When I volunteered to review the Roon Nucleus Plus Music Server, I didn’t completely understand the function of the device nor its design intentions. By the end of the review, I had received a significant education.

The Roon Nucleus Music Servers can access multiple library resources over the home network, stream to multiple endpoints (Roon’s term for streamers, DACs, and other analog-output devices), and access content from the internet. And unlike home computers that have resource limitations due to the overhead of the operating system and background programs, Nucleus Servers are custom-built for music and can devote ALL their resources to ensuring music delivery without slowdowns, gaps, or loss of quality.

Highlights

ROON NUCLEUS PLUS MUSIC SERVER

  • Fast response, even with large libraries
  • Familiar interface via Roon Remote
  • Streaming access to TIDAL, Qobuz, and internet radio sources
  • Small and quiet (no fan)
  • Capable of multiple zones of simultaneous output
  • Capable of multiple inputs via Ethernet
  • Limited digital audio outputs (USB & HDMI only)
  • Multi-channel capable
Glossary of Terms:
  • CODEC – A device or computer program which encodes and/or decodes a digital data stream or signal
  • DAC – Digital to Analog Converter
  • DSD – Direct Stream Digital, a CODEC for storing digital audio on SACD
  • Endpoint – Any device to which Roon can output audio, such as a streaming DAC
  • Internet radio – A digital audio service transmitted via the Internet
  • MQA – An audio codec using lossy compression and a form of file fingerprinting, intended for high fidelity digital audio internet streaming and file download
  • Music Server – The combination of storage media, media server software, and a DAC
  • NAS – Network Attached Storage, a networked hard disk or RAID
  • Nucleus Plus – A networked, custom-built mini-processor hardware platform that serves as the center of a Roon music system
  • Qobuz – A French, internet-based, subscription music streaming and downloading service
  • RAID – Redundant array of inexpensive (hard) disks
  • Roon – A networking media software-player program for digital audio systems designed by Roon Labs
  • SSD – A solid-state storage device that uses integrated circuit assemblies to store data persistently
  • Streamer – Any component that allows you to play music via network or wirelessly to your hi-fi system
  • TIDAL – A Norwegian, internet-based, subscription music, podcast, and video streaming service
Introduction

The Roon Nucleus Plus Music Server under review is the B version of the original Roon Nucleus and is optimized for Roon’s music playback software. The Nucleus and Nucleus Plus both use a customized operating system, Roon OS, that has been specifically modified by Roon for music quality. The Roon Nucleus and Nucleus Plus differ by the speed of their processors and the amount of internal memory (RAM) installed. The Plus version is capable of handling larger music libraries and multiple zones without delays. Both Nucleus products can access TIDAL and Qobuz online music streaming services, and work with high-resolution files (limited only by the endpoints’ capabilities), MQA encoded files, DSD content, internet radio, and multiple local libraries.

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Both Roon Nucleus servers are capable of streaming music to multiple “endpoints” (Roon-speak for playback devices including powered speakers, DACs, music streamers, etc.). These endpoints can be in multiple locations, so a single Roon Nucleus can suffice as a musical “traffic director” for an entire building. Since there is but one endpoint in my network, I did not test the use of simultaneous multiple endpoints.

Just as the Roon Nucleus series can stream to multiple endpoints, it can also draw content from multiple sources. Anything on the local network, network-attached storage, and shared drives from other computers can be simultaneously accessed by the Nucleus. It can also play from internal SSDs or 2.5-inch format laptop drives as sources. I used a standard external USB drive for my Roon Library.

The Roon Nucleus-Plus is designed to run “headless” (without a monitor), by way of the Roon Remote app on an Apple, Microsoft, or Android tablet. Cell phone displays are not recommended due to their small size.

Do-it-yourselfers can duplicate most of the features of the Roon Nucleus and Nucleus Plus at significant cost savings with off-the-shelf components and a bit of elbow grease. But for those wanting a turnkey hardware solution that is not only optimized for music but also can be controlled by a tablet, the Roon Nucleus and Nucleus Plus are readily available and work as advertised.

Background:

As a Roon user for over a year now, I wanted to see if the Roon Nucleus Plus had any sonic advantage over my previous Roon Core install on a Mac Mini. Because of the size of my music library (3.5TB on an external USB drive), I requested the Roon Nucleus Plus rather than the base Nucleus. Roon recommends the Plus model for large music libraries.

Although Roon has worked reliably on my Apple MacBook Pro and Mac Mini, I was curious to find out if there were functional or sonic advantages to the Roon-designed and produced Nucleus devices. The more I learned about Roon’s Nucleus, the more I realized how much functionality it offered. I also quickly realized that the Nucleus exceeded the needs of my system by orders of magnitude by including abilities that I would never use. But for a power user or a customer who needs any specific feature of the Nucleus, it has much to recommend it.

The Nucleus Plus is a solid and heavy component covered with cooling fins that eliminate the need for internal fans. With a recessed connector panel on the back and no light on the front, the Nucleus is designed to be minimally intrusive. With low heat production and zero noise, it can be placed virtually anywhere.

Since the Nucleus is primarily a networked device, peripherals such as storage drives, digital to analog converters (DACs), and audio streamers need not be in close physical proximity. Having Roon OS running at all times on the Nucleus means that no other computer on the network needs to run Roon at all. Another valuable aspect of the Nucleus is that it can run without a monitor, mouse, or keyboard (all of which a computer would need). In fact, the Nucleus can be completely operated from the Roon Remote app installed on just about any kind of tablet. Since the Nucleus is so low-powered and so robust, it can be left on all the time.

Music storage is similarly flexible. In addition to the operating system SSD, the Nucleus has a spare slot for an internal 2.5-inch format hard drive or SSD. With prices dropping on such drives, one could install a large capacity drive inside the Nucleus itself and probably need no other storage.

But the Nucleus can also access data from its own USB port, the HDMI ports, and/or a network. Connect one or more external, large, and inexpensive USB drives for virtually unlimited storage. For more than one, an adapter will be needed.

The Nucleus has support for streaming services to include TIDAL and Qobuz. If you wish to access other internet storage such as Dropbox, Google Drive, or others, just map the path and enter your username and password (if required).

Today, many users no longer bother to maintain their own music libraries. For streaming subscription services, the Nucleus products support both TIDAL and Qobuz access. With either or both of those, almost every desired musical performance you can think of is instantly available over the internet.

And finally, for users who want to have different music in different parts of their building, the Nucleus can feed multiple endpoint devices simultaneously with concurrent or independent programs.

ROON NUCLEUS PLUS MUSIC SERVER SPECIFICATIONS
LIBRARY CAPACITY:

>10,000 albums (100,000 tracks)

STREAMING:

More than six simultaneous zones

RESOLUTION:

Up to 512DSD, Up to 24/96 MQA, PCM to end-point limits

DIGITAL SIGNAL PROCESSING (DSP):

Available

PROCESSOR:

Intel i7 CPU

RAM:

8GB

STORAGE:

128MB Solid State Drive

POWER:

12-19V DC

USB I/O:

2x USB 3.0 (can be used for hard drive and/or DAC)

HDMI:

2x HDMI (stereo and multi-channel audio output)

LAN:

Gigabit Ethernet port RJ45

STORAGE SLOT:

2.5” SATA SSD or HDD up to 9.5mm drive height (drive not included)

REMOTE CONTROL:

Roon API, Control4, Creston

ACCESSORIES:

AC power supply (19V, 60W), US/UK/EU/AU power tips, Quick-Start guide

DIMENSIONS:

212mm (W) x 156mm (D) x 74mm (H) / 8.35”W x 6.15”D x 2.91”H

PACKAGE WEIGHT:

3.85kg / 8.49lbs

DEVICE WEIGHT:

2.5kg / 5.51lbs

MSRP:

$2,559.00 USD with a 1-year subscription to TIDAL streaming service

WARRANTY:

Repair or replacement within 2 years of purchase

WEBSITE:

www.roonlabs.com

Company Directory:

Roon

SECRETS Tags:

Roon Nucleus, Nucleus Plus, playback device, music server, streamer, multi-channel, networked, whole-house, Secrets, 2020, review 2020

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Setup

The Roon Nucleus Plus arrived with a quick-start guide, a power supply, and four mysterious screws with no explanation as to what they might be for, SSD drive installation perhaps?

Trivial Irritations:
  • The Nucleus connection panel is recessed, dark, and ergonomically hard-to-reach. But once connected, no repeat access should be required.
  • The Roon backup program misses some data when transferring a Roon installation from another computer to the Nucleus. Roon says they’re working on this.
  • The Nucleus units have onboard digital outputs limited to USB, HDMI, or Ethernet. Other on-the-box digital outputs such as S/PDIF coaxial, TOSLink optical, and/or AES/EBU might have been convenient, but since most use their Nucleus with one or more independent Roon endpoints, the existing outputs are enough for most users.
Design

The design intents of the Roon Nucleus and Nucleus-Plus are two: to provide an easy and simple way to experience Roon and to provide the best audio quality possible.

Power users can build their own Nucleus (or Nucleus Plus) equivalents from readily available parts for less than half the cost of the genuine Roon products. The miniature systems for this purpose are called NUCs (Next Unit of Computing). This is a small-format computer that allows low-power, quiet, and fanless operation. The Roon software for such devices is called “ROCK” (an acronym for Roon Optimized Core Kit).

But to go the economy route, the customer must either buy a compatible NUC or build one, install the ROCK kit then activate it. Technical issues are the customer’s to solve, but Roon does provide user-community forums and technical support for its software. Many would prefer to just buy the Roon Nucleus (with Roon OS pre-installed) and not have to bother with the DIY route.

Roon also claims that their hardware in the Nucleus is optimized specifically for music (unlike NUC or desktop/laptop platforms).

I will say that being able to operate the Nucleus Plus from my iPad was far easier and more elegant than having to use my Mac Mini. Playing music from my Mac Mini required a multi-step process that included:

  • Switching HDMI inputs on my TV (used as a monitor) from the cable box to the Mac Mini
  • Waking the Mac Mini and logging in
  • Using Disk Utility to mount the external Library drive, and then starting Roon
  • Waking the iPad, logging in, and waiting for Roon Remote to establish communication with the Roon Core
  • And reversing the process when the listening session was over

With the Nucleus Plus in the system, I don’t need the TV as a monitor, don’t need the keyboard or mouse, don’t need to mount/unmount the Library drive, and the Roon Remote app seems to connect MUCH more quickly. These conveniences make the audio system far more user-friendly for family members and visitors.

Of course, for users who leave their server computer on all the time, the startup may be significantly easier. But for those, like me, who prefer to manually put the server to sleep at the end of each listening session, the convenience of the Nucleus is almost worth its cost just to avoid the startup and shutdown tedium.

In Use

The associated components used to evaluate the Nucleus-Plus include:

  • Audioquest Dragonfly Black 1.5 DAC
  • Black Ice Fusion F11 tube integrated amplifier
  • Emotiva BasX T100 solid-state integrated amplifier with internal DAC
  • Starke Sound AD4.320 Class-D power amplifier
  • Emotiva PA-1 Class D monoblock power amplifiers
  • Ashly ATX-2001 MOSFET pro stereo power amplifier
  • Emotiva T2 loudspeakers
  • Tekton Design Double Impact loudspeakers
  • Kimber Kable interconnects and 4TC speaker cable
  • ATS Acoustics diffusers and absorbers

Comments in this section compare and contrast the sonic differences between my Mac Mini used as a Roon Core and the Nucleus Plus using Roon OS. My Nucleus Plus installation is probably atypical in that I use neither multiple zones nor multiple endpoints. My USB DAC (the Audioquest Dragonfly) was plugged directly into the Nucleus Plus for purposes of sonic evaluation. The Dragonfly was the only endpoint in my system. I used a local external USB HDD (Western Digital 4TB My Book) as the Roon Library location. Qobuz Studio was used for internet streaming, but TIDAL was not.

It is fair to say that with the possible exception of my 3.5TB Roon Library data content size, neither the Mac Mini’s Roon Core nor the Roon Nucleus Plus was at all stressed by the demands of my setup. It is possible that if I had multiple zones and/or multiple library drives, the Nucleus Plus might have had some sonic advantage over the Mac Mini. In theory, the Mini would be burdened with greater overhead such as the Mac operating system and other computer background processes that would simultaneously demand CPU clock cycles. The Nucleus Plus, not having as much load on its CPU might, therefore, sound better. But this is speculation on my part, and I didn’t have the hardware to test the theory. So onward to listening.

20 Best of Big Bands
The CD “20 Best of Big Bands” contains the BBC Orchestra’s classic version of “Sing, Sing, Sing.” This is an exceptionally well-recorded track that includes thundering bass, bombastic percussion, and a brass section that just doesn’t quit. Through the Nucleus Plus, transients just didn’t sound as brash and dynamic as they did when played through the Roon Core on the Mac Mini. I checked the DSP sections on both installs – no foolishness there – both were bypassed as they came from the factory.

The same DAC and amplifiers were used for both playback sessions, so why the difference? I don’t know. But this was one of the ONLY tracks that I could tell any difference at all between the Mac Mini and the Nucleus Plus, and the nod goes to the Mac Mini on this track. I switched back and forth twice just to make sure I was hearing what I thought I was, and the difference was audible and consistent.

Highwaymen”, A Celebration of American Folk Music, Johnny Cash, Willie Nelson, and Waylon Jennings
The track “Highwaymen” by Johnny Cash, Willie Nelson, and Waylon Jennings is not only well recorded, but also great fun. The different solo voices lend variety to the collection of “mini-stories” told within the song. In fact, the entire Readers Digest CD set “A Celebration of American Folk Music” is well worth listening to. But as to audible differences between the Mac Mini and the Nucleus Plus, I just couldn’t hear any. I’ll take that as a tribute to the stability of the Roon software despite running it on different platforms.

Skating”, A Charlie Brown Christmas, Vince Guaraldi
From the CD “A Charlie Brown Christmas” comes Vince Guaraldi’s popular “Skating.” I like to hear piano when evaluating music for differences because, knowing what a live one should sound like, I find it easier to hear distortion or tonal issues that shouldn’t be there. The piano sounded consistent regardless of which Roon install was playing, and it sounded consistently GOOD. It’s also fair to say that I particularly like this song…

Sun is Shining“, Bob Marley – 20th Century Masters Millennium Collection, Bob Marley and the Wailers
This is my favorite Bob Marley and the Wailers track of all time, “Sun is Shining,” My copy is found on the “Bob Marley – 20th Century Masters Millennium Collection” CD. The sound is unusually delicate for this track and again sounded equally great on both the Nucleus Plus and the Mac Mini Roon Cores.

A Passion for Tango”, Authentic Tangos from Argentina, Sexteto Mayor Orchestra
By the “Sexteto Mayor Orchestra” comes “A Passion for Tango” including, specifically, the excellent cut “Los Ojos Negros, Negritos.” The album is subtitled “Authentic Tangos from Argentina.” This is dynamic music, and once again, the Mac Mini’s Roon Core application seemed to be just slightly more boisterous than did the Nucleus Plus. And I definitely liked the extra “oomph!

Jenny Says!”, Ace of Clubs, Dash Rip Rock
Dash Rip Rock or The Reverend Horton Heat – Take your choice, but DEFINITELY get yourself a copy of “Jenny Says!” Clever lyrics, slamming dynamics, and vocals with LOTS of nuance make this cut just plain fun to hear. My chosen track was from the Dash Rip Rock “Ace of Clubs” CD. After the previous cuts, I was expecting it to sound better on the Mac Mini, but it surprised me. For some reason, I thought this sounded slightly better with better pitch definition and dynamics on the Nucleus Plus. Go figure!

Cast Your Fate to the Wind”, Allen Toussaint
Cast Your Fate to the Wind” is another one of my favorite songs. This time, it’s done by the Allen Toussaint band, although I really like the Vince Guaraldi version too. The well-recorded piano and bass were pitch-perfect and separated in the soundstage equally by both the Mac Mini and the Roon Nucleus Plus. I tried twice to hear any difference between the two devices and could not.

So, there you have it. On only three of the seven tracks could I hear ANY difference between the Roon Core of the Mac Mini and Roon OS of the Nucleus Plus. And, confoundingly, two of the three “I hear a difference” tests favored the Mac Mini, and the other favored the Nucleus Plus. And even when I could hear a difference, the differences were VERY minor. I think that for all intents and purposes, I’ll have to call the Mac Mini vs. Roon Nucleus Plus sound-quality comparison a tie.

Conclusions

The Roon Nucleus Plus Music Server is convenient, capable, and costly. Despite cheaper alternatives, the Nucleus Plus does exactly what it is advertised to do.

Likes
  • Compact and cool running hardware
  • Multi-zone output
  • Multi-device input (more than one networked/internet source can be simultaneously accessed)
Would Like To See
  • More clearly marked power switch (doesn’t affect function)
  • More reliable Roon backup and restore
  • Any color option other than black (doesn’t affect function)
  • Non-recessed connector panel (doesn’t affect function)

The Roon Nucleus and Nucleus Plus are amazingly capable devices. For a power user who needs the flexibility that the Nucleus series offers, and who wants to avoid the time and trouble of building their own Nucleus-type device, the prices are justified. Also, by buying the Nucleus, one gets a full two-year repair or replacement warranty from Roon.

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Using the Nucleus via Roon Remote is a very comfortable experience, particularly for users who are already familiar with the interface. Even for beginners, the Roon Remote software has a very mild learning curve, and users will quickly be able to access all the features. I’d have to conclude that Roon’s goal of user-friendliness for the Nucleus has been met.

Roon’s second goal, superior audio quality, is far more difficult to quantify, and its evaluation will rely entirely on the complexity of the user’s system. The more sources and endpoints in a Roon system, the more likely it is that the Roon Nucleus Plus will deliver a better audio experience. But since my system lacked sufficient complexity to test this, I am speculating. In my system, the Mac Mini based Roon Core install provided just as good a user experience and sound quality as did the Nucleus Plus. But my experience is not typical of all.