Indeed, a very nice write-up. One question- have you measured the input capacitance of the MM pre stage?
My second wife is the same way been with me 26 years. It payes to be left handed. Thus at least 2/infinite 😱
Could you make RFI-filtering wires by plating them with a resistive metal layer to increase skin effect? How resistive could you make the outer layer before surface currents moved back under it?
Also, since skin effect is nonlinear (dependent on dI/dT), does this mean when we use a feed-through cap or coaxial connector through a conductive plate to take advantage of skin effect and conduct CM currents to the chassis, that some of the resultant harmonics will pass as DM noise? When dI/dT is low, more of the CM RFI should be conducted into the signal line.
Also, since skin effect is nonlinear (dependent on dI/dT), does this mean when we use a feed-through cap or coaxial connector through a conductive plate to take advantage of skin effect and conduct CM currents to the chassis, that some of the resultant harmonics will pass as DM noise? When dI/dT is low, more of the CM RFI should be conducted into the signal line.
SY, the MM stage is not built yet. There's a note at the bottom of that page - those are target specs. I will start that in the next month or so - in the middle of a headphone/DAC project.
I just gotta keep soldering ya'know!
Thanks for the comment BH the way - Vacuphile also.
I just gotta keep soldering ya'know!
Thanks for the comment BH the way - Vacuphile also.
Looking forward to it. Keep input C in mind- it's really critical for MM and many people don't get it right. If you've got 100pF of input C inherent in the circuit (not uncommon!), then switching in the Cs becomes moot at the lower end of the range. Good cartridges like the A-T 150MLX can be quite fussy about C, and if the overall input C starts at a high value, then the frequency response will be highly unsatisfactory (I have some graphs in Linear Audio Vol 7).
Resistivity of free space? 377 is the magic number. Just a guess.keantoken said:
I think you mean dI/dt which, like skin effect, is linear so no harmonics generated. The RF guys don't see any harmonic generation from skin effect. People handling sharp pulses may see an effect which they wrongly assign to non-linearity; in reality it is just the various Fourier components suffering different amounts of skin effect according to their own frequencies so the pulse shape changes just like it will with any filter.
Yes and there is at least one patent I have seen on that! Maximum power transfer occurs when the source impedance matches the load impedance. But you knew that. Can't say more gets into NDA stuff.
Non-linear as in creating harmonics? The 17Mhz ADSL+ profile would be pretty much do-do if the magnitude of this was above the noise.
Scott,
Remember the to do about the word "Non-Ohmic?" Non-linear covers a lot of ground. Skin effect depth for one.
Did you look at the PIM cite from Demian, they also look at the issue.
ES
That simple cut and paste was for a 60 hz generator, and the proximity/skin effect nonlinearities are many orders of magnitude beyond signal stuff. Making widgits which rely on very high levels of dB/dt, high currents, and driving non linear loads is not the same thing.
jn
So Googling for nonlinearity and skin effect gives a 60Hz generator as the clearest result? Nothing about communications, or instrumentation? Places where even small amounts of unexpected nonlinearity in wires might be critical?
I'm not trying to repeat an old argument; people can use the forum search tool if they want to relive that. I am simply declaring what all the EM textbooks show, so others are not confused. I accept that you disagree, and I accept that I am not going to convince you.
I'm not trying to repeat an old argument; people can use the forum search tool if they want to relive that. I am simply declaring what all the EM textbooks show, so others are not confused. I accept that you disagree, and I accept that I am not going to convince you.
No, just the simplest. There were quite a few well above your "pay grade" as it were, but you didn't understand what was presented so far. (quite a few of the articles and books were pay as you go, so I "went".
Edit: So, now you've changed your argument from "skin effect is linear", to "ok, let's forget about 60 hz generators, but instead, you divert the argument so your erroneous blanket statement is forgotten??
There were. Again, I'm not going to do your research. A few good ones spoke about dealing with the slew based resistance change, and how it was dealt with far more exactly in the time domain instead of frequency domain, but again, you don't demonstrate understanding of the difference between the two, so why should I bother?
I did find some interesting point contact derivations, and how slew based skinning modulated the material resistivity at and close to the point contact, but again, that's above the "pay grade" of the discussion.
Sigh...."all textbooks show"...
You don't get out much, do you...
The current penetration depth of a self excited conductor goes as slew rate magnitude squared... You need better textbooks.
jn
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That's what the cartridge sees. If the preamp starts out with (say) 150pF of input capacitance and the cartridge is optimal with 150pF of capacitance, then you essentially have no possibility of optimum performance. So it's important to keep the preamp's input C as low as possible- if the cartridge wants more, it's easy to add more, but you can't go in the other direction.
sorry John but I think you are the one ducking here - I have spent hours on search for this - can't find your supposed references that actually say skin/proximity causes nonlinear distortion products in ordinary conductors
while sometimes people will use terms like "resistance modulation with frequency" - it is not correct to then assume nonlinear products - because it isn't "a modulation" - but rather a linear filter effect - current is steered by partial mutual inductance to a higher resistance path - the effect is linear
while sometimes people will use terms like "resistance modulation with frequency" - it is not correct to then assume nonlinear products - because it isn't "a modulation" - but rather a linear filter effect - current is steered by partial mutual inductance to a higher resistance path - the effect is linear
You didn't find the text I did the screenshot of? A generator uses normal copper (ordinary).
I've actually spent quite a bit more than just "hours" on this topic, both in search and in actual practice. Practice, as in, a part of what I do for a living. In actual hardware I build and test, skinning and proximity is a very large effect that I need to understand properly. Failure to understand the effect results in failure of hardware. Should hardware I build fail, it gets very very expensive.
Think about a coil of #10awg magnet wire. At DC, it has a resistance, current is uniform through the conductor.
Now, ramp the current very very fast to 20 amps. During the very fast ramp, proximity effect causes the current to bunch to one side of the wire, and during that slew, the resistance is higher as a result, and the IR drop at any current level is higher than the dc value.
Note two important things...I did not mention which polarity to raise the current. I did not mention which side of the conductor the current crowded to. The only statement which was absolute was "the resistance is higher as a result".
The increase of resistance is independent of the direction of the current slew.
That is nonlinear behavior..
jn
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