As I was working on another Leach amp board just now, I noticed that I had not 82 ohm resistors for R32 and R33. I looked over at my other board (the one I burned up trying to figure out why it was clipping) to figure out what I used for it, and I suddenly realized why it had been clipping at about 400mV in. I had used 7.5k resistors instead of 82 ohm (the "k" had somehow slipped by me when I was building that board). What a stupid mistake! If only I had paid more attention, that board would be up and running just fine.