I swapped the speaker cables at the amp and the crackle moved. It’s a channel on the amp.
I was excited about the Benchmark until I realized that the speaker binding posts will only take small spades. My Gryphon speaker cables have huge spades. To make matters worse, the Benchmark puts the speakers posts above the XLR inputs, almost guaranteeing that they’ll block my input cables. Sigh.
The reviewer of the Benchmark in Stereophile mentioned that he was looking for lighter amps because he could no longer lift or move heavier amps. I’m in the same boat, at the moment.