Technical description
OVERSAMPLING
TheaudiodataonCDsandDVDsisstoredatasampli |
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| ng | ||
rate of 44.1 or 48kHz i.e. for each second of m |
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| usic | ||
44.100or48.000sampledvaluesareavailablefore |
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| ach | ||
channel. In the SADV 1245 R the audio data read from | |||||
the DVD or CD is „multiplied“to a higher sampling |
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| rate | ||
(384kHz)beforeitisconvertedbackintoanalogue | music | ||||
signals.Thisprocessdeliversasignificantlybett | er,more | ||||
finelygraduatedsignalto theconverter, whichcan |
| then | |||
beconvertedwithcorrespondinglyhigherprecision. |
| The | |||
raised sampling rate is a calculating process for w |
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| hich | ||
there are many different mathematical methods. In | |||||
almost all digital audio devices which exploit the | |||||
advantagesofincreaseddigitalsamplingrateapro |
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| cess | ||
known as a FIR (Finite Impulse Response) filter is |
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employed for this purpose. At | we have been | ||||
carryingoutresearchformorethantenyears,aime |
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| dat | ||
improving the oversampling process, because the | |||||
standardFIRmethodhasonedrawbacktosetagainst |
| its | |||
indisputable advantages: it adds small pre and pos |
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echoestothemusicsignals.At | wehavedeveloped | ||||
mathematical processes (known as Bezier polynomial | |||||
interpolators)whichdonotsharethisdisadvantage |
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this reason they should sound better and more natur |
| al | |||
than the usual standard process. Since the calculat |
| ing | |||
procedure employed by us is considerably more | |||||
complex than the standard method, the | SADV 1245 R | ||||
features a highperformance digital signal processo | r | ||||
(DSP) which carriesouttheoversamplingprocess w |
| ith | |||
immense precision (56bit) using special algorithms | |||||
developedby . |
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ThefreelyprogrammableDSPwhichweuseiscapable | ||
of carrying out the oversampling process using any | ||
method of calculation. For this reason we have im |
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plemented two slightly modified Bezier processes | ||
(OVS2) in the SADV 1245 R in addition to the pure | ||
Bezierprocess(OVS3),togetherwithtwovariants | ofthe | |
standard process (standard OVS FIR filter and OVS1) | . | |
For more information on the different processes ple |
| ase |
refer to the next section. You can switch between t |
| he |
differentalgorithmsusingtheFILTERbutton,andd |
| ecide |
foryourselfwhichofthefiltersyouprefer. |
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Standard OVS FIR filter
ThelongFIRfilteristhestandardoversamplingpr | ocess |
in digital technology, offeringextremelylinear fr | equency |
response, very high damping, linear phase charac | |
teristicsandconstantgroupdelays.Thedisadvanta | geis |
thepreandpostechoeswhichareaddedtothesig | nal. |
These „time range errors“ tend to affect the music | |
signal’sdynamics,precisionandnaturalness,andr | educe |
spatialorientation. |
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Frequency response and transient characteristics of the long FIR filter
OVS 1(short FIRfilter)
Shorteningthefilter(lowercoefficient)reducesth etime rangeerrors,albeitcombinedwithaslightlossof linearity inthefrequencyrangeanddampingperformance.
Frequency response and transient characteristics of the short FIR filter
OVS 2( Bezier interpolatorplus IIRfilter)
InthisprocessanidealBezierinterpolatoriscomb | ined |
with what is known as an IIR filter. This eliminate | s the |
problematic preecho of the FIR method. This proces | s |
produceshighly„analogue“systemcharacteristics, | witha |
soundqualityandmeasuredperformancesimilartot | hose |
ofgoodanaloguediscplayers. |
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Frequency response and transient characteristics of the Bezier interpolator plus IIR filter
OVS 3(pure | Bezierinterpolator) |
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This process delivers a perfect reconstruction of t | he | ||
originalmusicsignal.Itexhibitsnopreorpost | echoesof | ||
anykind,anddoesnotaddcolorationortimingerr |
| orsto | |
theoriginalsignal. Insonictermsthismethodoff |
| ersan | |
impressive blend of naturalness, good dynamics and | |||
accuracy.Thisisourpreferredprocessduetoits |
| advan | |
tages in respect of sound, and is the basic (defaul | t) | ||
settingofthe | SADV 1245 R. |
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Frequency response and transient characteristics of the Bezier interpolator
Note:
For optimum performance of the oversampling algorithmspleaseselect
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