294:, 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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215:, 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
270:. 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
254:. 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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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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449:"Performance Assessment of DC-Free Multimode Codes"
49:. Unsourced material may be challenged and removed.
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367:and to two-dimensional transformations like the
230:DC offset is usually undesirable when it causes
16:Mean amplitude of a waveform in the time domain
355:can be done solely by changing the DC bias.
304:A DC bias is applied to the control grid of
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173:The term originates in electronics, where
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109:Learn how and when to remove this message
185:(AC) voltages or currents, hence called
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47:adding citations to reliable sources
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490:"DC offset - Audacity Wiki"
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328:, selection of the
316:Frequency selection
264:capacitive coupling
183:alternating current
516:"What Is Biasing?"
393:Electronics portal
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41:Please help
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159:DC balanced
131:time domain
99:August 2012
526:2012-08-16
500:2014-01-30
431:References
272:line codes
165:waveform.
69:newspapers
347:plus any
299:tape bias
240:capacitor
143:DC offset
58:"DC bias"
541:Category
494:Archived
379:See also
371:used in
365:waveform
342:baseband
232:clipping
155:waveform
475:dc-free
332:of the
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163:DC free
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169:Origin
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