4U032 - ResEQ

4U032 - ResEQ

The Resonant Equalizer is a unique, 10 band filter, designed specifically for electronic sound synthesis and processing. Except for the top and bottom frequency bands, all other bands are spaced at an interval of a major seventh.
This non-standard spacing avoids the very common effect of an accentuated resonance in one key, as will be the effect from graphic equalizers with octave or third-octave spacing between bands.
Spacing by octaves will reinforce a regular overtone structure for one musical key, thereby producing regularly spaced formants accenting a particular tonality.
The Resonant Equalizer's band spacing are much more interesting, producing formant peaks and valleys that are similar to those in acoustic instrument sounds.

There are three equalized outputs, two which mix the alternate filter bands,
and one which is a mix of all filter bands.
The upper (upper out) lets pass the outputs of frequency bands at 61 Hz, 218 Hz, 777 Hz, 2.8 kHz, and 11 kHz.
The lower (lower out) mixes the other bands (29 Hz, 115 Hz, 411 Hz, 1.5 kHz, 5.2 kHz).

This equalizer is different from other equalizers in that the bands can be set to be resonant. When the knobs are in the middle position, the response at the main EQ Output is flat. When the knobs are positioned between the 9 and 3 o'clock position, up to 12 dB of boost or cut is set at the band.
If the knob is set beyond the 3 o'clock position, the band will become resonant, simulating the natural resonance of acoustic instrument formant structures.
Below the 9 o'clock position, increased band rejection is achieved.

This version adds and additional secondary input.

1.6 mm thick, double sided, green
base material FR4-Standard TG 135-140
surface finish HASL
part values are silkscreened

no parts, just the PCB - LW format panel is available

Documentation (schematic, bom, wiring)