AM8440 JP-4 VCA


AM8440 Mockup

Overview I have gradually developed all the Jupiter 4 circuits as Eurorack modules, and the availability of a new BA662 clone in 2022 means its practical to do the VCA. The AM8440 VCA modules uses both OTA’s in the AS662 chip to provide the main VCA functionality but also a dynamics feature. This enables voltage control of the LFO or ENV signals, using a dynamics input that can be connected to velocity or aftertouch CV signals.

EuroRack Module:   10HP wide
User Manual:             
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Description The original VCA is based on the BA662 OTA chip, which I have replaced with the new AS662 chip from Alfa Rpar. This chip is a dual OTA, so the other side of the chip is used in creating the dynamics feature. The VCA has two audio inputs (INA, INB) with a rotary potentiometers for adjusting the level. The level of the output signal is adjusted by the VOLUME slide potentiometer, and there is an audio output (VCA OUT).

The AM8440 has an additional two slide potentiometers for controlling the level of the main VCA. The MOD and ENV pots adjust the amount these CV signals affect the level of the audio signals.  A third slide potentiometer (DYNAMICS) allows voltage control of either the MOD or ENV signals into the main VCA. A toggle switch selects whether MOD or ENV are affected by the dynamics CV. Velocity of aftertouch CV’s can be patched in to create touch response of the VCA modulation.

The module includes a LED for monitoring the overall audio output level and the slide potentiometers have yellow LED’s.

Outcomes & Availability The AM8440 module is at the development stage.

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