Yeah that's another project. MP3 related though. The "stamp" looking board is a carrier board that has a STA013 hardware MP3 decoder and a CS4334 DAC on it. I had a few samples and had hacked them onto a device we manufacture. It's always been something to add music/sounds to any product we make.

The bit appropriate to this thread is the smaller carrier board in the top left of the bread board. It's simply a CS4334 DAC and a HCT14 inverter used to buffer the signals.