AJH Synth MiniMod VCA - Manual

VCA User Guide
Thank you for purchasing the AJH Synth MiniMod VCA module, which like all AJH Synth Modules,
has been designed and handbuilt in the UK from the very highest quality components. We hope
that it will help and inspire you towards creating some great music and soundscapes!
The MiniMod Discrete Cascaded VCA exactly re-creates the VCA circuitry of the vintage Model D
synthesiser in Eurorack modular format. It features two fully discrete transistor VCA cores which
are hardwired in series, to which we have added full voltage control to both VCA cores along with
an overdrive facility. Particular attention has been paid to the selection and matching of compo-
nents in the audio signal path, including the use of audiophile grade capacitors and operational
amplifiers.
There are two Audio Inputs, each with their own level controls along with two CV inputs which
control the gain of VCA 1 and a Master CV Input and level control which controls the gain of VCA
2. An offset control allows a preset gain to be added to VCA 1. Internally it operates at the same
voltage and signal levels as the early Model D voltage controlled amplifier and the output of VCA
1 is hardwired to the input of VCA 2.
A high gain (overdrive) mode can be selected with an onboard jumper. This overdrives the Input
of VCA 1 by a factor of 3 and forces it into soft clipping - the second VCA can be used in a similar
way to the Master volume on a guitar amplifier to control levels so that variable levels of distor-
tion (or "grit") can be added to the sound and still maintain unity gain overall.
Module width is 10 HP of Eurorack space and it is compatible with standard Eurorack cases. The
height of the panel is 128.5mm and depth is 26mm . There are four mounting holes at the corners
of the module and we provide 4 of M3 rack fixing screws, along with a Eurorack compatible
power cable. Current consumption is 40mA from the +12V supply rail and 22mA from the -12V
supply rail.
All AJHSynth modules are covered by a one year guarantee against manufacturing defects.
Note:
It is very important that the power supply ribbon cable is connected correctly, see the “adjustment and
calibration” section for an illustration of the correct orientation.
Discrete Transistor Cascaded VCA
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