Hum Ham — Fixing mains hum and buzz in home and studio | humham.com
The number on the spectrum tells you which mechanism is singing — grid leakage at the base frequency, or a rectifier doubling it.
Every grid hums at its own base frequency. The UK, most of Europe and most of Asia deliver 220–240 V at 50 Hz; North America delivers 120 V at 60 Hz. Japan splits the difference: 50 Hz east of Nagoya, 60 Hz west of it. Whatever the region, mains-related noise enters at that base frequency.
What you call buzz is usually the base frequency doubled. A full-wave rectifier, the standard stage inside almost every power supply, doubles the mains frequency, so on a 50 Hz grid the supply radiates at 100 Hz with further harmonics at 150 and 200 Hz. On a 60 Hz grid the same supply sings at 120 Hz with 180 and 240 Hz above.
On narrow screens, swipe or scroll the plate sideways.
Harmonics are the fingerprint. A pure grid leak gives one strong low peak; a rectifier gives a stack, and the higher harmonics are exactly what makes buzz sound sharper than hum. If the spectrum shows 50 Hz with modest 100 Hz, think ground loop. If 100 Hz outweighs the base, think supply.
Grid discipline helps you trust the reading. European continental grids are held within 49.8–50.2 Hz in normal operation, so a genuine mains peak stays within about 0.2 Hz of 50 Hz. A peak that drifts further is not the grid being wild — it is more likely your measurement coupling to a switching device rather than true mains.
Once you have the number, route yourself: 50/60 Hz takes you to the ground-loop procedure, 100/120 Hz takes you to supply and shielding work. The two paths cross on cable choices, which the balanced-versus-unbalanced page maps out.
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