[cobaltmute]

Just waiting on the SumR transformer...

 
And yes, I did socket the open loop and closed loop gain resistors as well as the compensation caps.

 
5600uF on the PS rails.  I was going to go large on the heater supply cap, but it turned out I already had the 2200uF as a Panasonic FM in my parts bin.  Otherwise the heater board will fit a 8600uF FM.

 

[jdkJake]

Looks great cobalt mute.

I really like the look of that tube socket. What kind of material is that?

 

[cobaltmute]

It's teflon and something I believe.  They are from here (suggested by johnwmclean earlier in the thread):
Moulded Teflon 9 Pin Noval
 
I used these ones as Angela didn't want to ship to my address.

 

[jdkJake]

Update: "Unexpected distress..."
 
So, the detective work starts. I took the right channel out of the equation and am working strictly with the left channel.
 
The Power Supplies appear to be fine. When disconnected from the AMP, the rail puts out +/-30V. When connected to the amp, same +/-30V output with ~38V on the regulators. Things have changed a bit. With the single channel, I plugged my phones in and got a good dose of full volume (with max attenuation of the input). That was pleasant. Once I pulled the phones, something changed. I plugged them back in and right now, there is nothing coming out save for intermittent distortion (they are still function, I checked on an my receiver). The DC offset is stable (more or less).
 
Shifting to the TL081, VCC is at +/-15V respectively. Offset N1 and N2 are at -15V, Output settles at -3.6V. Most telling, both input pins measure 0V at this point regardless of attenuation.
 
The hunt continues...
 

 

[runeight]

Have you replaced the tube?

 

[runeight]

Also, can you please identify the pins by number on the opamp. Thx.

 

[jdkJake]

Have you replaced the tube?

Not yet. Measuring the tube, I have 1V on the cathode, 0V on the grid (with signal applied) and 27V on the plates.

 

[jdkJake]

Quote:

Also, can you please identify the pins by number on the opamp. Thx.

1- Offset N1: -15V
2- IN-: 0V
3- IN+: 0V
4- VCC-: -15.2V
5- Offset N2: -15V
6- Out: -3.6V
7- VCC+ 15.2V
8- NC
 

 

[runeight]

Thanks. The opamp numbers say that it is servoing properly and you have 0VDC at the output. Waiting to see what you find.

 

[jdkJake]

Well, that's a first. I think I found it.

Things just were not adding up, so, I bypassed the Alps (mounted on an epsilon27) and all the assorted wiring. I now have signal. Since it is earphone out of an iPod, it sounds like hell, but, it has consistent sound with perfect DC offset control. All other voltages seem fine.

Gonna recheck the wiring. I find it hard to believe it is the pot. I suppose you never know.

 

[stringgz301]

I had a similiar problem on my SOHA II.  After a couple of months use started to have noise in one channel.  Drove me crazy tracking it down.  I eventually reflowed the Alps connections to the board and all was good.

 

[cobaltmute]

Quote:

Here's a link:
 
EHHA Rev A BoM
 
Edit: And I forgot to thank jdkJake for the huge effort to finish out the BoM. Thanks!!!!

the PS supply schematic in the BOM linked above and here:
http://www.cavalliaudio.com/ehhaa/main.php?page=schematics/powersupply
 
have L2R and R6R in a different order from ground to the negative rail. It would seem that the one in the quoted link is correct.
 
When you use the bottom side trace between the two parts to decide which way to orient the the LED, it means that you get a LED installed backwards if you use the website version.

 

[runeight]

Ah, now I see the problem. The gif schematic is wrong. I'll fix it.

 

[runeight]

Fixed.

 

[jdkJake]

Well my friends, that was certainly one of the most bizarre and unexpected problems I have ever seen.
 
I air-wired in another Alps and everything was fine. Air-wired the existing Alps (wired directly to the pins, not epsilon27) and everything was fine. Air-wired to the epsilon27 molex pins and the problem was back in the left channel again. Reflowed all pins on the epsilon27 and viola, air wiring to the molex pins works fine. Reinstalled all of the original wiring and everything is fine. Works like a champ. Problem solved.
 
Then I saw this:
 
Quote:

I had a similiar problem on my SOHA II.  After a couple of months use started to have noise in one channel.  Drove me crazy tracking it down.  I eventually reflowed the Alps connections to the board and all was good.

 
Now I don't feel quite so bad about my apparent cold-solder joint in the most unexpected of places.  

 That was crazy, crazy weird. I certainly would never have suspected an issue on THAT board. The single LEAST complex thing I built for the entire project! Oh well, live and learn. One things for sure, the amp is rugged. I put it though some hell during the debug and it took it like a champ.
 
In any case, I am back in business. Now to get back to what I was supposed to be doing today which was working on my case. Thanks for all of the help and suggestions! Always most appreciated.