Now, you don't have to have a Nucleus to run the Roon Core. You can download and install the Roon Core for free on Mac, Windows, Linux, select QNAP and Synology NAS, and Intel NUC running ROCK. But know that if you use your computer as your Core, it has to be turned on and you have to be logged in -- all of the time. Even though you're using your iPad, and the Core is in another room, the Core has to be on so that they can communicate with each other in order to play music.

So if you don't want your computer on all of the time, you get a Nucleus. You leave it in your 2-channel system, you leave it on all of the time and it's always running in the background. You can also then put an internal hard drive in it or an external hard drive and add storage to it (whereas most people store music on their computer). You essentially become untethered from your computer.

The Nucleus does not come with any drives, but you have the option of adding 2-4TB (up to 8TB for the Nucleus+) via an internal 2.5-inch SATA SSD. Other storage options are external USB and NAS.

The internal drive is not used to store audio files. Instead, as well as hosting the Roon Optimized Core Kit (ROCK) operating system and the Roon server software, it's used to manage Roon's library (footnote 1). From the outset, Roon was intended to produce a rich metadata experience.From the moment you point the Nucleus Core to the location of your audio library, the system begins to create the waveform display for every track; starts scouring the Internet for metadata, artwork, biographies, and reviews; and builds an object database. This means, says Roon, that "instead of storing data in the traditional tabular form, we model your music as a web of interconnected entities and their relationships to one another. . . . They enable us to perform complex queries that would be impractical for a traditionally architected application, and they let us perform background processing on your music library in order to continually improve the user experience."

— John Atkinson, Stereophile | July 2018

• For my money, the Roon Nucleus is the absolute best server solution for large Roon libraries. It functions seamlessly and has almost totally eliminated cutouts.
• The Nucleus is extremely well made. The fit and finish meet or exceed other similar companies such as Aurender or Cocktail Audio. For almost $1,400 this is expected nowadays.
• The extreme simplicity of the hardware buttons and ease of setup make this unit as idiot-proof as a network attached music server could be.

— Matthew Partrick, Home Theater Review | September 2018

The Roon Labs Nucleus+ server has changed my thinking concerning the selection of an optimum playback device to use for the Roon music software. Enough cannot be said for the overall user-friendliness of this device. The outstanding integration of the OS with the hardware and the Roon music software is something that was quite apparent to me as I listened to the Nucleus+. I found the Nucleus+ to be a solid piece of engineering with its use of Intel's NUC and custom fanless design. The Nucleus+ is going to be a keeper for this computer audiophile.

— Steven Plaskin, Darko Audio | August 2018