E-Verb for Elektron Octatrack

A modulated feedback-delay reverb after the Erbe-Verb: size, decay past 100 %, absorb, chorus, grains, shimmer, reverse and tilt.

Module version 0.1.0-experimental. Base firmware: 1.40C.

About this module

Four delay lines with diffusing allpasses, absorbing low-passes and a soft-saturating decay feed each other through a Hadamard matrix at 22.05 kHz. DPTH sweeps from a cyclic chorus through random ergodic grains into octave shimmer; REV plays the pre-delay backwards; EDCY and ESIZ route the reverb's own envelope into decay and size. The dry signal is never processed.

• Size from a 2 ms box to a 143 ms hall, gliding without zipper noise
• Decay up to 120 %: sustains and saturates above about 106
• Cyclic, ergodic and shimmer modulation on one bipolar knob, with its speed beside it
• Reverse pre-delay, tilt EQ and envelope-to-decay/size routings
• MIX 0 is the exact dry signal

How to use it

1. Choose E-Verb in FX2 SETUP: hold FUNC, press FX2, turn LEVEL to the end of the list and press YES.
2. On the main page, MIX (encoder F) sets dry/wet; SIZE, DCY and ABSB shape the space; DPTH left is chorus, right is grains, the last sixteen steps are shimmer; SPD sets how fast it moves.
3. On the SETUP page, TILT darkens or brightens the wet, PRE sets the pre-delay, REV reverses it, and EDCY/ESIZ send the reverb's envelope into DCY and SIZE.
4. The six main-page knobs take parameter locks, LFOs, scenes and MIDI CC like any stock effect's; the SETUP knobs are set per Part.

Controls

SIZE

Scales every delay and allpass over six octaves: the longest line runs 2.2 ms at 0, 18 ms at 64 and 143 ms at 127. Moving it glides the pitch of the tail, smoothed per frame.

DCY

Reflection gain from 0 to 120 %. Below about 106 the tail decays (short at 40, minutes at 100 with large sizes); above, it sustains and the in-loop saturation holds the level.

ABSB

0..38 adds diffusion (allpass gain up to 0.8); 38..127 adds damping inside the loop, darker and shorter.

DPTH

Bipolar modulation, 0 at the centre. Left: cyclic chorus/doppler. Right: ergodic grains to +47; from +48 a growing share of grains glides up an octave (shimmer), about half at +56.

SPD

Modulation speed 0.5 Hz to 256 Hz (about 12 Hz at 64): the cyclic rate or the grain rate; in the shimmer zone SIZE sets the grain length.

MIX

Equal-power dry/wet. 0 is exactly the dry input; 127 is all reverb.

TILT

SETUP A. Bipolar wet tone. Left: lows below 250 Hz up to +12 dB, highs down (about -14 dB at 9 kHz). Right: highs above 2 kHz up to +24 dB, lows down 3 to 5 dB. Centre is flat. Not lockable (SETUP page).

PRE

SETUP B. Pre-delay 7 ms at 0, 42 ms at 64, 250 ms at 127; with REV on, the reverse window (at least 42 ms). Not lockable (SETUP page).

REV

SETUP C. Plays the pre-delay buffer backwards in crossfaded windows; a change ducks, switches in silence and reopens without a click. Not lockable (SETUP page).

EDCY

SETUP D. Bipolar: the reverb's envelope into DCY. Left reins the tail in when loud; right rings longer when loud, up to the decay of DCY 95, never into sustain (no effect from DCY 96 up). Centre is off. Not lockable (SETUP page).

ESIZ

SETUP E. Bipolar: the reverb's envelope into SIZE. Left shrinks the space when loud; right grows it. Centre is off. Not lockable (SETUP page).

Compatibility notes

• Owner reports working sound on MKII plus two distinct simultaneous T1/T5 instances, Part/project save and reload, and physical reboot on EVRB01T01. MKI, maximum-load silicon timing and broader hardware modulation/recovery tests remain unverified.
• FX2 only: the effect needs the 16K-word delay buffer the OS gives FX2 instances.
• With stock DSP code built in, E-Verb's 1,588 words take the space of two FX2-only stock reverbs. On its own it gives up SPRING REV and DARK REV: they leave the FX2 chooser, and a saved project that uses either on FX2 plays that slot dry. PLATE REV and every other stock effect stay. Other modules in the same build can change the choice.
• The SETUP page (TILT, PRE, REV, EDCY, ESIZ) is not lockable: the OS keeps parameter locks, LFO, scene and CC targets for the six main-page knobs of an FX slot only.
• Dearer than any stock effect: up to 376 executed instructions per sample without trig splits (SPRING REV 258, DJ EQ 293) and 382 with them (SPRING REV 314, DJ EQ 331). Four per core fit the static budget; real-chip headroom beside heavy FX1 effects is not measured.
• A sustained full-scale tone on a room resonance can clip at high MIX, and TILT far right or a sustaining DCY can clip the wet at the tank rate; DCY above about 106 sustains and saturates by design.
• No tempo sync: as on the hardware and the stock reverbs, SPD is in Hz and PRE in milliseconds.

Test evidence

Render gates pass on a native image: exact dry at MIX 0, pre-delay/decay/stereo laws, eight-instance isolation under guard and dirty start, garbage start, no zipper on any continuous knob, trig splits, REV switching, DPTH locked between shimmer and chorus, and EDCY unable to hold a tail. Static 468 cycles/sample, 381.7 instructions/sample measured against stock under the same cases; 32 s stress with eight instances, LFOs, locks and splits: no clobber, no hang. Owner reports a positive MKII functional audition on the exact EVRB01T01 image; detailed hardware coverage remains limited.