Soft Start module: when do you use them?

[ggetzoff]

I see a lot of builds without a soft/slow start module. Who is using them and what size trafo/cap bank do you use them?

I also see a lot of builds without speaker protection circuits/boards. Same question: when are people using them?

Thanks!

Greg

 

[scottjoplin]

A very comprehensive article on soft start Soft-Start Circuit For Power Amps

 

[xrk971]

I use a mosfet cap multiplier to feed my CRC - takes about 20 seconds to reach full voltage. No thump. Main reason is to prevent smps from shutting off due to it thinking caps are a virtual short. Look for Juma’s Easy Peasy Cap Multiplier thread. Only problem is loss of 4v headroom on smps or trafo.

 

[xrk971]

Another thing to try are CL60 thermal resistors leading to the primaries on a transformer on a big Class A that draws a lot of current. They start at 8ohms when cold and end up at about 0.5ohm hot.

 

[JeffYoung]

Around 50 - 100VA I'm happy with nothing; in the 300 - 500VA range I use CL60s.

With the larger transformers I've usually got around 150,000uF and a cap multiplier, or around 250,000uF straight up.

I haven't put speaker protection in any of them.

 

[nigelwright7557]

I designed my own soft start circuit using a triac instead of a relay and resistor.
It ramps up phase angle slowly until it reaches full power.
It uses an 8 pin PIC micro and simple resistive dropper for power supply.

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