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Old 2nd November 2010, 04:23 PM   #6491
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Quote:
Originally Posted by scott wurcer View Post
Tough question would be; "Since all the information about the signal is also contained in the Fourier domain what could not be done with a sufficiently sampled signal and DSP ?"
Scott,

That raises the interesting question about the theoretical versus actual limits. Time for me being finite, noise one bane, not to mention the issue of modeling versus reality, are some of the limits, properly controlled probably not an issue. A good topic for intelligent discourse. One I have personally benefited from. So thanks from me for your knife edge of intellect.

But looking sideways at a problem may yield a shortcut.

But then the Holy Grail is a single figure of merit. Even my clothier's mirror has three facets.

But the pursuit of the Grail is a noble if foolish task. The quest is enjoyable, the end leaves only memories, so a goal that cannot be reached is more fun, as long as you believe.

Santa will be visiting soon enough and it yields no benefit to disillusion small children, no matter how obnoxious.

ES
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Old 2nd November 2010, 04:58 PM   #6492
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Quote:
Originally Posted by simon7000 View Post
Scott,

That raises the interesting question about the theoretical versus actual limits. Time for me being finite, noise one bane, not to mention the issue of modeling versus reality, are some of the limits, properly controlled probably not an issue. A good topic for intelligent discourse. One I have personally benefited from. So thanks from me for your knife edge of intellect.

But looking sideways at a problem may yield a shortcut.

But then the Holy Grail is a single figure of merit. Even my clothier's mirror has three facets.

But the pursuit of the Grail is a noble if foolish task. The quest is enjoyable, the end leaves only memories, so a goal that cannot be reached is more fun, as long as you believe.

Santa will be visiting soon enough and it yields no benefit to disillusion small children, no matter how obnoxious.

ES
More from the Wall of Science...

" ... in the late Devouring period, fish became obnoxious. In the real late Devonian, fish became ubiquitous."

Let's not get to serious here, I'm not talking theory or simulation of reality.
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Old 2nd November 2010, 05:03 PM   #6493
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I might add some info on Ron Quan. We first met in the late '70's, when he worked part time for me while finishing his engineering degree at Cal Berkeley. He then went on to work at Ampex, Sony, and a number of other related companies in Silicon Valley. He has some patents, I remember seeing one assigned to Sony. He usually specialized in video designs. This gives him a unique perspective on circuit design.
Ron has always had a great ear for audio problems and he has liked tubes a lot even from the beginning. He and I have kept in touch as colleagues, and he was very helpful to me in the early 90's by giving me a copy of his engineering class notes to replace the ones that I had lost in the firestorm, from the classes taught by the same professors at UCB.
Ron, is quiet, courteous, and professional, (unlike me), he has studied the problem of PIM from a unique point of view, and he has not lost his belief in his own hearing ability. He is well aware of the research and measurements of others in the past on this subject, and he expects to see a few of these people in the audience. I only wish Matti Otala were there to 'defend' him, if it comes to that. I have not read the paper, so I cannot comment further.
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Old 2nd November 2010, 05:16 PM   #6494
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Quote:
Originally Posted by simon7000 View Post
No, the duty cycle is very low and the average power stays the same. It is a simple test just about anyone can do it.
I will try. Some cloudy memories keep telling me, that any impedance added to primary is subject to the transformation ratio. So a typical coil with 0,5 ohm wire resistance increases the transformers output impedance only by a fraction of it.
I'm curious how this affects a typical supply with rectifier and smoothing cap.
regards

Last edited by Juergen Knoop; 2nd November 2010 at 05:19 PM.
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Old 2nd November 2010, 05:23 PM   #6495
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Quote:
Originally Posted by scott wurcer View Post
More from the Wall of Science...

" ... in the late Devouring period, fish became obnoxious. In the real late Devonian, fish became ubiquitous."

Let's not get to serious here, I'm not talking theory or simulation of reality.
It is just a phase. 360 degrees of it. Give and take.
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Old 2nd November 2010, 05:41 PM   #6496
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Quote:
Originally Posted by Juergen Knoop View Post
I will try. Some cloudy memories keep telling me, that any impedance added to primary is subject to the transformation ratio. So a typical coil with 0,5 ohm wire resistance increases the transformers output impedance only by a fraction of it.
I'm curious how this affects a typical supply with rectifier and smoothing cap.
regards
With a "loosely coupled" power transformer the conduction angle approaches 45 degrees so the resistance is almost 4 times as bad per half cycle. An oversized tight transformer may have a conduction angle of 10 degrees so that .1 ohm resistance (an unreasonably high value, but used for illustration) will act as 1.8 ohms.

With a steady state current draw of say 3 amps that is a voltage drop of 5.4 volts. In the U.S.A. where the line voltage is 120 volts that can be enough to change things. At the 10 degree angle the effective input frequency is 2160 hertz here. A few microhenries will not change much but a millihenry will drop another 14 volts! Worse if you have an inductor in both AC legs.

So even with the transformer reducing the source impedance line, filters will sometimes have an effect. In my measurements line impedance is under .1 ohm but the electrical code allows almost a 10% drop in the total AC power line system. Even with a 45 degrees of power draw that makes a big difference.
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Old 2nd November 2010, 05:55 PM   #6497
PMA is offline PMA  Europe
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Quote:
Originally Posted by john curl View Post
I think this is "much ado about nothing". Of course, RFI is bad. ...
I do not think so that this is "much ado about nothing". And I do have evidence of sound change with different EMI/RFI contamined audio signal.
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Old 2nd November 2010, 07:29 PM   #6498
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Well, of course, PMA, but I have found that using the right kind of power transformer, the right grounding and input filtering can remove the NEED for a commercial line filter of the conventional kind. I am all for serious line filters, especially power line 'cleaners' for the entire audio electronics.
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Old 3rd November 2010, 07:33 PM   #6499
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Quote:
Originally Posted by simon7000 View Post
With a "loosely coupled" power transformer the conduction angle approaches 45 degrees so the resistance is almost 4 times as bad per half cycle. An oversized tight transformer may have a conduction angle of 10 degrees so that .1 ohm resistance (an unreasonably high value, but used for illustration) will act as 1.8 ohms.

With a steady state current draw of say 3 amps that is a voltage drop of 5.4 volts. In the U.S.A. where the line voltage is 120 volts that can be enough to change things. At the 10 degree angle the effective input frequency is 2160 hertz here. A few microhenries will not change much but a millihenry will drop another 14 volts! Worse if you have an inductor in both AC legs.

So even with the transformer reducing the source impedance line, filters will sometimes have an effect. In my measurements line impedance is under .1 ohm but the electrical code allows almost a 10% drop in the total AC power line system. Even with a 45 degrees of power draw that makes a big difference.
The ferroresonant transformers would be a good match with the squared off secondary waveform, regulation built in, rail collapse under sustained overload. The two downsides are the sound level coming from the transformer and the not so great efficiency depending upon the mains voltage going in.

Wrinkle
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Old 4th November 2010, 06:00 AM   #6500
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Ferroresonant transformers are a big problem in audio.
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