Calibration of CEM/AS3340 dual analog VCO eurorack-modul.
Required or recommended tools are:
- High precision voltage meter.
- Frequency meter.
- MoreVO_Core breadboard with 5.0V and 8.0V voltage references (if available).
- Eurorack for power (+12V/-12V) and keyboard-CV.
- 16pin Eurorack cable for modul-connection to the rack-bus.
- patchcables for modular synthesizers.
- all PCB's have to be mounted.
Table of Contents
- Reference-voltage-Adjustment
- MoreVO_Core-Adjustments
- VCO2 sinusodial output-Adjustments
- Final check
- License
Reference-voltage-adjustment is done with precision trimmers 'RV1' and 'RV12' on the 'Backplane'.
Backplane top side precision trimmer RV1 and RV12
Measurement-points are +2V and -2V on 'Backplane B'.
Backplane B measurment-points
| measuring point | adjustment on | measured voltage | remark |
|---|---|---|---|
| 'Backplane B' +2V (back side) | 'Backplane' RV1 (top side) | +2000 mVolt | adjust as close as possible to nominal value. |
| 'Backplane B' -2V (back side) | 'Backplane' RV12 (top side) | -2000 mVolt | adjust as close as possible to nominal value. |
For AS3340 calibration details see also URL: AS3340 tuning
If the MoreVO_Core breadboard (with 5.0V and 8.0V voltage references) is available, all required adjustments on 'MoreVO_Core's are done on that breadboard, else the '2MoreVO'-moduls must be stacked in the 'Backplane' and calibrated in the eurorack.
MoreVO_Core precision pot's RV1 ... RV5 location
Preparation:
- Connect GND to header J1-1.
- Connect +12Volt to header J1-2.
- Connect -12Volt to Header J1-3.
Be carefull and check that connections.
Switch on powersupply and warm up that board at least for 30minutes.
| Step Nr |
preparation | action | remark |
|---|---|---|---|
| 1 | Connect mV meter between TP1 and TP2 | Trim 'TEMPCO ADJ' pot (RV1) until: Voltage is 0.0mV |
|
| 2 | Close (short) jumper JP1 on top-side of the board | Trim 'REF PITCH C6' pot (RV2) until: Pitch is 1046.5 Hertz (C6) |
measured on SAW_Out (J2-2) |
| 3 | Apply +5.000Volt DC on 'Tune'-input (J1-4) | Trim 'REFIND C6' pot (RV3) until: Pitch is again 1046.5 Hertz (C6) |
measured on SAW_Out (J2-2) |
| 4 | Apply 0.000Volt DC on 'Tune'-input (J1-4) | Trim 'SCALE ADJ' pot (RV4) until: Pitch is 32.7 Hertz |
measured on SAW_Out (J2-2) |
| 5 | Apply +8.000V DC on 'Tune'-input (J1-4) | Trim 'HIGH FREQUENCY ADJUST' pot (RV5) until: Pitch is 8372.0 Hertz |
measured on SAW_Out (J2-2) |
Repead above steps for the second 'MoreVO_Core'.
After calibration put both 'MoreVO_Core' boards into the '2MoreVO' backplane.
Preparation:
- Set 'Tune 1'and 'Tune 2' pot's to center-position.
- Set all three-position switches to center-position: Off.
- Set 'Wave1 CV' pot to: CCW (Saw).
- Set 'Wave2' pot to: CCW (Saw).
- Connect the '2MoreVO'-modul with 16pin Eurorack cable to the rack-bus.
- Connect patch-cabel into jack '1V/Oct CV1' on 2MoreVO-modul to get that 1V/octave CV voltage from keyboard.
- Switch on Eurorack power.
- Check voltages at pin J1-4 on both MoreVO_Core's to be zero. If required adjust that related tune-pots 'Tune 1' and 'Tune 2' to get at close as possible to zero volt on pins J1-4.
warm up that '2MoreVO'-modul at least for 30minutes.
'2MoreVO' mounted MoreVO_Core's
Start calibration with one 'MoreVO_Core' and repeat it with the second one in following steps:
| Step Nr |
preparation | action | remark |
|---|---|---|---|
| 1 | Connect mV meter between TP1 and TP2 | Trim 'TEMPCO ADJ' pot (RV1) until: Voltage is 0.0mV |
measured and adjusted at: VCO1 and VCO2. |
| 2 | Close (short) jumper JP1 on top-side of the board | Trim 'REF PITCH C6' pot (RV2) until: Pitch is 1046.5 Hertz (C6) |
measured at: 'Osc1 Out' for VCO1. 'Osc2 Out' for VCO2. |
| 3 | Apply +5.000Volt CV on '1V/Oct CV1'-input pressing pitch-key 'C6' on the keyboard | Trim 'REFIND C6' pot (RV3) until: Pitch is again 1046.5 Hertz (C6) |
measured at: 'Osc1 Out' for VCO1. 'Osc2 Out' for VCO2. |
| 4 | Apply 0.000Volt CV on '1V/Oct CV1'-input with disconnected keyboard CV-voltage. patch-cabel plugged out at keyboard side. |
Trim 'SCALE ADJ' pot (RV4) until: Pitch is 32.7 Hertz |
measured at: 'Osc1 Out' for VCO1. 'Osc2 Out' for VCO2. |
| 5 | Plugin keyboard patch-cabel again. Apply +8.000V DC on '1V/Oct CV1'-input pressing pitch-key 'C9' on the keyboard. |
Trim 'HIGH FREQUENCY ADJUST' pot (RV5) until: Pitch is 8372.0 Hertz |
measured at: 'Osc1 Out' for VCO1. 'Osc2 Out' for VCO2. |
Repead above steps for the second 'MoreVO_Core'.
1V/Octave calibration done.
Preparation:
- patch-cabel plugged into jack 'Mod Out' and to any audio-input or waveform-display device.
- pot 'ModLevel CV' set to position: CW.
- switch on eurorack-power.
The waveform is adjusted with pot's RV9 (level) and RV11 (offset) on 'Backplane B'.
| Step Nr |
action | remark |
|---|---|---|
| 1 | Adjust signal-offset with offset-pot: 'RV11' | |
| 2 | Adjust sinusodial-waveform with level-pot: 'RV9' | |
| repead steps:1 and 2 to get the best result |
At least the output signal should look like the following waveform:
VCO2 sinusodial output on 'Mod Out'
Preconditions:
- Jumper J4 on 'Backplane B' must be closed to getting the 1V/Octave CV-voltage from euro-bus.
- Set all three-position switches to center-position: Off.
- Modul '2MoreVO' placed into eurorack connected to the bus.
- Eurorack power switched on and warmed up at least for 30 minutes.
| Step Nr |
action | result | remark |
|---|---|---|---|
| 1 | Set pot's 'Tune 1/2' to full CCW position | measure current pitches on 'Osc1 Out' and 'Osc2 Out' | remember currently measured pitch-values. |
| 2 | Set pot's 'Tune 1/2' to full CW position | measure current pitches on 'Osc1 Out' and 'Osc2 Out' | the pitches should be 4 octaves above the values measured in Step:1. |
| 3 | Set pot's 'Tune 1/2' to center position | measure current pitches on 'Osc1 Out' and 'Osc2 Out' | the pitches should be approximately 2 octaves above the values measured in Step:1. |
| 4 | Set switch 'Octave' to '+' and switches 'VCO1'-Octave-'VCO2' to '1' |
measured pitches must be one octave above the 'Off' position | measured or audible on 'Osc1 Out' and 'Osc2 Out'. |
| 5 | Set switch 'Octave' to '+' and switches 'VCO1'-Octave-'VCO2' to '2' |
measured pitches must be two octaves above the 'Off' position | measured or audible on 'Osc1 Out' and 'Osc2 Out'. |
| 6 | Set switch 'Octave' to '-' and switches 'VCO1'-Octave-'VCO2' to '1' |
measured pitches must be one octave below the 'Off' position | measured or audible on 'Osc1 Out' and 'Osc2 Out'. |
| 7 | Set switch 'Octave' to '-' and switches 'VCO1'-Octave-'VCO2' to '2' |
measured pitches must be two octaves below the 'Off' position | measured or audible on 'Osc1 Out' and 'Osc2 Out'. |
| 8 | Set all switches to 'Off' and the VCO's to be in tune with pot's 'Tune 1/2'. Play octave-steps on the keyboard. |
check the VCO-pitches to be in tune over the octaves. | measured or audible on 'Osc1 Out' and 'Osc2 Out'. |
| 9 | Tune pot 'Osc-Fade' from CCW to CW and backwards | Fading between Osc1- and Osc2-Output waveform must be possible | measured or audible on 'Osc-Mix Out'. |
| 10 | Tune pot 'Wave1 CV' from CCW to CW and backwards | Changing between triangle- and saw-waveform must be possible | measured or audible on 'Osc1 Out'. |
| 11 | Tune pot 'Wave2' from CCW to CW and backwards | Changing between triangle- and saw-waveform must be possible | measured or audible on 'Osc2 Out'. |
| 12 | Tune pot 'Mod.Level CV' from CCW to CW and backwards | Sinusodial signal-level must change on 'Mod Out' | measured or audible on 'Mod Out'. |
| 13 | Set pot 'Mod.Level CV' to CW and tune pot 'PWM' to CW and backwards | Pulswith must change on 'Puls2 Out' | measured or audible on 'Puls2 Out'. |
| 14 | Set switch 'FM1 Lin/Log' to 'FM1 Lin' and detune VCO2 against VCO1 | Linear frequeny-modulation on 'Osc1 Out' | measured or audible on 'Osc1 Out'. |
| 15 | Set switch 'FM1 Lin/Log' to 'FM1 Log' and detune VCO2 against VCO1 | Logarithmic frequeny-modulation on 'Osc1 Out' | measured or audible on 'Osc1 Out'. |
| 16 | Set switch 'Sync Hard/Soft' to 'Sync Hard' and detune VCO2 against VCO1 | Hard synchronisation done between VCO2 and VCO1 forced by VCO2 | measured or audible on 'Osc1 Out'. |
| 17 | Set switch 'Sync Hard/Soft' to 'Sync Soft' and detune VCO2 against VCO1 | Soft synchronisation done between VCO2 and VCO1 forced by VCO2 | measured or audible on 'Osc1 Out'. |
| 18 | Set switch 'FM2 Lin/Log' to 'FM2 Lin' and change modulation-level with pot 'Mod.Level CV' | Linear self frequeny-modulation on 'Osc2 Out' depending on modulation-level | measured or audible on 'Osc2 Out'. |
| 19 | Set switch 'FM2 Lin/Log' to 'FM2 Log' and change modulation-level with pot 'Mod.Level CV' | Logarithmic self frequeny-modulation on 'Osc2 Out' depending on modulation-level | measured or audible on 'Osc2 Out'. |
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