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

The difference you hear isn't on account of power!

Yes it is.

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.

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!"

@ieales , @atmasphere is absolutely correct. Debating opinion and supposition with facts presented by one of the foremost authorities on the subject is rather futile. You may wear down his willingness to contribute to educating others on the subject but you won't change the facts. @atmasphere is universally respected by amplifier designers, be they solid state or tube gear designers, who are universally respected.

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.