In 3f42d748.7307582@nntp, (Space Charge) wrote:

Need some informed opinion, as I've heard various things about finals
that use two 6146's, like my TX-1 Apache:

1. Make sure the transconductance on both is very close.

2. Make sure the plate current on both is very close.

3. Make sure BOTH are close, especially the plates, which should be
within 2ma, and _both_ should be either 6146, 6146A, or 6146B. Don't
mix types.

4. None of the above matter, so long as both test well on a good
checker. (I use a Hickock/'Hiccup' 539B.)

Can someone shed some light on this? What's correct?

Thanks to the group in advance,

Lin/KJ6EF
For email responses, remove "nospam_".

My understanding is that they should be matched to equalize the current through
the tubes. The way I match power tubes is by measuring the plate current of each
tube while in the amp -- first with low drive, then at full power. That method
has worked just fine for me for many years.





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