How to use Ferrite Clip ons correctly. - Page 1
Forum section: electronics / projects

author: grindcorehippie
author_rank: Newbie
timestamp: May 11, 2022, 06:46:42 am
content: So in my car when my Subwoofer has the volume up, with every beat it causes this static like fuzz lines that dance across the screen of my head unit while I have my front camera displaying on it. The picture goes perfectly clear when I turn off/down my Subwoofer, so I know it has to be the signal from Sub Audio RCA leaking into the video RCA of my front camera at the back of Head Unit where they both go to an input/output so can't really keep them apart more than they already are.From what I have researched it seems that a simple solution would be to just use those ferrite clips that just go around the wire. But I'm not sure what the best way to use them would be because I've seen using one that's bigger than the wire and wrapping the wire once or twice around before closing the ferrite clip, or if it's better to just use one that's closest to the same size as the wire so that it's snug fit to it. and last thing is I can't remember if I'm supposed to put them on just the video wire and close to the head unit, or if I should be putting one on the Subwoofer wires and the Video wire from the Camera?So should I just use the Ferrite Clip ons, or is there another/better way of rectifying the Audio signal bleeding into the Video wire? Like I said above the Video/Audio Wires only come close to each other right at the back of the head unit where they plug into their input/outputs, and cannot separate the wires apart anymore than they already are.thanks in advance for any advice!I hope that someone is able to help, just ask if any more information is needed

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 11, 2022, 07:01:10 am
content: Let me guess, unfiltered class D amp?You need a hell of a lot more filtering than ferrite beads can provide. Actually, for being one of the more visible/familiar items of electromagnetic compliance -- they really do very little; mainly they're used to treat resonant/antenna modes on cables.Don't suppose you have / can find some pics of the amp, what's its insides look like?How about your wiring, where's the power cable going, how's it routed? Speaker cables? Can you shorten either cable? Route it away from camera wires or other internal harnesses? If the amp's output is legit unfiltered, the best place for it is, well... second to the dumpster,is right by the speaker, absolute minimal wiring length -- it's the wire length that makes the antenna.After that, better grounding may help. Mount it on the car frame if you can, with conductive hardware. (This might be a terrible idea actually, I have no idea. Most interior body panel surfaces are painted, and subject to rain, mist or condensation at some point, so, cutting any holes in them will probably make for rusted out fasteners? Additionally, if it's one of those aluminum extrusion style amps, its anodized surface isn't conductive, either; star washers should cut through that alright though.) Then maybe a hash choke on the power line going back to wherever it's powered from (main battery I suppose). Make sure the choke is rated for the amp's maximum load current!Tim

author: grindcorehippie
author_rank: Newbie
timestamp: May 11, 2022, 09:37:12 am
content: Ha, I actually cannot remember what class the amp is right now, but I'll see about looking it up. I guess I should have mentioned that I have a Powered Subwoofer so the amp is built into the box. I have the power wire running from the trunk of my hatchback to under the middle of back the seat, then it runs up the middle of my car under the like center console (backseat cupholder, E-Brake, etc.), under the dash and through my firewall by my gas pedal, to a fuse on other side of my firewall under the hood and then straight to battery. basically the only other 2 wires that are within 1'-1.5' of my power wire run with it, and are the remote turn on wire and the bass knob control wire. I ran the audio RCA up from sub box and through the ceiling up to the front where it runs down the side of the driver side of my dash, then behind my steering wheel into the back of dash to the Head Unit. The closest the RCA get to the power wire is when it goes behind steering wheel to head unit it gets about 1' or so from it, and of course at the amp but then I run them in complete opposite directions from the amp. Like I said RCA runs straight from the amp up to ceiling, and power runs down under trunk carpet towards the back, then it runs straight down the middle of my car.I believe that the cause has to be right at the back of the Head Unit, because my backup cameras video wire runs through the ceiling right along with the RCA(that are supposed to be good quality and shielded) all the way up to the driver side dash, then the camera Video runs to my rearview mirrors display, and my backup cameras picture is crystal clear. It's just my front camera that shows the fuzzy lines that move with the bass, but then is crystal clear when my subwoofer is off or turned down, so I know for sure it's the audio signal causing the interference, just don't know how to fix it exactly. Also my backup camera used to show the fuzzy lines too when I used to have it connected to the Head Unit too, so I don't know maybe it's something inside the Head Unit?And I keep the wires as short as is possible, and I know my grounds are Solid. Sub ground is less than 2' from it, and I used sandpaper to make sure I cleaned all the paint off and was down to bare metal, and I also drilled a hole through and put a good bolt through to hold it.Sadly I cannot put the amp anywhere other than where it's built into the Subwoofer box. ha it's pretty far from being a garbage tear Sub/Amp, not Top Shelf either, but an easy midgrade. It's a Rockville Slim 12" Powered Sub w/ Ported Box, can't remember the model # and don't have the time to look it up right now.If it would help any, just let me know and I'll draw up a hopefully decent enough schematic of the whole setup.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 11, 2022, 10:21:43 am
content: Got it.Okay so it's not a standalone amp, but integrated. That's one less thing to worry about.Hmm, hash choke is probably the next best thing to try then.The audio cables being routed differently, may or may not be an issue. Thing is, since they're connected to the box -- they could be carrying noise around as well. Depends on how they're wired internally. Often they're just grounded right in and then will carry noise around by themselves, and then a choke on the power line might not do much. In that case, they're probably best to route together, but also you'd need some kind of choke that goes around all of them... (like a ferrite bead, in fact; but probably much larger than you'd want to actually use!). So, not really much in that case. Whereas if they used a somewhat isolated (differential) connection (as differential as you can get with RCA, that is), there wouldn't be much and it won't really matter where you route the cables.And to figure that out, I'd probably have to turn over the board in my hands to see, maybe a few up close, in focus photos would do, but yeh. Anyway, it's almost certainly a design issue, and you'd hope products are tested to avoid problems like this, but... well, I'm sure you're well aware what quality is like in the automotive aftermarket scene... all over the place.Tim