My first CMoy build.

By isendev.

 Posted on 2012/03/27 01:52.

 Tagged as: audio, diy.

Now I'm working on a second revision of my custom CMoy build, but before posting more details about it, I want to recap some information of my original build from April 2010.

But first of all... What's a CMoy?

Taken from the Wikipedia:

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 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.
I was searching for a simple electronic schematic to test the tone-transfer method for etching printed circuit boards at home, and this small headphone amplifier was a good point to start. I found tons of information about it at and community forums but, without a doubt, the best resource was Tangensoft's website. There you can find the most complete guide to design and build your own CMoy.

And here is my original Eagle PCB layout. It's easy to see the main modification done to the basic CMoy design: I used a rail splitter IC instead of a resistor bridge to obtain the required voltage levels for running the op-amp.

This is the full component list used in my build:

- Power section:

  • 1 x Panasonic FC 470uF. 25V. electrolythic capacitor.
  • 1 x Texas Instruments TLE2426CP rail splitter.
  • 1 x DIP8 socket.
  • 1 x Generic 1uF. 63V. polyester capacitor (TLE noise reduction).
  • 3 x Molex KK 2 pin vertical male connectors (power input connector, power switch connector and LED connector).
- Op-Amp section:

  • 2 x Matsushita/Panasonic metallized polyester film capacitor ECQE Series - 0.1uF./100V. - Mylar PET dielectric (input capacitors).
  • 1 x Texas Instruments / Burr-Brown OPA2134PA Op-Amp.
  • 2 x Generic 0.1uF. 100V. polyester capacitor (Op-Amp decoupling capacitors).
  • 1 x DIP8 socket.
  • 2 x Molex KK 3 pin vertical male connectors (audio input / output connectors).
  • 2 x Generic 100K. 1/4W. resistor.
  • 2 x Generic 10K. 1/4W. resistor.
  • 2 x Generic 2.2K. 1/4W. resistor.
- Other components:

  • 1 x M223-RS 6.5mm. female switched stereo connector - chassis mount (audio output jack).
  • 1 x Generic 3.5mm. female stereo connector - chassis mount (audio input jack).
  • 1 x Vishay P9A Series 100mW. 10K. logarithmic dual potentiometer - chassis mount (audio input attenuation).
  • 1 x Generic 5mm. red LED.
  • 1 x Generic 5mm. LED holder - chassis mount.
  • 1 x Generic 100K. 1/4W. resistor (LED resistor).
  • 1 x Generic switch - chassis mount.
  • 1 x Generic power Socket - chassis mount.
  • 3 x Molex KK 2 pin female connectors (power input jack, power switch and LED holder).
  • 2 x Molex KK 3 pin female connectors (audio input / output jacks).
  • 1 x Generic 12V. 1.25A. wall wart (power supply).
And here are some photos of the styrofoam layout test and the populated PCB:

After some testing, a few changes were done to the board:

  • 2.2K Resistors were replaced by 1.2K. resistors to modify CMoy┬┤s gain ((10/1.2) + 1 = 9.3dB.) and improve the output volume using the iPod stereo jack.
  • Panasonic ECQE 0.1uF./100V. input capacitors were replaced by Vishay MKT 0.47uF./63V. capacitors to improve bass handling.
  • 10K. 1/4W. LED resistor was replaced by 4.7K. 1/4W. resistor to make the power LED brighter.