Vintage/Current R2R DAC Owners Discussion, Insight, and Review Thread

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  1. yildiray
    All these informations are great.Eventually I reach these conclusions :

    1. I planed to make milled/engraving aluminium enclosure and take into account all other factors so thats right choise you verify me .
    2. As i understand i can buy PCM1704U-J from Rochester Electronic :

    https://www.rocelec.com/search?q=PCM1704U-J

    J or K not very critical also this supplier must sell original products.Is it more sensible ?

    3. My plan is OPA627 output stage + a tube preamplifier.Preamplifier planed to be with dac in same enclosure.Is it suitable for your opinion?
    4. Do you have a recommendation for presicion power supply for dac ?

    Thank you
     
  2. MojoAudio
    Hi Yideray,

    Please don't be offended, but you've obviously "drank the Kool-Aide."

    There are so many factors in all of this.

    To begin with, why are you going to spend a small fortune on a milled aluminum chassis? Because you've seen so many modern manufacturers use milled aluminum chassis?

    Milled aluminum looks cool and has fairly good at resonance characteristics, but it is a terrible shield.

    You would get better performance at a lower cost with a modest off the shelf steel chassis (much better shielding than aluminum) and coating the inside with anti-resonant sheeting.

    And that's not to mention using anti-resonant standoffs, such as the EAR Sorbothane or the Stillpoints, and feet under the chassis, and anti-resonance "weights" on top of the chassis. I've experienced over 30% performance improvement with just these simple anti-resonance products.

    Then why are you choosing the PCM1704 in the first place?

    It is not even a true R-2R DAC chip.

    No company can match more accurate than a 20-bit resistor ladder, so the highest performance true R-2R DAC chips are the 20-bit ones, such as the PCM63 and AD1862.

    The PCM1704 is a hybrid of two resistor ladders, a MSB and LSB ladder, with an algorithm that combines the sum of the LSB ladder at a fraction of the output voltage to the MSB ladder. To me the sound is a mix of a true R-2R ladder DAC and a modern single-bit DAC. Somewhat slow, smoothed over, and overly refined for my taste.

    Personally I prefer the sound of the legendary 20-bit DAC chips, and there are several other people on this thread that have compared and agree with me.

    The OPA627 is one of my favorite IC op amps, but it is no comparison to a good discrete op amp, such as the Sparkos Labs:

    http://sparkoslabs.com/

    Sparkos Labs also makes one of the best ultralow-noise regulator on the market - quite comparable to the Belleson I currently use.

    If you're asking the question you are asking about a power supply, then it is obvious you don't know enough to build a proper power supply, and that is likely the most important part of any DAC.

    I could write 10X as much on power supply alone, but this is not the tread for it. If you want more info contact me through PM.

    And don't get me started on how TOTALLY STUPID it is to put a DAC and a tube preamp in the same chassis. To begin with, the noise in a tube preamp's power supply is extremely high and would require significant shielding and physical distance from the DAC portion. And a tube preamp with a decent power supply would have to weigh over 20 pounds and take up quite a large chassis on its own. Anything less and you'll be killing a significant part of your DAC's resolution.

    By nature a DAC is a solid-state device. Most companies that manufacture tube DACs in fact are only adding a tube buffer to the output of a DAC so they can add a romantic attractive distortion. It is a marketing concept. If you have an all solid-state system with high wattage class A/B or class D amplifiers I could see the attraction of this type of DAC, but it still makes more sense to have a dedicated DAC and dedicated tube preamp. Not only would the result be a lower noise floor, this would also give you the opportunity to upgrade each component separately.

    And then, what about your DAC's input stage and clocking?

    The input stage is every bit as important if not more important than the DAC chip or output stage. A DAC chip can't decode and an output stage can't amplify what it doesn't have.

    When doing the R&D for our Mystique v3 DAC we compared several of the most highly regarded and some fairly obscure USB input boards on identical DACs. We even did blind listening tests. There was so much of a difference between so-called 24/192 USB boards it blew our minds. People that took part in the blind listening tests told us the differences were so extreme that they would have believed that we changed speaker systems or headphones with ones that cost several times the same price as opposed to just changing USB input boards.

    Oddly enough, the consensus least favorite of all the USB input boards was one of the most highly acclaimed XMOS boards (I can't mention names) that used the same XMOS chip, same brand and model femto clocks, and same brand and model IC regulators as our favorite. That just confirms everything I've been saying about the DAC chip being such a small part of the overall DAC performance.

    Our favorite USB input board is this obscure one made by JL Sounds:

    http://jlsounds.com/i2soverusb.html

    Not only does it have excellent performance, it has a built in L and R channel demultiplexer circuit that will allow you to connect it directly to most of the popular R-2R ladder DAC chips, including the PCM1704. Nice feature.

    Just in case some of you are not aware who I am and where my expertise comes from, I'm the owner of Mojo Audio, and my company has specialized in NOS R-2R DACs for nearly a decade. I've personally upgraded the whose who in vintage R-2R DACs and CDPs and personally compared most of the DAC chips, circuits, and component parts people mention in this thread.

    And this past year alone, our Mystique v3 NOS R-2R AD1862 20-bit DAC was awarded:

    "Best Sound" by The Absolute Sound at AXPONA'17
    "Best of Show" by The Absolute Sound at RMAF'17
    "Best Innersound at the Show" by Part-Time Audiophile at AXPONA'17
    "Star Component" by Audiophilia
    "Product of the Year" by Audiophilia

    So it would only stand to reason that I must know a thing or two about R-2R DACs :ksc75smile:

    Please feel free to PM me for more info on DAC chips, op amps, power supplies, input boards, etc.

    Bottom line is that the best 20-bit and higher DAC chips (such as the PCM1704) used in nearly identical circuits with nearly identical supporting parts will have less than a 20% difference in performance.

    Where as the circuits and supporting component parts make up over 80% of any DACs performance.
     
    erin and Wildcatsare1 like this.
  3. glina
    Do you have any measurements to prove this claim? Which parameters exactly have improved by 30%?
     
  4. GearMe
    Well...I don't have the experience that MojoAudio does but I can certainly relate to the USB issue. The biggest upgrade in sound quality from my electronics this year was switching from PC/USB to Network Player/SPDIF (coax). The DACs/Amps remained the same and I was surprised at the increase in clarity!
     
  5. MojoAudio
    The parameters that improve are: time, tune, tone, timbre, attack, bloom, decay, extension, depth, width, and harmonic overtones.

    You can't measure most of these things and the act of measuring them would often corrupt the actual performance.

    What I can say is that half a dozen audiophiles that were part of our blind testing100% agreed with each other as to which products performed better.

    There is an entire facet of the audiophile industry that is dedicated to anti-resonance products. And there are decades of audiophiles that have made claims regarding the improvement in performance of any component with proper anti-resonant treatments.

    My comments in regards to those anti-resonant products was to present them as a more significant performance alternative to a machined aluminum chassis as opposed to debate over the specific percentage of the significance of anti-resonance in general in the engineering of a DAC.
     
  6. Wildcatsare1

    Just wanted to add my 2 cents, first I’ll vouch for Ben’s work at Mojo, I’ve had a couple different versions of the Mystique in house and they are excellent (perhaps the best) R2R DACs I’ve heard. Second, regarding Ben’s input on DAC chips, the PCM63 is the cream of the crop of the vintage R2R chps.
     
    Liu Junyuan likes this.
  7. BucketInABucket
    Wonder how good the current production PCM-56 is in comparison to the PCM-63...I've seen several people say it's basically the same as the 63 but I'm curious as to what you guys think.
     
  8. MojoAudio
    Thanks for the vote of confidence Wildcatsare1.

    Hopefully I'll be able to loan you one of our Mystique v3 DACs to audition and review some time early 2018.

    I've been promising him one for months but we can't even keep up with orders. We've literally sold out of DACs for the year (even my personal demo unit) and we won't be starting another production run until mid-January. We're currently pre-sold out of our Mystique v3 DACs through mid-February.

    But as for the PCM63, I consider that to be the best DAC chip ever made, bar none. It is undisputed the best pure R-2R DAC chip ever made by Burr-Brown.

    Currently we're using another famous 20-bit R-2R DAC chip, the AD1862, in our Mystique v3. The AD1862 is my second favorite DAC chip.

    But I have a stash of PCM63P-K2 chips (yes, even better than a K) I've been saving for a higher priced DAC we're planning for some time in the future :ksc75smile:

    Point being, the difference in performance between the AD1862 and the PCM63 is quite subtle all things being equal.

    How subtle?

    Different anti-resonance products can make more of a difference in performance.
     
    Wildcatsare1 likes this.
  9. MojoAudio
    Hey BucketinaBucket,

    Every connoisseur of R-2R DAC chips I know prefers the original Japanese production of DAC chips as opposed to the modern one.

    This is true of both the PCM1704 and the PCM56.

    This has much to do with RoHS compliancy changing the materials they use.

    Personally I would go for a normal (not K or whatever) vintage Japanese PCM63 over any modern DAC chip.
     
  10. yildiray
    I had responsibility of RF Lab for MRI research.I usually made aluminium and copper shields for low noise preamplifiers so i didn't know the it can be bad shield for DAC.Also i have worked on suppression of MRI vibration.It showed to us increasing quality of image quality.So i will definitely listen your advices for DAC.

    I choosed 1704 because i read many times this chip about excellent sound quality and in best DAC chip lists as you know.I have not read before PCM63 and AD1862 chips as well as 1704.Just i see AD5791.I wonder about your views on this and did you listen it before ?It is also use for MRI DAC applications,it's interesting but i didn't have experience and i don't have circuit for this dac.

    For tube output stage and tube preamplifier examples is aveilable in market like Audio Note DACs.It always attract me and actually it will be first tube experience if i choose tube option.But your findings are extremely logical.I will consider.

    "And then, what about your DAC's input stage and clocking?"

    My first plan to make this design with amanero with an isolator :
    http://www.pavouk.org/hw/modulardac/en_pcm1704.html

    There are all schematic available.Do you have any opinion for it ? Also i should mention that; i will make just usb input and i can change amanero with JL Sounds.You explained it clearly.

    I'm very happy to write my problem here and meet with all of your professional DIYers.I wish you continued your success for Mojo Audio.

    My last says; I just plan to make best diy dac myself without a kit.First i looked for ES9038PRO DAC but circuits not available on internet.So PCM1704 easy to make and everybody say legandary chip.

    My question is electronic parts normally have shelf life.I work on also Product Lifecycle and Electronic Component Obsolescence Management at my job.These kind of obsolute (NOS) electronic parts can be very old.Won't it be problem for working healty?

    Best Regards
     
    Last edited: Dec 19, 2017
  11. MojoAudio
    Hi Yidiray,

    Copper is a much better shield than aluminum, but it is too expensive and too hard to work with for most chassis (too soft to thread).

    The reason aluminum is so popular for chassis has to do with cost to performance, ease of fabrication, thermal dissipation, and anti-resonance properties. Steel is more expensive, heavier, harder to work with, and has relatively bad thermal dissipation and resonance properties. Of course the shielding properties of steel are much better than aluminum for RF and EM noise.

    DACs and phono stages being relatively lower heat than most components can get away quite nicely with an all steel chassis. And because of their sensitivity to noise some companies prefer steel to aluminum for their chassis. My company uses a mixture of steel and aluminum.

    FYI, some of the best vintage Sony CDPs and DACs used copper plated steel shielding panels...likely the best option but relatively quite expensive.

    But these are all "factory" solutions. If you are a DIYer you can use all sorts of adhesive backed advanced shielding and resonance products (some are even both) that can be used in/on a modest steel chassis and yield higher performance than any aluminum chassis. Of course this is too expensive (manual labor) to install and not particularly durable (the adhesive fails) for manufacturers to do.

    I've been considering offering an ultralow-noise version of our DAC with advanced shielding and resonance control sheeting inside the chassis, but it always comes down to my fear of the durability of the adhesives. We're in the process of testing, and I would recommend using, these same shielding and anti-resonance materials with no adhesive backing and then using a high-temp epoxy cement to bond them to inside of your chassis.

    As for chips and board...

    It is rare that the best or the best value products are the ones that are recognized as such.

    Point being of all the whose who and obscure USB input boards we tested and did blind listening tests on the Amanero was the least favorite. So much so that no one ever asked to hear it twice. Performance was not even close to our top three favorite USB boards.

    Schematics for most DAC chips are on their data sheet: that is what I would recommend using.

    The big difference would be:

    1. Quality of parts.
    2. Quality of power supplies.
    3. Quality of shielding and anti-resonance.

    As I keep saying, the PCM1704 is not an R-2R DAC chip, but rather a hybrid DAC chip. Yes, it is "legendary" but that is mostly because it is one of the few vintage DAC chips that are still being manufactured, and it is used in so many modern DACs. Few people that we'ren't audiophiles 30 years ago have ever heard a PCM63, so few people have compared the PCM63 to the PCM1704.

    In terms of "shelf life" I've never heard that in terms of individual DIY parts. I would imagine that the paper tape that feeds reels of modern parts into robotic assemblers would have a shelf life, but I've not heard nor experienced that with solid-state parts or ICs. Yes, the contacts could oxidize, but that can easily be corrected.

    Polymers, adhesives, untreated paper, and other materials do have a shelf life. I've even experienced some of the polymer bases on NOS vintage tubes becoming brittle with age. But parts made of ceramic, silicone, and metals have a considerably longer shelf life.

    We've sold quite a few AD1865 and AD1862 vintage DAC chips over the past decade and we've rarely had a DOA IC and I can count on one hand with fingers left over the number of these vintage DAC chips that have failed in nearly 10 years of use by customers. And most of those died because of power surges (lightening) and static, not because of age.

    You mentioned the Audio Note AD1865 DAC. Certainly an iconic NOS tube DAC. Personally I find it to have the most colored, veiled, romantic, attractive distortion sound I've ever heard in a DAC. To me (just a matter of personal taste) the Audio Note NOS Tube DAC is "too much of a good thing" like that rich desert you take a bit of and love but by the third bit you don't want any more. Of course some people prefer the Audio Note sound, just like some people would eat their overly rich desert and finish the rest of mine :triportsad:

    Personally I find you get much better performance combined with just the right amount of that attractive distortion and romance so many of us like from an ultralow-noise solid-state DAC playing through a good SET amp. To me that's the best of both worlds. And that would be exactly what we are doing to win all those awards at audiophile shows: our solid-state R-2R NOS direct-coupled DAC playing through an insanely good Exit Level Audio Annapurna SET tube headphone amp :ksc75smile:
     
  12. glina
    My current DAC is the old generation Audio Note DAC3 based on 2x PCM63-K chips. I have converted it to USB input by removing the SPDIF receiver and digital filter and feeding the DAC chips with right justified serial data as decoded by the above mentioned JL Sounds USB interface. It's an amazing piece of hardware indeed.
    This DAC is nothing like MojoAudio described. Not veiled, not distorted. Very lively and dynamic would be my description, also fantastically detailed in a totally non offensive way. I would not really recommend anything based on the ESS Sabre. None of the applications I've heard come close to the tonally rich presentation of the PCM63-K or even plain TDA1543.
     
  13. MojoAudio
    Yildiray, if I had that Audio Note DAC you described I wouldn't be looking for a totally new DAC but rather to upgrade that DAC.

    You could:

    1. Upgrade the power supplies and add a dedicated power supply for the JL Sounds USB card.
    2. Upgrade the shielding and anti-resonance both inside and outside the chassis.
    3. Upgrade parts in the signal path, such as connectors, hook up wire, coupling capacitors, op amps, resistors, etc.

    You already have a world-class R-2R DAC - one of the best ever produced.

    Upgrading those areas would take you to that "rare air" level of performance :ksc75smile:
     
  14. glina
    This is the most absurd thing I've read in ages. Did you just claim relativistic effects for measurement of audio frequencies?

    While I wont argue that the PSU can always be upgraded, as I have done that indeed, your suggestion of upgrading opamps (on an Audio Note tube dac) or hook up wire (already pure silver) makes me question you actually know anything about that device.
     
  15. yildiray
    Why ? Don't you believe double slit experiment for quantum mechanics ? : )
     
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