Clive, Normally you have a left and right hot wire and a left and right ground wire. But sometimes you can combine the grounds if the amplifier allows it. If the amp has separate grounds, then keep the connections that way. Combining them in those circumstances can cause you to lose stereo separation on some amps....and on others the amps are not happy campers. On the VR, the 5 pin connection is also wired for microphone.
http://www.venturerider.org/forum/showthread.php?499-Headset-Pin-Out-Diagram
To make a minijack output.....just tie into the left, right and ground wires. You will have to google or search this site for the pin outs on the minijack...I've long forgot that tidbit of knowledge! The rest of that diagram is self-explanatory and not needed for adding a mini stereo jack to system....but fun to read.
Anyway, it's an easy thing to do. Although I simply ordered the edset adapter. I'm tired of soldering!
david