MiniMod VCO User Manual
Contents
1. A lt Saw Output D Sync Type SYNC LIN 8 Sync Input __ ea ye e lt _ Square Output 14 G v oc input ea 6 Linear Input Triangle Output 12 O Octave Switch Use the Octave switch to quickly select preset octaves the Lo setting reduces the oscilla tor frequency into the Low Frequency Oscillator range so that it can be used as a modula tion source Tune Control The tune control varies the oscillator pitch by around 8 notes Larger variations in pitch can be obtained by applying a positive or negative control voltage to the 1 Volt per Octave input 3 G 1V Oct Input This is the 1 Volt per Octave control voltage input Applying a positive voltage to this input raises oscillator pitch at the rate of exactly one octave for each volt applied and a negative voltage will reduce the pitch by exactly one octave per volt The acceptable input range is 7 Volts A limitation of the vintage oscillator core design means that tracking may not follow the 1V Oct law above 10KHz Distribution Buss 1V Octave CV signal The Eurorack power distribution buss can transmit a 1V Octave voltage from a Mini CV converter or similar source The MiniMod VCO accepts this signal by default as it is normalled through the 1V Oct socket however plugging a jack into the 1V Oct socket unswitches defeats this control voltage and allows the VCO to run free Exp CV Input This is the Exponential Control Vol2. MINIMOD VCO User Guide Vintage discrete transistor core VCO Thank you for purchasing the AJH Synth MiniMod VCO 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 The discrete all transistor core of this Voltage Controlled Oscillator is an exact emulation of the original and now very rare R A Moog Model D Oscillator from 45 years ago It features a fully matched PNP transistor expo converter and P FET transistor buffer amplifier section but with the advantage of much improved temperature stability and modern construction using reliable precision SMT components along with Eurorack modular synthesiser expandibility It features front panel switchable octave selection and four independent waveform outputs including the famous Sharktooth waveform Sawtooth wave Square wave and Triangle wave and when used as part of a full MiniMod system can provide a very accurate emulation of the Model D systhesiser and it s highly acclaimed fat vintage analogue sound The Square wave output has fully adjustable Pulse Width Modulation with manual and CV control rather than the more restricting selection of square wave or two static fixed pulse widths of the original design Also included are Exponential and Linear modulation inputs and two different types of oscillator sync which he
3. ckwise to increase VCO pitch and clockwise to reduce the pitch Adjusting this trimmer will not affect the scaling FOR MANUFACTURER ADJUSTMENT ONLY Sets the V Oct scaling for the VCO Specialist test equipment is needed to calibrate this trimmer correctly FOR MANUFACTURER ADJUSTMENT ONLY Sets the span for the Octave Select Switch Specialist test equipment is needed to calibrate this trimmer correctly FOR MANUFACTURER ADJUSTMENT ONLY Specialist test equipment is needed to calibrate this trimmer correctly FOR MANUFACTURER ADJUSTMENT ONLY This sets the current level through the P FET transistor buffer and incorrect adjustment can halt the Oscillator completely so NO ATTEMPT should be made to adjust this trimmer If you need any help using this module or have any technical questions please feel free to contact us at support ajhsynth com Copyright AJHSynth 2014
4. eform required for effective triggering The Sync effect is very level sensitive and the waveform level from the Sync Input 8 presented to the oscillator core can be set using this control Start with the control fully counter clockwise and gradually increase it until the desired effect is obtained The frequency relationship between this oscillator and the synchronising oscillator plays a large part in the resulting sounds created If using another MiniMod VCO as the sync source then Sync Threshold knob position 2 to 3 is a good starting point when the Sync Type switch is in the down position and control knob position 7 to 8 when this switch is in the up position Experiment This switches between the two different sync types With the switch down regular sync is effective which can be used to create ripping laser harp type sounds When the switch is set to up a rising ramp waveform is required as the sync source and this should be set to a higher frequency than the slave oscillator Different Sync threshold levels are required for the up and down Sync switch positions Rising ramp waveform output It has a level of 5 volts centred around Ov The output impedance is 1Kohm Triangle wave output It has a level of 5 volts centred around Ov The output impedance is 1Kohm The famous Sharktooth waveform from the early Model D synthesiser It has an output level of 5 volts centred around O
5. lp to make this a very versatile Eurorack VCO in its own right Module width is 14 HP of EuroRack space and it is compatible with standard Euro Rack cases The height of the panel is 128 5mm and depth is 38mm There are four mounting holes at the corners of the module and we provide 4 of M3 rack fixing screws along with a Eurorack compatible power cable Current consumption is 55mA from the 12V supply rail and 40mA from the 12V supply rail All AJHSynth modules are covered by a one year guarantee against manufacturing defects Notes As with all vintage analogue oscillators after powering up it is best to be allowed to warm up for 15 minutes or so before use Tuning immediately after power up is not advised as it takes time for the internal circuitry to get up to temperature and stabilise After the warm up period it will maintain pitch well much better than the original on which it is based 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 SYNTH www ajhsynth com Controls Inputs and Outputs MINI MOD VINTAGE ee CORE VCO O Octave Switch Linear CV Level Exp CV Level Tune Control 2 NS ENE o Age oe 9 Sync Threshold SYNC LEVEL 4 6 PWM Control 16 PWM CV PWM SHAPE 4 1 1 E PWM Shape Exp CV Input Shark Output aC EXP CV PWM K
6. tage input Acceptable input voltage range is 5V When a voltage is applied to this input it varies the oscillator pitch in a similar fashion to the 1 V Oct input however the amount of control voltage applied to the oscillator core can be regulated using the Exponential CV Level control 5 Exp CV Level This control adjusts the amount of voltage from the Exp CV input that is passed to the oscillator core its range is 0 to 120 6 Linear Input 7 Linear CV Level Sync Input 9 Sync Threshold Sync Type Saw Output Triangle Output Shark Output Square Output PWM Shape PWM Control This is the Linear Control Voltage Input Acceptable input voltage range is 5V This is a more subtle modulation effect which varies the oscillator pitch by up to 7 notes depending upon the setting of the Linear CV Level Control 7 Controls the amount of Linear Modulation applied to the oscillator core from the Linear CV Input 6 A rising ramp waveform of 5V e g the Saw waveform from another MiniMod VCO can be applied to this input to prematurely reset synchronise the oscillator waveform for interesting sonic results The sync effect is very level sensitive and is set using the Sync Threshold control 9 If it is desired to use a falling ramp waveform from a different oscillator for sync it will need to be fed through an invertor to convert it to the rising ramp wav
7. v The output impedance is 1Kohm Square wave output It has a level of 5 volts centred around Ov The duty cycle amount of time the waveform is high against low can be varied with the Manual PWM control 15 or under voltage control 16 The output impedance is 1Kohm Adjusts the duty cycle of the square wave between approximately 10 and 90 When set to the half way 12 o clock position the duty cycle is 50 which creates a regular Square wave A control voltage can be applied to the PWM CV Input to vary the PWM duty cycle The control voltage range should be between 5volts and the intensity can be controlled between 0 to 100 with the PWM CV rotary control knob A low frequency triangle wave to the PWM CV Input will give the classic sweeping PWM effect The PWM Shape Control is still effective when using PWM CV and it changes the offset level Note This information is given for completeness the MiniMod VCO is calibrated after manufacture Adjustment and Calibration and under normal circumstances should not require any user adjustment Octave Adjust A Tune Adjust Scale Adjust Octave Adjust D HFT Adjust E Shape Adjust HFT Adjust D Scale Adjust Shape Adjust E cr eS a SSS a Fs J Red Stripe aligns with 12V as shown Sets the default frequency for the VCO This is a multi turn trimmer that should be adjusted with a fine jeweller s screwdriver Turn counter clo
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