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New Audio-gd R7 (R2R 7) & R8 Flagship Resistor Ladder DACs

Discussion in 'High-end Audio Forum' started by Currawong, Jun 30, 2017.
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  1. FredA
  2. DACLadder
    Verify power requirements as it seems to be 220V only.
     
  3. LarsHP
    Note that the R2R 15 does NOT have the FPGA technology. This is from the Audio-gd R2R 7 page / description:

    R-2R basic design in the market:
    The R-2R DAC is very popular nowadays and available from DIY kits and completely up to of the shelf high-end products. In the low range DIY market, the R-2R design is often based on old technology designed a long time ago by MSB and only includes basic R2R ladder design and do not include the wonderful correction design of the original MSB technology. This design uses data shift registers logic chips in series mode to convert the data to an analog signal. The structural R2R technology issues cannot be avoided, and performance is solely depending on the accuracy of the ladder resistors.

    In the High-End of the shelf (finished products) market, the R2R design is much more complex only to reach best performance. A basic R2R ladder is simply not sufficient enough to achieve good performance and sound quality! Some manufacturers are using shift registers design. A less complex and less performing design based on traditional logic chips working in serial mode to correct the ladder.

    A far better design switches resistors in parallel mode. An ultra-fast FPGA controls and corrects the R2R ladder. The parallel design mode controls every bit respectively and therefore achieve unprecedented performance. (In parallel mode only 1 clock cycle is needed to output all data; serial design mode needs at minimum 8 up to 24 clock cycles) The parallel design is much more complicated. Once designed properly it can correct every bit of the ladder. Photo below shows a design with such FPGA, can correct the unavoidable imperfections of the R2R ladder caused by tolerance of resistors, glitches to achieve best performance.

    Accuracy of the ladder resistors (tolerance):
    Many people believe the tolerance of the resistors in the ladder is most important to reach best performance. Nowadays 24 bit resolution is standard. What tolerance is needed to achieve 24 bit resolution?
    When we look at 16 bit the tolerance of 1/66536, 0.1% (1/1000) is far not enough, even a tolerance of 0.01% (1/10000), the best tolerance available in the world today, still cannot handle 16 bit request correctly; we are not even calculating 24 bit here!
    The tolerance of the resistor will never solve Imperfections of a ladder. This would require resistors with a tolerance of 0.00001% and can handle 24 bit resolution. This is only in theory because the discreteness of the switch logic chips have already too much internal impedance and will destroy the impossible tolerance of a resistor.
    The solution is to correct the ladder and not only depend on the tolerance of resistors. It’s a combination of both: Ultra-low tolerance resistors controlled by a correction technology using very high speed FPGA are applicable in in our design.
    Importunacy of the FPGA in the R2R 7: FPGA stands for Programmable Array Logic.
    Nowadays the FPGA is applied in a lot high end grade DACs; like the popular ROCKNA WAVEDREAM DAC.
    The internal hardware design is fully controlled by complex software. A huge advantage is the fact the software in the FPGA can easily be upgraded offering new features or improve the performance. Such design is much flexible and future proof!

    FPGA tasks in the R2R 7

    The FPGA in the R2R 7 is responsible for:
    1. High performance SPDIF interface, replacing traditional less good performing SPDIF interface chips like DIR9001, WM8805 or AK411X,etc.
    2. Full re-clocking process with FIFO design applicable on all inputs. This way the output data keeps fully synchronized with the clock signal to reject any jitter.
    3. Built in 2X, 4X and 8X oversampling and digital filters and on top of this 4 different true NOS (only analog 6dB filtering) modes. To completely configure it to your liking!
     
  4. Hardtrancing
    This DAC looks very interesting. I am wondering though how it would compare to something like the new NFB-7.77 with dual ES9038.
     
  5. FredA
    The r2r 15 can't compare. But it has the r2r sound.
     
  6. FredA
    Yeah. Thanks.
     
  7. Wynnytsky
    makes two of us

    There should be a Tinder for our audiophile components. I should be able to search for the closest 7.77 that's interested in having a dance-off with my R2R7
     
    XVampireX likes this.
  8. drez
    How far is from NJ to Sydney Australia?
     
  9. Wynnytsky
    google maps tells me flights start at $1462 -- hmm that's the price of a Pontus

    in hindsight I should have volunteered to be an unpaid intern in Kingwa's lab, in exchange for the flight ticket
    They'd soon realize the only thing I'm qualified to do is break in DACs and order Chinese food
    A week of that and I'd have my answers
     
    drez and Currawong like this.
  10. barbas
    Hi everybody. First post over here. I'm very interested in FredA and Currawong (or anybody else owning an R2R 7) opinion and findings with the new AGD Dac. I now own an AGD Ref 5.32 upgraded to NOS and Amanero USB (very happy with R2R and NOS), thinking to upgrade this month to either R2R 7, Holo Spring L3 or Denafrips Venus (almost same price level). Anybody could please help me with my choice? Many thanks!
     
  11. FredA
    According to a review from the Netherlands (I posted a link in this thread), the r2r 7 beats the Spring Dac level 3. As for me, I can tell you the r2r 7 has a level of resolution that is very high. And a stereo image that is really tridimensional and very accurate, wide and deep. But I think my dac still need some burning time before I can give my final impressions on it. It is still improving after 800 hours. On some nights, it is perfect. On some other nights, i think i would prefer my old master-7. When it's perfect, it is clearly better and more enjoyable than the M7. The level of resolution is mind-blowing.
     
  12. barbas
    Thank so much for your reply FredA. Strange thing that after all that burning time the unit is still so volatile that you may still prefer your old M7.
     
  13. FredA
    Well, on every night now, the r2r 7 has the edge as far as resolution and soundstaging are concerned. I am just talking about overall enjoyment. It depends on the balance.

    Even with my M7, the sound was not exactly the same on every night. This is to be expected with cell towers around.

    Another important thing to consider: the M7 is a great dac using a great chip.

    And at last, the r2r 7 should take longer to settle than the M7, which took over 800 hours.
     
    Last edited: Aug 9, 2017
  14. Wynnytsky
    On the Summarize screen Kingwa says...
    "After d/a conversion by the R2R D/A modules the analogue signal is transported by fully discrete matched-transistor output stages. DC-coupled design with first class through-hole components"

    For me DC coupled amps have always been more immediate/present/there (ex: Job 225, Exposure 3010s, Parasound JC1) but they hear everything in my grid. There could be a dimmer lamp running on a different circuit on a different floor sending a slight buzz out my 105dB speakers (probably undetectable on speakers in the low 90s). Once DC is leaked into the AC lines those amps will tell you. I thought my amp was defective because a Bryston B60 didn't exhibit this. Usually the fix is to lift the amp's ground (3=>2 pin adapter) or find the offending dimmer and making it 100% or off.
     
  15. FredA
    I bought a balanced isolation transfo on ebay two months ago. Things are much more equal since then. Pretty good transfo, except for the fact there is some slight humming from It
     
    Last edited: Aug 9, 2017
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