The Mackie Big Knob is a routing system and controller for your digital audio workspace.  It is designed for home studio owners to have total control over their inputs and outputs in terms of monitoring.  It allows you to have a few sets of monitors going at one time and switching between them with the push of a button.  It also has two headphones jacks and three separate monitoring sections.  In addition, it has a talk back microphone built into it so you can use it for that as well.  There are tons and tons of connections in the back for all sorts of monitoring, most of which are 1/4 inch connections.  On the front of the unit there is a meter that monitors your overall output and will show if your signal is overloading.  You can select the input source on the front if you choose to, but I don't really use this feature of the Mackie Big Knob as I have other means of routing my inputs.  The 'big knob' itself controls the master volume output and there are buttons for mono, dim, and mute that concern the overall master output.  The unit is powered by a standard power adapter that comes with it and it is nice that the unit is small enough to carry around so you can bring it anywhere if you choose to.  While most of the features are pretty useful on the Mackie Big Knob, this isn't a necessary piece to your digital audio workstation as Mackie would like you to believe.  While it can be helpful, it is by no means needed to run your studio and for this reason I probably wouldn't recommend it to home studio owners unless you have a bunch of different monitors that you would want to easily switch back and forth between.  The price is too much for this to be used otherwise, so I recommend to keep this in mind when considering buying the Mackie Big Knob.