# SOHA II Builders Thread



## runeight

Hello SOHA II Builders. Now that the two stage prototype process has finalized the board and amp we're starting the buidlers thread. The original SOHA II thread is still around for parts questions, design questions, and other similar issues. This thread is here:

SOHA II - Super SE Hybrid

 The builders thread is for discussing and showing the builds.

 I don't have a picture of my stuffed board handy at the moment, but here is a 3D image created by Eagle 3D. Most of the parts are simulated on the board.







 For complete information on the SOHA II Super SE Hybrid amp see:

Cavalli Audio

 A group buy is in the works and should be announced very soon.

 Happy building.


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## Ferrari

Well, my build is a bit unusual and has not much in common with the 3D image in the previous post, but here are a couple of pics to start.
 I encourage everyone who are building or have completed the build to share your builds and experiences here.
 We are here to learn form each other!


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## pabbi1

Ferrari, I like how you suspended the tubes, and am looking at something similar, but isn't that aluminum a bit frail for inserting tubes, especially the more obstinate ones, and would channel of 2"w x 1"d have provided better support? Granted, I am looking at this for el34, s have to have channel...

 Other than that, IFF builders pay close attention to the transistors orientation, especially the plastic case (with no metal tabs), and the opamp orientations, this will go smoothly, assiming you can connect your power connections correctly (a not so subtle plea that a picture to help guide that is worth thousand of words in that one case). The stuffed board image is a great start toward that.


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## GeWa

*@Ferrari

*What value of cap did you used for C2R / C2L?

 Regards


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## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_*@Ferrari

*What value of cap did you used for C2R / C2L?

 Regards_

 

The red ones on the pic above are BG-NX 10µF/50V. On my other board, I'm using Wima MKS 10µF/16V.
 BTW, how is _the second Europeans SOHA II build_ going?


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## GeWa

Quote:


 BTW, how is _the second Europeans SOHA II build_ going? 
 

I'm kinda this far.






 Regards


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## Ferrari

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Ferrari, I like how you suspended the tubes, and am looking at something similar, but isn't that aluminum a bit frail for inserting tubes, especially the more obstinate ones, and would channel of 2"w x 1"d have provided better support? Granted, I am looking at this for el34, s have to have channel..._

 


 I’m actually using aluminum L-profile (50mm x 20mm, 3mm thickness).
 The tube sockets are mounted on the 50mm side, while the 20mm side (not visible on the pic above) provides the stability for the whole construction. I’s very rigid and I have experienced no frailness. 

 I think that channel of 2"W x 1"D can provide better support, however U-profile is also an option and probably easier to construct.


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## GeWa

Can I substitute the BD139 with 2SC2238?

 Regards


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## runeight

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Can I substitute the BD139 with 2SC2238?

 Regards_

 

Probably, but I can't be sure of the range on the O/P stage CCS. You may or may not be able to dial up 100mA with the values specified for the BD139.

 Give it a try and let us know. When you fire up the O/P stages make sure that P2L and P2R are set to their maximum resistance (fully counterclockwise). And then dial up the current from there.


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## GeWa

Thanks Runeight but I think I'll stick with the BD's than. I hate to desolder stuff, especially on plated through holes.

 Regards


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## meat01

Keep taking pictures as you put on more components GeWa, this is great


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## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Can I substitute the BD139 with 2SC2238?

 Regards_

 

I have not named it explicitely but Toshiba 2SC2238 output devices were tried out on this proto build a while back.
 Works like a charm, absolutely no problem to bias the quiescent current to *110mA* (slightly above the design goal).


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## GeWa

Quote:


 Keep taking pictures as you put on more components GeWa, this is great 
 

Another one with the coupling caps and LV+ / LV- regulators in place.





  Quote:


 Works like a charm, absolutely no problem to bias the quiescent current to *110mA* 
 

Good news, thanks Ferrari. Think I will give them a try than.

 Regards


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## Uncle Bob

Looking good! (especially as my boad hasn't arrived yet 
	

	
	
		
		

		
		
	


	




) Auricaps huh? not building to a budget then


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## GeWa

Quote:


 Auricaps huh? not building to a budget then 
	

	
	
		
		

		
		
	


	



 

Yes I do, they were simply calculated into the budget. 
	

	
	
		
		

		
		
	


	




 Regards


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## Arkku

Hi,

 I've built the power supply part of my SOHA II today, and much to my surprise it gave out correct voltages when I finally dared to plug it in (wearing safety goggles and rubber gloves =).

 I'll try to get started with the amp itself tomorrow… As for more BD139 alternatives, I seem to recall someone here using BD137s instead. Should these work without other changes to the BoM?


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## holland

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_As for more BD139 alternatives, I seem to recall someone here using BD137s instead. Should these work without other changes to the BoM?_

 

That would be me, and yes.


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## holland

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_...I'll stick with the BD's than. I hate to desolder stuff..._

 

I used transistor sockets everywhere. They are available at Digikey and Mouser, not sure about overseas. They work great not only for output transistors, but for the regs in the PSU as well. If you are using larger heatsinks, it's a downright PITA to replace any of those. Sockets there help a bit. I have all my TO-220 package ICs socketed on the SOHA II.

 Swapping transistors in the socketed versions are easy as pie. Only problem is how to handle reverse pinouts. You can socket both sides if you like. I didn't as I want more airflow.


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## runeight

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_Hi,

 I've built the power supply part of my SOHA II today, and much to my surprise it gave out correct voltages when I finally dared to plug it in (wearing safety goggles and rubber gloves =).

 I'll try to get started with the amp itself tomorrow… As for more BD139 alternatives, I seem to recall someone here using BD137s instead. Should these work without other changes to the BoM?_

 

That's great Arkku. Take your time and follow the steps and, if all the components are in the right places, it should come up without any problems.


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## rds

Has anyone figured out what kind of ventilation we need if we're using the 14551601? Is it possible to have no extra holes drilled?

 Also, on a similar train of thought, will there be a group buy for pre-drilled cases along with the pcb group buy?


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## luvdunhill

I heard pabbi1's SHOAII and was really, really impressed. I think he was using 5863 or something like that. Just curious, what's the gain with this tube? I say that, because it was definitely over 10 and I'd like to set another amp to around this much gain, as it was perfect given my low output sources.


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## runeight

This depends on the topology of the circuit as much as it does the tube. The raw gain (mu) of a 5963 (12au7) is about 17. In the SOHA II using a 5963 gives a gain of about 12 because a very small amount of NFB is applied to compress the wide spread of mu for all the possible tubes that can be rolled into a much narrower range. This is discussed on the website at Cavalli Audio.

 So, YMWV according to the topology of the circuit and the tube used. There is no hard rule.

 Edit: Ferrari's post below is correct on the mu which is 21 not 17.


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## Ferrari

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_I heard pabbi1's SHOAII and was really, really impressed. I think he was using *5863* or something like that. Just curious, what's the gain with this tube? I say that, because it was definitely over 10 and I'd like to set another amp to around this much gain, as it was perfect given my low output sources._

 

I think that you mean 5963 double triode (5863 ???). The voltage gain of this tube is 21x, however the effective gain of the SOHA II is lower. I have measured that once but can't remember the exact number. Effective gain depends on the tubes used in the front-end of the amp.



_Edit: runeight was beaten me for a couple of minutes._


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## runeight

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Has anyone figured out what kind of ventilation we need if we're using the 14551601? Is it possible to have no extra holes drilled?

 Also, on a similar train of thought, will there be a group buy for pre-drilled cases along with the pcb group buy?_

 

rds, I am currently talking with Jeff about pre-fab'd front, rear, and top panels for the long Hammond enclosure. The amp needs lots of ventilation and will probably get too hot if just the tube holes are opened and nothing else. I have been thinking of a perforated sheet (50% open) that is the right thickness to slide into the case with the holes drilled for the tubes and the B+ adjustment. Still working on it.


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## rds

Sounds good. My personal issue is that I will be building mine around Christmas, which might be too early to have those panels in hand. But I see someone has been kind enough to make dimensional pdf drawings - that's great for me. I can use a center punch, but I hate using rulers.


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## wiatrob

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_ But I see someone has been kind enough to make dimensional pdf drawings - that's great for me. I can use a center punch, but I hate using rulers._

 

I created a set of templates for the bottom - I think that Pabbi used them - they were pretty painstakingly laid out (I don't do CAD) by hand. Case drilling is pretty straightforward with a glued down template and a steady hand...

 Is anyone (other than Ferrari, who has a much bigger case) using an unventilated _top_?


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## holland

I posted my build in the other thread in this forum. My build has vents on the corners. The tops themselves have no other slits or holes. It does get warm, but I don't feel it is too warm. I don't recall seeing any builds that have a fully closed system.


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## runeight

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Sounds good. My personal issue is that I will be building mine around Christmas, which might be too early to have those panels in hand. But I see someone has been kind enough to make dimensional pdf drawings - that's great for me. I can use a center punch, but I hate using rulers._

 

rds there are dimensioned drawings on the website in various places. They locate the holes on the front panel and the holes on the tube for clearing the tubes and the hole for the B+ adjustment.


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## kklee

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Is anyone (other than Ferrari, who has a much bigger case) using an unventilated top?_

 

I originally built mine without a ventilated top, but it got extremely toasty, almost uncomfortable to touch. I ended up cutting a couple of ventilation slots in the top and it runs much cooler now.


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## dBel84

I am at this point too, I built a fan into mine which doesn't induce electrical noise but with open cans, I can hear it at the low levels I prefer when listening. I plan to cut a few vents into the top / sides of mine..dB


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## pabbi1

I used wiatrom's drill template for the bottom, and added top / side vent holes like this, and it gets a little warm, but nowhere near hot. The nod is toward Holland's case, where the bottom and top vents seem quite adequate, or a vented top / bottom as runeight aluded to. This is with all stock BOM except Auricap on c1.


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## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Is anyone (other than Ferrari, who has a much bigger case) using an unventilated top?_

 

The case I used does have vents on both sides of the enclosure + the two 1” diameter tubes holes on top, while the 2 tubes are actually located outside the enclosure (air-cooling). Moreover, the heater voltage regulator (in high current mode) is mounted directly on the 3mm thick aluminum enclosure, which serves as a large heatsink. The amp does get hand-warm in the long run, but never warmer than body temperature.

 I miss the amp a lot since my GF took the amp to her office.


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## Uncle Bob

I've just spotted a part number error in the UK BoM I sent to Alex which is hosted on the website

 The E12 Relay (component K1E) , the Rapid part no. reads 60-0432 - it *should* read 60-4032


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## runeight

Thanks Uncle Bob. I'll fix this.

 How's your SOHA II doing?


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## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The case I used does have vents on both sides of the enclosure + the two 1” diameter tubes holes on top...
 I miss the amp a lot since my GF took the amp to her office. 
	

	
	
		
		

		
		
	


	


_

 

So it does! don't know how I missed those, must've been focused on the tubes...

 My condolences on your loss!


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## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks Uncle Bob. I'll fix this.

 How's your SOHA II doing?_

 

Not so good 
	

	
	
		
		

		
		
	


	




 I still haven't received my board, it's looking like its been lost in transit. If it hasn't arrived by this weekend, I'll have to order another one from Jeff


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## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_...
 My condolences on your loss!_

 

Don't worry, that is a good reason for me to put this amp into this enclosure ASAP.


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## wiatrob

Anybody listening to the II with Denons? At our mini-meet, we again noticed the particular synergy of the II with all Sennheisers.

 With Denon 7000s, the II significantly lifted the soundstage, brightened the mids and highs and seems to decrease the bass. Very interesting...


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## runeight

IIRC, Postal_Blue did his entire review of the II with Denons. I can't find that link at the moment, but I'm pretty sure that he did.


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## meat01

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_IIRC, Postal_Blue did his entire review of the II with Denons. I can't find that link at the moment, but I'm pretty sure that he did._

 

There is a link from your site 
	

	
	
		
		

		
		
	


	




http://www.head-fi.org/forums/f6/soha-ii-review-360333/


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## runeight

LOL. I've got way too many projects going.


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## krisio06

Is anywhere avalible SOHA II build kit?
 I am very interested in this buliding amp but I don't like buying parts from a few shop.. 
 I know that the SOHA II build kit will be relised in a short time but is anywhere avalible SOHA II build kit?
 Cheers..

 Is the SOHA II good for RS1?


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## Ferrari

For SOHA II kit and PCB, you might contact Jeff Rossel.


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## krisio06

I've already send him an email..
	

	
	
		
		

		
		
	


	



 Have anyone tried SOHA II with RS1 or RS2?


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## gurusan

Builds look very nice. i think this will be my 3rd project


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## grendel23

I just finished my SOHA II, Very nice build, sounds great, a definite step up from my SSMH. now I need to save for HD600's.
 Has anyone else noticed that the excel BoM is missing P1P, the pot to adjust the high voltage? Luckily I had one that would work.


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## runeight

Congrats on the build grendel. How did you do the texture on the panels? They look like the Hammond panels that you have worked over. Yes?

 I didn't notice the missing pot. So I guess I'd better add it. 
	

	
	
		
		

		
		
	


	




 Let us know how it does after a while of listening.

 Also, if you have a mind to you can add a small access hole for the B+ pot on the top panel and you can actually adjust the B+ while you're listening to find a spot that you like best.

 Have you rolled any tubes yet? Etc.


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## krisio06

That's looks astonishing..
 I want that..
	

	
	
		
		

		
		
	


	



 Good job...


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## runeight

Yes, I agree. It's pretty amazing.

 I have updated the Excell BoM with Mouser and Digikey part numbers but not Farnell and RS numbers. Thanks for catching that grendel.


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## grendel23

I used rust-oleum copper hammertone paint. I didn't expect the birdseye effect, but I like it.
 I used a mill to drill the holes in the top, if the spacing wasn't perfect, it would look like crap.
 I only have 5963 tubes so far, but will obtain others to try.
 I am currently running B+ at 90V, does that adjustment make a big difference in sound?
 I have only listened for a few hours, but I am impressed so far. I am running with an Alien DAC and SR80's, but HD600's and a gamma DAC should make it sing.
 Does anyone have recommendations for other tubes to try?


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## runeight

It's hard to say on the B+ as there are so many different ears out there. My wife likes the original B+ of 60V. I can't really hear much difference between 60V and 100V. But others can and it may be different for different tubes.

 I've tried quite a few tubes in mine and I like the RCA 5963s the best. I think you should try ordinary 6922s and 12au7s just to see the differences. dBel84 and others like the 8416 the best.


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## wiatrob

All, please see some impressions from this weekends meet - not in depth, for a mini-meet there was a _LOT _of gear, but the SOHA II is featured...

http://www.head-fi.org/forums/f45/11...s-pics-377603/


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## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_It's hard to say on the B+ as there are so many different ears out there. My wife likes the original B+ of 60V. I can't really hear much difference between 60V and 100V. But others can and it may be different for different tubes._

 

I recently rolled the B+ back down to 60, for 'old times sake' 
	

	
	
		
		

		
		
	


	




 although I thought I noticed a difference before, I can't tell as much now..


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## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, I agree. It's pretty amazing.

 I have updated the Excell BoM with Mouser and Digikey part numbers but not Farnell and RS numbers. Thanks for catching that grendel._

 

P1P 10K 3/8" Trimmer
 Farnell Part No 9353186 (Bourns 3296W series)
 Rapid Part No. 68-1946 (3296W equivalent - TruOhm series)

 UB

 PS. my pcb arrived today


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## wiatrob

More great SOHA II Ancilliary inmpressions: http://www.head-fi.org/forums/f45/11...ml#post4941349

 'Monster Bass!'


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## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_P1P 10K 3/8" Trimmer
 Farnell Part No 9353186 (Bourns 3296W series)
 Rapid Part No. 68-1946 (3296W equivalent - TruOhm series)

 UB

 PS. my pcb arrived today 
	

	
	
		
		

		
		
	


	


_

 

Thanks Uncle Bob. I'll upload the new spreadsheet tonight.

 Keep us posted on the build.


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## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_More great SOHA II Ancilliary inmpressions: http://www.head-fi.org/forums/f45/11...ml#post4941349

 'Monster Bass!'_

 

Bass quality is no doubts a major positive character of this amp.
 No matter if I plug in a Philips HP 1000, AKG K 701, Beyer DT 880 (2005) or Sennheiser HD 600, always deep, controlled and very well defined. However I like it most with Sennheiser HD 600.


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## holland

wiatrob,

 a bit OT, but any direct comparisons with DV, WA6, etc.? Saw some mention relative to EF-1, but not much relative to the other amps present.

 Did you personally get to compare to the SSMH? I have my own opinion, owning both, but am interested in hearing others.

 Which tube and transistors are you using? I do know the sonics differ drastically with tubes and slightly with transistors, so you can definitely dial down or up certain areas.

 Looks like a fun meet.


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## runeight

Updated the BoM on the website to include the Farnell and RS part numbers


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## kklee

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Updated the BoM on the website to include the Farnell and RS part numbers_

 

For what it's worth, the Digikey P/N for the pot is 3296W-103LF-ND


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## Postal_Blue

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Did you personally get to compare to the SSMH? I have my own opinion, owning both, but am interested in hearing others._

 

I compared the SOAH II to the SSMH, no comparison. The SSMH is a great little amp, probably best you can do <100 but... The Soha II is a superb amp. Simply in a different league.


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## wiatrob

The amps were setup in groups of two:

 EF-1 and Singlepower Squarewave XL, Woo WA6's and GS/Starving Student (!) The Melos remote was left behind, we never got it out of mute 
	

	
	
		
		

		
			





 My Soha I and II...

 There were SOOO many phones and cables that I couldn't keep track of what was what
	

	
	
		
		

		
		
	


	




 (I had about $10K worth of phones and cables on my head over the course of a couple of hours - Overwhelming for my not -so - experienced ears.

 The D7Ks and Senns sounded very good on both the EF-1 and Singlepower. The EF-1 had quite a bit in common with the SS sq wave (a family resemblance to my SOHAS, solid bass, but without quite the definition on the bottom. )

 I didn't pay enough attention to the WA6s.

 The Starving Student sounded quite good, noiseless and clean, without the full sound stage of the SOHA II but quite good, and with less bass but still respectable. 

 Gentlemen, there wasn't one stinker in the room, as you can see form the pics! 

 I look forward to some mini-er meets in the near future, heck I may host one!


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## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_wiatrob,
 Which tube and transistors are you using? I do know the sonics differ drastically with tubes and slightly with transistors, so you can definitely dial down or up certain areas.
 Looks like a fun meet._

 

Stock transistors, closely matched RCA black plate 5963's, B+ @ 90V


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## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Stock transistors, closely matched RCA black plate 5963's, B+ @ 90V_

 

Have you tried the RCA grey plates? I was wondering if the black plates were worth it. The grey plates aren't really my thing (think thin and shrill).


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## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Have you tried the RCA grey plates? I was wondering if the black plates were worth it. The grey plates aren't really my thing (think thin and shrill)._

 

I like the BPs, I have a set of grey plates as well, but they are very microphonic and do accentuate the highs. I also have some RCA clear tops which I've been swapping in, as they look so freaking cool...

 -Bill


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## -=Germania=-

waitrob, 

 That SSMH isn't completely noiseless. 
 Throw in a set of CD3000 and turn the volume up all the way. If the room is dead silent, you should hear a VERY faint noise (My friend said no noise, but YMMV)
 I tried adding more capacitance to the power section to get silence and 100uf more was just a bit too much, changing the sound sig to be a bit wonky (~470uf should do the trick without changing sound too much). Pitch black came with a price, so overall SQ had to be chosen. 

 However, you really need to meet those conditions to hear it (something not likely in a room full of people).


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## grendel23

I was listening to my SOHA II, and noticed a bit of hum. I thought It was coming from the transformer or AC wires, but it turns out that touching the shaft of the pot induces a small amount of hum. I can make sure that the metal front of the pot is grounded and solve the problem, but am surprised to see this behavior with an decent pot. Is it normal to have to ground these to prevent hum?

 Grendel23

 Update,
 I found the problem, the ground wire was not solid, nevermind.


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## Beefy

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_Is it normal to have to ground these to prevent hum?_

 

Yes, I believe the casing of the pot should be connected to ground in some way. Normally just contact with a metallic case is enough, but connecting one of the screws to ground is also a good way to do it.


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## runeight

grendel, this hasn't come up yet, but there is a grounding pad between the pot and the input terminal block for just this purpose. 
	

	
	
		
		

		
		
	


	




 The way I grounded my pot was to remove the screw at the top right looking from the front. You can unscrew this screw out of the back and run a short wire from the grounding pad and wrap it around the screw and then tighten it back in. Depending on the type of wire, you won't be able to tighten if fully, but you'll get close. If you use something like 24awg stranded wire you'll be able to put the screw all the way back in.

 Update: Never mind.


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## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_grendel, this hasn't come up yet, but there is a grounding pad between the pot and the input terminal block for just this purpose. 
	

	
	
		
		

		
		
	


	




 Update: Never mind. 
	

	
	
		
		

		
		
	


	


_

 

I was heartbroken when I first touched the pot shaft of my proto build upon firing it up BZZZZZZ 

 Groundining with a thin strand from the upper rear screw to the G pad cured it.

 (all of my builds with ungrounded RCAs have had this issue, not just the II...)

 Grounding: an Art and a Science!


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## grendel23

I am glad this is a known and curable ill. I still had a bit of noise after fixing my loose main ground wire. I will ground pot and see if that takes care of it.
 Thanks,


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## wiatrob

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_...I still had a bit of noise after fixing my loose main ground wire. I will ground pot and see if that takes care of it.
 Thanks,_

 

Are you housing the transformer in the same case as the amp?


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## grendel23

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Are you housing the transformer in the same case as the amp?_

 

Yes I am, but moving the AC wires does not affect the noise. I will ground pot tomorrow and see if that helps.


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## wiatrob

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_Yes I am, but moving the AC wires does not affect the noise. I will ground pot tomorrow and see if that helps._

 

If the case is the stock hammond, some builders have found that rotating the transformer can alleviate hum, if it' snot the pot...


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## grendel23

Grounding the pot eliminated the noise. Now it is dead silent even at full gain.
 Thanks for the tip Runeight! 
 I ran into one other small issue. I had the holes for the tubes in the top plate very tight to the tubes. this worked fine until I tried to remove the tubes, the sockets are tight and it was almost impossible to remove the tubes because I couldn't rock them slightly. I am changing to larger openings.


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## runeight

That's great grendel. The amp should be silent. 
	

	
	
		
		

		
			





 On the holes, did you use the hole sizes shown on the diagrams on the website? If so, I should make them bigger. If you did use this hole size perhaps you can tell me, when you're through, what a good hole size is.

 If anyone else has a suggestion for the right hole size please let me know and I'll change the drawings.


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## rds

grendel - is your pcb in the 2nd slot or 3rd slot? I'm wondering cause I need the board in the second slot in order to squeeze in my pot of choice. On the other hand I want to have enough tube sticking out so I can grab onto it to roll tubes.

 Any word on the group buy and cases?


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## grendel23

Runeight, the top panel drawings on your web page give a 404 error when you try to access them, so I used the board drawing to locate the holes for the tubes. I made 1" holes with a chassis punch and put in plastic snap in bushings. I am going to enlarge the holes and use bushings with a 1" ID.

 Rds, I am using the third slot. There is not a huge amount of tube to hold on to. I use a piece of rubber to get a grip on the exposed glass. If you will use the second slot it will be harder. Maybe a short piece of 3/4" ID gum rubber hose would work well to grip the tubes?


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## runeight

Sorry about that. I guess I forgot to test those links. They are available now.


----------



## runeight

grendel I meant to ask if you have any further listening impressions?


----------



## FallenAngel

So I finally had a chance to build the the HV PSU. The amp still sounds wonderful, but I'm still also getting a little bit of hiss/hum with closed headphones and no music playing. The transformer is in another box so the noise is definitely from the amp.

 I also noticed that the left tubes is microphonic and it's very strange. I touch the left tube - there's some serious noise in the left headphone. I touch the right tube, there noise in the left headphones again. 
	

	
	
		
		

		
		
	


	




 When I follow the setup instructions everything looks good up until measuring between TBL and TB+L (or TBR and TB+R) - both values are around 15V, not 19V.

 EDIT: Just changed tubes, TBL to TB+L is now 20V and TBR to TB+R is 17V. Noise seems to have gone down a little bit as well. I'll see if I have any others as well.
 EDIT2: Changed from GE 5963 to GE 6680 tubes. Noise is less again, plus tubes not microphonic. Still a little hiss/hum though. voltages are 22V TBL->TB+L and 18 TBR->TB+R. Strange pattern that the left one is ALWAYS higher, no matter the tubes.


----------



## runeight

FallenAngel, the variations between tubes are normal. This is because you're measuring the difference between the B+ and the right triode. The plate voltage on the right triode varies according to how well the two triodes are matched. So, don't worry about this. You could, however, double check the tail current for both tubes just to have it the same amount.

 It's hard to diagnose the noise. I guess the obvious questions:

 1. Is the star ground connected to a metal ground point?
 2. Do the tube sockets have dirty contacts?
 3. Are all the solder joints on the board clean.
 4. Is the pot grounded?


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_...
 PS. my pcb arrived today 
	

	
	
		
		

		
		
	


	


_

 

How is your build going?


----------



## FallenAngel

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_FallenAngel, the variations between tubes are normal. This is because you're measuring the difference between the B+ and the right triode. The plate voltage on the right triode varies according to how well the two triodes are matched. So, don't worry about this. You could, however, double check the tail current for both tubes just to have it the same amount.

 It's hard to diagnose the noise. I guess the obvious questions:

 1. Is the star ground connected to a metal ground point?
 2. Do the tube sockets have dirty contacts?
 3. Are all the solder joints on the board clean.
 4. Is the pot grounded?_

 

Thanks for the info. The tail current is set to 2mA on both (400mV).

 You're going to laugh at the 4 answer 
	

	
	
		
		

		
		
	


	



 1) Not yet
 2) Should be clean
 3) Not yet
 4) Yep

 I'm also using unshielded signal wiring spliced, stripped and twisted together to a pair of "testing" RCA jacks. 
	

	
	
		
		

		
		
	


	




 I'm guessing these are all likely culprits and I'll make everything nice and pretty tonight and post results again.


----------



## Uncle Bob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_How is your build going?_

 

It's progressing, pretty much all of the passives are mounted and I'm hoping to get a few hours work on the board this weekend. 

 GeWa has been pretty quiet, wonder how he's getting along?


----------



## grendel23

I have had a chance to listen to my SOHA II for a few days now. I must preface my comments by stating that I am not a "golden eared" audiophile and can only compare this amp to my SSMH with my Alien DAC with Blackgate output caps and SR80s (recabled because one of my cats chewed up the cord).
 Given that, I can say that this amp is a big step up from the SSMH. On "funk is its own reward" by Stanly Clarke, the base line at first seems a bit stronger on the SSMH, but with the SOHA II the bass is tighter, deeper and there is a slight vibrato that is not audible with the SSMH. After comparing, the SSMH is slightly loose in comparison.
 On the California Guitar Trio's "Yamanashi Blues" off "an opening act: live with King Crimson" the sense of the hall around the musicians is more spacious with the SOHA II. The SSMH seems boxed in in comparison.
 This amp also is much less forgiving of poorly mastered or compressed material. Some of the music on my computer is in FLAC, now I will need to re-rip the rest.
 It is obvious this amp is better than the equipment I now have to use with it, but I have started saving for a pair of HD 600's, and will build a Gamma 1 DAC once boards are available.


----------



## holland

I agree with everyone's comments about the SSMH, so far. I would add that it's expected, because the design goals were different and the prices for building are quite different.


----------



## FallenAngel

Just cased the the first of the two prototypes I have been playing with. The noise has dropped considerably (and I really mean considerably); but it's still there, and quite noticeable with no music playing using closed Denon D5000 headphones. 
	

	
	
		
		

		
		
	


	




 Even with my RS-1, I can't hear it, but with those damn 25-ohm Denons, the noise is there.











_runeight_ - now the 4 answers are Yes, clean, clean and yes.


----------



## runeight

what kind of noise is it? hum? buzz? static? white noise?


----------



## GeWa

Quote:


 GeWa has been pretty quiet, wonder how he's getting along? 
 

I'm kinda busy with work lately. I wont go into detail because you will declare me insane! As far as the SOHAII, I'm a little over half way with populating the board. Still haven't figured out yet what I'm gonna use for C2L/R. I want to use a polypropylene cap here, but the ones I have are a little to big.






 Regards


----------



## runeight

Looking good gewa. Are you going to come in last in the EU race? Can you let that happen?


----------



## FallenAngel

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_what kind of noise is it? hum? buzz? static? white noise?_

 

Hmm... I'm not very good with describing noise, I would say it's white noise / hiss. Not static and not distinct hum of transformer and doesn't sound like a ground loop.


----------



## runeight

Hiss. Hmmm. Can be hard to find.

 Does it go away when the headphones are unplugged?

 Does it go away if you pull out the tubes and just listen to the buffers?


----------



## onform

I think I'm going to come in last on the European side as i have had to put my project on hold due to financial matters..bloody recession...


----------



## runeight

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Hmm... I'm not very good with describing noise, I would say it's white noise / hiss. Not static and not distinct hum of transformer and doesn't sound like a ground loop._

 

Say, FallenAngel, I just reread my response above. I think it sounds a little flip, but I didn't mean it to be. I think I'd better start including more smilies. 
	

	
	
		
		

		
		
	


	




 The source of hiss can be very difficult to locate and sometimes it comes from several different places.

 I asked about unplugged phones because I was wondering whether the hiss might be partly due to the clamshell effect. But, I know that this is a long shot.

 It will be helpful if we can isolate the hiss to either the front end or the back end of the system. Which is why I asked about pulling the tubes.


----------



## runeight

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_I think I'm going to come in last on the European side as i have had to put my project on hold due to financial matters..bloody recession... 
	

	
	
		
		

		
		
	


	


_

 

Sorry to hear that onform. But I can tell you that things are getting pretty rough here in the US too.


----------



## FallenAngel

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Say, FallenAngel, I just reread my response above. I think it sounds a little flip, but I didn't mean it to be. I think I'd better start including more smilies. 
	

	
	
		
		

		
		
	


	




 The source of hiss can be very difficult to locate and sometimes it comes from several different places.

 I asked about unplugged phones because I was wondering whether the hiss might be partly due to the clamshell effect. But, I know that this is a long shot.

 It will be helpful if we can isolate the hiss to either the front end or the back end of the system. Which is why I asked about pulling the tubes._

 

I don't know what "flip" is, not to stretch to being able to identify it. 
	

	
	
		
		

		
		
	


	




 It's not from the headphones "effect" because when I have the headphones on, I know just when the muting relay clicks and then the noise comes.

 I also checked without tubes, the hiss is still there and at the same volume, so I'm assuming it is the buffers.


----------



## runeight

Is there any way that you can remove the lead of C1 where it connects to the base of Q5 on both channels? This will disconnect the buffers from the B+. One source of the noise in the buffers could be the B+, although not likely.

 If it is not the B+ then something in the buffers is just noisy. Is the noise the same on both channels?

 One thing about the buffers is that they are pretty simple, not much to go wrong. So I'm not yet sure what can be causing this.

 Do you happen to have a scope available?


----------



## FallenAngel

That might be kind of difficult, but I'll try.

 The noise is the same on both channels as far as I can tell.

 Nope, no scope around and I wouldn't know the first thing to do with it if I get one (or considering how often I've wanted to measure something, it might be a "when I get one").


----------



## holland

Don't have my ultrasensative M-Audio Q40 around to test with higher impedence, but I plugged in one of my 16-ohm IEMs (Crossroads MylarOne X3) which are quite sensitive as well and I have a hiss too. I don't notice it with my other sensitive cans, like the ATH-ANC7 and the K81DJ.

 I recall checking this with the old B+ (pre-HV) config, and I recall not noticing this, but that was also before casing when it was sitting out on my desk.

 I'll see what I can find out tomorrow, if I have time. I will try to isolate the buffers first.

 I have a scope, but my 200MHz probes are broken. I think I have some 400MHz probes around somewhere, but I haven't used my 400MHz unit plugin so I'm not sure if it's functional.

 If I can measure, I will. What would you like done?

 With the protoboards we have, we should just be able to disconnect the external HV perfboard as well, if you don't want to desolder C1/C2 and you put terminals on. At least, I think that'll work.

 Edit: I hear it with my DT660, but it's slight.


----------



## Ferrari

I have looked at the instrinsic noise of the output buffer (more than once) during the prototyping phase and it is very low, so I’m quite sure that it’s not likely that the noise is coming from there.

 Take a closer look at the wiring of the input => volume pot => PCB, all these wires are unshielded and the distance is quite long. Pure from technical point of view, this can’t be healthy for the very sensitive input signal.


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_It's progressing, pretty much all of the passives are mounted and I'm hoping to get a few hours work on the board this weekend. 

 GeWa has been pretty quiet, wonder how he's getting along?_

 

Normally… the Belgians way is a bit slow, mostly (comparing to the Dutch way). 
	

	
	
		
		

		
		
	


	



 Hope that he’s not going to give it up.


----------



## GeWa

Taraaaaaa!!!!!






 Regards


----------



## dBel84

excellent 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Taraaaaaa!!!!!






 Regards_

 


 Well done GeWa. Looks like you are not going to come in as last. 
	

	
	
		
		

		
		
	


	



 Now testing and listening. Enjoy!


----------



## runeight

Quote:


 Don't have my ultrasensative M-Audio Q40 around to test with higher impedence, but I plugged in one of my 16-ohm IEMs (Crossroads MylarOne X3) which are quite sensitive as well and I have a hiss too. I don't notice it with my other sensitive cans, like the ATH-ANC7 and the K81DJ.

 I recall checking this with the old B+ (pre-HV) config, and I recall not noticing this, but that was also before casing when it was sitting out on my desk.

 I'll see what I can find out tomorrow, if I have time. I will try to isolate the buffers first.

 I have a scope, but my 200MHz probes are broken. I think I have some 400MHz probes around somewhere, but I haven't used my 400MHz unit plugin so I'm not sure if it's functional.

 If I can measure, I will. What would you like done?

 With the protoboards we have, we should just be able to disconnect the external HV perfboard as well, if you don't want to desolder C1/C2 and you put terminals on. At least, I think that'll work.

 Edit: I hear it with my DT660, but it's slight. 
 

Hiss is pretty hard to see on the scope because it's just noise on the trace.

 But, it's worth looking at the LV+ and LV- rails to see if there is noise on them. And then the base of Q5 and the O/P of the buffers. If there is visible noise on the traces then check whether it's larger at the O/P than it is at Q5. If it is, the buffer is introducing noise. If not the noise is coming from before the buffer.

 The only way the buffer can introduce noise is either noise on the rails or just plain noise generation in the components. Every element in the circuit makes some amount of noise, especially the BJTs. But there are a few zillion O/P buffers out in the world and most of them don't create additional audible noise.

 Edit: I missed Ferrari's post when I wrote this, but those are important things to check out too. And I see that Ferrari has already checked out the noise from the buffers and found it neglible.


----------



## runeight

So, Gewa, does it work??? I see that you used some other transistors on the backside of the heatsinks??


----------



## onform

@ runeight

 A newbie Q i apologise if this makes no sense but i'm trying to teach myself electronics here goes: as i have HD650's and only ever listen a very tame levels i find the gain on my earmax pro too high so dont really get much scope volume wise, Now if I were to use very linear tubes with high gain characteristics say 12at7's and then increase the negative feedback to reduce gain would the amp be more linear than say 12au7 with standard negative feedback?? does that make sense??


----------



## runeight

Theoretically yes the higher gain tube would be more linear if its gain were substantially reduced by the NFB.

 Practically speaking, however, this is almost never true. NFB always involves some amount of phase shift as the signal returns from the output to the input (or wherever it is injected). This means that the cancellation signal can be slightly out of phase with the signal it's supposed to cancel. This phase shifting causes other modulation products such as intermodulation distortion that add other harmonics to the signal and, audio-wise, make the sound worse.

 Some amps (like the beta22) are designed with such high speed and small phase shift that they can support what I consider to be large amounts of NFB and still be extremely audio clean.

 Most average amps cannot support large amounts of NFB and still sound good. In this case the better choice is to start with lower gain and either have no NFB or only a modest amount.

 The SOHA II, for example, has only about 6db of NFB. Just enough to reduce the gain for all tubes to a tolerable range and to reduce the THD without introducing too many sloppy harmonics into the mix.

 On a side note, opamps running in unity gain mode as buffers (which is the way many amps use them) have infinite NFB and this is the reason, IMHO, why they don't often sound as good as discrete buffers that have no NFB. Opamp amps where the gain is set to something reasonable with NFB also must use very high NFB to achieve low gain and, IMHO, still an audio issue. This last category includes some of the opamp based amps that are being built by headfiers (but not all of them).


----------



## holland

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I have looked at the instrinsic noise of the output buffer (more than once) during the prototyping phase and it is very low, so I’m quite sure that it’s not likely that the noise is coming from there.

 Take a closer look at the wiring of the input => volume pot => PCB, all these wires are unshielded and the distance is quite long. Pure from technical point of view, this can’t be healthy for the very sensitive input signal. 
	

	
	
		
		

		
			



_

 

That's good to know, Ferrari. My signal lines are shielded till it hits the PCB (didn't run it directly to the pot). The rest is unshielded. The hiss is there regardless of knob, so it's post-attenuator. There is some additional noise pre-attenuator, but it's characteristic is slightly different, and it's at knob positions I will never hit (75% and higher).

 I do know I have an issue. I knew it when I routed the power lines on my build, but I was hoping there would be no issues. I will re-route.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_But, it's worth looking at the LV+ and LV- rails to see if there is noise on them. And then the base of Q5 and the O/P of the buffers. If there is visible noise on the traces then check whether it's larger at the O/P than it is at Q5. If it is, the buffer is introducing noise. If not the noise is coming from before the buffer._

 

I'll look another day. My back is hurting and I can't bend over this thing any longer.

 FWIW, I knew I had some wiring problems when I initially did it. I have 1/8" spacers and I routed the AC lines back to front under the PCB. I figured I would redo it if I hit some issues. I redid them routing around the PCB, and I disconnected the B+ from where the perfboard runs into the PCB (terminal block) and the hiss reduces dramatically. With the tubes out but B+ in place, it's still there....and I have a bit of a buzz. The buzz reduces, when I pull the LED plug (terminal block). That is definitely wiring issues, with the LED for the switch, definitely. Kind of hard to route, since I have 1/8" spacers and amost no room side to side without crossing over my stepped attenuator or going under the PCB. Anyhow, the buzz doesn't concern me much.

 I think I'm getting noise in from the B+...but that can also mean that my AC lines inherently have noise. I didn't put a pi, CLRC filter, or any of the commercial filters in line from my wallwart. I probably should have.


----------



## GeWa

Quote:


 So, Gewa, does it work??? I see that you used some other transistors on the backside of the heatsinks?? 
 

Haven't tested it yet because of being busy for work!!! Correct about the transistors, I'm using the 2SC2238.
 According to Ferrari they should work also.

 Regards


----------



## runeight

It's really hard to tell with issues like this exacty what the cause is. It is possible that the new style B+ supply is adding more noise than before. I built a proto version of the new B+ supply and used it for a while to test it out. My headphones may not be as sensitive as others, but in my case I didn't hear any increase in noise. That is, the amp was as quiet as before with the original supply. 

 So, for the moment, I don't know . . .

 Ferrari, aren't you using a perf version of the B+? Is there additional noise?


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ferrari, aren't you using a perf version of the B+? Is there additional noise?_

 

I alos had some noise issues with the perfboard version of the HVPS - but I was embarrased to find (what I thought) was the probelm when I redid the B+ with KKLees PCB version - a bad RCA cable jack solder joint. 

 My amp is near silent now with the PCB HVPS - perhaps there was some noise I hadn't attributed correctly. I have some 32R phones on the way and will give another listen -although I'm not sure I am willing to hook the perfboard HVPS back up to A/B


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_...
 Ferrari, aren't you using a perf version of the B+? Is there additional noise?_

 

Botchery constructed HV B+ PS on perfboard can induce noise into the audio circuit of the amp.
 With my initial clumsy spaghetti style 95V B+ PS I did got some serious noise. 

 I then re-work my 95V B+ PS as depicted in the picture below, with more attention to the layout (keep AC traces as far as possible from DC traces, solider ground path…), my B+ works properly, without any audible noise.







 The 120V B+ PS (for my GF amp) has got a similar layout and works very well, without noise.


----------



## Uncle Bob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Well done GeWa. Looks like you are not going to come in as last. 
	

	
	
		
		

		
		
	


	



 Now testing and listening. Enjoy!_

 

No, he's definitely not going to come in last 
	

	
	
		
		

		
		
	


	




 I've ended up short of few parts - doh! Forgot to order C5 and for some strange reason I ordered only 1 each of the 10R and 200R trimpots. And I also don't have a suitable part for the relay. I bought two different parts from Rapid, one is only half the size and the other is the right size but the coil sensitivity is 200mA. 

 I've also not mounted the tube sockets as I'm still debating whether to 'air mount' them, mostly because I'm not confident I'll be able to drill the top holes in the enclosure in the right place to line up with the pcb.

 But I'll keep you posted on progress


----------



## runeight

Uncle Bob have you looked at the drilling templates on the website? There is one for the front panel and one for the top panel. Using these dimensions should line up all of the holes properly.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Uncle Bob have you looked at the drilling templates on the website? There is one for the front panel and one for the top panel. Using these dimensions should line up all of the holes properly._

 

LOL, I was referring to my inability to drill a hole in the right place - I had seen your templates on the website and I intend to make use of them, for the front panel certainly, but I am famously cack-handed when it comes to anything involving measuring, cutting or drilling. 

 I'm considering buying a drill stand, hopefully that will make things a little less error-prone, but then again it's more expense..


----------



## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Haven't tested it yet because of being busy for work!!! Correct about the transistors, I'm using the 2SC2238.
 According to Ferrari they should work also.

 Regards_

 

Take the necessary time to walk through the initial setup… step by step. You will get your amp playing music soon. 
	

	
	
		
		

		
		
	


	



 With these Toshiba output devices, I’m sure you will like it.


----------



## wiatrob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I'm considering buying a drill stand, hopefully that will make things a little less error-prone, but then again it's more expense.._

 


 Full size templates are a great help, printed out to the right size and mounted on thin (file folder) card stock. Then a punch with a steady hand to mark the hole and guide your step bit (you _do_ have a step bit don't you? 
	

	
	
		
		

		
		
	


	




) 

 I have been able to do quite nice work by hand this way.


----------



## grendel23

runeight,
 I am going to try to do a graphic for the front of my amp. Would it be possible to get a hi res image of the yin yang logo? That would look great if it works out.

 Thanks


----------



## Uncle Bob

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Full size templates are a great help, printed out to the right size and mounted on thin (file folder) card stock. Then a punch with a steady hand to mark the hole and guide your step bit (you do have a step bit don't you? 
	

	
	
		
		

		
			





) 

 I have been able to do quite nice work by hand this way._

 

No, that's something *else* I need to acquire 
	

	
	
		
		

		
		
	


	




 BTW You see them (step bits) being offered in sets of 3 with the 1st bit going 4,6,8,10,12 - the 2nd bit offering the same sizes as the 1st plus a few more, then a 3rd bit with a few more step sizes tagged on!, what the hell do you need the 1st two bits for then!, and why don't they make one of the set do 'odd' sizes i.e 5,7,9,11,13, etc - eh?


----------



## grendel23

Does anyone know of a good (cheap) source for the larger transformer, 15-0-15 1.5A needed to run tubes with 300ma heaters? I can find a Hammond at close to $60, Avel has it on their web page, but a search of the web comes up empty.
 I am aware of AnTek, but their voltage is rated at no load, not full load.
 I tried some GE 12BH7A's and like them better than the Sylvania 5963's I have been running. I am going to mount the regulator for heaters off board.
 Has anyone measured current draw? I wonder how far over the ratings I am with the higher current tubes?


----------



## wiatrob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_No, that's something *else* I need to acquire 
	

	
	
		
		

		
		
	


	




 BTW You see them (step bits) being offered in sets of 3 with the 1st bit going 4,6,8,10,12 - the 2nd bit offering the same sizes as the 1st plus a few more, then a 3rd bit with a few more step sizes tagged on!, what the hell do you need the 1st two bits for then!, and why don't they make one of the set do 'odd' sizes i.e 5,7,9,11,13, etc - eh?_

 

Cheaper than a drill press 
	

	
	
		
		

		
		
	


	




 I just got the one bit set - does most all I need it to...


----------



## runeight

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_Does anyone know of a good (cheap) source for the larger transformer, 15-0-15 1.5A needed to run tubes with 300ma heaters? I can find a Hammond at close to $60, Avel has it on their web page, but a search of the web comes up empty.
 I am aware of AnTek, but their voltage is rated at no load, not full load.
 I tried some GE 12BH7A's and like them better than the Sylvania 5963's I have been running. I am going to mount the regulator for heaters off board.
 Has anyone measured current draw? I wonder how far over the ratings I am with the higher current tubes?_

 

Have you removed R3P? If not, what's happening is that the voltage before the Heater regulator is probably pulling down close to the regulated voltage causing the regulator to drop out and produce a bad waveform at its output.

 If you remove R3P (as per the website) you will cook the Heater regulator from the power dissipation with the small heatsink. But, if you use an offboard heatink you might be able to skim by with the 1A transformer. Might. You'll have to try it and measure the voltages both before and after the heater regulator to see if you'll be successful.


----------



## grendel23

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If you remove R3P (as per the website) you will cook the Heater regulator from the power dissipation with the small heatsink. But, if you use an offboard heatink you might be able to skim by with the 1A transformer. Might. You'll have to try it and measure the voltages both before and after the heater regulator to see if you'll be successful._

 

I have not removed R3P. I only tried it for a few minutes to see how these tubes sound and see if it I want to run them bad enough to upgrade. They sound very good as the amp is now. I will probably buy a larger transformer, I just want to find a better price than I have found so far.


----------



## Arkku

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_Does anyone know of a good (cheap) source for the larger transformer, 15-0-15 1.5A needed to run tubes with 300ma heaters?_

 

How about Amveco TE62083, e.g. from Digi-Key?


----------



## czegevara

I'm new here and I want to say hello from Poland!
 I want to buil SOHA II but I have some troubles with completing components to it. And the first question - can I use caps in PS with different capacitance then it is in the design? I mean C3P and C4P - I have 3300uF/50V? And second question - resistors. I have almost all Dale but some of them have slightly diferent value (not above 1% - e.g. 33kohm - I have 33,2kohm).


----------



## runeight

Hi czegevara. Yes, you can use 3300u for C3 and C4 at 50V.

 And you can probably use the Vishay resistors everywhere where their value is close, such as 33.2k, 1.82k, etc. Within 1% is no problem.


----------



## czegevara

Thanks runeight. I thought so but I wont to make sure


----------



## czegevara

And one more question...
 Im not familiar with tubes so can you explain in few words how a higher voltage powering tubes affect their working? How it affect sound quality? Always higher voltage = better sound? And can I adjust HV (55-100V) without any other changes in circuit??
 And thanks for your patience for newbies


----------



## grendel23

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_How about Amveco TE62083, e.g. from Digi-Key?_

 

Digi-Key is the one major vender I did not check. Thanks for the heads up.


----------



## runeight

Quote:


  Originally Posted by *czegevara* /img/forum/go_quote.gif 
_And one more question...
 Im not familiar with tubes so can you explain in few words how a higher voltage powering tubes affect their working? How it affect sound quality? Always higher voltage = better sound? And can I adjust HV (55-100V) without any other changes in circuit??
 And thanks for your patience for newbies
	

	
	
		
		

		
		
	


	


_

 

This is actually a hard question to answer. 
	

	
	
		
		

		
		
	


	




 Most tubes are designed to run at voltage higher than the SOHA II uses. When they run at higher voltages they are more linear and create less distortion. There are exceptions. The 6922 can run very happily at 100V.

 So, theoretically, tubes should sound better at higher voltages. But, my experiences are that some tubes do very well at lower voltages. For example, in the SOHA II the 5963 sounds very good running at 60V even though it really should be running at 150V.

 I know that this is not a great answer, but so much of audio is subjective and everyone's ears are different.

 You can adjust the voltage from 55-100V while the amp is running as long as you do it slowly. If you change the voltage too fast, the e12 will trip, but if you change it slowly the e12 will not be tripped.


----------



## Arkku

Hello again,

 I've now finally had more time to work on my amp, and it's ready for initial tests. I adjusted P2L/P2R as per instructions on the website and got 220mV across R10L and R10R, but the relay on e12 won't trigger. When I measure the voltage across the coil on the relay, I can see it changing from zero to about 12V a few seconds after being powered on, but the relay stays silent and the connections won't change. I'm using the Omron relay in the official BoM.

 Any ideas what might be wrong?


----------



## Arkku

In response to my own post; the polarity of the relay was reversed. I didn't even know that some relays require a certain polarity to trigger, and the greatest thing about this particular one is that the picture showing the + and the − on the top of the relay is _reversed_. It does say “bottom view”, and apparently it means that the picture is inverted, not that it depicts what's actually on the bottom of the relay right under the illustration. Gah.

 Now it clicks.


----------



## runeight

Arkku, I'm not sure what you did to fix the problem. Did you alter the traces on the board? I'm using the BoM relay and it worked without problems when installed according to the board's pad locations.

 So, I'm trying to figure out if there is a problem that needs to be addressed.

 Thanks for the help.


----------



## Arkku

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Arkku, I'm not sure what you did to fix the problem. Did you alter the traces on the board? I'm using the BoM relay and it worked without problems when installed according to the board's pad locations._

 

For various reasons, I'm building my amp on protoboard, not the official PCB, so this was all my own fault. The PCB shown on the website has the relay with the correct polarity; I should have checked there instead of trusting the drawing on top of it. =)


----------



## runeight

OK. Now I see.

 We'll wait for further news from you.


----------



## Arkku

Whee, first sound. The bloody thing works! =)

 I'll report more later.


----------



## pabbi1

Post us the pictures, and no one gets hurt...


----------



## Arkku

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Post us the pictures, and no one gets hurt... 
	

	
	
		
		

		
		
	


	


_

 

I haven't had time to finish the case yet (e.g. drill the holes for the tubes), but here goes…

 The extra toggles on the amp are mostly explained by the selectable inputs and outputs, and the optional crossfeed circuitry with some fine-tuning options. The rest are not so explainable, but I happen to like toggles. =)

 The other box contains the transformer and the power supply (other than the high voltage regulator + capacitance multipliers following it).


----------



## Arkku

By the way, if I try other types of tubes, will I need to re-do the settings, e.g. the tail current with P1L/R? This is my first tube amp (and first DIY amp of any kind), so I'm not really familiar with the differences. =)


----------



## runeight

Well, first thing, arkku, congratulations on a successful build. 
	

	
	
		
		

		
		
	


	




 No, you won't need to make any further adjustments. Just make sure that you set the heater jumpers correctly for the tubes you're using, either 12.5V/150mA or 6.3V/300mA heaters.

 You can adjust the B+ while listening to see if you find a position where you prefer the sound.


----------



## FallenAngel

Just wondering, how hot can the tubes get? I've been running the amp for about 4 hours straight and damn these things heat up. It's unpleasant to keep my finger on the side of the tube for more than a couple of seconds.

 UPDATE: Amp has been running for about 8 hours straight. Tubes still around same temperature - hot enough that I don't want to keep my finger on it for more than 1 second (a real second, not a fraction of one).
 Also confirmed there is definite _hiss_ with 32-ohm Grado RS-1.


----------



## Arkku

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well, first thing, arkku, congratulations on a successful build. 
	

	
	
		
		

		
		
	


	


_

 

Thank you, especially for the excellent work on the amplifier, and also thanks to the entire forum—most of the questions I had about the build were already answered here before I even had to ask them. =)

 I've been listening to the amp now for a few hours today with RCA 5963 tubes, which seem very pleasant, but quite microphonic—any touch on the amplifier results in a “ping” sound from the headphones. Actually the sound is quite nice for the toggles, but a bit annoying when turning the volume. I also briefly tried Channel Master 12AU7A tubes, which weren't at all microphonic. Too soon to say about other differences.

 I also tried both the zener and resistor input buffers, but couldn't hear any notable difference with the equipment currently at hand. I left the resistors in for now.

 Overall, regardless of other parameters, I find the amp's sound very “airy” and pleasant, not at all tiring. Exactly what I was hoping for! =)


----------



## runeight

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Just wondering, how hot can the tubes get? I've been running the amp for about 4 hours straight and damn these things heat up. It's unpleasant to keep my finger on the side of the tube for more than a couple of seconds.

 UPDATE: Amp has been running for about 8 hours straight. Tubes still around same temperature - hot enough that I don't want to keep my finger on it for more than 1 second (a real second, not a fraction of one).
 Also confirmed there is definite hiss with 32-ohm Grado RS-1.
	

	
	
		
		

		
		
	


	


_

 

Tubes will get burning hot. Don't expect ever to be able to touch them. In this amp the heatsinks will also get very hot, which means that the entire amp is very warm in the box.

 This hiss is hard to find. What O/P transistors are you using?


----------



## wolf18t

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Also confirmed there is definite hiss with 32-ohm Grado RS-1.
	

	
	
		
		

		
		
	


	


_

 

I'm not familiar with SOHA II schematic, but did you try to short the input (L and/or R) to ground to check if the noise goes away? It could be related to the wiring from the RCA jacks to the PCB.

 Runeight: Do you still plan (with Jeff) to release FPE panels with the kit? I would be interested. The winter is hitting Canada and I get the itch to build something.


----------



## Ferrari

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_...
 UPDATE: Amp has been running for about 8 hours straight. Tubes still around same temperature - hot enough that I don't want to keep my finger on it for more than 1 second (a real second, not a fraction of one).
 Also confirmed there is definite hiss with 32-ohm Grado RS-1.
	

	
	
		
		

		
		
	


	


_

 

Can you post some close-up pictures of your perfboard HV B+ PS ?
 (both top and bottom including wirings)


----------



## FallenAngel

I'm using BD139 output transistors.

 Thanks for letting me know about the heat. It's now in a Hammond case with a perforated RF-shielded sheet on top.

 I'll post photos of the HV supply tonight Ferrari, thanks.


----------



## mdabro

Ferrari, I have found very nice power button in Your SOHA. Where did You buy it?


----------



## Ferrari

Quote:


  Originally Posted by *mdabro* /img/forum/go_quote.gif 
_Ferrari, I have found very nice power button in Your SOHA. Where did You buy it?_

 

mdabro, that 18mm solid aluminum power button came from ATI Thailand.
 Unfortunately, ATI is out of business a while back.


----------



## grendel23

I just finished the mods to allow the use of 12v 300ma heater tubes. Replaced transformer, moved the heater regulator off board and mounted it directly on the case. and jumpered out R3P.
 Amp sounds great, I really like the 12BH7A tubes I am using now. Much better than the Sylvania 5963's.
 I wish I had built the beefier power supply first time around, would have saved me about $50.


----------



## rds

If we want to use 2SC2238 output transistors do we just put them (reversed) in Q6 and Q7 and keep the other transistors the same as shown in the schematic?


----------



## runeight

Yes.


----------



## runeight

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_I just finished the mods to allow the use of 12v 300ma heater tubes. Replaced transformer, moved the heater regulator off board and mounted it directly on the case. and jumpered out R3P.
 Amp sounds great, I really like the 12BH7A tubes I am using now. Much better than the Sylvania 5963's.
 I wish I had built the beefier power supply first time around, would have saved me about $50._

 

Glad you got that working ok grendel. You can roll almost anything now as long as the pinouts are correct.


----------



## Arkku

Hi,

 I experimented some more with the amp, and decided to put the zeners back in. I still can't hear any increase in noise with them, and I seem to hear a slight improvement (though I may be just imagining it).

 Other than that, I noticed that one pair of my RCA 5963 tubes is insanely microphonic—the other pair is only slightly so, and works much better. I've also tried Electro-Harmonix 12AU7's and Channel Master 12AU7A's, both of which I like. Surprisingly the cheap Channel Masters may even be slightly better… As I'm also testing the SOHA II as a pre-amp, the least noisy Channel Masters are now my tubes of choice for that use. I may prefer the 5963's for headphones.

 I don't have any other tubes at the moment, but eventually I will test more types. I even built my power supply to be ready for the high current heaters (using heatsinks much larger than those specified, 1.6 A transformer and installed a switch to bypass R3P)… Any suggestions for tubes to try? =)


----------



## wiatrob

Arkku;4998811
 Other than that said:
			
		

> I have the same issue with 5963s - I also have two sets, one of which is definitely 'insanely microphonic' (however the microphonics reduced with burn in, but not significantly.) I have another set, nicer, matched closely and_ not _bought of flEabay that are much better.
> 
> I have switched back to Amperex 8416 for the month, and am quite enjoying them...


----------



## Ferrari

I have tried a pair of RCA 5963 (black plate) a while back too. These are indeed very microphonic. 
 Now I’m using a pair of GE 5963 (grey plate) in my GF’s amp and these are very good, much less (or non) microphonic.

 Arkku, when you have your power supply modified to support high current heaters, you might try 6N1P-EB (black plate, double getter supporters). This is a very good sounding tube at a fraction of the cost.


----------



## Arkku

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Arkku, when you have your power supply modified to support high current heaters, you might try 6N1P-EB (black plate, double getter supporters). This is a very good sounding tube at a fraction of the cost. 
	

	
	
		
		

		
		
	


	


_

 

Thanks for the tip, I'll be on the lookout for those. My power supply already supports the high current heaters, it's just a matter of flicking a switch to get R3P out of the way. (I installed it just to keep the regulator from running unnecessarily hot with the tubes I currently have. =)


----------



## Ferrari

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_Thanks for the tip, I'll be on the lookout for those. My power supply already supports the high current heaters, it's just a matter of flicking a switch to get R3P out of the way. (I installed it just to keep the regulator from running unnecessarily hot with the tubes I currently have. =)_

 

In one or other way, I have missed your post some page back.
 It seems to be that you are the first person around here who has built the whole amp on perfboard.
 You must have lots of patience. Enjoy the results!


----------



## Arkku

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_It seems to be that you are the first person around here who has built the whole amp on perfboard.
 You must have lots of patience._

 

Mostly I chose perfboard because I don't build things like this at all that often (indeed, this is my first DIY amp) and I wanted to put in some of my own additions while at it. I also feel a bit like an assembly worker when using pre-made PCBs… =)


 P. S. I posted a shot of the cased amp in the build-pics thread. Now it's suitably finished to remain on the desk while I ponder what to do about the front panel text.


----------



## pabbi1

Dude. that is seriously in a different league... quite impressive.


----------



## Postal_Blue

Wow... very impressive indeed.


----------



## Killercrush

Where can I buy a board and how much is it ?! I guess it's gonna be cheaper with the group buy ... when ?

 Glassjar Audio ?!

 Any help would be appreciated. Thank you!


----------



## runeight

Yes, the boards and kits will be available from Glass Jar. Please contact Jeff Rossel.

 Jeff is currently pulling things together to offer the kits. I believe they will be available towards the end of the month.


----------



## Uncle Bob

Just in case anyone was wondering what was happening with my build...

 Finally got the extra parts I needed and finished installing everything tonight (apart from the tube sockets - still haven't made a decision about that). Decided it was too late to do any testing so that will have to wait until tomorrow.


----------



## runeight

I was. But we can wait another day.


----------



## Uncle Bob

Oh dear! smoke! not a good start 
	

	
	
		
		

		
		
	


	




 D3P and D4P are toast! I've pulled them both from the board and the plated hole of D4P is completely burnt as is the trace from D3P to D4P.

 I'm sure they were installed correctly with the banded end uppermost and I've checked the remaining vertically mounted diodes and they're all installed the same way. 

 I've just verified all the PS capacitors are installed with correct polarity.

 J1,2 & 3 were not strapped so it's nothing downstream from the PS would be causing it.

 any ideas why?


----------



## Ferrari

Uncle Bob, what type of voltage regulator do you have at the 15V LV- position?


----------



## Uncle Bob

Ferrari,

 An L7915CV is installed at LV- with an L7815CV at LV+

 could it be anything to do with how they're mounted onto the heatsinks?

 I've used silpad400 insulated adhesive thermal pads between device and heatsink and the securing bolt has a metal washer and plastic insulator on the the device side, with a spring washer and nut on the other side. I can't take pictures atm so I hope that explains it clearly enough.


----------



## runeight

Can you measure the continuity between the metal tab on the regulators and the heatsinks?

 If these are all open circuit, then it's hard to know what might be wrong.

 The only next step that I can think of (if you're sure diodes and caps are oriented correctly) is to pull the regulators, reinstall D3 and D4 and fire it up to see what you get on the various filter caps.

 Also, please check the transformer wiring to make sure that it is 15-0-15 properly phased.


----------



## wiatrob

Thoughts about using a 6N30/6H30 in the II? Possible? I checked the pinouts against the 6Dj8, but I think the filament current is around 800mA - correct?


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Can you measure the continuity between the metal tab on the regulators and the heatsinks?

 If these are all open circuit, then it's hard to know what might be wrong.

 The only next step that I can think of (if you're sure diodes and caps are oriented correctly) is to pull the regulators, reinstall D3 and D4 and fire it up to see what you get on the various filter caps.

 Also, please check the transformer wiring to make sure that it is 15-0-15 properly phased._

 

I dont get any continuity between the metal tab and the heatsink body but I was getting continuity between the tab and the bolt which concerned me. 

 Some shots of the board after the burn out





















 I've managed to remove the regulators but it was a struggle and some of the caps had a bit of charge in them even after I tried using a bleed resistor as suggested. I ended up cutting the legs off the regulators and then removing the remainder of the legs from the pcb. Some of the pads are looking in quite a sorry state now 
	

	
	
		
		

		
		
	


	




 I won't have time to do anything more on it tomorrow due to prior commitments and, in any case, I have to order some more regulators.

 will keep you updated, but if anyone has any helpful comments in the meantime, please let me know.


----------



## Arkku

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I dont get any continuity between the metal tab and the heatsink body but I was getting continuity between the tab and the bolt which concerned me._

 

Did you measure to the black heatsink surface or the bare leg going through the PCB? The black anodised surface may not be very conductive, but the bolt may have scratched it.


----------



## runeight

Uncle Bob the next step, now that all of the regs are out, is to replace D3 and D4 and repair the evaporated trace (if possible). Then fire up the PS and measure the voltages across C3P, C4P, and C6P.

 If the amp blows up with no regs there is something very wrong in the basic rectifier filter section. It will be a challenge to find it, but I'm pretty sure that we can.

 If all voltages are normal and if you don't get explosions, then we replace the regulators one by one starting with the heater regulator.

 This is the only way I can think of to try to isolate the problem to a specific portion of the circuit.

 Also, one small housekeeping detail for when you case it up. You don't need a heatsink on the HV+ regulator. It won't get very hot and this will save you some space.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Also, please check the transformer wiring to make sure that it is 15-0-15 properly phased._

 

This is how I had the transformer wired, can you confirm this is correct?


----------



## runeight

Yep, that's the right wiring.


----------



## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Thoughts about using a 6N30/6H30 in the II? Possible? I checked the pinouts against the 6Dj8, but I think the filament current is around 800mA - correct?_

 

Unless the pin compatibility with the other SOHA II tubes, I think that the 6N30P-EB (or 6N30P-DR) is an exception since the heater current requirement of this tube is a bridge too far for the LM337 regulator. The LM337 maximum current rating is 1.5A while the current requirement of 2 6N30P tubes is ~1.6A (on average). 

 Other regulators like LM350 (3A) or LM338 (5A) can handle much more current but it requires a re-design of the heater circuit section, with the associated complications.


----------



## Uncle Bob

Sanity check on my board repair please... does this look ok?


----------



## adamus

the trace you repaired with green wire, follow it left, is there a component in there? if so looks like a bad joint. If not then apologies.


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Sanity check on my board repair please... does this look ok?_

 

Checked, it looks good to me.


----------



## Uncle Bob

thanks guys 
	

	
	
		
		

		
			





 I'll let you know how I get on


----------



## runeight

Yes, please let us know what those critical voltages are as soon as you can measure them.


----------



## rhester

got my kit today. can't wait to get started on the build.


----------



## runeight

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_got my kit today. can't wait to get started on the build._

 

Great news! Keep us up to date.


----------



## Uncle Bob

Sorry it's took a while for me to get back to this but I've now plugged the transformer back in and I've checked the voltages.

 I get about 24.5V dc across C3P,C4P and C6P and no smoke!


----------



## runeight

OK!! An auspicious start. 
	

	
	
		
		

		
		
	


	




 I assume you get 24.5 on C3 and -24.5 on C4 and C6?

 Next step is to install the regs one at a time starting with the heater reg, the LV+ and then LV-. Before you install each reg make sure that there is no continuity between the metal tab on the regulator and the metal pins sticking out the bottom of the heatsinks. Also make sure that nothing on the output side of the regulators is accidentally shorted to ground.

 And be sure to get LV+ and LV- in their correct spots.


----------



## Uncle Bob

er....

 If I measure voltage across those caps with the red probe on the + side of the cap each time then they're all +24.5V


----------



## runeight

OK. I see. And makes sense.

 We'll wait for the results of the next step.


----------



## Uncle Bob

thanks. I haven't ordered the replacement regulators yet - I wanted to wait and see if there was anything else I might need, some more insulating washers perhaps? lol

 anyway, I'll keep you posted.


----------



## rhester

What is correct way to wire up the Avel transformer?

 I have blue/violet tied to neutral and grey / brown tied to hot onj primary side. Then have yel / black tied together with orange and red alone. Should read 15V each at orange and red referenced to ground and 0V at the yellow / black combo?


----------



## runeight

Correct. Although on mine I tied the red/orange together as the CT and used the Yel and Blk as the 15VAC leads. But it makes no difference.


----------



## rhester

Did that and powered up. Not such good results. I got 120mV reading on TB+, 4mV reading on TL- and then smoke came out of C12. Where to start?


----------



## runeight

Well, first thing to do is to check the orientation of all the diodes (band facing up) and the capacitors. In particular, is C12P oriented backwards?


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Sorry it's took a while for me to get back to this but I've now plugged the transformer back in and I've checked the voltages.

 I get about 24.5V dc across C3P,C4P and C6P and no smoke!_

 

Uncle Bob I forgot to ask you what the voltage is at C12P?


----------



## rhester

C12 and C4 got swapped during populating the board (guess you really shouldn't have wine with youir solder).

 Swapped them back and still get only mV readings and no negative readings. Will order new caps just in case fried them. But where should I start checking V at? Check J1 and J2 to ground to see if +/- 15V (to check C4)?

 Do still have LEDs lit.


----------



## runeight

C4P (the one you put in for C12P) is certainly toasted since it was running 70V or so over its rating. You'll have to replace it before the negative supply will come up properly. You shouldn't power up with the old C4P in place and it won't be good for the regulator to power up with C4P removed so . . .

 After C4P is replaced with a good cap . . .

 This still could be hard to troubleshoot because other components in the HV supply could also be damaged. This would be C8P, C9P, C10P, and C11P along with all of the multiplier diodes.

 Try removing C12 to see if there is any voltage at its positive terminal. There will be a lot of AC here, but you should still get a DC reading. If this DC voltage is mV then I've got to think about what to do.

 Can you do some probing around with the power applied? If so:

 1. What is the TH voltage?
 2. What is TL+ voltage?
 3. What is the voltage at the + terminal of C8P
 4. What is it at the + terminal of C9P

 This will make a start.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Uncle Bob I forgot to ask you what the voltage is at C12P?_

 

Slightly over 124V dc


----------



## runeight

Thanks. It looks like all of your pre-regulator voltages are on target. 
	

	
	
		
		

		
			





 When do your new regs arrive?


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. It looks like all of your pre-regulator voltages are on target. 
	

	
	
		
		

		
		
	


	




 When do your new regs arrive?_

 

Still haven't placed an order. I rashly decided to build a PPA at the same time and I'm having a real headache with that at the moment, so I'm holding off until I know if I need any parts to fix the PPA.


----------



## rhester

I put the caps in correct and now read proper voltages. I am going to replace all the caps but know for now that they do work. Will continue testing tomorrow.


----------



## rds

Is there any news on the perforated case tops?

 This seems to be just what we need:


----------



## rhester

Any idea where those can be sourced from?


----------



## runeight

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Is there any news on the perforated case tops?

 This seems to be just what we need:_

 

I don't know gents. I haven't heard from Jeff R in a while now so I don't know what the status of the kits is and whether or not he's making the various metal panels.

 I'll email him again . . .


----------



## rds

Quote:


 Any idea where those can be sourced from? 
 

Unfortunately no. I got that picture from the M3 section of AMB's website. The builder is darkisz.


----------



## JamesL

I've seen a bunch of those at case-mod stores.
500mm


----------



## wiatrob

Earlier in the prototype process I thought about supplying these pre-cut (I have a bunch of perforated stock lying about). 

 Cutting with the precision necessary for an exact fit and alignment of tube holes is beyond my resources at this time. 

 However, I could easily do a rough cut - If anyone is interested in a blank that they could cut to exact fit, PM me..


----------



## FallenAngel

Sorry for such a long delay in posting HV supply photos, had this project benched for a week while I was getting other things together. I shortened and untwisted the HV wires after the photo was taken, they are now simply straight wires and about as short as they can be.

 I checked without tubes installed, the hiss is present here as well, so it's from the "front end".

 Here are photos of the HV board.







 I let the amp warm up a bit, the hiss is barely noticeable in anything except these blasted Denon D5000, but it's there, very persistent and quite loud with no music playing. 
	

	
	
		
		

		
		
	


	




 For the top of the case, I actually got this RF shielded screen
http://www.surplussales.com/Cab-Rack...nclosures.html

 Quite easy to cut and work with, costs $15 and enough to make a few amp covers.
 Looks like this:


----------



## Jules

Jeff should be getting the boards this week and he has the kits pretty much ready for ordering, so check your inbox, or email him if you have not received the info. Or, if you want me to email you the info (I can forward his email to you), pm me.


----------



## runeight

FallenAngel;5069257 said:
			
		

> Sorry for such a long delay in posting HV supply photos, had this project benched for a week while I was getting other things together. I shortened and untwisted the HV wires after the photo was taken, they are now simply straight wires and about as short as they can be.
> 
> I checked without tubes installed, the hiss is present here as well, so it's from the "front end".
> 
> ...


----------



## holland

I have hiss also. It's barely audible with my high sensitivity headphones, but very much so with 16-ohm IEMs.

 I haven't had a chance to do much of anything about it. I was just thinking, as well, that it's possible the HV is just a red herring.

 I am using all 3 cap multipliers on the original board.

 I probably won't have much time to look at it till after the holidays.


----------



## runeight

So, would this mean that the hiss is dependent on the impedance of the heaphones and not their sensitivity? That is, high Z sensitive heaphones have less hiss than low Z not-so-sensitive headphones?

 If so, then the hiss would have to be buffer related somehow.


----------



## FallenAngel

The hiss is equal on both sides. I did let the amp warm up some time, noise goes down a bit, but still there.

 I'm not sure what you mean by feeding regulated HV into cap multiplier, the reg is after the cap multiplier.

 I also had a little bit of hiss when I was using the older 60V PSU, can't recall exactly if it was better/worse, I only tested with KSC75.

 I'm not positive, but I don't think it's exactly related to impedance.

 My 60Ohm KSC75 has SPL of 101 dB and I can just ever so slightly hear a hiss, 32 Ohm Grado RS-1 is 98dB and I can hear it very lightly but 25 Ohm Denon D5000 with SPL of 106dB it's very noticeable.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So, would this mean that the hiss is dependent on the impedance of the heaphones and not their sensitivity? That is, high Z sensitive heaphones have less hiss than low Z not-so-sensitive headphones?_

 

I don't believe so. The 16 ohm IEMs would almost certainly have higher sensitivity than the 32 ohm headphones, wouldn't they?


----------



## Beefy

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I'm not positive, but I don't think it's exactly related to impedance._

 

A little bit of probably irrelevant apples v oranges......

 With my Mini Max, ATH-ESW9 (32ohm, 103dB/mW), SuperFi 5 Pro (16ohm, 119dB/mW) and output resistors including 0, 10, 22 and 33ohm, the SuperFi are noisier with 33ohm than the ATH-ESW9 are with 0ohm. That says to me that sensitivity is more important to noise than output impedance.

 Also, the noise drops to virtually zero in all cases if the tubes are removed. The buffer is dead silent.


----------



## holland

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So, would this mean that the hiss is dependent on the impedance of the heaphones and not their sensitivity? That is, high Z sensitive heaphones have less hiss than low Z not-so-sensitive headphones?

 If so, then the hiss would have to be buffer related somehow._

 

I'll have to double check, but my IEMs have the hiss really loud and I believe it's sensitivity is around 120dB (crossroads mylarone x3). I have some other IEMs I can try.

 I know I tested it with my other headphones, and heard a slight hiss with the K81DJ (32 ohm, 115dB/mW) and ATH-ANC7 (260ohm, 109dB) and DT-660 (32 ohm, 96dB). I have tested, but can't recall how loud it was with my M-Audio Q40 (64 ohm, 116dB/mW). I don't hear it with my DT-990, HD650, and K240 Sextett.

 The sensitivity ratings don't list the reference points for all the headphones, so it's hard to say if it's dB/V or dB/mW. Anyhow, it does seem to be more closely related to sensitivity, as the ATH-ANC7 is up there in impedance as well as sensitivity.

 I think it's in agreement with FA.

 Tubes removed, I hear no hiss. It definitely is something in the VAS stage, but where exactly it's hard to say. I did try turning down to 55V and it was quieter, and turned it back up to 95V and it was noticeably noiser. The regulator is worse at noise rejection in the higher voltages. So, it could still be the HV.

 I have pics of my reg I can upload in a few days.


----------



## Ferrari

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_
 I'm not sure what you mean by feeding regulated HV into cap multiplier, the reg is after the cap multiplier..._

 

The capacitance multiplier is the circuit around Q1P and Q2P, yellow marked on the left of the schematic, after the HV-regulator. 
 The red marked circuit on the right of the schematic, before the HV-regulator is the voltage multiplier to multiply the secundaire transformer voltage to a higher desired level.


----------



## FallenAngel

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The capacitance multiplier is the circuit around Q1P and Q2P, yellow marked on the left of the schematic, after the HV-regulator. 
 The red marked circuit on the right of the schematic, before the HV-regulator is the voltage multiplier to multify the secundaire transformer voltage to a higher desired level. 
	

	
	
		
		

		
		
	


	


_

 

Ah, in that case, yes, I am feeding regulated HV to the capacitance multiplier.


----------



## cfcubed

Don't like people posting silly suggestions & hope this isn't one
	

	
	
		
		

		
		
	


	




 Although perhaps not audible, I turn off all fluorescents near my amps when I scope/test them... I've cheap fluorescent lighting over my bench that hums & can show up on the scope (esp. for unboxed builds).

 BTW I'm on my 3rd build of essentially this HV mult/filter (albeit, less TL783 & feeding std SOHA frontends) and have had no problems. Edit: Using 25 ohm D2000s or 250 ohm DT880s.


----------



## runeight

OK. So Holland's info would say that the hiss is at a constant level but that more sensitive phones make it more audible. And, further, that it increases with increasing regulating voltage. Which would definitely point to the regulator.

 I have built the HV ps with the regulator and plugged it onto the proto board exactly as it is on the current boards. I dont' know, offhand, the sensitivity of my headphones, but I did listen for any increase in noise with the HV supply and I didn't hear any. Could just be my headphones are not sensitive enough, or possibly, that some of the regs are noisier than others??

 Does anyone else with the new HV supply have this hiss issue?


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 Does anyone else with the new HV supply have this hiss issue?_

 

Let me take a listen again now that I have a few more sets of cans to listen with. I do remember having more noise with my test headphones (cheap apple earbuds, melted testing the MCubed!) but silence with my 650s

 per cfcubed's comment - I took the amp over to a friends house and nearly soiled myself at the amount of noise coming out of it, until he pointed out the amp was on the same circuit as a flaky neon transformer. I imagine a 'scope would quickly show that noise...

 However, both holland and Fallen Angel have had quite a few builds across their benches, so I would think their baseline for judging noise was established there...


----------



## holland

yeah, most of my amps are quiet. the tube ones tend to be a bit noisier (soha 2 is my 2nd tube after ssmh) but the ssmh has a crappy power section. all my ss amps are dead quiet.

 i'll have to get this on my scope, but my scope is so damned big i hate pulling it out of the closet and i don't have time till the new year.


----------



## Ferrari

My balanced SOHA II is in the making and I have intensively listening to it in both SE and balanced mode this evening. Due to the recent posts here regarding the hiss issue, I have paid more attention to the possible audible hiss, but it’s definitely not on this amp in progress. The ground noise (without input signal) is lower than that from a MH Max, and approximately the same as from my M³, for example.

 Balanced mode: Marantz SA-11S1 => SOHA II (balanced mode) => HD650 
	

	
	
		
		

		
		
	


	



 SE mode: Marantz CD63-KI => SOHA II (SE mode) => HD600 / AKG K701 / AKG K240 / Philips SBC HP1000

 I don’t remember the sensitivities of all these headphones but the impedance of these headphones is ranging from 32Ω to 600Ω.

 I will ask my GF to bring her SOHA II home from the office next week to give it a close listen. 
 That amp is deviated a bit from the stock BOM (120V B+ voltage, current mirror with MPSA92, and some other changes…), but basically it’s a SOHA II.
 (To be followed).


----------



## holland

do you have IEMs? I don't hear it on my 650 and K240. I have the SBC HP1000 as well, I'll pull it out and give it a listen this weekend. I haven't tried it with the SOHA 2 yet.

 SBC HP1000 is 32ohm, 106dB.


----------



## Arkku

I get a very distracting hiss from my SOHA II as well if I plug in cheap IEMs (Creative EP-630, if I recall the model correctly). However, it's silent with both the AKG K-601s and MB Quart QP-280. I also get a slight hiss (inaudible with any actual audio present) if I use the SOHA II as a pre-amplifier for a speaker amplifier.

 In all cases, the hiss is independent of the volume control, so I figure it would be solved by padding the output signal from the pre-amp outs and the 3.5mm miniplug output (I have that as an alternative on my amp, with the switched 1/4" jack turning it off when in use). In both cases this would also give a more useful range of volume control… I'm just not sure yet what would be the best way to achieve this.


----------



## wiatrob

I got a chance to listen away from the noise of computers and heaters (winter is here in the Rockies!) tubes in, iPod source/no source (phones pressed to head):

 HD650's - (Imp. 300, Sensitivity 103dB @1 mV) No noticeable hiss with or without source at full volume

 Yh-3's - (Imp. 125, Sensitivity 97dB @1 mV) No noticeable hiss with or without source at full volume

 325i's - (Imp. 32, Sensitivity 98dB @1 mV) Noticeable hiss with volume >75% with no source ( Without pressing the phones and thereby covering the grills - hiss isn't audible until volume hits ~85%)

 So while it does appear to be there - I'd never subject my ears to that level with music with those 'cans


----------



## Uncle Bob

A quick progress report with my build and a couple of questions

 I've installed H- (LM337) and get -12.6vdc at TH which is correct according to notes on the website.

 I've been a bit paranoid about heatsink to device continuity as I think that's what caused my problems initially. I think that I perhaps overtightend the heatsink bolt and caused the insulating washers to deform on the narrower part that is designed to sit just inside the mounting hole on the heatsink. Because of this, I've been a bit concerned when I measured continuity between heatsink and devic after mounting LV+. But it appears that the centre pin and the heatsink lugs are both connected to ground on the pcb - is this correct? Similarly, LV- has pin 1 connected to ground as well as the heatsink.

 Just checking before I go any further.....


----------



## runeight

That's correct on the regulator pins that are grounded and the heatsinks.


----------



## runeight

Oh, reading your post again, even thought one pin on each of the regs is grounded, the metal tabs on the regs should not have continuity to the heatsinks.


----------



## Arkku

(Except LV+, as its tab is connected to the pin which is supposed to be grounded. Assuming the heatsinks themselves are grounded.)


----------



## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_So while it does appear to be there - I'd never subject my ears to that level with music with those 'cans_

 

My hiss is with the volume all the way down. disconnecting the pot and grounding makes no difference. I suspect FAs is the same, from the description.


----------



## runeight

Gents, I am still a bit stumped. Some of you are having an audible hiss, some are not, and some hear it when the vol pot is turned up with certain headphones.

 I think that all of you have the new HV supply on a breadboard. And we are pretty sure that the buffer is not the source of the hiss. This leaves the B+.

 And this would say that some of the PSs are noisier than others using the same component values (I assume). So why would this be so? It could be a grounding issue. That is, where do the grounds from the HV supply attach to the main board?

 I don't have any further insights at this moment.


----------



## Ferrari

Me neither. 
	

	
	
		
		

		
			





 Regarding the parts I used on my perfboard HV B+ PS, well… apart from the TL783 regulator, all other parts are deviated from the BOM a bit (or a byte) since these parts are what I have in my parts bin accidentally. C8P – C11P are 220/100V on one board and 220uF/200V on the other board while C12P is 680uF/200V bypassed by 1uF MKC. The PS output filter cap C13P on the 2 boards are 10uF MKC and 33uF MKP respectively. All diodes in the PS are 1N4007.
 The ground lead is directly connected to the transformer secondary center tap.

 I don’t know how the PS layout of the problem case here is done? how the AC and DC traces are wired/running?
 For audio applications, PS layout must be treated with utmost care and lots of dedication.
 Multiple crossing and paralleling AC and DC traces (for example) can induce noise in the circuit, which undoubtedly will be audible at the amp output.


----------



## holland

First off, my sincerest apologies for not being able to investigate this further. I seem to have misplaced my 400MHz probes and my 100MHz probes are broken. 
	

	
	
		
		

		
		
	


	




 I'll keep searching for them. I'll see if I can find someone with a scope...I'll bring it to work if I have to, but that's sort of frowned upon. AMB is near me, perhaps I can give him a buzz, if he's not too busy.

 I checked with the Philips SBC-HP1000 headphones, no hiss. It's very suspicious. The last time I saw something like this (though it wasn't a hiss), the buffers were oscillating due to the inductive load of very specific headphone cables. A zobel on the output jack was the solution.

 Here are my pictures. I moved the black wire. It used to be on top, running parallel to a diode. I figured I'd move it underneath with some space and see what happens. No change.

 The black wire is ground and goes to the xformer through the 3-terminal jack.

 also, yeah, busted, I didn't clean the flux off of it.

 The 3rd picture, I changed the routing of the wires. I didn't run wires under the PCB, but underneath the chunk of aluminum to the left. I also had some LEDs wired under the tubes from the proto phase to determine if it was on or not...those have been removed.


----------



## runeight

No apologies necessary at all. I am just grateful for the time you have spent already on this project. 
	

	
	
		
		

		
		
	


	




 Here's one experiment. Try running the ground of the HV board directly to the star point instead of somewhere else.


----------



## rhester

If I were to build this as a 2 box project (transformer in a separate box), how would grounding go? Still star ground the pcb to frame with screw / standoff, and in 2nd box tie incoming ground to chassis? Any benefit besides helpin gtake noise out of the question?

 And on signal input, how has everybody been running to that front input location? IS there a need for shielded, and if so, where do you ground the shield ?


----------



## runeight

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_If I were to build this as a 2 box project (transformer in a separate box), how would grounding go? Still star ground the pcb to frame with screw / standoff, and in 2nd box tie incoming ground to chassis? Any benefit besides helpin gtake noise out of the question?

 And on signal input, how has everybody been running to that front input location? IS there a need for shielded, and if so, where do you ground the shield ?_

 

Yes on the grounds. You may also want to include a means of connecting the chasses of the two boxes. You may or may not actually need this. However, if you run it in the cable where the trafo wires go, there is a risk of picking up hum in the grounds.

 MHO is that it's always best to shield the input wires unless the run is very short. In this case, the shield should be grounded at the end where the wires connect to the input terminal block on the board. There is a ground terminal there for this. The jacks should be insulated and the shield should also be connected to the grounds of the jacks at the other end of the wire.


----------



## holland

going to star ground with a solid 30awg wire seems a bit quieter, the shape changes as well. From a SSSSS to a zzzzz. I would guess (not measured as no eq to do it) about a 3-5dB drop (ears not so good a measurement device). The hiss to buzz could be the inherent noise floor of my environment. I know if I max the volume on any of my cans, I hear a buzz.

 Original was an 18awg solid core to transformer center tap. EI core wallwart with no earthing (3rd prong not connected). I could try to put that to the center tap, it's a pain since the wallwart enclosure is so small.


----------



## wiatrob

I'm using a homemade PCb per KKlee - Grounds from Phoenix connectors straight into the Transformer in connector. I've only removed about half the old PS components (C10 and 3 diodes), HV PS feeds in thru J3.

 I just noticed that my star ground appears to have loosened... I'll fix that when I return from travel next week...


----------



## bmwpowere36m3

I have a few questions regarding the SOHA II build:

 1. I'm assuming Ferrari's revised HV PS has been implemented in the production board, correct?

 2. Are there any modifications nessecary to the "stock" HV PS to run a B+ voltage of ~100V or around there?

 3. Using the most current BOM of Cavalli's site (7007b), are there any useful modifications to be made?

 4. Finally what components would benefit most from 'boutique' stuff, i.e. C1L/R to use a nice PIO film cap?


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## runeight

The SOHA II that is implemented on the board is shown on the website under SCHEMATICS. This implementation, with the trimpot, should give you a range of B+ from about 55V to 95V. Maybe a bit higher than 95V.


----------



## kklee

I hadn't retested the new HV PS with all my headphones, but my modded prototype amp seems to be fine with Grado SR-225's, HD-600's and ATH-W1000's. I get a little bit of hiss at max volume, with a DAC connected.

 The only headphones that exhibited hiss were Shure SE530's, which is expected due to their sensitivity.

 I'm running my home-made PCB for the HV-PS at 90V. I pulled all of the old HV PS parts from the prototype board and added a couple of jumpers to re-route the HV. The HV PS PCB is sitting right next to the SOHA-II and the wires connecting the two boards are about as short as I could make them. I layed out the connections on the HV PS PCB to match up with this mounting position and didn't make any special considerations for noise in the layout. If I remember correctly, I used the spec'd parts for everything.

 The second amp I made for a co-worker doesn't exhibit any hiss either. The only differences in this build were different coupling cap's and no protection circuit.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The SOHA II that is implemented on the board is shown on the website under SCHEMATICS. This implementation, with the trimpot, should give you a range of B+ from about 55V to 95V. Maybe a bit higher than 95V._

 

So that's a yes to Ferrari's original HV PS design and ~95V. To achieve higher B+ would require a modifed HV PS & voltage multiplier, correct?

 What about any useful mods besides those listed in the "tweaks" section and boutique components?


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Oh, reading your post again, even thought one pin on each of the regs is grounded, the metal tabs on the regs should not have continuity to the heatsinks._

 

Sorry for the delay in replying. On the 7815 regs, the centre pin is designated 'ground' and has continuity to the metal tab. As the pcb links the heatsink pins to ground as well as the centre pin, there is necessarily continiuity between regulator tab and heatsink via the pcb traces - or am I confused somehow?

 On the 7915 reg, the centre pin also has continuity to the metal tab but this pin is designated 'input'. In this case the heatsink and regulator tab have no continuity when mounted on the pcb.


----------



## runeight

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_So that's a yes to Ferrari's original HV PS design and ~95V. To achieve higher B+ would require a modifed HV PS & voltage multiplier, correct?

 What about any useful mods besides those listed in the "tweaks" section and boutique components?_

 

That's a yes to the HV design that the prototype team worked out, including Ferrari's excellent suggestion to use the HV regulator. You can add more stages to the HV mulitplier to get higher voltages. Each stage causes some amount of degradation to the output of the multiplier and reduces the current supply capability. However, I don't think that one more stage will matter too much. I think that Ferrari actually proto'd this up a while back.

 As voltages go up, of course, cap voltages need to go up with them and the BC transistors in the input stage should probably be changed to higher voltage PNP transistors.

 I have to let the other builders suggest the mods because my amp is stock.


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Sorry for the delay in replying. On the 7815 regs, the centre pin is designated 'ground' and has continuity to the metal tab. As the pcb links the heatsink pins to ground as well as the centre pin, there is necessarily continiuity between regulator tab and heatsink via the pcb traces - or am I confused somehow?

 On the 7915 reg, the centre pin also has continuity to the metal tab but this pin is designated 'input'. In this case the heatsink and regulator tab have no continuity when mounted on the pcb._

 

Yes, this is correct Uncle Bob.


----------



## Alcaudon

Just another question about grounding.....

 I was planing to build a DIY full wood enclousure for this project, using just an aluminium bottom panel, will this be enough for grounding issues? I can make an aluminium rear panel too if it helps, but I certainly would like to use wood for everything else.

 And...... what about going full wood?


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## runeight

MHO is that a single bottom metal ground panel will be sufficient, particularly if you connect it to the line ground. However, as you know, the wood does not provide any EM shielding for the rest of the amp.

 You might get away with all wood because the board has a full ground plane. You'll just have to try it out.


----------



## Alcaudon

Thanks for the answer runeight!

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_MHO is that a single bottom metal ground panel will be sufficient, particularly if you connect it to the line ground. However, as you know, the wood does not provide any EM shielding for the rest of the amp._

 

That's what i thought, however I just wanted to be sure. And about EM shielding, I was planing a dual case solution for this project, taking transformer far away from signal, and hope not to have any other noise source near 
	

	
	
		
		

		
			





. Maybe I could add some shielding material, like conductive foam or rubber or something like that...... but I will have to build the case and see how it turns out 
	

	
	
		
		

		
		
	


	




.

 Thanks!


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## bmwpowere36m3

what's the status on the Prod PCB boards? Also to run high-current heaters from my understanding you need a 1.5A trafo, removing R3P, and a bigger heatsink for H-. If I were to run 300mA tubes later on, would I need to replace the R3P? Any recommends switches to run for the heater headers (DPDT).


----------



## holland

yes to r3p, trafo, heatsink. you don't need to replace r3p if you're sinked properly. the regs do generate a good amount of heat, the most heat on the board. I'm considering opening some holes in my case above the regs.

 switches should be in the bom. because of the way the switches work, it's reversed from the silkscreen.


----------



## TimmyMac

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Just another question about grounding.....

 I was planing to build a DIY full wood enclousure for this project, using just an aluminium bottom panel, will this be enough for grounding issues? I can make an aluminium rear panel too if it helps, but I certainly would like to use wood for everything else.

 And...... what about going full wood?_

 

I built a Bijou case of wood, with plate steel top and bottom. Works great - but I mounted the tubes and transformer up top to keep heat down.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_yes to r3p, trafo, heatsink. you don't need to replace r3p if you're sinked properly. the regs do generate a good amount of heat, the most heat on the board. I'm considering opening some holes in my case above the regs.

 switches should be in the bom. because of the way the switches work, it's reversed from the silkscreen._

 

Yes there's a main power switch in the BOM but no switch for the heater circuit instead it uses headers and pins.


----------



## runeight

Right. No heater switches on the main BoM. However, on the PS Parts list page on the website, at the very bottom, there are some part numbers for switches that should fit the footprint.

 And another reminder that the switches work opposite to the jumpers so the board markings are reversed when using a typical switch.


----------



## Uncle Bob

Progress report - I know it's slow, but I keep being told to clear the kitchen table 
	

	
	
		
		

		
		
	


	




 Anyway it appears the ps section is now running OK, I get the following voltages

 TL+ 14.9V
 TL- -16V
 TH -12.4V
 TB+ 123.5V

 TB+ seems a little high, is this within an acceptable range to proceed to the next step?


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## runeight

Great. Are you sure about TL- ? Is it too high and out of spec for the regulator if it is really making 16V.


----------



## runeight

Oh, TB+ is ok. I will pull down when it's loaded by the tubes.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Right. No heater switches on the main BoM. However, on the PS Parts list page on the website, at the very bottom, there are some part numbers for switches that should fit the footprint.

 And another reminder that the switches work opposite to the jumpers so the board markings are reversed when using a typical switch._

 

Great, how about the PCB? I've tried contacting Jeff @ glassjar to no avail... are the production boards ready for sale?


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## runeight

I am still waiting to hear from Jeff on availability of boards and kits also. Last time we exchanged emails the board house was late in shipping them out due to their error.


----------



## rhester

Late last week he was trying ot track down the boards. He had everything else ready.


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## bmwpowere36m3

Who here has done the high-current heater mod? I know Ferrari has, I'm trying to find a replacement heatsink for H- and with the size constraints of the BOM case... Would mounting the regulator off-board right to the case provide enough of a heatsink? Or maybe even adding this under it: Mouser PN 532-507222B00


----------



## Arkku

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Who here has done the high-current heater mod? I know Ferrari has, I'm trying to find a replacement heatsink for H- and with the size constraints of the BOM case..._

 

I've done the high current mod (although I put in a switch to toggle R3P in and out as desired, so as not to heat up the regulator unnecessarily with low current heaters). The heatsink I used is Mouser P/N 567-647-15ABP - it just fits inside the Hammond case in the BOM, if the board is placed in either of the lowest two slots. (Note that it's also twice as wide as the BOM heatsink, and won't fit in the same space on the PCB, but you could build that part of the power supply separately on perfboard.)


----------



## grendel23

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Who here has done the high-current heater mod?_

 

I mounted the regulator directly on the case, works fine. The case has more surface area than any heatsink which would fit in the case.


----------



## FallenAngel

Great news. I just finished my second SOHA2 prototype, this one has no hiss with the Denon D2000. It's strange because I have the transformer closer to the board in the same case and the PSU wires are longer.

 The only real difference I can imagine is that I'm using Teflon caps and an Alps RK27 pot while the first one had VitaminQ caps and a stepper.


----------



## m0b1liz3

Hey FallenAngel,

 Can you give a comparison of the SOHA II against the SOHA with Jisbos?


----------



## FallenAngel

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hey FallenAngel,

 Can you give a comparison of the SOHA II against the SOHA with Jisbos?_

 

Soon, very soon. I'll take the SOHA+JISBOS home from work tomorrow and do some listening. The SOHA2 isn't burned in at all so I don't know if it's fair, but we'll see anyway.

 I still really want to figure out why the other one is buzzing, but with one working it's not as pressing of an issue.


----------



## runeight

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Great news. I just finished my second SOHA2 prototype, this one has no hiss with the Denon D2000. It's strange because I have the transformer closer to the board in the same case and the PSU wires are longer.

 The only real difference I can imagine is that I'm using Teflon caps and an Alps RK27 pot while the first one had VitaminQ caps and a stepper._

 

Ah ha. It is great news.

 I don't think the caps would make this difference, but the attenuator/pot difference might. But, mostly this seems like a ground noise issue to me.


----------



## holland

i use vit q and stepped att in my build as well. will try grounding the terminal blocks directly (remove pot) and see what happens. i put 3 pin terminal blocks on the rk27 pads for easy removal since the pot is air wired.


----------



## bmwpowere36m3

Bump for status on prod PCB's


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## runeight

I've just emailed Jeff asking him to post a status update.


----------



## FallenAngel

It really might be a grounding thing. With the HV board air-wired and the ground connected to case at the center, that means the HV board ground needs to travel half the board. I'll see if I can just connect the HV ground to center of the board. Might help.

 I also thought that perhaps it's an issue with the fact that I'm using MJE243 instead of BD139. If I don't get it fixed by playing more with ground, I'll change those out to something else.


----------



## runeight

It actually could be related to choice of O/P devices. Slim possibility, but still there.

 This is because the noise from the BJTs increases with idle current and temperature and the O/P devices are running at 100mA. Compared to the max current for these devices this is very small current, but there could be a small, but audible noise difference between different types of BJTs. 

 I guess I'd have to look at specs and do math to see if this could be real.

 Maybe a better BJT whiz than I am could offer some thoughts on this.


----------



## holland

i've used some toshibas and bd137, it didn't affect anything. i've also swapped tubes around with no benefits.


----------



## runeight

Then we can discount the BJT noise issue.

 Which leaves us with, most probably, either ground current issues or noise from some other components in the system such as the HV regulator.


----------



## FallenAngel

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_...such as the HV regulator._

 

Which you REALLY shouldn't touch, 100V through a finger sucks!


----------



## runeight

It does get your attention though doesn't it. 
	

	
	
		
		

		
			





 You, even the 100V in this, under the right circumstance, can be deadly. So, as always, I urge everyone to understand that you are working with HV and to use all the proper procedures.

 So, how does your new SOHA II sound?


----------



## holland

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Which you REALLY shouldn't touch, 100V through a finger sucks!_

 

LOL! Sorry for laughing at your expense, but it was a good laugh that I needed right about now.


----------



## Jrossel

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Bump for status on prod PCB's_

 


 SOHA II boards have arrived. If you are in the US, you can order the board through glassjaraudio.com International orders please PM (your email) or Email me directly.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_SOHA II boards have arrived. If you are in the US, you can order the board through glassjaraudio.com International orders please PM (your email) or Email me directly._

 

Awesome, already ordered and can't wait to build


----------



## Mikenet

Tube selection question: what tubes would give me the lowest gain in the SOHA II?


----------



## FallenAngel

Quote:


  Originally Posted by *Mikenet* /img/forum/go_quote.gif 
_Tube selection question: what tubes would give me the lowest gain in the SOHA II?_

 

Gain isn't very high, seriously. I'm using GE 5963 and GE 6680 (two builds), there's no problem with too much gain. In fact, I would say that the gain is pretty much perfect for me. I use the middle point of my POT (or Stepped Attenuator) which works perfectly.


----------



## FallenAngel

As promised, a few comments on SOHA+JISBOS vs SOHA2 (both with GE 6680 tubes).

 I'm been listening to the SOHA+JISBOS at work for hours on end and the SOHA2 at home. Tonight I have them side by side, both fed off a simple diyMod (Sonicap Gen1 output) and listening using MarkL modded D5000 headphones. I chose these headphones because they're very detailed and the "brightest" I have to try to catch all the nuances and faults of my music. I listen to a lot of music from French R&B (Jenifer, Koxie, Kenza Farah) to Rap (WuTang, 2Pac, Immortal Technique, Eminem - non-radio stuff, that stuff sucks) to rock (Linkin Park, Korn, System of a Down) to pop/dance (Kelly Clarkson, No Doubt, and even threw on Britney Spears for good measure).

 Both amps sound great and I really enjoy them both, but having them this close together and listening to the same song with both, the differences are clear.

 As some of you you know, I've been dealing with some background noise issues on the SOHA2 prototypes (yes, it's actually on both and when I let the amps warm up for a good 30 minutes, the noise is almost non-existent but still just barely there - definitely not something I notice when listening to music, even through the quiet parts).

 So on to sound comparison.

 First off, I have to say the SOHA2 is a speed demon! The bass (where it's most noticeable) is sharp, hard-hitting and very precise. The SOHA+JISBOS is a little slower and "mellower".

 Bass (continued): More prominent in SOHA2, just a very good quality punch or rumble (when the song has it) instead of what I hear in the SOHA+JOSBOS which is a more mellower drawn out bass line. Certain victory for SOHA2 for my music taste, and I love strong bass, I just don't want to be overwhelmed.

 Mids : Again the mids on the SOHA2 come out to the front a little, more in-your-face than the SOHA+JISBOS. You might say that SOHA2 is more analytical in the mids and it's easiest for me to think of SOHA2 as a strong classical singer while the SOHA+JISBOS is a more of a sultry jazz voice. Depends on mood to which I would prefer at the time; I would usually go for SOHA2.

 Highs : The highs seem more sweet in the SOHA+JISBOS. I would not say the SOHA2 is less detailed, it's not, but the top end does sound sharp (I am trying to avoid using the world "clear" because there is no muddying of the highs at all in the SOHA+JISBOS, the SOHA2 is just more "sharp", perhaps even leaning to shrill with some instruments).

 Note separation: SOHA2, no question. I'm pretty much note-deaf and I hear the instruments with this amp, not just a generalization of which notes they produce. The only other amp I hear that with is the Beta22.

 How everything works together : Both amps have their (as I learned only today) distinct sound signatures. I think both are really great amps and I am enjoying both; choosing one isn't something I would want to do.

 I will not have a final answer to which is better/worse, nor will I write a "conclusion". I like both, I'm very likely to keep both and use both regularly.

 I will leave this note though: for Sennheiser HD600 & HD650, the SOHA2 is a clear winner.


----------



## Mikenet

The gain doesn't seem to be excessive by any means, it's just that I listen at low levels, and hate fighting with the pot(pots have a lot of issues at the lower end of the range). My main amplifier is an output buffer with volume control--it has a gain of 1. The example tubes given on the SOHA II site show gains ranging from 8.7 to 13. It doesn't specify if these are power or voltage gains...most designers list voltage gains. In which case a voltage gain of ~10 would give me a power gain of ~20dB, which would cut my range by a factor of 4(since perceived volume doubles very roughly every 10dB). For most users this is perfect, for me it's just a little loud. If I could change tubes and reduce it somewhat, it'd be worth a shot for me I guess. Otherwise I can just try out one of the standard tubes.

 I wanted to try out tube amplifiers, and it looks like I can't get extremely low gain without sacrificing the sound I'm looking to try out. I could add lots of negative feedback, but that would cancel the "magic" distortion. I could build a cathode follower buffer stage(it would be almost exactly the same topology as my unity gain solid state amplifier...a mosfet source follower), but that would be extremely low distortion, and again, the tube "magic" would be lost. 

 I was looking for low gain tubes to try out in the SOHA II(I'm on winter break...so it looked like a good project to try), as that might help. Otherwise it looks like I'm stuck throwing an attenuator on the input, or doing something crazy like throwing a voltage divider between the input stage and the buffer stage(I'd need to think about it for awhile to see if the voltage divider would even work here...but that would give me some "magic" distortion by driving the tubes hard, and then throwing out the extra level...but it would destroy the negative feedback).


----------



## Mikenet

Great review FallenAngel.


----------



## wiatrob

Thanks FA, for elucidating the subtle yet distinct differences between the low ends on both amps. I've just started listening to the II with Ortho's (per dB's suggestion) and will have a report soon...

 Can't wait to start my second proto build (on the bench RSN), with Toshiba output devices and higher current support...


----------



## runeight

Quote:


  Originally Posted by *Mikenet* /img/forum/go_quote.gif 
_The gain doesn't seem to be excessive by any means, it's just that I listen at low levels, and hate fighting with the pot(pots have a lot of issues at the lower end of the range). My main amplifier is an output buffer with volume control--it has a gain of 1. The example tubes given on the SOHA II site show gains ranging from 8.7 to 13. It doesn't specify if these are power or voltage gains...most designers list voltage gains. In which case a voltage gain of ~10 would give me a power gain of ~20dB, which would cut my range by a factor of 4(since perceived volume doubles very roughly every 10dB). For most users this is perfect, for me it's just a little loud. If I could change tubes and reduce it somewhat, it'd be worth a shot for me I guess. Otherwise I can just try out one of the standard tubes.

 I wanted to try out tube amplifiers, and it looks like I can't get extremely low gain without sacrificing the sound I'm looking to try out. I could add lots of negative feedback, but that would cancel the "magic" distortion. I could build a cathode follower buffer stage(it would be almost exactly the same topology as my unity gain solid state amplifier...a mosfet source follower), but that would be extremely low distortion, and again, the tube "magic" would be lost. 

 I was looking for low gain tubes to try out in the SOHA II(I'm on winter break...so it looked like a good project to try), as that might help. Otherwise it looks like I'm stuck throwing an attenuator on the input, or doing something crazy like throwing a voltage divider between the input stage and the buffer stage(I'd need to think about it for awhile to see if the voltage divider would even work here...but that would give me some "magic" distortion by driving the tubes hard, and then throwing out the extra level...but it would destroy the negative feedback)._

 

Mikenet, the gains listed on the website are voltage gains as you suspected. MHO is that you could increase the NFB by a small amount with little affect on the SQ but a bigger effect on the gain. What gain do you want to have?

 As you read on the website the NFB reduces the gain spread of the different tubes making it possible to roll quite a few different types of tubes with having to make gain adjustments.

 Don't put a voltage divider between the tube and the buffer. That will simply ruin the HF performance of the tube stage.


----------



## wolf18t

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_As promised, a few comments on SOHA+JISBOS vs SOHA2 (both with GE 6680 tubes).

 I'm been listening to the SOHA+JISBOS at work for hours on end and the SOHA2 at home. Tonight I have them side by side, both fed off a simple diyMod (Sonicap Gen1 output) and listening using MarkL modded D5000 headphones. I chose these headphones because they're very detailed and the "brightest" I have to try to catch all the nuances and faults of my music. I listen to a lot of music from French R&B (Jenifer, Koxie, Kenza Farah) to Rap (WuTang, 2Pac, Immortal Technique, Eminem - non-radio stuff, that stuff sucks) to rock (Linkin Park, Korn, System of a Down) to pop/dance (Kelly Clarkson, No Doubt, and even threw on Britney Spears for good measure).

 Both amps sound great and I really enjoy them both, but having them this close together and listening to the same song with both, the differences are clear.

 As some of you you know, I've been dealing with some background noise issues on the SOHA2 prototypes (yes, it's actually on both and when I let the amps warm up for a good 30 minutes, the noise is almost non-existent but still just barely there - definitely not something I notice when listening to music, even through the quiet parts).

 So on to sound comparison.

 First off, I have to say the SOHA2 is a speed demon! The bass (where it's most noticeable) is sharp, hard-hitting and very precise. The SOHA+JISBOS is a little slower and "mellower".

 Bass (continued): More prominent in SOHA2, just a very good quality punch or rumble (when the song has it) instead of what I hear in the SOHA+JOSBOS which is a more mellower drawn out bass line. Certain victory for SOHA2 for my music taste, and I love strong bass, I just don't want to be overwhelmed.

 Mids : Again the mids on the SOHA2 come out to the front a little, more in-your-face than the SOHA+JISBOS. You might say that SOHA2 is more analytical in the mids and it's easiest for me to think of SOHA2 as a strong classical singer while the SOHA+JISBOS is a more of a sultry jazz voice. Depends on mood to which I would prefer at the time; I would usually go for SOHA2.

 Highs : The highs seem more sweet in the SOHA+JISBOS. I would not say the SOHA2 is less detailed, it's not, but the top end does sound sharp (I am trying to avoid using the world "clear" because there is no muddying of the highs at all in the SOHA+JISBOS, the SOHA2 is just more "sharp", perhaps even leaning to shrill with some instruments).

 Note separation: SOHA2, no question. I'm pretty much note-deaf and I hear the instruments with this amp, not just a generalization of which notes they produce. The only other amp I hear that with is the Beta22.

 How everything works together : Both amps have their (as I learned only today) distinct sound signatures. I think both are really great amps and I am enjoying both; choosing one isn't something I would want to do.

 I will not have a final answer to which is better/worse, nor will I write a "conclusion". I like both, I'm very likely to keep both and use both regularly.

 I will leave this note though: for Sennheiser HD600 & HD650, the SOHA2 is a clear winner._

 

Thanks FA for the nice review. What transistor did you installed on your SOHAII output stage? Stock BD139 or else? 

 I think they have their own color like tubes. Would be interesting to know if you have the same installed on your SOHA's JISBOS.


----------



## runeight

Let me add my thanks to FA for the review.

 One thought about the HF of the SOHA II. This feature of my amp is quite dependent on the tube. The 5963 have crystal clear highs whereas the 8416 (a 12V 6922) have a totally different character. OTOH the 5963 are very microphonic and the 8416 are not.

 If you have time to roll some tubes you might (or might not) see similar changes.

 One thing about the SOHA II is that you can roll different tube types, not just different versions of the same tube.


----------



## wolf18t

BTW I just ordered yesterday a kit from Jeff @ Glass Jar Audio. I'm eager to start it. 
	

	
	
		
		

		
		
	


	



 I will customize it a bit by changing the default PS+Audio channels electrolytic caps and buffer stage BJTs.

 I just wish there would be more interest to runeight's custom front and rear panels (from FPE) that fit the recommended hammond case.


----------



## runeight

Just to check one more time, is there anyone else interested in these FPE panels?


----------



## Mikenet

I like the idea of the panels, but I didn't get around to ordering the kit yet, so I didn't want to say yes yet...that, and I'm not thrilled about them costing >$50. How much interest has there been in them so far?


----------



## runeight

There has not been that much interest. Less than 5 people so far. I'm not, by any means, trying to push these on anyone. I am just trying to help those who may not want to do the casework. My panels were very easy to install and use, particularly the rear panel that has the power inlet, switch, and input jacks.

 But I think we need at lest 10 individuals to express interest before we order these so that we can at get the volume discount for 10 items.

 Anyone else?


----------



## Cxrazy

I might be interested.


----------



## m0b1liz3

So the kits are around 200 + over $50 for the face plates? So $250 USD to build a SOHA II? That is not so good with the current exchange rate to Aus $. Wish I had bought a prototype kit earlier!


----------



## luvdunhill

runeight:

 i'm trying to build this out of parts I have on hand. I think the 18K plate resistor is probably the one value I cannot substitute for, per your excellent write-up.. perhaps I can use a zener here instead? I have 15K resistors though. can I use 15K for R16? Also, R5 and R11 can vary slightly, such as 2.7K and 680 for R7? If so, yay for me.


----------



## runeight

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_runeight:

 i'm trying to build this out of parts I have on hand. I think the 18K plate resistor is probably the one value I cannot substitute for, per your excellent write-up.. perhaps I can use a zener here instead? I have 15K resistors though. can I use 15K for R16? Also, R5 and R11 can vary slightly, such as 2.7K and 680 for R7? If so, yay for me._

 

Yes on all counts. The zener will introduce a bit more noise, but you may not hear it. The only other possibility is that you might not be able to dial up 2mA tail current with 2k7. But, I'm pretty sure that that won't happen.


----------



## bmwpowere36m3

The build has begun...


----------



## wolf18t

Nice start! I love these red Wimas. Will you use some boutique parts? I don't know if I'll replace C1s.


----------



## holland

your workspace...it's sooo clean. wow.

 Good start. You're going to really enjoy this amp. It's very nice.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Nice start! I love these red Wimas. Will you use some boutique parts? I don't know if I'll replace C1s._

 

For C1L/R I'm going to use a VitQ .22uF and C5L/R a Muse ES 470uF and then I replaced all the original BOM amp film caps with Wima's. For the PS section I went with all Nichicon UHE, UFW, UPW wherever possible.


----------



## Ferrari

Looks like you are using Vishay Dale RN60D for R7L/R (620Ω). Was it not available as RN55D? or resistors from other brands (BC, Panasonic, Xicon) with the same size as RN55D? Nice start, BTW.


----------



## Uncle Bob

Finally got some time to finish off my SohaII but I've hit a problem 
	

	
	
		
		

		
			





 I've got a very narrow adjustment range of the output voltage of the TL783, I can adjust only from about 113V to 115V from end stop to end stop on the P1P trimmer. This is a 10K trimmer as specified. The voltage at J3 reads 117V.

 I may have damaged the TL783 as it has been desoldered and resoldered once, this would be a real pain as these devices are difficult to buy here in the UK.....


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Looks like you are using Vishay Dale RN60D for R7L/R (620Ω). Was it not available as RN55D? or resistors from other brands (BC, Panasonic, Xicon) with the same size as RN55D? Nice start, BTW. 
	

	
	
		
		

		
		
	


	


_

 

Yea, mouser was out of stock of RN55, so I just went with a RN60... to keep all resistors VD's. Thanks.


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Finally got some time to finish off my SohaII but I've hit a problem 
	

	
	
		
		

		
		
	


	




 I've got a very narrow adjustment range of the output voltage of the TL783, I can adjust only from about 113V to 115V from end stop to end stop on the P1P trimmer. This is a 10K trimmer as specified. The voltage at J3 reads 117V.

 I may have damaged the TL783 as it has been desoldered and resoldered once, this would be a real pain as these devices are difficult to buy here in the UK....._

 

Well . . . . . . . is there any way that you can get a replacement? I think you assessment is correct.


----------



## bmwpowere36m3

some more progress...


----------



## wiatrob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I may have damaged the TL783 as it has been desoldered and resoldered once, this would be a real pain as these devices are difficult to buy here in the UK....._

 

UB, I believe I have a spare I can send, PM me if you are interested... <EDIT> Yup, I have one...


----------



## Uncle Bob

Bill

 Thanks for your kind offer but I've found a seller on ebay. He's charging top dollar but needs must so I ordered one last night. With any luck it will be here before xmas.


----------



## bearmann

Hi everybody! 
	

	
	
		
		

		
		
	


	



 I'm very, very interested in the SOHAII, but I don't know if it'll fit my needs.
 I have a pair of Audio Technica W100, which are rather efficient and driving them with a CK²III (Gain 9) was quite impossible.
 Now I'm curious how they would perform with a gain around 12?! (which is the gain of most tube combos inside the SOHAII, afaik)

 Is the SOHAII capable of driving efficient headphones or should I stick with another project?!

 Thanks a lot and best regards,
 bearmann


----------



## bmwpowere36m3

I just finished assembling the PCB and have started to test the circuit out... TL+, TL-, and TH check out. TB+ is ~122V, is that okay, the setup says +103V?


----------



## runeight

Yes, I think that's ok. The B+ will be a little high when there is no load. I'm assuming that no jumpers are jumped right now. When you get the buffers going their load should pull the B+ down considerably and then the B+ into the HV regulator should be ok so that you can connect J3. But check this at each step.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, I think that's ok. The B+ will be a little high when there is no load. I'm assuming that no jumpers are jumped right now. When you get the buffers going their load should pull the B+ down considerably and then the B+ into the HV regulator should be ok so that you can connect J3. But check this at each step._

 

Yes, I haven't jumpered anything yet.


----------



## runeight

OK. I think you're good to set up the buffers. It might be good to recheck all resistor values before you jumper J1 and J2. Then go for it.


----------



## holland

Quote:


  Originally Posted by *bearmann* /img/forum/go_quote.gif 
_Now I'm curious how they would perform with a gain around 12?! (which is the gain of most tube combos inside the SOHAII, afaik)

 Is the SOHAII capable of driving efficient headphones or should I stick with another project?!_

 

About 9 with a 12AU7. More with different tubes.

 All amps are capable of driving efficient headphones.  FWIW, I use a 24-step attenuator, with a 2Vrms source. With my efficient headphones, I'm around 2-3 clicks, maybe 4 max for current production music. For stuff recorded around 89dB max, I'm about 4-5 clicks. With a 1Vrms source, I can probably extend another click or two.

 There are things you can do to reduce the gain, but it may be negative, depending on what you prefer. One thing is increasing the amount of negative feedback. Another is using a finer grained attenuator.

 It's entirely up to you, but I'm not sure you'll find many tubes or hybrids that are unity gain or a gain of 2. While it would be nice for another builder, you might be better off looking for a tube buffer, if you're looking for tubes.

 If you've ever played with gain, you might be surprised how little you really need for efficient headphones. I think for some of my high sensitivity headphones, the last time I measured, I really only need a range of 500mV rms swing and a current buffer to have good use of the volume knob.


----------



## bearmann

Thanks for the statement, holland. I think I'll stick with a non-tube low-gain design.

 best regards,
 bearmann


----------



## wiatrob

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Wish I had bought a prototype kit earlier!_

 


 FWIW, you probably would have spent MORE on a prototype


----------



## rds

Quote:


 FWIW, you probably would have spent MORE on a prototype 
 

Lol, yeah. Or spent something on prototyping nothing.
 Anyways, some day soon my production board will be showing up and it will all be well worth it I imagine.


----------



## runeight

Another small FWIW m0b1liz3 IIRC the kit comes with the transformer and the hammond case (the large one). So you won't have to buy these separately.


----------



## bmwpowere36m3

More testing is underway...





















 Test Values:

 TL+ 15V
 TL- -15.2V
 TH -12.5V
 TB+ 111V

 O/P Quiescent Current ~100mA

 TB+L/R ~65V

 Tail Current 2mA

 TPL/TPR ~60V

 For some reason, I'm not getting ~40V at TPL/TPR. When I measure the plate voltage at the socket I get Pin 1 on both ~40V but Pin 6 ~60V, so something isn't splitting the voltage between the plates?

 *Edit* the only things not connected are the pot, and inputs. Also the E12 relay continues to click once powered. It's fairly sporadic... This is with tubes installed, EH 12AU7A


----------



## luvdunhill

just curious, why would you expect things to work without the pot installed?


----------



## bmwpowere36m3

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_just curious, why would you expect things to work without the pot installed? 
	

	
	
		
		

		
		
	


	


_

 

I didn't expect the pot to make a difference at this point... if it's as simple as that than I'm relieved. But I don't want to solder it in and then things still won;t work. I thought, maybe Q1 or Q2 got damaged and are not "mirroring/splitting" the current thru the triodes, thus allowing full B+ voltage to the second plate.


----------



## runeight

bmw the pot needs to be installed for the input stage to bias properly. I should probably say this on the website.


----------



## Ferrari

bmw, if you have an Alps RK27 volumepot on hand, follow runeight instructions.

 In case you don’t have a volumepot on hand yet, you can temporarily shorted the input and go further with the initial setup. From the PCB top view, connect a lead (resistor snip) between the right and the middle solder point of the Alps RK27 volumepot. Do this for both channels of course. Hope your amp up and running soon.


----------



## DrkRipper

My kit is on its way...hope you guys are prepared for all the questions I'll have once it arrives


----------



## bmwpowere36m3

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_bmw the pot needs to be installed for the input stage to bias properly. I should probably say this on the website. 
	

	
	
		
		

		
		
	


	


_

 

Awesome, I have one on hand I just didn't want to put it to waste if it didn't work.


----------



## runeight

Quote:


  Originally Posted by *DrkRipper* /img/forum/go_quote.gif 
_My kit is on its way...hope you guys are prepared for all the questions I'll have once it arrives 
	

	
	
		
		

		
		
	


	


_

 

We're ready.


----------



## bmwpowere36m3

What a relief, got my SOHA II up and running 
	

	
	
		
		

		
		
	


	




 Everything checks out good and I'm running 90V B+ along with EH 12AU7's for the time being. So far the setup has great synergy with my HD580's, but as the amp continues to burn-in time will tell. I'm truly impressed by the sound and can't wait to start rolling in some tubes, next up hopefully will be some Russian 6N1P-EB's.

 I just like to say I have a SOHA II tube thread, that hopefully users can populate with their impressions & opinions.

 My "test" setup and test headphones:










 ^^^Listening to a little Pink Floyd


----------



## wolf18t

Congratulations, nice build! What have you finally used for C1L/R? They seem soldered below the PCB.

 My kit was shipped by Jeff last tuesday, I'm eager to get and start it. I've also ordered .22uF Jupiter caps (C1L/R) and NOS Sylvania JAN 12AU7 tubes from Parts Connexions. I'm a total tube newbie, I wish they will sound OK with my RS-1. 

 BTW do tubes will benefit from matching in the SOHAII design?


----------



## bmwpowere36m3

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Congratulations, nice build! What have you finally used for C1L/R? They seem soldered below the PCB.

 My kit was shipped by Jeff last tuesday, I'm eager to get and start it. I've also ordered .22uF Jupiter caps (C1L/R) and NOS Sylvania JAN 12AU7 tubes from Parts Connexions. I'm a total tube newbie, I wish they will sound OK with my RS-1. 

 BTW do tubes will benefit from matching in the SOHAII design?_

 

I have C1L/R mounted under the board yes, they're VitQ's .22uF. I wouldn't run Jupiter caps, since this amp runs pretty hot and those beeswax covered PIO caps definitely wont tolerate the heat, maybe I'm wrong but double check with runeight and others.

 From my understanding how "sellers" typically match tubes is no where near the operating conditions typical in most amps... so I think its fairly useless. If its free then go for it.


----------



## Ferrari

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_What a relief, got my SOHA II up and running 
	

	
	
		
		

		
		
	


	




 Everything checks out good and I'm running 90V B+ along with EH 12AU7's for the time being. So far the setup has great synergy with my HD580's, but as the amp continues to burn-in time will tell. I'm truly impressed by the sound and can't wait to start rolling in some tubes, next up hopefully will be some Russian 6N1P-EB's.

 Listening to a little Pink Floyd 
	

	
	
		
		

		
		
	


	


_

 

Good to know that your amp is up and running smoothly. 
 Enjoy!


----------



## runeight

Congrats bmw. Looking foward to your case up now and your listening impressions. I assume the build was straightforward with no problems? 

 wolf18t, tube matching is not necessary as the SOHA II can handle most typical mismatches. However, tubes that have really bad mismatches may not work and you will simply hear this as some form of clipping or audio distortion. So far, no one has reported a tube that has failed in this way.


----------



## Uncle Bob

Finally!

 My SOHAII is making music 
	

	
	
		
		

		
		
	


	




 It's fitted with a pair of 13D5A tubes which I wasn't sure would work.. it's not one that appears on most of the equivalents lists but the guy who sold them to me assured me they were ECC82 equivalents and it seems like he was right

 My only concern at this point, is the voltage drop between TB+ and TP is only around 13V. Should I be worried about this? I'm getting 400mV across R6 on both channels.

 Not had any chance to do serious listening yet, but I hope to spend a hour or two tonight enjoying the new amp.


----------



## runeight

Yaaaa!!! I am very happy to get this news. 

 I assume that you mean TB+L minus TPL is about 13V? And the same for the right channel? This means that the individual triode sections area bit more out of balance than typical, but not critically so. Let it run for a while and see if things change.

 What have you set the B+ to be at this point? Whatever it is you can be free to adjust it from it's lowest to highest value using the trimpot.


----------



## Uncle Bob

Yep, TB+L minus TPL is around 13V. TB+L/R is 70V, heater voltage for the tubes is set to 12.6V

 Just off to spend some time with my new toy, will report back any observations tomorrow


----------



## Ferrari

Very good news Uncle Bob. You have beaten Gewa, as far as I can see.
 Congratulations and enjoy your new toy!


----------



## Uncle Bob

I can't believe I've beaten Gewa, I reckon he's spending too much time listening to it to let us know he's finished. In any case, I still have the casework to do
	

	
	
		
		

		
		
	


	




 I think I'll go for one of those Galaxy cases from Italy.

 Anyway back to the matter in hand. I bought a 10 pack of tubes so I've gone through them with B+ @60V and get a spread of results from a low of 39.6V to a high of 46. Swapping tubes around doesn't seem to make any difference to the results, the votage readings follow the individual tube. Equally, setting B+ @80V just pushes the result of a given tube up exactly 20V although some of the tubes read 21 or 22 volts higher. I'm not using a branded meter so there's obviously room for error here as well. The max B+ I can get out of my Soha is 99.8V. I've ended up today with two of the closest matching tube pairs reading 63V each with B+@80V and that is the setup for tonight's session.

 It was a joy listening to it last night 
	

	
	
		
		

		
		
	


	




 Tried with my Grado SR225 and liked it a lot. I played Natalie Cole's "A Woman Who Knows" and was particularly impressed on how metallic the struck and brushed cymbals sounded, just like they should do. Her vocals were presented as intimate and warm but quite natural. I then moved onto Dire Straits "Love Over Gold" (yeah I know but it is one of my reference pieces and still one of my all time favourites) and it performed pretty well here except for a slight sense of squashed dynamics if I was being ultra critical. This may be down to the tubes of course, but atm I don't have any other brands/types to compare against - a situation I will have to address quite soon 
	

	
	
		
		

		
		
	


	




 I then switched to my Senn HD650's and Alan Parsons "I Robot". My initial impression is that I don't like this combo as much as the Grado. Some people refer to the HD650's as dark sounding and that's what they sounded like here. Again a different tube choice might change the sound signature entirely, so ymmv as they say. In any case, some more listening time is needed before any conclusions can be reached for me.


----------



## Uncle Bob

I was thinking last night about casing up my SOHAII and I thought it would be nice to have a bi-color led wired into the E12 circuit so that the led would initially be red to indicate power on and then green when the E12 enables the relay. 

 Would this be easy to implement?


----------



## runeight

Since you want to use a common cathode LED, this is about the easiest way that I can think of. The PNP devices can be 2N3906, BC560, 2N5087, etc, but anything with hfe over 100 should be suitable.

 Set the RLED for 10mA or less. This is to protect the TO92 regulator on the SOHA II board by keeping its power dissipation as low as possible. 10mA should light most LEDs that you might want to use.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Congrats bmw. Looking foward to your case up now and your listening impressions. I assume the build was straightforward with no problems? 

 ...._

 

Thanks, so far I'm really impressed by this amp. Definitely a lot better than the "SS" Hybrid and CMoY it has replaced. I've been listening to it with Senn HD580's and EH 12AU7 tubes thus far and I really enjoy the sound. The amp has been burning in for over now ~90hrs straight (have been listening here and there; at night letting it just run with a "test" set of headphones). I'll say the EH tubes have definitely settled in since when I first listened to them.

 The build was straightforward and nothing really stood out as problematic. I only had trouble since I didn't install the pot before testing and was worried something had been damaged. WHen that was alleviated, I finished up the build no problem. Since I changed up my build, I had some "problems" getting everything to fit... eventually figured out the layout.

 The EH tubes at first were a little harsh and very in your face, forward soundstage. As they burned in they've settled back, but still have a forward presentation. They have clear, defined highs, good midrange punch, and bass detail. I'd say the only thing they lack is maybe some more bass slam and midrange bloom, however like _Holland_ has mentioned elsewhere they sound wonderful paired with "Metal".

 I've listened to music ranging from Pink Floyd, Led Zeppelin to Metallica, Alice in Chains, In Flames, AC/DC, to some classical. It all sounds good and much more detailed than any other amp I've had thus far... when I start rolling tubes I'll be looking for something with a "warmer" sound (for Floyd, Classical, etc..), as the EH's are fairly neutral compared to my "SS" Hybrid which was very "tubey" sounding and a little overly warm.

 I'm impressed 
	

	
	
		
		

		
		
	


	




 and here are some pictures of it cased up for now, it'll stay like this till I get some more time to finish it up with a top. Also the knob is temporary, scavenged from my "SS"...


----------



## bmwpowere36m3

Guess I still have a couple questions
	

	
	
		
		

		
		
	


	




...

 First, is the BOM switch supposed to be lit when "OFF" and not lit when "ON". Since I've tried different wiring schemes and it either works that way or not at all.

 Second, what's the best way to "reset" or adjust the O/P quiescent current, with the tubes removed, tubes in, doesn't matter? Any advantages to running a higher current?

 Third, adjusting the "tail current", again are there any advantages to playing around with this? If I understand correctly the "tail current" (plate current?), plate voltage, and grid voltage sort of go hand in hand. With the Stock figures, plate voltage ~40V, plate current 2ma, the grid voltage is ~-1V (based on EH 12AU7 datasheet). I'm still learning these things, I know you want to keep the grid negatively biased, so if you input from a "CD-source" then you get ~1Vrms. So is -1V grid voltage enough or it just works, I also understand you don't want to much negative grid voltage, sort of counter productive.

 So to achieve a -1V grid voltage at ~80V plate voltage, you'd need ~5-6ma plate current... Maybe this is just a fruitless quest, does it really matter I guess. Any helpful advice or source of info to read would be great. Thanks and Happy New Year to all.


----------



## runeight

Nice job on packaging up that build bmw. I was wondering how you were going to fit the heatsink for the heater reg. But you went ahead and attached to the box. Good idea. 
	

	
	
		
		

		
		
	


	




 The switch is supposed to be lit when ON. This probably means that the power connections to the switch are reversed? Which would mean that my wiring diagram on the website is incorrect. I haven't wired the light because I don't want to have the extra illumination and so haven't verified the wiring.

 You can adjust the O/P current anytime, tubes or no tubes, but I recommend removing the headphones first.

 You might hear differences when you change the tail current because the idle current is so low. But, to keep the tube stage working properly you'll have to adjust R4 to drop 18V for whatever value of current you choose.

 Right now the tail current is 2mA making each triode pass 1mA. !8V, obviously, means 18k at 1mA. If you adjust the tail current to 4mA you'll have 2mA in each triode and you'll need 8k5 (or close) to get the right plate voltage.

 Alternatively you can use the 18V zener as shown on the website. Then the plate voltage will be independent of tail current. You may, however, hear zener noise. 

 You don't really need a grid bias equal to the maximum peak voltage of your input signal. This is because the common cathode input stage has some amount of negative feedback applied. You can probably get away with as low as 300mV before you'll start having problems. 

 The data sheets for tubes are notoriously bad at these low voltage low current conditions. Often the curves were extended from the actual data points using French curves. Having said that you can try to use the curves to figure out where the bias will be. It will be different for each different tube type and different for tubes of the same type. Don't forget that you can increase the B+ to over 90V. This will help to increase the cathode bias voltage for a given current.

 If you don't want to look at the plate curves then just try it and measure the cathode voltage. If it is above 300mV you're probably ok. If not, you'll hear it pretty quickly.

 Tube rolling - I have noticed that the 6922/6dj8/8416 tubes have a more tubey sound and better bass compared to the 12au7s types. Also, with your super heater supply you can try those 6n1ps and 12bh7s. I have no idea what they sound like.


----------



## runeight

bmw I have posted a new inlet wiring diagram on the website. I'm pretty sure that if you wire it this way the light will work properly.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Since you want to use a common cathode LED, this is about the easiest way that I can think of. The PNP devices can be 2N3906, BC560, 2N5087, etc, but anything with hfe over 100 should be suitable.

 Set the RLED for 10mA or less. This is to protect the TO92 regulator on the SOHA II board by keeping its power dissipation as low as possible. 10mA should light most LEDs that you might want to use.




_

 

Thank you for taking the time to work that out for me, it even looks simple enough for someone like me to implement 
	

	
	
		
		

		
		
	


	




 I'll let you know how I get on.


----------



## runeight

You're welcome. 
	

	
	
		
		

		
		
	


	




 Here's an alternate way to wire the LEDs that might be preferable because it keeps the LED current out of the ground flow. RLED is calculated using 24V instead of 12V.






 Edit: I've changed the drawing slightly to be consistent with common representations of dual LEDs. And, of course, one can always use individual LEDS.

 I've also changed one resistor value. It's not important, but it does serve to equalize the base currents for the alternate version.


----------



## holland

That's a really cool idea, Uncle Bob.


----------



## DrkRipper

Alright...question time:

 I have everything assembled and voltages set correctly. With tubes in and music playing I only get music from the right channel. TB+L is ~60V and TB+R is ~25V. When the tubes are out they are both 60V. Sometimes when I change the volume the relay trips, the music stops...then a few seconds later it comes back on. Also I may have screwed up a transistor...I did not use a heatsink which I read noobs like me are supposed to use...so it might be a bad transistor. Any ideas?


----------



## runeight

That's good, mostly. 
	

	
	
		
		

		
		
	


	




 The first thing to do is to replace Q1P. This is the cap multiplier for the right channel. This type of problem is usually caused by a shorted Q1P (or Q2P on the other channel).

 Let us know if this works. If not, the next step is to replace Q1 and Q2 in the amp section.

 If this doesn't work then we've got some thinking to do . . .

 It is normal for fast rotations of the volume control to trip the e12. But if this happens at all times then it also indicates a problem

 Were you able to set the bias currents for both the O/P stage and the tube stage?


----------



## DrkRipper

I replaced Q1P, and now TB+L and TB+R are both 60V. It also fixed the e12 tripping problem. However the left channel is much lower volume than the right channel. I assume this means I also screwed up a transistor in the amp circuit. And yes, the bias currents have been set.


----------



## runeight

Since all of the gain comes from the tubes the bjts in the amp can't do much damage except to mess up the voltages. And since you can set your O/P current in both buffers and the e12 works ok then these bjts are almost certainly working properly.

 So we have to figure out what's causing the left channel tube to not have enough gain.

 Could you kindly check all the resistor values around the tubes. Particularly the two feedback resistors R8 and R7. Are they possibly reversed?

 Also, what are your TPR and TPL??


----------



## DrkRipper

Well...I feel pretty dumb, after checking all the resistors several times, I figured out the problem with left channel. I had the headphone plug too far in, since I don't have the front panel on. 

 So I got to listen to it...sounds pretty good so far, however I'm noticing some distortion on certain notes, and on a particularly loud section of one song the e12 tripped. I thought this might have something to do with the bias current settings. I check the O/P and it was lower than I had set it, around 200mV so the current would be 90 mA. I tried to turn it up, but now I can't get it above 215mV before I run out of adjustment, I thought that was kind of odd, could it be causing the problems? The other measurements were fine, for the tail current and the difference between TP and TB on both channels. 

 Thanks for helping with all this


----------



## runeight

Hmmm. Not good. 
	

	
	
		
		

		
		
	


	




 Is it possible that when the jack was in too far it was shorting the output?

 In any case, there is a lot room on the bias pot to set the current properly. Please check all of the resistor values in the O/P stage.

 If these are ok then the first question is does the distortion happen on both channels or just one? Are the rail voltages correct?

 You might have to replace Q8 on the channel where you can't set the idle (or both if necessary). And then, possibly, Q7.


----------



## DrkRipper

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hmmm. Not good. 
	

	
	
		
		

		
		
	


	


_

 

That's what I was afraid of. 
	

	
	
		
		

		
		
	


	




 It doesn't look like the input was shorting out, it was just making a bad connection (hitting the resistive bands). As far as I can tell the distortion is in both channels, also both channels act the same when setting the current. Unfortunately I am leaving in the morning, so I won't be able to work on it for a couple days. I'll post back when I've had a chance to check all of the resistors, etc. 

 Thanks again for the help, and happy new year


----------



## holland

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Thanks, so far I'm really impressed by this amp. Definitely a lot better than the "SS" Hybrid and CMoY it has replaced. I've been listening to it with Senn HD580's and EH 12AU7 tubes thus far and I really enjoy the sound. The amp has been burning in for over now ~90hrs straight (have been listening here and there; at night letting it just run with a "test" set of headphones). I'll say the EH tubes have definitely settled in since when I first listened to them.

 The build was straightforward and nothing really stood out as problematic. I only had trouble since I didn't install the pot before testing and was worried something had been damaged. WHen that was alleviated, I finished up the build no problem. Since I changed up my build, I had some "problems" getting everything to fit... eventually figured out the layout.

 The EH tubes at first were a little harsh and very in your face, forward soundstage. As they burned in they've settled back, but still have a forward presentation. They have clear, defined highs, good midrange punch, and bass detail. I'd say the only thing they lack is maybe some more bass slam and midrange bloom, however like Holland has mentioned elsewhere they sound wonderful paired with "Metal".

 I've listened to music ranging from Pink Floyd, Led Zeppelin to Metallica, Alice in Chains, In Flames, AC/DC, to some classical. It all sounds good and much more detailed than any other amp I've had thus far... when I start rolling tubes I'll be looking for something with a "warmer" sound (for Floyd, Classical, etc..), as the EH's are fairly neutral compared to my "SS" Hybrid which was very "tubey" sounding and a little overly warm.

 I'm impressed 
	

	
	
		
		

		
		
	


	




 and here are some pictures of it cased up for now, it'll stay like this till I get some more time to finish it up with a top. Also the knob is temporary, scavenged from my "SS"..._

 

I missed this. It looks nice, bmw. I'm glad you're enjoying it. It's really no surprise it's better than the SS or a CMoy. It's a different class.

 I'm rolling 8416 and 6189 right now. Will roll some 5814s later. I'm finding I'd rather relax and listen to music than build my Bijou. 
	

	
	
		
		

		
		
	


	




 I really hate casework.


----------



## Hayduke

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Don't worry, that is a good reason for me to put this amp into this enclosure ASAP. 
	

	
	
		
		

		
		
	


	


_

 

Ferrari I have a question about this build. I'd like to build mine "upside down" too so the tubes will stick out further. I like they way they look 
	

	
	
		
		

		
		
	


	




 My question is about heat. By doing this, aren't you dramatically affecting how well the heat sinks work? The heat would travel up and get stuck on the board.

 Maybe it's not an issue, but it has me worried, so I thought I would ask how yours is working.


----------



## holland

^^ I missed that link too, Ferrari. Damn, you keep taking things further. That one is really badass.

 I think you had better stop. I don't know about others, but I'm starting to feel inadequate.


----------



## regal

Is it true that there will be front and back panels available for the Hammound enclosure?


----------



## onform

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Is it true that there will be front and back panels available for the Hammound enclosure?_

 

I don't think there was enough interest in them. To be fair Runeight did put it to the test to to see if enough people would buy them but he got very little feedback.. I might be wrong though of course..


----------



## Arkku

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I'd like to build mine "upside down" too so the tubes will stick out further. I like they way they look 
	

	
	
		
		

		
		
	


	


_

 

As an alternative to the “upside down” build, I mounted the tube sockets on a separate platform made from scrap aluminium. It slides into the second highest slot in the Hammond case, which leaves enough room for the stock heatsinks below if the amp itself is in the second lowest slot.





 See here for how it looks with the lid on—the tubes stick out almost completely. Also very convenient for tube rolling, as I don't have to worry about putting too much pressure on the board.

 I think Ferrari also made a similar platform for his other SOHA II build?


----------



## runeight

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_I don't think there was enough interest in them. To be fair Runeight did put it to the test to to see if enough people would buy them but he got very little feedback.. I might be wrong though of course..
	

	
	
		
		

		
		
	


	


_

 

This is true. I have offered on several occasions to have these panels made and sold through GJA but there hasn't been quite enough interest. Partly, I suspect, because they are so expensive.

 To make this worthwhile we need to make at lest ten sets. The price would be $18 for the front panel and $22 for the back panel. This adds $40 to the cost of the kit from GJA.

 Jeff was going to look into having the stock hammond panels (since the hammond enclosure comes with the kit) punched out by a local machine shop, but I don't think there has been progress on that front.

 That's all I know . . . let me know what I can do.


----------



## Ferrari

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Ferrari I have a question about this build. I'd like to build mine "upside down" too so the tubes will stick out further. I like they way they look 
	

	
	
		
		

		
		
	


	




 My question is about heat. By doing this, aren't you dramatically affecting how well the heat sinks work? The heat would travel up and get stuck on the board.

 Maybe it's not an issue, but it has me worried, so I thought I would ask how yours is working._

 

Yes, you are correct that the heat would travel up and get stuck on the board… _in a closed box_.
 The heat can simply not escape and will definitely accumulated in the enclosure, since there is no air convection.

 But as long as there is sufficient air convection (air flows bottom => top), it should be fine.
 The heat does travel up and then coming out the enclosure via the tube holes (28mm dia) and the vents on top of the enclosure.
 The enclosure I used is very well ventilated (vents on both top and bottom).
 On top of that, I have made 4 extra holes with 20mm diameter on the bottom plate, right under the area of the heatsinks.
 By doing so, cold air can enter the enclosure exactly where it needed most. 
 The invisible hand of Mother Nature does the remaining part of the cooling job.


----------



## wolf18t

Here's the nice panels runeight is refering to:
http://www.head-fi.org/forums/5120441-post699.html

 Runeight I've read than some tubes like 6DJ8 are rated @ 365mA for the heather current. Does that mean I need to upgrade the transfo (+ remove a resistor in the PS) to use them or 300 mA would be sufficient?

 reference:
The 6DJ8 / ECC88 / 6922 Tube


----------



## runeight

There shouldn't be any problems if you make R3P 8R2. This value was changed during the prototype process, down from 10R, for just this reason.


----------



## Hayduke

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_As an alternative to the “upside down” build, I mounted the tube sockets on a separate platform made from scrap aluminium. It slides into the second highest slot in the Hammond case, which leaves enough room for the stock heatsinks below if the amp itself is in the second lowest slot.

http://www.flickr.com/photos/arkku/3041860978/

 See here for how it looks with the lid on—the tubes stick out almost completely. Also very convenient for tube rolling, as I don't have to worry about putting too much pressure on the board.

 I think Ferrari also made a similar platform for his other SOHA II build?_

 

Is that the BOM Hammond case? (obviously the short one since you housed the toroid in a seperate enclosure)

 So there's not issues with air wiring the sockets to the board? (like picking up interference or anything)

 Case work is the hard part for me. I sure wish I could build as well as some of you. I'm not sure I could fabricate that support you and Ferrari mounted the sockets to, so I am inclined to think the "upside down" build will be easier for me. I know some have thought there might be an issue with flexing the board when inserting and removing tubes, but aren't there holes on the board to mount standoffs near the sockets?


 Sorry for all the questions. I just finished reading the original thread (47 pages with my preferences hehe). I already read all of this thread and Alex's site. Now that I've decided I'm building this amp, I'm eager to get started, but I have questions about a few parts options. Little things though 
	

	
	
		
		

		
			





 Anyway, here they are...

 Any DPDT switch should be OK to replace the jumpers, right? Any particular power rating I should look for?

 I want to maximize my tube options, so I'm planning to use the more powerful transformer. If I can source the Avel Y236203, will it still fit in the 1455T2202 (the long one) case? I'm planning to put a small DAC inside as well (a BantamDAC for now, perhaps a y1 later).

 There has been some talk about using different transistors. Would it be realistic to socket them to make swapping easier? Does it matter if the heatsinks are attached to the board, or can they just be resting there attached to the transistors?

 I'm planning to socket the opamp in the e12 circuit based on the suggestion in the other thread. That's all the changes I have in my notes so far 
	

	
	
		
		

		
		
	


	




 I want to thank everyone in advance for patience with all my questions. I'm skilled with a soldering iron (worked in manufacturing for many years), but I knew little about what I was soldering. I'm getting there though! I especially want to thank Alex for all the explanations of his circuit design. It has been extremely educational. I understood almost all of it! lol

 I sent an email to Jeff already asking about kits and options. Hopefully I can get everything ordered this week and have it built by the end of the month.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Any DPDT switch should be OK to replace the jumpers, right? Any particular power rating I should look for?_

 

Well, if you want to run the higher current 6N1P tubes then you need to account for the higher 600ma heater currents. I chose a 2A DPDT switch (panel mount) Mountain DPDT Switch

  Quote:


 I want to maximize my tube options, so I'm planning to use the more powerful transformer. If I can source the Avel Y236203, will it still fit in the 1455T2202 (the long one) case? I'm planning to put a small DAC inside as well (a BantamDAC for now, perhaps a y1 later). 
 

I sourced my Avel Y236203 trafo right from them (Power Transformers and Power Converters From Avel Lindberg), ~$ 34.00 shipped. Though you'll need to move some components around to make everything fit. For one the rear panel components will need to be all moved over and closer to together. Second with the higher heater currents, you need to provide for cooling for the H- regulator. I mounted mine off board with a heatsink and directly to the case. So that'll eat up the room left for a DAC...


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 To make this worthwhile we need to make at lest ten sets. The price would be $18 for the front panel and $22 for the back panel. This adds $40 to the cost of the kit from GJA.
_

 


 The case work is always the hardest part and these panels would save a few hours of time, I would be in for two sets.


----------



## bmwpowere36m3

Can anyone recommend some "bumpers" or pads to stick under the Hammond enclosure. The included ones are fairly short, ideally something from Digi-Key.


----------



## Arkku

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Is that the BOM Hammond case? (obviously the short one since you housed the toroid in a seperate enclosure)

 So there's not issues with air wiring the sockets to the board? (like picking up interference or anything)_

 

It's the BOM Hammond case, but actually the longer one since I built my entire amp on protoboard, made the high-current heater, used larger than stock heatsinks, added a crossfeed, multiple outputs and inputs, etc. So, mine just took more space. But the height of both cases is the same. =)

 I doubt the air wiring is of any consequence; after all, it's just an inch or so. Classic tube amps often have a lot more air wiring.


  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Case work is the hard part for me. I sure wish I could build as well as some of you. I'm not sure I could fabricate that support you and Ferrari mounted the sockets to, so I am inclined to think the "upside down" build will be easier for me._

 

If you are already going to make the holes for the tubes on the top of the case yourself, doing the elevated platform only requires drilling an additional set of holes for the tube sockets. Of course, there's the cutting of the plate to be used as the support, but it isn't very precise work (won't show outside anyhow). I took mine from a scrap piece of aluminium profile.

 That said, the upside down approach is easier still, I just prefer this way. =)


----------



## cfcubed

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_Can anyone recommend some "bumpers" or pads to stick under the Hammond enclosure. The included ones are fairly short, ideally something from Digi-Key._

 

I usu just get something from hardware store (e.g. HD has a lot of options)...
 If you want something large & fancy, I've used Elegant Anodized Aluminum ones


----------



## lacrossebowe8

i have the tube sockets from jeff r's kit and they have a metal rod i think where the led to light the tube would go. how do i remove this? 

 The part is from cascade surplus


----------



## lacrossebowe8

also i am confused on mounting the devices to the heat sinks. I have placed the "sticker" isolator on the heatsinks. Now i put the devices with the labels facing away from the heat sinks which brings me to the confusing part. I am not sure where to place my washer, under the screw head on the front of the device or against the back of the heatsink before the nut.


----------



## runeight

lacrossbowe8, I am, unfortunately, in a meeting right now and can't adequately help. I should be through in about an hour and a half. Perhaps someone else will offer help in the meantime. If not, I'll be back . . .


----------



## holland

There should be two washers, a plastic shouldered one and a metal one. The metal one goes on the backside of the heatsink. The plastic on the front side of the transistor. The screw will come in contact with the heatsink. The plastic shouldered one is to keep space between the screw and the transistor, to isolate the transistor completely. The direction of the screw doesn't really matter. I use whatever has more space for where I put it.

 If you are using plastic enclosed transistors (stock BD139 for example) then it doesn't matter. The hole on the plastic transistor is smaller. I keep the plastic shouldered washer on it, so I don't lose it, but it won't fit in the hole. I flip the shouldered washer around. It's fine.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_There should be two washers, a plastic shouldered one and a metal one. The metal one goes on the backside of the heatsink. The plastic on the front side of the transistor. The screw will come in contact with the heatsink. The plastic shouldered one is to keep space between the screw and the transistor, to isolate the transistor completely. The direction of the screw doesn't really matter. I use whatever has more space for where I put it.

 If you are using plastic enclosed transistors (stock BD139 for example) then it doesn't matter. The hole on the plastic transistor is smaller. I keep the plastic shouldered washer on it, so I don't lose it, but it won't fit in the hole. I flip the shouldered washer around. It's fine._

 

Like Holland said, if your using the BOM transistors (BD139) then are already "isolated" and the little isolating, shouldered washer doesn't really fit in. I just set it aside and installed it like this: Screw > Transistor > Heat Pad > Heatsink > Flat Washer > Lock Washer > Nut


----------



## wolf18t

Yippie! 

 I just received today my SOHA II kit from Glass Jar Audio. Add it to some alternative parts from BD (Toshiba 2SC3422), Digikey (Panny FC/FM), pcX (Mundorf M-CAP Supreme, upgraded RCA jack and Sylvania 12AU7) I'm now ready to start my build. Just missing Amperex orange globe 6DJ8 and I'll be ready for some tube rolling.

 I just noticed that the Mundorf caps are much bigger than what I expected and their leads larger than PCB holes. It will need some creative soldering.

















 Guess what I gonna do with my free time this weekwend?
	

	
	
		
		

		
		
	


	




Cavalli Audio SOHA II album | Wolf18t | Fotki.com


----------



## runeight

And you will keep us informed of progress?


----------



## wolf18t

Quote:


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





 And you will keep us informed of progress?_

 

For sure I will, and with some progress pictures. I'll keep my camera not to far from the workbench.


----------



## Hayduke

OK, I've thought about it some more and I don't want the tubes to stick out of the case so much. I'm going to just build that part normally.

 I still have a question nobody responded to though. Some folks have talked about sound differences using different transistors. What are your thoughts on socketing them? Is it important that the heatsinks are soldered to the PCB? I'm thinking it won't really matter. Or is the difference so small that it's not worth the effort?


----------



## Ferrari

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Yippie! 
 ...
 I just noticed that the Mundorf caps are much bigger than what I expected and their leads larger than PCB holes. It will need some creative soldering._

 

Good sounding caps are somtimes a bit big(ger), but with some creativity it can be done. 
 I also under-estimate the size of the Teflon caps I want to use in my amp... 
	

	
	
		
		

		
			










 (The stock Wima MPK on top for size comparasion).


----------



## wolf18t

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Good sounding caps are somtimes a bit big(ger), but with some creativity it can be done. 
 I also under-estimate the size of the Teflon caps I want to use in my amp... 
	

	
	
		
		

		
		
	


	




 (The stock Wima MPK on top for size comparasion)._

 

LOL, these are huge caps! They merit to be shown through amp top panels holes. Just beside the tubes. 

 Anyway that's something I'm considering now on my build. I think the Mundorf are quite nice looking.


  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I still have a question nobody responded to though. Some folks have talked about sound differences using different transistors. What are your thoughts on socketing them?_

 

Never done it or see it done by someone either. 

 Keep in mind that every time you will change a set, you will need to re-bias them. You will maybe also have problem mounting them on the heatsinks, if the screws don't align with holes.


----------



## wiatrob

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Never done it or see it done by someone either. 

 Keep in mind that every time you will change a set, you will need to re-bias them. You will maybe also have problem mounting them on the heatsinks, if the screws don't align with holes._

 

Holland rolls output transistors. He supplied me with a scoket part number, but I can't recall if it was on aHead-Fi thread or during the prototype discussions...


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Never done it or see it done by someone either. 

 Keep in mind that every time you will change a set, you will need to re-bias them. You will maybe also have problem mounting them on the heatsinks, if the screws don't align with holes._

 

There shouldn't be an issue with the holes not lining up. I'm thinking of the transistor and the heatsink being a unit that I "plug in" to the board. So swapping them out would mean I unplug the sub assembly, then take the screw out that holds the transistor to the sink, then attach the new transistor. So it won't be quite as easy as rolling a tube, but easier then soldering 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Holland rolls output transistors. He supplied me with a scoket part number, but I can't recall if it was on aHead-Fi thread or during the prototype discussions..._

 

Really? I have read both SOHA II thread on head-fi and the one on headwize. I'll go look again. Thanks

 So apparently it can be done fine, huh? I was worried because I had never heard of anyone using a socket with a transistor.

 The deviations from the original design I want to implement are:
 1. Socket the transistors.
 2. Put a DAC inside the case and use a switch to select the input.
 3. Use a switch instead of the jumpers for the heater voltage.
 4. Use the larger toriod to support 600ma tube heaters.
 5. Use a dual color LED on the e12 delay circuit.

 If anyone has any advice on potential issues with any of these, I'd appreciate it. I think I understand the effects of these changes, but I might be missing something.
 1. See my previous posts 
	

	
	
		
		

		
		
	


	



 2. This should be pretty straight forward with a DPDT switch. Planning to use a BantamDAC (at least to start).
 3. Easy to implement and already discussed.
 4. I just need to get a 1.5a transformer. Any other part changes needed? I also realize this may make it harder to fit the DAC in the Hammond case.
 5. This has been discussed, and Alex already posted the schematic to use. I don't anticipate any issues with this change.

 Are there any other things I can do to improve the amp? I'm considering different caps, but my understanding is that this mostly benefits coupling caps and this amp doesn't use them. Am I way off here?

 I was hoping to get my parts ordered this week, but work was too busy. I'm planning to finalize my BOM this weekend and order on Monday.

 Thanks in advance for everyone's help


----------



## holland

I use

10-18-2031 @ mouser

 or

Digi-Key - WM2551-ND (Molex Connector Corporation - 10-18-2031)

 I socketed all my TO-220.


----------



## Hayduke

Thanks Holland 
	

	
	
		
		

		
		
	


	




 That's what I'll use. Did you socket all the transistors? If not, which ones?


----------



## Ferrari

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_LOL, these are huge caps!_

 

Yes, those Teflon caps are indeed huge.
 To make things fit nicely, I have downsized the inter-stage coupling caps of my amp a bit.


----------



## dBel84

oooh , that is looking phenomenal , balanced SOHA II with exquisite attention to build detail (as always).

  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_The deviations from the original design I want to implement are:
 1. Socket the transistors.
 2. Put a DAC inside the case and use a switch to select the input.
 3. Use a switch instead of the jumpers for the heater voltage.
 4. Use the larger toriod to support 600ma tube heaters.
 5. Use a dual color LED on the e12 delay circuit._

 


 1. - the only issue is the weight of the heatsinks , you would need to screw them down as you noted
 2. I did this with an alien - I would recommend a separate power supply to avoid the chance of hearing nasty pc generated noise. I hooked up a simple 5V regulator that I pulled from the LV and it works a treat. 
 3. the switch is the default recommendation - I am sure someone has the part number and I thought it was part of the BOM - it is a board mount dpdt
 4. & 5. make sense - not sure how to implement 5, have a look at this thread to see if you can mod the layout. 

 ..dB


----------



## runeight

Ferrari, you just continue to do one beautiful amp after another, no matter which one it is. Will you design enclosures for me?


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ferrari, you just continue to do one beautiful amp after another, no matter which one it is. 
	

	
	
		
		

		
		
	


	


_

 

Without creative designers like you and amb, that would be impossible, to be honest.
 Trying to build amps with some love and dedication is my way to say: “thank you guys, I appreciate your hard work”.


----------



## DrkRipper

Update:

 Well, I finally got some more time to work on it. Things are looking much better. My headphone jack diagnosis from before was incorrect, I was using some really crappy headphones that must have a short somewhere. So when I was moving the headphone jack around it must have fully shorted the sound into both channels. Anyways I found a bad solder joint (grrr) on the pot between it and the left input. So that's fixed now, and I have sound in both channels 
	

	
	
		
		

		
		
	


	




 As far as I can tell everything sounds like it should, even though P2 on both channels are still at the end of their travel. I don't hear the distortion from before and the e12 isn't tripping, I assume that's because I'm not shorting the output anymore. I double checked the resistor's and can't find anything wrong, I also replaced Q8 on the left side and it didn't change anything. Should I try replacing Q7?


----------



## runeight

Yes, I think you'll have to make your way through the O/P transistors one at a time. First Q7 then Q6 then Q5 until you solve the problem. Because you should be able dial up 100mA on each channel.


----------



## rhester

Woo hoo, I finished my build this AM. And am now listening to some hot jazz on a cold nasty day. Now to finish the casing, but somebody will have to pull the cans off my head first.

 Somebody used VitaQ instead of Wimas on C1. HOw does it compare with the WIMAs in this amp?


----------



## bmwpowere36m3

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Woo hoo, I finished my build this AM. And am now listening to some hot jazz on a cold nasty day. Now to finish the casing, but somebody will have to pull the cans off my head first.

 Somebody used VitaQ instead of Wimas on C1. HOw does it compare with the WIMAs in this amp?_

 

I ended using VitQ's in the C1 L/R positions, but I also chose to use "boutique" caps in other sections as well. I say the amp sounds wonderful and has great synergy with my Senn HD580's. However I can't compare it to the sound of the stock Wima's, just for that position: my SOHAII build

 I'm curious has anyone listened to Grado's with this amp, specifically SR-80's. Yesterday I auditioned a pair of SR-80's and RS1 at an audio shop with their Grado RA1 amp. I got to take a pair of SR-80's back home for more auditioning with my setup (iMod DAC, SOHA II) and honestly the SR-80's aren't sounding too good. In the store, IIRC, they sounded pretty decent... yet different from my 580's.

 At home, their pretty grainy, at time harsh treble, and peaky in the mid-bass and upper-mid treble... so details I hear in the HD580's are lost in the very projected, in your face sound.


----------



## Ferrari

Quote:


  Originally Posted by *rhester* /img/forum/go_quote.gif 
_Woo hoo, I finished my build this AM. And am now listening to some hot jazz on a cold nasty day. Now to finish the casing, *but somebody will have to pull the cans off my head first.*_

 

Ask the wife for help! 
	

	
	
		
		

		
		
	


	



 Congrat with your amp, btw.


----------



## Uncle Bob

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_I ended using VitQ's in the C1 L/R positions, but I also chose to use "boutique" caps in other sections as well. I say the amp sounds wonderful and has great synergy with my Senn HD580's. However I can't compare it to the sound of the stock Wima's, just for that position: my SOHAII build

 I'm curious has anyone listened to Grado's with this amp, specifically SR-80's. Yesterday I auditioned a pair of SR-80's and RS1 at an audio shop with their Grado RA1 amp. I got to take a pair of SR-80's back home for more auditioning with my setup (iMod DAC, SOHA II) and honestly the SR-80's aren't sounding too good. In the store, IIRC, they sounded pretty decent... yet different from my 580's.

 At home, their pretty grainy, at time harsh treble, and peaky in the mid-bass and upper-mid treble... so details I hear in the HD580's are lost in the very projected, in your face sound._

 

I much prefer my Grado's (SR225) with the SOHAII to anything else I've used - CMOY, Creek OBH-11, CKKIII - while I find that the SOHAII/HD650 combination doesn't quite work for me. I've only the one tube type at the moment so this may be a factor, but while I agree the Grado sound is normally agressive, the tube sound tempers this to a degree and there is absolutely no harshness in the treble. By comparison, the Senns sound 'shut in' and dark, too soft and lazy, just comfy pipe-n-slippers presentation. However, I do enjoy them with the CKKIII and, since I upgraded the PSU and the opamp, I slightly prefer them on the Creek.



 On the SOHAII


----------



## adamus

I havent bulit a sohaII, but if you really want to tame grados then look for for some warm old valves (mullards etc). Certainly dont try the russians e.g. 6n1p.


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I much prefer my Grado's (SR225) with the SOHAII to anything else I've used - CMOY, Creek OBH-11, CKKIII - while I find that the SOHAII/HD650 combination doesn't quite work for me. I've only the one tube type at the moment so this may be a factor, but while I agree the Grado sound is normally agressive, the tube sound tempers this to a degree and there is absolutely no harshness in the treble. By comparison, the Senns sound 'shut in' and dark, too soft and lazy, just comfy pipe-n-slippers presentation. However, I do enjoy them with the CKKIII and, since I upgraded the PSU and the opamp, I slightly prefer them on the Creek.



 On the SOHAII_

 

Huh, well maybe it's my choice of current tubes as well. Since both Holland and myself have noted that the Electro-Harmonix 12AU7's have a very aggressive, neutral, and clear presentation. Very well suited to "Metal" kind of music, but sound great with everything else I've throw at them. I'd say the combo of those tubes with "bright" Grado's, maybe overemphasizes those characteristics more.

 Yes, the Senn's are little more laid back, but I think it's because they are so neutral. Whereas the Grado's have a funky peakiness in the upper-bass and upper midrange, so it really puts the music out there. I feel like I hear a lot more detail with the Senn's where the Grado's are overpowered by those to peaks. For example Hotel California, When Hell Freezes Over... with the Senn's my hearing focuses on Henley's vocals with everything else in balance. With the Grado's, I'm still sort of focused on Henley's vocals, but Walsh's guitar "licks" and Schmit's bassline kind of overpower the vocals...

  Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I havent bulit a sohaII, but if you really want to tame grados then look for for some warm old valves (mullards etc). Certainly dont try the russians e.g. 6n1p._

 

That what I was thinking, but I'm actually just trying out the Grado's currently. WHen I auditioned them in the store they sound better out of a Grado RA1 amp and I also listened to RS1's which had the characteristics of the SR80 but with a less harsh and overpowering treble and sweet mids.

 Why no to the 6N1P's? That was actually the next tube I was going to get for the amp, Ferrari had some nice reviews about them.


----------



## holland

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Thanks Holland 
	

	
	
		
		

		
			





 That's what I'll use. Did you socket all the transistors? If not, which ones?_

 

I socketed all of them, in case something happens to the regulators it's easier to access. I leave the heatsinks in, the only hard ones to reach are the regulators, but it's only because I am using much larger heatsinks (2.5" or 3" tall). The shorter heatsinks will still allow access to the bolts easily. The output transistors are in front and for me it's easy to access with a short screwdriver. I put the screws in the front side and the nuts in the back.


----------



## holland

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I've only the one tube type at the moment_

 

Perhaps I missed it, but which tube are you using?


----------



## wolf18t

First day progress - I was able today to solder all small signal diodes and resistors. I'm slow but I have the habit of double checking every solder joint and components value (R,C) or functionality (D,Q). Better safe than sorry.

 I socketed R4 as I plan to eventually replace with Zeners then play with the tubes tail current. Anybody tried some zeners yet? Were they noisy and, if not, what brand did you use?


----------



## Arkku

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Anybody tried some zeners yet? Were they noisy and, if not, what brand did you use?_

 

I have zeners installed in my amp, they are Fairchild Semiconductor 1N5248B's (Mouser 512-1N5248B). When I was building the amp, I asked here about the zeners and the response seemed to be that they increase the noise and most (all?) others had reverted to resistors. However, I am unable to hear any ill effects compared to the resistors with any of my headphones, so I decided to leave the zeners in. I _think_ that they sound a bit better, but it's probably mostly psychoacoustics. =)


----------



## Uncle Bob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Perhaps I missed it, but which tube are you using?_

 

Currently, I'm using some Pinnacle (possibly made by Toshiba?) 13D5A's. I've got several spare, so if you're interested in trying a pair - drop me a PM

 I've just bought a pair of Philips PCC88 off an ebay seller, so they'll be here in a few days. Once I've had chance to listen and compare - I'll put something in the SOHAII Tubes thread. There was little point before as I had nothing to compare with the 13D5A's.

 I've got my eyes on some other tubes - mainly ECC81/82/83/88 but I won't pay silly money for tubes so I have to wait for the right deals to come around.


----------



## wolf18t

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_I have zeners installed in my amp, they are Fairchild Semiconductor 1N5248B's (Mouser 512-1N5248B). When I was building the amp, I asked here about the zeners and the response seemed to be that they increase the noise and most (all?) others had reverted to resistors. However, I am unable to hear any ill effects compared to the resistors with any of my headphones, so I decided to leave the zeners in. I think that they sound a bit better, but it's probably mostly psychoacoustics. =)_

 

Thank Arkku, I'll check if Digikey carry them. Did you experiment with the tail current to see if it change the sound somewhat?

 If I understand correctly, that mod let you play with the triode plate current. Some tubes may benefit from rising it a little bit higher than 1 mA. The zener have the purpose of keeping the required near 19V voltage drop while you play with the tail current source pot.


----------



## DrkRipper

I might have good news...after replacing Q8R and Q7L and setting the idle currents I have about another full turn on each pot, does that sound right?

 Thanks again for your patience and help


----------



## runeight

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Thank Arkku, I'll check if Digikey carry them. Did you experiment with the tail current to see if it change the sound somewhat?

 If I understand correctly, that mod let you play with the triode plate current. Some tubes may benefit from rising it a little bit higher than 1 mA. The zener have the purpose of keeping the required near 19V voltage drop while you play with the tail current source pot._

 

Yes. Correct.


----------



## runeight

Quote:


  Originally Posted by *DrkRipper* /img/forum/go_quote.gif 
_I might have good news...after replacing Q8R and Q7L and setting the idle currents I have about another full turn on each pot, does that sound right?

 Thanks again for your patience and help 
	

	
	
		
		

		
		
	


	


_

 

So you can get 100mA in both channels with a little travel left over in the pot? Or are you dialing higher than this?

 If 100mA it's hard to say if this is ok. You may have transistors which are outliers in their specs pushing your bias control to this limit, but normally you should get 100mA with about half travel or thereabouts.

 What I am wondering is if there is still a transistor problem that will show up as poor audio quality. There would be no way to know this unless you had a companion unit.

 The main thing on my mind is whether or not the current sources (Q7 and Q8) are indeed acting like a CCS. There is a way to look at this, but you probably don't want to fool with it.

 How does it sound?


----------



## Hayduke

I realize this is a very newbish question, but that's never stopped me from demonstrating how dumb I am before 
	

	
	
		
		

		
		
	


	




 Why do you need to insulate the RCA inputs (Mouser 502-3501FPX) if you use a metal face plate?

 Seems like they are intended for use with a metal panel, so I'm confused 
	

	
	
		
		

		
		
	


	




 I know I'm asking a lot of questions before I've even ordered parts, but I'm trying to understand the logic behind the choice of every part. This also means I'll understand the amp better


----------



## DrkRipper

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So you can get 100mA in both channels with a little travel left over in the pot? Or are you dialing higher than this?_

 

It is set at 100mA now, I was able to turn it up to ~120mA. 

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The main thing on my mind is whether or not the current sources (Q7 and Q8) are indeed acting like a CCS. There is a way to look at this, but you probably don't want to fool with it._

 

What would be involved? I have access to an oscilloscope, if needed. 

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_How does it sound?_

 

It sounds good, I certainly can't hear anything that sounds wrong.

 *edit* A friend of mine was anxious to review it...so there will be some listening impressions posted soon.


----------



## Beefy

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Why do you need to insulate the RCA inputs (Mouser 502-3501FPX) if you use a metal face plate?

 Seems like they are intended for use with a metal panel, so I'm confused 
	

	
	
		
		

		
		
	


	


_

 

I believe that if the transformer is in the same case as the amp, then the case should be connected to your power earth/ground for safety. This means that signal ground should be isolated from the case to prevent ground loops that can cause hum.

 If you were to put the transformer in a separate case, then the signal ground probably should be connected to the amp case.


----------



## runeight

Quote:


  Originally Posted by *DrkRipper* /img/forum/go_quote.gif 
_It is set at 100mA now, I was able to turn it up to ~120mA. 


 What would be involved? I have access to an oscilloscope, if needed. 


 It sounds good, I certainly can't hear anything that sounds wrong.

 *edit* A friend of mine was anxious to review it...so there will be some listening impressions posted soon._

 


 Thanks. 120mA is about right. And you get from 100mA to 120mA with just one turn on the pot??

 In any case, if the amp sounds clean to you it's probably ok.

 To check the CCSs look at the voltage across P2. It should be constant when signal is applied. If it shows significant variation the CCS is not working and either Q7 or Q8 or both are bad.


----------



## Arkku

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Thank Arkku, I'll check if Digikey carry them. Did you experiment with the tail current to see if it change the sound somewhat?_

 

No, I haven't really experimented with the tail current setting, as I'm not sure of the possible benefits. It sounds good to me like it is. =)


----------



## DrkRipper

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks. 120mA is about right. And you get from 100mA to 120mA with just one turn on the pot??_

 

Good 
	

	
	
		
		

		
			





 I don't remember exactly, but it was less than 2 turns from the end of its travel to where I set it. 

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_In any case, if the amp sounds clean to you it's probably ok.
 To check the CCSs look at the voltage across P2. It should be constant when signal is applied. If it shows significant variation the CCS is not working and either Q7 or Q8 or both are bad._

 

I'm back at school and don't have my tools, but I'll try to measure it. 

 If anyone is interested, here is my friend's review:
http://www.head-fi.org/forums/f5/soh...5/#post5287301


----------



## Hayduke

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I believe that if the transformer is in the same case as the amp, then the case should be connected to your power earth/ground for safety. This means that signal ground should be isolated from the case to prevent ground loops that can cause hum.

 If you were to put the transformer in a separate case, then the signal ground probably should be connected to the amp case._

 

Thanks.

 Since I'm planning to put the transformer in the same case, I'll get some insulator washers.


----------



## wolf18t

runeight, with the SOHA II is there a good rule of thumb for presetting the trimpots for a safer initial startup? At least I guess it should be important for the output stage biasing pot (avoid BJT thermal runaway).

 Setting them halfway, like 5ohms for 10 ohms pots, should be safe?


----------



## runeight

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_runeight, with the SOHA II is there a good rule of thumb for presetting the trimpots for a safer initial startup? At least I guess it should be important for the output stage biasing pot (avoid BJT thermal runaway).

 Setting them halfway, like 5ohms for 10 ohms pots, should be safe?_

 

Good question. The way the buffer is designed it actually doesn't matter where you set them. Even at max current the O/P transistors won't burn up. 

 So, just pick a point on the wiper, halfway is a good place to start. It's what I did when I fired up mine the first time.

 BTW, I know I designed this amp, but I really like it. Been listening to it lately.

 Now if I could only afford the HD800s.


----------



## wolf18t

Thanks! I set them all halfway.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Now if I could only afford the HD800s. 
	

	
	
		
		

		
		
	


	


_

 

Me too. And the GS-1000. And the AD-7000. And the DX-1000. Ok I'm tired, time to go to bed and dream...


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Thanks.

 Since I'm planning to put the transformer in the same case, I'll get some insulator washers._

 

What exactly are you try to isolate? Both the IEC needs to be grounded to the case and the GRD point on the PCB. The only thing that's isolated, should be the input jacks.


----------



## Hayduke

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_What exactly are you try to isolate? Both the IEC needs to be grounded to the case and the GRD point on the PCB. The only thing that's isolated, should be the input jacks._

 

Yep, I was talking about the input RCAs. 
	

	
	
		
		

		
		
	


	




 Although I've been working on my BOM every night for awhile now, and I think I'm going to skip RCAs and just put a 1/8"/3.5mm phono for the input. My only sources will be USB (putting a BantamDAC inside) and modded iPods.

 What is the "IEC"?

 I'm rereading this thread (nearly the third time through) to get ideas of what others have done. I know you used some alternative parts. Did you list them anywhere? I started looking for it last night, but haven't found it yet. Did you use the supplied Excel BOM and save your own version? If so, wanna share?


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Yep, I was talking about the input RCAs. 
	

	
	
		
		

		
		
	


	




 Although I've been working on my BOM every night for awhile now, and I think I'm going to skip RCAs and just put a 1/8"/3.5mm phono for the input. My only sources will be USB (putting a BantamDAC inside) and modded iPods.

 What is the "IEC"?

 I'm rereading this thread (nearly the third time through) to get ideas of what others have done. I know you used some alternative parts. Did you list them anywhere? I started looking for it last night, but haven't found it yet. Did you use the supplied Excel BOM and save your own version? If so, wanna share? 
	

	
	
		
		

		
		
	


	


_

 

"IEC" is the Inlet Connector:





 I thought I did, but here it is (attached).


----------



## Hayduke

Is 2.21 ohm OK for R10?

 I'd like to use Mouser PN 71-RN55D2R21F to keep all the resistors Vishay. The only 2.2 ohm Vishay that Mouser stocks are 1 or 2 watts 
	

	
	
		
		

		
		
	


	




 I could always tombstone one of these if the value is critical. I'm slowing gaining a pretty good understanding of the amp's schematic, but I can't tell if .01ohm in R10 will make a difference.


----------



## runeight

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Is 2.21 ohm OK for R10?

 I'd like to use Mouser PN 71-RN55D2R21F to keep all the resistors Vishay. The only 2.2 ohm Vishay that Mouser stocks are 1 or 2 watts 
	

	
	
		
		

		
		
	


	




 I could always tombstone one of these if the value is critical. I'm slowing gaining a pretty good understanding of the amp's schematic, but I can't tell if .01ohm in R10 will make a difference._

 

Yes, you can use 2.21. The .01 is less than the 1% tolerance of the resistor itself. But the reason that this resistor is xicon is because of what you discovered about the available Vishay RN55D values. MHO is that you won't notice any difference whatsoever between the two brands used in the position in the circuit.


----------



## Hayduke

@bmwpowere36m3

 Thanks for sharing your BOM. I had already substituted a lot of the same parts 
	

	
	
		
		

		
		
	


	




 Why did you use a DPDT for your R3P bypass? In your BOM you show the same switch for this and your heater voltage switch. Wouldn't a SPST work fine here?

 I'm thinking I will use R13-603C-05 and R13-602B-05

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, you can use 2.21. The .01 is less than the 1% tolerance of the resistor itself. But the reason that this resistor is xicon is because of what you discovered about the available Vishay RN55D values. MHO is that you won't notice any difference whatsoever between the two brands used in the position in the circuit._

 

Thanks Alex 
	

	
	
		
		

		
		
	


	




 I didn't think that amount would matter too much. For no good reason, I just wanna use all Vishay. 
	

	
	
		
		

		
		
	


	




 I am gonna leave R3P alone though since the only Vishay equivalent available form Mouser is this:
CP00058R200JB14

 I ordered my transformer and boards today. I'll be placing a Mouser order after they get back to me about a question on some test probes. Hopefully today, maybe tomorrow.

 I'm still undecided on the case though. bmwpowere36m3 has me worried about fitting the larger transformer and the DAC inside the case. The BantamDAC is pretty small though. I am going to use a 3.5mm stereo plug instead of RCAs, so that's a little less stuff on the back. Plus, I'm putting the main power switch on the front, so that will help too. Only problem is I'm putting 2 small slider switches on the back panel for the heater voltage and to bypass R3P.

 I think it will all fit. I'll just have to be creative 
	

	
	
		
		

		
		
	


	




 Now that I'm ordering parts, my excitement to hear this amp jumped up a couple notches.

 Thanks for sharing your design Alex. Sorry for asking so many bonehead questions hehe


----------



## bmwpowere36m3

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_@bmwpowere36m3

 Thanks for sharing your BOM. I had already substituted a lot of the same parts 
	

	
	
		
		

		
		
	


	




 Why did you use a DPDT for your R3P bypass? In your BOM you show the same switch for this and your heater voltage switch. Wouldn't a SPST work fine here?_

 


 They are two different switches, however their P/N on differs by one letter "xx*MS*xxxx" vs. "xx*MD*xxxx" and yes, the other is a SPST

  Quote:


 I'm thinking I will use R13-603C-05 and R13-602B-05 
 

Those look like they'd work, seem kinda cheapy looking to me. If you like then 
	

	
	
		
		

		
		
	


	




  Quote:


 Thanks Alex 
	

	
	
		
		

		
		
	


	




 I didn't think that amount would matter too much. For no good reason, I just wanna use all Vishay. 
	

	
	
		
		

		
		
	


	




 I am gonna leave R3P alone though since the only Vishay equivalent available form Mouser is this:
CP00058R200JB14 
 

I like you wanted to use all Vishay, but it honestly wasn't worth the trouble... especially since those resistors are not that "important" and some of them are adjustable in conjunction with the trimpots, so... The replacement R3P you have listed appears to be way to big as well. Just use the BOM one.

  Quote:


 I ordered my transformer and boards today. I'll be placing a Mouser order after they get back to me about a question on some test probes. Hopefully today, maybe tomorrow.

 I'm still undecided on the case though. bmwpowere36m3 has me worried about fitting the larger transformer and the DAC inside the case. The BantamDAC is pretty small though. I am going to use a 3.5mm stereo plug instead of RCAs, so that's a little less stuff on the back. Plus, I'm putting the main power switch on the front, so that will help too. Only problem is I'm putting 2 small slider switches on the back panel for the heater voltage and to bypass R3P.

 I think it will all fit. I'll just have to be creative 
	

	
	
		
		

		
		
	


	




 Now that I'm ordering parts, my excitement to hear this amp jumped up a couple notches.

 Thanks for sharing your design Alex. Sorry for asking so many bonehead questions hehe 
 

Just draw out and dimension the amp and its components layouts. I wouldn't say you have no room, but with all that careful planning will be needed. Running the switch to the front, *might* induce some unwanted hum (maybe?) by running the power lines under the PCB.


----------



## Hayduke

Quote:


  Originally Posted by *bmwpowere36m3* /img/forum/go_quote.gif 
_They are two different switches, however their P/N on differs by one letter "xx*MS*xxxx" vs. "xx*MD*xxxx" and yes, the other is a SPST_

 

oops missed that letter 
	

	
	
		
		

		
		
	


	




  Quote:


 Those look like they'd work, seem kinda cheapy looking to me. If you like then 
	

	
	
		
		

		
		
	


	



 

I want small sliders and I wanted at least ~2A. That's all I could find. Mountain switch had some I liked better, but they were only .5A. I want sliders so they don't get changed on accident. I know I would hit those toggles you used everytime I messed with the cords. While not portable, I suspect this amp will get moved around a fair amount.

 If you can find a nicer slider from Mouser that will work, I'll be grateful for a link 
	

	
	
		
		

		
		
	


	




  Quote:


 I like you wanted to use all Vishay, but it honestly wasn't worth the trouble... especially since those resistors are not that "important" and some of them are adjustable in conjunction with the trimpots, so... The replacement R3P you have listed appears to be way to big as well. Just use the BOM one. 
 

I'm not using the one I linked to. I already decided to use the BOM one. I was just showing what I found as the reason why I wasn't using all Vishay. 
	

	
	
		
		

		
		
	


	




  Quote:


 Just draw out and dimension the amp and its components layouts. I wouldn't say you have no room, but with all that careful planning will be needed. Running the switch to the front, *might* induce some unwanted hum (maybe?) by running the power lines under the PCB. 
 

My plan was to put this power switch in the middle of the faceplate (between the knob and the headphone jack). I was thinking I would run the power wires down the side of the enclosure. You're right though, it had occurred to me that those long runs of wire might cause or pickup some interference. Maybe I'll get some shielding or order some shielded multi conductor wire.

 Any suggestions? I'd prefer to have the power switch on the front of the amp, but I don't want to introduce any noise obviously.

 I'm going to build it and have everything working before I even start any casework. My friend owns a business that has lots of metal fabrication equipment (mills, CNC machines etc). He said he can do my casework for me "no problem". 
	

	
	
		
		

		
		
	


	




 Might take awhile to get it back from him, but I know his work. It will be done well.


----------



## runeight

hayduke, bmwpower is right about running the power to the front. You can certainly try it, but I would test it before committing to a hole in the front panel. 

 Nice to hear about your build. Can't wait to see it.


----------



## Hayduke

hmmm I know I posted a reply last night. That's twice in 2 days my posts have disappeared. I guess I offended the forum fairies or something 
	

	
	
		
		

		
		
	


	




 I'm already planning to build it and get everything working before I do anything with the case. Since my friend who is going to do the machining lives out of state, I want to be able to provide accurate measurements to him. So I'll definitely test the switch in my proposed location.

 If everything thinks I will have a problem with this idea though, maybe I shouldn't order my nice, and expensive, chrome switch with an LED in it. If I end up putting the power switch on the back, then there's no point using the fancy one 
	

	
	
		
		

		
		
	


	




 So you don't think running the wire inside some braided copper shielding would help? My plan was/is to run it down the side of the enclosure. I'll try using one of the upper slots and see if that helps.

 Anyway, Mouser got back to me on my question, so I placed the order for the rest of my parts. Everything is coming now except the tubes. I'm still undecided on what tubes to get or where to source them. Right now I'm leaning towards Parts Connection.


----------



## runeight

It's hard to say if you will have problems. If you shield the power wire and keep it well out of the way under board it might work out alright. If you do an RMAA on the amp you may see 60Hz, but it may be at such a low level that you never hear it.


----------



## TimJo

I was wondering if anyone has built one of these with the tube sockets on top of the board, but all other components underneath. I've seen folks mention this, but has it actually been done?

 I'm thinking about doing it this way, but my concern is that it will no longer fit in the Hammond case if it is done this way.

 Also, I'm going with the 50VA Avel transformer, so I know I need more than the standard 1" heatsink for the H- regulator. Will a board mounted 1 1/2" heatsink be sufficient, or will it really need to be a case mounted heatsink?


----------



## dBs

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I was wondering if anyone has built one of these with the tube sockets on top of the board, but all other components underneath. I've seen folks mention this, but has it actually been done?

 I'm thinking about doing it this way, but my concern is that it will no longer fit in the Hammond case if it is done this way.

 Also, I'm going with the 50VA Avel transformer, so I know I need more than the standard 1" heatsink for the H- regulator. Will a board mounted 1 1/2" heatsink be sufficient, or will it really need to be a case mounted heatsink?_

 

Ive thought about this and the concern I have is that now the pins are mirror reversed and not in their original orientation. I am also curious if anyone has actually implemented this plan to see how they tackled that issue.


----------



## Hayduke

Ferrari has done this. Search the thread for his posts. He has built 1 with air wired sockets mounted on a support and another where all the tall components are mounted on the bottom of the board. One of the nice features of Alex's design is that there are 2 sets of holes for the transformers that allow you to mount devices with reversed pin outs, or in this case, flipped upside down on the board. The other devices with more then 2 leads (opamps and transistors) are pretty short, so you could still get most of the tube to stick out of the case. Assuming that's your goal


----------



## TimJo

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_The other devices with more then 2 leads (opamps and transistors) are pretty short, so you could still get most of the tube to stick out of the case. Assuming that's your goal 
	

	
	
		
		

		
		
	


	


_

 

That is the goal. 

 I'm just trying to weigh the pros and cons of doing it this way vs. air wiring the tube sockets.


----------



## Ferrari

When building the amp with all the tall parts "upside down", be sure to pay attention to good ventilation as I pointed that out in an earlier post.


----------



## holland

When running power lines under the PCB, move it to the side. Don't run it underneath the tubes in particular. I run mine underneath, but move it to the side. I have more room in my case than the BOM case, but what may help is if you can run them in the "slots" of the Hammond case. Or go up, to the side, over and run them towards the top of the case.

 I actually found I had more noise from the LEDs for the tubes underneath the PCB as the lines were closer to the PCB.

 I am using 1/8" spacers. YMMV with taller spacers.


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I actually found I had more noise from the LEDs for the tubes underneath the PCB as the lines were closer to the PCB._

 

Hmm. wonder if this may be a possible source of the mysterious noise some have heard? Any purists built without LED uplighting? I have LED wires and lines for test jacks running under mine (I run audio and power along the sides as a best practice as Holland suggests). I'm _finally_ about to start work on my high-current version, so I'll be able to A/B soon.


----------



## holland

I removed the LEDs on mine. It was just a prototyping thing when I was running it without a case. When I cased it, I found I had noise, and promptly removed the LEDs. The reason is that I am using 1/8" spacers. I would imagine with 1/2" spacers, I would be OK.

 I do have buzzing on mine. I scoped it briefly and I seem to be getting some noise through to the output. It's hard to tell if it's ground noise or if it's from the PS, but it did look like some noise from rectification. I never did find out why, but it's very hard to hear with headphones and since I have some tinnitus it's very hard to hear it through the ringing. I can hear it with IEMs, but that's about it.


----------



## Hayduke

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_When running power lines under the PCB, move it to the side. Don't run it underneath the tubes in particular. I run mine underneath, but move it to the side. I have more room in my case than the BOM case, but what may help is if you can run them in the "slots" of the Hammond case. Or go up, to the side, over and run them towards the top of the case.

 I actually found I had more noise from the LEDs for the tubes underneath the PCB as the lines were closer to the PCB.

 I am using 1/8" spacers. YMMV with taller spacers._

 

Thanks Holland

 I am going to try running the wire in the top left (looking from the front) case "slot".

 What slot do you have the board in using 1/8" spacers?

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Hmm. wonder if this may be a possible source of the mysterious noise some have heard? Any purists built without LED uplighting? I have LED wires and lines for test jacks running under mine (I run audio and power along the sides as a best practice as Holland suggests). I'm finally about to start work on my high-current version, so I'll be able to A/B soon._

 

I ordered some various LEDs, but I'm probably not going to use them.

 A co-worker friend brought up a good point. He asked me, "does it improve the sound?" I answered, "no." He replied, "I wouldn't bother with anything that didn't make is sound better."

 There is wisdom in those words, but there is also something to be said for aesthetics. If you don't hear any noise, I say use them. If you do hear noise, then remove them. I sure as hell don't need pretty lights at the expense of SQ


----------



## regal

Why not use the usual Digikey 35VA Amveco transformers? Will they not fit the standard Hammond enclosure?


----------



## rds

Quote:


 He asked me, "does it improve the sound?" I answered, "no." He replied, "I wouldn't bother with anything that didn't make is sound better." 
 

It doesn't improve the sound in theory only.


----------



## wiatrob

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Thanks Holland

 There is wisdom in those words, but there is also something to be said for aesthetics. If you don't hear any noise, I say use them. If you do hear noise, then remove them. I sure as hell don't need pretty lights at the expense of SQ 
	

	
	
		
		

		
		
	


	


_

 

Agreed, but I'd say aesthetics has quite a bit to do with DIY, but that's probably another thread (where perceived percentages of 'better' SQ are discussed). Otherwise all our builds would remain strapped to boards, and they'd be a heck of a lot quicker to finish!


----------



## wolf18t

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Agreed, but I'd say aesthetics has quite a bit to do with DIY, but that's probably another thread (where perceived percentages of 'better' SQ are discussed). Otherwise all our builds would remain strapped to boards, and they'd be a heck of a lot quicker to finish! 
	

	
	
		
		

		
			



_

 

I tend to put much effort and $$$ to higher SQ, but I think aesthetics will give more impact to resale value than boutique parts or contruction quality. 

 That 2 extra blue (yeah "blue" is very critical in this example 
	

	
	
		
		

		
		
	


	




) LEDs may give your amp an extra 25-50$ in resale value...

 But everyone know that we will all keep our SOHA II preciously


----------



## Hayduke

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Why not use the usual Digikey 35VA Amveco transformers? Will they not fit the standard Hammond enclosure?_

 

Alex recommended the Avid transformer originally, so all I did was get "the next size up" from them. It is slightly larger physically, but bmwpower36(sorry bmw I know I spelled this wrong) was able to squeeze it into the Hammond case.

  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_It doesn't improve the sound in theory only._

 

Are we talking cognitive dissonance here?

  Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Agreed, but I'd say aesthetics has quite a bit to do with DIY, but that's probably another thread (where perceived percentages of 'better' SQ are discussed). Otherwise all our builds would remain strapped to boards, and they'd be a heck of a lot quicker to finish! 
	

	
	
		
		

		
		
	


	


_

 

Actually, casing the amp could have a functional benefit. It would help block out EMI. 
	

	
	
		
		

		
		
	


	




 I agree with you though. I did order several different LEDs to try out. I even ordered some connectors to make them easily swappable. 
	

	
	
		
		

		
		
	


	




 But if I hear them (and I will be brutally honest when testing), they are gone. The tube glow will be enough for me


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_I tend to put much effort and $$$ to higher SQ, but I think aesthetics will give more impact to resale value than boutique parts or contruction quality. 

 That 2 extra blue (yeah "blue" is very critical in this example 
	

	
	
		
		

		
		
	


	




) LEDs may give your amp an extra 25-50$ in resale value...

 But everyone know that we will all keep our SOHA II preciously 
	

	
	
		
		

		
		
	


	


_

 

The only way I would part with a DIY project would be if that was the intention all along.

 I plan to keep my SOHA II forever though. 
	

	
	
		
		

		
		
	


	




 I'm actually looking forward to having a collection of headphone amps I have built. I'm up to 4 so far


----------



## lacrossebowe8

What size standoffs should I order for the amp? I am not using a hammond case so I will need to use all 7 standoffs. I want them to lift the board about 1cm off the case. Also I am about to place an order from digikey so if you know of a standoff there that will work please let me know.


----------



## Hayduke

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_What size standoffs should I order for the amp? I am not using a hammond case so I will need to use all 7 standoffs. I want them to lift the board about 1cm off the case. Also I am about to place an order from digikey so if you know of a standoff there that will work please let me know._

 

I had the same question. I can source standoffs locally though, so I'm just waiting until I get that close to finishing and I'll buy them at that point. Do you not have a hardware store nearby? I can get standoffs at my local Ace Hardware.

  Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_I just finished my SOHA II, Very nice build, sounds great, a definite step up from my SSMH. now I need to save for HD600's.
 Has anyone else noticed that the excel BoM is missing P1P, the pot to adjust the high voltage? Luckily I had one that would work.
http://i471.photobucket.com/albums/r...3/IMG_0967.jpg http://i471.photobucket.com/albums/r...3/IMG_0971.jpg_

 

What bushings are those around the tube holes?
 I'm not sure if Grendel will see this, so if anyone knows, please respond


----------



## holland

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_What slot do you have the board in using 1/8" spacers?_

 

I am not using the BOM case.


----------



## grendel23

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_What bushings are those around the tube holes?_

 

These are snap in plastic bushings from the hardware store. These were too tall, so I trimmed them down and glued them in with epoxy.

 By the way, I have replaced my original top with one made of perforated aluminum. There was more heat building up around the tubes than I was happy with. I used 3003 Perforated Aluminum Sheet .063" x 12" x 24" - eBay (item 350114083531 end time Jan-20-09 09:49:57 PST). Once painted to match case, it looks great and runs much cooler.


----------



## Hayduke

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You're welcome. 
	

	
	
		
		

		
		
	


	




 Here's an alternate way to wire the LEDs that might be preferable because it keeps the LED current out of the ground flow. RLED is calculated using 24V instead of 12V.






 Edit: I've changed the drawing slightly to be consistent with common representations of dual LEDs. And, of course, one can always use individual LEDS.

 I've also changed one resistor value. It's not important, but it does serve to equalize the base currents for the alternate version._

 

How much power is available here?
 I'd like to have this circuit power the LEDs in the tube sockets. When the E12 circuit is triggered, it will power a separate LED, but when everything is OK, I want the tube LEDs to come on.

 My thought is to put a bright red LED inside the case. So when the delay is on, the tube LEDs go dark and there will be a red glow coming through the various ventilation holes. When the delay circuit is being bypassed (ie music to the headphones), the tube LEDs come on.

 I know you have already provided 3 LED circuits on the PCB. I already ordered the parts to possibly use 2 of these (based on noise as posted above), but I'd really like a visual indicator that the delay circuit has kicked in.

 Alternatively, I can just hook up the red LED in the circuit provided, correct? Do I need to put the resistor in place for the other, unused, LED?
 In other words, I really only care if the delay is on. I don't need the green LED in the circuit.

 Sorry for all the questions. I ordered most of the parts, but then I realized I missed a couple small items. Since I'm placing another order, I thought I might like to implement this idea. If I have no sound coming from the headphones, I'd like an easy way to see if it was due to the E12 circuit.


----------



## lacrossebowe8

i do have plenty of hardware stores. I just wasn't sure they would have standoffs. Maybe I will get some tomorrow... if I can get anywhere due to inauguration.


----------



## runeight

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_How much power is available here?
 I'd like to have this circuit power the LEDs in the tube sockets. When the E12 circuit is triggered, it will power a separate LED, but when everything is OK, I want the tube LEDs to come on.

 My thought is to put a bright red LED inside the case. So when the delay is on, the tube LEDs go dark and there will be a red glow coming through the various ventilation holes. When the delay circuit is being bypassed (ie music to the headphones), the tube LEDs come on.

 I know you have already provided 3 LED circuits on the PCB. I already ordered the parts to possibly use 2 of these (based on noise as posted above), but I'd really like a visual indicator that the delay circuit has kicked in.

 Alternatively, I can just hook up the red LED in the circuit provided, correct? Do I need to put the resistor in place for the other, unused, LED?
 In other words, I really only care if the delay is on. I don't need the green LED in the circuit.

 Sorry for all the questions. I ordered most of the parts, but then I realized I missed a couple small items. Since I'm placing another order, I thought I might like to implement this idea. If I have no sound coming from the headphones, I'd like an easy way to see if it was due to the E12 circuit._

 


 You should only draw about 10mA for everything powered by this circuit, whether it's one LED or many.

 To use just the red LED replace the green LED and its resistor with about a 3k resistor. Then set the red LED resistor to provide 10mA or less through the red LED.

 If you want mulitple red LEDs then put them in series and adjust the resistor according to the new voltage drop. You can probably run to a maximum of 10V in the LED string and then a resistor to set the current.

 Does this help?


----------



## wiatrob

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_ I used 3003 Perforated Aluminum Sheet .063" x 12" x 24" - eBay (item 350114083531 end time Jan-20-09 09:49:57 PST). Once painted to match case, it looks great and runs much cooler._

 

Nice link, They've got some sexy hex perf as well...


----------



## runeight

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_These are snap in plastic bushings from the hardware store. These were too tall, so I trimmed them down and glued them in with epoxy.

 By the way, I have replaced my original top with one made of perforated aluminum. There was more heat building up around the tubes than I was happy with. I used 3003 Perforated Aluminum Sheet .063" x 12" x 24" - eBay (item 350114083531 end time Jan-20-09 09:49:57 PST). Once painted to match case, it looks great and runs much cooler._

 

I made a perf'd aluminum top too and had it anodized. It is a pretty standard way to make a ventilated top, but it actually looks good and the amp runs at a comfortable temperature. Plus, I can see inside.


----------



## Hayduke

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_These are snap in plastic bushings from the hardware store. These were too tall, so I trimmed them down and glued them in with epoxy.

 By the way, I have replaced my original top with one made of perforated aluminum. There was more heat building up around the tubes than I was happy with. I used 3003 Perforated Aluminum Sheet .063" x 12" x 24" - eBay (item 350114083531 end time Jan-20-09 09:49:57 PST). Once painted to match case, it looks great and runs much cooler._

 

Thanks for the response AND the link!
 I'll have to wander around my hardware store when I go get fasteners and stand offs. 
	

	
	
		
		

		
		
	


	




 btw, I love the way your case looks. I'm still undecided, but I'm considering copying your idea. That hammertone paint looks awesome! I have a lot of copper decor in my house. We have a coffee table and a sofa table, used to hold components under the wall mounted LCD TV, that are both hammered copper. That would blend well.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You should only draw about 10mA for everything powered by this circuit, whether it's one LED or many.

 To use just the red LED replace the green LED and its resistor with about a 3k resistor. Then set the red LED resistor to provide 10mA or less through the red LED.

 If you want mulitple red LEDs then put them in series and adjust the resistor according to the new voltage drop. You can probably run to a maximum of 10V in the LED string and then a resistor to set the current.

 Does this help?_

 

That helps a lot! Thanks Alex.

 So I'll just use only the red LED from the E12 circuit you supplied. The tube LED, if I use them, can stay on all the time 
	

	
	
		
		

		
		
	


	




 I will be happy to have a visual indication that the delay circuit is active.

 My parts should be here this week, so I should be able to get it all assembled this weekend. I'm excited to hear this amp! I probably won't get the case work completed for some time though. If I use this perfed top, I might do it myself. Otherwise it has to ship to CA for my friend to work on it.

 EDIT:
 Just tried to check the status of my Mouser order and it appears it didn't go through on Friday 
	

	
	
		
		

		
		
	


	



 I probably never hit submit or something. Oh well now I can get the parts I missed into a single order.

 Would anyone mind looking at my BOM and letting me know if you see any problems?

 I changed some of the colors to indicate vendors other then Mouser. Also, a purple cell means I changed the part from the original BOM so it will be easier to see what is different.

 Now to figure out what tubes to order


----------



## regal

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Alex recommended the Avid transformer originally, so all I did was get "the next size up" from them. It is slightly larger physically, but bmwpower36(sorry bmw I know I spelled this wrong) was able to squeeze it into the Hammond case.
_

 


 Should we add the Digikey Amveco transformer to the BOM? I'm sure people don't want to place a separate parts express order.


----------



## runeight

My understanding (could be wrong) is that the Amveco transformers are rated before regulation and that they pull down below their spec'd values when full current is drawn. I read this, I think, on this thread.

 Can anyone verify that this is correct or not? If it is true, then the amveco would not sub in this amp. And, obviously, if I'm wrong, we can put it into the BoM.


----------



## Hayduke

Mouser is out of TL783 until March 
	

	
	
		
		

		
			





 Since I couldn't find an alternative with Mouser, I got one from Digi-Key. I saved a few bucks on the case by getting that from them as well. Of course I ordered some extra supplies that I can't get from Mouser, so I actually spent more 
	

	
	
		
		

		
		
	


	




 Is it just me, or did Digi-Key change it's minimum order policy? I thought they used to require a $50 minimum to avoid a handling fee. That no longer seems to be their policy.

 Time to start tube hunting


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_My understanding (could be wrong) is that the Amveco transformers are rated before regulation and that they pull down below their spec'd values when full current is drawn. I read this, I think, on this thread.

 Can anyone verify that this is correct or not? If it is true, then the amveco would not sub in this amp. And, obviously, if I'm wrong, we can put it into the BoM._

 

I believe Holland reported it is the _ANTEK_ transformers that are rated unloaded (hence their 'enhanced affordability') I have an Amveco on my desk powering my M^3 - a quick measurement and I'll be back...


----------



## wiatrob

18.97V and 19V on each leg under load for an 18V Dual Amveco 62064. These are nice transformers... I'd vote to add it, I believe we left it out originally for cost reasons. Shipping difference will more than compensate.


----------



## Hayduke

When you order tubes, do you get more then 2 of a type?

 I just ordered a bunch form vacuumtubes.net. I only got 2 each of 5 different models. Now I'm wondering if I shouldn't have ordered extras. 
	

	
	
		
		

		
		
	


	




 Anyway I ordered:
 5963
 6189
 5814A
 6922

 He said 6922 are upgraded 6DJ8s and they were the most expensive at $25 each. Really nice guys though 
	

	
	
		
		

		
		
	


	




 Too bad they were out of 8416's 
	

	
	
		
		

		
		
	


	




 I found someone selling them on eBay, so I might pick some up there.


----------



## shellylh

Just ordered a SOHA II kit from Jeff at glassjaraudio.com. What a nice guy. Since this is my first REAL project, I am sure I will be asking a lot of questions as I go. [At this point, I have only made a cmoy, guitar hp amp from a kit and modded my X-can (installed new caps/diodes).] I figure that this will be a real learning experience. Anyway, I hope I don't kill myself or catch anything on fire. It would be even better if the amp actually works and sounds good at some point in the future.


----------



## rds

Quote:


 My understanding (could be wrong) is that the Amveco transformers are rated before regulation and that they pull down below their spec'd values when full current is drawn. I read this, I think, on this thread.

 Can anyone verify that this is correct or not? If it is true, then the amveco would not sub in this amp. And, obviously, if I'm wrong, we can put it into the BoM. 
 

I'd like to know this too, as I bought that Amveco in the original BOM. I have the rev1.1 board and haven't built the amp yet.

  Quote:


 Are we talking cognitive dissonance here? 
 

No. It's the fact that we really do, to a large extent, judge books by their covers. A good chef knows that their food always tastes better when presented well, for example.


----------



## lacrossebowe8

I have finished my build and am running through the setup. I got to measuring the voltage of TB+ and got 124 volts, not 103 volts. Is this a problem and if so what are likely culprits?


----------



## lacrossebowe8

I just did a better search and saw that if none of the jumpers are jumpered that my high voltage is ok.


----------



## wiatrob

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_I just did a better search and saw that if none of the jumpers are jumpered that my high voltage is ok._

 

Strong work!


----------



## wiatrob

I just checked the Amveco catalog - published ratings are under load, and include an unloaded voltage (higher than spec).

 The 35 VA specs: 

 Part: 62073 
 Secondary Full Load: 2x15 
 Current mA:1166 
 No Load Voltage: 2x17.6 

 There's also a 50VA for the high current version:
 Part:62083 
 Secondary Full Load: 2x15 
 Current mA:1666 
 No Load Voltage: 2x17.3


----------



## wiatrob

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_When you order tubes, do you get more then 2 of a type?_

 

I usually order only (claimed!) tested tubes in pairs, mostly from flea-bay. As noted elsewhere in this thread, exact tube matching is not so critical with the design of this amp.

  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Too bad they were out of 8416's 
	

	
	
		
		

		
		
	


	




 I found someone selling them on eBay, so I might pick some up there._

 

Sounds like a nice assortment to start rolling. I got Amperex 8416's here:

Vacuum Tubes, Inc. New Audio and Western Electric Tubes for Hi Fi and Guitar Amplifiers

 But they were cheaper when I bought 'em!


----------



## runeight

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_I just did a better search and saw that if none of the jumpers are jumpered that my high voltage is ok._

 

And so, is everything else working ok too?


----------



## rds

Quote:


 I just checked the Amveco catalog - published ratings are under load, and include an unloaded voltage (higher than spec).

 The 35 VA specs:

 Part: 62073
 Secondary Full Load: 2x15
 Current mA:1166
 No Load Voltage: 2x17.6 
 

Thanks for checking into that Wiatrob.

 I picked up the Amveco from the original BOM - the 62063.
 It is rated at 1.7A - is that going to be enough for the high voltage rev1.1?

 EDIT - I see that this is 1.7A parallel and 25VA - do I have a problem then?


----------



## lacrossebowe8

I just finished everything and am listening to some music. Sounds good. I will post some impressions later. I am using sr-80's but usually use sr-225's and I am hoping to pick up some senn 650's soon. Pictures and more to come. Thanks for a great amp design.


----------



## runeight

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Thanks for checking into that Wiatrob.

 I picked up the Amveco from the original BOM - the 62063.
 It is rated at 1.7A - is that going to be enough for the high voltage rev1.1?

 EDIT - I see that this is 1.7A parallel and 25VA - do I have a problem then?_

 

You might have a problem with 850mA in series usage. But try it and see. We may ask for a few voltage measurements to check this. And these measurements are not available at the test points, but they mey measure the input voltages to the regulators. If these are too low the regulators will not regulate properly. If so, you may need to select an alternative trafo.


----------



## runeight

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_I just finished everything and am listening to some music. Sounds good. I will post some impressions later. I am using sr-80's but usually use sr-225's and I am hoping to pick up some senn 650's soon. Pictures and more to come. Thanks for a great amp design._

 

OK. Great to hear this and will look forward to further results. Don't forget that you can freely adjust the B+ on the tubes.


----------



## runeight

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_Just ordered a SOHA II kit from Jeff at glassjaraudio.com. What a nice guy. Since this is my first REAL project, I am sure I will be asking a lot of questions as I go. [At this point, I have only made a cmoy, guitar hp amp from a kit and modded my X-can (installed new caps/diodes).] I figure that this will be a real learning experience. Anyway, I hope I don't kill myself or catch anything on fire. It would be even better if the amp actually works and sounds good at some point in the future. 
	

	
	
		
		

		
			



_

 

Welcome aboard shellylh. It's great to have another Texan building one of these.


----------



## pabbi1

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_Just ordered a SOHA II kit from Jeff at glassjaraudio.com. What a nice guy. Since this is my first REAL project, I am sure I will be asking a lot of questions as I go. [At this point, I have only made a cmoy, guitar hp amp from a kit and modded my X-can (installed new caps/diodes).] I figure that this will be a real learning experience. Anyway, I hope I don't kill myself or catch anything on fire. It would be even better if the amp actually works and sounds good at some point in the future. 
	

	
	
		
		

		
		
	


	


_

 

Marry me! A woman building amps and getting a hd800 - what more could any man want? 
	

	
	
		
		

		
		
	


	




 Seriously, did you get to listen to my SOHA II in Houston? It will be at the DFW meet thanks to the nasty dust conditions in Afghanistan. It is good enough that Marc is building one...


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_It is good enough that Marc is building one..._

 

yes, I'm plotting to get all Japanese transistors in mine


----------



## bmwpowere36m3

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_I just finished everything and am listening to some music. Sounds good. I will post some impressions later. I am using sr-80's but usually use sr-225's and I am hoping to pick up some senn 650's soon. Pictures and more to come. Thanks for a great amp design._

 

I curious as to your listening impressions, I have extensively listened to the SOHA II w/ HD580's and recently auditioned a pair of Grado SR-80s on it... 

 I also picked up a set of Amperex/HP 6DJ8 tubes to complement the EH 12AU7's I've already got.


----------



## lacrossebowe8

I will need a few hours of listening time to get some good impressions. The 80's are great, fun, cheap cans. Right now I am using beckman tubes that came with my glass jar kit at 6.3 volts. One day i will do some tube rolling. 

 What B+ are most people using?


----------



## shellylh

Haha... That depends on whether the KGBH/HE60 will be in the prenuptial agreement! I am not so sure the significant others would be too happy though. 
	

	
	
		
		

		
		
	


	




 Seriously though, I didn't get to listen to the SOHA II in Houston. There was too much gear and not enough time. I hope to get enough work done in the next week or so to make a road trip but it is not looking good. 

  Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Marry me! A woman building amps and getting a hd800 - what more could any man want? 
	

	
	
		
		

		
		
	


	




 Seriously, did you get to listen to my SOHA II in Houston? It will be at the DFW meet thanks to the nasty dust conditions in Afghanistan. It is good enough that Marc is building one..._


----------



## Ferrari

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_
 What B+ are most people using?_

 

I can’t speak for all, but on my builds the B+ voltage is sitting close to the limit of the HV section: 
 120V on the proto version on the first page of this thread and 90V on the balanced version I’m working on.


----------



## holland

I am using 95V.


----------



## Uncle Bob

My SOHA II has developed the infamous hiss problem 
	

	
	
		
		

		
		
	


	




 However, it's only in one channel......

 1. I'm positive, the hiss problem was not there when the amp was 1st built
 2. The problem appeared when I accidently caught the headphone cable and knocked the amp off the shelf it was sitting on. It didn't fall far as the shelf is quite low and the amp was tethered with the power and signal cables, but immediately afterwards I noticed the noise.
 3. I suspected I'd damaged the valve but swapping them around beween channels or leaving them out, or changing them for a different type doesn't affect the noise.
 4. It's not volume dependant - i.e it's not affected by moving the pot, and is only heard once the E12 relay engages.
 5. It's still present if the inputs are disconnected.
 6. It's not noise in my ear, if I reverse the headphones, the hiss moves to my other ear.
 7. I can only hear it with my Grado's. It may or may not be present with the Sennheisers but if it is, it's just below my hearing threshold.

 There's a possibility I might be able to do some checks with a friend's oscilliscope. I'll keep you posted.


----------



## Hayduke

Maybe it's relate to the headphone jack? You determined it was the tubes and it was a tug on the cord that triggered the problem. Maybe the headphones got damaged or the jack did since it took the brunt of the force. I would probably reflow the joints on the output jack and give the jack itself a visual inspection. Of course I have no idea how this could cause a "hiss" sound 
	

	
	
		
		

		
		
	


	




 My instinct just says to follow the source of the trauma.


----------



## Alcaudon

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_7. I can only hear it with my Grado's. It may or may not be present with the Sennheisers but if it is, it's just below my hearing threshold._

 

Maybe the problem is in the headphones. Where they pluged when the amp fell? Have you tried them with another amp?

 Hope you can fix it 
	

	
	
		
		

		
		
	


	




 Edit: Hayduke it's faster than me


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_My SOHA II has developed the infamous hiss problem 
	

	
	
		
		

		
		
	


	




 However, it's only in one channel......

 1. I'm positive, the hiss problem was not there when the amp was 1st built
 2. The problem appeared when I accidently caught the headphone cable and knocked the amp off the shelf it was sitting on. It didn't fall far as the shelf is quite low and the amp was tethered with the power and signal cables, but immediately afterwards I noticed the noise.
 3. I suspected I'd damaged the valve but swapping them around beween channels or leaving them out, or changing them for a different type doesn't affect the noise.
 4. It's not volume dependant - i.e it's not affected by moving the pot, and is only heard once the E12 relay engages.
 5. It's still present if the inputs are disconnected.
 6. It's not noise in my ear, if I reverse the headphones, the hiss moves to my other ear.
 7. I can only hear it with my Grado's. It may or may not be present with the Sennheisers but if it is, it's just below my hearing threshold.

 There's a possibility I might be able to do some checks with a friend's oscilliscope. I'll keep you posted._

 

Hmmm. Since this was physical stress on the amp, it's probably a mechanical problem. But it doesn't appear that the amp took any kind of concussion, just a dangling from its various cords. Is that right? Or did it actually hit the floor?

 In any case, the first electrical thing to do is to measure all of the testpoint to find out if the voltages are correct. And then measure the O/P idle current and the tube tail currents.

 If these are all correct then we almost certainly have a mechanical problem somehow.


----------



## mdabro

Ferrari, You have connected tubes to PCB board with long wires. Did not it cause any hum ?


----------



## Ferrari

Quote:


  Originally Posted by *mdabro* /img/forum/go_quote.gif 
_Ferrari, You have connected tubes to PCB board with long wires. Did not it cause any hum ?_

 

Not that I can notice. 
	

	
	
		
		

		
		
	


	



 To avoid possible bad effect, keep the wires as short as possible and use shielded cable for the sensitive input signal path (pin 2 of tube socket) and connect the shield to GND. 

 (Shielded cable was not implemented when I post pictures here, but it was implemented short after that).


----------



## wiatrob

Quote:


  Originally Posted by *lacrossebowe8* /img/forum/go_quote.gif 
_What B+ are most people using?_

 

I've gone back and forth between ~60 and 90V. There was an impression from the Designer that the original B+ offered someting special in the character of sound - but as soon as the new HVPS was designed, I (and I think about everybody else on the proto team!) dialed it to '11.' 
	

	
	
		
		

		
			





 I did not notice a lot of difference between plate voltages with the new PS, I've been at ~90V...

 -Bill


----------



## Hayduke

I got my board from Jeff, transformer from Avil, and a nice big box from Mouser. I thought I might get my tubes today, but it looks like they will come on Monday.

 So I have enough parts to start building the amp, but I have to leave town tomorrow morning 
	

	
	
		
		

		
		
	


	




 oh well, I guess I get to build it next weekend.

 /e wanders off humming "Waiting is the Hardest Part".


----------



## Ferrari

For those who would like to mount LED’s under the tubes of your SOHA II, but hate the cumbersome wires running under the PCB, this can be interesting. The pic below showing how it was implemented on my build.








 Have fun with your build!


----------



## Alcaudon

Really nice Ferrary!!!!

 So, with this implementation you won't be catching any hum from the leds as some people has mentioned?


----------



## Hayduke

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_For those who would like to mount LED’s under the tubes of your SOHA II, but hate the cumbersome wires running under the PCB, this can be interesting. The pic below showing how it was implemented on my build.

http://i72.photobucket.com/albums/i1...eelding597.jpg


 Have fun with your build! 
	

	
	
		
		

		
		
	


	


_

 

How come you wired them different? I see the one on the right is tied into the heater circuit, but I can't see where the one on the left is grounded to.


----------



## Ferrari

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Really nice Ferrari!!!!

 So, with this implementation you won't be catching any hum from the leds as some people has mentioned?_

 

I have never experienced hum/noise caused by LED's on my amps.
 I prefer doing it this way mainly to keep things as clean as possible (one of my personal rules). 
	

	
	
		
		

		
		
	


	




 My guess is that the hum some people have, is due to using (too long) unshielded wires for sensitive signals paths, which invites interferences. Also wires carrying DC voltage (-12.6V) running under the PCB, too close to the sensitive traces can be a source of problem.


----------



## Ferrari

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_How come you wired them different? I see the one on the right is tied into the heater circuit, but I can't see where the one on the left is grounded to._

 

Both LED’s are connected the same way: feeding by the same -12.6V heater voltage circuit via a 1KΩ resistor, while the anode connected to the same ground.


----------



## onform

All I need is the trofo now...


----------



## Uncle Bob

Sweet, looks like you'll be busy


----------



## onform

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Sweet, looks like you'll be busy 
	

	
	
		
		

		
		
	


	


_

 

Yep if I can find the time or should I say if the missus doesn't find something else for me to do!! 

 Any more news on your build?? is it cased up yet?


----------



## Ferrari

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_All I need is the trofo now... _

 

... and a nice enclosure. 
	

	
	
		
		

		
		
	


	



 Are you going to use the stock Hammond or do you have something else in mind? 
 Have fun with your build!


----------



## holland

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Also wires carrying DC voltage (-12.6V) running under the PCB, too close to the sensitive traces can be a source of problem._

 

Yep, that was my problem. Wires running under the PCB with 1/8" spacers. My LEDs were always meant to be temporary, as my amp is fully enclosed (tubes and all) so LEDs made no sense as well.

 You've got a good wiring scheme there.


----------



## Uncle Bob

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_Yep if I can find the time or should I say if the missus doesn't find something else for me to do!! 

 Any more news on your build?? is it cased up yet?_

 

My build has been running for a few weeks but is not yet cased up. I'm still keen on the HIFI2000 case but I've been putting off buying because of the euro exchange rate. It would seem that there's no short term prospect of that improving, so I'd better get my order in before it gets any worse!


----------



## onform

I purchased this one back when I first said I was going to get the kit so I gained there...


----------



## Ferrari

Ooh, one of my favourite! I have used that enclosure a while back too.


----------



## Uncle Bob

Nice, they are a smart looking case. Is that case tall enough to enclose the valves or will you have to cut holes in the top do you think?

 Do they come with all any accessories - like feet? How was modushop to deal with?


----------



## Ferrari

Modushop is very easy to deal with, however communications with the Italians from HiFi-2000 in English can be a pain in the “behind”. 
	

	
	
		
		

		
			





 They do sell feet but these are overkill for such small enclosures from the Galaxy (Max) line.
 I’m using those rubber feet for my β24 and Super Leach power amps, housed in Pesante Dissipante 5U enclosures.
 I would say… take a look at Modushop and find out yourself.


----------



## Alcaudon

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Ooh, one of my favourite! I have used that enclosure a while back too. 
	

	
	
		
		

		
		
	


	


_

 


 Hey Ferrary, can I ask you where did you get the jack connector for that soha II???? I've been looking for something similar, but the only thing I could find is the neutrik locking one, and I really don't like how it looks.

 Thanks!


----------



## tacitapproval

I just built the soha II from the glassjar kit. I am a novice at amp building, having only built a couple of cmoys and a pimeta before. Nonetheless, I managed to get the soha up and running on the first try. It sounds great. 

 I do have one issue though, which has emerged as I am doing the casework. I grounded the iec to a bolt through the case and ran another through the star ground on the board. I now have what sounds like a ground loop if I turn up the volume with no music playing. I experimented by running the power ground to a pair of pliers and the noise went away. Can someone tell me what I am doing wrong?


----------



## holland

that's just a ground loop.

The Cavalli-Kan Kumisa III Stereo Headphone Amplifier

 last paragraph. That should fix you. Make sure the jacks are of the isolating type. Note the grounding of the pot if you're using a plastic panel.


----------



## Ferrari

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Hey Ferrary, can I ask you where did you get the jack connector for that soha II???? I've been looking for something similar, but the only thing I could find is the neutrik locking one, and I really don't like how it looks.

 Thanks!_

 

It's a Neutrik NYS221, available at Mouser.
 This type is _non-isolated_. Therefore mounting directly on a metal faceplate is not recommended.


----------



## Alcaudon

Many thanks for your answers Ferrari. Non isolation is not an issue, since it's for a DIY wooden enclosure.

 Btw, someday I might ask you a few questions about your balanced SohaII if you don't mind of course 
	

	
	
		
		

		
		
	


	




 Thanks!


----------



## tacitapproval

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_that's just a ground loop.

The Cavalli-Kan Kumisa III Stereo Headphone Amplifier

 last paragraph. That should fix you. Make sure the jacks are of the isolating type. Note the grounding of the pot if you're using a plastic panel._

 


 Thanks for the suggestion. I implimented the ground loop breaker outlined on amb's site. It lowered the noise some, but it is still there. Anything else to try? I suppose I could live with it, as the noise is only audible well past the volume where I would ever foreseeably listen. Is this just the consequence of using a single case?

 Update:
 The main culprit seems to not be the soha after all, but the Ibasso D3 DAC I am feeding it. I switched to my pmp and the noise is greatly diminished-- not gone but much more faint.


----------



## lacrossebowe8

as you know i have finished my build and have liked it so far. I have run into an issue though. After a couple hours of playtime the right channel drops in volume and becomes quite distorted. If I power down then back up it works ok for a little, then back to the problem. If i turn down the B+ it seems to work ok for a while. Does anyone have any suggestions?


----------



## holland

swap tubes and see if it follows. Touch the buffer heatsinks. Does one side seem extraordinarily hot?


----------



## lacrossebowe8

None of the buffers seem hotter than the other. If I trip the relay by adjusting the B+ it goes away (then comes back later). I will swap tubes tomorrow and see if the problem follows. If I tap either tube I hear the microphonics in the left phone only.


----------



## holland

could be cold solder joint. If the tube swap doesn't follow the tube, then check the joints on that one side.

 You can also probe the B+, V+, V-, H-, when it happens.

 The microphonics could just be a "bad" tube.


----------



## tacitapproval

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_Thanks for the suggestion. I implimented the ground loop breaker outlined on amb's site. It lowered the noise some, but it is still there. Anything else to try? I suppose I could live with it, as the noise is only audible well past the volume where I would ever foreseeably listen. Is this just the consequence of using a single case?

 Update:
 The main culprit seems to not be the soha after all, but the Ibasso D3 DAC I am feeding it. I switched to my pmp and the noise is greatly diminished-- not gone but much more faint._

 

Further update: the actual culprit is the laptop power cord coming through the usb of the dac; if I unplug the laptop, no more noise. 

 My question is if I switched the groundloop breaker from the pcb ground to the rca or iec ground would it be more effective? Does this make sense?


----------



## runeight

tacitapproval, one question on your rca jacks. Are they grounded directly to the case or are they grounded to the input ground point on the board?


----------



## Ferrari

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_My question is if I switched the groundloop breaker from the pcb ground to the rca or iec ground would it be more effective? Does this make sense?_

 

I just want to ask but... runeight has beaten me on that.
 One remark regarding ground loop breaker: for safety reason, a ground loop breaker should not be connected to the AC input ground (IEC connector).


----------



## tacitapproval

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_tacitapproval, one question on your rca jacks. Are they grounded directly to the case or are they grounded to the input ground point on the board?_

 

I actually haven't wired the rca's yet, and have been using a plastic-cased mini-jack grounded to the board input thus far. I am concerned that the rca jacks I have are not isolated from case contact and I need to get some plastic washers.


----------



## tacitapproval

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I just want to ask but... runeight has beaten me on that.
 One remark regarding ground loop breaker: for safety reason, a ground loop breaker should not be connected to the AC input ground (IEC connector)._

 

Thanks. This is good information to have.


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Nice, they are a smart looking case. Is that case tall enough to enclose the valves or will you have to cut holes in the top do you think?

 Do they come with all any accessories - like feet? How was modushop to deal with?_

 

Uncle Bob you haven't said anything lately about your hiss problem. Is it still there? And have you had a chance to measure voltages?

 BTW, thanks for the request to put indicators on the e12. As you know I used them on the compact hybrid. It's a very cool feature.


----------



## runeight

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_I actually haven't wired the rca's yet, and have been using a plastic-cased mini-jack grounded to the board input thus far. I am concerned that the rca jacks I have are not isolated from case contact and I need to get some plastic washers._

 

OK. So the ground wriing is like this . . .

 IEC to enclosure ground. Input jack ground to board input ground. Board ground to enclosure ground through ground loop breaker?

 Also, have you grounded the volume pot? There is a small ground pad right near the back of the pot for this. You can unscrew one of the case screws on the pot, wrap a very fine stranded wire around it, put the screw back in, and solder the other end of the wire to the ground pad. In case you haven't done this yet it might help.


----------



## tacitapproval

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. So the ground wriing is like this . . .

 IEC to enclosure ground. Input jack ground to board input ground. Board ground to enclosure ground through ground loop breaker?

 Also, have you grounded the volume pot? There is a small ground pad right near the back of the pot for this. You can unscrew one of the case screws on the pot, wrap a very fine stranded wire around it, put the screw back in, and solder the other end of the wire to the ground pad. In case you haven't done this yet it might help._

 

That's exactly right, and I have grounded the pot to the board as described.


----------



## runeight

OK. And then when connect the board ground directly to the case the buzz is worse?

 What happens if you disconnect the input jack ground from the board when you have your source plugged in?


----------



## tacitapproval

Yes, the noise appears earlier on the pot travel when the board is connected directly to the chassis (not through the groundloop breaker).

 I tried disconnecting the input ground from the board and the noise is much, much worse this way.


----------



## wiatrob

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_Yes, the noise appears earlier on the pot travel when the board is connected directly to the chassis (not through the groundloop breaker).

 I tried disconnecting the input ground from the board and the noise is much, much worse this way._

 


 Have you checked/reflowed all the solder joints on the pot (I am assuming it is soldered to the board.) I had a cold joint on my M^3 that had a burst of noise appearing early in pot travel due to torque on the bad joint...


----------



## tacitapproval

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Have you checked/reflowed all the solder joints on the pot (I am assuming it is soldered to the board.) I had a cold joint on my M^3 that had a burst of noise appearing early in pot travel due to torque on the bad joint..._

 

I will check the pot soldering, but I don't think this is a problem. As I mentioned earlier, the noise is coming from the laptop while plugged into ac--unplug the laptop and the noise disappears. Kind of disconcering that it is traveling through the usb cord to the dac and on to the soha ii. I thought using an standalone dac was supposed to eliminate noisy onboard electronics.


----------



## runeight

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_I will check the pot soldering, but I don't think this is a problem. As I mentioned earlier, the noise is coming from the laptop while plugged into ac--unplug the laptop and the noise disappears. Kind of disconcering that it is traveling through the usb cord to the dac and on to the soha ii. I thought using an standalone dac was supposed to eliminate noisy onboard electronics._

 

So it is said about the DACs, but . . .

 Pardon these few dumb questions . . .

 What is the laptop brick plugged into? Does this matter? 

 Can you try another brick?

 Is the amp plugged into the same outlet as the laptop? 

 What happens if the laptop AC is plugged in but the laptop is turned off? Or just on standby?

 Laptops don't need UPSs (usually) so I assume that none is involved here?


----------



## wiatrob

I _always _have noise through my USB dac (especially usb powered dacs) when the computer is plugged in to mains. The only way I've found to eliminate it is to use optical or coax connections.

 More knowledgeable here may shed some light on things - I think I've even tried it with the amp/dac/ and computer plugged into the same circuit and had some noise. Granted, very little unless I turn the volume up all the way...


----------



## tacitapproval

I have tried plugging the laptop into a different outlet, power strip, no power strip and the noise remains. Amp has also been tried in different outlets.

 I don't have another brick, unfortunately.

 No noise if laptop is off or on standby, but this shuts down the dac as it is usb powered.

 No UPS.

 Update:
 Now the noise is nearly non-existent. I didn't do anything, other than leave it running for some time now (a property of warming-up?) I can hear it only with iems and not with my HD650 or DT770 all of a sudden. Why would it fluctuate like this? I guess I should't look gift horses in mouths.


----------



## wiatrob

Do you here the 'same' noise with your PMP plugged in as with the DAC? How does the output sound with the PMP vs. no input at all?


----------



## runeight

I don't use DACs from computers so I am far from expert, but it seems that wiatrob's solutions may be the only ones. This is really a ground noise problem and the only way to fix it is to break the ground connection between the dac and the amp. At least that's the only way that I can think of.

 Perhaps some others can offer other, better solutions.


----------



## tacitapproval

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Do you here the 'same' noise with your PMP plugged in as with the DAC? How does the output sound with the PMP vs. no input at all?_

 

The PMP is nearly black, same with no input--none of the computer noise

 Although now it is negligible--go figure.


----------



## tacitapproval

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't use DACs from computers so I am far from expert, but it seems that wiatrob's solutions may be the only ones. This is really a ground noise problem and the only way to fix it is to break the ground connection between the dac and the amp. At least that's the only way that I can think of.

 Perhaps some others can offer other, better solutions._

 

Thanks for your help. It is actually nearly fixed--despite my not knowing why. It must be magic.


----------



## wiatrob

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_Update:
 Now the noise is nearly non-existent. I didn't do anything, other than leave it running for some time now (a property of warming-up?) I can hear it only with iems and not with my HD650 or DT770 all of a sudden. Why would it fluctuate like this? I guess I should't look gift horses in mouths._

 

Hmmm. I'd say let it burn in a while more and see if there's a consistency. I am going to assume that the your IEMs are the most sensitive/lowest impedance 'phones you have. My test phones (cheaper earbuds) always pick up a wee bit of noise that I never hear on my other cans...

 Posts Crossed. Keep listening. Maybe it was the tubes??

 AFA Dac ground loops:http://www.head-fi.org/forums/f46/be...um#post4396311

 Looks like it happens with Dacs better than ours.


----------



## Hayduke

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_BTW, thanks for the request to put indicators on the e12. As you know I used them on the compact hybrid. It's a very cool feature. 
	

	
	
		
		

		
			



_

 

x2 
	

	
	
		
		

		
		
	


	




 I just returned home from a trip out of town. All my parts are sitting here waiting. I'm hoping to have music through this thing this weekend. Casework may take much longer.

 Edit:
 Bah! I just looked in my digi key box and I got a silver Hammond case 
	

	
	
		
		

		
		
	


	




 I wanted black. Oh well I think this will be another push to use the hammer tone paint like Grendel23 did. Of course I'll have to put some black on first. Oh well, casework is always the challenging part


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Uncle Bob you haven't said anything lately about your hiss problem. Is it still there? And have you had a chance to measure voltages?

 BTW, thanks for the request to put indicators on the e12. As you know I used them on the compact hybrid. It's a very cool feature. 
	

	
	
		
		

		
		
	


	


_

 

I'm still here, and unfortunately I still have the hiss problem - I just haven't had the opportunity to sit down and work on the board. I will keep you posted on progress - I still have to make an enclosure for it. I can't consider it a finished project until it's all cased up.

 I'm really glad that the LED idea has proved popular. I was grateful for the time you took to work out a solution when I requested it and the fact that other people think it's a cool feature makes the time spent worthwhile. Not that I've had time to make the board for mine yet


----------



## Hayduke

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I'm really glad that the LED idea has proved popular. I was grateful for the time you took to work out a solution when I requested it and the fact that other people think it's a cool feature makes the time spent worthwhile. Not that I've had time to make the board for mine yet 
	

	
	
		
		

		
		
	


	


_

 

hmmm on a board huh? I was planning to sort of air wire it. I'm only using a single LED to indicate that the circuit is active, so my plan is to have an LED on one end and 2 wires on the other. All the parts will be bundled together into some heatshrink. Heat shouldn't be an issue with these, right? I guess I'll now in the next couple of days. I can't wait to start building. I came back to work early from a trip and I'm wishing I had just stayed home and worked on my amp


----------



## wiatrob

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_x2 
	

	
	
		
		

		
		
	


	




 Edit:
 Bah! I just looked in my digi key box and I got a silver Hammond case 
	

	
	
		
		

		
		
	


	




 I wanted black. Oh well I think this will be another push to use the hammer tone paint like Grendel23 did. Of course I'll have to put some black on first. Oh well, casework is always the challenging part 
	

	
	
		
		

		
		
	


	


_

 

Which model case is it? I have few black hammonds, PM me if you want to swap...


----------



## wiatrob

Quick followup on the dac noise. OT but it's bugging me. Obtained isolation transformer. Hooked up my Imac and Dac/SohaII to it. Ran only a usb cable from the mac to the dac. Soha has noise when usb cable is plugged in , but only after 3/4 volume travel. Dead silent all the way to max without the cable. Swapped USB cables. Same result.

 Very happy TacitA's noise went away though!


----------



## tacitapproval

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Quick followup on the dac noise. OT but it's bugging me. Obtained isolation transformer. Hooked up my Imac and Dac/SohaII to it. Ran only a usb cable from the mac to the dac. Soha has noise when usb cable is plugged in , but only after 3/4 volume travel. Dead silent all the way to max without the cable. Swapped USB cables. Same result.

 Very happy TacitA's noise went away though!_

 

Sorry to hear that your noise remains.

 Mine seems to fluctuate, sometimes it is there, sometimes not. It is also only evident past 3/4 travel, so it doesn't affect listening volumes. 

 What about using a ground lifter on the laptop--is this a bad idea?


----------



## luvdunhill

what about including a CL60 thermistor from analog ground to earth?


----------



## wiatrob

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_Sorry to hear that your noise remains.

 Mine seems to fluctuate, sometimes it is there, sometimes not. It is also only evident past 3/4 travel, so it doesn't affect listening volumes. 

 What about using a ground lifter on the laptop--is this a bad idea?_

 

I can't hear it, so i don't let it bother me. I understand there are those with more sensitive ears here. 
	

	
	
		
		

		
		
	


	




 Does your laptop power adapter cord have a grounded plug? Many don't...

 EDIT: Me thinks this is veering a little off topic here, maybe we should move this thread to the one I referenced earlier if it's truly a DAC grounding issue?


----------



## tacitapproval

luvdunhill -- what about including a CL60 thermistor from analog ground to earth? 

 I've got a paralleled 10ohm resistor and .1uf cap as a ground loop breaker on the amp's board ground. Is this a different tack? (sorry, I'm still a noob)

 wiatrob --I can't hear it, so i don't let it bother me. I understand there are those with more sensitive ears here. 

 Does your laptop power adapter cord have a grounded plug? Many don't...

 EDIT: Me thinks this is veering a little off topic here, maybe we should move this thread to the one I referenced earlier if it's truly a DAC grounding issue? 

 Yes, sorry for the off topic, but that thread is on the benchmark. Perhaps a new thread?

 Yes, my laptop is three-pronged. Is it unsafe to use a ground lifter on a laptop?


----------



## wiatrob

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_
 Yes, my laptop is three-pronged. Is it unsafe to use a ground lifter on a laptop?_

 

The grounds are there for a reason... To keep you and your gear safe and to keep your house form burning down. A real Electircal Engineer and/or expert in the National Electric Code could answer all the technical reasons.

 It's all a a matter of risk - if you poured some water on the power adapter, it would be more dangerous without a ground. Will it become an electrocution hazard on it's own? Unlikely...


----------



## Hayduke

Since most (all?) laptops have a power block, the ground on that third prong ends there. Once it hit's the transformer, it's not doing anything. Waitrob has it right. That third prong is to help avoid a shock of something goes wrong. So short answer, it's fine to run the laptop that way. If you have an extra of the cord that goes between the power block and the wall, just break off that third prong. I did this to the power source for my Starving Student to try and get rid of hum, but it had no effect 
	

	
	
		
		

		
		
	


	




 /\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\

 Well I finished building my amp tonight, sorta. Other then the part I missed in my order 
	

	
	
		
		

		
		
	


	







 Funny part is, it was mentioned that P1L and P1R were missing from the BOM. It got added, but it is listed incorrectly as P2R and P2L. There are 2 items for those locations. When I was building my BOM I think I deleted the 200ohm trim pot thinking it was something that had been changed. I didn't notice there was no P1R or P1L.

 Oh well, I was really hoping to listen to it this weekend, but I'm too cheap to pay for 2 day shipping for $5 in parts lol I guess it will be sometime midweek before I get to hear it. I already placed an order with Digi-Key for the trim pots. Naturally I was able to find other things to order. 
	

	
	
		
		

		
		
	


	




 FYI, if anyone is thinking about socketing Q1-8, it's a major PITA! The sockets for Q6 and Q7 aren't too bad, but I used the same DIP sockets as the test points for all the TO-92 transistors. So 6 per channel, 3 pins each. That's 36 tiny little sockets to solder 
	

	
	
		
		

		
		
	


	




 Also I discovered my tube sockets don't have a hole through the center for the LEDs 
	

	
	
		
		

		
		
	


	




 There are some silver circles where the holes should be. I poked at them hoping it was just some thin foil-like cover, but no luck. I might take a drill to them if I decide I have to have the LEDs under the tubes. Otherwise, I might just use the 3 LEDs to light up the inside of the enclosure and have it shine through the ventilation holes.


----------



## rds

Wiatrob - 

 You've probably already gone through this, but I'm wondering if the one of the standoffs might be in contact with the DAC's ground plane? That could create a ground loop with the earth grounded case. Similarly could the usb jack or exposed part of the usb cable be touching the case?


  Quote:


 So short answer, it's fine to run the laptop that way. If you have an extra of the cord that goes between the power block and the wall, just break off that third prong. 
 

I have to take exception that. That is bad advice. The power supply is grounded for a reason. It is there in case the neutral were to get broken at some point (in the cord, the wall, a power bar etc). 
 Also, just having a 3 conductor cord with the ground removed laying around is a hazard in itself. Who knows what someone else might try to use it for not noticing that the ground has been cut.


----------



## Beefy

Potentially stupid idea coming up......

 Is it possible to transformer-couple a USB connection?


----------



## wiatrob

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_Wiatrob - 
 Similarly could the usb jack or exposed part of the usb cable be touching the case?_

 

My Dacmagic is insulated, my Alien is uncased and sitting on a rubber strip. I solved the noise problem at hone. iMAc has optical out!


  Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I have to take exception that. That is bad advice. The power supply is grounded for a reason. ._

 

As I pointed out. However, on the continuum of Dangerous Things, ground lifting is toward the 'safer' end, But as electricity is invisible and bad advice liable, it's probably best to find another solution...


----------



## runeight

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Since most (all?) laptops have a power block, the ground on that third prong ends there. Once it hit's the transformer, it's not doing anything. Waitrob has it right. That third prong is to help avoid a shock of something goes wrong. So short answer, it's fine to run the laptop that way. If you have an extra of the cord that goes between the power block and the wall, just break off that third prong. I did this to the power source for my Starving Student to try and get rid of hum, but it had no effect 
	

	
	
		
		

		
		
	


	




 /\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\_/\

 Well I finished building my amp tonight, sorta. Other then the part I missed in my order 
	

	
	
		
		

		
		
	


	







 Funny part is, it was mentioned that P1L and P1R were missing from the BOM. It got added, but it is listed incorrectly as P2R and P2L. There are 2 items for those locations. When I was building my BOM I think I deleted the 200ohm trim pot thinking it was something that had been changed. I didn't notice there was no P1R or P1L.

 Oh well, I was really hoping to listen to it this weekend, but I'm too cheap to pay for 2 day shipping for $5 in parts lol I guess it will be sometime midweek before I get to hear it. I already placed an order with Digi-Key for the trim pots. Naturally I was able to find other things to order. 
	

	
	
		
		

		
		
	


	




 FYI, if anyone is thinking about socketing Q1-8, it's a major PITA! The sockets for Q6 and Q7 aren't too bad, but I used the same DIP sockets as the test points for all the TO-92 transistors. So 6 per channel, 3 pins each. That's 36 tiny little sockets to solder 
	

	
	
		
		

		
		
	


	




 Also I discovered my tube sockets don't have a hole through the center for the LEDs 
	

	
	
		
		

		
		
	


	




 There are some silver circles where the holes should be. I poked at them hoping it was just some thin foil-like cover, but no luck. I might take a drill to them if I decide I have to have the LEDs under the tubes. Otherwise, I might just use the 3 LEDs to light up the inside of the enclosure and have it shine through the ventilation holes._

 

@!%#&@&*)#^@#

 I'm sorry. I just didn't see that in the BoM. I'll fix it, but not in time to help you now.


----------



## Hayduke

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_I have to take exception that. That is bad advice. The power supply is grounded for a reason. It is there in case the neutral were to get broken at some point (in the cord, the wall, a power bar etc). 
 Also, just having a 3 conductor cord with the ground removed laying around is a hazard in itself. Who knows what someone else might try to use it for not noticing that the ground has been cut._

 

I suspect the reason it's grounded has more to do with liability and the litigious nature of the US then any real need, but you're right that is less safe. I never claimed it was ideal 
	

	
	
		
		

		
		
	


	




 I only did it to test, and it didn't help anyway hehe

 As for having the modified cord around, that could be true, but it's just me and the wife here, and she wouldn't go rummaging through workbench area for a power cord 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_@!%#&@&*)#^@#

 I'm sorry. I just didn't see that in the BoM. I'll fix it, but not in time to help you now. 
	

	
	
		
		

		
		
	


	


_

 

No worries Alex. I should have caught it. Like I said, I did realize it at one point, but somehow it never made it into my final BOM.

 Thanks for fixing it though. It may help another builder 
	

	
	
		
		

		
		
	


	





 EDIT: so there was some good in having to place another order. I had forgotten the zeners for R4 
	

	
	
		
		

		
		
	


	




 since I went though the trouble of installing sockets there, it would be nice to have the parts lol

 I ordered all 3 brands of 18V 500mW zeners that Digi-Key had. Hopefully at least one is less noisy. Big price difference. The Fairchild's that someone else used earlier in the thread were only 8 cents, but the other 2 brands were 33 and 46 cents!

 If anyone had a recommendation for an R4 zener from Digi-Key, a link would be appreciated. I can change my order until Monday morning


----------



## wolf18t

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Also I discovered my tube sockets don't have a hole through the center for the LEDs 
	

	
	
		
		

		
		
	


	




 There are some silver circles where the holes should be. I poked at them hoping it was just some thin foil-like cover, but no luck. I might take a drill to them if I decide I have to have the LEDs under the tubes._

 

Hayduke, don't do this. I did it and I end up with one of the two tube socket slightly damaged. That silver part is used to hold the upper and lower portion of the tube socket together.


----------



## kklee

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Hayduke, don't do this. I did it and I end up with one of the two tube socket slightly damaged. That silver part is used to hold the upper and lower portion of the tube socket together._

 

If you drill out the plug carefully, the two halves can be glued back together (I used construction adhesive). The trick is to use a drill bit that's just big enough to break through the rolled over lip portion of the metal plug holding the socket together.

 I've done this for several sockets.


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Hayduke, don't do this. I did it and I end up with one of the two tube socket slightly damaged. That silver part is used to hold the upper and lower portion of the tube socket together._

 

 Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_If you drill out the plug carefully, the two halves can be glued back together (I used construction adhesive). The trick is to use a drill bit that's just big enough to break through the rolled over lip portion of the metal plug holding the socket together.

 I've done this for several sockets._

 

hmmm.. thanks for the feedback guys. I considered ordering some different sockets, but they seem like they would be difficult to remove with all that solder.

 That does make sense what it's for. if I only used a drill bit narrow enough for the LEDs, it wouldn't remove all of the silver material in the center. Maybe the 2 halves would stay together. If all it does is hold the 2 ceramic pieces together, then I can always use kklee' suggestion and glue them together.

 The LEDs aren't that important to me, so I may not do anything about the sockets at all


----------



## krisio06

Hi guys,
 Which manufacture did make the best 12AU7 tube? RCA, Sylvania?
 Which 12AU7 would be the best for Grado RS1? 
 I heard that the RCA Cleartop is the best of the best but i don't know the real truth.. Which is the "real best if the best" ?


----------



## Ferrari

A quick dry fit of my balanced SOHA II in the making. Everything seems to turn out as I have on my mind. 
	

	
	
		
		

		
		
	


	



 Due to my busy work schedule (and various giant builds at the same time 
	

	
	
		
		

		
		
	


	




 )… still far from finish though.


----------



## Alcaudon

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_A quick dry fit of my balanced SOHA II in the making. Everything seems to turn out as I have on my mind. 
	

	
	
		
		

		
		
	


	



 Due to my busy work schedule (and various giant builds at the same time 
	

	
	
		
		

		
		
	


	




 )… still far from finish though._

 

Please, let me be the first to say: Whoaaaaaaa!!!!!!!! 
	

	
	
		
		

		
		
	


	




 Really impressive, as always


----------



## Ferrari

Thanks for the kind words. I wish that I had the time to complete it.


----------



## Uncle Bob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I'm still here, and unfortunately I still have the hiss problem - I just haven't had the opportunity to sit down and work on the board. I will keep you posted on progress - I still have to make an enclosure for it. I can't consider it a finished project until it's all cased up._

 

Did some checks on my problem SOHAII today. All voltages checked out OK but I went over all the solder joints in the left channel anyway. Still got that hiss problem in the left channel. But I've found that minor flexing of the PCB makes the hiss come and go - so it seems I have a fractured connection somewhere (after I dropped the board). I've gone over the PCB with a magnifying lens but I cannot see any fault, but there must be break somewhere.


----------



## Ferrari

Sad to know, Uncle Bob. Hope that you can figure that out, sooner or later.


----------



## wolf18t

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_A quick dry fit of my balanced SOHA II in the making. Everything seems to turn out as I have on my mind. 
	

	
	
		
		

		
		
	


	



 Due to my busy work schedule (and various giant builds at the same time 
	

	
	
		
		

		
		
	


	




 )… still far from finish though.





_

 

Great workmanship Ferrari, as always. Where did you get this case? I like it a lot, seems like it's from an old Rotel integrated. 

 And what are the meters? Voltage or power meter? These are very cool add-on.


----------



## Hayduke

Ferrari, do you do your own casework?

 Your builds always look incredible. This one is no exception 
	

	
	
		
		

		
		
	


	




 I'd love to see some pics or guide to how you do you casework. Like what tools do you use and such.


----------



## Ferrari

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Great workmanship Ferrari, as always. Where did you get this case? I like it a lot, seems like it's from an old Rotel integrated. 

 And what are the meters? Voltage or power meter? These are very cool add-on._

 


 As a big fan of Accuphase, Marantz and Rotel for years… I’m undoubtedly inspired by them, in one or other way. Now you are talking about Rotel, I do have a set of Rotel Michi RHA-10/RHB-10 pre- power amp combo from the ’90 at my place. The symmetry, red illuminated ring are indeed inspired by Rotel.
 (The red ring on the Rotel pre-amp is non- illuminated red plastic, however.)

 The case for my balanced SOHA is originally a HiFi-2000 Galaxy GX348. I designed the front-, back- and top panels and let them milled/engraved by Schaeffer AG (FPE in Europe). The effective high of the case is modified (from 40mm) to 50mm to accommodate the use of 1.5” heatsinks.
 The meters are current meter (output signals). It’s there more for the looks.


----------



## Ferrari

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Ferrari, do you do your own casework?

 Your builds always look incredible. This one is no exception 
	

	
	
		
		

		
			





 I'd love to see some pics or guide to how you do you casework. Like what tools do you use and such._

 

Yes, I do my own casework… with some help from Schaeffer AG (FPE in Europe) of course.
 I will post some more pics when my amp is completed.


----------



## Uncle Bob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Did some checks on my problem SOHAII today. All voltages checked out OK but I went over all the solder joints in the left channel anyway. Still got that hiss problem in the left channel. But I've found that minor flexing of the PCB makes the hiss come and go - so it seems I have a fractured connection somewhere (after I dropped the board). I've gone over the PCB with a magnifying lens but I cannot see any fault, but there must be break somewhere._

 

Some more info

 Flexing the PCB makes the hiss come and go, but it also causes a change in volume in that channel. When there's no hiss, the left channel is noticeably quieter than the right channel

 Any ideas where I start to look for the problem?


----------



## runeight

No ideas where to start. But some ideas on where to start to start. 
	

	
	
		
		

		
		
	


	




 Put the DMM on each of the measurement points and flex the board while listening. See if any of them change when you hear the hiss come and go. This might help us to isolate what part of the circuit is croaking.


----------



## wolf18t

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Some more info

 Flexing the PCB makes the hiss come and go, but it also causes a change in volume in that channel. When there's no hiss, the left channel is noticeably quieter than the right channel

 Any ideas where I start to look for the problem?_

 

If flexing the PCB seems to change de amplifier gain, I would look first at all the traces and solder joint around output stage to R7L/R8L and tube socket (all the feedback loop on the schematic). I would guess you have a cold solder in that part of the circuit.

 But I don't think that will solve your hiss problem since reducing the ampifier gain also reduce amplifier noise.


----------



## Uncle Bob

thanks for the suggestions, I'll keep you posted.


----------



## Ferrari

Most likely it’s a mechanical issue caused by the fall. 
	

	
	
		
		

		
		
	


	



 I’m not sure if it has been asked before (I do missed posts sometimes) but… are the tubes sitting properly in the sockets? Have you tried different tubes?


----------



## Uncle Bob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Most likely it’s a mechanical issue caused by the fall. 
	

	
	
		
		

		
		
	


	



 I’m not sure if it has been asked before (I do missed posts sometimes) but… are the tubes sitting properly in the sockets? Have you tried different tubes?_

 

It's depressing because the amp sounds soooooo good except for the hiss. It's a worthwhile question but I've tried different tube types and swapped them between channels with the same results 
	

	
	
		
		

		
		
	


	




 I'm still trying to hook up with someone who has a 'scope. Presumably, with a 'scope I'll be able to trace the hiss back to the point it appears in the circuit?


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_It's depressing because the amp sounds soooooo good except for the hiss. It's a worthwhile question but I've tried different tube types and swapped them between channels with the same results 
	

	
	
		
		

		
		
	


	




 I'm still trying to hook up with someone who has a 'scope. Presumably, with a 'scope I'll be able to trace the hiss back to the point it appears in the circuit?_

 

If you can’t find the root cause of the problem and… at some point in the future, decide to re-build the amp on a new PCB, I will donate the output devices, all small signal BJT’s (BC550/560) and some capacitors I have on hand.


----------



## Uncle Bob

Ferrari

 Thank you for your very kind offer. I do like the amp very much and a building a new one is a definite possibility. 

 But I'm not going to give up on this one just yet. Besides if I do find the fault and fix it, it may give some clues as to the hiss problems reported by some IEM users.


----------



## lacrossebowe8

So the problem I had been experiencing with the amp definately follows the tubes. One is clearly bad and will need to be replaced (I will replace both). Any suggestions on which to choose? I may order a few different ones.


----------



## wiatrob

My high current version is almost alive... Parts from the bin and Toshiba 2SC3422 in the buffer... All PS voltages good!


----------



## eruditass

for a basic build of the soha II, how much does it come out? also, how similar is it to the soha I part-reuse wise?


----------



## shellylh

You can get a kit (including Hammond case) from glassjaraudio.com for around $200, quite a deal if you ask me. 

  Quote:


  Originally Posted by *DoomzDayz* /img/forum/go_quote.gif 
_for a basic build of the soha II, how much does it come out? also, how similar is it to the soha I part-reuse wise?_


----------



## wiatrob

Quote:


  Originally Posted by *DoomzDayz* /img/forum/go_quote.gif 
_for a basic build of the soha II, how much does it come out? also, how similar is it to the soha I part-reuse wise?_

 

 You could use the tube! 
	

	
	
		
		

		
		
	


	




 I don't believe there are a lot of parts overlapping, but I haven't explicitly checked...


----------



## wolf18t

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_My high current version is almost alive... Parts from the bin and Toshiba 2SC3422 in the buffer... All PS voltages good!_

 

Glad to see that your build is going well. In what enclosure are you going to install your SOHA II?

 I've just finalized initial setup procedures on mine last evening. I also did a first and brief sound check with two set of tubes and my complete headphone inventory. 

 Just to say I think I found a magical sounding tube/headphone combo. More info to come later, I'll finish casing and take more time for critical listening...

 I'll also post a progress picture tonight.


----------



## Ferrari

Good to know that you guys are making progress on your builds.


----------



## wiatrob

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Glad to see that your build is going well. In what enclosure are you going to install your SOHA II?

SNIP

 I'll also post a progress picture tonight._

 


 Pretty well, my e12 isn't tripping, but I think the TL081 I have got blown up during the proto stage. I have a bunch on order for the Compact Hybrid 
	

	
	
		
		

		
		
	


	




 I am working two different case ideas right now, I'll post some pics soon... Looking forward to yours!

 -Bill


----------



## wolf18t

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Pretty well, my e12 isn't tripping, but I think the TL081 I have got blown up during the proto stage. I have a bunch on order for the Compact Hybrid 
	

	
	
		
		

		
		
	


	


_

 

Well I hope you will have them pretty soon! If not let me know I think I have an extra TL081 in my parts bin.

 As promised here are some pics I took yesterday while listening for my SOHA II for the first time. As you can see my SOHA will be installed in the recommended hammond case. 







 The PCB parts layout is way too tight for the upgraded MCAP Supreme coupling caps. That's the reason I had to install them offboard between the PCB and transfo. This is not a very recommended location but I heard no hum (knocking on wood) so I think that will be ok.







 Now if only there was enough interest to the nice FPE panels group buy, my SOHA would have been almost completed.


----------



## wiatrob

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Well I hope you will have them pretty soon! If not let me know I think I have an extra TL081 in my parts bin._

 

Thanks for the offer - Turns out it's not the TL081 - swapped it with my proto and it's good, but that's another post...


  Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_As promised here are some pics I took yesterday while listening for my SOHA II for the first time. As you can see my SOHA will be installed in the recommended hammond case._

 

Looks nice! How's it sounding?


----------



## wiatrob

Hmm. My voltages all look good - but my e12 won't trip (yup, me an that e12 again!) J1 and J2 and the opamps are in place.

 I _think_ I'm measuring the DC offset between the input side of R1/2E and ground, it spikes way up and then settles down below 2mV - stable on both sides.

 Similar measurement on my working amp yield slightly higher mV.

 The relay trips without the TL081 in place.
*
 UPDATE - using 18ks for R1 and R2E* - but that should just chane the sensitivity, correct?

 Any ideas?


----------



## runeight

Yes, that's correct. The best way to test the offset is to measure between the lead of R8 (both channels) that sticks towards the center of the board and ground.

 If the offset is that low then maybe the transistors in the e12 are cooked? Are you using BC units? 

 If the offset settles to only a few mV measure the voltage at the output of the tl081. It should also be near 0DC. This will tell us if it's the opamp or the transistors.


----------



## wiatrob

Thanks Runeight. Yes, BC550Cs - 

 There's something else going on, looks like a bad tube - I only get 5V difference between TB+ and TP, follows the tube...

 After putting in the TL081 again, it works! Output is .07mV 

 Need to letthese old soviet tubes burn and see what happens...


----------



## wiatrob

It lives - looks like a bad tube, no sound on the channel with the tube with 5V difference (6n1ps) 

 Not a bad tube, bad channel, time for some snooping...

 EDIT: Hmm. seems to be a combination. One tube does produce a lower voltage difference across the anode (which follows the tube), but either still works in the left channel. Will bring home a meter capable of doing more precise Ac mV and see where the music stops. 

 The buffers on the dead channel are not getting as warm as the right. Currents are good across both R10s - 239mV.


 Input stage or buffer?


----------



## wiatrob

How about this for a cause: Test headphones have a fried driver!

 I found a pair of earbuds in my ski coat from last season, so I thought they'd be a good test set.

 Not so good.
	

	
	
		
		

		
		
	


	




 Sounds great through my px-100s - burn in time!


----------



## dBel84

that can be so infuriating - glad you isolated the cause before stripping your amp apart ..dB


 edit - listening to mine after some hiatus with the HP3's


----------



## pabbi1

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_edit - listening to mine after some hiatus with the HP3's 
	

	
	
		
		

		
		
	


	


_

 

Been listening to new builds?


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Been listening to new builds? 
	

	
	
		
		

		
		
	


	


_

 


 There's a lot of winking going on! I'm enjoying the YH-100s, thanks Don!


----------



## wiatrob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_that can be so infuriating - glad you isolated the cause before stripping your amp apart ..dB_

 

I did find a cracked resistor and two cold-ish joints: and I learned more about how the amp works - this is the most edifying kind of troubleshooting!


----------



## dBel84

nudge nudge wink wink say no more .

 well maybe one more Cavalli Audio rules ! 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## wiatrob

Fully up and burning in. I very much like the high current build.

 Excellent clarity/resolution- I don't know if it's the Toshibas - the bass seems tighter than with my proto build.
 Especially nice through the graciously loaned orthos from dBel!

 Kudos again Alex and all who participated in the process.


----------



## ssoaos

Hello all, I am new to this place. I am very interested in building the SOHA II. I have been calling and emailing Jeff at Glass Jar Audio and have no response from him. Any idea?
 Keep up the great work!
 Stan


----------



## scompton

I was wondering if this would be a good second build after a Starving Student? Or should I do something simpler with perf board to get used to using a board?

  Quote:


  Originally Posted by *ssoaos* /img/forum/go_quote.gif 
_Hello all, I am new to this place. I am very interested in building the SOHA II. I have been calling and emailing Jeff at Glass Jar Audio and have no response from him. Any idea?
 Keep up the great work!
 Stan_

 

I got a response within 24 hours using the contact page on his web site.


----------



## dBel84

keep a clear head, don't be afraid to ask and follow the start up / test directions on cavalli audio and it should all go smoothly..dB


----------



## wiatrob

Quote:


  Originally Posted by *ssoaos* /img/forum/go_quote.gif 
_Hello all, I am new to this place. I am very interested in building the SOHA II. I have been calling and emailing Jeff at Glass Jar Audio and have no response from him. Any idea?
 Keep up the great work!
 Stan_

 


 Great to here of your interest, and welcome! The SOHAII is a great amp, you won't be disappointed should you choose to build one.

 Jeff can be a very busy guy - give him some time to respond, up to a week if he's really swamped.

 -Bill


----------



## ssoaos

Hi Bill and Scompton,
 Thank you for your quick response. I am very interested in building it. Do you have tried it against the Little Dot MK III? I am debating between the two.

 Thanks!
 Stan


----------



## Hayduke

I have a question about some of the small signal transistors. ie Q5...

 I'm using the BC550Cs. Normally, I would trust the silkscreen on a board for the orientation of the part, but I'm confused. On the silkscreen, it shows the flat side of the transistor facing the rear of the board. This is also what it appears other builders did in their pictures. But being paranoid, I look at the data sheet. Based on the numbers labeled on the silkscreen vs the data sheet, it seems to me the flat part should face the front of the amp.

 Am I missing something? I have socketed them all so it's easy enough to switch them around, but I am not going to power up the amp until I am sure.

 Here is the data sheet Alex links on the site
http://www.cavalliaudio.com/soha%20ii/docs/BC550.pdf

 Here is the data sheet from Mouser
http://www.onsemi.com/pub_link/Collateral/BC549B-D.PDF

 They both show pin 1 on the left if the flat face of the transistor is towards you.

 So do I trust the picture of the part on the silkscreen or the pin labels?

 I'm going to look at the schematic to see if I can figure this out, but I think I must be looking at something wrong if nobody else has asked this question.

 Edit:
 OK I think I figured it out. It looks like the pin 1 on the silkscreen is the emitter, which is pin 3 on the transistor. So the shape on the silkscreen is correct, the pin labels are wrong.

 I'm pretty confident I'm reading all this right, but I'm not going to apply any power until someone confirms my findings.


----------



## Ferrari

The SOHA II PCB silkscreen and the data sheet pin labels are both correct.

 Pin 1: collector
 Pin 2: base
 Pin 3: emitter 

 When recommended transistors are used (BC550/560), just place the transistor as depicted on the PCB silkscreen and you are fine.
 This kind of things were pointed out and verified already. 
	

	
	
		
		

		
			





 In one of my build, I have used _different type transistors (MPSA42/92) for the current mirror_. 
 The placement of the mentioned transistors are 180 degrees rotated... but there is a good reason for that.


----------



## Hayduke

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The SOHA II PCB silkscreen and the data sheet pin labels are both correct.

 Pin 1: collector
 Pin 2: base
 Pin 3: emitter 

 When recommended transistors are used (BC550/560), just place the transistor as depicted on the PCB silkscreen and you are fine.
 This kind of things were pointed out and verified already. 
	

	
	
		
		

		
		
	


	




 In one of my build, I have used different type transistors (MPSA42/92) for the current mirror. 
 The placement of the mentioned transistors are 180 degrees rotated... but there is a good reason for that._

 

Thanks Ferrari

 I did use the silkscreen shape. I basically just double checked where the base, emmiter, collector were connected in the circuit. I actually powered it up before I read this, but I do appreciate the reply!

 The amp has passed the first check 
	

	
	
		
		

		
		
	


	



 Well except TB+ was 120V instead of 103V, but I think that may be due to using the larger transformer? I'm going to study the circuit and make sure I know why that is before I move on.

 I'll keep everyone posted. I should have went to bed awhile ago, but I'm too excited to hear this amp 
	

	
	
		
		

		
		
	


	




 Edit:
 Search is my friend 
	

	
	
		
		

		
		
	


	



 Found Alex's post on this
http://www.head-fi.org/forums/5113583-post256.html

 Time to move on, or should I sleep? hmmm.....

 Edit2:
 Didn't sleep, but I will now.
 I haven't heard the amp yet. I couldn't pass the last test 
	

	
	
		
		

		
		
	


	



 My TPL and TP+L are about the same. Not a little off from 19V, it's less then 1V difference. One channel is pretty much identical. I have a zener in R4, so is that it? I can't tell right now. Thinking isn't my strong suit this tired lol. I'm gonna quit now before I start frying parts.

 Good news is the tubes lit up fine and the relay is clicking. Wasn't brave enough to hookup the inputs yet.
 I think I'm doing something wrong, so I should probably go to bed 
	

	
	
		
		

		
		
	


	




 almost 5AM here.


----------



## Hayduke

I couldn't figure out why I wasn't getting the 19V difference between TB+ and TP. I wondered if I have the heater voltages wrong, so I tried the other position. Upon turning on the amp, I started to smell something burning and saw a tiny amount of smoke, but I had already cut power about the time I saw the wisp of smoke.

 I double checked the switch. It seemed to be in the right position, but I was still getting the same reading at TB+L and TPL (~60V). So my TB+L and TB+R are already a little low. The tubes were both lighting up though, so I went ahead and connected an input.

 I only have sound out of the right channel 
	

	
	
		
		

		
		
	


	




 While I worked on my BOM, I thought I had a good handle on how this amp worked, but now that I'm having trouble, I'm really at a loss for where to start. 
	

	
	
		
		

		
		
	


	





 In regards to the transistors and the silkscreen. I still think the pin labels are wrong. According to the datasheet for the BC550's, with the flat side facing you, pin 1 is on the left. All the transistors on the board have pin 1 on the right of the flat side. I know Ferrari says it's correct, so what am I missing?


 Update: It is a bad tube :x
 Moved tubes and the problem switched channels. I got others, so I'll do more testing later. So while I'm glad I figured out the dead channel, I'm bummed about the bad tube. Now to figure out why my voltages are weird.

 btw, the one channel does sound nice 
	

	
	
		
		

		
		
	


	





 Update2:
 It's not a bad tube. I ordered 6 different pairs of tubes. I've tried 5 now, and in all of them, only one channel. I have figured out that there is some sound in the bad channel, but it's faint and distorted. In fact, the good channel is distorted as well.

 What's really weird is that swapping the tubes makes the problem switch channels. 
	

	
	
		
		

		
		
	


	




 When it follows the tube, makes me think the tube is the problem, but this behavior has me stumped.

 I'm gonna walk away for awhile and hope someone has an idea what's going on.


----------



## wolf18t

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I couldn't figure out why I wasn't getting the 19V difference between TB+ and TP. ...

 I double checked the switch. It seemed to be in the right position, but I was still getting the same reading at TB+L and TPL (~60V). So my TB+L and TB+R are already a little low. The tubes were both lighting up though, so I went ahead and connected an input._

 

If you have less than 1V difference and are using a Zener at R4, is it possible that you installed it in the wrong way. Like a standard diode a Zener have about 0.6V forward voltage... 

 Set your DMM at DC position and what voltage you have directly across Zener (R4)?


  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I wondered if I have the heater voltages wrong, so I tried the other position. Upon turning on the amp, I started to smell something burning and saw a tiny amount of smoke, but I had already cut power about the time I saw the wisp of smoke._

 

I wish you didn't smoke the tube heater filament.


  Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I only have sound out of the right channel 
	

	
	
		
		

		
		
	


	




 Update: It is a bad tube :x
 Moved tubes and the problem switched channels. I got others, so I'll do more testing later. So while I'm glad I figured out the dead channel, I'm bummed about the bad tube. Now to figure out why my voltages are weird.

 btw, the one channel does sound nice 
	

	
	
		
		

		
		
	


	




 Update2:
 It's not a bad tube. I ordered 6 different pairs of tubes. I've tried 5 now, and in all of them, only one channel. I have figured out that there is some sound in the bad channel, but it's faint and distorted. In fact, the good channel is distorted as well.

 What's really weird is that swapping the tubes makes the problem switch channels. 
	

	
	
		
		

		
		
	


	




 When it follows the tube, makes me think the tube is the problem, but this behavior has me stumped.

 I'm gonna walk away for awhile and hope someone has an idea what's going on._

 

It's difficult to follow. If you install a new set of tube, the left channel doesn't work. Right? And if you swap channels (using the same tube set) then the problem swap to the right and the left channel now works fine. Right?


----------



## wiatrob

Hayduke,

 Are you not getting ~19V between TB+ and TP on both channels? Or just the channel that is now out?


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_If you have less than 1V difference and are using a Zener at R4, is it possible that you installed it in the wrong way. Like a standard diode a Zener have about 0.6V forward voltage... 

 Set your DMM at DC position and what voltage you have directly across Zener (R4)?_

 

good idea, I'll check that now and let you know

  Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_I wish you didn't smoke the tube heater filament._

 

Smoke seemed to come from the back right.


  Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_It's difficult to follow. If you install a new set of tube, the left channel doesn't work. Right? And if you swap channels (using the same tube set) then the problem swap to the right and the left channel now works fine. Right?_

 

hmmmm I can't say 100% it was always the left to start, but maybe. The zener in R4 backwards certainly would explain that huh?

 Hope I didn't just ruin a bunch of tubes.

  Quote:


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

 Are you not getting ~19V between TB+ and TP on both channels? Or just the channel that is now out?_

 

Both channels are within 1V of each other.


----------



## Hayduke

Eureka! The zeners were backwards!

 At first I was worried because I wasn't getting any voltage at all across them. I think I might have popped the fuse in the DMM during testing. I can't even get a reading across a battery now 
	

	
	
		
		

		
		
	


	




 I'll open it up and look later.


----------



## wiatrob

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Eureka! The zeners were backwards!_

 

Yay! 
	

	
	
		
		

		
		
	


	




 Alex, perhaps we should add the orientation of the Zener's to the tweaks section of the website?


----------



## runeight

Good idea. I'll try to get to that later.


----------



## wolf18t

I'm glad that what just the Zeners. And how your SOHAII sound?


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Good idea. I'll try to get to that later. 
	

	
	
		
		

		
			



_

 


 Busy ! Busy! Busy?


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_I'm glad that what just the Zeners. And how your SOHAII sound?_

 

It sounds very nice! Compared to my MHSS, I think it has a larger soundstage and more clarity. The differences are a little subtle, but they are there. I haven't listened a lot though, so it's hard to point out the differences. I did a quick comparison last night, and immediately could hear a difference, but it will take more time to really understand the differences.

 I think I'll go back and work through the setup steps again to verify the pots are set correctly though.


----------



## kostalex

Please, help. My friend has some questions regarding the SOHA II he is building now. He do not know English so I would ask 
	

	
	
		
		

		
		
	


	




 Current trough tubes (I think you name it "bias") is set to 2 mA. Both TB+L and TB+R are 60 V. There is big spread between TPL (44V) and TPR (30V). And the difference between TPR and TB+R is 30V, what is much higher than 19V recommended. Section "Setting the Ttail current for the input stage" recommends to see Troubleshooting, which does not help.

 Amp works fine anyway, both measurements and listening tests are OK.

 What should he do, if any?


----------



## wolf18t

Quote:


  Originally Posted by *kostalex* /img/forum/go_quote.gif 
_Please, help. My friend has some questions regarding the SOHA II he is building now. He do not know English so I would ask 
	

	
	
		
		

		
		
	


	




 Current trough tubes (I think you name it "bias") is set to 2 mA. Both TB+L and TB+R are 60 V. There is big spread between TPL (44V) and TPR (30V). And the difference between TPR and TB+R is 30V, what is much higher than 19V recommended. Section "Setting the Ttail current for the input stage" recommends to see Troubleshooting, which does not help.

 Amp works fine anyway, both measurements and listening tests are OK.

 What should he do, if any?_

 

Both L/R channels have a higher voltage drop than the expected 19V. That's probably not a big problem but if it is...: 

 - I would double check first the R4L and R4R resistor value to be sure these are 18Kohm. 
 - What tubes type are installed, and are these new/used? 
 - Also did he have to replace some suggested part in the BOM, like the BC560C and BC550C to other NPN transistors? If so, maybe a huge change in the Beta value could to this.


----------



## wolf18t

I also add that if he have another tube set I would also redo the tail current BIAS procedure with them to see if that change anything.


----------



## kostalex

Tubes are new, they are from the kit I bought at glassjaraudio.com in December. According to the order form tubes are NOS 5692, transistors are Mouser 863-BC560CG and 863-BC550CG. Tomorrow I may ask him for exact part numbers.


----------



## kostalex

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_I also add that if he have another tube set I would also redo the tail current BIAS procedure with them to see if that change anything._

 

Unfortunately, he has not.


----------



## runeight

Kostalex, as you know TPR is too low. This could actually be a bad tube. That would be the first thing to change if you can.

 Then you might try the tail current adjustment on the right channel again to be sure that it is right. If it is correct and if R4 is really 18k then it has to be a bad tube.

 Try measuring the voltages on both leads of R4R to ground and tell us what they are.


----------



## Hayduke

Swap the tubes, then measure again. See if the differences switch channels. If they do, then it's a tube problem. If it doesn't, probably not the tube.


 I have a problem related to my SOHA II 
	

	
	
		
		

		
		
	


	




 It sounds so good with my 650s, I don't like my work rig anymore (580s and MHSS) 
	

	
	
		
		

		
		
	


	




 Looks like I am gonna build another SOHA II for work


----------



## runeight

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_Swap the tubes, then measure again. See if the differences switch channels. If they do, then it's a tube problem. If it doesn't, probably not the tube.


 I have a problem related to my SOHA II 
	

	
	
		
		

		
		
	


	




 It sounds so good with my 650s, I don't like my work rig anymore (580s and MHSS) 
	

	
	
		
		

		
		
	


	




 Looks like I am gonna build another SOHA II for work 
	

	
	
		
		

		
		
	


	


_

 

I like to hear things like this.


----------



## fishski13

sorry if this has been asked already (i also performed a fruitless search), but could the SOHAII also serve dual duty as a pre-amp?


----------



## runeight

Yes, it should do very well as a preamp. In fact, it might make a really good preamp because it can drive cables.


----------



## scompton

I'm looking at ordering a kit and I had a couple of questions before I do. When I built my SS, I fried the mosfets when I was a little careless with the DMM probes. Can someone suggest what parts to order extras of if I'm similarly stupid while building this? I'd hate to have to wait on a Mouser order for one transistor.

 I noticed towards the end of the other thread there was discussion of prepunched panels for the case. Are these available?


----------



## runeight

Hi Scompton. It's a great amp. 
	

	
	
		
		

		
		
	


	




 The parts that seem to be killed most frequently are the MPSA42s followed by the opamps. There was one instance of blown up rectifier diodes. I don't recall anyone damaging anything else, but I'm sure I don't remember all of the posts.

 So you can order extras of those. Then to be really safe you might order one extra for each of the regulators and a few extra of the BC550/BC560. I would think this is enough.

 Others may have better ideas based on personal experience.


----------



## Hayduke

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I'm looking at ordering a kit and I had a couple of questions before I do. When I built my SS, I fried the mosfets when I was a little careless with the DMM probes. Can someone suggest what parts to order extras of if I'm similarly stupid while building this? I'd hate to have to wait on a Mouser order for one transistor.

 I noticed towards the end of the other thread there was discussion of prepunched panels for the case. Are these available?_

 

Alex had enough forethought to provide us with test points for most the places we take readings. If you use the DIP sockets at these points, it's extremely easy to test voltages without the probes slipping. In theory, you could even solder leads to each of these points, then attach alligator clips to the ends. Now way your DMM probe will mess anything up that way!

 I finished my build recently and did LOTS and LOTS of readings because I was trying to troubleshoot a problem (reversed diode). I didn't fry any components at all. I think you will be fine. The MHSS is a nice amp, but this one is much nicer from both the builder standpoint and, more importantly, the listener standpoint 
	

	
	
		
		

		
			





 One tiny piece of advice. When soldering in your resistors, make sure the solder doesn't wick to far on the topside of the board. I am used to seeing the solder come all the way through to the top from using wave solder machines, so I actually made sure I had a good connection on both sides. This made attaching to some of the resistor test points more difficult. Maybe take not of which resistors you will be taking readings on and make sure there is a little extra leg on top to grab with your gripper probes.


----------



## fishski13

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, it should do very well as a preamp. In fact, it might make a really good preamp because it can drive cables._

 

cool. BOM finished and will be placing my Mouser and GJA orders this weekend. i am building this for a friend and will be stuffing a gamma-1 DAC in as well for an all in one pre/HP/DAC - DIY enclosure.


----------



## Uncle Bob

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_ Maybe take not of which resistors you will be taking readings on and make sure there is a little extra leg on top to grab with your gripper probes._

 

Seconded on that last point, if I were building another, I'd make sure that R6 on both channels had a little extra contact area to get to.

 UB


----------



## wiatrob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Seconded on that last point, if I were building another, I'd make sure that R6 on both channels had a little extra contact area to get to.

 UB_

 

My first build actually has test jacks on the back for both sets of test points - the proto buffer test points were _behind_ the heat syncs. The design is stable enough that's it pretty much 'set and forget' (unless you need to adjust tail current when tube rolling). 

 I should look at the values again and see how they are doing after six months - still sounds great so I haven't bothered to check!


----------



## tacitapproval

A little D'uh! update--

 Some folks on this thread were helping me solve a ground loop problem that was revealed by the soha II. I was futzing with the connections recently and I realized the pot was not fully isolated from the chassis. I properly isolated it and now the ground loop is completely gone. I thought I had before, but... D'uh! and Yeah!

 I built a y1 DAC and the two sound outstanding together. Thanks Alex and Ti!


----------



## wolf18t

Since this thread was quiet lately, I just post some progress pictures 
	

	
	
		
		

		
		
	


	





 Casing isn't and will never be my cup of tea. But with the help of this newly acquired small bench drill, it's much easier.
















 Rear panel completed!


----------



## runeight

That looks really nice. Every bit as good as the FPE panels that I had made.

 Waiting now for the finished product.


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Since this thread was quiet lately, I just post some progress pictures 
	

	
	
		
		

		
		
	


	





 Casing isn't and will never be my cup of tea. But with the help of this newly acquired small bench drill, it's much easier.

http://images45.fotki.com/v1428/phot...CP_1561-vi.jpg

http://images46.fotki.com/v1453/phot...CP_1564-vi.jpg

http://images44.fotki.com/v1461/phot...CP_1566-vi.jpg

 Rear panel completed!_

 

Looks nice! I was about to ask how you did the nice lettering, then I spotted the transfer paper 
	

	
	
		
		

		
		
	


	




 I was pricing drill presses last week. That led to pricing mills, then CNC mills, then I got sane and closed the browser and listened to some music


----------



## wolf18t

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I was pricing drill presses last week. That led to pricing mills, then CNC mills, then I got sane and closed the browser and listened to some music 
	

	
	
		
		

		
		
	


	


_

 

LOL! 

 Got it a few weeks ago it was 33% off. If you stay with basic 8" or 10" drill press, it's very affordable.


----------



## wiatrob

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_LOL! 

 Got it a few weeks ago it was 33% off. If you stay with basic 8" or 10" drill press, it's very affordable._

 


 I took the plunge and got a 10" myself this weekend, after seeing the levels of build quality I need to keep up with... Now I need to turn my attention to my last SOHA II case...


----------



## kansei

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I was pricing drill presses last week. That led to pricing mills, then CNC mills, then I got sane and closed the browser and listened to some music 
	

	
	
		
		

		
		
	


	


_

 

I went through the whole loop as well. My brain finally processed it and decided that buying a $600 CNC apparatus to drill a few holes was a giant overkill. 

 I finally decided to pick up a used drill press from Craigslist for $39. I hope it turns out to be a working one.


----------



## runeight

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_A little D'uh! update--

 Some folks on this thread were helping me solve a ground loop problem that was revealed by the soha II. I was futzing with the connections recently and I realized the pot was not fully isolated from the chassis. I properly isolated it and now the ground loop is completely gone. I thought I had before, but... D'uh! and Yeah!

 I built a y1 DAC and the two sound outstanding together. Thanks Alex and Ti!_

 

You're welcome.


----------



## kostalex

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Kostalex, as you know TPR is too low. This could actually be a bad tube. That would be the first thing to change if you can.

 Then you might try the tail current adjustment on the right channel again to be sure that it is right. If it is correct and if R4 is really 18k then it has to be a bad tube.

 Try measuring the voltages on both leads of R4R to ground and tell us what they are._

 

R4 = 18.1k 
 voltages on R4R are 58,8v and 41,2v
 voltages on R4L are 58,8v and 41,2v

 He is also worried by the high temperature (90 Celsius degrees) of Q6, Q7 (both channels). So he reduced the quiescent current from 100 mA to 80 mA. Load is 30 Ohm.


----------



## Zippy

This is my first build with tubes and I'm having a bit of confusion I hope you guys can help clear up.

 I have finished stuffing a Soha II board and ready to start testing but I'm a bit confused about the heater jumper. I have a pair of 5963 tubes and according to this spec sheet I found
http://scottbecker.net/tube/sheets/127/5/5963.pdf
 I can run them in 12.6V series or 6.3V parallel.

 The Cavalli Audio site says
 "The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation."

 What do I strap the heater at? I think I'm overlooking something obvious here as those are backward from each other and the 5963 would be unusable.


----------



## wiatrob

Quote:


  Originally Posted by *Zippy* /img/forum/go_quote.gif 
_This is my first build with tubes and I'm having a bit of confusion I hope you guys can help clear up.

 I have finished stuffing a Soha II board and ready to start testing but I'm a bit confused about the heater jumper. I have a pair of 5963 tubes and according to this spec sheet I found
http://scottbecker.net/tube/sheets/127/5/5963.pdf
 I can run them in 12.6V series or 6.3V parallel.

 The Cavalli Audio site says
 "The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation."

 What do I strap the heater at? I think I'm overlooking something obvious here as those are backward from each other and the 5963 would be unusable._

 


 I believe 5963s will operate at either heater voltage... 


 Start at 6.3v if you want to be safe...


----------



## adamus

they'll operate at either voltage depending on how your wire them - they wont be happy with the wrong voltage.


----------



## Zippy

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_they'll operate at either voltage depending on how your wire them - they wont be happy with the wrong voltage._

 

I understand they can run at either voltage. The confusion is, the tube documentation says run them at 6.3V parallel.
 The documentation for the Soha is leading me to think if I strap it to 6.3V they will be in series.

 Is there a jumper I am overlooking that will change the series/parallel configuration of the tubes?


----------



## Hayduke

Quote:


  Originally Posted by *Zippy* /img/forum/go_quote.gif 
_I understand they can run at either voltage. The confusion is, the tube documentation says run them at 6.3V parallel.
 The documentation for the Soha is leading me to think if I strap it to 6.3V they will be in series.

 Is there a jumper I am overlooking that will change the series/parallel configuration of the tubes?_

 

I think they are describing how the tubes will be used in a circuit. If your circuit provides 6.3V, then you put the tube heaters in parallel so they both get 6.3V. If your circuit supplies 12.6V, then you put the tube heaters in series to so they both get 6.3V still. That's my interpretation (although there's a strong likelihood I'm mistaken).


----------



## wiatrob

Quote:


  Originally Posted by *Zippy* /img/forum/go_quote.gif 
_I understand they can run at either voltage. The confusion is, the tube documentation says run them at 6.3V parallel.
 The documentation for the Soha is leading me to think if I strap it to 6.3V they will be in series.

 Is there a jumper I am overlooking that will change the series/parallel configuration of the tubes?_

 

There is only one jumper block- Use the silk screen indicators from the PCB - 6.3V position is toward the front of the board, 12.6 toward the rear. 

The SOHA II Headphone Amplifier


----------



## Zippy

Thanks guys, I understand whats going on now. Looks like the backward wording threw me for a loop.

 While I'm at it. Does the center jumper position have any function?


----------



## wiatrob

Quote:


  Originally Posted by *Zippy* /img/forum/go_quote.gif 
_While I'm at it. Does the center jumper position have any function?_

 

Yes, please see the schematic page I linked to, under the box 'Heater Wiring Jumpers' - you'll see all the "J1" jumpers have connections. You need two jumpers taking up four of the pins...


----------



## rnickl

Hi folks,
 Another new guy here building the Soha. I've been following this thread from the start and finally decided to build but, I have a bit of a hangup with the epsilon circuit. The relay isn't kicking on.

 I think my problem is in the left channel. I have set my voltage across R10(R&L) at 200mV but when I check the voltage to ground I'm getting my full 15V at R10L.

 Any ideas on how to hunt down the culprit of the problem would be appreciated.

 Edit: For clarification, from ground to the input of R10L is 15V. Ground to the input side of R10R is 220mV.


----------



## runeight

Quote:


  Originally Posted by *Zippy* /img/forum/go_quote.gif 
_This is my first build with tubes and I'm having a bit of confusion I hope you guys can help clear up.

 I have finished stuffing a Soha II board and ready to start testing but I'm a bit confused about the heater jumper. I have a pair of 5963 tubes and according to this spec sheet I found
http://scottbecker.net/tube/sheets/127/5/5963.pdf
 I can run them in 12.6V series or 6.3V parallel.

 The Cavalli Audio site says
 "The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation."

 What do I strap the heater at? I think I'm overlooking something obvious here as those are backward from each other and the 5963 would be unusable._

 


 Use the 12.6V setting for 5963.


----------



## wiatrob

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_Hi folks,
 Another new guy here building the Soha.

 ...

 Any ideas on how to hunt down the culprit of the problem would be appreciated.

 Edit: For clarification, from ground to the input of R10L is 15V. Ground to the input side of R10R is 220mV._

 



 Welcome, sorry to hear you're having an issue. The Epsilon is not kicking in to protect the output from 15VDC. 15V positive, corrrect?

 More experienced folk will need to chime in here - but looking at the schematic of the buffers, my general troubleshooting process would lead me to look (after checking for solder bridges and shorts) at the BC550's, BD139 and servo opamp. What's the output of the opa134 (pin 6?) Please note that I'm just guessing to give you some direction...


----------



## wolf18t

What Wiatrob said. And what's the voltage at the base of Q5L and Q6L?


----------



## rnickl

I have double checked for any shorts, bridges or bad joints and all looks good.

 I'm reading 7.2V at the base of the BC550C (Q5), 14.95V at the base of the BD139 (Q6) and -15V at the OP134 output.

 I appreciate the help guys.


----------



## wolf18t

Hmmm... I think you have a problem with Q5L (collector/emitter junction shorted) or Q6L (collector/base junction shorted), look at the schematics. 

 With the SOHA turn off, check with your DMM if you have continuity or very low resistance from Q5 or Q6 collector to Q6 base. If so, unsolder and remove either Q5 or Q6 from the board and check again. Depending wich transistor you have removed from the board you will find the culprit.


----------



## rnickl

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Hmmm... I think you have a problem with Q5L (collector/emitter junction shorted) or Q6L (collector/base junction shorted), look at the schematics. 

 With the SOHA turn off, check with your DMM if you have continuity or very low resistance from Q5 or Q6 collector to Q6 base. If so, unsolder and remove either Q5 or Q6 from the board and check again. Depending wich transistor you have removed from the board you will find the culprit._

 

Thanks for the input. My first instinct was a problem with Q5 and after seeing no obvious problems with solder joints I tried to swap it out. It obviously didn't help.

 I didn't ohm out the collector emitter junction so the problem may very well be with Q6. I don't have the board with me so I'll have to check that out tomorrow morning.


----------



## rnickl

Well this problem has got me chasing my tail.

 I took some measurements and found I was short between pins 1 and 2 (collector and emitter) of Q6 so I pulled it out. To make a long story short I currently have Q5, Q6, C1 and the OP amp off the board yet I still read a short (0 ohms) between pads 1 & 2 at the Q6 location. 
	

	
	
		
		

		
			





 I did wick and clean up all the empty locations to make sure I didn’t have any bridging. 

 I guess my next step is to pull R9/R10 to isolate Q6 location further from the circuit. Any other ideas from you guys?


----------



## Hayduke

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_Well this problem has got me chasing my tail.

 I took some measurements and found I was short between pins 1 and 2 (collector and emitter) of Q6 so I pulled it out. To make a long story short I currently have Q5, Q6, C1 and the OP amp off the board yet I still read a short (0 ohms) between pads 1 & 2 at the Q6 location. 
	

	
	
		
		

		
		
	


	




 I did wick and clean up all the empty locations to make sure I didn’t have any bridging. 

 I guess my next step is to pull R9/R10 to isolate Q6 location further from the circuit. Any other ideas from you guys?_

 

So you have Q5 and Q6 removed, but you measure a short on pin 1 and 2 of Q6? Granted, I'm not an expert compared to many here, but looking at the schematic, it seems to me you should read ~820ohms from R9. I don't see anyway you could be getting a direct path between those pins. What do you measure across R9? I think you're on the right track to pull R9 and test it. Don't pull R10 yet, I don't see how it is causing this.


----------



## wolf18t

Then it may be a solder bridge or even a bad trace on the board. It's rare but it could happend. Check carefully the trace between R9/R10/Q6 and a possible contact with the +15V rail trace.


----------



## rnickl

I found it! Looks like someone may have left a hair on the fab during etch.

 I took a picture to show you guys what I found, perhaps it will help one of you out in the future. Check out the bridge between the traces at the solder pad for R10L (Q5L in lower right of frame). I cleaned a bit of solder off the pad so it would be easier to see and fix. I broke the bridge with an x-acto and all looks good now. Time to stuff the parts back on the board and double check everything.

 Thanks again for all the input guys

http://www.smugmug.com/photos/477442952_AzUW7-L.jpg


----------



## kostalex

Output transistors Q6 and Q7 are too hot on both channels (90 Celsius degrees). The load is Denon D2000, 25 Ohm. How much may I lower the quiescent current without any sound quality loss?


----------



## wolf18t

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_I found it! Looks like someone may have left a hair on the fab during etch.

http://www.smugmug.com/photos/477442952_AzUW7-L.jpg_

 

I'm glad you finally found that bug!


  Quote:


  Originally Posted by *kostalex* /img/forum/go_quote.gif 
_Output transistors Q6 and Q7 are too hot on both channels (90 Celsius degrees). The load is Denon D2000, 25 Ohm. How much may I lower the quiescent current without any sound quality loss?_

 

That's pretty hot. Runeight would be much, much, better than me to answer you. But I think there is no absolute answer on this one. It all depends at what level you listen to music and sensitivity of the phones. I feel that 100mA is a very safe biasing point, the CK2III is said to sound great and it is only biased at 35mA.

 I'll keep and eye open for answers too as I plan to use my SOHA II with 32ohm Grados.


----------



## wiatrob

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_That's pretty hot. Runeight would be much, much, better than me to answer you. But I think there is no absolute answer on this one. It all depends at what level you listen to music and sensitivity of the phones._

 

I believe the BD139 Junction temp is rated for 150 degrees C - of course we wouldn't want to approach that, and Junction temp will be higher than what you measure outside - is your measurement from the transistor surface or the sink? Does the part have a good thermal bond to the sink?


----------



## Hayduke

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_I found it! Looks like someone may have left a hair on the fab during etch.

 I took a picture to show you guys what I found, perhaps it will help one of you out in the future. Check out the bridge between the traces at the solder pad for R10L (Q5L in lower right of frame). I cleaned a bit of solder off the pad so it would be easier to see and fix. I broke the bridge with an x-acto and all looks good now. Time to stuff the parts back on the board and double check everything.

 Thanks again for all the input guys

http://www.smugmug.com/photos/477442952_AzUW7-L.jpg_

 

Good job!

 I recently read a discussion on the B22 mistakes thread where they talked about inspecting PCBs before a build. Everyone agreed it's very rare to find a mistake, but it happens. You just reinforced that. It's too bad you had to go through the headache though 
	

	
	
		
		

		
			





 I didn't give my board that close an inspection, but you can be sure I will from now on 
	

	
	
		
		

		
		
	


	




 If that had happened in other spots, it could have damaged something.


----------



## kostalex

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I believe the BD139 Junction temp is rated for 150 degrees C - of course we wouldn't want to approach that, and Junction temp will be higher than what you measure outside - is your measurement from the transistor surface or the sink? Does the part have a good thermal bond to the sink?_

 

It was measured on heatsinks, case was open. Transistors are very well bonded using the thermal grease.


----------



## Sathimas

I'm thinking of building a SOHA II for my dad as birthday present and saw that Jeff Rossel offers Kits for it.

 Does anybody know how much they cost?
 I wrote him an email this night but maybe someone here is quicker.

 I'd like to build something with tubes and don't want to spend much more than 150$.
 I've already got a SOHA I with Jisbos, would be boring to build that one again.
 Maybe somebody has another suggestion for me?


----------



## tacitapproval

The glassjar kit is @ $200 shipped for everything needed for the build except wire and solder.


----------



## scompton

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I'm thinking of building a SOHA II for my dad as birthday present and saw that Jeff Rossel offers Kits for it.

 Does anybody know how much they cost?
 I wrote him an email this night but maybe someone here is quicker.

 I'd like to build something with tubes and don't want to spend much more than 150$.
 I've already got a SOHA I with Jisbos, would be boring to build that one again.
 Maybe somebody has another suggestion for me?_

 

$210 shipped in the US with the case and transformer. Even without the case and transformer, it's still over $150.


----------



## mypasswordis

You could build runeight's Very Compact Hybrid Amp, although I'm not sure how hard it would be to get a PCB for it. I think there's a BOM for it; if not, I'm sure you could just ask runeight or cfcubed. Tube rolling is much easier and cheaper since there's only a single tube.


----------



## runeight

Quote:


  Originally Posted by *kostalex* /img/forum/go_quote.gif 
_It was measured on heatsinks, case was open. Transistors are very well bonded using the thermal grease._

 

Hi there. Sorry I'm late. 

 90C is too hot and shouldn't really happen with normal devices and heatsinks. Are you sure the current is 100mA through R10 and that you're reading a voltage drop of about 220mV on both channels? 

 If you are, then something else is wrong. First thing would be to check the TL+ and TL- test points for +/-15V.

 If all four of these measurements are correct, then the temp measurement could be wrong. You've probably answered this already, but the heatsinks are the ones specified in the BoM? Did the parts come from Glass Jar?

 Is there anything else not working correctly?


----------



## kostalex

TPL is 41.2V and TPR is 38.3V, both are pretty low.

 All parts are from GlassJar. I'll take a measurements tomorrow and let you know. Thanks for you help.


----------



## runeight

Quote:


  Originally Posted by *kostalex* /img/forum/go_quote.gif 
_TPL is 41.2V and TPR is 38.3V, both are pretty low.

 All parts are from GlassJar. I'll take a measurements tomorrow and let you know. Thanks for you help._

 

If you have the latest rev of the board then you can adjust the B+. The TPL and TPR are actually pretty good. But if you increase the B+ above 60V you'll get more plate voltage.


----------



## wiatrob

Hey - Guess what I did! Installed the heater jumpers in the wrong orientation 
	

	
	
		
		

		
		
	


	




 I quickly realized something was amiss - but the right channel is now gone, TPR reads very low negative voltage. The short was across the common and 6.3V jumpers - doesn't seem like I could hurt anything else but that leg of the PS - no tubes were in at the time... unless this is a coincidental failure...


----------



## runeight

First thing is to measure the heater voltage from the regulator. Is it -12.6V?


----------



## wiatrob

I checked all the test points, and recall them being 'normal' - I'm pretty sure H- was ~-12.6.

 EDIT: Confirmed -12.8V at TH, -12.87 at pin 4 of tube. Perhaps this is unrelated to the heater short.


----------



## runeight

Hard to know exactly what's wrong, but maybe test the buffers first. Do they still run at 100mA?

 What happens when you put tubes in? If the right channel is still bad, you might have to replace parts in the CCS one at a time.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hard to know exactly what's wrong, but maybe test the buffers first. Do they still run at 100mA?

 What happens when you put tubes in? If the right channel is still bad, you might have to replace parts in the CCS one at a time._

 

Buffers are good, and I can ever so faintly hear audio on the bad channel with a tube in... doesn't respond to volume increase.

 I am suspecting Q1R Q2R - I'll begin the testing transistors/troubleshooting as time allows. Thanks for your help...


----------



## rnickl

I found the bad trace on the board the other day but I still seem to be having a slight issue with the left channel. I'm getting a wild DC voltage swing at R10 from -5 to +5VDC.

 It does settle down and act nice when it warms up but, on rare occasion at power up it can take 2-3 minutes to settle down. Any thoughts on a direction to take this in?


----------



## Hayduke

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_I found the bad trace on the board the other day but I still seem to be having a slight issue with the left channel. I'm getting a wild DC voltage swing at R10 from -5 to +5VDC.

 It does settle down and act nice when it warms up but, on rare occasion at power up it can take 2-3 minutes to settle down. Any thoughts on a direction to take this in?_

 

I would give the rest of the PCB a close inspection. If it had one problem, there could be others. Maybe the equipment was giving the operator trouble during your board. It might have passed inspection (although that short should not have), but there could have been multiple problems.

 This sounds really bad and I feel for ya


----------



## wiatrob

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Buffers are good, and I can ever so faintly hear audio on the bad channel with a tube in... doesn't respond to volume increase.

 I am suspecting Q1R Q2R - I'll begin the testing transistors/troubleshooting as time allows. Thanks for your help..._

 

Or not - mechanical failure of one of the C1R joints (bottom mounted VitQs) from sliding the board in and out of the case... phew.


----------



## rnickl

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_I would give the rest of the PCB a close inspection. If it had one problem, there could be others. Maybe the equipment was giving the operator trouble during your board. It might have passed inspection (although that short should not have), but there could have been multiple problems.

 This sounds really bad and I feel for ya 
	

	
	
		
		

		
		
	


	


_

 

I did inspect the board under a scope for any more problems. I even had one of the girls at work inspect all my solder joints, she gave me %100 
	

	
	
		
		

		
		
	


	




 I ended up swapping Q5 and Q6 and all is looking good now. I wanted to swap them anyway (for sanity sake) but maybe one of them saw a bit too much heat or voltage that was giving me that wild swing.


----------



## runeight

rnicki does this mean that your amp is working now?


----------



## Hayduke

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_I did inspect the board under a scope for any more problems. I even had one of the girls at work inspect all my solder joints, she gave me %100 
	

	
	
		
		

		
		
	


	




 I ended up swapping Q5 and Q6 and all is looking good now. I wanted to swap them anyway (for sanity sake) but maybe one of them saw a bit too much heat or voltage that was giving me that wild swing. 
	

	
	
		
		

		
		
	


	


_

 

Grats on getting your SOHA II working!

 So how do you think it sounds? What were you listening to before?


----------



## rnickl

Yeah guys, the amp is working nice now.

 This is my first headphone amp and I don't have a decent set of headphones yet but, so far it makes my cheap (relatively) in ear plugs sound like I haven't heard them sound before. I can hopefully borrow a few sets of phones from friends in the next couple weeks while I decide on what to get for myself. So far I'm leaning toward the AKG 240S.

 I was listening to a Cayin TA-30 amp through a set of Ariel (DIY) speakers until my kids started getting to loud and I decided I would build the Soha


----------



## wiatrob

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_Yeah guys, the amp is working nice now.

 I was listen to a Cayin TA-30 amp through a set of Ariel (DIY) speakers until my kids started getting to loud and I decided I would build the Soha 
	

	
	
		
		

		
		
	


	


_

 

Nice work and nice choice! 
	

	
	
		
		

		
		
	


	




 I doubt you will be disappointed whatever headphones you choose. I spent a while listening the the 'II this evening, it is a wondeful amp...


----------



## Hayduke

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_Yeah guys, the amp is working nice now.

 This is my first headphone amp and I don't have a decent set of headphones yet but, so far it makes my cheap (relatively) in ear plugs sound like I haven't heard them sound before. I can hopefully borrow a few sets of phones from friends in the next couple weeks while I decide on what to get for myself. So far I'm leaning toward the AKG 240S.

 I was listening to a Cayin TA-30 amp through a set of Ariel (DIY) speakers until my kids started getting to loud and I decided I would build the Soha 
	

	
	
		
		

		
		
	


	


_

 

Wow, this was your first project! It's gonna be hard to improve on it. This is my 4th DIY amp and the SOHA II, by far IMHO, is the best sounding.

 I use my SOHA IIt with HD650s, and they compliment each other nicely. The nicest thing about this amp though is you can try many different tubes to find the ones with the best synergy with _your_ headphones. I'd highly recommend the 650s though. They probably appeal more to bass head types, of which I admit to being 
	

	
	
		
		

		
		
	


	




 They are also one of the best headphone deals I know of. Get them from J&R for $319.99 to your door! I've had them for a couple months now (shortly before completing my SOHA II), and almost everday I'm impressed by how great they sound


----------



## wiatrob

Quote:


  Originally Posted by *Hayduke* /img/forum/go_quote.gif 
_SNIP I'd highly recommend the 650s though. They probably appeal more to bass head types, of which I admit to being 
	

	
	
		
		

		
		
	


	




 They are also one of the best headphone deals I know of. SNIP_

 

Agreed, I have gone thorough a few pairs of cans but won't part with my 650s. Used 600s and then 580s are also an option if your budget is more modest.

 And now I can't count out the mid level Grados after hearing the RS-1s at our meet a few weeks back (and must investigate that synergy with all Alex' designs). Have fun choosing, as you've no doubt noticed - there is a wealth of info (and opinions 
	

	
	
		
		

		
		
	


	




 ) here...


----------



## Sathimas

I ordered my SOHA II Kit from Jeff today.

 I hope I'll just have to let you know when it's finished and working ...


----------



## wolf18t

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Agreed, I have gone thorough a few pairs of cans but won't part with my 650s. Used 600s and then 580s are also an option if your budget is more modest.

 And now I can't count out the mid level Grados after hearing the RS-1s at our meet a few weeks back (and must investigate that synergy with all Alex' designs). Have fun choosing, as you've no doubt noticed - there is a wealth of info (and opinions 
	

	
	
		
		

		
			





 ) here..._

 

Last night before sleep, I had my first significative SOHA listening session using my RS-1. I liked a lot what I hear. My first impressions: not as detailed as my B22 but not far behind. Tonally I heard also a little more midbass and smoother/fuller mids. It was a fun but still relaxing listening session.
	

	
	
		
		

		
		
	


	




 The tubes are (for now) NOS 6DJ8 Amperex Orange Globe and they are not fully burned-in yet. Still have to try the Phillips/ECG 5963 and Sylvania 5814A I have on hand.

 With this combo I think the SOHA is a better match with my RS-1 which can sound hard and thin with some lesser recordings. Take note that my SOHA II isn't totally stock from Jeff kit:
 - Replaced the .22uF coupling WIMAs with Mundorf MCAP Supreme
 - Replaced many electrolytics caps with Panasonic FC/FM
 - Replaced BD139 with Toshiba 2SC3422


----------



## Hayduke

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Last night before sleep, I had my first significative SOHA listening session using my RS-1. I liked a lot what I hear. My first impressions: not as detailed as my B22 but not far behind. Tonally I heard also a little more midbass and smoother/fuller mids. It was a fun but still relaxing listening session.
	

	
	
		
		

		
		
	


	




 The tubes are (for now) NOS 6DJ8 Amperex Orange Globe and they are not fully burned-in yet. Still have to try the Phillips/ECG 5963 and Sylvania 5814A I have on hand.

 With this combo I think the SOHA is a better match with my RS-1 which can sound hard and thin with some lesser recordings. Take note that my SOHA II isn't totally stock from Jeff kit:
 - Replaced the .22uF coupling WIMAs with Mundorf MCAP Supreme
 - Replaced many electrolytics caps with Panasonic FC/FM
 - Replaced BD139 with Toshiba 2SC3422_

 

I liked my 6DJ8's, but they aren't Amperex 
	

	
	
		
		

		
		
	


	




 I'm listening to 6189's now. I can hear a difference. It's not a dramatic difference, but it's definitely audible. I'm still undecided on which I prefer. I'll have to swap the 6DJ8's back in to compare. Thanks for proving a great amp that allows this Alex 
	

	
	
		
		

		
		
	


	




 Do you think the Toshiba transistors will make a big difference? I socketed all mine so that I could try others. The best source I found for them is Beezar.com, so next time I order from Tom, I'm planning to get a hold of some. When I compared the datasheets vs the BD139's though, it didn't seem like they would make a significant difference, so I wasn't in a hurry to try them.


----------



## rnickl

Well, after listening to the amp for a couple days I’m finding it is very susceptible to noise. I haven’t checked with an o’scope yet but I must have quite a bit of noise on some of my outlets at home, hiss is quite bad at some outlets and better at others. 

 I also found that without the top cover on the case I just get the hiss but when I install the top cover a couple outlets give me a bad 60Hz hum. I’m guessing since the top cover is grounded and the tubes pass through it I have some noise on my ground line from other devices plugged into the circuit. 

 I can hopefully get a hold of an o’scope over the weekend to look deeper into this. In the meantime have any of you guys any noise issues? Even at work I seem to get a bit of a hiss, how quiet are you guys finding your amps without an input on them?


----------



## runeight

Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_Well, after listening to the amp for a couple days I’m finding it is very susceptible to noise. I haven’t checked with an o’scope yet but I must have quite a bit of noise on some of my outlets at home, hiss is quite bad at some outlets and better at others. 

 I also found that without the top cover on the case I just get the hiss but when I install the top cover a couple outlets give me a bad 60Hz hum. I’m guessing since the top cover is grounded and the tubes pass through it I have some noise on my ground line from other devices plugged into the circuit. 

 I can hopefully get a hold of an o’scope over the weekend to look deeper into this. In the meantime have any of you guys any noise issues? Even at work I seem to get a bit of a hiss, how quiet are you guys finding your amps without an input on them?_

 

rnickl I had this problem when I build one of the first prototype boards. But when I completely cased up the amp in the Hammond enclosure, including a perforated top cover all of the noise disappeared (which in my case was low level hum). I don't have any audible hiss on different outlets here at home, but I have not tried another building, such as work.

 Some other folks have noticed hiss problems but I don't know if or how those issues have been fixed.


----------



## kostalex

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hi there. Sorry I'm late. 

 90C is too hot and shouldn't really happen with normal devices and heatsinks. Are you sure the current is 100mA through R10 and that you're reading a voltage drop of about 220mV on both channels? 

 If you are, then something else is wrong. First thing would be to check the TL+ and TL- test points for +/-15V.

 If all four of these measurements are correct, then the temp measurement could be wrong. You've probably answered this already, but the heatsinks are the ones specified in the BoM? Did the parts come from Glass Jar?

 Is there anything else not working correctly?_

 

Yes, our thermometer is working wrong. We measured with the right one and the temperature is 50C. I am sorry for this.


----------



## shellylh

I soldered the opamp socket in backwards in the SOHA II and, afraid that may lead to me putting the opamp in backwards in the future, I desoldered it. However, it took a lot of work/heat and in the process and I lifted one of the pads on the top side of the board. The pad on the bottom side of the board looks intact so I think I should be ok. Will this be ok? 

 Also, I can no longer fit the (new) socket into the holes. I guess I couldn't get all the solder out. Should I try and buy a new socket with thinner leads or do something else? I am afraid if I try more desoldering, I will just lifts more pads off the board and will have to start from scratch. At this point, I just have the resistors in place (I have been pretty busy) so it wouldn't be the end of the world to start over. Sigh...


----------



## rnickl

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_I soldered the opamp socket in backwards in the SOHA II and, afraid that may lead to me putting the opamp in backwards in the future, I desoldered it. However, it took a lot of work/heat and in the process and I lifted one of the pads on the top side of the board. The pad on the bottom side of the board looks intact so I think I should be ok. Will this be ok? 

 Also, I can no longer fit the (new) socket into the holes. I guess I couldn't get all the solder out. Should I try and buy a new socket with thinner leads or do something else? I am afraid if I try more desoldering, I will just lifts more pads off the board and will have to start from scratch. At this point, I just have the resistors in place (I have been pretty busy) so it wouldn't be the end of the world to start over. Sigh..._

 

Which opamp and pin #? Some of the pins actual make no connection on the top side of the board but the pad is there for a better mechanical connection, so you may be in better shape than you think. Even if there is a connection/trace, if you can get solder to flow up and make a solid connection you should be fine. If a trace is broken you can repair it with a bit more work although it sound like you just lifted the pad a bit, right?

 runeight,
 Thanks for the input. I was ignoring the noise in certainty it would just go away when I put it all in the case like you said.

 I might be being just a bit to critical to be honest. This is my first go with headphones and it seems they can be quite a bit more revealing of low level sounds. Maybe I need to hit my local shop and listen to some amps for a more honest impression.


----------



## shellylh

I think it is pin #8 on the ICE (on the board it is the pin closest to Q2E). The pad is lifted right off because I couldn't let it just hang there.... 

 As for the hole that I cannot get all the solder out of.... can I carefully drill the solder out or would that be really bad? It is in pin 3. 

  Quote:


  Originally Posted by *rnickl* /img/forum/go_quote.gif 
_Which opamp and pin #? Some of the pins actual make no connection on the top side of the board but the pad is there for a better mechanical connection, so you may be in better shape than you think. Even if there is a connection/trace, if you can get solder to flow up and make a solid connection you should be fine. If a trace is broken you can repair it with a bit more work although it sound like you just lifted the pad a bit, right?

 runeight,
 Thanks for the input. I was ignoring the noise in certainty it would just go away when I put it all in the case like you said.

 I might be being just a bit to critical to be honest. This is my first go with headphones and it seems they can be quite a bit more revealing of low level sounds. Maybe I need to hit my local shop and listen to some amps for a more honest impression._


----------



## Ferrari

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_I think it is pin #8 on the ICE (on the board it is the pin closest to Q2E). The pad is lifted right off because I couldn't let it just hang there.... 

 As for the hole that I cannot get all the solder out of.... can I carefully drill the solder out or would that be really bad? It is in pin 3._

 

Shelly, OpAmp pin #8 of the Epsilon 12 circuit is non-connected/not used. So don’t worry about that pin. 
	

	
	
		
		

		
		
	


	




 As for the hole (OpAmp pin #3) that you can not get all the solder out of it, it’s better to try other alternative than drilling. If you don’t have an air solder-sucker, you can get the solder out by melting the solder (add some solder if necessary)… while the solder is 100% melting, put a needle in the hole to push the solder out. Since the needle doesn’t stick into the solder, you can get the needle out of the hole and voila… the hole is back without damage.

 I have used this trick when I was a starving EE student many years back (and these were the needles used).
 Of course you can use other kind of needles, even dental tools can work (as long as it fits the hole).


----------



## shellylh

Ferrari,

 Thanks for the advice. I am a little confused about the needle trick. Why does the needle not stick to the solder? I do have a solder-sucker. It just didn't get all the solder out. Maybe I should add some more solder and try again. I just don't want to mess too much with it since I don't want to lift more pads. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Shelly, OpAmp pin #8 of the Epsilon 12 circuit is non-connected/not used. So don’t worry about that pin. 
	

	
	
		
		

		
		
	


	




 As for the hole (OpAmp pin #3) that you can not get all the solder out of it, it’s better to try other alternative than drilling. If you don’t have an air solder-sucker, you can get the solder out by melting the solder (add some solder if necessary)… while the solder is 100% melting, put a needle in the hole to push the solder out. Since the needle doesn’t stick into the solder, you can get the needle out of the hole and voila… the hole is back without damage.

 I have used this trick when I was a starving EE student many years back (and these were the needles used).
 Of course you can use other kind of needles, even dental tools can work (as long as it fits the hole). 
	

	
	
		
		

		
		
	


	


_


----------



## Ferrari

Quote:


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

 I am a little confused about the needle trick. Why does the needle not stick to the solder?_

 

That is due to the special metal (amorphous chrome) that often applied on the surface of the (medical) needles and dental tools.
 As opposite to copper (most resistors leads), amorphous chrome is more or less impossible to solder via the usual way, the way we do in DIY-electronics.


----------



## shellylh

Ok, I see now. I guess I was thinking of sewing needles. Is there anything you can buy at the local drugstore? I don't think you can buy medical needles without a prescription, right? Thanks. 

  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_That is due to the special metal (amorphous chrome) that often applied on the surface of the (medical) needles and dental tools.
 As opposite to copper (most resistors leads), amorphous chrome is more or less impossible to solder via the usual way, the way we do in DIY-electronics._


----------



## Ferrari

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_Ok, I see now. I guess I was thinking of sewing needles. Is there anything you can buy at the local drugstore? I don't think you can buy medical needles without a prescription, right? Thanks._

 

I don’t know how it is in the US, but in the Netherlands we can get that at the local drugstore.
 Sewing needles with a chrome surface can also work. Just put a little solder on it, if it doesn’t stick on the solder then it’s OK.
 Be careful with the heat, wrap one end of the needle in some paper tape (or something else) to avoid burning fingers.


----------



## pabbi1

A safety pin is best, as it has this same property, and you can hold it better - I keep 3 different sizes next to my soldering station at all times just for such an occasion, which sadly occurs all too often for me.


----------



## shellylh

I think I can successfully find a safety pin, thanks Al. Glad to know I am not the only one who makes mistakes.


----------



## Sathimas

How big should the inside of a Standard SOHA II case be? (in cm please)

 I payed mine today and hope that it won't need much longer
 than one week to get to Germany (think I'll have to collect it from the customs anyway.)

 But I could allready start building the case, material will be wood.


----------



## holland

Is anyone running this amp with 4mA tail current? I'm curious as to how it affects the sound.


----------



## wiatrob

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_How big should the inside of a Standard SOHA II case be? (in cm please)

SNIP

 But I could allready start building the case, material will be wood._

 


 Depends on if you want the transformer inside the case or not. The 'Enclosure' page on the website has some PDF's you can use to plan sizing:

The SOHA II Headphone Amplifier

 Or you could start with the dimensions of the recommended Hammond 1455T2201BK case: 

Hammond Mfg. - Extruded Aluminum (Metal End Panels) - 1455 Series Enclosures


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Is anyone running this amp with 4mA tail current? I'm curious as to how it affects the sound._

 

I've cranked my original build up to at least 3-4mA, but my tin ears did not detect a difference - can't recall which tubes though...

 May try again with the build on my bench awaiting casing...


----------



## kostalex

Please, advice tubes-rolling for SOHA II > Denon D2000.

 Music are jazz, blues, old rock and rock-n-roll. Ears are 60 old.


----------



## runeight

I have tried quite a few tubes. My favorite so far is an RCA 5963. If you like a more mellow sound the Amperex 8416 is my next choice. It is a 12V 6922.


----------



## holland

I've tried a few tubes too. I agree with runeight, depending on your preferences (and headphones used). I use black plate RCA 5963, very microphonic so you have to find a pair that isn't.

 5814A may do well also.


----------



## kostalex

Is matching pair necessary?


----------



## Hayduke

@Kosta

 My favorites so far have been the 6DJ8's but I'm not done trying out my 6 different tubes I ordered 
	

	
	
		
		

		
			





 Also I'm using HD650's so I can't really say for sure how they will sound with your Dennons.

 In regards to matching tubes, I believe Alex has said it's not necessary with this design.


----------



## mdabro

Another Soha 
	

	
	
		
		

		
		
	


	




 All is almost ok, sounds very nice, but I have one question: I can set only 120-210mV on R10L and R10R. Is it enough?


----------



## Ferrari

Quote:


  Originally Posted by *mdabro* /img/forum/go_quote.gif 
_Another Soha 
	

	
	
		
		

		
		
	


	




 All is almost ok, sounds very nice, but I have one question: I can set only 120-210mV on R10L and R10R. Is it enough?_

 


 Congrat with your successful build! 
	

	
	
		
		

		
		
	


	




 Probably parts tolerances are playing a role in this case, however… 120mV - 210mV across R10L and R10R correspondent to approximately 55mA – 95mA quiescent current at the output devices. This should be sufficient for (almost) any kind of headphones!


----------



## mdabro

Ferrari, can I use E88CC instead 5963 ?


----------



## Sathimas

Started my build today with the case ... the Amp itself went on his way today from Jeff.
 Hope it arrives until the beginning of next week so that I can finish it until sunday, my fathers birthday.


----------



## runeight

Quote:


  Originally Posted by *mdabro* /img/forum/go_quote.gif 
_Another Soha 
	

	
	
		
		

		
		
	


	




 All is almost ok, sounds very nice, but I have one question: I can set only 120-210mV on R10L and R10R. Is it enough?_

 

I think that Ferrari is right. It may just be component tolerances that all went in one direction.

 But there are a few things you should check. Are the rails +/-15V?? Are all of the resistors in buffers the correct values? Are you using the stock BD transistors or something else?

 210mV is enough for almost anything that you'll want to do. I'd just like to see you have more range on the high side of the setting.


----------



## TimJo

I'm about to order parts for my build and have a couple of questions.

 Mouser is backordered on a couple of parts. 

 One is the high voltage regulator. I took a quick look through the catalog and it looks like TI is the only one making this part - is that right Alex, or does Mouser have an alternative selection that I missed? I may need to order it from Digikey I guess. It will be my only Digikey part. 
	

	
	
		
		

		
		
	


	




 The other one is the UF4004 diode. I am going to use this one instead - unless you think I shouldn't. UF4004-E3/54

 Also, I noticed that on the SOHA II bom, C3E is a polar cap, but on the CTH bom, it is bipolar. Can it be bipolar here as well?


----------



## holland

That should be fine. You can use the UF4004_Q

 and you can use uf4005, uf4006, and uf4007 as well.


----------



## runeight

No probs on the diodes.

 TI is the only supplier for the reg.

 C3E can be bipolar. There should be pads on the board for the larger size.

 I see that Holland has already answered the diode question.


----------



## mdabro

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 But there are a few things you should check. Are the rails +/-15V?? Are all of the resistors in buffers the correct values? Are you using the stock BD transistors or something else?

 210mV is enough for almost anything that you'll want to do. I'd just like to see you have more range on the high side of the setting._

 

+15V and -15V is correct. I have checked all resistors few times, and have not found any errors. I use BD139.

 And, If You say, that 210mV is enough... I use Sennheiser 515. What do You think? Is it enough?


----------



## Hayduke

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_I'm about to order parts for my build and have a couple of questions.

 Mouser is backordered on a couple of parts. 

 One is the high voltage regulator. I took a quick look through the catalog and it looks like TI is the only one making this part - is that right Alex, or does Mouser have an alternative selection that I missed? I may need to order it from Digikey I guess. It will be my only Digikey part. 
	

	
	
		
		

		
			



_

 

I ended up having to get that part from Digi-Key too. At least they got rid of that minimum order policy they used to have (or was that Mouser? lol). I just price compared the parts they both carried and ordered the cheaper ones from Digi-Key and took them off the Mouser order. The Hammond case is cheaper at Digi-Key, just make sure you get the right part #. I order silver on accident


----------



## runeight

OK. I guess this one is on the far edge of the curves. Try running it for a while to see if the current increases.

 95mA is plenty for 300R headphones. You won't have any problems nor will you bump into any limits on the buffers.


----------



## Sathimas

I just finished building my SOHA, took more time than it should have ...

 Well - just as I expected and the same time hoped the opposite it does not work.
 In the very first step of the setup I'm stuck.

 TB+ Reading is only ~23Volts - not over a hundred as it should be.

 Normally this woulnd't bother me that much, I'm used to startup- problems with my DIY projects.
 But this special one is a birthday gift for my father - tomorrow ...


----------



## wiatrob

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I just finished building my SOHA, took more time than it should have ...

 Well - just as I expected and the same time hoped the opposite it does not work.
 In the very first step of the setup I'm stuck.

 TB+ Reading is only ~23Volts - not over a hundred as it should be.

 Normally this woulnd't bother me that much, I'm used to startup- problems with my DIY projects.
 But this special one is a birthday gift for my father - tomorrow ... 




_

 

Have you checked to see that the transformer wires are going to their proper terminals?


----------



## Sathimas

Well - this is the schematic on the transformer:

 Black - 0V
 RED - 15V
 Orange - 0V
 Yellow - 15V

 Black and orange are connected to the middle binding post - the 0V one
 Red is on the left side, yellow on the left side - should be correct this way - or not?

 What I forgot - the other readings of that step show correct values. (15, 15 and 12,6V)


----------



## runeight

Sathimas, the correct way to wire the transformer would be:

 Black to one outside post
 Yellow to the other outside post
 Orange/Red to the middle post

 Try this and see what happens.


----------



## rnickl

What do you read for an input voltage? (From the input connector on the board)
 What's voltage at TL+/- and TB?

 [edit] Never mind, I lack reading comprehension skills. Looks like Runeight cleared it up.


----------



## Sathimas

thank you very much runeinght - I misunderstood the transformer wiring somehow.

 Could someone explain it to me so that I won't make that mistake again?

 Now all readings are ok for the moment, I'll go on testing in a minute and keep you up to date


----------



## runeight

The transformer must be wired so that it give 30V center tapped. The two "outside" wires must be out of phase to get this arrangement.

 Now the transformer leads are marked with their phase relationships. This means that the two 0V leads are in phase with each other and the two 15V leads are in phase with each other. Using two 15V leads for the outside connections makes them both in phase and this is not what is needed for 30V center tapped. 

 To get out of phase "outside" leads you must use one 0V lead and one 15V lead. Then the two remaining leads are connected together to make the "center tap."

 It actually doesn't matter how you form the outside leads. You can do it the way I did or you can do it this way:

 Red - outside
 Orange -outside
 Black/Yellow - middle

 They are both the same.


----------



## Sathimas

Its alive now.

 Only thing I still have to change are the LED-resistors.
 The LEDs should be much brighter, at the moment you hardly notice them.


----------



## scompton

I started looking at the parts from my kit tonight in preparation for starting tomorrow. I discovered one disadvantage of using a kit. When I order from mouser, everything comes in nice labeled bags. The print on the Dale resistors is very hard for my old eyes to read. I realize I need to measure each resistor anyway, but it would be nice to be able to pick out the proper resistor easily.

 This is going to accelerate me getting bifocals


----------



## mattcalf

Are there any Australians who've built this baby?
 I'm looking to find out a rough price of importing the needed items.

 Even if someone could give me a rough price of all the needed items, it'd be much appreciated.


----------



## wiatrob

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I started looking at the parts from my kit tonight in preparation for starting tomorrow. I discovered one disadvantage of using a kit. When I order from mouser, everything comes in nice labeled bags. The print on the Dale resistors is very hard for my old eyes to read. I realize I need to measure each resistor anyway, but it would be nice to be able to pick out the proper resistor easily.

 This is going to accelerate me getting bifocals
	

	
	
		
		

		
			



_

 

If you have a voltmeter that reads resistance (most do - it's much easier than cyphering resistor codes!

 -Bill


----------



## scompton

Yeah, I know and when I built my Starving Student, I measured every resistor before putting it in even though it came out of a labeled baggie. It was just a rant about needing to get bifocals more than anything else


----------



## scompton

I want to make sure I have the right idea of the zener tweak. You replace the resistor R4P with a zener, correct? I didn't get one with my kit so I'll have to order one. On Mouser there's 14,000 options for zener diodes. What specs does it need to have?


----------



## wolf18t

Quote:


  Originally Posted by *scompton* /img/forum/go_quote.gif 
_I want to make sure I have the right idea of the zener tweak. You replace the resistor R4P with a zener, correct? I didn't get one with my kit so I'll have to order one. On Mouser there's 14,000 options for zener diodes. What specs does it need to have?_

 

I socketed R4 in my build and tried a few 1/2W 18V zener (1N5248) from Digikey (Fairchild, Diode Inc, On Semi...). The less noisy, and less expensive too, of the bunch were the Fairchild. But there was still some noise (faint background hiss) that could be hear on low volume musical passage. I installed back the 18K resistors. 

 I admit I didn't play with the tail current so maybe the noise would have gone with higher tail current. If I had only heard the SOHA II without the resistors, I would had probably be very happy with the zeners, the hiss was not very intrusive.

 Edit: I forgot what Runeight said below, install the zener in the right orientation. This is the most important advice


----------



## runeight

This info should be on the SOHA II web page under Tweaks.

 However, you replace R4L and R4R in the amp sections with an 18V 1/2W zener. Make sure you install it in the correct orientation. The cathode band goes towards the current mirror transistors.

 Edit: I see that wolf18t beat me to a reply. And a better one at that.


----------



## wiatrob

I've gone back and forth on the Zeners. The noise is audible only at the very highest volumes with the most sensitive 'phones I have. 

 I currently am using another proposed tweak - bypassing R4 with a 1uF film cap. I really can't tell the difference between it and a plain R4, but it's 'custom'


----------



## holland

Have you heard any difference in tail currents, wiatrob? I'm using the R4 cap bypass as well, but am considering increasing the tail current up to 4mA-6mA instead of 2mA.


----------



## runeight

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Have you heard any difference in tail currents, wiatrob? I'm using the R4 cap bypass as well, but am considering increasing the tail current up to 4mA-6mA instead of 2mA._

 

Just remember that you need the zeners to be able to change the tail current without affecting the plate voltage.


----------



## holland

Thanks. I was going to change the resistors to different values. I'm not sure I want to deal with zener noise, though I probably should give it a try too. 
	

	
	
		
		

		
		
	


	




 I don't want to open it up unless someone tells me it makes a difference, though.


----------



## adamus

have you guys seen the 'red light district amp' on the diyforums. could you not replace the 18v zener with a smallish led array (3x3 grid?).


----------



## runeight

No, haven't seen that amp but that's not a bad idea. The only question would be do 6-10 leds make more noise than one zener?


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Thanks. I was going to change the resistors to different values. I'm not sure I want to deal with zener noise, though I probably should give it a try too. 
	

	
	
		
		

		
		
	


	




 I don't want to open it up unless someone tells me it makes a difference, though. 
	

	
	
		
		

		
		
	


	


_

 

I have cranked it up to ~4mA - I couldn't hear a difference but my ears are not Golden. Depending on the sensitivity of your 'cans, I suspect the presence of the zener might take precedence in SQ over the benefits of increased tail current. Sorry I can't be of more help, except to offer:

 If it ain't broke 
	

	
	
		
		

		
		
	


	




 Of course that goes against the nature of tinkering. I don't think anyone has had the tail current up in the 6mA range (though Alex has probably sim'd it)


----------



## adamus

not sure on the noise of the leds' but the red light district amp uses a massive array with no issues at all (think 60 odd led's per channel). 

 best case scenario is you get all the positive of using leds.


----------



## runeight

Maybe someone can try it. The LED string needs to drop about 18V.


----------



## wolf18t

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Thanks. I was going to change the resistors to different values..._

 

Good idea. Runeight, in this circuit, doubling the tail current to 4 mA, is it just a matter to cut in half the value of R4 to keep around 19V drop to the plate (V=RI)?

 4mA ---> 9K
 6mA ---> 6K


----------



## runeight

Correct.


----------



## Hayduke

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_have you guys seen the 'red light district amp' on the diyforums. could you not replace the 18v zener with a smallish led array (3x3 grid?)._

 

Are you talking about this?
SYclotron Audio » The Red Light District

 If not, got a link?


----------



## adamus

yes indeed.

 Been thinking more about the idea, and its dont think it will ever be a runner. To drop 18v you'll need at least 10 led's by which time you will will have 10 lots of dynamic resistance, circa 40 ohms. This is greater than the zener.

 concept born.... concept deemed worthless.


----------



## adamus

oops.


----------



## ChrisX

Today I received the last parts to build my SOHA_II. The resistors and E12-diodes are already stuffed, the rest to follow soon. 

 Now I have some schottky diodes at hand (MBR1100, 1 A 100V) and I think they could be a nice upgrade over the UF4004 for the +/- 15 V supply (D1P-D4P).

 Anyone already tested different diodes? What do you think?

 Chris


----------



## runeight

Don't see any reason why not.


----------



## adamus

almost there on the sohaII I am building. Power supply checks out fine. Just waiting on a an order for the E12 parts. hopefully the suggested farnell relay should be ok. 

 having not followed th whole thread, are the step by step instructions for initial setup still ok considering the PS revision?


----------



## runeight

Yes, they should be correct.


----------



## runeight

That is, the ones on the website should be correct.


----------



## scompton

I'm happy this was posted as I'm almost to that point on my build. I assume that the proper setup is somewhere in this thread.


----------



## runeight

It could be, but the easiest place to find what you need is here:

Cavalli Audio


----------



## scompton

Sorry, I misinterpreted the posts at the end of a long day at work. I was already intending to use your site thanks.


----------



## rhester

Im built a 2 box version of this amp - transformer and switch in one box and amp in a separate box connected with a neutrik 5 pin plug. I have a little noise, especially with the Dennon D2000 plugged in. How should grounding be done on a 2 box solution? powere box grounded to its own case and amp board grounded thru a standoff at the star ground point? Any other way or better way? Also have wires hooked upo for tube leds - could that have extra noise?


----------



## shellylh

Ok, after about a month of guests and traveling I am finally able to get back to my SOHA II. I was looking at the place to solder the ICE and I noticed that (in addition to lifting the pad on pin #8, which is not connected to anything) the pad on pin #1 is starting to lift on the top of the board (maybe also on pin #2). 
	

	
	
		
		

		
		
	


	




 Everything looks ok on the bottom of the board. I have attached a picture. Is this going to be a problem? I would rather find out now and get a new board than to wait until the end and find out the amp doesn't work. At this point, I have only added the resistors and two of the IC sockets so it wouldn't be such a big deal to start over (the waiting would be a little annoying though). 

 I have to admit that I am a bit OC sometimes and *feel* that I want to start over with a nice new perfect board but maybe that is a ridiculous. [If I had second board and second set of resistors, I would start over.] 











 Also, my board seems a bit warped. I didn't notice this before. Should I be worried? I am wondering if this is another reason to get a new board. 







 Thanks!

  Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_I soldered the opamp socket in backwards in the SOHA II and, afraid that may lead to me putting the opamp in backwards in the future, I desoldered it. However, it took a lot of work/heat and in the process and I lifted one of the pads on the top side of the board. The pad on the bottom side of the board looks intact so I think I should be ok. Will this be ok? 

 Also, I can no longer fit the (new) socket into the holes. I guess I couldn't get all the solder out. Should I try and buy a new socket with thinner leads or do something else? I am afraid if I try more desoldering, I will just lifts more pads off the board and will have to start from scratch. At this point, I just have the resistors in place (I have been pretty busy) so it wouldn't be the end of the world to start over. Sigh..._


----------



## runeight

Edit: Ahh. My original text referred to the wrong amp. On this amp none of the pads are grounded so if the traces are solidly connected to the pads on the bottom of the board you are ok.


----------



## Hayduke

You may want to wait for another to respond and confirm this, but I think you will be fine. Pin 2 is used, but 1 and 8 are not. Your pad for pin 2 doesn't look too bad. You should solder your socket back in, then check for continuity between pin 2 and the resistor and cap pads that it connects to.

 In regards to not being able to get it back in. How are you removing the solder? I'm assuming your using solder braid. Are you using flux? If not, you need to. If you are, use more 
	

	
	
		
		

		
			





 You may also want to add a bunch of solder into the holes (again with flux) and then re-remove it with the braid. I usually put my liquid flux on the braid. It can be tedious to get the holes opened back up without a solder sucker, but I don't own one and I do fine 
	

	
	
		
		

		
		
	


	




 If you think it was heat that damaged the PCB, turn down the iron. You only need it hot enough to melt the solder. It's OK if it takes a second for the solder to melt. Especially when you're doing rework and you have the heat applied for a longer period of time.

 Good luck! I would try to salvage that board. I don't think you've damaged it beyond use. You got lucky on which pads have the most damage.


----------



## sachu

ummm..I think if runeright says it should be fine..it should be fine..that is if what he asking you to check is fine.

 He is the designer of the amp


----------



## shellylh

Thanks! The bottom of the board looks fine so it looks like I am in business. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Edit: Ahh. My original text referred to the wrong amp. On this amp none of the pads are grounded so if the traces are solidly connected to the pads on the bottom of the board you are ok._


----------



## wiatrob

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_Thanks! The bottom of the board looks fine so it looks like I am in business. 
	

	
	
		
		

		
		
	


	


_

 

I have lifted quite a few traced prototyping & tweaking various amps - even if the pad comes completely off you can scrape a little of the board away to expose the trace or jumper to the next component..

 That didn't look bad at all!


----------



## scompton

Quick question. I assume that I don't need to use the little plastic washers when mounting the BD139 transistors to the head sinks since they don't seem to fit.


----------



## runeight

No. In fact, you don't even need insulating pads, just thermal grease, because the packages are plastic.


----------



## 00940

I don't know which brand you have at hand but for newbies here: be careful as some BD139 (philips among others) have metal pads connected to collector.

 You don't need to isolate the screw from the plastic body but you need an insulation pad


----------



## scompton

It looks like they're Fairchild because the have a little stylized F. I bought a kit and I don't have access to the kit BOM right now. They're entirely plastic.


----------



## runeight

Quote:


  Originally Posted by *00940* /img/forum/go_quote.gif 
_I don't know which brand you have at hand but for newbies here: be careful as some BD139 (philips among others) have metal pads connected to collector.

 You don't need to isolate the screw from the plastic body but you need an insulation pad_

 

Thanks. I did not know this and have never seen one with metal pads in a TO126 package. But good to know for anyone who might have one of these.


----------



## Hayduke

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_ummm..I think if runeright says it should be fine..it should be fine..that is if what he asking you to check is fine.

 He is the designer of the amp_

 

He posted while I was posting 
	

	
	
		
		

		
		
	


	




 I had to look at drawings and the datasheet before I answered


----------



## adamus

could i use a bc547b as a sub for the bc 550 in the e12? they ahve been missed off a farnell order.

 Cheers


----------



## runeight

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_could i use a bc547b as a sub for the bc 550 in the e12? they ahve been missed off a farnell order.

 Cheers_

 

Yes.


----------



## adamus

thanks runeight


----------



## pabbi1

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_Thanks! The bottom of the board looks fine so it looks like I am in business. 
	

	
	
		
		

		
		
	


	


_

 

Hmmmm - you are using a socket, and not soldering the opamp in directly, yes?


----------



## scompton

Is it important to get a good solder joint when soldering the heat sinks to the board? My 15 watt iron is not really up to it.


----------



## runeight

It is not really necessary to solder the heatsinks to the board. The pads are there if someone really needs to do it, but the pins on the transistor (regulators) will hold the devices and heatsinks in place. I left them all unsoldered in my SOHA II.


----------



## scompton

Great because I won't be able to do it. 

 I need confirmation of one more thing so I don't do something stupid. The depression in the top of the op amps mark pin one, correct?

 Edit: I just realized pin 1 isn't labeled on the board either. Is it the pin to the left of the indentation on the socket?


----------



## runeight

Correct.


----------



## scompton

Thanks. Didn't want to screw that up.


----------



## shellylh

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Hmmmm - you are using a socket, and not soldering the opamp in directly, yes?_

 

Yes, is this a problem? I am worried about the beginning of your sentence.... "hmmmm."


----------



## zkool448

Finally received my soha II kit from glassjar - woohoo! The next few weeks is busy time for me but I intend to squeeze a few moments here and there to get this kit together. 

 Btw, I'm cross checking the parts kit received vs. the BOM and already I'm stuck 
	

	
	
		
		

		
			





 ...can someone clarify where VR+E and Vr-E are? I think they're part of the E12 circuit (TO92) but can't seem to locate where they're suppose to go on the pcb. Thx.

 zk


----------



## wiatrob

I believe they are LV-E and LV+E on the silkscreen.. they are TO-92's correct?


----------



## zkool448

wiatrob, yep they're TO92's... I see them (LV-E and LV+E) on the board, thanks!

 zk


----------



## Computer Blue

Has anyone solved the hiss yet? I just finished a glassjar kit and have some soft hiss going on. It is there with or without tubes in. Any ideas where to start looking to fix this?


----------



## runeight

Egads. 
	

	
	
		
		

		
		
	


	




 The problem with the hiss problem is that not everyone has encourntered it. Because of this we haven't been able to pin down a cause. That is, to determine what is differerent about some builds compared to other builds that are using the same components.

 At one time I thought it might be noise in the O/P transistors running at 100mA. But I think Ferrari measured this and it was negligible and inaudible.

 Is anyone else who has a recent build also having this problem?


----------



## runeight

Quote:


  Originally Posted by *shellylh* /img/forum/go_quote.gif 
_Yes, is this a problem? I am worried about the beginning of your sentence.... "hmmmm."_

 

No. A socket is the best way to go.


----------



## rnickl

I built 2 and I had a minor hiss problem in one of them that had the transformer in the same enclosure. A bit of a twist to the transformer fixed it up.
 I have also noticed that the tubes pick up a bit of noise from ground when I put the top cover on the case. The tubes sticking out of the case half way seem to be microphonic enough to pick up noise from the grounded case (on a noisy main line)

 I'm not sure if this is the same issue as others have been seeing.


----------



## wiatrob

Quote:


  Originally Posted by *Computer Blue* /img/forum/go_quote.gif 
_Has anyone solved the hiss yet? I just finished a glassjar kit and have some soft hiss going on. It is there with or without tubes in. Any ideas where to start looking to fix this?_

 

What headphones are you using?


----------



## scompton

What slot does the board go into to match the face plate diagram? And does anyone know what size standoff works with that slot?


----------



## runeight

Third from the bottom.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_No. A socket is the best way to go. 
	

	
	
		
		

		
			



_

 

Agreed - my curiosity was directly soldering an opamp to the board. I do know some folks (OCD types) who won't do anything but - and are masochistic enough to love the agony unsoldering when put in wrong or scorched.

 Carry on, Shelly - you are doing great.


----------



## holland

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Egads. 
	

	
	
		
		

		
		
	


	




 The problem with the hiss problem is that not everyone has encourntered it. Because of this we haven't been able to pin down a cause. That is, to determine what is differerent about some builds compared to other builds that are using the same components.

 At one time I thought it might be noise in the O/P transistors running at 100mA. But I think Ferrari measured this and it was negligible and inaudible.

 Is anyone else who has a recent build also having this problem?_

 

For me, I think the hiss is tube related. Going from a 12AU7 type to a 6DJ8/6922 type seems to have "cured" it. Within the various 12AU7s, some were noisier than others. When I first encountered it, I had a small sampling of tubes, now I have multiples of same types and brands and can pretty much say they were tube related on my end.

 With my current tube, it's quiet even with Denon AH-D2000s and my more sensitive headphones (ATH-M50, M-Audio Q40). I haven't tried my IEMs, but it's way overkill for IEMs (too much gain).

 YMMV.


----------



## wolf18t

Quote:


  Originally Posted by *Computer Blue* /img/forum/go_quote.gif 
_Has anyone solved the hiss yet? I just finished a glassjar kit and have some soft hiss going on. It is there with or without tubes in. Any ideas where to start looking to fix this?_

 

No hiss here using 32 Ohm grados. Hiss problems is generally more frequent with sensitive low-Z headphones.

 Hiss in both channels or in one channel only? Hissing isn't a very easy problem to solve. Could be ground issue, transformer interference or simply a part that emit more noise than usual.


----------



## scompton

All this talk about the gain make me think I need to add resistors to the input to lower it. The only thing I've built before is a Starving Student and it has way too much gain for me. I can only use it with orthos, and not all of them. With everything else, the cheap pot is just at the point of channel imbalance. Even with the orthos, it's close.

 So is adding resistors to the input the way to lower the gain, or is there another way? I'm not going to do it until I have the amp running.


----------



## runeight

scompton, there is a lot of information on the SOHA II website at Cavalli Audio, including gain information for a few different tube types.

 The gain of this amp is controlled, primarily, but the application of a small amount of negative feedback. For the 12au7 tubes the gain should be only about 9X. I suspect this is lower than your Millet. So you should try it first before making mods. Then, if you really have too much gain resistors in series with the headphones at the output are probably a better choice. Something like 100R.

 Keep us posted.


----------



## scompton

Thanks, I was going to try it first. Somehow I missed the information about gain. I thought I had gone though all of the pages on Cavalli Audio.


----------



## adamus

well, the sohaII is all soldered up, and checks out fine. One of the test tubes isnt great, only 17v dropped instead of the 19v, but i think its near enough 

 Just got to get it cased up and we are good to go.


----------



## runeight

Good news. 
	

	
	
		
		

		
		
	


	




 After you break it in for a while perhaps you can tell us how it compares to your Bijou. I don't think there are too many of us with both of these amps and I would most definitely like to have your thoughts.


----------



## pabbi1

I have both... but balanced Bijou vs SE SOHA II isn't quite fair.


----------



## runeight

Ah yes, I forget that you also have them both by virtue of the SOHA II coming back from operations overseas.

 Perhaps that comparison is a bit unfair and you've already extensively logged your thoughts on the Bijou. So, I won't ask.


----------



## zkool448

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_well, the sohaII is all soldered up, and checks out fine. One of the test tubes isnt great, only 17v dropped instead of the 19v, but i think its near enough 

 Just got to get it cased up and we are good to go._

 

congrats adamus 
	

	
	
		
		

		
		
	


	




 Mine is moving along pretty smoothly (surprisingly) and if I put 2-3hrs more into it tonight I'm pretty confident I'll be bringing up the amp for its initial setup by tomorrow.

 BTW, Jeff sent me a pair of Sylvania 5963's, when I set the heater voltage do I jump 12.6v or 6.3v? thanks.

 zk


----------



## runeight

You'll want 12.6V for the 5963 and the other variants of 12au7. Good luck.


----------



## zkool448

My soha II is making music 
	

	
	
		
		

		
		
	


	








 I must've really lucked out because the voltages came up correctly from the start. 
 TL+14.99V
 TL-14.95V
 TH -12.82V
 TB+ +123.2V (down to 104.6V with a pair of 5963)

 Adjustments were smooth and easily set to spec as per Alex's website. Manged to set R10L/R idle currents to 100mA (220mV), TB+L/R set to 60V, then tail current set to 2mA (400mV) 
 Voltage difference between TB+L and TPL was fairly close to 19V with the e12 delay clicking around ~7 sec

 I love my millett starving students, but I noticed right away a significant improvement in sq without any audible hiss/hum. It doesn't sound as 'tubey' like the ss and much prefer how this soha II sounds... really liking it a lot. I'll let it burnin for a while. Can't wait to do some tube rolling 
	

	
	
		
		

		
		
	


	




 Guess I can't say it enough -- thank you Alex, all the prototypers and previous builders who asked all the questions that I didn't have to. Cheers!

 I'll do the casework after I complete my next amp project (CTH). I hope to have matching wooden enclosures for both with enough ventilation, which I haven't figured out how to accomplish.

 zk


----------



## runeight

Very kool zkool448. It's nice to hear that it all came up as expected with no problems. And that you like the way it sounds. 
	

	
	
		
		

		
		
	


	




 I really like mine, particularly with 5963s.

 Looking forward to your casework now.


----------



## Hayduke

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_My soha II is making music 
	

	
	
		
		

		
		
	


	








 I must've really lucked out because the voltages came up correctly from the start. 
 TL+14.99V
 TL-14.95V
 TH -12.82V
 TB+ +123.2V (down to 104.6V with a pair of 5963)

 Adjustments were smooth and easily set to spec as per Alex's website. Manged to set R10L/R idle currents to 100mA (220mV), TB+L/R set to 60V, then tail current set to 2mA (400mV) 
 Voltage difference between TB+L and TPL was fairly close to 19V with the e12 delay clicking around ~7 sec

 I love my millett starving students, but I noticed right away a significant improvement in sq without any audible hiss/hum. It doesn't sound as 'tubey' like the ss and much prefer how this soha II sounds... really liking it a lot. I'll let it burnin for a while. Can't wait to do some tube rolling 
	

	
	
		
		

		
		
	


	




 Guess I can't say it enough -- thank you Alex, all the prototypers and previous builders who asked all the questions that I didn't have to. Cheers!

 I'll do the casework after I complete my next amp project (CTH). I hope to have matching wooden enclosures for both with enough ventilation, which I haven't figured out how to accomplish.

 zk_

 

congrats zkool! I too am eager to see how you case it. I think it's funny that you posted you would work a couple more hours and complete it tomorrow. Then, 5 hours later, we have pics of it running 
	

	
	
		
		

		
		
	


	




 I'm not surprised you like your SOHA II. My only other tube amp was the MHSS too. While that amp sounds lovely, the SOHA II is significantly better to my ears. With the 580s or the 650s it sounds great, but I do prefer the 650s. I think the MHSS might be a little warmer sounding, so it compliments the 580s better perhaps?

 I'll second the thanks to Alex. I know I've said it several times, but I do appreciate you sharing this design with us. I have 2 buddies that are in love with the amp. They want me to build them one, but neither has the cash right now. Thanks again Alex


----------



## TimJo

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_My soha II is making music 
	

	
	
		
		

		
			









 I must've really lucked out because the voltages came up correctly from the start. _

 

Congratulations zkool448 ! I'm not at all surprised that it worked right off the bat. After spending time with Alex's schematics for the SOHAII, Bijou, and now the CTH, I've learned that the designs are rock solid and careful attention during assembly is all that is required...

 I'm really looking forward to seeing what your going to do with the casing on this one. Your SSMH is certainly a favorite of mine (and many others based on all of the comments). I think you set the bar pretty high with that one - not to put any pressure on.


----------



## adamus

excuse the mess, but its almost done...






 no hiss, no hum, just clean clean sound. And may i say, with the 5963, quite a solid state sound. very very different to the bijou. but its way off being burnt in, the tubes have barely 10 mins on them.

 To get the tubes that high without air wiring them, i used a socket saver in each socket.


----------



## zkool448

hayduke, your build tips and watchouts helped me immensely, many many thanks again! 
	

	
	
		
		

		
		
	


	




 Btw, I mistakenly soldered the 2x3 header upside down (longer pins to board). When I tried the jumpers they would not stay on 
	

	
	
		
		

		
		
	


	




 I had to desolder the header and ended up melting its plastic in the process (what a pain that was - this was the time sachu's advice came in handy: "Put the iron down and walk away if you're ticked off!"). I replaced it with 6 sip sockets, although a dpdt switch would've been the ideal replacement I didn't have one on hand and I was eager to get it setup.

 TimJo, appreciate the kind words 
	

	
	
		
		

		
		
	


	




 In terms of the casework, actually can't wait to get started. I have a change of heart about "matching" cases with my next build (CTH). I'm under the impression that the SOHA II and CHT are fairly close like brothers, but it'll be nice to keep their own distinct 'personalities'. 

 Here's a quick mock up of what I've envisioned so far, of course it could change depending on how much ventilation is needed... we'll see how close the final product will look 
	

	
	
		
		

		
		
	


	









 zk


----------



## zkool448

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_no hiss, no hum, just clean clean sound. And may i say, with the 5963, quite a solid state sound. very very different to the bijou. but its way off being burnt in, the tubes have barely 10 mins on them._

 

very nice adamus! that's exactly the locking 1/4" jack I want to use for my case -- do you have a mouser/digikey P/N? thanks.

 zk


----------



## adamus

Zkool448, i dont as i got mine from farnell. 

 I let the soha play for 5 hour last night, its warming up nicely, and the bass has filled out. 

 its a hot little beastey, good job i have the vented case.

 whats the concensus on setting the B+. I have mine at 60v at the moment.

 Going to be sad to see this one go, as i am building it for someone else.


----------



## adamus

not being able to find a datasheet for the 8416, which heater setting do i want?

 EDIT - and here is is finshed, and here is stands with its big brother, the bijou.


----------



## runeight

Very nice. 
	

	
	
		
		

		
		
	


	




 8416 is 12V.


----------



## holland

Nice, adamus.

 Re: the Bijou. Were nameplates actually made? I guess I missed the buy on that.

 Re: the SOHA 2. Are you using a zener for R4 and 1mA per triode?


----------



## holland

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_I'm under the impression that the SOHA II and CHT are fairly close like brothers, but it'll be nice to keep their own distinct 'personalities'._

 

zk, that's a really nice case you're working on. Those with tooling access make those without envious. 
	

	
	
		
		

		
		
	


	




 CTH and SOHA 2 have their own personalities, particularly in the behavior of tubes. The same tubes sound slightly different in the amps. They have a different tube configuration. It's all on the Alex Cavalli site for reading.

 Also, if you're one who does ever push it to that extreme. The CTH is a class AB PP output buffer (diamond) with a healthy bias of 25mA. Though I've never pushed it out of A, there may be possibilities of crossover distortion for the nightly "concert" goers. The SOHA2 is class A SE with a 100mA bias (can push higher if you need with venting/heatsinking).

 They are quite different animals. The CTH is one beast of a transportable, and sits at about 1/8th the size of my SOHA 2....with much less heat generation too.


----------



## TimJo

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_very nice adamus! that's exactly the locking 1/4" jack I want to use for my case -- do you have a mouser/digikey P/N? thanks.

 zk_

 

Mouser - 568-NJ3FP6C 
	

	
	
		
		

		
		
	


	




 This p/n is for the all black version I believe...


----------



## TimJo

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_In terms of the casework, actually can't wait to get started. I have a change of heart about "matching" cases with my next build (CTH). I'm under the impression that the SOHA II and CHT are fairly close like brothers, but it'll be nice to keep their own distinct 'personalities'. 

 Here's a quick mock up of what I've envisioned so far, of course it could change depending on how much ventilation is needed... we'll see how close the final product will look 
	

	
	
		
		

		
		
	


	









 zk_

 

Wow, that's looking sharp. I like the idea of recessing the volume knob like that...


----------



## adamus

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Very nice. 
	

	
	
		
		

		
		
	


	




 8416 is 12V._

 

cheers runeight. I'll give them a go. Given my experience with the 8416 in the soha + jisbos i expect them to really take this on a step


----------



## adamus

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Nice, adamus.

 Re: the Bijou. Were nameplates actually made? I guess I missed the buy on that.

 Re: the SOHA 2. Are you using a zener for R4 and 1mA per triode?_

 

no, i had it made, only cost me £5 from ebay. and the tail is the resistor at 400mv = 2ma. no zener in sight.... surely too noisey.


----------



## zkool448

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_zk, that's a really nice case you're working on. Those with tooling access make those without envious. 
	

	
	
		
		

		
		
	


	


_

 

Thanks holland, I too like this design but it's something I have never attempted before -- It looks like it could be done (_fingers crossed_) 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_CTH and SOHA 2 have their own personalities, particularly in the behavior of tubes. The same tubes sound slightly different in the amps. They have a different tube configuration... <snip>_

 

Thanks for breaking down the differences between the SOHA II and CTH. I'm eager to try a variety of tubes and do some A/B comparison... although I realize only the 12.6v variants can be used on my SOHA II as I didn't opt for a high current transformer. 
	

	
	
		
		

		
		
	


	




 zk


----------



## zkool448

Quote:


  Originally Posted by *TimJo* /img/forum/go_quote.gif 
_Mouser - 568-NJ3FP6C 
	

	
	
		
		

		
		
	


	



 This p/n is for the all black version I believe..._

 

TimJo, I think you got the right p/n (jack with the metal plate). just placed my mouser order to day for the jack + other misc parts I needed -- thanks!

 zk


----------



## holland

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_although I realize only the 12.6v variants can be used on my SOHA II as I didn't opt for a high current transformer. 
	

	
	
		
		

		
			



_

 

You can still use 6.3V. The 12.6V configuration parallels the tube heaters, so the current demand of 2 tubes is 2x the heater specs. The 6.3V uses a serial configuration, so the current demand stays the same. The 2 6.3V heaters in serial make 12.6v.

 It sounds like you need to rewire the SOHA II and get a higher current transformer.


----------



## zkool448

Yes I do need to get a higher current one! 
	

	
	
		
		

		
		
	


	




 What I meant to say was the 300mAh max limitation of my current transformer. I got the stock glassar kit for the convenience and less chance of messing up the BOM -- I do regret not opting for the hi-current transformer indeed. 

 zk


----------



## wiatrob

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_ I replaced it with 6 sip sockets, although a dpdt switch would've been the ideal replacement I didn't have one on hand and I was eager to get it setup.

 zk_

 

I have a few mini-dpdt's from my SOHA II proto days, PM me if you're interested, I'd be happy to send you one. Haven't checked but they may fit directly into the sips...


----------



## zkool448

wiatrob, thanks for the kind offer -- I placed my mouser order for the jack and switches just yesterday 
	

	
	
		
		

		
		
	


	




 zk


----------



## wolf18t

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_...no hiss, no hum, just clean clean sound. And may i say, with the 5963, quite a solid state sound. very very different to the bijou. but its way off being burnt in, the tubes have barely 10 mins on them._

 

Adamus, you might try 6DJ8/6922 tubes. At least my Amperex 6DJ8 sound more tubey and less sharp than my Sylvania 12AU7/Phillips 5963. I prefer the Amperex while using RS-1.


----------



## adamus

I tried it with some bugle boys (6dj8). it was a good step up. Its a different presentation to bijou (as expected, its a hybrid). Its definately a quicker amp the the bijou, and slightly dryer. The best tube i tried was.....





 Not saying one is better than the other.... just different. For my listening preferences, the bijou is to my liking, but if was listening to a lot of electronic, hiphop, pop, dance... then the soha II would get a lot of play.

 The soha is one hot amp.... i assume its normal for the ouput fet sinks to get hot, too hot to keep your fingers on for a while.


----------



## holland

8416 is a mutha of a tube in the SOHA 2, IMO. I'm currently digging the 6N6P and the 6CG7. Both too early to really comment on.

 6DJ8/6922 are more tube-y, for sure.


----------



## holland

Alex, is 50 ohms safe for the R6 value? I can only dial up 600mV across R6 on the default config (using zeners now for testing). I figure with 50 ohms, I should be able to dial up to 8mA-9mA tail current using the 200-ohm trimpot. I can use a larger trimpot to get back to the 2mA tail current, if need be.

 Thanks!


----------



## runeight

Yes, that should be fine. Keep your eye on the power dissipation in Q3. It should about 200mW for the currents you want to run. That is ok for this package but the bjt will get toasty.


----------



## wolf18t

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_... I figure with 50 ohms, I should be able to dial up to 8mA-9mA tail current using the 200-ohm trimpot..._

 

Keep us informed if this higher tail current tweak make any positive difference


----------



## adamus

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_8416 is a mutha of a tube in the SOHA 2, IMO. I'm currently digging the 6N6P and the 6CG7. Both too early to really comment on.

 6DJ8/6922 are more tube-y, for sure._

 

6n6p?? you must have a hell of a heatsink on the 12.6v regulator, those tubes consume 800ma of heater current. they do sound superb though.


----------



## holland

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_6n6p?? you must have a hell of a heatsink on the 12.6v regulator, those tubes consume 800ma of heater current. they do sound superb though._

 

Not big enough. It gets hot. 
	

	
	
		
		

		
		
	


	




 I'm using the largest heatsink that fits on the PCB. I need to case sink this bad boy, as I'm running open chassis right now, due to the heat. Using a 1.6A transformer and it's not at full load yet, so there's still headroom on that.


----------



## zkool448

Finally the weekend has arrived.. will now have some time for some serious casework 
	

	
	
		
		

		
		
	


	




 Quick question about grounding. With wood enclosures, is an aluminum/metal bottom plate necessary to mount the board/torroid for "proper" grounding? I wasn't planning on using a metal plate or SG/standoff and was thinking of just using a 22awg wire from G pad on the pcb to the IEC ground -- this is how I have everything setup an mdf plank board right now until I finish the case... so is this setup acceptable? thanks.

 zk


----------



## runeight

This setup is ok but it offers more opportunties for noise and hum since the amp won't be grounded to a nice big piece of metal.


----------



## ChrisX

I finished my SOHAII right now. Everything worked fine (besides I forgot to put the OP amps into the sockets before starting the setup) until the last step: Check TPL and TPR. One channel measures 13,8 V the other one 22,6 V, the measurements follows the tubes when swapping them. Since the tube with the lower voltage also glowed a bit darker I changed it, the replacement tube reaches about 16,0 V. So still both tubes are far away from "approx. 19 V" one too high, one too low. 
 How much tolerance is acceptable?

 At first glance audibly it's ok and there doesn't seem to be a big difference between the channels, not to say the amp sounds great! It makes even the stock Archos phones bearable (I still didn't dare to connect my AKGs).

 Chris

 PS: Tubes are 6N23P (== 6922/6DJ8)


----------



## runeight

Do you mean TPL and TPR measured with respect to ground? Or measured with respect to the B+?


----------



## ChrisX

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Do you mean TPL and TPR measured with respect to ground? Or measured with respect to the B+?_

 

With respect to TB+L/R.

 Chris


----------



## runeight

OK. At least everything is working properly.

 These voltages are abnormally far apart because the two tubes that you happen tohave are mismatched in totally different directions. They are acceptable voltages, but it would be better find two tubes that gave you closer to the 19V design point.


----------



## ChrisX

Alex, Thanks for your diagnosis. I checked the first plate of the tubes (Pin 1) and there are the expected 19 Volts. So it's really only that my tubes are mismatched. I have four of them so I will try the others and stick with the best ones.

 Seems I have "luck" with mismatched parts. The 7815 in this SOHA_II delivers 14,8 V, the 7915 -15,3 V.

 Chris


----------



## zkool448

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_This setup is ok but it offers more opportunties for noise and hum since the amp won't be grounded to a nice big piece of metal. 
	

	
	
		
		

		
			



_

 

Thanks Alex, i took apart an old cd drive casing for use as my bottom ground plate 
	

	
	
		
		

		
		
	


	




 Quite happy with the casework so far but I'm having trouble deciding which wood stain to use (cherry vs. red mahogany)...


----------



## zkool448

Added above some pics of dry fit.. that is all for now until later this week, I'm now off to an easter turkey dinner!


----------



## onform

That is some serious example of what can be achieved when you have the tool's and the know how...well done


----------



## zkool448

Thanks onform. The wood case and the top/bottom "lids" must've took about ~8-10 hours to build and finished sanding. Tube holes still need to be cut and still waiting for a few mouser parts (jacks, switch). 

 I dread the staining part, I'd be really disappointed to screw this up at this point.


----------



## smeggy

Well it already looks damn pretty zk, really looking forward to the end result... I predict awesomeness


----------



## jonoliew

was wondering how this amp faired against the woo audio 6se or wa2? I'm thinking of building one after seeing all your beautiful works of art! ahaha


----------



## Ferrari

Very nice zkool448, really creative with wood. 
	

	
	
		
		

		
		
	


	




 I’m also busy with the casework for my balanced SOHA II, but no wood from this side of the ocean.
 It’s a 2 boxes solution…. the amp is feeding by 2 oversized transformers, 80VA each.


----------



## adamus

I spy an e24. 

 looks really good ferrari, i shudder at the cost! Schaeffer isnt cheap these days. 

 have you got any idea of what tubes you are going to use in it?


----------



## ChrisX

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Added above some pics of dry fit.._

 

Really Beautiful. 
	

	
	
		
		

		
		
	


	




 But I would be a bit concerned about ventilation. I finished my SOHA_II this week and still without any enclosure the heatsink temperature reaches 60 °C (with a few mA below the recommended bias of 100 mA), R3P yet reaches a few degrees more. And now it's spring not summer. Therefore I already changed my enclosure plans and sure will follow Alex' recommendation of a more than 50% open top plate. If I knew before I sure would have bought higher heatsinks (1.5") and accepted a resulting higher enclosure.

 Chris


----------



## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Very nice zkool448, really creative with wood. 
	

	
	
		
		

		
		
	


	




 I’m also busy with the casework for my balanced SOHA II, but no wood from this side of the ocean._

 


 It's sloooowly taking shape! Nice to see..

 I should post some pics of my latest 'II - it's in the case phase but ZK's wood and your metal work makes me a bit embarrassed to show mine.

 Darn DIY'rs continually raising the bar...mumble mumble...


----------



## Ferrari

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_I spy an e24. 

 looks really good ferrari, i shudder at the cost! Schaeffer isnt cheap these days. 

 have you got any idea of what tubes you are going to use in it?_

 

Yes, the ε24 circuit is on board.

 Since the heater power supply circuit on my amp is modified a bit: based on LM338 (instead of LM337), feeding by an 80VA transformer separately, I’m thinking of trying some current hungry tubes like 6N1P, 6N6P and 6N30P...


----------



## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_It's sloooowly taking shape! Nice to see..

 I should post some pics of my latest 'II - it's in the case phase but ZK's wood and your metal work makes me a bit embarrassed to show mine.

 Darn DIY'rs continually raising the bar...mumble mumble... 
	

	
	
		
		

		
			



_

 

Yes, you are right. It takes quite long time with my build, make me thinking of the casework for my Bijou last year: it takes about 10 months or so after the amp was up and running, playing music for the first time. 
	

	
	
		
		

		
		
	


	




 BTW, don’t hesitate to show-off your work. It’s about the fun you have with DIY and enjoying the music.


----------



## smeggy

x2, doing is half the fun.


----------



## runeight

Ferrari, I know that you do this superb casing on everything that you do, but I do want to say how much I appreciate that you think enough of my amps to put them into these stunning enclosures.

 I still want to know if you'll design product enclosures for me.


----------



## smeggy

That would be awesome.


----------



## sachu

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ferrari, I know that you do this superb casing on everything that you do, but I do want to say how much I appreciate that you think enough of my amps to put them into these stunning enclosures.

 I still want to know if you'll design product enclosures for me. 
	

	
	
		
		

		
		
	


	


_

 


 I like where this is going. By the way Alex, what particular products did you have in mind


----------



## zkool448

Thanks guys...

 Ferrari, glad I don't do aluminum casing since I too would be reluctant to post pictures in here 
	

	
	
		
		

		
		
	


	




 Your casework always look amazing.

 With each case I do, the more satisfaction I have from my woodworking. It always amazes me that one can start with an ugly pile of rough lumber and turn it into 'something' with enough tools, time, and very little imagination.

 Applying finish to the wood, on the other hand never ceases to frustrate me. After testing on a couple of scrap wood several times, I still hold the brush and can't bring myself to apply it to the case in fear that I will srew it up. (smeggy, how about some tips 
	

	
	
		
		

		
		
	


	




)

 ChrisX, I thought about cooling, I have the same concern and thinking about increasing the size of the top slots/vents. Also, I still have to cut the tube holes which I'll probably oversize the diameter for added ventilation.


----------



## runeight

Quote:


  Originally Posted by *sachu* /img/forum/go_quote.gif 
_I like where this is going. By the way Alex, what particular products did you have in mind 
	

	
	
		
		

		
		
	


	





_

 

You can probably guess.


----------



## smeggy

Don't look at me, I get all my finishing tips from others 
	

	
	
		
		

		
		
	


	




 I went to Lowes and got some Deft(?) spray on sanding sealer and satin, semi-gloss and gloss lacquer. Works pretty nicely and a quick buff with a soft duster when it's dry seems to be very nice. 

 Dries very quickly, doesn't need sanding between coats (I just wire wool it) and builds up nicely.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You can probably guess. 
	

	
	
		
		

		
		
	


	


_

 

I hate you both!


----------



## zkool448

smeggy, thanks for the tip 
	

	
	
		
		

		
		
	


	




 I've used deft before when they were avaialble in Canada, but every stores took them off their shelves for environmental hazard reasons (nitrocellulose lacquer)


----------



## smeggy

hmm, I guess most spray lacquers should be about the same. Any local woodstore should stock some variety or other.


----------



## wolf18t

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You can probably guess. 
	

	
	
		
		

		
		
	


	


_

 

So I am guessing too...


----------



## Johnthurston

I wanted to let folks know that my SOHA II is up, running and sounds great. I purchased it in kit form (with 5963 tubes) from Jeff at GlassJar and have nothing but good things to say about his service and communication.

 The soldering time was about four hours (spread out over several days as I found the time to spare) and the case time was about double that. I'm using it to drive my eighteen year old (!) Sennheiser HD530 headphones. There was some audible hiss when I first powered it up but it was gone the second time, and hasn't returned.

 Question time:
 Periodically, the epsilon 12 circuit will cut off the output. I am unable to find anything firm to correlate this. It doesn't seem to be related to the music being played or the volume. While it doesn't seem to be heat related, I've haven't experienced the cutout in the first fifteen minutes after powering it up.
 Can anyone suggest where I might look for the cause or correction to this behavior?

 John Thurston
 Juneau, Alaska


----------



## wiatrob

Congrats and welcome! The only time I have experienced nuisance trips with my production board 'II was when my power was waaaay out of spec - the HV supply was designed to prevent most all of these trips. Do you have anything else on the power circuit with the amp that might be producing surges or nooise on the line?


----------



## wiatrob

Ferrari;5604442
 
 BTW said:
			
		

> http://www.head-fi.org/forums/images/smilies/smily_headphones1.gif[/img]


 
 Thanks for the encouragement. As soon as I get the front panels drilled right, I'll post some pics (Layed out backwards - DOH! 
	

	
	
		
		

		
		
	


	




 )


----------



## zkool448

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Thanks for the encouragement. As soon as I get the front panels drilled right, I'll post some pics (Layed out backwards - DOH! 
	

	
	
		
		

		
		
	


	




 )_

 

wiatrob, looking forward to seeing your build -- post it! 
	

	
	
		
		

		
		
	


	




 I really miss listening to my SOHA II since it's been apart during the casework process. I'm almost done with it though, I just need to rewire everything back. Hopefully by tomorrow the paint on the top panel will be dry.

 Here's a sneak peak at how the casing is going so far. I'll post here a link to the builders gallery hopefully by tomorrow


----------



## smeggy

damn zk, that looks lovely! The stain really worked out very nicely indeed. It's a beautiful finish all round and I'm really looking forward to seeing the top.


----------



## Beefy

*jawdrop* That is really beautiful!


----------



## Forte

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_Here's a sneak peak at how the casing is going so far. I'll post here a link to the builders gallery hopefully by tomorrow_

 

Wow, the stain turned out nicely. Have you used any varnish or similar over the top to get that shine?

 Also were did you get the tube socket extensions and case feet from?


----------



## Alcaudon

How much current can I draw from the power supply?

 I want to put in the same case the soha, a sigma 1 (the lite version, usb powered), and a twisted pear Darwin selector. According to tpa site, the Darwin needs a 5 V, 60 mA source, and I was planning to take it from one of the leds in the ps section.

 I guess that using the default 1A transformer is ok, but I think is a good idea to ask, since I still haven't bought a transformer and I can get a bigger one (1,67 A) if needed.

 Thanks!!!!: dt880smile:


----------



## Yaka

yet another fine case by zcool


----------



## runeight

You can do this but remember that the LEDs come from the heater supply and are negative with respect to ground.

 You can pull from the +15V supply but the reg will burn 50% more power when you do. You might want a bigger heatsink.


----------



## zkool448

Thank you guys. I finally got my SOHA II cased up after several hours of labor (splinters, cuts, and oh let's not forget agony and tears).

 @ Forte, the tube socket extensions (or socket savers, credit to adamus) were ordered through ebay, as for the case feet, well they're not really case feet but more like chair feet sliders 
	

	
	
		
		

		
		
	


	




 Please take a look at the builders gallery thread if you'd like to see more pictures of my build.

 Thanks!


----------



## smeggy

Very sweet zk, wonder how it would look with a potted toroid on the top behind the tubes


----------



## adamus

mate, that really does go into my hall of fame for DIY. thats a really special and unique build.

 the socket savers work well dont they - I cant hear any negative effects from the slightly elongated signal paths.


----------



## mattcalf

Awesome build, really great stuff!


----------



## rds

Wow, that is one of the best looking amps I've seen period! Just beautiful work.


----------



## shellylh

zkool448, that is one sweet looking case!


----------



## dBel84

x10 ..dB


----------



## wolf18t

Wow! What others said, one of, if not the most elegant DIY enclosure I've seen. This one belongs to the Hall of fame.


----------



## TimJo

Wow that turned out really nicely zk. 
	

	
	
		
		

		
		
	


	




 When I saw the lid in the early pics, I had been thinking of it in wood tones in my head, so when I saw you painted it silver it took me by surprise. It really ties the whole thing together with the volume knob and the Nuetrik jack. That's quite a photo with the other two amps sitting in the back. 

 So does the lid just sit on the wooden frame, using the four silver things (_don't know what to call them???_) as centering devices?


----------



## zkool448

thanks all, want to crosspost it here also. -zk

 ___

 Hi everyone, wow... truly overwhelmed by your responses. I read each of your post and really means a lot to me guys. Thank you. 

 Special thanks to Alex Cavalli for designing and producing such a great sounding amp. 

 cheers -zk 
	

	
	
		
		

		
			





 In response to the questions/comments, the mounting bracket for the headscrews aren't installed as I wanted to monitor the cooling first. I'm happy to report that the tapped L-brackets will be added permanently -- the amp has been burning in for 10+ hrs without any heat issues! The top/bottom lids which appear 'metal' is really mdf wood machined using a table router.

 Casework felt like it took forever, won't be selling them but more than happy to help if you're looking for sme wood design ideas (ex. #1, #2), cutting tips, shop tools, etc. 
	

	
	
		
		

		
		
	


	




 Smeggy, I know nothing about hooking up a potted torroid (or any electronics for that matter), that option would've been awesome if I knew how to. Your woodwork finishing tips is what inspired the finish 
	

	
	
		
		

		
		
	


	




 Adamus, the socket savers works well indeed. Really helps in the cooling department since the tubes are fully (or almost) exposed.

 Thanks again to all DIY'er out there for their help, inspiration, tips ,and amp designs. It's now time for a nice break to enjoy the amp!


----------



## Alcaudon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You can do this but remember that the LEDs come from the heater supply and are negative with respect to ground.

 You can pull from the +15V supply but the reg will burn 50% more power when you do. You might want a bigger heatsink._

 

Many thanks for the answer runeight!!!!


----------



## holland

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Keep us informed if this higher tail current tweak make any positive difference 
	

	
	
		
		

		
		
	


	


_

 

I put a 56 ohm resistor in parallel, just tacked it on top. I was too lazy to remove the old one. 
	

	
	
		
		

		
		
	


	




 Anyhow, I was running at the max of the 200 ohm resistor for a while, and can't say I noticed a difference. However, I think I notice some differences in tone now. I'm running 10mA through the tail (5mA per triode). Things seem to be a bit more "extended" up top. I'm using a 6CG7 at the moment.

 Then again, it could all be placebo. 
	

	
	
		
		

		
		
	


	




 You know how audio memory is.


----------



## wolf18t

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I put a 56 ohm resistor in parallel, just tacked it on top. I was too lazy to remove the old one. 
	

	
	
		
		

		
		
	


	




 Anyhow, I was running at the max of the 200 ohm resistor for a while, and can't say I noticed a difference. However, I think I notice some differences in tone now. I'm running 10mA through the tail (5mA per triode). Things seem to be a bit more "extended" up top. I'm using a 6CG7 at the moment.

 Then again, it could all be placebo. 
	

	
	
		
		

		
		
	


	




 You know how audio memory is._

 

Placebo effect or not, you heard an improvement and that's what really count. 
	

	
	
		
		

		
		
	


	




 Seriously, thanks for the follow up Holland.


----------



## zkool448

SOHA II update:

 I didn't realize my SOHA II had a mild hum/buzz noise. Been using a DAC, sometimes the iPod ever since the build and didn't hear any hum/noise/hiss at all until last week when I tried my desktop sound card as source. No problems after I installed a wirewound 10R 5watts parralel with .1uF film cap between SG and IEC ground. Got rid of the hum completely.., I'm again a very happy camper.

 while I was tweaking around, thought I'd do some tail current adjustments with a pair of zeners. Swapped R4's with 18V 0.5W zeners but once I powered up there was a very audible hiss (regardless of volume level), so I just went back to the resistors as only way to rid of it.

 Lastly, I swapped the stock BOM caps (C5L/C5R & C6P/C7P/C12P) to Nichicons/Panasonic FMs -- ever since then I noticed the ε12 relay no longer triggers (?) I can crank the volume up to levels I couldn't set to before (read: unbearably loud). Is there a way fo me to test this to check or make sure it still acting as a protection circuit?


----------



## adamus

i take it is still delaying the output?


----------



## zkool448

Yes on power on, I hear a delayed click after ~7-8 seconds.


----------



## Ferrari

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_SOHA II update:

 Lastly, I swapped the stock BOM caps (C5L/C5R & C6P/C7P/C12P) to Nichicons/Panasonic FMs -- ever since then I noticed the ε12 relay no longer triggers (?) I can crank the volume up to levels I couldn't set to before (read: unbearably loud). Is there a way fo me to test this to check or make sure it still acting as a protection circuit?_

 

The caps you have replaced (C5L/C5R & C6P/C7P/C12P) are all PS filter caps. As long as the voltage rating is adequate and they fit the board then it’s OK. These caps have no impact on the behavior of the ε12 circuit. 

 To verify the other function of ε12 circuit -as a DC offset protection circuit- you can use the trimpot P1P in the B+ section to vary the B+ voltage. In/decreasing the B+ voltage quickly will result in transient which will trigger the ε12 circuit to shut down the output.


----------



## holland

Ferrari, IIRC you're running the B+ @ 125V. What did you do to the CW multiplier to get that? Just add another rung to the ladder and swap the odd and even sides so you can end on a cap?

 I have the prototype board, still. My plan, and final mod for the SOHA II before putting it away, is to do another HV perfboard that removes the TL783, and add back the 3rd cap multiplier in the original design to run B+ @ ~140V. Cap upgrades to 160V every where on the B+ string.. I never had the problem that required the TL783, but since the HV is external, it's easy to tweak and regulate to 125V if necessary....which is what you are doing, I believe.

 Thanks!


----------



## wiatrob

Quote:


  Originally Posted by *zkool448* /img/forum/go_quote.gif 
_SOHA II update:



 while I was tweaking around, thought I'd do some tail current adjustments with a pair of zeners. Swapped R4's with 18V 0.5W zeners but once I powered up there was a very audible hiss (regardless of volume level), so I just went back to the resistors as only way to rid of it._

 

That's the Zener noise. dBel even rigged up some low noise zeners and we sent them round during the proto phase, but never could quite get rid of the noise. The level of noise does appear to differ depending on setup, on my first proto I could barely hear it with the volume all the way up.


----------



## holland

FWIW, I found the low noise zener to be noiser than the 18V zener. Go figure. Either way, the zener seems to cause hiss no matter what, as wiatrob indicated. Since I've dialed mine up to 10mA, I just need to drop in some 3.6K resistors and that'll be set.

 I have zener diodes in mine, at the moment. I'm using Denon D2000 headphones and the hiss is audible. It's not horribly loud, but it's there. I can't really hear it with music, but between tracks, definitely. I agree that it can be annoying.


----------



## Ferrari

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Ferrari, IIRC you're running the B+ @ 125V. What did you do to the CW multiplier to get that? Just add another rung to the ladder and swap the odd and even sides so you can end on a cap?

 I have the prototype board, still. My plan, and final mod for the SOHA II before putting it away, is to do another HV perfboard that removes the TL783, and add back the 3rd cap multiplier in the original design to run B+ @ ~140V. Cap upgrades to 160V every where on the B+ string.. I never had the problem that required the TL783, but since the HV is external, it's easy to tweak and regulate to 125V if necessary....which is what you are doing, I believe.

 Thanks!_

 

Actually I’m running the B+ voltage of my amp at 120V DC to stay within the limit of the TI TL783 regulator (125V).
 The higher voltage can be achieved by an additional stack (C-D) on the existing CW voltage multiplier, or by using a transformer with higher secondary voltage while let the CW voltage multiplier unchanged. (Transformer with 2x18V secondary resulted in ~138V unregulated B+ on my amp). 
	

	
	
		
		

		
		
	


	




 I have experimented both ways, but finally go for the higher secondary voltage transformer solution. 
 On the symmetrical low voltage section, MC7818/7918 regulators were used instead of 7815/7915.
 For the OpAmps PS rails, a diode was added on each rails to keep the voltage a bit lower (- 0.7V) than ±18VDC (a couple of traces cuts needed). 
 The higher voltage has of course impact on the heat dissipation on the output stage, so don’t forget to pay attention to heatsinking.


----------



## zkool448

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_To verify the other function of ε12 circuit -as a DC offset protection circuit- you can use the trimpot P1P in the B+ section to vary the B+ voltage. In/decreasing the B+ voltage quickly will result in transient which will trigger the ε12 circuit to shut down the output._

 

Wonderful Ferrari, e12 is still working indeed -- thanks 
	

	
	
		
		

		
		
	


	




 Holland, yes the hiss is definitely a show stopper for me.


----------



## Arkku

As for the zeners and noise, here's a bit more on my experiments with them:

 When I first built the amp, I tried both the resistors and Fairchild 1N5248B zeners. I couldn't detect any difference between them, so I left the zeners in. Recently I tried tampering with the tail current (with zeners installed), and I noticed that even a 50% increase caused very annoying and very audible hiss. Take it back down to the default and it's silent again. (I also noticed that I can't set the tail current very high; at twice the default e12 trips at very low volumes while normally I can pretty much turn the knob all the way to unbearably loud, no problem.)

 Now I'm running with the zeners at default settings again, and no noise. With headphones, that is; I also use this as a pre-amp, and in that use there's a slight hum audible in a quiet room with no signal. It's at a constant volume regardless of volume knob position or input, so it could be dealt with by simply padding the output enough to mute the noise and then set the volume a bit higher (but I haven't gotten around to it). The reason I mention this noise is to note that the zener vs resistor has no effect on it.

 So, it _is_ possible to use zeners in this amp with no noise. (Just don't know if you can hear any difference. =)


----------



## Ferrari

Finally having the time to test my über SOHA II. As expected, all circuits work correctly at first power up.


----------



## dBel84

that looks like a fine tuned Italian machine - suites your online ID 
	

	
	
		
		

		
			





 - superbly done as always ..dB


----------



## shellylh

Very sweet Ferrari!


----------



## Ferrari

Thanks for the kind words, Don and Shelly.


----------



## Arkku

Beautiful work, Ferrari. May I ask what kind of a circuit did you use for those analogue VU meters and where in the SOHA II's did you hook it up? I recently scavenged some vintage VU meters from an old tape deck someone was throwing away and I've been thinking of using them in a DIY project, perhaps even on my SOHA II, but I haven't figured out how it would be best to install them. Obviously I don't want them affecting the output quality.


----------



## onform

I'm not really feeling the VU meter vibe but the craftsmanship and design are exquisite as per usual. can you put out an absolute dog of a build just to make us believe you are actually human.....


----------



## Ferrari

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_Beautiful work, Ferrari. May I ask what kind of a circuit did you use for those analogue VU meters and where in the SOHA II's did you hook it up? I recently scavenged some vintage VU meters from an old tape deck someone was throwing away and I've been thinking of using them in a DIY project, perhaps even on my SOHA II, but I haven't figured out how it would be best to install them. Obviously I don't want them affecting the output quality._

 

To drive the analogue VU meters, I used the driver circuit as depicted below. The working of this driver circuit is very simple: the amplifier around T1 and T2 amplifies the line level signal to the desired level, the signal is then passing through the rectifier diodes D1 and D2. C4 smooth out the signal a bit before the signal is feeding to the VU meter. 

 Before use, an adjustment needs to be made. 
 Connect the circuit + VU meter to a function generator which output a 1KHz signal, ~300mV.
 Dial P1 to its minimum (R=0), then dial P2 until the VU meter is reaching its maximum. 
 Next, turn P1 up until the VU meter is at ~ 50% of its total range (12 o’clock).

 Depending on the level of the input signal (SACD player, DAC…), you might have to re-adjust P1 to get a proper reading of the VU meter.
 For stereo application, 2 driver circuits are needed.


----------



## regal

Any news on the custom faceplates? Or cn someone send me the Files ?


----------



## regal

I can't believe no one can even send me a face-rear plate file for the Stacker II so I can have these made at that faceplate co (can't remember their name.) I hate case work btw. Would much rather spend the bucks on machined faceplates.


----------



## mattcalf

Absolutely stunning Ferrari, I wish we could clone and commission you for every build


----------



## Sathimas

Hello Guys,

 I've got a kind of strange problem here.

 I've got hum - relatively quiet, both channels - not changing with the volume level.
 First thought my cable was damaged ... 

 It disappaers when i connect one input (no matter left/right) and
 "brigde" signal and ground on the other cinch connector.
 Kind of fading out, turning to hiss and then disappearing.
 I also made it disappear by simply changing to position of the cable.
 Means twisting it or something like this.

 Cable is a 3,5mm jack to 2 cinch adapter.

 The hum also stays when no cable is connected.

 Just ask if my explanation is not clear, I'm no native Englishspeaker and this is really kind of hard for me to explain.


----------



## holland

use shielded cable and run it as far as you can from the tubes. tuck it up to the edge of the chassis as you run it back to front. For the shield, ground at one end only. I ground at the entry, that is the RCA jacks. The end that goes to the board, I leave floating.


----------



## Sathimas

I am using a shielded cable - the adapter cable is studio quality.
 But I think you're talking about the connection inside the case?
 Inside I don't use shielded cables but never had any problems with that.
 (Not with my SOHA I and my M³ ... all my builds are in wooden cases.)

 The strange thing is that the hum disappaers under the discribed circumstances.


----------



## Arkku

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_To drive the analogue VU meters, I used the driver circuit as depicted below._

 

Thank you for the details, I finally had the time to experiment a bit with the VU meters I scavenged from the dumpster, and this circuit seems very suitable for them. =)


----------



## Ferrari

Good to know!


----------



## holland

Ferrari, that's one nice looking SOHA II!!!!

 I modded my SOHA II prototype to run a B+ of ~241V and 219V on the plate using 5mA per triode (10mA tail current per tube).

 I can't say, right now, if there's much difference. Things do seem "thicker" with more depth. I'm sure psycho-acoustics are in full effect, but it seems nice. The voltage and plate current were influenced from the Bijou.

 If anyone is interested, I used the TL783 but floated it. I wired a 50VA transformer in reverse to output 230V. I don't have one that'll fit my case, so I'm trying to find something. I'm just using jumper leads now. I initially had a 6VA transformer in, but it didn't supply the voltage I wanted, too much current, I think. I have a 12VA and 20VA on order.


----------



## wiatrob

Well, it's not a _Ferrari_ - but I'm tuning up some casing for the Colorado Meet...


----------



## holland

where are the sides? are you going wood?


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_where are the sides? are you going wood?_

 


 In the paintshop... pretty plain metal case with top vent holes. This build is the high current version, production PCB (B+@~96V), all nichicon caps, Obligato couplers, R4L/R bypassed with 1u MKP caps. A few muse caps from the parts box here and there.

 It is really quite amazing sounding, especially driving my modded YH-3. We have taken a few detours lately with the CTH and EHHA (worthy ones to be sure) but this amp holds it's own with RCA 5963 Black Plates and 6H23's. I am going to set it up with matched Tungsram 12AU7s for some weekend listening with the Orthos - probably the setup I'll bring to the Colorado meet.

 It is DEAD BLACK silent with no input at full volume with either tube voltage - careful wiring and shielding pays off for these builds...


----------



## holland

Sounds great, wiatrob. I'm still modding my original. 
	

	
	
		
		

		
			





 I've got a Tungsram 12AU7 in my modded SOHA 2. It's pleasing, but odd at the same time. The highs are too smooth. It's a pleasing tonality though, but it just seems too artificial to me. I'll have to run it in longer and see if it changes.

 I think you should join me in HV land. 
	

	
	
		
		

		
		
	


	




 Can you remind me what is in the high current version? I can't remember except for higher heater capacity, which I have done as well. Did you change the buffer bias for more current too? I haven't done that, it gets hot enough for me as it is and I think 100mA is enough for my needs.

 I'm glad yours is dead silent. I don't think mine is at full volume, but it's quiet enough for me. I find the tubes have the largest impact. It's hit or miss with respect to noise. It kind of sucks when you go through a box and find more than a few that hiss or buzz or a microphonic.


----------



## wiatrob

The only mods are for the heater current. I have been using "Premium" (I paid someone to go through the box and select low noise, matching tubes in my SohaII's -I have the 5963s, 12BH7s and the Tungsrams) saving me the disappointment at somewhat-much greater expense!

 I flirted with the idea of higher voltage B+, as well as doubling the heater circuitry capacity to support 6H30 tubes, but I like the way this is sounding now so I will stick with Alex' sig mantra: *Don't mess with anything that is working.*


----------



## Ferrari

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I modded my SOHA II prototype to run a B+ of ~241V and 219V on the plate._

 

And no firework and smoke at the current mirror section???


----------



## zkool448

x2 
	

	
	
		
		

		
		
	


	




 Mine is probably the last stock build left in here (300mA max). I've stayed with 5963s for a while with great results, also a pair of tungsram ECC82s (hungary) which are actually pretty good.


----------



## holland

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_And no firework and smoke at the current mirror section??? 
	

	
	
		
		

		
		
	


	


_

 

None. 

 B+ is 241V, but after the cap multiplier it drops down a bit, I forget how much but I'm running @ 10mA per tube so it's quite a bit more than the standard 2mA configuration. The drop across the mirror is effectively the same as it was before the B+ was raised to ~241V. If they were to blow up, they should have blown up @ 90V too. They are floating relative to the plate. That's about the depth of my knowledge. There may be points during power up transients where the max ratings are exceeded, but that should happen @ 90V as well. Because of that, I assumed they floated well, and since you ran @ 120V, I figured it was all good.


----------



## holland

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I will stick with Alex' sig mantra: *Don't mess with anything that is working.*



_

 

LOL, that's just anti-DIY. I ignore it quite well.


----------



## cfcubed

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_LOL, that's just anti-DIY. I ignore it quite well. 
	

	
	
		
		

		
		
	


	


_

 

As long as you can FIY (Fix It Yourself) that's fine
	

	
	
		
		

		
		
	


	




. And we know _you_ can.


----------



## Ferrari

Quote:


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

 B+ is 241V, but after the cap multiplier it drops down a bit, I forget how much but I'm running @ 10mA per tube so it's quite a bit more than the standard 2mA configuration. The drop across the mirror is effectively the same as it was before the B+ was raised to ~241V. If they were to blow up, they should have blown up @ 90V too. They are floating relative to the plate. That's about the depth of my knowledge. There may be points during power up transients where the max ratings are exceeded, but that should happen @ 90V as well. Because of that, I assumed they floated well, and since you ran @ 120V, I figured it was all good._

 

I indeed ran my proto amp at 120V B+, but I modified the current mirror as well, using high voltage transistor in stead of BC560C.
 Good to know it works for you, without firework.

 On a side note, I’m listening to my balanced SOHA II via AKG K1000 while typing this, it sounds damn good.
 I can confirm that a well-constructed balanced SOHA II can drive AKG K1000 at a very loud level (the wife starts complain) without any sign of distortion or other shortage.


----------



## holland

I see. Thanks. I'll keep an eye on it. The mirror is only dropping ~19-20V which is within it's tolerances. The max is 45V collector-emitter. As long as the plate doesn't go to ground, I think it'll be OK.


----------



## jjazzyj

I just finished populating the SOHA II board. I hooked up the transformer according to the Inlet wiring, as soon as I turn the switch on the transformer buzzes for a few seconds and the fuse blows. The first time I noticed I reversed the Hot and Neutral according to the inlet wiring diagram. I fixed this and the next two times the fuse has blown. Now the last two fuses weren't slow-blo fuses, but they still shouldn't have blown in my opinion. Any ideas as to what is going on? Do I have a shorted transformer? I need to add, that I've checked and double checked for solder bridges, and I don't have any. I've also checked for short circuit between PS test points and I get a resistance value for each one.


----------



## zkool448

jjazzy, sounds like there's a short of some kind. Have you taken any voltage readings from the tx filaments?


----------



## jjazzyj

I don't have the amplifier section even hooked up yet. J1, J2, J3 remain unstrapped.


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## jjazzyj

I don't even get a chance to test voltage. I flip the power switch to perform the initial check and the fuse is immediately blown.


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## zkool448

Ah I see, are you using the BOM transformer? 115 or 220V?


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## jjazzyj

115V I have the Blue and Purple connected together and Brown and Grey. The Blue and Purple (according to transformer docs, 115V) are connected to the Neutral as per Inlet wiring diagram. Brown and Grey are connected to the BOM switch connector #2. On the secondary I have red and orange connected together. On the board power connector I have red&orange in the 15V Black in the 0V and Yellow in the other 15V. It is the BOM transformer.


----------



## zkool448

You have the primaries wired correctly, but not so sure about your 15-0-15V. It should be: 15V(yellow)-0V(red/orange)-15V(black)

 See if you have it wired like mine here. Other than that you may have a faulty transformer or a component/diode installed backwards pehaps(?).


----------



## jjazzyj

I have the secondaries hooked up wrong. I interpreted the Inlet Wiring Diagram incorrectly. I had red/orange in the 15V area, so I had reversed the phase of the secondaries. That explains the fuse blowing.


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## zkool448

Hope you're initial setup is a success, let us know how it goes and good luck


----------



## jjazzyj

Success! I wired the transformer as per your picture and surprise, surprise everything works. My initial setup readings are right on the money.


----------



## ROBSCIX

I think I am going to join the SOHAII crowd. I am interested in building one now. I have been trying to contact the sources for the Boards and kits but I haven't go a answer yet. Is there other location for Kits and PCB's?


----------



## ROBSCIX

Can I ask you experienced builders what the price is for the kits from Glasss jar Audio?
 Have many of you built the SOHAAII from a Kits or did you source all the parts yourself?
 Well looks like I have 62 pages of reading to go through.


----------



## wiatrob

I was part of the SOHAII proto team and have built a couple amps...

 It's my understanding that Jeff will send you a spreadsheet with options to pick that will determine the final pricing of your kit. Jeff's pretty busy (and the only source currently for SOHA II kits AFAIK) but he will get back to you... In the meantime, it's a great opportunity to read through the thread


----------



## ROBSCIX

I see, I can order what I need and the price will vary depending on what I need from him.

 Yes, I figured he was just a busy guy and would get back to me as soon as he can.

 I am off to read the threads..

 Thx for your help.


----------



## tacitapproval

My kit from Glassjar was @$200.


----------



## ROBSCIX

..and what all did that include?


----------



## tacitapproval

Everything needed for the build (parts, case, torroid, pair of 5963s) except solder and wire.


----------



## JamesL

That's a really great price, and the $25 hammond case keeps the total cost really cheap.

 After splurging $100 for the case/feet.. I ended up spending another $100 on machining, long-thread rca jacks, attenuator&knob, misc standoffs/bolts/screws, ε27 board + headers, neutrik jack pcb, etc for a total of around $350


----------



## ROBSCIX

Quote:


  Originally Posted by *tacitapproval* /img/forum/go_quote.gif 
_Everything needed for the build (parts, case, torroid, pair of 5963s) except solder and wire._

 

Great. I am not really into the case though I would rather build a custom one.
 I appreicate your informaiton.


----------



## jjazzyj

Anyone here try 6N2P tubes in the SOHA II? When I put mine in, I can only barely turn up the volume and then the amp cuts out? Any ideas?


----------



## jjazzyj

Actually it is the E12 relay cutting in and out, it appears that when I try to turn up the volume DC Offset must be getting too high, need to match the tubes maybe?


----------



## jjazzyj

More readings...it seems that the DC offset jumps past 100mA as soon as I try to adjust the volume, it settles back down again after a few seconds. Since I'm new to all this I'm interesting in hearing some ideas on how to solve this.


----------



## tacitapproval

Quote:


  Originally Posted by *ROBSCIX* /img/forum/go_quote.gif 
_Great. I am not really into the case though I would rather build a custom one.
 I appreicate your informaiton._

 

He sends a pricelist of options. You can omit anything you don't want.


----------



## tacitapproval

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_Anyone here try 6N2P tubes in the SOHA II? When I put mine in, I can only barely turn up the volume and then the amp cuts out? Any ideas?_

 



 6n2p are similar to 12ax7. I believe these are too much gain for this configuration. Do you have any tubes known to work with this circuit?


----------



## runeight

jjazzyj, tacitapproval is correct. If those particular tubes are similar to 12ax7 they will not work for you. If you can get something closer to the 12au7 the e12 should settle down.


----------



## royalflush

Been reading this thread as well. Tubes known to be compatible apart from 12AU7s are:

 12AT7
 E88CC
 5963
 6DJ8
 6922
 8416


----------



## jjazzyj

I'd been doing some research about the 6n2p and yeah, there's too much gain. They don't sound that great in the SOHA II when they're working anyway. I like the little bit of extra bass they have compared to the GE 5963, but the rest of the soundstage is muffled and dead. I don't mind the 5963 that came with my kit. Just wanted to try the 6n2p out.


----------



## runeight

I think 8416 will give you more bass. At least mine do.


----------



## ROBSCIX

I have been in Contact with Jeff, guess he is a busy guy. Anyway, I appreciate those who gave me help and informaiton. Will post ics when I get started building.


----------



## wolf18t

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I'd been doing some research about the 6n2p and yeah, there's too much gain. They don't sound that great in the SOHA II when they're working anyway. I like the little bit of extra bass they have compared to the GE 5963, but the rest of the soundstage is muffled and dead. I don't mind the 5963 that came with my kit. Just wanted to try the 6n2p out._

 

You could also try Amperex Holland orange globe 6DJ8. More bass than my 5963 and Sylvania 12AU7.


----------



## holland

I find the 6DJ8, 6922, 8416 thicker sounding.


----------



## ROBSCIX

Can I ask, what tubes are compatible with the SohaII design, since everybody is talking baout rolling tubes?


----------



## Ferrari

Have you read the ~10 posts before your post?


----------



## wiatrob

See also:

http://www.head-fi.org/forums/f6/soh...thread-390553/


----------



## royalflush

datasheet for 6dj8 indicates 365mAh max current. is the SOHA II capable of more than 300mAh tubes? I read omewhere there's a tweak you must do before it can.


----------



## Mr.Duck

Quick question about the DC servo. I havn't been following the SOHA II at all, so bear with me... but is the DC servo really needed? How about using a trimpot instead to offset the DC? Wouldn't that be a better way of doing it?


----------



## holland

^ thermal drift.

 Servo is better than trimpots.


----------



## Ferrari

Quote:


  Originally Posted by *royalflush* /img/forum/go_quote.gif 
_datasheet for 6dj8 indicates 365mAh max current. is the SOHA II capable of more than 300mAh tubes? I read omewhere there's a tweak you must do before it can._

 

Use a 50VA transformer in stead of 30VA and change resistor R3P to 0Ω (use resistor lead snip for this).

 Furthermore, to handle the higher current (up to 1.5A), the LM337 voltage regulator should be mounted on larger off-board heatsink. 
 The on-board stock heatsink is not sufficient for this task.


----------



## ROBSCIX

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_See also:

http://www.head-fi.org/forums/f6/soh...thread-390553/_

 

Thx for the link. I never seen this thread. 

 Got some more reading and research to do thx.


----------



## royalflush

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Use a 50VA transformer in stead of 30VA and change resistor R3P to 0Ω (use resistor lead snip for this).

 Furthermore, to handle the higher current (up to 1.5A), the LM337 voltage regulator should be mounted on larger off-board heatsink. 
 The on-board stock heatsink is not sufficient for this task._

 

Thank you Ferrari. 

 I'm assuming the negative regulator (H-) on the board is what you speak of. Where would be a good source for the 50VA tx? thanks in advance.


----------



## jjazzyj

I think Ferrari hooked up a switch to the R3P so he could switch to the lower/higher heater current on demand. Thanks for all the info on the tubes everyone. Now I just have to get some more tubes to try. It seems that FleaBay isn't the most cost effective place to buy NOS tubes. Anyone use vacuumtube.net?


----------



## holland

6DJ8 should work without any modifications (i.e. stock build). It's only 365mA. 6.3V heaters are in series, so the current is constant at 365mA. 6.3V+6.3V makes 12.6V which is what the heater regulator is regulating to. 12.6V tubes are in parallel, in that case the current is additive.

 Many of us used 6DJ8s when we had stock configurations.


----------



## Ferrari

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I think Ferrari hooked up a switch to the R3P so he could switch to the lower/higher heater current on demand. Thanks for all the info on the tubes everyone. Now I just have to get some more tubes to try. It seems that FleaBay isn't the most cost effective place to buy NOS tubes. Anyone use vacuumtube.net?_

 

NO, there is no switch on my amp. My balance SOHAII is set up for high current with a separate 80VA transformer in cooperation with 2 LM338 regulators (one for each stereo amp) for the heater circuits only. Another 80VA transformer serves the remaining low (±15V) and B+ voltage sections of the amp. By doing this way, the transformers can be run far under the limit of their max capacity. 
 Usually I prefer not to run transformers close to their rated maximum current ability (and there are reasons for that!!!). 

 The intention of the high current heater modification on my amp is to create more flexibility for any SOHA II equivalent tubes that require more than 300mA @ 6.3V each. Even current hungry tubes like 6N1P-EB/600mA, 6N6P-IR/900mA or 6N30P-DR/900mA (I have done that) can be rolling in without worrying about smoking amp. 


  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_6DJ8 should work without any modifications (i.e. stock build). It's only 365mA. 6.3V heaters are in series, so the current is constant at 365mA. 6.3V+6.3V makes 12.6V which is what the heater regulator is regulating to. 12.6V tubes are in parallel, in that case the current is additive.

 Many of us used 6DJ8s when we had stock configurations._

 

I don’t want to speak for runeight, but that is a bit beyond the design target of the maximum current draw from the heater supply.
 The circuit is heavily tressed using the stock configuration that way. 
 It can work however, and of course you are free to do that on your own risk!


----------



## wolf18t

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I don’t want to speak for runeight, but that is a bit beyond the design target of the maximum current draw from the heater supply.
 The circuit is heavily tressed using the stock configuration that way. 
 It can work however, and of course you are free to do that on your own risk!_

 

Already asked and answered in the past. IIRC The transfo upgrade, LM337 heatsink and R3P mod was for russian tubes support. 

 See post #369/360.
http://www.head-fi.org/forums/5236977-post359.html
http://www.head-fi.org/forums/5236987-post360.html

 I didn't mod my SOHA II this way and I'm an happy 6DJ8 user. They are the best sounding tubes I have in my inventory with my Grado, no contest.


----------



## royalflush

what if I just short r3p and use a large enough heatsink for H- would that be sufficient enough to run 6dj8s tubes with the soha ii?


----------



## holland

Yes. That's what I use in my modified PS (for high heater currents). I'm currently running 12AU7s.

 The resistor is to drop some voltage before the regulator. Either way, it burns displaces some heat from the reg to the resistor. A larger heatsink will handle that just fine.


----------



## jjazzyj

I'm 90% finished my SOHA II. I have crappy chassis making skills, though I was inspired by Zkool's amp when I built my chassis. Made lots of mistakes, managed to hide most of them. Trying to figure out what to do about the top. I have some hexagon perforated aluminum that I want to use, not sure how to make it look nice though. Here's some slightly fuzzy pictures.


----------



## yzriver

If I use 12AX7 in SOHA II, what modification I can do to the circuit? Can I change the gain by changing the NFB network?
 I have a few 12AX7s, and don't waste them.
 thanks.


----------



## runeight

yzriver, the front end design in this amp cannot accomodate 12ax7s with any modification. The operating point of this tube (and similar ones) requires much higher plate voltages to work properly.

 Sorry about that.

 OTOH, 12au7s, 6922s, and similar tubes are plentiful and relatively cheap unless you want to find rare NOS ones. 
	

	
	
		
		

		
			





 jjazzyj, that looks pretty good so far. And now there are lots of opportunities for your top.


----------



## cfcubed

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_ Trying to figure out what to do about the top. I have some hexagon perforated aluminum that I want to use, not sure how to make it look nice though._

 

Heh, I wonder if its that stuff you can get @ Home Depot... I've a sheet of brass looking stuff w/diamond cut holes in the garage..

 You could give wiatrob a PM about where he gets his perf top material that looks like this.


----------



## jjazzyj

Our Home Depot here has nothing. Can't even find 1" I.D. rubber grommets. I actually can't find them anywhere. There's a metals supply place here that will mill a sheet of hexagon perforated aluminum. That's where I think I'm going to go. 12$ ft2 plus 3$ a cut. Pricey, but I can them to cut the piece I need along with the holes for the tubes for ~$20. I decided to use these 3/16 low voltage staples with #4 1/2 inch black steel screws to create a little ledge for the aluminum top to sit on. Still don't know how I'm going to secure it though.


----------



## Sathimas

I already postet this a while ago:

 I got some strage hum on my SOHA II.
 It's not dependent from the volume - also hums when potentiomer is set to zero.

 Sometimes, it gets louder when I put my hands near the board and gets quieter when I move them away.
 If I just leave the amp running, it gets louder over maybe a minute, a hiss component joins the hum, hum disappears, hiss too.
 The then amp is dead quiet - no hum, nothing.
 Input wiring is now shielded - this did not touch the problem.


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## wiatrob

jjjazzyj-

 My perf material is all surplus, however, Online Metal Store | Small Quantity Metal Orders | Metal Cutting, Sales & Shipping | Buy Steel, Aluminum, Copper, Brass, Stainless | Metal Product Guides at OnlineMetals.com has been used by many here - eBay usually has a bunch as well.

 PM me if you want a set of grommets.


----------



## wiatrob

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I already postet this a while ago:

 I got some strage hum on my SOHA II._

 

Those are strange symptoms. Can you post some pictures of the inside of your amp? How is your transformer mounted and wired? Does this happen with different sets of tubes?

 Sounds like it might be a magnetics issue. Pics would definitely help...


----------



## Sathimas

I'll post pictures later this day.


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## jjazzyj

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_jjjazzyj-

 My perf material is all surplus, however, Online Metal Store | Small Quantity Metal Orders | Metal Cutting, Sales & Shipping | Buy Steel, Aluminum, Copper, Brass, Stainless | Metal Product Guides at OnlineMetals.com has been used by many here - eBay usually has a bunch as well.

 PM me if you want a set of grommets._

 

I bought some hex perf steel locally, spray painted it silver and figured out a quick and dirty way of attaching it. Not 100% happy with the results. But it does look ok from a far. No grommets yet 
	

	
	
		
		

		
		
	


	




 I'll PM you tomorrow.

 Pics:


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## wiatrob

I like the hex, the grommets will clean up the look - although you may need to vinyl due them like CFCubed did on his CTH - Chris, do you have a link to that process?


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## runeight

Quote:


  Originally Posted by *Sathimas* /img/forum/go_quote.gif 
_I already postet this a while ago:

 I got some strage hum on my SOHA II.
 It's not dependent from the volume - also hums when potentiomer is set to zero.

 Sometimes, it gets louder when I put my hands near the board and gets quieter when I move them away.
 If I just leave the amp running, it gets louder over maybe a minute, a hiss component joins the hum, hum disappears, hiss too.
 The then amp is dead quiet - no hum, nothing.
 Input wiring is now shielded - this did not touch the problem._

 

Sathimas, does this problem repeat itself or does it happen just once after power up?

 The photos help. Is it correct that you have a metal bottom and that the board star ground is bolted through a standoff to this metal plate? If so, is the plate grounded to the inlet ground?


----------



## Sathimas

Here is a picture of the inside.
 The case is entirely made of wood, so no grounding of the enclosure.





 The problem only appears on startup.
 Takes maybe 2 or 3 minutes to go away and does not return.

 Reminds me of my SOHA I, it has a similar hum at the beginning,
 but this disappears after only a couple of seconds.


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## runeight

The first thing that I would try is to ground the star ground point on the board to the ground on the IEC inlet.

 I guess you've measured all the voltages/currents and they check out?


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## Sathimas

Well ... could you tell me what the star ground point is? 

 The initial checked showed no problems.
 This problem doesn't seem appear everytime, but everytime the last time I switched the amp on.


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## runeight

There is a diagram at Cavalli Audio.

 Go to the Wiring and Ground section and then to Board Wiring.

 In the box at the top follow the link labelled Ground Wiring with no Standoff. Even though you have a standoff, it is not grounded so you'll need to use this grounding scheme.

 At some point it might be good to layer the bottom of the box with a thin sheet of copper and to use this as the ground. But let's cross that bridge later if we have to.


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## Sathimas

Thanks for the advice.
 I'll do that later this day or tomorrow, I don't have my soldering iron here.


----------



## cfcubed

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I like the hex, the grommets will clean up the look - although you may need to vinyl due them like CFCubed did on his CTH - Chris, do you have a link to that process?_

 

My vinyl dye link is in the Post Pics thread, could search my posts there for it but think its overkill for 2 little tube grommets... Vinyl dye is not cheap & not so available. I think the usu spray he used on the grid would work well enough for them, or could leave 'em black (ala the 1/2" jack).


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## yzriver

Is it possible to use SOHA II as a power amplifier to a pair of speakers, for example, those sensitive fostex full spectrum speakers. It looks the SOHA II has a few watt output capabilities.


----------



## runeight

Unfortunately, the SOHA II doesn't have enough juice to make much power since its maximum current output is less than 100mA.

 However, if you want a headphone amp that can also drive speakers, try the EHHA.

http://www.head-fi.org/forums/f6/cav...ne-amp-422429/

Cavalli Audio


----------



## yzriver

thanks runeight.
 Does a 2x18V transformer work for SOHA II?


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## jjazzyj

I'd leave them black. Too much silver IMO. 

 After a few days of listening to this amp, I've noticed a few things: But first a detail of the setup (which is definitely not 'audiophile' grade), PS3 source, HDMI to Panasonic Plasma, Acoustic Research RCA cable (10$ surplus special) and the piece de resistance: Signal Flex SF-140 32ohm?? closed headphones.

 These headphones require an amp. I've tried them in un'amped sources and there's no bottom/high end. Complete bandpass filter sound. My CMOY drove them ok, nice mid/high end, not much low end again. The SOHA II through these headphones makes all my old and new music sound like I was listening to it for the first time again. Perfect tight bass, super wide soundstage, the highs sound liquid smooth. I had no idea these no name headphones sounded so good. A former, former roomate of 2 houses ago forgot these when he moved out and never came back for them. I can't find any info on these phones. But I'm pretty happy with them for the moment. I have to say that the DAC in the Panasonic Plasma is better than the DAC in my Sony MP3 Walkman. It sounds grating to me through the SOHA II, as do MP3's lower then 256kbit. Even still the compression artifacts are distracting, 128kbit makes me grind my teeth. Thanks Alex for a great amp!

  Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_My vinyl dye link is in the Post Pics thread, could search my posts there for it but think its overkill for 2 little tube grommets... Vinyl dye is not cheap & not so available. I think the usu spray he used on the grid would work well enough for them, or could leave 'em black (ala the 1/2" jack)._


----------



## zkool448

Congrats on your amp build jjazzyj 
	

	
	
		
		

		
			





 Enjoy!


----------



## wolf18t

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I'd leave them black. Too much silver IMO. 

 After a few days of listening to this amp, I've noticed a few things: But first a detail of the setup (which is definitely not 'audiophile' grade), PS3 source, HDMI to Panasonic Plasma, Acoustic Research RCA cable (10$ surplus special) and the piece de resistance: Signal Flex SF-140 32ohm?? closed headphones.

 These headphones require an amp. I've tried them in un'amped sources and there's no bottom/high end. Complete bandpass filter sound. My CMOY drove them ok, nice mid/high end, not much low end again. The SOHA II through these headphones makes all my old and new music sound like I was listening to it for the first time again. Perfect tight bass, super wide soundstage, the highs sound liquid smooth. I had no idea these no name headphones sounded so good. A former, former roomate of 2 houses ago forgot these when he moved out and never came back for them. I can't find any info on these phones. But I'm pretty happy with them for the moment. I have to say that the DAC in the Panasonic Plasma is better than the DAC in my Sony MP3 Walkman. It sounds grating to me through the SOHA II, as do MP3's lower then 256kbit. Even still the compression artifacts are distracting, 128kbit makes me grind my teeth. Thanks Alex for a great amp!_

 

jjazzyj, what tubes are you using? The stock RCA 5963?


----------



## runeight

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I'd leave them black. Too much silver IMO. 

 After a few days of listening to this amp, I've noticed a few things: But first a detail of the setup (which is definitely not 'audiophile' grade), PS3 source, HDMI to Panasonic Plasma, Acoustic Research RCA cable (10$ surplus special) and the piece de resistance: Signal Flex SF-140 32ohm?? closed headphones.

 These headphones require an amp. I've tried them in un'amped sources and there's no bottom/high end. Complete bandpass filter sound. My CMOY drove them ok, nice mid/high end, not much low end again. The SOHA II through these headphones makes all my old and new music sound like I was listening to it for the first time again. Perfect tight bass, super wide soundstage, the highs sound liquid smooth. I had no idea these no name headphones sounded so good. A former, former roomate of 2 houses ago forgot these when he moved out and never came back for them. I can't find any info on these phones. But I'm pretty happy with them for the moment. I have to say that the DAC in the Panasonic Plasma is better than the DAC in my Sony MP3 Walkman. It sounds grating to me through the SOHA II, as do MP3's lower then 256kbit. Even still the compression artifacts are distracting, 128kbit makes me grind my teeth. Thanks Alex for a great amp!_

 

Happy to hear the good news!! Now you must listen to your entire music collection again.


----------



## jjazzyj

The tubes I'm using are the GE 5963 grey plates that came with the Glass Jar kit. I've listened to this amp with a few different 'generic' headphones and they seem to colour the sound far more than the tubes do. Those Signal Flex headphones sound like how people describe the AKG K601. The bass is there but is isn't 'enhanced' by any stretch. As an example, when I'm listening to trance, some tracks have lots of bass, and others seem like there is no bass. It all depends on the track it seems. When I plug in my POS Sony 'DJ' headphones everything is a horrible blurry mess filled with boomy bass. They really are the worst headphones I've ever used. That includes the airline ones...

  Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_jjazzyj, what tubes are you using? The stock RCA 5963?_


----------



## jjazzyj

Haha, my CD binder which was collecting dust is now by my SOHA II!! I'm doing the ADD music surfing dance, listening to a few minutes of every song to hear the nuances and detail that I didn't hear before.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Happy to hear the good news!! Now you must listen to your entire music collection again. 
	

	
	
		
		

		
		
	


	


_


----------



## wolf18t

Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_The tubes I'm using are the GE 5963 grey plates that came with the Glass Jar kit._

 

I think I'll order and give RCA or GE 5963 a try. The ones (Phillips ECG 5963) that came in my kit sounded quite lifeless. Or maybe they just aren't made for RS-1.


----------



## jjazzyj

I found some NOS Sylvania/Philips ECG 5963 and some Sylvania 5814A locally for 3$ each and I'm giving them a listen right now. I realize this is probably more for the SOHA II tube thread, but it seems sort of dead. I'll let you know what I think.

  Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_I think I'll order and give RCA or GE 5963 a try. The ones (Phillips ECG 5963) that came in my kit sounded quite lifeless. Or maybe they just aren't made for RS-1._


----------



## jjazzyj

Sylvania 5814A:

 Much deeper bottom end at the sacrifice of tightness, more relaxed perhaps. More relaxed sound in general. Soundstage is interesting, music sounds more '3d'. Wish it had more high end detail.

 GE 5963

 Very airy and pronounced mid and highs, borderline annoying but still enjoyable, Wall of sound. Bass is subdued but tight. Not as '3d' as 5814A. 

 Need to combine aspects of both tubes.

 Sylvania/Philips ECG 5963

 One of the tubes seems microphonic. It's ok. Nothing special. Slightly more high end detail than 5814A though it might be my imagination. 

 Someone with better ears and better equipment than my Signal Flex SF-140 might have better commentary.

  Quote:


  Originally Posted by *jjazzyj* /img/forum/go_quote.gif 
_I found some NOS Sylvania/Philips ECG 5963 and some Sylvania 5814A locally for 3$ each and I'm giving them a listen right now. I realize this is probably more for the SOHA II tube thread, but it seems sort of dead. I'll let you know what I think._


----------



## rolotube

Here's another first time poster on this thread. Just finished my SOHA II, hot on the heels of an extended tweaking & development period with the Bijou.

 The SOHA is very different from the Bijou, although IMO no less satisfying. Although significantly more complicated, it went together easily & following the excellent setup instructions, fired up without problems first time. All voltages & currents are as specified. 

 Using the GJ kit included JAN Sylvania 5963's, the sound is very tight & clean, with a good soundstage & 3D depth & air, but not to the same extent as the Bijou. I tried some Mullard CV4003's ("Box Plate", 1965) & these take it to the next level. Beautiful mids, especially female vocals (these tubes are famous for this) & a warmer more expansive sound than the 5963's. Highs are also a bit more extended. These old tubes with a classical "British" sound have softened the amp's sound, yet the beautiful deep tight bass is retained.

 I'm running HD650's (with Stefan AudioArt cables) & the match is excellent, IMO. The SS output buffer better controls the bottom end of the 650's than the Bijou. Another great aspect of the design is the capacity to roll in many different tubes with very little effort required to dial them in. Many hours of harmless fun ahead here.

 Other than a decent case/chassis (transformer & PCB are on two separate small chassis at present joined by a three core cable), the only other planned tweaks are upgrading some caps (C1, 2 & perhaps a few critical ones in the PS).

 Hats off & many thanks to Alex for another cracker design.


----------



## lacrossebowe8

After an extended period of not using my SOHA II, I decided to clean up my input wires and go through the initial setup again today. All was well until I had to measure TPR and TPL vs. TB+R and TB+L. I tried three sets of tubes and not one set was even close to the 19 volt difference. I believe this indicates that my tubes are all no good?

 When I was testing it, the epsilon tripped quite a few times. I have not tried to listen to it and hope that my problems will be solved simply by getting some new tubes. As a tube newbie, I believe I tried at least some of these tubes at 12.6 v, which they did not like and could have hurt the tubes. 

 Thanks for any and all help.


----------



## runeight

Possibly, but not necessarily. Can you please report the other voltages at the test points. Thanks.


----------



## wiatrob

What Runeight said. Please post your measurements. It's possible that some of your tunbes mught be bad, but unlikely ALL are... 
 I had a similar problem on one of my builds and it turned out to be a cold solder joint in one of the Resistors near the tube.

 Tripping e12 is normal when measuring some of the test points.


----------



## lacrossebowe8

Here are my test voltages:

 TL+ 14.9V
 TL- -14.95V
 TH -12.56
 TB+ 107.5 (with tubes in place)

 I have 216 mV through both R10 L and R

 TB+L 81.4V
 TB+R 81.4 V

 Both R6L and R6R are at 400 mV

 For the next part I will discuss measurements with specific tubes.

 Beckman 5963
 TPL 76v
 TPR 47.3v

 JAN 12AT7
 TPL 48.6V
 TPR 81.7

 If I switch the tubes
 TPL 16.5
 TPR 47.5

 JAN 6189
 TPL 1
 TPR 1

 If I switch
 TPL 3.3
 TPR 3.6

 I will let it warm up for a while with these tubes to see what happens.


----------



## runeight

lacrossebow, my first thought is that Q1P,Q2P need to be replaced. I hate to ask you to do this, but I don't think we can be sure about anything else until we are sure about these devices.

 Then, if you can, try to find tubes that you know are working and insert those. We can work from there.


----------



## holland

Runeight, do you mean Q1L, Q2L, Q1R and Q2R instead of Q1P and Q2P?


----------



## runeight

Not yet. It looks like the B+ for each side is pulling down. It's hard to say exactly what the cause is, but we first need to know that the final cap multipliers are ok. And if not, then we can move on to the other devices.

 However, I'm not married to this approach. What are your thoughts?


----------



## holland

I see. I understood. B+ to be steady at 107.5V, and TB+L and TB+R to be steady at ~81.5V but TPL and TPR is having a larger drop than expected. My first thoughts lead to the current mirror as TB+L and TB+R are after the multiplier.

 Some other thoughts. If TB+L and TB+R were purposefully set to 80V and not the max voltage, that's OK. If it's not then there may be some drop due to current flow through the multiplier (more current = more drop). That may also explain the large drop through (TB+L)-TPR and (TB+R)-TPR. Easy way to tell is to measure TB+L and then measure the output of the TL783 to get the drop across the cap multiplier. It should be a few volts at most. If it's not, then it's Q1P and Q2P.

 After verifying that, measure the tail current to make sure it's steady, if so, it's definitely the transistors in the mirror or the tube(s). It's unlikely it's all the tubes that were tried, so I would tend to think the transistors. 

 If it's not steady, that may explain the variances through the HV chain due to current draw.


----------



## runeight

OK. I see what you mean.

 The next step then would be to measure the CE drop across Q1P and Q2P to see if these transistors are good.

 Lacrossbow, try this measurement next before replacing these two devices. Let's see what condition they are in.

 Thanks Holland.


----------



## lacrossebowe8

I have set the TB+L and TB+R to around 80V. I am on vacation now so I will have to do this on friday when I get back. I will get my hands on some new tubes also. 

 Thanks for the help.


----------



## lacrossebowe8

How would I measure the CE drop across Q1P and Q2P?


----------



## runeight

Measure between the two outside pins.


----------



## holland

^what runeight said. If you can't reach you can measure the output of the TL783 (middle pin) and the test points such as TB+L and TB+R. If I recall the circuit properly, that is effectively the same.


----------



## lacrossebowe8

I got the tubes I have tested and they tested ok. I measured the voltage drop across Q1P and Q2P and found it to be:

 Q1P about 1V
 Q2P also 1V

 I measured using both methods, using HV- and across Q1P and Q2P

 What is the next step? Thanks.


----------



## runeight

Assuming that the tail current is set correctly, the next step is to replace Q1 and Q2 on both channels. And verify that R4 is 18k.


----------



## lacrossebowe8

I will need to order the parts to replace them. What else can I do/ what else should I order to ensure that I can fix the amp? I don't want to have to order 5 $3 orders and would rather order too many parts than too few.


----------



## runeight

If the problem is entirely the plate voltages on the tubes then the only parts that can be bad are Q1-Q4 on each channel. Assuing all resistor values are correct and that TB+L and TB+R are basically the same as the emitters of Q1P and Q2P. I think you just verified this.

 As I recall you can set the buffer properly and you were also able to set the tail current.

 There isn't much left to break other than those four transistors.

 Do I remember correctly?


----------



## lacrossebowe8

Every other measurement was fine. I only couldn't get the TPR to TB+R to be 19v. (same on left channel) 

 R4 is 18k. I will order the Q1-Q4 transistors. I can't wait to get the amp working again


----------



## runeight

lacrossebow I forgot to ask you - when you measured the voltage drops across Q1P and Q2P did you have tubes in or out?


----------



## lacrossebowe8

I had tubes in. Should I have taken them out?


----------



## runeight

No. Tubes in was the right measurement. Just wanted to be sure that Q1P and Q2P were under load. I guess you just keep going with the current plan.


----------



## lacrossebowe8

So I got the transitors soldered in and here are my new test voltages. Also, the relay clicks on, then off then on a lot of the time when I turn it on. Also, I have kept it on the 6.3 v setting and am worried that setting it to 12.6 will smoke something as that is what happened before with the amp.

 With 6189 tubes

 62.4v L 47.5R. Music is much louder out of right channel. 

 Switching tubes, 43.4L 67.8R louder out of left channel. Maybe this is a tube issue.

 With 12AT7

 18V L and 70R

 Switching tubes

 61V L and 18V R

 This tube upsets the relay with any turn of the volume knob.
 This tube sounds decent but has some background noise. 

 With 5963's

 11.4V L 25.3V R Left may be climbing. 

 Switched

 23V L and 12.5VR

 I tried the 12V heater setting and no led's lit up and then I smelled smoke and turned the amp off. Not sure why that would be as the 5963's are able to be run at 12 v also I believe. These tubes sound far and away the best but I still think the amp may not be performing at its potential.


----------



## runeight

The data helps. But ...

 All of the tubes you have used are 12V heaters and they should run in the 12V position. Part of the reason for the bad voltages might be that the tubes are not conducting so that no current can flow through the transistors that you just replaced and, hence, the voltages can't set themselves.

 It's hard to say about the smoke problem, but to get proper operation you'll have to run these tubes at 12V. 

 I don't know what to suggest except maybe to turn it on with a 12V heater supply and one of these tubes and see what happens. If it works ok a 6V nothing should burn up at 12V.

 But I don't know for sure what's happening at this moment ...


----------



## lacrossebowe8

When I turn it on at 12 v none of the LED's light up and then I smell smoke. I can't say for sure where its coming from but it is there.


----------



## holland

remove the tubes. set 12v, measure the heater voltages and check for smoke and shorts.


----------



## lacrossebowe8

R3P turned bright red. This is where the smoke is from and I assume that it is ruined now. And I get no voltage from TH test point. So looking at the schematic, something is wrong with the heater section when strapped to 12v. I'm not sure why the amp seems to sort of work at 6.3 but not 12.6


----------



## runeight

Yes, R3P is probably toast, but this is a very helpful result.

 Could you please check the orientation of the jumpers on the heater jumper block. Looking at the board from the front (the side with the pot) the jumpers should be oriented side by side each aligned parallel with the sides of the board.

 If the jumpers are oriented correctly then there is a short in the heater circuit somewhere between R3P and the tube sockets. The only way to find this will be first to inspect everything carefully.

 Also, do you have the regulator in the right orientation? As you know it has multiple pads for either topside or bottomside mounting. If topside the regulator should be mounted on the frontside of the heatsink towards the front edge of the board.


----------



## lacrossebowe8

So I am an idiot. I had the jumpers oriented the wrong way. The regulator was mounted the right way. Now it seems the led's light up. Now i will just try to get a new R3P. All the other power test points are correct. I just inserted tubes, the relay clicked and I will get the next measurements.


----------



## lacrossebowe8

Everything checks out. I hope any other newbie builders like me read this thread and set their heaters correctly.


----------



## runeight

Great. This means that R2P is not completely blown and you can probably run with it until you get a new one.

 In the meantime, does it play music now?


----------



## lacrossebowe8

Yeah it does play music now and sounds good. I will give it a more critical listen soon and report back.


----------



## commandercam

I'm in the middle of my SOHA II build and things are humming along. However, I have a question about resistor R3P. It is spec'd as an 8.2Ohm 3W 5% metal oxide resistor. However, I mistakenly purchased a 10Ohm 3W 5% metal oxide. (It actually reads as 10.2Ohm on the DMM.) Is it that critical that an 8.2Ohm resistor be used in this spot or would I be ok with the 10? Just wondering if this should be a concern (will 2Ohms make any difference in this spot?) and whether or not I need to put in an order to Mouser for the exact value. 
	

	
	
		
		

		
			





 Thanks!
 Cam


----------



## runeight

(EDIT out this incorrect sentence.) This resistor is there to burn some of the power that would otherwise be burnt in the heater regulator. However, if it is too large then the voltage at the input to the regulator will drop below its dropout voltage. 10Ohms is just a little too large to have a margin of error on the dropouts.

 But, in the meantime you can certainly run with 10Ohms to get things going. Then just replace R3P when you get around to it.


----------



## commandercam

Thanks for the quick response! I will finish the build with the 10Ohm R3P and replace it with an 8.2 the next time I order parts. I have another question. 
	

	
	
		
		

		
		
	


	




 I'm currently mounting the bigger caps and bought Nichicon Muse caps when I could find the appropriate values. In most cases the Nichicon caps are larger than the Xicon caps spec'd in the BoM. I expected this but the board is so tightly packed that they won't fit in some positions unless I resort to cap contortion. (Aesthetically unpleasing.) I have the specified Xicon caps as well because I thought this might occur. So my question is how much of a difference do the Nichicon Muse caps make over the stock Xicon? Is it worth it from a sound quality standpoint to stuff the Nichicons in? The locations in question are C8P, C9P, C10P, C11P and C5L, C5R. I suspect that the power stage caps are less critical to the sound than the C5L/R caps? (With some creative lead-bending I can get C5L/R in place but thought I'd ask.) Thanks!


----------



## runeight

I'm probably not the best person to answer this because I am not a big believer in cap swapping. What can I say? 
	

	
	
		
		

		
		
	


	




 But, I think you're right. The caps you mentioned are all in the PS section and MHO is that the xicons won't sound any different from the nichicons. I can be persuaded that C5 should be a better quality cap but since it is paralleled with a good film cap I suspect that it doesn't matter much here either. I bet that both the xicons and nichichons can handle the lower frequencies equally well. But, if you want to swap in better electrolytics this is the place to do it.


----------



## wolf18t

Except for the higher Voltage B+ cap, I have replaced all Xicon caps with Panasonic FM/FC caps. These are great caps for decoupling purpose and they all fitted the board just right. I think I still have my SOHA II BOM @ home so just PM me as a reminder and, if you are interested, I'll send you the digikey parts number later tonight. I can also post them here.


----------



## commandercam

Wolf - Nice looking board there. I went ahead and put in an order to Mouser last night for several different C5 caps. I bought the std Xicon caps along with Mallory and Vishay/Sprague. Have you ever heard of anyone who has used the latter two? In any case I'll have options should I want to change them out. I'll post some pics later this week when I get the rest of the board populated. It seems that the most critical caps would be in the C1 and C2 positions, right? For those I have Auricaps. In any case it will be interesting. Thanks!


----------



## wolf18t

Quote:


  Originally Posted by *commandercam* /img/forum/go_quote.gif 
_I went ahead and put in an order to Mouser last night for several different C5 caps. I bought the std Xicon caps along with Mallory and Vishay/Sprague. Have you ever heard of anyone who has used the latter two?_

 

None that I know.

  Quote:


  Originally Posted by *commandercam* /img/forum/go_quote.gif 
_It seems that the most critical caps would be in the C1 and C2 positions, right? For those I have Auricaps. In any case it will be interesting. Thanks!_

 

C1 is pretty critical to me since it's direct in the signal path (coupling). Auricaps should sound very nice there 
	

	
	
		
		

		
		
	


	




. I've used Mundorf MCAP supreme in mine.

 To my knowledge C2 is less important and doesn't really need anything "boutique" since it is used to set the frequency filter for the DC offset nulling section (Runeight please correct me if I'm wrong, that's the way I understand the circuit).


----------



## runeight

wolf18t that's correct on C2. It sets the servo integration time. Just an ordinary, good quality film cap will do. Wima, AVX, etc.

 C1 is the most important cap in the box.


----------



## commandercam

wolf18t and runeight - Thanks for all of the advice. My board is fully populated and I'm now finishing up the wiring. I have a question about wiring from the RCA jacks to the L/R/G connector on the PCB. I've done some research on DIY RCA interconnects (in a way this is basically a short run interconnect). Many of these show a three wire braided cable (why? crosstalk?). There is only a signal and ground for each channel, so shouldn't two wires be sufficient? Would a twisted pair for each channel work or is this something that is not very important over such a short distance? Just very curious.


----------



## runeight

commandercam, in general I like to use two single conductor shielded wires, one for each channel. Connection the shields to the jacks then to the pot and then from the pot to the IG on the board.

 This minimizes crosstalk through the input cables, although for these really short distances that's not a big deal. If your enclosure is really shielded you can try running unshielded wires. This has worked in many amps over the years without introducing any additional noise.


----------



## yzriver

I am building a SOHAII. It started to sing at last weekend, with a very clean, warm, very detailed sounds. The tubes are RCA 12AU7.
 The tested voltage:
 TB+ 92.2
 TB+L 75.2, TPL 56.3
 TB+R 74.9, TPR 56.4

 The audio source is a DAC board, which works with DIR9001 and PCM1793. It uses a 1875 to split a 12VDC to +-6V and GND. I will make a dual-rail +-6Vpower source to replace the 1875. 

 Then I will make a DAC-SOHA combo by putting these two module in a box.


----------



## runeight

Everything looks spot on. Send us the pics when you've got it all cased up.


----------



## JamesL

Hi all - I've started my soha II a couple days ago, but I'm not getting a 19v drop from TPR/L to TB+R/L.
 Every other measurement has been spot on until I put the tubes in.

 TB -108v
 TH - -12.8v
 TL+/- +14.9/-15.1v
 220mV across R10 and 400mV across R6
 (resistor values checked, for 10mA and 2mA across correspondingly)

 65v at TB+
 64.7v at TP
 ~300mV drop

 I tested it with the tubes off, and I got ~7v at TPR, and <1v at TPL.. both values varying quite a bit. If I recall correctly, touching the test probe to TP consistently tripped the relay.


 First batch of production boards
 Jumper set to 12.6v @ 150mA, EH 12AU7, advertised as new.
 BD139 transistors.. small signal transistors - BC550C & BC560C

 Some observations:
 I had a very difficult time getting a reading across R6 when I put my dmm to the mV setting; Even if I could consistently get 0.4v reading when set at the (auto)volt range, it would often read 'null' when using the mV range (it would sometimes read 400mV, but often times not.. I couldn't find a pattern)
 The relay will click off when adjusting P1P with tube in.
 The relay will click off randomly when touching multimeter probe to a resistor lead or less frequently when touching a test point.

 I've tested many times over for several hours, so I'm pretty sure the above behaviors are fairly consistent and accurate.

 I have the suspicion that something may be wrong with my fluke 87, so I will try using my a backup multimeter after posting.

 Some obligatory pictures 



 

 

 

 



 I've been dying to hear this amp since I ordered the board a year ago, so hopefully I can get it fixed and working ._.


----------



## tacitapproval

You might want to solder those tube socket pins more thoroughly.

 The tripping relay when probing test points or adjusting the trimpot is normal.

 I'm sure others will have more helpful suggestions.


----------



## JamesL

Thanks
 I only soldered the inner edge of the sockets since the holes were quite big but I'll go ahead and fill those just in case. 

 I woke up this morning, checked the polarity of all the electrolytes, transistors, opamps, relay, diodes, part numbers for each transistor, and resistor values.
 Also thoroughly examined each solder joint and they all seem to be good.

 I switched multimeters, and I still get the same readings, same problems with the dmm leads tripping the relays randomly. I know I'm not shorting anything with the leads when this happens.


----------



## tacitapproval

Two other things:

 Not having the pot in the circuit maybe throwing things off (someone more knowledgeable than me can confirm this).

 The jumper pins look like they are not soldered down?


----------



## JamesL

Yes, that's true. I haven't decided if I wanted to wire a switch, so I ghetto-rigged the jumpers hairpin-style so they clip on tightly onto the pcb. I checked for continuity and it seemed to work out alright. In fact, they "grip" on so tightly that I have a hard time budging them loose. 

 From what I can figure out, shorting ground to signal-out of the potentiometer is equivalent to having a pot set to a fully counterclock position. Should I try it out?

 I'm actually running on a very short supply of "hardware-store" wire; I'm trying to order more online but the new apartment I moved to can't accept packages larger than standard letter envelope, which has been giving me a lot of problems lately.


----------



## yzriver

JamesL
 It maynot relate to your problem, I just want to let you know you need to be awared of the connector for headphone. You soldered the screwconnector pin to the center 3 hole, of which lable is L,G, R, but the headphone from tips to sleeve are left/right and grond. I maynot explain well. Please look at my picture. I connect the socket to 3 holes close to relay.


----------



## JamesL

Thanks, and yes I'm fully aware of that..
 I haven't connected any load or source to the amp yet though. I don't want to proceed further until I find out why I'm not getting 19v drop across R4 =/


----------



## runeight

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Hi all - I've started my soha II a couple days ago, but I'm not getting a 19v drop from TPR/L to TB+R/L.
 Every other measurement has been spot on until I put the tubes in.

 TB -108v
 TH - -12.8v
 TL+/- +14.9/-15.1v
 220mV across R10 and 400mV across R6
 (resistor values checked, for 10mA and 2mA across correspondingly)

 65v at TB+
 64.7v at TP
 ~300mV drop

 I tested it with the tubes off, and I got ~7v at TPR, and <1v at TPL.. both values varying quite a bit. If I recall correctly, touching the test probe to TP consistently tripped the relay.


 First batch of production boards
 Jumper set to 12.6v @ 150mA, EH 12AU7, advertised as new.
 BD139 transistors.. small signal transistors - BC550C & BC560C

 Some observations:
 I had a very difficult time getting a reading across R6 when I put my dmm to the mV setting; Even if I could consistently get 0.4v reading when set at the (auto)volt range, it would often read 'null' when using the mV range (it would sometimes read 400mV, but often times not.. I couldn't find a pattern)
 The relay will click off when adjusting P1P with tube in.
 The relay will click off randomly when touching multimeter probe to a resistor lead or less frequently when touching a test point.

 I've tested many times over for several hours, so I'm pretty sure the above behaviors are fairly consistent and accurate._

 

JamesL it's not really possible to test with the tube out or off because then there is no current that can flow through the tail CCS and into the plate loads.

 However, there is clearly a problem with the tubes in. I guess you are sure that the tubes actually light up???

 If so, then they don't seem to be conducting very well. When you have the tubes in is that when you cannot adjust the tail current at R6. Or is when the tubes are out/off?


----------



## JamesL

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_JamesL it's not really possible to test with the tube out or off because then there is no current that can flow through the tail CCS and into the plate loads.

 However, there is clearly a problem with the tubes in. I guess you are sure that the tubes actually light up???

 If so, then they don't seem to be conducting very well. When you have the tubes in is that when you cannot adjust the tail current at R6. Or is when the tubes are out/off?_

 

Yes, the tubes light up, but it is quite faint/dim.
 I am reading 400mV across R6 regardless of whether the tube is connected or not. It is about 10mV higher with the tubes plugged in, or 10mV lower with the tubes left out. I measured R6 to be 200ohms.

 I wish I could tell you in more detail what exactly is happening, but I've little experience with tube circuits and can only describe to you the measurements I'm reading.


----------



## runeight

That's ok, we'll figure it out.

 First, have you measured pins 4&5 of the tube socket. If you haven't try that to make sure that you have 12V on the tubes. Ifyou don't this means that the jumper settings are set for 6V tubes instead of 12V tubes.

 The voltage across R6 cannot be the same when tubes are in or out. When the tubes are out there is not conduction path for the current in R6. If this is really what's happening then there is some other problem that we'll have to find. Are you absolutely certain that the voltage on R6 is the same with tube in and tubes out?


----------



## JamesL

Yup. 12.8v across pins 4&5 - Its the first thing I checked after rigging up the jumper pins.

 The voltage across R6 reads the same with both the tubes in and out; 10mV higher with the tube in.
 Double checked, triple checked, and then a half dozen more times after a good nights sleep. 
 I've checked the integrity of most of the parts, excluding mainly the IC's and vacuum tubes. Is there any way to check if they are functioning correctly without having to desolder them?


----------



## runeight

Yes, of course, because I was wrong. I was thinking of another amp. I should look at the schematics first. 
	

	
	
		
		

		
			





 The tube-in/tube-out readings on R6 are actually correct so measuring there won't help us.

 Now, the TB+ and the TP readings would say that there is no current flowing in the tubes.

 Have you measure the voltage across R4 on each channel with both tubes in? If not, try that first. And if you did can you please remind me of what you got?

 Edit: And while you're at it, measure the drops across R2/R3 on both channels.


----------



## JamesL

Across R4, I'm getting 20.9v on the left, 22.1v on the right.
 206mv R3, 233mv R2 on the right
 204mV R3, 229mV R2 on the left


----------



## runeight

Hmmm. Those are the correct numbers.

 What do you get if you measure pins 1 & 6 with respect to ground on both tubes?


----------



## JamesL

At pin 1, I'm getting 32.8v for the left, 41.6v on the right. 
 I'm getting the same numbers at pin 6 as I'm getting at the test point. Around 65v (~200mV under TB+ R/L)


----------



## runeight

OK. This is progress.

 It seems to me that either Q1 or Q2 or both are bad on both channels. Make sure that they are BC560 (not BC550) and if they are, I hate to ask, but the only next step is to replace them. I would just do all four of them to be safe.


----------



## JamesL

Ah, alright.

 I switched the tubes and measured pin 1 again and got 41.9 and 42.6
 I don't know if that changes anything, but I'll go ahead and order some replacement parts.
 Q1 and Q2 are both BC560s
 I don't know when I'll get them because I have to send them to my friend's address, but I'll let you know when I do.


----------



## runeight

Those numbers on pin 1 are nearly perfect. But you still get 65V at pin 6??

 Then it has to be the transistors.

 Please let us know how you do. The amp will work when all the parts are right and working.


----------



## yzriver

Can I use SOHA as a preamp?
 I have a Adcom GFA-5300 power amplifier, of which input impedance 47KOhm, sensitivity 0.1V for 1W and 0.9V for 80W.
 Thanks.


----------



## regal

How do you know which way to face the BD139's, the lettering toward the alps pot or toward the heatsink? This is bottom mounting the heatsinks.


----------



## nattonrice

I'm pretty sure it is towards the front/pot.
 I was just about to solder them so this is a good question =]

 Edit: Comprehension failure. You're bottom mounting. Would they not face towards the heatsink then?


----------



## regal

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_I'm pretty sure it is towards the front/pot.
 I was just about to solder them so this is a good question =]

 Edit: Comprehension failure. You're bottom mounting. Would they not face towards the heatsink then?_

 

Don't know very confusing. 


 Also is a 100 n capacitor big enough for the coupling C1's ?


----------



## Ferrari

For standard ECB devices such as BD139, MJE243, 2SC3422…:

 - the lettering should faced the front side of the PCB (Alps pot) when top mounted, and...
 - the lettering should faced the back side of the PCB when bottom mounted

 Regarding the smaller value of C1, the HP filter is mainly determined by C1 = 0.22uF and R15 = 1MΩ.
 With C1 = 0.1uF instead of 0.22uF, the corner frequency will be shifted a couple of Hz but a can work.


----------



## regal

I noticed that my R15 from JRossel was only about .8 Mohm, I have a good fluke meter so I better go with the bigger cap. I have some russian 1 uF pio caps that I think I can make fit in the hammond.


----------



## runeight

There are mouting diagrams on the Cavalli Audio website under the Instructions/Device Mounting section.

 These show top/bottom as well as different pin arrangement devices.

 Gotta get you guys to read the website.


----------



## nattonrice

Haha I've been at the bijou website for the past 2 days and didn't think of navigating to the soha2 page to check (palm to face).


----------



## yzriver

Ask this question again. If it works, I can save money for a preamp and space.

 Can I use SOHA as a preamp?
 I have a Adcom GFA-5300 power amplifier, of which input impedance 47KOhm, sensitivity 0.1V for 1W and 0.9V for 80W.
 Thanks.


----------



## runeight

Yes.


----------



## rds

Quote:


  Originally Posted by *yzriver* /img/forum/go_quote.gif 
_Ask this question again. If it works, I can save money for a preamp and space.

 Can I use SOHA as a preamp?
 I have a Adcom GFA-5300 power amplifier, of which input impedance 47KOhm, sensitivity 0.1V for 1W and 0.9V for 80W.
 Thanks._

 

You can of course, but do you want a pre-amp with a gain of 10+? My understanding is that pre-amps are usually unity gain.


----------



## yzriver

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_You can of course, but do you want a pre-amp with a gain of 10+? My understanding is that pre-amps are usually unity gain._

 

The power amp is unit gain, and preamp has some gain. Am I wrong?


----------



## rds

Quote:


  Originally Posted by *yzriver* /img/forum/go_quote.gif 
_The power amp is unit gain, and preamp has some gain. Am I wrong?_

 

That is possible I guess. But if an "amp" has unity gain then technically it's not an "amp", but a buffer instead.
 My understanding is that a pre-amp attenuates the signal before it is fed to an amplifier. Hopefully someone more knowledgeable will answer this for you.

 EDIT your GFA-5300 has a 29dB gain


----------



## yzriver

Quote:


  Originally Posted by *rds* /img/forum/go_quote.gif 
_That is possible I guess. But if an "amp" has unity gain then technically it's not an "amp", but a buffer instead.
 My understanding is that a pre-amp attenuates the signal before it is fed to an amplifier. Hopefully someone more knowledgeable will answer this for you.

 EDIT your GFA-5300 has a 29dB gain_

 

you are right. I should be careful to use SOHA II as a preamp, at least to GFA5300. 
 I have a DAC, which output is 3.2V peak to peak. I think this output will blow away my power amp. Probably the SOHA II at here should be used as a attenuator.


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There are mouting diagrams on the Cavalli Audio website under the Instructions/Device Mounting section.

 These show top/bottom as well as different pin arrangement devices.

 Gotta get you guys to read the website. 
	

	
	
		
		

		
		
	


	


_

 

But it doesn't show which side is which on the BD149's, the datasheet is no help either.


----------



## runeight

Ah. Looking at the bottom of the device the side that goes against the heatsink is the side that the pins are closest to.


----------



## regal

Thanks Alex.


----------



## JamesL

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Those numbers on pin 1 are nearly perfect. But you still get 65V at pin 6??

 Then it has to be the transistors.

 Please let us know how you do. The amp will work when all the parts are right and working._

 

hey again,
 I replaced q1/q2 on both channels and I am getting the exact same measurements as before(which are on posts #1033-#1050)
 Do you have any other suspicions on what could be wrong?


----------



## regal

I remember when the SOHA II was in its infancy there was a member that had a higher voltage PS, has that been incorporated in this final design I'm building?

 Also is there a thread about tube rolling/sonic impressions or is this the right one?


----------



## 00940

Stupid question maybe but... has anyone tried to replace the CCS by the heaters as a load (Starving Student-like) ?

 150ma @12.6V seems quite ok for this (with heaters in serie), with sufficient heatsinking for the bd139 of course. Running 12V for the positive supply would give a dissipation of less than 2W. The transistor can cope with that.

 I would implement a softstart in the heater supply (easy to do with the lm337).


----------



## regal

The Digikey heatsinks from the BOM have no hole to attach the transistors, just a knob protruding, do we have to drill them out?


----------



## wiatrob

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I remember when the SOHA II was in its infancy there was a member that had a higher voltage PS, has that been incorporated in this final design I'm building?

 Also is there a thread about tube rolling/sonic impressions or is this the right one?_

 


 Pretty much - Ferrari rolled his own HV plate supply, and then the amps plate supply was redesigned for higher voltage.


----------



## 00940

Quote:


 The Digikey heatsinks from the BOM have no hole to attach the transistors, just a knob protruding, do we have to drill them out? 
 

No. Those heathsinks normally have metal clips to keep the transistor in position.


----------



## wiatrob

Quote:


  Originally Posted by *00940* /img/forum/go_quote.gif 
_No. Those heathsinks normally have metal clips to keep the transistor in position._

 


 That's odd - I did the BoM and I don't think we vetted the Digi-key column as throughly as the Mouser - but I'm pretty sure some have used those part numbers. 

 I'll take a look and update the BoM when I get a chance. Sorry for the mixup...


----------



## 00940

Well, I just checked digikey. I don't have one at hand (but plenty of similar heatsinks).


----------



## regal

Those are the ones, they don't come with clips so I had to drill holes. They also made contact to a few resistors and had to be dremelled.


----------



## nattonrice

I am using the 2" aavid thermalloy version of the one that Ti sells except with solder pins.
 Fits very well =]


----------



## regal

Anyone else using PIO coupling caps? Wondering if I should ground their cases? I ended up mounting 1uF russian caps, only to find a better sized .22 uF vit C's in the mail box, I doubt a will switch them unless someone thinks they would be better.


 Also I really like the templates someone posted, helped the case work significantly.


----------



## 00940

Quote:


  Originally Posted by *00940* /img/forum/go_quote.gif 
_Stupid question maybe but... has anyone tried to replace the CCS by the heaters as a load (Starving Student-like) ?

 150ma @12.6V seems quite ok for this (with heaters in serie), with sufficient heatsinking for the bd139 of course. Running 12V for the positive supply would give a dissipation of less than 2W. The transistor can cope with that._

 

Anything wrong with the idea ? I'm about to build a p2p version of the soha (found some mullard 12au7 for free and a suitable case) and plan to go that way. 

 It saves one regulator, two transistors, two heatsinks and a few caps/resistors, all that at the cost of a slightly reduced voltage output swing. And it reduces the current draw on the PS.


----------



## Ferrari

I will not call it stupid but it has nothing to do with the SOHAII design. 
 If you want to save a couple of components the way you think, just give it a try. 
 You have nothing to loose with a p-p build.


----------



## 00940

Nothing to do indeed but the same input stage, the same power supply, the same buffer (minus the ccs) and the same servo 
	

	
	
		
		

		
			





 I see your point though. I'm gonna try.


----------



## regal

Having pS problems. With no jumpers installed I blow fuses. If I remove the LV- regulator I don't blow the fuse. Also LM337 is putting out 0V and R3P is getting very hot. I can find no shorts. Voltage at the rectifier D5P is 15V. The High voltage reg is putting out a good 120V.

 All evidence points to a bad LM337 and 7918, but I can find no shorts and would like to know why they died.


 Edit - put in a new LM337 that I had and same rsult 0V and R3P smoking hot. The odd thing is C6P and C7P measure as shorts when in the circuit but fine when pulled out.

 Must be a rectifier diode have now idea how to tell which one, is there a schematic with the voltages market at the diodes?


 Tested the rectifier diodes with my fluke and they are shorted, I did have one making contact with a cap casing.


----------



## runeight

First thing would be to check the orientation of the vertical diodes. All cathode stripes should be away from the board. Is this all true??

 Then the orientation of C6 and C7 since it's a negative regulator.

 If these are ok we'll find other tests to make.


----------



## regal

yea I checked all that, the anodes of the diodes on down on the circles of the board, caps are right.


----------



## runeight

I hate to ask, but you got the right regs in the right spots?

 And tubes are out, jumpers are not inserted?


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I hate to ask, but you got the right regs in the right spots?

 And tubes are out, jumpers are not inserted?_

 

Yes all right regs in right places, no jumpers but I do have the heater selectors in. I checked all the rectifier diodes with the fluke again and all gave a good reading. On the LM337 circuit all caps and resistors are right but I measure 1.8kOhm between #4 and #5 pin of the R tube socket (no tube insterted). 

 Again powering up with 7815 blows a fuse, pulling 7815, no fuse blows but the dropping resistor gets real hot and LM377 puts out 0V (second one I tried.)

 What voltages should I be reading before and after the rectifiers ?

 Edit: I believe I have found something. After the dropping resistor R3P there is a short. When I measure across C5P or C7P short. No short after the LM337. So do you think I have bad caps or a short in the board somewhere?


 .


----------



## regal

Pulled the LM337 and no short on the heater circuit, so somehow I have blown up two LM337's, maybe not letting the B+ bleed long enough before poking around. Although I haven't dived deep into the 7915 circuit.


 Edit: The LM337 tested fine out of the circuit, must have been poor isolation from the bastardized heatsink. We should probably change the Digikey heatsinks on the BOM, they are trouble because you have to drill the hole unless you have some clip that no one knows the part # for.


----------



## runeight

Sorry about the Digikey problem. Since I used the Mouser parts I didn't catch it.

 Do you think this will fix the problem?


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Sorry about the Digikey problem. Since I used the Mouser parts I didn't catch it.

 Do you think this will fix the problem?_

 

I'm sure it will fix the LM337 circuit, I think with the 7915 in it was shorting 'cause the Lm337 was basically pulling a ton of current to ground and the 7915 broke the camels back (fuse). Will put everything back together tomorrow.

 Glad you have all the jumpers to separate sections, or I would have surely blown up the rest of the amp.


----------



## yzriver

I had a similiar problem as regal has. The LM337 back matal is Vin pin, and the heatsink is to ground from its leg. You need a sleeve to isolate the screw/net to the heatsink.

 Try the LM337 without heatsink first.


----------



## regal

I got the LM337 circuit working with a new LM337 and a better sleeve, unfortunately the 7915 regulator is getting 25V and puts out 25V so I think that one is shot, I have a new one on order.


 When you drill these heatsink use one size larger drill bit than the knob.


----------



## regal

Having trouble with the E12 circuit. Buffers bias fine and have zero offset, but the relay isn't getting power, +_12V is present from the 78/7912's.


----------



## runeight

Measure the voltages at all the pins of the opamp. Let's see what we have there.


----------



## nick_c

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_To drive the analogue VU meters, I used the driver circuit as depicted below. The working of this driver circuit is very simple: the amplifier around T1 and T2 amplifies the line level signal to the desired level, the signal is then passing through the rectifier diodes D1 and D2. C4 smooth out the signal a bit before the signal is feeding to the VU meter. 

 Before use, an adjustment needs to be made. 
 Connect the circuit + VU meter to a function generator which output a 1KHz signal, ~300mV.
 Dial P1 to its minimum (R=0), then dial P2 until the VU meter is reaching its maximum. 
 Next, turn P1 up until the VU meter is at ~ 50% of its total range (12 o’clock).

 Depending on the level of the input signal (SACD player, DAC…), you might have to re-adjust P1 to get a proper reading of the VU meter.
 For stereo application, 2 driver circuits are needed. 
	

	
	
		
		

		
		
	


	








_

 

Hi,

 Is this a circuit you have actually used or is it just theory?

 Why im asking is ive just built this one up for my VU meters & it works great except for the fact that upon power up this circuit creates a nasty spike on the meters throwing them over to full deflection.

 I have tried everything I know (which isnt a lot I must admit) but cant fix this, ive even tried them from a seperate voltage source incase it was that, but still no luck, the throwing over of the meters probably wont cause any damage as its so short, but it looks bad.


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Measure the voltages at all the pins of the opamp. Let's see what we have there._

 

TL081

 Pin
 1 11.72V
 2 0V
 3 0V
 4 -12.04V
 5 0V
 6 0V
 7 11.96V
 8 11.72V


----------



## runeight

Pin 7 is the V+. It should be at 12V. Can you track this down?


----------



## regal

Pin
 1 11.72V
 2 0V
 3 0V
 4 -12.04V
 5 0V
 6 0V
 7 11.96V
 8 11.72V

 I edited my post these are the correct voltages


----------



## runeight

The output of the opamp is correct at 0V. What is the voltage at the collector of the MPSA14?


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The output of the opamp is correct at 0V. What is the voltage at the collector of the MPSA14?_

 

0V


----------



## runeight

OK. So if the collector is at 0V and the + of the relay is at 12V and if the - of the relay is connected to the collector then the relay has to be latched. But it's not??

 Maybe check the continuity across the relay?? And solder joints? Etc.


----------



## regal

No the relay is getting no power


----------



## runeight

I guess you've measured across the relay coil and it shows 0V? But the + rail is 12V and the collector is 0V??

 If this is true then there has to be a discontinuity somewhere. A bad solder joint at the relay coil?


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I guess you've measured across the relay coil and it shows 0V? But the + rail is 12V and the collector is 0V??

 If this is true then there has to be a discontinuity somewhere. A bad solder joint at the relay coil?_

 


 I was having trouble getting the proble on the coil, it is getting the 12V. The Rt channel is latching but not the left and I noticed that the left side got hit with my solder iron during construction, so I believe I have a bad relay.

 Thanks for helping me track this down and I have a better understanding of how the E12 circuit works.


----------



## runeight

You're welcome. Hope we found the problem.


----------



## regal

Yes the new relay is working great.

 But I am having another issue. TP+R dials to 60V just fine but TP+L is stuck around 10V, fickin C15P is in backwards (reversed polarity). Do you think I should replace Q2P when I have the board out or should it have held up to my stupidity


----------



## regal

Bigger problem now, reversed C15P to correct polarity.


 Got 60V on both sides. Plugged in the 5963 tubes set for 12.6V. Set the tail current to 400mV across R6. Went back to check TB+L/R and it dropped to 27V, thats all I can get out of it. Checked TB+ still a solid +120V. Tried running with just one tube or the other and can get the right voltage.

 Turned out one of the RCA5963 tubes was bad, glad I bought three. Just wanted to share this info in case anyone else loses plate voltage when they plug in the tubes and set the tail current.


 Will be plugging in the RCA inputs and headphones tonight, got my fingers crossed!


----------



## runeight

So you're finally going to hear music tonight?? 

 I hope you like the amp.


----------



## regal

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So you're finally going to hear music tonight?? 

 I hope you like the amp. 
	

	
	
		
		

		
		
	


	


_

 

yes great sound! beats the old Soha + Jisbos contraption by miles. Really glad you used the jumpers to bring everything up in stages I think this is essential when mixing HV tubes with LV SS.

 Couple questions:

 My tubes are off about 1V at the plate when set to the same current, which is more important to equal the gain, the current or the plate V?

 I am amazed at the sound of the 12AU7 with only 1.25mA. But is there any opportunity to push more current thru the tube by lowering the resistance of R6 ?


----------



## yzriver

I finished my case prototype of the SOHA-DAC combo. I know the cutting and wiring is shameful, but they are work well now. Next step is to find some good board and redo the wire.

 There are two LED that indicate the source is coaxial-DAC or RCA line in. Now source is DAC.





 On the top the metal net is a piece of officedepot's card holder. 






 The red board is the DAC, DIR9001+PCM1793. I got it from ebay. It used 12DC single rail input, and splited it into +-6V and virtual ground by LM1875. I removed the LM1875, and made a DC source on the yellow board, +-9V to the OPAMP, +6V to DAC, -6V for source switching and LED. Since the OPAMP is using the seperated DC source from DAC, I put the OPAMP, decoupling cap into another board. The opamp board is connected to the socket with pins. The two relays are for coaxial or RCA switching, and LED controling.


----------



## regal

Has anyone found a source for a grommet that fits the holes in the top for the tubes?


----------



## nattonrice

Would the one that wiatrob supplies with the CTH do?
 Perhaps you could ask him if you could pick up two.


----------



## regal

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_Would the one that wiatrob supplies with the CTH do?
 Perhaps you could ask him if you could pick up two._

 

greek to me any links?


----------



## nattonrice

Hehe here the site where you'll see a pic CTH

 I'm not sure if that is what you meant though.


----------



## regal

thanks


----------



## wiatrob

regal, am I sending you some? If I'd known it was you...


----------



## regal

Thanks these are hard to find, ought to have Runelight add them to the BOM.


----------



## regal

I'm using big 1uF russion 40 p-i-o coupling caps, would I be better off putting in .22uF vit C's. I initially went with these because my buffer input resistors measured low (around .8 MegOhms.)


----------



## runeight

I don't think you need 1u caps. 800k is a very high input impedance an your low freq response will be subsonic even with 100n. 220n should be more than sufficient.


----------



## regal

I have an "ebay" matched pair of 12AU7 that, well aren't well matched, at the same plate voltage the current differs almost .5mA. What is more important to balancing the gain, the plate voltage or the tail current ?


----------



## regal

One more question, when changing tail current and B+ is the recommended 19V drop across the CCS a minimum? I was always taught that a higher drop is OK ?


----------



## FairyTales

Hi, i've finished building my Soha II and i'm in the initial setup stage.

 What i would like to know is if TL+ is ok at 22,5v (i'm on 230v if it change anything)?

 Other readings are as follows:

 TL+ 22,5V
 TL- -15.06V
 TH -12.66V
 TB+ +117V

 I will probably need to bother you guys a few more times before it's completly finished ^^

 Thanks

 Arnaud


----------



## runeight

Unfortunately, TL+ can't be 22.5V. It is a 15V fixed regulator so there must be something wrong in the PS somewhere in order to get 22.5. We'll have to fix this before you can go any farther with the amp. Could you please check the orientation and values of everything, including the orientation of the vertical diodes. Let's see if you find anything.


----------



## FairyTales

Thanks for the quick reply, so far i've checked the orientation of all the diodes and they are all ok, but i've found a resistor with a value of 2.6kΩ instead of being 30kΩ (R6p) could it be the source of the problem?

 I will continue to check the rest of the components, thanks a lot for the help!

 Arnaud

 Edit:Nevermind it's not coming from the resistor i removed it, checked with the DMM and i get 30kΩ. 
	

	
	
		
		

		
			





. I will continue my investigation, where could it come from if it's not the diodes orientation?
 Is there a way to verify the LV+ regulator, i'm getting 26V between the first leg and ground and 22V between ground and the third leg, i was under the impression that it should give me 15V?


----------



## runeight

It could be that the positive regulator is reverse mounted. Or it could be that it's bad. There isn't much else that can go wrong.


----------



## FairyTales

I will try to source another regulator (see the edit in my previous post) tomorrow and see if it solves the problem as everything else seems to be ok.

 Thanks for helping me out as i don't really understand how all the bit and pieces works together, i know how to solder and the basic functions of the components but when it comes to solving those kind of issues i'm completely lost.

 Arnaud


----------



## runeight

Happy to help. While you're waiting it would be a good idea to check all of your solder joints on the board and all your resistor values. Make sure everything is well connected and in the right place.


----------



## regal

Quote:


  Originally Posted by *FairyTales* /img/forum/go_quote.gif 
_I will try to source another regulator (see the edit in my previous post) tomorrow and see if it solves the problem as everything else seems to be ok.

 Thanks for helping me out as i don't really understand how all the bit and pieces works together, i know how to solder and the basic functions of the components but when it comes to solving those kind of issues i'm completely lost.

 Arnaud_

 

With the new reg, make sure it is isolated from the heatsink. Also check for shorts between TL+ and ground before you power up.


----------



## FairyTales

The regulator was faulty now i have the following values 

 TL+ 15,05V
 TL- -15.06V
 TH -12.66V
 TB+ 118V

 But now i have another problem on step 2 when you have to strap jumpers, i put one jumper on both poles of 12.6 and the other jumper on both pole of TPR, i power up and started to see smoke coming from R3P
	

	
	
		
		

		
		
	


	




, so i unplugged it quickly and the resistor was super hot

 So i assume i should change R3P but where could the problem come from? The resistor itself?

 Arnaud


----------



## runeight

I suspect that you have the jumpers turned sideways. They should be aligned with the sides of the board from front to back and not side to side. Can you post a photo?


----------



## FairyTales

You're right i did turn them sideways now they are set according to the diagram of the PS on the site. Parrallel to the longer side of P1L. Stupid me.

 When i try the buffer settings part i don't get any values across R10L/R10R, so if i understand correctly i've toasted R3L?

 Arnaud


----------



## runeight

I think you mean R3P? You can verify its condition by looking at the tube filamaments. Are they lit? 

 And the buffer adjustments should be independent of the tubes or the heater supply.

 You get absolutely nothing across R10 on either channel and the trimpot P2 doesn't change anything?


----------



## FairyTales

Yep i mean R3P, when i put the tubes in only the very top of the filaments gets orange ,in the upper part of the tube you have 3 leads on each side, the outer one are holding what i would call a heatsink in the middle of the tube, only the filament in the middle of the 3 leads gets orange, even after a few minutes.

 I've got nothing on R10L and R10R using two different meters(my Fluke 87V and an old metrix DMM), and turning P2L doesn't change anything.

 Arnaud


----------



## runeight

Can you post any pictures of your board?

 Please check the LV supplies again. Are they really 15V?


----------



## FairyTales

Hope this pic will do.





 Let me know if you need a picture of a specific part of the board.

 LV supplies are as follow

 LV+ 1st pin= 22.91V
 2nd pin= 0V
 3rd pin= 15.05V

 LV- 1st pin= 0V
 2nd pin= -22.8V
 3rd pin= -15.06V

 1st pin is the one on the left, with the same orientation as in the pic.

 Thanks again for helping me out!

 Arnaud


----------



## runeight

This is what we needed. You'll need to strap and solder a wire across jumpers J1 and J2. These are marked on the board as two sets of pads for each jumper with a white line between them.

 Once the buffers are working you can strap J3 to adjust the HV.

 The instructions at Cavalli Audio talk about the setup procedure and which order to connect the jumpers. I'm sure you've read this many times by now, but all you need to do is wire the jumpers and follow the instructions.


----------



## FairyTales

When reading the instructions i was thinking that strapping the jumpers means putting the small plastic pieces over the 6 pins thingy, where you select the voltage, as the one below the HTR logo is marked as 1, i thought it was jumper 1....

 Will do the strapping right now and report back, thanks a lot!


----------



## runeight

Great. Please follow the instructions and do just J1/J2 first to set the buffers and then J3 for the HV.


----------



## FairyTales

I did and everything is working perfectly, all the values are fine now, i won't have time to test it tonight, but will put it to work tomorrow.
	

	
	
		
		

		
		
	


	




 How did your learn so much about electronic? I have other projects that i want to start (a DAC to complete my setup) but with those little issues i had, i realize that learning how things work would be really helpful. I was lucky to have you help me out on this one and wouldn't have figured it by myself

 Thanks a ton for your help, time and patience!

 Arnaud


----------



## runeight

Ah, good news. Let us know how it sounds.


----------



## FairyTales

Hey,

 I've been able to listen to the amp for a few hours and it's been pretty impressive so far, it brings out details in songs i wasn't able to hear with my previous setup (PC as a source on a M-audio 2496 soundcard direct to my AT ATH-A900), bass are nice and tight and guitars are a real joy to listen to. At times you have the feeling the group or instruments are right in front of you, sometimes a tad too much on certain songs but it may be due to the fact that i use closed cans, or poor audio enginering from the disc makers.

 I have a few questions:

 1) I have a slight hum even at low volumes and it becomes really present when i turn the volume knob a little more than half way up(3/4), is it possible to get rid of this or to make it less present? 

 2) Is it possible to implement a source switcher like in the following pics









 3)Would cat6 cables be better between the RCA and amp input than the cable i'm using?





 4) Temperature inside the case is 122°F (50°C) is it ok or should i add ventilation holes on the case?

 5)There is a pretty loud snap (clac?) sound that goes thru the cans when i power down the amp is it normal, or should i remove the jack plug before powering down?

 Arnaud


----------



## eruditass

I have a similar hum, only with lower impedance higher sensitivity phones that does not change with respect to the volume knob and am looking for advice as well. 

 I'm sure you can implement that source switcher if you don't mind your input going through that switch.

 I haven't measured my temperature, but more ventilation holes would never hurt!

 I noticed that snap when powering down, I take it safe and remove the headphones when powering down or up.

 Lastly, any comments on this mod?
http://www.head-fi.org/forums/6171572-post50.html


----------



## runeight

Hate to ask, but have those of you who have hum grounded the SG point to the chassis? And have you grounded the case of your volume pot?

 The snap is the e12 tripping off as the output DC swings away from zero. This trip occurs at about 200mV and should protect the headphones from higher voltages even though they pop off. However, it is safe to remove the headphones before power up or down.


----------



## scompton

I'm finally getting around to setting up my SOHA II. Everything is fine until the final measurements.

 I'm getting the following.

 TB+R: 59.9V
 TB+L: 59.9V

 TPR: 41.4
 TPL: 52.4


----------



## runeight

Check the tail current in the left channel again and check the resistor values too. If all is well there then the tube is probably way out of balance. Have you swapped the tubes L/R yet?


----------



## scompton

The tail current is 399.6 mV on both sides. I'll swap the tubes and check the resistor values tomorrow. I think I'm going to need a better magnifying glass to see the resistor values, or stronger reading glasses. They're easy enough to read off the board, but not on it.

 Edit: Obviously not the tail current, but the voltage across R6R and R6L.

 Edit: I swapped tubes and it didn't follow the tube so I'll check resistor values tomorrow.


----------



## scompton

Well I fried something. Rather than try to read the resistors, I measured them. All of them measured correctly. I had zeners socketed in R4. Thinking they may be bad, I replaced them with the resistors and remeasured everything. I got the similar results, but didn't write them down.

 My wife called so I went to pick her up. After getting back home, I powered back up to take document the measurements. With one probe on TB+L, I touched the other probe to ground and got a spark and a puff of smoke. Now all of the test points in the power supply measure around 30mV.

 Edit: It looks like it's my DMM. I tried to measure the household AC current and it comes up 140mV. I tried to measure a resistor and it flashes between 0 and 500 ohms. I'll have to buy a new one tomorrow.


----------



## runeight

Good luck. Did you possibly have the DMM on the DC amps setting when trying to measure the voltage? If so, maybe it's just the fuse? Grasping at straws.


----------



## scompton

That could be, although I just bought a new DMM from Radio Shack on my way into work. It has a diode test mode so it's worth it anyway.


----------



## pixeljedi

Hi All,

 Noticed in the BOM that C1P, C2P and C5P need to be rated for 105C? Would a cap rated for 85C suffice?

 Thanks!


----------



## regal

Quote:


  Originally Posted by *pixeljedi* /img/forum/go_quote.gif 
_Hi All,

 Noticed in the BOM that C1P, C2P and C5P need to be rated for 105C? Would a cap rated for 85C suffice?

 Thanks!_

 

Depends on the ventalation of the case, Mine run around 60c.


----------



## pixeljedi

Thanks Regal. Hmm... I'd better play it safe and go with the 105C rated ones then, as my case wont be as ventilated as yours.


----------



## jmf

Hi,

 I'm finishing my SOHA II amp. I'm in the setup procedure. I will use 5963 tubes, and have to set the jumpers either to :
 - 12,6V Series,
 - 6,3V parallel.

 If I check the 5963 datasheet, I see that 2 config are possible, the same as above :
 - 12,6V Series,
 - 6,3V parallel.

 Help : what should I do ? Do the two config work for 5963 ?

 Shall I set them to 12,6V ?

 It is my first tube project... and I prefer not to blow them.

 What should I look for experiments with other tubes ?

 Regards.

 JM.


----------



## regal

set it for 12.6


----------



## czegevara

Im not sure if it was in this thread but guys from polish forum Audiostereo.pl are now working on Soha MKIV clone. Here is link for forum thread: SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl 
 and links for MKIII schematics and pcb with some changes to original project:
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_sch.pdf
http://tan.lcf.pl/klon_soha_II/klon_....2_mozaika.pdf
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_top.pdf
http://tan.lcf.pl/klon_soha_II/klon_...2.6.2_elem.pdf
 We all here in Poland want to thank Alex Cavalli for such a great design!
 Peter.


----------



## jmf

Thank's for the info for the 5963. I terminated the setup... and it works !!!!

 First listenings with a USB Monica DAC and AKG701...

 The amp is very clear, precise, quick. Strings are beautiful...

 I do not know if amp and tubes require break in ...

 I'd say that the first listening lacks a bit from flesh on voices and piano...

 I also have RCA 6922 and RSD ECC82. What are the jumpers for those tubes ? Do I need to modify the different pot/currents on the board ?

 Oh, And I have 59,8 V instead of 60V for TB+R and TB+L. Is it Ok or to low (and if too low, how to raise it above 60V) ?

 Best regards and thank's for this project 

 JM


----------



## regal

Quote:


  Originally Posted by *jmf* /img/forum/go_quote.gif 
_I also have RCA 6922 and RSD ECC82. What are the jumpers for those tubes ? Do I need to modify the different pot/currents on the board ?

 JM_

 

6922 = 6.3V
 ECC82= 12.6 V

 This amp really shines with expensive tubes try Amperex 8416, Amperex 6DJ8, or Amperex 12AU7. Also see my post on the Soha tube thread that shows how to get 5.5mA of tail current which really makes this amp shine.

 Good Luck.


----------



## runeight

Quote:


  Originally Posted by *czegevara* /img/forum/go_quote.gif 
_Im not sure if it was in this thread but guys from polish forum Audiostereo.pl are now working on Soha MKIV clone. Here is link for forum thread: SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl 
 and links for MKIII schematics and pcb with some changes to original project:
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_sch.pdf
http://tan.lcf.pl/klon_soha_II/klon_....2_mozaika.pdf
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_top.pdf
http://tan.lcf.pl/klon_soha_II/klon_...2.6.2_elem.pdf
 We all here in Poland want to thank Alex Cavalli for such a great design!
 Peter._

 

You're welcome. 
	

	
	
		
		

		
			





 Do you have any amps built yet?

 Nice to see that the amp has a dedicated following in Poland. I see that you have made some mods. Would you mind making another post or two telling us what you are adding or changing?

 I'd certainly like to know.


----------



## regal

Does anyone know the output impedance of this amp? It seems to synergize well with Grados and I'm wondering if a low output impedance has something to do with it.


----------



## runeight

Zo should be about 1.5R.


----------



## pixeljedi

Quote:


  Originally Posted by *czegevara* /img/forum/go_quote.gif 
_Im not sure if it was in this thread but guys from polish forum Audiostereo.pl are now working on Soha MKIV clone. Here is link for forum thread: SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl 
 and links for MKIII schematics and pcb with some changes to original project:
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_sch.pdf
http://tan.lcf.pl/klon_soha_II/klon_....2_mozaika.pdf
http://tan.lcf.pl/klon_soha_II/klon_soha2_2.6.2_top.pdf
http://tan.lcf.pl/klon_soha_II/klon_...2.6.2_elem.pdf
 We all here in Poland want to thank Alex Cavalli for such a great design!
 Peter._

 

Here's a link to the Google translated version: 
	

	
	
		
		

		
		
	


	



SOHA CLONE MK III - projekt PCB - Do It Yourself - Forum Audio - Audiostereo.pl


----------



## eruditass

What is acceptable for the drop between TB+ and TP for R/L? Above 19v drop?

 I bought my SOHA II here a while ago, went to change tubes, I am getting 15v on both tubes. Changed tubes to the ones that came with it, tested 16v. Did all the other tests before this, everything was in pretty good shape, the worst regulator was off by .2v. 

 Adjust the tail current (set to 2ma)? Leave it alone? I've been listening to the amp for quite a while before I took these measurements.

 Also, my DT880s are pretty quiet but my more sensitive HD25's have a pretty audible noise floor. Is there anything I can do to fix this? It is independent of the pot, which is grounded.

 EDIT: After moving them in and out and switching them and whatnot, one tube is dropping 19v, the other is 15v still - they are ebay tubes, what are the implications of this? Also, when I keep testing these, the relay keeps tripping - is that normal?


----------



## regal

Quote:


  Originally Posted by *DoomzDayz* /img/forum/go_quote.gif 
_What is acceptable for the drop between TB+ and TP for R/L? Above 19v drop?

 I bought my SOHA II here a while ago, went to change tubes, I am getting 15v on both tubes. Changed tubes to the ones that came with it, tested 16v. Did all the other tests before this, everything was in pretty good shape, the worst regulator was off by .2v. 

 Adjust the tail current (set to 2ma)? Leave it alone? I've been listening to the amp for quite a while before I took these measurements.

 Also, my DT880s are pretty quiet but my more sensitive HD25's have a pretty audible noise floor. Is there anything I can do to fix this? It is independent of the pot, which is grounded.

 EDIT: After moving them in and out and switching them and whatnot, one tube is dropping 19v, the other is 15v still - they are ebay tubes, what are the implications of this? Also, when I keep testing these, the relay keeps tripping - is that normal?_

 


 The tubes are struggling to make the tail current at a plat voltage that is in range. Get some new ones.


----------



## pixeljedi

Hey all, For bleeding the caps, what power rating did you guys use for the 10K resistor? All I have is 1/4Watt's kicking around my parts bin - I'm guessing I'll need more than that.


----------



## regal

Quote:


  Originally Posted by *pixeljedi* /img/forum/go_quote.gif 
_Hey all, For bleeding the caps, what power rating did you guys use for the 10K resistor? All I have is 1/4Watt's kicking around my parts bin - I'm guessing I'll need more than that._

 

100V/10k= 10 ma 10 ma*100V= 1W, so 2W would be safest


----------



## pixeljedi

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_100V/10k= 10 ma 10 ma*100V= 1W, so 2W would be safest_

 

thanks!


----------



## rolotube

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_6922 = 6.3V
 ECC82= 12.6 V

 This amp really shines with expensive tubes try Amperex 8416, Amperex 6DJ8, or Amperex 12AU7. Also see my post on the Soha tube thread that shows how to get 5.5mA of tail current which really makes this amp shine.

 Good Luck._

 

regal

 My SOHA II is shining brightly with Mullard CV4003 "boxplate" tubes, but the higher current mod you mention sounds interesting. Could you please point me in the direction of the above mentioned post?

 Thanks.


----------



## nattonrice

http://www.head-fi.org/forums/6228710-post75.html


----------



## regal

My Mullards responded nicely to the additional current.


----------



## regal

Quote:


  Originally Posted by *DoomzDayz* /img/forum/go_quote.gif 
_I have a similar hum, only with lower impedance higher sensitivity phones that does not change with respect to the volume knob and am looking for advice as well. 


http://www.head-fi.org/forums/6171572-post50.html_

 

Did you find a solution? I am curious as I have a similiar problem with a similar amp. A hum that doesn't change with the volume knob would indicate interferance after the tubes IMO? Anyone else have any ideas?


----------



## Killercrush

Hi everyone, I got a simple questions for you guys, is the SOHA II that hard of a build for a beginner DIYer ? Should I start with something like a standalone 2-channel JISBOS to get some soldering/troubleshooting skills ?! ( I'm a student in electronics )


----------



## Killercrush

Quote:


  Originally Posted by *Killercrush* /img/forum/go_quote.gif 
_Hi everyone, I got a simple questions for you guys, is the SOHA II that hard of a build for a beginner DIYer ? Should I start with something like a standalone 2-channel JISBOS to get some soldering/troubleshooting skills ?! ( I'm a student in electronics )_

 

Anyone ?


----------



## runeight

MHO is that it is not a hard build at all. If you put everything in the right place and the tubes are good it will come up to working condition on the first power up.


----------



## regal

Yes its a quick build, use the mouser BOM and make sure you understand the hows & why's of mounting/insulating heatsinks (you need to do this on the Jisbos as well).


----------



## rolotube

Quote:


  Originally Posted by *nattonrice* /img/forum/go_quote.gif 
_http://www.head-fi.org/forums/6228710-post75.html_

 

nattonrice, belated thanks for the pointer, & to regal for the mods. I'm working on these now & will post results shortly.


----------



## rolotube

Quote:


  Originally Posted by *Killercrush* /img/forum/go_quote.gif 
_Anyone ?_

 

My 5 cents worth - the SOHA II isn't any more difficult a build than many other amps but does require extra care with heatsink insulation (as per regal's comments), as well as power up procedure (follow doco on the SOHA website _very carefully_).


----------



## kjetinho

Hi

 I've nearly finished my first build, the SOHA II. I've been testing it for hours, and think it sounds great. One problem thogh. The fuse blows when I turn on the power. Now I'm running it with 630mA fuse instead of 500mA that came with the kit. Is this ok?

 Some picktures:





 Nearly finished board in inner cabinet.




 Which is going into the chassis like this




 Almost finished, awaiting tube sockets for chassis-mounting and volume knob.


----------



## regal

Quote:


  Originally Posted by *kjetinho* /img/forum/go_quote.gif 
_Hi

 I've nearly finished my first build, the SOHA II. I've been testing it for hours, and think it sounds great. One problem thogh. The fuse blows when I turn on the power. Now I'm running it with 630mA fuse instead of 500mA that came with the kit. Is this ok?


 Almost finished, awaiting tube sockets for chassis-mounting and volume knob._

 

Did you use bigger caps anywhere? If not make sure your heatsinks are insulated. It could be an indication of a small short. There have been reports of the ground plane extending too far into the PS rails on the PCB.


----------



## kjetinho

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Did you use bigger caps anywhere? If not make sure your heatsinks are insulated. It could be an indication of a small short. There have been reports of the ground plane extending too far into the PS rails on the PCB._

 

I've used Mundorf ZN 0,22 uF as C1L/R, but it's the same value.

 What should the heatsinks be insulated from? Ground on pcb, or is it something on the regulators? I'm sorry, but I don't understand what the "rails" are.


----------



## pixeljedi

Quote:


  Originally Posted by *kjetinho* /img/forum/go_quote.gif 
_Which is going into the chassis like this




 Almost finished, awaiting tube sockets for chassis-mounting and volume knob._

 

The design is beautiful. Well done!


----------



## kjetinho

Thanks a lot. I think I will wax the birch plywood for better finish, and I might try to build a second wooden part for the cabinet later in a darker harder wood, to see how that will look.


----------



## regal

Quote:


  Originally Posted by *kjetinho* /img/forum/go_quote.gif 
_What should the heatsinks be insulated from? Ground on pcb, or is it something on the regulators? I'm sorry, but I don't understand what the "rails" are._

 

 Where the heatsink is soldered to the board, make sure it is an open circuit with the DMM , also make sure that the ground trace is an open circuit to the regulator output.


 Edit: better explaination on power rails: put your DMM pos lead on the TB+ the neg on grd and it should not beap as a short (less than 10 ohms), do the same with TL+. My first SOHA I board had a tiny trace of the ground plane connecting TL+ with the ground plain causing it to blow fuses.


----------



## kjetinho

Thanks! 

 I didn't know that the heatsinks should be soldered to the board. Could this be the problem? 

 I will check the ground trace when I get the time come sunday evening.


----------



## regal

Quote:


  Originally Posted by *kjetinho* /img/forum/go_quote.gif 
_Thanks! 

 I didn't know that the heatsinks should be soldered to the board. Could this be the problem? 

 I will check the ground trace when I get the time come sunday evening._

 

They don't have to be but that is where you check that the tab is insulated (should be an open circuit between there and the TO-220 device tab.


----------



## Tigerwoodkhorns

I have a few quick questions that I could not find answers to by skimming the threads. 

 About how much are the parts for everything to build a SOHA II?

 I would also like to add a DAC with UBS input to this amp. What plans do you suggest (I'd like to keep it all in one chassis). 

 Thanks.


----------



## kjetinho

200$ for standard version with cabinet and tubes and all parts. Without volume knob


----------



## kjetinho

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Where the heatsink is soldered to the board, make sure it is an open circuit with the DMM , also make sure that the ground trace is an open circuit to the regulator output.


 Edit: better explaination on power rails: put your DMM pos lead on the TB+ the neg on grd and it should not beap as a short (less than 10 ohms), do the same with TL+. My first SOHA I board had a tiny trace of the ground plane connecting TL+ with the ground plain causing it to blow fuses._

 

MY measurings on TB+ and TL+ to ground seems ok, no short. 

 I found a short on the output (right) leg of the H- regulator. Is that wrong?


----------



## regal

Quote:


  Originally Posted by *kjetinho* /img/forum/go_quote.gif 
_MY measurings on TB+ and TL+ to ground seems ok, no short. 

 I found a short on the output (right) leg of the H- regulator. Is that wrong?_

 


 Not right, make sure the LM337 tab is an open circuit with respect to the heatsink mounting tab.


----------



## kjetinho

Ok. Ifound a short on both legs of C5P. Is this damadged, maybe?


----------



## kjetinho

I desoldered the C5P, and measured the regulator and C5P again. No shortage. Must have been a solder bridge I could not see. I put C5P on the print again, and there was no short. Thanks for the advice!


----------



## tubesmuggler

Hey guys I'm just getting started on my build. Quick question: do the BD139 or other PS regulators need heatsink paste applied or will it be OK dry?

 TIA!


----------



## kjetinho

I use paste, and the sinks gets quite hot, but I'm not sure if you have to use it.

 From one thing to another. I now run my amp on a 500mA fuse, everything seems to be ok.


----------



## tubesmuggler

A couple more newb questions:

 What's the point of those 3 LEDs? 

 I found a top panel and front panel drilling template but nothing for the rear panel. Do we just "freestyle" the rear panel?


 TIA!


----------



## kjetinho

The leds are bling. You can light the tubes and have a pover on led, or let it be..
 Yes, freestyle the rear as the sockets are not pcb-mount components,


----------



## tubesmuggler

Thanks kjetinho.

 OK, I'll skip the LED bling. 

 Does anyone have a pic of how they layed out the rear panel when including a Bantam DAC? The recommended placement of the toroidal requires the AC inlet to be in the middle of the panel. My worry is that this will be too close to the DAC and induce hum/noise. Is it worse having the toroidal PT closer to the PCB so there is room for the AC inlet on the far side of the rear panel? That would keep it another 2 inches away from the audio inputs.


----------



## pixeljedi

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_Does anyone have a pic of how they layed out the rear panel when including a Bantam DAC?_

 

I haven't seen a build yet with a Bantam inside, but it wouldn't surprise me if it's been done before. Front panel designer would be my best friend here. Laying it all in there first and then printing out a 1:1 will give you a really nice template to follow for drilling the rear panel (assuming you want to do the drilling yourself).


----------



## regal

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_Thanks kjetinho.

 OK, I'll skip the LED bling. 

 Does anyone have a pic of how they layed out the rear panel when including a Bantam DAC? The recommended placement of the toroidal requires the AC inlet to be in the middle of the panel. My worry is that this will be too close to the DAC and induce hum/noise. Is it worse having the toroidal PT closer to the PCB so there is room for the AC inlet on the far side of the rear panel? That would keep it another 2 inches away from the audio inputs._

 

Try different orientations before you do the drilling, every "case" is different.


----------



## S3TUP

Hi! What is the height of completed board excluding the tubes?
 The radiators are 25mm height (as stated in their datasheet), is that correct?

 I want to fit the SOHA II into 38mm (internal) height case with holes for tubes in the cover... Is that possible?



 Thanks!


----------



## pixeljedi

Quote:


  Originally Posted by *S3TUP* /img/forum/go_quote.gif 
_Hi! What is the height of completed board excluding the tubes?
 The radiators are 25mm height (as stated in their datasheet), is that correct?_

 

Height of completed board is 30mm (or at least that's what mine is).


----------



## tubesmuggler

I'm back... Thanks for your help guys.

 I got the upgraded Neutrik headphone jack and I'm trying to get the front panel layed out right for it. It looks to me like the 3-pin connector I soldered onto the board there will be in the way. I assume I can remove that and then wire the Neutrik directly to the PCB?

 TIA


----------



## pixeljedi

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_I assume I can remove that and then wire the Neutrik directly to the PCB?_

 

Yup, that's totally doable.


----------



## tubesmuggler

Unlike the suggested layout from the Soha II webpage, I think I'm going to mount the toroidal PT closer to the PCB so the Ac inlet and switch can mount on the far side of the rear panel - away from the audio inputs. This also make more room for the Bantam DAC

 Does anyone think the Avel toroid will introduce noise/hum into the PCB if it's that close to the rear of the PCB?

 Thanks.


----------



## pixeljedi

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_Does anyone think the Avel toroid will introduce noise/hum into the PCB if it's that close to the rear of the PCB?_

 

Personally, I'd keep the thing as far away from the PCB as possible. But you could build it the way you want it (before drilling holes), test for hum, if there is, move it back and change your back panel configuration.


----------



## tubesmuggler

Thanks for your input pixeljedi. I think I'll do it the standard way. Then figure out a way to mount the Bantam dac or skip it. I'd rather have a 24bit dac anyway.


----------



## pixeljedi

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_Thanks for your input pixeljedi. I think I'll do it the standard way. Then figure out a way to mount the Bantam dac or skip it. I'd rather have a 24bit dac anyway._

 

Or you could throw the toroid in a separate enclosure and enjoy the extra room


----------



## tubesmuggler

Me again. I noticed the supplied RCA jacks are not the insulated type so they will be grounded at the rear panel. Is there still a need to run a ground from the RCAs to the ground lug on the input terminal strip, or can I just run the L and R channel leads up to the input terminal strip? And then ground from the PCB star to the enclosure.

 Thanks guys.

 Regarding the layout, I'm attempting to move the PT up to the PCB and install the bantam dac. I'll listen for hum and if it's noisy I'll move it back and start drilling the rear panel.


----------



## pixeljedi

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_Me again. I noticed the supplied RCA jacks are not the insulated type so they will be grounded at the rear panel._

 

I would isolate those RCAs from the chassis


----------



## Cloud

hi guys, 

 I need some help troubleshooting my SOHAII


 All was fine in the initial setup till the point where i am supposed to insert my tube. 

 The Left tube did not light up whereas the right tube light up albeit a little dim. 

 Both tubes were then removed and pin 4 measured 12.6V for both whereas pin 5 measured 0V. The voltages were measured with reference to ground. 

 A swap of tube was done and results is the same, i.e left tube did not light up. this cfms that both tube are working fine.

 Tubes used were 12AU7 and in parallel mode for 12.6V

 where should i proceed next for my trouble shooting?


----------



## tubesmuggler

I've started the intial setup procedure. The PS is fine. I've moved on and jumpered J1 and J2. Unfortunately I can't set the Buffers. I'm aiming for 220mV across R10L and R10R, but the lowest I get is 280mV. At start up they measured around 450mV...

 Any idea's what to check?

 TIA!!


----------



## regal

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_I've started the intial setup procedure. The PS is fine. I've moved on and jumpered J1 and J2. Unfortunately I can't set the Buffers. I'm aiming for 220mV across R10L and R10R, but the lowest I get is 280mV. At start up they measured around 450mV...

 Any idea's what to check?

 TIA!!_

 


 Make sure you have all the transistors properly orientated and in the right spots.


----------



## Killercrush

Alright, I got a question here.

 I have around $200 USD to play with to build an amp for my HP2.

 I thought about building a Soha+Jisbos amp but there's probably plenty lonely units now, left unused, maybe a deal will pop up. 
	

	
	
		
		

		
		
	


	




.

 Than I thought about it, could this amount be sufficient to build a Soha II ?!!

 What I want to know precisely is, the average BOM list price for both builts so I can estimate if the extra price difference would be worth it.

 Happy listening


----------



## tubesmuggler

Hey guys. I figured out the problem. I had the R10's installed on the R12 pads and visaversa! Oooops.. That's all fixed up now and the buffers are set correctly.

 Unfortunately I'm on to the next problem. The difference between TB+L and TPL is about 19V. However the TB+R and TPR is WAY off. About 45V difference. I've checked the tail current and both channels are at 2mA (400mV across R6). The TB+ is at 62V. 

 I have swapped the tubes around but the problem remains in the right channel. Does this mean I have a bad BC560C ?

 Thanks for any direction you guys can offer!

 (Geez I can't wait to listen to some music!!)


----------



## tubesmuggler

I've taken some more measurements:

 Pin1 = 36V
 Pin6 = 16V

 Tail current is set and stable. The Rp is 18K as required.

 What's the next step? New BC560C transistors??


----------



## regal

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_I've taken some more measurements:

 Pin1 = 36V
 Pin6 = 16V

 Tail current is set and stable. The Rp is 18K as required.

 What's the next step? New BC560C transistors??_

 

yes


----------



## tubesmuggler

No dice. I've just replaced Q1 and Q2 and the results remain unchanged. 
 Voltage measured across R2 is 300mV, across R3 is 330mV. I believe it should be 220mV and 230mV or so.


----------



## tubesmuggler

Got it! The ZN Mcap was damaged/shorted out. I removed that and everything was pretty much good.

 Unfortunately that leaves me with crappy Solens because I can't get anything else to fit. The Auricap leads are too fat for the pcb holes. How do the Wima's sound compared to Solens? Should I just stick with the Wima's?


----------



## Rooford

Hi,

 Completed my SOHAII build over the weekend after a few errors (E12 regulators were reversed) it sounds great. Kudos to Alex for the design and making it available to the DIY community.

 However, with sensitive earphones (Etymotic) I did get a constant amount of hum despite trying different ground methods. Volume control didn't make any difference to the loudness of it.

 Rotating the transformer worked wonders here, I'd consigned myself to moving the transformer out of the case.

 To complete it I need to find a suitable top and source some isolation washers for the input jacks.

 As the amp runs pretty hot I was thinking of using a perforated top, I found something that might work on Ebay here:
3003 Hex Perforated Aluminum Sheet .032" x 12" x 48" - eBay (item 350270376416 end time Mar-25-10 12:21:42 PDT)

 As the holes are pretty big there's potential for dust build up which I know can be a problem for very high voltages (arcing) although I'm not sure if this applies to the soha.

 While this gives 79% open area there's also a sheet perforated alu at 40% open area.

 Does anyone have an opinion on which would be more suitable, I'm erring on using the 79% to keep things as cool as possible?

 For isolation washers I'll try my local hardware store but I anyone has any other suggestions that would be appreciated too.


----------



## nattonrice

I seem to remember reading that it's recommended to have roughly the equivalent of the board surface area vented.
 I say cut a hole above the board of the same size and fit it with Al perf mesh.


----------



## pixeljedi

Quote:


  Originally Posted by *Rooford* /img/forum/go_quote.gif 
_Does anyone have an opinion on which would be more suitable, I'm erring on using the 79% to keep things as cool as possible?_

 

Do you have holes drilled on the bottom of the chassis? Doing so will create more airflow (bottom to top).


----------



## tubesmuggler

OK, I'm all done....at least for now. Everything checks out and the Bantam DAC fit nicely in the back with some sweet AmpOhm Copper Foil/PIO caps. Hopefully I can start burn-in tomorrow.

 One thing I can't figure out is why access to the B+ trimmer is needed? Why drill the hole to adjust B+?


----------



## regal

Quote:


  Originally Posted by *tubesmuggler* /img/forum/go_quote.gif 
_OK, I'm all done....at least for now. Everything checks out and the Bantam DAC fit nicely in the back with some sweet AmpOhm Copper Foil/PIO caps. Hopefully I can start burn-in tomorrow.

 One thing I can't figure out is why access to the B+ trimmer is needed? Why drill the hole to adjust B+?_

 



 The hole to adjust B+ is just so folks can hear the differences from low/high voltage, if you know the voltage you like it isn't needed.


 How do you like the copper AmpOhm's ? I just ordered a pair.

 .


----------



## tubesmuggler

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_
 How do you like the copper AmpOhm's ? I just ordered a pair.

 ._

 

I'll let you know. I haven't played music through this puppy yet.


----------



## igotyofire

how hard is this to build? i only built tangets cmoy....is this the next DIY project i should do or is there something else i should be looking at, also roughly what is the cost of this project?


----------



## nattonrice

The step up in parts count alone form a cmoy is quite extreme, not to mention the requirement of AC voltages, casing choices ect.

 Something a bit simpler with a fantastic kit (including machined case!) is the millet mini max from beezar.
 It will get you used to a higher parts count with out the added complications of straight ac outta the wall (it uses a wallwart which is supplied in the kit)


----------



## pixeljedi

Quote:


  Originally Posted by *igotyofire* /img/forum/go_quote.gif 
_how hard is this to build? i only built tangets cmoy....is this the next DIY project i should do or is there something else i should be looking at_

 

I would recommend a Mini³ for your next build. You wont have to work with AC mains and you'll get a bit of experience with smd soldering (if you don't already have it). Plus... it sounds amazing.


----------



## regal

Quote:


  Originally Posted by *igotyofire* /img/forum/go_quote.gif 
_how hard is this to build? i only built tangets cmoy....is this the next DIY project i should do or is there something else i should be looking at, also roughly what is the cost of this project?_

 

I would say if you can understand heatsink mounting and the concept you should be OK. Roughly $200 to build. I don't think it is much more difficult than a minimax.


----------



## JamesL

I hope you won't mind revisiting some stuff from the past.
 I was getting help troubleshooting my sohaII back here, but never really finished.

 To recap, every measurement I've taken so far is spot on, except TP (R/L)

 108v @ TB
 -12.8v @TH
 +/-15v @ TL+/-

 65v @ TB+ (r/l)
 64.7v @ TP (r/l)

 41.9v and 42.6v @ pin1 with respect to ground

 I replaced Q1 and Q2 on both channels, and all measurements are identical.

 I've been eager to listen to this amp for a long time, so I really hope I can get this up and playing music =)


----------



## runeight

The measurments seem ok to me. Are you having problems?


----------



## JamesL

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The measurments seem ok to me. Are you having problems?_

 

I haven't tested the amp, but shouldn't there be approximately 19v drop from TB+ (r/l) to TP(r/l)?

 Right now, TP is reading almost the same as TB+.


----------



## capernicus

Ok so I am in the middle of my SOHA II build - found a few errors but am getting ready to start working on the case. I am planning to use a different enclosure than the hammond and not planning to mount the pot to the board. Does anyone have a good way of soldering wires to the pot? Is there some kind of little connector that I could use? Any recommendations?

 Thanks


----------



## JamesL

Quote:


  Originally Posted by *capernicus* /img/forum/go_quote.gif 
_Ok so I am in the middle of my SOHA II build - found a few errors but am getting ready to start working on the case. I am planning to use a different enclosure than the hammond and not planning to mount the pot to the board. Does anyone have a good way of soldering wires to the pot? Is there some kind of little connector that I could use? Any recommendations?

 Thanks_

 

Have you looked at AMB's nifty little e27 boards?
 Otherwise, you can solder right onto the pins and heatshrink over it.


----------



## runeight

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_I haven't tested the amp, but shouldn't there be approximately 19v drop from TB+ (r/l) to TP(r/l)?

 Right now, TP is reading almost the same as TB+._

 

Yes, you're right. Did you use the right transistors??? If so, then one or both Q1/Q2 are still bad.

 You are getting the correct voltage on Pin 1.


----------



## JamesL

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, you're right. Did you use the right transistors??? If so, then one or both Q1/Q2 are still bad.

 You are getting the correct voltage on Pin 1._

 

Both Q1 and Q2 on each channel read BC560C737
Mouser #863-BC560CG

 I'll go ahead and put a few more of those on my next order.
 Are there any other possible reasons, or is the symptom pretty well isolated to that part of the circuit?

 I was checking the resistor values on my board, and I came across a discrepancy. The power supply values on your schematics and parts list are different across the board. Which one is correct?


----------



## runeight

Interesting catch on the parts page. Amazing that it has been wrong for so long, but I think the excel BoM is correct to the schematic.

 I must have done something when editing to damage the parts page. I'll try to fix it soon. Thanks.

 It is hard to see any other cause for this problem. It's either the tube or the transistors assuming that certain things are true.

 1. The tail current is 2mA
 2. Pin 1 is at around 40-45V.
 3. The triodes are reasonably matched
 4. They are both conducting
 5. There are not other unseen problems like solder bridges, etc.

 If the first triode is passing 1mA and if its plate is at 45V and if their cathodes are both connected to a CCS set for 2mA then the second triode has to bias very close to 45V. It has no choice.

 Maybe you could measure the voltages on all the pins of both tubes. Lets see if there is anything else weird going on.


----------



## JamesL

1. I read 400mV across R6(200r)
 2. Pin 1 reads 40.8v
 3. I'm unsure if the triodes are reasonably matched
 4. Again, its hard to be sure
 5. I can't see anything that remotely resembles a solder bridge or bad joint.

 Here are the measurements on each of the pins.

 1, 40.8v
 2, 0v
 3, 2.0v
 4, -12.8v
 5, 0v
 6, 60.6v
 7, 0v
 8, 2.0v
 9, -6.35v

 I love your sig btw =p


----------



## runeight

The voltages are near perfect except for pin 6, the second plate. So it just has to be the transistors. I can't think of any other problem.


----------



## runeight

Meant to ask you what tube you are using. Is it a 12AU7?


----------



## JamesL

Thanks Alex, I'll try replace them again let you know how they turn out.

 Yup. EH 12AU7


----------



## grendel23

I have been running my SOHA II for over a year with no problems.
 I recently did Regal's mod to increase the plate current on my SOHA II and now have an interesting problem.
 I had a small amount of hum/noise with Grados once I had it back up and running. The noise was only present with tubes in place. This noise would last for a couple of minutes, then stop. I checked the usual suspects, grounds, source, xformer and swapped tubes but found nothing to account for it. Once stopped, it would stay gone as long as amp was warm.
 I started probing with a scope and DMM and found that touching a meter lead to the heater circuit, especially at pin 4 of the left tube would make the noise disappear. The meter lead didn't even have to be connected to anything to have this effect. A non conductive probe had no effect, so the pressure of the probe was not flexing the board and causing the change.
 I replaced the heater regulator and C5P and resoldered everything in heater circuit, pulled the tube sockets and resoldered sockets and everything related to input circuit.
 At this point I checked for oscillation and found a 10 MHz signal on the cathode and the output plate of about 100mv. This signal disappears when the noise goes away.
 So it appears the amp is oscillating and the heater circuit is involved in the feedback path. Some characteristic is changing when the amp warms up which kills the oscillation, but I don't know what. I could probably go back to 2ma tail current, but I would prefer to make it behave at 5.5ma. Any ideas?


----------



## regal

Quote:


  Originally Posted by *grendel23* /img/forum/go_quote.gif 
_I have been running my SOHA II for over a year with no problems.
 I recently did Regal's mod to increase the plate current on my SOHA II and now have an interesting problem.
 I had a small amount of hum/noise with Grados once I had it back up and running. The noise was only present with tubes in place. This noise would last for a couple of minutes, then stop. ?_

 

I think it is normal for tubes to oscillate until fuly warmed up, remember this isn't tube rectified so we are flipping a switch and turning on 5.5mA of current thru the tube before it gets any heat. I don't have this issue with mine, my guess is if you try more tubes you will find a pair robust enough to handle without squeaking.


----------



## MrSlim

Would this sort of issue be prevented by having the heater turned on for a little while before the main power is turned on, ala the EHHA? I suppose since the current levels being used in the EHHA is considerably higher, the situation could be much worse, and thus the "pre-heat" requirement of the EHHA..


----------



## regal

Quote:


  Originally Posted by *MrSlim* /img/forum/go_quote.gif 
_Would this sort of issue be prevented by having the heater turned on for a little while before the main power is turned on, ala the EHHA? I suppose since the current levels being used in the EHHA is considerably higher, the situation could be much worse, and thus the "pre-heat" requirement of the EHHA.._

 

Yes but I don't think we are hurting anything here as opposed to the EHHA, I just consider it standard practice to turn on a tube amp at least 30 minutes before use. Never heard a tube amp sound good during the first few minutes after powering up.


----------



## Eokboy

It is mentioned that Antek uses unloaded voltage on its labels. Anyone using Antek transformers? 14.5V (50VA) secondaries at 1.6A load still seems fine.


----------



## JamesL

There was some talk about it on the prototype thread


----------



## Eokboy

Thanks for pointing out holland's post. But with the 2.5x CW multiplier, I should still get a B+ of 98V. 

 I'll get one anyway since its real cheap. 
	

	
	
		
		

		
			





 Edit: Wait, at 14V the LV supply would fall out of regulation.

 I could use their 20-0-20 instead, secondaries drop to 19.7V at 0.9A load. I'll get 137V B+ (still under TL783's 150V max Vin) and use 7818/7918 for the LV supply. Would I need a bigger heatsink? The LM337 needs to drop more voltage.


----------



## regal

Quote:


  Originally Posted by *Eokboy* /img/forum/go_quote.gif 
_Thanks for pointing out holland's post. But with the 2.5x CW multiplier, I should still get a B+ of 98V. 

 I'll get one anyway since its real cheap. 
	

	
	
		
		

		
		
	


	




 Edit: Wait, at 14V the LV supply would fall out of regulation.

 I could use their 20-0-20 instead, secondaries drop to 19.7V at 0.9A load. I'll get 137V B+ (still under TL783's 150V max Vin) and use 7818/7918 for the LV supply. Would I need a bigger heatsink? The LM337 needs to drop more voltage._

 

Just increase the resistor (and wattage) in front of the LM337 to take the addional load off.


----------



## Eokboy

Oh that is what R3P is for. I probably should use 5W 22-33R instead.


----------



## capernicus

please help!

 I have built up my board, the power supply checked out ok - everything looked good there. I strapped in J1 and J2 but wasn't able to read anything across R10L or R10R. Found out that my problem was because I had put Q6(L and R) and Q7(L and R) all in backwards. I ordered new parts, pulled all the Q6 and Q7s out and replaced them all. Powered everything back up again and was able to get the left side to work. I dialed in the current, no problems. Somehow I'm still not able to read anything across R10R. Next I tried replacing all of Q5, Q6, Q7, Q8 on the right side but i'm still not seeing anything across R10R however i am reading -15V with respect to GND at either side of R10R.

 I did double check all of the resistances for R9-R15 all look ok,

 Anyone have an idea of what could be wrong?


----------



## capernicus

OK here is a little more info:

 So, it turns out that on the base of Q5R I am getting -8.6v but on the base of Q5L (the working side) I am getting +6V. In both Q5(L and R) the collector is correctly at +15V. R15R and R16R are the correct parts, and measuring proper resistances.

 I double checked and I used the correct parts, Q5(L and R) both BC550Cs.

 Not sure if this helps... but I am stumped.


----------



## runeight

Please measure all of the pins on the opamps. Let's see what they are saying.


----------



## capernicus

Attachment 27974

 Here are my op amp voltages as looking at them from the top down. (Click on image to view)


----------



## runeight

Are these voltages measured from the bottom of the board or the top?? In either case they are almost all bad voltages. But as soon as you tell where you took the measurments we can start to debug the problem.


----------



## capernicus

These voltages were measured from the top with one probe on the board GND and the other probing each leg of the opamp where they exit the housing of the part.


----------



## tuna320

Having a little problem getting any kind of readout on PB+ test point. I have hooked up everything except the jumpers and am getting a reading of 18.6 volts on the screws holding the yellow and black wires coming into the board. My led on the tubes light up fine so i know some power is getting to the board. However when i measure the PB+ the DMM goes crazy with no steady reading. None of the other test points measure anything. i have not installed pins into the test points, would this help. Also i have installed 100v 100uf caps in C8P, C9P, C11P and C12P and its a little crowded on the board. I see the original parts list show 22uf for C11 and C12, does this matter. Any help would be appreciated, thanks


----------



## Eokboy

Quote:


  Originally Posted by *tuna320* /img/forum/go_quote.gif 
_Having a little problem getting any kind of readout on PB+ test point. I have hooked up everything except the jumpers and am getting a reading of 18.6 volts on the screws holding the yellow and black wires coming into the board. My led on the tubes light up fine so i know some power is getting to the board. However when i measure the PB+ the DMM goes crazy with no steady reading. None of the other test points measure anything. i have not installed pins into the test points, would this help. Also i have installed 100v 100uf caps in C8P, C9P, C11P and C12P and its a little crowded on the board. I see the original parts list show 22uf for C11 and C12, does this matter. Any help would be appreciated, thanks_

 

The parts list on the webpage is way off 
	

	
	
		
		

		
			





 I follow the schematic and excel BoM.


----------



## tuna320

Thanks Eokboy, they both ponit to 100uf for those caps, so i guess thats not the problem.


----------



## FairyTales

Hey there, 
 I have a small problem with my soha II which only appeared recently. I start the amp and after a few minutes of music listening, i hear the click of the relay and the music stops for a few seconds. The same behaviour happens 2 or 3 times during the first 30 minutes of use but not afterward
	

	
	
		
		

		
		
	


	




 I have quickly checked with the meter and nothing seems to be out of range (the amp is working flawlessly except for those random "pause"). 
 What should i check?


----------



## regal

Quote:


  Originally Posted by *FairyTales* /img/forum/go_quote.gif 
_Hey there, 
 I have a small problem with my soha II which only appeared recently. I start the amp and after a few minutes of music listening, i hear the click of the relay and the music stops for a few seconds. The same behaviour happens 2 or 3 times during the first 30 minutes of use but not afterward
	

	
	
		
		

		
		
	


	




 I have quickly checked with the meter and nothing seems to be out of range (the amp is working flawlessly except for those random "pause"). 
 What should i check?_

 

Normal behavior IMO, all tube amps need to warm up 30 minutes for the tubes to settle.


----------



## regal

Quote:


  Originally Posted by *tuna320* /img/forum/go_quote.gif 
_Having a little problem getting any kind of readout on PB+ test point. I have hooked up everything except the jumpers and am getting a reading of 18.6 volts on the screws holding the yellow and black wires coming into the board. My led on the tubes light up fine so i know some power is getting to the board. However when i measure the PB+ the DMM goes crazy with no steady reading. None of the other test points measure anything. i have not installed pins into the test points, would this help. Also i have installed 100v 100uf caps in C8P, C9P, C11P and C12P and its a little crowded on the board. I see the original parts list show 22uf for C11 and C12, does this matter. Any help would be appreciated, thanks_

 

Are you sure your heatsinks are isolated?


----------



## FairyTales

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Normal behavior IMO, all tube amps need to warm up 30 minutes for the tubes to settle._

 

The only problem is that behaviour only appeared recently, and it also happens after the 30 minutes, it's completely random, yesterday for example it did happen more than 2 hours after powering on the amp.

 Could the relay be toasted?


----------



## regal

Quote:


  Originally Posted by *FairyTales* /img/forum/go_quote.gif 
_The only problem is that behaviour only appeared recently, and it also happens after the 30 minutes, it's completely random, yesterday for example it did happen more than 2 hours after powering on the amp.

 Could the relay be toasted?_

 

Try running with your B+ 10V's lower than what its set at now.


----------



## FairyTales

There is a problem, i can't adjust B+, i get 107V on B+ without the tubes, but the P1P trimpot have absolutely no effect on B+


----------



## runeight

Quote:


  Originally Posted by *capernicus* /img/forum/go_quote.gif 
_Attachment 27974

 Here are my op amp voltages as looking at them from the top down. (Click on image to view)_

 

Many apologies for the delay. I am traveling far too much lately.

 Only two of these voltages are correct. Try replacing the opamps to see if you get any better results. If there are still problems we can debug from there.


----------



## runeight

Quote:


  Originally Posted by *FairyTales* /img/forum/go_quote.gif 
_There is a problem, i can't adjust B+, i get 107V on B+ without the tubes, but the P1P trimpot have absolutely no effect on B+ 
	

	
	
		
		

		
		
	


	


_

 

First, verify all of the components in the HV section of the PS. This is R4P, R5P, and R6P. Also measure all three pins on the TL783.

 Your HV regulator is probably bad, but let's do some testing before you replace it.


----------



## runeight

Are there other posted problems that have not been addressed?


----------



## FairyTales

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_First, verify all of the components in the HV section of the PS. This is R4P, R5P, and R6P. Also measure all three pins on the TL783.

 Your HV regulator is probably bad, but let's do some testing before you replace it._

 

Hey Runeight thanks for for the help (again), here are the measurements you asked for.

 R4P: 200 ohms
 R5P: 8.2KOhms
 R6P: 2.73 Kohms

 For the TL783 i have (no quite sure if it is what you're looking for 
	

	
	
		
		

		
		
	


	




)
 1.27vdc between out and adj
 34vdc between in and out
 35vdc between in and adj

 Thanks
 Arnaud


----------



## runeight

OK. Can please measure the regulator pins with respect to ground.


----------



## runeight

Also, R6P is in parallel with at 10k pot. Please take a look at the resistor markings to be sure that R6P is actually 30k and that the pot is 10k.

 Thanks.


----------



## capernicus

Quote:


  Originally Posted by *capernicus* /img/forum/go_quote.gif 
_These voltages were measured from the top with one probe on the board GND and the other probing each leg of the opamp where they exit the housing of the part._

 

Runeight, any ideas on what might be causing my op-amp voltages to be so far out of whack?


----------



## runeight

The first thought is that the opamps are toast. What are you reading for the DC voltage at R10 (on each channel) with respect to ground??


----------



## runeight

Or maybe the opamps are in backwards????


----------



## FairyTales

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Also, R6P is in parallel with at 10k pot. Please take a look at the resistor markings to be sure that R6P is actually 30k and that the pot is 10k.

 Thanks._

 

Values on the regulator are from left to right (to the ground)
 70.3VDC
 71.8VDC
 101.7VDC

 R6P is 30K and the pot is 10K.

 In case you missed my initial question, the amp stops randomly for a few seconds from time to time (your hear the click from the relay), and this behaviour only appeared recently. Regal did suggest to reduce B+ by 10V, which leads to the problem of not being able to adjust B+. Just to sum it up.

 If the regulator is fried could it be the reason why the amps stops from time to time?

 Thanks


----------



## regal

Quote:


  Originally Posted by *FairyTales* /img/forum/go_quote.gif 
_Values on the regulator are from left to right (to the ground)
 70.3VDC
 71.8VDC
 101.7VDC

 R6P is 30K and the pot is 10K.

 In case you missed my initial question, the amp stops randomly for a few seconds from time to time (your hear the click from the relay), and this behaviour only appeared recently. Regal did suggest to reduce B+ by 10V, which leads to the problem of not being able to adjust B+. Just to sum it up.

 If the regulator is fried could it be the reason why the amps stops from time to time?

 Thanks_

 

I can't explain how the ADJ (middle) is higher than the output. You can check the pot by turning it and seeing if the resistance changes just to rule that out, but I think you need a new regulator. 

 Yes without the regulator working correctly the amp will experience voltage drops-outs which will trip the E12.


----------



## JamesL

grr.. so FedEx lost my Mouser package so I'm still waiting on the parts 
	

	
	
		
		

		
		
	


	




 ...murphy's at work, FML


----------



## capernicus

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Or maybe the opamps are in backwards????_

 

so this is an interesting thought, which way is the right way? If I am looking at the board with the parts on top, the power supply in the back and the pot in the front right, I have each of the opamps such that the text on the parts is right side up - is this the right way?

 I suppose since I am about to order new opamps I could go turn them around and see what happens...


----------



## capernicus

Quote:


  Originally Posted by *capernicus* /img/forum/go_quote.gif 
_so this is an interesting thought, which way is the right way? If I am looking at the board with the parts on top, the power supply in the back and the pot in the front right, I have each of the opamps such that the text on the parts is right side up - is this the right way?

 I suppose since I am about to order new opamps I could go turn them around and see what happens..._

 

I did just double check my op amp installation with the part placement drawing and it does appear that I put them in correctly - with the notch on the left side.

 I'll place the order for the new op amps and give an update once I get them in.


----------



## capernicus

I did a little sketch of what I have envisioned for a case while sitting on a bumpy flight into the windy city. 

Attachment 28512

 I am thinking that the case will be a lighter color wood such as a flamed maple and the corners / feet will be something dark like ebony. We will see if I can actually pull it off and still keep the costs relatively in check.

 I'm thinking I will make the top and bottom out of aluminum plate. Somehow I have to work some ventilation in and I have a couple of interesting ideas for that but I'm quite sold yet. 

 Hopefully I can get this baby up and running soon, I'll start working the case in the mean time.


----------



## Eokboy

I will be using perforated sheet metal as the top plate: Amazon.com: Perforated Cold Rolled Steel 12" x 12" Sheet, .060" Thick, 0.078" Round Perfs on 0.125" Centers: Industrial & Scientific

 $7.68 free shipping. Its not stainless steel though, so I'll have to paint it.


----------



## capernicus

Quote:


  Originally Posted by *Eokboy* /img/forum/go_quote.gif 
_I will be using perforated sheet metal as the top plate: Amazon.com: Perforated Cold Rolled Steel 12" x 12" Sheet, .060" Thick, 0.078" Round Perfs on 0.125" Centers: Industrial & Scientific

 $7.68 free shipping. Its not stainless steel though, so I'll have to paint it._

 

Nice find - It looks like they also carry aluminum if you didn't want to paint it


----------



## capernicus

Hey Runeight,

 I replaced the opamps and it looks like the left side is in better shape now. Here are the voltages of the top four pins as looking at the part from above 
 from left to right:

 14.7V, 15.1V, 3.2V, 0V

 and the bottom 4 pins (L-R from above)

 14.7V, 0V, 0V, -15V

 I checked the voltage drop across R10L and was able to dial in the current so I think we have this side back on track.

 I also swapped out the opamp on the right side but i didn't get much change in the voltages and think I still have a problem.

 -13.9V, -14V, -14.5V, 0V

 and the bottom 4 pins

 -13.9V, -13.5V, -13.5V, -15V

 Any ideas of where to look next?


----------



## tuna320

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Are you sure your heatsinks are isolated?_

 

Sorry for the delay, checked the isolation of the heatsinks. The IC's seemed to be installed correctly with mica sheet and the nylon washers. However i am getting a reading of 0.5v on the heatsinks themselves. Still getting the crazy readings on the test points. the LED's still light fine. and am still getting an 18.6V reading on the screws on the yellow and black wires coming into the board from the T1.


----------



## regal

Quote:


  Originally Posted by *tuna320* /img/forum/go_quote.gif 
_Sorry for the delay, checked the isolation of the heatsinks. The IC's seemed to be installed correctly with mica sheet and the nylon washers. However i am getting a reading of 0.5v on the heatsinks themselves. Still getting the crazy readings on the test points. the LED's still light fine. and am still getting an 18.6V reading on the screws on the yellow and black wires coming into the board from the T1._

 

If you are reading 0.5V on the heatsinks they aren't isolated.


----------



## tuna320

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_If you are reading 0.5V on the heatsinks they aren't isolated._

 

thanks for the quick response. Is the problem the heatsinks isolation from the IC or from each other. Any suggestions on how to better isolate the heatsinks.


----------



## regal

Quote:


  Originally Posted by *tuna320* /img/forum/go_quote.gif 
_thanks for the quick response. Is the problem the heatsinks isolation from the IC or from each other. Any suggestions on how to better isolate the heatsinks._

 

Best practice: before soldering the IC attach the heatsink, then use your DMM to make sure it is isolated, if its not try different nylon washers, many aren't long enough. You have to check at a bare metal spot on the heatsink, many are coated and you can't get a reading.


----------



## JamesL

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, you're right. Did you use the right transistors??? If so, then one or both Q1/Q2 are still bad.

 You are getting the correct voltage on Pin 1._

 

Sorry about the delay - 
 The replacement parts got lost in the mail...
 I replaced Q1 and Q2 on both side a second time around, taking all precautions to make sure they didn't get damaged in the process.

 I am getting the same measurements, the difference now being that I get a 3.3v drop on one side. (0.2v on the other)

 I also received a PM this morning - it seems that another head-fi'er is experiencing the same issue.


----------



## Eokboy

My SOHA II lives! 
	

	
	
		
		

		
			





 I accidentally shorted R6 and Q4, smoked the trimpot. Good thing I have a 500R one.

 +/-18V LV supply, 90V B+, 7mA tail current, using BD137 output transistor.


----------



## runeight

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_Sorry about the delay - 
 The replacement parts got lost in the mail...
 I replaced Q1 and Q2 on both side a second time around, taking all precautions to make sure they didn't get damaged in the process.

 I am getting the same measurements, the difference now being that I get a 3.3v drop on one side. (0.2v on the other)

 I also received a PM this morning - it seems that another head-fi'er is experiencing the same issue._

 

Well then, we'll have to be a bit more exhaustive in our debugging. I hate to ask, but if you would kindly measure with respect to ground:

 1. All pins on both tubes.
 2. All test points
 3. All opamp pins

 I will transfer these to a paper schematic and see if I can figure out what gives.


----------



## Alcaudon

Quote:


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

 I also received a PM this morning - it seems that another head-fi'er is experiencing the same issue._

 

The other head-fi'er it's me 
	

	
	
		
		

		
		
	


	




.

 I'm having the same problem as JamesL, and also replaced Q1 and Q2 and obtained the same results.

 I was planning to spend a few hours debugging the amp over the weekend and see if I can solve this by myself.

 Since I'm getting a voltage drop between TB+L and TP of only a few milivolts, I'm assuming (and please correct me if I'm wrong) that almost no current is getting through the tubes). So I believe that there must be something wrong with the CCS, but can't figure out what. 

 If I can find some time before the weekend I will try to document all my results exhaustively and post them here, hopefully we can work this out together 
	

	
	
		
		

		
		
	


	




.

 Thanks!!!!


----------



## Eokboy

It is really easy to have your probes slip and short R6 and Q4 on the left channel. Found out I fried the trimpot when there is no voltage across R6, and the fried trimpot measured in the megaohms.


----------



## Alcaudon

Quote:


  Originally Posted by *Eokboy* /img/forum/go_quote.gif 
_It is really easy to have your probes slip and short R6 and Q4 on the left channel. Found out I fried the trimpot when there is no voltage across R6, and the fried trimpot measured in the megaohms._

 

That's the first thing I'm going to check.

 Many thanks for the advice!!!


----------



## stringgz301

Hi all. I'm trying to source parts for a SOHAII and everyone seems to be out of the MC7815 and MC7915 regulators. Mouser, Newark, and Digikey are all out. Are you guys hording them? Any suggestions where to find some? Are there any alternative parts?

 For example, could I use this instead of the 7815 and this for the 7915?

 Thanks in advance.


----------



## peppe

Can you substitute the MC7815 and MC7915 with a different manufacturer? I did a little research and it seems like a standard part and would be safe to find different manufacturer. 

 I was looking at the MC7815 and MC7915 for the CK2III build and I believe they are back-ordered till September or something crazy like that at mouser.

 Fairchild versions:
LM7815CT Fairchild Semiconductor Linear Regulators - Standard
 and 
LM7915CT Fairchild Semiconductor Switching Converters, Regulators & Controllers


----------



## Eokboy

Quote:


  Originally Posted by *stringgz301* /img/forum/go_quote.gif 
_Hi all. I'm trying to source parts for a SOHAII and everyone seems to be out of the MC7815 and MC7915 regulators. Mouser, Newark, and Digikey are all out. Are you guys hording them? Any suggestions where to find some?

 Thanks in advance._

 

You can get ST or Fairchild's instead if you omit the "MC". Just note that ST 7915 doesn't regulate without any load. Made me thought the one on my SOHA I was faulty during initial testing.


 Observation: I get more noise when I connect earth to ground. There's a ground loop as my USB DAC ground is tied to my LCD monitor's earth.


----------



## regal

Quote:


  Originally Posted by *stringgz301* /img/forum/go_quote.gif 
_Hi all. I'm trying to source parts for a SOHAII and everyone seems to be out of the MC7815 and MC7915 regulators. Mouser, Newark, and Digikey are all out. Are you guys hording them? Any suggestions where to find some? Are there any alternative parts?

 For example, could I use this instead of the 7815 and this for the 7915?

 Thanks in advance._

 

Digi-Key - LM7815CTFS-ND (Manufacturer - LM7815CT)

 and

Digi-Key - NJM7915FA#-ND (Manufacturer - NJM7915FA#)


----------



## stringgz301

Thanks all.

 Regal - the positive one looks good. The negative one you pointed to puts out 1.5A. Should I use that one or this one?


----------



## regal

Quote:


  Originally Posted by *stringgz301* /img/forum/go_quote.gif 
_Thanks all.

 Regal - the positive one looks good. The negative one you pointed to puts out 1.5A. Should I use that one or this one?_

 


 They only put out what the amp pulls, so either one.


----------



## Eokboy

WIP:









 Probably should have gone with a bigger case so I can put the toroid way back. Its enclosure is better at shielding EM than the perforated steel, but it does not cover the bottom of the transformer. Now I have to find some mu metal or something to solve the nasty buzz.


----------



## regal

Quote:


  Originally Posted by *Eokboy* /img/forum/go_quote.gif 
_WIP:


 Probably should have gone with a bigger case so I can put the toroid way back. Its enclosure is better at shielding EM than the perforated steel, but it does not cover the bottom of the transformer. Now I have to find some mu metal or something to solve the nasty buzz._

 

I doubt the transfo is the source of the buzz, mine is as close and silent.


----------



## Eokboy

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_I doubt the transfo is the source of the buzz, mine is as close and silent._

 

It is dead silent in the second picture. Only when I mount it on top (the transformer goes inside the black enclosure in the first pic) it buzzes.


----------



## Alcaudon

Hi all,

 As I mentioned in another post, I'm having the same issues with my build as JamesL has. Basicly everything went perfectly until I got to the final step of the initial setup. I can't get 19 V of difference between TB+L and TPL, just a few milivolts.

 I've tried with different tubes and got the same results (the measurements below are taken with a pair of new GE 5963 and 6,3 V heather). Also I've replaced Q1L, Q1R, Q2L, Q2R and nothing changed.

 I Need to spend some time debugging the amp, but I've taken a few measurements to see if someone has any idea of what's wrong (all the measurements are taken respect ground except voltage drop across R10 and R6):

 TB+ = 108,35 V
 TL- = -15,152 V
 TL+ = 14,873 V
 TH = -12,6 V

 R10L = 215 mV (voltage drop across resistor)
 R10R = 215 mV (voltage drop across resistor)
 TPL = 60,1 V
 TPR = 60 V
 R6L = 394 mV (voltage drop across resistor)
 R6R = 392 mV (voltage drop across resistor)
 TB+L = 60,4 V
 TB+R = 60,3 V

 TPL - TB+L = 236 mV
 TPR - TB+R = 234 mV

 Voltage drop across R4, R3, R2:
 R4L = 20,94 V
 R4R = 21,3 V
 R3L = 203 mV
 R3R = 202,6 mV
 R2L = 228 mV
 R2R = 228 mV

 Tubes (GE 5963 with 6,3 V heather)
 LEFT TUBERIGHT TUBE
 1 = 38,61 V1 = 38,47 V 
 2 = 0 V2 = 0 V
 3 = 3,29 V3 = 3,17 V
 4 = -12,59 V4 = -12,59 V
 5 = 0 V5 = 0 V
 6 = 60,17 V6 = 60,1 V
 7 = 0 V7 = 0 V
 8 = 3,3 V8 = 3,17 V
 9 = -6,27 V9 = -6,23 V

 Both opamps measure exactly the same (pin 1 is the one with the dot): 
 1 = 14,6 V
 2 = 0 V
 3 = 0 V
 4 = -15,15 V
 5 = 14,6 V
 6 = 14,8 V
 7 = 3 V
 8 = 0 V

 And a couple of pics, just in case they might help:











 Thanks everyone!!!!


----------



## GeWa

That's some nice clean soldering you did there.
 Where did you get those blue tube sockets from?

 Regards


----------



## Alcaudon

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_That's some nice clean soldering you did there.
 Where did you get those blue tube sockets from?

 Regards_

 

Thanks GeWa!!!, if only I could make it work 
	

	
	
		
		

		
		
	


	




 Sockets are from partsconnexion: socket_tefcom.html


----------



## regal

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Hi all,

 As I mentioned in another post, I'm having the same issues with my build as JamesL has. Basicly everything went perfectly until I got to the final step of the initial setup. I can't get 19 V of difference between TB+L and TPL, just a few milivolts.

 I've tried with different tubes and got the same results (the measurements below are taken with a pair of new GE 5963 and 6,3 V heather). Also I've replaced Q1L, Q1R, Q2L, Q2R and nothing changed.

 I Need to spend some time debugging the amp, but I've taken a few measurements to see if someone has any idea of what's wrong:

 TB+ = 108,35 V
 TL- = -15,152 V
 TL+ = 14,873 V
 TH = -12,6 V

 R10L = 215 mV
 R10R = 215 mV
 TPL = 60,1 V
 TPR = 60 V
 R6L = 394 mV
 R6R = 392 mV
 TB+L = 60,4 V
 TB+R = 60,3 V

 TPL - TB+L = 236 mV
 TPR - TB+R = 234 mV

 Voltage drop across R4, R3, R2:
 R4L = 20,94 V
 R4R = 21,3 V
 R3L = 203 mV
 R3R = 202,6 mV
 R2L = 228 mV
 R2R = 228 mV

 Tubes (GE 5963 with 6,3 V heather)
 LEFT TUBERIGHT TUBE
 1 = 38,61 V1 = 38,47 V 
 2 = 0 V2 = 0 V
 3 = 3,29 V3 = 3,17 V
 4 = -12,59 V4 = -12,59 V
 5 = 0 V5 = 0 V
 6 = 60,17 V6 = 60,1 V
 7 = 0 V7 = 0 V
 8 = 3,3 V8 = 3,17 V
 9 = -6,27 V9 = -6,23 V

 Both opamps measure exactly the same (pin 1 is the one with the dot): 
 1 = 14,6 V
 2 = 0 V
 3 = 0 V
 4 = -15,15 V
 5 = 14,6 V
 6 = 14,8 V
 7 = 3 V
 8 = 0 V


 Thanks everyone!!!! 
	

	
	
		
		

		
		
	


	


_

 

What is the voltage drop across R6 ?


----------



## Alcaudon

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_What is the voltage drop across R6 ?_

 

It's in the post, sorry, I should have been more specific when posting measurements 
	

	
	
		
		

		
		
	


	




, I've already edited the post.

 R6L = 394 mV (voltage drop across resistor)
 R6R = 392 mV (voltage drop across resistor)


----------



## regal

R6 current draw is good, which is odd.

 Did you check for a short between TPL & TB+L ?

 Also buy some SIP sockets to socket all your Q1-Q4 transistors, I think this is going to be a long road to find the answer, luckily the transistors are cheap buy a handful of each.


 It looks like your Q1 & Q2 transistors are failing, I beleive they are rated for a max 35V drop, something is causing a greater than 35V drop when you power up after first installing them. Need to find out what that something is. You may have a short to the ground plane which I have seen with many PCBs. I would remove all the jumpers and look for a short to ground in all possible places.


----------



## runeight

One problem would be that you are running 12v tubes at 6V. Try setting the heater for 12v and see what happens.

 Edit: Never mind. I see that you say 6.3V but are actually running at 12V. Off to look at the schematics.


----------



## runeight

Yes, I agree, the only possible failure here is Q1/Q2. Are you sure that these are BC560 and not BC550?

 Also, pin 7 of the opamps should be at 15V. Then you have pin 4 at -15V,15V. This is probably a typo. If not, pin 4 should be at -15V on both opamps. But pin 7 not at +15v indicates a problem.

 Before you do anything else remove C1 from both channels. Let's decouple the AC just to remove this as a possible transient startup problem.


----------



## Alcaudon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_One problem would be that you are running 12v tubes at 6V. Try setting the heater for 12v and see what happens.

 Edit: Never mind. I see that you say 6.3V but are actually running at 12V. Off to look at the schematics._

 

Aren't 5963 tubes supposed to work at both heather voltages?

 Anyhow I see what you mean, Instead of the jumpers I'm using this switch: Farnell Export, could it be the cause?


----------



## runeight

No, a switch is ok and the voltage readings at your sockets say 12.6V. 5963 can only work at both heater voltages through connecting the interal triode heaters in series or parallel modes. In the SOHA II all 12V tubes that have this feature are wired in series mode and hence they all must run at 12V.


----------



## stringgz301

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_You're welcome. 
	

	
	
		
		

		
			





 Here's an alternate way to wire the LEDs that might be preferable because it keeps the LED current out of the ground flow. RLED is calculated using 24V instead of 12V.






 Edit: I've changed the drawing slightly to be consistent with common representations of dual LEDs. And, of course, one can always use individual LEDS.

 I've also changed one resistor value. It's not important, but it does serve to equalize the base currents for the alternate version._

 

Is this diagram out of date? Why does it refer to 12V rails when the current design is 15v rails. Did I miss an update somewhere?

 Thanks


----------



## Alcaudon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Yes, I agree, the only possible failure here is Q1/Q2. Are you sure that these are BC560 and not BC550?_

 

Yes, they are BC560, and they where purchased in a differente place and long ago, so it's unlikely that they are faulty too.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Also, pin 7 of the opamps should be at 15V. Then you have pin 4 at -15V,15V. This is probably a typo. If not, pin 4 should be at -15V on both opamps. But pin 7 not at +15v indicates a problem._

 

Mmmm, I made a mistake numbering the pins when passing the measurements to the post 
	

	
	
		
		

		
		
	


	




, this is actually what I'm reading (top view of the opamp):





  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Before you do anything else remove C1 from both channels. Let's decouple the AC just to remove this as a possible transient startup problem._

 

Argh!!! Don't know if I could be able to do it now, my girlfriend is claiming some time for herself 
	

	
	
		
		

		
		
	


	




. I'll try to be quick, luckily I'll be finished before she finishes to dry her hair 
	

	
	
		
		

		
		
	


	




.


----------



## runeight

OK. Opamps are correct. Good luck.


----------



## Alcaudon

Ok, I've removed C1 from both channels, but still 230 mv of voltage drop between TPL and TB+L.

 I have to go now (if I want to keep my masculinity intact jejejeje
	

	
	
		
		

		
		
	


	




). Tomorrow I will spend a few ours more with the amp.

 Many thanks for your help runeight!!!


----------



## runeight

Try another tube, like 6922 running at 6.3V heaters. Just in case these tubes are bad.

 There are only two ways you can have this problem.

 1. The current mirror Q1/Q2 is not working
 2. The right hand triode is not conducting


----------



## runeight

Quote:


  Originally Posted by *stringgz301* /img/forum/go_quote.gif 
_Is this diagram out of date? Why does it refer to 12V rails when the current design is 15v rails. Did I miss an update somewhere?

 Thanks_

 

Diagram is out of date because there is a simpler solution. The 12v rails come from the 12V regulators that step down the 15V rails to get the correct voltage for the e12 relay.


----------



## Alcaudon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Try another tube, like 6922 running at 6.3V heaters. Just in case these tubes are bad.

 There are only two ways you can have this problem.

 1. The current mirror Q1/Q2 is not working
 2. The right hand triode is not conducting_

 

Ok, good news 
	

	
	
		
		

		
		
	


	




 I've replaced the tubes with a pair of new Electro Harmonix 6922 and with the heather selector set to 6,3 V I get white smoke coming from R3P resistor. I've replaced it with a new one and, again, white smoke. 

 The removed resistor still measures 8,2 Ohms, so I believe it's not really fried. Should I get a new resistor with more wattage?

 Is this a new sympton of what's happening or is it unrelated and does not give us any information?


----------



## stringgz301

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Diagram is out of date because there is a simpler solution. The 12v rails come from the 12V regulators that step down the 15V rails to get the correct voltage for the e12 relay._

 

Ummm. Ok. Can I ask what the simpler solution is? Pretty please!


----------



## runeight

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Ok, good news 
	

	
	
		
		

		
		
	


	




 I've replaced the tubes with a pair of new Electro Harmonix 6922 and with the heather selector set to 6,3 V I get white smoke coming from R3P resistor. I've replaced it with a new one and, again, white smoke. 

 The removed resistor still measures 8,2 Ohms, so I believe it's not really fried. Should I get a new resistor with more wattage?

 Is this a new sympton of what's happening or is it unrelated and does not give us any information?_

 

My guess is that your heater switch is wired incorrectly. Please check the jumpering information on the PS schematic on the website. I bet you have wired as though the jumpers are crosswise instead of lengthwise.

 If not, then there is another more serious problem.


----------



## Alcaudon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_My guess is that your heater switch is wired incorrectly. Please check the jumpering information on the PS schematic on the website. I bet you have wired as though the jumpers are crosswise instead of lengthwise.

 If not, then there is another more serious problem._

 

Actually, there's no wiring, it's an ultra-miniature switch (this one:http://www.farnell.com/datasheets/32938.pdf) soldered directly to the board.

 As per the datasheet, it should be ok. The connection diagram is like this:






 Hope that I'm wrong and it's just the switch 
	

	
	
		
		

		
		
	


	




 EDIT: Nevermind, the switch seems to be faulty 
	

	
	
		
		

		
		
	


	




, I've checked and there's continuity between pins that shouldn't be connected.

 I will replace it for a couple of jumpers and report back, hopefully the problem is just that


----------



## Alcaudon

I've replaced the switch for a couple of jumpers. No smoke now with 6,3 V heather selected and 6922 tubes in (though R3P gets pretty hot).

 Unfortunately TPL is still almost the same as TB+L (about 220 mV of difference). Should I try with another set of new BC560?


----------



## runeight

Yes, this is your only choice now, but before you put new transistors in do diode checks on the junctions and make sure that they are really pnp and that they are working.

 R3P will get hot so that your heater regulator doesn't.


----------



## Nevohteeb

Hello everyone.

 first of all, I haven't seen any "introduce yourself" thread on the forum, so if I just missed it, feel free to let me know.

 Having spent a lot of time to read this forum and to learn by heart the Cavalli Audio site
	

	
	
		
		

		
			





 I decided to jump the step and to start the construction of a SOHA II. I already received the PCB from Glass Jar Audio and I should receive the components from mouser by the end of the week. I feel like a kid on Christmas Eve...

 Well, I have a question about the enclosure : I plan to build the same one (well, at least I'll try...) zkool448 did, but on Alex Cavalli's website, I can read this :
  Quote:


 Warning: The SOHA II dissipates a lot of heat. The top plate must be opened so that there is a high amount of ventilation. More than 50% of the area of the top plate over the entire board must be opened for ventilation. 
 

Is zkool448's enclosure ventilated enough?

 Thank you very much for your answer.


----------



## JamesL

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well then, we'll have to be a bit more exhaustive in our debugging. I hate to ask, but if you would kindly measure with respect to ground:

 1. All pins on both tubes.
 2. All test points
 3. All opamp pins

 I will transfer these to a paper schematic and see if I can figure out what gives._

 

I see Alcaudon's been busy with his amp while my internet's been down. I took some measurements and overall they seem to be fairly similar to his measurements. 

 TB+ = 107.8 V
 TL- = -15.05 V
 TL+ = 14.92 V
 TH = -12.88 V

 R10L = 210 mV
 R10R = 211 mV
 TPL = 60.4 V
 TPR = 59.1 V
 TB+L = 60.7 V
 TB+R = 58.4 V

 TBL to TB+L, 295 mV
 TBR to TB+R, 247 mV

 Tube pins - Right, Left
 1, 40.5, 39.6
 2, 0, 0
 3, 2.02, 2.07
 4, -12.87, -12.87
 5, 0, 0 
 6, 59.1, 60.4
 7, 0,0
 8, 2.02 , 2.07
 9, 6.35, 6.48

 opamp pins.. right and left opamps are identical, all except pin 6.
 1, 14.54
 2, 0
 3, 0
 4, -15.08
 5, 0
 6, Right=3.28, Left=3.88
 7, 14.92
 8, 14.55

 I'm using EH 12AU7 tubes with the heater set at 12.6v. Q1L, Q1R and Q2L,Q2R has been replaced twice.


----------



## stringgz301

Quick q: In the SOHAII part list it specifies R5P as 1W but the Mouser part number in the .xls spreadsheet points to is 1/2W. Looks like I ordered the 1/2W one. Will this be an issue?

 Thanks


----------



## Nevohteeb

Quote:


  Originally Posted by *stringgz301* /img/forum/go_quote.gif 
_Quick q: In the SOHAII part list it specifies R5P as 1W but the Mouser part number in the .xls spreadsheet points to is 1/2W. Looks like I ordered the 1/2W one. Will this be an issue?

 Thanks_

 

Damn, you're right. I ordered the 1/2W too...


----------



## JamesL

the datasheet is kind of confusing.. It lists the ccf60 as being rated for "1/2w, 3/4w, 1w" at 70 C
 I interpret it as being rated to 1w given a lower lifespan tolerance.. I'm usually wrong though


----------



## huskydawg9

I've started to build mine, and unfortunately I now notice that the parts list on the Cavalli website does not match the schematic nor the excel spreadsheet. It appears the schematic and excel spreadsheet are correct...which means I need to unsolder R1P,R2P,C6P, and C7P since I sourced the parts from the other parts list...


----------



## Nevohteeb

I'm about to start my build today, and I noticed that some resistances I ordered (from the BoM mouser references) don't match the descriptions. For example, R9L and R9P are supposed to be 820 Ohms but the mouser and digikey references are 825 Ohms.

 Just so I know : do the 5 Ohms make a big difference?


----------



## regal

Quote:


  Originally Posted by *Nevohteeb* /img/forum/go_quote.gif 
_Hello everyone.

 first of all, I haven't seen any "introduce yourself" thread on the forum, so if I just missed it, feel free to let me know.

 Having spent a lot of time to read this forum and to learn by heart the Cavalli Audio site I decided to jump the step and to start the construction of a SOHA II. I already received the PCB from Glass Jar Audio and I should receive the components from mouser by the end of the week. I feel like a kid on Christmas Eve...

 Well, I have a question about the enclosure : I plan to build the same one (well, at least I'll try...) zkool448 did, but on Alex Cavalli's website, I can read this :


 Is zkool448's enclosure ventilated enough?

 Thank you very much for your answer._

 

Do you have a picture of zkool448's enclosure? Most of us with the standard enclosure are using perforated aluminum or copper sheet that can be bought at McMaster Carr or I think even Amazon now. I have P-I-O caps under the board so I driled a few holes around them to keep them cool.


----------



## Nevohteeb

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Do you have a picture of zkool448's enclosure?_

 

Here it is : http://www.head-fi.org/forums/f6/cas...0/#post5646690


----------



## regal

Can't say, certainly doesn't meet Alex's criteria on his website, but it may work only someone with experience with that enclosure would be able to make that call.


----------



## Jaivan

Hello, I have a question about the linear regulators.
 Mouser does not have any in stock of the three I need, but there are alternative except they put out 1.5 Amp instead of the nominal 1 Amp.
 Are these okay to get or should I look elsewhere.


----------



## runeight

They are ok so long as the pinouts are the same.


----------



## Nevohteeb

Hi everyone,

 my SOHA II is alive!





 The tubes are Telefunken 12at7 (I got them for free so...)

 I currently have a buzz noise, but I guess this is a ground/earth problem. I'll check that once my enclosure is finished.

 EDIT : I wired the board ground to the power inlet ground. Result : no more buzz


----------



## Jaivan

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_They are ok so long as the pinouts are the same._

 

Thanks a lot!


----------



## stringgz301

Another SOHA lives!  Just got it up and running and (no surprise) it sounds great.
   
  Quick question.  I built it incorporating Regal's mod from the start.  B+ is set to 85v and the tail current set to 2.75 mA per tube section.  However, the difference between TB+L and TPL is 22.6V (not 19V per the design website).  Is this correct?


----------



## regal

Quote: 





stringgz301 said:


> Another SOHA lives!  Just got it up and running and (no surprise) it sounds great.
> 
> Quick question.  I built it incorporating Regal's mod from the start.  B+ is set to 85v and the tail current set to 2.75 mA per tube section.  However, the difference between TB+L and TPL is 22.6V (not 19V per the design website).  Is this correct?


 


 Mine is about the same,  with this the danger is going _below_ the 19V, a few volt's higher hasn't hurt.   Only disclaimer is that if the voltage drop gets too high the upper tansistors could potentilly overheat.  With the 50% open top rule you should be fine.  I'm guessing that you could lower B+ a few volts and the 22.6V will come down.
   
  You did change R5?  Probably a good idea to measure the plate voltage on each section of the tube to make sure they are close,   if not you would want to adjust R5,  but the tube sections might not be matched perfectly,   I don't think its a thing to worry about too much.    Just make sure to check these voltages whenever you tube role.


----------



## JamesL

progress!
   
  So Alcaudon recommended I try take measurements with the potentiometer connected, and I gave that a shot.
   
  Instead of reading only a few millivolt drop from TB+R/L to TP R/L, I am now reading 11v drop on the left side and 15.6v on the right side.
  That's still not 19v, but its the first change I've gotten in a while.
   
  Something weird is going on though.
  When I measure the TB+R and TPR with respect to ground, I read 60.5V and 43.0V respectively.  However, the reading I get when I put the dmm leads across the two test points is 15.6V.  (i'm using the same scale/range).
  Last time I checked, 60.5 - 43.0 = 17.5, not 15.6.
   
  Same thing happened on the left side.  TB+L and TPL reads 60.6v and 47.0v respectively.  Reading the voltage across the two, I get 11.6v.
  60.6 - 47.0 = 13.6 != 11.6.
   
  I know the multimeter has a finite internal resistance, but should it make that much of a difference?
   
  I measured TL+, TL-, TH, TB+, R10, and R6 as well and the measurements haven't changed from before.


----------



## huskydawg9

Can use a 100volt Wima for C13P?


----------



## ShogunWarPig

Very interested in this project, but I am also having trouble sourcing the linear regulators for the power supply. From the looks of it, I'll be waiting until July 1st if I want to pick them up from either Digikey or Mouser unless I can find a suitable alternative. 
   
  Does anyone have any ideas for alternatives to the linear regulators listed on BOM or is it better just to wait for stocks to be replenished?
   
  Thanks
  -SWP


----------



## regal

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=LM7815CTFS-ND
  (this is 7815)
   
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=497-1477-5-ND
  (this is 7915)
   
   
   
  no need to wait just need to brush up on your digikey searching techniques


----------



## stringgz301

Hum - Argh!!!  My SOHA II build was dead quiet for the first two weeks.  Today, I did some minor surgery and replaced the big power caps (C3P and C4P).  It was quiet initially and then I walked away for an hour or so.  Came back and now have hum in the right channel only.  Definitely some kind of ground noise (when I touch the pot or other parts hum decreases a bit).  Some diagnostics:
   
  - removed the tube -> hum remains
  - disconnected C1R -> hum disappears
   
  Any other debugging ideas?
   
  Thanks in advance.


----------



## regal

Did you swap the tube left to right to see if the problem follows the tube?
   
  Did you discharge all the PS caps before you did this surgery?  If not you may have blown some silicone,  hard to tell which.   But I would replace everything silicone from MPSA42 foward to the tube on the bad channel.


----------



## stringgz301

Changing/removing the tubes doesn't have any impact.  I can start changing silicone, but before I do that, just ran through all the setup measurements and they're 100% normal.  What are the "normal" readings at the individual tube pins?


----------



## stringgz301

OK, more debugging.  I now have hum in both channels.
   
  And riddle me this, Batman: on 6 of the seven heatsinked transistors I have continuity from the heatsink to ground, but on LV+ I don't.  However, I do have continuity from the metal tab of LV+ to ground (but not on the metal tabs of LV- or H-).  What is going on?
   
  Help!


----------



## regal

The way to check your heatsinks for proper insulation is to check for continuity between the heatsink and the metal tab of the TO-220 device.   If there is continuity you need to check your washer, pad, and or screw because you want isolation not continuity.   Do this before you solder the heatsink to the board.   Also make sure you are contacting a bare spot on the heatsink (not coated.)
   
  In your case checking for continuity to ground from the heatsink tells us nothing really.
  The regulators are different,  some the metal tab is ground others not.  Check the datasheets and which pin is has continuity to the tab.  Either way you want isolation.  And all this needs done prior to soldering down the heatsinks,  else troublshooting becomes very difficult.
   
  I tell everyone who wants to build a SOHAII that they need to understand the principles of heatsink isolation as it is the most difficult part of the build.

  
  Quote: 





stringgz301 said:


> OK, more debugging.  I now have hum in both channels.
> 
> And riddle me this, Batman: on 6 of the seven heatsinked transistors I have continuity from the heatsink to ground, but on LV+ I don't.  However, I do have continuity from the metal tab of LV+ to ground (but not on the metal tabs of LV- or H-).  What is going on?
> 
> Help!


----------



## stringgz301

Thanks for the reminder.  I paid a lot of attention to the heatsink isolation during the build and it appears they are working properly.  I guess my hum is coming from elsewhere.  Any thoughts about how to isolate/pinpoint the source?


----------



## huskydawg9

I have my SOHA II together trying to run through the voltage checks.  1st step checks of the power supply were ok, but I get 0mv when trying to set the buffer on either channel.  I have jumpers 1 and 2 connected.  Any ideas as to the most likely reason?
   
  Never mind... I had OPA2134's instead of OPA134's.   All is well.


----------



## stringgz301

Resolved my issues.  Noticed that there was a lot of noise and random e12 trips when touching the volume knob or tapping the pcb.  Reflowed the volume pot and tube socket joints.  Fully up and running again.  Back to enjoying the music. 
   
  Thanks to those who offered help.  If I mess with it again please slap me upside the head.


----------



## regal

You're not alone there.  I have an amp that I continually upgrade and always miss silly things like that.  My wife says if I open the lid one more time she is going to sell it on ebay!
  Quote: 





stringgz301 said:


> If I mess with it again please slap me upside the head.


----------



## Jaivan

Just finished my build but I'm having problems.
  My R3P resistor gets really hot and starts to smoke, I've tried looking for shorts but I do not see any.
  I orginally had LV- and H switched around and it was working okay there, but after I corrected it this happened.
   
  EDIT: Fixed it forgot to put the plastic washer back onto the H reg I guess I should get some rest haha..


----------



## regal

Seems like 90% of the SOHAII issues are heatsink, heatsink, heatsink.
   
  Before you take on this project understand the how,what, where, and why's of heatsink isolation.
   

  
  Quote: 





jaivan said:


> Just finished my build but I'm having problems.
> My R3P resistor gets really hot and starts to smoke, I've tried looking for shorts but I do not see any.
> I orginally had LV- and H switched around and it was working okay there, but after I corrected it this happened.
> 
> EDIT: Fixed it forgot to put the plastic washer back onto the H reg I guess I should get some rest haha..


----------



## particleman14

hey guys so i am running through the initial setup of the soha II but I am only getting 24 volts for tb+ .  what would cause this low reading?  every other test point for the power supply checks out..  thanks!
   
  editr: ok nm I believe I wired the trafo wrong  voltages are cool!  proceeding to the next steps of setup..


----------



## Alcaudon

Hi all,
   
  After a few problems my Soha is finally up and running, but unfortunately I'm not completely happy with it...
   
  At high volumes the e12 trips (I can't go beyond 3/4 of the pot), this is not a problem with low impedance cans such as grados, but makes the amp unusable with a pair of HD650 or with a pair of K1000.
   
  I've tried regal's current mod, but I still get tripping and distorsion with my K1000's (not with my sr325i, though). I'm assuming this is not normal, since other head-fiers have reported good results with k1000 and HD650.
   
  I suspect this could be related to the fact that I can't adjust the idle current of the buffers beyond 94 mA. I reach the end of P2L and P2R at about 205 mV of voldage drop across R10. At first I thought that it was not that important, but now I realise that I should have a wider adjustment range. I've already replaced P2L and P2R pots with same results. I was about to replace Q6 and Q7, but thought that maybe was a good idea to ask before.
   
  Any idea???
   
  Thanks!!!!


----------



## particleman14

Hey i am getting the same results as you alcaudon.  I have done regals current mod using 6DJ8s.  However, when I set the hv to 80v, the dropout is far above 19v(I am getting about 55V on my tpl.  what does this mean?  otherwise the soha works at low volumes.  but I am still unsure about the current settings..


----------



## regal

Quote: 





particleman14 said:


> Hey i am getting the same results as you alcaudon.  I have done regals current mod using 6DJ8s.  However, when I set the hv to 80v, the dropout is far above 19v(I am getting about 55V on my tpl.  what does this mean?  otherwise the soha works at low volumes.  but I am still unsure about the current settings..


 


 Did you change R4?


----------



## particleman14

yes my r4s both read 9kohms.


----------



## regal

BC560's are 35V devices,  so yours must be toast if they are droping 55V's,  how old are your tubes?
  Quote: 





particleman14 said:


> yes my r4s both read 9kohms.


----------



## regal

With K1000's you are pushing the limits of the SOHAII high current,  you can try lowering B+ to see if it helps with the tripping.
  
  Quote: 





alcaudon said:


> Hi all,
> 
> After a few problems my Soha is finally up and running, but unfortunately I'm not completely happy with it...
> 
> ...


----------



## Alcaudon

Quote: 





> With K1000's you are pushing the limits of the SOHAII high current,  you can try lowering B+ to see if it helps with the tripping.


 
   
  Even lowering B+ down to 70V, I still get tripping. I guess that the best that I can do now is to un-mod the amp, make sure that even then I have tripping (right now I'm not sure but as far as I can remember the tripping was there before the mod 
	

	
	
		
		

		
		
	


	




) and see if I can drive k1000's 
   
  At least I can always use it with grados, but that would be a shame because I put a lot of time and effort into this amp thinking that It was going to behave better than my other amps with the k1000's 
	

	
	
		
		

		
		
	


	




.
   
  Anyway, many thanks for your help regal, much appreciated


----------



## particleman14

tubes are brand new matched..  the BD's arent dropping 55v more like 25V.  my B+ is set to 78V  and I get 52V at the tpr and 45V and the tpl and so about 26 V and 33V drop drop.. is this too much?  how can it be reduced?  when I turn down the B+ i still get the same differences.  blown BDs?


----------



## regal

This is a little high for the mod,  especially the -33V.   Measure both plates of that tube and see if there is a big bismatch. 

  
  Quote: 





particleman14 said:


> tubes are brand new matched..  the BD's arent dropping 55v more like 25V.  my B+ is set to 78V  and I get 52V at the tpr and 45V and the tpl and so about 26 V and 33V drop drop.. is this too much?  how can it be reduced?  when I turn down the B+ i still get the same differences.  blown BDs?


----------



## tamu

Sorry but I couldnt find your mod via search Regal. Could you please send me the link?
  I couldnt find it on the Soha II website either.
  ta


----------



## particleman14

ok swapped out one tube that was giving plate voltages of 53 and 45.. now both tubes get about 55V with my left tube there is a 1.5V (54.5v pin1 56v pin 6) difference between plates, is this significant? 
  otherwise my tpl now measures 56V and my tpr is 54.5V  with a B+ of 80V.  is this within range? 
  the switch still goes off when i turn the volume pot almost towards the top.. however if I move the volume pot very slooowly up then I it doesnt trip the relay.  when i turn it up or down too fast it seems to trip. 
  aside from this, the amp is singing, I just want to make sure it will be sustained.. also this thing puts off a ton of heat and I only have the small heatsinks.. should i upgrade?  also heatsink HV as well?
   
  cheers
   
  particleman14


----------



## regal

Yes and turning up B+ will cause trips.  Use the heatsinks mouser in the excell BOM
  Quote: 





particleman14 said:


> ok swapped out one tube that was giving plate voltages of 53 and 45.. now both tubes get about 55V with my left tube there is a 1.5V (54.5v pin1 56v pin 6) difference between plates, is this significant?
> otherwise my tpl now measures 56V and my tpr is 54.5V  with a B+ of 80V.  is this within range?
> the switch still goes off when i turn the volume pot almost towards the top.. however if I move the volume pot very slooowly up then I it doesnt trip the relay.  when i turn it up or down too fast it seems to trip.
> aside from this, the amp is singing, I just want to make sure it will be sustained.. also this thing puts off a ton of heat and I only have the small heatsinks.. should i upgrade?  also heatsink HV as well?
> ...


----------



## regal

Quote: 





tamu said:


> Sorry but I couldnt find your mod via search Regal. Could you please send me the link?
> I couldnt find it on the Soha II website either.
> ta


 


 Its in the SOHAII tube thread


----------



## tamu

ok. I'll have a look. thanks


----------



## particleman14

here is regal's current mod..
   
  Here's how to get the most of your tubes on the SOHA II. The issue I was hearing on some of the 12AU7s and 6DJ8's was a slight weakness or thinness. So here is how you can safely get more current thru the tube:

 1. Set B+ to 85V
 2. Add another 18k ohm resistor on top (parallel) of R4L&R (makes it 9k ohm)
 3. Add another 200 ohm resistor on top (parallel) of R6L&R (makes it 100 ohm)

 Adjust P1L&R to give .550 V across R6L&R

 Check to make sure you have at least a 19V drop across the top CCS (adjust P1 until you do)

 This gives 2.75 mA thru each tube section.
   
   
   
  also I am using the heatsinks in the excel bom, but they are fricken hot too.. but if they are enough then I guess I'll just heatsink HV and be done..


----------



## tamu

yeah found it in the tubes thread, thanks anyway. its very easy to do and easy to turn back to original. will definately try this..
   
  got some components delivered today. I forgot to add one of each pair of trimpots.


----------



## regal

In some homes you have to lower B+ to 75-80V depending on your wall outlet stability.   If your heatsinks are hot,  are you following Alex's rule for ventilation?
  Quote: 





particleman14 said:


> here is regal's current mod..
> 
> Here's how to get the most of your tubes on the SOHA II. The issue I was hearing on some of the 12AU7s and 6DJ8's was a slight weakness or thinness. So here is how you can safely get more current thru the tube:
> 
> ...


----------



## particleman14

I am currently running 80V, I'll try 75 or so.  I am unfamiliar with alex's guidelines..I am using the 1" tall heatsinks.  will this be ok?  or should I grab some 1.5"s or something?
  right now the soha has no cover or anything and there is a fan right next to me. here are some pics  it will be in this box for a while until I case it up..

  I have taped up some caps to test which ones I like best.  FT-3 teflon (big ones), sprague vitaminQ, and obbligato premiums.  getting ready to put in a good listening session this weekend..

  I am starting to think my alps pot is hurting my sound so I'm switching it up with this stepped atten from ebay.. we'll see how it works i'm about to solder it up after this post


----------



## regal

The guidelines for heat are when you case it to use a perforated aluminum cover and some holes in the case under the heatsinks,  you will be fine if you do that.

 For caps my favorites were the vitQ's and AmpOhm C-I-F,  let us know what you prefer.  80V may be fine for your house,  to test plug in an electric heater to the same wall socket,  if it trips the E12 you will have to lower the B+.
  Quote: 





particleman14 said:


> I am currently running 80V, I'll try 75 or so.  I am unfamiliar with alex's guidelines..I am using the 1" tall heatsinks.  will this be ok?  or should I grab some 1.5"s or something?
> right now the soha has no cover or anything and there is a fan right next to me. here are some pics  it will be in this box for a while until I case it up..
> 
> I have taped up some caps to test which ones I like best.  FT-3 teflon (big ones), sprague vitaminQ, and obbligato premiums.  getting ready to put in a good listening session this weekend..
> ...


----------



## thunder

Hi everyone ! As the topic seams to be heat ect... I have a Triad-Magnetics transformer # VPT30 -830 that I would like to use. It is rated 30Vct @ 0.83A  or 15 + 15 @ 1.66A, what mods would be needed to implement using this ? Would the output transistors half to be changed as I believe the Toshiba's are rated for 1.5A ? If so can someone point me in some kind of direction and/or what mods I should do ect...    Thank's


----------



## tamu

nothg you can use it as it is.


----------



## thunder

Tamu, Thank-you thats good news as I had picked 3 of them up for $ 25.00 usd at a local supply no longer selling Triad ect...


----------



## tamu

no problem enjoy the build!


----------



## particleman14

Hey so i am finally finding a use for my temperature tip that came w/ my dmm.  I am reading about 55-60C on all my heatsinks after running for about 8 hours constantly..
  this is actually not too bad when I look in the transistor datasheets which give like 125C-150C as their max rating.... hopefully my numbers won't go up much higher when I case it up.
   
  Also some initial listening tests have narrowed down my capacitor choice to the vitaminQ's and the FT3's.  both have their signature, I am still deciding what I like best with the music I intend to listen to.
   
  I plan on using a[size=x-small]*1*[/size]*[size=x-small]Galaxy Maggiorato GX283 230 x 230 mm[/size]*
  The case only has a small row of slits in the back so I'm not sure if this will be sufficient or not?  
  also my voltage difference between my tpr/tpl and tb+ is 25V instead of the suggested 19V.  will this extra 6V give me trouble down the road? or is it within an acceptable range?  
  gunna do some more listening tests; building amps are fun yay!


----------



## tacitapproval

25v is fine. 19v is a minimum amount of drop.


----------



## particleman14

well did a little building and listening this weekend, but now I have a problem.. I am paying the price for having an open top box sitting all on the same project table..
  apparently a clipped lead managed to get into the soha between the pin 4 and C1 lead on the right side of the board. 
  I started to see smoke coming from the tb+r area (looed like it was coming from the caps, but not sure)  the right side now doesn't work. I coudln't see any visible burn or char on the boards so i'm not sure what component is damaged.
  the tpr measures 80V which is my Hv setting.  so what have I blown? lol.  just when I was ordering a case for it and all too!


----------



## regal

Pin 4 is the heater,  check that the tube is getting proper heater voltage first.
  Quote: 





particleman14 said:


> well did a little building and listening this weekend, but now I have a problem.. I am paying the price for having an open top box sitting all on the same project table..
> apparently a clipped lead managed to get into the soha between the pin 4 and C1 lead on the right side of the board.
> I started to see smoke coming from the tb+r area (looed like it was coming from the caps, but not sure)  the right side now doesn't work. I coudln't see any visible burn or char on the boards so i'm not sure what component is damaged.
> the tpr measures 80V which is my Hv setting.  so what have I blown? lol.  just when I was ordering a case for it and all too!


----------



## particleman14

hmm ok so checking the test points, I am finding that the pin 4 on the right tube is about 10V vs about 5v for the left tube.  also pin 1 gives me about 58v on the right vs about 54v on the left. pin 6 is reading about 79V on the right vs 55V on the left. 
  kind of stumped at this point, damn you clipped leads!


----------



## particleman14

hey guys, so a little update.  I am fiddling with the jumpers to see if the heater settings are correct.  But I am getting some strange voltages.  When jumpered for 6.3 V, I am getting 10.97V on the right (damaged) pin 4  and 5.5V on the left pin 4.  when checking the jumper test point I am reading 5.5V.
  I can only guess that the 6.3V jumper position isn't working properly  and more of the voltage is going to the right heater.  any suggestions? what would cause the uneven distribution of voltage to the heaters?  thanks!


----------



## tamu

this is what Ive done so far.. I ordered a galaxy case so had to remove the caps and wire them to their points. Im thinking of getting the BOM caps for that position if I can find one in correct height. Also Im missing the c2e cap. I cant find it anywhere.. hificollective sells them here but that means I have to pay £4 for 40p cap.(anyone in Uk has any to spare?)
   
  also anyone has any ideas about how to stabilise the c1s?  maybe it might be easier if I wire connect them.?
   
  btw c1s are 2 months older than me


----------



## regal

Quote: 





tamu said:


> also anyone has any ideas about how to stabilise the c1s?  maybe it might be easier if I wire connect them.?
> 
> btw c1s are 2 months older than me


 

 Usually I put them under the board with shrink tubing and eletrical tape to prevent shorts.


----------



## tamu

Im pretty much done.. need to solder the last cap and ready to fire..


----------



## tamu

Got a question: my trafo is getting really hot. like I cannot touch it. its happening when nothg is connected.. it measures fine though.. is it normal? my other transformers never gets this hot..


----------



## tamu

crap my secondary is wrong


----------



## tamu

so I started checking the test points.. I cannot adjust the current (r10) with p2 trimpots. it doesnt move from 300mv on both sides..
  should I just leave it as it is? everything else measures ok.


----------



## tamu

could it be because Im using 4700uf caps in c3&c4?


----------



## regal

If you turned it on with your secondary in series I don't see how much of anything besides the resistors would have survived.


----------



## tamu

Nope I didnt.. it wasnt connected to the board.
   
  any comments on my r10 measurements?


----------



## tamu

so I kept on with the setup. now I am listening to the amp and the sound is somehow distorted but very low too.. Could the problem be the q6 and q7?
   
  Edit:Just checked them and q6 and 7s are reading wrong.. I'll change them and see what happens


----------



## METhomas

Would anyone be willing to give their opinion on how this amp and the DT990 600 sound together. I understand that tubes will have a great influence on this symmetry. I am looking toward an amp for these cans and would prefer diy, also looking at the BIJOU, as I would prefer a tube amp.


----------



## regal

For 600 ohm phones the Bijou is the king,  use 80uf-to 100uf motor run oil output caps and you will have an amp that can't be beat.  The SOHAII is a great amp for Grados but for 600 ohm cans I go to the Bijou as it fits them like a glove.  If you buy a PAR Metals enclosure the Bijou is actually a very easy build,  I found it went together quicker than my SohaII.
  
  Quote: 





methomas said:


> Would anyone be willing to give their opinion on how this amp and the DT990 600 sound together. I understand that tubes will have a great influence on this symmetry. I am looking toward an amp for these cans and would prefer diy, also looking at the BIJOU, as I would prefer a tube amp.


----------



## nullstring

Quote: 





regal said:


> For 600 ohm phones the Bijou is the king,  use 80uf-to 100uf motor run oil output caps and you will have an amp that can't be beat.  The SOHAII is a great amp for Grados but for 600 ohm cans I go to the Bijou as it fits them like a glove.  If you buy a PAR Metals enclosure the Bijou is actually a very easy build,  I found it went together quicker than my SohaII.


 

 Have you tried the bijou with any 600 ohm beyers?


----------



## regal

No they were 600 ohm AKG,  but the amp is famous for mating well to high impedance phones especially with the oil output caps
  Quote: 





nullstring said:


> Have you tried the bijou with any 600 ohm beyers?


----------



## METhomas

Regal,
  Thank you for the information.


----------



## rds

Just wondering about the reference to d1h-d5h in the parts list for the power supply on Cavalli Audio.  I'm guessing this no longer applies to SOHA II, which only seems to use UF4004 diodes in the PS.  Is that right?  Thanks


----------



## TimJo

I believe so...


----------



## runeight

Egads, the parts list is wrong. Please use the excel BoM. It looks correct to me.
   
  The parts list was right at one time so I must have overwritten it with the wrong page. Sorry about that.


----------



## ShogunWarPig

[size=medium]So, I finished my SOHA II recently with no notable hiccups throughout the build. Initial setup goes well. TL+, TL-, TH, and TB+ all measure what they should be and all is good in the world. Then, of course, things get a little weird. 
   
  While testing the buffers, I can not get any voltage readings across either of the R10 resistors. That said, 8-10 seconds after I power it up I hear the relay click on. I proceeded reluctantly, strapping J3 to test the regulator just to see what happens, but ran into trouble there too. For both TB+L and TB+R I get around 110V (the same reading I get for TB+ in the first step) and adjusting P1P does nothing to change this voltage. 
   
  Any ideas? 
   
  Thanks in advance for any help.
   ​[/size]


----------



## runeight

Several questions:
   
  1. What are the rails when the buffers are connected through the jumpers?
  2. Are the O/P transistors in the right orientation?
   
  You should get something if the devices are all correct and you have + and - rails.


----------



## ShogunWarPig

I put all the BD139s on backwards and feel really, really dumb right now. Right side of the board is working fine now (R10R voltage is 200mV), but the left side is all out of whack. Upon power-up, the voltage across R10L spikes up to 1.4V and the transistors on that side get VERY hot very fast. My gut tells me that I damaged the transistors while trying to desolder them from the board. That said, are there any other reasons this could be happening?
   
  Thanks for pointing me in the right direction runeight. 
  
  Quote: 





runeight said:


> Several questions:
> 
> 1. What are the rails when the buffers are connected through the jumpers?
> 2. Are the O/P transistors in the right orientation?
> ...


----------



## runeight

You should replace both BD139s on the bad channel and have some BC550Cs handy in case you need to replace those too.


----------



## ShogunWarPig

[size=medium]Well, I just replaced all the both the BD139s and the BC550Cs on the left side of the board.
   
Good news: I'm now able to properly set the voltage across R10 on both sides and currently have it at 230mV.
Bad news: Relay doesn't click at all now. (Which weirds me out because it was clicking even when I had the BD139 backwards)
I swapped out the opamp because I had an extra TL081 around, but the change yielded no effect. The diodes also check out.
   
Should I raise the voltage on both to produce a higher idle current? Could the e12 transistors be the culprits? 
(replaced the e12 transistors and still no click)
   
Again, thanks for the help.
   
I should also note that I was was only able to get the correct voltage across R10L after changing out the BC550Cs, which I did *after* changing out the BD139s did not work. 
   ​[/size]


----------



## capernicus

Just completed my build, thought I would share the finished photo.
   

   
  I have an interesting problem.  I get a buzz in the left ear that comes on in the phones when the e12 circuit allows the audio through and goes away about 5 minutes later.  I have tried swapping the tubes from side to side as well as using a different pair of tubes and the buzz stays in the left ear in all cases.  I have also tried grounding the volume pot as well as all other components to the star ground with no effect.  When the buzz goes away it is sudden and all at once.  One second it is there and fairly loud in the left ear and the next it is completely gone and quiet.  Also, this noise doesn't change by turning the volume pot up or down.  Any ideas what this could be?
   
  Thanks!


----------



## capernicus

Just finished my build and want to share a photo of the finished result.
   

   
  First off, this thing sounds incredible!  I'm currently running some 8416 tubes in it and love the way this little amp sounds!  Thanks Runeight for the help and for sharing the design.
   
  I do have one issue left unresolved.  On the left side I get a buzz that starts up as soon as the e12 opens up letting audio through to the phones but goes away after about 5 minutes.  I have tried swapping the tubes left to right and tried some different tubes as well with no effect.  The buzz stays in the left ear and is fairly loud.  The buzz goes away very suddenly, sometimes with a slight pop, and then its gone leaving very quiet (noise free) listening.  Also the buzz is not affected by the volume pot.  I do have some 60hz hum in the system but only at very high volume levels so i can live with that.
   
  I've tried grounding all of the various components to the star ground with no effect.  Anyone have any ideas what this could be?


----------



## Alcaudon

Quote: 





capernicus said:


> Just finished my build and want to share a photo of the finished result.
> ...


 
   
  Wow! Very cool capernicus, great job. It's very similar to a design I made for my SOHA II (I'm assuming it's a SOHA II, please correct me if I'm wrong), but finally I ended using a galaxy case (which is in progress right now...) instead of building my own wooden case (just got lazy 
	

	
	
		
		

		
		
	


	




).
   
  Are you having any issues with the heat? I see no ventilation holes in the top, and I'm a bit worried about heat dissipation in my own build, but if you have no problems with your case I should be safe.


----------



## capernicus

Thanks for the kind words, and yes its a SOHA II.  They Jury is still out with regards to heat.  The bottom has a lot of holes in it (maybe 20 .5" diameter holes) and I did make the holes for the tubes up top extra large so there is some good convection cooling going on through the box.  The top and bottom plates are very thick Al, about .2" thick, and get warm to the touch after it has been on for a while but but not so hot that you can't leave your hand there.
   
  I'm contemplating some additional vents on the top of the box but want to do it in a way that looks good.  I can't seem to drill nice clean holes in the Al plate - probably my cheap drill bits and drill press have something to do with it.


----------



## TimJo

Quote: 





capernicus said:


> I'm contemplating some additional vents on the top of the box but want to do it in a way that looks good.  I can't seem to drill nice clean holes in the Al plate - probably my cheap drill bits and drill press have something to do with it.


 

 Maybe you could just drill the holes through the aluminum and not worry too much, and then cover the series of holes with another wooden trim piece parallel to the one over the tube holes. 
	

	
	
		
		

		
		
	


	



   
  It's a sharp looking case.


----------



## capernicus

That was one of the ideas I was considering, I'm going to think about it a little and see what I come up with.  Do i make it square or maybe an oval, or something curvy with the band saw to contrast all of straight and square edges... its fun to think about.  
   
  I am more concerned about the buzz i hear on startup at the moment, not sure what is going on there.
   
  I LOVE the sound of this thing though.  Good luck with your build!


----------



## runeight

Quote: 





shogunwarpig said:


> Well, I just replaced all the both the BD139s and the BC550Cs on the left side of the board.
> 
> Good news: I'm now able to properly set the voltage across R10 on both sides and currently have it at 230mV.
> Bad news: Relay doesn't click at all now. (Which weirds me out because it was clicking even when I had the BD139 backwards)
> ...


 


 Please measure the voltages on all the pins of both channel opamps. Let's see what the amp thinks it's doing.


----------



## runeight

Capernicus, are you still having the buzz?


----------



## Alcaudon

Well....... I feel like there's something wrong with my build, but I really don't know what is it 
	

	
	
		
		

		
			





.
   
  It seems like it can't drive my HD650 correctly (not to mention my K1000). When I turn up the volume to not very high levels (a bit more than half the excursion of the potentiometer), the e12 trips off and on. Besides, even at low listening levels that don't cause the e12 to trip, sometimes the amp sounds somehow distorted.
   
  Everything seems to be ok, except for the voltage drop across R10. With P2L and P2R fully opened, all I can get is 200mv on both sides. I've already changed both potentiometers and changed Q6 and Q7 (replaced BD139 with 2sc2238 with same results). I have also tried with different tubes.
   
  I'm about to start a new one from zero, because I have the feeling that I've messed something and I don't know what 
	

	
	
		
		

		
		
	


	




.
   
  Any ideas will be very helpful.


----------



## capernicus

Quote: 





runeight said:


> Capernicus, are you still having the buzz?


 
   

 [size=medium]Runeight, yes I am, not sure what it is.
   
  As I mentioned, the buzz is only in the left channel and doesn't follow the tubes if I switch them and it only lasts for the first 5 minutes or so immediately after power-up, then it goes away instantaneously.  Turning the volume knob doesn't do anything.
   
  Other than that it works great!
   
  Thanks for the help!​[/size]


----------



## grendel23

I have had a similar buzz in mine for a while. It started after I did the mod to up the tube current, as I reported in this post:  http://www.head-fi.org/forum/thread/374941/soha-ii-builders-thread/1230#post_6500229
  I have just lived with it until now, it goes away after 2-3 minutes and is low level.


----------



## techenvy

beautiful work here


----------



## Cloud

Quote: 





alcaudon said:


> Well....... I feel like there's something wrong with my build, but I really don't know what is it
> 
> 
> 
> ...


 

 hi all, i have similar problem with my SOHA II. It was working fine for half of the year till yesterday when i turned it on, it wont play any music. When i adjust the volume, e12 will trip but no music was played.
   
  swapped tubes but it didnt help anything. Checked my source DC offset, its 0mV. any idea where should i check next?


----------



## runeight

If you would please measure both ends of R10 on both channels with respect to ground. Let's see what the buffers are doing.


----------



## Cloud

did some quick measurements
   
  at TB+ test point, the voltage is 19.5v with respect to ground
   
  pin1 of HV+ measures 19.6v with respect to ground
  pin2 of HV+ measures 16v with respect to groun
   
  The left side of R10L measures 220mv right side measures 2mv
   
  measurements for R10R is the same as R10L
   
  from this, can i say that HV+ need to be replaced?


----------



## runeight

No, not yet. Break jumper J3 and measure TB+ again. If it measures over 100V then it is probably the regulator. If it still measures low then the voltage doubler in the PS is failing.


----------



## Cloud

after breaking J3, the voltage measures 22.4v at TB+


----------



## runeight

Hmmm. Then something in the voltage doubler section is failing. First question is, have you changed your transformer wiring at all? Do you have the CT correct on the two windings? I know this is a ridiculous question now, but I have to ask. Can you please describe how the secondaries are wired to the power terminal block.
   
  This will be hard to diagnose if the transformer is wired correctly.
   
  Check all the caps and diodes in the doubler. This would be C8P through C12P and D7P through D12P. Make sure these are all in the right orientation for polarity. Diodes are cathode strip away from the board.
   
  Did TB+ at one time actually measure correctly?
   
  We'll figure this out eventually.


----------



## Cloud

the amp was working wonderfully for half a year till few days ago. 
   
  i noticed that the transformer was humming when the amp was turned on. i dont remember that happening till recently
   
  the secondary winding pairs, red black, yellow orange are wired as follows
   
  red to 15
  orange to 15
  black and yellow are connected together to 0
   
  the transformer output is giving 17v when its rated 15v, 1A. should i be concern with this?


----------



## regal

Quote: 





cloud said:


> the transformer output is giving 17v when its rated 15v, 1A. should i be concern with this?


 

 That should be normal.  
   
  I would would check all the doubler caps for continuity across their poles,  electrolytics tend to fail if the amp is too hot inside they should test as an open circuit if not, it(they) will need replaced.  Did you follow the 50% open "rule" ?
  Also if you have a diode test on your dmm you can check the rectifiers.


----------



## Cloud

would you mind to elaborate more on the 50% open rule?


----------



## Cloud

when i test the electrolytic caps for continuity with my dmm, it gives a short interval of beep, after which, there is no more beep sound. is this normal for caps?


----------



## regal

Quote: 





cloud said:


> when i test the electrolytic caps for continuity with my dmm, it gives a short interval of beep, after which, there is no more beep sound. is this normal for caps?


 


 Thats normal, they draw current till their capacitance is filled.  Do you have a capacitance meter?


----------



## Cloud

i dont have a capacitance meter. the physical of the caps seems okie. no bloats no leaks.
  i will check through the diodes when i get another dmm later


----------



## Cloud

I have checked through the diodes, they seem fine according to my DMM. Where shall i check next?


----------



## runeight

I really hate to ask this, but remove C12P and put another cap in temporarily. Needs to be at least 160V, but can be more for testing. Does this fix the problem?


----------



## Cloud

do i need to get the same capacitance as previous C12P?


----------



## runeight

anything close


----------



## Cloud

the previous C12P supplied by Jeff from GJA was 100uF 160V. i changed it to 22uF 450V. TB+ is still 22V after cutting J3


----------



## runeight

Hmm. With the 22u cap in place measure the DC across C8P, C9P, C10P, C11P.


----------



## Cloud

C8 -> 0.43V
  C9 -> 0.31V
  C10 -> 0.839V
  C11 -> 0.64V


----------



## runeight

Really bad numbers. Two of these voltages should be about 45V and the other two about twice that. 
	

	
	
		
		

		
			




   
  Are you sure about them?
   
  Measure the AC between the negative terminals of C8P and C9P. This should be 30VAC. If it's not then the multiplier is not getting the full transformer secondary voltage.
   
  If it is, then I don't know. Either something is wrong on the board (open trace??) or one or more of the components in the mulitiplier section i is(are) bad. To get the readings you're getting nearly all of them have to be bad.

 But for all of the capacitor voltages to be this low says that there is a global failure.
   
  On the transformer, to create the CT you have joined together one lead that has no black dot and one lead that has a black dot?


----------



## Cloud

At power input to the board it measures 15V at 15-0-15 input point. however it measures 3V between negative legs of C8P and C9P. Adding to the fact that i have been hearing occasionally cracking sound coming from the trans, i think the transformer is dead. I will replace it and i hope it should be ok after which.


----------



## runeight

IF the transformer measures 15-0-15 at the power terminal block, then it may not necessarily be bad.
   
  Sorry for being very particular about this, but I'd like to not cause you to waste time or money. 
	

	
	
		
		

		
		
	


	



   
  Did you measure that AC or DC voltage between the caps? What you want to measure is AC and this should be identical to the full secondary of the transformer, or 30VAC.
   
  If you get 30VAC at the inlet but only 3VAC between the caps then there must be an open trace between the inlet and the caps.


----------



## Cloud

I will check again when i get back home. The amp was working very well for past 6 months. It just stopped working last week. Can we rule out the possibility of open trace? Could the transformer be failing such that it does not provide enough current for the devices and thus the voltage drop ? Thanks for all the help Alex. I appreciate it alot


----------



## runeight

Possible, yes. Is the transformer spec the same as in the excel BoM?? If so, it should be more than big enough to handle the amp's requirements. It is unusual for a transformer to die if it is operating within spec, hence my puzzlement. Maybe there is something else wrong that caused it to croak?
   
  Even the transformer were too small and was just being pulled down by the current drain, it wouldn't be showing voltages that are this low. So, I am wondering what the hey is happening.


----------



## Cloud

i will go back and check.  i got a nudging feeling i got the wrong VA for the transformer. I might have gotten 15VA thus for each of the secondary its only 500mA. if thats the case, i dont know what else to say but sorry x 10 in having my carelessness for wasting your and regal's time in helping me to troubleshoot.


----------



## runeight

If that's the case, no apologies at all are necessary. I'd just be happy that you can get the amp back working again with a newer better transformer.


----------



## Cloud

turn out that the transformer was as spec. I removed all the wiring and reconnected them and TB+ was back to 100V+. good news!
   
  however, another problem surfaced. e12 keeps turning on and off, on and off in a cyclic pattern. When its on, there is alot of distortion
   
  Difference between TB+L and TPL and TPR and TB+R is around 24V
   
  R10L and R10R measures 220mv across
   
  Changed a pair of tubes, no difference.
   
  Where should i look into for the new problem?


----------



## Jaivan

So I've been using this amp for some time now and it's great, but I've always wondered what is it's max output using 12AU7's?
  How would I go about measuring this this?


----------



## egotrip

Just recently found this awesome amp, and I want to give it a try.
  I am new to head-fi, and want a good starter amp. I love the idea of a DIY project. So this is right up my alley.
  I have read the entire thread, but have overlooked some crucial informasion by all the reading.
  Do the kit from Glass Jar Audio come with a 110vac or 220vac transformer?
  I have contacted Glass Jar Audio trough their website, but haven't recieved any answer yet unfortenatly.
   
  Looked for the parts on the BOM, and not all of the parts are avaiable from one place, witch is a drawback, since I live over here in Norway, where this kind of parts is hard to find, and postal handling is slow. Therefore getting all the parts from one place, as a kit, so i know i got all the parts, and haven't overlooked some parts, would be great.  (sorry about the poor english, and some long sentences)


----------



## capernicus

Quote: 





egotrip said:


> Just recently found this awesome amp, and I want to give it a try.
> I am new to head-fi, and want a good starter amp. I love the idea of a DIY project. So this is right up my alley.
> I have read the entire thread, but have overlooked some crucial informasion by all the reading.
> Do the kit from Glass Jar Audio come with a 110vac or 220vac transformer?
> ...


 

 You should be able to get the entire kit from Glass Jar Audio - aka Jeff Rossel - with everything you need to build the whole kit.  He will give you an excel order form will all of the kitted parts on it.  If you decide like I did to build your own enclosure or would like better caps or whatever then you can elect to leave some parts out or buy extras of parts as well.  I bought the kit from Glass Jar but due to my design I ended up having to get a few more parts to make it all work the way I wanted to.  Be patient and I'm sure Jeff will get back with you.  If not, e-mail him again.  Best of luck!


----------



## egotrip

Quote: 





capernicus said:


> You should be able to get the entire kit from Glass Jar Audio - aka Jeff Rossel - with everything you need to build the whole kit.  He will give you an excel order form will all of the kitted parts on it.  If you decide like I did to build your own enclosure or would like better caps or whatever then you can elect to leave some parts out or buy extras of parts as well.  I bought the kit from Glass Jar but due to my design I ended up having to get a few more parts to make it all work the way I wanted to.  Be patient and I'm sure Jeff will get back with you.  If not, e-mail him again.  Best of luck!


 


  I just recieved an e-mail from jeff. just as you described, an excel orderform, neatly arranged.
  I also got an answer to my question of the transformer primary voltage.

```
The Transformer is dual primary so it will work for either voltage.
```
  My order will be placed in a near future


----------



## jjazzyj

So I've been using the SOHA II for a while now and I've noticed a problem creeping up. After about a year, when listening to the amp with increasing frequency I get a crackling noise in one channel (usually left channel) then the E12 kicks in. At first it seemed that it was due to me having the tube voltage set to 100v. I changed it back to 60v and it seemed that the problem went away, but now it is back. I've tested the amp and the only thing that is weird and has been weird since I built the amp is the difference between TB+R and TPR is 15V instead of 19V. TB+L and TBL measure 19V. The tail current is set correctly. I've tried a number of tubes as well. 6N2P, GE 5963, Sylvania 5963, Sylvania 5814A, CBS Hytron 5814A. I get the same problem with all.  I've already checked for shorts and cold solder joints and there's nothing obvious.
   
  Anyone have any thoughts on where to start troubleshooting?


----------



## Avro_Arrow

If you mean by "kicks in" that the E12 is muting, then the relay contacts are bad.
  If you mean it has un-muted then the problem is likely in the input circuit.
  The E12 shorts out the input when it's muting and releases the short when un-muted.
  The problem is not likely to be after the tube as it would be there weather the
  circuit was muted or not...
   
  Good Luck!


----------



## jjazzyj

What I mean by 'kicks in' is that I hear crackling and the E12 mutes. Then a few random seconds later it un-mutes, then some random time later more static/crackling and the E12 mutes again.
  
  Quote: 





avro_arrow said:


> If you mean by "kicks in" that the E12 is muting, then the relay contacts are bad.
> If you mean it has un-muted then the problem is likely in the input circuit.
> The E12 shorts out the input when it's muting and releases the short when un-muted.
> The problem is not likely to be after the tube as it would be there weather the
> ...


----------



## Avro_Arrow

In that case I would be looking at the output stage and servo.
  The DC offset protection of the E12 is probably kicking in.
  Can you monitor the output with voltmeter and see if you are
  getting excess offset?


----------



## jjazzyj

I will once I have the chance. I'm guessing at this point that Q1, Q2 for the right channel will need to be replaced. This is based on prior conversations in this thread. My first step should be to resolve the voltage difference issue that I described earlier. Then go from there I think. What are you thoughts?
  
  Quote: 





avro_arrow said:


> In that case I would be looking at the output stage and servo.
> The DC offset protection of the E12 is probably kicking in.
> Can you monitor the output with voltmeter and see if you are
> getting excess offset?


----------



## egotrip

I have finally ordered myself a Soha II kit.
  Just waiting for Jeff to process the orderform, pack and ship it.
  To bad International shipping is slow....


----------



## egotrip

Anyone knows the diam.. on the shaft of the alps pot (6,3mm)?
  and where to find powerswitch to use, I am looking for a on/off rotary switch w/same shaft diam.
  This for use with idetical knobs.


----------



## regal

Quote: 





egotrip said:


> Anyone knows the diam.. on the shaft of the alps pot (6,3mm)?
> and where to find powerswitch to use, I am looking for a on/off rotary switch w/same shaft diam.
> This for use with idetical knobs.


 


 6mm


----------



## stixx

Quote: 





> and where to find powerswitch to use, I am looking for a on/off rotary switch w/same shaft diam.
> This for use with idetical knobs.


 
   
  Have you searched the usual sources... like RS components, Reichelt, Conrad (all in Germany)?
  Don't know about shipping to Norway, but it should be cheaper than ordering from the US for a small
  number of parts.
   
  I'm getting most of my stuff from RS Components ...


----------



## egotrip

i am not sure of what i should search for.
  I was thinking of cutting the power for ether the 220 before the torodal, or the ground after the torodal and having a main powerswitch in the back.
   
  any ideas of witch would be best?


----------



## stixx

Always switch power on and off before the transformer... there are nice IEC power inlet modules
  like this one ->  http://de.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3521819


----------



## egotrip

edit


----------



## egotrip

Waiting for my kit to be shipped from Glass jar Audio.
  I am looking forward to build this amp.


----------



## egotrip

Still waiting for my kit to be ready for shipping.
  3.rd week of waiting. And no answers from Jeff.
  Guess he is really backed up.


----------



## egotrip

Waiting for my kit. Jeff shipped it today.


----------



## viking87

Hey everyone,
   
  First I want to say thank you to runeight for the hard work designing this amp and glassjar for the kit! I just got the amp working yesterday and it sounds great!
   
  Unfortunately, I do have an issue though. I am getting an annoying sound when the amp is on and I turn the volume knob or tap the tubes, or even move my hand across the desk that the amp is sitting on! Otherwise, the amp is very silent until I move lol, and its a little bit annoying which is unfortunate. I did some searching and while I couldn't find much useful, I think the term I'm describing is that the tubes are very "mircophonic." This is the standard kit from glassjar, same tubes 12au7, one says Bechman on it and the other RCA electron. When I remove the tubes and turn the amp on, I cannot hear this effect, but I do not know if that means anything. As far as a "hum" or "hiss" noise, the amp only does that very faintly at max volume (with the tubes in again) but that is being really nitpicky as I'll never get anywhere close to that volume with the headphones I have now with music playing, and even then its barely audible. This "microphonic" effect however is loud, and its a bit worse in the left channel.
   
  Did I screw something up? Or is this a characteristic of the tubes? Thanks all!


----------



## stringgz301

Do you have it cased up?  A lot of times these noises go away once it is.


----------



## viking87

That's a good point, no its not cased up yet. It's sitting in the standard hammond case with the top and back plate removed. I just wanted to get it fired up and worry about nice case work later  
   
  If it was a more subtle noise or one that changes with volume I'd suspect that it would be some ground issue or casing issue, but this is so prominent that I don't think thats it (but what do I know lol I'm very much a beginner!).
   
  It would be nice if it would go away over time! Wait and see I guess. Also if I had to pinpoint the tubes I'd say the Beckman one would be the trouble maker because it was in the left slot. The sound comes through both channel but is louder in the left, and tapping the right and left tubes it seems like the left one rings more if that makes sense lol.


----------



## holland

Quote: 





viking87 said:


> That's a good point, no its not cased up yet. It's sitting in the standard hammond case with the top and back plate removed. I just wanted to get it fired up and worry about nice case work later
> 
> If it was a more subtle noise or one that changes with volume I'd suspect that it would be some ground issue or casing issue, but this is so prominent that I don't think thats it (but what do I know lol I'm very much a beginner!).
> 
> It would be nice if it would go away over time! Wait and see I guess. Also if I had to pinpoint the tubes I'd say the Beckman one would be the trouble maker because it was in the left slot. The sound comes through both channel but is louder in the left, and tapping the right and left tubes it seems like the left one rings more if that makes sense lol.


 


  Some pictures may help.  It could be your wiring acting like an antennae.  It's hard to say.  Mine doesn't make noises when it's open, at least not to that degree.  One thing that does help is to make sure your chassis is grounded.  Coincidentally, my SOHA II proto is acting up (hiss on right channel and e12 firing off) and I have the top off on my desk and I'm in the middle of probing.  The sad part is I forgot what I'm looking at (part location) as the proto is a bit different than the final.


----------



## viking87

Thanks Holland. I'll try to put up some pictures up tonight when I get home. Though my wiring isn't pretty right now, I have a hard time believeing that's the source. If its acting like an antenna, wouldn't turning up the pot increase the noise? Also wouldn't it be kind of constant? The noise I am hearing is more like a physical noise amplified through the headphones. What I mean by that is when I touch the pot or move the pot to its stop I can hear it hit the stop. I can hear the tapping of the tubes through the headphone. This is why I really think its the tubes because they are the only things that I think can somehow turn these vibrations into an electrical signal that goes to my headphones? Again when I sit very still and don't change the volume, the amp is very nicely quiet lol.
   
  Hopefully I've done a decent job explaining what I hear, my guesses as to why are just that - guesses. I really don't know much about the inner workings of this or any amp! lol


----------



## holland

Quote: 





viking87 said:


> Thanks Holland. I'll try to put up some pictures up tonight when I get home. Though my wiring isn't pretty right now, I have a hard time believeing that's the source. If its acting like an antenna, wouldn't turning up the pot increase the noise? Also wouldn't it be kind of constant? The noise I am hearing is more like a physical noise amplified through the headphones. What I mean by that is when I touch the pot or move the pot to its stop I can hear it hit the stop. I can hear the tapping of the tubes through the headphone. This is why I really think its the tubes because they are the only things that I think can somehow turn these vibrations into an electrical signal that goes to my headphones? Again when I sit very still and don't change the volume, the amp is very nicely quiet lol.
> 
> Hopefully I've done a decent job explaining what I hear, my guesses as to why are just that - guesses. I really don't know much about the inner workings of this or any amp! lol


 

 Oh, that type of noise!  Noise from poor wiring can be affected by the pot or not.  It depends which section is being impacted.  I thought when you said you move your hands around you pick up noise, that could be wiring issues.  When I was a kid, I built a digital counter, a millisecond timer, and the wiring was bad.  When I waved my hand over the circuit, the clock jumped around.  Thus I rebuilt it with tight wiring, laid flat, and twisted if necessary.  It was just a breadboard experiment, but I learned alot from that.  Decades later, it still sticks with me.
   
  Your type of noise may be helped by using "those pointy feet" thingies.  I am drawing a blank on the name right now.  Different tubes may help too.  I have a stepped attenuator on mine and when I click it, I hear it, but it's not horrible.  I also have "those pointy feet" thingies due to microphonics and also the need to vent underneath.


----------



## viking87

Lol, I don't know what you mean by those "pointy feet thingies" but I'm sure its the tubes that are the problem. Or tube I should say. I just got home to play around with it and I switched the tubes from Left to Right, and now the sound is primarily in the right channel. It is quite annoying so I am buying a new set of tubes, although I think the RCA one is fine, its the Beckman that is the real trouble maker. If there is something else I am doing wrong, please let me know but I think it's just this funky tube!
   
  Thanks for your help holland!
   
  On another note, any tube recommendations? I know there is a separate thread and I should just try them out on my own but if your willing to throw me a recommendation I'll gladly accept! lol. I'm getting started earlier on the whole tube rolling thing than I had planned.  Bass seems a little recessed, but the highs seem to sparkle with what I have now. My description of audio sounds are pretty bad lol, I just like good music!


----------



## holland

Quote: 





viking87 said:


> Lol, I don't know what you mean by those "pointy feet thingies" but I'm sure its the tubes that are the problem. Or tube I should say. I just got home to play around with it and I switched the tubes from Left to Right, and now the sound is primarily in the right channel. It is quite annoying so I am buying a new set of tubes, although I think the RCA one is fine, its the Beckman that is the real trouble maker. If there is something else I am doing wrong, please let me know but I think it's just this funky tube!
> 
> Thanks for your help holland!
> 
> On another note, any tube recommendations? I know there is a separate thread and I should just try them out on my own but if your willing to throw me a recommendation I'll gladly accept! lol. I'm getting started earlier on the whole tube rolling thing than I had planned.  Bass seems a little recessed, but the highs seem to sparkle with what I have now. My description of audio sounds are pretty bad lol, I just like good music!


 


  You're very welcome.  It's been a long time since I've been on these forums, over a year I think.  It's good to see these projects still rolling.
   
  "pointy feet thingies", lol.  They are just spiked feet for amps and such.  I can't remember where I got mine.  It's been over 2 years since I built this amp!
   
  I am using the Tungsram ECC82.  I like it very much.  It's a bit different than the more common 12AU7s.  I also very much like the Amperex 8416 tubes.


----------



## viking87

Well welcome back! Thanks again for your help! I'll look into those tubes, and pointy feet thingies 
  
  Quote: 





holland said:


> You're very welcome.  It's been a long time since I've been on these forums, over a year I think.  It's good to see these projects still rolling.
> 
> "pointy feet thingies", lol.  They are just spiked feet for amps and such.  I can't remember where I got mine.  It's been over 2 years since I built this amp!
> 
> I am using the Tungsram ECC82.  I like it very much.  It's a bit different than the more common 12AU7s.  I also very much like the Amperex 8416 tubes.


----------



## egotrip

This can't be right?
  C3P and C4P gets really hot, really fast.
  And they has expanded on the top.

  I don't dare to reconnect it before I know it is right.
   
   
  edit: oh crap. i tried again, and this time magic smoke from lv-
   
  please help me 
   
  Could it be that i have reversed the P2L:R P1L:R and P1P s?
  could this have done this?


----------



## holland

Quote: 





egotrip said:


> Could it be that i have reversed the P2L:R P1L:R and P1P s?
> could this have done this?


 


  Yes.  Your caps are dead.  You need to order new ones after you fix the diodes.  It's a common mistake, so no worries.  While you're checking your diodes, double check *all* of them.


----------



## egotrip

Quote: 





holland said:


> Quote:
> 
> 
> 
> ...


 


  I thougth P2-1 L:R where resistors. oh well.. then a potmeter is as a diode then?.
  all other diodes and caps are installed correctly. and i need a HV- too..
  is it common to fry this one too? (fried it when i detached the caps and tried again to mesure voltages.
  Havent had the posibility to messure anything yet. :S
   
  have to tur thos trimpots, order a nec hv- and 2 new caps.


----------



## holland

Quote: 





egotrip said:


> I thougth P2-1 L:R where resistors. oh well.. then a potmeter is as a diode then?.  all other diodes and caps are installed correctly. and i need a HV- too..
> is it common to fry this one too? (fried it when i detached the caps and tried again to mesure voltages.
> Havent had the posibility to messure anything yet. :S
> 
> have to tur thos trimpots, order a nec hv- and 2 new caps.


 

 A potentiometer is a variable resistor.  Sorry, I wasn't clear.  I think you placed the diodes incorrectly and may have over-volted your caps.
   
  I'm not sure what you mean by detaching the caps.  You can measure voltages by flipping the board over and checking it.  Be careful of the HV side.
   
  Measure the voltages at the + pin for C3P and C4P.


----------



## egotrip

I have desoldered the C4P and C3P.
  I have to order another pair.
   
  2x Aluminum Electrolytic 2200μ 35V
  1x 15V 1A Fixed Negative Regulator TO220
   
  These three componets has been damaged.
  I am trying to find replacements nearby, becouse i dont want to wait 14 days for replacements.


----------



## holland

I think you should find out why the caps blew up.  Just replacing it may mean having to replace it again.


----------



## egotrip

The problem is that all the uprised diodes d1-12 is backwards.
  The cavalli site says that positive end is always upwards, this is ok.
  I know that both diodes and pcb is marked with a band to represent the direction.
  I just assumed that the circle on the upright diodes ment that the where supposed to be mounted with the cathodes pointing towards the circle.
   
  By investigating further on all of the photos postet in this thread, I now know I was wrong.
  It where an marking for where the bottom of the diodes was supposed to go.
   
  Oh well, I just have to turn them then.
   
  New parts is ordered, and i will begin desoldering a lot of diodes to prevent future ***-ups 
  Thanks for the help so far.
   
  Don't be supprised if i ask more novice q's since I am pretty new at this.
   
  I can make this work.


----------



## egotrip

Quote: 





holland said:


> A potentiometer is a variable resistor.  Sorry, I wasn't clear.


 
  Then you made my head spin. I thougt a pot was a variable resistor. You cought me off guard when i asked about the pots, and you mentioned diodes.
  No harm done. 
   
  Quote: 





> Originally Posted by *holland*
> 
> 
> 
> Be careful of the HV side.


 
   
  By HV side, do you then speak of High Voltage-side?
   
  I won't reconnect power untill i have visually inspected every cap and diode.
  Been inspecting a lot of photos from finished builds from this thread.
  I am pretty sure I have located the problem..  friggin' diodes.....


----------



## holland

Yes, you may want to touch the caps with a power resistor to drain them, before doing any work.  It can sting a good bit if you don't and you swipe it by accident.
   
  Sorry for the confusion.  When you showed a pic of the caps, it was immediately clear the diodes were put in wrong, causing over-volting of the caps.
   
  I may be wrong, but I think the prototypes had a mix of diode positioning (up and down), so it was not an unheard of problem.  It's good that it's a fixed position now...unless my memory recollection is failing and it always up band up.


----------



## egotrip

The thing that tricked me, was there where no positive (+) marking on the pcb.
  So i thougt that the circle (where the bottom is supposed to be) was the line to represent the band on the diode.
  I acually placed the diode posisitioned upwards, but the bottom of the diode outside the circle. since i thougt it represented the band of the diode.
  I am clearly no electronics expert 
   
  (btw, bleeding the caps with a 10k resistor should do it?)


----------



## holland

For something of relatively low voltage, something like that should work if you go up in wattage.  I generally use a 100k/1W resistor at least (higher wattage the better).  Light bulbs work too.   A 100W light builb or a string in series is a nice discharger.


----------



## S3TUP

Hi all!
   
  I've run into some problem with a power supply:
   
  The SOHA II requires 2x15v 1a PS with 300ma tubes. 30v*1a = 30VA.
  All i have are:
  15x2 18va x7
  15x2 25va x1
   
  And i plan to use russian tubes (6.3v 600ma heaters).
  Therefore i need to get 1.5A PS for the whole board, or separate the heaters PS from the board PS.
  The heaters PS is straightforward: 600mA @6.3v = 600mA 12v in series = 600mA 15v = 9VA minimum requirement.
   
  Then, how much current do in need for the board alone (without heaters)?
  My calculation shows the following:
  300ma heaters take 5va (600ma = 9va).
  Therefore the board requires 25va. (30 - 5)  
  Something is wrong here... Why should we change to 1.5A PS when going for 600mA tubes? All we need is additional 5VA, not 15...


----------



## holland

Quote: 





s3tup said:


> Hi all!
> 
> I've run into some problem with a power supply:
> 
> ...


 
   
  You just need the proper power transformer.  You basically need another 0.5A (AC) for the heater.  Voltage and current, though related, are not the same thing.  You are deriving your 12.6V from a 15V AC source.  It is the AC rating you need, not the VA relative to 12.6V.  If you had separate transformers for every voltage needed, you would need 3 transformers.  Heater, buffers, and tube.  To save space, a single transformer is fine, but you lose out on the current demands relative to the transformer.  We can't create power from nothing.  The tubes, though by default drawing 1-2mA each, is through a voltage multiplier, which in turn multiplies the current from the transformer (can't create voltage for free).  The same can be said of the heater.  The regulator consumes some current, and burns off voltage as well.  We can go down in voltage but must spec the VA relative to the 15V AC coming into it.  Also note, that the heater regulator is on the negative rail.


----------



## Alcaudon

After a looong loooong time I finally managed to finish my Soha II. There's an strange noise problem that I still need to solve, but it will take a bit more until I can find some time to work on the amp. Anyway the noise lasts only for less than 10 minutes from power on and the amp is dead silent after that.
   

   
  More pics here: http://www.head-fi.org/forum/thread/85561/post-pics-of-your-builds/7635#post_7163318

  Happy new year!!!!!!


----------



## holland

try different tubes.


----------



## sachu

^^ agreed...However i doubt if you will find a permanent solution to this as i feel it is rather normal. Besides, I never listen to my amps tube or not for the first half hour..they need to warm up to their operating temperature. All my amps sounds very different and more to my liking after a good warm up period.


----------



## Alcaudon

Thanks holland and sachu for your advice.
   
  Changing the tubes was the first thing I tried when the noise appeared. It's still there regardless of the type or the brand of the tubes.
  Quote: 





> ^^ agreed...However i doubt if you will find a permanent solution to this as i feel it is rather normal. Besides, I never listen to my amps tube or not for the first half hour..they need to witwarm up to their operating temperature. All my amps sounds very different and more to my liking after a good warm up period.


 
   
  I do the same sachu, that's why it doesn't bother me much, guess that I could just live with it.
   
  Thanks!!!!


----------



## stixx

Alcaudon,
  you didn't qualify the noise you are having in your SOHAII...is it some crackling, rustling noises during warm up or hiss or hum...?
   
  Tubes do sometimes generate noise when warming up... all the inner structures heating up, expanding and such. I've had that happen with an EZ81 rectifier and one 6H30 that made some random popping noises in the first minutes that I couldn't get rid off.
  Only when I bought a new pair...
	

	
	
		
		

		
		
	


	



   
  But you already tried new tubes, so maybe you can be a bit more specific about the kind of noise your SOHA emanates...


----------



## egotrip

TH    +12.56v
  TL+   +14,97v
  TL-    -15,14v
  TB+ +119.6v
   
  Are these acceptable values?
  How can I fine tune them?
   
  J1,J2,J3 are NOT strapped.
  Tubes NOT installed
  HTR jumpers NOT installed.


----------



## holland

Egotrip.....read the setup on cavalliaudio


----------



## egotrip

TL+​+15V​TL-​-15V​TH​-12.6V​TB+​+103V to +125V​
  ​  ​  12,56v is close enough to 12,6v.
  14,97v is close enough to 15v.
  I was wondering if 119,6v is close enough to 125v
  and is 15,14v close enough to 15v?
   
  And how do I reach 125v across TB+ ?


----------



## holland

Quote: 





egotrip said:


> TL+​+15V​TL-​-15V​TH​-12.6V​TB+​+103V to +125V​
> ​  ​  12,56v is close enough to 12,6v.
> 14,97v is close enough to 15v.
> I was wondering if 119,6v is close enough to 125v
> ...


 

 TB+ is a range where it should lie.  Needless to say, but I will anyway, is that if you are *in* the range, you are fine.
   
   
   
  Quote: 





> The voltage at TB+ will be close to 125V when the tubes are not installed and will pull down to near 103V when they are.


----------



## egotrip

That is great 
   
  Has been a bit jumpy after i blew up my caps and lv- after a series of reversed diodes


----------



## stixx

Yeah, been there done that...
	

	
	
		
		

		
		
	


	



   
  You remember what I said...? 
  In the end you will be very proud of your new amp and probably not wait too long until you go for the next one...


----------



## egotrip

Quote: 





stixx said:


> Yeah, been there done that...
> 
> 
> 
> ...


 
   
  Yeah. I remember. 

 Just strapped all the jumpers, all values seems ok.
  Tubes light up.
  Some crackeling from the volumepot. (it is not soldered due to casing, so the crackeling is due to loose pot)
  Taking the night off, and will try to connect a source tomorrow, after i have double checked the voltages.
   
  Getting really exited.


----------



## egotrip

Some work left, but coming together.
  I am no woodsman, either a designer.


----------



## stixx

Quote: 





> I am no woodsman, either a designer.


 
  But the woodwork is looking very good!  What kind of wood is that...?


----------



## holland

Pretty.  A nice urethane coat and it should look really nice.  Did you build the case yourself?


----------



## egotrip

Wallnut hardwood.
  I will coat it when i have drilled all the holes and fittet all the parts.
  I was thinking of using a charcoal transparent lack to highlight the wood, and then a few clearcoat.
  Yes I have sort off made the case myself.
  The aluminiumtop is cnc machined by "professionals" but the autoCAD drawing is mine.


----------



## egotrip

Finally, some descent sound.
   
  Unfortenatly I have som problems with it.
  From time to time, the e12 turns off, but turns back on after a few secounds.
  The problem is worse when it is cold, and gradualy fades away.
  After aprox 30minutes of playing music, and the amp is getting warm, the e12 almost never fails.
  The right channel is also slightly less volume than left.
  Any one got any good tips where the problem may be?


----------



## holland

not sure, it sounds like multiple problems.
   
  1) swap tubes left to right to see if the problem follows the tubes.  if so, replace tubes.
  2) when the e12 trips, measure the DC offset before the e12 with a DMM, to see if you can isolate the channel and by how much is the offset.
  3) remove the tubes and see if the e12 trips without the tubes.  make sure your DC blocking caps are actually working.


----------



## egotrip

I removed the tubes, and it does not trip.
  plugged them back in, no trip yet?
  and the difference in L & R channel is gone..
  The only way I can make it trip for now, is when i put a screwdriver on the trimpot of P1P?
  I think it might be a ground issue?
   
  I will keep it playing for a while to see if the e12 trips again.
  Fingers crossed
   
   
  edit: still trips


----------



## czegevara

After almost 2 years of lying on the shelf my SOHA II is now completed (well... almost - just waiting for some 0,22/1000V Caps. I hope this weekend I will finish this great amp and listen to it.
  For now all measurment are ok. Tubes are EH 12AU7, trans are Toshiba 2SC4793, C1 will be Jantzen Z-Silver Caps. Thanks Alex!


----------



## stixx

How will you finish the front and rear...?
  Otherwise it is looking good... very clean build!


----------



## czegevara

Its standard Fischer combination case (KO HL profile series - http://www.fischerelektronik.de/fischer/uploadfischerfcase/Fischer/M.1.2.pdf) so there will be a standard faceplates supplied with case, just drilled/milled for pot and sockets. In the rear panel I'm going to istall small Sunon 12V fan powered by a little lower voltage. For the front I have a really huge alu knob Now I must to think about protecting the tubes somehow...


----------



## stixx

I don't like tube cages... I always leave my tubes unprotected and never had an issue with it (and I do have children...). The tubes in a SOHA don't get really hot anyway


----------



## funch

Just finished my SOHA II.




   
  This is basically a kit from Glass Jar (thanks, Jeff). I used my own tube sockets, tubes (JAN Phillips 6922), RCA jacks,
  switch, electrolytic cap's (FC, FM, UPW), and Vitamin Q's for C1. Output devices are BD137's. Wiring is some cryo'd
  Vampire I had. Tube bushings are from ACE Hardware.
   
  Although it works with both my HD600's, and Denon 7000's, I think it's really much better suited to high impedence
  'phones. The right channel tube behaves fine with the 600's, but goes terminally microphonic when I plug in my
  7000's.


----------



## holland

@funch, try different tubes.  that's primarily a tube issue.  I use mine with low impedance and high impedance just fine, including the D2000, M50, Q40, etc.
   
  nice drilling job, it looks painful to do.


----------



## jdkJake

Funch,

Awesome drill job on the top cover! 

Did you use a pattern or was it more-or-less free form? After seeing some of your previous work, it is a legitimate question, as you are the consement perfectionist!

BTW, Ace hardware is a treasure trove of goodness. All kinds of great and wonderful stuff buried in various trays and cabinets. First stop for stainless #4 hardware.


----------



## funch

Quote: 





jdkjake said:


> AFunch, Awesome drill job on the top cover! Did you use a pattern or was it more-or-less free form? After seeing some of your previous work, it is a legitimate question, as you are the consement perfectionist! BTW, Ace hardware is a treasure trove of goodness. All kinds of great and wonderful stuff buried in various trays and cabinets. First stop for stainless #4 hardware.


 
  Thanks for the nice remarks Jake.

 I first lay out a pattern on the FPE software. I set all the holes to 1.5mm, the panel to 'clear', and print it out. Then I tape it to the panel and use a
  center punch to dimple the panel. I leave the paper on and use a pin vise to start each hole, using three sizes of bits. Once that's all done, I remove
  the paper and fire up the drill press. I start with a small bit, working my way up to the desired size. I finish up each hole with a hand held countersink
  tool I got at Harbor Freight. The real pain doing anodized panels are what I call 'spinners'; the shavings that can scratch circles in the finish. The process
  is painstaking enough as it is, but having to stop each 'plunge' 4 or 5 times to clear them is really a pain in the patootie. BTW, the pattern on this amp
  started out as concentric circles, and, uh, got a little out of hand. 
   
  Amen to your Ace endorsment. I also use the stainless #4 stuff. I also like to use M4 screws for the Hammond panels, as the #6 stuff, to me, is too
  easy to strip.


  
  Quote: 





holland said:


> @funch, try different tubes.  that's primarily a tube issue.  I use mine with low impedance and high impedance just fine, including the D2000, M50, Q40, etc.
> 
> nice drilling job, it looks painful to do.


 


   Yes, you're right. I'm noticing it with the HD600's as well, just way more noticeable with the D7000's. Of course, it's only when I'm touching the amp, so it's
  not a major deal. I'm thinking of ordering a couple of 8416's, so that would fix the problem (I hope). BTW, does anyone here know of a good source for them?
  I see Tube Depot has them. Just wondering if there might be a better, read cheaper source.


----------



## holland

Quote: 





funch said:


> Yes, you're right. I'm noticing it with the HD600's as well, just way more noticeable with the D7000's. Of course, it's only when I'm touching the amp, so it's  not a major deal. I'm thinking of ordering a couple of 8416's, so that would fix the problem (I hope). BTW, does anyone here know of a good source for them?
> I see Tube Depot has them. Just wondering if there might be a better, read cheaper source.


 


  LOL.  It's a crap shoot with tubes.  I have lots of used and NOS tubes.  Some work at the operating point I have for my SOHA II, some don't.  I have some new tubes which didn't hiss at the stock SOHA II operating points, but after modifying my SOHA II, it hissed like mad in one tube, but not the other.  tubes....it's a love/hate thing.


----------



## funch

O' course, there's always opamps.


----------



## funch

I think I'm going to revise my earlier impressions of this amp. It seems to work equally well with high or low impedence 'phones.
  My D7000's are sounding very nice through it. I have to say that, for the money (especially with the Glassjar kit), it's got to be one of the best hybrids around.
  It seems to be very revealing of the source, or source material. Easy to build, compact, and great sounding. Another triumph Lord Cavalli.


----------



## adydula

Hello,
   
  I got my kit from Jeff this week and started installing the power supply diodes, and so it starts!!
   
  I have a few simple questions, I havent dont this in awhile, but have a lot of experience in building stuff...
   
  1. What gauge hookup wire do you guys use? 20 or 24 ?
  2. Do you use shielded wirr from the isolated RCA input connectors to the amp board.
  2. Do yoy only ground this on one end, if so which end, and does it really matter?
   
  Going to use the Avil Y236203 to allow for 600ma and 12volt heater for the 12 v tubes etc...
   
  Thanks
  Alex


----------



## adydula

Intital checks for PS are ok, +15, -15 and 117 and 12.6 volts.
  Was able to set up the 220 mv across R10's.
   
  Unfortunatley the relay was not clicking, after a few hours of measuring one of the pins on the output of the ICE was low, not enough voltage to pick the relay.
  Solder it again and the relay clicked.
   
  Next problem after jumpering J3, the H+ adjust was not adjusting...checked all solder joints and the P1P has no effect on the voltage, just sits there at max voltage.
   
  Seems their are no shorts or opens, circuit checks out ok, I have ordered another TL873 and hope this fixes that.
   
  Alex


----------



## funch

Dunno if anyone checks in with this thread or not, but here goes. This is what I get for fooling with
  something that's working.
   
  I went back to check voltages, etc. and the voltage across R6L is being weird. It'll check fine, then
  go to 0, then jump up to 14V. The relay clicks on and off sometimes when I touch my probes to
  R6L. The other side, R6R is fine. Tried switching tubes. No change. BTW, I'm sure I didn't short
  anything with my probes.


----------



## funch

Well, it seems as if P1L has gone south. Mostly, it reads zero ohms at different settings.
  So, my next question is, did I damage anything else running 14V through the tail current curcuit?


----------



## Navyblue

Is SOHA II out of vogue now? This thread seems pretty dead. 

 I have been trying to get the kit from GJA for weeks, but Jeff is unresponsive. Anyone dealt with him lately? He used to respond and ship fast.


----------



## digger945

Quote: 





navyblue said:


> Is SOHA II out of vogue now? This thread seems pretty dead.
> 
> I have been trying to get the kit from GJA for weeks, but Jeff is unresponsive. Anyone dealt with him lately? He used to respond and ship fast.


 


   
  It could be possible that your email is going into Jeff's junk box?


----------



## Navyblue

It's possible I guess, the first time I mailed him he didn't reply for a week or so. The second time I used the webform and he replied almost immediately, but when I replied back and re send the mail a few times he hasn't responded for almost 2 weeks . I just tried the webform again and we'll see.


----------



## kchapdaily

Quote: 





navyblue said:


> It's possible I guess, the first time I mailed him he didn't reply for a week or so. The second time I used the webform and he replied almost immediately, but when I replied back and re send the mail a few times he hasn't responded for almost 2 weeks . I just tried the webform again and we'll see.


 


  i actually emailed him maybe 3 or 4 weeks ago asking about pricing for the soha II kits. he emailed right back within a few hours. you must have ended up in his junk box.


----------



## Navyblue

I got a reply today.He got my replies, I guess he was swamped. But he remembered me and he billed me right away. I guess I'll get busy soon.


----------



## Navyblue

Question:
   
  If I put the transformer at a separate enclosure as the amp, can I ground the amp enclosure to the signal ground instead of the mains ground?
   
  I don't see this mentioned in the website. Thanks.


----------



## Navyblue

People?


----------



## FallenAngel

Yes, you can.
   
  Generally you would use a ground loop breaker if everything is in the same chassis.


----------



## cfcubed

> _ If I put the transformer at a separate enclosure as the amp, can I ground the amp enclosure to the signal ground instead of the mains ground?_
   
  I'm doing exactly that for my EHHA, as I've done for most of my other 2-box builds (see links in sig), which is what you are suggesting.  Along the lines of Wiring & Ground - "Option 2" here:
http://www.amb.org/audio/beta22/
  I see no reason, e.g. schematics, that this approach would not work & be beneficial for a SOHA II build.... Perhaps someone who's done this will chime in.


----------



## Navyblue

Thanks guys, I really appreciate it.  I am a bit anxious that if I ran into problems and this design is "forsaken".

 Yep the Beta 22 page was my reference as well, and that's how I built mine. Since SOHA II uses a higher voltage, I thought may be there are other reason to mains ground the enclosure. Glad to know that there will be no problem.


----------



## sinae

Anybody can tell me if there is a good DC filter in this design because i bought a diy Soha II made by another headfier and it seems to be picked DC a lot. With my double online conversion ups. The humming is a lot less audible 

there might be other source of noise. I will have to verify everything 

would this work 
LC audio diy DC filter

Also anybody feel the Soha II soundstage to be too wide. I find it very very weird with my DT250 compare to my others amps. 
I can position the instruments better but they are all over my head in a weird way..

Also mids are detailed but kinda harsh... 

Also anybody can tell me if in the SOHA II the Toroidal transformer should be mounted.. mine isnt and maybe its causing interference or something...


----------



## Navyblue

Guys,
   
  As for using boutique stuffs on C1, would tombstone mounting, or air wiring cause any instability to the circuit?
   
  I intend to air wire C1 to another board where I can mount and roll capacitors but not sure if it would cause any harm.


----------



## particleman14

I have my c1s air wired after swapping a few caps to see which one I liked.  doesn't seem to affect the sound at all..


----------



## sinae

let us know if some caps are really better than others and where


----------



## particleman14

I tested vitaminq pio, obliggato golds, and russian ft-3s  I ended up with the russian ft-3s  but the vitaminqs were also quite nice...


----------



## sinae

And where are you using them? 

How do you find the soundstage and subbass on your soha II and what about internal DC filter effectiveness?

I have humming with mine cause by too much DC on my line and also placement of the toroidal transformer ( not sure but ground might be picking hum from toroidal since the ground bolt is near the transformer)

Also it might be my source and or headphones but my soundstage is too wide and very 2D in the head.. Also very mid centric but again might be my source. I will have to test it on another dac to be sure..

I would really appreciate if SOHA II owners could tell me how their soha built sound.. I need to know if it was wrongly built or if its by design by cavalli.


----------



## particleman14

C1.
   
  check your wiring scheme and transformer placement.  I get no excessive dc offset or hum in my build.  soundstage is nice and wide, esp with some HD800s.  the trick to this guy is the tube rolling capability.  you can swap in tons of different tubes to find your flavor....


----------



## Navyblue

Thanks Particleman, do you have some kind of contraption to allow easy cap rolling?


----------



## particleman14

I soldered alligator clips to my wires


----------



## sinae

particleman14 said:


> C1.
> 
> check your wiring scheme and transformer placement.  I get no excessive dc offset or hum in my build.  soundstage is nice and wide, esp with some HD800s.  the trick to this guy is the tube rolling capability.  you can swap in tons of different tubes to find your flavor....




What tube do you prefer with yours? Mines are 12AU7A

How about subbass quantity?

what do you mean by wiring scheme? 

How have you positioned your transformer.. mine is at the far left near power plug.. 
Its currently unmounted.. do you think this could be the cause

--
I opened the box and positioned the transformer outside the box ( should not do any interference there) even then still same humm problems..

also if i have nothing plug but AC power, volume to max. The 2 cables that are connected to the RCA jacks to the front volume on the board are picking a lot of noise by just moving my hand over them.. They are twisted together could this be the cause... 

actually at volume to max you hear a lot of garbage even when not moving my hand over them but when moving my hand over its even more garbarges..

---
also on cavalli web page he says
The 2 x 3 onboard header can be jumpered to select 12.6V parallel or 6.3V series operation.

what should it be 12.6v or 6.3v mine is currently 12.6v

Anybody have an high res zoom pic of all the parts of their SOHA II amp so that i can compare to make sure the dude did it right

that humm is killing me the guy sold me a defect amp.. 

I think i found something.. 

The C16P capacitor has melted a lot because the Q1P transistor was touching it or something... What is the use of those 2? anybody can tell me
and if the melted C16P capacitor could have an effect on all this ****..


----------



## particleman14

I have some 6922 JAN and they are pretty nice.  you have a damaged cap on c16p? replacing it might help.
   
    are the input wires shielded?  they could be picking up noise...   12au7s are 12.6V tubes so your jumpers are right..  post pics of your case and layout...


----------



## sinae

Yep i will replace both the caps and the transistor.

they are small wires with small plastic cover.. dont think they are shielded.. 

Do you recommend other cable in the box to be shielded?

did you compare 6922 JAN with 12au7 in the soha II


----------



## particleman14

never ran any 12au7s..  usually shielded input wires are recommended to prevent noise pickups.  replace the caps and see if that fixes your problems...


----------



## sinae

I will change the cable and the cap thx for your help


----------



## sinae

anybody can tell me what effect could be created by a melted 0.1uf Metalized Polyester/Polypropylene Film Capacitor 100n 100V place at position C16p based on this shemantic 
power supply shemantic

as for the shielded cable.. what AWG would you recommend
would this do
Cardas twinaxial

im sorry with all those questions im a new DIYer..


----------



## particleman14

I'm pretty sure that's a bypass cap.  As I understand its meant to "smooth" out the ripple current by providing a little store of charge to fill in dips in the voltage.  definitely get that part replaced...it's suposed to make your psu less noisy
   
  I like navships wire on ebay , it's cheap and solid.  or some belden cables are cheap and good as well.  that cardas wire won't be too bad either as you'll only need a foot or 2...


----------



## KWS

Hi all!I m building a SOHA ii but got some problems for the buffer DC offset.Please advise.
   
  I used
  1.5M for R15,
  Q6,Q7=2SC2238 from TOSHIBA,
  OPA627au for both opamps
  Ibias =100mA(Voltage accross R10(2R2) is around 220mV)
  V+ = 15V
  V- = -14.95V
  and no tube is installed for below measurement for both channels.
   
  For Left channel ,everything is just fine.DC offset is nearly 0~3mV constantly which is reasonably low as what i expected.
   
   
  For Right channel,DC offset is around -7.68V for the output and it will slowly decrease to -0.5V in 4 mins after the transistors was getting hotter and hotter(around 40C for the heatsink)
  After around 5mins,the offset is around -3-5mV for awhile but will soon increase to -30mV forever.
   
  After 10mins,offset =-30mV,Relay never close or toggle.
   
  So i tried to re-solder all the solder points again and check the direction of transistors and check any mismatch or wrongly assigned components.
  Also,i swapped or changed opamps for both channels but in vain.
   
  I was told that around 20-30s,the relay will toggle and music will be heard.
  I am now wondering some components may be broken but it would be very unhappy to solder off the old parts and replace them but new parts again.
  Please state some suggestions for me.Thanks.


----------



## Veiko

Hi,
  I'm building SOHA II as well. I bought the fuse listed in the BOM but now I'm wondering if it works in europe? My mains voltage is 230v so should I get a smaller fuse?
  Another thing that crossed my mind: I have a couple of meters of expensive coaxial cable, would that work for the input connection?
  I hope someone is still reading this thread.


----------



## Navyblue

Yes, and yes.
   
  Any metal that conducts well would work for input wiring for another amp, however whether it is suitable is another matter. FWIW I use Belden 1505A as my input wiring as it is double shielded, but it is a bit stiff to bend around. I probably will do the same for this amp, that is if I ever get started (again) on doing this.


----------



## Veiko

Thanks, relieving to see people still get help with the SOHA.
  My limited knowledge in electronics tells me the fuse should be 250mA so I'm going with that. With any luck I'll have it working tomorrow. Pics coming later!
  I'll just use the coax cable since it's shielded and the impedance level probably won't have any effect.


----------



## Navyblue

I am not sure if you can call that help. 
	

	
	
		
		

		
			





 I know little about electronics too. I have built another amp so I kinda know some general stuffs. However if I were to meet a real electronic problem I am very much clueless. On my own SOHA II board I only have stuffed a handful of resistors, it's been that way for many months already and it's not moving any time soon.


----------



## Veiko

Well, you helped with the fuse at least  The closest one I have is 315mA so it'll have to do.
  I'm 40% electronics engineer now so I should have some idea of what I'm doing. I'm seriously lacking some confidence in electronics though. Probably a positive thing. It's good to make sure when you want something to work right away.
  No idea how you can possibly wait that long to get your SOHA II running 
  I expected to have it done this week but ran into problems with the case so it got delayed. Today I powered it for the first time and got the following numbers:
   
  TL+: +15.02v
  TL-: -15.01v
  TH: -12.9v
  TB+: 115v
   
  TH seems a little off, what's the tolerance?


----------



## Navyblue

Is TH heater supply? If so I personally think it is not something very critical to achieve very close tolerance. I really have no idea, but if I were you I'd be comfortable to go ahead. However if I were you I probably won't be taking electronic advice from me. 
	

	
	
		
		

		
		
	


	



   
  My first amp (a 3 channels Beta 22), it took me 2 years and 7 months to get it running and boxed up. It was dormant for a long time, I basically resigned to fate that I spent quite a bit of money for a bunch of junk in my living room. I rushed it again towards the end because my pre amp in my speaker setup was dead and the cheapest way for me to get a decent replacement is to complete this amp. And more than half a year later I did some further minor addition that I was too lazy to perform initially. 
	

	
	
		
		

		
		
	


	



   
  I got into this SOHA II right after I finished the Beta 22, back then my preoccupation was with headphone amp. I don't think the need factor is going to kick in in the foreseeable future, so if I were to count on that I will probably never be able to complete it at all. I move from one hobby to another and I would come back. But even my current hobby came back to audio lately, I am more into headphones and less into amp at the moment. I really have no idea when I will get moving again. I'll see if this one would exceed the previous record.


----------



## Veiko

Yeah, TH is heater supply. I assumed it was ok and moved on.
  Now, however, I have no voltage drop at all across R10L (and R10R). Both ends are reading -14,98V. The only thing I got with the search function was someone who had Q6 and Q7 installed wrong way. Mine are text-side to front which is correct I guess. However, when I test those BD139s, I get 0,62v B-E AND E-B. Are my transistors fried or what could be the problem?
  Argh, I'm going to have to unscrew the board again.
  Only took half an hour to do it last time since my standoff isn't exactly the right height and my solution isn't very easy to implement 
   
  Wow, I guess I'd give up now too if I had a descent amp, but I broke my last amps pcb while modding it.  I think I'm going to replace the BD139s unless someone has a better idea. I really hope my SOHA II won't take as long to complete as yours


----------



## Navyblue

Quote: 





veiko said:


> Yeah, TH is heater supply. I assumed it was ok and moved on.
> Now, however, I have no voltage drop at all across R10L (and R10R). Both ends are reading -14,98V.


 


  As in, you place both probe at either side of R10 and you get 0 mV?


----------



## Veiko

Quote: 





navyblue said:


> As in, you place both probe at either side of R10 and you get 0 mV?


 


  Either side reads -14.98 to ground, and I get 0mV across the resistor, side to side.


----------



## Veiko

Yep, the BD139s are most likely all bad. Now, before I change them, what could have caused this?


----------



## Navyblue

I don't think I have enough understanding to provide any insightful answers.
   
  However, heat, static, bad components elsewhere or wrong orientation all could kill transistors.


----------



## Veiko

Ok, well, I'll have to be more careful with my iron, ESD, etc.
  Now that I think about it, there's a good chance I could have shorted something with my wrench while trying to get the board out. As said, it's a little harder than removing a screw.
  And it didn't cross my mind that I could probably somehow bleed the caps from the top of the board.
  Q5 and Q8 seem to be damaged as well so looks like I'm going to have to replace more transistors. Are there other parts I should check for damage?
  The test point voltages are still what they should be. Does that mean that the regulators are still good?


----------



## hyperbting

Hi,
  I'm building SOHA II as well.
  At this moment only 2 parts cannot be found in mouser and Digi-key
  They are
  Metalized Polyester/Polypropylene Film Capacitor 1μ 63V
  C1E, C2L, C2R, C6L, C6R

 Mouser 581-BF074D0105J   Digikey 478-3367-ND
  and
  C4E,C5E Metalized Polyester/Polypropylene Film Capacitor 10n 63V

 Mouser 581-BF014D0103JDC   Digikey 478-3373-ND
   
   
  just wondering if
505-MKS02.01/63/5 http://www.mouser.com/Search/ProductDetail.aspx?R=MKS0C021000B00JSSDvirtualkey50520000virtualkey505-MKS02.01%2f63%2f5
  and
505-MKS21/63/5T http://www.mouser.com/Search/ProductDetail.aspx?R=MKS2-1%2f63%2f5Tvirtualkey50520000virtualkey505-MKS21%2f63%2f5T
   
  are good alternate?


----------



## Veiko

Don't count on my opinion, but I see no reason why those caps wouldn't work. Just make sure the lead spacing is correct.


----------



## Veiko

Well, I got those BD139s off the board and they aren't broken after all.
  It's going to be over a week before I can continue this project, so, any ideas are welcome meanwhile.
  I couldn't get the BC550s off for now, I'll give those another try when I get back from my holidays.


----------



## Navyblue

Quote: 





hyperbting said:


> Hi,
> I'm building SOHA II as well.
> At this moment only 2 parts cannot be found in mouser and Digi-key
> They are
> ...


 

  
  Getting the right capacitor is not hard.
   
  Capacitor type - match the type, you can use a different type than specified but you need to know what you are doing.
  Capacitance - match the value, you can tweak the value a little sometimes but you need to know what you are doing.
  Voltage rating - match the value, higher is fine.
  Form factor - Try to match the lead type (radial or axial), lead spacing, lead diameter (smaller is fine) and package size (smaller is fine). If they don't match you would have to mount them the "creative" way which may sometimes cause instability.


----------



## Navyblue

Quote: 





veiko said:


> Well, I got those BD139s off the board and they aren't broken after all.
> It's going to be over a week before I can continue this project, so, any ideas are welcome meanwhile.
> I couldn't get the BC550s off for now, I'll give those another try when I get back from my holidays.


 

 I could be wrong here, since I am not familiar with the setup process (since I haven't got there yet).
   
  FWIW.
   
  Initially I kinda doubted the way you measure the voltage drop, I didn't say it obviously as I wasn't familiar with the process and I could well be wrong. It seemed to me the most intuitive way to measure the voltage drop across a resistor is to have both probes at both end of it. The resistor value is quite small, so the voltage drop would be small too. Thus to accurately measure it you need to have your DMM set to the low range. Could it be that you are setting your DMM at a range that is too high that it is unable to detect such a small voltage drop?


----------



## Veiko

Quote: 





navyblue said:


> I could be wrong here, since I am not familiar with the setup process (since I haven't got there yet).
> 
> FWIW.
> 
> Initially I kinda doubted the way you measure the voltage drop, I didn't say it obviously as I wasn't familiar with the process and I could well be wrong. It seemed to me the most intuitive way to measure the voltage drop across a resistor is to have both probes at both end of it. The resistor value is quite small, so the voltage drop would be small too. Thus to accurately measure it you need to have your DMM set to the low range. Could it be that you are setting your DMM at a range that is too high that it is unable to detect such a small voltage drop?


 


  I'm quite certain I measured it correctly. With both probes at both ends of the resistor, I couldn't get a reading other than about 0. With one probe at either end and the other at ground, I measured little over -15 volts. I tried with two meters. One was at 2000mV zone and the other one has auto-range. Looks like the positive voltage isn't getting where it should.
  It'd be really helpful to know where exactly on the schematic the TL+ and TL- points are. Either I have a couple of bad transistors (which I doubt now) or the positive voltage isn't getting to the transistors at all.
  I feel like I could find the problem easier now that I understand little more about the buffer. If only I had the board and a DMM/scope with me now


----------



## Navyblue

Does both R10 exhibit the problem?
   
  If you power down, measure the resistance across R10, do you get 0 ohm? And when you measure resistance from R10 to ground, do you get 0? Do you think there could be a short circuit somewhere? If there is a resistance, there should be a voltage drop?
   
  Just thinking out loud here, as mentioned, if there is a real problem I doubt I could be of any help.


----------



## Veiko

I get 2.7-3ohms across R10 depending of the DVM. And about 9k to ground. A voltage drop can only exist if there's current flow, which could be the problem here. Both ends of R10 measured -14.8V to ground if I remember correctly. And yeah, that was both resistors. I'm going to solder new transistors as soon as I have some time and see if it makes a difference.
   
  I really want to know where those test points are on the schematic. That would at least tell me if there could be a problem in the PSU.


----------



## Navyblue

I don't know if I understand you correctly, those test points look like the various outputs on the PS sections.
   
  Btw, there is a slight chance that I would get this amp moving again. I wonder if I chose the wrong amp to build. If so I would have to finish this up and try to sell it if I can.
   
  For those who have heard this amp, does it sound like solid state to you? I chose to do this so to have a different flavor than my solid state amp (Beta 22). I'd keep it if it sound different enough, but I have a feeling that I'd be better served with something like Pete Millett's Jonokuchi.


----------



## Veiko

Thanks, I was able to confirm that.
  My vote goes to get your SOHA II built asap  I personally can't wait to get this thing working.
   
  So, I got everything together again and measured the test points. Everything fine until I decided to see if my meter would pick any AC. There was about 32 volts of AC on TL+!
  Other test points measured 0V AC as they're supposed to.
  Do you think my transistors (and other parts) survived that?
  And where's that AC coming from? Ideas?


----------



## Navyblue

If there is indeed AC (I am doubtful actually), check the orientation of D1P-D4P.


----------



## Veiko

Your doubts were correct, I repeated voltage checks with a scope and there was no AC. PSU works! I don't know what's wrong with my DMM.
  After some troubleshooting I found a 14 volt drop across R11. No current flow in R9 and R10. P2 and R12 were fine.
  I got +15V on the collectors of Q5 and Q6 but it's not getting through.


----------



## Veiko

I couldn't sleep while thinking of my Soha and finally found the problem. J3 was jumpered. All this trouble and it was that simple. I'm going to remove the jumper tomorrow and hope I didn't destroy the board while changing parts.


----------



## Navyblue

Glad that you got it worked out. Yesterday I took out my SOHA II board and looked at it. Perhaps it's an omen that I will soon work on it.


----------



## Veiko

Relay clicks!
  It also required installing the opamp. I was sure the opamps weren't supposed to be installed yet and now I feel kinda stupid 
	

	
	
		
		

		
			




  Found out by studying the design on Cavalli's website.
   
  Out of interest, do you have all the parts ready?
  I think I soldered the everything in one night so it's not that much trouble for a fine sounding amp (hopefully).


----------



## Navyblue

I am missing the transformer, and also some caps which I want to replace from the kit (or I could just use those from the kit). I am also missing some parts for the some of the mod (the Regal mod). For others like enclosure, jacks and all that I had extra from my previous build. So I am one Mouser order away from being complete.
   
  I am working on the amp now btw, I have a hard time remembering what I was doing.


----------



## Veiko

It.. It Works!!
  And sounds absolutely beautiful. It's in a completely different class compared to the headphone output of my audio interface.
  The noise floor, however, is quite high. I think I got 50Hz hum here. Ideas?
   
  You've got to get yours built now


----------



## Veiko

I figured at least part of the problem was grounding-related. So I hit the ground-lift button of my sound card and 75% of the noise disappeared. The 25% of it still bugs me a bit tho. Still sounds like 50Hz hum.
   
  EDIT: Tried with my phone, total silence, noise-wise. I guess I'll have to build a DAC next.


----------



## Navyblue

Glad that it worked out for you.
   
  I have stuffed all resistors that I can stuff last night. That was the greatest accomplishment since I started. 
	

	
	
		
		

		
			





  I think I am going to stop here till I got more parts and some questions answered. If you can, I posted them here:
   
  http://www.head-fi.org/t/390553/the-soha-ii-tube-thread/90#post_8231418
   
  If you know the theoretical answer to the question, you can help me by measuring the voltage across those resistor. However, I don't want you to do it if you are not totally confident about it or have the right equipment. I said that because I blew out things before while trying to measure a live working amp.


----------



## Veiko

I can't be certain about this, but:
  R6 should be fine. I'd go for 1/4W R4 tho.
  Regal's post mentions 2.75mA current through each tube section. Now, if that's the current through each triode, you'd blow R4 because ((2.75mA)^2)*18k=0.136W.
   
  If you don't trust my answer, I can check the voltages later with my DMM.
  I wouldn't count on the equipment I have at home, but at least I got my SOHA II measured.  That damn multi-meter is a bit moody sometimes. Cheapest money can buy 
   
  EDIT: just noticed the resistor would be 9k. Go for it if you trust me.


----------



## Navyblue

Thanks, I think your assumption made sense.
   
  Btw, are you using the kit from Glass Jar Audio? What tubes are you using?


----------



## Veiko

No, Jeff emailed me the corrected BOM and I got most parts from Mouser. That way I got fast, free shipping and didn't have to deal with customs.
  The tubes are from a local collector, got a matched pair for about $12. I think he should have asked more for them 
	

	
	
		
		

		
		
	


	



  They're RCA 12AU7 (NOS, made in Mexico).
  I'm also going to try 6922 as soon as I can afford a nice pair.


----------



## Veiko

Is there supposed to be a connection between chassis ground and input ground? If not, my inputs aren't properly insulated.
  I tried to listen through my phone with usb connected, and the noise was back. Mostly digital sounding noise, though.


----------



## Navyblue

If you are housing the transformer in the same chassis, the chassis should be grounded to the mains ground for safety. You can not connect the signal ground to the mains ground or you would get ground loop. On the circuit board there is provision for star ground, which is to prevent ground loop while also shielding the circuits.
   
  http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=wiring/boardwiring
   
  What do you mean by the corrected BOM? Is there an uncorrected ones out there? (just in case I got the wrong BOM)


----------



## Veiko

The safety ground is connected and I'm using the standoff grounding method, so, that should be ok.
  Both ends of my input cable are connected, however. Is this my problem? Should the shield only be connected to the input terminal?
   
  Looks like I'm not allowed to attach the file here but where did you get your BOM? The one on Cavalli's website is wrong (according to Jeff from Glass Jar Audio).


----------



## Navyblue

Thanks for letting me know, I have to dig out the BOM from GJA some where.
   
  I don't quite understand what you mean on the grounding. Are you using isolated RCA and TRS jacks?


----------



## Veiko

Or you can PM me your email address and I can send you the file if you want.
   
  I'm using isolated RCA jacks (although there's a connection between chassis and RCA ground, no idea if there's supposed to be).
  I mean I have both ends of the shielding connected. In guitar amps you'd typically only connect one end. Should I only have the tips of the RCA jacks connected?
   
  I think I may have a ground loop because of the input wiring, but there's no hum with a battery powered source.


----------



## Navyblue

With RCA jacks, the outer conductor is the ground connection, so it has to be connected to close the circuit.

With isolated RCA jacks (and TRS too), there is an insulating washer that isolate the ground contact from the chassis. So yeah, I think that is where your problem is. Without the insulating washer the jacks would not be isolated.

I should have the BOM since I ordered from Jeff. Thanks.


----------



## Veiko

Looks like the hum disappears when I let the amp warm up for a few minutes. I still have some digital noise left when listening through USB, but that's not the amps fault.
   
  I also desoldered the RCA jacks and there was still a ground connection, so, guess it was fine after all.
   
  Here's some test results if you're interested http://www.sendspace.com/file/epqrmd
  I doubt anyone else is going to read this thread 
	

	
	
		
		

		
		
	


	



   
  EDIT: for those who can't open my link in the future, I measured a THD+N of about 0.22%, quite steady through the whole audio range (Mostly noise). Amplification @1kHz was 8.2dB, with a 0.5 decibel difference between channels.
  Test were run with RCA 12AU7 tubes, not exact pair but close enough.
  I could probably get rid of the level difference, but there's really no point since I wouldn't notice a difference below 1dB.


----------



## Navyblue

What do you mean by you desoldered the RCA jacks? I assume you are talking about the input RCA jacks?
   
  You are probably right that nobody is reading this. 
	

	
	
		
		

		
		
	


	




 Sadly most of these DIY design seems quickly forgotten. From what I see only the very affordable ones (like CMOY) or the very high end ones remains popular.
   
  I was trying to spot the difference between the BOM from Jeff and the one on the website. So far I spotted one difference, I am not sure how significant though. For C6L/R it is "Metalized Polyester/Polypropylene Film Capacitor 1μ 63V" on the website and "Boxed Metal Film Capacitors 63V 1.0μf 5%" on the Jeff's BOM. Does it matter to use "boxed metal film capacitor" over the Wima I have, which is a metalised polypropylene capacitor? It is interesting that on Jeff's Excel sheet it is listed separately from C2L/R, which are the same value as C6L/R but is a metalised polypropylene capacitor (Wima).
   
  Edit: In Jeff's Excel sheet, the C6L/R Mouser part number links to a polyester film capacitor, which from what I understand, are similar (if not slightly inferior) to polypropylene film capacitor. I wonder why Jeff do this?


----------



## Veiko

Yes I meant the input jacks, their insulation was fine.
   
  It's sad really that people forget good designs like this. I haven't really compared my SOHA II to many amps, but it sounds excellent to my ears.
  I'll most likely build even a better headphone amp after a diy DAC and a self designed headphone amp. And a couple of guitar amps. At least I know where all my extra cash is going this year 
	

	
	
		
		

		
		
	


	



   
  Interesting, Jeff told me there are actual errors (plural) on the SOHA II web page. 
  I'm quite sure all my non-electrolytics are Wima so you should be fine with them too.
  Some of the parts on Jeff's BOM were out of stock at the time I ordered from Mouser and I never updated the BOM myself, but I think I can find out what I'm using if you want to know something specific.


----------



## pixeljedi

Hey All,
   
  I finally (after a couple of years) have put together my Soha II. Powered up and getting the same voltages as on the site. Running into a snag though in the buffer section of setup. Everything worked great on the left side, but I'm getting 0VDC when I strap R10R. I've replaced Q8R and Q7R and nothing changed. P2R seems to work fine, so I'm kinda not sure what the problem is - anyone have some ideas?
   
  Thanks in advance


----------



## Veiko

Hi Pixeljedi,
  can you tell me the voltage on the collector of Q7? Also, can you somehow verify that your servo opamp is the correct one and working properly?
  Have you checked for short circuits and cold solder joints?
  I barely understand the circuit, but i don't think anyone else is going to try to help you here.


----------



## pixeljedi

Hi Veiko,
   
  Thanks for the reply. It was indeed a weak solder joint.
   
  Onto the next round of tests


----------



## Navyblue

I actually finished putting together the parts. I used quite a bit of Elna Silmic II, it is obvious that the board weren't designed to use largish capacitors and it looked a bit hilarious to me.

   
  Unfortunately, when I reach the last initialisation step I have a problem. I can not get get a 19V drop between TB+ and TP on both side. think I recalled getting about 19V on one of the channel at first, but later on all I have is 0.2V. Did I blow the top CCS? If so why?
   
  Btw, this is with the mod performed here with a lower R4 and R6:
   
  http://www.head-fi.org/t/390553/the-soha-ii-tube-thread/45#post_6171572


----------



## pixeljedi

Wow, this amp sounds pretty damn sweet.
   
  Thanks so much to Alex and everyone else who helped along the way.


----------



## MrSlim

Quote: 





navyblue said:


> What do you mean by you desoldered the RCA jacks? I assume you are talking about the input RCA jacks?
> 
> You are probably right that nobody is reading this.
> 
> ...


 

 Heh, funny you should mention "nobody is reading this".  I've been contemplating getting a SOHA II board from Jeff, but I really need another project like another hole in the head..
   
  Do you have a Mouser Part list saved you could share?  And do you have a total BOM cost from Mouser?


----------



## Veiko

Quote: 





mrslim said:


> Heh, funny you should mention "nobody is reading this".  I've been contemplating getting a SOHA II board from Jeff, but I really need another project like another hole in the head..
> 
> Do you have a Mouser Part list saved you could share?  And do you have a total BOM cost from Mouser?


 
   
  Jeff will send you the correct Mouser part list when you order the board. I tried to PM it to you but looks like it's not allowed.
  I believe SOHA II can be built for around $200, someone correct me if I'm wrong.


----------



## MrSlim

Thanks.. 
  Weird, I just got a PM from someone else last week..


----------



## Navyblue

I am supposed to get at least 19V voltage drop between the power supply and the plate.
   
  On one channel, I got about 27V of voltage drop, which is fine.
   
  On another channel, I got about 1V. And of course that channel isn't working.
   
  I swapped the tubes around, same thing. What is wrong here? Is any transistor toast? Or is there a bad joint somewhere? (although there isn't as far as I could tell)
   
  Thanks.


----------



## pixeljedi

Hey Navyblue,
   
  Just want to make sure I'm reading that right. So when you swap tubes you're still getting 1V from the non-working channel?
   
  What I would do, is measure the voltage from each of the tube pins on the non-working channel and compare with the working channel. Then trace back along the path(s) that is not giving the correct voltage(s). The good thing is, you do have a working channel to compare voltages  And yes, definitely check for bad welds. For my issue above, I just had to reheat a weld and my issue was solved.
   
  Hope that helps.


----------



## Veiko

Navyblue:
  Could you post some voltages? (tube pins, etc)
  Or just do what pixeljedi said.


----------



## Veiko

Did anyone by any chance download my test results, post #1586?
  I'd be grateful if someone could send the file to me. I lost it myself.


----------



## Navyblue

Thanks guys, I thought no one is reading this. 

I managed to trace the problem, it was some bad solder joint.

Btw, how did you guys do in the hum/buzz department? With my headphones it is pretty much silent, but I don't use any high sensitivity headphone at home. However if I use it as pre amp, I can hear some hum and hiss if I put my ear on the speaker. Of course it is inaudible at reasonable listening position.


----------



## Veiko

Nice to hear you got it working too.
  If it works for you, don't touch it  that's my rule anyways.
  Good tubes usually cause less noise. What are yours?
   
  As I wrote before, my hum levels are theoretically non-existent: 0.2% (600ohm load). What is your sound source?
  In real life, I blame my PC's cheap PSU for all of my hum and noise. Could also be the refrigerator in the next room, who knows. Very irritating.
  Anyways, I get zero noise at full output from most other sources.
   
  I'll have to build a DAC with an optical input to be able to listen through my computer again.


----------



## pixeljedi

Glad you got yours working Navyblue.
   
  I haven't noticed any noise in mine, using electro-harmonix 12AU7 tubes. I split the power off into it's own enclosure because I've integrated a Gamma2 in the signal housing for the signal processing (running optical from my laptop). Sounds pretty damn amazing.


----------



## Navyblue

I am using RCA clear top 12AU7A. Source is mainly Rega DAC through optical. Both the source and amp are behind power filter too.

Any of you did the 300mA heater mod? This allows you to use more tubes, including the 12BH7 which some people swear by over any 12AU7 including the exotic ones.

That said regarding the hum and hiss, my case is still open up top (still waiting for my sheet metal punch for the tube holes). And my PCB standoffs are 80mm tall, so shielding is near non existent.

I like the sound so far, and I haven't touched my Beta 22 since it is operational. I think it isn't done burning in yet, yesterday I just notice some really low bass coming out after feeding input at max volume for a few hours.


----------



## pixeljedi

I'm running the heater mod in mine. Yeah, I tried those rca clear tops, and they sounded a bit bright for me - which was a bit rough given the price for them. I just got some new tubes today, JJ ECC802s, so far I'm blown away with what I'm hearing - really ultra clear tone.
   
  Sucks about the hum you've got. Is everything grounded correctly (one central ground point?). A couple of years ago I had a really bad ground loop in my system - I traced it to the cable tv ground line (which is separate from the house electrical ground). I ran a copper line from that cable ground to my power conditioner's grounding lug - killed the buzz instantly.


----------



## Navyblue

Not sure if we are on the same page. I have no hum with headphones, I just have hum when I am using my floorstanders as headphones , I have no hum too when I use the floorstanders as speakers.  It's also not exactly a hum, more like white noise that has low frequency element, that varies with volume setting, so it has to occur before the input stage. I am guessing it is RFI related, and I haven't covered it up. My Beta 22 is similar (but better, though it is cased), although it used to be silent, I supposed I made some changes that I am not aware of.
   
  I don't recall paying a lot for the clear tops, but I got them used, I paid less than a pair of new production tubes for 3 of them. They may be a bit on the bright side, but I prefer to call it sparkly.  That only happens after a week, after I fed music at max volume for a couple of days. And only a few days ago I hear some really low bass coming out of this thing. I think my coupling capacitors aren't settled yet.
   
  I also ordered some Sylvania 12BH7 and Philips JAN 6922, let's see.


----------



## Veiko

So, how exactly do you have your speakers connected? I think I can presume you have an amp between your SOHA II and speakers?
  Can you lift the ground between your amp and SOHA II? Are your input wires well shielded? Do you have a ferrite bead you could try?
   
  The input design itself has a small-ish grid resistor. Increasing that would probably filter out some RFI. I don't know about any negative effects, tho. Probably less gain etc.
   
  Tubes always hiss a bit and that alone could be noticeable after extra amplification.
  But as long as your phones are silent, I wouldn't touch anything


----------



## Navyblue

Yes, the headphone amp serves as a pre amp, driving a power amp. The power amp is not grounded btw, it comes with a fixed 2 wires power cable.

In the past I managed to make it dead silent by installing a power filter at the source and pre amp (I still have it). Just that for some reason, I no longer have it, even if I don't use the SOHA II.

Yes I would not touch it.  And the SOHA II is most likely going to the bedroom anyway. Another tube headphone amp for the living room is already half build.  This SOHA II is making the Beta 22 sound clinical (although it is much cleaner sounding and more transparent). As far as home headphone amp goes, I think I am sold on tubes.


----------



## Veiko

I bet the noise is just from the unfiltered AC.
  I have got to buy a power filter myself as soon as I can afford one. Some Furman units are quite cheap actually.
   
  Nice man! Good luck with your new build. I think I have no need for another headphone amp in the near future thanks to my excellent SOHA II


----------



## preproman

I'm trying to get some information on the differences between the SOHA II and the EHHA.  What's the pro's and con's of each?  Which one pushes more current / voltage?  I would like one of these build in a balanced design.  4 boards for the EHHA and I think 2 boards for the SOHA II (not sure).  
   
  Any information is greatly appreciated.


----------



## WesternE

preproman said:


> I'm trying to get some information on the differences between the SOHA II and the EHHA.  What's the pro's and con's of each?  Which one pushes more current / voltage?  I would like one of these build in a balanced design.  4 boards for the EHHA and I think 2 boards for the SOHA II (not sure).
> 
> Any information is greatly appreciated.



 
 SOHAII is a low power design, the EHHA is a power house. See the designers webpage.


----------



## Taxihamster

I've got a build going but as I was scanning things over I noticed that I had opted for the M Cap's which are quite a bit bigger then the space reserved on the board for the C1's.
   
  Does anyone have any tips or suggestions on how to place/solder those points in? I'm not a electronics guru yet so I don't want to just jump in and McGyver it without getting a second opinion. I'm doing all top mount for my board so I'm wondering if I should extend the wires out from the caps and place them far from the board or what you guys would suggest.


----------



## Navyblue

You will want to keep the wire as short as possible, while keeping the cap body away from the tube and the heat sink.

FWIW, mine is a bottom mount build. I have one lead attached to one hole and connected the other end with wire. You can then place the cap body in front of the heat sink or at either side of the board.


----------



## Taxihamster

Oh ok good, I'm glad that a slight extension to the wires won't cause any issues.
   
  Very much appreciate that =)


----------



## nickodj

Hi, just curious about popping sound when turning off SOHA II, does everybody have the same problem or is it just me?
  Or maybe is it because epsilon 12 on my SOHA II have a problem?
   
  thanks,
  Nicko


----------



## Navyblue

Mine does that too, and I wonder if it is a design flaw.


----------



## cfcubed

The fact that SOHA II's (& CTH's)  epsilon 12 derivative circuit(s) can allow a pop or click at power-off has been discussed, perhaps search will find the discussions.
  This is not considered a design fault nor damaging to connected headphones, just an issue with timing/release of relay at power-off.  Note amb's epsilon 12 design has progressed since these derivative implementations & _may_ not exhibit this issue.
   
  BTW I've used DPDT on/off switches on a couple CTHs, cutting e12 relay coil voltage off at same instant as power-off.  A brute-force hack that works quite well.


----------



## Navyblue

cfcubed said:


> just an issue with timing/release of relay at power-off.




That is exactly what I meant by design fault.  Most (if not all) modern equipments have relay that can cut off output at the event of power failure/cut-off.

But you can argue that it was never designed for that purpose in the first place.


----------



## nickodj

Quote: 





cfcubed said:


> BTW I've used DPDT on/off switches on a couple CTHs, cutting e12 relay coil voltage off at same instant as power-off.  A brute-force hack that works quite well.


 
   
  Would you be so kind to share how to do that?
 thanks


----------



## cfcubed

Here is my write-up of this for CTH:  http://www.head-fi.org/t/542279/the-cth-compact-tube-hybrid-rev-a-thread/360#post_8100335
   
  The equivalent PCB trace for SOHA II:

   
  But I only did this in a couple CTHs because I could (the builds used toggle switches), prior to that & in other builds with this exact issue I just take the cans off my head @ power-off.


----------



## Taxihamster

So I just finished up my amp...sadly I have run into some issues which I think boil down to tube incompatibility from what I've been reading.
   
  My TPL was bang on, 41V but my TPR was 35V. Frustrated...I thought I'd rule it out with swapping the tubes. Now I have a TPL of 46V and TPR of 33V. Everything else checks out in the amp, all the amp lines, voltage test points, everything is 100%...
   
  Does that sound about right? My tubes are 5963's on 12.6v by the way. Just wanted to re-cap before buying some more on ebay. :/ was really looking forward to listening to this tonight.
   
  Edit: my TP+ was 108V and 125V without with tubes in, so I wonder if that's also an indication of tube issues...


----------



## Navyblue

I have a pair of 5963 and they should work fine.

What is your voltage between TB+L and TPL (and the right side too). If I were to hazard a guess, there is something wrong with the either the CCS or the current mirror.


----------



## Taxihamster

TB+L difference was 19v where TB+R difference was 25v even though my currents & voltages on my resistors all were perfect on P1P, PL and PR. My TB+L and TB+R were both set at 60V but the TB+ was sitting at 108 with the tubes in.
   
  What is the CCS?


----------



## KimLaroux

Quote: 





taxihamster said:


> What is the CCS?


 
   
  Constant Current Source. In the SOHA II, it's made up of everything between the cathode and ground. See http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=design/ipdesign the last part of the page, "_Finishing the Tail CCS_".


----------



## Taxihamster

Quote: 





kimlaroux said:


> Constant Current Source. In the SOHA II, it's made up of everything between the cathode and ground. See http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=design/ipdesign the last part of the page, "_Finishing the Tail CCS_".


 

 Ah, thank you. That makes sense.
   
  I'll go through the entire setup process once more to be 100% that every other part is bang on and see what comes of it. I'll post again if I still get a huge differential between my voltages again.


----------



## Taxihamster

Just found a post mentioning tube-mismatch and to check Pin 1 on the trouble side. Turns out the voltage is bang on at Pin 1, just a bad tube.
   
  Got more tubes on the way =D


----------



## Mikael109

Checked through this thread and I only found one instance where someone asked for a simplified transformer wiring diagram, but it was 240V and I need 120V.
   
  I've never been able understand electronic schematics but I've been doing all I can to figure this out..
   
  The transformer I found a picture of has this schematic: (should be same number of wires as "Y236103 30VA" just looks like different wire colors)
   

   
  So I think I have this correct..?
   
  Primary:
  Blue + Violet = Neutral
  Grey + Brown = 120V
   
  This one not so sure..
   
  Secondary:
  Black = 15
  Red + Orange = 0
  Yellow = 15
   
   
  Just struggling due to the lack of schematic knowledge..


----------



## Taxihamster

I went rooting around the thread to get you the picture to verify what you were looking for.
   

   
  Though on my end...I've changed out 2 transistors Q5 & Q6R and I still have a 37V on that channel with perfect voltage on the other side. This is driving me crazy...I still can't get it to run here. Also because I don't have the case ready for testing, I wonder if I can't hear any sound because I'm grounding my RCA's straight into the load side with the ground port running straight into my ground plug/transformer setup switch.
   
  Maybe they need to be all common ground?


----------



## Mikael109

Thanks so much for pulling that up!
   
  Can see the 15-0-15 clearly and it looks like I had it right.
   
   
  I'm pretty new to everything so if this is a completely incorrect thought feel free to ignore it or have me delete it.. but I noticed that in glass jar's kit "non-insulated" chassis mounted RCA connectors were specified.
   
  If it were to built up in the normal Hammond case which is all metal I'd assume that would result in them being commonly grounded by the Star Ground standoff.
   
  Maybe that's the issue?


----------



## Taxihamster

I have a aluminum Hammand but I haven't mounted the RCA's yet...so I dunno if that's the issue. I should just get the holes drilled & get the star ground dropped in to at least to see if sound goes through.
   
  Though the voltage thing is driving me friggin bonkers...


----------



## Taxihamster

Just hoping someone might have some insight here...
   
  I finished up my case, got all my grounding in place, I still have my 41v on one channel and 37v on the other channel, but I should be getting some audio output all the same though I would think right?
   
  That's the problem now, I have no audio output at all. None. Should I post some pics? Anyone have any kind of ideas? I just want to listen to this thing already :/


----------



## KimLaroux

I'm planning on upgrading the PSU and tube stage in my Starving Student based on the SOHA II design. I'm currently going trough my parts and making a list of what I'll need.
   
  Studying the power supply, there is something I don't quite understand. I'm hoping someone here will be able to clarify things for me.
   
  The TL783 datasheet recommends using a 82 ohm resistor between ADJ and output, to make sure to have enough current to maintain regulation. It recommends 15 mA of minimum load current. Looking at figure 12, we see that in the case of the soha II, 10 mA would be enough.
   
  The way I see it, the tubes will use 4 mA and the setup resistors of the regulator will use just over 3 mA. So the TL783 has a load of less than 8 mA. Am I missing something here?
   
  It seems to me as the regulator should be unstable in the SOHA II. Considering it's a proven design, I will take for granted it is stable. So is it really stable? And if so, anyone can explain to me why?


----------



## jmf

Dear all,
  
 I'm using my SOHA II since severql years, with a Monica USB DAC (from DIYparadise) and a AKG K-1000. I'm happy except that the sound stops from time to time and restart some seconds later. I was convinced thqt I had an issue with the laptop and the com with the DAC. But I recently understood that it is instead the SOHA II amp that trips for some seconds from time to time (e12 board, I can hear the relay thqt trips).
  
 I went through the thread and discuovered thqt it was somehow a knowwn issue, but did not identified solutions to, solve this issue. Would some of you have identified ways to improve the operation of the e12 in this circuit, and to suppress those trips of the protection circuit?
  
 Regards,
  
 JMF


----------



## jmf

So no fix proposal for this e12 trip issue?
  
 Best regards,
  
 JMF


----------



## Nevohteeb

I had the same issue when I used my PC as source. Since I have never had this issue while using an ipod‚ a regular CD player or a MyBook Pro I think the problem came from my PC‚ not the e12,


----------



## jmf

I really hear the e12 relays tripping. What could come and be an issue from the analog input of the SOHA II amp ?
  
 JMF


----------



## Nevohteeb

If I remember correctly the e12 is also a DC current protection circuit. Maybe your source is not well connected to earth ?

You should try another source ?


----------



## jmf

I have to consider this hint. Thanks,
  
 JMF


----------



## Navyblue

jmf said:


> So no fix proposal for this e12 trip issue?
> 
> Best regards,
> 
> JMF




Btw, did you implement the regal mod? Or the higher heater current mod?

Mine used to trip often if I set the B+ or the current too high. Then it happens when I used 12BH7 that draw more heater current (300mA) than stock (150mA). I suspected it had to do with power instability. But now it seems to trip no matter what I do, although it's been a while since I touched that amp.


----------



## jmf

It is a plain vanilla one, without mods. I use 12AU7. I don't know it it matters.
  
 This behavious seems to have been experienced by several users, but not really explained...
  
 Regards,
  
 JM


----------



## muskyhuntr

Hi,
  
 It is possible to reduce the sensitivity of the E12.  This is from AMB's website;

If the relay oscillates on and off, and adjusting the VR1 trimpot will not make it stop, then you may reduce the sensitivity of the circuit to tame this behavior by increasing the value of resistors R5-R8 to 22KΩ to 47KΩ.
If you encounter false cut-outs when playing program material with loud low frequency content, you may reduce the sensitivity of the circuit as above. Additionally, You can increase the value of C5 to 3.3µF to lower the input filter frequency.
 
 Hope this helps.
 Jim


----------



## vixr

it may be working properly...did you check for DC on the output? The reason I say this is because I built a single 12AU7 tube amp and I run it on a 7Ah sealed lead acid 12v battery...like the kind on a scooter. When the battery starts to run down the DC measured at the output jumps around...like 13-3-8-16-23-1 mA very quickly...maybe the e12 is just doing its job.


----------



## jmf

I come back to you, to have advice about how to check if I have ponctually some DC at the output:
 - where would be the best measuring point?
 - is it voltage or current to be measured?
  
 Regards,
  
 JMF


----------



## vixr

jmf,
    Measure DC voltage from output ground to the amplfiers left and right outputs, most easily done at the headphone jack. I usually check this with no source plugged in. You will be looking at the mV scale. Wait at least a minute for the tube to warm up before measuring...


----------



## jmf

Thanks,
  
 I'll try as soon as possible,
  
 JMF


----------



## Navyblue

You can not measure DC on the output jack with the relay inline, you have to tap it before it hits the E12.

However, if the DC transient is too fast you might not be able to measure it with a DMM, you need a scope for that. But if it stayed on for say a couple of seconds, this you can pick it up on a DMM.

Source or no source it doesn't matter, DC on source won't make it through the coupling cap. So of course if you indeed get DC the culprit is the output stage (the SE buffer circuit.)


----------



## vixr

Navyblue,
     my bad...the only amp I've ever built with the E12 was the old Millett hybrid about 8 years ago...I timed how long it took for the tubes to settle down and set the E12 accordingly. It worked perfectly, so I never had to troubleshoot it. All of my DC offset problems have been with SS amps with no E12.


----------



## cfcubed

Searching this thread for "tripping" yields this: http://www.head-fi.org/t/374941/soha-ii-builders-thread/570#post_5392652
 Read down a bit & it talks about how to make pre-e12 offset measurements.   And other related things.


----------



## jmf

Hello,
  
 I finally checked this DC issue.
  
 I measured the Voltage between ground and R8 (http://www.cavalliaudio.com/diy/soha%20ii/main.php?page=schematics/ampschematic). I use a DMM, as I don't have a scope.
  
 It is usually within few mV. But when the e12 trips, I can catch figures above 100 mV (sometimes 200 mV). Thius is for short time... but it is really annoying when listening to music seriously.
  
 So it seems that there is an issue in the amp stage. As I have only very basic knowledge in electronics, I have no idea what to look for in this amp stage.
  
 I'm going to check if it is the same on the other chanel.
  
 Regards,
  
 JM


----------



## jmf

So the DC event seems to appear on both channels.
  
 What could be the faulty commom cause of those DC events?
  
 Regqrds,
  
 JMF


----------



## Navyblue

Assuming the DC spikes happen simultaneously on both channels (this can only be confirmed by you), I think the only possible scenario is the power supply, since that is the only place where both channels shares. This could be due to some instability in the ±15V regulation, however I think it is somewhat unlikely. If this is true, it is either the regulator is faulty, or there is some ringing between the capacitors, or simply a case of bad solder joint.

Whatever it is, I suspect mine has the same problem as yours.


----------



## jmf

So maybe have a look to solders, and try to spot a cold/faulty one ?
  
 Let's see...
  
 Regards,
  
 JMF


----------



## jmf

Hello,
  
 I borrowed a scope for 2 weeks, and I started to investigate yesterday evening. I can catch some events, and I' m really puzzled:
  
 Facts:
 - events are between -100mV and + 100mV. They don't always have the same shape/amplitude,
 - they are exactly the same on L and R channels, so it should come from a part of the circuit common to the 2 channels,
 - I mesure at R8 level, so before e12 => issue should not come from there,
 - I measured (with several measures) the voltage at different test points, during the events, and in all cases Voltages from power supllies are steady, when the output of the amp at R8R and R8L derives. I tested: +15 and -15 rails (at J1 and J2), TB+, TR+, TL+, TL-, TH
  
 The events are much more frequent when the amp is cold than when hot.
  
 I would have imagined having one of those voltages moving with the event... but it is not the case.
  
  
 Below pictures:
 - yellow&blue= output at R8L and R8R
 - red and green= power supplies (various)
 - vertical gid: 100mV, horizontal= 500ms
  
 Would you see other possible common points and tests to perform?
  
 Regards,
  
  
 JM


----------



## Navyblue

Sorry, this is beyond me.

If you can't get help here, I suggest you head over to diyaudio.com. Post the schematic and the findings there, I'm sure the folks there can point you in the right direction.

If you do, let me know, I am interested in knowing the outcome. Like I said, I suspect mine has the the same problem as yours.


----------



## jmf

thanks for the advice. I will do that.
  
 Regards,
  
 JMF


----------



## lovesteveme

I can't be sure of the range on the O/P stage CCS. You may or may not be able to dial up 100mA with the values specified for the BD139.


----------



## jmf

lovesteveme said:


> I can't be sure of the range on the O/P stage CCS. You may or may not be able to dial up 100mA with the values specified for the BD139.




Sorry, I have not enough knowledge in electronics, but I'll try to understand. Could you precise your idea?

Regards,

Jmf


----------



## jmf

I checked and rechecked. All power supplies lines are clean up to their connection point to the right or left channel.
  
 Up to now, I was thinking that my measuring point was maybe not the last one, and that there could be issues between the measuring point and the client.
  
 It is not the case.
  
 Could there be some coupling through the e12 33kR resistors ? It is the last common point that I see in the circuit.
  
 I also posted on DIYaudio, (amp/headphone systems), but no answer at the moment.
  
 Maybe that Christmas is not the best time to sort out this issue.
  
 Regards,
  
 JMF


----------



## jmf

So I consider that I failed.
  
 I explored all ideas I had without success.
  
 I disconnected one input of the e12 (common point), and it changed nothing.
  
 I also inspected solders, redone few nice ones. looked for shortcuts between tracks...
  
 All seems OK, but the issue is still here.
  
 So either I will let the amp heat for 30-45 minutes (when hot, much less DC events), or I will retry my DiYparadise Charlize T amp.
  
 Regards,
 JMF


----------



## Navyblue

Hi, sorry, haven't been checking this forum for a while.

I saw your postings at diyaudio.com , I'd suggest you give one more shot at the preamp forum there, which is much more popular and active than its headphone forum.

For me the puzzling thing is that why it affects both channels identically. If it isn't may there is something wrong with the servo, or there is intermittent power connection to the servo or the transistor. But if the episode affects both channels identically, then there aren't that many places to look at. Very strange indeed.


----------



## jmf

Hi,
  
 I'm puzzled as you are. Even the servos are independant and I only identified a common point at the e12 level, that I disconnected without improving the situation.
  
 On DIYaudio, I initially published on the amp forum, but the thread was moved to the headphone one. Less active but with better/longer exposition.
  
 Difficult to troubleshoot through internet discussions. So I'll live like this.
  
 Regards,
  
 JMF


----------



## pddjsteve

It's been a while since I've last been active on head-fi, but I'm most of the way through a SOHA II build and having some problems. I'm doing a standard build (no mods). I've gotten through the setup process with all readings normal all the way through to biasing the buffers, where my problems start. I am in the process of reading through the entire thread, but thought maybe someone has a quick thought on my situation.
  
 The left channel bias is dialed in just fine, with a voltage drop of ~222mV. The right channel, however, is seeing 0 voltage drop. I've so far measured that:
    - both trimpots are reading the same resistance
    - measuring the voltage on the pins of Q7L and Q7R, they are roughly the same
    - measuring the voltage on the pins of Q6L and Q6R, the readings are different
  
 The output relay clicks on as described in the build instructions.
  
 I don't have the exact measurements on hand (I'm at work) but this leads me to believe that Q6R is bad. I desoldered it and replaced it to no effect. This leads me to believe that either:
    1. another part in the right channel buffer is bad (nothing looks burned or cracked or anything)
    2. I damaged the pads on the board when I desoldered the first Q6R
  
 Tonight I'm planning on using some jumper wire to solder from the pins of Q6R directly to the previous and next components, and hopefully everything will work. If not, what would be the next logical step to check in the buffer components?


----------



## sipsik

This thread is pretty much dead. 
  
 According to initial setup page:


> The difference between TB+L and TPL (or TB+R and TPR) should be approximately 19V.
> If it is you're finished.If it isn't, go back and check the tail current in R6 to make sure that it is 2mA.
> This voltage difference doesn't have to be exact. Approximately 19V is good enough.


 
 My tail current in R6 is 2mA, but the voltage difference between TB+L and TPL is <1V. Everything works just fine(including sound). Should I be worried about that?


----------



## Airstar

Hello there!
  
 Soha ii from glass jar audios kit is now finished and it was time to start testing. Jumpers J1, J2 and J3 are still cut, because TB+ voltage is too low at about +23.9v DC when it should be over +100V. I searched thru all forums and I seem to be the only one with TB+ problem...
  
 I would say I'm good in soldering but just average in understanding how these circuits really work.
  
 TL+, TL- and TH DC voltages are spot on correct.
  
 I'm puzzled about the TB+ as it should be the easiest to understand. It is built from just the six D7P-D12P diodes and five C8P-C12P electrolytic condensators, right? Should I measure the test point as DC or is it still AC in this point?
  
 I have checked the solder work, should be ok but maybe a reflow would work just to be sure for the TB+ components. Anyways all components are correctly positioned and all condensators give their correct values when using DMM underside the board and also the diodes work.
  
 Damn, the build came up really tidy and all. But something has to be wrong...
  
 Best regards, Mikko


----------



## Airstar

Ok I did some resoldering. No luck. I still get 23,8 volts from TB+.
  
 Sorry for the false term condensator, of course I meant capacitors.
  
 I draw the powersupply with Multisim 13 and when I measure voltage at TB+ it says a little over 100volts DC so at least virtually I got everything working 
  
 However when I'm causing faults (short the capacitors in Multisim) in order to get just 20+ volt at TB+ I have to short C8P, C9P, C10P and C11P. If thats the truth and I have to replace all four of them I'm really puzzled. I have never destroyed a single capacitor by soldering before...
  
 How do you check from a complete board a single capacitor if its faulty? Just by the legs and the others won't interfere the measurement? Because when I do that, I get 88,8uF from all these four that are supposedly bad and the correct 100uF only from the big C12P cap.
  
 Oh well maybe I just have to trust Multisim and order 4 100uf 100V caps as spares.


----------



## jmf

Hi all,
  
 It seems that I have solved my DC events, that triggered the e12 from time to time.
  
 I tried to see what happened if using only one channel. So I removed the tube of one channel at a time. I tried all permutations of channel tube removed and tube. As a conclusion: one channel at a time was always working. But two channels at the same time generated those DC events. It could comme from a load problem on the power supplies.
  
 So I went again through the initial setup sequence to check the voltages and idle currents. Not changed a lot, but had to adjust slightly the tail current of the input staage of one channel.
  
 And now seems to work wothout DC events. Let's see over what happens the weeks...
  
 Regards,
  
 JM


----------



## scottie4442

I am working on building my SOHA II and I have the BOM at mouser. Problem is two of the transistors are no longer avaiable, the fairchild MPSA42RA and the Fairchild MPSA14_D74Z.  Any ideas on replacements for these, the MPSA14_D74Z is Q1p and q2p in the power supply and the MPSA42RA is q3e on the epsilon 12. thanks


----------



## jm7775

scottie4442 said:


> I am working on building my SOHA II and I have the BOM at mouser. Problem is two of the transistors are no longer avaiable, the fairchild MPSA42RA and the Fairchild MPSA14_D74Z.  Any ideas on replacements for these, the MPSA14_D74Z is Q1p and q2p in the power supply and the MPSA42RA is q3e on the epsilon 12. thanks


 
  
 I think you've swapped the descriptions, the MPSA14 is part of the e12 and the MPSA42 are in the power supply
  
 Try these
  
 512-MPSA42_J18Z, you may need to bend the leads slightly, also EOL but they're still in stock now
  
 863-MPSA14G, works perfectly in a build I recently did that cloned the simplified e12 in the SOHA II


----------



## scottie4442

thanks, I will add them to the BOM at mouser.  I am also going to try 610-MPSA14 and 512-MPSA42, this is what mouser says are substitues for the original.  I will try both of the replacements for each of these transistors and post on here what I findout


----------



## GT Den

Running into problems with the initial setup/start-up and I can't find the cause. 
  
 Amp has all the correct (very close) voltages before strapping jumpers J1 J2 and J3
  
 TL+ = +15.14
 TL- = -15.20
 TH = -12.36
 TB+ = 128.8
  
 After strapping J1 and J2 I don't have any voltage on R10L or R10R and there is no current flowing across ether. I do hear the e12 relay click after a few seconds.
  
 The buffers are installed and I have the correct +15v and -15v at the buffer (OPA134).
  
 I am using the current Mouser BOM with no mods installed at this time. I have double checked for bad solder joints and did not find any, I have checked almost every point on the board with the DMM and getting readings that I would expect everywhere I have checked.
  
 After a few hours on this, I have replaced Q5/Q8 (BC550C) and Q6/Q7 (BD139) and even ICL/ICR (OPA134) and I still have the same problems.
  
 Anyone have any ideas what I might check next?
  
 Thanks in advance for any help!


----------



## Crazy Sam

Hi, I'm midway through my build. 

Can anyone give me advice on how to install Q6R/L and Q7R/L?

From data sheets it seems like the BD 139 part should be installed like in the standard ECB layout with the 3-dot side facing away from the heatsink,
BD139: http://www.mouser.com/Search/ProductDetail.aspx?qs=ljbEvF4DwONoQGCKnqafCQ%3D%3D
ECB layout diagram: http://cavalliaudio.com/diy/soha%20ii/images/SOHAIINormalOPMounting.png

Am I reading this all correctly?

I am pretty confident I have the ECB order correct, since there are plenty of data sheets available for the part in the TO-126 package. However, I don't know if I have to flip it around so the heatsink is mounted to one side or the other. I'm sure a bunch of you can easily answer this.


----------



## GT Den

In the event that anyone else reads this post - I found the problem.
  
 Continued checking all components and found that I had installed 4.99K resisters in R12L, R12R instead of 4.99Ω as needed. D'OH!
  
 After correcting my mistake everything is now working as it should and the amp sounds great!


----------



## GT Den

Crazy Sam,
  
 If you are installing them on the top-side of the board - then yes - the printed side with the three dots will be facing away from the heatsink and you will use the mounting position towards the front of the amp (towards the tubes).


----------



## Crazy Sam

Hi All,
I'm getting good start-up sequence voltages but no e12 trip. e12 trips without tlo81 installed, however.
If anyone is able to help I can give you more details, but in the event that this thread is pretty much dead in terms of people who could help troubleshoot I don't want to waist my time typing up a bunch of voltages. Thanks in advance if you see this and can help!


----------



## GT Den

Hi Crazy Sam,
  
 Have you looked at the voltage (DC) on R1E and R2E?  If the DC offset is high, the relay will not trigger.
  
 If the relay is clicking without ICE (TL081) installed I would think that voltages to the relay are good from LV+E.
  
 What voltage to you have on v- of the TL081? (Pin 4)
  
  
 You and I might be the only ones reading this thread so I'll do my best to help were I can.


----------



## Crazy Sam

Hi GT Den,
During initial start up a few days back, I fried r10L with a short on Q7L. I think this fried some silicon, since the DC offset at R8L is ~12V while the R8R reading is nearly 0. If I disconnect the left side from the e12 by removing I think R1E, the relay clicks and the right side functions. I ordered new transistors from mouser and I will redo the left channel when I get a chance.

I hope this works - the right side as a mono preamp sounded very good.


----------



## ndhennin

Hello,
  
 I have finished (well, I thought so..) building my SOHA II.
 I have done the setup and it makes music.
 But I have a problem with that music...I have no bass...and not a lot of mid also, as I can hardly hear the male voices...
 In the upper, everything is perfect....
 Where can it come from ??? It sounds like I would have a high pass filter... 
 I have check all the capacitors values and it seems OK to me.
 Any idea where it could come from ?
  
 I think I have to mention that I am not spot on all the values given in the setup, but from what I read it shouldn't have been a problem.
 - TL+ and TL- ok at +15 and -15 V
 - TH 12,96 instead of 12,6 V
 - TB+ at 117V instead of 125V without the tubes (107V instead of 103V with the tubes)
 - I had no problems to get the desired voltages with the different trimpots and had 60V at TB+L and TB+R during set up
  
 After everything done and tubes installed, TB+L and TB+R are at 59,7 where it is said it should be at least 60V...
 On one channel I have my 19V difference with TPL but only 15V for the other chanel. I guess it comes from the tubes that are not paired (but it was said it was not necessary).
  
 So then, why no bass/mids ?
  
 Thank you for your help !


----------



## ndhennin

HAHAHA !!!!! 
 Working now !!!!
 It was just my jack plug that was going too deep and so I guess the ground was linked to one of the channel ! By just pulling it a bit out, everything works perfect !
 Thank you for my help )


----------



## headphonejunkie

Hi Everyone.
 I was wondering how things are going with the SOHA II out there. I am listening to my SOHA and am getting the urge to build a SOHA II. Any new upgrades that help make this amp that much more?


----------



## headphonejunkie

From quick research I wonder if it would be possible to add JISBOS to slots where the op amps are on the SOHA II.
 Would it not add that much more fidelity to the amp?


----------



## tomb

headphonejunkie said:


> From quick research I wonder if it would be possible to add JISBOS to slots where the op amps are on the SOHA II.
> Would it not add that much more fidelity to the amp?




There's no need for the Jisbos on the SOHA II. The output is already a discrete topology. The opamps serve as servo circuits to zero out the voltage offset without having to use output coupling caps.


----------



## headphonejunkie

Oh,Then I stand corrected.
  
 Thanks TOMB


----------



## FallenAngel

headphonejunkie said:


> From quick research I wonder if it would be possible to add JISBOS to slots where the op amps are on the SOHA II.
> Would it not add that much more fidelity to the amp?




Nope, the opamp is only there for feedback, not the signal itself.


----------



## jmf

Hello,
  
 I'm the happy owner of a SOHA II amp (kit bought at www.*glassjar*audio.com). I decided last week to print and archive all information about my amp, from http://www.cavalliaudio.com. And I was too late... Disaster ! There is still a web page, but there are not anymore the schematics, BOM, initial start-up sequence, the board drawings... All those precious information needed for the maintenance of the amp.
  
 I sent a message on the website to know if it was possible to get those information for maintenance purpose, but I had no answer.
  
 Would somebody have archived those precious information and agree to share them ?
  
 I especially need them to tune some bias. My amp seems to drift, and it seems to be the reason for e12 spurious triggers.
  
 I really hope someone will be able to help.
  
 Best regards,
  
 JM


----------



## jmf

Hi,
  
 Up... Nobody has archived the elements related to the SOHA II ? I asolutly need them for maintenance.
  
 Help !    
  
 JMF


----------



## jmf

Oups, it is back on http://www.cavalliaudio.com/pages/soha-ii
  
 Thanks a lot !!!
  
 JMF


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## eruditass

jmf said:


> Hello,
> 
> I'm the happy owner of a SOHA II amp (kit bought at www.*glassjar*audio.com). I decided last week to print and archive all information about my amp, from http://www.cavalliaudio.com. And I was too late... Disaster ! There is still a web page, but there are not anymore the schematics, BOM, initial start-up sequence, the board drawings... All those precious information needed for the maintenance of the amp.
> 
> ...


 
  
  
 What do you tune to deal with the drift? 
  
 I'm having similar yet different issues with e12 spuriously triggering, but did not build this amp.  I've got some basic knowledge of electronics (studied a bit of EE back in the day).  I bought this amp a long time ago from another user here (who  separated the power supply into another box).  
  
 R8 does have some DC voltage with a multimeter during those times.  I thought I had seen it on both channels, but now it's definitely just the R channel
  
 I did tweak the tail currents to be exactly 200mA, but that did not solve the issue.  Now, curiously, it got in a state where if I have my basic DMM between ground and either R8L or R8R, the DC offset goes away and it plays sound.  And the instant I release it, the sound cuts off instantly.  Some time later, depending on how warmed up the tubes are, it comes back on its own.
  
 Any tips for what to investigate? What's the deal with the DMM fixing the sound: is it a grounding issue? All the test points from the website look good, though my drop from TPL and TB+L is only 15V (same for the right channel).  
  
 Source is a E-MU 0404 USB DAC off of a laptop.


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## eruditass

Looking closer and at the instructions, it appears my amp is missing the star ground stand-off screw between the two heatsinks? I'm a bit surprised I don't have bigger issues if that's the case. The only ground is through the power supply connection (a separate box which is grounded to the chasis) and the output pot / headphone-out's connection to the front plate (from what I can tell, the box and plates are all separately annodized and thus aren't connected)?
  
 Nevertheless, the DC offset is just the R channel, so would that indicate that it isn't a grounding issue? Test points on both sides all look good.  Issue does not follow the tube.


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## Swashinxzero

hello, all the links to cavalli website are dead... are the instructions to building this amp still available somewhere? looks like glass jar sells pcb but thats all i found...


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## tomb

You can try the wayback machine:
https://web.archive.org/web/2011042...iaudio.com/diy/soha ii/main.php?page=overview
You will need to go back to 2011, at least, then look for links to "DIY."  Also, don't confuse the SOHA II with the original SOHA, The Simple Opamp Hybrid Ampiflier.

You can also try e-mailing Jeff Rossel at GlassJarAudio.  Maybe he kept copies of the documentation.  I think you can find everything through the wayback machine, though.


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## Swashinxzero

tomb said:


> You can try the wayback machine:
> https://web.archive.org/web/20110423055317/http://www.cavalliaudio.com/diy/soha ii/main.php?page=overview
> You will need to go back to 2011, at least, then look for links to "DIY."  Also, don't confuse the SOHA II with the original SOHA, The Simple Opamp Hybrid Ampiflier.
> 
> You can also try e-mailing Jeff Rossel at GlassJarAudio.  Maybe he kept copies of the documentation.  I think you can find everything through the wayback machine, though.


Thanks!


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## onform (Dec 31, 2019)

Some of the schematics are missing but otherwise most of the info is there.

Also I Emailed glass jar, still no response.

thanks


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## Swashinxzero

new diy builds took over or people dont build so much these days? It feels like lots of diy tube amp kits/designs are being left in the past...


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## HGunn

it seems this thread is mostly dead but I am hoping someone can help me out. I found my old SOHA Amp in a box and thought I would get it up and running again. I have been able to find the original instructions for testing the voltage on the PBD but it seems mine are all completely wrong. Hopefully someone can point me in the right direction for where to start probing the components on the board. My measures values are as follows:
(Probed value vs measured value)
Input voltage = 30V 
+12V = + 12V
-12V = -4V 
40V and 60V = 104V

it seems the only voltage that is correct is the 12V. And to be sure I’m not doing something completely stupid this is all measured with the negative on the MM connect to the ground on the board and the positive lead connect to the test point.

Any tips or insights anyone could give would be greatly appreciated!


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