Synthesiser

This article is about an analogue synthesiser.

Figure 1: Analogue Synthesiser Amplitude Controls.

Figure 2: Analogue Synthesiser Frequency Controls.

When I was a student at university our engineering faculty dumped hundreds of 100k logarithmic potentiometers. To prevent those potentiometers from going to waste I decided to use them for frequency control in analogue synthesiser.

Step 1: Design the Circuit

I designed the circuit with six transistor flip-flop oscillators. Three are shown in the diagram below:

Figure 3: Circuit Design.

Step 2: Simulations

Simulations show how the circuit will work.

Figure 4: PSpice Simulations.

Step 3: Make the Circuit

I did not use a soldering iron I twisted the component legs and the wires.

Figure 5: Make the Circuit.

Step 4: Encasement

I used scissors to make holes in the cardboard box for the potentiometers, ON switch and earphone plug.

Figure 6: Put in the Cardboard Box.

Step 5: Testing

I used Hantek 6022BE USB oscilloscope to test the synthesiser.

Figure 7: USB Oscilloscope Plot.

I connected the synthesiser to a Class A transistor power amplifier.

Video of the synthesiser working:

Conclusion

Other alternative design solutions exist. The volume control potentiometers (Rc1b, Rc2b and Rc3b) can be 10 kohms and the mixing resistors (R1, R2 and R3) can be 1 kohms.