I have a J&M headset and a Zumo 550. I tried the CB adapter cable from J&M (had one here) and it was horrible - no volume, all distorted, etc... I suspect an impedance issue was to blame.
I'd like to use the headset I've already got with my Zumo 550 so I can get more than just outbound audio (using earbuds now) from it. Is there a love connection that can be made here?