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Old 4th May 2012, 04:36 PM   #11
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by Pano View Post
It doesn't have to be. A good design will have a harmonic spectrum that falls off evenly. 2nd, 3rd, 4th, 5th, 6th, etc.


<snip>
My general preference is for amps with predominantly 2nd and 3rd order distortions and very little above that. (with 3rd being at least 10dB lower than 2nd) I also generally aim for the lowest levels I can get with a given topology. I don't use global feedback in my current designs.
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Old 4th May 2012, 05:05 PM   #12
popilin is offline popilin  Argentina
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There was no mention another type of distortion in valve amps and its origin is electromagnetic.

In a push-pull amp, the DC current flows through the two halves of the OPT primary , then the magnetic field is canceled.
Fantastic, do not need an air gap in the OPT core, can also be smaller.
But the hysteresis loop is a closed curve, not a straight line, regardless of the quality of the core material.
This means distortion, not only for the non-linearity, but also for the zero crossing of hysteresis loop, the core must be magnetized cycle by cycle.

In a SE amp the DC current flows all the time through OPT primary, to avoid saturation of the core, we must add an air gap, the core must be larger.
But all is not lost, the air gap reduces the area of the hysteresis curve, and also the core is magnetized by the DC component all the time.
As a result we have a more linear hysteresis curve, and no zero crossing distortion.
This is a part of "SE Magic"
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Old 4th May 2012, 09:58 PM   #13
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It's pretty revealing to take a PC-based signal generator an dial in say 1000Hz on one channel and then listen to how it sounds when you mix in a 2000Hz signal at 5% level on the other channel. The difference is barely audible and not very displeasing.
Then proceed with 3, 4, 5,.....kHz. You will notice that 3rd harmonic is more audible but not extremely disturbing whereas higher harmonics tend to sound very dissonant.

/Olof
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Old 5th May 2012, 03:18 AM   #14
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My SE experiment, going to use Sovtek EL84m's. In the RH84 circuit.
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Old 5th May 2012, 03:29 AM   #15
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Quote:
Originally Posted by popilin View Post
There was no mention another type of distortion in valve amps and its origin is electromagnetic.

In a push-pull amp, the DC current flows through the two halves of the OPT primary , then the magnetic field is canceled.
Fantastic, do not need an air gap in the OPT core, can also be smaller.
But the hysteresis loop is a closed curve, not a straight line, regardless of the quality of the core material.
This means distortion, not only for the non-linearity, but also for the zero crossing of hysteresis loop, the core must be magnetized cycle by cycle.

In a SE amp the DC current flows all the time through OPT primary, to avoid saturation of the core, we must add an air gap, the core must be larger.
But all is not lost, the air gap reduces the area of the hysteresis curve, and also the core is magnetized by the DC component all the time.
As a result we have a more linear hysteresis curve, and no zero crossing distortion.
This is a part of "SE Magic"
Fascinating!

Can you please point me to a reference that shows a measurement of this phenomenon? I would like to see the nonlinearity of the magnetization curve without DC bias.

Thanks!
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Old 5th May 2012, 03:48 AM   #16
JZatopa is offline JZatopa  United States
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So how do you lower single end distortion without negative feedback? Siliconray showed some tests that seemed to show a lower distortion using his SMPS over a traditional PS. SMPS powered tube amp

Is this normal? How low can a SE tube amp get for distortion levels? Any chance feed forward error correction could work on a SE tube amp?
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Old 5th May 2012, 04:58 AM   #17
popilin is offline popilin  Argentina
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Quote:
Originally Posted by Michael Koster View Post
Fascinating!

Can you please point me to a reference that shows a measurement of this phenomenon? I would like to see the nonlinearity of the magnetization curve without DC bias.

Thanks!
Thanks, but I do not deserve.
You can see Maxwell equations here

Designing Transformers with J.C.Maxwell

From the constitutive relationship

B = u H

For ferromagnetic materials u is far from constant, then B and H are related by a curve called magnetic hysteresis loop, magnetization is related but not the same (it can be proved from Maxwell's equations) for now see the attachments.


But not so far away, from high school I know that in an ideal transformer (hysteresis in a straight line) a sinusoidal voltage corresponds to a sinusoidal current, in the real world transformers that does not happen, due to hysteresis.
In the book "Basic Electrical Theory and Practice" by Wolfgang Müller-Schwartz, Siemens Aktiengesellschaft, page 182 you can see nice pictures that best illustrate what I.
Also you can measure for yourself, you just need a transformer and an oscilloscope.

Best regards
Johann
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Last edited by popilin; 5th May 2012 at 05:24 AM.
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Old 5th May 2012, 03:07 PM   #18
dady is offline dady  Argentina
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When somebody listen some or determinate live music, IE, a Philharmonic orchestra you listen the fundamental of each timbre in each instrument. Ergo" "You listen live music".
Live music is impossible to rise with any electronic reproduction system. The problem is the distortion. The harmonics, even or odd, are harmonic. And those are distortion. Some of them are "euphonics", probable the even one. But if you listen a philharmonic orchestra with even forttisimos you eat the fundamentals more a lot of music (euphonic) that nobody generate with a particular intention, is collateral music, is a damage to the original program.
SE have pairs or even harmonics, the music that them produce are beautifully but because you listen a voice with a flute or a guitar for that reason SE amps are good for chamber or jazz. However when you try to listen Bruckner in a stupid SE you listen a barbecue with chorizzo and longaniza music with some reminiscence to the original one.
There are a sad story, sad for the mortal common listeners and HiFi followers about one of the big orchestra director of all the times, Celibidache avoid to record music because he considered the poor quality of the reproduction of the systems in those times and sadly for us because his entire most important performances we never couldn't today listen.
When somebody put a hand in a Piano instrument. If put the C and C, is euphonic, if you put a C and e bemol is disphonic or odd. Is an harmonico with a determinate character (major or minor) happy or sad, imagine with the music in a orchestra listen all the C of each instrument in a big fortíssimo plus the C of upper pairs are C but they never generate them. All if you not at this moment sum the odd harmonics.
Talk more about is talk about the sex of angels.
At least I recognize by myself i will continue to follow this kind of conversation
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Old 5th May 2012, 10:55 PM   #19
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Are you trying to say that SE amps can't reproduce classic music?
I strongly disagree...

Paul
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Old 5th May 2012, 11:10 PM   #20
MelB is offline MelB  Canada
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I am oblivious to any distortion in a SE amp.
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