[digitaldave]

Hi there! Me again

.

I've been looking a bit more at DVD/SACD players, and I've been reading that some players (Pioneer DV-575, or 578 as I think it's known in the US) convert the DSD signal on SACDs to a PCM signal. Other players I'm looking at include the Samsung DVD-HD950, the Sony DVP-LS785 or the Sony DVP-NS955. So, how does one know if a player converts the DSD signal to PCM or if it uses the raw DSD?

Thanks,

Dave.

 

[soundboy]

I don't think any of the manufacturers ever mention such conversion, if any, is done or not. Basically, you read about it when modders open up the machines. Or when e-zine reviews mention it....such as the case with the new Pioneer 588.

 

[Canman]

Is there any evidence that conversion between formats causes degredation of quality? I would imagine that a well implemented conversion would be imperceptible.

 

[soundboy]

Quote:

Originally Posted by Canman I would imagine that a well implemented conversion would be imperceptible.

You may be right that a DSD >>> PCM conversion can be totally transparent. But if you know such a conversion is taking place in your player, you will also have that nagging feeling in the back of your mind that the conversion is hurting the sound quality.

 

[PsychoZX]

Quote:

Originally Posted by soundboy You may be right that a DSD >>> PCM conversion can be totally transparent. But if you know such a conversion is taking place in your player, you will also have that nagging feeling in the back of your mind that the conversion is hurting the sound quality.

Yeah that placebo effect can be a pain in the ass sometimes.

 

[jefemeister]

Quote:

Originally Posted by soundboy ...But if you know such a conversion is taking place in your player, you will also have that nagging feeling in the back of your mind that the conversion is hurting the sound quality.

Just the opposite for me. Even Sony uses nulti-bit conversion in their new players (from a reliable source, but not personally fact checked)

 

[Glassman]

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.

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..

 

[digitaldave]

Thanks for all the informative replies everyone

.

Quote:

Originally Posted by Glassman 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..

Glassman,

The is very interesting! So the future of SACD is simply high sample rate PCM?

Also, do you have any links to information describing how CD and SACD players work (block diagrams, brief descriptions, that sort of thing)? I think it would make very interesting reading.

Overall, I don't think I'll have anything to worry about, even with entry level players

.

 

[Glassman]

sorry, I made it a bit unclear, the DXD (Digital Extreme Definition) format is pushed to be used as a recording format, not a distribution format, thats DSD for SACD.. the reason for employing this DXD is that single bit sigma delta modulator A/D converters have limited performace and to obtain better performance, higher bit A/D converters are needed and if you look at the product range of the companies producing A/D converter ICs, you will realise than 2-5bit converters are common.. in order to take advantage of the improved performance these higher bit modulators provide, you have to drop DSD as a recording format, because DSD is single bit.. but in order to still have very extended bandwidth and still reasonable bitrate, they choosed 24bit/8x44.1kHz format, which is then also much easier to work with.. after the mastering, the result is encoded into single bit delta sigma modulated stream at 64x44.1kHz, which is then released on SACDs..

regarding function block diagram of SACD/CD players, there is no magic in there really, SACD is just a DVD with watermarking detection added to it.. the raw signal from the laser pick-up is analysed and watermark is extracted and I believe this extracted data also contains part of the code needed to decrypt the data.. exactly this makes it impossible to duplicate SACDs, because even if you'd made bit perfect copy of the SACD layer on DVD (which probably IS possible), the watermarking would be lost just like part of the code needed to decrypt the data, such disc wouldn't work..

 

[digitaldave]

Glassman,

Thanks, very informative

.

 

[theaudiohobby]

Quote:

Originally Posted by Glassman 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..

Think about this, why are there no recorders that record in native 128X44.1 5-bit delta sigma? it is largely a commercial issue.


Quote:

Originally Posted by Glassman 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..

Sony/Phillips are not pushing the DXD format as a standard format for recording material on DSD, some of the recording equipment manufacturers for understandable reasons such as DCS and Pyramix are, namely larger market acceptance and the old bug bear limited native DSD editing facilities.

As thing stand, folks are also recording 128fs which is indeed better than 64fs, 64fs was indeed a compromise to shoehorn the format to the DVD format as well as permit a MCH implementation on that distribution format.

 

[Glassman]

of course it's all about the available data storage space on the distribution medium.. the idealised diagrams you can find in marketing brochures on SACD and DSD, where the 1bit/64Fs data goes from the A/D converter directly onto the SACD disc and from there directly to D/A converter, which in fact would be nothing more than a logic gate.. this is good to mystify people and try to impress them, however this is not how things work in practice.. if we had more storage space available on the distribution medium, it could have been DSD wide at 4bit/128Fs that would be the native format for the A/D converter, the distribution medium as well as the D/A converter.. now that would be a clean path.. where are you, blue laser?

 

[JaZZ]

Just in case it's not obvious to everybody: DSD as distribution format makes no sense. Logic would call for PCM with 24 bit and 192 or 96 kHz.

 

[Canman]

Quote:

Originally Posted by Glassman in other words - the conversion is in fact inevitable...

Very interesting Glassman, thank you for contributing your expertise.

 

[theaudiohobby]

Quote:

Originally Posted by JaZZ Just in case it's not obvious to everybody: DSD as distribution format makes no sense. Logic would call for PCM with 24 bit and 192 or 96 kHz.

Big laugh...I disagree...but 5bit/128fs or 1.5bit/128fs or something along those lines will be much better, downside humongous data storage requirements, delta sigma A/D and D/A is in the ascendancy, might as well also record in the native format.