I don't want to beat a dead horse but I'm bugged.

You posit they'll all sound the same,  apparently, you trust the measurements over human sensory perception.

We need to be clear about something. You specified that the measurements would be the same, and I have to assume that includes all measurements, not just 'some'. If that is true then indeed they will sound the same, having the same bandwidth, same distortion spectra, same distortion vs frequency curve, same output impedance and so on... yes, they will sound the same.

My point is that the important measurements just simply are not made nor presented. 

Most of the differences we hear between amps is their distortion signature, to which most audiophiles refer to as the 'sonic signature'. I've described how the distortion affects the sound of the amp earlier.

Ralph what you are referring to in terms of measurements is far removed from what we are presently being provided from these sites and their advocates. I would sincerely welcome legitimate and predictive measurements.

@charles1dad ASR is actually providing a lot of information, much of it quite useful. They don’t always hit the nail on the head (see the PSAudio regenerator review where Amirim pretty well missed the point). But they do graph distortion vs frequency and usually show the distortion spectra. I’d like to see the distortion spectra a -6dB of full power in addition to 1 Watt, and also see the distortion vs frequency at 1 Watt, -6db of full power and also full power. They could do all that if they caused their hands to move. So my opinion of them is higher than yours; and I think they can do better with little effort.

If you see distortion rising with frequency take that as a Bad Thing (likely bright and harsh, not what you like if my guess is right 😉). Your SETs don’t do that, neither do our OTLs or any zero feedback amplifier. Amps that run feedback need to not do that too. So right there you know something very useful that is routine on that site.

@atmasphere When I'm speaking of accuracy and it's association with color, I'm thinking about two components that measure exactly the same in every measurement undertaken. Now lets say those measurements are such that one was deemed to be an accurate component. Will these  two components, or any number of components tested, meeting the above criteria necessarily sound exactly the same.

There is a failure of logic in this post. If all the proper measurements are taken and they are the same, the two pieces will sound the same too.

Since the rest of your post is based on a faulty premise, you might want to rethink this.

40 years ago it really wasn't practical to do the measurements that we can today. Sometime in that period we turned a corner. But the important specs don't show up on spec sheets for the most part (I do remember seeing an Adcom spec sheet clearly showing an increase in distortion above 3KHz, showing why the amp had brightness and harshness- even 20 years ago, this stuff was starting to show up). But audiophiles for the most part are living their lives as if the only measurements we can make were those of the 1980s and before. Back in those days the spec sheets were the Emperor's New Clothes- an amp that looked good on paper rarely sounded good as well.

This problem of audiophiles living their lives according to how things were 30-40 years ago has caused a lot of suffering (and to be clear, when people have made up stories about life and life does not agree with those stories, that is the source of all human suffering). Back then, if the manufacturer, distributor or dealer's lips were moving, he was lying and this has been a way of life for so long that we collectively no longer think about the fact that we are being lied to, we just know and accept that we will have to take the damn thing home and listen to it to know how it really sounds!

We are living in a transitional time where the measurement tech has caught up with our subjective experience- now we can measure things that we hear with excellent correlation. The problem now is actually seeing the specs we need to see and knowing what they are telling us.

I've outlined all this previously.

Rather the point is that measurements aren’t reliably predictive of what a given audio product will sound like. They do not replace the act of listening.

@charles1dad 's comment here puts this dilemma in a nutshell- although I've always appreciated his comments as being some of the more level headed seen on this forum, the simple fact is that we have arrived at a point where the quote above was true at one point but isn't any more (although his advice of simply listening to see if it works for you is quite valid). If we do all the measurements (including in the room itself) we can quite reliably predict how things will turn out. Honestly it appears to me that people don't do all the homework. For example, how many here have run pink noise through their system to see how it fares in the room? FWIW these days that is quite easy compared to only a few years ago- as they say, 'there's an app for that'.

Pink noise can show you room issues, breakups in speaker cones, all sort of pesky stuff! It won't show you brightness caused by distortion, but you can get that information from proper measurements of the electronics.

FWIW I fault the 'objectivist' camp as much as the 'subjectivists' in this debate. Many of them don't know about all the specs that make a difference and allow their expectation bias to color their perceptions. IOW guilty of exactly the same thing as the people they fault. That is no way to make progress! Put another way if one is in possession of the facts, then one knows there is no good reason for objectivists and subjectivists to be at odds.

@charles1dad To my understanding the idea of tone color predates audio technology.

If we reach a point where sound quality can be accurately predicted by measurement I’d have zero resistance or issue with it. My point is acknowledging we are not remotely close to doing that now.

Currently used measuring techniques seemingly can’t hold a candle compared to the extraordinary capabilities of the human ear-brain axis processing pathways (Thank you @mahgister ).

You can use cheap off the shelf Op-amps to allow any mass produced entry level DAC to measure quite well and yet sound utterly underwhelming (Like crap).

AFAIK we're there already. Its just that for the most part we never see the important measurements; quite often they simply aren't made! This gives rise to the idea that we don't have the technology to do it.

The trick with opamps is to not use too much gain! The best of them are not good for about 20dB before you get into trouble with GBP. If a designer ignores the impact of that you get into colorations- even though it 'measures well'; but I suspect if the full battery of measurements were applied the problems would turn up easily enough!

I notice no takers on the accurate contention some objectivists maintain is optimal. How would this so called accurate system play with these recording colors? And that's a simple question to answer. Accuracy contentions in audio reproduction is a meaningless term. Prove accuracy is colorless, and further prove an accurate component or system is absolutely accurate. With some measure of critical thinking you'll find it impossible using objective analysis and/or reason.

@sns 

Well, I was out of town yesterday...

Its not exactly clear what you mean by 'color' but if you can accept the idea that the original performance has color and that the recording thereof also has color, then an accurate system will convey that color.

A less accurate system will convey additional color not present in the recording... two opposite example: the brightness of a system employing solid state amps or the excessive warmth of a system employing SETs.

The problem here might be the terms used, since 'coloration' is usually a bad thing in the context of getting as close to the musical event as is possible. But instruments have tone 'color'; one must be careful to not conflate the two ideas!

Many amplifiers on tested on Stereophile and ASR meet those criteria

This statement is misleading IMO. Most fail requirement 1) of my prior post. If you look at the distortion amount and its spectra, you’ll find that most amps have distortion rising with frequency and the spectra changing along with it.

This is because (as I’ve mentioned before) that they lack sufficient feedback, because they also lack sufficient Gain Bandwidth Product. There are exactly two ways around the problem of rising distortion and changing spectra:

1) build the circuit with zero feedback and wide bandwidth

or

2) build the circuit with really enough Gain Bandwidth Product to support over 30dB of feedback (such that feedback is actually the same at 15KHz as it is at 100Hz).

Most amps spec’ed to have ’30dB of feedback’ might have that at 1KHz but they will be less than that at 10KHz since the feedback is falling off due to insufficient GBP. This causes distortion to rise with frequency and it also means that the distortion caused by the application of feedback can’t be corrected by the circuit. That translates to ’harsh and bright’ and we’ve all heard amps with this problem; we’ve been hearing them for the last 60-70 years! There are plenty of amps made like that today and only a very few that actually meet the requirements stated in 2) of this post above if they have feedback.

I do believe at some future point this dilemma will be properly solved. It sure is not the case now.

Its not that we as an industry can’t do it, its that we lack the will, plain and simple. You do also need to know enough to understand how something will sound by looking at the distortion spectra... I’ve no doubt that some of these measurements don’t occur because there isn’t the education out there to really understand the data! Plus- heaven forbid- you know how something sounds by looking at the measurements!

It seems many amplifiers have lots of negative feedback and they have low distortion at 20Khz.

I don't think it is back in the day any more. There are lots of amplifiers on Stereophile and ASR that have very low distortion at 20Khz. Lower than this Rogue at almost any frequency.

It needs to be more than just low distortion at 20KHz although that certainly does not hurt. What is important is four things; if these four things are met, the amp will be easy to listen to, regardless of its technology:

1) the distortion will be consistent at all frequencies- the same at 100Hz, 1KHz and 10KHz.

2) the distortion spectra at 1 Watt will be such that the higher ordered harmonics will not be audible- for whatever reason.

3) The distortion spectra at 6dB below full power will also prevent higher ordered harmonics being audible.

4) IMD is well controlled.

These things sound simple and easy but they can be quite tricky! Most amps fail them outright- and sound bright and harsh as a result, even though they 'measure well' otherwise. The real problem isn't that they measure well, its that the proper measurements aren't made at all!