Raspberry Pi I2S to SPDIF Hat

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

  1. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Sounds like I might need to think about adding an active buffer to our RJ-45 board? There is a buffer on the PI2AES board already, but it is a fairly simple TTL logic device, not something really designed to drive long cables with high capacitance.

    Michael
     
  2. Scott Kramer

    Scott Kramer Friend

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    I wonder if adding buffers and new logic starts to impede as to why i2s is so pure in the first place, for example the master-clock M is directly off the crystal itself, BWD tapped right in the actual data, at least on the 502DAC. Adding circuity might push it back down into needing re-clocking, or compromised with the new parts chosen, might as well just use spdif at that point. These are weak, raw square wave voltages, shorter is better-- it's extending circuitboard traces!
     
    Last edited: Mar 3, 2020
  3. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Buffering would not change the timing relationship nor the "cleanliness" of I2S. Done right, it simply extends the reach. Of course, we have a fair number of guinea pigs (aka SBAF members) willing to test this out!

    I'll keep you posted. In the mean time I am starting to look at the Metrum I2S interface boards sent to me to try to clone.

    Michael
     
  4. neogeosnk

    neogeosnk Friend

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    I'm in. Was somewhat disappointed that my 3 foot $15 premium cat 7 cable sounded so bad.
     
  5. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    It is also important to remember that an ethernet cable is designed to provide twisted-pair between positive and negative signals. Single ended signals twisted with a ground will not have the same characteristics.

    This is why I2S over HDMI is less sensitive to cable distance (though cable quality still matters). Although the voltage levels of the LVDS used is not the same as true HDMI, they are still differential signals that require twisted pairs.

    Michael
     
  6. Ksaurav402

    Ksaurav402 Friend

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    Ya try to keep it below 1.5ft and it should be Ok.
     
  7. Ksaurav402

    Ksaurav402 Friend

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    pi2AES is added as HAT in Ropieee in latest release
    4363D597-A1D0-47BE-95DD-B33B968F99BE.jpeg
     
  8. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Awesome. I shall thank the ropieee guys.

    Michael
     
  9. gixxerwimp

    gixxerwimp Professional tricycle rider

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    Great comparison. I ordered a PI2AES and will be using coax to Bifrost 2. Guess I could have saved $40, but will have future compatibility in case I upgrade to a DAC with AES/BNC input, adapter free coax output, and the convenience of being able to order a stock PSU.
     
  10. earnmyturns

    earnmyturns Smartest friend

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    All of this discussion on Pi2AES makes me wonder if I should dip my toes again into the NOS I2S water ;) Resist, resist, this Pi2AES>Yggdrasil A2>EC Aficionado>ZMF Verité combo is magic for good old Redbook, bringing sadly departed Paul Motian, that unparalleled master of cymbal understatement, back to life on Dreamland with Joe Lovano and Bill Frisell.
     
  11. lehmanhill

    lehmanhill Almost "Made"

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    Don't resist, experiment.

    If you do go back to try the Metrum and i2s, then do yourself a favor and buy a cheap RJ45 crimper with connectors. It cost way less than a custom cable. Then take some CAT 5 or 6 wire, strip out what you don't need, and make a custom cable just a short as possible. The Ambre may have made different impedance choices (based on Mr. Rogers communication with Cees at Sonnet), but the Pi2AES with my home made 4" cable from the buffered i2s pins sounds great with the Onyx.
     
  12. earnmyturns

    earnmyturns Smartest friend

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    I'd not go back to Metrum, they seem to be AWOL. I'd either go to Sonnet, or back to Holo Audio, this time the new May KTE. I'll wait, though.
     
  13. neogeosnk

    neogeosnk Friend

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    Tested 4 different Cat 7 cables up to about $18 on RJ45/Pi2aes/Morpheus. For me this one came out on top: LINKUP Cat7 Ethernet Cable -1 FT (1 Pack) 10G Double Shielded RJ45 S/FTP

    Pitch black background, zero loss of resolution and very tight left/right separation (no cross-fade from bleed-through). I say it's about 10 to 13% better than any other cat5/6/7 cable tested.
    Cable nervousa for Pi2aes is done.
     
    Last edited: Mar 6, 2020
  14. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    New PI2AES case for the official Raspberry Pi 7" display is done. Price will be $35 for the case and HW. We will need about 2 weeks to gather the pieces and get it in the store. You still have to buy the display of course and you will need the fpc cable and power wires that come with it.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  15. Taverius

    Taverius Smells like sausages

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    @Michael Kelly does it support Pi 4?

    I still have a Blue Node 2 in the living room because it has to be WiFi and WiFi on the 3 suuuuuuuucks.
     
  16. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Absolutely. If you look closely at the pictures you will notice that the raspberry pi I am using is indeed a 4 (note the two micro HDMI connectors in the second photo).

    BTW, I just installed moode 6.4 and it is easy to get the display up and running as well.

    Cheers,
    Michael
     
  17. lehmanhill

    lehmanhill Almost "Made"

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    Interesting. Why do you say that the RPi3 sucks?

    With either the 502DAC as an SPDIF source or the Pi2AES as a source for SPDIF, AES, and i2s on an RPi3, I have had excellent sound and reliable playing. I admit I am using PiCore on the RPi3.
     
  18. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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  19. Taverius

    Taverius Smells like sausages

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    @lehmanhill Pi 3 is a great device, but it's WiFi isn't good and USB dongle WiFi isn't good either.
     
  20. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    I'm looking for a "work at home" project and thought a new Rpi based source with screen would be perfect... do you envision supply of the new case (along with hat & PSU) being affected by the current situation?
     

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