For mic/phone jacks the following connections are used:
Mic - Tip (PTT), Ring (Mic Audio), Base (Lo)
Phone (Stereo) - Tip (Left Audio), Ring (Right Audio), Base (Lo)
Phone (Mono) - Tip (Audio Hi), Base (Audio Lo)
In your case, with a PMA-4000, you will want to connect the 'audio hi' to both the left and right points on the jack (Just use a small jumper wire). Or, you could purchase a mono headphone jack that only has 2 terminals (audio hi, audio lo).
For your mic jack, there are also two wires for Mic 1 and Mic 2. You will notice a seperate pin that is for Pilot PTT and CoPilot PTT. Those single wires get connected to the tip of the mic jack. A lot of kit builders don't run that PTT line to the jack, only to the stick where the PTT is. Using 3 strand shielded wire allows you to also have the PTT wire connected at the mic jack should you ever need it. If you only have 2 strand shielded, you can just use an unshielded 22AGW wire to run to the jack. PTT lines do not NEED shielding like audio lines do.
To prevent future noise in your audio, be very careful with grounding your shields. Ground them all at the end where the audio panel is, and leave them floating (unconnected) at the jacks. If you don't already have them, you'll want isolation washers for your jacks so they arn't grounded to the airframe though whatever panel your mounting them in. Groundloops are nasty and difficult to fix later on down the road when everything is sealed up.
