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Even v. Odd Harmonics Can anyone explain?...

#1 User is offline   zigzag 

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Posted 16 January 2012 - 01:31 PM

Can any one explain even v. odd harmonics so that a dummy can understand? Why would one be more pleasant than the other? Why would a tube amp be more likely to produce one over the other?
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#2 User is offline   Warren_Z_ 

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Posted 16 January 2012 - 02:36 PM

I'll give this a shot! Others please chime in and help me out!.

I am making general assumptions here:


Marshall amps operate in Class A/B, also called "push pull". They produce both odd and even order harmonics but the even order harmonics are cancelled out by the fact that each output tube (or pair of output tubes if the amp has 4) only operates half the time. This "push/pull" action results in cancellation of the even order harmonics.

Single ended amps, called Class A, where the output tube never turns off, generate both even and odd order harmonics, and the even order harmonics are quite "up front". The even order harmonics are sometimes called "asymmetrical" or "soft" clipping. Asymmetrical clipping of the signal sounds good, but so does symmetrical. It's just different.

Remember as well that any distortion to folks in the high-end audio field is considered BAD. Us crazy guitarists find distortion of an amplifier GOOD! So, make sure you are reading material that sees an amp distorting as a good thing when interpreting if even or odd order harmonics are desirable or not.

There are many other classes of amplifiers but Class A/B and Class A rule as far as guitar amps go.
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#3 User is offline   JellyWheat 

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Posted 16 January 2012 - 05:31 PM

View PostWarren_Z_, on 16 January 2012 - 02:36 PM, said:

I'll give this a shot! Others please chime in and help me out!.

I am making general assumptions here:

EDIT: smarta$$ comments by J/W deleted as inappropriate



The following link provides some insight into even and odd series harmonic overtones, but is not very useful in understanding tube vs SS amp sound. I am not certain whether it is harmonics that are at the root of the difference. There are many other factors at play.

My link


J/W
[huh] B)

This post has been edited by JellyWheat: 17 January 2012 - 08:33 AM

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#4 User is offline   drumrnmuzik 

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Posted 17 January 2012 - 01:57 AM

I'm not a guitar guru but I have worked in electronics all my life. I can add is this;

- Class A amplifiers mean that the single driver tube works on the positive and negative sides of zero voltage
- Class A/B amplifiers mean that there are two output tubes (or 2 halves of one tube). One tube outputs the positive peak, the other, the negative.

The advantages are that a Class A amp is more precise. Less transient lag and distiortion. A Class A/B amp is cheaper to build. A Class A amp is much cleaner sound.

Harmonics are created every time that a string is plucked. From the primary note, for example 440hz, a first harmonic would be 880hz, doubling in frequency and reducing volume by more or less 1/2. Obstructions on the string will cause spurious harmonics. (squealies)

If you have the same frequency of opposing polarities and equal amplitudes, you will cancel out the signal. Noise canceling headphones work this way.

Now this is the point that I'm not too sure about, but it is reasonable to suppose that the transient point of the Class A/B amp could come into play here. At the cross over point, the ouput tube doesn't shut off at perfect 0 volts. There will always be some milllivolts +/-, these millivolts are sounds for us. If the input to the tube stays idle for some milliseconds it can hang on those spurious sounds or fade, depending on the circuits. These could be the "harmonics" that you are talking about.

I doubt if this helps but it was fun to write...
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#5 User is offline   badbluesplayer 

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Posted 17 January 2012 - 06:26 AM

I'm giving a minus 1 for the first time ever to J/W. [thumbup]
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#6 User is offline   JellyWheat 

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Posted 17 January 2012 - 08:03 AM

View Postbadbluesplayer, on 17 January 2012 - 06:26 AM, said:

I'm giving a minus 1 for the first time ever to J/W. [thumbup]


[confused] Why? Warren has not posted correct information about even and odd harmonic series. Period. It's not the end of the world, but why propagate false notions when the real answer is so easy to get and to transmit to others?

I responded the way I did because I feel this is the way a lot of "urban legends" get started. Then people get all freaked out because they don't have the right class of amp, instead of understanding that even and odd harmonic overtones on the instrument affect its timbre or tone.

You can believe all the mumbo-jumbo Warren posted if you want, but what he is talking about is phase cancellation and bias, not even or odd harmonics. You're free to believe what you choose, but the real answer, which is helpful in understanding how instruments get their characteristic tones, is so easy to get, I saw NO advantage in rewarding what amounts to speculation on the subject.

That's my story, and I'm sticking to it.

[flapper]
J/W

[BTW... aren't you an engineer? If I have got this wrong, please enlighten me. I don't mind eating crow if I'm wrong!]

This post has been edited by JellyWheat: 17 January 2012 - 08:31 AM

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#7 User is offline   zigzag 

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Posted 17 January 2012 - 08:19 AM

Thanks for your efforts guys. I understand the audible and physical part of harmonics as produced by strings and other types of instruments- vibrations and frequencies. What I don't understand is the differences in harmonics produced by amplifiers- solid state/tube, digital/analog, etc., and why. And remember, I'm a dummy.
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#8 User is offline   JellyWheat 

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Posted 17 January 2012 - 08:24 AM

View Postzigzag, on 17 January 2012 - 08:19 AM, said:

Thanks for your efforts guys. I understand the audible and physical part of harmonics as produced by strings and other types of instruments- vibrations and frequencies. What I don't understand is the differences in harmonics produced by amplifiers- tube/solid state, digital/analog, etc., and why. And remember, I'm a dummy.

[blush] OK, well then I'm out of line, then, and I owe Warren an apology, since he was closer to providing you a useful reply than was I. I'm still not sure his explanation about harmonic/overtone series holds water, but I have come across articles in the past the explain some of what you are looking for. I'll try to provide a link tonight.

So, Warren, I apologize for putting the boots to you, and to any others whom I may have also disappointed by doing so. I'll be more considerate in the future...

B)
J/W
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#9 User is offline   zigzag 

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Posted 17 January 2012 - 08:55 AM

It's all good J/W. drumr actually came the closest to answer my questions, but I'm still ignorant.
"If you don't play 'em, what good are they?" -Mike Campbell

#10 User is offline   JellyWheat 

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Posted 17 January 2012 - 09:38 AM

View PostMoishe, on 17 January 2012 - 09:11 AM, said:

While sometimes interesting, scientific fact, theory and explanation does little to illuminate why one thing sounds better than another. If you're an engineer designing instruments, amplifiers and such, it would be useful. I've perused guitar forums and such for years, and have seen myriad attempts to describe the indescribable. You can specify wavelength, but can you describe a beautiful shade of blue? You can list the physical phenomena, but can you describe an orgasm?


[unsure] You're right, of course, and I wonder why I even got into it, since an amp guru I'm not, already! My efforts generated more heat than light, I'm afraid!

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#11 User is offline   zigzag 

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Posted 17 January 2012 - 10:08 AM

Most rockers seem to prefer the harmonics from tube amps. Many jazzers tend to prefer the cleans from solid state amps. How come?
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#12 User is offline   FredD 

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Posted 17 January 2012 - 11:32 AM

View Postzigzag, on 17 January 2012 - 10:08 AM, said:

Most rockers seem to prefer the harmonics from tube amps. Many jazzers tend to prefer the cleans from solid state amps. How come?


Change the subject, why don't you ? :unsure:

Mind you, it is your thread !! [smile]

I play Jazz Rock Fusion, and like both harmonics and cleans, but from TUBE amps !! [cool]
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#13 User is offline   zigzag 

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Posted 17 January 2012 - 12:03 PM

View PostFredD, on 17 January 2012 - 11:32 AM, said:

Change the subject, why don't you ? :unsure:


I don't think so. Aren't all of the questions I've asked related to the same thing- amp harmonics? [confused] B)
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#14 User is offline   Warren_Z_ 

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Posted 17 January 2012 - 05:46 PM

View PostJellyWheat, on 17 January 2012 - 08:24 AM, said:

So, Warren, I apologize for putting the boots to you, and to any others whom I may have also disappointed by doing so. ...
J/W


Totally accepted and no harm done !l! Posted Image Posted Image Posted Image

Now let's continue the discussion about amps and guitar and stuff...!
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#15 User is offline   Warren_Z_ 

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Posted 17 January 2012 - 06:00 PM

Again to generalize, a lot of jazz players like to play clean with a predominantly bassy tone . Tube and solid state amps can both do clean tones and I'm not familiar with jazzers preferring solid state amps. The Roland Jazz Chorus amp is notorious for refusing to break up and it's a tube rig (I think originally intended for keyboards?)

However, amps with tube rectifiers introduce "sag" into the tonal equation. Sag occurrs when an amp is pushed hard and it's circuit momentarily struggles to meet the demand being placed on it. It's not a harmonics thing, put it has an affect on feel. Solid state rectifiers respond much more quickly to demands put on them.

There are actually so many differences between tube and solid state amps it would be hard to discuss them in a forum setting. Many tube amps have solid state rectifiers, for example.

I love Albert King, he's one of my favorite blues players ( even though I wish he had learned a few different licks... :) ) He played through Acoustic solid state amps, kicking in a lush phaser every now and then.

Also, check out the Mahavishu Orchestra led by John McLaughlin. They were a jazz-fusion group that played in front of a wall of Marshalls. Literally a front-line to rival that of the heaviest rock group.
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#16 User is offline   Warren_Z_ 

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Posted 17 January 2012 - 06:07 PM

View PostMoishe, on 17 January 2012 - 06:03 PM, said:

The Roland JC120/Jazz Chorus amps are all solid state, no tubes.


DOH! I coulda sworn...

I used to go to a open jam night at a studio. The curse for getting there late was that you had to plug in to the Jazz Chorus.

Am I at least correct in my recollection that it was designed for keyboardists???

Thanks Moishe for straightening that out.

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#17 User is offline   JellyWheat 

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Posted 17 January 2012 - 07:00 PM

[rolleyes] I play elevator music, yet all my amps are either tube or have a tube section in the preamp. I find the sound of tubes to be warmer and more complex. Fruity , if you will, with a hint of smokiness and just a hint of tannic bite borrowed from the charred oak. Jazz Chorus amps are great when you have to move a lot of air with no breakup. They are, without question, solid state.

I have NO idea what class my tube amps are, either!

[Thank you for accepting my apology, Warren.]
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#18 User is offline   Warren_Z_ 

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Posted 17 January 2012 - 07:18 PM

Sounds like you're talking about a Chenin Blanc and not a amp section there JW! :)

The "charred oak" and 'smokiness" likely comes from an improper biasing of the output tubes. The fruitiness is pure pre-amp distortion! Posted Image
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#19 User is offline   zigzag 

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Posted 17 January 2012 - 07:39 PM

I have a Mesa Express 5:50, and of course, it is a tube amp. I absolutely love it! The cleans are brilliant, warm, and bright. Overdriven, it is warm and creamy. And it is loud. I just bought a Roland Cube 80XL (80W, extra loud) solid state amp to replace my Fender Princeton Chorus solid state 2x25W amp. I bought the Roland because I tend to play more jazz, and it seems to have more of a cleaner, less modified, almost sterile, jazz tone. It doesn't have the brightness of the Boogie when the Cube is set at the JC Clean option. It actually seems to replicate the tone of my ES-335 unplugged better than the Boogie.

I'm trying to understand why that is. Does it have to do with harmonics?

Youtube demo for the 80X, model just before the 80XL.


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#20 User is offline   drumrnmuzik 

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Posted 18 January 2012 - 12:42 AM

Hi zigzag,

I've owned a Roland Cube 20 and must admit that it had a really increable sound.

I know that when a manufacturer designs an amp they go for a particular sound. Thats where they put in the eq circuits. Treble cuts, bass enhancers. They are just freqeuency filters. They tweek the sound.

If you play a Blackheart Ant, it doesn't have any eq color. It's a sub 1w amp with only a volume control. Of course you have to play really low volume or it breaks up, the tube saturates, and thats the way they designed it.

Also tube construction is a big deal too. Try 6L6s and EL34s, due to the internal tube construction and material, they also color the sound. Meaning that they promote certian frequencies and repress others. The famous American vs the British sounds.

My Gibby L6S has two treble cut tone controls, so if I put the tone controls at ten, then I get the pure guitar sound. BTW, the L6S is all maple, so it's extremly bright tone wood. Mohogany is much more warm tone wood.


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