The Power Line Conditioner - How it Works

The AC line conditioner is more than just a power protection device.

This article takes a look at the various aspects of line conditioning - from noise filtering to AC  power regeneration.

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

A Historical Note:

We thought prior to going into the operational details, it would be interesting to include a short historical brief on the issues that led to 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 producing 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 un-interruptible 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.

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 similarly important, improve the overall performance of your home theater system.

The basic 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. In this manner, anything that interconnects with your equipment would have to go first through the surge protection circuitry within the line conditioner.
	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 a degradation in the overall system performance.

Removal of Noise from AC Power Lines

For audio-and-videophiles alike,  the next most important reason other than system protection for investing in a power line conditioner, is the elimination of noise from the AC 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 an 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.

The cheapest form of power line conditioning gear uses this type of passive noise filtering approach. Unfortunately, these basic passive noise-filtering techniques have a rather limited noise reduction effect.

Isolation Transformer:  A second 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 earlier on.

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.  Its disadvantage is a higher cost, limited power delivery due to the damping effect of the 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 AV system performance.

---

Use of AC Regenerators: 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 Signature Series Automatic Voltage Stabilizer MP AVS 2000 SS

One such typical unit making use of AC regeneration is the Monster Cable MP AVS 2000 SS Signature Series Automatic Voltage Stabilizer. The MP AVS 2000 SS does not come cheap but it 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 to deliver a constant supply voltage to your home theater gear while providing surge protection as well as EMI and RFI noise filtering.

The MP AVS2000 Monster automatic voltage stabilizer uses a microprocessor control variable transformer to deliver full power to your home theater despite power fluctuations and surges. And thanks to AVS2000's sequential activation feature - available on its four switched power outlets, it is possible to 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 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, which has an electronic equivalent of a power generator inside.  Using the power from the wall, 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 the DC to AC inverter are very similar in design to those employed in computer grade uninterruptible power supplies UPS), where the DC in this case is being feed from a lead-acid battery. The main difference  being that most inexpensive computer-grade UPSs produce a stepped-sinewave instead of a pure sinewave as further explained in our article on uninterruptible power supplies.

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

	The complete elimination of noise on the line,
	Complete voltage regulation,
	Balanced power which is more suitable for AV equipment,
	Elimination of any 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.

In comparison, a power-line conditioner with surge protection and basic noise reduction would not cost more than few hundred dollars; a case in point is the APC AV H15 Home Theater Power Filter and Power Conditioner; this is a 1500VA power line conditioner with 5270 Joules surge protection, noise filtering, and voltage regulation for high performance AV systems.

APC AV H15 Home Theater 1500VA Power Line Conditioner

Admittedly, the APC power line conditioner module is not on par with the Monster MP AVS 2000 SS unit in that it lacks both AC regeneration as well as network protected connectivity. But at an online price tag of around $200, it is significantly much cheaper and still provides the much desired line conditioning and equipment protection that cheaper surge protection power strips can never handle.