The Aeromix 2+2 DC Mixer was designed specifically for Fitness instructors - the Aeromix has a limited number of knobs, yet gives instructors the ability to adjust the tone quality of the microphone independently from the music tone.  This allows instructors to adjust any feedback issues out of the microphone mix without effecting the music quality. The Aeromix is easy to reset on the fly if instructors have sound issues, preventing costly and timely service calls.  There is a front panel i-Jax input for the latest brands of MP3 players, eliminating the possibility of eager instructors digging in the back of the sound system for an auxiliary input jack.  Using an auto-sensing circuit, the Aeromix knows when you plug an MP3 player in the front of the unit and switches the source control for Music 1 to the front input.