The Models 704-IN Modular Matrix Mixers are designed to provide low cost, incremental matrix mixing of audio signals in professional, fixed installations. Inputs can be added, in increments of 6, up to a maximum of 24 (Model 704-IN). The design of the Model 704 is elegantly simple. Input circuits buffer the incoming signal, and pass the signal thru to a series of summing amplifiers. Each input may be assigned, via on-board DIP switches, to any or all summing amplifiers. Each summing amplifier will accept up to 24 separate, line level signals. Matrixes, from as small as 6 x 6, all the way up to 24 x 36, may be created. Other switching cards in the INTEGRA III SYSTEM, for example the Model 703-4 Remote Push-Button Program Selector and Volume Control, may be used to remotely select between custom matrix outputs. Inputs may be used in balanced or unbalanced configuration. Outputs may be used in balanced or unbalanced configuration. Selection of balanced or unbalanced operation of outputs, is made via push-on jumpers.