So you set up new gear and hear buzz, hum, hiss, or see banding on a TV. Retail demos often work fine because the store’s wiring and layout differ from your home’s. The noise could be bad wiring, defective gear, or environmental interference. Below are the common causes and practical fixes.
Ground loops
– What they are: Ground loops form when multiple pieces of equipment share AC power at different outlets while also being connected by shielded signal cables (RCA, HDMI, component, etc.). The cable shields and chassis provide a loop that picks up induced currents and produces audible hum or TV banding.
– Quick fix: Plug all interconnected equipment into the same AC outlet with a single power strip or surge protector so there’s only one ground path.
– If you can’t reach one outlet: Avoid using three-prong-to-two-prong adapters (they remove safety ground and create shock hazards). Instead use a hum eliminator/ground-loop isolator (e.g., Ebtech Hum X or inexpensive audio/coax isolators) or run an extension to the same circuit.
– Coax/antenna note: OTA antenna or cable-TV coax often has its own ground path. Disconnect the coax to test; if the noise stops, the problem is in that path or a related device (cable modem, splitter). Use a coax ground loop isolator or replace defective equipment.
AC line noise
– Sources: Motors (vacuum, hair dryer), dimmer switches, failing fluorescent lights, and other noisy appliances put spikes and hash on the AC line.
– Simple option: Avoid using noisy appliances while listening or watching.
– Robust options:
– Line-interactive UPS (battery-backed, continuous conversion) or a pure-sine UPS with continuous inverter stages can remove line noise and provide surge/back-up protection.
– Isolation transformer: A shielded transformer provides clean AC by magnetic isolation, removing line noise without batteries. Hospital-grade isolation units are overkill for audio but highly effective.
– Cost: UPSes and isolation transformers range from a couple hundred dollars to several hundred; they’re more effective than many expensive “audiophile” power conditioners.
Wires and cables
– Keep power and signal cables separated. Don’t run power cords across or alongside audio/video cables or antenna leads; induced hum can result.
– Balanced audio cables (XLR or TRS) use two inverse signal wires plus a ground and are much less susceptible to noise—use them when available.
– Speaker cables carry strong signals and are less prone to interference, but keep AC cords off them.
– Don’t loop twin-lead or coax; loops act like antennas and pick up interference.
– Cable quality: You don’t need boutique prices. Copper conductors with corrosion-resistant connector plating (gold used to prevent oxidation) are solid. Good cables in the $10–$20 range are adequate for most uses.
– Microphonic cables: In certain high‑impedance systems (turntables, guitars), a poor cable can make mechanical vibrations audible. Tap suspect cables while system is on to test for microphony.
– Gauge: Heavier speaker wire can slightly reduce amp stress on big loads, but for signal cables gauge beyond a standard size gives negligible audible difference.
RF (radio-frequency) interference
– Metal enclosures act as Faraday cages; cheap/transparent cases or poor shielding can let RFI in or out.
– Sources include cordless phones, cell phones, Wi‑Fi gear, wireless peripherals, and nearby transmitters.
– Reduce strength and proximity of RF emitters to your audio/video gear. Replace malfunctioning wireless gear if it radiates badly.
– Balanced inputs and well-shielded components help resist RFI.
USB/HDMI cable noise
– Current can leak into cable shields and contaminate audio, particularly with external USB audio interfaces.
– Fixes:
– Use cables with ferrite beads or clip-on ferrite chokes to suppress high-frequency noise.
– Ground shunt: Run a low-resistance wire from the device chassis (USB audio interface or HDMI source) to the computer or another common ground to redirect stray current away from the cable shield.
– USB noise filters/repeaters: Devices that isolate or re-transmit USB signals can break shield-ground currents; they cost more and are less commonly needed.
– Ferrite beads are cheap and often the first, simplest step.
PC audio noise
– Onboard motherboard audio often picks up RFI and switching noise from other PC components.
– Solutions: Use an external USB or Thunderbolt audio interface, or a PCI/PCIe dedicated sound card. External interfaces are usually quieter and offer better isolation.
Other practical tips and safety
– Replace faulty gear that creates noise (bad cable modem, splitter, or device).
– Avoid removing safety grounds. If you must isolate, use purpose-built ground-lift devices or isolators, not hacky adapters.
– DIY: There are inexpensive DIY hum‑eliminator plans online, but they require soldering and electrical skills. Know what you’re doing and follow safety rules.
– If a fix works only when you touch a certain part (you get a shock), stop and address grounding—do not rely on touching things for silence.
– If noise persists after trying the above, methodically isolate components: disconnect sources one at a time, swap cables, test with different outlets/circuits, and try balanced connections.
Summary
Most annoying audio and video noises come from ground loops, dirty AC, poor cable routing or shielding, and RF pickup. Start with the simplest fixes—single outlet power, rearrange cables, add ferrites—then move to ground-loop isolators, balanced cables, UPS/isolation transformers, or replace faulty equipment. These steps will eliminate the vast majority of hum, buzz, and visual artifacts.
Author: Jon L. Jacobi, Freelance contributor
