Dual VCO - Two classic sawtooth core oscillators

Constructional Difficulty: Moderate with surface mount parts


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. The circuitry is similar to the dual oscillator used in the 5U Oakley ASV module.

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 +/-57mA 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 main board on the rear of the module houses the power input and conditioning, the two VCO cores, and exponential convertors. The 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. The NPN transistor array is a through hole DIL14 THAT300P. The two temperature coefficient resistors are through hole KRL C-2AQ 1K.


Prices

Click here for ordering details.

DVCO (Euro) main board issue 1 PCB........................................... 14GBP

DVCO (Euro) pot board issue 1 PCB ............................................... 7GBP

1K +3500ppm/K temp co resistor (pack of two) .............................. 8GBP

Both boards are required to build the Oakley Dual VCO for Eurorack project.

All other parts can be purchased from your usual electronic component supplier.

All prices include VAT at UK rates. Shipping is additional to these prices. See also the FAQ page.


Project Downloads

Dual VCO Builders Guide

Construction Guide Our handy guide to building Oakley DIY projects

Parts Guide Our handy guide to buying parts for Oakley DIY projects

Schematics are only available to purchasers of the PCBs and will be sent via e-mail when the boards are shipped.

Front Panel database

A Schaeffer front panel can be made for this module. The database can be found by downloading the following link:

14HP Eurorack format in natural silver

To read, edit and print these files you will need a copy of 'Frontplatten Designer' from Schaeffer. Panels can be ordered via the program using its secure online ordering system.

Schaeffer are based in Berlin, Germany and can send panels to anywhere in the world. Delivery to the UK normally takes around ten days. For North American users you can also order your Schaeffer panels from Front Panel Express.



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Copyright: Tony Allgood.
Last revised: October 17, 2019.