An audiophile is a person with a strong interest in high-quality sound (usually music) reproduction.
Audiophile values may be applied at all stages of music reproduction: the initial audio recording, the production process, and the playback, which is usually in a home setting.
"Audiophile" recordings include those using conventional formats but with special attention to audio quality, as well as recordings in high-resolution formats such as Super Audio CD or DVD-Audio. Recently, there has been interest in lossless file formats such as WAV, FLAC, WMA Lossless, and Apple Lossless.
The term High-end audio refers to playback equipment used by audiophiles, which may be bought at specialist shops and websites. High-end components include turntables, digital-to-analog converters, equalization devices, preamplifiers and amplifiers (both solid-state and vacuum tube), horn and electrostatic speakers, power conditioners, subwoofers and acoustic room treatment.
A key goal of audiophiles is to capture the experience of a live musical performance in a room with good acoustics, and reproduce it at home. It is widely agreed that this is very difficult and that even the best-regarded recording and playback systems rarely if ever achieve it.
There is wide variation in the technologies used to record music, with corresponding differences in quality and realism. Audiophile publications typically contain discussion and reviews of musical recordings, with a focus on audio quality. Examples of recordings that are considered to have very high quality and realism are the classical works on the Mercury Living Presence label, and the albums of the Cowboy Junkies. There are companies which focus on producing recordings with audiophile values.
Signal cables (analog audio, speaker, digital audio etc.) are used to link these components. There are also a variety of accessories, including equipment racks, power conditioners, devices to reduce or control vibration, record cleaners, anti-static devices, phonograph needle cleaners, reverberation reducing devices such as speaker pads and stands, sound absorbent foam, and soundproofing.
The interaction between the loudspeakers and the room plays an important part in sound quality. Sound vibrations are reflected from walls, floor and ceiling, and are affected by the contents of the room. Room dimensions can create standing waves at particular (usually low) frequencies. There are devices and materials for room treatment that affect sound quality. Soft materials, such as draperies and carpets, can absorb higher frequencies, whereas hard walls and floors can cause excess reverberation.
Each step in capturing, storing, and playing back music might potentially damage the signal, as circuitry is prone to electromagnetic interference and electronic noise. Thus many audiophiles agree that the fewer and simpler the stages, the better. Many audiophile components, for example, lack tone control circuits.
Audiophiles play music from a wide variety of sources including phonograph records, compact discs (CDs), and digital audio file formats that are uncompressed as well as ones that are compressed using lossless data compression such as FLAC, Windows Media Audio 9 Lossless and Apple Lossless (ALAC). Since the early 1990s, CDs have become the most common source of high-quality music. Nevertheless, turntables, tonearms, and magnetic cartridges are still used, despite the difficulties of keeping records free from dust and the delicate set-up associated with turntables.
The 44.1 kHz sampling rate of the CD format, in theory, restricts CD information losses to above the theoretical upper-frequency limit of human hearing – 20 kHz, see Nyquist limit. Despite this, newer formats such as DVD-Audio and Super Audio Compact Disc (SACD), have sampling rates of 88.2 kHz or 96 kHz or even higher.
CD audio signals are encoded in 16-bit values. Some higher-definition consumer formats such as HDCD-encoded CDs contain 20-bit and even 24-bit audio streams. With more bits more dynamic range is possible; 20 bit dynamic range is theoretically 120 dB—the limit of most consumer electronic playback equipment.
In MP3 encoding, as well as with other lossy compression formats, musical information is lost as a function of the degree of compression
A preamplifier selects among several audio inputs, amplifies source-level signals (such as those from a turntable), and allows the listener to adjust the sound with volume and tone controls. A power amplifier takes the "line-level" audio signal from the preamplifier and drives the loudspeakers. An integrated amplifier combines the functions of power amplification with input switching and volume and tone control. Both pre/power combinations and integrated amplifiers are widely used by audiophiles.
Dedicated amplifiers are also commonly used by audiophiles to drive headphones, especially those with high impedance and/or low sensitivity, or electrostatic headphones.
The cabinet of the loudspeaker is known as the enclosure. There are a wide variety of loudspeaker enclosure designs, including sealed (acoustic suspension), ported (bass-reflex), transmission line, infinite baffle, horn loaded, and aperiodic. The enclosure plays a major role in the sound of the loudspeaker.
The drivers are the actual sound-producing elements, referred to as tweeters, midranges, and woofers. Driver designs include dynamic, electrostatic, plasma, ribbon, planar, ionic, and servo-actuated. Drivers are made from various materials, including paper pulp, polypropylene, kevlar, aluminum, magnesium, beryllium, and vapor-deposited diamond.
The direction and intensity of the output of a loudspeaker, called dispersion or polar response, has a large effect on its sound. Various methods are employed to control the dispersion. These methods include monopolar, bipolar, dipolar, 360 degree, horn, waveguide, and line source. These terms refer to the configuration and arrangement of the various drivers in the enclosure.
The positioning of loudspeakers in the room and of the optimum listening position (referred to as the "sweet spot") is of great importance in producing optimum sound. Loudspeaker output is influenced by interaction with room boundaries, particularly bass response, and high frequency transducers are directional, or "beaming."
Audiophiles use a wide variety of accessories and fine-tuning techniques, sometimes referred to as "tweaks," to improve the sound of their systems. These include filters to clean the electricity, equipment racks to isolate components from floor vibrations, specialty power and audio cables, loudspeaker stands (and footers to isolate speakers from stands), and room treatments.
There are several types of room treatment. Sound-absorbing materials may be placed strategically within a listening room to reduce the amplitude of early reflections, and to deal with resonance modes. Other treatments are designed to produce diffusion, reflection of sound in a scattered fashion. Room treatments can be expensive and difficult to optimize.
Headphones are regularly used by audiophiles. These products can be remarkably expensive, some over $10,000, but in general are much cheaper than comparable speaker systems. They have the advantage of not requiring room treatment and being usable without requiring others to listen at the same time. Newer canalphones can be driven by the less powerful outputs found on portable music players.
It is notable that at each stage of the audio pipeline, a variety of different technologies, with drastically different engineering characteristics, are deployed in pursuit of the same goal: Accurate sound reproduction.
For music storage, digital formats offer an absence of clicks, pops, wow, flutter, acoustic feedback, and rumble, compared to vinyl records. Digital is also claimed to have a higher signal-to-noise ratio, a wider dynamic range, less total harmonic distortion, and a flatter and more extended frequency response.  Despite this, vinyl records remain popular and many argue that the technology can produce high quality sound (see Analog sound vs. digital sound).
In the amplification stage, both solid state and vacuum-tube electronics remain popular, even though vacuum-tube amplifiers have been alleged to have higher total harmonic distortion, require rebiasing, be less reliable, generate more heat, be less powerful, and cost more. There is also continuing debate about the proper use of negative feedback in amplifier design. 
As noted above, the design variety in loudspeakers is remarkable.
There is substantial controversy on the subject of audiophile components; many have asserted that the occasionally high cost produces no measurable improvement in audio reproduction. For example, skeptic James Randi, through his foundation, has offered a prize of $1 million to anyone who can demonstrate that $7,250 audio cables "are any better than ordinary audio cables". In 2008, audio reviewer Michael Fremer attempted to claim the prize, and said that Randi declined the challenge. Randi said that the cable manufacturer Pear was the one who withdrew.
Criticisms usually focus on claims around so-called "tweaks" and accessories beyond the core source, amplification, and speaker products. Examples of these accessories include speaker cables, component interconnects, stones, cones, CD markers, and power cables or conditioners. 
There is disagreement on how equipment testing should be conducted and as to its utility. Audiophile publications frequently describe differences in quality which are not detected by standard audio system measurements and double blind testing, claiming that music contains elements which cannot be measured by electronic instruments, but without providing an explanation for those claims.