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

Showing 4 responses by unclejeff

unclejeff
1,313 posts
 
I had this problem. The first thing I did waw to reverse my interconnects to see if the sound moved from right to left. In my case it did not so the problem was in the amp.

Next, I reversed all of my tubes in the amp to see if the sound moved and i did this to see if indeed the problem is a tube or some other connection. The noise moved.

Then it was just a matter of time as I traded pairs of tubes until the sound moved again. I nest moved just one of the tubes and the noise moved again. Bingo!
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.
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.
unclejeff
1,313 posts
 
If you ever get a chance to try a pair of Mullard 12AT7 tubes you will find some improvement in bass on the 2102.
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