Power Protection - How-it-Works: Power Line Conditioner
Updated: December 10, 2012

The Power Line Conditioner
How-it-Works Guide

The Quest for Clean Power

A quality power line conditioner will do more than just protect your expensive gear from harmful voltage surges, dirty power lines, and over and under voltage conditions on the AC line; if chosen carefully, a good power conditioning device will also make a significant difference in overall system performance—one you can really hear and see!

In this article, we discuss the basic operational principles behind power conditioning, from the actual protection of sensitive equipment and removal of noise from AC power lines, to the correction of voltage fluctuations and correction of waveform distortions. In the process, we also explain how each of these processes affects overall system performance.


Designed to provide a stabilized 120V for power line fluctuations from 80-140 volts, thus protecting expensive home theater equipment for both under-voltage and over-voltage conditions.

Power Line Conditioner
More than just a power protection device

Many look at the power line conditioner as just another type of power protection device. Yet power conditioners are often multifunction devices which among others provide enhanced power protection for connected system components.

In this article, we discuss the various aspects of line conditioning, from noise filtering to AC power regeneration.

Surge suppression is also another important aspect normally associated with power line conditioning systems—however, this is being dealt with in detail in two separate articles appearing under this same section.

A Historical Note

Prior to going into the operational details, it would be interesting to include a short historical brief on what led to the development of the power protection industry for home entertainment system. Up to a few years ago, power conditioners and line protection gear were mainly used by the industry, research, and in laboratories. It was only after the advent of the home PC that power conditioning and power protection in the home became much of a 'discussed' issue. In fact, one may argue that it was the proliferation of the personal computer in the home that first raised the awareness of the homeowner to the benefits of power line conditioning.

It was also at this time that we saw the development of an entire industry dedicated to the production of power line conditioners and power protection equipment.

Following the increase in popularity of inexpensive surge suppressors for home computers—later followed by the development of reasonably priced uninterruptible power supplies (UPS)—the growing power conditioning industry began to design and manufacture AC power conditioners and protection gear specifically targeting the home entertainment industry.

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The Power Line Conditioner - A three-in-one device!

Today's state-of-the-art AC power conditioning gear would normally take a three-in-one approach to help both protect your sensitive equipment, and equally important, improve the overall performance of your home theater system.

      Basic Power Line Conditioner Functionality includes:

Protection of equipment from voltage surges on both the AC supply and any other connections such as phone line, coax TV inputs, and even LAN connections.

The scope is that anything interconnecting with your equipment would have to go first through the surge protection circuitry within the power line conditioner device.

Removal of noise from the AC line.

Correction of voltage fluctuations and waveform distortions.

While power surges on interconnecting cables and power supply feeds are a major cause for system failures, noise, voltage variations, and waveform distortions, are the main culprits for degradation in the overall system performance.

Removal of Noise from AC Power Lines

For audio-and-videophiles, the next most important reason for investing in a power line conditioner other than system protection, is the elimination of noise from the AC power line. Noise is created by a variety of everyday applications, including radio and television stations, mobile phones, motors, etc. The reduction or elimination of noise will have a beneficial effect on AV system's performance.

Passive-Type Filters

In its most basic form, noise reduction in a power line conditioner is achieved through the use of passive-type filtering. The typical filter arrangement consists of a coil of wire (known as inductor) in line with the input and a capacitor across the line.

The impedance of the inductor increases with frequency, while that of the capacitor decreases as the frequency components of the noise signal increases. This basic arrangement allows the higher frequency noise components to be shunted off through the capacitor to ground.

However, only the cheapest power line conditioning devices make use of this simplified passive noise filtering approach; basic passive noise-filtering techniques have a rather limited noise reduction effect and therefore active filtering is used to further enhance the filtering of noise from the AC line.

Balanced Transformer

Another common approach to noise reduction is the use of an isolation balanced transformer. This method of noise reduction is generally accepted as superior to the inductor-capacitor filter arrangement mentioned above.

Advantages include better noise reduction, and the creation of a balanced AC power feed. A balanced AC feed is considered far better for audio and video gear. But unfortunately, it has a number of disadvantageous as well; these include a much higher cost, rather limited power delivery due to the damping effect of the balancing transformer, and increased size, weight and mechanical noise. 

While these basic filtering techniques are capable of eliminating the very high frequency component of noise on the line, yet they have a major limitation.

They simply cannot address the real and significant problem associated with noise in the audio spectrum, nor can they regulate the AC voltage, or restore the symmetry of the AC waveform.

These are the real culprits to an overall degradation in performance of audio and video systems.

Use of AC Regeneration Techniques: Correcting voltage fluctuations, waveform distortions, and noise in the audio spectrum

A power line conditioner using a handful of passive components alone such as inductors, capacitors, and transformers can only eliminate the higher order frequency components from the power line.

In reality, the main culprits to poor audio and video performance in the home theater are not the higher frequency harmonics but rather the lower frequency harmonics in the audio spectrum. These lower order harmonics are generated by a variety of radiated noise sources, or as a result of clipping or uneven loads on the AC line, both in the home as well as within the surrounding neighborhood.

If what you are after is to regulate the AC voltage, correct the waveform symmetry, and possibly eliminate even the lower order harmonic noise, then your only way forward is a power line conditioner with AC regeneration. 

Monster Power AVS 2000 Home Theater Voltage Stabilizer

Monster Signature Series

Automatic Voltage Stabilizer
MP AVS 2000 SS

(available from amazon)

One such unit making use of AC regeneration is the Monster MP AVS 2000 SS Signature Series automatic voltage stabilizer (also available as MP PRO AVS2000 non-signature series rack mountable version featured at the top of this page).

The MP AVS2000 does not come cheap but it is an excellent heavy-duty unit design incorporating a 3000VA transformer to deliver 1800W/15Amps of clean stabilized power to your home theater. It is designed to stabilize the power line fluctuations, delivering a constant pure sine wave AV voltage supply to your home theater gear while providing surge protection and EMI/RFI noise filtering.

These types of high-end power line conditioners make use of automatic voltage stabilization circuitry employing a microprocessor controlled variable transformer to deliver full power to your home theater system components despite power fluctuations and surges.

Another important feature normally found on premium and high-end power conditioners is the sequential activation of its various AC power outlets; this helps avoid turn-on surges during start-up of power-demanding system components. Apart from tripping a circuit-breaker, these electrical surges at start-up can prove extremely damaging to delicate home theater system components.

AC Regeneration

AC regeneration is a more recent development and represents the state of the art in power line conditioning.

Basically, AC voltage from the wall socket is fed into the AC regenerator; this has the electronic equivalent of a power generator inside.  Using the power from the wall supply, the generator creates a completely new AC voltage source that is virtually noise free.

For the more technically minded, the whole setup normally takes a two stage approach or double-conversion process where the AC is first converted to DC, conditioned and then converted back to pure AC sine wave power. In this manner, it is possible to guarantee a pre-determined AC waveform and output voltage irrespective of the AC input.

The electronics used in DC-to-AC inverters are very similar in design to those employed in computer grade uninterruptible power supplies (UPS), where the DC in the latter case is being feed from a lead-acid battery. As further explained in our article on uninterruptible power supplies, the main difference between the two is that most inexpensive computer-grade UPS systems produce a stepped-sine wave output rather than a pure sine wave.

The advantages of AC regeneration coupled with a suitably rated surge suppressor and adequately designed line filtering, include:

- Complete elimination of noise on the line,

- Complete voltage regulation,

- Balanced power which is more suitable for AV equipment,

- Elimination of distortion components (harmonics), and

- Full system protection.

However, there is a price to pay for all this. Power line conditioners using AC regenerators bring about added heat, increased size, and a substantial higher cost. Expect to pay anything between USD1000 to USD2000 for a typical 1500W AC power regenerator. And you would have to pay even more for power line conditioners with higher power handling capabilities. The Monster 1800W MP AVS2000 power line conditioner referred to above is presently selling on amazon for $1,700.

In comparison, a power-line conditioner with surge protection and basic noise reduction but that lacks AC regeneration would not cost more than few hundred dollars.

APC H15BLK AV 1.5kVA H Type Power Conditioner

A case in point is the APC AV H15Blk AV Type Power Conditioner; this is a 1500VA power line conditioner with 5270 Joules surge protection, noise filtering, and voltage regulation for high performance AV systems. It is presently selling online at a reduced price of $265.

Admittedly, the APC power line conditioner module is not on par with the Monster MP AVS2000; it lacks both AC regeneration and network protected connectivity. But it is also more than $1,400 cheaper and yet, it still provides much better line conditioning and equipment protection than the cheaper surge protection power strip can never handle.

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 Article Content

Issues discussed in this article:

Blue bullet  The Power Line Conditioner: More than just power protection

Blue bullet  A Historical Note: How it all began!

Blue bullet  A Three-in-One Device: Basic functionality explained

Blue bullet  Noise removal from AC power lines: What does it take?

Blue bullet  Use of AC Regeneration: Correcting voltage fluctuations and voltage distortions

Power Protection Guides

Additional articles appearing under this section

Power Clean Up: Why invest in power protection

Surge Suppressors (1): A first line of defense

Surge Suppressors (2): A word of caution

Use of computer-grade UPS as a protection solution in AV applications

Power Projection Checklist: Selecting Your Solution

Detailed Index of power protection guides appearing on our site is available here.

Power Line Conditioners and Surge Suppressors

Featured power protection gear atbuy from amazon