Let me end the Premp/Amplifier sound debate ...

The question I always had with measurements, are we even measuring the correct things for human hearing parameters?  

We are, if all the measurements are actually made and often they are not.

I think I outlined what is needed to know the sound of any amplifier earlier in this thread. I find it interesting that those interested only in the specs discount the subjective aspect so vehemently. I think this arises out of not understanding that all forms of distortion are audible as tonality. That's a bit of connecting the dots. But once you understand that simple fact, the whole idea of things being 'audible and not measurable' goes away.

But you have to also understand what the measurements are saying.

Priceless remarks indeed like usual...

I will only add to "tonality" what is called "timbre" ....

The micro dynamic of the tonal playing instrument timbre reveal much about the system/room interaction...

In acoustic CORRELATION between measures and subjective timbre perception is crux of the matter...

Same in electronic engineering design like say atmasphere...

Then dividing subjectivist amd objectivist camp is preposterous ....

For sure it is always measurable but not always with a material external tool only like some claim but always measurable in the sense of correlating a tool measure with the subject hearing interpretation...It becomes after that a standard in acoustic and in engineering...

Dear @erik_squires  :  I know I arived late to your thread, an interesting one.

" And if that leads you to a crystal radio and piezo ear piece so be it.  "

well that could be something " extreme ". In general audio improved through the years and today any one can listen " differences ", only a deaf can't hear.

"  to remember Julian Hersch from Audio magazine and his very unscientific view that all amplifiers sounded the same once they met a certain threshold.  Now the site Audio Science Review pushes the same. "

In those vintage years electronics were designed and builded using the active and pasive devices that existed. Designers have not " hundred " of options about and along that the today high-end meaning was non-existent so de electronics designs were manufactured with way different targets than today units. In the other side the room treatment concepts was almost something new even for reviewers. Because of all those and several other reasons the systems were not high resolution ones and with this real limitation was not easy to find out quality differences.

I don't know today why ASR says " amps sounds the same "  because I don't have the specific link where they attest about.

But today it's almost imposible that 2  different manufacturer designs can sound the same.

As I said audio improved through the years, today passive and active devices improved really over those vintage years and exist more options that in the past. In the other side normally each designer has his own whole targets on what he will design and build. The circuit layouts are not the same in those 2 different manufacturer electronics and not only that but not only that because a designer can choose smd passive devices instead true hole and the power supply design of those amps will be different too with different choosed parts even the input/output connectors and internal wiring came from different parts manufacturers.Heatsinks are different too and even the amp class operation or the global feedback levels.

All those parameters/characteristics modulates each one amp quality performance and yes we can listen the differences no matters what because our system today has way higher resolution than in the past. Active/passive parts and design has its sound signature/coloration and this coloration is what we listen it. A few months ago I wanted to improve my external crossovers in the speakers and I posted a thread in Agon looking for help on capacitors: I was running V-caps and Soniccraft but already used Duelund/Mundorf/Jantzen/Audyn, Audicap, MIT/etc/etc suddenly I remembered that I have a lot of Wima caps that in the past I changed for " better " caps soI try the MKP10 and to my surprise it performed with higher quality levels, I finished using the FKP1 in combination with Kemet caps but I was using at the input of my monobloks ( cappacitor coupled. ) very expensive teflon cooper V-caps and I tested there the FKP1 and wonder what: outperforms the V-caps ! !Al these " unexpected ".

Today if electronics are working inside its specs develops very low distortions and when today amps are developing high distortion levels that we can listen is because those amps are been overloaded are been out of its headroom. Today is extremely difficult that we can listen amp distortions because those amp designs are well designed and the designer know that his competition just does not do it, today manufacturers puts high care about. Again, if the amp/preamp is running inside its design specs we normally will not hear distortions or almost no distortions.

@glennewdick  " are we even measuring the correct things for human hearing parameters?  "  Please re-read my last post because those kind of measurements you are asking for just does not exist and in my posts I try to explain about. Of course I can be wrong.

R.

But today it's almost imposible that 2  different manufacturer designs can sound the same.

That depends on how successful a design is with regards to its application of feedback. If there is enough feedback then issues of coupling caps and power supply design are rejected by the feedback itself. So two very different designs can sound the same if they have sufficient feedback and Gain Bandwidth Product. But it needs to be a lot in both cases, and such is really rare even today (as opposed to 20 or 50 years ago).

those kind of measurements you are asking for just does not exist and in my posts I try to explain about.

Certainly they do! But as I explained earlier, usually such measurements are not published if they are even made. So we have the 'obviously' persistent myth that we can hear something we can't measure.

@rauliruegas 

"  to remember Julian Hersch from Audio magazine and his very unscientific view that all amplifiers sounded the same once they met a certain threshold.  Now the site Audio Science Review pushes the same. "

When they have zero distortion, then by definition they will sound the same.
It is doesn’t take a lot of higher order harmonic distortion to sound pretty vile.
And a lot of low order harmonic distortion is hard to identify easily.

If we have one amp with only 2nd order harmonics, and another with only the orders of 3-N…. If their SINAD values are same (not zero), they will sound way  different.

So SINAD becomes most useful when the value is getting towards zero. If it is a long ways from zero, then we have a preference for the type of distortion that is listenable.

Maybe Mr Hirsch was hopeful that the ”certain threshold” was going to arrive sooner?