Upsampling, Oversampling And Sampling Rate Conversion In General - Wells JASON Owner's Manual

OWNERS MANUAL FOR WEISS JASON CD TRANSPORT
In the MEDEA we employ a two stage PLL circuitry which very effectively suppresses jitter. A
common problem with most PLLs used in audio circuitry is that they suppress jitter only for higher
frequencies. Jitter frequencies which are low (e.g. below 1kHz or so) are often only marginally
suppressed. It has been shown that low frequency jitter can have a large influence on the audio
quality though. The MEDEA suppresses even very low frequency jitter components down to the
sub-Hertz range.
This means that the MEDEA is virtually immune to the quality of the audio source regarding jitter.
For a CD player as a source this means that as long as the data is read off the CD in a correct
manner (i.e. no interpolations or mutes) you should hardly hear any difference between different
makes of CD players or between different pressings of the same CD. Also „accessories" like disk
dampening devices or extremely expensive digital cables will not make any difference in sonic
quality. Of course it is always a good idea to have a good quality cable for digital (or analog) audio
transmission - but within reason.
Upsampling, Oversampling and Sampling Rate Conversion in
General
In consumer audio circles the two terms oversampling and upsampling are in common use. Both
terms essentially mean the same, a change in the sampling frequency to higher values.
Upsampling usually means the change in sampling rate using a dedicated algorithm (e.g.
implemented on a Digital Signal Processor chip (DSP)) ahead of the final D/A conversion (the D/A
chip), while oversampling means the change in sampling rate employed in today's modern D/A
converter chips themselves.
But let's start at the beginning. What is the sampling frequency? For any digital storage or
transmission it is necessary to have time discrete samples of the signal which has to be processed.
I.e. the analog signal has to be sampled at discrete time intervals and later converted to digital
numbers. (Also see "Jitter Suppression and Clocking" above)). This sampling and conversion
process happens in the so called Analog to Digital Converter (A/D). The inverse in the Digital to
Analog Converter (D/A).
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Page: Date: 10/04 /dw