Philip Rees L mcv
This up-to-date interface midi to cv unit lets you use your MIDI keyboard, computer, sequencer or other MIDI master device to control your irreplaceable old analogue monosynths, with their fat bass sounds and friendly knobs.
The Little MCV responds fast and can generate control voltages for the common one-volt-per-octave (logarithmic VCO, as used by Roland and Moog) system and the so-called volts-per-hertz (linear VCO, as used by Korg) system. CV type is selected by a slider. The voltage law of the two types is contrasted in the graph above.
Superb 16 bit resolution
The use of a high quality, modern 16 bit DAC means that the logarithmic pitch CV output can be perfectly in tune across the full note range, with fine steps (a stunning 512 steps per semitone) for the firmware-implemented pitchbend, pitch vibrato and portamento. 16 bit conversion also lets the Little MCV generate an accurate linear CV of superlative stability over a very wide pitch range.
In V/oct mode, unlike other low cost units, the Little MCV responds properly to pitch over the full 128 semitone MIDI range. The CV output also has a wide range available: from -10V to +20V. A tuning preset adjustment is provided to set the V/oct offset or V/Hz slope. A trim preset lets you finely match your target instrument with respect to the slope for V/oct, or the offset for V/Hz.
The pitchbend firmware can use the full 14-bits of the MIDI pitchbend value. This combines with the 16-bit conversion to give clean stepless glissando if you have a suitable high resolution source of pitch wheel data. The default pitchbend range is plus-or-minus one octave. The standard MIDI 'pitchbend sensitivity' Registered Parameter is observed, so you can alter the bend range if required.
Under MIDI control, the Little MCV digitally generates a precise triangular low frequency oscillator (LFO) signal, which may be added to the CV output - to create a high quality pitch vibrato. The LFO depth is controlled by the product of the MIDI Modulation Wheel and a value derived from the Tremolo Depth Controller (see graph below). The LFO speed is conveniently set by MIDI Non-Registered Parameter Number 00.
The portamento (pitch-to-pitch glide) response is exponential and free of irregularities. The MIDI 'Portamento On/Off and Portamento Time messages are observed.
Little MCV defaults to last note priority, but overlapped notes are not lost, and hidden notes can restart when a more recent note is released - this is generally the most favoured algorithm. MIDI Controller Number 80 will switch over to highest note priority.
The three MIDI Sostenuto, Sustain and Hold 2 commands are all fully implemented.
A simple slide switch lets you choose between 5V positive, 10V positive and S-trig (negative current gate, Moog style) for the gate output.
The ACTIVE lamp indicates when the gate signal is asserted.
The table below lists the MIDI controller (Control Change) numbers used in Little MCV, and summarises what they do.Little MCV implementation of MIDI controller Numbers Dec Hex MIDI Controller Name Usage in Little MCV
1 01H Modulation Wheel MSB Coarse setting of LFO depth
5 05H Portamento Time MSB Coarse setting of pitch glide speed
6 06H Data Entry MSB Coarse setting of LFO speed and bend range
33 21H Modulation Wheel LSB Fine setting of LFO depth
37 25H Portamento Time LSB Fine setting of pitch glide speed
38 26H Data Entry LSB Fine setting of LFO speed and bend range
64 40H Damper pedal (sustain) Sustains all subsequently released notes
65 41H Portamento On/Off Enables and disables pitch glide function
66 42H Sostenuto Sustains only subsequently keyed notes
68 44H Legato Footswitch Selects gate logic for overlapping notes
69 45H Hold 2 Switches background hold feature
80 50H General Purpose #5 Selects highest-note or last-note priority
81 51H General Purpose #6 Enables and disables LFO synchronisation
92 5CH Tremolo depth Sets LFO depth gain parameter
96 60H Data Increment Step setting of LFO speed and pitchbend range
97 61H Data Decrement Step setting of LFO speed and pitchbend range
98 62H Non-Regd Param LSB Set to zero when setting LFO speed parameter
99 63H Non-Regd Param MSB Set to zero when setting LFO speed parameter
100 64H Registered Param LSB Set to zero when setting bend range parameter
101 65H Registered Param MSB Set to zero when setting bend range parameter
120 78H All Sounds Off Cancels Hold and clears all keyed notes
121 79H Reset All Controllers Clears pitchbend and all Control Change values
123 7BH All Notes Off Clears keyed notes but does not override hold
124 7CH Omni Mode Off Unit will respond only to selected MIDI channel
125 7DH Omni Mode On Unit will respond to any MIDI channel
126 7EH Poly Mode Off Clears keyed notes but does not override hold
127 7FH Poly Mode On Clears keyed notes but does not override hold