Re-Purposed Karaoke Amp

If you like experimenting with electronics, you might want to start going to thrift stores with an eye on things you can take apart and re-purpose. A while back, I picked up a Karaoke machine for $2.99 and transformed it into the amplifier (plus echo effect) for a DIY modular synth I made. As it turns out, I can plug my guitar into this odd little device and have a lot of fun, too.


If It Makes Sound and Runs on Batteries, There’s an Amp Inside

In this case, I started by taking the device apart to see what was inside. Since I couldn’t find (or yet understand) the datasheet for the echo processor chip inside, I decided to just take the parts as-is.

The Singing Machine, Model SML-383-P, Portable CD+G Karaoke Player, purchased secondhand for $2.99
The Singing Machine, Model SML-383-P, Portable CD+G Karaoke Player, purchased secondhand for $2.99
A view of the inside of the device.
A view of the inside of the device.
The initial salvage: main circuit board, speakers, and 1/4" input jacks.
The initial salvage: main circuit board, speakers, and 1/4″ input jacks.
I had to figure out where the power went in and how the audio came out.
I had to figure out where the power went in and how the audio came out.

I also had to figure out which features I wanted to use and control. Then, I needed to design an "interface" that matched my design vision.
I also had to figure out which features I wanted to use and control. Then, I needed to design an “interface” that matched my design vision.
After testing a variety of pulled speakers (from computers and TVs, etc.), I decided on this combo. I added a 3.5mm audio IN jack to match the OUT from my amp-in-progress.
After testing a variety of pulled speakers (from computers and TVs, etc.), I decided on this combo. I added a 3.5mm audio IN jack to match the OUT from my amp-in-progress.

I kept/used some features and buried others. I attached a wall wart as the power supply and the rest is history.
I kept/used some features and buried others. I attached a wall wart as the power supply and the rest is history.

Now, the way I’ve done this is a little dangerous. Or, as I sometimes say, “potentially zappy.” No, it’s actually super dangerous to have all of this exposed electronic business. So please consider this a lab prototype (versus a recipe for injury-free success). But hopefully this gives you an idea about how you can learn about and recycle some cheap item for audio- and music-making projects.


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