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Power Conditioner Buyers Guide

This page is dedicated to answering your questions about power conditioners. If we haven't answered your question on this page or want to talk to someone please contact us.

 

Protection topics covered:

 

Power conditioning technology topics covered:

 

How do I protect my equipment from surges, spikes and other power quality issues?

Surges and spikes cause gradual equipment degradation as well as catastrophic failure. Acoustic Frontiers recommends a two tier approach:

  • Place a whole house surge protector at the main breaker panel. Choose a device that offers 'three mode or 'all mode' protection (live-neutral, live-ground, neutral-ground).
  • Supplement that with series mode surge suppression close to equipment. Avoid using surge protectors with 'all mode' protection near to electronics as these devices couple noise and divert transients onto the equipment ground. Choose products without Metal Oxide Varistors (MOVs) since they degrade and fail over time.

If your home or studio frequently suffers from brownouts and overvoltage events then you should also choose a device that contain voltage regulation and/or shut down your system in the event of catastrophic under or overvoltage events.

 

Why should I have an uninterruptible power supply (UPS) to protect my projector?

CEDIAs (Custom Electronics Design & Installation Association) Home Theater Video Design bulletin (CEA/CEDIA-CEB23) states that:

"an Uninterruptible Power Supply (UPS)* is strongly recommended for proper shut down and cooling of the projector and lamp in the event of a power failure".

Without a UPS the projector lamp and electronics can overheat leading to failure and shortened lifespan. When a projector is shut down normally it will not turn immediately off. It goes first into a 'cool down mode' where the image is turned off but the fan continues on to cool the lamp in a controlled manner. The cool down process is there to protect the lamp as well as the surrounding electronics. Projector lamps operate at many thousands of degrees Fahrenheit and without a fan the lamp can sometimes cool unevenly causing the glass to stress fracture. More often the lamp temperature will increase beyond its safe temperature window significantly shortening lamp life. Without a fan to cool things down the surrounding electronics will also be subject to excessive heating, which can shorten equipment lifespan - the rule of thumb is that for every 10 degrees over 80 degrees Fahrenheit electronics life is reduced by half!

* If you're not sure what a UPS is click here.

 

Which devices should be on a UPS?

All devices with spinning hard drives - computers, music servers, home automation systems, etc should be on a UPS. Power outages can cause the hard drive head to 'crash' onto the platter and damage the disk. If you use a digital audio workstation (DAW), a UPS will allow you to save your work and shut things down properly in the event of a power outage. Projectors should also be on a UPS to lengthen bulb and projector life (see above).

 

What is a power conditioner?

The term power conditioner has a very loose definition in the industry. We define a power conditioner as anything that is used between audiovisual equipment and the utility powerline.

 

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.

 

  Spikes & Surges Noise Outages & Blackouts Sags & Brownouts Waveform Distortion Swells & Overvoltage DC on the Powerline
Surge Protectors            
Passive Conditioners          
Isolation Transformers * optional   * optional   * optional
Power Regenerators  
Standby UPS            
Line Interactive UPS        
Online UPS

* isolation transformers can incorporate voltage regulation and surge protection as an optional feature.

 

How should I determine which power conditioning products I need?

The three key questions you need to ask yourself are:

  • What power quality issues do I have in my home or studio? Some parts of the USA have over 100 days of thunderstorms per year whilst others have less than 5. Likewise over and undervoltage problems are mostly related to where you live. We recommend that you select power protection equipment based on an assessment of your needs and the risks. Read our power quality page to learn more about how these issues manifest themselves and to determine which power quality issues you might have.
  • What protection does my equipment need? If you have a simple two channel audio system with a vinyl front end you won't need any protection from power outages. Projectors, equipment with hard drives and digital audio workstations should always have an uninterruptible power supply.
  • How much power does my equipment need? A small system may only consume a couple of hundred watts of power and have all the equipment in a close physical proximity such that only one 15A circuit is required. On the other hand a large home theater with a powerful projector or a studio with multiple rooms may require thousands of watts and multiple electrical circuits.

 

Determine your equipment's power requirements as follows:

  • UPS systems are sized according to the maximum amount of power, measured in Watts (W) they can support.
  • All other power conditioners are sized according to the maximum amount of current, measured in Amps (A) they can supply.

The simplest way to determine the above is to purchase a Kill A Watt EZ Electricity Usage Monitor meter and plug all of the equipment you would have plugged into the UPS or other power conditioner into that. The Kill-A-Watt gives you the both Watts and Amps. With equipment that consumes power dynamically such as amplifiers you need to play a test signal such as pink noise through the system at the maximum volume you might listen to. This is because the power draw will be greater with a signal playing than without.

What is a surge protector?

Simply put, a surge protector or suppressor is a device designed to protect against short, high voltage transients that are created by devices outside or inside the home or studio.

 

All surge protectors should be Underwriter's Lab (UL) certified. The UL Standard for Safety (UL 1449 3rd Edition) for Surge Protective Devices (SPDs) came into force for all devices manufactured after late 2009. SPDs are also known as Transient Voltage Surge Suppressors (TVSS). The UL standard defines four device categories:

  • Type 1 - permanently connected devices installed before or after the breakers in the service panel.
  • Type 2 - permanently connected devices installed after the breakers in the service panel. Type 1 and Type 2 devices are also referred to as 'whole house' surge suppressors or protectors.
  • Type 3 - 'point of use' devices at least 30ft from the service entrance. These can be connected via a cord to a power outlet, directly plugged into the outlet or installed in place of the outlet.
  • Type 4 - devices installed within equipment.

The UL standard defines a test wave comprised of a 6000V surge at 3000A for point of use (i.e. type 3) devices. The rationale for this test is that at voltages over 6000V electricity will 'arc over' to safety ground at the main breaker panel and the test wave resembles what is left of the surge at 30ft from this point.

 

Acoustic Frontiers recommends using BOTH whole house surge suppressors AND point of use surge suppressors placed close to equipment. Whole house devices protect against disturbances arising outside your home or studio due to lightning or issues carried through the utilities powerlines. Point of use devices protect against the many small but damaging transients caused by equipment such as compact florescent lighting, motors, pumps, air conditioning units that are within your home or studio.

"Most SPD manufacturers and TVSS experts promote applying a a two-stage, or "cascaded," approach for surge suppression...this is the best method for providing surge suppression that allows the lowest let-through voltage to your electrical system and its connected devices."  Alan Christe - Surge Protection Selection.

 

Point of use (i.e. type 3) surge suppressors come in two flavors:

  • Shunt mode
  • Series mode

Shunt mode surge protectors are typically based on circuits that contain metal oxide varistor (MOVs) which, under normal operating voltages, act as an open circuit and allow no current to flow through them. The MOVs will start to conduct should the voltage level rise above the clamping voltage of the MOVs (i.e. a surge condition), shunting the potentially damaging surge away from connected equipment.  MOVs are sacrificial devices - they only have capacity to absorb a certain number of surges before they fail. The diagram below was sourced from Middle Atlantic's excellent power white paper and is known as a 'three mode' or 'all mode' MOV based device. This type of device probably represents 95% or more of all devices sold as surge protectors. Acoustic Frontiers recommends that these 'all mode' devices should not be used at points of use for sensitive audiovisual equipmentShunt mode surge supressors for the following reasons:

  1. They operate by diverting surge energy to ground. Because the ground has a finite, non-zero impedance resulting from its length, its voltage can rise to dangerously high levels in the event of a surge. The worst risk is when devices are interconnected and some are on shunt mode surge suppressors and others not. This can create high voltages on the ground of the shunt mode protected device that then flow across the interconnects to devices not on the same surge protector, crticially damaging input and output circuitry.
  2. They couple noise onto ground. MOVs have what is called leakage capacitance. From an electronic perspective leakage capacitance resembles a small value capacitor to ground. Since the impedance of a capacitor decreases with increasing frequency high frequency noise is coupled to equipment ground. This can cause noticeable hums and buzzes as well as degraded equipment performance, particularly with digital gear that uses ground as a reference point.

Single mode (hot or live to neutral) devices may be used, but we recommend using series mode technology instead. All mode protection can be used at the service panel in a whole house surge suppressor.

Series mode surge protectors use a large, carefully designed inductor in the hot or live circuit and incorporate other circuitry to roll off high frequency / high rate of change transients. A major benefit of this approach is that the components degrade much slower than in MOV based technology allowing companies like SurgeX to offer 10 year+ warranties.

 

'Let through' voltage.

"Let-through voltage is the surge remnant that passes through suppression devices and into your distribution system. The lower the let-through voltage, the better the protection". Alan Christe - Surge Protection Selection.

Each UL tested device is given a let through voltage or Voltage Protected Rating (VPR) which is measured at the output of the surge protectors when it is fed with the standard 6000V/3000A test.

Whole house surge suppressors (i.e. type 2) devices are subject to more stringent testing that represent the effects of a direct lighting hit to a nearby power line or that from a nearby lighting strike that has been electromagnetically coupled into the home or studio power wiring system.

Isolation transformers, if designed correctly, also provide some protection from surges, as do power regenerators and online UPS systems.

 

Shop for surge protectors. Need help? Contact us.

 

What is an isolation transformer?

Isolation transformers are oversized, specially designed versions of the transformers found in linear power supplies. They are called isolation transformers because there is no direct electrical connection through an isolation transformer (excepting the safety ground). Incoming electrical energy is converted to magnetic energy and then back to electrical energy. Carefully designed they can significantly reduce powerline noise. Properly sized transformers can increase audio system dynamics by allowing power amplifiers to draw higher instantaneous current than they would be able to from the wall outlet. This can be done because electrical energy is stored in the transformer's magnetic field.

 

Isolation TransformerPros:

  • Very reliable and long lasting.
  • High powerline noise isolation and surge protection potential - well designed units may offer 100dB of theoretical isolation at radio frequencies.
  • The highest instantaneous current capability of any power technology - a 15A unit can deliver 100A!

Cons:

  • Expensive, heavy and bulky.

Select an isolation transformer based on how many electrical circuits you need and how much power your system requires.

  • Single 15/20A/30A circuit - choose a unit that plugs into the wall outlet and then plug your components power leads into that.
  • Multiple 15/20A circuits - choose a large wall mounted transformer and then wire circuits back to this point. Units are available in sizes upto 35kVA (290A).

 

Shop for isolation transformers. Need help? Contact us.

 

What is an uninterruptible power supply (UPS) and what should I look for when choosing one?

A UPS is a device that provides battery power to connected electronics in the event of a power outage. There are three different types of UPS systems: standby, line interactive and online 'dual conversion'.

 

Pros:

  • UPS systems are the only solution that can protect your projector or hard drive equipped electronics in the event of a power outage.
  • Line interactive UPSs provide voltage regulation and online dual conversion UPSs go one step further by providing substantial input to output isolation.

Cons:

  • Ongoing costs due to battery wear and tear.
  • Most UPSs are designed for computers, not audiovisual systems, and may actually increase powerline noise. Specifications provided on datasheets are often into loads representing 50% of less of capacity.
  • Inability to supply peak current requirements for dynamic loads such as amplifiers.

 

In a standby UPS, a battery charger Standby UPSconverts AC to DC to keep the battery full for when it is required. The battery is not in the AC circuit. When the line voltage goes below a certain predefined level the inverter switches on and is connected via the transfer switch to the AC line. The inverter converts DC to AC.

The main advantages of a standby UPS are efficiency and low cost. The only things that are consuming power are the line voltage monitoring circuitry and the battery charger. Line Interactive UPSBattery life is longer than for other designs since it is generally out of the circuit. They cannot protect from under or overvoltage conditions and offer no input to output noise of surge isolation.

Line interactive UPS systems appear similar at first glance but they have a crucial difference - the inverter is always on, generating AC from the battery which is kept full by the battery charger. A sensing circuit monitors the AC waveform and determines how much current to draw from the inverter to keep the voltage within tolerances.

Online, Dual Conversion, UPSLine interactive UPS systems have the advantage of being able to support brownouts and undervoltages which standby UPSs cannot. Some of the more sophisticated line interactive solutions provide 'bucking' circuitry, which pulls down the AC voltage if it is too high.

The final type is an online or dual conversion UPS. In this design there is no direct path for AC. Power is converted from AC to DC by a rectifier which feeds the battery. An inverter then converts the AC back to DC.

The advantage of this approach is that it offers a very high amount of noise and transient isolation between input and output. Online UPSs are energy inefficient however, and batteries need replacing more frequently than in other designs since they are constantly being charged and discharged.

 

How to choose a UPS:

Major decision factors:

  • How much power does the UPS need to supply? In the event of a power outage the only devices you really need to keep on battery power are pieces of sensitive equipment such as projectors, computers and the like. To size the UPS add up the power consumption, in watts, of these devices. This information can be found in the manual, from your equipment manufacturer or by using a power meter. You should then compare this figure to the UPS rated capacity, which is also given in watts. We recommend specifying a UPS that is rated for 150% of the load you need since most manufacturer's quoted battery run time and THD performance is based on 50-75% load.
  • How long does the UPS need to supply power for? A UPS is intended to allow for proper shutdown of connected equipment, not continuous operation. If you want to operate your system in an extended blackout then the solution you need is a generator not a UPS. 10-15 minutes of run time is generally sufficient.

Additional considerations:

  • Does the UPS output a true or stepped sine wave? Most UPS systems do not output a true smooth sine wave but something that looks more like a set of steps. A stepped sine wave is, by its very nature, high in THD. Switch mode power supplies found in computers and projectors are fine running on stepped sine waves but our recommendation is that all audio gear using linear power supplies (which is nearly all of it) is fed a true sine wave output with distortion below 2%.True or pure vs stepped sine wave
    An important thing to note is that the UPS technology has nothing to do with what the output looks like. It is generally true that most standby devices output a square wave, most line interactive output a stepped sine and most online dual conversion ones output a true sine wave but this is not a rule just a reflection on the typical products available from most manufacturers.
  • What is the audible noise level? Most UPS systems are designed for computer use where the audible noise created by internal cooling fans is not an issue. If you must have your UPS in your studio or home theater then pick one that has very low ambient noise levels.
  • What is the level of powerline noise on the input and output sides of the UPS? The inverter found in UPS systems can produce a high level of powerline noise if not carefully designed. In a standby UPS this is not really a problem since all we want to do in an outage is safely shut down the system. Line-interactive and online UPS systems are always on, which means that noise performance is an important issue. Unfortunately manufacturers do not publish specifications on the level of powerline noise found on the outputs of their devices. Badly designed UPS systems can also couple noise to the input side, thus contaminating the powerline for all other equipment on the same electrical circuit.

 

Shop for line interactive UPS systems or online UPS sytems. Need help? Contact us.

 

What is a power regenerator?

Regenerators are conceptually very similar to online UPS systems except that there is no battery. They work by converting AC to DC and then back to AC again.

Pros:

  • Done right, with a low distortion sine wave inverter, power regenerators offer protection for all power quality issues except interruptions and the high degree of isolation between input and output significantly reduces powerline noise.

Cons:

  • Maximum wattage available is limited; PS Audio's flagship P10, for example, can only provide 1250W, which might not be enough for large home theater or studio systems.
  • Expensive.
  • Few manufacturers (Accuphase, PS Audio).

 

What is a 'passive' power conditioner?

A passive device is anything that doesn't contain any powered electronic circuitry. Examples of passive devices include isolation transformers, surge protectors and resistor-inductor-capacitor (RLC) type conditioners. Power regenerators and UPS systems are active devices.

Resistor- inductor-capacitor (RLC) devices represent the vast majority of 'audiophile' power conditioners on the market. The simplest devices, such as those from Audience, forego any resistors or inductors and simply place capacitors across live and neutral. More complex devices, such as those from Running Springs Audio are comprised of resistors, inductors and capacitors. All of these products are essentially just passive filters similar to those found in the majority of loudspeakers. They do a good job of filtering out powerline noise and if well designed may also incorporate surge protection and reduce powerline waveform distortion. Much depends on the design of the circuitry and componentry used inside these devices.

Pros:

  • A well engineered RLC conditioner can filter out a lot of powerline noise whilst adding negligible additional impedance to the AC powerline - Audience quote 30 milliohms resistance for their aR12.
  • Passive, very little can go wrong.

Cons:

  • Cannot supply more current than the wall outlet like isolation transformers or power regenerators.
  • No protection from under or overvoltage events or power outages.

 

What is voltage regulation?

A power conditioner with voltage regulation keeps its output at a fixed voltage of 120V for a range of input voltage conditions. There is normally a minimum and maximum voltage within which the regulator can maintain a constant output voltage. These limits vary from manufacturer to manufacturer but 90-140V could be considered a general range.

 

What is under / over voltage protection?

Power conditioners with this feature can turn off their outputs and hence connected equipment in the event of a potentially damaging and prolonged under or over voltage condition. Turn off points vary from manufacturer to manufacturer but could be generalized as below 90V or above 140V.

 

What is a whole house surge protector?

A whole house surge protector is a device connected at your service panel that provides protection across all of the phases entering your home or facility. Most residential houses are supplied with two 120V phases and so a whole house surge suppressor designed for such an installation would typically have 'four mode' protection: live 1-neutral, live 1-earth, live 2-neutral, live 2-ground.  Some products add additional live1-live 2 and neutral-ground protection to become a  'six mode' device.

Whole house devices are tested to withstand much larger surges than point of use devices - up to 20,000A. Many often forget that cable TV and telephone services originate from outside the home or studio and can carry damaging surges. The best whole house units therefore incorporate surge protection for the cable TV and telephone services.

We recommend the following Square D devices for residential two phase use. These units provide six mode protection and incorporate cable TV and telephone protection: the SDSB1175C  for indoor use and the SDSB1175R for outside use.

 

What is a whole room power conditioner?

Whole room power conditioning is a term we invented to refer to the use of a single conditioner to supply power to a number of dedicated electrical circuits feeding a single room.  The length of the dedicated circuits should be kept as short as possible to maximize the ability of the connected system to draw current. The approach is particularly effective for large home theaters and high end audiophile systems.

 

What is a dedicated line?

A dedicated line is an electrical circuit used solely for the purpose of supplying power to an audio or video system. No non-AV equipment should be connected to a dedicated line. The line runs back to the main service panel or a sub panel. A single high performance room may be fed by a number of electrical circuits, some dedicated lines supplying AV equipment and other non-dedicated lines shared with other parts of the home or facility supplying lighting and other loads.

Our recommendations for dedicated power lines:

  • Go for a 20A rather than 15A line
  • Use high gauge wire - preferably 10awg - to minimize impedance and maximize the ability of connected equipment to draw the instantaneous current they require
  • Minimize the length of wire between the outlet and the service panel for the same reasons as above
  • Use high quality 20A spec or medical grade outlets to minimize contact resistance and added noise
  • Ensure all lines are on same electrical phase to minimize cross phase current flows

 

References and further reading:

The Different Types of UPS Systems, Neil Rasmussen, APC

CEDIA Home Theater Video Design bulletin (CEA/CEDIA-CEB23), 2010.

Integrating Electronic Equipment and Power into Rack Enclosures: Optimized Power Distribution and Grounding for Audio, Video and Electronic System and the Addendum, Middle Atlantic.

PC Power Protection, Mark Waller, 1989.

Surge Protection Selection, Alan Christe, Electrical Construction & Maintenance magazine, Aug 2002.

Torus Power Isolation Transformer Catalog

UL 1449 Standard for Surge Protective Devices, 3rd Edition, 2006.