Actually, YES! The SUB 1 and SUB 2 outputs are TRS (Tip, Ring, Sleeve) insertion type jacks that double as line mixing inputs that take the input from the outside world and passively mix those signals so that they show up on the MAIN outputs. To use these inputs, you have to insert the plug HALF WAY into the jack, or to the "first click," or use an insertion type cable to send and return from an external device such as a processor or compressor. These inputs are very handy for mixing in effects outputs, or using them to connect additional samplers, synths, modules or drum machines together without using additional inputs on your mixer.