I just received a pair of matched Ei EL84 tubes from Doug's Tubes. They are replacing the original tubes, which are Groove Tubes. The new tubes beep like a metronome. The beeping gets louder/softer as the position of the guitar changes, and as the volume on the guitar is turned up or down. It eventually fades away if I stop playing. This did not happen with the GTs. Doug said he will replace them or refund my money, so I'm not out the $24 for the tubes. But I am curious as to what is going on. The amp is a Crate V16 Palomino. The V1 preamp tube has been replaced with a Mullard AU7, and the V3 has been replaced with an RCA Blackplate AT7, reducing the gain quite a bit. Thanks!