Ringing from the tweeter

Hello fellow Audiogoners,

The ringing began about a year ago or longer in the left tweeter. It sounded like tuning in to radio stations in the old days, which I attributed to my Rogue Audio 99 preamp's tubes going bad. At first it was intermittent, then more and more present. It was audible and annoying when changing sides or records, even with the volume all the way down, but not apparently audible with the music. I had a rare listening session when the ringing was not there, but once it began it was pretty much always there. Muting the preamp would get rid of the noise so I assumed the problem was the preamp tubes, not my M-180 tube monoblocks.

About a month ago, I installed new tubes in the preamp, four NOS hand-picked and thoroughly tested by Andy from the VTS. The tubes are dead quiet and sound terrific, but just a week or two after I put them in, the ringing from the right tweeter this time began again, first intermittent, now pretty much constant, just as before. Again, muting the preamp gets rid of it.

Andy told me that the 6SN7 tubes should last years so I'm quite upset the problem returned so fast. Any idea what may be causing the ringing other than the new tubes going bad so fast? Is the preamp somehow “overstressing” the tubes, for lack of a better word, and needs to be checked out? The tubes are the type that can handle higher voltage, btw. The only other source would be my solid state phono preamp or the cartridge, which I think is rather unlikely.

I’d appreciate your opinion or suggestions.