for the high power ML amps like the 333, 336, and the monoblocks, ML wanted to make sure that the end users don't accidentally use smaller gauge powercords and break the amps or cause a fire, so they decided to go the safe route and use attached PC to ensure the amps are operating with enough current. That was the answer I got when I owned the 333. I think it came from the factory tech, but not 100 percent sure.
FrankC
FrankC