For those of you freaked out by yesterday's thing where my fridge could turn off my laptop's sound, here's an update. It seems it's somehow due to my amp.
With the exact same setup, but listening on headphones rather than the amp, the fridge has no more power over my computer. My amp is old (1970s? no idea) and so I'm not surprised, but it's still a mystery how the chain of events occurs. Somehow, the glitch needs to propagate through the chain, fridge->amp->audiointerface->laptop, in such a way that the laptop gets a bad file descriptor error which makes the audio fall over.
Here's the full error message, in case it matters to anyone:
ALSA: prepare error for playback on "hw:1,1" (File descriptor in bad state) DRIVER NT: could not run driver cycle jack caught main signal 12 no message buffer overruns