"Andy Evans" wrote in message
ups.com...

That still may not be enough. You may well find that you are required
to have no DC at all on the chassis connector pins when the cable
connector is removed.

that would indicate all smoothing in the PSU box. Can be done.

Well, I thought it better to decouple at the amp end of the
umbilical with a pair of 220µF electolytics, and so used a relay there also.

Power amps with separate psu are quite unusual these days. I have a
feeling that the safety regs might well be the reason. Solutions that
were
common place in the 60s and 70s, like for instance the octal connector
between psu, amp and preamp, are now strictly forbidden, as are fixed
mains cables, and any other mains connector except the IEC type (with
the possible exception of the Speakon, I am not sure) You have to be
very wary. If your neighbour's world champion, best of breed
Rottweiler bites through your DC cable, it could cost you a pile of the
elusive spondoolicks.

Two monobloks is looking like the easy solution. I have all the
amplification and PSU stages on seperate top plates, so can plug them
into any chassis - stereo, mono. whatever.

Now that sounds like an excellent "modular" idea, Andy.

I was thinking of a seperate
PSU for development purposes, to try out different valve circuits,

That's what I do. I have a Solartron regulated bench PSU 600V at
0.5A plus heaters and a bias tap. I also have a separate Farnell reg
supply 10A at 10V for heaters, plus another 100V at 100mA which I invert
as a bias supply. With clean DC you know that your development modules
are as good as they can be.

but
I can do that in-house and then just construct the final units as
monobloks. Not sure what to do about the preamp - that's an easier
situation as you found.

Yes indeed. When you get down to 265VDC things are not quite so
problematic. But you will still need the safety relay.

regards
Iain