[audiofreek]

wow, that was quick.
First, my PSU is giving +14.85V
But at the DC in jack it's +11V

The V+ to ground(middle two bars is DC in, +11V)
V- to ground is -0.02V.

Picture coming up in a sec, gotta take it apart and it's a pita.

EDIT
Ok I think I found it. I had what could have been a solder bridge, but checked it for continuity when I soldered it, the meter didn't beep so I went on. I redid it now, cleaned the board and hooked the battery up to check (DC jack had to be taken off to get it out of the case). Check the pictures below.

before:


after:


I am now getting +4.4V on V+ and pins 8 of the opamps, and -4.4V on V- and pins 4. So, my next step is to stick opamps in, check DC offset and hopefully all will be ok!

Thanks for the tips FallenAngel!

 

[audiofreek]

ok, spoke too soon. Well, it sort of works. I'm getting clean audio on the right side. Nothing on the left. Decent sounding, haven't tried good headphones yet cuz I wanna get 100% first.

Checked the cable, seems ok. Guessing the left is shorting to ground somewhere but I don't know. Can anyone see something wrong in the pics? Thanks!

 

[audiofreek]

Another update.
I got it working. Sort of. If you look at the first picture, you'll see I had the right channel wired to the wrong pins on the in and out jacks. yeah I'm dumb, D-U-M. I still don't know how I was getting audio out the right side of the headphone and not the left. oh well...

With nothing connected, volume low, I get -1.9mV DC on the left and -3.2mV on the right. A-ok, right? BUT, when I connect it to the all-in-one line/speaker/headphone jack of my computer I started to hear some whining (mostly while gain was in middle 50%... it was gone at low and high gain) so I checked it again and I had something like 40mV on each side! With loudish music it was up to 70mV! What gives? I also have an EMU 0404 PCI card which I will try tomorrow, but this shouldn't be coming from the in-port, right? Isn't that what the input caps are supposed to block? So is my amp somehow creating DC?

for what it's worth, the amp sounds awesome! just can't use it til I know what is going on... Thanks again for all the help so far, Fallenangel...

EDIT I am finding out that this only seems to happen with my Sony MDR-V6 plugged in. I've tested with a cheap pair of Sony's and everything was normal, then plugged the V6 and got 60mV DC on each channel. Re plugged the cheapies and it went to -1.4 and -3.2. Tried my AKG 270s and got low DC. Weird.

 

[Pars]

DC offset should be checked with the input turned all the way down and nothing connected... shorted input is preferable. And with nothing plugged in on the output. No music playing.

When you start checking offset with music playing particularly it is going to be all over the place. I'd say your fine at 1.9 and 3.2mV or whatever it was.

 

[audiofreek]

That's what I read (somewhere) but Tangent says to do it with a source connected.

Input Capacitors for Headphone Amps

I am just wondering if there is a reason the DC is all over the place when I use it with the V6's and not with the AKG 270s and cheap(er) Sonys... I mean, if I use it with the V6s and DC is flying all over the place (mostly stays between 40-70mV), couldn't this damage the phones?

Thanks!

 

[Pars]

That article is discussing input capacitors and whether you need them or not. The DC offset portion is discussing measuring the offset of the source, not the amp...

As for your other issues, I don't know. Perhaps Tangent may have ideas?