I have had a Unison Research Unico amp (hybrid) for about three years. Just recently I noticed a squeal coming from the left channel. It basically sounds like a distant tea kettle whistling. The sound occurs no matter what input I'm using (CD, phono, AV). Recently, the squeal has also come out of the right channel, though not as loud. It's not a very loud sound and is not always present. Of course, I would like to solve this problem. I've done a little research and will probably just swap out the ECC82's and see if that changes anything. (I have not changed the tubes since I got the amp.) So, I turn to the collective wisdom of the Audiogon Community: any ideas?
That kind of intermittent whistling is probably coming from one of the small signal tubes. As Ncarv mentioned, you can try to reduce microphony by reseating the tube, or you could try tube dampeners. I have that problem, though nothing, except ignoring it, seems to help.