Advanced Digital And Analog Audio Concepts Explained - Wells JASON Owner's Manual

OWNERS MANUAL FOR WEISS JASON CD TRANSPORT

ADVANCED DIGITAL AND ANALOG AUDIO CONCEPTS EXPLAINED

Jitter Suppression and Clocking
What is jitter and how does it affect audio quality? In the audio field the term jitter designates a
timing uncertainty of digital clock signals. E.g. in an Analog to Digital Converter (A/D) the analog
signal is sampled (measured) at regular time intervals; in the case of a CD, 44100 times a second
or every 22.675737.. microseconds.
If these time intervals are not strictly constant then one talks of a jittery conversion clock. In
practice it is of course not possible to generate exactly the same time interval between each and
every sample. After all, even digital signals are analog in their properties and thus are influenced
by noise, crosstalk, power supply fluctuations, temperature etc.
Hence a jittery clock introduces errors to the measurements taken by the A/D, resulting from
measurements being taken at the wrong time. One can easily observe that the level of the error
introduced is higher during high audio frequencies, because high frequency signals have a steeper
signal form.
A good designer takes care that the jitter amount in his/her design is minimized as well as
possible.
What type of equipment can be compromised by jitter?
There are three types: The A/D Converter as described above, then there is the D/A Converter
where the same mechanism as in the A/D Converter applies and the third is the Asynchronous
Sample Rate Converter (ASRC). The ASRC is not something usually found in Hi-Fi systems. It is
used by Sound Engineers to change the sample rate from e.g. 96kHz to 44.1kHz, or e.g. for
putting a 96kHz recording onto a 44.1kHz CD.
You may now argue that in High-End Hi-Fi there are such things as „Oversamplers" or
„Upsamplers".
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Page: Date: 10/04 /dw