6SN7 tube question

Andy is great. But, has top-notch NOS tubes...is expensive...knows he is expensive... and thinks he is worth it - having bought $1k worth of tubes from him, so do I. By all means, get a price.
However, for someone who is concerned about $6 and has a $1k -$2k preamp, it may be a better recommendation to more directly answer your question with, "Low noise and microphonic, and matching".
Additional consideration- The Tube Store , new tubes mainly, and online audiogon Quebec vendor, "Mathieuvarian", NOS, have proven themselves as well.

Ask how they test their tubes, especially for noise and microphonics.

Thanks everyone. I'm a bit frustrated as I've had to replace the tubes just about once a year even though I listen on the weekends only, and my understanding is that the 6SN7 is one of the most reliable tubes and should last longer than that.
Sounds like I should give Andy a call.

There are three kinds of 6SN7s: GTs, GTAs and GTBs. If the circuit needs one of the latter two and you have been installing GTs, they won't last very long. GTs don't handle as much voltage.

We've been recommending Andy for decades- he is an excellent source.

Ralph (Atmasphere) beat me to it, as I was just about to post the same comment. The GTAs and GTBs are rated to handle considerably higher plate voltages and power dissipations than the GTs.

But be aware that there are some current production (not vintage) tubes identified as 6SN7s, with no suffix, which meet GTB specs, at least supposedly.

Regarding the original question, I would go for matched/balanced/low noise/etc., as that could very conceivably make a difference.

Also, FWIW, I've been very pleased with ca. 1950s Sylvania 6SN7GTBs in my amp, which I believe requires GTAs or GTBs.

Best regards,
-- Al