On Sat, 30 Apr 2016 12:44:07 +0100, Jim Lesurf
wrote:

In article , Don Pearce
wrote:
I certainly agree that there is very little point for the end user to
try and fix this. But it is a design flaw and should have been fixed by
the original engineers.

Speaker relay? Yes, that will stop you hearing it, but it doesn't fix
the problem.

FWIW When designing the 730/732 amps the development *preamp* design at
one point tended to give bursts of about 1MHz about ten secs after being
turned off. It was coming from ICs being used to regulate and stabilise the
rails.

I solved it by not using ICs in the PSU.

Jim

Fair enough. Why were you regulating the rails - couldn't get the kind
of CMRR you were after from the preamp?

d

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