Slim VCO

Constructional Difficulty: Moderate. Some careful calibration required.


The suggested panel designs for the SVCO-A (left) and SVCO-B (right) single width voltage controlled oscillators.

Two compact well specified audio VCOs for MOTM and MU based modular synthesisers.

The 'A' variant has a single tune control and three way octave switch. While the otherwise identical 'B' variant has an inc-dec switching system (with three way momentary switch and LED ladder display) to allow for easy control over five octaves and a wide range LFO setting.

SVCO-A modules are built with just the SVCO main board. The B variant uses the same SVCO main board with an additional SVCO-B daughter board that attaches to the main board via a tidy 10-way ribbon cable.

Both variants have a variable width pulse wave as well as a sawtooth waveshaper to generate a fully varying shape from ramp through triangle to sawtooth.

The SVCO uses a sawtooth core but with a different topology than our existing double width VCO. Hard synchronisation is possible from an external VCO. Expansion to a double width module would be possible to allow for further input and output capability.

To allow all the functions required by this module we have had to reduce the spacing between the pots. Instead of our usual 1.625" (41.3mm) we have opted for the smaller 1.375" (34.9mm). Used in conjunction with smaller 20mm (13/16") diameter knobs this still allows for an attractive module design and finger friendly tweaking.

The module accommodates either our standard Oakley/MOTM power header or a Synthesizers.com power header. Current consumption is approximately +40mA and -35mA for the SVCO-A, and +47mA and -38mA for the SVCO-B.

In LFO mode the SVCO-B's tune pot will operate over a range of 0.01Hz (one cycle every 1.5 minutes) to 500Hz.

The main SVCO PCB is 10.9cm (deep) x 12.3cm (height). As with all Oakley projects both PCBs are double sided with through plated holes, have tough solder mask both sides, and have bold component legending for ease of construction.

The prototype SVCO-B fitted to a natural finish Scheaffer panel. This shows the SVCO-B octave board mounted above the SVCO main board. A 10-way IDC interconnect carries the various signals and power between the two boards. Note also the use of the optional Sock6 socket board to help keep the wiring to the sockets neat and tidy .


Prices

Click here for how to order.

SVCO issue 2 PCB ...................................................... 20GBP
SVCO-B octave board issue 1 PCB .......................... 12GBP
Sock6 issue 1 PCB ........................................................ 6GBP

SVCO pot bracket kit ................................................ 0.75GBP

1K +3500ppm/K temp co resistor ................................ 4GBP*

The optional Pot Bracket Kit contains the three 16mm Alpha pot brackets required to complete one module.

*1K +3500ppm/K parts are only available to purchasers of the PCBs. They are not available to buy separately.

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

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

SVCO ready made modules may be available from Krisp1.com.


The prototype SVCO-A module in a natural finish Schaeffer panel. To build the SVCO-A module you only need the SVCO main board. The PCB in this photograph is issue 1 but issue 2 is similar. Note again the use of the Sock6 to make wiring the panel sockets so much easier.


Project Downloads

SVCO-A & SVCO-B User Manual

SVCO-A Issue 2 Builder's Guide

SVCO-B Issue 2 Builder's 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 available to purchasers of the PCB or module and will be sent via e-mail when the board(s) are shipped.

Front Panel database

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

5U format 1U wide SVCO-A module in traditional black

5U format 1U wide SVCO-B module in traditional black

5U format 1U wide SVCO-A module in natural finish

5U format 1U wide SVCO-B module in natural finish

To read these files you will need a copy of 'Frontplatten designer' from Schaeffer. The program also features on-line ordering, so it's easy to buy your panels from Scheaffer.

The company are based in Berlin in Germany and will send out 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.

The INC/DEC switch allows you to switch between five octaves or put the unit into the LO mode whereby the SVCO-B behaves as a wide range VC-LFO module.


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Copyright: Tony Allgood.
Last revised: September 27, 2017.