High fidelity or hi-fi reproduction is a term used by home stereo listeners and home audio enthusiasts (audiophiles) to refer to high-quality reproduction of sound or images that is very faithful to the original master recording. High fidelity equipment has minimal or unnoticeable amounts of noise and distortion and an accurate frequency response as set out in 1973 by the German Deutsches Institut für Normung (DIN) standard DIN 45500. The term was most widely used in this strict sense in the 1950s and 1960s; in subsequent decades, the term was applied more loosely to any mid-level stereo system. In the 2000s, the term "hi-fi" for expensive high quality home audio electronics was largely replaced with the term "high-end audio".
Modern hi-fi equipment usually includes digital audio signal sources such as CD players, Digital Audio Tape (DAT) and Digital Audio Broadcasting (DAB) or HD Radio tuners, an amplifier, and loudspeakers. Some modern hi-fi equipment can be digitally connected using fiber optic TOSLINK cables, universal serial bus (USB) ports (including one to play MP3 and Ogg files in an USB flash drive), or WiFi support.
One modern component that is making fast gains in acceptance is the music server consisting of one or more computer hard drives that hold music in the form of computer files. When the music is stored in an audio file format that is lossless (such as FLAC or Monkey Audio), unlike lossy file formats such as MP3, WMA, and Ogg (which all suffer from fidelity-degradation), the computer playback of recorded audio can indeed serve as an audiophile-quality source for a hi-fi system. However, it should be noted that lossy audio formats are not hi-fi in the stricter sense of the term. Some non-lossy file formats are AIFF and WAV; both are suitable for high fidelity audio, in a variety of resolutions. Resolutions which exceed CD quality are capable with such files and appropriate playback equipment (professional or semipro digital to analog converters).
