3031

This is my Oakley Sound TB3031. It's a great sounding 303 clone with some nice extras like sub-oscillator, filter-FM, overdrive, etc. Unfortunately the PCBs have now run out and I'm not sure if Tony Allgood (of Oakley Sound) will be making any more - however you can purchase the schematics and PCB gerber plots from him to make your own PCB.

This 3031 has my own MIDI to CV converter based on the Fat Controller design and PCB. It has been customised specially for the 3031 and has the following features:

MIDI In, MIDI Thru
3x gate outputs: Note on/off (0V/5V), Slide on/off (0V/5V), Accent on/off (0V/12V)

Up to 15 high-precision CV outputs, of which 7 are currently used:


Note value	0V to +10.6V	3031 input is 1V/octave
Velocity	0V to +10.6V
Modulation wheel	0V to +10.6V
Pitch bend	-4.4V to +4.4V	3031 input is 2.2V/octave
Software LFO	-4.4V to +4.4V	3031 input is 10V/octave
An extra pair of CV and Gate outputs (for controlling an external synth)

Adding more CV outputs can be done by just adding more S&H caps and opamp output buffers to the PCB, and changing the software in the PIC.

Comprehensive MIDI specification:


Note On (Pitch & Velocity)		0 = 0V, 120 = 10V, 127 = 10.58333V
Note Off
Modulation wheel	MIDI CC 1	0 = 0V, 120 = 10V, 127 = 10.58333V
Slide On/Off	MIDI CC 65	0->63=Off, 64->127=On
Accent On/Off	MIDI CC 80	0->63=Off, 64->127=On
All Sounds Off	MIDI CC 120
All Notes Off	MIDI CC 123
Pitch Bend		0x0000 = - full bend range 0x2000 = no bend 0x3FFF = + full bend range
Pitch Bend Range	MIDI CC 16	0 = no bend 60 = 1 octave bend (+/-2.2V) 120+ = 2 octave bend (+/-4.4V)
LFO Speed	MIDI CC 17	0 = slow (0.5 Hz), 127 = fast (65 Hz)
LFO Extra Speed *	MIDI CC 18	0 = slow (65 Hz), 127 = fast (146 Hz)
LFO Waveform	MIDI CC 19	0 = sine 1 = triangle 2 = falling saw 3 = rising saw 4 = square
LFO Depth	MIDI CC 92	0 = 0V ptp, 127 = 8.8V ptp
Legato Retrigger	MIDI CC 82	0->63=Off, 64->127=On

* LFO Extra Speed only has effect when LFO Speed is at maximum (127). LFO Extra Speed takes the LFO frequency further up into the audio range allowing different FM timbres. The frequency does not track note pitch so it has limited 'musical' applications, but is very nice for creating interesting timbres that will be played only on single notes (or at octave intervals).

The whole thing is housed in a 1U 19" rack mount case from Maplin Electronics (part no. N34AN, costs about Ł30) which has plenty of room for the MIDI to CV PCB (back left) and the mains transformer (back right). The front panel was made by Schaeffer AG.

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