Headphone amplifier 2193225 217094794 2008-06-04T16:06:54Z W.F.Galway 1218689 Changed "embedded to" to read "embedded in" [[Image:Hybrid-headphone-amplifier-Vincent-KHV111.jpg|thumb|250px|A hybrid headphone amplifier.]] A '''headphone amplifier''' is a kind of [[audio amplifier]] designed particularly to drive [[headphones]] instead of [[loudspeakers]]. Most commonly they are found embedded in electronic devices such as [[integrated amplifier]]s, portable music players and televisions, but standalone units are not uncommon. ==Consumer headphone amplifiers== '''Headphone amplifiers''' as referred to here are commercially available separate devices, sold to a niche [[audiophile]] market. These devices allow for higher possible volumes and greater audio clarity than the smaller, cheaper amplifiers that are used in most audio players. (In the case of the extremely-high-end [[electrostatic headphones]], such as the [[Stax Earspeakers|Stax]] SR-007, a specialized electrostatic headphone amplifier or transformer step-up box and power amplifier is required to use the headphones, as only a dedicated electrostatic headphone amplifier or transformer can provide the voltage levels necessary to drive the headphones.) Most headphone amplifiers provide [[power (physics)|power]] between 10 mW and 2 W depending on the specific [[headphone]] being used and the design of the amplifier. === How they work === Effectively, a headphone amplifier is a small [[power amplifier]] which can be connected to a standard headphone jack or (usually) the line output of an audio source. The headphone amplifier improves the sound quality by increasing the amount of power available to move the transducer, increasing the control that the source has over just where the transducer is in space. This is often expressed as [[damping factor]]. For example, a 32 Ω headphone (such as the [[Grado]] line) driven by a popular DIY headphone amp with a <1 Ω output impedance (the [http://headwize.com/projects/showfile.php?file=gilmore3_prj.htm Gilmore Dynamic]) would have a damping factor of >32, whereas the same headphone driven with an iPod (5 Ω output impedance) would have a damping factor of just 6.4. Of course, damping factor is not the only specification relevant to choosing a headphone amplifier — harmonic distortion, frequency response, IMD, and a myriad of other measurements are also significant. === The DIY approach === For those who are more electronically inclined, the low-power and fairly simple nature of the headphone amplifier has made it a very popular DIY project. There are a great many designs for headphone amplifiers posted on the Internet varying considerably in complexity and cost. The cardinal example is the simple opamp-based [[Cmoy]] design, arguably one of the most popular headphone amplifier designs available. The simplicity of the [[Cmoy]] makes it an easy build, while it can be made small enough to fit inside a tin of breath mints (including batteries). === Crossfeed and other audio processing === Crossfeeding blends the left and right stereo channels slightly, reducing the extreme channel separation characteristic of headphone listening that is known to cause headaches in a small fraction of listeners (and compensating for extreme separation in older stereo releases). While some swear by crossfeed, many prefer amplifiers without it. The introduction of DSP technology led a number of manufacturers to introduce amplifiers with 'headphone virtualization' features. In principle, the DSP chips allow the two-speaker headphone to simulate a full Dolby 5.1 (or more) surround system. This feature has not caught on in high-end audio circles. ==Professional audio (pro-audio) headphone amplifiers== [[Image:Heaphone_amp_pro_front.jpg|thumb|Distribution headphone amp - front]] [[Image:Heaphone_amp_pro_back.jpg|thumb|Distribution headphone amp - back]] In the pro-audio terminology a headphone amplifier is a device that allows multiple headsets to be connected to one or more audio sources in the same time in order to monitor progress of a recording session or a live performance. '''Headphone amps with sub-mixing capabilities''' allow the listener to adjust, mix and monitor audio signals coming from multiple sources in the same time. This kind of headphone amp is often utilized during recording sessions to sub-mix playback of individual stem-mixes or instruments coming from a mixing board or a playback device. In many cases the listeners have their own sets of controls allowing them to adjust various aspects of the mix and individual and global parameters such as, channel level, global loudness, bass and treble. '''Distribution headphone amplifiers''' are specialized headphone amps allowing a single signal to be fed to multiple headsets or multiple groups of multiple headsets in the same time. Many distribution headphone amps, like the one shown here, can be cascaded by connecting the audio input of one of the amps to the cascading output, marked "THRU", of another amp. There are also available various other combinations of pro-audio headphone amps with sub-mixing and distribution capabilities in the same time. ==References== {{unreferenced|date=June 2007}} [[Category:Audio amplifiers]]