Journeyman - Classic Diode Ring Filter

Constructional Difficulty: Easy to moderate with surface mount parts


This is a 6HP wide four pole dual mode filter module capable of either -12dB/octave low pass or -6dB/octave high pass responses.

The Journeyman's unlinear quirky discrete circuitry gives it a unique sound of its own. Partially modelled after the classic Japanese Traveller 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 a switch on the front panel. When two of these VCFs are used in series, one in HP and the other in LP, then the effect is astounding. While no one would call this filter hi-fi, it has many desirable characteristics that have stood the test of time.

The filter core is made entirely from a single ended discrete design and uses a ring of four diodes (actually the base-emitter junctions of four high quality matched NPN transistors) as the control elements. The filter behaves very differently depending on the input signal level hence the usefulness of a 'drive' pot on the front panel. Turning this up allows the filter to be overdriven, without changing the output volume, and dramatically changes the sound at higher resonance settings. At high resonance the filter will self oscillate across most of the audio band.

Two control voltage (CV) inputs are available on the front panel. CV1 offers the standard 1V/octave control over the cut-off frequency. While CV2 has a depth control which can be varied from off to up to 0.5V/octave, and has additional switch that can invert CV2 if negatively going sweeps are desired.

The module requires +/-20mA at +/-12V.


The PCB Set

The Journeyman module comprises of two printed circuit boards (PCBs) connected together with four 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 filter core, and CV processing circuitry. The pot board has the pots, switch, and sockets that are attached to the front panel, as well as the overdrive control and CV summing circuits. The main board is a four layer design, while the pot board is a two layer design. Each board is the same size; 29 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. All components are standard parts.


Sound Samples

Three simple sequences using a DVCO, a single Journeyman, and a Classic VCA. The VCA and Journeyman are each controlled by an Envelope module.

Here theJourneyman is being used in the low pass mode while the controls are manually tweaked.

This sample has the Journeyman being used in the high pass mode while the controls are tweaked.

Here the Journeyman is being used in the low pass mode, set to self-oscillate but with the drive control set high. The audio signal is damping the oscillation to give a distorted almost sync like quality to the sound. A bit of light reverb is applied to give some ambience.


Prices

Click here for ordering details.

Journeyman (Euro) main board issue 1 PCB........................................... 10GBP

Journeyman (Euro) pot board issue 1 PCB ............................................... 5GBP

Both boards are required to build the Oakley Journeyman 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

Journeyman 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:

6HP 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 web based 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: March 20, 2020.