davewantsmoore Posted October 7, 2020 Posted October 7, 2020 1 hour ago, bob_m_54 said: Dave, you may need to have a look at how RF is transmitted.. That is exactly how it works. In this case.... all you are measuring is the electric field, wrapped around the cable. When there is a magnetic field added (which there wasn't in the no load scenario.... but was once you added the rice cooker) .... then it is possible for it to be an antenna (that's what antennas do, turn mag fields into EM energy) ... .but it's completely the wrong size. So it won't at all in any significant way. The entire electric field (V/m) that was being measured in the pictures, is wrapped around the cable..... three is no EM energy being "radiated" out like people might imagine with their radio, or wifi.
pwstereo Posted October 7, 2020 Posted October 7, 2020 (edited) 44 minutes ago, davewantsmoore said: The field strength decreases by inverse sqrt distance..... so there is a field stength some distance from the cable... but it is extremely small. That is as opposed to how many might imagine it ..... as in something is "emitted", travlling away from the cable, like EM radiation from your wifi, for example. I get that the power cable can't be an effective antenna at 50 Hz, it's way too small, I don't think anyone was suggesting that it's transmitting a powerful signal. Edit: It'd need to be about 1500 km long to be a quarter wave at 50 Hz Edited October 7, 2020 by pwstereo Added wavelength 1
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 11 minutes ago, bob_m_54 said: I give up Dave, you clearly don't understand how it works. Mate, I've been in the trade for more than 40 years, I think I know a little about EM radiation... Let's break it down. The cable has an electric field around it..... even (as we saw) when there is no current flowing. The field is wrapped around the cable. The field strength falls with the inverse sqrt.... ie. it doesn't "radiate across the room like radiowaves". Now, if you connect the cable somewhere and current flows.... You also have a magnetic field. Now you can have an antenna.... as you have your E and H fields, and the nice (they don't make em like they used to) video shows. ... but it's not going to radiate anything. It's completly the wrong size to be an effective dipole antenna (50hz = 6000km long) Now.... if we were talking about it being an antenna for 500mhz. Then, we are in the ballpark. Is there frequencies this high (at some signficant level) coming out the powerpoint? People tend to imagine that EM energy is radiating across the room from their power cord like it does for wifi, and radio, etc. etc. (from antennas). This isn't happening with the powercord. The fields can be just understood by the inverse sqrt of distance.
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 Just now, davewantsmoore said: Let's .... but this is a long way from the topic... as none of this matters. Just compare the audio signal output under various condition.... and see what you get. The trick will likely be controlling well enough for things that you aren't trying to test.
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 27 minutes ago, pwstereo said: I get that the power cable can't be an effective antenna at 50 Hz, it's way too small, I don't think anyone was suggesting that it's transmitting a powerful signal. My point is that it isnt transmitting or "radiating" (ie. antenna) any signal.
kukynas Posted October 7, 2020 Posted October 7, 2020 5 hours ago, aussievintage said: (but yes I did hear of someone with a dedicated transformer and feed to his house just for the hifi.) lol, maybe the same Japanese dude san I've seen on YT couple of years ago
bob_m_54 Posted October 7, 2020 Posted October 7, 2020 (edited) 1 hour ago, davewantsmoore said: Now, if you connect the cable somewhere and current flows.... You also have a magnetic field. Now you can have an antenna.... as you have your E and H fields, and the nice (they don't make em like they used to) video shows. Which is the whole point of the exercise. No? What are we trying to test if there is no power through the cable, and subsequently no audio output? sarcasm? Funny, but the science behind it, is the same today as it was then. It's just that the youngsters keep thinking they reinvented it. 1 hour ago, davewantsmoore said: but it's not going to radiate anything. It's completly the wrong size to be an effective dipole antenna (50hz = 6000km long) Correct, in that it is a very inefficient antenna, but we were talking about whether or not the EM fields were radiated, not how far they radiated. The same can be said for the effect of the E field, it's there, but due to it being very small, it's only relevant in close proximity to the cable. The only difference between that and a radio station antenna is the efficiency of the antenna due to it matching the transmitted frequency, and the power you shove up it (technical term). Oh and the fact that you don't have a pair of opposed parallel radiating elements cancelling out the effect of each other, to a large degree. 1 hour ago, davewantsmoore said: People tend to imagine that EM energy is radiating across the room from their power cord like it does for wifi, and radio, etc. etc. (from antennas). This isn't happening with the powercord. The fields can be just understood by the inverse sqrt of distance. I think you are stuck on the term "Radiating" all that means is the fields emminate out from the source, the same as the heat from your heater. As in a gradient of lessening field strength the further out they reach, as you say, dropping in power in the inverse square, The same way radio waves do.... There are no squiggly things speeding across the sky. Edit:.. Missed a bit. Not sure why, but it posted in a separate post below.... Edited October 7, 2020 by bob_m_54
kukynas Posted October 7, 2020 Posted October 7, 2020 11 minutes ago, davewantsmoore said: My point is that it isnt transmitting or "radiating" (ie. antenna) any signal. once we hit lower uV / higher nV scale pretty much every cable carrying signal will becomes antenna, different is amplitude and frequency, do we care about uV interferences in mains cable? nope... look at the noise suppression of standard or shielded cable and look at which frequency they reject the noise and at which amplitude (db) 2
bob_m_54 Posted October 7, 2020 Posted October 7, 2020 1 hour ago, davewantsmoore said: Now.... if we were talking about it being an antenna for 500mhz. Then, we are in the ballpark. Is there frequencies this high (at some signficant level) coming out the powerpoint? Yep, every time your fridge motor cuts in and out, or any other decent sized current is switched Hot water system maybe. And that will be more of a worry for your audio system picking up noise, than any 50Hz EMI.
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 2 minutes ago, bob_m_54 said: I think you are stuck on the term "Radiating" I'm not "stuck" on anything.... and I have no misconceptions about how this works. I'm just (trying to) making sure nobody else (not you) is stuck on the term "radiating". As it is a common misconception that people end up with. 2 minutes ago, bob_m_54 said: all that means is the fields emminate out from the source, the same as the heat from your heater. As in a gradient of lessening field strength the further out they reach, as you say, dropping in power in the inverse square, The same way radio waves do.... Yes, but those "radio waves" .... require a (sufficient) antenna. There isn't one here.... so, the fields are just inv sqrt distance. That was my whole point. I was trying to make it without invoking antenna theory. I'm still at a loss as to why you tried to explain it to me.... or grumbled about kids being on your lawn (I was alive in the 70s too). .... but I'll never be able to communicate clearly enough to everyone.
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 7 minutes ago, bob_m_54 said: (power cable) picking up noise A completely different consideration to what I was talking about (power cable transmitting EM)
bob_m_54 Posted October 7, 2020 Posted October 7, 2020 5 minutes ago, davewantsmoore said: A completely different consideration to what I was talking about (power cable transmitting EM) You have misquoted me. what you said was: 1 hour ago, davewantsmoore said: Now.... if we were talking about it being an antenna for 500mhz. Then, we are in the ballpark. Is there frequencies this high (at some signficant level) coming out the powerpoint? What I said was: 17 minutes ago, bob_m_54 said: Yep, every time your fridge motor cuts in and out, or any other decent sized current is switched Hot water system maybe. And that will be more of a worry for your audio system picking up noise, than any 50Hz EMI. And they will be radiated way more than any 50Hz EMI..
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 1 hour ago, bob_m_54 said: And they will be radiated way more than any 50Hz EMI.. Ah, I see what you mean. .... they're quite powerful, but only occassional tho.
Stereophilus Posted October 7, 2020 Posted October 7, 2020 (edited) 2 hours ago, bob_m_54 said: Yep, every time your fridge motor cuts in and out, or any other decent sized current is switched Hot water system maybe. And that will be more of a worry for your audio system picking up noise, than any 50Hz EMI. These high frequency EMI products from, let’s say “dirty” SMPS, propagate or radiate along AC circuits and diminish in amplitude according to the inverse square of distance from their origin? Edited October 7, 2020 by Stereophilus
kukynas Posted October 7, 2020 Posted October 7, 2020 quoting Belden: Quote For instance, one of the worst noise offenders is 60 Hz power (50 Hz for much of the world). There is no shield of any kind that we can apply to a cable that has any effect on that low frequency. Even a solid steel conduit, perfectly installed, is only around 30 dB of noise rejection at 60 Hz. Their starquad cable can reject 50db... https://www.belden.com/blog/broadcast/How-Starquad-Works
Stereophilus Posted October 7, 2020 Posted October 7, 2020 6 hours ago, davewantsmoore said: I'm not really sure I understand what you are trying to say. By measuring the audio signal output of a "system" ...... and then tightly controlling the rest of the system, other than specific thing(s) you change (eg. the power cord) ..... then you need to make any "assumptions" about what you are measuring. If you are identifying some things to perhaps test.... then sure, test 'em. The "analysis" comes later once you have the results. I think you understand what I meant better from the later post. Essentially I’m asking for us to carefully consider appropriate methodology and be careful not to compromise our results for the sake of controlling all potential variables. For example, using regenerated AC in the study would tightly control AC variations, but potentially remove a variable that our study needs to examine. 5 hours ago, davewantsmoore said: The finding will tell you what further experiements you need to run.... to be sure about the results (ie. to test, or control for, any "inherent assuptions", or anything else not controlled for or examined). First you need to demonstrate some result using a very specifically controlled setup..... the reason, is that if it is not well enough controlled, you will not be able to know what/how your result was caused. Indeed.... You should be very specific about what/how you're testing.... so you can control for every possible variable that you're not testing. I understand your thinking, and I agree to some extent. I’m cautious about that approach of high specificity at least initially due to our (as demonstrated in this thread) questionable understanding of what we are looking for. By NOT controlling as many variables, we lose our specificity, but gain sensitivity. That is, we are more likely to see a difference that is worth exploring further. We would then seek to control more variables as our knowledge and testing advances.
kukynas Posted October 7, 2020 Posted October 7, 2020 1 hour ago, Stereophilus said: So, if we make an assumption that all of our hifi equipment is regulating and filtering mains AC adequately and within the manufacturers tolerances, then a dedicated circuit with (or without) additional filtering is redundant? no, but we should apply sufficient filtration and shielding where it matters, i.e. shielded signal cable from low noise environment to low noise environment (DAC>AMP) etc. , shielding between PSU and low noise part of the device circuit, better filtration and regulation from the PSU towards low noise circuit etc. but shielding mains cable which comes from dirty environment to the device socket? now we might have different discussion if we add power filter/regenerator between wall socket and the DAC/AMP, benefit would come more apparent on the other hand we won't know how much it would contribute to post filtration in the DAC/AMP unless it's all measured and tested...
Stereophilus Posted October 7, 2020 Posted October 7, 2020 4 minutes ago, kukynas said: no, but we should apply sufficient filtration and shielding where it matters, i.e. shielded signal cable from low noise environment to low noise environment (DAC>AMP) etc. , shielding between PSU and low noise part of the device circuit, better filtration and regulation from the PSU towards low noise circuit etc. but shielding mains cable which comes from dirty environment to the device socket? now we might have different discussion if we add power filter/regenerator between wall socket and the DAC/AMP, benefit would come more apparent on the other hand we won't know how much it would contribute to post filtration in the DAC/AMP unless it's all measured and tested... Do you think using balanced cables and common mode noise rejection would work adequately instead of shielding (in the example of DAC to Amp)? Sorry, off topic slightly.
kukynas Posted October 7, 2020 Posted October 7, 2020 never thought about such comparison so hard to tell, I was always using either shielded balanced or shielded single ended depends on application
Stereophilus Posted October 7, 2020 Posted October 7, 2020 38 minutes ago, kukynas said: never thought about such comparison so hard to tell, I was always using either shielded balanced or shielded single ended depends on application Food for thought. I have seen it posited that SMPS dump their high frequency noise into the ground connection, which then is, of course, used to connect to the shield of most cables (PCs and ICs if they are shielded). I don’t know if that is true, but it might go some way to justifying a cable manufacturer claiming unshielded cables sound better. And if you can remove the EMI noise from your balanced ICs using common mode rejection, then a shield is superfluous.
aussievintage Posted October 7, 2020 Posted October 7, 2020 13 minutes ago, Stereophilus said: Food for thought. I have seen it posited that SMPS dump their high frequency noise into the ground connection, which then is, of course, used to connect to the shield of most cables (PCs and ICs if they are shielded). It can only happen if a significant impedance exists between the "ground connection" and true ground, or at least that to which other equipment is grounded. If there is zero ohms (or a close approx.) in the ground connection(s), there is nothing for the voltage noise to dump onto and affect the signal which is referenced to it.
davewantsmoore Posted October 7, 2020 Posted October 7, 2020 3 hours ago, Stereophilus said: I think you understand what I meant better from the later post. Essentially I’m asking for us to carefully consider appropriate methodology and be careful not to compromise our results for the sake of controlling all potential variables. For example, using regenerated AC in the study would tightly control AC variations, but potentially remove a variable that our study needs to examine. You can study whatever you want to.... just "one at a time", so to speak. Switch between regenerated AC and not... and see if the signal output changes. 3 hours ago, Stereophilus said: see a difference that is worth exploring further. We would then seek to control more variables as our knowledge and testing advances. I doubt you are talking about the same things/terminology as I am. What I am trying to say is that at all times you need to have enough varibales controlled in the system so that when you make a change (Eg. switch the mains filter, or power cord) that you know that any differences you might measure, are actually the result of the change you made. It might sound simple, but it's not necessarily.
Stereophilus Posted October 7, 2020 Posted October 7, 2020 29 minutes ago, aussievintage said: It can only happen if a significant impedance exists between the "ground connection" and true ground, or at least that to which other equipment is grounded. If there is zero ohms (or a close approx.) in the ground connection(s), there is nothing for the voltage noise to dump onto and affect the signal which is referenced to it. Yes, that is my understanding as well. However, as we know, a lot of power supplies connect ground to neutral, which can raise the ground potential (referenced to true ground) depending on what load is being used across the circuit. This would create such an impedance I believe?
aussievintage Posted October 7, 2020 Posted October 7, 2020 (edited) 12 minutes ago, Stereophilus said: Yes, that is my understanding as well. However, as we know, a lot of power supplies connect ground to neutral, which can raise the ground potential (referenced to true ground) depending on what load is being used across the circuit. This would create such an impedance I believe? Raising potential doesn't create an impedance, that's an inherent property of the materials and contacts etc. and as for it raising the potential, it can only do that if you already have a bad earth, i.e. one with a significant impedance to ground (in the same way as noise does it, or not). These neutrals only connect to ground back at your switchboard, (and other places in the electricity companies distribution network), so that's your local reference for everything in your household. Unless you happen to have had your own dedicated clean earth created. It can be a real can of worms... Edited October 7, 2020 by aussievintage
Stereophilus Posted October 7, 2020 Posted October 7, 2020 3 minutes ago, davewantsmoore said: I doubt you are talking about the same things/terminology as I am. No, we are on the same page. My line of reasoning is perhaps more abstract, and the type of study I am thinking of is more difficult to do in a practical sense. Your approach is the more straightforward, and I think for those actually putting in the time and effort, more manageable.
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