Distortion, hum, ground loops, dropouts, latency and drivers.

Dirty sound is a symptom, rather than a diagnosis. The same description—it sounds odd, hums or cuts out—can mean problems requiring entirely different remedies: raising or lowering a level, changing an earth path, enlarging a buffer or installing a driver. This guide separates six cases: distortion, hum, ground loops, audio dropouts, latency and drivers.

The distinguishing criteria are timing and noise character. Continuous noise points to power or grounding; noise only with music points to levels; sound that cuts out and returns points to the computer.

Distortion: almost always level rather than equipment

Distortion appears with the signal: if music is clean at low level and breaks up when raised, the problem is level rather than the amplification chain. Find the exact point by raising the signal one stage at a time until it appears.

Follow the chain from input to output: each source’s trim leaves peak headroom, fader open, master at its working point, and downstream venue level. If the mixer signal is already clipped, no later adjustment repairs it. Gain discipline—each stage at its own level and master with headroom—prevents most cases, following the same principle as Gain staging.

Two common traps. First, confusing level distortion with speaker distortion, which appears at high volume despite a correctly adjusted mixer; reduce room volume and listen for disappearance. Second, effects and master tempo add perceived gain, so a chain clean at medium volume may clip when enabling a colour effect or echo. Raise the effect in the booth and check whether noise appears only then.

Hum: the buzz that appears when everything is connected

Hum is constant buzzing, typically at mains frequency, audible even without music. Neumann’s guide describes low-frequency 50 or 60 Hz hum, or noise changing when equipment is connected or disconnected.

The quick check follows the manual: disconnect inputs individually and listen. If hum disappears after removing one cable, the responsible path is identified. Then power equipment from the same strip or socket, avoiding different booth circuits, and check that sockets are correctly wired.

Order matters: power first, signal cabling second, transformers last. Hum almost always decreases with balanced connections, short well-screened cables and signal cables kept away from power supplies. The related electrical installation is covered in Earthing, loops and protection.

Ground loop: identifying and breaking it

A ground loop appears when two devices have two separate earth paths and a current through the signal cable becomes hum. Rane’s technical note is clear: the current’s presence is not the problem; the problem is current passing through equipment’s signal ground.

The distinguishing symptom: hum changes or appears when connecting a specific device and disappears on disconnection. A classic exercise is disconnecting all inputs in the suspect area, then reconnecting individually while noting which equipment reintroduces noise.

Solutions, from least to most invasive. One: power everything from one point. Two: use genuinely balanced connections, with ground separate from signal return. Three: lift signal ground on equipment allowing it, with equipment switched off. Four: insert an isolation transformer in the path. Never remove protective earth at the plug; it protects people rather than audio.

Audio dropouts: when the buffer is too small

Audio dropouts are abrupt interruptions without warning, lasting a fraction of a second and unrelated to volume. They occur because the computer cannot finish processing its allotted audio block in time.

Serato lists countermeasures in order: update software, remove corrupt files from the library, close other programs, disable wireless networks, Bluetooth, screen savers and sleep, increase buffer size, connect directly to USB without a hub, try different ports and power the laptop. Each targets a different cause, and most are free.

Measure before blaming the computer: dropouts appearing only in one project indicate load; those appearing with every project and freshly restarted software point to the system and driver. If increasing the buffer removes them, processing power was the limit; if they persist unchanged, the problem lies elsewhere.

Latency: the price of lowering the buffer

Latency is the delay between gesture and sound. Ableton documentation explains its origins in the audio buffer and delay-adding devices, and that lowering the buffer reduces latency in exchange for increased CPU load—the very operation pushing the system towards audio dropouts.

Adjustment is therefore a balance, rather than a universally optimal value. Scratching or vinyl control: low buffer. Long mixing with many effects: higher buffer. Change one parameter at a time and check two things: response remains comfortable, and five consecutive minutes of playback produce no dropouts.

Watch latency the buffer cannot fix: plug-ins with their own delay, manually adjusted track delay and open editor windows add time to the entire path. If overall delay does not match what you hear, review these layers before lowering the buffer further.

Driver: the link almost nobody checks

The driver lets the computer and audio interface speak the same language. On Windows, a generic or old driver causes absent output, dropouts or impossible latency; equipment with its own driver can behave very differently with the correct version versus the system’s.

Four checks: identify the interface or mixer’s exact model, download its driver from the manufacturer’s site, install with equipment restarted, and confirm the application’s audio settings use that device rather than another. Then keep driver, software and system updated: optimisation guides explicitly recommend driver updates and preventing USB ports shutting down for power saving.

This chapter’s checklist—correct driver, sensible buffer, level headroom, one earth point and balanced connections—is worth reviewing whenever a new booth first sounds odd, beginning with physical audio-chain connections.

Next step

Sound is now clean and timely. Make sure it continues when something fails: DJ changeovers, B2B, computer failure and emergency plans are covered in DJ changeovers, B2B and an emergency plan.