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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: Biasing anomaly for old audio research amp posted by Leslie Loh on April 20, 2007 at 08:33:43:
HI,
I just replaced the 32 tube set (20 6550's) in my ARC D-250. The output tubes were biased at 65ma for their entire life. For the first time I bought the replacements from ARC. Yes, expensive. Worth the money? Time will tell. I can say the new set sounds great.I have a timer set up so I can keep track of tube hours. I recorded 2002 hours at the time of replacement. I checked all the old tubes on my Hickok 539B tube tester after replacement.
Additionally, I checked the tubes when they were new and then every 500 hours (and also the bias which never changed) and kept the results in a spread sheet so I could see performance changes. They proved to be remarkably stable. After relacement, three 6550's were showing deterioration using the testers life test but the reduction in emission was not really serious. All of the remaining tubes did not need to be replaced yet. I did it because I felt I would be seeing tube failures soon. But maybe not. Only the cosmos knows.
I don;t know why you are getting poor tube life. Could it be that you are underestimating the hours. This is very easy to to. I say get a timer. Every tube amp owner should have one. All I know is your experience does not match mine.
BTW, ARC drives their tubes pretty hard. Compare ARC's 65ma bias to, for example, VTL's bias and you will see. ARC is not known for long tube life. VTL, OTH, is.
Sparky
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Follow Ups
- You should expect at least 1500 hours - Karma16 08:29:41 04/21/07 (0)
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