DOEPFER / A-138j Inverting/Interrupting mixer

Variations

This module is made by Doepfer, a German synthesizer manufacturer. This is a 4-channel mixer module with interrupting functionality, with polarity/mute switches on each channel.

The A-138j Inverting/Interrupting Mixer is a 4-channel mixer module with an interrupting function that has a polarity/mute switch on each channel. Setting the corresponding switch on each channel to the top position (inv.) inverts the input signal. When set to the center position (Off), that channel is turned Off (muted). Setting it to the bottom position (On) will result in a “normal” (not inverted) signal. Signal inversion is used especially for CV signals (LFO, ADSR, etc.). However, it is also useful for audio signals. It is used for feedback, mixing the original and processed signals (e.g., mixing the original and filtered signals to create a new filter type), etc.

Channel 1 has an “offset function”: when not plugged into the Input 1 jack, it produces a DC voltage (positive or negative, depending on the position of the polarity switch) that can be adjusted with the Lev.1 knob.

In addition, this module has two Single Outs and two Mix Outs. All inputs and outputs are DC coupled so the VCA can be used to mix both audio and CV signals.

Each input has a linear attenuator apart from the polarity/mute switch. The amplification range is 0?1.

The Single Out outputs the attenuated or inverted/muted signal of each channel, and the A-138j's signature Interrupting function is available by connecting a cable to the two available Single Outs. The single out is used to connect the cable to a single output. The functions are as follows

Single Out A : When a cable is connected to the Single Out A jack, the channel is excluded from the Mix Out.
Single Out B : If a cable is connected to the Single Out B jack, the channel is not excluded from the Mix Out. This Single Out is only available on channels 1 and 2.
With Single Out A, the A-138j can also be used as a 4-channel independent attenuator, inverter, or manual switch. (In this case, the mixer function is not used.)

Two Mix Out channels are provided, and both output the same signal.

■Width: 6HP
■Depth: 40mm
■Current consumption
+12V: 20mA
-12V: 20mA