Good presentation on Digital Volume Control and Jitter

Apr 3, 2010
16,022
0
0
Seattle, WA
#1
Nice to see the silicon guys, in this case ESS, present such data. Here, they talk about differences between digital and analog volume control, and jitter how their special async sample rate converter does away with problems of filtering out jitter in a DAC:

 

mojave

New Member
Oct 29, 2010
251
0
0
Elkhorn, NE
#4
ESS has had the digital volume control presentation part as a PDF on their website for several years.

I have never figured out why he is using a 16-bit DAC for an example. 24-bit DAC chips have been around for a long time. I've been using only 24-bit and have had at least 24-bit volume control for over 10 years.

He says on slide 5, "As a digital volume control operates on a fixed-width field (ie on that 16 bit number that the DAC receives) it creates noise because the DAC cannot make the fractional part of the number – And this is a large noise!"

So I think he is saying that the noise is due to quantisation errors. If so, then accessing the 32-bit internal data path of the DAC isn't the only solution. You could also access a 64-bit internal data path of the playback software. This will be even more accurate than the 32-bit DAC. In both cases, software or DAC, the final output to DAC chip is 24-bit (slide 14 says the Sabre chip is 24-bit externally). Also, he doesn't mention that you can basically eliminate the noise caused by quantisation errors by using dither.

The only noise a 64-bit digital volume control doesn't push down is the noise floor of the playback system.
 

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