on 8/29/02 1:15 PM, Austin Franklin wrote:
> Hi Todd,
>
>> This paper appears to speak to many of the issues discussed in
>> this thread:
>>
>> <>
>
> I had a chance to look over that paper. The diagram you mention (I believe
> you were referring to the sinusoidal wave +-5V signal...) that looked like
> the Higgins one, though is similar, is being used to show an example of 2's
> compliment arithmetic. Nothing really to do with dynamic range, as far as
> our discussion that is.
No man, I said: sec. 3.1, fig. 5, which illustrates DyR as a range
between the "noise floor" and "distortion region".
As per the rest, I'm really trying hard to move this AWAY from this being a
conversation of bit depth because I think bit depth is particular to digital
devices, which DyR is not. I'm trying to discuss the CONCEPT of DyR,
specifically whether is a resolution or a range.
Todd
> It says in a few spots, basically, that more bits is more dynamic
> range...and when talking about what dynamic range N bits can hold...that's
> true. Obviously, in a scanner, more bits may not give the SCANNER more
> dynamic range, but you certainly need a minimum number of bits to be able to
> represent all the different values.
>
> The definitions they use for dynamic range, as I've said in another post,
> are the same as I've been using, just don't forget that subtraction in logs
> is the same as division using non-log numbers. See my other post on that...
>
> This paper has a lot of superfluous information that is particular to DSPs
> and audio, and not as applicable to the scanning issues we've been talking
> about. Most scanners don't use DSPs that I'm aware of (at least the
> consumer ones, like the SS4k etc.), the Leaf happens to...BTW, one for each
> channel.
>
> The paper also says, quite clearly "Note that the "6-dB-Per-Bit-Rule" is an
> approximation to calculating the actual dynamic range for a given word
> width.", as well as "In theoretical terms, there is an increase in the
> signal-to-quantization noise or dynamic range by approximately 6 dB for each
> bit added to the word-length of an ADC, DAC or DSP."...which says that the
> dynamic range is DIRECTLY related to the number of bits, and each bit gives
> you 6dB more dynamic range for audio. Of course, as we've discussed, that
> is purely talking about being able to represent all the numbers of a
> particular dynamic range...it has nothing to do with whether the bits are
> actually "good". If you do the calculations your self, it shows how they
> arrived at that:
>
> 2 bits = 20log2**2 = 12dB
> 3 bits = 20log2**3 = 18dB
>
> Funny how that works out...
>
> So, I simply don't see anything that's in that paper that conflicts with
> what I've said. Perhaps you can elaborate on, specifically, where you
> believe the difference is. Don't get caught up in any of the DSP
> stuff...just stick to what they write about bits and dynamic range for the
> A/D, that may give you less confusion.
>
> BTW, the decibel (dB - deci being 10 BTW, so 10 deci-bels is 1 bel...) is
> defined as 10log10 (power ratio), but since power goes as the square of
> voltage or current (for constant impedance), the log of voltage or current
> ratios can be expressed in dB, with a factor of 20 instead of 10...and since
> that entire paper is talking about audio, they use 20 as the dynamic range
> multiplier.
>
> Austin
>
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