The VMDA-4 2-Channel Multi Format Audio Monitor from Wohler Technologies permits selectable monitoring of analog or AES sources, with excellent full-range fidelity far exceeding that of an ordinary monitor in a 1U rack-size. The unit monitors up to 4 stereo analog or AES audio sources. Individual lighted push buttons select and indicate which of the 4 sources is being monitored. Two or more pairs of the analog inputs may be summed (as pairs) by pressing the desired buttons simultaneously (note that AES inputs cannot be summed).