and other science fiction

The Basics

	fig. 1
	fig. 2a
	fig. 2b
	fig. 2c
	fig. 3

All stereo receivers (fig. 1), are made up of three parts: the tuner, the pre-amp and the power amp. (fig. 2a, b, c).

It is possible to purchase the pre-amp and power amp (fig. 2b, c) combined in one box. This is called an integrated amplifier (fig. 3).

We can take this one step further and purchase the pre-amp, power amp and tuner as three separate components. The theory behind this move is, the more components, obviously the better the sound.

This is not the case. Before you make better sound, there is an economic concern. Someone must pay for the extra cardboard boxes, sets of styrofoam, metal cases and instructional manuals, none of which contribute to the sound but do contribute to the cost.

Our recommendation, should you wish to spend less than $1200 for your amp, is a stereo receiver. If you're looking to spend $1200- $2,500 we recommend an integrated amplifier and tuner. Above $2,500 three separate components are viable.

What about watts?

fig. 6

How many watts do you need?

For that matter, what is a watt?

Believe it or not, when manufacturers measure amplifier output in watts, they disconnect the speakers and substitute the "standard 8 ohm load resistor" (fig. 6).

This is difficult to understand since the load resistor does not have any of the characteristics of a speaker. I am assured by my engineering friends that although this is a lousy test, it affects all manufacturers equally, thus making it relevant. Unfortunately, some manufacturers are now designing their amplifiers to suit the test so that they can quote larger than-life numbers. One example is a stereo amplifier (fig. 7): 65 watts RMS per channel into 8 ohms.

They did not lie. The fact that it does not sound very musical and has trouble playing speakers seems beside the point. In their literature they talk numbers, not music and speakers. Further, all manufacturers use the ultimate cop-out: "design and specifications are subject to change without notice".

Cut through the Marketing

When you can't trust the manufacturers and what they have to say about themselves, there is a test that you can perform. Most amplifiers and receivers are able to play two pairs of speakers at the same time (fig. 8). When playing a single pair of speakers, turn on the second pair at the same time. The volume of sound should increase.

On poor quality amps and receivers, the sound will either remain the same or diminish. This happens no matter how impressive the watt numbers are.

When Bad Things Happen To Good People

fig. 7

Over the years, we have had many consumers pose this problem. They tell us that they have too much amplifier and not enough speaker.

This has never been the case. When you have speaker distortion, almost consistently it is not the speakers' fault, it is the amplifier running out of power. This is due to the manufacturers not describing truly how to operate the equipment in their instruction booklets.

Where Is Full Power?

In most cases, depending on the type of music you play, full power should occur when the volume control is set as in figure 9.

When you use your "loudness" control, full power now is typically as in (fig. 10). Should you use tone controls and loudness, full volume is (fig. 11). If you should go beyond the full volume settings shown above, your amplifier or receiver will create a weird form of distortion called "amplifier clipping". If you persist, you will eventually destroy your speaker

Amplifier Clipping

When you run out of power, the amplifier does not just shut off. It begins to distort, called amplifier clipping (fig. 12). At full power we have a beautiful "sine wave", when you misuse the controls, the beautiful sine wave becomes a 'square wave'. This produces harmonics, or signals that were not part of the original music signal. These harmonics, at a very high frequency will ultimately ruin your tweeter. This is labeled as 'abuse' and not usually covered under manufacturers limited warranties.

Come and see how we created big, wonderful music in a garden, tennis court and swimming pool setting that's not seen or be heard by the neighbors.