8-Bit R2R DAC
Today I made an 8-bit R2R DAC buffered by a TI TLV2474 OP-AMP. I tested a 256-step sine wave and the results were much better than I expected. I didn’t notice any clipping as the signal approached VCC like some other posts I saw online and I’m attributing that to the rail-to-rail capable tlv2472. I also used lower than ideal values for the resistors, 1K & 2K. I thought using these low values would draw too much current effecting the overall voltage output but that didnt seem to be the case. Tomorrow I will try some audio samples to see how well it sounds and plot the actual voltages on the output.
The DAC is attached to an 8-bit AVR @ 16mhz .
After a week or so playing around I came up with a midi drum machine and synth based on the AVR + 8-bit R2RDAC. The synth is midi enabled and can generate and play 8 simultaneous (polyphonic) square,triangle, or sine voices @ 32khz sample rate. Here’s a video of it playing the theme music to Super Mario Brothers 1 from the NES via midi.
I also did a drum machine demo using 8-bit 808 samples, this too can mix 8 sounds in realtime and be controlled by midi or the 3 buttons on the button board.