[R-390] Sub 6AU6 for 6BA6? (or 6AK6)

[W. Li]

Tim:

I can not comment on your proposal....... BUT there is
a published older article re 6AU6 sub for a 6AK6 as
output audio, that appeared in HiFi Annual Audio
Handbook by Lawrence Fleming back in the 50's. It
involved dropping R614 from 560 to 220 ohms, and
adding a 33K ohm screen dropping resistor. He claims
that the audio output for 1.5v audio input would be
360mW as opposed to 65mW for a 6AK6. Seems to me that
it'll be an interesting exercise to see if that would
make any "rational improvement" over what the Collins
engineers planned. 

Frankly, I suspect not, and the idea of taking off the
signal from the diode load jack is much more appealing
for much better "hi-fi" as Chuck Rippel says.

What I eventually did was merely jumper R101
(connecting contact 6 with 8 on TB102) to gain
significant increase in phone audio output with no
alteration of the underlying Collins circuitry.

Thanks

W. Li
Mercer Island, WA

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