In article ,
Phil Allison wrote:
Dave Plowman (News) wrote:

Common way to stop the thump you can tend to get with a MOSFET amp at
switch on was a relay on the speaker output.

It occurred to me that in these days of cheap high power triacs it
might be better to ramp up the AC into the amp - even if it uses a
conventional power supply?

Comments welcome. ;-)



** Ramping up the AC with a Variac will show you if the idea works or
not - usually its no help or even makes the thump worse.

Sadly, not something I possess.

What you normally see is the output swings DC from the get go and then
at some point it suddenly jumps back to zero.

If I feed it from the bench power supply and start that at zero volts no
thump at any point as you turn it up to the working voltage.

The problem is not restricted to MOSFET amps, most amps thump at switch
on unless there is a speaker muting relay.

This one is pretty loud. ;-)

My own BJT amp has no thump if switched on after a long break, but a
rather loud one if cycled back on after 10 or 20 seconds - cos one rail
drops faster.



... Phil


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Dave Plowman London SW
To e-mail, change noise into sound.

In article , Dave Plowman (News)
wrote:

The problem is not restricted to MOSFET amps, most amps thump at
switch on unless there is a speaker muting relay.

This one is pretty loud. ;-)

Can you show a circuit diagram? It occurs to me that someone might be able
to spot a 'tweak' that helps reduce the thump.

Jim

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