od bogino 4. 1. 2015 11:48
Nesuhlasim s nazorom, ze 192/24 ma len studiove vyuzitie, ze nie je urcene ku pocuvaniu a ze posluchovy rozdiel nie je poznat. Nazory posluchacov na celom svete hovoria o opaku. Dovody, preco to moze byt pocut (zalezi na posluchovom retazci a posluchacovi) su cisto technicke a parkrat som ich uz aj na tomto fore vyjadril.
Drviva vacsina dnesnych DACov su delta-sigma DACy. Pre samotny prevod z digitalu do analogu sa pouziva signal, modulovany sirkou impulzov. Tento signal je svojou povahou ovela blizsi DSD signalu, nez PCM signalu.
Znamena to, ze dnesny delta-sigma DAC musi vstupny PCM signal komplikovane pretransformovat do podoby, vhodnej pre samotny prevod z digitalu na analog. Toto digitalne spracovanie v DAC chipe je urcitou slabinou tychto cipov. Nevyhnutnou sucastou tohoto digitalneho spracovania v DACe je digitalny interpolacny, castejsie nazyvany ako oversampling filter. Inak napisane: Aby sa dosiahlo nizsie skreslenie vysledneho analogoveho signalu, vstupny PCM signal sa v DACe vzdy prevzorkovava na ovela vyssiu vzorkovaciu frekvenciu. Limitom tohoto prevzorkovavania (oversampling, interpolation) su vypoctove prostriedky dnesnych DAC chipov. Toto prevzorkovanie je mozne ciastocne, alebo kompletne nahradit upsamplingom v pocitaci. Ide len o to a o nic viac, ze ktora metoda poskytne kvalitnejsi vysledok z hladiska skreslenia, sumu atd.
Nazor diskutujuceho z computeraudiophile.com:
... there are now powerful DSP chips available which can run as complex an oversampling algorithm as anyone needs, inside a DAC.
Dam sem reakciu - citat autora prehravaca HQPlayer a zaroven aj konstruktera DACov:
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I'm curious which chips you have in mind? Due to some requests I checked fastest DSP chips of Analog Devices and those are about half the speed of my many years old Core i5. They are also limited in terms of resolution. I also checked TI DSP chips and their 8-core ones are a bit better, but have some limitations too. Main problem with the DSP chips is that they don't manage to reach higher clock speeds. Latest CPUs can exceed 4 GHz which gives nice cycles-per-output-sample ratios especially important for some of the operations.
In addition, those are more expensive than the computer CPU, same goes for fast enough FPGAs. Computer CPU has unbeatable price/performance ratio since you already have it anway...
My new Haswell-EP based Xeon E5 is blazingly fast with DDR4-2133 RAMs and AVX2 instructions...
Stripped down DAC like my DSC1 (< $500) together with PC is pretty much unbeatable price/performance ratio. I'm not really interested on DACs that end up costing a fortune, not many people will have those.
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Softverovy prehravac HQPlayer je zaujimavy tym, ze umoznuje volit typ interpolacneho (oversampling) filtra. Na kvalitnom posluchovom retazci je mozne jednotlive typy filtrov od seba posluchovo rozlisit. V pripade hardveroveho riesenia mate typicky k dispozicii len jedno hardverove riesenie - take, ake je.
Podobny efekt sa dostavuje aj pri pouziti free prehravaca Foobar2000 a resampling DSP filtra. SoX resampler uzoznuje plynulu zmenu jeho parametrov a na kvalitnom retazci je mozne tuto zmenu rozlisit.
Okrem toho, samozrejmou vyhodou 192/24 DACov je moznost pocuvat HiRes PCM nahravky (digitalne HiRes downloady, DVD-Audio, Bluray) v ich nativnom rozliseni.
Naposledy upravil
bogino dne 4. 1. 2015 17:13, celkově upraveno 1
Linka na moje testy v mojom profile
HQPlayer Desktop ► Gustard DAC-X10 ► SPX2010TA ► HiFiMan HE-500