Power Quality for Audio Systems, Home Theater and Studios
This page will provide high level answers to the following questions:
- What is clean power?
- What are the common power quality issues?
- How do they affect the performance of our audiovisual systems?
- Which solutions deal with each issue?
If you need assistance selecting a power product or are not sure exactly what power quality issues you may have please contact us - we are here to help!
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' such as transients, noise, distortion and DC offsets.
The chart on the left shows what clean power might look like - purely sinusoidal AC at 120V RMS. RMS stands for Root Mean Square (RMS) and for a perfect sinewave RMS equals 70% of peak voltage.
The 7 Power Quality Issues
- Spikes and surges
- Noise
- Outages and Blackouts
- Sags and Brownouts
- Waveform Distortion
- Swells and Overvoltages
- DC on the Powerline
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 life.
These spikes, thought to represent 80% of all recorded transients, are most often caused by devices within your home or studio - such as appliances, air conditioning units, power tools and lighting - switching on and off.
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 dimmers and appliances.
Small levels of noise can result in degradation of sound and picture whilst larger levels sometimes manifest as audible pops, clicks and visual 'snow'.
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 of power outages.
Expensive projectors are particularly susceptible to damage from outages as the proper cooldown processes cannot occur resulting in the hot lamp overheating itself and surrounding circuitry.
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 cause no issues as most power supplies have enough stored energy to carry through these events. Longer sags will often result in loss of power, similar to an interruption.
Brownouts are longer events, most typically caused by the power utility 'stretching' the power they have available to meet times of high demand.
Linear power supplies, the type most often found in our high performance audio visual systems, are quite susceptible to prolonged low voltage. Power supplies may lose their ability to regulate voltage, causing equipment malfunction and damage. Amplifiers, which typically have unregulated power supplies, will show reduced ability to drive loudspeakers.
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 under 2%. In some locations measured THD has been 10 times higher than this!
All amplifiers, except Class A devices, draw current in response to the music waveform. 'Flat topping' restricts current delivery, leading to reduced dynamics, loss of articulation, bass extension and an anemic, uninvolving overall presentation.
Swells and Overvoltage
Long term overvoltage 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 the weekend and holidays) which can lead to higher than normal voltages.
Regulated linear power supplies will dissipate more heat in an overvoltage situation causing potential equipment overheating. High voltages can also cause breakdown of electronic components such as capacitors operating close to their rated voltage in the unregulated supplies typically found in amplifiers.
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, are more susceptible than smaller.
Which power conditioning technologies solve which power quality issues?
The table below enables you to cross reference each power conditioning technology against the power quality issues it solves. Clicking on the top links will take you back to the explanations of each power quality issue.
- Clicking on the links on the left will take you to the product category pages.
- If you'd like to know more about each technology read our power conditioner buyer's guide.
- If you need assistance selecting a power product or are not sure exactly what power quality issues you may have please contact us - we are here to help!
| Spikes & Surges | Noise | Outages & Blackouts | Sags & Brownouts | Waveform Distortion | Swells & Overvoltage | DC on the Powerline | |
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| Surge Protectors |
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| Passive Conditioners |
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| Isolation Transformers |
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| Power Regenerators |
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| Standby UPS |
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| Line Interactive UPS |
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| Online UPS |
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* isolation transformers can incorporate voltage regulation as an optional feature.
References and further reading:
IEEE Recommended Practice for Monitoring Electric Power Quality, IEEE1159-2009. The 1995 version is available online.
PC Power Protection, Mark Waller, 1989.
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