Multi Effect / Synth

The Multi Effect / Synth App lets you browse, load, and play any of the 50+ DSP plugins using the TBD-16’s hardware interface – no computer or web UI required.

At a Glance

Status

Shipping

RP2350 firmware

Plugin browser firmware

ESP32-P4

Standard DSP firmware with 50+ plugins

SD card file

tbd-apps/multi_fx.uf2

Tags

Synth, FX, MIDI, Ableton Link

What It Does

  • Browse plugins on the OLED with encoders – scroll, select, load

  • Two independent channels – run any two plugins at the same time

  • Mono or stereo routing per channel

  • Preset management – save and recall parameter snapshots

  • MIDI mapping – assign knobs and buttons to plugin parameters via MIDI CC

  • Ableton Link for tempo sync

Dual-Channel Architecture

The ESP32-P4 DSP firmware always has two plugin slots (Slot 0 and Slot 1). The Multi Effect / Synth App gives you direct hardware control over both:

Slot 0

Slot 1

Use case

Main synth or input effect

Second synth, effect chain, or parallel processor

Routing

Mono or stereo

Mono or stereo

Control

Encoders + buttons + MIDI

Encoders + buttons + MIDI

This means you can run a synthesizer in Slot 0 and a reverb in Slot 1, or two completely independent effects, or two synths layered together.

See the full list of 50+ plugins available for each slot.

How It Works

RP2350 (plugin browser firmware)

Displays the plugin list on the OLED. Reads encoder input to scroll through plugins and adjust parameters. Sends load commands and parameter updates to the ESP32-P4 via SPI.

ESP32-P4 (standard DSP firmware)

Runs the same DSP engine used by all Apps. Receives plugin load and parameter messages from the RP2350. Processes audio in real time with sub-millisecond latency.

Why This Exists

The Groovebox is great when you want a complete instrument. But sometimes you just want to plug in a guitar and dial up two effects, or play a single synth with full hands-on control. The Multi Effect / Synth App is that stripped-down, direct-access mode.