Forget about anything other than Tele smooth plates. They cost a lot, but they sound so much better. Recently put them in my cjPV-9A. Phono has never been better.
I would direct you to the AI website where the designer/manufacturer addresses this question. I would also suggest "Joe's Tube lore" over on Audioasylum. I've used both an M3 and a L1 for over 5 years and have tried many tubes. Due to reliability and value concerns I now use only NOS Tungsram 6922 or NOS Russian 6H23n-EB. Both work well and last a long time. The Tungsram has a warmer sound, tends to cost more (and keeps going UP in price), and doesn't last quite a long. The 6H23n-EB is more neutral (or brighter depending on your perspective), is available from several sources at reasonable prices, and lasts the longest of any tube I've tried. I have not had good luck with many of the very expensive NOS and would not recommend spending the big bucks on them for use in the AI. As always, this is just my opinion based upon my tastes and my experience.
I will be able to provide a detailed review by the end of July. I have bought multiples of the best reviewed tubes on the Web. (Three review sources including Joe's).
This includes pinched Amperex 6922's, grey-plate Seimans CCa's, Telefunken E188CC's, white SQ's, white and orange PQ's, white E188CC Miniwatt's, orange globe 6DJ8's, and many, many more. (Yes, my wife is pissed).
I have bought two pair each and a tester to ensure proper matching an ability to give each type a second chance. (Yes, really pissed).
I plan to give each tube a couple days of play and also do some immediate tube changes for comparision.
It is important to also note that I have Never had problems with my Audible 3A burning out tubes. The white Amperex 6922 JAN's that were in the driver positions for 3+ (maybe 4) years are Now driving my phono the past 6 months. Boy do they sound great as phono drivers!
You should talk to someone who knows, I am just passing along something I remember hearing, and that is that the Audible Illussions unit, through its design, stresses tubes much higher than almost all other designs and therefore severely limits your choices for replacements as many, many tubes will fail in this circuit in a matter of weeks.
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.
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.