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Old 7th May 2012, 06:34 PM   #31
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Quote:
Originally Posted by pauldune View Post
Somehow I cannot believe that you, of all people, didnt know this...
I knew the theory, and cannot find a flaw in it, but at the same time I am not able to measure or detect any hysteresis based distortion in my Parafeed SE amps. And with parafeed and SE it should be obvious.

What am I missing? You have an explanation?

Paul
Magnetic hysteresis is based on the reversal of direction, not crossing some absolute zero magnetization level.

This is exactly borne out in Maxwells equations, specifically Faraday's law.

You should find magnetic hysteresis based distortion at very low signal levels, in both SE and PP output transformers.

I don't find evidence or theory for an additional source of distortion in PP output transformers due to "magnetic zero crossing". What I do see is a general change in permeability due to the SE magnetic gap and DC bias which changes the shape of the B-H curve overall.
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Old 7th May 2012, 08:17 PM   #32
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Hi Michael,

So what you are saying is that if the "hysteresis" distortion is there, it is so small that it is almost impossible to detect?
Maybe that is why I NEVER saw actual measurements of changed distortion with changed permeability. Only theory.

Paul
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Old 8th May 2012, 06:36 AM   #33
dady is online now dady  Argentina
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Paul friend.
Hysteresis means delaying, is a phenomena that always happen because the magnetization of the core is not lineal and the demagnetization is delaying to, if you see the way of rise and the inverse they walk for different parts of the coordinates system and them describe a typical curve that delimiting an area. The more horizontal or vertical tendence depends of the permeability of the core. More force lines more vertical and "visceversa". The distortion produced for this phenomena became for its non linearity, If you inject a positive part of a sinusoid wave in a primary of a transformer a magnetic field rise there, that theoretically going to transfer to the secondary, but the magnetic field suffer an hysteresis (a delaying) And a part of the wave arrived to the secondary but late. Imagine this in going and returning 5000times for second. The hysteresis depend of the size in the grain and the orientation of the molecule in the core.
Sorry for my englpanish that I could understand of this phenomena.
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Last edited by dady; 8th May 2012 at 06:37 AM. Reason: ortography problem
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Old 8th May 2012, 08:06 AM   #34
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Hi Esteban,

My gut tells me that the hysteresis-distortion should be amplitude based, not time based. But I could be wrong.
I see it like this: in the time the field is reversing direction, until it is in the "straight" part again, coupling isnt ideal. so the amplitude is a little bit smaller as should be, and deformed. But how much influence I dont know; as I said to Michael, I have a parafeed SE with a air gapped transformer, and am unable to measure or "see" such events on the scope or distortion meter. Also it sound at least as good as the same transformers in a "normal" SE configuration.

Paul
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Old 8th May 2012, 09:50 AM   #35
dady is online now dady  Argentina
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If you have a parefed you don't need a gap in your transformer. You haven't DC there. You have not magnetization problem. Probably you waste some of the properties in have a gap, What transformer do you have? Maybe you can avoid the capacitor in serie and win a little with this measure. I read about hysteresis for confirm if I were wrong. Look at the the curves at the Popilin post http://www.diyaudio.com/forums/attac...hysteresis.gif is typical envelope of this phenomena. For watch this you need a couple of devices but I don't know exactly.
Avoid this problem completely is impossible. You need more big grains in the alloy but with this you lost some of the another advantages you got, Is a compromise solution between frecuency response, magnetization of the core, price, distortion, parasitic capacity, there are not perfect transformer. Why many persons protest against the vacuum tube amplifiers. Why they tried to develop OTLs? How much cost a Tango or a Tamura? Did them sound so different to the rest of well made one?
Some years ago I read Martin Colloms (I thinks is well write) He said that "you can measure amps that actually sound good more distorted than many amps that measure perfect. Why people continuate in listening with those amps with tubes if the technical development made a Solid State with not transformers that show undetectable distortion for our ears?" Is a subjective experience... Some times I like rock with punch and another day pop with mids. Some days i like strident sound with no NFB and another I feel dry music...
Best Regards
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Old 8th May 2012, 01:15 PM   #36
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Hey, Esteban

I know I dont need a gap; I bought the transformers before I knew it would be a parafeed SE

I even asked here on DIYaudio if that would be a problem, but other than that it made the transformer a lot larger than needed, it should be OK, they said.
And thats what I found out too; it sound terrific.

The rest of your post is clear to me; but I think there is more to it then it seems.
I believe it should be measureable if an amplifier sounds good, but we keep on measuring the wrong things. THD doesnt say much, higher order distortion at 0.01% is more detectable then 0.1% 2nd harmonic, IMD is more important, and so on....
In the end our ears are the judge!

But regarding transformers: maybe you are right, and is the core material and the hysteresis and permeability very important for the sound and what makes a good or bad transformer.

Oh and you asked what transformer I had: it is from http://www.ae-europe.nl/uitgangstrafo_engels.htm

This one: C-core output transformer:

One step further in refinement is the output transformer with high quality c-core. For some time now we use cores with a lamination thickness of 0,05mm. This is rare in the fabrication of output transformers. But the quality is sublime. These cores have better quality and less losses. Therefor they can be build smaller then an EI-core transformer, without given in on for example a deep bass response. Of course they are winded in multipal sections. The frequency range is unprecedented large. These output transformers will be potted in a fine housing.



Paul

Last edited by pauldune; 8th May 2012 at 01:32 PM.
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Old 8th May 2012, 01:20 PM   #37
popilin is offline popilin  Argentina
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Hi Dady
Nice to see you again.
Very clear your concepts, without wishing to offend you, you look like an electronics engineer, and I do not mean quacks, "opinionologyst" and critics by profession, but a good one !!!

IMO is far more simple than are thought, take a scope, a signal generator and any transformer, put a sinusoidal voltage at any winding, with the scope you can see a sinusoidal voltage, but what about the current? is not sinusoidal.
The effect is more noticeable the more you approach the working conditions of the amplifier (voltage, current, transformer)
Even more, with proper assembly, you can see the curve of the hysteresis loop on the scope.
I've seen many times in the lab, children watch with wonder the scope.
I can not believe that anyone, at least in this thread, what ever did.

Sinusoidal voltage and non-sinusoidal current means distortion, AFAIK.
I do not understand people who full with a lot of iron their amps.
Kondo San was so clever, he put only the indispensable.

Best regards
Popilín
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Old 8th May 2012, 01:49 PM   #38
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Hi Popilin,

I am not a electronics engineer, neither am I a critic or opinionologyst; only a hobbyist.
But I am trying to learn from everyone, and help some people here and there.

Do I have it correct that you mean this:
Put a sinusoidal voltage on the primary of a transformer, put a 1 ohm resistor in series so I can measure and see the current(shape) on a scope, and put a resistor on the secondary so I can do the same there.

I will try this, and put results here; I am all for experimenting. Theory is nice, but seeing is believing.

Popilin, i'm not trying to offend you, but maybe you could show a little bit more respect for your fellow DIY-ists. We all have to discover or own thruth!
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Old 8th May 2012, 02:02 PM   #39
popilin is offline popilin  Argentina
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Hi pauldune
Forgive me if I offended you, it was not my intention, I don't mean you.

My story in the forum is that every time I say something with the best intentions, always I am fiercely attacked.

Do not know if I am or do not like my flag.
Dady know who they are quacks, "opinionologyst" and critics by profession.

Just when it appeared your post was to praise your transformers.
BTW, the assembly you use depends on signal generator, transformer, scope, etc. 1ohm looks too small, but make your own science.


Best regards
Johann

Last edited by popilin; 8th May 2012 at 02:15 PM.
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Old 8th May 2012, 02:35 PM   #40
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Quote:
Originally Posted by mr2racer View Post
Why is single ended distortion so high? In looking at tube data it seems SE distortion specs for tubes is much higher than for push pull. If that is the case why would anyone build an SE amp in the first place? Is it mostly 2nd order?

In typical SE design, most of the noise from the power supply is impressed on the primary of the output transformer. The quality of output transformer does come into play as DC idle current is present ( how well the transformer is gapped and winding interleave).

When I build an SE amp, I make my power supply have less than 5mV of noise at idle (no signal applied) measured from the output of the power supply.
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