In article ,
Norman Billingham norman.at.tumulus.org.uk wrote:

Do any of you experts know if something like the Velleman 4700 would do
the job? Or of any other circuit? I'm perfectly happy assembling
something but I'm no circuit designer.

Not without considerable modification. It provides an initial delay at
switch on to prevent a 'thump' while the amp settles, and then checks for
excessive DC on the line which could destroy a speaker. You need an low
level AC sensing device which will switch mains. I'm not even sure the
relays in that kit would be suitable.

Haven't got time to look now as I'm about to go out, but Jaycar might well
do a kit which is just the job.

--
*Change is inevitable, except from a vending machine*

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