Uninterruptible Power Supplies

Is it really possible to make use of a computer-grade UPS in the Home Theater?

Computer-grade uninterruptible power supplies are reasonably priced, surely cheaper than 'home-theater-specific' power centers. The purist may not agree, but if budget is an issue, a computer-grade power protection solution may represent a better value.

In their quest to protect sensitive and expensive home theater gear, many system owners do not foresee the option of using computer-grade power protection as part of a possible solution to their needs.

It is as if uninterruptible power supplies and surge suppressors designed to protect expensive and sensitive computer equipment, will do a poorer job in the home theater. 

This article investigates the possible use of a computer-grade uninterruptible power supply as part of a power protection solution for your AV systems. 

There is a lot of controversy surrounding the use of computer-grade power equipment in the home theater.

Yet these systems come cheaper than their audio grade counterparts do; therefore, for the budget conscious, they may represent a possible alternative.

In reality, this is a technically acceptable approach - as long as one is aware of possible limitations that may arise when making use of equipment other than for its original designed purpose.

The Computer-Grade UPS Power Protection Solution

From a budget perspective, for the money you pay for a suitable 'home theater specific' high-end surge suppressor, you can get a good quality 'line interactive' or better still an 'online' computer-grade uninterruptible power supply (UPS).

A UPS is basically an AC Voltage Regenerator but with added battery backup. The electronics involved are very much similar in principle. However, not all computer-grade uninterruptible power supplies support the desired functionality to act as a suitable replacement for an AC Voltage stabilizer/line conditioning solution in the home theater.

The Different UPS Categories

It is important to highlight the differences between the different type of uninterruptible power supplies available for home PC use. Surprisingly as it may seems, some of these uninterruptible power supply solutions will not provide the much desired AC line conditioning and power protection for your electronics in the presence of a 'normal' AC mains supply.

Having an understanding of the different UPS categories is therefore important if you are seriously considering the cheaper computer-grade UPS option as part of a home theater power protection solution.

The main UPS categories include:

• Type 1: Standby UPS

• Type 2: Line-Interactive UPS

• Type 3: Online UPS

'Standby' Uninterruptible Power Supply

A standby UPS system, also known as an off-line system, powers equipment directly from the AC outlet. In the event of either a complete power failure, or a variation in the input AC voltage that exceeds pre-set limits, then the UPS kicks in and the unit goes to battery operation. However, there is a small delay in the process - in the region of a few milliseconds.

These are the low-cost UPSs. Batteries are charged as long as there is main power available. These units do provide some protection against spikes and switching transients, though not on par with a true surge protector.

The 'standby' uninterruptible power supply is the least suitable for use in the home theater - it do not protect against sags, line noise, frequency variation or brownouts unless the battery is delivering power to the protected system.

'Line Interactive' UPS

A line interactive UPS system differs from the cheaper standby type in that the line interactive system provides a voltage boost on sags without accessing the batteries. These are hybrid devices that offer a higher level of performance by adding better voltage regulation and filtering features to the standby UPS design.

These systems would typically make use of a 'tapped' or a 'ferroresonant' transformer to maintain the required output voltage. The transformer provides voltage regulation and minimal power conditioning for disturbances such as electrical line noise.

This setup allows for continuous line conditioning, increases battery life, and reduces electronic noise. These units do provide some surge protection, though not on par with a true surge protector.

However, complete elimination of line noise and frequency variations works only when the unit switches to battery operation. In addition, these systems are not very much effective against unstable frequency variations or sudden current changes.

'Online' Uninterruptible Power Supply

An Online UPS system differs from the less expensive line interactive UPS system in that the online system provides the highest quality power protection.

This is done via a double power conversion technique; the online UPS takes incoming power, converts it to DC, conditions it, and converts it back to AC. In such a setup, there is no delay to switch to battery.

Double conversion systems provide the same benefits of a standby UPS in conjunction with a line conditioner, at a price that is lower than buying the two components separately.

These systems offer complete protection and isolation from all types of power problems - power surges, high-voltage spikes, switching transients, power sags, electrical line noise, frequency variations, brownouts and blackouts.

It is also the only type of UPS that is capable of delivering TRUE sine wave power even in the presence of the AC supply. True sine wave represents the optimum power for most AV electronics - as it only delivers the 60Hz (or 50Hz) voltage with no presence of unwanted harmonics on the AC line feeding your gear.

In view of the higher expense, increased weight, and size associated with online UPS systems, use of these uninterruptible power supplies is normally restricted for critical applications, high availability servers, etc. However, in view of its capability to deliver TRUE sine wave power output, it also represents the ideal UPS solution to use as part of a power protection system in the home theater.

Unfortunately, the 'online' UPS is the most expensive of the trio, yet it represents the ideal solution in that it is equivalent to having an AC power line conditioner but with the added advantage of a battery backup.

Is it really a 'No-Go' Solution?  

Noise on the line: For the purists in audio and video systems - the use of a computer-grade UPS is simply a no-go approach. They would argue that uninterruptible power supplies designed for computer use might add more noise and distortion in the audio band.

To a certain extent, this may be true in that computer-grade power protection gear would normally incorporate EMI/RFI high-frequency noise filtering only. 

It is also a fact however, that even most mid-range priced power line conditioners designed for home audio, would most often fail to some extent in this respect. Filtering of noise in the audio spectrum is far from being a straightforward job.

But there is even more to the issue of noise and filtering of unwanted AC harmonics on the line. Most of these UPS would deliver a 'stepped output' instead of a pure sine-wave.  The stepped output is typical in digital circuits and leads to a simplified filtering on the inverter output of the UPS.

Unfortunately, the 'stepped output' is a good source for higher order harmonics that would appear across the UPS output. These added harmonics are in effect an added source of noise that would find its way into your AV system if not filtered out.

Surge protection: One should be aware that although computer grade uninterruptible power supplies would normally incorporate some sort of surge suppression on their AC input, yet the surge protection available is in most cases far from adequate.

Main advantage of a UPS

While the 'off line' UPS does not really provide much added value in home theater power protection, yet the use of 'line interactive' or better still, 'online' UPS systems, would guarantee a regulated AC power output independent of the fluctuations or waveform distortions on the AC power line feeding your system.

Protection against power line fluctuations in the home theater should not be underestimated. Fluctuations on the AC line can turn out to be a serious problem for any home theater setup, while prolonged fluctuations may lead to overheating and occasional damage.

Fluctuations by as much as ±10% of the nominal AC line voltage may cause a 200W amplifier to deliver only 160W.  Large power amplifiers found in subwoofers, multi-channel power amplifiers, projectors, and RPTV systems, are extremely power hungry, and therefore fluctuations of this magnitude on the AC line would mean a dimmer picture for a projector during a bright scene, or a significant loss of power for an amplifier during a loud passage of music.   

Concluding Remarks 

Surely, suitably rated computer-grade uninterruptible power supplies represent a possible power protection solution for any home theater set-up. Computer vendors can provide reasonably priced protection solutions that may represent a better value to your requirements.

It is all a question of analyzing what you will get when investing in a  computer-grade uninterruptible power supply as against an equally priced protection system specifically designed for home theater use. 

We are not saying that AC regenerators designed specifically for home theater such as the 'PSAudio Power Plant' series of products or Furman Sound power conditioners, are not worth the investment. These products are capable of delivering remarkable results and come with exceptional build quality, but...

Surely, there is a price to pay - expect to pay $2,000 to $3,000 for these products. 

It is all a question of available budget  - if you are working within a tight budget, the UPS solution may be the way to go.

One can improve on the 'raw' computer UPS solution and still ends up with a less expensive alternative to the 'dedicated' home theater AC Regenerator.

You can always include additional filtering on a computer-grade uninterruptible power supply AC line output.  Inexpensive units such as the Monster Cable MP HTS800 Home Theater PowerCenter HTS800 would provide enhanced surge suppression on both the AC line as well as protected connections for the phone line and the coax TV input.

Alternatively, the 'Home Theater Powerbar 2100 with Clean Power stage' from Monster Power, provides excellent AC line noise reduction and a high joule rating (2775 Joules) for surge absorption.

The Powerbar 2100 includes isolated audio and video noise reduction for improved component noise generated reduction. All contacts come in 24k gold-plating for maximum corrosion resistance and power transfer. This unit has 12 AC surge protected outlets, 3 pair ultra-low loss protected coaxial connections for cable TV/HDTV and  a pair of protected phone connections for satellite/TiVo/phone protection. 

The HTS2100 comes with a 5-year warranty from Monster Cable  and a $300,000 connected equipment guarantee. 

The use of the Powerbar HTS2100 in tandem with a computer grade uninterruptible power supply such as the APC SmartUPS INTL 1500VA, will surely represent a cost effective and highly efficient power protection solution for any home theater setup.

Power line protection strips, surge suppressors,  UPS, and home theater line conditioning equipment at affordable prices.

We have put together a vast selection of power protection gear from major suppliers at our online Home Theater Store.

Products range from small inexpensive power protection strips, reasonably priced uninterruptible power supplies, and complete home theater power centers for improved system performance.

The links below will take you straight to the respective product pages:

• Electronics: Power-Line Protection

• Electronics:  Uninterruptible Power Supplies

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Last updated on  21st February 2005

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