It’s true. Here’s my 555 Guituner circuit: go to 50 – 555 circuits web page on and search for “guitar tuner” and you will find my circuit. Actually they’ve modified it slightly. You can review my Guituner article here. My 555 Guituner circuit looked like this:

Their circuit looks like this:

To make things a little clearer, I’ve simplified the diagram to this:

The only difference is they left out the power switch, the 100K resistor, and the 68K resistor. They also used my picture—but it’s a little different too. Here’s the picture I shot:

Here’s the picture from their page:

They Photoshoped out the 100K resistor, and the 68K resistor, but left everything else as is.