Oakley Modular Euro Dual VCO

The 14HP wide Oakley Dual VCO, or DVCO, is two traditional sawtooth core voltage controlled oscillators in one module sharing a single common 1V/octave input. Each oscillator features a sawtooth (falling ramp) and variable width pulse wave output. VCO2 also has an additional triangle wave output. Except for the triangle wave output, the outputs are +/-5V, that is, 10V peak to peak. The triangle output is +/-6V, that is, 12V peak to peak.

The pitch of the two oscillators is controlled with a master fine tune pot on the front panel, the single 1V/octave CV input, as well as a global FM input with an associating modulation depth control. VCO2 can be individually controlled by its own FM input and associating pot. There are separate three position octave switches for each VCO. VCO2 also features an individual tune control that covers just over one octave.

VCO2’s frequency can be hard synchronised to VCO1 by a front panel switch.

Individual pulse width controls are available for each oscillator. The middle position on the pot gives a square wave from the respective pulse output. At each end of the pot’s travel the pulse output will be silent. Pulse wave modulation is available for each VCO separately and each has its own depth control.

Current draw is approximately +75mA and -85mA at +/-12V.

The PCB set

The DVCO module comprises of two printed circuit boards (PCBs) connected together with seven 0.1 (2.54mm) single in line (SIL) headers and sockets. The four layer main board on the rear of the module houses the power input and conditioning, the two VCO cores, and exponential convertors. The two layer pot board has the pots, switch, and sockets that are attached to the front panel, as well as the CV
processing circuitry for pitch and pulse width, and voltage references. The main board is a four layer design, while the pot board is a two layer design. Each board is the same size; 68 mm x 107 mm.

The majority of the components are surface mount parts. The ICs are SOIC, while the resistors and surface mount capacitors are 0805.