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Project Notes

#551 SN76477 Prop Plane

Testing the SN76477 propeller plane sound effect configuration


Here’s a quick demo..



The Texas Instruments SN76477 is a complex sound generator chip from the late 1970’s and still reasonably easy to find as refurb or new-old stock. It was covered in some detail in Elektor Magazine 1981-03, p3-22 - “Multiple Sound Effects Generator”.

It was apparently widely used in arcade games and synthesizers and does its magic by integrating a number of subsystems:

  • low frequency oscillator
  • noice generator
  • voltage controlled oscillator
  • envelope generator and modulator
  • mixer
  • output preamp

Features are variously enabled/controlled via pins with either:

  • resistor
  • capacitor
  • logic level
  • analog voltage level

The data sheet describes the configuration for a number of specific sound effects, including:

  • steam train/propeller plan
  • race car motor/crash
  • siren/space war/phasor gun
  • gunshot/explosion
  • bird chirp
  • musical organ
  • steam train with whistle

As a first simple demonstration, I’ve put the “propellor plane” on a breadboard below.

Breadboard Adapter

The SN76477 comes in unusual “N” and “NF” DIP sizes. I think these correspond to JEDEC MS-011 and JEDEC MS-010.

The pin and row spacing is not compatible with a breadboard so I whipped up a simple adapter with some protoboard. I didn’t go full dead bug, as I wanted to keep the pin assignments in conventional arrangement.



This is the “propeller plane” configuration described in the data sheet.

The “speed” of the engine is controlled with a variable resistor input to the low frequency oscillator on pin 20.




Credits and References

About LEAP#551 Audio
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This page is a web-friendly rendering of my project notes shared in the LEAP GitHub repository.

LEAP is my personal collection of electronics projects, usually involving an Arduino or other microprocessor in one way or another. Some are full-blown projects, while many are trivial breadboard experiments, intended to learn and explore something interesting (IMHO!).

The projects are usually inspired by things found wild on the net, or ideas from the sources such as:

Feel free to borrow liberally, and if you spot any issues do let me know. See the individual projects for credits where due. There are even now a few projects contributed by others - send your own over in a pull request if you would also like to add to this collection.