A CMoy is a pocket
headphone amplifier 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 ...
(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 ele ...
'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