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Project Notes

#521 CK9561 Audio Effects Chip

Figuring out how to use the CK9561 music chip with 4 sound effects - alarm/siren/weapon sounds that sound strangely familiar if you have ever walked through a toy department at Christmas!


Here’s a quick demo..



The CK9561 is the latest in a series of music effects chips I’ve been testing. The CK9561 is sometimes labelled KD9561 of XK9561 - I presume these are just different manufacturer’s names for boards based on the same chip.

The module,with pins attached for testing on a breadboard:


Usage and Schematic

The chip requires just a few external components to operate:

  • the resistor (100kΩ-390kΩ) controls the speed of the effect - higher resistance slows the effect down
  • a small signal NPN transistor (I used a 2N3904) for controlling the speaker
  • and switches - not shown in the schematic below:
    • the effect is “always on”, so a switch in the power line can be used for on/off control
    • switching connections “1” and “2” between unconnected/pulled-low/pulled-high select from the range of sound effects according to the following table
Pad 1 Pad 2 Effect
n/c n/c alarm
high n/c or low fire alarm
low n/c ambulance
any high machine gun


Testing on a breadboard:


I also added the chip to one of my “audio effects” copper-clad test boards. I’ve added a few components:

  • resistor is 100kΩ fixed + 200kΩ variable resistor
  • mini push-button switch on the power connection (effect on/off)
  • a 3-position switch for toggling pad 1 between unconnected/pulled-low/pulled-high
  • mini push-button switch on pad 2
  • external 8Ω speaker


Credits and References

Project Source on GitHub Project Gallery Return to the LEAP Catalog

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

LEAP is just my personal collection of projects. Two main themes have emerged in recent years, sometimes combined:

  • electronics - 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
  • scale modelling - I caught the bug after deciding to build a Harrier during covid to demonstrate an electronic jet engine simulation. Let the fun begin..
To be honest, I haven't quite figured out if these two interests belong in the same GitHub repo or not. But for now - they are all here!

Projects are often inspired by things found wild on the net, or ideas from the many great electronics and scale modelling podcasts and YouTube channels. Feel free to borrow liberally, and if you spot any issues do let me know (or send a PR!). See the individual projects for credits where due.