Thursday, November 18, 2010

How to get a really cheap stereo amplifier

I've been looking for a really cheap amplifier for my workshop,
so I can hear music over my MP3-player whilst building stuff.
I got my hands on some old computers and tried to use only them as part source,
and here it is: The zero-cost amplifier!

It is build of a CD-drive with headphone output.
The first thing I had to do was searching the amplifier circuit on the front panel board.

The front panel board without the end position switch
It was very clear to me that the amplifier is where the potentiometer sits.
It's on the left half.

The next thing was finding the chips datasheet.
The amplifier circuit with the MS6038
The MS6038 datasheet says its a Class AB Headphone amplifier.
It looks like an opamp and it's also that easy to use.
Now I cut it from the rest of the front panel board and desoldered the 3.5 mm terminal.
After this I pulled wires from the circuit to this terminal and to two external speakers I got from old PCs.
I used a mobile phone charger with 230V input and 5V output as voltage source,
but you can also use any other kind of power supply from 2.7 to 5.5 volts.
Finally, I built a small free air circuit to make use of the busy LED.
It contains of a capacitor with 3.3µF and some resistors to make it glim when the amp is in "standby" and light when music plays. 
I got all this parts out of my toolbox, so they were "free" to.

I found out that this kind of circuit is very likely to be in all kind of cd players.
Here is a photo of an portable CD-player.
Alternative circuit out of a portable CD-player  


If you once need such an amplifier, you know how you get one for zero cost! 
If I have updates, I'll post them in this blog, so keep looking.

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