Herbie's Hal-O tube dampener's on Calypso?

John, I don't think tapping on tubes is such a good idea. It's very unlikely that this is a proper way of finding the most microphonic tubes. You can probably end up damaging the tubes like that. Here is a pretty cool article about NOS tubes that I enjoyed reading - http://www.soundstage.com/tubeor/tube.htm

Yes indeed, audphile. That is not my std practice but I had two tubes that were ringing like crazy with just loud music so just a light tap was all it took.....nothing crazy!

didn't mean to read you a lecture...

Audphile1: No problem....your comment was right on. I just wanted to assure you that with a very light touch with the eraser end of a pencil, I found the two culprits immediately. I can now crank up the music and not hear the one tube in the Io singing on its own. And now I can't believe how quiet things are when I adjust the volume on the Callisto. Just about ready for JD and Lucinda to come back for more fun.
John

That's cool John. By the way, back to Herbie's hal-O damping instruments. I experimented with them in my pre-amp and found them to work best(improvement is most noticable) when they are installed at the very top of the tube. Installing them in the middle of the tube and things start sounding sterile. Towards the bottom of the tube the pre-amp sounds a little better than with hal-o rings in the middle of the tube but still not as good as it sounds when the Hal-O rings are installed at the top of the tube. How was your experience?