Post by Deleted on May 8, 2013 19:37:23 GMT -5
I've got to chime in with a bit more on this one....
There is nothing subjective about audio signals. There is nothing mystical that cannot be measured or quantified. As I like to say "if you hear a difference when measurements say there is no difference - then you just aren't measuring the right thing".
There are different types and "flavors" of jitter. A lot of jitter tends to blur the sound, which contributes to some of those other hard-to-name things... like "speed" and "focus". The easiest way to hear this sort of thing is to listen to something with wire-brush cymbals. If there's a lot of jitter (or some other problems), a cymbal hit will sound more like a steam release valve than like a bunch of pieces of wire hitting a piece of metal (presumably because the individual "hits" that make up the "tizz" sound get blurred together). How much this matters to you will depend on what you listen to. Even ridiculous amounts of jitter are inaudible on things like voice tracks or organ music (at least to me). It will also depend on your speakers (some speakers simply don't let you hear slight differences of this type. Our Airmotivs are VERY revealing of this sort of shortcomings.)
Different choices in digital filter design can also result in differences in whether specific types of sounds and frequency ranges are slightly blurred. If you listen to a DAC that offers multiple filter choices, you will hear the differences mostly in terms of "high frequency blurring" and high frequency rolloff. Some common choices mask the blurring introduced by less-than-perfect encoding, but at the cost of a lot of rolloff of audible high frequencies. Rather than offer a range of filters that sound different, we chose to simply use the one that is most correct
With apologies to certain folks, it is obvious from a technical standpoint that the whole "PRAT" (pace rhythm and timing) idea is not "real" (or, more accurately, it is an inaccurate characterization for a legitimate acoustic effect). Virtually ALL digital recording equipment sold today is absurdly accurate in terms of speed and pitch. Maybe an old cassette deck could get the speed wrong, or shift the pitch, but even the cheapest CD player will get it right to within a few THOUSANDTHS of a percent. You may hear a pitch shift with a defective turntable, or with a dub that originated on an old (and off-speed) tape, but no CD player is going to play a CD at the wrong speed, and neither will a digital player unless it's broken.
My guess here (which I know is true for me) is that what most people are actually hearing is a slight softening of transients. If transients are softened, or a shift in harmonic content makes things like drum hits seem less sharp, then music SEEMS to be "moving slower" or have "less excitement" - which we perceive as it's "being slower in pace". (This is that scale of how much you want to tap your foot in time to the music.) Now, you could get this effect by poor frequency response, or by poor phase response in a speaker, or by a badly designed digital filter in a DAC - and less so from a poorly designed amplifier that couldn't deliver enough oomph to accurately reproduce those transients. It is not, however, an actual difference in the rhythm or pace of the music - that is an "audio optical illusion".
And I think something similar is what's going on with "tone". No DAC, or amplifier, or speaker, is going to change the frequency of a note (its pitch). They can, however, alter the harmonic content such that it seems like the pitch is different (remove a lot of upper harmonics and the "overall tone" sounds like it's lower in pitch). Time blurring also affects the perceived frequency response of a device. If you have a DAC with a poor digital filter that blurs high frequencies like cymbals, they will sometimes seem like their level is too low (even though the actual frequency response is flat, we perceive the blurred cymbal as being "less there" than when it is sharp, and so we "hear" it as rolled off, even though measurements show that it isn't.) This is why better DACs often seem like they have slightly boosted high frequencies even though measurements prove that they are actually flat.
I think a lot of the confusing terms we see are simply failed attempts to convey "effects" like this by people who don't fully understand them...
Unfortunately, this leads to a lot of confusion....
A very chocolatey explanation I must say. ;D
with hints of spiced mocha and saddle leather.....