what are the pin outs for the 3.5mm mic jack on the 8400

k4em · May 20

The FHM-3 works fine with the 8400. But my Koss 45 does not work. I created a mic profile with Bias on I see no audio on meter at all. I tried adding the mic preamp to profile, nothing. The SB45 and another boom/mic works fine in my PC and Icom 7300 with an 8 pin adapter. I need the pinouts for the 8400 mic connector so I can make an adapter. Thanks Dave

Geoff AB6BT · May 20

DON · May 21

Here is an adapter I made to connect a cheap logitech computer headset to the mic in jack on the 8400. This should work for almost any headset that uses an electret mic (CM500, SB45, and most of the other electret equipped headsets. I found this drawing on one of the other discussion groups, tried it, and found that it worked. The value of the cap is not critical.

k4em · May 22

I have a Koss SB45 with electret element and it does not work plugged into the 3.5mm Mic jack on my 8400. I made an adapter following the above diagram, except I did not connect Flex Ring Mic (-) to GND. Since the 8400 ground's mic (-) in the radio. I used a 1uf Tantalum with 'positive' going towards the Flex TIP. I've made about 20 qso's so far and excellent audio reports and no RF on signal. I did not turn on the mic preamp just the Bias, I have plenty of audio without the preamp.
Dave k4em

what are the pin outs for the 3.5mm mic jack on the 8400

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