Jorge, that MCP4822 dual DAC and built in ref is a nice chip for sure, but look closer at the spec sheet for the "precision" voltage reference. It's 2.048 V, but +/- 40mV - that's +/- 2%. Hmm... "precision"?? It may well be better than that, but you can't know it.
Look at Dave's design philosophy. So far he has yet to introduce ANY hardware fine tuning in the form of variable trimmers, and so far has stated his abhorrence of software "tweaks" (we'll see how long that lasts!!) to calibrate the unit. Instead, he has adopted the approach of precision parts throughout (where it's critical), and is looking to produce an unadjusted close tolerance performance from the get-go.
Because it's a non-commercial project, and more about learning than making big bucks, Dave is quite OK to do that, just because he wants to. Were this a purely commercial design, the MCP4822 would have saved us the cost/space of a separate Vref chip, and the finished product would probably be calibrated as a quick operation on the production line with a pot or software tweak.
Having said that - a non-exhaustive check suggests that the MCP4822 is MORE expensive that the design's MC4922 AND Vref chip...
As ever in electronics, there are several ways to skin the cat!
Lots of great input on these blogs on how to tweak the project, and clearly there is no please-all-the-people-all-the-time combination of features, but this comes close.
WHAT I WANT is a loud Piezo sounder BLEEP that wakes the BLEEP dog up next BLEEP door, every time i change the BLEEP BLEEP voltage from 5.1 BLEEP to 5.0 volts... and where are the flashing lights, Dave? One little LED just doesn't cut it...
"Bang"