Saturday, August 29, 2015

DIY ka2209 chip phone amplifier

ka2209 amplifier on a perfboard
     I decided my devices speaker wasn't loud enough, but I didn't want to go buy a speaker that can be found online or at Walmart. That would be boring, so I headed over to the thrift shop and picked up a couple of old radios for a few bucks. All the parts needed were found in these two radios. In the first radio I found a ka2209 amplifier chip and built the headphone amplifier off of it.

Here's the parts list:
  • 1 x ka2209 chip
  • 3 x 100uf capacitor
  • 2 x 10k ohm resistor (can be a variable resistor) 
  • 2 x 470uf capacitor
  • 2 x 4.7 ohm resistor
  • 2 x .1uf capacitor (marked with a 104)
  • 1 x on/off switch
  • headphones 
  • hookup wire
My crappy soldering skills
      Everything except the headphones came from the radios, but I had to desolder it all. It should be pretty easy to desolder the components, it was finding them that was hard. I did need a few tools though:

  • soldering iron
  • solder
  • wire cutters
  • wire strippers
  • helping hands
Set it up on a breadboard first before soldering it because it is easier to test and fix when it isn't soldered. First cut the earbuds off the headphones, and there should be 2 wires for each earbud. For each earbud one will be input and one will be ground, as far as I could tell it didn't matter which wire was ground. For the 10k ohm resistor coming off each input it can be a variable resistor, but I just used a regular resistor. Put a switch between Vcc and pin 2 for an on/off switch,and have the positive wire of the speaker going to each output and the ground wire going to ground (obviously). Other than that you can follow the schematic and for my power I just used a 9v battery.
This is a pretty easy circuit to understand once you've put it together, and after you can put it into an enclosure, plug it into your phone and jam out with your own homemade amplifier.

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