PecanPi DAC (USB) Review

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Baten, Dec 20, 2020.

  1. Baten

    Baten Friend

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    I have purchased this DAC at the end of March 2020, so have gone quite some time using and listening to it. Mine is a Rev. 1 unit which I bought at considerable discount which made it a good deal to me (around €400 excluding VAT/duties). I see there is a newer Rev. 2 out right now, which includes S/PDIF input in addition to the USB, and a volume control knob. Mine has just the XLR+RCA outputs, USB in and a 9V barrel plug input. The new version comes in at a rather steep $750, but there are promos just about every typical cyber/seasonal occurance.

    Introduction:
    So what is this DAC exactly? Leo, owner of Orchard audio had been developing it since his "ApplePi" days, a name which he had been forced to abandon due to big Apple(©) harassment. It started with a Pi module featuring dual-mono "flagship" Burr-Brown PCM1794A chips specced at ~130dB SNR and <0.0004% THD, which the PecanPi reaches and even exceeds. More on that later. It also touts signal re-clocking with a Crystek oscillator, a low-noise output stage using OPA1612s amps and panasonic resistors, and multi-stage power filtering using a bunch of TI TPS-range voltage regulators. If you want the whole marketing shtick, check out the official specifications.

    The USB version of the otherwise Pi-based PecanPi is really just the bare board, but with I2S fed from a MiniDSP USBStreamer kit instead of the Pi. A little lazy perhaps, but I didn't really expect much more from a smaller company not well-versed in transports, XMOS coding etc. I wouldn't even have noticed it, if it weren't for the USB device to be recognised as a "Multi-channel USBStreamer". Thankfully, proper ASIO drivers are provided upon purchase which have worked issue-free for me.

    Side-note:
    Something I noticed while browsing online. There's a rival DAC called the "Digital Amp Company Cherry DAC DAC" (yes, really. DAC DAC o_O), costing upwards $1K and which.. seems to be based on mostly the same parts. Same dual mono chips, same re-clocking mechanism, same voltage barrel input... no USB input though. Still, the similarities are uncanny:

    [​IMG]
    [​IMG]
    Not sure who's copying who, but in terms of what's in these boxes they are more similar than different. The XLR connectors used even seem to be the exact same!

    Listening impressions:
    Disclaimer: I LIKE BURR BROWN. I bought this thing only to hear the flagship PCM1794As doing what they do best. The output of this DAC is 5V balanced 2.5V single ended, so right off the bat you'll notice some increased volume depending on what you're comparing with... my previous/trusted set-up was an Audial AYAII (downgraded from a holo spring :oops:) into either a Topping A90 when working/gaming or into an Asgard 2 when I want to jam out. During evaluation of the PecanPi USB, it effectively replaced the Audial DAC which also has nominal 5Vrms output. Worth mentioning, since after a month or so I bought a Radial Twin-Iso to get the full 5V balanced output into the Asgard2 RCA input, following the top recommendation in the Bal to SE thread. Thanks for that, purr1n. This works absolutely wonderful.

    As for the PecanPi sound.. it's quite great to my ears. First thing you notice is a full-bodied bass response, none of that rolled/veiled velvet stuff but proper bass with great heft to it. Also quite the improvement compared to NOS stuff I have gotten used to over the years. Gone are the romantic/slightly rolled highs though, yet in their place is a precise, yet not overly-accentuated top-end. Only rarely fatiguing, and I'm really quite sparkle-sensitive. Great PRAT to boot.
    I'm not one to evaluate stage. I use HD580/HD650 90% of the time and the head-space is legendarily constrained. However, the other 10% I use my HD800s (or AD2000s) and the width/playing field of the stage is quite improved over the Audial (or the holo spring for that matter). Nothing dramatic though, really, just enough to notice and appreciate.

    Where the burr brown chips take a hit is overall layering of the sound. R2R DACs just convey this better. There is no "wow" texture to the sound, no 3D/lifelike presentation.. but what you get in return is a "pretty" sound none the less. None too rounded, none too sharpened or glarey, simply great and well-rounded for a delta-sigma design. Admittedly by the end of the week, I'm still often in the mood for some NOS warm-poo sessions, but the PecanPi does a great job for day-to-day listening. After 9 months of daily use, I can confidently state I like it better than most AKM-based DACs I have heard over the years (my old fav the Aune S16, both Schiit modi/modius, Grace SDAC balanced) as well as the better Sabre ones I've owned or auditioned (Matrix X-Sabre pre-MQA version, Burson Swing rolled with my favourite op-amps, some others I can't immediately recall).

    Quirks
    Few devices come with zero drawbacks. This PecanPi is not immune and has quite a few
    • This DAC sounds better to me left powered on at least overnight, or longer if time allows (>24h ideally).
    • Rev. 1 is limited to the miniDSP-powered USB input. Might not suffice for the digital-picky. For me it's OK.
      Thankfully Rev. 2 embed an s/pdif input which allows the likes of Eitr, Pi2Aes to interface to it.
    • I noticed on Windows I sometimes need to unplug/plug the USB-B end to force a new handshake.
      Thankfully, once it is in place, it works without a hitch or stutter. Driver is rock-solid.
    • I learnt there is only an 48kHz oscillator. All 44k rates get resampled. Purists would lose their shit at this!
      I simply feed it only 48k multiples as a fix, resampled within OSX, which is 'fine', or through Roon (better).
    • The PecanPi claims to have head-amp capabilities since the RCA come with a low-ohm line-driver output.
      RCA>1/4" adapter can be bought as an add-on... Don't bother, lol. Extremely weak sauce. just don't...
    • PSU was not priced in with Rev. 1, but I see it's now included in the pricier new revision, as it should.
      I mailed back and forth and got one for free, but I mean, really?
     
    Last edited: Jan 12, 2022
  2. Baten

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    Thought I'd post some interesting measurements, comparing the DAC DAC and the PecanPi:

    Measurements:
    Jitter FFT:
    DAC DAC (borrowed from ASR)
    [​IMG]

    PecanPi (borrowed from Ochard Audio)
    [​IMG]

    Sidebands are better, but note how similar the spuriae are...!

    Multitone:
    DAC DAC
    [​IMG]

    PecanPi:
    [​IMG]

    Output level is a little different between the graphs but note overall nicer output, clear noise floor at -130dB.

    To finish, 128k FFT of -20dB 1kHz Output
    [​IMG]

    Mains rising a little but way too low in level to be of concern, more importantly distortion is very, very low.
     
    Last edited: Dec 20, 2020

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