audio-signal-flow-explainer

Audio Signal Flow Explainer

Core principle: Audio signal flow is a directed graph. Tracing it reveals hidden coupling,

latency paths, and places where the signal can be corrupted.

Step 1 — Map the graph

• [ ] Find all sources (oscillators, audio inputs, file readers, generators)
• [ ] Find all processors (filters, effects, gain stages, dynamics)
• [ ] Find all routers (bus sends, parallel splits, sidechain taps, mixer channels)
• [ ] Find all sinks (audio outputs, recorders, meters, analyzers)
• [ ] Note parallel paths — any branch that rejoins a main path
• [ ] Note feedback loops — any path where output feeds back into an earlier node
• [ ] Note sidechain connections — signals that control a processor without passing audio through it

Step 2 — Identify each node type

| Node type | What to note | |-----------|-------------| | Source (oscillator, audio input, file reader) | Sample rate, channel count, sync source | | Processor (filter, effect, gain) | In/out channel count, latency added, stateful or stateless | | Router (bus send, parallel split, sidechain tap) | Where signal copies go, gain staging at split | | Sink (audio output, recorder, meter) | Expected format, callback timing, buffer size |

Step 3 — Surface issues

• [ ] Latency compensation mismatches on parallel paths
• [ ] Channel count mismatches between connected nodes
• [ ] Sidechain input not wired — processor receives silence as control signal
• [ ] Uninitialized state in feedback loops (DC buildup, NaN propagation)
• [ ] DC leaking into output (missing highpass or DC-blocking filter)
• [ ] Sample rate mismatch between source and downstream processor
• [ ] Gain staging that causes clipping before a later limiter or saturation stage
• [ ] Missing denormal protection in recursive filter paths

Step 4 — Write the signal flow description

Use this format:

## Signal Flow: [component/system]

### Graph
Source → [gain: 1.0] → [Biquad LPF] → [Comp sidechain tap] → [Output]
                                            ↓
                                       [Compressor] → [Output]

### Latency path
Source → LPF (0 samples) → Compressor (64 samples lookahead) → Output
Total: 64 samples

### Issues found
- Parallel path to Output has no latency compensation for the 64-sample compressor delay

Quick reference

| Pattern | What to check | |---------|--------------| | Parallel split rejoining | Latency of each branch must match before summing | | Sidechain compressor | Verify sidechain input is connected and level-matched | | Send/return bus | Check send gain, return gain, and whether send is pre- or post-fader | | Feedback loop | Confirm a delay of at least 1 sample exists to break algebraic loop | | Multi-rate graph | Confirm resampling nodes at every rate boundary |