To power down or not power down? .....

[JonFo]

The amplifiers that I am talking about are the ones that don't have a typical linear power supply, they have what is called a commutating power supply which turns on voltage steps of the special transformer in sync with power demands using a triac. With low line voltage the triacs stay on to long and blowup. In olden days outdoor PA systems powered from a generator would take out lots of Carver amps. The generators voltage regulators couldn't keep up with the audio.

Speedskater, thanks for the detailed reply.

I hear you about things like generators and other inverter driven power sources. But a soft start should provide just a second or two of ramped voltage, then a relay closes and direct links the amp to the line as usual. Is that still an issue with Sunfire amps?
The amp is not really amplifying signals during power up (at least never in my system).
Again, just looking at managing inrush.

As I said "Big amplifiers draw lots of AC current for a very small portion of each power cycle" a 15Amp Variac acts like a series resistor in the primary AC circuit and limits current flow during that short time period. Any big amp and especially ones like Carvers and new ones with Switch Mode Power Supplies that is played real loud is happiest a very low source impedance AC supply.
For big amps I would run oversize AC power wires to the load center, I would not use a UPS or any filters or suppressors that add resistance to the AC line.
People often think that a 15Amp circuit breaker limits current to 15Amps. But that's the circuit breakers steady state (3 hours) current limit. A typical 15Amp circuit breaker will carry 90 or more Amps for as long as 1 second then taper to 15Amps over the next 3 hours.

Agreed on minimizing AC resistance and overspecing wires.

So a 15 AMP rated variac can’t deliver 15 Amps of steady state current flow?

That’s interesting, I was planning on using ganged 30 amp variacs to manage the voltage levels of my balanced power supply to my source components.
What ratio of rating (e.g. 15 amp) to actual max current flow would you spec for a variac?