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Nihilist 19th February 2009 03:25 AM

question about twin triode tubes

There are two sets of operating stats for this tube. Is one set of stats for the first triode and the second set of stats for the 2nd triode, or are the two internal triodes the same ? Are these stats just representative of what could be expected with different plate voltages ?

Basically , do the two triodes have the same specs, or are they as different as the two sets of specs indicate ?


Sheldon 19th February 2009 03:52 AM

The two different operating stats, are for two different operating points. They apply to each triode. The confusion is caused by the heading for the interelectrode capacitances shown above the operating parameters. Those are slightly different for each triode, because the tube is not a perfect mirror image section to section. The distance from component to pin varies a little. But, the triode 1, triode 2 heading only applies to the capacitances. Clear as mud?

Now to confuse you a bit more; sometimes tubes contain dissimilar triodes. Of course, those will have completely different operating parameters and are shown as such.

And some tubes, such as the 6922 have identical triodes, as far as an amplifier, but are designed to be used in a cascode. In this case, the tolerance for cathode to heater voltage can be different, as one section should be used for the top and one for the bottom of the cascode. If used a just a twin triode, they are treated the same.


Nihilist 19th February 2009 04:39 AM

Thanks. You hit the nail on the head. I wasn't sure if the heading showing the capacitance for the 2 sections dropped down to the rest of the stats. Now I see .

I was wondering why everyone thought 12AX7's were so great when they seemed to be such a mismatched set of triodes. :xeye:

That clears it up. Thanks again...........................Blake

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