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No manufacturer of tube gear would survive a year if the tubes lasted only three months !





PHOTO: Oracle III,SME V, AQ200 / Cambridge Audio 640C v.2/ McIntosh MR67 > Audio Research SP10 > Audio Research D115 > Vandersteen 2C. Interconnects are Audioquest King Cobra, and Speaker Cables 12' AQ Rocket 88 72V DBS. Oneac 11 Amp power conditioner for sources and preamp. Nitty Gritty 1.0 record cleaner.

Allen Wright,

I have owned two all tube ARC preamps the 12AX7 based SP8 since 1985 and the 6DJ8 family based SP10 since 1987. As far as I'm aware, the SP10 pushes the tubes along harder than any of their designs- and this was demonstrated to me when I tried Amperex white label 6DJ8s that made a greatr sound- I think 6DJ8's have a better sound than either 6922's or 7308's, but only lasted 10 hours before going noisy. So yes, if you use the wrong type and left it on all the time, the SP10 can eat even some respectable 6922's in a few months. A poster here, Thom used to write that he had such piles of Amperex Bugle Boys 6DJ8s that he didn't mind that they lasted only a few months, but he knew the score and that this was deliberately sacrificial. However, when the tubes are correct- quiet and can handle the current- they last a long, long time. A friend in Van Nuys, CA bought his SP10 at the same time as I- 1987, he is using that preamp today with a VS55 and all the SP10 tubes were put there by ARC in 1987. Certainly, it's got the Sovtek sound- a bit dry and not to my sonic standards either, but that SP10 is dead quiet- there's no question they worked that well because the tubes are correct- and he doesn't leave it on all the time! In addition, the SP8 has all it's original tubes from 1985- that's 25 years. To be fair, I did not use it for a total of about eight of those 25 years- should I have left it on continuously during that time? With the D115 power amplifier, I am on my 5th set of output tubes since 1985, but the 6922's and 6FQ7's therein date from a 1995 visit to ARC.

My and friends' experiences with Audio Research tube preamps seem to present a clear indication of the reason not to leave a tube preamp on all the time.

No manufacturer of tube gear would survive in business for a year- as ARC has for nearly 40 years- if the tubes lasted only three months! If that were true in general, it would sweep through the audio world in a few months. Audible Illusion Modulus series are said to require rugged and quiet 6DJ8 family tubes and as they did start to have complaints from people who tossed in any old thing not having satisfactory results, AI published on their website a guide to tubes that work well in Modulus series preamps. Do you assert that AI owners would have longer tube life if they left them on permanently? Do you ascribe to some kind of sloppy engineering standard that any preamp be capable of successfully using any tube as long as it's the proper type?

Please, if you wish to make a dramatic, sweeping claim that Audio Research preamp tubes typically last only three months, support it by citing the models of preamps and the exact version of the various tubes used. I can only guess the rapid failure was from either an improper tube type or the illogicality of leaving the preamp on all the time.


Cheers,

Bambi B



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