The Journeyman Voltage Controlled Filter Module

Constructional difficulty: Easy to moderate in 1U format, more difficult in 2U format.


The suggested front panel design for the 2U version of the Journeyman VCF.

If our Transistor Superladder and SVF are well behaved perfect sounding filters, then this one is the rude boy of filter design. Its completely unlinear response and discrete circuitry gives it a unique sound of its own. Partially modelled after a classic Japanese filter design from the mid to late 1970s, the Journeyman can be configured in either -6dB/octave high pass or -12dB/octave low pass modes by the flicking of a switch. When two of these VCFs are used together, one in HP and the other in LP, then the effect is astounding.

The filter heart is made entirely from a single ended discrete design and uses four matching diodes as the control elements. The filter behaves differently depending on the input signal level hence the 'drive' pot on the front panel. Turning this up allows the filter to be overdriven. At full resonance the filter will oscillate across most of the audio band.

The design is intended to fit into a 1U wide 'filter-core' module or a more fully featured 2U wide panel with seven control pots.

The 1U 'Filter Core' format is our way of handling filter modules. Although the 1U module can be used as a filter module on its own, it is expected that users will make use of external mixers to control CV and audio levels going into the filter. In this way, you will be able to have a collection of space saving 1U filter cores that can be used with any generic mixer module. The popular Oakley Multimix is the perfect choice for such a mixer module.

For the 2U design three audio inputs are provided each with its own attenuator. Three CVs can control the cut-off of the filter. One is fixed at approximately 1V/octave, the other two have input attenuators. CV2 features a reversible type attenuator with inverting/non-inverting properties.

Issue 2 of the Journeyman is a significant update to the original issue 1 design with, amongst other things, improvements to setting up, less CV breakthrough and better power supply noise rejection.

The module accommodates either our standard Oakley/MOTM power header or a Synthesizers.com power header. Current consumption is approximately 20mA per rail.

The PCB is 8.3cm (deep) x 14.3cm (height). The frequency, resonance, drive and CV depth pots are normally board mounted for easier construction.

As with all Oakley projects the PCB is double sided with through plated holes, has tough solder mask both sides, and has bold component legending for ease of construction.

The 1U format 'filter core' Journeyman filter. This offers the basic filter module without the extra CV and audio mixing that the full width 2U module provides.


Sound Samples

All the following samples recorded with a small Oakley set up comprising of one VCO, one VC-LFO, one Journeyman filter, two ADSR/VCA and one midiDAC to control them all.

jour-seq.mp3 1.40Mb 1min 1s. Using the low pass output. Simple sequence with an input from the sawtooth output of a single Oakley VCO. The filter is manually being swept via the 'freq', 'resonance' pots and altering ADSR sweep depth.

jour-seq2.mp3 1.45Mb 1min 4s. This time using the high pass output using the same simple sequence whilst the cut-off, sweep depth and resonance controls are tweaked.

jour-hit.mp3 1.28Mb 56s. Various one shot hits and blats at different settings of frequency, resonance and drive.

jour-sol.mp3 0.44Mb 19s. Low pass output; a bit of resonance, fixed cut-off frequency and a bit of reverb for ambience.


The Journeyman 2 'Filter Core' VCF as a single width MOTM format module in a natural finish Schaeffer panel.

Note also the use of the optional Sock4 socket board to help keep the wiring to the sockets neat and tidy . The various empty resistor and header locations you can see are used in the 2U wide full version. Please ignore the two black blanking plugs in the panel - this particular panel is my prototyping panel I use for testing all four pot/four socket modules.


Prices

Click here for how to order.

Journeyman VCF issue 2 PCB ................................... 20GBP
Sock4 issue 1 PCB ........................................................ 5GBP

Journeyman VCF pot bracket kit .............................. 0.75GBP

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

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

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

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


Project Downloads

Journeyman issue 2 Builder's Guide

Journeyman issue 2 User Manual

Construction Guide Our handy guide to building Oakley DIY projects

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

Links to schematics are available to purchasers of the PCB or module and will be sent via e-mail when the board(s) are shipped.

Use 'save as...' button to download and view the files. IE users need to right hand mouse click and then choose 'save as'.

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 (Filter Core) module in traditional black

5U format 2U wide (Full Version) module in traditional black

To read these files you will need a copy of 'Frontplatten designer' from Schaeffer. The program also features on-line ordering, so its now even easier 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.


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Copyright: Tony Allgood.
Last revised: June 14, 2016.