The Hear Technologies Hear Back Mixer is a personal mixing station that is used for monitoring while you are recording. It allows you to control four stereo pairs of tracks so you can dial in your own comfortable mixes while you are recording. I've been using the Hear Back system for about a year and I've found it to be a useful system for recording. It has nine knobs in total - eight that control four stereo pairs, and one to control the overall volume being sent to your headphones. It also has four link buttons so you can either control each track with the two stereo knobs, or just control one if you have the link button off. It has two inputs for headphones and also has 1/4 inch two line out jacks and a stereo aux input. The Hear Back Mixer is sent via ethernet cable to the Hear Back rackmount that is hooked up to your outputs so you can send your tracks to the system. Overall, I have found the Hear Back mixer to be well designed and haven't had too many problems using it at all. The price of these is pretty reasonable, and if you are going to buy the mixer you also need the rack to send this to. The whole system isn't too expensive, especially compared to a superior system like Mytek's Private Q. While I definitely prefer the Private Q over the Hear Back system, Private Q is much more expensive. The reason I like the Private Q better is because you can control more tracks, rather than just four stereo pairs on the Hear Back. All in all, I definitley recommend the Hear Back mixer and monitoring system to those bigger studios that might need something of this nature to monitor while they are recording.