[Elecraft] fixed audio for K2

[jeff_elecraft@burnshome.org]

I am investigating the best way to get a fixed level audio output from my
K2. EA3BLQ has designed a nice digital interface, but it has more
functionality than I need. Several people have tapped VOL2 on the front
panel board to take audio to the microphone connector. I prefer to have a
connector on the back panel, and include the side tone.

Receive audio and the side tone comes together at the audio amplifier U9 on
the control board. Is VOL1 (pin 2 U9) level fixed? If so, could a second
LM380N-8 be installed on top of U9? Pin 1,2,4,5,7, and 8 would connect
directly to the part below. Pin 3 would connect to ground. The fixed level
audio would be at pin 6.


One concern is the current the extra amplifier will draw when nothing is
attached to the fixed output connector.  If I understand the data sheet
correctly, this could be as high as 25mA. Is there another part that would
be a better choice? Is there a connector available with a switch that would
power on the amplifier when a cable is plugged in?


My understanding of how this all works is minimal, so I probably have the
details wrong. Can the concept work?

Jeff Burns
AD9T