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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: Tube eaters. posted by Poindexter on July 30, 2006 at 14:41:37:
Several causes; you hit the primary cause right on the head; the tubes are run at or near max voltages, but more importantly they are run SO FAR up on their plate curve in the AIs and many others that they just roast. Unnescessarily. Preamps like the Audio Reasearch SP10 are much easier on tubes (comparatively) The second major cause for tube eater phenomenon is that often the 7308s (or whatever version 6DJ8 type) being used are not CURRENT MATCHED per triode half; combine that with low or no negative feedback that would normally go a long way towards correcting this and other issues and the tubes die fast. Essentially the high current side becomes a "current hog" and radically overdissipates-- this of course reduces the high current section to junk quite quickly, but it also impacts negatively the low current half. Also after the higher currrent section wears way down, now the OTHER half becomes a current hog and thus the entire tube, which should (and does when PROPERLY selected and used in a proper design) last OVER 10,000 hours can toast in as little as a few hundred hours! OUCH for those who tube up with Telefunken CCa and other big $ tubes! Transconductance matching simply doesn't cut it in certain demanding designs. Personally, I cannot justify such designs as there are many ways to reach Valhalla without popping off 12 $350 tubes every 6 months!
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Follow Ups
- Re: Tube eaters. - ARC 14:57:54 07/30/06 (1)
- Understanding. - Poindexter 15:44:41 07/30/06 (0)
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