In Reply to: RE: "More DACs"..... posted by Todd Krieger on July 14, 2015 at 16:37:48:
"The question I've always had with using multiple DAC chips is *how* it would increase dynamics or lower distortion."
Here are two reasons for increasing signal to noise ratio:
1. Current mode DACs use a fixed resistor in their I/V converter. The Johnson noise (measured as a voltage) depends on the value of this resistor and its temperature. Most DAC chips (especially ones that use CMOS technology such as the SABRE chips) are current sources. If you parallel these you get more current into the same resistor, which means that the signal increases by a factor of N, but the Johnson noise remains the same. This improves the signal to noise ratio.
2. For sigma delta DACs such as the SABRE, the modulator produces noise which is a function of the number of current mode switches per audio channel and the master clock rate. If you parallel chips the signals add coherently, but the noise adds randomly. This also improves the signal to noise ratio.
These is really no different than the situation when comparing the signal to noise ratio of 2 track and 4 track tape. Here the first aspect of wide tape is more signal power to overcome any noise in the receiver amplifier, while the second aspect corresponds to the fact that the tape hiss is uncorrelated.
The situation is more complicated when it comes to distortion and depends more on the details and limitations (design and manufacturing) of the individual DACs. I don't know how to explain this in simple terms, unlike the situation with respect to signal to noise ratio.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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Follow Ups
- RE: "More DACs"..... - Tony Lauck 17:50:28 07/14/15 (9)
- RE: "More DACs"..... - 13th Duke of Wymbourne 21:43:24 07/14/15 (4)
- RE: "More DACs"..... - Tony Lauck 08:31:50 07/15/15 (2)
- RE: "More DACs"..... - 13th Duke of Wymbourne 15:43:18 07/15/15 (1)
- RE: "More DACs"..... - Tony Lauck 16:09:17 07/15/15 (0)
- RE: "More DACs"..... - Dynobot 23:46:22 07/14/15 (0)
- RE: "More DACs"..... - AbeCollins 18:02:40 07/14/15 (3)
- RE: "More DACs"..... - Crazy Dave 07:54:21 07/15/15 (2)
- RE: "More DACs"..... - AbeCollins 07:10:14 07/17/15 (1)
- ditto (nt) - Crazy Dave 08:11:51 07/17/15 (0)