You’re not satisfied with your desktop headphone amplifier? Then, just stop the complaint and DIY Class A MOSFET headphone amplifier!

First thing first, you will need to use a regulated power supply, which it can be purchased from the Radio Shack (10-20VDC and 750mA should be Ok for it). The regulated power supply is responsible for regulate the power supply will ripple the rejection and eliminate any noise in the power supply. In addition, An IRF610 MOSFET and a LM317 regulator will be used in the Class A Mosfet headphone amplifier.

Here is the step-by-step guide for the project, let’s get started…

Firstly, you have to prepare an external CD-ROM (It would be better if it has a power switch, power adapter receptacle, RCA inputs on the back and headphone jack on the front).

The amplifier is constructed on 2″ square protoboards from Radio Shack. You will need to assemble these components onto the board:

  • Plain metal film resistors
  • 1uF mylar input cap
  • 0.47uF polypropylene bypass cap (for the output)
  • 0.1uF decoupling polypropylene capacitor

By the way, you have to isolate the MOSFET and regulator from the heat sinks.

After it, test your headphone amplifier by using a regulated power supply at very low voltage. For the bias purpose, you have to varying the 100k variable resistor until the output side of the MOSFET is nearly or exactly half the supply voltage. Be sure to check and reset the bias several times in the first few hours, as it will drift while everything settles in. Remember that the amp only worked well in between the 10 and 20VDC range! [link]

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