Do all amplifiers sound the same thread

[Steve81]

I would just say that if the sound quality of your speakers is awesome to you at all the volumes your heart desires, then don't worry so much about the "measurements and specs" of the amps.

That's what it comes down to. Measurements and specs are only a means to an end, not the end itself.

 

[Irvrobinson]

I like his methodical approach. What he says makes sense based on background. However, I would like to see more of a correlation between the subjective experience and measured levels of distortions

That may not be practical. In most cases we're talking about levels of distortion that are below the perception level that makes things obvious. Even with tube amps we're usually talking about frequency response aberrations more than we are distortion.

The challenge is that humans often respond to influences that aren't obvious. Background conditions that you learn to ignore can still fatigue you. This test was run at a level of 40db, which is very quiet. I wonder how seriously listening to music compares to mental arithmetic?

 

[ski2xblack]

I like his methodical approach. What he says makes sense based on background. However, I would like to see more of a correlation between the subjective experience and measured levels of distortions

I found it interesting in that he specifically minimized any discussion of correlation. He did make a case for how complex signals when amplified by multi-stage amps with heavy use of nfb can cause unexpected distortion products, significant enough that they should be audible.

Then again, Mr. Pass is a shrewd marketer of extremely minimalist (and expensive) designs, and I can't help but read the article with that in mind. That's why I wanted to pick your brains.

 

[Hobbit]

This are exactly the kinds of tests I was suggesting doing. This graph is the output of a spectrum analyzer with the input to the amp (AVR in this case) under test being a frequency generator. I'm an EE, and admittedly not the best versed in audio engineering (particularly terminology), but the concepts are not rocket science. However, I do get to run tests like this for various top secret projects

 

[3db]

That may not be practical. In most cases we're talking about levels of distortion that are below the perception level that makes things obvious. Even with tube amps we're usually talking about frequency response aberrations more than we are distortion.

The challenge is that humans often respond to influences that aren't obvious. Background conditions that you learn to ignore can still fatigue you. This test was run at a level of 40db, which is very quiet. I wonder how seriously listening to music compares to mental arithmetic?

Good article. This poses yet another question.... if auditory memory is poor and distortion levels are below perception, how can one hear the difference between amps? Does the distortion influence from the very start or is there some threshold of time where it begins to affect us?

When I swapped in the Yamaha RXV-1800 for the Technics SA DX940 AVR, I could not tell any difference in performance between the two until I pushed their limits. The Technics being not as powerful began to distort earlier then the Yamaha but until that point was reached, no difference in sounds were perceived. Even at levels into the high 80 dbs, both sound identical...I think. I say and I'm wondering if the auditory memory factor influenced my perception.

 

[Irvrobinson]

Good article. This poses yet another question.... if auditory memory is poor and distortion levels are below perception, how can one hear the difference between amps? Does the distortion influence from the very start or is there some threshold of time where it begins to affect us?

I don't know. Several years ago I came to the conclusion that while I couldn't differentiate between the sound of amps while trying to listen for differences, assuming the amps were well within their performance envelops, I still found myself developing preferences for amplifiers, sometimes with amps I did not want to have a preference for (like the Class A Krell monoblocks I used to own). I tried to explore why this might be the case, and went down the behavioral sciences path, which is where that link came from. There are many studies available for how very subtle sensory input affects the brain. (There is more research on visual input than audio input.) I came to the conclusion that I would never find a conclusive answer, but I also began indulging my unexplainable preferences more in amplifiers.

 

[KEW]

I don't know. Several years ago I came to the conclusion that while I couldn't differentiate between the sound of amps while trying to listen for differences, assuming the amps were well within their performance envelops, I still found myself developing preferences for amplifiers, sometimes with amps I did not want to have a preference for (like the Class A Krell monoblocks I used to own). I tried to explore why this might be the case, and went down the behavioral sciences path, which is where that link came from. There are many studies available for how very subtle sensory input affects the brain. (There is more research on visual input than audio input.) I came to the conclusion that I would never find a conclusive answer, but I also began indulging my unexplainable preferences more in amplifiers.

Intriguing post!
I have a hard time believing such differences don't show in lab results. Maybe they do and we don't know how to view the data.
Or maybe your blood sugar was a touch higher when you listened to the amp that sounded better?

 

[AcuDefTechGuy]

Or maybe your blood sugar was a touch higher when you listened to the amp that sounded better.

I would say its related to the serotonin and norepinephrine levels; decreased levels are associated with depression.

Or it's related to the opioid levels; increased levels are associated with euphoria.

Or it could be alcohol levels.

 

[Gordonj]

Or it could be alcohol levels.

Im going with that one....

Maybe an alcohol level to IM distortion test showing the relevance increase in sound quality with increased alcohol content...

 

[3db]

Im going with that one....

Maybe an alcohol level to IM distortion test showing the relevance increase in sound quality with increased alcohol content...

Perhaps it works the same way visually as well....... waking up in the morning and pulling a coyote

 

[Jeff R.]

Im going with that one....

Maybe an alcohol level to IM distortion test showing the relevance increase in sound quality with increased alcohol content...

It's about time somebody solved this question.....

 

[KEW]

Im going with that one....

Maybe an alcohol level to IM distortion test showing the relevance increase in sound quality with increased alcohol content...

Friends don't let friends buy speakers drunk!

 

[Gordonj]

Perhaps it works the same way visually as well....... waking up in the morning and pulling a coyote

BINGO -

UREKA - A/V*%ALCin/AGL=IMp

where:
%ALCin = Percent of Alcohol intake
AGL= Age of Listener
IMp = Perceived IM

Done

 

[Adam]

Friends don't let friends buy speakers drunk!

True, but friends also don't let friends drink alone. See the problem?

 

[Gordonj]

Im just going to use this amp for my system and be done with all of this testing , sound better, alcohol content thing....


http://www.crownaudio.com/media/pdf/legacy/belchfire_datasheet.pdf

 

[KEW]

True, but friends also don't let friends drink alone. See the problem?

My system sounds worse because you made my brain hurt!

 

[Irvrobinson]

Intriguing post!
I have a hard time believing such differences don't show in lab results. Maybe they do and we don't know how to view the data.
Or maybe your blood sugar was a touch higher when you listened to the amp that sounded better?

I know there has been some work in software that takes any signal, like music, and uses a hi-res ADC on the input and the amp's output to produce a difference signal between the input and the output that can literally be analyzed. Perhaps I'm just not looking for it, but I haven't seen a product or any papers on this yet. I wonder if that's the ultimate answer. In theory you could analyze everything, including timing and phase differences that might be audible.

 

[Irvrobinson]

Or it could be alcohol levels.

Not in my case. I don't drink.

 

[Gordonj]

I know there has been some work in software that takes any signal, like music, and uses a hi-res ADC on the input and the amp's output to produce a difference signal between the input and the output that can literally be analyzed. Perhaps I'm just not looking for it, but I haven't seen a product or any papers on this yet. I wonder if that's the ultimate answer. In theory you could analyze everything, including timing and phase differences that might be audible.

Are you referring to a dual function FFT measurement. Where it takes the input from any type source (pre system) and compares it to the output of the device or system and shows the delta in freq., phase, time etc.? This function along with MLS testing and Impulse Response FFT exist currently more often these testing functions are utilized for speaker testing though.

 

[PENG]

I know there has been some work in software that takes any signal, like music, and uses a hi-res ADC on the input and the amp's output to produce a difference signal between the input and the output that can literally be analyzed. Perhaps I'm just not looking for it, but I haven't seen a product or any papers on this yet. I wonder if that's the ultimate answer. In theory you could analyze everything, including timing and phase differences that might be audible.

In practice too, someone just has to do it. People had been to the moon and back, the science and tech behind amps are pretty basic in the grand scheme of things. Problem is, no matter what the labs do and show, there are always die hard ones who would insist on "well, those aren't the ends, got to trust your ears.....even a low cost amp makes a huge ....and yep at any volume blablabla..... and being open minded we have to find ways to rationalize why at 2W or less a low cost amp would do such wonder to a high cost AVR. For me I stick with high quality media source and speakers where I hear the difference easily and can enjoy the improvements instantly without the need to beat the dead horse first with 3 DB and Steve.