Xbox video sparkles

[guiddruid]

Not really sure if this is the right place to post this, but I figured it might be of interest to some of you.

Since I connected my Xbox up permenantly to my ADSL router (Draytek Vigor), via the cat5 I ran through the walls at home, I have had some nasty sparkly noise on the Xbox's video output. Yanking the cat5 cable out of the back of the Xbox would fix it, but that's not really a great solution.

I fiddled around trying to isolate the source of the noise and it looked like it was the router itself (I had expected it to be noise from my pc, via the router). With the router disconnected from everything apart from its power supply and the Xbox, I got the noise.

As a really quick hack I tried wrapping the cable from the small plug-mounted power supply to the router around a toroidal ferrite, and was stunned to see a visible reduction in the sparkles. I grabbed the only other ferrite I had, and wound as many turns as I could on to each ferrite (about 3 turns on each), and the noise is now pretty much gone!

So anyway - something quick & easy to try if you run into a similar problem... Those little ferrites worked _way_ better than I had any right to expect.

gd

[randombs]

whats a ferrite?

[guiddruid]

ferrite is a magnetic material that looks a lot like pencil lead, used in high frequency transformers and inductors.
when you see a lump on a cable (i.e. VGA monitor cable, or good quality console scart lead) the lump is often a ferrite bead that the cable is threaded through and then the bead is held in place with moulded plastic.

just did a quick google for ferrites, and got a nice link:

http://www.ukradioamateur.org/full/html/c9-1-3.htm

and a pic:

http://www.suhilcorp.com/image-mn/f_mn_bo_pi02.jpg

the ferrites I had kicking around were taken from an old pc power supply (i think... they have been in my spares drawer for about 8 years)

cheers,
gd

[randombs]

oh that - those ring things. yeah ok thanks

i think that'll come in handy for something. Do they clear up interference? What about when using a pc soundcard? My laptop is especially susceptible to interference. Even right now, the speakers are muted but they still give off sounds when the hdd does stuff. I'm gonna unplug them i think (they're a bit knackered anyway - crackle like mad if the volume is turned up a teeny bit)

[guiddruid]

Do they clear up interference?

not so much "clear up" interference as stop it happening in the first place... kind of.

with my situation the little power supply was noisy and the noise was getting all the way to the video output of my xbox.
sticking ferrites on the video cable from the xbox would probably not have fixed the problem.
sticking the ferrites on the power supply cable to the router stopped (or at least reduced significantly) the noise getting into the system.

noise from an hdd getting through to the sound output on a pc is probably going to be via the power supply to the disk drive. I doubt it would be particulary easy to fit a ferrite there though.

As noise propagates through a system it may change (get 'rectified' by diode junctions and so on), which can cause the frequency of the noise to change... for instance it could be that the HDD noise is quite high frequency originally (head seeking currents or something). You could filter that out nicely with a ferrite probably. By the time it has gotten to your speakers it must be less than 10kHz or so, as you can hear it. The ferrites won't work very well at all at such low frequencies. Even if you did have something that would filter at low frequencies then that would obviously affect the audio itself too...

hope that is a bit clearer? I find it kind of hard to be concise ;o)

gd

[Spatial]

Well, what do you know. I was thinking of asking what those ferrite cores were for a few weeks back and then forgot about it again.

Nice one !

[steve_dynamic]

For a moment there, I thought you meant a ferret.