OCS-2 User Documentation

OCS-2 User Documentation
This is the audio path wired inside the synthesizer.
VCO 1 and 2
Available waveforms are a mix of classic ones: sinus, triangle, saw, square, pulse, PWM,
noise – and less common ones : (sinus+1)², double saw, squared ramp, digital noise – and
even some that haven’t been named yet.
• 2 modulation faders allow to modulate VCOs frequency with the CV connected via the
digital connection matrix.
• All waveforms are band-limited to remove digital synthesis artefacts.
• VCO 1 and 2 frequencies can be adjusted separately, or linked together. In this case
VCO 2 frequency fader tune between 0-1 octave against VCO 1 frequency.
• A ring modulator option mixes the signal of the 2 VCOs.
• PWM is controlled via LFO1 or LFO2 depending on the VCO.
• Noise color can be adjusted using the VCO frequency control.
• The 16th waveform is the audio in : Left for VCO1, right for VCO2.
The VCF is a custom version of the Moog filter. It mimics its most important features :
• 24dB low pass / resonant frequency response
• high resonance creating auto-oscillations
• no amplitude increase with high Q
This filter has some specific features :
• No distortion of the signal, allowing a clear pass-through.
• 4 frequency responses are available : the classic Low Pass 24dB/Octave is the
default configuration, but there is also a Low Pass 12dB/Octave, a Band Pass
12dB/Octave, or a High Pass 12dB/Octave.
2 LFOs with variable waveform
These two LFOs offer a unique feature : you can adjust the shape of the CV using faders
instead of switches. This allows to continuously change from a rising saw, to a triangle and
then to a slope down. Or stop halfway between sinus and square.
The waveform (WF) fader controls the shape of the transition. It changes from a straight
ramp (like in triangle or saw), to a sudden change of value (like in a square), passing through
a sinusoid shape.
The other fader (SYM) adjusts the symmetry of the output, i.e the ratio between rise/fall
times. It passes from a rising saw to a triangle and then a falling saw.
Frequency range of these LFOs is huge : the period can go from 45 seconds to 1/40 second.
When this LFO is synchronized with a GATE signal (from keyboard, or midi), the LFO phase
is reset at the beginning of every note.
LFO3 : VCLFO with selectable waveform
The 3rd LFO is completely different as it is wired to the gate and can trigger notes.
In addition to classic waveforms (sinus, triangle, square, pulse), it provides waveforms
dedicated for simple rhythmic generation : [1 0], [1 0 0 0], [1 1 0 0], [1 1 1 0], [1 1 0 1 0], [1 1
1 1 0], [1 1 0], [1 1 0 0 1 0 0 0].
It also provides a random generator, because… well, it’s nice.
LFO 3 frequency range is the same than LFO 1 and 2, BUT it’s a VCLFO : LFO3 frequency
can be controlled by another CV.
You can also add groove to your rhythm!
This is LFO3 waveform :
This is a standard analog ADSR :
Attack, Decay, Sustain and Release can all be adjusted with faders.
Custom CV Generator module
In this slot you can use one of the following modules :
AR : Attack Release envelop generator
The modulation is a standard analog type Attack-Release generator.
PARAM 1: Attack time / PARAM 2 : Release time.
LFO : Dual LFO
The modulation is the sum of 2 sinusoidal LFOs.
PARAM 1 : LFO frequency 1 / PARAM 2 : LFO frequency 2.
RND : Random generator
A random value, updated periodically is filtered using a low pass filter.
PARAM 1 : frequency of the random value generator / PARAM 2 : cutoff frequency the filter.
STEP : a Step Oscillator.
This module generates strange rhythmical patterns that can mutate.
PARAM 1 : step frequency / PARAM 2 : steps evolution speed.
The VCA amplifies the filter output with the ADSR signal.
The MOD fader can modulate the amplitude of the audio signal using one of the modulation
The MIX fader allows to adjust the amplitude of VCO1 regarding VCO2.
The MOD fader can also be used to modulate the MIX amount.
If the ring-modulator option is enabled, the MIX fader mixes between VCO1 and the ringmodulator.
A master volume is also available.
Audio effect
You can choose one of the four available audio effects :
• Distortion
WET : distortion amount. MOD : WET modulation.
• Bit crush
WET : bit crush amount. MOD : WET modulation.
• Delay
WET : level of audio sent to the delay line. It mixes between the VCA out and the delay line
At 0%, the delay does not have any effect.
At 50%, the delay line input is a mix between the VCF out and the delay line out.
At 100%, no external sound is sent into the delay line. Only the delay line out is sent to the
delay line in.
MOD : delay time, ranging from almost 0 to more than 900ms.
Unlike the other effects, the delay is after the VCA in the audio chain.
• Waveshaper
WET : Waveshaper amount. MOD : WET modulation.
When toggle is on NOTE, this is a 2 octaves keyboard controlling the frequencies of the
VCOs. It also controls the frequency of the VCF if “PITCH VCF” option is ON. The
portamento filters the frequency change of the keyboard.
When toggle is on MENU, the keyboard is used to patch the matrix and to edit all options.
Digital patching matrix
Connection between modules are made via a digital matrix. You will not be short of cables
anymore, and you can even save your patch! The Matrix allows to connect any CV to any
modulation fader.
CVs are :
• VCO 1 out
• VCO 2 out
• LFO 1
• LFO 2
• LFO 3
• LIGHT sensor
• AUDIO IN envelope
• MIDI NOTE ON velocity
• EXTERNAL CV 1 (or MIDI pitch Bend)
• EXTERNAL CV 2 (or MIDI Modulation Weel (CC 1 + CC 33))
• EXTERNAL CV 3 (or MIDI CC 2 (+CC 34))
Modulation faders are :
• VCO 1 MOD 1 and 2
• VCO 2 MOD 1 and 2
• VCF MOD 1 and 2
Light Sensor
The light sensor is located near the keyboard :
Use the shade of your hand to control the sound! The light sensor generates a Control
Voltage that can be routed to any modulation fader thanks to the patching matrix.
Audio In
Audio in (stereo – line level) is plugged on the 16th waveform of the VCOs, it allows to input
any audio source in the synthesizer audio path using a 3.5mm stereo jack plug. The audio
signal can be used as any other waveform.
It can also be used to generate a CV thanks to an an envelope follower.
When AUDIO option is selected as GATE mode, a gate is triggered when the audio left
signal is above a threshold.
External CV
3 analog inputs (-6v/6V) and an external GATE IN (0/5V) are available using 3.5 mono jacks,
compatible with most modular setups.
You can also control your synthesizer with a MIDI cable : using a keyboard to play notes, or
the pitch bend or modulation wheel to control the sound. Connect an external sequencer, a
computer etc. The midi data used is :
• Note On / Note Off – channel 1. Note On velocity is accessible in the digital patching
matrix so you can use it like any other control CV.
• Pitch bend, modulation wheel (CC1 – 7 bits / CC1 and CC33 – 14 bits) and after-touch
(CC2 – 7 bits / CC2 and CC34 – 14 bits) – channel 1. When sending one of this data in
midi, the CV IN 1, 2 or 3 are disconnected from the analog input and connected to this
midi data.
• Program change from 1 to 10 – channel 1 : load one of the memory.
• Control Change (1CC – 7 bits / 2CC – 14 bits) – channel 2 : control all faders in midi.
Midi data is added to fader value to control the corresponding parameter. For 14 bits
MIDI, use CC N for MSB, and CC N+32 for LSB. Always send MSB after the LSB.
• MIDI Clock : As soon as MIDI syncro signal (F8) is received : the LFO3 synchronize
on this signal. Few seconds after you stop sending the syncro, or unplug the cable, the
LF03 frequency goes back to a non synchro mode. During the synchro mode, the LFO
FQ fader change the frequency to 1/16, 1/8, 1/4, 1/2, 1, 2, 4 or 8 times the frequency
of a MIDI note.
Here is a map of MIDI CC number :
This is a 2 octaves keyboard. The portamento filter the frequency control of the keyboard.
Thanks to a switch, the keyboard is also used to control the menu in order to edit all OCS
How to use the key as a midi keyboard?
Switch the toggle to NOTE.
How to use the menu?
Switch the toggle to MENU.
All options are available using 2 keys combination.
How to change the patching matrix?
– Hold the modulation fader key to assign
– Press the modulation source key
For example, to use LFO3 as VCO 1 modulation 1, you have to press on the same time this 2
key :
How to know what modulation source is assign to a modulation fader?
When holding a modulation fader, the 7 led show the current assignation.
• LED VCO 1 -> VCO 1
• LED VC0 2 -> VCO 2
• LED LFO 1 -> LFO 1
• LED LFO 2 -> LFO 2
• LED LFO 3 -> LFO 3
• LED CV GEN -> CV Generator (AR, LFO, RND, NL)
• all LED except VCO 1 -> Light Sensor
• all LED except VCO 2 -> Audio envelop
• all LED except LFO 1 -> MIDI Note On velocity
• all LED except LFO 2 -> EXT 1 (External CV 1)
• all LED except LFO 3 -> EXT 2 (External CV 2)
• all LED except CV GEN -> EXT 3 (External CV 3)
How to change LFO3 Wave Form?
Press simultaneously the 2 key :
LFO3 WF and the WF key to select
How to link/unlink the VCO frequency?
Press simultaneously the 2 key :
When linked, the VCO2 frequency follow the VCO1 frequency.
How to enable/disable the Ring Modulator?
Press simultaneously the 2 key :
When the ring modulator is enable, the VCO2 signal is replace with the ring modulator signal.
How to enable/disable the Filter keyboard tracking?
Press simultaneously the 2 key :
When the filter keyboard tracking is enable, the cut-off frequency of the VCF follow the
keyboard pitch.
How to enable/disable the LFO 1 synchronization?
press simultaneously the 2 key :
When this option is enable, The LFO1 phase is reset at every GATE signal.
How to change the MIX/VCA modulation?
press simultaneously the 2 key :
MOD MIX/VCA and YES (for MIX) or NO (for VCA).
How to know what is the current status of the various options?
When holding the option « LINK VCO », « RING MOD », « PITH VCF », « SYNC VCO1 » or
« MOD MIX/VCA », the 2 led « VCO 1 » and « VCO 2 » indicate if the option is enable or
disable : « VCO 1 » for YES, « VCO 2 » for NO.
How to change the filter mode?
Press simultaneously one of the key :
LP24 (Low Pass 24dB/Octave), LP12 (Low Pass 12dB/Octave), BP12 (Band Pass
12dB/Octave), HP12 (High Pass 12dB/Octave)
When holding one of the VCF option key, the 2 VCO leds indicate current VCF option :
• « VCO 1 » OFF and « VCO 2 » OFF : LP24
• « VCO 1 » OFF and « VCO 2 » ON : LP12
• « VCO 1 » ON and « VCO 2 » OFF : BP12
• « VCO 1 » ON and « VCO 2 » ON : HP12
How to change the audio effect?
Press simultaneously one of the key :
DIST (distortion), BTCRH (bitcrush), DELAY (delay), WSHP (waveshape)
When holding one of the FX option key, 4 leds indicate the current EFFECT :
• « LFO 1 » for DISTO
• « LFO 2 » for BITCRUSH
• « LFO 3 » for DELAY
How to change the GATE source?
Press simultaneously one of the key :
KB (keyboard), LFO3, AUDIO, ON
When holding one of the GATE option key, the 2 VCO leds indicate the current GATE
• « VCO 1 » OFF and « VCO 2 » OFF : KEYBOARD
• « VCO 1 » OFF and « VCO 2 » ON : LFO3
• « VCO 1 » ON and « VCO 2 » OFF : AUDIO Envelope
• « VCO 1 » ON and « VCO 2 » ON : ON
How to change the CV Generator algorithm?
Press simultaneously one of the key :
AR (Attack release), LFO (dual LFO), RND (random), NL (Non Linear)
When holding one of the GEN option key, 4 leds indicate the current CV GENERATOR
module used :
• « LFO 1 » for ATTACK / RELEASE
• « LFO 2 » for Dual LFO
• « LFO 3 » for RANDOM
How to Load / save configuration?
Press simultaneously one of the LOAD or SAVE key and one key from the top row
I don’t have sound, what is the problem?
The VOL fader is too low.
The VCO frequency is to low.
The VCO Waveform selector is on “IN Left” or “IN Right”, and no external signal is
The VCF cutoff frequency is too low/high (depending on the filter type).
The ADSR sustain is too low.
The ADSR attack is too high (you need a long GATE in order to have a sound).
The keyboard is on MENU mode (no GATE signal is generated).
The GATE mode is on AUDIO and the external audio is not above the threshold (no
GATE signal is generated).
The VCA/MIX MOD fader is configured as VCA modulation, and the modulation signal
and fader are too high.
The Delay audio effect WET fader is too high (no sound is feed to the delay).
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