Curious about using a dynamic microphone on the IC-7300? What you need to know, including a great preamp review, all explained in this video.
So how did you wire it? From the preamp to transceiver: HOT to MIC IN, COLD to MIC GND, and GND to PTT GND? Is it correct? Last time I looked at circuits I didn't notice balanced input (like Kenwood has). Or you've just used interface (external soundcard) to pick a signal from the microphone and then virtually routed it to TRX's built-in soundcard via computer? Phantom power is definitively not needed for dynamic mike however it won't harm it anyway.
