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SOHA II Builders Thread - Page 45

post #661 of 1688
Thread Starter 
First thing is to measure the heater voltage from the regulator. Is it -12.6V?
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #662 of 1688
I checked all the test points, and recall them being 'normal' - I'm pretty sure H- was ~-12.6.

EDIT: Confirmed -12.8V at TH, -12.87 at pin 4 of tube. Perhaps this is unrelated to the heater short.
post #663 of 1688
Thread Starter 
Hard to know exactly what's wrong, but maybe test the buffers first. Do they still run at 100mA?

What happens when you put tubes in? If the right channel is still bad, you might have to replace parts in the CCS one at a time.
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #664 of 1688
Quote:
Originally Posted by runeight View Post
Hard to know exactly what's wrong, but maybe test the buffers first. Do they still run at 100mA?

What happens when you put tubes in? If the right channel is still bad, you might have to replace parts in the CCS one at a time.
Buffers are good, and I can ever so faintly hear audio on the bad channel with a tube in... doesn't respond to volume increase.

I am suspecting Q1R Q2R - I'll begin the testing transistors/troubleshooting as time allows. Thanks for your help...
post #665 of 1688
I found the bad trace on the board the other day but I still seem to be having a slight issue with the left channel. I'm getting a wild DC voltage swing at R10 from -5 to +5VDC.

It does settle down and act nice when it warms up but, on rare occasion at power up it can take 2-3 minutes to settle down. Any thoughts on a direction to take this in?
post #666 of 1688
Quote:
Originally Posted by rnickl View Post
I found the bad trace on the board the other day but I still seem to be having a slight issue with the left channel. I'm getting a wild DC voltage swing at R10 from -5 to +5VDC.

It does settle down and act nice when it warms up but, on rare occasion at power up it can take 2-3 minutes to settle down. Any thoughts on a direction to take this in?
I would give the rest of the PCB a close inspection. If it had one problem, there could be others. Maybe the equipment was giving the operator trouble during your board. It might have passed inspection (although that short should not have), but there could have been multiple problems.

This sounds really bad and I feel for ya
post #667 of 1688
Quote:
Originally Posted by wiatrob View Post
Buffers are good, and I can ever so faintly hear audio on the bad channel with a tube in... doesn't respond to volume increase.

I am suspecting Q1R Q2R - I'll begin the testing transistors/troubleshooting as time allows. Thanks for your help...
Or not - mechanical failure of one of the C1R joints (bottom mounted VitQs) from sliding the board in and out of the case... phew.
post #668 of 1688
Quote:
Originally Posted by Hayduke View Post
I would give the rest of the PCB a close inspection. If it had one problem, there could be others. Maybe the equipment was giving the operator trouble during your board. It might have passed inspection (although that short should not have), but there could have been multiple problems.

This sounds really bad and I feel for ya
I did inspect the board under a scope for any more problems. I even had one of the girls at work inspect all my solder joints, she gave me %100

I ended up swapping Q5 and Q6 and all is looking good now. I wanted to swap them anyway (for sanity sake) but maybe one of them saw a bit too much heat or voltage that was giving me that wild swing.
post #669 of 1688
Thread Starter 
rnicki does this mean that your amp is working now?
Dr. Cavalli gained notoriety with his first DIY amplifier projects. His success has blossomed into Cavalli Audio, a world leader in amplifier design.
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post #670 of 1688
Quote:
Originally Posted by rnickl View Post
I did inspect the board under a scope for any more problems. I even had one of the girls at work inspect all my solder joints, she gave me %100

I ended up swapping Q5 and Q6 and all is looking good now. I wanted to swap them anyway (for sanity sake) but maybe one of them saw a bit too much heat or voltage that was giving me that wild swing.
Grats on getting your SOHA II working!

So how do you think it sounds? What were you listening to before?
post #671 of 1688
Yeah guys, the amp is working nice now.

This is my first headphone amp and I don't have a decent set of headphones yet but, so far it makes my cheap (relatively) in ear plugs sound like I haven't heard them sound before. I can hopefully borrow a few sets of phones from friends in the next couple weeks while I decide on what to get for myself. So far I'm leaning toward the AKG 240S.

I was listening to a Cayin TA-30 amp through a set of Ariel (DIY) speakers until my kids started getting to loud and I decided I would build the Soha
post #672 of 1688
Quote:
Originally Posted by rnickl View Post
Yeah guys, the amp is working nice now.

I was listen to a Cayin TA-30 amp through a set of Ariel (DIY) speakers until my kids started getting to loud and I decided I would build the Soha
Nice work and nice choice! I doubt you will be disappointed whatever headphones you choose. I spent a while listening the the 'II this evening, it is a wondeful amp...
post #673 of 1688
Quote:
Originally Posted by rnickl View Post
Yeah guys, the amp is working nice now.

This is my first headphone amp and I don't have a decent set of headphones yet but, so far it makes my cheap (relatively) in ear plugs sound like I haven't heard them sound before. I can hopefully borrow a few sets of phones from friends in the next couple weeks while I decide on what to get for myself. So far I'm leaning toward the AKG 240S.

I was listening to a Cayin TA-30 amp through a set of Ariel (DIY) speakers until my kids started getting to loud and I decided I would build the Soha
Wow, this was your first project! It's gonna be hard to improve on it. This is my 4th DIY amp and the SOHA II, by far IMHO, is the best sounding.

I use my SOHA IIt with HD650s, and they compliment each other nicely. The nicest thing about this amp though is you can try many different tubes to find the ones with the best synergy with your headphones. I'd highly recommend the 650s though. They probably appeal more to bass head types, of which I admit to being They are also one of the best headphone deals I know of. Get them from J&R for $319.99 to your door! I've had them for a couple months now (shortly before completing my SOHA II), and almost everday I'm impressed by how great they sound
post #674 of 1688
Quote:
Originally Posted by Hayduke View Post
SNIP I'd highly recommend the 650s though. They probably appeal more to bass head types, of which I admit to being They are also one of the best headphone deals I know of. SNIP
Agreed, I have gone thorough a few pairs of cans but won't part with my 650s. Used 600s and then 580s are also an option if your budget is more modest.

And now I can't count out the mid level Grados after hearing the RS-1s at our meet a few weeks back (and must investigate that synergy with all Alex' designs). Have fun choosing, as you've no doubt noticed - there is a wealth of info (and opinions ) here...
post #675 of 1688
I ordered my SOHA II Kit from Jeff today.

I hope I'll just have to let you know when it's finished and working ...
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