drone synth

555 Based Drone Synthesizer With LFOs

Sam

Today I have an update to the 555 Based Drone Synthesizer which I posted last week. I was having a lot of fun with my Drone synth but wanted to expand on it to get a bit more variation from the sound. To do this I added a set of LFOs to modulate the frequency of the drone oscillators.

To accomplish this I built a second set of three 555 based oscillators. These new oscillators are identical to the ones in the drone synthesizer except for a change to the capacitor between pin 2 and ground. By increasing this capacitor from 0.01uf to 1uf I was able to lower the frequency of the square wave they produce. This makes them perfect for use as LFOs.

I then connected the output (pin 3) of each of these new oscillators to the control voltage input (pin 5) of the corresponding oscillator in the drone synthesizer through a 1K resistor. An additional modification that can be made to this circuit to provide further control would be to replace this 1K resistor with a 10K or 50K ohm potentiometer which would allow you to modify the amount which the LFO modulates the oscillator in the drone synth.

In this experiment I have used LFOs but you could easily control the drone synth in other ways as well by providing a control voltage to pin 5. I am interested to see how this set-up would react to a control from a sequencer or keyboard and may try this in the future.

Simple 555 Based Drone Synth

Sam

Today I have another very simple breadboard project based around the 555 timer. I’ve built three 555 astable oscillators similar to what I used in my 555 Serial Oscillator Project. This time however instead of connecting the oscillators in series I have run their square wave outputs through a simple mixer onto a single audio channel. This is known as a drone synthesizer.

As you can see from the schematic this drone synth is a fairly straightforward build. If you are familiar with 555 oscillators you probably recognize the layout of the 555 chips as a basic astable oscillator almost directly out of the 555’s datasheet. Once the three oscillators were created I added a 1K ohm resistor to the output of each (pin 3) and connected these outputs together. Once the three outputs are connected you can run this through a large capacitor (I used 330 uf) and out through your output jack. It is also possible to connect this circuit directly to a speaker though the audio level may be a bit low without amplification.

Once you’ve built this circuit you can begin experimenting with it. Pin 5 on the 555 chip can be used as a control voltage input so you could easily add a method of control voltage to this circuit. The easiest way to do this would be to build three more 555 oscillators and connect their outputs to pin 5 of the 555 chips in your drone synth. These will function as basic LFOs and modulate the frequency of the drone’s oscillators. You could also experiment with other voltage controls like a sequencer or keyboard. You could also replace one or more of the potentiometers with things like photo-resistors or body contacts to make the project even more interesting.

Lastly I wanted to mention that this drone synth is not limited to three oscillators. You can add as many 555 oscillators as you want in parallel to make an even deeper and stranger sound. If you’re interested in seeing the extreme of this a YouTube user by the name of Look Mum No Computer recently built a 100 Oscillator Drone that is definitely worth checking out.