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R2R/multibit vs Delta-Sigma - Is There A Measurable Scientific Difference That's Audible

Discussion in 'Sound Science' started by goodyfresh, Aug 31, 2015.
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  1. bfreedma
    No problem and agree that unless the filters are in use, I highly doubt the two DACS sound any different.
  2. theveterans
    Some claim differences in different NOS multibit DAC (not referring to NOS vs OS). For example: Metrum DACs vs Holo Audio DACs in NOS mode
  3. bfreedma
    Some form of controlled testing (blind, ABX) would be necessary to validate those claims.
    chaos215bar2 likes this.
  4. Joe Rasmussen
    Yes, come'on indeed. Would you like to know the technical details?

    Keep in mind, what follows below is not everybody's cup-of-tea and that is the reason that it is not stated explicitly on my website. There is no intention of sleight of hand or to be deceptive. So here goes.

    The Sabre DAC family is a little different from what others offer. The output has a DC offset 1/2 of Vcc, which means half of 3.3V and hence 1.65V. So far so good, if we were to put a scope there, we would see that it is acting as a 'voltage' DAC capable of swing 6V peak-to-peak (the half voltage is a D-S DAC is 50% of the pulses are 'on' and the other 505 'off' - at least that is the easiest explanation.

    If this was a normal voltage DAC, we should be sure that it looks into something that matches that 1.65V or else we might damage it. So then, even if we should use ESS recommendation, and we connect it to an I/V converter that will not shorten it with respect to DC (that could damage the DAC), but it will see a short with regard to AC, which is our music signal.

    This is known as a virtual earth as opposed to a physical earth.

    In a similar way to conventional voltage DACs, they too usually have around half of 5V, hence the offset tends to be around 2.4V to 2.5V. This has to be matched to a similar DC or potential damage (been there).

    Hopefully not boring too many, but at least here things does get a bit more interesting: The Sabre DAC is different.

    Take the ES9018 DAC, it has four phases, that is 8 pins, and each pin has an output impedance of just under 800 Ohm. This impedance is permanent (very stable indeed). Because of this higher stable impedance, it means that we can shorten the phase to ground. No we shall have zero voltage DC offset, but what we have done is created a current offset.

    This is the mode I was alluding to. You have turned what looks like a voltage DAC into a current DAC with an offset current. The offset current is 1.65V/795R = 2.1mA and as I do in the Oppo 105, I parallel two pairs of phases up and create an offset current near 4.2mA per side.

    So I am now using a physical earth rather than a virtual earth.

    So I made a comment on my website that I am indeed using a different mode and I wonder if ESS the manufacturer knew that this could be done this way?

    What did I do wrong?

    But seriously, to most people this is boring stuff. I have a website that tries to be as informative as possible, so I have to draw a fine line, how technical do I get? I want it to be readable as I can make it.

    At the top of every page on my website is my phone number, I get phone calls from many parts of the world. When I hear and understand their level of understanding, I will indeed get into far more technical details - indeed I am more open about what I do than just about anybody else out there.

    Give me a call!

    Let us now resume normality. :beerchug:

    Cheers, Joe
    Last edited: Aug 7, 2019
  5. bigshot
    Generally, before you go looking for reasons something sounds different, you determine if an audible difference exists. I’ve compared a Sabre DAC to other DACs and I can’t hear a difference with a controlled listening test. I’d be interested to hear about a controlled test that revealed clearly audible differences.
  6. Joe Rasmussen
    People perform poorly under so-called ABX tests. They often make things sound the same, and who or what is being tested? Is it the person or is it the equipment?

    When I demonstrate a piece of equipment I never ask the question "What do you think?" and instead I ask if there is another piece of music to play. I keep doing this, after a little while the listener relaxes knowing that the dreaded question is not going to come. In time he will freely express what he feels comfortable saying. I make sure that I never get him to become a performing monkey, that he is never put on the spot. I also believe a person who walks into a shop should be treated this way. I don't have a shop, but this is the approach that should always be used, IMHO.

    As for getting into an argument that has more to do with ideology than the real world, I beg off please. The average person needs to be treated respectfully and not as a target, that you have a responsibility that goes way beyond dollars and cents - you have an obligation to make things better for your fellow human being and that this will be something that will enable him to enjoy music in a better way than before.

    Or else you have failed miserably!

    So why has this ideological battleground opened up? I can see reasons why. I have noted many audiophiles seems to be frustrated reviewers. They seem to be able to make instant judgements about a piece of equipment under all sorts of uncontrolled conditions, by that I mean in unfamiliar systems. I am not a reviewer and I think others should avoid it (a professional reviewer would want to live with the equipment over a reasonable period of time) - and perhaps for this reason there is a push-back and ABX is part of that push-back. I can to a certain extent understand that.

    But both sides are quite capable of throwing the baby out with the bathwater.

    Perhaps one more thought. There have been occasions, in a system with I am familiar and comfortable with and a single change has been done something in that system - and then heard instantly that something better and so much more right has happened. Other than that, I tend to be quite conservative and often keep my mouth shut while others go of. Like I said, I won't get into any ideological battles over this and I recommend that stance to others.

    I have a recording and I realised at the intro, in a good system, that it became obvious that the guitar was double-tracked. Only with a decent setup was this obvious. Then a change in the amplifier (to me most amplifiers on the market are not that good, even expensive ones) made me realise that the guitar was in fact triple-tracked.

    To me that is an objective experience - and hence as valid as any ABX test.

    BTW, I have always thought that everybody should have a stint in a good recording studio. It would straighten out a lot of people on both side. Heard a grand piano on a live feed? Wow! But even better than that, in this family we own and have a grand piano in the room opposite the sound room. Want to go from one room with the real thing and walk into another room with the ability to play the same instrument convincingly!

    Way better than any ABX test will ever be, trust me. Everybody is welcome to come here to experience it.

    But what if you heard a difference under different circumstances? Would you trust your hearing? What if you heard a double-tracked guitar was now triple-tracked? Would you trust your hearing? :)

    Cheers, Joe R.
  7. Joe Bloggs Contributor
    There can by definition be NO PROOF EVER that people perform better in non-blinded conditions than in blinded, since when asked whether they're listening to A or B, they can always simply point to the box they see connected to their headphones, whether or not they hear any difference!

    And if you don't know what confirmation bias is, I won't bother starting an argument with you.

    It's stupid to design for improvements that can only be "heard" by an oscilloscope and not by a blinded listener, since I can name a baker's dozen improvements that WILL make an improvement, blinded or not, in any state-of-the-art playback system, that have hardly ever been touched on commercially.
    Last edited: Aug 7, 2019
    SilentNote likes this.
  8. Joe Bloggs Contributor
    There's also nothing in the definition of ABX that puts "pressure" on anybody to perform like a monkey. In fact people have been put into long-term ABX tests without even knowing they were part of such a test, to validate / invalidate the audible improvement of various technologies.
    SilentNote and chaos215bar2 like this.
  9. bfreedma
    Such a long post yet not a single indication, let alone a measurement of any audible change.

    Feel free to post comparative's between the original product and your modified version that actually show audible improvement. Until then, I see no reason to believe that the hundreds (thousands?) of implementations are technically incorrect or that ESS is unaware of their own product.

    I remain unconvinced by your sales spiel and the usual attempts by mod vendors to discredit ABX while failing to provide hard evidence to support made claims.
  10. Joe Rasmussen
    I am sorry you feel that, at this point I don't think I can say or do anything that would satisfy you. You asked about the Sabre DAC's unusual 'mode' and I explained in quite detail what it was. I would have thought that you should at least have something positive to say about that?

    Besides, I don't make "claims" and if I did I would get it peer reviewed by appropriate people (like engineers and scientists) and not public/social media. I accept criticism, but it has to be constructive. Here is not the place, so I apologise that I shall disappoint you. Goes with territory, so I have sadly learned.

    As for suggesting that I am something along the line of being a charlatan, because you are suggesting that I fool people into giving me money, I find exception to that. You have not even met me, you have not talked to me on the phone (the number which you can easily find) and after fourty plus years as a reputable person in this area, have you anything to match that?

    Cheers, Joe R.
  11. bfreedma


    I could be very easily satisfied and described how in the section of my post you didn’t quote.

    Simply provide measurements of your mods compared to the original design showing an audible difference. You must have them - how could someone design and engineer a modification without them?

    I find the statement that you won’t make claims because they would be peer reviewed by engineers to be quite telling. As is asking about my background as an attempt to validate your mods.
    SilentNote and chaos215bar2 like this.
  12. Joe Rasmussen
    Very odd. As if I was seeking an argument? Not me. You?

    Confirmation bias is why Google Search has proven deadly, taking into consideration what has happened in the last few days. So yes, I know what confirmation bias is. I have even warned many people about it and not just recently. It works on many levels and audio too. Why I gave a warning about too many audiophiles wanting to be instant reviewers. Did you not read that?

    I wish audiophiles could spend some time is a respected recording studio. Those guys know how to listen and can teach all of us a thing or two. You have no idea what 'critical listening' means unless you have spent time with those guys. I can even mention significant names like Barry Wolifson, Phil Punch and Garth Porter. You don't have their reputation without an acute hearing ability.

    Here is an example of Garth's work: http://www.customanalogue.com/IfThisIsLove.flac

    Cheers, Joe R.
  13. bfreedma
    Your next Google search should be "Appeal to Authority"
  14. Joe Rasmussen
    I could, but 1) it would be viewed as promoting a product and that I am pretty sure is against the rules. And 2) they do in fact measure very differently. Not a little bit, but in an obvious and BIG way.

    Ouch! Not very nice. What does "how could" mean? That is just pejorative speech, is it really necessary to go that far?

    If you want to win an argument, then you just have! You win. If that is what you need, so be it. I don't have an ego to defend.

    I won't give what you ask on social media. I don't know you.

    Cheers, Joe R.
    Last edited: Aug 7, 2019
  15. bfreedma
    You have measurements but won't post them? I'm back to where we started - Come on.

    If you feel that posting the measurements on head-fi is a violation of the TOS (highly doubtful), you could always post them on your web site. If they showed a significant audible improvement, why wouldn't you? That would certainly help you sell your product.
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