Tube reliability in amps

How long tubes last in a circuit will depend both on the maker of the tube as well as the circuit design. I've known McIntosh tube amp owners who have left their amps on for years continuously with hardly any wear on the output tubes. My ARC Classic 150's lasted me 5 years on a set of Philips 6550 tubes, where the same vintage tubes barely went for more than 15 months in my Jadis JA80s. But NOS Gold Lion KT88s in the Jadis have gone over 3-1/2 years with very little wear. So no hard and fast rules here.

Of the brands out there now of which I have knowledge, the VTL and ARC designs, as well as Macs, seem to be easy on their tubes; I'm not that familiar with how long tubes last in VAC or CJ products, I'm sure others can comment here.

As far as power goes for your 804s, the only way to really know is to try them out, but if you're not after the deepest bass (and you won't get it out of the 804s, anyway), and you don't have a large room or listen too much at 90+db levels, you'll be surprised how well tubes will drive your speakers. Some of the best sound I ever heard from a pair of Dunlavy SC-Vs came from a VAC Renaissance 30/30 (it wasn't organ music or earthshaking volume levels, admittedly, but certainly a normal listening level), and I remember years ago hearing a pair of B&W 801 Matrix speakers being driven beautifully by Kebschull 35 watt tube monoblocs. It would pay to give some of the manufacturers, like VAC as noted above, CJ or VTL a call and see what they think they have which will drive your speakers (I'm sure ARC's 100+ watt designs would work well on them, but I consider them expensive amps). Good luck--I think given your musical tastes you'd like tubed amplifiers with your speakers.

Check out the Wollcott amps. They have an auto biasing circuit and do not neet to be left on or have extensive warmup, thus a very long tube life. they also are one of the few tube amps with descent bass.

the life of a tube is like a tank of gas. there is a finite amount which is determined most greatly by how much you use it and how far the amp pushed its operating envelope in making the amp (read how much bias required - the more bias required, the shorter the life. i would expect on average that you should get at least 1500 hours on power tubes - up to about 3000 is possible. you should get at least twice as much on the driver tubes. its helpful to have an amp that lets you easily bias the tubes yourself, and if you can do this having matched pairs/quads, is not as important (look for amps with individual biasing for each tube. keeping spares around is like keeping gas in the tank - you won't have to walk.

hey newbie, instead of me calling up a whole lot of manufactuers, can you give me an idea of what is a lot or little bias on a tube, so I can hone in on the guys with longer life tube designs?

drjjpdc, you inquired about tube life - thats easy stuff. there are just too many varibles involved in answering your question re biasing of any particular tube absent a specific application and i am not a resource on the tube amp market.in my opinion you are much better served not being concerned with the life expectancy of tubes but by finding an amp which will sound good with your speakers. after going thru some arc and sonic frontiers amps i settled on a mesa baron - its a fairly powerful and neutral amp using 6L6's biased at 38ma. i have speakers by paragon which are full range and very neutral which are rated 86dba @1watt. using a power stage w/120wpc and a little neg feedback i get the kind of sound i want, however someone with speakers tilted up in the midrange, or high end, would hate it. this is not a testimonial to mesa - the point is you sould consider auditioning push/pull pentode based tube amps with your speakers to find the sould you like. once found you won't care how long the tubes last. cj, arc, vac, cary, sonic frontiers, are all good high end amps to try. if you want to start out on the cheap just to experience the tube sound there is much available and talked about in this and the audio asylum forums.