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Old 10th February 2013, 02:04 PM   #34691
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Quote:
Originally Posted by PMA View Post
This "quasi DC" appears or not depending on integration averaging time. Effect depends on low-frequency response of the system.
Multi-tones can be generated on arbitrary time scales and with large "quasi-DC" components. I suspect they would reveal any of the effects mentioned.
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Old 10th February 2013, 02:14 PM   #34692
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Originally Posted by DF96 View Post

If even-order harmonics derive from even-order distortion (they need not, although usually they do) then the even-order distortion will create a DC term too. This disappears completely at the first coupling cap or transformer encountered by the signal. So DC does not necessarily imply even-order distortion; even-order distortion does not necessarily imply DC. Similarly for any asymmetric waveform: DC and asymmetry do not necessarily accompany each other. Having said that, I'm not sure why we are discussing such elementary issues.
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Originally Posted by scott wurcer View Post
I don't either, but twice this week "asymmetrical waveforms have DC" was stated as an obvious fact. In xDSL as in audio large plus or minus crest events are not matched by the opposite polarity but the time average is 0 (especially in xDSL where there is complete galvanic isolation on both ends).
The case is DC component on the primary of psu mains xformers .
And Scott, average may be 0 indeed over a considerable time period but for small periods it certainly may not be. During this time then, the xformer saturates.
In total, my understanding is that even harmonics on mains are present only when waveform is asymmetric (and their presence is a good way to test for mains wave asymmetry ).
This asymmetry -for the time it occurs- creates a DC component . I am in agreement (for the first time) with JC here.

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Originally Posted by john curl View Post
NO, when second harmonic is generated from a primary sine wave, it CREATES A DC OFFSET as well as adding second harmonic. This is WHY we sometimes have DC on the AC power line, and this then makes toroid transformers BUZZ. There are online fixes for this, check it out.
Online fixes in these two threads:
http://www.diyaudio.com/forums/solid-state/2080-dc-filter.html#post15943

Variations of DC Main Filter against buzzing Toroid Transformers - what is the right?

If one objects to presence of DC at times on utility’s mains AC or has another explanation of it’s generation there, please explain.

George
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Last edited by gpapag; 10th February 2013 at 02:17 PM.
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Old 10th February 2013, 02:16 PM   #34693
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Well, that's one for the 'books': NAMEDROPPING
I'm sorry, but I can't help it, because these are the people that either I or my colleagues have worked with over the decades.
Usually, these 'famous' people were or are my colleagues, many are not still alive, and I have had serious interaction with them at some point in my audio history.
Let me give you an example:
I met Richard Heyser in 1968 when I was sent to the AES because I worked in the Audio Department at the time, and I wanted to go.
I can't remember how I got introduced to him, but it was probably through Paul Klipsch, because I knew him previously as I used to sell K-horns part time at a hi fi store, while working my way through college. In any case, Richard, Paul, and I wound up during a break in the proceedings in Paul Klipsch's room where we shared a few shots of premium Kentucky bourbon together, the bottle brought especially by Paul for the occasion.
We got together for dinner, etc for years, and I would call him on the telephone when I had a technical question like: What is time delay, really? Is it phase delay, group delay or is there some sort of 'real delay'? How could to signals, with real time delay come together and LOSE their respective time delay? That was a question I had for him in 1977, when I was working on the Symmetry Xover. He gave me the answer, at least to the second part, at the time.
Visiting my office that I had in Berkeley for about 12 years was:
Dr. Malcolm Hawksford
Dr. Vandenhul
Michael Gerzon
Dr. Diamond
And a great number of others.
The rest, I have met on their home turf, being that Norway, Denmark, Finland, Great Britain, France, etc. , or at AES Conventions in either Europe or the USA.
The two most brilliant people in audio that I have ever encountered were:
Richard Heyser and Michael Gerzon. I will always hold them in my memory as such.
Now is there anything wrong with what I just said? Am I supposed to hide my connections, behind some veil of intellectual modesty? That's one for the etiquette books! '-)

Last edited by john curl; 10th February 2013 at 02:38 PM.
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Old 10th February 2013, 02:22 PM   #34694
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Quote:
Originally Posted by john curl View Post
Real music has a dynamic DC component just like Richard says. It has been measured, and written about. It is the FUNDAMENTAL factor in detecting dielectric absorption in Walt's, Scott's and my testing of caps, back in the middle '80's.
Why when I showed how Peases' linear model could be used to fit the data to an arbitrary amount, no one was very interested.

Richard note, I had forgotten about this. I was interested in showing how to use our bridge to build a capacitor model based on Peases' R/C ladder model. Unfortunately no good story, no "memory", unknown distortions, you know how it goes.
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Old 10th February 2013, 02:26 PM   #34695
SY is offline SY  United States
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Originally Posted by john curl View Post
Now is there anything wrong with what I just said?
Only when it's used as a substitute for actual evidence and analysis.
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Old 10th February 2013, 02:28 PM   #34696
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It is NOT PEASE'S MODEL. It derives from Dow, et al, from analog computers in the 1950's. One day I will again find the 1985 letter that you sent that shows the DIFFERENCE between two caps, one with the 'Pease model' added in, in a computer simulation that you did then. You won't mind, will you? Do you refute your earlier analysis?

Last edited by john curl; 10th February 2013 at 02:35 PM.
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Old 10th February 2013, 02:29 PM   #34697
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I've done my share of 'analysis' and published it too in both the AES and IEEE.
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Old 10th February 2013, 02:34 PM   #34698
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Thanks Dan for your comments. I don't like 'fashion' either. Dr. Dree's headphones are a good example. I also know the people who work behind the scenes, and while they are nice to me, and technically capable, they are VERY CYNICAL about audio quality, and it does rub me the wrong way. In fact, I am going to have lunch with them, today! Can't pass over a home cooked meal! '-)
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Old 10th February 2013, 02:37 PM   #34699
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A typical asymmetric sound waveform (speech, word "below"). Still, only 0.006% DC. Some DC may be found over very short time passages. Some DC resulting from asymmetry may be found in Telarc 1812, short time, again.
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Old 10th February 2013, 02:38 PM   #34700
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Dr. Dree's headphones are a good example.
An amazing example of audio marketing. Right up there with Bose and Monster. The marketing talent is hard to deny.
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