CMoy

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title: "CMoy" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["audio-amplifiers"] topic_path: "general/audio-amplifiers" source: "https://en.wikipedia.org/wiki/CMoy" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/77/Cmoy_there.jpg" caption="Common CMoy in [[Altoids]] tin"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/9/9f/Cmoy_headphone_amplifier_in_parts.jpg" caption="CMoy in parts"] ::

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 (op-amps) such as Burr-Brown'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.)

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 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.

References

References

  1. Hertsens, Tyll. (March 15, 2016). "A Memorial to the Grandfather of Headphone Enthusiasm".
  2. "A Pocket Headphone Amplifier".
  3. Northwest Audio & Video Guy. (August 10, 2011). "Op Amps: Myths & Facts".
  4. Großklaß, Stephan. (2014-07-15). "A Classic Hi-Fi Misconception".
  5. Young, Warren. (October 31, 2016). "Notes on Audio Op-Amps".
  6. Rutter, Daniel. (20 March 2004). "Review: Chu Moy headphone amplifier".

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audio-amplifiers