FRCL: Fixed low-pass filters (3HP)
Think of it as a buffered mult with an RC filter on each output, because that's basically what it is.
The outputs consist of a set of 1-pole RC filters - these roll off at 6db/octave. You're not going to be getting shrieky resonance out of these, but they are good for 'tidying up' some sounds (lower frequencies are good at reducing the effects of high-frequency transients, aka 'pop'). Modules are cascadeable should you wish to increase the filtering effect.
The following are implemented, with their associated resistor/capacitor pairs in brackets should you feel the need to tinker.
- 63Hz (R3/C1)
- 250Hz (R4/C2)
- 500Hz (R5/C3)
- 1.5kHz (R6/C4)
- 3kHz (R7/C5)
- 5kHz (R8/C6)
- 8kHz (R9/C7)
The exact cutoff frequency will depend on the accuracy of your components - to keep costs down I use E24 range components for both resistors and capacitors, meaning that the cutoff frequency is there or thereabouts. If this sort of thing bothers you then you can either shell out far more for a similar module or get a PCB/panel set and provide your own components - keep in mind that resistor tolerances tend to be a lot tighter than those of capacitors.
If you'd prefer to DIY it, a set containing the PCB, panel, power cable and necessary ICs is available - all you need to supply is appropriate jacks and passive components. You can get the BOM and schematic from here: https://github.com/yorkmodular/frcl
If you'd prefer to DIY it, you can get a PCB/panel set here.