Raspberry Pi I2S to SPDIF Hat

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

  1. HumanFly

    HumanFly Acquaintance

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    Hi Michael,

    Believe me,I would be very happy if you send me a board to test but I think you are confusing me for someone else though.
    I didn`t sent you the ALLO-board and I don`t know who did but I remember reading something about it.
    Did I already mention that it is OK for you to send me a board? And I will certainly test it.
     
  2. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    My apologies. It was hifiandrun that lent me the Allo! But, send me a message and we’ll talk about a loaner for you to do a review.

    Cheers,
    Michael
     
  3. hifiandrun

    hifiandrun Almost "Made"

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    Hi Michael, I found your production PI2AES in my mailbox yesterday evening - many thanks.

    Yes, it was me providing the Allo Digione Signature for Michael's jitter measurement. Two things I can say after brief listening are:

    1), The PI2AES digital output is at least two-step up compared to the previous 502DAC board's BNC digital output. Significantly improved micro details (plankton) for one.

    2), The difference between the PI2AES and the Allo Digione Signature is very, very subtle. I have been splitting my hair trying to find a way to describe the subtle difference between the PI2AES and Allo Digione Signature. It is so subtle that I think that I need several long-term listening sessions before I could post anything about it. So be warned - You would see a very TLDR post later.

    I highly recommend Michael's new PI HAT. By the way, the new raspberry Pi 4B is very promising. With a raspberry Pi, a PI2AES, and one of the free streaming programs such as piCorePlayer, you've got one of the best media streamers to date, at a total cost around $200.
     
  4. lehmanhill

    lehmanhill Almost "Made"

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    Micheal,

    Thanks for the plots. It may be slightly higher floor, but it is very good. Especially when cost and the i2s outputs are considered. You already have my pre-order.

    Jac
     
  5. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    That is awesome! I have to say, the reactions and feedback that I get from you guys is easily the best part of the whole process. As an engineer I take a fair amount of enjoyment from the creative process all by itself. But getting feedback from customers who are willing to spend their money, makes it feel real. So to all of you a big thanks!

    Cheers,
    Michael
     
  6. dreambox

    dreambox New

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    @Michael Kelly
    It's our pleasure to test and be part of this development. And thank you so much for design and produce this for us.
    As I mentioned, my system never ever sound before as 3 dimensional and holographic.

    @hifiandrun I also compare to Digi One Signature, and for me its really far from PI2AES to reproduce scene depth and dimensionality. I use headphones only. And PI2AES just do it so right. All instruments separation and distribution make me feels inside music. Unbelievable. I had many sources before (all details will come in my review..). But never hear anything similar. Just curious what other testers comment on this. Are you using speakers or headphones?
     
  7. hifiandrun

    hifiandrun Almost "Made"

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    The Allo Digione Signature is not a lame design. What type of power in your Allo setup? The power quality on the "clean side" makes a significant difference. This is why I am delaying my report. I have been trying different types of power supplies on both Allo and PI2AES. I wanted to be as objective as I could, well, for a subjective listening comparison anyway, LOL. Happy listening.
     
    Last edited: Jul 6, 2019
  8. haywood

    haywood Friend

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    Even Michael’s jitter plot showed the Digione Signature to be very good but the pi2aes is significantly less expensive (in pi hat dollars) and offers connectivity options that the DS doesn’t. If your dac is significantly better with i2s or aes then no-brainer.

    I’ll be interested to see the results of your power supply testing, and whenever anyone gets a Pi4 to test to make sure there are no conflicts. Hopefully for audio we can just underclock to avoid the throttling that other people are seeing right now and we’ll get the better usb and ethernet.
     
  9. dreambox

    dreambox New

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    In both I use battery for power.
    Allo Signature - for clean 4x li-ion battery as suggested by Allo
    PI2AES - 12V 4.5Ah battery (try this if you can.. just connect any 12V battery you may have around.. ;))

    I think its good as power supply

    Agree, but I am talking about scene representation.. jitter for each channel can be excellent, BUT if phase transients between channel not preserved and reproduced well, the stereo information will be easly distorted.. as results, instruments separation and depth will be not reconstructed correctly by our brain. At the moment I can say PI2AES and 502 do it very well (thanks Michael), Allo Signature not that good from this point. Now, as you see, measurment as we have them, not all what we need for good sound. Not at all. Precisely preserved perfect timing between channel, this the secret for "magic". PI2AES from first accords (even from background noise of song) bring me right inside the scene... instruments sounds echos, reflections from walls.. all this is so holographic, you can feel volume of each sound from the stage. This what you can get if provide right numbers to right DAC. And this will be lost first if even small errors introduced it the path.

    I am really looking for some measurement approach to address this. It's need to take some complex reference signal applied to both channales and spectral coherence, inter channel timing need to be estimated if we want to be objective. Somehow the best instrument for this is our brain (ears), but it will be always subjective this way.
    And as I see non of the presented measurements around here target this.
    May be just sending same signal in contraphase to the left and right channel simulataneously and see how perfect zeros will comes out as a sum of them after DAC conversion (or just go for digital.. before DAC, even better).. to check how perfectly spectrum is symmetrical after processing.. we need some engineers here I guess )
     
    Last edited: Jul 3, 2019
  10. hifiandrun

    hifiandrun Almost "Made"

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    “Michael’s PI2AES” vs. “Allo Digione Signature” based on subjective listening.

    Bear with me please - it will be long. I will describe how I did the comparison followed by what I was looking for in the listening sessions. Then it is the listening impression with a brief ‘blind” test. I listed my equipment at the end of the post for your references.

    1. Disclosure. I provided a Gustard X-26 DAC with I2S input for Michael to test the prototype and an Allo Digi Sig for jitter measurement. In return as promised, I got a first-batch production version of PI2AES for free – thanks Michael. However, I was not required to write a review.

    2. How I did my comparison. I only tested SPDIF coax outputs (BNC or RCA) on both. At first, I connected one using RCA coax cable and the other with the BNC cable. I could switch the digital source on-the-fly between PI2AES or Allo Digi Sig by click the input button on the Schiit Gungnir MB. I did this A/B test at the beginning. Then I realized that the differences in sound between the BNC cable and the RCA cable could be equal to or larger than the differences between the two digital boards. The later comparisons were done by manually switching the BNC cable between these two pi HATs. The music was still synchronized thus it didn’t affect the A/B test much.

    3. What I was looking for. My goal was to find the best streamer (or digital-digital-converter, DDC) for my DAC which is at best using BNC input. Although the SPDIF has a sample rate limit of 192khz, I was not worried. One of the Schiit Multi-bit DAC’s magics is that they can play 44.1K music extremely well. I was looking for natural sound presentation, not exactly the neutral sound. It doesn’t have to be a live-event-alike, rather, I wanted the sounds were authentic and real. The second was the enjoyment of the music which is related to be engaging and emotional. Then there were those extras such as sound stage, precision, macrodynamic, microdynamic, plankton, et cetera.

    I wasn’t limit myself to pi HAT because they are cheap. I started with USB-SPDIF converter. Here is the link of my previous report how I found and settled with 502DAC (Raspberry Pi I2S to SPDIF Hat). At that time, the primary goal was to find one had enough details without sounding “digitized”. I can say that all the three pi HAT I have, both Michael’s 502DAC and the new PI2AES and the Allo Digi Sig don’t have that digitized sound.

    4. Listening impression.

    I bought the Allo Digione Signature board in April this year. I paid $260 to get it shipped from India plus another $30 for the rechargeable batteries and the 4X battery holder. First and foremost, I was impressed by the “black” background. It was very quiet in between the music passage compared to the 502DAC. A lot more details and a lot better instrument separation compared to the 502DAC. However, after the “wow” factor gone, I felt that all music was kind of sounded a little “weird”. The midrange was recessed, which made all human voice sounded a little veiled and unnatural. Later I learned that the following aspects were important for getting the Digi Sig right. First, the “clean side” power is critical. Basically, 4 AA battery pack > USB charger for phones > or = 5V+ linear regulated power supply > switch power supply. The “dirty side” power doesn’t matter much, although I used a 5V+ linear regulated power supply. The Digi Sig board also needs a long time to break-in, because it uses many expensive film capacitors. The weirdness was almost gone after about 200 hours and when powered by AA battery pack. The blackness and other strengths of the board were still there. However, the midrange improved significantly. It sounded better than 502DAC in many ways but the 502DAC has a very musical sound which I still like. Before I heard the PI2AES, I though the Allo Digi Sig was the end game for several years as the DDC in my main system. I fit the Allo board in a nice little aluminum case.

    The PI2AES board. The first impression was jaw dropping. The remarkable microdetails and the plankton bring the music alive and shine. The decay of cymbals was very clear and natural which was unheard of in my system. It sounded “louder” and a little bit grainy at the beginning. The PI2AES also need at least 50 hours of break-in. After the break-in period, it was still a little louder than the Allo board. But the grainy was gone. The louder impression was subjective. The radio shack sound level meter showed the same reading. I tried two switching power supplies. The power supply in picture (https://www.amazon.com/gp/product/B07G56LF9C) is slightly better than an old RadioShack switching power supply. I have not tried lead-acid car battery. I like the simplicity of the PI2AES. One power supply does all. You could see that I did not have much to say about the PI2AES. Because it simply does things quite right without any special sound signature.

    The Allo’s sound stage was wide, however, the voice and the instruments were kind of blend together as if the players were sitting closer in a large room. The human voice was a litter further than the instruments, which might be related to the hint of “weirdness” I mentioned in the above paragraph. The PI2AES sound stage was a little closer than but equally wide as Allo’s. At the same time, I felt that the instruments and singers were spread out on the stage.

    Edit: I find that the PI2AES sounded better using Saga passive mode where as Allo Digi Sig sounded better using Saga tube mode.

    5. The “blind” test.

    First, it was a brief test, last in 10 minutes. I asked my teenage son to have a listen. He used to play piano and violin. He has been in the choir at school. I played two of his favorite songs. I did A/B/A/B/A/B playback for him. I told him when I switched, but he had no idea about these two boards. After first song, the Sgt. Pepper’s Lonely Hearts Club Band, he could easily distinguish the A and B. When I played the second song, Jimi Hendrix’s “All along the watchtower” from album Electric Ladyland, I tricked him because I didn’t switch after A/B test of the first song. He said, “Did you switch? I think you didn’t. This is the B”. And he was right. He described that the “A” was like live music, very detailed and real, in contrast the “B” was a little “veil and dull”. The A was PI2AES and the B was Allo Digi Sig.

    To conclude this report, I think that the PI2AES and the Allo Digi Sig are two of the best boards in the market. But they do carry different sound signatures. From the pure Hi-Fi point-of-view, the PI2AES wins as it has more plankton and more dynamics. The sound stage is wide, and the imaging/position of instruments is pinpoint, clear, and stable. In contrast, the Allo sounds polite and less detailed. Someone might prize Allo’s sound as organic and forgiving if the rest of the system was on the “bright” side. Now I am thinking to fit the PI2AES in an aluminum case.

    My doubt is, why those big-name websites such as Darko audio haven’t reviewed Michael’s 502DAC HAT?

    Happy listening !

    [​IMG]
    [​IMG]

    Note 1. all above have been focusing on the SPDIF BNC sound. If you own an I2S input DAC and you wanted to use it, such as Holo Spring or PS Audio DAC, you don’t have a choice but PI2AES.

    Note 2. Equipment.
    Power conditioning: Monster HTS 3500.
    Digital source: The LMS server is installed on a Cubietruck SOC (like raspberry Pi but with SATA connection and Giga Network) running Armbian Linux. I played local file stored on the SSD drive, I also streamed CD and HD music from Qobuz (LMS plug-in). Two raspberry Pi 3 running PiCorePlay 5.00 audio. The two Pi was synchronized in the LMS streaming the same music.
    DAC: Schiit Gungnir MB A1.
    SPDIF COAX cables: 1, with BNC connectors: BlueJeanCable High-flex 3G/6G HD SDI patch cable using Belden 1505F (www.amazon.com/gp/product/B007EELW4S). 2, with RCAs: Straightwire “Video Link II”.
    Pre-amp: Schiit Saga original. I use both passive and tube for the evaluation.
    Power amp: 2 x Schiit Aegir, single-ended RCA input, Bi-amp configuration.
    Interconnect cables: WORLDS BEST CABLES using Mogami 2549 wire and Amphenol ACPR Die-Cast, Gold Plated RCA, directional (www.amazon.com/gp/product/B01ALG04IA)
    Speakers: B&W Nautilus 803. Speaker cables: Kimber 8TC for bass; Kimber 8PR for midrange and tweeter.
    Room treatment: Three 2x2 feet acoustic panels on the rear wall. Acoustic foam panels behind speakers, one bass trap in one of the corners. (Acoustimac.com).
    The Schiit Aegir bi-amp is a good match with the B&W Nautilus 803. Aegirs bring tube-like warmth without losing grips of the bass. N803 speakers are neutral and detailed after some trial-and-error gear matching. Yes, they can sound awful if setup is not right.
     
    Last edited: Jul 6, 2019
  11. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    Great review, thank you.

    Also, note that In addition to the PI2AES being the only option for direct I2S, the 502DAC and PI2AES are the only PI hats with balanced AES output for interfacing with pro audio equipment.

    Cheers,
    Michael
     
  12. trung225

    trung225 Facebook Friend

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    @Michael Kelly
    From what I see in manual of Pi2AES in your website, I saw an ADP150 as voltage regulator for NDK clock. But you also said you will try to use LT3045. So I would like to ask, which one do you use in production?
     
  13. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    The production version uses the LT3042 to power the clocks.

    Cheers,
    Michael
     
  14. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I actually thought the DigiOne Sig sounded best with two of Allo's included switching PSU. Basic one they sell on their site.

    Batteries and a basic LPSU sounded "cleaner" in a sense but tended to soften transients and dull/blur the sound a bit. This helped the leaner sounding, original DigiOne, but the Sig seems to go too far into mush with batteries and some LPSUs. (Batteries weren't so bad but still not my favorite.)

    Of course, even to Allo that was akin to heresy, that my preference wasn't for batteries. So I didn't hit on it too hard. But I don't think LPSUs and batteries are necessarily always the answer to better sound.

    Plus, there is quality variety in batteries. They're not all made equal.

    I similarly found the Eitr less "polite" than the DO Sig, but after extensive testing across a wide variety of music found its performance less consistent. It seemed to have less control in the low and high regions, which on some tracks was exciting and gave the impression of a larger stage. On other tracks, it made for a grainy, bloated, collapsed sound compared to the DO Sig. The DO Sig was always consistent.

    That the Pi2AES sounded louder is concerning for an SPDIF source, either from a technical perspective or validity in your subjective findings. I've heard plenty of stark differences from SPDIF, but never volume differences.

    That said, given I was not shy to stick with switching PSUs on the DO Sig, I'm certainly open to judging the Pi2AES with my own ears. I'm not so worried about super low level jitter measurements.

    Nitpickiness aside, I'm just happy to finally see excellent SPDIF sources available at low prices, that don't use USB (shit) or CDs (inconvenient), and with relatively good ease of use.
     
  15. trung225

    trung225 Facebook Friend

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    Hi Machael,
    Thanks for your quick answer. I have another question, can I power Pi2AES from 5V RPI GPIO like in 502DAC, or I must use +12-48V external power supply?

    Cheers,
    Trung
     
  16. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    You must use the external power supply to power the PI2AES. But you can power the raspberry pi itself separately at the same time.

    Cheers,
    Michael
     
  17. hifiandrun

    hifiandrun Almost "Made"

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    Hi Hands, Just found your review on Allo Digione Signature on the Audiostream website. Very good read, thanks. I will try switching PS I had on hand. I don't have the switching PS from Allo website. Regarding to the louder presentation with PI2AES. I took several long listening sessions in the last couple of days to make sure it was not related to the digitized sound. I couldn't find a better analog about this phenomenon. Say, when I switch from Saga passive to Saga tube follower mode (no amplification), I feel the tube mode sounding louder. The magnitude of perceived difference of sound level between PI2AES and Allo Signature was much less than those from Saga's mode change. Others might describe this as "bright" versus "dark".
     
  18. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I am curious if you'd notice any difference between a variety of 18650 batteries. I had some very high quality ones I got back from when I used to vape. Most 18650s aren't super great! I opted for lower mAh in exchange for better output capabilities and safety.

    Even then, there were times I'd go back to the switching PSUs, since I appreciated the incisiveness they brought to the table.

    It's been a while since I've heard the DO Sig, but I'd be curious to try the Pi2AES nonetheless.
     
  19. hifiandrun

    hifiandrun Almost "Made"

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    Hi Hands, Thanks for the suggestions. I listened to Allo Digi Sig with a switching power (an official raspberry Pi 2.5A PS) again. Yes. It was like what you have described. I heard improved macrodynamics (meaty) thus the musics sounded fuller. But I didn't hear improvement on microdetails nor sound stage. I was using NiMH batteries (Eneloop Rechargeable). I don't have 18650 batteries.

    Out of curiosity, I also tried removing the 5V+ jumper on the left upper corner of the PI2AES board, powering the raspberry Pi and the PI2AES separately. Having been busy at work and didn't have any time to do a A/B test on "power Raspberry Pi 3 through PI2AES" versus "powering Pi separately", but the later may sound even better, slightly - wider sound stage and more relaxed sound. All the differences I have been comparing are very subtle. My ears are so tired now, LOL. But this could be a way of fun tweaking for PI2AES. Happy listening!
     
  20. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Yes, the general details or staging didn't change much on the DO Sig, but I was surprised that their generic switching PSUs sounded relatively lively and sharp!
     

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