AVM EVOLUTION CD2 Manual de instrucciones - Página 3

Navegue en línea o descargue pdf Manual de instrucciones para Reproductor de CD AVM EVOLUTION CD2. AVM EVOLUTION CD2 19 páginas. Cd-player evolution

THE CONCEPT OF THE EVOLUTION CD2

The C02 has been optimized to a sure and extremely jitter free read out of the digital information where-

by the quantity of information is unmistakably defined by the CD format 16 Bitl44.1 kHz at the converter

input. Additional information in the sense of a higher resolution or an extended frequency range is not achie-

vable. Most of the currently used digitallanalogue (D/A) converters are not able to completely convert the

information offered on the CD to analogue signals for the following reasons.

A n in built problem with systems when reconverting digital information is the so-called quantization noise.

This results from slight inaccuracies displayed by the discrete existing values in comparison to the original

analogue signal. With the CD format these inaccuracies are defined by the 16 Bit word breadth, in other

words that during the production of the CD a pendant with a maximum resolution of 65,536 stages is atta-

ched to the analogue signal. If an analogue signal lies between these stages a principle error occurs during

recording which limits the achievable tonal quality. The recording is therefore produced with a far greater

resolution than can actually be stored on the CD in an attempt to minimize the error.

The remaining inaccuracies are randomly distributed and become apparent during re-conversion as an even-

ly distributed noise over the useful frequency band. This noise limits the dynamic characteristics approaching

the lower ranges and ieads to concealment of the fine information held on the CD. If the digital signal is

upsampled to a higher frequency prior to re-conversion the quantization noise is distributed over a greater

frequency spectrum. However because the noise energy remains constant the greater noise band width leads

to a lower noise level. A large part of the noise is now situated outside the relative audio frequency band

and can be filtered out relatively easily.This does not mean that new information is gained however that part

of the information that was previously covered by the noise becomes audible.

For this reason the digital signal of the C02 is upsampled to 24 Bitl96 kHz prior to the DIA conversion.The

enlargement of the word breadth to 24 Bit leads to a clear reduction of the quantization noise of the DIA

converter.

At the end of the frequency range the low frequency signals must be filtered to separate aliasing compo-

nents from the useful signal. The filtration causes drastic phase shifts under normal circumstances which can

be detrimental to the spatial image.Aliasing components become apparent from a frequency of 22 kHz with

standard CD format. This makes the employment of steep sloop analogue filters of a high order necessary

which lead to an increase of the phase- and amplitude distortions. In comparison upsampling to 96 kHz

aliasing components first become apparent beyond 48 kHz. This means that impulse optimized filters can be

utilized which treat the analogue signal with great care within the audible range. Phase- and amplitude

distortions do not occur and the tonal image remains correctly pitched and stable.

Special attention was paid to the minimization of jitter. Deviation in the pulse rate of the digital signal is

known as jitter.These deviations, which are for the most part caused by the drive, results in the offered infor-

mation being processed at the wrong moment of time.This causes distortion and noise in the analogue range

that in their turn are responsible for faded and slightly roughened tonal characteristics.

There are many ways of ensuring that the offered information is processed in its exact chronological

sequence. AVM has decided to proceed along a radical and uncompromising path. All of the clock pulse

frequencies that are necessary for signal processing are generated in a special module that is not timed by a

normal quartz crystal but instead by a high precision quartz oscillator. It can be assured through this that the