Odium: Spectral Filter Bank

The Odium is a eurorack take on the classic Buchla 296 Spectral Processor. It has 16 channel band pass filter bank with VCAs and envelope followers. There filter bands are for 100, 150, 250, 350, 500, 630, 800 Hz, 1.0, 1.3, 1.6, 2.0, 2.6, 3.5, 5.0, 8.0, and 10.0 kHz. The high and low pass filters, at 10 kHz and 100 Hz, have a slight resonance built in. The Odium can be used as a programable filter, equalizer, or even vocoder. There are inputs for odd and even combs of the filter; each is normaled to the other. The enelope follwers are following on the odd and even input signal after the filters, but before the VCAs.

The spectral transfer functions can be performed with switches for Odd-to-Even and Even-to-Odd switches. Spectral transfer is when all of the envelope followers from one comb are used to modify the VCA control voltage of the other comb. Both can be active at the same time. A pair of Odium can be used with spectral transfer of all 16 bands patched between them to create a 16 band vocoder.

The Odium does not have the scan with width and center features of other 296 implmentations. Future versions may, but at this time testing needs to be done on the designs. Instead there is a voltage controlled crossfade between odd and even combs of the filter. Crossfade allows some great stereo style animating effects with single or disparate inputs.

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