USB HiFi and Hi-Res Audio

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USB HiFi Glossary

Digital Audio and HiFi with the PC - A Glossary

This professional standard audio connector is used for the transport of digital audio signals between audio devices. Mostly used in Studio-Equipment.

Audio Stream Input/Output. Computer sound card driver protocol for digital audio with low-latency. Mostly used for audio-recording.

Audio File Formats
A distinction is made between compressed and uncompressed as well as lossless and lossy audio formats. For Hi-Res only uncrompressed respectively lossless formats are recommended (e.g. for PCM-Files use WAV / FLAC, otherwise DSD)

  • Uncompressed Audio Data
    WAV: Waveform Audio File Format (.wav)
    AIFF: Audio Interchange File Form (.aiff, .aif or .aifc)

  • Lossless Data Compression
    ALAC: Apple Lossless Audio Codec (.mp4 or .m4a)
    FLAC: Free Lossless Audio Codec (.flac)
    DXD: PCM Format that is a very high sampling rate of 352.8kHz / 24bit. Also used for mastering of SACDs

  • Lossy Data Compression
    MP3: MPEG-1 or MPEG-2 Audio Layer III (.mp3)
    AAC: Advanced Audio Coding (.aac, .mp4 or .m4a)
    OGG: OGG Vorbis, free audio compression format

  • Direct Stream Digital
    DSD: A digital format based on Delta-sigma modulation, storing audio-signals as a sequence of single-bit values at a very high sampling rate. Not supported by all the DACs (.dsf - with metadata / .dff - without metadata)

A bit can have only one of two values (0 or 1) and is the basic unit of information in computing / digital communications.

Bit Depth
This describes the number of bits of information recorded in an individual audio sample (= resolution). For example: Audio-CD quality can support up to 16 bits / DVD-Audio can support up to 24 bits.

Bit-perfect Playback
The audio-file is provided by the DAC without any modifications like up sampling etc.

The bit rate refers to the amount of data per second is obtained from a transfer from unit A to unit B. The bit rate is always specified in kilobits (Kbps) or megabits (Mbps) per second. For example, an MP3 file reproduce 128 Kbps, therefore a device is required that can process the least amount of data.
The bitrate can easily be calculated by itself: Sampling rate (resolution) x Bit Depth x Number of channels = Bitrate. For the CD, the 44.1 kHz x 16 bit x 2 channels (stereo) = 1,411,200 bits per second (1411.2 kbps).

DAC / Digital Analog Converter
The Digital Analog Converter converts digital audio-signals into analog audio-signals.

ID3 Tag
Provides meta-information in audio-files like cover, song-title, artist etc. (available only for some audio-file-formats).

Software to play and stream digital music-files. Highly recommended:
- MPD (Music Player Daemon) for Linux based audio computers
- foobar2000 for Windows computers
- Sonic Studio Amarra for Mac

The resolution refers to the word length and the sampling-rate of digital audio data and is responsible for the dynamic range.

For the quality of a digital signal it is important how often the audio-signal is scanned per second (Kilohertz / kHz). This value is called thus as a sampling rate. For example: the frequency of the CD is 44100 kHz, the DVD up to 96000 kHz.

Studio Master Download
Downloads that guarantee the best quality of the audio-file without any compression. Often directly taken from the master-file of the recording studio.

This technical feature increases the sampling rate of an audio signal.