A CMoy is a pocket
headphone amplifier
A headphone amplifier is a low-powered audio amplifier designed particularly to drive headphones worn on or in the ears, instead of loudspeakers in speaker enclosures. Most commonly, headphone amplifiers are found embedded in electronic devices ...
originally designed by Pow Chu Moy.
The headphone amplifier is designed around single or dual-channel
operational amplifiers
An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to c ...
(op-amps) such as
Burr-Brown
The Burr-Brown Corporation was an American technology company in Tucson, Arizona, which designed, manufactured, and marketed a broad line of proprietary, standard, high-performance, analog and mixed-signal integrated circuits (ICs) used in elec ...
's OPA2134 or OPA2132PA, however, a wide variety of op-amps have been successfully implemented. As the op-amp directly drives headphones, some care should be given when choosing an op-amp. Some op-amps are not suitable for such low impedance loads and will result in poor performance. (See
Op-amp swapping
DIY Audio means "do it yourself" audio. Rather than buying a piece of possibly expensive audio equipment, such as a high-end audio amplifier or speaker, the person practicing DIY Audio will make it him/herself. Alternatively, a DIYer may take an ...
.)
The amplifier's design is quite simple. It consists of only a few components, can be assembled on a small section of
protoboard, has a lower parts cost than other headphone amplifiers, and can run for many hours on a single 9 volt battery.
Circuit
A typical CMoy consists of two identical
AC coupled,
non-inverting operational amplifier circuits each with a 100k
Ω input impedance.
Power is supplied to the opamps using a dual power supply, which effectively divides the input voltage source in half to create a
virtual ground. Many virtual ground circuit options are presented in the various CMoy tutorials found online.
References
{{reflist
External links
How to Build the CMoy Pocket Amplifier
Audio amplifiers