[sdiy] Another protecting inputs question...

Eric Brombaugh ebrombaugh1 at cox.net
Thu Nov 20 02:21:45 CET 2008


Seb Francis wrote:

> This is the audio input buffer for the CODEC:
> http://burnit.co.uk/sdiy/stuff/audio-buffer.png

Mind if we back up a step and ask a more fundamental question?

This isn't AH, so why use an analog VCA for feedback? Why not do the 
feedback internal to the dsPIC and implement gain control digitally?

OK - you can argue that analog gain control is going to have more 
resolution than a gain CV quantized to 12 bits via the dsPIC ADC, but is 
that _really_ a driver here? Is it worth the extra expense & board 
space? Can you hear the difference?

The advantages are fewer parts, cheaper board and cleaner feedback (not 
adding ADC & board noise on every cycle through).

Just askin'...

Eric



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