Jea48 11-17-2017Yes, 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).
...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.