I have some good news! The amp is working 100% when I select the input to be the front 1/8" jack. However, when I select the rear inputs, I have the same problem as before, where the right channel is fine but the left channel you can barely hear. I had 2 327 ohm resistors lying around, and so I did the hum mod listed on Pete's website. That seems to have gotten rid of the noise/buzzing/hum. Also, shorting JP1 seems to have almost no effect for me, so I removed the jumper.
If anyone has any idea how to fix the left channel problem for the rca inputs, I am all ears (yes, pun intended)! You guys have been great so far, thanks for all the help!
Edited by guppysb - 2/22/15 at 2:17pm