Which is why Rick Miller has specified split bobbin transformers (see Galo design)
That is basically equipotential bonding. At least in UK that is done in every house as every metal pipe needs to be bonded and grounded. possibly has benefits if you know what you are doing.
In the UK every house already has a ground rod driven into the soil and connected to the fuse box, and the sparky will not connect the incoming feed without it. My house is old enough to still have the connection to the incoming water pipe even though it has been upgraded to the correct modern solution. A seperate technical earth should be considered very very carefully to make sure it doesn't make anything dangerous (depending on voltages supply feed and local code).
The more interesting question is, what problem is it supposed to be fixing? The Protective Earth (PE) has the function to save your life if the live wire touches a metal case. I don't see that question being discussed.
Cheapskates who don't order the electrostatic shield option for a few $ more only have themselves to blame...
Point missed. The transformer and diode pack can form a resonant circuit spewing wideband noise about and back out onto the mains for something else to pick up. However the fix is not a fancy mains cable, it's snubbing the transformer with a few pennies worth of parts and a little time!
In a well designed power supply with proper attention paid to components layout this really isn't a problem.
I have a toroid transformer with electrostatic shielding and with a gauss band. Just added an external AC line filter because the transformer powered the very sensitive dac Vref supply. When the microwave was running in the kitchen the dac sound became slightly grainy. The sound is reproduced though very sensitive electrostatic speakers. Presume the sneak coupling path was through the electrostatic shield which then introduced ground coupled noise. This is despite the shield being connected to AC line ground which is separated from Vref ground by a ground isolator circuit with a diode bridge, resistor, and cap all in parallel. Could be removing and or reducing the cap, and or increasing the resistor would have helped too. In any case its fixed now 🙂
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The dac and the microwave are on different circuits. Everything in the kitchen is on GFIs back the main panel. However, wiring from both circuits back to the main panel may run in close parallel over the garage ceiling back to the panel. Could be some stray coupling there.
but you presumed the problem without investigating and now are blaming something without knowing. This is how disinformation starts.
Not blaming anything per se. The AC line filter is only fitted to the Vref supply. And there is a ground isolator circuit. My interest was in fixing the noise, not necessarily a detailed investigation. The fact remains that the transformer has a shield and an external filter fixed the noise problem. Thus the presence of a shield is probably an often helpful noise attenuating factor but not necessarily an iron-clad guarantee of zero AC line coupled noise. My take on it for now anyway.
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Most commercial line (entry) filters are pretty ineffective below a couple hundred KHz. Below 100KHz where a lot of switcher noise is, they often times don't even chart the insertion loss.
I don't use line entry filters for that reason. This is a filter which I have used which has pretty good specs. Not cheap though.
Corecom 6FC10
I don't use line entry filters for that reason. This is a filter which I have used which has pretty good specs. Not cheap though.
Corecom 6FC10
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So this has become yet another of the many threads seen here and other places over time that discusses whether or not power cords in audio systems can make any difference in what you hear.
It all started with the initial post by ceulrich that stated something as being factual when it is not factual at all. Here is that post again just for reference:
“The utility of power conditioners and cords is well established, particularly for those living in cities or in industrial areas, but it is more difficult, at least for me, to make a case for that utility for those living in rural areas. I am wondering if there are any evaluations a DIYer can conduct that would indicate the need for such equipment?”
The simple fact is that the ability of power conditioners and cords to make any sonic difference at all in audio systems, regardless of where you live, has never been established by well designed blind testing. There are, of course, a great many opinions on the matter and lots and lots of entirely subjective claims, but no real serious testing.
Until such time as someone conducts and publishes a serious, well controlled, blind test to prove that a difference in power cords can actually be heard, many of us, particularly with engineering backgrounds, will continue to call this nothing more than wishful thinking by people who don’t really understand it and fall prey to the market for expensive 'do nothing' cables and cords.
It all started with the initial post by ceulrich that stated something as being factual when it is not factual at all. Here is that post again just for reference:
“The utility of power conditioners and cords is well established, particularly for those living in cities or in industrial areas, but it is more difficult, at least for me, to make a case for that utility for those living in rural areas. I am wondering if there are any evaluations a DIYer can conduct that would indicate the need for such equipment?”
The simple fact is that the ability of power conditioners and cords to make any sonic difference at all in audio systems, regardless of where you live, has never been established by well designed blind testing. There are, of course, a great many opinions on the matter and lots and lots of entirely subjective claims, but no real serious testing.
Until such time as someone conducts and publishes a serious, well controlled, blind test to prove that a difference in power cords can actually be heard, many of us, particularly with engineering backgrounds, will continue to call this nothing more than wishful thinking by people who don’t really understand it and fall prey to the market for expensive 'do nothing' cables and cords.
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I would think so. Although strictly speaking it could part of one as well.
I use one in conjunction with a Line Isolation Transformer and fuse in a box to feed my home intertainment system.
I use one in conjunction with a Line Isolation Transformer and fuse in a box to feed my home intertainment system.
On the subject of wishful thinking: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3501709/#:~:text=Wishful thinking (WT) implies the,interest to others we like.
A quote from the article:
"Wishful thinking (WT) implies the overestimation of the likelihood of desirable events. It occurs for outcomes of personal interest, but also for events of interest to others we like."
Imagine then someone with engineering training who would find it desirable if power conditioners and or power cords had no audible effect. Thus far there have been no carefully controlled published studies showing that power cords and or power conditioners can have no audible effect on audio reproduction systems whatsoever under any conceivable conditions. Claims to the effect that such is the case require carefully controlled published studies if the claims are to be deemed credible. Otherwise it would no more than wishful thinking.
Aside: How does it feel to be on the receiving end of that type of logic? Also, is it motivating when approached that way to produce the demanded proof? Probably not, might not be a bad guess.
That’s because it is virtually impossible to prove a negative.
The only issue here is whether an AC power cord for a product with a well designed and implemented power supply can make any audible difference. The science clearly says that it can’t. By the time the needed voltages are rectified and filtered with a large capacitor bank the AC power cord is completely out of the picture.
So if and when someone can prove the positive - can prove with well controlled objective testing that there is an audible difference - then we can believe it.
You would think that by now at least one of the many companies offering expensive power cords would have conducted a scientific test to prove their case. But to the best of my knowledge that proof has never been done. Or perhaps it has been attempted by one of those companies and they don’t really want to publish the results. One can only wonder.
Certainly. Post #107
Why do I have an impression that posting any measurement here is a fool’s errand? 🙄
This thread has run its course (several times over).
Fair reply, thank you.
Here is some what what science says about energy flowing in a circuit:
https://physics.stackexchange.com/q...oes-energy-flow-in-a-circuit-which-is-correct
Suppose AC line noise encounters an IEC filtered inlet module. Further suppose the AC line ground conductor is at RF frequencies is not a shorted to ground exactly, rather its more like there is standing wave node at the power system ground rod. Since the ground conductor is bonded to the audio device chassis, now there RF on the outside of chassis. RCA connectors are or aren't bonded to the chassis, but most often bonding them to the chassis is considered the correct EMI/RFI practice. Thus shield currents in RCA connectors may flow between devices. Power ground RF currents may flow in the RCA coax shield. Due to shield resistance and ohms law, an electric field potential may be produced between one end of coax shield and the other end. The voltage differential thus developed can capacitively couple into the inner signal conductor, a process sometimes referred to as a type of mode conversion. AC line noise thus may bypass the power inlet module, the transformer, the rectifiers, etc. That's not the only possible mechanism of course. Not every piece of audio equipment historically was built with filtered IEC inlet modules. In that case wiring inside the device from where the power cord enters to where it attaches to the power transformer can act as a radiating antenna to couple external RF energy into the inside of the chassis. A well-seasoned EE I once knew described these sorts of things as 'sneak circuits.' They aren't shown on a schematic so we tend to take it for granted that they don't exist. Sometimes that's where EMI/RFI consultants get called in, because they specialize in finding and correcting such problems. Again, not saying I have covered all possibilities, just loosely sketched out a few of the types of things that have been known to happen.
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