DB - Revision history

Brad Johnson at 23:23, 27 February 2019

2019-02-27T23:23:53Z

Brad Johnson at 23:40, 10 April 2018

2018-04-10T23:40:01Z

Brad Johnson at 23:39, 10 April 2018

2018-04-10T23:39:08Z

Brad Johnson at 23:08, 18 July 2017

2017-07-18T23:08:21Z

Brad Johnson at 20:40, 23 February 2017

2017-02-23T20:40:50Z

Brad Johnson at 20:40, 23 February 2017

2017-02-23T20:40:10Z

Brad Johnson at 20:39, 23 February 2017

2017-02-23T20:39:02Z

Brad Johnson at 20:37, 23 February 2017

2017-02-23T20:37:33Z

Brad Johnson at 20:36, 23 February 2017

2017-02-23T20:36:12Z

Brad Johnson at 20:35, 23 February 2017

2017-02-23T20:35:18Z

@@ Line 44: / Line 44: @@
 In a similar manner, the output level of a DA converter can be adjusted so that the same digital level can result in a wide range of analog levels. The DA converter is typically calibrated to the same peak analog level as the AD converter, so that the digital audio recording system is calibrated for “unity gain.” This results in the playback of the digital audio recording system to be the same level as the analog signal feeding it.
 [[Category:Terminology]]
 [[Category: Analog interconnects]]
 [[Category: Digital interconnects]]

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 ==dBu (dBm)==
-In audio electronics, the “'''0dBm'''” standard for power was 1 milliwatt; because most early audio transmission utilized 600 Ohm impedance-matched systems. This power level was achieved when an RMS [[voltage]] of 0.775 volts was applied to a 600 Ohm load. In most contemporary audio systems, the signal appears as a voltage [[waveform]]; thus the dBu ''voltage'' scale is used instead of the dBm ''power'' scale.  To make this system applicable to pure voltage level measurements; the “dBu” scale is used with the same zero reference of 0.775 Volts.
+In audio electronics, the “'''0dBm'''” standard for power was 1 milliwatt; because most early audio transmission utilized 600 Ohm impedance-matched systems. This power level was achieved when an [[RMS]] [[voltage]] of 0.775 volts was applied to a 600 Ohm load. In most contemporary audio systems, the signal appears as a voltage [[waveform]]; thus the dBu ''voltage'' scale is used instead of the dBm ''power'' scale.  To make this system applicable to pure voltage level measurements; the “dBu” scale is used with the same zero reference of 0.775 Volts.
 ==VU==

@@ Line 17: / Line 17: @@
 ==dBu (dBm)==
-In audio electronics, the “'''0dBm'''” standard for power was 1 milliwatt; because most early audio transmission utilized 600 Ohm impedance-matched systems. This power level was achieved when an RMS voltage of 0.775 volts was applied to a 600 Ohm load. In most contemporary audio systems, the signal appears as a voltage [[waveform]]; thus the dBu ''voltage'' scale is used instead of the dBm ''power'' scale.  To make this system applicable to pure voltage level measurements; the “dBu” scale is used with the same zero reference of 0.775 Volts.
+In audio electronics, the “'''0dBm'''” standard for power was 1 milliwatt; because most early audio transmission utilized 600 Ohm impedance-matched systems. This power level was achieved when an RMS [[voltage]] of 0.775 volts was applied to a 600 Ohm load. In most contemporary audio systems, the signal appears as a voltage [[waveform]]; thus the dBu ''voltage'' scale is used instead of the dBm ''power'' scale.  To make this system applicable to pure voltage level measurements; the “dBu” scale is used with the same zero reference of 0.775 Volts.
 ==VU==

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 In order to give a dB measurement an absolute value; it must have a “zero reference.” One analogy is temperature in “degrees.”  Without knowing what “zero degrees” is; we can only talk about the difference between two temperatures (a form of ratio). Unfortunately; the analogy fails when you bring in the differences between Fahrenheit and Centigrade because (unlike the decibel) the “one degree” has different definitions in each system!
 ==SPL==
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 In a similar manner, the output level of a DA converter can be adjusted so that the same digital level can result in a wide range of analog levels. The DA converter is typically calibrated to the same peak analog level as the AD converter, so that the digital audio recording system is calibrated for “unity gain.” This results in the playback of the digital audio recording system to be the same level as the analog signal feeding it.
 [[Category:Terminology]]
 [[Category: Analog interconnects]]
 [[Category: Digital interconnects]]

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 ===Calibration levels===
 Depending on the calibration of the [[AD converter]] used to encode the audio signal; a wide range of analog input levels can result in the same digital level. Because no signal information is retained once the signal level exceeds 0dBFS; the most important level for calibration purposes is peak level.
 In a similar manner, there is no fixed relationship between digital level (relative to 0dBFS) and the analog output level of a [[DA converter]].
 Professional level analog audio equipment typically has a peak output level of between +18 and +24dBu. Because the standard for VU meters is “0dBVU = +4dBu,” this results in “0dBVU = -14dBFS” for a peak level of +18dBu and “0dBVU = -20dBFS” for +24dBu. The use of “-14” as a calibration standard for digital audio gear thus means the analog input is calibrated to accept a peak analog level of +18dBu. Lavry converters are set at the factory for a reference level of “-20” where “0dBFS = +24dBu.” Which reference calibration level works best depends on the application. For example; the “-14” level works well for Mastered audio program where the difference between “VU” (or “average”) level and peak level has been controlled with compressors and/or limiters. For recording “live” tracks that are not compressed or limited; the “-20” reference level may be a better choice. There is no standard in the professional audio industry for this calibration; only a range of calibrations that are typically used in recording, mixing, and mastering. The important point is to match the peak analog output level of the source device to “0dBFS” digital level.

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 The term '''dBFS''' or “dB Full Scale” is used to describe the level of a [[linear PCM]] digital audio signal relative to the highest (peak) level that can be encoded, and has no fixed relationship to dBu or "analog level."
 ===0dBFS===
-dBFS is sometimes referred to as “digital [[clipping]]” level. Because this is the only “fixed” level in digital audio, the dB level scale typically starts at 0dBFS and all other levels below 0dBFS are in “negative dB” (for example -14dBFS).
+[[0dBFS]] is sometimes referred to as “digital [[clipping]]” level. Because this is the only “fixed” level in digital audio, the dB level scale typically starts at 0dBFS and all other levels below 0dBFS are in “negative dB” (for example -14dBFS).
 ===Calibration levels===
 Depending on the calibration of the [[AD converter]] used to encode the audio signal; a wide range of analog input levels can result in the same digital level. Because no signal information is retained once the signal level exceeds [[0dBFS]]; the most important level for calibration purposes is peak level.

@@ Line 28: / Line 28: @@
 ==dBFS==
 ===Definition===
-The term '''dBFS''' or “dB Full Scale” is used to describe the level of a [[linear PCM]] digital audio signal relative to the highest (peak) level that can be encoded, and has no fixed relationship to dBu or "analog level." '''0dBFS''' is sometimes referred to as “digital [[clipping]]” level. Because this is the only “fixed” level in digital audio, the dB level scale typically starts at 0dBFS and all other levels below 0dBFS are in “negative dB” (for example -14dBFS).
+The term '''dBFS''' or “dB Full Scale” is used to describe the level of a [[linear PCM]] digital audio signal relative to the highest (peak) level that can be encoded, and has no fixed relationship to dBu or "analog level."
 ===Calibration levels===
 Depending on the calibration of the [[AD converter]] used to encode the audio signal; a wide range of analog input levels can result in the same digital level. Because no signal information is retained once the signal level exceeds [[0dBFS]]; the most important level for calibration purposes is peak level.