# SOHA II - Super SE Hybrid



## runeight

Hello folks. I've had a few enquiries about the SOHA II. So here is an update.

 The SOHA II is a vast improvement over the SOHA. You won't need any addtional buffers (such as the jisbos) because it already has a high current SE buffer built into it. And I already know about making buffers with a high Zi when loading tubes so you won't have to wait for another release to get this feature.

 The front end no longer needs a plate CCS or a trimpot adjustment, but it will still maintain the correct plate voltage. It doesn't even use an opamp servo to do this. 
	

	
	
		
		

		
			





 The SOHA II will have the basic topology of the SOHA I with just a small coupling cap between the input stage and the buffer. It WILL NOT require a big output capacitor to interfere with the sound.

 The SOHA II has an improved voltage doubler to create the B+ and like the SOHA I, it all runs from a single 15-0-15V/1A transformer.

 But, better than the SOHA, the SOHA II Super SE will allow you to roll different tube types into the front end. Want to run 12au7s? No problem. Want to run 6922s, just flip the heater switch (or change the jumpers) and replace the tubes. Any set of triodes where two of them can run with 12.6V/300mA (series or parallel) will work without requiring any adjustments for voltage. 600mA can be supported with a bigger transformer and larger heatsinks.

 The amp fits into a Hammond 1455T2201 (160mm x 220mm) enclosure. The extra room at the back of the box is for the tranformer and a DAC (if you want one). The amp board alone will fit into the shorter 1455T1602 hammond enclosure so that you can put the toroid in a walwart.

 The amp also has a built-in e12 delay/offset unit. The board is 160mm x 115mm.

 dBel84 has built the first proto on homemade boards. The amp works as designed.

 I'll be looking for prototypers soon who are willing to build on the first commercial boards to test the fit and finish of the amp. If you're interested I think we may want about 5-10 prototypers.

 So you can put your SOHA away with other amps that you've been building and try the next generation of hybrid amp from the guy who actually DESIGNED the original SOHA amplifier, the remake of the CKKIII amp (in collaboration with AMB), and the Bijou.


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## Postal_Blue

Sounds exciting. I am always on the lookout for a new build. Sign me up as a prototype volunteer.

 Edit: And of course I will buy only an official board from the designer.


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## shallbehealed

sounds delicious. can't wait to hear more.


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## FallenAngel

That's pretty awesome Alex, can't wait to build this thing. When you're ready to look for prototypers, I'll definitely be interested


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## dBel84

I can tell you all that this amp has been well thought out and has a really good layout. I am a fan of symmetry and form - no disappointment here and it is a very compact amp considering everything that has gone into it. The good news is that it is fairly straight forward to build and once I had everything in the correct place, it fired up as designed. 

 I am still working on small tweaks which we feel would be beneficial to the builder and although have had a preliminary listeing session or 2, I want to spend more time before I give a critical appraisal of its performance. I will say that it has enough bass which is well controlled to satisfy even the biggest basshead fans and overall impressions thus far are very very good. 

 Thanks to runeight for making this one happen ..dB


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## runeight

And I would like to thank dBel84 for ALL of the work he's done to get this amp built. NOTHING would have happened without his efforts to build this amp on a homemade PCB so that we could test it before committing to commercial boards.


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## dBel84

the fun was all mine 
	

	
	
		
		

		
		
	


	




 ..dB

 A picture - I haven't taken any more with the board fully populated but in case some of you missed my teaser post in the build thread


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## Tridacnid

Drool....


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## synaesthetic

Does the SOHA II still keep the original SOHA's goal of a low-cost hybrid amplifier in mind?

 Or is it more akin to the Millet Max, with performance superseding cost?


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## dBel84

Quote:


  Originally Posted by *synaesthetic* /img/forum/go_quote.gif 
_Or is it more akin to the Millet Max, with performance superseding cost?_

 

 I take it you are excluding the papaya oil-rice paper caps in this statement. 
	

	
	
		
		

		
		
	


	




 The SOHA II - Super SE retains simplicity in circuit design and optimizes all aspects to offer a high performance LOW VOLTAGE amplifier. It costs proportionally more because it has more components but in the grand scheme of things, it will still be relatively cheap to build. If you want creme of the crop, build a Stacker II as it is designed to squeeze every nuance out of the tube's performance , BUT be prepared to spend more money to get that performance and work with 300V. I believe SOHA II Super SE will get you 95+% of the way there, but I am not going to commit to that until I have spent more time with this amp and had time to "objectively" compare them. My Stacker is on a small trip to the NoCal meet (so enjoy Fallen) and I will be able to have a good listen when I get it back. Based on memory - this new amp is no slouch ..dB


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## runeight

Quote:


  Originally Posted by *synaesthetic* /img/forum/go_quote.gif 
_Does the SOHA II still keep the original SOHA's goal of a low-cost hybrid amplifier in mind?_

 

Yes, but the SOHA II SSE/H expects to get excellent performance at reasonable cost. It will cost more than the SOHA, but it will have quite a few additional features (and fewer quirks) to go along with that additional cost.


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## synaesthetic

I'm glad I waited before building a SOHA, then. I still need more tools, as this recent failed PIMETA build has demonstrated. But once I'm set up adequately, I'll definitely give this amp some serious thought. <3


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## keyid

cant wait to build one! the soha has been my main amp for awhile. 
 Its got almost everything I wanted! delay built-in is pretty sweet. 
 Glad to hear 12au7 will still be compatible. In the picture there's two tubes. Do they need to be matched?


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## runeight

The tubes don't need to be matched to each other. However, the operation of the input stage will be helped if the two triodes in each envelope are reasonably close. That is, no more than 20% difference in plate current for the same voltages. But, even if the tubes are more different than this, the front end will still work perfectly alright.

 When I make the website available with an explanation of the design, you'll see why this is so.


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## JamesL

Great job like always runeight and the amp looks fantastic dbel!
 I can't say I'm thrilled about the MHM-styling of the board, but I've been looking forward to this for a while, and I'm definitely looking forward to building and listening <3


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## regal

Runelight for my education what is the downside to a tube with non-matching triodes? I imagine that the current thru both sections has to be the same but the resting p-k voltage will be different, what does this lead to ?


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## n_maher

Quote:


  Originally Posted by *regal* /img/forum/go_quote.gif 
_Runelight for my education what is the downside to a tube with non-matching triodes? I imagine that the current thru both sections has to be the same but the resting p-k voltage will be different, what does this lead to ?_

 

The real question is how to test the tubes for matched operation in this specific circuit. I've had a fair number of conversations with various tube vendors over the years and those whom I trust most have almost always advised against any sort of matching service (to their own financial detriment, I might add). Their reasoning is this, most tube testers that do matching are going to test the tubes at radically different operating points compared to how the end user might. And given that tubes are not a linear device there is no guarantee that tubes that test as "matched" will perform as such in-circuit. Of course this means that the converse is also true, tubes that don't test as matched might very well perform just fine in a particular circuit.

 At least that's the layman's explanation that I've put together, I'd love to hear from more knowledgeable folks.


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## runeight

n_maher, this is is all quite true. In this case, even more so as tubes are not likley to be tested at 40V on the plates.

 I probably shouldn't have even commented on this because the TUBES DON'T HAVE TO BE MATCHED IN THE FRONT END.

 regal, i am happy to answer this at a later time. Digi01 (why he keeps following me around I cannot figure out) has posted to the Headwize thread offering to make boards. So far I have not posted any schematics so he can't do that and I was about to post some further circuit information to explain some of the amp's innards.

 Because of Digi's post, no further explanations for a while. Sorry. 

 Now perhaps some of you guys can get Digi out of my hair by insisting that you won't buy boards from him if he once again hijacks my work.


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## n_maher

I didn't realize there was such a fiasco with the original SOHA boards, sorry to hear that.


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## user18

Is SOHA II == Stacker II?


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## dBel84

No SOHA II SE is a completely new amp, it uses a low voltage power supply and is all incorporated onto a single board with a compact footprint. Stacker II is a modular HV hybrid that is propotionally more complex..dB


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## vixr

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 Now perhaps some of you guys can get Digi out of my hair by insisting that you won't buy boards from him if he once again hijacks my work. 
	

	
	
		
		

		
		
	


	


_

 


 count me in to only buy "real" boards, from designers or authorized sellers...


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## DolbyR

Quote:


  Originally Posted by *vixr* /img/forum/go_quote.gif 
_count me in to only buy "real" boards, from designers or authorized sellers..._

 

I double that.
 If there qill be a GB for the "official" boards, I'll definitely use that opportunity just so it wont be necessary to get Digi's boards on a later time. Although I still don't consider my current SOHA 100% ready, I can't miss by any means the building of SOHA II.


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## Clutz

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_regal, i am happy to answer this at a later time. Digi01 (why he keeps following me around I cannot figure out) has posted to the Headwize thread offering to make boards._

 

digi still doesn't seem to realize, or accept, that what he did was unacceptable behaviour. I think it would be fantastic if everyone would post that if they are going to build this board, they will only use boards officially sanctioned by runeight.


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## adamus

Runeight, does this have a similar sound sig to the original soha + Jisbos? 

 I have just wired up my jisbos and the difference in sound (fuller, more powerful) is fantastic, even over a good opamp (2107)


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## Tridacnid

I will only build with an official board, from a sanctioned seller.


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## Ferrari

runeight & dBel84, thanks for sharing this new amp! 
	

	
	
		
		

		
		
	


	




 I have noticed that there are 3 OpAmps on the SOHA II board. The one on the front belongs to the ε12 circuit (?), then there are 2 other OpAmps on the left and the right of the board, does it means that the output buffers included an OpAmp based DC servo circuit, similar to the one used in the CK²III ? 
 Btw, where is the relay of the ε12 circuit mounted? (arggg... I can't find it on your pic 
	

	
	
		
		

		
		
	


	




, dB).


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## MoodySteve

I'm not even done with my SOHA + JISBOS, can't you guys slow down?! 
	

	
	
		
		

		
		
	


	




 I will respect the wishes of the designer (who is, after all, kind enough to share his designs) and only use approved boards.


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## dBel84

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Btw, where is the relay of the ε12 circuit mounted? (arggg... I can't find it on your pic 
	

	
	
		
		

		
		
	


	




, dB)._

 

my bad for not taking new images after I had it all tested and working. These were earlier images and had not been fully stuffed. So yes, relay and then some is missing. Interestingly, this amp does not suffer the start up / shut down transients that we have experienced with other hybrids. I think the e12 circuit is still a good idea as it will protect the headphones in case of failure or behaviour different from this build and it is a small price to pay in terms of additional components. The opamps are not in the signal path and are indeed part of the servo/e12..dB


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## runeight

adamus, I don't know about the sound compared to the SOHA/JISBOS. Only dBel84 has a version of the amp at this moment. I guess one or two of you intrepid builders might have to build one and then compare.

 But, there is no surprise that putting a discrete buffer on the SOHA significantly improves the sound. This was my next step before the amp was hijacked.

 Ferrari, the other two opamps are indeed for the output stages. But they are isolated from the AC signal paths by 1M resistors. They will not influence the signal. In the picture that dBel84 has posted, the relay is not mounted yet.

 MoodySteve, I've got even more designs lined up behind this one. 
	

	
	
		
		

		
		
	


	




 Many thanks to each of you who has agreed not to buy "unauthorized" boards.


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## JamesL

+1, I'd never buy boards not permitted by the original designer.
 I don't want to open up a can of worms, but the sort of tension with the first SOHA... does it have anything to do with this?


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## Beefy

Official boards all the way!


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## runeight

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_+1, I'd never buy boards not permitted by the original designer.
 I don't want to open up a can of worms, but the sort of tension with the first SOHA... does it have anything to do with this?_

 

No probs JamesL. Yes it is a direct consequence of what happened to the SOHA. Now I don't care much about that anymore. The SOHA is a popular amp and has provided lots of diyers plenty of hours of fun and a few of them an opportunity to provide add-ons for the amp. But I wonder how many of the SOHA's builders actually know who designed the amp? And whose idea it was in the first place? 
	

	
	
		
		

		
		
	


	




 The main thing that this history is doing right now is preventing me from telling you about the amp's design and showing you schematics.

 But quite a few folks have signed up to prototype the amp and we'll go forward to make it available. It is a cool amp. Of the many I have designed, I like this one a lot. I'm hoping that it sounds really great too.


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## V-DiV

I'm looking forward to building a SOHA II using the official board once the design is finalized. Thanks for all of the work you guys put in for the DIY community. You should get your due recognition.


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## keyid

- will buy "official" boards but I will also buy the first run of boards which should be the "official" boards. Anyone seeking knowledge at headwize would know the designers.


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## pabbi1

If I were to build this (after somehow not liking the Bijou), it would be with official boards. Looks like Digi has bowed out - iff he is to be believed.

 Crap, spoke too soon...Digi's response - what chutzpah.


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## jonjon0nline

I'm clueless with the controversy but I'd like to buy a couple boards when they're out


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## Beefy

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_If I were to build this (after somehow not liking the Bijou), it would be with official boards. Looks like Digi has bowed out - iff he is to be believed.

 Crap, spoke too soon...Digi's response - what chutzpah._

 

I don't like dragging up the unpleasant past..... but is there anywhere that would supply a nice little summarised history of the 'problems' with the SOHA?

 From what I have gathered so far, the low quality of the boards Digi produced almost killed the project.......?


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## Clutz

Quick version:

 runeight designed a new hybrid amp called the SOHA, and had released the pre-release schematics to headwize for comments, so the design could be improved by community discussion.

 digi went and made his own boards based on the pre-released schematics and started selling them to people - this was despite the fact that he was asked by numerous people NOT to do this.


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## synaesthetic

This is a much more "all in one" solution than the original SOHA and I would be very interested in building one. Eagerly awaiting boards. <3


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## runeight

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_I don't like dragging up the unpleasant past..... but is there anywhere that would supply a nice little summarised history of the 'problems' with the SOHA?

 From what I have gathered so far, the low quality of the boards Digi produced almost killed the project.......?_

 

Our friend Digi01 has posted some comments on the headwize SOHA II thread.

 The best thing for us to do is to move forward to prototyping this amp. It is better than the SOHA, it will have a better board, and better audio. It will allow you to tube roll different tube types which you cannot do with other popular hybrid amps.

 I am going to contact each of you who has agreed to prototype the amp and we'll get started. I may even have to build one of these myself. In fact, I've already bought the enclosure and a few other parts just to test the fit in the box.


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## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The best thing for us to do is to move forward to prototyping this amp. It is better than the SOHA, it will have a better board, and better audio. It will allow you to tube roll different tube types which you cannot do with other popular hybrid amps._

 

Check! 
	

	
	
		
		

		
		
	


	




 I'm looking forward to final versions, complete with hand-holding commentary. I don't nearly have the experience to be involved with prototyping just yet.....


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## ericj

I should probably finish my Stacker II before asking to prototype this amp . . . . 

 maybe I'll do that tomorrow.


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## m0b1liz3

Any idea of how long the prototyping process will take?? I will likely wait till it is done!


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## dBel84

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I should probably finish my Stacker II before asking to prototype this amp . . . . maybe I'll do that tomorrow._

 

we all wait diligently 


 @ m0b1liz3 very good question , perhaps ericj would have a better handle on this >:-D 





 ..dB


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## GeWa

Is there a preliminary BOM available so we can start shopping around for parts?

 Regards


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## ericj

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_we all wait diligently 


 @ m0b1liz3 very good question , perhaps ericj would have a better handle on this >:-D 






 ..dB_

 


 "how long prototyping lasts" is an issue of the fact that this is all volunteer labor. Those who prototype these amps are doing it on their own time, with their own budgets. 

 We could have all been done prototyping the stacker II two or three weeks ago, but, we're not. I'm very close to testing the whole amp, as i suspect are others. 

 Some pressing situations have come up that distracted me from the stacker II, and i can only assume that the other prototypers have had one sort of setback or another. 

 So while i sure feel like i'm holding back the stacker II release, i have to ask, where's donalds, or shanes, or marks, or jeffs . . . . I expect they're in much the same place at this point: 95% complete and not fully tested.


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## dBel84

just ragging you, I fully understand the trials of protoyping and that there is no such thing as "normal" ..dB


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## ericj

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_just ragging you, I fully understand the trials of protoyping and that there is no such thing as "normal" ..dB_

 

Yeah, I know. And my Stacker II could still be met with catastrophy, too.


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## runeight

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Is there a preliminary BOM available so we can start shopping around for parts?

 Regards_

 

GeWa, I have a BoM. I'll be publishing that soon. Right after we gather the prototypers together.


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## runeight

OK everyone. I have sent either an email or a PM to anyone who expressed interest in prototyping. If you don't receive an email or PM from me in the next day it means that I missed you. Sorry. But please PM or email me.

 I will be out for business tomorrow most of the day and won't be able to check emails, but I'll be back tomorrow night.

 Time to get things moving.


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## runeight

Hello folks. Emails have been sent to everyone interested in prototyping. Along with a ton of information for them to look at.

 In the meantime, it seems reasonable to post some aspects of the design so you all can begin to see where this is headed.

 This is the SE output buffer. I'd been working on this, on and off, for a while. There is a headwize thread where some emitter follower buffers were discussed too.






 The nice thing about this buffer is that it is simple and, for a self-zeroing buffer, has a fairly low component count. The top two transistors are a Darlington emitter follower. The 820R resistor ensures that the BC550C stays in class A at all times. The darlington pair has a high current gain which translates into a high Zi.

 The bottom pair of transistors is a ring-of-two CCS. Notice that the two transistors are different. The power BJT is necessary to source the 100mA idle current where the buffer is designed to operate. The BC550C provides the needed gain to make the BD139 a respectable CCS.

 "C" class BC550s are needed to ensure enough HFE for both devices.

 The CCS exhibits a dynamic resistance of about 37k. This is pretty good for a power transistor CCS and is plenty good for this application. It would not be good, for example, as a plate load where Gig ohms are desired, but for this location its suitable. 37k is thousands of times larger than the Zo of the follower and more than 100 times larger than the headphone impedances. 

 The servo is straighforward, using a single inverting opamp configuration to set the base voltage of the BC550C. This is where the Darlington really helps us because, the very low base current of the small signal device makes it possible to use 1M resistors to couple the servo to the input, keeping the servo very well isolated from the signal path. The 18k resistor forces the opamp to draw about 1mA continuously, keeping it in class A operation under all normal conditions.

 The theoretical Zi of the buffer is about 950k for the audio band and somewhat beyond. This is sufficient for any of the tubes that will be driving it.

 In dBel84's build these buffers are adjustable from about 60mA to 125mA. If you run high Z headphones all the time, then 60mA idle will be sufficient to stay very far into class A for almost any condition. If you run lower Z phones, then you can dial up the idle current to ensure that you are in deep class A. Of course, the more current, the hotter the devices will get.

 In the prototyper the buffers zero their outputs in less than 5s, with only a very small voltage spike.

 Edit: Someone pointed out to me that the rail decoupling caps for the opamp were left out of the schematic. I've put them in.


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## Ferrari

Thanks for the elaboration of this nice compact output buffer… very smart approach 
	

	
	
		
		

		
		
	


	




.
 Can’t wait to try some Toshiba transistors (2SC2238, 2SC3422) I have on hand out on this buffer. 
 Anyway, I will do my homework and report back soon.


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## Gross

Since this is called the SE version, is there plans for a Balanced version?

 Oh yeah, and I sign the 'Only Authentic Boards' Petition too.


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## dBel84

finally got round to taking a few more images - here is how it all lays out..dB


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## runeight

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Thanks for the elaboration of this nice compact output buffer… very smart approach 
	

	
	
		
		

		
		
	


	




.
 Can’t wait to try some Toshiba transistors (2SC2238, 2SC3422) I have on hand out on this buffer. 
 Anyway, I will do my homework and report back soon._

 

Thanks Ferrari. We'll look forward to your results. I'm curious to know. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Gross* 
_Since this is called the SE version, is there plans for a Balanced version?_

 

Do you mean balanced or complementary output? If balanced, this would be very easy to do. Each board (two channels) will make a single channel balanced amp. Two boards will get you a fully balanced amplifier. The boards are small and self-contained, casing should be easy.

 If you mean complementary output buffer, why yes, there is a version in the works with a fully complementary, high Zi buffer.


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## Gross

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If you mean complementary output buffer, why yes, there is a version in the works with a fully complementary, high Zi buffer. 
	

	
	
		
		

		
		
	


	


_

 


 You kick ass. That is the answer I was hoping for (and suspected)


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## amb

Gross, "SE" here refer to the single-ended output stage topology (as opposed to "push-pull"). You're confusing the terminology where it's SE vs. balanced (i.e., ground-referenced vs. differential). Very different concepts.

 The term "single-ended" is _very_ overloaded and causes lots of confusion. That's why I prefer to use the word "unbalanced" rather than "SE" in the second scenario.


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## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_In dBel84's build these buffers are adjustable from about 60mA to 125mA._

 

My knowledge of these things is still very limited. But that seems like a high current for those BJTs - much higher than the PPAv2, CKKIII, MHM, although these do have smaller/no heatsinks.

 Is it only a matter of heat management to be able to set the current that high?

 Also, I'm a little curious as to what the three heatsinks are attached to in the top right, which I am guessing is the power supply section......?

 Cheers!


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## runeight

It is a high current, but not extraordinarily high. The buffers you mentioned are all complementary buffers and idle at lower current. But, to keep an SE buffer in class A it has to idle at much higher currents. This is because on the signal swings the buffer will traverse most of the idle current range if the idle current is not set high enough. Getting too close to the idle current limits generates increasingly more distortion the closer you get. So, in class A you want to stay far away from the idle current.

 The heatsinks are 13C/W and the devices dissipate about 1.5W. There will be a temp rise of more than 20C in a closed space. The devices will run over 50C. The buffer will heat up considerably and will require really good ventilation.

 The other heatsinks are the PS, as you guessed.


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## Blooze

Quote:


  Originally Posted by *ericj* /img/forum/go_quote.gif 
_I should probably finish my Stacker II before asking to prototype this amp . . . . 

 maybe I'll do that tomorrow._

 

Well, as soon as I get my heatsink insulators from Jeff (on their way!!!!), I'll be able to fire my Stacker II up as well. Why is it I always forget one little thing on that Mouser order?

 I've got a lot of tubes I'd like to throw in it.

 For me it was a choice between waiting on the SOHA II kinks to be worked out when we were messing with it over a year ago, and going forward with the Stacker II. I just have too many different tubes I'd like to try. I'm hoping the Stacker II also makes a great pre, because of the ability to try those different tubes.


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## dBel84

I am looking forward to hearing your impressions. I took some time out to paint the soha ii chassis and managed to get the image on the top plate - got a little damaged but overall worked out to my liking..dB


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## Gross

Quote:


  Originally Posted by *amb* /img/forum/go_quote.gif 
_Gross, "SE" here refer to the single-ended output stage topology (as opposed to "push-pull"). You're confusing the terminology where it's SE vs. balanced (i.e., ground-referenced vs. differential). Very different concepts.

 The term "single-ended" is very overloaded and causes lots of confusion. That's why I prefer to use the word "unbalanced" rather than "SE" in the second scenario._

 


 Oh, I think we are all on the same level here, it is just a matter of lingo used. I work for a prosound company and deal with balanced and unbalanced connections all day. I guess ultimately what I was asking was if the amp will have a unbalanced input, with a push-pull buffer output. 

 But thanks for trying to clear things up.


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## TimJo

I look forward to reading about the impressions from the folks doing the prototypes. The tube rolling option is a nice design addition. Great work!

 I have to say I stayed away from the SOHA partly because of the whole Digi issue. It is great that you have forged ahead and have improved the design in the process. Have no worries, I will only build this using the official board purchased from an authorized source.


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## GeWa

Awfully quiet here! 
	

	
	
		
		

		
		
	


	



 I hope it's because the prototypers are hard at work to get the amp ready for the mass. 
	

	
	
		
		

		
		
	


	




 Regards


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## Ferrari

Yes... a bit quiet at this place, but behind the scene we are busy (as good as we can).
 Patience will be reward!


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## runeight

Thanks Ferrari.

 As are result of input from the team and dBel84's prototype, we've made a few mods to the board. Final version went to Jeff R for making proto boards.

 The rest of the proto team has been very helpful in looking at enclosure opportunities and helping me ensure that the website is ready to go.

 Things will have to wait a bit now for the boards to come back. Should be soon.

 If I am persuaded enough that the theft of my designs has stopped, I may post the front end design so you all can see the whole amp. 
	

	
	
		
		

		
		
	


	




 -ac-


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## djbob

This sounds like an awesome design with alot of options. I especially like the tube-rolling ability. I'll be on the look-out for a group buy, unless you need another prototyper
	

	
	
		
		

		
		
	


	




 I'm in-between projects and quite bored. So bored, that I have started doing things around the house before my wife asks me to


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## MrMajestic2

Quote:


  Originally Posted by *djbob* /img/forum/go_quote.gif 
_So bored, that I have started doing things around the house before my wife asks me to
	

	
	
		
		

		
		
	


	


_

 

That cant be good


----------



## runeight

Quote:


  Originally Posted by *djbob* /img/forum/go_quote.gif 
_So bored, that I have started doing things around the house before my wife asks me to
	

	
	
		
		

		
		
	


	


_

 

We'll try to fix that.


----------



## 04BluMach

Glad to see that the SOHA II appears to be approaching a release to the masses point finally with Proto boards being produced.

 Have been anxiously awaiting the release of the "Real" SOHA by runeight since the original SOHA thread was posted and then rapidly derailed....

 I had no interest in buying the original SOHA Digi hacked board. Thought about building a P-P circuit, but decided I would just wait till the "Official" runeight design would be brought out as a thru-hole PCB offering.

 I suppose that says, I have no intention of participating in any venture that involves the theft of anothers intellectual capital. I eagerly await a runeight santioned release of the SOHA.

 If you need any other proto builders or help in reviewing tech data (BOMS, write ups, etc), I offer to help in any way. I really would like to see this project come to fruition. 

 It is very unfortunate that runeight (and others) feel that they can not actively present their designs (due to concerns over the loss of intellectual data rights) in these DIY forumns as a collaborative environment to gain Peer review and comment to various circuit implementation approaches and concepts. As such, all suffer from not being exposed to that design process, nor the designers benefiting by others inputs/comments) and the community from the learning oppurtunity that is lost.

 Certainly, it would be easier if all respected the individual's rights to ownership of intellectual data, but maybe the forumns rules need to be ratcheted up a couple notches and more rigorously enforced (ie Don't allow group sales of "unsanctioned" PCB's). Maybe a separate forumn topic area could be established just to afford circuit developement and prototyping to be accomplished in a "No Stealing ZONE"..... Don't know if this is possible or even desireable - just a thought. 

 Again, glad to see the SOHA II approaching a release point - its been a long time coming...


----------



## runeight

Thanks very much 04BluMach. We're getting very close to having boards for the prototype team. 

 I appreciate your thoughts here. I have almost completely stopped introducing collaborative threads because of the way many individuals (not just Digi) participated in sidetracking the SOHA.

 But, I am going to try again on this forum to see if those very same individuals will do the same again. I guess you can say, "Fool me once shame on you, fool me twice, shame on me." We shall see.


----------



## runeight

Alright, now it's time to talk about the input stage.

 There were several problems with the input stage of the SOHA:

 1. A difficult CCS situation
 2. The need for a trimpot to adjust the plate voltage every time tubes are changed
 3. Inability to run tubes other than 12AU7s

 The first problem to tackle is #2. How can we automate the equivalent of the trimpot adjustment? Well, the first necessary item is a way to sense the voltage at the plate of the triode. We must be able to measure this to compare it against a reference so that we can adjust some control point on the triode (such as the cathode resistance).

 But, remember that an important design parameter is the impedance that the input stage sees. We want to keep it very high. Now the only way to sense the plate voltage is to put a resistor there connected to some active circuit (like an opamp servo). And this resistor will always reduce the load on the tube. Unless we make it something like 10M in which case it will introduce noise. Furthermore, using an active mechanism like an opamp servo introduces complexity that we really shouldn't have in the input stage (but it's ok in the buffer where we MUST control the DC offset).

 So, what do we do? Well, we need another kind of sensing and reference scheme. For the SOHA II, the sense/reference scheme is a common cathode amplifier (a sibling of a differential amp) that uses two triodes connected at their cathodes. Like this:






 Now much explanation is required so hang in there.

 First, the tail of the triode pair is loaded with an adjustable CCS. Don't panic yet because the trimpot has a different function than the SOHA. This CCS is typically set to run at 2mA.

 Second, the plate loads are a current mirror with the control (diode) side of the mirror on the first plate. This current mirror divides the current between the two triodes exaclty in half (within component tolerances) setting the current in each triode to 1mA.

 The behavior of these two CCSs never changes unless the stage goes out of its operating region (say by being way over driven). The fact that they never change is really important. Why?

 Well, look at the circuit on the first plate. It consists of a 220R resistor, the BE junction of the BJT, and an 18k resistor in series. Remember that these three components are always seeing 1mA of current which means that they will always drop approximately 19V. If the B+ is at 60V (the design center) then the plate voltage on the first triode will be 41V.

 So far so good. 
	

	
	
		
		

		
		
	


	




 Now, what happens at the second triode? Well, the tail CCS adjusts the cathode voltage so that the first triode will pass 1mA with 41v on its plate. This is the same cathode voltage that is on the second triode. Now since the second triode has the same cathode voltage as the first triode and since it is conducting exactly the same current, 1mA, then its plate voltage MUST be the same as the first triode, namely 41V.

 Of course, how close the second triode's plate voltage is to 41V depends on how well the triodes are matched. In general, triodes in the same package of a functioning tube are farily well matched. Furthermore, the circuit will tolerate some amount of mismatch. The voltage on the second plate won't be exactly 41V, but gents these are tubes and a few volts in either direction really doesn't matter. Still, the closer the triodes, the closer the plate voltages.

 If you look carefully you will also see that the first triode operates as a cathode follower because its plate voltage is held constant. The cathode follower drives the second stage which is wired as a grounded grid amplifier. So, this is not a differential amplifier. One othe feature of this configuration is that it does not invert the phase of the signal.

 Notice that there is no tube type on the schematic. This is because the CCS and mirror do their jobs no matter what type of triodes are there. The only thing that changes is the cathode bias that will set that triode's operating point to be 41V and 1mA.

 Back to the trimpot. The trimipot only needs to be set once to establish 2mA in the cathode circuit. After that you can roll tubes until you drop and the circuit will do the right thing without your having to make any adjustments.

 And if there are tubes that are way out of balance, you'll just hear it in when the second triode hits the rails too soon. Bad tube.

 Also, any triode pair will work providing that they can operate at the low voltage, low current conditions. A good rule of thumb is that the triodes are safe if the cathode voltage is at least 300mV above ground.

 The current mirror's dynamic half presents over 3M resistance to the plate. This resistance is in parallel with the buffer's Zi (about 950k), making the actual plate load about 720k. This is high enough for any triode pair that I can think of using in this amp.

 So here we have it. The replacement of the SOHA front end that removes its problems and lets you tube roll, not just different tube of the same type, but different types of twin triodes too.

 The last step is to put the buffer together with the input stage to make a single channel amp. There is one more feature when this happens that will have to wait until that post.


----------



## Heady

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks very much 04BluMach. We're getting very close to having boards for the prototype team. 

 I appreciate your thoughts here. I have almost completely stopped introducing collaborative threads because of the way many individuals (not just Digi) participated in sidetracking the SOHA.

 But, I am going to try again on this forum to see if those very same individuals will do the same again. I guess you can say, "Fool me once shame on you, fool me twice, shame on me." We shall see._

 

runeight,
 I think it will be hard to avoid what happened the last time. For example, there were clones of Tangent's PPA boards being offered for sale in the Far East. When people have the capability but not the ethics then it will not occur to them that it is wrong.

 But to be fair, even though I am no fan of the person who sold the SOHA board, the SOHA incident was not a case of piracy but an individual who used an opportunity of a community desire for a PCB, to profit from it by organising the PCB production.

 Rather then being continually haunted by this incident, we should just learn from it and move on. Just my 2 cents.

 Regards.


----------



## runeight

Quote:


  Originally Posted by *Heady* /img/forum/go_quote.gif 
_runeight,
 Rather then being continually haunted by this incident, we should just learn from it and move on. Just my 2 cents.

 Regards._

 

Thanks Heady. I am counting on it.


----------



## pkjames

very exciting! can't wait to see the boards roll out!


----------



## Alcaudon

Very nice explanatory post runeight, thank you very much, I've appreciated it very much.......... can we, tube noobs, have more like this??? 
	

	
	
		
		

		
			





 Btw........... is this project going to have a helping web page???


----------



## fordgtlover

Any thoughts on how the SOHA II stacks up in SQ against the Bijou.


----------



## m0b1liz3

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Very nice explanatory post runeight, thank you very much, I've appreciated it very much.......... can we, tube noobs, have more like this??? 
	

	
	
		
		

		
		
	


	




 Btw........... is this project going to have a helping web page???_

 

I would imagine that there will be one as soon as it is officially released. 
	

	
	
		
		

		
		
	


	




 Then there will be this forum too where people can discuss their builds.


----------



## runeight

Quote:


  Originally Posted by *fordgtlover* /img/forum/go_quote.gif 
_Any thoughts on how the SOHA II stacks up in SQ against the Bijou._

 

fordgtlover, only dBel84 has both amps at the moment. I'm going to be part of the SOHA II proto team and I will have them both when mine is built. Perhaps dBel84 will have time to comment on his SOHA II.

 Alcaudon, m0b1liz3 is right on. There will be a website for the amp. The proto team has really helped to make website as good as we can when it goes public.


----------



## dBel84

my thoughts are slowly being compiled from illegible scribble..dB


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Alright, now it's time to talk about the input stage._

 

Thanks for the post runeight. I just printed it so I can study the circuit.


----------



## runeight

This post brings the input stage and the buffer together into a single channel amp. 

 You'll remember from the previous input stage post that the grid of the second triode is grounded. But this grid is an extraordinarily handy place to apply some negative feedback. We don't want a lot of feedback, but a little bit will be a good thing.

 Here's the schematic:






 The output is brought back to the second grid through a voltage divider (an extremely common and broadly applied technique). With the component values shown the NFB is only about 6db. This is not much NFB, but it has two really nice effects:

 1. It extends the effective bandwidth of the amp, causing the high freq rolloff to be higher.

 2. It almost takes control of the gain of the amp. Not quite completely because there is not much NFB, but mostly.

 The second feature is important because you can roll different kinds of triodes into the front end, including triodes that have vastly different mu values. For example, the front end will support 12au7, 12at7, and 6922 (among others). The mu for these tubes is 17, 60, and 33 respectively. This means that the open loop gain of the amp will change dramatically when you swap these tubes in and out.

 However, with the NFB the gain of the amp for these three different tubes is:

 12au7 - 9
 6922 - 10
 12at7 - 13

 Notice that the gain hardly changes. This means that when you roll these tubes you won't have widely gyrating volume pot issues. If you want slightly less gain, increase the value of R8 by some small amount.

 So folks, there you have it. Assuming that the amp will work as well as it has in dBel84's prototype, this is about as flexible, low voltage, tube hybrid amp that you can make.

 The power supply also has some upgraded features compared to the SOHA. The B+ supply uses a much better voltage doubler, for example. In fact, the SOHA PS will not work for this amp.

 But now I think we wait for the prototype team to get their boards. If you're anxious to get things moving you can rag on JeffR at GlassJarAudio.


----------



## Beefy

I _sort_ of understand _some_ of that 
	

	
	
		
		

		
		
	


	




 You noted before that the power supply needs to be configured/tweaked with tube rolling. When do we get a sneak peak at that?


----------



## runeight

The PS will not need any active adjustment whether tubes are rolled or not. It's all fixed.

 But, it needs to be better than the SOHA PS to support what this amp does.

 I think we'll wait on the PS until the prototypers begin to prove out the amp design. Hang in there 'cause I'm anxious to get my boards and to start building too.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The PS will not need any active adjustment whether tubes are rolled or not. It's all fixed._

 

Just re-reading back to your first post..... you don't need to adjust the heater voltage anymore? That _is_ impressive!


----------



## runeight

LOL. You got me. 
	

	
	
		
		

		
		
	


	




 Yes, you will need to either change the heater jumpers or, if you wired a switch, throw the switch.


----------



## dBel84

Seeing as Alex has been asking me about my impressions and he has provided the guts of the circuit, I guess it is about time for me to compile some sense of my the few notes from my listening sessions. 

 I do not know exactly how many hours the amp has on it but I am sure it is going on 50 odd. There have been a few mods in between and I did not sit down and listen to all this music back to back. I did most of my listening with NOS 6080 tubes ( a 12AU7 variant ), it is not necessarily the best tube for this amp but after getting it all working correctly and testing the tube rolling ability, I defaulted to a tube that I was familiar with. There are noticeable differences between tubes so, as with the original design, this amp will be very sensitive to tube rolling which will afford people the ability to tweak the amp to suite there specific likes or dislikes. Some tubes had more bass but less control of it, the ampere 6922s for example have an incredibly liquid midrange while the Tungsol sound a little recessed. In fact, I started off listening with the buffers idling at 75mA and then turned them up to their designed operating point of 100mA, because I felt the mids were too recessed. Red label CD’s were the standard medium. Headphones were either K501 or DT770. 

 I listened to a lot of music over the course of evaluating this amp and I have listed a few of the tracks below. I was especially aware of the fact that this was a new amp and that I wanted it to sound good. I hope that I have been as objective as possible and I believe I have, something we have not mentioned on the thread is that I had a small noise issue and after much trouble shooting, narrowed it down to a very nifty feature that runeight had designed into the amp, unfortunately because of my findings, we have had to eliminate it. 

 Chesky ‘s Ultimate Demonstration Disc – this is a collection of music that has been recorded by Chesky Records to highlight specific aspects of music, it is a useful disc to get a feel for a systems strengths and weaknesses. Spanish Harlem by Rebecca Pidgeon begins with her singing unaccompanied and allows you to appreciate the sense of space and tonal accuracy of the recording. SOHA II allowed her voice to float centre stage, projected slightly forward and when the accompanying instruments join her, the subtle tonal changes of the rhythm shaker are clearly apparent. The instruments have their own stage, never intruding on Rebecca’s voice but not fading into the background either. This particular track made me very aware of how accurate the sound was being presented; no sugar-coated “tubeyness”, however, not as clinical as some SS amps I have heard that teeter edge on sibilance. Speaking of which, I find sibilance and female vocals to be a problem with some gear and I like to listen to Diana Krall’s “The Girl in the other room” and Katie Melua’s “Piece by piece” both of which have crisp vocal which has the ability to degenerate rapidly if the upper mids are overemphasized. They are both well presented with attention to acoustic instruments, sudden deep bass notes are fast and the music has a good sense of rhythm and pace. To test the amps ability to deal with bass, I listened to Stings “Desert Rose” which begins at subsonic levels and even had my AKG’s shaking. The transition to the opposite extreme of the frequency scale helps to highlight the top extention and the amps ability to represent the entire audible frequency spectrum. The other tracks which really give the bass a workout are the African drum albums from Chesky : Babatunde Olatunji - Love Drum Talk and Mapleshade Records – Asante. The bass is tonally accurate, fast and well controlled ie it was able to keep up with both drummers and retain the incredible dimension these musicians create without losing the sense of rhythm. 

 I am running out of steam here, a few more that really stand out. Jacquline DuPre’s rendition of Dvorak’s Cello Concerto – pure raw with emotion and the Cello’s sound is just breathtaking. YoYoMa can make it sing, but not with this degree of emotion. And while on the topic of expensive instruments which have age nurtured tone, Tao Ruspoli ‘s flamenco recordings for mapleshade are presented with such realism that you feel as though you are sitting on the wood floors in that old Baltimore house listening to him perform a personal show for you. Patricia Barbur’s raw vocals are also evident in her live Parisian recording. I like dramatic effects from time to time and Roger Waters Pros and Cons is no exception – the moment the drill enters the brain is mind numbing as the complexity of the sound is so clearly portrayed. Just as dramatic is the decrescendo in the penultimate movement of Giulini’s Beethoven 9th when there is an extended pause before the powerful tenor vocals make the hair follicles on the back of arms stand up or the sudden blast of a lonely piper on William Jackson’s Incholm. Rawness of a different genre is well portrayed in Jimi Hendrix’s bluesy “Hear my train a comin’ ” or the feedback from Stevie Ray Vaughn’s tube stack when he holds that incredible sustained note in “Little Wing”. 

 I have a few more scribbles but reading through what I have already written, it is clearly not objective, but then when is music objective. SOHA II just passes it through to the headphones uncluttered and with great authority. 

 I am enjoying listening to this amp very much. It does some things extremely well, in particular its authoritative bass reproduction. It separates instruments very well, perhaps not as well as some $2K amps I have heard but it performs well above it’s commercial price point and then some. I will leave the final word for others when they have built and tested theirs. 

 A further word of thanks to Alex for sharing his work even after all the adversary..dB


----------



## fordgtlover

dbel84

 Thanks for your views. A new amp is always exciting. It seems thatthe SOHA II is shaping up to be a real treat.

 I read a comment recently in the NorCal meet impressions that at least one person felt that the Bijou lacked bass. You comment above that the SOHA II has authoritative bass. Are you able to offer a comparision between the Bijou and the SOHA, and particularly in regards to bass reproduction.


----------



## Cankin

Any estimates of the cost of the kit or PCB board?


----------



## dBel84

I have not compared the SOHA II to any amp directly and as incredulous as this may seem , the Bijou is still bare on a breadboard and with the kids about, it gets very little use. I don't recall feeling that the Bijou lacked bass, in fact everytime I do listen to the Bijou, I wonder why it is still on a breadboard 
	

	
	
		
		

		
			





 ..dB


----------



## dBel84

Quote:


  Originally Posted by *Cankin* /img/forum/go_quote.gif 
_Any estimates of the cost of the kit or PCB board?_

 

PCB's have yet to be made but you can work on the ballpark of about $15, while parts costs will depend how boutique you build the amp - base cost with chassis, connectors etc is $150 odd. 

 I think you could build this amp comfortably below $200, and this includes high spec components..dB


----------



## dBel84

I don't like Grado's. There I said it. The only Grado's I have heard that I liked were the RS1's and generally use my pair (the lowly SR60s) as a test phone to make sure the amp makes sound and doesn't fry the drivers. sad admission but true. 

 Well I had been doing a lot of fiddling and was using the grados while doing so and it actually made me stop and think that they just might be half "listenable". After a little more listening, I think this amp has real synergy with Grado's - wouldn't have thought it were possible for me to actually enjoy using them but there you go. 

 I also ended up completely dismantling the bread board to case it up , here is a "in-progress" pic:






 and seeing as I was going to be sans amp ( all others are out and about at the moment) I decided to finish wiring up the original proto which I am not sure what to call , so perhaps for the moment "The amp that won't be" . It's a real pity the servo was unstable as it really is an elegant design and also has an amazing sound. 

 A few pics of it too:

 Front:






 Back:






 Top off:






 Dark shot:







 and I did start the process of casing up the Bijou, so hopefully one day I will be able listen to each of them..dB


----------



## Ferrari

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_...
 and I did start the process of casing up the Bijou, so hopefully one day I will be able listen to each of them..dB_

 

It reminds me that I still have to finish the case work for mine too. Free time is something very scarce for me lately. 
	

	
	
		
		

		
		
	


	



 Btw, thanks for your first impression of the SOHA II.


----------



## mwofsi

Whilst this project comes towards a happy beginning, can I question the name?

 I'm fond of the SOHA name, but is the SOHA II really an opamp hybrid amplifier?

 Someone has mentioned this before.

 Shouldn't it be an SDHA or Child Of SOHA?


----------



## Ferrari

Quote:


  Originally Posted by *mwofsi* /img/forum/go_quote.gif 
_Whilst this project comes towards a happy beginning, can I question the name?

 I'm fond of the SOHA name, but *is the SOHA II really an opamp hybrid amplifier?*

 Someone has mentioned this before.

 Shouldn't it be an SDHA or Child Of SOHA?_

 

As you can see in the schematic posted by runeight in post #83, the SOHA II is NOT an OpAmp hybrid amplifier. SOHA II uses tubes as input/VAS stage while the output stage is discrete transistors based. The OpAmp is part of the DC servo circuit (to zero out the unwanted DC components) and is isolated from the audio path.


----------



## mwofsi

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_ ........the SOHA II is NOT an OpAmp hybrid amplifier......_

 

Thanks Ferrari, that is the point I was trying to make 
	

	
	
		
		

		
		
	


	




 Any thoughts about whether the name is appropriate?


----------



## Ferrari

It's a further development of the original SOHA with HUGE improvement.
 So, why not SOHA II?


----------



## mwofsi

Sorry Ferrari, you posted at the same time as I edited.

 The original SOHA name is an acronym(?) for "Simple Opamp Hybrid Amplifier", 
 which the SOHA II no longer is


----------



## mwofsi

Actually it appears that the original name stood for "Stoopid Opamp Headphone Amp" from the original article!

 The title of that Headwize project page has it as "A Simple Tube/Opamp Hybrid Amplifier"

 Kind of stepping all over my own point here 
	

	
	
		
		

		
		
	


	




 It's still a two stage amp with no global feedback and is a development of the original. No longer Opamp based though.


----------



## Beefy

Quote:


  Originally Posted by *mwofsi* /img/forum/go_quote.gif 
_No longer Opamp based though._

 

Does it _really_ matter?


----------



## mwofsi

Does it really matter in the big scheme of things?

 No.

 Can Runeight call his amps anything he wants to?

 Yes.

 I'm just asking though before it's all finalised.


----------



## mwofsi

Whilst I'm being controversial:

 By the way just noticed that there is feedback, separating this even further from the first published SOHA 
	

	
	
		
		

		
		
	


	




 The use of dual tubes on the input is also quite a change.

 Is it necessary to use a matched pair of tubes?

 I take it that it's just not possible to use two tubes in series (ie one half of the first tube combines with one half of the second for each channel), opening the possibility of non-matched or two different front-end tubes? I think that is answered in this post http://www.head-fi.org/forums/f6/soh...ml#post4412207
 but I'm not sure?

 .


----------



## dBel84

The naming of this amplifier was no easy matter and although several names were bandied about, SOHA II Super Single Ended Hybrid Amplifier was what it has become and the name is here to stay. The SSEHA part is easy enough , the SOHA II part is historical and if you are even vaguely aware of the history, you will understand that this is runeight reclaiming his design. The principles remain the same, the means of achieving the goal have changed. 

 As for the tubes, the design theory has been well explained in an earlier post. They do not need to be tightly matched but if they are significantly different, the plates will not bias equally. You can use any number of tubes with a similar pin configuration to the 12AU7 , either 6.3V heaters or 12.6V - there really are quite a few tubes you can choose from..dB


----------



## regal

I guess I really disagree with the comment that the Bijou lacks bass, but there really isn't any OTL tube (non-hybrid) that performs great with something like Grado's. This new Hybrid should be just the ticket for Grado's and the like.


----------



## dBel84

Oh I agree, I never found the Bijou to be lacking in bass. I hope I never made such a comment or insinuated such..dB


----------



## onform

Lol thats what happens when you start thinking of other projects, (loudspeakers), you miss important updates. I posted a little while ago in the soha thread to ask whether it was worth waiting for the soha II, I cant beliave i missed this. 

 How close are we to a finished PCB/BOM??? I will purchase only from source. I was always wairy of the digi boards.... 
	

	
	
		
		

		
			





 Does anyone else miss the single valve design???? It is part of what got me interested in the SOHA. 

 I cant wait to build it...tee hee


----------



## dBel84

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_Does anyone else miss the single valve design???? _

 

 I can't say that it was from lack of trying. See post # 93 , that blue thingamebob was the initial attempt at a self biasing design but the servo wouldn't settle and refelcted as mild variation at the output. I am still rather gobsmacked at how good it sounds, knowing that there is this dc bouncing about. 

 I reckon about a month for pcb's to be available..dB


----------



## onform

what sort of case dimensions are we looking at?? just so i can start thinking of an original design,, i have to do something to keep my mind off work until i can get the bits to build this amp..


----------



## dBel84

It has been designed to fit the Hammond 1455T2202 or 1455T1602, the former will take the transformer in the same chassis, the later will need an external wallwart for the transformer..dB


----------



## m0b1liz3

Has anyone tried it with a wallwart yet? 
 Any suggestions for acceptable supplies like this?

 Any comparisons yet between the SOHA I and SOHA II sq-wise?


----------



## runeight

Hello gents. Been gone for a while, but I see that you guys have been talking.

 Yes, SOHA originaly stood for Stoopid Opamp Headphone Amplifier because when Bill proposed the idea I thought it was stupid. But he and Mark persuaded me that it was worth a try to make a better low voltage tube amp. After a while I decided that I liked the idea of making a good low voltage hybrid.

 SOHA II uses the acronym just to keep the lineage of low voltage hybrid. The amp is a natural successor to the SOHA. If the SOHA had tracked the way I wanted it to (and you can go look at my posts on the headwize threads) it would have had a discrete buffer very quickly. I also never liked the trimpot adjustment, but it was there in the interest of making things as simple as possible for guys who wanted a tube amp that wouldn't kill them.

 The amp board is 160mm x 115mm and will fit the Hammond cases that dBel84 mentioned. It has a built-in PS, just like the SOHA, that provides the LV split supply, the B+ for the tube, and the heater supply all from a single 15-0-15/1A transformer. You can walwart it, but a normal walwart will not work because it doesn't have the CT supply. All of this has been discussed in the orignal SOHA threads and builders have bought walwart boxes to put the toroids into. You can do that here also while using the shorter Hammond box.

 I've probably missed some things in this response.


----------



## Beefy

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_and builders have bought walwart boxes to put the toroids into. You can do that here also while using the shorter Hammond box._

 

I've seen this idea before, and I really like it. I found that one of the really useful aspects of the Millett Max is that the transformer is so far from the amp, and that the casework is for just a small barrel plug instead of an IEC socket.


----------



## m0b1liz3

Does anyone have a link to one of these Wallwart boxes for transformers? Wouldn't they be bigger than a typical wallwart? 

 I am assuming that you meant there are empty wall wart type boxes that plug into the wall that will house a transformer. I can't seem to find such a product when I do a search though. Does anyone have a link for one?


----------



## dBel84

This is what you are looking for..dB


----------



## m0b1liz3

Now I just have to find a mains transformer with dual primaries so I can use it in Aus and NA...


----------



## Beefy

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Now I just have to find a mains transformer with dual primaries so I can use it in Aus and NA..._

 

It took me 10 seconds to find this: RS Australia | * 91938-P2S2, Nuvotem, Toroidal transformer,15VA 2x0-15V o/p, 257-4913

 If you had followed the links I posted in the specific thread where you were looking for toroids, you would have found it quite easily as well.


----------



## m0b1liz3

I asked about toroidal transformers for a different project. I like the idea of the mains transformer with the case dbel showed to make for a smaller profile case for the amp itself. (Planning to build a SOHA II later). A mains transformer should work almost as well and be much cheaper in theory. Since it would be so far away from the amp I would hope there would be no hum heard either. The dimensions on the one you put up a link for are pretty small though so it would work well too. I can worry about it later when the SOHA II pcbs are actually available. 

 Most high VA toroids wouldn't fit into a wallwart type ext case. I was asking about toroids for a gainclone. Thanks for the link btw, it will come in handy for that one. I suppose the same idea could work with an external case for a toroid but it wouldn't plug directly into the wall. It could be sort of like a laptop style PSU for the torroid if I really want to make the box for the amp as small as possible. 

 I have found a few examples here but the prices are much higher than NA even with shipping still. Might just have to bite the bullet and get it since I want to make things small.


----------



## Beefy

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Those are toroidal transformers. That is for a different project. I like the idea of the mains transformer with the case dbel showed to make for a smaller profile case for the amp itself. (Planning to build a SOHA II later)._

 

One of us is confused, and I don't think it is me. The case that dbel posted _is for a toroid like I linked_.

  Quote:


 A mains transformer should work almost as well and be much cheaper in theory. Since it would be so far away from the amp I would hope there would be no hum heard either. 
 

A mains transformer is essentially a toroid in a box anyway (sometimes with a very cheap rectifier setup for DC). But you don't nearly have the flexibility with an all-in-one product as you do compared to choosing your own toroid.

  Quote:


 I have found a few examples here but the prices are much higher than NA even with shipping still. 
 

I would be very surprised if that was true, considering shipping weight. And if you give up the idea of having both 115V and 230V supply capability, then Altronics has some VERY competitive prices.


----------



## m0b1liz3

Well it is just a box with a plug in it and if the mains was small enough it would fit. No confusion, that is why I mentioned the mains thing.

 In the end you are probably right beefy. I am trying to keep the cost of any of these projects low but the general consensus seems to be not compromise on power supplies. I don't plan on giving up flexibility either so will likely need to pay the $ to get what I want locally and not wait for the longer shipping times from overseas.


----------



## mwofsi

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_..........SOHA II uses the acronym just to keep the lineage of low voltage hybrid. The amp is a natural successor to the SOHA........_

 

Yes, that makes sense to me now.

 runeight, Alex, your designs are terrific and to me at least always have hidden depths, such as the use of the centre tapped transformer in the power supplies.

 This one is fascinating too. Low voltage mains amps are indeed a great way for the likes of me to get introduced to tubes, and having you to explain the issues and design decisions really helps alot.


----------



## holland

The case can be used for EI or Toroidal types. I have used it for a toroidal type before.

 I am not sure the case will fit the toroid for the SOHA II, however. As I said, I have used that case in the past for an Avel Lindberg 15VA toroid for a CK2III. The SOHA II requires a 30VA, which is a bit bigger. The 15VA barely fit in there, had to shove it in and it bulges the sides a bit. The dimensions on Jameco's site is the external case dimensions, and the case is slightly sloped/angled.


----------



## Beefy

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_The SOHA II requires a 30VA, which is a bit bigger. The 15VA barely fit in there, had to shove it in and it bulges the sides a bit. The dimensions on Jameco's site is the external case dimensions, and the case is slightly sloped/angled._

 

30VA? When runeight said 15-0-15/1A I just assumed that it was 1A total current secondary, rather than per-winding. If it is indeed the larger toroid, that makes it a bit more difficult!


----------



## Daveze

It is 1amp through the total of the secondaries. Either 2 of 15Vx1A or 1 of 30Vx1A...


----------



## runeight

Sorry for any confusion gentlemen. Daveze is correct. Two transformers that will work are:

 Avel Lindberg Y236103 and Hammond 182J15. There are surely others too.


----------



## onform

Hey guys any chance of some more photo's of the fully populated boards and or cased up pics?? cheeky grin..


----------



## runeight

onform, JeffR has just submitted the prototype board order. Should be about a week before he gets boards and then a little time to ship them to the prototype team. After that, I guess they will all post pics as they make progress and have something to show.

 Also, when the prototype boards arrive at Glass Jar I will make the new website available. There will be lots of info there. But it will not be complete while we wait in feedback from the prototype team.

 Hang on . . .


----------



## 04BluMach

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_......... I have a few more scribbles but reading through what I have already written, it is clearly not objective, but then when is music objective. SOHA II just passes it through to the headphones uncluttered and with great authority. 

 I am enjoying listening to this amp very much. It does some things extremely well, in particular its authoritative bass reproduction. It separates instruments very well, perhaps not as well as some $2K amps I have heard but it performs well above it’s commercial price point and then some. I will leave the final word for others when they have built and tested theirs. 

 A further word of thanks to Alex for sharing his work even after all the adversary..dB_

 

From this initial set of listening impressions, sounds like the SOHA II has tremendous potential to be a Low-Voltage Tube-Rollers dream in the making. Certainly sounds like Runeight has licked both the Buffer instability problems along with very low DC current with this new Servo'd design to allow for output signal path Cap Free operation into Low Z Phones.

 I would assume we still have a real Tweakers platform here also to roll Boutique Film caps into that signal path Interstage position, try out different BJT's in the Output Buffer position, along with opputunity to try out some signal path resistor changes especially with that Final Buff output stage. That is, assuming that you ever get tired of rolling triode pairs...
	

	
	
		
		

		
		
	


	




 By the way - can you offer any details on the interstage cap (it appears to be a lowly Dayton film cap) used for the prototype? 
 Also, appears that near commecial quality Xicon Caps were used for the Elytics! Following true to the SOHA low cost build approach.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_onform, JeffR has just submitted the prototype board order. Should be about a week before he gets boards and then a little time to ship them to the prototype team. After that, I guess they will all post pics as they make progress and have something to show.

 Also, when the prototype boards arrive at Glass Jar I will make the new website available. There will be lots of info there. But it will not be complete while we wait in feedback from the prototype team.

 Hang on . . ._

 

Hang on...? From the initial listening impressions I am left drooling. Glad to hear this is moving forward into a full group proto stage.
	

	
	
		
		

		
		
	


	




 Closer and closer... 
	

	
	
		
		

		
		
	


	




 ......he slowly moves unnoticed by those around him torwards the early queing line at the soon to be announced GB site 
	

	
	
		
		

		
		
	


	




 LoL 

 Any further details to offer on your Power Supply topology to link with this Amp design. I would assume with the lower PSRR of the tube stage we have a little more sophisticated lower ripple circuit on tap?


----------



## runeight

Thanks for the post 04BluMach. I'm kind of waiting myself since I'll be one of the prototypers. 
	

	
	
		
		

		
		
	


	




 dBel84 did use the Dayton caps for his proto. But the actual stock cap is a 220n Wima (or similar) box film cap. The board is very tight. It will be hard to sub other caps into the interstage slot when the board is used in the Hammond enclosure. There is another set of pads for a different pitch cap, but not much room for anything else.

 So, cap rolling will require an enclosure where you create a bit more room for the larger caps, probably on the bottom of the board. 

 Most of the caps are spec'd from Xicon sizes, but there are a few multiple pad sets on the electrolytics so that you can use Nichicons and others.

 You're right the PS is a bit more sophisticated than the SOHA for the reasons you guessed. Slightly lower PSRR of the mirror demands lower ripple from the B+. 

 I think you guys will like the PS. Coming soon.


----------



## GeWa

Any updates on this one?

 Regards


----------



## runeight

Proto boards have been shipped and are scheduled to arrive at Glass Jar on Wed of this week.

 Prototypers are busy collecting their parts while waiting for the boards to arrive.

 Making progress . . .


----------



## runeight

A few posts back I promised to post the SOHA II PS. Here it is.

 The LV supply is a typical IC regulated split supply from a full wave bridge on the 15-0-15 secondary. There is nothing much new here. But it is a simple, dependable supply for this amp and its large, high current SE buffers. Remember that both buffers will consume 200mA of idle current.

 The Heater supply is similar to the SOHA. It uses a full wave rectifier wired to generate a negative supply of -12.6V. The resistor R3P is there to consume some of the power that would otherwise have to be burnt in the regulator, reducing heatsink requirments. Three LEDS are available for lighting the tubes and a panel light.

 The most interesting feature of the heater supply is the jumper for swapping heater voltages. This jumper is on the board. And, as you can see, it is a simple matter of moving two jumpers to go from 12.6V to 6.3V and back. Maximum current is intended to be 300mA for both tubes. 6.3V tubes are wired in series by the jumper. 12.6V are wired in parallel. Notice that the jumper is wired exactly like a DPDT switch so you can connect a switch to the jumper pads. That way you can mount the heater switch on the front or back panel. No jumper swapping!!

 The big difference between the SOHA PS and the SOHA II PS is the B+ supply. First, the voltage multiplier is independent of the LV+ supply rail. It is a stand alone multiplier that generates an B+ that is 1.5X the full voltage of the secondary. This would be 1.5 * 1.414 * 30 = ~63V.

 The filter section must have better ripple rejection than the SOHA so it uses a series of cap multipliers to maximize ripple rejection while minimizing the voltage drop in the filter section. The goal is to get 60V B+.

 The cap multipliers are not regulators, however, so I decided to separate the B+ outputs for the channels to minimize crosstalk through the plate supply.

 Like the SOHA, everything runs from a single transformer. 
	

	
	
		
		

		
		
	


	




 That's about folks. I'll release the full SOHA II website in a day or two. But this should give you something else to look at for a while.


----------



## Alcaudon

Thanks for another great explanation runeight 
	

	
	
		
		

		
		
	


	




 Can't wait for the boards......


----------



## dBel84

making slow progress
















 ..dB


----------



## 04BluMach

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_A few posts back I promised to post the SOHA II PS. Here it is._

 

Thanks for follow up! Definitely building on the SOHA improvements you made on the initial design and a lot of improvements brought to bear for the II.

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The Heater supply is similar to the SOHA. It uses a full wave rectifier wired to generate a negative supply of -12.6V. The resistor R3P is there to consume some of the power that would otherwise have to be burnt in the regulator, reducing heatsink requirments. Three LEDS are available for lighting the tubes and a panel light.

 The most interesting feature of the heater supply is the jumper for swapping heater voltages. This jumper is on the board. And, as you can see, it is a simple matter of moving two jumpers to go from 12.6V to 6.3V and back. Maximum current is intended to be 300mA for both tubes. 6.3V tubes are wired in series by the jumper. 12.6V are wired in parallel. Notice that the jumper is wired exactly like a DPDT switch so you can connect a switch to the jumper pads. That way you can mount the heater switch on the front or back panel. No jumper swapping!!_

 

Designed in switchable heater voltages for flexibilty of tube selection is a great touch and a touch elegant in the approach. Very Nice!

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_The most interesting feature of the heater supply is the jumper for swapping heater voltages. This jumper is on the board. And, as you can see, it is a simple matter of moving two jumpers to go from 12.6V to 6.3V and back. Maximum current is intended to be 300mA for both tubes. 6.3V tubes are wired in series by the jumper. 12.6V are wired in parallel. Notice that the jumper is wired exactly like a DPDT switch so you can connect a switch to the jumper pads. That way you can mount the heater switch on the front or back panel. No jumper swapping!!

 The big difference between the SOHA PS and the SOHA II PS is the B+ supply. First, the voltage multiplier is independent of the LV+ supply rail. It is a stand alone multiplier that generates an B+ that is 1.5X the full voltage of the secondary. This would be 1.5 * 1.414 * 30 = ~63V.

 The filter section must have better ripple rejection than the SOHA so it uses a series of cap multipliers to maximize ripple rejection while minimizing the voltage drop in the filter section. The goal is to get 60V B+.

 The cap multipliers are not regulators, however, so I decided to separate the B+ outputs for the channels to minimize crosstalk through the plate supply._

 

The voltage regulator approach for the B+ certainly simplifies the LRC filtering that would be needed to come close to its equivalent ripple reduction and voltage regulation.

 The Quasi Dual Mono B+ is a great approach to solving potential channel crosstalk and provides double voltage regulation for the HV delivery to boot.

 The PS certainly looks like a great building block for delivering high end performance in the SOHA II. 

 Like prior poster said - Thanks for another great explanation runeight!

 ...........Bring it on


----------



## runeight

You're welcome. 
	

	
	
		
		

		
			





 First phase of the website is now available at:

Cavalli Audio


----------



## TimJo

Thanks for posting the power supply overview. The design looks really good.

 Taking a quick look at the website, it appears like we should be able to start gathering parts in advance of the first batch of boards. Or should we hold off until after the prototype phase?


----------



## runeight

I don't think that many of the parts will change during prototyping. A few might, but not very many.

 I always like to suggest, however, that you wait a bit. This just in case there is something that turns up in the new prototypes that we didn't see in dBel84's prototype. I'm always very cautious at this stage until I am sure that a few other folks can build the amp dependably and reproduceablty.

 I also think that Glass Jar will be offering both boards and kits. So it's your call if you want to buy one of the kits or supply your own parts.


----------



## TimJo

I will just buy a board and put together the parts myself. I guess I need to be a bit more patient and wait to see how the prototypes turn out. 

 In the meantime I can at least begin building up parts lists at Mouser and Digi-Key in anticipation.


----------



## dBel84

I had glued up the front plate yesterday and thought to drill it quickly this evening - cracked it. I should know not to try and squeeze these things into short time slots, after all there is no rush!!






 and a night shot 






 It is sounding very good indeed. I have Mullard 12AT7 tubes in at the moment and having a lot of fun listening to the lossless files on my Q1U, it was a very good plan to stick a dac in there too
	

	
	
		
		

		
		
	


	




 ..dB


----------



## Uncle Bob

I'm just wondering why C2 and C6 are specc'd to be 5mm and 7.2mm types when they're both the same type, value and rating?


----------



## runeight

Well Uncle Bob, I gotta tell ya, I designed the board and I don' t know. But I think they were originally different caps and then things changed, but the form factor didn't.

 We can fix this on the production boards.


----------



## Postal_Blue

I think c6 was added during proto discussion and used a size which is more readily available because space was not an issue. However, space was an issue for c2 as it was originally a bipolar cap but changed to film when the bipolar proved unstable.


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well Uncle Bob, I gotta tell ya, I designed the board and I don' t know. But I think they were originally different caps and then things changed, but the form factor didn't.

 We can fix this on the production boards._

 

Don't worry too much about a small typo error in the descriptions of the dimension of the C2 and C6 film caps on the amplifier part of the SOHA II, which are visible at the website currently.

 C6L/R (decoupling caps next to C5 L/R) = 1 µF film caps ... you (runeight) have added these caps to the amp on my request, the dimensions of these caps (5mm lead spacing and 7.2mm width) are that of some type I have on hand (AVX, BC, Wima), accidentally.

 C2L/R (belonging to the DC servo circuit) were originally specified for both 10 µF non-polar electrolytic and 1 µF film cap type.
 The 10 µF non-polar electrolytic type has ~2.5mm lead spacing and 5mm diameter while the 1 µF film cap is 5mm lead spacing and 7.2mm width.

 The small typo error in the parts descriptions is probably due to the change of C2L/R on the schematic from 10 µF non-polar electrolytic to 1 µF film cap (as showed in the schematic now). The desciption here should be 5mm lead spacing and 7.2mm width too (instead of 5mm lead spacing and *5mm width*... *5mm width *is coming from the 10 µF non-polar electrolytic originally on the schematic, I think).

 For C2L/R, the PCB accepts caps with both 2.5mm and 5mm lead spacing, so no modification is needed.
 Hope that this will clearing the confusion about the dimension of the C2 and C6 film caps up a bit.


----------



## runeight

Thanks Mazuki. As you can see, I couldn't remember. 
	

	
	
		
		

		
		
	


	




 Is there a mistake on the website?


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks Mazuki. As you can see, I couldn't remember. 
	

	
	
		
		

		
		
	


	




 Is there a mistake on the website?_

 

runeight, I wouldn't call it mistake, it's more likely due to _"copy and paste" _thing. Personally I don't worry too much about the exacte dimensions (in mm more or less) of these caps, since the dimensions of cap of the same value from different manufacturers can variate a bit !!! I just put in what I accidentally have on hand as long as it fit. Sent you a PM about the details.

 And hee... I'm not Mazuki


----------



## runeight

yes, i knew that. 
	

	
	
		
		

		
		
	


	




 mazuki and i are exchanging emails on another project.

 i think it's time for me to wink out.


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_i think it's time for me to wink out._

 

Enjoy your holiday!


----------



## runeight

Here are some pics of the prototype boards from Jeff R. Better ones coming soon.


----------



## dBel84

I think those boards are looking awesome 
	

	
	
		
		

		
		
	


	




 Final image of mine all cased up and doing what it is meant to be doing best 






 ..dB


----------



## m0b1liz3

Hmm, I don't know if this is just me being silly but I was thinking it would be nicer aesthetically if the hp jack and the vol pot were not right in front of the tubes.

 How does it sound?


----------



## d0td0t

Eagerly Awaiting~~


----------



## dBel84

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hmm, I don't know if this is just me being silly but I was thinking it would be nicer aesthetically if the hp jack and the vol pot were not right in front of the tubes._

 

I wanted some symmetry and a sense of the 'inner workings' of the amp. In the end I didn't have too much choice in exact location as the board is designed this way. I hadn't particularly wanted the tubes to be the focus, or else I would have popped them out the top. 

  Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_How does it sound?_

 

Extremely good 
	

	
	
		
		

		
			





 , definitely on par with the high end amps I have heard. simply put - you gotta build one 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## GeWa

Quote:


 simply put - you gotta build one 
	

	
	
		
		

		
		
	


	




 ..dB 
 

OK, when will the boards be up for sale than?

 Regards


----------



## dBel84

soon!! One official run through of the proto boards and then it will be time..dB


----------



## runeight

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Hmm, I don't know if this is just me being silly but I was thinking it would be nicer aesthetically if the hp jack and the vol pot were not right in front of the tubes._

 

m0b1liz3, I thought about that when designing the boards. I did offset the tubes and jack/pot a bit so that they are not in a direct line. But still the pot/jack do hide the tubes some.

 This design is meant to go into the slim Hammond case where the tubes will stick up through the top cover. I know that some folks will also put a transparent front panel. There are LED provisions on the board to light the tubes.

 Mainly, however, there was not a really good way to layout the board with having the tubes, jack, and pot in rought these positions. This was dictated by placing the PS on the back of the board, creating symmetry between the tubes, location of the e12, get the best possible trace routing that I could think of, etc. When you get a board you'll see that it is pretty tighly designed and very small for everything that is on it.

 But, an alternative of course is to not board mount the pot/jack so that you can move them out of the line of sight of the tubes. Or you can bottom mount all of the large components so that the tubes can stick up through the top of a chassis.


----------



## 04BluMach

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_...........
 Extremely good 
	

	
	
		
		

		
		
	


	




 , definitely on par with the high end amps I have heard. simply put - you gotta build one 
	

	
	
		
		

		
		
	


	




 ..dB_

 

Thats it rub it in....
	

	
	
		
		

		
		
	


	




 Ring the bell.... and the Dogs immediately start to salivate. Drool is found all over this threads area. 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_........This design is meant to go into the slim Hammond case where the tubes will stick up through the top cover. I know that some folks will also put a transparent front panel. There are LED provisions on the board to light the tubes.

 .................But, an alternative of course is to not board mount the pot/jack so that you can move them out of the line of sight of the tubes. Or you can bottom mount all of the large components so that the tubes can stick up through the top of a chassis._

 

Argggh, now I need to buy at least three PCB's to try each of those combo's out.
	

	
	
		
		

		
		
	


	




 Or is that four - tubes _and _ Heat Sinks sticking out of case!

 ........Curse you Head-Fi!


----------



## runeight

LOL. I hadn't thought of the fourth one, but I guess you can do that too.


----------



## GeWa

No boards and already a question!
 Are the regulators VR+E and VR-E mounted on the same heatsinks as LV+ and LV-?

 Regards


----------



## dBel84

no , the epsilon vregs are small TO92 devices that don't get hot at all. They are dropping the rail voltage from 15V to 12V ..dB


----------



## GeWa

I really need a pair of glasses 
	

	
	
		
		

		
		
	


	



 Thanks dBel84

 Regards


----------



## runeight

Right. The extra pads for the heatsinks are for mounting them on the bottom side of the board.


----------



## Ferrari

Still not sure if I really going to do it this way... but it's part of the fun when it comes to deciding how to build a new amp.


----------



## dBel84

now that's one I hadn't anticpated  , this would be interestig ..dB


----------



## Ferrari

It was just a fast thought, in the meantime I have changed that faceplate design a lot.
 Initially I was cosidering a single-ended amp with the 2 tubes on top but... why not balanced amp when I have balanced source? 
	

	
	
		
		

		
		
	


	




 Moreover, the SOHA-II design has the ability to bottom-mount all heatsinks and other big components and let the tubes showing out on top, with the advantage of air cooling and of course... the looks! The 2 PCB's can be fitted nicely in an enclosure I have on hand, adding a 50VA (or 80VA) transformer into it and... voila.


----------



## runeight

Ferrari is kind of a sneaky guy dBel84. I hadn't expected this either.

 But, this is one thing I really like about making a new design available and working in a diy community - what everyone does with his particular build and the mods that people come up with.


----------



## Ferrari

LOL, thank you very much 
	

	
	
		
		

		
		
	


	




. Got a message from JR that my board will be shipped tomorrow.
 I'm currently in Hungary for work but will be back home next saturday. By that time, my board should probably be arrived.
 Looking forward to start this build.


----------



## Postal_Blue

Just to let everyone know, We (that is me) now have a second working Soha II. I am at work so dont have tome to give much in the way of impressions. But i will say that it is VERY good. The seperation/soundstage is exceptionaly good. People should be getting very excited about this amp it is gonna be a real contender in the mid-price DIY amp arena.


----------



## dBel84

Excellent news indeed. Now we just need to hear your finer impressions but we will allow you a little grace to enjoy it first :-D ..dB


----------



## Ferrari

Cogratulations!
 Really great news for Hybrid lovers who appreciate the sound of *"audio tubes"*, in co-operation with sand output buffers.
 Looking forward to see more SOHA II up and running in the coming weeks, months...


----------



## GeWa

Quote:


 Looking forward to see more SOHA II up and running in the coming weeks, months... 
	

	
	
		
		

		
		
	


	



 

If only I would have a board 
	

	
	
		
		

		
		
	


	









 Regards


----------



## dBel84

They look so sad and lonely. All hyped up and nowhere to PARTY 
	

	
	
		
		

		
		
	


	




..dB


----------



## runeight

Oh my!! Jeff R is away from home until this weekend. When he returns we will remedy this situation.


----------



## kklee

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_If only I would have a board 
	

	
	
		
		

		
		
	


	



_

 

I've got the opposite problem right now.

 I've got a board, but all the parts haven't shown up yet. I suppose if I get desparate enough, I could desolder the tube sockets from another amp I haven't cased yet


----------



## GeWa

To be honest, I'm still missing one part and that's C2. Haven't figured out what I'm gonna use in that spot.

 Regards


----------



## Ferrari

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_I've got the opposite problem right now.

 I've got a board, but all the parts haven't shown up yet. I suppose if I get desparate enough, I could desolder the tube sockets from another amp I haven't cased yet 
	

	
	
		
		

		
		
	


	


_

 

No need to be desparate! 
	

	
	
		
		

		
		
	


	



 One good way to solve your problem is: *send your board per EMS to GeWa*.


----------



## onform

is anyone else in the uk watching this thread with bated breath...?


----------



## onform

Oh and can anyone tell me what the parts cost is so far?? and if jeffr ships to the uk??


----------



## dBel84

The others can correct me if I am wrong but a complete basic build cost is approx $170. This includes board, chassis, transformer etc. 

 I am not sure what level of kit Jeff is going to put together but being in the UK you are better off sourcing the transformer locally than having to pay shipping on it. 

 AND then of course there are so many finishing options that you could well spend double that for customized casing etc ( lets not forget a healthy supply of various tube types to roll - start collecting those 12AU7 / 12AT7 / 6DJ8 6922 etc tubes ) 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## Uncle Bob

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_is anyone else in the uk watching this thread with bated breath...?_

 

Yeah, me for one... I've already bought some tubes & sockets 
	

	
	
		
		

		
		
	


	




 and I've been passing the time making/costing bom's in case I decide to buy parts from Farnell.

 JeffR does ship to the UK and he's nice to deal with - I bought a CKKIII kit from him a little while back.


----------



## wiatrob

Thought I'd post a teaser to stoke the fire:

 My SOHA II _SHOULD_ be up tonight (fingers crossed!)


----------



## onform

Uncle Bob

 Have you got a bom for UK supplier? would it be a good idea to buy from america due to the exchange rate. or would we just get stung in taxes.....


----------



## kklee

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_No need to be desparate! 
	

	
	
		
		

		
			




 One good way to solve your problem is: *send your board per EMS to GeWa*. 
	

	
	
		
		

		
		
	


	


_

 

That would present me with a different (and less preferable) problem!

 I may have to canabalize another amp after all. My parts Connexion order won't be getting here until next week due to a mistake on my part


----------



## Beefy

All looking very good! 
	

	
	
		
		

		
		
	


	




 Maybe it is just the perspective from the photo, but the board in wiatrob's post seems shorter than I imagined......


----------



## JamesL

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_All looking very good! 
	

	
	
		
		

		
		
	


	




 Maybe it is just the perspective from the photo, but the board in wiatrob's post seems shorter than I imagined......_

 

I thought the very same thing - but great work guys. Can't wait to get started on this project =]


----------



## adamus

uk'ers: I seriously doubt you will get anywhere close to jeffs kit price. I know through experience, the US'ers ge parts so much cheaper.


----------



## Beefy

Quote:


  Originally Posted by *adamus* /img/forum/go_quote.gif 
_uk'ers: I seriously doubt you will get anywhere close to jeffs kit price. I know through experience, the US'ers ge parts so much cheaper._

 

From Australia, for any order over ~US$100, it is cheaper for me to buy at Mouser than anywhere locally. That is despite the US$45 international shipping fee.

 We get absolutely rorted down here, and stock levels are terrible


----------



## MrMajestic2

Quote:


  Originally Posted by *Beefy* /img/forum/go_quote.gif 
_From Australia, for any order over ~US$100, it is cheaper for me to buy at Mouser than anywhere locally. That is despite the US$45 international shipping fee.

 We get absolutely rorted down here, and stock levels are terrible 
	

	
	
		
		

		
		
	


	


_

 


 Same here in Sweden. I order from Mouser with FedEx shipping and even though I have to pay VAT and customs, its still cheaper.


----------



## onform

There is still no sign of a kit on jeffR website, any idea's on what taxes i would pay from us?? am just being impatient?? : )


----------



## MrMajestic2

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_There is still no sign of a kit on jeffR website, any idea's on what taxes i would pay from us?? am just being impatient?? : )_

 

The prototyping phase is not over yet, so you will have to wait a bit longer.


----------



## Ferrari

Have a little patience... and patience will be rewarded.
 JeffR is travaling at this moment, but I know that he is working on the SOHA II kits.

 Regarding import tax to the UK, you can find this kind of information on the UK customs website (probably ~same as other EU countries).


----------



## Uncle Bob

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_Uncle Bob

 Have you got a bom for UK supplier? would it be a good idea to buy from america due to the exchange rate. or would we just get stung in taxes....._

 

I didn't get caught for taxes last time, maybe I was lucky, but the general view is that you get away with it more often than not. 

 If you do get stung, AFAIK you would be looking at cost + 9% duty, then 17.5% VAT on top of that. You would probably (certainly!) also have to pay an administration charge to the carrier as well as they have to pay customs first and then they invoice you before they will deliver.

 The current BOM from Farnell stands at just over £100 inc VAT, this is just components, no enclosure, or i/o connectors. There could be scope for savings if a UK group buy could be organised to save costs due to Farnell's minimum quantities on some items.

 If you want a copy of the spreadsheet with details, drop me a PM with your email addr.

 We do still need to buy the boards from the US in any case so JeffR may still be cheaper in the end.


----------



## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Have a little patience... and patience will be rewarded.
 JeffR is travaling at this moment, but I know that he is working on the SOHA II kits.
_

 

Well put, Ferrari - I can now vouch for that reward! I'm happy to announce that after a few hours of noob handholding - the third SOHAII lives.

 It's burning in but I am already very impressed - Thanks Alex for another great design!


----------



## dBel84

3 cheers for wiatrob 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## wiatrob

Quote:


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











 3 cheers for wiatrob 
	

	
	
		
		

		
		
	


	




 ..dB_

 

I'm merely riding the coattails of those who've gone before - yourself, Postal_Blue. I expect we will see a bit more detail on the amp here soon.

 Cheers and beers for all, especially Runeight!

 I have been unable to stop listening to it since I got it up and running. I don't want to wax - but it's added new life to the tired music on my test iPod!

 I have it up with the AlienDac now... still burning in...


----------



## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I'm happy to announce that after a few hours of noob handholding - the third SOHAII lives.




_

 






 This is a really pleasant wake up for me (after a long sleep).
 Well done, wiatrob !


----------



## holland

nice work so far.


----------



## Ferrari

I'm starting collecting some good audio tubes that can be rolled into the front end of this amp.
 Among them are many tubes belonging to the family E88CC, 6DJ8, 6922... as we know.
 But how about the Russian 6N1P, which needs 600mA @6,3V filament ?


----------



## runeight

The stock PS only supports up to 300mA heater current in any configuration.

 The website has details on how to increase the available current. Good idea to read about it there.

 This will require a bigger transformer with a higher current secondary and more heatsinking for the heater regulator. The heatsink footprint on the board is not large enough for the size required. So the heater regulator and its heatsink will have to go off board.

 But, it can be done without much difficulty.


----------



## Ferrari

Thanks for pointing me to the right direction.
 Ahh... how could I overlooked that part of the website?


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_nice work so far._

 

Thanks -the case is always the hard part for me, not a fabricator...


----------



## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I'm starting collecting some good audio tubes that can be rolled into the front end of this amp.
 Among them are many tubes belonging to the family E88CC, 6DJ8, 6922... as we know._

 

Hmmm, sounds like we might start a thread/database with tube specs and impressions?


----------



## thunder

Can pre-outs be installed for additional use use as a preamp to power a poweramp ? If so what if any changes are needed ? Would there be to much gain, voltage or to little output resistance for driving anything other than headphones ? I was thinking of a pre for a Aleph 30 amp ect....


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Hello folks. I've had a few enquiries about the SOHA II. So here is an update.

 ..........

 But, better than the SOHA, the SOHA II Super SE will allow you to roll different tube types into the front end. Want to run 12au7s? No problem. Want to run 6922s, just flip the heater switch (or change the jumpers) and replace the tubes. Any set of triodes where two of them can run with 12.6V/300mA (series or parallel) will work without requiring any adjustments for voltage. 600mA can be supported with a bigger transformer and larger heatsinks.

 ...........
_

 

I don't see any provision for switches and/or jumpers to change tube configurations on the final pcb, I assume this was found to be un-necessary or un-workable in the end? 

 Anyway I've already bought some tubes, some 13D5A's which were sold to me as an ECC82 equivalent, so I'll be happy if I can get a board up and running with these tubes. Anyone heard of these tubes before? Google doesn't throw up much on them....


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I don't see any provision for switches and/or jumpers to change tube configurations on the final pcb, I assume this was found to be un-necessary or un-workable in the end?_

 

Uncle Bob, This provision is already included in the current PCB. 
	

	
	
		
		

		
		
	


	



 It's the 6 pins connector named *HTR* on the PCB, near right tube (V1R).
 How the filament voltages (6,3V or 12,6V) can be changed is depicted here.


----------



## Uncle Bob

Ah...


----------



## runeight

Quote:


  Originally Posted by *thunder* /img/forum/go_quote.gif 
_Can pre-outs be installed for additional use use as a preamp to power a poweramp ? If so what if any changes are needed ? Would there be to much gain, voltage or to little output resistance for driving anything other than headphones ? I was thinking of a pre for a Aleph 30 amp ect...._

 

no reason why the amp can't be used as a preamp. No changes are needed. Depending on the tubes used, gain will be between 10X and 14X. You can decrease the gain by changing the feedback resistors. There is only a tiny bit of feedback in the amp so you can increase the NFB to reduce gain without affecting the audio.


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I don't see any provision for switches and/or jumpers to change tube configurations on the final pcb, I assume this was found to be un-necessary or un-workable in the end? 

 Anyway I've already bought some tubes, some 13D5A's which were sold to me as an ECC82 equivalent, so I'll be happy if I can get a board up and running with these tubes. Anyone heard of these tubes before? Google doesn't throw up much on them...._

 

Uncle Bob, the website describes the flexible heater arrangement pretty well. However, as Ferrari noted the arrangment is limited to either 12.5V or 6.3V and the maximum current from the stock heater supply is 300mA. You can increase this to 600mA as described on the website too.


----------



## dBel84

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Anyway I've already bought some tubes, some 13D5A's which were sold to me as an ECC82 equivalent_

 

you are quite right about an internet search not throwing much up - I haven't found any data sheets and from what I can garner from forum discussion seems it is "similar to ECC82 but not" . I don't know where that leaves you and what the pin format is for this tube. It might work but make sure that the pins are indeed similar to the 12AU7 and not just that it's electrical characteristics closely resemble the tube..dB


----------



## dBel84

Finally finished the chassis - pics here ..dB


----------



## Uncle Bob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_you are quite right about an internet search not throwing much up - I haven't found any data sheets and from what I can garner from forum discussion seems it is "similar to ECC82 but not" . I don't know where that leaves you and what the pin format is for this tube. It might work but make sure that the pins are indeed similar to the 12AU7 and not just that it's electrical characteristics closely resemble the tube..dB_

 

Thanks for taking the time to look, seems like you found the same sources as me. Oh well, I suppose I'll just have to try them and see what happens.

 I've been working on a UK BoM and I can't find any sources for C3E, the bipolar cap. This is specified to be 25V and 6mm in diameter. The only types I can find that will physically fit are 16V types, anything higher rated is at least 10mm and board space does look pretty cramped around there. I suppose the cap could be soldered in underneath or the leads bent 90deg but it will look a little untidy.


----------



## dBel84

You should be able to look at the pins and look where they connect internally to figure out what the pin configuration is. 

 what size caps are available at the spec'd voltage ? 

 ..dB


----------



## Uncle Bob

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_You should be able to look at the pins and look where they connect internally to figure out what the pin configuration is. 

 what size caps are available at the spec'd voltage ? 

 ..dB_

 

dB

 I can get a 22uF@35V/6.3mm or 10uF@50V/6.3mm, the 47uF variants are 8mm which might fit?

 UB


----------



## wiatrob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_dB

 I can get a 22uF@35V/6.3mm or 10uF@50V/6.3mm, the 47uF variants are 8mm which might fit?

 UB_

 

There's about 1 - 1.5mm between C3E and the corner of the IC socket, 'bout 2mm clearance from Q3E with the 6.3mm part. 

 Probably be a tight fit, but the 8mm might make it in, especially if you weren't scared to pare off the corner of the IC socket with a sharp blade... 

 -Bill


----------



## Uncle Bob

Sorry, my mistake - the NP cap is C2E, but the problem is still the same. Cap size is 10mm, board size is 8mm. Would we be able to use 47uF in this position??


----------



## dBel84

The values for the e12 may change so why not sit tight on that for a while. If the final value remains 100uF , I am sure Jeff would be obliging and add the necessary caps into the board shipment for you..dB


----------



## wiatrob

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Sorry, my mistake - the NP cap is C2E, but the problem is still the same. Cap size is 10mm, board size is 8mm. Would we be able to use 47uF in this position??_

 

Duh, I should've caught that. There's NO room between C3E and C4E - this is a very tightly laid out board. 

 As dB said, patience, there may yet be some value changes to the e12 circuit... 

 -Bill


----------



## Uncle Bob

Well if changes are still being discussed...

 It would certainly simplify things if both C2E and C3E could be the same type of cap...

 UB


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Well if changes are still being discussed...

 It would certainly simplify things if both C2E and C3E could be the same type of cap...

 UB_

 

From electronics engineering point of view, C2E _has to be_ non-polar type, while C3E can be a normal (polar) type.
 But to make parts ordering easier, you can use non-polar capacitor for both C2E and C3E. It's should work fine!


----------



## Uncle Bob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_From electronics engineering point of view, C2E has to be non-polar type, while C3E can be a normal (polar) type.
 But to make parts ordering easier, you can use non-polar capacitor for both C2E and C3E. It's should work fine! 
	

	
	
		
		

		
		
	


	


_

 

I had assumed that a NP type would work for C3E as AMB's original schematic and parts notes make the same points. What I was trying to say was, that it would be nice, if the board layout was tweaked, to allow enough room so a 10mm cap would fit in the C2E and C3E positions on the pcb. 

 It's not a major problem as I'm sure JeffR would be able to supply any of these parts when PCB's are ordered. It would just keep everyone's options open for the future

 Still, I'm hoping it won't be tooooo long before production pcbs are available.


----------



## runeight

If this is really important, I can try to make the change for the production boards.

 The question is do you want both caps to be 10mm and the same size or do you want C2 to have multiple pad arrangements?


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_If this is really important, I can try to make the change for the production boards.

 The question is do you want both caps to be 10mm and the same size or do you want C2 to have multiple pad arrangements?_

 

I suppose it depends on whether you are planning to make any other changes for the production boards (the preceding posts suggested that might be the case) and how difficult it will be to implement. Would changes to the layout also mean that there would have to be a second trial run before a full production order of PCB's?

 I'm sure that there are plenty of builders eagerly waiting for production boards to be available and I wouldn't be popular if they have wait unduly on account of some localised supply issues. I'm also assuming that builders in other markets worldwide would also face the same component sourcing issues but I don't know that for fact.

 It's certainly not a 'show stopper' issue as builders can either buy these components from JeffR when they order boards or mount oversized caps on the underside of the pcb, etc.

 IF.. some changes were going to be made before the production run, then I would personally ask for both C2E and C3E to be able to accept the same physical size of cap, at least 10mm - 12.5mm if there's room, so that the same 100uF NP part could be used. We have to buy at least 5pcs of the NP cap from both Farnell and RS so it makes it more economic to use at least 2 per board. Another supplier - Rapid - sells Suntan branded NP caps in single units (and much cheaper as well) but at 35V they're 12.5mm diameter caps hence the request for extra board space if possible. They're all 5mm pitch, so multiple pads shouldn't be an issue.


----------



## runeight

At this moment it appears that the only changes from prototype to production will be a few small resistor adjustments in the e12 circuitry.

 But, looking at the board layout, I might be able to make both caps 10mm. There isn't enough room for 12mm. 

 There won't be any delay caused by this change and now is the time to do it.


----------



## TimJo

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_At this moment it appears that the only changes from prototype to production will be a few small resistor adjustments in the e12 circuitry._

 

Cool, I've been waiting to read something along these lines. It sounds like no major design changes are in the works, so I think I'm going to put together an order for parts. I'm not too worried about a few resistors changing.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_At this moment it appears that the only changes from prototype to production will be a few small resistor adjustments in the e12 circuitry.

 But, looking at the board layout, I might be able to make both caps 10mm. There isn't enough room for 12mm. 

 There won't be any delay caused by this change and now is the time to do it. 
	

	
	
		
		

		
		
	


	


_

 

OK, that's cool then - I'm really looking forward to building one of these


----------



## Ferrari

A really pleasant coming home today... 
	

	
	
		
		

		
			




 I found SOHA II boards from JR along with a couple 6H8C (1578, metal base) tubes in the mail today.
 Hope that I will have the time get my SOHA II build up and running this weekend.

 [size=xx-small]The 6H8C with metal base tubes are of course not for the SOHA II but for my own proto, made from Russian craps (ehh... tubes) only.[/size]


----------



## 04BluMach

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_At this moment it appears that the only changes from prototype to production will be a few small resistor adjustments in the e12 circuitry.

 But, looking at the board layout, I might be able to make both caps 10mm. There isn't enough room for 12mm. 

 There won't be any delay caused by this change and now is the time to do it. 
	

	
	
		
		

		
		
	


	


_

 

This is all outside of Tube rolling of course - which for the SOHA II should offer the biggest SQ improvement!

 From my quick read of the circuit and board layout, whatever extra space could be wiggled out of the available real estate for C1 and C5 would offer the biggest bang for the buck.

 The C1 220nf interstage coupling cap appears to be the most critical passive component in the audio signal path. This should be the most critical component for potential Sig quality improvement on the Board. Space for a nice fat Film Cap (.5"Diax1"L)would be grand or at least enough space to tompstone a film cap (.5"Diax1"H) in that area would be highly desireable. 

 The C5 470uf 25v cap comes closest to the audio stream and could contribute to an improvement in sound quality. While a Panasonic FM 470uf to 820uf are readily available at the 10mm size, some may like to consider Elna RFS, Nich KZ, or even BG (Gasp) for this position. The Elan RFS 470uf 25v is 16mm Dia.

 I know that the board is really tight, so there may be no way to accomplish this without extensive rework.... But any space would help a little. I'm sure there will be many who will find a way to shoehorn in some amazing components. Just a lot easier if it is designed into the board.

 Of course - I don't want to hold up the release of the Production Boards!


----------



## eruditass

ah I haven't even started building my SOHA I board.. any idea what parts can be used from the SOHA I kit?


----------



## Zigis

Ferrary, where you get thees tubes and what year issue is this?
 thees old (50') metal is known as the best 6H8C, better then many 6SN7


----------



## Postal_Blue

Quote:


  Originally Posted by *04BluMach* /img/forum/go_quote.gif 
_From my quick read of the circuit and board layout, whatever extra space could be wiggled out of the available real estate for C1 and C5 would offer the biggest bang for the buck._

 

Just a couple comments. I am by know means a master board stuffer, but I managed to cram some Vit Q's @ C1. This was accomplished with all components top mounted. I think the amp will sound very very nice sticking with the stock BOM and is a relatively easy build. But for those who want to tweak, I don't think it will be difficult. Bottom mounting selected components could open up tons of real estate.

 I am headed to Oklahoma for three weeks and apart from 4 hours in school, I have zero to do. I intend to get a full write up posted complete with pics and likely some comparisons. I plugged in my D5000 for the first time today, and I am _very_ pleased with what I am hearing. The SOHA II is an equal opportunity arse-kicker, it drives my 580's and D5000's with ease and sounds fantastic with both.


----------



## dBel84

looking forward to your ramblings, it truly is a great sounding amp..dB


----------



## wiatrob

Oops, double post, sorry


----------



## wiatrob

Quote:


  Originally Posted by *Postal_Blue* /img/forum/go_quote.gif 
_Just a couple comments. I am by know means a master board stuffer, but I managed to cram some Vit Q's @ C1.._

 

Postal,

 I did too - tombstone mounted and they actually looked quite good, though they will obviously be protruding from the top of a standard Hammond case with the tubes. Uplighted caps anyone? 
	

	
	
		
		

		
		
	


	




 . I reverted to the spec'd Wimas for an A/B, and the amp sounds quite good both ways.

 Depending on Cap diameter, bottom mounting is quite possible, especially with a slippery plastic case like the Q's...

 I look forward to your review... I have been enjoying this amp immensely, and hope to gave it cased up this weekend..


----------



## Ferrari

Quote:


  Originally Posted by *Zigis* /img/forum/go_quote.gif 
_where you get thees tubes and what year issue is this?
 thees old (50') metal is known as the best 6H8C, better then many 6SN7_

 

Yes, these tubes are indeed _"la crème de la crème"_ in its 6SN7/6N8S family. The 6H8Cs I have are made in 1954, nevertheless they are in excellent condition. 
	

	
	
		
		

		
		
	


	




 I got them as a present (along with some 6N30P-DR which will be used in my Bijou tube amp) from an old colleague from Ukraine.


----------



## runeight

Folks, the Designer has actually built his own amp. Pic attached.

 It's been running now for a while with a pair of old Amperex ECC88s from an old Tektronix scope.

 The amp sounds very nice. The build was easy and everything came up in stages as described on the website.

 I'll be making two small mods to the boards as result of building this myself. These mods will make life easier for the rest of you when you try to make the required measurements during the setup process. 
	

	
	
		
		

		
		
	


	




 I think you guys will like this amp. I am looking forward to the general release and everyone else's thoughts on this new and unique design.


----------



## dBel84

Hooray , he still has it in him 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## wiatrob

And then there were Three! (er, Four, dB 
	

	
	
		
		

		
		
	


	




) Looking good!


----------



## wiatrob

Got my amp cased, posted pictures in the build forum. Standard Hammond, plastic end panels:

http://www.head-fi.org/forums/f6/pos...ml#post4621917


----------



## fishski13

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Folks, the Designer has actually built his own amp. Pic attached.

 It's been running now for a while with a pair of old Amperex ECC88s from an old Tektronix scope.

 The amp sounds very nice. The build was easy and everything came up in stages as described on the website.

 I'll be making two small mods to the boards as result of building this myself. These mods will make life easier for the rest of you when you try to make the required measurements during the setup process. 
	

	
	
		
		

		
		
	


	




 I think you guys will like this amp. I am looking forward to the general release and everyone else's thoughts on this new and unique design._

 


 ...i'm waiting 
	

	
	
		
		

		
		
	


	




. any prediction when the boards will be available? 

 PACE


----------



## d0td0t

Still eagerly waiting.. Where to queue? nLOL


----------



## Uncle Bob

Info for UK builders, I've just had an email promo from Rapid. Tomorrow, from mid-day for 24hrs, they're selling all items at the maximum price break regardless of qty purchased.

 I'm not associated with Rapid btw, but there's savings to be had especially on high value items like ALPS pots and Toroidal Transformers


----------



## onform

Uncle bob, have you or are you ordering the tranny and pot from Rapid then? which tranny are you thinking?

 Wow no posts for two days...I suppose everyone is too busy getting the Soha II tested and ready for board production...


----------



## Ferrari

I can't speak for all but personally it's the busy work schedule that keep me from finishing the amp.
 However... mine should be up and running in the coming weekend.


----------



## gurusan

ooh that's going to be purdy!


----------



## onform

ferrari thats two beefy looking caps at the top there underneath an even beefier heatsink.. All for the soha??


----------



## FallenAngel

I would imagine so, likely output caps and judging by the size of the standoffs, I'm guessing they'll be mounted under the board.


----------



## kklee

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_Wow no posts for two days...I suppose everyone is too busy getting the Soha II tested and ready for board production..._

 

 Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_I can't speak for all but personally it's the busy work schedule that keep me from finishing the amp.
 However... mine should be up and running in the coming weekend. 
	

	
	
		
		

		
		
	


	


_

 

If I'm lucky, I may have mine running later tonight. Between waiting for parts and finding enough free time, it's taking a while. There are couple of issues that we still need to work through with the prototype.


----------



## cetoole

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_I would imagine so, likely output caps and judging by the size of the standoffs, I'm guessing they'll be mounted under the board._

 

Look more like Russian FT3 Teflon caps to be used for interstage coupling to me. Gonna be sweet!


----------



## Ferrari

Yes, the long standoffs are necessary due to the bottom mounted electrolytics capacitors and the 2" heatsinks of the output devices and the ±15V votage regulators. Since I'm planning to try out a dozen of audio tubes on this amp (6DJ8/E88CC/6922 family including the 6N1P with 6.3V heaters voltage), the heater votage regulator is therefore temporarily mounted on a beefier heatsink I found in my parts bin. 

 The 2 beefy Teflon caps are indeed used as interstage caps C1L/R (SOHA II has no output cap). These caps will be mounted off-board. Some other caps (Mundorf silver/oil, silver mica, polystyrene...) which I have on hand will also be tried out here as well.


----------



## FallenAngel

Oops, my mistake, was preparing a Millet MiniMAX BOM, still in my mind.


----------



## Uncle Bob

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_Uncle bob, have you or are you ordering the tranny and pot from Rapid then? which tranny are you thinking?
 ._

 

I couldn't resist those prices - I bought the 50VA toroidal (order code 88-2620) and two ALPS pots (and Rapid are normally cheaper for these than anywhere else anyway), plus nearly everything else I'll need to put a SOHAII together.

 My problem now will be getting over Farnells min £20 order value without buying stuff I don't really need.


----------



## kklee

Another teaser pic.


----------



## dBel84

keep em comming ..dB


----------



## wiatrob

Cheers! Looking good!


----------



## onform

is it possibble to mount everything taller than the valve bases on the underside, so that only the valves are potruding out of the case????


----------



## Ferrari

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_is it possibble to mount everything taller than the valve bases on the underside, so that only the valves are potruding out of the case????_

 

Yes!


----------



## onform

Sweet....lol...thanks ferrari....


----------



## onform

yaaaay i just became a 100+er...oh dear.


----------



## kklee

Just a warning before people order too many parts, we've encountered a slight power related glitch and are working on a resolution.

 Please hang on a little while longer, your patience will be rewarded.


----------



## GeWa

[size=medium]NOOO!!

 [size=x-small]
	

	
	
		
		

		
			





 Regards
 [/size][/size]


----------



## Ferrari

Gewa, don't worry. Your parts -as far as I can see from the pic- are not obsoleted!


----------



## dBel84

Don't fret folk, this is a minor issue which only affects some people. It seems to be dependant on where they live and the quality of their electricity, Runeight had planned to post a detailed update of progress and possible solutions to this unexpected behaviour are being worked on. The basic BOM should not change very much but it is probably wise to hold off until the prototyping process is complete. This is the aim of prototyping after all..dB


----------



## pkjames

can't wait !


----------



## Ferrari

Up and running smoothly... 
	

	
	
		
		

		
		
	


	













 ... with bottom mounted heatsinks and electrolytics capacitors.


----------



## runeight

Ferrari, remember to remove R3P for running higher heater currents.

 Folks. I'll be making a post soon describing the two issues that we've encountered and asking for your thoughts.


----------



## dBel84

That looks very cool Ferrari, you always have the most interesting collection of caps. 

 I look forward to seeing it all cased up in true Ferrari style ..dB


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ferrari, remember to remove R3P for running higher heater current..._

 

runeight, thanks for remind me with that power resistor.
 I have been listening to a couple of CD's with this amp since it was up and runing this afternoon via Sennheiser HD600... sounds surprisingly good unless it's brand new and definitely needs some time to burn in. 
	

	
	
		
		

		
		
	


	



 The case work will probably have to wait untill next weekend.


----------



## onform

ferrari
 do have an extensive collection of caps or have you brought these to try out?? I notice your going to top mount the board. looking good. 

 All i have so far is the case on order and all the ancillaries for the case, awaiting the finalised board and kit pricing from glass jar.

 Are there any benefits to having a larger tranny say 50VA over the 30VA version previously mentioned??


----------



## runeight

OK folks here's the update.

 First, the amp is easy to build and to get working. Mine went together in an evening of about 2 hours work and then the next morning. I had music by lunchtime. The three stage scheme (on the website) for bringing up the amp worked just fine, although the voltages came up correctly from the start. I was able make the current adjustments easily enough. After some break in I readjusted the currents and they have been stable since then.

 I've done quite a bit of tube rolling between 12au7s and 6dj8s and their variants. The front end works as designed, balancing the plate voltages reasonably closely depending on the matching of he triodes. The worst mismatch that I have seen is with one of my EI Elite 12au7s which shows a 5V differenc ein plate voltage between the two halves. All of the other tubes are within a few volts, a few within less than one volt.

 The amp sounds very good to me and is well broken in. It gets hot, but not unacceptably so. The tube rolling has been great fun with a very simple jumper swap to go from one tube type to another.

 Here are the two things that have surfaced in the prototypes:

 1. Hum - my build shows some audible hum depending on where I put the toroid in the back of the box and exactly how I position it (that is, rotating it changes the hum). Other builds (some in a single box, one in a two box build) are not showing hum. To clarify this, full volume exhibits a small amount of hum in one of these builds, but nothing until about 85% of the travel.

 I am able to rotate the toroid until I don't get any hum, but I have not fully cased the amp yet.

 The peculiar feature of this in my case is that the hum only appears when the amp is in the Hammond enclosure. When it is on the workbench, I can move the toroid very close the board with no induced hum. But when the transformer and board are slotted into the case I get the hum. This seems to be related to the transformer inducing currents in the case that are affecting the tubes. I think.

 On option is, of course, a two box solution with the transformer in a separate box. But, then again, single box builds seem to be working ok with respect to hum.

 The result here is, therefore, inconclusive. So we don't know what your mileage may be on this.

 2. Dropouts - the built in epsilon 12 is dropping out on some of the builds. This appears to be a sensitivity to line (mains) voltage variations and not the music. In some of the builds when there is a transient change of the AC line voltage this transient makes its way (I can explain later how) to the output as a few hundred mV of DC that trips the e12. Eventually the servo responds and resets the output offset to 0VDC.

 But, during this time the music is interrupted.

 The appearance of the issue is also inconclusive. That is, my build has never dropped out over many many hours of operation with my entire house running (Air conditioning, washer/dryer, etc.). OTOH, one of the builds seems to show more of this issue (in another part of the country). There is a third build that has traveled around the country with no dropouts and a fourth that is in Canada that has had a few, but not many.

 Thus, this item is also inconclusive and we don't know what will happen in any specific build or location. We are also suspecting that a number of other amps may exhibit this behavior but just don't have an e12 to detect it. But, we really don't know for sure that this is the case.

 These two issues have caused the prototype team to delay a release of the amp until a few more are built and tested. My position as the originator is that I don't want you guys to spend money and time on this unless it is very solid.

 And, actually, it is pretty solid with just some concerns that are giving us a bit of a pause.

 We would appreciate any of your thoughts.


----------



## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The case work will probably have to wait until next weekend.
 [/i]
 [/td] [/tr] [/table]


Nicely done! what What model transformer are you using? 

 (All, there is an option to run the amp current at 600mV, which I believe Ferrari has taken advantage of, hence runeight's comment on the removal of R3P...)_


----------



## Ferrari

Quote:


  Originally Posted by *onform* /img/forum/go_quote.gif 
_ferrari
 do have an extensive collection of caps or have you brought these to try out?? I notice your going to top mount the board. looking good. 

 All i have so far is the case on order and all the ancillaries for the case, awaiting the finalised board and kit pricing from glass jar.

 Are there any benefits to having a larger tranny say 50VA over the 30VA version previously mentioned??_

 

I have some in my parts bin but I don't think that I would call it an extensive capacitor collection.
 The only parts I have bought for this build are some small values resistor, which I don't have on hand.
 All other parts are from my parts bin. As a result... a mix of caps (MKP, MKC, silver mica...) from different manufacturers.
 A 50VA transformer (NOT tranny !!! 
	

	
	
		
		

		
			





 ) can be useful when running high current @6.3V.


----------



## Ferrari

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Nicely done! what What model transformer are you using? ..._

 

The transformer is a potted 50VA one from Talema. I got it from RS-components Netherlands.


----------



## GeWa

@Ferrari

 Is it a good idea to place all the heatsinks at the bottom of the board?

 Regards


----------



## Ferrari

Quote:


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

 Is it a good idea to place all the heatsinks at the bottom of the board?

 Regards_

 

If the heatsinks are of sufficient size and if there is adequate air convections (air flows bottom-top), it's will be fine ! 
 I'm using 2" heatsinks and on the workbench the heatsinks temperature is ~20°C warmer than room temperature.
 When cased up, the heatsinks temperature can increased 10-15°C further (from my experiences).
 So, the expected maximum heatsinks temperature is in a range of 50-55°C, ... quite resonable numbers to me. 
	

	
	
		
		

		
		
	


	




 The sound of this amp is really a feast for the ears and definitely the best hybrid HP amp I have built so far.
_(it's NOT my intension to compare this amp to an overhyped hybrid amp here at HF)._


----------



## runeight

The reports from the proto team are very positive at this point. I'm sure that they will be posting here soon.

 Gewa, you can also locate the heatsinks on the top side of the board. The amp will get hotter, but mine is not self-destructing due to the heat.

 I don't understand why comparisons can't be made to other amps. That's done all the time. Comparisons are helpful for others to know what category a particular amp fits in by giving them some known references. Is this other amp sacred somehow? If not, then I think fair and honest comparisons should be made.


----------



## kklee

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_If the heatsinks are of sufficient size and if there is adequate air convections (air flows bottom-top), it's will be fine ! 
 I'm using 2" heatsinks and on the workbench the heatsinks temperature is ~20°C warmer than room temperature.
 When cased up, the heatsinks temperature can increased 10-15°C further (from my experiences).
 So, the expected maximum heatsinks temperature is in a range of 50-55°C, ... quite resonable numbers to me. 
	

	
	
		
		

		
		
	


	




 The sound of this amp is really a feast for the ears and definitely the best hybrid HP amp I have built so far.
(it's NOT my intension to compare this amp to an overhyped hybrid amp here at HF)._

 

I'm running 1" heatsinks and I don't have a cover on the amp yet, they're measuring around 57°C with an IR heat probe. Warm, but not too hot to touch. I expect that the temp will jump up a few degrees with a ventilated lid, but that's still acceptable.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I don't understand why comparisons can't be made to other amps. That's done all the time. Comparisons are helpful for others to know what category a particular amp fits in by giving them some known references. Is this other amp sacred somehow? If not, then I think fair and honest comparisons should be made._

 

Agreed, let the detailed comparisons fly. An honest comparison might not start with 'X vs overhyped Y'. It is all in the wording, but I think Ferrari is alluding to some historical criticism of the MH, while not sacred, per se, has a rather faithful following. That some folks (myself NOT included) are emotionally invested in their builds, honest critiques are not well understood as a rule in Head-fi DIY except in the more experienced builders. 

 Hey, I like my MH - a LOT. I hope to like my Bijou even better. Would I like a SOHA-II even better? There is where the previous conflict arose - I had asked for a comparison between Bijou and MH (I would also like an honest comparison between SOHA-II and Bijou), but Apples-Oranges erupted, and the point became lost, well, to others. Pity the heads up comparisons cannot seem to occur, without the groan of the grinding axes - on all sides.

 Does no one realize that it is precisely those comparisons that is fueling this absolutely astounding period of headphone amp designs?


----------



## runeight

Well, I can't speak for people on other threads but on this thread feel free to make honest and fair comparisons. We all recognize that audio can be amazingly subjective, but people can still give their opinions without slamming someone's amp.

 I don't expect any of those fireworks on this thread. And I do expect the prototypers will begin to say what they think about the SOHA II, pro or con. After all, if we're not straight with everyone about the amp, how can you possibly know whether or not to spend your money on it?


----------



## runeight

On another note, while we're still waiting for a few more builds to complete, I've been thinking about the front and back panels for the Hammond enclosure.

 Here some preliminary designs. The rear panel includes an IEC connector with fuse, power switch, and input jacks.

 Front panel is obvious.

 I'd appreciate your opinions because I'm going to have a set of these made and then, if they work and you guys like them, we can offer them as part of the kits.

 (Man this file size limit really makes you work)


----------



## Beefy

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The sound of this amp is really a feast for the ears and definitely the best hybrid HP amp I have built so far.
(it's NOT my intension to compare this amp to an overhyped hybrid amp here at HF)._

 

I like comparisons. Comparisons are healthy, and help *everyone* learn to improve. That being said, I like the comparisons fair..... A lot of early Millet Hybrid Max builders, for example, probably haven't heard that amp at its best. There were a fair number of 'upgrades' to key components on that amp over time that have apparently improved sound dramatically.

 In any case, the SOHA II looks like a great little project. Though I think that I might extend my horizons and go straight for the Stacker next time I get the DIY itch......


----------



## Cankin

Stacker is better(better topology or design) than SOHAII?


----------



## Beefy

Quote:


  Originally Posted by *Cankin* /img/forum/go_quote.gif 
_Stacker is better(better topology or design) than SOHAII?_

 

Different. Higher voltage and more demanding build.

http://www.head-fi.org/forums/f6/sta...hybrid-318479/
HeadWize: DIY Workshop > The Stacker II Hybrid - A Tube Rollers Dream Headphone Amp


----------



## runeight

The SOHA II and the Stacker have different design goals.

 The SOAH II is designed to be a low voltage hybrid (so it can't kill you) with reasonably flexible tube rolling capability and a nice SE buffer on the output.

 The Stacker is designed to show off the tube at high voltages. Its buffer is designed to be as transparent as possible so that the only thing that comes through is the tube. Edit: The Stacker is also designed to allow rolling of many more types of tubes than the SOHA II.

 In general the Stacker is a more expensive, more complex, higher end amp compared to the SOHA II (or the Millet or SOHA I).


----------



## Cankin

I don't build amp myself, but there are more nice choices available for me as an end user, thanks for the effort guys


----------



## wiatrob

runeight;4647733 said:
			
		

> ... And I do expect the prototypers will begin to say what they think about the SOHA II, pro or con...QUOTE]
> 
> Hmmm, is that a hint? I think we are all just too busy enjoying this amp to post!
> 
> ...


----------



## kklee

As wiatrob mentioned, we're too busy enjoying the amp to do any comparing
	

	
	
		
		

		
			





 I did a quick A/B comparison between a Millet Max with MOSFET's and the SOHA II. I have to say that the SOHA II has a fuller, richer, more detailed sound.

 I'd compare it to my Bijou, but it's currently in pieces while I finish its chassis.


----------



## holland

I put a quick build together.





 I need to spend more time doing critical listening and letting the components settle. My initial impressions are that the tubes have a significant impact on sound (as I'm sure others already know). I have 2 tube sets, basically, Electro-Harmonix 12AU7 and a Mullard 12AT7. The 12AT7 has really real meat to the bottom end, and an overall much warmer sound. The EH 12AU7 is crisper and lighter, with more air, but still offers a noticeable thump on the bottom end.

 I have used BD137 instead of BD139 as the output transistors.

 I have done quick comparisons with the Dynalo and CK2III, as they are in this amps price range. My initial impressions are that this amp exceeds those. There's more "meat" to the sound. A livelier, more engaging experience. This is only a quick comparo, however. More detailed listening will need to be done in a few weeks, with extensive time spent between the amps aforementioned.

 Hopefully in that timeframe, I can properly case the amp as well and properly ground the pot.


----------



## Ferrari

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_As wiatrob mentioned, we're too busy enjoying the amp to do any comparing
	

	
	
		
		

		
		
	


	




 I did a quick A/B comparison between a Millet Max with MOSFET's and the SOHA II. I have to say that the SOHA II has a fuller, richer, more detailed sound._

 

Funny, I'm currently doing a A/B listening test between my SOHA II and a BJTs MH Max (spiced up with Black Gate NX and PIO) too. The BJTs MH Max was using by my colleague at work for almost 1 year (well burned in) while my SOHA II is just started playing music last weekend and still needs some time to burn in. Maybe a bit unfair for a comparison right now, but my first impression is very in line with yours... especially the transparancy and the 3rd dimension in the music! I have no clue what does the tricks here... but sound wise, it's really a feast for the ears (as I mentioned earlier). 
	

	
	
		
		

		
		
	


	




 Further impressions will follow after my extended A/B listening test in the coming weeks (as long as my colleague is on holiday, I can keep his amp for testing).


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Dropouts - the built in epsilon 12 is dropping out on some of the builds. This appears to be a sensitivity to line (mains) voltage variations and not the music. In some of the builds when there is a transient change of the AC line voltage this transient makes its way (I can explain later how) to the output as a few hundred mV of DC that trips the e12. Eventually the servo responds and resets the output offset to 0VDC.

 But, during this time the music is interrupted.

 The appearance of the issue is also inconclusive. That is, my build has never dropped out over many many hours of operation with my entire house running (Air conditioning, washer/dryer, etc.). OTOH, one of the builds seems to show more of this issue (in another part of the country). There is a third build that has traveled around the country with no dropouts and a fourth that is in Canada that has had a few, but not many.

 Thus, this item is also inconclusive and we don't know what will happen in any specific build or location. We are also suspecting that a number of other amps may exhibit this behavior but just don't have an e12 to detect it. But, we really don't know for sure that this is the case.

 These two issues have caused the prototype team to delay a release of the amp until a few more are built and tested. My position as the originator is that I don't want you guys to spend money and time on this unless it is very solid.

 And, actually, it is pretty solid with just some concerns that are giving us a bit of a pause.

 We would appreciate any of your thoughts._

 

I've been waiting for the more experienced builders to comment on this and I'm surprised there's been no public feedback so far
	

	
	
		
		

		
		
	


	




 Given that AMB's E12 design has been in use for quite some time in a number of projects I am surprised that this behaviour (or susceptibility) has not been noted before. Or is it a consequence of the modifications to the original design?

 If the cause is understood then presumably a solution is possible. Hopefully without too much delay 
	

	
	
		
		

		
		
	


	




 I know that I wouldn't like to suffer a problem like that on any music playing equipment I might own.

 UB


----------



## MrMajestic2

Almost done populating my board now. Yeah yeah, I know Im slow 
	

	
	
		
		

		
		
	


	




 Realizing now when seeing Ferraris board that maybe I should have gone for taller heatsinks. I have the standard 1" sinks mounted on the bottom of the board. Im not going to solder them so I can swap them later. Hey Ferrari, you dont happen to have a few left over?


----------



## runeight

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Given that AMB's E12 design has been in use for quite some time in a number of projects I am surprised that this behaviour (or susceptibility) has not been noted before. Or is it a consequence of the modifications to the original design?

 If the cause is understood then presumably a solution is possible. Hopefully without too much delay 
	

	
	
		
		

		
		
	


	




 I know that I wouldn't like to suffer a problem like that on any music playing equipment I might own.

 UB_

 

Thanks for the feedback. The e12 is working as designed. This issue is a very unusual kind of behavior that seems to show up in certain circumstances and it seems to be an amp behavior.

 I (and others) are still thinking about a fix or even if a fix is necessary given that the problem is not consistent or universal.


----------



## dBel84

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Given that AMB's E12 design has been in use for quite some time in a number of projects I am surprised that this behaviour (or susceptibility) has not been noted before._

 

I know of several people who have either desensitized the e12 or pulled it completely in both SS and Hybrid amps, myself included. I think it is a very useful circuit and conceptually brilliant but it doesn't always work out practically for all amps. 

 We feel that it is necessary for the SOHA II because of the nature of the SE buffer , unfortunately this dropout is not as consistent to reproduce as we would like it to be and thus it is proving difficult to resolve in all builds. 

 ..dB


----------



## kklee

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_Given that AMB's E12 design has been in use for quite some time in a number of projects I am surprised that this behaviour (or susceptibility) has not been noted before. Or is it a consequence of the modifications to the original design?

 UB_

 

I've had nothing but bad luck with the e12 and ended up pulling it from every amp I installed it in. Then again, there are many others who have successfully implemented the e12.

 In the case of the SOHA II, I think there are at least two factors that contribute to the problem:
 1. How clean your power source is. I live in an older house with crappy wiring, so my line voltage goes all over the place and the wiring isn't spread out between enough circuits. When I bring the amp to work (I work at our local electric utility's data centre), it doesn't experience any drops.
 2. There's variance with parts, especially transformers, so even though we're using the same value components, there's bound to be differences due to tolerance variations. Therefore one build may be more susceptible to power fluctuations than another.

 Having said that, part of DIY is tinkering, so although it can be frustrating (my wife can attest to the swearing that goes on in my workshop), it's part of the 'fun' of this hobby.

 Enough said, I'm going back to listening to my SOHA II. I just can't get over how good it sounds with Grado SR225's.


----------



## Ferrari

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Almost done populating my board now. Yeah yeah, I know Im slow 
	

	
	
		
		

		
		
	


	




 Realizing now when seeing Ferraris board that maybe I should have gone for taller heatsinks. I have the standard 1" sinks mounted on the bottom of the board. Im not going to solder them so I can swap them later. Hey Ferrari, you dont happen to have a few left over?_

 

MrMajestic2, I have 2 pieces left but that is not sufficient for this amp unfortunately.


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_MrMajestic2, I have 2 pieces left but that is not sufficient for this amp unfortunately. 
	

	
	
		
		

		
		
	


	


_

 

Thats ok, thanks anyway. They are available here but they cost more around $10 each 
	

	
	
		
		

		
		
	


	




 Hopefully the amp will survive a while until I can order some from Mouser.


----------



## Ferrari

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Thats ok, thanks anyway. They are available here but they cost more around *$10 each *





 Hopefully the amp will survive a while until I can order some from Mouser._

 












 Conrad Netherlands has 1.5" heatsinks for ~2 Euro each, if you buy 10 pieces at once.
 I think that Conrad Sweden also have these heatsinks too (product code: 187976 - 89).
 May be is that an option.


----------



## runeight

Quote:


  Originally Posted by *MrMajestic2* /img/forum/go_quote.gif 
_Thats ok, thanks anyway. They are available here but they cost more around $10 each 
	

	
	
		
		

		
		
	


	




 Hopefully the amp will survive a while until I can order some from Mouser._

 

MrMajestic2, the amp does perfectly alright with the 1" heatsinks. I've been running mine for at least 30 hours now. Maybe longer. I am not experiencing any heat related issues. And the amp sounds great everytime.


----------



## MrMajestic2

Quote:


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











 Conrad Netherlands has 1.5" heatsinks for ~2 Euro each, if you buy 10 pieces at once.
 I think that Conrad Sweden also have these heatsinks too (product code: 187976 - 89).
 May be is that an option._

 

Nah, half an inch is not worth it 
	

	
	
		
		

		
		
	


	




 Ill go for bigger later unless the amp is happy with the ones I got. Runeight says it might be fine so Ill give it a go.


----------



## Ferrari

Quote:


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

 In the case of the SOHA II, I think there are at least two factors that contribute to the problem:
 1. How clean your power source is. I live in an older house with crappy wiring, so my line voltage goes all over the place and the wiring isn't spread out between enough circuits. When I bring the amp to work (I work at our local electric utility's data centre), it doesn't experience any drops.
 2. There's variance with parts, especially transformers, so even though we're using the same value components, there's bound to be differences due to tolerance variations. Therefore one build may be more susceptible to power fluctuations than another.

 Having said that, part of DIY is tinkering, so although it can be frustrating (my wife can attest to the swearing that goes on in my workshop), it's part of the 'fun' of this hobby._

 

Agreed about these two factors. 
 Probably I'm just lucky living in a part of Europe with relative clean AC lines.
 I have about 30 hours listening time with my amp now without one single unwanted activation of the E12 circuit.


----------



## wiatrob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Agreed about these two factors. 
 Probably I'm just lucky living in a part of Europe with relative clean AC lines.
 I have about 30 hours listening time with my amp now without one single unwanted activation of the E12 circuit._

 

Ah, Europe! At home my power is consistent except when some big loads cycle (i.e. 240V pump motor) and my build has not experienced any drop outs after some e12 component value tweaking.

 I have some of the _worst _power at work, and continue to have issues. Runeight is coming up with some ideas, however.

 As far as heat is concerned, my amp has 1" sinks and has been cased and running for at least 60 hours (plus some all night burn-ins for NOS tubes) without any issues. I like the heat, it's comforting somehow 
	

	
	
		
		

		
		
	


	




 I have been doing some A/B with the original SOHA, and while I am still trying to describe the differences, I can say I prefer the II for it's greater depth and breadth (soundstage!), separation and while both amps have good bass, I prefer the SOHA II.


----------



## Ferrari

How are your builds going guys? I'm still busy with the case work, have posted a primarily pic here.


----------



## MrMajestic2

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_How are your builds going guys? I'm still busy with the case work, have posted a primarily pic here. 
	

	
	
		
		

		
		
	


	


_

 

Im having some problems with my build and I havent had the time to fully investigate it. I have some things too look for, but I just dont have the time right now.


----------



## Ferrari

I have lots of builds on the work bench, but lacking of free time is also a major problem over here.


----------



## runeight

Folks, despite the quiet, a lot of work has been going on. Here is an update.

 The hum problem seems not to be a problem. No one really experienced it but me and mine turns out to not be an issue when the amp is properly cased.

 The PS problem was a little more difficult because it was so unexpected.

 We have developed two possible solutions, one of which will make it into production:

 1. Simply add a zener to the current PS. This will eliminate nearly every dropout issue except where your power is absolutely pathetic.

 2. Increase the mulitplier effect to get more initial B+ giving more headroom in the PS for line voltage drops. I have proto'd this and it works. One nice thing about this option is that it puts 70V on the plates instead of 40V. The tubes will like this a lot more.

 I think we're going to decide very soon which option makes it into production.

 You all have been remarkably patient with this thread. Gewa, only a very few of your parts will need to be changed for option 2. For option 1 you'll just need a pair of zeners.


----------



## GeWa

Quote:


 Gewa, only a very few of your parts will need to be changed for option 2. For option 1 you'll just need a pair of zeners. 
 

I can live with that 
	

	
	
		
		

		
		
	


	



 If it was me I would opt for option 2 because, as you said it, of the higher plate voltage. Big possibility to make a good amp even better! 
	

	
	
		
		

		
		
	


	




 Regards


----------



## runeight

So you guys will actually see the new HV supply that I've just tested, here's the schematic. It needs only two extra diodes and two extra caps to generate the 2.5X multiplier that makes the 105V. It works great. I'm listening to it now. 71V on the tubes.


----------



## kklee

Since I'm waiting for parts to arrive for further prototyping, I finished up the case a little more on my first build. The top consists of the original top panel cut in half and the other half is a piece of Lexan. The front panel is a temporary piece of Lexan (waiting for a custom panel).

 A second build is in the process of being cased in a similar manner.

 Once the extra parts show up, I'm hoping to use the two builds to A/B test the two potential power issue solutions.


----------



## dBel84

That window is a smart idea, kklee. Have you vented it? 

 looking forward to seeing the FPE panel too..dB


----------



## kklee

Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_That window is a smart idea, kklee. Have you vented it? _

 

Not yet, I'll see how hot it gets before I decide if I'm going to vent it. I'm not that great in drilling neatly lined up holes.

 The idea for the top window actually came from a fellow Headfier.


----------



## cfcubed

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_Not yet, I'll see how hot it gets before I decide if I'm going to vent it. I'm not that great in drilling neatly lined up holes._

 

Looks great kklee... No master builder here & seems pretty much every time I try to do a nice grid of perfectly spaced holes they don't come out perfect
	

	
	
		
		

		
		
	


	




 Lately I've come around for settling for thin, parallel cooling slots by using a table saw & raising the blade into the material. Key here was use of test material & permanent marker on the table surface to access entry/length/centering of slots.

 Good luck!

*runeight* - I've got a little research project I may dive into this winter & *am considering mating something like the SOHA II * voltage multipler with the original's buffer... When available & approved I assume a *larger res PS schematic* will be available
	

	
	
		
		

		
		
	


	




 P.S. dBel84 has shared some ideas on this with me (thanks!) & believe it or not those little guys even have RED eyes on their tips to pressure me further into doing something with them someday...


----------



## daveip

oh man .... i've just been readin bits of this thread and i'm so looking forward to the release! loved building and listening to my SOHA!


----------



## kklee

Quote:


  Originally Posted by *cfcubed* /img/forum/go_quote.gif 
_Lately I've come around for settling for thin, parallel cooling slots by using a table saw & raising the blade into the material. Key here was use of test material & permanent marker on the table surface to access entry/length/centering of slots._

 

I'll have to give that a try. I've had the amp on for for about two hours solid this morning and it's a little toasty without the venting.


----------



## onform

What valves are you guys using/planning to use?? which will sound best? IYHO

 P.s loving all the proto photo's guys.


----------



## runeight

I have tried:

 EI Elite 12AU7
 RCA NOS 5963
 RCA NOS 6DJ8
 Amperex 6922
 Amperex 8416
 EI Elite 12AT7

 The 5963s have the best sound for my tastes (and my wife's, who thinks the amp sounds absolutely beautiful).

 The 8416s come in second. The rest are good.


----------



## dBel84

Interesting that you like the 5963 - I recall Batman liking this tube too. 

 I have not done any serious tube comparisons but have rolled a few including :
 westinghouse 12AU7
 RCA 5814
 Amperex 6922 / 8416 
 Mullard 12AT7
 zenith 12AT7
 ? brand 6680

 Although I liked the 8416 very much , I use these tubes in another amp and have thus settled on the Mullard 12AT7

 ps - they all sound seriously good though, so don't be put off trying anything you may have or stumble upon.

 ..dB


----------



## kklee

I've tried:

 GE 5963
 Mullard 12AU7
 JJ Tesla ECC82
 Electro Harmonix 12AU7

 I like the GE 5963's the most, but they're extremely microphonic, you can hear the volume pot being turned.

 I'm scouring the web to buy other tubes.


----------



## keyid

Try the GE 6680, they sound great on soha I with senns and should match well with low voltage. Are you guys matching tubes? have you found the input tube has some impact on the sound?


----------



## Postal_Blue

Just a quick update. I have completed all my listening/comparing and have every intention of posting a full-on review late tonight. It will be resoundingly positive.


----------



## runeight

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_Try the GE 6680, they sound great on soha I with senns and should match well with low voltage. Are you guys matching tubes? have you found the input tube has some impact on the sound?_

 

keyid, i have some 6680s and I am going to try them soon. The little PS issue that we had has taken my attention for a while. I'll let you know.

 I am not matching tubes and I am finding that the tubes are generally pretty close.


----------



## wiatrob

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_I've tried:
 I like the GE 5963's the most, but they're extremely microphonic, you can hear the volume pot being turned._

 

My RCA 5963's Black Plates exhibit the same issues. They were so microphonic before burn in that I despaired of using them, but they've toned down quite a bit and now I can only hear the pot turn. Sound very good though...

 Also:

 JJ ECC82 ( an early favorite)
 RFT ECC81
 Amperex 8416 (a recent favorite

 Right now I'm listening to John Williams playing Schubert on guitar with RCA 12AU7 Clear Tops - not only do they look extremely cool, but the sound is smooooth, the guitar is vibrant and alive...sigh...
	

	
	
		
		

		
			





 The Clear Tops and JJs are matched but not closely (10%) I have not found matching to be that important....


----------



## GeWa

Them boards better be ready by the time I get back from my holiday 
	

	
	
		
		

		
		
	


	



 Just a few hours away from a well deserved vacation in Madeira!

 Regards


----------



## Arkku

Hi,

 Although this is my first post on this forum, I've been following this project with great interest for a while now, and have read every post in this thread, hoping to build the final version once the plans are finalised.

 One thing came to mind as I read the recent posts about possible power supply revision; how about substituting a 18-0-18 transformer for the 15-0-15? I'm not really experienced in power supply design, but shouldn't this make it easier to maintain a steady 15 VDC supply as well as possibly increase the B+ voltage (to, say, 90 V with the proposed higher voltage modification)?


----------



## runeight

Hello Arkku. Welcome to the forum!!!

 This is a good question. And a tricky one.

 Increase the voltage on the transformer will increase the voltage at the input to the regulators. By quite a bit. If the rails are kept at 15V this means that much more power must be dissipated in the regs. Larger heatsinks will be required and the amp won't fit into the Hammond box.

 So then why not increase the rails to 18V? This just shifts the power dissipation to the O/P devices (all four of them). Necessitating larger heatsinks on them.

 In essence the amp was pretty tightly designed around 15V rails with a 15-0-15 transformer. This includes the voltage op points and the power op points.

 It's hard to change it without going back and making many changes to the amp.

 Thus, I think providing you guys with a separate HV board that uses the 2.5X multiplier will be the most useful option for those who cannot resolve their power issues with the standard configuration.

 This is all being worked out for the production run. 
	

	
	
		
		

		
		
	


	




 Thanks for the suggestion though. I'm always looking for help.


----------



## runeight

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Them boards better be ready by the time I get back from my holiday 
	

	
	
		
		

		
		
	


	



 Just a few hours away from a well deserved vacation in Madeira!

 Regards_

 

Working on it!!!


----------



## runeight

Gents, I believe this has all been worked out. The boards are being readied for production runs. Group buy info will follow in appropriate threads.

 Here's how things will work.

 1. The SOHA II Super SE Hybrid board will be available as prototyped with just a few tweaks for better convenience in building/testing. The amp that the prototypers love won't change.

 2. For those builders who experience e12 dropouts due to power fluctuations, two addional tweaks will be available on the main board to handle this. In many cases these tweaks will be sufficient to stop the dropouts.

 3. If the main board tweaks are not sufficient we are also providing a high voltage (100V) separate multiplier board. This board is about 2" x 2.5" and will create over 100V for the B+ supply. This board will provide more headroom in the B+ supply for eliminating the drops completely. The main board is jumpered to use either its internal B+ supply or an external one.

 4. Even if you are not experiencing drops you can experiment with the higher plate voltages offered by the auxilliary HV board. So it gives you even more things to do besides just tube rolling. 
	

	
	
		
		

		
		
	


	




 I have incorporated as many of your suggested changes as possible. When the boards are sent off to production I will start updating the website with these changes.

 I do want to profusely thank the prototype team. These were:

 dBel84, wiatrob, kklee, holland, ferrari, postal_blue, mrmajestic2, fallenangel, rds, and misterx. I particularly want to thank dBel84 for doing the first prototype on a homemade board to validate that the design would work. It would have been impossible to get this far without the help from this team.

 More to come . . .

 Oh, if you haven't read postal_blue's review, please look here:

Review by Postal_Blue

 Edit: We are also working on front and back panels and, possibly, ventilated top panels.


----------



## Ferrari

Yes, the fun with this amp is not restricted to tubes rolling only.
 There is definitely room for experimenting with the the B+ supply...
 just finished this regulated B+ power supply, rock solid at 90V.


----------



## runeight

Say, Ferrari are you using that HV TI chip?? And it works ok?? Are you loading it at all?

 Don't forget to bleed both HV supplies before you connect anything. Or transistors will die.


----------



## Ferrari

Yes, I'm using the TL783C chip from TI. Under test condition it's loaded with a 47KΩ/25W resistor.
 Ripple voltage is reasonably low at ~1mV. The BJT capacitance multipliers are not used on my proto, so no fears for dead MPSA42 transistors. But it's my old habit to bleed PS caps before doing any soldering/modifications or connecting to other circuit.

 In the mean time, I have connected it to the B+ section of SOHA II for about 2 hours... sounds really good.
 (the Roederstein and Nichicon Muse KZ electrolityc capacitors from my parts bin are doing good job here)


----------



## runeight

OK. I figured that you would, but I didn't know that you had left the cap multipliers completely out. 
	

	
	
		
		

		
		
	


	




 I did notice a difference in sound between the two B+ supplies. I had to listen a bit, but it was there.


----------



## Ferrari

The ~50% increased B+ voltage does have impact on the sound, no doubt! There are clearly audible differences at the first listen session. To know what I like more, I need some more listening time to draw my conclusions though. (also to give the new PS caps the necessary time to burn in)


----------



## JamesL

Quote:


  Originally Posted by *mwofsi* /img/forum/go_quote.gif 
_The original SOHA name is an acronym(?) for "Simple Opamp Hybrid Amplifier", 
 which the SOHA II no longer is 
	

	
	
		
		

		
			



_

 

It's alright. It can still stand for Superbly/Second Outstanding Hybrid/Headphone Amplifier
 Or maybe SOAH for alex'*S* *O*ver*A*c*H*iever

 Anywayyyys... Waiting patiently on board release. 
 I just realized I had a case on hand that would fit the amp nicely.


----------



## mwofsi

Goodness James, I thought I'd lived that down already


----------



## Alcaudon

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_It's alright. It can still stand for Superbly/Second Outstanding Hybrid/Headphone Amplifier
 Or maybe SOAH for alex'*S* *O*ver*A*c*H*iever

 Anywayyyys... Waiting patiently on board release. 
 I just realized I had a case on hand that would fit the amp nicely. 
	

	
	
		
		

		
		
	


	


_

 

What about: *S*acred *O*racle of *H*i-fi *A*udio????

 yes......I'm bored too... 
	

	
	
		
		

		
		
	


	




 Any news on the boards???


----------



## JamesL

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_What about: *S*acred *O*racle of *H*i-fi *A*udio????

 yes......I'm bored too... 
	

	
	
		
		

		
		
	


	




 Any news on the boards???_

 

hehe, very nice.
 I think I might just go ahead and start on the casing.

 Sanity check. Are the 1" heatsinks actually 1" off the board? (I'm working on tight constraints), and are they the tallest parts on the board?

 Also, whats the diameter of a standard noval tube. I'm wondering if a 7/8" bit would leave enough clearance on the sides, let alone fit the tubes.


----------



## runeight

Man, you guys _are _ bored. 
	

	
	
		
		

		
		
	


	




 I guess I'd better get moving.

 Just a little bit more time . . . work is distracting me some.


----------



## runeight

Quote:


  Originally Posted by *JamesL* /img/forum/go_quote.gif 
_hehe, very nice.
 I think I might just go ahead and start on the casing.

 Sanity check. Are the 1" heatsinks actually 1" off the board? (I'm working on tight constraints), and are they the tallest parts on the board?

 Also, whats the diameter of a standard noval tube. I'm wondering if a 7/8" bit would leave enough clearance on the sides, let alone fit the tubes._

 

1" heatsinks are 1" off the board. The spec diameter of the tube is 7/8" IIRC. If you are planning to poke the tube through a hole I think that a 1" hole would be about right.


----------



## stixx

Quote:


 Man, you guys are bored. 
 

I'm not too bored, but I'd suggest

 Smart Opamp Hybrid Amplifier




 OK, gone...


----------



## Ferrari

My regulated B+ power supply based on TI HV chip has been passing a 100 hours endurance test, loaded with a 10KΩ/100W resistor. The recorded results are as expected… rock solid. Ripple voltage varies somewhat in the long run, but in any case less than 2mV. 

 No need to say that I prefer this regulated B+ power supply above other solutions (however these solutions can work).


----------



## runeight

Ferrari suggested a while ago that we look into this regulator for the B+. This was after we created the 105V multiplier supply.

 Part of the reason for the last minute delay is for Ferrari to test out his reg and for me to prototype mine, using the same HV multiplier.

 If both tests prove successful, we will probably incorporate this reg into the B+ supply.

 This will solve the dropout problems and will give you a variable B+ from about 60V to about 100V. What more could you want?

 Ferrari, what bias chain resistors are you using?


----------



## Ferrari

Quote:


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

 Ferrari, what bias chain resistors are you using?_

 

A 100Ω resistor and a 10KΩ trimpot.
 (simply parts that I can grab from my parts bin, same as other parts in the circuit).


----------



## runeight

OK gents, I've also built the TL783 supply with the 105V multiplier. Works like a charm. I've dialed the B+ from 55V to 100V. Doing this too fast causes the e12 to dropout, but at a nice steady slow speed you can dial the B+ up and down and listen to your heart's content.

 Working on the final decision whether or not to make this the production PS, although I think it will be. Then we charge forward.


----------



## Ferrari

Good to know!


----------



## wiatrob

This is great news. I've been running at 75V with an interim B+ multiplier solution since last night. Looking forward to the tweakability of the adjustable regulator.


----------



## Ferrari

The endurance test on this HV PS counts 24 hours more, now @95V instead of @90V, loaded with a 10KΩ/100W resistor as before.
 Its good performance remains unchanged. 

 I'm pretty confident that this HV PS is able to deliver clean and stable power for the SOHA II B+ section, from at least 60V up to 95V DC... lots of room to play with!


----------



## dBel84

More good news !! 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## Ferrari

After running an endurance test for ~150 hours with all-round solid results, it's time to put an end on this test and go further with the case work. But before breaking the test setup down... a pic of the PS output voltage @95V DC.


----------



## Ferrari

I have spent some hours listening to the SOHA II with regulated 95V B+ power supply this weekend, and I have to confess that I like it a lot.

 The increased B+ voltage does have impact on the sound in a positive way, and to be honest... I don’t want to go back to the original unregulated PS.


----------



## runeight

That's good!! Because that's what's going into the producion version.


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_That's good!! Because that's what's going into the prodution version. 
	

	
	
		
		

		
		
	


	


_

 

Any estimation on when the SOHA II PCB's will be made available for the DIY community?


----------



## runeight

Eagle layouts are finished and ready to go. Waiting on Jeff R to come up for air. Then we go.

 In the meantime, I'm working on front and back panels along with pre-punched tops.


----------



## Jrossel

Yes, the air here in Silicon Valley is lovely today. Oh yes, I do need to go order some boards. Who would like to test the first batch of production boards? PM or Email please and I will give you the details. I am also putting together parts kits for stuffing the boards, if you are interested.

 JR

  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Eagle layouts are finished and ready to go. Waiting on Jeff R to come up for air. Then we go.

 In the meantime, I'm working on front and back panels along with pre-punched tops._


----------



## runeight

Jeff is being most gracious. To be fair, he only got the final production layouts from me about 24 hours ago and is ready with his usual speed.


----------



## runeight

Oh, if any of you decide to work with Jeff on the first production run, don't grab your BoM from the website yet. There are some changes due to the new HV multiplier.

 For those of you who already have a bag of parts, there are some new components and one or two changes to old components. But there is nothing major. I'll be putting up the new info very soon. It just takes time to build all of the diagrams and pages.


----------



## Arkku

Excellent news! I already have the case and transformer, but I've been waiting for the final list of parts before getting anything else. =)

 By the way, did any of the prototypers try both the zener and non-zener input stage? Which is now recommended?


----------



## dBel84

BEWARE of the zeners 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## runeight

Quote:


  Originally Posted by *Arkku* /img/forum/go_quote.gif 
_Excellent news! I already have the case and transformer, but I've been waiting for the final list of parts before getting anything else. =)

 By the way, did any of the prototypers try both the zener and non-zener input stage? Which is now recommended?_

 

Several of the prototypers tried the zeners. In every case they felt that there was increased noise. Enough increase for this to be not recommended. But, you can try it to see if you can get a different result. Nothing will be damaged.

 An alternative, less noisy alternative to the zener is the resistor with a 1u film cap in parallel with it.


----------



## runeight

Gents, all of the important information on the website had been updated. Be sure the read the comments on the first page of the SOHA II section.

 And pleeeaase let me know if you find mistakes.


----------



## runeight

Also, check out the new HV page in the design section. Thought some of you might like some explanation of the voltage multipler.


----------



## 04BluMach

Quote:


  Originally Posted by *Jrossel* /img/forum/go_quote.gif 
_Yes, the air here in Silicon Valley is lovely today. Oh yes, I do need to go order some boards. Who would like to test the first batch of production boards? PM or Email please and I will give you the details. I am also putting together parts kits for stuffing the boards, if you are interested.

 JR_

 

PM on the way! Great to hear into intial production!!!

 Me Want...
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *dBel84* /img/forum/go_quote.gif 
_BEWARE of the zeners 
	

	
	
		
		

		
		
	


	




 ..dB_

 

Will beware the nasty Zeners. Thanks for the tip.


----------



## JamesL

Yay. Free classes =] 
 Always appreciated - 
 whereas.. my school tuition goes towards watering the sidewalks and fixing elevators.


----------



## runeight

While Jeff is now preparing to order boards, would you guys kindly take some time to look at these front and back panels for the Hammond enclosures. Any and all thoughts are welcome and now is the time to make suggestions. We may not be able to include all of your ideas, but we can try.


----------



## Ferrari

Good to see that the _"SOHA II train"_ starts rolling.


----------



## Alcaudon

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Good to see that the "SOHA II train" starts rolling. 
	

	
	
		
		

		
		
	


	


_

 

Me too, today I've spent about 130€ in tubes


----------



## Ferrari

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Me too, today I've spent about *130€* in tubes 
	

	
	
		
		

		
		
	


	


_

 

Hee... for that amount (approximately) you can also get a standard SOHA II kit, accidentally.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, all of the important information on the website had been updated. Be sure the read the comments on the first page of the SOHA II section.

 And pleeeaase let me know if you find mistakes._

 

Regarding the C2E cap size, is the max size on the new boards 8mm? 

 UB


----------



## runeight

Correct. C2E has not changed.

 I created an alternative to C3E that is also 8mm. As per your request a while back.


----------



## runeight

Gents, none of you has made any comments on the proposed panels. I am going to assume for the moment that this means you are not too fond of them.

 If so, I won't mind hearing that. And you won't hurt my feelings.

 What I'd like to do is to get a design that most of you like so that the panels can be offered with the kits from Glass Jar. And so you don't have to drill everything out.


----------



## onform

sorry runeight,the panels look very good, but I for one am looking to make the amp look a little individual by using another case, some people will want the ease of the pre drilled panels. but there is definately a trend for people on here to personalise there builds to their liking.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Correct. C2E has not changed.

 I created an alternative to C3E that is also 8mm. As per your request a while back. 
	

	
	
		
		

		
		
	


	


_

 

Yes, it was me who requested that change. C2E is the non-polar cap position and local sources can't supply a part smaller than 10mm (unless we can get away with a 16vdc rated part?) I know where the confusion has crept in, I was also asking if both C2E and C3E could be made 10mm (post #222) so that the same part could be used in both positions. 

 I know your attention was (rightly) focused on much more fundamental improvements to the design and the board layout does seem a bit more complex to acommodate the new HV feature. 

 Regards the panels, I would definitely be interested in buying a set and I'd be quite happy with the design you've suggested. I take it that there would still be a need to drill holes in the top of the case to allow the tubes through?

 UB


----------



## runeight

I'm sorry UB, my mistake. There is not enough room for 10mm caps in both those positions. I just tried to make C3E 8mm too. I trust you'll be able to find caps somewhere. However, you CAN use 16V parts here since the rails are only 15V.

 If there is enough interest in pre-fab'd panels, I'm planning to make a drilled top panel too. The standard Hammond top panel, even when drilled for the tubes, will not provide enough ventilation. This amp gets pretty hot. So I'm working with Jeff on highy perforated top panel that are punched for the tubes and a small access hole so you can use a screwdrive to adjust the B+ without opening the top.

 onform, that is very alright with me. Whatever anyone wants to do to make their particular build in their style.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I'm sorry UB, my mistake. There is not enough room for 10mm caps in both those positions. I just tried to make C3E 8mm too. I trust you'll be able to find caps somewhere. However, you CAN use 16V parts here since the rails are only 15V.

 If there is enough interest in pre-fab'd panels, I'm planning to make a drilled top panel too. The standard Hammond top panel, even when drilled for the tubes, will not provide enough ventilation. This amp gets pretty hot. So I'm working with Jeff on highy perforated top panel that are punched for the tubes and a small access hole so you can use a screwdrive to adjust the B+ without opening the top.

 onform, that is very alright with me. Whatever anyone wants to do to make their particular build in their style. 
	

	
	
		
		

		
		
	


	


_

 

I'd be in for a top panel too. Personally, I find the drilling cutting & measuring the *least* pleasurable part of the whole thing.


----------



## onform

sounds to me like youve dotted all the i's and crossed all the t's lol

 looking forward to the official birth of your baby..


----------



## wiatrob

UB - there's also the option of bottom monting C3E - I have 10MM VitQ's stuffed under the board, no problem...


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_... However, you CAN use 16V parts here since the rails are only *15V*...._

 

The rail voltage for the Epsilon12 circuit is actually only 12V due to the 12V VR+E/VR-E (12V relay used in the circuit).

 BTW, if size is a problem, you (Uncle Bob) can use smaller value/size CE3, for example 47uF and change the value of RE5 to 1MΩ. Functionally, the circuit is unchanged! 
	

	
	
		
		

		
		
	


	




 However I am sure that it should not be too difficult to find 8mm caps elsewhere.


----------



## JamesL

I'm looking for a clear-anodized top(case T1601) for another project, so if anyone wants to trade for a black-anodized one, or wants to sell me one, shoot me a pm. =]


----------



## mwofsi

I'm not in the market but I think those panels are excellent. Very classy, cohesive (had to look that up in a thesaurus!) and professional.


----------



## Ferrari

Tinkerman was busy today... 
	

	
	
		
		

		
			









 SOHA II with a personal touch in the making






 Regulated 120V PS under test


----------



## holland

Ferrari, I thought you were going to top mount. Did you redo the board to bottom mount or is that a separate amp entirely?


----------



## Ferrari

There are 2 different amps, but this amp will also have the tubes on top, on a different way.
 The other one is (more or less) built as SOHA II prototype according to the specs, without modifications and running at lower B+ voltage (95V).


----------



## runeight

Ferrari, have you become the zen master of voltage multipliers now?


----------



## GeWa

OK, I'm back from my holiday so where are them boards? 
	

	
	
		
		

		
		
	


	




 Regards


----------



## runeight

Jeff and I finalized them last night. The PCB house reported back two small errors as a result of adding alternate caps to the original board. We fixed those. So, without speaking for Jeff, I think the final production order goes in today. Send him a PM.


----------



## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Ferrari, have you become the zen master of voltage multipliers now? 
	

	
	
		
		

		
		
	


	


_

 

Hehee… playing with Cockroft Walton voltage multiplier is fun, I can tell you.
 And if you have some appropriated parts in your parts bin to play with (accidentally) … more fun. 
	

	
	
		
		

		
		
	


	



 However in this case, the fun is limited by the TI regulator.


----------



## Uncle Bob

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The rail voltage for the Epsilon12 circuit is actually only 12V due to the 12V VR+E/VR-E (12V relay used in the circuit).

 BTW, if size is a problem, you (Uncle Bob) can use smaller value/size CE3, for example 47uF and change the value of RE5 to 1MΩ. Functionally, the circuit is unchanged! 
	

	
	
		
		

		
		
	


	




 However I am sure that it should not be too difficult to find 8mm caps elsewhere._

 

Thanks for that info, having had it confirmed by the gurus that using 16V parts isn't going to cause issues then getting 8mm caps is no longer a problem. 

 Whilst we're talking about the e12 circuit, am I right in thinking that any 12V dpdt or dpco relay with a coil rating of less than 150mW will be OK?

 UB


----------



## runeight

Correct on the relay. About 12mA coil current, give or take some.


----------



## GeWa

Am I correct that the main board is now so that the B+ multiplier is incorporated or will this be on a separate board?
 (sorry if this was already clarified but I'm still a bit in holiday mode)

 Regards


----------



## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_Am I correct that the main board is now so that the B+ multiplier is incorporated or will this be on a separate board?
 (sorry if this was already clarified but I'm still a bit in holiday mode)

 Regards_

 

Yes, the new regulated HV B+ ~(55V-100V) is incorporated on the main SOHA II board. (There is thus no child board).


----------



## GeWa

Thanks Ferrari.

 Would it be possible that the man in charge could put an updated image of the board on the website?

 Regards


----------



## Ferrari

Gewa, it's already there. The HV regulator (TO-220 device) is located at the lower left corner.


----------



## runeight

Gewa, the website has been updated for a few days now, including new images, new schematics, and new parts lists. Have you looked?

 Edit: I see that I posted on top of Ferrari's post.


----------



## GeWa

Quote:


 Gewa, it's already there. The HV regulator (TO-220 device) is located at the lower left corner. 
	

	
	
		
		

		
			




 

 Quote:


 Gewa, the website has been updated for a few days now, including new images, new schematics, and new parts lists. Have you looked? 
 

I did look but apparently not good enough, even updated my personal BOM according to the changes. I told you I was still in holiday mode [size=xx-small]([/size][size=xx-small]feel like an ass now
	

	
	
		
		

		
		
	


	




)

 [/size]Ah well, at least I'm a 100+ Head-Fi'er now 
	

	
	
		
		

		
		
	


	




 Regards


----------



## runeight

Gewa, I hope this hasn't changed your BoM too much. I know that you've already got the parts for the original.

 I think you should stay in holiday mode. As long as you can.


----------



## MrMajestic2

Man, I've been offline from this for a bit. Havent finished my prototype build yet 
	

	
	
		
		

		
		
	


	




 Got stuck on some voltage issue. Time to get back on the horse


----------



## kklee

Got my amp running with the new HV circuit via a DIY PCB. I removed all of the parts for the old HV circuit from the board.


----------



## holland

Nice, kklee. I'm doing mine on perfboard right now and it's going so slow (lack of motivation), and I removed all the old HV as well. I'm going to feed mine into D9P/D10P and use the old HV cap I have there. It seems you did something similar, but put a terminal block on the old cap position. Good idea as well.

 Nice PCB. I wish I did that now.


----------



## Ferrari

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_Got my amp running with the new HV circuit via a DIY PCB. I removed all of the parts for the old HV circuit from the board._

 

kklee, have you made your own PCB for the HV B+ PS?
 Well done!


----------



## kklee

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_kklee, have you made your own PCB for the HV B+ PS?
 Well done! 
	

	
	
		
		

		
		
	


	


_

 

Thanks!

 I can make one for anybody else from the prototyping team that wants one. The only issue you may have is whether there is enough space for it. The PCB isn't that small since it was the first time I ever made a PCB using toner transfer and wasn't sure how tight I could get the traces. I have a fair amount of space in my amp chassis so it worked out perfectly.


----------



## wiatrob

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_... The only issue you may have is whether there is enough space for it..._

 

It's about half the size of the one I perfboarded! 
	

	
	
		
		

		
		
	


	




 Have you had a chance to do any A/B testing yet? I currently only have one amp - plan is to build up the other after I return from vacation next week...


----------



## kklee

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_It's about half the size of the one I perfboarded! 
	

	
	
		
		

		
		
	


	




 Have you had a chance to do any A/B testing yet? I currently only have one amp - plan is to build up the other after I return from vacation next week..._

 

The A/B testing will have to wait until next week when I go back to work (the other amp's at the office). It's sounding pretty good so far at 90V.


----------



## holland

My perfboard, or PC board rather, looks to be about the same size as kklee's. There's some space that can be compacted further. I'm using the smallest Ratshack PC board, about 1.85x2.85.

 I made a small mistake and put a diode in the wrong direction. I've never seen a lytic blow up before, but it was interesting. Kind of like a geyser, quite impressive.

 I think my diving under the table was probably more interesting. It blew up right under my nose, as I was probing around....I think I'll start wearing eye protection.


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_... It blew up right under my nose, as I was probing around....I think I'll start wearing eye protection._

 


 Being a bit of a noob - I've been putting on the safety glasses when working with my perfboarded HV supplies - Facial scars build character - but I could do without the glass eye!

 Given the amount of transistors I've blown up on this project (4 MPS42s - glad we took the first cap multiplier out of the circuit!) it's awonder nothing else has gone poof!


----------



## runeight

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I think my diving under the table was probably more interesting. It blew up right under my nose, as I was probing around....I think I'll start wearing eye protection._

 


 Good idea. CW voltage multipliers are one of the ways we physicists get zillions of volts for our crazy experiments. I am always wary around them because I've been around ones that generated 60KV (low current, but still dangerous). I've been hammered hand to hand by 1KV. I do not know why I am still alive, but I haven't forgotten the feel of that.

 We are at the low end of the voltage scale where the voltages begin to get dangerous. I guess I'd like to remind all of the new builders that 100V is nothing to trifle with. But, build the amp right and the multiplier should be tucked safely away inside the box. And you'll be running the tubes closer to where they want to be.


----------



## runeight

Here are some photos of the prototype panels. I messed up the mounting holes in the corners and I had to countersink them with a drill bit. They are a bit ugly but won't be on a production panel. I've fixed the hole size and the countersink on the FPE drawings.

 Knob needs to be natural aluminum, but I had this black lying around. Parts on the back panel are from the prototype BoM except for the jacks which I stole from a preamp that has been out of service forever.

 Everything fits. Furthermore, the amp is dead quiet when fully cased and grounded. Now I need to make the top. And this prototype is one for the books.


----------



## dBel84

That turned out really well. Is that a white inlay or aluminium ..dB


----------



## runeight

It's natural Al.


----------



## Ferrari

Lots of precision work, but it slowly takes the shape of how it finally should look like...


----------



## m0b1liz3

Ferrari, what case is that?

 And a general question to all. Any idea on the range of time it should take someone to complete this once it is an official kit? Any ETA on when the full kits will be available?


----------



## runeight

I started at about 7pm one evening and worked until 9pm. Then I started the next morning at 9am and finished at noon. So about 5 hours for me.

 I brought the amp in stages as outlined on the website. Everything came up perfectly and within 1/2 hour I was listening and rolling tubes.

 If I had had a pre-fab'd case with front, rear, and top panels, I'd have been finished a half hour after that. YMWV on your casing.


----------



## holland

Mine was a bit longer as I'm not using the spec'd volume, and jack, and am using a wallwart, so I had a bit more wiring to deal with and a few extra terminal blocks. My first transformer was bad after building the wallwart and wiring, and switched the setup to a toroidal, had the regs in the wrong spots, and I was still able to get it up with sunlight to spare.

 The only advice I would give is to write down what you want to do, as far as tweaks, and whether or not you need sockets for some items. Some things I forgot, as the process was a bit more drawn out than a normal build and I wasn't expecting nor planning to build it the day I started building it (if that makes sense). Some time opened up and I went for it, as I had parts on hand already.

 I would say this build is easily doable by a post CMoy beginner, if you follow the basics, use the spec'd cases and the panels runeight is working on. 

 If you're going custom casing, double or triple the amount of time for case prep and planning.


----------



## m0b1liz3

runeight, what are the the dimensions of the case that will be available? and about how much will it cost with pre-drilled holes?


----------



## Ferrari

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_Ferrari, what case is that?_

 

It's a ATI-738U. ATI is unfortunately out of business.


----------



## runeight

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_runeight, what are the the dimensions of the case that will be available? and about how much will it cost with pre-drilled holes?_

 

m0b1liz3, the board is designed to fit into the Hammond 1455T2202. It will also fit into the 1455T1602 if you want to put the transformer into another box.

 The board is 160mm x 115mm. 

 I don't recall what the Hammond case costs. $20-$30???

 I am trying to also provide pre-drilled front, back, and top panels. I don't know the cost of these yet. There are two dimension diagrams on the website. I will put the additional ones for the front and back. So you can drill your own.

 Does this help??


----------



## m0b1liz3

Just trying to figure out if I want to get into building one of these yet. Casing an amp seems to take a long time so having pre-drilled plates would be good. I have a chip amp kit that I thought I could put into a matching case. Can't build it until the kits are available anyways!


----------



## adamus

something that speeded up my case work 10X is basic drawing software (with rulers, i actually use MS Visio, it lets you feed the measurements in very quickly and set the origiin of each shape), a set of digital calipers ($10) and a cheap stepped drill bit. Its now a pleasure to do casework.


----------



## Ferrari

While many of you are waiting for boards to arrive, I was manage to finish the case work of my proto-amp this evening. 
 It was a pleasure to do the prototyping for this amp as it turns out as I thought how it should be.
 A couple of details: the tubes used are 6N1P's, 120V B+ with Audyn MKP output filter capacitor, all small signal BJTs are matched within 2%, output devices are Toshiba 2SC3422.

 It sounds excellent. 
	

	
	
		
		

		
		
	


	




 Here are some (tease) pics...





 B+ voltage rock solid @120V 
	

	
	
		
		

		
		
	


	








 ... DIY regulated power supply for the B+ section 





 ... and a night shot


----------



## dBel84

magnificant as always. 
 It really is a great amp and I have no problems recommending it to anyone at all..dB


----------



## pabbi1

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_A couple of details: the tubes used are 6N1P's, 120V B+ with Audyn MKP output filter capacitor, all small signal BJTs are matched within 2%, output devices are Toshiba 2SC3422.
_

 

I have read through the web site, and cannot for the life of me find where the 'tweak' is for running a 15-0-15 at 300ma for the heaters, as I would like to use 6n1p as well (consistent with the Bijou). I have an Avel Lindberg y236163 laying around - will this be enough? Also, did you air wire the tubes?

 Alex: What is the part # for the IEC (and fuse drawer) you used on the panels? VERY nice on the panels. Got any extras?


----------



## runeight

pabbi1, tweak for 300mA heaters running in parallel (600mA) total is:

SOHA II Tube Rolling

 I can't find your transformer number on the Avel website. Do you have the right number?

 IEC is:

IEC from Mouser

 No extras on the panels, but Jeff and I are getting them ready for production along with the kits. Assuming that there is enough interest.


----------



## pabbi1

Oops - y236103... boy, my reading comprehansion skills are really lacking today, re: tube tweak, but my transformer is only 1.0, so the 6n1p won't go.


----------



## runeight

Y236103 is the standard 1.0A toroid for the SOHA II. To get the higher heater current you'll need the Y236203.


----------



## Ferrari

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_... Also, did you air wire the tubes?_

 

Yes, I air wired the tubes sockets.







 (I see that runeight has answered your questions regarding heaters voltage and transformer).


----------



## pabbi1

Does anyone know Mouser part numbers for the header/jumpers?


----------



## dBel84

we thought a switch would be better ..dB


----------



## mwofsi

Can I ask a couple of power supply design questions (this isn't about the SOHA II, it's more to improve my comprehension) ?

 What roll does the size of caps in the voltage doubler play? Presumably too small and they'd be fully charged before each phase change? Can they be too large? Do they also play a role in smoothing and ripple removal?

 Also what are the advantages of using capacitance multipliers?


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Here are some photos of the prototype panels. I messed up the mounting holes in the corners and I had to countersink them with a drill bit. They are a bit ugly but won't be on a production panel. I've fixed the hole size and the countersink on the FPE drawings._

 

Can I get the FPE files, on the proviso that it is a truly one off? I am making but one of these, but since it is for my brother, I want it done as well as possible.


----------



## runeight

Quote:


  Originally Posted by *mwofsi* /img/forum/go_quote.gif 
_Can I ask a couple of power supply design questions (this isn't about the SOHA II, it's more to improve my comprehension) ?

 What roll does the size of caps in the voltage doubler play? Presumably too small and they'd be fully charged before each phase change? Can they be too large? Do they also play a role in smoothing and ripple removal?

 Also what are the advantages of using capacitance multipliers?_

 

mwofsi, there is some new information on the Cavalli Audio website about voltage multipliers under the SOHA II design section.

 The capacitors in the multiplier pass large current pulses as they charge and discharge. The larger the capacitor the less "resistance" it offers to these pulses. At some point the capacitor is "big enough" and further increases in size generate only small returns. The values in the SOHA II PS are chosen to balance capacitance value (bigger is better) vs. physical size (smaller is better).

 In a full Cockroft Walton multiplier some of the capactors can play the role of reducing ripple, but this depends on how you set it up.

 In the SOHA II multiplier only the last capacitor acts as a filter capacitor as well as a multiplier cap.

 The advantage of a voltage multiplier is that you can get high voltages from a low voltage transformer. In the SOHA II we get 105V from the same transformer that generates the split 15V supply. This is pretty good work and permits us to stick to the SOHA design philosophy of using only one transfomer to power the hole amp.


----------



## mwofsi

Thankyou for explaining that.

 Capacitance multipliers? Q1/Q2P, are they just about size constraints or do they improve the capacitors performance as well?


----------



## runeight

In this case they are the same result. A cap multiplier allows you to use a small capacitor that acts and performs like a much bigger capacitor. The capacitance value of the cap multiplier is approximately the value of the real capacitor multiplied by the hfe of the transistor.

 There is a nice article at Wikipedia here:

Cap Multiplier


----------



## holland

I cased up my build this weekend. HV on a PC board, running @ 95V. It's feeding into the prior D9P and D10P using a 2 pin Molex connector.

 I need a new knob, it's not big enough to cover the keyhole.


----------



## holland

Quote:


  Originally Posted by *uhcmos* /img/forum/go_quote.gif 
_SOHA II - Super SE Hybrid_

 

err...yep, that's the name of the thread alright.


----------



## dBel84

been meaning to say I like this case - a very good hammond alternative. 

 What is the power switch you have used? I thought it was the momentary switxh for the e22, but it must be a regular type as I don't see anything else in there? ..dB


----------



## holland

Thanks dB. It's a Hammond 1402FV. The board fits in the side rails as well, but I wanted full internal mounting. It's more pricey than the typical aluminum and a bit bigger, and heavier since the top and bottom is pretty thick steel with nice front and back plates.

 I was seriously going to go for the top mounting, but just couldn't make myself do it. The shades of yellow theme would play better in gradations of yellow/amber. I'm still keeping an eye out for a nice gold/amber 1/4" jack.

 The power switch I got off e-bay from PartsPipe. It's a Bulgin imitation or copy, but it is the latching variety so the button depresses in and sticks. I have to hit it with my pinky, fat fingers apparently. I am using a wallwart and am using the DPDT switch to pull the 2 15V AC rails. There's no room in the case for a toroidal, after the PC board. It's illuminated as well, and takes a 12V input for the internal LED. I'm not sure if there's a current limiting resistor in it, there's no docs on this switch, but I had to use a 120 ohm resistor to get something that's at least visible in daylight so I presume there is. I didn't want to try a link, but I have a feeling it would work.


----------



## dBel84

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_It's a Hammond 1402FV. ...._

 

aaah , does it show that I have never explored hammond or most other commercial offerings.

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_The power switch I got off e-bay from PartsPipe. It's a Bulgin imitation or copy, but it is the latching variety so the button depresses in and sticks_

 

 Oh thats great, thanks. He is the guy that does the heavy aluminium knobs..dB


----------



## pabbi1

Follow up, since you never explicitly said no...

 Can I get the FPE files, on the proviso that it is a truly one off? I am making but one of these, but since it is for my brother, I want it done as well as possible.

 Pretty please?


----------



## pabbi1

Well, all my parts arrived today for the SOHAII build (I am shocked - really)... and, though production boards are due this week, are there any spare pre-pro boards out there, that, maybe, someone didn't get around to building? If so, ping me...

 Oh, and what fuses are you guys using? I have 1a and 3a slo-blo on hand.


----------



## runeight

pabbi1, I trust that you ordered from the latest parts lists on the website? With the newer HV supply and regulator?

 If so, the original proto boards will not be suitable for your parts set since the HV supply was changed during the prototype effort.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_pabbi1, I trust that you ordered from the latest parts lists on the website? With the newer HV supply and regulator?

 If so, the original proto boards will not be suitable for your parts set since the HV supply was changed during the prototype effort._

 

oops - yes, as of Saturday pm... so, that answers that.


----------



## holland

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, and what fuses are you guys using? I have 1a and 3a slo-blo on hand._

 

It depends what you are fusing and where. 1A sloblo total would be fine for the stock build, if it's at the IEC inlet, before the transformer. I do recall that you were considering doing the higher heater current build. You will need 1.5A for that.

 I have 2 500mA sloblo in my build, post transformer.


----------



## kklee

I'm running with 1A SloBlo in the IEC.

 As a side note, I think the new HV circuit running at 90V sounds better than the original design. I've now upgraded both amps to the new HV circuit.

 I also added heater switches to both amps, they definitely make tube rolling much easier. The thing to bear in mind if you go with a switch is that the switch position may be opposite to what is marked on the PCB for heater voltage (especially for toggle switches).


----------



## Ferrari

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_As a side note, I think the new HV circuit running at 90V sounds better than the original design. I've now upgraded both amps to the new HV circuit._

 

Same impressios here with regulated HV PS circuit.


----------



## dBel84

ok ok ok , I am going to have to pull mine apart again . Now stop with these "upgrades" ..... please 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## holland

Quote:


  Originally Posted by *kklee* /img/forum/go_quote.gif 
_As a side note, I think the new HV circuit running at 90V sounds better than the original design._

 

 Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Same impressios here with regulated HV PS circuit. 
	

	
	
		
		

		
		
	


	


_

 

x3 for me as well.


----------



## wiatrob

I'd recommend trying the HV dB...

 A pair of Senn 650's seem to have showed up whilst I was on vacation - the amp is fitted with the HV running a hair above 90v, NOS 12AT7s.

 I've just had a session with Gould's 'Goldberg Variations' and the Beastie's 'Paul's Boutique' - this amp seems to be a great combination with the 650's.


----------



## FallenAngel

Ok, I gotta find the schematic for this HV supply, I must be blind, but I can't see it.


----------



## holland

wiatrob, I agree. I am using my HD650s more and more with the SOHA 2. It's quite lovely. I am, however, finding the EH 12AU7 very good from a general purpose view. Some things are a bit thick with the 12AT7. The 5963 is also very nice.


----------



## runeight

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Ok, I gotta find the schematic for this HV supply, I must be blind, but I can't see it. 
	

	
	
		
		

		
		
	


	


_

 

Try the Cavalli Audio website.


----------



## dBel84

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I'd recommend trying the HV dB..._

 

Oh I believe y'all. I had the original proto running at 170V on the plates 
	

	
	
		
		

		
		
	


	




 . I remember the effect it had when it bumped up. There is less change from 100 to 170V but that initial jump is very effective. I have just been a lazy .... as I didn't want to pull the amp apart again.

 ..dB


----------



## holland

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Ok, I gotta find the schematic for this HV supply, I must be blind, but I can't see it. 
	

	
	
		
		

		
		
	


	


_

 

Upper Right. Perfboard or PC Board everything from the AC lines up to and including the TL783 portion (looking from the right, up to the 100n cap after the TL783). J3 has moved, so ignore it from the prototype PCB you have.

 A cap multiplier was removed in the final rev, but with the external HV, I believe most of us have utilized it.


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I am, however, finding the EH 12AU7 very good from a general purpose view. Some things are a bit thick with the 12AT7. The 5963 is also very nice._

 

I'll give them a try, thanks for the recommendation!


----------



## runeight

This is a good time for me to thank the prototype team again. Ferrari, Kklee, holland, dbel84, wiatrob, and fallenangel were all part of the team and because they were willing to take time to prototype and test the amp, we were able to come up with a change (to fix an unanticipated problem) that made it a better amp.


----------



## holland

You're very welcome, runeight. It was interesting and a pleasure.


----------



## dBel84

You mean there will be no more changes 
	

	
	
		
		

		
			





 always a pleasure 
	

	
	
		
		

		
		
	


	




 ..dB


----------



## kostalex

When the kits will be available?


----------



## FallenAngel

So do I take out Q1P or leave it in?


----------



## holland

I left it.


----------



## wiatrob

Runeight - you are entirely welcome, it has been quite an edifying experience. 

 Many thanks to you for your contributions to the hobby...


----------



## onform

Can we play now???


----------



## wiatrob

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_So do I take out Q1P or leave it in?_

 

Just to confuse matters - I took it out, I blew up about four during HV PS tweaks and the pads were in pretty bad shape. I think you are OK either way...


----------



## runeight

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_So do I take out Q1P or leave it in?_

 

My amp is back to its original PS section, but when I tested the new HV supply I took out the Q1 section, including the cap and resistor. Just like in the schematic.

 Q1 doesn't really add anything to the PS when the regulator is in use and actually may be somewhat detrimental to the PS behavior. Hence its removal in the final design.


----------



## holland

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_actually may be somewhat detrimental to the PS behavior. Hence its removal in the final design._

 

I think I missed that. Can you expound on it? Thanks.


----------



## runeight

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_I think I missed that. Can you expound on it? Thanks._

 

It's not a big deal, but just a matter of tuning everything as best we can.

 The ripple reduction from the regulator and the two final cap mulitpliers is enough for the B+ supply. However, each BJT that is added contributes some amount of noise to the B+. Q1 contributes some noise and so it's better to leave it out.


----------



## holland

Ah. That's understood. I thought you were going to say something about the cap multiplier interacting with the reg in a negative manner. 

 At least now I don't have to open up and fix that.


----------



## pabbi1

Anyone try any different opamps, or is it just not worth bothering? And, I haven't seen any discussion about solder vs socket on the opamps - any recommendations on the _correct_ Dip8 sockets?

 I'm also reading a lot here about heat - will substantial bottom and top plate holes be sufficient for the Hammond 1455T2202? Standard config, 6.3v heaters, 5963 tubes mounted on the board.


----------



## holland

Not worth it. It's a servo.

 Sure. I'm not exactly sure what you mean by substantial, but if you look at my case, I think it's fine with the amount of venting. I'm running 12.6v.


----------



## runeight

as holland says, opamps are just a servo. however, you can sub any high beta jfet input opamp with the same pinouts. if you happen to have some lying around. if you don't, however, just use the opa134s.

 i recommend sockets though, just in case you have a problem and you accidentally destroy one of the opamps. this is unlikely in this amp, but it can happen with the right kind of short. almost any good quality 8 pin dip socket will work.

 i think that 5963s are the best sound in my amp. they are 12.6V tubes, so the jumpers should be set to 12.6V. the tubes will run with heaters in parallel. if you use 6922s and similar, you'll set the jumpers to 6.3V so the tubes can run in series.


----------



## GeWa

Maybe a silly question but are C8P, C9P, C10P and C11P in the new PS design not a little on the narrow margin at 100V?

 Regards


----------



## runeight

Actually, it's a really good question. The proto team had some amount of conversation about it.

 These caps run at about 85VDC on them. (Edit: Only C10 and C11 see 85V). The operating voltage, of course, affects the life of electrolytics. But, the real enemy of electrolytics is temperature. This affects the life much more than the voltage as it causes the fluids in the electrolyte to evaporate out of the can.

 I actually went back and reminded myself of various electrolytic life calculations vs voltage and temperature. And while this voltage is high, it is still 15V below the maximum. Unless that caps are defective, they won't be damaged by this and they should last a very long time.


----------



## luvdunhill

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_Not worth it. It's a servo.

 Sure. I'm not exactly sure what you mean by substantial, but if you look at my case, I think it's fine with the amount of venting. I'm running 12.6v._

 

OPA134PA is a good choice for a servo, as there are definitely worse choices out there. There is some good discussion on the Dynahi threads at headwize (if my memory doesn't fail me) why this makes a good choice.


----------



## Pars

As for sockets, I would recommend either the Aries (535-08-3518-10) or the Mill Max (575-199308). You're search criteria were too restrictive (Dip8)... take a look at this one.


----------



## holland

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_OPA134PA is a good choice for a servo, as there are definitely worse choices out there. There is some good discussion on the Dynahi threads at headwize (if my memory doesn't fail me) why this makes a good choice._

 

Yeah, I use OPA132 or OPA134 almost exclusively. The spec'd part is OPA134.


----------



## holland

It might be a good idea to drop the latest BOM out on the forums. What do you think, wiatrob (great keeper of the BOM)?


----------



## runeight

Good idea. I've mostly been waiting to ensure the Jeff R can source all of the parts. Although that really doesn't make any difference now that I think about it.

 It think I'll put it on the website.


----------



## wiatrob

Agreed. here are the credits and disclaimers:

 The Mouser section is complete and should be accurate, I've ordered parts for two amps and the changes for the HV power supply from it.

 KKlee did the Digi-key section, it has not been updated for the HV PS.

 Uncle Bob provided a pre-HV PS Farnell BoM, but I have not included it at this time.

 It's in Excel format, I exported a version in Open Doc format but can't test it...


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_I'm also reading a lot here about heat - will substantial bottom and top plate holes be sufficient for the Hammond 1455T2202? Standard config, 6.3v heaters, 5963 tubes mounted on the board._

 

 I drilled sets of holes under the heat sinks and tubes (See the build pics posted earlier...)

 I've attached my template, I think I might have needed to size tweak but got them pretty close.


----------



## pabbi1

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_I drilled sets of holes under the heat sinks and tubes (See the build pics posted earlier...)

 I've attached my template, I think I might have needed to size tweak but got them pretty close._

 


 Thank you, that is very timely, as I finished the rest of my casework today, and that strategic ventilation makes me feel a bit better.


----------



## Uncle Bob

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Agreed. here are the credits and disclaimers:

 The Mouser section is complete and should be accurate, I've ordered parts for two amps and the changes for the HV power supply from it.

 KKlee did the Digi-key section, it has not been updated for the HV PS.

 Uncle Bob provided a pre-HV PS Farnell BoM, but I have not included it at this time.

 It's in Excel format, I exported a version in Open Doc format but can't test it..._

 

I'll update the UK BOM to incorporate the latest changes


----------



## kklee

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I'll update the UK BOM to incorporate the latest changes_

 

I'll do the same for the Digikey P/N's.


----------



## onform

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_I'll update the UK BOM to incorporate the latest changes_

 

Have you built yours already??


----------



## Uncle Bob

not yet.. I've asked to be included in the 1st roll out of production boards so hopefully it won't be too long


----------



## Ferrari

So you are probably the second Europeans SOHA II builder?


----------



## pabbi1

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_not yet.. I've asked to be included in the 1st roll out of production boards so hopefully it won't be too long 
	

	
	
		
		

		
			



_

 

Jeff sent me an email Saturday indicating that boards were not in yet - maybe today?


----------



## GeWa

Quote:


 So you are probably the second Europeans SOHA II builder? 
	

	
	
		
		

		
		
	


	



 

That is not funny Ferrari!

 Regards


----------



## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_That is not funny Ferrari!

 Regards_

 

Oh... of course GeWa, you are _the_ second Europeans SOHA II builder. I was totally forgot that.


----------



## GeWa

You're really enjoying this aren't you.

 Regards


----------



## Uncle Bob

After your good self 
	

	
	
		
		

		
		
	


	




, just waiting for that email from Jeff


----------



## Uncle Bob

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_You're really enjoying this aren't you.

 Regards_

 

we could have a race


----------



## Ferrari

Quote:


  Originally Posted by *GeWa* /img/forum/go_quote.gif 
_You're really enjoying this aren't you.

 Regards_

 












 The 3rd Europeans SOHA II builder is also a possibility.


----------



## runeight

Gents, I don't think I can help this competition, but I can provide a more updated BoM. 
	

	
	
		
		

		
		
	


	




 Wiatrob created all of the BoMs during the proto process and I have just tweaked his latest version to conform to the final production board, which is designated 7007b.

 The BoM is on the website under Parts (in the menu). I'm enclosing it here also.

 If you guys would be kind enough to make additions to this BoM for digikey and UK suppliers that would be helpful. Wiatrob is out of town for a few days so I'm going to try to offload this from him while he is away.

 See attachment.

 Edit: The BoM also contains a second sheet that has just two columns for cutting and pasting into Mouser's spreadsheet BoM tool. I've used this tool and it works great for those of you who can order from Mouser.


----------



## keyid

my how the parts list grown from the orginal Soha, Jeff waiting for your email too!
 Rune thanks for quick order tab may future BOMS come with such user friendly editions, is there a way to add our own part names with mouser BOM import? Its very convenient having this when ordering one by one as its on the sticker on each bag.


----------



## wiatrob

Quote:


  Originally Posted by *keyid* /img/forum/go_quote.gif 
_my how the parts list grown from the orginal Soha, Jeff waiting for your email too!
 Rune thanks for quick order tab may future BOMS come with such user friendly editions, is there a way to add our own part names with mouser BOM import? Its very convenient having this when ordering one by one as its on the sticker on each bag._

 

This amp is a bit different beast than the original!

 I may have some free time while traveling later this week. If there's no answer to the part name question by then. The new BoM format is very clean - let's try to preserve this format (or keep to the spirit of it) as we expand it...


----------



## wiatrob

At last! I have as close to a production SOHA as possible. 

 Thanks Kklee for the HV PS board, I've got one up and running, and my original proto reassembled to travel with me this week.

 Still sounds great running at 90V... Hope everyone can get some boards soon so we can move this out to the masses...


----------



## GeWa

Just received a very positive email from Jeff Rossel 
	

	
	
		
		

		
		
	


	




 Regards


----------



## Alcaudon

Any info on when Jeff is going to start selling boards???

 Is going to be a group buy or directly from glass jar???

 Thanks!


----------



## runeight

So far as I know, there wil be a group buy. The first produciton run is deliberately small to ensure that the changes from the proto team have been correctly made to the board. Once the early production buyers verify the build, we'll start the large group buys.

 We should check with Jeff on this, but this is how I expect things to go. 

 There are still some early production boards/kits available if you don't want to wait. Contact Jeff R at Glass Jar to get one.


----------



## Alcaudon

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So far as I know, there wil be a group buy. The first produciton run is deliberately small to ensure that the changes from the proto team have been correctly made to the board. Once the early production buyers verify the build, we'll start the large group buys.

 We should check with Jeff on this, but this is how I expect things to go. _

 

Great!!!!! 
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_There are still some early production boards/kits available if you don't want to wait. Contact Jeff R at Glass Jar to get one._

 

Thanks for the offering runeight, but starting this project right now it's the last thing I need. I'm just trying to finish my Thesis, and having a board laying around would do nothing but distract me 
	

	
	
		
		

		
		
	


	




. 
 Houpfully I'll be finished when the goup buy starts....... hopefully.

 I must be strong, I must be strong, I must be strong.....................


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_So far as I know, there wil be a group buy. The first produciton run is deliberately small to ensure that the changes from the proto team have been correctly made to the board. Once the early production buyers verify the build, we'll start the large group buys._

 

How large was this run? I am getting a queasy feeling, having all the parts secured, and the spector of waiting for the larger group buy...


----------



## runeight

I believe the run was 20 boards. Last time I talked with Jeff they were not all taken since we are not pushing the amp just yet. If you want one, you should write to him soon.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I believe the run was 20 boards. Last time I talked with Jeff they were not all taken since we are not pushing the amp just yet. If you want one, you should write to him soon. 
	

	
	
		
		

		
		
	


	


_

 

Si - multiple times... Tuesday, Saturday and twice today... 
	

	
	
		
		

		
		
	


	




 Just being impetuous.


----------



## runeight

OH. Well then, I'll ping him too to see what's what.


----------



## pabbi1

Gracias...

 One other thing for the builders to comment on are all these fancy caps - who is hearing what based on what has been used? I have seen C1, C5, and C6 get some fancy treatments - just wondering what some recommendations are?


----------



## wiatrob

As I've said here and elsewhere - I don't have Golden Ears -but this amp sounds great with 'stock' Wima Film caps for C1. I have some Vitamin Qs in now, but will have to await amp build #2 to A/B them. I have all Xicons (Original PS) /cheap nichicons (HV PS). I know Ferrarri used some teflons/micas for C1, and dB Daytons...comments gentleman?

 It would be interesting to A/B with a more Boutique build (say Ferrari's)... 

 I think one of the appealing qualities of this amp is that it sounds great with affordable components. I have an L2 SOHA I kit from Jeff with Auricaps, and the II sounds better overall with Xicons.

 I'm sure it won't be long 'til we see a build with all Black Gates/ Muses/Teflons! I do have some Toshibas for the buffers of my next build!


----------



## pabbi1

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_As I've said here and elsewhere - I don't have Golden Ears -but this amp sounds great with 'stock' Wima Film caps for C1. I have some Vitamin Qs in now, but will have to await amp build #2 to A/B them. I have all Xicons (Original PS) /cheap nichicons (HV PS). I know Ferrarri used some teflons/micas for C1, and dB Daytons...comments gentleman?

 It would be interesting to A/B with a more Boutique build (say Ferrari's)... 

 I think one of the appealing qualities of this amp is that it sounds great with affordable components. I have an L2 SOHA I kit from Jeff with Auricaps, and the II sounds better overall with Xicons.

 I'm sure it won't be long 'til we see a build with all Black Gates/ Muses/Teflons! I do have some Toshibas for the buffers of my next build! 
	

	
	
		
		

		
		
	


	


_

 

Mine is coming in with a combo of Muses / Rubycon / Auricaps, so I was hoping there were some comments regarding that - I saw Dbel with Auricap, I think... and one or two others.


----------



## Jrossel

Quote:


  Originally Posted by *Alcaudon* /img/forum/go_quote.gif 
_Any info on when Jeff is going to start selling boards???

 Is going to be a group buy or directly from glass jar???

 Thanks!_

 

I have a limited stock at this moment. They are in. I will contact the people who expressed interest with payment requests. If there are extra from this first lot I will put them up at the web site.

 Jeff


----------



## kklee

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Mine is coming in with a combo of Muses / Rubycon / Auricaps, so I was hoping there were some comments regarding that - I saw Dbel with Auricap, I think... and one or two others._

 

I've built one with Vitamin Q's and the other with Auricaps. Both sound very nice. The main thing to what out for is size. There's isn't much room on the top of the PCB, so you have to bottom mount them. Depending on which case you use and how the PCB is mounted, you may have limited space underneath the PCB.

 I had bought some Solens for this project, but they're big enough that I can't mount them anywhere without having to resort to mounting them offboard, which I'm not willing to do.

 Here's the Digikey BoM. There are a few P/N's missing because I already had some parts on hand (besides, I've got to leave some work for you other builders to do
	

	
	
		
		

		
		
	


	




).


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Mine is coming in with a combo of Muses / Rubycon / Auricaps, so I was hoping there were some comments regarding that - I saw Dbel with Auricap, I think... and one or two others._

 

Pabbi1, pardon me for asking, but have you checked the fit for all of these components on the board? As kklee notes, the board is very tight and if it is placed in the Hammond box, there is not much room for larger caps anywhere. Sorry to say, but I had to pack a whole lot of components into a small space. Just checking to be sure that you're going to have a happy build experience.


----------



## runeight

kklee, thanks for the BoM update. I'll put this on the website later.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Pabbi1, pardon me for asking, but have you checked the fit for all of these components on the board? As kklee notes, the board is very tight and if it is placed in the Hammond box, there is not much room for larger caps anywhere. Sorry to say, but I had to pack a whole lot of components into a small space. Just checking to be sure that you're going to have a happy build experience. 
	

	
	
		
		

		
		
	


	


_

 

Well, I have both spec'd specimens AND some trials... so, it will work out one way or another. The C1 / C6 for sure are ok, as I have seen those used in other builds (and checked the size), but some others may not make it, or I can always do a different case. Since this is an amp for my brother, he probably won't notice the difference - depending on how much mortar activity they have... but, I do want this as nice as possible for thr Houston meet - which, btw, you should try to make (Oct 25). 

 Several of your builds will be there (Ron?  ), as well as other electrostatic builders - it would be an honor, especially since the Austin guys flaked out.

 Edit: After determining that the Auricaps will fit (easily) on C1, and on C6 (easy one side, a challenge on the other), what is the orientation, or will it matter?


----------



## Uncle Bob

Ordered my board yesterday..

 Still working on updating the BOM


----------



## Uncle Bob

For anyone interested, here's the BOM updated with part numbers for Farnell and Rapid


----------



## runeight

Thanks UB. When does your board arrive?? 
	

	
	
		
		

		
		
	


	




 Also, we only ran 20 production boards in Rev b. I see that there was one electrolytic that you couldn't source. I can add some additional pin spacings to help with this in what will be Rev c board.

 I am waiting for more folks to have a crack at this amp to see how the builds go and how you like it.


----------



## pabbi1

Well, I would be hitting the setup right about now, having received the board in today's mail... but, I ordered 60 series VD instead of 55, so, of course, they won't fit. Mouser will have me all the correct parts on Tuesday.


----------



## Uncle Bob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Thanks UB. When does your board arrive?? 
	

	
	
		
		

		
			





 Also, we only ran 20 production boards in Rev b. I see that there was one electrolytic that you couldn't source. I can add some additional pin spacings to help with this in what will be Rev c board.

 I am waiting for more folks to have a crack at this amp to see how the builds go and how you like it. 
	

	
	
		
		

		
		
	


	


_

 

I'm hoping it arrives early next week, (and I've told JR that GeWa's not ready for his board yet 
	

	
	
		
		

		
		
	


	




) but I've just asked Jeff if he can supply an TL783 voltage regulator along with the board so that might delay things a little.


----------



## GeWa

Quote:


 (and I've told JR that GeWa's not ready for his board yet 
	

	
	
		
		

		
		
	


	




)


----------



## pabbi1

A few construction questions - are the 4004 except d5 & d6 tombstoned? the banded side to the large hole on the silkscreen?

 I have some 'generic' led from Frys (the green 5mm) - any clues about what default type rled will work?


----------



## holland

The SOHA II Headphone Amplifier

  Quote:


 Mount vertical diodes with cathodes up and anodes down 
 

LED is probably not ultrabright. Try to hit 10mA first. The SOHA II board feeds 12.6V into the LED circuit. Try using a 9V battery and various resistors to find the intensity you want and recalculate/scale for 12.6V.

 Edit: Green LEDs should have a forward voltage of ~1.9V-2.1V. If you go for 10mA with a 9V battery, that should be ~700ohm. For 12.6V, that's around 1.2K-1.3K. V=IR where V is Source Voltage - Forward Voltage. In the 9V battery case, that's ~7V or ~10.6V for the SOHA II.


----------



## pabbi1

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_The SOHA II Headphone Amplifier_

 






 Not even the most embarrassing thing for today, I'm afraid.


----------



## Ferrari

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_... and I've told JR that GeWa's not ready for his board yet 
	

	
	
		
		

		
		
	


	


_

 

Well done !


----------



## pabbi1

Runeight, can you post a pic of your IEC / switch / toroid wiring? I'm over being embarrassed.

 And, which slot does your FPE file assume, just for future reference?


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Runeight, can you post a pic of your IEC / switch / toroid wiring? I'm over being embarrassed.

 And, which slot does your FPE file assume, just for future reference?_

 

Yes, I need to add this page to the website. I'll try to get to that tonight.

 I see that you found the tombstoned diode orientation. 
	

	
	
		
		

		
		
	


	




 I'm happy about this fight over there in the EU. This keeps you guys from realizing that we have just destroyed your economies.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I'm happy about this fight over there in the EU. This keeps you guys from realizing that we have just destroyed your economies. 
	

	
	
		
		

		
		
	


	


_

 

Judging from the enthusiastic crowds at the Rocky Mountain Audio Fest, both sides of the pond will continue to distract themselves by spending what discretionary (or not) income they have....


----------



## m0b1liz3

So are we just about at the point where a kit be talked about? Any idea how soon, how much etc??


----------



## kostalex

I am also awaiting for the kit. I will buy it for my friend birthday gift.


----------



## kostalex

May I preorder or subscribe for the notification somewhere?


----------



## runeight

Gents, there are still a few kits/boards available from the first small production run from Glass Jar. This is not the group buy yet, it was just a small run to ensure that the new boards, with their changes from the prototype, were accurate. You can get these now by contacting Jeff R. Or, if you prefer, there will be a group buy as soon as the boards and builds are verfied.


----------



## m0b1liz3

Ok. There have been a few builds prototyped now so the question is how much will a kit with the necessary parts cost? I am just curious since I will likely want to wait for a kit in order to avoid multiple shipping costs to Aus. Any estimates on this? I would consider the group buy if I could do it all in one order.


----------



## runeight

My apologies m0b1liz3, but I don't yet know the final kit cost. I'm afraid you'll have to contact Jeff.


----------



## m0b1liz3

I contacted Jeff. It looks like it will come in around 200 with the case and torroid. Sounds reasonable.


----------



## pabbi1

Well, the balance of my parts are in, now if someone could post a pic of the toroid wired up to a discrete IEC and switch... now I remember why I always use the switched IEC.


----------



## runeight

Ahhhhh!!! Been busy and meant to do this last night.

 I'll draw you pictures soon.


----------



## pabbi1

Gracias...


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *m0b1liz3* /img/forum/go_quote.gif 
_I contacted Jeff. It looks like it will come in around 200 with the case and torroid. Sounds reasonable._

 

WOW, 200 including the case and torroid!!! That is in US Dollars right? That's a STEAL!! I would guess way less than what you'd pay if you bought all the stuff yourself from the various vendors and had to pay shipping on all of it.


----------



## JamesL

Really a great price... 
 I was just putting together a BOM, and I calculated over $200 just for the attenuator/case/jacks/accessories.. course, I'm not using the standard Hammond and alps for this build. =]


----------



## FallenAngel

One of mine should be in the $250 range with a stepped attenuator and High-Voltage PSU addon which forces me to have the transformer in another case, but that also means I get to put a fat AC filter in there as well. 
	

	
	
		
		

		
			





 The other will be likely in the $300 range with some Teflon caps and a somewhat larger Par-Metal case.


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Gracias..._

 

OK Pabbi1, I've updated the website with new wiring and ground sections. I did these fairly quickly but they should have enough information to tell you what you need to know. Please let me know.


----------



## pabbi1

So, from this, you can tell I am 180 degrees backwards, yes?

 <sigh>

 Oh, and for grins, does the orientation matter on C1 for the Auricaps?


----------



## runeight

Auricaps with leads have red and black insulation. The red side goes to the higher voltage side. In this case the tube side.

 The power switch wiring is a safety issue because here in the US the Neutral wire is basically grounded. So you switch the L (hot wire).

 You must be getting close if your transformer and switch are in the box already.


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_So, from this, you can tell I am 180 degrees backwards, yes?_

 

Ah, I did it too, but with the wires on the OTHER side! runeight was very patient through about 50 troubleshooting messages...

 Even the quick drawings are a great addition!


----------



## pabbi1

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Ah, I did it too, but with the wires on the OTHER side! runeight was very patient through about 50 troubleshooting messages...

 Even the quick drawings are a great addition!_

 


 And, it finally dawns on me - the top tab on the switch is the outgoing current - maybe I can wire it correctly tonight.

 Yes, dangerously close to being completed - fire in the hole tonight for sure.


----------



## Uncle Bob

From the website
_The SOHA II PCB is designed to insert into the third slot from the bottom in the Hammond enclosure. This position leaves room at the top for the heatsinks and at the bottom for small boutique caps and standoffs to fasten down the board._

 From the drawings on the Hammond website, I've calculated that this places the bottom of the pcb at a distance of *11.94mm* from the bottom of the case, so a 12mm standoff should suffice for implementing the star ground scheme? Can anyone confirm this is correct?

 And what size hole is provided on the pcb?

 thanks peeps


----------



## runeight

Yes, I think that's correct on the height. The US screw size is 4-40 with lots of clearance. The actual hole size should be about 0.140" (3.5mm). This is suitable for a 3mm screw I think.


----------



## JamesL

Yup. A 3mm screw fits in the hole perfectly.


----------



## luvdunhill

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Oh, and for grins, does the orientation matter on C1 for the Auricaps?_

 

The Auricaps should be connected so that the signal enters the black wire and exits the red wire.

 So, were there any fireworks tonite?


----------



## pabbi1

Well, is not this special - finally get the torroid wired correctly, and, nothing. Nada. Zip. Absolutely nothing from the outs, measured as suggested, measured as indicated.... even measured in every other way.

 Any different ways to verify the toroid is dead rather than hooking it up to wall current?


----------



## runeight

Well, what AC voltage do you measure across the secondary of the toroid when the two CT wires are connected together?

 Also, have you put the fuse into the IEC inlet?


----------



## FallenAngel

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_The Auricaps should be connected so that the signal enters the black wire and exits the red wire.

 So, were there any fireworks tonite? 
	

	
	
		
		

		
		
	


	


_

 

Why would a polypropylene cap be polarized?

 I can definitely say I've connected Auricaps in both directions, in different directions on the same DAC outputs even.


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Well, what AC voltage do you measure across the secondary of the toroid when the two CT wires are connected together?

 Also, have you put the fuse into the IEC inlet?_

 

Fuse is in - I get 117v from the top lug of the switch (when on) and the N on the IEC, allegedly making sure power is going into the toroid. 

 Using jumper clips, with negative to ORA / RED, I get 0 on yellow OR black. If I connect Red & Black on one meter, and Yellow & Orange on the other, I get nothing - and I swapped Black / Yellow just in case I was backwards. Edit: Using 20vdc scale, except when measuring AC.

 Hopefully I am just measuring wrong...


----------



## runeight

You have the Avel transformer? Correct?

 Then on the primary side do you have brn/gry connected together and then blu/prp connected together?

 On the secondary do you have org/red connected together?

 If so, what is the AC voltage between the brn/gry and blu/prp wires when the power is on?

 What is the voltage from yel to org/red and then blk to org/red?


----------



## Uncle Bob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Edit: Using 20vdc scale, except when measuring AC.

 Hopefully I am just measuring wrong..._

 

It's AC coming out of the transformer, so you need to be set to measure 20v ac on your meter.

 UB


----------



## Uncle Bob

I think UPS tried to deliver my board yesterday.. yikes! Jeff only sent it on Monday


----------



## pabbi1

Quote:


  Originally Posted by *Uncle Bob* /img/forum/go_quote.gif 
_It's AC coming out of the transformer, so you need to be set to measure 20v ac on your meter.

 UB_

 

OY Vey!! I am an idiot for all time... but, 17.8v on both sides? 
	

	
	
		
		

		
		
	


	




 Lowering the bar for DIY, one notch at a time.


----------



## runeight

17.8V unloaded is about right.

 I think you can hook up the transformer to the board now.


----------



## pabbi1

Ya think? Dunno - but, fire in the hole tonight. And, yes, I will (re)read all the fire up instructions... again... and again. THEN start.


----------



## pabbi1

No jumpers - no smoke / sparks / spew / joy... well, at least I have current.

 Test Point Voltage 
 TL+ +30.9V 
 TL- -0V 
 TH -0V 
 TB+ +263V or so


----------



## runeight

pabbi1, what reference are you using to measure those voltages?

 The 263V is impossible to get from the transformer and multiplier. So there has to be something wrong in the measurement. Otherwise your caps would have blown up by now.


----------



## luvdunhill

Quote:


  Originally Posted by *FallenAngel* /img/forum/go_quote.gif 
_Why would a polypropylene cap be polarized?

 I can definitely say I've connected Auricaps in both directions, in different directions on the same DAC outputs even._

 

It isn't polarization in the traditional sense. It has to do with the inner versus outer foil lead. Connecting some film caps in "anti-parallel" like you did on your DAC can have benefits, but IMHO the Auricap isn't one of them. Best to follow the manufactor recommendations on this one (Auricaps).

 edit: for example, this is what Percy writes for the Reliable Capacitor brand:

 "Exclusively for our customers we have measured for & marked the outer foil lead
 end of most larger value capacitors with a black dot for optimum orientation.
 For most series signal path applications I recommend orienting the outer foil lead
 toward the load, as though the signal were exiting the cap at the end with the
 dot. For shunt and power supply bypass applications, orient the black dot toward
 ground. At the very least, observe the same alignment in the left & right channels."


----------



## pabbi1

Uh, back to dc.... then...


 Test Point Voltage 
 TL+ +14.7V 
 TL- -15.1V 
 TH -12.5V 
 TB+ +119.50V 

 Is TB+ tolerable, or...???


----------



## runeight

Now those voltage are right on target. The B+ will pull down when it's under load.

 So now you can follow the procedure to test the buffers.

 Should I wait up for this tonight? If you're planning to work on it I'll stay up for a while.


----------



## pabbi1

No, that is enough success for one day... gracias, as always. Hopefully things more faster tomorrow.


----------



## runeight

OK. Unfortunately, I'm going to be busy tomorrow night until about 10pm.

 But, if all the parts are in the right places, there is no reason why it won't come up successfully. Just take it one step at a time. And don't short anything out when you take the measurements. Mine came up first time without any additional effort.


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_OK. Just take it one step at a time. And don't short anything out when you take the measurements. ._

 

Sage Advice - the king of replacing transistors seconds that! 

 Great Success so far. We'll look for an update this evening?


----------



## wiatrob

I've FINALLY finished my JISBOS (had 'em done, but never wanted to disassemble my SOHA I to install). 

 Now that my SOHA II is my work-amp, I took the plunge. SOHA with JISBOS is up and running. Sooo... I will do some comparative listening this weekend - even though the II has evolved with a bit higher plate voltage... 

 Thanks again runeight for some fine sets of designs...


----------



## pabbi1

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_Sage Advice - the king of replacing transistors seconds that! 

 Great Success so far. We'll look for an update this evening?_

 

Mos def. For good or ill...


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Mos def. For good or ill... 
	

	
	
		
		

		
		
	


	


_

 

For good - with those volatges, listening can't be too far away... Careful with the test leads when measuring!


----------



## pabbi1

OK... j1 & j2 strapped (not j3)... meter set to 2v, but nothing across either r10L nor r10R... but, at 7-10 seconds, the relay clicks on.


----------



## wiatrob

Let me check the proto thread - the initial test points were for r12L/R - but these were rather hard to get to. Stand by, if I can clarify I will, but we may have to wait for someone more saaavy..


----------



## wiatrob

I believe you could also try R12 - here's the quote from runeightI was looking for:

_runeight:_

 "wiatrob, I am going to change the 2R2 resistors to have 12mm pitch. This will make plenty of lead for attaching clip leads to set the O/P idle. On the web page I'm using R12 to set the idle, but we can also use R10 when there is no load. R10 is on the front side of the heatsinks and with a little more lead length this measurement will be easy."

 My buffers are tweaked, and I've strapped J3, but I get 223mV across R10 = ~100mA (I'm actually reading mV -does your meter have a mV scale? For me, this measurement would be either .223V or 223.x mV _*(DC) *_

 If you are hearing the e12 click - that's a good sign. Getting a measurement on R12L should be fairly easy? (notethat r12 will be about 2x voltage of R10)


----------



## wiatrob

*PS* Bleeding the power supply down regularly per the setup instructions is a _VERY_ good pratice... I'm paranoid so I bleed down below 1V


----------



## pabbi1

OK, there is just a LOT of travel before any readings, then it is really sensitive in the relevant range, but I am moving along to the right side - and roger that bleed down, though I get to 5v.


----------



## runeight

You should have easy access to R10L and R10R. Use the 300mV scale and you should be able to dial in.

 As wiatob says, if you get a click from the e12 things are probably working.


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_...but I am moving along to the right side..._

 

PS bleed -> 5V is fine - when you say you are moving to the right side - do you mean of the voltage, or the amp? 
	

	
	
		
		

		
		
	


	




 Measurement?


----------



## holland

if it helps, i just soldered wires to the pads and ran them out from underneath the board and put clips on the wires as I go along. I used R12L/R as well.


----------



## wiatrob

Good to see you home early Runeight, my courage was waning!


----------



## wiatrob

Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_ I used R12L/R as well._

 

It should be noted that the instructions have been changed on the web site from the proto pages - the divisor for R10 to determine the current has changed from the one used for R12, correct runeight? PLus - R10 is much easier to get to!


----------



## runeight

Correct. I've extended the leads on R10 to make it easy to clip on the test leads. Don't use R12 because it's too hard to get to.

 I = V(R10) / 2.2.

 So 220mV means 100mA.

 This is written correctly on the website (at least I'm pretty sure it is).


----------



## wiatrob

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_
 This is written correctly on the website (at least I'm pretty sure it is)._

 

It is - I checked my voltage at R10 and I am 223mV/2.2 = ~100mA.

 That's pretty much _zero _drift in two months...


----------



## pabbi1

I can measure the resistor value with the clips in place but get absolutely 0 reading on the right, even up to 100% travel (yes, to a click on the trim pot), so, apparently there is bad solder somewhere, or...

 Left is rock solid @98mv... I'll tweak that later if needed.


----------



## holland

try a reflow. q5, q6, q7, q8, r9, r10, r11, r12, p2. got a loupe? i cant live without mine.


----------



## pabbi1

Will do - and, yes the loupe (actually a Sherlock Holmes size magnifier) is required - I'll pat particular attention as you suggest,


----------



## pabbi1

Daylight makes things clearer - reverse mounted q6 & q7 - can I just clip and use the alt pads and if so, what direction?

 I have already lifted half the 1st top pad on surgery removing q6, so that does not bode well...


----------



## holland

I'm not entirely sure, but I don't think you can. The problem is the heatsink needs to go on the back of the device, not the front...though I'm not sure what happens if you put it on the front. I would guess the heat transfer is not as effective as the source of the heat is on the back side.

 How are you removing the transistors? Here's how I do them. I take a resistor leg (diode leg preferred), and solder it to the 3 pins on the underside. Then I flood the resistor leg with solder so that all 3 pins are covered with a blob. What this is doing is using the leg as a means of attaching the solder. It doesn't work well to flood it over the board as it heats it could contract and leave a leg uncovered.

 Turn you soldering iron up to about 650 or 700. Touch to the solder blob and melt it. From the other side, gently wiggle the transistor out (use some pliers due to the heat), while at the same time pushing on the pins from the other side with the soldering iron. Take breaks and let the device and board cool. Meaning touch, heat, wiggle, try no more than 10 seconds. Wait 30 seconds, try again.

 You don't want to pull/yank the transistor. You can pull out a pad (done that before plenty of times). Don't worry too much if you do, you can repair it with wire if you need to.

 You may have to turn up the heat higher, if the solder ran through the hole and up the leg of the device. It's hard to melt the solder all the way through the board, so you may have to heat it a little longer.

 One thing you can use are those heat sink clips from radio shack. The ones that look like a tweezer. Clip it onto the transistor and use it to wiggle out instead of pliers. It'll give you some extra time before you overheat the device, though I would be more concerned about further board damage.

 If you don't care, clip the transistor and toss it, and push out the pins individually.

 It's best if you can stand the board on edge and see both sides of the board.
 The reason I say toss it is because the legs will not be long enough to attach to the heatsink unless you've got multiple holes and you were mounted on the top hole. If you are using the standard BOM, the transistors are cheap anyway.


----------



## holland

wait a minute, not sure what you mean, when you say reverse mounted.

 Can you take a picture? If you just put it so the transistors are on the backside of the heatsink (put it on the wrong set of pads to begin with) then you can clip it and push the pins out. Most likely you cannot reuse the device as the legs will be too short for heatsink mounting, but that depends on the heatsink and where you mounted them initially.


----------



## JamesL

On the Excel BOM, I think there's a extra component;
 R9 L/R - 200ohm resistor(row 28)


----------



## runeight

Thanks JamesL. I've removed that extra row. But, while I was staring at it I realized that R7 and R8 had their values reversed. So that's fixed too.

 I also changed the mouser sheet to remove the extra resistors.


----------



## pabbi1

Well, God only knows how I got the left side right as I simply attached the 4 devices to the heat sinks, then mounted l to r in random order... yes, right channel was in the default pads, with the devices (bd13916stu) turned around backwards. Everything else has been rechecked / reflowed.

 So, I clipped off the devices, and am pushing the pins back through with my trusty safety pin. Since I have many extra (always), no worries yet, IFF surgery is not successful, then we'll consider the alt pads


----------



## wiatrob

Even if you lift a pad - it's a fairly short jumper run to the nearest components...


----------



## pabbi1

Devices fixed, left side changed to 265mv (was 98, set back to 101mv), and NO relay engage on power on/off. Nothing across r10r (0 mv) on the right side.

 What can I check on the right side to see what else might be at issue? Anything likely toasted due to the inverted bd139?


----------



## runeight

Pabbi1, have you been looking at the silkscreen diagrams, etc. that are posted on the website? These show the proper orientation for all of the heatsunk devices.

 Also, when measuring R10 you want a value of 220mV not 100mV.

 The only thing to suggest on the R channel is to replace both BD139s. If you get no current at all, it is probably one or both of these devices. Sorry.


----------



## pabbi1

Left channel reset to 220mv. 

 Both q6 and q7 have been replaced, but still 0v at 100% travel on p2r. Any other readings I can take to see if they are truly in circuit (having been replaced)? And if there are additional culprits?

 Re: bd139 orientation - I knew the orientation, but was probably doing that late at night when tired. No excuse, but that is all I can figure out.


----------



## runeight

What is the voltage on each lead of R10 measured with respect to ground?


----------



## pabbi1

-3.2v, each side.


----------



## runeight

What is the voltage a pin 6 of the R opamp?


----------



## wiatrob

When I had my e12 fail after replacing another component (one of the solder joints was accompanied by a blue spark!), I had killed the opamps.

 <EDIT> SERVO opamps


----------



## pabbi1

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_What is the voltage a pin 6 of the R opamp?_

 

Correct, sir, and inverted opamp... 
	

	
	
		
		

		
			





 Moving forward, in my own way.

 But, no e12 relay, though both r10 are at 220mv... servo opamp?


----------



## holland

Could be the servo opamp, but let's check the DC voltages first. On the resistors R1E and R2E, with the side closest to the headphone output pads, check the DC voltage relative to ground. That is the output of the transistors feeding into the e12 circuit, at that junction.

 But do double check the opamp orientation. Pin 1 should be pointing to the headphone output pads.


----------



## pabbi1

Opamp oriented correctly.

 R1 = 9.6v
 R2 = 1.7mv (dropping from ~3.5mv)


----------



## runeight

Obviously only one channel is zeroing the output. Try changing out the opamp on the channel where you're getting the 9V.

 To determine this measure the voltage at the leads of R8L and R8R that face towards the center of the board. This is the same point as the R1E and R2E measurements. Then change the opamp on either R or L where th 9V is.
 -ac-


----------



## holland

What runeight said.

 R1 is the right side...the same side you've had trouble with. Your opamp might be blown from being disoriented. Temporarily swap the opamps and see what happens.


----------



## runeight

I think I'm going to leave this to holland. He's doing a better job than I am.


----------



## pabbi1

Latest in the saga. e12 functional (hear switching on at ~11sec, and off on power down.

 j3 strapped., regulator current set at 60v.

 Tubes (5963) inserted, switched to 12.6v jumper... and no heaters. Tried a second pair of tubes to verify.


----------



## holland

was it a blown opamp?

 For the heaters, are you using jumpers or a switch? When using the switch, it is the opposite of what is on the silkscreen. Meaning, to get 12.6V, you move the switch handle to 6.3V. That is because of the way the switch works. If using jumpers, then put the jumpers on the pin closest to the heatsink and the middle position.

 Measure the voltages of pins 4 and 5 on the tubes. It should be reasonably accessible since the tube sockets are elevated.


----------



## pabbi1

So close, or so I think...

 Ok, after the intiutive heater voltage switch 
	

	
	
		
		

		
			





, I have biased everything - voltage 60.2, r6 is 400mv on both sides, then TBL - TPL is 17.6v, and TBR - TPR is 15.6v.

 What now?


----------



## runeight

If all of your component values are correct and the tube is lit, then this usually means that Q1P and Q2P are blown and need to be replaced.


----------



## runeight

Another thing to check is that Q1L, Q2L, Q1R, and Q2R are actually BC560 and not BC550.


----------



## pabbi1

Verified q1 & q2 are both BC560 on both sides - any sure verification on q1p and q2p?

 Then, I assume, all will have to be rebiased from regulator forward?


----------



## runeight

Pabbi1 where are you measuring the 60V?


----------



## pabbi1

TB+L to G, and TB+R to G = both at 60.1v.


----------



## runeight

OK. My mistake then. So you have 60V at TB+L and TB+R when the tubes are in or out?


----------



## pabbi1

That is with the tubes in...


----------



## runeight

Oh. And I assume that you can adjust this voltage with the regulator adjustment.

 But TPL and TPR are around 18V? with TB+L and TB+L at 60V?

 Can you verify that R6 on both channels is 200R and has 400mV across it?

 And then verify that R4 on both channels is actually 18k.

 There is very little that can go wrong from this point if the tubes are working properly.


----------



## holland

I think pabbi1 is saying that TB+L-TPL is 17.6V and TB+R-TPR is 15.6V and he/she wants to get them closer in range and to the 19v that is spec'd. That'll have to go back to you to find what is not operating properly. 
	

	
	
		
		

		
		
	


	




 That said, it should be generating music now. Is it not?

 Edit: Just to be certain, they are all C types (and not intermixed C and B)?


----------



## runeight

Oh. I swear I'm not going to try to debug this anymore holland. I'm wasting Pabbi's time by misunderstanding what he's asking.

 So, if this is the real question then those votlages are just fine and Pabbi1 you shouldn't be concerned about them.

 What is the voltage from TPL and TPR to ground? Please report this to holland. 
	

	
	
		
		

		
		
	


	




 Is it making music?


----------



## holland

haha, don't be silly. 
	

	
	
		
		

		
		
	


	




 Would it be worthwhile to hFe match q1 and q2 in quads for left and right, and to 0.1% match R4? Those deltas seem to be a varied by a good amount, much more than mine, mine were closer matched. I would presume some of that is dependent on the tube as well?


----------



## pabbi1

TPL is 43.3v and TPR is 40.8v - is this kosher, prior to plugging in any phones?

 Just have to put in the standoffs under the tubes and hook up the inputs - about 20 minutes away from music.


----------



## runeight

holland, these numbers are ok because they are measuring the difference between the B+ after the cap multipliers and the plate voltage of the right half triode. Since the right half varies around some this is ok. There is no test point for the left half triode where the R4 is. But if you measure that point I think you'll see voltages that are very close between both channels.

 Pabbi1 these numbers are right on target. Fire it up.


----------



## holland

Yes, runeight has mentioned that the deltas are fine and to not worry about it. IIRC, the delta is for headroom.

 It's acceptable, but not perfect, probably due to a number of factors which is at my limit of understanding as far as tubes go. I can only presume that matching everything upstream from the tube to B+ would give you a closer match for the SS part.

 Edit: runeight has answered already.


----------



## pabbi1

Success! I am playing it through some tossable phones for a few hours before I hook up the hd600, since my test hd650 are at Burning Amp... I think...

 Now, remember, this is a build for some soldiers - Generation Kill, a Marine unit in particular. Gotta make sure the bodies will hit the floor, so I'll run through some Drowning Pool later.

 Pimp the ride (and, yes, you can take the tubes out), but the FPE delivery should be Wednesday:







 Big shout out to Wiatrob and Holland for getting me over several humps. And, to runeight for an outstanding design. I have proven that if I can do this, darn it, anyone can... so, please, I appreciate the rep, but I cannot build units for others. 

 Oh, and if Bijou don't rock (while I do own 'Take 5', don't listen to that much), guess what will be balanced next? But, that is a LONG time from now.


----------



## Arkku

I've just placed my order for the parts on Mouser, now waiting for them to arrive and some time to actually build this thing. I'm going to put in a crossfeed filter (with genuine bypass) while I'm at it. =)


----------



## runeight

Yeah!!! 
	

	
	
		
		

		
		
	


	




 Pabbi1, my apologies for my densenes in the few previous exchanges.

 I think that's a pretty cool build. Kind of reminds me of some of the toughbook technology that we worked with when we were doing video game training SW for the guys at Ft. Hood.

 Let us know when you listen through the Senns.


----------



## pabbi1

Couldn't wait - right out of the chute, it drives the hd600 very well - my normal listening levels on my 'office rig' are several notches above where the SOHA is. There is absolute command on the bottom end, and really good resolution straight out of a cheap DVD player (too lazy to unplug the Electrostats from the Azure), and my only other DAC is buried in the Balanced Millett Hybird. Maybe later in the week I'll give it a whirl on the Azure with really good interconnects and a decent power cord (yeah, I doubt you are a believer)... pity, I only have a stock 650 Senn cable in SE.

 Going to leave for others to compare and comment next weekend - makes me realize next weekend in Houston will be fun, especially of the Bijou makes it in.

 Sounds really good, given an hour of burn. No microphonics on these 5963, but I have tube dampers if it comes to that. Curse the ability to roll so many tubes in this thing... 

 Just outstanding design work - it really sounds sweet - well, for single ended... 
	

	
	
		
		

		
		
	


	




 Thank you, Alex. We never say that enough to you guys.


----------



## holland

That's awesome, pabbi1.

 It's a great amp, and definitely well worth the money and time spent. It definitely has impressed me, particularly in the price range. I have to admit, I did not keep track of costs for this one, so I don't really know where it ended up.

 (don't forget to roll some output transistors too) 
	

	
	
		
		

		
		
	


	




 I would love to hear some impressions with other hybrids, from the meet. Do post some impressions when it happens.

 Which 5963 are you using?

 I only have a stock 650 cable on my 650, and I think it sounds great as it is.


----------



## runeight

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Couldn't wait - right out of the chute, it drives the hd600 very well - my normal listening levels on my 'office rig' are several notches above where the SOHA is. There is absolute command on the bottom end, and really good resolution straight out of a cheap DVD player (too lazy to unplug the Electrostats from the Azure), and my only other DAC is buried in the Balanced Millett Hybird. Maybe later in the week I'll give it a whirl on the Azure with really good interconnects and a decent power cord (yeah, I doubt you are a believer)... pity, I only have a stock 650 Senn cable in SE.

 Going to leave for others to compare and comment next weekend - makes me realize next weekend in Houston will be fun, especially of the Bijou makes it in.

 Sounds really good, given an hour of burn. No microphonics on these 5963, but I have tube dampers if it comes to that. Curse the ability to roll so many tubes in this thing... 

 Just outstanding design work - it really sounds sweet - well, for single ended... 
	

	
	
		
		

		
		
	


	




 Thank you, Alex. We never say that enough to you guys._

 

Say, Pabbi1, I see that the Houston meet is closed. What does that mean exactly? There is no hotel space left? 
	

	
	
		
		

		
		
	


	




 Or there is just no more room in the room?


----------



## pabbi1

Well, it is in a limited space, but we have reserved a few spots for 'honored guests', and we would be honored if you could attend - even if for a limited time. 

 Might have to send out a rescue party for Ron...


----------



## wiatrob

Congrats, and welcome to the club! 
	

	
	
		
		

		
		
	


	




 Just wait till you hear it after some burn-in (tubes plus passives).

 Although - it looks like you've had it built all the while and were testing the proto team on experience. 
	

	
	
		
		

		
		
	


	




 runeight - no worries for context switches- we know you also have umpteen other current and future designsin the works!

 Who's next?


----------



## dBel84

Congrats Pabbi , I followed the epic journey from a distance and very glad to see you made it with all the good advice on the forum. Looks great too ..dB


----------



## pabbi1

Well, it really is not my taste in design, but since it was for the Jar Head(s), it had to go somewhat that way. I love Ferrari's work, which looks inspired by the Woo GES (which I happen to have on loan for a few days). One day, iIwill aspire for the form to be at least as nice as the substance - but that day is not here yet.

 Again, thanks for everyone who helped - the kits should prove VERY successful


----------



## Uncle Bob

Congrats Pabbi1, and well done, that looks really nice! (did Ferrari do the casework?)

 Can't wait to get started on mine


----------



## mdabro

Hi, 

 I am new member of this forum. I am interested in SOHA II, and I woluld like to buy kit to assembly this amplifier (all elements, pcb boards but without transformer and enclosure). Could You help me?

 Marek


----------



## runeight

Hi Marek. Happy to see that you are interested in this amp.

 You can get kits from Glass Jar Audio : Home. Please contact Jeff Rossel there. There are a few kits left from the first small production run.

 We are also preparing a large group buy to be announced soon.


----------



## pabbi1

Just for grins, what trafo spec would be needed to run 2 boards at the default config?


----------



## holland

60VA dual secondaries 15V (default is 30VA). Wire from one SOHA 2 board to the other, basically, or to some junction point (terminal strip) to the SOHA 2 boards.


----------



## mdabro

Thanks, Runeight. I have wrotten e-mail to Jeff.

 Marek


----------



## wiatrob

Quote:


  Originally Posted by *pabbi1* /img/forum/go_quote.gif 
_Just for grins, what trafo spec would be needed to run 2 boards at the default config?_

 

You mean for like:

SOHA II - Super SE Hybrid - Page 17 - Head-Fi: Covering Headphones, Earphones and Portable Audio


----------



## GeWa

NANANANANANAAAA !!

 Received a greenish looking board today from Jeff Rossel 
	

	
	
		
		

		
		
	


	




 Regards


----------



## pabbi1

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_You mean for like:

SOHA II - Super SE Hybrid - Page 17 - Head-Fi: Covering Headphones, Earphones and Portable Audio



_

 

Yeah, except I will actually build it...


----------



## mdabro

Thanks, Runeight. I have wrotten email to Jeff.

 Marek


----------



## Ferrari

Quote:


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

 Received a greenish looking board today from Jeff Rossel 
	

	
	
		
		

		
		
	


	




 Regards_

 


 So... there is a small chance that you are _the second Europeans SOHAII builder_? NANANANANAAA...A


----------



## espressogeek

I received my board this weekend and I am very excited. I am finishing up the BOM after work today. 
 I'll probably go with Panny FC caps because they are available for everything except the 160v positions.

 Will 1/4 watt resistors fit in this thing all the way around? I already have several and I would like to keep my stock the same.

 I order some 6922 JAN-Phillips tubes to start with. Hopefully they work well.

 Are there any worthwhile upgrades to the smaller non-electrolytic that are a good bang for the buck?

 Also, what toroid should I get. The one in the BOM is available from partsexpress but is there a suitable one that I can pickup from either Mouser or Digikey that will let me run the higher heater current later like Ferrari did? ( I think this is right )

 Thanks!


----------



## wiatrob

From the Power Supply parts list page:

182J15


----------



## espressogeek

Quote:


  Originally Posted by *wiatrob* /img/forum/go_quote.gif 
_From the Power Supply parts list page:

182J15_

 

Sorry, somehow I missed that. Would this have the extra gusto that is needed for the higher voltage option that I have seen mentioned around here? I am still a bit fuzzy on transformers.

 Also, I just looked and it is twice the price of the one over on partsexpress!

http://www.partsexpress.com/pe/showd...ewRand=8170223


----------



## 04BluMach

Quote:


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

 Received a greenish looking board today from Jeff Rossel 
	

	
	
		
		

		
		
	


	




 Regards_

 

Got back from a week long trip - opened up the mailbox and guess what was waiting for me from Jeff 
	

	
	
		
		

		
		
	


	




 ......... a greenish looking board just like GeWa received 
	

	
	
		
		

		
		
	


	




 Now I guess better finish up the my BOM determine what I have on hand and get some parts on order that I need right away.

 Will probably go with some inexpensive new 12AU7 types (EI or JJ) just for check out and also snag a couple NOS 5963s.

 Anyone have some recommendations on the NOS 5963's? 

 Thanks to Runeight and Jeff for the greenish boards! Looking forward to building this up....


----------



## Ferrari

The 182J15 from the BOM is a 30VA transformer.
 To run higher heater current (later) you can better go for a 50VA transformer, for example 182K15 at Mouser. 80VA is cheaper





 .
 The price at Mouser is much too high 
	

	
	
		
		

		
		
	


	




, maybe you can find it cheaper else where.


----------



## espressogeek

Thanks Ferrari. Now that I know what I am looking for I will finish my BOM.
	

	
	
		
		

		
		
	


	




  Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_The 182J15 from the BOM is a 30VA transformer.
 To run higher heater current (later) you can better go for a 50VA transformer, for example 182K15 at Mouser. 80VA is cheaper





 .
 The price at Mouser is much too high 
	

	
	
		
		

		
		
	


	




, maybe you can find it cheaper else where._


----------



## Ferrari

For those living in the US and looking for a 50VA toroidal transformer for your SOHA II, you might take a look at the Antek AN-0515. 
 Comparing to the 30VA Hammond 182J15 from the BOM, the price of the Antek AN-0515 is very reasonable at US$ 13 / piece + US$ 10 shipping cost within the US.


----------



## holland

I have one of those, but decided not to use it because of the prototype HV perfboard not leaving any room for that transformer in the case I chose.

 Just FYI, for those in consideration. The Antek over rates their voltage. Most transformers rate voltage loaded. The Antek rates voltage unloaded. The VA is accurate though.

 It also is a bit larger than others.

 There's nothing really wrong with the Antek, other than the voltage. With the old B+ it was pulling voltage a bit under the 60V spec'd where other transformers were coming in around 63V or so, loaded. With the new adjustable HV, it's less of an issue.


----------



## pinkfloyd4ever

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_For those living in the US and looking for a 50VA toroidal transformer for your SOHA II, you might take a look at the Antek AN-0515. 
 Comparing to the 30VA Hammond 182J15 from the BOM, the price of the Antek AN-0515 is very reasonable at US$ 13 / piece + US$ 10 shipping cost within the US. 
	

	
	
		
		

		
		
	


	


_

 

Oh ya fo sho!! I'm trying to decide on a diy speaker amp kit and have decided to use one of their toroidal transformers. Since I've never bought a transformer other than a wallwart, the only transformer companies I've heard of around here are hammond, avel, amveco, and plitron. I only heard of Antel a week or so ago (ERRORRR





), but after reading alot on diyaudio.com and 41hz.com I've found that apparently they sell quality toroidals for significantly less $ than Avel and WAY less than Plitron. For some reason most of us headphone diyers haven't 'discovered' them...till recently
	

	
	
		
		

		
		
	


	




 Much better selection than Avel too. And to add to what holland said, you can see their loaded voltages by clicking on the red link to each model's datasheet. And no I don't work for em
	

	
	
		
		

		
		
	


	




 EDIT: while we're on the topic, I'm confused about the difference in a transformer with dual secondaries and a true center tapped secondary. How does it affect their ratings (voltages and VA) and can they both be used either in parallel or series? I really don't know much so I'm prob calling something wrong


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## FallenAngel

If you're building a speaker amp, take a look at this beauty.
DIYCable.com : Intro » Home » Exodus/Hypex Amps » Amp Parts »


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## holland

Quote:


  Originally Posted by *pinkfloyd4ever* /img/forum/go_quote.gif 
_Much better selection than Avel too. And to add to what holland said, you can see their loaded voltages by clicking on the red link to each model's datasheet._

 

Yes. The datasheets need to be checked and not assumed. It needs to be brought to the forefront, in most cases it is not an issue.

 I buy all my toroids from Antek. I think they are a great value and will continue to use them. I usually buy about 5 at a time, and have at least 10 toroids of different values in my closet.

 I have yet really have to fall back to a different brand, but the only real issue that would make me consider another is the size. They are a bit larger in diameter than most. They say it's because they use thicker wire, but who knows. Most of the time, I just use a larger case. It may not work for all people. Again, the datasheet shows the size.


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## espressogeek

Wish I had seen this Antek thing before I placed my order with Part Express.  I went ahead and got the transformer mentioned on the spreadsheet. Not a bad deal but not as cheap as these guys. I'll have to remember them for future projects of which I am sure there will be many.


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## holland

to be fair, I had brought up the Antek during prototyping discussions and requested that it be added to the BOM. Upon further analysis and discussion, I had determined that it would be incapable of reaching the spec'd B+ and requested that it be removed. It was specifically the 0515 because due to the higher VA it would not dip as much in the voltage due to the lighter load in the default configuration. This was with the early HV multiplier/setup. While this would be OK for me, it would not be OK for a broad recommendation. In the default configuration with the standard load using the original HV setup, I was getting a B+ of about 58V (spec was a bit over 60V) which was about what I had calculated for loaded and about 59.x for unloaded which also matches what I had calculated.

 I have not tested it, nor done the math, for the existing HV setup. I have not tested it and probably would not recommend it for the higher current load configuration unless you can live with not having the highest of possible B+ voltages. One will have to decide for themselves what is acceptable or not.

 While this is not a big deal, and many probably won't even notice th voltages or not care, some will find it a big deal.


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## runeight

Although I understand the wish to use the Antek and Holland's point about the new HV supply not being quite as sensitive to the secondary voltage, MHO is that sticking with one of the two recommended (or same spec) trafos will minimize problems that you might encounter.


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## espressogeek

Holland, I appreciate the detailed explanation and history. I'm sure a lot of this will make more sense once I build this thing and try to digest the design and it's philosophy
	

	
	
		
		

		
		
	


	




. I am still in the technical weeds here.

  Quote:


  Originally Posted by *holland* /img/forum/go_quote.gif 
_to be fair, I had brought up the Antek during prototyping discussions and requested that it be added to the BOM. Upon further analysis and discussion, I had determined that it would be incapable of reaching the spec'd B+ and requested that it be removed. It was specifically the 0515 because due to the higher VA it would not dip as much in the voltage due to the lighter load in the default configuration. This was with the early HV multiplier/setup. While this would be OK for me, it would not be OK for a broad recommendation. In the default configuration with the standard load using the original HV setup, I was getting a B+ of about 58V (spec was a bit over 60V) which was about what I had calculated for loaded and about 59.x for unloaded which also matches what I had calculated.

 I have not tested it, nor done the math, for the existing HV setup. I have not tested it and probably would not recommend it for the higher current load configuration unless you can live with not having the highest of possible B+ voltages. One will have to decide for themselves what is acceptable or not.

 While this is not a big deal, and many probably won't even notice th voltages or not care, some will find it a big deal._


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## Uncle Bob

Now that the 1st boards have been delivered (except here, but maybe tomorrow 
	

	
	
		
		

		
		
	


	




), might it be a good idea to start a new topic Soha II builders blog?

_whoops.. a few replies to this topic have gone missing? I posted a question about transformer specs earlier, but it's not showing now ???_


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## Ferrari

Yes indeed, we are missing some posts. Also one of mine, in which I mentioned the need of a transformer that can properly fulfill the job in the SOHA II for all PS sections (in high current mode when desired): 6.3V heaters, ±15V section and the B+ HV section (~105V unregulated). From this point of view, the Antek AN-0515 will probably not suitable due to the lower output voltage, which can drop to 14VAC under heavy load (according to Antek spec).
 The one I’m using in my amp (for my GF) is also a relative cheap one (50VA, 2x15V), but it does output ~18.3V unloaded.

 As runeight noted in some posts back -to minimize possible problem- it’s better to use transformers with a similar spec as the ones recommended, either 30VA or 50VA type (Hammond, Avel Lindberg, Amveco, Talema Nuvotem…).


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## holland

Yes, agreed, minimize problems.

 Also note, that you can do a wallwart build. Mine is. I am using an EI core. I can't recall if I'm using a Hammond or something else.


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## espressogeek

I would have never thought about doing a wall-wart. I have seen folks run copper shielding between the amp and the toroid. Is that effective? If so, where can I get some to shield this thing with?


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## holland

good question, I don't know. 
	

	
	
		
		

		
		
	


	




 I was just throwing it out there in case cost was an issue. For me, it was space, with the prototype HV perfboard going in I could no longer fit a toroidal transformer in my case without it sitting on top of signal lines.

 I'm not sure about the shielding or where to get it. You may have to google. You can build a "box" with mu-metal. That's probably what I would do. I would actually take mu-metal and wrap the entire rear section (including IEC) in a big box. Drill some holes to run some wires out to the PCB side or attach a terminal strip to the box and run wires to/from it (still need holes).

 During my proto build, I had the toroidal up against the PCB, moved it around and had no hum. I didn't measure anything, but it may or may not have been measurable. Runeight had some hum from eddy currents being generated in the case, but it went away and I forgot what he did. Nobody else had issues, but I don't think anything was measured, again.


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## runeight

I did have some hum issues at the start, but they went away during the final caseup. I just put the toroid in the far left back corner (viewed from front). I ran the wires away from the input shielded cable which is on the other side of the box.

 The website (Cavalli Audio) shows diagrams of where to locate the components in the enclosure for best effect.


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## meat01

Quote:


 Now that the 1st boards have been delivered (except here, but maybe tomorrow ), might it be a good idea to start a new topic Soha II builders blog? 
 

I agree with this idea


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## runeight

I'm good with this too. I am happy to start that thread, but if one of you guys wants to do that just let me know so I can subscribe.


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## kostalex

I want to gift amp kit to my old friend. I've been waiting for SOHA II kit for a while. Just checked glassjaraudio and found that Bijou kit is available.

 What would you recommend for D2000 - Bijou or Soha II?
 What would you recommend for HD650 - Bijou or Soha II?


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## meat01

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I'm good with this too. I am happy to start that thread, but if one of you guys wants to do that just let me know so I can subscribe._

 

I nominate you to start the thread and call it "SOHA II Builders thread". On your first post, you can have a link to your site and maybe a description and picture of the board layout. Hopefully people don't just make a bunch of posts about waiting for their parts, they can do that in this one.


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## runeight

OK. I'll do that. A question though. Do you mean the PCB layout as shown on the website or a stuffed board or a silkscreen image or a 3D image or ????


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## meat01

Stuffed board would be cool 
	

	
	
		
		

		
		
	


	




 or the 3D layout.


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## runeight

OK. New builders thread is here:

SOHA II Builders Thread


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## onform

Runeight: when you say group buy do you mean for individual parts/board or for the entire kit??


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## runeight

Jeff R has always prepared group buys that include both boards only and complete kits. Complete kits generally do not include the enclosure, but in this case I believe they will include the transformer and pot.

 Jeff also usually offers a few options on the kits including upgraded caps, etc.

 I don't know exactly what the offering will be this time, but should follow this general pattern.


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## wiatrob

Quote:


  Originally Posted by *kostalex* /img/forum/go_quote.gif 
_What would you recommend for D2000 - Bijou or Soha II?
 What would you recommend for HD650 - Bijou or Soha II?_

 

There has been a synergy between the HD650 and Soha II noted by myself and others. But that's all I can speak to...


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## pabbi1

And, the hd600...


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## meat01

I believe Jeff will add a choice of some Hammond enclosures in his kits, but Jeff will have to confirm.


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## wiatrob

All,

 I've just received my Cmbridge DACMAgic B and have been playing with optical and SPDIF - my USB hookups are notorius for noise with my crappy home power situation.

 The II is DEAD silent and gorgeous sounding with this DAC ('course my 650s are just starting to break in as well.)

 Also, I will be bringing the II to a mini-meet in Denver this Saturday. If anyone's around and interested PM me for details.

 More impressions in _reviews _as I break this setup in...


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## Jrossel

Quote:


  Originally Posted by *meat01* /img/forum/go_quote.gif 
_I believe Jeff will add a choice of some Hammond enclosures in his kits, but Jeff will have to confirm._

 

Yes, there are a few to choose from. The standard kit will have a long T size case in clear (silver), with metal faces 1455T2201. Optional choices are the shorter T size case in clear or black (metal faces) and the 1455T2201 in black. The shorter T cases don't have room for the torroid, you would have to enclose it separately.

 The next run of boards are on order and should be ready near the end of November and will be available at glassjaraudio.

 Jeff


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## kostalex

Jeff,

 what will be available - boards or kits?


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## onform

Quote:


  Originally Posted by *kostalex* /img/forum/go_quote.gif 
_Jeff,

 what will be available - boards or kits?_

 

I have recently been in contact with jeff and I think i'm correct in saying both full kits inc boards and all ancillaries as well as individual items ie boards are availible for purchase. jeff will also leave out certain parts of the kit if you already have them or for shipping/weight reasons, jeff has assured me that a kit minus traffo, case and valves is fine for me to order. 

 I have found jeff to be very helpful with regards to answering all my questions. 

 unfortunately my build has to be put on hold until i can free up some cash....bloody recesion.


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## FairyTales

Hey guys,

 Let me ask a somewhat stupid question, what changes needs to be made to run it on 220 volts AC? 

 Arnaud


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## Postal_Blue

Wire your Transformer primary in series instead of parallel.


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## wiatrob

Quote:


  Originally Posted by *FairyTales* /img/forum/go_quote.gif 
_Hey guys,

 Let me ask a somewhat stupid question, what changes needs to be made to run it on 220 volts AC? 

 Arnaud_

 

A 115/230V transformer with the proper secondaries should require only that the primaries be wired in series. Here's an example of the Avel trafo specified in the BoM's wiring options:

Transformers and Power Converters From Avel Lindberg, Inc.

 Alex, perhaps we (er, you 
	

	
	
		
		

		
			





) should update the wiring diagrams on the web site for our European friends...


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## Ferrari

For Europeans builders, there are transformers with 230V primaries available on the market.

 Arnaud, take a look at RS-Components Netherlands (this one is quite inexpensive) or Amplimo Netherlands.
 Of course, there are many other places in Europe where transformers with 230V primaries are available.


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## runeight

Say, gents, were a handful of posts lost? There was one by grendel23 on 12bh7s and a few others.


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## Ferrari

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Say, gents, were a handful of posts lost? There was one by grendel23 on 12bh7s and a few others._

 


 Ee..ehhh, those posts are in the other thread.
 I think a fresh cup of coffee can help.


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## runeight

Quote:


  Originally Posted by *Ferrari* /img/forum/go_quote.gif 
_Ee..ehhh, those posts are in the other thread.
 I think a fresh cup of coffee can help. 
	

	
	
		
		

		
		
	


	





_

 

LOL. I think I'll go do that right now.


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## FairyTales

Postal_Blue, wiatrob and Ferrari, thanks for the help!

 Arnaud


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## wolf18t

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_Gents, none of you has made any comments on the proposed panels. I am going to assume for the moment that this means you are not too fond of them.

 If so, I won't mind hearing that. And you won't hurt my feelings.

 What I'd like to do is to get a design that most of you like so that the panels can be offered with the kits from Glass Jar. And so you don't have to drill everything out._

 

Runeight, are the predrilled front and back panels abandonned or still some chances to get them with the coming kit?


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## runeight

Wolf18T, Jeff (Glass Jar) is not going to offer Front Panel Express prefabricated panels. He is, as of our last conversation, trying to have the stock Hammond panels punched out to include with the kits.

 Are you just interested in the pre-drilled panels or are you interested in the FPE panels?


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## wolf18t

The predrilled hammond panels will do just fine.


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## Jules

Hmm, I was wondering, theoretically, what if a company like Grado labs (I'm just using their name as an example) came up with this design, made it, and sold it. How much do you think they would sell it for? I mean the parts and all are under $200, right?... but that would not factor in build cost/manufacturing, fancy enclosures, r&d, advertising and warranty repairs and a profit margin. 

 I just really appreciate what you all have done, and all the time and effort that has gone into the development, and you've done it all out of a love for the hobby and the community... it's a wonderful thing. I can't wait to get a crack at building one. The builds look amazing. 

 I built a pair of SET monoblocks, the bottlehead paramours, and that was a challenge and very satisfying to me. I also built the foreplay preamp they offered. When I fired up the foreplay, and it worked, and it was the first major piece of electronics I had ever built, I was thrilled. My first paramour worked, but the second, I had to get Doc at bottlehead to help me fix it, I believe I had knicked a resistor with the soldering iron. It really is rewarding building something yourself, especially for the first time. I can't wait to take a crack at this amp. I've never soldered onto a board before, only, I guess what you would call point to point wiring, but this looks easier and I bet I could do it no problem if I am careful.


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## Postal_Blue

Well as a point of comparison there is another recent DIY design that you can build for ~50 that is being sold commercially for 180 and they did non of the R&D. So... your guess is as good as mine but I would not be surprised to see a commercial offering (if it ever happened) in the 500-600 range. Which IMHO it is worth every penny of that when compared SQ wise to current commercial offerings.


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## pabbi1

The rule of thumb is 3x parts - my SOHA II was ~$300, so $895 sounds right, with a street price of $750-800.

 Now, the Ferrari version is SE, which means $1195, $1k street...


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## holland

It's hard to really base this solely on parts cost. The reason is that some amps have an output coupling cap. If you do a Ferrari version, you can spend about $1K on coupling caps alone to do justice to the SS buffer at driving low Z. Fortunately this amp does not have output caps, which makes it cheaper for those looking for boutique.


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## Beefy

Quote:


  Originally Posted by *Jules* /img/forum/go_quote.gif 
_Hmm, I was wondering, theoretically, what if a company like Grado labs (I'm just using their name as an example) came up with this design, made it, and sold it. How much do you think they would sell it for? I mean the parts and all are under $200, right?... but that would not factor in build cost/manufacturing, fancy enclosures, r&d, advertising and warranty repairs and a profit margin._

 

Consider the US$350 Grado RA-1. Not far from $20 in parts in a VERY expensive wooden box......


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## onform

unless you had been cap rolling it's very difficult to say what the differences are from standard to modified! unless you had both side by side of course.

 Ferrari is the man to ask he, i think, has satisfied both criterion.

 I do however know that the wima cap which is part of the kit is a very capable cap and can hold it's own sq wise well above it's price range see: http://www.head-fi.org/forums/4674667-post134.html


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## Mikenet

Did anything ever come about with the either the pre-drilled enclosures or the FPE panels? I'd love to build one, but I'm dreading the casework.


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## runeight

I am still waiting to hear if Jeff is fabricating the panels for the kits. I know that he is quite busy now, but that he was looking into having the Hammon panel pre-punched for the kits.


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## wolf18t

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_I am still waiting to hear if Jeff is fabricating the panels for the kits. I know that he is quite busy now, but that he was looking into having the Hammon panel pre-punched for the kits._

 

Any confirmation from Jeff about the availability of the pre-punched panels? Read in the SOHA II builder thread that the kit is almost ready. Only PCBs missing. 

 Need to fix my build itch and the holidays season is coming...


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## luvdunhill

are the new PCBs any different the the proto versions?


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## FallenAngel

Quote:


  Originally Posted by *luvdunhill* /img/forum/go_quote.gif 
_are the new PCBs any different the the proto versions?_

 

Yep, bigger HV voltage multipler caps and slightly different.


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## runeight

Quote:


  Originally Posted by *wolf18t* /img/forum/go_quote.gif 
_Any confirmation from Jeff about the availability of the pre-punched panels? Read in the SOHA II builder thread that the kit is almost ready. Only PCBs missing. 

 Need to fix my build itch and the holidays season is coming..._

 

wolf18t, I am emailing with Jeff now. He is not providing pre-punched Hammond panels.

 However, as you know, I have created FPE designs that fit the Hammond box and work with the BoM parts.

 A while ago I asked if anyone would be interested in these pre-fab'd panels, but at the time there was little interest.

 SO, I guess it's good to ask again. Would anyone be interested in FPE panels for the front and back?? They are not cheap. One of them will be $25 and the other $35. These are cost to me in small quantities. 

 I realize that this is pretty expensive which is why Jeff was looking into having the Hammond panels punched somewhere in California.

 You all just let me know . . .


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## luvdunhill

How thick are the panels at the quoted price? Also, I sent you a PM for another option.


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## runeight

They are 1.5mm.


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## runeight

By simplifying some of the fonts, I've managed to reduce the cost of these panels to $22 and $31. In quantities of 10 these prices drop to $18 and $25.

 Attached are PDFs of the current design. The front is very simple and the rear has the Cavalli Audio logo on it. Originally I had the logo on the front, but I like the front simpler like this one is.


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## wolf18t

I'm in for sure! 
	

	
	
		
		

		
			





 They aren't cheap at first but after considering the time saved to drill and cut the panels plus the nice logo (I could easily live with it in the front panel!), they're pretty cheap after all.

 Maybe you will get better attention if an IC is posted in a separated thread here and on HW. Some folks could be intrested to order them even if they don't plan to order/build the SOHAII very soon.


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## jonoliew

Quote:


  Originally Posted by *runeight* /img/forum/go_quote.gif 
_By simplifying some of the fonts, I've managed to reduce the cost of these panels to $22 and $31. In quantities of 10 these prices drop to $18 and $25.

 Attached are PDFs of the current design. The front is very simple and the rear has the Cavalli Audio logo on it. Originally I had the logo on the front, but I like the front simpler like this one is._

 

I'm interested! If you ship to australia, i'll definitely take a set. Which hammond case is it for?


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## regal

I am building this for my brothers B-Day, I am definetaly in for the panels. Let us know how to make payment


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## wiatrob

Gentleman - If you notice this thread is rather old. I have made arrangements with runeight to offer the panels. But with the CTH taking up most of my time haven't gotten to it yet. 

 If there's significant interest I may bump that priority up a bit. Pricing would be TBD at this point, but a quick load of the panels in FPE shows the price has gone up a bit from last year.


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## Cloud

hi folks,

 i am a little confused and require a little help

 according to the part list here, The SOHA II Headphone Amplifier

 Q1p and Q2P are BC550C
 Q3P and Q4p are MPSA42
 but in the excel bom and schematic, Q1P and Q2P are MPSA42.

 whereas there is no Q3P and Q4P.

 can i say the part list in the site is wrong?


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## TimJo

Yeah, it looks like it wasn't updated. You should use the schematic and the BOM.


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## runeight

Thanks for catching this. Should be fixed now.


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## Cloud

okies. Thanks both for the help ^^


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