Introduction: Quad Speaker Synthesizer

About: I am an electronics engineer as well as a hobbyist in many other areas. My Instructables are based on engineering and electronics. I also like to do DIY projects involving other disciplines such as audio.

Here is a simple synthesizer that has:

22 keys

volume control

tone change

different sound effects

pan (for the speakers)

four speakers

light (for the speakers)

Anyone can build it, except for the electronic components, everything else can be found at home. This synthesizer is a great way to experiment sound and electronics.

Step 1: Material, Components & Equipment Needed


Plenty of cardboard (recommend 2 or 3mm), lots of wire(24-30awg), 9v battery, 2x AAA/AA battery.


22x 4k resistors, 1x 1k resistor, 3x 100ohm potentiometer, 1x 10k/100k potentiometer, 1x555 timer ic, 1x 10uf capacitor, 1x 0.01uf capacitor, 11x 2pin tactile switch, 11x 4pin tactile switch, 4x 8ohm speakers, 9v battery connector, 3v battery holder,breadboard.


Super glue/glue gun, solder + soldering iron + soldering kit, cutting knife, ruler/safety ruler, pencil, tape.

Step 2: Building the Circuit

Now you have everything, you can start building the circuit. Just build the breadboard diagram (above) onto your breadboard. If there is any confusion with the component footprints, then look at the 4th image, it may help.

Circuit explanation: the whole circuit runs on a 555timer ic, each button plays a different, 3 of the potentiometer (the 100ohm ones) controls the pan & volume, while the other controls the tone or pitch. The polarised capacitor controls the sound effect and also a bit of the volume.

Once this is done, its a good idea to just plug everything in to see if it works (see 3rd image for reference), if it does then move on but if it does not then check your connections. It may help rebuilding parts of the circuit.

Step 3: Cutting Cardboard 1

We now have the breadboard, we can start building the main control board. First we have to mark everything out on a piece of cardboard (A4 recommended). Here are the dimensions:

Piece A: 2x 16*9cm

Piece B: 2x 9*2.5cm

Piece C: 1x 16*2.5cm

Base: 1x 16*8.5cm

Once all the cardboard is cut out, take one of the A pieces and cut two holes (2mm smaller that the radius of your speaker). Then cut a smaller hole (diameter: 4mm) in between the big holes and 1cm above the bottom.

Step 4: Assemble the Synthesizer 1

Once you cut out the cardboard, use glue to glue the two speakers in (only if the speaker has wires, if not then solder some on, wire length: 15-20cm). Then pull the wires through the whole, after that glue both piece Bs onto the side of piece A. Finally, glue piece C onto the side of piece a and both piece B.

Step 5: Assemble the Synthesizer 2

If you use a clear speaker (speaker with a see-through plastic cover), then you can consider to put a strip LED it to make it all cool and fancy. Connect two 20cm wires to 10-15cm of strip LED. Bring the wires to one corner then stick the second piece A on.

Next, take your breadboard and the base, stick the breadboard onto the base (note: make sure the breadboard is facing you, with 3cm of space behind). Take the assembled speaker box and stick it onto the space behind the breadboard (note: speakers facing you). Connect the wires of the speakers and the LED according to the digital breadboard footprint. (Look for the circled area on the digital breadboard)

Step 6: Cutting Cardboard 2

We will now be cutting out the cardboard for the two external speakers. Dimensions are below:

Piece D: 4x 9*9cm

Piece E: 8x 9*2.5cm

Once all pieces are cut out, take two of the D pieces and cut the same size circle you cut before for the speakers.

Step 7: Assemble the External Speakers

Solder 30cm wires onto the speakers. Glue a speaker into the hole of the D piece. Glue 4 E pieces around the D piece with the speaker. Stick the LED in (4-8cm with 30cm wire). Bring all wires to the middle of one E side and glue it down. Make sure you either mark or remember which wire leads to what. Then take a D piece (without hole or speaker) and stick it on. After you finish, repeat this step for the second external speaker.

Step 8: Connect Everything

Connect everything according to the digital breadboard footprint. Areas circled in red is where you need to par attention to.

Step 9: Finish!

Test everything, if it works then every button should produce a different sound (one higher than the one before) and all the potentiometers should either change the sound or the tone.

Experiment! Try replacing the polarised capacitor with capacitors with different values. I tried some capacitors around 5000uf and it gave some pretty cool sound effects.

Have fun with the synth!

Step 10: Troubleshoot

If there is any problem with assembly the synth successfully, here are some suggestions:

Check all wire connection

Check if any wires are mixed up

Check if your batteries are working properly

Try replacing the 555timer with a new/unused one

Try to replace other components.

Resolder some connections

If this does not help then you can always use the comment section below and ask.

Audio Contest 2018

Participated in the
Audio Contest 2018