DC Blocker
A circuit that blocks a direct-voltage offset on the AC mains supply before it reaches connected equipment.
A small DC offset on the mains can affect a transformer’s magnetic operation and contribute to mechanical hum. A DC blocker targets that offset while passing the intended AC supply. It addresses a particular electrical condition, rather than every cause of noise.
DC Blocker — Power Filter
In a power conditioner, a DC blocker may help when mains offset makes the connected equipment’s transformer vibrate audibly. This is mechanical noise from the component, which should be distinguished from hum heard through the loudspeakers. Confirm that the unit explicitly includes DC blocking.
Compare its current and voltage ratings with the intended equipment and follow its installation instructions. A general mains filter does not necessarily block DC, and DC blocking alone does not regulate voltage or provide surge protection. Hum caused by grounding, wiring or another fault may require a different remedy.