As the Hack A Day crew notes, we should particularly admire the cleanliness of the prototype shown in the video above, with each part given ample room on its own board – and interconnected by 10-pin IDC ribbon connectors.
So, how does it work? Well, to generate audio from the digital microcontroller, Mike built his own R2R digital to analog converter. A resistor ladder – created from 16 resistors – feeds a rail-to-rail amplifier. And although the sound is mono, playback is actually polyphonic due to Atmel’s stalwart ATmega1284.
“It is reading MIDI commands coming in from an external controller (we assume it’s the computer on which the hardware is sitting),” Hack A Day’s Mike Szczys explained.
“The chip’s 128 KB of Flash memory leave plenty of room to store samples, which are selected from a lookup table based on the MIDI data. If more than one sample is to be played the chip averages the data and sets the 8-bit output port accordingly.”
Additional information about the 8-voice 32 kHz synthesizer can be found here.