Ok, I swapped the inputs to the amp and the crackle stayed in the same channel as before, so, I guess it is the amp. Sigh. I really wanted an excuse to upgrade the preamp.
I’ve shut down the power to the amp and will see about getting it repaired. I hope Soundsmith is still repairing Gryphon gear.
Now, I need some kind of amp to stand in for the Gryphon
Colosseum. I hate those Class D amps but may have to get one.