Ferrite choke on mains cable

I have just received to MCRU mains cables and they appear to have ferrite chokes inside the plug and iec. One small choke on each core at each end of the cable. They sound a little wooly in the bass, almost sat on. Does anybody have any experience with these or do you think thinks will improve as they burn in?
I’m tempted to just burn them in for a week or two and then A/B them with my original Naim cables, but I want to be sure the ferrite chokes aren’t doing something weird. They are easy enough to remove if needed.

I put ferrites at the terminating end of my PowerLines. Can’t say it negatively impacted anything.


These are intended to suppress high frequency noise, You will not hear any difference with them on or off as ferrite has no effect on frequencies as low as power with 50/60Hz
It does not start to have any effect until the noise frequency is in the mHz ranges. One or two of the ferrite alloy formulas work in the high kHz range, but these are expensive & I very much doubt they are on your cable.


Thank you Mike-B. Its probably just burn in that is required then. I will persevere for a few weeks and then A/B against the originals.

OK, but what MCRU cable is this, I’d like to see what this looks like out of curiosity.

Hi Mike, I’ll take a picture when I get home tonight. It is described as a filter, so assuming its for RF. Its on a 752 mains cable and 79 mains block.
As they are slipped over the individual wire cores, the would be fairly simple to remove, if not a bit of a faf. It just means opening up the plugs to disconnect terminations, slip the rings off and reconnect.



A picture would be good if no trouble. I just read the MCRU blurb for 752, tells me nothing.
I’m intrigued with this, I’m an electrical engineer & I can’t imaging anything that fits inside a standard 13A & IEC plug will do much.

I’d send them back to MCRU if you’re not getting on with them. Dave has a good returns policy (I’m assuming these were new from MCRU)

1 Like

Mike, they are just like little black polo’s (other mints are available), over the cable core inside the plugs. I’m sure the picture will help.

James N, I will see how they get on. It could just be the CD’s I’ve spun have sounded a little wooly in the bass. They were all new releases, so no experience of them with the old cables. These were the cables recommended by Dave when I spoke to him, so I’m hoping its just my imagination. Might do a quick swap back tonight for a sanity check. Unfortunately I forgot to hit play as I left this morning, so they have current passing through, just no music playing.

1 Like

I know what a ferrite choke is but I read the subject (rather too quickly) as a Ferret had choked on a mains cable. :roll_eyes:


OK Ian, I understand what they are, little black polo mints is all I need, no photo required.

1 Like

Ferrites on mains leads are not that unusual. Naim put one on the Unitiserve kettle lead. I find it hard to imagine they are the cause of your woolly bass, though.

1 Like

Ferrites are often put on mains leads feeding equipment with internal sources of RF such as TVs & computers (bear in mind a streamer contains a computer): the purpose is not to stop RF getting into the equipment, but to prevent the equipment polluting the mains or using the mains cable as an aerial, and is often a part of a manufacturer’s intended preventative measures to comply with regulations on electromagnetic interference.

The ferrites themselves work the same regardless of which side pf them the RF originates.


Hi Chris, I’m sure its just burn in thats making things weird. Its always like this when you put something new in the system. Put a new HC in a month ago and it was up and down for a week or two before it settled.
I know that surge protectors and conditioners can be the devil to a Naim system, so its just a niggling doubt at the back of my mind. I was trying not to splurge on Powerlines, so my own fault for being tight.

FWIW, I have ferrite all over the place at home. I put them on the equipment end of the fridge cable, the airconditioner, hanging LED lights, the phone, most of the computer leads etc.

It’s hard to judge whether this always helps, but for sure they don’t harm and even several bags of 20 in various sizes costs very little.


Ditto, I have them in many places.
And yes they do no harm, but how effective is the question.
The unspecified general purpose clip on type that the www stores offer are normally in the 100MHz & upwards range, OK for what they do as general purpose noise suppressors.

My main concern is with SMPS’s associated with my audio, this is NAS, broadband & phone.
SMPS’s operate at low frequency, typically 50KHz to 3MHz & there are only two ferrite mixes that are effective at these frequencies. I use Fair-rite ‘75’ with its impendence peak around 1.8MHz.
Wherever possible I fit clip-on cores with multiple cable passes thru the ferrite core, this multiplies up the impedance & slightly lowers the effective peak frequency.
This is my broadband hub SMPS

1 Like

Ferrite chokes are simply there to add inductance and therefore impedance to high frequency currents flowing as common mode currents in all the conductors in the cable relative to ground.
As long as the choke is around all conductors of the cable, there will be no affect to the signal in the cable, including mains.

They are usually a good thing to have, as they reduce high frequency emmisions radiating from or travelling through the attached cable and for some devices are a legal requirement so as to meet EM compliance for the connected device. You sometimes see ferrite chokes on switch mode powersupply mains leads for TVs, computers and such like.

1 Like

Thank you for the explanation.

Thank you Simon-in-Suffolk, that is just what I was looking for. Very well explained.

As it happens, I did some further listening last night with some more familiar discs. I reinstalled the original mains cables and prepped some discs. First was Rumours on the CDX2, then Diana Krall on Vinyl. Then I switched the new cables back in. Back to Rumours and It was almost as expected but with a little more bass depth. Highs all sparkly and sweet. Then I went onto Diana Krall on vinyl, well blow me sideways, what a smooth coherent sound. Crystal clear and smooth as silk, certainly no evidence of a wooly bottom !!! I then treated myself to Bowie and the Rise and Fall of Ziggy Stardust. This was convincingly the best it has ever sounded on my system. SWMBO even approved.

Hi again Ian, I suspect the changes you hear are more down to the cable itself rather than ferrite. A ferrite ring small enough to fit inside a plug will not have enough mass to do much, but whatever, you like what you have & the significant other approves, what’s not to like.
This is my power dist board, ferrite giganticus on the cable.

1 Like