2. amps-preamps
  3. 1085115335

How to track down bad tube and what can it mean?

I recently changed the tubes in my preamp and all but the driver tubes on my amp, but these tubes didn't work out. I replaced these with the stock tubes which had been good before. Now I get distortion from the left channel which sounds like a buzzing that comes and goes with the music. It increases with the volume. I've checked all the tubes and they are placed OK. At one point with the volume loud but not too loud the system turned itself off which had never happened before. My speakers are efficient and it was not putting out more than 10 wats max when this happend.

So how can I track down a bad tube if I have one? I suppose I could replace the tubes one by one with the new ones I tried, but this is extremely tedious and makes me dream of SS. Any idea what this problem, this sound indicates?

Any help is appreciated. My sick system depresses me. Thanks.
budrew
unclejeff
1,313 posts
 
McIntosh 2102? I have that amp. The stock tubes used to be Svetlana KT 88 and a bunch of Chinese-made smaller tubes. I understand that the newest 2102 amp has Electro Harmonix Kt 88s, but I don't know what the rest are.

My 2102 sounds great with the Svetlana tubes and I traded out the 12AT7 tubes for some 1960-era Sylvania and the 12AX7A to Electro harmonix. This made a terrific differance as the stock tubes never reached my espectations.

I am told that the Electro Harmonix KT 88s are fine, but if McIntosh is still using those Chinese other tubes, junk them.
budrew OP
467 posts
 
I don't know if I should feel stupid or relieved. I switched speaker cable channels and the problem still occurred in the left channel. I was sure it was not a speaker problem but I checked it out to see what was what. It turns out there is a ficus tree next to the left speaker that had grown a limb between the speaker grill and the bass driver and when the bass driver started thumping some of the leaves were vibrating off of it. Doh!!!

I'll check into the EH KT-88s. My amp is from late last year. I still have the EH tubes and may try them again someday.

Anyway, thanks to you all!
newbee
4,093 posts
 
My hat's off to you!!!!! Talk about a mistake that would be hard to own up to, most folks would be running around looking for a place to bury that one. You're on the honor roll for honesty, if nothing else. :-)
rockvirgo
587 posts
 
As Maxwell Smart would say: the old tree growing in the speaker routine, eh? Glad you solved the mystery!
unclejeff
1,313 posts
 
Being a fellow owner of the marvelous 2102, I had serious doubts it was the amp itself. This thing is built like a tank.
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