Raspberry Pi I2S to SPDIF Hat

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

  1. earnmyturns

    earnmyturns Smartest friend

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    Update on piCorePlayer standalone music server: Thank you again to @hifiandrun and @lehmanhill for all the suggestions. My standalone system is working stably. To summarize for others who might be interested, here's what I ended up doing. I'm writing this from memory as the device is at work, so there might be something missing/incorrect. YMMV.

    1. Music server hardware: Pi 2, AdaFruid 7'' touchscreen, SmartiPi stand, Pi2 Designs 502 DAC. Music storage: Samsung 1TB USB-C SSD. Power supply (likely overkill): sBooster ECO 5-6v LPS.
    2. Software: piCorePlayer 3.5.0.
    3. After downloading and unzipping, used Etcher on my Macbook Pro and a SD-2-microSD carrier to flash the piCorePlayer image onto a 64GB SanDisk microSD.
    4. Inserted card into Pi 2 microSD carrier, reassembled the unit, connected it to LAN, DAC, USB SSD, and power.
    5. On boot-up, boot messages on touchscreen are upside-down. Don't worry, it will be solved later.
    6. Connected to piCorePlayer with Web browser (Chrome) from my Macbook Pro. For convenience (and will come especially handy later), I assigned a fixed IP on my LAN to this device, which is really easy to do with the Web interface to the Ubiquiti EdgeRouter that manages my home LAN.
    7. Enabled Beta software on the main piCorePlayer control Web page. This will come in handy later.
    8. Using the piCorePlayer Web interface, installed LMS. This requires resizing the boot partition, which involves several rebooting dialogs, and then actually installing LMS.
    9. Set up your preferred name for the piCorePlayer, and also tell LMS about it on the LMS configuration page. Mine is "Ebnefluh," after a memorable ski tour I did in April (Google it!)
    10. Make sure that the LMS flag to bypass mysqueezebox is set and saved.
    11. Install jivelite package to manage the touchscreen.
    12. Once that is installed, use its configuration page on your browser to adjust screen rotation. In my setup, I had to flip upside-down.
    13. Use the LMS Web interface to tell LMS where your music library is in the USB drive, and to get it to index it. There's a page that shows indexing progress. If you did 9 above, you won't be prompted to get a mysqueezebox account.
    14. Wait until your music is indexed. In my case, this stopped somehow, and I had to poke it on the LMS Web interface. But it got done.
    15. Now you can test that you can control play to your DAC from the touchscreen. Enjoy testing with some known tunes!
    16. Just to be sure everything so far is remembered, use the "Backup" option on the piCorePlayer control page to save your current configuration to the microSD card.
    17. The final step is to make your device work standalone. On the beta options on the piCorePlayer control page, click to set a fixed IP address. That gets you to a network configuration Web page. Set DHCP to off, enter your fixed IP address, netmask, default gateway, and default DNS. You should set this to what you have on the LAN you are configuring the device on, so that it talks correctly to it when you bring the device to it for software updates etc.
    18. Backup your whole configuration again to microSD. This is critical!
    19. Shut down the device, unplug it from power, and let it rest for a while so that its RAM resets. Also unplug it from your network.
    20. Power up the device again. Once it is up, you should be able to access your music and control play from the touchscreen.
    21. Troubleshooting: at step 20, if you see a boot-up message that the device is waiting for network and that stays for a while, outputting periods on the screen, that means that you did on 17 did not stick, probably because you forgot to backup the configuration to microSD before power down. If that is done correctly, the network should come up right away, and LMS will also boot-up quickly. If not, after the long failed wait for network, LMS will not spin up and Squeezelite won't find your music.
     
    Last edited: Jul 25, 2018
  2. lehmanhill

    lehmanhill Almost "Made"

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    Just to round out the conversation, I asked the Metrum designer, Cees, on the Metrum Acoustics forum about the two voltages. I have one of their DACs on order, so I'm kind of interested. I'm afraid his response doesn't match what you and I have been saying. Quoting his reply;

    "Both voltages is no problem from a technical point of view but 0.5 Volt PP will be better as we have optimized for the standard levels."

    I'm not sure how it might have been optimized, but it is consistent with other Metrum forum posts. Metrum designs and develops DACs to strictly meet the technical standards so that they don't get user problems. I can't fault them for that.

    I suspect that your experience is typical, but the Metrum response opens up the possibility that using the lower voltage may be the best choice with some DACs. Actually, its great that you have the option of two voltages. It gives people options for different set ups.

    For clarity, I used the specs in this Rane document in my discussion on the Metrum forum. These numbers are a little different than we've been discussing, but close enough.

    https://www.rane.com/note149.html
     
  3. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Hmm, perhaps I was hasty in removing the option in the latest rev. I would love to hear from anyone who has connection issues over coax. It is possible that this is at the root of the issues that astromo mentioned a few posts back. If ti is, or if anyone else posts about this issue then I will certainly put the option back for the next build following this one that is already underway now.

    BTW, SPDIF over coax @ 0.6V is the consumer standard, but the pro audio standard is 1V. That's why we originally had the two options. Can you ask Cees about this?

    Michael
     
  4. lehmanhill

    lehmanhill Almost "Made"

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    I was the one that mentioned 0.5V that I found in the Rane document. I'm curious about this level. Most documents I find on the subject don't address the level. The Rane document I linked (see below) is considered pretty authoritative. Their table shows more kinds of interface than most and they reference SPDIF as 0.5V nominal, 0.6V maximum. I find it interesting that they talk about AES3id as an unbalanced connection with 1.0V level. I hadn't been aware of that one.

    https://www.rane.com/note149.html

    The next best reference I found is this link. It seems to be based on IEC958 standard and they reference "about 500 mV for coax interface. They also list 0.5 to 1.0 for SPDIF (maybe consumer and pro?).

    http://www-inst.eecs.berkeley.edu/~cs150/fa01/labs/project/SPDIF_explanation.pdf

    As you say, you found other standards. It seems clear that 0.6V should be fine. Even the 1.0V.

    Were I in your shoes, I would put the option back in, assuming it doesn't cost much. That gives your customers more options if they run into compatibility issues. But then again, I don't think you have had any issue that you can trace back to the high voltage as an issue.

    Jac
     
  5. doozboo

    doozboo New

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    Got this issue in early indiegogo release. I've modded my setup with insulating tape on top of the Pi USB shield ;)
    Michael, is this possible to install quality bnc inlets in next releases? I'm not talking about this ridiculously overpiced audiophile stuff, but something like Canare BCJ will be much better.
     
  6. bilboda

    bilboda Florida boomer

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    My Modi Multibit ran fine at 0.6 volts but my Soekris 1321 did not. I had to increase it to 1.0 volts. The designer admits his spdif is a bit sensitive. Maybe he will change it in future builds. So, having the option was really a big plus for me. I did not try the Modi Multibit at 1.0 volts because it was already working.
     
  7. earnmyturns

    earnmyturns Smartest friend

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    My Soekris 1541 works fine with the default 502DAC voltage, via BNC+coax.
     
  8. astromo

    astromo New

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    Apologies. I've yet to report back. I've had a DIY PC build go pear shaped on me and I've been sucked down the vortex trying to work through that piece of joy.

    I did trim the BNC connectors as suggested, because on close inspection the blobs of solder looked like they were a gnat's 4-skin away from touching the top side of the LAN connector's metal housing.

    However the behaviour of intermittent audio with SPDIF Optical selected did not resolve.

    I've yet to check the other HAT. Maybe this weekend.
     
  9. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Thanks. I will look at that. I agree that most of the adapters out there ate not of the highest quality, and so we took a chance on a particular vendor. And in all honesty, I looked at it as a bit of a throwaway and did not put the amount of time and effort into it that I should have. I greatly appreciate all the feedback.

    Michael
     
  10. bigbear1997

    bigbear1997 Acquaintance

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    Btw, can I get a confirmation that the 502DAC board works with the new RPI 3B+ ?
    Plan to upgrade to the B+ :p
     
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    It should, but I will need to get a 3B+ to test with. Give me a few days.

    Michael
     
  12. haywood

    haywood Friend

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    It does. Just make sure your distro is up-to-date and supports the 3b+.
     
  13. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Thanks for the update. I figured as much, as it was the same when the pi 3 came out.

    Michael
     
  14. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Just a heads up that we are testing and finishing and will be shipping the current batch of 502DAC’s by the middle of next week. We have also put another 20 in the store for pre-order. I think two are already gone! Anyway if you or your friends are looking to get another board now is the time.

    Regards,
    Michael
     
  15. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Well, those 20 went fast! We are now buying the parts to build a batch of 100 in about 4-5 weeks. Maybe that will catch us up!

    Thanks for all the great support!

    Michael
     
  16. HumanFly

    HumanFly Acquaintance

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    I think by now it`s safe to say that nothing sat longer on top of my pi than the 502. Still enjoying it and nothing better came along sofar. So thanks again!
     
  17. bigbear1997

    bigbear1997 Acquaintance

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    Still using it on a daily basis.
    1 thing I noticed is the coaxial contact is week. I will lose the connection if I touch the coaxial cable at the 502 end.

    I am not sure if it is the bnc to rca adapter or the bnc socket itself.
     
  18. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    It is most likely the BNC to RCA adapter. As I mentioned earlier they work the highest quality, and I unfortunately looked at them it’s just sort of a throwaway. I did not fully understand how many people only used a RCA. We are looking for better adapters, but ultimately RCA will always be a wesky link, no pun intended.

    If you have Amazon prime it is pretty inexpensive to buy a pack of five and just replace them as they wear out.

    It’s very unlikely that we will put down a BNC future projects. Instead we will put a high-quality switchcraft RCA gold plated.

    How about it informal poll? How many people would prefer that we do that for the next revision? I realize it may not fix your problems, but at least it would end the issue going forward.

    Thank you again for all the great feedback.

    Michael
     
  19. Scott Kramer

    Scott Kramer Friend

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    upload_2018-7-25_21-4-50.png
    upload_2018-7-25_21-5-8.png
    Screen Shot 2018-07-25 at 9.19.53 PM.png

    The 502's a pretty serious board to get rid of BNC. I'd toss the AES/XLR before that (and you don't want to do that!).

    Another option for the 502 as it is-- get a proper pure BNC spdif cable, that includes adapters. Then you could mix and match: BNC:BNC BNC:RCA RCA:RCA.

    Love this edge BNC connector, robust as hell (board pictured is @Michael Kelly's 1 competitor lol)... here they were serious about bnc, then added RCA (stepped down to 0.7 volts) as a throw-away convenience connector.
     
    Last edited: Jul 25, 2018
  20. haywood

    haywood Friend

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    Keep it as-is and recommend people spend $20ish and get a BNC -> RCA cable.
     

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