high frequency intermittent noise

@whart Are you thinking tin foil as well?

@james1969 - no, I was not. I was thinking of that braided stuff that is sold by electronic parts wholesalers or specialty suppliers, like the guy that sells the Duelund? cable that in certain cases needs shielding.

I reserve tin foil for hat lining, but make sure it covers the back of my neck. :)

Jea48 11-17-2017
...how about when james1969 used the pro-audio monitors for the test. When he hooked them up he heard the same RFI noise. Just a guess the amps are SS.

Yes, I had thought of that, and the fact that the same noise occurred with both amps does make it seem less likely that the possible absence of stopper resistors is a factor. But note that Ralph’s comment referred to the use of such resistors in solid state as well as tube designs. (Of course, in the case of a solid state design they wouldn’t be referred to as "grid stopper resistors," that being the term I used in connection with James’ tube-based Lamm amplifiers).

Best regards,
-- Al

Tin foil had no affect on the power cord.

For those who thought the noise is GSM, I did correlate the noise with the Hf35c Rf Analyzer, but the device only correlated the noise, did not show me the frequency.  I think it was a defective unit in that the display did not work properly.