Raspberry Pi I2S to SPDIF Hat

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Michael Kelly, Apr 30, 2016.

  1. earnmyturns

    earnmyturns Friend

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    Curious about the meanings of 502DAC LEDs, which are not explicitly explained in the datasheet or in the reference manual. As currently operating, I see the red and the green LEDs on, the yellow one off.
     
  2. dBel84

    dBel84 Friend

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    It is in the manual

    - red = std 44.1KHz
    - Yellow = High bitrate
    - green - power is on
    ..dB
     
  3. earnmyturns

    earnmyturns Friend

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    I guess so if you combine the schematic in Figure 1 with the specifications for GPIO3 and GPOI6 on Table 3. A bit cryptic, though ;)
     
  4. dBel84

    dBel84 Friend

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    it's all cryptic to me :confused: ..dB
     
  5. bilboda

    bilboda Acquaintance

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    for the 502dac amateur, er, I mean not pro
    - red = std 44.1KHz clock in use, lights for 88.2, 176.4 as well 22.5792Mhz clock
    - Yellow = High bitrate 48khz clock in use, 96 and 192 too ... 24.576Mhz clock
    - green - power is on
     
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  6. SoundSound

    SoundSound Rando

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    "I wonder how much better the 1000euro and up highend streamers sound when paired with the Yggdrasil."
    Yes, indeed!
    Let us consider two simple use cases (RPi is controlled over Ethernet and DASD with Hi-Res files is attached to RPi):
    1. RPi + 502DAC (AES/EBU out) + into Yggdrasil (USB Gen 5)
    2. RPi (USB out) into Yggdrasil (USB Gen 5)
    Is there any objective evidence the signal Yggdrasil outputs would be different in case 1 vs. case 2?
    In case there is a difference, I would certainly like to know the reason... Shared bus for the Ethernet and USB in current RPi implementation? Something else?
    Please chime in!
     
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  7. bigbear1997

    bigbear1997 Rando

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    1. On the Yggdrasil, AES is consider better than USB gen5 & Coax. while USB gen 5 & Coax are considered the same SQ.
    2. Rpi3 has shitty USB bus which share the same bus as Ethernet. If USB on Rpi3 is that good then no one will be buying any Rpi Digi hat.

    Conclusion 1 will be better than 2.
     
  8. zeed

    zeed Rando

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    @Michael Kelly, do you know approximately when the 502DAC hat will be back in stock?
     
  9. SoundSound

    SoundSound Rando

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    Thank you Bear for the input. Appreciated.

    I have seen anecdotal accounts coming to the same conclusion. What I am looking for is objective evidence in favour of one or the other configuration.

    I have a gut feeling you maybe right…

    Please chime in!
     
  10. SoundSound

    SoundSound Rando

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    502DAC board is equipped with a couple of oscillators for 44.1kHz and 48kHz families of sample rates.

    I wonder if @Michael Kelly would be kind enough to provide some data as to the "typical phase jitter" on these chips?

    I would expect it to be measured on the order of a few hundred femtoseconds at least, but I maybe wrong…
     
  11. HumanFly

    HumanFly Acquaintance

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  12. SoundSound

    SoundSound Rando

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    Thank you Human!

    I am sorry, I couldn't find any data on jitter there... Did I miss it?
     
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  13. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Soon. Our biggest issue has been the NDK low noise clocks. 6 months ago there were plenty available, but they have slowly dried up. We recently found another source, though they cost us $6 USD per clock instead of the $2 USD we were paying before! So that sucks, but not enough to prevent us from buying them. Long term we will end up buying two full reels direct from NDK at $3K USD per reel.

    Anyway, once the clocks show up we will get the boards finished up and in stock. I wish I could give a hard date, but that seems to be impossible to predict!

    Cheers,
    Michael
     
    Last edited: Jan 13, 2018 at 4:12 AM
  14. earnmyturns

    earnmyturns Friend

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    Looking for power supply suggestions: in the interests of desktop tidiness, I'm powering the following with a single 3A USB SMPS: Pi 2, PiTouch, 502DAC, and WD Elements drive containing my music, all with a WD PiDrive cable. But RuneAudio is warning me of low voltage (lightning bolt on screen) intermittently, so I guess 3A is marginal for all this stuff. Should I give up on trying to power everything with a single power supply?
     
  15. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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  16. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    FYI the 502DAC uses .5A max. Happy power budgeting!

    Cheers,
    Michael
     
  17. SoundSound

    SoundSound Rando

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    Thank you @Michael Kelly for the info. Much appreciated. Looks like NDK NZ2520SD series is a good choice for the application. Get the boards finished up and in stock: I am positive they will just fly!

    This makes me wonder why a respected forum member noted in another thread discussing RPi + HiFiBerry Digi+ Pro that "This solution is best suited to driving inexpensive DACs like the Mimby and the Bimby. ... but once you're into four digits for your DAC, you can probably justify a more expensive source. If you are using a Yggy or similar, you probably already have a kickass AES source, and probably don't need to read this, unless you fancy tinkering with a tiny second system."

    RPi + 502DAC is "a kickass AES source"! Why would anyone want to spend $$$ on the likes of ARIES escapes me...

    I do apologize if I am seriously out of the line here, but my inquisitive mind just wants to know...

    Please chime in!
     
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  18. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Yes, welcome to the wonderful world of audiophile nonsense! in all figured out, sound reproduction is incredibly complex. There is so much about how the human ear and brain combine to interpret the sounds that we do nit fully understand. Our human system has been developed over millions of years to interpret the world around us. Predators, prey, lovers, children etc. all have a sound signature that we are wired to listen for.

    Music, in all it’s beautiful complexity and I daresay magic, is simply not measurable! As an engineer I follow certain sets of rules and engineering principles that when executed properly provide for a very good experience. But in no way perfect.

    This is why different systems have a different effect on different people. How’s that for vagueness! But into this somewhat undefinable space step unscrupulous and/or ignorant vendors who are happy to allow you to associate more money with better something. And, unfortunately, users who cannot be sure of vendor claims often follow word-of-mouth and anecdotal information from others. Unfortunately, users who cannot be sure of vendor claims often follow word-of-mouth and anecdotal information from others. This is very reasonable, but it also means some users claim a mantle of authority that perhaps they shouldn’t have.

    To your point though, with digital (AES) transmission we have a little more clarity than we do with analog. This is because the source material has been encoded into a fixed format. If we transmit that data to another entity with the exact same bits and at the same sampling rate, then we have performed our function 100%. Another source and transmission vehicle can perform the same results, but it cannot do better. In this case the knob does not go to 11!

    If the raspberry pi combined with our 502DAC sends 100% accurate digital data to your DAC, then no other device will be better. In this area have provided objective measurements that show all 24-bits are sent from our device accurately, without fail. Nuff said!

    Cheers,
    Michael

    PS sorry if this is a bit of a rant.
     
    Last edited: Jan 13, 2018 at 10:27 AM
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  19. SoundSound

    SoundSound Rando

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    This should nail it for everybody! Thank you very much Michael!
     
  20. JuleZ3C

    JuleZ3C Rando

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    Hello Michael,

    After many months of nonstop happy usage, I'm having troubles with my 502DAC pro (rev. P3) that I'm using with piCorePlayer/Squeezelite.
    I can't remember something of interest prior to not being able to play music anymore.
    The symptom is Squeezelite not being able to run. I've tried to get it to run by messing with parameters to no avail (autonomous update of piCorePlayer and Squeezelite among others), even thought LMS was crapping itself (never before did I open the server's log, thought
    Slim::Networking::UPnP::ControlPoint::_gotError (289) Error retrieving device description: 500 Internal Server Error
    was the culprit, but nope)
    I then burned a new image for the pi to execute. Still no way for Squeezelite to work.
    In despair, I put my 'old' HiFiBerry Digi+ Pro on the pi, works like a charm.

    502DAC is powered (green light ON, and pi is booting (powered through the 502DAC)), and no component smells or looks like it overheated... and that's about all I can say in terms of debugging the thing.

    Any help would be much appreciated.
    Thanks!
     
    Last edited: Jan 14, 2018 at 8:56 AM

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