Even the most novice audio buyer understands what a watt is... a measure of power, how strong, how loud an amplifier will play. More watts means more sound. But not always... The Difference Lies in the music. When we test an amplifier we use a standard test so one test can be compared with the next. That standard test requires we hook up our amp under test to a precision 8 ohm resistor. We feed a pure, single frequency test tone into the amp, and then we measure everything in the speaker outputs that is not the frequency we fed into the amp under test. That's RMS power. Anything else is distortion... Total Harmonic Distortion or THD. But, we don't listen to amplifiers with precision 8 ohm resistors, we listen to speakers. The speaker load is not pure 8 ohms, but a combination of resitors, capacitors, and inductors, which vary with frequency and loudness. And music is not made up of one frequency, but all different frequencies all mixed up. And these sound are constantly changing, not continuous single frequency. So the standard test is not really a very good test of how loud and clean an amplifier will play. MOSFETS. Metal Oxide Semiconductor Field Effect Transistors. A mouthful that creates an earful. They are a different kind of transistor.

There are those who think old fashioned tube amplifiers sound more like music than transistor amps. MOSFETS combine the advantages of both. MOSFET output transistors are usually found on expensive separate power amps. They use them because they sound more musical. In a regular bipolar transistors there are two currents (hence the same bipolar) and this slows down the transfer of current through the transistor. Bipolar transistors are sensstive to heat and as you drive them harder they heat up and without eleaborate protection circuits would blow up. Bipolar transistors produce odd order distortion wihich is objectionalble to the human ear. MOSFETs produce mostly even order harmonic distortion which is less objectable to the human ear. MOSFETs have a totally different structure. There is actually a source and a drain, and when the MOSFET lets current flow it is more like a dam opening, lots of current flowing fast. Music seems more dynamic and lifelike. Compare this to accelleration of a car, compared to the same car, with blocks holding it in place as you rev the engine and take remove the blocks an you zoom off. That's how MOSFETs work. Clipping is soft and the MOSFET amp plays significantly louder than a bipolar transistor amp rated the same power. MOSFETs have reverse coefficient of temperature so as they get hotter they allow less current, sort of a self protection system.

The Fantastic Pioneer Elite A-35 Amplifier $200

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