Serge Modular - Resonant EQ (ResEQ)

The Random Source Resonant Equalizer is a filterbank with ten bands, a licensed and authorized adaption of the legendary Serge Resonant EQ for Eurorack. It is designed for electronic sound synthesis and processing, providing formant peaks and valleys similar to those found in acoustic instruments. Over the original the module from Random Source adds a two-channel mixer with attenuators and a Feedback section which allows to feed back the output signal or the inverted output signal. A powerful tool for sound processing but also for sound creation!

The Random Source Resonant EQ is a replica of the legendary Serge Resonant EQ, under license from Serge Tcherepnin. The module provides a unique ten-band filter capable of resonating. Except for the top and bottom frequency bands, the bands are spaced at an interval of a major seventh.

This equalizer is special 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.

There are three equalized outputs: the two Comb outputs provide the sums of the two alternate filter bands while the two top outputs are the mix of all filter bands. Please note that there is no sharp separation between the bands, moving any frequency knob will have an influence on both Comb outputs.

Following frequency bands are provided by the Comb outputs:

• Comb1: 29 Hz, 115 Hz, 411 Hz, 1.5 kHz and 5.2 kHz
• Comb2: 61 Hz, 218 Hz, 777 Hz, 2.8 kHz, and 11 kHz.

The Random Source Version adds an input mixer with two inputs, allowing for two signals to be mixed, amplified or attenuated. Additionally a feedback section with attenuator and phase switch has been added. Inverted feedback leads to phase cancellation effects.

Furthermore the module can be used for sound generation using the feedback control and the resonant behaviour of the bands, without any input signal. It provides a controllable and organic sound!