OK, I see what you are saying about the power supply and that does make sense.
However, the other thing I noticed were the caps being used for c1, c3, c4 and c6. They were large "audio type" non-polarized .22uF capacitors that didn't fit very well. One of the leads from c1 and/or c4 were touching the body of the output rca jacks which are connected to ground.
I replaced them with the digikey P3224 caps as called out in the parts list.
(I just happen to have a few extras.)
I never tested the unit when I received it, only after I was done putting it all back together. I don't know what it originally sounded like.
cheers