It's no secret that it takes a lot of knowledge to truly understand the world of home audio, which is littered with confusing numbers and terms. Wattage, current, distortion, frequencies, and impedance are just a few of the specifications anyone looking for an amplifier of home theater receiver is going to come across. With the thousands of choices in each category, it takes a little bit of background to use these specifications to make a great choice.

In steps the watt...

Evaluating and stating the wattage of an amplifier has become the single most important number to the amplifier shopper. Unfortunately, wattage is a highly misunderstood specification, which dupes people into buying products with a level of performance much lower than what is anticipated. 100 watts seems to be the magic number for most, thinking that as long as you have 100 of them, and no less, they'll be fine. However, even the passenger side mirror on your car states that things aren't always as they appear.

To be fair, wattage is an important number that can give a clear understanding of an amplifiers performance. A Watt, named after the British scientist James Watt, is a unit of power. And since power is expressed as a unit of energy divided by a unit of time, a watt is commonly defined as a unit of power equal to one joule per second. Simply stated, a watt is the amplifiers ability to do work, like make the drivers in a loudspeaker move.

Wattage in an amplifier is like horsepower in a car. The more horsepower a car has, the faster the car goes. But unfortunately, this isn't always true. Take into consideration that a 150 horsepower engine might be able to rocket a 1200-pound car, but it's not going to budge a 5-ton semi-truck. The weight of the car is similar to the weight (efficiency) of the speaker connected to an amplifier.

Standardizing the Specs (sort of...)

In the competitive atmosphere that has taken over the entire electronics industry, manufacturers and marketers struggle to make their products appeal to the masses. Of which, massaging the specifications of their products is a sure fire way to attract buyers in a sea filled with similar products.

There is, to this day, no truly defined way to measure the power output of an amplifier. As you will learn below, the numbers do not mean much until they can be understood in context, and broken down in a manner that allows fair comparisons between products.

When amplifiers went from tube amplifiers (that use vacuum tubes) to solid-state amplifiers, power ratings for amplifiers got extremely confusing. Finally, the FTC stepped in ruled that all power claims had to include the conditions in which they were measured. Unfortunately, the FTC did not rule that amplifiers had to be tested on the same playing field. This means that in order to make fair comparisons, one would need to know how to interpret what the conditions of the measurement means. Specifically, the FTC ruled that:

• Power measurements must be stated in RMS (sustained) watts.
• The bandwidth (band of frequencies) used in the measurement must be stated.
• The impedance (load) had to be stated.
• The number of amplifier channels played into that load had to be stated.
• Total harmonic distortion figures had to be stated.

Continued on page 2: Specifications Explained