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.

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

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

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