I got many replies on that one. Thanks everyone! I have
solved the problem by liberal use of RF filtering thoughout
the power supply.
To clarify what the problem was, whenever I used the preamp
I suddenly had what appeared to be noise from switching
power supplies on many frequencies where I have never
experienced it before. During investigation I found
several volts of RF garbage on my AC mains! Some of
this managed to get through the PS and into the preamp.
With added RF filtering I now have clean power to the
preamp and the noise is gone.
This was a separate issue from the constant switcher noise I
have at 1812-1820 kHz, though perhaps not completely
unrelated. If I come up with any useful information on
that problem I will pass it along.
73,
Paul
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