Questions about Preamp Tubes

Peterb is right, although to clock 10000hours or over, you'll need premium types. The pres you mentioned are very well designed. They are anything but tube killers. In my opinion you need not worry but insist, should you buy, that the tubes are in good working order and not noisy in the critical places. A bit of tube rush is normal, but it should not interfere with your listening pleasure, even in very soft passages of music.

Small signal tubes, like the 12AX7, etc.. do last considerably longer than tubes such as the 6L6 in most cases. I wouldn't worry about how long they last because they can go on for years. Small tubes are replaced more often because of defects rather than normal wear & tear.

Tube preamps, in my opinion do sound considerably better! Try and get one that's point to point wired but not 40+ years old. Look for basic models without tone controls and tonnage of bells & whistles. Old is OK if it's been refurbished.

Preamp tubes (as opposed to output tubes in a power amp) are ordinarily long-lived. I can't remember having one go bad in my last three tubed preamps, two of which were by Conrad Johnson.

Audio Research and C/J are always good pieces to find..Tubes aren't usually that big a deal..The biggest question wether tube or s/s is how well the piece has been taken care of and if it has been back to the factory ( or reliable tech. ) for a service check..Keep in mind the peices are old and do need upgrading and upkeep..Also give us more info in the models you seek and maybe we can provide more info................

With tube preamps, tube replacement is not the problem: the above posters are correct about small-signal tubes, and I would add that the studies done in the 1950's all confirmed that longest life and best sound is achieved by keeping gear using small signal tubes turned on 24/7. Why? Most gear uses solid-state rectification, which is very hard on tubes when the unit is powered up. The thermal cycles they experience at power up and power down also beat them up over time. They pass little current in most preamp circuits. For these reasons, they are, generally speaking, best left on.

Tube preamps have other problems, specifically, noise, the inability to drive long interconnects without bass rolloff, and impedance mismatches with power amps, which also causes bass rolloff (I have written at length about these issues in other threads). However, only top-shelf solid-state preamps layer space and have the musicality of tube preamps. Thus, the conundrum.

A couple of suggestions: for solid-state, the Rowland Synergy IIi can be had for roughly $3k used and performs well; for tube, the basic VAC Renaissance preamp comes in around $3.5-$4k used - it uses output transformers that eliminate the problems of driving long cables and impedance mismatches with amps.

Good luck.