Bitbox Micro Firmware: The Master EQ and Filter

The patch adds a master EQ and filter across the whole mix, which the module never had. Ten modes sit on one encoder: a DJ sweep, a dual cut and a band pass, then shelving and bell EQs, a tilt, a notch, a phaser and a formant filter. One knob picks the mode. Three more play it.

It comes after the Character chain and before the compressor, so it shapes the delay and reverb tails too. Out 3–6 stay clean. See where they sit.

1Centre Is Always Neutral

In every mode, every control is neutral at its centre. With all three knobs centred, the EQ does nothing.

You can sweep the mode dial with the controls centred and hear nothing, then pick a mode and move one knob. To back out of anything, return that knob to centre.

On a controller with endless encoders, give each of the three a centre-line LED style and a reset-to-middle gesture. You will use both constantly.

2The Ten Modes

#	Mode	Encoder 2	Encoder 3	Encoder 4
1	DJ Filter	filter, dull to thin	resonance	knee
2	Dual Cut	high cut	low cut	resonance
3	Band Pass	centre frequency	width	gain
4	Mixer EQ	high	mid	low
5	Tone + Filter	high	low	filter, dull to thin
6	Tilt	tilt	hinge frequency	—
7	Notch	frequency	Q	depth
8	Peak	frequency	Q	gain
9	Phaser	sweep	depth	spread
10	Formant	vowel, I to U	intensity	shift

DJ Filter: the one-knob sweep. Anticlockwise closes it to a dull thump, and clockwise thins it to hats.
Dual Cut: a cut at each end, set separately.
Band Pass: a band you can move, narrow and lift.
Mixer EQ: a three-band desk EQ.
Tone + Filter: two shelves and a filter on one panel.
Tilt: a see-saw, lifting the treble by exactly what it drops the bass.
Notch and Peak: one surgical cut and one sweepable bell.
Phaser: four notches sweeping together as one body.
Formant: three bells on the resonances of a human vocal tract, morphing between vowels.

3Working the Four Encoders

The EQ uses nine CCs, all on MIDI channel 1.

Control	Turn	Push
Encoder 1	CC 50 — mode	CC 57 — master bypass
Encoder 2	CC 51	CC 54
Encoder 3	CC 52	CC 55
Encoder 4	CC 53	CC 56
A button	—	CC 59 — filter slope, 12 or 24 dB

Encoders 2, 3 and 4 should be plain linear encoders across the full range. Set the mode encoder to ten steps from 6 to 122, not the full sweep. Each click then lands in the middle of a mode, never on a boundary.

Send CC 50 as plain 7-bit. As a 14-bit pair it would also move a pad's granular window every time you changed mode.

The pop-up names the mode, and each control by that mode's name for it, with its value in hertz, decibels, octaves or a vowel. Pushes show too, such as Kill High On.

4Kill, Open and Slam

The pushes are momentary performance controls. Hold a push to act. Let go to return. The encoder's own position comes back untouched, so nothing jumps.

Gesture	What it does	Where
Kill	that range disappears from the mix	Mixer EQ's three, Tone + Filter's two
Open	that band stops acting, letting more through	Dual Cut, Band Pass width, Tone + Filter's filter
Slam	forces a control to maximum effect	Notch, Tilt, Peak, Phaser, Formant

Sixteen pushes do something across the ten modes. On the rest, spend the push on a reset-to-centre gesture instead. Most controllers switch a push between the two with one setting.

5Bypass and Slope

CC 57 takes the whole EQ out. Press once and it is gone. Press again and it is back. Unlike the other pushes, it latches. Give it encoder 1's push.

CC 59 switches the filter slope between 12 and 24 dB per octave, on the modes that have one. Set it up as an on-off button. Band Pass ignores it, because its gain control needs the same bands and gain wins.

6How the EQ Arrives

It powers on in DJ Filter, with all three controls centred, bypass off and the slope at 12 dB. Centred controls pass everything through, so a freshly flashed module sounds exactly as before. Like the other devices, its settings survive a preset change and reset at power-on. See what they have in common.