MEASUREMENTS: Intel NUC [6i5SYH] (and Audio)

Packaged contents of the NUC - mounting screw, universal power jack attachments in the bubble wrap, metal VESA mount plate under the power supply, basic instructions.

Like most of my computer upgrades lately, it's not because I need the speed, or expect much power saving, or necessarily to silence a noisy machine... Speed, efficiency, and quietness have been achieved to the level I'm satisfied with for years now! No... It's because I wanted to upgrade my work computer to something that handles 4K resolution :-). As discussed here and here, over the last year, I've been transitioning to what I think is going to be the target resolution for the foreseeable future (in a way very much like how audio CD resolution has been completely fine for decades). Beyond 4K, the reasons for even higher resolutions drop off exponentially based on the physical limitations of vision. (Of course, beyond spatial resolution, HDR color range and contrast ratios are important and those are catching up nicely.)

A few months ago, I decided to upgrade an aging 24" Dell monitor with a new ASUS PB287Q - quite a nice reasonably priced 28" 4K unit. (If I were to buy today, I would take a good look at the LG 27UD88 or consider the 21:9 LG 34UC98.) Alas, for the last while, I've been running the monitor at 1200p resolution with the current work computer. Though the upscaling doesn't look bad, it's noticeably compromised compared to actual native resolution of course.

As a simple way to upgrade instead of buying all the parts and assembling a new computer, I decided to go with the current generation Skylake NUC "Next Unit of Computing" - the Intel NUC6i5SYH which houses the Core i5-6260U processor with the Iris Graphics 540 integrated GPU. This NUC case allows for a 2.5" SSD/HD and M.2 SSD. If you want an even smaller, flatter unit, consider the similarly-priced NUC6i5SYK, the same innards but with a smaller case removing the 2.5" bay so the internal SSD will have to be an M.2 card.

To get it working, you'll need the SSD/hard drive and some DDR4 SO-DIMM memory (make sure you grab these smaller form factor RAMs usually for laptops!). I chose the fantastic Samsung 250GB 850EVO and Kingston HyperX Impact 2x8GB, DDR4 SO-DIMM 16GB kit.

Easiest install I've ever done... As expected for a simple kit computer. Unscrew the 4 "feet". Pop off the bottom of the unit to reveal this:

Slide the SSD into the 2.5" bay (you can see the SSD partially in already in the picture above to the right). Then snap in the SO-DIMMs as below:

Now just close it up, connect cables - power supply, HDMI/DisplayPort, USB keyboard/mouse. Push the power button up top and away you go with the usual Windows/OS install (typically USB thumb drive or external disk drive). As an eventual work computer, I installed Windows 10 x64. You'll probably want to update the BIOS/firmware and grab some drivers here.

The UEFI firmware (Intel Visual BIOS) has more settings and graphical eye-candy than I expected. Most interesting are the settings for fan speed if you're using this in the media room.

Notice the "CPU Fan Header" panel has the option to run this at various settings for the "Fan Controller Mode". Default is "Balanced" where there's a bit of audible fan noise when listening close to the machine. In the very quiet sound room in my basement, I could still hear the soft hum from 10' away. If the ambient temperature is cool and there's good air circulation, "Quiet" worked well and was essentially silent for me. I watched a Netflix movie in "Quiet" setting and did notice the case getting moderately warm after about 2 hours... Not hot to the touch by any means. There's even a "Fanless" mode which I did not try.

NUC6i5SYH side-by-side with the little ODROID-C2 on the right; both sitting on top of my TEAC UD-501.

A. OBJECTIVE Testing:

My measurements are now being conducted with the Focusrite Forte ADC system as reported recently. Notice that in the picture above, both the NUC and ODROID are sitting on top of my TEAC UD-501 DAC! Let's just say right now that this made no difference to the measured output whether the NUC was seated on top like that or 3 feet away on the equipment stand. This speaks to very low EMI radiation from low-power computers these days as well as how well the TEAC is shielded from interference (remember, we're looking at an i5-6260U processor using 14nm litho, 15W TDP in the NUC; very electrically quiet compared to the measurable anomalies I showed with the electrically "noisy" i7 + nVidia GPU running at full tilt a number of years ago!).

Here's what I'm going to do... Let's measure the analogue output from 2 DACs - the recent Light Harmonic Geek Out V2 which I tested late last year as an example of a simple USB-powered DAC, and a good desktop DAC like the TEAC UD-501 using a few computers as "digital transports". I'll select from the NUC, my Skylake i5 HTPC (Gigabyte motherboard), Microsoft Surface Pro 3 laptop, ODROID-C2 low-power ARM SBC. Each machine will be set-up a little differently in terms of audio file storage and/or playback as highlighted:

NUC 6i5SYH: Test files streamed off internal built-in WiFi with router 20' away. Files stored on my Windows Server 2012 R2 machine. Foobar used for playback with ASIO driver. Geek Out plugged into one of the front USB3 ports. TEAC UD-501 plugged into one of the rear USB3 ports.

Skylake i5 medium tower HTPC (Gigabyte motherboard): Geek Out DAC plugged into standard rear USB3 port (not the supposedly low-noise port). TEAC UD-501 plugged into rear USB3 port with a 15' generic USB cable. Foobar used, ASIO driver. Files played off gigabit ethernet from Windows Server 2012 R2 computer in another room in the house.

Microsoft Surface Pro 3: Geek Out plugged into single USB3 port. TEAC UD-501 likewise plugged into this single USB3 port when being tested with 3' generic USB cable. Foobar again used with ASIO. Files played off internal SSD.

ODROID-C2: Only USB2 ports for both the Geek Out V2 and TEAC UD-501. The TEAC was plugged into one of the USB2 ports with a 3' generic USB cable. Audio being streamed off JRiver 21 from the Windows 2012 R2 server computer off gigabit ethernet through DLNA protocol controlled with an Android tablet.

Measurement chain:

Transport machine (NUC, HTPC, ODROID, Surface) --> (USB cable) --> DAC (Light Harmonic Geek Out V2 / TEAC UD-501) --> 6' single-ended (phono-RCA or just RCA) interconnect --> Focusrite Forte --> shielded USB cable --> Windows 8 measurement computer

No special power filtering used for the computers. My TEAC DAC and ODROID-C2 are plugged into the Belkin PureAV PF60 though.

Part I. Geek Out V2 DAC - small, USB-powered DAC

Let's start with the Light Harmonic Geek Out V2 DAC. A simple unit previously measured in this blog which works well objectively although I'm still not quite happy about the plastic 3D printed casing (they've actually produced an upgrade version with a metal case based on some recent E-mails I've received). Nonetheless, the quality of this little DAC provides an easy platform for measurements and in the service of this post, allows an apples-to-apples comparison of the different computers using the USB-powered device.

16/44:

As usual, we start with 16/44 measurements of course. Yes, 16/44 is "old skool" now but it is the foundation and essential to get right! Looking at the field of devices, you see that there's no difference between the machines. No surprise.

Yup. 16/44 is easy to handle these days and there's no significant difference here at all.

24/96:

24/96, clearly "hi-res" now and a little more challenging. Already looking at the numbers, we're not seeing anything unusual at all between the machines.

Indeed, looks the same to me. Any difference basically is a result of inter-test variation.

24/192:

There's an issue with the 192kHz graphical display in RightMark for the crosstalk and THD+N sweep results, I've included instead (perhaps even more usefully!) the "raw" measurements used to calculate the THD and IMD results. I trust the conclusion is rather obvious! No difference.

Part II. TEAC UD-501 - full sized, desktop DAC

Likewise, let's do the same with the full-sized DAC...

16/44:

As expected, 16/44 is a breeze and it would be rather unusual to expect any variation between the different machines.

Nope. Nothing much to see here... No difference between machines.

24/96:

Tiny, tiny differences.

Yup... Tiny (insignificant) differences between tests. Just the usual variability between runs. Notice the small 60Hz mains hum in the noise floor.

24/192:

Even at 24/192, numerically this these insignificant differences.

If not essentially perfect overlay, then pretty darn close even at 24/192 between the different computers!

Part III. Noise level between devices - a closer look

I was interested in having a good look at just the noise levels between the different computers so I took the 24-bit J-Test (24/48, -6dB primary signal at 12kHz + LSB jitter modulation tone) and plotted the FFT from 20Hz to 25kHz. WaveSpectra software was used with the highest FFT resolution of 128k points, 24/96 sampling through the Focusrite Forte ADC. All signal peaks targeted to an arbitrary -12dBFS using the gain setting; my main interest here is to look at the relative differences between the different computers connected to the DACs.

Geek Out V2:

TEAC UD-501:

As you can see, the noise floor of the TEAC is lower than the Geek Out V2. No surprise as this is what was demonstrated in the RightMark results above, just with higher resolution FFT plot.

Is it surprising after all the claims about audible difference between computers/streamers that the noise floor curves for each device overlaid remarkably precisely on top of each other? Despite the Geek Out plugging directly into the computer's USB port, including what should be a much noisier HTPC machine, there was actually no evidence that this was any more noisy than a low-power ODROID, or the NUC or the battery-powered Surface Pro laptop.

Likewise, the TEAC DAC is capable of even lower noise floor (you can see a little bit of 60Hz low frequency mains), again, we don't see any relative change in the noise floor between devices. Again the full-sized Skylake Gigabyte motherboard HTPC was no noisier than any other. Whether the file was played off SSD or WiFi or ethernet made no difference. Whether the computer was plugged into the wall (HTPC), or a small switching power supply (NUC and ODROID), or battery powered (Surface Pro) also made no difference to the final analogue output from these DACs. Whether using foobar with ASIO driver (HTPC, NUC, Surface Pro) or Linux MPD-based streaming off JRiver through DLNA (ODROID) made no difference.

Although the FFT here is zoomed out to encompass the whole audible spectrum, note that the signal is the 24-bit J-Test. As you can see, there is no evidence of significant sidebands with any of these machines suggesting that indeed asynchronous USB interfaces like these are jitter-free as I have shown many times in the past.

B. SUBJECTIVE Listening:

Here's the thing when "reviewing" a digital source device like the NUC connected to various DACs. Objectively, you already know what we're dealing with here as laid out above. Nonetheless, I guess I could say a few things here hopefully for entertainment value and might provide some music recommendations (this is how I typically view subjective reviews anyway - potentially useful look-and-feel comments about ergonomics and reliability, plus music recommendations)...

First let me say that although I don't consider the NUC a particularly good looking machine, it's at least small and won't look out of place on a 'tech rack'. I mentioned that in "Standard" fan controller mode setting it is audible close up, and indeed the low pitched hum was audible over the ambient sound level from the sweet spot of my sound room (yes, especially in the evenings, my sound room is very quiet). I changed the BIOS setting to "Quiet" for my listening - the rest of my stereo sound system runs fanless.

Setup: NUC connected to the TEAC UD-501 with generic USB, analogue output wired through balanced XLR to the Emotive XSP-1 preamp, dual monoblock Emotiva XPA-1L to my Paradigm Signature S8v3 and SUB 1 subwoofer. All interconnects are generic gold plated XLR. Speaker cables homemade Canare 4S11.

I've been listening to some of Rachel Barton Pine over the last while. Her most recent release Testament: Complete Sonatas and Partitas for Solo Violin (2016, Avie) sounds great with the soloist standing/playing front and center going through these works by Bach. It's recorded in St. Pauls United Church in Chicago and the spaciousness is reproduced well with just a hint of natural reverb. Resolution of the recording is excellent and every little nuance like the fingering and occasional breaths taken are easily heard (not that I'm specifically listening for these things of course!).

Another artist I've been listening to has been He Xun Tian (何训田), a Chinese composer who worked on Dadawa's Sister Drum (1995) which I mentioned in this blog previously. One of his more recent albums, Paramita (2002) carries on that new age sound with Tibetan, Buddhist-influenced chants, ethnic instrumentation like the Chinese pipa mixed with synth sounds in quite a distinct ethereal soundscape... Think Enya with an Eastern vibe :-). Seriously beautiful collection of compositions. The title track (track 2) will give your subwoofer an impressive workout. "Song of the Pipa" is hauntingly emotional presented with an amazing sense of spatial depth and precise, delicate detail of the strings.

On the pop side of music, I've been listening to Roxette's latest Good Karma (2016). Well, what can I say? A throwback to the earlier 90's with the Swedish duo! Per Gessle is back with his rockish tunes like "Why Dontcha" and "This One" and Marie Fredriksson performing songs like "From A Distance", typically the slower ballads on the albums. As expected we are listening to a modern pop production with limited dynamic range. DSP effects permeate the whole production from start to end with vocal pitch changes, phasic "surround" effects, and complex multitrack layering. Tonality can be a bit bright and harsh - it is what it is. Of course an album like this isn't the kind of work one would use as an "audiophile" if the goal is to show off realism and resolution of a sound system, but it is fun and that goal's satisfied for the "music lover" in me. Similarly, I've been enjoying Pet Shop Boys' new one Super (2016). This is almost the polar opposite of the "natural" sound! Hard driving electronic rhythms and syrupy sweet pop all in dynamic compressed DR6. Again, not something to show off the realism of an audiophile system but fun music nonetheless with volume pumped up!

Finally, I listened to some of my own recordings of piano works and live band performances by family and friends. Over the years, I've recorded many tracks in 24/96, no compression, no DSP, no multitracking, simple stereo ORTF recordings with dual cardioid condenser mics. Whether it's the NUC or ODROID or HTPC or laptop, I've never thought any bit-perfect computer digital source made an audible difference using the same DAC.

Conclusions:

As a small form-factor microcomputer, the Intel NUC6i5SYH is a nice little machine. It's easy to build, the 2.5" drive slot is convenient, the i5 is reasonably fast, and will be unobtrusive even in very quiet rooms when the BIOS is set to "Quiet" (remember, you can also turn it to "Fanless" mode assuming adequate air flow and lower ambient room temperature).

For the main purpose I bought it for - 4K screen resolution as a work computer, the Intel integrated video does the job with HEVC decoding to boot (remember the hardware decoding tests I did my with Skylake HTPC build last year) using the Display Port output. By the way, for the forward looking HTPC crowd, realize that the Skylake hardware video decoding will not handle 10-bit color depth and as I noted before, was not capable of 60fps decoding. For hardware 10-bit color decoding, wait for Kaby Lake which will also integrate HDCP2.2; at this point I'm not sure if 60fps hardware decoding will be part of the updated feature set in late 2016 - not that there's much content at 4K/60Hz! Nonetheless, until such time as a low-powered CPU is available with hardware decode of HEVC up to 4K/60Hz/10-bits, I'd be hesitant to crown "the ultimate HTPC CPU" quite yet :-).

As for using the NUC6i5SYH as an audio player connected to an asynchronous USB DAC, as you can see, it works well and measures well. I've use foobar on it and the newest JRiver 22 also. At no point with bitperfect playback settings did I notice any change in sound quality between the software players, local SSD playback, or off the gigabit ethernet network. The speed is great with audio applications. For example, CPU utilization is <5% total after the initial buffering burst while streaming stereo 24/96 in JRiver through a strong WiFi signal from a DLNA server with convolution DSP turned on (64k taps filter), playing to the TEAC UD-501 DAC via USB.

Up to now, I have not tried Roon but I suspect in the near future that would be worth a look/listen and I suspect the horsepower of the i5 NUC would make it an excellent server/player... Stay tuned - will have a look at this after the summer!

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Greetings from Taipei.

A view from the Sun Yat Sen Memorial Hall.

I figured it would be nice to post something in August despite being away :-). I managed to get all the objective analysis and subjective impressions done by the time I left Canada for vacation.

Needless to say, there are some obvious implications in the measurements here. I'll discuss more of this in a followup "musings" post.

Have a great summer folks... Enjoy the music!