Description
The CleanAmp DC Blocker is an inline passive filter that prevents DC voltage offset on the mains from reaching a connected audio device. Direct current on an alternating current supply is a widespread and poorly understood problem in domestic electrical environments — particularly in areas where the local distribution transformer serves many households and DC injection from half-wave rectifier loads skews the AC waveform. The most audible symptom is a 50 Hz mechanical hum from the power transformer in any device connected to the affected mains supply.
Why DC Offset Causes Transformer Hum
A mains transformer is designed to operate with a symmetrical AC waveform centred on zero volts. DC offset — a positive or negative shift in the waveform’s midpoint — causes the transformer’s magnetic core to saturate asymmetrically during each half-cycle. Asymmetric saturation pulls more current on one half-cycle than the other, which causes the transformer laminations to vibrate at twice the mains frequency:
– DC offset as low as 100 mV can cause audible transformer hum in sensitive audio equipment
– The hum is mechanical — it originates from vibration in the transformer body, not from the audio circuitry
– Volume control position has no effect on mechanical transformer hum — this distinguishes it from signal-path noise
– Turning the equipment off stops the hum — this confirms the supply rather than internal resonance as the cause
CleanAmp DC Blocker Specification
The CleanAmp DC Blocker connects inline between any Schuko mains outlet and the affected device:
– Series capacitor bank rated to block DC while passing 50 Hz AC without significant voltage drop
– Rated to 10A continuous / 2,300W — appropriate for any domestic audio component
– Compact extruded aluminium housing: 95 × 45 × 30 mm
– Schuko input plug, Schuko output socket — no modification to the device or its cable required
Backed by a two-year warranty.
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