Doepfer A-135-5 Eurorack Polyphonic Voltage Controlled Mixer Module

Module A-135-5 is a combination of a voltage controlled polyphonic mixer and a polyphonic suboctave generator. It is made of 12 voltage controlled amplifiers (VCAs) which are arranged in form of a 4×3 matrix. Herewith up to three four-voice polyphonic signals (e.g. the outputs of three polyphonic VCOs A-111-4) can be mixed. The level of each of the three polyphonic channels (A, B, C) with four voices each can be controlled manually or by means of an external control voltage with associated attenuators.

In addition the module features four frequency dividers which derive the suboctaves from the four input signals of channel A. The suboctave signals are wired to the switching contacts of the sockets of channel B. As long as the sockets of channel B are not patched the suboctave signals of channel A are used as inputs for channel B. The suboctaves are symmetrical rectangle waves with half the frequency of the corresponding signal A. For example two polyphonic VCOs A-111-4) can be used and patched to the channels A and C. Channel B then provides the suboctaves of channel A.

As the module is fully DC coupled it can be used also for the mixing of control voltages in a polyphonic environment (e.g. for envelopes, LFOs or other control voltages).

The switching contacts of the 12 input sockets and the four outputs are internally connected to pin headers. That way the module can be internally pre-patched to other polyphonic modules (e.g. the four inputs A to an A-111-4, the four inputs C to another A-111-4 and the outputs to the polyphonic filter A-105-4). As the switching contacts of the sockets are used for the internal pre-patching the internal patch can be overridden by using the sockets at the front panel.

The module has these controls and in/outputs available:

• Controls Lev.A, Lev.B, Lev.C: manual level adjustment of the channels A, B and C
• Controls CV A, CV B, CV C: attenuators for the corresponding control voltage inputs
• Toggle switches Mute A, B, C: mute function the channels A, B and C, in the lower position of the switch the corresponding channel is muted
• Sockets A1…4: inputs channel A
• Sockets B1…4: inputs channel B (if the sockets are not patched the suboctave signals are used for the inputs B)
• Sockets C1…4: inputs channel C
• Sockets CV A. CV B, CV C: control voltage inputs for the channels A, B and C
• Sockets Out 1…4: outputs
• Socket Sum: sum output, especially for paraphonic applications, i.e. only one VCF/VCA for all voices

Technical notes:

• If required two or more modules can be cascaded when more than three polyphonic channels are required.
• the max. overall amplification is less than 1 to avoid clipping (can be altered to amplification 1 by replacing resistors, but then clipping may occur)
• the max. input levels without distortion are about 16Vpp (or -8V … +8V for the processing of control signals)
• the voltage range for each of the CV inputs is about 0…+5V (with corresponding attenuator control fully CW),  higher control voltages (e.g. 0…+10V) can be adjusted by means of the attenuator control
• the suboctave levels are about 5Vpp
• the module should be used only with DC coupled VCO outputs (e.g. A-111-4, A-111-3). With AC coupled VCO outputs (e.g. A-110-1, A-110-2) a DC offset will occur at the outputs when the suboctave option is installed.

Specifications

• Width: 10hp
• Depth: 51mm
• Power: Unknown

Manufacturer product page here.