Since music is comprised primarily of sine waves this is not a problem as the sine wave response was fine across the audible range. Fortunately I had a dead Plextor external CD-ROM kicking around that would make for the perfect enclosure and blend in well on my desk. The smaller heat sinks are about 1. The heat sinks were salvaged from various dead components.
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You can use carbon resistors, but I suggest you use metal film, particularly for the CCS due to their superior temperature stability over carbon.
For a simple single-ended amplifier design, the sound is pretty good to my ears. The amplifier concept is simple and follows a typical single-ended class-A circuit utilizing an active constant current source CCS in place of a passive resistor.
The open hole you see on the back is where the USB header resided, but I had previously salvaged irff610 for another project. That was not the case with an unregulated supply. Using a simple application of a common LM voltage regulator it is configured as a very accurate CCS set to draw mA.
IRF MOSFET Datasheet pdf - Equivalent. Cross Reference Search
Plain but matched metal film resistors, 1uF mylar input cap and 0. Created 30 June The top trace green is the input waveform and the bottom trace yellow is the output.
In this instance I had plenty of voltage gain, but the sound card just runs out of gas with good headphones. Last update 17 February There are a couple of items to note. A FET follower circuit will be able to supply high current, but the voltage gain will be less than one.
I only used parts that I had on hand and irrf610 can see that I did not use any boutique parts. Suitable inexpensive regulated wall wart power supplies can be purchased from Radio Shack.
DIY IRF MOSFET Class-A Headphone Amplifier Project
Even better yet, it already had a power switch, power adapter receptacle and RCA inputs on the back as well as a headphone jack on the front. The heat sinks were salvaged from various dead components. For that reason, you will need to use a regulated power supply. This headphone amplifier will reside primarily on my desk at work, so it needs to fit into an office environment.
For the power supply I am using is a 20VDC power supply from an older laptop. Since music is comprised primarily of sine waves this is not a problem as the sine wave response was fine across the audible range. Tilting gradually decreases as the frequency increases and beyond about Hz the square wave response is excellent up to 20kHz which is the limit of my signal generator.
My signal generator is not great and that is reflected in the quality of the input waves. This amplifier will only be suitable in setups where the input signal does not require voltage amplification such as the output of a preamplifier, mp3 player or computer.
DIY Class-A Mosfet Headphone Amplifier
As you can see in the Hz trace, the square wave response is slightly tilted but stable. The final touches were to epoxy the CD-ROM faceplate to an aluminum plate and put the enclosure back together.
This amplifier will only be suitable in applications where the input signal does not require voltage amplification such as the output of an mp3 player or computer.
Also, a simple single-ended circuit like this will have no power supply ripple rejection and thus any noise in the power supply is going to go right through amplifier. Not thrilled with how a computer soundcard drove my 32 ohm Grado SR80 headphones, I decided to build myself a desktop headphone amplifier for the office.
The headphone amplifier was first tested smoke test using a regulated power supply at very low voltage.
The smaller heat sinks are about 1. I checked the sine wave response and irg610 expected, the results were good across 20Hz to 20kHz the limits of my function generator.
The amp drives my Irr610 SR80 headphones with ease, while my portable mp3 does not. Plain RCA jacks are used for input source. Next I got a chance to try out my new USB oscilloscope. This amplifier will delivery plenty of current to drive more demainding headphone types.