Why an AC Power Cord cannot make a difference

[Holmz]

This what we do with motors...

https://literature.rockwellautomation.com/idc/groups/literature/documents/in/520-in012_-en-p.pdf

Page 2 of that attachment should individual conductors running through the ferrite.
Which is what I was talking about, when wondering how a twisted pair has enough inductance to interact with the ferrite.

Hence my question remains…

 

[antcollinet]

How do those ferrites work?
Shouldn’t only a single wire goo through the ferrite?
It seems like a twisted pair going through it would not really have any effect from the ferrite.

Page 2 of that attachment should individual conductors running through the ferrite.
Which is what I was talking about, when wondering how a twisted pair has enough inductance to interact with the ferrite.

Hence my question remains…

Because common mode noise current is going in the same direction in both conductors (or is in just one conductor (eg earth) - and not returned in the others). Thats what common mode means. The return current is to ground elsewhere and hence outside the ferrite.

 

[Paffi]

For example, Wuerth WE-AFB LFS series model #7427727, alternating with WE-AFB series model #74270077. Those are for direct cable mounting, not clamp-on type (which are less effective and more expensive), so you have to remove the connector on one side of the cable.
These are high quality products and thus a bit costly but they are very effective... which often is not the case with any random far-east clamp-on ferrite you can buy on the usual platforms.
Together with Eupen ferrrite-loaded and shielded mains cable (e.g. Eupen GNLM 2.5, a bit hard to get, though) this as good as it ever gets, laboratory-grade EMC level.

WE-AFB LFS | Passive Components | Würth Elektronik Product Catalog

Low Frequency Specialist | Core Material MnZn | Frequency Range 300 kHz to 30 MHz | Ø Cable 4.55 to 9.7 mm | Order Samples Free of Charge & Request Quotes Online | High Quality | Fast Delivery

www.we-online.com

WE-AFB | Passive Components | Würth Elektronik Product Catalog

Multi-purpose Bead | Core Material NiZn | Frequency Range 1 MHz to 1 GHz | Ø Cable 3.3 to 17.4 mm | Order Samples Free of Charge & Request Quotes Online | High Quality | Fast Delivery

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Thank you - I hoped for clamp-ons as I don´t want to destroy my cables A pitty.

 

[JSmith]

Where power cords really matter is when one is playing a power chord on electric guitar... power chords will not sound right without the most expensive power cord attached to the amp. Of course one must always be careful not to trip on the power cord whilst playing said power chord...

JSmith

 

[solderdude]

The question is would ferrites help in most cases where audio gremlins are popping up in home situations with audio gear ?

In most cases the audio gremlins are not common mode >> audio frequencies but rather leakage currents within the audible band.
Ferrites only lower common mode RF. In some cases the RF, however, could be 'demodulated' by some semiconductors in a circuit and in that case can solve a problem.

It works a little different than mains filters.

That, however, does not have much to do with power cables unless they are built into the cables (they exist). And even there the question remains... is it really needed for audio in home situations ?

 

[wwenze]

I have a pack of them that I try when I encounter any noise or spike issue. So far they have done nothing.

They don't even do anything to the USB3.0 2.4GHz interference because they have pretty much no impedance at said frequency. Wonder if that's why they stopped showing up.

 

[DSJR]

Thirty years ago, I lived in a town that seemed to have mains quality issues (my memories are of subjective differences, so maybe not at all relevant here). A ferrite or two on my active speaker power cables *did* seem to 'improve' the sound a little (very cheap things to buy and very easily added or removed). My preamp and CD player of the time, designed by an electronics and RF (ex-military-aerospace I believe) expert engineer, were totally immune to the charms of cable ferrites (a previous amp he designed was tested by Paul Miller as very clean indeed at very high frequencies compared to the competition of the time.

The legacy of the above - and living in a coastal area with seemingly 'cleaner' power, is that today, I use ferrites on almost all power cables to audio and computer/TV equipment, knowing they make next to no difference, but I 'feel' happier doing so. The things are cheap and easily removed.

 

[KSTR]

Thank you - I hoped for clamp-ons as I don´t want to destroy my cables A pitty.

clamp-ons are of course OK, no doubt. You just may need more of them but if you can get like dozens of them for less than $1/pc in a surplus sale then go ahead, for example: https://www.ebay.com/itm/363222428103 (with quality ferrite from TDK, #ZCAT2035-0930A)

 

[KSTR]

Wonder if that's why they stopped showing up.

No. Cables with integrated ferrites are costly to produce. EMC regulations and practice have improved so there is little need for them.

They don't even do anything to the USB3.0 2.4GHz interference because they have pretty much no impedance at said frequency

This might be true for the usual simple clamp-on ferrites but much of the better core materials are still OK at 1..3Ghz. For excellent effectiveness above 1GHz, ferrite-loaded coax is the proper choice, also known as stealth cables. They have a layer of ferrite paste between the outer shield and the jacket sleeve.

 

[solderdude]

ferrite-loaded coax is the proper choice, also known as stealth cables. They have a layer of ferrite paste between the outer shield and the jacket sleeve.

I like to see some mains cable manufacturer use those as mains cables..

 

[Sokel]

I like to see some mains cable manufacturer use those as mains cables..

That's how some "regenerators" were made ,they had a coax inside the box looped around a large ferrite (Choke Balun) same as for RF connections.
I think I have seen couple of tear downs around.

 

[KSTR]

I like to see some mains cable manufacturer use those as mains cables..

Easier to use the existing mains cable variant, the mentioned Eupen GNLM 2.5. Some stores sell ready-made cables, at quite resonable prices.

 

[jpslittleworld]

Would it not make sense to understand that you probably have a hundred feet or more of Romex 14/2 or 12/2 running from your electrical service to what ever outlet is powering your amplifier. You can defiantly have wire that is too small but there is no magic. In my eyes all that matters is that the wire is OFC and the proper gauge.

If you really want to be anal then make your own wire using 14/2 or 12/2 Romex and put your own ends on it. You should not be able to gain anything considering the amount of Romex that your power is already traveling on.

This is my opinion

 

[Salt]

Vacuum cleaners' cords are subject to a lot of mechanical stress; amplifier cords, not so much (I hope!).

Exceptions may be with (vacuum) tube amps.