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In Reply to: Audio Research or Tube Depot 6922's posted by StephenJK on February 22, 2007 at 06:24:51:
Phono tubes must be rigorously tested and specifically selected for low noise for best results. And this goes double or tripple if we're talking about MC phono sections. There is SO much amplification of the signal going on that even the slightest bit of tube noise can come out the other end sounding like a roaring ocean. If the Tube Depot did not specifically state that they were phono quality and you did not specify that they needed to be phono quality, then you very likely did not get phono quality. Do you have any other non-phono uses for them? If yes, chances are they'll sound okay in lower gain appliactions.
Follow Ups:
Good point, as I mentioned I was hesitant to go back to them. They still list that tube on their web site, and there's no mention of being suitable for a phono stage.The SP-9 is the only tube equipment I have, so the Amperex Holland tubes will likely never be used.
I note the Tube Depot does offer the type as ‘low noise and microphonics’ as well as ‘matched and balanced’. Have a word with the Tube Depot and see if they might exchange. After all, the tube is presented as used, and the use you have made surely is but negligible. Talk to them, you’ll never know what might be accommodated until you do.I have bought ECC88 and E88CC from them, for line stage amplification and transformer-coupled output stage of DAC, and found the examples offered, Tesla in both cases, as matched and balanced, excellent examples.
I should have mentioned that the Tesla ECC88s and E88CCs were NOS.
I'm glad you specified that your tubes were NOS Teslas and not JJ Teslas, because I bought a pair of JJ 6922's from Jim McShane, and when used in my preamp the JJ's are very hissy/noisy. I should mention that with normal listening through speakers the noise isn't a problem, but because of my living arrangments I've been forced to listen to my Quicksilver Mini-Mites through headphones, and it's under those conditions that the JJ's noise has become objectionable. I should also mention that when I run my Amperex 6922 PQ's or my Phillips JAN 6922's in my preamp very little noise comes through my headphones, so it's definitely the JJ's that are the source of the noise.
Thanks for the advice, I just may do that. The tubes had about 2 minutes of operational time. If I strike out, I'll throw them up for grabs....Stephen
I have purchased tubes from Tube Depot for my AI L2. I purchased
Sovtek matched pairs and specified low noise. They were very low noise. Worked great. In regards to JJ's---you need to specify
low noise for preamp. If not, you can get noisy tubes. If they
come noisy---send them back. But low noise must be specified.;
I learned after the fact that even low-noise JJ's are known to be noisy, so there's not much I can do about it. In spite of the noise the JJ's do sound pretty good though.
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