DSP—DSP, or Digital Signal Processing, refers to an type of computer programming in which analog waveforms, or variations in sound pressure or an electrical signal (representing music or sound in this context) get converted to numbers so that you can store, transmit, and alter the waveform or signal with a computer processor in logical or mathematical ways generally impractical without first converting the waveform or signal to numbers. The analog waveform gets converted to numbers using an ADC (Analog to Digital Converter, such as an Apogee Duet 2 or Ayre QA-9), fed into a computer processor, manipulated in a way intended to alter the sound in a subjectively pleasing way, then gets converted back to an analog waveform or electrical signal using a DAC (Digital to Analog Converter, such as an Ayre QB-9 DSD or dCS Debussy) and played through an amplifier into a pair of headphones or loudspeakers. Even devices as simple an iPod, DAP (Digital Audio Player), or mobile phone use specially-designed microchips and software to store, transmit, alter, and play music or sound as lists of numbers rather than pure electrical signals.
Core Audio—In most devices capable of DSP, you have something called an OS (Operating System) that controls the device, dividing different methods of controlling the devices (such as CD players and mobile phones) into encompassing circles like the layers of an onion. The more central to the device’s operation, the closer to the innermost part, or core, of the metaphorical onion the software for those operations resides, because the device relies most fundamentally on those operations. As example, both Apple’s iOS and macOS (formerly named OS X)—both examples of Operating Systems—have layers of software very close to their core that process sound. Because Apple, in this example, allow other companies to add to that sound processing core, or Core Audio, in the field (for example, at your home), you can add new DSP or sound processing software techniques to the device that enhance its capabilities without detracting from the most essential sound processing techniques that come with the device when you get it at, say, the Apple Store.
Plugin—The way that Apple, as an example, allows you to enhance the Core Audio processing software of an iPhone or MacBook Pro involves a fragment of software called a Plugin that you download onto the device, install into the Core Audio layer, then run as a part of Core Audio to enhance the basic sound processing of the device every time you use your iPhone or MacBook Pro unless you disable the Plugin through the System settings. This “open architecture” allows for third parties (software developers outside of Apple) to “extend” the essentially capability a device, like an iPhone, without having to wait for the next release of iOS or buy a whole new iPhone or iPad. Because Plugins “extend” the capabilities of the Core Audio layer, they can carry the name Extension or Extensions as well, as one example, in Roon.
NAS—An NAS, or Network Attached Storage device, contains a set of fixed drives that store and deliver data all over your home network using various “protocols” or standards that allow individual devices from computers to Media Servers or Streaming DACs to read and write data, often media files including digital music files, all from and to centralized storage mechanisms (the NASs) that you can then backup archive from a single point not contained inside of any one mobile phone, tablet computer, laptop computer, Media Server, etc. Some of the simplest and best NASs come from the company Synology. You can purchase them on amazon.com. Other, more sophisticated NASs that have higher quality fixed drives with better power supplies and tighter manufacturing tolerances that generally offer better sound from the digital music files stored on the NAS can be found from companies like Melco, including the N1A and N1Z among others, Almost all NASs connect to your home network via Ethernet patch cables, not Wi-Fi, and run software that allows them to be “discovered” and indexed on your home network through various Apps and computer applications, including software built into Windows, Linux, and macOS.
Streaming DAC—A DAC (Digital to Audio Converter) with a built in home network “bridge” to allow playback of music from streaming services such as TIDAL or from collections of digital downloads on, as example, an NAS. Some Streaming DACs can serve as Roon devices or endpoints and they almost all involve a dedicated App written for a mobile phone and/or tablet computer that allows you to choose collections of music files to play utilizing a graphical, touchscreen interface. For best performance, most Streaming DACs require connection to your home network through an Ethernet patch cable, not necessarily via Wi-Fi.
Media Server—A Media Server controls the flow of music files (and sometimes video files) from one place to another in a home entertainment systems. Some Media Servers, like the Aurender N100H, can both stream music from sources like Spotify or TIDAL and/or can store digital music files on their own, internal fixed drives. In some cases, such Media Servers have built in DACs and, in other cases, you have to run the Media Server into a separate DAC, often connected by a USB cable. In all cases, Media Servers require connections to your home network through Ethernet patch cables or via Wi-Fi. Some Media Servers, like the Sonore microRendu and the Bluesound Node 2, have no internal storage of their own and require connection to the Internet to stream, say, TIDAL or to a storage device such as an NAS, also connected to your home network.
Some more sophisticated Media Server systems, like Roon, use a distributed solution where you download the Roon Server software onto a computer (Windows, Linux, or macOS) that act as central control points through which all musical information flows in the form of data files, or lists of numbers, to various Roon-capable devices, such as the Bluesound Node 2 or Ayre QX-5 Twenty, to have different regions or “zones” of music in your home. In most cases, Media Servers have no built in user interface but use a mobile phone, tablet computer, laptop computer, and/or desktop computer Apps or applications to control the flow of music throughout your home. Because of the greater processing power provided by a computer such as a MacBook Pro, distributed systems can offer overall more flexible functionality and better sound quality than standalone devices relying on a built in set of computer chips and a control App on, say, a Wi-Fi connected iPad. Like other other devices capable of DSP, most media servers use Plugins to let you extend or enhance the Core Audio processing provided by, e.g., Roon.
Roon—Roon, a distributed media server software system running across Windows, Linux, and macOS. Roon evolved from Merdian’s proprietary Sooloos media server software system and offers substantially more processing power and functionality than media server systems embedded in, for example, Streaming DACs. It has an open architecture allowing third parties to develop Plugins or Extensions to extend or expand its functionality and uses certain intelligent algorithms in conjunction with metadata available on the Internet to categorize and organize your music collection to create automatic, continuous playlists based on your choice of an original album to play in a given listening session. Subjective assessment indicates that music served via Roon often sounds substantially better than the same music files sent directly to a Streaming DAC using an App-only approach to connect streaming services or an NAS to a network-enabled (i.e., Streaming) DAC.
iOS Core Audio-The layer of the Operating System used by iPhones and iPads the process all of the music and sound passing through the device. Core Audio has an “open architecture”, meaning that you can extend its functionality with third party Plugin modules just as you can with Roon.
macOS—Formerly called OS X, the Operating System used by Apple computers that incorporates an open, or Plugin compatible, Core Audio processing layer. Other Operating Systems with potentially “open” Plugin capabilities include Windows and Linux.