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In Reply to: BPT Plug-Shield posted by Todd B. on March 5, 2007 at 00:44:05:
the earth or screen of the cable itself ? I cant see how its going to work.
Follow Ups:
If the jacket is intended to improve the shielding, then it will have to be connected to earth somehow. This will increase the capacitance and may do more harm than good, but it might also be a net benefit.However, if it is to absorb energy from standing waves on the cable, then it can remain floating. The energy is dissipated by internal conduction mechanisms that respond to induced emf from the standing wave's electric and magnetic field components. No connection to earth is needed.
The drawback is mechanical vibration in the jacket. A floating conductive jacket that vibrates will inject electrical noise by the same coupling mechanisms working in reverse. Acoustic damping will help this problem.
My understanding of electrical theory is certainly lacking, but would the physical barrier itself not provide some amount of RFI shielding by way of reflection or absorption, even without being able to drain to ground? Is the Acrolink housing part of the ground circuit?
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A grounded metal sleeve the same dimensions would be a shield for radio noise up through the microwave bands. A floating object just causes the fields to be deflected, and if the wavelength is much longer than the longest dimension of the object, the changes in field shape are minimal.Where this device is useful is in dissipating RF energy rather than reflecting or deflecting it. Most power cords support standing electrical waves. Since they are made from low-loss materials (good conductors and good insulators), their resonant 'Q' is quite high and a little external RF noise energy that covers the resonant frequency of the cord will excite a strong tone on the cord.
This is similar in concept to an organ pipe. The input energy is the turbulent motion of air across a sharp edge at one end of the pipe. The pipe tone is quite loud compared to the actual sound of the turbulent air because of resonance in the pipe.
The sleeve here contains carbon fibers, which act as resistors to dissipate energy from the electric field component of the standing RF waves. This lowers the 'Q' of the cord and reduces the strength of the resonant tone. It does not block all background RF noise from the system, but that noise is a much smaller problem than the resonance.
Hi AlThe dissapaiting resistor effect of the carbon fibres would only work if there is an electrical circuit formed (unless its is relying on the impedance of free air to accomplish this task) i dont think the capacitive coupling from the screen of the cable to this after market sleeve (only a few pf in my guestimate) would be accomplish this , but as always i might be wrong.
The capactive coupling to the wires inside the plug would also be very small given the distances involved ( <50pf at a guess)
I agree the mechanical damping effect might do something but so would anything wrapped around the cable including plasticine or a bandage.
We are not dealing with circuits at these frequencies. The standing waves on a cable extend into the space around the cable to some extent, and as much as the electric field extends to where the carbon fiber is placed, it will dissipate energy into the fiber.A dark object gets warm in the sun, and it is not connected to the sun by a circuit.
This brings up a good point, though. There are two basic types of standing waves. The normal mode waves comprise voltages between individual conductors (including any shield). The common mode waves comprise voltages on all conductors acting as though they were a single conductor. The external carbon fiber damping arrangements work best on the common mode waves, since the electric field extends radially into space around the cable.
External carbon fiber arrangements do not work as well on the normal mode waves. Some sort of circuit is required to dissipate energy from them. I've found that composite R-C networks, where a series of capacitors of different sizes is used, can reduce the effects of normal mode standing waves without loading the cables in the audio band.
I had the impression that RF was the main culprit that needed to be addressed. Thank you for disabusing me of that notion, LOL, and for your clear explanations in this thread.
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............"Where this device is useful is in dissipating RF energy rather than reflecting or deflecting it."If the CF sleeve dissipates RF that is radiated from the cord, would it not also scatter RF that bombards the outer surface of the shell?
"This lowers the 'Q' of the cord and reduces the strength of the resonant tone. It does not block all background RF noise from the system, but that noise is a much smaller problem than the resonance."
Could one surmise that in addition to the CF, the machined aluminum housing would mitigate the "Q" of the cord even further and could possibly be "tuned" to the "Q" of the cord with it's mass? A mechanical notch filter maybe?
Also, how would the CF barrel and say a CF wall plate such as the Oyaide WCP-Z combine to dissipate RF? Could they be thought of as "opposing barriers"? One from the cord side and one from the outlet side?
TIA and cheers,
An aluminum sleeve would also have mechanical resonances, which would have to be dealt with separately. As a good conductor, though, it would reflect RF.Carbon fiber in an area where the standing waves have high values of electric field will dissipate energy from the standing waves. Thus, a CF wall plate will complement a sleeve containing CF to increase the dissipation for standing waves on the cord.
I don't know the relative balance of CF and conductors in the subject sleeve, so I don't know whether it would mostly reflect or absorb energy. I believe a sleeve made mostly of CF would absorb the energy that reaches it. It looks black to visible light and would look black to radio waves. This is similar in concept to stealth aircraft technology.
"My understanding of electrical theory is certainly lacking, but would the physical barrier itself not provide some amount of RFI shielding by way of reflection or absorption, even without being able to drain to ground?"The Carbon Fiber barrel will shield RF from entering around the connector. Al is more adept at explaining this aspect of the connectors performance than I.
The machined aluminum housing will mitigate parasitic resonances much better than molded plastic which IME imparts a monotonous quality to the resultant sound especially in the low frequencies.
" Is the Acrolink housing part of the ground circuit?"
No. It has no electrical connection to Earth Gnd.
"The machined aluminum housing will mitigate parasitic resonances much better than molded plastic which IME imparts a monotonous quality to the resultant sound especially in the low frequencies."That's an interesting observation. Did you determine that by comparing plastic-housing plugs to the Acrolink, or maybe by trying some sort of mechanical dampening on plastic housings?
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I first made the observation when I was utilizing Marinco AC plugs in my system.I first removed the outer barrel from the plug and briefly used it in that state and found that the whole audio spectrum became more focused, especially the bass, which portrayed a better sense of agility.
I then played around with dampening the barrel of the Marinco with Oatey's plumbers putty and that improved the audible focus but was too messy.
I then removed the blades and the GND pin from the plug body and safely soldered them to the power cord. I covered each connection in heavy duty heatshrink and plugged it in and sat back.
Holy #@$%!! THAT was a real ear opener as it completely transformed
the audio presentation from top to bottom but it was in the bass range that it had the greatest impact. It also spread the soundstage out quite a bit and greatly improved PRaT.Since the PC with no plug body/barrel is not what one would consider safe, I tried an Oyaide P-079 from recommendations here and was surprised that it came very close to matching the sonic presentation as the cable without the plug body and from there, my AC obsession really took off.
Cheers,
But I guess it IS the only way to isolate the plug body's effects. Thanks for sharing the info.
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