HEX row is an analogue dual resonant filter with versatile routing capabilities, sidechain/envelope follower and mischievous character, stemming from (mis)use of transistors as variable resistors in the signal route.

There are two channels, each controlled by three potentiometers: GAIN (2), RES (3), FREQ (4) and sidechained by CENTER (5). Both channels have the same topology. Inputs •| and |• are fed into each channel’s gain stage and then passed to their filters. The input signal level can be adjusted by setting the GAIN which can either attenuate or amplify a signal x20. Note that the amplification affects the filter’s behaviour—high GAIN disrupts self-oscillation, conjuring PLL-esque harmonics and other sound design artefacts. FREQ and RES are used to manipulate individual filter’s cutoff frequency and resonance. Each channel has a side-mounted switch (6) for selecting low-pass or band-pass filtering. Touch the golden touch pads (1) to manually route the flow of audio and control voltages.

SIDECHAIN – Left channel’s (•I, •O) post-gain signal is filtered and fed into an envelope follower. Envelopes polarity and amplitude are adjusted by using CENTER. The adjusted envelope is then mixed in the right (|•, O•) channel’s FREQ parameter. Left half of the CENTER causes the filter to “duck” and the right half produces a gating response. In the middle position, the sidechain effect is inactive.