The module Doepfer A-135-1 Voltage Controlled Mixer / Quad VCA is a quad voltage controlled mixer. It is made of 4 independent linear VCA’s. The VCA outputs are mixed to a common output. For each VCA the following inputs and controls are available: audio input with attenuator, control voltage input with attenuator, gain (pre-amplification). The VCA’s are realized with high-quality CEM VCA’s (CEM3381 for version 1 and SSM2164 for version 2).

Doepfer A-135-1 Applications:
voltage controlled mixing of up to 4 audio signals with separate control voltages (e.g. delivered by LFO’s, ADSR’s, Random, Shepard generator, MIDI-to-CV interface or other control voltage sources). In connection with the Morphing-Controller A-144 the soft fade-over of 4 audio signals with only one control voltage is possible.

Doepfer A-135-1 features:
– Inputs: 4 x Signal in, 4 x CV In
– Output: Signal Out, Version 2 in addition: 4 x Single Out
– Controls: 4 x Signal In Attenuator, 4 x CV Attenuator, 4 x Initial Gain

From January 2014 a revised version 3 of the Doepfer A-135-1 is shipped. Compared to the previous version 2 of the A-135-1 the inputs and outputs of the new version are normalled adn for the sum output it can be chosen between all and selected VCAs:

– All signal inputs are normalled, i.e. signal input #1 is normalled to signal input #2 unless a plug is inserted into signal input socket #2, same is valid for the signal inputs 2 > 3 and 3 > 4, each normalling (1>2, 2>3, 3>4) can be interrupted by removing a jumper
– All CV inputs are normalled, i.e. CV input #1 is normalled to CV input #2 unless a plug is inserted into CVl input socket #2, same is valid for the CV inputs 2 > 3 and 3 > 4, each normalling (1>2, 2>3, 3>4) can be interrupted by removing a jumper
– the mode of the sum output can be chosen between “All” and “Selection” by means of a jumper. In “all” mode all four VCAs are mixed together. In “selection” mode a VCA is removed from the sum signal when a plug is inserted into the corresponding single output.
– It’s not possible to add the All/Selection feature to the first version of the A-135-1 module. But it’s possible to add the normalling of the signal and CV sockets.
– This pdf document shows the positions and explains the functions of the additional jumpers: A135_1_V3_jumper.pdf
– if your A-135-1 is version 3 can be identified by the additional jumpers shown in this document. The two versions can be distinguished also by the pcb printing on the smaller board (BOARD A): “V2 2013” for version 2 and “V3 2014” for version 3.

Doepfer A-135-1 Specifications:
– Width: 18 TE / 18 HP / 90.3 mm
– Depth: 50 mm (gemessen an Rückseite der Frontplatte / measured from the rear side of the front panel)
– Current: +60mA (+12V) / -50mA (-12V)