Tube Life Question: 12AX7 Drivers

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.

I'm honored by you checking in on this thread, Ralph! Been meaning to call you as it's been a while for us, but I wanted you to have a chance to reenergize after CES first...

The three Jadis amps I have owned all use 12AX7; the Orchestra Reference, DA30, and DA60. The JOR was Class A/B, the other two are Class A. I never rolled the 12AX7 in the JOR, but my experience with the DA60 has proven it has quite an effect on the sonics. The DA30 was not so pronounced.

As usual, you are most perceptive. The amp in question, the DA60, does have the Standby/Operate feature, as does my M60 monos. And, from the experience with my Atmas, I generally power up, wait 1 - 3 minutes, then switch to operate. Not sure if it makes a difference on shutdown, but I also find myself doing the reverse for what it's worth - which may be nada.

Depends on the tubes - I know the NOS RCA black plate tubes last about 5000 hours (input tubes) while others are supposed to last 2000 hours.

12AX7 driver tubes in my amp (SEP Class A circuit)5-6 mounths last (3-4 hours listening a day)they are EH 12AX7s
preamp tubes are 12AU7 and power tubes are KT88 and they last
atleast a year but driver tubes getting dull,dry and lifeless
in 6th mounth. I do not know why?

Ben, not to be a wiseguy, but you might want to check either the guy you're buying tubes from, the bias settings on that amp, or what the voltage coming out of the wall actually is. Honestly, you are seeing probably the worst tube life I've ever encountered.