I have tried my RAT phones plugging the 2 black (stereo)ring in the detector and get NO sound at all....While turning the cord around and plugging the single ring (Mono ?)connector atleast gets some audio,,,,,,,it is still weak ,,,requiring a detector volume setting of 25 to be audible,and in noisy areas,,,even 30 is faint......I liked the fact that RAT phones have a DB rating of about 28 ?  To keep outside noise out,,,,but like you said Bill,,,,,RAT phones must have an issue with Minelab machines......Tsk......Too bad,,as they work great on my other machines.........
                Minuites ago I tried a set of KOSS UR-30's  I had laying around that ARE recomended for Minelab use.I got ALLOT better audio volume ,and quality with them,and I will be using them from now on with my Xterra.........I hadn't used them because they let too much outside noise in 22 DB rating ?
              One thing is for sure,,,,,,,,,,,even my RAT phones have better audio,and fit ALLOT better than the ones furnished with my Xterra 70 that I  purchased from Kellyco.. 
 I have heard that TROY Pros ? work good ..