The only equipment that runs directly off the power in our wall sockets are electric heaters, light bulbs, and some motors. Everything else requires a power supply. And when it comes to stereo and video equipment, the quality of that power supply can make or break performance.
The job of a power supply is three fold: convert AC into DC, generate the correct voltage, and isolate users from potentially lethal AC voltages. The two types of power supplies that achieve these common tasks are classified simply as unregulated and regulated. Power amplifiers generally use unregulated supplies, while everything else uses regulated. If we look closely at both types; unregulated and regulated, we note they all share three essential elements: a transformer, DC bridge, and capacitors. A regulated supply adds a fourth element not found in an unregulated version, a small power amplifier at its output.
Let's look today at the product most sensitive to the quality of the incoming electricity, the power amplifier–its basic, unregulated power supply the weak point in its design.
I wrote yesterday that an amplifier is a simple valve controlling the output of a power supply. The valve connects your loudspeaker directly to your amplifier's power supply, like a garden hose is fed from a faucet. Musical signals turn the amplifier's valve up and down, your hand controls the water faucet. Simple, eh? Now, visualize what happens if you're washing your car with muddy water, and then relate that image to dirty power fed to your speakers. In both cases, the quality of what's fed to the valve is reflected at the output of that valve: dirty water, or dirty power.
Taken to an extreme, it's clear what the negative effects of poor quality electricity or water would have on the end result. But there are things we can do to make it better. In both cases we can filter some of the unwanted dirt to get cleaner power or water, but not without consequences. Too aggressive a water filter and you restrict its flow; cleaner–yes–but less powerful. The same is true with electricity. Too aggressive a filter in series with the power supply and you restrict the instantly available energy that can be delivered when demanded.
And so this is a great argument for quality power supplies in amplifiers; supplies that provide clean, unrestricted flow–though that lofty goal turns out to be an elusive one–achieved with size and dollars, occasionally with cleverness, sometimes all three. But here's what's clear. In both water and power, the cleaner the source of either, the more effective the power supply feeding the valve.
But is filtering enough? That's the mystery we'll touch on tomorrow.