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Old 30th October 2011, 07:04 PM   #17131
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Originally Posted by simon7000 View Post
Gee,

The dither math I've looked at shows that you also have to account for the sampling bandwidth. So at upper midrange frequencies (where the ear is most sensitive) a perfect dither will only allow the equivalent of 19.5 bits of resolution.

If you have a different math treatment I'd be interested.
Sorry, I have no idea what you're talking about.
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Old 30th October 2011, 07:07 PM   #17132
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Quote:
Originally Posted by simon7000 View Post
The dither math I've looked at shows that you also have to account for the sampling bandwidth. So at upper midrange frequencies (where the ear is most sensitive) a perfect dither will only allow the equivalent of 19.5 bits of resolution.
You've illustrated by earlier point perfectly. As long as we consider signal-to-noise, noise floor, and resolution as being the same thing, we can make all sorts of incorrect conclusions.
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Old 30th October 2011, 07:10 PM   #17133
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You've illustrated my earlier point perfectly. As long as we consider signal-to-noise, noise floor, and resolution as being the same thing, we can make all sorts of incorrect conclusions.
How do you distinguish between ultimate S/N (dynamic range) and number of bits for a given bandwidth?

Last edited by simon7000; 30th October 2011 at 07:14 PM.
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Old 30th October 2011, 07:27 PM   #17134
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You used the term "resolution," then used an equation for dynamic range. You'll have to define "ultimate S/N" to get a sensible answer, and it is not the same as "dynamic range." "Number of bits for a given bandwidth" is another fuzzy term. I don't mean to be pedantic, but if you're going to be quantitative, you have to be clearer about what you're calculating.
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Old 30th October 2011, 07:39 PM   #17135
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weighting has already been mentioned but some (Dolby?) use ITU-R 468 instead of "A" so more care is going to be needed in the cassette vs CD comparison - where are you puttting cassette tape peak = digital 0 dbfs, @ 30% 3rd harmonic??

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Old 30th October 2011, 08:07 PM   #17136
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weighting has already been mentioned but some (Dolby?) use ITU-R 468 instead of "A" so more care is going to be needed in the cassette vs CD comparison - where are you puttting cassette tape peak = digital 0 dbfs, @ 30% 3rd harmonic??
If you do an ANSI standard articulation test of a cassette recording vs a 16 bit digital stream at peak modulation of 100% they measure the same. If you reduce the peak modulation to 1% they still give the same results.

I am not comparing CD to cassette just pointing out that with our hearing mechanism a high performance dolby cassette will yield the same results as a 16 bit linear dsp system.

SY,

I use 20 log (2exp (#bits)) to give a digital equivalent to the Ultimate S/N ratio of an analog system. Ultimate S/N is from the noise floor at 15.9k bandwidth to clipping. Clipping is when the peak output voltage of the DUT is reached and is roughly equal to 5% distortion of a sine wave. This is pretty much the way the engineers I work with measure things.

What seems to be missing is an understanding of monoticity. An "X" bit linear D/A will have the most significant bit and all lesser bits accurate to the least significant bit. But the least significant bit will not be any better. So on an 8 bit D/A you will have 256 levels but if it is putting out 2.55 volts full scale the step size could be .01 volts but when the LSB is toggled it is more likely the change is .049 or .0149 volts. That is why dither does allow more information to pass but at a rising rate of distortion.

Resolution of an "X" bit D/A is as used by my cronies is 1/(2 exp "X").

S/N is the ratio from a standard operating point for Analog this is defined as 0 db(x?) and that is often based on the voltage equal to 1mw into 600 ohms, but not always. The peak operating level is then specified with a given distortion. As the limit is clipping the difference between .1%, .3%, 1% and the traditional 5% is very small, but different folks use different spec.s (.1% to 5% often has a difference of .4 db!)

S/N for a digital system has become from 1/2exp(Bits) to Full scale.

Ultimate S/N as mentioned is from the wide band noise floor (15.9K) to clipping. I use 5% when I make a measurement. To me this is the same as dynamic range.

So far there have been issues with i vs I and Sabin vs Sabine, and other of what I always thought was standard nomenclature.

ES

Last edited by simon7000; 30th October 2011 at 08:10 PM.
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Old 30th October 2011, 09:03 PM   #17137
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For historical interest this was one of the first test disks from CBS/Sony in 1983. They did not always believe in dither.

Of further interest the "pop" music sample is Johnny Rotten in a Tokyo PIL concert. PIL = Public Image LTD. not exactly bluegrass.
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Old 30th October 2011, 09:39 PM   #17138
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For historical interest this was one of the first test disks from CBS/Sony in 1983. They did not always believe in dither.

Of further interest the "pop" music sample is Johnny Rotten in a Tokyo PIL concert. PIL = Public Image LTD. not exactly bluegrass.
Checking further this is a true artifact part of the initital CD rollout.
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Old 30th October 2011, 10:11 PM   #17139
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Leibnitz invented digital so relax Scott.
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Old 30th October 2011, 10:24 PM   #17140
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Leibnitz invented digital so relax Scott.

Actually the Jesuits invented digital in the 17th century, even Shirley knows that.
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