Eurorack Dual VCO using the public CEM3340/AS3340 chip.
Table of Contents
This eurorack-modul is designed for modular-synthesizers as dual Voltage Controlled Oscillator.
The oszillators are build around two IC's: AS3340, a clone of that wellknown CEM3340.
Another benifit is the three cannel VCA: AS3363 included to control the modulation-level, waveform output of VCO1 and oscillator-signal fading between VCO1- and VCO2-outputs.
The '2MoreVO'-PCB's are:
- one main backplane ('Backplane'), holding all switches, pots, jacks and voltage-references.
- two VCO-PCB's stacked on the 'Backplane'.
- one another backplane-PCB ('Backplane_B') hodling the 'three cannel VCA', operational-amp's and the eurorack-connection stacked on the 'Backplane'.
All parts are common available and DIY-friendly designed, most parts are SMD on the VCO-PCB's.
(Details see attached pictures)
- Modul Frontpanel
- Modul Backpanel
- Modul function-blocks
There are twelve 3.5mm jacks available for patching audio- and CV-signals.
| Jack-Name | Function | Comment | Detail |
|---|---|---|---|
| 1V/Oct CV1 | CV-input for VCO1 pitch control | fixed 1Volt/Octave scaling | This input is normalised with the eurobus Control-Voltage and connected with the '1V/Oct CV2' input. Patch-cabel plugged in breaks the default connection to eurobus CV but the connection to '1V/Oct CV2' is still available. |
| Fade CV | CV-input for fading oscillator-signals | The Fading between Osc1- and Osc2-signals on 'Osc-Mix Out' is controlled with this CV | CV level adjustable between 0 ... max. with 'Fade CV'-pot. works together with 'Osc-Fade'-pot. Bipolar signal input. |
| Wave1 CV | CV-input for VCO1 wave-control | The waveform on 'Osc1 Out' is controlled with this CV | CV Level adjustable between 0 ... max. with 'Wave1 CV'-pot. Bipolar signal input. |
| Mod.Level CV | CV-input for modulation level control | Control of modulation level on 'Mod Out' | Modulation Level adjustable between 0 ... max. with 'Mod.Level CV'-pot. Bipolar signal input. |
| Mod. In | Modulation signal input | input for external signals controlling FM(Lin/Log) and PWM on Osc1 and Osc2 | This input is normalised with the sinusoidal-signal from Osc2 if no signal is plugged in. Bipolar signal input. |
| 1V/Oct CV2 | CV-input for VCO2 pitch control | fixed 1Volt/Octave scaling | This input is normalised with the '1V/Oct CV1' input. Patch-cabel plugged in breaks the default connection to '1V/Oct CV1'. |
| Osc1 Out | output for VCO1-oscillator signal | triangle- to saw-waveform output, morvable manually or with external CV | Waveform morvable with 'Wave1 CV'-pot and CV-signal. |
| Osc-Mix Out | output for mixed VCO1-/VCO2-oscillator signal | mixed signal from Osc1- and Osc2-outputs | Waveforms fadeable between Osc1- and Osc2-signal outputs. Fading can be done with 'Fade CV'-pot and CV-signal. 50%/50% Osc1/2-signal level on 'Osc-Mix Out', if 'Osc-Fade'-pot is in centerposition and no 'Fade CV' is plugged in. |
| Osc2 Out | output for VCO2-oscillator signal | saw- to triangle-waveform output, morvable manually | Waveform morvable with 'Wave2'-pot between saw- and triangle-signal. |
| Sync In | Sync-signal for VCO1 (optional VCO2) | this signal can be switched to: 'Sync Hard', ' Sync Soft' or 'Off' | This input is normalised with the 'Puls2 Out'-signal from VCO2. Patch-cabel plugged in breaks the default connection to 'Puls2 Out'. |
| Mod Out | output for modulation-signal controllable with 'Mod.Level CV' | modulation-signal used for 'FMx Lin/Log' and 'PWM' default sinusoidal-signal from VCO2 used for VCO1 modulation |
sinusoidal-signal from VCO2 is available on this output if high impedance connection is used. optional an external low impedance signal plugged in can overwride the internal modulation. |
| Puls2 Out | output for puls-signal from VCO2 | output-signal for synchronisation and audio the pulswith is controllable with 'PWM'-pot using the 'Mod Out'-signal |
This output is also internally linked to 'Sync In'. Bipolar output with +-5.0Volt level. |
There are eight potentiometers with following functions:
| Pot-Name | Function | Comment | Detail |
|---|---|---|---|
| Tune 1 | Pitch for VCO1 | default pitch in center-position | tuning-range +-2 octaves. |
| Tune 2 | Pitch for VCO2 | default pitch in center-position | tuning-range +-2 octaves. |
| Osc-Fade | manually fading between Osc1- and Osc2-signals on 'Osc-Mix Out' | works as CV offset for the 'Fade CV'-signal | pot to CCW: Osc2-signal output. pot to CW: Osc1-signal output. pot to centerposition: equal level output. |
| Fade CV | CV Level amount pot for fading between Osc1- and Osc2-signals on 'Osc-Mix Out' | works together with 'Osc-Fade' for fading Osc1/2-signals | CV Level adjustable between 0 ... max. |
| Wave1 CV | CV Level amount pot for Osc1 waveform-selection on 'Osc1 out' | manually selection of waveform is possible if no CV-signal is plugged in | CV Level adjustable between 0 ... max. |
| Mod.Level CV | CV Level amount pot for modulation control | manually modulationlevel control is possible if no CV-signal is plugged in | CV Level adjustable between 0 ... max. |
| PWM | pulswith pot to control amount of PWM | the modulation-signal on 'Mod Out' is used for PWM | PWM amount adjustable between 0 ... max. Pulswith is 50% on 'Puls2 Out' if pot is in CCW-position (set to 0). |
| Wave2 | waveform selection pot for Osc2-signal | manually morving between saw- and triangle-signal | pot to CCW: SAW-signal. pot to CW: Triangle-signal. pot to centerposition: mixed signal. |
There are six switches to control the behaviour of signals.
| Switch | Function | Comment | Detail |
|---|---|---|---|
| FM1-switch | switch for VCO1 FM modulation using signal on 'Mod Out' | FM controll for VCO1 | FM1 Lin := Linear FM modulation. Off := function off. FM1 Log := Logarithmic FM modulation. |
| Sync-switch | switch for VCO1 Hard- or Soft-synchronisation with puls-signal from VCO2 | switched synchronisation-signal from 'Puls2 Out' | Sync Hard := hard synced to VCO2. Off := sync. function off. Sync Soft := soft synced to VCO2. |
| VCO1 Octave-switch | switch for VCO1 pitch setting | octaves up or down depending on 'Octave switch + or -' | 1 := one octave (up/down). 2 := two octaves (up/down). |
| Octave up/down switch | switch for VCO1- and VCO2-switched pitchcontrol | selecting pitch up or down for VCO1 and VCO2 | + := pitch up. - := pitch down. |
| VCO2 Octave-switch | switch for VCO2 pitch setting | octaves up or down depending on 'Octave switch + or -' | 1 := one octave (up/down). 2 := two octaves (up/down). |
| FM2-switch | switch for VCO2 FM modulation using signal on 'Mod Out' | FM controll for VCO2 | FM1 Lin := Linear FM modulation. Off := function off. FM1 Log := Logarithmic FM modulation. |
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size:
width: 16HP
depth: 45mm -
power:
5Volt, 0 mA
+12Volt, 60mA
-12Volt, 60mA -
frequency range: 20Hz to 20kHz.
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frequency CV scale: 1V/Oct on '1V/Oct CV1'- and '1V/Oct CV2'-inputs.
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frequency pot tuning range: +-2 Octaves.
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frequency switchable pitch range: plus or minus 1 or 2 octaves for oscillator 1/2.
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signal inputs, DC-coupled signal path.
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signal outputs, DC-coupled signal path.
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signal input impedance: > 50kOhm.
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signal output impedance: 500 Ohm.
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expandable with more '2MoreVO' dual-oscillator('s) used in master-/slave-configuration.
Hardware:cc by-nc-sa 4.0 (details)