Just got this to see how it would work to make me sound like the commercial stations do...quite a difference! Instead of having a "thinner" sound and having to be significantly "quieter" than the other stations, or go into bad distortion, this does dynamic compression and gives the sound more "body". A switch can disable the active circuitry for bypass so you can compare the sound normal from source to transmitter and then hear the difference when the compressor is activated. The compression is achieved by 16 different presets that vary the amount of compression and other effects and an LED meter shows the amount the dynamics are being limited. Works in stereo or mono, simple 1/4" jacks in and out. Adaptor audio cables take the 1/8" stereo jack to two 1/4 jacks. Good quality and adds no noise or hum. Not bad for $40. Alesis has something similar but doesn't have the front panel meter to let you see what's going on. Takes up little space, weighs nothing and does the trick.
Mark
I used one of them for a while before I got my Behringer Ultramizer. It worked well. I now use the Minicom on my monitor spoeakers. It evens out the sound so you dont jump whem a loud track comes on.