The simple_filter_bank or lx-bank-001 is a digital filter bank (with unique feedback resonance implementation) based on the daisy seed by electrosmith and the Simple Designer by Synthux Academy.

Alternatively, the software can be run on the Simple Touch also by Synthux Academy.

Making a digital filter bank adds the possibility to tune the filter perfectly. Thanks to this ability, the lx-bank-001 is tuned following the circle of fifth with 12 banks tuned accordingly to G3, D3, A3, E4, B4, F#5, C#6, G#6, D#7, A#7, F8, C9.

This make the 12 banks cover a large spectrum up to 8.4kHz. The whole filter bank is made resonant with a feedback loop inspired by the Make Noise Music QPAS filter. The feedback can either be disabled, set to low or high.

When the filter bank feedback is set to high, the filter bank become a unique drone like instrument where two adjacent faders are distant of a fifth and therefore will sound beautiful to your ears.

The lx-bank-001 has two monos inputs and two monos outputs. Each filter bank has a fader controlling the strength of the filter and a switch that can enable or disable the filter bank. Additionally, a switch controls the mode (described below), routing the input and output differently, and the feedback level: disabled, low or high.

Mode Description

• 0 : input 0 goes to out 0, input 1 goes to out 1. Switch enable or disable filters on both output

• 1 : input 0 goes to out 0 and 1 isn't used Switch enable or disable filters only on output 1, output 0 has all filters enabled

• 2 : input 0 and 1 are mixed to out 0 and 1 Switch enable or disable filters only on output 1, output 0 has all filters enabled

The lx-bank-001 has a custom 32HP eurorack compatible PCB front panel. The Simple Designer PCB is 42HP so take your best saw or dremel and cut the excess 10HP.

In my case, I recommend using PCBWay services. I chose to go with a white solder mask, black silkscreen and HASL surface finish.

Everything is open source (code and front panel PCB design) and can be found on GitHub.