Saturday, 7 May 2016

MEASUREMENTS: ODROID-C2 with Volumio 2, and USB digital music streaming.

ODROID-C2 & unused "Fujifilm" 5V 1.0A wallwart ready for testing...
For those following along, you're recall back in March, I purchased a Hardkernel ODROID-C2 Linux-based credit-card sized single-board computer; the hardware described in my preview. I loaded up and customized the machine with Volumio 2 (RC1) a couple weeks back. And now as promised, I'll be showing some measurements using this machine with my TEAC UD-501 DAC. (Note that there has been a new Volumio image update since my last post. The current version is "VolumioRC1-fix-2016-05-03-odroidc2.zip" found here. Only fixed some boot issues apparently.)

Before I begin, let's discuss what we're trying to figure out objectively here... It has been claimed by some that the USB interface (which the ODROID will be streaming through to the DAC) can be "bad". Supposedly, it's electrically "noisy" (of course a noisy fan and spinning hard drives are also very bad). And, this is especially "bad" with computer audio because computers are electrically noisy devices and will end up polluting the output from your DAC. Hence, by this reckoning, a general-purpose computer isn't supposedly a good thing to have doing high-fidelity audio duties. Furthermore, it has been surmised by some that power supplies can be problematic. Specifically, an inexpensive switch-mode power supply (like the one in the picture above) can be noisy and again, will have deleterious effects on the sound quality.

It has been said that devices like the recently released Sonore microRendu among more fancy audio streamers like the Auralic Aries line of devices can "sound" better because they reportedly take into account the various sources of noise and supposedly have optimized hardware/software. True or not, the price of such "audiophile" grade devices can be rather substantial especially when it's a device without internal storage and acts as a digital conduit to feed a DAC.

So, what then should we evaluate objectively for an audio streaming device? If you look at Stereophile's measurements for the Aurender N10, evidently not a heck of a lot :-). So long as it's reliable, does the streaming job without undue hassle, and for me sonically unobtrusive (ie. no noisy fans disrupting the playback), then the likelihood is that there's not much that can go wrong unless one can find noise anomalies as per the above perfectionist-audiophile claims.

Here's then what I am going to do... Let's put this little ODROID-C2 + Volumio streamer through the test bench with my USB TEAC UD-501 DAC. Over the years, I have measured the sound output of this excellent DAC with all kinds of computers. Can I find any difference between machines? Let's also include the usual Dunn J-Test to look for evidence of jitter/time-domain issues. And finally, let's check and see if I can detect the 8kHz PHY microframe packet noise as I did last year due to sensitivity of the Emotiva XSP-1 preamp's RCA analogue bypass input which was able to pick up noise in my more complex home-theater setup.

Part I: Differences between computers compared to ODROID-C2 driving the TEAC UD-501 DAC (USB)

Here's the setup for these measurements:
"Streaming Device" [Computer / ODROID-C2] --> generic shielded USB --> TEAC UD-501 DAC --> shielded 6' RCA --> E-MU 0404USB ADC --> USB cable --> Windows 8.1 computer
All upsampling and DSP in JRiver 21 turned off of course for the testing (I have already shown previously the frequency response when the convolution DSP with JRiver is activated). Volumio 2 using its underlying Linux mpd and ALSA infrastructure streaming through gigabit ethernet. All Windows 10 machines are using the latest TEAC ASIO driver (v108e from late 2015). For some (like the Surface Pro 3 and Pentium G3220 computers), the test signal was on the SSD in the computer so not streamed through the network. The Gigabyte HTPC is playing off my Windows Server "NAS" through Samba over ethernet. And of course JRiver sending through DLNA/UPnP for the ODROID-Volumio 2.

Let's dispense with 16-bit audio, doubtful that "standard resolution" signals will yield anything when we can examine higher resolutions for anomalies... So starting with 24/96 RightMark test signal, this is what we see as a numerical summary:

To the left is the ODROID feeding the TEAC UD-501. Then next is the new Skylake Gigabyte Z170X-Gaming 7 motherboard HTPC. This is followed by my Microsoft Surface Pro 3 running battery powered feeding the UD-501. The last two columns were measurements done months ago with my previous Pentium G3220-based HTPC computer with ASUS B85M motherboard - playing 24/96 straight from Windows 10 or Windows 10 plus Fidelizer and JPLAY software optimizations as described previously.

Numerically, despite some expected inter-test variability and the fact that these measurements were done over months, there is no significant difference... At most <1dB difference here and there with key measures like the noise floor way down below -110dB! Notice too the lack of any difference with the measurements of distortion. As demonstrated in the past, I have never been able to show that software optimization like Fidelizer and JPLAY have ever changed the output of a good external DAC.

A few choice graphs to examine for those inclined:

Okay... Let's go to 24/192 resolution:

And more choice graphs for your consideration:

Again... As you can see, there is no difference to be found whatsoever with the different computers I have feeding the TEAC UD-501 DAC. Whether it's a latest generation Skylake i5-6500 computer, or a much slower Pentium G3220, or a battery powered Surface Pro 3 with i5 processor, or the little low-power ODROID-C2 ARM-based processor. The sonic output is a reflection of the quality of the DAC itself, NOT the streaming device.

Part II: Jitter

Alright, how about using the J-Test measurements for hints of time anomaly?



Anyone see a difference they think may be audible between the ODROID, Surface, and Gigabyte motherboard computers? :-)

As demonstrated time and again, the asynchronous USB interface dissociates whatever timing irregularity might be in the USB stream from the clocking of the DAC playback. The effect from a streaming device is minimal unless you're using an interface like S/PDIF which has the clock signal embedded... To demonstrate a gross example, we can look at the 24-bit J-Test accelerated to 96kHz from 48kHz comparing the asynchronous USB conversion from the ODROID and Surface Pro 3 with what I showed previously with the Google Chromecast Audio and TosLink S/PDIF interface:
Note the X-axis was a little different for the Chromecast Audio. The ODROID-C2 and Surface 3 plots are essentially the same...
Again, before anyone freaks out about the horrible looking Chromecast results, remember the sidebands are still at least 70dB below the primary signal which is at 24kHz!!! This is just an extreme test to demonstrate the point about the robustness of asynchronous USB with a test signal that is beyond the needs of human hearing... (It's also another example of the power and sensitivity of objective measurements.)

I've seen recent claims that USB --> S/PDIF converters are somehow beneficial to good sound. I suppose this only makes sense if one absolutely needs galvanic isolation with optical TosLink and willing to pay the price of potentially higher jitter. Remember that I looked into one of these inexpensive devices (CM6631A-based asynchronous USB converter) back in 2013 and found that it did work well. But I would not advocate adding yet another device in the digital chain unless it's clearly necessary.

Part III: SMPS's (Switched-Mode Power Supplies) Are Horrible! (So says some perfectionist-audiophiles...)

I know... We all know that linear power supplies are "much" better, right? Well, alas, I don't have a linear power supply handy (though I was thinking of getting a lab unit for experiments). However, because the ODROID-C2 can be powered by the micro-USB cable, why not just use a simple 5V Li-ion battery?

As you can see, the little 2200mAh Duracell (5V, max 1A output, presumably typical LiCoO2 chemistry) I got from Costco as a bulk pack is capable of running the ODROID with no problem (for maybe a couple hours, didn't bother timing exactly)! Let's have a look at what the measurements look like with this:

As you can see, both the 24/96 and 24/192 measurements are here ("ODROID-Battery" obviously indicating the measurement with the Duracell battery used to power the machine). Essentially no difference here folks! Here are the 24/96 graphs...

As you can see, using a Li-ion battery with the ODROID as streamer made no difference to the TEAC UD-501 output... If in fact there was a difference, then it's below the noise floor of the E-MU 0404USB which means it's below -110dB with this DAC and I can't imagine how this could make a true audible difference! Clearly, we see the 60Hz powerline hum in these measurements. The DAC output as one would expect is logically more affected by the power supply inside the DAC rather than whatever power supply is feeding the digital streaming device upstream.

I had a listen to a couple tracks off Andrea Bocelli's recent album Cinema (2015) with the ODROID powered by the Li-ion battery versus the SMPS wallwart. No discernible difference as far as I can tell... Of course, there was a delay in shutting down the machine and rebooting so it's not a quick A/B comparison. Even if there were a difference, it wasn't obviously better that I felt compelled to run the device in a battery operated mode (or to grab a linear power supply and try given what I see here).

Part IV: Search for 8kHz PHY Microframe Noise

Remember back last year, I showed that there was an 8kHz noise I could hear out of my preamp's analogue "home-theater bypass" input when the HTPC USB was plugged into the DAC? Recall from that post that I was able to attenuate it with the Corning USB3.0 Optical Cable to a significant degree.

Let's see if I can measure it with the ODROID-C2:

As you can see, taking the analogue output from the Emotiva XSP-1 preamp set to the "home theater bypass" analogue input with the TEAC DAC plugged into the Skylake HTPC directly, we can pick up the 8kHz microframe noise at a low level (on the top left we see the loudest tone is measured at -102dB at 7998kHz). In comparison, the ODROID-C2 was nice and quiet with the "loudest" level being a 60Hz powerline hum at -105dB.

That's encouraging... I suppose it says something about the low-power ODROID not emitting as much electrical interference. Remember though as I warned previously, I feel this is a rather idiosyncratic finding likely related to the complexity of the home theater system and the sensitivity of this "home-theater bypass" analogue input on the pre-amp. It's a way to show myself that the 8kHz noise can be amplified in certain circumstances and probably has to do with how I'm hooking up the HTPC to my system (just like ground loop hum from the computer was an issue and needed to be addressed in that previous post).

Part V: Conclusion

I hope this post answers a few questions you might have been curious about and provides answers about the role of digital streaming devices on sound quality when used as a USB source. In general I can state the following:

1. Yes folks... "Bits are bits" when dealing with accurate digital data transfer to an asynchronous DAC. Some people don't like to believe this but it is consistent both in my personal subjective observations and consistent with the objective results. Indeed, the universe seems to "work" as expected within the domain of engineered electrical devices meant to reproduce audio frequencies :-). Measurements like frequency response and distortion characteristics do not change based on what computer or streaming device is used to feed the DAC asynchronously. These qualities are inherent to the DAC itself. Also, the sound of the DAC of course does not change based on the streaming device since they're all feeding the same (bit-perfect) data.

2. Time-domain jitter is not an issue with asynchronous DAC's as I have shown many times before irrespective of the source. I hope the jitter "boogey man" can be laid to rest when it comes to most reputable modern asynchronous DACs. And even when there are differences in jitter, audibility is unlikely unless very severe.

3. While a switched-mode power supply (SMPS) might be noisier than a linear one (high frequency switching noise for example), I fail to see how going with a linear power supply will make any difference when used to power the digital streaming device unless there is evidence that this noise affects the digital interface and the DAC is further susceptible. I don't have any qualms with advocating for a good power supply in the DAC of course (for example, it would be nice to not have that 60Hz hum in the output of my TEAC DAC). In any event, I found no difference going from the "freebie" SMPS I have been using for the ODROID-C2 compared to a Li-ion battery on the DAC analogue output...

Needless to say, I am rather impressed by the little ODROID-C2 computer for audio streaming. It's very easy to set up, for weeks it has worked without an issue in the background sucking up little power and always on the ready to play whatever is requested through JRiver 21. I have not experienced any instability while running Volumio. The quad-core 64-bit processor is speedy for audio-related tasks. And like I showed last week, the gigabit ethernet is really quite capable! By the way, Volumio operates in a "headless" fashion so while it's running, the HDMI video output is turned off for those who are concerned that somehow this may affect sound quality. Remember that although I'm testing Volumio here, Archphile already has an image out and a RuneAudio release is imminent. Always good to have options!

For significantly less than $100, I think one can't really go wrong with this little unit or the Raspberry Pi 3 or numerous others. The benefit of the ODROID-C2 is its speed, 2GB RAM, and the potential to be a good audio/visual streamer in the future if you want 4K/60 HDMI 2.0 plus excellent gigabit ethernet speed.

Looking around at the audiophile offerings, I'm scratching my head at the mark-up and seriously questionable claims out there. For example, what's with the redacted texts in the Sonore microRendu "review"? Is that not just a bit pretentious considering that we're talking about a rather pedestrian dual core i.MX6 Cortex-A9 machine!? BTW, anyone see the clockspeed of the processor listed anywhere or how much memory? And can we also dispense with the name-dropping and cult of personalities as if there is some kind of "wizardry" at play? It's one thing to romance sentimental old technology like vinyl, turntables and glowing vacuum tubes, but can we not see how ridiculous this all sounds with contemporary ARM-core computers running off Linux and using mostly open-source code? Do we have to euphemistically justify the use of a slow SD card interface (the SDHC slot has been there since the dawn of the Raspberry Pi)? If it doesn't seem silly already, look back on articles like this in a year's time. The magical thinking which has been applied to traditional "High End" audio really does not work when applied to computing appliances like this. IMO, simple digital streaming devices like this should be inexpensive since the technology advances quickly and there's just no "luxury" value to the hardware. I bet just reading articles like the microRendu "review" will turn off many technologically savvy audiophiles as being yet another example of how out of touch this hobby can be at times.

As usual, it would be great if manufacturers of some of these streaming devices could publish some evidence of claims. How does that expensive linear power supply plugged into the streamer affect a good quality DAC's sonic output? Where is the noise/EMI anomaly we should be concerned about in the USB output? In sum, where are the benefits to be found based on the eventual analogue output from the DAC to justify the expense considering that claims may be biased by financial incentives? I think this is a very fair question. Of course I would not be holding my breath in anticipation of any actual objective results beyond likely wordy apologetic testimony of supposedly "complicated" details from the manufacturers and faithful practitioners.

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Okay, got a few "real work" projects on the go for the next couple of weeks. Also have a few new albums to check out plus playing catch-up on the latest The Walking Dead and Game of Thrones episodes :-). Hope you're all having a great time with the music!

55 comments:

  1. Nice stuff Archi. I'm a big fan of Raspberry Pi boards which I assume would be very similar to the Odroid. Thanks for the work.

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    1. Yup. Very similar and certainly from the software side clearly has an edge with newer kernel support and larger repository of apps!

      Cheers...

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  2. Wow. I've been following your blog for a couple of years now. Incredibly impressed with your work on this and other aspects of audio reproduction. Thanks so much for helping to dispel some of the audiophile myths surrounding this hobby.

    Your current topic of network music streaming to a DAC is very timely for me as I'm in the process of trying to decide which way to go on this. I'm currently using a Raspberry Pi 2 + Volumio + HiFi digi+ to stream to my Stello Ai500 Integrated Amp + DAC, connected by coax spdif. As a DLNA server I use my custom built HTPC running JRiver MC21 + JRemote app for control. Music is on a NAS.

    I want to buy a Teac NT-503 DAC/streamer to upgrade the aging DAC in the Stello (no DSD). This will give me four possible connection options:

    1. Raspberry Pi (DLNA) > HiFi Berry digi+ > spdif coax > Teac NT-503
    2. Raspberry Pi (DLNA) > USB > Teac NT-503
    3. Teac NT-503 (DLNA renderer) - this is the way this device was designed and might be the best solution but no one can tell me if it's gapless with JRiver/JRemote
    4. HTPC > USB > Teac NT-503

    Based on your experience with various combinations similar to these, do you feel that any of these options would sound better or worse?

    Thanks for any advice you can provide. Keep up the good work!

    Terry from Victoria, BC

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    1. I'm in a similar situation. Currently using a Pi 3 + RuneAudio + HiFi Digi+ to Rega DAC-R via coax. I'm wondering if the USB output from the Pi 3 will give objectionably "better" sound, thus rendering the Digi+ unnecessary.

      Archimago: Do you have a little tutorial one could follow to do the same tests you do? Particularly the comparisons in the green boxes.

      Kind regards,
      Robert.

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    2. Hey guys, nice to see all the DIY activity going on! That's truly how you find out for yourselves what works and what does; and if certain changes make a difference...

      Okay. So, the data in the green boxes are the result of tests I've done over the years with different computer gear hooked up to the TEAC UD-501 in comparison to the ODROID. I don't have a tutorial per se basically because I'm just using RightMark (I paid for the Pro license but the free version is just as good) and my ADC (the E-MU 0404USB). The numbers and screenshots are what's displayed by RightMark and comparisons done through the software.

      As for what is better from a sound quality perspective; IMO a direct USB --> asynchronous DAC works for me. IMO, S/PDIF introduces the possibility of extra jitter to the system simply because of the nature of the interface. Although obviously I cannot speak about all DACs, of the ones I have looked at, the old ASUS XONAR Essence One is the only one I thought the USB interface had a bit more low-level jitter than S/PDIF input. Everything else in the last few years like the TEAC UD-501, TASCAM UH-7000, Oppo 105, looked to perform better with the USB than S/PDIF.

      I guess ultimately, you'll have to try out the combinations yourself and have a good listen! Have fun :-).

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    3. I gave RMAA a go, first testing the loopback on my soundcard, then feeding my Rega DAC-R from my laptop over USB, then testing the Raspberry Pi USB to the Rega DAC and the Hi Fi Berry coaxial to Rega. I'm getting some wildly differing results. Can these be correct? http://postimg.org/image/ofvnxvojl/

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    4. Hi Rob. Yikes. There are major problems with those results. When you see massive anomalies in the swept frequency response numbers and THD numbers that look like that, it usually means there's a problem; maybe something to do with latency or the recording got truncated. What do the graphs look like?

      Once you figure out what's wrong, it's not hard to get very consistent results like what I found with the various computers and ODROID.

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    5. I played around with the RMAA software more and got proper results for my soundcard and Laptop USB out to DAC. I then tested the USB out and HiFi Berry coax out from my Pi 3 and got terrible THD results. Note that the THD is "okay" from the Pi's analogue out. I'm using RuneAudio, attached USB drive, and ethernet. So I tried over wifi, over NAS, and over wifi & NAS. Still got the same results. For each test I recorded the output to Audition and used RMAA's "analyse wav" tool, rather than recording directly into the software: http://s32.postimg.org/tz1p0kg45/Pi_THD.png

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    6. A breakthrough: http://www.runeaudio.com/forum/high-amounts-of-thd-over-usb-and-coax-t3586-20.html#p14653

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    7. It appears the Pi's digital output produces huge THD levels at any volume above 89%. Did you find that too, Archimago, or were you able to test with Pi volume at 100% (volume mixer disabled)?

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    8. Hi Robert,
      Strange. Remember I'm just looking at the USB output to my TEAC DAC and I don't have a digital daughter board or DAC attached to my ODROID's internal connector. Make sure there's no other volume settings in place - typically 100% output, no ReplayGain, turn off any DSP. Is RuneAudio accessing a NAS for this or are you sending audio through DLNA?

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    9. Hi,
      I get the same high THD with USB out from the Pi. Data accessed via attached USB driver but I've gotten the same results over NAS, Ethernet, Wi-Fi, different power supply etc. There is a six page thread linked above. I'd appreciate your input :)

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    10. Hmmm... I'm afraid of posting to the RuneAudio forum given the suggestion here: can you try installing Volumio on the Pi and see if this is still a problem? :-)

      Reason being that I'm still awaiting on the release of the RuneAudio build for the ODROID-C2. If you give the beta Volumio 2 a try, then it'll be closer to what I'm using to measure here and can provide some info if this is a RuneAudio issue or the build you're using.

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    11. BTW Rob. Another possibility is with the recording setting itself? Have you tried other devices playing into the ADC to see if that's OK?

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    12. Same results with Volumio.
      Good results, no issue, with Rega DAC.

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    13. * good results when Rega DAC is fed by laptop.

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    14. Hmmmm... Strange. So if you connect Pi --> Rega DAC via USB, playing with Volumio & RuneAudio, you're still getting this compressed signal / abnormal measurements but if you use laptop --> Rega DAC via USB, the results look good???

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    15. Strange man... I see your measurements on Steve Hoffman and those look good out of the Rega through the laptop USB.

      Something weird going on with your streaming setup.

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    16. I've raised the issue on the Hifi Berry forum (I bought the whole kit from HiFiBerry). Hopefully someone there will be willing to repeat my test! So far on the RuneAudio forums I've run into plenty of computer geeks, but no audiophiles...

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    17. One more test to try could be to try picoreplayer. Volumio/Moode based on Raspberian. Rune is based on Archlinux and picoreplayer is based on Microcore linux.

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  3. Just one small point regarding the battery power pack: It does have a small switch-mode PSU inside to convert the 3.7 volts or so from the Li-ion cell to the regulated 5 volt output, so it could be generating noise. It is obviously isolated from ground, of course.
    But as you said, it's a moot point, because it made no difference to the performance.

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    1. Thanks for the note Don. Wondering if you've ever seen measurements of noise and ripple comparing these Li-ion batteries and actual wallwarts? That could be very interesting! I was looking around and didn't find any links...

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    2. I don't think LPS (Linear Power Supplies) will do much better than SMPS (Switch Mode Power Supplies) in most circumstances.

      The few things LPS have over SMPS is lower emission (into the mains and into equipment) when it concerns common mode noise and maybe even differential noise.

      Depending on how 'sensitive' connected devices are for these types of noies there could be negative effects like weird sounds/noises.
      If you aren't plagued by this in some cases an LPS could reduce those noises maybe even below your audible limit.

      Then there is the question what OTHER devices in the entire chain have SMPS connected to mains.
      One should realise that any PC MoBo, laptop and many other devices have lots of SMPS INSIDE that work even when operated on batteries or from a linear power supply.

      In LPS groundloop current(s) in general could be smaller than from many SMPS (depends on the type of transformer used).
      Leakage currents (not the same as common mode currents) could be smaller in LPS as well.

      SMPS intended for medical purposes usually have lower common mode currents and leakage currents than 'regular' ones.

      Another thing an LPS has over (cheap) SMPS could be ripples/dips on the power supply when dynamic peak powers are consumed.
      A linear regulator in general can handle this somewhat better and may have better regulation.
      This could potentially be a problem for designs that have a poor PSRR (Power Supply Rejection Ration) or PSSR (Power Supply Suppression Ratio)
      That COULD increase distortion in those cases.
      Fortunately these days the PSRR of most circuits is quite high or measures have been taken to ensure this won't happen (internal regulation)

      Also some SMPS don't like added or higher than usual power supply capacitances, which some circuits have.
      In general audiophiles like to 'exaggerate' power supply capacitances and increase capacitances many fold some times believeing more = better.
      Some SMPS react quite poorly to this or 'die' sooner than later.
      Linear regulators also may not be very fond of a surplus of capacitance though, depends on the regulator circuit.
      Could very well be that LPS may function better than SMPS.

      I don't think it will be sonic degradation though but rather unwanted sounds/noise.

      Another thing LPS have over SMPS is longevity.
      SMPS usually don't live very long unless they are expensive.
      Cheaper wallwarts often stop working within a few years.

      What do SMPS have over LPS ?
      Weight is lower, efficiency is higher, size is smaller, high power capabilities on a small footprint, price.

      Pick your poison.

      Yes, I DO think many of the 'reports' of better sound using LPS over SMPS are all based on KNOWING what type of power supply is being used rather than actual improvements in performance.

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    3. Hi Frans!

      Thanks again for the detailed note (as I have always expected :-).

      Ahhh, yes... Isn't it amazing how often we choose the more expensive product when we "know"??? :-)

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  4. Thank you Archimago for this test.
    I didn't expect differences between computers feeding DAC with USB.
    I just saved some $ on LPS for my Raspberry Pi.

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    1. :-)

      At the very least, I would wait until a manufacturer can demonstrate what benefit to expect out of one's DAC before dropping the $$$!

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  5. Wow, I too just got into the whole raspberry Pi " movement" and you have already quite few post about it. I am running Dahpile as music server for my Squeezebox Boom and was looking to find a replacement "mini" PC to keep on using the excellent Squeezebox server software. I am interested to hear if you measured the HDMI out on these mini pcs? I am planning to use it with my Anthem MRX receiver and could connect it via HDMI or coaxial once I get a Hifiberry Digi+. I I have been reading a bit and seems that the HDMI out is limited to 48Khz sampling rate where as the the Digi+ has not such limitation. What is your thoughts?

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    1. Nice Anthem receiver, Eugene!

      Not sure about HDMI only limited to 48kHz on the Pi. The Digi+ of course should be very good.

      I have not measured HDMI in awhile since I only have my ONKYO TX-NR1009 receiver from 2011. It managed pretty well all the way to 24/192. My hope is that later this year, I'll go 4K/HDMI 2.0 with my TV and receiver. Maybe then I'll have another look!

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    2. BTW: Here's the old HDMI measurement. It didn't do too badly against the TosLink and coaxial S/PDIF!

      http://archimago.blogspot.com/2013/10/measurements-onkyo-tx-nr1009-as-hdmi.html

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    3. I doubt that there will be a big difference too in measurements. I found some information that the sample rate by default is limited to 48khz for HDMI on the raspberry,but can be over ridden and seems to pretty OS dependant - I have now tried Volumio, RuneAudio and PiCore player. The financial outlay is rather small so I think will try the Digi+. Next step is probably the linear PSU. I think next I will try a DIY Linear PSU, just too see if there is a noticable difference to a standard SMPS.

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    4. Cool Eugene. Enjoy playing with the DIY LPS! Let us know what you think... Even better if you have access to measurements, I'd love to know if it makes a difference in the noise floor!

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    5. I saw the picore player supports HDMI output all the way to the 192khz. The measurements I will leave to you, as I do not have the proper testing equipment. To be continued...

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    6. Yeah, the ODROID Volumio actually is capable of sending audio to the HDMI already from looking at the settings... The problem is the lack of many HDMI DACs other than typical receivers.

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  6. Hi , great work , demystifying tests , "Bits are bits", and as i suspected; cheap, no noise, mini PC's/Raspberries, with JRiver or other software, not so expensive DAC's, and Dutch, even cheap, Hypex DIY class-D amps with, yes, SMPS power-supplies should do it; nothing to see here; drive by -))
    we finally can turn to the best investment: transducers (or speakers)
    thanks for your good work
    greetz from the Netherlands
    Douwe

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    1. Absolutely.

      Most of the $$$ should go into speakers. I calculated awhile back that in my setup I spent 80% on the speakers (fronts, center, rear, sub). Everything else only got 20% of the total budget.

      Although there is truth that in digital, there is a contribution from time inaccuracies (ie. jitter), indeed it's *mainly* about BIT-PERFECTION. No need for anyone to freak out about the "bits are bits" summary since that is 99+% truth.

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  7. Guys... Still think switching power supplies noisier than linear power supplies?

    Check out this post from John Siau with Benchmark:
    http://benchmarkmedia.com/blogs/application_notes/152143111-audio-myth-switching-power-supplies-are-noisy

    Make sure to view the video as well.

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  8. Debunking the SMPS are NOT noisy myth (part 1).

    Yes, I still 'believe' that, in general, SMPS are noisier than linear power supplies.
    And with 'believe' I mean measurably quieter !
    For my work I have to do EMC tests for emission and immunity and know how much 'garbage' can be fed back into the mains as well as into circuits.
    I also know that most SMPS have a rather high leakage current.

    Most SMPS have to comply to rules (FCC or alike) and most of them have spurious emissions JUST below the required limits.
    The reason for that is MONEY !

    Filter components (especially on the mains side) are relatively expensive so manufacturers try to save as much money as they can on these parts.
    Less parts = more emission and sometimes poorer immunity.

    I have seen power supplies that conform to rules STILL perform so badly that they do NOT comply any more ... simply because of a wiring error.
    For instance an SMPS having a ground prong and not being connected to (proper) ground or not using prescribed parts around it can have too much emission.

    The reason why many manufacturers use SMPS wall warts = MONEY.
    Savings on weight, size, costs, available power, a regulated output voltage and availability are THE reasons most electronics 'stuff' we buy has those included.
    MOST all off these are MUCH noisier and may have much higher leakage currents than a simple transformer + rectiefier + linear regulated of equal power.

    Try to find a transformer based regulated 5V power supply that is small, weighs and costs next to nothing and can supply 2A or more.... you can't.

    All LED lamps etc have small SMPS on board. Some Chinese lamps do not even comply to any rules !

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    1. part 2 (whole story doesn't fit in one relpy)

      Now... is Joh Siau wrong ?

      Nope of course he is not when it comes to HIS power supply used in his power amps.
      Are ALL SMPS poor in longevity, conducted* and radiated# emission and cheap ?

      * conducted emission is, usually very high radio frequency' signal that are inserted back into the mains and/or circuit the SMPS feeds via the cables it is connected with.
      These signals can both be 'differential' which is between Live and Neutral (or + and - output voltage) and/or 'common mode'. Common mode signals are signals that exist in equal amplitude on the L and N wires (or the + and - output wires) and are present between those wires and the actual ground. The ground we walk on AND the safety ground in your wall outlets.
      # Radiated emission are actual signals relaeased in the the 'ether'. In other words unwanted radio signals that can interfere with reception of wanted signals.


      Hell no... there are lots of SMPS around that have lower leakage currents than a toroidial transformer.
      There are lots of them around that are quieter in emission than a transformer+rectifier (yes, a rectifier can emit HF spurious signals).
      There are lots of them around that still work after 10 years or so.

      But these cost SERIOUS money and generally aren't very small and consist of many, many parts and have serious input and output filtering and or virtually no leakage currents.

      These SMPS can be better and perform better on many fronts than simple Linear Power Supplies.
      A Linear Power Supply has a mains transformer + rectifier + reservoir/smoothing capacitors and sometimes a linear regulator.

      In short... Most (generally small and low cost) SMPS supplied with all kinds of electronics DOES perform worse than LPS.
      But properly (often purpose built) SMPS can outperform LPS on many aspects.

      Final question is though WHAT influence do (cheap) SMPS have on the sound ?
      Usually NONE ... but in the wrong circumstances there could be strange 'noises' coming from your speakers because of it.

      Wrong circumstances:
      Amplifiers, or other used circuits, with poor PCB designs or poor internal wiring layout.
      Improper grounding.
      Poor quality interlinks (and I mean no proper screen or too high resistance screen).
      Audio cables and mains cables running closely and neatly, densely packed next to each other over certain lenghts.

      Fortunately, in MOST cases, SMPS just work fine and noise free in audio equipment even though emission of all sorts is there.
      Emission just doesn't reach levels where equipment is influenced.
      Equipment that isn't influenced in performance from said unwanted signals is having a good 'immunity'.

      In the end, whether or not 'noise(s)' can become audible depends on emission levels and immunty of said equipment and the amplitude(level) and frequencies of the unwanted signals making it to the speakers/headphones.
      When it is below audible limits ... who really cares.

      Can sound quality 'degrade' because of SMPS... I don't think so when looking at circuits that do not have to deliver real power (think speaker amps).
      In the end how well any (combined) circuits performs depends on the circuit designs (filtering, wire routing/usage), the PCB (Printed Circuit Board things like ground planes, wire routing on the board, connector placement on those boards)designs.
      Many factors ...

      But as mentioned in MOST cases even cheap wallwarts will work just fine.

      Delete
    2. Yeah... I think you're right. Ultimately it is one example that is being used by Siau - the Benchmark one. Must be careful generalizing the results beyond that.

      Nonetheless, the point in taken that unless we see evidence of SMPS clearly messing up the sonic output, should also be cautious with assuming that spending more money on a LPS will somehow make things sound better.

      Delete
  9. Last night I performed a listening test out of pure curiosity. This is of course totally subjective and for my own amusement. Setup was Surface pro via USB and foobar too my Hegel HD12 and the Pi3 with digi+ with ipcoreplayer to the coaxial. Both wireless my. Sennheiser HD650 connected to the headphone output. In short the pi3 sounded more bloomy in the bass with softer top end compared to the Surface PC. Notice in did not say worse. Would be really interesting too understand why they sound different... could this be because of software, hardware or combination of both? Would a good linear PSU be the key to get same sound? I am sceptical.

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    1. Interesting Eugene. Did you check if the coaxial input and USB input resulted in the exact same volume?

      Also, would it be possible for some kind of blind switching of the 2 inputs and seeing if you can accurately identify the change?

      Many times for myself, I think that I can hear a difference but the moment I put it to a test with blind conditions, I realize I'm struggling with noticing that sonic difference I *thought* I heard just moments before.

      Linear PSU? I remain skeptical as well. Especially for something like a Pi which is just feeding the USB to the DAC. Like I showed above, no difference between cheap "FujiFilm" wallwart and a Li-ion battery :-). I certainly don't expect a LPS to work miracles since the results look great already!

      (And may I remind everyone, there does not appear to be any objective evidence out there that a LPS would make any difference when powering the streamer device feeding the USB DAC. Don't understand why one should look at these >$1000 LPS units!)

      Delete
  10. Archimago, I am not sure how to check that the volume is exactly the same from both sources (how to measure that?).
    This test was done blind. I would put the same song to repeat on both players and then my "assistant" would switch between inputs and I have to say which one is playing ad the she would write it down . There is about a 3 second fade-in done by the Hegel between in switches. I got it right 9/10, but only since only test with songs from Infected Mushroom (electronic). Other genres I would be doubt I could tell the difference.
    Conclusions of course cannot be made, to many variables involved here...

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    1. Hmmm... At least for the volume, do you have test signals and at least a Radio Shack SPL meter to check? For example, you can measure the amplitude of the same white noise signal coming out of speakers through the DAC from both the USB and S/PDIF to make sure they're the same.

      Robertzombie above also had an interesting issue with the Digi+ measured output. Wondering if there are settings I'm not aware of with that to make sure it's sending bit-perfect output. Alas, without an actual Pi + Digi+, I'm not able to check on my end here...

      Delete
    2. I have a Umik microphone I can test with speakers. I am researching to see of I can find some more info about this "bit perfect"settings for this kind of OS. Probably also redo my test with speakers to see if I hear the same thing. I am sure if there was this kind of issues other here would have mentioned...without testing equipment and the necessary experience to get reliable results, it is pretty much just shooting in the dark. Most probably after reboot they sound the same.

      Delete
    3. Yes. Give it a try Eugene. And that's the thing isn't it? So many people will just say something they *believe* is the case but won't ever test to make sure... this kind of thing perpetuates ignorance and snowballs into communities that eventually hold on to multiple bizarre beliefs

      Delete
  11. Finally someone debunked all this myth about jitter and power and so on: I've used a low powered HDMI stick player for the past year(windows 10 based though) and it sounds amazingly good, even better than my $1500 PC. All because I have a very good async DAC:) I am glad that my ears have NOT proved me wrong and now there is actual proof:)

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    1. Hi Basil,
      The funny thing is that it doesn't take a ton of work to check... Just a willingness to let go of preconceptions of the audiophile world and open one's mind to the "potential" that many beliefs and claims are just wrong.

      I believe it's no big deal for any magazine for example to test some cables or streamers like these. But they never really test with a good DAC to check claims their own writers make. It would be bad for business of course and would stop moving product, damage advertiser credibility, and kill value in the resale market.

      I trust the "true believers" will continue to proselytize their faith. But I suspect the numbers will dwindle over the years as they have over the decades already.

      Delete
    2. Well said: big money talk much louder in the audiophille world than $100 devices which achieve the same results:)

      Delete
  12. Great analysis. Please could you add a microRendu to your testing and publish the results alongside the rest so those that will argue it's somehow better can be silenced too...you know of course that until you do they'll argue that it was deliberately omitted because the results don't suit your argument.

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  13. Always a great fan of your articles, Archimago :-)

    As I was reading this particular article I clicked on the link to the webpage of "Sonore microRendu Review, Part 1" (more to come obviously). I browsed the text and then saw the price of the thingy: 640 dollars !!! I rolled off our couch from laughing (and due to some backpain that did not feel good afterall ;-)). I can't wait for the 2nd part of this hilarious piece (hopefully my backpain is gone by that time). And how serious are those comments-writers?!?
    Mon Dieu, I thought that in the past a lot of audio stuff was overpriced and clouded with mystification, but nowadays it seems as if the "highend" audio buffs have found their new goose with the golden egg. And people are litterally buying the crap the HiFi magazines/websites are writing about based on such subjective articles. I have spend quite some money on my audio gear in 40 years time, but for me I've come to a point to say "been there, done that" when it comes to all those shiny new gizmos.

    I think I've said enough now :-)

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    1. I bought a Sonore microRendu recently. I had signed up for email updates when the thing was announced quite some time ago, and at very infrequent intervals an email would pop into my inbox with more information on it.

      Anyway, I got the opportunity to be one of the first to buy, so I took the plunge and bought it. I baulked at the price, but I knew I could get most of my money back by selling it second hand, so the risk was low.

      What do I say: I took it out of the box, plugged it in, followed the very simple instructions, and was up and running in seconds. I haven't taken it out of my system since. I simply listen to my music free of hassles, and with no concern for sound quality. The thing sits there out of sight, has worked reliably, and sounds darn good to my ears.

      It may well be that the Odroid would get me to the same position too, I simply don't know, but I do know enough about HiFi not to try and fix something if it's working. My Sonore microRendu works, and works very well.

      Values are very personal things. $650 for a cigarette pack size single board computer is expensive. For a piece of HiFi equipment that doesn't get noticed because I'm enjoying the music; that money is at the low end of the scale.

      I'm happily sat on my couch loving the sound of my HiFi.

      Delete
  14. What about the quality of the i2s output on this C1+ ? No measurements of that ? Thanks

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  15. Hi Archimago
    I really enjoy your blog and might like to emulate some aspects of your projects.
    I'm using JRiver on Win10 and Ubuntu (dual boot) and Acourate DSP on my Martin Logans.
    I'm intrigued by your conversion to DSD for final transfer to the DAC, as I think I might hear a difference with DSD playback and would like to check it out further. I recently got a DSD-capable budget Aune DAC, but I get loud pops any time a file stops playing- completely unacceptable. J River has a WASAPI setting for this but the XMOS USB driver appears to support ASIO only.
    Have you experienced any of this with your setup or does the streaming somehow magically get around that? Or does the Teac cure that?
    If the Teac is the answer, I'll kick myself for trying to save a few bucks.
    Thanks
    Phil

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