Protection circuit kicked in(whew!).
That's great! What sort of circuit is it?
My Quad electrostatics (not the '57s) protect themselves by compressing signal voltages over 40-Volts, and 'clamping' (short-circuiting the amplifier) at 56-Volts.
Most amplifiers shut themselves down when presented with a short circuit, and then power back up OK. But I once tried a Luxman which sent a spike when switching on, which caused the speakers to clamp and the Luxman to power down. Never did get them to work together ...