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In the Forum: Audio For Dummies ™
In the Thread: Get, or made up a tube tester, it’s necessary
Post Subject: just keep spending more money on equipmentPosted by hagtech on: 1/27/2007
do two tubes at once then it make sense to have one selected reference tube


I see.  Yes, the digital scope option would work.  I have one, might try it out.  With a 6c33, the VacuTrace has only enough power to trace one tube at a time.  For its built-in dual sweep function to work, the tubes must be completely cutoff at -70V, as their plates and cathodes are tied together.  Otherwise, the currents start to combine at higher plate voltages. 

Hmmm, that gives me an idea.  You can straighten out the curves of a 6c33 by combining the two sections at different bias.  That is, bias the grid of one side 50V lower than the other.  Then ac couple audio signal to both.  Basically, you get the power of one section, but use the other side to improve linearity!  At higher plate voltages the secondary section adds output, thus preventing the rp slope of the curves from changing.  Same for mu spacing.  Might be able to create an uber-tube.

jh

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