One thing lacking from the Arduino Uno and compatible boards is a true digital to analogue converter, that is an output to create a varying output signal. Although it's possible to create the illusion of a DAC using the PWM (Pulse-Width Modulation) pins, this is just a 5V square wave turned on and off at with a varying period. However with some inexpensive passive components it's possible to generate some analogue output.
This has been demosntrated by Instructables member DavidW10 who shows us how to use an RC circuit (resistor and capacitor) to convert a pulsed signal into a flatter signal. For example in the following image you can see the PWM signal before and after being passed throug the RC circuit:
Although this is not an accurate replacement for an external DAC IC, the methods demonstrated are very simple an inexpensive to implement - and can form the basis for some fun sound effects and more. So to learn how, visit the project Instructable page. And for more, we're on facebook, Google+, and twitter - so follow us for news and product updates as well.