Sculpt-O-Sound presents Rest-O-Matic.
Rest-O-Matic is a utility that makes it possible to produce rests when using a B960 (or similar style) sequencer. The B960 sequencer outputs control voltages and gates. It will ‘play’ all steps all the time unless you skip one or more steps. Skipping a step however will shorten the sequence by 1 step and sometimes this is not what you want. So I came up with Rest-O-Matic.
Rest-O-Matic’s inputs are connected to the B960 CV out (connect to ‘CV-in’) and the clock the B960 uses (connect to ‘gate’). Rest-O-Matic from these two produces a gate on its output only if the CV voltage is above a certain threshold. This gate can then be used to control the VCA of the oscillator who’s frequency is controlled by the B960 CV voltage. Thus, by choosing the CV-values on a B960 you can determine whether a note is played or a rest is ‘played’.
Build
This was just a quick project, so I did not make a PCB but used a bit of perf board and 3D-printed a front panel.
Schematic
How it works
The opamp amplifies the CV value so that it can be a logical 1 or zero. An external gate or clock combined with this fed into a logical AND will result in an output gate which is high only if the input gate is high AND the CV-value is high (or amplified enough). So if the CV-voltage is too low, no gate will appear at the gate output. So if the output gate is used to control the VCA of some noise source, like a VCO, no tone is produced but a Rest.
The double NAND gates are combined to be a logical AND. Because I sometimes need an inverter in my rack, I added a jack between the 1st and 2nd NAND (this is the extra bit on the left that connects point A to B; the switch here is the one in the jack connector). So as an aside I can also use this module as a single NOT / inverter port. The opamp is powered with -12 and +12 Volt, the quad NAND gate with 5V. The diodes at the inputs of the NAND-gates make sure the output voltage of the opamp on the input of the NAND-gate does not exceed 5V (much).
All diodes are BAT85.
I first contemplated using a comparator as input stage to convert the CV-voltage into a logical 0 or 1 (depending on its amplitude) but given that the B960 has 3 voltage ranges (0-2V, 0-4V, 0-8V) I wanted it to work for all of them so I needed a variable threshold. But then I wanted to add some hysteresis and things became complicated. So I opted for a simple design and used a gain stage relying on the NAND-gate to threshold the signal.
To use Rest-O-Matic, turn up the gain from 0 until the LED starts flashing.
There is a short demo here:
