# 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.

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## 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).

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## 🎺 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):**
1. Revise I2S HAT for 1590BB + combo jacks + XLR driver
2. Order boards (Gerber export → JLCPCB)
3. Assemble + test with Focusrite 2i2 in 4CM
4. Wire touchscreen display
5. 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:
1. I2S HAT Rev 2 (combo jacks + XLR driver + 1590BB fit)
2. Touch display integration
3. Full assembly + test with Focusrite 4CM
4. Then order real boards