305:, a DC offset is an undesirable characteristic. It occurs in the capturing of sound, before it reaches the recorder, and is normally caused by defective or low-quality equipment. It results in an offset of the center of the recording waveform that can cause two main problems. Either the loudest parts of the signal will be clipped prematurely since the base of the waveform has been moved up, or inaudible low-frequency distortion will occur. Low-frequency distortion may not be audible in the initial recording, but if the waveform is resampled to a compressed or lossy digital format, such as an MP3, those corruptions may become audible.
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226:, for example, a network of resistors is used to apply a small amount of DC to the base terminal of the transistor. The AC signal is applied at the same terminal and is amplified. The bias network is designed to preserve the applied AC signal. Similarly, amplifiers using
281:. Bit errors can occur when a series of 1's create a DC level that charges the coupling capacitor, bringing the signal input down incorrectly to a 0-level. In order to avoid these kinds of bit errors, most
265:. For stored digital signals, subtracting the mean amplitude from each sample will remove the offset. Very low frequencies can look like DC bias but are called "slowly changing DC" or "baseline wander".
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capacitor can be used to block or remove it, leaving only the AC component on the other side. In signal processing terms, DC offset can be reduced in real-time by a
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also have bias circuits. The operating point of an amplifier greatly affects its characteristics of distortion and efficiency;
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codes, as they are often called, have a long history and their application is certainly not confined to recording practice.
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or other undesirable change in the operating point of an amplifier. An electrical DC bias will not pass through a
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The concept has been extended to any representation of a
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was used in early tape recorders to reduce distortion.
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460:"Performance Assessment of DC-Free Multimode Codes"
60:. Unsourced material may be challenged and removed.
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378:and to two-dimensional transformations like the
241:DC offset is usually undesirable when it causes
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366:can be done solely by changing the DC bias.
315:A DC bias is applied to the control grid of
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184:The term originates in electronics, where
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120:Learn how and when to remove this message
196:(AC) voltages or currents, hence called
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58:adding citations to reliable sources
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501:"DC offset - Audacity Wiki"
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527:"What Is Biasing?"
404:Electronics portal
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110:August 2012
537:2012-08-16
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442:References
283:line codes
176:waveform.
80:newspapers
358:plus any
310:tape bias
251:capacitor
154:DC offset
69:"DC bias"
18:DC offset
552:Category
505:Archived
390:See also
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