Raspberry Pi I2S to SPDIF Hat

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

  1. Scott Kramer

    Scott Kramer Friend

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    fyi: HifiBerry: diyaudio--> 10
    Also Allo has done great work building on these original drivers, it's all in GitHub to see and they communicate about it while developing.
     
    Last edited: Jul 26, 2019
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  2. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    And they deserve all the credit. I am not a SW engineer, just a HW guy so I do take advantage of the work that is out there. And I hope I was not disrespectful.

    Michael
     
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  3. Scott Kramer

    Scott Kramer Friend

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  4. toddrhodes

    toddrhodes Friend

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    Apologies if I missed it but any idea when the next shipment will go out?

    Thank you!
     
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  5. lehmanhill

    lehmanhill Acquaintance

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    I guess you could say that I am approaching the Pi2AES from a different direction than Mister Rogers. I don't have an appropriate linear power supply for the Pi2AES on hand,so I dug into my junk drawer and found a switcher that would do the job. These evaluations are with the Pi approved 5V switcher powering the RPi3 and a separate switcher powering the Pi2AES.

    For these evaluations, I used my speaker system with either the 502DAC or the Pi2AES feeding a Metrum Onyx, followed by a Reliaxed2 DIY pre-amp, Fremen Edition DIY amplifer, and DIY 2 way speakers using Dynaudio drivers and a passive crossover. When using balanced AES, I used a cable with Mogami digital wire and Neutrik XLR connectors.

    502DAC vs Pi2AES


    The first step was to compare the 502DAC to the Pi2AES using single ended, coax at the 1V level (technically AES3-id). I used a Blue Jeans digital cable with a BNC on one end and a Canare “75 Ohm” RCA on the other end and swapped the BNC connector between 2 Rpi3's, one with Pi2AES and the other with the 502DAC.

    These two are remarkably similar and both sound very nice. They are close enough that its hard to pick out differences, but I did find a small improvement in dynamics in the case of the Pi2AES. Overall, differences were small enough that I would be happy with either in my system.


    Pi2AES Coax, AES balanced, and buffered i2s


    Here the differences are a little bigger, but again all are very nice sounding. Using the coax as baseline, the balanced AES has a bit blacker background, perhaps due to the common mode noise cancellation of the balanced configuration. Both macro and micro dynamics were improved and that gave the music more of a presence in the room. With the quieter background, you could hear the notes decay to a lower level and that adds to the feeling of detail in the music. There was also a sense of slightly improved bass with the Pi2AES. Once again, all of these differences are small, but if I had to choose between single ended coax and balanced AES, I would choose the balanced configuration for the Pi2AES. As I had previously commented on this thread, I prefer the single ended coax for the 502DAC, so this is a step up in the Pi2AES.

    The Metrum Onyx accepts i2s if you have the i2s module and uses direct i2s rather than differential i2s used in other dacs. I made up of little 4” cable from CAT5 wire and a RJ45 connector. To be honest, my expectations for the i2s was rather low because the signal comes directly from the Rpi with the Pi2AES only buffering the Rpi signals to lower their output impedance so that they can correctly drive some length of cable. That said, my favorite output is the i2s. From the balanced AES, there is more punch across the frequency range and a bit more bass slam. The micro and macro dynamics are a further small improvement over the balanced AES. The stage is a bit closer with more depth.

    In sum, all of these outputs are very good and differences can only be found by direct comparison. Of these, I prefer the i2s, followed by the balanced AES, and closely followed by the coax. Michael is to be congratulated for offering all 3 high quality output formats in a cost effective package. This one definitely stays in my best system.

    My next step is build a power supply with low ripple and low output impedance to feed the Pi2AES. To be honest, I'm not sure it will offer much in sound quality, but I will feel better knowing I'm doing everything I can to keep things clean.
     
  6. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Thank you so much for this great detailed report. I am especially pleased that you were able to test direct I2S.

    I would like to offer one small point of clarification. The I2S signals are actually sourced from the Wolfson WM8804 using a pair of very low jitter NDK clocks. Only the audio data itself comes from the pi, for all the other signals the pi acts as a slave. This is what allows the pi to perform at a level far above its price point!

    Regards,
    Michael
     
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  7. lehmanhill

    lehmanhill Acquaintance

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    I did not know that. That is very good news. My expectations were low for i2s because I had assumed incorrectly that the RPi clock was still involved. Very nice.
     
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  8. lehmanhill

    lehmanhill Acquaintance

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    One other thought. The LEDs are like a bright Christmas tree (red and green for power on and 44k) and can be blinding at night. A little lower current would hurt a bit. Easier on the eyes and saves a tiny bit of money.
     
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  9. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    We are building a batch right now, we were a bit delayed waiting for the optical/RCA combo jack.

    Michael
     
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  10. toddrhodes

    toddrhodes Friend

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    Thank you sir! No rush, was just curious.
     
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    It would seem I can never find the right balance when it comes to things like LED‘s. However, you might want to try the trick my wife does for the various gadgets in our bedroom, she simply puts a small piece of cardboard with a tape flap that you can lift up or put down at night to cover any offending lights!

    As a former Marine I can fall asleep in broad daylight, but she, on the other hand, is very sensitive to light. Typical civilian! ;)

    Michael
     
  12. toddrhodes

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  13. toddrhodes

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    Got mine up and running today. It was simple except for the fact that I couldn't recall what kind of image was on my Pi and I couldn't SSH into the thing. Finally just broke down and installed RoPieee and from there it was a cakewalk.

    Running AES/EBU out to my DM2 DAC and while it's very early, I will say that without a doubt I prefer it over the last device I tried along these lines, a Sonore MicroRendu with Uptone PSU. I am only using the MW PSU from Pi2Design. Very smooth and open sounding, with no irritable glare like I'm used to from these kinds of devices.

    DM2 is set to auto clock, so it is using the clock in the Pi2AES, so I don't have to constantly switch rates. I may try out the DM2 clock at some point but for now, I see no reason to change. I don't listen to files that often but when I do, I have some very good ones and I'd like to do them some justice, and this thing seems like an incredible value.
     
  14. toddrhodes

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    Listened quite a bit last night, didn't spin a CD or record the entire time, and loved it. Frankly my CD player is sitting over there sweating, now. I will say that even though this is vague, I'd put the PI2AES at about 98% of what i get out of my Sonic Frontiers transport - the transport is just a tiny bit warmer-sounding (may be a plus or minus material dependent) and seems to project just a bit more believable image but honestly, I feel like I'm reaching even there. But there is something, it's just not much and I could easily see myself being content if my transport weren't operational for some reason.

    As a true testament to the Pi2AES, very late into my session I decided to put on one of my references, Clapton Unplugged. This is an album that I never knew other versions existed but when I put on the ripped CD I had in Roon, it was just off from what I'm used to hearing. So I looked into that version and it's from 2011, where my physical CD is an original. So I ripped that quickly and took a listen - 100% better. Sounded just like my transport, to the point I'd not be able to pick them out in a blind test IMO. Maybe extended listening will reveal some subtle pros and cons, but I can't imagine anything noteworthy will bubble up.

    So in short, this little device was able to make readily apparent the differences, in not so subtle terms, between two versions of the same CD. I'm not at all sure what's up with that 2011 Clapton, but it was a great feeling to hear it, think "yea something's not right" and in fact, it wasn't. But with the "right" disc data, it was flawless.

    Well done, very happy with this thing. And even better, it affords me the ability to listen to a "high-rez" version of an album that is my current personal favorite, and that high-rez version, while sounding like it is mastered identically, does have better dynamics and more details (it's a very busy recording) that pop out versus the CD. I can't explain how happy that made me, to take my favorite album right now and all of a sudden be able to hear it in an even better presentation.
     
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  15. rlow

    rlow A happy woofer

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    Getting very interested in this. I was on vacation when the last round of ordering was opened up and I missed the window.

    @Michael Kelly when do you expect to open up orders again?
     
    Last edited: Aug 13, 2019
  16. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    We will open up for orders again tomorrow or Friday. Delivery time will be 2 to 3 weeks after ordering. Within the next month or two we should be fully up and stocked. This next batch is 30 boards and then we plan to build another 100. And then we will see how successful this is long-term!

    Cheers,
    Michael
     
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  17. toddrhodes

    toddrhodes Friend

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    For what it's worth, I just added a new amp to my chain today. Really wasn't sure I was going to find it superior to my current amp, an upgraded Odyssey Stratos Extreme. I'm happy to say that, only listening through the Pi2AES into my DM2 DAC using Roon behind it all, your little board scales well - it's not even difficult to tell that this amp I have now, a Bedini 200/200, is superior to my Odyssey. If not superior, absolutely different. And to me, it takes a very good source to help those differences expose themselves.
     
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  18. Ksaurav402

    Ksaurav402 Acquaintance

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    Pi2AES is available to order. Anyone interested can place their order
     
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  19. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Hey that’s my line! :)

    Please note that lead time is 2-3 weeks.

    Cheers,
    Michael
     
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  20. rlow

    rlow A happy woofer

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    Ordered (along with case and Meanwell supply). This will be my first RPi + Hat build. Should be fun to mess around with, and I’m hopeful the sound quality is as good as folks are suggesting.

    Even if it isn’t quite up to my current streamer’s SQ (Sotm SMS-200ultra Neo), it will be far cheaper that’s for sure, and a good backup. And if it gets close enough (or somehow exceeds it), I’ll be selling the SOTM. Just need to order an actual RPi board now, and I should be off to the races once the Pi2AES arrives.
     
    Last edited: Aug 15, 2019 at 11:53 AM
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