Tube Life Question: 12AX7 Drivers

Hi Joe, 10,000 hours is the number i have heard.

I own a vintage Realistic (yes RAT SCHACK) Stereoline/40 tube integrated from the fifties and the 12AX7 drivers are original Realistic tubes. They still test «good» in my Hickok tube tester. How's that for longevity.

Trelja, 10,000 hours for NOS tubes. I have heard that family of Chinese 12AX7's, 12AU7's, and 12AT7's have a considerably shorter lifespan. The good news is that they are cheap, and have low noise, which makes them a good candidate in the phono section

Thanks for the responses!

Yes, the usual number is 2000 hours for output tubes, and 10000 hours for drivers and preamp tubes. But, I have often found conventional wisdom has little relevance in how things actually work. As Goldorak's experience shows, 10000 hours might be just some measuring stick that who knows came up with. I have heard others say this as well.

Personally, I've been lucky when it comes to tubes. I recently sold a pair of monos that had an appreciable number of hours on them, with the original output tubes. As the builder is a friend, he has made the point to me numerous times that he really is easy on the output tubes. When I tested the tubes, I realized just how easy he was talking about - they tested virtually new.

The reason I'm asking is that I recently came into an amplifier that is a lifetime purchase for me. And, I seem to have found the ideal 12AX7 driver tube. It's not new production or inexpensive, and I want to ensure that I have sufficient stock to last many, many years.

Hi Joe- 12AX7s can't make a lot of current, which usually means they get voltage amplifier service in a power amplifier. Using them as a driver tube is quite unusual. I take it the amp is Class A? That would be about the only type of service that a 12AX7 would work for.

Delayed B+ voltage on warmup will also help prolong the life of the tube. You might look into adding this feature if it is not already on the amp.