Core Studio: Dirty Baby

Iltimas Doha
3 min readDec 20, 2016


Finals! What an amazing time to use a passion project for a grade! This semester I decided to tackle one of my life goals, building my first synthesizer.

Sound is the oscillation of an object, a tuning fork for example,which vibrates and oscillates the air. The wave of moving air reaches the eardrum and vibrates sympathetically, which the brain interprets into sound.

When you have an instrument you need something to vibrate: strings of a guitar, the skin of a drum, the air inside a trumpet. But what about synths. What do you do? Well, when we play music from our phones or laptops, we send electrical pulses to the magnet in a speaker to pull/push it back and forth.

Can’t explain how angry it makes me that + is black and - is red

Synths use the oscillating electrical signals between power and ground(0V) to drive a speaker back and forth. In synth-speak we call this the VCO, or Voltage Controlled Oscillator. A popular and super simple oscillator is the 555 timer. In astable mode, one of the three available configurations, 2 resistors and a capacitor dictate the frequency(pitch) that it produces, replace one of those resistors with a variable resistor and now you have a chip able to produce a range of frequencies.

Maybe when I finish this book I can properly explain what’s going on inside the 555:

In the above GIF we see the insides of the 555 in the grey box, on the left side are the 2 resistors and capacitors. The 555 timer flips between high and low depending on the charging and discharge of the capacitor, thus producing an oscillation.

I used the following schematic for the VCO

As you may have noticed, this is a 556. This essentially 2 555 on a single chip. Here I’m producing two tones, one of which actually controls the triggering of the other 555.
The reason for using a 556 schematic vs a 555 is to produce tones that have deeper and richer tones.

The next module is a VCF, Voltage Controlled Filter, it is primarily run through an LM741, an op-amp. An op-amp, to my understanding, is a component that compares two signals to be amplified. For this, it compares an audio-source and ground(and feedback from audio for resonance), then based off the two variable resistors and cap, the op-amp works as a low pass filter. This is the schematic I used:

And finally I used another 555 timer as an LFO, Low Frequency Oscillator. This works the same way as one of the halves of the 556, but it generates a slow frequency(<20Hz). Because this is under the audible range it doesnt do much on it’s own. But when connected to one of the CV pin of the 556 it is able to switch back and forth at a rate set by a variable resistor.


Originally published at on December 20, 2016.



Iltimas Doha

EYEBEAM Resident ‘14-’15 ⁠ Parsons’ Design+Technology BFA ‘15-’19 ⁠ Eid and Chill 🕋