Raspberry Pi I2S to SPDIF Hat

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

  1. Ksaurav402

    Ksaurav402 Friend

    Pyrate Contributor
    Joined:
    May 7, 2019
    Likes Received:
    2,062
    Trophy Points:
    93
    Location:
    NY
    So if we order acrylic case now, will we get the new one with RJ45 cutout and easy access to SD card
     
  2. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    yes
     
  3. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    Photos of PI2AES case with PI4 + AKM DAC (left) and PI3 with RJ45 I2S (right)

    [​IMG]

    [​IMG]

    [​IMG]
     
  4. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    Working on a case for the PI2AES and Raspberry 7" display. Below are some 3D captures. I need to order a display before I cut the case for real. One item in question is the RJ45 adapter. Currently the connector comes out the rear of the case, but the display case rear panel is set away from the board. I was thinking of turning the RJ45 connector to come out next to where the optional AKM DAC RCA jacks come out. This would mean two different RJ45 boards depending upon what case you ordered. Or changing the existing case (again) and RJ45 adapter to make it come out the side. Of course it does not help that I just ordered 100 sets of the latest case design! Oh well, I can make that switch and make the needed pieces here.

    Here are the snapshots. Note that final case will be clear. The colors here are just to make it easy to see the notches and tabs.

    [​IMG]

    [​IMG]

    [​IMG]
     
  5. StageOne

    StageOne Friend

    Pyrate
    Joined:
    Sep 23, 2018
    Likes Received:
    1,121
    Trophy Points:
    93
    Location:
    US
  6. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    Understood. It is my plan to use a longer 3rd party fpc cable since there’s nothing magic about the cable they supply. I know others have used it at longer links, that I have to do some research to make sure I stay within operational boundaries. That’s part of what testing will reveal.

    Thanks for the heads up though!

    Cheers,
    Michael
     
  7. joch

    joch Friend

    Pyrate Contributor
    Joined:
    Oct 8, 2015
    Likes Received:
    1,397
    Trophy Points:
    93
    Location:
    the other side of the big ocean
    @Michael Kelly would you consider some vents on the plexi panels? The Pi 4 runs a bit warm.
     
  8. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    If you look at the captures I posted you’ll see that there’s a fair size gap between the display and the top shield, because of the display interface board. But this is also a good spot for heat to vent out.

    It’s certainly something we can adjust over time but every opening takes a certain amount of time on the laser cutter and if it’s not necessary I’d rather not do it.

    Michael
     
  9. edd

    edd Almost "Made"

    Contributor
    Joined:
    Nov 18, 2015
    Likes Received:
    463
    Trophy Points:
    63
    Location:
    california
    That looks great and something I'd snap up in a second. I'll second @joch 's suggestion regarding ventilation, and quite honestly, I think it would be fine if you just left the back & sides more open in general, so the case can accommodate any future HATs. When people like me use cases like SmartiPi, the entire HAT ends up being exposed anyway. And, as someone who uses their Pi as a standalone/non-networked device, I think it would also be great if there was a spot to tuck away an SSD hard drive (I use the Samsung T5), but I suppose I could just place it on top of the back (plus, my use case is probably in the minority anyway).
     
  10. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    I would think you could just mount it to the top plate. As for accommodating other hats, I learned a long time ago that is very difficult to be Uber flexible. Given that these are acrylic and will not cost a significant amount of money to replace, our strategy is to simply work with what we have and may be a step ahead such as we did with the RJ 45 and the AKM DAC add on.

    But the SSD idea is intriguing and something I can look at before we end up wrapping everything up. Another nice feature of the PI2AES is that we supply the PI with 5V@4A so that it is easy to use an SSD and the display without an extra power supply required.

    Michael
     
  11. HAL9000

    HAL9000 Almost "Made"

    Contributor
    Joined:
    Apr 4, 2016
    Likes Received:
    233
    Trophy Points:
    63
    Location:
    Fairfield, IA
    Quick (perhaps dumb) question for @Michael Kelly: If I am using SPDIF coax to interface to my DAC, is there any difference in timing stability between PI2AES and the 502DAC? I have a Bifrost 2, which does not support AES...
     
  12. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    There is a very small difference due to the way the PI2AES clocks are generated. On the 502DAC the analog DAC (PCM5122) is used to generate the clocks, while on the PI2AES the Wolfson WM8804 is used. For some reason the WM8804 has slightly less jitter.

    Bear in mind that these differences are very small and are likely not even audible. We have many customers who use the 502DAC and are very happy with it.

    We do also have customers who have use the 502DAC and moved on to the PI. Perhaps some of them can weigh in and give you their impressions. Our position is that the primary benefit of the PI2AES is the extended number of outputs available making the PI2AES that much more flexible. As many users have noted, just being able to match the interface to the one that gives your DAC its best performance can be quite noticeable.

    Michael
     
  13. earnmyturns

    earnmyturns Smartest friend

    Pyrate
    Joined:
    Sep 25, 2016
    Likes Received:
    3,218
    Trophy Points:
    113
    Location:
    Palo Alto
    Home Page:
    Great idea, I also have a T5 :)
     
  14. lehmanhill

    lehmanhill Almost "Made"

    Contributor
    Joined:
    May 3, 2018
    Likes Received:
    545
    Trophy Points:
    93
    Location:
    Home of Jiffy Mix
    I made that comparison, but using an Metrum Onyx rather than a Bifrost. I couldn't hear a difference between the 50DAC and the Pi2AES using SPDIF. One note, I did have Bluejeans cables make me an SPDIF cable with an RCA on one end (Bifrost, in your case) and a BNC on the other end for the 502DAC/Pi2AES end. There is an BNC to RCA adapter with the 502DAC, but I felt it was not the tightest fit and chose to eliminate the adapter with the cable. I haven't tried the RCA out of the Pi2AES, but assuming it sounds the same as the BNC, then the Pi2AES would make cabling more convenient. Can anyone comment on the Pi2AES RCA output?

    As a side note, I did find that the balanced (XLR) output of the 502DAC didn't sound as good as the SPDIF or as good as the XLR output of the Pi2AES. I'm not sure why.
     
  15. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

    Pyrate
    Joined:
    Apr 22, 2016
    Likes Received:
    4,112
    Trophy Points:
    113
    Location:
    Rhode Island, USA
    Home Page:
    I expect it is most likely because the 502DAC uses a 6.35 mm to XLR adapter, which does not maintain the 110 ohm impedance that you get when using XLR to XLR.

    Michael
     
  16. neogeosnk

    neogeosnk Friend

    Pyrate
    Joined:
    Sep 28, 2015
    Likes Received:
    1,882
    Trophy Points:
    93
    Location:
    Los Angeles, CA
    Decided to test various connectivity and power options to try to get the best sound quality out of the Pi2AES and here are my conclusions.

    Dacs used: Yggdrasil, Sonnet Morpheus and Matrix X-Sabre Pro (MQA).

    Optimal Power Setup: Linear power supply for Pi & Pi2Aes Hat. Stock power supply at 24 volts gets you 97% of the way there. Linear power kills any nervousa you may have but you probably don’t need it. Using: Audiophonics LPS & cheap Chinese power supply or stock power

    Note on I2s connections; only use one per unit or the signal is degraded. Tested various configurations and looks like it loses the 100 ohms independence when adding more than one device. If you plan on using more than one dac you should probably buy another unit.

    Connectivity preference starting with the best first and going down from there:
    • HDMI - good across the board, cable length is not as critical but no longer than 2 feet, couple of percentages off the resolution vs. RJ45. Using: Apollo AV Lightning v2 0.5M HDMI
    • AES – Loses some 5% or so high frequency to the connections above. Transients are slightly blurred together. This is the best connection to the Yggdrasil; have never heard it sound so good. Using: Canare Pro Co AES/EBU
    • BNC – Just slightly less than above. Using BlueJeans cable and Japanese cable (name forgotten)
    • Coax/Spdif – Macro dynamics less defined, shielding on cables do make a slight difference, works well with ADI-2 DAC. Using BlueJeans cable, Japanese cable (name forgotten) & glass spdif
    PI2AES vs. 502DAC – AES and above, no contest the PI2AES is better in any every way. BNC and Below they sounded identical to me.

    USB Implementation of Dacs vs Pi2aes: PI2Aes > Unison> Adi2-DAC> Xmos xu-216=Morpheus Usb
     
    Last edited: Mar 5, 2020
  17. FlySweep

    FlySweep Friend

    Pyrate
    Joined:
    Sep 27, 2015
    Likes Received:
    1,412
    Trophy Points:
    93
    Location:
    Portland, OR
    Good stuff @neogeosnk .. regarding your 'stock' rec.. is that a separate (standard 5V charger) PS running the Pi and the stock 24V PS just running the Pi2AES?; or the stock 24V PS powering both the Pi & Pi2AES?
     
  18. earnmyturns

    earnmyturns Smartest friend

    Pyrate
    Joined:
    Sep 25, 2016
    Likes Received:
    3,218
    Trophy Points:
    113
    Location:
    Palo Alto
    Home Page:
    Interesting... When I had Metrum Ambre and Onyx, the Ambre came with 3ft Ethernet cable for the I2S connection. It never occurred to me to try a shorter cable, maybe I should have. and I'd still own the Metrum gear, which felt less precise in the low end than the Yggdrasil I have now in that role. Or is this length sensitivity a specific Pi2AES>Morpheus issue?
     
  19. neogeosnk

    neogeosnk Friend

    Pyrate
    Joined:
    Sep 28, 2015
    Likes Received:
    1,882
    Trophy Points:
    93
    Location:
    Los Angeles, CA
    U get slightly better sound with separate generic power sources but its negligible, stock power for both is really good. With the LPS rabbit hole, everything is more fleshed out, slight increase in resolution and lower noise floor.
     
  20. neogeosnk

    neogeosnk Friend

    Pyrate
    Joined:
    Sep 28, 2015
    Likes Received:
    1,882
    Trophy Points:
    93
    Location:
    Los Angeles, CA
    Morpheus came with a 6 foot cable that sounded bloated with some weird phase shift, just sounded off. Might just be Pi2AES or Sonnet i2s implementation, not sure.
     
    Last edited: Mar 3, 2020

Share This Page