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Common CMoy in Altoids tin
CMoy in parts

A CMoy is a pocket headphone amplifier originally designed by Chu Moy on the Headphone Resource Site and public discussion Forums.

The headphone amplifier is designed around single or dual-channel op-amps such as Burr-Brown's OPA2134 or OPA2132PA, however, a wide variety of op-amps have been successfully implemented. The op-amps directly drive headphones, making the over all quality of the sound very dependent on the suitability of the chosen circuit.[1] 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. The CMoy headphone amplifier can be fit into Altoids tins and can often be found for sale on eBay by searching for "CMoy".[2]


A typical CMoy consists of two identical AC coupled, non-inverting operational amplifier circuits each with a 100kΩ 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.


  1. ^ Op Amps: Myths & Facts- "Some op amps have been judged in the wrong applications. The Cmoy headphone amp is just such an example..."
  2. ^ "Review: Chu Moy headphone amplifier". Retrieved 2009-06-03. 

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