MATRIXSYNTH: SOUNDMIT 2019 Lilla Midi Expander

Saturday, November 02, 2019

SOUNDMIT 2019 Lilla Midi Expander

Published on Nov 2, 2019 BAMTV

"The Lilla midi expander is currently a prototype/hobby project. It is based on the Teensy 3.6 microcontroller which has powerful features. The code is open source, the machine has an eurorack format but is controlled by midi. Lilla’s controls features 12 rotary encoders and 8 pushbuttons and includes MIDI in, MIDI thru, and stereo out. Via the SD card it can load samples, layered across the keyboard, and those can be changed with pitch and envelopes. It plays back with 8 voice polyphony. It also has effects like distortion, bit crusher and compressor on board.


"Lilla is an open source project for a polyphonic midi expander, based on Teensy 3.6 microcontroller. Lilla includes:


n.1 Teensy 3.6 - overclock 240MHz
n.1 Teensy Audio Adaptor
n.1 flash memory chip W25Q256FV (32Mbyte serial flash memory)
n.3 CD74HC4067 (16-Channel Analog Multiplexer)
n.1 128x160 TFT color display
n.1 HCPL260L (single-channel optocoupler)
n.1 CD4093B (quad 2-Input NAND Schmitt Triggers)

n.12 rotary encoders with pushbutton
n.8 pushbuttons
Teensy program pushbutton
i/o interfaces:

midi in (DIN)
midi thru (DIN)
stereo line output
micro-SD socket

reading files from flash memory: 8
reading files from RAM: 12
Audio files and presets

Lilla uses 44.1kHz 16bit mono .RAW (header-less) audio files, imported from micro-SD card. Lilla can store up to 100 Sounds; a Sound is described by these elements:

an audio file
interval to be played (first sample A - last sample B): from 100 samples to full length
play mode: A -> B, B -> A, loop A -> B, loop A <-> B, loop B -> A, loop B <-> A
fine tune
ADSR parameters
Attack ramp: fast, slow
Audio file is played from flash memory until the interval to be played contains more than 675 samples. Below 675 samples, audio is played from RAM: in this case, an automatic pitch-correction keeps the sound in tune with the standard tuning (middle C: 261.6Hz).

Lilla can store up to 30 setups called Sessions; a Session is a group of up to 8 Instruments; each Instrument is defined by:

a Sound
keyboard span (first key - last key)
keys mode: momentary, hold
In a Session, all 8 Instruments can also be layered on each other.

Additional details at pics at

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