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On Sep 13, 9:18 am, Truth wrote:
On Sep 13, 11:17 am, (Scott Dorsey) wrote:

In article , AndyP wrote:

Does a preamp with a transformer balanced input do a better job rejecting
RF?

Almost always. There are some poorly-designed transformer inputs out
there too, though.

What kind of preamp, microphone, and cable are we dealing with here?
And what makes you think it's AM?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

My chain:

House Power
Ribbon Mic's Power Box
Ribbon Mic's non standard cable, very long about 20 feet( I can't swap
it out to test it with something else)
2 Royer 122V Ribbon Mics
DH Labs 6 feet 110 Ohm XLR
Pendulum SPS1 and Weiss ADC2(has good preamps as well, problem occurs
with both)
DH Labs 12 feet to Computer Sound card DI
Lynx Two C Sound Card

This is in response to the individual who is experiencing interference
with a Royer R-122V ribbon microphone. I just found out about your
problem and want to inform you that the issue is likely due to a
defective vacuum tube. Not any of the other things that you may have
been trying in an effort to cure the problem. The oscillation that
occur randomly (between 6.5K-8.5K) are the result of mechanical design
changes in the 5840 tube. Certain date coded tubes exhibit this
phenomenon. It's a problem that is easily fixed, even if the mic had
been sent in previously for service and still exhibited the problem.
The actual source of the problem was not discovered until fairly
recently. Please contact Royer Labs and speak to Rick Perrotta for a
technical explanation and an arangemnet to get the mics replaced or
repaired at no charge. Our number is (818) 847-0121