"Eric K. Weber" wrote in message ...
For the AC power part of the issue have a look at.....
http://www.corcom.com/catalog/filters/default.htm

Aren't these for 120vac service? The preamp has an external
transformer with a secondary voltage of 18-20 vac. Would a filter be a
good thing at these voltages?

As for the Microphone input issue..... my solution on a Millennia Media HV-3
was to connect the pin 1 ground to a lug on one of the XLR mounting bolts
with a very short piece of wire..... then run shielded cable from the XLR
to the PCB with the shield connected at the XLR pin 1 end and floating on
the PCB end. You should be able to try this with minimal change to
your existing unit. The shields on the input will not be part of your star
grounding scheme but I believe you will not find any negative effects.

I see what you mean. I guess I was hesitant to think about changing
the grounding, but that sounds like a very logical solution. Consider
it done!

If you are in a very strong RF environment it would also be good to put a
couple of ferrite beads or RF chokes in series with the signal leads at the
XLR.... then add RF bypass capacitors on the input of the PCB.

I have ferrite beads on the inputs and outputs of the preamp.

http://www.mixposse.com/attach/CB01.jpg
http://www.mixposse.com/attach/MP01.jpg

What value of cap would you use for rf bypass at the point where the
wires from the XLR enter the PCB?

The HV-3 had the pin one ground at the PCB about 4 inches inside the
case.... I had trouble with it before modification in a venue with bad light
dimmer noise. I have previously had problems with an Ampex mixer picking
up an FM broadcast station about a mile from the transmitter prior to it
being modified in a similar fashion.

Regards:
Eric

Thanks again for your input!
Roger Foote