In article ,
Rob wrote:
I take it your physics teacher had a degree in physical education? Because
it's basically rubbish. Although some devices like projectors have cooling
fans which are meant to run after powering down, but I'll bet he wasn't
thinking of those.


No, she (it was a 'she', Dave, and not a 'he' - Ms Lyons, class 3C, BVGS
Birmingham 1976) was/is a physics graduate although she didn't have a
PhD - or at least she didn't use the title 'Dr' (most of the other
staff did). I'm afraid I can't remember if she was a member of any
chartered or similar organisation - sorry.

I was trying to remember last night - I asked her 'why?', and I'm pretty
sure the answer had the word 'surge' in it, and tailed off into a 'this
doesn't apply to everything but as a rule you shouldn't switch a
switched device on or off at the mains. Device first, mains second'. I
tried it with my system - 3 valve amps, TT and CD, and left them
switched on at the appliance and just flip the switch at the mains.
Mighty convenience, but hell of a thump at the speakers when it's
switched on, fine when switched off.

That's rather different as there's no way you could switch all the devices
simultaneously except at the socket.

But I'd be worried if a valve power amp produced a thump at the speakers
when powered up.

--
*60-year-old, one owner - needs parts, make offer

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