6SN7 tube question

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

Thank you, Al and Ralph. I was actually looking at the Sylvania tubes, but this particular era looks a little bit out of my budget. Circa 1970s is very reasonably priced, on the other hand, and I'd think probably better than any new stuff on the market.