Signal flow is the path audio takes from its source to the speakers. Knowing it means you can find problems quickly and decide where each process belongs.
The basic chain
In a typical channel the signal passes through these stages in order:
- Source: a microphone, instrument or playback device.
- Preamp: raises a weak signal to a usable level.
- Insert processing: effects placed in the channel itself, such as EQ or compression.
- Fader: sets the channel’s level in the mix.
- Bus: a group or mix path that collects several channels.
- Master: the final stereo output heading to monitors or a recording.
Signal levels
Different sources produce very different voltages, which is why the first stage matters.
| Level | Approximate value | Typical source |
|---|---|---|
| Mic | roughly -60 to -40 dBu | microphones |
| Instrument | between mic and line | guitar and bass pickups |
| Line | +4 dBu (professional), -10 dBV (consumer) | mixers, synths, interfaces |
These are approximate figures. Mic level is very small and needs the most gain, instrument level is higher but needs a high-impedance input, and line level is already strong enough to connect directly to line inputs. The two line standards differ by a few decibels, so a mismatch can leave a level too quiet or too hot.
Inserts versus sends and returns
An insert places a processor directly in the channel. All of the signal passes through it, so it suits tools that should affect the whole sound: EQ, compression, gating.
A send copies some of the signal to an aux bus, and a return brings the processed copy back into the mix. The original stays untouched. This suits effects shared by many channels, such as reverb or delay, because one processor serves the whole mix and the send knob sets how much each channel feeds it. Reverb on a send also keeps a consistent space across instruments.
Pre-fader and post-fader sends
A send can be taken before or after the channel fader.
- Post-fader sends follow the fader. Turning the channel down also turns the effect down, so the balance stays the same. This is the normal choice for reverb and delay.
- Pre-fader sends ignore the fader. The send level stays fixed while the fader moves, which is used for monitor and headphone mixes where each performer needs a stable level.
Buses and groups
A group bus sums several channels, for example all drums, into one fader. Processing the bus treats them as a unit: a single compressor can glue the kit together, and one fader rides the whole group. Groups then feed the master.
A DAW mixer follows the same model
A software mixer copies the console layout:
- A track’s plugin chain is the insert section, processed in order from top to bottom.
- The track volume fader is the channel fader.
- Send controls route to return or aux tracks holding effects.
- Group tracks or busses sum several tracks.
- The master track is the final output.
Plugin order matters. A compressor before an EQ reacts differently from the reverse, because each stage processes what the previous one produced.
Troubleshooting with the chain
When there is no sound, move along the path stage by stage: source output, input, preamp gain, insert bypass, fader, bus routing, master, monitors. When there is distortion, work out which stage is overloaded; see the article on gain staging for how levels should be set at each point.