As it might be immediately obvious, you can use non-USB PC microphones
with the K2 by using a straight through microphone jumper block and a
stereo line socket with pin 1 on the microphone connector connected to
the tip connection, pin 8 connected to the barrel and pin 6 connected to
the ring, through a resistor (5k6 seems good). (The Elecraft
configuration, with the ring unconnected, should also work for most,
i.e. electret ones.)
The PC microphone logic seems to be that electret microphones have ring
and tip connected together in the plug, so the resistor provides the
load and pull up for the internal pre-amplifier, and dynamic ones use a
mono jack, which shorts the resistor to ground. Using the pure Elecraft
configuration will put a DC bias on the dynamic microphone, which might
not be good for it. (I suppose there could be microphones that use the
ring but don't connect it to tip.)
As always, electret microphones are preferred, as dynamic ones have
rather a low output level.
Obviously, you have to use them VOX, or use the key input for the PTT
function. You could wire a separate switch on the microphone connector.
I haven't evaluated the RF tolerance of PC microphones, yet.
Incidentally, I was surprised to find that the shell on the microphone
connector is floating, although I was aware of a mod for better
grounding, although that is old and says that better support for
grounding is planned.
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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