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Originally Posted by RandallNeighbour
Jack, I see what you're saying... so what do the high end amp manufacturers do to eliminate the ever-present alternator whine without filtering that "chokes" down the power?
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The "whine" is more of a problem in the head units than in high power amps.
Why, you ask? The head units use the 12vdc as-is to power the unit. Radio tuner, CD player, and amplifier section are all powered by the 12v.
An amplifier that provides, say, 75w RMS per channel to the speakers can't do that using 12vdc. The amplifier uses a DC-DC converter to step up the voltage to something higher internally that allows more power to be delivered to the speakers. The process of converting the 12vdc to an AC voltage, feeding it through a transformer, then converting back to the internal DC voltage very effectively isolates the amplifier from any impurity on the 12v line. That's also why these amps are large, heavy, and expensive... it takes a bit of circuitry and space to do this conversion... and is also why head units, even the high power ones, don't have much power. You just can't cram that much stuff into a DIN sized chassis.