AC Power thread from Cable Asylum.

[FLZapped]

Accepted.

-Bruce

I'll also add thankyou to that, so far, you've been more introspective than any of the other new mods I've encountered so far.

[Monstrous Mike]

According to engineers with whom I've spoken, the main villain targeted by aftermarket cords is noise generated not hundreds of miles away at some power sub station, but hundreds of feet away inside your home by computers, fluorescent light fixtures, refrigerators, digitally controlled appliances, and even inches away by digital sources like CDPs. All of which generate RFI that is transmitted through the power line and ultimately through the audio components. Good electronic components will happily amplify the noise along with the signal.

Print this post out and take it back to your engineer friends.

The only way to make an electronic component power cord able to filter EMI/RFI is to shield it. This will reduce the effect of the cord acting like an antenna. However, there are two problems with this. First, this will only protect against radiated interference and secondly, there is a direct connection with the house wiring so this shielding is essentially useless since the house wiring will act like an antenna and conduct the interference right to the power input on the amp.

The other major form of EMI/RFI is conducted interference which comes from noise on the AC line. Please have them explain how a power cord can filter this type of interference and noise.

This explanation can be in layman's terms or as technical as they want. And if the answer is that these superior cords simply sound better, then you don't really need any engineers at all, do you? No wait, you still need the ones who design these cords but can't explain how they work. Personally, I haven't met an engineer like that yet although hanging around here, I feel I am getting close.

[FLZapped]

According to engineers with whom I've spoken, the main villain targeted by aftermarket cords is noise generated not hundreds of miles away at some power sub station, but hundreds of feet away inside your home by computers, fluorescent light fixtures, refrigerators, digitally controlled appliances, and even inches away by digital sources like CDPs. All of which generate RFI that is transmitted through the power line and ultimately through the audio components. Good electronic components will happily amplify the noise along with the signal.

Not always, most engineers are smart enough to put broadband filtering in their designs. However, this is a different topic than what the poster was after. Certainly, if you can positively identify a souce of interference causing degradation of your equipment's performance, a proper solution should be sought. If it is a radiated problem, a filtered power cord may not help at all, or be only a portion of the solution.

BTW - you can make a cheap rf choke by sliding a cardboard tube over your powercord and stuffing it tightly with steel wool. The fun part is keeping the cord in the middle of the assembly whilst stuffing away. Then you can cap off the ends and slide the whole assembly up and down the cord to see where it has the most effect.

My method? You mean hearing deeper into my music? Discovering subtle details for recordings that I've heard hundreds of times before? Reading a book on EE theory will tell me more about the harmonic structure of a piano? Don't think so.

No, but a book on acoustic instrument physics might.

-Bruce

[markw]

Who said anything about a cord maintaining voltage variations?

rw

Mr Wizard's second post hits at this. If those teeny tiny micro mini volts are lost in the power cord and it adversely affects the performance of the gear, it indicates a major problem in either the power supply in the unit or the wall. A power cord ain't gonna do squat.

That's like putting a Sponge Bob band aid on a gaping chest wound and expecting it to be all better.

[markw]

My guess is that none of the three of you have used an aftermarket cord in your system. If I am in error, I will stand corrected.

rw

Although I'm pretty sure my listening was done in at least as scientific manner as others around here, I didn't hear any difference. How much does one need to spent to qualify for "aftermarket" status?

[E-Stat]

Although I'm pretty sure my listening was done in at least as scientific manner as others around here, I didn't hear any difference. How much does one need to spent to qualify for "aftermarket" status?

I assign no particular value to that question. One of mine ran $60, with the plugs and labor covering most of the cost. Unfortunately, there are umpteen variables given environments, components, and lastly, the cords themselves. My recommendation is not to buy any component without trying it out first.

rw

[E-Stat]

The only way to make an electronic component power cord able to filter EMI/RFI is to shield it. This will reduce the effect of the cord acting like an antenna. However, there are two problems with this. First, this will only protect against radiated interference and secondly, there is a direct connection with the house wiring so this shielding is essentially useless since the house wiring will act like an antenna and conduct the interference right to the power input on the amp.

There are a number of shielded cords with built in filter networks at both ends to prevent such "backwash". Perhaps that is sufficient enough for the audible result.

The other major form of EMI/RFI is conducted interference which comes from noise on the AC line. Please have them explain how a power cord can filter this type of interference and noise.

Ditto.

rw

[Tony_Montana]

There are a number of shielded cords with built in filter networks at both ends to prevent such "backwash".

E-stat

To understand the concept of power cord and RF/noise better, you also have to look into what happens after they enter a component. The AC is down stepped, converted to DC and THEN filtered. Since it is much easier and "more" effective to filter DC than AC, then it will be redundant, less effective [and unnecessary] to have filter at the AC end.

Usually power cord shielding is done to prevent it from contaminating other component and wires, not the other way around

[E-Stat]

Usually power cord shielding is done to prevent it from contaminating other component and wires, not the other way around

I think we're saying the same thing. By backwash, I mean sending digital hash from a CDP back through the AC mains.

rw

[markw]

I think we're saying the same thing. By backwash, I mean sending digital hash from a CDP back through the AC mains.

rw

I think Tony is saying is that the shielding on the AC cable is to prevent it's radiating anything to the surrounding wires/interconnects and any EMI/RFI sensitive equipment, thereby being the cause of the problem, not the victim of one.

The AC cable, unlike a line level interconnect, isn't in the signal path so there is no way any impurities that could possibly impinge themselves on that 60hz, 120 vac signal will be amplified.

Likewise, any junk coming into the AC cable from outside sources would be removed by the power supply, which would pretty much remove 'em by stepping the voltage down and then converting it to a quite pure DC. And, to get that DC requires a pretty low, low pass filter so any RF type stuff will be pretty much dissipated to ground.

Of course, I may have totally misread Tony and, if that's the case, I apologize.

[Tony_Montana]

I think we're saying the same thing. By backwash, I mean sending digital hash from a CDP back through the AC mains.

HI E-Stat

Could you elaborate as how hash from CDP can get back into AC main?

I think Tony is saying is that the shielding on the AC cable is to prevent it's radiating anything to the surrounding wires/interconnects and any EMI/RFI sensitive equipment, thereby being the cause of the problem, not the victim of one.

Hi Mark

That is exactly what I am saying

With today's home theater environment where we have all type of wires and IC running every where and in every directions, shielding a power cord might be one way to reduce EMI-since power cord are "big" source of it

[jneutron]

The AC cable, unlike a line level interconnect, isn't in the signal path so there is no way any impurities that could possibly impinge themselves

HOLY MACKERAL...

Why would you say that?? If that were the case, my job here at work would be so much easier..

Cheers, John

[FLZapped]

HOLY MACKERAL...

Why would you say that?? If that were the case, my job here at work would be so much easier..

Cheers, John

Well, well, lookie who crawled out from under the baseboards....find any good flat wire under there?

So how ya been stranger??

-Bruce
(hmmm, now why would anyone wanna cut JN slack....hmmm.....)

[jneutron]

Well, well, lookie who crawled out from under the baseboards....find any good flat wire under there?

So how ya been stranger??

-Bruce
(hmmm, now why would anyone wanna cut JN slack....hmmm.....)

Ummmm..actually....been strange...

Flat wire?..been lookin at that diy post, I see..

Man, just couldn't get a jpeg to show up there to save my life, so had to plant that gobblygook equational stuff..man, I hate doin that when a good pic will do...AHA...tried to upload here, guess the height was the problem...

Actually, haven't had much to say here..watchin the fireworks from a cheap seat..

I come back from vaca, and see that Terrence closed the thread, leaving me no ability to respond to his response to me...be it agree, disagree, whatever...man I hate that..
(I assume Terrence is not an "attack", but..hey, these are confusing times).

Now that I see the pic showed up, guess I have to explain to all here...

The Q was how to calculate the inductance of a pair of flat conductors that are on each other. This is a graph of the inductance of two cylindrical conductors which are coaxial..without the internal inductance of a round wire. The lines are the thickness of the dielectric..the x axis is diameter, .3 is approximately the same as 1 inch wide foil.

This equation will break down as the aspect ratio of the insulator heads up, this is good for wide conductors with thin insulation. For wide spacing, ya gotta go back to the Terman equation.

Cheers, John

[FLZapped]

Ummmm..actually....been strange...

Flat wire?..been lookin at that diy post, I see..

Yep, like my DIY solution?

Actually, haven't had much to say here..watchin the fireworks from a cheap seat..

Ah yes, Uekers favorite.

Thanks for the chart, I'll go study it some more.

-Bruce
(no more bruised nail beds....)

[FLZapped]

The Q was how to calculate the inductance of a pair of flat conductors that are on each other. This is a graph of the inductance of two cylindrical conductors which are coaxial..without the internal inductance of a round wire. The lines are the thickness of the dielectric..the x axis is diameter, .3 is approximately the same as 1 inch wide foil.

Cheers, John

Ya know, it would be interesting to see at what diameter those lines all converge at . . .

-Bruce
(as if you don't have enough to do already)

[jneutron]

Ya know, it would be interesting to see at what diameter those lines all converge at . . .

-Bruce
(as if you don't have enough to do already)

They don't..along either axis..the x-y products are constants..

It's like a graph of 1/x, 2/x, 3/x....they never converge.

Cheers, John

[FLZapped]

John,

Being that you used a cylindrical model, there are no edges to suffer from various fringing effects....


-Bruce
(I know, I'm a real big pain)

[jneutron]

John,

Being that you used a cylindrical model, there are no edges to suffer from various fringing effects....


-Bruce
(I know, I'm a real big pain)

Correctamundo..(first part, not second)

There are two reasons I said it falls apart as the aspect ratio gets too large..one is because it neglects the edges as you say, where the magnetic field will spill out into space as a dipole field...the other is the curvature of the dielectric, as the inner dielectric surface has a higher e field density than the outside surface of the dielectric..so the overall capacitance will begin to stray off...(actually, the reason the jpeg was so tall was because I had two pictures in the origional, the second being the capacitance vs diameter for various insulation thicknesses.

Cheers, John

[FLZapped]

They don't..along either axis..the x-y products are constants..

It's like a graph of 1/x, 2/x, 3/x....they never converge.

Cheers, John

Hmmmmm....so when you drop the ball, it falls half way, then half way again, and half way again . . . . . .



-Bruce
(I'm sorry, but you can't get there from here.....now go eat your pi)

[jneutron]

Hmmmmm....so when you drop the ball, it falls half way, then half way again, and half way again . . . . . .



-Bruce
(I'm sorry, but you can't get there from here.....now go eat your pi)

Yup...

I was also 'd to see a plot of L vs C, C vs diameter, characteristic impedance vs C and vs L and vs diameter, really interesting to find how the fields work..

Enough thread hijacking...back to our currently scheduled program...

The cable which delivers the power to any appliance completes a ground loop which is shared by the input wires...that loop is susceptible to e/m fields, and will intercept them and generate a loop voltage..that is why all the really good pro type stuff (not to mention 30 kiloamp power supplies) will use differential input circuitry..

And, why some amps, even with diff input, can still be susceptible to ground loop currents..

And yet, Nobody in the world (I am aware of, anyway), tests for it, measures it, or even discusses it..

That's why I put my 2 cents worth into this thread..

Cheers, John

PS....Hasn't anyone heard their subwoofer pop when an appliance turns on or off????Where do you think that sound gets in?? Hint: it ain't because of power supply inadequacies..

[Tony_Montana]

PS....Hasn't anyone heard their subwoofer pop when an appliance turns on or off????Where do you think that sound gets in?? Hint: it ain't because of power supply inadequacies..

Ok John, I will bite. What causes the pop, and what is the cure?

I always get this nasty pop sound from subwoofer when I turn off my flourescent light

[jneutron]

Ok John, I will bite. What causes the pop, and what is the cure?

I always get this nasty pop sound from subwoofer when I turn off my flourescent light

Ummm, Tony...

I already posted a pic, with the relations...here..

And, in return, you mashed me about the quality of my drawings, and my handwriting..

So, poo poo to you..you naysayer..

He he..

HI Tony...hey, notice the deletions over there in the Heaviside discussion...took what, less than 12 hours? I'm so bad, pointing out poor behaviour..got another nastygram too...man, I'm just thiiiiiis close to "history".

I am really getting tired of all this "miles and miles of wires" stuff..

Yes, there are miles of wires...

Yes, the electrons are slow...

But, no...audio equipment does not refer it's input to a ground located at the power generator...in fact, most refer their inputs to the ground of the ac outlet, in one way or another.

External entities, like lights, motors, all bounce the ground reference, or by loop pickup, cause ground currents..here, since the ground currents can be large, in the tens of amps, and fast (12 phase scr based power supplies).

Re:your sub...how is it connected to the power?...How is the input cable routed?

BEFORE DOING THE NEXT: Make absolutely sure all your outlets are wired correctly!!! no neutral/hot reversal...

Take a DVM, and measure the ground to ground voltage (NOT THE NEUTRALS) between the sub and your source (receiver) with the signal cable not connected. Then, measure the AC amps between the grounds..then, at each outlet, measure the neutral to ground voltage. (In my office, the outlets have between 1/4 volt and 1.5 volts between grounds with no office load..)

Then, repeat each while turning the light on and off..

Answer with a nice description of your setup (perhaps a crude drawing???):-), and then we can troubleshoot more.

Note: a cable hookup can also give problems...Since it is physically separated from the ac house feed, it forms a really big loop. Any unbalanced ac draw can broadcast to the cable...unbalanced being currents that go from your neutral/ground at the panel, through the ground wire into the house water main feed in. This current does not neutralize at the house mains input, wreaking havoc..

Cheers, John

PS..a pic woulda been better, Tony...maybe my 9 year old can draw one you'd consider quality...as mine just don't meet your standards...:-)

[FLZapped]

Of course, it could also be an arcing of the switch due to the inductive kickback from the ballast.....

-Bruce

[jneutron]

Of course, it could also be an arcing of the switch due to the inductive kickback from the ballast.....

-Bruce

I'm confident you are correct.

What I describe is the path the transient takes to get to the sub input..

Sure, anybody could just say get rid of the light...like when the guy says doc:it hurts when I do this.......Well, then....don't do that....badaboom..

But, what fun would that be???

Cheers, John

What...did I wake you?