Questions about Preamp Tubes

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.

I've had my Mapletree Audio 2A/SE for > 2 years and no tube issues yet. It is by far the cheapest piece in my system at only $675, but the sound is glorious IMO. If you rank gear by price I guess it is "lower-end", though certainly not by sound.

The only problem with tubes is you might get the bug and try different types of tubes to play with the sound. I now have 5 sets of 12ax7/cv4004 and 4 sets of 12au7/5814a tubes and having a blast :)

"Tubes in preamps normally last 5000 to 10000 hours of playing time"

It makes sense to me that tubes in a pre-amp would have greater reliability than in power amps.

But is it all or nothing? In other words does the system sound the same for this long and suddenly die?

Or do subtle changes for better or for worse occur in the sound as the tubes age?

My guess would be the latter, but I do not know for certain.

Some high end tube vendors like VAC even offer automated health monitoring systems in their products to address this. IS this a frivolous feature that does not add value or the real thing? I suspect the latter.

The first case would not concern me much. The second would, in particular if many tubes are involved. I want to spend my time listening, not having to constantly check tube health if I think something does not sound right.