Sound Card Oscilloscope

Earlier this year I came across an old Make post about building your own oscilloscope. I messed around with it a little bit at the time, but I didn’t have the necessary potentiometers, so I set it aside. Then the topic came up again when the tutorials accompanying HackerBox #0018 made use a 3.5mm audio breakout module and some PC oscope software. So in my next Digi-Key order, I got the pots I needed and I picked up some cheap test leads on Amazon. It’s several months later, but I got around to building my own sound card oscilloscope.

First, a couple of notes…

You’ll definitely want to read through the Make post to get familiar with the project. As mentioned in their guide, there really isn’t any good oscope software for the Mac like there is for the PC. With Audacity, which is what I used, at least you can see the signals in wave form.

I spliced an old audio cable. There are several different styles of 3.5mm connectors, but if you’re doing 2 channels, you’ll want to make sure you your cable has the tip, ring, and sleeve.

3.5mm-Male-Connections.png
Source: blog.audio-technica.com

A lot of MacBooks only do mono microphone input. Several Mac bummers in this build! It wasn’t easy, but I found a USB adapter on Amazon that does stereo mic input (most of them only do mono). It’s pricey at almost $30 for something I’m not even sure I’ll use after this build.

Enough of that, on to the build…

I added the LEDs to my build as a visual reference a signal was coming through, but they can be left out, just like in the Make build. If you’re interested in the Fritzing I showed in the video, head over to sound-card-oscilloscope on GitHub. Whenever I’m soldering up a final project I prefer to have the Fritzing for reference instead of looking at my prototype, which typically has a lot of extra wires hanging around. Having a nice clean diagram helps me from making mistakes.

I also found another guide on a site called Home DIY Electronics, which I didn’t end up following.

If you have any questions or build your own version of this, let me know in the comments.

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