Beers 4047 VCO

We are delighted to be offering these eurorack modules designed in Australia. 

8HP, White Panel

Isaac’s original VCO design, slightly cleaned up.

This is an otherwise standard analogue triangle-core VCO design with a 4047 CMOS IC in gated astable mode shoved in the middle.

The oscillations are 'gateable': when given a trigger or gate the oscillation will complete one cycle then repeat if the gate is still present.

With nothing patched into GATE it will run freely like a regular VCO.

There are 6 outputs:

TRI1: triangle, SQR: square, PLS: pulse-width modulated output,

TRI2: sub-octave triangle, Q: sub-octave square, !Q: sub-octave square (opposite phase)

LIN, EXP, GATE, RESET, PWM are inputs.

The GATE input is held high with nothing plugged in, but when a cable is inserted the VCO will only run when the GATE input sees more than approx. 1V

RESET only affects the sub-octave outputs: TRI2 and Q will be held low and !Q held high while RESET sees more than approx. 1V

EXP input is for 1V/oct CV

LIN input (with attenuator) for linear frequency modulation ***note: LIN input is inverted, +ve CV will lower frequency, -ve CV increases frequency.. oops!

PWM input (with attenuator) controls pulse width of PLS output, PW pot sets initial pulse width.

CAL trimmer accessible from front calibrates 1V/octave tracking. Expect at least 3 octaves of good tracking using 3300PPM 2k tempco resistor for R17 in good thermal contact with Q1. A dab of the dreadful white goop recommended between them.

C1 should be a good quality C0G/NP0 cap.

Using 10n for C1 and 4n7 for C3 gives a range of approx 25 seconds per cycle up to around 10kHz.