Microdesignum MIDI Expressione 1A1F

The Microdesignum MIDI Expressione 1A1F is a MIDI expression pedal with a switch under the toe of the pedal¹. Instead of controlling one effect through a TRS cable, it sends MIDI Control Change messages: the pedal's position is converted to a CC value across the full 0 to 127 range, and the toe switch sends a value of 0 or 127 depending on its state¹.

The point of the toe switch is wah behavior. Microdesignum says the pedal "greatly simplifies the operation of wah-wah in multi-effects, including turning on and off by pressing the toe of the pedal"¹. On a multi-effects unit without an external switch input under the expression pedal jack, this gives you the same foot motion you would use on a conventional wah: press the toe to switch the effect on, rock the pedal to sweep it.

Controls and MIDI messages

The pedal has no knobs. What you control is the pedal itself and the switch under its toe³. The built-in module converts two things into MIDI:

• Pedal position: the value of the expression pedal potentiometer is converted to a MIDI CC value in the full range from 0 to 127⁴.
• Toe switch: pressing the toe sends a MIDI command that turns the effect (such as a wah) on and off, with an indicator LED showing the state².

The module also has a calibration switch, which calibrates the range of the pedal to the full range of MIDI values, 0 to 127¹. The Czech product page describes the same control as a button for calibrating the pedal range to the full MIDI range⁵. This matters if the pedal's mechanical sweep does not match the potentiometer's travel: after calibration, the full sweep maps to the full 0 to 127 range.

MIDI setup: channel, CC numbers, in and out

The MIDI channel and the CC numbers can be changed in two ways⁴²⁶:

• MIDIConfig, a web-based configuration interface that lets you set the MIDI channel and the CC numbers for both the toe switch and the expression pedal⁶.
• A SysEx message, in the form F0 4D 69 63 00 00 00 03 kk cc pp F7, sent to the module².

The MIDI Expressione line has one MIDI IN and one MIDI OUT for connecting to an effect². On the 1F variant the MIDI IN is used only for configuration messages², but the 1A variant also works as a MIDI merger, safely forwarding MIDI messages from MIDI IN merged with the messages from the potentiometer converter². The 1A1F combines both functions, the toe switch and the pedal position conversion².

The built-in version of the pedal (not the standalone module) has two identical power connectors: one can be the input and the other an output of the same supply voltage, for powering further effects².

Pedal and module versions

The Expressione 1A1F is sold in two forms:

The module is intended for builders who want to add the same toe-switch expression control to their own pedal. It has one analog input for the expression pedal potentiometer, with a calibratable range⁴.

The 1A1F sits in a wider family. The MIDI Expressione 1F is the toe-switch-only design, originally aimed at guitar effects such as the Line 6 M13 that lack an external switch input under the expression pedal²¹. The MIDI Expressione 1A converts pedal position only, and the MIDI Expressione 1A1F module is the builder's version of this pedal. The 1F circuit is based on the Sardonyx 8 Mikron MIDI module, Microdesignum's smallest, while the 1F1A converter is based on the more powerful Sardonyx 20 Direttore²¹.