I got this CMoy about two months ago (I did not build it myself) and I noticed that it has a rather odd problem with distortion on the left channel. The amp has a volume control pot and two output jacks, and a 2132. I can get pictures of anything if necessary. I am using one of those thick $13 1/8" to 1/8" gold-plated cables between the CMoy and my MZ-R900 MiniDisc unit, though I notice this with all other sources I've tried. It also gets significantly worse as the battery gets worn down, but it is still quite bad even with a fresh battery.
When used with my MZ-R900: There is a crackling noise in the left channel, but it goes away if the volume knob on the CMoy is turned all the way up. This is only noticeable with my Panasonic RP-HJE50 earphones. It goes away for about a second if the power is swiched off, then on again, or if the earphones are unplugged and then plugged back in. When there are two sets of 'phones plugged in, it becomes a lot worse, to the point where the sound is unrecognizably distorted on the left side, and you can hear it in both sets. Turning the volume knob all the way up makes it go away. Also, having one set only partially plugged in to the point where the plug is just barely hanging in will make the other set sound perfect.
When used wth other sources: Exactly the same, except the problem doesn't completely go away when knob is turned all the way up.
Anyone have any insight to what may be causing this? Thanks.
You might try turning the source volume down, temporarily shorting the pot's wiper pin to the signal input pin (on both L & R channels) to see if the noise persists.
That it gets worse with two phones, suggests a lack of output current. A single opamp alone (a la CMOY amp) isn't idea for a single headphone alone, so it's no wonder two make the matter worse).
You don't mention the power source but I presume a 9V battery? You might try a slightly higher voltage- a 2nd 9V battery wired in series with the first (check that the capacitors are rated high enough though, minimum of 16V but if your virtual ground channel is achieved with resistors (as a standard CMOY would) then it may need >= 18V caps for saftey margin were the virtual ground to collapse with 2 x 9V in series.
Since this dual output on your CMOY is a bit nonstandard, the question arises as to what else might have deviated from std. CMOy. If you can determine the schematic and post it, that might be helpful.