Audiophile Glossary

All essential terms for Hi-Res audio streaming, self-hosting and audiophilia, explained clearly.

AAC: Advanced Audio Coding. A lossy audio codec developed as the successor to MP3, offering better quality at equivalent bitrates. Used by Apple Music, YouTube and many streaming platforms. Transparent quality at 256 kbps for the majority of listeners.
AirPlay: Proprietary Apple protocol for wireless audio (and video) streaming to compatible devices: HomePod, Apple TV, AirPlay speakers. Automatic discovery via mDNS/Bonjour on the local network. AirPlay 2 adds synchronized multi-room and Siri control.
ALAC: Apple Lossless Audio Codec. A lossless compression format developed by Apple, the functional equivalent of FLAC in the Apple ecosystem. Preserves 100% of the original quality while reducing file size by approximately 40-60%. Used natively by Apple Music for Hi-Res streaming.
Headphone Amplifier: An amplifier dedicated to headphones, designed to provide the appropriate power and impedance for headphone transducers. Essential for high-impedance headphones (300+ ohms) that cannot be properly driven by a standard headphone output. Often integrated into a combined DAC/amp unit.
Bit Depth: The number of bits used to represent each audio sample. Standard CD uses 16 bits (96 dB dynamic range), Hi-Res goes up to 24 bits (144 dB theoretical dynamic range). Higher bit depth reduces quantization noise and increases dynamic range.
Bit-Perfect: Audio transmission without any alteration of the digital data between the source and the DAC. The bitstream sent to the converter is identical bit-for-bit to the original file. No resampling, no software mixing, no volume processing. Guarantees maximum fidelity of the digital chain.
Chromecast: A streaming protocol developed by Google for sending audio (and video) to compatible devices over the local network. Supported by many connected speakers and soundbars. Enables multi-room via speaker groups in the Google Home app.
Convolution (FIR): A digital signal processing technique using Finite Impulse Response (FIR) filters to apply acoustic correction. The convolution filter is calculated from room measurements and applied in real-time to the audio stream. Used by Dirac Live, Audiolense, REW and other correction software.
Crossfade: A gradual transition between two audio tracks: the volume of the current track decreases progressively while the next one increases. Eliminates silences between tracks for fluid listening. Crossfade duration is typically configurable (1 to 12 seconds).
DAC: Digital-to-Analog Converter. A component that transforms the digital audio stream (bits) into an analog signal usable by an amplifier and speakers. The quality of the DAC directly influences reproduction fidelity: noise floor, distortion, linearity.
DLNA: Digital Living Network Alliance. A home networking standard enabling media sharing and streaming between compatible devices (TVs, amplifiers, streamers). Based on UPnP AV, it defines the roles of server (provides content), renderer (plays content) and control point (controls playback).
DSD: Direct Stream Digital. A high-resolution audio format using 1-bit sigma-delta modulation at very high frequency (2.8 MHz for DSD64, 5.6 MHz for DSD128, etc.). Developed by Sony and Philips for SACD. A radically different approach from PCM: instead of multi-bit samples, a single bit toggles at very high speed.
FLAC: Free Lossless Audio Codec. An open-source, royalty-free lossless audio compression format. Reduces file size by 40-60% without any quality loss. The de facto standard for Hi-Res digital music, supported by Qobuz, Tidal and virtually all players and streamers.
Gapless: Uninterrupted playback between consecutive tracks. Essential for live albums, operas, DJ mixes and any music designed as a continuous flow. The server must pre-buffer the next track and chain playback without micro-silence or audible artifacts.
Hi-Res: High-resolution audio. A term designating any audio format whose quality exceeds that of CD (16-bit / 44.1 kHz). Typically 24-bit / 96 kHz or 24-bit / 192 kHz in PCM, or DSD64/128/256. The "Hi-Res Audio" label is certified by the Japan Audio Society, adopted by Sony and embraced by the industry.
Lossless: A category of audio codecs that reduce file size without altering the original data. The decompressed file is identical bit-for-bit to the original. FLAC, ALAC and WavPack are the most common lossless formats. As opposed to lossy formats (MP3, AAC, OGG) which sacrifice data to reduce size.
Metadata: Descriptive information embedded in audio files: title, artist, album, year, genre, track number, cover art. Stored in ID3 tags (MP3), Vorbis Comments (FLAC) or atoms (AAC/ALAC). Good tagging is essential for browsing and organizing a music library.
MQA: Master Quality Authenticated. A proprietary audio format that "folds" (encapsulates) high-resolution audio into a CD-compatible container (16/44.1). Requires an MQA decoder (software or hardware) to "unfold" the data and restore the original resolution. Controversial in the audiophile community for its proprietary nature and measurable losses.
Multi-Room: A system for playing music in multiple rooms simultaneously, either synchronized or independently. Each zone (room) can have its own renderer (speaker, amplifier) and its own source. Common protocols include AirPlay 2, Chromecast, DLNA and proprietary solutions (Sonos, HEOS, MusicCast).
MusicBrainz: An open, community-maintained music database run by the MetaBrainz Foundation. Provides unique identifiers (MBIDs) for artists, albums, tracks and releases. Used by music servers for automatic metadata enrichment, cover art retrieval and disambiguation of artists with identical names.
RAAT: Roon Advanced Audio Transport. A proprietary network protocol developed by Roon Labs for bit-perfect audio transmission between the Roon server and endpoints (audio outputs). Handles synchronized multi-room, native DSD, MQA and volume control. Requires a Roon license (subscription).
Renderer (DLNA): In the DLNA/UPnP architecture, a network device capable of receiving and playing an audio stream sent by a control point. Examples: network streamers (Yamaha, Denon, Cambridge Audio), certain TVs and connected speakers. The renderer decodes the stream and converts it to an analog signal via its built-in DAC.
REW (Room EQ Wizard): A free acoustic measurement and analysis software. Measures room frequency response, reverberation time (RT60), distortion and other acoustic parameters. Generates correction filters (PEQ, FIR) to optimize listening. The reference tool in the DIY audiophile community.
Roon Ready: A Roon Labs certification indicating that a network audio device is natively compatible with the RAAT protocol. Roon Ready devices appear automatically in Roon and support bit-perfect streaming, synchronized multi-room and control from the Roon app. It's a paid certification for manufacturers.
Room Correction: A set of DSP (Digital Signal Processing) techniques aimed at compensating for the acoustic deficiencies of a listening room: resonance modes, early reflections, excessive reverberation time. Common solutions: Dirac Live, Audiolense, REW with convolution, miniDSP.
Sample Rate: The number of audio samples captured per second, expressed in Hz or kHz. Standard CD uses 44.1 kHz (Nyquist theorem: reproduces up to 22.05 kHz). Hi-Res uses 96 kHz or 192 kHz, allowing capture of frequencies beyond the audible range and reducing anti-aliasing filter artifacts.
Self-Hosted: Software installed and run on the user's own hardware (NAS, Raspberry Pi, PC, home server) rather than on a third-party cloud service. Benefits: full data control, no recurring subscription, offline operation, unlimited customization. Tune is a self-hosted music server.
Smart Playlist: A dynamic playlist automatically generated based on rules and criteria defined by the user: genre, year, rating, play count, date added, audio quality, etc. Automatically updates when new tracks match the criteria. Equivalent to iTunes/Apple Music 'Smart Playlists'.
Streamer: A dedicated network audio playback device. Receives audio streams over the network (DLNA, AirPlay, Chromecast, Roon) and converts them to analog signal via its built-in DAC. Examples: Cambridge Audio CXN, Yamaha WXC-50, Bluesound Node. Not to be confused with "streaming" (online services like Tidal or Qobuz).
UPnP: Universal Plug and Play. A set of networking protocols enabling automatic discovery and communication between devices on a local network. In the audio context, UPnP AV (the multimedia layer) is the technical foundation of DLNA. The SSDP (Simple Service Discovery Protocol) handles device discovery.