User Guide
Thank you for purchasing the AJH Synth Gemini 2412 Dual VCF 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!
Comprising two completely independent Vintage SEM style filters, with a central mixing bus for
both audio and frequency control voltages which allow the two VCF's to be combined in both
serial and parallel modes, and VCF1 can be inverted against VCF2. So the two VCF's can be com-
bined to behave as a 24dB SEM filter, vocal formant filter and much more!
Each of the two filters are based on the vintage SEM filter, with FET transistor buffers and feature
Low Pass, Band Pass and High Pass outputs and a useful Vary output which can be faded from LP
to Notch to HP. All outputs can be used simultaneously.
The two filters can be used independently, or can combined in the following modes:
Dual (Parallel) Mode -
The input to VCF1 is normalled to VCF2, and the two VCF’s are placed in
parallel, the output mix of VCF1 (OUT 1) against VCF2 (OUT 2) is controlled by the setting of the
Audio Mix control, with the output routed to the D-OUT jack.
Dual (Parallel) INVERTED Mode
- this is the same as Dual mode, however the output of VCF 2 is
inverted against VCF 1.
Cascade (serial) Mode
- The output of VCF 1 is normalled to the IN 2 jack, so that the two filters
are cascaded, signals are first processed by VCF 1 and then by VCF 2. In this case the Audio Mix
control crossfades between the ouput of VCF 1 (single VCF) and VCF 2 (dual cascaded VCF’s).
Again, the Cascade output is routed to the D-OUT jack.
Module width is 28 HP of Eurorack space and it is compatible with standard Eurorack cases. The
height of the panel is 128.5mm and depth is 24mm . There are four mounting holes at the
corners of the module and we provide 4 of M3 rack fixing screws along with a Eurorack compat-
ible power cable. Current consumption is 50mA from the +12V supply rail and 45mA from the
-12V supply rail.
All AJHSynth modules are covered by a two 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.
Dual Vintage style State Variable Filters
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2412
