YouTuber XrayTonyB has a video on how to add a Pioneer-style soft start to any amp; it includes a relay and a hefty power resistor that functions as described above by Larryi. The current to initially charge the capacitor power bank runs through the power resistor until the capacitors approach full charge and then the relay contacts change state and the power resistor is dropped from the circuit.
The circuit works well because of the way capacitors charge. The curve is exponential, so that, if memory serves, 4/5ths of the current is consumed in the first 1/5th of the time it takes to charge them fully, then 4/5ths of the remaining current in the next 1/5th of the charging cycle. The power resistor is dropped out of the circuit well before it reaches full charge, but well after the capacitor bank has received the bulk of the current it needs. This way, it doesn’t kick back in during normal operation when the capacitors may need to be resupplied after heavy transient responses. At least that is my understanding.
The circuit is fairly simple and I think Tony even went so far as to come up with a small circuit board that can be installed in nearly any power amp or receiver short of a design like Devaliet (if I’ve spelled their name correctly).
