How close to the real thing?

Irvrobinson,

how does that 4ohm+ output impedance affect interaction with the loudspeakers

As Atmasphere states, provided that the output impedance is purely resistive in nature, that is, it does not behave like a capacitor or coil to any degree over the frequency range mentioned, then its effect will be totally benign. Even if it were ridiculously high, say 100ohms, same applies. All the latter would mean is that the speaker would never get very loud!

I also agree with Atmasphere regarding "decrease the propagation delay of the circuit", this is exactly what needs to be done to allow any feedback to do its job. Some people may not be aware that several highly regarded SS amps consisted of nothing more than an output stage driven by a high quality opamp, with, by normal standards, extremely high levels of GFB.

"objectivist's" belief system usually can't include a reality outside simple regurgations of common-practice electrical analysis found in an average undergraduate EE textbook, and the "subjectivist's" belief system is so fundamentally undisciplined as to be able to include some really silly, wacky sh*t.

Human ears (and brains)are complex sensors and information processors of an order far exceeding science or technologies ability to model exactly.

Agree 100% with both of the above

Frank

Irv raises a good point about the interaction of high amplifier output impedance with speaker impedance vs. frequency variation. An OTL amp having a 4 ohm or other comparably high output impedance will not be a suitable match for some speakers. See Ralph's Competing Paradigms paper for additional discussion of this subject.

Regards,
-- Al

Kirkus, I think you missed my point! The quote you put up is edited and not what I said. Try re-reading my post, without the idea that I am trying to make you wrong- that was not my intent at all.

Irv, maybe you were joking but Sound Labs have anything but a flat impedance curve. Just because a speaker has a variable impedance curve does not mean that an amplifier with a high output impedance cannot drive it well, without tonal anomalies. It is all in the intention of the designer, as the article that Al linked points out.

A vital point here is that distortion in amplifiers and speakers is perceived by the ear as a tonality, and without this understanding that tonality won't get measured. This is close to the heart of the subjectivist/objectivist debate. Once you understand how the ear/brain perceives things, a lot of this debate goes away.

Atmasphere, maybe I did miss your point, but I did re-read your post . . . and I think my quote was verbatim. But the logical problem remains -- I'll see if I can't address it first via Mapman's quote:

Human ears (and brains)are complex sensors and information processors of an order far exceeding science or technologies ability to model exactly.

Given this truth, any hypothesis regarding being able to accurately predict the outcome of an individual's listening experience based on science alone, even in a properly executed scientific experiment or series or experiments, has to come into question.

This argument is closely akin to Progress ad Infinitum, one of the tropes of skepticism as outlined by Roman philosophers (Sextus Empericus?) in the first century A.D. . . . that is, anything that can be regarded as proof must in and of itself be proved, on and on to infinity. So under this line of thinking, knowledge in and of itself cannot advance or become closer to the truth . . . leading to the trope of Assumption, that all scientific knowledge is merely theory and not truth.

But our entire craft of audio is among countless obvious artifacts that indicate that our knowledge of the physical world is indeed expanding and becoming more precise, thus closer to the truth. Karl Popper dealt extensively with the logical basis for this through his concept of "verisimilitude", or the extent to which a scientific theory resembules the truth.

It is through this concept that we can look at the evolution of ideas from Copernicus, to Galileo, and to Newton . . . with today's knowledge that all their views of the physical world were false. But each of them was able to formulate ideas with greater verisimilitude, building on the work of those that preceeded them. And for the original topic of this thread, I think it's indeed undeniable that our ideas about the understanding of sound perception and reproduction have greatly increased in verisimilitude, and gotten us closer to the truth . . . especially when viewed over the span of the last 150 years or so.

It is on this basis that I fundamentally disagree with the popular audiophiles' notion that Mapman articulated. We can indeed use science to predict the outcome of an individual's listening experience, even though the extent to which we can is still significantly inconsistent and variable. But we are continuously improving our ability to do so, as the logical result of our scientific theories ever evolving toward increasing verisimilitude.

My point to Atmasphere is this: as people involved in the design and manufacture of artisan audio equipment, we are of course required to evaluate the "truthiness" (Stephen Colbert's word) of the performance of our own, and others', equipment. And we then use such an asessment to determine the verisimilitude of our theoretical ideas.

It's my impression from many of your past postings that there are a handful of conceptual errors in your understanding of the traditional application of negative feedback and its Nyquist stability criteria . . . to the point that a discussion of the associated theory and measurement performance is moot.

But I (very respectfully) remain curious as to whether or not you've ever had an auditory experience that pegs the needle on your own personal, internal "sonic truthiness" scale? And has it ever been delivered by equipment that has a design approach that's incongruous with your own? (Please note that the phrase "pegs the needle" is an important one, meaning that at the time of the experience, an experience closer to the truth cannot be imagined and/or is simply irrelevant).

My friend, a viola player ("violist") recently tried out for the "Marine Chamber Orchestra" (also known as "the President's own") so I asked him if he had ever heard a high end audio system. He said he once went to the home of a conductor who had a stereo system that "took up the whole wall" - (clearly fitting the description of the impoverished musician who is unable to afford high end audio!).

I asked him how it sounded and he said "Great!".

I then asked him if it sounded "real" and he looked puzzled and wanted to know what I meant by that. I responded that I wanted to know if it sounded like a live performance (knowing that he plays live, unamplified music in an orchestra) and he looked at me smiling and said:

"Are you kidding? Of course not! It can't, its not possible to reproduce those sounds and the sense around you."

Ed