I'm sure it's the amp, I've swapped the speaker connections, and changed the input from phono to DAC. The left channel is definitely dead. There was no abuse here, it just died, and I'm sad. Hopefully it's a fuse, but that leaves the question as to what tripped the fuse in the first place. Now I'm listening in mono using the biwire of the right channel to drive my left speaker. Fortunately I have a mono switch, and a lot of mono records that I love, but this is going to end up costing me!