# Cavalli EHHA Embedded Hybrid Headphone Amp



## smeggy

I thought I'd get this thread rolling. This is another of Alex Cavallis amp designs which is available in kit form from Glass Jar audio. It's an interesting design and the basic kit is a very reasonable $110 or so plus shipping etc. 

 The amp also needs a PSU like the AMB Sigma 22 which is about another $100 or so. There are very few of these in the wild, though a small number of us intrepid explorers are putting a toe into the EHHA waters. Both Don and sachu have heard these and posted favorably on it. Sachu is currently building his and I'm shortly going to start mine 
	

	
	
		
		

		
			





 It's all very confusing for a DIY n00b like myself and I'll be asking plenty of questions along the way and posting impressions once completed. I'll be trying to log my progress and mistakes as I go, but first off, here's a pic of the raw kit (glass jar will send a BoM on request) as it arrived.






 The kit includes all components needed to populate two boards with parts, tubes, heatsinks and even a pot.

 If anyone else is interested in this amp or buys one, please join in the fun.


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## MrSlim

Hey Smeggy, Congrats on jumping into the deep end of the DIY pool.. I'm looking forward to reading about your experience, and hoping to find out more about the sound quality of the EHHA.


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## dBel84

I am sure this amp is going to receive a lot of love once there are a few more to be heard. 

 Here is the obligatory image of an early proto 
	

	
	
		
		

		
		
	


	









 ..dB


 EDIT: 

 Headwize link (for when the forum re-opens)
 &
Link to Steinchen's K1000 EHHA


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## sachu

*EHHA build count :*

 1> a balanced build completed by *wiatrob *(BJT version)
 2> passive ground SE by *Smeggy*
 3> same as above by *sachu*
 4> same as above by *digger945 *(but might be scaled to a balnaced soon as he has the parts)
 5> ongoing active 3 channel build from *Holland*
 6> ongoing passive ground SE from *rhester*
 7> planned balanced build from *MrMajestic2*
 8> planned 3 channel active ground from *wiatrob *(MOSFET version)
 9> ongoing 3 channel active ground from *Ferrari*
 10> 


 damn it!!..I wanted to start the thread 
	

	
	
		
		

		
		
	


	




 I love this amp. I mean i really love it. I am smitten by it as Don put it. 

 I have his amp on my desk as I type this out and mine as well in the final stages of completion. I heard this amplifier first 2 years ago at my first head-fi meet ever in Portland. Needless to say it made a huge impression on me. The orange stacker was there as well, but the EHHA made a bigger impression on me than the stacker. 

 However over time I have come to realise that the stacker is a very special amp indeed. Each of these two amps have tremendous potential and a lot going for them .

 While there has been a lot of excitement around the stacker for obvious reasons, I was dumbfounded to see that there was no info pertaining to this wonderful amplifier here on HF. I was told only 3 were in existence. Such a shame that beautiful elegant designs such as this one get lost in the hullabaloo until someone like me comes along and clears off the dust.
	

	
	
		
		

		
		
	


	




 I will get pics up later tonight on the progress of my build. I hope to get the amp up and running later this weekend. Hope everything goes well and the gremlins stay away.
	

	
	
		
		

		
		
	


	




 Smeggy, look forward to seeing your build take shape.

 I know that wiatrob is planning to make a 3 channel (active ground) version of the EHHA which should be something to look out for.

 here is a pic of Don's EHHA alongside his original Stacker!


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## digger945

Dang bubba, looking at the Cavalli website for a minute and looks like a HOT design. I didn't even know about it 'till I saw this thread.
 *checks wallet*

 Is yours the MOSFET version?


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## holland

^ was gonna ask. BJT or mosfet, or does GJA sell both?


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## digger945

I see the pcb at GJ but no kits. Maybe need to contact Jeff or just order my own parts.
 I can see now this will be a MUST build.
 *checks bank account* LOL


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## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I see the pcb at GJ but no kits. Maybe need to contact Jeff or just order my own parts.
 I can see now this will be a MUST build.
 *checks bank account* LOL
	

	
	
		
		

		
		
	


	


_

 

Yep..email and ask him for an EHHA kit.
 Don's and mine is the MOSFET version. So is Smeggy's am sure. 
 Don't think Jeff sells the BJT version, though you could ask.


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## dBel84

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Is yours the MOSFET version?_

 

there's an option 
	

	
	
		
		

		
		
	


	







 ..dB


 I had meant to comment on Sachu's long standing LUST for this amp 
	

	
	
		
		

		
		
	


	




 ( he has wanted to take it off my hands on more than one occasion and I nearly relented once, in fact I came close to selling it some time ago but am very glad that all passed ) Getting distracted, this particular amp has always received favourable comments from people at the local meets. "effortless" is one comment I recall from the first meet, I would encourage anyone interested in hybrids to build this as it is not your standard tube VAS followed by SS buffer - read the gory details at Cavalli Audio 

 BUT
 1. it is not really a beginner build
 2. Bargain on spending around $350 for a no frills build - 2 X EHHA boards, 1 x S22 power supply ( you can use a more simple supply to keep costs lower but it is worth the S22 ( which is a helluva bargain itself) , a tread or S11 for the tube heaters. 

 Also consider that you can run the 6H30 in this amp for higher power output and with the necessary mods, it could run small speakers ( altough Alex may be persuaded to open his magic pockets and reveal the most awesome power amp centered around this design ) 

 enough said


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## holland

lol, dBel84. My first smile of the day.


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## MrSlim

Just to stir the pot, has runeight shared any secrets about the EHHA II he has in the works?


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## dBel84

would that be the first version or the second ..... ROFL , I will wait for the master to say his piece ..dB


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## runeight

Well it's about time!! 
	

	
	
		
		

		
		
	


	




 I don't think I can ever thank dbel84 enough for building the protos of my amps. But the other important person here is Snoopy who inhabits the headwize forum.

 I have been buried beyond recognition for the last several weeks and have not been able to attend to all the diy efforts that are afoot.

 I must admit that this is a very special amp and like the b22 it will drive small speakers. Although a few small component values would be changed for that.

 And yes, there has been an EHHA II done for quite a while. No one has built it yet, but it is not just a headphone amp but capable of making about 100W into 4ohms.

 However, it would be insane for me to try to introduce this amp now with everything that's going on. Nonetheless don't be surprised if dBel84 finds the time to build one anyway. Just to prove it can be done.

 Thanks to all of you pioneers on this thread. I'm looking forward to what you find.


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## dBel84

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_ Nonetheless don't be surprised if dBel84 finds the time to build one anyway. Just to prove it can be done._

 






 it is on the cards but time will not be my friend for a while 
	

	
	
		
		

		
		
	


	




 ..dB


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## digger945

Nothing can derail a feller's budget quite like mentioning 6h30 and MOSFET in the same sentence.






, indeed.


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## wiatrob

Runeight! Welcome back from across the river styx! 
	

	
	
		
		

		
			





 As I mentioned, i'm thinking of an active ground or balanced version - has one been attempted? 

 I'm actually leaning toward BJT...

 For balanced, I reckon I'll need a CL gain of less than 7.5 - is there a formula available for determining R13 or should I buckle down and try to understand the circuit?


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## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Runeight! Welcome back from across the river styx! 
	

	
	
		
		

		
		
	


	




 As I mentioned, i'm thinking of an active ground or balanced version - has one been attempted? 

 I'm actually leaning toward BJT...

 For balanced, I reckon I'll need a CL gain of less than 7.5 - is there a formula available for determining R13 or should I buckle down and try to understand the circuit? 
	

	
	
		
		

		
		
	


	


_

 

If I could only get you guys to look at the website.


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## smeggy

Ok, I'm confused... and excited. What mods are needed for the higher power version? I want names and addresses! 
	

	
	
		
		

		
		
	


	




 I have some insanely hard to drive phones which need all the power they can get (though not 100w 
	

	
	
		
		

		
		
	


	




 ). Is this something easy to do?


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## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If I could only get you guys to look at the website. 
	

	
	
		
		

		
		
	


	





_

 

OK, I promise to read the pages of the site OTHER than the parts list!


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## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ok, I'm confused... and excited. What mods are needed for the higher power version? I want names and addresses! 
	

	
	
		
		

		
		
	


	




 I have some insanely hard to drive phones which need all the power they can get (though not 100w 
	

	
	
		
		

		
		
	


	




 ). Is this something easy to do?_

 

I believe the implementation would have to be a bit different to support those levels of power, so modding the current EHHA to perform to that spec may not be possible. Just a guess though...


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## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ok, I'm confused... and excited. What mods are needed for the higher power version? I want names and addresses! 
	

	
	
		
		

		
		
	


	




 I have some insanely hard to drive phones which need all the power they can get (though not 100w 
	

	
	
		
		

		
		
	


	




 ). Is this something easy to do?_

 

If you use a s22 supply with 30V rails you'll get all the power you need for headphones. Many watts in fact. But to drive speakers needs some resistor changes. I don't remember what they are anymore, but I can go back and figure it out if someone really wants to do this.

 And, I should add, because of the different ways bjts and fets work, the bjts will be the higher power version.


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## smeggy

Well this will do just as it is, no need complicating what I'm already over my head with 
	

	
	
		
		

		
		
	


	




 I've already bumped into hurdle number one.. trying to figure out all the values of all these resistors. They're nearly all identical looking brown Dale RN55D resistors with different numbers/letters above and below that. How can you tell what they are?

 I guess this is one reason it's not a beginners amp.


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## holland

The RN55 line is very easy to read. Turn the resistor so that you can read the words, rotate it so you go to the bottom (big gap before the top, as you turn it). That's the resistor value. Put it on a DMM, and you'll figure it out, I'm sure.

 Small DIY advice. When populating boards, I always put the RN55 resistors so the value is visible right on the top. This way you can read the values right off the resistors as you troubleshoot. It's much easier than decoding color bands.


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## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_OK, I promise to read the pages of the site OTHER than the parts list! 
	

	
	
		
		

		
		
	


	


_

 

wazzat? There are other pages?


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## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_wazzat? There are other pages? 
	

	
	
		
		

		
		
	


	


_

 


 Quite edifying too, 'though I think I'm going to need more brainpower to figure setting the relationship/values for R13/22/23.


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## zkool448

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_The RN55 line is very easy to read. Turn the resistor so that you can read the words, rotate it so you go to the bottom (big gap before the top, as you turn it). That's the resistor value. Put it on a DMM, and you'll figure it out, I'm sure._

 

dang... all this time I thought those were just part numbers! 
	

	
	
		
		

		
		
	


	




 I'm such a noob.


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## smeggy

you and me both...

 so it looks like the first three are the value numbers and the fourth digit is the number of zeros at the end.


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## tomb

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_you and me both...

 so it looks like the first three are the value numbers and the fourth digit is the number of zeros at the end._

 

With V-D RN-type resistors, the fourth digit is the exponential notation. So "1001" is a 1K resistor - 100 x 10. "1000" is actually a 100R resistor - 100 x 1. Note that V-D's CMF-type resistors that you can buy at DigiKey are identical, but use a more traditional notation.

  Quote:


  Originally Posted by *holland* 
_Small DIY advice. When populating boards, I always put the RN55 resistors so the value is visible right on the top. This way you can read the values right off the resistors as you troubleshoot. It's much easier than decoding color bands._

 

This should be made a LAW.


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## smeggy

Thanks, I will abide by it


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## MrSlim

I had a lot of fun building the CTH, and finally finished one of the SOHA+JISBOS I've had on the shelf for a while, and now my bro-in-law has asked for his drill press back..(It was such a pleasure using it to do the case work) What was my first reaction? Where can I get one for myself cheap.. and I'm picking up a good used one tomorrow. 

 Is this the beginning of the end.?


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## smeggy

Yes!
 I have two of them


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## MrSlim

Hey guys, I noticed on Alex's EHHA page, he mentions that it's a good idea to have 2 power switches, one for the heater supply to warm up the tubes for about a minute before turning on the main supply, so there isnt any funny business going on with the tubes as they warm up. 

 I said to myself, hey that sounds like a perfect place for a little delay circuit that would be controlled by the heater supply.. Turn on the 12 v supply. the delay counts down for a minute, then trips a relay to turn on the main supply.. 

 And since the internet is all about not re-inventing the wheel here's a circuit to do it:

LM555 Timer Circuits 

 I particularly like the one called: Delay circuit with flashing indicator LED. 

 Even the basic delay circuit would be useful.. 

 It would be pretty simple to breadboard, and the main expense would probably be a relay with heavy enough contacts for the main power suppy..


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## dBel84

if the tubes aren't warm, there is a slim chance that the amp could swing to one of the rails. I don't think it has ever happened to any of the prototypes but the possibility remains. 

 I have the math for the gain wiatrob - I will post the resistor values ..dB

 so I cheated 
	

	
	
		
		

		
		
	


	




 - this was from old e-mail communication (compliments of Steinchen) - R21 is currently R13 iirc - someone correct me if I am wrong

 "R21 sets the gain, thus the ideal value depends on the headphone impedance
 you're using. Usually 6 for low-Z phones (32 Ohms), around 8 or 9 for
 high-Z cans (250 to 300 Ohms) and 12 or 13 for old 600R cans or K1000.
 That means resistor values for R21: 2k, 1k5, 800R (roundabout)"


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## smeggy

Q, is 4752 the 4k7 or 47? I think its the 4k7 but want to make sure.

 I seem to be missing 4 resistors and it one of the above, either R5,7 or R27, 28.

 Also, R32,33 are reading 2.2 ohms. ??


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## dBel84

I thought you said you have 2 DMMs 
	

	
	
		
		

		
		
	


	




 4752 = 47500 = 47.5K = 47K5 

 ..dB


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## smeggy

No, two drill presses, much less useful for electrics 
	

	
	
		
		

		
		
	


	




 Well in that case I'm even more confused, R5 and 7 want 47, R27 and 28 want 4k7... erm, so what I have isn't for anything?

 Bugger, that means I need to get 4 of each!

 One point of information you should probably be aware of. In high school, I came bottom of my class in math two years in a row... yeah, Mr Thicky, thick McThick


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## dBel84

aaaah , didn't click back to see what the 2 referred to 
	

	
	
		
		

		
		
	


	




 I need to check the schematic to see which ones you are referring to. You are right , I am sure Jeff will replace the parts not in the kit. The 47.5K would be good to play with in the global feedback position ( R22/23 ) ..dB


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## smeggy

Gah, the RLED resistors are missing too. I'll need to run through the whole board to make a list for Jeff.


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## zkool448

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Gah, the RLED resistors are missing too. I'll need to run through the whole board to make a list for Jeff._

 

Make that list quickly smeggy, then send me a copy for when I'm ready to build one


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## smeggy

Hmm, I need to have the Glass Jar MOSFET BoM verified against the circuit diagram as there seems to be some discrepancies. 

 BoM doesn't list RLED, R27, r28.

 R5, R7 are listed as 47.5k

 R32, 33 are listed as 2R2

 What is correct and what do I actually need?


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## MisterX

Quote:


 BoM doesn't list RLED, R27, r28. 
 

 4.75kΩ for R27, R28

 (those values are provided on the schematic and parts list page)

 RLED should be somewhere around 10K depending on the LED. 

  Quote:


 R5, R7 are listed as 47.5k 
 

The schematic sez they should be 47 ohms. 
 The parts list sez 47.5
 (the half ohm doesn't matter but 10X the specified value does...)

  Quote:


 R32, 33 are listed as 2R2 
 

2R2 = 2.2ohms. And they should be 2Watt resistors 
 (they should be the big blew ones in the bag on the right in the picture you posted on the first page)

 What parts were included?


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## sachu

The 2.2ohms resistors are 1/2 watt resistors....


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## smeggy

This was from the glass jar BoM.

 no RLED, R27, r28 listed or supplied.
 R5, R7 are listed and supplied as 47.5k ohm
 R32 and 33 are listed as 2.2 ohm 1/2 W

 I'll need to check through the rest tomorrow.

 Luckily I have some 10ks I can use for RLED.


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## sachu

Smeggy, 

 You need 4.75k for R27, R28..look at the schematic , on the far right edge.

 I think the supplied R32 R33 resistors are actually 2 W..there may be a mistake in the BOM.

 You calculate RLed based on the LED you are using and the brightness/current you want flowing through it. The Formula for it is listed on the Cavalli Audio site.

 Indeed R5, R7 seem to be supplied as 47.5k when the schematic is listing it as 47 ohm..

 We need Alex to chime in and correct his for us . 

 I wil dig in my parts bin or go pick up a few of them from the surplus store just in case.

 I do have a bunch of 22 ohm resistors to use in series to get 44ohms if I don't find the 47 ohm ones at the store.

 Cheers,


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## smeggy

Yeah, I can see that. I was more concerned about them being missing from the bom and the wrong values for the others.

 That's why I was asking in the first place. Noobs like me can easily miss this stuff and go on regardless with wrong values etc. also, there is no value for the LED supplied so formulas don't help


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## sachu

And I really can't compare against Don's build as his boards are different from our versions..


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## runeight

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Smeggy, 

 You need 4.75k for R27, R28..look at the schematic , on the far right edge.

 I think the supplied R32 R33 resistors are actually 2 W..there may be a mistake in the BOM.

 You calculate RLed based on the LED you are using and the brightness/current you want flowing through it. The Formula for it is listed on the Cavalli Audio site.

 Indeed R5, R7 seem to be supplied as 47.5k when the schematic is listing it as 47 ohm..

 We need Alex to chime in and correct his for us . 

 I wil dig in my parts bin or go pick up a few of them from the surplus store just in case.

 I do have a bunch of 22 ohm resistors to use in series to get 44ohms if I don't find the 47 ohm ones at the store.

 Cheers,_

 


 Yes, all correct. 

 R5, R7 are 47R (RN55D is 47.5R).

 R27, R28 are 4k7 (RN55D is 4k75)

 R32, R33 are 2R2. 1/2W will do for headphones. 2W is in case you want to push 18W into speakers.

 Is there anything else missing or seeming to be wrong?

 On this amp I do recommend the heater-first power up sequence. This is because the tube is DC coupled to everything else. When the amp first turns on the tube is not conducting at all and the bjts just don't know what to do.

 One thing about this amp, because of the design, it is blazingly fast. See the performance web page for the measurements that snoopy made on it.


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## digger945

For the 2705/1145's, do you use "O" or "Y" hfe class?

 Yes I noticed the speed in your "performance" section. What software is the one with "Audio Spectrum" in the header?


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## holland

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_And since the internet is all about not re-inventing the wheel here's a circuit to do it:

LM555 Timer Circuits 

 I particularly like the one called: Delay circuit with flashing indicator LED. 

 Even the basic delay circuit would be useful.. 

 It would be pretty simple to breadboard, and the main expense would probably be a relay with heavy enough contacts for the main power suppy.._

 

You would probably need a transformer for the voltage supply to the LM555. To kill another bird with one stone, you can use AMB's e24 momentary switch driver. Once the power switch latches you can drive a relay for the heater and a 12V circuit (LM555) and in turn drive the power relay for the s22.


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## wiatrob

Somebody asked about filament warm up in a thread somewhere and this was suggested:

Power Supply Delay Action Board 300B 2A3 KT88 tube amp - eBay (item 150342422865 end time May-06-09 14:51:43 PDT)


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## holland

hey, that's awesome. I didn't think there were heavy relays that actuate with such little voltage across the coils.


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## smeggy

I need to get one of those delays. 

 *oh sweetie, I just need one more little thing from ebay...*


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## holland

"what a coincidence! There's this really cute Prada bag..."


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## smeggy

hehe.

 So, slow progress so far.











 at this rate I should have it complete by 2011.


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## wiatrob

Double Post


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## wiatrob

Smeggy, SLOW is better than BLOWN up 
	

	
	
		
		

		
		
	


	




 I'm still working on my BoM and chassis design. I do have a few tubes... <Gloat>


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## wiatrob

Also, Smeggy (you probably don't want to hear this now), might I suggest OpAmp Sockets? Just In Case...


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## smeggy

no you may not.. already in 
	

	
	
		
		

		
		
	


	




 What tubes have you collected? I'm not even sure what tubes arrived in the package, not like I'd know any different anyway being a toob noob. I'll probably wait until later to experiment 
	

	
	
		
		

		
		
	


	




 Gotta finish this, millions of other things including the S22 before any of will work. Still, it'll be great having the EHHA and Beta 22 up and running.


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## dBel84

those tubes look like they need a special home now !! 
	

	
	
		
		

		
		
	


	




 ..dB


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## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_those tubes look like they need a special home now !! 
	

	
	
		
		

		
		
	


	




 ..dB_

 

yeah...mine!! 
	

	
	
		
		

		
		
	


	




 20$ for the 3 of them ought to cover eh?


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## digger945

I wonder if they are 6GM8/ECC86's. They are not that easy to find anymore.


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## dBel84

The glassjar kits ship with 6GM8 ( until Jeff's stash runs out at least) and he is selling them at incredibly reasonable prices considering how rare they are lately.

 my hat goes off to the man 
	

	
	
		
		

		
			





 ..dB

 ps smeggyman - looking good me lad


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## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah...mine!! 
	

	
	
		
		

		
		
	


	




 20$ for the 3 of them ought to cover eh?
	

	
	
		
		

		
		
	


	


_

 


 Sachu knows - I paid $12.00 each for those! (need one more for my fully balanced build) I have 4 Philco 6GM8s.

 There are also the 6922 and 6H30 options...

 Jeff is indeed offering a good deal...


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## smeggy

Cool, so the stock tubes are pretty well regarded? However, rare doesnt sound good, I may need to find a spare set.. just in case 
	

	
	
		
		

		
		
	


	




 I wish I didn't feel like such crap, it's hard to get going when you're in bed most of the day


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## runeight

The design center tube is the 6gm8. But I knew that they would start to get rare because of other designs and so I also worked this out for 6922s and 6H30s. If fact the original design used the 6H30 because it is a good low voltage tube for being a high voltage tube. 
	

	
	
		
		

		
		
	


	




 However, this amp is not like the CTH or the SOHA II. It is not made for tube rolling. Just want you guys to know that you should not expect to roll tubes in this amp except for a very limited set of tube types. Tubes like the 12xxx series will simply not perform well. 

 You'll have to have fun with the other features of this amp.


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## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_...You'll have to have fun with the other features of this amp. 
	

	
	
		
		

		
		
	


	


_

 

Like it's stellar performance? 
	

	
	
		
		

		
		
	


	




 Or so I hear...

 6GM8/ECC86s are around, tubeworld has some, as does upscaleaudio. The 6922 (or even 7922) would be an economical sub.

 I have a line on some 6GM8s locally, depending on qty, condition and price, I'd be happy to group buy if there is interest. Communication has been slow, I'll update when I hear something...


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## smeggy

I was gonna ask, if the 2W resistor = 18wpc, what will the 1/2 W resistor output? Ideally I'd like enough juice to run stax transfo boxes, K1000, super inefficient orthodynamics etc. Ideally around 5wpc or over. Also, does that output pwer get fed through the phone jack or is there some other wiring setup to allow that output level?


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## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I was gonna ask, if the 2W resistor = 18wpc, what will the 1/2 W resistor output? Ideally I'd like enough juice to run stax transfo boxes, K1000, super inefficient orthodynamics etc. Ideally around 5wpc or over. Also, does that output pwer get fed through the phone jack or is there some other wiring setup to allow that output level?_

 

Actually, looking at your board pics they look like small 2W resistors to me. Are they really 1/2W?

 In any case, you can run multiple watts with 1/2W.


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## dBel84

It's called a volume control 
	

	
	
		
		

		
		
	


	




 The ideal way for you to do this would be to set a rotary switcher that changes the gain of the closed loop - that way you can still have fine control with the conventional pot and adjust the overall gain for the headphone of your choice ..dB


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## smeggy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Actually, looking at your board pics they look like small 2W resistors to me. Are they really 1/2W?

 In any case, you can run multiple watts with 1/2W._

 

Awesome, sounds ideal then. I dunno the actual wattage of the resistor but it's listed as 1/2w in the BoM so..

 BTW, did you look at that delay circuit on ebay? If that would work should I feed it into the Sigma22 after the heater supply. Power >heater >delay >sigma.

  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_It's called a volume control 
	

	
	
		
		

		
		
	


	




 The ideal way for you to do this would be to set a rotary switcher that changes the gain of the closed loop - that way you can still have fine control with the conventional pot and adjust the overall gain for the headphone of your choice ..dB_

 

I have no idea how to do that, but if it can feed multiple watts through the normal output I'll rig something


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## runeight

Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?


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## sachu

How about using a couple of damper tubes instead? Or would the transformer required for the heater circuit be too great?


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## smeggy

Not that I'm aware of. Hopefully somebody will buy one to see. Going off the blurb it looked like it would be suitable, ac and supposedly strong enough for big tube amps but who knows.

 I'm so new at all this DIY I have little real clue. This is only my second build so I'm in the dark on a lot of the technicalities and rely on the knowledge of others until more of this stuff sinks in


----------



## sachu

Here is a sneak peek at my progress... 
	

	
	
		
		

		
		
	


	




 Its a one chassis solution..everything (heater supply, S22 supply, included) is going to be on that chassis.








 Just testing to see my chassis work was ok...

 Going to bring up the S22 board later tonight and then the heater supply. 

 If all goes well with the supplies, tomorrow its going to be mounting the heater supply to the chassis and the S22 toroid needs to be bolted down as well ( i have a piece of acrylic cut out to secure it on.)

 Also tomorrow, will try to design the end panels which will be made out of wood. However, this might come a few weeks down the line as I am trying to cajole my boss to do it for me


----------



## dBel84

I just love these type of recycled chassis - going to be one very unique amp. 

 good luck with the testing phase ..dB


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?_

 

The relay was suggested on the OTHER forums, let me see what comments were posted....

 It probably would not be too difficult to design (or swipe one) a simple heater delay circuit.


----------



## wiatrob

Sachu,

 Looking good. I was puzzling over a case last night. Looks like you are air wiring your mosfets for chassis heat sink mounting?


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?_

 

Apparently it's an AC rated Relay. No specs though, but Spritzer has one so perhaps we could contact him offlne.

 Off course there is the time honored approach of Two Switches...


----------



## MrSlim

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?_

 

Check out my post #32 on the thread, I posted a link for some 555timer circuits that I think would do a good job. A relay with the appropriate contact rating would have to be chosen to drive the Sigma 22. 


 You mentioned that the EHHA is capable of putting out about 18 watts into speakers. Are there any other changes besides the 2 watt rating on the resistor in question? It's making me think it might be a very sweet amp for a pair of efficient Single driver speakers like the Zigmahornets that I've been thinking about, when I don't want to listen to headphones. 

 *sigh* that would mean I would have 3 amp projects capable of driving speakers.. 
 good thing we have understanding wives.. (or at least I do, for now..)


----------



## digger945

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Does anyone have a schematic for that delay circuit? Or the specs on the relay contacts?_

 

Sophia Electric's Home Page


----------



## smeggy

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Check out my post #32 on the thread, I posted a link for some 555timer circuits that I think would do a good job. A relay with the appropriate contact rating would have to be chosen to drive the Sigma 22. 


 You mentioned that the EHHA is capable of putting out about 18 watts into speakers. Are there any other changes besides the 2 watt rating on the resistor in question? It's making me think it might be a very sweet amp for a pair of efficient Single driver speakers like the Zigmahornets that I've been thinking about, when I don't want to listen to headphones. 

 *sigh* that would mean I would have 3 amp projects capable of driving speakers.. 
 good thing we have understanding wives.. (or at least I do, for now..)_

 

Yeah, you and me both, this Beta and another on the horizon all capable of driving speakers. 
	

	
	
		
		

		
		
	


	




 Anyway, that switch does look ideal to my simple mind


----------



## TimJo

So I read through the design section yesterday - very creative Alex. 
	

	
	
		
		

		
		
	


	




 I'm still working my way through the details of the schematic, and I'm sure I'll have a few questions down the road, but once again thanks for putting together so much info on the website. This is a unique design for sure, and it'll take awhile for it all to sink in. I really love the symmetry of the design...

 I did notice one typo on the schematic I believe. The signal path between the second triode and the lower VAS (Q6) passes through a unity gain mirror. The transistor pair in the mirror is labeled Q2-Q3, but I think it is supposed to be Q2-Q4, based on the parts list. Correct?


----------



## spritzer

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Apparently it's an AC rated Relay. No specs though, but Spritzer has one so perhaps we could contact him offlne._

 

The relay is rated at 240VAC but I'm sure some other relay could be soldered in its place. I'm currently running it in my Egmont with 280VAC on each side of it and no arcy sparky yet.


----------



## sachu

We have a working S22 and heater supply.

 Unloaded the S22 outputs +/-41 volts DC.

 Unloaded the heater supply outputs about 8.3 volts DC. 

 Do I need to adjust the heater supply down to 6.4 , 6.5 volts unloaded?

 Off to get some chassis work done while I await a reply.


----------



## Ferrari

What voltage is your σ22 PSU intended to be? I assume ±30V as recommended for the EHHA?
 Even unloaded, the σ22 should give approximately ±30V (if it was cofigured for ±30V). ±41V seems to be an odd value.


----------



## smeggy

sachu is an odd builder


----------



## sachu

Ferrari, yes, it is configured for +/-30 volts...There must be something wrong with the mosfets or gotten a resistor value wrong perhaps..


----------



## digger945

Yea a22 should give the same no matter what, loaded or unloaded. What's your R10 value? Should be 6.81k or thereabouts for +/-30V.


----------



## sachu

My R10 is 6.81k

 It looks like there is a problem with Q13 and Q14 mosfets...

 The voltages are off..I think on the drain of both are reading less than 100mV DC.


----------



## digger945

R8, R10 and D5 will determine the output voltage.
 I was gonna give you some measurements but this should be all you need. 
 Lemme know if there is something you want measured as I have the hood up on mine.


----------



## sachu

Thanks for the help Scott...

 Turns out i made a rookie mistake 
	

	
	
		
		

		
			




 I had switched one each of IRFZ24 and Z34 on both rails.
	

	
	
		
		

		
		
	


	




 I now have +/-28.8 volts DC


----------



## digger945

Yep, that's why I'm shopping for a desoldering gun/station right now.
 LOL


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Yep, that's why I'm shopping for a desoldering gun/station right now.
 LOL
	

	
	
		
		

		
		
	


	


_

 

I don't know how I went about without the desoldering pump till now..

 In any case switching the MOSFETs out was easy as they are air wired on to the chassis.

 The same MOSFETs are going to be air wired for the amp section next.

 I found a few metal oxide 2W 47 ohm resistors for R5,R7 on the EHHA..
 going to use them and make do for now..


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I had switched one each of IRFZ24 and Z34 on both rails.

 I now have +/-28.8 volts DC_

 

phew , now you can get down to the fun part ..dB


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So I read through the design section yesterday - very creative Alex. 
	

	
	
		
		

		
		
	


	




 I'm still working my way through the details of the schematic, and I'm sure I'll have a few questions down the road, but once again thanks for putting together so much info on the website. This is a unique design for sure, and it'll take awhile for it all to sink in. I really love the symmetry of the design...

 I did notice one typo on the schematic I believe. The signal path between the second triode and the lower VAS (Q6) passes through a unity gain mirror. The transistor pair in the mirror is labeled Q2-Q3, but I think it is supposed to be Q2-Q4, based on the parts list. Correct?_

 

Thanks!! You'll love the EHHA II. 
	

	
	
		
		

		
		
	


	




 You're right about the schematic. After all this time . . .


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks!! You'll love the EHHA II. 
	

	
	
		
		

		
		
	


	




 You're right about the schematic. After all this time . . ._

 

ALex, as I have already let you know, of course I want to be in on the proto team for the EHHA2..


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ALex, as I have already let you know, of course I want to be in on the proto team for the EHHA2..
	

	
	
		
		

		
		
	


	





_

 

That's all well and good, but I think Alex has some *-Ahem*- other protos *-AHEM*- to work on so he shouldn't be distracted!


----------



## runeight

Yes, he does, and has been having a hard time getting into the workshop.


----------



## smeggy

It's not even built and you're already talking upgrades! 

 *sigh*


----------



## sachu

We have a working heater supply. Using Pete Millet's heater supply without the choke filter

 Set it at 6.4 volts unloaded. The transformer is capable of 4 amps into 6.3 volts each rail so this one is wired in parallel so plenty of current to run 6H30s on the amp.

 Now Don as you say 'comes the fun part'.

 going to use separate AC cords to act as switches to bring up heater first, then S22 for the time being. Once test phase is complete I will move to install separate switches or put the timer+ relay .


----------



## smeggy

Nice going sachu!


----------



## sachu

Alright..brought up one board..tube lit up, LED lit up as well as I brought up the S22 a few seconds later.

 Ran through the checklist..

 Was hard finding resistor locations as the numbering is covered up by the resistors.

 Also, the picture of the board up on the Cavalli audio website is not the current version which makes it even harder.

 All the voltages checked out except for the two. 

*1>* R32 and R33 measured 0volts and varying R21 made no difference. plus side though, no smoke 
	

	
	
		
		

		
		
	


	




*2>* Also the voltage on pin 6 of the opamp measured 0.4 volts instead of 0 volts.


 Kinda tired to hook up the second board...will report back with setup results for that board in a few minutes.


----------



## sachu

Similar resuslts with the second board. Except here
 1> Voltage across R32 R33 was at 0 volts regardless of the R21 trimpot position.

 2> Pin 6 on the opamp was at 1.8 volts

 Alex,Don, Where do we go from here?


----------



## amb

Sachu, I just stumbled upon your build pics and have a comment about air-wiring the MOSFETs on the heatsinks. The inductance in the wires form an LC resonant network with the MOSFET gate capacitance, and could lead to instability (ringing square waves or even outright oscillation). The gate wiring to a MOSFET should be as short as possible and the gate stopper resistor should be immediately adjacent to the gate pin, this is why MOSFETs should be directly soldered on the PCB.

 This is not related to your current problems but I thought you might want to be aware of this issue.


----------



## sachu

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Sachu, I just stumbled upon your build pics and have a comment about air-wiring the MOSFETs on the heatsinks. The inductance in the wires form an LC resonant network with the MOSFET gate capacitance, and could lead to instability (ringing square waves or even outright oscillation). The gate wiring to a MOSFET should be as short as possible and the gate stopper resistor should be immediately adjacent to the gate pin, this is why MOSFETs should be directly soldered on the PCB.

 This is not related to your current problems but I thought you might want to be aware of this issue._

 

Thanks for the info Ti. Will be keeping the length as short as possible (less than 2 inches).


----------



## runeight

sachu I would like to reaffirm Ti's comments. I didn't realize what you were doing but even 2" lead length is a potential problem. I'd also recommend you put the fets onto the board. Their heatsinks are quite large and will handle any reasonable amount of power.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, he does, and has been having a hard time getting into the workshop. 
	

	
	
		
		

		
			



_

 

Take your time, I'm a week away


----------



## looser101

If you don't mind being the delay timer you can use one of these.


----------



## TimJo

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Sachu, I just stumbled upon your build pics and have a comment about air-wiring the MOSFETs on the heatsinks. The inductance in the wires form an LC resonant network with the MOSFET gate capacitance, and could lead to instability (ringing square waves or even outright oscillation). The gate wiring to a MOSFET should be as short as possible and the gate stopper resistor should be immediately adjacent to the gate pin, this is why MOSFETs should be directly soldered on the PCB.

 This is not related to your current problems but I thought you might want to be aware of this issue._

 

 Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Thanks for the info Ti. Will be keeping the length as short as possible (less than 2 inches)._

 

 Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_sachu I would like to reaffirm Ti's comments. I didn't realize what you were doing but even 2" lead length is a potential problem. I'd also recommend you put the fets onto the board. Their heatsinks are quite large and will handle any reasonable amount of power._

 

If it's too hard/too late to make the change and move away from air wiring, I suppose you could at least remove the gate stoppers from the board, and solder them directly to the mosfet pin, and then position the fets as close as possible. Just a thought... 

 But it is probably best to mount them on the board if possible.


----------



## sachu

Its not possible to mount the heatsinks onto the board in the current setup.

 The options I have are :

 1> To remove the transformer and put it in a separate box, at least the S22 transformer. 

 2> Install a board underneath amp boards on as a chassis base and mount the S22 board there along with heatsinks

 I am going to play around with placement a bit more and see what's possible..


----------



## zkool448

Sachu I'm sure you recall and TimJo's comment actually reminded me of when air wiring the MOSFETs on the starving student, to solder the resistor right up its leg/pin to prevent oscillation.


----------



## dBel84

I can at least atest to the EHHA being stable with air mounted mosfets - mine has been air mounted from the time I cased it up. My initial setup and test of the boards were with heatsinks on the board but once the amp was working, I cased it up and it has been going strong for the past 2 years. 

 If the S22 needs more stringency, you may be able to bolt the mosfets onto the chassis you have Sachu. We can stick the entire thing on the scope to see if there is any oscillation. 

 As for why your mosfets on the EHHA are not conducting, not sure - could you measure the gate voltage. The pin 6 opamp is ok - that is the offset correction, the 1.8V is higher than I recall..dB


----------



## sachu

just wanted to break the nelson count so we can all stand on two feet now 
	

	
	
		
		

		
		
	


	




 Don, I put standoffs on the S22 board, need to drill 4 holes on the chassis so I can mount the MOSFETs directly onto the board.

 I will report back with the gate voltages on the EHHA board in a few minutes.


----------



## sachu

The voltages on the two MOSFETs ont he EHHA are

 On the IRFZ34, Q9M, 
 the gate voltage is -1.36 ..but it varies from -1.36 to -1.45 volts.
 The Drain voltage is at negative rail : -28.8 volts
 Source is at 0 volts..less than 1 mV

 On Q8M the IRFZ24, the gate voltage is +1.75 volts.
 The Drain is at positive rail : +28.8 volts
 Source is at 0 volts


----------



## runeight

So what is the voltage at the output with respect to ground? And what are the voltages across the two 2R2 resistors?


----------



## sachu

Alex, both are reading 0 volts..Output is at 0.4mV with respect to SG


----------



## runeight

Then set the idle current to 100mA and see if it makes music.


----------



## sachu

Alex, i thought you need more than at least 2V on the gate for the MOSFETs to conduct


----------



## sachu

Took some measurements:

 Q7 has 
 -1.33 on the emitter
 +1.67 on the collector
 -0.61 on the base.

 Something clearly is wrong.

 Q10,Q11 have +27.7 volts on the base
 Q12, Q13 have -27.6 volts on the base


----------



## dBel84

I don't think the mosfets are conducting - this is similar to the scenario we had in the proto phase but we changed the trimmer to 1K and adjusted the bias resistor values and it came up fine - I was measuring around 3.2V at the gates ..dB


----------



## dBel84

check voltages around Q5 and Q6 ..dB


----------



## runeight

What values do you have for R19, R20, and R21?


----------



## sachu

I take it back..adjusting R21 seemed to do the trick..didn't think that trimpot had so many turns on it.

 Am now reading 0.2 volts across R32 and R33.

 Voltages around Q7 check out as well..they are slightly higher than 3.2 volts..more closer to 4 Volts all around.

 Going to bring up the second board and check if that works too with changing R21.

 Alex, R20 and R19 are 220 and 3.3k respectively. R21 is a 1k trimpot


----------



## runeight

Those are the correct resistors and I see that you have dialed up the right idle current.

 There some other measurements to take that I'd be interested to know, but these are not important now. Just follow the website instructions.


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I take it back..adjusting R21 seemed to do the trick..didn't think that trimpot had so many turns on it._


----------



## sachu

Success!...both boards are now up and running fine.. 
	

	
	
		
		

		
		
	


	




 Thanks Alex, Don.

 Next up, connect inputs and outputs and have a listen


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Those are the correct resistors and I see that you have dialed up the right idle current.

 There some other measurements to take that I'd be interested to know, but these are not important now. Just follow the website instructions._

 

Sure thing ALex..Let me know as I have a board connected now. Will only be testing one board. Will have to disasemble everything on the chassis as I have some work left to do on it. SO now is the best time.

 I have followed everything listed on the website and everything checks out.


----------



## dBel84

great news sachu, i had forgotten about the first time I fired it up and it took forever to adjust those trimmers. This is a good reminder for the folk who follow in your footsteps, especially as everything else seemed to check out and make sense ..dB


----------



## runeight

Sachu, I would like to know the voltage at the output of the opamp (pin 6 I think).

 Then I would like to know if you can zero this voltage by carefully adjusting R6 (at the cathodes of the tube).

 Then I would like to know what this did to your idle current.


----------



## sachu

Woohoo!!We have music 
	

	
	
		
		

		
		
	


	




..one channel at least.. 
	

	
	
		
		

		
		
	


	




 Am excited now!! Can't wait to get the case work all done.. Planning on getting this  for the heater supply +S22 delay.

 A pic of my amp under testing..


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Sachu, I would like to know the voltage at the output of the opamp (pin 6 I think).

 Then I would like to know if you can zero this voltage by carefully adjusting R6 (at the cathodes of the tube).

 Then I would like to know what this did to your idle current._

 

Alex, I didn't check to see the idle current but the voltages across R32, R33 dropped from 0.2Volts to 0.128 volts as I zeroed the output on the opamp.

 On a side note, there is a hiss in the channel but I think its mainly becuase I am running really long wires from the RCA input to the Pot and then to the amp. Minor things that can be dealt with later.


----------



## digger945

Congrats sachu! Really looking forward to your listening impressions *thumbs up, I've ordered boards and tubes from Jeff* 
 Wish I could keep my work area that tidy.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Congrats sachu! Really looking forward to your listening impressions *thumbs up, I've ordered boards and tubes from Jeff* 
 Wish I could keep my work area that tidy.
	

	
	
		
		

		
		
	


	





_

 

Awesome Scott! Be prepared to be amazed at what was hidden away in the shadows all this while cause this amp is amazing I tell you. I take full credit for dusting off the cobwebs 
	

	
	
		
		

		
		
	


	



 Even with one channel going I can tell you this is going to be one sweet sounding amp. I have Don's EHHA hooked up to my computer as I type this. After having listened to this amp almost two years ago (and ever since have I been trying to acquire one) and on many other occasions since then I can't wait to finally have one that would be mine and mine alone. 

 This to me is one of the best headphone amps out there.

  Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Wish I could keep my work area that tidy.
	

	
	
		
		

		
		
	


	





_

 

heheh..believe me that is neat by my standards..I had just finished 2 other amps yesterday and the day before..that's why its so dirty and haphazard.


----------



## runeight

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Alex, I didn't check to see the idle current but the voltages across R32, R33 dropped from 0.2Volts to 0.128 volts as I zeroed the output on the opamp.

 On a side note, there is a hiss in the channel but I think its mainly becuase I am running really long wires from the RCA input to the Pot and then to the amp. Minor things that can be dealt with later._

 

Thanks. Can you adjust the idle current back up to 100mA now?


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. Can you adjust the idle current back up to 100mA now?_

 

Can I bias it higher? Like 150mA? Would there be a problem in doing so? Unless there is no advantage to be gained from biasing it so high.


----------



## runeight

I don't think there is any significant advantage to 150mA but you can try it.

 At 100mA the fets will burn 3W each. At 150mA they will burn 4.5W. You'll need to pay attention to the temps on the heatsinks.


----------



## sachu

Right..The opamp takes a long time to settle down the output to 0. a bit more than 5 minutes actually.

 Adjusted the idle current to 150mA now.. Output of opamp at 0.


----------



## digger945

Have you tried inserting the pins on the Aavid's into the pcb yet?
 I have 4 boards here and all the holes are a bit too close for the HS to fit. Not a problem as one could remove one of the pins to get it to seat all the way or maybe get out the Dremel.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Have you tried inserting the pins on the Aavid's into the pcb yet?
 I have 4 boards here and all the holes are a bit too close for the HS to fit. Not a problem as one could remove one of the pins to get it to seat all the way or maybe get out the Dremel._

 

Digger, all my MOSFETs are going to be air wired onto the chassis. Even my heater supply regulator which will eventually sink about 2 amps with the 6H30s is going to go on the chassis. I do have about 2 dozen on those 2 inch heatsinks in my parts bin which was intended for a 4 channelB22, dual S22 build (which might or might not happen as I am pretty sure it would not sound as good as the EHHA). It just happened i came across this chassis for a bargain basement price of 7$. It was impossible for me to resist.
	

	
	
		
		

		
			





 Are you going to build a balanced EHHA?


----------



## digger945

Yep. I think this will be a fun build. I'm gonna try the Aavid's on the board and see how it goes. I don't really see it being much different from the Beta22 output, thermally.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Yep. I think this will be a fun build. I'm gonna try the Aavid's on the board and see how it goes. I don't really see it being much different from the Beta22 output, thermally._

 

Well that is going to be one mother of an amp..I am very much looking forward to your version of the amp. A balanced EHHA does not exists as far as I know.
 I wouldn't be surprised to see you sell your dynamite in a heart beat after you have this going.
	

	
	
		
		

		
		
	


	




 My EHHA with just one channel after 4 hours made my chassis slightly warm, and it is a huge chassis at that.


----------



## digger945

The Dynamite is good for me but it isn't that far ahead of the Aikido, which is a different circuit but the same principle, mosfets driven by a tube.
 I paid for a pair of cases from a HF'er here about a month ago and have yet to hear from him. I hope he is OK. If I don't hear from him soon I guess I'll go ahead and think about something else.
 I really look forward to hearing your impressions of this amp when you get it up and running.


----------



## smeggy

Balanced will be awesome, good luck with the build digger. I'm sure you'll get that finished before my SE version


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_The Dynamite is good for me but it isn't that far ahead of the Aikido, which is a different circuit but the same principle, mosfets driven by a tube.
 I paid for a pair of cases from a HF'er here about a month ago and have yet to hear from him. I hope he is OK. If I don't hear from him soon I guess I'll go ahead and think about something else.
 I really look forward to hearing your impressions of this amp when you get it up and running._

 

Yeah, haven't been able to get that case work done...will have most done by tomorrow. The pot, inputs and outputs would still be air wired as I don't have end panels yet for the chassis.


----------



## wiatrob

Digger,

 Are you planning a blanced build as Sachu mentioned? I have four boards as well and was originally thinking of an active ground version - but I'm tempted to have a go at fully balanced and see if i can hear a difference.

 You're ahead of me as I'm working up the BoM myself. I do have some case skecthes down though!


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Digger,

 Are you planning a blanced build as Sachu mentioned? I have four boards as well and was originally thinking of an active ground version - but I'm tempted to have a go at fully balanced and see if i can hear a difference.

 You're ahead of me as I'm working up the BoM myself. I do have some case skecthes down though!_

 

awesome..so we have at least 4 confirmed EHHA projects..any one else want to chime in if they are working on starting/started one?


----------



## digger945

I would still like to know from runeight if he designed this to use "O" or "Y" class hfe toshibas, or if it matters. The O's are cheap from Mouser, the Y's are a little more elsewhere.

 wiatrob, I basically had everything already except a few resistors and caps. 
 Balanced...."we need more power Scotty!"
 LOL


----------



## Lingwendil

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_awesome..so we have at least 4 confirmed EHHA projects..any one else want to chime in if they are working on starting/started one?_

 

After I get my new 66 beetle primered and running I may bread up the headphone version with 6111 or 6112 subminiature tubes and mosfets. When there's more information on it, I'll probably try the power amp version too.


----------



## Ynis Avalach

I will definatly build one. A balanced one too, but it's gonna be summer, or that around. First there are some other projects (inluding, pretty sure) a 384kHz NOS dac.
 Greetz Ava


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_wiatrob, I basically had everything already except a few resistors and caps. 
 Balanced...."we need more power Scotty!"
 LOL
	

	
	
		
		

		
		
	


	


_

 

Have you picked a CL gain setting? I am thinking I'd like a gain lower than 15 (7.5x2 for R13 = 1K5) So I am assuming that R13 value can be increased upwards as the "performance" page has test values of the amp at Unity and 4.3 gain...


 Runeight encouraged me to read the website for more info, it looks like R13/R12 form a volatage divider so i should be able to extend the gain chart lower.


----------



## digger945

I already have 1.2k and 121R's so i'll go with that first. Gain of 11.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I already have 1.2k and 121R's so i'll go with that first. Gain of 11._

 

Same here..except mine will be slightly higher as I used 1k instead of 1.2k


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I already have 1.2k and 121R's so i'll go with that first. Gain of 11._

 

I believe balancing doubles CL gain, so 2x11=22. Unless I'm missing something from the documentation... In which case I'm sure somebody will set me straight in short order... 
	

	
	
		
		

		
			





 I think I will be socketing R13, maybe R22/23...


----------



## dBel84

yep, you are quite right. balanced, doubles the gain ..dB


----------



## digger945

Right. I was referring to the calculation for just one board. I haven't really done enough reading to know exactly what the sweet spot is for this amp. 
 Good news, I just heard back from the chap I got the Parmetal cases from and they have already been shipped along with some other parts that should work well for this build. I will try to get the Mouser/Digikey order completed this weekend. I'm open for any suggestions or changes, whether it be for values or tweaks.


----------



## sachu

I have a timer based relay board coming in for the stggered turn on that is recommended for this amp.

 Hoping it will arrive soon so I can figure out where on the chassis it will go.Looks like it might be a while before it is all ready. at least another week.


----------



## wiatrob

Just got my heater supply and three position ac switch - going lo-tek with my power delay


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Just got my heater supply and three position ac switch - going lo-tek with my power delay 
	

	
	
		
		

		
		
	


	


_

 

i thought about going that route...but it was about 11$ as against 21$ for the delay+timer..


----------



## Jrossel

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Have you tried inserting the pins on the Aavid's into the pcb yet?
 I have 4 boards here and all the holes are a bit too close for the HS to fit. Not a problem as one could remove one of the pins to get it to seat all the way or maybe get out the Dremel._

 

The holes need to be widened a bit to fit both pins. Going up a few drill bit sizes fixes it. Sorry about that problem.

 JR


----------



## digger945

Nothing major at all Jeff. I initially thought that maybe they were intended for another HS of some kind. I must say that the price for the 6GM8's is outstanding. I would really love to have some extras but in no way want to be a hog. Others should really enjoy building and listening to this amp.


----------



## runeight

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I would still like to know from runeight if he designed this to use "O" or "Y" class hfe toshibas, or if it matters. The O's are cheap from Mouser, the Y's are a little more elsewhere.

 wiatrob, I basically had everything already except a few resistors and caps. 
 Balanced...."we need more power Scotty!"
 LOL
	

	
	
		
		

		
		
	


	


_

 

Sorry. I am still in the middle of a project.

 Either class is ok. Just buy the same class for everything.


----------



## sachu

Darn it..

 I was all ready to finish up the amp tonight. I had finished mounting the power supplies and relay board. Turned it on and nothing...
 Looks like the heater transformer just died on me..damn Chinese crap. Since the surplus store is closed tomorrow, the amp is going to have to wait a few more days. Wiring up the rest of the amp is about 30 mins to an hour job. Sucks that the transformer is not working for no apparent reason all of a sudden.


----------



## sachu

A progress report...















 You can see the timer based relay board in the last pic near the bottom left of the case. To the right of the relay board I will have the heater transformer. I just removed it since it was not working.


 I have problems with the secondary tabs on the heater transformer. Will get the transformer replaced and I should be good to go.

 Just hooked up everything to make sure the wires were all going to fit fine. Still need to sqaure away the wiring which will be when I get the new transformer.


----------



## Ferrari

Very unusual construction, but you have done a very good recycling work on that enclosure for your amp Sachu.
 It gives me the idea to recycle this crazy enclosure & heatsink for… well, you know what it is.


----------



## sachu

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Very unusual construction, but you have done a very good recycling work on that enclosure for your amp Sachu.
 It gives me the idea to recycle this crazy enclosure & heatsink for… well, you know what it is. 
	

	
	
		
		

		
		
	


	







_

 

hahaha..now we are talking..I just love the way boards for this project are popping up in members hands now. 

 Ferrari, I am expecting another masterpiece regardless of whether you use a recycled case or not. Can't wait to see how this turns out.

 I got my chassis for a mere 7$ (came with parts and a transformer). IT won't be fully done for a while as I will be getting wooden end plates which will also act as feet for the chassis lifting it off by at least an inch. I am also getting a perforated sheet from wiatrob for the top with holes so the tubes can stick out.

 Total build cost is coming around to about 225$...This has got to be the best vaue for money amp once I am done with it.


----------



## sachu

Disaster today...

 I finally cased everything up and powered on the amp...The S22 MOSFETS blew and the output resistors one channel on the EHHA burnt out. I am guessing the EHHA MOSFETs blew out as well as with the S22 MOSFETS blown +/- 40 volts was being supplied instead of +/-29 volts.

 I will be lucky if this is just a case of the MOSFETS being blown out.

 I suspect what happened is that one pin of the relay on the timer delay board shorted out one of the MOSFETS on the S22.

 Looks like I will have to wait quite a bit longer for my amp to be operational.


----------



## adamus

mate, i feel for you!


----------



## smeggy

Poop, now we both have screwed up S22s... 
	

	
	
		
		

		
		
	


	




 The E82CC got here though 
	

	
	
		
		

		
		
	


	



 Sweet tube!


----------



## sachu

Already put in an order through amb for about 8 pairs of the MOSFETs..
 going to get a digikey order in for the output resistors and pray that the problem is not any more severe.

 I really want this amp running..if that is al it is, then this weekend I might give it another shot.

 ANyone know how fast amb ships out an order? If he ships out tomorrow am sure I will get it on saturday. Hopefully it will be so


----------



## sachu

Just removed the entire power supply section from the chassis. Looks like the wax had come off of one of the MOSFETs on the S22 board shorting out the MOSFET's drain, gate and source.

 I know for sure Q16 on the S22 smoked out.

 Then the output 2.2 ohm resistors on one of the EHHA boards burnt and glowed like LEDs.

 Going to have to go through the painful process of bringing up the S22, then testing each amp board again. sigh...there goes a lot of hours that could have been saved if I were a bit more cautious.


----------



## amb

Wax?


----------



## sachu

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Wax? 
	

	
	
		
		

		
		
	


	


_

 

yeah..I had used wax to insulate the MOSFET pins from the chassis as the MOSFETs were air wired with about an inch and a half length of wire.

 In my moment of weakness, laziness rather, I used wax to insulate it rather than the plastic standoffs that I had installed earlier.

 Ti, is it possible to get that MOSFET order ot tomorrow?


----------



## amb

Of course.


----------



## sachu

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Of course._

 

Excellent...I have the digikey order in as well..should be all set for a debug session this saturday.

 Btw, I am getting +/- 39 volts on the outputs..which means the rectifier section is alright and the caps are alright. So for all purposes, it does look like it is just the MOSFETs on the S22. 

 Any thoughts Ti?


----------



## amb

One or both of Q13/Q14 is most likely shorted, allowing the unregulated supply voltage to get through to the V+ rail output. Since the V- rail tracks the positive, even if its MOSFETs (Q15/Q16) are ok, it would also go to the negative equivalent voltage. But there is also a chance that Q15/Q16 are shorted too. With the power off and all caps discharged, measure the resistance across the drain and source pins of each MOSFET. On a good MOSFET you should get high-Z (basically open circuit on the DMM's low-ohm scale).

 I would also measure R12-R14 to make sure they're ok, then replace any blown MOSFETs or other damaged parts and re-test.

 Heat-shrink the air-wired MOSFET pins to prevent future shorts, and make sure you use proper TO-220 mounting isolation pads. The MOSFET body is internally connected to the drain pin.


----------



## wiatrob

Sachu -

 Sorry to hear about your mishap. No rush on those perftop measurements. You should have mentioned you needed insulators, I have micas and/or spare silpads that i would have been happy to send along 
	

	
	
		
		

		
		
	


	




 Ti - thanks for piping up here. Slightly OT, but do you know when/if the builder threads on 'wize will be back up? We've lost a whole bunch of info there (along with the original EHHA thread...)

 I've scaled back my plans to build a fully balanced amp. So it's active ground for now. Since recycled cases seem to be a trend here (nod to Sachu). I may end up with another longer case depending on if the toroids fit in the PS unit.


----------



## amb

Chu Moy, who runs headwize, had posted some status info on the main page, but it hasn't been updated in a while). I really hope that it comes back up soon, but Chu has a day job and the work to update the site is apparently non-trivial. He indicated a possibility to enable a read-only version of the forum, so that people can browse previous posts while he works to make it more secure. I don't know whether he would actually do that.


----------



## sachu

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_One or both of Q13/Q14 is most likely shorted, allowing the unregulated supply voltage to get through to the V+ rail output. Since the V- rail tracks the positive, even if its MOSFETs (Q15/Q16) are ok, it would also go to the negative equivalent voltage. But there is also a chance that Q15/Q16 are shorted too. With the power off and all caps discharged, measure the resistance across the drain and source pins of each MOSFET. On a good MOSFET you should get high-Z (basically open circuit on the DMM's low-ohm scale).

 I would also measure R12-R14 to make sure they're ok, then replace any blown MOSFETs or other damaged parts and re-test.

 Heat-shrink the air-wired MOSFET pins to prevent future shorts, and make sure you use proper TO-220 mounting isolation pads. The MOSFET body is internally connected to the drain pin._

 


 On the EHHA board with the fried output resistors, one of the MOSFETs D->S resistance reads about 200 ohms while the other is shorted completely. Undoubtedly those need to be replaced.

 On the S22, I am reading resistance in the k ohm range and even though the capacitors are dischraged the resistance keeps changing.


 R12-R15 reads 0.7 ohm on my multimeter.

 I am using mica insulators for the MOSFETs.


----------



## sachu

Received the parts today. Thanks Ti for the quick shipment.

 Replaced the MOSFETs on the S22.. Plugged it in with my fingers crossed. 
 No smoke..Everything works fine on the S22....
 After breakfast going to tackle each of the EHHA boards and see what comes off it.


----------



## digger945

I'm finishing up the Mouser/Digikey order today. Should have parts middle of next week and hopefully be listening by next Saturday.


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I'm finishing up the Mouser/Digikey order today. Should have parts middle of next week and hopefully be listening by next Saturday._

 


 Mine are on the way as well. Race you! 
	

	
	
		
		

		
			





 Actually, gotta wait for the S22 xfromer from Avel - probably get here while I'm on vacation over memorial day!


----------



## digger945

I'm gonna cheat and use my existing S22 for the time being. I have 2 more kits but kinda want to shop for some Silmics or maybe Panasonics to go with it.
 And where would we be vacationing?


----------



## sachu

looksl ike S22 gremlins yet again..

 I am getting positive voltage alright. Negative though is a different matter. Getting +4.xx volts on the output.

 I changed MOSFETs and that didn't help.

 Wonder if Q12 is not working? Any idaes?


----------



## sachu

looks like it could be CR4 as both the collector and emitter of Q12 read -41 volts



 Collector of Q10 has -40 volts

 There is a drop of -41 volts across CR4 which has got to be wrong.

 Anyone got a spare?


----------



## digger945

How does it compare to the operating points?
 42 and 41 volts are on the operating points prior to the mosfets and at the emitter of Q12, respectively.

 I can give you a 5314 if you need it.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_How does it compare to the operating points?
 42 and 41 volts are on the operating points prior to the mosfets and at the emitter of Q12, respectively.

 I can give you a 5314 if you need it._

 

Yeah.. but the collector of Q12 needs to be at 32 volts and it is not. It is at 40+ volts. Also I don't think we should be seeing 40 volts across CR4.
 Edit: As Scott mentioned in the PM the drop across CR4 needs to be 32 volts instead of 40 volts.

 You got a PM on the 5314 Scott.


----------



## sachu

Ok,

 I checked R14 and R15 and they were reading as open circuit.

 I replaced them and turned it on again and the S22 worked. I had -28.8 volts on the negative rails.

 So, I connected up the EHHA boards and turned on the amplifier.

 When the S22 kicked in after the delay on the timer/relay board, I saw smoke from the two resistors I had just replaced. I quickly turned off the amp.

 I then removed the power connections to the EHHA boards and turned on the S22 by itself. Everything was fine.

 Then I proceeded to connect the EHHA board that had not shown any problems thus far. The amplifier powered up fine, no smoke, i had music out of the one channel that was connected.

 Turning off the amp and disconnecting the working channel I then hooked up the second EHHA board on which I had changed MOSFETs and output resistors once already.

 I made sure there were no shorts between the MOSFETs and the chassis, between the MOSFET pins. I turned on the amp and sure enough R14, R15 on the S22 started burning like LEDs..and I turned off the amp.

 Why the negative rail is getting hammered I donot know. Any one care to hazzard a guess? A variac would be so helpful with what I am doing. Guess it would be worth the 35$ investment.


----------



## sachu

Well, negative rail and ground on the EHHA board causing the problems is shorted. No wonder the negative rail on the S22 got screwed.

 I removed the OPA134 servo opamp on the board to see if the opamp was shorted internally, but it was not the case. Something else is shorteing the negative rail to ground. Next suspect is IC2 the negative voltage regulator. I will try replacing it tomorrow and see if it makes any difference.

 EDIt: It is not IC2...


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I'm gonna cheat and use my existing S22 for the time being. I have 2 more kits but kinda want to shop for some Silmics or maybe Panasonics to go with it.
 And where would we be vacationing?_

 

Los Angeles, the weekend BEFORE Can Jam


----------



## digger945

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Well, negative rail and ground on the EHHA board causing the problems is shorted. No wonder the negative rail on the S22 got screwed._

 

Lemme know if there is anything else you need (or if you think you still need the current regs) by 3am in the morning and I'll throw it in the mail tomorrow. I don't have much but I may have what your looking for.


  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Los Angeles, the weekend BEFORE Can Jam 
	

	
	
		
		

		
		
	


	


_

 

Bummer. Maybe next year. It would have been really cool to go to this one as I'm sure many HF'ers will be there as well as some great gear.


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Well, negative rail and ground on the EHHA board causing the problems is shorted...._

 

I would firstly check the air wiring and make sure there is no bridge to the groundplane. The next option is more daunting and it may be easier to just build another board 
	

	
	
		
		

		
		
	


	




 but start with Q12) , the small caps could also be to blame - no real way of identifying which but it will need a stepwise removal of parts and recheck for shorts after each piece is removed . 

 AC might have a more theory directed approach but this is the way I would do it - one piece at a time until short goes away. Then replace them all again.


  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ A variac would be so helpful with what I am doing. Guess it would be worth the 35$ investment._

 

couldn't recommend one enough - they have so many uses besides allowing you to power up gear slowly ,eg instant variable speed drill etc and $35 is daylight robbery 


  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Los Angeles, the weekend BEFORE Can Jam 
	

	
	
		
		

		
		
	


	


_

 

now THATs gotta smart 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

Can you guys throw a variac recommendation my way, I'm not sure what they do (autoformers?) but if it's gonna save me grief I'd like to look into it as well as a bench psu.


----------



## dBel84

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Can you guys throw a variac recommendation my way, I'm not sure what they do (autoformers?) but if it's gonna save me grief I'd like to look into it as well as a bench psu._

 

I use a bigger version of this but 5A would be ample for our use. A surplus store would save you a bit of cash and shipping costs. 

 Circuit specialists also have a good selection of dual bench supplies . 

 ..dB


----------



## sachu

Alright..so when the resistors on the S22 blew last night, they took two more IRF9Z34s with them.

 So down to my last two Z34s I prayed that nothing would go wrong and replaced them. The S22 came back to life.

 I then proceeded to remove the faulty EHHA board and looking at the schematic tried to make sense of what components are between negative rail and ground. I had thought IC2 wasn't the culprit, but it turned out to be that it indeed was.

 I replaced IC2, plugged everything back in and it worked!

 I am however getting intermittent sparks from Q9M , an IRF9Z34N MOSFET. I have put insulation tape around the two outer pins to prevent accidental shorts. I wonder what could be causing those sparks.I will take a closer look at the mounting and check.


----------



## digger945

Should we wait to change your name to Sparky?(J/K)
 You do have adequate isolation on the tab of the mosfet I presume. 

 Many thanks to db for the links, just what I was looking for in a bipolar PS.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Should we wait to change your name to Sparky?(J/K)
 You do have adequate isolation on the tab of the mosfet I presume. 

 Many thanks to db for the links, just what I was looking for in a bipolar PS._

 

hehhe...man I have burnt 12 MOSFETs on this particular amplifier. 8 of them being IRF9Z34s 
	

	
	
		
		

		
			





 Not to mention 6 output resistors (1 pair on the EHHA and 2 pairs on the S22).

 A variac would have paid for half of its price by now if I had it.

 No more sparks..its all working fine. Adjusted the bias (0.22 across output resistors, 100mA) and balanced the tubes.


----------



## digger945

We eagerly await your listening impressions.




 Sparky.


----------



## smeggy

sachu, official member of team arcy-sparky


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_sachu, official member of team arcy-sparky 
	

	
	
		
		

		
		
	


	


_

 

heheh...I believe I was a member of that team a long time back...more like a membership renewal this time.

 listening impressions you say?...i love it..I love this amp. Compared to the CTH it is like a night and day difference. The impact that this amp has is unbelievable. The highs are nice and airy, no harshness whatsoever and the mids are spot on.
 Given that I have everything on the same chassis and that the inputs on one of the amp boards is only 4 inches away from the toroid, I have absolutely no hiss that I can hear from my Yamaha HP-2s. 
	

	
	
		
		

		
		
	


	





 I have had the amp running for about an hour and half and I can see that the chassis gets slightly warm, its at 42 deg C.

 Going to hook up Smeggy's K1000s later tonight and see what's what.


----------



## digger945

I'll take it you don't need the 5314 reg now.


----------



## sachu

Some pics of the glowy beast... The chassis is 17 inches long. The amplifier weighs about 20-25 pounds. 












 Just the end panels left to finish and I won't touch this beast ever. The panels should take a week or two.


----------



## dBel84

suh-weeet 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## cfcubed

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_listening impressions you say?...i love it..I love this amp. Compared to the CTH it is like a night and day difference. The impact that this amp has is unbelievable. The highs are nice and airy, no harshness whatsoever and the mids are spot on._

 

Now if we could build an EHHA for $150 and carry it in the spare space in our briefcases that'd be great
	

	
	
		
		

		
		
	


	




 But I'm afraid I won't be able to do those things with the β22 I plan to build either
	

	
	
		
		

		
		
	


	




 Great you got the beasty going & like it... Always a good ending. Now clean up your work area lest a fire marshal stop by.


----------



## TimJo

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_
 I did notice one typo on the schematic I believe. The signal path between the second triode and the lower VAS (Q6) passes through a unity gain mirror. The transistor pair in the mirror is labeled Q2-Q3, but I think it is supposed to be Q2-Q4, based on the parts list. Correct?
_

 

FWIW, I noticed one other minor typo on the schematic when I was studying it yesterday. 

 The rail cap for the 78L15 regulator is labeled C5, but it should be C6 based on the parts list.

 ~~~~~~~~~~~~~~~~~~

 So I was curious what heater configuration you guys are using in your builds?

 6.3v or 12.6v - AC or DC ?

 I'm trying to decide what transformer to use.


----------



## sachu

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Now if we could build an EHHA for $150 and carry it in the spare space in our briefcases that'd be great
	

	
	
		
		

		
		
	


	




 But I'm afraid I won't be able to do those things with the β22 I plan to build either
	

	
	
		
		

		
		
	


	




 Great you got the beasty going & like it... Always a good ending. Now clean up your work area lest a fire marshal stop by._

 

hahha..quite true..and the reason why I will keep my CTH. The EHHA cost me about 230$ to build including the extra burnt MOSFETs and such. If I had not been stupid the first time round I would have been looking at 200$ even, which was the target price to start with.

 ANd what do you mean clean up the work area...I just did before I took those pics 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_FWIW, I noticed one other minor typo on the schematic when I was studying it yesterday. 

 The rail cap for the 78L15 regulator is labeled C5, but it should be C6 based on the parts list.

 ~~~~~~~~~~~~~~~~~~

 So I was curious what heater configuration you guys are using in your builds?

 6.3v or 12.6v - AC or DC ?

 I'm trying to decide what transformer to use. 
	

	
	
		
		

		
		
	


	


_

 

Don uses a 12.6V DC heater configuration.

 I am using a 6.3V DC configuration with a maximum current of 3A on the rail.
 I can use 6H30 super tubes in my amp as they consume about 2A at the heaters.


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Don uses a 12.6V DC heater configuration._

 

just to qualify that statement - I use a simple LM317 reg to get 12.6Vdc and then string the 6.3V tubes in series. This amp is not designed to work with 12xx series tubes and works best with 6GM8 , 6DJ8 or for those needing more cojones 6H30 ..dB


----------



## wiatrob

You know Sachu - it's a well known fact that, when used as an amp foot, a dog eared copy of The Dark Tower is known to cause shorts in Mosfets, up to a dozen before it loses it's _puissance 
	

	
	
		
		

		
		
	


	



_


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_You know Sachu - it's a well known fact that, when used as an amp foot, a dog eared copy of The Dark Tower is known to cause shorts in Mosfets, up to a dozen before it loses it's puissance 
	

	
	
		
		

		
		
	


	



_

 






 There is another Dark Tower book holding up the other end..


----------



## wiatrob

I don't see any dissipation info for the output devices on the website. Anyone with a Kit (or db!) know a recommended heat sink size?

 I'm going bjt, but it would nice to know both, There's room for some beefy sinks on the PCB...


----------



## runeight

3W per device if you're just driving headphones and stay in class A. I would use at least 1.5" high heatsinks although I don't recall what's in the parts list on the website.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_ I would use at least 1.5" high heatsinks although I don't recall what's in the parts list on the website._

 

Heatsinks 2 TO-220 Vertical






 I cobbled together an Excel BoM for the EHHA - I'll send it on when I proof it


----------



## runeight

Thanks. Hopefully my websites have improved since the the first few sections were done. And a lot of this thanks to to all of you for helping to create better information (such as Excell BoMs).


----------



## dBel84

There should be an excel BOM in circulation - not sure how updated mine is but it is more than likely pretty much all there..dB


----------



## wiatrob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_There should be an excel BOM in circulation - not sure how updated mine is but it is more than likely pretty much all there..dB_

 

I searched and didn't see one. Most of the choice info is gone now that Chu Moys site went offline. I read through the thread once but wish I had grabbed it.

 If you want to send me yours I'll be happy to incorporate stuff i don't have (mine is 90% with Mouser part numbers)


----------



## dBel84

it's all yours 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

I still need to order a couple of resistors for mine but at least my S22 is working now so when I do finish it I'll have power


----------



## digger945

There are two Q3's on the schematic at Cavalli Audio. The 2SA1145 should be Q4 as it is on the pcb?

 Almost done with one board. I'll be listening to this booger pretty soon. I'll try to post some pics later today. I think this amp is gonna sound great.


----------



## runeight

Yes, that's correct about Q4. I've changed the schematics on the website and I've also fixed C6 (which was mistakenly labeled C5).

 Good luck!!


----------



## digger945

Yea I forgot about that cap.
 A couple pics to wet your appetite. 




 I ended up leaving the inside pins in the Aavids and driving out the outer pins(the ones closest to the edge of the pcb) for now. The inner pins seem to line up good and give good placement to the HS's. Even then the holes in the pcb need to be drilled out some to get the pins in.
 Epcos and FM caps, Vishay RN55D resistors(Vishay PR-02 2W for output), "O" class Toshiba's, R13,22 and 23 socketed. C2 and C3 unpopulated, I plan to start witha gain of 11 and go from there.




 Went to the initial setup page and *aw shucks* totally forgot about the 6.3V PS so I got another pcb to stuff (Glass-ware H-PS-1). Maybe I can have it listenable by tomorrow sometime. Ain't made up my mind if I wanna put the terminal blocks on top or bottem yet.
 Ideas welcome.


----------



## dBel84

it is really great to see a few more of these popping up, looking forward to hearing more impressions/opinions as things get going. so far all I have had is Sachu's nagging for the past 2 years and perhaps one day I will get mine back too 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_it is really great to see a few more of these popping up, looking forward to hearing more impressions/opinions as things get going. so far all I have had is Sachu's nagging for the past 2 years and perhaps one day I will get mine back too 
	

	
	
		
		

		
		
	


	




 ..dB_

 

heh...you know the EHHA is nag worthy..and definitely hoard worthy..

 Guess I will return your amp to you now that I have mine going. Though I serisouly wish I had the end panels done so i can call it a day with my 'baby'.


----------



## dBel84

What wood did you decide to use - I am sure you have mentioned it but my memory is a tad wobbly. No rush on my amp , better to take your time and get yours done right than have to mess about with it at a later date..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_What wood did you decide to use - I am sure you have mentioned it but my memory is a tad wobbly. No rush on my amp , better to take your time and get yours done right than have to mess about with it at a later date..dB_

 

poplar or oak is what am thinking..something dark to go with the clear aluminum chassis.


----------



## digger945

I'm guessing that .5 to .8V offset on the output is OK and can be handled when the opamp is inserted and powered up again.
 I don't see anything at Cavalli Audio about adjusting offset prior to inserting the opamp, only quiescent current of the outputs.

 Initially had 2.7V offset on one board and swopped tubes to get her down to .8 on one and got lucky with .5V on the other one right off the bat.

 EDIT: They seem to have settled down to negative .4V and negative .5V now.


----------



## dBel84

those are EXCELLENT numbers ..dB


----------



## digger945

OK, guess that's to be expected with tubes.
 Just need to troubleshoot why I aint got the .22V across the output resistors and we should be listening soon(mosfets are dead cold). All measurements are spot on with the Cavalli initial setup page except the .22V across those 2.2ohm's.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_OK, guess that's to be expected with tubes.
 Just need to troubleshoot why I aint got the .22V across the output resistors and we should be listening soon(mosfets are dead cold). All measurements are spot on with the Cavalli initial setup page except the .22V across those 2.2ohm's._

 

Crank up R21 on either side until you see the voltages go up across the output resistors.
 Once you have 0.22Volts across the resistors, then adjust R6 to get pin6 of the opamp to read 0 volts. 

 Then check voltage across output resistors again and readjust R21 if need be to get 0.22Volts across o/p resistors.


----------



## digger945

Got it!
 OK i got like 60 and 70mV on pin 6 so I'm gonna power down and put the opamps in now.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Got it!
 OK i got like 60 and 70mV on pin 6 so I'm gonna power down and put the opamps in now._

 

Cool..once you have the tubes balanced and bias set..prepare for total awesomeness!!
	

	
	
		
		

		
			




 This truly is the Emperor of Hybrids!!..


----------



## digger945

Thanks for the help Sachu!
 We might just have an Aikido beater here boys.




 Initial impression after just a couple of minutes, this little booger ROCKS!!! I totally love the (fill in your fav audio adjective here).
 Biased at just under .22V on the outputs, the heatsinks are not so hot that you can't hold your hand on 'em for as long as you want.
 Can't wait to try the bugle boy 6gm8's, 6dj8's, 7dj8's(thanks Ludoo/Donald/wiatrob), and of course the 6H30's.


----------



## Ynis Avalach

Is(has) anyone building the BJT version?


----------



## digger945

I have two more boards. I think I'm gonna socket the outputs and associated parts to try different stuff like BJT's. I also have some Renesas mosfets I'de like to give a listen to.
 You can see the sockets in the upper right of the pic above, I came close to doin it on this one but wanted to hurry up as we have just closed on a new home and will be busy moving all this and next week. This will be my last work at the bench for at least a week or more.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Thanks for the help Sachu!
 We might just have an Aikido beater here boys.




 Initial impression after just a couple of minutes, this little booger ROCKS!!! I totally love the (fill in your fav audio adjective here).
 Biased at just under .22V on the outputs, the heatsinks are not so hot that you can't hold your hand on 'em for as long as you want.
 Can't wait to try the bugle boy 6gm8's, 6dj8's, 7dj8's(thanks Ludoo/Donald/wiatrob), and of course the 6H30's._

 

hah! wicked!!toasting another EHHA with a Widmer's IPA..
	

	
	
		
		

		
		
	


	




 enjoy the wonderful amp..can't wait to see it all squared away in a case.
	

	
	
		
		

		
		
	


	




 I was however expecting to see 4 boards in balanced config or is that at a latter stage.


----------



## smeggy

Excellent work, looks great and I'm itching to hear mine.. one day 
	

	
	
		
		

		
		
	


	




 Got the new case ready for it, just need to finish the boards


----------



## dBel84

congrats ..dB

 edit :  Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_We might just have an Aikido beater here boys._

 

interesting 

  Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_.......and of course the 6H30's._

 

now this I am very interested in


----------



## digger945

Widmers must be better than Bud eh.
	

	
	
		
		

		
		
	


	



 You know I think I'll wait and see how this one does before considering a balanced configuration. Besides that leaves me with two more boards to play with(see post above). I didn't mention that I couldn't find the schematic with the H-PS-1 power supply parts so I just used a 12V 1A wallwort for the heaters in series. I have a wee bit of low freq hum but I'm sure it will probably go away witha better heater supply maybe. I noticed that the ground on 6.3V heater supply on the Cavalli website is connected to the board star ground in Alex's wiring section.
 Still gotta do the S22. It would be killer if the S22 had a tube heater output.

 One more thing I noticed. As soon as I powered down and installed the opamps I checked the offset not 2 seconds after powering up again and it was at zero already.
 Stuck a piece of wire between the 12V ground and star ground and the hum went way down.


----------



## smeggy

how is it rigged up now, bench psu?


----------



## dBel84

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_Is(has) anyone building the BJT version?_

 

yes, the proto team built up 2 - verdict at the time was the the BJT and mosfet sounded similar but if you can build with a mosfet , why not 
	

	
	
		
		

		
		
	


	




 I did build one channel and test the BJT version but I never listened to the BJT as an amp..dB


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Widmers must be better than Bud eh.
	

	
	
		
		

		
		
	


	



 You know I think I'll wait and see how this one does before considering a balanced configuration. Besides that leaves me with two more boards to play with(see post above). I didn't mention that I couldn't find the schematic with the H-PS-1 power supply parts so I just used a 12V 1A wallwort for the heaters in series. I have a wee bit of low freq hum but I'm sure it will probably go away witha better heater supply maybe. I noticed that the ground on 6.3V heater supply on the Cavalli website is connected to the board star ground in Alex's wiring section.
 Still gotta do the S22. It would be killer if the S22 had a tube heater output.

 One more thing I noticed. As soon as I powered down and installed the opamps I checked the offset not 2 seconds after powering up again and it was at zero already.
 Stuck a piece of wire between the 12V ground and star ground and the hum went way down._

 

My heater ground is separate from the star ground. No hum whatsoever considering that the input side of one of the boards is only 4 inches away from the S22 toroid.


----------



## digger945

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_how is it rigged up now, bench psu?_

 

Sigma used for Dynamite.




 Kinda like stealing from the electic company
	

	
	
		
		

		
		
	


	



 Wallwort on the floor is for heaters.
 I really wish I could figure out how to make my new camera get a little bit better pictures. Not enough time in the day.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Sigma used for Dynamite.

 Kinda like stealing from the electic company
	

	
	
		
		

		
			




 Wallwort on the floor is for heaters._

 

ummm..is it too early to ask how it sounds compared to the dynamite?


----------



## digger945

I think your right(and thanks to you and db for the comments, notes taken for future reference and hookup when casing it up).
 I do sense a little bit of flabbiness in the ultra low end spectrum but hey you know we really need to let things settle in a bit, caps and all that. I don't think it's too early to say that this amp will be close if not surpass the Aikido I have listened to for so long now. Actually I'm not a bit embarassed to say that the Aikido steals a little bit of glory from the Dynamite in the space and presence catagory. It's just a fun amp to listen to, and I think the EHHA will be also.
 I'm listening to a Bob James "Restless" CD that I've enjoyed almost every day for a month now and so far I'm not one bit dissapointed. This amp makes beautiful music to my ears. I'm sure it will only get better with time.
 In the end it's the tube that makes all the difference to me, I just like(addicted actually) the sound


----------



## dBel84

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Sigma used for Dynamite._

 

wicked 

 and 

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ummm..is it too early to ask how it sounds compared to the dynamite?_

 

relentless 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I think your right(and thanks to you and db for the comments, notes taken for future reference and hookup when casing it up).
 I do sense a little bit of flabbiness in the ultra low end spectrum but hey you know we really need to let things settle in a bit, caps and all that. I don't think it's too early to say that this amp will be close if not surpass the Aikido I have listened to for so long now. Actually I'm not a bit embarassed to say that the Aikido steals a little bit of glory from the Dynamite in the space and presence catagory. It's just a fun amp to listen to, and I think the EHHA will be also.
 I'm listening to a Bob James "Restless" CD that I've enjoyed almost every day for a month now and so far I'm not one bit dissapointed. This amp makes beautiful music to my ears. I'm sure it will only get better with time._

 

Yeah I have noticed that flabbiness you talk about...more noticeable with Don's EHHA than mine. It sounds much better controlled on mine.


----------



## digger945

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_wicked 

 and 



 relentless 
	

	
	
		
		

		
		
	


	




 ..dB_

 

My goodness I could have built a house in the same amount of time it took me to research and build that thing. And to think I actually considered building another one just like it! Someone somewhere has it in thier sig, "there's a fine line between a hobby and a mental illness"..LOL.

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Yeah I have noticed that flabbiness you talk about...more noticeable with Don's EHHA than mine. It sounds much better controlled on mine._

 

Maybe we can start to tweak and roll some tubes and see how it goes, maybe get the master Alex involved. I really do think this amp has all kinds of possibilities. I think the overall sound is gonna come from the tube up front though(see this is where Alex could give a pointer or two). It's all good.


----------



## smeggy

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_
 Maybe we can start to tweak and roll some tubes and see how it goes, maybe get the master Alex involved. I really do think this amp has all kinds of possibilities._

 

That's why there's eventually gonna be a Mk II


----------



## digger945

Punishing bass, especially the track "Restless".
 I love bass, both the horizontal and vertical kinds.

 Yea Smeggy we gotta get some schematics and pics of this Mk II sometime soon.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Punishing bass, especially the track "Restless".
 I love bass, both the horizontal and vertical kinds.

 Yea Smeggy we gotta get some schematics and pics of this Mk II sometime soon._

 

heh..way ahead of you on that my friend..EHHA 2 has been in the works for a while now..
 But with the Poormans taking priority so expect the EHHA2 to be a couple of months away from prototype at least.

 The EHHA2 is going to be a much more powerful beast..in the B24 league in terms of power output.


----------



## digger945

I have some *blasphemy* [size=xx-small]speakers.[/size]


----------



## dBel84

sometimes that little red guy is soooo hard to ignore 




 seriously 
	

	
	
		
		

		
		
	


	




 ..dB

 but in cavalli tradition - that board ( being 2 years old) has been surpassed many times over


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_sometimes that little red guy is soooo hard to ignore 




 seriously 
	

	
	
		
		

		
		
	


	




 ..dB

 but in cavalli tradition - that board ( being 2 years old) has been surpassed many times over 
	

	
	
		
		

		
		
	


	


_

 

*drool*..me wants it...wants it now!!


----------



## smeggy

Is that one or both channels in there?


----------



## dBel84

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Is that one or both channels in there?_

 

good spot - tis both channels and this is not the beastie that will take you to 100W either , this was more like 25W . iirc It uses bipolar 100V and 40V power supplies , the 3rd tube is a driver for the other 2 tubes. I will leave Alex to tell you more when the time is right , this would have moved forward earlier but there did not seem much interest and then "other stuff" happened. It has been my plan to build the latest version a power amp and to use the current EHHA as a pre / headphone amp . Perhaps it is time 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

heh, well here's my EHHA case






 I think I'm gonna get another S22 kit seeing as how I have a spare toroid here and just make this a separate amp from the others, though I may put the CTH and mebbe SS in it too. Keep all the tube amps in one box and Solid states in the other


----------



## sachu

ba!..i hate you...that is one gorgeous looking case smeggy..

 I suspect you plan to drill out holes for the tubes to stick out.

 What kind of heatsinks are you using?


----------



## dBel84

have to agree, that is one sweet looking chassis , you going to lie the tubes flat and tucked away inside the case ( seeing as this is not a tube roller ) or punch holes as sachu eluded to? 

 just out of curiosity - what was it originally ? => nvmd saw that it was a Par Metal from the other thread

 ..dB

 ps - if you want to see them lying flat - have a look at steinchen's amp (pasted below)


----------



## smeggy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ba!..i hate you...that is one gorgeous looking case smeggy..

 I suspect you plan to drill out holes for the tubes to stick out.

 What kind of heatsinks are you using?_

 






 yep, gonna drill some holes and the heatsinks are the ones in the kit. I gave myself plenty of ground clearance so I can mount the boards lower if needed.

 DB, that's a nice amp, very clean inside.


----------



## wiatrob

Quote:


  Originally Posted by *Ynis Avalach* /img/forum/go_quote.gif 
_Is(has) anyone building the BJT version?_

 


 My power supplies are done, and all the parts are here for a BJT version. Hopefully by next weekend I'll have something to report


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_My power supplies are done, and all the parts are here for a BJT version. Hopefully by next weekend I'll have something to report
	

	
	
		
		

		
		
	


	


_

 

Look forward to that Bill...

 I just bought a pair of supertubes ..man are these expensive..but for my beloved EHHA even 145$ for a pair of these NOS 6N30P-DRs is worth it. 
	

	
	
		
		

		
		
	


	




Keep you chaps posted on this.


----------



## wiatrob

Power supplies are completed and tested. EHHA board stuffing begins this evening


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Power supplies are completed and tested. EHHA board stuffing begins this evening 
	

	
	
		
		

		
		
	


	


_

 

heh..very cool..have you decided on going balanced or active groundSE?

 What HV power supply are you using? 6.3V heater voltages? you going to accommodate the supertube in your heater supply?


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_heh..very cool..have you decided on going balanced or active groundSE?

 What HV power supply are you using? 6.3V heater voltages? you going to accommodate the supertube in your heater supply?_

 

Haven't decided, but will be building up all four boards. I will at least test it on the bench in balanced mode.

 My 6.3V heater supply is good for up to 2.5A - but I only plan on 6GM8s and 7DJ8s for now. My planned case is not tall enough for 6H30s 
	

	
	
		
		

		
		
	


	




 $$$


----------



## smeggy

I finally got around to putting in my Mouser order last night to get the rest of the parts needed for the boards etc but forgot the crap for the heater circuit.. I have a small transfo 6.3 + 6.3V 1.3A center tap, just need to get the other bits so I'll need to go check the thing sachu is using and order those.

 Also ordered one of those delay switches from ebay, hopefully I'll get it all and done soon.


----------



## dBel84

you can run AC heaters if need be - we all ran dc to keep the noise floor down but this could be done at a later stage , i probably have the bits you need to throw a heater supply together too if you can wait for me to go digging ..dB


----------



## smeggy

Cheers Don, the transfo is a small radio shack thing but it's probably as good as needed for heaters. I'm not sure what parts I'd need for the supply but I have a perfboard ready for it. I can't believe I forgot to look before ordering the other stuff. Anyway, it's going to be quite the packed front panel when I'm done, 2x 1/8" socket, 1x 1/4" socket, 4 pin XLR, three power, one heater toggle and three pots 
	

	
	
		
		

		
		
	


	




 gonna be quite full, good job it's 16" wide.


----------



## digger945

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I just bought a pair of supertubes ..man are these expensive..but for my beloved EHHA even 145$ for a pair of these NOS 6N30P-DRs is worth it. 
	

	
	
		
		

		
		
	


	




Keep you chaps posted on this._

 

I already have 4 new Sovtek 6H30Pi's I got when Microsoft had the 30% Live Search thing going on here while back. Is there anything all that special needed to use these other than the 1A heater supply needed per tube? Should it be expected that they will need to be balanced using R6?

 Whatcha think about me sending two of these Sovteks and maybe sometime you can give them a listen and compare them to the DR's.
 Curious minds want to know


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_





 I already have 4 new Sovtek 6H30Pi's I got when Microsoft had the 30% Live Search thing going on here while back. Is there anything all that special needed to use these other than the 1A heater supply needed per tube? Should it be expected that they will need to be balanced using R6?

 Whatcha think about me sending two of these Sovteks and maybe sometime you can give them a listen and compare them to the DR's.
 Curious minds want to know_

 

Lucky you..however I bought the Reflektor (Saratov factory made) 1985 made 6H30P-DRs and not the newer production ones which I could have had for half the price.

 The tubes that normally run at higher plate voltages will have a higher imbalance at the lower 30Volts that we are feeding in our EHHAs.

 haha..sure thing..send me a pair and i would love to compare to the older NOS DRs..I hope I won't be disappointed with my investment else they will end up on the bay real fast.


----------



## digger945

Yea, these are brand new, not NOS.
 Exactly like these...




 I'm guessing yours look something like these, although I don't think the ones listed here are DR tubes.
 I really look forward to seeing what you think of them, not a lot of opinions on these tubes except for owners of BAT's(that I've been able to find online). I think I remember a pair sold here not too awful long ago.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Yea, these are brand new, not NOS.
 Exactly like these...




 I'm guessing yours look something like these, although I don't think the ones listed here are DR tubes.
 I really look forward to seeing what you think of them, not a lot of opinions on these tubes except for owners of BAT's(that I've been able to find online). I think I remember a pair sold here not too awful long ago._

 

yeah those are the new production ones...the onees from ebay are Reflektors made in 2002.

 The ones I bought are these..


 Sending you a PM scott..would love to try those out in the EHHA..I know Don is looking forward to listening to these in the EHHA as well..


----------



## smeggy

I thought the EHHA wasn't tube fussy, is that wrong?


----------



## dBel84

the tubes don't have to be balanced as there is the trimmer to balance the tail current. BUT, they cannot be grossly mismatched. I would not look to be rolling tubes in this amp = use the 6GM8's from the kit and see what you feel..dB


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I thought the EHHA wasn't tube fussy, is that wrong?_

 

Smeggy, the EHHA needs well matched triode sections. If not, then you use R6 to balance out each of the triode sections in one tube. The imbalance is more pronouced in tubes that are normally operated at higher voltages like the 6DJ8 and 6922..The 6GM8, R6 is not really needed unless the tube is really of poor quality.


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ the EHHA needs well matched triode sections_

 

as above 
	

	
	
		
		

		
			





 , the tubes cannot be way out of spec though and it won't hurt for them to be matched. The trimmer allows for some compensation as sachu noted..dB


----------



## runeight

Hopefully won't add any confusion.

 The EHHA is not designed as a tube rolling amp. It's primary tube is the 6gm8 and it will work well with 6922 and 6h30 because they are both pretty good low voltage high voltage tubes.

 I don't recommend any other tube type in this amp although you can probably force them to work. 
	

	
	
		
		

		
		
	


	




 R6, as mentioned, is there to balance the triode sections. It should be set at its midpoint on the first power up. If the O/P DC offset is zero (or small mV) then it shouldn't be necessary to adjust R6. Although if you are an absolute purist you can make two possible adjustments.

 1. Adjust R6 until the voltage drop across R3 and R4 is the same. Then ensure that the O/P DC offset is zero.

 2. Measure pin 6 of the opamp and adjust R6 until this voltage is close to zero. This balances the sand section of the amp by unbalancing the tube section.

 You may or may not hear any audible differences ...


----------



## digger945

I already tried some 6dj8's and some 7dj8(PCC88) with OK results. Each tube has it's strengths and it's own signiture. They both balance out very well and sound great. I have used these in another amp with less than 12V on the plate. 

 Another thing I wanted to try was to change R22,23 from 33.2K to 62K as per your website, and maybe lower the gain a bit. I'm looking forward to playing around with this amp, you don't know how many times I thought about using a tube as differential long tail pair input for an amp like this.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hopefully won't add any confusion.

 The EHHA is not designed as a tube rolling amp. ... SNIP_

 

Hmmm, that *Tube Rolling *section title on the tweaks page of the EHHA website is misleading


----------



## runeight

Yes, using a tube diff pair is a fun idea for many reasons, including that you get a fully DC coupled hybrid amp. Maybe we will eventually get to the EHHA II, but I absolutely must solve some other problems first. 
	

	
	
		
		

		
		
	


	




 Your idea about playing with the gain is a good one. The amp is designed for this (as opposed to the tube rolling) and I think you will hear differences.

 Increasing R22, R23 will increase the OL gain which, if you leave R12, R13 alone, effectively increases the NFB which effectively increases the BW of the amp. And vice versa.

 I know that you've looked at the tweaks sections to see the possibilties and I am very interested in what you think of the different variations. You will be the first person to explore this aspect of the amp.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, using a tube diff pair is a fun idea for many reasons, including that you get a fully DC coupled hybrid amp. Maybe we will eventually get to the EHHA II, but I absolutely must solve some other problems first. 
	

	
	
		
		

		
		
	


	




 Your idea about playing with the gain is a good one. The amp is designed for this (as opposed to the tube rolling) and I think you will hear differences.

 Increasing R22, R23 will increase the OL gain which, if you leave R12, R13 alone, effectively increases the NFB which effectively increases the BW of the amp. And vice versa.

 I know that you've looked at the tweaks sections to see the possibilties and I am very interested in what you think of the different variations. You will be the first person to explore this aspect of the amp. 
	

	
	
		
		

		
		
	


	


_

 

yes, besides, I want people to listen to the EHHA1 first as it is in my opinion right up there with the best if not the best (but it _really really_ is *the best*





).


 Of course we will be on the EHHA2 once we get past the poormans. I might end up playing with the NFB and BW too...but one thing at a time.


----------



## dBel84

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Your idea about playing with the gain is a good one. The amp is designed for this (as opposed to the tube rolling) and I think you will hear differences._

 

I could not agree more - when sachu started down this road I emailed him a portion of the proto discussion surrounding this and the thiing that amazed me then and still appeals to me now, is the fact that you can change this amps signature from ultra sharp clinical piercing holes in bleeding ears all the way down to a warm sounding amp ( without the fuzzy edges of a vintage tube amp ) 


 ..dB


----------



## smeggy

Cool, I'm really looking forward to getting mine going.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Your idea about playing with the gain is a good one. The amp is designed for this (as opposed to the tube rolling) and I think you will hear differences.

 Increasing R22, R23 will increase the OL gain which, if you leave R12, R13 alone, effectively increases the NFB which effectively increases the BW of the amp. And vice versa._

 

Might it be possible to replace R13 with a 2K5 trimpot, and R22,23 with 500k's (trickier...)

 Also, the compensation capacitors (C2/C3) mentioned in the Performance section do not relate to any of the gain settings in the Tweaks tables - so am I correct in assuming they only affect slew rate/FreqRes for gains below 7.8?


----------



## runeight

Yes, it would be possible to replace those fixed resistors with pots.

 R22, R23 will be very tricky as mismatched pot settings will imbalance the complementary halves of the O/P stage.

 Correct on the comp caps. You don't even really need them below 7.8. They were just needed to prevent the sq wave from ringing. You can see how much the slew rate drops with the big comp caps and I think you might notice this on very fast transients even though your ears can't possibly follow the audio at these speeds. 
	

	
	
		
		

		
		
	


	




 BTW, I know that the heatsink holes are a bit off. This is not Jeff's fault but mine because I suggested a particular supplier. This was for necessary reasons at the time to prevent the EHHA from going the way of the SOHA. No more to be said on this.

 However, since none of you are likely to solder the heatsinks into the board, the easiest thing to do is to pull the mounting pins out of the heatsinks rather than trying to drill out the holes.


----------



## smeggy

Anyone here still awake? I'm about to put in another mouser order and want to know what components I'd need for a heater supply.

 I have a 6.3-0-6.3v 1.2A transfo. I'm also getting one of those Sofia delay circuit but I don't know what else I need for the heater.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Anyone here still awake? I'm about to put in another mouser order and want to know what components I'd need for a heater supply.

 I have a 6.3-0-6.3v 1.2A transfo. I'm also getting one of those Sofia delay circuit but I don't know what else I need for the heater._

 



 here you go smeggy...

Mouser project for the 6.3 volt heater supply..


----------



## smeggy

cheers sachu 
	

	
	
		
		

		
		
	


	




 Seems like a lot of parts for a heater.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_cheers sachu 
	

	
	
		
		

		
			





 Seems like a lot of parts for a heater. 
	

	
	
		
		

		
		
	


	


_

 

Naa..check it now..I updated it


----------



## digger945

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 BTW, I know that the heatsink holes are a bit off. This is not Jeff's fault but mine because I suggested a particular supplier. This was for necessary reasons at the time to prevent the EHHA from going the way of the SOHA. No more to be said on this.

 However, since none of you are likely to solder the heatsinks into the board, the easiest thing to do is to pull the mounting pins out of the heatsinks rather than trying to drill out the holes._

 

If you just remove one pin from the HS then you can use the other pin, you'll have to try inserting it both ways to see which way it centers up with the pcb silkscreen. The hole that the pin goes into can be reamed out with a 3/32" drill bit by hand or with a pair of pliers. I can't remember but I think the inner pins are the ones that line up with the silkscreen. Since I'm halfway into moving into a new home I just used the drill bit to knock out the one pin. I'll take some pics sometime this weekend to show how it looks. The pins in some of these Aavid HS's are stubborn to get out.

 Another option is to order HS's without pins. They are no more than the one with pins.


----------



## holland

What VA is required for the main trafo?


----------



## sachu

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_What VA is required for the main trafo?_

 

Depends on what you are driving..I have a 160VA for mine. But a 60VA ought to do fine as well if it is just a headphone amp.


----------



## holland

what options would require the use of 160VA? Speakers? If so, how much can this (mosfet ver) put out?


----------



## wiatrob

The suggested trafo values for headphone use are on the wiring page (in the diagrams):

Embedded Hybrid Headphone Amlifier

 2ch 400mA
 3ch 600mA
 4ch 800mA

 Can't comment on speaker use. I went with a 1.0 amp Avel so I could get good case fit...

 EDIT: and not to pick nits, but there's a typo in the web page title, apparently


----------



## smeggy

Hopefully I'll now have everything I'll need to get it up and running... finally! 
	

	
	
		
		

		
		
	


	




 BTW, anyone got a pair of 9 pin socket savers they want to sell?


----------



## dBel84

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_what options would require the use of 160VA? Speakers? If so, how much can this (mosfet ver) put out?_

 


 I will let Alex answer this more completely but in it's current configuration , the EHHA is set up as a headphone amp. If you make a few adjustments and parallel output mosfets, it can put out 25W. No one has set up an EHHA to do this and you would be exploring new territory , my suggestion is to build it as a headphone amp and if you are interested in a speaker amp with similar topologies, nag the hell out of the man in the overcoat 
	

	
	
		
		

		
		
	


	




 ..... [size=xx-small]EHSA awaits its turn 
	

	
	
		
		

		
		
	


	




[/size] ..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_I will let Alex answer this more completely but in it's current configuration , the EHHA is set up as a headphone amp. If you make a few adjustments and parallel output mosfets, it can put out 25W. No one has set up an EHHA to do this and you would be exploring new territory , my suggestion is to build it as a headphone amp and if you are interested in a speaker amp with similar topologies, nag the hell out of the man in the overcoat 
	

	
	
		
		

		
		
	


	




 ..... [size=xx-small]EHSA awaits its turn 
	

	
	
		
		

		
		
	


	




[/size] ..dB_

 

I want to do this with my EHHA....**goes away to send the main man an email**


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Hopefully I'll now have everything I'll need to get it up and running... finally! 
	

	
	
		
		

		
		
	


	




 BTW, anyone got a pair of 9 pin socket savers they want to sell?_

 


 PM sent - I may have a pair.


----------



## dBel84

It is such a pity that the headwize thread is down as this is all clearly documented over there , which reistors to beef up , how to parallel output devices etc. 

 I have never tried but I suspect my EHHA could drive sensitive speakers as is, I am no mood to overdrive the S22 or the output mosfets so I will defer from such tom foolery 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The suggested trafo values for headphone use are on the wiring page (in the diagrams):_

 

I looked all over the page 3x until I saw your parenthetical. I apparently did not see it as I didn't expand the diagrams. 
	

	
	
		
		

		
		
	


	




 Let's have that pulled out into text.


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_It is such a pity that the headwize thread is down as this is all clearly documented over there , which reistors to beef up , how to parallel output devices etc. 

 I have never tried but I suspect my EHHA could drive sensitive speakers as is, I am no mood to overdrive the S22 or the output mosfets so I will defer from such tom foolery 
	

	
	
		
		

		
		
	


	




 ..dB_

 

hah..I am pretty sure mine can drive small speakers..160Va transformer, plenty of heatsinking potential..I will probably just wait for the EHHA 2 to use with speakers and put a pair of RCAs as lineouts on the EHHA1. So the EHHA1 can be paried along with the EHHA2 to make a kickass pre+power combo. Yes yes Don..I am definitely going to borrow this idea of yours..


----------



## smeggy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_PM sent - I may have a pair._

 

Thanks, my PM thing is broken at the minute but I'll read the email


----------



## digger945

Listening to some Foreigner/Doobies/Ambrosia(date me will ya) with PCC88's and wow. I like this alot. Can't wait to get moved and try some tweaking on this booger, and have more juice to run the 6H30 heaters.

 Yea I hope Chu has Headwize up and running soon, you don't realize how much you use and read the forum until it's down. I have heard that he is gonna make it bulletproof when he's finished and it's back online.


----------



## sachu

Just received the perf board from Wiatrob for my EHHA..man did i screw up the measurements on this. I meant to type 41cm x 12cm, but ended up sending 41 x 20 in my email. 
	

	
	
		
		

		
			















 Well will have to get this cut down to size locally..somone with a table saw should be able to do this in a matter of seconds.


----------



## dBel84

aaaah now I get what you meant by perfboard 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## wiatrob

Curse of the Dark Towers! 
	

	
	
		
		

		
		
	


	




 I'd be happy to make you another...


----------



## runeight

I don't seem to be getting notifications properly.

 Anyway, there were some speaker questions a while back.

 I don't remember the resistor changes but the BJT version will make almost 25W with the 30V supply into 4R. No need to parallel.

 The mosfet version due to the SG voltage needed to open up the channels can't swing as close to the rails. I think about 18W is the absolute max.

 I think there is just one change to one of the feedback resistors. If anyone really wants to do this I'll track this down. This was a while ago.

 Please tell me what else I may have missed.


----------



## smeggy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Curse of the Dark Towers! 
	

	
	
		
		

		
		
	


	




 I'd be happy to make you another..._

 

Oooh, I want some.. 16x16"

 pweeeeeezeeee!!






 EDIT*

 Does this amp mind headphone swapping while live or should I add a ground breaker switch before the headphone socket to prevent shorts on 1/4 and 1/8" jacks.


----------



## bjarnetv

did someone mention jeff selling a kit for this amp?
 i just finished my mini3, which means i am an expert builder, so its time to move up to the big stuff 
	

	
	
		
		

		
		
	


	




 how does it measure up to the M3? (sound, price and difficulty of build)
 i currently have an ef1, and its not a good match with my orthos, so i am lusting for something with moar power.


----------



## digger945

Yes, Jeff told me in an email about 2 weeks ago that he had the kits ready to ship. You may have to email him if he doesn't have them on the GJ website yet.
 I have never heard the M3.
 I don't know what the output power is for the EHHA but I would guess it's capable of passing something close to the limit of the PS.


----------



## smeggy

Apparently this has ample power with more on tap if needed. I would think this is probably easier to make than the M3 but it will need a S22 as well, along with heater circuit and a delay of some description so it does get a little heavy on parts in the end.

 Jeff does sell kits and they're $110 or so give or take plus postage and this is for two fully populated boards worth. The rest is upto you, though he will sell you a S22 as well for another $100 or so.


----------



## sachu

An M^3...this eclipses the B22..not that I have heard a B22..I will find out soon enough though as to the charecteristics of the B22..

 Build the EHHA..and you won't need another SE amp ever!!

 Oh and it just lays the smackdown when it comes to orthos..you won't believe how good the Fostex T50Rp is until you have heard it through this or the Stacker amp.


----------



## bjarnetv

guess ill save up some money for some EHHA and sigma22 kits then


----------



## MrSlim

Digger, did you end up doing a 3 channel unit or are you just listening to a 2 channel?
 I'd love to do a 3 channel. If the EHHA is everything Sachu is saying, it could be a giant killer.. 

 Oh, Sachu, I've decided to keep the extra ECC82, that I mentioned on the other thread..
 I'm really enjoying it in my CTH right now, and I want to keep it as a backup.. or for the second one I was planning on building..


----------



## smeggy

After putting in two mouser orders I discovered I don't have any friggin mosfet mounting kits... This crap gets really frustrating sometimes.


----------



## digger945

Just 2 channels for now.


----------



## looser101

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_After putting in two mouser orders I discovered I don't have any friggin mosfet mounting kits... This crap gets really frustrating sometimes._

 

These are nice.


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_After putting in two mouser orders I discovered I don't have any friggin mosfet mounting kits... This crap gets really frustrating sometimes._

 

Don't use Wax! (Sorry Sachu
	

	
	
		
		

		
		
	


	




) Thinking ahead about all you need for a project is actually a skill you will hone as you do more DIY -And accumulate bins of leftover parts!)


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Just 2 channels for now._

 

CTH Kit assembly has been eating my spare time, but here's some EHHA pr0n:


----------



## dBel84

they just look so sad without their jewelry - waiting to see them spring to life ..dB


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I have never heard the M3.
 ._

 

I like it and am interested to see how the three channel topologies compare. Digger, let me know if you are interested and I will loan you my M^3 to audition after my comparo...


----------



## holland

wiatrob, 4 boards? You're going balanced?


----------



## smeggy

luckily for now I have a dead beta 22 board with just the right number of mounting kits attached, time to strip it down. I'll get some of the beezar kits soon.


----------



## dBel84

why is it that I get this itch when I other folk start building STUFF 
	

	
	
		
		

		
			





 ..dB


----------



## digger945

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_CTH Kit assembly has been eating my spare time, but here's some EHHA pr0n:_

 

Speaking of kit, I still have all the parts for a CTH if anyone is interested. I haven't robbed anything from the pink baggy...._yet!_

  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_they just look so sad without their jewelry - waiting to see them spring to life ..dB_

 

Like yourself, I tried therapy but it didn't work very long for me either
	

	
	
		
		

		
		
	


	




(I hope it isn't the solder fumes LOL)


  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I like it and am interested to see how the three channel topologies compare. Digger, let me know if you are interested and I will loan you my M^3 to audition after my comparo..._

 

I am so busy moving and when I'm finished I will be helping the kids do the same. I appreciate the offer, maybe later sometime.

  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_luckily for now I have a dead beta 22 board with just the right number of mounting kits attached, time to strip it down. I'll get some of the beezar kits soon._

 

Well that's better than robbing parts from a working amp (yea I'm guilty). I do have all the loose parts somewhere so lemme know if you want me to stuff an envelope and send it your way.

 I'm gonna leave the computer here 'till I have internet hooked up at the new pad. I think a man is officially moved when he takes his computer and the mayonnaise to his new cave. I will be taking the EHHA with tonight and listen to the nano for awhile.


----------



## smeggy

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_why is it that I get this itch when I other folk start building STUFF 
	

	
	
		
		

		
		
	


	




 ..dB_

 

It's because deep down you know you have this gnawing urge to populate a Bijou kit for me


----------



## dBel84

ha ha ha ..dB


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_wiatrob, 4 boards? You're going balanced?_

 


 My plan is three channel - but what's one more board? 
	

	
	
		
		

		
		
	


	




 I've been curious about balanced for a while, so I will build a balanced version on the bench, but the plan (and case fit) is active ground...


----------



## dBel84

why not both - 4 channel with active ground SE and balanced configurations - be a neat little speaker amp in balanced mode 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## TimJo

I'm ordering three kits (and a S22 kit) from Glass Jar today. For the cost of a third kit, I figured why not give it a go, and Jeff was more than happy to oblige. 
	

	
	
		
		

		
		
	


	




 For the ground channel, would you want to configure the OL and CL gain at the same level as the R & L channel boards? I'm going to be socketing the resistors anyway, so I can always play around with it, but I'm curious about thoughts on this.

 Also, I haven't seen any discussion about pin 9 (the shield) on the 6gm8's - what are the effects of using the capacitor vs. ground vs. floating?


----------



## holland

ground should be unity gain.


----------



## TimJo

Makes sense... Thanks.


----------



## wiatrob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_why not both - 4 channel with active ground SE and balanced configurations - be a neat little speaker amp in balanced mode 
	

	
	
		
		

		
		
	


	




 ..dB_

 

Cause that's a lot of wiring! :^) But it's a distinct possibility - wired like a balanced M^3 (two separate SE amps or one balanced amp?)


----------



## digger945

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Also, I haven't seen any discussion about pin 9 (the shield) on the 6gm8's - what are the effects of using the capacitor vs. ground vs. floating?_

 

Using a small cap grounds the shield from AC. I haven't seen the shield grounded directly in anything yet, but I haven't seen everything yet either.


----------



## dBel84

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Cause that's a lot of wiring! :^) But it's a distinct possibility - wired like a balanced M^3 (two separate SE amps or one balanced amp?)_

 

I was thinking more along AMB's 4 channel B22 set up on his website - not given this much thought , just seemed like a good idea at the time. But it did get me thinking about a 4 channel EHHA with an S22 for each side 
	

	
	
		
		

		
			








 ..dB


----------



## runeight

I'm reminding you guys that the 3 and 4 channel wiring diagrams are on the website, including how to wire the ground channel's input, etc. Just in case you haven't looked.


----------



## dBel84

you guessed right - it has been a while since I browsed your fine site 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## holland

dBel84, regarding 3 and 4 channel configurations using 4 boards. How would that work? Are you suggesting a bridged mode of operation for the ground? I'm not sure how that would work. If you have an idea about how to "share" output ground between 2 boards without causing problems I'd really like to hear about it.

 A 6-channel configuration would work, with 2 active ground SE configs. I haven't seen one of those, in B22 guise, in a long time though. That probably means it's not worth it.


----------



## dBel84

This is what I was remembering 







 so no active ground option - just SE or balanced

 ..dB


----------



## digger945

The only advantage to having 6 amps over 5 is the ability to listen to 2 cans SE(with active ground) simultaneously. I can only listen to 1 at a time, and prefer listening balanced to SE with the one and only balanced amp I own.

 You fellers aint gonna stop 'till you see a balanced amp are ya
	

	
	
		
		

		
		
	


	



 I'll have to order a few more parts to replace the ones I messed up on (mosfet gate stoppers, put 'em in the wrong holes), but if I can manage to finish moving the bench stuff I'll see if I can stuff the other two boards next week sometime and give 'er a listen. I will need some jacks too, and probably one or two more things I'll end up forgetting on the first order.


----------



## dBel84

I have always thought this would make a fine balanced amp - I have no balanced source so it has never been a consideration for me but the day will come and it will be good to have an idea in mind for when it does. 

 I don't see the point of a 6 channel amp in any form but that is just me. At the moment I am still waiting to see an amp wow me more than the one I already have 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

Too many bits for me 
	

	
	
		
		

		
		
	


	




 Unfortunately the rest of the parts I ordered aren't here yet so it'll be another week at least before I can try to get mine going. I'm gonna be so happy (and surprised) if it fires up and works


----------



## wiatrob

Hmmm, well I seem to have a balanced source, and looks like I will balance my Senn600 and RS-1s (connectors are on the way). I would think having two amps in one box would make an awesome headphone A/B Box 
	

	
	
		
		

		
		
	


	




 but would probably need two volume controls.

 Here's a kwestion: Who device matched? And [how important/notice a difference] other than the output devices and (Q5&6?)


----------



## sachu

Donald matched his devices..he matched all the devices since he was having oscillations. However no such problems with the production builds. But how much it would benefit Donald can answer best..

 I am digging the EHHA love. I am glad my harping about this amp has finally dusted off the cobwebs it seems. It is like a NOS tube being found now..a gem that has been re-discovered. 
	

	
	
		
		

		
		
	


	




 and damn it you guys...you are making me want to build two more boards and go balanced..now that I have a balanced source (courtesy of the Canjam raffle 
	

	
	
		
		

		
		
	


	




)


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_...now that I have a balanced source (courtesy of the Canjam raffle 
	

	
	
		
		

		
		
	


	




)_

 

I heard - congrats 
	

	
	
		
		

		
		
	


	




 There are some transistors which are more important to have matched - mostly the bjt mirrors, I will have to go back and see specifically which ones Tom and Alex mentioned , unless Alex recalls this information himself. 

 ..dB


----------



## wiatrob

The ones I mentioned - Courtesy of Alex Fine Site:

Embedded Hybrid Headphone Amlifier

 I had a breadboard setup for matching - I was just being laaaazy - but it will be good experience.


----------



## dBel84

I don't know why I even question - I should know all that information is there. It has just been a while since I seriously thought about this amp or visited the site. ( yes shame on me ) ..dB


----------



## TimJo

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_For the ground channel, would you want to configure the OL and CL gain at the same level as the R & L channel boards? I'm going to be socketing the resistors anyway, so I can always play around with it, but I'm curious about thoughts on this._

 

 Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_ground should be unity gain._

 

So if I'm understanding this circuit correctly, it seems that CL gain below 7.8 is determined by the value of C2 & C3. Based on the site, a value of 56pf produces unity gain. Correct? 

 What about R13 in this mode?

 Also, what about the OL gain set with R22 & R23? Are the default values (33k) sufficient when running the board in unity gain?


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So if I'm understanding this circuit correctly, it seems that CL gain below 7.8 is determined by the value of C2 & C3. Based on the site, a value of 56pf produces unity gain. Correct? _

 

It's my understanding that the capacitors are ONLY for compensation. Lower gain would be produced by higher resistor values than those listed in the table.

  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_What about R13 in this mode?

 Also, what about the OL gain set with R22 & R23? Are the default values (33k) sufficient when running the board in unity gain?_

 

There seems to be a complex relationship between closed loop gain (Gain) and Open Loop Gain (Amount of Negative Feedback).

 It would be cool to have a spreadsheet that calculated all these values, but I'm too dumb to know the formulae...


----------



## sachu

I recceived two packges today.one had Scott's Sovtek 6H30s and the other had a pair of Mullard 6DJ8s.

 Unfortunately for some reason one of the 6H30s don't seem to work. I don't see the filament lighting up at all. 

 Right now I have the 6DJ8s doing duty and they sound quite wonderful.


----------



## smeggy

I received my latest goody bag from mouser today and now have all the bits to finish the EHHA except for the knobs and 3.5mm jacks 
	

	
	
		
		

		
			





 That Sophia delay switch needs a 6.3V AC supply, I don't know if my transformer outputs ac or dc, how can I tell?


----------



## adamus

tranformers output ac unless you recitify it


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I received my latest goody bag from mouser today and now have all the bits to finish the EHHA except for the knobs and 3.5mm jacks 
	

	
	
		
		

		
		
	


	




 That Sophia delay switch needs a 6.3V AC supply, I don't know if my transformer outputs ac or dc, how can I tell?_

 

Just connect the 6.3 colt AC leads directly across one of the 6.3V secondaries of your transformer...


----------



## smeggy

Thanks, I seriously have no clue


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Thanks, I seriously have no clue 
	

	
	
		
		

		
		
	


	


_

 

Post lots of pics smeggy if u have any doubts..this is not exactly an easy build. Lots of potential for that magic smoke to escape


----------



## holland

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So if I'm understanding this circuit correctly, it seems that CL gain below 7.8 is determined by the value of C2 & C3. Based on the site, a value of 56pf produces unity gain. Correct? 

 What about R13 in this mode?

 Also, what about the OL gain set with R22 & R23? Are the default values (33k) sufficient when running the board in unity gain?_

 

wiatrob answered your other questions, but it's best (and easiest) to think of this as a discrete/hybrid opamp....because it essentially is just that.

 Gain is explicitly R12 and R13. C2 and C3 are for compensation.

 The CL gain is the operating point, i.e., how much total gain do you have through the circuit as a whole. The open loop gain, is just that, the gain of the amp without feedback.

 I would think you would want to move to the lowest OL gain, and the appropriate CL gain you need for your system as the first tweak. This will allow you to utilize a low amount of NFB. If you want to operate in full op-amp type mode, then remove R22 and R23 for very high OL gain.

 Default values for R22 and R23 should be fine for any gain setting.

 Remove R13 for unity gain. I'm not sure if R12 should decrease for that, or not.


----------



## digger945

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I recceived two packges today.one had Scott's Sovtek 6H30s and the other had a pair of Mullard 6DJ8s.

 Unfortunately for some reason one of the 6H30s don't seem to work. I don't see the filament lighting up at all. 

 Right now I have the 6DJ8s doing duty and they sound quite wonderful._

 

They take some juice, plan on at least 1 amp per tube for the heater. I originally planned on one PS per tube for the Aikido I got these for, but I think just one PS capable of 2 amps would work just fine.

 On the gain, I remember Ti giving a formula with the large resistor in the feedback loop divided by the smaller resistor to ground, plus 1. Something like R1/R2 + 1. I don't have my books unpacked yet to give some more info on compensation.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_They take some juice, plan on at least 1 amp per tube for the heater. I originally planned on one PS per tube for the Aikido I get these for, but I think just one PS capable of 2 amps would work just fine.

 On the gain, I remember Ti giving a formula with the large resistor in the feedback loop divided by the smaller resistor to ground, plus 1. Something like R1/R2 + 1. I don't have my books unpacked yet to give some more info on compensation._

 

Scott my heater circuit is capable of delivering up to 3A(limited by the regulator IC, transformer is rated at 4A)..

 So I don't know what is up with the other 6H30s..


----------



## digger945

Do they make music?

 Does it get warm at all?


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Do they make music?_

 

Just one channel..the other tube's plates don't light up at all..


----------



## digger945

You swop tubes to see if the problem follows the tube or remains with the amp board?


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_You swop tubes to see if the problem follows the tube or remains with the amp board?_

 

I just did and it looks like it is in the board..too late for me to trouble shoot this tonight..maybe tomorrow evening.


----------



## digger945

It's gotta be perty simple if it's in the heater circuit. I really wanna know what you think of them, and when are you supposed to get the reflektors?
 I contacted that guy and he has some later 1970's reflektor DR's for $99 a pair.
 These are supposed to be a very quiet and neutral tube, everyone brags on them in the right amp/pre, and we know what the feeling are for this one.


----------



## TimJo

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_wiatrob answered your other questions, but it's best (and easiest) to think of this as a discrete/hybrid opamp....because it essentially is just that.

 Gain is explicitly R12 and R13. C2 and C3 are for compensation.

 The CL gain is the operating point, i.e., how much total gain do you have through the circuit as a whole. The open loop gain, is just that, the gain of the amp without feedback.

 I would think you would want to move to the lowest OL gain, and the appropriate CL gain you need for your system as the first tweak. This will allow you to utilize a low amount of NFB. If you want to operate in full op-amp type mode, then remove R22 and R23 for very high OL gain.

 Default values for R22 and R23 should be fine for any gain setting.

 Remove R13 for unity gain. I'm not sure if R12 should decrease for that, or not._

 

Okay, I thought about this all day yesterday, and consulted the Morgan Jones text to refresh my memory regarding feedback in amps, but I think I get it now.

 I can now see that the caps are simply being used to attenuate the signal in the VAS at high frequencies, and the closed loop gain is really just a function of how much feedback the tube is seeing.

 I'm not sure if I'm over simplifying the circuit, but the overall gain of the amp should be governed by the following:


> _Gain = Ao/(1+beta*Ao)_


where Ao is the open loop gain, and beta is the feedback fraction.

 beta is determined by the voltage divider feeding the grid of the second triode - R12 & R13.

 The default schematic produces a beta of 1.2k/(10k+1.2k) = 0.1071

 Using 33k resistors at R22 & R23, this produces an open loop gain of 320 according to Alex's simulations.

 Plugging this into the formula above, then the gain using the default values should be around

 Gain ~ 320/(1+0.1071*320) = 9.069

 which is what the website indicates.

 Based on this, I played around the equations, knowing R12 is a fixed value at 10k. If I lower the open loop gain to somewhere around 150 (maybe using 15k resistors), then R13 needs to be around 1.5M - I think. 
	

	
	
		
		

		
			





 beta = 1500/(1500+10) = 0.9934

 gain ~ 150/(1+0.9934*150) = 1

 It looks like even a one meg resistor would be close enough to work.

 Is this at all correct? I may have oversimplified things here, and running the amp like this may be in uncharted waters, so I'm hoping if I'm way off base, someone chimes in...

 Alex ???


----------



## holland

Timjo, the amp is an operational transconductance ampifier. The overall gain is controlled by the feedback resistorin ratio with the resistor to ground on the negative input for the amp. That is it is just like configuring gain on a cmoy, dynalo, etc. Only the closed loop gain sets the actual gain. The open loop gain sets the amount of global negative feedback not in terms of ratios but in terms of the absolute quantities.

 In otherwords if you set the closed loop gain to 10 it will be 10 regardless of what you set for the open loop gain. Use the open loop gain to adjust the total amount of feedback used to achieve the closed loop gain.


----------



## TimJo

Thanks for the reply and your patience with a nooby. I haven't built that many amps, and so I'm learning as I go.

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_The overall gain is controlled by the feedback resistorin ratio with the resistor to ground on the negative input for the amp.... The open loop gain sets the amount of global negative feedback not in terms of ratios but in terms of the absolute quantities._

 

Well, I think this is what I was attempting to describe in my previous post, I may not have done a very good job of it though. 
	

	
	
		
		

		
		
	


	




 When you go back to the general feedback equation,


> Gain = Ao/(1+beta*Ao)


as Morgan Jones explains, _if beta*Ao is very large compared to 1_, then the feedback factor (1+beta*Ao) approaches (beta*Ao), and the general equation reduces to


> Gain = Ao/(beta*Ao)


which reduces to


> Gain = 1/beta


where beta is what you describe above as the 'feedback resistor ratio' and in the case of the EHHA, the voltage divider made up of R12 & R13.

 So, provided the open loop gain is high enough, and beta is large enough, then the following _is true_.

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_...if you set the closed loop gain to 10 it will be 10 regardless of what you set for the open loop gain._

 

But, as can be seen by the general equation, as beta is decreased (i.e. less negative feedback) then the closed loop gain begins to approach Ao - the open loop gain.

 ~~~~

 Back to the question at hand, it does seem like we are dealing with high enough open loop gain to generalize things to


> Gain = 1/beta


so for unity gain, beta should approach 1.

 In an earlier reply, you suggested that removing R13 was the way to go (beta will certainly be 1 by doing this 
	

	
	
		
		

		
		
	


	




) but it seems like a very high value in the voltage divider may work as well (like the math indicated in my earlier post with R13 being 1.5M).

 The only issue I would begin to worry about here is stability, but I'm really not sure.


----------



## digger945

If you'll do some digging for "differential pair" and/or "long tailed pair" you can see that what is amplified is the difference between the input(I'm looking at a printout of the schematic) and the feedback circuit(which must be attenuated obviously), or the difference between the two triodes. Normally this would be a pair of transistors. This is used for not only in a SE application like this but also a balanced as well. An example of one balanced channel would be a Beta24 board.

 (I hope this is taken as a help, I don't know hardly anything about the negative feedback/compensation circuit except what I've read in books)


----------



## digger945

Give us the good word Sach.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Give us the good word Sach._

 

Hey Scott..

 I really don't know what is happening here.. I took measurements last night and I was getting 28.4 volts on the plates (pins 1 and 6) and the heater was getting 6.3 volts. However, that one board doesn't seem to light up the plates on the 6H30. Switching tubes on that board didn't help either.


----------



## digger945

That's OK, I just wanted to digg a little before I have to go to the new place, no internet there 'till Friday it looks. Still I can get on at work, like this morning, but only a short time. I'm sure you'll figure it out, can't be much. I don't see the S22 power probably being an issue, it's probably the load the heater puts on the heater supply. 
 I gotta go now but maybe you can try just pluggin in a tube into the amp board that's not working, leaving the tube out of the one that worked this morning, and see if it'll fire up by itself alone. If it does then the pair are probably too much load for the heater supply you have.
 2 amps at about 6.3 volts is better than 12 watts, doesn't sound like much but it may be stressing some of the parts a little bit in the heater supply.
 I'll see ya in the morning if your online. 
 Still can't wait to see what you think about it. I wanna do it myself perty bad but work is killin' me right now. I've spent so many hours reading about these tubes and the BAT amps it's not even funny.

 EDIT: Yet another something to try would be to just swop the heater supply lines between boards. I'm guessing your 6.3V parallel since one works and one don't.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_That's OK, I just wanted to digg a little before I have to go to the new place, no internet there 'till Friday it looks. Still I can get on at work, like this morning, but only a short time. I'm sure you'll figure it out, can't be much. I don't see the S22 power probably being an issue, it's probably the load the heater puts on the heater supply. 
 I gotta go now but maybe you can try just pluggin in a tube into the amp board that's not working, leaving the tube out of the one that worked this morning, and see if it'll fire up by itself alone. If it does then the pair are probably too much load for the heater supply you have.
 2 amps at about 6.3 volts is better than 12 watts, doesn't sound like much but it may be stressing some of the parts a little bit in the heater supply.
 I'll see ya in the morning if your online. 
 Still can't wait to see what you think about it. I wanna do it myself perty bad but work is killin' me right now. I've spent so many hours reading about these tubes and the BAT amps it's not even funny.

 EDIT: Yet another something to try would be to just swop the heater supply lines between boards. I'm guessing your 6.3V parallel since one works and one don't._

 


 Tried the first one (only one tube and the other removed) last night..the tube did not light up..something definitely wrong there with that board.

 I will try swapping lines and see what happens..and yes they are in paralle..so I just don't see how that could be contributing to the problem we are seeing. Both heater inputs on the boards read identical 6.3 volts..and plate voltages are all spot on.


----------



## smeggy

Bad socket joint?


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Bad socket joint?_

 

no way..the pair of 6DJ8 mullards were working perfectly fine and so were my 3 pairs of 6GM8s..


----------



## smeggy

Very odd indeed. Still, you and Don will hopefully come up with an answer soon enough. I'd love to find out what it is.


----------



## runeight

Very interesting feedback discussion and correct too. Yes, this is a discrete, transconductance, hybrid opamp. 
	

	
	
		
		

		
		
	


	




 Remember that as you decrease the values of R22, R23 to lower the OL gain and decrease the effective NFB you will also increase the THD.

 The 33k values were chosen to give a decent THD value at about 30db of NFB. This choice was somewhat arbitrary, but the amount of NFB came from what is typical in tube amps. Usually between 20db and 30db of NFB. Higher than that and most tube circuits really don't like it. But because the VAS stages here are sand and because the amp is pretty stable higher NFB is possible. Opamps typically run 100db or more.

 And remember too that NFB has its own effects so using large NFB to cancel THD is not always a good idea. Phase shifting in high NFB leads to IM distortion.

 There is no need to operate the amp in unity gain mode even for the three channel configuration. The ground channel can have its input grounded and then use the same component values as the other two channels. This will ensure that the ground channel can operate at the same speed as the amplifying channels. The amp is unity gain stable with reduced bandwidth as you can see by the very large Cdom caps that Snoopy needed to stablize the SQ response. I think it's better to give the ground channel the same bandwidth as the amp channels.

 There may be other reasons to make the ground channel unity gain, but I am not aware of them. Which doesn't mean they aren't there, it just means that I don't know.

 This whole discussion has been a real joy for me to read. Thanks for all of the contributions.


----------



## digger945

Given both tubes work in one of the boards if you swop them, and on the board there is only the phoenix connector and two traces to carry the power to the heater, the only two things I can think of would be the heater PS or a cold joint at the connector on the board or a tube pin, I think 4 an 5 are the ones for the heater. I had this problem on the millet hybrid and it ended up being the ground trace for the heater on one of the tubes.


----------



## TimJo

Thanks everyone, especially holland, for putting up with my questions and my ramblings.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Very interesting feedback discussion and correct too. Yes, this is a discrete, transconductance, hybrid opamp. 
	

	
	
		
		

		
		
	


	


_

 

If this amp didn't already have a name, I think holland came up with a great one - the discrete, transconductance, hybrid opamp - otherwise known as the DTHOA. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Remember that as you decrease the values of R22, R23 to lower the OL gain and decrease the effective NFB you will also increase the THD.

 The 33k values were chosen to give a decent THD value at about 30db of NFB. This choice was somewhat arbitrary, but the amount of NFB came from what is typical in tube amps. Usually between 20db and 30db of NFB. Higher than that and most tube circuits really don't like it. But because the VAS stages here are sand and because the amp is pretty stable higher NFB is possible. Opamps typically run 100db or more.

 And remember too that NFB has its own effects so using large NFB to cancel THD is not always a good idea. Phase shifting in high NFB leads to IM distortion._

 

Interesting...

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There is no need to operate the amp in unity gain mode even for the three channel configuration. The ground channel can have its input grounded and then use the same component values as the other two channels. This will ensure that the ground channel can operate at the same speed as the amplifying channels. The amp is unity gain stable with reduced bandwidth as you can see by the very large Cdom caps that Snoopy needed to stablize the SQ response. I think it's better to give the ground channel the same bandwidth as the amp channels._

 

I was curious about this as well when I was looking at the chart of slew rates. There is a five to one difference between unity gain and a gain of 7.8, which seems fairly significant.

 Well I'm going to go ahead and build the three boards (and socket R22, R23, R13, and the compensation caps) and start out with the same values as you suggest Alex. Then, just for fun, I will play around with the ground channel, and see if I can hear any difference in performance as I reduce the gain towards unity.

 Who knows, maybe these boards will be enough to get me to invest in a scope and a frequency generator. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This whole discussion has been a real joy for me to read. Thanks for all of the contributions. 
	

	
	
		
		

		
		
	


	


_

 

Agreed - this is why I have gotten into DIY amps. It's good for the mind...


----------



## wiatrob

So, can I be safe in assuming that for this amp:

 Gain = 1/[R13/(R12+R13)]

 I ran the numbers for gain 11 and 13 and they seem to work. Boy my Algebra's rusty!


----------



## runeight

Yes, pretty much so.


----------



## holland

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There is no need to operate the amp in unity gain mode even for the three channel configuration. The ground channel can have its input grounded and then use the same component values as the other two channels._

 

Interesting. I always thought ground was to have as low gain as possible (i.e., Pimeta, PPA, Beta22 has gain of 2 on ground, M^3). I'm hardly the expert, but a ping on AMB might get some answers. I'll try to follow up on that sometime in the future. 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Thanks everyone, especially holland, for putting up with my questions and my ramblings._

 

Anytime. I'm too busy to really follow these forums these days, so I can't really respond actively. I'm glad Alex came in.


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Anytime. I'm too busy to really follow these forums these days, so I can't really respond actively. I'm glad Alex came in. 
	

	
	
		
		

		
		
	


	


_

 

But good info none the less - I've been hinting for a 'gimme' for the gain calculation since the first page of the thread - and now I know how to figure it out. Balanced gain 9 or 11 - here I come!


----------



## sachu

ok..thisis disheartening....
 all of a sudden all my other tubes are not working in that one board.

 I am seeing full negative rail voltage on pin 8 of the tube.

 The heater is not lighting up on the first board at all now regardless of which tube I put in.

 I reflowed the solder on the heater pins and checked to verify that I was getting 6.34 volts between pins 4 and 5.

 I tried and checked a few more things..looks like there is a short in the heater circuit..measuring current with the tube in the current across pins 4 and 5 is 4.75A.

 And now it looks like both board heaters are not working.

 Will have to go in and check what happened with the heater circuit tomorrow


----------



## smeggy

Wow, bummer dude


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Wow, bummer dude 
	

	
	
		
		

		
		
	


	


_

 

no kidding dude...Ithis amp is giving me so much heartache...but she's my baby..

 I just hope the huge currents didn't take out the tbes. 

 I am going to haul all the EHHA tubes with me down to a surplus store whihc has a tube tester and check to see if they are working


----------



## smeggy

fingers crossed that they aren't fried, that was an expensive set of bottles.


----------



## digger945

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_no kidding dude...Ithis amp is giving me so much heartache...but she's my baby..

 I just hope the huge currents didn't take out the tbes. 

 I am going to haul all the EHHA tubes with me down to a surplus store whihc has a tube tester and check to see if they are working_

 

I don't think your gonna hurt them, they are pretty robust. Don't think the filament will be damaged as it will only pass what it's resistance will allow, kinda like a light bulb. I have a tube tester at the other house and can check one of the two I have for you to compare numbers with but if you have someone close who checks tubes regularly he will no doubt be able to tell you if its good. I got these when Microsoft had the live search rebate thing goin so I don't have that much in em anyways. Still I really don't think you hurt them but just the opposite, they hurt your heater supply. It could be very possible that you will read good voltage from your PS even with the tube plugged in but just not have the current to make her get hot.
 I know you probably mentioned it before but what kinda supply do you have for the heaters exactly, and do you have a good pic of it with the transformer?


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_It could be very possible that you will read good voltage from your PS even with the tube plugged in but just not have the current to make her get hot._

 


 Sachu, I tested my heater PS by test clipping four tubes' heater pins with (my DVM measuring current draw in-line... )As (digger?) said, if the voltage is right, it'll be difficult to hurt the tubes, especially if only the heater's connected...


----------



## digger945

Sach, you think maybe the timer/relay might be the problem, is it between the Pete Millet PS unit and the boards?
 Maybe you could bypass the timer and see what happens.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Sach, you think maybe the timer/relay might be the problem, is it between the Pete Millet PS unit and the boards?
 Maybe you could bypass the timer and see what happens._

 

Checked the tubes on the tester and everything checked out. I didn't test the 6H30s..I am guessing they are okay as well. *wipes his brow*


 I had totally forgotten that the regulator chip I have used the LM1085 is only rated to 3A. SO it must be fried.

 Am going to replace it and give it a shot again. Strange thing is that it is regulating the output at 6.34 volts.

 I am using pete millets DC filament supply circuit as shown below.


----------



## dBel84

hope that resolves the problem , make sure you have a good thermal seal when connecting it up again as that will need to dissipate a lot of heat ..dB


----------



## digger945

Yea I went back and looked up all your posts to see what you were using. I am guessing that the transformer you spoke about is indeed capable of 4.75 amps at 6 volts. I couldn't tell too good from your pics. I think the 1085 should be good for the less than 2 amps you need for the heaters if it's not dropping a great deal of voltage. I noticed that you had the timer board on the bottom side of the amp and couldn't find any schematics for how you had it wired. At first I thought that maybe the relay on the timer might not be able to handle the current but again I don't know anything about your timer or how it's wired.
 Obviously something got stressed pretty good if it wont power the lower current requirements of the other tubes.

 Also, like Don said, the 1085 will need some good heatsinking.

 If upon power up the heater PS gets immediate voltage the timer is to delay power to the amp then disregard my comments on the timer. Again, I don't know how it's wired.


----------



## fishski13

i'm no EE, but did run the heaters DC for a guitar amp i recently built. after full-wave rectification, doesn't the current drop by, I DC = 0.62 I secondary? so at 4A pre-rectification, the resulting available current = 2.48A?


----------



## fishski13

i have a few 6N1P tubes lying around. factoring in the extra heater current, could this be a drop in for a 6922?


----------



## runeight

Yes, that's correct. The general rule of thumb is that when using a bridge rectifier the transformer AC current rating should be 1.6X the DC current load from the supply.

 Given the wide range of good to crappy transformers available I tend to use a factor of 1.8 or even 2.0. Especially with a regulated supply where the input voltage can be high if there is enough heatsinking.


----------



## fishski13

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, that's correct. The general rule of thumb is that when using a bridge rectifier the transformer AC current rating should be 1.6X the DC current load from the supply.

 Given the wide range of good to crappy transformers available I tend to use a factor of 1.8 or even 2.0. Especially with a regulated supply where the input voltage can be high if there is enough heatsinking._

 

thanks. what about the 6N1P???


----------



## sachu

Quote:


  Originally Posted by *fishski13* /img/forum/go_quote.gif 
_i'm no EE, but did run the heaters DC for a guitar amp i recently built. after full-wave rectification, doesn't the current drop by, I DC = 0.62 I secondary? so at 4A pre-rectification, the resulting available current = 2.48A?_

 



 The heater transformer is rated at 4A when the secondaries are in series to produce 12.6 volts at the output. So with the secondaries in parallel it should be capable of 8A.

 So out of a total possible 8 Amps the DC rectified current draw of 4.75A is in tune with your calculations.


 Scott, The relay powers the heater first.

 The relay is powered off one of the heater transformer secondaries. 

 The relay itself is rated at 125VAC 10A. So on the input set of pins of the relay there is 120VAC instantly as the power is turned on. After a 45 second delay the relay trips to apply that 120VAC onto the HV transformer.

 I will replace the LM1085 and see what happens.


----------



## digger945

Jolly good ol' chap.
	

	
	
		
		

		
			




 I can't really think of anything else right now, except that maybe the contacts inside the relay are caput, but I don't think they are with such a small draw on them, unless maybe something got momentarily shorted a bit and damaged something.
 Look at it this way Sachu, you can get all the bugs worked out now witha cheaper pair of tubes and then you won't have to worry so much when you plug in the high dollar ones later, allowing you to enjoy listening
	

	
	
		
		

		
		
	


	




...and to share the experiences with us.

 On a positive note, I got the internet hooked up at the new cave, and almost everything DIY is moved over and in boxes, including the EHHA. I am gonna try to put together something to fire up these 6H30's and see what they can muster. I don't know what it is about this amp that makes me get worked up thinkin' 'bout tinkering with. I've already decided that I'de like to build the EHHA II to power my monitors when Alex gets finished tinkering with it himself.


----------



## fishski13

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The heater transformer is rated at 4A when the secondaries are in series to produce 12.6 volts at the output. So with the secondaries in parallel it should be capable of 8A.

 So out of a total possible 8 Amps the DC rectified current draw of 4.75A is in tune with your calculations.


 Scott, The relay powers the heater first.

 The relay is powered off one of the heater transformer secondaries. 

 The relay itself is rated at 125VAC 10A. So on the input set of pins of the relay there is 120VAC instantly as the power is turned on. After a 45 second delay the relay trips to apply that 120VAC onto the HV transformer.

 I will replace the LM1085 and see what happens._

 

ahh...i was assuming 4A in parallel.

 glad to see one of Runeight's designs is stroking the DIY love here. i'm looking for another HP amp to build myself.


----------



## sachu

Guys, I think it is confirmed that the heater circuit is at fault. 

 When I hooked up just one tube to a socket with only pins 4 and 5 soldered it was sinking 4.8A across the heater. 

 The thing that I don't get is that the resistance between pins 4 and 5 ont he tubes measures less than 5 ohms or so. Do I am inclned to think " No wonder it is sinking that much current".

 I made sure the tubes were alright on a tester and also tried them in Donald's EHHA after they checked out fine on the tube tester nd they worked flawlessly.

 Am I missing anything else?


----------



## fishski13

have you tried the heaters with AC?


----------



## Ferrari

I have measured the resistance between pin 4 and pin 5 (heater pins) of some of the 6N30P-DR from my parts bin and they all have a little resistance of ~ 3.5Ω… seems to be normal for this tube. 

 Talking about 6.3V heater PS, I’m going to use this (recycled) 4A switching PS in my amp (to get rid of possible AC heaters noise). 







 Maybe a bit unconventional to use switching PS here, but this one is not just an ordinary switching PS.
 Actually it’s a very good PS design, including an EMI filter on board. The noise measured at various output loads is very similar to that of a regulated PS based on LM338 used in my Bijou.


----------



## wiatrob

Ferrari, interesting approach. Is the PS 6 or 12V (or indeed actually 6.3V)?

 My build is progressing:


----------



## TimJo

What heater supply are you using wiatrob?

 Also, is the Amprex ECC86 from Glass Jar? (I'm waiting to hear back from Jeff on the status of my order, so I haven't seen the tubes yet...)


----------



## TimJo

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Maybe a bit unconventional to use switching PS here..._

 

Well, the CTH uses a switcher for the heater supply, and it works great. 
	

	
	
		
		

		
		
	


	




 It's cool that you were able to reuse the supply for this project. What did it come out of?


----------



## Ferrari

These switching PS are originally 5V. I have a box of these, sitting useless in my garage for a long time.
 In my attempt to find a useful application for them, I modified it to output 6.3V.
 The pic below shows the relative low ripple (AC noise) at the output.


----------



## dBel84

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_My build is progressing:_

 

That is looking great , I suspect this amp is going to make a lot of folk stop and listen again. 

  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_ Talking about 6.3V heater PS, I’m going to use this (recycled) 4A switching PS in my amp (to get rid of possible AC heaters noise)._

 

I have a few of these that I have been collecting with just this in mind. I hadn't realized that there noise levels were that low , this is really good to know. 

 EDIT: I haven't messed with them, is adjusting the voltage a simple trimmer or is the mod more involved


  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Also, is the Amprex ECC86 from Glass Jar?_

 

no , he supplies a different brand of NOS tube.


----------



## Ferrari

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_...
 It's cool that you were able to reuse the supply for this project. What did it come out of?_

 

These PS were made for medical equipments.


----------



## TimJo

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_These PS were made for medical equipments. 
	

	
	
		
		

		
		
	


	


_

 

Well I'm sure they are great quality knowing that... 

 With a whole box of those supplies, it seems like you will have a lot more amps in your future.


----------



## Ferrari

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_...
 I have a few of these that I have been collecting with just this in mind. I hadn't realized that there noise levels were that low , this is really good to know. 

 EDIT: I haven't messed with them, is adjusting the voltage a simple trimmer or is the mod more involved_

 

The modification is quite simple. 
 In the middle of the picture below, there is a zener-diode in between of a capacitor and a transistor. 
 You have to remove this zener-diode (I have cut it due to my laziness), then power up and dial the output voltage up to 6.3V, using the white trimpot on the right of the picture.
 Done!


----------



## sachu

dammit you guys...am really starting to get anxious about my EHHA..especially now that you guys are starting to catch up on me... 
	

	
	
		
		

		
		
	


	




 Bill, can't wait to see how that mother of an amp turns out..god will you be astounded by it..better have that ready to take it to the denver meet.

 Ferrari, its awesome to see your build nearing the finish line as well..and tinjo i suspect you might just stop at the EHHA and not care to finish the BIjou..

 am off to go try and see if direct AC will work with the heaters.


----------



## looser101

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Guys, I think it is confirmed that the heater circuit is at fault. 

 When I hooked up just one tube to a socket with only pins 4 and 5 soldered it was sinking 4.8A across the heater. 

 The thing that I don't get is that the resistance between pins 4 and 5 ont he tubes measures less than 5 ohms or so. Do I am inclned to think " No wonder it is sinking that much current".

 I made sure the tubes were alright on a tester and also tried them in Donald's EHHA after they checked out fine on the tube tester nd they worked flawlessly.

 Am I missing anything else?_

 

Certainly I'm no expert but... the heater in a tube is like a light bulb filament. The resistance is low when cold and increases as it heats up. In a tube it only takes a few seconds to reach equilibrium. Measuring its resistance is useless except to verify that its not open circuit. 

 The only way to measure current is to disconnect one of your heater connections and put your meter (connected for amperage readings -start at 10A) in series with the circuit. You can also use a very low value, high power, resistor in series with the heater circuit. Measure the voltage across it and use ohms law to calculate the current.

 Your heater transformer is CT'ed so you can not parallel the secondaries as you can with dual secondary transformers.

 The 6h30's (at least the ones I own) barely glow at all when on, so keep that in mind. Some other tubes glow like light bulbs.


----------



## sachu

okay..so hooking up the heater pins of one tube directly to the secondaries of the transformer draws current in the mA range and the filament lights up. so this definitely rules out the boards. Might sit down and redo the heater supply circuit or just hook up the heaters to AC for now.


----------



## smeggy

Can we actually connect the transfo output directly to the heater terminals? That would make life a lot easier.


----------



## Ferrari

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Can we actually connect the transfo output directly to the heater terminals? That would make life a lot easier._

 

Yes, you can connect the secondary of a 6.3V transformer to the heater connector on board directly, if you prefer to run AC heater supply. 
 Whether it should make life a lot easier or not, I dunno. 
	

	
	
		
		

		
		
	


	



 More over that can be found at the EHHA website.


----------



## smeggy

Mine is a 6.3 + 6.3 1.2A center tap which I assume can allow bridging for a straight 12.6 v AC. I imagine that will do just what Alex was alluding to on the site gegarding momentary 18v.

 ..or am I being dim again?


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Mine is a 6.3 + 6.3 1.2A center tap which I assume can allow bridging for a straight 12.6 v AC. I imagine that will do just what Alex was alluding to on the site gegarding momentary 18v.

 ..or am I being dim again? 
	

	
	
		
		

		
		
	


	


_

 

^^ yep..you can do that


----------



## smeggy

Cool because apart from that heater thingy it's pretty much ready to fire up 
	

	
	
		
		

		
		
	


	




 I'll try to figure out the Sophia delay thing and attach it up to the S22 and heater transfo, go through the setup routine and see what happens.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Cool because apart from that heater thingy it's pretty much ready to fire up 
	

	
	
		
		

		
		
	


	




 I'll try to figure out the Sophia delay thing and attach it up to the S22 and heater transfo, go through the setup routine and see what happens._

 

Smeggy there is a high probability that you will encounter noise on the outputs. I hear it in mine.


----------



## dBel84

just my 2c

 AC heaters can be used but because of the nature of this amp , the proto team even considered an S11 as an option for the heaters and not overkill . I would personally look at low noise DC supplies as default. 

 ..dB

 EDIT - well done sachu, good bit of detective work


----------



## sachu

Donald, 

 Everything is working fine now..turned out to be a loose tube socket. 

 However, the thing that puzzles me is that the current reads 4.5 A across the heater pins with the 6H30Ps plugged in and 4.75A with the 6GM8 plugged in...

 I don't feel the regulator IC getting all that hot..but 4.5 A at 6.3 volts = about 30Watts of dissipation from the regulator IC which doesn't sit well with me.

 Am I reading this wrong somehow?

 Btw, initial thoughts there definitely seems to be a diference between the new Sovkets and my NOS reflektor tubes.


----------



## digger945

A little motivation for you fellers.
 They stand proud in the sockets dont they.




 Even though that little 12V 1000mA 12Watt wallwort is strainin' it's little guts out and I have some 60Hz buzz I can already tell that these are gonna be good soundin' tubes. Absolutely fantastic music. It's as if a veil has been lifted and now I'm "there". Neutral ain't the word for it. I won't rest until an adequate heater supply is in place. Actual voltage across the heaters in series is 11.79V.

 Bob James never sounded better
	

	
	
		
		

		
		
	


	




. Gotta get outta my head the idea of taking the battery outta my car now.
	

	
	
		
		

		
		
	


	




 Thanks for joining in and helping out R.


----------



## sachu

ummm guys..is it normal for the 6H30P-DR tubes to get hot..I mean like 92 deg C hot?


----------



## digger945

Mine are stinkin' hot. Yea I think so. So you got em in do ya?




 Can't touch it but for a split second.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Mine are stinkin' hot. Yea I think so. So you got em in do ya?




_

 

nice..yeah I got them in..initial listening tests indicates to a difference between the newer production 6N30Ps and the older NOS ones...right now got the 1985 Reflektor made ones playing with some Steve ray Vaughn.That amp is like a space heater now.

 The current readings still trouble me though.


 p.s: Turns out I have the most perfect transformers to build a dual mono supply for the massive EHHA2.


----------



## digger945

Congrats feller!
 Exactly how are you measuring the current?
 More importantly, wadda ya think about the sound? Pretty good stuff eh?

 Various data sheets for the 6h30 will vary but these guys are gonna knock down somewhere between 800 and 980mA per tube, and if you think about it most of the others like 6gm8 and 6dj8 are gonna be in the 325 give or take area, so these are gonna be like 3 of the others put together, both current and heat wise.

 Big time Stevie Ray fan here, I was living in Dallas when he passed away.
 Listening to SRV radio on Last.fm now, good stuff.
 If I lived close enough I'de buy you one of those beers you talked about a few posts back.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_





 Congrats feller!
 Exactly how are you measuring the current?
 More importantly, wadda ya think about the sound? Pretty good stuff eh?

 Various data sheets for the 6h30 will vary but these guys are gonna knock down somewhere between 800 and 980mA per tube, and if you think about it most of the others like 6gm8 and 6dj8 are gonna be in the 325 give or take area, so these are gonna be like 3 of the others put together, both current and heat wise.

 Big time Stevie Ray fan here, I was living in Dallas when he passed away.
 Listening to SRV radio on Last.fm now, good stuff.
 If I lived close enough I'de buy you one of those beers you talked about a few posts back._

 


 Hey Scott, 

 Will take you up on that beer when/if we happen to meet.

 I am measuring the current across pins 4 and 5 of the tube. It is reading 4.5A with the 6N30Ps and 4.75A with the 6GM8s.

 Am I missing something here?


----------



## digger945

Are you in series with the heater circuit, or trying to measure the voltage drop and calculating the current? Like Renato said, the resistance of the filament will be near zero when cold but will increase significantly as it heats up almost instantly. I really don't think your drawing that much current, or something would be getting pretty hot or cooked, aside from the tube.

 EDIT: If your putting the probes onto pins 4 and 5, tube in or out, you'll effectively be shorting the two pins together and drawing everything the PS has, possibly damaging it. This is of course if your DMM is configured to measure current and the leads are in the correct holes to measure current.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Are you in series with the heater circuit, or trying to measure the voltage drop and calculating the current? Like Renato said, the resistance of the filament will be near zero when cold but will increase significantly as it heats up almost instantly. I really don't think your drawing that much current, or something would be getting pretty hot or cooked._

 



 I will have to double check this. No I am measuring in current mode on the DMM. The wires of the DMM get real hot though.

 Nothing is cooking thus far, just that the amp has is a nice hand warmer on this cool summer day. 

 I have my MOSFETs biased to 200mA at the moment.


----------



## digger945

^See my edited post above.
 I think your shorting the PS circuit. You need to break the circuit somewhere and be in series with everything else. Maybe take one of the heater wires outta the pcb and connect one probe to that wire from the PS, then connect the other probe to another wire and connect that wire to the heater terminal.


----------



## looser101

Ammeter usage : BASIC CONCEPTS AND TEST EQUIPMENT


----------



## sachu

doh!!..i should be shot for this..seriously!!
	

	
	
		
		

		
		
	


	




 I kept forgetting that the heater loses its low resistance when the power is turned on and becomes more of an open circuit...

 Got the DMM wired in series and the 6N30P-DR is drawing about 820mA now.

 I can rest easy.

 Also dialed back the bias to 150mA.
 Thanks fellas.


----------



## digger945

Beers are on me. Look forward to a comparison before I consider a pair of the DR's.
 Hey did I hear you won a DAC at Canjam or something? Have you ever listened straight out of the juli@, I don't even know if it's got audio out, just read alot about it when considering the 0404 or some other source.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Beers are on me. Look forward to a comparison before I consider a pair of the DR's.
 Hey did I hear you won a DAC at Canjam or something? Have you ever listened straight out of the juli@, I don't even know if it's got audio out, just read alot about it when considering the 0404 or some other source._

 




 hehe..yeah I did win the Audio-GD reference 1 DAC at Canjam. The last and most expensive raffle prize at this years Canjam
	

	
	
		
		

		
		
	


	




 I have the Juli@ currently hooked up to Don's EHHA straight and it sounds wonderful. I am now sitting outside listening to my own EHHA though out of a Onkyo DVD player.

 I also had the EMU0404 for a while concurrently with the ESi Juli@ and preferred the Juli@ over it.

 The Ref1 DAC should be arriving on Monday.

 Oh and you know what...I have 2 of the greatest SE amps in my house at the moment...surprise surprise..they are both EHHAs!! 
	

	
	
		
		

		
		
	


	




 p.s: Will let you know about the comparision test between the NOS DRs and the new production DRs.


----------



## runeight

Hello Gents. I am on the road right now for about 2 weeks in the DC area. But it is just great to see all of these EHHAs. Special thanks to dBel84 and Sachu for bringing the amp out from its hiding place.


----------



## digger945

Hey Alex, ya know the Toshiba's are rated to 150V.(Wheels are turnin' LOL)
 I know this is my first time listening to a 6h30 in anything, but these boogers sound really nice. Gotta hand it to ya for a heck of a design.


----------



## runeight

Yes, I know. You can turn this into a power amp but the TO220 O/P devices can only support about 50W power dissipation.

 However, put some Hitachi lateral fets on the output instead of the what's there now and put the rails to 42V you can do 100W with a few adjustments, a zobel network, and maybe a bit more compensation on the output.


----------



## digger945

I was thinkin' more along the lines of simply putting a few more volts on the plate of the tube. Maybe like 90 or 100. The IRF parts are rated at 55V. Renesas, and others, can be had up over 100V. Wouldn't be hard to parallel outputs if you needed some more umph, don't need to much for Denons though. I think I'll wait patiently for the EHHA II when power is needed for speakers or something.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, I know. You can turn this into a power amp but the TO220 O/P devices can only support about 50W power dissipation.

 However, put some Hitachi lateral fets on the output instead of the what's there now and put the rails to 42V you can do 100W with a few adjustments, a zobel network, and maybe a bit more compensation on the output. 
	

	
	
		
		

		
		
	


	


_

 

Heheh..Alex, 

 I have these two transformers waiting to be used for this exact purpose. 

 Am guessing they are rated at at least 350VA at 34 volt secondaries.








 Dual mono supplies for the EHHA2. The EHHA1 will be wired to be able to use as a preamp. Can't wait to get this combo going...
	

	
	
		
		

		
		
	


	







 Thanks Alex for this wonderful design. I have shouting about this ever since I heard it first two years ago. With atleast 4 more EHHAs about to come out..am super excited that this amp has finally got its place in the Cavalli Audio lineup...which is right at the very top. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I was thinkin' more along the lines of simply putting a few more volts on the plate of the tube. Maybe like 90 or 100. The IRF parts are rated at 55V. Renesas, and others, can be had up over 100V. Wouldn't be hard to parallel outputs if you needed some more umph, don't need to much for Denons though. I think I'll wait patiently for the EHHA II when power is needed for speakers or something._

 

Nay nay..we want the EHHA 2 now !! 
	

	
	
		
		

		
		
	


	




 I think there is a HV section in the EHHA2 around the same ballpark that you have mentioned..though this is for another thread...Alex, I am ready to prototype the EHHA2 if you are


----------



## dBel84

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Mine are stinkin' hot. Yea I think so. So you got em in do ya?





 Can't touch it but for a split second._

 

man that 's just gorgeous , now I really do need to get myself a pair. 

 ..dB

 edit - sachu, never occurred to me you were sticking the probes in parallel and measuring current , my fault for not asking , I usually default to measuring voltage and calculating current.


----------



## digger945

$25 or less for current production Sovteks, one guy has free shipping. Electro-Harmonix are not much more. Don't have a clue what the difference would be. I've seen DR's now for $99/pr Buy it Now on ebay. That same guy has DR's for more, they increase with price as they get older.
Sachu's tubes.
Another pair. I sent this guy a PM, he has other stuff. 
This cat's eat up in DR's


----------



## dBel84

I will give them a listen seeing as I can and then decide if they truly lift this amp "right at the very top" 
	

	
	
		
		

		
		
	


	




 Sachu and I differ slightly on this opinion 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

C2 and C3, I wasn't supplied with these, are they optional? I can't quite tell from the website.


----------



## digger945

You wont need them for a gain of 7 or higher IIRC. I don't have them in mine, gain of 11.
 Some more pics, wish I could work the camera better....


----------



## dBel84

not used if you are building the mosfet amp 

 wish there was a wee professor smiley to remind you to read the web site  = smugface and I will give myself a spade - seems this changed since the proto build as the webpage reflects it in both circuits. Mine doesn't use them , as noted above for gain stability

 ..dB

 ps very cool pics Scott


----------



## sachu

A few pics of my 6N30PDRs..was trying out some things with my camera..i suck at this..need to learn how to work a camera.


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_What heater supply are you using wiatrob?

 Also, is the Amprex ECC86 from Glass Jar? (I'm waiting to hear back from Jeff on the status of my order, so I haven't seen the tubes yet...)_

 

Broskie's H-PS-1. The tube is from my stash of Amperex and Telefunkens


----------



## smeggy

Ok, I think I'm gonna officially give up electronic DIY. It's getting too costly in time, money and patience. I got the thing wired up and when I switched it on the power resistors lit up light christmas light along with copious amounts of smoke. 

 I dunno what else might have gotten fried along with them and frankly don't want to know at this point. So far I've fried a S22, a beta board and now an EHHA board. I think it's safe to say amp building isn't really isn't my calling.

 Oh well, fun while it lasted.


----------



## dBel84

BAH

 what else is there to say 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## sachu

nuts!!


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_A few pics of my 6N30PDRs.._

 

they look great sachu , now you need some small single driver speakers to hook up and you will be away with the faeries. 

 ..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_they look great sachu , now you need some small single driver speakers to hook up and you will be away with the faeries. 

 ..dB_

 


 I've been meaning to make some speakers for the computer..time I did it I suppose. I have a pair of awesome binding posts itching to be used.


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I've been meaning to make some speakers for the computer..time I did it I suppose. I have a pair of awesome binding posts itching to be used._

 


 then you need to check these guys out . I heard their unconventional speakers at VSAC - very cool, here is a 6moon review

 ..dB

 maybe too big to stick on the desk


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_then you need to check these guys out . I heard their unconventional speakers at VSAC - very cool, here is a 6moon review

 ..dB

 maybe too big to stick on the desk 
	

	
	
		
		

		
		
	


	


_

 






 damn looks like I missed out on a lot of fun at VSAC last year..perhaps I will make it this year.

 Am thinking a small ported design ought to be nice and easy to do.


----------



## wiatrob

Hey Smeggy - I feel your pain. Don't use really sharp meter probes - I was testing R3 and I think the probe punctured the solder mask to the ground plane. POOF Smoke and weld.


----------



## smeggy

I wasn't testing, I just powered it up and poof, both resistors glowing a bright Chernobyl red. I only plugged one board in.


----------



## spritzer

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ok, I think I'm gonna officially give up electronic DIY. It's getting too costly in time, money and patience. I got the thing wired up and when I switched it on the power resistors lit up light christmas light along with copious amounts of smoke. 

 I dunno what else might have gotten fried along with them and frankly don't want to know at this point. So far I've fried a S22, a beta board and now an EHHA board. I think it's safe to say amp building isn't really isn't my calling.

 Oh well, fun while it lasted._

 

You will bounce back young grasshopper. 
	

	
	
		
		

		
			





 I always feel like that after some spectacular and devastating failure but it doesn't last long.


----------



## wiatrob

True, what Spritzer said. And you will learn much!


----------



## wiatrob

So I have only 50% of the voltage I'm supposed to have across R3, 4, 10, 14 (.675V) on all four boards. Input voltage is good, so is heater voltage.

 Checked all the resistors and caps. Puzzling. I'll look for a misplaced transistor..


----------



## dBel84

Bill , what is your voltage across the 200R Cathode resistor ( R9 ) - should be about what you are getting across the 1K resistors. This sets the cathode current draw and will affect the voltages you are seeing above. Might also be useful to know the voltage at the anode ..dB


----------



## wiatrob

R9 = .523V 28.1V at pin 6 of the tube. I am also getting only ~.6V across my output resistors...


----------



## TimJo

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_R9 = .523V 28.1V at pin 6 of the tube. I am also getting only ~.6V across my output resistors..._

 

Well that's 2.6 mA - the website says the "tail is loaded with a constant current source set to approximately 3mA."

 Is that too low then? The current is being controlled by D1 & D2, correct ?


----------



## dBel84

The expected voltage is 0.65V which gives a tail current of 3.25mA , this sets the current in the differential pair. The anode is also a little high, unless your rail voltage is greater than 30V. 

 What tubes have you tried Bill = I wonder if this is a tube issue. You seem to be drawing 1/2 - 2/3 of the predicted current all round. Have you tried turning that trimmer to the end of its range - this seems to have been both sachu and diggers problems at the initial set up. I am not sure it should have affected the other readings though. It has to be something simple. 

 ..dB

 D1 and D2 should indeed control this current.


----------



## wiatrob

3 different 6GM8s - maybe I'll try a 6922...

 My rail is actually a tad lower than 30 - 29.7 or so. Let me go through and check voltages and see...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_R9 = .523V 28.1V at pin 6 of the tube. I am also getting only ~.6V across my output resistors..._

 

ummm..0.6 volts across R32 and R33 is a bit excessive. It should be set to -.2 volts (100mA). 0.6 volts is like 270mA.

 Edit: Never mind..
 I forget you are building the BJT version.

 Well try turning R21 on either side to get the voltage across the output resistor get up to 1Volt. That is the same problem I had with mine and Scott's as well.


----------



## wiatrob

Yes, the lone BJT version!

 Same voltages with a 6922...

 I have 1 volt on the output - trim pot! Let me get the opamp in and see where I end up. Should probably just see if it makes sound now...


----------



## digger945

What Sachu said, you'll be kinda puzzled until the output voltage is set with R21. Once your up close to the spec. 1 volt for you, and it doesn't have to be right on the money for now, you can begin to make sense of the other measurements in the initial setup page at CA. You don't need exactly 30V on the rails either.

 Sorry to hear about your amp Smeggy. Give us some pics of the boards and maybe we can help troubleshoot some. I'll make the same offer that I made for the Beta22 board. Really like to see you listening to this one.


----------



## digger945

wiatrob, maybe just do a quick check and see what the output offset is first, to make sure the tubes are good and balanced OK.


----------



## dBel84

it sounds like he is on target once the opamp goes in 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## sachu

come on Bill..and better get some pics up of your monster on the testbench...me like to see lots of tubes on the EHHA


----------



## wiatrob

Ok, Ok - I'm re-siding the house, but there was a thunderstorm, _et voila_:

 Current is still askew, but output voltage is correct, and both sides within a mV of each other. Offset is ~.5mV How are you gents grounding your DC heater supply?

 I don't know about the board with the short to ground plane. So I will attempt a three channel for now.

*EDIT*:

 Smeggy - I thought this project was a write off this morning. Take a break, let things settle, and come back, taking what little consolation exists in knowing that blowing things up is the most effective way to learn..


----------



## dBel84

oh hook them up already 
	

	
	
		
		

		
		
	


	




 ..fB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_oh hook them up already 
	

	
	
		
		

		
		
	


	




 ..fB_

 

^^ WHAT HE SAID!!


----------



## wiatrob

They're like rabbits! 
	

	
	
		
		

		
		
	


	




 The more boards I add the more hummmm I'm getting, but the wiring is squirrely...

 I will attempt to get the fourth board working as a ground, but then I'll need to wire up the XLRs and Stepped Atten. Not Today


----------



## digger945

I put my negative heater supply ground to the star ground like Alex has it on the wiring schematic. Calmed right down. Also have the S22 ground and input signal connected. Depending on your source you'll also probably need to connect the shield of the balanced connectors.

 Good lookin' bunch of kids ya got there. If you get a minute you could snap a shot of that schematic for the H-PS-1 and post it. I lost mine in the move.


----------



## sachu

bah..slacker!! 
	

	
	
		
		

		
		
	


	




 well hope to see that thing up and going soon.


----------



## wiatrob

RIP - the fourth board. It's getting ~40(!?) volts on the output, along with a raft of other issues. 

 So this may just live as a three channel for now. Or i might order another set of boards, I've got until the meet to get her going...

 EDIT: grounding the heaters silenced all hum, now I can actually give her a listen...


----------



## rhester

For those building a 2 channel verasion with a Sigma22 PS, what size transformer is needed? Will 50VA suffice or do you need 80VA, just in case you add a 3rd or 4th channel later? Any disadvantage to larger trans?


----------



## wiatrob

IMO, Moar is better, disadvantages would be cost, size and stray magnetic fields...


----------



## wiatrob

Well, I've spent a little time with this amp, with Amperex 6GM8s and Phillips 7DJ8s (no balancing needed.) Worked my way up from the Ipod/PX100s to the eOne Dac3/HD600/RS-1s. Very black background (this is the quietest amp I've ever had splayed out on the bench.) Very, very nice sounding. I can't wax about specific amp characteristics, but "I Like It!" 
	

	
	
		
		

		
		
	


	




 I still plan to build a balanced version, and I'd like to compare the BJT to MOSFET someday. Soon.


----------



## sachu

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_For those building a 2 channel verasion with a Sigma22 PS, what size transformer is needed? Will 50VA suffice or do you need 80VA, just in case you add a 3rd or 4th channel later? Any disadvantage to larger trans?_

 


 my transformer is a 160VA at 28.4 Volt secondaries..sure it is overkill..but I like to go overboard on the powersupply.

 Besides, I can always go balanced if I want to later on.

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, I've spent a little time with this amp, with Amperex 6GM8s and Phillips 7DJ8s (no balancing needed.) Worked my way up from the Ipod/PX100s to the eOne Dac3/HD600/RS-1s. Very black background (this is the quietest amp I've ever had splayed out on the bench.) Very, very nice sounding. I can't wax about specific amp characteristics, but "I Like It!" 
	

	
	
		
		

		
		
	


	




 I still plan to build a balanced version, and I'd like to compare the BJT to MOSFET someday. Soon. 
	

	
	
		
		

		
		
	


	


_

 

aah come on...you can gloat about how good this amp is ..we...ahem..I won't mind 
	

	
	
		
		

		
		
	


	




 ...awesome you got the 3 channel version going.


----------



## TimJo

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, I've spent a little time with this amp, with Amperex 6GM8s and Phillips 7DJ8s (no balancing needed.) Worked my way up from the Ipod/PX100s to the eOne Dac3/HD600/RS-1s. Very black background (this is the quietest amp I've ever had splayed out on the bench.) Very, very nice sounding. I can't wax about specific amp characteristics, but "I Like It!" 
	

	
	
		
		

		
		
	


	




 I still plan to build a balanced version, and I'd like to compare the BJT to MOSFET someday. Soon. 
	

	
	
		
		

		
		
	


	


_

 

That's great Bill. I can't wait 'till Jeff has time to send my boards... 
	

	
	
		
		

		
		
	


	




 So, did you end up running the ground channel with the same gain as the L&R channels?


----------



## digger945

Checked the output for voltage and offset, found it at only .17 so cranked it up to .23 and put on some Sinatra, my favs: "Fly me to the Moon" and "Summer Wind". I think it's beginning to open up a bit, especially in the low end. Starting to get a little growl now. Very well balanced throughout the spectrum.

 Using the 0404 for source and Denon 2k's. Still listening to the 6h30's, now with a 6 volt 1800mA wallwort heater supply.

 Thanks for that schematic Bill. I appreciate it.


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_
 So, did you end up running the ground channel with the same gain as the L&R channels?_

 


 Yes, gain of 11 and feedback resistors and 30dB of NFb because that's the values I had on hand...


----------



## rhester

I have my boards stuffed except for the R27,28 which don't come in Jeff's kit for some reason. Have sigma 22 built and waiting on tanny for it, have broskie low v ps coming with tranny. can't wait to hook this all up and compare to Bijou and SOHA II. Got to get around to selling some stuff soon, before the wive finds it all.


----------



## sachu

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have my boards stuffed except for the R27,28 which don't come in Jeff's kit for some reason. Have sigma 22 built and waiting on tanny for it, have broskie low v ps coming with tranny. can't wait to hook this all up and compare to Bijou and SOHA II. Got to get around to selling some stuff soon, before the wive finds it all._

 

hah..the Bijou and SOHA 2 are sure to find their way to the chopping block once you got this going. They don't stand a chance.

 Look forward to your build and impressions.


----------



## zkool448

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_hah..the Bijou and SOHA 2 are sure to find their way to the chopping block once you got this going._

 

sachu, noooooooo! 

 ...I'm just about to build my Bijou


----------



## sachu

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_sachu, noooooooo! 

 ...I'm just about to build my Bijou 
	

	
	
		
		

		
		
	


	



_

 

I have heard all amps from the Cavalli stable. The EHHA and the 'other' amp are the best among them all, IMO of course 
	

	
	
		
		

		
		
	


	




. 

 I have heard these amps over a 2 year period and the EHHA and the 'other' amp never cease to amaze me. I know I have one of the best SE amplifiers out there. I don't feel the need to build the B22 that I was planning on. Which is why you will see most me post those parts up for sale sometime soon.

 I am in the process of securing two perfect enclosures for the EHHA2...so Alex whenever you are ready


----------



## wiatrob

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have my boards stuffed except for the R27,28 which don't come in Jeff's kit for some reason._

 

I just grabbed some 33.2Ks from the parts box - you could always strap these for that 'op amp' sound, which I would guess in the case of this amp, may well be quite nice.

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I have heard these amps over a 2 year period and the EHHA and the 'other' amp never cease to amaze me._

 

What is this 'Other' amp (the S****er XX?!) 

 And I feel that there are some Bijou owners who might disagree with you...We'll have both at the upcoming Colorado meet if Naaman shows up...


----------



## digger945

You don't have to use 33.2k if you don't want, Alex has a list of different values that could be used on the tweaks section. I have these positions socketed and already have added a few to the Mouser order to experiment with. This is a part of what determines the feedback.

 Yea I listened to (can't remember his name)'s Bijou at the Mid-Indiana meet in March and it was, in my opinion of course, a remarkably good sounding amp. Probably one of the best that I've heard, which isn't saying alot but I also listened to a SP amp at that same meet and I wouldn't miss the SP much for the Bijou.


----------



## runeight

Gents, while I am away for a few weeks with little free time on my hands, perhaps I can contribute something to get your thoughts going.

 One thing I've always wanted to do with the EHHA is to make all of the gain stages tube. In the current version, of course, the VAS stage is symmetrical BJTs.

 The first problem right off the bat is that we don't have p-channel tubes. This means that the symmetry goes away. But we can utilize the p-channel VAS portion of the amp to create a different kind of offset servo. 

 With only an n-channel device (a triode) we can only replace the bottom VAS device with a tube. But we still need a connection from the top of the Vbe to the V+ and this connection must be a high dynamic resistance. Usually in this type of amp topology this load is provided by a CCS, either a sand one or a bootstrapped one using capacitors and resistors.

 However, since I'm figuring we'll use dual triodes for all tubes, we can use a tube and a current mirror for the current source.

 Here's the schematic:






 Notice that the B+ for the tubes is now 100V. Many of you will like this. 
	

	
	
		
		

		
		
	


	




 And notice how the bottom triode replaces a bjt for the vas section.

 Because of the high voltages the simple current mirrors must be replaced by Wilson current mirrors. The third transistor is the HV device. It must be at least 250V because it will see the rail-to-rail B+/B-.

 The other half of the VAS triode is used as a current source for the other current mirror loading the Vbe. This triode is slaved to the opamp which is detecting the output offset and zeroing the DC. 

 The VAS triode pair use cathode LEDs to eliminate bypass caps.

 The mosfets are fronted by BJT emitter followers to increase the load seen by the VAS triode. Otherwise the gate capacitance of the mosfets is too much for the tube to drive. But with the followers the amp is still pretty fast, although not quite as fast as the EHHA I.

 This amp will need an additional B+/B- supply which makes the PS a bit more complex than the EHHA I. OTOH, the amp itself is a bit simpler.


----------



## dBel84

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_sachu, noooooooo! 

 ...I'm just about to build my Bijou 
	

	
	
		
		

		
		
	


	



_

 

don't stress ZK , this is just Sachu's way of justifying to himself that he doesn't need to build a Bijou 
	

	
	
		
		

		
		
	


	




 I too have lived with all 3 ( 4 ) amps for quite some time and while I have my preference , it has more to do with my taste preferences rather than the performance of any one amplifier. The Bijou brings a smoothness with it without compromising clarity and that is rare in all but the more expensive all tube amps. I wold like to say that the EHHA has a more SS sound but I don't really buy into that SS/tube philosophy as I have heard examples of either sound like good and poor versions of each other. So lets just say that the EHHA has a more "aggressive" sound with an awfull lot of clout in the bottom end. I could ramble on but this is not the place and I see Alex has posted while I have been musing and I am interested to see what he has brought to the party 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## digger945

At just a glance, I LOVE IT! Isn't the Wilson mirror supposed to be more stout anyway Alex?
 Have you , or anyone else in the club, tested any of this circuit yet? Can we assume that there will be a pcb for this, someday?


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, while I am away for a few weeks with little free time on my hands, perhaps I can contribute something to get your thoughts going._

 

This is good. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Because of the high voltages the simple current mirrors must be replaced by Wilson current mirrors. The third transistor is the HV device. It must be at least 250V because it will see the rail-to-rail B+/B-._

 

It looks like I need to read about Wilson current mirrors. Looks like I have some studying to do...


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_You don't have to use 33.2k if you don't want, Alex has a list of different values that could be used on the tweaks section. I have these positions socketed and already have added a few to the Mouser order to experiment with. This is a part of what determines the feedback._

 

True, i was just suggesting using whatever was on hand for feedback resistors... The amp will likely sound great whatever the value, tho' I haven't experimented with this yet. I will jumper them tonight for arguments sake :^)


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_And I feel that there are some Bijou owners who might disagree with you...We'll have both at the upcoming Colorado meet if Naaman shows up..._

 

I heard Namaan's Bijou at Canjam. Amazingly beautiful build. IT was sounding pretty good and i think Donad put it best, the EHHA is more aggressive, more forward. The Bijou is laidback for my taste and lacks the fantastic control in bottom end that the EHHA has while still retaining that silky buttery mids taht the tubes offer and jsut the right amount of details in the highs...I don't know , it just suits me better...yes even better than the 'other' amp.

  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_don't stress ZK , this is just Sachu's way of justifying to himself that he doesn't need to build a Bijou 
	

	
	
		
		

		
		
	


	




 I too have lived with all 3 ( 4 ) amps for quite some time and while I have my preference , it has more to do with my taste preferences rather than the performance of any one amplifier. The Bijou brings a smoothness with it without compromising clarity and that is rare in all but the more expensive all tube amps. I wold like to say that the EHHA has a more SS sound but I don't really buy into that SS/tube philosophy as I have heard examples of either sound like good and poor versions of each other. So lets just say that the EHHA has a more "aggressive" sound with an awfull lot of clout in the bottom end. I could ramble on but this is not the place and I see Alex has posted while I have been musing and I am interested to see what he has brought to the party 
	

	
	
		
		

		
		
	


	




 ..dB_

 

sacrilege!!..the EHHA does not have a SS sound..
 Bah..As much as the thought of having a Bijou is appealing, i know I don't need one. That money's better be spent on prototyping the EHHA2 
	

	
	
		
		

		
		
	


	




 Speaking of the EHHA2...what do you chaps think of this as the case


----------



## runeight

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_At just a glance, I LOVE IT! Isn't the Wilson mirror supposed to be more stout anyway Alex?
 Have you , or anyone else in the club, tested any of this circuit yet? Can we assume that there will be a pcb for this, someday?_

 

Yes, the Wilson mirror does a better job of matching the currents because it shields the the "matched" bjt from the voltage variations at its collector. In this case it also gives us the ability to protect the matching bjts with an HV transistor.

 There is already a PCB design for this as a power amp (EHPA, Embedded Hybrid Power Amp). It uses huge output devices although the board is very small.

 The only problem is that it's a four layer board and I can't easily get it down to two layers. This because the topology of the circuit is a bit more intertwined than normal.

 I have not tested the circuit yet, but all of the pieces are present in other designs, including my own. There really shouldn't be any problems with the build. But then I've said that before . . . 

  Quote:


  Originally Posted by *TimJo* 
_It looks like I need to read about Wilson current mirrors. Looks like I have some studying to do..._

 

Here's a nice read on designing analog chips. It has a good section on current mirrors.

Designing Analog Chips


----------



## digger945

I first read about the Wilson in "The Art of Electronics" which gives a lot of examples using audio related circuits when your in the transistor and fet chapters.

 I think it looks great and would not hesitate to give it a go even if it does have a thick pcb. I gotta be honest, I have never built an amp for speakers before, and not much in the way of HP amps either.

 Thanks for updating us and giving a little history and info on the design, it's always a pleasure to read your posts. I am studying the feedback circuit now and looking stuff up to see how it works.

 I am smitten


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_
 I am smitten
	

	
	
		
		

		
		
	


	


_

 

Heh..You and me both man.And Donald knew I was crazy over this ever since I first gave it a listen two years ago.


----------



## dBel84

yep, resisted the temptation to sell lit to you too many times to recall, came very close at that first meet tho 
	

	
	
		
		

		
			





 .

 EHPA will be one helluva hybrid power amp , been my goal to build one of these for some time.

 ..dB


----------



## zkool448

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_don't stress ZK , this is just Sachu's way of justifying to himself that he doesn't need to build a Bijou 
	

	
	
		
		

		
		
	


	


_

 

ah no worries dB, I now see where sachu’s rationalization comes from 
	

	
	
		
		

		
		
	


	




 But simply put, here I quote about how we all hear differently -- It's like ice cream, some prefer vanilla and others prefer chocolate. Together, they create a celebration for the senses. 

 Guess I'll have to build them all


----------



## dBel84

once that momentum sets in, it is indeed hard to stop 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

Bah!!


----------



## wiatrob

Speaking of Bah! Smeggy, have you had the chance/willingness to revisit your build? Are both channels shot?


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Speaking of Bah! Smeggy, have you had the chance/willingness to revisit your build? Are both channels shot?_

 

I believe both his channels are making a quick trip down south


----------



## wiatrob

K Sachu - let me know if you need spares, I have quite a few and can drop them in your second to next mailing...

 Along with my blown up fourth board is you are now Saachu's DIY repair Depot!


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, the Wilson mirror does a better job of matching the currents because it shields the the "matched" bjt from the voltage variations at its collector. In this case it also gives us the ability to protect the matching bjts with an HV transistor.

 There is already a PCB design for this as a power amp (EHPA, Embedded Hybrid Power Amp). It uses huge output devices although the board is very small.

 The only problem is that it's a four layer board and I can't easily get it down to two layers. This because the topology of the circuit is a bit more intertwined than normal.

 I have not tested the circuit yet, but all of the pieces are present in other designs, including my own. There really shouldn't be any problems with the build. But then I've said that before . . . 



 Here's a nice read on designing analog chips. It has a good section on current mirrors.

Designing Analog Chips_

 

Thanks for the link Alex. I wasn't expecting it to be a pdf. 
	

	
	
		
		

		
		
	


	




 I'm all about learning something new. 

 I need to pick up a copy of "The Art Of Electronics" as well, digger...

  Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I first read about the Wilson in "The Art of Electronics" which gives a lot of examples using audio related circuits when your in the transistor and fet chapters.

 I think it looks great and would not hesitate to give it a go even if it does have a thick pcb. I gotta be honest, I have never built an amp for speakers before, and not much in the way of HP amps either.

 Thanks for updating us and giving a little history and info on the design, it's always a pleasure to read your posts. I am studying the feedback circuit now and looking stuff up to see how it works.

 I am smitten
	

	
	
		
		

		
		
	


	


_

 

Yeah I have an extra set of floor standing speakers that are just waiting to make music again.


----------



## TimJo

http://www.head-fi.org/forums/f6/cav...5/#post5756420

 EDIT: I just saw sachu started a dedicated thread for the EHPA, so I moved my question over there... Feel free to respond on the other thread.


----------



## smeggy

I really have no clue how to fix these things, I can replace parts all day and still not know what's wrong.


----------



## runeight

Smeggy, how big is the damage?


----------



## smeggy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Smeggy, how big is the damage?_

 

I built both boards the same, tried first powering the heaters, that went fine. After about 40 seconds I switched the S22 on with one board connected and within seconds the two output resistors were glowing brightly and smoking. 

 The second board is still untested as I didn't want to fry both. I don't know what aside from the big resistors, I was too depressed to check the MOSFETs so I can't say what might be wrong. 

 Guaranteed it is something dumb I did, but know not what. Thankfully the S22 didn't blow up this time


----------



## dBel84

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I built both boards the same, tried first powering the heaters, that went fine. After about 40 seconds I switched the S22 on with one board connected and within seconds the two output resistors were glowing brightly and smoking. 

 The second board is still untested as I didn't want to fry both. I don't know what aside from the big resistors, I was too depressed to check the MOSFETs so I can't say what might be wrong. 

 Guaranteed it is something dumb I did, but know not what. Thankfully the S22 didn't blow up this time 
	

	
	
		
		

		
		
	


	


_

 

i thought the whole thing had smoked, those output resistors are a common delight in the EHHA - just ask snoopy, his lit up during one of the meets 
	

	
	
		
		

		
		
	


	




 It sounds like you have a short to ground on the output, at least too much current flowing through the output ..dB


----------



## smeggy

so any Idea what do I check to find out? I guess I could just run the meter over everything and see what happens.


----------



## dBel84

you could use the meter to see if you have continuity between ground and output , this would be the easiest way to check that concern ..dB


 edit - did you make sure that the trimmer (R21) was fully counterclockwise? - assuming all trimmers behave equally


----------



## smeggy

That was one of the things I did from the EHHA checklist. I went through all of it before switching on, which was last on the list.

 I'll recheck the other board.


----------



## digger945

It's kinda funky the way that 3 position terminal is there at the output with the HP output being between the +30 and -30 terminals. It might help a little if we had a pic Smeggy, could be something obvious. I made more than one mistake building this amp, just caught them before power up after I went over it ten times.


 EDIT: Looking at the schematic, indeed you would probably smoke those output resistors fast if the S22 ground were accidentally hooked up to the output between those +/-30V terminals. I almost did that, almost.


----------



## smeggy

One thing I forgot to mention, one trimpot on both boards doesn't have a click. Can't recall which one but on both boards there was no clickstop. I wound them dozens of times but never reached a click. Same trimmer on both boards.

 here's a pic I took for something else







 As you can see the output goes to the jack. I wired up the star ground but it's mostly disconnected now.

 Mmmm, lovely cooked resistors....


----------



## digger945

I see you like Mogami too.
 Kinda tough to see much, but looks to be wired properly. Looks like both pots are oriented the right way. Lemme study the schematic again and see what can make those output resistors barbaque like that.

 I had one or two that didn't click either when going one way, so I just counted the turns until I was sure I had 25 or so and stopped.
 It could be as simple as the pot was turned all the way the wrong way. You know what size output resistors those are?


----------



## smeggy

I think they're 2W, I still have a few of them.


----------



## digger945

Looks like D1 and D2 are in backwards, on both boards.


----------



## smeggy

you can see that from that crappy picture? 
	

	
	
		
		

		
		
	


	




 I'll check when I get home, cheers.


----------



## digger945

LOL it aint easy, my eyes aint much pumkin any more.
 I just blew the picture up to 400% and compared it to mine here on the desk.
 I'm not so sure having them in backwards would be a bad thing, and certainly won't hurt them in this amp, but correcting them will be necessary to make music.
 I gotta hit the sack for now, I'm confident we can get this amp going without a fuss Smeggy. It really looks good to me, gotta be something simple.


----------



## sachu

yep..D1 and D2 both seem reversed...nice catch digger.


----------



## dBel84

even blown up I can't make that out  ..dB


----------



## smeggy

Ok, big pics

Imageshack - dsc8016.jpg

Imageshack - dsc8015.jpg

 click on pics for the giant view. 

 On the dead board the burnt resistors still read ok but look a little unwell. The MOSFETs are both shorted and you can read from input to output where you couldn't before it was BBQ'd. Very unhappy all-in-all.

 I still have no clue what caused it to fry. I'm not sure which way the diodes are supposed to go so I probably did put them in wrong, but at least they're all wrong the same 
	

	
	
		
		

		
		
	


	




 MM set to 2k Ohms, R21 is reading 0.784 on the dead board and 1.005 on the good one. Winding the adjuster seems to make little to no difference and still no click.


----------



## wiatrob

The diodes are oriented with the black band matching the white stripe on the PCB ( that' s the cathode end)


 Will take a look versus my good PCB when I get a chance, other than a few iffy solder joints, nothing pops out at me, but I bet Digger might spot something with his eagle eyes...


----------



## smeggy

I'll swap the diodes around, and the solder joints, yes, they look a bit ratty in places but I think they're ok. I still need to get more mosfets to replace the dead ones. Chances are it'll still go to sachu to fix.


----------



## spritzer

I would reheat most of the solder joints and even add some solder on the top of the board to those connected to the ground plane. All that copper dissipates the heat, making it harder to get a good joint. Also, make sure there is plenty of clearance between the resistors next to to the mosfets, and the empty solder pads on the board.


----------



## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ok, big pics

Imageshack - dsc8016.jpg

Imageshack - dsc8015.jpg

 click on pics for the giant view. 

 On the dead board the burnt resistors still read ok but look a little unwell. The MOSFETs are both shorted and you can read from input to output where you couldn't before it was BBQ'd. Very unhappy all-in-all.

 I still have no clue what caused it to fry. I'm not sure which way the diodes are supposed to go so I probably did put them in wrong, but at least they're all wrong the same 
	

	
	
		
		

		
		
	


	




 MM set to 2k Ohms, R21 is reading 0.784 on the dead board and 1.005 on the good one. Winding the adjuster seems to make little to no difference and still no click._

 

This may not be all of the problems, but D1 and D2 look backwards to me. The black band on the diode should be aligned with the white band on the silkscreen image. Am I seeing this correctly that these diodes are reversed?


----------



## wiatrob

Diggers eagle eyes pointed the diodes out. We wonder: could that have been disastrous?


----------



## smeggy

More worrying to me is why neither R21 trimpot is doing anything. Is there another type I can use that actually does adjust and has a clickstop? I imagine this is more likely to have done damage than reversed diodes but I'm no sparky.


----------



## zkool448

I remember having a faulty trimpot with my SOHA, measured between the pins while turning but the value never changed (no click stop either). I ended up ordering another and worked like a charm.


----------



## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Diggers eagle eyes pointed the diodes out. We wonder: could that have been disastrous?_

 

Oh. Sorry. Late into the game.

 Yes, this is potentially disastrous. Reversed diodes would cause the the CCS on the diff amp to conduct hugh currents. This will cause the O/P stage, in turn, to conduct in the amperes range. The Vbe section will also see potentially several hundred mA.

 Smeggy, sorry for the news here but there could be quite a few components that are toasted. It is hard to know which ones to pinpoint.

 But, if you're not too frustrated, flip the diodes and replace R21. If we're lucky this might pull everything back in line. Assuming that the O/P devices are still alive.


----------



## digger945

I'm hoping it just burned the output resistors quickly before anything else got too hot. It's kinda hard to tell but the Toshiba's usually have a bump or crack on them when they have the full current of a S22 on them(don't ask me how I know that LOL). I had some laying around but trashed them so I wouldn't accidentally re-insert them into a board.

 I had to turn R21 for quite a few turns before I saw any voltage appear on the outputs.


----------



## smeggy

I need to swap all four diodes, replace both R21, two output resistors and two MOSFETs so far. Dunno what else may have blown. It may be simpler just to get a single channel off glassjar and start over.

 The second board hasn't been christened yet so I can try reversing the diodes and getting a new adjustable R21 and see if that board works. if it does then I'll know better what the problem was. If that fries I'll kick sachu in the nuts for getting me to do it in the first place 
	

	
	
		
		

		
		
	


	




 BTW. What is the CCS, diff amp and Vbe?





 Digger, the output resistors still measure well. They're just a bit suntanned.
 I turned R21 lots of times, no difference at all


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_The second board hasn't been christened yet so I can try reversing the diodes and getting a new adjustable R21 and see if that board works. if it does then I'll know better what the problem was. If that fries I'll kick sachu in the nuts for getting me to do it in the first place 
	

	
	
		
		

		
		
	


	




 BTW. What is the CCS, diff amp and Vbe?



_

 

Smart move on preserving the second board. Do you mean you are seeing no change in measured resistance when turning the non-clicking trimpot?

 BTW: Constant Current Source, Differential Amplifier, and Base Emitter Voltage Drop - not that you need to know what they mean to successfully build or troubelshoot....


----------



## smeggy

Yeah, the resistance doesn't change with turning the screw measured across it's tags on either board.

 Thanks for the descriptions, i like to at least know what the terminology is even if I don't understand it 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Smart move on preserving the second board. Do you mean you are seeing no change in measured resistance when turning the non-clicking trimpot?

 BTW: Constant Current Source, Differential Amplifier, and Base Emitter Voltage Drop - not that you need to know what they mean to successfully build or troubelshoot...._


----------



## digger945

Of the parts that you can see the print on, none look out of place or wrong to me. Those don't look like Bournes pots to me, maybe that's why they don't click when you get to the end. I say switch the diodes around and set the pot for what you think is the middle and plug 'er in. I'll keep looking, post more pics if you have time and want to.


----------



## smeggy

the other timpot is set midway but there's no way to set R26 anywhere as I can't adjust it from 0.74x and 1.005 on the other board measured @2k Ohm range. I need a trimmer I can wind down to minimum so I need to replace both with something else. Just gotta find an alternative to the supplied ones.


----------



## digger945

This is what I used for R21. The same for the 100 ohm. The 3296 line is skinnyer and fits better. The "W" means it has the adjustment on top(if you were to want to shop for other values later or something)

 I have some extras.


----------



## smeggy

Nice, thanks Digger. I'll add these to my next order which I need to put in soon.


----------



## wiatrob

Smeggy - nice to have you back after a cooling the cooling off period. Persist! You will be rewarded.


----------



## smeggy

Heh,

 It only means more stupid questions for you all to be pestered with until the thing works. It'll probably be another week before spares arrive. In the meantime I still have a Starving Student kit to make and a Beta 22 to repair. 

 On top of all that I need to build another S22 so both amps have one *sigh*

 Blasted DIY! Grrrrrr.


----------



## wiatrob

Well, its supposed to be _fun_! But there can be a few frustrating moments: I started to troubleshoot my broken EHHA board, hooked everything up, checked all the wiring, and still managed to reverse +/-30V. It's *REALLY* dead now...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, its supposed to be fun! But there can be a few frustrating moments: I started to troubleshoot my broken EHHA board, hooked everything up, checked all the wiring, and still managed to reverse +/-30V. It's *REALLY* dead now... 
	

	
	
		
		

		
			



_

 


 aah man...that sucks dude..


----------



## smeggy

Did it play all your music backwards and tell you to do evil things?


----------



## TimJo

Could one of you guys measure a EHHA board and post the dimensions. I don't see the board size on the website, and I'd like to start planning the casework...

 Thanks.


----------



## wiatrob

3 1/2" x 4" from memory... Can check this eve...


----------



## runeight

Very close: 3.6" x 4.2"


----------



## TimJo

Thanks...


----------



## DoYouRight

From help by Sachu on deciding, I think the EHHA will be my Tube amp to compliment the B22 when I finish it. Very excited about this.

 Deciding to go DIY was very smart considering I can build a B22 for the same price as a Compass AMP/DAC is really frustrating but good learn


----------



## smeggy

Yay, same as me. Beta22 and EHHA 
	

	
	
		
		

		
		
	


	




 Well, along with the CTH and others..


----------



## TimJo

Well, I originally thought I'd just go with AC heaters, but now I'm thinking about building a DC regulator, especially after reading Don's advice.

  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_just my 2c

 AC heaters can be used but because of the nature of this amp , the proto team even considered an S11 as an option for the heaters and not overkill . I would personally look at low noise DC supplies as default. 

 ..dB_

 

I've been looking at the options and in reading what Morgan Jones had to say about heater supplies, he brought up the topic of cathode poisoning. Since it sounds like the recommended startup sequence on this amp is to preheat the cathodes before B+ is applied, it seems like cathode poisoning may be relevant here. He lays out a fairly simple heater supply that uses an LM317T regulator and Schottky diodes, but is configured to output ~4 V on standby, and then kick in to 6.3 V when B+ is applied. He says that running the heater's at 63% of full power will reduce any ill effects during warmup.

 Any thoughts on this, or practical experience in any other tube amps?


----------



## smeggy

I'll be using a plain AC heater until I get time to put a regulator together. I have the parts, just no time or inclination right now. I'll get to it one day though.


----------



## adamus

I really wouldnt bother with the low voltages on offer here.

  Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, I originally thought I'd just go with AC heaters, but now I'm thinking about building a DC regulator, especially after reading Don's advice.



 I've been looking at the options and in reading what Morgan Jones had to say about heater supplies, he brought up the topic of cathode poisoning. Since it sounds like the recommended startup sequence on this amp is to preheat the cathodes before B+ is applied, it seems like cathode poisoning may be relevant here. He lays out a fairly simple heater supply that uses an LM317T regulator and Schottky diodes, but is configured to output ~4 V on standby, and then kick in to 6.3 V when B+ is applied. He says that running the heater's at 63% of full power will reduce any ill effects during warmup.

 Any thoughts on this, or practical experience in any other tube amps?_


----------



## smeggy

I measured my heater transfo and it seems right on the mark and it lit the tubes fine so I'm not gonna fret over it. Alex does specify either way will do.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I measured my heater transfo and it seems right on the mark and it lit the tubes fine so I'm not gonna fret over it. Alex does specify either way will do._

 

You are sure to have noise on the outputs this way. I did on mine and with orthos that too.


----------



## looser101

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_You are sure to have noise on the outputs this way. I did on mine and with orthos that too._

 

Try connecting a small cap (.1uF) to ground on one of the heater pins. Also make sure heater leads are tightly twisted and not near any signal wiring.

 x2 on Adamus comment. My understanding is that delaying the B+ is only necessary at much higher voltages.


----------



## sachu

Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_Try connecting a small cap (.1uF) to ground on one of the heater pins. Also make sure heater leads are tightly twisted and not near any signal wiring.

 x2 on Adamus comment. My understanding is that delaying the B+ is only necessary at much higher voltages._

 

yeah the way i have my heater wiring laid out, they pretty much go past the signal wires..hence i went with a LDO reg DC supply.


----------



## looser101

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah the way i have my heater wiring laid out, they pretty much go past the signal wires..hence i went with a LDO reg DC supply._

 

Even better. How are the 6H30's?


----------



## TimJo

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I've been looking at the options and in reading what Morgan Jones had to say about heater supplies, he brought up the topic of cathode poisoning. Since it sounds like the recommended startup sequence on this amp is to preheat the cathodes before B+ is applied, it seems like cathode poisoning may be relevant here. He lays out a fairly simple heater supply that uses an LM317T regulator and Schottky diodes, but is configured to output ~4 V on standby, and then kick in to 6.3 V when B+ is applied. He says that running the heater's at 63% of full power will reduce any ill effects during warmup.

 Any thoughts on this, or practical experience in any other tube amps?_

 

 Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I really wouldnt bother with the low voltages on offer here._

 

 Quote:


  Originally Posted by *looser101* /img/forum/go_quote.gif 
_x2 on Adamus comment. My understanding is that delaying the B+ is only necessary at much higher voltages._

 

Thanks for the input guys - it's a great thing having this forum to bounce ideas around.

 It's interesting that both of you mention high voltage being a factor. As Morgan Jones explained it, cathode poisoning is a function of running the heaters at full power with no current passing through the tube. Basically the electrons on the cathode are excited, but they have nowhere to go, and so the surface of the cathode becomes altered. As described, it would seem this effect can take place on any tube, independent of plate voltage. On the other hand, maybe it's effects are more pronounced at high voltages - I'm not sure...


----------



## adamus

typically people delay the B+ to stop 'cathode stripping'. 

 why would you be warming up with no B+ (forgive if this is the case with the ehha)


----------



## smeggy

Given how inexpensive tubes are I'll buy a few and not worry about it. I can just swap out to see if anything is deteriorating, if not, back in they go until they're toast.


----------



## wiatrob

Inexpensive 6GM8s or 6H30s? Can I get your source


----------



## wiatrob

Not authoritative but informative: Cathode Stripping vs. Poisoning vs. Bombardment


----------



## wiatrob

Just got the parts to repair my blowed up EHHA board (~12 transistors. TRIPLE check before hooking up polarized voltage after a looong day 
	

	
	
		
		

		
		
	


	




)


----------



## smeggy

Good luck, no more sparks and pops.

 And tubes.. inexpensive whatever Jeff sells with the kits


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Good luck, no more sparks and pops.

 And tubes.. inexpensive whatever Jeff sells with the kits 
	

	
	
		
		

		
		
	


	


_

 

yeah..but he's got a limited stock i belive and intended for EHHA kits.


----------



## TimJo

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_typically people delay the B+ to stop 'cathode stripping'. 

 why would you be warming up with no B+ (forgive if this is the case with the ehha)_

 

Well, my understanding is that there is a risk in starting the EHHA amp boards with cold tubes in that the servo may swing to one of the rails before stabilizing. So, it is suggested that the tube heaters should be powered up for about a minute before the the B+ power supply is powered. Maybe Alex or Don can shed some light here.

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Not authoritative but informative: Cathode Stripping vs. Poisoning vs. Bombardment_

 

Thanks, I'll read what they wrote about it.

 Just for clarity, what I was referring to from the Morgan Jones book was poisoning, rather than stripping. 

_



			If a cathode is kept at full operating temperature, but little or no current is drawn, a high resistance layer of barium orthosilicate forms at the interface between the barium oxide emissive surface and the nickel cathode structure. The interface resistance eventually reduces emission, but more significantly, it increases the noise generated by the valve.
		
Click to expand...

_ 
 I guess a common design to prevent this is to have the LT heater supply default to a lower voltage in 'stand-by' mode, and then go to the rated voltage when the amp is powered up. He says that the default value is 63% of the rated heater voltage, based on the design of color tv cameras that used tube sensors.

 I may just build the PS this way for the fun of it.


----------



## Lifthanger

Hey all 
	

	
	
		
		

		
		
	


	



 This might be the wrong thread to ask this, but I was looking to build my first hybrid.
 Till now I leaned towars the millet maxed or the SOHAII, but now I found the EHHA.
 Main criteria is performance Phones will be HD595 and HD650...
 Any pointers? 
 Thanks.


----------



## sachu

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_Hey all 
	

	
	
		
		

		
		
	


	



 This might be the wrong thread to ask this, but I was looking to build my first hybrid.
 Till now I leaned towars the millet maxed or the SOHAII, but now I found the EHHA.
 Main criteria is performance Phones will be HD595 and HD650...
 Any pointers? 
 Thanks._

 

The first headphone I ever listened to with the EHHA was the HD580 and I was floored. I have been in 'love' with this amp ever since.
 The SOHA2 is an easier build compared to the EHHA..but the EHHA will be that much sweeter once you have it going.


----------



## Lifthanger

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The first headphone I ever listened to with the EHHA was the HD580 and I was floored. I have been in 'love' with this amp ever since.
 The SOHA2 is an easier build compared to the EHHA..but the EHHA will be that much sweeter once you have it going._

 

That's what I wanted to hear 
	

	
	
		
		

		
		
	


	




.
 Just wanted to make sure because I thought the SOHA2 was better.
 Millet Max < SOHA2 < EHHA sound quality wise I guess?


----------



## digger945

I'de say study them both and pick one to build now with the intent of building the other one eventually so you can compare them later. You can print out the BOM for both and maybe order parts for both, maybe saving a little by buying for both.

 Wow, I'm a lot of help, ain't I


----------



## wiatrob

I do agree with Digger (and I have built both, including proto'ing the SOHA II - which is quite good with all Senns). 

 I won't get into SQ comparisons here, as that's for another thread! But-

 The SOHA 2 is an easier build - all parts specified and fits in a standard case. The EHHA will require some knowledge of component selection and casing skills. 

 I will say that the reward is certainly there if you are up to it...


----------



## Lifthanger

thanks for your input 
	

	
	
		
		

		
			





.
 honestly, I fear that sooner or later I'll build all three of them.
 It's the sickness, you all know 
	

	
	
		
		

		
		
	


	




.
 I'll read the SOHA2 and EHHA pages again and make a decision then.


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah..but he's got a limited stock i belive and intended for EHHA kits._

 

Yes - 6GM8s have taken a turn for the more expensive over the last 16 months...


----------



## dBel84

Been out of town for a while and trying to catch up. 

 I thought I would post the heater supply I used , the idea was borrowed from KG's psu for his original dyna amp and uses a high power opamp to deliver the current necessary for tubes like the 6H30's - I run the tubes in series and set the voltage to 12.6V , can idle at 3A and supply up to 5A 







 The reference voltage chip can be changed if you want to drop the output to 6.3V ( or run the power chip at near unity gain with the 5V reference ) ..dB


----------



## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Yes - 6GM8s have taken a turn for the more expensive over the last 16 months..._

 

Which is why ... the amp can run 6h30s and 6922s.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Which is why ... the amp can run 6h30s and 6922s. 
	

	
	
		
		

		
		
	


	


_

 


 AND - 7DJ8s 
	

	
	
		
		

		
		
	


	




 Not that 6H30s are budget tubes....

 I gave up on fixing my blown up EHHA board and am building another up. Hopefully I will be able to report on a balanced version soon...


----------



## runeight

Well hurry up wouldja. I think you'll be the first balanced EHHA to be built.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well hurry up wouldja. I think you'll be the first balanced EHHA to be built. 
	

	
	
		
		

		
		
	


	


_

 

OK already. I burned the midnight oil last night and got the fourth board up. 

 It is reading like my others - only .6V across R3, 4, 10, 14 - but strong 1V across the output and ~0 Mv offset...

 Now to find the time to hook it up . Then case it.


----------



## dBel84

sweeet 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## sachu

Looking forward to the beast Bill..

 Just about finished fixing Smeggy's EHHA boards here..need to reflow some joints and hope to fire them up in the next couple of hours..They are just drying off now from the alcohol rubbing I gave them


----------



## wiatrob

I also have to balance a set of headphones


----------



## sachu

ANother EHHA lives!!

 I have 3 under my roof right now 
	

	
	
		
		

		
		
	


	




 Repaired and here we are testing Smeggy's EHHA boards..I just love how it sounds..no audible hiss or humm..brilliant.





 Smeggy my brother...you are going to love this.

 Unfortunately the LED on the board that got fried is not working..gonna try and replace it else send it back to you to have you deal with it.

 Not a bad weekend at all, 5 CTHs populated and repaired and tested an EHHA..very happy. 
	

	
	
		
		

		
		
	


	




 Time to sit back and listen to some great sonds from the EHHA. 
	

	
	
		
		

		
		
	


	




 Cheers,
 Sachu


----------



## dBel84

well done Sachu - great achievement and I am sure we will have a happy pink haired, tight arsed Mandexer 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## digger945

Looks like better success building on newspaper than Steven King novels...
 can't wait to hear Smeggy's comments.


----------



## wiatrob

I need to pay more attention to the Secrets of Sachu's Workbench!


----------



## smeggy

WOOHOO!!

 Sachu is mah hero, I'll have to give you a big wet sloppy kiss when we finally meet (but no tongues) 
	

	
	
		
		

		
		
	


	




 hehe

 I can't wait to hear the thing either, I'm sure it'll be amazing


----------



## wiatrob

Power wired and tested. I will be experimenting with wiring runs on the board. I have a par-metal case but might split the PS and amp to two cases...


----------



## smeggy

That is gonna be awesomeness x 10

 Excellent!!


----------



## sachu

alright Bill!..that is going to be one mighty beast of an amp...Look forward to your impressions.

 Had some trouble with Smeggy's EHHA again today. Turned it on to test it before packing it away and the output resistor on the previously bad board let out some magic smoke..replaced it and turned it back on andeverything was fine and dandy. 

 However it seems like I have lost a 6GM8 tube on that same board. I got back from home and noticed the tube to be cloudy. The glass was broken clean. sigh...at least the amp is working fine again.


----------



## smeggy

Erm, would an Epsilon 12 be useful given the potential flakiness of that board, I'd be happier if it zapped the epsilon than my phones if it decides to freak out again. I think I have some of those resistors but I think I'll need to order some tubes.


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Erm, would an Epsilon 12 be useful given the potential flakiness of that board, I'd be happier if it zapped the epsilon than my phones if it decides to freak out again. I think I have some of those resistors but I think I'll need to order some tubes._

 


 An e12 will protect you from some DC offset - but the board should not be randomly smoking resistors (or tubes). I find that the DC offset on my boards stabilizes in seconds (much faster than advertised).

 This seems like an intermittent problem where a LOT of current is moving through that channel of the amp. I'd try (to get Sachu 
	

	
	
		
		

		
			





) to keep looking at it until the cause is found...


----------



## TimJo

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Power wired and tested. I will be experimenting with wiring runs on the board. I have a par-metal case but might split the PS and amp to two cases..._

 

Looking great Bill! Can't wait to hear what you think...

 Did you get a pair of balanced phones wired up? What hp's will you be using?


----------



## TimJo

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Erm, would an Epsilon 12 be useful given the potential flakiness of that board, I'd be happier if it zapped the epsilon than my phones if it decides to freak out again._

 

 Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_An e12 will protect you from some DC offset - but the board should not be randomly smoking resistors (or tubes). I find that the DC offset on my boards stabilizes in seconds (much faster than advertised).

 This seems like an intermittent problem where a LOT of current is moving through that channel of the amp. I'd try (to get Sachu 
	

	
	
		
		

		
		
	


	




) to keep looking at it until the cause is found..._

 

I'd keep looking for the cause as well. An e12 will help if the transient is slow enough to catch it, but if it's frying resistors (and now blowing up tubes 
	

	
	
		
		

		
		
	


	




 ) it sounds like it may happen so fast, with so much current, that the e12 might not be able to respond in time to save your headphones...


----------



## TimJo

Well, I'm getting closer to joining you guys in building the EHHA - I got an email today saying my package from Glass Jar has shipped. 
	

	
	
		
		

		
		
	


	




 Since the Headwise archives are not available to peruse, I have another question that may have been discussed before, but I'll go ahead and ask again. 

 When I was looking at the data sheet for the 6GM8 I saw that the max plate voltage is 30v and the curves tend to indicate that the upper end of the typical operating range falls in the 25v zone. 

 So my question is, if R3 & R4 are dropping about 1.5v, then that's about 28.5v on the plates. Is this too high, or should the rails be adjusted to produce something closer to 25v at the plates?


----------



## smeggy

Ok, in that case is the somewhere to potentially put a fuse or trip in the circuit to prevent excessive current spikes, maybe wired to the board input. I'd rather not blow the components or phones if at all possible.


----------



## sachu

Smeggy, I will stress test the amp tonight..will make sure it is all working before i send it out to you. Basically I will try and fry the amp


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Looking great Bill! Can't wait to hear what you think...

 Did you get a pair of balanced phones wired up? What hp's will you be using?_

 

Signal wiring is in the planning stages - I plan to wire this up as suggested earlier in the thread (ala 4 board b22) as two unbablanced and one balanced amp.

 I will be balancing my HD600 and RS-1s - I got all the connectors out


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_So my question is, if R3 & R4 are dropping about 1.5v, then that's about 28.5v on the plates. Is this too high, or should the rails be adjusted to produce something closer to 25v at the plates?_

 

dBel mentioned this as well when I was setting up - My plate voltage is around 28V (measured) and Don indicated this was a bit high... 

 Were earlier builds running at lower plate voltages?


----------



## smeggy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Smeggy, I will stress test the amp tonight..will make sure it is all working before i send it out to you. Basically I will try and fry the amp 
	

	
	
		
		

		
		
	


	


_

 





 just try to not burn your house down in the process


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_just try to not burn your house down in the process 
	

	
	
		
		

		
		
	


	


_

 

Those Steven King novels are quite flammable!


----------



## runeight

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Well, I'm getting closer to joining you guys in building the EHHA - I got an email today saying my package from Glass Jar has shipped. 
	

	
	
		
		

		
		
	


	




 Since the Headwise archives are not available to peruse, I have another question that may have been discussed before, but I'll go ahead and ask again. 

 When I was looking at the data sheet for the 6GM8 I saw that the max plate voltage is 30v and the curves tend to indicate that the upper end of the typical operating range falls in the 25v zone. 

 So my question is, if R3 & R4 are dropping about 1.5v, then that's about 28.5v on the plates. Is this too high, or should the rails be adjusted to produce something closer to 25v at the plates?_

 

This was factored in during the design. 28.5V won't hurt the tube. Even 30V won't hurt the tube. Don't sweat this one.


----------



## dBel84

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_dBel mentioned this as well when I was setting up - My plate voltage is around 28V (measured) and Don indicated this was a bit high... 

 Were earlier builds running at lower plate voltages?_

 

I did? must be been licking too many toads, we all ran our amps at 30V rails and were well aware that this is the upper end of the operating point for the 6GM8 

 my apologies for stirring the pot of confusion ..dB


----------



## TimJo

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_I did? must be been licking too many toads, we all ran our amps at 30V rails and were well aware that this is the upper end of the operating point for the 6GM8 

 my apologies for stirring the pot of confusion ..dB_

 

No worries! I'm just full of questions as usual. 
	

	
	
		
		

		
			





 I kinda figured if there was an issue, it would be on the website, but I just wanted to be sure. I'm hoping Headwise will be back up before too long to read more about the design process.


----------



## wiatrob




----------



## dBel84

and ???? 

 the suspense is killing me ..dB


----------



## wiatrob

Right off the bat - Pretty damn amazing. I have the very slightest hum in one channel at full volume (surprising looking at the rat's nest?)

 Driving with a bel canto DAC3 into the hd600s. 

 Burn n time, then more impressions. Then casing.

 Thanks Alex for the design and Don for championing this amp.


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_and Don for championing this amp._

 

*cough cough*..ahem


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_*cough cough*..ahem 
	

	
	
		
		

		
		
	


	


_

 

_*
 AND SACHU *_for cheerleading!


----------



## sachu

Fixed it for you!!

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_*
 AND SACHU *for bringing the amp to the forefront and restoring it to its rightful place, at the top of the Cavalli Audio lineup_


----------



## wiatrob

Yes, we know how you feel. 
	

	
	
		
		

		
		
	


	




 Wait until you hear this one! MOSFETishists!

 I fixed the hum, ground issue. Now dead silent all the way up to max volume (with gain still at 11 - this amp will deafen you.) NFB at min.

 It's easily handling anything i throw at it with authority.

 Rolling Stones Emotional Rescue, Beastie Boys , Black Devil Disco club, Vivaldi Bassoon Concert #23...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Yes, we know how you feel. 
	

	
	
		
		

		
		
	


	




 Wait until you hear this one! MOSFETishists!

 I fixed the hum, ground issue. Now dead silent all the way up to max volume (with gain still at 11 - this amp will deafen you.) NFB at min.

 It's easily handling anything i throw at it with authority.

 Rolling Stones Emotional Rescue, Beastie Boys , Black Devil Disco club, Vivaldi Bassoon Concert #23..._

 

Darn it Bill..Don't tempt me to build a BJT version now..am already thinking about it..

 do you have extra output devices?


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Darn it Bill..Don't tempt me to build a BJT version now..am already thinking about it..

 do you have extra output devices? 
	

	
	
		
		

		
		
	


	


_

 

Matched even - let me know. I have parts to build an active ground MOSFET version at some point in the future.

 I have a gut feeling the design of this amp cuts out many of the differences in component choice. Has anyone ever listened to a BJT vs. MOSFET version?


----------



## dBel84

I believe Steinchen was he only one, snoopy may have but I don't recall. The verdict at the time was that they sounded similar..dB


----------



## TimJo

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Right off the bat - Pretty damn amazing._

 

That's great! 

 So how does it compare to the CTH ? 
	

	
	
		
		

		
		
	


	




 EDIT: ^^ Not so much in terms of better or worse, but in things like soundstage and detail. We know what sachu thinks.


----------



## wiatrob

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_That's great! 

 So how does it compare to the CTH ? 
	

	
	
		
		

		
		
	


	




 EDIT: ^^ Not so much in terms of better or worse, but in things like soundstage and detail. We know what sachu thinks. 
	

	
	
		
		

		
		
	


	


_

 

The EHHA is a great amp, but I haven't spent enough time with it to make any judgments. Plus it's balanced and I'm not used to that.

 I have to be careful what I say about the CTH here, as I am technically MOT. 

 But I'll get some impressions of the EHHA as soon as I get my RS-1's reterminated.


----------



## TimJo

That's cool. I just figure you've spent a lot of time with various versions of the CTH and so it would be interesting to see what you think. 

 In the meantime, I'm going to be busy because my order from Glass Jar was on the front porch when I got home yesterday. 
	

	
	
		
		

		
		
	


	




 So does anyone know the make of the 6GM8's that Jeff includes in the kits? My tubes have no markings except for an etched code along the bottom part of the tube reading _45E3_ and what looks like a capital _N_ above it.


----------



## digger945

These are the first 6gm8's i've had that have no markings and plain white boxes. You would think no markings mean they may have been handled some.


----------



## dBel84

I will buzz Jeff and ask him, I recall he bought them as a bulk lot. I was thinking that they were national brand but i couldn't find the e-mail when he mentioned them. They are NOS , so most likely made by one of the big manufacturing houses and rebranded..dB


----------



## digger945

Well, hard as they are to find, and seeing how ultra low(to me) the price is, it wouldn't matter to me where they come from. NOS is even better. I didn't know that. Tell ya one thing, he could be making a heck of a lot more selling them elsewhere, and I'm tickled he has made these available to the community, along side all the kits.


----------



## dBel84

~$6 at antique electronic supply ..dB

 but don't tell anyone else or they won't be no more


----------



## digger945

I haven't looked very hard lately (<that's code for haven't looked at all in 6 months).
 Thanks for the link.


----------



## wiatrob

$5.40! Let us know if they actually have any


----------



## smeggy

Ladies and gents, we have a beautifully working EHHA!

 Damn it's nice. Fast, very fast, extremely open and detailed treble, very nice everything. Doesn't slam in the bass to the extent the Beta can manage but it does sound very 'right'.

 Excellent amp 
	

	
	
		
		

		
		
	


	




 Any idea if this would have the balls for running my Stax adapter, they like a few watts and from what Alex has been saying, it may provide enough to do it.


----------



## Currawong

I've got a DIY itch to scratch, so I've put an order in for a kit + all the necessary bits for single-ended so far. 

 As for bass, a friend suggested I try Herbies tube dampers with the tubes in my Stax amp. Unexpectedly, the result was considerably more bass. I wonder if one would get the same result with the tubes in the EHHA.


----------



## wiatrob

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_
 Any idea if this would have the balls for running my Stax adapter, they like a few watts and from what Alex has been saying, it may provide enough to do it._

 

I would imagine so (if it'll drive speakers - it should drive your adapter - heck, a CTH will drive your stax adapter but DON'T tell the Stax Mafia!)

 Thanks for reminding me to try that out!


----------



## dBel84

Very pleased to hear Smeggy and I concur with Wiatrob. As for bass, it may be time to whip out the 6H30 and start playing with your OL feedback. 

 I have never tried tube dampers myself but Currawong's suggestion is easy enough to implement and test. 

 When do we get to see the creation 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## digger945

Good point. Yea you can just breath on my 6H30 and you can hear them ring in the drivers with nothing playing. 
 One more thing to look for whilst shopping. Wonder if Smeggy can give us some leads on dampers, I noticed some on his SS? I think. He always seems to find the great bargains.


----------



## wiatrob

I have no lack of bass with the Telefunken 6GM8s currently installed - but I haven't listened to a SS amp in a while to compare. 

 Don, you mentioned OL gain/Neg feedback. I've heard this amp with minimum value and in "opamp" mode - what's your take on Negative Feedback <> bass response?
 (Since we don't have the headwize thread to review...)


----------



## dBel84

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Don, you mentioned OL gain/Neg feedback. I've heard this amp with minimum value and in "opamp" mode - what's your take on Negative Feedback <> bass response?
 (Since we don't have the headwize thread to review...)_

 

I dug around my e-mail as I had done a mini review at the time- found it previously and e-mailed it to sachu so perhaps he can find it, but it escapes me at the moment. 

 I seemed to think that decreasing FB ( higher value Resistors ) made bass more prominent and increasing NFB improved overall resolution and microdetail . 

 I have added a quote from an e-mail with steinchen who recommended leaving the resistors off of the BJT build . 

  Quote:


  Originally Posted by *steinchen* 
_ I tried all values I have in my box for R33/R34, from 10k to 200k, but you get the best sound with no resistor at all. With decreasing open loop gain bass gets recessed / weak and highs brighten up_

 


 I also stumbled across another discussion we had during proto and that was the use of the ECC99 as a tube option for the EHHA - don't think anyone tried but for those who own a Bijou, this would be a cool experiment. 

 ..dB


----------



## runeight

These NFB issues are straightforward and tricky at the same time.

 Pictures will be helpful, but I'll try to do some explanation, most of which you guys already know.

 Theoretically it works like this . . .

 Imagine the amp with no NFB. Its bandwidth can be defined in a variety of ways. When does it go 1db down from the 1kHz(abritrary) point? When does it go 3db down?

 But the standard way is to ask when the amp goes to unity gain. This is the unity gain bandwidth. If you find the headwize thread you'll see snoopy ask this question.

 Now, in a decent amp the unity gain point can be be in the many MHz range. But the curve from 1kHz is somewhat flat and then usually drops like a stone.

 So, if you ask when is the amp 1db down from 1kHz this point happens fairly quickly and well before the unity gain point. Same is mostly true for the low freqs. In a capacitative coupled amp the low freq response is never down to DC, but in amps like the b22 or the EHHA it does go down to DC. So, there can be a unity gain point at the low freqs, although in both of these amp the response is pretty flat to DC.

 Now, back to the high freqs. When you add NFB to the amp you reduce the gain everywhere, but faster at the intermediate frequencies. This has the equivalent effect of increasing the bandwidth. But what this really means is that the curve is flatter so that as you travel away from the 1kHz point the curve does not dip as quickly. Hence the 1db (or 3db) point "appears" to go ,out farther. But not because the amp is faster. It is not. It's because the intermedate frequency gain has been lowered closer to the extremity gain and, hence, a flatter curve.

 The more NFB you add the flatter the curve gets and the wider the apparent bandwidth is. In fact, the bandwidth does get wider in the sense that the width of the frequency spectrum over which the gain is audibly constant gets larger. 

 So, more NFB tends to even out the amplitude at the extremities (low and high) giving you the sense that there is more there relative to the mid freqs.

 Hence, why you think the bass comes up with more NFB. The bass doesn't come up, it's the mids that go down. Same for the highs.

 So, the extreme logic here is to use maximum possible NFB before instability. But NFB has its own bad effects, including introducing IM distortion due to phase shifting from across the amp and back to the input. Thus there is always a balance between gain and NFB.

 Now, the flatter you can make the OL response the less NFB you need to get good results. Similarly, the less phase shifting you introduce the more NFB you can supply with good results.

 All this to say that Steinchen's results make sense. That is, leaving out R22/R23 maiximizes the OL gain so that when you apply NFB you get flatter and flatter response and better results at the low and high ends. And as long as the increasing NFB does not introduce other bad effects this can be a win.

 OTOH, at some point, all high NFB amps start to sound the same because the NFB erases any of the unique characteristics of the amp. This is why in my amps I have tried to minimize the amount of NFB needed so that the character of the amp can come through (whatever that is). I'm doing this because, actually, most audiophiles don't like a perfectly neutral amp (a wire with gain), but would rather hear the nuances introduced by the different amp charactersitics (which is why you guys tube roll until you drop 
	

	
	
		
		

		
		
	


	




). But, of all the CA amps, the EHHA will be about the closest to the ideal wire as one can get with a hybrid that doesn't cost you your life.


----------



## smeggy

It is extraordinarily good and I can live with the slightly less deep smacking the B22 gives to keep the rest. By no means is it either weak or lacking in any way that would pull me away from the sound I'm getting.

 I just plugged my Stax adapter in and it's sounding great with my Beyers and Smegma Pro 
	

	
	
		
		

		
		
	


	




 Seems to have ample power for the box and perks the smooth beyer 'stats right up.


----------



## dBel84

I see a new ES amp flowering 
	

	
	
		
		

		
			





 ..dB


----------



## MrSlim

Hey Smeggy, since you have a Beta 22 and the EHHA, maybe you can do a head to head for us?


----------



## smeggy

I will once I get them all strapped up together. Right now it's all loose bits in the case until I can figure out how to switch them over


----------



## DoYouRight

that would be amazing as I wanted to do the EHHA first but got swept up into the B22, now I want tube magic after I get the B22 up. So B22 Buffalo32 for SS and MDHT havana EHHA for tubes? or should I mix tube and ss for 2 mixed rigs?


----------



## wiatrob

DoYouRight - I would experiment with all the permutations of Dac/Amp/(phones) and see which gives you the 'sound signature' you're most comfortable with.

 I prefer tubes in the mix somewhere along the path. YMMV!


----------



## smeggy

I was listening to a beta with buffalo today, very nice indeed. A step up in clarity and depth over my Pico DAC as you should expect given the price and size differences. The Buffalo is very good indeed to my not too well trained ears. I was mighty impressed. 

 I did do something potentially stupid earlier but what the hell. I wired both amps together so they share Sigma 22, Input and volume pot. 

 They're both the same gain, give or take, both supply multiple watts from their phone sockets and I can now run both amps simultaneously through their own phone sockets. I can run 'stats from one while running orthos from the other and so-on. 

 It does have a big beefy toroid, 160VA though I'll need to upgrade the S22 sinks as it runs a tad hot. Both the Beta and EHHA suck juice but it seems quite happy at the moment, long term it will be much happier with bigger sinks. I already upgraded the EHHA sinks and it runs beautifully. Comparisons will take a little time as I need time to get more familiar with both as they're still new to me. 

 I certainly have no problems with saying both amps are in the same league and have excellent sonics. I am very lucky indeed to have a pair of such great amps. Having them in one case makes it even better


----------



## atothex

That is ridiculous. Good stuff!


----------



## smeggy

Yay, sweet stuff! 
	

	
	
		
		

		
		
	


	









 I put a metal box over the heater transfo to add a little extra shielding. Still need to wire in the speaker posts with zobel network for the Beta. BTW, does the EHHA need a zobel for speaker duty (stax box actually)?


----------



## amb

Wow, β22 and EHHA as roommates... Can they get along?


----------



## smeggy

I hope so otherwise it could get quite spectacular in that box 
	

	
	
		
		

		
		
	


	




 Amb, what do you thing of S22 heatsinking for this? 2" sinks enough? They have the 1.5" ones right now but I have no idea what their meltdown potential is like that running both amps


----------



## amb

I don't know what the combined current draw is on your σ22, but σ22 was designed to support up to four β22 boards at their default bias settings, for headphone duty only, on the stock 1.5" board-mount heatsinks, and assuming good case ventilation. The ventilation is probably a bigger variable than the height of the heatsink in any given build.

 If you have an IR thermometer, measure the heatsinks' surface temperature after running with the cover closed for a good while. I would recommend keeping the temps no higher than 65-70°C.


----------



## MrSlim

Hey Smeggy, you still have room to shove a CTH in the middle there..


----------



## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yay, sweet stuff! 
	

	
	
		
		

		
		
	


	









 I put a metal box over the heater transfo to add a little extra shielding. Still need to wire in the speaker posts with zobel network for the Beta. BTW, does the EHHA need a zobel for speaker duty (stax box actually)?_

 


 Yes, the EHHA needs a Zobel for driving speakers. The one used for the b22 should be about right. But I don't know about the stax box. What does its input look like?

 I see that you managed to get Ti to post to this thread. 
	

	
	
		
		

		
		
	


	




 I imagine that when you put the cover on the boards will turn into transformers (as in the transforming robots) and start to duke it out. Or maybe they'll light up some cigars and be happy to finally be in the same box wondering why the other guy looks so weird. 
	

	
	
		
		

		
		
	


	




 Current draw for the two EHHA boards (headphone duty) should be less than 250mA if you're biased at 100mA in the O/P stages. The s22 should handle both amps easily if you're not driving speakers.


----------



## cfcubed

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Hey Smeggy, you still have room to shove a CTH in the middle there.._

 

Don't give him (more) any ideas
	

	
	
		
		

		
		
	


	




 Smeggy - A little while back I built a combo clone FirstWatt F1/F2 switchable amp. Since HS & PS could be shared the incremental cost of adding a 2nd bank of amp channels was low & I'd the room. Used relays to switch inputs & outputs between them.

 It was fun & helpful to compare the amps and ID the fav w/my speakers. Now I'll making them two separate amps & will be using them in separate rooms.


----------



## wiatrob

Kudos Smeggy on your Transformer amp! An excellent idea! Now I have to shoehorn six boards into a case myself....


----------



## TimJo

That's great smeggy! Nice idea to combine the two amps... So is the torriod in another enclosure?


----------



## smeggy

Cheers guys.

 Fortunately sharing cases is the only way of fooling wifey into thinking I have lass amps than I really do otherwise I'd get an earful, especially with a KG amp coming too 
	

	
	
		
		

		
			





 Plus, saves space, money, wiring and all the other stuff associated with two seperate amps. Worked out pretty well overall so I'm happy


----------



## dBel84

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Current draw for the two EHHA boards (headphone duty) should be less than 250mA if you're biased at 100mA in the O/P stages. The s22 should handle both amps easily if you're not driving speakers._

 

Just as well you read this 
	

	
	
		
		

		
		
	


	




 , my first response was "he's missing the other output device" then humble humility as I realised I had doubled the current for the 2 mosfets even though you are adjusting for both on each board. 

 I like the idea of the amps kicking back and smoking a cigar with each other, probably the closest one of Ti's amps will ever get to being a hybrid 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

I just hope they don't drop the cigars and set fire to the place, it's hot enough in there already. 
	

	
	
		
		

		
		
	


	




 I'm thinking of adding a 92mm silent 12v fan in there to help it out a bit...


----------



## dBel84

I did this with my soha ii as it was pretty much closed in, used a 12V reg pulled from one of the transformers (to minimise noise) and added a switch to allow me to keep it off or run it when it needed it, a simple temperature sensor would be a "cool" option ( I know bludy pathetic 
	

	
	
		
		

		
		
	


	




 ) ..dB


----------



## smeggy

I was considering fan and a 12v wallwart as I have a buttload of those around and placing it under the chassis as I don't have any 12v points inside..


----------



## dBel84

my biggest concern with fans is that they generate noise ( both mechanical and electrical ) If it is an essential component , I would make sure that it can be killed easily when it matters. Placing it under the case , powered by a wallwart is easy to remove and kill so it would work in my simple scheme of things ..dB


----------



## runeight

Ya know smeggy, some well-placed holes in the bottom and top of the box would probably ventilate well enough for your purposes. But, just holes in the top probably would not.

 Furthemore, I think you guys worry too much. Tube equipment used to get unbelievably hot. Televisions had 5 million tubes inside and they lasted a pretty long time before the caps dried out or something else failed. And the sand, for the most part, can take it.


----------



## smeggy

It has big holes in the bottom, 7/8" step bit holes. There are two of these big holes under each board and another set of them in the lid. Both sides are fully perforated top and bottom to the full depth of the case and it has it's standard vents across the top too. It should have enough ventilation to keep it happy but an external, silent fan with it's own psu can't hurt


----------



## smeggy

Ok, I just nipped off to get a small 4" 21 dB 2000 rpm fan (with sexeh blue LEDs) and wired it to a 12v adapter and within seconds the S22 and Beta boards were fully cooled to comfy touch temp and with the lid on it's almost inaudible and doesn't seem to be introducing any nasty noise. Just need to fix it in there permanently with a DC jack so I can use it when needed.

 Pretty sweet, the case is barely warm now.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Current draw for the two EHHA boards (headphone duty) should be less than 250mA if you're biased at 100mA in the O/P stages. The s22 should handle both amps easily if you're not driving speakers._

 

So in a layout like this (multiple amp boards being fed from a single s22) could the amp's power input be handled by a DPST relay switching the rails on & off. Most relay based power control seems to be switching the ac lines, but could you switch the 30vdc lines instead, or is the inrush current when the contacts close too high to be handled by a switch like this for example? These are rated at 5A @ 30VDC.


----------



## amb

The σ22 was not designed to have its load switched like that, it has no output current limiting or short circuit protection. During power-on, any uncharged rail capacitors on the amp board will "look" like a momentary short circuit and cause a very large current spike, and could damage the σ22. When you switch on the power on the AC side, σ22 starts up softly and ramps up its output voltage in a controlled manner, so no such spike occurs.


----------



## TimJo

Well, that's kinda what I figured, but thought I'd ask. I was picturing the contacts in the relay being arc welded at turn on. 
	

	
	
		
		

		
		
	


	




 Thanks for the quick reply Ti.


----------



## holland

2.2pF is listed on the schematic. It's not listed anywhere else on the website that I can see. Is there a list of gain + compensation caps? At what point is 2.2pF utilized? Is there a listing for a gain of 2 and 3?

 Thanks much.


----------



## sachu

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_2.2pF is listed on the schematic. It's not listed anywhere else on the website that I can see. Is there a list of gain + compensation caps? At what point is 2.2pF utilized? Is there a listing for a gain of 2 and 3?

 Thanks much._

 

Alex has a listing for the caps for different low gains here


----------



## holland

Thanks sachu. That only lists 1, 4.3 and 7.8, but I'm interested in 2 and 3. I'm also curious about the 2.2pF in the schematic and what gain that actually matches. It looks like the schematic calls for 2.2pF for the gain of 9, but that's not what is on the website.

 I'm building a 3-channel, and will "play" with gain on the ground. I'll start with 1, but would like to try 2 and 3 to see if slew plays any effect (shouldn't 20V/us is plenty fast for audio). I don't really want to go to 4 unless I have to.


----------



## smeggy

I'm hoping to have mine back up and running tonight after a recase and rewire. A lot more compact than the Beta/EHHA and be better all-round.


----------



## DoYouRight

Awww, I thought the combo was INSANE! The best DIY of both realms! Though it was very cool! After my Buffalo and B22 I am plannin on a EHHA with a similar chassis


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_
 I'm building a 3-channel, and will "play" with gain on the ground. I'll start with 1, but would like to try 2 and 3 to see if slew plays any effect (shouldn't 20V/us is plenty fast for audio). I don't really want to go to 4 unless I have to._

 

I am finding that I need to UP the gain a bit, and I am at 11 (1kΩ R13) balanced. 

 What is everybody else' gain? Maybe I'm going deaf or this source is low...

*EDIT*: 11 Gain with 10KΩ R22,23 for OL gain of ~21dB

 Am I correct in thinking there is a change in OL gain based on CL gain?


----------



## smeggy

Quote:


  Originally Posted by *DoYouRight* /img/forum/go_quote.gif 
_Awww, I thought the combo was INSANE! The best DIY of both realms! Though it was very cool! After my Buffalo and B22 I am plannin on a EHHA with a similar chassis 
	

	
	
		
		

		
		
	


	


_

 

It would still be that way if the Beta hadn't blown up *again*..


----------



## wiatrob

Bummer Smeggy! I thought I remebered seeing a cool case for the EHHA a few (hundred) posts back...


----------



## smeggy

yeah, modded version of that because the case is actually too shallow to fit the boards with sinks.


----------



## sachu

wiatrob am actually keeping the gain at about 12-12.5.

 edit: Ooh and can you throw a bunch of BJT output transistors in the care package. Would love to try them on my amp


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_edit: Ooh and can you throw a bunch of BJT output transistors in the care package. Would love to try them on my amp_

 

Let me know if you need the resistors too


----------



## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_*EDIT*: 11 Gain with 10KΩ R22,23 for OL gain of ~21dB_

 

That's some monster gain. Balanced it should double that. Are you sure you're hearing is OK?

 hehe, j/k. Check your wiring?

 Also, try this, RME Intelligent Audio Solutions - Audio Test Files

 Try the 0dBFS file(s). Measure the out of the amp at full volume. Measure your source. What is amp divided by source? Use AC measurement on your DMM (or scope it). Amp V / Source V should be roughly the amp gain.

 Are your heater voltages OK?


----------



## fishski13

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_That's some monster gain. Balanced it should double that. Are you sure you're hearing is OK?

 hehe, j/k. Check your wiring?

 Also, try this, RME Intelligent Audio Solutions - Audio Test Files

 Try the 0dBFS file(s). Measure the out of the amp at full volume. Measure your source. What is amp divided by source? Use AC measurement on your DMM (or scope it). Amp V / Source V should be roughly the amp gain.

 Are your heater voltages OK?_

 

thanks for the education - that's a keeper.


----------



## wiatrob

Heaters are 6.23V - close enough... I will double check my wiring, although it'd have to be a pretty gross error to unbalance the output of both channels, this is my first balanced build...

 Yes, I'm used to measuring output AC m/v at work, I'll bring home the scope and check it out.

 BTW:

_"Values of R22, R23 less than 10k are not recommended because the bias point of the VAS stage will be upset."_

 Like 33.2*R* - Instead of 33.2*K* it'll give you nil, and cause you to pull your hair out troubleshooting a previously perfectly working amp!


----------



## smeggy

It's back up and running in the new case, there is one small thing going on which I read about but now can't find.

 Hum. I have no hum with the volume low and high, inbetween it gets louder with volume ubtil it goes away and the hum (buzz really) increases when I touch the knob... (insert knob joke here)... and I can't recall what causes volume dependent hum like this that goes away when getting close to max.

 any clues?


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_It's back up and running in the new case, there is one small thing going on which I read about but now can't find.

 Hum. I have no hum with the volume low and high, inbetween it gets louder with volume ubtil it goes away and the hum (buzz really) increases when I touch the knob... (insert knob joke here)... and I can't recall what causes volume dependent hum like this that goes away when getting close to max.

 any clues?_

 

try running a wire from SG on one of the boards to one of the screws in the back of the ALPS pot or to its 'shaft' 
	

	
	
		
		

		
		
	


	




 and report back.


----------



## smeggy

Yep, that works. Thanks


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Yep, that works. Thanks_

 

NIce...so how is the T50 "thunder pants" sounding with the EHHA..was the beta a better match with it or does the EHHA trump it?


----------



## smeggy

Hmm, should I fall into sachus obvious trap... why not 
	

	
	
		
		

		
			





 It's damn close but for the full thunderpants effect the Beta wins. It has a more solid and tighter bass end. The rest of the spectrum the EHHA is as good and better to me at the top end. The EHHA has a very nice openness to it that's very sweet. Very good air and space. The EHHA is no slouch in the rear end but the Beta is famed for it. The EHHA is a truly excellent amp imo. Still, I do miss that Beta bass.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Hmm, should I fall into sachus obvious trap... why not 
	

	
	
		
		

		
		
	


	




 It's damn close but for the full thunderpants effect the Beta wins. It has a more solid and tighter bass end. The rest of the spectrum the EHHA is as good and better to me at the top end. The EHHA has a very nice openness to it that's very sweet. Very good air and space. The EHHA is no slouch in the rear end but the Beta is famed for it. The EHHA is a truly excellent amp imo. Still, I do miss that Beta bass._

 

bah..I'll put it down to old ears can't tell the difference between bloated bass and well defined bass..
	

	
	
		
		

		
		
	


	




 Sounds like I need to A/B the beta and the EHHA cause i think with the supertubes the EHHA just rocks.


----------



## smeggy

Well mine's just as you had it, standard toobs etc. Do the supertoobs make any significant difference? I wouldn't mind a bit more heft.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Well mine's just as you had it, standard toobs etc. Do the supertoobs make any significant difference? I wouldn't mind a bit more heft._

 

They do.. Everything sound more fuller. You will need a beefier heater transformer though as they sink almost an amp each..and really good ventilation around the tubes.


----------



## smeggy

hehe, my tubes are almost cold. The vent system installed in it keeps them very cool. The top of the tube has no heat that I can feel with my fingers anyway.

 So what tubes are they and what heater transfo is needed?

 Not saying I'll do it if the tubes are super expensive but I can look around. I think it's bedtime now that I'm finally done tinkering


----------



## dBel84

I saw the pics in the PPOYB thread - looks superb smeggy, am glad this finally came together even if it is missing it's evil twin. 

supertubes  there are cheaper non DR versions but this is Sachu knob to shaft the beta twin ( .. i tried to resist , honestly 
	

	
	
		
		

		
		
	


	




 ...) ..dB


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_They do.. Everything sound more fuller. You will need a beefier heater transformer though as they sink almost an amp each..and really good ventilation around the tubes._

 


 They will also SINK your wallet 
	

	
	
		
		

		
		
	


	




 per dB, they can be had for cheaper if you keep your eyes peeled on flEabay, or go with the non-dr version.
 Don't know how the non-DR sounds, and not likely too in this version as my heater PS is only good for 3A.


----------



## digger945

I have a listing for a pair of DR's that go for $99 plus shipping on ebay. I can't link here at work. Just go to ebay and search for 6h30 and it will be one of like 3 or 4 results. I sent the seller a message and he said that they are basically the same tube just not a desirable date.


----------



## holland

^ what's a desireable date?


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_^ what's a desireable date?_

 

X2! Perhaps they mean 'matched' date codes...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_X2! Perhaps they mean 'matched' date codes..._

 

anything from the 80s and prior is good. 

 The new ones, most of which are 09 02 (2002 made) are supposed to be not all that 'super'.

 The ones i have are from 85.


----------



## holland

Thanks Sachu.

 Another question on 6H30. It's my understanding that 6H30 likes to run hot, and there was debate that even the Bijou w/ regal mod can't properly utilize the 6H30 for driver tubes. Sonics aside, wouldn't that make the EHHA less than ideal at even lower currents and plate voltages?


----------



## holland

BTW, anyone using AC heaters? I'm thinking of using AC as I've got a 6.3VAC/1A xformer in the closet which is only enough to drive 3 channel 6GM8, 6922, 6DJ8 in AC mode, not DC.


----------



## sachu

That is correct holland. It isn't ideal at all. However, it seems to work fine on my amp. The 6DJ8 though with similar max DC plate voltages didn't do all that well on the EHHA. The 6GM8s bested them easily.

 Edit: Smeggy is using AC heaters from a 0.6 A @12.6VAC transformer or in effect 1.2 A at 6.3 volts.


----------



## smeggy

yeah, plain old AC from a rat shack transfo







 Runs lubberly too. Now they just increased our hours to 10 a day plus Saturdays and two hours a day in traffic.... Bleh, I needed something to keep me sane.

 Well dogpoo! I was just looking at the prices for them thar toobs... erm, I'll stick with what I have for now


----------



## looser101

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Well dogpoo! I was just looking at the prices for them thar toobs... erm, I'll stick with what I have for now 
	

	
	
		
		

		
		
	


	


_

 

You don't need the DR's just get some Sovtek 6H30s (and a bigger transformer 
	

	
	
		
		

		
		
	


	




). Looking good!


----------



## smeggy

How much bigger we talkin'?

 Pair of supertubes about $100+


----------



## holland

sovtek 6h30 ~$30 each.
 EH 6h30 ~$35 each.


----------



## looser101

2A @ 6.3VAC
 or
 1A @ 12.6VAC


----------



## sachu

I would suggest a bigger transformer smeggy....like at least 4A @6.3VAC.

 You need to run that delay board as well. It is very useful i tell you.


----------



## digger945

I bought my Sovtek 6h30's for $25 each on ebay, and used the live search discount to make it about $85 for a quad shipped back last year. 
 I am currently powering the heaters on the two tubes in the EHHA boards with a 1800mA Radio Shack wallwort. Got it on sale for $1.97.


----------



## smeggy

I keep forgetting I have a honking big variable output transformer I bought for my T-amp. Perfect!

 Hmm, I'll look into the tubes. Are they bigger than the teeny things that come with it?


----------



## dBel84

roughly the same diameter but twice the length ..dB

 edit - you could use a switcher smeggy


----------



## smeggy

Cool, I don't wanna redrill the tube holes 
	

	
	
		
		

		
		
	


	




 What's a switcher?

 I just went down to look at my transformer and it's a 2 amp 1-12V DC regulated supply. Dunno if that'd do the trick with those tubes.


----------



## dBel84

"Heater... 6.3V, 0.9A (.825 nominal spec)"

 so your 2A tranny will just do the trick if run in series at 6.3V. If you are running them in parallel then you have some headroom. 

 I switcher is a switching supply (DC) which are usually used for laptops, hard drives etc - but this is no longer relevant 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

Ah, switching power supply! I get ya 
	

	
	
		
		

		
		
	


	




 Thanks, the PSU only hits 6 or 12v, not 6.3 etc. Hopefully it won't matter too much.


----------



## smeggy

So I've secured a pair of EH 6h30pi golds for $30 and I also read that the 6n6p is essentially the same tube, any thoughts? I have a bunch of those here if it would work the same with my big transformer.

 Also, trying to follow to many threads I lose track of what's what. So is there a way to increase the bass presence (fullness) by adjusting feedback or changing resistors with the EHHA? I'm looking for a slightly thicker, more solid sound. The bass is nice and deep but feels less full than the beta and if I can find a way to add mass to the sound I'd be extremely happy.


----------



## looser101

6N6P should work but it's at it's low voltage limit. Doesn't hurt to try. 6H30 is a bit better suited for lower voltages.

For reference


----------



## dBel84

Smeggy, for OL gain try the following

 remove resistors R22 and R23 - give that a long listen, then replace them with 10K ( or anything above 10K but aim for 10K ) finally try 300K and see which sound sig you like the most. this will give you extremes of OL NFB vs stock recommendations ( 33K ) 

 ..dB


----------



## wiatrob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Smeggy, for OL gain try the following

 remove resistors R22 and R23 - give that a long listen, then replace them with 10K ( or anything above 10K but aim for 10K ) finally try 300K and see which sound sig you like the most. this will give you extremes of OL NFB vs stock recommendations ( 33K ) 

 ..dB_

 


 I've listened most at 10K, some with none, some with 33k, but have yet to critically compare. Do NOT use 33*R* as I did, or the sound signature you'll get will be _silence _*




*


----------



## smeggy

so which end is better for bass, I take it no resistor is most NFB and 300k is least or did I get that backwards?

 Cool, 6n6p up and running until the 6h30s arrive


----------



## wiatrob

None is (0dB), 300k is more (for mosfets- 41.5dB? ) - least is 10K (21dB):

Embedded Hybrid Headphone Amlifier


----------



## smeggy

Working very nicely, no problems whatsoever except the heater transfo runs damn hot.

 I'm using this for the heaters
DC Power Supply Model MW122A


----------



## dBel84

I was going to make you try and then report back 
	

	
	
		
		

		
		
	


	




 , thanks Bill 
	

	
	
		
		

		
		
	


	




 so let me get this straight , you are using an external heater supply? what is the transformer in the box then? Is that for the pico ?? I guess I need to stare at your build a little more closely. 

 Are you running the 6n6pi now that it is hot? you're holding out on us to tease yeah!! 


 ..dB


----------



## smeggy

Patience my dear Don, I'm still working out final details..


----------



## dBel84

you want me to look for a small smps for you , could probably fit inside the case. e-mail me if you want to consider this option ..dB


----------



## smeggy

Ok, so final wiring for the 6n6p tubes is a 12V 2A DC wallwort I found on my shelf. Wired the heaters in series and it's going great 
	

	
	
		
		

		
		
	


	




 The tubes are nice and don't run hot at all as I have a big-ass fan inside the case blowing soothing cool air all around. The external variable psu I used earlier was getting dangerously hot so I swapped for the wallwort, much more betterer. It's very happy now. The tubes are helping to fill out the bottom and sound a little more like the Beta in that regard.

 Nice as the tubes are cheap and seem a decent match. I'll have some 6h30 golds arriving next week to compare.

 The small transfo is the original heater supply but it's only rated for 1.2 amps and these tubes need more so the internal one isn't being used right now. I may do a singlepower and mount the wallwort inside the case in it's place 
	

	
	
		
		

		
		
	


	




 also, what is smps and was that aimed at me or Bill? (NM found it on teh webs)


----------



## wiatrob

That's the Switching Power Supply I'd wager. We could raid the ones from four CTH builds but it sounds like you have it ironed out...


----------



## dBel84

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_The small transfo is the original heater supply but it's only rated for 1.2 amps and these tubes need more so the internal one isn't being used right now. I may do a singlepower and mount the wallwort inside the case in it's place 
	

	
	
		
		

		
		
	


	




 also, what is smps and was that aimed at me or Bill? (NM found it on teh webs)_

 

ROFL 
	

	
	
		
		

		
		
	


	




 sorry about the terminology, smps = switch mode power supply = switcher = dork for not sticking to the same lingo

 ..dB


----------



## smeggy

I really need to brush up on my acronyms and thingies.


----------



## wiatrob

*!@*#&#!*&!!!! *You Smeggy and *your loaner K1Ks!!! *_Argh... Argh..._* mumble wallet grumble 
	

	
	
		
		

		
		
	


	




* Sounding *great *on the EHHA in Single Ended mode...


----------



## dBel84

yes , i concur . they are special headphones ..dB


----------



## smeggy

Hey, at least you've heard the damn things on the EHHA, I have to wait for my turn


----------



## dBel84

well not exactly, but i did hear them on a worthy amp 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## runeight

Regarding NFB.

 You'll get the maximum NFB with R22, R23 left out of the circuit. Any other values there reduce NFB by reducing the OL gain.

 Smeggy, try no R22, R23 and see if you get bass that you like.

 Regarding tube rolling. 6GM8, 6922, and 6H30 should all work well at this low voltage. I don't expect that 6n6p will work very well, but I could be wrong. 
	

	
	
		
		

		
			





 Someone mentioned 6h30 cathode currents. This is true for this amp. Each triode is running about 1mA and this is quite low for a 6H30. It would be better to run higher but the operating point does not permit this. Still, 6h30 is so highly conductive that it doesn't mind running at 30V. It was the tube I originally designed into this amp.

 Wish I had a bit more time ...... but I do appreciate all the work you guys are doing with this amp.


----------



## smeggy

Thanks Alex, your time is much appreciated on this. 

 Surprisingly the 6n6p is doing remarkably well, now they've had some warm up time and the right heater current they are blasting out the bass in large quantities and though the sound is much fuller than the stock tubes, it's also a bit softer all round and doesn't quite have the bite and air of the originals. 

 It is a very smooth creamy and warm sound now which I like a lot but a tad more definition and bite wouldn't go amiss along with the more solid sound. The reason I'm trying this is because I found the standard confg a little lean. Hopefully the 6h30s will give me the best of all worlds.


----------



## smeggy

this is pretty interesting, I took out 22 and 23 and swapped the original tubes back in and it sounds fantastic. the 6n6p were sounding a bit too soft and flabby at that point. Now it's great.


----------



## dBel84

this was steinchen's favourite setting , glad you played and found something you liked ..dB


----------



## holland

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Someone mentioned 6h30 cathode currents. This is true for this amp. Each triode is running about 1mA and this is quite low for a 6H30. It would be better to run higher but the operating point does not permit this. Still, 6h30 is so highly conductive that it doesn't mind running at 30V. It was the tube I originally designed into this amp._

 

Done deal, buy some 6H30s!


----------



## smeggy

I did 
	

	
	
		
		

		
		
	


	



 Can't wait for them to arrive. If they work out even better than the stock tubes I'll be over the moon, this is already the best amp I've heard now that 22 & 23 are out of the circuit and it's hard to imagine better but I'm willing to be surprised.

 I don't know how a <$300 amp is managing to sound this good. It really is something else.


----------



## digger945

^^^So you just pulled them out and that's it, no adjustments or anything?


----------



## dBel84

yeah, just removed the OL feedback , nothing else to adjust except the volume or your hearing aid request ..dB


----------



## smeggy

yeah, basically it's been slightly evolving as I swap some parts around. Nothing on the boards except those two resistors but I did add a bigger heater transfo, wire my fan in parallel and then the heaters in series but nothing else. 

 Oringinally the stock tubes sounded a bit lean in the ass end and extremely defined at the top. Removing those resistors filled out the bottom end giving a more solid sound and it gives a wonderful all over sound for my tastes. Of course this is with my ears and my phones etc.

 Damn spectacular!


----------



## wiatrob

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_^^^So you just pulled them out and that's it, no adjustments or anything?_

 

Yup -OpAmp mode, correct?? I've listened briefly like this but I'll Dup soon...


----------



## digger945

I been listening for about 30 minutes so I could have an idea of what kinda change it would make.
 OH YEA, I like!!!! 

 Anything else we can yank outta this to make it slam more? LOL!!!

 Yea can't wait until you get the 6h30's Smeggy. 
 I'm listening to 0404 and CD-3000's now, with 6h30's in. 
 Perfection I tell ya.


----------



## sachu

damn amateurs..where were you guys when I was talking about this amp almost two years ago..when I was just a "newbie"...B22 can kiss EHHA's ass..

 hats off to Alex and to Donald..there wouldn't have been a EHHA without ALex and we wouldn't have been here talking about it without Donald's amp that I fell in love with 2 years ago.


----------



## smeggy

yeah, I had no idea a pair of resistors would make such a fundamental change to the sound but there it is. Much better bass and slam, and if the 6h30 can take the bass level to what the 6n6p had it'll be pretty spectacular.

 The NFB adjustment has made the whole much more cohesive and it gels in a way that synergizes with my phones perfectly. This is indeed the sound I've been trying to achieve.


----------



## wiatrob

Very interesting. I only have one 6h30 here. I do have the Telefunken 6GM8s and phillips 7Dj8s... 

 I think maybe a three channel mosfet w/ 6h30s is in the future...


----------



## smeggy

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_damn amateurs..where were you guys when I was talking about this amp almost two years ago..when I was just a "newbie"...B22 can kiss EHHA's ass..

 hats off to Alex and to Donald..there wouldn't have been a EHHA without ALex and we wouldn't have been here talking about it without Donald's amp that I fell in love with 2 years ago._

 

Ok, you win 
	

	
	
		
		

		
		
	


	




 But don't be crabbin on the Beta, mine will rise from the ashes to sing to me again some day 
	

	
	
		
		

		
		
	


	




 Alex, Don 
	

	
	
		
		

		
		
	


	




 you guys are awesome!


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_damn amateurs..where were you guys when I was talking about this amp almost two years ago..when I was just a "newbie"..._

 

Well, where was this thread my friend? I wasn't even into _this stuff_ then 
	

	
	
		
		

		
			





 Better late then never...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, where was this thread my friend? I wasn't even into this stuff then 
	

	
	
		
		

		
		
	


	




 Better late then never..._

 

heh..there isn't a thread at all about the EHHA except for the IC thread taht Donald put up here This particular amp is on my desk right now actually running some bugle boys in it.

 I got Smeggy going on the EHHA a few months back after i gave up on waiting for parts for the B22 and found out that Jeff had kits for the EHHA in december 08. It makes me very happy to see this amp being built by so many of us here...Can't wait to hear impressions from the Colorado meet.
 Cavalli Audio FTW!!!!

  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_But don't be crabbin on the Beta, mine will rise from the ashes to sing to me again some day 
	

	
	
		
		

		
		
	


	


_

 

Bah..you just wish you had heard and built the EHHA before buying a B22..would've saved you an AKG K1K 
	

	
	
		
		

		
		
	


	




 Btw, Am listening to a very special amp here


----------



## dBel84

I cannot tell you how pleased I am that this amp is finally comming out of obscurity. It is no secret that I have a special appreciation for Alex's designs and this one was one of his predicted favourites. It just happened to be pursued by bad karma and would have been in the forefront had the actual process not been hijacked as in a previous design. BUT bygones be bygones, lets celebrate Alex's ability to pull things together and hope it brings happiness ot many more folk ..dB


----------



## holland

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_damn amateurs..where were you guys when I was talking about this amp almost two years ago..when I was just a "newbie"...B22 can kiss EHHA's ass..

 hats off to Alex and to Donald..there wouldn't have been a EHHA without ALex and we wouldn't have been here talking about it without Donald's amp that I fell in love with 2 years ago._

 

LOL, pretty harsh on the B22 there. 
	

	
	
		
		

		
		
	


	




 Don't forget Snoopy. I think they (EHHA and B22) are different enough that they can co-exist, at least from the design (pure sand vs. hybrid). I don't know about others, but I like to cycle amps, just like my cheap headphones. I don't think I can have just 1 of anything.


----------



## holland

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_heh..there isn't a thread at all about the EHHA except for the IC thread taht Donald put up here This particular amp is on my desk right now actually running some bugle boys in it._

 

LOL. I find that quite amusing.

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I got Smeggy going on the EHHA a few months back after i gave up on waiting for parts for the B22 and found out that Jeff had kits for the EHHA in december 08. It makes me very happy to see this amp being built by so many of us here...Can't wait to hear impressions from the Colorado meet._

 

I'm interested in hearing impressions too. Please link them, I don't make it into the other sub-forums much. Everytime I do, I'm grossly disappointed and want to disappear from head-fi.

 I have a 3-channel + S22 sitting on my desk in bits. It should take just a weekend to stuff and another 6 months to wire.  I hate wiring, and panel work, yuck. I think I'm going with a digital volume control for this build. It should be interesting to work with. However, I need to get back to my cars, they are hurting from neglect due to amp building.


----------



## sachu

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_LOL, pretty harsh on the B22 there. 
	

	
	
		
		

		
		
	


	




 Don't forget Snoopy. I think they (EHHA and B22) are different enough that they can co-exist, at least from the design (pure sand vs. hybrid). I don't know about others, but I like to cycle amps, just like my cheap headphones. I don't think I can have just 1 of anything._

 

yes indeedy..Tom did do a lot of work on the EHHA from what i hear. THanks a ton Tom!!

 yeah I am just blinded by my love for the EHHA that i go blathering crap about other great amps. 

 The B22 is the best solid state amp i have heard thus far. I still have parts to build a balanced B22 and will probably end up building a passive 2 channel just cause i can't have just one either. 
	

	
	
		
		

		
		
	


	




 Both are great amps..pick your poison i already chose mine...both, with a slightly larger dose of the EHHA!!


----------



## smeggy

yup, as much as sachu likes slagging the beta, it's an awesome amp (if only I could keep it working) and I love them both. They are different enough to want to keep both so I'll be happy if the Beta eventually works. 

 The EHHA is very, very good and makes me want to keep listening and trying new tracks. The sound is very clear, detailed, fast and beguiling. The sound is very moreish and can't wait to listen to it again tomorrow.


----------



## sachu

smeggy..the offer still stands...send the beta down..will fix it and send it back.


----------



## dBel84

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_LOL. I find that quite amusing._

 

a moment of need and weakness 
	

	
	
		
		

		
		
	


	




 As for the credit for this amp = Alex and Tom ALL the way ( not to mention Ti and Jeff ) 

 ..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_a moment of need and weakness 
	

	
	
		
		

		
		
	


	




 As for the credit for this amp = Alex and Tom ALL the way ( not to mention Ti and Jeff ) 

 ..dB_

 



 absolutely..Thanks Jeff for making the kit available.

 And Ti Kan whose S22 is powering almost all the EHHAs that have been built.


----------



## smeggy

So it looks like another new tube has just arrived on the market *here*

 it's a E813CC and supposedly equals the ECC83 / 12AX7 which should work fine in the CTH, just wondering about the EHHA. They are about $70 a piece shipped to the US but it may be worth it if their blurb isn't total BS. Using CRT tech.







 Alex?


----------



## cfcubed

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_it's a E813CC and supposedly equals the ECC83 / 12AX7 which should work fine in the CTH, just wondering about the EHHA._

 

Though they may _operate_ in a CTH they would likely have way too much gain (100x?)... Even 12AT7s at 54x or so were found to be too much for the CTH AFAIR.


----------



## wiatrob

*EDIT*: just saw Chris beat me to the punch - It looks like you may want to try the E812CC - 12AU7- version (although I think this should move to the CTH thread...) 12AX7 and 12AT7 _don't_ work so well in the CTH (I've tried 12AT7 and can confirm that...)

 I don't think any of them will work in the EHHA...


----------



## smeggy

Oh well, just a thought..


----------



## MrSlim

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_
 Btw, Am listening to a very special amp here 
	

	
	
		
		

		
		
	


	


_

 

Ok Sachu, I'm out of the loop.. Fess up...


----------



## wiatrob

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Ok Sachu, I'm out of the loop.. Fess up..._

 

We might all be out of the loop...


----------



## sachu

ummm..lets not digress here..so right now we are looking at

 1> a balanced build completed by *wiatrob *(BJT version)
 2> passive ground SE by *Smeggy*
 3> same as above by *sachu*
 4> same as above by *digger945 *(but might be scaled to a balnaced soon as he has the parts)
 5> ongoing active 3 channel build from *Holland*
 6> ongoing passive ground SE from *rhester*
 7> planned balanced build from *MrMajestic2*
 8> planned 3 channel active ground from *wiatrob *(MOSFET version)
 9> 


 Are there any more builds that we should be aware of?


----------



## smeggy

Don has one too.

 It`seems like there must be more than six!

 Were at 50 pages of posts an thats all we mustered so far? Bah, unacceptable... need moar builds.


----------



## sachu

Smeggy, this is discounting Don's and original proto builds. The count is for builds that are yet to start, in progress and completed since this thread took off.


----------



## rhester

I have mine built and ready to test over the weekend. no casing yet. But simple 2 channel with s22 and h-ps-1 to power it up with.


----------



## sachu

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_I have mine built and ready to test over the weekend. no casing yet. But simple 2 channel with s22 and h-ps-1 to power it up with._

 



 nice!! All the best 
	

	
	
		
		

		
		
	


	




..make sure to bring up one board at a time.


----------



## MrSlim

Well, I want to build one.. but I still have a SOHA+JISBOS, another CTH, 2x y1's and waiting for the y2 prototype, along with a 41hz Amp6 to finish first.. I might have to use the SOHA+JiSBOS and the CTH to finance it.. 
	

	
	
		
		

		
		
	


	




 oh.. and what happend to summer.. ours is the pits here.. more like October.. 
	

	
	
		
		

		
		
	


	




 Oh.. and not to mention trying to sell a house and buy another one.. sheesh..


----------



## smeggy

I'll take that Y2 off your hands to lighten your load


----------



## dBel84

was thinking just that myself 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## MrSlim

Hey, Ti asked for Prototypers.. everyone had their chance.. 
	

	
	
		
		

		
		
	


	



 I just got the y1 boards last week, and the the new cases that he spec'd for the y2, and god are they cute little boxes.. Until you hold one in your hands, you don't realize how small they are.. I think you guy's would have to wrench it from my cold, dead hands..


----------



## dBel84

this can be arranged, i know a friend who knows people. probably best to wait for you to finish it first though 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## MrMajestic2

Does Jeff still have kits for this? I'm considering doing a balanced version


----------



## sachu

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Does Jeff still have kits for this? I'm considering doing a balanced version 
	

	
	
		
		

		
		
	


	


_

 

Yep..he still does. Kit cost for a fully balanced version should come out to about 200$ excluding power supplies (S22 + heater) and balanced pot.


----------



## MrMajestic2

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Yep..he still does. Kit cost for a fully balanced version should come out to about 200$ excluding power supplies (S22 + heater) and balanced pot._

 

Not too shabby. I'll drop him an email.


----------



## wiatrob

My volume control seemed to cost as much as Jeff's kit 
	

	
	
		
		

		
		
	


	




 MrM2 -You won't be disappointed in the balanced version. 


 Sachu, I also have a MOSFET 3 channel version in the works...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_My volume control seemed to cost as much as Jeff's kit 
	

	
	
		
		

		
			





 MrM2 -You won't be disappointed in the balanced version. 


 Sachu, I also have a MOSFET 3 channel version in the works..._

 

Man you are too much...am toying with the idea of a 3 channel BJT version myself 
	

	
	
		
		

		
		
	


	




 since the Poormans has gone dormant


----------



## wiatrob

I have some BJTs for you...


----------



## smeggy

Nice. I wonder how different the two types sound and whether 3 or 4 chan really benefits things.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Nice. I wonder how different the two types sound and whether 3 or 4 chan really benefits things._

 

Only one way to find out 
	

	
	
		
		

		
		
	


	




 Build or get wiatrob to send the balanced version out on tour


----------



## smeggy

If I could find a cheap (or inexpensive) but good way to get a USB>balanced out DAC, I might srsly consider a balanced version. I suppose the AMB Y2 with offboard balanced outs might work.

 Have to wait and see on final prices.


----------



## MrMajestic2

Ok, so I got reply from Jeff 
	

	
	
		
		

		
		
	


	




 While waiting I would like to ask what transformers you guys are using, both main and heater? Is it better to run DC than AC for the heater, and if DC, which supply do you use. I have seen several designs here, but which one to pick, hmm. I think I even saw a TREAD in there somewhere.


----------



## sachu

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Ok, so I got reply from Jeff 
	

	
	
		
		

		
		
	


	




 While waiting I would like to ask what transformers you guys are using, both main and heater? Is it better to run DC than AC for the heater, and if DC, which supply do you use. I have seen several designs here, but which one to pick, hmm. I think I even saw a TREAD in there somewhere._

 

Awesome ...added you to the list...can't wait to see the Maroon Audio EHHA to debut.

 AS for the transformers, myself and Smeggy are using the same Avel Lindberg toroids rated at 28.4volts @160VA. Plenty of enough power to run 4 boards in balanced config if we ever decide to. However both our EHHAs are SE versions and it works great with the amp. I like to build PSUs with decent power so would suggest at least 30volts @120VA for a balanced build. 
 Use the S22 for the HV power supply. It is the best bargain out there. Ti's done a great job with that. 

 As for the heater voltage, you could use the glassware product which costs about 22$ for an assembled board or the treads would work perfectly. AC heaters work fine as well though I would go with regulated DC heater supply for this amp.

 I am using this particular Peter Millet circuit for my heater supply that i put together on a perf board. Again, my heater circuit is capable of putting out 5A in regulated DC mode (8A in AC). So I can always scale my amp to balanced if I ever choose to by just adding two more amp boards.





 Since you are running balanced I would suggest you have a similar heater supply as mine. This way if you plan to run 6H30s in balanced mode your heater supply will be able to put out the almost near 4A that is needed to power those monsters.

 Edit: Come to think of it, my EHHA is using circuits by 3 great design houses ..Cavalli Audio for the amp boards, AMB for the HV supply and Peter MIllet for the DC heater supply. If only I could squeeze some circuit of Kevin Gilmore's into my EHHA..


----------



## MrMajestic2

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Awesome ...added you to the list...can't wait to see the Maroon Audio EHHA to debut.

 AS for the transformers, myself and Smeggy are using the same Avel Lindberg toroids rated at 28.4volts @160VA. Plenty of enough power to run 4 boards in balanced config if we ever decide to. However both our EHHAs are SE versions and it works great with the amp. I like to build PSUs with decent power so would suggest at least 30volts @120VA for a balanced build. 
 Use the S22 for the HV power supply. It is the best bargain out there. Ti's done a great job with that. 

 As for the heater voltage, you could use the glassware product which costs about 22$ for an assembled board or the treads would work perfectly. AC heaters work fine as well though I would go with regulated DC heater supply for this amp.

 I am using this particular Peter Millet circuit for my heater supply that i put together on a perf board. Again, my heater circuit is capable of putting out 5A in regulated DC mode (8A in AC). So I can always scale my amp to balanced if I ever choose to by just adding two more amp boards.
http://www.pmillett.com/images/DC_fil6.jpg

 Since you are running balanced I would suggest you have a similar heater supply as mine. This way if you plan to run 6H30s in balanced mode your heater supply will be able to put out the almost near 4A that is needed to power those monsters.

 Edit: Come to think of it, my EHHA is using circuits by 3 great design houses ..Cavalli Audio for the amp boards, AMB for the HV supply and Peter MIllet for the DC heater supply. If only I could squeeze some circuit of Kevin Gilmore's into my EHHA.. 
	

	
	
		
		

		
		
	


	


_

 

Great, thanks for all the info. Did Pete ever release the eagle files for the heater supply?


----------



## smeggy

My heaters and case fan (i know....) are being run from a 12v regulated wallwart stripped of it's casing. Before that I was running the heaters straight from a Rat shack 6.3-0-6.3v AC transffo @ $4.50


----------



## Lifthanger

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Ok, so I got reply from Jeff 
	

	
	
		
		

		
		
	


	




 While waiting I would like to ask what transformers you guys are using, both main and heater? Is it better to run DC than AC for the heater, and if DC, which supply do you use. I have seen several designs here, but which one to pick, hmm. I think I even saw a TREAD in there somewhere._

 

could you tell me, how you contacted him? I tried with the contact formular on gja, but there was no answer.

 I'd love to build this amp, because its sexy and not too expensive. 
	

	
	
		
		

		
		
	


	




 Anyone have an idea what the EHHA2 will be about?


----------



## smeggy

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_could you tell me, how you contacted him? I tried with the contact formular on gja, but there was no answer.

 I'd love to build this amp, because its sexy and not too expensive. 
	

	
	
		
		

		
		
	


	




 Anyone have an idea what the EHHA2 will be about?_

 

Hi powered speaker amp. Jeff is sometimes hard to get a hold of so you just need to keep trying


----------



## digger945

http://www.head-fi.org/forums/f6/cav...r-ehpa-428795/ aka EHHA II.
 Yea Jeff is kinda busy at times, he will answer though. You may want to just send him another email every week or so.


----------



## Lifthanger

thanks 
	

	
	
		
		

		
		
	


	




 will send him another mail soon. and I'm glad the EHHA won't be replaced by the EHHA2. balanced kit for 200$ is almost too good to be true


----------



## sachu

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_thanks 
	

	
	
		
		

		
		
	


	




 will send him another mail soon. and I'm glad the EHHA won't be replaced by the EHHA2. balanced kit for 200$ is almost too good to be true 
	

	
	
		
		

		
		
	


	


_

 

Heh..it is quite unbelievable isn't it..Keep in mind power supplies will run another 100-120$ for the HV and heater put together.
 You still have a chassis and pot to consider as well. A no frills balanced EHHA can easily be put together for about 450$ case and all.


----------



## Lifthanger

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Heh..it is quite unbelievable isn't it..Keep in mind power supplies will run another 100-120$ for the HV and heater put together.
 You still have a chassis and pot to consider as well. A no frills balanced EHHA can easily be put together for about 450$ case and all._

 

yeah that's about what I estimated. Due to my limited headphone arsenal, I'll build two boards only at first and the other two later on. 

 saves a lot of hassle to buy an ehha and a sigma22 kit. sourcing is the worst part of this hobby most of the time. 
	

	
	
		
		

		
		
	


	




 (especially when you're from europe)


----------



## wiatrob

I haven't totaled the cost of my balanced build. 
	

	
	
		
		

		
			





 It soounds quite nice three channel too...


----------



## MrMajestic2

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_could you tell me, how you contacted him? I tried with the contact formular on gja, but there was no answer.

 I'd love to build this amp, because its sexy and not too expensive. 
	

	
	
		
		

		
		
	


	




 Anyone have an idea what the EHHA2 will be about?_

 

I used the online form as well. But he is on vacation right now for two weeks, so that's probably why he is not replying.


----------



## smeggy

Happy to report the EH 6H30Pi Gold pin tubes are here and sounding glorious after a couple of hours running. It's a very natural sound with good dynamics and a very sweet organic presentation. Smooth fast and solid sound with beautiful full bass and they do combine most of the best aspects of the 6N6P and the stock tubes from GJA. 

 It's a superb amp and I'm extremely impressed once again. I love listening with the EHHA and it keeps begging for more music.


----------



## digger945

^Did you get Sovtek's or Electro Harmonix?


----------



## sachu

he got the electro harmonix...


----------



## digger945

Either one of you try some tube dampers yet?


----------



## smeggy

Not yet, I should get some ordered one day. I'm not sure what they'll do to improve things, It's no different if I hold the tubes with my fingers but it can't hurt


----------



## digger945

I'm reading more stuff lately about the improvements in bass with the use of dampers, in particular Herbies brand. I want to try something soon so I've started keeping my eye's peeled.


----------



## smeggy

Seems like the ultrasonic 9 will do the job and not overly costly at 14 each. I may give them a try, though silicone rings would fit better in my case. Not much room for big dampers. I guess I could air wire the tubes (1.5") with chassis mounts unless that's a really bad idea.


----------



## wiatrob

Well, sad to report the EHHA balanced has not made it into it's case yet. It's here, it's nice, but between some unpleasantness with a CTH build and work - less time than I thought before the meet to get it done.

 Maybe I'll build a foam core box so people will listen to it!


----------



## sachu

dammit..the EHHA takes precedence over the CTH...haven't you realized that yet 
	

	
	
		
		

		
		
	


	




 well I know how CTH gremlilns can bog you down. I have had my fair share of it.

 Its all good my friend..those interested will listen to it even if it is uncased.

 can you give some specifics of the setup? 

 Tubes you are running, NFB setting?


----------



## smeggy

slap it into a cardboard box, as long as it works. It has to make it to the show!!!!!!


----------



## wiatrob

It will be at the show!

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_
 can you give some specifics of the setup? 

 Tubes you are running, NFB setting?_

 

Telefunken 6GM8s or Phillips 7DJ8s, gain 11, NFB 21dB.

 Sigma 22 and Broskie's H-PS-1

 DACT stepped attenuator, wired with milspec SPC...


----------



## Sherwood

It had damn well better be at the show. It's one of the three things I'm there to hear!

 How will I get the nerve to have Sachu build me a ridiculous balanced version with an SRD-6SB cased inside if I don't hear it first?

 P.S. beers friday or saturday this week?


----------



## wiatrob

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_It had damn well better be at the show. It's one of the three things I'm there to hear!_

 

It will be there. This amp will also be on loan after I get it tidied up - first to Smeggy as he so graciously loaned me his K1000s (which will be paired with the EHHA at the meet).

 The mebbe to you depending on:

  Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_P.S. beers friday or saturday this week?_

 


 Whether I get all my pre-show chores done. I am almost at the point to let things fall where they may...


----------



## Sherwood

That CTH still giving you grief Bill?


----------



## smeggy

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_It will be there. This amp will also be on loan after I get it tidied up - first to Smeggy as he so graciously loaned me his K1000s (which will be paired with the EHHA at the meet).




_

 

Wait, whut?? 
	

	
	
		
		

		
		
	


	




 I've been thinking of balancing mine... just need to find a cheap balanced USB DAC. Another pair of boards is only 110 so why not.


----------



## Sherwood

^^^
 Do keep us updated. If I have Sachu build me one I intend for it to strain the limits of credulity. What better way for him to realize his dream?


----------



## wiatrob

Um, I'm closer than Sachu... And I am the ONLY ONE to have built a balanced EHHA 
	

	
	
		
		

		
		
	


	




 BTW - the CTH is purring nicely, see that thread for my bone head move.

 Sachu - the TP Opus is a dac that will fill the bill for ya...


----------



## smeggy

have you tried SE Vs Balanced yet to see if there's any difference as I keep reading varied opinions on whether balanced actually makes much of a difference?


----------



## MrSlim

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_have you tried SE Vs Balanced yet to see if there's any difference as I keep reading varied opinions on whether balanced actually makes much of a difference?_

 

And Adding a 3 Channel active ground config into the mix doesn't help either. 


 Soo, what we need Mr Bill, is for you to come up with a wiring scheme where you can switch between 2 channel, 3 channel or fully balanced configurations. and then have a pair of cans terminated balanced, with an unbalanced adapter to be used in the 2 and 3 channel configs. 

 Oh.. I guess we'd have to have a Balanced/unbalanced output DAC as well, but I guess there are enough of those around.


----------



## Sherwood

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Um, I'm closer than Sachu... And I am the ONLY ONE to have built a balanced EHHA 
	

	
	
		
		

		
		
	


	


_

 

Oh it's on.


----------



## sachu

bah..I don't have a need for going balanced. I prefer to remain in the monetarily saner SE world. 
	

	
	
		
		

		
		
	


	




 If I had a balanced rig for sure I would've gone balanced. And like smeggy says it is only a matter of slapping on two more amp boards as I already have the PSU built up to handle the load from 6 boards if need be.


----------



## Sherwood

Riposte!


----------



## wiatrob

MrSlim, add switchable MOSFET/BJT into that matrix 
	

	
	
		
		

		
		
	


	




 Always wanted to use that smiley...


----------



## wiatrob

Supremely sad news - The Amp Gremlins have gotten my Sigma22 - it is nonfunctional. 'Twas working perfectly last time I put the amp away - I just got it down for one last check before casing - AC in no DC out.

 Try a little troubleshooting, but my op points don't match TI's PDF (42V in on a 30V trafo...)

*EDIT: DUH, rectified DC...*

 I have parts for another one I think , just don't know if I have time to build it up...


----------



## runeight

Oh no. I was looking forward to hearing it. Believe it or not I have never heard an EHHA.


----------



## wiatrob

Well, a superhuman effort will be made to get this one fixed or replaced then!


----------



## zkool448

oh no 
	

	
	
		
		

		
		
	


	




 It needs to get there Bill! if only I had an s22 I'd ship it out overnight.


----------



## smeggy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Oh no. I was looking forward to hearing it. Believe it or not I have never heard an EHHA. 
	

	
	
		
		

		
		
	


	


_

 

jeez, what a slacker!

 Where have you been? This design has been out forever


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Supremely sad news - The Amp Gremlins have gotten my Sigma22 - it is nonfunctional. 'Twas working perfectly last time I put the amp away - I just got it down for one last check before casing - AC in no DC out.

 Try a little troubleshooting, but my op points don't match TI's PDF (42V in on a 30V trafo...)

*EDIT: DUH, rectified DC...*

 I have parts for another one I think , just don't know if I have time to build it up..._

 

man..you've got to be kidding me. That's just criminal in its timing. 
	

	
	
		
		

		
			





 Give us some info will ya...let's see if we can troubleshoot that bugger.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Oh no. I was looking forward to hearing it. Believe it or not I have never heard an EHHA. 
	

	
	
		
		

		
		
	


	


_

 

You really need to get with the program dude. Kits are only 110$
	

	
	
		
		

		
		
	


	







 I will ship mine out to you once it is cased up. (getting there finally)


----------



## wiatrob

Well, I decided to build up my second s22 - positive is regulating but negative is not (40V) I have yet to troubleshoot, i'll post over in the Sigma thread...

 EDIT: thought there was a _*σ22*_ thread on here... back to checking things...


----------



## smeggy

man that's sucky, I hope you can get it all cleared up quick.


----------



## wiatrob

Oh, eventually it'll get sorted... just hope it's sooner..


----------



## Lifthanger

Quote:


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



_

 

I realize this is not the best timing, but could you tell me which common mode choke you used? I found this TKD one TDK|ACM7060-701-2PL|DROSSEL, GLEICHTAKT, 700OHM, 4A | Farnell Deutschland

 4A max (I'll use two of these boards, so it'll see at most 2A) , 15mOhm and 700Ohm at 100MHz.

 The other available CMCs are wound on a common toroid.


----------



## wiatrob

Cold solder joint on one of the Current limiting diodes, yippie! thanks for the good vibes, EHHA is making music again, on the board. Dare I case it?


----------



## Sherwood

Dare you let Larry say it sounds the same as his Qinpu?


----------



## wiatrob

Dare he hook up some K1000 to his Qinpu? 
	

	
	
		
		

		
		
	


	




 (Smeggy, listening to your freshly balanced K1K's now...

 I passed over in to 'all these amps sound awesome + .x%" land a while ago... 

 Plus he won't even listen to it unless I get it into a case


----------



## Sherwood

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_ Plus he won't even listen to it unless I get it into a case 
	

	
	
		
		

		
		
	


	


_

 

Precisely. I'll listen to it either way, of course. So hey, Bill, what kind of values of "x" are we talking for our "awesome + x%"?


----------



## wiatrob

Notice that was *POINT*X% as in (decimal place). I have reached a point where the differences are more subtle than my ability to descern...

 Conflict of interest prevents me from saying exactly how the EHHA would compare to say, a CTH. You decide tomorrow!


----------



## Sherwood

Way to recuse yourself, MOTMOTMOT.

 I'll be there bright and early, covered in bells, taking pictures of embarassed nerds and their publicly-derided toys.


----------



## runeight

You know, a certain geeky designer might be there too if you wait long enough.


----------



## looser101

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_I realize this is not the best timing, but could you tell me which common mode choke you used? I found this TKD one TDK|ACM7060-701-2PL|DROSSEL, GLEICHTAKT, 700OHM, 4A | Farnell Deutschland

 4A max (I'll use two of these boards, so it'll see at most 2A) , 15mOhm and 700Ohm at 100MHz.

 The other available CMCs are wound on a common toroid._

 

It's not necessary, me thinks. I believe the original design was for a DHT tube heater.


----------



## smeggy

I still think the CTH is pretty awesome too.


----------



## sachu

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_I realize this is not the best timing, but could you tell me which common mode choke you used? I found this TKD one TDK|ACM7060-701-2PL|DROSSEL, GLEICHTAKT, 700OHM, 4A | Farnell Deutschland

 4A max (I'll use two of these boards, so it'll see at most 2A) , 15mOhm and 700Ohm at 100MHz.

 The other available CMCs are wound on a common toroid._

 



 Don't worry about the choke. It is only there for filtering. Even without the choke you will have a pretty solid Heater supply there.


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Notice that was *POINT*X% as in (decimal place). I have reached a point where the differences are more subtle than my ability to descern...

 Conflict of interest prevents me from saying exactly how the EHHA would compare to say, a CTH. You decide tomorrow!_

 

Nice going on the EHHA Bill. Am so looking forward to impressions from this meet. Wish I could be there. The CTh is on a different playing field compared to the EHHA. For eg: I can't take the EHHA with me to India in october but I can take my CTH with me 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_I still think the CTH is pretty awesome too._

 

Aye!..for its size, with a 6CG7 tube in it, it scares me with the level of detail and musicality it can dish out.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You know, a certain geeky designer might be there too if you wait long enough. 
	

	
	
		
		

		
		
	


	


_

 

Whoa!..u serious...damn! Now there's a meet I would want to be at.


----------



## Lifthanger

This is my very first PCB layout. If someone is interested, I could post the BOM and eagle files. It's PMillets design and I tried to get it in one layer to diy the board.

 Reason for posting this here is as a sanity check. Never did that before.

 The distance between traces is 15mil and traces are 50mil wide, to stand the current.


----------



## sachu

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_This is my very first PCB layout. If someone is interested, I could post the BOM and eagle files. It's PMillets design and I tried to get it in one layer to diy the board.

 Reason for posting this here is as a sanity check. Never did that before.

 The distance between traces is 15mil and traces are 50mil wide, to stand the current._

 

Looks good. Might want to make sure its okay with Pete before you release the gerber files.
 I would just personally make it on a perf board. Faster and it works perfectly fine.


----------



## looser101

Or you can just buy a kit for $24. Just add a transformer.

KIT


----------



## sachu

^^Probably a better idea..parts cost for the DIY one is almost 15$


----------



## Lifthanger

thanks sachu and looser!

 the reason I'm doing this on PCB is, because I've finally got some free time, to learn eagle and try out the toner transfer method.


----------



## looser101

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_thanks sachu and looser!

 the reason I'm doing this on PCB is, because I've finally got some free time, to learn eagle and try out the toner transfer method._

 

No harm in that. Have fun.


----------



## looser101

Quote:


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





 This is my very first PCB layout. If someone is interested, I could post the BOM and eagle files. It's PMillets design and I tried to get it in one layer to diy the board.

 Reason for posting this here is as a sanity check. Never did that before.

 The distance between traces is 15mil and traces are 50mil wide, to stand the current._

 

Two things. Making the distance between traces wider would probably make it easier to etch without bridges. Get the electrolytics away from the heatsink. Depending on what you are powering that heatsink can get quite hot.


----------



## wiatrob

Sorry to keep you all in suspense- the EHHA is Done Enuf For The Meet (needs final AC wiring) but it's cased. Pics soon - or make you wait til tomorrow!

 Oh, Cased AND working ...


----------



## sachu

nooo..post now!!..now dammit


----------



## Sherwood

Man, Bill, cutting it down to the wire. Good show!


----------



## wiatrob

What? I got like six or seven hours left! 
	

	
	
		
		

		
		
	


	




 Here she is - a bit plain but I like simple...


----------



## sachu

very cool Bill..though was expecting to see the surplus cases.

 Now to wait for the impressions to flow.


----------



## Sherwood

You running that K1K SE? What's the output wattage/imp. of the EHHA?


----------



## wiatrob

Quote:


  Originally Posted by *Sherwood* /img/forum/go_quote.gif 
_You running that K1K SE? What's the output wattage/imp. of the EHHA?_

 

Balanced (I re-terminated Smeggy's). Don't know the numbers offhand, but you can search this thread!

 EDIT: Found it - MEGAWATTS


----------



## Sherwood

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_ "R21 sets the gain, thus the ideal value depends on the headphone impedance you're using. Usually 6 for low-Z phones (32 Ohms), around 8 or 9 for high-Z cans (250 to 300 Ohms) and 12 or 13 for old 600R cans or K1000. That means resistor values for R21: 2k, 1k5, 800R (roundabout)"_

 

Can do, friend.


----------



## smeggy

Very cool indeed, I'm sure she'll be the belle of the ball 
	

	
	
		
		

		
			





 Nice work!


----------



## sachu

Make sure that the amp +headphones make a stop at Portland before continuing on their way to Smeggy..that is if you do plan to ship it out to Smeggy along with his headphones.


----------



## smeggy

I'm watching you sachu, I'm watching....


----------



## wiatrob

Sherwood, I have r21 at about an ~800R equivalent...


----------



## cfcubed

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_ < snip > Believe it or not I have never heard an EHHA. 
	

	
	
		
		

		
		
	


	


_

 

Unless you haven't let on, think you could say the same for the CTH
	

	
	
		
		

		
		
	


	



 Here's to hoping you do make it to the meet to hear these creations.


----------



## runeight

Alas, I had an event today in Denver that lasted until 5pm. But when I flicked on my cell phone again there was a text message from wiatrob telling me that the meet had wound down and that driving on over to the hotel would probably find no one home.

 So gents, I just want you to know that I tried. I really did, but wiatrob sent me home. 
	

	
	
		
		

		
		
	


	




 Edit: You're right cfcubed, I have not heard a CTH yet either. I do have a pair of EHHA boards, but I gave all of the CTH proto boards away. Kind of strange isn't it??


----------



## sachu

aww man..that sucks. Alex, once my EHHA is cased up and complete I will ship it out to you and will probably include the CTH along with it.

 Edit: Bill, you couldn't wait half an hour for the main man to arrive? 
	

	
	
		
		

		
		
	


	




 well there is always another time.


----------



## wiatrob

I would happily have waited - and welcomed him to a room devoid of even power adapters.

 I'll bring Alex a CTH before he leaves town!


----------



## dBel84

There will be more opportunities. It is a pity non the less. 

 How did the amp go down at the meet?

 ..dB


----------



## holland

^ yeah, how'd it go?


----------



## wiatrob

Well (excpet that the EHHA wasn't loud enough for the soon-to-be-deaf-philes at the meet) - I'll have pics and impressions up early this coming week...


----------



## sachu

hah..but what a shame ...well look forward to impressions from you and Tyler.


----------



## smeggy

not loud enough? WTH? 

 I'm not what you'd call a quiet listener and even I rarely get past one o'clock. Still yours is balanced and running K1Ks and I dunno what your gain is . The only one mine still struggles with is the Wharedale, but most amps have that trouble.

 Humph!


----------



## dBel84

I NEVER got past 12 on mine, but then I default to low levels and when things are so loud that I feel front row, it's time for ear plugs or to pull the plug ..dB


----------



## Sherwood

Yeah, I spent some good time on the EHHA, and it was an excellent amp (save for the gain issue). Not sure what was up with the gain, but i'm sure Bill will get to the bottom of it before too long. As it stood, it was easily detailed enough to compare my K1000s to Smeggys, and to definitively tell the difference. That's plenty competent in my book. 

 K1Ks aren't terrifically suited to meet conditions, of course, but the EHHA drove them very well, and was a very impressive amp.


----------



## wiatrob

The gain issue is fixed, along with a host of other problems, due to a component error on my part.

 We should get together and give it another listen...


----------



## Sherwood

^^^
 I agree with this. In a week or two, I'll have something worthy to compare it to.


----------



## tennisets

I searched through this thread for a while, but I still have a couple of questions.

 I was intending to build a balanced M^3, but this project is tempting. My questions: is there anything else that needs to be done to drive speakers other than use 2W resistors for R32 and R33 and a Zobel network across the speaker terminals? I saw mention of paralleling the output devices. Any more info on this? Headwize being down kind of sucks.

 In addition, would two sigma22's be recommended for speaker use (as in the b22), or could I get by with one (with appropriately sized transformer)?

 Thanks!


----------



## runeight

tennisets, to turn the EHHA into a speaker amp you need to do three things:

 1. Set R32,R33 to 2W (as you note)
 2. Set R13 to 10k
 3. Off board heatsinking for the mosfets

 You can adjust R22,R23 for the NFB that suits your tastes. The amp will be fastest with these resistors left out.

 You will need the zobel, about the same as the b22 as nearly as I can tell. But I have not looked extensively into this. The amp should be stable into speakers, but I have not actually done this. OTOH, the amp topology is identical to many other, stable amps.

 With 4 ohm speakers each channel can put about 4.5A into its speaker. You'll need the supplies to handle this if you intend to listen at this level. This is 40W RMS into 4R.

 The amp should make close to 25W (IIRC) into 8R (about 2.5A per channel).

 The power fets will burn about 22W at full output. You'll need sufficient heatsinking capacity for this. For example, the tallest onboard heatsink that will fit is the Wakefield 647-25ABP. The curves show a 60C temp rise for 20W power dissipation. Thus, off board heatsinks will be needed.

 With these component values the amp should make full power at about 1.25VRMS at the input.

 This using 30V supplies. The amp can make more power with higher rail voltages providing that the PS is big enough.

 Does this help?


----------



## wiatrob

Well, things are settling nicely. Tempted to say two words:

 New Reference.

 I do like this amp better with the Sennheisers than Grados, so far. 

 I no longer wish to make comparisons with the CTH (_until _I build a balanced version with a Stepped Attenuator that costs more than the entire amp).

 Bass torture test time!


----------



## wiatrob

Thunderous and tight with the NOS Telefunken 6GM8. Bests my M^3...

 Alex, Technically - how much difference in sonic signatures could a tube roll impart? More/less than say a SOHA II or CTH?


----------



## runeight

You know, I'd like to be able to answer that, but I've kind of given up on predicting what you guys will hear with tube changes.

 The theoretical answer is that there is so much NFB in this amp that this will wash out a lot of the tube differences. But then again, the diff amp section of this type of amplifier has a lot of impact on the sound.

 So I don't know ...

 But I am happy to now that you got it working right.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This using 30V supplies. The amp can make more power with higher rail voltages providing that the PS is big enough.

 Does this help?_

 


 Am about to finalize the end panels for my EHHA and am really tempted to slap on a pair of binding posts, if I can find some space for it.

 Alex, wouldn't higher plate voltages hurt the life of the tube if we use the 6GM8?


  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, things are settling nicely. Tempted to say two words:

 New Reference.

 I do like this amp better with the Sennheisers than Grados, so far. 

 I no longer wish to make comparisons with the CTH (until I build a balanced version with a Stepped Attenuator that costs more than the entire amp).

 Bass torture test time!_

 

We think alike my friend 
	

	
	
		
		

		
		
	


	




 I was smitten by this amp listening to my Senn HD580s when I first heard it. The synergy was like magic with this amp. 
 Glad to see you have the amp running fine and that it has found its rightful place in your setup. 
 Oh, and the perf top arrived and fits perfectly! Thanks a lot.


----------



## runeight

My guess is that you could get away with 35V or even 40V on the tube for a long time for most of them. Tubes are pretty tough.

 But, since this is a low voltage tube the spacings will be closer together to achieve the same values of the electric fields to move the electrons. So there is definitely a risk of internal arcing.

 In this case the tail CCS will prevent the cathode current from getting too large.

 Also, we know that smeggy is running 6GM8s in his CTH. Eventually there could be a problem, but OTOH it might run forever like that.

 And, as you know, the amp was originally designed around the 6h30. You can always those or the 6922. They both don't mind the low voltages.


----------



## holland

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_ The amp should make close to 25W (IIRC) into 8R (about 2.5A per channel)._

 

Single ended? So, balanced it would be quite a bit. Hmm, tempting to go balanced now as I've been wanting to make a small power amp out of balanced Beta22s with a balanced DAC. I normally don't do balanced.

 Tempting, very tempting...


----------



## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Well, things are settling nicely. Tempted to say two words:

 New Reference.

 I do like this amp better with the Sennheisers than Grados, so far. 

 I no longer wish to make comparisons with the CTH (until I build a balanced version with a Stepped Attenuator that costs more than the entire amp).

 Bass torture test time!_

 

That's great. What configuration are you running now.

 Sadly, everything is still in bags for me. I'm on break from building anything. Motivation just disappeared in a flash.


----------



## smeggy

Pity. I hope it returns soon as it's a damn fine amp. The thing just oozes power and quality. Once my funding returns to some form of normality I'm balancing mine.


----------



## runeight

tennisets, I left something out of the list of changes. It's been a while.

 R32 and R33 also need to be changed from 2R2 to 0.47R.

 holland, yes, you can probably pull close to 9A from a balanced version. But I don't think these particular fets can handle that. It needs bigger ones.

 And since you will need offboard heatsinks we should look at the Hitachi 2sk1058 and 2sj162 lateral fets or the irfp140n and irfp9140n.


----------



## wiatrob

CL Gain <11 (x2), OL Gain 10k, Telefunken 6GM8s,

 I still have to replace R5,R7 with the correct value, have *100Rs *in there now, close enough according to Alex...


----------



## runeight

Perhaps you mean 100R??


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_And since you will need offboard heatsinks we should look at the Hitachi 2sk1058 and 2sj162 lateral fets or the irfp140n and irfp9140n._

 

And what for us BJT's? 
	

	
	
		
		

		
		
	


	




 I think I'll gibe the Hitachi's a shot for my three channel MOSFET build. Would there be any other part changes?


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Perhaps you mean 100R?? 
	

	
	
		
		

		
		
	


	


_

 

DOH! that's what got me last time, yes* 100 R*!


----------



## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_And what for us BJT's? 
	

	
	
		
		

		
		
	


	




 I think I'll gibe the Hitachi's a shot for my three channel MOSFET build. Would there be any other part changes?_

 

Or, if I had a bit more time, we could start prototyping the EHHA II. It's already designed to use the Hitachi and IRF BIG fets. Then you guys wouldn't have to work so hard to heatsink the output devices. And these fets will drive a truck.


----------



## wiatrob

[size=small]MJ15004/[/size][size=small]MJ15003? Or I just resign myself to Fets 
	

	
	
		
		

		
		
	


	



[/size]


----------



## runeight

Well ...

 You'll notice in the normal build that the BJTs have higher emitter resistors than the mosfets. This to ensure that they don't thermally run away.

 As you guys know BJTs have a positive temperature coefficient. This means that they hotter they get the more then conduct. Mosfets have a negative coefficient so they conduct less as they warm up. The fets don't have thermal runaway.

 For headphone amps the 10R resistors on the BJTs are no big deal, but for a power amp 10R makes the amp impractical. We can make these smaller, like 0.47R but then we REALLY must ensure that the BJTs stay cool and never get into a runaway condition.

 Which means that it will just be easier to use the fets ...


----------



## runeight

Quote:


  Originally Posted by *tennisets* /img/forum/go_quote.gif 
_I searched through this thread for a while, but I still have a couple of questions.

 I was intending to build a balanced M^3, but this project is tempting. My questions: is there anything else that needs to be done to drive speakers other than use 2W resistors for R32 and R33 and a Zobel network across the speaker terminals? I saw mention of paralleling the output devices. Any more info on this? Headwize being down kind of sucks.

 In addition, would two sigma22's be recommended for speaker use (as in the b22), or could I get by with one (with appropriately sized transformer)?

 Thanks!_

 

tennisets, I'm going to repeat my reply because I just wrote it out too fast.

 To make an EHHA power amp you should.

 1. Change R32, R33 to 0.47R at 2W.
 2. Change R13 to 1k.
 3. Supply bigger heatsinking for the fets.
 4. Remove R22, R23

 I think it's right this time.


----------



## tennisets

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_tennisets, I'm going to repeat my reply because I just wrote it out too fast.

 To make an EHHA power amp you should.

 1. Change R32, R33 to 0.47R at 2W.
 2. Change R13 to 1k.
 3. Supply bigger heatsinking for the fets.
 4. Remove R22, R23

 I think it's right this time. 
	

	
	
		
		

		
		
	


	


_

 

Thanks for the detailed replies! I don't know if I want to have to deal with offboard heatsinks, so perhaps I will stick with just a headphone amp for now. I think I am going to give this amp a go as opposed to the M^3 though. Sounds like a fun build.


----------



## runeight

Don't let this necessarily discourage you on the speaker amp. It's necessary to give the worst case conditions so that there are no surprises. 
	

	
	
		
		

		
		
	


	




 However, as we know, music is not a sine wave and most listening is done a low power levels, often only 1W or so. The extra power in the amp is used to get dynamic range in the transient peaks.

 With the big heatsinks that are on this board, if you use the tallest ones, you can probably get pretty loud without overheating the fets. It will be a very rare circumstance where you will hammer out a 40WRMS sine wave, unless you're trying out test tones.

 If you socket a few resistors you could have both a headphone amp and a speaker amp.


----------



## tennisets

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Don't let this necessarily discourage you on the speaker amp. It's necessary to give the worst case conditions so that there are no surprises. 
	

	
	
		
		

		
		
	


	




 However, as we know, music is not a sine wave and most listening is done a low power levels, often only 1W or so. The extra power in the amp is used to get dynamic range in the transient peaks.

 With the big heatsinks that are on this board, if you use the tallest ones, you can probably get pretty loud without overheating the fets. It will be a very rare circumstance where you will hammer out a 40WRMS sine wave, unless you're trying out test tones.

 If you socket a few resistors you could have both a headphone amp and a speaker amp. 
	

	
	
		
		

		
		
	


	


_

 

Thanks for the response. So you think I would be ok with something like this? I might just go with offboard sinks anyway, since my case will have room inside. I saw mentioned earlier in the thread that the hole locations for the heatsink pins are off. Is that still the case or was it corrected?

 Also, why do you recommend no negative feedback for the power amp version? I would probably implement variable NFB with a rotary switch anyway, but I am curious.

 Is a second power supply strictly necessary, assuming I would use a large enough transformer for a single supply? Thanks!

 Edward


----------



## tennisets

Oops, removed.


----------



## runeight

The heatsink that you want is this one:

Aavid TO220

 Except that this is the 2" tall version and Mouser doesn't seem to have the 2.5" tall version. The 2.5" is the one you want if you can find it somewhere.

 The holes seem to be slightly off on the boards. We don't know why. However, I have a pair of board (unpopulated) and I have the correct heatsinks and they fit with no problems at all.

 If you're using s22 supplies, I think that they are spec'd at 1A continuous current and much higher peaks. You can try one and see what happens. You can always build another one if you really need it.


----------



## tennisets

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The heatsink that you want is this one:

Aavid TO220

 Except that this is the 2" tall version and Mouser doesn't seem to have the 2.5" tall version. The 2.5" is the one you want if you can find it somewhere.

 The holes seem to be slightly off on the boards. We don't know why. However, I have a pair of board (unpopulated) and I have the correct heatsinks and they fit with no problems at all.

 If you're using s22 supplies, I think that they are spec'd at 1A continuous current and much higher peaks. You can try one and see what happens. You can always build another one if you really need it. 
	

	
	
		
		

		
		
	


	


_

 

Thanks, I actually just saw the heat sink specs on your site (not sure how I missed it before). The heatsink supplied with the Glass Jar kits is a smaller one, I guess.

 As far as the supply, I guess I'll try one first. If it doesn't work out I can always just use the amp as a headphone amplifier until I get another s22.


----------



## smeggy

finally got around to doing the shunt mod on my RK27 pot tonight using 51k resistors. Sounds very nice. Dunno if It's my imagination but it seems clearer than standard. My audio memory is notoriously unreliable but I've been wanting to try it since I first read about it. So, mission accomplished!


----------



## wiatrob

Well, the EHHA has broken in nicely since I fixed my stupid resistor mistakes. Full, defined bass and a LOT of power and speed.

 Now treats my Balanced RS-1 just as well as the HD600's - in fact, it evens out some of the differences in both cans, if you can believe that.

 I still have to finalize the AC wiring (switches and removable line cords). But this amp is _really _nice. Wishing I had the K1Ks again (thanks for the loaner Smeggy!)


----------



## smeggy

No probs. I'll be balancing mine shortly so that'll be fun, just gotta get another kit, heater transfo and another set of 6h30s and a balanced pot 
	

	
	
		
		

		
			





 What pot are you using?


----------



## wiatrob

A DACT CT-4. Looking for Quad pots for another project, only thing I can find:

Familygate


----------



## FallenAngel

Cheap stepper on eBay : Balance XLR 23 stepped attenuator volume control 50K - eBay (item 270432581072 end time Aug-23-09 07:55:13 PDT)

 DACT from HeadAmp : HeadAmp Audio Electronics (Order)


----------



## smeggy

High Quality Audio & Industrial Attenuators

 sexy looking.


----------



## wiatrob

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Cheap stepper on eBay : Balance XLR 23 stepped attenuator volume control 50K - eBay (item 270432581072 end time Aug-23-09 07:55:13 PDT)

 DACT from HeadAmp : HeadAmp Audio Electronics (Order)_

 

That's where I got my DACT. I haven't had the best success with the Ebay attenuators (well, I had one bad one... but many have used without issue)


  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_High Quality Audio & Industrial Attenuators

 sexy looking._

 

Bling-Freaking-Tastic! I'm gonna get one and take the EHHA to the Chromer!


----------



## smeggy

it is rather sweet huh. If I had one it'd have to be externally mounted just so I could see it


----------



## wolf18t

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_High Quality Audio & Industrial Attenuators

 sexy looking._

 

Wow they look wonderful, seem top quality and good price! Ladder type, 48 steps and wide range of value.

 If I was gona build another B22 it would make top on my list.


----------



## wolf18t

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_If I was gona build another B22 it would make top on my list._

 

Or for a "if ever available" Stacker II?


----------



## sachu

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Or for a "if ever available" Stacker II? 
	

	
	
		
		

		
		
	


	


_

 

I still maintain my opinion.

 EHHA > Stacker 2


----------



## FallenAngel

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_High Quality Audio & Industrial Attenuators

 sexy looking._

 

Any experience with these?


----------



## smeggy

not personally. Like everyone else looking for a reasonably priced balanced pot, this seems like a cheaper and maybe better made option than the more pricey pots out there. I'm sure I'll get one eventually.


----------



## smeggy

well everyone is hoping it'll be a great pot for a not too astronomical price, so fingers crossed! It certainly looks the part and I'd like one for my soon to be balanced EHHA


----------



## Sherwood

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_If I had one it'd have to be externally mounted just so I could see it 
	

	
	
		
		

		
		
	


	


_

 

And with that fell swoop, Smeggy created socketed pots and pots that stick up straight out of the top like tubes. Thanks a bunch.


----------



## smeggy

must have teh sexeh lookz.


----------



## wolf18t

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I still maintain my opinion.

 EHHA > Stacker 2 
	

	
	
		
		

		
		
	


	


_

 

Seriously? You had the chance to compare it to one of the rare Stacker 2 build? 2 boards or 3 boards configuration? BJT or MOSFET version?

 Well, maybe I'll give the EHHA a try. I didn't bother to build it because of the extra filament PS and delay thing which look quite complex and have to hunt for required PCBs from many source ($$$ international shipping).


----------



## smeggy

I have my heaters wired directly from a rat shack 12v transfo running AC. I have the delay circuit but it's not wired in yet, I power on the heaters and then the amp about 30 seconds later.

 Not very complex and it sounds wonderful with 6h30 tubes.


----------



## dBel84

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I still maintain my opinion.

 EHHA > Stacker 2 
	

	
	
		
		

		
			



_

 


 Maggie been with holding the lithium again 
	

	
	
		
		

		
		
	


	






 and this is what the hobby is all about - personal preferences. I love them both, one just collects more dust than the other 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_I love them both, one just collects more sachu than the other 
	

	
	
		
		

		
		
	


	




 ..dB_

 

FIFY


----------



## wiatrob

Wolf18t - this may be heretical, but there was some talk here earlier about ignoring filament warmup delay - cathode stripping maybe not so bad with low voltage tubes.

 I use the two step approach and I like it- turn on heaters, wait for good glow, turn on amp (Old Skool!)


----------



## smeggy

yup


----------



## digger945

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Wolf18t - this may be heretical, but there was some talk here earlier about ignoring filament warmup delay - cathode stripping maybe not so bad with low voltage tubes.

 I use the two step approach and I like it- turn on heaters, wait for good glow, turn on amp (Old Skool!)_

 

Hey ain't nuthin wrong with old skool I tell ya. It gives you a sense of accomplishment that you know what your doing and switching and when and why your switching it. I think the delay boards and relays are neato too(and you guys who use 'em know what's goin on too so...) but hey, I guess I'm just from a slightly different time and background, and being a little weirdo does help some in this dept.


----------



## dBel84

yep, got 3 switches on the front of mine, nice tactile experience - you know what it is that you want to do when powering it up 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## smeggy

with my balanced one I could have a whole cockpit experience...

 fan - click
 heater one -click
 heater two - click
 heater three - click
 heater four - click
 pause...
 Main Power ------- ON!

 *insets cool imaginary jet engine startup noises here


----------



## sachu

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Seriously? You had the chance to compare it to one of the rare Stacker 2 build? 2 boards or 3 boards configuration? BJT or MOSFET version?

 Well, maybe I'll give the EHHA a try. I didn't bother to build it because of the extra filament PS and delay thing which look quite complex and have to hunt for required PCBs from many source ($$$ international shipping)._

 

 Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Maggie been with holding the lithium again 
	

	
	
		
		

		
		
	


	




 and this is what the hobby is all about - personal preferences. I love them both, one just collects more dust than the other 
	

	
	
		
		

		
		
	


	




 ..dB_

 

Absolutely. the stacker 2 and the EHHA are both very special amps. Some do things better than the other. It boils down to a matter of preference at this level of performance.
 The filament supply is only 30$ including a transformer and another 20$ for a relay board. Course as others have noted..cheaper options exist.

  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_FIFY_

 

haha..


  Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_with my balanced one I could have a whole cockpit experience...

 fan - click
 heater one -click
 heater two - click
 heater three - click
 heater four - click
 pause...
 Main Power ------- ON!

 *insets cool imaginary jet engine startup noises here 
	

	
	
		
		

		
		
	


	


_

 

U just do one switch for all the heaters smegster..


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Wishing I had the K1Ks again (thanks for the loaner Smeggy!)_

 

Its soon going on a permanent loan out to me.


----------



## wiatrob

Well, Fallen Angels pair has been tempting me. but I have some 'stats on permi-loan *I *need to pay for


----------



## wiatrob

For your edification:

EHHA Thread on headwize back up!


----------



## dBel84

Can it really be Feb 2007 ??? no wonder I am having a hard time recalling the finer details of when we got the protos running !!! 

 time flies when you're havin fun 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## wiatrob

The Grand Old Days when you were building things !


----------



## smeggy

ok, I did it... I just ordered one of those sexy Khozmo steppers. 
	

	
	
		
		

		
		
	


	




 Aaaaah...


----------



## MrMajestic2

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_ok, I did it... I just ordered one of those sexy Khozmo steppers. 
	

	
	
		
		

		
			





 Aaaaah...









_

 

Be sure to give us the full lowdown on it when it arrives


----------



## smeggy

will do.


----------



## wiatrob

Please use a moar sexier knob than the one in the photo - talk about hiding your lamp under a bushel!


----------



## runeight

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_The Grand Old Days when you were building things !_

 

dBel84 is on an undercover mission right now. We must leave him alone so as not to expose his cover.


----------



## smeggy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_dBel84 is on an undercover mission right now. We must leave him alone so as not to expose his cover. 
	

	
	
		
		

		
		
	


	


_

 

Ok dammit, you can't just come strolling in here and blurt that out without expecting to get a bit of a grilling... spill the beans or the heavies will be around to pay you a visit!


----------



## dBel84

just me strolling around forest park in an overcoat looking for me undies 






 or mebe this when you wear them back 2 front 











 ..dB


----------



## smeggy

Bah!

 You will pay for this, oh yes, there will be consequences....


----------



## runeight

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_Ok dammit, you can't just come strolling in here and blurt that out without expecting to get a bit of a grilling... spill the beans or the heavies will be around to pay you a visit!_

 

What can I say. It looks like dBel84 is REALLY doing some DIY.


----------



## MrSlim

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_dBel84 is on an undercover mission right now. We must leave him alone so as not to expose his cover. 
	

	
	
		
		

		
		
	


	


_

 

so, we should start speculating?


----------



## smeggy

Hrm... Stackehha


----------



## Lifthanger

just finished reading the headwize thread and this one here...
 nothing but EHHA in my head now. 
	

	
	
		
		

		
		
	


	




 And : 



 guess what's in there! 
	

	
	
		
		

		
		
	


	




 edit: wow, that's almost too fast


----------



## smeggy

Cool, I'm sure you'll have a blast with it.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_And since you will need offboard heatsinks we should look at the Hitachi 2sk1058 and 2sj162 lateral fets or the irfp140n and irfp9140n._

 

Can these MOSFETs be used for regular headpohone listening as well.
 I was thinking of replacing the BOM MOSFETs with these bigger ones you suggested so I can use the amp to drive speakers as well. 

 cheers,
 Sachu


----------



## runeight

Yes they can. The will be major overkill for headphones and I don't know how they will sound, but you can use them.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes they can. The will be major overkill for headphones and I don't know how they will sound, but you can use them._

 

Got it...will order a handful and see what's what. Thanks Alex.


----------



## smeggy

The stock bom ones seem to have ample power to run the stax box but yeah, should be an interesting experiment. Keep us informed


----------



## runeight

OK. Other changes will be needed. Particularly the Vbe multiplier to set the correct bias. These are lateral fets and they bias differently from the vertical fets that are there now.


----------



## sachu

Zobel not included yet..rosewood end panels not here yet..but you get the idea


----------



## dBel84

Beautifully executed Sachu ..dB


----------



## Ferrari

A bit delayed (due to the prototyping work of my other amp) but not forgotten, … finally I have the time to pick the build of my balanced EHHA up.
 There are still lots of things to do, but hopefully I will get it up and running next weekend.


----------



## runeight

It appears that several of you guys are making speaker amps. Yes?

 Have I given the the resistor value changes needed for this? If not, let me know and I'll post a schematic.

 Looking forward to these builds now.


----------



## Ferrari

Alex, a modified schematic is always welcome! 
	

	
	
		
		

		
		
	


	




 Mine is mainly intended to drive my AKG K1000 (kind of little speakers) and it really needs some healthy juice to do the job well.
 As you have noticed, I have put some tweak-able parts (C2, C3, R13, R22 and R23) on sockets and 
 changed the power resistors R32 and R33 to 0.5Ω (Mills resistors from my parts bin), convenience for the case that the amp is connected to 8Ω speakers. 
 I think that I will set the CL gain to 11x (effective gain of 22x in balanced mode).

 DT


----------



## sachu

That is just going to look killer...looking forward to this build Ferrari..more than anything else.


----------



## Ferrari

Have a little patience. 
	

	
	
		
		

		
		
	


	



 For the time being, here is a raw CAD drawing of the enclosure for my EHHA.
 Face- and top plate design is not included.


----------



## sachu

That looks sweet..not trying to hurry you friend..hell i took 8 months for my EHHA build and it is still not complete


----------



## Ferrari

Do you guys know where we can source Toshiba 2SC2705 with Hfe class *Y* ?
 A while back, I got some 2SC2705/2SA1145 from B&D, but they gave me a bag with 2SA1145-*Y* and a bag with 2SC2705-*O*. 
	

	
	
		
		

		
		
	


	




 I know that Mouser has 2SC2705/2SA1145 in stock, however only Hfe *O* class.


----------



## Ferrari

The source for the BJT transistors has been found (thanks to Scott)!
 I was busy this evening, the σ22 PSU and 6.3V power supplies are up and running and … the amp sloo…owly takes the shape.


----------



## DoYouRight

wow that is an excellent picture! the tube looks magical.


----------



## smeggy

it's always nice seeing that first glimmer of life


----------



## runeight

I see that Ferrari is creating another masterpiece.

 Then I'm going to ask him again if he'll design amp enclosures for me.

 Then he's going to say, "No, I'm just a little old banker."

 And then, sometime down the road, this will happen again.


----------



## smeggy

heh, the accidental masterpiece 
	

	
	
		
		

		
			





 Ferrari just has a natural knack of doing these things in an amazingly clean and neat way.


----------



## dBel84

yeah, he throws a bankers roll at them 
	

	
	
		
		

		
		
	


	




 ..dB

 EDIT: this was tongue in cheek of course, the man is talented without doubt


----------



## smeggy

yeah, that too


----------



## Ferrari

A step closer to completion.


----------



## sachu

Very cool Ferrari...Curious...what is that small tube board in the middle?


----------



## Ferrari

That is a level meter as I often used in my other amps (1, 2).


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_That is a level meter as I often used in my other amps (1, 2). 
	

	
	
		
		

		
		
	


	


_

 

Something like this?
YouTube - Tube level meter


----------



## Ferrari

Yes, something similar!


----------



## DoYouRight

more pictures of that when its done Ferrari, I love the silver and black.


----------



## Ferrari

Will do. Due to the busy work schedule I have to wait until the weekend to go further with it. 
	

	
	
		
		

		
		
	


	



 In the meantime, here are a couple of pictures during the build…






 MOSFET’s mounting on bottom heatsink, beneath the amp PCBs.






 As usual, volume knop back lighting with one single LED.


----------



## rhester

When doing intital testing, does pot need to be connected? Input shorted? or anything else special. ready to hook up and see how it goes.


----------



## nullstring

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_When doing intital testing, does pot need to be connected? Input shorted? or anything else special. ready to hook up and see how it goes._

 

errrr, I am just browsing, and so I know little about this project.

 In any case, I would say that if you short it and hook it up to something with volume control... like an ipod, and start the volume off very low, that'd be fine for testing.


----------



## runeight

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_When doing intital testing, does pot need to be connected? Input shorted? or anything else special. ready to hook up and see how it goes._

 

For DC power up and adjustment you don't need to do anything so long as you have R1 on the board. It's a grid leak resistor and keeps the grids grounded if there is no input pot.


----------



## Dougie085

I was planning on building the SOHA II but then someone showed me this project and I have to say it looks much much more interesting. So I think I'm going to go this route in a fully balanced build. I'm curious though which is the better version the Mosfet version or the BJT version? Also who can I get matched tubes for and what is consensus on what are the best tubes for this particular amp? Also need a source for matched transistors I suppose. Hopefully in a week or so I can order this.


----------



## sachu

Quote:


  Originally Posted by *Dougie085* /img/forum/go_quote.gif 
_I was planning on building the SOHA II but then someone showed me this project and I have to say it looks much much more interesting. So I think I'm going to go this route in a fully balanced build. I'm curious though which is the better version the Mosfet version or the BJT version? Also who can I get matched tubes for and what is consensus on what are the best tubes for this particular amp? Also need a source for matched transistors I suppose. Hopefully in a week or so I can order this._

 

Contact glassjaraudio for the kits. Email Jeff as the kit is not up on his website but he does supply full EHHA kits (MOSFET version only).


 No consensus as to which one is better..Those who prototyped the amp said there wasn't much between the two. In any case you could always try them both as it wold only cost another 20$ to get BJT s and associated few passive components for that version.

 I have only heard the MOSFET version and I love it. 

 You don't necessarily need matched tubes as you have adjustments on the PCB to balance the offets between the two triode sections of the tube. It wouldn't hurt though.

 Glass jar provides you the 6GM8 tubes as well which IMO are really the best VFM.

 6GM8s are very good with this amp but building a heater power supply for the 6H30 in mind would be beneficial if you are feeling spendy.


----------



## Dougie085

Well this will be my first tube build, I've built quite a lot of solid state circuits though so I don't think this ones going to be a problem. the 6GM8's seem to be what most use.

 Thanks for the info, I'll have to research a bit more. I wish there was some place to get a high quality chassis here in the states. Shipping costs from HiFi-2000 and the likes are crazy! Hah.


----------



## smeggy

dunno whether mosfet or bjt is better, but for tubes there are a number you can try depending on how you decide to do the heater supply. The standard tubes that come with the kits are ok, my preference is for either the 6n6p (cheap) or 6h30 (not cheap) the 6h30 does sound great but for the price the 6n6p is outstanding, both will be running close to their lower limits voltage-wise.

 Both these tubes require a fair bit of heater current but luckily you can wire them as AC which means a cheap Radio Shack 12.6v 3.5A transfo can be used to power them directly. Some prefer a regulated DC supply but mine runs fine like this.

 Another good tube is the Bugle Boy version of the original type. Very nice sounding and middling price.


----------



## Dougie085

Thanks. So with the 6GM8's you don't really have to do anything to the heater supply but with the 6H30's and what not you do. 

 How much would a matched set of 6N6P or 6H30's run?


----------



## smeggy

I bought a set of 8 6n6p tubes from Ukraine or similar for about $15.

 6h30's are costly and some of the new ones like the sovtek version is complete crap. The Electro Harmonix ones are 30-ish per tube new and the 'supertube' version can run $70+ per tube.

 Initially I'd stick with the supplied ones as they're perfectly good tubes and sound pretty nice anyway.


----------



## Dougie085

That's probably what I'll do, and when I start getting used to the sound and get it well broken in and get to the point of "what more can I get out of this?!?!?" then I may try swapping in some nicer tubes and what not.


----------



## dBel84

good choice , the amp sounds pretty fantastic with the 6GM8's..dB


----------



## wiatrob

I have been perfectly happy with 6GM8s on my (one of the few!) BJT build.


----------



## Dougie085

Guessing you haven't been able to compare it to the Mosfet version?


----------



## Dougie085

Here's another question, is one σ22 sufficient enough for a fully balanced version (4 mono boards)? What other PSU's do you guys use? The σ22 looks to be pretty nice so not really sure if any other option would really be that much better. If I add a lot more capacitance for the filtration would it better it much? I know when I've built large power amps the more filtration the better.


----------



## sachu

Quote:


  Originally Posted by *Dougie085* /img/forum/go_quote.gif 
_Here's another question, is one σ22 sufficient enough for a fully balanced version (4 mono boards)? What other PSU's do you guys use? The σ22 looks to be pretty nice so not really sure if any other option would really be that much better. If I add a lot more capacitance for the filtration would it better it much? I know when I've built large power amps the more filtration the better._

 

Highly recommend sticking to the S22 as it does have very good performance at a reasonable cost. 
 Just a single S22 would be plenty enough for pure headphone duty and more stiffening capacitance would help I suppose.

 Use a 100VA or higher rated toroid for the transformer.


----------



## runeight

Quote:


  Originally Posted by *Dougie085* /img/forum/go_quote.gif 
_Here's another question, is one σ22 sufficient enough for a fully balanced version (4 mono boards)? What other PSU's do you guys use? The σ22 looks to be pretty nice so not really sure if any other option would really be that much better. If I add a lot more capacitance for the filtration would it better it much? I know when I've built large power amps the more filtration the better._

 

As sachu says you only need one s22 for headphone duty (even four channels) and the s22 is a good enough PS that you don't need any additional caps or other components. In fact, adding O/P caps the the s22 might destablize it. MHO is use a bare s22. It will do what you need it to do.


----------



## rhester

Got my 2 channel build all dialed in tonite and functioning. Now to find a suitable case big enough for 2 transformers, o22, 6.3V power supply and the 2 boards. what have others used? One case or 2?


----------



## sachu

I would just go with one case. Reduces the casework necessary. Try to keep the transformers away from the boards as much as possible.

 Depending on the type of headphones you use, there should be no problem with respect to transformer noise. I don't have any and the transformer is only 4 inches from the amp board. I also like the fact that everything is in one case and compact.

 Edit: Btw..congratulations!! 
	

	
	
		
		

		
		
	


	




 too early for first impressions?


----------



## liwei

Hey all. I've contacted Jeff about getting an EHHA kit, S22 kit and B22 kit so I guess I will be joining you guys. I was originally going to build the S22 and put it into a separate enclosure but after thinking about all that wiring, I've decided just to put it all into one box and buy another S22 when I build the B22 later. 

 I've got a question about the tube heater transformer and LDO. I'm going off of the 12.6VDC regulated supply given on the website. Any suggestions for the transformer (something like a Hammond 166J12?) and LDO?


----------



## sachu

Quote:


  Originally Posted by *liwei* /img/forum/go_quote.gif 
_Hey all. I've contacted Jeff about getting an EHHA kit, S22 kit and B22 kit so I guess I will be joining you guys. I was originally going to build the S22 and put it into a separate enclosure but after thinking about all that wiring, I've decided just to put it all into one box and buy another S22 when I build the B22 later. 

 I've got a question about the tube heater transformer and LDO. I'm going off of the 12.6VDC regulated supply given on the website. Any suggestions for the transformer (something like a Hammond 166J12?) and LDO?_

 



 Nice..you won't be disappointed.

This transformer would be perfect for the EHHA heater supply. 

 You can wire it up in 12.6 volts (wire the secondaries in series) or in 6.3Volts (parallel the secondaries).


Peter Millet's DC filament supply is very nice and robust if you want to go the DIY route which is what I am using.

 Just use the necessary resistors to set the output voltage on the LDO regulator (12.6 volts or 6.3 volts..look at the datasheet for that).

 Alternatively you could just buy Glassware's heater supply which is actually very modestly priced.


----------



## liwei

I see. Took a look at the LT1085 datasheet and it looks fine for this.
 1.25(1+(1800/200)) = 12.5

 Already need to get some parts from Mouser or Digikey so I might as well
 save a few bucks and just do this myself. Though I may reconsider if the pcb
 is much better than what I'm assembling. Did you need to put a heatsink on the regulator?


----------



## wiatrob

Quote:


  Originally Posted by *Dougie085* /img/forum/go_quote.gif 
_Guessing you haven't been able to compare it to the Mosfet version?_

 


 I don't know if anyone's had the chance. I hear that a MOSFET version might make its way to RMAF - if that's the case the comapro can be made there. I have the parts to build a three channel mosfet version - someday.


----------



## Dougie085

Why would you build a 3 channel version? This confuses me a bit lol. Or would it not be for headphone use?


----------



## sachu

Quote:


  Originally Posted by *liwei* /img/forum/go_quote.gif 
_Did you need to put a heatsink on the regulator?_

 

Yes..you will need a heatsink for sure. If you are driving 6H30s or 6N6Ps then use a bigger heatsink as they draw close to 2A through the heater(for a 2 amp board pasive ground EHHA setup).


  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I have the parts to build a three channel mosfet version - someday._

 

 Yeah 3 channel seems such a waste of components, but that's me. I do need to buy a stereo kit from Jeff before/he runs out of them so I can build the BJT version.


----------



## luvdunhill

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Peter Millet's DC filament supply is very nice and robust if you want to go the DIY route which is what I am using._

 

perhaps that isn't what you think it is


----------



## sachu

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_perhaps that isn't what you think it is 
	

	
	
		
		

		
		
	


	


_

 

Could you elaborate please Marc. I thought that was a simple regulated DC heater supply which is what I am using it for.


----------



## spritzer

That's a filament supply not a heater supply, as in DHT's.


----------



## sachu

I thought the filament was the heater. Am I wrong? Isn't filament = heater ? I am still a noob when it comes to toobs so excuse my question if it sounds too basic 
	

	
	
		
		

		
		
	


	




 . Never heard of the term Direct Heated Tube (DHT) before.

 What is the difference between DHTs and say the 6GM8 tube? Would be much obliged if you could point me to some information on this. 

 That supply does great work as a heater supply though. Hardly any ripple and can source full 5A.


 Edit: NM, nikongod filled me in on what the basic differences are. Need to read up more on DHTs.


----------



## spritzer

Good to know that Ari stepped in for me.


----------



## liwei

What's a good fuse value? I'll have both the S22 and heater pulling from there.


----------



## runeight

Try 1A SB.


----------



## gabriel-dan

Hi,
 This question might not make any sense to most of you, but I have to ask. Is the 6.3v transformer heater absolutely necessary? Can I get away by omitting it all together and just wait a couple of minutes for the tubes to warm before attempting to listen to music?
 Thanks,
 gabriel


----------



## smeggy

No, the 6.3v transformer is what heats the tubes up. No transformer, no heat.

  Quote:


  Originally Posted by *gabriel-dan* /img/forum/go_quote.gif 
_Hi,
 This question might not make any sense to most of you, but I have to ask. Is the 6.3v transformer heater absolutely necessary? Can I get away by omitting it all together and just wait a couple of minutes for the tubes to warm before attempting to listen to music?
 Thanks,
 gabriel_


----------



## lybbert

Does any one still have a copy of the .XLS BOM i have seen one talked about several times but cant seem to find it. Thinking of building this for my next project to feed the new HD650's i have on the way.

 -Lybbert


----------



## sachu

Quote:


  Originally Posted by *lybbert* /img/forum/go_quote.gif 
_Does any one still have a copy of the .XLS BOM i have seen one talked about several times but cant seem to find it. Thinking of building this for my next project to feed the new HD650's i have on the way.

 -Lybbert_

 

I would strongly suggest you email Jef at Glassjaraudio. He will email you the BOM if you plan to buy the kit from him, which is well put together and cheap.

 The details of the parts list of the amp is up online here

 Great choice though..i fell in love with this amp the first time after listening to my HD580 (which I had at the time).


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ Yeah 3 channel seems such a waste of components, but that's me. I do need to buy a stereo kit from Jeff before/he runs out of them so I can build the BJT version._

 

I take it you've not heard one. I have, as that was the stepping stone to my balanced version. Think of it in the way the M^3 is to the b22. My M^3 is gone...


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I take it you've not heard one. I have, as that was the stepping stone to my balanced version. Think of it in the way the M^3 is to the b22. My M^3 is gone..._

 

Hmmm...I can't say I have done an extensive side by side comparison between a 2 channel passive ground and a 3 channel version..

 I just don't know if I am ready to go with a balanced rig just yet..


----------



## smeggy

sachu, we should get together and buy a kit and split it then we can both do active ground 
	

	
	
		
		

		
		
	


	




 Bill, is there a small component difference with an active ground channel like there is with the beta?


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_sachu, we should get together and buy a kit and split it then we can both do active ground 
	

	
	
		
		

		
		
	


	




 Bill, is there a small component difference with an active ground channel like there is with the beta?_

 

Yes there is Smeggy.

 Heh..I would love to do taht except I don't know where I would put that extra board in my case. I Like the way it is so compact, with the power supply all in one case.

 I would'nt mind building the ground channel up for you and test it out on my amp


----------



## HeadphoneAddict

Hey, I just want to say the balanced EHHA wiatrob built and brought to CanJam is a fantastic amp, and great with my K1000 and HD800. I'll be listening to it more here at my home and will give my final thoughts later.


----------



## DoYouRight

Sweet I cant wait for HPA's summary of it vs the big production model tube gears.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *DoYouRight* /img/forum/go_quote.gif 
_Sweet I cant wait for HPA's summary of it vs the big production model tube gears._

 

I can tell you right now that it beats my ZDT with K1000. Will have to see about everything else...


----------



## DoYouRight

that statement right there shows the effectiveness of DIY price difference!


----------



## sachu

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I can tell you right now that it beats my ZDT with K1000. Will have to see about everything else..._

 

Heh..I am not surprised..now, I would like to see how it does against the Balancing Act.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Heh..I am not surprised..now, I would like to see how it does against the Balancing Act. 
	

	
	
		
		

		
		
	


	


_

 

Well, Craig says the BA with 300B will do better with K1000, but I don't know if it can top the EHHA with K1000. 

 Also, the WA5 at RMAF wasn't that much better with K1000 than my ZDT, and it still sounded too laid back. Back in July the ZDT was better with K1000 than the borrowed prototype WA22 - while the WA22 had the power it didn't have the punch and control the K1000 needed. However, the new final revision of the WA22 at RMAF also sounded better to me with K1000 than the ZDT, or even the WA5. I don't think Jack Wu agreed with me on the WA22 vs WA5 (which uses 300B).


----------



## sachu

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Well, Craig says the BA with 300B will do better with K1000, but I don't know if it can top the EHHA with K1000. _

 

Interesting..I would love someone with the ability to do this comparison to try and do it. The EHHA was after all designed with the K1000 in mind while also catering to other headphones..so I would expect it to be quite formidable. 

 Now I have heard the AKG K1000 in singe ended configuration on my EHHA (same AKG K1K that Tyler has) but have no exposure to Craig's amps. 

 The EHHA made such a big impression on me when i had just started getting into this hobby that it was just unbelievable that only 3 or 4 of them existed till early this year even though the design had gone live back in 2006..


----------



## johnwmclean

Oh my where have I been, I’ve read this thread for the last 2 hours or so, my wallets just begging for mercy. Thank you sachu and smeggy for kicking this off and putting it on the map, I’m very keen for a balanced build.


----------



## sachu

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Oh my where have I been, I’ve read this thread for the last 2 hours or so, my wallets just begging for mercy._

 

 Well at least it will only bleed your wallet half as much as your balanced B22 did for sure 
	

	
	
		
		

		
		
	


	




.


----------



## johnwmclean

First steps to heaven, I have a question regarding gain - has anyone completed a balanced build yet? I’m thinking headphones only, my source outputs ~4VRMS - what would be a good starting point with 300ohm phones in balanced config? Maybe socketed resistors would be advisable.


----------



## nattonrice

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA HAHA

 I knew when I sent you that pm worded as it was that it'd only be a matter of hours until you were in here


----------



## sachu

Socketed resistors are an excellent idea..i have them on mine.

Wiatrob  and Ferrari have completed balanced builds
Impressions on wiatrob's balanced EHHA at RMAF

 I have a gain of 11 set on my EHHA. I find it plentiful for all headphones including the AKG K1000 (a bit higher would be desirable perhaps) except for my wharfedale ID1s which are just power hungry monsters.

 I think I would go with a total balanced gain of 14 or 16 in your case.

 My source outputs more than the normal 2VRMS as well.


----------



## johnwmclean

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA HAHA

 I knew when I sent you that pm worded as it was that it'd only be a matter of hours until you were in here 
	

	
	
		
		

		
			



_

 

I can’t help it, I’m weak - you bait me too well. LOL. 
	

	
	
		
		

		
		
	


	



 Any Mogami? You must be tearing your hair out if not, I must admit though just looking at that rig probably rivals the listening experience.

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Socketed resistors are an excellent idea..i have them on mine.

Wiatrob  and Ferrari have completed balanced builds
Impressions on wiatrob's balanced EHHA at RMAF

 I have a gain of 11 set on my EHHA. I find it plentiful for all headphones including the AKG K1000 (a bit higher would be desirable perhaps) except for my wharfedale ID1s which are just power hungry monsters.

 I think I would go with a total balanced gain of 14 or 16 in your case.

 My source outputs more than the normal 2VRMS as well._

 

sachu that’s a great help! I see Ferrari has gone crackers with tour de force eye candy piece. Lovely!


----------



## nattonrice

OMG no... the fedex arrives tomorrow while I'm teaching. Very crap.
 For the last 3 days I've been listening to the dac with a mini3 and some um3x iems.
 Awesome but it is not the b22 lol.

 Yeah Ferrari's build is out of this world. I love the tube sound meter thing.


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Socketed resistors are an excellent idea..i have them on mine._

 

Yes, I have sockets for gain and CLG on mine as well. I have a gain or about 14 now (7*2). Get's thunderously loud but haven't heard it clip - it'll drive the K1Ks quite well...


----------



## HeadphoneAddict

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_First steps to heaven, I have a question regarding gain - has anyone completed a balanced build yet? I’m thinking headphones only, my source outputs ~4VRMS - what would be a good starting point with 300ohm phones in balanced config? Maybe socketed resistors would be advisable._

 

EDIT - I had the window open for hours, and replied, and lo and behind the master replied before me.


----------



## dBel84

Agreed with wiatrob, you don't want more than 7 per board , you may get away with 3 or 4 per board as balanced doubles this. Socketing the open and closed feedback resistors would be strongly advised, both to tweak the sound and adjust the gain. 

 ..dB

 edit 

 an alternative option is to set up the amp the way steinchen did - he used a switch to adjust the gain between 6,9 and 12 with no other volume control. ie choose your gain, fire up the amp and sit back and listen. 











 a few pics of his prototype


----------



## sachu

I love the simplicity in that build...Wish I had though of the gain switch for my build. Getting rid of the pot is a fantastic idea.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I love the simplicity in that build...Wish I had though of the gain switch for my build. Getting rid of the pot is a fantastic idea._

 

Well, I think it's a bad idea myself. I would never give a second thought to an amp that effectively has a volume control with 3 steps + power off.


----------



## johnwmclean

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Agreed with wiatrob, you don't want more than 7 per board , you may get away with 3 or 4 per board as balanced doubles this. Socketing the open and closed feedback resistors would be strongly advised, both to tweak the sound and adjust the gain. 

 ..dB

 edit 

 an alternative option is to set up the amp the way steinchen did - he used a switch to adjust the gain between 6,9 and 12 with no other volume control. ie choose your gain, fire up the amp and sit back and listen._

 

Nice heatsinks, are they for show only?


----------



## HeadphoneAddict

I have the EHHA here on loan, and while it still isn't perfect with the K1000 it is clearly better with the K1000 over the ZDT in a few areas. 

 (1) the bass is tighter and more defined with the EHHA and K1000, with not as much of a bass cloud although still a little muddy vs the HD800 tight bass, 
 (2) The mids are not as forward or over-present as they are with the ZDT and it's less colored, and 
 (3) the treble with the EHHA has a slight increased sparkle over the ZDT with the K1000, although the ZDT treble improves as it heats up for a couple of hours.

 I am going to try rolling some 12AX7/5751 tubes in the ZDT and see what that does. The GE grey plate 5751 in the ZDT right now is perfect with the HD800/600 RS-1/HF-2 and LA7000, while the stock Mullard re-issue was a little brighter and edgier and this one is smoother and softer. I have a GE black plate 5751, a couple of Tung Sol 5751, a Telefunken smooth plate 12AX7, and the old 12BZ7 from the GES that Craig says is okay to use. He said my Mullard 12AU7 or Siemens ECC82 wont bias right.

 Will have HiFlight's SAC K1000 amp here Monday or Tuesday to compare the two.


----------



## dBel84

HPA , how is the EHHA set up?

 Tubes, closed loop , open loop etc - this amp can be tweaked to sound just about anyway you want it to. 

 ..dB


----------



## smeggy

Yeah, I have the snipped resistor feedback thing going and 6h30 tubes through a bigger 4A heater supply, shunted pot attached directly to the DAC output and it's just fantastic sounding. Tweaking on this is key to getting the sound you want.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_HPA , how is the EHHA set up?

 Tubes, closed loop , open loop etc - this amp can be tweaked to sound just about anyway you want it to. 

 ..dB_

 

I don't know abut feedback or tubes - you'd have to ask Bill (wiatrob). Other details - I hooked it up to the PS Audio DLIII XLR out with anti-cables XLR IC, and the ZDT is hooked up to the PS Audio RCA out with anti-cables RCA IC, with Macbook as optical source. I believe the gain is set up as 2x7.

 It's similar to what I remember Naamanf's B22 sounding with his K1000, but that was back in February.


----------



## Pars

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Agreed with wiatrob, you don't want more than 7 per board , you may get away with 3 or 4 per board as balanced doubles this. Socketing the open and closed feedback resistors would be strongly advised, both to tweak the sound and adjust the gain. 

 ..dB

 edit 

 an alternative option is to set up the amp the way steinchen did - he used a switch to adjust the gain between 6,9 and 12 with no other volume control. ie choose your gain, fire up the amp and sit back and listen. 











 a few pics of his prototype_

 

Where do you find right-angle tube sockets like those? I realize this is Steichen's build...


----------



## dBel84

they are "home jigged" thick wire soldered and bent for the purpose ..dB


----------



## wiatrob

It's got ~11-12 gain (5.5 or 6 x2) now. It has lower OL gain (10K or 33K) controlling the negative feedback. All these resistors are socketed.

 Also, Larry - does it seem to have enough power? I think the amp as built produces about 18 Watts, but with MOSFETS and some tweaks it could go to 25W...

 Yes, as it's setup, it does sound a bit B22 ish... 
	

	
	
		
		

		
			






  Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I don't know abut feedback or tubes - you'd have to ask Bill (wiatrob). Other details - I hooked it up to the PS Audio DLIII XLR out with anti-cables XLR IC, and the ZDT is hooked up to the PS Audio RCA out with anti-cables RCA IC, with Macbook as optical source. I believe the gain is set up as 2x7.

 It's similar to what I remember Naamanf's B22 sounding with his K1000, but that was back in February._


----------



## jjazzyj

Well, I'm enjoying my SOHA II so much, that it seems weird to want to build another amp, but I'm bored and I like electronics DIY. I want to use the EHHA as a headphone amp/preamp. Is the 3 channel version really that much better than the 2 channel version for headphones? It will mostly be used as a headphone amplifier as I haven't decided which power amp to build yet. I really like the FET Circlotron on the PassDIY site but I'd need to build a balanced EHHA and follow the wiring diagrams at the AMB site to convert my unbalanced source to balanced. But in any case, how well would the EHHA perform as a preamp and would it be limited to certain power amps?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_It's got ~11-12 gain (5.5 or 6 x2) now. It has lower OL gain (10K or 33K) controlling the negative feedback. All these resistors are socketed.

 Also, Larry - does it seem to have enough power? I think the amp as built produces about 18 Watts, but with MOSFETS and some tweaks it could go to 25W...

 Yes, as it's setup, it does sound a bit B22 ish... 
	

	
	
		
		

		
		
	


	


_

 

I sent you some PM last night, and was planning to post some of those impressions when I am done listening to the EHHA.

 It definitely has enough power vs the ZDT. I was worried the SAC KH1000 amp would have too much power for K1000 phones, but HiFlight assures me they can take it.

 The EHHA with my re-cabled HD800 and PS Audio DL III DAC in 192Khz mode is a little bright sounding, while the ZDT is just right. The PSA tone changes with the 96K/192K up-sampling toggle and is less bright but also less expansive/wide sounding in 96K mode. So, if I switch the PSA DAC to 96K up-sampling then the EHHA soundstage closes in a little, while the brightness goes away and sounds better. At that point EHHA with PSA at 96K sounds very similar to the ZDT with the DAC still in 192K mode, in both freq response and sound stage width but not depth. As it was, the ZDT soundstage is a little deeper either way, and the ZDT was a little more refined and rich sounding as well. Maybe with the right tweaks making the EHHA useable with re-cabled HD800 + the PSA in 192K mode, the EHHA could have a little more expansive soundstage with more separation than the ZDT. But I don't know if the refinement and richness of the ZDT would be surpassed. 

 I can't guess which amp would be better without hearing the imaginary tweaks first. Regardless of HD800 or K1000, the EHHA is a great amp. It comes close to the ZDT with HD800, while driving the K1000 a little better than the ZDT. With K1000/EHHA the 192K mode in the PSA was much better than with the DLIII 96K mode. But it doesn't drive the K1000 quite as well as the SAC KH1000 amp but it is close, and the EHHA soundstage is still better than the SAC soundstage. The EHHA is tubier warmer richer than the SAC with K1000, but it is not quite as tight, detailed or extended as the SAC amp with K1000. The K1000 sound duller with the ZDT than EHHA, but even with the improved treble via EHHA the K1000 still sound duller with the EHHA than with the SAC amp. So, the EHHA splits the fence between the better K1000/SAC or better HD800/ZDT combo - being good with both but not the best with either.

 Both the ZDT and the EHHA were a better match for my re-cabled HD800 than the SAC KH1000 amp which made the HD800 a bit bright and edgy, but I will try the HD800 stock cable to tame the SAC highs and see how that sounds tonight. And, I'll see if the stock HD800 cable allows me to use the DAC in 192K mode with the EHHA as well.


----------



## funch

Can someone give me the dimensions of the EHHA board? 
 Pleeeeeze?! And thank you.


----------



## runeight

It's approximately 4" x 3.5".

 I was not as careful about board sizing back then as I am now. 
	

	
	
		
		

		
		
	


	




 I'd post the silkscreen but the pdf exceeds the attachment size of 19.5kB.


----------



## digger945

Zackly:

 3.6425"(3 41/64") or 92.52mm
 X
 3.9800"(3 63/64") or 101.10mm







 EDIT: Big un beat me to it LOL.


----------



## funch

Thanks, guys.


----------



## wiatrob

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_Well, I'm enjoying my SOHA II so much, that it seems weird to want to build another amp, but I'm bored and I like electronics DIY. I want to use the EHHA as a headphone amp/preamp. Is the 3 channel version really that much better than the 2 channel version for headphones? It will mostly be used as a headphone amplifier as I haven't decided which power amp to build yet. I really like the FET Circlotron on the PassDIY site but I'd need to build a balanced EHHA and follow the wiring diagrams at the AMB site to convert my unbalanced source to balanced. But in any case, how well would the EHHA perform as a preamp and would it be limited to certain power amps?_

 


 There's some debate about the benefits of a three channel EHHA. I'v enever heard a two channel - only three and fully balanced with fully balanced sources. I think much of the benefits of this design coulod be realized in a two channel build.

 That said I love my balanced BJT EHHA - but am thinking about building atwo/three channel MOSFET version to compare...(nuts? Yup!)


----------



## johnwmclean

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_It's got ~11-12 gain (5.5 or 6 x2) now. It has lower OL gain (10K or 33K) controlling the negative feedback. All these resistors are socketed.

 Also, Larry - does it seem to have enough power? I think the amp as built produces about 18 Watts, but with MOSFETS and some tweaks it could go to 25W...

 Yes, as it's setup, it does sound a bit B22 ish... 
	

	
	
		
		

		
		
	


	


_

 

wiatrob could you please let me know what value of the resistor for R13 for a gain of 5.5


----------



## jjazzyj

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_There's some debate about the benefits of a three channel EHHA. I'v enever heard a two channel - only three and fully balanced with fully balanced sources. I think much of the benefits of this design coulod be realized in a two channel build.

 That said I love my balanced BJT EHHA - but am thinking about building atwo/three channel MOSFET version to compare...(nuts? Yup!) 
	

	
	
		
		

		
		
	


	


_

 

Ok, I've been thinking about what I want to do. Because this amp is going to be upstairs, it is more than likely going to be doing triple duty. Light speaker amp and headphone amp. I'll probably include a pre/loop out just because. If I build a balanced EHHA will I need 4 S22's just like the B22? I'm thinking so. 

 I was planning on using a 500VA Xfmr with the 4 S22's (If I need them), it might need to be in a separate enclosure. The heater supply will be a 100VA Xfmr with LM338K To-3 based regulator circuit as the EHHA web page specifies.

 All of the FET's on the EHHA boards and the S22 will be upgraded to 2.5" heatsinks. 

 Is this going to work okay for mostly headphone with light speaker/preamp duty?


----------



## wiatrob

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_wiatrob could you please let me know what value of the resistor for R13 for a gain of 5.5 
	

	
	
		
		

		
		
	


	


_

 


 I made a spreadsheet that calculates arbitrary gains, let me find it and I'll send it on - there is a discussion earlier in this thread where the formula was mentioned.


----------



## wiatrob

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_Ok, I've been thinking about what I want to do. Because this amp is going to be upstairs, it is more than likely going to be doing triple duty. Light speaker amp and headphone amp. I'll probably include a pre/loop out just because. If I build a balanced EHHA will I need 4 S22's just like the B22? I'm thinking so. 

 I was planning on using a 500VA Xfmr with the 4 S22's (If I need them), it might need to be in a separate enclosure. The heater supply will be a 100VA Xfmr with LM338K To-3 based regulator circuit as the EHHA web page specifies.

 All of the FET's on the EHHA boards and the S22 will be upgraded to 2.5" heatsinks. 

 Is this going to work okay for mostly headphone with light speaker/preamp duty?_

 


 You will need only a single S22 for a balanced EHHA. Pay attention to your heater supply though, especially if you plan on using 6H30s...


----------



## jjazzyj

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_You will need only a single S22 for a balanced EHHA. Pay attention to your heater supply though, especially if you plan on using 6H30s..._

 

Even if I'm planning on running speakers off the EHHA?

 That's why the 100VA xmfr with the LM338K.

 12v @ 4.3A and the LM338K handles a maximum of 5A So that should cover me.


----------



## Ferrari

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_Even if I'm planning on running speakers off the EHHA?

 That's why the 100VA xmfr with the LM338K.

 12v @ 4.3A and the LM338K handles a maximum of 5A So that should cover me._

 

Balanced EHHA with one σ22 PS is fine for headphones but for speakers duty… NO!!!
 For speakers duty you are better off with 2 σ22 PS, with adequate heatsinking of course.

 I’m driving AKG K1000 via my balanced EHHA with one σ22 PS, soundwise excellent performing however, the 2” heatsinks are getting very hot in the long run.


----------



## jjazzyj

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Balanced EHHA with one σ22 PS is fine for headphones but for speakers duty… NO!!!
 For speakers duty you are better off with 2 σ22 PS, with adequate heatsinking of course.

 I’m driving AKG K1000 via my balanced EHHA with one σ22 PS, soundwise excellent performing however, the 2” heatsinks are getting very hot in the long run._

 

I thought as much. I was reading the PS req's on the AMB site and figured that the same rules applied to the EHHA. I just bought a pair of AKG K240MKII and realized that with some surgery I won't be able to balance them 
	

	
	
		
		

		
		
	


	




 A 3 pin mini XLR can't be made into a balanced connection. The thought of being able to run two unbalanced Headphones with separate volume controls is a nice option when a friend comes over to watch movies/play games when the wife is sleeping though!!

 So here's the plan:

 4 EHHA channels with 2.5" heatsinks
 500VA xfmr running 4 S22's with 2.5" heatsinks
 100VA xfmr attached to a LM338K based regulated DC heater supply
 2 Neutrik Combo XLR/TRS Jacks
 Pre Out switch/Loop out Switch
 Heaphone/Speaker output switch(es)

 I think that will satisfy the power requirements, the only question will be if the 2.5" heatsinks are enough.

 Anyone here have any input?


----------



## wiatrob

Runeight will have to weigh in - but I think you are going way overkill with 4 sigma22s. The output devices won't draw/handle the amount of juice they'll generate.This amp, while it performs in the b22 league, is NOT designed to draw like 4 b22 boards.

 Cut two out and spend the money on a great stepped attenuator...


----------



## wiatrob

Can't find the calculator - but here's the simplified gain formula:


  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_So, can I be safe in assuming that for this amp:

 Gain = 1/[R13/(R12+R13)]
_


----------



## jjazzyj

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Runeight will have to weigh in - but I think you are going way overkill with 4 sigma22s. The output devices won't draw/handle the amount of juice they'll generate.This amp, while it performs in the b22 league, is NOT designed to draw like 4 b22 boards. 

 Cut two out and spend the money on a great stepped attenuator..._

 

Hey, I'm all for saving money. I just want to make sure I don't over tax the S22. I've seen some people around here build a 2 channel B22 that runs speakers off of 1 S22. I didn't realize that the B22 draws so much more power than the EHHA.

 According to the EHHA website the 2.5" heatsinks are adequate for speaker duty, however my calculation show that it is coming close to max Junction temp for the mosfets.

 There is one piece of info that I don't know to calculate the value accurately: How much voltage is across the mosfets?

 I used 22V but that may not be accurate.


----------



## johnwmclean

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Can't find the calculator - but here's the simplified gain formula:_

 

Champion! Thanks wiatrob


----------



## wiatrob

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Champion! Thanks wiatrob 
	

	
	
		
		

		
		
	


	


_

 


 No problem - Solve for your target R's and pick the next closest common resistor value...


----------



## luvdunhill

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_my calculation show that it is coming close to max Junction temp for the mosfets_

 

Hopefully your calculation is wrong. The maximum I'd ever run a device would be half of the max junction temperature. Care to show your math?


----------



## jjazzyj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Hopefully your calculation is wrong. The maximum I'd ever run a device would be half of the max junction temperature. Care to show your math?_

 

I = √(Po / 8) 

 P=V * I

 Tj = Ta + (P * (Rjc + Rcs + Rsa))

 Po=18W
 Rjc=3.3C/W
 Rcs=.9C/W
 Rsa=2.6C/W
 V=22V (voltage across mosfets, B22 example)
 I=1.5
 Ta=40C
 P=9.9W


 I've assumed that playing real music I'll only be using 30% of the current calculated which makes I=.45 instead of 1.5.

 Tj=107.32C

 Max Junction temp of the Mosfet is 175C

 So my initial calc was a a little off as it showed 165C.

 It is entirely possible for the internal temp of the chassis to exceed 40C which would be cutting it close IMO.

 I am planning a perforated metal top, so that may never happen.


----------



## runeight

I believe this number if you're using the EHHA as a speaker amp??

 A while back in the thread I'm pretty sure that I mentioned that external heatsinks would be needed for speaker duty. My apologies if this comment did not reach you. I know it is not mentioned on the website which only considers the amp as a headphone amplifier. Hopefully, this doesn't make a whole lot of build trouble for you.


----------



## HeadphoneAddict

I reluctantly returned the EHHA to wiatrob Wednesday. I highly recommend the EHHA to any DIY'ers out there.

 To summarize - It's a great amp with my balanced phones (HD600/800 and K1000), that has better soundstage and separation than my WA6 (using SE adapter with same phones), and beats my WA6 and ZDT with K1000 due to better power and control. Bill says it's good for about 18 watts as it is configured. So, I don't know if it is very good with IEM like the WA6 because my IEM are not balanced, but I suspect the gain would be too high for them.


----------



## jjazzyj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I believe this number if you're using the EHHA as a speaker amp??

 A while back in the thread I'm pretty sure that I mentioned that external heatsinks would be needed for speaker duty. My apologies if this comment did not reach you. I know it is not mentioned on the website which only considers the amp as a headphone amplifier. Hopefully, this doesn't make a whole lot of build trouble for you. 
	

	
	
		
		

		
		
	


	


_

 

The website actually mentions 2.5" heatsinks for speaker duty.

 Heatsinks

 * For headphone amplifier use use Wakefield 647-15ABP or equivalent.
 * For speaker amplifier use Wakefield 647-25ABP or equivalent.

 According to the calculations in my previous post they should be okay as long as I don't crank it too much. I do have some salvage heatsinks that I could use.






 Probably excessive. They're from old tv broadcast tower equipment.


 EDIT: I found the post you were referring to. It details the resistor changes that need to happen as well (beyond the 2W resistor changes). You mentioned that the 2.5" heatsinks would be ok and my previous post more or less indicates the same. Though if I started to stray beyond the 30% too much external heatsinks would be required. You also mentioned that one S22 is ok for 1A peaks. My previous calculations indicate a peak of 1.5A for the full 18W but that might not ever happen. If I found I was running into issues I could always add an S22 later.

 Thanks for pointing me in the right direction!


----------



## liwei

Going through the initial setup and getting 29v on R3, R4 on both of my boards. Anything specific I should look at?
 Unfortunately, I already soldered the opamp so does that mess things up? One board passed the output quiescent current and DC offset checks before I shorted a mosfet. Q9M is gone but what other components should I check? R33 is fine.


----------



## sachu

umm..are you checking voltage across R3 and R4? Am guessing you have one probe on R3/R4 and the other to ground in which case you will probably see close to rail voltage.

 You should be having the probes set on either side of the resistors...can you confirm this?


----------



## liwei

Oh, sorry. I was checking relative to ground. I think it was about .6v across R3 and R4. I'll check the boards again later when I get a new fuse.


----------



## luvdunhill

In my opinion, those heat sinks are woefully small. Also, the fin orientation doesn't help much either. I would not run the devices anymore than half their max junction temperature, as stated above. I know for example Nelson Pass has been known to quote the same estimate, and it's a good one.

 There are a few flaws in your calculations. You aren't considering the thermal resistance of the isolator and/or thermal compound. Also, the thermal resistance of the heat sink is not constant across its operating temperature. Thus, you may need to derate the quoted spec, depending at what ambient temperature it was given. Here is one manufacturers derating curve:






 If you're looking for a number, I'd recommend something in the 0.5 C/W range, per channel. Perhaps you can inquire what size Conrad heat sink Farrari is using, it looks to be about the right size and fin orientation.


----------



## sachu

Quote:


  Originally Posted by *liwei* /img/forum/go_quote.gif 
_Oh, sorry. I was checking relative to ground. I think it was about .6v across R3 and R4. I'll check the boards again later when I get a new fuse._

 

yeah...good strategy.

 That Q9M really is a PITA...well it was for me at least..i ended up blowing a half a dozen of them due to various reasons, only on one particular board though. Once you have it going though, the amp is rock steady.


----------



## Lifthanger

Hi fellow EHHA builders. My GJA kit arrived months ago, but I was out with a broken clavicle. The sigma22 is done now. But it only reads 28.5V unloaded. Is this common? Used the parts for the 30V build.


----------



## digger945

Depending on one resistor and one zeners accuracy, and the output of your transformer, I would say your probably right on the money for your build.


----------



## johnwmclean

Lifthanger yes is fine, expect some variation in tolerances within the D5 zener diode and resistors.

 Beat me to it digger945.


----------



## MrMajestic2

Ok, I'm finally gearing up to order my first EHHA kit. Fully balanced with the PSU section in a separate case. Only a few questions to answer first:
 6.3V or 12.6V heater supply?
 Delay circuit for the heater supply?

 For the heater supply I'm thinking of going with H-PS-1 from Glassware, seems like a good kit. What are the pros and cons of the respective voltages?

 I know I saw a ready made delay circuit, but I cant seem to find it again. What are you guys using?


----------



## Lifthanger

thanks


----------



## jjazzyj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_In my opinion, those heat sinks are woefully small. Also, the fin orientation doesn't help much either. I would not run the devices anymore than half their max junction temperature, as stated above. I know for example Nelson Pass has been known to quote the same estimate, and it's a good one.

 There are a few flaws in your calculations. You aren't considering the thermal resistance of the isolator and/or thermal compound. Also, the thermal resistance of the heat sink is not constant across its operating temperature. Thus, you may need to derate the quoted spec, depending at what ambient temperature it was given. Here is one manufacturers derating curve:







 If you're looking for a number, I'd recommend something in the 0.5 C/W range, per channel. Perhaps you can inquire what size Conrad heat sink Farrari is using, it looks to be about the right size and fin orientation._

 

That picture doesn't really show how large those heatsinks are. They are 12" long 5 3/4" wide and 2" thick. They weigh around 2lbs each.

 I am taking the isolation compound into consideration, that's Rcs=.9C/W according to the Aavid Thermalloy specs.


----------



## dBel84

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_...Only a few questions to answer first:
 6.3V or 12.6V heater supply?
 Delay circuit for the heater supply?_

 

This amp is designed for the 6GM8 , you can use the 6DJ8 or 6H30. Thus 6.3V is the choice for parallel, 12.6V if you want to run them in series. Take note of the current requirement of the heaters before deciding what you want. 

 I will let others answer your delay circuit Q as I use manual delay 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## sachu

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I know I saw a ready made delay circuit, but I cant seem to find it again. What are you guys using?_

 

Here you go...Tube B+ delay kit


----------



## runeight

Gents, I am finally able to pay more attention to this thread.

 First, jjazzyj, I want to apologize for the previous post. Whoever put on the EHHA website that 2.5" heatsinks were adequate for speaker duty is an idiot. The best explanation I can offer is that I wasn't really paying attention.

 You guys have mostly sussed this out, however. At 18W into 4R each mosfet will burn about 18W itself. This is they typical effiency for class AB (mostly B) operating condition.

 If we can live with a 40C temp rise over a 25C ambient this will put us at 65C, ten degrees less than the halfway point to 150C.

 Now I know we won't have ambient but just to get a ballpark number this is 40C / 18W or about 2C/W. Given all the various thermal barriers between the junction and the air I think that Marc's recommendation that the heatsink itself needs to be 0.5C/W is a good one.

 And, of course, only off-board heatsinks can do this.


----------



## MrMajestic2

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Here you go...Tube B+ delay kit_

 

 Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_This amp is designed for the 6GM8 , you can use the 6DJ8 or 6H30. Thus 6.3V is the choice for parallel, 12.6V if you want to run them in series. Take note of the current requirement of the heaters before deciding what you want. 

 I will let others answer your delay circuit Q as I use manual delay 
	

	
	
		
		

		
		
	


	




 ..dB_

 

Great, thanks guys.


----------



## johnwmclean

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_This amp is designed for the 6GM8 , you can use the 6DJ8 or 6H30. Thus 6.3V is the choice for parallel, 12.6V if you want to run them in series. Take note of the current requirement of the heaters before deciding what you want._

 

So what are the pros and cons for in series vs parallel?
 I've lost it here...


----------



## luvdunhill

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_So what are the pros and cons for in series vs parallel?
 I've lost it here..._

 

My opinion is that when you can run lower _current_ heaters, do it. That means you have some sort of choice via a center tap heater. Otherwise, there isn't much you can really do.


----------



## sachu

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_My opinion is that when you can run lower current heaters, do it. That means you have some sort of choice via a center tap heater. Otherwise, there isn't much you can really do._

 


 Humbly suggest the opposite, atleast for the EHHA..Run it in 6.3 volt configuration so you can use the 6H30 which has a fuller sound all around albeit a bit rolled off at the top compared to the 6GM8..doesn't cost all that much more to up the heater supply circuit to handle the extra current.

 You can always play around with the NFB to get taht top end back with the 6H30s


----------



## luvdunhill

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_That picture doesn't really show how large those heatsinks are. They are 12" long 5 3/4" wide and 2" thick. They weigh around 2lbs each._

 

how do you plan to attach the devices to the heat sink, via angle bracket? That's how I'd do it... Don't forget to add that in. But really, the fin orientation is the big hurt with those... Now, how can you measure the thermal resistance? I'd tell you, but it was a scarring experience that started when I got in between my wife and the oven in the kitchen


----------



## luvdunhill

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Humbly suggest the opposite, atleast for the EHHA..Run it in 6.3 volt configuration so you can use the 6H30 which has a fuller sound all around albeit a bit rolled off at the top compared to the 6GM8..doesn't cost all that much more to up the heater supply circuit to handle the extra current.

 You can always play around with the NFB to get taht top end back with the 6H30s_

 

er? What I meant is, either you have a center tap to work with or you don't. When you do, use the lower current option (assuming you are willing to change the heater voltage when you roll in new tubes, perhaps that's what you're getting at).


----------



## sachu

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_er? What I meant is, either you have a center tap to work with or you don't. When you do, use the lower current option (assuming you are willing to change the heater voltage when you roll in new tubes, perhaps that's what you're getting at)._

 

Don't bother running the EHHA at 12.6 volts is what I am getting at. Just run them in parallel at 6.3 volts instead of series.


----------



## luvdunhill

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Don't bother running the EHHA at 12.6 volts is what I am getting at. Just run them in parallel at 6.3 volts instead of series._

 

ahh... ok 
	

	
	
		
		

		
			





 I figured johnwmclean's was a more general question I guess. Carry on..


----------



## jjazzyj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I am finally able to pay more attention to this thread.

 First, jjazzyj, I want to apologize for the previous post. Whoever put on the EHHA website that 2.5" heatsinks were adequate for speaker duty is an idiot. The best explanation I can offer is that I wasn't really paying attention.

 You guys have mostly sussed this out, however. At 18W into 4R each mosfet will burn about 18W itself. This is they typical effiency for class AB (mostly B) operating condition.

 If we can live with a 40C temp rise over a 25C ambient this will put us at 65C, ten degrees less than the halfway point to 150C.

 Now I know we won't have ambient but just to get a ballpark number this is 40C / 18W or about 2C/W. Given all the various thermal barriers between the junction and the air I think that Marc's recommendation that the heatsink itself needs to be 0.5C/W is a good one.

 And, of course, only off-board heatsinks can do this._

 

My calculation were for 8ohm drivers, and even then it was really close. So the recommendation for .5C/W is definitely required. Thanks.

  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_how do you plan to attach the devices to the heat sink, via angle bracket? That's how I'd do it... Don't forget to add that in. But really, the fin orientation is the big hurt with those... Now, how can you measure the thermal resistance? I'd tell you, but it was a scarring experience that started when I got in between my wife and the oven in the kitchen 
	

	
	
		
		

		
		
	


	


_

 

Via Aluminum Angle, yes. And I would have to guess at the thermal resistance on that as well. Grease between the two as well. The fin density on those heatsinks isn't that great, they are a big honkin' piece of aluminum however. And I'd have no idea how to measure the terminal resistance on that bad boy. And the shape doesn't lend itself to chassis manufacture very well. 

 What do you think of this heatsink?

NEW HEATSINK ALUMINUM EXTRUSION LARGE 7.29" WIDE on eBay.ca (item 170397104041 end time 27-Oct-09 17:23:14 EDT)

 The shipping from Australia(Conrad) seems like it would be a killer.

 I'd cut the heatsink into 4" length with the fins upright so that I'd have 2 EHHA channels(Balanced) on both sides, each with their own heatsink. It is very similar to the Conrad MF-20-100 which is .47C/W.


----------



## jjazzyj

This is probably another nub question as I know you really should try to avoid this...

 When air wiring the mosfets you should solder the gate resistor directly to the pin? Is this correct? To prevent oscillation. I hope I read that right.


----------



## runeight

That certainly would work. You say shipping from Oz. Is there no US manufacturer for something like this?

 As an aside, how is it working as a speaker amp. I don't think anyone else has yet done this unless maybe Ferrari.


----------



## runeight

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_This is probably another nub question as I know you really should try to avoid this...

 When air wiring the mosfets you should solder the gate resistor directly to the pin? Is this correct? To prevent oscillation. I hope I read that right._

 

Yes.


----------



## jjazzyj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_That certainly would work. You say shipping from Oz. Is there no US manufacturer for something like this?

 As an aside, how is it working as a speaker amp. I don't think anyone else has yet done this unless maybe Ferrari._

 

I mentioned Australia because of the previous mention of Conrad Heatsinks. The ebay link is an American seller with a 25$ flat rate shipping fee to Canada.

 I can't find any other heatsinks like that around here.

 This is mostly going to be used as balanced/dual headphone amp, with occasional speaker use. I'm excited about getting it to work. SOHA II was too easy


----------



## luvdunhill

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I'd cut the heatsink into 4" length with the fins upright so that I'd have 2 EHHA channels(Balanced) on both sides, each with their own heatsink. It is very similar to the Conrad MF-20-100 which is .47C/W._

 

yup, the heatsinkusa stuff would work well. In case you'd prefer to order outside of Ebay, here's a link to their website:

HeatsinkUSA, llc

 Since the boards don't seem conducive to using angle brackets, why not mount the board on the heat sink itself, then mount the devices in the following "bottom mount" configuration:






 It looks like the hole on the board could be enlarged in order to fit a screwdriver through in order to secure the device... make sense?


----------



## jjazzyj

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_yup, the heatsinkusa stuff would work well. In case you'd prefer to order outside of Ebay, here's a link to their website:

HeatsinkUSA, llc

 Since the boards don't seem conducive to using angle brackets, why not mount the board on the heat sink itself, then mount the devices in the following "bottom mount" configuration:






 It looks like the hole on the board could be enlarged in order to fit a screwdriver through in order to secure the device... make sense?_

 

Thanks for the website address. I've been thinking about your mounting idea in combination with chassis configuration. I was hoping to expose the tubes for the 'coolness' factor. Though with a perforated top you could still see them I suppose  The tubes would be horizontal inside the chassis with the heatsinks on the side. On the upside a simple vented top could be used and then the amp could be stacked a lot easier. 

 Thanks for the ideas. I think that I will forgo the coolness factor for practicality this time.


----------



## Dougie085

That guy on ebay's heatsinks are fantastic, I've ordered several before.


----------



## johnwmclean

I have my kits coming from GJA early next week 
	

	
	
		
		

		
		
	


	




 I’m planning something very special, monoblocks 
	

	
	
		
		

		
		
	


	



 There will be a total of 4 enclosures, 2 of them for sigma22’s and the other 2 for balanced EHHA amps. This of course means 2 IEC’s sockets and 2 stereo attenuators as well as umbilicals, not to mention relays and heater psu’s for each monoblock.


----------



## sachu

ooh...waay too complicated a setup for something that isn't as sensitive to noise pickup as a B22...but yeah..whatever works for you.


----------



## nattonrice

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_I’m planning something very special, monoblocks 
	

	
	
		
		

		
		
	


	



 There will be a total of 4 enclosures, 2 of them for sigma22’s and the other 2 for balanced EHHA amps._

 

Dear God O.O

 At the next meet we'll need a third person to get back to your car =P


----------



## johnwmclean

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ooh...waay too complicated a setup for something that isn't as sensitive to noise pickup as a B22...but yeah..whatever works for you._

 

I know this is despicable overkill 
	

	
	
		
		

		
		
	


	





  Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_Dear God O.O

 At the next meet we'll need a third person to get back to your car =P_

 

hehehe, “where gonna need a bigger boat”


----------



## sachu

Oh wait...you mean two balanced EHHA confgured as mono block speaker amps?

 Yeah then the idea works fine....sweet..looking forward to this one.


----------



## nattonrice

I think he meant the HR Block head but with out the "stitch together" face and back plates.
 ... 4 box solution lol


----------



## runeight

Go for it. 
	

	
	
		
		

		
			





 Just don't forget the off-board heatsinking.


----------



## wink

Johnwmclean said "I know this is despicable overkill "

 What's overkill for some is necessity for others.


----------



## les_garten

How about this for a PS for the heaters?
BJB06SA-U ETA-USA Linear & Switching Power Supplies

 There is a PDF showing the 6v version. Also says you can adjust 10% Any downside?


----------



## Arlekiin

Hello people, 

 So I keep reading about EHHA II but on the Cavali audio site it says its in the works? So I am confused if there are EHHA II's built already or not? And if they are where can I find the partslist and the schematic?

 Also has anyone made any comparisons EHHA vs Darkvoice 337SE etc?


----------



## TimJo

My memory is that the EHHA II is a speaker amp rather than a headphone amp (but I might be wrong). As far as I know, it doesn't exist yet, other than the schematics Alex is working on, but he will know for sure...


----------



## sachu

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_How about this for a PS for the heaters?
BJB06SA-U ETA-USA Linear & Switching Power Supplies

 There is a PDF showing the 6v version. Also says you can adjust 10% Any downside?_

 

Too spendy Les,

 Suggest getting the one from glassware instead


----------



## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Too spendy Les,

 Suggest getting the one from glassware instead_

 

I think price will work out about the same. I wold need two of these for the 6H30s. But the lack of switching would be an advantage with the Glassware product. The switching PS does not need a Transfo winding.


----------



## Arlekiin

Thanks for clearing that up for me TimJo.

 Aight after some searching around I am starting to think that if I want something really tubesounding I should go with Morgan Jones or something....


----------



## jjazzyj

I haven't followed up on my EHHA plans for a while. I have ordered my kit from Glass Jar. But knowing how busy Jeff is I have some time yet to order the rest of my parts.

 Since I'm doing a speaker amp, I got a custom transformer made 60VCT @ 5amps, 12V @ 5amps. 360VA Total






 It's quite large and heavy.

 I made a mistake and only ordered one o22 power supply when I should have ordered two as suggested by Ferrari. So until I get the second o22 I'll have to stick to headphones. Speaking of headphones, does anyone know of any additional modification to the amp required to run both headphones or speaker on the same amp? Or is none needed?


----------



## les_garten

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I haven't followed up on my EHHA plans for a while. I have ordered my kit from Glass Jar. But knowing how busy Jeff is I have some time yet to order the rest of my parts.

 Since I'm doing a speaker amp, I got a custom transformer made 60VCT @ 5amps, 12V @ 5amps. 360VA Total






 It's quite large and heavy.

 I made a mistake and only ordered one o22 power supply when I should have ordered two as suggested by Ferrari. So until I get the second o22 I'll have to stick to headphones. Speaking of headphones, does anyone know of any additional modification to the amp required to run both headphones or speaker on the same amp? Or is none needed?_

 

That table knife does suggest that thing is pretty good size!


----------



## jjazzyj

It's pretty hard to gauge size from a photo without some reference. When I ordered the trafo I had no idea it was going to be so large. That's what I get for being a nub. It's a good thing I'm planning a 4U chassis.


----------



## johnwmclean

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_Speaking of headphones, does anyone know of any additional modification to the amp required to run both headphones or speaker on the same amp? Or is none needed?_

 

You’d need some kind of gain switch, the output resistors might need to be swapped for 2W versions, not 100% on this tough - I saw that comment somewhere when it was in it’s prototype form.

 I also got my kits yesterday, also a speaker/headphone build 2 x 100VA trannies and 2 x σ22 supplies and balanced EHHA, heater supply is still being worked out.


----------



## MrMajestic2

Those of you guys who are running balanced, what gain are you using?


----------



## les_garten

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Those of you guys who are running balanced, what gain are you using?_

 

Good question. I'm going to piggyback on. Is Gain, Gain? Is a gain of 5 on a B22 the same as a Gain of 5 on a EHHA?


----------



## luvdunhill

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_Good question. I'm going to piggyback on. Is Gain, Gain? Is a gain of 5 on a B22 the same as a Gain of 5 on a EHHA?_

 

yes... well, as long as you don't cause one to clip I suppose.


----------



## johnwmclean

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Those of you guys who are running balanced, what gain are you using?_

 

I’m starting with 5.5 (total 11) balanced for my build, wiatrob was running this value with his balanced build.
 I’m going to be socketing C2, C3, R13, R22 and R23 and have also included resistors between 2K and 1.5K for R13 for some experimenting.


----------



## les_garten

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_I’m starting with 5.5 (total 11) balanced for my build, wiatrob was running this value with his balanced build.
 I’m going to be socketing C2, C3, R13, R22 and R23 and have also included resistors between 2K and 1.5K for R13 for some experimenting._

 

What do you use for a socket?


----------



## MrMajestic2

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_I’m starting with 5.5 (total 11) balanced for my build, wiatrob was running this value with his balanced build.
 I’m going to be socketing C2, C3, R13, R22 and R23 and have also included resistors between 2K and 1.5K for R13 for some experimenting._

 

Great, sounds like a nice starting point. On another note, I was just about to order the Glassware PSU when I realized the shipping charge is almost the same as the board (ouch). Any chance I could modify a TREAD to work?


----------



## sachu

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_I’m starting with 5.5 (total 11) balanced for my build, wiatrob was running this value with his balanced build.
 I’m going to be socketing C2, C3, R13, R22 and R23 and have also included resistors between 2K and 1.5K for R13 for some experimenting._

 

Sounds good...Can't wait to see all these new builds take off and get some face melting impressions going. 
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_What do you use for a socket?_

 

use this Les..

  Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Great, sounds like a nice starting point. On another note, I was just about to order the Glassware PSU when I realized the shipping charge is almost the same as the board (ouch). Any chance I could modify a TREAD to work?_

 

I would rather suggest emplying a simple LDO voltage regulator (LD1085) for the job. You could build one for under 20$ capable of handing upto 5A in like 10 minutes.


----------



## les_garten

Quote:


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

 use this Les..


_

 

IC and Component sockets, that name makes sense!

 Thanx!


----------



## digger945

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_IC and Component sockets, that name makes sense!

 Thanx!_

 

These are what I use. I hatch them out one at a time by cutting one edge of the plastic. Then I fill the hole on the pcb with solder, pick up the socket with sharp tweezers and hold it against the pre-soldered hole and heat with an iron on the other side until it slips through. Remove iron and hold straight the socket until it cools and your done.
	

	
	
		
		

		
		
	


	




 One note to make, while your shopping for these pin sockets. Look at the data sheet and make sure it is big enough to take the lead of whatever your planning on socketing. Usually for me it's a resistor or small feedback cap.


----------



## MrSlim

I snagged a couple of these: Voltage Regulator Kit, AC/DC in, DC out, Based on LM317 - eBay (item 260479385900 end time Dec-18-09 05:57:25 PST) to make some Gamma2 power supplies, but was also thinking they would do fine as heater supplies for the EHHA, just add a small transformer, or even a Wallwart..


----------



## johnwmclean

SILLY IDEA DELETE


----------



## johnwmclean

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Here you go...Tube B+ delay kit_

 

sachu, what about this one:

Power Supply Delay Finish PCB for DIY Tube Amplifier - eBay (item 310182999079 end time Nov-28-09 18:26:05 PST)

 so many options....


----------



## sachu

^^ yep..that would work great.


----------



## MrMajestic2

Quote:


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

 I am using this particular Peter Millet circuit for my heater supply that i put together on a perf board. Again, my heater circuit is capable of putting out 5A in regulated DC mode (8A in AC). So I can always scale my amp to balanced if I ever choose to by just adding two more amp boards.




_

 

Was looking through the posts and found this. Might actually do a board layout of this myself. Is the L1 common mode really needed and if so, what value?


----------



## sachu

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Was looking through the posts and found this. Might actually do a board layout of this myself. Is the L1 common mode really needed and if so, what value?_

 

The inductor is basically for additional filtering. That supply was meant for filament supply for DHT tubes, but it works great for a heater supply as well.

 I can sink upto 5A with that circuit and it has worked flawlessly in my EHHA with a pair of 6H30P-DRs.

 Would cost you about 15$ to rig it up..if U can, dew eet i say.


----------



## MrMajestic2

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_The inductor is basically for additional filtering. That supply was meant for filament supply for DHT tubes, but it works great for a heater supply as well.

 I can sink upto 5A with that circuit and it has worked flawlessly in my EHHA with a pair of 6H30P-DRs.

 Would cost you about 15$ to rig it up..if U can, dew eet i say. 
	

	
	
		
		

		
		
	


	


_

 


 I weel dew eet 
	

	
	
		
		

		
		
	


	




 I will skip the choke, add a meaty heatsink and a 5A LDO.


----------



## funch

I have a quick question.
 I just finished my EHHA. I can set the quiescent current to .22V with no
 problem, but my bias voltages are around .1V low. I'm using a pair of
 JAN Phillips 6922's. Should I be overly concerned with the low bias readings?


----------



## runeight

It's ok for the bias voltages to be slightly off. .1V is ok.


----------



## funch

Thanks. First listening impressions are very impressive, and a little 
 disturbing. A little disturbing because this thing is sounding almost as
 good as my Bijou at about half the cost. Of course, my Bijou is crammed
 full of Auricaps, DACT SA, etc., so I guess I shouldn't snivel too much.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Thanks. First listening impressions are very impressive, and a little 
 disturbing. A little disturbing because this thing is sounding almost as
 good as my Bijou at about half the cost. Of course, my Bijou is crammed
 full of Auricaps, DACT SA, etc., so I guess I shouldn't snivel too much._

 

It should easily eclipse the Bijou..for me it does..I guess it is a preference of hybrid over full tube topology.

 I find it disturbing that not many people even know about an EHHA, let alone looked at the EHHA design on Alex's website.

 What resistors do you have at R22, R23 and R13?

 Look forward to your in depth impressions.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_It should easily eclipse the Bijou..for me it does..I guess it is a preference of hybrid over full tube topology.

 I find it disturbing that not many people even know about an EHHA, let alone looked at the EHHA design on Alex's website.

 What resistors do you have at R22, R23 and R13?

 Look forward to your in depth impressions._

 

If I had known about the EHHA and how good a balanced one sounds, I would have had one a long time ago and maybe not some of the other amps that I have. I prefer wiatrob's EHHA to my Square Wave XL or ALO Amphora. It probably sits somewhere between my maxed WA6 and my EC ZDT.


----------



## sachu

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_If I had known about the EHHA and how good a balanced one sounds, I would have had one a long time ago and maybe not some of the other amps that I have. I prefer wiatrob's EHHA to my Square Wave XL or ALO Amphora. It probably sits somewhere between my maxed WA6 and my EC ZDT._

 

Well you can take the EHHA further..Bill i believe had his telefunken 6GM8 tubes in them...stick a set of 6H30P-DRs in the EHHA and it gives you a whole another level, noticeable improvement in the bass with a slight roll off in the treble. Then when you start playing with the feedback resistors you can change the tonality of the amp altogether..They act almost like a balance control on the amp albeit a finer adjusting one.


----------



## smeggy

yes, EHHA with 6h30 or even the cheapo 6n6p is a real treat as sachu says. Tweak the feedback resistors (I removed mine) and it's a pretty thunderous amp. Very clean and clear. Those tubes do need a good amount of current to run the heaters so make sure your supply can handle it. Mine currently runs AC heater directly off the transfo but I do have a nice DC supply to go in it.


----------



## johnwmclean

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_but I do have a nice DC supply to go in it._

 

What DC supply you adding smeggy?


----------



## smeggy

it's one of a pair of supplies I bought from ebay. No idea if any more would be available but they have multiple taps with different adjustable voltages and ranges from 1.5 - 10A. Big hairy monsters..

Imageshack - dsc8294t


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_ Big hairy monsters.._

 

So much like you..i see the attraction now for you to use those insanely big boards


----------



## smeggy

It's probably a compensation issue 
	

	
	
		
		

		
		
	


	





 heh


----------



## funch

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_It should easily eclipse the Bijou..for me it does..I guess it is a preference of hybrid over full tube topology.

 I find it disturbing that not many people even know about an EHHA, let alone looked at the EHHA design on Alex's website.

 What resistors do you have at R22, R23 and R13?

 Look forward to your in depth impressions._

 

Nothing in 22/23, 1.21K in 13.


----------



## jjazzyj

In a previous post in this thread it was mentioned that R13 needed to be changed to 10k in order for the amp to run speakers. Would that not reduce the CL gain? Am I wrong in assuming we want more gain with speakers or is that incorrect? I am going to be running a balanced EHHA with speakers.


----------



## runeight

I hope I didn't say that. 
	

	
	
		
		

		
		
	


	




 R13 can stay the same for lightweight speaker duty.

 With 1k2 an SE amp should reach about 18W (4R) with a little over 1V peak at is input.

 With a balanced amp you'll have twice the effective gain.


----------



## MrSlim

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_it's one of a pair of supplies I bought from ebay. No idea if any more would be available but they have multiple taps with different adjustable voltages and ranges from 1.5 - 10A. Big hairy monsters..

Imageshack - dsc8294t_

 

Smeggy, with the kind of crazyness you get into, you should probably be dead...


----------



## jjazzyj

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_it's one of a pair of supplies I bought from ebay. No idea if any more would be available but they have multiple taps with different adjustable voltages and ranges from 1.5 - 10A. Big hairy monsters..

Imageshack - dsc8294t_

 

I'm using a custom transformer that has a 12V 5A winding on it. After that I'm following the circuit Alex has on the EHHA website with a 5A LDO (LD1084V) I'm probably going to try and get 12V and run the heaters in series. I'm aiming for slightly under 6.3V to hopefully prolong the life of the heaters. I'm also placing a CL-60 Thermistor and .047uf line rated cap on the mains line before the transformer primary in the hopes of having the heater supply coming up more slowly to stop the 12V from slamming into the heaters as they take a while to get to their full resistance. I may also try putting a thermistor on the 12V secondary to help achieve the same result.


----------



## sachu

Alex,

 Could you please post the necessary mods to the MOSFET circuit if we are to be able to run speaker loads with the amp? I plan to finalize my ehha tonight and tomorrow.
 edit: could you also sticky it on your website?


----------



## sachu

ALex, confirmation please on the component values to use to run the amp for speaker duty. Can i still have 2.2 ohms for R32, R33 ? or do i need to change it to 0.47 ohms?


----------



## runeight

Yes, they must be changed to 0.47 @ 3W.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, they must be changed to 0.47 @ 3W._

 

OK, Any other changes? What should the bias voltage be across the output resistors? Can this be documented on the website please?

 I have some 2ohm Dale mil spec 3 watt resistors..would they do for light speaker duty?


----------



## runeight

Voltage across the output resistors should be 47mV (100mA).

 At full power sine wave these resistors will burn about 1W. You can probably use 2W since music is never really a sine wave and most of the time the power delivery will be way less than 18W.

 And don't forget that in order to deliver the full 18W into 4R you must have off board heatsinks at about 0.5C/W.


----------



## jjazzyj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Voltage across the output resistors should be 47mV (100mA).

 At full power sine wave these resistors will burn about 1W. You can probably use 2W since music is never really a sine wave and most of the time the power delivery will be way less than 18W.

 And don't forget that in order to deliver the full 18W into 4R you must have off board heatsinks at about 0.5C/W._

 

Using the R-Tools simulator that lundvill (sp?) kindly provided a link for I've determined that a 8.5" X 4" heatsink per EHHA Board works well enough. I did a simulation @ 22W power dissipation and the mosfets burn @ 77C with 30C ambient. My limited experience tells me that this should be adequate headroom. I will me mounting the boards directly to the heatsinks with the mosfets bottom mounted and tubes will be horizontal with a vented top.


----------



## sachu

bah..tried biasing the left channel and soon as i turned R21 clockwise a plume of smoke arose from the output resistors. I think they took Q9M with them.


 The other channel is fine but I am not able to bias the voltages right. I am reading 0mV across the output resistors. But am afraid tho vary the R21 trim pot thinking the same would happen to this channel, i.e output resistors going up in smoke taking the output mosfets with them..and who knows perhaps then would take out my S22 supply asa well.

 Any help would be appreciated in biasing the one good channel left Alex.

 edit: don't think i have replacement mosfets for the channel that has gone kaput, so will have to wait a few days now if I order them now. But hopefully i'd like to get the other channel dialed in right by then


----------



## runeight

Hmmm. Could be oscillating, although it shouldn't. Are you using for C2 and C3?

 Then, there might be a biasing issue in the Vbe multiplier. I guess now that several of you are actually trying to make a power amp I will go over the entire thing and, as per request, post to the website.

 Don't order anything until I do.


----------



## les_garten

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_bah..tried biasing the left channel and soon as i turned R21 clockwise a plume of smoke arose from the output resistors. I think they took Q9M with them.


 The other channel is fine but I am not able to bias the voltages right. I am reading 0mV across the output resistors. But am afraid tho vary the R21 trim pot thinking the same would happen to this channel, i.e output resistors going up in smoke taking the output mosfets with them..and who knows perhaps then would take out my S22 supply asa well.

 Any help would be appreciated in biasing the one good channel left Alex.

 edit: don't think i have replacement mosfets for the channel that has gone kaput, so will have to wait a few days now if I order them now. But hopefully i'd like to get the other channel dialed in right by then_

 

You can recover from this.

 Unless it did this!






 Damn those SinglePowers!

 .


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hmmm. Could be oscillating, although it shouldn't. Are you using for C2 and C3?

 Then, there might be a biasing issue in the Vbe multiplier. I guess now that several of you are actually trying to make a power amp I will go over the entire thing and, as per request, post to the website.

 Don't order anything until I do. 
	

	
	
		
		

		
		
	


	


_

 

I don't have C2 and C3 installed.

 I have 1k at R13.

 The other channel i haven't touched yet.
 Will wait for your reply before ordering any replacement parts.


  Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_You can recover from this.

 Unless it did this!






 Damn those SinglePowers!

 ._

 

damn indeed! yeah i've blown up my ehha enough times to know taht she is very resilient. I know she will come back.
 Just disappointed casue i had everything else ready.


----------



## runeight

Sorry gentlemen. I have turned full attention to this (and away from the exstata) to get the details right. I have added a section under TWEAKS on the website to show you what to do for the power amp.

 Sachu, R20/R21 were the wrong values for this amp and there was far too much range. You probably ran 10s of amps through the output devices. My apologies for this. I hope it doesn't interfere with your build schedule too much.

 Let me know if there are any further questions...


----------



## sachu

haha..indeed i think i did.

 Well i don't have the 50 ohm trim pot with me. Also instead of running the 2 watt panasonics ordered a few mills. Hopefully I will have it by the weekend. 
 Might just put things back in order so as to run the amp as a headphone amp till then.

 edit: thanks for putting up the info on the website alex


----------



## jjazzyj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Sorry gentlemen. I have turned full attention to this (and away from the exstata) to get the details right. I have added a section under TWEAKS on the website to show you what to do for the power amp.

 Sachu, R20/R21 were the wrong values for this amp and there was far too much range. You probably ran 10s of amps through the output devices. My apologies for this. I hope it doesn't interfere with your build schedule too much.

 Let me know if there are any further questions..._

 

Thanks for the update Alex. With those changes would you still be able to run headphones as well or would you have to have a gain switch?


----------



## runeight

You can still run headphones. But you can leave out the zobel.


----------



## jjazzyj

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You can still run headphones. But you can leave out the zobel._

 

I'm planning on P2P the zobel right on the speaker posts. I'd be able to do both if I'm reading the B22 wiring page right.

 In the past I've also used .7mH air core inductor as a zobel as well. I'm too much of a nub to know which one would be better. I got some used magnet wire from used solenoids. Alternator repair shops give me as much as I want for free. I was using it for custom flyback transformers for outdoor LED lighting. In the end I ended up using an IC as it was less of a PITA.


----------



## johnwmclean

runeight, why is no gain switch necessary for the power amp version if headphones are to be used in conjunction? Like jjazzyi I’d put a zobel over the speaker posts only per AMB’s β22 wiring diagram.


----------



## runeight

I'm not sure which is better either. I haven't really tried to learn much about zobels. But the RC version sure seems easy to do.


----------



## runeight

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_runeight, why is no gain switch necessary for the power amp version if headphones are to be used in conjunction? Like jjazzyi I’d put a zobel over the speaker posts only per AMB’s β22 wiring diagram._

 

Well, if R13 is roughly the same for both versions (1k or 1k2) then they will have the same gain. So an amp with R13=1k can power both headphones and speakers so long as the other values are set up for the power amp.

 What I don't know is if a zobel affects the headphone audio.


----------



## runeight

However, I a making some assumptions that maybe I shouldn't make.

 I'm assuming that your sources can do about 1.4VRMS. If so then the amp with R13=1k or 1k2 will power 8R to about 20W and 4R to more if the PS and heatsinks can handle it.

 In this configuration it will also easily power 32R and 300R headphones.

 If the assumptions are not right then we DO need to make adjustments.


----------



## johnwmclean

Thanks runeight, 
 my source is 4Vp-p the EHHA build will be balanced. PSU is dual σ22’s with 100VA transformers.


----------



## runeight

Oh. Then you'll have plenty of everything. 
	

	
	
		
		

		
		
	


	




 I will be sweating this out though because no one has tried this mod yet. Just you and sachu so far as I know.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I will be sweating this out though because no one has tried this mod yet. Just you and sachu so far as I know._

 

oh man..am going to have to use some other resistors instead of the mills as a test subject..lest i burn those up..haha


----------



## johnwmclean

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_oh man..am going to have to use some other resistors instead of the mills as a test subject..lest i burn those up..haha_

 

Your the man sachu... 

 ...or is that Guinea Pig. heheehe


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_However, I a making some assumptions that maybe I shouldn't make._

 

Alex,

 can i use 100R trimpots instead of the 50 R ones for R21 and leave R20 at 220ohm?


----------



## runeight

You can use 100R trimpots, but R20 MUST be changed to 330R. This will prevent the huge current draws at the output.


----------



## MrMajestic2

Just double checking here: If I want a gain of ~5.5 would 2.2K on R13 be correct? Also, would the C2, C3 value of 2.2pf suffice?


----------



## runeight

Yes. Leave C2/C3 out of the circuit on your first try and only put them in if you see oscillation. 2.2pf should be enough.


----------



## MrMajestic2

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes. Leave C2/C3 out of the circuit on your first try and only put them in if you see oscillation. 2.2pf should be enough._

 

Great, ordering up the kit now


----------



## funch

I just tried a pair of 6H30's from my Bijou. I can't adjust any of the bias 
 voltages up to 1.5V, and I get a buzzing in the 'phones. Any thoughts?


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_I just tried a pair of 6H30's from my Bijou. I can't adjust any of the bias 
 voltages up to 1.5V, and I get a buzzing in the 'phones. Any thoughts?_

 

I assume your heater supply is capable of at least 2A if you have the tubes in parallel at 6.3 volts or 1A if you have them in series at 12.6 volts.

 If you do, then have you gone through the checklist posted on the website?


----------



## funch

Yep. Heater tranny is the Radio Shack one listed earlier, 12.6V/3A and wired
 in series. Although the bias readings are slightly low, the amp works fine
 with the 6922's.


----------



## sachu

what voltages do you read on the 3 pins of Q7?


----------



## funch

Pin 1: -3.08V, Pin 2: 3.88V, Pin 3: -3.77V with 6H30's.


----------



## sachu

Those seem right to me..i have about 3.7 on pin1..but i think you are still in the ballpark. Your mosfets should be conducting..
 A few more test points.
 voltages at pin 3 of Q11 and Q13?

 Also voltages at pin 2 and pin 6 of the tube?


----------



## dBel84

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_I just tried a pair of 6H30's from my *Bijou*. I can't adjust any of the bias 
 voltages up to 1.5V, and I get a buzzing in the 'phones. Any thoughts?_

 

Just checking to make sure we are referring to the right amp here?

 ...am assuming that you took the tubes from the bijou for the ehha..

 ..dB


----------



## funch

Q11, pin3 = 28.9V Q13, pin3 = -28.8V Tube pin 2 = 0V Tube pin 6 = 27.5V


----------



## funch

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Just checking to make sure we are referring to the right amp here?

 ...am assuming that you took the tubes from the bijou for the ehha..

 ..dB_

 

I meant that I temporarily robbed them from my Bijou.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Q11, pin3 = 28.9V Q13, pin3 = -28.8V Tube pin 2 = 0V Tube pin 6 = 27.5V_

 

those voltages all check out fine..i wanted pin 3 and pin 6 there ..not pin 2..sorry..pin 3 you should read about 1.7 volts..can you double check that?

 also is the tube lighting up?


----------



## funch

1.9V on one channel, 2.08 on the other.


----------



## sachu

yeah all the points check out fine..and you have 220mV across R32 and R33?


----------



## funch

Yep.


----------



## sachu

Don't know what to tell you man..am stumped now 
	

	
	
		
		

		
			




 Hopefully Alex with chime in soon.


----------



## funch

OK. Thanks a bunch for your help.


----------



## sachu

so you are not reading 1.5V across R3,R4, R10 and R14?

 what do you read on pin 1 of Q1 and Q2?

 Also what are your rail voltages? is it a solid +/-30V?


----------



## funch

These are with R6 fully clockwise.

 R3L/R 1.39/0.98 R4L/R 1.39/1.67

 R10L/R 1.40/1.69 R14L/R 1.33/1.62

 Q1, pin 1 L/R 27.5/27.9 Q2, pin 1 L/R 28.1/27.3

 Rail voltage is +/- 29.3V

 As you might expect, the R ch. tube is the more noisy one. They both seem to work fine in the Bijou. 
 I ordered a new pair from Parts Connexion last night as a spare pair. I'll try them when they arrive.

 I'm thinking, since I bought my 6H30's used, they may work fine at the higher voltage in the Bijou,
 but have become marginal at best running on 30V. My $.02.

 BTW, has anyone here compared the sound of the 6GM8's against 6922's?


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_These are with R6 fully clockwise.

 R3L/R 1.39/0.98 R4L/R 1.39/1.67

 R10L/R 1.40/1.69 R14L/R 1.33/1.62

 Q1, pin 1 L/R 27.5/27.9 Q2, pin 1 L/R 28.1/27.3

 Rail voltage is +/- 29.3V

 As you might expect, the R ch. tube is the more noisy one. They both seem to work fine in the Bijou. 
 I ordered a new pair from Parts Connexion last night as a spare pair. I'll try them when they arrive.

 I'm thinking, since I bought my 6H30's used, they may work fine at the higher voltage in the Bijou,
 but have become marginal at best running on 30V. My $.02.

 BTW, has anyone here compared the sound of the 6GM8's against 6922's?_

 

Yeah otherwise your values all look spot on. 

 The 6H30 will work on the EHHA. They are the only pair of tubes i use and I paid a small fortune (for me at least) for the NOS versions.

 But you say both channels aren't working right?
 You are getting noise on both ?


----------



## funch

Yes, noise in both, but the R channel is much worse. I've put the 6922's
 back in and readjusted everything and am going to leave it be until the
 new 6H30's come in. I'll report back when I've tried the new ones.
 Thanks for all your help.

 BTW, are yours the DR Supertubes, like the ones from Tube Store?


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_BTW, are yours the DR Supertubes, like the ones from Tube Store?_

 

Yes they are.


----------



## les_garten

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Yes, noise in both, but the R channel is much worse. I've put the 6922's
 back in and readjusted everything and am going to leave it be until the
 new 6H30's come in. I'll report back when I've tried the new ones.
 Thanks for all your help.

 BTW, are yours the DR Supertubes, like the ones from Tube Store?_

 

Those tubes are kinda expensive so it might be worth your while to do this. I have a _really_ nice Tube Tester(Triplett 3444). If you pay the ticket both ways, I'll test and match them for you.


----------



## digger945

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Yes they are.
	

	
	
		
		

		
		
	


	


_

 

Never did get the full lowdown on how they compare to the "non-DR" Sovteks


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Never did get the full lowdown on how they compare to the "non-DR" Sovteks
	

	
	
		
		

		
		
	


	


_

 

hmm thought i did 
	

	
	
		
		

		
		
	


	




..

 There wasn't a huge difference, better spatial presentation, a bit more sparkle to the highs, tighter bass with the DRs. 

 Okay, 100R trimpots have been installed, gonna go with using a 121R in series with the 220R for R20 that is already installed. Waiting for the mills order to come in which won't be for 2 weeks i think.


----------



## KeeChoon

Hi all,

 I have been reading through the some of the pages from this thread and got interested in the EHHA.

 I am looking at the 3 board active ground configuration and wonder how different does it differ from the 2 board passive ground option. 

 I had enquired Jeff from Glassjar about the active ground and I need to find out what is the recommended gain for the ground channel. Any suggestions?

 Thanks!


----------



## runeight

Kee, there is a wiring diagram for this at Cavalli Audio which shows how the ground channel is connected. It's gain is the same as the amps IIRC.


----------



## KeeChoon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Kee, there is a wiring diagram for this at Cavalli Audio which shows how the ground channel is connected. It's gain is the same as the amps IIRC._

 

Thanks for the quick reply!

 By the way, how critical is it for the mosfets and transistors to be matched?


----------



## sachu

Quote:


  Originally Posted by *KeeChoon* /img/forum/go_quote.gif 
_Thanks for the quick reply!

 By the way, how critical is it for the mosfets and transistors to be matched?_

 

I believe they had some oscillation issues during the proto phase which were addressed with matched transistors, but the newer crop of EHHAs seem to have no such problems.


----------



## johnwmclean

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT
 MrSlim recommended these for heater psu duties earlier in the thread, I bought 2 and just received then today. They are very well make, I haven’t fired them up yet - but for cost they’re top shelf.

 Specifications:
 AC Input : 4 - 22V ( Transformer No-load Voltage must be less than 22V )
 DC Input : 4.5 - 30V 
 Output Voltage : 1.5 - 27V
 Maximum Current : 1.5 Amp ( If Drop-Out or Output Power Very High, Must Increase the Heat-sink )
 PCB Size : 50 x 50mm ( 2 x 2 inch )
 PCB Thickness : 1.6mm ( 0.063 inch )
 Maximum Height : 37mm ( 1.46 inch ) 

 I’m building a balanced EHHA, I was going to assign one psu per 2 EHHA boards - or should one do the overall job?


----------



## digger945

If you plan on trying the 6H30, then plan on 1A per tube at 6.3V.
 I think .4A will cover each 6GM8(actually a little less, but I like a small amount of overhead for turn on/power up)


----------



## johnwmclean

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_If you plan on trying the 6H30, then plan on 1A per tube at 6.3V.
 I think .4A will cover each 6GM8(actually a little less, but I like a small amount of overhead for turn on/power up)_

 

Thanks Scott, looks like I’ll be at .75A per tube at 6.3V - do you think I could scape in with 6H30’s?


----------



## sachu

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Thanks Scott, looks like I’ll be at .75A per tube at 6.3V - do you think I could scape in with 6H30’s?_

 

nope..each 6H30 draws atleast .9A from the heater supply and i tis recommended you have some headroom.


----------



## johnwmclean

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_nope..each 6H30 draws atleast .9A from the heater supply and i tis recommended you have some headroom._

 

Ok cool I’ve ordered 2 more, now I have one per board 1.5A each. Thanks sachu!


----------



## les_garten

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Ok cool I’ve ordered 2 more, now I have one per board 1.5A each. Thanks sachu!_

 

JM,
 How much are you feeding these with off off your Transfo, volts and current wise?


----------



## johnwmclean

Since these puppies can run off DC, I've been tapping off my dual S22.


----------



## sachu

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Since these puppies can run off DC, I've been tapping off my dual S22._

 

That might not be such a good idea..you'd be dropping well over 20 volts across the regulators for your heater supply..i'd imagine they'd get really hot just regulating down to 6.3 volts let along handling the current they'll be sinking


----------



## les_garten

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Since these puppies can run off DC, I've been tapping off my dual S22._

 

OK, I get it. Thanx!


----------



## johnwmclean

noob post please delete


----------



## sachu

yeah your S22s look umm capable enough 
	

	
	
		
		

		
			





 i meant the regulator you will be using to drop the 30 volts down to 6.3V for the heater?
 That would require some major heatsinking as well..


----------



## luvdunhill

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah your S22s look umm capable enough 
	

	
	
		
		

		
		
	


	




 i meant the regulator you will be using to drop the 30 volts down to 6.3V for the heater?
 That would require some major heatsinking as well.._

 

what he said... and


----------



## johnwmclean

sachu, I am such a bloody noob sorry, but going from this am I not in spec? Otherwise I’ll run them from a trannie.

 AC Input : 4 - 22V ( Transformer No-load Voltage must be less than 22V )
 DC Input : 4.5 - 30V 
 Output Voltage : 1.5 - 27V
 Maximum Current : 1.5 Amp ( If Drop-Out or Output Power Very High, Must Increase the Heat-sink)


----------



## luvdunhill

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_sachu, I am such a bloody noob sorry, but going from this am I not in spec? Otherwise I’ll run them from a trannie.

 AC Input : 4 - 22V ( Transformer No-load Voltage must be less than 22V )
 DC Input : 4.5 - 30V 
 Output Voltage : 1.5 - 27V
 Maximum Current : 1.5 Amp ( If Drop-Out or Output Power Very High, Must Increase the Heat-sink)_

 

well, you sorta disregarded a very important part of those "specs":

 "If Drop-Out or Output Power Very High, Must Increase the Heat-sink"

 *both* of those "or" conditions are present in your situation.

 There is no better place to learn how an adjustable regulator works than here:

Power Supply Parameter Estimator

 Plug in your numbers and enjoy.


----------



## Pars

Per the note on current output, your dropout is quite high (not sure what you are getting off the s22?), but 30V down to 6.3V output is ~14V dropout.

 EDIT: And what Marc said, above


----------



## johnwmclean

Thanks Pars and luvdunhill that’s a great resource. Just a thought before I jump on the separate trannie bandwagon would an appropriate zenor diode in series from a 30V s22 work/advisable?


----------



## regal

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_yeah your S22s look umm capable enough 
	

	
	
		
		

		
		
	


	




 i meant the regulator you will be using to drop the 30 volts down to 6.3V for the heater?
 That would require some major heatsinking as well.._

 

Use some big high wattage dropping resistors after the S22 to take some of the load off the heater regulator.


----------



## luvdunhill

Just because you have big heat sinks, doesn't mean they can produce current out of nowhere. How big are your toroids and what is the total current draw (including heaters) that you're looking at? Since you removed the above picture, I cannot tell, but I remember thinking that they were rather dinky transformers.


----------



## johnwmclean

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Just because you have big heat sinks, doesn't mean they can produce current out of nowhere. How big are your toroids and what is the total current draw (including heaters) that you're looking at? Since you removed the above picture, I cannot tell, but I remember thinking that they were rather dinky transformers._

 

luvdunhill, 2 x 100VA trannies.


----------



## luvdunhill

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_luvdunhill, 2 x 100VA trannies._

 

ok, and what percentage of that are you going to be using power the heaters?


----------



## johnwmclean

luvdunhill, I’ll be drawing 12.6v from each s22, now I really don’t know how that equates at a percentage of the transformers VA rating.


----------



## luvdunhill

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_luvdunhill, I’ll be drawing 12.6v from each s22, now I really don’t know how that equates at a percentage of the transformers VA rating._

 

you might want to find that out.

 hint: no, you're not drawing 12.6v from each sigma22


----------



## johnwmclean

Ok I'm stumped, anything of the grid like this, is my biggest weakness, thanks for your help thus far - your hint suggests you know the answer - you tease.


----------



## luvdunhill

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Ok I'm stumped, anything of the grid like this, is my biggest weakness, thanks for your help thus far - your hint suggests you know the answer - you tease._

 

I'll oversimplify it, but think of it this way. 

 If you're tapping off of the 30V sigma22, then even if you regulate down to a 6.3V power supply and can overcome the heat dissipation it takes to do so (which honestly, you can't, this is (30V - 6.3V) * heater current per tube * number of tubes per regulator board (in Watts).. given the example below, this is like 100W (!)), then you *still* have to source this current from your main trafo. 

 In other words, say you are heating four tubes that draw 1A each. Then of that 200 VA you have to work with, approximately (very crude) 30V * 1A * 4 = 120VA will be consumed by the heaters (!)


----------



## mugdecoffee

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I'll oversimplify it, but think of it this way. 

 If you're tapping off of the 30V sigma22, then even if you regulate down to a 6.3V power supply and can overcome the heat dissipation it takes to do so (which honestly, you can't, this is (30V - 6.3V) * heater current per tube * number of tubes per regulator board (in Watts).. given the example below, this is like 100W (!)), then you *still* have to source this current from your main trafo. 

 In other words, say you are heating four tubes that draw 1A each. Then of that 200 VA you have to work with, approximately (very crude) 30V * 1A * 4 = 120VA will be consumed by the heaters (!)_

 

Running the tubes in series would make this very doable though. 30V-4*6.3V=30V-25.2V=4.8V drop and at 1A that's around 5W heat to deal with. Also you'd only be drawing 30VA from the transformer.


----------



## luvdunhill

Quote:


  Originally Posted by *mugdecoffee* /img/forum/go_quote.gif 
_Running the tubes in series would make this very doable though. 30V-4*6.3V=30V-25.2V=4.8V drop and at 1A that's around 5W heat to deal with. Also you'd only be drawing 30VA from the transformer._

 

This gets complicated, and that's where Alex can step in 
	

	
	
		
		

		
			





 For example, the first tube in the chain will not be happy when the amp is powered on, so you'll need to implement some sort of turn on protection or controlled warm-up for the tubes, probably involving a CCS.

 Just use a separate transformer.


----------



## sachu

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_This gets complicated, and that's where Alex can step in 
	

	
	
		
		

		
		
	


	




 For example, the first tube in the chain will not be happy when the amp is powered on, so you'll need to implement some sort of turn on protection or controlled warm-up for the tubes, probably involving a CCS.

 Just use a separate transformer._

 

Totally!


----------



## johnwmclean

luvdunhill, I owe a big thanks - this has helped my understanding immensely.

 Cheers
 John


----------



## digger945

I've run my 2 6H30's in series with a 12V 1000mA wallwort, and now in series with a 6V 1800mA wallwort. The Aikido 24V runs all 4 6GM8's in series using 24V, ideally you could use 25.2 to make a perfect 6.3 per, but it's not really necessary. Thing about using the heaters in series is, for each doubling of the voltage, the current required halves.


----------



## smeggy

you can also do what I did for the more hefty tubes, run AC directly in series from a 12.6V 4A Rat shack transformer for the princely sum of about $8 or so.

 It works very nicely with just a basic transfo.


----------



## sachu

Quote:


  Originally Posted by *smeggy* /img/forum/go_quote.gif 
_you can also do what I did for the more hefty tubes, run AC directly in series from a 12.6V 4A Rat shack transformer for the princely sum of about $8 or so.

 It works very nicely with just a basic transfo._

 

Strongly urge folks to consider running DC heaters on the EHHA. There was a big enough difference going from AC to DC ones for me.

 Black levels were much higher with DC heaters....YMMV ofcourse


----------



## luvdunhill

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I've run my 2 6H30's in series with a 12V 1000mA wallwort, and now in series with a 6V 1800mA wallwort. The Aikido 24V runs all 4 6GM8's in series using 24V, ideally you could use 25.2 to make a perfect 6.3 per, but it's not really necessary. Thing about using the heaters in series is, for each doubling of the voltage, the current required halves._

 

Does this first one in the string glow extra bright when they're flipped on? I'd expect it to, now how hard this is in the tubes in the long run, I have no idea, but seems like it's not to hard to use an adjustable regulator as a current source to soften the initial blow.


----------



## digger945

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_Does this first one in the string glow extra bright when they're flipped on? I'd expect it to, now how hard this is in the tubes in the long run, I have no idea, but seems like it's not to hard to use an adjustable regulator as a current source to soften the initial blow._

 

Yes, you're correct. With some tubes the first one will glow a bit brighter when first turned on. I really depends on the tube used. With some it's really hard to notice, others it's very apparent. No idea the affect on filament life.
 I'de say this happens because each filament heats up at a slightly different rate, and thus also changes resistance at a different rate. If the first 6xxx tube gets voltage and begins to warm at 12V and the second tube has not warmed much yet, then the second tube will apprear to the first as almost a dead short. 
 I've read Broskie comment that tubes should last longer with a slightly lower heater voltage.


----------



## bada bing

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_Yes, you're correct. With some tubes the first one will glow a bit brighter when first turned on. I really depends on the tube used. With some it's really hard to notice, others it's very apparent. No idea the affect on filament life.
 I'de say this happens because each filament heats up at a slightly different rate, and thus also changes resistance at a different rate. If the first 6xxx tube gets voltage and begins to warm at 12V and the second tube has not warmed much yet, then the second tube will apprear to the first as almost a dead short. 
 I've read Broskie comment that tubes should last longer with a slightly lower heater voltage._

 

Why would the first tube in series heat up faster ? That makes no sense (to me). The instantaneous current is the same throughout the circuit, or if not quite instanteous, it stabilizes at the speed of light in conductor. The tube with the greatest resistance in the series circuit should heat up first/most regardless of position in the circuit.

 I run the 4 tube filaments in my balanced EHHA with two series loops paralleled off a 12.6v dc supply. Works splendidly. I don't like the idea of 4 tubes in series on 25v. Seems like too much chance of imbalance though.


----------



## luvdunhill

The resistance of a heater is not fixed, it has a PTC.


----------



## digger945

Quote:


  Originally Posted by *bada bing* /img/forum/go_quote.gif 
_Why would the first tube in series heat up faster ? That makes no sense (to me). The instantaneous current is the same throughout the circuit, or if not quite instanteous, it stabilizes at the speed of light in conductor. The tube with the greatest resistance in the series circuit should heat up first/most regardless of position in the circuit._

 

While the instantaneous current may be the same, it will vary over the period of time it takes for all filaments to completely heat. If the supply voltage is relatively constant, and the resistances are changing, then what else must also be changing? I have measured several 6gm8 filaments cold. They are usually around 3 to 4 ohms.
 6.3v / .350A = 18ohms (hot)
 6.3v / 4ohms = 1.575A (cold)

  Quote:


 I run the 4 tube filaments in my balanced EHHA with two series loops paralleled off a 12.6v dc supply. Works splendidly. I don't like the idea of 4 tubes in series on 25v. Seems like too much chance of imbalance though. 
 

I run the Aikido with 4 tube filaments in series off a 24V supply and it works great. I have tried series parallel and parallel and can detect no audible difference. Same for my unbalanced EHHA series or parallel. Nonetheless, when the heaters are powered on in series, one will glow way bright for a second or two, while the others slowly begin to glow. This tube is, on my amp(s), always closest to V+. 

 I'm not a heater guru, it's just my observation.
	

	
	
		
		

		
			





  Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_The resistance of a heater is not fixed, it has a PTC._

 

Exactly.


----------



## bada bing

Yes, but both heaters see the exact same current at any instant in time in a series circuit ?
 Why would the first heater necessarily heat up faster. I am not getting it. The higher resistance heater, in whatever position it is installed, gets hot faster as it drops more voltage across it's greater resistance. The heater filaments only "know" how much current is passing through them. They have no way of "knowing" what position they are in. The PTC has the effect of balancing the load as it comes to equilibrium. 

 Or not maybe. That's what I don't understand. It's of no big practical importance, it's just that your observation doesn't seem to be explainable because of the proximity to V+. Something else in your particular set up is causing the observation.


----------



## digger945

I am not alone in this observation. The phenomenon is not confined to my particular setup. The statement was originally directed from luvdunhill, as he has noticed the same thing happening in his amps also. This is much more noticable using 4 in series.

 The discussion began with a simple question. Will this first heater glowing very noticably brighter than the other 3 in series, somehow shorten it's lifespan? Our lack of understanding or the ability to grasp what is happening does not discount the fact that it is indeed happening.

 EDIT: It could possibly have something to do with the fact that each filament in the Aikido circuit is bypassed with a .1uF cap.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Yes, noise in both, but the R channel is much worse. I've put the 6922's
 back in and readjusted everything and am going to leave it be until the
 new 6H30's come in. I'll report back when I've tried the new ones._

 

Any luck running those supertubes in the ehha?

 my mills resistors should get to me by saturday, hoping to finish up the amp and test it again this weekend.


----------



## funch

I'm still waiting for the tubes to get here. Should be any month now!


----------



## regal

What is the output impendance of the EHHA ?


----------



## sachu

Should be just about 2.4 ohms for the MOSFET version in headphone amp configuration and 0.6 ohms when configured for dual use as a power/headphone amp.


----------



## runeight

The EHHA mosfet version should have a Zo of about .04R when the stock resistor values are use (R22/R23=33k). This is due to the NFB.


----------



## runeight

Gents, I've been meaning to remind you of something.

 Those of you who are building this as a speaker amp should put the gate stopper resistors on the output mosfets right at the gate lead.

 One of the risks of using offboard heatsinks and putting leads between the fets and their pads on the board is that even the introduction of this small amount of capacitance may cause the fets to oscillate. Since I've never tried the amp as a speaker amp we don't really know how it will do.

 However, the best way to minimize the possibility of oscillation is to attach the gate stopper right to the gate lead at the fet and then run the wire to the pad on the board.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, I've been meaning to remind you of something.

 Those of you who are building this as a speaker amp should put the gate stopper resistors on the output mosfets right at the gate lead.

 One of the risks of using offboard heatsinks and putting leads between the fets and their pads on the board is that even the introduction of this small amount of capacitance may cause the fets to oscillate. Since I've never tried the amp as a speaker amp we don't really know how it will do.

 However, the best way to minimize the possibility of oscillation is to attach the gate stopper right to the gate lead at the fet and then run the wire to the pad on the board._

 

Thanks for the heads up Alex..will make appropriate changes.


----------



## funch

Well, I just got my new tubes in (EH 6H30Pi gold pins), and I still have
 the same problem. I only get output in the right channel, along with
 a strong buzzing. 

 I'm not too impressed with the overall sound of the 6922's; too much
 HF, not enough LF. I guess I'll see if I can find a reasonably priced 
 pair of 6GM8's.

 BTW, I'm using an Avel 80VA tranny for the B22 PS.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Well, I just got my new tubes in (EH 6H30Pi gold pins), and I still have
 the same problem. I only get output in the right channel, along with
 a strong buzzing. 

 I'm not too impressed with the overall sound of the 6922's; too much
 HF, not enough LF. I guess I'll see if I can find a reasonably priced 
 pair of 6GM8's.

 BTW, I'm using an Avel 80VA tranny for the B22 PS._

 

What do you have installed at R22, R23?

 Try taking those out and leaving them open.


----------



## runeight

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Well, I just got my new tubes in (EH 6H30Pi gold pins), and I still have
 the same problem. I only get output in the right channel, along with
 a strong buzzing. 

 I'm not too impressed with the overall sound of the 6922's; too much
 HF, not enough LF. I guess I'll see if I can find a reasonably priced 
 pair of 6GM8's.

 BTW, I'm using an Avel 80VA tranny for the B22 PS._

 

Funch, could you please check the values of R5/R7 to make sure that they are 47R.

 Thanks.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Funch, could you please check the values of R5/R7 to make sure that they are 47R.

 Thanks._

 

Aye...a mistake that can easily be overlooked.


----------



## funch

Never installed R22/23.

 R5/7 are 47.3R.


----------



## sachu

wow interesting..R22, R23 in the open position should give the most bass with the highs a bit more rolled off than stnadard config when you have 33k installed there.
 Never tried a 6922 pair before. Do you have the pair of 6GM8s that Jeff sells the kit with?


----------



## funch

Nope. I didn't buy Jeff's kit, and I don't have any 6GM8's to try.


----------



## funch

Maybe I'll revise my comment about the bass. It's there, and it's very
 tight, but not in overly great quantities like I normally get listening to
 most of the Fourplay albums. 

 I have another question. How long should it take for the quiescent 
 current readings to stabilize? With mine, it drops for quite a while, quickly
 at first, then gradually slows. Takes maybe 5 minutes or so.


----------



## sachu

The quiescent current stabilizes within 10 seconds on mine..the servo probably takes 10 more at most to zero out the DC offset completely.


----------



## funch

Interesting. Perhaps my 6922's arent' so good in this amp. I'm thinking I should 
 get a pair of 6GM8's to try. Anybody out there got an extra pair to sell, or know
 a good source? Too bad I missed out on AES's price, seeing as how they're a half
 hour from my house, and all, 'cuz now they're out of 'em. S'what I get fer thinkin'.


----------



## wiatrob

My servos (on four boards) stabilize almost instantly with 6GM8s and 7DJ8s (all I've tried...)


----------



## sachu

Fucnh,

 can you describe your heater power supply. Transformer rating, DC or AC? parallel or serial?


----------



## funch

It's the Radio Shack tranny mentioned earlier in this thread (can't 
 remember who, sorry). Rated at 6.3V-0-6.3V/3A. It's configured
 @ 12.6 V in series. I'm reading 7.12V R ch., and 6.84V L ch.


----------



## digger945

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Maybe I'll revise my comment about the bass. It's there, and it's very
 tight, but not in overly great quantities like I normally get listening to
 most of the Fourplay albums._

 

What track are you using? CD?
 Have you ever tried anything from the "Restless" album?
 Have I asked this question before? Can't remember.


----------



## digger945

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_It's the Radio Shack tranny mentioned earlier in this thread (can't 
 remember who, sorry). Rated at 6.3V-0-6.3V/3A. It's configured
 @ 12.6 V in series. I'm reading 7.12V R ch., and 6.84V L ch._

 

Is that DC at the heater?


----------



## funch

diggger945:

 I don't have the 'Restless' album. Yet.

 The heater voltages are measured at the connection
 for the heater wires on each board.


----------



## sachu

bah...rigged up the boards today and tested one...blew instantly..

 Hooked upo the other after checking it again..it works.
 But the MOsfet bias current isn't stable..if I set it to 50mV across the output resistors which is about 100mA, the voltage across the output resistor gradually starts dropping at 0.1mV and keeps going.

 Funch, is your EHHA setup for power amp duty as well?

 I think I am just going to revert back to basics and just leave it how it was before all the craziness.


----------



## johnwmclean

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_bah...rigged up the boards today and tested one...blew instantly..

 Hooked upo the other after checking it again..it works.
 But the MOsfet bias current isn't stable..if I set it to 50mV across the output resistors which is about 100mA, the voltage across the output resistor gradually starts dropping at 0.1mV and keeps going.

 Funch, is your EHHA setup for power amp duty as well?

 I think I am just going to revert back to basics and just leave it how it was before all the craziness._

 

You not painting a pretty picture for the power amp version, I’m starting to get cold feet.


----------



## funch

sachu:

 No, mine is only configured for 'phones. Sorry.


----------



## funch

Update:

 I just reinstalled the new 6H30's, and did the initial setup
 from the very beginning. The spec's are actually a little better
 than with the 6922's, but I still get the godawfull buzz. It's
 independent of the volume setting and music plays fine, but
 the buzz is pretty loud. Also, it buzzes whether I have the 
 source connected or not. 

 Why the buzz with the 6H30's but not the 6922's?
 Major bummer, 'cuz the 6H's sound mucho better.

 I'm stumped.


----------



## adamus

could it be related to heater current? 6h30's are rather more demand than 6922


----------



## funch

My heater tranny is rated at 3A, so I don't think that's the problem.
 It's center tapped, but I'm running it in series at 12.6V. Maybe I'll
 try running it parallel to see what happens.


----------



## johnwmclean

6H30's may need to be broken in? Keep them in for a couple of days and see if there’s an improvement.


----------



## funch

Update (to the update).

 I rewired my heaters in parallel, with the CT disconnected from
 the star ground. The buzz is down by at least half. When I touch
 the CT to ground, the buzz goes back up to its original level. 

 I'm wondering if a DC heater would solve the probelm?


----------



## digger945

Wait a minute. By CT do you mean center tap on the transformer? Your connecting the center tap to the star ground?

 If so then that is your source of "buzz". Whether your using AC or DC heaters, the center tap of your transformer should not be connected to any ground(especially amp ground) except the input to a power supply. On the EHHA the heater circuit is completely seperate from the amp circuit and amp ground(on the pcb). 

 Do you have a single wire center tap or do you have dual secondaries, ie just three wires or two pairs of wires for the secondaries?

 By star ground, do you mean you have a grounding point to connect the center tap and one lead of each heater to so you can use 6.3v?

 I diagram of your wiring would be most helpful.
 Sorry to run on, I just hate to see you hook AC up to the amp ground and possibly damage something.


----------



## funch

Yah, CT = center tap. My tranny has 3 wires; 6.3-0-6.3. Before, I used just the 'hot' leads and wired the heaters in series, with the 'jumper' wire also
 connected to ground, as per Alex's diagram. Result = buzz galore.

 When I rewired it in parallel, I first tried it without connecting the CT
 to ground, and the buzz went way down, but still was there. Then I
 connected a fourth wire to the junction with the CT wire/wires to 
 boards, and momentarily touched it to the star ground. When I did that,
 the buzz went back to the original (higher) level.


----------



## digger945

Ah, I see.
 In series(12.6vac) with your transformer, using the two "hot" leads, one connected to each boards heater connection, you would then just connect the two other heater connectors together with a single wire, leaving the center tap unconnected to anything.
 To wire the two heaters in parallel 6.3vac, you could connect the two "hot" leads to one each of the two heater connections, then split the center tap and connect to the other two heater connections. Or connect the center tap to one heater connection on one board and run a jumper wire to the other board.
 I looked at the wiring diagram on the Cavalli website, and it shows a connection to star ground, but I am not sure if this is meant for AC, but DC. 
 I tried the AC heaters connected as you have them, and could not get it to work without buzz until I disconnect the heaters from star ground.

Cavalli wiring diagram.


----------



## funch

I've got it wired as your first description, and, yah, I don't know if Alex's
 diagram is for AC or DC.


----------



## digger945

It says AC, I just looked again. I just tried it on mine and it buzzes pretty good, until I disconnect from the star ground. 
 I dunno.
 My normal setup uses a DC wallwort for the heaters, 1800mA 6vdc for two 6h30's parallel. I still don't connect to star ground though. I keep the heaters seperate, and have no problems.

 What say you Alex?


----------



## sachu

oh wait a minute..u have the heaters in AC..i strongly recommend going DC. I had the same buzz when i hooked it up in AC. The EHHA design begs for a DC heater IMHO.


----------



## funch

So did you end up using the Millet design for the DC heaters?
 If so, I might be begging your BOM.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_So did you end up using the Millet design for the DC heaters?
 If so, I might be begging your BOM._

 

Yes I did..shared the project with you..simple build so not many components.

 Alternative is to get the glassware heater supply which comes ready made for about 30$ shipped.


----------



## funch

Got it. Thanks. I take it you didn't use a choke? What about a heat sink?

 I've looked at the Glassware, but it's not available, and I'm not sure of
 the board dimensions. I've got some space available, but not a bunch.


----------



## sachu

Yeah you will need atleast a 1.5 inch size aavid heatsink , safer to go with a 2 inch one if you'll be running the 6H30s. 
 No need of a choke..that's just extra filtering not needed. 
 You could easily build that circuit in a 1.5 x 2 inch bare PCB.


----------



## funch

Yah, I figured I'd need at least a 2" sink for the 6H30's.
 Thanks for all your help.

 Right now I'm listening to the amp. Even with the hum, it 
 still sounds better than with the 6922's.


----------



## funch

sachu:

 Is the output of your heater circuit 6.3V or 12.6V?


----------



## sachu

6.3 Volts..


----------



## funch

Kinda what I thunk. I have the Radio Shack 12.6V tranny, but ordered 10V cap's
 without thinking. I'm assuming I can run one side of my tranny and the CT, and 
 run my heaters in parallel.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Kinda what I thunk. I have the Radio Shack 12.6V tranny, but ordered 10V cap's
 without thinking. I'm assuming I can run one side of my tranny and the CT, and 
 run my heaters in parallel._

 

Well you could use both your secondaries in half wave rectification mode and thus each secondary will drive the heaters every half cycle. THat's how I have it in my heater supply. It may inject DC into the transformer but i've had no problems whatsoever even when running it continuously for 2-3 days at a stretch.


----------



## funch

Ah, time to up the learning curve. I found this nifty diagram:Half-Wave Rectifier
 while searching for more info. Click on 'Next' to see the full-wave animation.

 So, I'd only use one diode instead of four? I'm not too clear in this area.
 I'm one of those who know enough to get myself into trouble, but not 
 enough to get myself out.


----------



## sachu

Yes, You would use one diode each for the two 6.3 volt secondaries.
 Forward bias them and tie the cathode of (the stripe marked end) of both these diode together. SO now, at every half cycle one of the secondaries forward biases its respective diode, so in effect you end up with a full wave rectified output using the two secondaries out of phase.

 Connect the center tap to the ground of the heater supply.

 Edit:Its late and I am kinda tired..so if anyone has any objection or correction to make to what i have posted above please feel free.


----------



## funch

OK, gotcha'.

 Like the mains here, right?http://www.hagtech.com/images/castanetschem.jpg

 This is Jim Hagerman's Castanet headphone amp.


----------



## sachu

Thisis just unbelievable.
 Again i had everything up and running and now my S22 dies!!

 Went trhough thte test points and the voltages on either side of R4 and R6 aren't matching up right.

 The MOSFETs seem to be ok, i did the basic multimeter short test on them. But replaced them to be sure.

 I am thinking CR3 and CR4 are blown.

 On the S22, I am reading 18.6 (give or take 0.2 volts difference ) volts on either side of R4 and -19.2 volts on either side of R6 with respect to ground.

 The output voltages are reading +/- 13.6 volts or some such.

 The LED light comes on too. I am so bummed. 
	

	
	
		
		

		
			





 Appreciate any inputs on this? What do you reckon could be wrong?


----------



## sachu

I am having problems with my EHHA in which I am using the Noble AP25 10k pot.


 One of the channels is sounding like it is being grounded. Specifically the right channel. The vocals instead of being centered is heavily focused on the left channel with the mids having an echo signature to it in the right channel albeit faint, the bass sounds sucked out as well.

 So if I disconnect the right channel RCA cable, I am hearing from both channels of the amp board but it sounds like it is in mono with everything being centered.

 If I disconnect the left channel, I only hear the right channel which is how it should be and it is sounding just fine.

 I have tried replacing the Noble pot with another AP25 and the results are the same.
 Any theories, ideas?


----------



## johnwmclean

Are your RCA’s still isolated?

 Edit: One of the inputs might be reversed also.


----------



## wiatrob

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Thisis just unbelievable.
 Again i had everything up and running and now my S22 dies!!


 Appreciate any inputs on this? What do you reckon could be wrong?_

 

Did you get it fixed, and if so, what was the issue?

 The s22 is persnickety in this app, I had one die mysteriously as well. Seemingly just sitting on the shelf. Luckily I had a spare, but I still have one to troubleshoot. Luckily AMB is really good about helping.


----------



## sachu

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Did you get it fixed, and if so, what was the issue?

 The s22 is persnickety in this app, I had one die mysteriously as well. Seemingly just sitting on the shelf. Luckily I had a spare, but I still have one to troubleshoot. Luckily AMB is really good about helping._

 

Hey Bill, 

 Agree, the S22 is really temperamental with the EHHA. I was taking measurements near Q11 and Q12 and all of a sudden the S22 started putting out the right voltages. 
 THere were no cold solder points to speak of, and i hadn't even touched it since the last time it was working fine for it to go down.
 Ti, is of major help in troubleshooting this though, no doubt about it.
 ANyways, am glad that's no longer the problem, but this grounding isssue is really starting to bug me now


----------



## Ferrari

I’m using my balanced EHHA with 2 σ22 PS for my AKG K1000 almost daily. 
_(The same dual σ22 PS that's feeding my Dynamite and balanced β22)._

 It seems to be that I’m the only balanced EHHA owner who has no issues with the PS.


----------



## sachu

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I’m using my balanced EHHA with 2 σ22 PS for my AKG K1000 almost daily. 
(The same dual σ22 PS that's feeding my Dynamite and balanced β22).

 It seems to be that I’m the only balanced EHHA owner who has no issues with the PS. 
	

	
	
		
		

		
		
	


	


_

 

Wow..so the EHHA is permanently doing duty for the AKG K1000? Ferrari, some comparisons of all those great amps you've got would be helpful and insightful. Quite curious to know how you would rank them all. 

 I haven't had S22 problems since i got my amp boards to stop blowing MOSFETs (they just sink all the current blowing the MOSFETs on the S22, mainly on the negative rail).


----------



## sachu

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Are your RCA’s still isolated?

 Edit: One of the inputs might be reversed also._

 

Double checked this.. They are isolated. The inputs s far as i can tell they seem fine..Reads continuity from jacks to pot to input on the board.

 Makes me want to take a closer look at the boards once again..especially the one that has given me most of the problem to date.

 But have confirmed that it definitely isn't a potentiometer problem

 Will report back later.


----------



## luvdunhill

sachu:

 Perhaps contact pabbi1 and compare where you purchased your pots from. He has a very similar issue, when dealing with a shunt configured pot, but I'm not sure where he stands on fixing it.


----------



## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I’m using my balanced EHHA with 2 σ22 PS for my AKG K1000 almost daily. 
(The same dual σ22 PS that's feeding my Dynamite and balanced β22).

 It seems to be that I’m the only balanced EHHA owner who has no issues with the PS. 
	

	
	
		
		

		
			



_

 

Maybe I should have sprung for _two_ σ22s 
	

	
	
		
		

		
		
	


	




 I have room in the case...


----------



## sachu

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_sachu:

 Perhaps contact pabbi1 and compare where you purchased your pots from. He has a very similar issue, when dealing with a shunt configured pot, but I'm not sure where he stands on fixing it._

 

Hi Marc,

 Well, I switched out the noble with an ALP RK27 (that was originally doing duty with the EHHA before all this )and the result is the same. 
 So there is something else going on.


----------



## funch

I just installed a DC heater PS I built from Pete Millet's 
 schematic, and reinstalled the 6H30's. Result: absolutely
 no buzz/hum. As sachu has said, the EHHA really needs a
 DC heater circuit, at least if you're gonna run 6H30's. 
 However, I had no hum with AC heaters with either 6GM8's
 or 6922's. 

 sachu, I hope you solve your problem soon, and thanks
 again for your help.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_I just installed a DC heater PS I built from Pete Millet's 
 schematic, and reinstalled the 6H30's. Result: absolutely
 no buzz/hum. As sachu has said, the EHHA really needs a
 DC heater circuit, at least if you're gonna run 6H30's. 
 However, I had no hum with AC heaters with either 6GM8's
 or 6922's. 

 sachu, I hope you solve your problem soon, and thanks
 again for your help._

 

very nice...s hows it sounding now? the bottom end good now?


----------



## funch

Oh yah! Mucho goodo. The only weird thing (still) is that I'm having
 a tough time getting the output quiescent current to stabilize. If I set
 it to .22V at start up, it will drop slowly down to around .18V, then 
 head slowly back up, over a period of about a half hour or so.

 Dunno what that's all about, but it's sounding great.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Oh yah! Mucho goodo. The only weird thing (still) is that I'm having
 a tough time getting the output quiescent current to stabilize. If I set
 it to .22V at start up, it will drop slowly down to around .18V, then 
 head slowly back up, over a period of about a half hour or so.

 Dunno what that's all about, but it's sounding great._

 

Excellent!!..Be sure to post impressions in detail later 
	

	
	
		
		

		
		
	


	




 As to the bias current not stabilizing..i know you've probably checked for it..but maybe its a cold solder joint perhaps?
 is it on both boards or just one channel?


----------



## sachu

I think I am just going to rebuild my EHHA..start a fresh with two new boards...disappointing yes but safer and more durable in the long run perhaps. These two boards have seen way too many burned MOSFEts and resistors.


----------



## funch

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Excellent!!..Be sure to post impressions in detail later 
	

	
	
		
		

		
		
	


	




 As to the bias current not stabilizing..i know you've probably checked for it..but maybe its a cold solder joint perhaps?
 is it on both boards or just one channel?_

 

Forgot to mention that it's in both boards. I've triple checked the boards
 for correct components, and all is well.


----------



## funch

Here's my build. Post #6151.
  
http://www.head-fi.org/t/85561/post-pics-of-your-builds/6150


----------



## pabbi1

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Hi Marc,

 Well, I switched out the noble with an ALP RK27 (that was originally doing duty with the EHHA before all this )and the result is the same. 
 So there is something else going on._

 

Real pity - as I have a rk27 inbound (50k) hoping that would 'work' for lack of a better term. At least it will determine if the pot has any bearing on my issue, which is a bit more complex (shunt design residing on a board). But, I have a remarkably similar issue on a completely different topology.


----------



## sachu

Booyah!!

 My EHHA is finally reborn..yet again!! Am done working on it ..not gonna mess with it ever. I've lost count on how many times i've rebuilt this thing.

 Alex, these are some friggin tough PCBs you've designed..hats off to you again. 
	

	
	
		
		

		
		
	


	




 I am finally able to listen to sweet music from my beloved EHHA. 
	

	
	
		
		

		
		
	


	




 Good thing I didn't give up and trash the boards as planned 
	

	
	
		
		

		
		
	


	




 Now for the money shot


----------



## johnwmclean

Amazing sachu.


----------



## dBel84

I was beginning to despair , glad you got them back . So what was it in the end? ..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_I was beginning to despair , glad you got them back . So what was it in the end? ..dB_

 

Too embarrassed to reveal..It was that idiotic of me


----------



## smeggy

Congrats sachu, glad to see the old gal working again


----------



## pabbi1

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Too embarrassed to reveal..It was that idiotic of me 
	

	
	
		
		

		
		
	


	


_

 

Do tell - may guide others out of the darkness...


----------



## johnwmclean

X2 pabbi1 

 I’m guessing the headphone jack wasn’t pushed in all the way


----------



## sachu

Quote:


  Originally Posted by *smeggy;* 
_Congrats sachu, glad to see the old gal working again_

 

Aye..that it is Smeggy..she's a tough sweet angel. Those boards have been to hell and back and still manage to sound just as good as the day she was new. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Do tell - may guide others out of the darkness... 
	

	
	
		
		

		
		
	


	


_

 

 Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_X2 pabbi1 

 I’m guessing the headphone jack wasn’t pushed in all the way 
	

	
	
		
		

		
		
	


	


_

 

haha..close enough...but yeah I had messed up the wiring on the output jack. Had wired left channel as ground and vice versa...no wonder i was having all those channel problems..cost me 4 good mills and a quad of Mosfets..but live and learn right 
	

	
	
		
		

		
		
	


	




 I had made the exact same mistake on a CTH i was working and was getting the same problems with the left channel. Immediately checked my output wiring which resulted in *facepalm*...and me crying FUUUUUU!!! 
	

	
	
		
		

		
		
	


	




 Anyways..she's all done now..replaced the mills with dale MIL spec non inductive resistors i picked up locally for small change.

 Top panel in and set..no more touching the EHHA.


----------



## funch

Quote sachu:
 Top panel in and set..no more touching the EHHA.
	

	
	
		
		

		
		
	


	





 Sure. Uh huh.


----------



## sachu

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Sure. Uh huh._

 

lol..well in truth i still have an inline fuse i need to put in..need to go pick one up at ratshack. but everything else is done..bias has been set, front panel wiring is complete, shunt resistors are back in place..so am hoping she keeps going strong from here on.


----------



## smeggy

tsk, n00b


----------



## aloksatoor

I need recommendations for a decent DC heater supply for the EHHA build m planning. Is the sigma 11 a good one?


----------



## HeadphoneAddict

Quote:


  Originally Posted by *aloksatoor* /img/forum/go_quote.gif 
_I need recommendations for a decent DC heater supply for the EHHA build m planning. Is the sigma 11 a good one?_

 

I seem to recall wiatrob had a Sigma 22 inside his balanced EHHA (if that helps you at all).


----------



## MrMajestic2

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I seem to recall wiatrob had a Sigma 22 inside his balanced EHHA (if that helps you at all)._

 

But that's not for the heaters though. I guess a Sigma 11 would work, or even a TREAD and the e25 if you don't push them too hard.


----------



## HeadphoneAddict

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_But that's not for the heaters though. I guess a Sigma 11 would work, or even a TREAD and the e25 if you don't push them too hard._

 

I only briefly saw the insides with the top of the amp off. I don't recall seeing an extra PSU inside. I might not have been paying enough attention. You could search this thread for "Sigma 11" or "S11" and for "heaters".

 I did a search for posts by wiatrob and this issue, don't know if any of this helps:

http://www.head-fi.org/forums/5715175-post262.html
http://www.head-fi.org/forums/5743845-post443.html
http://www.head-fi.org/forums/5745811-post467.html
http://www.head-fi.org/forums/6097879-post1032.html


----------



## MrMajestic2

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I only briefly saw the insides with the top of the amp off. I don't recall seeing an extra PSU inside. I might not have been paying enough attention. You could search this thread for "Sigma 11" or "S11" and for "heaters"._

 

Maybe he didn't have a heater supply, only a transformer for AC supply instead. On my EHHA, that I will eventually build, I will try to build a Pete Millet supply for.


----------



## MrMajestic2

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_I only briefly saw the insides with the top of the amp off. I don't recall seeing an extra PSU inside. I might not have been paying enough attention. You could search this thread for "Sigma 11" or "S11" and for "heaters".

 I did a search for posts by wiatrob and this issue, don't know if any of this helps:

http://www.head-fi.org/forums/5715175-post262.html
http://www.head-fi.org/forums/5743845-post443.html
http://www.head-fi.org/forums/5745811-post467.html
http://www.head-fi.org/forums/6097879-post1032.html_

 

Found a post where Wiatrob states he is using this:
H-PS-1 low-voltage regulator


----------



## HeadphoneAddict

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Found a post where Wiatrob states he is using this:
H-PS-1 low-voltage regulator_

 

Yeah, that's in the second link I supplied.

 I'm still in this thread because I was very impressed with wiatrob's balanced EHHA, seeing how it gave my $2500 EC ZDT amp a run for the money and competes very well.


----------



## MrMajestic2

Quote:


  Originally Posted by *HeadphoneAddict* /img/forum/go_quote.gif 
_Yeah, that's in the second link I supplied.

 I'm still in this thread because I was very impressed with wiatrob's balanced EHHA, seeing how it gave my $2500 EC ZDT amp a run for the money and competes very well._

 

I was going to go with the Glassware supply, but the shipping to Sweden kind of killed the deal. If I get lazy I might order it anyway though 
	

	
	
		
		

		
		
	


	




 I'm really looking forward to hearing the EHHA after reading all the raves about it.


----------



## johnwmclean

Voltage Regulator Kit, AC/DC in, DC out, Based on LM317 - eBay (item 260479385900 end time Feb-16-10 05:57:25 PST)

 I bought 4 of these, one for each board of my balanced build. They are rated at max current of 1.5A.

 I have a question is relation to the calculation of amps, would four heater psu’s rated at 1.5A give a total of 6A?


----------



## Ferrari

Mattias, another (cheaper) alternative is just picking one of this power supply.
 Connect a 50W/2x9V toroidal transformer to it and dial the output to 6.3V and you are done.
 This PS has two 6.3V outputs (instead of only 1 output of the H-PS-1), use each output for 2 EHHA boards to reduce the heat.


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Mattias, another (cheaper) alternative is just picking one of this power supply.
 Connect a 50W/2x9V toroidal transformer to it and dial the output to 6.3V and you are done.
 This PS has two 6.3V outputs (instead of only 1 output of the H-PS-1), use each output for 2 EHHA boards to reduce the heat.



_

 

That looks nice, I'll go for that one, thanks.


----------



## les_garten

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_That looks nice, I'll go for that one, thanks._

 


 Check with that vendor. I asked them about this application and believe they told me the current draw was too high for it. Maybe I posed the question incorrectly, who knows.


----------



## Ferrari

Quote:


  Originally Posted by *les_garten* /img/forum/go_quote.gif 
_...
 Maybe I posed the question incorrectly, who knows._

 

Hint: It's based on a pair of LT1083. 
	

	
	
		
		

		
		
	


	



 How much current does a pair of 6GM8 or 6N30P need ?


----------



## dBel84

Quote:


  Originally Posted by *aloksatoor* /img/forum/go_quote.gif 
_I need recommendations for a decent DC heater supply for the EHHA build m planning. Is the sigma 11 a good one?_

 

I would say that the Sigma 11 is the "ultimate" DC supply for the heaters. It is probably an overkill but if you wanted to build an OTT amp, this would be the way to do it. You have already been given a few options in response to your question. I made mine out of a high current , high speed opamp - OPA548 , just one of many ways to create power supplies. 



 Seeing as I am posting, I may as well stir the pot as well. 

 Tube choices:: 

 I have Sachu's EHHA on loan at the moment and I couldn't understand why it sounded lifeless. On a whim I pulled out the Russian 6H30 supertubes and replaced them with a set of amperex 6GM8's - a night and day transformation. I know many folk have reported fantastic things with the 6H30, but my personal experience has not been a positive one with these tubes in this amp. With the 6GM8s the amp shines, has great levels of microdetail and all the slam I could ever want. I am suggesting that new builders keep this in mind and recommend a fair try of the 6GM8 for which this amp was designed. The 6H30 are not only significantly more expensive but need high current heater supplies too. ( 6GM8's are however becoming more pricey themselves. ) 

 ..dB


----------



## les_garten

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Hint: It's based on a pair of LT1083. 
	

	
	
		
		

		
		
	


	



 How much current does a pair of 6GM8 or 6N30P need ?_

 

I sent them an email asking if it would do 6.3v @ 3.6A and they said it was too close to the thermal envelop. Basically telling me "No", it was not right for my application. I arrived at 3.6A as (.9A x 4 tubes).

 Where did I go astray?

 It could have been a different product, but I sure think it was that one.

 p.s. now I see the difference. I am looking at balanced. That makes the difference of course.


----------



## liwei

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Voltage Regulator Kit, AC/DC in, DC out, Based on LM317 - eBay (item 260479385900 end time Feb-16-10 05:57:25 PST)

 I bought 4 of these, one for each board of my balanced build. They are rated at max current of 1.5A.

 I have a question is relation to the calculation of amps, would four heater psu’s rated at 1.5A give a total of 6A?_

 


 I also got those regulators a few weeks ago and noticed that the heatsink isn't isolated from the chip. I had an issue with my metal riser touching the heatsink and possibly getting 12 volts.


----------



## johnwmclean

Quote:


  Originally Posted by *liwei* /img/forum/go_quote.gif 
_I also got those regulators a few weeks ago and noticed that the heatsink isn't isolated from the chip. I had an issue with my metal riser touching the heatsink and possibly getting 12 volts._

 

I noticed there were no isolation pads as well. They are a nice quality build all the same, they have also increased in price since I last bought mine.


----------



## jjazzyj

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_I was going to go with the Glassware supply, but the shipping to Sweden kind of killed the deal. If I get lazy I might order it anyway though 
	

	
	
		
		

		
		
	


	




 I'm really looking forward to hearing the EHHA after reading all the raves about it._

 

Embedded Hybrid Headphone Amlifier

 Details some easy to build supplies that work just fine. Here's a BOM from digikey for the 12.6V supply.

 (4) SB560-E3/51GI-ND 5A 60V Schottky DO201 Diode
 (1) 497-3413-5-ND LDO POS ADJ 5A TO-220
 (1) 493-1572-ND 4700uF 25V UHE Cap
 (1) 493-1549-ND 220uF 25V UHE Cap
 (1) 493-1297-ND 10uF 25V UPW Cap
 (1) CMF1.82KQFCT-ND 1.82Kohm 1/4w Resistor
 (1) CMF200QFCT-ND 200ohm 1/4w Resistor

 It would be easy to find parts for the 6.3V version.


----------



## MrMajestic2

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_Embedded Hybrid Headphone Amlifier

 Details some easy to build supplies that work just fine. Here's a BOM from digikey for the 12.6V supply.

 (4) SB560-E3/51GI-ND 5A 60V Schottky DO201 Diode
 (1) 497-3413-5-ND LDO POS ADJ 5A TO-220
 (1) 493-1572-ND 4700uF 25V UHE Cap
 (1) 493-1549-ND 220uF 25V UHE Cap
 (1) 493-1297-ND 10uF 25V UPW Cap
 (1) CMF1.82KQFCT-ND 1.82Kohm 1/4w Resistor
 (1) CMF200QFCT-ND 200ohm 1/4w Resistor

 It would be easy to find parts for the 6.3V version._

 

Yeah, I have seen that part. I'm just not into bread boarding so I would "have" to order up a board for it. To save myself from that I would like to order a finished product for once 
	

	
	
		
		

		
		
	


	




 I might end up designing a board anyway, but in that case I'll go for the Pete Millet design.


----------



## funch

If you're interested, I have a couple of breadboarded Millet-circuit
 boards similar to the one in my EHHA that I was going to use for
 my Bijou, but didn't. PM me if you would like more info.


----------



## AffeX

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Mattias, another (cheaper) alternative is just picking one of this power supply.
 Connect a 50W/2x9V toroidal transformer to it and dial the output to 6.3V and you are done.
 This PS has two 6.3V outputs (instead of only 1 output of the H-PS-1), use each output for 2 EHHA boards to reduce the heat.



_

 

@ les_garten: Each output for two EHHA boards = 4 boards = balanced setup.
 But I think you might be right, that 4x0.9A would be a little too much for the device Ferrari points at. Anyway a nice on, thanx for the link Ferrari!


----------



## Ferrari

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_@ les_garten: Each output for two EHHA boards = 4 boards = balanced setup.
 But I think you might be right, that 4x0.9A would be a little too much for the device Ferrari points at. Anyway a nice on, thanx for the link Ferrari!_

 

I thought it was clear in post #1312. 
	

	
	
		
		

		
		
	


	




 Once again:

*Each LT1083 (7.5A rated) => one 6.3V PS output => connects to 2 EHHA boards which need ~ 2x0.9A = 1.8A max.*

 Assumming 6N30P tube is used, the 6GM8 needs much less current.
 The same is true for both 6.3V PS outputs !!!

 In my own balanced EHHA, the mentioned PS is used for 4 pieces 6N30P-DR for a couple of months now 
	

	
	
		
		

		
		
	


	




. 
 And FYI, the measured current needed for a pair of these tubes was ~1.62A.


----------



## AffeX

And now even I get it......ordering one of those today. Thanx Ferrari!

 Sorry if I only added confusion. I guess that's the difference of building this amp and actually know what your doing and (like myself) just trying to read all the thousands of posts to try and grasp the good stuff.

 I'm planning this amp for a balanced build at the moment and have all the same questions as les_garten, johnwmclean and many other users. 
 Sadly much of the info available is only about the SE version.

 The heater issue just add that little bit of extra complexity.
 If only Alex would elaborate the info on the EHHA site and maybe give direct guideline on sourcing the heater current.
 In my opinion AMB does this part slightly better documenting builds on his website, and maybe avoiding the same 'stupid' questions over and over in here.

 Anyway. EHHA seems to be a fine amp, and I'm going for it.


----------



## regal

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_.
 In my opinion AMB does this part slightly better documenting builds on his website, and maybe avoiding the same 'stupid' questions over and over in here.

 ._

 


 AMB has a store and sells his amp boards, Alex comes up with designs and they are so downright good that folks make them work. The heaters aren't any more complicated than any triode amp. Just use a tread or two with a case mounted heatsink .


----------



## AffeX

@regal: Yeah, I recon the difference between the two. You really don't need to defend Alex, as I don't intend to attack him cause I have the deepest respect for his work and his contribution to this community - all services free of charge. 
 But having 'someone' to sum up all the valuable info would still be great, but of course if I only had the knowledge I could do it myself.

 To someone like me, that has not had any previous experience with tubes and triode amps, this is just new stuff. I have found myself reading a whole lot of pages here, without really finding the answers I needed to plan my own build or maybe just failing to see it among all other info and build pics.


----------



## regal

Just study Pmillets DC heater page and adapt a tread (tangent website) to it. Makes perfect low cost DC heaters, use a case mounted heatsink. Use the Hammond 8.5V 2A transformer from Digikey. Wire the heaters in parallel.


----------



## dBel84

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_But having 'someone' to sum up all the valuable info would still be great, but of course if I only had the knowledge I could do it myself._

 

Have you read the info on his website? If you have and it still doesn't make sense then I would recommend that you take a step back and rethink your plan. This amp might not be the best to build "blind" ; either do more reading so that you know what you are doing or find someone locally to help you. 

 ..dB


----------



## ujamerstand

A quick question from the curious, a protection circuit such as the epsilon12 is recommended to zero the DC offset at start up; to change the start up delay to the amount of time that is similar in Millett hybrids, one could simply change the values of R11 and C7 to values to let's say, 1M ohms and 470uF? Should C6 be changed as well?


----------



## regal

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Have you read the info on his website? If you have and it still doesn't make sense then I would recommend that you take a step back and rethink your plan. This amp might not be the best to build "blind" ; either do more reading so that you know what you are doing or find someone locally to help you. 

 ..dB_

 



 I agree with dB here, you don't want to end up with a fustrating mess. Start with the SOHAII, its pretty easy if you can understand the heatsink mounting/isolation concept.


----------



## AffeX

@regal and dBel84
 I see what you mean and I appreciate your concern. I can see that EHHA might not be as much a beginners build as the SOHA, but I'm determined on the EHHA, and I'll just have to read more and investigate further until I know what I'm dealing with. But I thank you both for help and hints and hope you will be just as helpful further on. 
 I also appreciate dBel84's view on choice of tubes, as I almost had the impression from this thread, that 6H30dp would be the only tube worth listening to and prices on these tubes almost put me off. Now I go for 100% standard build as provided in the kits from Jeff Rossel. And to be honest this has made it all a little simpler.


----------



## les_garten

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Tube choices:: 

 I have Sachu's EHHA on loan at the moment and I couldn't understand why it sounded lifeless. On a whim I pulled out the Russian 6H30 supertubes and replaced them with a set of amperex 6GM8's - a night and day transformation. I know many folk have reported fantastic things with the 6H30, but my personal experience has not been a positive one with these tubes in this amp. With the 6GM8s the amp shines, has great levels of microdetail and all the slam I could ever want. I am suggesting that new builders keep this in mind and recommend a fair try of the 6GM8 for which this amp was designed. The 6H30 are not only significantly more expensive but need high current heater supplies too. ( 6GM8's are however becoming more pricey themselves. ) 

 ..dB_

 

Hey!
 Was there anything positive with the 6H30's?


----------



## dBel84

They are moar SEXY ..dB


----------



## ujamerstand

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_A quick question from the curious, a protection circuit such as the epsilon12 is recommended to zero the DC offset at start up; to change the start up delay to the amount of time that is similar in Millett hybrids, one could simply change the values of R11 and C7 to values to let's say, 1M ohms and 470uF? Should C6 be changed as well?_

 

Any takers? How did you guys implement your delays?


----------



## AffeX

Can't guide you there, ujamerstand.
 I'm planning to implement epsilon12 as is - no tweaks.


----------



## AffeX

I'm planning this NT-LN 250.30-6 (250VA/2x30v/2x6V) shielded audio torroid from THEL for my balanced EHHA build. 
 My idea is to use 2x30V as is for the s22 psu, and from same torroid connect the 2x6V in series to provide 12V for this power regulator a dual LT1063 power regulator, suggested by Ferrari for powering tube heaters. I will connect the two sides of this power regulator in parallel to the 12V, and set output to 6,3V.

 Any comments on this would be most welcome.
 In particular I'd like to know, if it affects sound quality to pull both amp power and heater power from same torroid?


----------



## ujamerstand

I think if you want to use the epsilon12 circuit you must use the values in modified versions of it. Such as the millett minimax. The higher values in R11 (1M) and C7 (470uF) helps to lengthen the delay at startup to around 47 seconds. The default delay time is apparently three seconds, so your headphones would still see the much of the DC offset after the delay (remember the tubes needs 30 seconds or so to heat up.) And I found out that apparently smaller values at C6 (47uF) helps to get the mute function at shutdown faster; So I'm using those values instead. 

 As for the trafos, I'm thinking along the same line as you are, using a 15V trafos for the heaters, and down regulate it with DC regulators. I don't know if that's going to affect the sound, you might want to try out different configuration to see which one is best.


----------



## dBel84

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_A quick question from the curious, a protection circuit such as the epsilon12 is recommended to zero the DC offset at start up; to change the start up delay to the amount of time that is similar in Millett hybrids, one could simply change the values of R11 and C7 to values to let's say, 1M ohms and 470uF? Should C6 be changed as well?

 ....

 Any takers? How did you guys implement your delays? 
	

	
	
		
		

		
		
	


	


_

 

Well there is a fundamental misunderstanding of what the e12 does in this instance. The DC offset is zeroed by the active EHHA circuitry. The e12 merely acts to monitor this offset and switches the output if the offset is greater than 60mV iirc. Hence at power up and shut down the transients are larger and thus the e12 will protect the headphones in these circumstances. If for some reason the amp fails, the offset will ramp up and the e12 will once again protect the headphones. 

 The Millett Max, minimax etc do not implement a true e12 circuit in the that it does not "sense" the output for dc offset , it is more of a timer for start up and shut down. The questions you ask are not relevant if you use AMB's e12 . 

 ..dB


----------



## AffeX

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_I think if you want to use the epsilon12 circuit you must use the values in modified versions of it. Such as the millett minimax. The higher values in R11 (1M) and C7 (470uF) helps to lengthen the delay at startup to around 47 seconds. The default delay time is apparently three seconds, so your headphones would still see the much of the DC offset after the delay (remember the tubes needs 30 seconds or so to heat up.) And I found out that apparently smaller values at C6 (47uF) helps to get the mute function at shutdown faster; So I'm using those values instead._

 

I see it this way: epsilon12 is not a delay to allow tubes to preheat, but as smeggy just explained it, just to protect headphones for a short period of time after the amp is turned on.
 So first I turn on main power for the tube heater psu. Then either manually or after a timed delay of 30-60 seconds I turn on s22 and as the epsilon12 is powered from the 30V main rails like the amp, the epsilon turns on at the same moment protecting the headphones with the 3 seconds delay.
 For timed startup delay, have a look at this delay as mentioned earlier in his thread.


----------



## Ferrari

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_... I will connect the two sides of this power regulator in parallel to the 12V, and set output to 6,3V.

 Any comments on this would be most welcome.
 ..._

 

It's not a very good idea to use 12V secondary voltage to make 6.3V DC.
 The heatsink will get unnecessary hot, even without load.
 Remember that the voltage after the rectifier bridge is ~16V - 17V.


----------



## ujamerstand

Yes, the mute function protects the headphones, but not the circuit. Would turning on both the heater and the circuit on at the same time be detrimental to the circuit? I mean, would the transistors blow up if I don't wait for the tube to heat up before feeding power into the amp? I hope I am expressing myself clearly, it just seems like the extra complexity is not needed.


----------



## ujamerstand

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_It's not a very good idea to use 12V secondary voltage to make 6.3V DC.
 The heatsink will get unnecessary hot, even without load.
 Remember that the voltage after the rectifier bridge is ~16V - 17V. 
	

	
	
		
		

		
		
	


	


_

 

Would it be okay if the power supply outputs 12.6V DC, and feed the tube heaters in series? Is the wiring like this: V+ ---> V+ Tube1 GND ---> V+ Tube2 GND ---> GND


----------



## digger945

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_Would it be okay if the power supply outputs 12.6V DC, and feed the tube heaters in series? Is the wiring like this: V+ ---> V+ Tube1 GND ---> V+ Tube2 GND ---> GND_

 

Not sure if I understand your hieroglyphics there, but yes you can use 12v and put two heaters in series. Just connect heater ps 12v to one of the heater connections on board #1, and then run a wire from the other connection on board #1 to one of the connections on board #2, then the other connection on board #2 to heater ps ground. The heater connections on the boards are not polarity sensitive, so you can connect positive or ground to either terminal you like.
 Using 12v you'll only need about half the current of a 6v ps.




Embedded Hybrid Headphone Amlifier


----------



## ujamerstand

Ah, why didn't I see that. It makes sense now. Besides that, would it be safe for the tubes and the rest of the amp be power on at the same time? (providing that the headphones are not plugged in, or a muting delay is in effect.)


----------



## digger945

My heater supply is a Radio Shack wallwort. I just plug that in for about 10 seconds and then power up the amp supply(Sigma22), then plug in the phones.
 There is a lot of debate about this, and to be honest I don't know the right way to power up things. I would like to do some tests to see what happens in different scenarios, but don't have the time. 
 I think if nothing is plugged into the phone jack, you should be OK powering up everything at the same time.


----------



## johnwmclean

There’s been quite a few post regarding EHHA set-up, I’d like to run through exactly my plan which may not be the best way but it’s simplistic without the hassle of delays and other components I’m not confident in implementing properly.

 My balanced only build is for both speakers and headphones I’m strictly using all recommended components outline on the EHHA site. I will be using three separate enclosures.

 The psu will use two σ22’s, Conrad heatsinks, two SumR 120VA transformers housed in a separate customised Par-Metal enclosure together with ε24 and σ24 for a Bulgin power switch, a single 8 pole speakOn connecter will perform umbilical duties. 

 The heater psu will be housed in a small separate enclosure, using 4 small 1.5A regulators at 6.3V for each board, together with a suitable transformer, I’m also using a single 8 pole speakOn connecter will perform umbilical duties.

 Which now leaves the amp enclosure, which will have the two umbilical inlets for the heater psu and the psu for the amp boards, customised heatsinks from Conrad will be used as well as a DACT CT2 attenuator. The enclosure is a modushop slimline 415mm x 350mm x 40mm design, 10mm front panel with thicker style tops and base panels, the tubes will sit up on top of the amp.

 So the plan is to basically always turn on the heater psu first, and wait a minute or so before starting up the σ22’s.


----------



## dBel84

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_Besides that, would it be safe for the tubes and the rest of the amp be power on at the same time?_

 

"Two power switches are recommended for the EHHA, one for the heaters and one for the +/- 30V rails, because the tubes needs to warm up (for about a minute) before powering up the amp. Otherwise, the EHHA may be prone to misbehavior while the tubes reach their stable operating point."


 it is all on the website if you care to read it. 

 ..dB


----------



## ujamerstand

Okay, I thought I've read through that site enough times now. I guess not.


----------



## dBel84

lol, it is perhaps that I know it too well - it is a slow learning experience. 

 There were people who built it with a single power switch for rails and tubes to come up at the same time. The theoretical problem is that if the tubes do not conduct, the amp can oscillate and go to one of its rails - this would be a bad thing. 

 ..dB


----------



## AffeX

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_It's not a very good idea to use 12V secondary voltage to make 6.3V DC.
 The heatsink will get unnecessary hot, even without load.
 Remember that the voltage after the rectifier bridge is ~16V - 17V. 
	

	
	
		
		

		
		
	


	


_

 

Thank you for noticing this Ferrari. I also wondered if the 12V would be too much, as you earlier suggested 2x9V.

 So from your post I read this:
 1. I can run both s22 and heater psu from same torroid without compromising sound quality - otherwise I'm sure you would have said so 
	

	
	
		
		

		
		
	


	



 2. As 12V AC rectified gives 16-17V DC, then 6V AC rectified might give me 7-8V DC. So why don't I just use the 2x6V secondary as they are?
 I was afraid, 2x6V AC wouldn't be enough to give me 2x6,3V DC as I believe the rule of thumb says, AC supply larger than DC needed.


----------



## AffeX

Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_Would it be okay if the power supply outputs 12.6V DC, and feed the tube heaters in series? Is the wiring like this: V+ ---> V+ Tube1 GND ---> V+ Tube2 GND ---> GND_

 

I believe so. Sinking from your 15VAC to 12,6V DC sounds more right, than my first idea of sinking 12V to 6,3V.
 Then you just feed tube heaters in series as explained by digger945. If balanced setup, then in series two by two, and then in parallel.


----------



## ujamerstand

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_I believe so. Sinking from your 15VAC to 12,6V DC sounds more right, than my first idea of sinking 12V to 6,3V.
 Then you just feed tube heaters in series as explained by digger945. If balanced setup, then in series two by two, and then in parallel._

 

Yep, I've already got a 50VA transformer with dual secondaries at 15VAC that I can use. I'll use that to power the tube heaters and some more.
	

	
	
		
		

		
		
	


	




 On a side note; dBel84 how did you like the HE-5 with your EHHA?


----------



## dBel84

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_There’s been quite a few post regarding EHHA set-up, I’d like to run through exactly my plan which may not be the best way but it’s simplistic without the hassle of delays and other components I’m not confident in implementing properly._

 

Sounds like an excellent layout , looking forward to the completed product. 

  Quote:


  Originally Posted by *ujamerstand* /img/forum/go_quote.gif 
_On a side note; dBel84 how did you like the HE-5 with sachu's EHHA?
	

	
	
		
		

		
		
	


	


_

 

The amp drives the headphones with ease. As for the headphones themselves, they are superb and even better after redamping and tuning to suite my tastes. 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## ujamerstand

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_The amp drives the headphones with ease. As for the headphones themselves, they are superb and even better after redamping and tuning to suite my tastes. 
	

	
	
		
		

		
		
	


	


_

 

Nice! Its good to hear that. I've just bought a pair for myself, and I can imagine what an awesome combo it'll be.


----------



## AffeX

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_Thank you for noticing this Ferrari. I also wondered if the 12V would be too much, as you earlier suggested 2x9V.

 So from your post I read this:
 1. I can run both s22 and heater psu from same torroid without compromising sound quality - otherwise I'm sure you would have said so 
	

	
	
		
		

		
			




 2. As 12V AC rectified gives 16-17V DC, then 6V AC rectified might give me 7-8V DC. So why don't I just use the 2x6V secondary as they are?
 I was afraid, 2x6V AC wouldn't be enough to give me 2x6,3V DC as I believe the rule of thumb says, AC supply larger than DC needed._

 

Would be very big help for me if someone had a final conclusion on this, so I can get on with my amp, one way or the other. Anyone? Ferrari, maybe?


----------



## digger945

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_Would be very big help for me if someone had a final conclusion on this, so I can get on with my amp, one way or the other. Anyone? Ferrari, maybe?_

 

It depends on what transformer you're going to use and what voltage you decide on. 
 Do you already have a transformer, and if so what voltage and how many primary/secondaries(or a part #)


----------



## AffeX

ok digger945, I'll post a resume, saving you the scrolling 

  Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_I'm planning this NT-LN 250.30-6 (250VA/2x30v/2x6V) shielded audio torroid from THEL for my balanced EHHA build. 
 My idea is to use 2x30V as is for the s22 psu, and from same torroid connect the 2x6V in series to provide 12V for this power regulator a dual LT1063 power regulator, suggested by Ferrari for powering tube heaters. I will connect the two sides of this power regulator in parallel to the 12V, and set output to 6,3V.

 Any comments on this would be most welcome.
 In particular I'd like to know, if it affects sound quality to pull both amp power and heater power from same torroid?_

 

 Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_It's not a very good idea to use 12V secondary voltage to make 6.3V DC.
 The heatsink will get unnecessary hot, even without load.
 Remember that the voltage after the rectifier bridge is ~16V - 17V. 
	

	
	
		
		

		
		
	


	


_

 


  Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_Thank you for noticing this Ferrari. I also wondered if the 12V would be too much, as you earlier suggested 2x9V.

 So from your post I read this:
 1. I can run both s22 and heater psu from same torroid without compromising sound quality - otherwise I'm sure you would have said so 
	

	
	
		
		

		
		
	


	



 2. As 12V AC rectified gives 16-17V DC, then 6V AC rectified might give me 7-8V DC. So why don't I just use the 2x6V secondary as they are?
 I was afraid, 2x6V AC wouldn't be enough to give me 2x6,3V DC as I believe the rule of thumb says, AC supply larger than DC needed._


----------



## digger945

I have already looked back and read all or your posts.
 Give me a minute to translate the specs for your NT-LN 250.30-6.
 It says 250VA and 3.5A. 
 Let me see what I can figure out.
 You are probably going to get quicker answers from Ferrari though.


----------



## digger945

No indication as to how the current is divided between the 30v and 6v secondaries.
 Perhaps you would be better off looking at a transformer that is rated at 6.3v with a load on it.
 The one you are looking at, the NT-LN 250.30-6 has a +7% rating with no load(ohne Last/Leerlauf?), so I assume the given voltages of 30v and 6v are the loaded specs.

 Not only does Duc speak the language, he probably has the correct part for you and one that is close to you as well. 

 Let me look back to his EHHA built and see if I can tell what transformer he used.

*EDIT* I must say that 250VA is kind of overkill for this amp, even in balanced fashion. I run 2 amp boards on one 80VA transformer no problem. You can figure a safe estimate of ~7VA per tube to cover all possible tubes including the 6H30.


----------



## dBel84

I had a quick look at the THEL site (my German is dodgy at best) , it looks like you can run each set of windings at current ratings that should not exceed 50% of the specified voltage. I read the 7% variation as loaded - unloaded so the output should be pretty close to spec'd loaded or unloaded. 

 The LT1083 should be able to regulate ( it has a min 6.5V input requirement ) and current draw will be a fraction of what is needed. I have to agree that 250VA is overkill but if you have already bought, so be it. 

 ..dB


----------



## Ferrari

I have to agree that the NT-LN 250.30-6 transformer from Thel is a bit overkill for the EHHA, especially when using it for a headphone amp. Output voltage at no load (Leerlauf spannung) of this type transformer is +7% higher than the specs, thus 32.1V and 6.42V secondary voltage respectively.

 As digger945 and dBel84 already said, if you already bought this transformer, just use it. 
	

	
	
		
		

		
		
	


	



 Personally I have used an 80VA / 2x9V toroidal (Eur 10 from local discount store) for the heater circuit for my balanced EHHA.


----------



## AffeX

I really appreciate your comments, you are very helpful digger945 and dBel84!
 I have not bought the transformer yet. Looked at this transformer because it's supposed to be 'audio grade', shielded etc 
 I know 160VA would be more than enough for the amp, but they have no 160VA/30V versions of this quality. The s22 kits at GlassJar are limited to 100VA max, and that seemed too little. So I need a different transformer anyway, and figured I could save some space (and money) by using only one transformer for both heater and amps. 
 I want it all in one enclosure, so the shielded transformer to avoid noise/humming seemed like a good idea. 
 You are both right, the 30V is min. loaded, and +7% can be expected unloaded, but what is said about the 50% is, that if eg only one of the 30V outputs is used, it can deliver as much as 3.5 + 50% = 5.25A. 
 I figure that I need 1-1.5A for tube heating 4x6GM8 and about the same for 4xEHHA.
 I'm sure 250VA is enough for both amp and heaters.
 My only worries, except spending money on a total overkill, is that 2x6V won't be enough for the LT1083 power regulator, even though the specs on the Ebay site, says 5-25V AC
 I might just have to try it out or search for similar housed transformers with two secondaries.

 Edit: Just noticed Ferrari already posted - thanx Ferrari. Following your suggestion though, I would need two transformers each about 8-10 cm wide.


----------



## tonearm

You might want to go the dual transformer route. Separate one for the heaters so you can fire them up first using a delay circuit.

Apex Jr has 160VA Avel Lindberg transformer (with dual primaries for 230volt operation) that are suitable for the HV section of the EHHA for about 22$ a piece. He could easily ship it to Europe via USPS small flat rate box for another 12.50$.


----------



## Ferrari

Quote:


  Originally Posted by *AffeX* /img/forum/go_quote.gif 
_...
 My only worries, except spending money on a total overkill, is that 2x6V won't be enough for the LT1083 power regulator, even though the specs on the Ebay site, says *5-25V AC*
 ..._

 

... to get *3V ... 20V DC *out.


----------



## AffeX

Quote:


  Originally Posted by *tonearm* /img/forum/go_quote.gif 
_You might want to go the dual transformer route. Separate one for the heaters so you can fire them up first using a delay circuit.

Apex Jr has 160VA Avel Lindberg transformer (with dual primaries for 230volt operation) that are suitable for the HV section of the EHHA for about 22$ a piece. He could easily ship it to Europe via USPS small flat rate box for another 12.50$._

 

So $35 total but to get it through danish customs would probably add about 50% and I would need dual transformers as you mention. The THEL 250V would easily be a better option, as it's cheaper all in all, shielded, better quality than Avel Lindberg I believe, and I would only need space for one.
 About the delay circuit, I thought of just switching on the transformer with one switch allowing 6V to heat the tubes but delaying the 30V output for a minute using this device also powered from the 2x6V output.


----------



## AffeX

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_... to get *3V ... 20V DC *out. 
	

	
	
		
		

		
		
	


	


_

 

Yeah, I see the hinted voltage drop. So 6V AC may only give me 4.5-5V DC and my plan suck. 6V AC is too low and using the 6V output in series to get 12V is too much for the LT1083. I guess it was too 'perfect' to be a true success. 
	

	
	
		
		

		
		
	


	



 But thanx to all of you for working this through with me.


----------



## digger945

I have used heater voltages from 5.8v to 7v for 6.3v tubes and I really don't see much difference. No difference at all in sound to me.
 I will be looking for something that I think you could use. Do you ever shop ebay? Have you decided if you want to use a seperate transformer and off the shelf PS for the heaters? This info will help when looking for stuff online(if you haven't already purchased the PS unit).


----------



## ujamerstand

Why not just breadboard a regulator? You can add a voltage follower using something like MJE3055 to a LM7812 to provide all the current you'll need. Its a cheap solution too. Instead of spending 30 bucks a regulator, you can spend around 10 bucks for 2 12V regulators, and spend that extra 50 bucks on something else.


----------



## AffeX

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I have used heater voltages from 5.8v to 7v for 6.3v tubes and I really don't see much difference. No difference at all in sound to me.
 I will be looking for something that I think you could use. Do you ever shop ebay? Have you decided if you want to use a seperate transformer and off the shelf PS for the heaters? This info will help when looking for stuff online(if you haven't already purchased the PS unit)._

 

I already paid and ordered, the LT1083 based dual psu from Ebay, that Ferrari suggested. I believe it's a good circuit, and it can provide the current, should I ever roll the tubes and try 6H30. Best alternative would probably be a couple of Avel L. transformers, 160VA/2x30V for the s22 and 80VA/2x9V for the heater psu. I know that's straight forward, but I'd loose the other benefits of the THEL trafo; the space saving and the shielding.

 I may just go the dual transformer route, as tonearm suggested - or use the 6VAC for heating as is. But I know I would hate doing that because of the risk of AC noise.


----------



## jjazzyj

This is the 12V power supply as per the EHHA website. I posted the Digikey BOM earlier. Almost ready for chassis work.

















 I need to build my power supply chassis get the IEC entry module and fuse installed and then time to test the O22 and 12V heater supply.

 I do have a question though, can you put a switch for the 12V secondary and the 30V secondary along with a master switch? I think you can and would it be like this? Though instead of "AC Power" it would be 12VAC and B+ would be 30VAC...


----------



## dBel84

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I do have a question though, can you put a switch for the 12V secondary and the 30V secondary along with a master switch? I think you can and would it be like this? Though instead of "AC Power" it would be 12VAC and B+ would be 30VAC...




_

 


 neat little board for the DC circuit. 

 Your switch idea sounds fine , make sure you use a "shorting" ON-ON type DPDT ie "make before break" type switch and not a "break before make" type. Also not an ON-OFF-ON type for obvious reasons. 

 Another single switch option would be TubeCad's power up rotary switch. 

 ..dB


----------



## jjazzyj

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_neat little board for the DC circuit. 

 Your switch idea sounds fine , make sure you use a "shorting" ON-ON type DPDT ie "make before break" type switch and not a "break before make" type. Also not an ON-OFF-ON type for obvious reasons. 

 Another single switch option would be TubeCad's power up rotary switch. 

 ..dB_

 

This is a blurb from the webpage I got the idea from:

 Combined Power / Standby Switch
 If you move the power switch off the tone (treble on Reverb 12) control (moving power wiring away from signal wiring is a good idea; it reduces hum and in extreme cases improves safety) you can use a DPDT On/Off/On switch for power and standby; wire one side of the switch for power, and the other for standby. Wire it so that when it's in Standby, you have AC but no DC (B+); in the On (Play) position you should have both. These switches are usually off in the middle, but that's OK; just mark things appropriately. Switching through Off to go from Standby to Play seems scary to some folks (it did to me initially) but the duration is brief enough that no harm is done. Lots of Ampegs did this, and Ampegs are known as tough amps. Use a switch with a 250VAC, 1A or higher rating.


----------



## dBel84

The reason for using an ON - ON DPDT switch which does not break contact when switching is that you do not want the heaters to shut down in the process of powering up the rails ( I realize this will only be a fraction of a second and it will most likely not be very significant but it is the sole reason you are going to the trouble of doing this in the first place ). Your motivation for using 2 switches is so that when you power the main power switch , the heaters will automatically come on as you have the second switch wired to do just that. When the heaters have warmed the tubes, you switch on the rails and the amp comes up without a fuss. These 2 switches mimic the rotary idea I linked you. 

 You are not using the switches for a standby mode or anything else, you are acting as a delay , allowing the tubes to warm up before bringing the rest of the amp up. 

 Hope that makes sense..dB


----------



## jjazzyj

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_The reason for using an ON - ON DPDT switch which does not break contact when switching is that you do not want the heaters to shut down in the process of powering up the rails ( I realize this will only be a fraction of a second and it will most likely not be very significant but it is the sole reason you are going to the trouble of doing this in the first place ). Your motivation for using 2 switches is so that when you power the main power switch , the heaters will automatically come on as you have the second switch wired to do just that. When the heaters have warmed the tubes, you switch on the rails and the amp comes up without a fuss. These 2 switches mimic the rotary idea I linked you. 

 You are not using the switches for a standby mode or anything else, you are acting as a delay , allowing the tubes to warm up before bringing the rest of the amp up. 

 Hope that makes sense..dB_

 

I get it now. Thanks for the help.


----------



## pidesd

hi guys,

 maybe it has been said before but within what voltage range should the ehha PSU operate? 30V +-...?

 i ll be using a sigma22 and i m wondering whether to get a 25ac or 32ac transformer and i dont want the psu transistors to heat up too much


----------



## johnwmclean

Have you checked out the website? PSU must be 30V + 30V, your transformer spec looks too low, check the AMB site for the correct VAC.


----------



## pidesd

i d like to know what voltage range the EHHA is comfy with because if it can take +-25V happily i d take a 25V AC trafo, so that i have 9V drop across the mosfet. if i choose the +-32V AC trafo, then to get +-30V the mosfet drop would be around 15V(IIRC).


----------



## jjazzyj

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I get it now. Thanks for the help. 
	

	
	
		
		

		
		
	


	


_

 

Just so I get this switch wiring straight in my head. Here's how I 'think' it should be wired on the secondary...


----------



## MrMajestic2

My PSU box is starting to get really cluttered and Im only at the planning stage 
	

	
	
		
		

		
		
	


	




 Would it be a safe assumption that I could run the Sophia Electric delay boards from the Heater supply with 6.3V DC if I remove the input caps and the diodes on it?


----------



## Symphoenix

I finished soldering a classic stereo EHHA yesterday night and decided to give it a try... Oh my ! I stayed up all night listening to my favorite tracks and finally took some pictures of the glowing tubes (6H30P-DR fed with DC from HPS1). Of course, the circuits are all naked so i tried to kept them in the dark (shy person those ones).




































 Sigma 22:


----------



## stew1234

Very nice looking. 

 As far as choosing a heater supply I'm surprised I haven't seen people go with the sigma 11 more. Not including a transformer or shipping its $40 from Glass jar audio which if you're ordering the s22 and EHHA kit from there anyways doesn't really add to shipping. If you're in the US it's less than than some of the ebay supplies posted earlier in the thread. 

 Even if it's overkill it's not really much more.


----------



## sachu

well a simple heater circuit like the one Allex Cavalli has on his website is easy enough to throw together for under 20$ including transformer.

 Very cool pics Symphoenix...i guess you staying up all night listnening to it summed up your thoughts on its sound quality 
	

	
	
		
		

		
		
	


	




 Btw, have you tried the 6GM8s at all in the amp as against the 6H30? Would love to know your opinion on it.


----------



## TheShaman

Would the (theoretically) lower noise of the Sigma11 add anything to the performance of the amp over a plain vanilla PSU like the one Cavalli suggests?


----------



## regal

Quote:


  Originally Posted by *TheShaman* /img/forum/go_quote.gif 
_Would the (theoretically) lower noise of the Sigma11 add anything to the performance of the amp over a plain vanilla PSU like the one Cavalli suggests?_

 

Doubtful on indirect heated triodes


----------



## johnwmclean

Not to mention getting a Sigma11's output close to 6.3V would be trial and error.


----------



## nattonrice

I think I am being blind here so if I am please feel free to yell at me...

 I noticed in the NorCal meet photos someone has a recently completed EHHAII prototype.
 I've searched around and I can't seem to find any information on this.
 Is it a complete redesign or just a small modification?
 Was/is there a thread that I seem to have searched right over?


----------



## TheShaman

I think EHHA II was initially planned to be a speaker amp. Was there a change of plans?


----------



## johnwmclean

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_I think I am being blind here so if I am please feel free to yell at me...

 I noticed in the NorCal meet photos someone has a recently completed EHHAII prototype.
 I've searched around and I can't seem to find any information on this.
 Is it a complete redesign or just a small modification?
 Was/is there a thread that I seem to have searched right over?_

 

I’ve just searched http://www.head-fi.org/forums/f45/no...ssions-474994/ I can’t find any reference to an EHHAII, what was the post number?


----------



## nattonrice

LOL comprehension fail... 

 I meant the Seattle/Portland thread!
 2nd post by dbel84.


----------



## johnwmclean

Thanks Tom!


----------



## dBel84

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_I think I am being blind here so if I am please feel free to yell at me...I noticed .. someone has a recently completed EHHAII prototype._

 

Sorry to be the tease, but this was a one off build which came about after several years of intermittent communication between AC and myself. This particular amp will not be released as DIY. 

  Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_I've searched around and I can't seem to find any information on this. Is it a complete redesign or just a small modification?_

 

There is no information available about the amp. It is to some level a complete redesign but retains the principles of the EHHA. In essence it runs high voltage rails, has a tube gain stage and remains DC coupled. 


  Quote:


  Originally Posted by *TheShaman* /img/forum/go_quote.gif 
_I think EHHA II was initially planned to be a speaker amp. Was there a change of plans?_

 

The DIY EHHA II was originally pegged as a 4 layer PCB with a very small footprint and purely a speaker amp. 

 ..dB


----------



## sachu

The EHHA-2 is sure to make waves when and if it does get released. 

 It has closed the gap right up to the stacker 2 and even surpasses it in some areas. I am finally glad to say the EHHA(albeit version 2) is back at the top of my list of headphone amps. I didn't get a good chance to listen to it however so look forward to having a coupleof mini meets at my place comparing all the best of the Cavalli amps side by side. TO pick a clear winner would be tough..the two have their own individual sound signatures which is quite easy to notice.


----------



## aloksatoor

should be simple enuff by buying a handful of 6.3V D5 zeners and testing them out. And would not need to install the R10 resistor which makes it simpler.

  Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Not to mention getting a Sigma11's output close to 6.3V would be trial and error._


----------



## Symphoenix

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Very cool pics Symphoenix...i guess you staying up all night listnening to it summed up your thoughts on its sound quality 
	

	
	
		
		

		
			





 Btw, have you tried the 6GM8s at all in the amp as against the 6H30? Would love to know your opinion on it._

 

Thanks man. Yeah great sound quality : rich bass, very good separation of the instuments, highs aren't agressive (important for my taste).
 I haven't tried the 6GM8s yet but intend to very soon. I'll keep you informed


----------



## nattonrice

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_Sorry to be the tease, but this was a one off build which came about after several years of intermittent communication between AC and myself. This particular amp will not be released as DIY._

 

Oh that's a shame~ it looked really wicked.

 Perhaps sometime in the future a variant may be released under the same name


----------



## sachu

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_Perhaps sometime in the future a variant may be released under the same name 
	

	
	
		
		

		
		
	


	


_

 

Sure..one can dream 
	

	
	
		
		

		
		
	


	




 Back to the EHHA, I was wondering what kind of circuit adjustments need to be made to run the tube hotter. WIth only 1.5mA on the plates and 30 volts we are barely dissipating anything on the plates. I was wondering if we could increase the plate current to about 7.5mA. We should still be well within dissipation limits for the 6GM8.

 This would mean changing R3, R4 and then the current mirror appropriately..

 Any changes in the VAS? any other changes?


----------



## adamus

i get slightly lost, but there is a css in the tail. 

 two diode drops -vbe = 0.7v ish

 0.7v / 200 = 3.5ma
 so just over 1.5ma per triode

 so r9 is setting the tail current.


----------



## pidesd

can i use 2 6gm8 and 2 6n27p in a balanced config.? to they behave they same way?

 @adamus,

 thanks for the link about the shunt reg on diyaudio


----------



## jjazzyj

This is my work on the S22 power supply so far. The transformer is sized to be able to drive speakers and although it is a tight fit, I will be able to add an additional S22 board. The umbilical cable will also be able to accommodate a separate 30GND-30 run to the second set of EHHA boards. I kept the umbilical extremely short for obvious reasons. I hate acrylic, but unfortunately no one sells translucent white polycarbonate. The bottom is 1/4" polycarbonate. That way you will see a nice blue glow from the bottom of the power supply as well as the translucent plastic giving you a nice warmth from the LED as well. Next is drilling and tapping the polycarbonate for the standoffs/xfmr mounting. AC GND will be tied to the aluminum frame. The Balanced EHHA amp will be in an identical chassis. And by doing this I can build a B22 and use the same power supply if I want 
	

	
	
		
		

		
		
	


	

























 The umbilical cable:









 This project was certainly a little bit over my head. I can almost see the light at the end of the tunnel. Once I get the power supply assembled and tested I'll feel a little better.


----------



## sachu

Excellent work..i love the poly carbonate...giving me quite a few ideas for future builds. Look forward to seeing the EHHA take shape.

 Be careful when setting up the EHHA boards. I have lost not just the EHHA output mosfets, but sadly the S22 mosfets as well when something goes wrong. The costs can add up real quick. A steady hand and triple checking the boards go a long way in avoiding disaster here.


----------



## jjazzyj

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_Excellent work..i love the poly carbonate...giving me quite a few ideas for future builds. Look forward to seeing the EHHA take shape.

 Be careful when setting up the EHHA boards. I have lost not just the EHHA output mosfets, but sadly the S22 mosfets as well when something goes wrong. The costs can add up real quick. A steady hand and triple checking the boards go a long way in avoiding disaster here._

 

I've read your misadventures, that's why when I ordered my mosfets I ordered twice as many as I'd need.


----------



## jjazzyj

So I just finished up my S22/12V power supply. Everything tests good, looks like I did a good job. However the LED does not light. Now I ordered a kit from Glass Jar and it came with 2 10kohm resistors for the LED's but according to my calcs that value is too high, it should be 2 1.5kohm resistors. What LED resistors did anyone here use?


----------



## johnwmclean

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_So I just finished up my S22/12V power supply._

 

12V what for? Is the LED orientation right?


----------



## jjazzyj

The 12V is the heater supply for the EHHA. The funny part is my LED tester lights up the LED on the board when I connect it with the same orientation that is on the board. I used an online LED resistor calculator to come up with the 2 1.5kohm value.


----------



## johnwmclean

A σ22 for the heater supply? OMG that’s overkill on steroids 
	

	
	
		
		

		
		
	


	




, are you sure you didn’t mean the σ11?


----------



## jjazzyj

You misunderstood me the power supply for the EHHA is the S22 and in the same power supply chassis I also have a 12V power supply. So it is a S22/12V power supply.


----------



## johnwmclean

Good gratuitous, thank goodness for that. hehe.

 There’s also a LED calculation on the AMB site, under the σ22 parts list, maybe check that out and see if the both calculations match. 
 I’ve used 10KΩ resistors for all my σ22 builds all parts were from GJA.


----------



## jjazzyj

I used that calculator just to make sure and it told me for a source voltage of 60V (as the LED sees both voltages and AMB sites says to do so) to use a 2900ohm resistor, hence the 1.5kohm resistor for each rail comment earlier.


----------



## sachu

Agreed, 10k is a bit too much to get the LED to glow well enough on the amp boards..1.5k should be plenty good here.


----------



## Horio

So I am in the process of finalizing my BOM for my MOSFET EHHA build. Question about the R32/R33 2Watt resistors. I am having a hard time finding metal film resistors to fit the bill. As an alternative I thinking of using a 2.2ohm 5% metal oxide resistor, or a 2.0ohm metal film 5% resistor. What would be the affect of using a 2.0ohm resistor anyway? Higher output?

 Thanks


----------



## sachu

panasonic Metal oxide 2.2ohm resistors are fine. You could also try going for non-inductive wire wound type from Mills here. 
 As to using 2 ohm resistors, i think you may have to bias the quiescent current a tad higher to make sure the Mosfets are conducting and operating optimally. If I am missing something else here am sure someone else will chime in.


----------



## Horio

Thanks Sachu!

 Another question, on the Cavalli website it shows C8 as polypropylene/polyester film capacitor with a lead spacing of 2.5mm. Was this a typo by any chance? I'm not seeing any 2.5mm L.S. polyester caps and looking at the 3D rendering on the boards page, it looks more like a multilayer ceramic capacitor.


----------



## sachu

Am sure you could make do with just a MLCC cap..I used a 5mm pitch polypropylene box cap on my builds.


----------



## jjazzyj

Well here are some photos of the finished EHHA power supply. It contains a 360VA SUMR custom transformer with 30-0-30 and 12-0 secondary windings each rated @ 5A. The 'glowy' concept of the chassis design was for the most part a success. The fit and finish of the final chassis, well I'd say about 75% I could get it to 90% but I'm being lazy for now. If I could have gotten the acrylic panels cut on a table saw with a plastic blade I'd have been happier then scoring and snapping which didn't turn out as nice as I'd hoped. Maybe later I'll redo the panels as the entire chassis design is modular. Now to build chassis #2 for the balanced EHHA preamp/headphone amp. I apologize for the bad pictures as my camera and skills for dark photos are extremely bad. Actually my photo taking skills are just bad in general.


----------



## sachu

Very cool stuff Jazzy..very cool indeed.

 In fact i just turned on my own EHHA after more than 2 months after being only on the stacker 2..the EHHA is one sweet amp for sure. Enjoy.


----------



## TheShaman

Looks cool! Any pics of the inside? 
	

	
	
		
		

		
			





 Did anyone have the chance to compare the EHHA to an Aikido (pref. high voltage)?


----------



## Horio

So I'm thinking about using one of the Glassware H-PS-1 heater supplies in my balanced build. I want to be able to run 6H30's which need roughly 1A each. So if I use this kit at 12.6V and wire the tubes in (2) parallel sets, my draw should be 2A. 

 If I go with a 6.3V-0-6.3V (wire in series) center tapped transformer, the rectified voltage is roughly 12.6V x 1.3 = 16.4V. My understanding is the LM1085 has about 0.6V drop, so power dissipated would be:

 V drop => (16.4V-0.6V)-12.6V = 3.2V
 P to dissipate => 3.2V*2A = 6.4Watts

 Per the TubeCad.com blog, with the LM1085 with the 2.5" heatsink can shed about 8Watts.

 Does this look correct to you guys? Please be kind, I am no EE guy but I am trying to learn...


----------



## Lifthanger

it's 12.6V x squareroot of 2 ( 1.414) = 17.82V


----------



## Horio

Quote:


  Originally Posted by *Lifthanger* /img/forum/go_quote.gif 
_it's 12.6V x squareroot of 2 ( 1.414) = 17.82V_

 

Thanks Lifthanger. So the revised calc:

 Vdrop => (17.8V-0.6V)-12.6V = 4.6V
 P to dissipate => 4.6V x 2A = 9.2W

 Looks like that puts me over, so I'd need another heatsink option or perhaps two supplies.


----------



## mideel

Quote:


  Originally Posted by *Horio* /img/forum/go_quote.gif 
_V drop => (16.4V-0.6V)-12.6V = 3.2V
 P to dissipate => 3.2V*2A = 6.4Watts

 Per the TubeCad.com blog, with the LM1085 with the 2.5" heatsink can shed about 8Watts._

 

You might be a little off on your calculations, using the guide from AMB I get:

 P = (Vin - Vout) * I
 Tj = Ta + (P * (Rjc + Rcs + Rsa))

 P = ((12.6V*sqr(2)) - 12.6V) * 2A = 10.44W
 Tj = 30°C + (10.44W*((3.0°C/W) + (0.0045°C/W) + 2.60°C/W)) = 88.51°C

 * Tj = junction termperature (LM1085)
 * Ta = ambient temperature
 * P = power to be dissipated
 * Rjc = thermal resistance of junction to device case (LM1085)
 * Rcs = thermal resistance of device case to heatsink (Thermal Paste I use)
 * Rsa = thermal resistance of heatsink to ambient ( 530002b02500g)

 This is still in the recommended temperature range of the LM1085 by: 125°C-88.51°C = 36.49°C and well under 100°C (even If Rcs would be as high as 1°C/W we get 99°C)

 EDIT: Also the "8W @ 30°C" is based on air circulation near the heatsink or the air velocity, as is stated on the aavidthermalloy page
 So in conclusion:


----------



## Horio

Mideel, thanks for the info/calc.

 One issue I see, is the unit is going to be enclosed in a chassis with two o22. Though there are some vents on the top panel, I could potentially see the internal temperature rising above 30C. If you do the calculation with say 40C, you bump right up to the 100C recommended threshold.

 So maybe if I went with a 12VAC toroid xformer, and I re-run the calc I get about 89C. Maybe that would work...


  Quote:


  Originally Posted by *mideel* /img/forum/go_quote.gif 
_You might be a little off on your calculations, using the guide from AMB I get:

 P = (Vin - Vout) * I
 Tj = Ta + (P * (Rjc + Rcs + Rsa))

 P = ((12.6V*sqr(2)) - 12.6V) * 2A = 10.44W
 Tj = 30°C + (10.44W*((3.0°C/W) + (0.0045°C/W) + 2.60°C/W)) = 88.51°C

 * Tj = junction termperature (LM1085)
 * Ta = ambient temperature
 * P = power to be dissipated
 * Rjc = thermal resistance of junction to device case (LM1085)
 * Rcs = thermal resistance of device case to heatsink (Thermal Paste I use)
 * Rsa = thermal resistance of heatsink to ambient ( 530002b02500g)

 This is still in the recommended temperature range of the LM1085 by: 125°C-88.51°C = 36.49°C and well under 100°C (even If Rcs would be as high as 1°C/W we get 99°C)_


----------



## Lifthanger

Quote:


  Originally Posted by *Horio* /img/forum/go_quote.gif 
_Thanks Lifthanger. So the revised calc:

 Vdrop => (17.8V-0.6V)-12.6V = 4.6V
 P to dissipate => 4.6V x 2A = 9.2W

 Looks like that puts me over, so I'd need another heatsink option or perhaps two supplies._

 

no problem, I'll run into the same problems as soon as I start working on my 4 EHHA boards


----------



## johnwmclean

Horio,

 For a 12.6V output wouldn’t the transformers secondaries need to be a few volts higher (a little bit of headroom needed), your more likely looking at a 15VAC.


----------



## Horio

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Horio,

 For a 12.6V output wouldn’t the transformers secondaries need to be a few volts higher (a little bit of headroom needed), your more likely looking at a 15VAC._

 

Someone please correct me if my understanding is wrong, but the rectified voltage of 12VAC is:

 12V x 1.414 = 16.98V

 LDO regulators (like the LM1085) only drop the voltage about 0.6V so:

 16.98V - 0.6V = 16.4V

 So this means the regulator has to shed another 3.8V to get down to 12.6V. Am I thinking of this correctly?


----------



## tomb

Quote:


  Originally Posted by *Horio* /img/forum/go_quote.gif 
_Thanks Lifthanger. So the revised calc:

 Vdrop => (17.8V-0.6V)-12.6V = 4.6V
 P to dissipate => 4.6V x 2A = 9.2W

 Looks like that puts me over, so I'd need another heatsink option or perhaps two supplies._

 

Actually, you've got drop in the rectifiers as well - 1.4V in a bridge. Plus, you're only going to hit ~0.9 of the 1.414 times the AC voltage when fully rectified. So, you'd have (17.8V x 0.9) - 1.4 = 14.62V going into the regulator. The voltage drop that would have to be dissipated would then be (14.62VDC) - 12.6VDC = 2.02V. Power is then 2.02 x 2A = 4.04W. Say, 4W.*

 Of course, this also depends on the current rating of the transformer. If significantly over-rated, it may supply up to a volt or more extra voltage. I've not found too many transformers that supply more than about a volt over rating in this range when under almost any kind of load, though, so use your best judgment. At any rate, it's probably a lot less power to dissipate than first thought.


----------



## Horio

Quote:


  Originally Posted by *tomb* /img/forum/go_quote.gif 
_Actually, you've got drop in the rectifiers as well - 1.4V in a bridge. Plus, you're only going to hit ~0.9 of the 1.414 times the AC voltage when fully rectified. So, you'd have (17.8V x 0.9) - 1.4 = 14.62V going into the regulator. The voltage drop that would have to be dissipated would then be (14.62VDC - 0.6VDC) - 12.6VDC = 1.42V. Power is then 1.42 x 2A = 2.84W. Say, 3W.

 Of course, this also depends on the current rating of the transformer. If significantly over-rated, it may supply up to a volt or more extra voltage. I've not found too many transformers that supply more than about a volt over rating in this range when under almost any kind of load, though, so use your best judgment. At any rate, it's probably a lot less power to dissipate than first thought.
	

	
	
		
		

		
		
	


	


_

 

Thanks Tomb. This is all very helpful and informative. So, say I went with a 12VAC toroid xformer:

 Rectified Voltage => (12V x 1.414 x 0.9) - 1.4V = 13.9V
 Power to Sink => (13.9V - 12.6V) x 2A = 2.6W

 So per this calculation, the 2.5" heatsink has to only dissipate 2.6W. Even if the toroid xformer was putting out an extra volt, that still only bumps it up to 4.6W, which shouldn't be too much of a problem.


----------



## Horio

So the 6GM8 tubes are pretty expensive/hard to come by, but the 6922's are much easier to find. How do the 6922 tubes stack up against the 6GM8's or 6H30's? I'm looking for a decent tube for setting up the amp and to get it up and running.


----------



## digger945

Quote:


  Originally Posted by *Horio* /img/forum/go_quote.gif 
_So the 6GM8 tubes are pretty expensive/hard to come by, but the 6922's are much easier to find. How do the 6922 tubes stack up against the 6GM8's or 6H30's? I'm looking for a decent tube for setting up the amp and to get it up and running._

 

I've also used 6DJ8, 7308, and 7DJ8/PCC88.
 I only have one pair of Sylvania 6922s. They are ok, to me. I like the 7308s better. Each one is different.

 EDIT: I'de loan ya a pair of Sovtek 6H30s but I loaned them to a HF'er over a year ago and haven't seen them since.


----------



## sachu

Quote:


  Originally Posted by *digger945* /img/forum/go_quote.gif 
_I've also used 6DJ8, 7308, and 7DJ8/PCC88._

 

Yeah, but I didn't find the 6DJ8 to sound as good as the 6GM8 in the EHHA.


----------



## funch

FWIW, these guys Antique Electronic Supply have 6GM8's for
 $5.40 each. I placed an order for 5 yesterday 'cuz that's all they had,
 so I figured I'd snatch 'em up and pass the deal along to those who
 were building an amp, but this evening their website shows that they
 have 6 more. Dunno what's up with that. I'll post the brand when mine
 come in.


----------



## funch

What a grab-bag lot of 5. 
 1. Amperex - made in Germany, original Amp. green and yellow box.
 2. Amperex - made in Holland, ditto on the box.
 3. Bugle Boy - made in Germany, in new white box.
 4. GE - made in Holland, orig. box.
 5. Admiral - made in Holland, Admiral 'Supertron Tube' box.

 I'll try to post pix tomorrow. Now I see AES is out of them again.


----------



## funch

Pix:






















 Good news: 6GM8's for cheap.
 Bad news: not a match in the bunch.


----------



## digger945

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Bad news: not a match in the bunch._

 

They don't test the same?
 Many tubes can be identical and have all sorts of brand names or print.


----------



## funch

Oh, I have no way of testing them. I was just saying that none of them are
 the same by appearance, although they all may be Amperex manufacture.
 I really don't know enough to say.


----------



## johnwmclean

Thanks funch, for letting us know!


----------



## jjazzyj

Quote:


  Originally Posted by *funch* /img/forum/go_quote.gif 
_Oh, I have no way of testing them. I was just saying that none of them are
 the same by appearance, although they all may be Amperex manufacture.
 I really don't know enough to say._

 

I always buy my tubes from AES. They have the best prices on any tubes. I ordered my 6gm8's from them 6 months ago when they were on sale for 4.80. Out of the 8 that I ordered 6 were amperex and 2 were Zenith made in Germany so in other words amperex made those too. Tube rebranding happened alot back then.


----------



## johnwmclean

The EHHA I’m building is for speaker and headphone use, I’ve become stuck with switching/wiring, would it be a simple matter of wiring up the outputs for speakers, is there a need for switching? I will be socketing all gain positions and a zobel network will be added to the speaker jacks. Looking for the best way to implement this into the build, I’m using customs heatsinks, which will allow me to keep the FET’s on board so oscillation shouldn’t be an issue. 
 Thanks guys!


----------



## runeight

Good question. Did we change the value of R13 for the speaker build?? If so, you might need to switch here for HP or speakers. If not you're good.

 The zobel shouldn't affect the headphones too much, but if you really want to be pure about it you could switch those in/out too. However, you'll have to be careful about the leads to/from the zobel as the zobels need to be on the jacks if possible and leads will add some small amount of inductance. 

 This is not an area where I have looked deeply into best practices etc. so others may have better info or suggestions.

 These changes would be enough.


----------



## johnwmclean

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Good question. Did we change the value of R13 for the speaker build?? If so, you might need to switch here for HP or speakers. If not you're good._

 

Alex, R13 is 1k2 which is the default value, under TWEAKS > Power Amplifier it remains unchanged.

 Looks like I can omit switching


----------



## sachu

I gave the power amp tweak a try and it burned two pairs of my output mosfets immediately. Was too tired with the problems in my EHHA so ended up defaulting to the speaker setup for the VBE multiplier.

 So are you going to go speaker out on the VBE multiplier John?

 I do have a switch on my amp however..I have the amp wired to the binding posts with a zobel (but VBE multiplier is for headphone loads only)..I use the switch (an On-ON DPDT switch) so I can just use it when I turn on /off my amp or change headphones without having to turn the volume down.


----------



## johnwmclean

I’m *very* sketchy with this Sach, I was planning to use the same outputs for BOTH headphones and speakers.
 I guess from what you’ve said they need to be kept separate, as they need different voltages? I’m also in lala land with how the VBE multiplier thingy works in this situation, so, from PCB, where would the I connect outputs for speakers?


----------



## sachu

No,

 the same outputs go to the speaker binding posts as well..jsut that on the binding posts you have the zobel..

 With a 10A DPDT (in you case you will need a 4PDT for balanced) on-on switch, the output of the amp boards go to the input of the switch and from there you will wire one possible output set of pins on the switch to the speaker (put the zobel in there on the binding posts) and then the other set of outputs from the switch go to the headphone out.

 My amp boards are configured for headphone load, but I am guessing i should be able to run small efficient speakers with it as well.

 The VBE multiplier controls the operting point of the output MOSFETs..in the power amp configuration with R20 being smaller (100R trimpot) you push though a higher voltage out to the gates of the mosfets, thus you need to replace the output resistors with smaller ones at 0.47 ohms instead of th standard 2.2R which is used for headphone loads.. If any of this is wrong, please feel free to correct me folks.


----------



## nattonrice

John, the zobel network should be (air) wired directly to the binding posts.
 If you are worried about mechanical stability just you a small dab of hot glue to fix the cap and resistor to the back panel next to the post.


----------



## johnwmclean

sachu, that’s the info I need! Thanks a bunch for all the help you’ve been thus far through this thread.

 Tom, that’s a great tip! Cheers.


----------



## mideel

I recently bought MrMajestic2 balanced EHHA kit and my build is going along nicely:



 The build includes o22 PSU with 100VA 2x30V Trafo, 12.6V o11 heater with 25VA 2x15V Trafo. All gain resistors are socketed, for tweaking. I'm still undecided on the volume control. I'm thinking of using two shunted alps pots at first and then maybe doing something crazy ie. using 17 switches and a PGA2320. What ever I end up doing case work is going to be a pain 
	

	
	
		
		

		
			




 But at least I'm making good progress, the o11 just tested OK, I used 12V zener diode (measured 12.01V) and a 220kohm resistor to set the voltage at the output to 12.6V.


----------



## johnwmclean

Quote:


  Originally Posted by *mideel* /img/forum/go_quote.gif 
_I recently bought MrMajestic2 balanced EHHA kit and my build is going along nicely:
 The build includes o22 PSU with 100VA 2x30V Trafo, 12.6V o11 heater with 25VA 2x15V Trafo. All gain resistors are socketed, for tweaking. I'm still undecided on the volume control. I'm thinking of using two shunted alps pots at first and then maybe doing something crazy ie. using 17 switches and a PGA2320. What ever I end up doing case work is going to be a pain 
	

	
	
		
		

		
		
	


	



 But at least I'm making good progress, the o11 just tested OK, I used 12V zener diode (measured 12.01V) and a 220kohm resistor to set the voltage at the output to 12.6V._

 

Congrats mideel, just curious about your transformer for the σ11, going from the AMB site 2x8V would be best for a 12VDC output. A 25VA might be a to a little low for balanced (depending on what tubes you intend to use). I ran into some pretty tight thermal figures for making a σ11 viable for heater use, looks like the σ11 may be a heater in itself 
	

	
	
		
		

		
		
	


	




 Someone correct me if I’m wrong on this!


----------



## Horio

Even though I am planning to use 6gm8's on this amp, I wanted to option to power 6h30's. The thermal issues I kept encountering with a o11 heater supply eventually led me to order a glassware H-PS-1 (shows up today). I'll be interested to see how it the o11 works out for you mideel.


----------



## mideel

25VA with 2x15V in parallel, each 6GM8 draws 330mA (6.3V). Two tubes in series will draw 330mA (12.6V), so 4 tubes will draw 660mA (12.6V). The transformer is rated at 25VA/15V=1.66A.
 The 6H30 tube is rated: Voltage: 6.3V Current: 0.825 A, so I wont be able to use 6H30 with this transformer.

 P = (Vin - Vout) * I [Vin and Vout measured with 47Ohm test load]
 P = (20.25V - 12.6V) * 0.66A = 5.05W

 "Since two paralleled MOSFETs serve each rail, each MOSFET will dissipate half the power."

 Tj = Ta + (P * (Rjc + Rcs + Rsa)) 
 Tj = 30°C + ((5.05W/2) * (3.3°C/W + 1°C/W + 3.7°C/W)) = 50.2°C

 "if the two MOSFETs will be mounted on the same heatsink, then the full power dissipation figure should be used."

 Tj = 30°C + ((5.05W) * (3.3°C/W + 1°C/W + 3.7°C/W)) = 70.4°C

 With the 6H30 tubes I would get 2.5 current draw resulting in: 
 Tj = 30°C + ((12.625W/2) * (3.3°C/W + 1°C/W + 3.7°C/W)) = 80.5°C

 And just to confirm my measured results with 0.26A current draw (the mosfet heatsinks measured in at 34°C after 10 minutes):
 Tj = 24°C + ((2.051/2) * (3.3°C/W + 1°C/W + 3.7°C/W)) = 32.2°C

 Unless there is an error with these calculations, the default heatsinks should be enough even for 6H30 tubes and I can always use a fan or two from the 12.6V to cool the case down, if the heat proves to be a problem.


----------



## Horio

I'm not seeing anything in your calculation. Runing 6gm8's versus the power hungry 6h30's really helps the thermal issues. Let us know how it turns out.


----------



## rhester

Have there been any one box builds of this or should 2 boxes be used to minimize noise? Ready to box up but want to make it as nice sounding as pssible.


----------



## sachu

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Have there been any one box builds of this or should 2 boxes be used to minimize noise? Ready to box up but want to make it as nice sounding as pssible._

 


 I have built a one box SE EHHAs thus far and have had no problems at all. I just made sure when i laid it out I had maximum distance from the transformer to the amp boards and signal wring (used shielded cables here). But on my main build no shieldded wires nothing, it just works perfectly. The caveat however is that I use orthos for listening. I did notice however it performed with the blackest of backgrounds with the AG K701 as well. But, when I had the JH13pro on loan and plugged it in, i could hear some hiss.


----------



## sachu

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Have there been any one box builds of this or should 2 boxes be used to minimize noise? Ready to box up but want to make it as nice sounding as pssible._

 

Rhester, to answer your question, I think this is as compact an EHHA (with an S22, DC heaters and relay ) can be built. Case dimensions are roughly 3.5 x 14 x 7.


----------



## mideel

Just a small update on my EHHA progress, I got my o22 power supply assembled and tested with two 2x15V 25VA transformers (my 100VA transformer might be weeks away from arriving because of the ban on air flight over Europe). After trying several 12V zeners I got the o22 measuring at 29.2V, I assume this is acceptable for an EHHA, or should I try to fine-tune the o22 to exactly 30V? and would 50VA be enough for balanced build? (the recommendation for balanced b22 is 100VA, this would be temporary until I get the 100VA transformer)
 I got the gain resistors matched down to 0.1%, all of the transistors to ~5%, but the mosfets are only matched to 10% 
	

	
	
		
		

		
		
	


	



 Is this close enough or would it be better to order more?

 On a more positive note I finally got my eXstata boards populated 
	

	
	
		
		

		
		
	


	



 now I only need to make a DIY stax socket, since the ones I ordered won't be arriving anytime soon.


----------



## sachu

I think you might be able to get away with 50VA.

 As for the DC voltage..you are fine..doesn't need to be exact 30V.


----------



## aloksatoor

I was powering up the boards today and noticed I failed on the first test. The voltages accross both boards for R3 and R4 are around 0.68V. Also I left the board running without the servo opamp for a while and noticed that my 2W resistor R32 is glowing red hot. It still measures 2.2 ohms though. Have I blown a mosfet? Does anyone know what could be off? I verified no shorts on the board.


----------



## sachu

I'd say replace those output resistors.

 For checking the Mosfets. power down, put your multimeter in 200 ohm mode and measure resistance between the metal tab and the two outer pins. If any of these read short or less than a few couple of hundred ohms they need to be replaced.


----------



## aloksatoor

The Q8M both pins measure around 300 ohms. I guess that is ok?
 and what about the voltage across R3 and R4? is 0.68V normal?


----------



## sachu

No it isn't..it should be double that. can you check to see if the resistors are 1k each?

 I know this is stupid but, you are testing them with the tubes in?


----------



## aloksatoor

yep tubes are in. the heater is working as expected and the tube glows orange. I wired the heater ground to star ground (Sigma 22 gnd) and also inputs star gnd to the sigma 22 gnd. ANd also the resistors are 1K each. Only discrepancy is the R32 33 are the wrong wattage (1/2 watt instead of 2). I did not verify the GJA kit when it came i guess.


----------



## sachu

1/2 watt will do for headphone duty.

 We'll figure out the problem with the tube biasing. What's the voltage on either side of R3 and R4 with respect to SG? ANd voltage at pins 1 and 6 of the tube again with wrt SG.


----------



## mideel

After spending 2 hours troubleshooting (under rated fuse 
	

	
	
		
		

		
			





) I finally got my first EHHA board tested and it measures OK! 
	

	
	
		
		

		
		
	


	



 R3 1.513V, R4 1.475V (1.5V)
 R10 1.494V, R14 1.444V (1.5V)
 R15 0.888V, R17 0.795V (0.85V)
 R16 0.564V, R18 0.674V, R26 0.535V, R29 0.644V (0.65V)
 DC voltage at the output stays bellow 1mV.

 I'm having trouble with cooling the mosfets though, the heat sinks that came with the kit are the equivalent of 11C/W heat sinks and the recommended ones are 2.6C/W heat sinks. In minutes the heat sinks get hot enough to burn my fingers, so I need to place this build on hold for now


----------



## sachu

YOu probably have the bias point turned up waay too high. A mistkae i made too when i got my first EHHA going..had the mosfets burning nearly 450mA. Fortunately i had offboard heatsinks.

 So assuming the output is towards you and the tube is on the other end of the board, turn R21 counter clockwise a few times while measuring the voltage across either R32 or R33. Keep your multimeter in the 2V range.

 Turn the trimpot R21 counter clockwise till you read 0.22V or 220mV.


----------



## mideel

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_YOu probably have the bias point turned up waay too high. A mistkae i made too when i got my first EHHA going..had the mosfets burning nearly 450mA. Fortunately i had offboard heatsinks.

 So assuming the output is towards you and the tube is on the other end of the board, turn R21 counter clockwise a few times while measuring the voltage across either R32 or R33. Keep your multimeter in the 2V range.

 Turn the trimpot R21 counter clockwise till you read 0.22V or 220mV._

 

R32 and R33 are at 270mV at start up. After a few minutes they are bellow 220mV, so I think the bias is set correctly. 
 I need to find something better than those 11C/W heat sinks, I'm thinking of using old CPU heat sinks (if I can get them mounted) and the 12.6V o11 heater supply for the fans. This is overkill, but at least it won't cost me anything extra.


----------



## sachu

The sinks really shouldn't be getting that hot. You are only dissipating about 3 Watts in each mosfet with 100mA. Can you measure the temperature? if the sinks are at about 60 deg C or so they should be fine.


----------



## mideel

I really appreciate the help sachu, the heat sinks are ~65C. I know that these devices are designed to withstand temps even up to 175C, but I just don't feel comfortable letting these run that hot if I can help it. I'm going to try and fit some better off board cooling.


----------



## dBel84

for what it's worth, mine was a great morning coffee warmer. This is what class A is all about imho ..dB


----------



## sachu

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_for what it's worth, mine was a great morning coffee warmer. This is what class A is all about imho ..dB_

 

hehe..most definitely..running the amp boards at 200mA was good enough for me to never turn on the heater in the study the whole of winter.


----------



## aloksatoor

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_1/2 watt will do for headphone duty.

 We'll figure out the problem with the tube biasing. What's the voltage on either side of R3 and R4 with respect to SG? ANd voltage at pins 1 and 6 of the tube again with wrt SG._

 


 Thanks Sachu here are the voltages

 R3 with Star Ground 29.39 and 28.76

 R4 with Star Ground 29.4 and 28.78

 Pin1 of tube with Star Ground 28.15

 Pin2 of tube with Star Ground 28.14


----------



## sachu

^^ am thinking you mean pin1 and pin6. 

 Those voltages seem to be around the right ballpark..you need to have about 2.5V less than rail on the plates of the tubes..so its alright. The voltage across the resistors is definitely off by 0.3-0.4Volts. 

 WE'll worry about this later. 

 Try going through the rest of the setup and see what you come up with.


----------



## mideel

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_ for what it's worth, mine was a great morning coffee warmer. This is what class A is all about imho ..dB  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
hehe..most definitely..running the amp boards at 200mA was good enough for me to never turn on the heater in the study the whole of winter. 
	

	
	
		
		

		
		
	


	




 

_

 

You can say that again, not even small off board cooling seems to be enough. The heat sink temps are a little worrying. 
 The old heat sinks and the new ones side by side:



 Even though the new heat sinks have at least 4 times the surface area, they still get to ~55°C. I'm trying to get the temps down to ambient+15°C , but this seems to be an unattainable goal 
	

	
	
		
		

		
		
	


	



 I still have plan B though, just like the engineer said: "and if that don't, work use more gun". I have even bigger heat sinks lined up 
	

	
	
		
		

		
		
	


	






 I'll need to get this heat problem sorted out before moving on to working on the case. The case I had originally planned for this build became too small, due to the need for increased cooling, but everything else to this point has worked on the first go with only minor problems and even though I have burned ~15 fuses in the process. I have yet to burn out anything on any of the boards. 
 So THANK YOU ALL 
	

	
	
		
		

		
		
	


	




 (especially runeight). Without the help and information available here (and on cavalliaudio) this build would have been impossible to do. It's so good, that even a first timer builder (like myself) can feel comfortable undertaking something as complex as a balanced EHHA.


----------



## sachu

Dude.. seriously 55deg is nothing. Let it be. And its not about how big your heatsinks are its the C/W ratio that matters.

 And yeah, those smaller heatsinks are not the ones i'd use on a stock EHHA. Use the larger 1.5 inch width ones.

 Oh, also those gain resistors needn't have such long leads to socket them in. That is asking for trouble.


----------



## runeight

The simple problem is that the heatsinks are too small and not the ones spec'd for the project. The simplest solution would be to buy the right heatsinks.


----------



## dBel84

indeed, those are skinny runts , mine were a little heftier 
	

	
	
		
		

		
		
	


	









 ..dB


----------



## sachu

^^ yep..the ones in the spec are something like 

this.

  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_indeed, those are skinny runts , mine were a little heftier 
	

	
	
		
		

		
		
	


	









 ..dB_

 


 hah..pales in comparison my EHHA heatsink


----------



## johnwmclean

Boys settle down, here’s some sinks...


----------



## sachu

^^ thats just COLD man..we need to change that soon


----------



## johnwmclean

... getting closer 
	

	
	
		
		

		
		
	


	




 One pay check at time. lol


----------



## aloksatoor

V nice John you would totally need those offboards 
	

	
	
		
		

		
		
	


	




 just on 5 second power up tests for my boards my heat sinks (stock) were too hot to touch


----------



## aloksatoor

Hey I think I found the problem with the BOM. The one Jeff sent me has r5 and r7 as 47.5 K ohms and the one on Cavalli audio is 47.5 ohms 
	

	
	
		
		

		
		
	


	




... Should have verified... Thanks for the help I hope this would solve my issues. Liwei also had the same voltages so I had PMed him too that got me rechecking against Cavalli audio.

  Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_^^ am thinking you mean pin1 and pin6. 

 Those voltages seem to be around the right ballpark..you need to have about 2.5V less than rail on the plates of the tubes..so its alright. The voltage across the resistors is definitely off by 0.3-0.4Volts. 

 WE'll worry about this later. 

 Try going through the rest of the setup and see what you come up with._


----------



## sachu

aah yes..I sent him an email about that a few months back and he said he'll rectify it.


----------



## Horio

Quote:


  Originally Posted by *johnwmclean* /img/forum/go_quote.gif 
_Boys settle down, here’s some sinks...
_

 

I was waiting for you to chime in John...


----------



## runeight

Quote:


  Originally Posted by *aloksatoor* /img/forum/go_quote.gif 
_Hey I think I found the problem with the BOM. The one Jeff sent me has r5 and r7 as 47.5 K ohms and the one on Cavalli audio is 47.5 ohms 
	

	
	
		
		

		
		
	


	




... Should have verified... Thanks for the help I hope this would solve my issues. Liwei also had the same voltages so I had PMed him too that got me rechecking against Cavalli audio._

 

This will definitely mess up the amp. In fact, it will hardly work at all with 47k5 resistors. Your amps, if they make noise, must sound like crap. 
	

	
	
		
		

		
		
	


	




 Maybe everyone should check this.


----------



## johnwmclean

mmm... my BOM states 47.5 K ohm, but I’ve been supplied 47 ohm. Would .5 ohm be anything to quibble about?


----------



## sachu

^^no. So long as it is 47R and not 47k it will do fine.


----------



## johnwmclean

ok cool


----------



## wink

John,
 47 ohm to 47.5 ohm is only about 1% difference.

 Cool, as in heatsinks?


----------



## johnwmclean

Thanks Erwin!

 Another query, I’m wanting to chassis mount the tubes, to do so I’ll need to run a short length of cable. Would there be any foreseeable problem doing this? Cable length would need to be around 80mm.


----------



## runeight

Probably not a problem. Just remember that every wire extension adds inductance, capacitance, and resistance to the circuit.


----------



## johnwmclean

Joy! That solves the problem lining up the top plate holes.

 Thanking you Alex.


----------



## nattonrice

John this build is gonna be amazing!
 Seriously out doing me here =P


----------



## johnwmclean

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_With a 10A DPDT (in you case you will need a 4PDT for balanced) on-on switch, the output of the amp boards go to the input of the switch and from there you will wire one possible output set of pins on the switch to the speaker (put the zobel in there on the binding posts) and then the other set of outputs from the switch go to the headphone out.._

 

Sachu why 10A, I can only find goliath switches with that rating, would this really be needed for the signal path?

 ... also would an on-off switch be better suited, switching the outputs to the speakers on and off, and leaving the headphone outputs as intended, from the pcb straight to the jack.
 With an on-on switch, I’ll have to run the signal output wiring back through the amp to the headphone jack.


----------



## sachu

Not really, even the miniature ones that are rated for 3A-5A would do.
 Don't use the wiring scheme you just mentioned. I ended up blowing up my amp boards with something like that. Use an ON-ON switch for output switching not an ON-OFF switch. An ON-OFF switch is likely to blow your amp boards as well is what I have heard. I will get back to you on why this happens when I can get dBel to jog my memory about it. I am guessing because when you switch it on and off it creates a momentary short in the output (similar to those caused by the TRS jack) blowing your output MOSFETs and resistors.


----------



## jjazzyj

Well, I've been procrastinating a lot about finishing the EHHA. Mostly because I love/hate chassis work. So here's an in progress view of my 50% completion. 







 Front Panel:

 4PDT switch for Pre Out
 4PDT switch for headphone enable

 Dual 1/4" Stereo/XLR Mono for Headphone(s)

 Dual Stereo/Mono volume controls






 RCA/XLR input with selector switches. Can convert unbalanced to balanced.

 RCA/XLR for unbalanced/balanced pre-out

 AMP CPC 9pin power connector to Sigma22/heater supply






 One EHHA board left to go!!! Then cleanup, mounting, wiring and testing.


----------



## sachu

wow..nice to see so many EHHA builds and balanced too coming along at once. Sweet work there jjazzyj


----------



## jjazzyj

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_wow..nice to see so many EHHA builds and balanced too coming along at once. Sweet work there jjazzyj _

 

I forgot to add, that just like the matching Sigma22/heater power supply chassis the bottom is clear polycarbonate. So all the EHHA boards have bottom mounted LED's for sexy blue under amp glow.

 I'm sure that 1 month in that 'feature' will irritate the crap out of me when I watch movies.

 Thanks for the feedback sachu! As long as I don't blow up too many MOSFETS when I hook it all up I'll be happy!!! Luckily I have enough extras to build another Balanced EHHA or Balanced B22...


----------



## sachu

^^^ lol i don't quite mind the blue and super bright orange LEDs(for amp boards) on mine..it kinda lights up the room at night. The coolness of it hasn't waned for me...yet


----------



## aloksatoor

hehe im going with bright white ones orange and blue wont match the brown wood of my chassis......


----------



## jjazzyj

First post on this thread with the new BBS!
   
  Well, I did a bonehead manoever last night, soldering one of the trimpots in the wrong orientation. De-soldering plated through holes sucks. Took me 30 minutes to do. I usually use my fingers as a heatsink on the component or in the case of resistors a hemostat. Tested ok after removal so I probably didn't damage it, hopefully.


----------



## adamus

erm.... arent they symetrical?


----------



## jjazzyj

The part is, but a pot is a resistor divider, so just because it is symmetrical doesn't mean you can swap the orientation around.


----------



## jjazzyj

Now the wiring extravaganza begins. The wiring harness is not attached but here is the star ground wiring which the rest of the wiring looks like.


----------



## jjazzyj

Ok, so I got all my wiring hooked up. (One board at a time, though I have to insert two tubes and hook up the heaters for two boards because I'm using 12.6V heater supply). Turned on the heaters and they lit up just fine. Waited a minute then turned on the S22 (which tested @ 28.9V pos and neg) Within 10 sec R4 starts to smoke. I immediately killed the power. Checked for shorts a third time. None. Check resistor values, check transistor values. Tried again, R4 smokes again. Adjusted R6 from what I thought was halfway. Tried again, this time R14 smokes, but not R4 (luck probably). This time hooked up my grippy probes across R14, this was one probe on one side and one on the other side of R14. After waiting a minute with the heaters turned on again, turned on the S22 again. Measure the full 28.9 volts across it, as if something was shorted to GND it seems. S22 is ok through all this BTW. I tested the -30 and +30 inputs on the EHHA board to Star GND and did not get a short but around .500 ohms. Nothing seems shorted.
   
  I did not test for shorts after I put the tube in. Is is possible that the tube has a short in it? I'm not sure what is going on at this point since all my values and orientations are correct. Unless IC2/3 are toast.
   
  Any suggestions?


----------



## sachu

Sorry to hear about the problems Jazzyz..
   
  It is really hard to say what could have gone wrong...
   
  can you post a pic of the board..a macro shot with a link to it in high resolution would be useful.


----------



## runeight

It is possible but unlikely that the tube has a short. This is a very unusual problem in this amp.
   
  Are you sure that Q1, Q2, and Q4 are PNP (2SA1145) devices and that Q3 is NPN (2SC2705)? The first thought is that Q2 and Q4 are either shorted or the wrong polarity and are passing too much current.


----------



## jjazzyj

I've double and triple checked all of the transistors they are all the right polarity. I'll post pics later but I did do some more measurements and it seems like R4 is fine as is R10 just R4 and R14 are having problems. I made an error last night in telling you that it was R4 that was having the problem. Out of curiosity I measure between one side of R3 or R14 and Star GND and the DMM shows the printed resistance value, when I measure from the other side of R3 or R14 it is a short to GND. All of the boards I have are like this so I assume that this is correct. I re-measured +30V, -30V, Input, Output, Heaters to Star GND. -30 and +30 measure 1Kohm to Star GND, Output and Input is 10kohm to Star GND. Heaters are not connected at all. IE Infinite resistance.
   
  I also examined the bottom and top of the board for shorts between pins on all of the transistors and it does not appear to have any shorts unless they are shorted internally. Short I check for a short between Base and Collector?
   
  I don't know if maybe the S22 when first turned on is maybe having an inrush current problem?
   
  Again I'll post pictures later tonight, today I have a complete datacenter reorganization day, 8 hours of re-cabling and moving servers yaay.


----------



## runeight

When you have a minute could you please explain your resistor numbering? I am confused concering R4.


----------



## jjazzyj

Sorry for the confusion, my fault. I'll be able to straighten everything out with these photos and descriptions. There's even char marks on the one resistor!
   
  Here is the board diagram from the website with the resistors in question circled in red.
   

   
  Here is a close up pic of the whole top of the board:
   

  
  Positive Rail
   

   
  Negative Rail:
   

   
  And the underside:
   

   
  Hope this helps, I'm at a loss atm. I might try another board and see if this is systemic to the S22 or maybe I've made the same mistake to every EHHA board. Ugh


----------



## sachu

Aaah dude..
   
  You need to leave C2 and C3 open instead of shorting them. They are only used if you are gooing for a low gain which it looks like you are not. The standard value is in R13 for a gain of 10. So just leave C2 and C3 open on all boards.
   
  Edit: Actually, shorting C2 and C3 is what toasted your resistors. I don't know if you toasted your transistors or not, but definitely remove those jumpers. 
   
  The mistake you have done however is tshorting R22 and R23 which dictate how much NFB you have in the amp.
   
   
  YOu can't have a value lower than 10k in those positions. YOu have shorted them which is what is causing the problems.
   
  Leave R23 and R22 open for a meatier bottom end while rolling off the highs a tad bit or leave them at default value of 33k to strike a nice enough balance.
   
  Don't ever use less than 10k in the R22 and R23 positions. Shorting these is what is causing you the problems.


----------



## jjazzyj

I misunderstood the instructions. I will remove those immediately. Easy fix. I also have a lot of spare mosfets. And the resistors aren't toast I tested them and they are still reporting the correct resistance. Yaay.


----------



## jjazzyj

I just looked at the schematics. Are you sure that you aren't supposed to short C2 and C3? Other wise the drain of the Mosfets won't be connected. R22 and 23 I can see
   
   
  EDIT: Err never mind..,,


----------



## sachu

Trust me..I've built enough of these to know my way around it now. Now i know why I never encountered the problems you have been having.
   
  Oh, and make sure R21 is turned all the way counter clockwise before you turn on the boards. At the very least make sure it is in the middle position or below.  Cuase if this is set too high by default, you risk burning your MOSFETs out along with the output resistors as it sets the bias for the output stage.
   
  C2 and C3 are compensation capacitors and is left off for gain higher than 7.


----------



## jjazzyj

Success. I had socketed R22, R23 so I just pulled out the jumpers. For C2 C3 I just cut the jumpers off. I might socket those as well later. The socket pins will easily push out the left over leads in the holes saving me too much trouble from solder sucking. Believe it or not, none of my MOSFET's or resistors bit the dust. I was very diligent at not letting them smoke much 
   
  R3 1.7V
  R4 1.35
  R10 1.35
  R14 .126
  R15 1.07
  R17 .6
   
  R16 .5
  R18 .5
  R26 .5
  R29 .5
   
  Output .14
   
  R22 .22
  R23 .212
   
  11V Pin 6 Opamp
   
  Output Offset less than 1mv
   
  Took quite a few turns of R21 to get any voltage I was wondering if I was doing something wrong hahaha.
   
  So now I can blow through the power up of all the boards and next the daunting task of the input and output jack wiring. Ugh.
   
  A question, i know how to wire an unbalanced input so that is get converted to a balanced output. In essence the - amp boards as a sort of "active ground" when you do that. Is there any way to turn that one unbalanced input to the amp boards so that you can run two pairs of headphones? I'd probably need a DPDT switch of some sort to switch the - signal and a copy of the + signal to the Volume pots if what I'm saying makes any sense. I'll post a diagram of what I'm thinking later. I'm tired but feeling better thanks to Sachu 
	

	
	
		
		

		
		
	


	




. I was having a bad enough time today making 26 Cat6 cables having 4 of them test good in the tester and then not work. Grrr


----------



## sachu

Sweet!! 
	

	
	
		
		

		
		
	


	



   
  Yeah please do drawa a diagram of what you are thinking cause i couldn't follow your description lol
   
  Oh and you might want to try balancing the tube by varying R6 a little while monitoring pin6 of the opamp. You can zero it out by varying R6. This will basically balance the two triode sections of the tube. And going by the 11V output on the opamp it seems there is quite a bit of imbalance in the triode sections of the tube.


----------



## runeight

I might recommend that you replace the resistors that smoked anyway. They may appear to be ok but over time may degrade. Or they might change value. Or they might unexpectedly open circuit.
   
  Just to be safe.


----------



## jjazzyj

I'll do that. As I was testing my third board, I shut off power to insert the opamp. At this point I had all 4 tubes inserted with heaters connected (12.6v heater circuit) After inserting the opamp and attempting to turn on the power again, I received an instantaneous blown fuse. I've had quite a few issues with blown fuses. The Heater/S22 comes up just fine disconnected from the EHHA. As soon as I connect it and turn on the heaters blown fuse. The 4 tube heaters came up the first time. So I removed one of the tubes effectively only have 2 tubes on the heater which worked just fine for all my previous testing. Still immediate blown fuse.
   
  I may not have a properly sized fuse to run the 4 heaters plus 4 amp boards, but why blow as soon as I turn on the heaters....? especially since it worked fine for many hours of testing. Just to let you know I have a custom toroidal transformer that has a 30-0-30 5A secondary and a 12-0 5A secondary. I have the "Heater/Main" power switch on one of those 10A 120V DPDT mini toggle switches. The 12-0 secondary is directly connected to the 12V power supply board. I have the 30-0-30 secondary hooked up as follows.  Both 30VAC wires are connected to A 10A 12V DPDT mini toggle switch. The 0V wire is connected to the S22. So I flip the "Heater/Main" power switch and the heaters come on, which has been working just fine up until just recently. Then after 30sec to a minute I flip the "high voltage" switch and the S22 comes on and the everything has been fine. Something weird which has been happening is when I try to turn off the S22 and just keep the 12V/heater supply up, the S22 never shuts off. And even if I turn off the "Heater/Main" switch after my failed attempt to shut off the S22, The next time I turn the amp of, I burn a fuse. At least that's what was happening now it just burn fuses every time I have the EHHA connected. The problem I described earlier still happens which the S22 is on its own.
   
  I have been using a 2A slow blow rated fuse, but I'm thinking that it isn't enough to handle the inrush current of the transformer. Or power draw of the heaters/amp. I know when I was first testing I used a 500ma fuse and it popped the minute I tried turning on the S22. I might have developed some sort of short in the heater circuit on one of the EHHA boards
   
  Any thoughts?


----------



## runeight

I think you need to draw this out for us.


----------



## digger945

Pictures wouldn't hurt either. Even with 4 tubes drawing 1amp each you shouldn't need more than a 1amp fuse on the 120V inlet.


----------



## runeight

Which reminds me to ask, since you have a 12V supply are you running the tubes in series-parallel operation?


----------



## jjazzyj

Yes, I am running the 4 tubes in series-parallel. I tested the heater supply before I started testing the boards. Each tube heater is getting 6.1v. I'll take some pictures of the power supply and describe what is what later today.


----------



## jjazzyj

So I got another 4 fuses to test with. I'm using a 9 pin AMP CPC connectors as link between the power supply and the amp. So I discovered that when I remove pins 7 and 8 from the amp chassis (that's what I'm running the heater supply through. The fuse does not blow. But if I have either pin 7 or 8 connected a flash of light occurs around the fuse holder and the fuse is cooked. I can have the S22 supply connected and it is fine. I was next going to try plugging in the wire that pin 7 or 8 directly into the connector bypassing the amp chassis connector. But since I'm blown through 4 more fuses, that will have to wait until I get yet more fuses. It's almost like I'm getting a short in the connector itself. though I'm not sure how unless the AMP CPC connector has broken somehow inside and is shorting against something though I've tested for shorts with the 30V -30V wires and I'm getting nothing. Argh. I'm not sure what could have happened in that connector since it was working just fine.
   
  Pics below that hopefully illustrate some of what I'm talking about.
   
  Back of AMP Chassis CPC connector on the right. Wires are not inserted at this point.
   

   
  This is the umbilical cable. This tests fine, I can have this connected to the S22/heater power supply and no fuse blowing action occurs.
   

   
  The S22/Heater Power Supply.
   

   
  The Heater/Main switch is on the right, the S22/30V-30V switch is on the right. The two "hots" of the 30-0-30 are connected to this switch with the 0 being directly connected to the S22. You can turn on the Heater/Main switch and the heaters light up (or were) and then 30 sec/1min later flip the S22 switch and the amp boards come up. If you try to switch the S22 switch off with the main power still on, the S22 stays on. If you flip the main switch off then, and try to power back on the fuse blows. I worked around this issue by always turning off the mains switch first and then turning off the S22.
   

   
  The EHHA with wiring (except one untested board) in place. The one tube was removed for testing. I have since removed all wiring from the boards to start testing the wiring/connector itself which led to the discovery I wrote about above.
   

   
  So it turns out nothing on the boards is bad but something in the CPC connector itself is causing issues. I wonder if I shouldn't just replace the CPC connector. I'm going to try to test the wires individually without the connector on the amp chassis, and that should help narrow it down.
   
  Thoughts?


----------



## sachu

The only reason I can think of why the fuse is blowing is, assuming that the APC connector is alright (you can easily verify if there is a short on the connector or not) that your wiring on the switches is wrong.
   
  Can you draw labels and arrows on the power supply pic indicating the wires coming in from the transformer (the 2x 30VAC lines and heater secondaries on that switch) and the output wires going from the switch.


----------



## jjazzyj

Well, like I said. The Power supply works fine with the umbilical cable disconnected from the EHHA amp. The moment I reconnect the umbilical with pins 7 or 8 connected which is the 12VDC power supply the fuse pops violently. I will try plugging in the wires that are attached to pins 7 and 8 directly to the umbilical cable to test if something is wacko with the wire or something else weird is happening. That will isolate if the CPC connector on the EHHA amp is for some reason defective. During all of this testing all of the wires from the CPC connector on the EHHA amp chassis are disconnected from the amp board. yes, that's right with the heaters wires disconnected and isolated from each but still connected to the CPC connector the fuse pops. the EHHA amp boards aren't even in the picture atm.
   
  Anyway here's an annotated pic of the power supply.
   

   
  BTW, are subscription emails working for you. I've gotten 2 out of 10 of them so far when this thread gets updated. Something must not be working correctly yet.


----------



## aloksatoor

finally found time to replace the blown resistors and mosfets on my boards (R5 R7 R32 R33 and Q8M Q9M). All of the voltages in the checklist before we pop in the opamp check out fine. However, when I measure output voltage with star ground it hovers around 2.1 volts. I let it settle for around 2 minutes. The guide wants it below 1.5. Is there more debugging I need to get done? could it be a blown transistor or something?


----------



## sachu

You need to have the opamp in the circuit before u measure the DC offset on the utput. How will the servo zero the DC without the opamp ?


----------



## aloksatoor

duh 
	

	
	
		
		

		
		
	


	




  im gonna carry on with the checklist


----------



## sachu

Jazzyz, I am sorry, I am at a loss as to what's going on with your PSU.You only have two boards with the tubes hooked up as of now right and the heaters are in series?
   
  Can you try isolating the heater GND from S22 GND.
   
  I forget the fuse rating is 2A was it slow-blow type? I don't think it is the inrush current that is blowing your fuse, but it could be possible. One way to test this would be to replace the slow blow with a fast blow one so instead of blowing the fuse during turn on for a second time the fuse should blow the first time you turn it on if you use a fast blow one if inrush current is indeed the culprit.


----------



## jjazzyj

Heater GND is isolated from S22 GND. I thought bad things would happen if you did that   I must say that I think that I do have fast blow fuses instead of slow blow. They came from the electronics store bin that said slow blow, but last time I checked GMA type fuses were fast blow. I'm going to continue my testing once I get some verified slow blow 2A fuses.


----------



## aloksatoor

I have the heater grounds tied up to start ground. Does not cause any problems.


----------



## aloksatoor

Hi Sachu,
   
  I read in a previous post about you getting around 0V for the R32 R33 resistors. I tried modifying the R21 position around 10 turns or so but still there was no change in the voltage accross the mosfet resistors. Any clue what could be wrong did not wanna blow up another Mosfet


----------



## aloksatoor

Got it  both boards read dc offset around 0.7mV....


----------



## sachu

^^ nice...How far are you from casing it up? Have you had a chance to listen to it yet?


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## aloksatoor

Casing is 90 percent done.... bottom steel plate needs to be drilled and the wood chassis needs to be done over with 2-3 watco danish oil layers and 3-4 wax layers.... all the mountings are drilled  Should give it a listen maybe thursday can't wait for it!! this project started for me all cos I had a few extra pieces of california walnut wood lying around from a beta 22 build


----------



## sachu

NIce..soo you have a B22 eh..you know I never got a chance to compare them side by side. And those who have built both haven't really posted detailed impressions comparing the two. I know funch preferred his Bijou over the EHHA, while i went the other way and I think this was just down to the synergy with headphones we were both using. And digger945 preferred his Aikido 24V version to the EHHA which I want to hear sometime  asi feel i might end up liking it too over the EHHA.
   
  LIstening individually the B22 did have a more defined bottom end over the EHHA while they both were quite similar in impact levels and speed.
   
  So do take time to get used to the amp and then post impressions comparing the two when you can. I for one am curious about the differences between these two giants. The differences i feel are going to be rather subtle and come down to preference rather than outright this is better or that is better.


----------



## jjazzyj

Well, 26 fuses later my mysterious short in my power supply mysteriously disappeared. I fear that the short was in the switch that I have the two 30V hots connected to. Right before it started working I turned it on and off again. It hasn't blown a fuse in over 20 cycles now, which is almost how fuses I went through. I did an desperation Digikey buy of 50 2A Slow Blo fuses since I didn't know how many I'd go through before figuring out what the problem was. They have Schurter fuses for 25c each, well when you buy 50 of them anyway  I also ordered all the parts for a mini3 while I was at it, I was paying 8$ shipping regardless. The boards are all tested and outfitted with Zenith 6GM8 tubes which are of course made by Amperex. Curious thing is the Zenith tubes seem to be made more rugged...then say the orange globes or Bugle Boys that I have.


----------



## sachu

lo..What!! that's the craziest thing I've read on DIY threads all year...well am glad it all worked out for you now. 
   
  The Orange globe/BB are awesome..spendy tubes. 
  Onwards with the build then.


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## jjazzyj

You can get lucky with Amperex BB/OG 6GM8 tubes. I only paid 5.45ea for mine. I bought 8 6gm8 tubes some were Zenith, some were OG and some were BB. Every once and a while I buy a whole bunch of tubes to stock pile for the upcoming nuclear holocaust, I might need to build a tube radio.....


----------



## johnwmclean

Glad to hear you solved the mystery jjazzyj,
   
  sachu, I’m thinking about not doing the switch thing and just leaving the zobel on the speaker jacks without switching. I’m not sure if there will be problems with headphone listening or not doing it this way, the switch just gets messy having route through output wire back and through the amp. What do you reckon?
   
  One other thing too, for R32 and R33 I got some 0R47 3W, but are wirewound as opposed to metal film, these ones:
  http://ie.farnell.com/vishay-draloric/ac03000004707jac00/resistor-3w-5-0r47/dp/1735072


----------



## sachu

Those will do for now John. It would be nice if they were non-inductive type. If you are interested PM me, I have a few Mills 5W 0.47R wire wound non-inductive resistors.


----------



## jjazzyj

Well, I got the pots wired in dual SE mode and wired one of the headphone jacks. Was able to listen for a few minutes with my testing headphones before the right channel cut out with buzzing. I think my cable that was hooked up to the MP3 player doesn't seat properly. Anyway, I turned the amp off to troubleshoot, and when I tried to turn it back on again, the switch I'm using for the 30V (the one giving me problems with the burnt fuses) has now ceased to function, you can flip the swtich but the power is always on. This is the second switch that has done this to me on this project. I think that the current going to the switch from the 30-0-30 secondary is too much for it's contacts. It's just a cheapy 120v 10a switch, which works fine with high voltages but not so much with a higher current lower voltage situation. The inrush current from the transformer could be what's causing the issue. The transformer is rated @ 5A. I'm going to replace both switches with the larger toggle switches that have heavier duty contacts since I'm at a loss as to what is exactly happening.


----------



## jjazzyj

Ok more updates on the fuse blowing situation. The switch in question has had it's contacts fused. So I bought a heavier duty switch thinking it was the switch that was the source of the fuse blowing extravaganza. So I hooked up the new fuse and tested power on. Switch works now. But after 2 successful power ups 6 more blown fuses upon flipping the main/heater power switch. So I decided that inrush current MUST be the reason for the blown fuses. My transformer is too powerful for that puny 2A fuse. So I installed a CL60 thermister (as per most of Nelson Pass's power supply's) after the fuse on the hot mains line. Aaaaannnnnd....
   
  Problem is now fixed. Everything seems to run better now, I actually have less noise in the amp since I tested last night. The EHHA is a very smooth noiseless amp. It's far more detailed then the SOHA II that I built previous. I have to try it with my DAC instead of my crappy Sony Mp3 walkman. The sound it produces is muddled and weird compared to my Technics Digital Decoder.


----------



## sachu




----------



## sachu

jazzyz..you finish wiring up the amp? Get more listen time on it?


----------



## jjazzyj

I finished wiring it up in dual SE format. I put all Amperex Orange Globe tubes in. I honestly was surprise at the level of details that this amp reveals. I'm hearing things in movies and music that I never heard before. It's almost creepy. The amp is so smooth that I never tire of listening to it, and almost don't even notice where even the SOHA II was grating after a while. I hear of people complaining of a lack of bass but I have not experienced this. I find that the Technics Digital Surround Processor that I use as my DAC had lots of bass. I wouldn't call my AKG K240/EHHA/DSP/PS3 combo bass heavy, I would call it balanced, or "as the artist/producer intended" I have a hard time imagining the B22 sounds any better, though it might sound different. And the beauty of my two chassis design is that I can build a B22 and hook it up to my Sigma22 power supply with the same umbilical cable 
	

	
	
		
		

		
		
	


	




. I haven't finished the top of the EHHA chassis yet, as I'm trying to figure out what to do for venting. But I can post some pictures of its blue glowy goodness later.


----------



## sachu

Hell yeah!!...of course we need pics dammit!!
	

	
	
		
		

		
		
	


	




 
   
  Yep..it sure does bring out the details..and it is a smooth effortless amp. Congrats jazzyz!! Finally it is ready AND you are still left with a few dozen fuses 
	

	
	
		
		

		
		
	


	




..enjoy now dude.


----------



## sachu

Quote: 





aloksatoor said:


> Casing is 90 percent done.... bottom steel plate needs to be drilled and the wood chassis needs to be done over with 2-3 watco danish oil layers and 3-4 wax layers.... all the mountings are drilled  Should give it a listen maybe thursday can't wait for it!! this project started for me all cos I had a few extra pieces of california walnut wood lying around from a beta 22 build


 
   
   
  So did you get to listen to it?


----------



## jjazzyj

I finally got a chance to take some pictures of the almost completed amp. (top still not done).


----------



## sachu

crazy blueness going ont here..lol
   
  very nice Jazzyz..so glad you finally got it done. I love to see new EHHAs being born.
  Detailed impressions should follow my man. You should post the pics in the main general builds thread as well. That is definitely worth shouting about my friend.


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## ujamerstand

Jjazzyj: what is the height of your case?


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## johnwmclean

Congrats Jjazzyj, looks awesome, love the glow.


----------



## sachu

You are up next mate...should have those output resistors latest by end off next week. I know its going to be off the hook.


----------



## johnwmclean

Whoa yeah, I'm itching now - the next Sydney meets at my place on July 11, it will be hopefully it's first debut on these shores.


----------



## jjazzyj

Case height is 4" + 1/4" with the rubber feet.


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## ujamerstand

Thanks. Hopefully my case could look as good as yours!


----------



## jjazzyj

I can tell you the tools I used and construction methods used to build it if that would help. Don't know if it's deviating too much from this build thread. The techniques used allow you to use any material you want for the side/front/back panels. And even change your mind later and switch to something else if you get bored of your amps appearance.


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## sachu

Not at all diverting from the thread jazzz..I think your casework is excellent and would be very interested to know how you make them. Detailed info would be awesome as i too have a couple of builds coming up.


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## jamesbobo007

Quote: 





sachu said:


> Not at all diverting from the thread jazzz..I think your casework is excellent and would be very interested to know how you make them. Detailed info would be awesome as i too have a couple of builds coming up.


 

 I dont post very often, but I have to say DITTO on this. Please do share.


----------



## jjazzyj

Modular Chassis design:


 For 12"X12"X4" chassis, with instructions on how to scale up
 Assuming 1/8" thick front, back, and side panels. Can be wood/metal/plastic.
 Bottom can be 1/8" for metal but should be 1/4" or 1/2" for wood/plastic. Especially if housing a heavy transformer. The bottom keeps the frame from twisting and gives it strength.

 Tools:

 A power mitre saw 10" is fine. With an aluminum cutting blade. You can also use a hacksaw and mitre box. The edges won't be as nice without filing.
 A fine person file to remove burrs.
 A #6 NC tap with wrench.
 7/64 drill bit
 A center punch
 Cordless Drill or preferably a small benchtop drill press (You can usually buy the drill press for 80-100$ which is actually cheaper then a half decent cordless drill and you will use it a lot in this hobby)
 A #6 deburr/countersink use one made for metalworking not for wood if using plastic or metal.
 You can get the aluminum panels cut at a metal shop or if you've got a table saw cut it yourself with an aluminum cutting blade.
 Acrylic panels can be cut by scoring and snapping. Polycarbonate needs be cut with a saw.

 Materials:

 Frame:

 8' of 3/4"X3/4" anodized aluminum angle cut into 8 11.75" pieces. Mitered at both ends. /_____________\
 4' of 3/4"x3/4" anodized aluminum square tubing cut into 3.125" pieces. You could use more 3/4"x3/4" angle but I feel the square tubing makes things stiffer.
 64 #6 flat head machine screws stainless steel if possible. If you can find them use 1/4" or 3/8" long screws, other wise you'll need to use a bolt/screw cutter. Your crimper may have this built into it. Mine does. Longer ones are okay for attaching the panels, and are necessary for the bottom. The screws sticking out on the inside of the chassis from attaching the panels are nice to bolt Earth GND and Star GND.

 Panels:

 Any material you can dream up here, 1/8" preferred as stated before. If you go thicker side/front/back you will have to adjust your frame dimensions if you wish to maintain the final dimensions of the chassis you desire. When you cut the panels. Follow the following rules:


 1. Measure and cut the bottom panel first. Attach the bottom panel. Measure from the top of frame to the bottom of the bottom panel. This should be 3 7/8" in this example. If you wish to recess the 1/8" top in the side/front/back panels then add the remaining 1/8" to make 4". This ensure that you do not see the edges of the top panel (I did not do this). This is the height of your side/front/back panels.
 For the sides measure from the back of the frame to the front of the frame. This will be the length of the side panels. the Front/back panels you will add the thickness of the both side panels to the length.

 In this example:

 Side Panels: 11 3/4" L x 4" W
 Front/Back Panels:12"L x 4" W
 This is to hide the edges of the panels and maintain the target chassis dimensions.


 Assembly:


 Loosely fit one of the aluminum angle pieces to one of the pieces of aluminum square tubing. The tubing goes on top and underneath the angles. Mark the first hole on the angle after you've aligned the inside corner of the mitre you cut on the angle with the edge of the square tubing. the hole on the angle should be in the middle of the square tubing. Repeat with another piece of the square tubing on the other side of the angle. Once finished mark 4 holes in equidistant manner along the piece of angle. Use a center punch on your marks then drill the mark holes with the angle supported with a piece of scrap wood. Use this piece of angle as a template to mark all of your other pieces of angle on one side. Mark four of the angles on both sides. This will be the bottom of the chassis. From there take each angle and mark a hole on the square tubing with the hole closest to the end. Center punch and drill. You should have a hole on two sides of the square tubing top and bottom. Use the countersink and countersink the holes that you used to mark the square tubing. Tap the holes the square tubing and use the ~1/8" long #6 screws to assemble the frame.

 Tap all remaining holes.

 Using the frame mark the holes in your panels beginning with the side panels. It helps to write which part of the frame is Right, Left, Front and Back. From there drill and countersink the holes in your panels. Screw the bottom, Sides to your frame.

 From there mark, drill and tap your panel components. Once you have done so, attach your panels to the frame.

 For attaching the top I usually drill and tap 1/4" holes in the four corners. I then use 1/4" Cap Screws to attach the top. It can be perf material or whatever you want. I used 1/8" acrylic which would recess in the panels. Other materials you will need to fit as necessary.

 I used rubber stick on bumpers for the feet.

 I will provide some detailed photos of how the angles attach to the square tubing later tonight.
 Hopefully my build log isn't too convoluted.


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## ujamerstand

Very informative! Thumb up! (Could this be the first time somebody uses this feature?)


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## aloksatoor

My EHHA Cased up quick and dirty ... Still needs the tube holes widened and a final wax coating and buff..... Sounds awesome.... did not like it much with the HD650s but it sings with the HD600s... Wish I had my old K701s to test this(broke em while recabling) The psu case is a big context engineering, housing the power switch driver from Ti, relay sigma 11 22 and 2 transformers... Bit perplexed how to make the volume knob ring glow brighter... a shiny paint on the inside would help maybe....
   

   
  Had made a matching stand a few months before from scrap pieces.....


----------



## sachu

Very nice indeed!! Totally feeling all the love the EHHA-1 is getting. Awesome builds both of you.
   
  yeah, increasing the size of the holes for the tubes a must there..you could try fashioning rings like the ones Smeggy uses here. 
   
  I think the reason you find the HD650 sounding not so great on the EHHA is the mid bass bloom that the HD650 has..THe EHHA has a nice big impact in this region and coupled with the almost boomy nature of the HD650 it wouldn't surprise me if it muddled things up higher up the frequency.
   
  And yes, totally agree about the HD600..listening to the HD580 on dBel84's EHHA is what did it for me 3 years ago..
   
  Furthermore..you should definitely try the AKG K701s on the EHHA..hate that headphones but recently when i heard it on my system on the EHHA, for the first time I had a smile on my face. Its a friggin great match.


----------



## ujamerstand

eh, a) use brighter led, b) grab a some plexisglass samples off eplastic.com, cut some circle pieces with a hole saw, and see which one defuses light most effectively?


----------



## sachu

Just run more current through the LED..


----------



## aloksatoor

thanks for the help debugging my issues esp sachu and alex   I am planning to get a second pair of the akgs in couple months...I was planning on putting nice brushed stainless steel rings but dont know where I can find those Smeggys's look like acryllic maybe? I never knew the 600s could have so much space and bass impact until I used this amp  super happy with it since its gonna mainly sit at work where my 600s are.
   
  So for the LEDs glow maybe ill go down to the local tap plastic (esplastic would be online only i assume) and pick up some plexiglass....  I already have rled as 10 KOhms would the LED be able to handle 5Kohms or lesser? I have a xicon clear white something LED gotta check mouser invoice for that part number


----------



## sachu

Are you using the LEDs from the amp boards to illuminate the back of the volume knob?
   
  If yes, you may have to use a higher  power rated resistor depending on how much current you want to run through the LED. 
   
  yeah, checking the specs of the LED is a good thing to do here. 
   
  Stainless steel rings or brass rings would look wicked cool there. 
	

	
	
		
		

		
		
	


	



   
   
  Quote:


aloksatoor said:


> thanks for the help debugging my issues esp sachu and alex



   




  Quote: 





aloksatoor said:


> thanks for the help debugging my issues esp sachu and alex




  Aaah just seeing these amps take shape is thanks enough


----------



## ujamerstand

Quote: 





sachu said:


> Stainless steel rings or brass rings would look wicked cool there.
> 
> 
> 
> ...


 

 Stainless steel ring AND plexiglass base!


----------



## aloksatoor

Yep using the 2 board LEDs for the volume ring lighting. Saw few steel washers online which would fit around the 20 mm diameter tube. Will buff it so I can get that brushed metal look as the knob and switch has....


----------



## sachu

Yeah, you should be able to run more current through the LEDs..I'd say replace the resistors with 2k/1W resistors to run them super bright or to find middle ground use a 3.3K/1W resistor.


----------



## johnwmclean

I bought some ceramic tube sockets from parts conneXtion, I haven’t soldered them to the board yet but I did try inserting a tube to check out the fit. The socket only seems to grab the tube at the last 1-2 mm when I insert a tube, it seems kind off weird as all the sockets I’ve ever used seem to grab a tube vigorously and you really have to work at inserting or removing.
  These are the sockets:
  http://www.partsconnexion.com/CONNEX-73283.html


----------



## sachu

Shouldn't be a problem..some sockets are easier to put tubes in and out. Only thing I would suggest is to remove the tubes when transporting in such cases.


----------



## rolotube

Its been a while coming but I finally got to listen to my recently completed SE EHHA for the first time last night.  Initial impressions are similar to what others have posted - sound is incredibly detailed & clean with a wide soundstage & excellent "presence".  I won't be shelving my modded SE Bijou just yet - its remains my reference amp - but after just a few hours of listening, the EHHA is running a very close second.  I fired it up with the kit-supplied Amperex 6GM8's & whilst the sound was very good, substituting these with 6H23P-EB's made an immediate & noticeable improvement. 
   
  Similar to other builds, I'm using S22 & S11 PS's.  All voltages appear to be within specified limits but the whole plot (EHHA, S22, S11) runs very warm to hot.  I gather from these pages that this is fairly normal but its so much warmer than other amps I've built that I'm now wondering whether the standard kit-supplied heatsinks (1.5 inch) are sufficient, or whether I've missed something in the setup.  Any comments or opinions on the following would be appreciated:
   
  1.  how hot is too hot?  The amp's output MOSFET's run at ~ 80 degrees celsius & one of the S11 pass MOSFET's is cooking at ~100 degrees.  Would 2.5 inch heatsinks improve this much?  I know the devices are rated to 175 degrees junction temp so 100 shouldn't faze them but it feels too high to me, especially when total current draw is < 700 milliamps.  The S22 heatsinks remain under 50 degrees.  Planned use is for headphones only so off-board heatsinks shouldn't be necessary, but I'd like to see it running cooler.
  2.  is there a procedure for balancing the two halves of the tube using R6?  Correct voltage across R32 & 33 (0.22V) is easily achieved using R21.  Voltages at op amp output (pin 6) are ~ 8V on one channel & < 1V on the other.  Output offset is < 1mV both channels.   Whilst these values are within the ranges specified in the setup instructions, I'd like to optimise the tube halves, if possible.
  3.  the S11 output is 11.9V.  I suspect this is borderline too low for the heaters?  Is there a way to tweak this up closer to 12.6?  If not, should I be looking another heater PS design?
   
  This is my third Cavalli amp following on from the Bijou & SOHA II.  Thanks again to Alex again for another brilliant design & many others on this forum for sharing their knowledge & wisdom.


----------



## sachu

1.5 inch heatsinks are too small for this amp..at least 2 inchers need to be used.
   
   
  As for balancing the two halves on the tube..varying R6 so output of opamp will go to zero will balance the halves..but then you have to recheck the bias voltages on the output stage.
  These details are there on the Cavalli AUdio website.
   
  Could you go into some detail about how the 6H23P improved the sound compared to the amperex?
  btw, congrats on getting yours going! 
	

	
	
		
		

		
		
	


	




 Do post pics please when you can.
   
  I am contemplating a Bijou build myself now. The PSU is ready..just a matter of P2P ing the amp


----------



## johnwmclean

rolotube, what transformer are you using with the S11? My thermal calculations with 12.6V output was way under 100 degrees with a 60VAC transformer.


----------



## rolotube

sachu, thanks for the welcome & advice.  I've suspended further development until much larger heatsinks arrive (ordered today), but not before putting in a pair of 6H30's & carefully balancing the tube halves. No problems getting the op amp output down to a few millivolts & bias set to 0.22V.  I ran with AC heaters for this exercise due to the much higher current required by the 6H30's.  There's a slight hum but what a fantastic sound.  I now understand why others on this forum rave about the EHHA.  The only amp i've heard to equal or eclipse this is the Bijou.  Can't wait to get the heater PS sorted & lower thermal stresses throughout so I can start re-listening to my music collection - again!  Will post some pics shortly.
   
  Re 6GM8 vs 6H23P, the latter seemed tighter, slightly cleaner & smoother, not necessarily more extended in top or bottom but overall a more polished sound.  I didn't listen to either for very long (this is probably needed before drawing any firm conclusions) but the differences were certainly evident.  I found much the same with the the 6H23 in the Bijou; it was clearly better than the kit supplied 6922.  The 6H30 is terrific in this amp.  Didn't sound as good in my Bijou for some odd reason.
   
  Re Bijou, I've been developing mine for around two years & can heartily recommend it as a "must do" build.  Sound is very 3D & atmospheric compared to most other amps.  Its magic with vocals, especially female, as well as solo instruments & small groups.
   
  John, I'm using a 30VA Avel I got with the S11the parts kit from Jeff Rossell.  It doesn't get warm or drop the secondary voltage much under load but the S11 pass devices are frying.  Strangely, all voltages within the circuit are book spec.  I'll report on improvements (hopefully) when large heatsinks are installed.  BTW, your meet in July sounds like a hoot.  If there's room for one more, I'll try to get down.  Gear I could bring includes well developed Bijou & EHHA (both SE), NAD c542, heavily modded MF A324,  HD650 with Stefan AudioArt cable, custom digital & IC cables, etc.


----------



## johnwmclean

rolotube, there’s a spot reserved for you at the meet, I thought I was going to be the first EHHA is Oz - dang you’ve taken away the title, congrats mate I want to see pics.
   
  What are your transformer secondaries? I wonder if your dropping too many Vs.


----------



## nattonrice

Hearing a fully filmed bijou would be lovely!


----------



## TigzStudio

Im curious, if all of these DIY style AMB amps are so popular and sound so nice, why isn't there more commercialization of them?  I would imagine people would pay a pretty penny for them above parts cost.


----------



## dBel84

Quote: 





tigzstudio said:


> Im curious, if all of these DIY style AMB amps are so popular and sound so nice, why isn't there more commercialization of them?  I would imagine people would pay a pretty penny for them above parts cost.


 

 Not sure what you mean by AMB style amps as the EHHA is designed by Alex Cavalli who just launched his commercial series at CanJam. 
   
  Ti Kan who is AMB has a strong DIY support and the cost make his B22 commercially has been discussed in depth in the B22 thread - it is just not a prosperous commercial venture in these times. 
   
  and just to get on my DIY soapbox for a second, some people equate DIY with second rate products which cannot compete in the "Big Leagues" well this is bs as we all know that much of the cutting edge is initially tested in DIY. 
   
  ..dB


----------



## TigzStudio

I sort of lumped them all together,as the popular DIY projects Cavalli and AMB, my bad.  But I am curious as I would definitely buy these amps if they were available commercially, which is why I was asking.  That is excellent news about Mr. Cavalli releasing his amps commercially.  So that keeps hope alive. I just personally don't have the time to DIY my own amps and I am sure there are a lot of other people out there in the same situation.  It's too bad about the b22 not being prosperous in their analysis.


----------



## stringgz301

As a DIY project, where you're getting the design (intellectual property) for free (or for the cost of a PCB),  all you're paying for is the parts.  The latter can be very significant once you get into some more complex designs like the B22 or into balanced amps where all the internals are mirrored.  Also some components are more spendy, like transformers, quality capacitors, connectors, pots, and enclosures.  All that being said, there are quite a few designs out there that are an incredible deal compared to commercial parts if you're prepared to build it yourself.
   
  Now say you wanted to commercialize a design.  You'd have to pay for:
   
  - labor for the build
  - custom packaging
  - storage/warehousing for inventory
  - distribution costs
  - advertising and promotion (going to Canjam and giving away a few of your products in the drawing)
  - customer support (including warranty for the device which equates to roundtrip shipping and cost of a replacement unit)
  - building and supporting a dealer network (many small companies are skipping this today and going with direct to consumer over the web)
  - all the other costs of running a company, like rent, insurance, payroll taxes, back office staff, ...
   
  When you add all that in, your $500 DIY product that is a screaming deal is now a $2000 product in a very competitive space selling to a small number of enthusiasts.
   
  The middle ground is finding a builder and working with them to customize a DIY product to your specs.  If you pay them $250 they'll probably make a little more than minimum wage given the hours that it takes, and you'll have to wait a little bit to get it because this is probably not their day job.  However, you'll end up with something of very high quality, customized to your needs, and often reflecting the state of the art in the field.
   
  My 2 cents.


----------



## toidcans

First, please let me know if this should be its own thread, instead of being lumped into this one.
   
  Some history:
  I am interested in building this amp in a balanced configuration. Also would like to build a buffalo II DAC but that is another thread. These two are really the projects that interest me, and I know that they are not really for a beginner. I have done soldering in the past when I was in the HAM Radio hobby, and have started again practicing on making my own DIY cable modifications. But I know that there will still need to be some learning done.
   
  The request:
  As others here, my time is limited as I have a family, so I have narrowed it down to what I find would be the most enjoyable for me to do. As much as I would like to source each individual resistor, capacitor etc, that is one of the items I would like to cut out. Which is ok from a build perspective as the amp is sold in a kit form. Now though, having read this thread there are several ways to skin this cat and there are many pieces that are not in a kit.
   
  My thoughts on this was to see if I could find someone to partner with on this build from a support perspective (Someone who has built one before and knows it well). What I would like to ask of this partner is someone that can tell me what exactly to order to be able to do the complete build (from the exact tube heater to the enclosure). Once I start the build, will probably need some help with any questions that crop up. I can ask the forum when the time arrives, but would like to be able to have that partner involved in these questions and answers as they might help troubleshoot any issues that arise during testing of the build. Also would like to have the individual involved when the individual components are being brought up, to make sure I do not screw or forget to check something.
   
  I know it is a lot to ask for someone else's time, but please let me know if anyone is willing to do this, and help me enjoy the journey as well as the end result. Hopefully it will do some of the same for you. Also hopefully, being fairly new here, would help build some camaraderie.
   
  My other alternatives would be to commission the build (partial or complete)  or buy a used one. Neither which would provide the DIY enjoyment I am looking for.
   
  Thanks.


----------



## sachu

You've got my support to build one of these.... 
	

	
	
		
		

		
			




   
  Whatever questions you have fire away and I will do my best to answer them
   
  Buying the kit from glass jar audio is easily done. As for the heater supply, the broskie heater supply is easily available. I might have one to spare on the cheap..hit me up via PM.
   
  Getting the delay circuit pre built on ebay is easy enough
  then its a matter of casework and soldering. One can put together a balanced amp in under 50 hours, IF all goes to plan


----------



## toidcans

Thanks Sachu, I will send you a PM later today to see if I can get the parts sorted out so that I can order them then.
   
  I really appreciate it.


----------



## rolotube

Quote: 





nattonrice said:


> Hearing a fully filmed bijou would be lovely!


 
  Mine is & it is.
   
  This isn't the place to discuss the Bijou but I'm happy to discuss either privately (PM me) or on the Bijou forum if you're interested in the details.


----------



## johnwmclean

Hey Sachu, are 1 watt resistor strictly necessary for RLED? I have some 2k0 and 3k3 1/2 watters, do you reckon they’ll be ok? The LEDs I’m using are the Ultra Blue T3 5000 MCD 3.2 - 4V @ 30 - 100ma peak.


----------



## sachu

In your case..absolutely.
  I would suggest paralleling 2 2kohm resistors. You will be dissipating close to a watt through RLED if you run about 30mA.
  So double up by paralleling two 1watt 2kOhm resistors for RLED.


----------



## johnwmclean

Sachu you’ve stumped me, what do you mean by “in my case”, wouldn’t the value through RLED and the LED be generic for all builds if supplying +/- 30v supply to the board? My calculations work out something like this:

   
  Have I got something wrong here?


----------



## sachu

Well I said In your case as I thought you might want to run 30mA, normally i set it at 10-15mA where in I can use a 1/2 or 1 watt resistor. With 30mA I would want to run 2 watt resistor for safety reasons. Anyways, seems you have this figured out now.


----------



## rolotube

Quote: 





johnwmclean said:


> rolotube, there’s a spot reserved for you at the meet, I thought I was going to be the first EHHA is Oz - dang you’ve taken away the title, congrats mate I want to see pics.
> 
> What are your transformer secondaries? I wonder if your dropping too many Vs.


 

 Here are some lo-fi pics of my EHHA build to show it really does exist & work!  Its currently spread out on 3 chassis (EHHA, S11, S22) but this will be reduced to two in the final cased version.  I've spent the last few weeks sorting thermal & heater PS issues.  All good now with 2.5" (63mm) heatsinks all round & 9+9V (previously 15+15V) heater transformer.  John, you were right, the S11 was working way too hard.  It is now outputing exactly 12.6V, runs 6H30's with ease & stays cool.  I've tried a range of tubes including 6H23P, 6H6P, 6N1P but 6H30 seems to sound the best.  I love the sound of this amp.  Incredibly clean, detailed & totally dead quiet, its definitely the best thing I've heard, with the single exception of the Bijou.
   
  Unfortunately I won't be able to make it to the Blue Mtns meet next weekend due to family commitments.  I hope there will be more.


----------



## johnwmclean

[size=12.0px]Sachu thanks once again, I now know where you were coming from regarding the LED’s.

 Rolotube, glad you worked it out, congrats mate on getting it up and running. Sorry you can’t make the meet, if this goes off well there’s sure to be others.[/size]


----------



## Br777

does anyone know of any cavalli cth for sale? or anyone on this threat have one for sale?


----------



## MrSlim

Quote: 





br777 said:


> does anyone know of any cavalli cth for sale? or anyone on this threat have one for sale?


 
   
  I sent you a PM on this..


----------



## Br777

aside from a CTH amp (still interested)  are there any other Cavallis anyone is willing to part with these days?  ehha/stacker II ???
   
  thanks


----------



## ujamerstand

I think it would be almost impossible to find a stacker II for sale anywhere in this world. But you can always build an EHHA from the ground up. Hell, you don't even need much fancy tools; just a $14 soldering iron would be sufficient. Plus, there's always people here willing to help you out if you need them.


----------



## Br777

i cant imagine i would have the time or skill for that, I've literally never soldered before, and im quite busy most of the time...  reading through some of the DIY help threads, sounds like things can get pretty complex...


----------



## johnwmclean

[size=12.0px]I’m using a DC regulated supply (σ11) set to 12.6VDC, I want to wire in series, so each tube will be feed 6.3VDC.[/size]


   
[size=12.0px]I’ve noticed this diagram on the Cavalli site is for a 12.6VAC transformer, so does this wiring apply in my instance? In other words the + and – rails of my DC supply will be connected to a different boards and grounds will be connected together, making 6.3VDC.[/size]
   
  I’m a little lost here, I’ve done a bit of digging around but want to be positive.


----------



## ujamerstand

Looks about right. Not sure if you'd still want to tie the ground to the star ground like the diagram though. Could I ask why you are using a series supply?


----------



## johnwmclean

Thanks ujamerstand, basically the reason I opted for 12.6V is current draw, I’ve 4 boards to power. May I ask why you have reservations about tying ground to the star.


----------



## ujamerstand

It just didn't felt right because its different from what I've seen in the millett hybrid max. In that amp, the ground is not connected in between the tubes. But then that amp is not using a dual supply either, that's why I'm not sure. I'm hoping to use a DC heater supply as well, but I'm going to use 6.3V heaters instead, so I don't think I'll encounter the same problem. I should be able to have enough current if I use either LM338 or LT1083. After all, its what? 1.32A for 4 6GM8? Add a 6.3V transformer rated at 4-6A and I should be fine.


----------



## johnwmclean

I powered up one side of my amp both boards pass initial checks and power up.
   

   
   
  The output quiescent current is giving me grief, at full turn of R21 gives me around 0.144V, this is a speaker/headphone build so the output resistors are 0.47ohm 5W, R21 is this replacement 50ohm: http://au.farnell.com/jsp/search/productdetail.jsp?SKU=9353275.
   
  Here’s a progress pic of my EHHA set-up:
   

   
   
  All components are as per the BOM, plus power amp parts as per the EHHA site, again both boards read pretty much exactly the same. Any help would be appreciated.


----------



## les_garten

Sweet Job that!


----------



## ujamerstand

Wow, what an impressive setup. I hope you get it up and working soon, I see a build quality that could rival or even surpass commercial offerings here.


----------



## Br777

beautiful build for sure... but the real question is... how much are you going to sell it to me for?!?!  
	

	
	
		
		

		
			





  (thats a wink, as in.. ha ha im just joking... but not really)


----------



## nattonrice

Go John!
  I love triple box solutions.
  Pics do not do justice to the attention to detail.
  As soon as the fixed top panel gets back... just damn


----------



## sachu

Very cool .John.. Did you make sure that R20 is 330R?
  This power amp configuration hasn't been tested by anyone successfully before. SO it is kind of uncharted territory.  If you haven't changed the value of R20 yet, make sure that you set R21 is set counter clockwise else you might risk blowing the output devices.


----------



## johnwmclean

Thanks Guys.
   
sachu, R20 is indeed 330ohm, now because the output resistors are 0.47ohm it goes like this V = 100mA * 0.47 = 47mV, I’ve set mine a little more aggressively at 94mV which will reduce THD and keep the amp slightly more in class, this also depends on sink size, so I’ll see how I go. Alex gave me these pointers btw, I would never have worked this out on my own lol.
   
I did run into a little problem though, I’ve got a new fluke and the probes are bloody sharp and I cut through the solder mask to ground on one board and blew the FET’s (dam big spark too), for some reason I had a hell of a hard time desoldering one sucker and lifted the trace and had to jumper some of the circuit, real bitch. But both boards are running perfectly now.


----------



## sachu

aah right..i forgot about that..posting at 4 in the morning does that sometimes. Well glad you got your boards up and running again. First time hearing about probes punching through the solder mask haha.


----------



## ujamerstand

has anyone else noticed that pete millett updated his filament supply page, and now offers his heater supply pcb on ebay?


----------



## funch

Yep. http://cgi.ebay.com/DIY-PCB-2x-Regulated-DC-power-supply-filament-supply-/160454559896?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item255bd64898


----------



## johnwmclean

I dont know if I’m the first, I think so - but not sure...
   
*EHHA Speaker Amp Premier 
	

	
	
		
		

		
		
	


	


*
   

   

   
  As one of the four boards is still waiting for some parts and a bit of troubleshooting, I thought I’d give a pair of 4ohm bookshelf speakers a whirl with two of my working boards a single σ22 and do a bit testing. I’m delighted to say the EHHA makes a fantastic speaker amp, it’s running steady at 100mA and the sinks are still cool I reckon I could probably push 200mA easily. The speakers sound awesome for what they are, much better than than I ever expected these cheap arse things could ever muster, if fact I spent the entire day listening... oh and I’m only using the kit supplied 6GM8’s.


----------



## runeight

Congratulations John. So far as I know you have built the first working EHHA speaker amp. And, fortunately for both of us, it sounds pretty good too. 
	

	
	
		
		

		
			





 (I notice there is no speaker amp smiley).
   
  When do you think the last board will come online?


----------



## Horio

Great job John.  You are making me regret not setting up my EHHA for speaker duties.  Looks like the Beta22 will have to be in charge of that one.
   
  I love the speaker stands by the way.


----------



## qusp

nice work as always John!! hey wow so it actually does happen, I have actually sharpened my probes, as I do a lot of fine SMD work, but I have always been paranoid about exactly what happened to you happening to me. glad you sorted it out


----------



## sachu

Nicely done John!! First ever EHHA speaker amp indeed. Eagerly looking forward to reading impressions once the final board comes online. Its about time


----------



## TimJo

Hmmm. EHHA and some Fostex full range drivers. I wish I had more free time...
   
  Can't wait to hear more about your system John. Nicely done!


----------



## johnwmclean

thanks guys,
   
  I should have a fully working balanced amp in a couple of weeks I reckon. All the panels are now done as well I just have to get time to get to it.
   
  I was up late again last night listening tried as hell right now, just awesome. Thanks sachu and Alex for a all your help.


----------



## Horio

I'm very jealous John.  Maybe someday I will finish my EHHA/B22/O22 project that is about 70% done.


----------



## johnwmclean

Well 70% better is quite a bit done, congrats! Have you had any panels fabricated yet? I’ve used Cam-Expert and I’m very happy, although there was a couple of major stuff ups (not my fault) they were very accommodating and fixed things quickly.
   
  I put the chassis together last night to check fit, so excuse the back panel being upside down, but you’ll get the idea.
   

  The volume has 4 holes behind frosted perspex for some LED lighting and an inset knob.
   

   
   

   
  Still a ways to go with testing/wiring... I’m very happy with how 2 boards drove speakers very well it sounded awesome, the above mentioned Fostex would be a very nice fit IMO.


----------



## sachu

holy smokes batman...that made me shed a tear.
  Amazing build John. Eagerly looking forward to impressions.


----------



## ujamerstand

Jesus. You are my hero.


----------



## Lil' Knight

That's an amazing case work, John!
   
  What's up with the Left and Right Output? Looks like the back panel is opposite.


----------



## johnwmclean

Thanks Guys,
  
  Quote: 





lil' knight said:


> That's an amazing case work, John!
> 
> What's up with the Left and Right Output? Looks like the back panel is opposite.


 

 In my haste to check the new top panel fit I received yesterday (third time lucky) I inadvertently had the back panel upside down.


----------



## primer

Nice work John.


----------



## Lil' Knight

Quote: 





johnwmclean said:


> Thanks Guys,
> 
> 
> In my haste to check the new top panel fit I received yesterday (third time lucky) I inadvertently had the back panel upside down.


 

 Ah. Can't wait to see this thing finished.


----------



## nattonrice

Holy crap John did that turn out well!
  I love the backlit knob provision.
  I guess this time they figured out that when you request counter bores to be colinear you aren't joking?  =P


----------



## TigzStudio

That is one hell of a sexy looking chasis.  Beautiful work!


----------



## aloksatoor

amazing casework!!


----------



## gabriel-dan

Beautiful job johnwmclean!


----------



## qusp

youve outdone yourself yet again John, sexy!! I love the frosted perspex, how is that mounted behind? I might look at doing something like that for my hexateq chassis, because I need to recess the titanium knob as its quite deep and large, so looks wrong on the outside, but the case isnt really thick enough to do this, so I need to add another layer behind and mount it to the front either with countersunk hex bolts and make a feature of this, or mount it to the base and have no visible mounting holes at all


----------



## johnwmclean

Crikey, thanks guys for the nice comments!
   
  Quote: 





qusp said:


> how is that mounted behind?


 

 Like this

  The panel is 10mm thick, the large cavity hole was to bore to 7mm, the front panel bearing bush locks the perspex in place and the LED’s will be glued into the four small holes.


----------



## rolotube

Can only agree with what's already been said; its a stunning looking build.  Good that the sound measures up as well.  Will be interested in your comments on performance when fully completed.


----------



## johnwmclean

All 4 boards are now inline!
   
  The amp is as quite as a church mouse, the change from going to 2 boards to 4 is profound to say the least, the power and grip has much better conviction. The bass is deep and detailed, as I’m typing I have some Ben Webster blowing his horn in the background, this is one hell of a good speaker amp.
   
  I’ve tried the 6GM8 and the 6H30’s, to be honest I had a hard time picking between the two, if anything the 6H30 is slightly leaner whilst the 6GM8 has a little more bloom and character. The heater is a σ11 with a 60VA 15V Sumr transformer, it runs warm too hot with 4 6H30’s around 58° after half an hour (by my fluke 87V). *   *
   
  I haven’t hooked up the headphone output yet, I’ll give the HD800’s a go later in the week.
   


  The LEDs for the backlit volume have not been installed yet, the light emitting through is from the four LED’s on the boards.
   
   

   
   
   
   
   

   
  Excuse this mess, it’s a work in progress at the moment, the extension shaft and final wiring are yet to be completed.
   
  Alex you’re a legend! Thanks for your guidance, help and super quick responses. I have some smoked output resistors that have your name on them.
   
  Sachu, I now understand your passion for this great amp, thanks for all your help.


----------



## sachu

Sick!!..I am so happy with the way that turned out man.


----------



## FallenAngel

Looks awesome, congrats!


----------



## runeight

Quote: 





johnwmclean said:


> All 4 boards are now inline!
> 
> The amp is as quite as a church mouse, the change from going to 2 boards to 4 is profound to say the least, the power and grip has much better conviction. The bass is deep and detailed, as I’m typing I have some Ben Webster blowing his horn in the background, this is one hell of a good speaker amp.
> 
> ...


 


 I think that everyone is blown away by this build John. Maybe you could design amps for me???
   
  And I am really happy to know that the electronics is equal to the enclosure. I especially appreciate the fact that you took a pretty big risk with only my prediction that this would make a decent speaker amp, but without a previous build to prove it. I must admit I did sweat it out a bit when you were bringing the amp up for the first time. 
	

	
	
		
		

		
			




   
  Most of all, I am touched in having burnt resistors named after me.


----------



## wink

If it sounds as good as it looks, it will be a Beta22 beater.................


----------



## TigzStudio

I would buy this amp in a heartbeat!  Cavalli name + sexy looks, for sure!  I might of used white leds instead of blue....but that is just personal preference.  Everything about it is stellar though, nice work.


----------



## johnwmclean

Thanks Guys.
   
  Quote:


wink said:


> If it sounds as good as it looks, it will be a Beta22 beater.................


 
   

 [size=medium][size=13.0px]Well...

 I had a careful listen with my HD800’s for the first time last night...

 The EHHA has as much detail as my balanced Beta22 and it presents music with a little more ebb and flow. The Beta22 can be analytical especially with the HD800’s, I was looking for something with a fun character that would put a different spin on my music - with the EHHA I think I’ve achieved a nice contrasting amp to my long standing reference Beta22. Both are world class performers, I’m really liking the contrast the EHHA is giving me at the moment, it’s really growing on me.
 [/size][/size]


----------



## Racio

Quote: 





johnwmclean said:


>


 

 One of the most beautiful headphone amp I've seen so far, well done indeed!


----------



## Horio

Well said Racio.  He always does great work but John really made something special this time.


----------



## johnwmclean

Thanks gents! Really nice words,
   
  Greg I’m looking forward to seeing your build completed!


----------



## Horio

I finally mailed off the panels on my CKK3/Gamma2 project, so that is almost finish finally!  After that, all my attention can go to finishing up the EHHA/o22.  I've got the EHHA boards built and the o22 running already (not cased up though).  Still need a few more parts though.  I will post some pictures on here in the next few weeks when I make some more progress.


----------



## johnwmclean

*Free for anyone interested*
   
   I don’t know what else to do with these so...
   



   
  These panels were for my 1u 350mm Modushop chassis, they all had something that wasn’t done right from Cam.
   
  The back panel was supposed to be black anodised. The front panel has the cavity for the inset volume knob dug out of the wrong side (on the other side from this photo, I was initially going to use it as is and mount the perspex on facing side it worked fine and lit up nicely, I have spare perspex rings also. I have two top panels like the one in the picture, these were drastically different from the files I had supplied CAM. The tube holes were too small and in the wrong position, the holes will still fit around a tube comfortably, but with little slip for tolerances that are out of whack with the base.
   
  I have all component data sheets also, along with computer drawings.
   
  All you need to pay for is shipping. First in first served


----------



## primer

Much expletives when you noticed the errors.  I'm glad everything turned out well.  Looks good.


----------



## Horio

John,
   
  I might be interested in the top panel for my build.  I'm using the same chassis as you but just the 2U version.


----------



## RockinCannoisseur

how does ehha 1 compare to soha II or bijou? and why no phono stage at cavalli?   i had thought the bijou but nope?
  and how does cav compare to hag?  im pretty much sold on the piccolo or bugle unless cavalli has any competition hopefully?
  the hag cornet 2 also looks very nice


----------



## sachu

I prefer the EHHA over the SOHA2 or the Bijou.


----------



## johnwmclean

I’ve been following the ehha-rev-a-interest-thread closely, jdkJake measured his DC offset at power on as 1.5V even 1.7V possibly 1.9V.
  I’ve measured dc offset over my four boards and I’m happy to say they are all 0mV. But I hadn’t done a dc offset test at turn on, so tried it out over the four boards of my amp to see the results.
  I set my DMM (fluke 87V) to capture the highest amount, the measurements were 1.5V best result and 2.4V being the worst.
   
  Virtually within a spit second these voltages drop and within 5 seconds were down to 0V.
   
  Unfortunately a ε12 for me is not doable as my build is a speaker amp. I will be plugging my phones in after 10 seconds or so after power from now on.
   
  Now I’m pretty sure a lot of EHHA builds will have similar readings, do you guys think this is a concern?


----------



## runeight

2.4V for most speakers should not be a problem. For 4 ohms this would be about 600mA transient. Not enough to hurt the speaker.
   
  Did you measure with or without the speakers connected.
   
  Now for 32R headphones, the current would be 2.4/32 = 75mA. Some headphones might be damaged by this, I'm not sure. My guess is that most would not. Maybe none.


----------



## sachu

I almost never unplug my headphones, not something i recommend. But it helps when all your headphones are orthos that can take some serious power.


----------



## johnwmclean

Thank you guys that’s great info, measurements were made without anything connected to the outputs. HD800’s should be no problem in that case.
   
  I have some some Horns Shoppe speakers on the way, I’m hoping for a great match with this amp.


----------



## jdkJake

Johnwmclean,

 Worse comes to worse, you could always build and install a simple hard-switched (manually-switched) relay circuit. Adding a time delay would also be pretty straight forward. No where near as sophisticated as the e12, but, certainly functional. My main receiver ( commercial) has such a circuit to keep it quiet until things settle. Just a thought.

 Too bad you are so far away, I would love to hear that amp through speakers. I suspect it would be quite the treat! You are a fortunate man.


----------



## rx7mark

John,
  What a great build!!    It's great to see a EHHA speaker amp up and running.
   
  Would you mind summarizing the details of the build, gains, upgrades, transformers, rev to the BOM, etc. 
   
  I know some of it is on this thread, but a summary post would be great.
   
  Thanks in advance!
   
  Mark


----------



## johnwmclean

Thanks Mark, I'm camping up the coast at the moment, when I'm back in a few days I'll post up some more details.


----------



## adamus

john - Are you considering speaker protection for this build? I am going to build a hybrid soon, and i just dont think i can trust a servo without protection.
   
  If them amp developed a fault that meant it went to one of its rails, then i can only see one outcome... dead speaker!


----------



## johnwmclean

Adam, I'm considering something like this
 http://www.designnotes.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=M4701B&Category_Code=hiehp
 I'm not too concerned about soft start, but definitely would want protection from going to a one rail fault.


----------



## jdkJake

This looks interesting as a potential solution. A bit pricey though.
   
     http://www.borbelyaudio.com/eb292132.asp


----------



## johnwmclean

Yeah they are a bit pricey, I'll also need two as the psu is dual mono. The circuit I've referenced although not relay or soft start protecting should kick in if there's a gross error with the amp, it's also its passive. The thing I'm unsure is how this would effect sq.


----------



## jdkJake

Yeah, I hear you on the sq question. The less in the signal path the better.
   
  Well, at least they are not too expensive if it does not work out.


----------



## fishski13

Quote: 





johnwmclean said:


> Adam, I'm considering something like this
> http://www.designnotes.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=M4701B&Category_Code=hiehp
> I'm not too concerned about soft start, but definitely would want protection from going to a one rail fault.


 

 i would go with the K4700 - the relay trips at 1V DC vs 10V of the K4701.  they're big and expensive.  i was researching for DC protection in an old Harman Kardon Citation 12 amp i picked up.  i don't trust 40 yr old sand running into my speakers.  i've decided to gut and rebuild it with new components.
   
  Fostex has also discontinued quite a few of their drivers recently.  i would nab up a second pair for you Horn Shoppes if the drivers are on the cutting block.


----------



## cfcubed

BTW, Ed's great about support for his stuff.  Before I knew to *always* check DC offset, an inexpensive commercial tube pre w/o delay or offset protection used the nice DC amping of my DIY F1 to fry the FE126s in my horns.  IIRC Ed shipped out matched/treated driver replacements for less than I could get raw/unmatched drivers for.   
  I now have a better pre w/relay but have yet to add speaker protection... I'd probably just grab "speaker protection" from e bay if I did it.
  Quote: 





fishski13 said:


> <snip>
> Fostex has also discontinued quite a few of their drivers recently.  i would nab up a second pair for you Horn Shoppes if the drivers are on the cutting block.


----------



## rx7mark

Quote: 





rx7mark said:


> Would you mind summarizing the details of the build, gains, upgrades, transformers, rev to the BOM, etc.
> 
> I know some of it is on this thread, but a summary post would be great.


   
  Just a reminder John, if you wouldn't mind posting the data on you build when you have a moment.
   
  Ignore this if you are still camping.
   
  Mark


----------



## johnwmclean

Besides these components listed everything else was exactly
as per the BOM on the Cavalli Audio site. Most if not all the components
necessary for the power amp option follow are as per recommended under Tweaks.
   
My Power Amp Recipe:
   
R21 *50Ω*
[size=medium][size=14.0px]R13 *1.82kΩ*
 R22, R23 *33.2kΩ*
 C2, C3 *2.2p 250V*
 R20 *330Ω*
 R32, R33 *5W .47Ω Mills MRA-5*[/size][/size]
  
[size=medium][size=14.0px]Tubes: Telefunken white diamond ECC86.

 Zobel: 22Ω 2W and 0.047µF 100V film capacitor.[/size][/size] 

[size=medium][size=14.0px]The Conrad sinks I used were custom made, so I’m not sure of any thermal spec,[/size][/size]
[size=medium][size=14.0px]they only ever get warmish, the boards are biased at 200mA.

 The gain is slightly too high for the HD800, I would have preferred more travel on[/size][/size]
[size=medium][size=14.0px]the pot especially as it’s a 24 stepper (Dact). It’s also too low for inefficient speakers,[/size][/size]
[size=medium][size=14.0px]as I’ll be using Horns it won’t be an issue. Perfect for K1000’s.[/size][/size]


----------



## rx7mark

Thanks John!  
   
  That is exactly what I was hoping for.  What are the specs for your transformers and what are you using for the tube heaters?
   
  And any more listening impressions?   B22 comparison?
   
  I am very envious and inspired, and hope to build something similar when I get back to the states.  Currently on a job in Italy.
   
  Mark


----------



## johnwmclean

The tube heater is a Sigma11, configured for 12.6V output, using a Sumr 60VA 15V (single secondary) custom transformer. Be careful with the Sigma11 it’s not the best idea as a heater supply, running continuous highish current is not really what this linear supply was intended for. The temp with 6GM8 is around 45 degrees and with the 6H30’s runs hot, I’ve clocked them at 65 degrees. I’ve used the chunkiest on board http://au.element14.com/jsp/search/productdetail.jsp?SKU=1213475     
   
  The psu is a dual Sigma22, Custom, SumR 120VA transformers, surprisingly even with these big Conrad heatsink’s it also gets warm.


----------



## martinz

Quote: 





johnwmclean said:


> The tube heater is a Sigma11, configured for 12.6V output, using a Sumr 60VA 15V (single secondary) custom transformer. Be careful with the Sigma11 it’s not the best idea as a heater supply, running continuous highish current is not really what this linear supply was intended for. The temp with 6GMA is around 45 degrees and with the 6H30’s runs hot, I’ve clocked them at 65 degrees. I’ve used the chunkiest on board http://au.element14.com/jsp/search/productdetail.jsp?SKU=1213475
> 
> The psu is a dual Sigma22, Custom, SumR 120VA transformers, surprisingly even with these big Conrad heatsink’s it also gets warm.


 

 so what is the best heater for EHHA?


----------



## johnwmclean

I don't think there's any such thing as best just different, but I do like the H-PS-1:
 http://glass-ware.stores.yahoo.net/hps1.html

 There's also Pete Millets supply:
 http://www.pmillett.com/DC_filament_supply.htm

 The Sigma11's fine for 6MG8's, it's overkill, pricey and runs hot, but not excessively, still well within spec.


----------



## martinz

Quote: 





johnwmclean said:


> I don't think there's any such thing as best just different, but I do like the H-PS-1:
> http://glass-ware.stores.yahoo.net/hps1.html
> 
> There's also Pete Millets supply:
> ...


 
   
  I'm planning to use AC 12.6V regulator scheme from cavalli's website
   
  Are those two (pete millets' & H-PS-1) a lot better than this one?


----------



## sachu

Not particularly..the one on AC's website is just perfect for the amp. I have used this in two of my EHHA builds.


----------



## martinz

thank you sachu
   
  is it better using its own transformer or sharing with S22? I'm using Avel Lindberg 100VA transformer for my S22


----------



## sachu

I prefer to go with a separate transformer.
   
  This way I can use a tube delay circuit to bring up the heaters first and then the HV supply.


----------



## arteom

I have been considering building this for a long time now, sold my x-can and have an excuse now 
	

	
	
		
		

		
			





. I like the idea of this because it can also power efficient speakers if properly setup. I am a bit new to DIY however, have previously built a cmoy and a cth. Have a few questions about the build; If setup for speaker use, I assume the headphone out would also be setup for high gain use. Is it possible to have a switch for the gain on this amp? Allot of the headphones in my inventory at the moment are low impedance. Or do you just have to socket resistors and switch them?


----------



## sachu

a switch for the gain will definitely be the way to go. Perhaps John can pitch in with his observations/comments as he is the only person thus far to have built one for dual duty.


----------



## johnwmclean

As Sachu pointed out a gain switch in your case will be necessary.
   
  My amp has no gain switch, in my scenario I’m using it with efficient horn speakers and various high impedance phones.


----------



## gurubhai

Finished my first DIY build - EHHA.
	

	
	
		
		

		
		
	


	



  Its a BJT build with Toshiba 2SC2238 / 2SA968.Here are a few pics:


----------



## arteom

Thanks for the replies sachu and john, I will have to do some research on how to make a gain switch. Nice build gurubhai!


----------



## sachu

Nice build indeed gurubhai..love the use of the adapter for the heaters lol 
	

	
	
		
		

		
		
	


	



   
  Need better shots of the amp fully cased up buddy.


----------



## les_garten

Nice Job!
   
  One quick suggestion about the Adapter.  De-nude it and mount on stand-offs.
   
  Don't be offended --
   
  A few suggestions about the Nude adapter:
   
  1) Would look More professional
  2) Would look less "SinglePower Inspired"
  3) Probably would run Cooler
   
  Sweet Work!
   
  What are the Specs on the adapter?
   
   
  Quote: 





gurubhai said:


> Finished my first DIY build - EHHA.
> 
> 
> 
> ...


----------



## gurubhai

Thanks Sachi : your encouragement & support has been invaluable.
   
  Thanks arteom.
   
  @ les : Not offended at all, all suggestion are welcome. Considering I didn't even know how to solder 4 months back I am just happy that the amp is running even if the workmanship looks 'SinglePoweresque'. 
	

	
	
		
		

		
		
	


	



  I have a custom stand-off plate on order for the adapter & will shift it once its ready.
  The adapter doesn't generate much though.
   
  Edit : Its a 12V, 1A SMPS


----------



## sachu

guru...you need to up the size of the heatinks for the output devices on the amp and also on the S22 power supply..only just noticed them now. Monitor the temperature on the heatsinks and it might be a good idea to either run the amp off of a un-interrupted power supply to avoid risking blowing the output devices when you get those power cuts 
	

	
	
		
		

		
		
	


	




. And I highly recommend it in your case as you have the locking headphone jack (hate those)
   

  You will need to use these ones
   
  One other tweak would be to shunt the potentiometer using some takman or riken resistors depending on the value of your potentiometer. Use anywhere from 40-47k resistors for shunt modding it if its a plain ALPS blue velvet 50k pot.


----------



## sachu

Quote: 





arteom said:


> Thanks for the replies sachu and john, I will have to do some research on how to make a gain switch. Nice build gurubhai!


 


  Just use a simple miniature SPDT ON-ON switch..One resistor value (depending on gain setting) for each switch position and you are done.


----------



## gurubhai

Ya, I have been keeping an eye on the heatsink temperatures & they have been fine even after 6 hours of continuous running. Anyway it shouldn't be issue during the winters, I shall look into it later.
   
  Can you point me to some detailed info on 'shunt' mod. I have alps 'blue velvet' 100k pot.



sachu said:


> guru...you need to up the size of the heatinks for the output devices on the amp and also on the S22 power supply..only just noticed them now. Monitor the temperature on the heatsinks and it might be a good idea to either run the amp off of a un-interrupted power supply to avoid risking blowing the output devices when you get those power cuts
> 
> 
> 
> ...


----------



## les_garten

You've come a _*LONG *_way then.  Congratulations!
   
  Shoot a PIC back at us when you strip the PS, that would be sharp!
  
  Quote: 





gurubhai said:


> @ les : Not offended at all, all suggestion are welcome. Considering I didn't even know how to solder 4 months back I am just happy that the amp is running even if the workmanship looks 'SinglePoweresque'.
> 
> 
> 
> ...


----------



## ujamerstand

out of curiosity, which transistors are you using to replace 2SC2705/2SA1145 in your EHHA? Also, is it just me or are those 6GM8s are awfully bright?


----------



## fishski13

Quote: 





gurubhai said:


> Ya, I have been keeping an eye on the heatsink temperatures & they have been fine even after 6 hours of continuous running. Anyway it shouldn't be issue during the winters, I shall look into it later.


 

 i forget what the quiescent current of the EHHA is, but the o22 is rated for 1A continuous with the recommend heatsinks per AMB's BOM. .  i used the recommended 1.5" Avid Therm. for a +/-30V o22 powering a 3-board B22, with each board drawing 200mA.  my o22 heatsinks barely get warm.


----------



## fishski13

Quote: 





gurubhai said:


> Can you point me to some detailed info on 'shunt' mod. I have alps 'blue velvet' 100k pot.


 
   
  sorry, i don't have a pic.  
   
  on a pot:
  Input = input signal from RCA
  W = wiper
  G = ground
   
  connect W and G together for each channel.  place a 100K resistor in series from the RCA to Input on the pot to each channel.  from the Input after the 100K resistor, connect to the signal inputs on each channel.  the ground from each of the RCAs to should connect at their respective channels on the pot at W and G.  connect the W and G of each channel on the pot to their respective input ground on the boards.  
   
  instead of the signal being across the wiper and conductive material,  the signal is "only" across the in-series input resistor.  in this configuration,  the potential divider is adjusted on the ground leg and not the input leg.


----------



## gurubhai

Quote: 





ujamerstand said:


> out of curiosity, which transistors are you using to replace 2SC2705/2SA1145 in your EHHA? Also, is it just me or are those 6GM8s are awfully bright?


 
  Using the BC556/BC546.
  You caught me on the 6GM8s. Just the regular tubes with the LEDs in the background.
  
  Quote: 





fishski13 said:


> i forget what the quiescent current of the EHHA is, but the o22 is rated for 1A continuous with the recommend heatsinks per AMB's BOM. .  i used the recommended 1.5" Avid Therm. for a +/-30V o22 powering a 3-board B22, with each board drawing 200mA.  my o22 heatsinks barely get warm.


 

 These are the 1.5" heatsinks, only the branches aren't as spread out as in some of the other pics I have seen.
  The mosfets on S22 are getiing only lightly warmed up but the BJTs on EHHA are getting a bit hot.

  
  Quote: 





fishski13 said:


> sorry, i don't have a pic.
> 
> on a pot:
> Input = input signal from RCA
> ...


 
  Thanks. This is how I understand it - shunt ( on top) as against normal (bottom ) connection. Is it ok ?

  edit : replaced the pic with the correct one.


----------



## fishski13

looks good.


----------



## jdkJake

What is the advantage of using the shunt?


----------



## gurubhai

I did the shunt mod & but now the volume decreases on turning the pot clock-wise & vice-versa. What am I doing wrong ?


----------



## les_garten

Well Homes, I think you have it wired backwards.
   
   
http://www.world-designs.co.uk/forum/showthread.php?t=5795
  
  Quote: 





gurubhai said:


> I did the shunt mod & but now the volume decreases on turning the pot clock-wise & vice-versa. What am I doing wrong ?


----------



## fishski13

Quote: 





les_garten said:


> Well Homes, I think you have it wired backwards.
> 
> 
> http://www.world-designs.co.uk/forum/showthread.php?t=5795


 

 that's the pic i was looking for.  yes, you probably have the pins on the pot reversed.


----------



## les_garten

It would work perfectly in the Anti-Universe...
  
  Quote: 





fishski13 said:


> that's the pic i was looking for.  yes, you probably have the pins on the pot reversed.


----------



## fishski13

Quote: 





les_garten said:


> It would work perfectly in the Anti-Universe...


 

 i hope we get beyond the theory and i can buy a ticket to get there.


----------



## gurubhai

Quote: 





les_garten said:


> Well Homes, I think you have it wired backwards.
> 
> 
> http://www.world-designs.co.uk/forum/showthread.php?t=5795


 

 That diagram explains it.Signal wire is being connected to terminal 1 (ground in the default config)


----------



## BebopMcJiggy

Started building one of these but after seeing that dude who threw Alan Rickman from the Nakatomi building's beautiful case work I am gonna be embarrassed to show what I'm working with.  Most of the parts are still in transit anyhow 
	

	
	
		
		

		
			





.


----------



## gurubhai

For people who have fiddled with NFB/OLG  by changing R22/23, what is the value you have preferred for best sound quality ?


----------



## BebopMcJiggy

Is it going to be a problem if my heater supply is putting out 7 VCT instead of 6.3? ;p  Should I replace it with a weaker filament transformer?  I haven't really got room in the case for much else... should I scrap the case and use a regulated 6.3v supply?  Expand my build to 4 channel and hope the voltage droops a bit? ;p  Ignore it?  And yes that is 7 volts while it is on and hooked up to 2 ehha boards.  Is it going to do anything besides slightly reduce the lifespan of my tubes?


----------



## johnwmclean

The specs of most of in-direct heating tubes specify +/- 10%, your 7V is 1% over tolerance @ 111%.
   
  Personally I wouldn’t worry...


----------



## adamus

i would worry, and use a couple of resistors to drop the extra  V. you know the current draw (tube datasheet), you know the drop you need.... ohms law does the rest


----------



## BebopMcJiggy

So I need 2 approximately 21 ohm resistors rated at least 2.5watts eh?  Guess I should use 4 10 ohm power resistors?  I have the 2 boards wired up in parallel to the transformer should I put 1 10 ohm resistor per heater supply connection wire, or do 2 in series from the transformer to those wires?  Or 2 in series on only 1 side of each heater supply?  Sorry, this was actually my first diy amp and honestly I think I'm doing pretty good if my only problems are I broke 1 1$ mosfet and my filament transformer is giving me a bit too much voltage/current.
   
  or is it .33a = 6.3 / R, R = 19.0909 so I = 7.1/19 == .372A and to get .33A I need an additional 2.5ohms? (.33 = 7.1/R, R= 21.51515?) guess I will find out when I get home regardless ;p.


----------



## nikongod

Since nobody else asked:
  Are you running the transformer loaded? IE were the tubes in when you measured that voltage? 
   
  What load is your transformer sized for? A transformer rated for 10A@6.3v wont light up at 6.3v under a 2.4A load - It will probably be much higher.
   
  A few posts ago you asked if you should get a smaller transformer. If you measured the voltages under load I would probably do that. Resistors to drop heater voltages work if your in a bind, but they mean several watts more heat floating around the chassis which is no fun. Unless you have very good reasons* for using a resistor to drop heater voltages dont do it.
   
  *good reasons:
  You want to do the 6/12V heater with no switch trick on tubes like 6/12SN7
  The heater windings are in the same custom wound transformer as the B+ windings and they just didnt work out right.


----------



## BebopMcJiggy

Okay I will just get a smaller transformer then, it was loaded.  Thanks for the help, I was wondering about the heat a bit myself :O.  I suppose I wasted 6$ on some resistors at radio shack but oh well.


----------



## BebopMcJiggy

So it was definitely that I needed 2.5 ohms or so... I used 1 10w 1.1ohm resistor to drop the voltage to 6.4 and the 10w is definitely some serious overkill, it barely gets warm at all.


----------



## BebopMcJiggy

Meh I think I'm just gonna leave it with the resistor, I don't even think it is dissipating 1 watt (should be 1/10th of ~2 watts per filament? so 2/10ths of ~2 watts?)  If my math is right anyhow and it's 6.4 volts through 21.090909 (21.290909? ;p) ohms (twice).


----------



## adamus

P=I x V
  V=I x R
  therefore P=R x I^2


----------



## BebopMcJiggy

Well it's rated for .33a @ 6.3v so I assume it is 19.090909 ohm resistance when loaded...  theres 21.090909 ohm resistance now @ 6.4v (1 1ohm resistor wired before the filaments which are in parallel) but I'm not clear how you separate the 1 (2...) ohms out of that and figure out the current going through it only but I think the whole 21.090909 dissipates 1.94207 watts in heat or so? or like 2.5ish watts if you use the source voltage?  Regardless I don't see how the resistor could be responsible for more than a small amount of heat :O


----------



## BebopMcJiggy

Sigh so upon arriving home today one of my boards no longer seems to work.  I now get 0v across R4 and 3v across R3, obviously something is horribly wrong.  The mosfet gets really hot on the +30v input side and well I don't know what else as I shut it off.  For the life of me I can't find a short or anything...  should I replace IC3 and all the transistors on that side or what?  Kind of really furious right now and about to smash that particular board as it was working fine before and I am a sad sad panda


----------



## BebopMcJiggy

Not that anyone really cares but my terrible case work  It looks better on the outside heh... evil locking 1/4" plugs :O
   

   
  and the non working channel 
   

   
  I replaced the mosfet  But yeah r3 and r4 are all messed up, I don't even think the old mosfet was broken   Will replace the transistors and try again I guess :O  not really sure what is wrong here but the voltages to q8m are ridiculously high by the end of it and it heats up really fast.
   
  So the one channel that is working sounds good, except when I tried with the athM50 there was a bad hiss but I am just assuming that hp was too sensitive... sounded great with LCD2...


----------



## gurubhai

Q : Which opamps can be substituted for OPA134 in EHHA ?
        Would the TL081 ( used in rev.A} do ?


----------



## sachu

Will do fine.


----------



## BebopMcJiggy

Well I fixed the other channel and I am not one for flowery language about how the amplifier tickled my ear's prostate but it sounds pretty good so far.  I have a slight hum in the right ear when I put the output (input?) to max.  Not really noticeable while things are playing and also I would never listen to things loud enough for it to be audible, I just notice when there is no input and the volume is set as high as it can go.  I think it is from the heater transformer but oh well.  It really only seems to get slightly warm above the tubes and that is it, and they're not so hot I can't touch them... the heatsinks barely heat up at all so far.  I think perhaps I went overboard perforating the lid now but it can always use more ventilation I suppose.


----------



## francisdemarte

Quote: 





bebopmcjiggy said:


> Well I fixed the other channel and I am not one for flowery language about how the amplifier tickled my ear's prostate...


----------



## arteom

Can anyone help me with some casing option for this amp? I want to build an end all amp for my bedroom, so really wanted to configure it for speaker use as well. I have seen some build b22's in a box type enclosure, and was wondering if such an enclose might work for the ehha as well, also no idea where I would source such a case. Really want to build this or the Rev. A, just thinking it might be a bit over my head as I've never had to do such casework, also never worked with transformers. Have a cmoy and compact tube hybrid I've built. Any help nudging me along is appreciated .


----------



## ujamerstand

If you look over the past couple of pages or so you'll find johnwmclean's excellent build that works for speaker duties.


----------



## arteom

Yeah I saw that, one of the sexiest builds I've seen. But I don't know if it would be too proper to copy it, wouldn't mind at all doing so if it was, and of-course if he didn't mind .


----------



## ujamerstand

You don't have to copy him. There are many places to buy custom enclosures. Par-metal and hifi2000 cases come to mind. You can buy large heatsinks from conrad heatsinks, or an ebay seller like this one. http://shop.ebay.ca/barrredboss/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p3686


----------



## arteom

Yeah I was thinking of just ordering all the electronics and worrying about enclosure later, have some spare space to work. I think once I get all the parts it will be much easier to evaluate what case would work.


----------



## jdkJake

I think building the amp proper, getting it fully functional and then considering casing options is a perfectly valid approach. At least you have a better idea of what you are really working with before you commit too many resources.

As for copying John's design, well, I doubt anyone could truly capture the look and feel John has obtained in his most magnificent implementation. Better to pay homage to his ground breaking work with the EHHA as a speaker amp and put you own unique spin on the final implementation, at least in casing it up.

Now if you order something from the horn shoppe as well, that is another matter altogether. 

Then again, while they say imitation is the strongest form of flattery, ultimately, John's opinion on the matter is all that truly counts.


----------



## johnwmclean

Totally flattered, thanks guys!
   
  arteom if want to copy by all means please feel free! If you need files for cutting I have them too as well as any help you should need. Goes for anyone interested!
   
  Happy to give something back into the community.


----------



## arteom

Thanks John. Like said, it would definitely be a copy of one of the best looking amps out there, be it diy or commercial. I probably should go ahead and get the boards populated and running before I think enclosures. I will definitely keep in contact, I am grateful for the help you and the community here are offering John. God knows I wouldn't even think of going forward with this build without the great community here .


----------



## holland

after 1.5 years, i'm going to start my build.   i dusted off my kit from GJA, checked my kit contents, and some bits are missing or incorrect (resistors are missing and/or wrong values, and heatsink is 1/4 the size of what's spec'd).  For whatever reason, the board is also not drilled correctly for the heatsinks.  The pins are spaced a bit wider than the pin holes.  Oh well, it must be an early board or something.  The heatsink has a 1 inch spacing on the pins, but the board is a tad smaller. 
   
  Sachu, did you have that problem when you built your first ones?  Unfortunately, I measured the pin spacing with my caliper after placing the order for the missing pieces.  Bummer.  I might have to resort to off-board heatsinks, which means I probably can't fit my build in one case.  Another bummer.


----------



## ujamerstand

Which BOM are you comparing to? The EHHA rev.A or the original EHHA? It seem that you have the original version, and you should follow the original BOM as well. The heatsink pads are made for a different heatsink in the original boards, that's why the heatsink would not fit. But yeah, the supplied heatsink is a little small. If you want to build the rev.A version you can get boards from jeff, and if you want, I've got a BOM at mouser that takes the difference between the two versions.


----------



## Lifthanger

the same thing happened to me this summer. My kit was also the same age as hollands. I didn't check the heatsinks yet, but there's some wrong and missing resistors.


----------



## BebopMcJiggy

The heatsink holes have always been a bit weird with the original ehha board I think, I think it had something to do with the pcb manufacturer or something and you are supposed to remove the pins and just not use them or something (from the heatsink).  Mine definitely have no pins at all on them.  But really, your heatsinks are 5/8" tall?  Maybe it would be different being used for speaker duty or something but my heat sinks really never even get very warm.


----------



## holland

Quote: 





ujamerstand said:


> Which BOM are you comparing to? The EHHA rev.A or the original EHHA? It seem that you have the original version, and you should follow the original BOM as well. The heatsink pads are made for a different heatsink in the original boards, that's why the heatsink would not fit. But yeah, the supplied heatsink is a little small. If you want to build the rev.A version you can get boards from jeff, and if you want, I've got a BOM at mouser that takes the difference between the two versions.


 

 I have the original EHHA.  I bought the kit around the same time as Smeggy started this thread.   I'm using the parts list from Cavalli Audio's website.  The heatsink is 1.36" wide x 0.49" thick x 1.5" high.  I don't really want to go to the rev A as I'd prefer the S22 regulation and I already built a homegrown heater supply based around the LT1085 about 1.5 years ago too.
   

  
  Quote: 





lifthanger said:


> the same thing happened to me this summer. My kit was also the same age as hollands. I didn't check the heatsinks yet, but there's some wrong and missing resistors.


 

 check your heatsinks too.  they might undersized.  I was missing 10K resistors, the 47.5 ohm resistors were 47.5K.  No matter, I needed different resistors for gain anyway, and I needed compensation caps for the gain I intend to use.  I wish there were values for stuff other than 1 and 4.3 though, but I'm building a 3 channel, so 4.3 on the L and R and 1 on the G.  I try to avoid gain on G to avoid floating the G too much.
   
   
  Quote: 





bebopmcjiggy said:


> The heatsink holes have always been a bit weird with the original ehha board I think, I think it had something to do with the pcb manufacturer or something and you are supposed to remove the pins and just not use them or something (from the heatsink).  Mine definitely have no pins at all on them.  But really, your heatsinks are 5/8" tall?  Maybe it would be different being used for speaker duty or something but my heat sinks really never even get very warm.


 

 1.36" wide x 0.49" thick x 1.5" high.  I do have some of the right heatsinks on hand from other projects (only have 2), but they are quite petite in comparison to what is spec'd.  I think I use heatsinks this size for some small regulators.  No worries totally, as I'll just use them for something else.  Really, remove the pins?  I guess, I've never been good at that.
   
  I intend to bias at 160mA instead of 100mA.  From what I understand even at 100mA your heatsinks should get quite toasty, somewhere between 50C and 70C.


----------



## BebopMcJiggy

Quote: 





runeight said:


> Yes, it would be possible to replace those fixed resistors with pots.
> 
> R22, R23 will be very tricky as mismatched pot settings will imbalance the complementary halves of the O/P stage.
> 
> ...


 

 Was searching for this to make sure I was not giving you bad advice.  I don't think my heatsinks are any higher than 2" at the most and they barely get warm.


----------



## holland

Thanks Bebop.  My heatsinks are also 1/2 as thick at 1/2" instead of 1".   No worries though, I have the correct ones on the way from Digikey and Mouser.  I may still go offboard, not sure though, as I'll be going 160mA for bias, more if the heat is in check.  I need to do some calculations first.  Thanks again, very helpful post dig....this thread is a bit large to read through entirely.


----------



## Lifthanger

ok I checked it and the sinks are too small too. I'll solve this when I find some time next year. good luck with your build .


----------



## gurubhai

I am having some trouble with one channel of my BJT EHHA.
   
  The output resistors gave smoke so I replaced them. I checked the voltage against new output resistors at startup &  it was 7 volts.I also replaced the BJTs but still the same issue.
  Can anyone help ?


----------



## johnwmclean

Is R21 completely counterclockwise? IC1 and IC2 are definitely not mixed up? All other initial checks are correct before you get to the output quiescent current?


----------



## holland

did you plug the bjt into the mosfet spots?


----------



## gurubhai

@ Holland : No.
   
  @ John : R21 is completely counterclockwise, IC1 & 2 are correct. I can't do the initial checks since the output resistors start lighting up.
  The other board which is identical measures perfectly.
   
  I am thinking of a faulty component upstream.
  Could be the ICs or the diodes.
  The toshiba transistors I had matched before using so they should be fine.
   
  It seems that smeggy had a similar issue when he had his diodes inverted. Sachu seems to have fixed his amp but didn't outline the steps  involved.
  Paging sachu..


----------



## sachu

If the VBe is fine, then the problem most probably lies with the output transistors.
   
  Also check Q7 (if this is on the old version board), making sure that the VBe transistor is good.
   
  Use the diode check feature ont he multimeter for this.


----------



## gurubhai

Q7 was faulty indeed. I replaced it & all is fine again.
  Thanks for the help sachu & everybody.


----------



## sachu

excellent...enjoy!! 
   
  edit: and what was the reason Q7 failed btw??


----------



## BebopMcJiggy

Redoing my case work... Ahhh man I should have just sourced the parts myself for the 2nd 2 channels (my dac is balanced so I figured what the hell... was moving the psus to a separate case anyhow) instead of GJA ;O  Not that I have a problem with GJA, dude is awesome... I am just overly impatient and I won a bunch of telefunken tubes off ebay recently.  I suppose a full set of 4 amperex tubes couldn't hurt.  My case work is much prettier this time around, but I think it's just gonna be kind of out of commission for weeks while I wait for the other 2 channels.  Actually not quite out of commission as I could still build it as a 2 channel with just the other 2 channels mia for now.  Kind of waiting on a single drill bit to finish my case work anyhow, but that should come this week.  Sadly, I've already drilled out the case for the EHHA because I have another amp I am building laid out for the same style case (using the same psu, won't be able to use both at the same time but oh well) that I will almost certainly be able to finish before I get my other stereo ehha kit.
   
  So I am kind of torn between just using ac power for the filament heater still or making it dc...  With the trafo in another case is it really necessary?  I had a slight hum before but I think it was from the trafo being so damned close to the right channel input.  I could I suppose figure out how to fit possibly up to a sigma11 in there but is that gonna run real hot at a constant 1.32a?  Something else I should use?  Kind of leaning towards being lazy with just ac heater lines  for heat as much as any other reason... or at least it certainly seemed like my attempted cheap dc regs so far were not really gonna be good for heating 4 tubes at once without some ridiculous heat sinking and I don't really have room to put 4 of them in there with the current psu case :O.  Any suggestions here would be appreciated.  I can use the case itself as a heatsink possibly if necessary but again the regulator itself can't be too huge.  (To use the case as a heatsink I would probably need something with the transistors near the edge of the pcb, s11 would be really tricky to heatsink that way.)  Would shielding over the input or heater ac lines be helpful here at all or completely unnecessary?


----------



## gurubhai

I would say go with te DC filament supply. Its worth it for this amp.
  I had slight hum with my EHHA, so I made a simple LM317 based DC supply(similar to one in EHHA rev. A ) & the hum is completely gone.
   
  @Sachi :No clue. The mosfets were socketed earlier & I have my suspicion on a faulty socket but I am not sure how that would lead to Q7 getting damaged.
  Today has been a good day. The EHHA 1 is back online & I also was able to finally finish my rev. A build. The first impressions are really positive.


----------



## BebopMcJiggy

Quote: 





gurubhai said:


> I would say go with te DC filament supply. Its worth it for this amp.
> I had slight hum with my EHHA, so I made a simple LM317 based DC supply(similar to one in EHHA rev. A ) & the hum is completely gone.
> 
> @Sachi :No clue. The mosfets were socketed earlier & I have my suspicion on a faulty socket but I am not sure how that would lead to Q7 getting damaged.
> Today has been a good day. The EHHA 1 is back online & I also was able to finally finish my rev. A build. The first impressions are really positive.


 

 I made a LM317 based DC supply myself... it got ridiculously hot powering just 2 boards.  Maybe I can try it again with different transformers... I tried with a 7v and a 18v (only used half?) and it was getting way too hot powering 2 6gm8 filaments.  Maybe this is something that would actually improve by increasing the load from 2 to 4 filaments... then again the weaker trafo was incapable of reaching 6.3v under load and it (the lm317) was still overheating.  Maybe a 12.6v with lower current?  The 18v trafo was supposed to be a 12v trafo but apparently the website I got it off of is dumb?  In any event I don't have room for ridiculous heatsinks in the PSU case really, I could mount it to the side (rear?) of the case possibly but I dunno... I guess I'll experiment with other transformers maybe...


----------



## sachu

Very nice stuff Ravi.
   
  And yes, DC heaters an absolute must for this amp.
   
  Weird about Q7..
	

	
	
		
		

		
		
	


	




..well atleast you got it working agian.


----------



## holland

AC heaters are more susceptible to noise, but you may be able to pull it off with careful wiring choices.  I'm not quite sure how, but it'll be tricky due to the positioning of the inputs.  I haven't checked the PCB traces.
   
  FWIW, I tend to favor regulation being next to the circuit, so DC travels less distances and the noise filtering occurs with short travel.  I tend to favor AC for running wire around outside the box.  If DC were generated in a separate box, I would presume a need for a filter on the power rails next to the amp boards, IMHO.


----------



## BebopMcJiggy

I mean I guess I will figure out a way to work the filament dc reg into the amp case and leave the trafo with the psu case (actually simpler than trying to stuff more potentially hot things into the psu case) if this thing still is way too hot when I try other transformers I am just going to stick to ac probably .


----------



## BebopMcJiggy

So should I get a 9v 2.75a toroidal for my dc reg trafo or should 9v 1.66a be sufficient?  (4 6gm8s should be 1.32a @ 6.3v?)  I guess I could order both heh.  Does a 15va 9v toroidal sound good enough? or should I go for the 25va?  I'm leaning towards the 15 ;O.   Sorry to be a bother.


----------



## holland

There is current loss for rectification.  For a full-wave bridge rectifier you need to allow for 1.7-1.8x the DC current you need on the AC side.  2.3A should suffice.  For 9v, 15VA is not enough.  You need about 21VA for 9V, so a common transformer power rating would land you around 25VA.


----------



## BebopMcJiggy

Okay, thanks.  I got both anyhow will use the smaller one till I receive the other 2 ehha boards anyhow :O


----------



## BebopMcJiggy

Soooooo.... anyhow my ehha is in pieces.  But my 4 channel space heater is up and running, waiting on the other 2 channels for the ehha, no idea when those will come.  I am considering adapting the ehha for speaker use, but I probably won't as I would have to get creative with my heatsinking.  I got my little 9v toroidals in but my little lm317 regulator may be ill equipped for the job.  I'll give it a shot though when my new case comes in early next week.  I suppose I could try it as is now since the tube filament current should be constant anyhow (just doubled soon).  I have it screwed to the back panel of the current box that now houses a b22 but it's like a giant aluminum heatsink anyhow...  Will see how hot it gets .  I have parts coming in for an lt1084 regulator that will be slightly bigger than my lm317 regulator but better equipped to handle a constant 1.32a I think...  Hopefully I can find a good way to mount it inside the amp case.  Shouldn't be too hard... the b22s are really squished into the case and that seems to run far hotter than my ehha ever did.  I am seriously considering practically cutting out almost all of the top panel and attaching a metal screen of some sort there...
   
  That said I haven't really done any work on the psu case besides filing out the hole for the iec plug a bit.  I could get a bigger case to accommodate off board heat sinks and use the case I was gonna use for the ehha to house multiple S22s and go ahead with the speaker amp :O.  Ahhh decisions


----------



## Horio

Question regarding a input selector switch.
   
  I'm planning to use a goldpoint selector switch for my balanced EHHA.  I'm going to have (3) pairs of XLR inputs to choose from.  Do I need to be switching the ground (pin-1), or can I simply tie the grounds for each channel together and wire as shown here?  Not sure if this will create any ground loop issues.  I'm hoping to get by with a single (4) Pole - (3) throw selector.  If I have to run the input grounds through the selector switch, then I am stuck spending more money a multi-deck selector.


----------



## holland

Separate, switch the ground, don't tie together, IMO.


----------



## Horio

Yea, the more I think about it, it makes more sense to switch the input grounds.
  
  Quote: 





holland said:


> Separate, switch the ground, don't tie together, IMO.


----------



## holland

Another one lives.  I need to vacuum the interior and put the cover on, but here's an inside shot right now, as I am tweaking the bias.  I was going to do a 3-channel, but when I started calculating the interior space, that plan fell apart.  2-channel it is.


----------



## sachu

Sweet!!..nice one Holland..what's the input selector and attenuator board you are using there?
   
  What tubes are you using and is it aBJT or MOSFET?
   
   
   
  ANd of course..first impressions ??!!


----------



## holland

Quote: 





sachu said:


> Sweet!!..nice one Holland..what's the input selector and attenuator board you are using there?
> 
> What tubes are you using and is it aBJT or MOSFET?
> 
> ...


 
   
  Thank Sachu.  It's from diyclub.biz, the dual mono selector and relay attenuator.  99 steps.  I got their case as well, it has a nifty remote, so I can sit back and control the volume.  I'm running a gain of ~4.3x.
   
  MOSFET of course, you BJT junkie   I am using the default 6GM8 from GJA, MOSFETs at 160mA, but might dial it back a bit.  Preliminary temps have the FET case temperature of ~60C.  I have some 6N27P coming from Russia, but it's been a month so I'm wondering if it got lost.
   
  First impressions.  Using my Buffalo DAC (ES9008), it's very nice.  Impactful, good separation, good soundstage, and good tone.  It's definitely up there with a B22.  The upper frequencies seem spot on, not harsh.  It's going well with my HD650 so far.  I've only heard a few tracks, but will need a much longer listen for other sonic traits.


----------



## jdkJake

Very Nice build Holland! I really like the concept of the 99 step attenuator. What kind of a pot do you use to control it?

Where is your diode bridge-based ground loop isolator? I am interested in seeing that implementation.


----------



## holland

Thanks jdkJake.  It's pushbuttons with a remote control.
   
  http://www.head-fi.org/forum/thread/85561/post-pics-of-your-builds/7770#post_7281909
   
  You can see part of the ground loop breaker here.  The 10W wirewound power resistor is hidden under the ribbon cable.  In the first picture, next to the perfboard, you can see the diode bridge.  In the second picture in the link, you can see the cap, but the diode bridge disappears in the background color.  The power resistor is under the ribbon cable.
   
  I used a terminal strip, then connected the diode bridge to the lug that connects to the chassis and another pin.  The AC side goes to chassis earth.  The DC side, goes to DC ground.  I use a ground bus from that, the long 10 gauge bare copper wire.  The cap goes between those 2 points, the start of the ground bus and the earth connection, as does the power resistor.  This setup has never failed me.  Points of contact for chassis earth has been sanded with a dremel to get to the bare metal, then I put dielectric grease on top to avoid corrosion.  The earth connection to the chassis is on the 6.3V transformer, oversized so I get ~7.3V AC under full load.
   
  The heater board is a homebrew, basically a standard LT1085 reference implementation, but I used a low voltage drop diode bridge for space.  It's fine for heaters, but would use different rectifiers if not for heaters.
   
  Edit: Damn this thing is big.  It dwarfs my other builds, particularly being a single chassis build and full rack component size.  I'm pulling out my other Cavalli amps to compare, but I don't recall the SOHA II sounding as clean.


----------



## johnwmclean

[size=medium][size=13.0px]Holland congrats mate that’s an awesome build, I’m looking forward to further impressions against your [/size][size=13.0px]SOHA II.[/size][/size]


----------



## holland

Thanks John, will do.  I haven't listened to the SOHA II in a while.  I meant to, but I'm going to give it a few weeks for the EHHA I to settle and more time for my ears and mind to adjust.


----------



## Horio

So I started my initial checks on my balanced EHHA.  I have a 33.2kOhm resistors installed at R22 & R23 (negative feedback) and 2kOhm resistors at R13 for a gain of 6x (12x balanced).  My o22 is putting out about 29V +/-.  Trim-pot R21 is turned fully counter-clockwise, and R6 is at the mid-point (counted turns).  With the 6GM8's in I am getting the following readings on my first two boards:
   
  Resistor:  Board 1/Board 2 (Target Voltage)
   
  R4:  1.29V/1.31V (1.5V)
   
  R10 & R14: 1.31V/1.29V and 1.26V/1.28V (1.5V)
   
  R15 & R17:  0.50V/0.55V and 0.57V/0.60V (0.85V)
   
  R16 & R18:  0.65V/0.65V and 0.59V/0.59V (0.6V)
   
  R26 & R29:  0.58V/0.58V and 0.58V/0.58V (0.6V)
   
   
  So the voltages seem a little low across  R3/R4 and R10/R14.  They are even more off (low) for R15 and R16.  The others seem to be reasonably close.  You guys have any thoughts?


----------



## gurubhai

Adjusting the R6 trimpot should balance the voltage across R3/R4.


----------



## Horio

So I tried rolling in some other different tubes (Amperex 6GM8) I had, and the voltage came up but only a little bit.  R3 is exceptionally low, so I am wondering if the problem is related to this value:
   
  Resistor:  Board 1/Board 2 (Target Voltage)
   
  R3:  1.16V/1.19V  (1.5V)
   
  R10 & R14: 1.36V/1.36V and 1.30V/1.30V  (1.5V)
   
  R15 & R17:  0.57V/0.60V and 0.61V/0.63V  (0.85V)
   
  R16, R18, R26, R29:  All between 0.58V and 0.65V


----------



## Horio

I double checked all the parts and made sure they were in the right spots.  So the only thing I didn't do was install C2 and C3 yet.  Could this have something to do with the low voltage readings (especially at R3)?  I'm a little stumped at the moment.


----------



## holland

Mine aren't exact neither.  There are tolerances in everything.  It could be part variations.  It could also be your DMM, since most everything reads low except for the 0.6V test.


----------



## johnwmclean

[size=12.0px]Horio, one thing to check would be the resistor values over R5 and R7 if your parts came from GJA kit. My supplied kit as well as some others here came with [/size][size=medium][size=13.0px]47.5k when the schematic/parts on Alex’s is listing it as 47ohm.[/size][/size]
   
  ...just in case.


----------



## Horio

Thanks for the suggestion guys.  I checked the resistors at R5 and R7, and I have 47.5ohm resistors in those spots.  I've been using my new Fluke 287 DVM, but I'll try my old Fluke 117 to see if it gives similar numbers.
   
  I did try turning up the quiescent current to 0.22V across R32 and R33.  One thing I noticed was the left sink (Q8M) definitely gets pretty warm, while the right sink (Q9M0) stays cooler in comparison.  Even after only a couple of minutes the Q8M heatsink gets pretty hot.  I can hold my hand on there for about 5-10 seconds, before it gets uncomfortable.  Have you guys noticed this same behavior.
   
  So what would be the effect on the amp if I ran it at these lower values (across R4, R10, etc)?  Will it have a significant effect on performance or reliability?
   
  Thanks for the help guys, I'll keep trying things and studying the schematic.


----------



## holland

I did not match my transistors, so I get the same effect...it's why I bought a kit, so I could be lazy.  If I did it again, I would buy a bunch of parts and match it myself.  One thing I did wish I would do was to center R6 via a DMM instead of by the number of turns.
   
  The bias is different between top and bottom on the PP section, so yes I have the same issue but not to the degree you state.  It's not horribly off, just a bit.  I believe my readings on the initial setup was closer to your first post than the 2nd.  I don't have other tubes to try though.


----------



## holland

I'm just curious to know what everyone's power consumption is.  I'm pulling about 630mA from the wall, according to my DMM, which is a bit higher than I expected.  I expected around 40W instead of 75W.


----------



## Horio

I found my problem.  It was a wiring issue.  Thanks holland for the help!


----------



## johnwmclean

Oh dear!
  I had a mishap with my EHHA, it still works and sounds good... but stupidly forgot to turn the heater supply on the last night. I had the amp on for an hour to warm up and noticed my mistake! 
  There’s something to be said for automatic delays... anyways with the filaments dead cold for an hour or so with the amp on what the chances I’ve ruined my set of quad tele’s?


----------



## jdkJake

I doubt it hurt it at all. Might have sounded like hell at the time as the tubes certainly were not conducting at anywhere near optimum levels if at all, but, I suspect there is no real damage done.

At least based upon my understanding how a tube works. I could most certainly be wrong.


----------



## sachu

no worries John. She'll be fine.
   
  And as for automatic heater delays, i've put one in every EHHA I have built so far. Easily worth the 20$ for the peace of mind and ease of use.


----------



## qusp

Horio, i dont really get the conundrum of switching pin 1 on your XLR inputs i personally wouldnt bother, these are shields, they should be all directly connected to the chassis at a single point, what purpose would switching them serve? or are you running a redundant signal ground on pin 1? if so i recommend deleting it, it serves no purpose other than providing a path for possible ground loops. or are you running some sort of dual single ended input (mutton dressed as lamb ) rather than your balanced dac? imo best thing to do is draw out your signal inputs and see if any return currents are actually flowing on pin 1, if not, delete them.


----------



## johnwmclean

Thanks jdkJake and sachu and yes the next amp will definitely support sport the delay


----------



## qusp

haha John gets to see my pin 1 rant again


----------



## wink

Quote: 





> haha John gets to see my pin 1 rant again


 
  Sometimes rants are so necessary to get the point across..........


----------



## johnwmclean




----------



## capernicus

So I am getting ready to start another amp build project and looking for some input.  
   
  Bijou, EHHA, or EHHA rev A? (I realize I might be asking this in a slightly biased thread) 
   
  My first build was the SOHA II (Below) I simply love it - its used several hours a day at work each week.  
   

   
  I'm still working my way through the EHHA and EHHA rev A threads (there is a TON of info here!) but thought some of you more experienced builders (and listeners) might be able to offer some insightful knowledge.
   
  EHHA vs EHHA Rev A: the costs are about the same except for the additional enclosure - housing the PS separately is attractive from a noise standpoint but has that been an issue at all in the rev As?
   
  Bijou is only slightly cheaper for the glass jar kit but I am not a big fan of the electrolytic in the output although from what I have read everyone who builds one seems to love it...
   
  Can anyone offer any suggestions or insight?
   
  Thanks!


----------



## wdahm519

Quote: 





capernicus said:


> Bijou is only slightly cheaper for the glass jar kit but I am not a big fan of the electrolytic in the output although from what I have read everyone who builds one seems to love it...
> 
> Can anyone offer any suggestions or insight?
> 
> Thanks!


 

 Well, I'm listening to my Bijou right now and I'm extremely happy with mine.  I can't really see myself putting the time in to build another desktop tube amp for a while (had this one since April now).  My next desktop build will be a Beta22.  I'm going to spend my Autumn season building some portable stuff first.
   
  I think you'll be happy either way, and keep in mind that I haven't had a lot of experience listening to many different desktop tube amps, so my opinion might be tainted.  Nevertheless, I know when my ears are happy.


----------



## funch

I've built all three, and will say the the Bijou really does its best work when paired with high-impedence 'phones, like my HD600's.
   
  I would recommend the Rev. A over the original EHHA because of the all inclusive design of the board, and that it can be configured
  to work with either high or low-impedence 'phones. On my Rev. A build I socketed the output devices so that it could be easily set
  up with either BJT's or MOSFET's.
   
  To sum up, the one that I kept is the Bijou, although it's anything but stock.


----------



## capernicus

Thanks for the input... I was all set to place the EHHA Rev A order with numerous comments in this thread suggesting its up there with the B22 but your Bijou praise has me making second thoughts.  Currently I only have a pair of lower end Grados and have been giving some thoughts to maybe buying a pair of some AKG 701s - so I'm definitely on the low Z side of things and have heard the Bijou Grado combo leaves a bit to be desired.   (Although I have been considering some HD600s...)
   
  How is the build complexity between the Bijou and the EHHA?  The Bijou circuit seems to be a little more straight forward circuit...
   
  Looks like the solution is to build both... unfortunately I only budget for one.
   
  Bijou with some HD 600s? or
   
  EHHA as with my current Grados and possibly a future procurement of AKG 701s or something else...
   
  Any insight?


----------



## sachu

I prefer the EHHA hands down. Not a big fan of the Bijou. It is a nice amp, don't get me wrong on that front, but I never felt like I wanted to build one. ANd I have built a ton of Cavalli DIy amps in the last 3 years.


----------



## capernicus

Thanks Sachu, I've been reading a bunch of your posts in the EHHA forums...  Great to know there is a lot of experience bringing these amps to life - I hope my build goes smoothly.
   
  From what I have read most seem to really like the EHHA and I've seen a few raving reviews that really caught my attention comparing it to a b22.  Looks like I'll be placing an order this weekend!  Need to start thinking about what I want the case to looks like...


----------



## funch

Good choice. You might consider socketing the ouput devices so you can try both MOSFET's and BJT's.
   
  BTW, when I sold my first EHHA (original), Sachu thought I was nuts for prefering the Bijou.


----------



## Cloud

Finished up my EHHA Rev A along with some modifications which yields great results. 
   
  1) If you prefer punchier, deeper bass and a more full bodied sound, consider swapping the 2200uF caps in the power supply to 4700uF. I uses a pair of Rifa 4700uF 63V on each power supply to excellent results. Terrific sound on my LCD-2
   
  2)I use AMRG(Amtrans) 300ohms resistor for R2(plate loading resistor) as advised by a DIY shop dealing with tubes. More transparent, wider soundstage and silkier highs! 
   
  These are the 2 mods i tired and really like the effect, especially the caps mod. Try it folks!
   
  I will post up some pictures this weekend.


----------



## Audiodoc

Had a complete rework, resoldering of my year old EHHA which I had assembled last September with gurubhai. Here are a few pics of the metamorphosis. Need better heatsinks for powering speakers at a later date.


----------



## Audiodoc

Had a complete rework, resoldering of my year old EHHA which I had assembled last September with gurubhai. Here are a few pics of the metamorphosis. Need better heatsinks for powering speakers at a later date.


----------



## fishski13

Quote: 





audiodoc said:


> Had a complete rework, resoldering of my year old EHHA which I had assembled last September with gurubhai. Here are a few pics of the metamorphosis. Need better heatsinks for powering speakers at a later date.


 

 looks awesome.  no offense, i don't know what you have the EHHA biased at, but the heat sinks on the o22 are skimpy.  the MOSFETs are tough and all, but....


----------



## Audiodoc

No offence taken 
	

	
	
		
		

		
		
	


	




.
   
  I myself am worried about the adequacy of the heat sinks. Good efficient ones are hard to come by in smaller cities in India. Am searching for them online. Although I have used the amp in an airconditioned room for hours will possibly get better heat sinks in the near future.


----------



## gurubhai

^ Its nice to hear from you after such a long time. Can't believe its been a year since we built this amp working through the whole night.
	

	
	
		
		

		
		
	


	



   
  I won't worry about the sigma22 heatsinks. I have measured their temperature & they hardly ever cross 40 degrees. But the heatsinks on output BJTs must be replaced.
  I have managed to source some better ones, will pm you the details.


----------



## sachu

should have told me guru, would have thrown a bunch of the aavid together when i sent the TP over.


----------



## gurubhai

^ I surely would have troubled you buddy, if there was any issue.
  But I found a source for aavid sinks a while back.
  Imagine my surprise though when the delivery guy told that he was delivering these directly from Aavid factory here in New Delhi. :facepalm:


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## Audiodoc

My EHHA is doing fine but I have few questions:
   
  1. One of the heat sinks in the sigma 22 is heating more than the other 3. The one on the right side along the output side length Q15 on silkscreen. Why should it be so. Amps works and sounds flawless.
   
  2. Have ordered larger heat sinks for my EHHA boards but their is not enough space to mount them. This is a BJT version. Is it possible to somehow adjust them in the mosfet holes. I know anything wrong and it will fry my transistors. Something I won't try. Rather put the 2 inch thinner heat sinks coz heating is less likely to fry them.


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## Audiodoc

Need to add one more thing that I observed the transistor besides Q15 i.e. Q16 is cool. On the opposite side both the transistors are almost equally hot.


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## gurubhai

^ Isn't Q15 the one which lies in corner in your new case, seems poorly ventilated to me.


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## Audiodoc

Not a ventilation problem I think. Checked the AMB forum, possibly its brother in parallel (Q16) is bad as its heatsink is damn cool while Q15 is carrying its load and overheating. Will replace it as suggested in the AMB forum if I find one in the market otherwise will need your help to source it!
   
  It explains why the power rails are delivering enough power and the amplifier is running fine. Rest of the MOSFETs on the S22 as well as the BJTs on the amp boards are equally hot (can touch them and count to 10).


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## rhythmdevils

I auditioned an EHHA RevA made by local Head-fier BK8569er and loved how it sounded.  I would describe it as sounding fast, clean, linear, airy.  In comparing it to my SOHA1, I kept coming back to comparing the EHHA to the stax headphone sound while the SOHA had the more dynamic sound.  Similar to Stax, my only complaint with this amp was it seemed to lack dynamic punch or a sense of weight on certain phones.  But that's a minor quibble and not necessarily a bad thing.  Other than dynamics I thought it clearly bettered the SOHA1 in every way and made the SOHA sound colored. 
   
  So I bought one on the forums made by a HF'er from a glassjar kit.  I'm not here to name names, I know he's a good builder and the amp seems to be well done.  But it doesn't sound nearly as good as the other EHHA I heard (and borrowed for a week).  In fact, as far as I can tell my SOHA1 beats this EHHAreva in every way including speed and detail, things the other EHHA was clearly superior in before.  BK8569er has been kind enough to check out the amp for me and do some tests for obvious problems and hasn't found anything glaring, and he confirmed it looked like a good build at least on the surface.  He also lent me some tubes which didn't change much.  I also tried switching from BJT's to Mosfets. 
   
  Maybe I just shouldn't be buying DIY amps if I know nothing about DIYing.  But I like owning things that have so little marketing buzz behind them and instead have lots of love!
   
  So I'm wondering if anyone here would be willing to have a look at it.  If you own an EHHA it might be better so you can compare but not necessary.  I'm not listening to it at all and not sure what else to do.


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## fishski13

Quote: 





rhythmdevils said:


> I auditioned an EHHA RevA made by local Head-fier BK8569er and loved how it sounded.  I would describe it as sounding fast, clean, linear, airy.  In comparing it to my SOHA1, I kept coming back to comparing the EHHA to the stax headphone sound while the SOHA had the more dynamic sound.  Similar to Stax, my only complaint with this amp was it seemed to lack dynamic punch or a sense of weight on certain phones.  But that's a minor quibble and not necessarily a bad thing.  Other than dynamics I thought it clearly bettered the SOHA1 in every way and made the SOHA sound colored.
> 
> So I bought one on the forums made by a HF'er from a glassjar kit.  I'm not here to name names, I know he's a good builder and the amp seems to be well done.  But it doesn't sound nearly as good as the other EHHA I heard (and borrowed for a week).  In fact, as far as I can tell my SOHA1 beats this EHHAreva in every way including speed and detail, things the other EHHA was clearly superior in before.  BK8569er has been kind enough to check out the amp for me and do some tests for obvious problems and hasn't found anything glaring, and he confirmed it looked like a good build at least on the surface.  He also lent me some tubes which didn't change much.  I also tried switching from BJT's to Mosfets.
> 
> ...


 

 i would look for measured differences in the the bias points, including the tube, VAS, and quiescent current on the output devices.  do both amps sport the same pot and output devices?  how did you roll the output devices - are they socketed and was the bias reset?  pics could be helpful.


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## fishski13

forgot to mention, the amount of NFB can influence the sound as well.  what are the open and closed loop gains for each amp?


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## BK_856er

I'll add a bit of color since I apparrently own the "magic" RevA and also messed with rythmdevils unit at his place quite a bit.
   
  With his original BJT setup I verified correct R17/22/23 and quiescent current.  Heatsink temps were normal.  I swapped in my GE/Amperex and later my Telefunken tubes for long term testing.
   
  The output devices were socketed for easy changes, so we swapped in MOSFETS, changed to the appropriate R17/22/23, and adjusted the quiescent current per the setup instructions.  Everything measured and behaved normally.
   
  R13/14 is 75k, but R11 is 1.5k as opposed to the BOM value of 1.2k.  jdkjake informs me that this will have the consequece of reducing the gain from ~9 to ~7.5 and increase NFB ~1.7dB.
   
  The build itself is very well done with lots of attention to detail and solid workmanship.  The grounding scheme is executed differently than mine, and this build employs an Alps pot and dual Avel-Lindberg transformers.  FWIW, my own build closely follows the MOSFET BOM with individually sourced components and uses a TKD pot and a shielded SumR transformer.
   
  I didn't do any critical listening, but to my ears, with his gear, rythmdevils unit functioned correctly and without major fault.  It made music.  Rythmdevils probably has some very senstive ears, but he reports that none of the changes we made (rolling tubes, BJT --> MOSFET, etc.) had any appreciable influence on the SQ.  I find that a little surprising - as if something is being masked.  As I recall the only source was a gamma-2 via optical.  I think at this point he wants to turn it over to an expert to work some magic on it - any takers?
   
  BK


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## fishski13

Quote: 





bk_856er said:


> I'll add a bit of color since I apparrently own the "magic" RevA and also messed with rythmdevils unit at his place quite a bit.
> 
> With his original BJT setup I verified correct R17/22/23 and quiescent current.  Heatsink temps were normal.  I swapped in my GE/Amperex and later my Telefunken tubes for long term testing.
> 
> ...


 

 all things being equal, as long as _all_ bias points are reasonably matched, including 1.5mA through each triode, both amps should sound identical.  the fact that RD's amp is from a GJ kit and your's hand selected shouldn't matter.  while more expensive, as long as there's no noise, i don't believe the SumR will improve the sonics.  
   
  i've done comparisons between the TKD and Alps - as in 2 identical amps side by side with the only difference in one sports an Alps and the other the TKD.  i've done this A/B comparison with 2 different amp designs as well.  they _do_ sound subtly different from one another and can influence the final sound.  each have trade offs and i don't have a preference for either.


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## jdkJake

So, this being DIY, no two realizations will be *exactly* the same. Potentially different parts from potentially different manufacturers from potentially different batches with potentially different tolerances, well, you get the idea.
   
  That said, I would drop the MOSFETs back in and bring R11 down to 1.2k  --OR-- bring R13/14 down closer to 56k. The R11 mod is easier.
   
  During my experiments, the NFB setting was very important to the overall sound presentation. Changes of 2db were fairly pronounced while 1db changes were noticeable upon critical listening. Perhaps you are more sensitive to these nuances than others.
   
  If that does not yield the desired results, then you may need to compare each and every part used between the two builds to see what might be the issue. Perhaps an off spec'ed part or two got inserted. Perhaps a part or two got swapped. Impossible to say without a deep, carefully comparison between the two instances. Tedious no doubt, but, certainly an exercise in intellectual curiosity that might yield the sound that you seek. Or not. Hard to say.
   
  As for pots, I used both alps and TKD. The TKD seemed to be the better choice, but, I may have been biased by the seductive smoothness of it's operation. The TKD is one smooooth pot! Much love here for the TKD.


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## rhythmdevils

Thanks for the responses!  And a big shout out to BK for meeting up at least a few times and looking at the amp (and hanging out of course   I'm constantly surprised and amazed by Head-fiers. 
   
  To clarify, the amp doesn't sound _bad_ necessarily.  It just doesn't sound very good.  It is pretty flat and lacks depth, air, detail, speed, etc.  It honestly sounds like a portable amp and I can't imagine anyone preferring it over the SOHA1 I have here.  So I can't see it being a simple matter of preference.  But who knows.  I should compare it to my portable PPAS and see which one wins.  I honestly think the PPAS might sound better just in the way of dynamics, sound stage, imaging, etc.
   
  I don't have the ability to look over the amp like that due to some fairly serious health issues I'm facing right now and lack of knowledge about it.  So the 2 options I see is to sell it to someone for whatever it's worth or try to have it fixed.  I'm open to offers for either one.  I'm sure with the right tweak this would suddenly be an awesome EHHA.  It's got the Mosfet and BJT's socketed, and I have mosfets in there now. 
   
  Anyone want to fix or buy?  I hate to see it just sitting here.  It's also kind of a big investment not to be using it.  Kind of sad, would be great with my orthos.


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## Pars

Quote: 





bk_856er said:


> The build itself is very well done with lots of attention to detail and solid workmanship.  *The grounding scheme *is executed differently than mine, and this build employs an Alps pot and dual Avel-Lindberg transformers.  FWIW, my own build closely follows the MOSFET BOM with individually sourced components and uses a TKD pot and a shielded SumR transformer.


 
   
  I don't know the EHHA amp very well at all, but you might look at this...


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## FOXY

What are the differences between the EHHA and BETA22 in terms of sound?


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## johnwmclean

Quote:


foxy said:


> What are the differences between the EHHA and BETA22 in terms of sound?


 

 Depends...
  I prefer the HD800 with the EHHA and Beta22 with the LCD-2.
  Overall I prefer the LCD-2 with the Beta-22 by a very wide margin. Possibly my very early serial numbered HD800’s were just too bright for me and the EHHA tamed them.


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## runeight

Quote: 





bk_856er said:


> I'll add a bit of color since I apparrently own the "magic" RevA and also messed with rythmdevils unit at his place quite a bit.
> 
> With his original BJT setup I verified correct R17/22/23 and quiescent current.  Heatsink temps were normal.  I swapped in my GE/Amperex and later my Telefunken tubes for long term testing.
> 
> ...


 


 Gents, I don't know if I can be helpful, but ...
   
  Despite the variations in components, the various versions of this amp should sound reasonably similar. I don't think it's likely that one amp can sound really great and another flat and lifeless, particularly if the same tubes are moved from one to the other. Even if we take into account the effects of the NFB (within reason), they should not sound like two completely different beasts.
   
  I don't know how to pinpoint a potential problem without asking for many measurements, but is there a way to get some measurements on the current configuration?


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## funch

Does anyone here know of a replacement for the 2SC2705?


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## Jose C

...


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## Jose C

...


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## cfcubed

The first obvious thing to do is the Setup measurements and report any measurement deviations (from expected and perhaps between channels):
http://cavalliaudio.com/diy/ehha/main.php?page=setup


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## Jose C

...


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## cfcubed

Was hoping someone more familiar w/the circuit might chime in...  
  In the absence of real insight into this, from looking at the schematic & searching this thread for "cold" and "R21" would suspect one or more of the 8 transistors toward the center of the schematic - e.g. R21, the sand parts + resistors that influence the output transistors & the output transistors themselves.
  Here's a couple diag sessions from this thread:
http://www.head-fi.org/t/422429/cavalli-ehha-embedded-hybrid-headphone-amp/225#post_5710684
http://www.head-fi.org/t/422429/cavalli-ehha-embedded-hybrid-headphone-amp/1725#post_7120477
   
  Good luck.


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## flynhawaiian

Sorry to drum this back up.  But I am about to start my build up and need a power supply.  Which one should I use, or at least what do I need in terms of power requirements?
   
  I want to use an telefunken ecc 86 to start with.  I’m not sure if I need a heater power supply as well, and if so can you tell me what I would need?  If you have mouser part numbers that would be cool.  I’m about ready to make an order from them


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## funch

Here's the power supply: http://www.glassjaraudio.com/product.sc?productId=3&categoryId=2


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## flynhawaiian

It seems like most people are using two Avel Lindberg toroidal transformers.  I’m just not sure what model number they are using.  Also what heater transformer are people using?


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## flynhawaiian

Is the Avel Y236653 the correct one to use for the REV A?  Do I only need one if I use that one?  I also see I need a 6.3V/1A heater transformer - Any recommendations?


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## funch

My reply was for the original EHHA. If you are building the Rev. A, then you don't need a separate power supply, just the two transformers: one for the heaters, and
  one for the amp PS.


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## flynhawaiian

Do you think the Avel Y236653 would be the correct transformer to use?  Any thoughts on a model for the heater?


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## funch

That one is waaay over spec @ 4A. You only need 0.5A.
   
   
  For the amp PS, use Avel #Y236107: 30+30V @ 0.5A.
   
  For the heater PS, use the UF4004 diodes and use Avel #Y236101: 9+9V @ 1.67A.


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## arteom

It has been years since I had considered building one of these, life has gone up and down, left and right, I hadn't used headphones in a long while. I finally got back into the hobby. Got another pair of MS-Pro's and bought funch's EHHA from a member that had purchased it from funch couple of years ago. This thing sounds amazing! Just such an effortless presentation of sound, highly detailed, excellent instrument separation, no grain, its smooth but never syrupy. This is it folks.
   
  The tubes on this are still the original A Frame German GE's, I have ordered a set of NOS Pope Holland 6GM8's, anxious to hear those.


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## arteom

I know this has probably been discussed (couldn't find it with search), but anyone swap capacitors? Recommended?


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## arteom

I've started getting some distortion on the board connected to my right channel, I'm trying to go through initial setup steps posted on the cavalli site but am having a hard time making out part marking on the board that is listed on the site, does anyone have alternative image. Or if anyone has a clean board and can take some pictures that show part markings, it would be well appreciated!!


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## arteom

Emailed Alex through the Cavalli site, he came through with a cleaner board layout. That dude rules 
	

	
	
		
		

		
			




  
 Anyway, since this is the only real build thread for this amp I thought it would be of some value to add the board layout here for anyone looking in the future.


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## Jose ant.

Hello all
  
 It´s my first post and I need some help.
  
 I have finished my EHHA I (MOSFET versión)) but I have an issue. R32/33 always burn. The volt. on initial checking is correct (I think):
  
 R3,4= 1,5 volt
 R10,14=1,5 volt
 R15,17= 0,80~ 0,85 volt.
 R16 & R18, R26 & R29= 0,5~0,6 volt
 The voltage at pins 4 and 7 of the opamp DIP socket: +15V and -15V
 Pin 6=0 volt.
  
 When I turned on, the R32/33 has been burnt and I don't know what fail.
  
 Where is the problem? Any idea? 
  
 Thanks


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## saur12 (Dec 11, 2017)

Hi! Is the diagram for the original EHHA or the newer revision?

I have been gifted a non working revised model. Where can I get instructions, diagrams to troubleshoot the amp?
Any help on this will be greatly appreciated.

EDIT: Whoops did not realize that this was such an old thread. Any help will be needed.


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## funch

You might check with Jeff here: http://www.glassjaraudio.com/  He sells kits for both versions of the EHHA, and may be able to provide the doc's.


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## Zulkr9

Hi there anyone know where I can get the kits, Glassjar audio seems to be unresponsive TIA


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## tomb

Zulkr9 said:


> Hi there anyone know where I can get the kits, Glassjar audio seems to be unresponsive TIA


Keep trying ... AFAIK, Jeff is still in business, just typically busy.  He may travel in his day job, too.


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## Zulkr9

tomb said:


> Keep trying ... AFAIK, Jeff is still in business, just typically busy.  He may travel in his day job, too.


I've tried a few times already, I guess just gotta wait I guess.


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