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Old 25th February 2004, 01:02 PM   #1
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Default What harmonic does to sound?

As an amateur, I always wanted to built a good sounding power amp. From this site, I learn alot and it comes to this question. A good sound reproduction cannot be separated to its harmonic. While in theory, harmonics are distortion, which should be eliminated, I found that good sounding amps in the market are not completely doing that. Tube amps are the main example. It is said that tube amps produces big second harmonic so it sounds good to most of the people.
In some thread, I read that an audio power amp with excellent measurement figures do not sound so good. Also in some thread, it is said that audio power amp that is too "clean" produces sterile sound.
From the cct itself, like if we use differential at the front end, it is said to eliminate the even harmonic. Maybe this is why the JLH power amp do not use differential, only use 1 transistor for its front end. This can be seen more in tube amps.
What harmonic is really add pleasant sound? What is really the meaning of odd harmonic, even harmonic, second harmonnic etc? If differential is canceling even harmonic, is there a circuit that cancels odd harmonic? It seems even harmonic is the one that makes good sound.
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Old 25th February 2004, 05:13 PM   #2
lucpes is offline lucpes  Romania
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There is no recipe on how to bake a good sounding amp. In a SS amp, even order harmonics are said to give a more pleasant, tube-like sound, but it's not really going to sound like a tube amp, 'tube sound' also involves some dynamic compression. The nature of the second & even harmonics make the sound have 'more body' and be less harsh. Accurate is not always good, but accurate does not have to mean that it sounds worse than a tube amp That's why there are people who won't put a tube amp in their system no matter what (this, BTW, is the solid-state forum

One can not just say that what measures good sounds bad. It's just that measurements cannot say how an amplifier will sound, and similar (in measurements) amps sound totally different. You may find amps that measure very good and have a very good sound, amps that measure good but sound like crap or any other combination.

I don't know if I read this in these forums but a wiser person said:

If it sounds bad and measures bad it's bad.
If it sounds bad and measures good then something's wrong with it.
If it sounds good and measures good everything's fine.
If it sounds good and measures bad then you've measured the wrong thing.

I'd also mention that the degree of subjectivity in audio is rather high, not to mention the very short-term memory when it comes to qualifying sound/quality.

Anyway, I'd say that you have to trust your ears to judge a bad amp from a good one
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Old 25th February 2004, 05:30 PM   #3
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Quote:
If it sounds bad and measures good then something's wrong with it.
nah, you just have to wait for it to break-in.
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Old 25th February 2004, 06:00 PM   #4
sam9 is offline sam9  United States
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My personal rant follows - take it how you will.

The question also is what does it mean to "sound good". I have found the following link confirms some of my suspicions/pejudices:

http://www.enjoythemusic.com/magazin.../audiohell.htm


My problem with "good sounding" tube amps is that they really do sound "good" but that after while everything played starts to have sound the same in some sense and the experience becomes boring. I presume this to be the a sign of harmonics overlaying the artists creation.

By analogy, it is like wearing rose tinted glasses in to an art museum. The first couple of painting look REALLY PRETTY, but after while one notices the same coloration over everything from medeval alter pieces to Rembrandts to Otto Dix to Warhol and you realize something is very wrong. Not only should some of these look radically different from each other, but some are NOT supossed to be pretty at all! You might as well be viewing a collection Elvis-on-black-velvet portraits (or at least tourist-trap seascapes).

Thus for me "nice sounding" amps in the sense of colored with harmonics ultimately turn everything into elevator music.

Yeech.
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Old 25th February 2004, 06:40 PM   #5
sreten is offline sreten  United Kingdom
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there are cogent arguments that each harmonic should
be weighted by n^2/n, over simply summing THD.

Class aB amplifiers produce liberal harmonics to at least n=20,
exacerbated by the fact these harmonics are effectively
differentiated by the effects of falling feedback in single pole
compensation.

It is entirely true that two amplifiers with the same THD can
sound different due to harmonic spectra, and that a amplifier
with a given THD can sound better than another with lower THD.

I am not of the school of thought that says some 2nd harmonic
distortion is good, I am of the school of thought that would
ignore 2nd harmonic distortion (and THD) if it meant higher
harmonics could be reduced.

I'll also point out that generally even harmonics (2,4,6,8 etc)
are reduced by symmetry whilst odd order (3,5,7 etc) cannot
be by topology.

I'm generally of the opinion that fully symmetrical amplifiers are
missing the point somewhat, and that fully symmetrical is not
desirable per se as a design goal if single ended is better.

And that for frequency dependant distortion, which applies to
an input stage, any distortion should be avoided if possible.

And as a final caveat, amplifiers distortion figures at high power
are not directly related to those at around 1W to 5W, which
most of the time is what counts.

edit : just a final note - tube amps produce low levels of high
harmonics and the spectra is not distorted so much because
of low levels of overall feedback, they do not sound better
than transistor amplifiers because second harmonic is higher.

sreten.
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Old 25th February 2004, 07:23 PM   #6
Svante is offline Svante  Sweden
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Popping in here... If you are interested in hearing how different harmonics *sound*, you could try this little singing synthesiser. It has a lot of things that are not relevant for this topic, but just set flutter and vibrato amplitude to 0 and uncheck all formants. Now you can combine partials by dragging on the partial graph.

http://www.speech.kth.se/music/downl...tool/madde.exe

Not that it is the same as distortion, but it is fun...
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Old 25th February 2004, 08:08 PM   #7
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Quote:
In some thread, I read that an audio power amp with excellent measurement figures do not sound so good. Also in some thread, it is said that audio power amp that is too "clean" produces sterile sound.
Disagree. There is a bad premise in these all-too-common statements. It is that the measurements are comprehensive. Which they aren't.

I want to hear the instruments and their harmonics as recorded. I am confident that they are perfectly fertile. So an amp that changes nothing about them is the one for me. I don't want any modification or extra harmonics thrown in, nor should it be necessary to do so. These "sterile" amps are modifying the original music content: it's not that they are too clean, rather it is that they are too dirty.
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Old 25th February 2004, 08:33 PM   #8
sam9 is offline sam9  United States
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Default sam9

"And as a final caveat, amplifiers distortion figures at high power
are not directly related to those at around 1W to 5W, which
most of the time is what counts."

To expand on the above, single point distortion figures are pretty useless. Even a boom box gets good figures at 1W at 1kHz! If I were king, distortion data would alway be presented as a 20-20kHz plot at 1W, at 3db below clipping, at rated power and at 50% of rated power. Or at least something along those lines. I would also dictate that graphical presentation have some standards about scaling the axes. Oh yes, do all of the above for both nominal 8 ohm and 4 ohm loads. The chance of this happening is virtually zero, of course.

The reasons I would like the above scheme are:
A- some designs may be ok but unstecpacular at 1kHz but have much better results at high freqencies

B- different designs figures change at different rates as rated power or clipping is approached

C- "Rated power" is ambigous when one maker calculates is from the rail voltage while another calculates at peak voltage before near-clipping distortion sets in.

D- Ones particular circumstances (speakers, room size, favorite source material, and even age based hearing loss) could be better addressed with more complete information which would allow one to make the trade-offs ther best suit ones needs.
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Old 25th February 2004, 08:41 PM   #9
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Hi,

My 2 cents:

http://www.zainea.com/multidimensionalaudio.htm

Note that this was written 35 years ago. I love this one:

"Before the days of so-called Hi-fi systems there were no audio measurements, there were only natural sounds with a perfect signal to noise ratio, unlimited power handling capability, no distortion of any kind, but the number of people with a possibility of ever listening to music was rather limited. Then came Hi-Fi. The invention of the phonograph record ruined high fidelity, but made music universally available."

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Old 25th February 2004, 09:46 PM   #10
azira is offline azira  United States
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Default Re: What harmonic does to sound?

Quote:
Originally posted by lumanauw

What harmonic is really add pleasant sound? What is really the meaning of odd harmonic, even harmonic, second harmonnic etc? If differential is canceling even harmonic, is there a circuit that cancels odd harmonic? It seems even harmonic is the one that makes good sound.
There is already quite enough posts and information about the technical stuff which is very valid. If you listen to music instead of pure sine waves, here's a slight twist.

Music Theory 101...

Music is made up of notes. This includes voice; Acapella singers generally try to vocalize notes. For simplicity lets just take a simple instrumental piece, piano or classical guitar. It would be boring if music was played using single notes at a time. This begs the question: what also sounds "good" with a particular note? Well music theorists have answered this. "good" in music is a term called: consonant. The most consonant note to go with a note is obviously the same note. This is known as octaves of that note. Octaves in frequency terms are doubling or halving of the frequency. This means harmonics, specifically the 2nd, 4th, 8th, 16th, etc... notice all even. Well that's good, but what else sounds good with a note. Ask any trained musician and you'll find out that the next most consonant note is something called a 5th. 5ths in frequency terms are 1.5x a fundamental. Wait a minute, that means it's the 3rd harmonic. It's odd. Are there other odd harmonics that are consonant? Actually yes, for example, the 5th harmonic is known as a major 3rd. It would be the next most consonant sound.

There is a pattern. Low order harmonics are more consonant, they become more dissonant as they get to higher order.

Now, to answer your question: Lets take a standard chord from music. The notes in that chord are these: A fundamental, an octave, a fifth, and a major 3rd. So you see, if this were what was played, the 2nd, 3rd, 4th, and 5th harmonics would all be enhancing the sound. Actually since the 6th harmonic is actually a minor third, I would even argue that the 5th harmonic would be more "musical" than the 6th although the opposite would be true for a minor chord.
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