C7H5NO3S - harmonic 'enhancer' (8HP)
THIS MODULE IS BUILT TO ORDER - PLEASE ALLOW 3-4 WORKING DAYS FOR CONSTRUCTION AND TESTING.
This module is based on a schematic called a 'harmonic sweetener', a schematic for which I found in a 1970s electronics magazine. The input signal is paralleled with a pair of cascaded Sallen-Key high-pass filters (fixed frequency in the original schematic, tunable in this one). The filtered signal, with the lower frequency harmonics attenuated, is then remixed with the input. To add a bit of interest, the filtered signal also has a clipping section (provided courtesy of two LEDs) with adjustable gain in order to give the filtered signal a bit more presence.
Obviously it works best with harmonic-rich signals (eg. sawtooth and square waveforms) but you can get interesting results from triangle-based waveforms.
What's in a name?
C7H5NO3S is the chemical formula for saccharine, which Wikipedia describes thus:
"[it] is about 500 times sweeter than sucrose, but has a bitter or metallic aftertaste especially at high concentrations"
which is actually a pretty apt description of what the module does (and that's the pearl of wisdom on the rear side of the faceplate) - it can add a bit of sweetness to a sound in small doses, but rapidly becomes rather overpowering once you start to crank it up.
The graphic on a faceplate? That's a saccharine molecule, because why the hell not.
8HP wide.