DC protection

[Vrystaat]

Gooday all,
I need some advice please. When I switch off an amp,then there is a crack on the speakers because the protection circuit relay takes too long to switch off. If I decrease the 470uf capacitor to something smaller like 100uf or even smaller, would that be the best option to make the relay release faster ?
Thanks all.

 

[Keruskerfuerst]

What do you want to do exactly?
Change the amp or something else?

 

[Vrystaat]

I want the relay in the DC protection circuit to release faster to avoid the cracking on the speakers when you switch the mains power off.

 

[Keruskerfuerst]

Can you post the relevant circuit of the amp (relay circuit)?

 

[scottjoplin]

You could do with a loss of AC detection muting circuit incorporated into the DC protection, this will ensure that the relays open as soon as the amplifier is switched off, they usually include a switch on delay as well Loudspeaker Protection and Muting

 

[DF96]

Switch-off clicks cannot usually be prevented by relays, as no relay will be quick enough. The solution is to put an X-rated cap across the mains transformer primary - maybe 10-47nF. If there is one already there then it may need replacing as they gradually lose capacitance over a number of years.

 

[Vrystaat]

Thanks guy's,
Would adding a snubber like this be helpful ?

 

[Mooly]

Can't disagree with anything that has been said above.

One thought would be to try adding a reverse biased diode across the 330k to discharge the timing cap on power off... but it still wouldn't be instant off.

Fwiw, I use schemes that Doug Self put forward back in the 1990's and that include AC drop out detection. I've never had the slightest noise whatsoever on power off when switching even 600VA toroids.

Maybe the mains switch is a bit suspect and prone to arcing more than it should.

 

[Vrystaat]

Thanks guy's, Ill give it a try, advise is much appreciated !!