Jan, I agree if the controller is just doing control of the PGA. If you are driving a display and doing a whole lot of other things, then it's not that easy. Since the controller is also powered off a separate transformer and power supply, isolation also makes sense from this perspective as well. BTW, even if I use something else here (e.g. relay volume control), I will still isolate the digital and analog sections.
I tried WM8816, PGA2310, CS3310, PGA2320 is(IMO) best.
Practical resuts:
http://www.bvaudio.sk/PGA/PGAE.htm
Controler is driving display, PGA, input selector (relays) and receiving IR.
Practical resuts:
http://www.bvaudio.sk/PGA/PGAE.htm
Controler is driving display, PGA, input selector (relays) and receiving IR.
Bonsai said:Great set of results - so much for all the crap about how bad the PGA's are. Use optos. The noise will go down even further
Doesn't matter, the PGA's can't sound good. They have more than three legs!
Seriously, I played extensively with the PGA2311 and the results were very similar (noise) or slightly better (THD). PGA2311 max output should though stay under 2V.
if the problem with digital breakthrough only happens when the PGA is set to provide gain, then why not simply provide the gain ahead or after the PGA, and use it only for attenuation?
Alternatively, couldn't you put RC filters on the digital lines to reject high frequency crap without being so high as to distort the digital control signals ? These are only low speed anyway... so i would imagine an RC filter would work quite well.
Alternatively, couldn't you put RC filters on the digital lines to reject high frequency crap without being so high as to distort the digital control signals ? These are only low speed anyway... so i would imagine an RC filter would work quite well.
Bonsai said:
You're right about that. It's a good idea to isolate ground loops if there is a chance that ground currents in one part (digital) invade the ground on the other (analog) part. But that has nothing to do with digital noise of the 2 or 3 control lines into a VGA, because there isn't any. It is an issue for instance in a DAC where active high speed signals and analog signals co-exist side by side and simultaneously.
And I still feel that when the ucontroller sleeps all the time except when you change volume, there is no issue with ground currents because their ain't any.
Jan Didden
hi all,
i am very interested in this subject, to date i have never considered using a chip for volume adjustment, never liked the specs. however some of the later generation devices dont look bad at all. But which one to try?
i would like to ask for a vote of types that have been tried by folks and their recommendations. this would be extreamly useful.
i am very interested in this subject, to date i have never considered using a chip for volume adjustment, never liked the specs. however some of the later generation devices dont look bad at all. But which one to try?
i would like to ask for a vote of types that have been tried by folks and their recommendations. this would be extreamly useful.
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