To be quite honest that was mostly about DACs...
However, the part about preamps was about that Audio G*D preamp.
And, point blank, I would not own a preamp that purports to "have a sonic signature"... even if it supposedly "makes things sound better"... unless I can bypass it.
I am quite simply not convinced that there is any such thing as "a coloration that makes
EVERYTHING you play through it sound better".
Any coloration I have ever heard that made some things sound better also made other things sound worse.
(So I want both the option to compare with it on and off and the option to bypass it if I prefer it that way.)
Now, as for DACs, I agree that DACs are a bit of a "grey area".
On the one hand, as you say, there is no way to actually know for sure which one is closer to the original.
If the numbers are bad enough you can usually count on it sounding obviously bad... or at least obviously colored.
But there are also a significant number of ways in which the numbers can be quite good but the end result can still sound different.
HOWEVER, to some degree, if you listen to enough of them, and know enough about the ones you listen to, you can eventually discern "patterns".
For example, to me, many poorly designed DACs tat use Sabre DAC chips sound what I would describe as "oversharpened"...
While I have my suspicions, I cannot tell you the exact cause, and many of them have exemplary specifications.
However I can tell you that this is a common symptom of a poorly implemented Sabre DAC chip.
(I've never heard a DAC with a different brand of DAC chip that sounded bad in exactly that same way.)
It's also worth noting that, with DACs, while we may not have "the real original", we
DO have the digital content we're playing.
Therefore we can determine "what an accurate analog conversion
OF THAT DATA should be".
We can also at least sometimes look at the response characteristics of the filters a certain DAC uses and actually characterize "where and how they're wrong".
What we have are
measurements of the audio signal...
And we can expect the DAC to be making its best attempt at giving us a match to those measurements.
So, if I were to ask ten different people to "cut me ten inches of string", there would definitely be slight variations...
But, if someone were to give me a piece that was
SIX inches long, we would both agree that it was clearly wrong.
We can at least hope that all DACs are "approaching the correct answer", even if they do so from different directions, and with varying degrees of accuracy.
I should also point out that, with some experience, it is possible to learn, to at least some degree, how filters affect the sound.
For example... ringing is a characteristic of how a DAC handles transients...
Therefore, if several filters are equally flat, but have different transient characteristics, then, if the difference is audible, you should expect to hear it on transients...
(So listen for it on plucked guitar strings and brush cymbals...)
And, in a different situation...
A DAC requires a reconstruction filter... it is required by the "math that governs the conversion"...
The reconstruction filter
MUST be applied at the proper point in the conversion process in order to get the correct result.
(And anyone who claims otherwise is either misinformed or they are lying to you.)
So, if some boutique DAC omits that filter, we can only guess if it sounds good or not...
But we
CAN know for an
ABSOLUTE CERTAINTY that its output is
NOT correct...
(And we can also infer that whoever designed it doesn't understand the technical underpinnings of A/D and D/A conversion very well... or they just plain don't care.)
From my experience DACs come in four basic "types"...
1. DACs with a single filter - where the designers did their best to provide an accurate rendering of the original (by whatever metrics they use)
2. DACs with a single filter - where the designers deliberately designed their DAC to color the sound so that it has a unique sound signature
3. DACs with multiple filters - which offer the end user the choice of "which minor discrepancy from reality they prefer"
4. DACs with multiple filters - which offer a huge variety of filters, each of which sounds entirely different, with no attempt at accuracy, "to give their customers a choice"
I would also say that "neutral sounding DACs
DO converge on a similar sound...
(And, after you listen to enough of them, you get at least some idea of what it is.)
You've shifted gears on us here,
KeithL - We
were talking about DACs, now we're on preamps?
...That's why I would never "trust" a DAC or preamp that "makes things sound different in a pleasing way" unless I had the option of bypassing that "improvement" if I choose to...
OK - back to DACs again? What DAC have you ever heard of that offered bypassable "improvements?" On a preamp, maybe, but DACs are usually "plug and play" devices whose sound (excepting the possible choice of filters) offers no option of "bypassing improvements." Which filter is the "real" sound? You can choose the one you THINK sounds most real or sounds best, but you've no way of knowing which is the most accurate to the original recording.