DOEPFER / A-135-4AB VC Performance Mixer

Variations

This module is made by the German synthesizer manufacturer Doepfer. It's designed to build a performance mixer with CV control capabilities.

The A-135-4 series is a set of modules for building CV-controlled performance mixers. It includes three modules: the A-135-4A main module with four input channels and manual controls; the A-135-4B expansion module with CV inputs and attenuators for each control; and the A-135-4C envelope follower, which generates an envelope for each channel from the audio signal input to the A-135-4A. It can also be used in combination with the A-138p, a simpler performance mixer without CV control.

*This module requires the A-138o Performance Mixer Out. Audio signal output is not possible with the A-135 series alone.

*A-135-4A VC PERFORMANCE MIXER
This is the main module of the A-135-4 series. All parameters except gain can be controlled by external CV input to the A-135-4B. The A-135-4A and A-138p are very similar, but the A-135-4A features LEDs that display the magnitude of all CV control parameters. This is because it is controlled by both manual control and external CV input to the A-135-4B, and the position of the manual control does not necessarily correspond to the actual parameter.
Each channel of the A-135-4A is equipped with four high-quality VCAs: one for the main level, two for the left and right pan, and one for the AUX, for a total of 16 VCAs. High-end linear VCAs, CEM3381, produced by Curtis USA, are used. All parameter control scales are linear curves. The 16 LEDs roughly indicate the VCA amplification.

• A-135-4B VC PERFORMANCE MIXER CV INPUTS
This module takes an external CV signal as input and sends it to the A-135-4A. Each channel allows control of four parameters via CV signals:

* Level: Main volume control
* Pan: Left/right panning
* Aux: Send level to Aux
* Mute: Mute control

Each CV signal has an input jack and polarizer. You can adjust the depth and polarity of the change the CV signal has on each parameter. For example, if you input the same CV signal (LFO or ADSR) to the Pan of two channels and set one to positive and the other to negative, they will operate in opposite directions. The external CV signal is added to the voltage generated by the manual control of the A-135-4A main module. The sum of both voltages is used to control the corresponding VCA and can be visually confirmed by the A-135-4A's LED.

The Mute CV input operates similarly to the Level CV input, but with reversed polarity and higher sensitivity (approximately twice as high). When used as a standard mute control, turn the polarizer all the way to the right and apply a voltage of +2.5V or higher to completely mute the signal. When not using the mute function, it can be used as a second CV input for level control (with twice the sensitivity and reversed polarity compared to the standard CV input).
The A-135-4A and A-135-4B are internally connected using a 20-pin ribbon cable. With a long ribbon cable, the two modules can be mounted at different locations. Since all functions are only available when the two modules are internally connected, they are sold as a set only.

Width: 16HP | 10HP
Depth: 45mm | 45mm
Current Consumption: +12V: 150mA | 40mA
-12V: 100mA | 40mA