Today I wanted to show you guys something new I’ve been playing with on the breadboard. Essentially what I have here is a twist on a classic project. I’ve taken an Atari Punk Console (Stepped Tone Generator) and added two 555 timer based oscillators as LFOs to add more depth and interest to the sounds produced.
This modification is built on one simple characteristic of the 555 timer (and by extension the 556 which consists of two 555 timers). This is the control voltage pin which allows you to use an external voltage source to modify the chips performance. On a traditional 555 timer the control voltage input is located on pin 5 while on the 556 you would use pins 3 and 11 as I have here. By connecting the outputs of two 555 oscillators to these pins on the 556 we are able to use them to modify the frequency of the stepped tone generator.
You may notice in the video I play mostly with the left LFO knob. This is because in my experimentation I was able to illicit much more noticeable effects from the first oscillator connected to pin 3 of the Atari Punk Console. The second oscillator (connected to pin 11) only seemed to have a pronounced effect at fairly high frequencies. For this reason you may want to try switching the 500K pot on the second oscillator for something smaller like a 100K or 50K. Another option to increase the frequency range is to change out the 3.3uf capacitor for a 0.1uf cap.
Another thing you can do with this circuit to gain further control is to add a potentiometer to control the modulation of the LFOs on the Atari Punk Console. To accomplish this you can add a potentiometer in place of the 10K resistor at the output of the LFO oscillators. A 50K pot would likely work best for this.
Finally if you enjoyed this project I did build an Atari Punk Console back in the early days of this site with jacks for control voltage inputs. Feel free to have a look if you are interested.