DACs don't set an idea as to flat. The "idea" of flat isn't an idea, it's a mathematical definition (as detailed by
@VNandor). If a DAC or anything else complies with that, then it's flat and we can test that with a null test and by specifically measuring frequency response. Virtually all DACs do comply (to a level of accuracy which isn't audible) up to the limit of their anti-imaging filter transition band.
B. Mostly, yes, but there are many variations. However, a variation does not necessarily imply a difference, for example, 1 - 1 = 0 but a variation of that, for example 0.5 + 0.5 - 1 gives us exactly the same result. There are almost always some differences between ADCs, even those employing the same methods but they're outside or more typically, way outside audibility.
C. Yes, very different, for starters it's analogue!
D. That's never going to happen. The analogue world is limited by the physics of electronic components, the digital world isn't, it's just math.
E. You don't have to beg, you're entirely free to argue here, the only requirement is that if you're going to contradict science, then you must provide some reliable evidence to support your argument. Also, there's a requirement to be honest! No one has stated that "digital is fully pristine" just that it's pristine beyond the limits of human audibility, given some obvious conditions.
F. And here you fail to comply with those requirements! You're not being honest, what people here in SS don't fully embrace the fact of intrinsic attributes (artifacts) of analogue?
G. Some are "profoundly inept" but the majority range from good to excellent, considering the limits they had to work with.
Again, you need to be honest! I did directly answer your question at some length, I told you that a null test can reveal a flat response and I even explained the basic principle of how it works. You however, DID avoid the questions presented to you! For example, do you believe 1 - 1 does not equal zero? What digital reproduction do you think you're listening to, if we apparently can't measure everything but digital audio is just a measurement to start with?
1. A flat response is flat, which means it's identical. How can sound (digital, analogue or anything else) that's identical sound different? Again, do you think 1 - 1 does not equal zero?
2. And you wouldn't be alone if you suggested the Earth is flat, does that mean the Earth IS flat?
2a. The response is flat, there is nothing missing and therefore nothing to "add back, even with EQ". Again, does 1 - 1 equal 0 or is there something missing and it equals something less than zero?
3. And maybe you don't realise that hundreds and probably thousands of people still feel the Earth is flat, does that mean the Earth IS flat? What you or anyone else "feels" is irrelevant because it doesn't change the facts. 1 -1 = 0 is a fact, maybe you're happy about that, maybe you're sad about it and of course, you're free not to believe it, but 1 -1 = 0 will still true regardless of what you feel about it and regardless of whether you and thousands of others believe it or not.
4. Then why keep presenting false answers and arguing with the proven/demonstrated scientific answers?
1. How do you improve on audibly flat/perfect? The only place to go from perfect is, by definition imperfect!
2. Who said it's the end all? "All" includes the human musicians, the transducers and the humans who subjectively mix and master the recording, none of which are digital and all of which can therefore be improved!
1. How is it an improvement to "bring to digital" all those things that digital was specifically invented to avoid? By definition, that's not an improvement, it's a degradation! 2. Correct, digital is not just analogue without the pops and surface noise, it's also without the rumble, wow/flutter, distortion, signal loss, generational losses and various other analogue artifacts.
2a. What "extra additive"? You can't seem to make your mind up, a few paragraphs above you said something was missing, now you're saying something is added. Either assertion could easily be verified, a null test will easily reveal if digital conversion is adding or missing something and exactly how much it's missing or added ... and guess what null tests actually prove? Does 1 - 1 equal something more or something less than zero?
1. Of course you cannot bring "life" into a digital signal, there is no life, it's just zeroes an ones and you can't bring life into an analogue signal either, it's just an electrical current. If you mean change the digital signal so that you perceive it to have more "life", then that is by definition a distortion, an audibly non-flat response. A very serious flaw in modern digital audio, as even relatively cheap digital devices have managed to avoid audible distortion for many years.
2. Digital is already complete. I, science and the whole world would love for you to someday demonstrate that Shannon was wrong and therefore that the whole digital age (not just audio) doesn't exist. Good luck with that!
2a. Vinyl plugins do degrade the signal, the same as vinyl does, which is why of course they call them vinyl plugins in the first place! If you perceive that degradation to be an enhancement, that's obviously an issue with your perception.
1a. Again, how can giving digital all the analogue faults it was specifically invented to avoid, be an enhancement? That's like saying, we can enhance the performance of a Ferrari to make it perform more like riding a donkey!
3. Digital is already the best of both worlds, that's why it was invented!
G