Stop Audio Hum and Buzz: Ground Loop Fixes for AV Cables

Quick answer

A steady low hum or buzz that changes with volume is usually a ground loop, not a bad cable. Before buying anything, unplug every source from the amplifier or mixer and reconnect one at a time until the noise returns; that device is the culprit. For line-level RCA connections, a ground loop isolator on the noisy input often removes the hum. If the noise stays with nothing connected, the problem is inside the amp or the mains wiring, and an isolator will not fix it.

Tell hum apart from buzz, hiss, and interference

Hum is a low, steady tone around 50 or 60 Hz. Buzz is that tone plus harmonics, so it sounds harsher and more electrical. Hiss is high-frequency noise that stays roughly the same at any volume, and it usually comes from gain staging or a noisy source, not a ground loop. Crackle, pops, or a radio station bleeding through point to a bad shield, a loose connector, or a cable running alongside mains wiring.

The key test is behaviour. Ground loop hum and buzz usually appear as soon as a device is connected, stay constant when you change the volume on the source, and may get louder when you touch the chassis or a metal connector. Interference from a cable usually changes when you move the cable. Hiss changes when you turn up a gain knob. Match the symptom first, then choose the fix.

Run the one-at-a-time disconnection test

Power everything down, then disconnect every source cable from the amplifier, mixer, or powered speaker. Power up and listen. If the hum is gone, reconnect one source at a time, listening after each connection. The moment the noise returns, you have found the loop path. If the hum is still there with nothing connected, the loop is inside the unit or in the building wiring, and cable changes will not help.

Once you know which device causes the hum, try moving its power plug to the same outlet or power strip as the amplifier. Different wall circuits are a common cause of ground loops in home and small studio setups. If the hum disappears when both devices share one outlet, you have a cheap fix that costs nothing but a power strip.

Choose the right correction for the connection type

For unbalanced RCA line connections, a ground loop isolator inserted between the source and the amplifier is the standard fix. It breaks the ground path while passing the audio signal. For balanced connections, use a transformer isolator or a DI box rather than an RCA isolator. If the noise is on a microphone or instrument line, a passive DI box with a ground lift switch is usually the better tool.

Cable quality matters less than cable routing. Keep audio cables away from mains leads, power supplies, and USB chargers. If a cable must cross a power lead, cross it at 90 degrees rather than running parallel. For long RCA runs, a shielded cable helps against interference but will not cure a true ground loop, because the loop is a wiring problem, not a shielding problem.

When the noise is on a camera or CCTV feed

Video systems can suffer the same ground loop problem. A CCTV ground loop isolator on the video line, or a ground loop isolator on the audio line if the recorder captures sound, is the usual fix when a camera and recorder sit on different power circuits. If the picture also rolls, tears, or shows a dark bar, treat the video and audio paths separately, because one isolator on one line may not clean up both.

Do not lift the mains earth on a camera or recorder to chase a hum. That removes a safety path. Use an isolator on the signal cable instead, and keep the earth connection intact.

Ground loop diagnosis: symptom, cause, action, and stop point

• Steady low hum that appears when one source is connected: Most likely a ground loop between that source and the amplifier. Unplug sources one at a time to confirm which device brings the hum back. If the hum returns only with that device connected, fit a ground loop isolator on its line-level output.
• Harsh buzz that gets louder when you touch a metal connector or chassis: This points to a ground potential difference, often from devices on different wall circuits. Try powering both devices from the same outlet or power strip first. If sharing one outlet removes the buzz, keep it that way and do not lift the mains earth.
• Hum or buzz that stays with nothing connected to the amplifier: The loop is inside the unit or in the building wiring, not in your cables. Cable swaps and isolators on the signal path will not remove it. Stop buying cables for this symptom. Have the amplifier or the mains wiring checked by a qualified person.
• Noise that changes when you move a cable or a device: That is interference pickup, not a ground loop. Reroute the cable away from mains leads and power supplies, and cross power cables at 90 degrees if they must cross. If rerouting fixes it, you have solved an audio cable interference problem without spending on new gear.

Cables that help with routing and connection problems

• RCA to 6.35mm (1/4") TS Audio Cable – Mono Right-Angle Jack to RCA Male Patch Lead 2m: RCA to 6.35mm (1/4") TS Audio Cable – Mono Right-Angle Jack to RCA Male Patch Lead 2m, with a right-angle 6.35mm TS male plug and a straight RCA male connector. The right-angle jack is useful in tight rack spaces and rear-panel connections, and the 2 m length gives you room to route the cable away from power leads instead of stretching it across a power supply.
• USB-C to 6.35mm TRS Stereo Aux Cable (1/4") – Type-C Audio Adapter for Amp, Mixer & Speakers: USB-C to 6.35mm TRS Stereo Aux Cable (1/4") – Type-C Audio Adapter for Amp, Mixer & Speakers, with a stereo TRS 1/4" jack for line/aux inputs. If your hum started after connecting a USB-C device to a mixer or powered speaker, this cable gives you a direct line-level connection so you can test whether the noise follows the USB-C source or the analog input.
• Mini DisplayPort Male to Female Extension Cable – Video Extension Lead 1m: Mini DisplayPort Male to Female Extension Cable – Video Extension Lead 1m, designed to extend an existing Mini DisplayPort connection. When a display or dock sits on a different power circuit, extending the video run can let you reposition equipment and test whether the hum changes when devices share a circuit or are separated.