allanhurst:
Nice to hear from people who've worked in this field.
The Due only has 12-bit ADC's and DAC's - I wouldn't reckon that good enough for serious quality.
Serious quality isn't necessary for all guitar applications. That gives you a 70dB dynamic range. It would exceed the real life noise floor in most cases. But some DAC/ADC IC have a built in anti-aliasing filter and that is a really important part that is missing from most microprocessors (or all?).
Not only is the noise floor usually pretty high, but in a mix or performance situation, the noise is eclipsed by the sound from all the other instruments.
Unless you're Pat Methany, you don't need 16 or more bits for this.