Doepfer - A-138B: Mixer
Module a-138 is a four channel mixer, which can be used with either control voltages or audio signals. each of the four inputs has an attenuator, and there's a master attenuator, so that the mixer can be used at the end of the audio chain - ie. it can be used to interface directly with an external mixer, amplifier, etc.
a-138b: potentiometers with logarithmic response, so especially suitable for audio signal mixing.
this module has a maximum current draw of 20ma. it requires 8 te/hp worth of space to fit in a eurorack frame