Mains power
Distribution, filtering and grounding: the invisible link
Everything you hear is mains energy modulated by the signal. A noisy electrical supply, careless grounding or a random connection order shows up as a less black background, softer bass and grainy treble. This guide keeps priorities straight: topology and grounding first, filtering second.
Topology: a star, not a daisy chain
Feed every audio device from a single distribution point connected to one wall outlet. Cascaded strips create potential differences between chassis, a direct source of hum.
A dedicated line from the panel (3 × 2.5 mm², its own breaker) separates audio from polluting loads: induction hobs, dimmers, switching supplies, freezers.
Never share a strip between audio and a screen, computer or charger: those inject high-frequency noise back into the line.
Hum and ground loops
A 50 Hz (or 100 Hz) hum appearing when you connect a device almost always signals a ground loop rather than a faulty component. The usual culprit is a parallel ground path: TV aerial, Ethernet, set-top box, or a second electrical circuit.
Method: disconnect everything but amplifier and speakers, then reconnect one device at a time while listening to the residual noise. The device that triggers hum identifies the loop.
Clean fixes: a galvanic isolator on the offending link (aerial, Ethernet, USB), a floating-shield interconnect at the source end, or a move to balanced XLR. Never remove protective earth.
Filters, conditioners, regenerators
A passive filter suits digital sources and small devices well. On a power amplifier, an over-restrictive filter limits peak current and softens bass: use a high-current unfiltered outlet or a device designed for amplification.
Regenerators (synthesising a clean sine wave) solve genuinely degraded or unstable mains, but must be generously sized for peak demand.
A conditioner will not fix a ground loop and will not improve an already clean installation: listen or measure before spending.
Details that matter
Respect polarity (live/neutral) on unbalanced gear: reversal raises chassis leakage voltage and audible noise. A cheap socket tester is enough.
Power-up order: sources, then preamp, then power amp; power down in reverse. This avoids thumps through the drivers.
Keep mains cables away from interconnects; cross at 90° when unavoidable. Do not leave switching bricks against analogue links.
Common mistakes
- Cascaded strips and outlets spread across several circuits.
- Filtering a power amp behind a current-limited outlet.
- Lifting earth to silence hum: dangerous and it hides the real cause.
- Buying a conditioner before hunting the ground loop.
Checklist
- One distribution point, one wall outlet.
- No polluting loads on the same circuit.
- Hum checked device by device.
- Socket polarity verified.
- Mains cables routed away from analogue links.