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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: how close should the mA matching be on power tubes?does it matter posted by blazter on November 2, 2002 at 04:52:28:
Hi Reg,
To achieve the maximum in sonics and stability, and create the easiest load on the power supply, it helps to have power tubes that are matched in transconductance and current draw. Typically, all tubes falling within a 5% spead would be considered a pretty tight match. However, there is a school of thought that maintains that mismatched tubes will tend to level out over a period of time. In other words, the stronger tube will tend to "compensate" for the weak tube, and over a period of time the tubes will drift closer together in their demands and their output. I've no practical experience to back this up, but in some ways it makes some sense. The current draw that you're citing is about a 10% match, and that's still not so far off the mark to be really problematic. Most production facilities were shooting for 15% above or below bogey value for the tubes they produced, with tighter tolerances for the premium tubes, so it's said. I wouldn't be concerned with running the tubes you have as a quad, although it probably wouldn't hurt to check them periodically to make sure they're not drifting farther apart, and also to swap them around occasionally so the newer tube shares some time with each of the others. Just my opinion--hope that helps.
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Follow Ups
- It does matter, to an extent. - foolno1@blazenet.net 20:35:00 11/04/02 (0)
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