John Curl's Blowtorch preamplifier part II - Page 3267 - diyAudio
 John Curl's Blowtorch preamplifier part II
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 14th January 2013, 06:15 PM #32661 Banned   Join Date: Jul 2011 Location: Portugal Something in relationship with the moon's position in this fighting club or just temporary shortage of peanuts ?
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Join Date: Dec 2009
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Quote:
 Originally Posted by Esperado Something in relationship with the moon's position in this fighting club or just temporary shortage of peanuts ?
I vote for the peanut shortage . Their moms must have sent them out for more . After they return from the store go down the stairs in to the basement the show will continue . This is just intermission .

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Join Date: May 2007
Quote:
 Originally Posted by scott wurcer If absolute value is bothersome I think in the solution you will find some square-root of quantities squared which has the same effect as taking the absolute value.
I have just had a quick look at two textbooks. I can't see anything in the maths of skin effect which involves either squares of field quantities or squares of square roots. The geometric field distribution is a function of just frequency, then multiplied by the field strength at the surface. So if you double the surface field, you get exactly the same pattern but everywhere the field is doubled. The linearity of Maxwell's equations require this to be true.

As proximity effect is just the mutual version of skin effect I would expect the same there.

Now if the Lorenz force is moving conductors around then 2nd harmonic is quite possible. That may be what is happening.

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Join Date: Jan 2004
Location: dorchester ma
Quote:
 Originally Posted by DF96 I have just had a quick look at two textbooks. I can't see anything in the maths of skin effect which involves either squares of field quantities or squares of square roots. The geometric field distribution is a function of just frequency, then multiplied by the field strength at the surface. So if you double the surface field, you get exactly the same pattern but everywhere the field is doubled. The linearity of Maxwell's equations require this to be true. As proximity effect is just the mutual version of skin effect I would expect the same there. Now if the Lorenz force is moving conductors around then 2nd harmonic is quite possible. That may be what is happening.

Certainly the energy lost from heat from the (very) slight change in resistive loss at twice per cycle is always positive. In fact the change in real part of the resistance is the only thing that could matter in this case.
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Join Date: May 2007
Quote:
 Originally Posted by scott wurcer Certainly the energy lost from heat from the (very) slight change in resistive loss at twice per cycle is always positive.
Yes of course.

Jn is claiming more than that: he says that the current flow geometry changes too with signal level. That is what I dispute.

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Join Date: Jan 2004
Location: away
Quote:
 Originally Posted by DF96 Yes of course. Jn is claiming more than that: he says that the current flow geometry changes too with signal level. That is what I dispute.
No, I did not say that. It is important you be clear on that.

The effect is slew rate dependent. The current density modification is directly proportional to the currents induced within the conductive material. The currents are directly proportional to the induced voltage ala Faraday's law of induction.

The resistance increase is a function of the absolute value of the rate of change of the current within the wire which is creating the magnetic field. That is why Ed sees the second harmonic.

jn

 14th January 2013, 08:37 PM #32667 diyAudio Member   Join Date: May 2007 Slew rate derives from two parameters: frequency and amplitude. You are attaching significance to the latter. The theory attaches significance to the former.
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Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
 Originally Posted by DF96 Slew rate derives from two parameters: frequency and amplitude. You are attaching significance to the latter. The theory attaches significance to the former.
.... because 'rate' doesnt change by amplitute.

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Join Date: Apr 2002
Location: Prague
Quote:
 Originally Posted by RNMarsh .... because 'rate' doesnt change by amplitute.
Yes from the amplifier point of view when driven by step.

But for sine wave, slew rate (derivative at zero) is amplitude times frequency times 2pi.
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Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
Quote:
 Originally Posted by PMA Yes from the amplifier point of view when driven by step. But for sine wave, slew rate (derivative at zero) is amplitude times frequency times 2pi.
yes, there is Slew rate, too. For amplifiers. Physics or amps? What's the focus here? -RNM

Last edited by RNMarsh; 14th January 2013 at 10:21 PM.

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