Eliminate EMI Troubles?


This might have been discussed but I’m trying to eliminate EMI which is affecting the 8k X when touched in certain spots.

I’ve tried grounding the Mige servo motor. Changed the power cables to Shielded types on the SFX-100 DIY servo motors. Attached a USB to USB isolation switch. Going to try ferrite chokes. Any help would be great.


Hi - I had similar troubles when I put together my SFX100 a year ago when using my 5k+. I solved them by shielding the power cables to the motors & using specific ferrite cores.

I also hear a few reports from index users that if one of the following EMI filters is used on the servo power cord it elimites any EMI leaking back into your ring main and works well enough to no longer require the ferrite cores on your HMD cable (FYI I am yet to try this myself but Its on my to do list): https://www.ebay.co.uk/itm/CW4L2-20A-S-Screw-Type-AC115-250V-Suppressor-Power-Supply-Bipolar-EMI-Lin-Filter/254706520854?ssPageName=STRK%3AMEBIDX%3AIT&var=554482216794&_trksid=p2057872.m2749.l2649

If youre going to try the ferrite core approach - it requires 5-6 loops of the All in One HMD cable through 4x FT240-31 ferrite cores. I glued the cores together to make it one solid core then hung it from my ceiling above the rig.


Will the 6M Fiber Optic cable for the 8K X work against EMI?

Any comfirmed reports out there that it does stop the grey outs when touched on the sides?

I Sim Race and the Simucube OSW wasn’t working correctly yesterday. It was loosing FFB and had Erratic behavior. I found out just by pure luck that plugging it into another power board, it started working correctly. Must of had interference caused from being on the same power board as the SFX-100 DIY Motion platform.

Yes the fiber optic cable solved the grey outs for me completely. Before I lost tracking and image every single time I touched the headset, now it doesn’t happen at all.

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The optic cable solves nothing for me. If my motors are on, touching the front half of headset, the tracking is lost.

I just found out that the pimax cables, both the original and the optical one, cause an earth ground loop through the DisplayPort connector. According to an ELT device. But maybe it’s a false positive.
I don’t know the significance of that, except that ground loops are considered problematic.

@prosb6 What can be done to break the loop?

Hm right now I’m actually not sure if there is a loop. I’m using a ELT tool by a community member but maybe it is detecting the ground coming from the DisplayPort and false positively reporting a ground loop, I’m checking with the creator :slight_smile:

@prosb6 Let us know what you find out cause I bought the Fiber Optic Cable in the hopes of combating EMI when the headset is touched.

I recieved the Pimax Fibre Optical cable yesterday and had an issue straight away when I plugged it in. I managed to overcome this issue by plugging the USB Cable into a PCIe USB 3.0 card I installed before. I bought this cable in the hopes of eliminating EMI when the hmd is touched. It did NOT stop it.

I’m still annoyed that the 8K X has this issue when the USB is plugged into the Motherboard. I’ve also read that One of the DPs on the GPU has a higher bandwidth than the rest, is this true?

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What kind of motion rigs are you guys using?

I’m on a DOF P3 and only lose tracking when I grab bother exterior short sides at the same time and afaik that happens due to sensor occlusion.

In any event, to eliminate EMI interference just use @AndrewUK1990 's method via ferrite cores.

I‘d be interested to hear the results on the ground loop. VESA certification requires for this to be actively eliminated for a reason.

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@AndrewUK1990 Tried the line filter, unfortunately same result. I’ll try the FT240-31 ferrite cores. I have the Optical cable and you think it would still work possibly?

It should still work (ferrite core method) but as far as I know nobody else has tested it yet using an 8KX with the fibre-optic cable.

The important thing to do is loop the all on one section of the cable through 4-6 times, through 4 of the ferrite rings. This provides sufficient EMI supression to eliminate it. If it doesn’t work it’s usually because people use the wrong ferrites, or forget to loop it through several times etc; if done correctly it definitely works on pimax 5k+, 8k, OG Vive, cosmos and Index. I haven’t seen anyone do it with an 8kx yet but I would be surprised if it didn’t work as it uses the same tracking system.

By the way, regardless of emi if you cover the sides of your HMD, for instance with your hands it will grey out because it loses tracking. Just making sure someone doesn’t confuse EMI related issues with general loss of tracking from blocked sensors. It will come straight back though when you move the obstruction away where EMI isn’t the problem.

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I‘m not sure if i‘m really lucky with my 5k+ or if it has something to do with basestation placement but it is actually really hard for me to lose tracking by touching the headset. Even if i cover the whole front with both hands or touching both sides, it is still tracked. The worst i can get is loosing tracking for a second at most.

So maybe it has something to do with basestation placement? :man_shrugging:

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It has to do with the older Pimax HMDs having more robust sensor positioning or a better permeability of the housing material or both.


I’m running the SFX100 and a 8KX with a ferrite core.

I’ve found running the HMD onto of the seat and up my back, so I’m sitting the cable has massively improved the issue. Another plus, sitting on the cable is it no longer snags on things at the back of my rig seat.

@twack3r @Douglarse @AndrewUK1990

I’ve all but given up on trying to Eliminate EMI when the 8K X is touched. It’s more sensitive when the SFX-100 DIY motion system is on. I’ve learnt to Not touch the corners of the HMD which covers the inbuilt trackers.

I might try the Ferrite Cores when they arrive and see what happens.

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