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Cmoy Audio Amplifier Circuit for Headphones with Printed Circuit Board. Cmoy is a small headphone amplifier circuit, the original design was developed by Chu Moy from the website headwize.com, which specialized in headphone-related topics, as well as a discussion forum on the subject.
The presented amplifier is designed around a dual op amp such as Burr-Brown’s OPA2134 or OPA2132PA, but other operational amplifiers can be used. The amplifier design is simple and can be assembled on a small piece of printed circuit board, the cost of the components is cheap compared to a commercial headphone amplifier. It can operate for several hours with a 9 Volt battery.
A typical CMoy consists of two identical (stereo) non-inverting operational amplifier circuits with an input impedance of 100KΩ. The power supply for the op-amp needs to be symmetrical and can be achieved using either one (±4.5V) or two batteries (±9V), divided into two sources to create the virtual ground. Many tutorials found on the internet about CMoy present many options for creating the virtual ground. One of these options is the one presented in this circuit. S1 should be connected to an on-off switch.
As there are various categories of components that can be used in this circuit, I am providing the files for Eagle 6, so that when the reader needs it, they can make the necessary changes.
If only one battery is used, the voltage will be +4.5V and -4.5V, and if two batteries are used, the voltage will be +9V and -9V, this will be the symmetrical power supply with virtual ground. The LED should be 3 mm and any color. The capacitors at the input can have values ranging from 100nF to 1µF, the output resistors can be removed in numerous instances and replaced with jumpers.
The application is for a non-inverting operational amplifier and the gain is defined by the formula G = R6/R5 +1, and with the selected components, it has a gain of 11. You can modify the gain to better suit your needs.
To assemble the circuit, use a box that can accommodate the board and the batteries. The LED, potentiometer, power switch, and P2 connectors (In and Out) should be mounted on the side of the box.
Several dual op-amps can be used in this circuit, such as OPA2132, OPA2134, OPA2227, NE5532, AD744, AD823, AD825, AD843, OP275, OPA2107, OPA604, LM6171, LF355, among others.
Schematic CMoy Headphone amplifier circuit
Printed circuit board PCB suggestion
Bom CMoy Headphone amplifier circuit
| Part | Value/Description. |
| Resistors 1/4 Watt 5%, the most demanding may prefer 1% tolerance. |
|
| R+, R- | 4.7K — Yellow, Violet, Red, Gold |
| R1, R5 | 1K — Brown, Black, Red, Gold |
| R2, R6, RLED | 10K — Brown, Black, Orange, Gold |
| R3, R7 | 100K — Brown, Black, Yellow, Gold |
| R4, R8* | 68 — Blue, Grey, Orange, Gold |
| Capacitors | |
| C+, C- | 220µF/25V — Polarized Electrolytic Capacitor |
| C1, C2 | 100nF a 1uF— Metallized Polyester Capacitor |
| Semiconductors | |
| IC1 | OPA2134PA or equivalent — Dual operational amplifier |
| LED | Led 3 mm |
| Miscellaneous | |
| P1 | 10k — Dual potentiometer |
| IN (J1) | P2 audio input connector. |
| OUT (J2) | p2 connector Audio output. |
| B1, B2 | 9 Volt batteries, if they are rechargeable, nature will thank you. |
| S1 | Switch to turn on the circuit. |
| Solder, Wires, Cable, PCB, Box, Potentiometer Knob, etc. | |
*Optional — You can use a jumper instead of these resistors.
If you want to modify the circuit, read this article Cmoy Tutorial Tweaks
Visit the page in memory of author Chu Moy
Download files in PDF, PNG, Postscript, and Gerber to assemble the circuit.
Download PDF Mirror
Download Datasheet in PDF OPA2134
