Module A-138u is a simple, low-cost mixer with two units. Each unit is equipped with three inputs and one output. The upper unit has for each input a trimming potentiometer available that works as attenuator and allows to adjust the amplification in the range 0...+1. In the lower unit only the third input is equipped with such an attenuator. The factory setting is amplification = 1 for all inputs.

The output of the upper unit is normalled to the first input of the lower unit. That way the module can be used also as a mixer with five inputs: for this the inputs 1, 2 and 3 of the upper unit and the inputs 2 and 3 of the lower unit are used. The sum output for all five signals is then the output of the lower unit. As soon as a plug is inserted into input 1 of the lower unit the module becomes a dual 3-in-1 mixer again.

Inputs and Outputs are DC-coupled, i.e. audio and control signals can be mixed.

Application examples:

Mixer for audio signals, e.g. three VCOs preceding a VCF, when the amplifications are adjusted slightly different no signal extinction occurs during the beat of the VCOs

Mixer for control voltages (e.g. LFOs, envelope generators, random voltages)