Schlappi Engineering Boundary Layer
Triple cycling slew — envelope, LFO, oscillator, filter, divider in one.
16 HP Eurorack module
Boundary Layer is a triple cycling slew/function generator from Schlappi Engineering — a 16HP descendant of the Serge DUSG and Make Noise Maths lineage that pushes three independent slope cores into LFO, audio-rate oscillator, AD/AR envelope, voltage-controlled portamento, frequency-divider, and low-pass-filter territory. Each channel has its own RISE/FALL/CV(SHAPE) controls, CYCLE/INVERT/CV-SELECT toggles, and TRIG/SLEW/CV/BOUND inputs plus EOC/OUT outputs; three GLOBAL inputs (TRIG ALL, CV ALL, SLEW ALL) bus across all channels, and analog comparator logic on the right produces MAX/MID/MIN-of-three outputs that double as stereo drone material at audio rate.
Features
- 3 independent cycling-slew channels (LFO, oscillator, AD/AR envelope, slew, filter)
- Each channel cycles from sub-LFO (~1 minute period) to >10kHz audio rate
- RISE/FALL/CV(SHAPE) knob per channel with linear/log/exp shaping via feedback
- Per-channel CYCLE switch and INVERT (LOG/EXP) switch and CV-Select (RISE/BOTH/FALL)
- Per-channel TRIG, SLEW, CV, and BOUND inputs + EOC and OUT outputs
- BOUND input replaces the high threshold for bouncing-ball, pseudo-VCA, AM/FM effects
- EOC output switchable per channel (rear header) between End-Of-Rise and End-Of-Fall
- Trigger-input retrigger lockout enables clean audio-rate frequency division
- Three GLOBAL inputs (TRIG ALL, CV ALL, SLEW ALL) bus across all channels
- MAX / MID / MIN comparator-logic outputs from all three channels
- Rear header swaps MIN output for a clean ÷3 MIX of all three envelopes
- MAX/MIN at audio rate work as a patch-programmable stereo drone synth
Controls & Jacks (54)
- Ch 1 Rise
- Ch 1 Rise LED
- Ch 1 Out LED
- Ch 1 Cycle
- Ch 1 Fall
- Ch 1 Fall LED
- Ch 1 Invert
- Ch 1 CV LED
- Ch 1 CV
- Ch 1 CV Select
- Ch 1 TRIG In
- Ch 1 SLEW In
- Ch 1 CV In
- Ch 1 BOUND In
- Ch 1 EOC Out
- Ch 1 Out
- Ch 2 Rise
- Ch 2 Rise LED
- Ch 2 Out LED
- Ch 2 Cycle
- Ch 2 Fall
- Ch 2 Fall LED
- Ch 2 Invert
- Ch 2 CV LED
- Ch 2 CV
- Ch 2 CV Select
- Ch 2 TRIG In
- Ch 2 SLEW In
- Ch 2 CV In
- Ch 2 BOUND In
- Ch 2 EOC Out
- Ch 2 Out
- Ch 3 Rise
- Ch 3 Rise LED
- Ch 3 Out LED
- Ch 3 Cycle
- Ch 3 Fall
- Ch 3 Fall LED
- Ch 3 Invert
- Ch 3 CV LED
- Ch 3 CV
- Ch 3 CV Select
- Ch 3 TRIG In
- Ch 3 SLEW In
- Ch 3 CV In
- Ch 3 BOUND In
- Ch 3 EOC Out
- Ch 3 Out
- TRIG All
- CV All
- SLEW All
- MAX Out
- MID Out
- MIN Out
How-To Guides
- Classic AD Envelope
- Voltage-Controlled Portamento
- Patch-Programmable Stereo Drone Synth
- Audio-Rate Frequency Divider
- Low-Pass Filter with Resonance
- Strum / Round-Robin Envelope Chain
- Bouncing Ball with BOUND
- Hard-Synced Audio Oscillator
Explore the interactive Boundary Layer panel on BleepDex — tap any control to learn what it does.