Originally Posted by David Susilo
Anybody who have actually heard wow and flutter would never, in their right mind, saying that jitter is analogous to wow and flutter.
Says you, based on what?
There's a good chance that you've never ever heard jitter from a digital source, as audible jitter is pretty rare in correctly operating digital systems.
OTOH there's a good chance that you've never ever heard audio without jitter from an analog source, as audible jitter is pretty common in even the best analog playback digital systems.
Jitter is clock related, in analog there is no clock, hence there is no jitter. Plain and simple, no?
I will repeat a pretty good formal definition of jitter from http://en.wikipedia.org/wiki/Jitter
"Jitter is the undesired deviation from true periodicity of an assumed periodic signal in electronics and telecommunications, often in relation to a reference clock source. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of periodic signals."
Notice that it says "often in relation to a reference clock source" but not "always in relation to a reference clock source".
Analog playback has a presumed time base just as surely as digital playback. In analog the presumed time base is related to the motion of the media that has the sound engraved on it (Vinyl) or embedded in it as magnetic variations (magnetic tape). Since the velocity of these media with respect to the stylus or playback head is prone to small variations, there is an variation in the time base of the signal just as surely as if it were sampled.
In reality all of these things are FM distortion.
FM distortion in speakers is a little more complex to visualize, but it is again just another example of FM distortion.
I can intentionally create digital jitter, analog flutter or FM distortion with the same modulating frequency and modulation index or degree of modulation and it will all sound pretty much the same.
There is even audio editing software that was originally designed for doing things like pitch correction that was found to be capable of identifying and correcting jitter in analog recordings:
For over a hundred years, music has been recorded on mechanical mediums. And for over a hundred years, there has been a problem with this: wow and flutter. Who isn’t familiar with the wobbling and warbling, the droning and dragging? Mechanical degradation caused by defective devices or sticking tapes, by ageing or defective storage. In the past, it was usually impossible to get rid of wow and flutter.
Countless recordings of renowned orchestras, big bands and rock groups are currently slumbering deep in archives. Yet they are unusable, simply due to wow and flutter. The tapes worthless, the recordings lost to posterity. Until now.
For, in Capstan, there is now for the first time a program capable of removing wow and flutter from recorded music. Whether on tape, compact cassette, wax, shellac or vinyl.
Wow, flutter, FM distortion, Jitter, even vibrato - they are all different names for the identical same basic physical process - time distortion.