Quote:
Originally Posted by Canman
Is there any evidence that conversion between formats causes degredation of quality? I would imagine that a well implemented conversion would be imperceptible.
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well, I've tried the DSD->PCM conversion into 88.2 and 176.4kHz, with various filter lenght and shape and let many people listen to the various samples I made and guess what, nearly everyone told me his impressions, but once trying ABX, they couldn't really notice anything.. and even the impressions from those people were contradictory.. so you can imagine how much does it hurt, when there is probably no audible difference detectable between various styles and types of doing that conversion.. and also remember that 24/176.4 holds more data than the raw DSD and 24/88.2 theoretically also (talking about the useful audio information)..
regarding players that do/don't convert - well, this is more complicated than it might look at the first glance.. sure the players at the lower end can't even afford to use D/A converters with DSD interface, because they cost maybe a few cents more or such or maybe there is another reason also, like the ability to work with the audio data - remixing, attenuating and such, because this is all a lot easier to do at lower frequencies.. yes I'm talking about lower frequencies, no word about doing it in DSD because this is not possible at all and people should realise that.. in any case the DSD has to be low pass filtrered and converted into PCM although it might stay at higher samplerate than 176.4, and after the DSP operations are completed (even stupid attenuation), this PCM has to be encoded back into DSD, that means running it through sigma delta modulator again..
and now the most interesting thing: I don't know of any D/A converter at the market today, which wouldn't convert DSD to PCM and instead just push the incomming DSD data out.. yes there is no such converter, for a good reason - filtering out the inherent noise in DSD.. if you look at today's converters, majority of them are using more than just single bit modulators and also works at twice higher frequency than DSD.. if you look at their block diagram, it just says that the DSD signal skips the oversampling filter - yes this is understandable, we don't have to increase the samplerate when it is already high, but then they get filtered and each filtering means conversion into PCM.. after this filtering they enter the converter's sigma delta modulators and become say 128x44.1 at 5bit instead of DSD's 64x44.1 at 1bit..
in other words - the conversion is in fact inevitable, it just depends on where it is done, if it's before entering the D/A converter, so that the player can apply effects to it, or if it's inside the D/A converter itself, so that it can work at all, dramatically attenuating the inherent noise in single bit sigma delta signal..
and another interesting thing - Sony/Philips are pushing DXD format intended to be the standard format to record material on SACD and this format is nothing more than 24bit/352.8kHz PCM (2x176.4).. so you have the picture I think..