The 2U Journeyman Voltage Controlled Filter Module
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 issue 2.1 PCB is 79 mm (deep) x 143 mm (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.
Available as an assembled Module and as a DIY project.
This Module is currently available.submitted May 23rd 2019, 19:49 by denieldiniz