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In Reply to: Re: Not Really a Great analogy posted by Presto on February 13, 2007 at 09:59:29:
RF is very sensitive to impedance. By manipulating specific electrical characteristics to purposely alter impedance in a controlled manner, the susceptability to picking up external RFI and / or conducting existing RFI already on the line can be drastically reduced and / or negated. The same can be said about EM fields to varying extents.As to believing that shielding is a cure all to RFI, i am not of that school. In fact, i know that shielding can create as many ( if not more ) problems IF improperly applied. If you've read any of the hundreds and thousands of posts that i've made either here or on Audiogon, you would be well familiar with this fact. Most all commercially available products that i'm aware of apply shielding in what "I" consider to be a less than optimum manner. I'm sure that there are some products out there that don't fall into this generalization on my part, but i'm simply not aware of them at this point in time.
As to "measuring" the differences in performance when changing cabling, i've done that more than a few times. Not only in the amplitude and bandwidth of distortion characteristics, but also by taking in-room frequency response measurements. I can do this with good and repeatable accuracy due to having the necessary test equipment ( HP distortion analyzers, HP spectrum analyzers, HP tracking generators, Tek scopes, etc... ). I've discussed this in the same hundreds and thousands of posts that i've made both here and on Audiogon.
Obviously, i'm not of the audiophile persuasion that thinks that one can wave a magic wand or sprinkle fairy dust and hear a difference. I know that much of what we hear can easily be measured. Having said that, i also know that much of what we hear is not easily interpreted by standard test procedures. As such, this gives us further reason to expand our knowledge and the test methodology used. Hopefully, we will continue to do so until we can not only measure and quantify such things, but also understand and explain them in both reasonable and logical terms.
At one point in time, the greatest, most learned minds in the world thought the world was flat. Many of these same folks would have also sworn that the Earth was the center of the universe. As such, they were promoting certain ideologies that were less than fully understood, even though they were accepted as fact. In the long run, those very learned and great minds ended up being a stumbling block to further knowledge and exploration. In effect, they were part of a problem that they helped create, not part of the problem that they helped resolve by working towards a solution.
Those that found the solution were those that ignored conventional wisdom. They took it upon themselves to learn and experiment on their own. That's how i got to where i am today, as i too was once a "cable naysayer". That is, until i actually tried, tested, heard and later measured the differences.
All of this does not make me smarter than anyone else, but it does change my level of understanding and therefore provide a different perspective. As i've said many times before, i know what i do because someone else took the time to help me explore and understand what was already common knowledge to them.
With all of that in mind, your ears & brain are more sensitive than you think. If you do some testing, you'll find that proper testing and interpretation of the results will, most of the time, verify what your ears & brain have already told you. That is, if you're a skilled listener and have the technical background to properly interpret the results.
Most people aren't skilled listeners, even though they might qualify as "dedicated audiophiles" or "avid music enthusiasts". Most people also don't have the technical background to properly interpret test results, so they resort to trusting their ears and picking what they like most or seems to work best in their system. Since everyone hears slightly differently, and has slightly different personal preferences, there's no wonder that it is hard to reach a general consensus in this area. That doesn't mean that we can't hope to achieve such results though, through further testing, experience and education. Even with all of that, removing personal bias from the equation would be a tough task to conquer. Sean
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Follow Ups:
"RF is very sensitive to impedance."I have to assume you mean radio frequency currents driven by radio frequency induced voltages (since the only thing that is 'sensitive' to impedance is current).
"By manipulating specific electrical characteristics to purposely alter impedance in a controlled manner, the susceptability to picking up external RFI and / or conducting existing RFI already on the line can be drastically reduced and / or negated."
Excellent. Now explain how and we're done here. A mathmatically model is usually best for explaining this electrical stuff.
"The same can be said about EM fields to varying extents."
That's funny because "EMI" and "RFI" are the same thing. What causes RFI? Is it not an EM field resulting in induced voltage (transformer action) in cables that drives a current commonly referred to as noise? Does not an induced "noisy" voltage drive a "noisy" current?
Again, we're seeing much "this is how it works" with no mathmatical models behind it. Your "explanations" are more thesis statements than explanations - they offer no explanation at all, they merely state a theory.
Proof may be in the pudding with listening tests. But not in engineering. Proof is in the math. Feel free to post some of the many measurements you have taken to demonstrate your claim in the bold typeface above, if you feel that would help demostrate your theory.
In fact, until you step up to the plate and define WHICH electrical characteristics you are manipulating, how you are manipulating them, and how this directly (or indirectly) affects RFI conductivity, there is nothing to prove or disprove here because nothing has really been said.
Since you claim to have a high level of understanding of both electronics and math, start juggling various levels of inductance and capacitance around while looking at bandwidth, conductivity and power transfer. In order to achieve desirable levels of specific electrical attributes, one may have to play with certain conductor geometries, possibly even multiple different geometries in the same cabling.Since your so well versed in electronics, you'll know that multiple complex impedances can be summed up according Thevenin's Theory. As such, a multiple geometry cable such as described above would provide us with a nominal impedance. With that in mind, the impedance at any given point might be quite varied as frequency is altered due to the distributed impedances along the length of the line. In effect, one could build "traps" into a PC should they desire to do so. How effective these "traps" are would depend on how involved or complex the cable builder wanted to get.
Amongst the various geometries, one might also find varying levels of sensitivity to both radiating and receiving RF and EM fields. The key here is to find geometries that achieve the desired results within a given frequency range while rejecting or lowering the ability to transfer signals outside of that bandwidth.
As a side note, RF & EM fields are typically considered to be two different things when discussing audio. As a general rule, EM fields typically pertain to low frequency fields surrounding transformers and power cabling, etc... RF is typically considered to be high frequency energy generated by some type of transmitting device.
In case you weren't aware of it, there are vast differences in the range / field intensity that these two different frequency ranges are typically radiated. On top of that, some forms of "shielding" can work reasonably well over a given bandwidth but are almost useless in another frequency range. Trying to deal with both EMI and RFI as being one in the same, which many "engineers" and home-brewer's do, may result in designs and products that are anything but optimally designed. It is this single minded simpleton's approach that introduces many of the other side effects that some audiophiles find particularly objectionable.
For the record, varying the impedance of a circuit most assuredly alters BOTH the current and voltage. You can't change the voltage or the current without altering the other. The only way to alter either voltage or current, with one directly effecting the other, is to alter the impedance of the circuit.
I'm not about to put you through school though, especially since you already have all of the answers and know everything that there is to know about the subject at hand.
"...start juggling various levels of inductance and capacitance around while looking at bandwidth, conductivity and power transfer."Conductivity does not change with frequency as it is a function of static resistivity , conductor cross sectional area, and length of the conductor. Perhaps you meant conductance . Or maybe admittance .
"In order to achieve desirable levels of specific electrical attributes, one may have to play with certain conductor geometries, possibly even multiple different geometries in the same cabling."
Define: "desirable levels of specific electrical attributes" (Or perhaps just name the electrical attributes, and explain what a "desireable level" for each would be.)
So basically, if I am to understand your very detailed approach to AC cable design, if one "juggles" RLC values and "plays" with multiple geometries, he can lower "excessively high" series inductance from somewhere in the order of a few pH/ft to ?????? (some unmeasureable value?) and create traps to block "certain" radio frequencies by some "desireable" amount.
WOW! So far we're doing a whole lot of juggling and playing, but you're still nowhere near a definitive explanation.
Perhaps cite some known phenomena or electrical principles (so far you've mentioned Thevenin where good old Ohm's law would have sufficed - you don't need a Thevenin equivalent circuit to add parallel complex impedances or at least you didn't when I went to school back in '93). Maybe put forth some measured data or name some specific geometries or talk about which geometry is GOOD for lowering inductance. Maybe mention ONE SINGLE ORDER OF MAGNITUDE for just a few "electrical attributes" instead of repeating the word "desireable" all the time. Maybe tell us *why* a stock cords inductance is unacceptably high for most audio circuits.
If juggling and playing is the best you can describe the mathmatics and methodology for implementing RFI suppression in AC cable design, then maybe you could have your "guru" post here. I am afraid your version of his story is far to watered down to be of any value.
Oh, and "for the record", if you want to put me through some schooling, be my guest. I'll take your money. So long as the courses are being taught by actual professors and mathmeticians.
First of all...Sean: "On top of that, i'm not going to hand anyone a bone when i normally get paid for the research that goes into my design / consultation work ( which is non-audio based )"
He he he... that was pretty obvious. Don't worry - you didn't give any trade secrets or methodologies away in your explanation!! :o)
Second of all... (both of you's guys)Q: If we are stuck with a certain source impedance (looking back from the wall plug) we get an X/R ratio that is pretty much set (unless we tear the Romex out of the walls - which has the worst possible geometry for inductance). This being said, how is having 6 feet of cable with a minimized series inductance (referring to the low frequency model of a cable here) going to make a difference in the source impedance seen by component's power supply? How can we "pretend" the source is a perfect source when it's connected in series and far from perfect? Sean: are you for replacing the Romex? I know you don't like it. (I think if I was finally CONVINCED that I need a $2000 AC cord for my sources and amps I would have a hard time justifying connecting them to a branch circuit with 40+ feet of #14 Romex!)
Third of all....(again, fire at will...)
Q: Let's say we are looking at an AC cord that is connected to a power supply that has both line-line and line-ground coupling capacitors in the microfarad range to deal with the RFI in the sub 30Mhz range (ballpark for RFI that is conducted and not induced), then how does manipulating cable capacitance in the PICO farads make any difference? Are not the capacitances of the cable also from L-L and L-G, putting them (effectively) in parallel with the caps in the power supply filters, thus making the capacitances of the filters and the cable additive? If so, then how is adding a few picofarads to a few microfarads of filtering going to change RFI conductivity for the "conducting" portion of the bandwidth?
Oh - Sean is allowed to leave blanks in his answers, but he must use the correct number of underscores to represent the correct number of characters in each word, and must allow us to "buy a vowel" at current market prices. When a word is guessed correctly, he must then procure the services of an aging but still really hot woman to flip the letters around.
Fourth of all:
Q: RFI is everywhere. Good thing we can't hear it - we'd go crazy. Let's say we can objectively reduce, minimize or even eliminate RFI. From either (or both) or you: are there some components that will benefit more than others (inherently) from reduced RFI? When does "reducing RFI" become an audiophile feel-good psycho-somatic pipe dream? If amp and source designers are getting their gear to spec and sounding really good, why would they investigate better AC cords and make them "part of the power supply?" If they can reduce RFI with power supply filtering and do it well, maybe they figure the cable's contribution to reducing RFI is too small to be worth the bother and expense? Or are these guys really that bad that they filter to meet FCC requirements and call it a day?
Questions are just brain-teasers to provoke thought and discussion...
Cheers,
PrestoAnd thanks for chiming in J Neutron. I was thinking when I was circling around this topic with what little theory I know on the subject... "I bet Neutron knows something about this!"
Nothing in what I have said related to the transfer of any bad stuff through the cord from the wall outlet.Everything I speak of is related to the amplifier ground reference being bounced about by magnetic flux changes.
The inductance of a line cord comes into play in my discussion simply because the higher the cord inductance, the better the cable is able to create an external magnetic field. THAT is what is picked up by the ground loop, and mucks up the amplifier's ground reference.
Historically speaking, tying (either hard or soft) the amplifier input ground to a wall socket safety ground is a huge no no. I've experienced this problem and solved it more times than I care to count..
Oh, and romex in wall? If you want to create a dipole 60 hz magnetic field, how better than with parallel wires? This guarantees flux entrapment.
I'm not about to tell you inch by inch of what works, what doesn't work and why. This was all something that i had to learn on my own AFTER many lengthy debates coming from a "cable naysayer" point of view. Some here will remember these debates, as they were "schooling" me based on their own personal experiences and audible observations.The education that i picked up along the way has been quite valuable. That education, along with the test results that i obtained, helped to confirm the aural observations that i had made with my own two ears using very differently designed gear. I could only wish that you might have a similar experience and awakening. Without actually doing something and trying things out for yourself, there's little hope in convincing a follower of theory / desk jockey. Not everything goes according to theory in the real world, simply because the real world is far more complex with tons of unknown variables present at any given time. Sean
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-I have custom braided AC cords (just for fun). I got about 1 whole twist per inch into that 12gauge wire!! (I want to experiment with multiple twisted pairs next, or maybe some concentric geometry stuff. Or maybe BOTH as you suggested! Bwah ha ha ha ha!!-I have custom UTP unbalanced interconnects using various kinds of wire - PVC insulation, FEP Teflon, Kynar, with small gauge / mega-twist construction. No shielding at all. Just UTP. Work great.
-I also have MIL Spec teflon insulated and jacketed silver plated OFC cable for my balanced to unbalanced 6-channel conversion cable/snake for using 3-way stereo digital or analog active crossovers with unbalanced gear. Very pretty.
-I made a digital cable out of 75ohm CATV cable with a nice copper braid (the foil and foil drain wire stuff doesn't solder worth a lick). Added nice nylon braiding and blue heat shrink for added psychoacoustic benefit. Did not use transmission line theory to come up with the length - which I chose to be 3.128954348 feet. SNIP!! Cable is RCA to XLR, pins 1-3 tied, conversion cable for 2-wire SPDIF to 3-wire XLR AES/EBU/SPDIF input. (Works nice with Behringer AES/EBU/SPDIF input)
-I have a nice pair of Allen Wright's braided 2+1 conductor "three-nine" solid silver 'fine-wire' interconnects using teflon tubing (and some air!) as a dielectric (similar geometry Kimber braided stuff in theory).
-I have custom speaker cables, some are from Allen Wright's super-cables cook book (similar to interconnect design) and some CAT V jobbies I whipped up using 3 parallel twisted pairs, re-twisted and re-wrapped in their original skin and sealed up with black expanding nylon brade. Used banana jacks for amp end and Neutrik Speak-On cord ends and sockets for the speakers. Pairs were separated and color matched in true "audio obessive" manner. In the end, I only used the blue and white ones.
C'mon Sean. Does this sound like the work of a desk-jockey propeller head engineer?? No way man. This is shoot-from-the-hip DIY madman stuff done by a technologist caught in the chasm between theory and practive man!
Do these crazy DIY products make a difference? I can't honestly say. Sometimes I believe it does and other times I think lamp cord and $10 interconnects and IEC cords sound just as good. One thing that scares me... if I didn't engineer these products and they sound good it means that either:
a) the basic topologies are of sound design
b) the topoligies used are crap and I just can't hear it
c) the topoligies really don't matter as much as once thoughtWhich is it?? And for which cables?
Ah... but there is the RUB!
Sounds like you've been busy building and trying various cabling. Kudo's to you and thanks for sharing that. You originally came across as a "cable naysayer" that simply wanted to crunch numbers with no concerns for actual real world component interaction.I started out doing much the same, then i let the science that i knew and understood start working for me. Optimal or near optimal cable designs aren't that hard to figure out when you make a list of the pertinent criteria and analyze it. Then you have to come up with a design that meets all of that criteria as best possible with the least amount of compromises and / or the best that one can do within a given price range. In most cases, phenomenally good cabling can be made for pretty reasonable prices without bending over backwards or resorting to highly exotic materials.
It has been my experience that most people buy poorly designed gear or gear that isn't well suited to work within the same system and then try to band-aid the less than stellar results via cable changes. While this is completely backwards in my way of thinking, it is my opinion that this method of system assembly is what has fueled the high end cable market since the beginning.
Most people end up using cabling as an impedance transformer, hence the inconsistent results from system to system and component to component. When you try to get them to understand what is taking place and how best to deal with it, most folks will typically shrug their shoulders and carry on as if nothing had happened. They are content to waste their money and ignore common sense, even though much of "high end cabling" doesn't really seem very logical when you first get involved.
When it all comes down to it, it is all about impedance and frequency. Nothing more, nothing less. Think about that and how it pertains to the various designs that you've already built and are thinking about building. Sean
>PS... Ohm's law is not a substitute for Thevenin's theory or vice-versa. They are quite different even though they work along similar lines.
"You originally came across as a "cable naysayer" that simply wanted to crunch numbers with no concerns for actual real world component interaction."I don't really want to KNOW how I come across most times! :o)
"It has been my experience that most people buy poorly designed gear or gear that isn't well suited to work within the same system and then try to band-aid the less than stellar results via cable changes."
HA HA HA! You sounded like me there. That was priceless. Using "cable equalisers" to fix problems cables can't really fix? Yeah - sometimes this happens I think.
"Most people end up using cabling as an impedance transformer, hence the inconsistent results from system to system and component to component."
Sucks when you try and mate two otherwise exceptional components with an impedance mis-match. But, some folks don't know when to say when. I tend to avoid gear with atypical impedances because I try SOOOOO many iterations of gear, I like maximum flexibility.
"PS... Ohm's law is not a substitute for Thevenin's theory or vice-versa. They are quite different even though they work along similar lines."
Oh, this I know. In fact you don't need either to add two complex impedances. You just need to know soh-cah-toa or how to draw a triangle! :) (I'm an electrical designer)
In any case, your posts (and Neutrons, and Al's and Jon Risch's) has inspired me to learn more about t-line theory, propagation velocity and delays, RFI transmission concepts (induction versus conduction), cable resonance, traps, filters, shielding for different noise spectra.
What I really want to study is what makes an "end" (reflection point) an end, and what happens when you connect two cables (or wiring methods) in series with different resonances.
This is all Johnny Neutron territory. Real propeller head stuff. :o)
Thanks for being nice even after I was a dick.
presto: ""
Conductivity does not change with frequency as it is a function of static resistivity, conductor cross sectional area, and length of the conductor.""It doesn't? Crap, there goes my edjumakation. If y'all's gonna get all technical, conductivity is consistent as long as you stay below the terahertz range. Course, he didn't state that conductivity changes, he referred to it as a parameter as well as bandwidth.
presto: ""
"excessively high" series inductance from somewhere in the order of a few pH/ft to ?????? ""If ya's gonna lambast someone, please use numbers that are realistic. pH per foot??? Try pH per mil... A single parallel wire pair can only go down to about 150 nH per foot, and that is with zero insulation thickness.
presto: ""
WOW! So far we're doing a whole lot of juggling and playing, but you're still nowhere near a definitive explanation.""Here, I must concur. There is a lot of verbage, but absolutely no meat upon which to define a model from which a solution can be had.
presto: ""
Maybe mention ONE SINGLE ORDER OF MAGNITUDE for just a few "electrical attributes" instead of repeating the word "desireable" all the time.""Cord inductance, 180 nH per foot..cord capacitance defined by dielectric and insulation thickness..LC = 1034 EDC, assume an EDC of 10..
C = 10K/L...C = 55 pF per foot. Characteristic impedance of 57 ohms..(seems low, but I assumed EDC was 10, this implies high capacitance.)Ground loop coupling, waaaay dependent on geometry, power cord pitch..ground loop current dependent on loop resistance, amp internal coupling, dependent on how crappy the internal wiring is..star grounds suck.
presto: ""
Maybe tell us *why* a stock cords inductance is unacceptably high for most audio circuits.""Inductance is the measure of how much magnetic field is created by the current within the wire. Non constrained systems typical of parallel wire cords, spash the magnetic field outward in a dipole configuration. The more the cord inductance, the more field. One half of this field (in the upper limit) will pass between the source cord and the power amp cord. "Upper limit" includes the cancellation of the helix field, and the flux that passes outside the loop, this is not part of mutual coupling to the loop.
Given the lack of geometric control afforded any audiophile, it is not possible to come up with specific equational solutions to faraday's law of induction as it applies to the ground loop, other than to state that the coupling is proportional to frequency. Nor is it possible to generically apply Amperes law to the power cord, as pitch, spacing, and integrated total flux within the plane of the loop cannot be adequately predicted. Nonetheless, the flux will be consistent with the haversine currents drawn by the power amp supply.
It is possible to describe how to minimize the power loop effects, but numbers without controlled geometry...you ask for that which is not obtainable in uncontrolled circumstances.
Oh, btw..I would differentiate between RFI and EMI as follows:
EMI is local, and is concerned with the trapping of flux through a loop, such as the ground loop. Typical of 60 hz, as well as the low spectra for transient events like motor starts and stops. RFI I consider as a planar wavefront from a source which is not local. How either enter a system may not be clear cut..
Cheers, John
While the nominal impedance of the cable that you mentioned is pretty reasonable, the capacitance per foot is too low / inductance per foot is too high. Juggling these figures further in the direction that i have mentioned would provide not only a lower nominal impedance, but also greater rejection to RFI and EMI. Having said that, the cable that you described would be a good starting point and should provide benefits as compared to a generic power cord.I'm glad that you made the comment that you did about star grounding being far less than adequate, as i've publicly battled with several different manufactuers about this very subject. Several of them post here and manufacture products that are highly respected on this and other audio forums.
We are also basically on the same page as to the differences between RFI and EMI, although RFI may be considered "local" if within very close proximity to a transmitter. In such cases, one might be experiencing "front end overload" due to the concentrated EM field. This can occur by itself or in addition to AC based noise due to RFI entering the "long wire antenna" feeding the mains.
Obviously, there are a lot of various factors to consider in most every aspect of this discussion, hence my reluctance to present anything as being "concrete". On top of that, i'm not going to hand anyone a bone when i normally get paid for the research that goes into my design / consultation work ( which is non-audio based ). Sean
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sean: ""
While the nominal impedance of the cable that you mentioned is pretty reasonable, the capacitance per foot is too low / inductance per foot is too high. ""Inductance too high?? What kind of parallel wire are you talking about that is below that?? Remember, we're talking about a cord that must withstand 6 kv transients , so the insulation is certainly not very thin.
Did you mean the other direction??
And I was being generous with EDC, real values would bring capacitance down. Do not forget, that was not a measured value, but a generic one with the equation to calc the capacitance ...(hey, he was pingin for equations, so I did..:-)
RFI...I condider any energy transfer which satisfies energy balance and therefore, the wave equation, as being "planar".. (did ya know that transmission in any media or cable at it's propagation velocity requires the e and m field energies be equal ?...tidbit..)
Any field which does not satisfy energy balance, I consider EMI .
Star: You are the first person I am aware of that hates star ground techniques. It is an excellent technique when high impedance circuits are involved (aka tubers). , but sucks big time for low impedance ones (aka zistors, ala power stages, and when big loop areas or rich magfield areas... ).I wuz not aware you made a livin doing this stuff..I'll send ya my bill...(note, I made it easy for you, I highlighted the billable items in red for you..:-)
Cheers, John
ps..I crack myself up sometimes..It's a shame that while others do indeed laugh, I don't think it's with me...:-)
You offered estimated figures, providing numbers to crunch. I've measured real world products that are beyond the figures quoted. Whether or not they'll withstand a 6KV blast, i sincerely doubt it. Then again, i sincerely doubt that the majority of generic 18 or 16 gauge power cords made in China will hold up too well to that test either. I havent tested such things, nor am i aware of the specifics of the test methodology used, so i'm strictly guesstimating here.As you noted, star grounds suck for most everything BUT high impedance circuitry. In the grander scheme of things, that means that star grounds suck for the mass majority of modern electronic circuitry. This makes them a valid design approach for a rather limited number of applications. Too bad all of these "high tech, high end" audio manufacturers don't know this. Too bad the "high tech, high end" audio magazines haven't taught the end user this. Then again, when engineers with a handful of degrees can't / don't understand this, i guess it would be hard to get the average citizen to grasp such a concept.
As to making my living, i work strictly with RF, not AF. Most of my time is spent fixing / re-designing / modifying products designed by degreed engineers. It doesn't pay as much as i'd like, but i usually enjoy my work. Until the economy took a dump, that was reward enough in itself.
From what i can gather, i think that you may be in a similar situation, hence our having similar outlooks in many cases. THAT is why i can laugh along with you. The fact that you bring logic to what is many times an emotionally based exchange also makes it easy to enjoy your posts. At least, most of the time : ) Sean
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Sean: ""
You offered estimated figures, providing numbers to crunch. I've measured real world products that are beyond the figures quoted. Whether or not they'll withstand a 6KV blast, i sincerely doubt it. Then again, i sincerely doubt that the majority of generic 18 or 16 gauge power cords made in China will hold up too well to that test either. I havent tested such things, nor am i aware of the specifics of the test methodology used, so i'm strictly guesstimating here."'
The figures were estimated just to afford sometin to talk on. Don't take them seriously. It is possible a cable has those exact values, and I could easily construct one, but above and below are certainly viable. Higher inductance just means farther apart.The 6Kv is actually the accepted flashover voltage that is supported by the 120 volt outlets in the USA. 6kV is considered the highest transient that can therefore get to a piece of equipment that is plugged into line. Back at the circuit breaker panel, that number is 15 Kv.
For my purposes, I would just go with a 5Kv DC Hi-pot test, limit of 5 microamp leakage for 30 seconds or so. (Note, this is not a recommendation for safety testing of any equipment, just a "druthers" of mine. For true safety test regimes, gotta go with the national specs..
SEan: ""
The fact that you bring logic to...""Hey, gotta bring sumptin in..if I can't bring in intelligence, at least logic will do...:-)
*
Music making the painting, recording it the photograph
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