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Tag Sync Link

Discussion in 'TAG McLaren Audio Owners' Forum' started by Chippy99, Jun 29, 2005.

  1. Chippy99

    Chippy99
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    As you know Tag introduced the Sync Link feature to synchronize the reference clocks in the AV32R & DPA32R with the DVD32R and CDT20R-T2L.

    It strikes me that this is quite a common approach in the professional audio arena and most (all?) decent pro soundcards have external clock inputs.

    Does anyone know if Tag implemented this in a completely proprietary way, or is there any chance the Tag sync link might actually sync up with a pro soundcard (e.g. Lynx).

    It strikes me that a PC with a decent soundcard synced up with an AV32R would sould absolutely amazing playing bit-perfect wav files.

    If the Tag link *is* proprietary, how difficult would it be to produce a little gadget to extract the clock signal and pass it on?

    Any ideas?

    Cheers

    CHip
     
  2. memmerson

    memmerson
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    I too would be very interested if this can be done.

    Recently I've been thinking about going down the HTPC route and CD sound quality is pretty much the only thing stopping me at the moment. As much as I enjoy my DVD32R the money I could free up by selling it would get me a lot HTPC!
     
  3. lenny

    lenny
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    That's for Graham.
     
  4. edward

    edward
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    I wouldn't bet on freeing up funds, memmerson.

    Ask Graham what he spent. I wonder if John Mulcahy spent much less. I think we can safely assume these guys have done it right so have a fair idea of what that costs.
     
  5. babaroga

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    But then again, you won't be playing your CD's through your HTPC DVD drive, would you ?

    Instead, you would have all of your CDs ripped using EAC http://www.exactaudiocopy.de with AccurateRip http://www.AccurateRip.com plugin into lossless compression (FLAC or ape). You should still have a decent soundcard (RME or maudio).

    Now, if you have good set of ears, you might still hear the difference in quality, but that would be quite negligible to the dvd32r...

    This is my current approach....
     
  6. memmerson

    memmerson
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    Thanks, I will look into that Babaroga. TBH I'm a bit wet behind the ears when it comes to modern HTPCs so advice is more than welcome. I will start a new thread re:htpc as I don't want to hijack this one.
     
  7. Chippy99

    Chippy99
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    Correct. I will be ripping using EAC and storing the files as either lossless wma's or apes. (I might even just leave them as .wav's - I only have around 500CD's so that's only 300 GB even as wav's.)

    Regarding the sound card, then yes I will be using an M-Audio to start with. I might go down the Lynx Studio 2 route and doing the D-A conversion in the PC and drive my power amps directly. But to start with I am going to take sp-dif out of the m-audio into the AV32R. The problem with this approach is that the clock should really be sitting right next to the DACs for optimal sound quality, and of course it isn't. So the sync-link would offer all of the same benefits you get with an AV32R/DVD32R, if I could get it to work.

    So, any takers on how easy/difficult this might be?

    Cheers

    Chip
     
  8. babaroga

    babaroga
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    Chippy,

    do not even think to use "lossless" wma's !!!
    M$ has announced recently that this format is "lossless enough" but not totally lossless.

    I should suggest to use FLAC as it is very adaptable with the bitrates from 44.1KHz CD to any sampling rate in the future (considering that will be cracked for ripping :D).

    Lynx Two, bit on the expensive side for the analog output only, considering all interference witin computer case (especially having multi GHz processors around unshielded and other components that do not really care about that). It is better suted for studio work and its analog output should be used only for monitorring the sound.

    I would prefer the option of external USB soundcard like http://www.m-audio.com/products/en_us/AudiophileUSB-main.html , however, you would probably need to upgrade to the quality "wallwart" AC/DC converter.

    Graham on this forum has been messing about with sync-link to his av192r (I think had RME soundcard), but he gave up after a while...

    regards
    Darko
     
  9. Chippy99

    Chippy99
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    babaroga,

    Thanks for the tips. I did some testing of WMA's some while back and converted wav to lossless wma and then back to wav again and compared the files. They were nothing like the same! I thought it must have been a bug in the software I was using, but from what you say, perhaps not.

    My reservations around flac are that there are not that many things will play it. I want to use Windows MCE (so that my wife can work it) and for day-to-day listening we'll probably be using native MCE to do that. Yes, I know its lossy and yes I know it will inevitably go through kmixer, but it will sound "OK" for background music. Then when I want to do some *serious* listening, I can fire up fubar - or whatever - and listen "bit perfect".

    Bearing this in mind, I am leaning more and more to staying with wav's. For the sake of maybe 100GB or so fo disk (compared to flacs), I can keep everything as wav maybe convert later if I see a need. Of course staying with wavs saves me all the encoding time too, and whilst that's not an incredibly big deal, I do have 500 CD's to do!

    Your concerns about the Lynx Two are not in keeping with what I have heard. There are a couple of people I have come across who have started using a Lynx Two to drive their power amps direct - and bypassing their AV32R's. The concensus is that the performance of the Lynx far surpases the soundquality of the AV32R-192. My guess is that's because the Lynx has a super stable (60ps jitter) master clock sitting right next to the DACs. But that's only a guess. Anyway, whatever the reason, its supposed to be incredible.

    Regarding the sync link question, I guess the first thing for me to do will be to try it. My m-audio audiophile 192 can sync up off an incoming clock over sp-dif. I guess there's no harm in hooking it up to the AV32R's sync link out, and seeing what happens.

    Cheers

    Chip
     
  10. alexs2

    alexs2
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    I've been using an HTPC(from UVEM) for a couple of yrs now as the front end of my system,alongside a TEAC VRDS transport.
    The sound card in my PC is simply there as digital throughput to the upsampler and DAcs in the TAG,although going to a Lynx would be a viable option,in terms of quality,if not in terms of added inconvenience and cost!

    The HTPC runs into my AV32R/DP via a Perpetual Technologies upsampler,run at 24/96,and really does do a lot to improve the sound quality of anything ripped to the PC.
    As to formats like FLAC/WMA etc,it's still easy to tell the difference between CD and even so-called lossless formats,especially with a decent system,and a recent HiFiNews article which reviewed and looked at the various lossless encoding formats went a long way to explaining it,in terms of the added distortions etc from poor encoding.

    If you are interested in HTPC's,it'w well worth having a chat with Phil Hale of UVEM,who will give you good solid advice,without pushing for a sale....in my case,his product sold itself,and I've been very pleased.
     
  11. Chippy99

    Chippy99
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    Thanks Alex for your help.

    As to the comment above, that really puzzles me. I find it hard (if not impossible) to imagine how that can be true.

    The beauty of ripped data is that it is jitter-free. Its simply data. There is nothing "hidden" in the ripped data, and therefore nothing to be "magically" missing from the encoded output.

    The compression algorithms (for a lossless format) are merely taking that data and tranforming it from one format to another. And providing its lossless, then all of the information is retained (or its not lossless, obviously). There's nowhere any extra information could be hiding; its either in the data bits, or its not there.

    When it comes to playback, the encoded data is decompressed and clocked out in the same way as if raw, uncompressed data was being played.

    If there is to be any truth your above claim, then my only thought is that (somehow) some extra jitter appears at the output stage, over and above the amount seen when playing a .wav file. I fail to see why this might be the case however. There cannot be any extra information in the .wav output's bits, compare to the .ape (say) output bits. The bits will be identical, so if there is to be any possibility of sound differences, then it can't be in the bit stream.

    My concern is that perhaps the snake-oil oriented hifi media are desperate to find nuances of sonic difference in order to justify their existance. And just maybe those nuances really aren't there at all.

    It wouldn't do the hifi industry (nor the journalists) much good if the conclusion was

    "buy an htpc and output bit-perfect data, and then you will have a "perfect" audio source. Alll audio such sources - irrespective of cost - sound completely identical and there is no need for us to ever write another review. Goodbye."

    I'd be very interested to read the hifinews article.

    Chip
     
  12. Stevesky

    Stevesky
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    Jitter in the digital domain will not affect quality as long as the link can hold data integrity. the affect is when that jittery data (and derived clock) reaches the DAC as that's where the distortions are introduced. If a CD/DVD player can extract the data correctly in realtime then it is no different to an HTPC. A DVD player has to do this for the DVD compressed formats otherwise audio will drop out/pictures will pixelate/freeze. CD's can have interpolated samples due to error correction and this can affect quality when played by a traditional CD player. Ripping software has the privillage of not having any realtime demands of getting the data off the disc and hence can aim for the perfect digital extraction.

    Saying this HTPC has it's flaws. Firstly a sound card has a fixed analog output gain and has no headroom making it compromised for doing proper AV. In AV quite often you have to mix channels into others (eg. LFE into mains, L,R into centre when doing Prologic) and this means that you need analog domain headroom to avoid clipping in the digital domain. The best way to do this is to scale things down in the digital domain to ensure you don't clip when doing the summations and then scale it back up in the analog domain, hence your final output signal could go above 0dB. In a HTPC all you can do is scale in the digital domain and have inconsistent output levels depending on format/configuration, or allow clipping (not good).

    HTPC can work well for Pull formats where the PC has control of how fast it reads the data and then just has to throw it at the soundcard ensuring the output buffers never under-run. In a Push format like an external SPDIF feed you have no control over the speed of the incoming data and the rate coming in may not exactly match the rate you clock data out. Under this situation most soundcards will lock their output clocks to the input clock but most become quite jittery. In a Push format that comes from a source that is not input via the soundcard it becomes more complex as you have two independent clocks (external source clock vs soundcard output clock) and somehow you have to syncronise them otherwise eventually there will be a slow drift and you will have a buffer overflow/underflow situation. At the moment (to my knowledge) there isn't a nice way to do this on a PC as the PC cannot bend the clocks on the soundcard.

    Also when dealing with 44.1k 16 bit audio you can get improvements by adding dither, doing noise shaping to the original signal and of course the strategy for doing the reconstruction filters. For best results just shoveling the raw 16 bit data to the DAC isn't necessarily the best way forward for accurate reconstrcution back into the analog domain.

    So to sum up although I agree that doing ripping can give a consistent bit perfect copy of the data, it still doesn't resolve the issue of the best way to convert it back into the analog domain, expecially when used in a home theatre application.
     
  13. Chippy99

    Chippy99
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    Since I am at work I don't have chance right now to reply to all of your post, but this part at least is incorrect.

    Jitter induced distortion is not about data integrity. We are not talking about the wrong bits being received by the dac, merely about the timing at which they are received. In virtually all dacs, the clock signal is extracted from the sp-dif input (complete with jitter). Unless buffering and reclocking is done, the 16-bit words are decoded and output slightly late or early. Jitter effectively frequency modulates the output signal, which is of course a form of distortion.

    Of course good dacs attempt to reduce this effect. Some double buffer the input with two phase locked loops. Others attempt to solve the problem by driving the dac off a high precision crystal right next to the dac itself. And solve the problem of data syncronisation by using a link cable to clock the data out of the source using the dac's crystal as a driver.

    But most htpc gear does neither of the above and the jitter in the source signal comes through loud and clear. That's why its important to look at the jitter characteristics of the soundcard if you will be using sp-dif out.

    Chip
     
  14. alexs2

    alexs2
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    Chippy...rather than me trying to give some sort of digest of a rather lengthy article,written by far more worthy persons than myself with respect to the digital domain,I'd suggest tracking it down and reading it in full,as it's findings with respect to the various encoding formats was interesting.

    Personally,I'm not at all interested in any snake oil,but I am interested in getting the best sound quality out of the gear I own,and if I find that a lossless encoding format results in audibly poorer sound quality via exactly the same equipment chain,then I don't use it.
     
  15. Chippy99

    Chippy99
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    No-one can say fairer than that. However, I do question some of the reviews you come across, where I am not altogether convinced about the impartiality or the reviewers.

    Chip
     
  16. alexs2

    alexs2
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    It's certainly worth a read,as none of the contributor(s) involved really had anything to gain from the article,other than reviewing the sound qualities of the codecs,and the differences between them.

    Partialty or otherwise is usually very obvious,and certainly didnt seem apparent in that article.

    In any case,for me,it merely provided some possible explanations as to why I prefer CD to lossless storage formats on the PC....it all goes through the same system from source to output,but the result to my ears was clear....and gave me an excuse to resurrect the vinyl and spend more money!
     
  17. Chippy99

    Chippy99
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    It certainly would be worth a read, but as hifinews want me to pay to download it, I will probably have to give it a miss.

    With respect to the reviewers having no axe to grind, perhaps. On the other hand turkeys don't vote for christmas do they. Its just not in the blood of any hifi reviewer to say "they all sound the same to be honest".

    Chip
     
  18. alexs2

    alexs2
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    LOL....but then turkeys do have rather small brains and may just vote for it given the chance.

    My point with respect to all of this was that an HTPC can give excellent results,providing the innards are chosen carefully,along with the software,and in most respects,that also applies to hifi in general...careful choice in partnering equipment,and not being swayed by anyone's opinion other than your own,since you end up listening to it.

    My views about reviewers would be similar to yours,with the exception of a few whose opinions etc have fallen roughly alongside mine,and thus I would afford a bit more trust to!
     

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