Pi2AES Impressions only thread

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by rhythmdevils, Dec 6, 2020.

  1. Melvillian

    Melvillian Friend

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    Had the Pi2AES for a week and I'm very impressed with it. Compared to the digione, the Pi2AES has a bit of inherent warmth that is very pleasant without any loss of detail. I was hearing a bit of harshness in the upper mids of the Soekris DAC2541 that I was attributing to the dac, but I could no longer hear this with the Pi2AES. You also don't have to worry about expensive linear PSUs and battery packs, which is a huge bonus.

    I ended up ordering two of these. One for myself and one for my dad. Great stuff!

    It really is a game changer having a digital source without any of the nastiness that comes with digital for such an affordable price. Add the convenience of controlling the streamer from any device.
     
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  2. Merrick

    Merrick A lidless ear

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    I caught on to RPi HATs for SPDIF/AES connections since it was first posted about here. When Michael began workshopping the 502DAC here, I joined the beta and have been using that unit for SPDIF connections ever since. As such I'm late to the Pi2AES as I was already very happy with the 502DAC, and I only had one DAC with a SPDIF input anyway. I've been putting together documentation for the Pi2AES and Michael was gracious enough to comp me a Pi2AES unit, power adapter, and cases, with the caveat that I write up my honest impressions here. The timing was perfect as I had just gotten a Bifrost 2 and had been using the Unison USB on it with a Jot 2 and a SW51+.

    To my ears, Unison USB is very capable. I don't detect any major faults with it and it certainly didn't seem to be holding the BF2 back as USB gen 2/3 (and, depending on who you ask, Gen 5) did previously on the Schiit DACs. As such as I was extremely curious to plug the Pi2AES in. Was it possible that I would hear no difference, or perhaps the difference would simply be that, a different flavor, and not an improvement?

    Now, these are all sighted impressions, but to me the Pi2AES is at least a step above, if not several steps above, Unison USB. It's a more refined sound. I can make out individual instruments more easily, and I do feel that the background is blacker with the Pi2AES (and this is something Unison is pretty good at with the BF2 to begin with). It also sounds more, hmm, relaxed might be the wrong word, but effortless. Like the Pi2AES is just presenting the music as it is, whereas the Unison feels like it's rendering it. It's less of a single element standing out between the two inputs, and more an accumulation of smaller improvements that add up to a noticeable change in the sound for the better. There is also a slight sense of blurriness with Unison that is wholly absent with the Pi2AES, which is crisp, clean, clear.

    There probably are USB implementations that can best SPDIF/AES, but the cost of those aren't worth it to me. Similarly, I'm sure there are top tier CD players whose SPDIF/AES output can best the Pi2AES, but again, the cost isn't worth it to me. The Pi2AES and the power brick are $180, and a RPi 3 is under $50. For this level of sound quality, that is an absolute steal. How much would you have to spend to get to one of those high end USB or CD sources? $800, $1200, $3000? More? The Pi2AES offers audible improvements at a minuscule cost compared to the vast vast majority of digital sources, and you completely bypass USB nervosa. I mean, how many of us tried USB decrapifiers of various types, obsessing over the changes in sound they made, some of them making the music sound worse! And here we have a pretty much bulletproof solution for less than some of those USB decrapifiers. It's ridiculous how much great sound we can get for so little money these days. I've long been a SPDIF convert, and an RPi HAT evangelist in particular. And the Pi2AES is as good of a RPi HAT as I've ever heard.
     
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  3. SpeedSmith

    SpeedSmith Rando

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    Merrick, your review resonates with me. I think your remarks about the sound having an effortless presentation verses being rendered is the same thing I experienced when comparing it to the Unison implementation on Bifrost2. Unison for me was a big step up from the EITR/Modi Multibit combination I was previously using. But that was an apples/oranges comparison. What was unexpected was finding myself switching to a Pi with a Hifiberry HAT for the same reasons you preferred SPDIF. I was preparing the Hifiberry as a Roon endpoint to service background music needs in our dining room at the time and had every intention of sticking with Unison for my office.

    I purchased my original Pi2AES after a fellow SBAF member had loaned me his Allo DigiOne. I found the Allo superior to the Hifiberry I was using in my two channel setup. But he recommended I try the Pi2AES based on early feedback here. I've been very happy with the Pi2AES which is currently feeding a Roon stream to a Gungnir A2 via BNC. A word on BNC, like you I find SPDIF to present music naturally and effortless when compared to Unison which sounds a bit etched at the edges. BNC adds to the natural timbre/realism and in particular extracts more from the deepest regions of bass reproduction (big fun for EDM). But also I hear more mid bass articulation, being able to quite clearly pick out each note of electric bass or even upright bass being played. Drums and bass sections of songs have more separation/layering/depth.

    I've since purchased a 2nd Pi2AES to supply the Bifrost2 in my home office with Roon via SPDIF. This allowed me to A-B and confirm (to my ears) my thought that Unison while is a big step up from earlier USB implementations, hasn't bested SPDIF (at least for me). In this chain, Roon >> Pi2AES >> Bifrost2 >> Saga OG >> Crown CDi-1000 >> Spatial M4TM, music listening becomes an intoxicating/emotional experience to the point that it has interrupted the workday at times.

    TLDR; version - the Pi2AES helps to enhance the things I listen for: instrument separation, sound stage width/depth, presentation of layers, sweetness of treble, grip of bass, extraction of mid range. I find myself listening longer vs analyzing.
     
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  4. M3NTAL

    M3NTAL Friend

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    I'll leave a quick simple review since Michael has gone very far for us as a community and he's stuck with us through all our crotchety-ness.

    My lazy bedroom setup has become my "main" setup since my "main" setup slowly became a 2 channel / 5.1 and gear slowly started moving around.

    My bedroom setup became a Squeezebox Touch running Enhanced Digital Out with a dedicated Sigma 11 power supply. It then ran coax -> neutrix aes xlr 110ohm adapter -> SFD-1 Mk2 lightly modified -> SS (KSA-5) / BBQ Sauce (T3) -> Sennheiser of choice / Clear / IEM of the Day / Lots of other shizz

    I really wanted some PEQ / VST plugins (Audeze) / Quick Access to my library. I went with the Eitr to bridge my laptop to the SFD-1. Honestly it gets the job done, but doesn't sound as good, leaves my laptop running with the lid cracked on its side of my bed all night / and god forbid you knock the USB cable at all and have to restart everything. F-That at 1AM and you're already hanging out with either the dead or the Grateful Dead.

    Along comes the Pi2AES. It is much closer to the SBT and honestly it punches a little past the SBT with that extra 1-3%. The things that it brings are what any good digital brings. It brings that "gel" or that extra bit of holographic effortless-ness. I guess you can say it another way - it allows the SFD to deal out a-bit more nuance with the very clean signal being sent from the Pi2AES.

    It got me as close to the best my personal digital collection has come without the hassle of a cd-spinner or any other wonky-ass ethernet / usb / thunderbolt / insert whatever digital-dongle-cable-connection-shit.

    I'm currently continuing to run LMS / Squeeze because I'm already a "few" (still have a spare SB2) years deep on the environment. I've tried roon and it was just too much to relearn with how large and weird my library is.

    I guess I should mention this since I've never mentioned it on here before about how "weird" my library is. Electronic folks might understand.

    Anyways - I still purchase physical discs and rip them, but here's the catch - most of my crap taste music is electronic music that has been curated by a DJ. The songs are meant to all come together as one artistic story. I do not skip tracks as the "story" is meant to be heard start to end. I rip the CD as one ALAC file usually since I was also really invested into iPod with a HDD as my travelling music. (We remember the ALO / Red Wine Audio days) So.... yeah - most modern music software is trying to figure out WTF is with my collection when it's literally thousands of 2 hour long single files that can only be sorted by album or artist. iTunes has been pretty darn good at helping me keep it all sorted, but J.River essential is setup to be pretty close to the same now. iTunes works more often than J River. JRiver sometimes likes to take audio/video drivers hostage and kill the system.

    I'm almost positive I'm going to buy another (the new one Michael is working on) and have a second one that I can tweak a little more while keeping this one "safe" running LMS / Squeeze.

    Thanks again Michael. The hardware is awesome! Now lets hope someone can get a software package that all of us can agree upon and has enough functionality for all our weird situations. (vst plugin / full peq / possible hrtf or x-feed options)
     
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  5. shotgunshane

    shotgunshane Floridian Falcon

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    Pi2AES Loaner Impressions:

    I’m sold on the Pi. I compared my Airport Express via optical to Pi via AES and there were 2 easily detectable differences. The AE only has optical output and is known to have slightly high jitter. Busy cymbal heavy sequences sound cleaner and more delineated on the Pi. They are more hashed and blurred on the AE. Also bass is tighter on Pi, whereas it sounds a little fuzzier/looser on the AE.

    For casual listening, these differences are small but during critical listening, particularly when comparing in-ears, it’s a very nice revelation.

    Sometimes if I’m comparing something, when I keep restarting a song, the AE can ‘stutter’. What I mean by this is it can skip a second or two of music or produce no sound. Almost like a buffering/memory/processor problem. It never does this for regular music listening and the occasional skip song.

    The Pi never did this. It always started and always started where it was supposed to. The only slightly downside is that it’s not instantaneous. There is a split second delay when starting a track over or skipping to next. It’s a very minor con though. I totally don’t mind it. I’d rather it do that than the stuttering.

    Minor quibbles:
    • The clear case is pretty fugly. The few black versions I’ve seen on the web look a lot better. Plus the lights. Is this a Christmas ornament?!?!
    • I don’t like the power coming out the side and the audio connectors coming out the back. Makes for a slightly messy arrangement cable wise. Right angle adapters for power should help clean this up.
    Minor quibbles aside, I definitely want one.
     
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  6. rlow

    rlow A happy woofer

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    Your minor quibbles will be addressed by the AiO version/unit upcoming (CM4AES), in case you’re not aware. But it will cost more:
    https://www.superbestaudiofriends.o...-go-rpi-aes-streamer.10471/page-6#post-339881

    Edit: Nvm I see you already commented in that thread :). But will leave the link for others.
     
  7. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    Or... take off the inside paper, wipe with acetone and spray paint whatever color you want. I sprayed mine a metallic bronze to match the metal on my BH Crack.
     
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  8. shotgunshane

    shotgunshane Floridian Falcon

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    Nice! Have a pic?
     
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  9. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    [​IMG]

    Here's a closeup of the top - this is the 7" screen version of the case, but you get the idea. Leave the paper on the outside, acetone wash the inside, spray away. LET IT DRY (don't get anxious, let it dry 24 hrs so the paint on the little tabs isn't soft when you put the thing together).

    Then peel the outside paper, put it together and there you go. The plexi now has a depth to it, like a really good paint job on a custom car. It looks way better than the black case... and bonus, it doesn't show fingerprints nearly as much as the black case.

    I have three Pi2AES's, one with a black case and the other two painted. The black case is the one hidden behind the components... the other two are sitting on the desks.
     
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  10. wormcycle

    wormcycle Friend

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    I already have Pi2AES and I am pretty enthusiastic about it, otherwise I would look at your review as simply comparing USB to SPDIF/AES. And your final conclusions are spot on but why would anyone pay not $3000 but even $10 more to run USB is incomprehensible to me, unless there is no other option.

    EDIT: First sentence in initial post did not make any sense :( I fixed it now
     
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    Last edited: Mar 19, 2021
  11. econaut

    econaut Facebook Friend

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    I remember impatiently waiting for the Unison upgrade to be available in Europe in early 2020. I also remember reading about the Pi2AES here and discarded it because it seemed to complicated and I also wanted that bloomy Unison sound in particular. I also had no understanding of network streaming and RPis at all.

    I eventually got my Yggdrasil upgraded, it was an improvement over Gen5 and I moved along. BUT although listening fatigue was less than with Gen5, it was not gone. And especially because of reading @rlow 's comparison many times I couldn’t get out of my head that there was an improvement available.

    This would eventually lead me to spend 90 Bucks just for shipping and getting into the Pi and network streaming world.

    I rarely do critical listening, I prefer to hear changes immediately. And this was definitely the case with the Pi2AES in my two channel system. I could quickly adapt to the abundance of clarity and especially I can now crank up the volume to ear damaging levels and it's still fun to listen. Not so with Unison as stated above.

    Although I started with Audirvana+ and RoPieeeXL, this combo stopped working after a few weeks. This showed me that UpnP implementation is a hit or miss and introduced me to other distros like Volumio, moOde and DietPi. Since I just wanted an UpnP renderer and liked the approach (and support by Harry) of RoPieee, I eventually got into Roon, which I would have never done without getting the Pi2AES in the first place. I am a happy lifetimer now and also use better DSP for room correction, because Roon does not support VST plugins (one among other reasons I never checked Roon out).

    Now everything is better than two months ago!

    A few quick notes:
    • upgrading the Pi’s USB firmware with RoPieee decreased board temperature about 8° C

    • I also added some small heat sinks just because

    • XLR cable for digital AES needs 110 Ohm impedance, but I didn’t hear a difference vs. the analog one I used before

    • one can turn off the LEDs of the Pi with Ropieee (but not the LEDs of the Pi2AES)

    • for use with Roon I recommend RoPieee

    • for use with Audirvana+ I would recommend RoPieeeXL, when Audirvana fixes their UpnP implementation (I don’t blame them, I just think they need to fix it, not Harry of RoPieee, he really tried a lot to make it work for me, but to no avail)

    • right now DietPi Allo Edition works reliably with Audirvana+ and Pi2AES (mind that the Allo Edition is needed, normal DietPi does not include drivers and software out of the box to be able to use the Pi2AES)

    • one of these right angle adapters available in Europe worked for me
     

    Attached Files:

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    Last edited: Mar 19, 2021
  12. wbass

    wbass Almost "Made"

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    I had the Pi2AES for about a week on the loaner program. (Thanks, y'all!) I compared it to my Lumin U1 Mini (which is obviously a more expensive unit) through my Matrix X-Sabre Pro and more briefly my Yggdrasil (Analog 2, USB 5).

    Rest of the set-up: Bryston BHA-1 into HD800 (stock). I also have used a Bluesound Node2i and an ultraRendu and microRendu as my streamer solution. I used the AES output with both the Lumin and the Pi2AES and briefly experimented with the i2S output on the Pi2AES. I heard no difference between the two into either DAC.

    Note: I really dislike comparing digital components. I find even the differences between DACs maddeningly subtle. However, I have heard, with very close listening and immediate ABing, just about noticeable differences between streamers. Primarily, as others have noted, in the technicalities.

    To my ears, compared to the Pi2AES, the Lumin is ever so slightly more resolving and offers more fine grain detail. It can be subtle, and not every recording shows up the differences, but some do. On Brad Mehldau's Blues and Ballads, I heard, with the Lumin, a little more clearly the ringing overtones of a sustained chord and a more coherent sense of how Mehldau phrases his lines. A little more of the subtle brush stuff Jeff Ballard does on his kit.

    On Rickie Lee Jones S/T record, I heard a bit more coherence, with the Lumin, in the various electric and acoustic guitar lines, a bit more of the room ambience on Steve Gadd's kit, and the bass lines came across as a bit more solid and growly in the way I think an electric bass should sound.

    The Pi2AES struck me as ever so slightly closed-in sounding, with a bit more haze between the instruments. Perhaps this is another way of saying that the Lumin U1 Mini has better separation.

    BUT--and this is a big but--I think I'd be hard pressed to tell one streamer from the other in blind listening. The Lumin is better, is my somewhat hesitant conclusion, but it should be at the price.

    My ranking of streamers I've heard, on sound quality, partly from memory:

    Lumin U1 Mini > Sonore ultraRendu (sBooster LPS) --> Pi2AES --> Sonore microRendu (sBooster LPS) = Bluesound Node 2i.


    By ergonomics and ease of use:

    Bluesound Node 2i (the Blue OS app is fuss-free) --> Lumin (also has a good app) --> Pi2AES (plug and play for me, as I used a Roon trial, and Roon recognized it immediately) = microRendu = ultraRendu (both via Roon, with some fiddling).

    The new Pi2Designs all-in-one should solve the minor ergonomic concerns I have with the Pi2AES: the inconvenience of the placement of the various outputs and inputs and the interior lights, which are too bright and a touch gaudy.

    Conclusion: the Pi2AES is an excellent streamer for a modest outlay. It is almost but not quite as good as the Lumin U1 Mini, which is in a significantly higher price tier. It is better sounding (more clarity, less muddy, less rounded) than the Bluesound Node 2i, but the Node 2i has great ergonomics. It is better than the Sonore microRendu with a good PSU. But the ultraRendu has the lowest noise floor of all of the above and is a slightly better box (to my ears).

    All of this said, differences between all are subtle. Purely on sound quality alone, I think many, many people would be happy with an ultraRendu or a Pi2AES just about equally. (The Pi2AES has more output options, so that's a big plus.) However, my favorite streamer, thus far, as I haven't heard more than the above, is the Lumin U1 Mini. It does more--has its own dedicated app, upsamples, offers various configuration options--but is significantly more expensive.

    Thanks again for letting me be part of the loaner tour.
     
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  13. bilboda

    bilboda Florida boomer

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    Ifi has added another new power brick, this one at 24 v and 2.5 amps, suitable for the pi2aes. Happy with my noise nuke, it may or may not help improve the sound but here is. https://ifi-audio.com/products/ipower-elite/
     
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  14. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    wow... $300.:eek:
     
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  15. gaspasser

    gaspasser Flatulence Maestro

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    Why start up the PS nervosa? @earnmyturns already looked at powering separately with SBooster and he didn’t seem impressed enough to not use stock Meanwell PS.
     
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  16. Ksorota

    Ksorota Almost "Made"

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    Pi2AES…my intention is not to come in and parrot the praise that has already been typed in the above posts, but it is hard not to. I have been using streaming services like Tidal HIFI, Spotify premium and Apple Itunes (free with Verizon) for the last bunch of years using a combination of PC, MAC and cell phone. My most used current setup is via Mac mini M1 through USB to Soekris 2541. The sound is good, nothing to crazy and no stray pc noise or grayness that I knew of. That was until I tried out the Pi2AES.


    Setup was easy, although I am not sure I was using it to its fullest potential. I plugged the ethernet into my network and it immediately showed up as a target for streaming via the MAC. The one annoyance with playing this way was the delay between pressing the controls and the Pi2AES responding…several second delay.


    Soundwise, the Pi2AES is a legitimate upgrade over streaming via MAC. Although I did not try an apples to apples comparison with USB. Using BNC with the Pi2AES presented the music with more clarity and a sense of ease that is hard to really explain. The best analogy I can do is not original, but the many times repeated comparison between looking out an open versus a closed window (a clean window even). The bit of grayness was gone and more nuance existed between instruments and harmonies were more developed/natural sounding. All this is to say that I was impressed by the little streamer.


    On its appearance…not a fan, but as others have said, its small enough to easily hide away. I would choose to paint the housing if I were to purchase the streamer…but I am currently waiting for Mercury to put my money where my mouth is.


    Add me to the list of the users who want the magical music streamer to come pre-assembled and ready to plug in!


    Thanks again for including me on the tour and I look forward to more impressions.
     
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  17. Imraan

    Imraan Friend

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    Thank you @loadexfa @rhythmdevils and @Michael Kelly for making this loaner possible!

    I'll be comparing the Pi2AES to a Hifiberry Digi+ Pro HAT and to the BF2's Unison USB input, all setup as Roon endpoints.
    TL;DR - My impressions are in line with the majority posted above.

    I currently use the Hifiberry for more focused listening sessions and Unison as a utility input when doing less single task work, browsing etc.

    Pi2AES Vs Hifiberry Digi + Pro:
    • Better separation, placement & space, focus
    • Not as upfront, less 'wall of sound'
    • Less strained, feels effortless, more dynamic
    • Bass tighter, less bloomy, a touch more extension and slam
    • Midrange smoother, touch richer
    • High frequency transients much less sharp, finding myself able to crank the volume up, less pain and fatigue
    • I do not hear a difference in background noise between the units
    • I do not hear any difference in resolution between the two units either, to my ears the delta is in sonic presentation

    Pi2AES Vs Bifrost 2 Unison USB
    • Better separation, placement & space, focus
    • More impact and weight with Pi2AES
    • Unison sounds a less real, thinner and more smeared/congested
    • I do hear a bit of greyness/background noise with Unison v Pi2AES
    • I do not hear any resolution difference between the two units
    Notes:
    • I'm using the isolation transformer Hifiberry with an iFi 5V power supply. My understanding is that the primary hardware differences of that config vs the Pi2AES are the clocks and even better PS.
    • I setup the 2 HATs and the Bifrost 2 USB as grouped zones in Roon for ease of comparison, I did not directly A/B.
    • Ethernet connection to my network for the 2 HATs, direct USB to my computer for the Unison input.
    • I tested streaming to the unit from the Tidal, Qobuz, Apple Music apps (using my own accounts). This worked reliably, and is **to all intents and purposes** functionally identical to connecting to a BT speaker for non-technical people. (I know it's not the same thing!)

    Final Conclusions

    • To my ears the Pi2AES sounds 2 steps more musical, realistic and engaging, whilst being 2 steps less fatiguing when compared to the Hifiberry, which splits the difference and is in turn a little better sounding than Unison.
    • The Pi2AES matches my preferences more closely than either Unison or the Hifiberry Digi + Pro.
    • Unison is far from objectionable, and has a very strong utility use case in my setup, I can't do without it.

    End result - I'll be looking to buy a Mercury Streamer for myself a bit further down the line. I'm very grateful I got the opportunity to solidify that decision in the comfort of my own home, and before the Mercury release.

    Thanks once again to all involved for your time and resources!
     
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  18. epistrophy42

    epistrophy42 Rando

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    Contrary to what wbass says, I find the Pi2AES (in combination with a Farad Super 3 power supply) much more musical than the Lumin U1 mini. Compared to the Pi2AES, I think the Lumin U1 sounds less-alive, 2-dimensional, dark and closed-in.

    I have been using the Pi2AES for 18 months as an EAS-EBU streamer via a Cardas Clear AES-EBU cable in a Vitus SCD-025 Mk2 CD-player/DAC. Just like to share some experiences :)

    Last year I further improved my audio set with Ansuz products from Danmark, with a Signalz C2 XLR interlink and a Mainz C2 Power Distributor and Mainz C2 powercable. The Ansuz products have many positive effects, they increase speed, timbre, three-dimensionality and energy without ever sounding technical or clinical.

    The Pi2AES-hat that I'm using is powered by the beautiful, yet precious Farad Super 3 power supply, the RPi-board simply by the standard RPi power supply. I was wondering: will the sound improve with the upgrade of the Raspberry Pi's power supply?

    First I listened to an RPi/Hat both fed (by placing the jumper) with the Farad Super 3: this sounded considerably more restless so less good. Then I fed the Pi2AES-hat dedicated with the Farad Super 3, and the RPi-board with an iFi iPower Low Noise DC Power Supply instead of the standard RPi power supply. The iFi made the sound dull, fine details disappeared, and phase shifts were easily heard in the stereo image. Even after 24 hours, no improvement was noticeable. When I placed the original RPi power supply back, the good sound was back. So what I heard was that even the power supply of the RPi-board has an effect on the overal sound, and the iFi iPower Low Noise DC Power Supply was NOT an upgrade, not by far!

    Then I found the Magna Mano Ultra Mk2 streamer on the internet, sold by Magna Audio in the Netherlands. Also a RaspberryPi-based streamer with I2S and AES/EBU outputs. I installed moOde audio and was listening to it for 3 weeks.

    What I liked about the Magna Mano Ultra Mk2 compared to the Pi2AES:
    - sounds fresher in the highs; seems to be more 'tunefull', as if the player is able to better grasp the 'tone';
    - very tight bass reproduction;
    - nice 1-cabinet solution with beautiful connection terminals (power, AES-EBU) and quality clocks (Crystek 957) and Class-A power supply;

    What I disliked about the Magna Mano Ultra Mk2 compared to the Pi2AES:
    - less 3-dimensional, less wide;
    - less sonorous in the midrange: voices lost 30% body;
    - (sometimes) a kind of 'coloring' of some mids, as if a tube/pipe is being held in front of the loudspeaker: I heard the same thing (to a lesser extent) with the dCS Bartok;
    - less energy (-40%) in the sub-layer (<35Hz). This also has an effect on somewhat older music (CDs from the 80s) that are often sound thin: they then become a bit unpleasant;

    The CD drive in my Vitus SCD-025 is my reference, and I am looking for an AES/EBU streamer that comes as close as possible to that quality (for Redbook CDs).
    Again, I found that the Pi2AES is closer to the CD than the Magna Mano Ultra Mk2. The Pi2AES just misses a bit of 'punch', but otherwise it is very close (95%) to the CD-sound. Perhaps its because the Pi2AES is designed as an AES-streamer, and the Mano Ultra as an I2S-streamer.

    So I stick with the Pi2AES! Keep up the good work, Michael :)

    @Michael Kelly: could the Pi2AES potentially benefit from an upgrade of the clocks, like the ones from Crystek?
     
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    Last edited: May 13, 2021
  19. Michael Kelly

    Michael Kelly MOT: Pi 2 Design

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    In general it could. But at what cost. The next possible step would be oven controlled oscillators that are much bigger and much more expensive. Allowing for external clock input might seem like a good idea. But it risks introducing noise even if there is no external clock attached.
     
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  20. Woland

    Woland Almost "Made"

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    Thank you @loadexfa @rhythmdevils and @Michael Kelly for this loaner!

    [​IMG]


    I compared the Pi2AES to a Hifiberry Digi2 Pro HAT. For most of my testing, they were feeding a Schiit Gungnir Multibit via BNC (Pi2AES) and Coax (Digi2) connections. I connected the BNC directly to the Pi2AES, and also tried using a Sescom AES to BNC connector. As far as possible, I used the same setup for the Pi's software (Volumio) and source material (local server of FLAC files).

    My testing included short and extended listening sessions, usually to Chesky recordings, notably their Ultimate Demonstration Disk and some recent samplers. I used Chesky because I wanted to ensure subtle cues about spatial location would be present. Live performances with binaural recording should have these, while studio mixed recordings are more likely to have mixing artifacts.


    The Boards
    The Digi2 Pro is a small board with few components. It uses the Pi's own power supply and outputs to Coax and Optical. The BNC connector is an optional user-installed add-on. The Digi2 provides a pass-through of the Pi2 connector bus, and a connector for a DSP add-on board. The Digi2 Pro is fairly new with little online discussion, however it has a lot of commonality with the HiFiBerry DAC2 which is reviewed and analysed by Archimago here. The Digi 2 has a jumper that was removed for galvanic isolation. With the jumper, there is a high-resistance ground connection to make sure the receiving side isn't on a floating potential (which creates problems with the transformer shielding).


    [​IMG]


    The Pi2 AES is a much larger board with many more components driving many more outputs. It uses its own power supply (a Meanwell switching power supply was included) and powers the Pi. It has connectors for add-on boards. There is far more information about the board on SBAF than I was able to digest or summarize.

    [​IMG]


    I will separate the discussion by DAC because the conclusions are somewhat different.


    Testing on the Gungnir Multibit

    After many hours of testing, there were zero perceived differences between all the sources tested. This was somewhat psychologically draining, because it became hard to care about the analysis after the 20th switch of configurations revealed no differences at all. Sometimes I had to check the cabling, power off the unused devices etc to be sure the switch had actually occurred. Late in the testing, whenever a possible difference arose, I switched sources and compared and found that the perception had been illusory.

    There are good reasons for there to be no differences. Firstly, the 'bits are bits' argument is a powerful one for digital data, which suggests that all digital sources should sound the same. My experience is that all digital sources have the same tones, which is usually what we mean by sound. However, there are goods arguments for difference in jitter to translate into differences in apparent spatial nuance.

    @GoldenOne's linked video provides an excellent discussion of jitter, with specific reference to the Pi2AES and differences in sensitivity of different DACs with the Holo May mentioned as a DAC that overcomes jitter problems. The Holo May allows user control over the PLL so A-B comparison is straightforward.

    Like the Holo May, the Gungnir should not be sensitive to source jitter, provided the source is reasonable or better. The Gungnir processes incoming digital audio with Adapticlock, so its audio should be based around the quality of the internal clock, not the one used in the digital source. "Adapticlock analyzes the incoming signal quality and automatically routes it to the best clock regeneration system—either VCXO or VCO-based". The Gungnir has an indicator of which is active, and throughout my analysis the more precise VXCO (crystal clock) was being used. There's no user control over the process.

    I spend some hours researched the Gungnir's clock regeneration, but information seems a little sparse. Some online discussions seem definitive that source should not matter at all if VXCO reclocking is active:

    If BBG does not come on [VXCO mode], then output quality from Gungnir will be same for irrespective of whatever source gear I use? For example, if I play particular CD using a $100 DVD Player and $1000 CD Player through Gungnir and if BBG remain off [VXCO mode] on both case, would the output from Gungnir be same quality on both case?"

    Jason replied- Correct... Performance of the clock regeneration system (not just reclocking) is invariant when using VCXOs, so yes. Gungnir is VERY different than most DACs.​

    I wasn't able to find any statement that unambiguous directly from Schiit. That's despite searching through the Schiit Happened blog-posts which highlight the importance of Adapticlock and clock regeneration, but don't go into the details.

    I then wrote to Schiit seeking more information and received a response that they do not provide additional information other than in their description on the website.

    I am unable to reconcile the assertion of source invariance with my experience that switching from a Chromecast Audio to a PiFi , and then to the Digi 2 Pro made a perceivable difference. I will go back to using the Chromecast Audio for a while and see if a difference is still apparent.


    Testing on entry level DACs

    Suspecting that the lack of audible difference between the sources was because of the Gungnir's clock regeneration, I obtained an entry level DAC with Coax input. The Topping E30 should be more reliant on the source's clock, so differences should be more apparent. I then switched source by moving the Coax cable between the two sources while they were playing the same audio.

    Spatial presentation wasn't great from either source, likely because of the DAC. However, I did feel that there may have been a slight advantage using the Pi2AES. Extrapolating from that observation, the Pi2AES may be of benefit in all DACs that rely on the source's clock rather than their internal clock.


    Conclusions

    In my experience, both of these inexpensive sources are a significant step up from a USB connection, providing a more spatially precise listening experience.


    Advantages of the Pi2AES:
    • There may be significant benefits for other DACs which are solid but have no regeneration or different regeneration approaches. In writing that, I'm assuming the Pi2AES has a better clock / lower jitter.
    • Additional connectivity options, which I did not test.

    Advantages of the Digi 2 Pro:
    • Much lower cost.
    • Capability for a DSP board.
    • Passthrough of the Pi connector. I use the connector and Volumio plug-ins to control a power relay for the amplifier, and there are many other use cases for sensors, controls and add-ons.


    What would it take for me to switch to the Pi2AES?

    I'd like to see measurements comparing sources. Even though I cannot hear a difference now, it's not unusual for downstream changes to 'unlock' benefits from upstream. Maybe a measured improvement would translate into an audible benefit with the right headphones or amplifier in the future. Maybe my ears are compromised by vaccination, and they will recover and reveal more differences in future. For now, I am very happy with the Digi 2 Pro.


    Edit: removed tangential comment on Bifrost 2 clock regeneration.
     
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    Last edited: May 16, 2021

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