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Entries found for search: clock

AES/EBU null clock : See null clock.

clock : (1) Any of several types of timing control devices, or the periodic signals that they generate. Clock pulses are usually derived from crystal-controlled oscillators. See also MIDI Clock, master clock. (2) In recording sessions for jingles or film scores, a stopwatch.

clock noise : An artifact of digital-to-analog conversion that creates staircase-like changes in voltage produced by the converter. Most clock noise is caused by shifts in the zero-crossing times. See quantization noise, reconstruction filter.

clock reference : See master clock.

clock resolution : The precision (measured in ppq) with which a sequencer can encode time-based information. A sequencer’s internal clock is always set to some ppq value, and this setting is one of the main factors that determine how precisely the sequencer can record time-dependent information. The actual clock speed is usually determined by the bpm setting. See MIDI clock.

master clock : A separate clock signal which is sent from a master device to all slaves to maintain tape position synchronization. In this process, the master clock device sends a signal from a dedicated word-clock output to a dedicated word-clock input on all slave devices over a separate cable, typically terminated with a BNC connector. Master clock generators are available at various accuracies, measured in ppm (parts per million): The AES defines Grade 1 clocks as having a long-term accuracy of ±1ppm and Grade 2 clocks as ±10ppm. The IEC specifications are Level I ±50ppm for "pro" equipment, Level II (consumer) accuracy at ±1,000ppm, and Level III has inaccuracy measured in days. It is important to be aware of the master clock spec on digital mixers, as some are specified with IEC Level II clocks, making attachment to high-resolution recorders problematic, and in this case, an external clock would be necessary to provide sufficient timing accuracy.

MIDI Clock : A timing reference signal sent over a MIDI cable a the rate of 24ppq; a System Real-Time message used to communicate timing information among instruments in a MIDI system. Also known as MIDI Sync. See also MTC.

self-clocking : A device synchronization system whereby the clock information is embedded within the datastream, and the receiving device locks to it, as opposed to a master clock system. This system is not as stable as an internal clock as cables and network problems may introduce jitter. On professional systems, self-clocking protocols will be augmented with a master clock interface which sends word clock data.

reclock : To align bars and beats in a digital editor to music recorded without a tempo reference.

null clock: The word clock null

Super Clock : Digidesign’s proprietary version of word clock, used as a master clock for all Digidesign interfaces. Super Clock runs at 256 times the sample rate; word clock runs at the sample rate.

timing clock : See MIDI clock.

word clock : A signal internally by all digital audio devices, and externally for locking together high-end digital audio devices. Word clock is , accurate to a single sample word, usually 44.1kHz or 48kHz, i.e., the sampling rate.. Specialized hardware is required for syncing a digital audio recorder’s word clock to SMPTE timecode or some other timing reference, usually through a BNC-type connector, rather than the XLR connector used by an AES/EBU null clock signal. . See self-clocking, master clock, Super Clock.

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