 1+2 of the tubes, which seems normal.

I'll take another look later, but does anybody have any ideas that could save me any time? I do realise that its next to impossible without seeing it. I'm not getting anything on the output at all. I have a feeling that its something fairly stupid, as by the time I'd finished the soldering yesterday I was starting to loose all sense of feeling in my fingers .


----------



## KimLaroux

Quote: 





dudemycans said:


> Well I spent a very wet and miserable Irish afternoon yesterday building my MSSH as I want it to drive my DT880/600s. I have the electronics all done, but so far I'm not getting any output.
> 
> I went for the 19J6 version built on strip board.
> ...


 
   
  Where did you find 19J6 tubes?!? If there's more where they come from, I know someone who'll buy them all. 
	

	
	
		
		

		
		
	


	



   
  As for your problem, I'm guessing you made an error in the signal path. Verify that the interstage coupling capacitors are connected to the right places. In my build, touching those capacitors introduces a hum at the output. Same thing if I move a metal screw driver close to the signal path. If this is normal for every build, it may be a way for you to narrow down the source of the problem.


----------



## DudeMyCans

Hi Kim.

I got them off eBay. He was a seller in the US selling NOS tubes. I don't want to pi$$ anybody off but I actually bought 4 as I'm thinking off building one as a wedding present for my brother later this year.

Anyway. Now for the embarrassing bit. (Shuffles awkwardly and looks down to his shoes).

I found the problem with the amp. I was right. It was something stupid and it was the last thing I soldered before I went inside out of the cold....I'd wired the jack socket to the wrong (switched) side. 5 minutes with the iron and its now singing. Well actually Adel is, but you know what I mean.

Sound great. Way better than my Creek that I've been using until now.

There's a very slight hum, only audible when its idling, which I'm hoping will go away when I box it up next weekend and spend more time on laying out the wiring.For now its sat in a shoe box and still sounds great.  

I'll post some photos next weekend when its boxed and if anybody wants my sketches for the strip board layout I'll post them as well.


----------



## Lighthouse

Looks (and hopefully sounds) nice Oeufdepoire!


----------



## metallo97

Hi all, i'm new in the forum and even in electronics, and i want to do this amplifier, looking at the schematics, for me, it's a bit difficult, did someone create a pcb sort of thing or a more particular schematics?
 Thanks in advance, and sorry for my english, i'm from Italy


----------



## tomb

Quote: 





kimlaroux said:


> Where did you find 19J6 tubes?!? If there's more where they come from, I know someone who'll buy them all.


 
  Someone PM me if they find 100 or more - we'll do another PCB run, custom case and kits.


----------



## Ikarios

Quote: 





tomb said:


> Someone PM me if they find 100 or more - we'll do another PCB run, custom case and kits.


 
  Would you be able to do such a large run with 12AU7 tubes? When I had my SSMH I found 12AU7s that were affordable enough, around $5-10. Sure, they're not top-notch quality, but I doubt you'll be able to find so many 19J6s at their old price.


----------



## tomb

Quote: 





ikarios said:


> Would you be able to do such a large run with 12AU7 tubes? When I had my SSMH I found 12AU7s that were affordable enough, around $5-10. Sure, they're not top-notch quality, but I doubt you'll be able to find so many 19J6s at their old price.


 
  No, it would be a different amp.  Dsavitsk and I really went another route in using dirt-cheap tubes with the Torpedo.  It's more expensive, but the 6J6 tubes (the 6V heater version of the 19J6) can be found for $2 a piece and less if purchased in high quantities.  They number into the tens of thousands.  Some dealers may have that many on their own.
   
  If you really want a hybrid that uses 12AU7 tubes, I suggest the SOHA II. As always, of course, if you are willing to build point-to-point, then you can do anything you want. 
   
  I still have several extra 19J6 tubes and even the Cisco power supplies.  Maybe it's time I tried to sell them.


----------



## KimLaroux

I went looking on Ebay after the comment. There's a couple for sale, but at outrageous prices. Most listings advertise them has "Starving Student" tubes, and ask 45$ for a pair. It's quite shocking when you think the original design had a total cost lower than that.
   
  It'll be quite the day when someone finds a rotten box filled with hundreds of 19J6 in the back shed of an old shop. Gotta keep dreaming, right?


----------



## tomb

Quote: 





kimlaroux said:


> I went looking on Ebay after the comment. There's a couple for sale, but at outrageous prices. Most listings advertise them has "Starving Student" tubes, and ask 45$ for a pair. It's quite shocking when you think the original design had a total cost lower than that.
> 
> It'll be quite the day when someone finds a rotten box filled with hundreds of 19J6 in the back shed of an old shop. Gotta keep dreaming, right?


 
  Yep.  However, the Starving Student Millett Hybrid PCB kit with custom case sold for $120.  It's extremely doubtful that it could be sold for that again, even if the tubes were still $2.


----------



## Shrew

Would anyone give me an estimate on how much a pre-assembled would cost, and if anyone would be interested in selling one to me?


----------



## scootsit

The cost of parts for a regular Millett is somewhere in the neighborhood of $100-$200. Not sure about the starving student, but the regular Millett is pretty straight forward on strip board.


----------



## scootsit

The cost of parts for a regular Millett is somewhere in the neighborhood of $100-$200. Not sure about the starving student, but the regular Millett is pretty straight forward on strip board.


----------



## dustinsterk

Hey everyone,
  Thanks for all of the input into building this amp.  It sounds great!  I have a few questions about some minor issues I am having:
   
  1)  If one of the RCA inputs are unplugged I get one of the headphone channels spike to max volume....when both are plugged in, everything is fine.  Could this be due to the fact that I grounded my headphone jack to one of the RCA inputs?  I did this as I was having a loud hum/buzz when it was grounded to my ground plate.  I am not sure why.
   
  2)  I have a hum when I touch my volume knob (I already tried to ground the POT without success as someone stated in the past posts).
   
  3)  When the POT is turned up to MAX volume, I have a constant buzz (is this what is referred to as the ceiling max?).  When it is at a normal volume I hear no buzz at all and everything is crystal clear.
   
  4)  Just an FYI, when this amp is plugged into a DAC (from my computer) I can hear noise that is related to my hard drives (reading and writing data), keyboard, mouse movements, etc.  I am assuming this is due to Electrical Interference or RFI the tubes are picking up.  Anyway to fix this?
   
  5)  A question about grounding.....At first I was not thinking and just following the schematic.  I grounded the POT, RCA inputs, and Headphone amp as seperate lines all connecting to a single point on the grounding plate.  I had a TERRIBLE loud buzzing to the point I thought it was going to blow my headphone speakers.  After walking away and thinking about it, I realized I needed to run the ground from the RCA inputs to the ground terminals on the POT.  I also grounded my headphone socket to one the RCA input.  I then ran one single ground from this "circuit" to a single point on the ground plate.  Is this correct?
   
  Thanks! 
   
   
   

   

   

   
   
  Dustin


----------



## Ikarios

Quote: 





scootsit said:


> The cost of parts for a regular Millett is somewhere in the neighborhood of $100-$200. Not sure about the starving student, but the regular Millett is pretty straight forward on strip board.


 
  When I built my SSMH the total parts cost was around $100 including case, tubes and everything. I added a GrubDAC to that, which was another $20-30 or so. I built mine point to point, it wasn't really that hard after I got all the parts mapped out and rechecked the schematic for the zillionth time. There's a million P2P builds and pictures in this thread for reference, and there was some work with a stripboard layout at some point, which there was a separate thread for.


----------



## scootsit

Quote: 





ikarios said:


> Quote:
> 
> 
> 
> ...


 

 I think my price had a skeletonDAC, too, an E12 muting circuit, and a PS. That all was close to $150 ish
   
  That's unbuilt, of course. Though, building it isn't as hard as you might think. I could really help you with that. I laid it out on stripboard in DIY creator and would be happy to share the board layouts. If you wanted it custom built, I'd bet you'd pay closer to $200 or $250. If you were buying someone's used amp, it would probably be closer to or less than parts cost.


----------



## KimLaroux

Quote: 





dustinsterk said:


> Hey everyone,
> Thanks for all of the input into building this amp.  It sounds great!  I have a few questions about some minor issues I am having:
> 
> 1)  If one of the RCA inputs are unplugged I get one of the headphone channels spike to max volume....when both are plugged in, everything is fine.  Could this be due to the fact that I grounded my headphone jack to one of the RCA inputs?  I did this as I was having a loud hum/buzz when it was grounded to my ground plate.  I am not sure why.


 
   
  Does it do this regardless of which RCA is unplugged, or is it the same for both? If it's only for one, I'm guessing you have one of the RCA not grounded properly.
   
  Quote: 





> 2)  I have a hum when I touch my volume knob (I already tried to ground the POT without success as someone stated in the past posts).


 
   
  If you used an off-board PSU, it's probably not earthed. In this case, you don't even have a ground to ground it to. Connecting the pot's shaft to 0 V may help, or it may make it worse. I'm clueless how one should go about fixing this... anyone else got experience with this?
   
  Maybe you should start by verifying, using a DMM, that the pot's shaft is indeed grounded.
   
  Quote: 





> 3)  When the POT is turned up to MAX volume, I have a constant buzz (is this what is referred to as the ceiling max?).  When it is at a normal volume I hear no buzz at all and everything is crystal clear.


 
   
  Any amplifier will output some audible noise when the volume is maxed. It's normal, and not really a problem. If you listen to music at this volume, you have more serious problems to take care of. 
	

	
	
		
		

		
			




   
  Quote: 





> 4)  Just an FYI, when this amp is plugged into a DAC (from my computer) I can hear noise that is related to my hard drives (reading and writing data), keyboard, mouse movements, etc.  I am assuming this is due to Electrical Interference or RFI the tubes are picking up.  Anyway to fix this?


 
   
  By "DAC from my computer", do you mean that you're using your sound card's audio out? If yes, then it's normal. The inside of a PC is drowned with all sort of RFI and EMI. If your sound card is not shielded, as most cheap cards are, then its audio signal gets polluted with all this junk.
   
  Quote: 





> 5)  A question about grounding.....At first I was not thinking and just following the schematic.  I grounded the POT, RCA inputs, and Headphone amp as seperate lines all connecting to a single point on the grounding plate.  I had a TERRIBLE loud buzzing to the point I thought it was going to blow my headphone speakers.  After walking away and thinking about it, I realized I needed to run the ground from the RCA inputs to the ground terminals on the POT.  I also grounded my headphone socket to one the RCA input.  I then ran one single ground from this "circuit" to a single point on the ground plate.  Is this correct?


 
   
  It depends on your religion. There is no consensus on how one should wire grounds inside an audio device. Just look at the mess created by ground loops in commercial products... it's endless.
   
  You're the only person able to answer this question. Did changing the ground scheme improve on the buzz? The level of the buzzing is your only gauge telling you if one scheme is better than the other.
   
  As for the discussion on the cost, should I start counting how much mine cost? I lost count at around 500, but I'll do the math again if anyone cares. 
	

	
	
		
		

		
		
	


	




 Though honestly, I think I'll sleep better if I don't know.


----------



## dustinsterk

Quote: 





kimlaroux said:


> Does it do this regardless of which RCA is unplugged, or is it the same for both? If it's only for one, I'm guessing you have one of the RCA not grounded properly.
> 
> 
> If you used an off-board PSU, it's probably not earthed. In this case, you don't even have a ground to ground it to. Connecting the pot's shaft to 0 V may help, or it may make it worse. I'm clueless how one should go about fixing this... anyone else got experience with this?
> ...


 
   
  Hello KimLaroux,
  Thanks for the response.
   
  The loudness only happens when one of the channels is unplugged....I will double check the grounds, etc.  Thanks for the suggestion!
   
  In regards to the max volume, I am not listening to it that loud, trust me this thing cranks.  I just noticed that you can start to hear that hum as you get closer and closer to the max volume....I was just making sure that was "normal".  
   
  By "DAC from my computer"...I am referring to a DAC (the Schiit Modi) that I have attached via USB cable.  The funny part is when I connect the same RCA cables (from the DAC) to another amp I dot NOT hear any computer noise.  It is only when it is connected to this amp.  That is why I am wondering if the tubes could be picking up the noise.
   
  Thanks for the feedback on the grounding....I was unsure if there was a "proper" way to do it.  I think I have found the best way for this amp considering the case I used.
   
  Thanks again!
   
  --Dustin


----------



## ahshan06

Finished the Starving Student chassis today

Unfortunately, I am solder-challenged. I've soldered past projects but I mostly ended up with bad joints, perhaps I can blame my cheap soldering iron. In other words, this is currently a paper weight. Lame-sauce :/

If someone lives close to Houston and can help solder the components, then please contact me!

This is the original millet schematic based on 19J6 tubes


----------



## Oeufdepoire

Pimpest switch ever.


----------



## dustinsterk

Just an FYI, if anyone needs the Cisco power supply for this project, I have about 100-125 of them.  I would sell them for $10 if you are interested.  Just send me a PM.
   
  They are Cisco part number:  34-1977-03       48V, .38A
   
  Thanks,
  Dustin


----------



## cpdelc

Hi everyone, just bought a built SSMH from a friend, but one of the channel (left to be precise) doesn't sound correctly. It crackles and sounds very low, almost no sound at all. What could possibly be the problem? I suspect one of the caps is broken, but no idea which one. Any help?


----------



## tomb

Quote: 





cpdelc said:


> Hi everyone, just bought a built SSMH from a friend, but one of the channel (left to be precise) doesn't sound correctly. It crackles and sounds very low, almost no sound at all. What could possibly be the problem? I suspect one of the caps is broken, but no idea which one. Any help?


 
  Could be a bad tube, have you switched them to see if the problem follows the tube?


----------



## Goobley

Quote: 





cpdelc said:


> Hi everyone, just bought a built SSMH from a friend, but one of the channel (left to be precise) doesn't sound correctly. It crackles and sounds very low, almost no sound at all. What could possibly be the problem? I suspect one of the caps is broken, but no idea which one. Any help?


 
  Right, it's fairly easy to work along the signal path in this amp. There is of course a risk of shock when working on a live amp, so all the usual caveats... I'm not responsible for any harm you may do to yourself or if you set fire to your house... but honestly it's not a very dangerous amp (I did get a decent belt off one of the my big decoupling caps a while ago whilst trying to discharge it).
   
  Carefully power up the amp with case open and the innards accessible.
   
  First of all, stupid question do both the heaters light up?
   
  When following these instructions if any step doesn't read like it should report it here so we can try and work out the problems.
   
  Now let's check the power supply path. With your DMM on VDC you should see 48V at the power input to the amp and going to pin 2 of each mosfet. You should also have a CRC pi filter with about 45-47V on the other side of the 2k resistor. Then check the voltage at the top of R1 and R7, they should be the the same as the voltage you measured after the pi filter. After this measure the voltage on the tube cathodes (pins 3 and 8 on 12a_7s and pin 7 on 19J6s) it should read around 2V from memory, but the most important thing is that both tubes read the same.
  You can also check the heater voltage now (between pins 4 and 5 on a 12a_7 or pins 3 and 4 on a 19J6), it should read either around 13V or 19V.
   
  Now for a signal path check:
   
  I recommend connecting a cheap source that you're not fussed about and then play some music or test tones at a decent volume from your source (test tones are best due to them being constant power). Set your DMM to AC 20V or similar then measure the power on both RCA input jacks (or just both channels of whatever input jack type you're using). Left and right should have the same voltage, if not you're problem is before the amp, if its the same move down the signal wires to the pot. I turn the pot to about 50% and then measure the voltage on the wiper (with the source still playing). Once again the left and right channels should measure the same (I recommend turning the pot half way because they are rather imbalanced in the first 10-20%). 
   
  Now you want to measure the AC voltage on the tubes plates (pins 1 and 6 on 12a_7 builds pins 1 and 2 on 19J6  builds) you should now see your amplified voltage and it should be very similar across both channels (allow a bit for valve differences). If it is the same continue this process if not go the note a. Next I would ask you to measure the AC voltage on the other side of the coupling capacitors C2 and C4, it should be the same as on the other side. Now, set your DMM to DC 20V and measure the voltage at the mosfet gates (in the same place as you took your last AC measurement). Once again they should be the same and about 16-17V for 12a_7s and 24V for 19J6s. If this is the case then switch back to AC and measure the output of the mosfet, where it connects to coupling capacitors C3 and C5. Once again report any difference you find here. If everything is still the same then check the voltage on the other side of these capacitors. If you still haven't found your problem then I would say to check your headphone jack for damage, beyond that I'd be at a loss.
   
  note a: So if your not getting the same voltage out of your tubes then check the plate voltage (same place as the AC signal but in DC this time) it should read around 24V for both channels. If it's not an issue and your tube heaters are correctly powered then I'd reckon that your left channel tube is damaged. To test this swap the left and right tubes around, the faulty channel should now have switch over (only swap tubes with the amp powered down!)
   
  Good luck with your debugging,
  Chris


----------



## DudeMyCans

I'm just casing up my MSSH which I've built to drive my DT880 600ohms. I was wondering if there's anything I should do to optimise it for high impedance phones.


----------



## cpdelc

Quote: 





tomb said:


> Could be a bad tube, have you switched them to see if the problem follows the tube?


 
   
  Did switched it but the left channel still won't sound up.. I suppose my tubes are okay, thankfully. 19J6 tubes are very rare these days 
   
  Quote: 





goobley said:


> Right, it's fairly easy to work along the signal path in this amp. There is of course a risk of shock when working on a live amp, so all the usual caveats... I'm not responsible for any harm you may do to yourself or if you set fire to your house... but honestly it's not a very dangerous amp (I did get a decent belt off one of the my big decoupling caps a while ago whilst trying to discharge it).
> 
> Carefully power up the amp with case open and the innards accessible.
> 
> ...


 
   
   
  Yes, both of the heater lights up.
  Will do the debugging as soon as I can get my DMM.. Lost it somewhere at home.. 
  Anyway, suppose I did get a broken Caps, I have to replace it on both channels right?
  And, sorry for the basic question, am I going to break the amp if I prod the DMM sticks at the wrong points? I'm a bit bad at reading schematics and deciding on where to prod. Hahaha. If it's the AC measurement I suppose it's safe, it's the DC measurements I am afraid with.


----------



## Goobley

You won't break things with a voltmeter unless you short across multiple wires with one of the multimeter probes. We can give you some ideas where to look if you post a picture of the inside of your amp.


----------



## KimLaroux

Just make sure your DMM's probes are *not* in the A socket, as this socket creates a short between the probes. Always leave the probes in COM and V.
   
  I know it's a noob thing, but I've seen people shorting circuits using their DMM with the probes in A instead of V.
   
  Also, it's been shown that cheap DMM can have an influence on the circuit. In V mode, the DMM has an impedance between it's probes. Cheap DMM can have relatively low impedance, which, when placed in parallel with high impedance circuits, will modify the electric characteristics of the circuit. One such circuit is the MOSFET bias. If you try to measure the voltage at the gate, chances are your DMM will change the bias and therefor not show you the actually bias the MOSFET operates at. You won't damage the circuit, but your measurements will be meaningless.


----------



## cj208

Does anyone know where I can buy the 19J6 tubes under 10ea
  also
  is there a way to have dual outputs on this amp so that me and a friend could use it or would I need double the components?
  and is there any Parts lists for this project with part numbers from mouser?


----------



## nikongod

Quote: 





cj208 said:


> Does anyone know where I can buy the 19J6 tubes under 10ea


 
   
  19j6 are basically extinct. Building an amp around them now is a very bad idea. 
   
  Just build it for 12au7. Really cheap 12au7 come in around $10 each, you have tons of options for tube rolling, and future availability should be very good thanks to the high popularity of the tube.


----------



## cpdelc

goobley said:


> You won't break things with a voltmeter unless you short across multiple wires with one of the multimeter probes. We can give you some ideas where to look if you post a picture of the inside of your amp.






kimlaroux said:


> Just make sure your DMM's probes are *not* in the A socket, as this socket creates a short between the probes. Always leave the probes in COM and V.
> I know it's a noob thing, but I've seen people shorting circuits using their DMM with the probes in A instead of V.
> Also, it's been shown that cheap DMM can have an influence on the circuit. In V mode, the DMM has an impedance between it's probes. Cheap DMM can have relatively low impedance, which, when placed in parallel with high impedance circuits, will modify the electric characteristics of the circuit. One such circuit is the MOSFET bias. If you try to measure the voltage at the gate, chances are your DMM will change the bias and therefor not show you the actually bias the MOSFET operates at. You won't damage the circuit, but your measurements will be meaningless.




I just opened it again and just realized that there were 2 stray cables. 1 from the left channel and 1 from the right channel. It's quite a mess.. Should I post the images here or can I email you instead?
Just 1 question first, is it correct that the number 4 pin from the tube goes to the ground? It seems that the problem is the soldering from previous owner.

Edit: Resoldered the stray cables. Still got the crackles on left. Strangely, sometimes the crackles dissapear for like 2 secs, then it come back. 
Btw, I also get humm noise on both channels, and the loudness of the humming depends on the position of the pots.

I'll make the photo of the amp as simple as I can so that you can help me easier


----------



## Grumus

Very inspirational thread! Right now I have HD598 phones and would like to build an amp. Will this amp be future proof for higher impedance phones and will it suffice sound wise further down the road?


----------



## ahshan06

grumus said:


> Very inspirational thread! Right now I have HD598 phones and would like to build an amp. Will this amp be future proof for higher impedance phones and will it suffice sound wise further down the road?




Future proof? Sure, until you meet Mr. Woo out on a fine afternoon stroll that is
High-Impedance? 600 ohms will still yield hearing damage
Recommend? Indeed

Cheers!


----------



## ahshan06

MSSH is now my workhorse; however, a friend has convinced me to look into building an all-tube amp (possibly based on the common 12a_7)

Any rec's for a schematic/build?


----------



## Grumus

Ahshan06 thanks for the reply! I think you just sold me on my first DIY amp


----------



## cpdelc

Grumus, this amp is actually strong enough to drive my high impedance beyers.. Go for it! Just be cautios that the 19j6 build can be troublesome, as the tube is very rare atm.. 

Btw guys, here is the pics of my amps guts. A bit messy though..


Spoiler: pic


----------



## DudeMyCans

I've built a MSSH to drive my DT880's and although I've only used it for 15mins or so as its not boxed up yet, they do sound good. I'm still looking at whether or not its possible to drive them directly from the speaker terminals of a power amp as well as I think that this may give them the voltages they need to really sing.


----------



## Grumus

I tried asking some questions in the stripboard thread but I think it's a bit dead right now so I'll try here! Before I order parts and get the iron hot I need abit of help. I will build the 12UA7 version.
 Source: Laptop
 Phones: Sennheiser HD598 (50 Ohm)
  
  
 1. Is there any advantages to using a ground plate and point to point wire it over a strip board? As I see it strip board is a sure way to reduce the length of wire used. Of course I will wire the rest as tidy as I can to my ability to reduce noise. Probably do a preliminary CAD design and place the parts out so I get a better feeling of it.
 2. I mostly sit at the computer when I use my headphones, which includes gaming, movies and music(=long hours). Can I use this amp for long sessions at the time since it gets hotter than 19J6 builds?
 3. What should I be looking for in heat sinks. What values do you recommend since I want to use it for long sessions at a time?
 4. Would it be feasible to hide the heat sinks inside the build with openings to let air in and out? (mainly for aesthetics)
 5. I have heard turning the amp on or off could release DC voltages straight to the phones damaging them. Is this true? If so is there a way to build in protection for this? I want the amp to sit pretty on my desk and just be turned on and off by anyone without problems.
  
 Appreciate any answers! Oh any particular advice to a first time builder? Looking forward to the build so much I am dreaming about it 
	

	
	
		
		

		
			




  
 Edit: stripboard thread is alive!


----------



## Captn Dave

nikongod said:


> 19j6 are basically extinct.




There are plenty of them on eBay now.


----------



## tomb

Quote: 





captn dave said:


> There are plenty of them on eBay now.


 
  At $15 - $25 a piece ... and I wouldn't call 6 listings "plenty."


----------



## Captn Dave

There are something like 20 tubes in total. How many amps do you want to build this week? 

The substitute tube, the 12au7 isn't free. The difference is the issue. Ten bucks? Well, tuition in the US has been trending upward since about the same year vacuum tube production was discontinued. I guess why its named for starving students.


----------



## tomb

Quote: 





captn dave said:


> There are something like 20 tubes in total. How many amps do you want to build this week?
> 
> 
> 
> ...


 
  20 is an optimistic estimate in that listing.  The 19J6's are out of stock in two of those listings. 
	

	
	
		
		

		
		
	


	




  Plus, there's only one in that listing that was below $13.49 and its shipping was $7.76.  You'd still have to buy another one from one of the other listings that are even more expensive.  Remember that buying NOS or used tubes is not like buying opamps - you may get 4 good ones out of 5 even if they claim "tested."  There are things that are not tested with most tube testers.
   
  Just saying that posting, "There are plenty of them on eBay now." is a bit misleading.


----------



## Captn Dave

I plan to build one of these amps. I'm putting together a mouser order now. It seems like a mistake to corrupt Mr. Millett's elegant design. The genius of his design is that it uses a very inexpensive power supply, with what was once an unloved tube with a very clever twist. Now the tube is better appreciated. Is that a reason to throw out the clever twist?

I have a poor opinion of the 12au7. It is not a very linear tube. There is one interesting outlier, the Conrad Johnson PV series of preamps. i was so surprised to learn that it uses the 12au7 that I once downloaded the characteristic curves, drew the load lines and operating points to see how they did it. That circuit operates with a high B+ and a very flat load line and about 2.4 ma current in order to operate in one of the very few linear regions. The modified design of this amp starts with a very low B+ and operates with a steeper load line and a fraction of the power. I just don't see it as sounding as good as the J6. 

My thinking is that if one wishes to build a headphone amp with a 6 or 12 v tube, there are probably better ways to do that.


----------



## tomb

Quote: 





captn dave said:


> I plan to build one of these amps. I'm putting together a mouser order now. It seems like a mistake to corrupt Mr. Millett's elegant design. The genius of his design is that it uses a very inexpensive power supply, with what was once an unloved tube with a very clever twist. Now the tube is better appreciated. Is that a reason to throw out the clever twist?
> 
> I have a poor opinion of the 12au7. It is not a very linear tube. There is one interesting outlier, the Conrad Johnson PV series of preamps. i was so surprised to learn that it uses the 12au7 that I once downloaded the characteristic curves, drew the load lines and operating points to see how they did it. That circuit operates with a high B+ and a very flat load line and about 2.4 ma current in order to operate in one of the very few linear regions. The modified design of this amp starts with a very low B+ and operates with a steeper load line and a fraction of the power. I just don't see it as sounding as good as the J6.
> 
> My thinking is that if one wishes to build a headphone amp with a 6 or 12 v tube, there are probably better ways to do that.


 
  No, I completely  agree with everything you've just said. 
	

	
	
		
		

		
		
	


	



   
  My only issue was with telling everyone that ebay was a plentiful source for 19J6 tubes.


----------



## Captn Dave

Okay, I guess that we can agree that their availability in somewhere in that narrow rage between extinct and plentiful. I'm going to hit the junk shops on Monday and see what I can find. I'll report back.

 BTW, how many do you want?


----------



## tomb

Quote: 





captn dave said:


> Okay, I guess that we can agree that their availability in somewhere in that narrow rage between extinct and plentiful. I'm going to hit the junk shops on Monday and see what I can find. I'll report back.
> 
> BTW, how many do you want?


 
  Heh ... if you find 50 or more, shoot me a PM.


----------



## KimLaroux

Btw I just placed an order at digikey... yet another for this project. Now I seriously need to find a name for this thing, because it'll not be a starving student any more after this upgrade.


----------



## Goobley

Are you separating the valve and mosfet power supplies then? It really is a great up grade drop a heat point of view and allows you to push B+ higher


----------



## KimLaroux

Yes, I'm going for ~30V for the MOSFETs and ~170V for the tubes. Though I'm not entirely sure what the B+ will end up at. I'll just build it and see what I can get. It should be between 150 and 200, so I'll just build the thing so it can operate within these values and tweak it after. I'll also build a tail CCS for each tube, and add global feedback. I think I'll aim for 3mA per triode, or 6mA per tube. I may tune this once I know where I can get the B+ at. It's kinda pointless to draw load lines when your B+ could be anywhere between 150 and 200... so I'm almost going in blind.
   
  College is keeping me insanely busy. I may not have time to do all this before next summer, and even then...


----------



## DudeMyCans

Sorry for multiple posts, as I've just posted this in the 'post photos of your build', but here's my attempt. Built with 19J6's.
   
   

   
  It's still unfinished as there's no sound in the right hand channel, but it worked ok when I first built it in a shoebox to test it, so hopefully it's nothing too serious. I'll post some better photos next weekend when I've finished it completely.


----------



## ProTofik

Hi. 
  I am not able to get capacitors mentioned in the original design "539-150104K100AA". Would it be ok if I will get these?
  In the original design it says "film capacitor 0.1uf - 0.22uF, 63V or higher". The one I want to buy seems to meet these criterias but they don't look like original ones. 
  It is safe to use them? I am building 12SR7 version.
  Thanks.


----------



## Goobley

Quote: 





protofik said:


> Hi.
> I am not able to get capacitors mentioned in the original design "539-150104K100AA". Would it be ok if I will get these?
> In the original design it says "film capacitor 0.1uf - 0.22uF, 63V or higher". The one I want to buy seems to meet these criterias but they don't look like original ones.
> It is safe to use them? I am building 12SR7 version.
> Thanks.


 
  Those replacements look just fine, I recommend the 220nF over 100nF if possible. Good luck with your build


----------



## ProTofik

Thanks for quick reply. 
  What's the difference between 220nF and 100nF and why is it better to get 0.22uf? Sorry for stupid question but I have no experience with electronic.
   
And one last stupid question. It doesn't matter which direction I will install them, right? I can't see "+" sing beside C2 and C4.


----------



## Goobley

The higher the input impedance of the current gain stage (in this case the mosfet) the smaller the capacitor (C2 or C4) needs to be, if the input stage has a lower input impedance the tube has to output more current , and in this case the lower frequency waves are limited by the size of the capacitor. I have personally found that the IRF510s can be quite variable in input impedance (before taking into account a mosfets high frequency roll off), so I very much advocate the decision that was made in the PCB version to bulk those coupling capacitors to 220nF, the cost difference is negligible at best and the larger values not going to have a noticeable sound colouring effect over the smaller ones, the difference just isn't great enough. All in all the caps keep the DC on both halves of the amp separated larger ones are more easily going to provide the best frequency response (no need to go over 220nF though).
   
  And yes, these capacitors are non polar, you can install them either way around.
   
  Cheers!


----------



## ProTofik

I will go for 0.22uF then.
  Thanks.


----------



## Makiah S

Bout 2 by one of these tuesday,  lets see how much better it is than mu silly little indeed


----------



## KimLaroux

Quote: 





protofik said:


> Hi.
> I am not able to get capacitors mentioned in the original design "539-150104K100AA". Would it be ok if I will get these?
> In the original design it says "film capacitor 0.1uf - 0.22uF, 63V or higher". The one I want to buy seems to meet these criterias but they don't look like original ones.
> It is safe to use them? I am building 12SR7 version.
> Thanks.


 
   
  For the price they ask, I'd recommend this instead:
   
http://www.ebay.co.uk/itm/2x-Capacitor-0-022uF-22nF-630V-DC-Polypropylene-Axial-Valve-Vintage-Metal-Film-/190787080008
http://www.ebay.co.uk/itm/5x-0-22uF-100V-Wima-MKS4-Metallized-Poly-Film-Capacitor-Radial-10mm-/170921769646
   
  Cheaper, and better suited for coupling audio signals.


----------



## scootsit

Tomb also sells those vintage paper in oil caps over on beezar. They are great for bypassing the output caps.


----------



## ProTofik

The one from first link are 0.022uF. Is that correct? I thought that they have to be between 0.1uF - 0.22uF.


----------



## KimLaroux

Quote: 





protofik said:


> The one from first link are 0.022uF. Is that correct? I thought that they have to be between 0.1uF - 0.22uF.


 
   
  AH! You're right! Sorry I thought they were .22uf. Ebay's search is just that lame.
   
  There's also these:
http://www.ebay.co.uk/itm/0-22uF-220nF-630V-Axial-Audio-Capacitors-5-pcs-for-Valve-Amplifiers-UK-STOCK-/121065832139
http://www.ebay.co.uk/itm/ICEL-MPW-0-22uF-10-400V-Capacitor-/270748103302
http://www.ebay.co.uk/itm/1-pair-2pcs-of-Mundorf-MCap630-Capacitors-3-630V-all-values-/160972125059
   
  Personally I used the last ones. But they may be overkill in this design. And if you consider shipping, they are expensive in this listing.


----------



## ProTofik

Thanks but I've already ordered these.
   
  My case is ready so once I will receive all the parts I will start making it.


----------



## DudeMyCans

I fixed the problem with the right hand channel on my MSSH. After some time troubleshooting it turned out to be a dodgy connection to one of the pins on the tube.

I now have it running of the output from my Roksan Caspian CD player and it sounds superb. Drives the Beyer DT 880's really well.


----------



## tdubl07

Hey guys,long time lurker on this thread and decided to finally build one. This is my first tube build and have to say it was a blast. Thanks to everyone who constantly update this thread with all of the updated info. I was gonna attach a couple pics but it's not letting me. Oh well I'll try back later.


----------



## tdubl07

OK here she is


----------



## Captn Dave

Congratulations on your first! That heat sink looks great. Does it run warm?


----------



## tdubl07

Quote: 





captn dave said:


> Congratulations on your first! That heat sink looks great. Does it run warm?


 
  Thanks man, it runs a warm but not ultra hot. I can set my hand on it and it doesn't get to terribly hot. It is warm though for sure 
	

	
	
		
		

		
		
	


	




 Question for you guys. The bass on my amp seems to be lacking with my dt990 pros compared to my little cmoy bb. Wondering if I upped the output caps if that would help some. It's definitely less bassy than my little cmoy, which I thought it would be the other way around. I'm gonna have a go at the millet mini max from beezar sometime soon so I can compare. Since it's my first tube amp I've ever heard and built, I'm not sure how they compare to solid state. Thanks again to everyone, this is just a blast building and tinkering. I love it!


----------



## Grumus

Does anyone know if there's a switch that goes:
 on1+on2   top
 on1          middle
 off            bottom 

 Would be nice to have on1= amp power and on2=L+R output. Would make it easier to use with plugged in phones. Just wait 30sek in the middle for start up and instant shutdown. All three pole switches I have seen have been on-off-on.
  
  Quote: 





tdubl07 said:


> I was gonna attach a couple pics but it's not letting me.


 
  You need to post 5-6 times before you can post pics. Don't forget the inside pics!


----------



## tdubl07

Oh the inside is a disaster. I need to clean it up before pics. Haha


----------



## tdubl07

grumus said:


> Does anyone know if there's a switch that goes:
> on1+on2   top
> on1          middle
> off            bottom
> ...


 how about just add dpst switch for the headphone jack. I just swing into radio shack yesterday and did that myself. Turn on the amp then turn on my headphones. Same with powering off. Just an idea


----------



## the_equalizer

Quote: 





tdubl07 said:


> Thanks man, it runs a warm but not ultra hot. I can set my hand on it and it doesn't get to terribly hot. It is warm though for sure
> 
> 
> 
> ...


 
  Congratulations on your build! It looks like quite a neat job!
   
  Your Cmoy BB is intentionally amplifying the bass frequencies more than it amplifies the rest of the audio spectrum; it is boosting the bass. On the other hand the SSMH is not intentionally emphasizing any area of the audio band.
   
  Increasing the value of the output caps in the SSMH will only increase the extension of the amplifier's frequency response, it will not increase the apparent volume of the bass frequencies.
   
  While it is certainly possible to add filtering circuits to the SSMH so that it boosts the bass, it should be more practical to check if your source offers equalization and boost the bass there.
   
  cheers!


----------



## tdubl07

Thanks equalizer. I figured that was the case. And thanks for your updated schematic! Without it this wouldn't have happened for me. Can read schematics fine, but designing/modifying is out of my league. Haha


----------



## Makiah S

Quote: 





tdubl07 said:


> Thanks equalizer. I figured that was the case. And thanks for your updated schematic! Without it this wouldn't have happened for me. Can read schematics fine, but designing/modifying is out of my league. Haha


 
  bought a Millet Max Hybrid in the FS forum [the Heat Sink on it is HUGE] it comes in today I'm super excited
   
  http://www.head-fi.org/t/650018/fs-12au7-starving-student-sold
   
  it came with 3 pairs of tubes
   
  rca clear tops n 5963 rca 12ua7s


----------



## Grumus

Very nice looking amp tdubl07! I am going for a similar design my self. Yes I will add a low and high gain switch as this thread suggests hissbuster and make it a high/off/low and use it for turning on and off while plugged in aswell


----------



## tdubl07

Quote: 





grumus said:


> Very nice looking amp tdubl07! I am going for a similar design my self. Yes I will add a low and high gain switch as this thread suggests hissbuster and make it a high/off/low and use it for turning on and off while plugged in aswell


 
  Thanks man, You will have a good time building this thing. My wiring is a mess, I'm actually embarassed it's so bad but it works perfect and you can't see it, so oh well. Maybe I'll redo it someday. It took me the entire day Saturday to build it, but that included drilling all the holes in my case as well which took some time. Also remember that the mosfets have to be insulated from ground. You can't ground the back of the mosfet out or it will blow, or so I've read. Thankfully I read that comment before I mounted mine. Good luck and have fun!


----------



## Captn Dave

I went searching the local shops for 19J6 tubes and picked up enough to share. I thought I post them in the sale/trade forum. Is there a minimum number of posts required to post there? I'm not seeing a reply box when I visit that forum.


----------



## scootsit

You aren't really allowed to make any money over there. But, Tomb may be interested, if you got enough, he was talking about starting selling a full kit with boards and the old enclosure, if he found enough tubes.


----------



## Captn Dave

I see. Tom mentioned 50. I thought he was joking!


----------



## Captn Dave

Scootsit, 

Thanks. I read the rules. There was a mention of knuckleheads. That's me. Thanks for the heads up.


----------



## scootsit

Quote: 





captn dave said:


> Scootsit,
> 
> Thanks. I read the rules. There was a mention of knuckleheads. That's me. Thanks for the heads up.


 

 I mean, it's okay to make a few dollars on a deal here and there, I think - the real point is to prevent people turning head-fi into a business. I will admit, that there are some deals I've made where I made a couple of dollars and probably even more deals where I've lost a few. I've come pretty close to breaking even. I think if you were to make those tubes available at or near to what you paid for them, many would be appreciative, and few would balk. But, I could be mistaken.


----------



## Makiah S

I got my Millext Hybrid in and it sounds nice! Although I'm sure EVERYONES sounds different since they are hand built and customized by each of u e.e still. I'm glad I bought one


----------



## Captn Dave

Scootsit, 

I think the point is they don't want members competing with paid advertisers. That's understandable.


----------



## tomb

Quote: 





captn dave said:


> I see. Tom mentioned 50. I thought he was joking!


 
  Actually, I was going to say 100, but I thought I might be just able to support another run if we had 50.  The original kits were based on lots of 30 kits.  However, that means you need _*60 PERFECT tubes*_.  You can't sell someone a kit and then say, "too bad you got a bad one - there are no more tubes."  The bad thing is with the 19J6 and its rarity now - about 1 in 5 tubes are bad right out of the box.  So, you really need 72.  Then there's the odd microphonic tube that doesn't show up in testing - you're up to 80-85, now, so with matching - you might as well make it 100.
   
  Keep in mind that a PCB run of only 30 PCB's will be fairly expensive.  The other parts are best bought at 100, too.  So if we only get 30, that's going to drive the cost up even more.  The original SSMH PCB kits sold for $120 with the machined case from Hammond, but we had at least 3 rounds  of 30 kits if memory serves - maybe 4.  Then again, *the number of tubes I had to support that when we started was 400*.  There's the proof, unfortunately: a single run of 30 kits means about 100 tubes.
   
  I still have about 2 dozen tubes - for the reason stated above.  I had to be certain that everyone who bought a kit had a pair of good, working tubes.  In my mind, that meant holding the extras for at least a year.  It's been longer than that now, but that's why I still have them and haven't sold them.
   
  Anyway, I thought we might think seriously about it if we found another 50 and I could add the ones I already had.  That's the practicality of the situation.


----------



## Captn Dave

Tom, 

I am finding about the same reject ratio. I have discarded two shorted tubes and set aside another two with low readings on one section and i have more to go. i intend to test in circuit and listen to those with low readings in one side to see if they are usable. Given the circuit design, it wouldnt surprise me. 

The Emerson branded seem to be the best for matching but in this application, with paralleled sections, I don't think that mismatching is a particular liability. Do you have an opinion on that? 

Have you used MYRA for boards? I have some Maida boards that they did. They were very nice and crazy cheap. 

I'm always looking for good SE and PP output transformers. I have quite a few of these and I'd trade with you if you have something interesting.


----------



## ProTofik

Hi again. I've almost finished my amp. I have one question. This is schematic that I'm using:
   
   

   
  I noticed that pins 4 and 5 are unused. Is it ok to leave them like this or I should connect these pins to the ground? 
  Thanks.


----------



## tomb

Quote: 





protofik said:


> Hi again. I've almost finished my amp. I have one question. This is schematic that I'm using:
> 
> 
> 
> ...


 
  Those are pins for the diodes features in the 12SR7 tubes.  The Millett Hybrid amp family (MAX, MiniMAX, MOSFET-MAX) uses tubes that have diode connections.  We tie them to ground.


----------



## ProTofik

Not sure if I understood you correctly.
  So in my amp I simply connect pin 4 and 5 to the ground, right?
   
  And one more question. My amp is almost finished. What pre-cautions I should take before plugging anything into it? 
  The only thing I can think of is to measure both AC and DC voltages on the output.


----------



## the_equalizer

Quote: 





protofik said:


> Not sure if I understood you correctly.
> So in my amp I simply connect pin 4 and 5 to the ground, right?
> 
> And one more question. My amp is almost finished. What pre-cautions I should take before plugging anything into it?
> The only thing I can think of is to measure both AC and DC voltages on the output.


 
   
  Yes, tie pins 4 and 5 to ground.
   
  Yes, you want to turn the amp on, with no headphones connected to it and measure DC volts on the output. If you have your meter hooked up while measuring the output you'll see up to three spikes, as the tube heater, power supply and output caps interact while the tubes warm up. After that, the DC volts should dissappear from the output.
   
  If you measure AC volts, hum and or noise can show up as low voltages AC at the output, even with the volume turned fully down.
   
  Congratulations on trying a 12SR7 build and be sure to post pics of your build with those cool octal tubes.
   
  cheers!


----------



## tdubl07

Hi guys, I went thru last night and shortened/tidied up my wiring a fair amount. I have a question. I get an audible hiss that does not change volume with the pot. So no volume I have the same amount of hiss as full volume. It's in amp, not input, because it happens weather or not a source is plugged in. It's not horrible but it's noticeable. When music is playing you really can't here it, but it still bothers me it's there. I've got everything grounded to my metal chassis nicely. I do not have the resistors R3/R9 for the FETs soldered to the FET pins directly, rather they are inside the chassis a few inches away. Could these be the problem, or is a little hiss in these amps just normal? Basically does anyone have the 12au7 build with zero hiss? This is my first Tube amp so I'm new to all of this 
	

	
	
		
		

		
			





. I'm going to start the mini max kit tonight so when that's done I'll be able to compare but I would still like to know about the hiss I'm hearing.
   
  Thanks Trav


----------



## vixr

Trav,   how is the pot grounded? Most of the hiss issues I've had were pot grounds...


----------



## tdubl07

I have the ground wire braided/twisted around the signal wires to the chassis ground in the same spot as all my other grounds, minus all of my direct chassis grounds from the dc jack, headphone jack, and inputs.


----------



## tomb

MOSFETs can actually oscillate quite easily.  It may very well be that what you hear is oscillation and indeed, the resistors need to be soldered to the pins.  That was a warning from Pete Millett in the very first post of this thread, I think. 
	

	
	
		
		

		
		
	


	




  That's just a guess, of course - only you can try it out and tell us for sure.
   
  As for Vixr's question, I don't think he's talking about the ground wire of your signal input.  Rather, the volume pot body itself must be grounded to the amp for many pots.  I don't think it would be a problem simply because you have the signal input ground twisted with the L & R leads. Although, two ground wires would be better. 
   
  It's hard to tell what you mean by "hiss."  Power supplies and lack of grounding can be a source of hum or ripple - that's usually around 60 - 180Hz.  Hiss is normally a much higher frequency noise and often results from a slightly unstable output - not enough resistance on the output of an opamp, for instance.  Oscillation can often be mistaken for exagerrated highs and a sometimes accompanying lack of bass.


----------



## tdubl07

Thanks guys. I'll try moving the resistors and hopefully that'll do it. The pot is indeed grounded straight to the chassis and all my jacks/inputs are grounded to the chassis as well. I ground off the paint in all those places so they have good grounds. Now that I think about it, I have a question. My rca inputs are grounded to the chassis and then I have a wire going from the rca ground to all other grounds in the amp. They all connect to the rca ground/chassis at the same point. That in essence is my star ground point. Is this a bad thing and do I need to isolate the rca's instead as well as my headphone jack? In other words every single input/output jack is grounded to my chassis. I ground down all the paint around all jacks/inputs to make a good ground connection. But maybe that's why I'm getting hiss? I thought that would be a good thing when I was drilling the holes in the chassis. Hopefully with some more experimenting I can quiet it down some more. Because besides the hiss it sounds great. Tom got the mini max in and ready to be built tonight. Nice kit sir! Although I broke one of the tube sockets last night trying to drill it out. Got one out successfully, the other broke. So ordered new ones from you already 
	

	
	
		
		

		
		
	


	




 Darn things are fragile.
   
  Thanks Trav


----------



## tdubl07

Hi guys. I fixed my hiss. I'm thrilled. I ran the ground of the first big capacitor after the switch back to the dc jack directly instead of tying into all the other grounds and that did it. And it sounds better to boot!


----------



## vixr

awesome...I used the copper clad and just soldered every ground straight to it...


----------



## tdubl07

Quote: 





vixr said:


> awesome...I used the copper clad and just soldered every ground straight to it...


 
  Yea I used a hammond metal enclosure so I figured I could just ground everything to the chassis. Thanks for the help man.


----------



## KimLaroux

Quote: 





tdubl07 said:


> Hi guys. I fixed my hiss. I'm thrilled. I ran the ground of the first big capacitor after the switch back to the dc jack directly instead of tying into all the other grounds and that did it. And it sounds better to boot!


 
   
  This is how I fixed the hiss in my build too. Power decoupling capacitors should not to connected to the star ground. They have to be connected directly across whatever they decouple. Reservoir caps work the same way: they essentially decouple what is after them from what is before them.
   
  I originally had all the capacitors in my PSU connected to a star ground, and it was noisy. I rebuilt the PSU with the ground going from one cap to the next, and the noise was significantly lowered.
   
  You did a great job on the case work. I like how you maintained the same color scheme trough out. It looks clean and professional.


----------



## tdubl07

Thanks for the kind words Kim. Chilling out listening to my new hiss free amp as I type this. My case is nice and simplistic, definitely not as cool looking as yours though!


----------



## tomb

Quote: 





tdubl07 said:


> Tom got the mini max in and ready to be built tonight. Nice kit sir! Although I broke one of the tube sockets last night trying to drill it out. Got one out successfully, the other broke. So ordered new ones from you already
> 
> 
> 
> ...


 
  Shipped them out Friday!  Yeah, drilling the sockets can be a pain sometimes.  I've tried the screwdriver-prying method, too, but the gold-pin sockets seem a lot more "fixed" than the silver ones.  The silver-pin ones we used for the SSMH could be pryed open without damage - most of the time.


----------



## Grumus

I have a question. I just ordered all the parts for the 19J6 build because I got two tubes for 12 dollars. But if they don't work or I need to replace them in the future I might have to rebuild it for 12AU7 if I can't find any 19J6s. Will the mounting holes for the tube sockets line up between the 9pin and 7pin? I don't want to wreck the case if the mounting holes aren't the same. Should I just buy the parts for 12AU7 and then drill and build everything according to that from the start?


----------



## tomb

Quote: 





grumus said:


> I have a question. I just ordered all the parts for the 19J6 build because I got two tubes for 12 dollars. But if they don't work or I need to replace them in the future I might have to rebuild it for 12AU7 if I can't find any 19J6s. Will the mounting holes for the tube sockets line up between the 9pin and 7pin? I don't want to wreck the case if the mounting holes aren't the same. Should I just buy the parts for 12AU7 and then drill and build everything according to that from the start?


 
  A 9-pin socket is bigger than a 7-pin one. So no, the mounting holes will not line up.  If you are simply punching holes for the tubes in the top of the case, as in with a PCB- or perfboard-mounted sockets, then the same hole that the tube pokes through can very easily accomodate a 9-pin tube.  1" is a good diameter that will work for both.
   
  If you're mounting the sockets to the case, you won't have an issue, either.  Drilling out the hole to accomodate a 9-pin tube socket will "clear out" the 7-pin socket's mounting bracket holes.  This is easily shown comparing the dimensions of the most-used new-manufacture ceramic sockets:

  (7-pin socket pic from vacuumtubesinc.com)
   
  and this one:

  (9-pin socket pic from vacuumtubesinc.com)
   
  Here are the comparative dimensions:
   
  9-pin:
 22mm hole
 28mm on-center mounting holes (2)
   
  7-pin:
 16mm hole
 22.5mm on-center mounting holes (2)
   
  As you can see, drilling out the hole for the 9-pin socket in the future would leave 1/4mm of the 7-pin bracket mounting holes on either side of the socket hole (22mm hole for the 9-pin socket vs. 22.5mm on-center mounting holes for the 7-pin).  That's not enough to even worry about.  You will also have to drill new mounting holes for the 9-pin socket, but the socket's top rim, bracket, etc. will cover any overage.


----------



## vixr

Mechanical Engineers rock...


----------



## tomb

Quote: 





vixr said:


> Mechanical Engineers rock...


----------



## Grumus

I was looking at the different specs for tube sockets and wasn't enterly sure I got the right ones, thanks alot for clearing that up!  I will probably mount them with the bracket on the opposite side witch leaves me with a problem. The longest distance the mounting holes will make is 25-25,5mm and even more if i countersink the screws. So maybe my best option is to make an adapter and use the 28mm on-center holes. It's going to be one small adapter though! (28-22,5)/2 = 2,75mm wont leave enough space for two screws so it has to be glued on. Maybe I should just glue it on without holes from the start.


----------



## Shrew

nevermind, found good deal on tubes


----------



## ProTofik

Hoo kay. So my 12SR7 starving student is done. I wanted to post some pictures for you guys.
  I would like to point out that this is my first ever tube amp and first ever DIY project of any kind so please be nice to me 
   
  So here is the case I decided to use for my amp. This is an aluminium case that my external HDD used to be in. 
   
   

   
   
  Modding just the case took me a few hours.  I drilled few holes in top cover for pot, mosfets and tubes. I also repainted it. I am not happy with how the side panel looks like but I couldn't manage anything better with my skills. 
   
   

   
  So I soldered everything together and... it didn't work. I checked everything once again and I found few stupid mistakes that I've made. I corrected them in less than few minutes and the amp started to work.
   
  My cable manag... let's skip this part... I still need to work on that one.
   

   
  Anyway, here is how it looks like finished:
   
         
   
   
  I measured the output impedance. If I calculated everything correctly then it is 2.63Ohm.
   
*The sound: *
  I was listening to it just for a couple of hours but I think I can give you my brief impression. My setup was ODAC-Student-HD600
  I don't have much experience with amps, especially tube ones (this one is first I've ever been listening to) so I will be comparing it to ODAC/O2 combo.
   
  The sound is more fun on my HD600. There is definitely more bass that seems to have better punch (like HD650? maybe even better). I'm not a person that like bassy amps/dacs/headphones/anything but I must admit that this amp makes my HD600's bass very nice to listen to.
   
  Midranges seems to be a bit quieter than with O2 but they still sounds quite good. 
  Treble sounds like it's being a tiny bit emphasized but they still sounds very well. 
   
  The overall clarity and amount of details through this amp is definitely worse than O2 but I still like it. "Normal" music such as Gorillaz, Eurythmics, Europe or Depeche Mode sounds very enjoyable and for this kind of music I prefer student over O2. This amp is definitely more forgivable for bad recordings than O2. However for classical music, metal or any kind of instrumental music I prefer O2. I hope you get what I mean 
   
  So that were my impressions for now. I hope you like it.
  Now I have one technical question to you guys. Is it normal that the heatsinks are getting really warm? I don't want to sound paranoid but I am getting a bit worried...


----------



## KimLaroux

Looking great. Well done.
   
  One thing I noticed is the ground wire on the pot. It may be cleaner to run this wire directly to the RCA sockets, instead of having the signal return path go trough the enclosure. It is preferable to ground the enclosure at a single point, and keep the signal and power ground separated for as long as possible. 
   
  And yes, the heat sinks do get hot. Just about everybody who built the amp write about it. I use a fanless, slot socket, Pentium II heat sink to keep mine cool. And even then... it's great to keep your tea warm! 
   
  Funny thing about the genre of music you prefer... It's the other way around for me. I prefer Electronic trough my NFB-12 and classic, instrumental music trough the tubes. 
   
  It's also normal that the amplifier is bassy at first. It's a well known phenomenon with tube amps. Apparently it has to do with capacitor burn in.


----------



## ProTofik

Thanks. I will re-wire the pot ground cable soon.
   
  If I would ever happen to build another student I will use larger heatsinks. Because my case is aluminium and there is a direct contact with heatsinks the case is getting quite warm but guess that it's a good thing.


> It's also normal that the amplifier is bassy at first. It's a well known phenomenon with tube amps. Apparently it has to do with capacitor burn in


 
  I hope it would take a long time. I acually enjoy this bass.
   
   
  I've heard that 12SW7 tubes sounds almost the same except that the mid-range is not muffled. Can anyone confirm?
  I have one more question. What power supply you can recommend for my amp? For now I am using 3 different PSUs connected in series to get 48V 
	

	
	
		
		

		
		
	


	




 I was thinking of getting this one.


----------



## KimLaroux

If you're asking me about a PSU... wrong person to ask. 
	

	
	
		
		

		
		
	


	



   
  Conversely:
http://www.ebay.co.uk/itm/2A-SECONDARY-120VA-TRANSFORMER-WITH-30-0-30-VAC-OUPUTS-/250970010874
http://www.ebay.co.uk/itm/TEXAS-INSTRUMENTS-TL783CKCSE3-IC-ADJ-REGULATOR-HIGH-V-/170998399847
   
  It's actually a good thing that your case is getting warm. It means the whole enclosure is being used as an heat-sink.


----------



## tdubl07

Protofic nice build man! Looks like it came out great. I think it looks pretty cool! Like that case a lot. Good job


----------



## ProTofik

I'm glad you guys like it.
   
  I did a bit of cable managament. I got rid of most of the electric type and used hot glue instead. It's still not perfect but definitely better than before.
   
   

   
  As *KimLaroux* suggested I rewired pot's ground to RCAs and the buzzing noise that I heard before is gone. The amp is almost dead silent now.
   
  If you wonder why I changed C1 capacitor then here is the story.
  I accidentaly connected the power supply incorrectly (swapped + with -) and it exploded...


----------



## KimLaroux

Glad that was the issue. It's a common mistake when one begins in audio to think that "ground is just ground" and connect things to the closest ground point they can find. Turns out grounding is one of the most tricky, if not THE most tricky part of any audio design. Looking at your build, it looks like you're used to grounding stuff in cars.  There's a whole ideology in electronic audio where the enclosure should only serve as a shield, thus being grounded at a single point, and never ever carry any current. Some go as far as create separate "ground" rails for signal and power, and keep each of them as a mirror of the V+ it's referred from. They connect these together at a single point. It helps to keep return currents from "hijacking" each others.
   
  Have you measured the resistance of the enclosure between the different ground points you're using? It may be less reliable than you think.
   
  The black wire with a red line on it grounded to the lower right corner, is this the ground of the RCA? If yes then I'd recommend grounding it to the same screw as the DC input ground, or simply getting rid of it and adding a wire between the ground on the pot and the closest tube's pin 5 (assuming pins 5 are grounded, and not 4). You may want to try both these scheme and compare them. I know I did and the result wasn't the same.
   
  What's the use of those 5W ceramic resistors?


----------



## ProTofik

> it looks like you're used to grounding stuff in cars.


 
  I don't even have a car. I couldn't get used to anything because this was my first DIY electronic project ever.
   
   


> Have you measured the resistance of the enclosure between the different ground points you're using? It may be less reliable than you think.


 
  I can do it but it wouldn't mean anything to me. I don't even know ohm's law.
  I am able to read schematics and use soldering iron quite well but I have no idea how this stuff works. 
	

	
	
		
		

		
		
	


	



   
   
   


> The black wire with a red line on it grounded to the lower right corner, is this the ground of the RCA? If yes then I'd recommend grounding it to the same screw as the DC input ground, or simply getting rid of it and adding a wire between the ground on the pot and the closest tube's pin 5 (assuming pins 5 are grounded, and not 4). You may want to try both these scheme and compare them.


 
   
  I didn't ground pins 4 and 5. I simply forgot to do it. I will rewire the black-red cable to DC jack's ground tomorrow and see how it goes.
   
   
   


> What's the use of those 5W ceramic resistors?


 
  When I asked my friend to check if this schematic is correct he suggested me to put these resistors in there because he was afraid that too much voltage can go through tube's heater.
  With these resistors the heaters work on 11.5V. I tried run the amp without these resistors and the heaters were getting 12.5V which is ok but since it work on lower voltage I prefer to leave it this way (if it's safe). I don't know if it affects the sound anyhow. I haven't got the time to test it.
   
  Here is my schematic:


----------



## KimLaroux

It's alright, we all start somewhere. I wasn't much more knowledgeable than you are now when I built my SS. And that was not long ago.
   
  As for the heater's voltage, if your friend had read the datasheet for the 12SR7 he'd learned the heaters are rated for 12.6 V. So the 12.5 V you had was spot on. They also tell you it's safe within 10% of this voltage, so it'll be just fine with anything between 11.3 V and 13.9 V. These tubes were designed to be used in cars, so they have heaters able to work on a wide range. If my math is correct, your heaters should really be seeing 11.0 V. This may be too low.
   
  And if your friend studied the schematic correctly, he would have learned that you can change the heater voltage by simply changing the voltage at the gate of the MOSFET. No need for a 5 W resistor when a normal 0.25 W would do. 
	

	
	
		
		

		
		
	


	



   
  And about the pins 4 and 5... I forgot you built a 12SR7 version! In your amp, pin 5 (ground) becomes pin 8 and pin 4 (heater supply) becomes pin 7. In the 12SR7 pins 4 and 5 are diode plates.... *Do not ground those pins!* Leave them as they are!


----------



## ProTofik

Well, my friend told me that 6Ohm resistor would be perfect but I couldn't get one so I installed 10Ohm and it works.
  I will measure what I am getting in there tomorrow, just to be sure.
   
  My experience with PCs tells me that if something works on lower voltage it would overheat less and lasts for longer. Does it work like this for tubes as well?
   
  Edit:
  I soldered this black-red cable directly to DC socket and the buzzing is still there but even quieter than before. I am happy with it.
  The voltage on heaters is 11.6VDC.


----------



## Grumus

I just completed my amp but it won't start. When I turn it on my power led flashes periodically but does not stop even after 2min. I built the 19J6 version with the uppdated optional parts. I tried using one tube at the time and no tubes but it still flashes on and off.

 The tab on the mosfets were isolated from ground before I soldered anything to them but now they are connected even when fully off from the casing. Is this normal?

 I have checked the wiring but can't see anything wrong with it. The powersupply I am using is this one http://se.mouser.com/Search/ProductDetail.aspx?R=GS25A48-P1Jvirtualkey63430000virtualkey709-GS25A48-P1J which is rated for 0.52A so that should be enough for the amp + 1 led that i run from a 10k resistor. 
   
   

  Edit: Picture added


----------



## KimLaroux

Quote: 





grumus said:


> I just completed my amp but it won't start. When I turn it on my power led flashes periodically but does not stop even after 2min. I built the 19J6 version with the uppdated optional parts. I tried using one tube at the time and no tubes but it still flashes on and off.
> 
> The tab on the mosfets were isolated from ground before I soldered anything to them but now they are connected even when fully off from the casing. Is this normal?
> 
> ...


 
   
  The tab is connected to the drain, which is connected to V+ in the MSSH. So if there's conductivity between the tab and the case, it means your V+ rail is shorted to the case somewhere. What's confusing is the LED still works. For the LED to work, the short must not be a perfect 0 ohm short. A 0 ohm short would not allow the LED to turn on. What's the impedance between the tab of the mosfet and the case?
   
  My first thought was maybe there's a short downstream of R13, but even a shorted R13 would not be able to overload the PSU. You need a short less than ~90 ohm to overload your PSU.


----------



## Grumus

I have not found the short yet. The resistance between the tab and case seems to be 560 ohm. My ddm is very cheap but around there anyways. 

When it's tuned on the led cycles with the psu fully on and fully off ever 1-2 seconds. When I then shut it off it stays on abit dim until the caps is discharged.

Edit: Solved the issue. I had connected pin 3 and 4 together last night... Well I am happy I found the problem, thanks for the help KimLaroux! 
Pics coming later.


----------



## Grumus

This was one fun amp to build! Thanks for all the help and the vast amount of knowledge there is in this thread. I sure learned a thing or two building this amp and I am sure it will come in handy for future builds. 
	

	
	
		
		

		
			





 So far it has paired up great with my HD598 and thanks to this thread it's dead silent. The gain switch is a hissbuster with an off position for turning the amp on and off. The text is etched in to the aluminum.
   
   

   

  RCAs and 3.5mm input
  

  On/Off Led is abit on the bright side with 10k resistor might add another resistor to dim it down some.
  

  The tubes were alot brighter than I first thought!


----------



## KimLaroux

Wow it looks great! I like what you did with the faceplate - except the blue LED. It just clash with the rest of the design. An orange LED would have been cleaner.
   
  Glad you found the issue. It's always satisfying figuring things for yourself. Great way to learn.
   
  You even countersunk the screws... nice attention to details.


----------



## livewire

What a beaut! Nice to see that 19J6's  are still showing glowing up.


----------



## Grumus

Thanks Kim and livewire for the kind words! 
	

	
	
		
		

		
		
	


	




 I am with you on the led, it's too bright and blue does not fit in with the glow of the tubes. 
  I was extremely lucky to find the tubes. They come from a radio museum 5 minutes walk from my collage, never thought I would find a source of 19J6 that close. Unfortunaly they only had 2 of the same and 3-4 odd ones, not a box full of them as I hoped. I asked them if they would know of another possible source here in sweden but they couldn't think of any.


----------



## DudeMyCans

Deleted.

(Had submitted a reply to Grumus, but realised KimLaroux and live wire had beaten me to it).


----------



## DudeMyCans

I've been wondering if there'd be any value in building a 48v linear PSU for this amp rather than the standard switch mode unit. Has anybody tried it?


----------



## KimLaroux

I did, but since I've never tried the SMPS, I can't tell if it's actually an improvement.
   
  If done badly, as were my first couple of layouts, then it'll be worse.
   
  If done correctly, as is my current version, then it's probably overkill.
   
  Personally, I did it because I already owned a usable transformer. It's the whole reason why I built a Starving Student, actually. Building a vanilla SS using an SMPS seemed boring to me. Designing and building a linear power supply for it was the challenge that motivated me to build the thing.
   
  If you were to buy parts to build a 48 V linear supply that would actually perform better then the SMPS, you'd probably spend more money on the power supply itself than the rest of the amplifier.
   
  Not to mention the added complications of introducing AC inside the enclosure. You have to be very careful with your physical layout, and may be forced to use either a very large enclosure to keep things far apart, or place metal shields between the modules. I built everything in point-to-point, even the power supply. It's good to have a schematic, but a schematic is no guarantee of performance. The physical layout, the way you build the schematic, will have a significant impact on performances. It took me many revisions, in which I rebuilt everything, before the power supply performed to an acceptable level. I also had to build ferrous cages around the tubes to shield them from magnetic coupling from the transformer, and I'm using a shielded transformer.
   
  I have the opinion that the Starving Student is the "Cmoy" of tube amplifiers. You can power a Cmoy using a Sigma 11, but it'll still just be a Cmoy.


----------



## DudeMyCans

Fair enough, thanks Kim. Maybe I'll leave it for a while !


----------



## jarscar

Hi all, I just got a huge assortment of tubes, and it made me want to really try building this amp. A lot of these tube boxes are mislabeled but just from what I've gone through I've got:
   
  2 pair of 12SR7s, but they look a tad rusty but two look fine
  3 12AH7-GTs (in so-so condition)
  an assortment of 6SN7-GTs,
  and 2 beautiful 12SN7-GTs.
   
  The 12SN7-GTs are the nicest looking of the lot and are probably in the best shape, they look brand new. But I know next to nothing about tubes(so these might be terrible for this project for all I know) and I'm not confident enough to go modifying the 12AU7 schematic too much on my own. My question to anyone here who might know, which, if any of these would be best to use and how would I go about applying them to the existing circuit. Or should I just buy some 12AU7s and shelve all these? Thanks in advance!


----------



## DingoSmuggler

Quote: 





jarscar said:


> Hi all, I just got a huge assortment of tubes, and it made me want to really try building this amp. A lot of these tube boxes are mislabeled but just from what I've gone through I've got:
> 
> 2 pair of 12SR7s, but they look a tad rusty but two look fine
> 3 12AH7-GTs (in so-so condition)
> ...


 
  I believe there is a 12SR7 version of the MHSS floating around somewhere, but I might be getting confused.
   
  EDIT: I wasn't getting confused, its back on page 189, courtesy of Logistic


----------



## ProTofik

I made 12SR7 based student. The schematic for it is like 2-3 pages back.


----------



## HolyCheese

How about PCC189 or 6H23p rocket tube russian tubes?


----------



## JBal4

Hi I am very new to headphone amps and was going to try this build. i was wondering how hot the amp will get? the reason i am asking is to understand what kind of materials i would be able to use for the case/body. any help would be greatly appreciated, thanks everyone.


----------



## jarscar

Quote: 





dingosmuggler said:


> I believe there is a 12SR7 version of the MHSS floating around somewhere, but I might be getting confused.
> 
> EDIT: I wasn't getting confused, its back on page 189, courtesy of Logistic


 
   
  Thanks, I'll most likely end up doing that build, I was kinda hoping these 12SN7-GTs would work because they're the best looking/condition tubes I've found in my pile, but for the sake of simplicity I'll probably just use the 12SR7s or even buy some 12AU7s


----------



## DingoSmuggler

Quote: 





jarscar said:


> ...I was kinda hoping these 12SN7-GTs would work because they're the best looking/condition tubes I've found in my pile...


 
  The tube parameters for the 12SN7  are quite similar to the 12AU7 *BUT* the heater current is double, being at 300mA, not the 150mA of the 12AU7 (or 12SR7). Because the heaters are used in the biasing of the mosfets, this makes the 12SN7 impractical.


----------



## KimLaroux

Actually the MOSFET would not care, as they are biased using voltages and not currents. You'd just have to use very large heat-sinks. The problem is the PSU already has troubles with the 150 mA heaters, so doubling the load is out of the question in the default setup. You could do it with a larger PSU, say 1 A. But the thing would be dissipating so much heat you could make your breakfast on it.
   
  I say go with the 12SR7. Not only will it be easier to build,  you won't need to add shields to the tubes.


----------



## unhinged17

Nice!  Looks like a good weekend project.  Thanks Pete!  And thanks for all the great priceless technical books on your website!!!


----------



## proid

Sorry for my silly question but can the MSSH modify to using only 1 tube like the other simple 12au7 hybrid amp?


----------



## KimLaroux

I believe it does. It is is my plans to build a single-tube starving student next. If you know what you're doing and can do the maths, it should not be very complicated. But then the circuit would be so much different that you're probably better off just building the "super simple" amp.


----------



## tomb

Just an FYI, but after personally testing thousands of dual-triode tubes with my years at Beezar, single-tube designs are a dead end.

The triodes in a dual-triode tube probably match within 10% about every 1 in 10 tubes. Finding one is the exception, not the rule. You can adjust somewhat with trimmers for the biases, but you'll never be able to fully compensate for the differing outputs.

EDIT: fixed the spelling from my lousy Droid.


----------



## vixr

Quote: 





tomb said:


> Just an FYI, but after personally testing thousands of dual-triode tubes with my years at Beezar, single-tube designs are a dead end...


 
  I built this Single tube Amp for grins, mostly because I had all the parts and a few pieces of copper clad left over, and it sounds OK...I have an ancient Mullard 12AU7 I have been running in it and it's not bad...the brand new JJ sounds like crap, it must be what you are talking about...


----------



## the_equalizer

Quote: 





proid said:


> Sorry for my silly question but can the MSSH modify to using only 1 tube like the other simple 12au7 hybrid amp?


 
   
  Quote: 





kimlaroux said:


> I believe it does. It is is my plans to build a single-tube starving student next. If you know what you're doing and can do the maths, it should not be very complicated. But then the circuit would be so much different that you're probably better off just building the "super simple" amp.


 
   
  I agree with the last part of KimLaroux's statement. A characteristic design trait of the SSMH is the use of the tube heaters as loads for the output MOSFETs. Using a single tube rules out that possibility and leads to a different design like the "super simple" amp pointed out by KimLaroux, which I believe is the same one which Vixr built. 
   
  cheers!


----------



## KimLaroux

Actually, you can still use the heaters the same way as they have a center tap on the 12AU7. Ground the center tap, and use each end for each channel. The problem, of course, is that you now only have 6 V bellow the MOSFET, which may not be enough. You'd have to add a resistor between the heater and the MOSFET to bias the MOSFET up.


----------



## the_equalizer

Quote: 





kimlaroux said:


> Actually, you can still use the heaters the same way as they have a center tap on the 12AU7. Ground the center tap, and use each end for each channel. The problem, of course, is that you now only have 6 V bellow the MOSFET, which may not be enough. You'd have to add a resistor between the heater and the MOSFET to bias the MOSFET up.


 
  I know about the center tap... I hadn't really dedicated much thought to this topology but now that I think about it I guess you're right. In the "normal" SSMH configuration, with one end of each of the two separate heaters connected to ground, it looks electrically equivalent to a single center tapped heater with the center tap connected to ground, yes.
   
  About the 6 volts, well, you can always use a lower supply voltage for the MOSFETs, say, 24V. That would keep the voltage drop across the MOSFET at 18V and supply the 6V for the tube heater.  
   
  You could even try 6J6 tubes that way, just scale the MOSFET heatsink for the 450mA heater current!!!


----------



## jarscar

Ok I got everything built and done, put the tubes in and fired it up, clear as a bell out of the left side, right side I hear just a hint of sound, the MOSFETs seem to heat up and the tubes light up, I basically rebuilt the whole right side in case I had a bad connection or got a wire in the wrong place but same problem. I checked the voltage at the MOSFETS and both seem to be OK and I seem to be getting the same voltages for everywhere I'd think the voltages should match. 
  An odd thing I noticed is that I was using earbuds to test it and they actually got warm, Is it normal to get 9 volts at the headphone jack? I consider myself fairly good at reading schematics and considering quite a few people have used this project as an entry into this kind of thing I'm bummed I'm having this much trouble with it. I regret using an enclosure on the smaller side as I basically have to undo certain parts just to work easily on other parts(all said and done it fits perfectly though). 
  If anybody can shine a light on what my shortcomings may be I'd be forever in their debt. Thanks.


----------



## DingoSmuggler

Quote: 





jarscar said:


> Ok I got everything built and done, put the tubes in and fired it up, clear as a bell out of the left side, right side I hear just a hint of sound, the MOSFETs seem to heat up and the tubes light up, I basically rebuilt the whole right side in case I had a bad connection or got a wire in the wrong place but same problem. I checked the voltage at the MOSFETS and both seem to be OK and I seem to be getting the same voltages for everywhere I'd think the voltages should match.
> An odd thing I noticed is that I was using earbuds to test it and they actually got warm, Is it normal to get 9 volts at the headphone jack? I consider myself fairly good at reading schematics and considering quite a few people have used this project as an entry into this kind of thing I'm bummed I'm having this much trouble with it. I regret using an enclosure on the smaller side as I basically have to undo certain parts just to work easily on other parts(all said and done it fits perfectly though).
> If anybody can shine a light on what my shortcomings may be I'd be forever in their debt. Thanks.


 
  No! You shouldn't have any DC voltage at the headphone jack at all. 9V will cook your headphones in a fairly short space of time.
  For anyone building any headphone amp, always measure the DC offset before connecting headphones, it should be less than 10mV for almost any design.
   
  The output capacitors - C3 & C5 should block any DC from the output. Check that you haven't shorted out the leads of the ride side output cap, or it may even be internally shorted and need replacing.
   
  If you did have a large DC current across the right side earphone, this will magnetically saturate the earphone, preventing the smaller AC signal (the music) from actually making any sound. So what I'm trying to say is, the output capacitor short might be the only thing wrong.
   
   
  If you can't find the issue, how about some pictures.


----------



## jarscar

Quote: 





dingosmuggler said:


> No! You shouldn't have any DC voltage at the headphone jack at all. 9V will cook your headphones in a fairly short space of time.
> For anyone building any headphone amp, always measure the DC offset before connecting headphones, it should be less than 10mV for almost any design.
> 
> The output capacitors - C3 & C5 should block any DC from the output. Check that you haven't shorted out the leads of the ride side output cap, or it may even be internally shorted and need replacing.
> ...


 
  Thanks, I'll look after work. If I had to be honest then I'd have to say that last part, with the parallel capacitors(one electrolytic, one not), threw me for a loop at first. I looked at the original P2P builds from earlier in this post and tried to match the wiring but I probably just have it wrong. I'll check those capacitors, make sure I didn't get the polarity backwards, I did it kind of late and I think for a while I began to go mad. Thank you for your help.


----------



## jarscar

Yup, had my capacitor polarity off, works fine now, have a pretty ugly hum though, I've got a couple ideas what that is though, a little more tinkering and I think I've finally got a winner! Thank you so much for the help, I have only asked a couple questions but I can't help but me a little moved by how nice and helpful you guys have been, thank you.


----------



## jarscar

Looks like I was a little too optimistic about that buzz/hum, I checked all my soldering, made sure nothing was shorting, checked and rechecked voltages, made sure everything was properly grounded, etc etc. 
   
  The buzz/hum is only in the the right ear and is independent of the volume, if I put my headphones on and turn the amp on then as soon as it warms up the buzz shows up, audio plays clearly along with the buzz. Also the buzz never gets louder as the volume is turned up either, likewise for all the way down. It is loud enough that I can't ignore it, it imposes on music.
   
  There is a second, more normal volume related hum as the volume gets louder I begin to hear, it goes away if I touch the inner enclosure where there is no paint, is there a more permanent solution to that? The case itself is a ground according to my multimeter.
   
  I'm quite proud of how it's turned out, regardless of the problems. If I could get rid of that buzz then I'm home free. The sound on this thing is pretty amazing though, I wasn't sure what to expect, but it's more than just "louder" music, a simple MP3 took on a whole new life.
   
  I was going to attach pictures but I keep getting an error message, I'll try again later.


----------



## ProTofik

I had similar problem. I had to ground RCA inputs, Headphone jack and pot directly to the DC jack's ground. Before that I had connected these things to different part of enclosure and it was causing buzzing.


----------



## KimLaroux

I believe your grounding scheme is not efficient enough. It's kind of a common problem here, as it's usually a first project for most of us. You have to think of the ground as a return path for different signals, and not as a "neutral" point where everything gets nullified. Ground is nothing more than the opposite of the power rail, after all. A perfectly silent tube amplifier uses a balanced wiring for V+ and Gnd throughout the amplifier, with proper decoupling at each stage.
   
  The voltage you get at any single point is in reference to the ground at the other side of this point. If that ground point is noisy, the end result is the same as if your V+ was noisy.
   
  Power supply grounds are noisy. Signal grounds are sensitive to noise. Therefore, make sure the power return paths are not going across your signal return paths. 
   
  This is why the first recommendation most people have is to tell you to use a Star Ground. Connect all your return paths to a single point. Connect this point to the power input jack using a single wire. Connect the star ground to the chassis at a _single_ point, making sure no current flows trough the enclosure. This is not a car, it's an audio device. The enclosure should be used as nothing more than a shield.
   
  I had to rebuild my whole amplifier many times to learn all that. Now it's dead silent.





   
  ps: You can't upload pictures yet because you don't have enough posts.


----------



## jarscar

Quote: 





kimlaroux said:


> I believe your grounding scheme is not efficient enough. It's kind of a common problem here, as it's usually a first project for most of us. You have to think of the ground as a return path for different signals, and not as a "neutral" point where everything gets nullified. Ground is nothing more than the opposite of the power rail, after all. A perfectly silent tube amplifier uses a balanced wiring for V+ and Gnd throughout the amplifier, with proper decoupling at each stage.
> 
> The voltage you get at any single point is in reference to the ground at the other side of this point. If that ground point is noisy, the end result is the same as if your V+ was noisy.
> 
> ...


 
  That's actually very helpful, sadly as you just said, I'd have to rebuild the amp to achieve total silence, as it sits I fixed the nasty buzz in the right ear, and it is dead silent with volume at off, at high level maybe 75% volume I begin hearing an audible but mostly harmless volume hiss along with a very slight oscillating "wom wom wom" but together these sounds are not enough to detract from the music especially not at that level of volume. That's also a reasonable explanation as to why I couldn't post pictures, however I must have reached the threshold because the photo uploader is now appearing for me so here it is:
   
  EDIT: the oscillating sound is gone as far as I can tell, dunno why, it's probably explainable but whatever I'm happy.


----------



## proid

My amp has quite imbalance channel, it go about 60% on the right and 40% on the left. What can be the source of problem?


----------



## kchapdaily

Quote: 





proid said:


> My amp has quite imbalance channel, it go about 60% on the right and 40% on the left. What can be the source of problem?


 
  could be a bad volume pot, how low is it turned when this is happening? regular stereo pots have pretty bad channel matching when turned very low. if it isnt the pot, check and make sure all your resistors are the correct values.


----------



## scootsit

Quote: 





jarscar said:


> Quote:
> 
> 
> 
> ...


 

 Where'd you get that case? It's nifty!


----------



## jarscar

I got the case at taydaelectronics.com it's a diecast aluminum case, I had to prime and paint it myself but I love the size. I sanded the edge of the bottom plate to give it a brushed finish.


----------



## Grumus

When I was doing research before I built the amp someone mentioned to ground the first decouple cap directly to DC jacks ground. I built mine with everything going to a star ground (except first decouple cap) and I have zero hiss until way beyond listning levels on the volume knob. The the star ground should only be soldered on to the chassi in one spot, this make the case a faradaycage effectivley. You can see that Pete did so him self if you look at the inside picture.
   
  Edit. Kim beat me to the punch. Very nice looking amp you got there!


----------



## jarscar

Quote: 





kchapdaily said:


> could be a bad volume pot, how low is it turned when this is happening? regular stereo pots have pretty bad channel matching when turned very low. if it isnt the pot, check and make sure all your resistors are the correct values.


 
  That's how mine is, at anywhere from 0-30% my right channel is a little bit louder, but if I turn down the source audio and turn up the amp volume the audio levels out and both ears have even sound, it's probably because I spent about 50 cents on the pot :/


----------



## the_equalizer

Quote: 





jarscar said:


> Looks like I was a little too optimistic about that buzz/hum, I checked all my soldering, made sure nothing was shorting, checked and rechecked voltages, made sure everything was properly grounded, etc etc.
> 
> The buzz/hum is only in the the right ear and is independent of the volume, if I put my headphones on and turn the amp on then as soon as it warms up the buzz shows up, audio plays clearly along with the buzz. Also the buzz never gets louder as the volume is turned up either, likewise for all the way down. It is loud enough that I can't ignore it, it imposes on music.
> 
> ...


 
  Have you tried swapping the tubes? If the hum 'follows' the tube, then you can be certain it's a defective tube, otherwise, it's definitely a circuit problem.
   
  cheers!


----------



## jarscar

the_equalizer said:


> Have you tried swapping the tubes? If the hum 'follows' the tube, then you can be certain it's a defective tube, otherwise, it's definitely a circuit problem.
> 
> cheers!




 I actually went back and redid a large portion of the grounding, it reduced the loudness of the hum by about 50% and now I have to have the volume up a little higher before the hum is really apparent, it's probably still not as good as many of the amps built by people here but this has taught me a whole lot. I've already got some ideas for a new and improved amp.


----------



## JBal4

hi i was wondering if anyone had a link to a pcb layout for the 12au7 model. i am was going to try to etch one myself but i have not been able to find a layout to use.


----------



## pingu turbo

Well, all I can say is what a learning curve! I have just built my 12au7 version. What great fun! I was thoroughly chuffed when it didn't explode on initial turn on and even happier when it played some sound.

Just one thing though, mine seems to be mono. Is this correct? I have checked the volume pot and checked both channels signals are separate, but yes mono. You can remove either RCA lead and each channel goes out in turn, but I did notice that when re inserting the RCA, when the centre pin touches the inner socket without being fully inserted the channel comes back before both signal and earth are connected. I don't think this is right, I think I have a grounding problem.

If I do this with both channels I get a furious hum in both ears. I'm not sure where to start looking... Any pointers?


----------



## jarscar

*Edit I just did a quick thread search, tons of heat is apparently normal. I'm seriously giddy over how awesome this thing sounds though.
   
  Well I've been using this happily for a while now, sounds awesome. One question though: just how hot is this supposed to get? cause after about an hour of listening it is really hot, like I can only hold my fingers on it for about 7 seconds hot. It's not damaging anything and the performance doesn't degrade but it just seems awfully hot for having an aluminum body and heatsinks, though it would kind of confirm everything I've heard about tubes soaking up energy, I just have zero experience with these things.


----------



## Beftus

Quote: 





jarscar said:


> *Edit I just did a quick thread search, tons of heat is apparently normal. I'm seriously giddy over how awesome this thing sounds though.


 
   
  It does indeed get hot, that's perfectly normal for this amp. How hot it gets is also a function of how large the heatsinks you used are. Bigger heatsinks cool things better.


----------



## pingu turbo

Well I managed to sort my 'mono' problem. After re wiring my whole amplifier to achieve the same result. :mad:

I have a faulty 'iDevices' phono lead. It's band new ***! I did learn a lot more about grounding and have improved any hum issues no end.

Casually enjoying some stereo sound now.


----------



## jarscar

I had to take my amp apart to fix an issue I was having with the paint job, upon putting it back together one of my MOSFETs is getting well over 40v from the source pin instead of ~13v
  I didn't have to change any wiring when I took it apart, aside from having to disconnect the RCA jacks and the power plug because those disconnect from inside the case instead of outside, I've checked and re-checked 4 times, I guess I'll try replacing that MOSFET 
  I took the tube out and left the other in, I'm getting a crackle on start up from the empty line, I'm assuming that's the capacitor reacting with the excessive voltage from the source. The other MOSFET works fine and the sound coming out is normal.


----------



## KimLaroux

What voltages do you get at the gates of the MOSFETs? It could be that the voltage divider no longer connects to ground, which means the gate got pulled to the 48 V line.


----------



## jarscar

Quote: 





kimlaroux said:


> What voltages do you get at the gates of the MOSFETs? It could be that the voltage divider no longer connects to ground, which means the gate got pulled to the 48 V line.


 
    I'm getting around 34v at the gate for the MOSFET acting up and 15v for the one working fine


----------



## KimLaroux

You're getting 40 V at the source, but 34 V at the gate? Sounds like a burned MOSFET. Or you're messing up the source and the drain. 
   
  You could try to disconnect R2/R8 of the misbehaving fet and see what it does. Just beware that if you disconnect the wrong resistor (R4/R10), I can guarantee you you'll blow a tube. Been there, done that.
   
  If it's not a blown mosfet, then I'm guessing you have a cold joint on one of the pull-down resistor, R4 or R10.


----------



## jarscar

Quote: 





kimlaroux said:


> You're getting 40 V at the source, but 34 V at the gate? Sounds like a burned MOSFET. Or you're messing up the source and the drain.
> 
> You could try to disconnect R2/R8 of the misbehaving fet and see what it does. Just beware that if you disconnect the wrong resistor (R4/R10), I can guarantee you you'll blow a tube. Been there, done that.
> 
> If it's not a blown mosfet, then I'm guessing you have a cold joint on one of the pull-down resistor, R4 or R10.


 
  Thanks a ton, that tells me enough to play it safe and just rebuild that section of the amp, I've got enough spare parts so there's no reason not to


----------



## jarscar

Quote: 





kimlaroux said:


> You're getting 40 V at the source, but 34 V at the gate? Sounds like a burned MOSFET. Or you're messing up the source and the drain.
> 
> You could try to disconnect R2/R8 of the misbehaving fet and see what it does. Just beware that if you disconnect the wrong resistor (R4/R10), I can guarantee you you'll blow a tube. Been there, done that.
> 
> If it's not a blown mosfet, then I'm guessing you have a cold joint on one of the pull-down resistor, R4 or R10.


 
  Edit: I turned it off and walked away, I guess I shouldn't jump to conclusions, the voltages are all correct now, I guess I should have unplugged everything then tested again, but thank goodness it was just user error and not mechanical failure. Also I'm buying a new multimeter, and not one from Harbor Freight this time, I spent the longest time thinking my power supply was dead, turns out I had to solder the positive lead back on in my brand new multimeter, that should teach me to stop buying anything but a hammer from there.
   
Well I replaced the MOSFET and all the resistors for that side, I switched it on and was getting the correct 15v at pin 1, 48v at pin 2 however I was getting 18v at pin 3, went back to my work table and double checked things.
Then when I was double checking my measurements my multimeter probe slipped and connected pins 2 and 3 for a split second, now I'm getting 33v at pin 3, so there goes another MOSFET I guess.


----------



## ProTofik

I have a question to everyone that built a student.
  Has anyone tried to measure a crosstalk? I am getting quite bad result:
   
   

   
  The lowest my sound card is able to measure is about -75db so I don't think that it's a problem in here.


----------



## Goobley

What pot are you using? As far as I'm aware this part has the greatest impact on crosstalk. I know my starving student doesn't have any audible crosstalk. I'll measure it when I get home on Friday to compare.


----------



## ProTofik

Can't say much about the pot except that it is 50k stereo.
  I think that the crosstalk may be caused  by the cable mess in the case.


----------



## Martinus

Hi guys.

 I've been visiting for a while and keeping tabs on this thread. First I'd like to thank everyone who put time and effort into this project, not least Mr. Millett.

 I prototyped my version on stripboard and put it all into an ugly little case pending my finding a more aesthetically pleasing enclosure. Whilst not exactly pleasing to the eye it worked first time. I haven't ever listened to music with an amp of this kind so my aim was to build it fast and cheaply to get a feel for how much effort I should put in. The amp has all of the additional parts suggested on the 12AU7 schematic. I didn't get a pair of matched valves (they were very cheap though).

 I'm glad to say that I really enjoy the sound through my Sennheiser 595's fed from a Nokia N900. However, some minor grounding issues remain and the voltage at pin 4 is closer to 16V on one channel. I'm hoping there's an easy fix for this so I'm going to re-trawl the thread.

 Many thanks.


----------



## audi0lurker

How's It going guys?  So I have recently embarked on this project and am stoked to see how it will turn out.  Having recently finished the one and only circuits class I will ever need to take, I am not the most astute electrical engineer, but one of the reasons I started this project was to learn more about circuits and theory and also I'm a bit of an audiophile and this is the perfect project for me considering I am indeed a starving student.  
   
  SO my question regards the Tube LED's.  I have drilled out the tube sockets, easy, but I do not know where to attach the LED and led resistor in the circuit?   Could some one shed some light on this for me?
   
  Also, I using the specs on a 3mm LED I have and this website I calculated I need a 1kohm resit or rated for 2.5 watts.
   
  So ya thanks for the help Ill be posting build pictures along the way, I wight even construct a small bass boosting circuit as well who knows!!


----------



## Martinus

Connect each led + resistor between Vin and ground. You can use this calculator to determine the appropriate resistance value:

 http://ledcalculator.net/


----------



## DingoSmuggler

Quote: 





audi0lurker said:


> Also, I using the specs on a 3mm LED I have and this website I calculated I need a 1kohm resit or rated for 2.5 watts.


 
  That doesn't sound right, how much current you gonna be passing through it? A 1k ohm will give over 40mA and fry the average LED.
  A typical LED has a rating of 20mA, but at higher temps (such as in a tube socket) you will need to de-rate this down to a lower value.
  Also LED brightness is proportional to current, the resistor sets this current.
   
  Most LEDs these days are fairly bright, you probably don't want to light your tube socket up so brightly as to completely overpower the tube glow.
  I'd probably aim for a current ~2mA (22k 1/2W resistor). Anywhere between 10k (brighter) and 100k(dimmer) would also work.
   
  Also, if you prefer, you can string both tube LEDs in series, saving yourself one resistor and a small amount of power draw from the supply.
  48V(+) ---- (+)LED1(-) ---- (+)LED2(-) ---- Resistor ---- 0V/ground
  The resistor can go anywhere in the series circuit you like, on the positive side, on the ground side, or in between the LEDs.


----------



## KimLaroux

Connect them across the tube heaters. There is only 13 V across them, so you don't need a high power resistor. And since this voltage is already at the sockets, you don't even need to add any wires. Win-win.


----------



## Amatsu

Quick question, Currently I have the amp build on a wood case, but since it's not very well build because it was my first time, I'm planning on redoing it on a metal case.
  Can someone tell me what do I need to watch out for while bulding on a metal case? The mosfets already have an insulator for the heatsinks but what about the rest of the parts that will be screwed to the metal case?


----------



## jarscar

Quote: 





amatsu said:


> Quick question, Currently I have the amp build on a wood case, but since it's not very well build because it was my first time, I'm planning on redoing it on a metal case.
> Can someone tell me what do I need to watch out for while bulding on a metal case? The mosfets already have an insulator for the heatsinks but what about the rest of the parts that will be screwed to the metal case?


 
  The case being metal isn't a big deal, everything that connects to it will be grounded and in the end your case will be grounded also, the only thing you really need to worry about is shorting the circuit by accidentally touching a solder joint or stray wire to the case. The only thing that gave me any problems was the MOSFETs, I had to brush liquid black tape on the connectors because the leads were a lot longer than the insulators I used. But other than those everything should mount directly to your case.


----------



## KimLaroux

Quote: 





jarscar said:


> The case being metal isn't a big deal, everything that connects to it will be grounded and in the end your case will be grounded also, the only thing you really need to worry about is shorting the circuit by accidentally touching a solder joint or stray wire to the case. The only thing that gave me any problems was the MOSFETs, I had to brush liquid black tape on the connectors because the leads were a lot longer than the insulators I used. But other than those everything should mount directly to your case.


 
   
  Only two pages back:
   
  Quote: 





kimlaroux said:


> I believe your grounding scheme is not efficient enough. It's kind of a common problem here, as it's usually a first project for most of us. You have to think of the ground as a return path for different signals, and not as a "neutral" point where everything gets nullified. Ground is nothing more than the opposite of the power rail, after all. A perfectly silent tube amplifier uses a balanced wiring for V+ and Gnd throughout the amplifier, with proper decoupling at each stage.
> 
> The voltage you get at any single point is in reference to the ground at the other side of this point. If that ground point is noisy, the end result is the same as if your V+ was noisy.
> 
> ...


----------



## jarscar

uote: 





kimlaroux said:


> Only two pages back:


 
  Yeah and I fixed my grounding scheme, all my problems had to do with a daisy chain grounding. I no longer have  any noise at all, and I didn't directly ground my parts to the case, but l didn't insulate them from the case either, the ground of the RCA jacks for instance connect to the nut which screws directly to the case. I didn't mean to speak out of turn I was just trying to tell him he wouldn't fry a tube or anything by mounting to a metal case.


----------



## sanguinicus

I love this. I'm thinking of building the 12AU7 version. Man, the price of valves have gone up in the last year or so (I usually get guitar amp valves).
   
  I have a question about integrating a power supply within the box. Is this recommended? If so, which power supplies do everyone use? Does the star ground to chassis go back to main unput plug or GND of PSU output.
   
  Also, regarding the Cisco power supply, there are plenty on ebay, but don't have the exact part number, however they are 48V 0.4A. Is that fine too?
   
  -sanguinicus


----------



## Beftus

Quote: 





sanguinicus said:


> Also, regarding the Cisco power supply, there are plenty on ebay, but don't have the exact part number, however they are 48V 0.4A. Is that fine too?


 

 The minimum is 48 volts, 0.38A, so 0.4A is enough to get it up and running.


----------



## audi0lurker

Dumb question. How do i ground this? Like I have a capacitor going to ground


----------



## vixr

Quote: 





audi0lurker said:


> Dumb question. How do i ground this? Like I have a capacitor going to ground


 
  the minus pin from your power supply connector is the ground...google  "star ground" There can be local grounds connected together and ran to a central star ground. Look at "star ground" on google images too.


----------



## Fivetide

Hi guys 0/ I’m new to the forum so be gentle please J .
  I’m just in the process of finishing Pete’s Might Midget, just a matter of casing up and getting it to my friends to hook up to his many boxes that beep and make pretty patterns on the front, I think they are called oscillators , not sure lol. Anyway I love the idea of the starving student but I have searched for a supplier of the toobs in the uk and can’t find anyone so far. When I search on eBay I get suppliers in the US and these “5 Tubes 10GF7A, 6Z106J10, 19DQ3, 6Z10/6J10, 6CG36BW3” . I’m not a toob expert is there an alternative toob because it looks like they will cost nearly £10 each if I get them from the US and that really defeats the object of the low cost amp ?


----------



## sanguinicus

Well, there's been mention that the market has been depleted of 19J6 valves. There's a few on eBay but they cost a fortune and it can't be garaunteed that they are matched; they aren't sold in pairs. Many users here have had much success building a variation with 12AU7 valves and their variants. I've just finished my BOM for a 12AU7 one.
   
  And the thing with the pretty patterns, I think you're referring to an Oscilloscope 
   
  See here for the variation: http://www.diyforums.org/SSMH/SSMHvariants.php Or, have a look back through the 400+ pages haha.


----------



## Fivetide

Thanks for that .. just looked and its still going to be £9 each for the valves.. rip off Britain same ones in the US £3 ! Think I'll build an O2 instead


----------



## sanguinicus

Why don't you just ship them from USA? I live in Australia and I'm looking to USA for valves...


----------



## Argax

Wow, thanks for the great idea. I'm hoping to try my hand at it soon and can't wait to see what the results might be! I just hope I can find all the items as it seems everyone is jumping on your awesome idea.


----------



## jasonf

If it helps, Fred_fred2004 made some circuit boards for the linked 12au7 design. I am currently waiting on the shipping since he is located in Australia but he is selling them at a great price and still has some left. 
   
http://www.head-fi.org/t/664191/starving-student-pcbs/15#post_9503650
   
  That's the post. He mentioned he still has a few left if you are interested. Let me know if you have any issues with the link.


----------



## Fred_fred2004

Hi those boards ship worldwide for $3.00 for up to 2 boards
   
  if you want more than two I can quote
   
  cheers
  FRED


----------



## audi0lurker

Thanks for the help guys its coming along nicely.  I had to switch most of the caps from 63 to 100v as that is what my local surplus electronics shop, HSC, had on the shelves and could only find an 100k stereo POT as opposed to the 50k Pot specified in the diagram.
   
  SO I am wondering what changes I need to make inorder to accomodate this ie. changing resitors R16 and 17.  When the Pot is turned all the way there will be a 50k resistor impeding the signal.  SO I am guesing I should just leave the 50k resistors and the 100k pot will just attenuate the signal faster than the 50k.  Can anyone shed some light onto this?


----------



## KimLaroux

A pot is only a resistor voltage divider. The voltage at the output is a ratio of where the wiper is in respect with the total rotation range. The pot can be 10k, 50k or 1 Meg, it doesn't change anything. The only thing that changes is the load the DAC sees.
   
  Adding a 50K resistors before a volume pot virtually lengthens the resisting surface by 50K. Say you have a 50K pot that you never go over half its rotation range. Adding a 50K resistor before pushes that useless half outside the rotation range (not really on a log pot, but you get the idea). It's effectively stretching the first half of the pot across its whole rotation range. The value isn't important, you chose it after experimenting with your system until you find the right value. It depends on the voltage out of your DAC and the voltage your headphones need.
   
  Personally I went with the largest knob I could fit to the enclosure instead of attenuating the signal with resistors. I find this a cleaner solution to the same problem.


----------



## KimLaroux

I'll just drop this here...


----------



## Goobley

Looking pretty schmexy...
You've decided on a design now then? Well keep us posted.

I'm still going round in circles with mine due to budget concerns... I have a plan but it'll cost about 120€, so I'm going to try to get some work done right after my exams so that I can get on with it.


----------



## the_equalizer

Quote: 





kimlaroux said:


> I'll just drop this here...


 
   
  Are those CCS boards I see right beside the tube sockets?


----------



## KimLaroux

Quote: 





the_equalizer said:


> Are those CCS boards I see right beside the tube sockets?


 
   
  Yes. 
	

	
	
		
		

		
			




   
  They are the same tail CCS as in the SOHA II. I also built a voltage multiplier like the SOHA's, which you can see between the AC inlet and the audio inputs. Now, the tubes run on a 165 V rail and the MOSFETs on a 25 V one.
   
  I'll start a new thread once I'm done to share the story of this project. It's not really a MSSH now anyways, so I'll need to rename it.


----------



## Undisclosed

just ordered my tubes and sockets to go along with the pcb from fred_fred2004.
   
  Trying to finish my BOM from mouser but would like some input about a switch and fet heat sinks. I have some ebony from another project so I'm going to case this amp up with that. I'm going to use a big 1.5 inch alum knob and I'm looking for a good looking switch to match that. I'm also looking for those curved heat sinks ive seen used, but Icant seem to find them on mouser.
   
  Thanks


----------



## alphaman

Quote: 





kimlaroux said:


> Yes.
> 
> 
> 
> ...


 
  Nice job on your amp. CCS with tube can stress filaments if not carefully done. I assume you are using something like:
http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=design/opdesign


----------



## KimLaroux

Quote: 





alphaman said:


> Nice job on your amp. CCS with tube can stress filaments if not carefully done. I assume you are using something like:
> http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=design/opdesign


 
   
  I am using the tail CCS as shown at the bottom of this page: http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=design/ipdesign
   
  The only difference with mine is instead of having it powered between the negative rail and ground, I power it between ground and the 25 V rail.
   
  I paralleled the triodes and use a single 7.52 K cathode resistor instead of the mirror. The tubes are powered from a 160 V rail.


----------



## vixr

Quote: 





kimlaroux said:


> ...It's not really a MSSH now anyways, so I'll need to rename it.


 
   
  Super Starving Student? MHSSS?


----------



## Goobley

My vote would be for : 'This amp came in over budget, but who's counting? Hybrid Student amp'


----------



## KimLaroux

I totally lost count of the money I poured into this project. I stopped counting somewhere around 500$. I don't really feel like going back and do the sum... 
	

	
	
		
		

		
		
	


	




 Though this was a learning project which went trough many redesigns and tweaks for the sake of experimenting and learning. So I'd consider the money more like tuition fees than project costs.
   
  I think I'll simply name it 12AU7/MOSFET hybrid, or something. It's not a commercial or published DIY project so I don't really care if it remains nameless. I may draw and share the final schematic at some point, but it may be useless. This whole project was designed around a 30-0-30 transformer I salvaged from an old stereo amp. Buying such a transformer for a high voltage hybrid may not be the smartest idea. If you count in the price for the voltage multiplier, I bet it'll end up being the same price as a high voltage transformer designed to power tubes. And then there's the problem that I didn't design the schematics, the amplifier is a patchwork of schematics from already published DIY projects and datasheets. I simply did the math to make all these schematics work with the voltages I managed to get out of the transformer.


----------



## Goobley

... Mines gone/going the same way! But yeah, I've learnt so much from it. I know have a (hopefully) final design idea taking shap that I'll be able to build after my Baccalaureat.


----------



## alphaman

This is a LONG thread, and many may not have the time to trudge thru it all. Not a bad time, methinks, to post an UPDATED schematic and BOM.


----------



## tomb

Quote: 





alphaman said:


> This is a LONG thread, and many may not have the time to trudge thru it all. Not a bad time, methinks, to post an UPDATED schematic and BOM.


 
  The first post of a forum thread is always the easiest to find. 
	

	
	
		
		

		
			





  Then there was the PCB version, here: SSMH PCB
   
  The 12AU7 variant has been stored for posterity here:
SSMH Variants
   
  As for the  BOM, etc., you can find it on that site (except the PCBs are no longer available).  In addition, the very first post in this thread has the original schematic and the original BOM.  Almost nothing has changed from that, except the addition of some bypass caps, differences in volume pots, and your choice of heat sinks.  If you go with different tubes, then as stated, the 12AU7 version is archived above.


----------



## Amatsu

Quote: 





jarscar said:


> The case being metal isn't a big deal, everything that connects to it will be grounded and in the end your case will be grounded also, the only thing you really need to worry about is shorting the circuit by accidentally touching a solder joint or stray wire to the case. The only thing that gave me any problems was the MOSFETs, I had to brush liquid black tape on the connectors because the leads were a lot longer than the insulators I used. But other than those everything should mount directly to your case.


 
   
   
Quote:


kimlaroux said:


> I believe your grounding scheme is not efficient enough. It's kind of a common problem here, as it's usually a first project for most of us. You have to think of the ground as a return path for different signals, and not as a "neutral" point where everything gets nullified. Ground is nothing more than the opposite of the power rail, after all. A perfectly silent tube amplifier uses a balanced wiring for V+ and Gnd throughout the amplifier, with proper decoupling at each stage.
> 
> The voltage you get at any single point is in reference to the ground at the other side of this point. If that ground point is noisy, the end result is the same as if your V+ was noisy.
> 
> ...


 
   
   Thanks a lot guys, I have already finished the amp on the new metal case. I used the star ground method and surprisingly everything works perfectly from the start and the amp is completly silent. Now I just need to wait for the new usb dac to arrive since I don't have the X-Fi modded anymore.


----------



## alphaman

*tomb:* Thx for summarizing! [FYI: My main ref to this project has always been: http://www.pmillett.com/starving.htm ] So, based on your  succinct summary ..._this thread_ seems ridiculously long...i.e.,  if your two external links (Millet's DIY site pages) are the ONLY major topological changes/ mods to the orig. design... then I'm guessing much of the discussions in THIS ~440-page  thread have been ...  ... about what ... MSSH _cosmetics_  ??
   
  IAC ... I'm perhaps most curious about the addition of CCS. Not sure whether KimLaroux's recent mention of it is new to this thread and, in general,  the MSSH design. How does CCS improve sound over orig.?


----------



## Goobley

In general a CCS will force a tube to have a much flatter load line and make it operate in a considerably more linear manner. Kim is using cathode CCSs which I am personally not as keen on as it means that your don't gain any AC impedance to the plate. An anode CCS provides a very high load to the plate and increases PSRR (power supply ripple rejection) by a factor of 10 even for the most basic CCS. (But you do end up needing high voltage transistors etc. as opposed to standard toolbox stuff in the cathode CCS). Swings and roundabouts...


----------



## alphaman

Starving CCS ,,, just need one part:

  from:
http://web.archive.org/web/20080303170808/http://www.borbelyaudio.com/eb804421.asp


----------



## Goobley

That amp is pretty different to a MHSS and the CCS is controlled by CCdiodes which many people aren't particularly keen on for actual music use. If you're using the original power supply scheme then the minimax CCS scheme http://www.diyforums.org/MiniMAX/MiniMAXccs.php* * is a good place to start due to its decent performance and ease of implementation (2 transistors, 2 resistors). The Equalizer was the first (AFAIR) to implement this mod, then I also added it back when my SS operated at standard voltages. Its main effect (that I noticed), was giving me a blacker background (the SMPS is far from perfect) and increased the bass punch a bit. I've never come across a CCS that has completely changed a circuit, when it comes to tubes they generally just seem to be a final layer of gilding (one may therefore deduce that if plated in Rhodium they'll sound much better!  )
   
  If you use a CCS like the minimax's one then you'll always be able to retrofit it like I did, so don't be afraid of just building the amp first using a standard resistor bias.
   
  Cheers!


----------



## tomb

Quote: 





alphaman said:


> *tomb:* Thx for summarizing! [FYI: My main ref to this project has always been: http://www.pmillett.com/starving.htm ] So, based on your  succinct summary ..._this thread_ seems ridiculously long...i.e.,  if your two external links (Millet's DIY site pages) are the ONLY major topological changes/ mods to the orig. design... then I'm guessing much of the discussions in THIS ~440-page  thread have been ...  ... about what ... MSSH _cosmetics_  ??
> 
> IAC ... I'm perhaps most curious about the addition of CCS. Not sure whether KimLaroux's recent mention of it is new to this thread and, in general,  the MSSH design. How does CCS improve sound over orig.?


 
  I apologize for not knowing where to find it specifically, but there is another variant that used metal tubes.  Maybe someone else will point it out.


----------



## dsavitsk

If I were feeling adventurous and wanted an interesting tube to use for this design, I think I'd be inclined to look at the 3A5. There will be a few design challenges and changes, but it looks like a good candidate to me.


----------



## Goobley

Just looked that tube up, wish I'd known about it before building mine with 12AU7s, with some modification those could really sing on the 48V supply


----------



## alphaman

I haven't seen a schematic for the Bottlehead Crack .And while that is a different style of tube amp than MSSH, I did note that Bottlehead offers a CCS upgrade called "Speedball" for the 12AU7 section:
http://www.bottlehead.com/store.php/products/speedball-upgrade-for-crack-amplifier
   
  Will it work with the 12AU7 SSMH variant?
   
  EDIT: Here's the C4S Camille Cascode Constant Current Source kit:
http://www.bottlehead.com/et/adobespc/C4S/c4s_kit.htm
  ... it's an LED-based CCS design from VALVE magazine, Oct 1997 and 1999 here.
  ...some related info here: http://www.pimmlabs.com/
  ==================================
   


> What yields an even more intense experience than Crack? The most hardcore users say it's a Speedball. Speedball is our Camille Cascode Constant Current Source upgrade for the Crack headphone amplifier. The 22k1 ohm plate loads of the 12AU7 input triodes are replaced by C4S loads, as are the 3K ohm cathode load resistors of the 6080 triodes. The PC board for the loads on the 6080 tube has very ample heat sinks to assure high reliability.
> 
> We consider this a skill level 2 kit, meaning that it is intended for someone who has construction of a kit under their belt (like the basic Crack kit). The new skills you might acquire will be those of stuffing and soldering a PC board, and removing a few components to allow installation of the upgrade. Assembly and installation is an easy one evening session, requiring only the removal of four resistors from the previously assembled Crack kit.


----------



## the_equalizer

Quote: 





tomb said:


> I apologize for not knowing where to find it specifically, but there is another variant that used metal tubes.  Maybe someone else will point it out.


 
   
  You're probably refering to this post by user Logistic. One of these days I have to build one...
   
   
  EDIT:  Also, for the more adventurous, you can try building a 12AE6 version. 
   
   
  cheers!


----------



## alphaman

Quote: 





goobley said:


> That amp is pretty different to a MHSS and the CCS is controlled by CCdiodes which many people aren't particularly keen on for actual music use. If you're using the original power supply scheme then the minimax CCS scheme http://www.diyforums.org/MiniMAX/MiniMAXccs.php* * is a good place to start due to its decent performance and ease of implementation (2 transistors, 2 resistors). The Equalizer was the first (AFAIR) to implement this mod, then I also added it back when my SS operated at standard voltages. Its main effect (that I noticed), was giving me a blacker background (the SMPS is far from perfect) and increased the bass punch a bit. I've never come across a CCS that has completely changed a circuit, when it comes to tubes they generally just seem to be a final layer of gilding (one may therefore deduce that if plated in Rhodium they'll sound much better!  )
> 
> If you use a CCS like the minimax's one then you'll always be able to retrofit it like I did, so don't be afraid of just building the amp first using a standard resistor bias.


 
  Sorry for just getting around to replying to your reply 
  The amps ain't THAT different in that both are "vacuum tube and discrete solid state hybrid headphone amplifier"
  About that diode ... my bad on stating that being the ONLY part needed for a drop-in type CCS upgrade for the MSSH -- and YOUR bad for not noticing that 
  Specifically ... if you look at the  the Borbely ckt you'll note two addit. transistors and three Rs  (Q4, Q5,R11/12/13 )., sorta similar to MiniMax CCS topology, but the borbely uses one MOSFET and one BJT


----------



## the_equalizer

Quote: 





alphaman said:


> Sorry for just getting around to replying to your reply
> The amps ain't THAT different in that both are "vacuum tube and discrete solid state hybrid headphone amplifier"
> About that diode ... my bad on stating that being the ONLY part needed for a drop-in type CCS upgrade for the MSSH -- and YOUR bad for not noticing that
> Specifically ... if you look at the  the Borbely ckt you'll note two addit. transistors and three Rs  (Q4, Q5,R11/12/13 )., sorta similar to MiniMax CCS topology, but the borbely uses one MOSFET and one BJT




   
  While it is true this amplifier uses vacuum tubes and solid state devices, the WAY they are used is certainly different. Otherwise one might conclude that all hybrid amplifiers are very similar simply because they use the same basic components... 
   
  For starters, the input stage above looks like differential pair with D1A and D1B acting as a tail CCS; a topology similar to the SOHA II. On the other hand the SSMH is a simple common cathode triode voltage amplifier.  
   
  The circuit around Q4 and Q5 is a CCS acting as source load for the output MOSFET stage, not for the tube stage. On the SSMH it is the tube heater that acts as the MOSFET load.
   
  Finally, you can see that in the above diagram both the tube and MOSFET as well as the output load and MOSFET are directly coupled, thanks to the use of a bipolar power supply, whereas the SSMH uses a simple +48V supply and coupling caps to isolate it's two stages as well as the headphone load.
   
  Cheers!


----------



## alphaman

Quote: 





the_equalizer said:


> For starters, the input stage above looks like differential pair with D1A and D1B acting as a tail CCS; a topology similar to the SOHA II. On the other hand the SSMH is a simple common cathode triode voltage amplifier.
> 
> The circuit around Q4 and Q5 is a CCS acting as source load for the output MOSFET stage, not for the tube stage. On the SSMH it is the tube heater that acts as the MOSFET load.


 
  Are you referring to the *standard* SSMH? In #6561, Goobley brought in the MiniMax (with its CCS tweak) into the discussion . So that's what I was kinda comparing the Borbely to.
   
   
  IAC ... your point-by-point contrasts are good. However, I was largely referring to semantics and nomenclature used to *generically* describe BOTH amps, which is why I used quotations in #6567's remark:
  [size=17.600000381469727px]The amps ain't THAT different in that both are "[/size]vacuum tube and discrete solid state hybrid headphone amplifier".


----------



## the_equalizer

Quote: 





alphaman said:


> Are you referring to the *standard* SSMH? In #6561, Goobley brought in the MiniMax (with its CCS tweak) into the discussion . So that's what I was kinda comparing the Borbely to.
> 
> 
> IAC ... your point-by-point contrasts are good. However, I was largely referring to semantics and nomenclature used to *generically* describe BOTH amps, which is why I used quotations in #6567's remark:
> [size=17.600000381469727px]The amps ain't THAT different in that both are "[/size]vacuum tube and discrete solid state hybrid headphone amplifier".




   
The Minimax has also a triode common-cathode voltage amplification stage, like the SSMH, but with CCSs acting as plate loads. The CCS SSMH tweak I did involves adding these plate load CCS to the tube stage. This is of course just what I did, other's could try other kinds of CCS, like buffer op-amps or diodes. Morgan Jones' "Valve Amplifiers" has a very nice section on CCS for use on vacuum tube circuits.
   
  As to the Minimax's output stage, it is significantly different to both the SSMH and the Borbley, these last two being single-ended while the Minimax uses a BJT diamond buffer output stage using complementary semiconductor devices.


----------



## audi0lurker

alright one last question and it's about the tube socket wiring... I'm using 12au7 tubes which have a nine pin configuration and am using the modified plans by the equalizer which I am sure you are all familiar with. my question is m the tubes for this have nine pins while the diagram only specifies what to do with eight of then. What do I do with the ninth pin? And they are numbered out of order as I am familiar with pins being numbered radially and sequentially starting with one one the left side of the had. So if anyone can shed Adobe light on how to ruin three tube wiring I works appreciate it .
The nine pin mini of course 

http://electriciantraining.tpub.com/14178/img/14178_24_2.jpg


http://diyforums.org/SSMH/schematic/SSMH-origPCB-sm.gif


----------



## KimLaroux

Pin 9 is the center-tap of the heater, so it can be used with 6.3 V.


----------



## audi0lurker

awesome thanks. So how does the pin numbering correspond to the numbering on the schematic? why isn't pin 9 specified in the diagram?


----------



## KimLaroux

Quote: 





audi0lurker said:


> awesome thanks. So how does the pin numbering correspond to the numbering on the schematic? why isn't pin 9 specified in the diagram?


 
   
  The pin number on the schematic correspond to the pin number on the socket. They are not in order on the schematic because the part drawing used has them this way, which is common on schematics. Schematics are drawn to be quickly understood, not to match physical components packages.
   
  Pin 9 is unused in the SSMH, so there's no reason for it to be shown anyways.


----------



## the_equalizer

Indeed, pin 9 is the heater center tap (used in circuits where the heaters are fed in parallel with a 6.3 V source), it is not used  in the SSMH circuit and SHOULD NOT be connected to *anything*, as there's a voltage present at that point.
   
  Sorry about the confusion with the pin numbers, to make it easier to produce a schematic diagram, I simply took the existing 19J6 schematic and relabeled the pin numbers 
	

	
	
		
		

		
			





. My apologies, I should have been more careful with that detail.


----------



## holland

Quote: 





goobley said:


> The Equalizer was the first (AFAIR) to implement this mod, then I also added it back when my SS operated at standard voltages.


 
   
  I used a CRD shortly after I built this, some 5 years ago    I did a number of minor mods to it (original SSMH with 19J6).  CRD (0.56mA) on the plate, changed the CRC filter to reduce the voltage drop from increased current, global negative feedback, and removing local negative feedback (cap on the cathode).  I can't recall why I bypassed the cathode.  I actually don't mind the CRD here, just to keep in the goal of a Starving Student.  I did everything on the cheap.
   
  Decent amp but still too much gain for my headphones.
   
  One thing I have wanted to experiment with was putting the potentiometer after the gain stage, with additional caps to block DC from the voltage divider for the MOSFET.
   
  This has to be one of the longest running threads I've ever seen.  Good luck to anyone who can read 6576 posts.


----------



## ProTofik

Hello again.
   
  I got a question capacitors C2 and C4.
   

   
   
  What is the purpose of these 2 capacitors? Are they used to block the DC?
  I currently have 0.22uF ceramic capacitors installed in that place. I believe they're the reason for which I am getting a bass roll-off problem (tested with RMAA).
   
  Few days ago I was trying to design my own solid state amp. I used 0.22uF capacitors to block the DC and they were causing a bass roll-off below 100-150hz. Replacing them with polarised 2.2uF fixed the problem for me. I wonder if I can do the same in starving student since I know very little about tubes.
   
  So is it safe to replace these capacitors with 2.2uF 63v polarised ones? The positive pin of capcitor must face the MOSFET, right?
   
  Thanks.


----------



## KimLaroux

Quote: 





protofik said:


> Hello again.
> 
> I got a question capacitors C2 and C4.
> 
> ...


 
   
  You can't compare the values of these caps between amplifiers. You also need to take into account the value of the resistor following, in this case R4 and R10.
 http://en.wikipedia.org/wiki/High-pass_filter#First-order_continuous-time_implementation
   
  The interstage filter using a 0.22 µf cap has a cut off frequency of 4 hz.
   
  What is the impedance of the headphones you're using with the amp? What value capacitor did you use for C3 and C5?
   
  If you're using 32 R headphones with 150 µf capacitors at the output, you get a cut off frequency of 33 Hz. This would more likely be your problem.


----------



## ProTofik

For RMAA tests I used 33ohm resistors as a load. C1, C3, C5 and C6 that I am using are 220uF.
   
  So if the C2 and C4 are not my problem, then what is?
   
  Tomorrow I will make another RMAA test with 300ohm load (since this is what my HD600 are) and see if I will get the same result.


----------



## KimLaroux

Quote: 





protofik said:


> For RMAA tests I used 33ohm resistors as a load. C1, C3, C5 and C6 that I am using are 220uF.
> 
> So if the C2 and C4 are not my problem, then what is?
> 
> Tomorrow I will make another RMAA test with 300ohm load (since this is what my HD600 are) and see if I will get the same result.


 
   
  You don't need RMAA to test that... any calculator will do, even google.
   
  33 ohms and 220 µf: 1/(2*Pi*220*10^-6*33) = 22 Hz
  300 ohms and 220 µf: 1/(2*Pi*220*10^-6*300) = 2.4 Hz
   
  So with your HD600 there should be no bass roll off due to parts selection. It is more probably due to the character of the tubes themselves.


----------



## audi0lurker

All that is very interesting.  One of my motivations for building this was to learn some circut theory and what not(being a 3rd yeach ME wondering why he isnt an EE)
   
  So Im wondering if someone could give me the reason to add Capacitors C3a and C5a(.22uf at 250v)  in parallel with the 470uf caps at 63v.  It seems funny to add these.  So Now I have a 470.022uf cap? that seems so insignigigant.  Such a low capacatance and such a high voltage rating.
   
   
   Please, higher minds enlighten me

 http://diyforums.org/SSMH/schematic/SSMH-origPCB-sm.gif


----------



## Avro_Arrow

The larger the value the cap, the more inductance it tends to have at higher frequencies.
  This can cause some high frequency roll-off.
  Adding a smaller value cap in parallel counteracts this effect.


----------



## holland

Quote: 





protofik said:


> For RMAA tests I used 33ohm resistors as a load. C1, C3, C5 and C6 that I am using are 220uF.
> 
> So if the C2 and C4 are not my problem, then what is?
> 
> Tomorrow I will make another RMAA test with 300ohm load (since this is what my HD600 are) and see if I will get the same result.


 
   
  Your output caps, C3 and C5, are too small.  I used 1000uF, but 470uF is a minimum.  KimLaroux's formula is almost correct.  You need to take into account that the high pass filter is C3 (or C5) interacting with the parallel resistance of 2K and the output headphones.
   
  Anyway, the corner frequency, which the equation 1/(2*pi*RC), is about the -3dB point, and it bends about it at 6dB per octave.


----------



## audi0lurker

avro_arrow said:


> The larger the value the cap, the more inductance it tends to have at higher frequencies.
> This can cause some high frequency roll-off.
> Adding a smaller value cap in parallel counteracts this effect.



That makes perfect sence. Isn't it wonderful glee the world works out? Do what is the relation to capacitors and low frequencies? ie very low and deep bass. Will larger capacitors discharge more current to drive deep low frequencies? How could I get a bit more low end in theory?


----------



## Whil

Hello All, 
    I've been getting into the audiophile ways for a while now, and have decided to tinker my way into the DIY realm.
   
    Thus I'm going to go for the SSHA build.  However I'm looking to add in a bit of protection for the headphones.  I've seen multiple posts on this, and I'm unaware of what the general consensus was.
   
    Thus I have a couple questions that I'd love some input on.  
   
    First is the headphone delay worth putting in?  Lets say I have a friend fire this up while I'm away, I'd rather not lose some nice Sennheisers.
   
    Second, I've been looking at the e12 circuit and the simplified version from the HybridMax at http://www.diyforums.org/MAX/MAXe12.php .  If this is put into the system what then is the current load that the power supply needs to be able to output?  If this goes into the system, are two of them needed, one for each channel?
   
    Third, how well does the diode method of bypassing the headphones at startup / shutdown work?  (Seen here: http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/5805#post_7413132)  Do the LEDs continue to blink indefinitely? 
   
  Thanks!

 -Whil
   
  Parts are on the way!


----------



## holland

Quote: 





whil said:


> First is the headphone delay worth putting in?  Lets say I have a friend fire this up while I'm away, I'd rather not lose some nice Sennheisers.
> 
> Second, I've been looking at the e12 circuit and the simplified version from the HybridMax at http://www.diyforums.org/MAX/MAXe12.php .  If this is put into the system what then is the current load that the power supply needs to be able to output?  If this goes into the system, are two of them needed, one for each channel?
> 
> Third, how well does the diode method of bypassing the headphones at startup / shutdown work?  (Seen here: http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/5805#post_7413132)  Do the LEDs continue to blink indefinitely?


 
   
  Sure, the e12 would help.  If you go with the e12, there would be 2 channels on the board.  If you build your own, you would replicate the circuit, it's for 2 channels as it's a DPDT relay.
   
  I've not used the diode method to bypass.  I do have a LED with a series resistor to visually indicate when I should insert the headphones.  You'll still get a pop.  Also, I wouldn't short the output to ground with the diode.  I wouldn't bother with this for protection.  A visual reminder, sure.
   
  I'm not sure how much the e12 draws, but I would guess no more than 40mA.


----------



## Whil

Thanks Holland, 
    I think I've gotten this down but let me make sure I'm clear, and not doing something stupid.
    I'd put the modified e12 into the circuit (http://www.diyforums.org/MAX/MAXe12.php) with the power to the relay coming in across DM2 on the contact pins for the relay, while the L&R output from the amp (to the head phones) is coming in on the respective relay pins which get closed to the headphone jack when the relay closes?
   
   Second clarification, the e12 circuit calls for 12 to 30 V and says to draw the power directly from the power supply, as to have the e12 portion of the circuit start working when the amp is turned on.  However, the power supply is 48V.  Should the V+ terminal on the e12 then be ran in series with a resister to drop the voltage over the e12 to somewhere between 12 and 30V?

 Thanks for the help!


----------



## holland

Quote: 





whil said:


> Thanks Holland,
> I think I've gotten this down but let me make sure I'm clear, and not doing something stupid.
> I'd put the modified e12 into the circuit (http://www.diyforums.org/MAX/MAXe12.php) with the power to the relay coming in across DM2 on the contact pins for the relay, while the L&R output from the amp (to the head phones) is coming in on the respective relay pins which get closed to the headphone jack when the relay closes?
> 
> ...


 
   
  In that circuit, you'd put the amp power into V+.  The circuit drops it down to 12V to drive the relay (QM1 and DM1 will drop to DM1's voltage spec, 12V zener means 12V output).  You do not connect the amp power rail to DM2.  Yes, you wire the amp output and the headphone jack to the relay pins (the normal closed pins).
   
  No, no series resistor only.  You need to supply a voltage splitter.  A resistor divider will work.  There's already two on the Starving Student, to set the voltage for the gate of the output mosfet.  Replicate it (don't connect it to that point), with a 3rd divider (2 more resistors) to set the voltage you want.  Power the e12 circuit in parallel to the resistor that is connected to ground.  For a real Starving Student, that is roughly at 24V.  I haven't looked at the modified version with the 12AU7, but it will be over the heater voltage.


----------



## Goobley

As far as I'm aware an e12 will draw too much current for a voltage divider to work, the realy will draw continuously around 10mA (wi more consumption when the capacitor is charging) and a resistive divider is normally designed to run at about 1mA with e same current going through the top and the bottom resistors as it is used as a reference, not as a place to draw current. Personally I would be inclined to increase RM1's value by a factor of 1.5 or 2 and then just put a heatsink capable of a couple of Watts on the bd139 (it's a Zener controlled voltage regulator anyway) and just use that.

Cheers!


----------



## holland

Quote: 





goobley said:


> As far as I'm aware an e12 will draw too much current for a voltage divider to work, the realy will draw continuously around 10mA (wi more consumption when the capacitor is charging) and a resistive divider is normally designed to run at about 1mA with e same current going through the top and the bottom resistors as it is used as a reference, not as a place to draw current. Personally I would be inclined to increase RM1's value by a factor of 1.5 or 2 and then just put a heatsink capable of a couple of Watts on the bd139 (it's a Zener controlled voltage regulator anyway) and just use that.
> 
> Cheers!


 
   
  Build it and find out.  It's not hard to tweak the circuit and power it with the power brick directly.  A voltage divider is just something that does what it does and has no restriction, it'll just burn some power.  The e12 circuit just needs voltage and some small current.  I'm not sure how much, haven't done the math and too lazy to do an analysis with pen and paper and looking up datasheets.
   
  A series resistor may work too, perhaps about 68K, I'm not sure.  I had thought about just heat-sinking it, but figured it's not really necessary if you can burn off power in other parts.
   
  After you build it, you can measure current draw and voltages at certain points.  Build it with a very long delay, so your DMM can settle.  You'll see active and inactive currents and voltages.
   
  Edit: Ah, well, you made me get off my ass and take a look at some parts.  There's a 48V relay from Omron that I recalled.  You can "repart" the circuit to operate around that.


----------



## JBal4

will the 12au7 version of this amp be strong enough to power a set of beyer dt990 600 OHM?


----------



## holland

Quote: 





jbal4 said:


> will the 12au7 version of this amp be strong enough to power a set of beyer dt990 600 OHM?


 
   
  Yes.


----------



## tomb

Quote: 





holland said:


> Build it and find out.  It's not hard to tweak the circuit and power it with the power brick directly.  A voltage divider is just something that does what it does and has no restriction, it'll just burn some power.  The e12 circuit just needs voltage and some small current.  I'm not sure how much, haven't done the math and too lazy to do an analysis with pen and paper and looking up datasheets.
> 
> A series resistor may work too, perhaps about 68K, I'm not sure.  I had thought about just heat-sinking it, but figured it's not really necessary if you can burn off power in other parts.
> 
> ...


 
  We "reparted" (I prefer re-designed) the relay-delay for the MOSFET-MAX.  It uses a 24VDC relay.  The switching is much faster.  You can get a noticeable turn-on/turn-off thump with the lower-voltage relays (speed of contact closing, not the delay in the circuit).  At higher voltages, it becomes nothing more than a click with most headphones.
   
  Higher voltage relays are more susceptible to arcing and burning the relay out over time, though, so we also changed the protection diode to a voltage suppressor.  Overall, the circuit is more simplified and works better (at least in the MOSFET-MAX and MiniMAX):
   





   
  Full details are here: MOSFET-MAX Relay-Delay


----------



## holland

Quote: 





tomb said:


> We "reparted" (I prefer re-designed) the relay-delay for the MOSFET-MAX.  It uses a 24VDC relay.  The switching is much faster.  You can get a noticeable turn-on/turn-off thump with the lower-voltage relays (speed of contact closing, not the delay in the circuit).  At higher voltages, it becomes nothing more than a click with most headphones.
> 
> Higher voltage relays are more susceptible to arcing and burning the relay out over time, though, so we also changed the protection diode to a voltage suppressor.  Overall, the circuit is more simplified and works better (at least in the MOSFET-MAX and MiniMAX):
> 
> ...


 
   
  That's pretty cool.  What accounted for the speed increase?  Probably the cap charging time?  There's probably about 200ms or so for the voltage to come up in the prior stuff.  I can't say I've noticed the arcing with higher voltage (24VDC, haven't tried the 48VDC relay), how did you discover that?  AMB's e12 uses 24V for the split rail relays.  I hadn't heard about problems with that, at least when I was active a few years ago.  I'm not sure if there were recent discoveries about that on his site.
   
  Also, why not have a resister in parallel with CM3 to discharge faster?


----------



## tomb

Quote: 





holland said:


> That's pretty cool.  What accounted for the speed increase?  Probably the cap charging time?  There's probably about 200ms or so for the voltage to come up in the prior stuff.  I can't say I've noticed the arcing with higher voltage (24VDC, haven't tried the 48VDC relay), how did you discover that?  AMB's e12 uses 24V for the split rail relays.  I hadn't heard about problems with that, at least when I was active a few years ago.  I'm not sure if there were recent discoveries about that on his site.
> 
> Also, why not have a resister in parallel with CM3 to discharge faster?


 
  My guess is the higher voltage.  If that causes a shorter cap charging time, then maybe that's it.
   
  I haven't noticed arcing in these relays, either - they're sealed. 
	

	
	
		
		

		
		
	


	




  However, I've seen plenty of it in my old model railroad days.  Turnouts are often run at 12V-16V with open coils.  (There are other methods to deal with it in that hobby.)  I think cetoole suggested it after reading the recommendations for the smaller relays used in the MOSFET-MAX input signal relay system, so it seemed a prudent thing to do on the headphone relay-delay.
   
  The resistor idea is intriguing.  We have probably gone the other direction from AMB's e-12: toward simplicity and fewer parts.   However, the bump-on/bump-off scenario can leave a headphone unprotected if the delay is set on the short side.  So, anything to discharge that cap faster might be a good idea.


----------



## tomb

Here's a table I found from Tyco Electronics that details typical contact materials, the melt voltage, the arc voltage, and arc currents:




   
  As you can see, we may be in the optimum range with all of these at 24V - some of them even at 12V (I don't know what the current is, either, but it doesn't look like it takes very much.).
   
  Tyco describes the use of the protection diode (1N4148 in previous designs) and its result in holding up the relay coil:
  "Some relay users connect a diode across the inductive load to prevent
counter voltage from reaching the contacts. When the relay contacts
open, the stored energy of the inductance recirculates through the diode,
not through the arc. While this is an acceptable method of protecting the
contacts, it does result in lengthened hold-up time of the inductive load."
   
  So maybe the use of the suppressor diode is what speeds things up?


----------



## plumcakk

I was just wondering whether there would be any repercussions for using a normal diode instead of an LED for the tube.
  I find the glow kinda tacky, but using a huge resistor to dim it would be alright also.

 If the voltage drop is the same, does it matter?


----------



## Beftus

If you don't want tube LEDs just omit them and their associated resistors.


----------



## plumcakk

Thanks.
   
  So they're not actually part of the signal path?


----------



## holland

Quote: 





plumcakk said:


> Thanks.
> 
> So they're not actually part of the signal path?


 
   
  decoration if it's a LED sitting underneath the tube socket.
   
  If there's a mod for the cathode resistor using a LED and transistor, then that's part of the signal path.  I don't know what's the current documented tweaks.


----------



## holland

Quote: 





tomb said:


> Here's a table I found from Tyco Electronics that details typical contact materials, the melt voltage, the arc voltage, and arc currents:
> 
> 
> 
> ...


 
   
  Thanks for the info, Tom!  You might find this interesting.
   
  http://sound.westhost.com/project33.htm
   
   
  Quote: 





> I carried out some tests to see just how quickly the relays could be operated. The results were something of an eye-opener (and I _knew_ about the added delay caused by a diode!). The relay I used was a small 24V coil unit, having a 730 Ohm coil and with substantial contacts (at least 10 Amps). With no back-emf protection, the relay opened the contacts in 1.2ms - this is much faster than I expected, but the back-emf went straight off the scale on my oscilloscope, and I would guess that the voltage was in excess of 500V. When a diode was added, the drop-out time dragged out to 7.2ms, which is a considerable increase, and of course there was no back-emf (Ok, there was 0.65V, but we can ignore that). Using the diode / resistor method described above, release time was 3.5ms, and the maximum back-emf was -30V, so this seems to be a suitable compromise.
> I was not able to test the zener method prior to publication, since I did not have the 24V zeners needed on hand. I would expect this scheme to be as good or better than the diode / resistor combination. The graphs below show the behaviour of the circuit with and without the resistor and diode. The estimated 500V or more is quite typical of all relays, which is why the diode is always included. This sort of voltage will destroy most transistors instantly. It is exactly the same process used in the standard "Kettering" ignition system used in cars, but without the secondary winding, or the "flyback" transformer used in the horizontal output section of a TV set.
> 
> 
> ...


----------



## holland

I found some more information in some app notes.  Diode + Zener is equivalent to the zener suppression diode.


----------



## tomb

Wow - very interesting!  That certainly explains the transients we were seeing back in the day.  I never really guessed it was back-emf, but it makes a lot of sense.  I was trying to find out in the documentation for suppressor diodes whether they were a "combo" component, but I couldn't find it anywhere.  Anyway, unless I'm misinterpreting, the suppressor diodes are a good choice to control these transients.


----------



## holland

Quote: 





tomb said:


> Wow - very interesting!  That certainly explains the transients we were seeing back in the day.  I never really guessed it was back-emf, but it makes a lot of sense.  I was trying to find out in the documentation for suppressor diodes whether they were a "combo" component, but I couldn't find it anywhere.  Anyway, unless I'm misinterpreting, the suppressor diodes are a good choice to control these transients.


 
   
  Yeah, back EMF.  Wow, -750V from a 12V relay, but man it switches fast.  It makes sense for sure, blocking the back EMF keeps the coils charged.  Yep, suppressor is the best choice.  All I found for suppressors is that it's modeled as 2 zener diodes, anode to anode.  But, since I have a ton of diodes and some a hundred or so zeners, I think I might go and retrofit. 
   
  One thing I'm not sure about is the voltage ratings used for the suppressors and subsequent zeners.  For the mosfet max, it's 48V.  In the data above, they also use 2x the relay voltage.  I take it that's "standard"?
   
  Anyhow, to make this SSMH related, forgoing the regulator will probably work if one is still using the 48V SMPS.  That leaves, a resistor, a cap, a diode, a transistor, a TVS diode (96V?), and a 48V relay.  It seems simple enough, I might retrofit mine and actually rebuild the whole thing with a mix of the Torpedo and the SSMH in a non-starving build.


----------



## ilkafrv

Hi every one. I need some help on debug the SSMH amp DIY (12AU7 version). I decide to make SSMH as my very first DIY project. I plan to seperate two chanels to two board. So I did one chanel first. 
   
  But when testing:
   
  - When no input, output | input V = 0, output V = 0.75V (not ok?). When connect headphone (not input), I hear eh eh eh eh eh eh eh ru ru ru ... in series.
  - When connect input, output. I hear the music but have some ru ru ru in delay.
   
  Check
  - Input V = 47V.
  - Tube heater vol is about ~ 12-13 V.
  - Tube Cathode voltage = 0.5V (seem not ok?)
   
  So what could cause this problem? Any ideals? BTW, I place C3 (470uF) and C6 (680uF) too close to each other. Could this be a problem?
   
  EDIT: Turn out to bad solder. I redid some and it work perfect now.


----------



## Eerie

Is this power supply good for the SSMH?
   
  http://i2.minus.com/ikKN0HMLDN9Ic.jpg


----------



## Goobley

It's probably fine but everything depends on it's output noise and you can't tell that without putting a scope on it or just trying it.


----------



## Whil

I finally got everything together in my SS Amp, and much to my chagrin... it did not work. I can plug everything in and I hear a *click click click* at about 2 times / second. If I turn the volume all the way up I can hear the music faintly in the background immediately preceding the click. I think this is all related to my C1 popping. For what ever reason my C1 popped, I'm not sure why that happened, I figured I may have damaged the capacitor at some point, so I replaced it. However the second one just popped as well. Any one have any idea what would cause this? Let me get a quick idiot check, the Long wire on the capacitor is the + terminal correct? (It says so on its data sheet...) And that should be attached to the node after the switch with the - terminal on the capacitor going to ground correct? ... Time to order some more caps . Thanks for the feedback.


----------



## Goobley

Well it sounds like reverse polarity, did you get the wires from the DC input socket the right way round?


----------



## Whil

Do C1 and C6 have to be the same?  I have one 500uf cap left.  C6 is 220uf.  I could replace the C1 with the 500uf.  And yes, the power supply was opposite of what I thought it was.  Good call & Thanks!


----------



## tomb

Quote: 





whil said:


> Do C1 and C6 have to be the same?  I have one 500uf cap left.  C6 is 220uf.  I could replace the C1 with the 500uf.  And yes, the power supply was opposite of what I thought it was.  Good call & Thanks!


 
  Generally speaking, you want parts of one channel to be identical to the parts of the other channel with *stereo* electronics/devices.  C1 is the "power" cap for the Right channel and C6 is the same thing for the Left channel.  You might get different responses between channels if the parts are not the same.
   
  Just an FYI, but we upsized C1 and C6 to 680uf minimum for the Starving Student PCB amplifier.


----------



## KimLaroux

Quote: 





tomb said:


> Generally speaking, you want parts of one channel to be identical to the parts of the other channel with *stereo* electronics/devices.  C1 is the "power" cap for the Right channel and C6 is the same thing for the Left channel.  You might get different responses between channels if the parts are not the same.
> 
> Just an FYI, but we upsized C1 and C6 to 680uf minimum for the Starving Student PCB amplifier.


 
   
  Sorry to have to say that but... nop, you misread the schematic on that one.
   
  C1 is the first power deoupling capacitor, used directly by both output MOSFETs.
  C6 is the second power decoupling cap, used by both tubes.
   
  C6 is isolated from C1 by R13, creating a CRC filter for the tubes.
   
  So no, they don't have to be identical. 
   
  edit: And I'll add that if you have two different sizes for those positions, make C1 the larger one.


----------



## tomb

I suppose you're right - I was going more by the PCB that Dsavitsk designed and perhaps not by schematic.  You know what they say when you assume ...


----------



## Whil

Something about introducing a tertiary condition...
   
  Anyways, good call on the power supply having an opposite-of-normal polarity!  And I put a 580uf capacitor in the c1 position (220uf in the other positions) and it works like a charm (Save one of my mosfets not working  haha.  So close to operational .)
   
  Next up, I'm going to introduce the 48V DP relay and get the delay circuit working with some LED's in there as well...
   
  Thanks!

 Pics to come!


----------



## mawoca

Last Thursday at about 10pm CST, another 12AU7 variant Millett Starving Student was born! I'm thrilled to say that the first power-on went flawlessly, all systems go right out of the gate with nothing to troubleshoot! Dead quiet too, omg. After a weekend of off and on burn in, this thing absolutely sings! I love it! Mates up well with my grubDAC and my slightly modded Grado SR60i's. I did somewhat of a perfboard design to keep the guts from turning into too big of a mess and used a copper board ground plane. It's using some 50's RCA long black plate 12AU7 tubes.


Here's a couple of glamour shots and the obligatory pic of the guts.







I broke up the resistors and capacitors into two perfboard sections, essentially one for the tubes and one for the output. They fit in nicely I think!

Cheers!


----------



## mosshorn

Quote: 





mawoca said:


> Last Thursday at about 10pm CST, another 12AU7 variant Millett Starving Student was born! I'm thrilled to say that the first power-on went flawlessly, all systems go right out of the gate with nothing to troubleshoot! Dead quiet too, omg. After a weekend of off and on burn in, this thing absolutely sings! I love it! Mates up well with my grubDAC and my slightly modded Grado SR60i's. I did somewhat of a perfboard design to keep the guts from turning into too big of a mess and used a copper board ground plane. It's using some 50's RCA long black plate 12AU7 tubes.
> 
> 
> Here's a couple of glamour shots and the obligatory pic of the guts.
> ...


 
   
  Wow, that yellow is gorgeous! Great work!


----------



## awesomebob

Thats really nice, I now reading through this thread to make my first amp, I'll be extremly happy if it turns out half as good as that...


----------



## Tjj226 Angel

Hey guys, I am looking at building one of these for a friend. Not too long ago I saw a web page for the 12AU7 mod, and now I can not find it. However, as I look through the pages of this post, it seems like you can just build the amp and throw 12AU7s in it and call it done. I am not sure if this is true or not. 
   
  Provided that the 12AU7 mod is not a mod at all, does anyone know of a kick arse mod to do to this amp to really make it sound warm, dark, and lush?


----------



## Goobley

It is a slight mod, the bias point for the MOSFET and valve heater has to be moved slightly. Here's the page for the mod with the schematic: http://diyforums.org/SSMH/SSMHvariants.php

This amp sounds good on its own, but if you want a slightly blacker background (also increases the gain slightly) then you could think about adding a constant current source to the tube, this does however add some complexity to the tube stage.


----------



## holland

Warm, dark, and lush is the opposite of what a CCS would do.  You sound like you want tube distortion, and lots of it.  Resistors.  The "sound" of the 19J6 at the operating point for the SSMH is warm, but not really dark and lush, even though it's not in the best operating point for the tube.  The 12AU7 mod, I have no idea, but I've heard plenty of 12AU7s and I wouldn't necessarily say it's as lush a a 6DJ8, generally speaking.  There may be a tube that exhibits that, however.
   
  Depending on what headphones you're using, you may get the sound you want with a Morgan Jones amp from Headwize, if it's even still alive as a site.


----------



## anachronsimic

Quote: 





tomb said:


> I apologize for not knowing where to find it specifically, but there is another variant that used metal tubes.  Maybe someone else will point it out.



  
 Quote: 





alphaman said:


> *tomb:* Thx for summarizing! [FYI: My main ref to this project has always been: http://www.pmillett.com/starving.htm ] So, based on your  succinct summary ..._this thread_ seems ridiculously long...i.e.,  if your two external links (Millet's DIY site pages) are the ONLY major topological changes/ mods to the orig. design... then I'm guessing much of the discussions in THIS ~440-page  thread have been ...  ... about what ... MSSH _cosmetics_  ??
> 
> IAC ... I'm perhaps most curious about the addition of CCS. Not sure whether KimLaroux's recent mention of it is new to this thread and, in general,  the MSSH design. How does CCS improve sound over orig.?



  
  
 I know that this is probably a moot point at this point but: http://www.head-fi.org/t/319231/millett-starving-student-hybrid-amp/2820#post_5584504
  
 The reason I've held on to that link is that I'm actually planning on making that version at some point but it's sort of a pipe dream at the moment.  I'm expecting to actually make it some point this year though, as I'm gonna start my EE education soon.  
  
 Anyways, continue.
 Edit: Aw man I'm already beat to it. My bad, sorry.


----------



## ProTofik

Quote: 





holland said:


> Your output caps, C3 and C5, are too small.  I used 1000uF, but 470uF is a minimum.  KimLaroux's formula is almost correct.  You need to take into account that the high pass filter is C3 (or C5) interacting with the parallel resistance of 2K and the output headphones.
> 
> Anyway, the corner frequency, which the equation 1/(2*pi*RC), is about the -3dB point, and it bends about it at 6dB per octave.


 
   
  I replaced these capacitors with 1000uF, 25V ones. Here is the result.
   

   
  Thanks. Are there any other recommended modifications that I can make to my student? This is how it looks right now:
   

   
   
  And one more thing. I would like to make a linear 48V power supply (I use switching one right now). I know that my amp at start need about 1.5A and it drops after few seconds to 380mA. Can you recommend me what transformer and parts I should use? I know how to make simple LM78xx based power supplies but I never done anything above 15V.


----------



## Tjj226 Angel

NVM. 
   
  I answered my own stupid question


----------



## plumcakk

Here is my first build! Chose the 17EW8 because it was cheap. Made an absolute mess of the wire management so there's not many pics of the internals (it's not pretty). That'll teach me for not using a ground plane/using #18 in a 4.5" x 7" x 2.5" box!
   
  Relatively trouble-free start up with no hiccups, aside from the fact that apparently I wired the pot backwards. So now it turns counterclockwise.
   

   

   

   

   

   

   
   
   
  I am curious though, I seem to be hitting my personal volume limit on my DT880/600s with the pot turned maybe 10 degrees, and that's with 50kohms input resistance(the second switch on the top of the box is meant to engage the input resistors). If I want to be able to utilize more of the pot, that means I should try a larger resistance on the input, right?


----------



## holland

Quote: 





plumcakk said:


> Chose the 17EW8 because it was cheap.
> 
> I am curious though, I seem to be hitting my personal volume limit on my DT880/600s with the pot turned maybe 10 degrees, and that's with 50kohms input resistance(the second switch on the top of the box is meant to engage the input resistors). If I want to be able to utilize more of the pot, that means I should try a larger resistance on the input, right?


 
   
  Bad choice.  The 17EW8 has a mu of 50.  The 19J6 is about 39, IIRC.  The 12AU7 is around 17-19.
   
  Larger resistance will reduce signal, and with noise in the amp getting amplified, your signal to noise ratio decreases.  It'll work, but I think it's a crappy solution.  If you look at Pete Millett's original design with the 19J6, he had some feedback to reduce the gain.  You can add some more, but what you started with is a poor choice.
   
  How did you select the operating point of the 17EW8?


----------



## plumcakk

Quote: 





holland said:


> Bad choice.  The 17EW8 has a mu of 50.  The 19J6 is about 39, IIRC.  The 12AU7 is around 17-19.
> 
> Larger resistance will reduce signal, and with noise in the amp getting amplified, your signal to noise ratio decreases.  It'll work, but I think it's a crappy solution.  If you look at Pete Millett's original design with the 19J6, he had some feedback to reduce the gain.  You can add some more, but what you started with is a poor choice.
> 
> How did you select the operating point of the 17EW8?


 
   


 Yeah, I noticed that the amount of noise increased with the input resistance. I went with the schematic that was posted earlier in this thread done by the_equalizer, because honestly my knowledge of how triodes work is fairly limited. They don't teach you valves anymore in EE, haha.
   
  I guess my next step would be to try to implement some negative feedback though. The sound right now is perfectly acceptable, with almost no noise at normal listening levels unless I'm touching the volume pot (probably a sign that not all of my grounds are done correctly...)


----------



## KimLaroux

Quote: 





plumcakk said:


> Yeah, I noticed that the amount of noise increased with the input resistance. I went with the schematic that was posted earlier in this thread done by the_equalizer, because honestly my knowledge of how triodes work is fairly limited. They don't teach you valves anymore in EE, haha.
> 
> I guess my next step would be to try to implement some negative feedback though. The sound right now is perfectly acceptable, with almost no noise at normal listening levels unless I'm touching the volume pot (probably a sign that not all of my grounds are done correctly...)


 
   
  Not that hard to do since the amplifier is inverting. Just run a wire from the output to the grid trough a 10 K resistor or so.
   
  I'm planning on doing something similar... once I get the damned thing working =/


----------



## holland

Quote: 





kimlaroux said:


> Not that hard to do since the amplifier is inverting. Just run a wire from the output to the grid trough a 10 K resistor or so.
> 
> I'm planning on doing something similar... once I get the damned thing working =/


 
   
  I've done it, not hard as you say, but one would probably not want tons of global negative feedback.  It, IMO, would be better to use a tube with lower mu and reduce the amount of feedback.
   
  FWIW, I have the original 19J6, as I got on this when it was published.  I needed local (keep cathode resistor unbypassed) and global feedback (somewhere between 6dB to 12dB), to bring it to a reasonable point.  10K may be too small.  I think I'm running through 100K, and 10K from the pot to the grid.  Injecting after the 10K, to the grid.


----------



## Tjj226 Angel

Three last questions guys. 
   
http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
   
  1: As I look at the schematic for the 12au7 mod, I see that there are two 0.22uf caps in parallel with the 470uf caps. The 0.22uf caps are optional, and with such a little change in capacitance, I am wondering if it would be smarter to buy higher quality 470uf caps, or simply add in the 0.22uf capacitors and leave it alone. 
   
  2: Resistors R2 and R8 on the schematic are listed as 390K ohm resistors. However, on the BOM page, they are listed as 220K ohm resistors. Which one should I get? 
   
  3: Resistors R15 and R14 look like they just essentially lower the volume a bit. Is this true, or do they serve a greater purpose?


----------



## KimLaroux

Quote: 





tjj226 angel said:


> Three last questions guys.
> 
> http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
> 
> ...


 
   
  1: I got Elna Silmic II in there and can't hear any difference with or without the 0.22µf film caps in parallel.
   
  2: The BOM is probably for the 19J6. Those resistors were changed in the 12AU7 to lower the heater voltage from 19 to 12 V.
   
  3: See http://www.aikenamps.com/InputRes.htm


----------



## holland

Quote: 





tjj226 angel said:


> Three last questions guys.
> 
> http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
> 
> ...


 
   
  1.  They are "supposed" to affect the sound quality, by using high end film caps you can get better sound.  I quote "supposed to" because I don't have golden ears.  I didn't bother using them on mine.  Others argue that bypasses smear the sound.
  3.  They prevent oscillation.  Kim's link explains it.  It's the same for the mosfet gate stoppers.  R3/R9.
   
  Edit, when you wire it (assuming you don't have the PCB), put the stoppers right on or very close to the device.  I put them right on the socket, and the mosfet pin.


----------



## tomb

Quote: 





tjj226 angel said:


> Three last questions guys.
> 
> http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
> 
> ...


 
  The last two posts kind of give you an indication that the opinions for capacitor bypassing run the gamut.  It depends on an awful lot of things - including the amp circuit design and the capacitors involved.  You guessed correctly that they're not there for the extra capacitance.  They're there to "bypass" the electrolytic capacitor.
   
  Capacitor bypassing is based on a few things that are empirical except #3:
   
  1. Film capacitors sound better than electrolytic capacitors
  2. Large film capacitors - enough to match an electrolytic in ratings - are so large and so expensive that they're impractical.
  3. This is the based-in-engineering part: any audio output capacitor (used for AC-coupling) is going to form an RC circuit with the load (headphones).  This means that depending on the farads and impedances, certain frequencies will pass through better than others.
   
  Because of the RC "filtering" effect, it can be argued that the bulk of the very detailed frequencies - highs and midrange - will by and large pass through the small film cap, while the mid-bass and deep-bass will go through the electrolytic.  One might say it's an ingenious way of applying a high-quality film cap for the "most" sound, while the electrolytic ensures that all the bass frequencies still get through.  Some people say there's actually a cross-over of sorts and claim they can hear a "smear."  Others may notice that the highs are clearer, less-distorted and that the bypass arrangement sounds better than the electrolytic alone.
   
  One could also argue that the capacitor pair actually forms a brand-new, hybrid-style of capacitor and that the actual frequency bandwidth is the same for both, but the combination itself sounds/performs better.
   
  I don't know which is true, but I can tell you that there are definitely cases where the pairing sounds better than an electrolytic along.  There's also very little predictability in whether one pairing sounds better than another.  Generally speaking, Wima film caps (typically MKP10's at 0.1uf, 0.22uf, 0.33uf) perform fairly consistently with many electrolytics.  Even then, though, some combinations work, some don't.  Pairings of other type of capacitors are a crapshoot.  Luckily, there are several sources of documented results with bypass capacitor combinations - Dsavitsk's "Some Notes on Output Coupling Capacitors" at ECP Audio, Humble Homemade HiFi capacitor reviews, etc.
   
  Finally, Pete Millett uses Wima's as capacitor bypasses in many of his designs.  We thought it was a nice touch to put on his Starving Student, too.


----------



## ProTofik

I wonder one thing. Why C3/C3a/C5/C5a is said to be 63V or even more? There is no more than 12/19VDC on that line. I used 25V capacitors and they're doing the job. Nothing has exploded yet.


----------



## tomb

Quote: 





protofik said:


> I wonder one thing. Why C3/C3a/C5/C5a is said to be 63V or even more? There is no more than 12/19VDC on that line. I used 25V capacitors and they're doing the job. Nothing has exploded yet.


 
  If I'm not mistaken, if you short a MOSFET (which has happened with a number of builders in this thread), those caps could be exposed to 48V.  Granted, it's a conservative choice, but you usually choose cap ratings on the basis of failure.  It's one thing to short something out or have a bad tube, but it's something else again to blow electrolyte all over the place.  Only C7 and C8 (if you use them) are totally protected - the higher voltage would have to pass through the vacuum in the tubes and that's impossible if they fail.


----------



## ProTofik

Looks like I will have to replace them with 63V ones. Anyway, what are C7 and C8 caps used for? I don't have them in my build.


----------



## tomb

Quote: 





protofik said:


> Looks like I will have to replace them with 63V ones. Anyway, what are C7 and C8 caps used for? I don't have them in my build.


 
  Those are cathode bypass capacitors.  They're optional, but many people use them in this type of tube circuit.  I don't understand it all myself, but it's explained on pages 75-80 of Morgan Jones' book, "Valve Amplifiers."  The Starving Student circuit uses biasing resistors on the cathode side of the tubes - R5 and R11.  The resistance allows an additional current loop that produces a bit of feedback and reduces gain and available voltage to the tube (I may be stating that incorrectly).  Placing a capacitor across this resistor allows signal frequencies to "bypass" the resistor and pass through the circuit.  This removes the feedback/gain reduction for those frequencies.
   
  The cap itself forms an RC circuit with the resistance of the cathode, so you have to size it properly to prevent bass frequencies from being filtered out.  We use 1000uf on the MiniMAX/MOSFET-MAX, for instance, but those are different tubes and trimmers are used as the biasing resistors.  Dsavitsk sized C7 and C8 for the Starving Student PCB, so I'm sure they're sufficient if you want to use them.
   
  Truth be told, the gain is so high already on the Starving Student using the 19J6 or the 12AU7 that it may be better to leave them out, but that's up to you.


----------



## holland

It funnels the AC through the cap, allowing the resistor to set DC bias.  It increases gain also (there are equations for it).  Without the cap you get some negative feedback through the resistor, which reduces gain and also increases output impedance of the tube.  You do need to size the cap properly, as tomb indicated, due to RC filtering.  I don't use the cap.  I had it, but removed it in favor of a more usable range on the pot, coupled with global negative feedback.


----------



## plumcakk

Quote: 





tomb said:


> Those are cathode bypass capacitors.  They're optional, but many people use them in this type of tube circuit.  I don't understand it all myself, but it's explained on pages 75-80 of Morgan Jones' book, "Valve Amplifiers."  The Starving Student circuit uses biasing resistors on the cathode side of the tubes - R5 and R11.  The resistance allows an additional current loop that produces a bit of feedback and reduces gain and available voltage to the tube (I may be stating that incorrectly).  Placing a capacitor across this resistor allows signal frequencies to "bypass" the resistor and pass through the circuit.  This removes the feedback/gain reduction for those frequencies.
> 
> The cap itself forms an RC circuit with the resistance of the cathode, so you have to size it properly to prevent bass frequencies from being filtered out.  We use 1000uf on the MiniMAX/MOSFET-MAX, for instance, but those are different tubes and trimmers are used as the biasing resistors.  Dsavitsk sized C7 and C8 for the Starving Student PCB, so I'm sure they're sufficient if you want to use them.
> 
> Truth be told, the gain is so high already on the Starving Student using the 19J6 or the 12AU7 that it may be better to leave them out, but that's up to you.


 
   
  Quote: 





holland said:


> It funnels the AC through the cap, allowing the resistor to set DC bias.  It increases gain also (there are equations for it).  Without the cap you get some negative feedback through the resistor, which reduces gain and also increases output impedance of the tube.  You do need to size the cap properly, as tomb indicated, due to RC filtering.  I don't use the cap.  I had it, but removed it in favor of a more usable range on the pot, coupled with global negative feedback.


 
   
  This was really helpful! I had the bypass caps on the cathode without realising that they negated the feedback from the resistor. With the gain on my EW178 so high, I have a lot more usable range on my pot now.


----------



## Eta power

I got a pair of Grado SR80is last Christmas, and I've been listening to them daily since then. I've always read that they really open up when amped, but I had no idea just how much until I plugged them into my brand-new-build-by-me 12SR7GT Starving Student Millet Hybrid headphone amplifier.
   
  Some of the brightness went away, but the detail is amazing and the sound stage really opened up. Some of the music I listen to has a very lo-fi vibe, but on others, like classical and acoustic, the change is stunning. Definitely worth the effort! I think I did pretty good job on wire management, but it's late, so I'll post pictures tomorrow. All in all, I'm very pleased with my first amp build! Can't wait to get some more listening time in.


----------



## Colin94

Hello Head-Fi!
 
After reading the 433 pages of this thread over the last couple if weeks, I figured I'd be prepared to build this thing properly with the wealth of knowledge that everyone has provided - apparently not. 
 
I took things slow during the build, making sure I didn't make any mistakes (~24 hours into this thing), but apparently I didn't go slow enough. When I turned it on, the tubes glowed (19J6 version) and nothing seemed to be going wrong, so I was pretty happy. I didn't have a 1/4 inch adapter that fit with some cheap earbuds, so I plugged in my HD 25-1 II. Big mistake. Right channel is now blown (thankfully still under warranty).
  
 I opened the amp back up - one of the output caps had split open.  As far as my knowledge extends, I believe this is the problem. (May have put it in with reverse polarity... 1st timer mistake) From what I understand, this would be supplying the 'phones with too much voltage, right? 
 
I originally thought this problem was just channel imbalance, but upon playing a left channel/right channel only track, I'm getting a LOT of crosstalk as well. Where in the circuit could this be coming from? Or could it simply be because my output cap was bad?
 
I originally had the BOM Pot, but I just ordered the Alps pot, so I'm confident that any channel imbalance that I may have had won't be a problem in the future. 
  
 I also noticed that I get a massive amount of 'static' when I unplug and plug in my headphones. It only happens during the process of plugging in and unplugging.  I don't think that this is the 'turn on thump' that people are talking about, because it still happens when the amp is left on for more than 5 minutes.  I haven't heard of anyone else having this problem, so I'm interested in finding out what the problem could be.
  
 Thanks for any input guys!


----------



## Eta power

colin94 said:


> I opened the amp back up - one of the output caps had split open.  As far as my knowledge extends, I believe this is the problem. (May have put it in with reverse polarity... 1st timer mistake) From what I understand, this would be supplying the 'phones with too much voltage, right?


 
  Yes, if the cap fails, it could expose that channel to 19VDC. However, unless you wired it backwards, it's just an unfortunate component failure. I wired mine point to point and it worked fine from the get go, so you never know.

   
  Quote:


colin94 said:


> I originally thought this problem was just channel imbalance, but upon playing a left channel/right channel only track, I'm getting a LOT of crosstalk as well. Where in the circuit could this be coming from? Or could it simply be because my output cap was bad?


 
  If it was me, I would replace the capacitor before I started trouble shooting other things. My 2 cents.
   
  Good luck and keep us updated!


----------



## holland

I would fix the problem before replacing the cap.  You don't need the output cap to debug, pull it out, no need to connect the headphone jack.  The condition that blew the cap exists.  Also, what size cap are you using?
   
  Pictures help, before you remove the cap.
   
  Always check your build with a DMM.  The final step is plugging in headphones, not the first.
   
  Going slow is not really the best method.  Build and test.  You can go as fast as you feel comfortable doing.  I build quick, double check the circuit before applying power, apply power and probe points I feel are relevant (don't short out or you may blow something).  Sometimes I build in probe points if there is no resistor to probe against.  Then, if all is good, I pull out cheap headphones and connect them.
   
  Channel imbalance can be caused by a bad circuit, not just the pot.  The incorrect resistors in certain spots will do it.  Bad tubes can do it too.  If you suspect the pot, pull it and hard wire in a resistor divider.


----------



## Sodacose

So, I've got a bunch of extra 19J6's (I think it's 4 sets) at home and I need a new project. 
   
  Has anyone seen it used in any other circuits?  I'm thinking preamp or possibly a tube buffer, though it may be a little silly to build something with the funky heater requirement when I could just as easily go with something more common.  All the same, these extra tubes are just gathering dust.


----------



## tomb

Quote: 





sodacose said:


> So, I've got a bunch of extra 19J6's (I think it's 4 sets) at home and I need a new project.
> 
> Has anyone seen it used in any other circuits?  I'm thinking preamp or possibly a tube buffer, though it may be a little silly to build something with the funky heater requirement when I could just as easily go with something more common.  All the same, these extra tubes are just gathering dust.


 
  Your best bet would be to sell those to someone who wants them for a Starving Student or build another Starving Student yourself.
   
  There's nothing the 19J6 can do that the 6J6 can't do, except for the Starving Student.  Meanwhile, the 6J6 tube numbers in the tens of thousands and the 19J6 ... well, let's just say you could become a 19J6 tube dealer - for a little while, anyway.


----------



## Sodacose

Tomb,
   
  I just bought the iron for a Tubelab Simple SE build, so selling these is probably what I'll do.  I may keep one set, but I use the starving student so infrequently that even those may not ever be used.  I'll put them up in the FS/FT forum at some point soon.  Maybe some one has some KT88's they want to trade


----------



## H3nk

I found a pair of RCA 5963 for a decent price.
  After reading a bit it seems like they should be a suitable replacment for the 12AU7.
  Searched the thread and I couldn't find any comments on them.
  Will they work?


----------



## tomb

Quote: 





h3nk said:


> I found a pair of RCA 5963 for a decent price.
> After reading a bit it seems like they should be a suitable replacment for the 12AU7.
> Searched the thread and I couldn't find any comments on them.
> Will they work?


 
  To be honest, they've always been my favorite tubes in a low-voltage, 12AU7 circuit (like the original SOHA).  They generally have everything a 12AU7 has, but operate at a much lower plate voltage.*  I think they were originally made for WWII walkie-talkies, which needed lower voltage tubes to operate with the batteries at hand.  The data sheets say 67.5V is the typical operating plate voltage.  That's not too far from the Starving Student's operating voltage at the plates.
   
  * The closer a tube operates at its data sheet operating voltage, the more linear its response (better its performance).


----------



## johng1337

Hi everyone, 
  
 I'm a noob (very much so) and i've been trying to figure this out for an hour or so, and i can't seem to understand. Here's the thing. I thought i'd built a starving student (12au7 version), and it would be great if you guys could explain to me why these schematics http://diyforums.org/SSMH/variants/SSMH-12AU7.gif show 8 pins on the tubes, where as 12au7 have 9. What am i not getting? 
  
 Thanks in advance


----------



## Fred_fred2004

Pin nine is the centre tap of the heater and is not used so it's not being shown on the schematics
  
 cheers
 FRED


----------



## johng1337

Thank you very much, i feel much better knowing that


----------



## Zashoomin

johng1337 said:


> Thank you very much, i feel much better knowing that


 
 If you feel unconfortable doing a SS point to point the first time Fred is selling SS PCB's right now so you could PM him.


----------



## johng1337

It's very nice of you to suggest, but it wouldn't as much fun. The whole point of the exercise, i find, is the challenge of it. To be honest i thought about buying it (i saw it a few days ago), but i'd rather try on my own. I'll keep that in mind as a plan b though.


----------



## linhhonlangdu

Hi guys, I am new member and lack of experiences. I wonder that: can adapter Ciso IP phones be used as power source for Starving Student (using 12AU7 bulbs) ?


----------



## DrivenKeys

johng1337 said:


> It's very nice of you to suggest, but it wouldn't as much fun. The whole point of the exercise, i find, is the challenge of it. To be honest i thought about buying it (i saw it a few days ago), but i'd rather try on my own. I'll keep that in mind as a plan b though.


 
 Also, Fred is shipping from Australia. It's a beautiful little board, I may buy another, but you've gotta wait at least a week (usually more) to receive it in the states.


----------



## camdat

Hey guys, I had a question about the Nichicon 220uf 16v capacitor, Beezar no longer sells them and I was wondering if I could use this capacitor since Mouser is out of stock on the other one. They seem to be the exact same capacitor as far as I know but I just wanted to make sure.


----------



## domsch1988

Hey all,
after reading around 150 of the pages in this thread, i ordered a pcb from fred (thanks for this) for the 12au7 version. I plan on building it like reference. But, since i ordered 2 pcb's (you never know^^) i'd like to ask: is it possible to blow this thing up? Like using other opamps to boost this to like 5 - 10 Watts output?
Background: I'm using a Onkyo suround reciever to power two controll ones. Apart from this being overkill, i just don't like the sound of the onkyo. Since i have the pcb anyways, i thought i might give it a shot.
Adding to this, i would need a sub out (for a active sub). Would i add this before the amp, or after the preamp?

I know that this is all about headphones here, but since i'm using the SS as a base, i figured this might be the right place to ask. Thanks in advance for any input provided.

Rock on
Dominik


----------



## Kaaf

Fellow SS'ers
 I finished my SS with the PCB of Fred. Sounds good and fairly happy with it. But fairly is not 100%. Because I have a slight hum on my can's. This isn't bothersome when playing music, but during silent parts it's noticable. 
 The volume of the hum doesn't change when using the pot meter. Most likely a grounding issue. But I think my grounding is pretty OK, but there is alway room for improvment. Any clue on where to look/improve? Help is greatly appreciated
  
 (update)
 I totally rewired it, with shielded cables. works flawlessly right now. Now enjoying the AMP with a internal odac.


----------



## vixr

I was listening to my MHSS at work and I realized I never did post any pictures of the finished amp...its dead quiet and sounds pretty darn good...


----------



## Zashoomin

vixr said:


> I was listening to my MHSS at work and I realized I never did post any pictures of the finished amp...its dead quiet and sounds pretty darn good...


 
  
 That looks sick.


----------



## ProTofik

vixr said:


> I was listening to my MHSS at work and I realized I never did post any pictures of the finished amp...its dead quiet and sounds pretty darn good...



Are you sure that you have never posted it on here? I think I seen ss like this before.


----------



## alpha421

^Not in this thread.  Vixr did make a CKK2 SS amp that utilized Plexiglas walls that doubled as headphone stand.  Whoever owns it got a really great build.


----------



## vixr

I was able to get a moment to point a seaFLIR IIC thermal imager at my MHSS...here are the results.


----------



## Makiah S

vixr said:


> I was listening to my MHSS at work and I realized I never did post any pictures of the finished amp...its dead quiet and sounds pretty darn good...


 
 IF you are willing to build and sell those


----------



## the_equalizer

vixr said:


> I was listening to my MHSS at work and I realized I never did post any pictures of the finished amp...its dead quiet and sounds pretty darn good...


 
  
 That's a *fantastic* build vixr! Congratulations! I can only imagine what the other people at your wokrplace thought when you brought it in!  Which tubes did you use in your build?
  
 cheers!


----------



## vixr

the_equalizer said:


> That's a *fantastic* build vixr! Congratulations! I can only imagine what the other people at your wokrplace thought when you brought it in!  Which tubes did you use in your build?
> 
> cheers!


 
 The folks at work are used to my unusual amps, but this one got some curious looks...we are in a low static, clean lab, so visitors are pretty rare.
 I am swapping between some NOS 12AU7 RCAs and some used 12AU7 Mullards I got from a British guy on ebay...the Mullards sound fabulous but the RCAs have a bit more gain...


----------



## vixr

mshenay said:


> IF you are willing to build and sell those


 
 Thank you for the kind comment, it probably will be for sale in the future.


----------



## tomb

Beautiful work as you've always done in the past, Vixr!!  This one may have outdone all the others, though.  It's a long way from a Millett Hybrid in a lunch box (which I thought was great)!  Simply fantastic!!


----------



## vixr

tomb said:


> Beautiful work as you've always done in the past, Vixr!!  This one may have outdone all the others, though.  It's a long way from a Millett Hybrid in a lunch box (which I thought was great)!  Simply fantastic!!


 
 Thank you sir...


----------



## Makiah S

vixr said:


> Thank you for the kind comment, it probably will be for sale in the future.


 
 Oh dang I'd better start saving up now >.> so what are the power specs!


----------



## jshaffe

Well friends, I'm a long time lurker of the forum, first time tinkerer, first time poster here.
 I decided I was going to see if I could build a SSH amp and it turns out I cannot.
 When I turn her on she makes a quick chirp and nothing else. No smoke or flaming balls of fire but also, no glow from the tubes, no sound.

  
 Any diagnostic help you could provide would be much appreciated.  I think I'm a little depressed about the whole thing and the time I've put into it so far.
 Thanks!


----------



## vixr

I built a MHSS in a similar aluminum enclosure...I found that the kapton film in the isolator kits was too thin and the back of the transistors was able to bite through it and short. The aluminum was just rough enough to have some high spots...remove the isolator film and see if they dont have holes in them. Although, I must say your enclosure looks a bit smoother than mine.


----------



## jshaffe

Thanks for the speedy reply! I pulled the the isolator kits off and they seemed to look okay, I did a quick power on/off with them 'floating' and the result is the same as before. I probably should mention I am attempting to do the 12au7 with most of the equalizer mods.
 
Edit:
One thing I don't understand is the middle mosfet pin AKA pin 3, is wired to the bridge of tube pins 4/5 AKA the heaters, which are then connected to ground, so doesnt that mean the mosfet is grounded?
 
It appears I had my 48v line from the on/off switch attached to the right most pin, not the center pin. I made the switch back and tossed in a tube to test things out. My c1 cap on one side Git extremely hot in the matter of a few seconds and my heater glowed way too brightly. The heater thing tells me I have too much voltage on the heater like but the hot cap I don't get.


----------



## jshaffe

After tinkering around with my multimeter, I was able to correct the ground short, but my voltages seem to be all different than what others have posted on this thread.  Both channels of tube heaters glow brightly, and my C1 Cap heats up dangerously and quickly.  (Not C6, just C1 so it is isolated to one channel) Does anyone have a clear photo of a PCB that might help me see where I have gone wrong? I think I may be misinterpreting some part of the wiring diagram.


----------



## the_equalizer

jshaffe said:


> After tinkering around with my multimeter, I was able to correct the ground short, but my voltages seem to be all different than what others have posted on this thread.  Both channels of tube heaters glow brightly, and my C1 Cap heats up dangerously and quickly.  (Not C6, just C1 so it is isolated to one channel) Does anyone have a clear photo of a PCB that might help me see where I have gone wrong? I think I may be misinterpreting some part of the wiring diagram.




C1 is a decoupling capacitor for the power line. If we are talking about the same relative part numbers, it's tied to ground on one end and R13 and the power line on the other.

Please double check the voltage rating for that cap, as well as the voltage output of your power supply.

Cheers!


----------



## jshaffe

With the power switch in the off position:
 PSU---+48.6---DC Pin--+48.6--SW----------+C1-----------Ground
                                              |
                               ...Drain----------R13-------....
  
 When I hit the switch:
 PSU---(-22)---DC Pin--(-22)--SW----------+C1-----------Ground
                                          |
                           ...Drain----------R13-------...
  
 Both tubes glowing very brightly. This is super wrong.


----------



## Fred_fred2004

You are going about this the wrong way, you have made a wiring mistake somewhere
  
 get a copy of the schematic and a highlighter and trace everywire and connection, marking them off as you go - it's painful but it works 
  
 cheers
 FRED


----------



## jshaffe

fred_fred2004 said:


> You are going about this the wrong way, you have made a wiring mistake somewhere
> 
> get a copy of the schematic and a highlighter and trace everywire and connection, marking them off as you go - it's painful but it works
> 
> ...


 
  
 Can anyone verify that the 12au7 schematic: http://diyforums.org/SSMH/variants/SSMH-12AU7.gif is the same as this layout? http://cdn.head-fi.org/9/96/96ce0a3a_4f98a810_StripBoard_Layout_Revised.png
  
 I just want to make sure as I'm rechecking everything that the issue wasn't with a misinterpretation of the wiring diagram.


----------



## Fred_fred2004

Use the schematic rather than a layout, they both work but the schematic is easier to trace and understand
  
 cheers
 FRED


----------



## jshaffe

fred_fred2004 said:


> Use the schematic rather than a layout, they both work but the schematic is easier to trace and understand
> 
> cheers
> FRED


 
 Okay, I've been through everything twice using the highlighter and trace method stated above. I cannot find an error between what is there and what I have. Could fried out mosfets or some other messed up part account for the issues my amp is having?


----------



## jshaffe

Its working beautifully now! My wiring was correct all the way, but I read the tip+ picture wrong so my v+ was switched with my ground in the DC jack.


----------



## fugelpitch

Hi everyone!
  
 I have decided to build one of these nice amps after viewing the Instructables-page of eh1080.
  
 I'm wondering if anyone know or can guess how he fitted the tube sockets to the box without screws.
  
 Cheers,
 Jonas


----------



## awesomebob

He may have attached the sockets directly to a pcb like this http://www.head-fi.org/t/664191/starving-student-pcbs, the pcb could then be attached to the housing.....


----------



## fugelpitch

> He may have attached the sockets directly to a pcb like this http://www.head-fi.org/t/664191/starving-student-pcbs, the pcb could then be attached to the housing.....


 
  
 Judging from this picture: http://www.instructables.com/id/Headphone-Hybrid-Tube-Amp-SSMH/step3/Time-to-wire/
  
 Looks like he has soldered the tube sockets to the aluminium housing in some way. How to do it?
 Maybe use epoxy glue instead?


----------



## Avro_Arrow

My guess would be the combination of a very close fit and cyanoacrylate glue.


----------



## awesomebob

I am now trying to mount some screws to the inside of a case with epoxy, I will try to post pics later.....


----------



## awesomebob

so here is what I am trying to do.... mount 4 screws on the inside of the housing, this way I can remove it any time I want to....
  


 however whilst taking these photos one of the screws broke off, I have glued it back on, an tomorrow I will give them all a good 'wiggle', if they break off again, I will drill holes, counter sink them and then fill over the top  of the heads of the screws...
  
 I will let you know how it goes..


----------



## jshaffe

awesomebob said:


> so here is what I am trying to do.... mount 4 screws on the inside of the housing, this way I can remove it any time I want to....
> 
> 
> 
> ...


 
  
 Can you not use PCB spacers? http://www.hifizine.com/files/2011/06/Stack-3.-Installing-the-PCB-spacers-on-the-miniDSP.jpg
  
 they're pretty cheap.


----------



## awesomebob

jshaffe said:


> Can you not use PCB spacers? http://www.hifizine.com/files/2011/06/Stack-3.-Installing-the-PCB-spacers-on-the-miniDSP.jpg
> 
> they're pretty cheap.


 

 they would be good, I'll see if I can find some this weekend... cheers!


----------



## jshaffe

radioshack sells them


----------



## awesomebob

Thats a bit far for me, I live in Italy! But the glue seems to have held, and I can set the distance of the pcb from case by adjusting the nuts, so it seems ok.... But I wish we had radioshack here.....


----------



## vixr

awesomebob said:


> Thats a bit far for me, I live in Italy! But the glue seems to have held, and I can set the distance of the pcb from case by adjusting the nuts, so it seems ok.... But I wish we had radioshack here.....


 
 awesomebob... I think the problem is the length of the bolts you are using. You are able to put a good bit of leverage on the longer bolt, causing them to break the bond with the adhesive. Try using as short a bolt as possible if another one breaks off.


----------



## awesomebob

I agree, its not a solution that I am entirely happy with, but I would like to find a way to avoid having any screws visible on the outside of the case... I have limited skills/tools, resources, and I am reluctant to drill more holes in the case that may be ineffective..... Like you say I think the problem with the screws is the length in proportion to the surface area of the head.... The leverage is too much... I'll figure it out somehow... but any suggestions are welcome!


----------



## jshaffe

I'm not sure if it is because the channels are run using dual triodes but changing tubes in this amp seems to have a lot more effect on the sound than changing tubes in other amps. Has anyone else noticed this?


----------



## doors666

I am eagerly waiting for the pcb for the 12au7 version.I have the cisco 0.38a supply, headphones are realistic pro30 (32 ohms) and koss porta pro (60 ohms). Chain would be PC->ODAC->B1 preamp->SSMH. I have a few doubts that wanted to clarify while I wait for the pcb to arrive.

 1. Is there an error on the 12au7 schematic. why is c1 coming before r13 but c6 is coming from after r13, wont r13 act as a charging resistor for C6. Is this there on pcb also.
 2. There is no earth with the psu, should I use 0v for chassis earth also.
 3. does this psu have overcurrent protection. Couldnt find a datasheet on the web.
 4. do i need to insulate the rcas, headphone out, pot from the chassis.
 5. which are good places for carbon film resistors and which are for metal film.
 6. can chassis ground point be used as a star ground.
 7. Can i safely leave out the pot and control the volume from my B1 preamp.
 8. any changes recommended for component values needed for my setup.
 9. which caps. can i use:
 220uf panasonic FC and FM, Elna RE-3 – which is the best option. Does it help to bypass this with a film cap of say 10-15nf
 680uf, 63v – I only got Nichicon PW with this rating, Is it good enough or should I look for something else. Does it help to bypass this with a film cap. I also have 1000uf, 100v Nichicon PJ, can the psu handle this.
 470, 63v – only got UCC LXZ. Is it good enough or should I look for something else.
 220nf – got wima mkp2 and mks4. I guess mkp2 wins.


----------



## 00940

using this schematic:  http://diyforums.org/SSMH/variants/SSMH-12AU7.gif
  
 Quote:


doors666 said:


> 1. Is there an error on the 12au7 schematic. why is c1 coming before r13 but c6 is coming from after r13, wont r13 act as a charging resistor for C6. Is this there on pcb also.


 
  
 R13-C6 form a filter, reducing PS noise for the low current stages.
  


> 2. There is no earth with the psu, should I use 0v for chassis earth also.
> 4. do i need to insulate the rcas, headphone out, pot from the chassis.
> 6. can chassis ground point be used as a star ground.


 
  
 2. you can connect the chassis to 0V (at only one point preferably).
 4-6. not knowing how the pcb is setup, I'll let someone else answers that.
  


> 3. does this psu have overcurrent protection. Couldnt find a datasheet on the web.


 
  
 It would seem so, reading this, "_The power supply current limit cycles"_
  


> 5. which are good places for carbon film resistors and which are for metal film.


 
  
 r14-r15, r3-r9 are best carbon film, all others can be metal. But you'll probably have no trouble with using all metal film.
  


> 7. Can i safely leave out the pot and control the volume from my B1 preamp.


 
  
 If you do that, you need to wire a 50k resistor from the junction of r16-r14 to ground (same for the other channel)
  


> 9. which caps. can i use: 220uf panasonic FC and FM, Elna RE-3 – which is the best option. Does it help to bypass this with a film cap of say 10-15nf
> 680uf, 63v – I only got Nichicon PW with this rating, Is it good enough or should I look for something else. Does it help to bypass this with a film cap. I also have 1000uf, 100v Nichicon PJ, can the psu handle this.
> 470, 63v – only got UCC LXZ. Is it good enough or should I look for something else.
> 220nf – got wima mkp2 and mks4. I guess mkp2 wins.


 
  
 - 220uf: panasonic FC or FM. In this application, both are good enough (better than the Elna).
 - 680uf: the nichicon are fine
 - 470uf: the UCC are good (same league as the panasonic)
 - 220nf: mkp is usually a bit better.


----------



## jddiyer

I think i've read this thread a dozen times and im feeling lost. 
 I have ambitiously decided this would be my first diy amp project, it has me drawn in but im yet to finish....
 My question is  could this drive a very small set of speakers? I was thinking of trying to make a minimalist and very small speaker set to sit with the amp but i really have no idea.

 im fine with it only being a headphone amp, i have larger speakers for larger amps anyway. Thanks for your time.  

 I need to stop second guessing myself, solder everything together and finish this amp!
 then move on to the next one, thanks for getting me hooked guys! hahahaha


----------



## jshaffe

jddiyer said:


> I think i've read this thread a dozen times and im feeling lost.
> I have ambitiously decided this would be my first diy amp project, it has me drawn in but im yet to finish....
> My question is  could this drive a very small set of speakers? I was thinking of trying to make a minimalist and very small speaker set to sit with the amp but i really have no idea.
> 
> ...


 
  
 I hooked mine up to a set of logitech speakers and the sound was much less than ideal.  It was actually surprisingly loud, but the kind of speakers that are small enough to be powered by this amp are the same kind of speakers that you don't really want to listen to.  Plug in a pair of HD600s or HE-400s, you'll be a lot happier with the results.


----------



## iso-b

Hello everyone. This is my first audio project. Lets start with couple photos(shot with iPhone 4), quality is not that good, but I hope that you get idea.
  
  

  

  

  

  
 Case is made from Heat threated Magnolia and its coated with clear lacquer. Tubes are 12AU7 from Sylvania. Building case took like 6h and electronic side almost 10h.
  
 Sound is good. There is hum/buzzing sound when volume is turned high enough(without source) and I gets louder when touching pot. Grounding pot shaft would probably solve that. For that other hum/buzz I wont probably do nothing because it wont appear on volume area that I am using while listening. I am not using any grounding plate and desing is point-to-point. Would adding grounding plate solve my problem or is there some other ways to elminate that hum.


----------



## jddiyer

So last night i finished my build (at 2:30am) and got some crackles and very low volume. Im using a old cd player and some simple senn earbuds, but today all im getting is a loud smooth buzz in the right ear and no music at all. I have tried using my phone and other cans but still no luck. 

Any suggestions? Tubes are glowing nicely, mofsets are warm without being hot. I do have a DMM but zero idea how to use it :/ 

Thanks for all the help!

here is a photo of the build, i have a few others on my flickr too. http://www.flickr.com/photos/93935860@N05/11333145253/


----------



## soram

Hi All,
 I haven't really listened to music properly in a few years due to disillusionment with a lot of (expensive) equipment and sound quality. One of my loudspeakers gave up the ghost a while back and I've had some temporary replacements that are not great. Rather than spend the money one new ones, a couple of weeks ago, I decided to try some headphones first and see if it was my hearing or the equipment that was the issue! So after some searching I came across this thread and decided to build the amplifier. I also purchased some Sennheiser 650s secondhand.
  
 I bought the components from Farnell, nothing fancy or expensive, a pair of JJ Tesla 12AU7s from Watford valves and wired everything point to point.
  
 I must say I was awestruck at the sound quality! It was spectacular. Deathly quiet and totally engaging. I thought the gain was a little low at first but really I just had it too loud. It is perfectly adequate at around 75% volume.
  
 So I decided to add de_equalizers CCS last week. I got the components as listed and soldered them up, again point to point, turned it on and.......nothing. Well not nothing but very low volume. So I measured up and found the voltage supplying the CCS had dropped to 30V. The addition of the CCS added 7mA across the power supply resistor. I couldn't figure it out as the CCS itself was designed to deliver 1mA only. I eventually realised it was the 10K collector load. I measured 3mA through this. I figured I could just up it so I put in a 220K I had left from the build. This seemed to sort it all out. The voltage came back up to 41.8V and the amp played.
  
 The sound gains were as described. The gain increased, the bass is much tighter and more impressive and I think the upper mid range is much smoother but I need to listen to it a little more to be sure! In any case it is pretty awesome. I would recommend anybody to build it and to add the extra €5 components for the CCS. The BC327s seem to be fine!
  
 That being said I would appreciate any comments on the CCS.
  
  - Is the 220K resistor a bad thing? 
  - Would it be better to stay at 10K but connect the CCS to the unfiltered power rail instead?
  - How did de_equalizer get the measurements with the 10K in place?
  - I also put in the trim pots and trimmed the plate voltage to half the supply (20.9V and 41.8V respectively). However, this left me with a cathode voltage of 0.3V and not 0.9V as described in the post. I left it at that rationalising that the plate voltage was more important than the cathode voltage. Is this a bad thing or just a function of my valves?
  
 I guess I will have to get the school books out and make the calculations but I'd prefer just to be listening to it!


----------



## Jawmare

Nevermind, stupid questions.


----------



## the_equalizer

soram said:


> Hi All,
> I haven't really listened to music properly in a few years due to disillusionment with a lot of (expensive) equipment and sound quality. One of my loudspeakers gave up the ghost a while back and I've had some temporary replacements that are not great. Rather than spend the money one new ones, a couple of weeks ago, I decided to try some headphones first and see if it was my hearing or the equipment that was the issue! So after some searching I came across this thread and decided to build the amplifier. I also purchased some Sennheiser 650s secondhand.
> 
> I bought the components from Farnell, nothing fancy or expensive, a pair of JJ Tesla 12AU7s from Watford valves and wired everything point to point.
> ...


 
  
  
 Sorry for the long time in replying; lately I spend 99% of my time listening to music and only 1% around here    As to the numbers, as mentioned in my original post on the CCS mod, the source of the CCS and values is this section of the MiniMax site. Have a read and see how I arrived at the 1K / 10K resistor values.
  
 A couple of posts below that first post, I did mention that if you set your CCS for higher currents, it would be best to bypass R13, because of the increased voltage drop. In fact I did just that with my amp and it works just fine. Because the CCS loads isolate the triodes from fluctuations in the power supply (great PSRR: Power Supply Ripple Rejection) the RC filter for the triode sections becomes redundant.
  
 Finally, as to the matter of why your CCS are working with that 220 Kohm resistor, I'm at a loss. I would however, advise you to carefully check the circuit layout, wiring and values of the involved resistors in your CSS loads.
  
 Please note that measuring voltages across some parts of the CCS circuit and the triode stage is very tricky because of the high-impedances involved; your meter's input impedance get's clamped in parallel while measuring and can have a very high impact in the measured values. I had to resort to a very old, analog FET input meter and some indirect measurements to reliably 'see' the current values and voltages.
  
 Good luck and keep enjoying your amplifier!
  
 cheers!


----------



## soram

Many thanks for the reply. I wanted to measure all the voltage points again but I too want to spend more time listening! It is a really nice sounding amplifier and spurred me on to make some new power supplies for my LP12 and phono stage! I am again enchanted by the music.....
  
 I am running the same current through the bias but is was the feed to the CCS base drawing too much current. The 220K I think should work but probably won't be as stiff as your design. I will do the calcs over the next few days. I may just bypass the RC filter as you suggest but at the moment the sound is still magic and the bass is totally transparent compared to not having the CCS in place.
  
 My meter is >30 years old! Who knows what input stage it has. I'll check it out before I start measuring away.
  
 Cheers


----------



## scorp997

Well I finally built a 12au7 version of this amp, I have been watching this thread for a long time.
  
 My brother turned me onto this project and he had built one with the pcb board and is really happy with it. I too purchased a pcb, but once I started looking for a suitable enclosure I changed my mind and went for a point to point build.
  
 What I came up with is shown in my avatar. I can't upload photos yet, since my account is too new. I will post more when I can. The box is from a Kenwood CB-44 Dual Amp Balancer I found at a local PC recycle center and the heat sinks are just clamp-on style CPU heatsinks mounted to the sides of the box. The volume pot was already a 50k and the power switch made a perfect location for the 1/8" headphone jacks. The box is very tight and the way it opens makes it somewhat difficult to keep some of the leads short. I know the heatsinks may work better if turned 90deg, but there is plenty of heat rejection and I feel it looks much better this way. Another really cool thing about this case is that the volume knob has a lit ring around it that will work as a power indicator.
  
 Using all of the optional components, I found the gain was too high when I use my Shure SE315s and an iPod dock outs as a source. I removed the cathode caps and upped the input resistors to 500k and it seems to be working much better. After removing the cathode caps to floor noise is much less, though there is still a little there.
  
 This was a very cool project, thanks to all who made it possible.


----------



## the_equalizer

soram said:


> Many thanks for the reply. I wanted to measure all the voltage points again but I too want to spend more time listening! It is a really nice sounding amplifier and spurred me on to make some new power supplies for my LP12 and phono stage! I am again enchanted by the music.....
> 
> I am running the same current through the bias but is was the feed to the CCS base drawing too much current. The 220K I think should work but probably won't be as stiff as your design. I will do the calcs over the next few days. I may just bypass the RC filter as you suggest but at the moment the sound is still magic and the bass is totally transparent compared to not having the CCS in place.
> 
> ...


 
  
 It's great to read that this little project inspired you and helped keep you enchanted by the music!  
  
 If your meter is 30 years old, analog and it does NOT use batteries, then most surely you got mis-leading voltage measurements from it. The problem is the low input impedance of analog, passive meters. We discussed a bit about these problematic measurements back around page 421 in this same thread. You can read more about the meter input impedance problem here and here.
  
 You might want to re-check your measurements to make sure the CCS's are working as intended.
  
 cheers!


----------



## the_equalizer

scorp997 said:


> Well I finally built a 12au7 version of this amp, I have been watching this thread for a long time.
> 
> My brother turned me onto this project and he had built one with the pcb board and is really happy with it. I too purchased a pcb, but once I started looking for a suitable enclosure I changed my mind and went for a point to point build.
> 
> ...


 
  
 Great to hear you had fun and enjoy your new amp. The gain is hard to control indeed. I've been thinking about experimenting and adding a little bit of global negative feedback, as some builders in the thread mentioned they had done it and it had worked wonders. You might consider doing the same to help tame this little beast.
  
 By the way, as some posters say: pictures of  your amp or it didn't happen. 
  
 cheers!


----------



## scorp997

the_equalizer said:


> Great to hear you had fun and enjoy your new amp. The gain is hard to control indeed. I've been thinking about experimenting and adding a little bit of global negative feedback, as some builders in the thread mentioned they had done it and it had worked wonders. You might consider doing the same to help tame this little beast.
> 
> By the way, as some posters say: pictures of  your amp or it didn't happen.
> 
> cheers!


 
 I'd love to post a couple photos, but each time I try and insert a picture I get the popup "Your account does not have the required permissions to access this page"... I have a request into the moderator to see what they can do about this..
  
 As for the negative feedback, is it just as simple as adding a 10K (or so) resistor from the output (pin 1) of the tube to the grid (pin 2), or does it have to be further downstream? I'm still new to tubes, sorry if this is a silly question. I didn't see a definite answer to this when I searched.
  
 thanks in advance


----------



## DingoSmuggler

scorp997 said:


> I'd love to post a couple photos, but each time I try and insert a picture I get the popup "Your account does not have the required permissions to access this page"... I have a request into the moderator to see what they can do about this..


 
 There's a minimum number of posts before you can post pictures. I think it is 15 posts.
 Just put in links to the pics.


----------



## drabina

While I am waiting for the PCBs from Fred (the MHSS 12AU7 version), I have a couple of questions. I know that the answers are probably in one of the 6700+ posts but I hope you realize that going thru all that is almost impossible. So  here are my questions:
  
 1. Can the heatsink be mounted on the top or on the side of the enclosure and the MOSFET mounted inside the enclosure (touching the heatsink) so it is not visible on the outside? I am just trying to find a solution that will not expose parts outside of the enclosure.
  
 2. Is the CISCO power supply still the best power source for the 12AU7 version? I want to add two LEDs to light up the tubes. I know that they are only about 20mA each but the power supply is only rated at 380mA.
  
 3. Any problems with grounding in a wood enclosure?
  
 Thanks.


----------



## awesomebob

I went through a lot of it, but it is really hard, and its even harder to go back and find something later! If you check the starving student website they explain how to mount the mosfet on the inside of the case: (but it is a metal case so aids in the heat transfer)
  
 http://www.diyforums.org/SSMH/SSMHconstruct5.php
  
 For the power supply, I personally am having problems getting one for under 30 euros (italy), and I may actauly find it easier to get one shipped from the states!!!


----------



## iso-b

Quote:


drabina said:


> 1. Can the heatsink be mounted on the top or on the side of the enclosure and the MOSFET mounted inside the enclosure (touching the heatsink) so it is not visible on the outside? I am just trying to find a solution that will not expose parts outside of the enclosure.


 
 I can't see why you can't do so, but its probably more efficient for cooling to keep MOSFETs outside so you dont heat air inside of enclosure. My MOSFETs run quite hot even with http://item.ebay.com/390627718088/ those or atleast my heat sinks are quite hot so I think MOSFETs are too.
  


> 2. Is the CISCO power supply still the best power source for the 12AU7 version? I want to add two LEDs to light up the tubes. I know that they are only about 20mA each but the power supply is only rated at 380mA.


 
 That 380mA is @ 48V so you will be ok when your leds take 20mA @ 3.3V or so.
  


> 3. Any problems with grounding in a wood enclosure?


 
 I am using point-to-point with wooden enclosure and I don't have any grounding problems. Only small problem is with volume pot when I am touching it, but it could be fixed by grounding that shaft/knob thingy. There is some posts about that in this thread. For me it is only hearable with very high volumes, that I am not even using so not going to do anything to it. Might be same thing with metal or plastic enclosure not sure.


----------



## drabina

Thanks for the replies.
  
 One more question (for now): If needed, can I extend the legs of MOSFETs or that's not recommended? Just thinking that if I need to mount them outside, I may not be able to reach the PCB.


----------



## awesomebob

if you are based in the states I have the name of a user on here who had some power supplies, (I am not linked to him in anyway), if you want I can pass you his name, for me the price with shipment worked out slightly more expensive than buying here in Europe so I gave it a miss, up to you, let me know if you want his name...


----------



## dustinsterk

In case anyone is looking for some power supplies for this build....I have a post here that should help you out.
  
 http://www.head-fi.org/t/698662/cisco-power-supply-for-starving-student-amps
  
  
 Thanks!
 Dustin


----------



## drabina

Another noob question: What tube makes should I be looking for on Ebay? I am new to the tube world so I have no idea what to look for. I want a decent sound out of the SSMH but I do not want to lose the "SS" in the name by paying $50 for tubes.
  
 Thanks


----------



## tomb

drabina said:


> Another noob question: What tube makes should I be looking for on Ebay? I am new to the tube world so I have no idea what to look for. I want a decent sound out of the SSMH but I do not want to lose the "SS" in the name by paying $50 for tubes.
> 
> Thanks


 

 19J6 tubes are scarce enough that brand is not going to matter.  If you're building the 12AU7 version, note that the 5963 is often a great substitute.  It was designed to work at much lower voltages than the typical 12AU7 and is usually cheaper, to boot.  As you've probably noticed, the 12AU7 is one of the premier pre-amp tubes on the market and the variance is all the way from a few dollars to several hundred.


----------



## drabina

tomb said:


> 19J6 tubes are scarce enough that brand is not going to matter.  If you're building the 12AU7 version, note that the 5963 is often a great substitute.  It was designed to work at much lower voltages than the typical 12AU7 and is usually cheaper, to boot.  As you've probably noticed, the 12AU7 is one of the premier pre-amp tubes on the market and the variance is all the way from a few dollars to several hundred.


 
 I forgot to mention that I am building the 12AU7 version of SSMH. So can I use 5963 tubes without any modifications to the circuit?
  
 Though even with those, there are RCA, Raytheon, GE, Sylvania, etc. Any of those are better than the rest or it doesn't matter?


----------



## tomb

drabina said:


> tomb said:
> 
> 
> > 19J6 tubes are scarce enough that brand is not going to matter.  If you're building the 12AU7 version, note that the 5963 is often a great substitute.  It was designed to work at much lower voltages than the typical 12AU7 and is usually cheaper, to boot.  As you've probably noticed, the 12AU7 is one of the premier pre-amp tubes on the market and the variance is all the way from a few dollars to several hundred.
> ...


 

 Yes, you can use 5963's in a 12AU7 circuit, period.  JMHO, but I'm not sure any of those brands really matter if you're building the amp yourself.  After all, DIY-ing sort of implies that you're not "susceptible" to the marketing BS.  That said, tube rolling is a very fun thing to do with tube amps.  So, if you can get different brands and different tube structures for a decent price - heck, yes - _go for it!_  That's what makes this hobby fun.  All I'm saying is keep things in perspective.  The 5963 might keep you off of the "audiophile $$$ treadmill" with the Starving Student.  If you can get them cheap (IMHO, <$10 ea), then by all means - give them a shot.  You might find that one-in-a-thousand that "sounds fantastic" tube pair that can keep you happy for a long time.


----------



## jddiyer

So I rebuilt my attempt of point to point soldering into a stripboard version and I can get both tubes glowing, one mofset heating up and a buzz out of that channel.
 But no audio. I will replace the dead mofset and see if it works but any suggestions for fixing no audio? I checked my cables and headphones and they worked fine.

 I would really appreciate any help, this forum is amazing.
 thankyou.


----------



## Greystoke

What are people using for the internal case wiring for these amplifiers?  I see references to "silver wire," is that better for wiring up circuits?  I'm still putting together the parts for one of these projects, and wanted to make sure I had everything on hand.


----------



## Zashoomin

greystoke said:


> What are people using for the internal case wiring for these amplifiers?  I see references to "silver wire," is that better for wiring up circuits?  I'm still putting together the parts for one of these projects, and wanted to make sure I had everything on hand.


 
 The wire that most people use are solid core silver plated copper or plain old copper for the internal wiring inside amps.  If you want you can invest in silver wire but that is going to be very very expensive and honestly I don't think it will make a difference.  If you want something that is cheap and easy to use get some wire from navships on ebay.  Even though its stranded it will work wonderfully.


----------



## Greystoke

zashoomin said:


> The wire that most people use are solid core silver plated copper or plain old copper for the internal wiring inside amps.  If you want you can invest in silver wire but that is going to be very very expensive and honestly I don't think it will make a difference.  If you want something that is cheap and easy to use get some wire from navships on ebay.  Even though its stranded it will work wonderfully.


 

 I appreciate the lead for Navships' store!  I was looking at the OFC from vt4c, but if I can get something similar without the long shipping time that sounds preferable.


----------



## tomb

greystoke said:


> zashoomin said:
> 
> 
> > The wire that most people use are solid core silver plated copper or plain old copper for the internal wiring inside amps.  If you want you can invest in silver wire but that is going to be very very expensive and honestly I don't think it will make a difference.  If you want something that is cheap and easy to use get some wire from navships on ebay.  Even though its stranded it will work wonderfully.
> ...


 

 I don't like to be contradictory with a very helpful post, but stranded is all I've ever used or heard recommended for hookup wire.  Then again, maybe PTP is different than just "hookup" wire.
  
 As for Navships - agree 100%.  The best is 22ga SPC multi-strand.  It tends to be a little stiff, but not nearly as much as a solid variety.  I've used it on everything I've built for years and years.  It's outstanding stuff and the insulation won't shrink and pull back from a solder joint.


----------



## wakibaki

Solid wire is good for hookup or P-t-P because it can be 'dressed' into corners or otherwise shaped and it'll stay put.

We use 'trirated', a stranded wire rated for high voltage , to wire mains-voltage instrument panels with coiled strain reliefs, which also serve to allow replacement of a breaker or instrument in the event that a wire should need to be stripped back. Stranded is good in looms.

w


----------



## tomb

I'm not sure anyone was talking about switchgear. 
	

	
	
		
		

		
			





 
  
 Quality stranded is still best for DIY-ing small stuff, which is just about everything in do-it-yourself audio equipment.  Stranded is its own strain relief, whereas solid can easily break, torque loose less-than-perfect solder joints, and generally create a stiff mess for casing up the typical DIY amplifier.  Yes, solid will stay where you put it and it may be adequate for PTP, but you can still do the same with stranded and probably have safer joints.  JMHO.


----------



## wakibaki

No experience of wire-wrap, tomb? http://en.m.wikipedia.org/wiki/Wire_wrap

There is a _reason_ why solid, insulated wire is made. Your humble opinion notwithstanding, users should _think_ about which type of wire will give best service in their particular application, rather than trying to apply some Procrustean rule-slicing to make stranded hook-up wire fit your class of DIY items.

I understand the Bottlehead tube amp and preamp kits are all supplied with solid wire for hookup.

I always use solid wire when wiring tube equipment PtP (except when I don't). I keep a supply in various colours for just that purpose. Try it, it's easier.

w


----------



## tomb

wakibaki said:


> No experience of wire-wrap, tomb? http://en.m.wikipedia.org/wiki/Wire_wrap
> 
> There is a _reason_ why solid, insulated wire is made. Your humble opinion notwithstanding, users should _think_ about which type of wire will give best service in their particular application, rather than trying to apply some Procrustean rule-slicing to make stranded hook-up wire fit your class of DIY items.
> 
> ...


 

 Nope.


----------



## the_Samurai_chicken

Hi just wondering if anybody could please help out with a first time build that has been 3+ years in the making.
  
 One of the tubes does not light.  I have tried the following:
 - checked wiring
 - changed mosfet
 - tested voltage points (19v and 63v), both ok
 - swapped tube
 - swapped out capacitors
  
 I have trawled the thread for any other solutions and think that a total rebuild may be brewing.
 Before I do so can anybody suggest any other courses of action?
 Are there any other voltage points I should test to isolate the problem?  My electronics knowledge is limited so I have been paranoid about too much prodding in case I destroy a 19j6 as they are pretty rare/expensive nowdays.
 I have been told that it is very unlikely, but is there any chance of a dud resistor?
  
 Sorry about the curt-ish post, I did type an elaborate more detailed post earlier but for some reason the browser refreshed and I had to start this one again.
 Thanks for reading and I hope somebody can lend a hand.


----------



## tomb

the_samurai_chicken said:


> Hi just wondering if anybody could please help out with a first time build that has been 3+ years in the making.
> 
> One of the tubes does not light.  I have tried the following:
> - checked wiring
> ...


 

 Pics, pics, pics.
  
 1. It's highly unlikely that you can destroy a tube, unless the heater voltage is way out of spec.
 2. Chances of a dud resistor are indeed, extremely unlikely.


----------



## wakibaki

Good news! Only one of the tubes does not light.
  
 This means that at least some of the other stuff is working.
  
 You say 19J6, so I'm guessing that you have built this schematic:-
  
http://www.pmillett.com/starving.htm
  
 It sounds like you have already tried most sensible possibilities, now we have to look for less likely possibilities.
  
 Check that you actually have ~19V on pin 3 of the tube that doesn't light. Not 'at pin 3 of the tube socket', but actually on the pin. Most sockets will still let you access the pin from the bottom, or you'll have to try to get by pulling the tube partway out of the socket. On occasion corrosion can prevent a good contact.
  
 Check for continuity between pin 4 (of the tube) and ground.
  
 Check for continuity between pins 3 and 4 of the affected tube. 19V/150mA, you should have a resistance of ~123 ohms.
  
 If you have these things, the tube will light.
  
 Now - you can have ~19V showing at pin 3, and there still be a fault, if there is no continuity to ground (the tube is open circuit or pin 4 is not making good contact to ground), if there is a poor joint somewhere further up towards the PSU. This will result in there being ~19V measured (through a high impedance), but it will collapse when a good ground is made, so you need to be sure that the 19V is there when the tube is not O/C _and_ pin 4 is securely grounded.
  
 w


----------



## the_Samurai_chicken

Gentlemen,
 Thankyou both for your input.
  
 Sorry tomb but I didn't have a photo taking device at time of post.  BUT I think that I have it sorted.  Ends up that the copper board I was earthing to had a plastic-y layer which melted/adhered to the solder and appeared okay solder.  But wasn't earthed....
  
 Couldn't understand why I kept frying mosfets after torquing them down nicely.  Forum search reveals they have to be insulated... head slap moment.
 SO assuming I can track down some silicon/mica insulation material. I think we are good to go!
  
  
  
 Finally a question on the sound characteristics of this amp.  Admittedly I used a cheap pair of buds to test, but the sound was thin/tinny and detached. Kind of like a kids telephone (think can-string-can jobbie).  I used nichicon muse 220uf cap's and some other 0.1uf random film caps (limited choice). Would this be the culprit or some other gremlin?
  
 Thanks again!


----------



## tomb

the_samurai_chicken said:


> Gentlemen,
> Thankyou both for your input.
> 
> Sorry tomb but I didn't have a photo taking device at time of post.  BUT I think that I have it sorted.  Ends up that the copper board I was earthing to had a plastic-y layer which melted/adhered to the solder and appeared okay solder.  But wasn't earthed....
> ...


 

 It's slightly possible that it was the earbuds.  If they are low impedance (16 ohms or less), the 220 uf caps are not going to be big enough to prevent cutting out a lot of bass.  However, "detached" and "can-string-can jobbie" sound pretty severe.  Based on your description above, it does not sound like you've listened to the amp yet with all components working, so I would not be concerned about what it sounds like until you get it all fixed.


----------



## wakibaki

http://www.ebay.co.uk/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.H0.Xto220+insulator&_nkw=to220+insulator&_sacat=0&_from=R40

w


----------



## swek

Hi!

I've been pondering the power supply for a 12AU7 build (got a hold of some new Philips tubes, anybody try those out?).

I've found a cheap switched 48V 25W supply here in Sweden where I'm located.

Does anybody have thoughts on putting that inside a case together with this amp? Major source of noise? The supply itself comes in a metal casing with screw terminals for VAC in and VDC out. It would save me at least USD10 vs buying the spec.ed Cisco/Delta supply..

I've been simulating the amp with a 30V supply too. Seems to do fine in sim, but has anybody tried a lower anode voltage on a 12AU7? I read somewhere that the 12A7, IIRC, has the same low-voltage params as the AU7, in which case I'm guessing it should be fine...?

Lovely thread, lots of info, lots and lots of info. 

Edit: Here's a link to the aforementioned psu: Linkedylink


----------



## swek

Edit: *facepalm* ...so it was being reviewed. Fry this.. Sorry


----------



## KimLaroux

I am guessing the PSU you found is a switcher. If it was me, I'd not encase this inside the same enclosure as the amplifier itself. It's asking for troubles.
  
 As for powering the amp from a lower voltage... Why would you even wanna do that? Tubes benefit from more voltage, not less.
  
 It'll work, but you'd have to recalculate all the resistor values. I currently have my output stage working at 25 V just fine. Though the tubes are powered from a 138V rail.


----------



## swek

Hi Kim!
  
 I have read a bit about your build of the SSMH and it seems you've had a great deal of trouble, I'm sorry to hear that. What are the key issues that you needed to resolve? You are the only one I've seen with cages around your tubes, Why is that? Why does it not go well with sitting on top of your DAC?
  
 The reason for wanting to power it from a lower supply voltage is only because I had found a 30V supply readily available as well. I do believe you're right in that it's asking for trouble to box a switched supply within the amp. In the meantime I found wall warts available in a range of wattages as well, so I'm gonna go for that anyway.
  
 What is the benefit of more voltage in this application? Does it reduce noise?
  
 My big question now is: Will a 313mA (15W) power supply will suffice? I know the suggested one is around 387mA IIRC. Has anybody measured the actual current draw of the amp? I have simulated the quiescent current to about 151mA/channel. Which only leaves me with 28,65mA to spare if the supply delivers exactly to spec up to its worst case OL protection. If I find one I'll make sure to go with a beefier one though.
  
 //Swek


----------



## the_Samurai_chicken

Wakibaki, tomb,
 We now have a fully fledged SS.
 Assembled, tested and it still sounded terrible (can string styles)... grabbed my 880's and wow what a difference. Night and day.
  
 Anyhow thanks again, much appreciated!  And big thanks to Pete!  I'm off to listen to some music.


----------



## KimLaroux

*Well, Yesterday I modified it again and I am happy to report I finally nailed it. My amplifier is now quiet to an acceptable level! *




  
  
 After two years, it was about time. And wow did I learn a lot in the process.
  
 I'll borrow my friend's camera tomorrow to take good quality picture. Though it's not much of a MSSH anymore.
  
 Quote:


swek said:


> Hi Kim!
> 
> I have read a bit about your build of the SSMH and it seems you've had a great deal of trouble, I'm sorry to hear that. What are the key issues that you needed to resolve? You are the only one I've seen with cages around your tubes, Why is that? Why does it not go well with sitting on top of your DAC?
> 
> ...


 
  
 The only problem I've been fighting ever since day one was noise. For me this project started when I salvaged a transformer from an old stereo. The transformer has many taps, with the outmost set offering a nice 27-0-27 volts. Rectified, it gave me well enough tension for a linear regulated 48 V rail. When I figured that out, I went "Challenge accepted!". The goal of this project was to learn, not to have a final product.
  
 The problem is, going this route means introducing mains AC into the enclosure, and bathing the whole thing in electromagnetic interference from the transformer. Those two things together means I'm shooting myself in the foot from the start. Even a perfectly quiet linear PSU will have its output corrupted if the wires pass too close to any wire carrying AC. I learned the hard way how important the layout of the internals is. Once you mix AC and DC together, building the amp becomes a lot more than replicating a schematic. Oh and grounding scheme is the most voodoo thing ever.
  
 The cages around my tubes are there because the tubes are so close to the transformer, there was some magnetic coupling between them and the transformer. They picked up a 60hz wave along with all the nastiness of AC. It was ugly. The cages are ferrous and grounded, allowing them to efficiently shield the tubes from electromagnetic fields. Oh and not to mention I keep the amp on my desk surrounded with wifi, bluetooth, cellphone, wireless mouse... Unshielded, the tubes picked up the modulation of these signal. 
  
 As for the DAC, I suspect there was some coupling between the circuit of the amplifier and the toroidal transformer inside the DAC. But that's almost expected if I stack them directly on each others. There is no problem if they are side by side.


----------



## tomb

the_samurai_chicken said:


> Wakibaki, tomb,
> We now have a fully fledged SS.
> Assembled, tested and it still sounded terrible (can string styles)... grabbed my 880's and wow what a difference. Night and day.
> 
> Anyhow thanks again, much appreciated!  And big thanks to Pete!  I'm off to listen to some music.


 

 OK - guess it was the coupling capacitors on the output, then.  You could always upsize them if you really wanted to use it with those earbuds/IEMs.  470 uf can make a huge difference and if you've built everything custom, 1000uf might solve the entire issue.  The only thing you have to worry about is the size of the capacitor (they get bigger).


----------



## drabina

Question to all the SSMH owners: What's your source for the amp?
  
 I am building SSMH and would like to use it as a bedroom headphone system but space is limited so turntable or HTPC as a source are out of the question. This leaves me with DAP (digital audio player) but maybe I am missing something that would also work with SSMH.


----------



## fugelpitch

Hi everyone!
  
 My name is Jonas and I'm from Uppsala, Sweden.
  
 Been working on this amp (12AU7 version) for a week or so after waiting for all parts to arrive. Maybe it's wise to state that this is my first real electrical project ever so I am a novice (who might make stupid novice mistakes, but hey, that's what life is for).
  
 After putting it together I tried to power it up and I'm experiencing some problems that I need some help with, I can post pictures and more detailed info if needed.
  
 Anyway, I'm using the Cisco 0.38A PSU and my problem is that I don't get sufficient power into the circuit. When I have the tube sockets empty (tubes disconnected) voltage between the drain-pin and ground is 48V. When I insert the tubes, voltage starts to fluctuate (at regular intervals of XXXms). When I have one tube in, voltage at MOSFET drain fluctuate between 10 and 15 volts. At tube pin 1+6 it fluctuates between 3 and 6 volts. I don't know what this could indicate (if I've broken some component or if I have made some mistakes with the wiring). I might add that at first start up, I had the MOSFETs short circuit through improper isolation from the chassis (used metal screws....). Could the MOSFETs have burnt (what does this mean) and causing this behavior? Is there a way to test them using a multimeter?
  
 Anyway, if someone has any ideas on how to proceed with troubleshooting I would appreciate it. As I said, if picures are needed I can supply them.
  
 Oh, I can post a picture of the (non-working) exterior: http://imgur.com/dt8IlgG
  
 /Jonas


----------



## bristto

Hi
  
 Total newbie but inspired by the whole DIY thing ...
 I have had a go at the SSMH and I am very happy with the case and look, but something is not quite right 
 The sound is *very* quite!!  Probably my interpretation of the schematic to stripboard... (experts out there will probably laugh at the design!)...
 Any help or pointers would be greatly appreciated!
 (link to pics and a jpg of my board setup - hopefully understandable!!)
  
 Thanks....Tony
  
 http://1drv.ms/1cBni9e


----------



## bristto

Phew!! solved 
  
 Forgot to break the tracks under the 2 vertical resistors (R1, R7)  
  
 LOVE the sound!!!
  
 Thanks to Pete and all who have put useful info on this forum (and the creator / modifier to accept 12AU7's... ) - from total newbie and hooked!! - now looking for next project (where do I progress from here folks?!)
  
 Tony


----------



## fuens

Hi mates.
 I begin to build an SSMH amplifier. Is my firts DIY 
	

	
	
		
		

		
		
	


	



 I wish to know what configuration you recommend to me for a SSMH 12au7:
 10K pot and R16 & R17 10K or prefer 50K pot and R16 & R17 50K?
 I will use for headphones from 80ohm up to 250ohm.
 Thanks on advance.
  
 Cheers
  
 toni
  
 P.D.(If you can tell me pros and cons, thanks 
	

	
	
		
		

		
		
	


	




 )


----------



## proid

I'm drawing a PCB with 12au7 version but i'm wondering that does pin 9 of tube need to connect to ground?


----------



## drabina

proid said:


> I'm drawing a PCB with 12au7 version but i'm wondering that does pin 9 of tube need to connect to ground?


 
 I do not know the answer to your question, but you can get PCBs from Fred. Check this thread for more info:
  
http://www.head-fi.org/t/664191/starving-student-pcbs
  
 I have ordered two and they arrived fast (though remember that based on where are you located, they may be shipped across the World). Price is good too.


----------



## Fred_fred2004

proid said:


> I'm drawing a PCB with 12au7 version but i'm wondering that does pin 9 of tube need to connect to ground?


 
 Leave pin 9 unconnected, it is the center tap of the two heaters and we need them to be in series
  
 cheer
 FRED


----------



## fuens

Hello
 Solved the potentiometer matter now:
 Can I use tinned wire? or is prefered use a normal copper for pot and tubes extension cables.
 I read in one forum the tinned wire do bright and syntetic sound, is it true?
 Thanks so much.
 Toni


----------



## Fred_fred2004

Copper is fine, don"t over think it 
  
 cheers
 FRED


----------



## fuens

You are right
 Thank you very much again Fred! 
  
 Cheers
  
 Toni


----------



## soram

I just used the 50K and 50K pots. Plenty loud in my Sennheiser 650s especially with the CCS!


----------



## Jawmare

I am looking for a DIY USB DAC that will play nice with SSMH, any idea?


----------



## UKToecutter

GrubDAC or pupDAC from beezar.com (TomB)


----------



## Kaaf

Mine is working with a PCB version of the odac


----------



## Amatsu

Anyone with the 17ew8 build finds the highs a little piercing? I'm using the DT770 pro 250ohm. It's specially noticeable when watching action movies with moderate to high volumes. If I switch to my portable amp (Fiio e6), everything is fine.
  
 Is there something I can do to decrease high frequencies on the amp?
 I'm thinking my problem could be the combination of the DT770 and the MSSH, because the DT770s are known to have piercing treble and the amp is probably adding even more.


----------



## Jawmare

amatsu said:


> Anyone with the 17ew8 build finds the highs a little piercing? I'm using the DT770 pro 250ohm. It's specially noticeable when watching action movies with moderate to high volumes. If I switch to my portable amp (Fiio e6), everything is fine.
> 
> Is there something I can do to decrease high frequencies on the amp?
> I'm thinking my problem could be the combination of the DT770 and the MSSH, because the DT770s are known to have piercing treble and the amp is probably adding even more.


 

 No such problem with my 17ew8 & dt1350


----------



## AHorseNamedJeff

Hey all I just finished my build, original schematic using the 19j6 tubes, and the thing doesn't work. tubes don't light, sound doesn't come through, nothing. any ideas? everything looks hooked up correctly.
  
  
  
 also, got a nice 2nd or third degree burn on my arm from my soldering iron whilst building it.


----------



## tomb

ahorsenamedjeff said:


> Hey all I just finished my build, original schematic using the 19j6 tubes, and the thing doesn't work. tubes don't light, sound doesn't come through, nothing. any ideas? everything looks hooked up correctly.
> 
> 
> 
> also, got a nice 2nd or third degree burn on my arm from my soldering iron whilst building it.


 

 Sorry about your arm!  You might try a soldering station that has an iron holder.  That tends to keep the hot iron off the table where you might brush it with your arm. 
	

	
	
		
		

		
			




  
 As for the rest - assuming you have two good tubes (it's a bit against probability that both would be bad) - you should be able to light the tubes.  One thing to look for in the Starving Student is that the MOSFET tabs are part of the circuit, so they must be properly insulated from the rest of the amp.  If not, they will be shorted.  Since the tube-heater circuit is connected to and used to bias the MOSFETs, that might be why you don't get the tubes to light.
  
 Just a guess ...


----------



## AHorseNamedJeff

tomb said:


> ahorsenamedjeff said:
> 
> 
> > Hey all I just finished my build, original schematic using the 19j6 tubes, and the thing doesn't work. tubes don't light, sound doesn't come through, nothing. any ideas? everything looks hooked up correctly.
> ...


alright thanks for your help! I'm gonna post a picture or two for you to look at because I kinda get what you're saying but I could use some more help...


----------



## AHorseNamedJeff




----------



## tomb

I can't get anything from those pics about the MOSFETs.  They're obviously on the other side of the copper plate.  How are they attached?  What are the tabs connected to?  (Must be something.  Otherwise, they'd burn up.)


----------



## AHorseNamedJeff

tomb said:


> I can't get anything from those pics about the MOSFETs.  They're obviously on the other side of the copper plate.  How are they attached?  What are the tabs connected to?  (Must be something.  Otherwise, they'd burn up.)


I used the heater kit that's listed in the BOM sheet and installed it correctly (I think)


----------



## tomb

ahorsenamedjeff said:


> tomb said:
> 
> 
> > I can't get anything from those pics about the MOSFETs.  They're obviously on the other side of the copper plate.  How are they attached?  What are the tabs connected to?  (Must be something.  Otherwise, they'd burn up.)
> ...


 

 The "I think" part is what we're trying to confirm. 
	

	
	
		
		

		
		
	


	




  Can you show us a pic of the MOSFETs?  Or, can you measure to see if there's resistance between the MOSFET tabs and the copper plate?


----------



## AHorseNamedJeff

Here ya go. I'll try measuring right now


----------



## AHorseNamedJeff

just got back from measuring, the resistance on the 2k ohm scale is (.02, .002, no reading) and (.019, .002, no reading) for each tab, going from left to right looking at it from the powerswitch side.


----------



## KimLaroux

ahorsenamedjeff said:


> just got back from measuring, the resistance on the 2k ohm scale is (.02, .002, no reading) and (.019, .002, no reading) for each tab, going from left to right looking at it from the powerswitch side.


 
  
 I think we need to clarify here the difference between the tab and the pins.
  

  
 The tab and middle pin are internally connected. That's why you're supposed to electrically insulate the tab from the heat sinks.
  
 On this amp, the drain/tab/middle pin is connected directly to the 48 V supply. If your heat sinks are grounded and the tab touches them, you're shorting your PSU. That would explain why nothing works.
  
 And well, if you're getting 2 ohms between the middle pin and the copper plate, which I assume is ground, you've pretty much confirmed a short.


----------



## tomb

Good clarification, Kim.  I also agree with your assessment - pretty much suspected that this was the case.


----------



## AHorseNamedJeff

kimlaroux said:


> ahorsenamedjeff said:
> 
> 
> > just got back from measuring, the resistance on the 2k ohm scale is (.02, .002, no reading) and (.019, .002, no reading) for each tab, going from left to right looking at it from the powerswitch side.
> ...


okay I'll look into that when I get home from school. Pete also PMd me about the FETs being wired wrong.

Edit, yeah I looked at the pictures and I got the red and green wires backwards...


----------



## AHorseNamedJeff

alright got the wries all fixed and yep the tabs ARENT insulated form the heatsinks, how should I mount the MOSFETS but still keeping them insulated?


----------



## tomb

ahorsenamedjeff said:


> alright got the wries all fixed and yep the tabs ARENT insulated form the heatsinks, how should I mount the MOSFETS but still keeping them insulated?


 

 You need a heat sink insulator:
http://www.diyforums.org/SSMH/SSMHheatsink.php
  
 EDIT: (middle diagram)


----------



## KimLaroux

ahorsenamedjeff said:


> I used the heater kit that's listed in the BOM sheet and installed it correctly (I think)


 
  
  


ahorsenamedjeff said:


> alright got the wries all fixed and yep the tabs ARENT insulated form the heatsinks, how should I mount the MOSFETS but still keeping them insulated?


 
  
 The BOM lists a kit from beezar, but the website does not seem to be selling any kit with a shoulder washer anymore... 
  
  
 A shoulder washer is a piece of plastic the insulates the tab from touching the screw and washer.
  

  
  
 You also need an insulating pad behind the transistor, which you seem to have in the pictures.


----------



## tomb

kimlaroux said:


> ahorsenamedjeff said:
> 
> 
> > I used the heater kit that's listed in the BOM sheet and installed it correctly (I think)
> ...


 
  
 I only referenced that page because it has this:




  
 Which is also similar to this on the MiniMAX site:





 




 However, I don't think anyone implied that he was using a BOM from Beezar/DIYForums.org.  He built a p2p version with a copper plate.  That pretty much indicates the original Pete Millett version and BOM, I would think.  You are correct to point out the shoulder washer - that could indeed be causing the problem.  However, those heat sink pads (if that's what they are) look like they could be copper film and might be quite conductive.
  
 In any event, I'll change the stock on the shoulder-washer heat sink kits on Beezar tomorrow - just have to make some more of them up - but he can get them almost anywhere, I also wasn't suggesting that he should order them from me.


----------



## KimLaroux

Oh right, you just made me realize the BOM I have is the one you made for the complete kits you used to sell. Is there even a BOM from Millett? I've never seen one. Really curious now which BOM he's referring to.


----------



## tomb

Well, if Pete's BOM reference is not in the very first post of this thread, then it's definitely on his website -pmillett.com.


----------



## AHorseNamedJeff

Yep its on the webpage for the amp..
  
 Good news everybody! IT WORRRRKS.
  
 One of the gentlemen at the recent meet fixed it, turns out the only problem was the FETs were shorting because they weren't insulated on their mounting!
  
 This amp is wonderful sounding! lush and warm with plenty of impact in the bass! loving it with Pink Floyd right now on their Division Bell album.


----------



## tomb

Just an FYI, but I came across a relatively decent supply of 19J6's.  I'm going to test them all out and depending on how many of them are good, I will offer SSMH PCB kits again.  This is just in the beginning stages, but I wondered if there was still interest in using the 19J6 tubes and doing an all-up kit again with custom-machined case.  If I can get all the rest of the parts, it would be exactly as originally offered and still described here:
  
http://www.diyforums.org/SSMH
  
 I think the last time the kits were sold at $120.  That may have to go up some, but we'll see.  It will probably be for full kits, only, because of the up-front investment I'd have to make.  If the tubes test out OK, perhaps 30-40 kits, just to be safe and leave enough tubes for replacing ones that end up microphonic.


----------



## Mullet

I'd be interested in bringing this project back from the dead.


----------



## UKToecutter

I've built a few of the kits and they're superb.
  
 I'd definitely buy another one.


----------



## Kaaf

I have a strange issue
 When I'm using my Senn HD600 I don't receive any humm, But when I connect my new NAD viso HP50 I receive an annoying humm in my right ear. Not audiable when playing music but very annoying during silence. It isn't affected by the volumeknob
 The HD600 has an impendace of 300ohm and the NAD has a impedance of 25 ohm. Could this cause this rather high pitched hum? And does somebody knows if it's caused by something in particular (already swapped tubes, problem remains right)


----------



## AHorseNamedJeff

kaaf said:


> I have a strange issue
> When I'm using my Senn HD600 I don't receive any humm, But when I connect my new NAD viso HP50 I receive an annoying humm in my right ear. Not audiable when playing music but very annoying during silence. It isn't affected by the volumeknob
> The HD600 has an impendace of 300ohm and the NAD has a impedance of 25 ohm. Could this cause this rather high pitched hum? And does somebody knows if it's caused by something in particular (already swapped tubes, problem remains right)


 
 definitely the impedance of the headphones not being high enough for the output impedance on the amp... people had the same problem using low impedance cans with Schiit's Vali.


----------



## the_equalizer

ahorsenamedjeff said:


> definitely the impedance of the headphones not being high enough for the output impedance on the amp... people had the same problem using low impedance cans with Schiit's Vali.




Quite unlikely. I regularly use my Grado phones (32 ohms) with my SSMH and I remember testing it with my Etymotic ER-6i (16 ohms). 

It's probably a grounding/shielding issue which, unfortunately, can be a headache to eliminate. 

I can suggest you can start by trying your amp with a different source, different input cables, in a different room, and maybe even a different power supply.


----------



## ximamp

Hi All,
 I've been planning to build a PTP version for quite some time, been reading this (long) post for quite some time. Currently at page 249 (no spoilers please). Unfortunately some of the old posts no longer have linked images working so I may have missed a few things. 
 This would be my first point to point so I wanted to make sure I'm following correctly. I drew this diagram from the schematics. 
 Does this look correct or am I completely off in my understanding of how to do ptp?
 I can't post images so here is a link: http://bayimg.com/aapNCaAFk
  
 - The pot is a dual, did not have it in the components of the program I used. 
 - Grounds would all go to a star grounding.
 - I'd follow indications I found across the thread re. positioning of resistors/caps close to certain components. 
 - I'd be using 12AU7 tubes
  
 Thanks,
 xmx


----------



## the_equalizer

ximamp said:


> Hi All,
> I've been planning to build a PTP version for quite some time, been reading this (long) post for quite some time. Currently at page 249 (no spoilers please). Unfortunately some of the old posts no longer have linked images working so I may have missed a few things.
> This would be my first point to point so I wanted to make sure I'm following correctly. I drew this diagram from the schematics.
> Does this look correct or am I completely off in my understanding of how to do ptp?
> ...


 
 C6 doesn't look right. It should go from the junction of R13, R1, R2, R7 and R8 to ground. In your image it seems it's 'bridging' the junctions of R13-R1-R2 and R7-R8.
  
 Aside from that I can't see anything wrong... BUT I just took a quick look and did not confirm the MOSFET pinouts 
  
 cheers!


----------



## ximamp

wow thanks for spotting that, I had messed out big time. 
  
 http://bayimg.com/EapOLAAfK
  
 I numbered the MOSFET, 1=G, 2=D, 3=S and made the connections clearer, another thing I need to watch carefully when building. 
  
 Thanks again!


----------



## the_equalizer

That looks fine. But don't take my word for it! Verify against the schematic (and MOSFET pinout) as you build.  Good luck!


----------



## GlowGale

Allright, first post on the forum!
 
Anyway, time to jump right in. This is some work in progress I'd like to share with you guys & ladies. I’d like to build a simple hybrid headphone amp and the SSMH is really ideal for my purpose. I'm having some fun adding minor tweaks to the SSMH's design to make it a bit more flexible for my build. It's basically one way to bring the "Starving Student" back to the SSMH. Since the 19J6 is a bit scarce, I'm currently using the 12AU7-modded SSMH-schematic from Dsavitsk and the_equalizer as a baseline. With the appropriate adjustments, the SSMH can actually run with E88CC/6DJ8's and 6J6's, next to the already existing 12AU7-version. In fact, the standard PSU can run any reasonable 6,3V or 12,6V preamp tube with a current between 0 and 350 mA.
 
As I’m not allowed to upload pictures within the first few posts, I’ll just have to explain per keyboard. If you want to follow, get a schematic of the 12AU7-style SSMH by the hand. 
	

	
	
		
		

		
			




 
Basically I used the same schematic, with only a few minor tweaks. Say I want to use a couple of E88CC’s instead of the 12AU7’s. Both are a dual triode but have different pinout’s. The 12AU7 has 2 heaters (one for each halve, rated at 6,3V at 150mA) internally in series. The heater has an accessible center tap so the heater can be externally configured in series (12,6V/150mA) or parallel (6,3V/300mA). The E88CC actually has the exact same heaters (2 times 6,3V at 150mA) but are internally connected in parallel. This means that it only can run in 6,3V mode at 300mA.
 
The first problem is the lower heater voltage of the E88CC and the 6J6 being 6,3V. So I added a couple of LM317HV constant current sources (IC + one resistor) between the mosfet sources and the tube heaters (a bit like the Sijosae MHHA v2.0 or the Bravo Audio V2 but at 48V). This decouples the heater voltage from the mosfet source voltage. The heater can then be configured according to one's wishes (6,3V or 12,6V) independent of the mosfet bias voltage. This is akin to putting a beefy power resistor in series with the heater to get a higher voltage drop. You can for example put a 21 ohm resistor in series with the E88CC heater and it will be equivalent to a 12,6V heater at 0,3A. The difference with a CCS is that the power resistor will pass AC voltage variations while the CCS will actively block most of the AC voltage variations, the constraint being the constant current draw. Since the Bravo Audio V2 is a working amp, I assume this tweak will certainly work, provided you use the HV-rated version of the LM317.
 
Now here’s where things get experimental. The second problem is that the current in these lower voltage heaters is a lot higher than your typical 150mA of the 12AU7. 300mA and 450mA are typical values for the E88CC respectively 6J6. So one mosfet carries the full heater current. Some tube amps use a string of preamp heaters in series as a cathode resistor to bias the output tubes of a push pull stage. This means you can e.g. have a couple of E88CC heaters in series giving you a compound heater of 6,3V - 12,6V - 18,9V - 25,4V at the same current of 300mA. Each output tube then gets 150mA of this heater current. The same concept can be applied to the SSMH. You use one or more tube heaters in series and the current then splits up into the mosfets for the left and right output stage. This can be done by having the heater shared between the left and right channel. The PSU can now be dimensioned at half the current of the traditional SSMH.
 
As an example, for a cool running SSMH I could use the heaters of a single 12AU7 in series, which gives me 12,6V at 150mA. Then I split the current into 2 times 75mA with each LM317HV configured as a 75mA CCS-load for it’s respective mosfet source follower. This can still be enough for some 90mW or more (e.g. 53mArms into 32 ohm) into the more sensitive medium to low impedance headphones while simultaneously halving the heat production to 7.2W (48V * 0,15A) instead of 14.4W (48V * 0,3A). Of course, nothing stops you from running the heater in center tapped 6,3V mode at 300mA and push 150mA per mosfet as in the original SSMH, while still using only one tube.
 
The following should be feasable for the original Cisco 48V PSU:

Single 12AU7 at 150mA with shared heaters
Single or dual 12AU7 at 300mA with separated heaters - this one contains the 12AU7-mod by Dsavitsk & the_equalizer
Single or dual E88CC/6DJ8 at 300mA with shared heaters
  
And for a more powerful 48V PSU:

Single or dual E88CC/6DJ8 at 365mA with shared heaters
Dual 6J6 at 450 mA with shared heaters - possibility to get the authentic SSMH 19J6 tone at a very low tube price
  
The next logical step could be to DC-couple the mosfet to the tube plate. So on the schematic, remove C2,R2,R4 and C4,R8 and R10 and attach the resistors R3 and R9 directly to the tube plate and done. You can then play with the plate load resistors and the cathode bias resistors of the tube to find a good quiescent point of the tube while simultaneously biasing the mosfet for the most optimal voltage.
 
These small tweaks should actually have little impact on the sound quality (except for fooling around with the plate load and cathode bias with a DC-coupled mosfet) while bulletproofing the amp for first time builders. Provided you solder the current setting resistors of the CCS correctly, then too high a mosfet bias cannot burn out tube heaters.
 
A tone altering tweak could be to add a plate CCS to the tube. This would compromise the tube swing as any active CCS uses a bit of voltage to operate. So make it passive. We already have a mosfet source follower hanging up there. Split the plate load resistor into 2 equal resistors and add a capacitor from the mosfet source to the midpoint of the two resistors. The mosfet source follower is a unity gain stage so couples all the AC-variations back to the midpoint of the two resistors. The lower resistor sees a constant voltage drop and a constant current. This is called a bootstrapped current source and requires only one extra resistor and capacitor.
 
The schematics are still experimental but look promising. The DC-coupled version actually looks simpler than the 12AU7-modded SSMH. I’ll upload ‘em as soon as they are trustworthy for some fooling around on my breadboard. In the meantime I’ll be happy to answer any questions. And if this whole contraption doesn’t work: I’m GlowGale, pleased to meet you. And I like subtile first posts. 
	

	
	
		
		

		
		
	


	



 
Greetings from a real starving student,
GlowGale
 
EDIT:

Had to remove the single 6J6-option due to the common cathode between the triodes


----------



## Avro_Arrow

Welcome to Head-Fi and sorry about your wallet....
  
 Great first post!
 You seem to have done your homework.
 We will be pleased to see how your project turns out.


----------



## GlowGale

Thanks for the warm welcome, Avro_Arrow.
  
 Of course everything has it's upsides and downsides. The standard SSMH averages the tube characteristics because of the two tubes in parallel, so with a single tube you will have a greater unbalance. Depending on the type of the tube, this could mean that you need to have bias pots on the cathodes and rebias every couple of months or so. The big advantage is that you can buy a good single NOS tube. The tube halves should have better balance than between different tubes, or at least a repeatable unbalance. The tube halves also have a greater chance of similar aging because they are being used both at the same time (assuming a good amp design they were in). So this is where flexibility comes in. Don't want adjustment pots, run a dual tube amp. If you want to be social & leave the second tube for your fellow SSMH-builder and don't have any problem adjusting pots once in a while, then go for a single tube amp. For the same pile of 6J6's, you can build double the amount of SSMH-amplifiers. 
	

	
	
		
		

		
		
	


	



  
 By the looks of it, I think i'll be having a go at a DC-coupled single 12AU7-build for starters and if the shared heater thing works, progress to a single E88CC-build.
  
 Greetings,
 GG


----------



## vixr

glowgale said:


> Thanks for the warm welcome, Avro_Arrow.
> 
> Of course everything has it's upsides and downsides. The standard SSMH averages the tube characteristics because of the two tubes in parallel, so with a single tube you will have a greater unbalance. Depending on the type of the tube, this could mean that you need to have bias pots on the cathodes and rebias every couple of months or so. The big advantage is that you can buy a good single NOS tube. The tube halves should have better balance than between different tubes, or at least a repeatable unbalance. The tube halves also have a greater chance of similar aging because they are being used both at the same time (assuming a good amp design they were in). So this is where flexibility comes in. Don't want adjustment pots, run a dual tube amp. If you want to be social & leave the second tube for your fellow SSMH-builder and don't have any problem adjusting pots once in a while, then go for a single tube amp. For the same pile of 6J6's, you can build double the amount of SSMH-amplifiers.
> 
> ...


 
 welcome, and looking forward to your E88CC version!!!


----------



## mawoca

Welcome!

I've been thinking about building another Starving Student (this time for my desk at work), so I'm excited to see how your project turns out! Good luck with it!


----------



## GlowGale

Thanks guys for the warm welcome!
 
I did some field testing today with two LM317 current sources driving a light bulb (2,7W at 6V, nominal impedance 13,3 ohm). This test basically proves the concept that you can feed a common load with a positive temperature coefficient from two parallel current sources. Since I love fooling around with circuits, they survived several direct shorts and open circuits across the light bulb without the PSU shutting down. I also noted the soft start effect of the light bulb slowly coming on so little to no inrush current and no hiccuping of the PSU trying to drive cold filaments.
 
For those wanting to recreate the experiment: abused ATX PSU running at 21,49V when loaded with the experiment. Cold light bulb impedance was 1,3 ohm. One 10 ohm current set resistor per LM317 so configured at 125mA per CCS and measured 127mA when running (resistor & LM317 tolerances). Voltage drop over the light bulb was 2,354V and voltage drop over the CCS'es was 19,1V. This gives me a warm resistance of 9,2 ohm.
 
Cheers,
GG


----------



## the_equalizer

I'm also very interested in seeing how your prototype turns out!
  
 Cheers!


----------



## Tubehunter

This design seems really cool and simple! Are there any specifications or power measurements? Lots of pages, I only dug through the first several but it I am interested.


----------



## GlowGale

Hello Tubehunter, welcome to Head-Fi!
  
 I can only give some approximate theoretical values for the 12AU7 version because I'm still having a go at completely understanding the circuit. The output power of the SSMH is mainly defined by the mosfet load, which is the heater. Here it is configured at 12,6V and 150mA.
  
 As a side note: These are the quiescent values so you get 1,89W of heat dissipation per tube and 5,31W of heat dissipation per mosfet, 14,4W in total. This whole thing pulls 300mA from the PSU so the standard PSU is a Cisco 48V at 350mA, accounting for some inrush current at startup.
  
 Anyway, I hope my calculation method is right. Basically take the square root of the heater values which is 8,9Vrms and 106mArms so these are the theoretical limit values. To find the max. output power, simply take the minimum value of the following equations: P = 0,106² x R and P = 8,9² / R where R is your nominal headphone impedance. The actual output power is defined by your audio source voltage and the amp gain. Gain should be somewhere between 10 and 16 (20 and 24 db) I think. Amplifier input impedance of the 12AU7 version is at 100k.
  
 Frequency response, THD analysis and more of the original 19J6 amplifier can be found by following the link in the opening post of this huge thread.
 Anyway, the SSMH seems to have enough power to drive most of the standard headphones on the market to a decent loudness.
  
 Cheers,
 GG


----------



## GlowGale

Okay, Saturday is schematic day.
  
 I'm still figuring out some tweaks here and there but this one should already be functional. I tried to keep it as close to the original SSMH as possible. So let's dig in!
  

  
 My build type number should say everything: 12AU7-1-48DC150. So we have a 12AU7 build using a single tube with an 48V PSU and a DC-coupled output stage biased with 150mA of current per channel. These are the original specs of the SSMH, except for the single tube. For the record, the heater is configured with the center tap grounded and a split heater at 6,3V and 150mA. This should give the same 300mA total quiescent current as in the original build.
  
 I'll be working my way from input to output. Since I'm running on a single tube I added a dual gang (linear) balance pot to compensate for any channel imbalance. This then connects to a resistor and the typical dual gang (log) volume pot of your preference. Credit goes to Rod Elliott from ESP for this input network. The whole thing has 3dB attenuation with the balance pot centered and should give quasi constant loudness when turning it. The input impedance is somewhere around 10k instead of the 100k of the standard 12AU7-mod. This should be both less noisy and has enough juice to push the tube grid closer to 0V without distorting. The output of the volume pot then runs into a low pass filter composed of some grid stoppers and an extra capacitor to account for RF interference. The grid stoppers and the cap should be soldered directly onto the tube socket for maximum effectivity.
  
 The tube gain stage and mosfet output stage are next. The cathode and plate resistors are approximately doubled in value because I'm only using one tube half per channel. Again, I added some DC bias pots for any channel imbalance due to the single tube. I decided to recycle the original SSMH mosfet source follower output stage and simply stack another voltage follower on top. The lower one is connected to a soft-start DC voltage reference, which sets the heater voltage. The top one follows the tube plate voltage. AC couple the audio out with some output caps and done.
  
 The voltage follower mosfets are the logic level versions (IRL510, not IRF510!) and have a gate stopper and a 5V protection zener to prevent any oscillations and ESD casualties, while also preventing a large turn on thump from charging the output caps too fast. Again, solder these directly on the mosfet pins. In fact, this should be done before anything else to prevent dead mosfets. The input impedance of the mosfet is practically one zillion ohms so maybe solder the plate resistor directly to the gate stopper of the mosfet and run a wire to the tube socket.
  
 I added some typical expected voltages for debugging. As I’m still guessing for the exact tube operating point, the plate voltage is just a guideline for optimal bias of the voltage follower. This stuff is still experimental so proceed only if you have some crappy test headphones and know how Ohm's law works.
  
 Have fun prototyping! 
	

	
	
		
		

		
			




 GG
  
 Edit list:

Anode voltage tweak
Balance pot polarity (pot wiper arrows point to the clockwise setting)
Soft-start time constant


----------



## jshaffe

I've been looking all over for someone who has tested the total per channel output of the starving student in mW at say 32 and/or 300 ohms.  It seems that a dummy load would be required for such a test, of which I do not own.  Anyone know if this has been done and published somewhere?


----------



## DingoSmuggler

jshaffe said:


> I've been looking all over for someone who has tested the total per channel output of the starving student in mW at say 32 and/or 300 ohms.  It seems that a dummy load would be required for such a test, of which I do not own.  Anyone know if this has been done and published somewhere?


 
 Get a couple of 2W or 5W resistors in each required value and then you will have some dummy loads, cheap as chips.


----------



## jshaffe

Forgive my ignorance please, but if it only requires a single resistor, why do all the diy dummy loads look like this?


----------



## ximamp

That looks like a fairly large dummy load that is probably immersed in oil. each one of those resistors is prob 2W or more. You don't need that much power dissipation for this amp. 
 They are made like that because you need to use a purely resistive load (i.e. no induction that wirewound resistors have). So easier to put together many smaller carbon resistors. Immersed in oil so you can dissipate more heat (with large amps). I believe those dummy loads are used also in transmitters (ham radios) but in that field I know half of someone who knows nothing. 
 Others should pitch in with a better explanation but I think in a nutshell this is accurate.


----------



## jshaffe

Awesome. Thanks for the reply. I'm picking up 33, 120, & 300 ohm 5w resistors from digikey.  
  
 Process;
 -----Amp Output----Multimeter-----Resistor-----Ground-----
 Measure peak voltage with DMM, divide by the square root of 2 to get RMS voltage. 
 (RMS^2)/load impedance = Wattage
  
 Correct?


----------



## the_equalizer

glowgale said:


> Okay, Saturday is schematic day.
> 
> I'm still figuring out some tweaks here and there but this one should already be functional. I tried to keep it as close to the original SSMH as possible. So let's dig in!
> 
> ...


 

 Great post, thanks for that!  I'm looking at prototyping this. I have just one question, about the output section, why are the logic version of the MOSFETs required?
  
 cheers!


----------



## GlowGale

the_equalizer said:


> Great post, thanks for that!  I'm looking at prototyping this. I have just one question, about the output section, why are the logic version of the MOSFETs required?
> 
> cheers!


 
  
 No prob, you're welcome. The lower doesn't actually need to be the logic version as it's Vg (and thus Vs) is static and defined by the voltage divider in the PSU. Buying in bulk is cheaper than having 2 types of mosfets in a design and the logic version costs only a few cents more. The Vgs can be compared to the "width" of the mosfet. The wider the mosfet is, the less room it has to wiggle around between ground and 48V, so it will clip at lower AC voltage levels than with a logic type. Standard types have a Vgs somewhere around 5V, while logic types have a Vgs around 2,5V. So you gain 2,5V of clean headroom for any high impedance headphones. If you want to use the standard IRF510's, recalculate R4 and R5 to get Vg 2,5V higher and rebias the plate voltage 1,25V higher than on the schematic. You'll know the mosfet Vgs better than me as I don't have anything laying around for the moment.
  
 By the way. I'm in need of some measurements from the SSMH as I'm basically flying blind on where the 12AU7 is operating (currently no prototyping rig here). I doubled the plate and cathode resistor values from the original design but I'd like to know the plate voltage, plate current and cathode voltage of the 12AU7-modded SSMH (and a resistance measurement of the cathode and anode resistor values). This post is my best guess for the moment. The lower one gives me something around 642µA per tube.
  
 Let me know if it works,
 GG
  
 PS: Mind the turn-off thump, it will be larger as the output capacitors will charge to 26V instead of 12,6V.


----------



## the_equalizer

glowgale said:


> No prob, you're welcome. The lower doesn't actually need to be the logic version as it's Vg (and thus Vs) is static and defined by the voltage divider in the PSU. Buying in bulk is cheaper than having 2 types of mosfets in a design and the logic version costs only a few cents more. The Vgs can be compared to the "width" of the mosfet. The wider the mosfet is, the less room it has to wiggle around between ground and 48V, so it will clip at lower AC voltage levels than with a logic type. Standard types have a Vgs somewhere around 5V, while logic types have a Vgs around 2,5V. So you gain 2,5V of clean headroom for any high impedance headphones. If you want to use the standard IRF510's, recalculate R4 and R5 to get Vg 2,5V higher and rebias the plate voltage 1,25V higher than on the schematic. You'll know the mosfet Vgs better than me as I don't have anything laying around for the moment.
> 
> By the way. I'm in need of some measurements from the SSMH as I'm basically flying blind on where the 12AU7 is operating (currently no prototyping rig here). I doubled the plate and cathode resistor values from the original design but I'd like to know the plate voltage, plate current and cathode voltage of the 12AU7-modded SSMH (and a resistance measurement of the cathode and anode resistor values). This post is my best guess for the moment. The lower one gives me something around 642µA per tube.
> 
> ...


 

 Thanks, got it. I'll probably prototype with the IRF; getting electronic components where I live is not at all easy and they barely know what I'm talking about when I ask for an IRF MOSFET.
  
 The current you're calculating per tube for the 12AU7 SSMH is in the ballpark, yes. I seem to remember measuring mine and getting ~700µA per tube, cathode voltage ~0.9 Volts.  Unfortunately I don't have a "standard" 12AU7 build anymore as mine is running with CCS plate loads hooked directly to the 48 volt line. If I could find the original plate load resistors, I might replace the CCSs and measure but I'm away from home now and will be unable to get to my build for another 2 weeks.
  
 About the operating point, I'm not sure how feasible it is to *choose* one for the 12AU7 in this build; given that the voltage and current are sooo low compared to what the optimum environment would be for the tube, I'm sure it's operating in a very unlinear area of it's characteristics anyway (a compelling reason to use CCS plate loads and get improved linearity from the tube). I think it was in Morgan Jones' "Valve Amplifiers", 3rd. ed. where I read that around 200 volts at the plate are required to bias a 12AU7 out of grid current...
  
 Back when I did the mod, I asked Dsavitsk about drawing a load line for the 12AU7 at such low voltage and current; you can see his answer below that post of mine.
  
 That turn-off thump does not look good, power failures are not infrequent where I live (one of the main reasons why I moved to a Millet Mini-Max).
  
 cheers!


----------



## GlowGale

the_equalizer said:


> Thanks, got it. I'll probably prototype with the IRF; getting electronic components where I live is not at all easy and they barely know what I'm talking about when I ask for an IRF MOSFET.
> 
> The current you're calculating per tube for the 12AU7 SSMH is in the ballpark, yes. I seem to remember measuring mine and getting ~700µA per tube, cathode voltage ~0.9 Volts.  Unfortunately I don't have a "standard" 12AU7 build anymore as mine is running with CCS plate loads hooked directly to the 48 volt line. If I could find the original plate load resistors, I might replace the CCSs and measure but I'm away from home now and will be unable to get to my build for another 2 weeks.
> 
> ...


 
 Too bad they don't make any current production car audio tubes (at least that I know of). Don't dismantle your build just for some resistors! I'll just leave those 66-68k resistors like in the schematic and will fiddle around myself for the optimal value. Thanks for the reference, should come in handy.
  
 The only thing I'm a bit afraid of is running hot audio sources with a cathode voltage of only 0,9V. As far as I read, you should have a nice low input impedance to drive the grid close to 0V without grid current distortion, so that's why I used such a wacky input network.
  
 The best way to avoid the turn-off thump alltogether (without any propagation delay) is by wiring your audio output through a 3PDT or 4PDT power switch. Problem solved. If you're using the Cisco PSU (and the PSU is always plugged in), use a 48V or 2x24V relay in series (with some freewheeling diodes) to remotely switch on the power to the system without having PSU and audio wiring in the same switch. So the power switch only has a connection to the relay and across the audio output. The relay coil should actually work a bit noise reducing so you have no PSU hash on the switch.
  
 The turn-on thump shouldn't be too high due to the RC low pass filter on the mosfet gate controlling the heater voltage.
  
 Greetings,
 GG


----------



## Jo-Sur

hi im new here.i want to ask if i can use irf520 without modifying the schematic parts.because is difficult to find in Greece irf510.thnks to all


----------



## vixr

glowgale said:


> Too bad they don't make any current production car audio tubes (at least that I know of). Don't dismantle your build just for some resistors! I'll just leave those 66-68k resistors like in the schematic and will fiddle around myself for the optimal value. Thanks for the reference, should come in handy.
> 
> The only thing I'm a bit afraid of is running hot audio sources with a cathode voltage of only 0,9V. As far as I read, you should have a nice low input impedance to drive the grid close to 0V without grid current distortion, so that's why I used such a wacky input network.
> 
> ...


 
 Here is something I've been fooling around with... For a single side etch.


----------



## GlowGale

vixr said:


> Here is something I've been fooling around with... For a single side etch.


 
 I almost spilled my coffee when I saw this! Cool design, I can tell it's not your first pcb. You get better heat dissipation with 4 heatsinks so lower temperatures. You can also put 2 mosfets on one of those heatsinks (front & back) and isolate them completely from each other and from the heatsink. This should give a more compact design, albeit with higher temperatures.
  
 The balance pot just looks like a copy paste from the volume control, which is my fault. I copy pasted the input control for the other channel and forgot to adjust the balance pot polarity. I will do a reupload in a few minutes. If the balance control is turned clockwise, the volume on the right channel should go up, while the volume on the right channel should go down. If I'm right to understanding the balance pot, swap the left-in and the ground on your balance pot. If looks matter, I designed the balance pot to actually be a trimmer, so it will not be centered perfectly if your tube is unbalanced. Quick 'n dirty solutions: use a potentiometer knob without center marking or first adjust for balance and then mount the knob so the marking is centered. Btw, does the Alps pot also have a linear 25k version?
  
 For preliminary testing without a tube: Use two 2W power resistors instead of the filaments. R12 and R14 will act as pull-up resistors for Q1 and Q3. This dumps most of the voltage on Q2 and Q4 which should get warm. Check that the voltage across the power resistors is approximately 6,3V. Use 47 ohm resistors to get the same current, or 100 ohm to get the same power dissipation as with the tube inserted.
  
 Otherwise this looks quite neat. Go for it!
 Greetings,
 GG
  
 PS: You should be able to put some Wima FKP's in for C4 and C5.


----------



## vixr

glowgale said:


> I almost spilled my coffee when I saw this! Cool design, I can tell it's not your first pcb. You get better heat dissipation with 4 heatsinks so lower temperatures. You can also put 2 mosfets on one of those heatsinks (front & back) and isolate them completely from each other and from the heatsink. This should give a more compact design, albeit with higher temperatures.
> 
> The balance pot just looks like a copy paste from the volume control, which is my fault. I copy pasted the input control for the other channel and forgot to adjust the balance pot polarity. I will do a reupload in a few minutes. If the balance control is turned clockwise, the volume on the right channel should go up, while the volume on the right channel should go down. If I'm right to understanding the balance pot, swap the left-in and the ground on your balance pot. If looks matter, I designed the balance pot to actually be a trimmer, so it will not be centered perfectly if your tube is unbalanced. Quick 'n dirty solutions: use a potentiometer knob without center marking or first adjust for balance and then mount the knob so the marking is centered. Btw, does the Alps pot also have a linear 25k version?
> 
> ...


 
 Sir,
     thanks for the tips...I figured I would have to wire the balance control off board anyway, so I did copy and paste the library volume pot. It didn't occur to me to stack the mosfets! Great idea! I have found a few 25k balance controls but some dont list if they are linear or not. I will tweak the PCB a bit and see if I can get it smaller. As it is, the board would be 3.5" x 5.5". Thanks for the kind comments.


----------



## GlowGale

vixr said:


> Sir,
> thanks for the tips...I figured I would have to wire the balance control off board anyway, so I did copy and paste the library volume pot. It didn't occur to me to stack the mosfets! Great idea! I have found a few 25k balance controls but some dont list if they are linear or not. I will tweak the PCB a bit and see if I can get it smaller. As it is, the board would be 3.5" x 5.5". Thanks for the kind comments.


 

 Sir, I salute you! Doing single sided pcb design without any jumper wires is a black art in itself.
  
 If you can find a dual gang trimmer or 2 simple 25k trimmers, go ahead and use them on the board. The main idea of the original circuit was to get constant loudness while tweaking the balance of your typical hifi speaker amp. Just set both to 50% with a DMM and turn the more silent side up untill both channels match in loudness. Just make sure you use the right tongue angle when tweaking those trimmers.
  
 Greetings,
 GG


----------



## vixr

glowgale said:


> Sir, I salute you! Doing single sided pcb design without any jumper wires is a black art in itself.
> 
> If you can find a dual gang trimmer or 2 simple 25k trimmers, go ahead and use them on the board. The main idea of the original circuit was to get constant loudness while tweaking the balance of your typical hifi speaker amp. Just set both to 50% with a DMM and turn the more silent side up untill both channels match in loudness. Just make sure you use the right tongue angle when tweaking those trimmers.
> 
> ...


 
 OH, sweet! two trimmers are easily swapped in, and are eaiser to get... I enjoy the challenge of the single side. I dont know how many times I have had to scrap a PCB design and start over to avoid jumpers.


----------



## vixr

Ditched the balance control for trimmers, shortened some traces and removed another 1/2 inch from the length of the board. I'm attempting to stack the mosfets onto just two heat sinks...its pretty tough.


----------



## vixr

Etched a board... turned out pretty good. Sorry about the lame phone pic.


----------



## GlowGale

vixr said:


> Etched a board... turned out pretty good. Sorry about the lame phone pic.


 

 Is that "Vixr Labs 2014" in the top left corner? Looks like a neat & compact pcb, nice work man. It looks awesome with the blue tint!
  
 Greetings,
 GG


----------



## vixr

yes... vixr Labs. It's silly, I know. Here is my progress on the amp, I am waiting on the 10K alps pot, and I dont have any 68k resistors at home, so I have to use my resistor stash I have at work tomorrow. Anyway, here it is...


----------



## GlowGale

vixr said:


> yes... vixr Labs. It's silly, I know. Here is my progress on the amp, I am waiting on the 10K alps pot, and I dont have any 68k resistors at home, so I have to use my resistor stash I have at work tomorrow. Anyway, here it is...
> 
> ...


 
  
 Holy glowing triode!!!
  
 Now that is going to be one fine build. I'm following this step by step as you have the only prototype of this design in the world. May I ask what brand/type of electrolytic caps you're using? That orange wrapping looks a bit familiar to me. Panasonic FM?
  
 For people still scratching their head, this diagram may help you figure out how everything clicks together on a more general level. The original SSMH merges the tube heater and the mosfet load, whereas I separated them to make things a bit more flexible. The dashed lines are possible addons or places where tweaking is necessary. E.g. the mosfet source voltage needs to be set by the tube bias, which is set by the DC-bias pots at the cathodes.
  

  
  
 Please be careful debugging this thing. The schematic says experimental after all. 
	

	
	
		
		

		
			




  
 Keep up the good work!
 GlowGale


----------



## vixr

The electrolytics are Nichicon FG series... audio grade


----------



## DingoSmuggler

***derp***


----------



## Avro_Arrow

vixr said:


> The electrolytics are Nichicon FG series... audio grade


 
  
 Those are really nice capacitors...but you seem to have used them everywhere...
  
 Nichicon FG, or any "Audio" rated cap are designed for use in the audio signal chain, ex. input caps, output caps and coupling caps.
 They don't do so well when used in the power supply role.
 There, something along the lines of Panasonic FR or Nichicon HW would be more appropriate.
 Otherwise, great project!


----------



## vixr

avro_arrow said:


> Those are really nice capacitors...but you seem to have used them everywhere...
> 
> Nichicon FG, or any "Audio" rated cap are designed for use in the audio signal chain, ex. input caps, output caps and coupling caps.
> They don't do so well when used in the power supply role.
> ...


 
 Thank you for the tip, I did not know this... are they going to cause problems?


----------



## Avro_Arrow

They won't cause a problem, you could just get better performance with the recommended caps.
 You can always order some with your next order and swap them in to see the difference.
 You will probably find they tighten up the sound, especially in the bass region.
 A Panasonic FR can provide two to three times more ripple current than the Nichicon Muse FG.
 For "audio" caps, me, personally, I prefer the ELNA Silmac II series.


----------



## vixr

avro_arrow said:


> They won't cause a problem, you could just get better performance with the recommended caps.
> You can always order some with your next order and swap them in to see the difference.
> You will probably find they tighten up the sound, especially in the bass region.
> A Panasonic FR can provide two to three times more ripple current than the Nichicon Muse FG.
> For "audio" caps, me, personally, I prefer the ELNA Silmac II series.


 
 Again, thank you sir, for the tip... I will be swapping them for the Panasonic FRs


----------



## GlowGale

avro_arrow said:


> Those are really nice capacitors...but you seem to have used them everywhere...
> 
> Nichicon FG, or any "Audio" rated cap are designed for use in the audio signal chain, ex. input caps, output caps and coupling caps.
> They don't do so well when used in the power supply role.
> ...


 
  
 I noticed Mr. Millet uses Nichicon HE caps in his original 19J6 build, also for the output to the headphones. Audio caps everywhere are of course overkill, but what the other way around? I am thinking of sprinkling some 680µF Nichicon PW caps on my own build and I'll bypass the output electrolytics with some 220n Wima MKP's like in the original 12AU7-mod. The main question being, what is the performance difference between a regular elko with a film bypass versus an audio grade elko (without extra film cap)? I personally think this would be a beneficial compromise for people who can't source audio grade caps, although I do not know what tonal impact this will have. I think this should at least be good enough for a bit of prototyping.
  
 Greetings,
 GlowGale


----------



## vixr

With extreme patience and sheer expertise on the part of GlowGale, my "only one on the planet" single tube MHSS prototype is working beautifully, thank you for your awesome kindness sir. The balance control is the coolest feature I've seen in a long time. Right now I'm waiting on my 10k Alps pot to show up in the mail, and I need to come up with a clever case.
  
 GlowGale this 18yo scotch is for you...


----------



## muskyhuntr

Great work, as always!
  
 Me


----------



## GlowGale

vixr said:


> With extreme patience and sheer expertise on the part of GlowGale, my "only one on the planet" single tube MHSS prototype is working beautifully, thank you for your awesome kindness sir. The balance control is the coolest feature I've seen in a long time. Right now I'm waiting on my 10k Alps pot to show up in the mail, and I need to come up with a clever case.
> 
> GlowGale this 18yo scotch is for you...
> 
> ...


 
 Vixr, I'd like to thank you for all the feedback on the initial design, this gave me an excellent insight into the real world version of this design. Bottom's up!
  
 The secret of the design is of course the floating volume pot, which gives an "airy" feel to the sound. The balance system should work even better if you use a dual gang 25K linear pot instead of trimmers. I'll be looking into some further optimisations to make things less variable on assumptions I made.
  
 The main disadvantage I still see in the design are the output capacitors. Not when you're listening to music, but when you forget to unplug your headphones & fire the thing up. The output capacitors will charge & discharge through the headphones. I understand that this is inherent to a design with output capacitors, and this also happens in the original SSMH. I noticed someone advising to not plug in your headphones during startup & shutdown, but I don't find this safe enough according to Murphy's law. So I'm looking for a simple & elegant solution to make the startup safer with your headphones plugged in.
  
 The simplest way is to reference the headphones to 48V, but this only works if you won't be interconnecting the output to anything else but headphones. So I'm thinking of flipping the voltage the other way around toward -48V. This would only need an extra capacitor at the audio input, and maybe a DPDT power switch instead of a SPST. The main problem would then be that you need a PSU with a very clean output voltage. Another way would be to just implement a simple headphone protection relay circuit like in the MiniMax.
  
 To make things more debug friendly, I also need to have less potentiometers & resistors to fiddle around with because they can confuse beginner builders and I'm too lazy to adjust them. Chassis mount pots also have a rather high price, so I'd rather spend this to a much cheaper addon circuit which does the bulk work for me. This either means running the tube in non optimal conditions, or having some kind of 'automatic' potentiometer setting the right output voltage for you. This should also allow for variations such as wear & tear, replacing the tube and using other tube types like the E88CC without any major retweaking.
  
 Stay tuned,
 GlowGale Audio Design


----------



## the_equalizer

*Fantastic* work from both the designer and the prototyper! Congratulations!


----------



## tomb

A new run of SSMH PCB kits is close to becoming a reality.  PCB's have been ordered and Hammond Mfg is fabricating the cases.  There will be 50 kits, period.  No substitutions, no modifications, and no extra PCB's or other parts. BOM is the same as it's always been on the SSMH PCB website (with the exception of price).  You'll get two tested 19J6 tubes with each kit, but if they are microphonic or go bad soon after, you may be on your own.  I will have a handful of spares, if any.  However, onesie-twosie's have always been available through reputable tube dealers and on ebay, although a bit expensive (typically $10 ea). I'm still acquiring parts, so I'm not sure of the final kit price, yet - perhaps $30 more than last time.  Remember that the last time we sold these was around *2009!  *I will have the BOM corrected within the next week or two, so you'll be able to see.
  
 They may go on-sale on Beezar in mid-November/Thanksgiving, I'm hoping.


----------



## pinkfloyd4ever

So, maybe I missed it, but am I reading correctly that there's not an easy mod that can be done to the SSMH to keep it from damaging sources without output protection? I have an Alien that I was thinking about listings to some tunes with through my SSMH


----------



## tomb

pinkfloyd4ever said:


> So, maybe I missed it, but am I reading correctly that there's not an easy mod that can be done to the SSMH to keep it from damaging sources without output protection? I have an Alien that I was thinking about listings to some tunes with through my SSMH


 

 I would not use the AlienDAC with the Starving Student.  The susceptibility seems to be limited to those DIY DACs that take their output directly from the DAC chip, save for a couple of DC-blocking output capacitors.  If you have a DAC that uses an output buffer, an opamp, or has its own internal output amplifier, those DACs seem fairly resilient in operating with the Starving Student. Otherwise, extreme caution is advised ...


----------



## pinkfloyd4ever

I see, well my SSMH is staying on hiatus for the time being then.

Which of the popular DIY DACs around here are safe to use with it?


----------



## tomb

pinkfloyd4ever said:


> I see, well my SSMH is staying on hiatus for the time being then.
> 
> Which of the popular DIY DACs around here are safe to use with it?


 

 I can only tell you about Beezar DACs, to be certain: PupDAC, GrubDAC, SkeletonDAC should all be OK.  For other DACs, try to apply the description I gave above.  IOW, what's after the "pure" DAC output in the circuit?  Does the DAC chip have it's own inherent amp/headphone amp, is there active buffer circuitry after the DAC chip, is there an opamp used for the output?  All those things have active circuitry acting on the output beyond the DAC and thus, provide a firewall of protection against spurious static charges that might back-feed into the DAC chip's output and fry it.


----------



## GlowGale

tomb said:


> I can only tell you about Beezar DACs, to be certain: PupDAC, GrubDAC, SkeletonDAC should all be OK.  For other DACs, try to apply the description I gave above.  IOW, what's after the "pure" DAC output in the circuit?  Does the DAC chip have it's own inherent amp/headphone amp, is there active buffer circuitry after the DAC chip, is there an opamp used for the output?  All those things have active circuitry acting on the output beyond the DAC and thus, provide a firewall of protection against spurious static charges that might back-feed into the DAC chip's output and fry it.


 
  


> Originally Posted by *vixr* (PM)
> 
> 
> ...
> ...


 
  
 So the ground of the amplifier is floating w.r.t. ground. I'm guessing there is no connection or maybe a (parasitic) capacitive coupling between the protective earth (PE) and the ground of the PSU output. My guess is the SSMH still needs a ground reference to be safe for coupling with earthed audio sources (PC-connected, ...). Otherwise the capacitor will discharge through the DAC.
  
 I found these solutions floating around (no pun intended) on the forum/internet:

Easy: connect all the audio cables before starting up the amplifier
Intermediate: connect the protective earth to the signal ground of the SSMH (gives a ground loop between the audio source and the amplifier)
Hard: install a proper ground loop breaker (with an optional ground lift switch)
  
 The third solution is courtesy from ESP (link) and is what I will probably use in my SSMH-mods. The left ground (with the horizontal stripes) is the PE-connection coming from the mains installation of your home (yellow/green wire). The right ground (triangle) is the signal ground from the amplifier.
  

  
 The clean way to modify a point to point SSMH is maybe to use an IEC splitter (link) or a dual IEC power cord (link). Run one of these IEC plugs to the Cisco PSU, and the other to an extra IEC socket on the amp itself. Seal off the live & neutral connections on the socket with some heat shrink/electrical tape and connect the ground breaker to the protective earth pin on the socket. For the pcb-version you'll probably need to make a separate box with the extra IEC-socket and run a signal ground from the amp to this "ground conditioner" box. Any metal chassis, switches, etc should preferably stay connected to the PE. This also means that audio ground should be isolated from safety PE ground.
  
 I don't know if everything I wrote is true, I'm just a beginner here. At least I hope this info may bring somebody on a nice idea to make the amplifier safe.
  
 Greetings,
 GlowGale


----------



## tomb

Just a thought, but the DoodleBug might solve all the issues of connecting DACs to the Starving Student ...


----------



## GlowGale

tomb said:


> Just a thought, but the DoodleBug might solve all the issues of connecting DACs to the Starving Student ...


 
  
 Unfortunately any audio source which doesn't work with USB (Apple products, CD-player, vinyl record, ...) will still be at risk of getting zapped. I'm more inclined to tackle the problem at the source, namely the PSU and the grounding scheme of the amplifier. But that's just the way I think.
  
 Another way to protect the audio source would be to use "ground-first" connectors like XLR instead of RCA or jack. This would discharge the capacitor and equalize the ground potentials before making the (hot) audio connection. But that would certainly mess up the signal conventions since XLR is used for balanced interconnects. Check out these fancy RCA "ground-first" connectors.
  
 It certainly looks like an excellent piece of equipment, nice work guys! It should work a treat for anybody who already built the Starving Student & uses an USB audio source.
  
 Greetings,
 GlowGale


----------



## Avro_Arrow

glowgale said:


> It certainly looks like an excellent piece of equipment, nice work guys! It should work a treat for anybody who already built the Starving Student & uses an USB audio source.
> 
> 
> Greetings,
> GlowGale


 

 Thanks!


----------



## ChrisCaubin

smeggy said:


> Took more pics after making the small wood tube surrounds for those who wanted more views.


 
 Hi,
 Long time lurker... I want to try replicate this word of art of Smeggy's, could anyone tell me what parts he used for the chassis (under the wood), the volume knob and the heat sinks? Also, any ideas on what wood that is?
 Thanks,
 Chris


----------



## nealric

Sorry to jump in with a noob question, but I thought this thread was as good a place as any... 
  
 I have a Millet hybrid that I bought from a head-fi member about five years ago. Worked great when I initially received it.  It went through a couple of moves and fell into disuse 2-3 years ago. In any event, I went to fire it up today and initially got no sound. Swapping the spare tubes the seller had provided (GE 12Fm6) got me sound, but with extreme distortion on loud bass notes. 
  
 Does this sound like the tubes just need to be replaced (they were probably jostled quite a bit in the moves) or is it perhaps something else? There is no visual sign of any burned out caps or anything. TYIA.


----------



## DingoSmuggler

nealric said:


> Sorry to jump in with a noob question, but I thought this thread was as good a place as any...
> 
> I have a Millet hybrid that I bought from a head-fi member about five years ago. Worked great when I initially received it.  It went through a couple of moves and fell into disuse 2-3 years ago. In any event, I went to fire it up today and initially got no sound. Swapping the spare tubes the seller had provided (GE 12Fm6) got me sound, but with extreme distortion on loud bass notes.
> 
> Does this sound like the tubes just need to be replaced (they were probably jostled quite a bit in the moves) or is it perhaps something else? There is no visual sign of any burned out caps or anything. TYIA.


 
 You need to set the bias when changing tubes.
 Go here, http://www.diyforums.org/ ,  click on the appropriate link for your style millet, then follow the "Setup & biasing" instructions.


----------



## Dean N.

Hi everyone!
  
 I have a couple questions regarding an upcoming SSMH build.  If this is not the appropriate place to ask questions about a build, please let me know and I can start a new thread (or mods can move the post).  
  
 1.  I'd like to add a 3.5mm line input on the faceplate (in addition to the standard RCA rear panel input).  So I'd need a 3.5mm switched stereo panel mount jack (I think) like this.  Unfortunately, that's a 1/4 jack, and I can't find any 3.5mm panel mount jacks.. they're all PCB mount.  Furthermore, I'm going to do a wood case, so the faceplate will be considerably thicker than a metal case/faceplate.  Can anyone help me source an appropriate jack?  I've looked at the usual places (Mouser, Digikey, even Alibaba).  If it's not available, the only option I can think of is to simply use a 1/4 jack, though I don't really dig that option.  Can anyone advise?
  
 2.  What would you guys recommend for grounding (and shielding) a wood-cased SSMH?  A grounding plate, or completely lining the interior with metal like copper or aluminum foil?  Both?
  
 3.  I have some experience with soldering, but I'm not sure if it'd be easier (or a better learning experience) to do a P2P or a PCB build as a first project.  What do you guys think?
  
 Thanks for any help!


----------



## Avro_Arrow

For the 3.5mm input, look here.
 You don't need a switched jack.
 You can use a DPDT switch or just make sure
 no to have both inputs connected at the same time...


----------



## Dean N.

One more thing:  I cannot find anywhere a complete BOM for the 12au7 version of the SSMH.  Every link points to the 19J6 BOM (http://www.diyforums.org/SSMH/bom/SSMH.htm).  Surely there's a complete 12au7 version for the BOM..?


----------



## tomb

dean n. said:


> One more thing:  I cannot find anywhere a complete BOM for the 12au7 version of the SSMH.  Every link points to the 19J6 BOM (http://www.diyforums.org/SSMH/bom/SSMH.htm).  Surely there's a complete 12au7 version for the BOM..?


 

 This is DIY.  A little effort is expected on your part. 
	

	
	
		
		

		
			




  
 Compare this:
http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif
  
 To this:
http://www.diyforums.org/SSMH/variants/SSMH-12AU7.gif
(found under the "Variations" menu selection on the SSMH website).
  
 A separate BOM would be a bit of overkill to simply list new values for R2 and R8.


----------



## Dean N.

Ha.  Point taken.  Impatience + DIY = frustration for me.    I guess I have some homework to do.  Thanks for all your patience with us noobs.


----------



## nbkgudx

tomb said:


> A new run of SSMH PCB kits is close to becoming a reality.  PCB's have been ordered and Hammond Mfg is fabricating the cases.  There will be 50 kits, period.  No substitutions, no modifications, and no extra PCB's or other parts. BOM is the same as it's always been on the SSMH PCB website (with the exception of price).  You'll get two tested 19J6 tubes with each kit, but if they are microphonic or go bad soon after, you may be on your own.  I will have a handful of spares, if any.  However, onesie-twosie's have always been available through reputable tube dealers and on ebay, although a bit expensive (typically $10 ea). I'm still acquiring parts, so I'm not sure of the final kit price, yet - perhaps $30 more than last time.  Remember that the last time we sold these was around *2009!  *I will have the BOM corrected within the next week or two, so you'll be able to see.
> 
> They may go on-sale on Beezar in mid-November/Thanksgiving, I'm hoping.


 
 Hello Tomb,
  
 Any updates on this run? I checked the Beezar website and didn't see the full kit available for sale.


----------



## tomb

nbkgudx said:


> tomb said:
> 
> 
> > A new run of SSMH PCB kits is close to becoming a reality.  PCB's have been ordered and Hammond Mfg is fabricating the cases.  There will be 50 kits, period.  No substitutions, no modifications, and no extra PCB's or other parts. BOM is the same as it's always been on the SSMH PCB website (with the exception of price).  You'll get two tested 19J6 tubes with each kit, but if they are microphonic or go bad soon after, you may be on your own.  I will have a handful of spares, if any.  However, onesie-twosie's have always been available through reputable tube dealers and on ebay, although a bit expensive (typically $10 ea). I'm still acquiring parts, so I'm not sure of the final kit price, yet - perhaps $30 more than last time.  Remember that the last time we sold these was around *2009!  *I will have the BOM corrected within the next week or two, so you'll be able to see.
> ...


 

 Any time now, maybe tomorrow ...


----------



## tomb

Well, it turned out that I'm still lacking some parts.  I have them ordered, but it will be a few more days ...


----------



## Vortaku

tomb said:


> Well, it turned out that I'm still lacking some parts.  I have them ordered, but it will be a few more days ...


 
 I may jump on this deal myself!


----------



## GlowGale

This is a sneak preview of what I'm currently working on. It's a proof-of-concept prototype to test out some of my ideas in real life. I tried to keep the look, feel and sound as close as possible to the original amplifier by Mr. Millett. This means point-to-point wiring, a simple metal box and using two cheap & cheerful 6J6 tubes. ($2 a pop at Beezar)
  
 Concept:
  

  
 Outside (front, back, idling tubes):
  
          
  
 Inside (front, back):
  
     
  
 Main circuit (overview, tube details):
  
          
  
 Stay tuned,
 GlowGale


----------



## KimLaroux

I was in awe of your dead-bug soldering until I noticed you're using the steel case as a ground return for both power and signal. Heresy! D=


----------



## GlowGale

kimlaroux said:


> I was in awe of your dead-bug soldering until I noticed you're using the steel case as a ground return for both power and signal. Heresy! D=


 

 In what way can that give problems? Please explain, I'd like to know more about it.


----------



## KimLaroux

glowgale said:


> In what way can that give problems? Please explain, I'd like to know more about it.


 
  
 http://www.valvewizard.co.uk/Grounding.pdf


----------



## GlowGale

kimlaroux said:


> http://www.valvewizard.co.uk/Grounding.pdf


 

 Thanks for the reference, but what page precisely? That's a whole chapter from Merlin's book. Anyway, just checked section 15.6 and now I'm left wondering why I don't have any problems.
  
 My first guess is we're running in class-A, so the current taken by the output stage is rather constant. This probably means I have a lot less interference than with a class-AB amplifier. Secondly, the impedance between the input and output ground are immeasurably low. Just went and measured 0.2 ohms, which is by coincidence also the lead resistance from my multimeter. Maybe I'll check for DC-offset between the two grounds when the amp is running, that should be more precise than a quick-n-dirty resistance test.
  
 Anyway, thanks for the heads up, I'll look into it if I'm running into any trouble. If you want some more heresy, forget about the thumb tacks and search for the hex wrenches. 
	

	
	
		
		

		
		
	


	




 
  
 PS: I'm looking to make some isolated islands on the ground plane, e.g. for a signal ground. I'm looking for some kind of dirty version of terminal strips or turrets. I don't like drilling or glueing, since soldering is a lot faster when prototyping things like this.


----------



## Amatsu

Quick question. On the_equalizer's mod, are the tube's pins 4 and 5 connected together? I have 5 to ground now but I'm not sure if I need to connect 5 to 4.  Thanks.


----------



## tomb

amatsu said:


> Quick question. On the_equalizer's mod, are the tube's pins 4 and 5 connected together? I have 5 to ground now but I'm not sure if I need to connect 5 to 4.  Thanks.


 
  
 Pin 4 must be connected to the voltage source in each case.  The heaters are connected within the tube, but you must have 18-19V going through them.  If pin 5 is connected to ground (correct), the only way that will happen is if you connect pin 4 to the voltage source.


----------



## KimLaroux

tomb said:


> Pin 4 must be connected to the voltage source in each case.  The heaters are connected within the tube, but you must have 18-19V going through them.  If pin 5 is connected to ground (correct), the only way that will happen is if you connect pin 4 to the voltage source.


 
  
 Actually 12.6 V for a 12AU7 build.
  
 The pins are not connected together as there is no dot on the schematic. They need 12.6 V across them. You connect one pin to ground and the other to pin 3 of the MOSFET.


----------



## tomb

kimlaroux said:


> tomb said:
> 
> 
> > Pin 4 must be connected to the voltage source in each case.  The heaters are connected within the tube, but you must have 18-19V going through them.  If pin 5 is connected to ground (correct), the only way that will happen is if you connect pin 4 to the voltage source.
> ...


 

 He posted the schematic for the 17EW8.  That's what I was going by ...


----------



## KimLaroux

tomb said:


> He posted the schematic for the 17EW8.  That's what I was going by ...


 
  
 That's what I figured... But I felt obliged to clarify things in case he was using the same mod but on a 12AU7 build.


----------



## Amatsu

I'm using the 17EW8 version. I was just re-doing the amp in another enclosure because I didn't like how it sounded before compared to my portable Fiio e6 (bad mids and harsh/piercing highs) and had the feeling something wasn't right. Anyway I finished the new build just now with the same parts, it sounds promising for now but I'll give it a little more time to decide. 
  
 Could a bad grounding affect the sound quality or grounding only affects hum/noise?


----------



## Darkstar77

tomb said:


> Well, it turned out that I'm still lacking some parts.  I have them ordered, but it will be a few more days ...




I just saw the kits pop up on your site. Ordered. Looking forward to this project. Thanks!


----------



## tomb

amatsu said:


> I'm using the 17EW8 version. I was just re-doing the amp in another enclosure because I didn't like how it sounded before compared to my portable Fiio e6 (bad mids and harsh/piercing highs) and had the feeling something wasn't right. Anyway I finished the new build just now with the same parts, it sounds promising for now but I'll give it a little more time to decide.
> 
> *Could a bad grounding affect the sound quality or grounding only affects hum/noise?*


 
 That's a circular question.  Noise and hum affect sound quality.  Therefore, bad grounding effects sound quality.


----------



## tomb

darkstar77 said:


> tomb said:
> 
> 
> > Well, it turned out that I'm still lacking some parts.  I have them ordered, but it will be a few more days ...
> ...


 

 Yep - processing starts Monday, with shipping soon thereafter.


----------



## Peridot

darkstar77 said:


> I just saw the kits pop up on your site. Ordered. Looking forward to this project. Thanks!


 
  
 I bought one of these kits from Beezar some years ago and for some inexplicable reason it has remained one of those things 'I must get around to' ever since 
	

	
	
		
		

		
		
	


	



  
 Well, having a completely free day today I decided to tackle it. 
  
 I have to say that the quality of the components and kitting, together with the superb step by step instructions from tomb, made it one of the most straightforward and rewarding projects I have ever tackled.
  
 Good luck to everyone embarking on building the new kits


----------



## tomb

peridot said:


> darkstar77 said:
> 
> 
> > I just saw the kits pop up on your site. Ordered. Looking forward to this project. Thanks!
> ...


 

 Many thanks for your kind comments.
  
 Just to be clear, the new kits are identical in every way except that they have black knobs and the fact that I gave up on labeling every single parts bag.


----------



## nbkgudx

tomb said:


> Many thanks for your kind comments.
> 
> Just to be clear, the new kits are identical in every way except that they have black knobs and the fact that I gave up on labeling every single parts bag.


 
 Hey Tomb,
  
 I just ordered a kit. I'm very excited as this will be my first build. Does this kit come with detailed instructions on how to build it?


----------



## DingoSmuggler

nbkgudx said:


> Hey Tomb,
> 
> I just ordered a kit. I'm very excited as this will be my first build. Does this kit come with detailed instructions on how to build it?


 
 Beezar kits won't come with instructions, but you'll find tomb has them comprehensively documented at diyforums.org


----------



## tomb

dingosmuggler said:


> nbkgudx said:
> 
> 
> > Hey Tomb,
> ...


 

 Thanks! SSMH Documentation
  
 Or ... in this thread: http://www.head-fi.org/t/437075/starving-student-millett-hybrid-pcb-step-by-step-build-guide
 (also in my sig)


----------



## tomb

For those who've already ordered - I apologize, but shipping will commence on Friday.  I forgot the connectors that are needed for the power switch.*  I went to several hardware stores in town today (all sold out) until I gave up and went to Fry's.  They had what was needed, but I only got back a little while ago, so I won't be able to get to the Post Office until Friday (closed tomorrow).  It seems there's always a few glitches when trying to start up a big effort like this.  Please be patient.
  
  
 * It's best not to solder directly to the tabs on the power switch.  You need to use those pink things in the pic below:


----------



## Darkstar77

No worries from here. Thanks for the attention to detail.


----------



## tomb

All outstanding kits have now shipped.


----------



## Darkstar77

My kit arrived in the mail today. It arrived after its journey from Beezar to Canada intact, and well packed. I am terribly excited, going to start it this weekend.


----------



## tomb

darkstar77 said:


> My kit arrived in the mail today. It arrived after its journey from Beezar to Canada intact, and well packed. I am terribly excited, going to start it this weekend.


 

 Glad to hear it!


----------



## Darkstar77

tomb said:


> Glad to hear it!




Okay, stupid question for the day. I've done lots of PCB soldering in the past, and somewhat recently in building multi-rotor RC helicopters (the power distribution and controller boards require a lot of soldering to complete). I have never bothered cleaning off the rosin flux residue before, and so far as I can tell I have never had any problems. I know rosin flux is non conductive and non corrosive. Is the thorough cleaning of the board after soldering in the detailed directions for cosmetic reasons, or for functional reasons?

I googled around on this topic for a while last night, and found a lot of conflicting opinion and "fact"; as well as a lot of "how to solder" articles.


----------



## Avro_Arrow

Sometimes residue left over from soldering is conductive/corrosive.
 It is better to error on the side of caution when writing instruction
 that others will follow. If you KNOW your flux is safe to leave on
 then feel free to do so. Otherwise, better safe than sorry...


----------



## tomb

avro_arrow said:


> Sometimes residue left over from soldering is conductive/corrosive.
> It is better to error on the side of caution when writing instruction
> that others will follow. If you KNOW your flux is safe to leave on
> then feel free to do so. Otherwise, better safe than sorry...


 

 Agreed.
  
 It's just me, but I always rinse a PCB of all flux residue.  If nothing else, I absolutely hate the appearance/texture of flux residue after a period of time.  It turns into really nasty stuff and is not something that I would personally like to leave on a project that I built.  When it comes to SMD work in DACs/etc., it becomes even more important to get it clean, IMHO.
  
 I'm so particular, I've probably turned proper rinsing of a PCB into a mini-science.  This section on rinsing the Torpedo PCB can give you an idea:
http://www.diyforums.org/Torpedo/TORPEDOconstruct9.php
  
 The Torpedo PCB is very much larger than the SSMH PCB, so it probably warranted that kind of documentation. 
	

	
	
		
		

		
		
	


	




  You should not have that much of an issue with cleaning the SSMH PCB.  Try to use the 91% alcohol shown in the website page above.  It's ridiculously cheap at Walmart and works better than commercial flux removers, IMHO (and is not dangerous in an un-ventilated environment).  Combine the rinsing (an old toothbrush is recommended) with patting up the dissolved-flux-alcohol mix with paper towels.  If you don't pat up the liquid with each rinse, all you're doing is moving the flux around on the PCB.  When it's dry, if you see white deposits around the solder joints - it hasn't been rinsed enough.  It may take up to a half-dozen rinse actions to get things perfectly clean.


----------



## Darkstar77

tomb said:


> Agreed.
> 
> It's just me, but I always rinse a PCB of all flux residue.  If nothing else, I absolutely hate the appearance/texture of flux residue after a period of time.  It turns into really nasty stuff and is not something that I would personally like to leave on a project that I built.  When it comes to SMD work in DACs/etc., it becomes even more important to get it clean, IMHO.
> 
> ...




Thank you for the responses gentlemen. I've never really encountered any whitish buildup in the past, but I do have a small amount after placing the resistors on the SSMH board. Alcohol and a tooth brush sounds like a plan.


----------



## nbkgudx

Hello all,
  
 I recently completed my first build. I make sure to pay close attention and follow the guide. When it came time finally power on the amp i noticed two small electrical sparks at the top of the standoff screw on the outside of the case. I decided to let the amp run for about 10 minutes. I then went to turn it off, as I attempted to turn it off a large blue spark quickly shot the moment i flipped the power switch off. This spark was right above the switch. Would this be a grounding or wiring issue? I've attached some photos of the build. 
  
 I also made the mistake of soldering the switch wires into the Terminal Blocks because I was not aware that they were screw in design.
 http://s27.postimg.org/4ue8g018j/image.jpg
 http://s27.postimg.org/k5o1glykj/image.jpg
 http://s27.postimg.org/ynl8olpvn/image.jpg
 http://s27.postimg.org/9k464ls8z/image.jpg


----------



## tomb

nbkgudx said:


> Hello all,
> 
> I recently completed my first build. I make sure to pay close attention and follow the guide. When it came time finally power on the amp i noticed two small electrical sparks at the top of the standoff screw on the outside of the case. I decided to let the amp run for about 10 minutes. I then went to turn it off, as I attempted to turn it off a large blue spark quickly shot the moment i flipped the power switch off. This spark was right above the switch. Would this be a grounding or wiring issue? I've attached some photos of the build.
> 
> ...


 

 I don't think I see any shoulder washers on those MOSFETs.  If the tabs come into contact with the screws and case, it will short things out.  It may be an optical illusion, but it also appears that there's stray solder touching between the two connections on the power jack.  That would short things, too.


----------



## nbkgudx

Thanks. You are correct there are no shoulder washers on the mosfets. Do you think I might have permanently damaged the device when I powered it on?


----------



## tomb

nbkgudx said:


> Thanks. You are correct there are no shoulder washers on the mosfets. Do you think I might have permanently damaged the device when I powered it on?


 

 MOSFETs are pretty tough.  I'm more concerned, however, because I read you let it run a while even after you saw the sparks.
	

	
	
		
		

		
		
	


	



  
 Still, put the shoulder washers in, double check that power jack, and try it again.  (You might try a DMM to see if you have zero ohms between the MOSFET tabs and ground.)  If it works, then you dodged a bullet.  If not, then you need to replace those MOSFETs.


----------



## nbkgudx

tomb said:


> MOSFETs are pretty tough.  I'm more concerned, however, because I read you let it run a while even after you saw the sparks.
> 
> 
> 
> ...


 
 Thanks for the help. I don't understand basic hardware, can you provide me more details on the order in which i should place the washers and rings in relation to the mosfet that is currently resting on the case?


----------



## tomb

nbkgudx said:


> tomb said:
> 
> 
> > MOSFETs are pretty tough.  I'm more concerned, however, because I read you let it run a while even after you saw the sparks.
> ...


 

 This page on the SSMH website has everything you want to know:
http://www.diyforums.org/SSMH/SSMHheatsink.php


----------



## nbkgudx

tomb said:


> This page on the SSMH website has everything you want to know:
> http://www.diyforums.org/SSMH/SSMHheatsink.php


 
 If i lost the shoulder washer can i use a standard washer?


----------



## UKToecutter

You really need to use a shoulder washer.
 It stops the fixing screw from touching the inside of the hole on the device's tab.


----------



## Amatsu

Just as a curiosity, you can usually find up to 6 mosfets with screws, washers and insulation pad inside computer power supplies. If someone has a dead power supply it can be a good way to recycle some parts. Just be very careful if you're gonna poke inside a power supply, be sure to fully discharge it, I don't recommend opening one if you don't know what you're doing. 
  
 I actually did a p2p version of the amp inside the case of a power supply after removing everything, using it's own power switch and cables.


----------



## tomb

nbkgudx said:


> tomb said:
> 
> 
> > This page on the SSMH website has everything you want to know:
> ...


 

 No.  Plus, the shoulder washers supplied with the Starving Student kit are the best you can get - phenolic resin.  I would hesitate to put anything else in there, including a typical nylon one that comes in a standard TO-220 mounting kit.  The MOSFETs on the Starving Student can get very hot.
  
 PM me your address or just your real name.  (I can't match up Beezar customers with Head-Fi usernames.)  I'll drop a couple in the mail to you tomorrow - if you promise not to lose them, this time.


----------



## Darkstar77

One of the parts of this build that has been stressing me out is drilling out the tube sockets. Mainly after looking at the guide, and reading that 2 sockets were broken while taking the photos. I have all the right tools (up to a couple of years ago I had a small benchtop mill), but just holding those sockets screamed fragile at me. I've been putting it off since Thursday, and decided I might as well go for it today.

I did the first socket as outlined in the guide, but after looking at the socket, and the aftermath of the first one (10 minutes of careful, successful, drilling), I decided to take a different approach on the second one. I flipped the socket over and, using a #3 centre drill, drilled off the head of the pin from the bottom of the socket in about 5 seconds. Small tap with a 1/8" drill bit shank, and the pin falls out the front of the socket. Here is a picture of the socket after with the pin, and what remains of the head:

https://lh4.googleusercontent.com/--K6DvEggfLo/VLKrqTBwc4I/AAAAAAAAAeA/9_NxkRORRYE/w1150-h853-no/IMG_20150111_115304.jpg

I highly recommend using a centre drill; the #3 pictured there cost a whopping $0.50 at a local shop that deals in machining equipment. They are extremely rigid and do not deflect like a conventional drill bit, and are used primarily with lathes to setup for a live centre, or to pilot drill for a drilling operation. I happened to have a half dozen kicking around. You need to use a drill press, not a hand drill.

In respect to clamping, I recklessly held the socket against a piece of wood with my fingers while I drilled it out slowly. Slowly being about 5 seconds for the head of the pin to pop off. You could clamp it with some wood and a vice, but honestly there is next to no torque applied to the socket in this way, and I felt more comfortable steering the pin to the drill bit. Disclaimer, using a drill press in this manner could be dangerous; do so at your own risk.


----------



## tomb

Good thoughts!
  
 Some people have been able to simply pry them apart with a screwdriver, but I've found it depends on the socket manufacturing run whether this is possible or not.  Some sockets might as well be glued together rather than come apart.
  
 Whatever cleverness or idea works for you - by all means, use it.
  
 Just remember when you glue the halves back together, let them cure/dry right side up.  If the glue flows into the top of the socket, the pin clamps will be useless.
  
 JMHO, but I wouldn't stress too much over the sockets.  The silver-tinned ones in the kit are quite inexpensive:
http://www.ebay.com/itm/7-PIN-TUBE-SOCKETS-PC-MOUNT-6AU6-6AQ5-0B2-/390343499665?pt=Vintage_Electronics_R2&hash=item5ae2491f91
  
http://www.ebay.com/itm/New-7-pin-Ceramic-Vacuum-Tube-Sockets-PC-Mount-12AX7/150491434014?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D27673%26meid%3Dcb5d3425e4ac4c40bfe69ecb77e52fa4%26pid%3D100005%26prg%3D11378%26rk%3D2%26rkt%3D6%26sd%3D390343499665&rt=nc (Pay no attention to the 12AX7 reference!)
 Those two are US suppliers, so delivery should be fairly quick.
  
 I also have a few silver ones left in stock and have placed them up for sale on Beezar again.   (I normally only stock the gold ones.)


----------



## Darkstar77

Success! I finished the last of the wiring about 20 minutes ago and have been listening to it for the last 5 minutes.

https://lh4.googleusercontent.com/geUdPY64Vk1TYC51LEDEPZObJ9oNlm8VAwe_lcTPJ28=w1151-h853-no

No troubles. Everything went together smoothly. Great kit, well put together with thorough directions. Thanks!


----------



## tomb

darkstar77 said:


> Success! I finished the last of the wiring about 20 minutes ago and have been listening to it for the last 5 minutes.
> 
> https://lh4.googleusercontent.com/geUdPY64Vk1TYC51LEDEPZObJ9oNlm8VAwe_lcTPJ28=w1151-h853-no
> 
> No troubles. Everything went together smoothly. Great kit, well put together with thorough directions. Thanks!


 

 Congrats!  Looks great!


----------



## nbkgudx

I managed to find the should washer. That fixed the grounding issue. Amps turns on and sounds great. I've done about 10 hours worth of listening and I'm in love.
 I'm having some issues figuring out how to get the knob on. I might have misplaced a washer that used to space it but aside from that I'm up and running!
 http://postimg.org/image/e4j81k9z1/
 http://postimg.org/image/jwbxzee49/


----------



## tomb

nbkgudx said:


> I managed to find the should washer. That fixed the grounding issue. Amps turns on and sounds great. I've done about 10 hours worth of listening and I'm in love.
> I'm having some issues figuring out how to get the knob on. I might have misplaced a washer that used to space it but aside from that I'm up and running!
> http://postimg.org/image/e4j81k9z1/
> http://postimg.org/image/jwbxzee49/


 

 Looks great!  Just a hint, though - the endplates go on the _outside_ of the bezels.  The holes on the corners of the endplates are counter-sunk expressly for that purpose.  The PCB should be flush with the end of the case.  The headphone jack and volume pot should stick out just enough to be flush with the endplate.  Use the washer and nut that came with the volume pot, then put the knob on.  The set screw goes on the flat of the pot shaft.  You can use a temporary plastic spacer between the knob and the endplate before tightening down on the flat with the volume knob setscrew - or just eyeball it.  That will keep the knob from scratching the endplate.
  
 Get those endplates on the outside of the bezels and it'll probably seem more straightforward.


----------



## tomb

P.S. The headphone jack has three black plastic spacers. Then there is one special tapered spacer.  The special tapered spacer goes against the chrome ferrule.  Use one plastic spacer between that and the front of the endplate.  That will look best.  You should not need any spacers between the jack housing on the PCB and the endplate.  (You'll have two black plastic spacers left over.)
  
 Pic from Neutrik:


----------



## Dean N.

I'm planning a SSMH build in a wood case, and mounting the heat sinks directly on top of the case.  Can anyone give a recommendation for a way to thermally insulate the case (say, with some sort of washers) to protect it from heat discoloration/damage?  I've looked and looked, and haven't come across anyone that has done something like this.


----------



## miig

Hi,
  
 Finished my SSMH build some month ago but forgot to post some feedback.
 It was my first electronic build, a very instructing experience.
  
 Below are some photos :
 http://s1363.photobucket.com/user/mbourrin/media/SSMH/SSMH01_zps0e6479e7.jpg.html?o=2
 http://s1363.photobucket.com/user/mbourrin/media/SSMH/SSMH02_zpsf39a7926.jpg.html?o=0
 http://s1363.photobucket.com/user/mbourrin/media/SSMH/SSMH03_zpsd84e6da2.jpg.html?o=1
  
 Since it was before Beezar kit reissue, this build is based on a Fred2004 PCB (many thanks to him & other contributors).

 Some infos :
  
 - It's a 12au7 version.
  
 - My starting BOM was the one in this post : http://www.head-fi.org/t/664191/starving-student-pcbs/165#post_10256930
 I made some changes like upgraded output capacitors.
 Also, insulation pads for mosefts are not silicon stuff but aluminium oxyde. Anyway it works good, heatsinks are not too hot.
 The 4 front LEDs were an attempt to add diode protection for the headphones but are currently disconnected.
  
 - Drilling & adjusting the case can take the most time in the build
 If you're working with Fred PCB, my advice is to select a larger case than the small Hammond one I selected : tube socket traces are not centered so I had to air wire the sockets to keep the things centered. Also, PCB was a bit larger than the case so I had to file & grind to slide all the stuff inside.
  
 - After checking for DC at the jack & testing with cheap buds, I can say that this amp drives my Q701 nicely with plently of power (input resistors are 47k, pot 50k).
 I had to ground the pot metal body to get rid of noise when touching the case.
 Now amp is silent with full size headphones, but I get some noise floor when using <16ohm buds, don't know if I can solve this.
 I'm using the 48V cisco PSU.
  
 Miig


----------



## tomb

Very nice variation on the Starving Student!  I especially like that you used those heat sinks.
	

	
	
		
		

		
		
	


	




  Some people think they're ugly, but we selected them for the Beezar/ECP Audio SSMH kits because they have just about the most power/heat rejection you can get unless you go to a custom machined heat sink.
  
 Is that blue paint or is Hammond using blue anodizing with more cases besides the 1455C801?


----------



## Jo-Sur

hi to everyone.i have two quick question,you will help me?if i put pot 100k must put and 100k resistor,i will have problem with 100k pot?and i have two different polyester cap.one noname 5% tolerance and phillips mkt 370series with 10% tolerance.who is better to use.thnks a lot


----------



## tomb

jo-sur said:


> hi to everyone.i have two quick question,you will help me?if i put pot 100k must put and 100k resistor,i will have problem with 100k pot?and i have two different polyester cap.one noname 5% tolerance and phillips mkt 370series with 10% tolerance.who is better to use.thnks a lot




50K is the happy medium for headphone amplifier volume pots, but 100K is ok. As for the additional input resistance, there is no relationship with the volume pot impedance. Rather, the added input resistance is to deal with the high gain of the tubes. Only you can judge how much is needed with the srength of your source and efficiency of your headphones. 50 - 100K is a good starting point guess. If you don't have much volume travel before reaching uncomfortable volumes, then increase the input resistance.

As for the capacitors ... in the signal path, it's more important whether the film cap is polypropylene rather than polyester (not as good). Precision ratings mean little.


----------



## lukeanderson

I finished my SSMH kit from beezar.com a few days ago and at first things were good but I've now developed a problem. I've got about 3 hours of time on it and just last night something went terribly wrong with the volume. It is inconsistent between left and right channels. I also still have sound when the volume is turned all the way down and it will seems to randomly increase and decrease and can get painfully loud.  Could this be the volume control or do I have a bigger problem somewhere else? If I get a multimeter can I check that the volume pot is operating correcting as I sweep across the range?
  
 Thanks,
 Luke


----------



## tomb

I don't think there's any way the volume pot would cause this. I think you have a bigger problem elsewhere.

Carefully disassemble the amp. Check all the wiring to see if there's any chafing with the case. Then carefully inspect the wiring at the terminal blocks. These can come loose over time, especially if the wiring is chafing or binding with case.

Check all of your solder joints - re-flow them where necessary. Look to see if you've got any bridging you didn't notice before. See if the MOSFETs show signs of burning and whether the tabs have contacted the case.

Finally, while it's still disassembled, check the operation again. Let us know if you find anything.


----------



## Jo-Sur

hi.i finish my build today but i have little problem.the right channel the sound is a bit poor,for example the sound of voices not heard much,i measure everything,i change resistors and transitors i swap tubes but nothing.the only strange is that the pin 5 of tube the left have 19v and right have 11,6v.the other measures have normal difference between and parts and pins.any idea???thnks


----------



## lukeanderson

I took the amp apart and everything looked ok. No bridging or burning. I reflowed some of the solder joints that didn't look as good as others.  It has been operating correctly for the last couple of hours. I hope that fixed it and the problem does not come back. Thanks for the help.


----------



## tomb

lukeanderson said:


> I took the amp apart and everything looked ok. No bridging or burning. I reflowed some of the solder joints that didn't look as good as others.  It has been operating correctly for the last couple of hours. I hope that fixed it and the problem does not come back. Thanks for the help.




Sounds like you fixed it - congrats!


----------



## miig

Hi Tomb,
  
 Thanks for the kind words about my tiny SSMH.
  
 Despite mine is an original build, your construction guides & BOM lists at diyforums.org were very usefull.
 It's a great reference for those building the kit : http://www.diyforums.org/SSMH/SSMHconstruct6.php
 The folded metal heatskins are looking OK and are barely hot in use.
  
 The case is a new Hammond reference in anodized blue, I can say the colour actually looks better in true daylight.
  
 I got it in my mouser order, plently of version available :
 http://www.mouser.fr/Enclosures/Enclosures-Boxes-Cases/_/N-5g3p?P=1z0z2q1Z1z0z2km&Keyword=hammond&FS=True
  
 My ref is 1455K1601BU, quite tiny, better get a bigger box 
  
 ----------
  
 A note about tubes :
  
 I started rolling tubes just 2 weeks ago after running the same pair for six months.
 I've no experience in this field but I feel some obvious differences with each tube swap.
  
 - RCA 5963 : my first ones (pictured in photo), sound is dark & deep, very coloured
 - HP 12au7a : this pair sounds very thin, not my taste
 - HP 12au7 (Amperex, 1966 Heerlen factory) : my prefered so far, sound is detailed & punchy, very natural
  
 Regards,
  
 Miig.


----------



## tomb

Great!
  
 I understand Hammond has red anodizing now, too.  They sent me a sample the other day.  It looks very cool.


----------



## noemaillard

Hi all,
  
 i just built the starving student kit from beezar, and i am having trouble getting it to work.
 sound comes out of the headphones, but there is a very loud crackling.
 i checked the voltages and there appears to be only 9.6V where the schematics says it should be approximately 19V (pin 3 of the tubes and pin 3 of the mosfets)
  
  
 Any help or advice would be really appreciated


----------



## tomb

noemaillard said:


> Hi all,
> 
> i just built the starving student kit from beezar, and i am having trouble getting it to work.
> sound comes out of the headphones, but there is a very loud crackling.
> ...


 

 We need pics ...
  
 Please understand that there is no basis with which we can even start to guess what's wrong until we can confirm the basics of your build.
  
 I hate to suggest this, but with another customer having trouble with his, I am suspecting the worst when it comes to the resistors.  Once upon a time when selling the MiniMAX, I discovered that a couple of builders had no idea that the resistors all had different values and installed them willy-nilly in the PCB.  After that, I started writing the resistor designations and all of their values on every package.
  
 Well, I do not have the time to do that anymore in the case of the SSMH.  So, if there's a chance this is happening, I'm sorry.
  
 Here are some basic questions to answer that I shared with the other builder:
  
Do us a favor and measure each resistor (measure ohms with power OFF) with your DMM and fill in this table for us.  Do not go by memory or the SSMH website.  If the resistor designation in the table does not agree with the label on the PCB, do not fill in the measurement for that space – find the right one and measure it, instead:
  

*SSMH Resistor Check*ResistorOhmsResistorOhmsRightBOMMeasuredLeftBOMMeasuredR133K R733K R2220K R8220K R32K R92K R4220K R10220K R52K R111K R62K R122K R141K R151K R16100K R17100K       R132K NANANA      * Depends on what you installed  
 Also – just to check the easy stuff:

 Confirm for us that you have the center post wire of the power jack screwed into the “B+” position on the 4-terminal block.  The outer post wire should go to “G.”
 Confirm that the two switch wires (should be crimped to the pink connectors and pushed onto the switch terminals) are connected to the two “Switch” terminals.  Ensure that none of these wires are touching the other.
 Confirm for us that the large wide vertical stripe on the capacitors C3, C5, and C6 are facing the front of the PCB (toward the volume pot and headphone jack).  C1's stripe should face toward C6.
 Confirm for us that the 220uf 16V writing on the green ES caps face forward at the headphone jack for C8 and away from the 3-position terminal block for C7.
 The tube sockets are on the bottom of the PCB, along with the RLED, right?  Everything else is soldered to the top, right?  I’m sorry for asking that, because I’m not sure you can even assemble the amp if you haven’t done this, but without pics, we're going to have trouble figuring out how to confirm even the basics.
  
Please reply specifically to each question in turn, unless you post pics that can answer some of these.
  
Oh - assuming these are all confirmed, the most common error beyond that is if you have your MOSFETs shorted to the case.  Did you install the shoulder washers?  Were you careful not to torque down the mounting so much that it cut through the insulating pads?  Can you measure zero resistance between the mounting screw/nut and the MOSFET tab (silver metal thing)?
  
Thanks!
  
EDIT: Forgot R10 at 220K.
EDIT2: Revised the entire chart - had it messed up.


----------



## tomb

Another quick question that I should always ask first (maybe I didn't cause I'm in the middle of helping someone else with this) - is the issue in one channel or the other?  If you swap the tubes, what happens?


----------



## slimzim

Hello, I'm a new member of the Head-Fi community. I've been reading this thread for quite some time now since I'm going to build myself a Starving Student amp.
 I have bought everything I need, so now I wait for it all to arrive! 
	

	
	
		
		

		
			




  
 I have read around 170 pages already but one thing I can't manage to find is information about cable dimensions inside of the amp. For example, I''ll need to have a short cable between my DC-socket and the powerswitch, since they'll appear on different sides of the chassi. I really don't want to have voltage drops or such.
 Would AWG 24 cables be thick enough?
  
 Hope I made myself clear, thanks in advance!
 Great thread btw!


----------



## tomb

slimzim said:


> Hello, I'm a new member of the Head-Fi community. I've been reading this thread for quite some time now since I'm going to build myself a Starving Student amp.
> I have bought everything I need, so now I wait for it all to arrive!
> 
> 
> ...


 

 24ga is OK, but I use 22ga (stranded) exclusively for all hookup wire.  It's about as big as you can go and still fit into most holes.


----------



## slimzim

Okey, then I think I'm ready to go. Thanks a lot Tomb!
	

	
	
		
		

		
		
	


	




 Hope my stuff shows up tomorrow, itching in my fingers!


----------



## chuckworkb

Hello all,
  
 I just built one of these kits from Beezar and I have one issue. The left channel comes on slightly before and is louder than the right. I tried switching the tubes to see if it changed, and it didn't. I checked all my solder connections and they  look fine.  Do you have any ideas on where to look further for the issue?  I wondered if it could be the pot? I sounds real nice, just unbalanced.
  
 Thanks in advance of any ideas you might have for me to check.


----------



## tomb

chuckworkb said:


> Hello all,
> 
> I just built one of these kits from Beezar and I have one issue. The left channel comes on slightly before and is louder than the right. I tried switching the tubes to see if it changed, and it didn't. I checked all my solder connections and they  look fine.  Do you have any ideas on where to look further for the issue?  I wondered if it could be the pot? I sounds real nice, just unbalanced.
> 
> Thanks in advance of any ideas you might have for me to check.


 
  
 The Alpha pot is not the best balanced pot in the world, especially at low volume - but it's low cost, as in "Starving Student." 
	

	
	
		
		

		
		
	


	




  That's the reason extra resistors are supplied in the kit for the input resistance.  The idea is to "push" the listening range volume into the middle-range adjustment of the pot 's travel.  The Alpha is adequately channel balanced in that range.  You should install the appropriate resistors for your source/headphones if this is irritating you.
  
 If you've installed the 100K resistors at the input and this is not enough, try removing one leg of each and soldering the 50K resistors in series with the 100K (for a total of 150K at the input to each channel).  You'll form a resistor "peak" with the joint between the two resistors angled up above the PCB - if you can visualize that.  In other words, two resistors soldered one after the other, bent in the middle so that the combination still fits between the two pads on the PCB.  If you've installed the 50K resistors instead, then take them out and try the 100K's.


----------



## chuckworkb

OK, thanks I will try that.
  
 Or, maybe I'll see if I can get a different pot at some point down the road.


----------



## slimzim

Hello again. I've been thinking for some time now and looking for answers in this thread, but i can't find what I'm looking for.
My question is if there is any chance that this amp(12au7 build) will fry any low impedance headphones? The only thing I've seen is that you can protect your
headphones during the startup sequence by adding diodes. Is there any good tutorial on how to do this since I didn't really understand how it's done.

:rolleyes:
Thanks in advance!


----------



## tomb

slimzim said:


> Hello again. I've been thinking for some time now and looking for answers in this thread, but i can't find what I'm looking for.
> My question is if there is any chance that this amp(12au7 build) will fry any low impedance headphones? The only thing I've seen is that you can protect your
> headphones during the startup sequence by adding diodes. Is there any good tutorial on how to do this since I didn't really understand how it's done.
> 
> ...


 

 Buy a Millett Hybrid MiniMAX.
  
 Seriously, I don't often make a statement like that because I sell the MiniMAX.  I also sell the current kit offering of the Starving Student.  However, it's a valid statement.  If you are really concerned and don't trust yourself to wait until the amp is warmed up before plugging in your phones, then you need to build something else that has a true, delay-relay circuit (or transformer output) that will protect headphones under most circumstances.
  
 Search this thread.  There have been numerous discussions about relay-delays - both early on in this thread and relatively recently.  As with everything else, it will take more effort and money.  At some point, you enter into diminishing returns about whether it's a better decision to upgrade the Starving Student, or build something else that was designed to include more features at the outset.
  
 Seriously, the Starving Student offers fantastic performance at an extremely low cost (Thank you, Pete Millett!).  However, there are certain limited expectations that you should temper as a result of that low cost.
  
 EDIT: Sorry - it seems like Groundhog Day for some of these questions and I am perhaps over-reacting a bit.


----------



## KimLaroux

slimzim said:


> Hello again. I've been thinking for some time now and looking for answers in this thread, but i can't find what I'm looking for.
> My question is if there is any chance that this amp(12au7 build) will fry any low impedance headphones? The only thing I've seen is that you can protect your
> headphones during the startup sequence by adding diodes. Is there any good tutorial on how to do this since I didn't really understand how it's done.
> 
> ...


 
  
 It's simple, and to be done with any tube amp: Only plug the headphones in once the amplifier has warmed up and unplug them before powering it down.


----------



## fuens

Is what KimLaroux say. Always do that.
  
 Cheers


----------



## tomb

Well, not _any_ tube amp ...  a true, transformer-coupled amplifier doesn't have capacitors that are needed to block the DC.  The transformers do that already.  You can leave a pair of headphones plugged in all the time.


----------



## fuens

Hello mates.
 It is a technical question, about Dsavitsk 12au7 additions highlighted.
 If I install a toggle switch (two ways) in the input signal, switching R16 & R17 with values 10K and 50k (using 50k potentiometer)
 Does this would work as high and low gain?
 Or signal become unstable? :O
  
 Thanks on advance.
  
 Cheers
  
 Toni


----------



## tomb

fuens said:


> Hello mates.
> It is a technical question, about Dsavitsk 12au7 additions highlighted.
> If I install a toggle switch (two ways) in the input signal, switching R16 & R17 with values 10K and 50k (using 50k potentiometer)
> Does this would work as high and low gain?
> ...


 
  
 Should work fine.  The Starving Student that was sold long ago at Whiplash Audio did almost exactly what you describe.  I haven't had personal experience with the 12AU7 version, so maybe the gains are different.  If it was the 19J6, you should be switching 50K and 100K, not 10 and 50.


----------



## slimzim

fuens said:


> Hello mates.
> 
> It is a technical question, about Dsavitsk 12au7 [COLOR=636466]additions highlighted.[/COLOR]
> 
> ...




I completed my build a week ago, and I used 150k ohm resistors and I also used a 50k ohm stereo pot. I also read that capacitor C7 & C8 increases gain so I did not use them. The gain is more than enough this way. Turning the volume up more than 1/3 makes it way to loud for me.
The point is you may want resistors with higher value than 50k. I hope this is to any help!


----------



## fuens

Great!
 I'll test it.
 Cheers
  
 Toni


----------



## fuens

slimzim said:


> I completed my build a week ago, and I used 150k ohm resistors and I also used a 50k ohm stereo pot. I also read that capacitor C7 & C8 increases gain so I did not use them. The gain is more than enough this way. Turning the volume up more than 1/3 makes it way to loud for me.
> The point is you may want resistors with higher value than 50k. I hope this is to any help!


 
 Hello Slimzim
 The matter is adjust the gain for high an low impedance headphones.
 What kind of headphones do you use?


----------



## fuens

Now, I have not on my home my Starving Student. Is in my work. (I'm convalescent of work accident)
 With a low impedance 32ohm (I remember) I have a little hum.


----------



## slimzim

fuens said:


> Hello Slimzim
> The matter is adjust the gain for high an low impedance headphones.
> What kind of headphones do you use?


 
 I'm using 32 Ohms at the moment. Audio Technica M50. I have no hum at all, I used a full alu case tough. I think I'll do a remake on the 12au7 schematic for my build. When it's complete i could PM it to you


----------



## fallen angel

Years later, it's time I get to building my amps. I'm going to gift one to a bud that is lending me some great equipment. I'll be running a pair of 19j6 tubes that I've been hording for the last 5 or so years . Just need to find someone with a table saw and perhaps a router for me to cut up the wood I've got set aside.
  
 Before I get started, I wanted to ask about grounding. I will be using a central grounding plate (copper psb) and running that to the power adaptor by wire. I believe I've seen places where some grounds should be isolated and run separately to the power jack?


----------



## tomb

Nice to hear from you again, FA!
  
  
 On a separate subject, I have a customer who may have experienced great difficulty with his SSMH with regard to the LED resistor.  I'm not certain yet whether that is the cause, but additional warnings come at no price whatsoever.  So, for those contemplating building the SSMH kit, please note the following about the LED resistor and standoff provided in the kit:
  


> Here is the standoff assembly. This will be provided in the kit with several washers. At least one washer is required for spacing along with the standoff - perhaps two. The only caveat to this you'll see in a moment. There are some smaller washers you can pick from and you'll want to use those next to the PCB, *or you may short the standoff against the tube LED resistor* - more on that later.


 


> *This is critical!!* *Note the spacing between the standoff, washer/spacer and the tube LED resistor lead. Be certain that you have some space here as shown. Otherwise, disaster will ensue*. Note also that the flat side of the hex standoff is also facing the resistor lead. This is an additional insurance that a space is maintained. Note that a small washer must be used here - a regular sized flat washer will contact the lead, so don't use one. Nevertheless, the spacing with only the standoff is not sufficient, so some additional spacing is needed and the small washer provides that.


 
  
 These quotes are taken directly from the SSMH website, here: http://diyforums.org/SSMH/SSMHconstruct5.php
 and the SSMH Build Thread in this very same section on Head-Fi: http://www.head-fi.org/t/437075/starving-student-millett-hybrid-pcb-step-by-step-build-guide
  
 Further, here is the photo used to illustrate the situation:




  
 Please note the proximity of the resistor lead to the standoff!  If you are not careful to solder the resistor flush to the PCB and bend the leads at the absolute joint at the end-surface of the resistor, you may short the LED resistor onto the standoff.  Since we are always looking for good grounding in our amps, there are also specific instructions for scraping the anodizing off around the standoff mounting hole in the case lid.  So, a short at this standoff can cause significant problems.
  
 As you can see in the photo, it should not be an issue and there is adequate clearance if you follow the recommendations.  Further, be absolutely certain you use the smaller washers for spacing beneath this standoff.  A regular #4 washer will definitely short out on the resistor lead.
  
 I suppose if someone were really wishing to be extra-cautious, you could literally bend the leads to offset the resistor to the right in this photo.  That would give you some additional clearance, even.


----------



## caiafa

I'm very new at building electronic stuff.
 If anybody could give me some hints about troubleshooting my problem with my amp it would be great.
  
 I forgot to isolate the mosfets from the heatsinks and I shorted them when powering on. Now I only get sound in the left channel. Any guides on what to check for failures? Both of the tube heaters light up.


----------



## tomb

caiafa said:


> I'm very new at building electronic stuff.
> If anybody could give me some hints about troubleshooting my problem with my amp it would be great.
> 
> I forgot to isolate the mosfets from the heatsinks and I shorted them when powering on. Now I only get sound in the left channel. Any guides on what to check for failures? Both of the tube heaters light up.


 

 Well, my guess is that you damaged the MOSFETs.  Replace them with proper insulating kits and see what you get.


----------



## SlimSwaly

I'm thinking to buy the "Starving Student" hybrid amp kit and i have some questions:
 1. If you compere the "Starving Student" amp to other tube amp witch it would be?
 2. I didn't understand the the point that i must "warm up" the amp b4 i plug my headphones and unplug b4 im done>why?can someone explain me?
 2.1 How long do i need to warm up?
	

	
	
		
		

		
			





 Coz nowdays i don't use an amp and mu headphones plugged directly to my "Roland quad capture".
 3. What do you think is worth to invest in a tube amp with k702 headphones?


----------



## tomb

1. It's sort of like the Millett Hybrid MiniMAX, but a bit less refined/featureless and with much more current capability.

2. See above.  One of the lack of "features" on the Starving Student is a headphone relay-delay.  Upon turning an amp on, a relay-delay keeps the headphone jack disconnected until the output coupling capacitors have had a chance to charge up.  Tubes are biased above a DC voltage of zero.  In the case of the Starving Student, 18VDC are on the headphone jack until the capacitors charge up and start blocking the DC.  Interestingly enough, this usually coincides with how long it takes the tubes to warm up.  So ... once warmed up, it should be safe to plug the headphones in without worry of exposing them to direct DC voltage.

This situation is common to all OTL tube amps and most tube hybrids.  Unless a relay-delay is employed, you could perhaps damage your headphones if you had them plugged in when you turn the amp on.

2. 30-45 seconds is safe.  When you see the orange glow as very bright in the center of the tubes, that means the heaters have heated up fully and the tube is warmed up. Again, it's really whether the capacitors have charged, but you can't "see" them. So we look at the tubes, instead.

3. I don't understand the English in this question.  Are you asking how much should you invest in a tube amp for the K702?  Or are you asking whether it's worth it to invest in a tube amp for the K702?


----------



## SlimSwaly

3. Im asking Whether it's worth it to invest in a tube amp for the K702? and if yes how much should you invest in it?


----------



## tomb

slimswaly said:


> 3. Im asking Whether it's worth it to invest in a tube amp for the K702? and if yes how much should you invest in it?


 
  
 Well if I was really a smart*ss, I might say ... "Yes - $10,000" and leave it at that.
  
 That wouldn't be very nice, but it does sort of make a couple of points:

No one should tell you what makes a truly worthy investment or how much to invest - in anything.  Even qualified financial consultants present recommendations that are full of disclaimers and caveats.
There's an opinion that's widely shared: the AKG K7-series of phones are one of the truly great headphones.  Before the advent of $1000+ headphones, there were three series that stood at the top of the world: AKG K7-series, Sennheiser HD580/600/650, and Beyer DT880 (impedance ranges).  It's safe to say you can throw ever-increasing quality amps at these phones and they will respond with ever-increasing improvements.  As with most things, you end up in a diminishing returns condition that at some point will reach the limit of your financial capability.
  
 You should be careful with tube amps concerning the AKG K7-series, though.  IMHO, OTL tube amps are not appropriate.  This is because the K7-series is known for needing a lot of current.  An OTL (output transformer-less) tube amp will be very limited in current capability.  A output transformer-coupled tube amp will work well, as will a tube hybrid, such as the Starving Student.  The Starving Student has enough current to power even the most stubborn planar headphones, much less the K701/2/12/etc.


----------



## DutchGFX

tomb said:


> Well if I was really a smart*ss, I might say ... "Yes - $10,000" and leave it at that.
> 
> That wouldn't be very nice, but it does sort of make a couple of points:
> 
> ...




If you double/triple etc csthodr followers in an OTL you can, in theory, provide massive currents  but it takes up too much current from transformer to heat more tubes 

I wanted to build an amp with 4 12AU7 per channel, but that went downhill lol

Anyways, the K7__ series is fantastic. When I owned mine, I didn't find any tube amps that worked well, but the Starving Student seems to be a good option. I wasn't DIY capable at the time. I think the SS is a good project because of its simplicity and relatively low voltages, so it is easier to work with. The SS uses a MOSFET as a follower (like a tube cathode follower) to provide current, which will allow the K701 to pair well, since it has plenty of current and a low output impedance, which is crucial since the headphones are only like 62ohms


----------



## Wisor

Hello,
  
 Recently I upgraded my setup with Objective2 amplifier 
  
 Since I am a new "audio enthusiast" I want to build Starvig Student as well.
  
 As far as I looked on the net, I saw only great reviews about this amp.
  
  
 My question now is:
  
 Is it possible to get a PCB somewhere ?
  
 I texted user Fred_fred2004 about buying few PCBs, but he didn't replay.
  
  
 Regards,
 Z


----------



## tomb

I am selling the original Starving Student that was based on Pete Millett's design. It uses the 19J6 tubes as in the original. The PCB was designed by dsavitsk of ECP Audio.

However, I am only selling full kits, not separate PCBs. The kits were last sold in 2010. It's taken that long to find enough 19J6 tubes to make it worthwhile to sell kits again - but the stock is limited. When these run out, it could be another 5 years before they're offered again, if ever.


----------



## adevriesc

I'm considering this for my first DIY tube amp project. I'd prefer not to purchase tubes as I already have a ton on hand; would any of these models work? (I checked for dual triode/heater current and narrowed the field based on that.)
  
 14B6
 12AU7
 12AU7A
 12SQ7GT


----------



## tomb

adevriesc said:


> I'm considering this for my first DIY tube amp project. I'd prefer not to purchase tubes as I already have a ton on hand; would any of these models work? (I checked for dual triode/heater current and narrowed the field based on that.)
> 
> 14B6
> 12AU7
> ...


 
 The 12AU7 and 12AU7A are simply different versions of the same tube.  The 12AU7 version of the Starving Student is fairly well known at this point and is documented here:
http://diyforums.org/SSMH/SSMHvariants.php


----------



## unhinged17

Hey Tomb,
  
 Where can I find out more about the Starving Student hybrid amp kit you're selling?
  
 Thanks!


----------



## tomb

unhinged17 said:


> Hey Tomb,
> 
> Where can I find out more about the Starving Student hybrid amp kit you're selling?
> 
> Thanks!


 
  
http://www.diyforums.org/SSMH
  
 Hint: You might also look in my signature.


----------



## Martinus

Hello again everyone.

A while back I built a rather ugly ECC82-based variant of the amp on stripboard and put it in a little project box. It was a bit noisy thanks to poor shielding but worked well otherwise.





I recently rebuilt the amp using a PCB Fred_fred2004 kindly offered me (quite some time ago). I found a nice enclosure, shielded the inside and installed everything.





I now have an absolutely excellent amp that's about as silent as I can detect when there's no input. I'm really pleased with the results. 

Many thanks again to everyone on the forum who helped with advice and good humour.


----------



## urshurak776

Martinus, can you post a picture or two showing how you shielded it?  That part of it and doing grounds is confusing me a little bit....


----------



## GingerBeard

I've been poking through this thread for days...
  
 I built mine and it is working (sort of).  I get good sound, but I am reading voltages that, to me, seem a bit low and the tubes aren't quite heating up as warm as they should.
  
 1=27v
 4=8v
 6=27v
  
 Are these values right? - I am using the 12AU7 schematic here: http://diyforums.org/SSMH/SSMHvariants.php
  
 EDIT:  Found the problem.  I was putting the led resistor between R1 and R2 which was pulling that voltage down.  I realized it when I noticed that when I plugged in the LED, the voltage at Pin 1 of the IRF510 was dropping on that side.  I move the resistor to a spot on my stripboard before C1.  All is now right with the world.  Thanks.


----------



## JamesBr

tomb said:


> http://www.diyforums.org/SSMH
> 
> Hint: You might also look in my signature.


 
 Thanks hehe, good that you pointed it out


----------



## Kaaf

wisor said:


> Hello,
> 
> Recently I upgraded my setup with Objective2 amplifier
> 
> ...


 
 Winsor, did you magage to build it? How does the Starving student compare to the O2 amp? I was wandering, because I'm also interested in the O2. And I love the ssh, but it's not very sturdy. And would like a seperate AMP


----------



## Wisor

Hey Kaaf,
  
 My starving student project is on hold at the moment. I am still seeking for tube sockets and tubes. 
  
 To be honest I am building few CmoyBBs, so I really don't have any time for SS.
  
 I would recommend that you buy O2.
  
 Starving student is cheaper than O2 (but not a lot), but to let you know a good tube costs around 15€ + socket is 3€ and you need to multiply that by 2 (you need two tubes) and you also need a 48V power supply which is around 10€ on ebay.
  
 Other material is very cheap. I payed around 5€ in local store for elements. I would say SS costs around 50€ to build.
  
  
 O2 DIY Kit from Switzerland (http://www.headnhifi.com/diy-kits/o2-kit-full) costs 64€ + shipment. If you live in europe, they can send you a package from Germany, so you don't need to pay for customs and other import fees (of corse you need to wait a bit longer).
  
 You get everything you need (closering box is included, knobs.....)
  
 If you are familiar with soldering I would strongly recommend you to start with O2, because you won't have any logistical problems with material and you get everything you need to build it.
  
 Meanwhile you can still buy a PCB from DAVE for 4€, search for material and build it.
  
 Specifications of O2 are stunning, and for the price it goes at headnhifi just get one already 
  
 On the other side SS is a tube amp, but it has mosfets so it's not a "true tube amp" 
  
  
 Specifications of SS are not nearly as good as O2s, but some people prefer tubes over solid state amps, the choise is yours.


----------



## JamesBr

wisor said:


> Hey Kaaf,
> 
> My starving student project is on hold at the moment. I am still seeking for tube sockets and tubes.
> 
> ...


 
 Good info here, thanks alot!


----------



## brokentofu

Is there a PCB available that has the modifications for using the 12au7 tubes? I'd love to build a 12au7 Millett Starving Student with the 12au7 tubes, but I don't want to try my hand at a P2P build.


----------



## Forte

brokentofu said:


> Is there a PCB available that has the modifications for using the 12au7 tubes? I'd love to build a 12au7 Millett Starving Student with the 12au7 tubes, but I don't want to try my hand at a P2P build.


 
  
  
http://www.head-fi.org/t/664191/starving-student-pcbs


----------



## Fail

This seems like an interesting project. I'm gonna have to see what kind of spare parts we have laying around at work that will allow me to build this. Then I'll order the rest that I have missing.


----------



## djonesii

Just in case any one is interested, over in this thread, the PCB is still available ....
  
 Got mine on order from down under.
  
  
http://www.head-fi.org/t/664191/starving-student-pcbs
  
 Dave


----------



## OrangePower

Hi Guys
  
 I`m new here and I`m building starving student.
 PCB are rdered from down under. I have problems finding lamps in my country.
 I can get 12AX7, ecc82 (7418, 5963).
 Which one of these can I use in this amp?
 I`m working with lamps first time...
  
 Thank you for help
  
 BR
 OP
  
 P.S. What do you think about that
http://www.tech-diy.com/Headphones/AsceticStudent/AsceticStudent.htm


----------



## Nathan P

Hi OrangePower,

I just finished trolling this whole thread as I think this is a perfect first project for me. I can pass on what I've gleaned but don't take it as gospel. I don't have a working amp yet. 

Any of those tubes should work. I believe ecc82 is just a different designation for the 12AU7. The 12AX7 will work but is extremely high gain, so for most headphones it isn't a great choice. From my research, people really like the 5963. That's what I've chosen. GE's are a favorite among SOHA builders. Their nominal usage voltage is a bit lower so they'll get closer to the linear range than the standard 12AU7 according to some. Personally, I just found a great deal on some. I was bouncing back and forth on tube choice for my first set until I found some for literally half the price of what I was finding before that. Dilemma solved. 

Cheers
Nathan


----------



## Scarface81

Hi guys, I'm new to the forum, I've been doing a lot of reading and search etc, I have decided to build a 12au7 version of this amp with the optional parts, this will be my first build using a schematic and NO pcb, I have a couple of questions though, on the schematic it shows resistors between the rca in and the volume pot, however I can't see them in most pictures I see of the amps insides? Do people not put them in? Or they're just somewhere else in the wiring? Higher kOhm pot? My other question is about these caps I got, they are suntan brand part number ts08s, under the part number they have 224k 275v, if I google the latter it shows as a .22uf cap, if I google ther first part number it's shows me something different, will these caps be ok for c3a and c5a? I may have other questions later, thanks guys


----------



## tomb

scarface81 said:


> Hi guys, I'm new to the forum, I've been doing a lot of reading and search etc, I have decided to build a 12au7 version of this amp with the optional parts, this will be my first build using a schematic and NO pcb, I have a couple of questions though, on the schematic it shows resistors between the rca in and the volume pot, however I can't see them in most pictures I see of the amps insides? Do people not put them in? Or they're just somewhere else in the wiring? Higher kOhm pot? My other question is about these caps I got, they are suntan brand part number ts08s, under the part number they have 224k 275v, if I google the latter it shows as a .22uf cap, if I google ther first part number it's shows me something different, will these caps be ok for c3a and c5a? I may have other questions later, thanks guys


 

 The SSMH PCB version, which is what the 12AU7 schematic is based on here: http://diyforums.org/SSMH/SSMHvariants.php, uses an Alpha stereo volume pot.  The basic amplification of either the 12AU7 or original 19J6 tube means the gain is too high for most headphones and sources.  The result - without correction - is that most comfortable listening is way down in the lowest travel of the volume knob.  Unfortunately, this where almost all stereo volume pots (except something like the Alps RK27) perform poorly with channel matching - including the Alpha pot.  The use of the input resistors "throws" the volume adjustment range further into the middle of its travel, where the channel matching is much better.  This is something you will need to play with, typically in increments of 50K for a 50K volume pot.  Use increments of 10K for a 10K volume pot, etc.  If gain is still too high and all of your listening is at 9 o'clock and below, then throw in a 100K resistor for a 50K volume pot instead of a 50K resistor.  Still too high, make it 150K.  Keep doing this until you get to the range on the volume pot that satisfies most of your headphones.  That sounds more complicated than it is, really.  At least with the 19J6, most opted for 50K, I believe.  I think I supply both 50K and 100K resistors in the SSMH kit, since the Alpha pot is 50K.
  
 About the caps - According to the mfr's data sheet: http://www.suntan.com.hk/pdf/Plastic-Film-Capacitors/TS08V.pdf, these caps can vary from 0.022 to 2.2uf.  Unless you can find something written on the case that says "uf" with it, you will need to measure them with a meter to find out.  It's curious that even in the photo on that data sheet, the "224K" is showing, but no "uf" rating.  I have no idea what the 224K means - does it have writing on the other side?  Surely it says "uf" with a number somewhere.


----------



## Scarface81

Hi, thanks for the info on that, I understand it now, about the caps, there is no writing on the other side of them, I think I'll take the safer route and source some that are more clear on what they actually are, I got them from jaycar as they didn't have anything else, I live in Australia, can you suggest where I could get some?


Sent from my iPhone using Tapatalk


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## Scarface81

Never mind guys, got myself a meter and checked them out, they measure between 223nf and 218nf, thanks for taking the time to help out, I really appreciate it


Sent from my iPhone using Tapatalk


----------



## tomb

scarface81 said:


> Never mind guys, got myself a meter and checked them out, they measure between 223nf and 218nf, thanks for taking the time to help out, I really appreciate it
> 
> 
> Sent from my iPhone using Tapatalk


 
  
 Ah ... so the 224K was referenced to picofarads.  So, you have what you need - 0.22uf.


----------



## Danthrax

So I'm making the 19j6 variant (actually 2 of them) and I'm wondering how this variant: http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif is different from the original Pete Millet design I haven't found any clear answers. I'm trying to figure out which one would deliver the most current. Or if there is an alternate configuration that would give me better results.


----------



## tomb

danthrax said:


> So I'm making the 19j6 variant (actually 2 of them) and I'm wondering how this variant: http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif is different from the original Pete Millet design I haven't found any clear answers. I'm trying to figure out which one would deliver the most current. Or if there is an alternate configuration that would give me better results.




Think maybe the yellow highlighting means something?

The strike-outs look suspicious, too.

BTW, changing any of the passive devices is not going to increase the current. Besides, the MOSFETs are biased by the tube heaters. You're not going to find another amp in this category with more current capability.


----------



## Scarface81

The highlighted text at the top of that schematic says optional BOM, BOM meaning Bill Of Materials, you don't have to have those parts in there


----------



## Danthrax

I understand that it's optional, but i'm wondering what those options accomplish? More power, less noise, etc...


----------



## tomb

danthrax said:


> I understand that it's optional, but i'm wondering what those options accomplish? More power, less noise, etc...


 
  
 You keep focusing on power (or current), but that is all determined by the basic circuit and power supply of an amplifier design.  You can't buy or build an amplifier and drop a bigger engine into it.  The "engine" is the amplifier design itself.  Carrying the analogy to its logical extreme, if you had an amplifier enclosure, you could drop another amplifier assembly into that enclosure and get more power, but it would be a completely different amplifier in the same skin.
  
 As for the schematic, the answer to your question is less noise, less distortion, better frequency response, and more convenient usability.  It all depends on which parts you're talking about.  Keep in mind that Pete Millett's principle in designing this amplifier was for a _Starving Student_.  As Pete put it in terms of _Starving Student_ costs, "about two delivery pizzas and drinks."
  
 When Dsavitsk (of ECP Audio) designed the PCB version of the Starving Student Millett Hybrid, he chose to add some additional parts that made improvements (some significant) with a minimum of cost.  Keep in mind that once you design a PCB, you're already increasing the cost significantly from the original.  Likewise, design that PCB to fit into a custom-made case, you increase the cost even more.  The comparison of the added parts becomes insignificant.  To understand the perspective, however, realize that Pete's version was absolutely the lowest cost possible - similar in concept to a Tube CMoy.  There was no case - you had to come up with it on your own.  This led to many creative concepts in the early days of DIY-er's constructing the Starving Student.  Nevertheless, _casework often represents fully half the cost_ of building an amplifier.  It also involves a completely different skill set than populating a PCB by soldering - often compared to a paint-by-number painting you might purchase in an arts and crafts store.
  
 So, keep in mind that the goals between Pete's original design and the SSMH PCB are slightly different.  The goal in the SSMH PCB was to reach more of the masses by greatly simplifying the construction in providing a PCB and a custom-made case.  This makes assembly a piece of cake by comparison to Pete's original design, but it necessarily increases the cost.  The SSMH PCB version is currently $150 at Beezar.com, whereas Pete's original Bill Of Materials (BOM) totaled about $36.
  
 One complicating factor to this is that due to the overwhelming popularity that Pete's design caused, the tube prices of the 19J6 increased radically.  Today, you will find 19J6 tested and matched pairs for as much as $49.95 on ebay.  When Pete first made the design available, these tubes cost about $2 each.  So just the tube costs alone have far exceeded Pete's _total_ Bill Of Materials for the design.
  
 Anyway, with all of that background, here are the reasons for the parts we added in the schematic you referenced from www.diyforums.org/SSMH/SSMHschematic.php :
  
*Strike-Through Parts*

*C1, C6* - These are the classic "power" caps in most amplifier circuit designs.  While replacing these do not increase power, they lower the impedance of the power supply ahead of the amplification circuit and provide more ripple removal.  In other words, upsizing these caps will have a good result in increasing the availability of current in the circuit and decreasing noise.  They were up-sized to 680uf to make use of the Dsavitsk-PCB and Beezar-custom-case space.  The 63V rating was considered the safest (with an ample safety factor) for the 48V power supply (Cisco VoIP power adapter).
*C2, C4* - These are the interstage capacitors that AC-couple the tube output to the MOSFET buffer.  Simply put, if these caps are not sized large enough, you may lose some bass response.  This is also related to the amplifier's output coupling caps.  More on that next.
*C3, C5* - These are the primary output coupling caps for the Starving Student.  Any output coupling capacitor on a headphone amplifier will combine with the impedance of the connected headphones to form an RC circuit.  This type of circuit forms a bandpass filter, meaning some frequencies are filtered out.  In this case, if the value of RC is not high enough, audible bass will be filtered out.  Pete originally specified 150uf capacitors to keep costs down.  However, this results in -3dB at 33Hz for a 32 ohm headphone.  Actual bass begins dropping at much higher frequencies than that.  Up-sizing these capacitors to 470uf means the cutoff frequency is down to 10.5 Hz.  That still has some audible drop above 20Hz, but not enough for most headphones.  Once these capacitors were up-sized, it made sense to also up-size C2 and C4 above to ensure that these did not cut out any bass frequencies, too.
  
*Yellow-Highlighted Parts*

*C3a, C5a* - Common practice, especially with many of Pete's designs (such as the original Millett Hybrid in AudioXpress magazine) is to use bypass film capacitors with electrolytics, particularly in the signal path.  The reason for this is that electrolytic capacitors do not sound well with high-frequencies and can add distortion.  Bypassing with a small film cap allows the film cap to actually pass those frequencies, instead.  Keep in mind that this part is mostly empirical and listening preference, but it will make things sound better than just the electrolytic itself.  This can be mitigated further by use of true, audiophile-quality grade electrolytics, too (Black Gates, Muse ES, FG, KZ, Elna Cerfine, Silmics, etc.).
*C7, C8* - without going into the specifics of the design with cathode bypass tube circuits, use of this capacitor can also increase the bass frequencies around the tube.  Again, a small tweak that may or may not cause much of an audible difference, but on paper - very little cost for some gain.
*R14, R15* - these are normally referred to as _grid stop resistors_.  In some cases, they can lower distortion in tubes and ensure that the tube does not oscillate.  They can also cut down on outside interference that tubes can sometimes pick up.  It can be argued that none of that is a concern in this amp, but in this case - very little downside to adding these resistors for only pennies.
*R16, R17* - These resistors were specifically suggested by Dsavitsk and can vary in 50K increments - 50K, 100K, 150K, etc.  The reason for these resistors is again - "Starving Student."  One of the most expensive components of an amplifier can be the volume control.  In this case, an inexpensive Alpha stereo volume pot (RV1) is specified in the BOM.  Unfortunately, cheaper volume control pots are sometimes not well matched at lower volume knob travel (9 o'clock and below).  Because the 19J6 tubes already have a pretty high gain compared to most headphones, it means that without correction, most of your listening may be in the 9 o'clock positions and below.  These resistors (must be coordinated with your particular headphone's sensitivity) "push" the volume range further into the mid-travel of the pot's rotation.  The idea is to use the best increment of 50K that results in comfortable listening levels around the 12 o'clock position of the volume pot.
  
 This is the reason you didn't get much response the first few times because you were not asking a simple question with a simple answer.  Hopefully, this covers it.  If not, there's not a whole lot more that I've got.


----------



## Danthrax

Interesting, is there any reason that the c3 and c5 need to be rated for 63v I see that there are KZ caps that are 470uF but are only rated for 50v, would those be fine since that line should only be 19v max anyway?


----------



## tomb

danthrax said:


> Interesting, is there any reason that the c3 and c5 need to be rated for 63v I see that there are KZ caps that are 470uF but are only rated for 50v, would those be fine since that line should only be 19v max anyway?


 
  
 You're welcome. 
	

	
	
		
		

		
		
	


	



  
 If the MOSFET shorts, you'll have 48V to ground at the output.  I'm not going into any more details again (ever?), but if you read this thread, you'll find that shorting out the MOSFETs is a common occurrence.  If you feel comfortable with 2V headroom - a 4% safety factor - for your headphones, go ahead.


----------



## Danthrax

Sorry I appreciate the time you took to explain everything I'm at work and doing a few things at once and didn't even realize how that post came off. I'm generally very to the point which comes off as rude at times I'm more used to irc where there is a continuous conversation I have to get back into delayed read forum posting mentality. I do thank you for the help in understanding this. It looks like all of the audiophile quality caps are under 50v (edit: just found some FG's at 100v), does it matter if the cap is larger than 470uF? I'm essentially trying to make an over-built one, it doesn't really need to fit on a pcb or within a certain container, so space isn't a concern for me. I'm just trying to find a way to make it as good as it can be.


----------



## vapman

This is still a great sounding amp  and glad to see people are still building them 
  
 I would have no problem going larger than 470uF if the increased resistance doesn't pose any issue.
  
 I think more important is making sure you pick a good cap with a low SNR. With this design you would probably see more benefit adding decoupling capacitors to the design to reduce noise.


----------



## Danthrax

Hmm I'll have to take that into consideration but I think I'm set as I found some FG series 470uf caps to use for that part I'm also going to implement a few of the other optional components, I do think I'm going to use 1000uf instead of 680uf for the power caps since I can get those in FG as well, unless it doesn't make sense to use those there. I was planning on putting this together on this: https://www.radioshack.com/collections/connectors-connectivity/products/universal-component-pc-board?variant=5717555141 Unless there is a reason to avoid using one of these? I'm actually going to be making two so I think I'll leave one at the original (or close to original) design and make the second one have all of the changes.


----------



## tomb

danthrax said:


> Hmm I'll have to take that into consideration but I think I'm set as I found some FG series 470uf caps to use for that part I'm also going to implement a few of the other optional components, I do think I'm going to use 1000uf instead of 680uf for the power caps since I can get those in FG as well, unless it doesn't make sense to use those there. I was planning on putting this together on this: https://www.radioshack.com/collections/connectors-connectivity/products/universal-component-pc-board?variant=5717555141 Unless there is a reason to avoid using one of these? I'm actually going to be making two so I think I'll leave one at the original (or close to original) design and make the second one have all of the changes.


 
 There is nothing wrong with using 1000uf, either on the power caps or the output coupling caps.  I would highly recommend the film bypasses on the output, however.  Wima MKP10's are usually the standard.
  
 As for the board you referenced, I think you'll find the parts are too large on the SSMH for that to be of any use.  Yeah, the Dsavitsk PCB is not much bigger than that, but that's an optimized PCB layout.  Things are a lot different when you start working with real leads and wiring with a point-to-point construction.  You need to study the pics in first few posts in this thread (Pete's and Nate Maher's) and Pete's website: http://pmillett.com/starving.htm .  The biggest thing you need to worry about with a point-to-point layout is grounding.  Some use a star ground, ensuring that every ground is taken back to a common point and then grounding that.  Or, you can look at what Pete used - a copper plate and built everything around that.  A PCB (a good one) incorporates a ground plane integral with the PCB.  Neither point-to-point or the Radio Shack board you referenced has that - you have to make it happen.


----------



## tomb

You also can't skimp on the heat sinks in this design.  Those tube heaters mean the MOSFETs are biased into Class A with 150ma.  That's significant and will require huge heat sinks.  You can't get that on the Radio Shack perf board.  If you use a metal case and properly plan it, you should be able to use heat sinks and grounding all in the case.  Note, however, that's one of the reasons it's very easy to short the MOSFETs in this design.  Be certain you use insulating washers on the MOSFET mountings.


----------



## tomb

One final thing - Pete gave plenty of warning about the MOSFET gate resistor - R3 and R9.  If you don't get these very close to the MOSFET itself, they will oscillate.  So, if you mount the heat sinks and MOSFETs on the case away from the rest of the circuit (a common practice when trying to heat sink and ground at the same time), you need to carry those resistors with the MOSFETs, not down on the rest of the circuit with a big separation distance between MOSFET and resistor.


----------



## Danthrax

Those are definitely things I'll keep in mind what I was planning on doing was using the metal top plate for one of the radio-shack kit boxes and having the heatsinks outside of the box: http://imgur.com/WGuQFAn and mounting everything to that plate, the perf board was mainly just going to be for holding caps/resistors that weren't attaching directly to any other components like audio jacks or tubes I may or may not keep that idea. Thanks for the tip with the r3 and r9 resistors I had built one of these a while ago that had a lot of issues and was therefor not used and lost. Now while I know the mosfet gets hot but is there any concern with using heatshrink on the leads out of the mosfet after the wire is attached?


----------



## tomb

danthrax said:


> Those are definitely things I'll keep in mind what I was planning on doing was using the metal top plate for one of the radio-shack kit boxes and having the heatsinks outside of the box: http://imgur.com/WGuQFAn and mounting everything to that plate, the perf board was mainly just going to be for holding caps/resistors that weren't attaching directly to any other components like audio jacks or tubes I may or may not keep that idea. Thanks for the tip with the r3 and r9 resistors I had built one of these a while ago that had a lot of issues and was therefor not used and lost. Now while I know the mosfet gets hot but is there any concern with using heatshrink on the leads out of the mosfet after the wire is attached?


 
 Non concern about heat-shrink - it's a great practice to do all of the time, anyway.  If the heat sinks are doing their business, the wires won't get hot, anyway.
  
 I still think the perf board is just going to get in your way.  For what you need, you should really use a few of these:
 https://www.radioshack.com/products/radioshack-5-position-terminal-strip?variant=5717454853 .  Again, that's why I referenced Pete's and Nate's photos in the first posts of this thread.  Study those pics.  There are reasons why they built them that way, all the way to using grommets around the holes for the MOSFET mounting.  Those terminal strips are certainly self-evident in both of their builds.
  
 I could be wrong, though - maybe you should work out a layout drawing to scale, using the all the part dimensions, and see if  you can make it work on that perfboard.  If so, have at it.


----------



## Danthrax

The one thing I was wondering is if I used an all plastic box then just used the perf board as the the central grounding point would that be bad? I basically bought one of these and it has a metal top and a plastic top I was back and forth about how to do grounding thinking that it might be better to mount to plastic and then have the grounds all go to the perf board. I guess It's something I can always re-work if it doesn't work out well.


----------



## tomb

danthrax said:


> The one thing I was wondering is if I used an all plastic box then just used the perf board as the the central grounding point would that be bad? I basically bought one of these and it has a metal top and a plastic top I was back and forth about how to do grounding thinking that it might be better to mount to plastic and then have the grounds all go to the perf board. I guess It's something I can always re-work if it doesn't work out well.


 

 There is no ground plane or solid plate on that perf board.  The pads are simply tied together with traces in certain instances.  It's not the same thing as a ground plane or plate.  There are other issues, as well.  I apologize for continuing to harp on it, but seriously - you have two tube sockets with 14 connection points and two MOSFETs with 6 connection points, plus heat sinks that have to be mounted.  None of those will work on the perf board.  In addition, you have four caps - perhaps eight if you use the bypasses - that will span 3 to 5 of those holes in the perf board with their leads, much less the physical size of the caps' cans themselves.  You also have 5 components in addition to this that all need panel mounting.  In addition to the tube sockets, MOSFETs and capacitors, that represents another minimum of 13 leads going from those components to somewhere on the perf board, perhaps several more than that.  At some point, having a little board with holes in it doesn't give you much advantage.
  
 Like I said the last time, draw it out.  This isn't the Starving Student, but it might give you some ideas with that perf board: http://benfeist.com/wp-content/uploads/2012/12/a47_assembly_and_schematic.png
  
   If you can make it work - fine, but I have doubts. Good luck.


----------



## Danthrax

I understand your concern but I think you are misunderstanding my intention with the perf board. I don't plan to have major components mounted directly to it, it's more of a collection space to tidy things up a bit so it's mostly going to be point to point. But I'm stating to think that's a bad idea. My other though was to use the larges sets of traces as a point to tie all the grounds into but I'm guess the concern is that there isn't enough copper there to handle the power going through it? I'm assuming that there would likely be a greater advantage in reducing overall cabling length inside the box though. I'll probably pick up some terminal strips and use those with the metal plate as well? or do you think I should just use the terminal strips and a plastic cover? This was a rough non-spaced out version of all the parts I was going to mount to the board (ignore r3 and r9 I'll attach those to the mosfet): http://imgur.com/0RmpySH


----------



## Fishline

Having built a couple of the original 19J6 version (P2P) of the amp a few years ago, I thought I'd try another P2P 12AU7 version.  I basically used the same case and heatsink as what's on instructable.  Just finished wiring everything.  Turned it on and no sound was coming out of the left channel.  I measured the 48v and 12v points indicated on the schematic and got 45v and 12v in both channels.  Pin 1 of both MOSFETs measure 14-15v.  I tried reflowing the solder at anything that might be suspicious but to no avail.  Can anyone offer some idea of what to try?  I'd very much appreciated it!


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## Fishline

Never mind... i solder the wire to the headphone jackfor the left channel to the same side of the jack as the right channel and gnd, and voila! Sweet music! All is well.


----------



## Fishline

fishline said:


> Never mind... i solder the wire to the headphone jackfor the left channel to the same side of the jack as the right channel and gnd, and voila! Sweet music! All is well.




I actually forgot about the mica insulation for the MOSFETs. I just put a thin layer of thermo compound on the back of the MOSFETs before bolted them to the heatsink. Would thatbe ok? I've run the amp for a few hours already and everything seems just fine. What can go wrong without the mica?


----------



## tomb

fishline said:


> fishline said:
> 
> 
> > Never mind... i solder the wire to the headphone jackfor the left channel to the same side of the jack as the right channel and gnd, and voila! Sweet music! All is well.
> ...


 
  
 It's probably OK with just thermal compound, but more importantly - did you use an insulating washer on the MOSFET tab?  That's where the short will occur - between the MOSFET tab and the screw.  This happens because the inside of the hole on the heatsink often has very little anodizing, or it creates a short with whatever the heat sink is mounted on.


----------



## Fishline

tomb said:


> It's probably OK with just thermal compound, but more importantly - did you use an insulating washer on the MOSFET tab?  That's where the short will occur - between the MOSFET tab and the screw.  This happens because the inside of the hole on the heatsink often has very little anodizing, or it creates a short with whatever the heat sink is mounted on.




Hmmm, i just bolted the MOSFETs onto the heatsink directly. I ran it all day yesterday and left it on overnight. It still runs just fine today. If there is going to be short, wouldn't it happened already?


----------



## vapman

fishline said:


> Hmmm, i just bolted the MOSFETs onto the heatsink directly. I ran it all day yesterday and left it on overnight. It still runs just fine today. If there is going to be short, wouldn't it happened already?


 

 There's nothing wrong with this. My Yamaha M4 power amplifier which has been running beautifully every day since the very early 1980's does this.
  
 edit: Didn't notice you didn't have a washer. Add one. I thought this was a post about if having a MOSFET that close to the heat sink is safe or not.


----------



## tomb

fishline said:


> tomb said:
> 
> 
> > It's probably OK with just thermal compound, but more importantly - did you use an insulating washer on the MOSFET tab?  That's where the short will occur - between the MOSFET tab and the screw.  This happens because the inside of the hole on the heatsink often has very little anodizing, or it creates a short with whatever the heat sink is mounted on.
> ...


 

 Not unless you breathe on it.


----------



## Fishline

OK.  I've pulled the insulating washers from the 1st SSMH I built to put in the new one.  I don't see them listed in the BOM.  It should be Mouser part # 532-4880SG, correct?  I dug that out of the Mouser order history from 6 years ago.  Amazing they kept that record.


----------



## tomb

fishline said:


> OK.  I've pulled the insulating washers from the 1st SSMH I built to put in the new one.  I don't see them listed in the BOM.  It should be Mouser part # 532-4880SG, correct?  I dug that out of the Mouser order history from 6 years ago.  Amazing they kept that record.


 
  
 I always provided heat sink hardware kits as a special product from Beezar and that's how it was listed - as a kit.  Self-serving, I guess, but then who else has ever supplied socket-head machine screws for heat sink mounting kits?  In addition, the shoulder washers I supplied were genuine Aavid, glass-filled shoulder washers.  Most kits supply the cheapest of machine screws and a cheap nylon shoulder washer that can often distort and compress upon torquing down the assembly.
  
 If that means my BOM was not as detailed as it should've been, so be it.


----------



## Danthrax

Well I finished the first one I planned on making: http://imgur.com/a/n9LTx , this one is actually using some 18j6 tubes instead of 19j6 (had them from a friends failed build) when I make the better one I plan on laying things out a bit better but overall this wasn't too bad, I may go back and try to tidy up the wires a bit but most of the long runs are going to ground and it looks a lot busier than it really is due to the small size. I'm also going to throw some jb weld on heatsink connectors as they really didn't want to solder to the metal plate. I'm thinking I may just go with a plastic plate for the new build but I'm still not sure. The thing that surprised me is that with a 100k pot the sound was still rather loud really quickly I would say an 1/8 of a turn on the knob was dangerously high volume on some lower impedance headphones and I wasn't really expecting that, even when I added in 50k resistors on the rca input it still seemed rather high. I also noticed a bit of a noise floor when using these with my Sony MDR 7506 (is it bad when $80 headphones become your test/beater headphones?), but it was not audible with my q701 or he400i. The radioshack I went to didn't have any terminal strips but I'm going to check another one today and get some, I may redo some of the grounding on this build to see if I can reduce the noise floor a bit.


----------



## Fishline

In case anyone find this helpful, here's my project on mouser (grand total of $63):
*http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=0b0ae93f48*
 ​(Can mouser projects be shared like this?)
  
 This is for the 12AU7 version.  It includes everything (case, heatsink, etc.) except wires, tubes, tube sockets, and the CISCO PSU.  It's basically the version as seen on Instructables:
 http://www.instructables.com/id/Headphone-Hybrid-Tube-Amp-SSMH/
  
 Some notes:
 1. There is a smaller Hammond case that can be used, but the heatsink will occupy the entire top of the that case, so holes will need to be drilled on the heatsink for tubes to poke through if you go with the smaller case (~$4 cheaper).  The case has several color options (BK for black, RD for red, YL for yellow, etc.)
  
 2. I put in the Alps RK097 pot/switch combination.  It's about the same price as the Alpha, but has the builtin switch.  Saves a separate switch and drilling another hole in the case for it.


----------



## tomb

danthrax said:


> Well I finished the first one I planned on making: http://imgur.com/a/n9LTx , this one is actually using some 18j6 tubes instead of 19j6 (had them from a friends failed build) when I make the better one I plan on laying things out a bit better but overall this wasn't too bad, I may go back and try to tidy up the wires a bit but most of the long runs are going to ground and it looks a lot busier than it really is due to the small size. I'm also going to throw some jb weld on heatsink connectors as they really didn't want to solder to the metal plate. I'm thinking I may just go with a plastic plate for the new build but I'm still not sure. The thing that surprised me is that with a 100k pot the sound was still rather loud really quickly I would say an 1/8 of a turn on the knob was dangerously high volume on some lower impedance headphones and I wasn't really expecting that, even when I added in 50k resistors on the rca input it still seemed rather high. I also noticed a bit of a noise floor when using these with my Sony MDR 7506 (is it bad when $80 headphones become your test/beater headphones?), but it was not audible with my q701 or he400i. The radioshack I went to didn't have any terminal strips but I'm going to check another one today and get some, I may redo some of the grounding on this build to see if I can reduce the noise floor a bit.




Input resistors are keyed to the volume pot impedance. 50K resistors assume a 50K pot. You should be using resistors in increments of 100K for a 100K pot.


----------



## Danthrax

Ok that makes sense, without the 50k it was way worse but it's still not ideal, I was under the impression that using a 100k pot to begin with would allow for a little more play, but I guess I was wrong. Thanks for all the help.


----------



## tomb

danthrax said:


> Ok that makes sense, without the 50k it was way worse but it's still not ideal, I was under the impression that using a 100k pot to begin with would allow for a little more play, but I guess I was wrong. Thanks for all the help.




Nope. You get more noise with a 100K pot.


----------



## RanDiesel

I built the SSMH 12AU7 version about 2 years ago and have been using it happily until recently I noticed that the left channel was really quiet compared to the right channel. So I cracked it open and found a bloated capacitor, C5 (63v 470uF) to be specific. I am wondering if this is just bad luck with these nichicon caps I found on ebay or if I could possibly have caused it with heat or a short? Seems like if it was a short it would have happened right away.


----------



## vapman

randiesel said:


> I built the SSMH 12AU7 version about 2 years ago and have been using it happily until recently I noticed that the left channel was really quiet compared to the right channel. So I cracked it open and found a bloated capacitor, C5 (63v 470uF) to be specific. I am wondering if this is just bad luck with these nichicon caps I found on ebay or if I could possibly have caused it with heat or a short? Seems like if it was a short it would have happened right away.




Ebay caps sound sketchy. I would only buy caps from a distributor personally.

Even good cap brands can fail and this design has been safe and stable for many, is your enclosure not allowing heat to vent properly?


----------



## RanDiesel

vapman said:


> Ebay caps sound sketchy. I would only buy caps from a distributor personally.
> 
> Even good cap brands can fail and this design has been safe and stable for many, is your enclosure not allowing heat to vent properly?


 
  
 It was an ebay store front and not a random guy, and at the time Mouser didn't have the nichicon caps I wanted. The enclosure is the standard one in the BOM for the 12AU7 build. There are no air holes besides the ones that the mosfets poke thru to the heat sinks. I suppose I could add air holes but I am starting to think I just got a bad cap. Here is a pic:


----------



## vapman

Duds show up even in good brands once in a while... weird that they were on ebay and not on site. I would replace it and should be ok after that...


----------



## RanDiesel

Actually, that specific voltage is difficult to find. Do you think a 50v version would work? Found this one:
 http://www.mouser.com/ProductDetail/Nichicon/UKZ1H471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oiS%252b9HFuzN1rI%3d


----------



## Danthrax

It's not recommended to run below 63v for safety reasons and I they do not make a KZ series capacitor with 470uF above 50v 330uF is the max for 100v I ended up getting one of these: http://www.mouser.com/ProductDetail/Nichicon/UFG1J471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oi7zPc9z1C2rY%3d for the 470uF I needed. EDIT: ignore that the 12au7 build doesn't appear to use a 48v power supply like the 19j6 build so I would think 50v is safe as they recommend a minimum of 16v, leading me to think a 25v would also work but I'm not sure what benefit that would give you. If that was a 470uF 100v KZ capacitor that you already had in there it could very well be likely that it was indeed fake (unless this was a cap that previously existed and has since been discontinued) and in that case I would recommend replacing any that you had in use...


----------



## RanDiesel

danthrax said:


> It's not recommended to run below 63v for safety reasons and I they do not make a KZ series capacitor with 470uF above 50v 330uF is the max for 100v I ended up getting one of these: http://www.mouser.com/ProductDetail/Nichicon/UFG1J471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oi7zPc9z1C2rY%3d for the 470uF I needed. EDIT: ignore that the 12au7 build doesn't appear to use a 48v power supply like the 19j6 build so I would think 50v is safe as they recommend a minimum of 16v, leading me to think a 25v would also work but I'm not sure what benefit that would give you. If that was a 470uF 100v KZ capacitor that you already had in there it could very well be likely that it was indeed fake (unless this was a cap that previously existed and has since been discontinued) and in that case I would recommend replacing any that you had in use...


 
  
 So the capacitor I was using in there was a FG series one just like the one you have in your striked out post.
  
 I will just order the same one again this time from Mouser, since I really don't want to completely dismantle my amp to replace both caps to the 50v versions. As you can see in the picture I have each channel on its own perf board so I can just yank one and fix it. Thanks for all the help.


----------



## tomb

randiesel said:


> danthrax said:
> 
> 
> > It's not recommended to run below 63v for safety reasons and I they do not make a KZ series capacitor with 470uF above 50v 330uF is the max for 100v I ended up getting one of these: http://www.mouser.com/ProductDetail/Nichicon/UFG1J471MHM/?qs=sGAEpiMZZMtZ1n0r9vR22e0BBN1kF1oi7zPc9z1C2rY%3d for the 470uF I needed. EDIT: ignore that the 12au7 build doesn't appear to use a 48v power supply like the 19j6 build so I would think 50v is safe as they recommend a minimum of 16v, leading me to think a 25v would also work but I'm not sure what benefit that would give you. If that was a 470uF 100v KZ capacitor that you already had in there it could very well be likely that it was indeed fake (unless this was a cap that previously existed and has since been discontinued) and in that case I would recommend replacing any that you had in use...
> ...


 
  
 Those are not FG caps in that photo.  FG's are exactly opposite of that color scheme - they are gold with a black stripe (as in Nichicon Muse *Fine* *Gold*).
  
 Pretty much all the voltage will run across those caps if a short occurs - that's 48VDC using the Cisco power supply.  However, no one would spec 50V caps in that scenario.  2V is just too small a safety factor.  It's why we went with 63V.  Electrolytics are made in definite voltage rating increments - 16V, 25V, 35V, 50V, 63V, etc.  I can't comment if you are using a different power supply, but use of a 12AU7 tube wouldn't change anything in that regard if the same power supply were used.
  
 Also, the 16V rating you refer to is for the cathode bias capacitors.  There is very little voltage across those capacitors.  We need to be careful about which capacitor is which, here.


----------



## RanDiesel

tomb said:


> Those are not FG caps in that photo.  FG's are exactly opposite of that color scheme - they are gold with a black stripe (as in Nichicon Muse *Fine* *Gold*).
> 
> Pretty much all the voltage will run across those caps if a short occurs - that's 48VDC using the Cisco power supply.  However, no one would spec 50V caps in that scenario.  2V is just too small a safety factor.  It's why we went with 63V.  Electrolytics are made in definite voltage rating increments - 16V, 25V, 35V, 50V, 63V, etc.  I can't comment if you are using a different power supply, but use of a 12AU7 tube wouldn't change anything in that regard if the same power supply were used.
> 
> Also, the 16V rating you refer to is for the cathode bias capacitors.  There is very little voltage across those capacitors.  We need to be careful about which capacitor is which, here.


 

 Ah, yes, I see that now, thank you! Luckily I hadn't clicked the checkout button yet. As I read the descriptions on these different capacitor series, I wonder if the difference between the KW series and FG series would be noticeable. The description certainly makes it seem like I would get "a rich sound in the bass register", according to Nichicon. I realize that any SQ questions are purely subjective, but I figured I would ask anyways since these capacitors are very close to the output


----------



## tomb

KW's are power caps, only. If these are at the output, you'll definitely do better with the FG's.


----------



## Danthrax

tomb said:


> Those are not FG caps in that photo.  FG's are exactly opposite of that color scheme - they are gold with a black stripe (as in Nichicon Muse *Fine* *Gold*).
> 
> Pretty much all the voltage will run across those caps if a short occurs - that's 48VDC using the Cisco power supply.  However, no one would spec 50V caps in that scenario.  2V is just too small a safety factor.  It's why we went with 63V.  Electrolytics are made in definite voltage rating increments - 16V, 25V, 35V, 50V, 63V, etc.  I can't comment if you are using a different power supply, but use of a 12AU7 tube wouldn't change anything in that regard if the same power supply were used.
> 
> Also, the 16V rating you refer to is for the cathode bias capacitors.  There is very little voltage across those capacitors.  We need to be careful about which capacitor is which, here.


 
 Oh yeah you're right, apparently whatever design I was looking at was incorrect. I wonder if his use of the 50v kz cap lead to it's premature death. I would definitely go with the FG cap that I crossed out instead of the KZ. tomb what would the effect of running 2 lower uF KZ caps in parallel have on the signal quality? I know that in theory it would be equivalent capacity but in practice I'm guessing there is a reason not to do that.


----------



## tomb

Well, paralleling electrolytic capacitors in a power supply is done all the time. In the signal path, however, electrolytics always sound worse than the alternatives (even compared to output transformers). That includes "boutique, audio-quality" electrolytics as well. So, if a 2nd cap is used in the signal path, it's almost alwayssome sort of film bypass, which can take over passing most frequencies and relegate the electrolytic to the lower frequencies. Whether it really happens that way or not is a subject of debate. It's not something that can be objectively tested with current technology/understanding. Some combinations work well, others do not.


----------



## Nathan P

Another Fred Starving Student joins the fray! I used Wima Polypropylene film caps, but a smaller size than what comes in the Beezar kit since the Fred PC boards are a bit different. In hindsight, I could have easily bent the leads and fit the larger caps for 3a and 5a. Ah well, I have another whole board to build with different components to see what differences I can hear.  
  



  
 Initially had one of my caps polarity messed up but switched that around and it's working great. Aside from the fact that I wired my L/R backwards on the input side.
  
 I'll fix that and I think I may swap out the 50k resistor prior to the pot to a 100k... I'm getting some channel imbalance and methinks using more of the volume will ameliorate that somewhat. Then it's time to get my case finished. 
  
 So far I'm not super super loving the sound of the GE tubes I grabbed. It's sounding just a bit thin in instrumentals. Vocals are cutting through like crazy though. Even without a case background noise is negligible so I have high hopes for a practically zero noise floor once buttoned up.
  
 Question-I picked the Nichicon output caps based off of the BOM here:http://www.diyforums.org/SSMH/SSMHbom.php They appear to be the same used in the Beezar kit from photos. Would replacing these with the FG series net any real improvement? I'm also curious why C7/8 is recommended to be a signal quality cap. I chose a basic Panasonic since it's an optional cathode bypass. Is something special going on here that I'm missing?
  
 For anyone wanting to use a parts list for this, it's here: https://www.mouser.com/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=ED556D7D-F5AA-4079-B0F2-385EB79A7395 I used all vishay metal film resistors as well. Note-I made at least two orders from Mouser. I'm not sure if I added everything from that so double check if you use it. Everything is labelled so that if you get one of Fred's boards you can drop in where the packages tell you to.
  
 -Nathan


----------



## tomb

Signal goes through the cathode bypass, that's why signal-quality caps (Muse ES) are used.


----------



## Nathan P

tomb said:


> Signal goes through the cathode bypass, that's why signal-quality caps (Muse ES) are used.


 
  
 Gotcha. Any comments on the C3/C5 Nichicon cap choice? And do you have any of those muse caps in 220 uF in stock?
  
 Also, for the Wima capacitors, there is no polarity correct?
  
 Thanks!
 Nathan


----------



## Fishline

fishline said:


> In case anyone find this helpful, here's my project on mouser (grand total of $63):
> *http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=0b0ae93f48*
> ​(Can mouser projects be shared like this?)
> 
> ...


 
 Here's the one I just built using the smaller Hammond case.  Drilling the tube openings through the heatsink and have them lined up with those on the case was the biggest challenge (without proper tools-- with a drill press I'd imagine it would be _much_ easier).  The small size of the case also makes the p2p wiring more challenging, but manageable. This is using the ALPS RK097 pot with the integrated switch, so there's not a separate power switch.


----------



## Nathan P

Very nice!


----------



## FallenAngel

fishline said:


> Here's the one I just built using the smaller Hammond case.  Drilling the tube openings through the heatsink and have them lined up with those on the case was the biggest challenge (without proper tools-- with a drill press I'd imagine it would be _much_ easier).  The small size of the case also makes the p2p wiring more challenging, but manageable. This is using the ALPS RK097 pot with the integrated switch, so there's not a separate power switch.


 
  
 That's very nicely done. I really like the tube sockets placed through the heat sink. Very cool.


----------



## Nathan P

So I have a couple of questions.
  
 Firstly, what are the comparative advantages/disadvantages to the C7/8 bypass caps? I removed the cheap panasonics I had in there and honestly I think it sounds better. Would it be even better with some nice Muse ES caps in there? I do not need the extra gain by any means. I've already switched R16 and R17 out for 100kOhm resistors and at least now I can use the first 1/3 of the volume pot. Channel balance seems much improved but I still kind of thing there's a bit of imbalance. Probably the 20% tolerance pot I'm using or a combo of it and tube mismatch. I'm using GE 5963s I got unmatched from Ebay. I ordered a set of Sylvania 5963's that are matched to 10% to play with.
  
 Regarding the volume pot, at what point should I consider using a lower impedance pot to sway the volume adjustment? Right now I've got 100k resistors and a 50k pot. Would 50k resistors and a 10k or 25k pot be a better combo as far as input impedance goes? How much does the input impedance matter? Even uncased the noise floor seems reasonable as long as I don't have something electronic sitting right next to it.
  
 Thanks!
 Nathan


----------



## Fishline

fallenangel Thanks! that's not original though. The idea was from post #1840 of this thread. There are similar build elsewhere as well. The tube sockets were mounted from below to the case. I had to use 1/2" #4 screws to mount the sockets.


----------



## tomb

nathan p said:


> So I have a couple of questions.
> 
> Firstly, what are the comparative advantages/disadvantages to the C7/8 bypass caps? I removed the cheap panasonics I had in there and honestly I think it sounds better. Would it be even better with some nice Muse ES caps in there? I do not need the extra gain by any means. I've already switched R16 and R17 out for 100kOhm resistors and at least now I can use the first 1/3 of the volume pot. Channel balance seems much improved but I still kind of thing there's a bit of imbalance. Probably the 20% tolerance pot I'm using or a combo of it and tube mismatch. I'm using GE 5963s I got unmatched from Ebay. I ordered a set of Sylvania 5963's that are matched to 10% to play with.
> 
> ...


 
  
 Yes, as stated in a previous post - the signal definitely goes through the cathode bypass caps.  So, "audio-quality" electrolytics are important, here.  Since the cathode bypass caps are optional in either case, I'm not surprised that you note the sound is better without "non-audio-quality" caps being used.
  
 Yes, Muse ES caps will probably sound the best as cathode bypass.  I can't explain it, but if you use cathode bypass caps, it seems more often than not, bass frequencies become most critical.  For example, if the caps are not sized large enough, the use of a cathode bypass cap can actually decrease the bass.  For this reason, many "old-timer" tube designers go way overboard and spec something much, much larger than what we've suggested for C7/C8.  That usually happens because it's not a straightforward calculation to determine, so they go way overboard to ensure that bass frequencies are not lost ... just in case.  One very well known current amplifier designer has the exact philosophy I just described.
  
 However, Dsavitsk made the calculation - based on real-world measurements - that 220uf was sufficient.  We have supplied these caps - Muse ES - with every kit that Beezar has sold or built and there has never been a complaint about lack of bass. 
	

	
	
		
		

		
			




  
 About the volume pot - This may seem strange and I can't go into the theoretical details, but changing the impedance of the volume pot is not going to have any effect on the overall volume adjustment, except for how it matches up with the input resistors.


----------



## Nathan P

Thanks for the info! I would have bought your kit but I'm on a shoestring budget here. I'm kind of sad that I didn't understand the importance of that cap beforehand. I'll find an excuse to make a mouser order and throw them in. 

In the meantime I'm enjoying the heck out of this thing and need to figure out a case for it. I have some nice tigre caspi and canary wood boards i could use, or, I have access to a 3D printer... Decisions decisions.


----------



## Nathan P

This is seriously a sickness. I needed to order a couple of things from Mouser so just for fun I ordered some WIMA MKP10 caps for the output bypass (To compare to the MKP2's I have in there now) and some Vishay-Roderstein MKT's to compare for fun as well. I have another board so I figure why not try some stuff out before I make another one. I can combine what I learn into one ultimate version. 
  
 Question-what do C3 and C4 do and are they as important when it comes to sound as the output bypassing caps?
  
 Thanks!
 Nathan


----------



## tomb

nathan p said:


> This is seriously a sickness. I needed to order a couple of things from Mouser so just for fun I ordered some WIMA MKP10 caps for the output bypass (To compare to the MKP2's I have in there now) and some Vishay-Roderstein MKT's to compare for fun as well. I have another board so I figure why not try some stuff out before I make another one. I can combine what I learn into one ultimate version.
> 
> Question-what do C3 and C4 do and are they as important when it comes to sound as the output bypassing caps?
> 
> ...


 

 Do you really mean C2 and C4 or C3 and C5?
  
 C2 and C4 capacitively couple the tube output to the MOSFET.  Every bit of the signal passes through these caps.  So yes, audio quality is important.  Luckily, they don't have to be very big to pass all the bass frequencies needed (that RC circuit stuff again).  So, a good film cap such as the Wima MKP10 will do nicely.  We upsized those two caps in the Beezar SSMH kit from Pete's original 0.1uf to 0.22uf.  Again, this is in order to eke out every bass frequency that we can.  Strictly speaking, they're probably more important than the bypasses on the output.


----------



## Nathan P

tomb said:


> Do you really mean C2 and C4 or C3 and C5?
> 
> C2 and C4 capacitively couple the tube output to the MOSFET.  Every bit of the signal passes through these caps.  So yes, audio quality is important.  Luckily, they don't have to be very big to pass all the bass frequencies needed (that RC circuit stuff again).  So, a good film cap such as the Wima MKP10 will do nicely.  We upsized those two caps in the Beezar SSMH kit from Pete's original 0.1uf to 0.22uf.  Again, this is in order to eke out every bass frequency that we can.  Strictly speaking, they're probably more important than the bypasses on the output.


 
  
  
 Sorry, meant C2 and C4. Good to know. I've got MKP2's on there now. I'm not super well versed in the differences between the different lines of Wima's caps but it seemed to have similar specs and I thought I needed something a bit more compact than the 10's for Fred's board layout. Looking at the board in the flesh it'd be pretty easy to bend leads to get things to fit if necessary.


----------



## Nathan P

Just as an FYI, I purchased some Beckman branded 5963's made by Sylvania and they sound killer in this amp.


----------



## GingerBeard

OK - So finally finished my second build and I am much happier with it than my first.  I gave my first to a very good friend of mine and he is enjoying it to the fullest.
  
 My second build is a refined version of my first and is made entirely on a small stripboard.
  
 Pic of the stripboard design...
  
 http://i.imgur.com/4DXSgQe.png
  
 PM me if you want the DIYLC file.
  
 Nearly finished board:
 http://i.imgur.com/gwsAIU8.jpg
 http://i.imgur.com/hdcHv2F.jpg
  
 I added the contact plugs so I could completely remove the board for maintenance.
  
 Here is the completed board mounted to the enclosure:
 http://i.imgur.com/x93k7ay.jpg
 http://i.imgur.com/j7Qv8z6.jpg
 http://i.imgur.com/1cMam1C.jpg
  
 And the completed amp
 http://i.imgur.com/jr8i2Ym.jpg
 http://i.imgur.com/Reec3zi.jpg
  
 I added both an RCA as well as a 1/4" input
 http://i.imgur.com/d9OsGCy.jpg
  
 I tried to do the Constant Current Source mod but was unable to get it to work - I did, however, add 2 100KΩ trimpots to input for balance though I only had to make very minuscule adjustments.
  
 It sounds great! Better than the Bravo Ocean I have.


----------



## 39points

Looks nice, I might even build my own amp if i have enough free time


----------



## fuens

Here another amp 
 Best regards mates!
  
 Toni


----------



## vapman

fuens said:


> Here another amp
> Best regards mates!
> 
> Toni


 
 All those jacks and the power switch/AC plug are incredible. What are those? I've never seen them.


----------



## fuens

vapman said:


> All those jacks and the power switch/AC plug are incredible. What are those? I've never seen them.


 
 Hello Vapman.
 The AC switch and socket is : Panel Mount Fuse Holder IEC320 C14 Inlet Red Lamp SPST
 The audio sockets are: Neutrik NJ3FP6C-BAG 1/4" 6.35mm Jack Chassis Panel Mount, Neutrik NF2D-B-9 Phono RCA Chassis/Panel Female Socket RD and Neutrik NF2D-B-9 Phono RCA Chassis/Panel Female Socket WH.
 Have a nice project!
  
 Cheers mate


----------



## GingerBeard

the_equalizer said:


> Ok, so here are a couple pictures from my amp with the CCS mod. Since I built it just as a test it's not very neat and I haven't removed the unused parts from the regular build (cathode bias resistor and bypass electrolytic capacitor). Now that it's working I'll split the CCS board in two and fix each little module between the tube socket and the terminal strip. The location will also help with lead length and I could also use a couple connectors for the wiring so the modules are easy to replace or service.
> 
> 
> 
> ...


 
 the_equalizer - 

 Thanks for all your input on this - without you I wouldn't have been able to get as far as I have with this build.
  
 I'm trying to wrap my head around this - Can you take a look at this rough schematic I did and let me know if that is right?
 http://i.imgur.com/JMt2pPk.png
  
 I take it the pot replaces R5?  (I the wrong label in the pic)
 Thanks, Man...
  
*EDIT*
 Answered my own question.  That seemed to work.  I'm on my third build now - for funsies - and integrated the CSS into it. Now I'm working on plate voltages...


----------



## snafu1

Sorry, a noob question.
 I just discovered the Starving Student Amp. While I would like to construct it based on the information on the original post, I have a feeling there are now numerous changes. The almost 500 posts on this thread is pretty intimidating. 
 I suspect there's a better version somewhere here.... Can anyone point me to a post(s) that might help me out here?
  
 Thanks.


----------



## Nathan P

fuens said:


> Here another amp
> Best regards mates!
> 
> Toni


 
  
  
 Beautiful! Details?


----------



## Nathan P

snafu1 said:


> Sorry, a noob question.
> I just discovered the Starving Student Amp. While I would like to construct it based on the information on the original post, I have a feeling there are now numerous changes. The almost 500 posts on this thread is pretty intimidating.
> I suspect there's a better version somewhere here.... Can anyone point me to a post(s) that might help me out here?
> 
> Thanks.


 
  
 Here's a summary I wrote up on another forum:
  
  Quote:


> You can get the PCBs from here:
> 
> http://www.head-fi.org/t/664191/starving-student-pcbs
> 
> ...


----------



## snafu1

Excellent! Thank you.


----------



## the_equalizer

gingerbeard said:


> the_equalizer -
> 
> Thanks for all your input on this - without you I wouldn't have been able to get as far as I have with this build.
> 
> ...


 

 My apologies GingerBeard. "Real" life took over since late 2014 and I don't come around here too often know. I hope you're enjoying your amp. I'd very much like to know what do you think about the amp with the CSS plate loads and which transistors you chose to implement them.
  
 Cheers!


----------



## GideonW

fuens said:


> Here another amp
> Best regards mates!
> 
> Toni


 
 I assume that you used the TL783? what kind of transformer did you use?
  
 I'm looking into building one with a transformer myself because I don't trust those 48 volt powersupplies off ebay


----------



## fuens

gideonw said:


> I assume that you used the TL783? what kind of transformer did you use?
> 
> I'm looking into building one with a transformer myself because I don't trust those 48 volt powersupplies off ebay


 
 Hello mate.
 You are right, I'm using a tl783 voltage regulator (see this item http://www.ebay.com/itm/High-Voltage-Adjustable-Regulator-Module-Based-TL783-/130669696724?hash=item1e6c8556d4 )
 About the transformer I'm using RS part no. 223-8049 (it's too big but it's what I found)
 I will use a little one in my next project RS 223-7995  223-7939  223-7850
 I recommend to you use an external and bigger bridge diodes, because when capacitors charge those burn the little bridge diodes. And replace the heatsink for one more bigger.
 Also I have a psu (still need to try) RS 466-6890
 Have a nice project.
 Toni


----------



## GideonW

So you are feeding the TL731 with 70 volts, wouldn't things cool down quite a lot if you tried to get closer to your 48 volt output voltage? now you are turning 22 volts @ whatever current you are using into heat. A transformer with 2*18 or 2*20 volt would seem more sensible to me if you can find it, but correct me if I'm wrong.
  
 anyhow, thanks for the info I think that I am going to try to replicate your build albeit with a slightly lower voltage transformer  
  
  
 EDIT:
  
 i think that I found a nice transformer:
 http://www.tme.eu/nl/details/tst50w_2x19v/toroidale-transformatoren/indel/tst50010/
  
 50VA 2*19 volt
  
 gives you 53.6 volt after rectification (minus some diode losses) and you only have a 5.6 volt difference between input and output voltage which limits the heat a lot


----------



## fuens

gideonw said:


> So you are feeding the TL731 with 70 volts, wouldn't things cool down quite a lot if you tried to get closer to your 48 volt output voltage? now you are turning 22 volts @ whatever current you are using into heat. A transformer with 2*18 or 2*20 volt would seem more sensible to me if you can find it, but correct me if I'm wrong.
> 
> anyhow, thanks for the info I think that I am going to try to replicate your build albeit with a slightly lower voltage transformer
> 
> ...


 
 Hello again 
 I tried with an 2x18v 80va, but the maximum dc voltage was around 40v. I don't know why (the theory and the practical was not the same)
 Waiting news about your lineal psu.
 Best regards
 Toni


----------



## GideonW

I'll have a try after I finish my LM3886 amplifier.
  
 the well known endless list of projects needs to be shortened first


----------



## everkeen

Hey all, I've built this amp using Fred's PCB. It's working except for something is wrong with the left and right channels. Right channel is okay and is outputting just that channel.  The left however, while louder when playing left side sound, is also playing the right side sound. I have gone over everything so many times, everything seems to be in place. Any ideas what would cause this issue?


----------



## GingerBeard

Check your Heater Voltage (Pin 4) and your Plate Voltage (Pin 6) on both tubes.  What are they for each tube?


----------



## moosefet

I just signed up to post my build but I am not allowed to post pictures yet


----------



## moosefet

A friend of mine who had also built one of these had a heap of 12SR7s that he decided to ship all the way from NY (I live in Australia) to me for my birthday.
  

  
 So far I had only built guitar amplifiers and guitar pedals so this was my first hi-fi project. So easy though!
  
 First step was to find a bigass heatsink, I found some cpu for $5 with its heatsink and fan still attached from a second hand shop and grinded away all the bits I didn't need.
  

  
  
 I do a lot of acid etching with my pedals and amps so decided to do a design for the top of this
  

  

  
  

  
  
 heres a little video of some of the etching in progress: https://www.instagram.com/p/BNniDEPjhxp/
  
 I forgot to take a photo of it before I hit it with the colour fill
  

  
  
 came out great after wet sanding, you never really know how it will turn out until you get to this step. This was also my first negative coloured etch.
  

  
  

  
  

  
  
 didn't dig the silver knob much
  

  
  

  
  
 I usually like to be a bit neater than this
  

  
  
 First fire up and test was a success B)
  

  
  
 then I just added a mammoth 16mm pwr led
  

  
  

  
  
 Hope some of you dig it. It sounds brilliant, great job to Peter Millet for the design.


----------



## whm3223

nathan p said:


> Here's a summary I wrote up on another forum:


 
 Sorry for more noob idiocy, but is that parts list in the cart from Mouser complete aside from the tubes, tube mounts, PSU, and a box?


----------



## Nathan P

I believe it should be, unless someone messed with the BOM (I've had trouble sharing the wrong link before and had people change my bom thinking they're making their own). If there's something I forgot in there I apologize.
  
 Moosefet-that thing looks baddical.


----------



## Isophon

Hi,
  
 I have a quick question regarding the 17EW8 version of this amp, I believe 'The equaizer' had discovered this tube as a replacement but back in 2010 couldn't find the spec sheet with the load lines.
  
 Tried reading the 400+ pages but this is very confusing.  The actual 17EW8 load line are now available on-line so I wonder if a schematic showing the optimal value has been created.  Would someone with good tube knowledge be willing to find a nice linear bias region with not such a high gain as 50 ? Even a text with the right value found woud be really awesome.
  
 Also, has someone come up with a good idea to reduce the very high gain of this tube amplifier ?  The 17EW8 has a mu of 50.  My other headphone amps have a overall gain via global feedback of 5.
  
 Data sheet for 17EW8 including load line can be found here :  http://tdsl.duncanamps.com/show.php?des=17EW8
  
 The sound is really good but the excessif gain is ruining the whole experience.  My pot has 20 clicks and past the 4th click it's already too loud...
 For fun I have included a pic of the HA.
  
 Thanks for your help.
 Eric


----------



## tomb

isophon said:


> Hi,
> 
> I have a quick question regarding the 17EW8 version of this amp, I believe 'The equaizer' had discovered this tube as a replacement but back in 2010 couldn't find the spec sheet with the load lines.
> 
> ...


 
  
 The 19J6 has a lot of gain, too.
  
 We took to a practice of implementing input resistors in the SSMH design.  This doesn't necessarily affect gain, per se, but it "pushes" the comfortable volume level out to the midrange of the volume pot travel, lessening the effects of poor channel matching, etc.
  
 Most SSMH's used a 50K pot.  So, some multiples of 50K worked well - 50K, 100K, 150K.  These can be standard RN55 resistors, one each in series with the signal input for each channel.  If memory serves, I think most people ended up using a pair of 100K resistors, but try a few values to see what works for you.


----------



## Sodacose

isophon said:


> Tried reading the 400+ pages but this is very confusing.  The actual 17EW8 load line are now available on-line so I wonder if a schematic showing the optimal value has been created.  Would someone with good tube knowledge be willing to find a nice linear bias region with not such a high gain as 50 ? Even a text with the right value found woud be really awesome.
> 
> Data sheet for 17EW8 including load line can be found here :  http://tdsl.duncanamps.com/show.php?des=17EW8


 
  
 Nice build, Eric!
  
 Unfortunately the datasheets don't seem to have any plate curves that we might use to easily find a good operating point.  It looks like the plate resistance is around 11k though if judging by the amplification factor and transconductance (Mu = Rp * Gm).  That makes the 33k load resistor on the high side if the two halves are wired in parallel but certainly in the ball park of what we usually want (typically 2-3x Rp, though Rp is halved here because of the parallel tubes). You could try a 15k anode load resistor.  That might reduce gain a bit, but it's always hard to tell what kind of effects changes to the operating point have at such low supply voltages.
  
 Rather than adding large resistors on the input, which will create Johnson-Nyquist Thermal Noise, I wonder if anyone has tried experimenting with some negative feedback.  A voltage gain of 50x is a bit over 30db.  According to Peter Baxandall and John Linsley-Hood, negative feedback will increase higher order harmonic distortion up to about 15-20db of feedback, at which point all distortion harmonics begin decreasing linearly. See a good discussion by Nelson Pass here (around Figure 10). So if you can add 20db of feedback or so, you won't suffer the creation of new distortion and you'll end with gain a bit over 10db (which is probably plenty).
  
 The tube stage inverts the signal and the MOSFET follower does not. We have an inverted output which means we need a non-inverting input for it be negative feedback. The only place in such a simple circuit would be the grid of the input tube. With some quick back of the envelope calculations, it looks like a 2k resistor in series with the grid (which will also function as a grid stopper, just in case) and a 10k feedback resistor from the output (after the cap) to the junction of the grid and 2k grid stopper would get you in the ball park.  
  
Here's some more useful reading on feedback. Someone may want to check my math!  Getting late here and I don't usually play with feedback much.


----------



## henkeman

I have a bunch of E180F 6688 6J9 tubes that Im wondering if they could work in a Starving Student build? They are pentodes but could be run in triode mode.


----------



## dsavitsk

henkeman said:


> Im wondering if they could work in a Starving Student build?




Could they? Sure. Should they? Probably not. You have neither sufficient voltage nor current in the SS application, the heater's need a lot of current and are too low voltage, the mu is too high, and they are tricky to work with.


----------



## Gofspar

Has anyone used a DACT Type 21 Stepped attenuator on their starving students?


----------



## tomb

Yes, but this is sort of the question that Dsavitsk answered - should they have? 

The Starving Student is special, but it's because of its niche. A CMoy is special, too, but probably most builders wouldn't put an Alps RK27 in one - not when they could easily build something better.


----------



## audiophilenoise

I've never built an Amp before, but I really fancy this so I'm going to give it a go. A quick question for the techier peeps out there. Earlier in the thread it was said the phono inputs could be replaced by a Jack if prefered. Would it then be possible to do away with it altogether and replace the jack/phono input with this or something like it

https://www.aliexpress.com/item/PCM2704-USB-DAC-to-S-PDIF-Sound-Card-Decoder-Board-3-5mm-Analog-Output-F-PC/32724517687.html?spm=2114.01010208.3.1.UxwpzV&ws_ab_test=searchweb0_0,searchweb201602_2_10065_10068_10000074_10000032_119_10000025_10000029_430_10000028_10060_10000067_10062_10056_10055_10000062_10054_10059_10099_10000022_10000012_10103_10000015_10102_10096_10000018_10000019_10000056_10000059_10052_10053_10107_10050_10106_10051_10000053_10000007_10000050_10084_10083_10000047_10080_10082_10081_10110_10111_10112_10113_10114_10115_10000041_10000044_10078_10079_10000038_429_10073_10000035_10121,searchweb201603_2,afswitch_2,single_sort_3_price_asc&btsid=6922bd54-b764-421e-92da-b398bd722123

by un-soldering the 3.5mm jack on the PCB and soldering wire straight of it and use that as my signal input? In essence I would thereby have created a USB valve headphone amp. Has this been done? I've tried searching but this thread is so big and so technical, its easy to get lost in.


----------



## Nathan P

audiophilenoise said:


> I've never built an Amp before, but I really fancy this so I'm going to give it a go. A quick question for the techier peeps out there. Earlier in the thread it was said the phono inputs could be replaced by a Jack if prefered. Would it then be possible to do away with it altogether and replace the jack/phono input with this or something like it
> 
> https://www.aliexpress.com/item/PCM2704-USB-DAC-to-S-PDIF-Sound-Card-Decoder-Board-3-5mm-Analog-Output-F-PC/32724517687.html?spm=2114.01010208.3.1.UxwpzV&ws_ab_test=searchweb0_0,searchweb201602_2_10065_10068_10000074_10000032_119_10000025_10000029_430_10000028_10060_10000067_10062_10056_10055_10000062_10054_10059_10099_10000022_10000012_10103_10000015_10102_10096_10000018_10000019_10000056_10000059_10052_10053_10107_10050_10106_10051_10000053_10000007_10000050_10084_10083_10000047_10080_10082_10081_10110_10111_10112_10113_10114_10115_10000041_10000044_10078_10079_10000038_429_10073_10000035_10121,searchweb201603_2,afswitch_2,single_sort_3_price_asc&btsid=6922bd54-b764-421e-92da-b398bd722123
> 
> by un-soldering the 3.5mm jack on the PCB and soldering wire straight of it and use that as my signal input? In essence I would thereby have created a USB valve headphone amp. Has this been done? I've tried searching but this thread is so big and so technical, its easy to get lost in.




Definitely! If you tie the ground of the USB circuit to that of the amp you should avoid the DAC frying issues as well, though I'm unsure if that could cause noise via ground loops. I'm sure there's a way to do it that wouldn't. I personally might look into something like the grubDAC/pupDAC or one of the hifimediy boards vs the AliExpress example as those are known quantities. It'd suck to get bad sound due to the DAC. An integrated odac would be awesome but spendy.

Another option would be to get the raspberry pi board from hifimediy and integrate that with a wireless connection. Add volumio: https://volumio.org and all you have to do is power it, plug in your headphones, and control it wirelessly from your phone.


----------



## rmhuntley

Following along here and decided to give this build a try. I'm going to swap out the RCA jacks for a single 3.5mm jack as it will be mostly sitting on my desk at work.  one thing I want to do but can't really find a good answer for. I'd like to install a single VU meter. I was looking at this meter. would I also need to incorporate this driver board?


----------



## Gofspar

By any chance do you guys think I could skate by with a 20Kohm stepped attenuator vs a 50k.
  
 It's a spare $100 attenuator I have laying around and was wondering if I get by with it.


----------



## Sodacose

As long as your source can drive a 5k impedance (worst case input impedance scenario with a 20k pot), the concern with using a different pot value is the input capacitance of the 19J6 and whether it will create high frequency roll-off.
  
 Let's do the math!
  
_Cmiller = Cg-k + Cg-p * (stage gain + 1)​_  
 From the 19J6 datasheet, Cg-k is 2.6pf and Cg-p is 1.5pf. Let's call stage gain Mu (though it's much lower in reality).  So Cmiller is about 60pf.  But we have two 19J6s in parallel for each channel so double this to 120pf.
  
_f = 1 / (2 * pi * Cmiller * Z)​_  
 We'll use the full 20k impedance from the pot as Z and remember to express Cmiller in farads, not micromicrofarads (uuf or pf). 
  
 1 / (2 * pi * 20,000 * 120 x 10^-12) = a little over 60khz
  
 The 50k pot PM spec'd gives a roll off at about 26khz using the same Cmiller as above. You'll actually have a little more high frequency bandwidth. I don't think we have to worry about oscillation here (60khz is still pretty low in the grand scheme of things), but you could add a 300-1k grid stopper if it worries you.


----------



## Gofspar

sodacose said:


> As long as your source can drive a 5k impedance (worst case input impedance scenario with a 20k pot), the concern with using a different pot value is the input capacitance of the 19J6 and whether it will create high frequency roll-off.
> 
> Let's do the math!
> 
> ...


 
 holy crap, thanks for the awesome reply and explanation. )


----------



## Sodacose

You are welcome!


----------



## Sodacose

Here's a Starving Student variation that I finished recently:
  

  
 It's a different tube, but same basic overall topology (tube voltage gain feeding MOSFET source follower) and same power supply. The tube is resistor loaded single-ended and it's direct coupled to the MOSFET, which is CCS loaded. All Class A, of course. The 7370 tubes are pretty cheap on the 'bay. The rest of the parts are very inexpensive and easy to source. If you are having trouble finding 19J6s or otherwise want to try something other than 12AU7, I highly recommend this amp.
  
 Note both the MOSFET and LM317 should be heatsinked. I used one heatsink at about 3" x 5" x 1" and bolted all the chips to it with insulating mounting kits (it only gets a little warm). The amp dissipates about 5W per channel in the TO-220 devices (48V @ 100mA per channel) so it doesn't need a ton of heatsink, but you're better off with too much than not enough.


----------



## 93EXCivic

I am ordering parts to do a Starving Student build using Fred_fred PCB. I want to use a Hammond 1455 enclosure. How tall does the enclosure need to be fit this setup?


----------



## rmhuntley

I really like the 1455nhd.  I"ve not seen board specs yet, but I hope one fits in that enclosure


----------



## rikk009

First timer here too. Decided to give it a go. Just one question for starting, should I go with the stock 19J6 tubes or a different pair for Hd650?
  
 Terribly sorry if it has been answered before, feeling lazy to search 450+ odd pages.


----------



## CarlosUnchained

I want to build my own tube amp and I'm looking for a design that can drive hungry LCD-X.

Can anybody help?


----------



## tomb

rikk009 said:


> First timer here too. Decided to give it a go. Just one question for starting, should I go with the stock 19J6 tubes or a different pair for Hd650?
> 
> Terribly sorry if it has been answered before, feeling lazy to search 450+ odd pages.


 It's really a personal decision.  If you want the classic Starving Student, then go with the 19J6.  Every part will be bog standard.  The 19J6 is a bit expensive now, but still not as much as an audiophile-version of the 12AU7.  Try to get a matched pair, if you can.


----------



## tomb (Jun 9, 2017)

CarlosUnchained said:


> I want to build my own tube amp and I'm looking for a design that can drive hungry LCD-X.
> 
> Can anybody help?


Just my personal opinion, but I would look for something more than an amp with $35 worth of parts (orig. Pete Millett SSMH) to power a $1500 headphone.  If you view it as the beginning of an ever-increasing path of capability, maybe it would be OK.

Keep in mind that the Starving Student in its basic form incorporates no headphone protection measures.  If you have a headphone plugged in when powering up the amp, the headphone can be subjected to some pretty severe DC spikes.  If you always remember to only plug headphones in after the amp is powering up, then things will be perfectly safe.  Just a point, however, to show that there's more to consider than just amplifier quality if pairing with a very expensive pair of headphones.

The unique power supply used to power a Starving Student also has been know to fry certain DACs.  Similar to a lack of headphone protections with an inexpensive DIY amp, inexpensive commercial and DIY DACs may have a complete lack of output protections.  Connecting one to a Starving Student can subject a DAC to a static charge sufficient to burn out the DAC chip.

Building something yourself also contains risks simply from the building process itself.  Those of us who have DIY-ed for a while know to use a pair of $2 headphones after building an amplifier.  You need to ensure that everything works and that sound tests are done with something that's not going to break the bank if it gets damaged from a mistake in building the amp.

IOW, DIY-ing an inexpensive amplifier is not necessarily a method to save money.  I don't mean to scare you too much, I would rather encourage the DIY community at every opportunity.  However, I get worried when I see questions such as these - someone buys a $1000+ pair of headphones and then maybe wants a shortcut to an amplifier.


----------



## Andy Mac

Built my amp, ran good on start up. 
The music sounds to my ears good but vocals are stronger in the left channel with the vocals in the right channel quieter and with a distinct echo....

Any ideas?

I've switched the tubes with out success as the problem stays the same.

Otherwise it's a very quiet amp with virtually no hum or background noise.

I notice it doesn't like the iPhone as the source, it hums a lot.....


----------



## Andy Mac

Stand down, I figured it out.
I had the earth and one of the input signal wires switched.
After testing and retesting everything it's now perfect.
No hiss, no hum, just clean tube music!
It drives my Grados beautifully as well as my Yamaha HP-1's

Thank you to all involved in this project. Simply awesome!

Now it finish the case and post a pic I guess...

One last thing, anyone know how hot these heatsinks get up to and will Perspex withstand the temperature?


----------



## Andy Mac (Jun 27, 2017)

Done. Sounds awesome. I'm more than happy for a first time build...


----------



## rikk009

Cool build and nice touch with glass top. Ever built a BH crack?


----------



## Andy Mac

No, this is my first ever build.
What's a BH crack???


----------



## Andy Mac

Stand down, Bottlehead Crack... 

Any good for a follow on build from the SSMH?

What's a speedball in relation to this amp?


----------



## Andy Mac

Don't worry, bottlehead crack.
Yeah I'm keen to build one but I can't afford a kit sent to me in NZ.... heck, I built a SSMH for a reason...

I'm keen to get my hands on a schematic and manual though but I can't find one anywhere!!


----------



## Andy Mac (Jun 30, 2017)

Double post sorry.


----------



## XZJ_Jono

Andy Mac said:


> Done. Sounds awesome. I'm more than happy for a first time build...



That looks amazing!!
I'm inspired to build my own as a starter amp for HD650s. NZ life is difficult though. 

How did you get all the components? Did you find a power supply with an NZ plug etc? 

I'd immensely appreciate your guidance


----------



## Andy Mac

Thanks.
I got most of the components from RS Components in NZ, the rest off Mouser NZ I believe.
The PCB was from Fred on this forum, but on a different thread.
If you cant get one, I have a spare that I can sent you as a last resort.
I made the case from custom wood that I skinned with Rimu Heart veneer which was then clear polyurethaned.
The top is a piece of polished copper with a sheet of clear perspex over that.
I was concerned about the heat from the mosfet heatsinks on the perspex but it seem fine.

The PSU I found on Trade Me, got it for $12.00 from memory.

Im using it with my Vintage Yamaha HP-1 and my modded Grado SR60's
Both sound amazing!!
Source is from a Fiio X3 2nd Gen.


----------



## XZJ_Jono

Andy Mac said:


> Thanks.
> I got most of the components from RS Components in NZ, the rest off Mouser NZ I believe.
> The PCB was from Fred on this forum, but on a different thread.
> If you cant get one, I have a spare that I can sent you as a last resort.



Thanks heaps man, I'll let you know if Fred is out of PCBs.  

I've got a few specifics to ask.. 

What tubes did you use? 
Which final design? 
What was your total build cost in the end?
How does your computer onboard dac sound through it? 

Looking forward to taking the plunge with this as my first DIY project ever.


----------



## Andy Mac

Sweet as Man, I'm in Tauranga so not that far away..
Tubes: 12AU7 Chinese ones. Not sure if "boutique" tubes sound any different but these sound impressive enough...
Final design ??? I just filled the PCB as required using the best components I could get / afford.
The trick for a quiet end result is a good solid ground plane with everything that can be grounded connected to it, and a good quality pot.
Total cost I wanted to keep under $100.00 NZ which I did... JUST!!
I dont drive it through an onboard DAC, The Fiio is a DAC as well as a music player so I use that....
.
I have previously built a small single 12AU7 tube amp that is driven from a 12v lead acid battery. Works well enough too.

Also did a opamp build in a "skeleton" configuration, this was to test my soldering skills.... tricky little build...

Ill throw up some pics.


----------



## XZJ_Jono

Andy Mac said:


> Sweet as Man, I'm in Tauranga so not that far away..
> 
> Final design ??? I just filled the PCB as required using the best components I could get / afford.
> 
> ...



Oh, I mean which schematic - this 2008 one? http://www.diyforums.org/SSMH/schematic/SSMH-origPCB.gif
That's amazing you managed to sneak under $100! The amp market in NZ is so awful, DIY seems far better value. Did you manage to source a local power supply too?
Ahh right. Just wondering because I don't have an external DAC and will be listening through my PC.

Do you think this is a viable 1st-time project?

Thanks heaps, looking forward to the pics


----------



## Andy Mac

Yeah that's the one I used. Went together nicely, no real issues or tricky bits.
For a first time project it's definitely a viable option.
For what you put into it you get a very decent sound!!
I got lucky and found the power supply on trade me so they are around...

Here are the other amps I made...


----------



## XZJ_Jono

Andy Mac said:


> Yeah that's the one I used. Went together nicely, no real issues or tricky bits.


Good to know! What kind of equipment is needed - basically just a soldering kit?
Also, re: needing a solid ground plane, isn't that what the PCB is for?



Andy Mac said:


> Here are the other amps I made...


Damn, nice work. Is that last one a solid-state rather than a tube?


----------



## Andy Mac

Have a look at Pete Millets original build thread, explains the ground plane. It's basically a decent sized piece of whatever material (copper, aluminium...) that everything grounds to including the pcb, volume pot body, input and power negative etc.... helps a lot with ground noise etc... 

A good soldering iron with a fine point is a must!

30-40w is sufficient enough power.

The last one is a solid state. Works pretty good too... I want to encase it in a block of solid clear resin.... one day....


----------



## Detectit

Is this project still alive? 

I am looking to build one. And I guess it's going to be the Minimax but most of the the links on the BOM on diyforum.org are dead linking to beezar.com. 

Also the latest updates on the sites are 7 years or more old. 

Has someone has the latest and updated BOM?


----------



## Andy Mac

Just use the latest build you can find. Differences are minimal and they all sound wonderful. 
I use mine every day.


----------



## Guerito

https://www.head-fi.org/f/threads/starving-student-pcbs.664191/

Fred_fred2004 can sell you a PCB for a very reasonable price, PM him if you want one. Mine arrived yesterday, I've ordered parts based on that thread above - resistors and caps from first post, other parts from the most recent BOM posted in the thread. Just waiting for the tubes and sockets to arrive to get started.


----------



## Detectit

Thanks... Been sourcing parts yesterday and looks pretty straight forward indeed. 

I have sent Fred a message and hope he can send one. Otherwise some fly wiring to do. PCB is more convenient. 

What brand 12au7 tubes do you guys mounted?


----------



## Guerito

In keeping with the ethos of this amp, I bought the cheapest ones I could find on eBay and picked up an old metal cigarette box for pennies at flea market.


----------



## Detectit

Ordered the PCB with Fred. 

And ihave ordered a pair of matched JJ 12au7. 
Seller says it's great for the money and as a starter. You can always change it to something else. 

Found a killer case for it. 

Can't wait to start.... Went from buying a secondhand Lyr to Diy... How strange things can went. 

The Minimax looks also great but also no pcb's available does anyone knows why?


----------



## tomb

Detectit said:


> The Minimax looks also great but also no pcb's available does anyone knows why?


Yes.  Sales no longer supported the costs of stocking up again for the casework and PCBs.  The Millett Hybrid MAX v1.2 PCB is still available, though.


----------



## Detectit

tomb said:


> Yes.  Sales no longer supported the costs of stocking up again for the casework and PCBs.  The Millett Hybrid MAX v1.2 PCB is still available, though.


So nobody is building anymore. Or has the market shrunk? 
Just wondering why...


----------



## tomb

Detectit said:


> So *nobody is building anymore*. Or has *the market shrunk*?
> Just wondering why...


You answered your own question ...

When the MiniMAX was first designed and sold, about the only way to get a headphone amplifier was by building one.  Now, it's a different story.


----------



## Schenkelini

I have a question. How do you mount the Ohmite heat sinks that I see in most of the completed amp photos to a chassis? The 2 pins at the bottom look like they are designed for soldering to a pc board. From some of the under side pictures it appears that the sinks are held down by screws. Do you remove the pins and replace them with screws? If so how do you remove the pins?


----------



## Andy Mac

Just pull them out with pliers or side cutters. Screws will go in their place easily enough...
They are supposed to be soldered to a PCB but are easily adaptable...


----------



## Sodacose

If you want to get fancy, the ohmite pins are mounted in a 2.3mm channel. You can easily thread this for a 3mm or 4-40 mounting bolt.


----------



## tomb

*Starving Student Millett Hybrid (PCB version) Kits Again?*

I happened upon some more 19J6 tubes recently and am thinking about offering SSMH complete kits again (PCB by Dsavitsk of ECP Audio).  As before, this would include the completely machined, black-anodized Hammond case, PCB, two tubes, all parts and hardware except for wiring, and the Cisco-compatible power supply.  Details for the original kits are in my sig.  Price would probably be around $165 plus ~$3-$4 for a power cord.  Since the power supply works for international voltages, there are a number of power cord options that would be available.

The last time I offered full kits was back in 2014, so I don't have a good feel for the demand of the Starving Student anymore, especially with all the nice/inexpensive Schiit available lately.  So, if you could reply or shoot me a PM, that might give me an idea if I should make the investment again. 

Please check out my signature for details below or the documentation website for the Starving Student Millett Hybrid (PCB version).  Nothing will have changed except that the knobs will be black instead of silver (Mouser doesn't seem to stock the silver ones anymore).
Thanks!


----------



## ThermalAlchemy

tomb said:


> *Starving Student Millett Hybrid (PCB version) Kits Again?*
> 
> I happened upon some more 19J6 tubes recently and am thinking about offering SSMH complete kits again (PCB by Dsavitsk of ECP Audio).  As before, this would include the completely machined, black-anodized Hammond case, PCB, two tubes, all parts and hardware except for wiring, and the Cisco-compatible power supply.  Details for the original kits are in my sig.  Price would probably be around $165 plus ~$3-$4 for a power cord.  Since the power supply works for international voltages, there are a number of power cord options that would be available.
> 
> ...


 Signed me up I'll order a kit .  I was nearly complete trying to duplicate your PCB making it myself on EasyEDA.com  The one problem I was having I was going to add a modification to use a Alps pot and because I'm a beginner and new at this it was a sticking point for me to complete my PCB. 
      Can you please consider a addition and redesign of possibly the Millard  hybrid max adding balanced outputs .  Or any other design like the torpedo in balanced or a modification to pre-existing amps for entry-level users like the DarkVoice 336 or the  La Figaro 339  in today's marketplace to be able to get one of these amps with balanced outputs included would just take the marketplace by storm at their price point to quality .  Thank you


----------



## skajohyros

Man, why didn't you post this a week ago? Just ordered most of the parts. Anyway, hope you will be around as I have no idea what I am doing.


----------



## Schenkelini

I am in the process of building a 12au7 amp point to point. I might have joined in other wise.


----------



## dhaninugraha

tomb said:


> *Starving Student Millett Hybrid (PCB version) Kits Again?*
> 
> I happened upon some more 19J6 tubes recently and am thinking about offering SSMH complete kits again (PCB by Dsavitsk of ECP Audio).  As before, this would include the completely machined, black-anodized Hammond case, PCB, two tubes, all parts and hardware except for wiring, and the Cisco-compatible power supply.  Details for the original kits are in my sig.  Price would probably be around $165 plus ~$3-$4 for a power cord.  Since the power supply works for international voltages, there are a number of power cord options that would be available.
> 
> ...



sign me up. I've been wanting to have an amp for work but never got around to building one, so I ordered the NS08E off of fleabay a week ago. but now that there's a chance of SSMH made available again, I'd wanna build one for work and relegate the NS08E to my home/bedside setup.

PS: I bought your HD25-1 last month. always wondering how it would sound off of a tube amp!


----------



## Guerito

If I didn’t have a half-finished one on one of Fred_fred’s boards I’d bite your hand off. Now, if you were to bring back the Millett Max...


----------



## skajohyros

Hi, need some help. All 3 pins on one MOSFET read 48v. Already burnt a tube.


----------



## Wiljen

bad mosfet with the gate already burnt up.   if you overload the mosfet it will burn through the shield on the gate and all sides will read 48V.    Replace it first before you put any more tubes in it.


----------



## Wiljen

On a side note, anybody else built a SSMH using a 12at7 for pushing planars or other impossible to drive cans?   I built one using a pair of RCA Blackplate 12at7s from 1963.   With 32ohm headphones like the B&W p5 I can only use the first 5% of the pot but with the big planar magnetic I can use  50%-60% before it is beyond listenable.    That little amp is easily the most potent I have for the Fostex.


----------



## skajohyros

Wiljen said:


> bad mosfet with the gate already burnt up.   if you overload the mosfet it will burn through the shield on the gate and all sides will read 48V.    Replace it first before you put any more tubes in it.


Thanks mate. Any idea how I burnt the MOSFET?


----------



## Wiljen (Dec 27, 2017)

Check all your wiring, and make sure you don't have something cross-wired.  You either have a wiring problem that is pushing too much current or voltage into the mosfet and burning it open so the voltage then flows freely on all legs, or you had a bad mosfet that was open to begin with.   The good news is mosfets are dirt cheap, the bad news is tubes are not and 48V on the wrong pin will turn a nice tube into an expensive flashbulb.   A wiring problem will probably be measurable even without a tube in place, so I would first put in a new mosfet and check the voltage on all legs.  If they measure as expected - Ground to source, nothing on gate and Load at drain, then put in another tube,  If you see 48V across all legs of the new mosfet, then you definitely have a wiring problem.


----------



## skajohyros

Bloody he'll. Can't get my hands on any irf510 here.. immediately.


----------



## Wiljen

skajohyros said:


> Bloody he'll. Can't get my hands on any irf510 here.. immediately.



https://www.mouser.com/productdetai...=sGAEpiMZZMshyDBzk1/Wi1F3z9PgzPBnjAas2zQPJco=
https://www.digikey.com/product-detail/en/vishay-siliconix/IRF510PBF/IRF510PBF-ND/811710


----------



## skajohyros

I'm in Greece. 20€ shipping.


----------



## skajohyros (Dec 31, 2017)

@Wiljen thanks for your help. Finally paid €10 shipping from Poland to Greece for 40 cent MOSFETs.
Not the prettiest amp on the block but it's working.


----------



## Wiljen

Sounds good is what counts, none of my DIY projects will win any beauty contests either.


----------



## skajohyros




----------



## Wiljen

The SSMH with a pair of tube savers makes a great starter for tube rollers.  I have no less than 12 different tubes that work and all bring their own differences to the sound.   When you add different brands into the equation, you could easily have 100 different tubes to choose from.


12au7
12au7a
ECC82
5963
CV491
5814
6189
6201
6211  <-- Favorite of mine  (Sylvania 6211 from 1966 production)  Higher mu than 12au7 with same specs - really drives a Fostex without being too much for B&W P5.
5965
6414  <-- Another low mu AT or high mu AU depending on how you look at it.  These have 10,000 hour rated heaters so should last very well.  (1/2 inch taller than standard if that matters to your enclosure)
12AT7

I avoided others that would probably work as well due to differing heater current requirements etc.   With a few resistor swaps you could open up another 10-15 varieties.


----------



## skajohyros

Wiljen said:


> The SSMH with a pair of tube savers makes a great starter for tube rollers.  I have no less than 12 different tubes that work and all bring their own differences to the sound.   When you add different brands into the equation, you could easily have 100 different tubes to choose from.
> 
> 
> 12au7
> ...



Very useful list. I will definitely look into some of the cheaper options just to keep the good times rolling.


----------



## Nathan P

Finally finished mine!

Took some troubleshooting with grounding and isolating signal connectors (notice the wooden spacer spliced into the back plate. That wasn't always there. ) to get the noise floor down, but it's dead silent now and sounds amazing with the GE 5963 tubes I picked up.


----------



## Nathan P

Can anyone comment on whether this design has the heater current capacity for 12BH7a tubes?


----------



## Wiljen

The short answer is technically yes but realistically with the power supply constraints and the fact that the mosfet is tied to the heater, it is a poor choice and will limit the lifespan of the device.  Also worth noting the 12BH7a tubes are high enough mu that anything below 600 Ohm will likely be so overdriven that it will not sound very good.   With you being as close as you are to me, I'll offer a couple of my better choices in low Mu 12at7 equivalents to try if you want to increase gain without changing heater specs.


----------



## caenlenfromOCN

Sorry to revive an old topic from the dead... just wanted to inform everyone a friend built this amp for me, here is a pic... I love it... sounds much much better than my Vali 2 amp did. I need to get feet for it and a volume knob, but I must stay overall it is a definite upgrade from the Vali 2. Thanks @Tjj226 Angel  for building it for me. He rushed it out to me since I am flying out soon for grad school, hence the lack of feet and volume knob, not a big deal, I put some temporary rubber feet on it for now. I am surprised no one is making a side business of building these.


----------



## Wiljen

I've been really pleased with mine.  I have an original that runs the 19j6 tubes and another running the 12au7.   Both are better than they should be for the $ for sure.


----------



## caenlenfromOCN

Wiljen said:


> I've been really pleased with mine.  I have an original that runs the 19j6 tubes and another running the 12au7.   Both are better than they should be for the $ for sure.




Yep, it is amazing no one has built these as a side operation, it beats everything on the market under $300 imo


----------



## Wiljen

I think Pete Millett may still have some rights regarding commercial use of the design.  I know some other common DIY amps have "no commercial use" or "no derivatives" clauses.


----------



## tomb

Some of you guys need to read more of this thread and even Pete's website, where the following is found near the top of the home page:

*PLEASE READ - Commercial usage of information on this site:*

I consider all the information that I post here to be in the public domain.  So, you can use it however you want, for commercial or non-commercial use.

That said, I would appreciate it if you at least let me know if you are going to use any of the circuits or especially PCB Gerber files to make commercial products, or to sell bare PCB's.

Also, Beezar Audio has sold a series of kits (the SSMH) on at least 2 or 3 occasions since 2009.


----------



## Trower (Jan 21, 2018)

Wiljen said:


> I've been really pleased with mine.  I have an original that runs the 19j6 tubes and another running the 12au7.   Both are better than they should be for the $ for sure.



How do you like the 12au7s compared to the 19j6 version? I have an amp that untill last month has been running since Pete had posted his design. I tried to get a pair of matched 19j6s, but the only matched set I found was from overseas and one came in pieces :/ So now I'm considering changing the circuit to accommodate the 12au7s, but really liked the 19j6 version.

If anyone has leads on matched 19j6s that don't cost a ton I'm one to that as well!

Thanks,
Nick


----------



## Wiljen

The 12a_7 version is definitely cheaper to feed at this point.  I have a few pairs of 19j6 left but like you mentioned, they have become unobtainable without spending ridiculous money.  For that reason, I am not letting go of the few I have as once gone, I'll have to convert that amp to 12a_7 too.   The variety of the 12au7 and 12at7 variants give you a lot of options from ridiculously cheap to ridiculously expensive.   I have found some really nice sounds at <$50 a pair.


----------



## Trower

Okay thanks for the info!

Any good suggestions for 12au7s you liked?


----------



## caenlenfromOCN

Trower said:


> Okay thanks for the info!
> 
> Any good suggestions for 12au7s you liked?



E182CC ( This is the tube I would upgrade to. This is a true special version. It is designed with much larger tube elements to reduce noise, microphones, and increase signal clarity. Mullard is the only one I know of that makes a E182CC).


----------



## Wiljen

There is no easy answer to this as it largely depends on what you are pairing with. 

WIth the Senn HD700s I really like the the GE 5 Star 5814.  The RCA Command Version of the same tube is also very good.
For the Fostex T50RP and mods it would be very hard to go wrong with the 6829.  it is a low Mu 12at7 variant that has a lot in common with the e128cc mentioned above but a lot cheaper. 

A word of warning for enclosed units the E182cc and 6829 are both about 1/2 an inch taller than the standard 12a_7 series tubes and may cause fit problems.


----------



## Nathan P

Aaaand complete with enormous volume knob. Switched to some JAN 6829 tubes on Wiljen's suggestion. Huge amount of gain from these, I can run my Fostex at 30-40% volume. Plus, they look awesome!

Cheers,
Nathan


----------



## JImmye00

Can anyone provide me with the schematics or drawing that DIYfoums.com uses for the hammond enclousre?


----------



## tomb

JImmye00 said:


> Can anyone provide me with the schematics or drawing that DIYfoums.com uses for the hammond enclousre?


I sent them to you ...


----------



## JImmye00

tomb said:


> I sent them to you ...


THANKS TOM


----------



## JImmye00

tomb said:


> I sent them to you ...



So i tried to get a quote on how much to do the machining for the case and Hammond, guess they only do it if you order 20 units. Now i am out of luck on the machining.  Can anyone recommend any vendors to have the case machined?

Thanks


----------



## Wiljen

If you own a drill press, it is something that can be done at home as really no complex machining is involved, just punching a couple holes for tubes and a couple smaller one for volume knob and connections.


----------



## drabina

Anybody made a Starving Student amp with a built-in source (i.e. Raspberry Pi + DAC running volumio)? Few years back, I have built SS amp but it is not being used much because I always forget to either charge my Sansa Clip ZIP or load new music on it. I would like to put Raspberry Pi Zero W with PhatDAC as a source for the amp. Then I can pull all my music from the NAS and control all via phone. I am just not sure what to use for the power supply as the Cisco brick is only 380mA or so. Can't really squeeze much more out of it to power the RPi.


----------



## Nathan P (May 3, 2018)

drabina said:


> Anybody made a Starving Student amp with a built-in source (i.e. Raspberry Pi + DAC running volumio)? Few years back, I have built SS amp but it is not being used much because I always forget to either charge my Sansa Clip ZIP or load new music on it. I would like to put Raspberry Pi Zero W with PhatDAC as a source for the amp. Then I can pull all my music from the NAS and control all via phone. I am just not sure what to use for the power supply as the Cisco brick is only 380mA or so. Can't really squeeze much more out of it to power the RPi.



I bet if you used a little switched mode step down converter you could use the Cisco to power both. Remember, the Cisco is running at ~48v (IIRC) * 380mA =  18.24W of power. With an efficient switched dc-dc converter the Rpi would take 5v * 250mA = 1.25W. Should easily be within the power budget once the tubes are warmed up at least. 

The power brick only cares how much wattage it sees, the current rating is at it's output voltage. Since the Rpi runs at a much lower voltage if you're smart about it it shouldn't be an issue.

If you tried to use a linear regulator to do the voltage drop, yeah you'd have a problem. But modern switched regs can be extremely efficient.


----------



## drabina

Nathan P said:


> I bet if you used a little switched mode step down converter you could use the Cisco to power both. Remember, the Cisco is running at ~48v (IIRC) * 380mA =  18.24W of power. With an efficient switched dc-dc converter the Rpi would take 5v * 250mA = 1.25W. Should easily be within the power budget once the tubes are warmed up at least.
> 
> The power brick only cares how much wattage it sees, the current rating is at it's output voltage. Since the Rpi runs at a much lower voltage if you're smart about it it shouldn't be an issue.
> 
> If you tried to use a linear regulator to do the voltage drop, yeah you'd have a problem. But modern switched regs can be extremely efficient.


Would something like that work?
https://www.ebay.com/itm/DC-DC-Buck...988244?hash=item2cd3717194:g:3vkAAOSwuxFYyQyb

I guess with the step down converter, I can move the two LEDs that light up the tubes from the 48V to 5V.


----------



## Nathan P

That looks reasonable. Buck converters are generally efficient, they're a type of switching power supply. I was looking into DC-DC switchmode regs on Digikey/mouser. You might find one that's monolithic (a single part) that's preset to 5v output.


----------



## viivo

I'm really interested in this and have been wanting to take on a DIY project. Would it pair well with low impedence and high sensitivity/high power handling headphones? Also, it seems some of the parts have increased in price over the years - a preliminary list I put together has the cost over $75 and that doesn't include buttons and connectors.


----------



## Wiljen

Your cost figures sound about right unless you are building an 19j6 variety and then a pair of tubes may cost you something ridiculous as they have become very scarce.  The 12Au7 variant is much more realistic these days as tubes are cheap and plentiful.   If memory serves, the original design with the 19J6 tubes had an output impedance of roughly 3 ohm so using the standard rule of thumb would be best suited for headphones above 24 Ohm.   So if by low impedance you mean 32 or 50 ohm designs, you should be fine,  if you mean 16 ohm it might be a bit on the low side for optimal performance.


----------



## drabina

Nathan P said:


> That looks reasonable. Buck converters are generally efficient, they're a type of switching power supply. I was looking into DC-DC switchmode regs on Digikey/mouser. You might find one that's monolithic (a single part) that's preset to 5v output.


Would that work as a single piece drop down converter?
https://www.mouser.com/ProductDetai...GsmoEFRKS8Koqt8Pjkl39FxTMu/O/e8N2JBpmakm9Lw==


----------



## Nathan P

That's exactly the type of thing I was thinking of.


----------



## tomb

JImmye00 said:


> So i tried to get a quote on how much to do the machining for the case and Hammond, guess they only do it if you order 20 units. Now i am out of luck on the machining.  Can anyone recommend any vendors to have the case machined?
> 
> Thanks



There will be another round of Starving Student kits available in about a month on beezar.com.  This includes the Dsavitsk-designed PCB and custom-machined Hammond case.  As before, they will be based on the original 19J6 tubes.  I have enough for about 40 kits.  Details on the SSMH kit and how to build it are in my signature below and on the SSMH website.


----------



## JImmye00

tomb said:


> There will be another round of Starving Student kits available in about a month on beezar.com.  This includes the Dsavitsk-designed PCB and custom-machined Hammond case.  As before, they will be based on the original 19J6 tubes.  I have enough for about 40 kits.  Details on the SSMH kit and how to build it are in my signature below and on the SSMH website.



Tom, will there be an option to buy only the case?


----------



## tomb

JImmye00 said:


> Tom, will there be an option to buy only the case?


Probably not initially, but it will depend on how things go.  Everything is predicated on the number of tubes.  I have 90 tested, but some will still end up bad in the long run or microphonic.  I will try to replace them for a customer if that happens.  So, if I end up with less tubes, then there will be some cases left over.


----------



## Wiljen

Will you have a kit of the necessary parts for those wanting to build the 12au7 variant to go with the package?  Not a ton of changes, but would be nice to see it all in one place rather than having to hunt them down.


----------



## tomb

Wiljen said:


> Will you have a kit of the necessary parts for those wanting to build the 12au7 variant to go with the package?  Not a ton of changes, but would be nice to see it all in one place rather than having to hunt them down.



The 19J6 is a 7-pin tube, whereas the 12AU7 is 9-pin.  Unfortunately, when considering tube sockets and PCB-based circuitry, that's about as big a change as it can get.  So no, there will be no provisions for 9-pin tubes.


----------



## WhiteSpyder (Jun 7, 2018)

Wiljen said:


> Will you have a kit of the necessary parts for those wanting to build the 12au7 variant to go with the package?  Not a ton of changes, but would be nice to see it all in one place rather than having to hunt them down.



I've actually been thinking about offering a pcb and/or parts kit for a 12au7 SSMH for well over a year now. Offering a full kit including the enclosure would get costly because of shipping and the initial cost for ready-made enclosures, but a parts kit with international shipping would definitely be possible if there's demand for it. Making a custom enclosure is part of the project for many anyway. I'd be able to include some new production tubes too. My pcb design includes a power input tweak to make the amp more compatible with different switch mode power supplies as well as built-in optional tube leds.

I know myself how great it is to build something from a good kit without having to worry about the pcb or getting all parts so I'll make it happen if there's enough interest in it!


----------



## tomb (Jul 25, 2018)

The original Starving Student Millett Hybrid kits are again available at Beezar Audio.  These kits are based on the Dsavitsk of ECP Audio's PCB design, all based - of course - on Pete Millett's original.  The kit includes a black-anodized Hammond case, custom machined by Hammond.  Tubes are the original 19J6 tubes.  Power supply is the original Cisco power supply.  All parts are included to make a fully functioning headphone amplifier - including knob, tube LEDs, even thermal grease for the heat sinks.  The only thing not included is wiring and solder.

There are 40 kits total, while they last.  The last time these kits were offered was in 2014.  It may be that long - or longer - before they're available again.


----------



## skajohyros

International shipping is a killer.


----------



## tomb

skajohyros said:


> International shipping is a killer.


I can't help that.  USPS is as cheap as it gets, but the package is more than 3 lbs.  That works out to only $37.25 for Canada, but Mexico is $47.50.  Those are the two cheapest, while most of the others are over $50.  I also offer UPS and FedEx, but both of their cheapest international services are close to $200 for most countries.

If you have a suggestion for another carrier, I'd be happy to look into it.


----------



## antdroid

tomb said:


> The original Starving Student Millett Hybrid kits are again available at Beezar Audio.  These kits are based on the Dsavitsk of ECP Audio's PCB design, all based - of course - on Pete Millett's original.  The kit includes a black-anodized Hammond case, custom machined by Hammond.  Tubes are the original 19J6 tubes.  Power supply is the original Cisco power supply.  All parts are included to make a fully functioning headphone amplifier - including knob, tube LEDs, even thermal grease for the heat sinks.  The only thing not included is wiring and solder.
> 
> There are 40 kits total, while they last.  The last time these kits were offered was in 2014.  It may be that long - or longer - before they're available again.



Just ordered one of these from you last night. I needed a new DIY project and this looks like something that satisfies my urge to DIY and a little amp to bring to the office at work.


----------



## Wiljen

antdroid said:


> Just ordered one of these from you last night. I needed a new DIY project and this looks like something that satisfies my urge to DIY and a little amp to bring to the office at work.



You should have a blast with the little Millett as there is a ton you can do with one if you choose to go the not-so-starving route.


----------



## antdroid (Aug 29, 2018)

I just finished the @tomb Beezar version of the SSMH. It was a fun little project that took me 2 nights to complete. Really appreciate Tom's great information and advice he gave me while I was waiting for the package to arrive. Now I need to go build a proper XLR to 1/4" adapter. I have 3 different adapters going on in the photo


----------



## ThanosD

Hello, I was thinking about building on of these for my self, the 12AU7 version, and I was wondering if I could use another power supply, such as a simple switching 48V 3A from ebay


----------



## skajohyros (Aug 31, 2018)

ThanosD said:


> Hello, I was thinking about building on of these for my self, the 12AU7 version, and I was wondering if I could use another power supply, such as a simple switching 48V 3A from ebay


Why don't you just use the recommended one?
https://m.ebay.com/itm/CISCO-PSA18U...m=262614838118&_trksid=p2059210.c100148.m2813


----------



## ThanosD (Aug 31, 2018)

skajohyros said:


> Why don't you just use the recommended one?
> https://m.ebay.com/itm/CISCO-PSA18U-480C-POWER-ADAPTER-48V-0-38A-34-1977-03/262614838118?_trkparms=ao=1&asc=20140127102845&meid=a6d5a0a963ed4b48a0dce131be17011c&pid=100148&&itm=262614838118&_trksid=p2059210.c100148.m2813


I don't mind buying it, I just thought to ask, as I think I have one laying around somewhere, and wanted to know if I could use it. The switching one is more expensive over the cisco anyways


----------



## Wiljen

The Cisco is a switch mode supply as well so as long as the specs are similar it should work. The only caveat is that the power supply is minimal and getting the tube heaters running can cause the power supply to reset as the current draw at startup can overload it.  This was more so the case with the 19j6 than with the 12AU7 but still worth considering as If I were going to substitute a power supply, it would be for one with a higher amperage rating and a heavier duty cycle.  Anything smaller (electrically speaking) is probably courting mishaps.


----------



## skajohyros

A bit ghetto but it works.


----------



## antdroid

skajohyros said:


> A bit ghetto but it works.



Nice computer, i mean, amp


----------



## tomb

antdroid said:


> I just finished the @tomb Beezar version of the SSMH. It was a fun little project that took me 2 nights to complete. Really appreciate Tom's great information and advice he gave me while I was waiting for the package to arrive. Now I need to go build a proper XLR to 1/4" adapter. I have 3 different adapters going on in the photo



Great job!


----------



## tomb

Anyone have any experiences with the Starving Student and the HD58X or the HD660, which I understand is similar (low impedance)?  Someone is asking in the SSMH build thread and I thought this might be a better place.


----------



## caenlenfromOCN

tomb said:


> Anyone have any experiences with the Starving Student and the HD58X or the HD660, which I understand is similar (low impedance)?  Someone is asking in the SSMH build thread and I thought this might be a better place.



I use my starving student with the HD58X, sounds fantastic.


----------



## Wiljen

I've used the SSMH with the HD700 as well and really like it depending on which tube you put in.  There are a couple industrial tubes with slightly lower gain than the standard 12AU7 that I find give me more usable range on the volume control when using the HD700s or other low impedance cans.


----------



## kickngas

Wiljen said:


> There are a couple industrial tubes with slightly lower gain than the standard 12AU7 that I find give me more usable range on the volume control when using the HD700s or other low impedance cans.


Care to share what tubes you have used?


----------



## Wiljen

RCA 5963 Black Plates are a favorite for me.  Slightly lower Mu 12au7 varient that takes a bit lower plate voltage which is perfect for the SSMH.


----------



## kickngas

Thanks, but what is "Mu"?  New to tubes vernacular.


----------



## Wiljen

Also IBM 6350s work well but you need to swap the grid and plate wires for each triode as the 6350 reverses those pins.   IF (and that is a big IF these days) you can find a good supply of 6350s  (most were either GE or Sylvania for IBM) it is worth doing the rewiring of the pins  as the low mu combined with very tight tolerances on these makes for very low microphonics and really good sound with lower impedance cans.


----------



## kickngas

I found "Mu", apparently it basically is the tube amplification.  I'm sure there is more to it than that, but for now, I am satisfied with the simplistic definition.


----------



## Wiljen

kickngas said:


> Thanks, but what is "Mu"?  New to tubes vernacular.



Mu is roughly equivalent to gain.    Typically:
12au7   = 19 
12av7    = 40
12ay7   =  45
12at7    = 60-70 depending on variant
12ax7    = 100

You can substitute 12at7s into a SSMH but when you do you usually only get about 30% of the volume pot that is usable before you reach ear-splitting levels.   Putting an 12ax7 in the SSMH would probably result in it being too loud even with the volume pot set at the lowest audible level.

On the other end, there are very few tubes that are directly replacements for the 12au7 with a lower Mu as they were a pretty low gain tube to begin with (as you can see from the chart)  so you are left looking for makes and years that are known for being slightly underpowered, or industrial tubes that were dual triodes with similar specs and lower mu like the 6350 I mentioned. 

If I was new to tubes I would start out with the Sylvania 5963 and remember that with the geometry of the SSMH you don't need matched pairs.  Matching will likely help with tubes lasting roughly the same length of time so you'll wear both out at once, but are not required to balance the output like they can be in some other designs.    The Sylvania tubes should be something you can find for <$20 each and make a good starting point.  For many, the journey will end right there as they sound good and follow the original concept of the SSMH of budget concious sound.


----------



## kickngas

Thanks for the tube lesson!!


----------



## Wiljen

its worth noting that if you have the 19J6 version of the SSMH, I am unaware of any acceptable direct substitute for the 19J6 tube.   all of the tubes I was previously referencing work in the modified SSMH that uses the 12a_7 tubes by default.   Count the pins on the sockets if  in doubt 19J6 is a 7 pin while 12au7 is a 9.


----------



## kickngas (Oct 31, 2018)

Yeah, I messaged member Fred_fred2004 for one of his pc boards.  His is modified for 12_7's, not sure what other options are out there for modified versions.  I would rather not use ptp wiring.


----------



## tomb

kickngas said:


> Yeah, I messaged member Fred_fred2004 for one of his pc boards.  His is modified for 12_7's, not sure what other options are out there for modified versions.  I would rather not use pto wiring.



Just to be clear, the current kits on beezar.com are the original 19J6 tubes and use the original Dsavitsk-designed PCB.


----------



## kickngas

Tomb, clear as a bell.  Is there a supply chain for the 19J6 tubes, or a suitable replacement (possibly 18FY6A?) In case one would be needed in the future?


----------



## tomb (Nov 1, 2018)

kickngas said:


> Tomb, clear as a bell.  Is there a supply chain for the 19J6 tubes, or a suitable replacement (possibly 18FY6A?) In case one would be needed in the future?


Yes, but they're about the price of run-of-the-mill 12AU7/12AT7s these days, instead of the $2 or less they cost when Pete first designed the amp.  Keep in mind that you can pay $hundreds for certain 12AU7s or 12AT7s.  However, a run-of-the-mill NOS 12AU7 should cost you about $8-$10.

A quick search on ebay for "19J6 tube" gives 6 legitimate domestic results and 2 international - ranging from $6.95 to $27.95 for a single tube.  I believe most tube sellers sell them for $8 - $10 - vacuumtubes.net, vacuumtubesinc.com, tubedepot.com, esrcvacuumtubes.com, etc.  You'll just have trouble if you call one of these places and ask for a dozen or more.  That would be an issue.

Again - just to be clear: I am not saying they are as _common_ as 12AU7s or 12AT7s.  Actual, new manufacturing sources exist for those tubes, not just NOS.  But if you need a replacement 19J6 tube, there are readily available sources and they don't cost an arm and a leg, figuratively speaking.


----------



## kickngas

Got it, thank you for the information.  Very helpful!


----------



## Nestade

Hi 

Anyone got the Eagle-Files for the 12AU7-version?
I'd like to etch the PCB on my own.


----------



## jlav10

Nestade said:


> Hi
> 
> Anyone got the Eagle-Files for the 12AU7-version?
> I'd like to etch the PCB on my own.


I was wondering the same thing


----------



## tomb

Just an advisement while you're asking for free stuff - the thing that's proprietary/intellectual property is not the circuit.  It's the PCB layout.  I pay royalties to the designer for every single PCB that I sell, regardless what it is.

There are some who share the Eagle files for some things (like Pete Millett - but he doesn't share everything), but they're probably the exception, not the rule.

If I'm not mistaken, the SSMH PCB designs (dsavitsk and Fred) are small enough to fit into the Eagle free version size constraints (12.4 sq in).  That free Eagle download is here:
https://www.autodesk.com/products/eagle/free-download

Here's one of the best beginner tutorial series for Eagle:
https://learn.sparkfun.com/tutorials/using-eagle-schematic/all

You can get esoteric parts libraries (like PCB tube sockets) from Pete Millett's free Eagle library (wheat.lbr) here: http://pmillett.com/file_downloads/wheat.zip

Finally, I won't try to talk you out of etching your own board.  However, for others looking for a simpler path, I recommend OSHPark: https://oshpark.com/.  You can check the correctness of your PCB design directly on their web site. Their prices are also very reasonable and the purple PCBs look pretty cool.

Good luck!


----------



## prof.utonium

tomb said:


> Just an advisement while you're asking for free stuff - the thing that's proprietary/intellectual property is not the circuit.  It's the PCB layout.  I pay royalties to the designer for every single PCB that I sell, regardless what it is.
> 
> There are some who share the Eagle files for some things (like Pete Millett - but he doesn't share everything), but they're probably the exception, not the rule.
> 
> ...


 Or you could download and use without any limitations KiCad: http://kicad-pcb.org totally free and will import all your eagle projects.

Here is a comparison review: https://www.build-electronic-circuits.com/kicad-vs-eagle-2018-comparison/


----------



## alup17

I am trying to build my own, and I have a few questions. (I am fairly new to DIY things in general) I am also building the 12au7 version

1. I have been looking around, and people have mentioned grounding the heat sinks. Does this mean connecting them to the ground on the power socket, or to the case? If it is connecting it to the power socket, do I need to do the same thing for the case?
2. I already have a 10k pot, and I am using low impedance headphones (32 Ohm). What size resistor should I use for R16/17?
3. I am having a hard time finding a switch rated for 48 VDC. The switch that is recommended is not rated for 48v. Is this important?
4. As long as I am using Panasonic/nichicon capacitors, does it matter which Panasonic/nichicon series I am using?
5. Are there any other modifications that I should make that differ from the original BOM?
Thank you!


----------



## Wiljen

1.) most times you connect the heatsinks to the case and you hook something on the case to the earth ground on the power socket.
2.) Sorry, I'm gonna have to pass on this one as I need to go back and look before I answer.
3.) I had this problem too and ended up finding some at both Mouser and Digikey.
4.) Maybe in the sense that tolerances are tighter on some series than others.  Making sure they are matched closely helps so you don't have channel imbalances.
5.) for a first build I'd stick with the build as-is so you have a good reference point.  The further you go away from the original bom the harder it will be for others to help you without seeing it.

Hope that helps.


----------



## tomb (Jan 12, 2019)

1. It actually helps if you _don't_ ground the heat sinks.  The reason being is that the MOSFET tabs are carrying current that's not the ground.  I suspect the comments you've been seeing are instances where someone has grounded the MOSFET tab to the heat sink.  That will cause a short and while damage may take longer than you think (more than a couple of seconds), the amp will certainly not operate properly.  It's been a common issue with many builds.

2. As for the pot and headphone impedances, neither mean anything in rating R16/R17.  It's the headphone sensitivity that's the concern.  The pot spec'd for the Starving Student (Alpha) is not very good at channel matching at the low end of its turn.  So if your headphones are very efficient, you'll find yourself going crazy with very little adjustment on the volume and poor channel matching.  The intent of the resistors are to artificially depress the gain so that it throws the "common range" of volume listening to somewhere in the middle of the pot's turning - 12 o'clock instead of 7 or 8, if you imagine looking at a clock.  Even then, it's a trial and error thing.  It's probably best to start with 50K for R16/R17 and see if you end up with most of your listening with the pot's turn at 12 o'clock or somewhere close.

While we're talking about the pot - I would choose 50K if you have an opportunity.  The impedance of the pot has little to do with the gain conversation in the paragraph above.  However, the higher impedance you use, the less chance you'll end up cutting out the bass on some sources.  The pot is the first thing in the circuit after the RCA jacks.  So, if your source has output capacitors (many do, especially portables), they will form an RC circuit with the impedance of the Starving Student's pot.  10K is low enough that it may cut out the bass if those output capacitors on the DAC/DAP/whatever are not very big.  There are three volume pot impedances in common use for headphone amplifiers - 10K, 50K, and 100K.  With 100K, you will never, ever have to worry about cutting the bass and have a huge safety factor to boot, too.  However, 100K is noisy on very good amps.  50K seems to be the Goldilocks choice for most headphone amps.  It's why you see AMB and myself (Tangent once, too) selling 50K Alps RK27s.  10Ks are really used mostly in portables.  There the low bass below 50Hz is seldom heard anyway.

3. If I'm not mistaken, you're finding switches that are rated at 110V or 250V.  There is no issue with using a higher-rated switch.

4. Yes, it matters what type or series Panasonic or Nichicon capacitors you're using.  Pete spec'd the basic excellent power-quality capacitors such as Panasonic FM or FC and Nichicon UPW or UHE.  However, the music signal goes directly through C3 and C5.  At the same time, good power-quality capacitors sound like cr*p.  So, it's beneficial to use something of audio-quality for C3 and C5, not power quality.  I actually spec'd Nichicon UKW in those positions in the SSMH kits.  They're not very expensive and Nichicon developed them for audio applications in small portable players.  If you really want to splurge, look for Elna Silmic RFS capacitors (the best right now), or Nichicon ES, FG, or KZ capacitors.

5. The use of bypass capacitors can help, but the only ones that are dependable are Wima MKP or FKP capacitors (others will be an experiment you may not want to fool with).  You can find details on the SSMH website.

EDIT: if you are using at least 50K resistors for R16/R17, please neglect my comments on the pot impedance.  It won't matter - 10K might even be better.


----------



## CarRamrod

Hi All... noob question here...
I just built the kit from Beezar.com and have 1 issue. Occasionally it throws a spark when I flip the 'on' switch. Otherwise it functions perfectly and sounds great. Where would I start to troubleshoot this issue? It's only upon startup and only 1 or 2 quick spark(s). The 1st time I started it outside the case and before heatshrink I watched an arc jump from the 2 posts on the back of the power switch. Any and all advice is appreciated. Thanks!


----------



## tomb

I'm sorry to hear that this is happening.  In my defense, however, I've never heard of something like this - especially at the voltages we run with the Starving Student.

One might suspect the switch itself, but I wonder if it's a grounding issue.  One other customer contacted me with a different issue and we solved it by ensuring grounding through the case.  If you don't have a good ground, it's possible that a charge can develop between two contacts on a switch and cause what you are witnessing.  This is especially true with the Starving Student, because the CISCO power supply - as best we can determine - is not grounded through the wall power connection.

In the new kits, I substituted a nylon standoff for the case lid attachment to the PCB.  That removed the issue of shorting with the LEDs resistor or its PCB pad.  However, it also cut down on the grounding if there are no other contiguous connections from the PCB to the case.  Inspect your RCA connections on the back plate.  You should have scraped away the anodizing on the inside surface of the backplates around the RCA jack holes.  In addition, do not use insulating washers on the inside for the RCA jacks.  Combined with the self-tapping case screws, this should ensure that the PCB is grounded through all parts of the case.

Just a guess, but I'd give it a try.


----------



## antdroid

CarRamrod said:


> Hi All... noob question here...
> I just built the kit from Beezar.com and have 1 issue. Occasionally it throws a spark when I flip the 'on' switch. Otherwise it functions perfectly and sounds great. Where would I start to troubleshoot this issue? It's only upon startup and only 1 or 2 quick spark(s). The 1st time I started it outside the case and before heatshrink I watched an arc jump from the 2 posts on the back of the power switch. Any and all advice is appreciated. Thanks!



This happened to me too, but I checked how i was grounding the rca inputs and washer was in the wrong order causing it to spark.


----------



## tomb

antdroid said:


> This happened to me too, but I checked how i was grounding the rca inputs and washer was in the wrong order causing it to spark.


OK - that's twice now that we've heard of this.  So CarRamrod - check this out!


----------



## CarRamrod

I suspected the nylon standoff had something to do with it since the PCB is kind of 'floating' in there. I'm listening to it right now and it didn't do it when I turned it on this time. The anodizing is all scraped off and I didn't install the led's bc I didnt have this enough gauge w


----------



## CarRamrod

Still occasionally doing it, I'm going to get a metal standoff and see if that helps.


----------



## antdroid

I'd take a photo for you but my SSHT is at my other work office location and I'm too lazy to go over there today. If I do end up going over later in the day, I'll try to find a screwdriver and snap a photo.


----------



## tomb

CarRamrod said:


> Still occasionally doing it, I'm going to get a metal standoff and see if that helps.



Admittedly, I was guessing at this, but there have been quite a few built already with the nylon standoff.  No one has ever reported this issue.  So, it may be Antdroid's suggestion or another problem entirely.


----------



## antdroid

tomb said:


> Admittedly, I was guessing at this, but there have been quite a few built already with the nylon standoff.  No one has ever reported this issue.  So, it may be Antdroid's suggestion or another problem entirely.



The one I built 5 months ago from @tomb had the nylon standoff. It was not the source of my problem. I dont remember if I put the washer between the chassis and the metal tab of the RCA or vice-versa to fix the sparking issue.


----------



## longballlumber

Hello everyone,

I read thru the last couple of posts regarding grounding issues.  Ironically, I just completed assembly of my Kit from Tom and I seem to be having some issues that I could use some input on.  When switching on the LED light up. This is while neither cover is screwed in.  If I position the board and fasten the front plate (4 screws), it will power up find.  If I then position the back plate into loose assembly (no screws), it will power on.  As soon as I try and install ONE of the four back plate screws I no longer have power.  I do intermittently hear aching when trying to install the back plate screws.

I have assembled the RCA posts in both configurations with white washer and w/o white washer (interior side).  The white washers are used on the exterior of the panel.  The anodizing has been removed from the back side.  I used a dremel tool with a wire brush to remove vs. "scraping" with a knife or file.

Like many others this is my first build and have more of a mechanical background vs. electrical.

Thoughts or ideas would be appreciated!

Mike


----------



## tomb (Feb 16, 2019)

longballlumber said:


> Hello everyone,
> 
> I read thru the last couple of posts regarding grounding issues.  Ironically, I just completed assembly of my Kit from Tom and I seem to be having some issues that I could use some input on.  When switching on the LED light up. This is while neither cover is screwed in.  If I position the board and fasten the front plate (4 screws), it will power up find.  If I then position the back plate into loose assembly (no screws), it will power on.  As soon as I try and install ONE of the four back plate screws I no longer have power.  I do intermittently hear aching when trying to install the back plate screws.
> 
> ...





> hear aching



Outside of whatever "aching" means, it doesn't sound like a grounding issue to me.  Instead, it sounds like the classic problem of assembling casework, only to cause a short.

Did you use heat shrink on any exposed leads?  If not, the wire gets compressed and bends into different shapes when you push the casework together in assembly.  This may not be apparent as you take it apart again, because the wire springs back into its original shape.
Or, you could be capturing some of the wiring inside one of the slots near the assembly screw.  Screwing the screw in may touch an exposed lead or worse, cut into the insulation so that the screw touches the bare metal of the wire.
Look carefully at the wiring as you assemble and push the parts together.  See if the wiring is bending such that an exposed part of the wiring is touching bare metal.  Be very careful when you screw in the assembly screws.  Look to see if any wiring is getting close to the slots and getting trapped by one of the screws.

P.S. If you look at my documentation on diyforums.org, you'll find that I tightly twist the wire so that there are no errant leads flopping around everywhere.  You still have to be concerned, because the design of the SSMH PCB amplifier needs to have wire slack to assemble and dis-assemble.  However, you can minimize the issues by twisting the leads into a few bundles, not many single pieces of wiring.


----------



## longballlumber

Thanks for taking time to reply.  I will take another look, but it seems everything should be ok.  I did use shrink tubing in all of the locations suggested and shown in the instructions. One leg of each LED, and the signal connection for each RCA jack.  Evidently I am restricted from posting pictures since I’m a newer member.  

Thanks again for the help
Mike


----------



## tomb

longballlumber said:


> Thanks for taking time to reply.  I will take another look, but it seems everything should be ok.  I did use shrink tubing in all of the locations suggested and shown in the instructions. One leg of each LED, and the signal connection for each RCA jack.  Evidently I am restricted from posting pictures since I’m a newer member.
> 
> Thanks again for the help
> Mike


You didn't mention the power connections and whether they get compressed upon case assembly.  Also, the signal wiring runs along the side of the PCB inside the case.  If you haven't put a good bend in them where they connect to the terminal block, it's very likely that they will get caught in the slots on the side of the case.

Let us know and good luck!


----------



## drabina

Has anybody built a source into your SS amp? Something like bluetooth, Raspberry Pi or something else? I have asked this question couple of years ago but did not get many replies. Hopefully, this has changed since then and somebody can provide some feedback. Ultimately, I would like to put Raspberry Pi Zero with Phat DAC into the same enclosure so I do not need external source. All would be controlled by the phone. I am just not sure about two different power supplies (48V for SS and 5V for RPi - grounding issues, hum, etc) and RPi's wi-fi range in an all aluminum enclosure.


----------



## drabina

Nobody? No Starving Student amps with built-in sources?


----------



## tomb

drabina said:


> Nobody? No Starving Student amps with built-in sources?



No offense, but a DAC inside an amp is fairly obvious.  You want one?  Then put it in there.  It's DIY, after all.

Allow me to note that the Millett Hybrid MAX V1.2 PCB has had an area identified for a DAC - either the GrubDAC, SkeletonDAC, or the BantamDAC, when we were still offering it.  This DIY PCB has been in existence since 2010, I might add.







Here's a couple of pics of the board in action:









As for your idea of placing a Raspberry Pi, if the case has room - put it in there, too.  It would have to be a lot more involved, because you'd probably need some sort of touch-screen interface, but you could probably make it work with some effort.  I'm not sure that would be a real advantage, though, because then you'd be including the kitchen sink.  AMB did an Arduino interface for his Gamma 3 DAC and it would only be a simple step after that to include an amp - assuming you used casework that was big enough.

There are several versions of the ODAC and O2 being housed together, too.  Just look at JDS Labs or Mayflower Electronics.  As long as you're using a USB-powered DAC, these are all pretty simple.  It gets a lot more complicated when the DAC is high-end enough that it needs power.  Then things get complicated enough that housing them in the same case has diminishing returns.


----------



## longballlumber

tomb said:


> You didn't mention the power connections and whether they get compressed upon case assembly.  Also, the signal wiring runs along the side of the PCB inside the case.  If you haven't put a good bend in them where they connect to the terminal block, it's very likely that they will get caught in the slots on the side of the case.
> 
> Let us know and good luck!



Hello,

I wanted to circle back.  I have been using the amp successfully for a couple of weeks now with zero issues.  Although, I never really identified root cause from my previously posted issue about a possible short.  I spent a couple of days using it at work using my Iphone as a DAC source and powering thru a set of Beyerdynamic IME’s (idx 160’s).  The SSMH replaced a Bravo V2 while auditioning at work. 

The real reason I bought the SSMH was to keep at home and to use with a set of Sennheiser HD 6XX from massdrop (same as Sennheiser HD 650), and listen to my vinyl records.  Here is where my challenges started up again.  My turntable doesn’t have a built in pre-amp.  That wasn’t a problem, because prior to buying my headphone set up I played my vinyl thru an Onkyo TX-NR1007 which had a phono stage built in.  In addition to the phono stage, the Onkyo also has pre-outs.  I think this is where I made the wrong assumptions and my novice level is being exposed.  I planed on running my turntable through the phono pre-amp of my Onkyo then use the pre-outs on my RX to the SSMH to power my headphones…   I found out quickly, it doesn’t work that way.  I am now looking for a separate phono pre-amp to place in-between my turntable and my SSMH for a new listening experience.  

I will eventually get something assembled.


----------



## tomb (Mar 8, 2019)

longballlumber said:


> <snip>
> I am now looking for a separate phono pre-amp to place in-between my turntable and my SSMH for a new listening experience.
> 
> I will eventually get something assembled.



The Hagtech Bugle is probably the highest quality, lowest cost phono pre-amp available.  It's essentially an opamp phono pre-amp, but it will beat the pants off of almost any vintage receiver phono input or any small converter phono preamp you might buy on Amazon.  The Bugle 2 is a PCB only, for $39 right now.

If you are really adventurous, Pete Millett has a no-capacitor-in-the-signal-path phono preamp design that you can buy from him on ebay.  He has the bipolar power supply (assembled, complete!) for sale right now for $39 and the phono preamp board also assembled, even with the Cinemag inductors, for $59.  You would still need to do the casework, but that's a helluva deal right now, IMHO.  Keep in mind that the casework and grounding is a big deal with a phono pre-amp.  The gain is so high that you will be lucky if you don't get hum at high volume levels.  Separate casework between the power supply and pre-amp board is probably better.  I didn't do that with mine.  If I place it too close to anything with a transformer, it gets noisy.  Other than that, it's fantastic.  You'd probably have to spend $1-$2K to get better sound than Pete's design.  Just the idea of RIAA equalization without capacitors in the signal path is outstanding.

Here is Pete's website detailing the LR Phono Preamp design and building instructions:
http://pmillett.com/LR_phono.html

Here is the Bipolar Power Supply (assembled!) on ebay:
https://www.ebay.com/itm/Pete-Mille...048138?hash=item23b798030a:g:JPIAAOSwiAFcfs8q

Here is the Millett LR Phono Preamp (assembled!) on ebay:
https://www.ebay.com/itm/Pete-Mille...035947?hash=item23b797d36b:g:zuEAAOSwzMlcfs~U

It's more than helpful that Pete has the PCB assembled.  Some of us went through a number of extra AD797 opamps before finding the right ones that made the circuit stable.  Again, that's another quirk of working with phono pre-amps.  The gain is so high, that even manufacturing tolerances among the same opamps are enough to throw the circuit off.


----------



## Wiljen

On the Raspberry Pi idea, would placing a wireless antenna in that proximity to the tubes not present a huge potential for interference?


----------



## docentore

AD8397 is no go with NuHybrid. Made DIY dual2single adapter but the opamp is oscilating, heating a lot.


----------



## tomb

docentore said:


> AD8397 is no go with NuHybrid. Made DIY dual2single adapter but the opamp is oscilating, heating a lot.



Unless I'm lost, this is the Starving Student thread, not Pete's NuHybrid thread.

Oh - by the way: the AD8397 will oscillate in even friendly opamp sockets, much less the NuHybrid.  Typically, a custom layout and circuit is required to use an AD8397 without oscillation.  They should probably outlaw the use of Brown Dog with an AD8397.


----------



## docentore

tomb said:


> Unless I'm lost, this is the Starving Student thread, not Pete's NuHybrid thread.
> 
> Oh - by the way: the AD8397 will oscillate in even friendly opamp sockets, much less the NuHybrid.  Typically, a custom layout and circuit is required to use an AD8397 without oscillation.  They should probably outlaw the use of Brown Dog with an AD8397.


Right, I mixed up threads  thanks for pointing this and the tip.


----------



## drabina

Wiljen said:


> On the Raspberry Pi idea, would placing a wireless antenna in that proximity to the tubes not present a huge potential for interference?


Well, I guess I will have to try and report my findings. The wi-fi adapter is usb so if I position the raspberry strategically, it could be outside of the case. My new enclosure will have the tubes inside the metal case so it should be separated from the antenna.


----------



## mcmillant (Mar 24, 2019)

Hi, i am fresh new and i am starting learn to make a quite good ampli for my grado sr60....
Mostly the question is about the powersupply. The only good powersupply i can find in my local is a 33vdc from hp printer.. Can 33v can do well with this build (i using 12au7 mod by Dsavisk) ? .
I plant to use pcb (which i do by myself) so Do it have any advices for me to prevent the hum (i tried to build cmoy before and it comes with huge hum and noise ...).


----------



## tomb

mcmillant said:


> Hi, i am fresh new and i am starting learn to make a quite good ampli for my grado sr60....
> Mostly the question is about the powersupply. The only good powersupply i can find in my local is a 33vdc from hp printer.. Can 33v can do well with this build (i using 12au7 mod by Dsavisk) ? .
> I plant to use pcb (which i do by myself) so Do it have any advices for me to prevent the hum (i tried to build cmoy before and it comes with huge hum and noise ...).


I'm not sure the 33VDC supply will be enough.  The resistors and other parts of the circuit are designed for the 48VDC power supply.  The power supply is easily available on ebay.  Just search for "cisco psa18u-480" on ebay and you'll get many economical choices.

As for the hum, I suggest you find out what you did wrong with the CMoy before you try building another amp.  Maybe thousands of CMoys have been built without any hum and noise.  The CMoy design uses batteries.  It's sort of difficult to get hum from a battery.


----------



## mcmillant (Mar 24, 2019)

tomb said:


> I'm not sure the 33VDC supply will be enough.  The resistors and other parts of the circuit are designed for the 48VDC power supply.  The power supply is easily available on ebay.  Just search for "cisco psa18u-480" on ebay and you'll get many economical choices.
> 
> As for the hum, I suggest you find out what you did wrong with the CMoy before you try building another amp.  Maybe thousands of CMoys have been built without any hum and noise.  The CMoy design uses batteries.  It's sort of difficult to get hum from a battery.


oh yeah i use a 12v ac dc converter power so get the hum, i testing it with 16850 batteries is ok, the hum very low.
And about irf510, can i repalce it with irf610  or irf520 ?


----------



## onesojourner (May 18, 2019)

Could some one take a look at my mess and help me troubleshoot it? When I plug in some cheap ear buds all I get is a light hum. I am not sure where to begin the troubleshooting process. The pot does not appear to have any effect.


----------



## tomb

Print out the Starving Student schematic.  Look at each leg and connection in the schematic, match it up with what you've built, and mark both as checked and valid.  Eventually, you'll find the issue.

Just an FYI, but I've tried a couple of times to follow your wiring in those photos and I can't because almost all of the wiring is that same red color.  I suggest you get out a magic marker or some colored tape and color code some of that wiring.  You might find the issue a bit easier when you do that.  Good luck and sorry you haven't had more input, but that may be why.


----------



## DrivenKeys

Wow, I love the use of an old pc cooler, wish I had thought of that. I haven't seen that type of potentiometer before, are the extra 2 prongs for on/off? Also, my tubes don't glow that bright, I wonder if I need to fix something? I built the 12au7 version.


----------



## onesojourner

DrivenKeys said:


> Wow, I love the use of an old pc cooler, wish I had thought of that. I haven't seen that type of potentiometer before, are the extra 2 prongs for on/off? Also, my tubes don't glow that bright, I wonder if I need to fix something? I built the 12au7 version.



Mine is not working so don't use it as an example. I have no idea what I have done wrong. I have gone over the diagram several times and from what I can tell it is all correct. I am not sure what those other two posts are for on the pot.


----------



## DrivenKeys

onesojourner said:


> Mine is not working so don't use it as an example. I have no idea what I have done wrong. I have gone over the diagram several times and from what I can tell it is all correct. I am not sure what those other two posts are for on the pot.


 I'm sorry to hear it's still not working, I've looked at the pix and it's beyond me. That's unfortunate, I really like this build.

It turns out my tubes aren't as bright because they're the type with heat spreaders covering the elements.


----------



## tomb

onesojourner said:


> Mine is not working so don't use it as an example. I have no idea what I have done wrong. I have gone over the diagram several times and from what I can tell it is all correct. I am not sure what those other two posts are for on the pot.



You might entirely re-wire that pot, or better yet: get a different one.  If your tubes are on and glowing and other things seem OK, that volume pot may be your entire problem.  You should have six connect points on a stereo volume pot, plus one to ground - usually just to the metal somewhere on the pot to keep the amp from humming.  Some of your wiring/soldering looks pretty dodgy around that pot.  I also don't recognize that pot, so have no idea how to help with the connections.  (Not that I'm some sort of volume pot expert, but I have seen quite a few over the last ten years or so - never saw that one from what I remember.)


----------



## onesojourner

tomb said:


> You might entirely re-wire that pot, or better yet: get a different one.  If your tubes are on and glowing and other things seem OK, that volume pot may be your entire problem.  You should have six connect points on a stereo volume pot, plus one to ground - usually just to the metal somewhere on the pot to keep the amp from humming.  Some of your wiring/soldering looks pretty dodgy around that pot.  I also don't recognize that pot, so have no idea how to help with the connections.  (Not that I'm some sort of volume pot expert, but I have seen quite a few over the last ten years or so - never saw that one from what I remember.)



Thanks. I will get a different one ordered and see what happens.


----------



## DrivenKeys

Come to think of it, I ruined my cheap Alpha pot with sloppy soldering, I believe my issue was applying too much heat and allowing flux to run into it. Mine was full of static, with one sweet spot, ground hum, etc. If I had done much more, I may have had the same issue you've experienced.

I had allowed my soldering tips to go black, and couldn't re-tin them with normal solder. So I was seriously overheating components before the tip finally melted the solder. I also rely heavily on a helping hands when soldering wires onto pcb pins. The pins leave very little room for error, and clamping the pot upside down on a table is how I let flux into it.

I really like this build, I hope the new pot fixes it.


----------



## onesojourner

I will keep you posted. I don't think I over heated anything but who knows.


----------



## ThermalAlchemy

DrivenKeys said:


> Come to think of it, I ruined my cheap Alpha pot with sloppy soldering, I believe my issue was applying too much heat and allowing flux to run into it. Mine was full of static, with one sweet spot, ground hum, etc. If I had done much more, I may have had the same issue you've experienced.
> 
> I had allowed my soldering tips to go black, and couldn't re-tin them with normal solder. So I was seriously overheating components before the tip finally melted the solder. I also rely heavily on a helping hands when soldering wires onto pcb pins. The pins leave very little room for error, and clamping the pot upside down on a table is how I let flux into it.
> 
> I really like this build, I hope the new pot fixes it.



 A good cheap Chinese knock off adjustable T – 12 soldering tip , iron Station.   I have bought three of these it was so good one went to my son to for me one in case I need it as a back up but so far I have not needed it because it has never broken down yet after two years of use.  I also purchased one of death cheap three and one soldering stations that had a built-in volt amp meter with a hot air station gun.  Do your research as example here is a YouTube video on soldering stations very cheap and affordable will definitely improve your soldering skills because you can adjust the heat and on larger pads and components the heat to self adjust keeping the temperature. 
 Also the addition if your having a really hard time possibly dirty components a small dispensable container of liquid flux meant for electronics in very good quality lead bearing solder With flux core again cannot stress how important it is to stay away from leadfree solder.  Especially for beginners.  For beginners for video  tutorial  on soldering search YouTube for Mr. Carlson labs and then seek his solder tutorial.  There is also excellent old black-and-white videos from the 40s 50s and 60s produced by the manufacturers of electronics companies and solder production companies.  Usually after watching these videos you will no longer be a beginner. With a adjustable self heat correcting  soldering iron.


----------



## tomb

onesojourner said:


> Mine is not working so don't use it as an example. I have no idea what I have done wrong. I have gone over the diagram several times and from what I can tell it is all correct. I am not sure what those other two posts are for on the pot.


Just to be clear, it's not the quality of the solder joints I was commenting on.  Rather, it's the wiring technique used to connect to the pins and whether the pins are correct.  At first glance, I thought two strands of wire were used to connect to the pot's signal ground.  Upon a closer look, I guess those are resistor leads, so perhaps not so bad.  I suspect the back two pins are an integral on/off switch attached to the back of the pot, which is fairly common.

That said, I still suspect the pot: whether it works, whether the connections are correct instead of reversed, etc.  You should be getting some symptoms in the audio - hum static, etc.  If not, it implies that the signal is completely disconnected from the circuit.  Where is the first place the signal goes after the RCA jacks?  The volume pot.


----------



## DrivenKeys (Jul 22, 2019)

Since we're on this subject, I wanted to ask about the pot/resistor combo. I searched and scoured the results, I think I know what to do, but wanted to ask before more surgery:

12au7 version on a Fred pcb. I currently have a 100k Alps blue pot combined with 47k resistors at input. The amp sounds perfect, except I really have to boost my source to drive my 250 ohm Beyers. My computer and monitor can't output enough, I switch to lower impedance cans for movies.

If I remove the resistors and just use the 100k pot, will that raise my input volume enough? It's a premium pot, so I'm not worried about staying in the lower range with easier phones. I'm fine with getting a new pot or resistors, but only want to dig in again once, if I can help it.

Also, I had a balace issue that was fixed when I wiggled the c7 cap. Power was on and tester phones plugged in, I could hear the pop as I wiggled  the cap and it came back online. Does that sound like an issue with the cap itself, or its connection? Things are cramped. Whenever I remove the board, these caps get bent around. I'm wondering if I should replace them when I pull out the resistors.


----------



## tomb

DrivenKeys said:


> Since we're on this subject, I wanted to ask about the pot/resistor combo. I searched and scoured the results, I think I know what to do, but wanted to ask before more surgery:
> 
> 12au7 version on a Fred pcb. I currently have a 100k Alps blue pot combined with 47k resistors at input. The amp sounds perfect, except I really have to boost my source to drive my 250 ohm Beyers. My computer and monitor can't output enough, I switch to lower impedance cans for movies.
> 
> ...



Short answer: Yes.

If you're having to rack the volume pot to maximum all the time, then you need to remove the input resistors.


----------



## DrivenKeys (Jul 22, 2019)

tomb said:


> Short answer: Yes.
> 
> If you're having to rack the volume pot to maximum all the time, then you need to remove the input resistors.



Cool, I'll try that 1st. Thank you. Any idea about that loose cap? I'm trying to determine if it's a sign to replace it.

Also, I was asking the community if I should reduce pot impedance while I'm at it. That's why I detailed the issue is with 250 ohm cans, not just ask about theory. I hope those who have gone through this experimentation already could perhaps save me a few hours and expense of my aimless troubleshooting (admittedly breaking things as I go). I wish I had the time and cash to just try whatever comes to mind, not there right now.

Thank you, anybody who can help.


----------



## DrivenKeys (Jul 22, 2019)

tomb said:


> Short answer: Yes.
> 
> If you're having to rack the volume pot to maximum all the time, then you need to remove the input resistors.



Well, now that I'm looking at it, I wonder about the resistors directly after the pot. EDIT Nevermind, I finally re-read the very informative post by yourself explaining the optional parts and grid stop. You are very patient and helpful. I'm still wondering what happens if the resistor values are changed.

Thank you for your patience as I'm learning. I search all I can, but this has become a very, very long thread.


----------



## tomb (Jul 23, 2019)

DrivenKeys said:


> Well, now that I'm looking at it, I wonder about the resistors directly after the pot. EDIT Nevermind, I finally re-read the very informative post by yourself explaining the optional parts and grid stop. You are very patient and helpful. I'm still wondering what happens if the resistor values are changed.
> 
> Thank you for your patience as I'm learning. I search all I can, but this has become a very, very long thread.


I'm not sure what you're asking when you say, "I'm still wondering what happens if the resistor values are changed."

Every volume pot is designed for zero volume at the bottom of the range, and zero-resistance/maximum volume at the end of the range.  The only question becomes, "Where in that travel does your comfortable listening volume take place?"  As mentioned many times previously, the stereo volume pot used in the Starving Student is not the best (low cost and the "starving student" theme applies). Cheaper volume pots, among other symptoms, exhibit poor channel matching, often at the extremes of the volume travel - both at the bottom of the range and the top of the range.  If your comfortable listening volume happens to fall in either of those ranges where the channel matching is bad in the volume pot, then your listening experience is full of irritation.

What determines where the comfortable listening volume falls?  Three variables apply: 1) the gain of the amp, 2) the efficiency (sensitivity) of the headphones, and 3) your personal listening preference.  There is also the recorded gain setting of the music, but let's assume you've adjusted that through your media player, or that the differences are typically small enough that the change in volume pot setting is trivial.  You can't change #2 unless you change the headphones.  You can't change #3 unless you train yourself to listen at different volumes (could be ear damage as a result).  So, you're left with doing something with the amp.

If the Starving Student were a typical solid-state amp with feedback, you could change the resistors forming the voltage divider ratio in the feedback loop.  However, the Starving Student is not a typical solid-state amp.  Neither does it have feedback.  The basic gain is provided by the tubes and is not variable.  Unfortunately, the basic gain is quite high with the tubes and circuit in the Starving Student, meaning that for most headphones and sources, the comfortable listening range for most people occurs within the first quarter turn of the volume knob.  This is a bad place for comfortable listening.  It does not give you much precision in adjusting the volume and the channel matching in that area with a cheap volume pot sucks.

In order to remedy that, we began the practice of applying resistors to the signal input of the circuit.  Why?  Well, the goal is to put the comfortable listening range further in the volume travel than sooner.  In other words, we want to "push" the comfortable listening range of the volume pot from 9 o'clock to 12 o'clock.  How do we do that?  Well, continuing to turn the volume pot does what? It decreases the resistance.  So, if we add resistors to the input, we increase the resistance in the circuit before it even gets to the volume pot.  Done perfectly, the input resistors push the range to 12 o'clock, where once the comfortable listening range was at 9 o'clock, .

This is not rocket science, but the actual variable values are hard to determine.  Every headphone is slightly different and so is your hearing.  We supplied (or suggested) resistors in the 50K, 100K, and 150K range to take care of the differences.  If you lower that input resistance or remove it altogether, it will have the effect of moving the comfortable listening range down to the bottom of the dial (with most headphones).  However, if you happen to have an uncommonly high headphone impedance (affects how easily the amp drives the headphones) or low efficiency headphones, you may find yourself at the end of volume pot travel, yet still not receiving sufficient volume.  In that case, lowering/removing the input resistance may mean that you end up in the 12 o'clock range, instead.*


*  At some point, the power the amplifier can supply enters into the mix, but this has usually not been a problem with the Starving Student.


----------



## DrivenKeys

Thank you, I really appreciate your detailed response, and continue to learn.

Please forgive my lack of detail. Before I posted at all, I understood the basics of the input resistors before the pot, but just needed to confirm I hadn't missed anything. I've been working with speakers my whole life, so I understand a basic series circuit. Since there's a lot I don't understand here, I tread lightly and question everything I think I know. Even if I feel stupid asking, a question is never stupid if it prevents a stupid mistake.

I was wondering about changing the values of the grid stop resistors, just out of curiosity and conversation. Please don't think I expect you to spend the time educating me on this whole circuit. I don't really plan to change the grid stop resistors, but I don't yet understand the purpose. That's ok, I haven't even learned what the tube does yet, and I'm not asking you to type that out, unless you really want to. 

I'm in a fairly desperate work situation right now, and don't have the time to experiment like I'd like. I'm really just trying to get some basic answers from those with experience, so I can stop opening this thing up and just enjoy it. Basic beginners stuff that most ppl wish they knew before learning the hard way. I like learning the hard way, but must throw this in a box if I can't just wrap it up. Basically, I only have the time to take it apart once more, so I need to get the most out of that one time. Replacing a few affordable parts all at once is an acceptable expense, especially when I know that leaving it in one piece prevents me from breaking anything.

If a cylindrical capacitor soldered to a board, stops working, but works again when pressed on and wiggled, is it typically damaged? Will it continue reliably, or should I pre-emptively replace it next time I remove the board from the case? I believe it's been knocked around and the leads have been bent back and forth many times as I've worked near it. It's not that expensive to replace. Should I just replace it while I have it open?

From everything I've found through search, I'm under the impression that my 100k pot without signal resistors will allow me to comfortably drive 600 ohm cans. I've only gathered this anecdotally, and wanted to know if I have a realistic expectation, or if I should move to a lower impedance pot. Anybody who has played with this idea could save me a lot of time.

Thanks again for all your help, I'm very happy for this community and hobby.


----------



## tomb

OK - it was early in the morning and combined with your earlier comments about lack of volume control with 250 ohm Beyers, it was a reasonable assumption to explain the input resistors - especially since the grid-stop resistors have _absolutely nothing_ to do with that.

If you've read somewhere that grid stopper resistors attenuate gain, that's absolutely wrong.  They are there to increase the stability of the tube performance and stop potential oscillation, among other things.  The only thing they attenuate are frequencies well above the audible range.  Maybe you should think of them as a safety valve for a tube. 

Are they needed for the Starving Student?  Probably not and Pete's original schematic didn't include them.  However, among other things, they could address some of the comments in this huge thread where Starving Students were susceptible to cell phone noise or even radio signals.


----------



## DrivenKeys

tomb said:


> OK - it was early in the morning and combined with your earlier comments about lack of volume control with 250 ohm Beyers, it was a reasonable assumption to explain the input resistors - especially since the grid-stop resistors have _absolutely nothing_ to do with that.
> 
> If you've read somewhere that grid stopper resistors attenuate gain, that's absolutely wrong.  They are there to increase the stability of the tube performance and stop potential oscillation, among other things.  The only thing they attenuate are frequencies well above the audible range.  Maybe you should think of them as a safety valve for a tube.
> 
> Are they needed for the Starving Student?  Probably not and Pete's original schematic didn't include them.  However, among other things, they could address some of the comments in this huge thread where Starving Students were susceptible to cell phone noise or even radio signals.



Ahhhh, thank you. I'm glad to have them, lotsa potential rf probs around here. 

I'm excited to finally be back in this hobby. I'm thirsty for knowledge, wanna learn this thing. Looking forward to reading all about tubes, etc.


----------



## onesojourner

My pot is on the way from mouser. Hopefully I will have time to get it installed this weekend.


----------



## DrivenKeys

onesojourner said:


> My pot is on the way from mouser. Hopefully I will have time to get it installed this weekend.



Nice, take your time! Which pot did you get?


----------



## onesojourner

DrivenKeys said:


> Nice, take your time! Which pot did you get?


I went with the one from the parts list. 

313-1240F-50K
RV122F-20-15F-A50K-0072
Audio D-Shaft 50K


----------



## bdbell

I built a SSMH several years ago, but never used it much because all of my headphones at the time were low impedance - but recently got a pair of 250 ohm  DT990 and none of my DAP's could really drive them well enough so I pulled out the SSMH - there was too much noise and hum so I decided to mill a new PCB for it on my CNC.  I did up the design in eagle and started milling my PCB, took several tries because I haven't done many PCB's on it for a while...finally have a PCB that works and has everything in the proper location to fit into the enclosure I already had built (aluminum).  But when I got it all installed inside the case and tried it last night there was a very annoying noise mostly in right ear even with volume at 0.  Did some searching on this thread and found I should connect the ground from the first power capacitor directly to the DC jack instead of to the ground plane - that fixed the noise problem.  I now have no hum or noise at 0 with the DT990's, as the volume is increased I get hum and a little noise - but with lower impedance earphones it is much more noticeable...I will really only be using it with the DT990's so the hum is not really noticeable with them when playing music, but...want to try to get it as good as possible as I will be using it a lot.

All the grounds are connected to the ground plane on my single sided PCB - should connect grounds of all of the capacitors to the DC jack, or should I connect all of the grounds for everything to the DC jack, or just the two big 680 uF caps?  I would like to get it right before I put it back into the case so would appreciate any advice on how best to deal with it.


----------



## onesojourner

Alright I got the new pot and got it soldered in. I get a hum and nothing else. There is some popping when turning it on but other than that just a steady hum. Turning the pot does not change the volume of the hum.


----------



## tomb

bdbell said:


> I built a SSMH several years ago, but never used it much because all of my headphones at the time were low impedance - but recently got a pair of 250 ohm  DT990 and none of my DAP's could really drive them well enough so I pulled out the SSMH - there was too much noise and hum so I decided to mill a new PCB for it on my CNC.  I did up the design in eagle and started milling my PCB, took several tries because I haven't done many PCB's on it for a while...finally have a PCB that works and has everything in the proper location to fit into the enclosure I already had built (aluminum).  But when I got it all installed inside the case and tried it last night there was a very annoying noise mostly in right ear even with volume at 0.  Did some searching on this thread and found I should connect the ground from the first power capacitor directly to the DC jack instead of to the ground plane - that fixed the noise problem.  I now have no hum or noise at 0 with the DT990's, as the volume is increased I get hum and a little noise - but with lower impedance earphones it is much more noticeable...I will really only be using it with the DT990's so the hum is not really noticeable with them when playing music, but...want to try to get it as good as possible as I will be using it a lot.
> 
> All the grounds are connected to the ground plane on my single sided PCB - should connect grounds of all of the capacitors to the DC jack, or should I connect all of the grounds for everything to the DC jack, or just the two big 680 uF caps?  I would like to get it right before I put it back into the case so would appreciate any advice on how best to deal with it.



We're not actually sure the grounding does much through the power supply.  The Cisco power supply may actually be isolated from ground inside its circuitry.  It's one of the reasons we theorized that static charges can develop on the RCA jacks (killing some DIY DACs that output directly from a DAC chip).  The primary grounding in the SSMH takes place through the casework.  Did you scrape the anodizing away around the inside surface of the back plate at the power jack and RCA jacks?  The RCA jacks will work better if they are _not_ isolated with insulating washers.

This pic may help:






Note that it's still important to provide a ground between the DC jack and the back plate.

The other possibilities are the tubes and the power supply.  If either one are bad, they can cause some bad humming.


----------



## tomb

onesojourner said:


> Alright I got the new pot and got it soldered in. I get a hum and nothing else. There is some popping when turning it on but other than that just a steady hum. Turning the pot does not change the volume of the hum.


I'm sorry that replacing the pot doesn't appear to fix it.

I just reviewed your photos again.  Let me ask a question (don't hit me if this was obvious) - are those MOSFETs connected directly to the copper of the heat sink?  If so, they are directly shorted to ground.  The Drain pin (center pin) is the same as the tab on the MOSFET.  The tabs must be insulated from ground.

If they are isolated, then sorry for the suggestion, but I can't see any insulating washers or pads in the photos.


----------



## onesojourner (Jul 26, 2019)

tomb said:


> I just reviewed your photos again.  Let me ask a question (don't hit me if this was obvious) - are those MOSFETs connected directly to the copper of the heat sink?  If so, they are directly shorted to ground.  The Drain pin (center pin) is the same as the tab on the MOSFET.  The tabs must be insulated from ground.
> 
> If they are isolated, then sorry for the suggestion, but I can't see any insulating washers or pads in the photos.



They are screwed directly to the heatsink with a bit of thermal paste. and that means the drains are both tied together I guess? I have some of that cheap thermal tape that seems like it would insulate ok. Should I try that?

:edit: I decided to just unscrew the fets from the heatsink (breaking the connection between the tab and the heatsink) and turn it on for a second. There was no noticeable change.


----------



## tomb

onesojourner said:


> They are screwed directly to the heatsink with a bit of thermal paste. and that means the drains are both tied together I guess? I have some of that cheap thermal tape that seems like it would insulate ok. Should I try that?
> 
> :edit: I decided to just unscrew the fets from the heatsink (breaking the connection between the tab and the heatsink) and turn it on for a second. There was no noticeable change.


I guess I was thinking about the "normal" situation where you have a metal case and the heat sinks are bolted to the case, effectively grounding them.  In any event, the MOSFET drains are supposed to be tied together, if you look at the schematic.  The difference is that both drains are then connected to the "+" portion of the power supply.  If your heat sink is not grounded to anything, then maybe it's OK.

Well, I'll keep looking when I get a chance.  At least this suggestion didn't cost you any money.


----------



## DrivenKeys

tomb said:


> I'm sorry that replacing the pot doesn't appear to fix it.
> 
> I just reviewed your photos again.  Let me ask a question (don't hit me if this was obvious) - are those MOSFETs connected directly to the copper of the heat sink?  If so, they are directly shorted to ground.  The Drain pin (center pin) is the same as the tab on the MOSFET.  The tabs must be insulated from ground.
> 
> If they are isolated, then sorry for the suggestion, but I can't see any insulating washers or pads in the photos.



I actually had the same thought when I first looked. I forgot to ask, figured it was just the photo.


----------



## onesojourner (Jul 31, 2019)

Can someone confirm that I do have the fets wired correctly?


----------



## bdbell

tomb said:


> We're not actually sure the grounding does much through the power supply.  The Cisco power supply may actually be isolated from ground inside its circuitry.  It's one of the reasons we theorized that static charges can develop on the RCA jacks (killing some DIY DACs that output directly from a DAC chip).  The primary grounding in the SSMH takes place through the casework.  Did you scrape the anodizing away around the inside surface of the back plate at the power jack and RCA jacks?  The RCA jacks will work better if they are _not_ isolated with insulating washers.
> 
> This pic may help:
> 
> ...



Thanks for the quick reply tomb - I connected the other 680uf cap to the DC jack and that also reduced the hum/noise - tried connecting the 220uf caps also but that increased the noise.  So I disconnected the 220uf and reconnected them to the PCB ground plane and then put everything back into the enclosure - and all the hum/noise went away!  So, at least for my setup connecting the 2 680uf caps to the DC jack was necessary to eliminate all the noise.  BTW - my case does not have any anodizing on the front/back plates.

One last question - I am currently using Elna 470uf RE3 caps and Wima 0.22/100v caps for C3/5 - the wima 0.22 caps are quite a bit smaller than the 250v ones - will it make much difference if I switch to Elna 470uf RFS and the 250v Wima caps?


----------



## tomb

bdbell said:


> Thanks for the quick reply tomb - I connected the other 680uf cap to the DC jack and that also reduced the hum/noise - tried connecting the 220uf caps also but that increased the noise.  So I disconnected the 220uf and reconnected them to the PCB ground plane and then put everything back into the enclosure - and all the hum/noise went away!  So, at least for my setup connecting the 2 680uf caps to the DC jack was necessary to eliminate all the noise.  BTW - my case does not have any anodizing on the front/back plates.
> 
> One last question - I am currently using Elna 470uf RE3 caps and Wima 0.22/100v caps for C3/5 - the wima 0.22 caps are quite a bit smaller than the 250v ones - will it make much difference if I switch to Elna 470uf RFS and the 250v Wima caps?



No, it won't make much difference - most likely.  The voltage is not important in this case.  48V is as much as the entire circuit will see (with the Cisco power supply) and 100V capacitor ratings are plenty more than that.  What's really important, audio-quality wise, is the actual type of Wima film caps.  The MKP10 and perhaps the FKP4, are the best.  Metalized polypropylene is superior to polyester.  Wima makes both kinds and many in-between.


----------



## moosefet

I posted a 12SR7 build I did of this in here a couple years ago (this post) and I just built another one for a friend who wanted one. This time I etched the front with control labels. The silly lizard poking his tongue out is a bit of an inside joke and he's also a big tumbleweed fan who have a song called silver lizard. Here's the process:

etchant mask






etch






filled, sanded, clear coat












some hardware






wired up and finished


----------



## DrivenKeys

moosefet said:


> I posted a 12SR7 build I did of this in here a couple years ago (this post) and I just built another one for a friend who wanted one. This time I etched the front with control labels. The silly lizard poking his tongue out is a bit of an inside joke and he's also a big tumbleweed fan who have a song called silver lizard. Here's the process:
> 
> etchant mask
> 
> ...


This is one of my favorites so far. Very nice and clean.


----------



## Swashinxzero

Are people still building these? Ive been looking at diy amps and (not that its a issue at all) the starving student is a pretty old design right? How is the amp details wise with a hd600?
If i understand it correctly the 19j6 tubes are not cheap anymore and im in eu sooo... rip, ive seen people modify the amp to use different tubes, wont this result in not ideal performance due to it being designed for th 19j6's originaly?
If different tubes can work just as fine are there any tubes available in europe anyone would recomend for using in a starving student build?

ps. if im being rude or anything pls let me know... first time posting in the first forum ive ever joined..


----------



## ThermalAlchemy

Swashinxzero said:


> Are people still building these? Ive been looking at diy amps and (not that its a issue at all) the starving student is a pretty old design right? How is the amp details wise with a hd600?
> If i understand it correctly the 19j6 tubes are not cheap anymore and im in eu sooo... rip, ive seen people modify the amp to use different tubes, wont this result in not ideal performance due to it being designed for th 19j6's originaly?
> If different tubes can work just as fine are there any tubes available in europe anyone would recomend for using in a starving student build?
> 
> ps. if im being rude or anything pls let me know... first time posting in the first forum ive ever joined..



http://www.diyforums.org/SSMH/SSMHoverview.php

this is the original website for Pete millet For the starving student headphone amp

https://diyaudiostore.com/products/starving-student-ii

This is the new location at do it yourself audio.com website store with the newest version and new tubes

         I believe on Pete Millets website he had a alternative tube that was used I believed it was a 12AU very common not expensive at all. 
        I believe on his personal website you can download the Gerber files or the schematics and build your own board on Proto board or etch your own PCB. 
         I own and have built the very original with the unobtainable vacuum tubes and it’s an excellent match for the SeenHeiser HD 650 headphones

       You can also go to Pete’s Ebay online store look for pmillite and through one of these above sources you could go directly to his.com website to read more


----------



## tomb

Swashinxzero said:


> Are people still building these? Ive been looking at diy amps and (not that its a issue at all) the starving student is a pretty old design right? How is the amp details wise with a hd600?
> If i understand it correctly the 19j6 tubes are not cheap anymore and im in eu sooo... rip, ive seen people modify the amp to use different tubes, wont this result in not ideal performance due to it being designed for th 19j6's originaly?
> If different tubes can work just as fine are there any tubes available in europe anyone would recomend for using in a starving student build?
> 
> ps. if im being rude or anything pls let me know... first time posting in the first forum ive ever joined..


ThermalAlchemy pretty much summed it up above!

However, if you are interested in the original without the 19J6 tubes, the 12AU7 change has been successfully built by many on the forum.  I'm pretty certain the 12AU7 version works a bit better than the 19J6 version, simply because the 12AU7 is a much better tube.  That schematic, with its very few changes, is documented here: http://diyforums.org/SSMH/SSMHvariants.php.  Given the simplicity of the circuit, changing to another tube does not have a bad effect on sound quality.  It might be different if the circuit was more complicated and highly optimized for a single tube type.  Personally, I'd settle on the 12AU7 and go from there.

Remember that the entire theme of Pete's original design was _Starving Student_.  He chose the 19J6 tube because at the time, it was $2 each (even less if bought in volume).  Fortunately or unfortunately - depending on how you look at it - the design became so popular that stocks of 19J6 tubes were bought up everywhere within a year or two.  Now, it's become a rare tube.  No dealer has them in stock in useful numbers (100 or more) anywhere.  So, given the laws of supply and demand, the price went up - so much so that the more expensive (and plentiful) 12AU7 became an economic alternative.  Use of the 12AU7 is not all because the 19J6 is scarce/expensive; it's also an inherently better tube, period.

The downside is that you are locked into about $30 for a pair of tubes (or much more, if you want to spend it).  That's almost the same price as the entire Bill Of Materials (including the original 19J6 tubes) when Pete first design the amp: $35.80 (minus casework).

That said, Pete's new Starving Student design attempts to hearken back to that original premise, with another type of inexpensive tube.  You have lots of choices - all of them good.


----------



## Swashinxzero

tomb said:


> ThermalAlchemy pretty much summed it up above!
> 
> However, if you are interested in the original without the 19J6 tubes, the 12AU7 change has been successfully built by many on the forum.  I'm pretty certain the 12AU7 version works a bit better than the 19J6 version, simply because the 12AU7 is a much better tube.  That schematic, with its very few changes, is documented here: http://diyforums.org/SSMH/SSMHvariants.php.  Given the simplicity of the circuit, changing to another tube does not have a bad effect on sound quality.  It might be different if the circuit was more complicated and highly optimized for a single tube type.  Personally, I'd settle on the 12AU7 and go from there.
> 
> ...




Thank you !! both of you! 

looks like im prob gonna start planning a SS build around the 12au7 (*ECC82 in eu i think ?*) tubes. my electrical knowledge is literally rudimentary at best so this is gonna take a while 

Thanks again!


----------



## FIz3r0

I know I'm a bit late, but I recently built my first Starving Student with 12SR7 tubes instead of the 19J6. I swapped all the capacitors and resistors according to a schematic I found here. Did a couple modifications (adding a 3.5mm input and changing the Pot to 100k since my 50k was faulty on arrival), shouldn't be the problem though. Anyway, it works, but the bass is non-existent. It's like the volume for frequencies below ~800 Hz Drops linearily. It sounds weird, and kind of cool on some instrumental songs, but obviously not what I was hoping for.
Can post pics if needed.
I'm also very new to audio and DIY, so any help would be appreciated.


----------



## Tjj226 Angel

FIz3r0 said:


> I know I'm a bit late, but I recently built my first Starving Student with 12SR7 tubes instead of the 19J6. I swapped all the capacitors and resistors according to a schematic I found here. Did a couple modifications (adding a 3.5mm input and changing the Pot to 100k since my 50k was faulty on arrival), shouldn't be the problem though. Anyway, it works, but the bass is non-existent. It's like the volume for frequencies below ~800 Hz Drops linearily. It sounds weird, and kind of cool on some instrumental songs, but obviously not what I was hoping for.
> Can post pics if needed.
> I'm also very new to audio and DIY, so any help would be appreciated.



We will need a schematic. 

Right off the top of my head, I would check the value of your output capacitors. They should be like ~300-400uf. The stock schematic says to use 150uf capacitors, but that will only work with higher impedance headphones.


----------



## FIz3r0

Can't figure out how to post pics right now, linking from imgur gives me an error message. Maybe because I don't have enough posts.
I used Logistics' schematic (only changes being the mods).
The output caps are electrolytic ~400uF ones. Actually, I'm using 3 capacitors wired in parallel for left and right. Don't know if that makes a difference.

 Used to have 150 uF, but it didn't change much from what I could hear.

My headphones are 250 Ohm (DT1990s)


----------



## Tjj226 Angel

FIz3r0 said:


> Can't figure out how to post pics right now, linking from imgur gives me an error message. Maybe because I don't have enough posts.
> I used Logistics' schematic (only changes being the mods).
> The output caps are electrolytic ~400uF ones. Actually, I'm using 3 capacitors wired in parallel for left and right. Don't know if that makes a difference.
> 
> ...



I see lots of potential spots where you could loose high frequency, but not bass. 

Best I could recommend is to start measuring each solder point for voltage. Make sure you give the tubes a minute or two to warm up. Also triple check that the voltage from your power supply is 48v.


----------



## tomb (Jun 4, 2020)

FIz3r0 said:


> Can't figure out how to post pics right now, linking from imgur gives me an error message. Maybe because I don't have enough posts.
> I used Logistics' schematic (only changes being the mods).
> The output caps are electrolytic ~400uF ones. Actually, I'm using 3 capacitors wired in parallel for left and right. Don't know if that makes a difference.
> 
> ...



The output MOSFETs are capacitively coupled to the tubes.  That capacitor is critical for proper bass response.  In the 19J6 and 12AU7 version, that capacitor is 0.1uf and 0.22uf, respectively.  It could be that the 12SR7 needs a much bigger cap to connect to the MOSFETs.  Generally, there's not much of a downside to making it bigger, except for room.  Film caps get very big quickly.  Maybe you could get your hands on a 1uf film capacitor just to try?

Just curious also - why three electrolytics in parallel for each channel's output capacitor?  If they are all 400uf each (should be 470uf?), there is no perceived advantage to that.


----------



## FIz3r0 (Jun 4, 2020)

The only other caps I have are 100uF and 220 uF electrolytic caps. Would that be a problem?
Also, I've wired it point to point in a stiff cardboard-type box. It crackles when being moved and sometimes the right channel cuts out, which I can temporarily fix by tapping the amp. Tubes also crackle upon being touched and the amp turns off when I try to open it or move any wires.
How hot can the Mosfets run before it becomes a problem? I think my heatsinks might be a too small, they become so hot I can't touch them for longer than a split second.
I use three caps in parallel that are about 130 uF each because as far as I know, the capacitance of each individual cap is added together, so I'd get slightly less than 400 uF per channel. I use this simply because I don't have any other caps.


----------



## FIz3r0

tomb said:


> The output MOSFETs are capacitively coupled to the tubes.  That capacitor is critical for proper bass response.  In the 19J6 and 12AU7 version, that capacitor is 0.1uf and 0.22uf, respectively.  It could be that the 12SR7 needs a much bigger cap to connect to the MOSFETs.  Generally, there's not much of a downside to making it bigger, except for room.  Film caps get very big quickly.  Maybe you could get your hands on a 1uf film capacitor just to try?



I have now changed the 0.1uF film caps to 100uF electrolytic ones, and it all seems to work now! Thanks for that!
BTW, is there any downside to using electrolytic caps instead of film caps here? I'm not going to get my hands on any right now, but I might order some when I start ordering stuff for my next project.
Also, my dad says that using electrolytic caps in the output stage isn't good, but I've never noticed anything. Any merit to that?


----------



## Tjj226 Angel

FIz3r0 said:


> I have now changed the 0.1uF film caps to 100uF electrolytic ones, and it all seems to work now! Thanks for that!
> BTW, is there any downside to using electrolytic caps instead of film caps here? I'm not going to get my hands on any right now, but I might order some when I start ordering stuff for my next project.
> Also, my dad says that using electrolytic caps in the output stage isn't good, but I've never noticed anything. Any merit to that?



You shouldn't use 100uf for the coupling capacitors. It won't hurt anything, but a film cap will sound a lot better. 

If increasing the value fixed your problem, then you should try using 0.47uf film capacitors. Maybe even 1uf if you can find a good deal on some.


----------



## tomb

FIz3r0 said:


> I have now changed the 0.1uF film caps to 100uF electrolytic ones, and it all seems to work now! Thanks for that!
> BTW, is there any downside to using electrolytic caps instead of film caps here? I'm not going to get my hands on any right now, but I might order some when I start ordering stuff for my next project.
> Also, my dad says that using electrolytic caps in the output stage isn't good, but I've never noticed anything. Any merit to that?


Remember that it's a Starving Student amplifier, so some shortcuts have been taken.

Basically, there are several types of capacitor construction.  One is electrolytic, another is film.  Electrolytics, quite frankly, are the only technology that can economically produce uf's in the hundreds.  So, electrolytics range in size from about 10uf to 2000uf or more.  Film caps range from about 0.01uf to 10uf.  A polypropylene or polyester film cap of 10uf is about the size of half a pack of cigarettes.  A film cap of 150uf might be as big as a typical headphone amplifier.  Some people have built amps with film caps that big - by paralleling more than a dozen 10uf caps together.  That's an extreme case, but you can see why film caps are limited to lower values of uf.

So, as you essentially asked, "What's the difference?"  Well, electrolytic capacitors do wonders for power supplies, but when you put one in the signal path - they sound like a dog's rear-end.  Electrolytic capacitors are reasonable size for many hundreds of uf's, but they are slow and add significant distortion to audio high-frequencies.  They're fairly OK for bass frequencies, but that's mostly because the human ear typically doesn't discern a lot of detail in lower bass frequencies.  It's more of an impact feel, rather than nuanced detail.

You will see electrolytic capacitors made in special "audio-quality" selections.  These versions of electrolytic capacitors are almost always more expensive, but less effective in power circuits.  Their ESR is higher than other electrolytics and their ripple current ratings is much lower.  Both of those qualities are important in power circuits, but less so in audio signal circuits.  Typically, mfrs don't even publish the ESR and Ripple Current specs for those caps. So, audio-quality electrolytic capacitors are designed to sound better, but not necessarily sound that great. Some of the more notable audio quality caps are Nichicon Muse KZ, ES, FG, etc.  Elna Silmic RFS II and Elna Cerafines are also great audio-quality electrolytic capacitors.  Black Gates used to be the Holy Grail of electrolytic audio capacitors until they quit being made.  I've found that Elna Silmic RFS II capacitors are every bit as good, though. 

Film caps, on the other hand, sound better than any other type of capacitor in the signal path.  It's difficult to put a number on things like this, but let's just say that film caps probably - on average - _sound 10 times better than any electrolytic capacitor_ - audio-quality electrolytics, included.  Even so, there are special audio-quality film caps available, too.  In fact, the most expensive capacitors for audio applications are boutique, audio-quality film caps.  They can run into the $hundreds of dollars for something like a 10uf capacitor.  That said, there are many film capacitors that are used for their speed in power supplies, but can sound quite good in an audio application - certainly, better-sounding than ANY electrolytic capacitor.  These are typically box-style film caps like WIMA MKP10, FK4, or similar box film caps like Vishay-Roederstein and Epcos.  You can find these capacitors for a few dollars each in sizes like 1.0uf.  They won't sound as good as a Dueland or Jupiter, but will blow away any electrolytic capacitor in terms of sound quality.


----------



## jeanba3000 (Oct 10, 2020)

Hi
I had the components in a drawer since 2009, the confinement gave me some time to complete this project !
So here are some pictures of the finished product















The sound is nice but not impressive due to my old Sony CD1700 headphones : lack a bit of bass and too much highs, I tried with some cheap AKG IEMs with a more bassy (and muddy) result so I think now I need a new pair of better headphones ! (don't tell my wife) ;-D

Anyway I'm glad I finally did it, I designed and made the PCB, I milled the holes on the enclosure faces and the heatsink for the tubes, the volume knob cavity was the difficult part.
The power supply is integrated and the global design matches my UGS pre-amp (its face was milled by a pro), even if the Starving Student will be standing on my desk connected to my computer, not near my main hi-fi system.

Thanks again for Pete Millett and all the great people involved in helping the community all theses years on this thread, you helped a lot as I read all the 484 pages to be sure to not miss an information !

Place to the music now


----------



## marcus76 (Jan 3, 2021)

Happy New Year!!
This looks really nice and pretty similar to what I had in mind...I built one years ago (p2p) which still works perfect and still have two of FredFred's pcb...

Found a pretty cheap enclosure (around 19 € incl. shipping) which has all holes needed already milled. This has the "cold device power socket" aswell but without the switch and I thought about integrating the original Cisco power outlet into the enclosure.

Did you use a custom one ? Would it introduce something (noise or ?) I don't want ?? Would be a pretty tight fit with FredFred's Pcb + Power but I'd like to try 
Something like this



internal dimensions of the case : 108mm wide X 42mm high X 130mm deep


----------



## jeanba3000

Hello everyone

I'm building another SS with a slightly redesigned PCB, basicaly a little smaller, and it doesn't work, the tubes don't glow and no sound or any noise comes from the headphones : 
the power supply delivers 48V,
I checked resistor values, shorts, I checked and rechecked my circuit compared to the schematic
I measure 48V on the drain and ~23.5V on the source of both IRFs
I tried two pairs of tubes including the ones from the working SS I posted above, no difference

Any clue ?


----------



## baseonmars

jeanba3000 said:


> Hello everyone
> 
> I'm building another SS with a slightly redesigned PCB, basicaly a little smaller, and it doesn't work, the tubes don't glow and no sound or any noise comes from the headphones :
> the power supply delivers 48V,
> ...



Are the LED’s wired correctly? Positive / Negative the right way around. They should be on the tube side of the board inside the tube sockets.

A picture of the board may help.


----------



## jeanba3000

There is no led on my version, here is my circuit drawing and photos of both sides :
It's a double sided PCB with a ground plane on one side, 10x10 cm
IRFs and tube sockets are mounted on the opposite side from the components side


----------



## tomb (May 16, 2021)

I believe you have the MOSFETs reversed.  Pin 1 (the Gate pin on your PCB/schematic), which should be directly connected to R3, is the pin on the LEFT side of the MOSFET when facing the plastic body with the tab in the back.  It appears you have them reversed from that.  Your schematic is correct, but the build photo has Pin 1s connected to the tube/C3/C3A for the Right channel and tube/C5/C5A for the Left channel.


----------



## jeanba3000

Yesss ! You're right !
Comparing to my previous schematic, I reversed the R3/R9 and the opposite path connexions to the IRFs


----------



## tomb

jeanba3000 said:


> Yesss ! You're right !
> Comparing to my previous schematic, I reversed the R3/R9 and the opposite path connexions to the IRFs


Glad I could help!


----------



## Andy Mac

Having been away from this scene for a while I decided to dig out the SS and crank it up again…. Sounds SO sweet through my Grado’s…
I got to thinking that I would like to pair this little amp with a power amp so I can play music through some loud speakers instead of headphones.
What I would like to do is build my own power amp using tubes and solid state output along the same lines as the SS.
I don’t want transformers unless I really have to.
My end goal is to have the Starving Student drive a power amp into speakers all hand built by me…. Something to hand onto the kids one day…
Any ideas where to start with this power amp project?


----------



## Amatsu (Nov 14, 2021)

Does anyone have any idea why the Cisco power supply enters protection mode after 1-2 hours? It just started happening all of the sudden, I have to disconnect the power supply and wait a minute. The amp works fine, it just turns off all of the sudden, I also notice the power supply is quite hot and maybe a bit of a smell.

This is already the second power supply I bought, the first one I remember was also getting very hot eventually.

I'm using this version of the amp: https://i.imgur.com/LcKo3of.jpg with a pcb.

Thank you.


----------



## tomb

Amatsu said:


> Does anyone have any idea why the Cisco power supply enters protection mode after 1-2 hours? It just started happening all of the sudden, I have to disconnect the power supply and wait a minute. The amp works fine, it just turns off all of the sudden, I also notice the power supply is quite hot and maybe a bit of a smell.
> 
> This is already the second power supply I bought, the first one I remember was also getting very hot eventually.
> 
> ...


I believe unless you connect R3 and R9 directly to their respective MOSFET pins, the MOSFETs will oscillate.  Oscillation may cause the circuit to draw much more current than normal, potentially heating things up and perhaps exceeding the power supply's current rating.

There could be other reasons, but assuming you're not just unlucky in buying the Cisco power supply, drawing too much current could cause what you're experiencing.  I doubt that it's a direct short; that would cause things to react much more quickly.

On the other hand, it's not unheard of to have a bad power supply,  In selling all the SSMH kits I have, I've run across 2 or 3 dead power supplies.  That's not many by comparison to the numbers I sold.  Still, all of the Cisco power supplies are used, so defects should be expected every once in a while.  Happening twice to you?  That's not likely, but still possible.


----------



## Amatsu

tomb said:


> I believe unless you connect R3 and R9 directly to their respective MOSFET pins, the MOSFETs will oscillate.  Oscillation may cause the circuit to draw much more current than normal, potentially heating things up and perhaps exceeding the power supply's current rating.
> 
> There could be other reasons, but assuming you're not just unlucky in buying the Cisco power supply, drawing too much current could cause what you're experiencing.  I doubt that it's a direct short; that would cause things to react much more quickly.
> 
> On the other hand, it's not unheard of to have a bad power supply,  In selling all the SSMH kits I have, I've run across 2 or 3 dead power supplies.  That's not many by comparison to the numbers I sold.  Still, all of the Cisco power supplies are used, so defects should be expected every once in a while.  Happening twice to you?  That's not likely, but still possible.




Interesting, can I test the current with the multimeter? At what point would be best? 

The mosfets are connected with cables to the pcb, maybe I should connect them directly to the pcb.


----------



## tomb

Amatsu said:


> Interesting, can I test the current with the multimeter? At what point would be best?
> 
> The mosfets are connected with cables to the pcb, maybe I should connect them directly to the pcb.


Most likely, that's your problem.  Pete warned, in the very first couple of posts in this thread, I believe, that those resistors must be connected directly to the pins, otherwise oscillation will result.  That's probably causing the amp to draw too much current and burn out the Cisco power supplies.


----------



## Amatsu

tomb said:


> Most likely, that's your problem.  Pete warned, in the very first couple of posts in this thread, I believe, that those resistors must be connected directly to the pins, otherwise oscillation will result.  That's probably causing the amp to draw too much current and burn out the Cisco power supplies.



I connected R3 and R9 directly to the pins but it didn't make a difference unfortunately, power supply still turned off after around 2 hours. 
I tested the current and it was drawing 0.28A. (This PSU is rated at 0.38A).


----------



## tomb

Amatsu said:


> I connected R3 and R9 directly to the pins but it didn't make a difference unfortunately, power supply still turned off after around 2 hours.
> I tested the current and it was drawing 0.28A. (This PSU is rated at 0.38A).


Well, it was only a guess.  If that's the case, then maybe you've been plagued with two-in-a-row bad power supplies.


----------



## Amatsu

tomb said:


> Well, it was only a guess.  If that's the case, then maybe you've been plagued with two-in-a-row bad power supplies.


Well I appreciate your responses anyway, at least I fixed the resistors .  Maybe I'll try to find a higher rated psu, I think the_equalizer had a 1A cisco psu.


----------



## Dean N. (Jan 14, 2022)

Hi everyone,

I have been inactive for some time, and my 12au7 SSMH project never got off the ground. I'm restarting the project. At risk of sounding like every lazy user on every forum ever, could someone please direct me to an updated BOM for this?  The one I have seems to be missing R14 and R15 and is quite old. I've read through this monster thread (again) and the threads on other sites too, but I'm having no luck finding a reliable-looking BOM. I'll be using Fred's 3x3 PCB and a wood case.

Edit: Nevermind, I think I have the BOM info I need. I would, however, like to hear any wisdom you may have about building in a wood case regarding shielding and grounding. Do you simply shield the entire inside say, like a guitar cavity?   

Thanks for any help!


----------



## tomb

Dean N. said:


> Hi everyone,
> 
> I have been inactive for some time, and my 12au7 SSMH project never got off the ground. I'm restarting the project. At risk of sounding like every lazy user on every forum ever, could someone please direct me to an updated BOM for this?  The one I have seems to be missing R14 and R15 and is quite old. I've read through this monster thread (again) and the threads on other sites too, but I'm having no luck finding a reliable-looking BOM. I'll be using Fred's 3x3 PCB and a wood case.
> 
> ...


Shielding would probably have minimal effect, since the tubes are typically totally exposed and they represent the greatest antenna for cell phones and other various interferences.  You may be thinking of the need to shield components from AC voltage (60Hz hum) in a guitar amp.  The Starving Student uses a DC brick power supply, so that's not in play here.


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## treydufrene

Built one of these PTP a couple years ago. Grabbed it out of storage and have found a slight hum (seems to be electrical noise, persistent across sources) mostly when the pot is not 100% turned "up."
Going to open it up to check it out this weekend but if anyone has tips for what to look for that would be helpful. Currently my inclination is the pot is bad/not shielded well?


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## tomb (Feb 3, 2022)

treydufrene said:


> Built one of these PTP a couple years ago. Grabbed it out of storage and have found a slight hum (seems to be electrical noise, persistent across sources) mostly when the pot is not 100% turned "up."
> Going to open it up to check it out this weekend but if anyone has tips for what to look for that would be helpful. Currently my inclination is the pot is bad/not shielded well?


If the hum disappears when you touch the pot, then the case or shaft needs to be grounded (depends on the pot how you do that).  If the hum is still there when you touch the pot (volume knob), then look elsewhere.  I doubt seriously that a pot could ever induce hum if it's not a grounding issue.

Maybe a capacitor dried out while it was in storage?  Or, the power supply could be going bad from age (maybe caps drying in the power supply).  The original Starving Student power supply was a VoIP Cisco brick supply and *all of them* _*were used*_ when purchased.

Finally, storage might have allowed a dodgy solder connection (likely to ground) to come loose or corrode enough to cause a problem.


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## vlads

In the kit from beezar the pcb is effectively mounted upside down, but would that not make the potentiometer work by turning it anticlockwise to turn up the volume and vice versa? Thanks in advance.


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## tomb

No.  It only makes the 0 and 100٪ position at the top, instead of bottom.  The knob/pot still turns the same way.


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