[time-nuts] Oh dear

[David]

Analog Devices and Linear Technology have application notes on this
subject.  At least with sampling converters, jitter directly limits
dynamic range.

My back of the envelope calculation comes up with about 25ps of RMS
jitter for an ideal 16 bit sampling converter at audio frequencies but
most delta-sigma converters should tolerate higher levels.  Analog
Devices says 100s of ps of clock jitter is acceptable for them.

How low can the dynamic range be before it becomes audible?

On Mon, 7 May 2012 09:48:39 -0700 (PDT), "J. Forster"
<jfor at quikus.com> wrote:

>Suppose you have a perfect, ideal clock that puts out 'convert' pulses at
>an exact rate is used to strobe a high precision A/D.
>
>Now suppose you add jitter to that perfect clock so that the rate stays
>the same but time interval between successive pulses varies randomly
>between P(1-x) and P(1+x).
>
>How big would x have to be before anyone could detect any difference in
>the sound?
>
>I have my opinion, but what is yours and why?
>
>-John
>
>===============
>
>> On Mon, 7 May 2012 10:02:25 -0600
>> Tom Knox <actast at hotmail.com> wrote:
>>
>>>
>>> Actually the numbers are quite real, play with the math, a small amount
>>> of jitter in a DAC (X) can have a large difference (Y) when sampling a
>>> complex wave form especially in the audiophile world where the sound of
>>> 24bit dac 16,777,216 discrete levels is clearly superior to older
>>> 16 bit dac 65,536 possible levels in 44.1 KHz to 192 KHz formats.
>>
>> Yes, i know that jitter is a pain when it comes to ADCs, but keep
>> in mind that your audio ADC does have a jitter of a couple
>> 100ps itself. If it's a high end ADC that is. The standard ADCs are
>> usually
>> in the ns range. For a normal 10MHz XO you measure the jitter in in the
>> lower
>> 10ps at most, a good one at lower than 1ps cycle-to-cycle. Of course, you
>> have
>> to keep the clock signal clean of any disturbance that might add
>> modulations
>> to it. But that's a matter of keeping the power supply clean and having
>> the
>> signal shielded. It's not an inherent property of an Rb to have low
>> jitter.
>> And as we all know from the recent  hype on the FE-5860As and the
>> following measurements, not all Rb's are low jitter.
>>
>> 			Attila Kinali
>>
>> --
>> Why does it take years to find the answers to
>> the questions one should have asked long ago?