Upgraded and ready for action. The best built, best sounding, easiest to use mixer on the market is back. 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 (bass & treble) 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. A new feature is the Sound Ear Brand SPL Meter Input for attaching a Sound Ear SPL meter to monitor room volume and attenuating or cutting the volume (for a user determined amount of time 2 - 60 seconds) of the sound system on those extra loud instructors. For initial set-up, the Aeromix has a hidden Master Volume on the back of the unit to preset the room master volume. The Aeromix 2+2 was road tested and QC'd by the Aeromic lab team for optimal sound quality (clean highs, punchy bass, no low volume hiss) when used with Aeromics, Cyclemics, and E mic microphones and Fitness Audio brand mic systems. Other mixers make promises on features but don't deliver on sound quality - for the best results go with the best. iPod and SoundEar not included.