AM1042 Triple VCA

AM1042 Triple VCA

Overview The ARP 1042 module was announced back in 1970 but it never made it into production. It was intended to be a triple voltage controlled amplifier and would have provided a set of basic VCA’s to be used for CV and signal control with having to tie up a 1006 or 1005.

I have recreated the module using the transistor based ARP 2600 VCA design (4019). which is a slight improvement over the 2500 stock VCA and a nice warm circuit with Linear and Exponential modes.

AM1042 Module The module uses the same proven schematic as in the AM8019 VCA which uses matched transistor arrays from THAT and SSM. The design has been upgraded with the removal of the useless HF circuit that ARP put in, and some capacitors to smooth the current mirror power rails.

A high quality OPA134 op amp is used at the output and a Yellow LED is driven by a TL072 driver circuit to show the output level. Modern era metal resistors have been used rather than a move back to ARP style 5% carbon composite.

The module has the following front panel controls for each of the three VCA’s:

  • Gain
  • 2x Audio Levels
  • 1x CV Level
  • 1x black slide switch for VCA mode (linear or expo)

There are 12x 3.5mm jack sockets mounted at the base of the front panel, each VCA has:

  • Audio Inputs (x2)
  • CV Input
  • Signal Output
  • Yellow LED

Build History I had the idea in June 2015 and laid out the PCB in February 2016 into Eagle CAD, and the prototype PCB populated on 09 April. A front panel was ordered at the same time, with 3x pot PCB’s holding the front panel components, with ribbon cables back to the Main PCB. This also makes the wiring A LOT easier! I am getting tired of hand wiring 20 cables back into the panel using x-Roland 1980’s cable. Nice though it is, I don’t have much time…

2019 Update The lettering on the panel quickly rubbed off due to manufacturing defects, and the module was scrapped.

2024 Update The AM1042 has been relaunched as a Eurorack module, more details are here.



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