SOHA II Builders Thread

[tomb]

From quick research I wonder if it would be possible to add JISBOS to slots where the op amps are on the SOHA II.
Would it not add that much more fidelity to the amp?

There's no need for the Jisbos on the SOHA II. The output is already a discrete topology. The opamps serve as servo circuits to zero out the voltage offset without having to use output coupling caps.

 

[headphonejunkie]

Oh,Then I stand corrected.
 
Thanks TOMB

 

[FallenAngel]

From quick research I wonder if it would be possible to add JISBOS to slots where the op amps are on the SOHA II.
Would it not add that much more fidelity to the amp?

Nope, the opamp is only there for feedback, not the signal itself.

 

[jmf]

Hello,
 
I'm the happy owner of a SOHA II amp (kit bought at www.glassjaraudio.com). I decided last week to print and archive all information about my amp, from http://www.cavalliaudio.com. And I was too late... Disaster ! There is still a web page, but there are not anymore the schematics, BOM, initial start-up sequence, the board drawings... All those precious information needed for the maintenance of the amp.
 
I sent a message on the website to know if it was possible to get those information for maintenance purpose, but I had no answer.
 
Would somebody have archived those precious information and agree to share them ?
 
I especially need them to tune some bias. My amp seems to drift, and it seems to be the reason for e12 spurious triggers.
 
I really hope someone will be able to help.
 
Best regards,
 
JM

 

[jmf]

Hi,
 
Up... Nobody has archived the elements related to the SOHA II ? I asolutly need them for maintenance.
 
Help !   
 
JMF

 

[jmf]

Oups, it is back on http://www.cavalliaudio.com/pages/soha-ii
 
Thanks a lot !!!
 
JMF

 

[eruditass]

  Hello,
 
I'm the happy owner of a SOHA II amp (kit bought at www.glassjaraudio.com). I decided last week to print and archive all information about my amp, from http://www.cavalliaudio.com. And I was too late... Disaster ! There is still a web page, but there are not anymore the schematics, BOM, initial start-up sequence, the board drawings... All those precious information needed for the maintenance of the amp.
 
I sent a message on the website to know if it was possible to get those information for maintenance purpose, but I had no answer.
 
Would somebody have archived those precious information and agree to share them ?
 
I especially need them to tune some bias. My amp seems to drift, and it seems to be the reason for e12 spurious triggers.
 
I really hope someone will be able to help.
 
Best regards,
 
JM

 
 
What do you tune to deal with the drift? 
 
I'm having similar yet different issues with e12 spuriously triggering, but did not build this amp.  I've got some basic knowledge of electronics (studied a bit of EE back in the day).  I bought this amp a long time ago from another user here (who  separated the power supply into another box).  
 
R8 does have some DC voltage with a multimeter during those times.  I thought I had seen it on both channels, but now it's definitely just the R channel
 
I did tweak the tail currents to be exactly 200mA, but that did not solve the issue.  Now, curiously, it got in a state where if I have my basic DMM between ground and either R8L or R8R, the DC offset goes away and it plays sound.  And the instant I release it, the sound cuts off instantly.  Some time later, depending on how warmed up the tubes are, it comes back on its own.
 
Any tips for what to investigate? What's the deal with the DMM fixing the sound: is it a grounding issue? All the test points from the website look good, though my drop from TPL and TB+L is only 15V (same for the right channel).  
 
Source is a E-MU 0404 USB DAC off of a laptop.

 

[eruditass]

Looking closer and at the instructions, it appears my amp is missing the star ground stand-off screw between the two heatsinks? I'm a bit surprised I don't have bigger issues if that's the case. The only ground is through the power supply connection (a separate box which is grounded to the chasis) and the output pot / headphone-out's connection to the front plate (from what I can tell, the box and plates are all separately annodized and thus aren't connected)?
 
Nevertheless, the DC offset is just the R channel, so would that indicate that it isn't a grounding issue? Test points on both sides all look good.  Issue does not follow the tube.
 

 

[Swashinxzero]

hello, all the links to cavalli website are dead... are the instructions to building this amp still available somewhere? looks like glass jar sells pcb but thats all i found...

 

[tomb]

You can try the wayback machine:
https://web.archive.org/web/2011042...iaudio.com/diy/soha ii/main.php?page=overview
You will need to go back to 2011, at least, then look for links to "DIY." Also, don't confuse the SOHA II with the original SOHA, The Simple Opamp Hybrid Ampiflier.

You can also try e-mailing Jeff Rossel at GlassJarAudio. Maybe he kept copies of the documentation. I think you can find everything through the wayback machine, though.

 

[Swashinxzero]

You can try the wayback machine:
https://web.archive.org/web/20110423055317/http://www.cavalliaudio.com/diy/soha ii/main.php?page=overview
You will need to go back to 2011, at least, then look for links to "DIY." Also, don't confuse the SOHA II with the original SOHA, The Simple Opamp Hybrid Ampiflier.

You can also try e-mailing Jeff Rossel at GlassJarAudio. Maybe he kept copies of the documentation. I think you can find everything through the wayback machine, though.

Thanks!

 

[onform]

Some of the schematics are missing but otherwise most of the info is there.

Also I Emailed glass jar, still no response.

thanks

 

[Swashinxzero]

new diy builds took over or people dont build so much these days? It feels like lots of diy tube amp kits/designs are being left in the past...

 

[HGunn]

it seems this thread is mostly dead but I am hoping someone can help me out. I found my old SOHA Amp in a box and thought I would get it up and running again. I have been able to find the original instructions for testing the voltage on the PBD but it seems mine are all completely wrong. Hopefully someone can point me in the right direction for where to start probing the components on the board. My measures values are as follows:
(Probed value vs measured value)
Input voltage = 30V
+12V = + 12V
-12V = -4V
40V and 60V = 104V

it seems the only voltage that is correct is the 12V. And to be sure I’m not doing something completely stupid this is all measured with the negative on the MM connect to the ground on the board and the positive lead connect to the test point.

Any tips or insights anyone could give would be greatly appreciated!