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OTL Asylum OTL, Output Transformerless Amplifier User Group. |
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In Reply to: Re: 12SX7s posted by bryan on November 18, 2004 at 14:42:30:
First of all, the "N" in the acronym "NOS" stands for "new", meaning never used. So when you first said that your tubes were NOS I assumed they were never used before. (The term "used NOS" is an oxymoron.) In fact, I think I wrote back on ASOG that your test results might indicate your tubes were not truly NOS but were in fact used ones. If you found bad tubes among a bunch of used ones, that is no surprise. Second, you apparently found that a majority of known truly never used NOS tubes tested OK in your friend's tester AND work well in your amps, so there is no discrepancy between your experience and mine.BUT what I wrote yesterday was just to confirm that one cannot necessarily rely on a tester like mine and most other Hickoks to select tubes for matched sections because of the big difference between the plate voltage developed in a tube tester and the typical plate voltages developed in actual use (probably much higher in the latter case). Tubes are nonlinear devices; you cannot necessarily extrapolate performance at one set of conditions from measured performance at another set of conditions. It just so happened that testing in my Hickok seemed to correlate with function in my amplifiers, but results could have been otherwise. There are a rare few testers that do permit the application of selected plate voltage and bias voltage and with which one can truly emulate the conditions of actual use in an amplifier.
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- Re: 12SX7s - Lew 07:11:11 11/19/04 (0)
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