OK, I'm tired so I hope this makes sense when I am done.:D
I recieved some tubes I bought from 2 different sellers the first set are Siemens CCa tubes and the second are some Siemens E88CC tubes. Both sellers claimed they were tested in a tube tester and for microphonics, etc. I switched out the Amperex Buggle Boy D-getter 6DJ8 tubes and I installed the Siemens this afternoon and turned on the BAT VK-3i. Started playing "Hidden treasure" by Traffic with no problems. I then switched to Robert Plant's Shaken N' Stirred and finally Plant's "Fate of Nations" CD. I played the first 2 tracks no problem. I skipped to "Memory Song (Hello Hello)" and the last part of the song the final note(s)? kept ringing through the speakers after the song ended. I got up and walked up to the CD player and stopped it. The note continued to "ring" through the speakers. I then turned the volume all the way down on the preamp and the "ringing note" stopped. I turned it back up and the not continued to ring. I muted the preamp and it stopped. Unmuted it and the note was still ringing. I finally shut down the preamp and waited a few minutes and turned it back on....No ringing.
I continued playing "If I were a carpenter" from the same CD. No problem. I played the bonus track "Colours of a Shade" and again toward the end of the song a note was ringing again through the speakers. I tried the mute with the same results as the last time. Volume...same. I then thought if it's a microphonic tube, when I tap the preamp case it should ring. I did lightly tap the case and sure enough one or more of the tubes made a ting sound. The ringing note stopped ringing. I tapped again on the preamp case and ting-ting again.
My question is: Can the audio from some speakers cause a microphonic tube to "ring" a note through it? I have never had a problem like this before and I have been using tubes for about 12 years now. Any help would be appreciated.