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Re: Tube rolling...I'm a happy man

Posted by Lew (A) on September 17, 2004 at 06:52:42

In Reply to: Tube rolling...I'm a happy man posted by JRF on September 16, 2004 at 17:17:05:

If the differences are that profound, I would guess that your previous set of 12AX7s may have
been worn out and in need of replacement.

I agree with Jack re the wonderfulness of an Atma preamp, but I don't think it's a good idea to
run tubes at more than about a 10% variance from the recommended filament voltage. (Jack says
he runs his 5751s at a filament voltage of 10.7; but a 12.3V filament probably should not be run
at less than 11V for prolonged periods of time.) Inadequate filament voltage over a long period
of time could result in "cathode stripping" and shorten the lifespan of the tubes. Also take note
that a 5751 is NOT electrically identical to a 12AX7, and it will work well in most circuits
designed for the 12AX7, but probably not all of them.

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