Ralph, aliasing should be included within a typical "THD plus noise" spec, and I see no reason to call it out separately. Harmonic, inharmonic, IMO it’s okay for all artifacts to be lumped together. If the sum of them all is below 80-90 dB, none of it will ever be heard anyway. With a typical converter the sum of all artifacts is well below 100 or even 110 dB.OK- we’re on the same page, except for one thing. And that is that if the artifacts are at -80 or 90 db, that’s no guarantee that they can’t be heard!!
You have to understand that the rules of human hearing have to be the number one thing in audio. But the industry in generally usually finds them a bit inconvenient.
This is an example:
Even if the artifacts are really down that far (and I question that as aliasing is really best detected with an analog-sourced sweep tone, and further just because a DAC is pretty good at it has nothing to do with how good the ADC was- and without the ADC you’ve got no software....), the human ear uses higher-ordered harmonics to calculate loudness. In addition, the ears are tuned to be most sensitive at bird-song frequencies (and aliasing produces ’birdies’ all the time), meaning that the artifacts can be that low and yet easily detected.
Of course we won’t hear the artifacts as they are- the ear converts them to tonality.
This is why there is a digital/analog debate!!
Many people object to the ’brightness’ or ’hardness’ of digital as opposed to analog, and there is no way that such can’t be interpreted as a **coloration**.
There has been an analog/digital debate going back to the early 1980s and you’re looking right at the reason in this post. When you have a coloration like that, there is no way it can be considered neutral and ridding digital of this problem is the cutting edge of where real advancements in the digital art are being made. The thing is, the distortions of analog are less audible to the human ear, and so even if on the bench they **appear** larger, in reality (because our ears are the reality, not the bit of paper) they are in fact **smaller**!
If you don’t understand how human hearing perceptual rules work, you will have trouble understanding how this is so. Think of it in a logarithmic fashion, but instead of being related to sound pressure (decibels), its instead related to higher ordered harmonics and intermodulations.
This is why I have been harping about the fact that our understanding of how human perceptual rules work is where the big advances in audio are occurring, and why it is that as an industry we fall well short of knowing all that should be known for **real** high fidelity. This is why high end audio exists, to plumb these issues and offer solutions, since mid-fi is only dollar-oriented and has to be pushed pretty hard to change. Of course, some high end audio things don’t work because in a way many of us are stumbling around in the dark due to the industry’s overall lack of interest in human hearing perceptual rules!
Because things like equipment stands can reduce tiny amounts of microphonics and other HF artifacts, they have a value; this is due to how our ears work- and I concede that the differences can be hard to measure because our test equipment lacks the required sensitivity that our ears easily have. There are many things where our ears are less sensitive than test gear; higher ordered artifacts just happen to be an exception.