Here's how it works:
I could have made a very complicated voltage ladder, but that would have made the board a lot more complex and cost a lot of pins (so no more expansion port!)
So you'd like to generate a beautiful audio tone from your LameStation. That's nice.
A computer can only operate on data, ones and zeroes and such, but your ear can't listen to a bit stream, because that would just sound like dial-up internet*.
There's lots of ways to generate an audio signal electronically, but one of the simplest is Pulse Width Modulation. That's a fancy way of saying turn the pin on and off really, really fast, depending on the level of the signal at that moment.
The result is a blocky, horrible-sounding signal that, on average, is equal to the original waveform.
*for those of you born after dial-up internet, I feel old. Listen here: https://www.youtube.com/watch?v=gsNaR6FRuO0. You've been warned...)
Two filter average this out to a smooth lower-frequency signal.
A volume knob behaves like an adjustable voltage ladder, determining how much of the input voltage reaches the amplifier.
An amplifier takes the signal and gives more power to it, so that it has enough current to drive speakers.
Another filter reduces noise from the amplifier.
A large capacitor removes the DC offset, so that the speaker won't be stressed as much. (more explanation needed)
The signal is output to either a speaker, or headphones if some are connected thanks to a small switch inside the jack.
Word of caution: The speaker is magnetic and will pick up small components if it gets too close. If you can't find one of the small capacitors, you should look there first! |
In this section, you will build a totally awesome amplifier that you can use to pump some sweet LameStation tunes. |