AM8133 – Dual DC VCA (100M)

Overview When Roland developed the System 100M they created a rather nice Dual VCA module (130). This is a fantastic module but the signal path is AC coupled, which means the VCA cannot be used for adjusting the level of CV signals. Although Roland added more modules over time, including a DC Mixer, they never produced a DC coupled VCA.

In 2023 AMSynths developed a set of new 100M modules in Eurorack, to complement and expand upon the Behringer System 100. One of the new modules is the AM8133 Dual DC VCA, which is an important addition to the original system. There are two VCA channel’s rather than four, to enable the components to be mounted onto the same PCB as the controls, keeping costs down.

EuroRack Module:  16HP wide
User Manual:             
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AM8133 Module

The AM8133 Module The design is based on the AS3360 chip which contains two precision VCA’s. There are two 30mm CV input level slider pots for each VCA and a rotary pot for GAIN. The sliders have subtle green LED’s and the rotary pots have Roland TR808 style knobs.

There are jack sockets for the CV inputs at the top of the panel, and input and output sockets at the base. This makes for easy patching into a Eurorack system whilst maintaining visibility of the controls. There are two green LEDs that indicates the level of the output signals.

There are no capacitors in the signal path, and high quality Op Amps have been used to ensure minimal DC offset, so that the VCA’s can be used with pitch signals. A grey powder coated panel, with white silk screen, has been custom manufactured for the module.

Outcome & Availability The circuit was laid out in Eagle CAD during February 2023 and a prototype set of PCB’s ordered. The prototype works well and production modules are available on our webstore.

Copyright AMSynths 2022