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Thoughts on a bunch of DACs (and why delta-sigma kinda sucks, just to get you to think about stuff)

Discussion in 'Dedicated Source Components' started by purrin, Dec 5, 2013.
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  1. KeithEmo
    All oversampling DACs perform their oversampling using a digital filter - and the type of digital filters used all produce at least some of what I would call "time smear". (This is a non-technical name the "pre-ringing" or "post-ringing" that you see mentioned.) What this means is that, while the correct amount of energy at each frequency is passed through the filter, some of that energy is "offset in time". In other words, what might theoretically start out as a perfectly sharp drumbeat would end up with "a slight reverb tail" and quite possibly a "pre-verb tail" before the actual drum hit. While the time intervals involved are very short, and whether this time error can be heard at all is hotly debated, it is the major difference between the various filter choices offered by many DACs, and a lot of us hear differences between the various choices - at least with some DACs. It makes perfect sense to me that spreading out a sharp transient like a drumbeat in time might make it seem "less lively". (Of course human perception is tricky; it could also be that spreading out a very short transient might make it easier to hear, and so might make the overall rendition seem "more lively".) The point is that this is a way in which the analog output of oversampling DACs is KNOWN to differ from the analog output of NON-oversampling DACs, so it seems like a good place to start.
    For those who aren't familiar with the details, ALL D-S DACs use oversampling (it's part of the D-S process); MANY R2R DACs don't oversample (because R2R and NOS are part of the same "retro" or "anti-D-S" philosophy), which may mean that a lot of people may be confusing the characteristics of non-oversampling DACs with those of R2R DACs. However, there are R2R DACs that use oversampling - like Yggdrasil. (Of course, Yggy also has lots of other features and design differences, so we shouldn't be too quick to assume how much of the way it sounds is specifically associated with its being R2R.)
    arnaud likes this.
  2. KeithEmo
    And what about jitter.....
    It just occurred to me that a lot of the attributes I see being applied here to D-S DACs are associated in my mind with jitter.
    To me, excess jitter often seems to cause sharp transients to become somewhat indistinct (I like to say that it makes a wire brush on a cymbal sound more like a steam leak). It is also a reasonably well documented fact that D-S DACs are more sensitive to jitter if it is present. (The amount of distortion that results from a specific amount of jitter is dependent on the ratio between the amount of jitter and the sample rate. If you have the same absolute amount of jitter, and a higher sample rate, then the jitter will be a proportionally higher percentage of the time between samples, and so will produce more distortion. D-S DACs operate at a very high sample rate, and so a given amount of jitter will affect them more severely. Whether jitter will be passed from the input to the DAC, and whether or not it will be reduced along the way, depends on the circuit topology of the particular DAC.)
    Since actually measuring jitter is rather difficult, my test methodology is to place a "jitter remover" (which reduces jitter but doesn't otherwise alter the digital signal) between the input signal and the DAC and see if it makes a noticeable difference - or not. Since there is a known difference between the sensitivity of D-S and R2R DACs to jitter, and the resistance to jitter of any specific DAC is largely unknown, it seems like we should eliminate this as a possible variable.
    (If you have a source with lots of jitter, and it sounds better on an R2R DAC because the R2R DAC is less sensitive to the jitter than a D-S DAC, then you may be able to make them sound the same by simply reducing the jitter to a level low enough to not affect either one. It could also mean that the audible differences between the two DAC types will vary depending on your signal source. And, to put it bluntly, a good jitter remover is a lot cheaper than a good R2R DAC. The Audiophilleo 2 has ridiculously good jitter specs - and it's only around $600; even the jitter performance of the V-Link is a lot better than that of many source components.)
    BirdManOfCT likes this.
  3. Articnoise

    I definitely agree with you that it’s better if we can use terms that mean the same thing for everybody. So any attempt to clarify the meaning and definition of ordinary audio terms or audiophile world is a good thing, especially as we often have a bit different backgrounds and ages here.


    I can’t say that it bugs me if someone want to buy a truly expensive tube (or anything else for the matter) and I don’t think that the difference between tubes should be seen as “mystique” or pretend as if "there's something else going on".  The high price of some NOS tubes is often related to the fact that they are rear, just as old clocks and whisky.


    As I see it we already have DACs that combines the low cost of 1 bit D-S modulation with the sound of R2R DACs. Not for $2, but for $10-15. Sabre has for example multi-bit hybrid converters like the ES9018-2M. They use delta-sigma modulation and the upper 6 bit is multibit. TI, AD, Wolfson also has multi-bit delta-sigma DAC chip. I don’t know if the true 1 bit DAC chip really has been used much currently in any mid or high end gear.    

  4. artur9
    Only if both are pure HCl.  The salt from the earth will almost certainly have impurities that lend it a distinctive flavor compared to the lab version.  Then the lab guys can go off chasing all the barely measurable impurities to get them to have the same flavor.
    How relevant this is to DACs?  No idea but in a sense the situation is reversed.  At least theoretically, the DAC will be adding impurities to the pure original sounds. (I hope that's clear.)
  5. KeithEmo
    As relates to DACs, I was using that as an analogy to the fact that, even if a certain type of digital filter "throws away all the original samples and calculates all new ones", that doesn't specifically imply that the analog output that results will be any less accurate if you do it that way. Many people seem to be "intuitively certain" that calculating new samples must be less accurate than using the original ones when, in act, that may or may not be true. (I know a few people who would never get over an emotional certainty that the lab made salt would somehow "just not be the same" as "natural" salt - with the implication that, because it wasn't "natural", it was inferior for some reason. I even know one fellow with a Chemical Engineering degree who insists that, even though that lab salt may analyze as "pure salt", it is somehow "less healthy" to eat. He might even go so far as to suggest that the impure natural salt tasted "right" and the pure lab salt tasted wrong.
    When we're discussing DACs - as compared to other DACs - then the "pure original sounds" are already out of the picture. We have a digital audio file, and no access to any presumed analog original, so the only course we can follow is to do the conversion in as accurate a way as possible. (We can't even reasonably try to compensate for errors introduced in the A/D conversion - because we have no way of knowing what errors might be there, or whether any attempted correction actually made things better or worse.)
  6. haywood
    I think that's a pretty big part of it, along with poor USB implementations. The second highest rated dac on the updated list is now the EAR Acute, though at least some of that was due to tube output stage which they liked better than Yggy's solid state one.
    BassDigger likes this.
  7. Lord Raven
    Guys, I am looking for a DAC to pair it with my Tube Amplifier, what are good options in under 200$. I don't really want to spend a lot of money on different low cost DACs and buy something good in the end, my eyes are set on Oppo 105D atm but I am unable to source it locally. What do you think should I just buy 105D and wait for it or is there something as better as Oppo 105D out there in low cost? I would only use 105D as a DAC and might play movies, that's it. Don't need a lot of 7.1 outputs or XLR's, I am just looking for a decent DAC.
    This is going to be my first DAC ever, so I am trying hard not to make a mistake. Thanks for your advice, btw I read the whole first post and still not sure what to do as I am a newbie in DACs.
  8. Stillhart
    It's a bit more than your budget, but I'd recommend an Audio-GD NFB-15.  I tried some cheaper DAC's and wasn't impressed with the improvements until I jumped up to this one.  The warm Wolfson DAC goes really well with tube amps, in my experience.
    Lord Raven likes this.
  9. bixby
    you might want to ask your question in the help and recommendations thread:  http://www.head-fi.org/f/7840/introductions-help-and-recommendations
    And you may want to be real clear on your budget.  You mention $200, then talk about a dac that is over $1000.
  10. Lord Raven
    Sorry if I did not make my point clear, I was saying if anything as better as 1000$ exists in 200 range, since that 1000 Oppo has tons of other functionalities that I will not use. I just want a DAC. I have almost found a similar unit for 250 with the help of Stillhart!
    I will post in the suggested thread. Thanks!
  11. richard51

    read about  [​IMG]bushmaster mk II
    Lord Raven likes this.
  12. wahsmoh

    Pretty sure the guy who was behind the bushmaster DAC was banned from Head-fi a few times for using different usernames and self-advertising his product?? am I mistaken for someone else?
    Lord Raven likes this.
  13. richard51

    i dont know this story..... but the service of this guy [​IMG] is first class... its that the important thing.......
  14. HeatFan12 Contributor
    LOL.  Yup, you are correct.  Those were some crazy times here.  He would pop up everywhere.  Stanley Beresford
  15. wahsmoh
    Just as notorious as nwavguy, definitely not as elusive.
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