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Massdrop x Airist Audio R-2R DAC: A Discrete Resistor Ladder DAC For $350

Discussion in 'Dedicated Source Components' started by jude, Jun 4, 2018.
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  1. sosolar

    Also, I doubt the THD spec.
    How about to post FFT result, let customer see if it is that low level.
    Once using that noisy power source, it is really difficult to achieve -118dB SNR. For my design, it can go deep to -140db@1k further(fully tested). Just one bulk more.
  2. Baten
    That's good specs. One bulk more ?
  3. sosolar
    My design cost one more buck than airist, 350 times or 22db lower noise.
    CrownLands likes this.
  4. CJG888
    Is it available on Taobao?
  5. sosolar
    Yes, you can find that. However, I dont recommend to use tht old one. We developed balanced version with much faster firmware(PCM32x) installed, will release this August in Hongkong Exhibition.
  6. CJG888
    Will this be a board or a finished DAC with case and PSU?

    The idea of a balanced output looks interesting...

    Will it take a direct I2S input (from my modified Shinrico D3S)?
  7. sosolar
    Got that. Thank you very much. To be honest, I got the same result using QA400. But becareful, using 0.1%resistor could worse 10db at least. I presume that they are using 0.05% the same as.
    bunkbail likes this.
  8. Inorbit8
    I'll be in Hong Kong around that time. What's the name of the expo and the dates? Would love to go take a look.
  9. randytsuch
    My opinion, FWIW, layout is obviously a copy. They even used the same connectors, and located them in the same places. I can't believe this was by coincidence.
    Only way to know about the trace routing is if both companies provided the routing, and someone compared them. Would be easy enough to do.

    And in the end, afaik, Soekris came up with the general idea first, and others have copied his idea of using a FPGA to feed shift registers tied to precision resistors to generate the output waveform. People copy ideas all the time though, no laws against that.

    But, I always thought the real magic and the most important IP for this type of DAC was in the FPGA. I would expect companies to lock the FPGAs, so you can't read what's inside, and so you can't steal this IP.

    Would also be really interesting to see if anyone gets both, and compares the sound.

    Also, would be great if the board was sold on Aliexpress, opens it up the DIYers who want to experiment with it.

  10. sosolar

    Some of my customer have done so much expriment on it, says Li-on power supply, direct transformer output bypassing opamps, insanely pricy silver foils capacitor, metal-can OpAmps, LPF alterations, reclokings, better isolations....so much creative ideas. All of them are enjoying DIY.
    That exactly is the scene we want to see.
    Sapientiam and XERO1 like this.
  11. SamusAran
    I might be wrong, but I was under the impression that the connectors were not located in the same places. Someone can correct me.
  12. randytsuch
    If there was an english website, either ebay or ali that had your modules, I think it would open it up to a lot more diy'ers

    Looking at the pic here

    Comparing the black board on far left to the hibiki red board, connectors look the same. The spacing between connectors is slightly different though.
    Now I wonder if the pinouts are the same?
  13. Zachik
    June 7 update (relative to my original post #3 in this thread):
    OK, so I had the opportunity to spend more time with the RDAC, get a high-quality switcher for better A/B with other amps, so following are my impressions.

    Initially, I theorized the volume is higher from the RDAC compared with my Metrum Amethyst DAC. It has been confirmed that RDAC outputs 2.5V whereas the Amethyst is outputing 2.0V
    I wanted to further verify those spec numbers, so using my iPhone 6S with SPL meter app, Sennheiser HD600 headphones and a 1KHz tone playing... I confirmed that when RDAC fed the amp - the volume level was almost exactly 2dB louder. Tried various listening levels and the 2dB was pretty consistent. Introducing a passive preamp between RDAC out and amp input, volume knob max'd - the volume dropped by 2.5dB. So now, difference between 2 DACs is 0.5dB (this time, the Amethyst is the louder one, but only by 0.5dB).

    Now, that I have a more even field signal levels feeding my A/B switch, I was ready to repeat my comparisons.

    Let me recap my 2-DAC setup:
    1. Mac mini -> USB cable -> Gustard U12 -> Coax cable -> Metrum Amethyst -> A/B switcher -> amp
    2. Mac mini -> USB cable -> Gustard U12 -> SPDIF (optical) cable -> RDAC -> passive preamp (to lower voltage) -> A/B switcher -> amp

    The bold components are shared between 2 audio paths.

    This time around, I have used Massdrop's LCX and CTH amps, as well as the Schiit Lyr3 (with stock Tung Sol tube).
    I have used both the HD600 headphones as before, but also Mr. Speakers AEON Flow Closed.

    After spending several hours, listening to MANY tracks from various genres (but mostly Rock, Pop Rock, Heavy Rock, Metal) here are my observations:
    a. In most tracks I could NOT hear any difference at all. Switching back and forth (using the A/B switch, mid-song) I could not even tell the DAC was switched..... Just identical.
    b. In very few tracks, the male and female vocals sounded tiny bit different. I thought the Amethyst might be a tiny bit more detailed? or maybe better dynamic range? Again, VERY small difference. Would never have heard it if not A/B during playback with a switch that takes zero time to change source.
    c. In other very few tracks, the RDAC sounded a tiny bit better. Trying to describe it I would say maybe the whole presentation felt like fuller / thicker sound. So for those very few tracks I would give the tiny edge to the RDAC.

    I must caveat that my hearing is good but I do NOT have golden ears, and I was never musically trained. So others with better hearing or golden ears might hear things I do not.

    MY conclusions:
    1. Both DACs sounded great! Very natural and musical. Not dry or analytical. Both made me want to keep listening to the music :)
    2. Those observations did not change much switching between amps and headphones. So, I do not think it is a synergy thing, but a real (tiny) difference.
    3. Knowing the sound difference is almost non-existant, and knowing the price difference is 3x between those DACs - I have no problem saying that:
    If I were in the market today for a DAC, with a budget of $1000 - I would absolutely buy the RDAC!
    (and it absolutely is worth the 6 months wait)
    Josh Englert and maximus69 like this.
  14. maximus69
    Thanks for the continued updates!
  15. maximus69
    Thanks for update...i am looking forward to watching things unfold
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