Doepfer A-135-1 Quad VCA Mix

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

For more detailed information please look at the English user's guide: A135_man.pdf.

Remarks:

• The first version of the A-135-1 was able to process audio signals only because the signal in/outputs were AC coupled. The first version cannot be used to process slowly varying control voltages! It has been manufactured until about April 2013 and can be identified by the missing single outputs, the 22 HP front panel width and the VCA circuits (CEM3381 or PA381)
• The second version of the A-135-1 is able to process also slowly varying control voltages because the signal in/outputs are DC coupled. It has in addition four single outputs available and can be used as four independent linear VCAs. The new version is manufactured since May 2013 and can be identified by the additional four single outputs, the 18 HP front panel width and the VCA circuits (SSM2164 or V2164)

• It is not possible to modify version 1 for DC signal coupling or single outputs !

• From January 2014 a revised version 3 of the 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.