I have a wired headset that I love but it has 2.5mm instead of 3.5mm. I went to Radio shack and bought an adapter and it worked but it sounded like crap because the mic on the pre was still working when the headset was plugged in causing echo muffled sound. It was a stereo adapter plug so I got a mono plug to see if that helped but it didn't work at all. Any suggestions. Thanks