Turning off power amps with noisy power switrches from mains plug socket..........

wizons

Wammer
Wammer
Apr 19, 2009
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Paul
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I have a Quad 909 with an on/off switch that can sometimes be noisy when turned off. Quite often a sharp popping sound is made when the amp is switched off and I am concerned this could damage the speakers (is it caused by DC?).

The noise can be avoided by turning the amp off at the mains plug socket. The socket is switched and flicking the switch off causes no such noise. Given that the 909 has no 'soft start/finish' mechanism, is it OK to turn the amp off this way?

I intend to send the amp off to Quad for maintenance at some point.

 

AmDismal

Wammer
Wammer
Apr 22, 2007
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I would say that dodgy power switches are something to sort out as a priority. You really don't want problems there.

Quad's service is legendary; if you just wanted the power switch sorted than any competent local engineer could do this for you at low cost.

 

Beobloke

Wammer
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Jul 29, 2005
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Adam
HiFi Trade?
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It depends on the internal configuration of the amplifier. Years ago I had an Armstrong 621 amplifier and its mains switch literally fell apart on me one day. It turned out that it was a bespoke item with two contacts to switch the live and neutral on and off, but a third contact that worked in opposition to the other two (i.e. when they were 'off', it was 'on'). This switched in a discharge capacitor for the output stage so that you didn't get big bangs and thumps when switching off. Unortunately, finding one of these switches was impossible and so I had to replace the switch with a standard one and omit the discharge contact.

In this case, the big thump every time I switched it off would have been identical to its behaviour had I switched it off at the plug.

As other Adam says - a service would be the best bet.

 

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