Best Tubes for Audible Illusions 3 Pre-Amp

This is what I love about this site, So much detailed information from knowledgable sources. Thank you all! Imin2u, I will be waiting for your review on the different tubes you will sample. For the record, I never had a problem with the AI in stressing tubes. I had the same pair in for years. The unit actually sends a small charge through the unit keeping them "warm" so when the unit powers up it does not "shock"the tube. Again all, Thanks.
Basil

One thing to keep in mind - I Never turn the power off on Any component (except the turntable). I never even "mute" the AI 3A. I feel, with all electronics, that it's the warming/cooling./warming effect that kills components. I may be wrong but it works for me.

I must second Imin2U's last comment about keeping hi-fi gear powered up.

The proprietor of one of the high end's more noteworthy and successful tube gear companies explained to me that the studies done in the 1950's on tube wear all confirmed that small signal tubes such as those used in preamps and DAC's last much longer (and as a corollary, also sound better) if powered up 24/7. Basically, he said that, if left powered up 24/7, they either die at some point in the first 250 hours (infant mortality of sorts) or they basically last forever.

I leave all of my equipment except turntable and tube amps powered up 24/7. Over the years, this has included a tubed DAC (Cal Audio) and three tube preamps (Jadis, CAT and Hovland). In fourteen years combined of these tube components being left on 24/7, I have never had to replace a tube (nine years now on the DAC), nor has any of my equipment, tube or solid-state, required service. As for the preamps, when I am not listening to them, I am careful to keep the volume turned all the way down and the mute engaged.

Tube amps cannot be left powered up because the output tubes pass a relatively large amount of current that stresses the tubes, and do last longer if turned on and off.

As a general rule, however, I believe that Imin2u is correct -- it is the thermal cycles that occur when equipment is powered up and down (i.e., repeated expansion and contraction of the components as they heat up and cool down) that kills components, even tubes - it is basic physics.

Surfgod ... You may have had that experience with your AI with the factory tubes as they are selected to withstand the design - but choosing many of the standard NOS tubes that sound so good elsewhere may not be possible due to the "on the edge" design. Again, I am dealing from hear-say and someone else should elaborate on this point.

You know Ez2hear I just re-tubed my whole system. In the AI, I put a quad of Tunsgram ECC88, In my amp, Sonic frontiers 80 I put as drivers Tesla Ecc88 (NOS) and EH KT-90. The pre-amp tubes sound wonderful. I do not believe the improvement. I am waiting for the KT-90's to burn in (400 hrs burn in time I hear) I am also turning off my pre-amp when not in use. I have not had any problems with my old pre-amp tubes, but only time will tell. Thanks for the tip.