I'm sure it was super distorted! A sine wave that occupies just the lowest one or two bits is by definition totally distorted.
I hope the larger point is not missed Ethan. Those low order bits are what represents the finer detail in the music. Without it, we might as well say that CD is overkill and we should have had a 14 bit system at 44.1Khz.
All I have to go on is the graph I showed from Ken Pohlmann's book, repeated here for your convenience:
The graph is showing the effect of a 2ns jitter. The paper said hundreds of nanoseconds is inaudible. So other than proving the same point that I did in that random jitter simply raises the noise floor, in what way is it proving your point?
It also says the system signal to noise ratio is now nearly 80db in the presence of jitter noise, not 100db. I personally don't feel comfortable with a system that has such low level of signal to noise ratio.
There's also one from John Watkinson's Art of Digital Audio, attached below.
That is also for random jitter, not for periodic or correlated jitter which are the two we also worry about. At the outset I mentioned that the ear is not as sensitive to broadband noise as it is to noise that comes and goes and/or is related to music. So neither one of these references are helpful in this regard.
I have already addressed random jitter showing how it is quite difference than periodic or program related jitter.
If anything that confirms my point, that even when not way down at -100 dB, such artifacts are still not audible. I got the lower than -100 dB figure from Pohlman's graphs. I do understand the difference between individual components that soft, versus the sum of all components which is of course much louder. So I probably should have been clearer when I said the artifacts from jitter are 100+ dB down.
I showed you graphs where the noise spikes were at -80db. If you want to stick to some graph, why not consider those also? I also showed you that music could be at that level. Note that there, I used real content showing that its high frequency level dips to the same level as the jitter.
In practice, 60 or 70 dB is soft enough for artifacts to be inaudible even under the most favorable conditions.
Really? Here is another graph I have saved up on my server of real music:
You want to tell me that that decay is illegal and can't occur in real music? I assume not
. As that signal decays into nothing, we hear the room reverb and other cues which gives music its life and character. If the DAC is non-linear or jitter too high, you get an abrupt and distorted finish as that signal decays.
Sure, when the signal is loud such as in your example, none of this matters. We are not disputing that. Digital is king when it comes to loud signals. It achieves perfection that way in the way it is able to kill analog. Invert the equation though, and tables are turned. You have to look at how well digital can reproduce those fine details if you want to have luscious sound which can replace analog.
Again, you can't pick test tones or even sample music tracks to prove your point. Your point must be true of
all music or it is not valid. We can't say this noise is this much db below music unless you can show that music can never be fainter than that. As I have shown, music can and is faint very often.
When I tested this I made a recording of a 100 Hz tone at nearly full scale, then added a 3 KHz sine wave that pulsed on and off at various levels below the music. These two frequencies are far enough part that masking is not a factor, and 3 KHz is where our ears are most sensitive. So this was a worst-case test favoring audibility.
It is not. It is the best case per above. We are not interested if we can hear faint noise when the music is blasting our woofers and ears. We are in agreement there. Where we are taking past each other is that you seem to be assuming that music is always that loud and that it only has a single component like the 100 Hz tone. In reality, music has high frequency detail whose level is very low relative to low and mid-bands. Yet that faint level conveys how "bright" the music is. Mess with those high frequencies even a little, and the tone changes.
That is a reason why compressed music can sound "bright." The increased quantization noise is not audible in the way you imagine it above, but instead, spreads into the high frequency bins and causes that increased edginess.
So even in your AP example of jitter sidebands at -80, it makes sense to me that nobody could hear it.
Would you say that is true if the signal is at -60db?
BTW, is that AP example at -80 real or simulated? If real, what device did you measure?
I did not measure the jitter diagram. It comes from other sites. AP graphs are real measurements as for simulations, we don't need that device. My measurements were done using a Blu-ray player feeding my AP.
Then we're getting closer. Didn't you already acknowledge in your Post #8 that jitter is a fixed level below the signal, rather than steady as is noise?
--Ethan
I am sorry but I don't understand the question. I have said that jitter has infinite profiles so it is not any one thing anyway. But that if you want to put it in buckets, you have three kinds:
1. Random jitter. This raises the noise floor and reduces the dynamic range of the system. At high enough level, it reduces fidelity of the system but it is not as bothersome as other forms below. All of your testing and papers you have cited fall in this category.
2. Periodic. This is one more more pure tones which change the signal timing. This could be the USB frame buffer timing, power supply noise, front panel high voltage oscillator, video clock related (e.g. as in HDMI that has video as master timing), etc. This can be more audible as each one of these tones modulates the music and creates sidebands that could fall within the music levels especially at high frequencies. I have shown examples of this type of jitter and consider it a potentially audible problem (depending on frequency).
3. Program related. This is jitter that is self-dependent on the signal itself! A good example is cable induced jitter. A poor digital audio interconnect, changes the shape of the pulses, causing the time they are accepted by the receiver to change. This again from Julian's book:
Unfortunately, those pulses change as the music changes, modifying the waveform as seen by the receiver and hence its timing. There, jitter comes and goes with music which can be most offensive to listeners. It also be very tricky to test for as you need to find conditions which aggravate it.