8.7 KiB
Ourpad Modular Band System — Module Catalog
Vision: A family of stackable DSP modules, one per band member, sharing a common platform. Each module is a self-contained RPi-powered effects unit in a compact enclosure. Modules sync over the network for sample-accurate multi-channel mixing.
Status: Planning phase. Guitar module prototype is furthest along.
Platform Spec (All Modules)
| Spec | Standard | Premium Option |
|---|---|---|
| CPU | RPi 4B (2GB+) | RPi 5 (for drums/keys) |
| OS | DietPi (minimized) | Same |
| Audio I/O | I2S HAT per module type | USB Audio Class 2 (for high channel count) |
| Sample Rate | 48kHz / 24-bit | 96kHz (keys/synth) |
| Latency Target | < 10ms round-trip | < 5ms (drums) |
| Display | 5" DSI touch (800×480) | None (drums — rack UI only) |
| Network | WiFi + Ethernet | AES50 for drums |
| Sync | NTP / manual | AES50 embedded clock |
| Enclosure | 1590BB (140×78mm) | 1U rackmount (drums) |
| Power | USB-C PD (5V/3A) | PoE (drums in stage box) |
| Control | Touch, Web UI, MIDI DIN/BT | All of the above |
🎸 Module 1: Guitar
Status: Prototype — Phase 1 (I2S HAT + DSP) complete. Phase 2 (touch + XLR) pending.
| Spec | Value |
|---|---|
| Inputs | Combo XLR/1/4" with hi-Z switch, 1/4" Return (4CM) |
| Outputs | 1/4" Send (4CM), XLR balanced DI |
| Preamp | TL072-based (existing) + hi-Z buffer for piezo |
| Line Driver | DRV134 or THAT1646 for balanced XLR |
| Phantom | Not needed (instrument level) |
| Patching | Front: Combo in, XLR out. Side: Send/Return |
| FX | 32 total: Gate, Comp, Boost, OD, Dist, Fuzz, NAM Amp, IR Cab, EQ, Parametric EQ, HPF, LPF, Mod, Delay, Reverb, Pitch, Looper + all modulation |
| HAT | PCM1808+PCM5102 (existing Rev 1.0 — mono 1ch in/out) |
| HAT Rev 2 | Add combo jack footprint, XLR driver, 4CM Send/Return |
| Edge | NAM A2 neural amp modeling |
Current state: All DSP and 4CM routing done. I2S HAT designed (needs Gerber export). Touch integration pending 1590BB enclosure.
🎸 Module 2: Bass
Status: Concept. Shares guitar HAT with different preamp.
| Spec | Value |
|---|---|
| Inputs | Combo XLR/1/4" with hi-Z, pad switch |
| Outputs | XLR balanced DI, 1/4" thru |
| Preamp | FET Neve-style (SansAmp character) — dedicated op-amp stage |
| Tone Shaping | 3-band active EQ (bass/mid/treble sweepable), blend control |
| FX Priority | Compressor (always-on), Octaver, Envelope Filter, Chorus, EQ |
| RPi | Zero 2W sufficient (lighter DSP load) |
| Enclosure | 1590BB or smaller (125B) — fewer controls needed |
| Display | 3.5" DSI or small OLED + knobs |
| HAT | Same PCM1808+PCM5102 as guitar (mono instrument) |
Edge: Analog blend — mix dry bass tone with processed signal (critical for bassists).
🎤 Module 3: Vocal
Status: Concept. Needs different analog front-end.
| Spec | Value |
|---|---|
| Inputs | XLR with 48V phantom power |
| Outputs | XLR balanced |
| Preamp | INA163 or SSM2019 instrumentation amp (low noise, 20-60dB gain) |
| Phantom | MAX1771 or similar DC-DC converter for 48V |
| Pad | -20dB pad for hot sources |
| FX Priority | Gate, Comp, De-esser, EQ, Reverb, Delay, Harmonizer, Pitch Correction |
| RPi | 4B (pitch detection is CPU-heavy) |
| Enclosure | 1590BB with touch |
| HAT | Custom — mic pre + phantom + balanced driver |
Edge: Real-time pitch correction (auto-tune style), harmony generation from MIDI input.
Cost impact: Phantom power adds ~$8-12 in components (DC-DC converter, filtering).
🎹 Module 4: Keys / Synth
Status: Concept. Simplest analog stage — line level only.
| Spec | Value |
|---|---|
| Inputs | 2× TRS (stereo line in) |
| Outputs | 2× TRS or XLR (stereo out) |
| Preamp | None needed (line level) — just buffer + protection |
| FX Priority | Reverbs, Delays, Chorus, Phaser, Rotary, Tremolo, Ring Mod |
| RPi | Zero 2W sufficient |
| Enclosure | 1590BB or rackmount half-width |
| Display | 5" touch or headless (MIDI CC control) |
| HAT | PCM1808 stereo ADC (already stereo-capable) + PCM5102 stereo DAC |
Edge: Uses the existing HAT's full stereo capability (PCM1808 has 2 ADC channels, PCM5102 has 2 DAC channels — the guitar module only uses half).
🎺 Module 5: Horns / Misc
Status: Concept. Vocal variant with simpler FX.
| Spec | Value |
|---|---|
| Inputs | XLR (mic) |
| Outputs | XLR balanced |
| Preamp | Same INA163 as vocal |
| Phantom | Yes (condenser mics) |
| FX Priority | Comp, EQ, Reverb (minimal — horns sound great dry) |
| RPi | Zero 2W |
| Enclosure | 125B (small, simple) |
| Display | None — web UI only |
Edge: Minimalist. Three knobs: Reverb, Compression, EQ. Designed to not get in the way.
🥁 Module 6: Drums
Status: Concept. Different architecture — network audio + stage box.
| Spec | Value |
|---|---|
| Inputs | Ethernet (AES50) from stage box |
| Outputs | Ethernet (AES50) to FOH, stereo monitor out |
| Stage Box | 8× XLR input → AES50 transmitter (dedicated hardware, not a Pi) |
| RPi Job | Mixer + FX per channel + routing to stereo out |
| FX Per Channel | Gate, Comp, EQ per drum — summed into stereo mix |
| RPi | RPi 5 (8-16 channel real-time processing) |
| Enclosure | 1U rackmount |
| Display | 7" HDMI or headless (iPad control) |
| HAT | AES50 XMOS board → I2S bridge, or USB Audio interface |
Stage Box Details
Front: 8× Combo XLR/TRS input
Back: Ethercon (AES50 out), Power in
Size: Half-rack or floor box (aluminum, rugged)
RX: XMOS AES50 receiver module → I2S → RPi
OR: Behringer S16-style design with custom PCB
AES50 Hardware Options:
- XMOS XU208 dev board (~$25) — programmable AES50 transceiver
- Off-the-shelf AES50 <-> ADAT converter (~$60) — simpler but less flexible
- DIY PCB with XMOS chip — for production
Edge: Uses AES50 (open protocol, proven in live sound), sub-1ms latency, standard CAT5e cabling, 100m+ range.
🌐 Module 7: Sync / Mix Bridge (Optional)
Status: Concept. Only needed for multi-module setups.
| Spec | Value |
|---|---|
| Role | Master clock + mix bus for multi-module band setups |
| Inputs | Ethernet from each module |
| Outputs | Stereo XLR (FOH), headphone monitor |
| Sync | AES50-derived word clock, distributed to all modules via network |
| Mix | Web UI mixer — each module's stereo output blended + headphone sends |
| RPi | RPi 5 |
| Enclosure | Rackmount 1U |
Edge: Without this, modules run independently (each with its own output to the mixer). The bridge lets you control the entire band mix from one device and gives the drummer a click track.
Module Comparison Matrix
| Module | I/O | Preamp | Phantom | RPi | Enclosure | Complexity | Est. BOM | Status |
|---|---|---|---|---|---|---|---|---|
| Guitar | Combo + 4CM | TL072 | No | 4B | 1590BB | Medium | ~$175 | Prototype |
| Bass | Combo + DI | FET Neve | No | Z2W | 125B | Medium | ~$150 | Concept |
| Vocal | XLR in/out | INA163 | Yes | 4B | 1590BB | High | ~$200 | Concept |
| Keys | Stereo TRS | None | No | Z2W | 125B | Low | ~$120 | Concept |
| Horns | XLR in/out | INA163 | Yes | Z2W | 125B | Medium | ~$160 | Concept |
| Drums | AES50 + stage | Varies | Yes (box) | 5 | 1U | Very High | ~$400+ | Concept |
| Bridge | Ethernet | — | No | 5 | 1U | High | ~$200 | Concept |
Next Steps
Immediate (guitar prototype):
- Revise I2S HAT for 1590BB + combo jacks + XLR driver
- Order boards (Gerber export → JLCPCB)
- Assemble + test with Focusrite 2i2 in 4CM
- Wire touchscreen display
- Full prototype test: guitar → pedal → amp + FOH
Short-term (bass + keys):
- Bass uses same HAT as guitar (just different preamp circuit)
- Keys uses existing HAT's stereo capability — zero PCB changes
- Both can be validated with the Focusrite before ordering HAT PCBs
Medium-term (vocal + horns):
- Need new HAT design (mic pre + phantom power)
- Major analog design effort
Long-term (drums + bridge):
- AES50 research and prototyping
- Stage box PCB design (8-channel preamp + phantom + AES50 encoder)
- Mix bridge software design
Want me to save this as a reference doc and task up the guitar prototype completion plan from here? That'd cover:
- I2S HAT Rev 2 (combo jacks + XLR driver + 1590BB fit)
- Touch display integration
- Full assembly + test with Focusrite 4CM
- Then order real boards