SELF OSCILLATION MODE
Using the GEMINI 2412 as a Sine Wave Oscillator
Usually 12dB state variable filters such as those in the Gemini 2412, Oberheim SEM and other synthesisers do not go into
self -scillation at high resonance settings, this is because of damping in the filter core itself which prevents this from
happening. However, we have included some additional circuitry that can be connected into the filter using a PCB
mounted jumper on the back of themodule. The effect of this circuitry is to overcome the internal damping and force the
filter core into self oscillation, and it then behaves as a Sine Wave Voltage Controlled Oscillator (VCO) that tracks
1V/Octave over (approximately) a 4 octave range.
See the “Adjustment and calibration” page for information on the location of the self oscillation jumpers.
There are a few points to note about self oscillation mode:
1) Because we have to force the circuitry into self oscillation the resulting signal level is quite high - around 19V p/p
rather than the usual 10V p/p that most Eurorack modules produce, this is not a problem as long as it is feed into
another module that has a level control - for example the AJHSynth MiniMod VCA - this has input level controls and
simply turn these down to the point where the are of similar volume to other VCO’s etc and there will be no problem. If
you feed it at full output into other Eurorack modules without attenuating the level then you may get some ugly clipping
distortion. With this in mind, if using the GEMINI 2412 in CASCADE Mode with VCF 1 as a Sine wave oscillator and then
feeding the output into VCF 2 then do keep the IN 2 LEVEL control turned down to 5 or lower to prevent overloading the
input of VCF 2.
(Cont.)
1 V/Oct CV
SINE OUT
0
0
0
5
0
0
10
5
0
5
0
0
LP
LP
DUAL
VCF 2
0