Quad 2905 ESL Arcing Sparks

That is great news Goofyfoot, I'll have to look into that. I already have the Quad voltage clamps which limit the input to them.

Bdp24, what are Quad voltage clamps?

Goofyfoot, the voltage clamp is just a simple electronic limiter I believe, allowing only a certain amount of, duh, voltage to pass through it, to prevent the 57's panels from arcing. There is no button etc. to reset after it has engaged, but I did hear that the clamp itself can be damaged from repeated high voltage levels, then needing to be replaced.

That's interesting and I do know that even valve amps blew up ESL's on a regular basis. So this must have been Quad's reassuring answer to a farsighted concern.
The 2905's are supposed to shut down when they detect loud volumes but my amp has always shut down first. This time, an arc occurred for a different reason than loud volume but rather high gain between the amp and app transport. I couldn't hear a poor live Grateful Dead recording via Sirius XM and so I turned the amp up to 60 and the transport gain to 20 something and ouch!

I'll bet when your amp has shut down it was because of the typical ESL brutal impedance/phase angle it presented to the amp. If I was going to get a new pair of ESL's, or amps for a pair, I'd look into the Roger Sanders stuff. His amp is made specifically for ESL's, as are his speaker cables. I heard his speakers at this years T.H.E. Show in Irvine and loved them.