Anyway, my "soft-start" circuit did require an independent supply. I did a network of optocouplers and zener diodes that basically gave me a signal that all of the supplies (4) were up to about 2/3 their value. When they reached the 2/3 mark, a flame-proof resistor in the AC line was shorted out and the audio was unmuted (actually ramped up exponentially) with another optocoupler and the speakers connected. The "timing" was the RC time constant of the power supply and the approximate on value in the opto circuit set by a zenier diodes and a resistor.
Since there is no set-timing or no certain off-time the flame proof resistor ends up being the fuse. The added benefit is that each (2 x +-50) supply is fused, so if a fuse pops, the resistor will pop too and the amp never operates on one supply.
Since there is no set-timing or no certain off-time the flame proof resistor ends up being the fuse. The added benefit is that each (2 x +-50) supply is fused, so if a fuse pops, the resistor will pop too and the amp never operates on one supply.