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Category Archives: Power Quality

What is DC on the powerline?

Half wave rectification from devices within the home such as older hair dryers causes DC offset. It can also be caused by industrial devices outside the home that load the power line unevenly. The typical observed effect is transformer buzzing and ‘growling’ due to saturation of the magnetic core. Larger transformers, often found in amplifiers, […]

What are swells and overvoltages?

Long term over-voltage events are generally rare but when they occur can be damaging. Undersized distribution infrastructure coupled with periods of high demand can lead to utility companies increasing voltages so that the power required can be supplied. In some rural areas utilities will leave capacitor banks in during periods of low demand (i.e. on […]

What is AC waveform distortion?

  The power supplies in electronics, both linear and switching, draw current only at the peaks of the AC voltage creating a characteristic ‘flat topped’ waveform. The amount of distortion of a waveform can be quantified by its Total Harmonic Distortion (THD). Ideally, for high performance audio, studio and home theater systems, THD would be […]

What are sags and brownouts?

We’ve probably all experienced the momentary ‘flickering’ of lights when a heavy load such as a vacuum cleaner or amplifier is switched on within our home or studio. The flicker is a result of a short term ‘sag’ in the powerline voltage. Short duration sags, say between 20 and 40 thousandths of  a second often […]

What are outages and blackouts?

Storms and accidents are frequent causes of power loss. Faults in transmission infrastructure can also sometimes occur. Equipment such as media servers, control / automation systems, computers, DVRs and gaming consoles containing hard disk drives are becoming core parts of our systems. They can all suffer information loss and even disk failure as a result […]

What is powerline noise?

  The exact effect of noise is dependent on the quality of the power supply inside your equipment, but unfortunately there is no relationship between equipment price and power supply performance! Noise is created by a large number of things, including radio frequency interference (RFI), electro-magnetic interference (EMI), computer and switch mode power supplies, lighting […]

What are spikes and surges?

  Lightning* is perhaps the most well known surge event as it is capable of causing catastrophic equipment damage where whole systems are destroyed with one 6000V+ strike. More nefarious are the effects of the multiple daily spikes that slowly destroy your capacitors, chips and other electronic components causing lockups, decreased performance and shortened equipment […]

What is “clean” power?

Ideally the AC power that feeds our high performance audio, home theater and studio systems would be rock steady –  it would not go up or down in voltage depending on the time of the day and it would not get interrupted by storms or accidents. It would also be free of power line ‘nasties’ […]