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

It's not that the distortion signature is too small, it's that no one measures it. No SPL meter is going to be better than ±0.1db @ 85dB. It likely has a nonlinear response. In absolute terms, it's not even close.

It gets measured alright. But I think I see what the confusion is. An SPL meter is only useful if the speaker is making sound, whereas we've been talking about measured output power. The two are not the same, owing to tube amps having a slightly higher output impedance in most cases- that will cause minor FR errors. My prior statement in this regard is correct:

at any given frequency, for a given amount of power into a given load (8 Ohms for example) the voltage and current will be the same on account on the power formula (1 Watt= 1 Amp times 1 Volt).

Back in the 80's Bob Carver tweaked an amp to sound exactly like another: The Carver Challenge | Stereophile.com

I remember that. He failed too; a 35dB match was all he could get.

FWIW, we gave up on matched level listening tests in the 70's simply because it's about as worthless reading the spec sheet.

If one amp was making more higher ordered harmonics, it likely would have sounded louder. An SPL meter gets to the bottom of that pretty quickly.

Don't conflate the spec sheets with the measurements. Spec sheets are IMO the Emperor's New Clothes. Measurements are not.

"The Final Achievement
After this last bit of tweaking, where Bob was able to reinstate his 70dB null while driving a very difficult load, we now had what sounded like two absolutely identical amplifiers." [emphasis added]

If one amp was making more higher ordered harmonics, it likely would have sounded louder. An SPL meter gets to the bottom of that pretty quickly.

¿Que? Loudness? Never mentioned it. We were matching level w SPL meter @ 1Khz and Pink Noise and also measuring amplifier voltage output w AC voltmeter. Some amplifiers were sonically very close and some not. Some better with one speaker and others with another. In the end, we came to the conclusion that synergy exists and it's not predictable.

Spec sheets report measurements, or at least some do. 😉

@ieales

FWIW, I’ve never measured a tube amp output voltage into a loudspeaker that was anywhere close to what an SS amp delivered into the same load... going back to the 70’s. Admittedly, it’s a small sample, and largely irrelevant as measurements mostly don’t mean diddly. 😎

if the voltage is within, say 10%, then the SPL will be also be very close.

 

Yes it is.

It’s not that the distortion signature is too small, it’s that no one measures it.

BS - it is measured ad naseum, and produces nausea in people that do not understand it.

No SPL meter is going to be better than ±0.1db @ 85dB. It likely has a nonlinear response. In absolute terms, it’s not even close.

BS - most people probably max out at 0.5 to 1 dB difference.
So getting the two systems within a fraction of a dB is a great start to a controlled listening test.

And I further disagree as I have the NIOSH app on my iPad as many low distortion speakers do not sound like they have a lot of SPL happening.
Then when I turn to someone in the room, we have to shout to hear each other… and when I look at the app says 90dB or more.

However on my wife’s old system it sounds loud at 65dB.
On my old system at about 95dB.
And on some state of the art systems mote like 100+ dB before it “SOUNDS” loud.

Back in the 80’s Bob Carver tweaked an amp to sound exactly like another: The Carver Challenge | Stereophile.com

FWIW, we gave up on matched level listening tests in the 70’s simply because it’s about as worthless reading the spec sheet. An amplifier is but one component in a system. Change one thing, change everything. I think it’s stood me in good stead when a guitarist says "Joe Pass is sitting RIGHT THERE!"

I trust Bob Carver about as much as a preacher.

1. He had some good designs, back in the day, but he’s prone to hyperbole and wild eyed ranting.
2. Some of his current designs do not meet specs and appear to be dangerous to safely use.

Other the other hand I have heard only good things about Ralph, and his writing indicates that he is learned in the subject and is rationally presented.

Lastly the use of the word “Synergy” has a magical tone to it, that to me is sort of like a synergy of faults summing to zero.

(IMO) It is easier to build systems were output impedances are low, input impedances are high, the FR and PR is flat… than spicing up bright and warm gear like a sweet-n-sour pork where things are starting out in major conflict.

There is difference between any piece of gear and any other one generally and in most cases for many reasons...It is common place experience...

Dont ask for a blind test please... 😁😊

There is also acoustic conditions which OFTEN make difference in gear minute one compared to room control...

And if you want good S.Q. buy first and to begin with some good gear....It is not so difficult because electronic audio engineering is mature technology for many DECADES... 70 years ? or 60 ? or 50 ? We must ask atmasphere for that, he knows....

But nothing will rival acoustic control and treatment to optimize and put your well chosen gear ON HIS PEAK WORKING POTENTIAL... NOTHING....

Certainly not upgrading a good piece of gear already for an alleged "better" one because of publicity by reviewers...

What we hear at the end is acoustically determined anyway ...A bad amplifier compared to a good one will not be changed by the room control in a good one for sure...but any good one will be TRANSFORMED in a miraculously good one...

All basic good design of amplifier and speakers are the starting point not the destination... Acoustic is the key....Nothing else...

i sell acoustic creativity not gear....

i concur with this post:

"If it measures good and sounds bad, –– it is bad. If it sounds good and measures bad, –– you’ve measured the wrong thing." –– Daniel R. von Recklinghausen, HHScott

The only measurement that matters is how it sounds in your system in your room with your program. Evaluation by any other method is foolish unless you are buying HiFi Jewelry or Furniture.

@mahgister it does not matter how well one treats a room in terms of the direct path sound.
If that sound is filled with distortions, then no amount of room treatments can work by going backwards in time to remove the distortions.

One would hear the direct path sound before any reflections arrive. Whether or not those reflections are high level or super reduced.

While the room may be important, it is not going to fix the amplifier.