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APC Sound Box

This little guy was my first excursion into audio circuits. It’s a Stepped Tone Generator that puts out some great lo-fi-Atari-esque square waves with a little bit of practice.


  • 2 knobs for controlling the pulse frequency and width
  • volume knob
  • on/off toggle
  • tact switch to pulse the sounds on and off quickly
  • 1/4” audio jack for stero or headphone use
  • 9-volt powered
  • spiffy blue LED


  • have the tact switch do double duty as a kill switch when the toggle switch is in the on position
  • built in speaker
  • dc power input
  • blinking LED representation of wave pattern