[sdiy] Mixed-signal problems (dsPIC digital delay project)

Tom Wiltshire tom at electricdruid.net
Fri Jan 27 17:40:40 CET 2017


Hi Paul,

> so with DAC as per normal you have 5mv to 7mV of noise. With DAC outputting 0v you get 4mV of noise. So the DAC, at it's worst is giving you 3mV of noise.

I don't follow that. In my view, if it's outputting 4mV of noise when there's no signal, it's giving me 4mV of noise. It's the input signal and the processing by my algorithm that's adding the extra 3mV. At this point, I'm not arguing about 1mV here or there though!

> Question, what frequency band is the noise in? I mean, are you looking at the noise on the scope, or are you hearing it on speakers?

Both. From the scope, it looks like some of that noise is high frequencies that might be amenable to filtering.

Tom






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