Ground Loop Hum: What It Is and How to Eliminate It

That low, steady 60 Hz buzz that creeps into your recordings (50 Hz outside North America) is almost never coming from your mic, your instrument, or your room. It is ground-loop hum — an electrical-engineering artifact of how your gear is wired together — and it is fixable. Importantly, it must be fixed the right way. Several "easy" solutions you will see suggested online are dangerous, illegal in most jurisdictions, and absolutely off the table here.

This explainer covers what ground loops actually are, how to identify them, the safe and effective fixes, and the unsafe "fix" you must never use under any circumstance.

The Required Safety Callout — Read This First

To be unambiguous: the safety ground (the third pin on a US plug, the earth pin on a UK plug, etc.) exists to keep a metal chassis from ever sitting at line voltage if a fault develops inside the gear. OSHA's standard interpretations are explicit that "a grounding terminal or grounding-type device on a receptacle, cord connector, or attachment plug shall not be used for purposes other than grounding" — i.e. it is not legal to defeat the equipment grounding conductor for noise reasons or any other reason (OSHA Standard Interpretation, "Grounding requirements for equipment connected by cord and plug," 1999-12-21). Bill Whitlock — president of Jensen Transformers and the AES Life Fellow whose 1995 JAES paper on balanced interfaces is the most-cited reference in the field — makes the same point bluntly in his Jensen seminar handout: lifting the safety ground is "potentially deadly" and is never the correct solution to a ground-loop problem (Jensen Transformers, "Understanding, Finding, & Eliminating Ground Loops in Audio & Video Systems," Whitlock seminar handout). Use the techniques in this article instead.

What a Ground Loop Actually Is

A ground loop is a closed electrical path that forms when two pieces of equipment are connected through both their safety grounds (via the AC outlet) and their signal grounds (via the audio cable shield). If those two ground references are at slightly different voltages — which is the norm, not the exception, in real buildings — current flows around that loop. The current is small, but it shows up as induced voltage on the audio cable shield, and that voltage rides into the audio signal as the characteristic 60 Hz buzz (50 Hz on 50 Hz mains).

Whitlock's Jensen technical paper attributes the underlying voltage difference to magnetic induction in ordinary premises AC wiring, which creates small voltage differences "normally found among system ground connections, even if 'isolated' or 'technical' grounding is used" (Whitlock & Fox, "Ground Loops: The Rest of the Story," AES paper, Jensen Transformers PDF). Sound on Sound's long-running "Sound Advice" coverage of mains hum frames the practical version the same way: hum is almost always a wiring-topology problem, not an audio-component problem (Sound on Sound, "Q. How can I cure mains hum?"). The fix is to either break the loop without breaking safety ground, or eliminate the voltage difference that drives current around the loop in the first place.

What ground-loop hum sounds like (vs. other noise)

The Safe Fixes — In Order of What to Try First

1. Plug all audio gear into the same circuit

This is the highest-leverage, lowest-cost fix. If every piece of audio gear shares one outlet (or one circuit, traced back to the same breaker), they share a ground reference and the voltage differences that drive the loop largely shrink. Use one good-quality power strip; do not daisy-chain strips, and do not use long thin extension cords — added resistance reintroduces the voltage offset you were trying to eliminate. Whitlock's Jensen seminar identifies "single-point grounding" — driving every chassis ground from one common return — as the canonical mitigation for inter-chassis voltage difference (Jensen Transformers, Whitlock seminar handout).

If your studio room has outlets on more than one circuit, your electrician can identify which outlets share a breaker. Outlets in the same room are often, but not always, on the same circuit.

2. Use balanced cabling end-to-end where possible

Balanced XLR or balanced TRS connections carry the audio twice on two conductors with opposite polarity, plus a separate ground. Any noise picked up on the cable hits both conductors equally, and the differential receiver subtracts it out — including most of the ground-loop-induced noise. Sound on Sound's Hugh Robjohns explains that the balanced input "works differentially, meaning the signal voltage on one input leg is subtracted from that on the other. If the signal voltages are exactly the same on both legs (a common mode signal), they cancel each other out" — which is why a properly balanced run rejects the hum a ground loop induces on the cable (Sound on Sound, Hugh Robjohns, "Q. How do balanced signals work in audio gear?"). Whitlock's 1996 AES paper "A New Balanced Audio Input Circuit for Maximum Common-Mode Rejection in Real-World Environments" is the deeper-dive reference for why real-world CMRR depends on impedance matching, not just having three pins (Whitlock & Fox, AES paper via Jensen Transformers; Sound on Sound glossary, "Common Mode Rejection"). Replacing an unbalanced TS run with a balanced TRS run is often the entire fix.

Caveat: a balanced cable that is wired wrong (shield bonded to a signal pin, or a "Hi-Z" guitar fed through a TRS-balanced cable) can make the problem worse. If you suspect a cable, swap it; if a swap fixes the hum, the cable was the issue.

3. Use an isolation transformer / hum eliminator

An audio isolation transformer (sometimes sold as a "hum eliminator" or "ground isolator") magnetically couples the audio signal across an air gap, breaking the ground path entirely while passing the audio cleanly. Whitlock describes this as "the fundamentally correct way to eliminate system ground loop problems" — the transformer "magnetically couples the signal across an electrically insulated barrier" so the audio shield no longer carries loop current, while the AC safety ground in the wall stays intact (Jensen Transformers, "What is a Ground Loop?").

Common, well-regarded options include:

• Ebtech Hum X — designed specifically for this problem; Ebtech's product literature explicitly states the device "removes ground loop hum… without lifting the safety ground," which is the correct, code-compliant behavior (Ebtech, Hum X product page).
• Ebtech Hum Eliminator (HE-2) — passive 2-channel transformer-isolator, inserted in the audio path rather than the AC path (Ebtech, Hum Eliminator product page).
• Jensen Iso-Max line — Jensen's line of inline transformer isolators built around the same audio transformers used in their OEM modules (Jensen Transformers, Iso-Max product line).
• The transformer-coupled outputs on professional DI boxes such as the Radial JDI, which uses a Jensen JT-DB-EPC transformer (Radial Engineering, JDI product page).

Each of these isolates audio shields, not the AC earth conductor — that is the entire design intent.

4. Use a DI box with proper isolation (not a "ground lift" on a power cord)

Active and passive DI boxes typically include a ground-lift switch. To be unambiguous: the ground-lift switch on a DI box lifts the audio cable shield's connection between input and output sides of the box — it does not lift the AC safety ground on any power cord, and it does not create a shock hazard. This is a perfectly safe and standard tool, and it is documented as such on every reputable DI box's manual, including Radial's (Radial JDI product page; ground-lift switch description). The only "ground lift" you must never use is the one that defeats the third pin on an AC power cord (see safety callout above).

5. Reroute cables to reduce induced noise

Keep audio cables physically separated from AC power cables. When they must cross, cross at right angles. Loop excess cable in figure-eights rather than tight coils. None of this fixes a real ground loop, but it reduces the EMI burden on top of whatever loop noise exists, and on borderline systems can drop the audible noise floor below threshold.

When the Hum Won't Go Away — Time to Call a Professional

If you have:

• Plugged everything into one circuit,
• Confirmed end-to-end balanced cabling on every signal path that supports it,
• Tried isolation transformers on the connections that resist fixing,

… and the hum is still there, you may have an actual electrical fault in the building wiring. Common culprits include an open neutral on a shared circuit, a missing or improperly bonded ground at the panel, or a neutral-to-ground bond in the wrong place (it should exist only at the main panel). All of these require a licensed electrician to diagnose and repair.

An additional indicator that you have an electrical, not audio, problem: if you ever feel a tingle from touching the chassis of any audio device, stop using it immediately and call an electrician. That is a leakage-current condition, and it is the exact failure mode the safety-ground pin is supposed to prevent. Continuing to use the gear (or "fixing" the tingle by lifting ground) is how electrocutions happen — and Whitlock's Tape Op interview makes the same point about audio engineers' unfortunate habit of treating safety-ground as something optional (Tape Op, "Bill Whitlock: Solving Audio System Noise & Grounding").

Note on diagnostic measurement: some online guides will instruct you to use a multimeter to read voltage between the chassis of two devices. This requires comfort with electrical measurement around mains-adjacent metalwork; an electrician will do it safely as part of the diagnostic. We recommend you let them.

Common Misconceptions

"A 3-prong-to-2-prong adapter is a quick fix for hum." No. It defeats the safety ground that protects you from a chassis fault, and OSHA's standard interpretation is explicit that the equipment grounding conductor cannot be used or defeated for any purpose other than grounding (OSHA Standard Interpretation, 1999-12-21). Use isolation transformers instead — they break the ground loop without breaking the safety path.

"All hum is a ground loop." No. Pure 60 Hz hum that doesn't change with gain is the classic ground-loop signature. Buzz that varies with cable position is usually EMI. Hiss that rises with preamp gain is gain-staging or preamp noise. Whine that tracks the screen refresh is digital interference. Diagnose before treating (Sound on Sound, "Q. How can I cure mains hum?").

"Expensive 'audiophile' power conditioners eliminate ground loops." No. A power conditioner filters noise riding on the AC line; it does nothing about the wiring topology that creates the loop in the first place. Conditioners can help with other noise, but they are not the right tool for this — a point Whitlock has made repeatedly in his Jensen technical writing (Jensen Transformers, Whitlock seminar handout).

"Cheap audio gear creates ground loops because it is poorly grounded." Mostly no. A ground loop is a property of how two grounded devices are connected to each other, not a defect in either device. The same gear in a different room with a different outlet topology often shows no hum at all.

"You can EQ the hum out." Not really. A 60 Hz notch can attenuate the fundamental but its harmonics extend up well into the audible band, and they are correlated with the source signal in ways EQ cannot remove cleanly. Fix the cause; don't paper over the symptom.

When This Affects You — Practical Scenarios

• You added a new piece of outboard and now there's hum: the new gear plugged into a different outlet has shifted the ground reference. Move it to the same circuit as the rest of your rack first.
• You're recording in a hotel room or unfamiliar location: bring an isolation transformer in your kit. Hotel wiring is unpredictable.
• You have a guitar amp that hums whenever you touch the strings differently: classic guitarist ground-loop scenario, often involving the cable from a pedalboard to the amp on a different circuit. A DI box (with the audio ground-lift on the box, not a cheater plug on the power cord) usually handles it.
• Your monitors hum only when the computer is plugged into the wall (not on battery): the laptop's switching power supply is sharing a noisy ground with the monitors. Use balanced TRS to the monitors; if that's already in place, add an inline isolation transformer on the monitor feed.
• You hum even with everything on one outlet, balanced everywhere: stop, do not start lifting safety grounds, call an electrician. The building has an issue.

Sources & Citations

1. On safety-ground integrity / why never to lift ground: OSHA, Standard Interpretation, "Grounding requirements for equipment connected by cord and plug" (1999-12-21), osha.gov (accessed 2026-04-20).
2. On ground-loop physics, single-point grounding, and isolation as the correct fix: Bill Whitlock, "Understanding, Finding, & Eliminating Ground Loops in Audio & Video Systems" (Jensen Transformers seminar handout), jensen-transformers.com (accessed 2026-04-20).
3. On magnetic induction creating inter-chassis voltage differences (AES paper): Bill Whitlock & Jamie Fox, "Ground Loops: The Rest of the Story" (Audio Engineering Society), via Jensen Transformers, jensen-transformers.com (accessed 2026-04-20).
4. On transformer isolation as the canonical solution: Jensen Transformers, "What is a Ground Loop?", jensen-transformers.com (accessed 2026-04-20).
5. On 60 Hz hum being a wiring-topology problem (Tier-1 audio outlet): Sound on Sound, "Q. How can I cure mains hum?", soundonsound.com (accessed 2026-04-20).
6. On balanced audio and common-mode rejection (Tier-1 explainer): Hugh Robjohns, "Q. How do balanced signals work in audio gear?", Sound on Sound, soundonsound.com (accessed 2026-04-20).
7. On the definition of common-mode rejection: Sound on Sound glossary, "Common Mode Rejection," soundonsound.com (accessed 2026-04-20).
8. On Whitlock's career-long advocacy for safe grounding (Tier-1 pro audio outlet): Tape Op, "Bill Whitlock: Solving Audio System Noise & Grounding," tapeop.com (accessed 2026-04-20).
9. Product reference — Ebtech Hum X (preserves safety ground while removing ground loop): Ebtech, Hum X product page, ebtechaudio.com (accessed 2026-04-20).
10. Product reference — Ebtech Hum Eliminator (in-line audio transformer): Ebtech, Hum Eliminator product page, ebtechaudio.com (accessed 2026-04-20).
11. Product reference — Jensen Iso-Max isolators: Jensen Transformers, Iso-Max product line, jensentransformers.com (accessed 2026-04-20).
12. Product reference — Radial JDI passive DI with Jensen JT-DB-EPC transformer (audio-side ground-lift switch): Radial Engineering, JDI product page, radialeng.com (accessed 2026-04-20).

Last verified: 2026-04-20