Mains Cable EMI/RFI Ferrite Coils

[worthingpagan]

I've noticed many audio mains cables are fitted with ferrite coils close to the IEC plug. Should a coil also be fitted along the same cable close to the mains plug or is this unlikely to make any difference? If a cable is already screened does it need any coils fitted? Cheers

[DSJR]

I don't know about ferrite coils, but ferrite tubes are often fitted to cables to minimise, I think, RF and higher frequency mush getting through. Thing is, they're CHEAP and many of them can be clipped or unclipped around the cables concerned, so no need for mass re-soldering etc...

I found they worked a treat with my ATC actives, made no difference at all with the AVI CD player and amp I had, yet the Micro-Seiki CD player needs a high-current filter as well (maybe not here, but I continue to use it anyway).

Give 'em a try. they won't cost you much and just may help a tough if the mains has an off day (Luton was terrible I remember, and the least said about the mains supply at KJ W1 when I spent some time there, the better - a £200 RA block was a bigger difference than going from a Copland amp to a Krell costing many thousands more ;) :eek:)

[sq225917]

For ferrites to work the cables really need to be looped through them multiple times, just going through them once really does very, very little.

[prestonchipfryer]

These are what I use with good effect. Worth a try at this price. Because they are quite long the cable(s) don't need to be passed through multiple times.

.http://www.ebay.co.uk/itm/8-TDK-11mm-1130-Cable-Wire-RFI-EMI-Noise-Filter-Ferrite-/220744535652?pt=UK_ConsumerElectronics_SpecialistR adioEquipment_SM&hash=item3365664e64

:) John

[Spectral Morn]

I have personally found that they have a cumulitive effect. The addition of one or two in a system may have an audible difference, sometimes not but putting lots in, on cables both signal and mains has. Once you remove them you will be aware of the loses.

However I suspect there maybe locations (and systems) where the effects maybe less or greater or even none at all.

Suck it and see is the best advice, they are cheap enough.


Regards D S D L

[worthingpagan]

much obliged guys

[DSJR]

These are what I use with good effect. Worth a try at this price. Because they are quite long the cable(s) don't need to be passed through multiple times.

.http://www.ebay.co.uk/itm/8-TDK-11mm-1130-Cable-Wire-RFI-EMI-Noise-Filter-Ferrite-/220744535652?pt=UK_ConsumerElectronics_SpecialistR adioEquipment_SM&hash=item3365664e64

:) John

Thanks very much - just bought a set for the computer "stuff."

DSDL above is also absolutely correct here, one or two "may" make a difference depending on the gear and location, but adding more doesn't make that much extra. Since I often have SMPS PC gear running, any help to stop muck getting back into the mains can't be a bad thing I reckon..

[prestonchipfryer]

Thanks very much - just bought a set for the computer "stuff."



That's a very good idea. Let us know how you get on with them.

Thanks very much. :)

John

[DSJR]

Already got loads on the stereo and they were essential in former locales, if not really needed here. Anything to help that costs little and is easily removable suits me :)

[prestonchipfryer]

Already got loads on the stereo and they were essential in former locales, if not really needed here. Anything to help that costs little and is easily removable suits me :)

Got loads on mine as well. The only thing 'without' is my phono pre; placing ferrite round the phono leads to and from the phono pre just seemed to make things worse. Got them on all power leads and interconnects between preamp and power amp though - certainly cuts out a lot of 'hash'.

John :)

[worthingpagan]

Looking around, I found this useful:-

http://www.audiomisc.co.uk/mains/filters2.html

[Wakefield Turntables]

Right I've fitted roughly 20 of these TDK ferrite coils to my system. I have them at the beginning and end of all my power cords, and a couple fitted to my IC's and tonearm cable. I'm gonna keep them in place for 2-3 weeks and see if they make any difference and I'll update this thread.

[worthingpagan]

Right I've fitted roughly 20 of these TDK ferrite coils to my system. I have them at the beginning and end of all my power cords, and a couple fitted to my IC's and tonearm cable. I'm gonna keep them in place for 2-3 weeks and see if they make any difference and I'll update this thread.

Put some on your speaker cables at the cabinet ends. Also your interconnects at the source end. I don't know that you need more than one on each mains cable, again, at the source end. :cool:

[Wakefield Turntables]

I've done all that and I think things have become more detailed. Midband seems to have cleared up and I think I'm hearing more micro detail. This could all be psychological of course, I need more time to evaluate.

[prestonchipfryer]

I've done all that and I think things have become more detailed. Midband seems to have cleared up and I think I'm hearing more micro detail. This could all be psychological of course, I need more time to evaluate.

Certainly on my system they are used on power and mains cables. Not on speaker cables as this seemed to rob some drive and energy. Keep experimenting, it's all good fun.

John

[Marco]

I've bought some of these to try from Maplin (the large diameter variety):

http://www.maplin.co.uk/ferrite-rings-and-beads-32792

And I intend fitting them around the incoming 16mm armoured cable, in my CU, feeding the dedicated mains spur for my system.

The reason for this is that Mark Grant brought round his Blue Horizon mains sniffer, and I could hear a bloody radio station very clearly coming through my mains supply (even though the noise readout level was low)!! :doh:

However, that was without my TD mains filter, in-line. When we plugged the noise sniffer in, via the filter, things were deadly silent, which goes to show just how effective Anthony's filter is :)

I'd like to try and kill the RFI at source, though, which is why I'm giving the ferrite rings a go. I'll report back with my results :cool:

Marco.

[prestonchipfryer]

Marco, you will probably find it's trial and error but it should be able to kill most of the RF interference. Look forward to your results.

John

[Themis]

And you should try both ends of the cable equipped, imho. Results may vary. ;)

[Welder]

I’ve used split ferrite rings on my power leads for a few years now.
It’s interesting that manufacturers use them as standard pretty much on power leads for laptop SMPS and external hard drives for example.
Given they increase the self inductance of the cable they surround I’m not sure I would want them on signal leads such as interconnects and speaker cables.

[Themis]

Given they increase the self inductance of the cable they surround I’m not sure I would want them on signal leads such as interconnects and speaker cables.
Very good point. :)

[Wakefield Turntables]

I've had the ferrite coils in now for about 2 weeks. I have listened to various types of music. The results so far are that micro dynamics have improved but the impact of the music seems a little reduced. This may be down to the fact that I have ferrite coils on every cable :eyebrows: I'm going to experiment and see if we can get some of the slam back! The soundstage appears more cohesive, tighter and slighter wider. I've found myself staring at my right wall a couple of time wondering why an instrument has suddenly appeared from nowhere :lol: I think for £25 its been a worthwile investment. Its not night and day but I'm nicely surprised with the improvement.

[Barry]

I've bought some of these to try from Maplin (the large diameter variety):

http://www.maplin.co.uk/ferrite-rings-and-beads-32792

And I intend fitting them around the incoming 16mm armoured cable, in my CU, feeding the dedicated mains spur for my system.

The reason for this is that Mark Grant brought round his Blue Horizon mains sniffer, and I could hear a bloody radio station very clearly coming through my mains supply (even though the noise readout level was low)!! :doh:

However, that was without my TD mains filter, in-line. When we plugged the noise sniffer in, via the filter, things were deadly silent, which goes to show just how effective Anthony's filter is :)

I'd like to try and kill the RFI at source, though, which is why I'm giving the ferrite rings a go. I'll report back with my results :cool:

Marco.

Pray O Grand Inquisitor, what is this "Blue Horizon mains sniffer" of which thou doth speak?

I've 'Googled' it and not come up with anything. :scratch:

Cheers

[Mark Grant]

Its a new product that I have been testing for about a month.

It's an excellent product.
Not for retail sale - dealer only as far as I know although I will hire them out soon :)

Temporary photo until I take some better ones, its so new there is no official information anywhere yet, not even on the manufacturers web site :)

http://i759.photobucket.com/albums/xx234/server9/forum-pictures/blue-horizon-IMG_0112copy.jpg

[MCRU]

Nice :)