Amplification Classes

Technology / Home Audio / Amplification Classes: All sound is a sinosoidial waveform. It has alternating peaks and valleys. The center point of each wave is the zero, or switching point that separates the positive (top) from the negative (bottom) portion of each wave. When a tube or transistor amplifier operates in Class A, the output tubes or transistors amplify the entire waveform without splitting it into positive and negative halves. In Class AB, used in the overwhelming majority of amplifier designs, the signal is split into two halves, positive and negative, and each half is sent to a tube or transistor circuit for amplification. Both sides work in tandem, and the two halves are recombined at the output section to reconstruct the whole signal. This technique increases the amount of power that can be applied, but increases distortion. Class A amps usually provide lower, often imperceptable distortion, but at the expense of reduced power output.Class D or High Current operation is essentially rapid switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle. Theoretically, since the output devices are either completely on or completely off they do not dissipate any power. If a device is on there is a large amount of current flowing through it, but all the voltage is across the load, so the power dissipated by the device is zero; and when the device is off, the voltage is large, but the current is zero. Consequently, class D operation (often, but not necessarrily digital) is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product yet to be made; meanwhile designs do exist with efficiencies approaching 90%. This is a design that is increasimgly popular for use in bass systems, where maximum power is necessary, and slightly elevated levels of distortion are easily tolerated.

Online Classes

Life Style / College / Online Classes: Online classes meet via computer, through an online learning management system, like WebCT. Online students log in to attend class. There they access course lectures, receive assignments, and correspo MORE

Risk Classes

Business / Finance / Risk Classes: Groups of projects that have approximately the same amount of risk. MORE

Schedule of Classes

Life Style / College / Schedule of Classes: Colleges prepare a Class Schedule for each semester during the previous semester. With the help of academic advisors and/or faculty members, students make up their own individual class schedules for e MORE

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