Bill and Will's Synth
Oakley Sound Systems
Triple VCA Construction

June 2010 -

Well - what can I say - we wanted a few simple VCAs.  We came across this on the Oakley Site.  Presto - a relatively easy build - took us a little more than four hours start to finish.

Table of Contents

This page has become really long, so here's a table of contents that we hope will make it easier to traverse:

Background - presents Jurgen's initial description of the effect

Parts - presents a Bill of Materials and notes about it

Panel - Bridechamber fabricated the MOTM format one

Construction Phase 1 - Resistors, Capacitors, IC Sockets, Power Plugs, MTA headers

Construction Phase 2 - Trimmers, Panel connections

Set up / Testing

Background

The Oakley Sound Systems Page describes the Module:

"One can never have enough voltage controlled amplifiers (VCA) in a modular synthesiser. The VCA allows you to control any signal, be it CV or audio, with another control voltage (CV).

"In the typical application one uses a VCA to shape the volume of the final output signal of the synthesiser. But a good VCA can do much more.

• You can use a VCA to control a low frequency oscillator's (LFO) output that is modulating the pitch of a VCO. Thus the depth of vibrato can be controlled directly with a CV. This CV could be the aftertouch CV from the midi-CV convertor for truly powerful performance playing.
• A VCA can control audio feedback around a filter module giving you voltage controlled resonance.
• A VCA can control the depth of audio rate frequency modulation (FM) of filters and oscillators. Control the depth with an envelope generator for beautiful bell tones.
• A VCA can give you voltage controlled mixing when used with a conventional passive mixer module.
• You can use a VCA to produce ring modulation effects when used with the Oakley MultiMix.

"The Oakley VCA module consists of three high quality voltage controlled amplifiers (VCA) suitable for audio and CV. This design uses standard parts in a very unconventional manner to give a superb sounding VCA with low noise and the minimum of CV breakthrough. Unlike my older 'Basic-VCA' design, all three VCA sections are one board to facilitate quick and troublefree building.

"Each VCA has two controls. Firstly, there is GAIN, a fixed bias to set the initial gain of the VCA, it can also be used a volume control. Secondly, the CV pot allows you to alter the sensitivity of the external CV that controls the VCA's gain.

Click here to get to the Oakley EFG page.

Click here to view the User's Manual .pdf file.

Parts

Will and I have developed a parts-list / bill-of-materials in the form of an XL spreadsheet based on the parts list from Oakley.

In the BOM, the left-most column is the "part."  The parts we've ordered have a green background.  These parts we have a high (but not perfect) level of confidence that we've specified correctly - we caught a mistake or two in part numbers / prices as we were ordering.  please double-check us and let us know of mistakes you find.

Corrections to BOM:

None yet -

Notes:

None yet -

Click here to download the spreadsheet (apx. 48K). 

Pots / Brackets from Oakley

Panel

We got ours from Bridechamber.

Construction Phase 1

All the stuff in Phase 1 gets soldered using "Organic" Solder.  At every break in the action, we wash the board off to get rid of the flux.

  
PCB Front and Back (click on images for larger ones)

Resistors

Capacitors

Semiconductors, IC Sockets, Misc.

Construction Phase 2

All the stuff in Phase 2 gets soldered using "No-Clean" Solder and the PCB doesn't get washed off from here on.

Potentiometers, Trimmers

Oakley provides a description of how to install the pots and mounting brackets, and we detail the process on our Envolpoe Follower page here.

Panel Mounted Pots

The three pots that mount on the panel, Oakley provides "chicklets" for:

PCB Wires

The wires soldered in:

Grounding the Jacks

installed with the bevel in the upper left

wire jumpers joining the ground lugs

Installing the ICs

Connections

Done

Set up / Testing

Use Notes