Behold, Judah Smith signalled from keyed 4-1000A filament:


I often wondered if an audio filter, or equalizer would help if hooked
up to the radio. I wonder if you could adjust it to improve the bass
response.

I had a jack on the back that sent the audio from the pre-amp transistor
out and in back to the audio power amp IC. One of those things that short
when the jack is out for normal operation and you could plugin audio
processing equipment.

Since I maily DX'd Lowfers and aero NDB's with it, a high-Q filter was a
must. Worked good.

The normal audio circuitry in the DX-200 attenuates everything below 200Hz
for optimum voice reception.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca