The quick and dirty amplifier
Оригинал на русском: http://shura.luberetsky.ru/2008/12/13/delaem-usilitel-dlya-kolonok/
The test of an anti-crisis loudspeaker proved that it does not work fine with a MP3 player as a source. So we will add a simle amplifier, like the one in “PC multimedia speakers”.
I have bought a Samsung KA2026 chip, as it is one of the simplest and cheapest chips for a small amplifier.
KA2206 as is
This chip costs about 0.75$ (18 rubles) in Moscow. There are many pin-to-pin compatible chips by different vendors, the most popular are: LA4180, LA4182, LA4183, LA4550, LA4555, LA4558, TEA2025. All this chips contain a two-channel audio amplifier, that also allows usage in a “bridge” circuit – with combined power of two channels. The parameters are good for a “multimedia system” – with 9-12 V supply the amplifier has a power of 2 W on a 8 Ohm load with 10% non-linear distortion. By the way, the “300 W” stickers on Chinese boomboxes and active loudspeakers are all lies. Most of them are built around a similar chip, that can’t deliver such power.
The datasheet stereo amplifier circuit is as follows:
The circuit
You will need just some electrolytic capacitors, which I get by desoldering old PC motherboards. You don’t even need to make a PCB – all can be done by point-to point wiring on a piece of copper-clad board.
Point to point - that is cool
I used the wires from a twisted pair cable for the audio connector and power wires – it’s a real pleasure to tin and solder them.
The amplifier is finished
After finishing the amplifier, we connect the speakers – the left and the right channel. As the power source, you can use a PC power supply – it has a 12 V channel, or a 9 V battery. The sound quality is similar to the chinese “active speakers” with “300 W PMPO” sticker.
In the second part of the video you can hear the “Corrosion of metal”, yeah!
