[Elecraft] K2: Using PC Microphone - How To.

[David Woolley]

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
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