A-138m Matrix Mixer
Doepfer A-138m Matrix Mixer
The Doepfer A-138m is a 4x4 matrix mixer with switches for unipolar / bipolar mode for each column. Unipolar means that the controls work as attenuators. Bipolar means that the controls work as polarizers. In this mode the amplification is zero in the middle position of the corresponding control. Turning the knob anticlockwise from the centre position the signal is subtracted from the output sum with increasing amount (i.e. negative). Turning the knob clockwise from the centre position the signal is added to the output sum with increasing amount. The module is DC-coupled and can be used for both audio and control voltage mixing.
By means of an internal jumper one can select if the four upper controls work as DC offset generators - provided that no patch cord is plugged into the upper input socket. If this feature is not required it can be deactivated by removing the jumper on the top left of the pc board.