I'm building a stereo amplifier, my first ever build. It will be a dual-mono design.
This amplifier will be based on the carcass of an old , broken, Adcom GFA-2535. I have discarded everything except the two hefty transformers (center tap) which supply 35V to their secondaries. There will be two power supply sections, each with 40,000uf filtration. The two amplifier sections will be MOSFET kits I purchased from AMPSLAB. 60W per channel. Everything goes back into the original ADCOM case.
I am also installing soft-start modules. One for each channel. These are the relay type. I purchased the bare boards from that auction site. They are USA designed and manufactured. I now have built and tested the boards.
Here is my idea. I would like to keep the existing wiring harness that supplies 120V to the transformer primaries intact (as is). Can I connect the soft-start modules to the 35V secondaries, ahead of the rectification boards? I'd appreciate your thoughts. I'm sure there are some good reasons not to do this but to me, it seems like it shouldn't make a whole lot of difference. And it would make wiring a little simpler (I think).
This amplifier will be based on the carcass of an old , broken, Adcom GFA-2535. I have discarded everything except the two hefty transformers (center tap) which supply 35V to their secondaries. There will be two power supply sections, each with 40,000uf filtration. The two amplifier sections will be MOSFET kits I purchased from AMPSLAB. 60W per channel. Everything goes back into the original ADCOM case.
I am also installing soft-start modules. One for each channel. These are the relay type. I purchased the bare boards from that auction site. They are USA designed and manufactured. I now have built and tested the boards.
Here is my idea. I would like to keep the existing wiring harness that supplies 120V to the transformer primaries intact (as is). Can I connect the soft-start modules to the 35V secondaries, ahead of the rectification boards? I'd appreciate your thoughts. I'm sure there are some good reasons not to do this but to me, it seems like it shouldn't make a whole lot of difference. And it would make wiring a little simpler (I think).
On the secondaries you need four relay, one for each rail. If you install the soft-start module to the incoming AC in front of two transformers primaries join together, one module will get the job done.
Well, I already have two soft-start modules built (two relays per module). I guess I could just go with one module for both transformers (primary) and save the other soft-start module for a different project. It sounds though as if I could attach to the secondaries if I wanted to use, as you said, all 4 relays.
Most importantly, if any one of the relay fail to close, the amplifier will get unbalance +/- voltage. Worst case is the resistor in series overheated and burned open due to relay fail to close! Why not keep it simple install soft-start on transformer primary?
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Also it depends on the VA rating of the transformers, with a KVA rating you would still have some in-rush current on the primaries even with a soft start on the secondary's. Main purpose of the soft start is to keep from blowing the circuit breaker in the supply wiring. Secondary purpose is it is easier on all the components in the power supply.