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.
Project Downloads
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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