Are there any benefits to having ferrite cores integrated into HDMI cables?

Question

Although many do not, some HDMI cables have a ferrite core integrated near one or both ends.

Are there any benefits to having ferrite cores integrated into HDMI cables?

I read these related Super User QAs:

1. Does the presence or size of the ferrite bead cylinder on my USB cable affect its performance?
2. How to deal with HDMI cable interference?

It appears that there may be some benefits for lower quality USB cables, but there is little information regarding HDMI cables.

The closest I read is when Mokubai mentioned, when referring to a group of cables that includes HDMI cables:

"Ferrite may well attenuate signals in those ranges and I have not seen any cables with ferrite fitted on them."

It seems a little ambiguous if Mokubai is considering the possible signal attenuation a good or bad quality. If I'm reading that statement correctly, it seems like Mokubai is perhaps hypothesizing it would be bad, and that's why they haven't seen HDMI cables with ferrite cores.

But HDMI cables with integrated ferrite cores are reasonably common (I happen to be looking at a couple right now), and I'm wondering what are the benefits, if any, of using them?

Answer 1

Ferrite cores effectively add some level of resistance to voltage changes within the cable, effectively reducing common mode noise in the cable. They are generally more effective at particular frequencies than others due to core size, material and construction.

Ferrites are generally chosen to limit particular kinds of noise in cables, and the most common unwanted noise in modern computers will be the various switch mode power supplies which sluice current back and forth through an inductor at anywhere between 100kHz and several MHz. That noise can be picked up by pretty much every wire in a system or transferred through any device connected to that power supply.

Many digital signals are much faster than that so a well chosen ferrite can add a high level of noise suppression at chosen frequencies while affecting other frequencies to a far lower degree.

Ferrite cores on an HDMI cable will reduce leaked noise from power supplies in the computer and monitor, in theory better isolating their supplies from each other and allowing less interference on the remaining cable runs. You should end up with less noise both inside the computer and monitor, as they are receiving less noise from each other, and the signal should be cleaner as it isn't reacting as much to noise while in the cable.

A ferrite will have some effect on almost all signals, but depending on the types and speeds of signals it may not be important.

Not all applications or devices will need ferrites. Some devices may implement an equivalent in the port hardware, or work around it in another way, and so not need or want a cable with ferrites in it.

Answer 2

I could be wrong but, adding a ferrite core on an HDMI cable will reduce the EMI (electromagnetic interference) on the cable (can be useful for long cables >2m).

But it won't do anything to the data since HDMI transmits digital signals so if the data transmission is successful (with or without ferrite core), the video and audio quality remain perfect.

EDIT: As JW0914 mentioned in the comments, in the context of a home theater the amount of EMI should be very limited, and as far as I know, most of HDMI cables are shielded with at least one layer.

Maybe adding ferrite core can help if you have an HDMI cable running in a wall with a power cable near it, but again as JW0914 says, it is not a good practice to put data lines near power cables.