groundloop

A ground loop is an electrical condition in which multiple ground paths exist between two or more pieces of equipment that are wired together, creating a closed loop through which current can flow. In audio and video systems, ground loops are especially problematic because even small differences in ground potential can generate hum or buzz that is picked up by signal lines.

Ground loops arise when devices connected to each other share a common return path but also have separate grounding connections with nonzero impedance. This is common in home and studio setups where equipment is plugged into different outlets, power strips, or power conditioners, or where long shielded cables and multiple earth grounds are involved. The result is a loop that carries stray currents at mains frequency or harmonics, which can modulate signal lines and degrade performance.

Symptoms typically include a persistent hum or buzz in speakers, headphones, or audio interfaces, often at 50 or 60 Hz and/or its harmonics. In some cases, grounding issues can also cause intermittent noise, clicks, or instability in measurement systems.

Prevention and remedies focus on minimizing potential differences and breaking the loop. Practical steps include using a single power outlet or power conditioner for all equipment, employing balanced connections (TRS/XLR), keeping signal cables separate from power cables, and ensuring proper shielding. Isolation methods such as isolation transformers, ground loop isolators, or DI boxes can break the loop. In complex installations, a single-point or star grounding scheme and careful grounding design are recommended. If safety concerns are present, professional electrical assessment is advised.