I recently upgraded from a Flex 6500 to a 6600. I use a Yamaha CM500 headset as I find it more comfortable to wear for long periods than my Heil Proset.
The 6500 uses an 8 pin Foster-type connector on its front panel for microphone and PTT connections. I had wired up an adapter for the CM500, which uses a 1/8” TRS (tip-ring-sleeve) plug for passing the mic signals and the +3vdc the CM500 needs for biasing its electret mic element.
The new 6400(M)/6600(M) models use a 1/8” TRS jack on the rear for pseudo-balanced mic connections. The tip is Mic(+) and passes +3vdc when “bias” is activated in the SmartSDR settings (Phone/CW tab). The ring is Mic (-) and the sleeve is Ground.
I wired a new adapter consisting of a 1/8” TRS jack (to receive the mic plug from the CM500), three wires, some heat shrink tubing to cover the wires, a 10μF capacitor and a 1/8” TRS plug that goes into the 1/8” TRS mic jack on the 6400(M)/6600(M). Here’s how it is wired:
The value of the capacitor is not critical. I used a small 10μF capacitor so I could fit it into the shell of the 1/8” TRS plug at one end of the adapter. The capacitor allows the Mic(+) signal to pass through from the CM500m while blocking the +3vdc bias that needs to be applied to the ring of the CM500 mic plug.
I know there are a number of Flexers who use the CM500 headset and who plan to upgrade to a 6400(M) or 6600(M). If you’re using one of these headsets I hope this brief “how-to” will help make the transition as quick and as painless as possible.
Dale – K4DG