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kt88 base temperature

hi , the other day I noticed that when I tapped the side of my tube amp , I could hear my output tubes ringing and rattling, as if they were rather loose. I know that loose
connections are not good for sound , it causes distortion.
so my solution to dampen the tubes was pure silicon tape, rated to at least 500 degrees rapped around the base of the tube, now when I tapp my amp it is dead quite, but I am worried about how hot the base of the tube might get , I dont want melted crap in my amps. has anybody else tried this ? could rapping the metal base at the bottom of a kt88 cause shortened tube life ? If this helps the sound I will let everyone know how It turns out. thanks, chris
chrissain
swampwalker's avatar
swampwalker
5,138 posts
 
What you heard was microphonics. try tube dampers rated for output tubes.
nsgarch's avatar
nsgarch
2,524 posts
 
Since you were tapping on the chassis, how do you know it is a power tube problem? Usually, microphonics develop in the gain/driver tubes (most often the smaller 9-pin twin triodes like 12 (AX,AT,AU) 7's, etc.

Try tapping the top of each tube individually with a WOODEN instrument like an ice cream stick or a pencil (not the eraser end ;-) to find out which tube(s) it really is.

Personally, I don't like dampers, but . . . . My position is either a tube is microphonic or it isn't. If it is, I replace it.
.
4est
507 posts
 
I am with Nsgarch for the most part. Microphonics used to be less of an issue in the day, as they were selected out and often rebranded. If the tubes are truly loose in their sockets (common) you should carefully tighten the pin connections of the tubes. Tube dampers usually shorten the life of the tube by not allowing the heat to escape...
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