YM2149Fx3-Pi PSG and Multi-Timbre SID Emulation Synthesizer and Drum Sampler

Three real Yamaha YM2149 sound chips. Nine voices. Zero emulation.

The YM2149Fx3-Pi is a hardware MIDI synthesizer built around three genuine Yamaha YM2149 sound chips, the same silicon that gave the Atari ST, Amstrad CPC, and countless arcade cabinets their unmistakable sound. We're not sampling it. We're not modeling it. We're driving the actual chips, and we're pushing them further than Yamaha ever imagined. This is my third iteration of a YM2149F based synthesizer, and this device is by far superior to any of the previous models.

More than chiptune.

Each YM2149 gives you three square wave voices with independent pitch, volume, and noise. Multiply that by three chips and you get nine voices of raw, crunchy polyphony, playable over USB MIDI or TRS MIDI, across up to nine independent channels. This is a fully multi-timbral instrument: every voice can have its own envelope shape, vibrato, tremolo, portamento, detuning, octave shift, and pitch envelope. Set up a bass on channel 1, a lead on channel 2, pads on channels 3-6, and arpeggiated textures on the rest, all at once, all from real hardware.

SID mode: when three chips aren't enough character.

Flip into SID mode and the YM2149Fx3 transforms into something entirely different. Using a technique inspired by the Commodore 64's SID chip, we hijack the volume registers at 50,000 times per second to synthesize waveforms that a YM2149 was never designed to produce. Square waves with sweepable pulse width. Double-pulse waves with duty-controlled harmonic complexity. Per-voice PWM modulation running on a phase accurate engine. Six voices of SID-style synthesis from chips that are supposed to only do square waves and noise. We squeezed blood from a stone and it sounds incredible.

A dedicated dual-core brain.

Under the hood, an RP2040 runs the show with both it's 133mhz cores. Core 0 handles everything audio: MIDI parsing, voice allocation, envelope processing, pitch modulation, effects, and all three YM2149 bus writes with interrupt safe timing down to the microsecond. Core 1 runs the display, encoder input, and menu system completely independently.

Eight built-in effects, all running on real hardware.

• Echo : configurable delay, repeats, and decay
• Arpeggiator : four patterns (up, down, up-down, random) with tempo and octave control
• Bit Crush : lo-fi digital degradation
• Pseudo Reverb : multi-tap delay with per-tap detuning for spatial depth
• Chorus : dual detuned voices with optional LFO modulation
• Harmonizer : twelve chord types from octaves to dominant 7ths
• Gate : rhythmic volume chopping with four patterns and variable duty cycle
• Sample Trigger : 24 built-in 1-bit drum samples with GM mapping
• All effects sync to external MIDI clock if you want them locked to your DAW or sequencer.

Hands-on control.

• Three analog pots with deep assignment options: map them to any parameter across any voice or chip. A rotary encoder with push-button navigates the full menu system on the 128x64 OLED display. Four real-time visualization modes let you see your sound: volume bars, oscilloscope, a 3x3 voice matrix, and a channel matrix view, all rendering at up to 25fps.

Features:

9-Voice Polyphonic YM2149F Synthesis

• 3x YM2149F sound chips providing 9 independent tone voices
• Mono, Semi-poly, and Poly voice allocation modes
• Per-voice settings: detune (cents), octave shift, max volume, noise frequency
• Chip linking: mirror Chip 0 settings across chips for massive unison sounds
• MIDI channels 1-9 mapped to voices (3 per chip)

SID Emulation Mode (NextSID)

• Software-emulated SID-style waveforms on Chips 1 and 2 (6 voices)
• Waveforms: Square and Pulse with adjustable duty cycle (default duty: 11)
• PWM sweep with configurable rate and depth
• Per-voice sync and ring modulation between voices within a chip
• Noise mixing per voice
• Portamento/glide fully supported in SID mode
• ~50kHz timer-driven volume flipping for waveform generation

Sample Playback (SMPL Mode)

Timer-based 8-bit PCM playback at 8000 Hz on Chip 2 (3 polyphonic voices)

Three sample sections:

• DRUM : 24 Bitkits drum samples: kicks, snares, hi-hats, toms, claps, cowbell, tambourine, shaker
• 1SHT : 24 Bitkits one-shot samples: beeps, blips, buzzes, glitches, metals, noises, stabs, vocals, zaps
• DIGI :16 legacy ST-Sound DigiDrum samples (classic Atari ST sounds)
• Four playback modes:
• SNGL : Always play the selected sample
• SEQ : Play samples sequentially (s00, s01, s02...)
• RND : Random sample each trigger
• GM : General MIDI drum map (notes 35-58 mapped to samples). OneShots use chromatic mapping from C2
• Per-section GM drum maps (Bitkits and DigiDrum have independent mappings)
• Pitch control : -12 to +12 semitones fine tuning plus -3 to +3 octave shift (8.8 fixed-point)
• Adjustable sample length (1-127, 127 = full sample)
• Volume scaling (1-15)
• Voice stealing with same-sample retrigger and round-robin allocation

Per-Voice Modulation

• Vibrato : Rate (1.0-15.0 Hz), depth (0-200 cents), delay (0-2550ms)
• Tremolo : Rate (1.0-15.0 Hz), depth (0-100%)
• Pitch Envelope : Amount (0-24 semitones), time, direction (up/down)
• ADSR Envelope : Attack, decay, sustain, release
• Portamento/Glide : On/off per voice, adjustable speed

Preset System

• Save and load complete synth states to flash (8 user slots)
• 4 factory SID presets
• Stores all voice settings, FX, SID config, sample section, mode, and more
• 8-character preset naming

MIDI Implementation

• USB-MIDI and TRS-MIDI (Serial1 at 31250 baud) simultaneously
• MIDI channel filtering (per-channel, OMNI, or OFF)
• Channel remapping (route any incoming channel to any internal channel)
• CC support: Mod Wheel (CC1), Volume (CC7), Expression (CC11), Portamento (CC5/CC65), All Notes Off (CC123), Reset All Controllers (CC121)
• CC4 volume envelope shaping (optional)
• Pitch bend
• MIDI Real-Time: Start (0xFA), Continue (0xFB), Stop (0xFC) with proper note/controller reset
• MIDI clock sync
• Note range: A-1 to C8 (MIDI notes 9-108)
• Velocity curve with configurable gamma, min, and max
  

What's in the box:

YM2149Fx3-Pi synthesizer module

3x genuine Yamaha YM2149F sound chips (installed)

USB-C connection (MIDI + power) cable

Specs:

• 9 voices (YM mode) / 6 voices (SID mode)
• Multi-timbral: independent settings per voice per MIDI channel
• USB MIDI + TRS MIDI (31250 baud) (optional serial mode over USB)
• Mono/semi-poly/full-poly voice allocation
• Voice linking across chips for massive unison sounds
• ADSR envelope per voice
• CC Control of many parameters
• Persistent flash storage for presets and settings
• Handmade by HobbyChop.

More information on the Github

Special thanks to Ben Baker for his support and code contributions: https://baker76.com, https://github.com/benbaker76

Special thanks to em00k for explaining SID emulation