Roon Labs Nucleus+ music server Page 2

The Nucleus also has an internal bay for a 2.5" drive, either HDD or SSD, but this drive can't be more than 7mm in height. The Nucleus+ is powered by a wall wart—a linear power supply should be available later this year—and is turned on or off with a rear-panel pushbutton. With its minimal system overhead, it boots up incredibly quickly. One of Roon's goals for the Nucleus was that it dissipate heat only passively, without a cooling fan, and even after prolonged use the prominent heatsink fins on the top and sides of its dark gray case barely got warm. I measured the top panel's temperature as 92.6°F (33.7°C).

To use the Nucleus servers you'll need a subscription to Roon (free 14-day trial, $119/year, $499/lifetime, footnote 2). I began my auditioning of the Nucleus+ with v.1.4 of the Roon app running on my iPad mini, and v.1.4 of the Roon Core and v.1.0 of the Roon OS running on the Nucleus+. Toward the end of the review period, both app and Core were updated to v.1.5, which allows the unfolding of MQA-encoded files. Using the iPad app, I pointed the Roon Core to my library, initially stored on a 2TB USB drive.

Roon's metadata library continues to amaze me. The Radio function, akin to iTunes' Shuffle mode, digs deep into the data to find connections. It followed Robert Silverman's Chopin's Last Waltz/ (DSD64 files, IsoMike 5606) with an MQA-encoded version of his recording of a Beethoven piano sonata. But who then would have anticipated it cueing up "Soul Intro/The Chicken," from the late bass guitarist Jaco Pastorius's Truth, Liberty & Soul (24/192 AIFF file, Resonance HCD 2027)? And Roon's ability to instantly discover a particular performance of a composition is frightening. While playing Henry Love's Das alte Lied, from pianist Stephen Hough's Dream Album (16/44.1k WAV, Hyperion CDA68176), I asked Roon what other performances there were of this work. It immediately responded that while there was just the one in my library, eight others were available from the Tidal streaming service.

While Roon supports PCM resolutions up to 24 bits, sample rates up to 384kHz, and DSD up to DSD128, it downsamples the data to match the limitations of the D/A converter in use. For example, my PS Audio DirectStream DAC is limited to PCM sampled at 192kHz via its Bridge II network adapter. Clicking on the colored dot to the right of the track name at the bottom of the Roon app's screen displays the signal path. With the Trondheim Soloists' performance of Kim André Arnesen's Magnificat (24/352.8k FLAC, 2L), the Nucleus first converted the 24-bit integer data to 64-bit floating point, then converted the sample rate from 352.8 to 176.4kHz, then the 64-bit float data to 32-bit integer, finally sending the 32/176.4 data to the Roon Ready PS Audio over the network using the Roon Advanced Audio Transport (RAAT), which Roon says "delivers bit perfect audio to local outputs, networked outputs, and Roon Ready devices." The processing speed was listed as "13.7x"—ie, plenty of margin. Similarly with Christian Tetzlaff and Lars Vogt's performance of the Brahms Violin Sonatas (DSD128 files, Ondine ODE1284-2D/HDtracks), the Nucleus converted the sample rate from 5645 to 2822MHz, then applied a DSD64 sigma-delta modulator to the data before sending them to the PS Audio. This time, the more intensive processing cut the conversion speed to "3.8x."



With Roon 1.5, I used the Internet Radio Stations feature to access a live streaming event that MQA Ltd. had arranged to coincide with May's High End show, in Munich: a jazz sextet led by double bassist Misha Mullov-Abbado playing four songs in a London studio. Roon identified the stream as "FLAC 48kHz 24-bit, 2ch, MQA 192kHz," noted that Authentication was "MQA 192kHz," and used RAAT to send the data over my network to the PS Audio. The PSA's screen indicated that it was receiving data sampled at 192kHz, though the bit depth was indicated as "16 bits" rather than 24, apparently due to a bug in the PSA Bridge's firmware (since fixed).



You'll note that I've said nothing about sound quality. Having used the Nucleus almost every day since it arrived, I have nothing specific to say about the sound other than that it was always excellent. So . . .

I've written before that I've found that a DAC fed data via USB doesn't sound as "solid" as when the DAC is fed the same data via an AES/EBU link. I didn't listen to the Nucleus+'s USB output—the server sits in a rack too far from the PS Audio DAC for a USB link to be practicable. But what about data sent from it via Ethernet, where the length of the link is immaterial? As I left Michael Fremer's place after measuring the Moon by Simaudio 888 amplifier reviewed elsewhere in this issue, he pressed on me the CD of Van Morrison and Joey DeFrancesco's You're Driving Me Crazy (Exile/Legacy 19075820041). Comparing a WAV file of "Like Young Lovers Do," sourced from the Roon over my network, with my Ayre Acoustics C-5xeMP disc player via AES/EBU, it was difficult to hear any significant difference. Perhaps the Hammond organ's bass pedals were a bit fuller with the Nucleus+; perhaps the Ayre's output sounded a little more open. Perhaps.

Before introducing the Nucleus servers, Roon used to recommend Intel's NUC mini PCs. Jason Victor Serinus lent me his NUC7i7BH ($469 in kit form). This takes longer to boot—and from 3' away I could hear its cooling fan—but it was then recognized by the Roon app as "Roon Optimized Core Kit." I pointed Roon to ROCK as the music source and enabled the PS Audio DAC as the audio device.


Who knew Jason would have the B-52's in his library? "Rock Lobster," sourced from Tidal and the NUC, had excellent impact, with good low-frequency extension. Streaming the same track from Tidal via the Nucleus+, perhaps there was a touch more authority in the bass. Perhaps. With "Every Day I Have the Blues," from the Morrison-DeFrancesco album, the sound through the NUC was less authoritative, less open. However, the comparison was unfair: Though both versions were 16/44.1, I was streaming from Tidal with the NUC, and playing a WAV file from local storage with the Nucleus+. Nevertheless, while changing to the Tidal stream with the Nucleus+ reduced the difference between the servers, the Nucleus+ sounded still a tad tidier.

For those who, like me, don't want to go the hair-shirt, DIY route to networked audio, the fit'n'forget functionality and routinely excellent sound quality of Roon Labs' Nucleus+ through both of the DACs I used it with make it an easy recommendation. It's not going back!

Footnote 2: For a full description of Roon's capabilities, see here and here.

John Atkinson's picture
DH wrote:
Roon works with sample rates up to PCM 768 and DSD 512, and isn’t limited as you indicated. The only limitation of rates below these would be a limitation imposed by your DAC.

Accidentally deleted DH's posting, which had been posted twice. Apologies,

I made this point in my review - see the iPad screenshots.

John Atkinson
Editor, Stereophile

tonykaz's picture

I accept.

Thanks for discovering.

Tony in Michigan

bierfeldt's picture

I am running Roon server on a "Vintage" tower. I replaced the hard drive recently and upgraded to Windows 10. Roon is blisteringly fast and the Radio function is better than Apple's Genius.

All of my irritation is due to the Windows PC I am running on as Windows updates cause it to re-boot constantly and I am suddenly having issue with my Airport Extreme. Okay, constantly maybe excessive, every couple days is more like it and I think my network issues are partially my cable companies problem but it is still irritating.

But again, this would solve most of my issues. May pick one up.

Great review.

dalethorn's picture

On my PC (I also have a Macbook Pro) I run Windows XP, which is very stable. If the drive ever crashes, I just go to my tech and get another XP drive and copy my files from my backup drives.

Bogolu Haranath's picture

Apple just released a new 15 inch Mac Book Pro with 4TB SSD built-in storage, 6 core processor and up to 32GB RAM .......... $7,000, if got the dough and willing to spend .............

dalethorn's picture

And all of that "enormous power" filtered through a slow, turgid, sometimes frozen pipe owned by AT&T, Verizon, etc. Oh yes - your IP isn't one of those. But your IP has to use their pipes.

My Mac uploads to and downloads from the Internet - when the Internet is working. Real work gets done on my PC, which is isolated from all networks. It's a heavenly combination.

Bogolu Haranath's picture

5G wireless is coming soon (to a sky near you) :-) ...........

dalethorn's picture

Pay attention: 5g specifies the width of the pipe, not the actual throughput. When cable companies became dominant by the 80s, they established that their pipes to your house were "shared" with nebulous anomolous "persons" in your area. Not as bad as "party line" telephones, but still slow-to-useless at certain times for Internet use.

Now you talk about 5g as though you're offering a solution. You're offering nothing except another shared pipe that brings the same as everything else - poor throughput.

Bogolu Haranath's picture

Ok ......... I Googled it ........... According to the info available on Google, 5G is supposed to increase speeds (as well) ......... You can check it out, on Google, if you are interested ............

dalethorn's picture

How many times do I have to repeat this? 5G is the *potential* or maximum bandwidth. Your provider can dribble the data through that pipe at 200 bytes per second during "peak hours", which they always do.

Pay attention. You will never get 5G speeds consistently on a 5G network, and oftentimes, you'll be begging for 3G speed and still won't get it. Get it?

Bogolu Haranath's picture

"Itsy Bitsy Spider" .......... Carly Simon :-) ...........

woodford's picture

should have taken the mini to tekserve on w. 23rd; they could have fixed it.

John Atkinson's picture
woodford wrote:
should have taken the mini to tekserve on w. 23rd; they could have fixed it.

Tekserve closed a couple of years back. These days I go to Mike's Tech Shop on W. 20th. The cost of repairing the Mac mini was not much lower than the price of a new one.

John Atkinson
Editor, Stereophile

woodford's picture
Thanks- it's been a while since i needed to visit them- sad to hear they closed. in the days before the apple store it was almost the only place one could get a mac repaired.
CG's picture

Have you ever considered trying a test such as this where sample averaging is turned off? Perhaps instead using "Max Hold" or "Peak Hold" over several seconds of sampling time in order to capture random and pseudo-random events?

PeterMusic's picture

That's a long review on a critical product that costs quite a bit to skip the listening notes. Kind of disappointing

rzr's picture

So your mac mini went down 2 times in the last 7 years and you went to the mac store and they said they don't fix older computers. So why didn't you just buy a new mac mini? You rant about how you have all of this computer background, which coming from me with over 40 years of a REAL computer background, you really don't have much computer experience, so i'll call you a hack which dabbles into the computer sector. If you knew anything about computers, you would know that the Nucleus+ is just a computer, and a very expensive 1 at that. What happens when the Nucleus+ won't boot up? What happens when the internal SSD fails? What will you do when an error pops up? You will need to call Roon Labs. Forget about taking it down to your local Apple store or any computer store. If you would have gone out and bought a new Mac Mini with 8GB ram, i7 processor, 1TB Fusion drive with 256G PCI-E flash storage, you would have paid $1200. But if a mac is way over your head to deal with, then go for paying double for another computer and hope nothing goes wrong with it. Before I spend $2500 on a nucleus+, and if I wanted 24/7 computer access, I would buy 2 refurbished Mac Mini's, setup a RAID disk, and if 1 Mac Mini would fail, hook up the other Mac Mini to the RAID disk and off you go.

anonymusicdude's picture

So wait a second. JA uses a MAC Mini and PS Audio DS DAC ? You mean the one that changes every 6 months to a different sound ? lol Sirenus uses a $469 intel NUC ? I thought these guys were Audiophiles ? whats up with that ? wheres the gear boys ? At least have a custom build server like the guy above says except screw Apple BS Linux is far better for a server

vkennedy's picture

There's a huge issue with how Roon Rock running on Linux, and an incompatibility with XMOS based DAC's.

Read this thread:

Scattered accross Roon's forum's are dozens and dozens of reported issues.

mauidj's picture

I am a new Roon user and I am deciding how to set it up in my system. Right now Roon Core is on an iMac feeding the house via WiFi to various different endpoints. But i would like to have a dedicated Core machine directly connected to my main system DAC via ethernet. (or via a bridge???)
I just dont understand why a Nucleus is a better deal than a Mac Mini? A base Mini with storage is half the cost of a Nucleus+ with no storage.
I currently have just over 100,000 tracks on an external HD.
I am a complete digital audio idiot so am I missing something?

shp's picture

Hi mauidj

Why we need these audiophile servers is a bit confusing. And "need" is a strong word.

I use a MacMini wired directly to my main DAC and streaming to my work computer and my phone using Roon.

There are two main challenges with the MacMini:
* System updates often leave the computer stuck. Either the OS couldn't install the upgrade (e.g., Roon or another app was running) or it failed to reboot properly. Roon needing to install server software upgrades can cause similar issues.
* Usually I can resolve the above without needing to access the Mac desktop. But when I can't, it's a whole additional set of steps to revive it.

I can fix it when things go wrong. But my girlfriend can't. To her it's just "not working." Because the Nucleus only does one thing, I would assume it's significantly more reliable.

Additionally, it has been designed to eliminate a lot of electrical noise.

That's not to say that you need a Nucleus, only that it probably does a couple of things better than a MacMini.

ChevChelios's picture

Hi rzr. The Roon Nucleus is merely a NUC - it's right in the name. Why not use a NUC rather than be a condescending A-hole who brags about their computer chops all while proving their sub-par grasp of English.