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In Reply to: RE: What Makes SET Amps Tick? posted by morricab on May 21, 2025 at 00:45:33
What really happens is masking occurs from lower harmonics being louder than the higher orders.
Lower ordered harmonics definitely add a coloration! Audiophile words like 'warmth' and 'bloom' describe this coloration, which is not objectionable unless it gets really profound. But don't fool yourself! The lower ordered harmonics are audible, and are not 'filtered out'. Wherever you got that is simply incorrect.
So its more accurate to say 'This means that what you are hearing, as long as you don't push the amp too hard, is effectively nearly pure because the lower ordered harmonics are not objectionable and mask the higher orders.'
Follow Ups:
Low order harmonics are audible only when they surpass the levels of self generated harmonics. Tests show 2nd harmonic is inaudible up to about 2%. for example.
If you are then the simple answer is he is simply incorrect.
You don't need me to hold your hand do you?
I saw this back in the day but I was less critical in my thinking back then so I will look afresh. Skimming some of it yesterday I was struck by how this is a Masters thesis from an EE department? Shouldn't psychologists be doing this work and, presumably hearing psychologists did not peer review it? None of the hearing data underpinning this work was created by him, and he goes from sweeping statement to sweeping statement. In my small perusal of this subject I found there were no sweeping statements but a lot of small steps and each one had some data that countered the main conclusion. He used the phrase 'all analog chain' at one point so we should be on guard as confirmation bias is a real thing in research. And when he talks of subjective results they are his and not unsighted panel results. This is more reviewer than researcher. Anyway, I shall read more and more thoroughly while staying aware of my own conformational bias that if the brain subtracts distortion from signals entering the ear how do we tell the difference between instruments and voices that get their character through distortion?
I can only say that having measured rare violins myself, the harmonic content of that particular instrument is very different from the monotonic decay the ear's mechanical mechanism makes. So, even if it did cut that out, there would be plenty to distinguish the rest...plus the levels are not really comparable. A violin playing at 85dB will be much louder than the ear's self generated harmonics.
However, I suspect that the wet supercomputer between your ears has other ways to determine the source and correlation between harmonics from the violin vs. harmonics from the ear mechanism. Could be related to phase adn locality proximity etc. etc. This could also then be why such small levels of amplifier distortion are still having an audible impact.
Maybe. Occam's razor might suggest that the addition of distortion provides the character that is missing from low distortion designs. However, I don't think the simplest explanation works in the audiophile world, it is usually the most expensive solution :)
I don't agree that this is the simplest explanation. To agree to this explanation is to then assume that nearly all recordings are deficient with regard to realistic sound quality. Is that likely? I think not.
A simple explanation following Occam's razor should not then open up a can of worms around the recordings.
For me the simplest explanation is that the most correct sounding amp must therefore be the one that is most free of audible distortions. The objective numbers are not so relevant.
IMO, believability in audio from the electronics is the absence of audible artifacts not necessarily measurable ones.
It also becomes clear to me that when a system makes most recordings sound grey and lifeless then it is not the recordings but the gear reproducing them...something is psychoacoustically off.
Whether you disagree with the idea of SETs adding something, as you do, I don't think it strengthens your argument if you fail to see that as a simpler explanation. Audiophilia does tend towards the exotic and expensive and, perhaps, that extends to theories also. I noticed that you did not simply measure the harmonic content of real instruments but of 'rare violins'.
Anyway, back to the topic in hand. It seems Cheever took his aural harmonic generation creation data from Olsen. A copy of that book should arrive today...
Read the Keith Howard experiment in Stereophile where he added different distortions to audio files. He found that NO added distortion sounded best but the least worst was alternating even and odd in an exponential decay. The worst was all odd harmonics, like most PP amps produce.
You used to be able to download the code and play with it yourself. I did and came to essentially the same conclusion as Mr. Howard.
I enjoy all of Keith Howard's writings. IIRC, there is not a big difference between any of the patterns and he struggled to order them.
There is a utility that allows you to add a desired amount of distortion see link. If I want to add a lot of low order distortion I simply play a record.As to Cheever, I obtained Olsen's text book referenced by DC and it contains the same graph but Olsen attributes it to someone else. I obtained that paper and though relevant it is not the source for that graph so more searching required. What I can say is that Cheever misinterprets that graph - it shows the level of a fundamental at which it's harmonics are detectable. They are not the absolute level of the harmonics as the author suggests! The next graph is probably the most important, similar data attributed to Olsen but that must come from a different book. I will seek it out to find how the testing was done.
Edits: 06/01/25 06/02/25
I think he didn't think it through. I explained why elsewhere on this thread.
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