Power off pop even using speaker relay

redal

Member
2012-08-08 12:42 pm
I'm using a chip amp LM1875 with a protection relay to the speakers.

Relay wired to the amplifier in the NC terminals & ground in NO terminals, powered by a separate 12v DC wall wart through a switch on the front of case.

When I switch the amp off using the relays switch there is a slight 'POP'.
If I pull out the wall warts connector from the rear of the amp, no 'POP'.
So I'm thinking that the relay is sound, but the switch is causing the trouble.

I would appreciate any thoughts, I have seen reference to RC networks across the switch contacts, but I'm unsure how to calculate the values needed.
 

redal

Member
2012-08-08 12:42 pm
Thanks for the advice djoffe!

I tried your suggestion this morning with an ultrafast recovery rectifier diode I had spare from a PSU project (200V, 1.5A rated) and it works an absolute treat :)

Absolutely no noise on relay power off and on, I really appreciate your advice, made even better by the fact I had something lying around