gofar99 Messages: 1969 Registered: May 2010 Location: Southern Arizona
Illuminati (5th Degree)
I Just posted this on another site ...but it seems to apply to this thread.
Hi Everyone, as most of you know I use lots of tubes. Just this week I ran into an issue with KT120s that was rather surprising. I had moved my quad of amps to a shelf behind the the main speakers and slightly off to the side of the subs. The sound was off. I heard a sort of harmonic distortion in the approximate 2K range that was not there before. I accidentally bumped one amp and a sound came from the speaker on that side. I then tapped the tubes. Sure enough all 8 of the KT120s were microphonic. Some badly so. The sound I heard was them "singing" when the music got loud. All are early production ones and have many hours. I don't know how wide spread the issue is ...but if you are using some and get some strange sonic effects you might check it out. Putting the amps where they could not pick up any vibrations stopped the problem. Newer production ones may not do this.