# Millet Starving Student Build



## rds

I thought I'd detail my build of some starving students as some of the information may be useful to other people building diy amps without panel layouts or pcbs.







 My ad hoc work station in a guest room (didn't do the casework here 
	

	
	
		
		

		
		
	


	




)






 You can't really tell from this picture but I've used 5mm graphing paper to draw the layout for the top of the amp. I then taped this layout onto the metal panel with painter's tape and used a center punch to mark the holes. 
 Then I drilled the panel (shown top) with a small bit (exact size isn't important). After the intial holes were drilled I covered the panel with painter's tape (to protect it from scratches / shown left) and punched out the holes by hand using the small drill bit.






 Here are the cases with the metal work completed. I am showing the back of the panels to show where I've used a dremel to expose bare metal for grounding. One grounding spot is for one of the rca ins, one is for the top of the case and the other two are for the pot and the headphone jack. Yeah, it's a little overkill, but imo proper grounding is a good place to go a little overkill.
 Also, keep in mind if you're using an active ground you don't want to ground the headphone jack. This amp is two channel, so this configuration is best.






 Bottom right of this image is the board so far. Left is the same with various capacitors missing to show what's going on. 






 Heavy vice grips are great for holding things like this for soldering. The trick is to use the absolute minimum pressure. With a little practice it is very quick and easy. 
 Here I've trimmed the bottom of the phone jacks (space restrictions 
	

	
	
		
		

		
		
	


	




 ) and am soldering the wire connections as this will not plug into my board.






 The completed board without the output caps or power and rca wires. Notice I'm using the same wima .22 uF mkps I used for coupling to bypass the output caps. The result is very nice.






 The rear panel with rca and mini plug inputs. I've put the C1 filter cap here, since there is no room on the board.






 There's been a few questions as to how you use thermafilm. This is the best method (read safest). Grease to heatsink, thermafilm, grease, mosfet. In this case the mosfet is isolated from the heatsink.







 The finished rear panel. I'm missing a couple screws here as I this was still in the testing phase. Notice the switch on the top left. That is the gain switch which uses parallel resistances to attenuate the input. There's a few good reasons to have this switch. The obvious one of using different headphones. But I've also found low gain is good for AKGs when you want to listen quietly as it gives you a lot more sweep. On the other hand the high gain is good even with grados when using a weak source like an ipod.







 This is how I wired the "gain" switch. Those resistor values give the amp a good range of amplification for a large range of headphones.








 I love these glowing pictures ...too bad I don't have a better camera. Here the amp is running from a mini plug from the ipod.






More pictures and information here
 Well that's it.
 I'm really happy with the final build. Partially I'm impressed with myself for fitting all this in the tiny case. But mostly I'm impressed with how good this amp sounds. 
 Try this one out, you won't regret it ...unless you try my version. In that case there's a good chance you will regret it. Fitting all this in an enclosure this small is not easy. 

 Thanks again Pete!


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## J.D.N

Very nice work rds, looks like the start of a great tutorial and some great amps!


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## jonjon0nline

Quote:


  Originally Posted by *J.D.N* /img/forum/go_quote.gif 
_Very nice work rds, looks like the start of a great tutorial and some great amps!_

 

+1 on the tutorial! The cases look awesome.


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## malldian

This is great. I will be using it to help me when i start my build for sure.


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## Spasticteapot

Very nice workmanship!

 Everything I make on stripboard either looks awful or shorts out and catches fire.


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## jonjon0nline

If you can make a DIY with these builds you'd be a GOD.


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## pabbi1

Quote:


  Originally Posted by *jonjon0nline* /img/forum/go_quote.gif 
_If you can make a DIY with these builds you'd be a GOD._

 

Well, here is proof - no if involved.


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## jonjon0nline

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Well, here is proof - no if involved._

 

Ah yes, I've seen the thread. I meant a DIY guide for us noobs


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## fierce_freak

Very nice.


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## rds

Well that's it


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## FallenAngel

Very nice, thanks for the build log, now I'll have to build one


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## m0b1liz3

So what did your costs come out to for one amp with the nice enclosure? Esthetically that looks like one of the best looking HP amps. It is small and compact and shows off the tubes while still looking fairly professional. Exactly what you want for a desktop amp.


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## rds

$108 shipped to Canada with 4 tubes.
 But keep in mind I added stuff and bought expensive things. You could do it cheaper, but if you're paying $22 just for the case it doesn't really make sense to go cheap on the other stuff.


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## hax

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Notice the switch on the top left. That is the gain switch which uses parallel resistances to attenuate the input. There's a few good reasons to have this switch._

 

This part is confusing. Is that really a gain switch?


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## rds

Strictly speaking the switch does not change the gain. It attenuates the input signal. The gain of the tubes is constant.






 So when the switch is open there is 261k in series with the pot. When the switch is closed there is 22.8 k in series with the pot. 
 I found these resistance values work well with this amp to suit a large range of uses. You may prefer other values.


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## jamess71

Nice work rds. Thanks for the nice pics during the build. 

 Is there any loss in SQ using that type of input attenuater?

 James


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## Phenic

Impressive job.


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## trains are bad

Quote:


 So when the switch is open there is 261k in series with the pot. When the switch is closed there is 22.8 k in series with the pot. 
 

Why would you do this, instead of just turning the volume down? Is it in aesthetic preference to have the knob somewhere in the middle of it's swing?


 What alterations to the SS circuit would improve bass with K701s? Bigger output coupling caps? Something tells me 220uF is plenty with such high-impedence phones, but just checking.


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## kilgoretrout

I'm seriously considering building this amp. What exactly do you mean by this:
  Quote:


 Also, keep in mind if you're using an active ground you don't want to ground the headphone jack.


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## Postal_Blue

The quote does not apply to this amp. If you were building a more complex circuit that uses active ground, of which there are many examples mini 3 M^3, CKK3 to name a few, than this would be a concern.


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## JamesL

Really nice work rds. The best starving student build I've seen so far.
 I don't think I could bring myself to use what looks like vishays and wimas for a build thats meant to cost $25 though. $108 is starting to get dangerously close to what a Millet Hybrid Max costs...


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## rds

Quote:


 Why would you do this, instead of just turning the volume down? Is it in aesthetic preference to have the knob somewhere in the middle of it's swing? 
 

It's not an aesthetic preference, it is because this is where the pot tracks best. That means in this area the channel resistances are most closely matched. 
 Try turning your pot down around 10 o'clock. You will hear the imbalance very clearly.

  Quote:


 What alterations to the SS circuit would improve bass with K701s? Bigger output coupling caps? Something tells me 220uF is plenty with such high-impedence phones, but just checking. 
 

The k701s are not high impedance. Their impedance is 62 ohms. Off the top of my head, with those caps, that puts the cutoff around 12 hz. 
 I've found 470 uF is a good value. That would give a cutoff around 6 Hz.
 However, the most likely cause of the lacking bass is that akgs are not bass heavy headphones.


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## fierce_freak

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_$108 is starting to get dangerously close to what a Millet Hybrid Max costs..._

 

There are those silly ones amongst us that will spend more on the SStudent than what some spend on a Max ;D


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## rds

I don't think there's any chance of building this for $25. Even if you're in the US you're going to end up paying around $20 in shipping (You need to order stuff from at least 3 different sources).
 If you're using a free enclosure and you're in the US expect to pay at least $50 shipped.
 But why not double that cost while you're at it


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## m0b1liz3

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I don't think there's any chance of building this for $25. Even if you're in the US you're going to end up paying around $20 in shipping (You need to order stuff from at least 3 different sources).
 If you're using a free enclosure and you're in the US expect to pay at least $50 shipped.
 But why not double that cost while you're at it 
	

	
	
		
		

		
		
	


	


_

 

Which is why it would be nice if Glass Jar Audio could source the parts for us in one simple kit!


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## trains are bad

Quote:


 It's not an aesthetic preference, it is because this is where the pot tracks best. That means in this area the channel resistances are most closely matched.
 Try turning your pot down around 10 o'clock. You will hear the imbalance very clearly. 
 

Oh I see. I never noticed any imbalance but that makes sense. What pot did you use?


  Quote:


 The k701s are not high impedance. Their impedance is 62 ohms. 
 

Oh. I thought they were higher. Guess I didn't know my own phones.


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## rds

Quote:


 What pot did you use? 
 

I used the Alpha pot Pete has in the BOM (part #: RV122F-20-15F-A50K)
 I've found it tracks really well from 9 to 3 o'clock. Below 9 o'clock the tracking is very poor (all taper pots are bad in this area). This is best reason to have a "gain" switch if you're using efficient headphones.


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## bhjazz

Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_There are those silly ones amongst us that will spend more on the SStudent than what some spend on a Max ;D_

 

Myself included. I think the beauty of the design is it's simplicity: for me, I can look at the parts and decide if or where I would want to upgrade. Also, if you have most of the parts around already, and those happen to be Vishays or something...use 'em! I'll admit my current parts list is at around $60, but I opted for an extravagant $18 Context Engineering case.


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## fierce_freak

My parts list is stupid really, but I don't care. As I mentioned elsewhere I plan to build two of them, one boutique, one using Pete's BOM for actual starving students and compare.

 For the boutique, I'm planning to use PRP resistors in all positions, JJ 550uF 385v caps for the filtering caps, Wima MKP2's for the interstage coupling, and Blackgate WK power tank caps for output (bypassed with either VitQ's or MKP1837's). I'm also either using an Optivol or a TKD pot. I've got the layout figured and will just be waiting a few weeks to get some other projects out of the way before ordering.

 Anyone have any suggestions on possible changes for the boutique version?


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## rds

Quote:


 Anyone have any suggestions on possible changes for the boutique version? 
 

Put a film cap in the 0.5 uF range in parallel with C1
 Use around 500 - 800 uF for C6
 You could try to find a higher current regulated power supply
 How about 3 channels? Just add another tube and mosfet for the ground. In this case you will definitely need a higher current ps.


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## fierce_freak

I do plan on using a higher current PS, though I'm undecided on regulated or not. The ground is a neat concept, but my current case choice and layout won't allow it. I'll consider it though ;D


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## holland

I don't really think regulation is completely necessary on this build. If you look at the circuit, the FETs are filtered by C and the circuitry is filtered by a CRC for reduced ripple. I would probably put a choke on it and make it a CLCRC for the circuitry and a CLC for the FETs...or a CLRCRC.

 You can probably build a "ripple eater" as well or go simple with a shunt type regulator. I'm thinking about upgrading mine as well, but I'm not sure which way I'll go yet.

 I'm not sure if it matters entirely, but you may want to hang a larger cap off the drain pin of the FETs and bypass it if your run from C1 is "long". I would put the bypass of C1 on the FETs directly and bypass C6 if you don't "need" a cap on the FET.

 You can make C1 and C6 relatively large. C1 can probably be 1F depending on your PSU. C6 can be large as well with no adverse affects. I currently use 1mF for both C1 and C6.

 have you found a replacement fet?

 optivol sounds interesting.


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## rds

I guess I'll keep updating the original post with additional information. If someone has a question I can add the answer to the op. 
 I think doing a complete part by part build guide for this one would be too involved for me to do right now.


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## fierce_freak

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I don't really think regulation is completely necessary on this build. If you look at the circuit, the FETs are filtered by C and the circuitry is filtered by a CRC for reduced ripple. I would probably put a choke on it and make it a CLCRC for the circuitry and a CLC for the FETs...or a CLRCRC._

 

I've thought about this too, but I don't think I have the room in my chosen case. Maybe I should consider using a larger case (currently have a 5x5x3 case chosen, with filter caps, heatsinks, and tubes sticking roughly 2" out of the top, giving me a 5x5x5 cube ;D).

  Quote:


 You can probably build a "ripple eater" as well 
 

I've never ran into this. Can you give me a quick explanation?

  Quote:


 I'm not sure if it matters entirely, but you may want to hang a larger cap off the drain pin of the FETs and bypass it if your run from C1 is "long". I would put the bypass of C1 on the FETs directly and bypass C6 if you don't "need" a cap on the FET. 
 

Maybe I'll add a bypass hanging off the drain just to be sure. The run won't be that long, but why not?

  Quote:


 have you found a replacement fet? 
 

I haven't looked yet, but I probably will shortly. Unless I get some pin sockets it'll be a pain in the ass to swap them out to compare. I'm hanging almost everything off the FET pins.


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## holland

Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_I've thought about this too, but I don't think I have the room in my chosen case. Maybe I should consider using a larger case (currently have a 5x5x3 case chosen, with filter caps, heatsinks, and tubes sticking roughly 2" out of the top, giving me a 5x5x5 cube ;D)._

 

Yep, with all your boutique stuff, it's really tight. My almost basic build (but with tubes inside) was tight as well, but I found some extra room by breaking from my initial intent. My case has an internal space of about 5.5x5x2.7 or 2.8.


  Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_I've never ran into this. Can you give me a quick explanation?_

 

Capacitance multiplier. Capacitance Multiplier Power Supply Filter

  Quote:


  Originally Posted by *fierce_freak* /img/forum/go_quote.gif 
_I haven't looked yet, but I probably will shortly. Unless I get some pin sockets it'll be a pain in the ass to swap them out to compare. I'm hanging almost everything off the FET pins._

 

I looked a bit, but not extensively and need to look at the datasheets to be sure. 2sk216 may work (pins are different), but I'm not sure how it sounds, and it's a bit on the pricey side. need to read the datasheets, to check on a few things.


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## holland

btw, it's used on some of AMB's amps (a smaller degree of it). Look on the power rails.


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## fierce_freak

Oh, I know it by that name. Thanks holland.


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## fierce_freak

IRF540 for FET maybe? As far as the FET goes...I'm not as knowledgeable about them as I'd like to be, but it seems that in this circuit as long as you have an N-channel mosfet that can handle the same the right voltage and current it will work...of course, that's not to say it'd be optimal (transfer characteristics and the like).


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## pabbi1

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Put a film cap in the 0.5 uF range in parallel with C1
 Use around 500 - 800 uF for C6_

 

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?


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## fordgtlover

How did you attach those heatsinks to the case?


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## rds

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? 
 

Don't waste your vitQ for this purpose. I used a film cap to lower the ESR to higher frequency ripples (any cheap film cap is good). These capacitors are just for reducing the noise in the power supply. You can use 470 uF or 680uF (or 150 uF as Pete recommended). Any of these are fine.
 BUT for c6 I recommend something big like 680 uF to reduce the power cycling when the amp turns on (Pete recommended this at some point a while ago).

  Quote:


 How did you attach those heatsinks to the case? 
 

I soldered washers to the pins on the heatsink.


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## fjc

ok a quick question , i want to make one of these hybrids as my next proyect. but would it be possible to "replace" the fet output stage with a class A MOSFET circuit as the  Szekeres  , also would it be possible to make it double as a starving student preamp to drive a gainclone power stage

 francisco


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## utilisateur

You'd be better off in the original thread with those questions i think, and the answers can be found in there aswell..

 It was said the gain was to high to use it as a preamp, this design is just not intendet to be used in this way.

 For your question about combining it with with a szekeres output stage you'll get better answers if you ask in the original thread but i think you'd have to significantly alter the circuit to the point were you're better off with something different(pretty much the same reason as using it for preamp).


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## scompton

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I don't think there's any chance of building this for $25. Even if you're in the US you're going to end up paying around $20 in shipping (You need to order stuff from at least 3 different sources).
 If you're using a free enclosure and you're in the US expect to pay at least $50 shipped.
 But why not double that cost while you're at it 
	

	
	
		
		

		
			



_

 

I ordered exactly what's on the BOM, and it came out to $52 from 4 vendors. I didn't buy a case so that may add something.


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## tomb

Quote:


  Originally Posted by *fjc* /img/forum/go_quote.gif 
_ok a quick question , i want to make one of these hybrids as my next proyect. but would it be possible to "replace" the fet output stage with a class A MOSFET circuit as the  Szekeres  , also would it be possible to make it double as a starving student preamp to drive a gainclone power stage

 francisco_

 

1st, you guys may want to continue using the original Pete Millett thread instead of this one. I think rds created it specifically for his builds of the SSMH. I'm not sure Pete watches this one for questions.*

 2nd, I think perhaps from your question you are assuming that the Szekeres is "Class A" and "MOSFET" while the Starving Student is not? Neither is true. The Starving Student's IRF510's are Power MOSFETs. Also, the Starving Student is most definitely CLASS A, as anyone who's felt the heat sinks on one can certainly attest.

 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!


 * By no means am I suggesting that you not post in rds' thread. He has an outstanding build interpretation of the SSMH and deserves support and kudos for it. I'm only _suggesting_ that _general_ questions about the Starving Student should be kept to Pete's thread, perhaps.


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## rds

Quote:


 I'm only suggesting that general questions about the Starving Student should be kept to Pete's thread, perhaps. 
 

I agree. 
 This is intended as an example of how to build one of these. I didn't want to hijack the original thread with all this stuff.


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## fjc

you´re all right sorry for the hijack, I´m taking my questions to the original thread.

 sorry again for the hijack
	

	
	
		
		

		
			





 Francisco


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## moonboy403

How does this sound compare to the Little Dot MKIII?


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## Drag0n

Quote:


  Originally Posted by *moonboy403* /img/forum/go_quote.gif 
_How does this sound compare to the Little Dot MKIII?_

 

I liked the Little Dot MK lll, when i heard it, but i heard it at a noisy meet on Sennheiser HD595's, and i plugged in my SR80, which im more used to, but it was noisy and hard to tell, but it was good.
 I dont have a comparo with the Mini Millet, but i can say i love it[Mini Millet]so far.

 The original RCA tubes sound good, but slightly shy in the bass, but the upper mids are clearer and more pronounced than the other 2 sets ive rolled.
 The mids are a bit more forward. 

 Switching to the Westinghouse, the highs get slightly warmer and rolled in comparison, but sweet and nice, and the bass is fuller and theres more of it, and its more pronounced,but it depends on the song which i would prefer.
 The mids are pulled back into a more natural position.

 With the CBS Hytron, everything is more tubey, smoothed over and would probably smooth over some rough spots on siblant recordings, players, etc.
 You kinda miss the edge of the highs and the definition of the mids a bit, but some people may prefer this sweeter sound.

 All this was listening on my PC with grado SR80's with Senn 414 pads ,Quarter-Modded. 
 The amp only has about 3 hours or so on it. The RCA tubes for 90% of it, and only tested the other two sets, so nothings really burned in. 

 Sweet little amp. Kudos RDS.


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## Akabeth

Wow that thing is tiny!
 I would like to hear one of these in the future

 Nicely done m8


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## fzman

beware of excessive leakacge current in the output caps, which will pu too much dc on the can's drivers. when in doubt, measure under load, with no signal. anything over a few mv of dc is probably too much!!!!


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## rds

Excessive leakage current? When has that ever been a problem?
 Also, this is best posted in the main starving student thread.


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## fzman

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Excessive leakage current? When has that ever been a problem?
 Also, this is best posted in the main starving student thread._

 

sorry if this is the wrong forum, but the point is that leakage current can put dv on your cans -- measure sometimes, and check the specs on various caps. this is more of a problem, i am told, with higher impedance cans.


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## rds

I hate it when I read a post of mine and realize that was kind of jerky. 
 I agree it is always best to measure and know for sure.


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## fzman

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I hate it when I read a post of mine and realize that was kind of jerky. 
 I agree it is always best to measure and know for sure._

 

no offense taken. imagine my surprise when in a cap coupled output, i had 22mv of dc!!!!! i didn;t figure this out myself, i was warned about it by someone far more knowledgable than i am. it is a problem though, with large value aluminum 'lytics. live and learn.


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## effcleff

I noticed a pair of k701s in your pictures. How do you like them with the Starving Student?


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## krisjan

WOW RDS - you are the meister! it looks so good - well i'm just starting to collect the parts now for my first starving student - i think i'll aim for some recycled container - nothing as pro-looking as this - but man it looks inspiring - and thanks for the close-ups. This build is a little more challenging than the cmoy, which was very step-by-step etc. on tangent's site...i'm so new on this - still trying to get my head around MOSFETs, tubes and all the tech jargon...wish me luck...k


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## digger945

rds, 
 Dude! I love your SS build! How appropriate to have the "Grant" beside for size comparison LOL, love it.
 How do you like the way it sounds?
 You gonna be a toob lover now?
 It's all good, aint it.


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