2. amps-preamps
  3. 129043-3520

Tube Life Artifacts

I've been using the same tubes for almost 12 years. They are RCA EL84s (6bq5) in 1959 Leak TL12 plus monoblocks. Recently, I have noticed that one channel seems to be "deeper" in soundstage, almost like there was more reverb on that channel. It's a mild difference, more noticeable on some recordings than others. This difference is consistent with both vinyl and CD, and switched sides when I switched the speaker connections.

Is this evidence of tube deterioration? I have a set of unused Philips tubes somewhere in the basement (made by Mullard, I believe) and I'm about to switch them. If I can find them...
dragunski
dragunski OP
113 posts
 
After swapping tubes around, the problem seems to have disappeared. I also tried the tap testing, with no obvious differences. Perhaps I should try cleaning all the pins. A friend of mine suggested that I bring him all the tubes and he'll test them on his Hickcock.

I have to say that 12 years doesn't sound all that long to me for amps that only get used 2 to 3 times a week. Maybe 15-20 hours? I have radios with 50 year old tubes that sound great, but they don't get used much. 
mechans
3,048 posts
 

I still think it prudent to get some new output tubes.  That family of tubes run hard, and even with limited use, it's time. 

he tap test, no matter how widely used , even by some dealers, isn't a good test. Even the gentle focused tap test isn't what I would use.  A microphinic tube with make bad sounds, when moved and more importantly,  when played- they produce  a feedback sound and ring and they also transmit any physical perturbation. 

As for figuring out which of multiple potential tubes go I would be inclined to remove the suspect and roll in another tube.  That does require a set of "good" back up tubes.

  I was going to say remove and replace but I didn't want to get political.

wolf_garcia
6,796 posts
 
To deny yourself the experience of the "High Fun to Expense Ratio" of tube rolling seems to ignore the fact that life is too short to not at least try to enjoy new things. 
dragunski OP
113 posts
 
I tend to "roll" signal tubes and preamp tubes more than the power tubes. This has made larger differences in my mind. But once I've got it sounding good, across different sources, I don’t want to mess with it.

In any case, just shifting the tubes around and cleaning connectors seems to have solved the problem. But I'm going to find those damn Philips tubes in the basement. It's bugging the hell out of me.
mechans
3,048 posts
 
You really should get those Mullards or whatever Philips brand you have hidden in your basement.  The Mullards are really good sounding if you like a warmish signature.   In addition  true NOS command serious money these days.
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