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In Reply to: RE: Try these posted by Tony Lauck on April 06, 2012 at 12:02:00
"The SABRE chip performs digital volume control at 32 bit precision and the chip itself has about 130 dB S/N ratio."
I doubt the output stage of any Sabre DAC would come near a SN of 130dB.
Let alone the rest of the system as a whole.
Follow Ups:
"I doubt the output stage of any Sabre DAC would come near a SN of 130dB.
Let alone the rest of the system as a whole."
The link shows claimed S/N numbers for several models. The actual S/N ratio depends on the model number (e.g. the more expensive chips are selected for lower noise) as well as the configuration (more switches are used in parallel when the chip is run in mono than in stereo or multi-channel).
There is no theoretical reason why these chips couldn't meet their claimed specifications. However, the numbers are likely to be as good as any available test instruments, making it difficult to argue with the advertised results. ESS has a white paper that describes how the chip works.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Tony, you appear to have misunderstood me.
Most power supplies don't achieve 100dB SN. It is unlikely in the real world that the Sabre can achieve anywhere near its theoretical SN ratio.
As I recall the test setup for the test circuit for the SABRE DAC calls for an active power supply filter right at the DAC chip to reduce noise. There was a test board and measurements. I don't think the quoted numbers were total BS. Whether an actual product does as well is problematic.
In any event, my point was that there were other limiting items that lowered resolution more than the DAC chip, since what was being discussed was digital volume controls. The most likely source of noise in a 24 bit digital recording is going to be the microphone preamp or even the random microphone noise caused by air molecules striking the microphone's diaphragm, at least for classical recordings where the microphones are some distance from the instruments. Most microphones have self-noise of 10-20 dB or so and SPLs might peak at 110 dB, giving a maximum S/N ratio at the microphone of 90-100 dB. When played back at similar volumes (very loud) this noise will be below ambient room noise.
Perhaps someone who has the Mytek DSD192 DAC can compare the results of using this products digital volume control vs. its analog volume control.
I was going to order one of these, but was put off by the big queue. This DAC uses the "cheap" 128 dB version of this chip set.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
No worries Tony, I see that you understand SN ratio in a real world situation.
S/N specs tell you very little. Why? Because of the measurement conditions. Steady-state sine-waves. There is nothing in this to tease-out the dynamic performance of the system. The closest thing we have to that is an impulse response, which is lame at best.
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