> ADC, MCU, DAC, done. Cheaper, too -- I think 50 cent ARMs can do that these days.

And yet smart engineers keep using Analog Devices SHARC DSP's for effects on audio interfaces.

So SOMETHING must not be quite as simple as your claim.

(The answer is that most of these guitar effects are VERY non-linear and simulating non-linear stuff digitally is very much NOT straightforward in real-time.)