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S/PIDIF Clock rates

Discussion in 'Blu-ray & DVD Players & Recorders' started by jason.bond, Jul 31, 2005.

  1. jason.bond

    jason.bond
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    Greetings.

    Can anybody tell me what S/PIDIF clock rate I should be seeing with the different types of media?

    I have a Samsung DVD-HD950 connected via S/PIDIF to a Terratec Universe soundcard in my PC. This card allows me to see the current clock rate.

    CD is obviously seen as 44.1kHz
    DVD is seen as 48kHz

    Now here is the bit I do not understand. DVD-Audio is supposed to be a 96kHz/24bit source.

    DVD-Audio is seen 48kHz ?

    I have yet to test a SA-CD, but will do so as soon as I can get my hands on a couple.

    Why am I seeing the DVD-Audio at 48kHz? Is the Samsung player down clocking (limiting) the signal?

    What clock rates do other people get from DVD-Audio discs?
    What clock rate are people seeing from SA-CD?

    Thanks
    Jason.
     
  2. Nic Rhodes

    Nic Rhodes
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    Jason

    these are the sample rates not clock rates but to help with your info I think you are after

    CD always 44.1kHz
    DVD has a variable rate (to allow it to play CDs etc), this rate depends on the format and disc (and even the player). The majority of discs are 48kHz but can go as high as 96kHz and as low as 32kHz I think.

    SACD uses a different system of 1 bit but at 2.8Mhz and therefore you will not see this with you sound card (in general), what you will see is a CD compatible (44 kHz) down mix. Copy protection.

    DVD A is another variable format and can go upto 192kHz but it does not out anything over 48Khz even if it is higher, again copy protection. Straight DVD 'can' output higher SPDIF rates!!

    DVD A and SACD limit their outputs to lowly 48kHz or lower SPDIF signals, however internally they work at very different rates.

    2 channel PCM from DAD is 24bit / 96Khz and can be outputted by SPDIF, this is the highest numbers you will see over SPDIF. It is after all an old interface with no copy protection. Only some players can do this, player limitation here, others with the identical disc down mix to 48kHz.

    Confused, yes you should be!!
     
  3. jason.bond

    jason.bond
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    Thank you for the clarification, and yes I am confused :)

    I had assumed that the clock signal would be equal to the sample frequency, and that I would see 96kHz on the S/PIDIF.

    I was hoping to use the superior DAC's in the soundcard to convert the signal to analogue.

    I will have to try the 48kHz decode vs the analogue output of the Samsumg player to see which sounds best.

    Does anybody have any links to useful articles on the Copy Protection downsample to 48kHz?

    Cheers
    Jason.
     
  4. Crustyloafer

    Crustyloafer
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    In order to get the full 96kHz or 192kHz sound from DVD-Audo or SACD you need to use the analogue outputs from the player. It is not allowed to output higher than 48kHz from these sources due to copyright protection.
     
  5. ianh64

    ianh64
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    Some manufacturers have proprietry protocols that allow 96khz via the digital link - Meridian with MHR smartlink for example. There are also some manufacturers that offer PCM digital output for a limited range of SACD players - http://www.dvdupgrades.ch/digital_audio.html

    -Ian
     
  6. CJROSS

    CJROSS
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    Jason just an addendum to Nics usually informative post above. The only PCM data available above 48Khz ie in raw data form is from the old DVD-V stereo 24/96 Digital Audio Disc DAD format, a few years ago I bought the “whole hook line and sinker” press reports that we audiophiles were on the cusp of something wonderful from the DVD-V format, and bought kit that could harness such a signal from this DVD-V standard, namely a Pioneer 717 DVD-V player which sent pure 24 Bit 96Khz Linear PCM data from its digital output towards an offboard DAC that could accept such a signal, the MF X-24K to be precise. The results were very good TBH. But a lack of software (one reason Ive avoided SACD & DVDA) meant that its 24/96 use was very very small. Thus I replaced that 96Khz able DAC with a superior 48Khz DAC from TAG.

    So what happened next, well as an adopter of DVD-V and using a DVD transport into a DAC for CD use, I started to experiment with different types of “high resolution” data, ie HDCD – still 44.1khz as per redbook CD but with an extra 4 bits of wordlength, 20 Bit instead of 16 for CD. I also got into the best 48Khz PCM data I could get my hands on, ie DVD-V stereo tracks and having heard 24 Bit 48Khz LCPM (Dave Gilmours Meltdown concert) I think higher bitrates have more to do with getting pristine audio from PCM than freq. sampling rates ala 96 or 192 Khz. A good processor is IMHO a must TBH. I was more impressed with what I heard from 20 Bit 44.1 & 16/24 Bit 48 Khz PCM from DVD-V than I was from my old, 24/96 DAD kit, I even overlapped the kit and played these discs before I sold on the old DAC. FWIW I still enjoy the 96Khz discs I have I stereo both DAD & DVD-A, sold the DAC on a few months ago and before that compared the DAC in my DVD player (ie full 96Khz & 192Khz DVDA) and the offboard DAC with 48Khz digital out downsample (due to copyright protection) of PCM data. And guess what both sounded truly stunning to these ears. The quality of procesing will have a large effect on what you hear. Outright levels of resolution does not matter, it’s the kit that processes it.

    FWIW I have an upsmaling circuit on my current player that I only notice works on 16 Bit 44.1 CD. On the 20 Bit HDCD & 16/24 Bit 48 PCM its makes very little different, the upsampler though on my Toshiba @ 176.4Khz (a 4 times 44.1 up/oversampler), well it does something to 44.1 CD that even my sceptical ears can hear.
     
  7. jason.bond

    jason.bond
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    Thanks for the info.

    I used to use a Arcam Black Box DAC for 44.1kHz, driven by an old Technics cd player. I quite liked the sound improvements over the onboard DAC.

    At the time I was playing it back through a Audio Research valve pre, coupled to a Carver 1000 amp, through a good set of tower speakers.
    Alas it is all in storage in another country at present :)

    Hence I am starting up a second rig, and thought I would go DVD-Audio / SACD.

    My main kit at the moment is a pair of Sennheisser HD650's driven by the Terratec soundcard.

    I was hoping to use the DAC in the Terratec card, but then noticed the 48kHz signal and was stuck.

    Does anybody have any opinions on the sound of the onboard DAC at 96kHz using the analogue output vs the S/PIDIF at 48kHz?

    I don't have a quality set of rca leads at present to test. I am probably going to chase down a set of Audioquest King Cobra cable to link it up. I can then do a proper comparison.

    Cheers
    Jason
     
  8. CJROSS

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    1) Jason Ive done a fair bit of listening evulations with my USB 24/96 External M-Audio Transit Soundcard/DAC, its worth searching the forum for those threads, in both listening to the 24/96 DAC via headphone and using my PC / Transit as a transport to an offboard DAC.

    2) Ive also experimented with a couple of DACs and their corresponding transports that feed them signals via their SPDIF outputs, comparing the anlg outputs of transports & DACs, Ive been convinced that what matters is the quality of conversion & anlg output stage, these are what affect the sound to my ears, even though a transport may have a 96Khz or 192Khz DAC onboard, sending a 48Khz signal to a decent DAC can and does IMHO better it. I found that with my old TAG DAC, now comparing my current DVD-A player with the highest rates of PCM data available on a disc ie 96 or 192 Khz stereo and listening to the players onboards DACs working at that resolution is very impressive, but the real shokcer was how a 48 Khz SPDIF signal sounded into a 48 Khz DAC. Damned stunning. Both transport & DAC, had/have wonderful conversion& anlg output stages. This is where you will find a difference though between players/transports & DACs. So get listening as we all vary in what we hear.

    3) Leads … hmmmmmmm. Well before you spend anything more than £25 on a 1m pair of anlg ICs you should read the cable forum before you start worrying about a set of “quality” leads to do listening tests to, I speak as someone with a set of £15 Ixos ICs off my LP12. One last tip also do a search on Mark Grant cables on the forum, he does cheap, well built and ultimately the same job sonically as say a pair of £1000 Nordost Valhallas for £20.

    ATB.
     

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