Easy Audio Effects Circuit + Amp

Introduction: Easy Audio Effects Circuit + Amp

About: Co-owner of Reach and Teach - Books, Toys, and Gifts

Here's how to easily assemble a fantastic audio effects circuit that will give you the ability to add great quality audio with very flexible triggering (up to 11 settable triggers) for your next project that needs sound. It can all be done for under $50 in parts thanks to a couple of easy to use circuit boards from Adafruit. You will need a laptop to setup the audio board but the circuit will work standalone once it is setup.Total time to build (once you chase down parts) should be under 2 hours. NO PROGRAMMING NECESSARY (unless you want to). You will need to a do a tiny bit of soldering to attach a few connectors to the circuit boards.

This is what you will need:

Adafruit Audio FX Sound Board with 2MB flash

Adafruit Audio 3.7 W Stereo Class D Amplifier

A couple of 4 or 8 ohm speakers

Push buttons or other switches



Data USB cable and outlet plug

PC/Mac laptop to setup the audio board

Audacity audio editing software (FREE)

The instructions for the Adafruit Audio FX board are extremely good on the Adafruit website but I still felt that there would be a value in creating this primer for my Reach and Teach customers to get them started. Hopefully this is also of value to the larger Instructables community.

Step 1: Solder in Speaker Terminal Blocks and Header Kits

This is a straightforward step but provided here for completeness. For the Audio FX board, there are a couple of male to male headers that are provided to make it possible to mount the Audio FX into a circuit board or in this case, a breadboard. The headers provided may be longer than the 14 pins that you will need. If so, just use a pair of needle nose pliers to snap off the extra pins.

The audio amplifier board will also have a header that can be soldered into the board and a couple of terminal blocks for attaching wires from your speakers. There is also a two row header that should be mounted with the longer set of pins pointing up so that the included shorting jumper can be used to select the volume of the amplifier. I also soldered a couple of single pin posts into the corner holes to provide a little extra support for the amplifier board's attachment to the breadboard. (I made single pin posts by snapping off pieces of unused male to male header with my needle nose pliers.) Finally, I mounted 4 small wires into the speaker terminal headers for attaching to the breadboard.

Step 2: Wire Up the Circuit Board

Referring to the Class D Amplifier board as CDA and the Audio FX Board as AFX, make the following connections:

CDA/VDD to Breadboard pos(+) rail

CDA/GND to Breadboard neg(-) rail

CDA/L- to Breadboard neg(-) rail

CDA/R- to Breadboard neg(-) rail



AFX/Bus to Breadboard pos(+) rail

AFX/Gnd to Breadboard neg(-) rail

I also attached wires from the speaker terminal headers to the adjacent breadboard holes so that I could easily connect or disconnect the speakers without having to screw them into the terminal headers.

Attach external speakers to the speaker terminal headers. The photo shows connection for only the left speaker.

Attach push buttons or other switch actuators between AFX/n and AFX/GND where n is 0 - 10 (so AFX/0, AFX/1, ... AFX/10). These can be individually grounded to provide up to 11 selectable triggers for your audio as described in the next step.The photo shows only the connection for one of the selectable triggers (AFX/3) to GND.

NOTE: This wiring is intended to support powering the circuit using a USB data cable attached to a power outlet. (You will not be able to power the board with your laptop for the reason described in Step 3.) You can also power this circuit with 3 or 4 AA batteries. If you wish to do this, you need to wire the positive end of the battery holder to AFX/Vin. Add a wire that connects AFX/Vin to the breadboard pos(+) rail.

Step 3: Setup the Audio FX Board

The Adafruit Audio FX Sound Board can be loaded with any sound you want and supports up to 11 selectable audio triggers (AFX/0 to AFX/10). Depending on which input pin you connect to ground will determine what sound(s) you hear. Sounds are assigned by simply downloading and naming the file as described below:

Your sound board will look just like a thumb drive when you attach it by USB cable to any PC or Macintosh computer. Just drag audio files (.wav or .ogg format) and rename the file to get the effect you want (where nn is audio channel 00 to 10).

  • Basic Trigger - name the file Tnn.WAV or Tnn.OGG to have the audio file play when the matching trigger pin nn is connected to ground momentarily
  • Hold Looping Trigger - name the file TnnHOLDL.WAV or .OGG to have the audio play only when the trigger pin is held low, it will loop until the pin is released
  • Latching Loop Trigger - name the file TnnLATCH.WAV or .OGG to have the audio start playing when the button is pressed momentarily, and repeats until the button is pressed again
  • Play Next Trigger - have up to 10 files play one after the other by naming them TnnNEXT0.WAV thru TnnNEXT9.OGG. Playback will start with #0 and each one on every momentary button press until it gets through all of them, then go back to #0
  • Play Random Trigger - just like the Play Next trigger, but will play up to 10 files in random order (TnnRAND0.OGG thru TnnRAND9.OGG) every time the button is pressed momentarily

I recommend using OGG formatted files to maximize your use of the board's memory storage. I use Audacity to convert raw audio files into OGG format but there are other solutions online and offline available.

Check out http://adafru.it/2133 for more information on how to create and load customized sounds

You can find a nice article on sources of free audio that you can use for your projects by clicking here. If you want to create your own audio, Audacity ( http://www.audacityteam.org/ ) is a good, multi-platform and free audio editor. There is also a very nice instructable by Jason Poel Smith which will provides a great introduction to DIY Sound Effects.

IMPORTANT NOTE: You cannot simultaneously use the Adafruit Audio FX board as a USB storage device and play audio at the same time, even if you 'eject' the drive. To play the audio, you must power the board from an external battery pack (3 or 4 AA cells) or a power-only USB port like a USB wall adapter.

Finally, the Reach and Teach webpage http://www.reachandteach.com/audiofx will give you additional ideas for using the Adafruit Audio FX board.

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