Ferrite Bead | Hacker News Reader

Ferrite Bead

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25 pointsDevOfNull12 comments

I have something weird with my Edifier speakers. Maybe a ferrite bead can resolve my issues.

I have my setup as follows:

    Lenovo P1 --[hdmi]--> Samsung monitor  ---[3.5mm]----> Edifier speakers
    Desktop computer with Creative Soundcard --> [3.5mm] --> Edifier speakers
                         --[displayport]---> Samsung monitor

I don't have any noise or scratching when I work on my Lenovo. I don't have any noise or scratching when I work on my desktop without having the connection from Samsung monitor to speakers connected. However, when I have everything connected I get a slight noise and scratching sound which gets more pronounced when I start to load my GPU more, for instance when running a game.

At first I thought this was a ground loop, but the noise isn't constant, and isn't directly coming from my computer or sound card but indirectly via the Samsung monitor when I start to game and my computer draws more power.

Interesting, I have a similar issue when I work with CAD models. If I rotate a particular model in a certain way, I can almost hear a 'scratching' noise coming from my GPU as the frames draw. If the GPU is already loaded, it seems like the noise escapes to my powered sound monitors? I think it is some sort of 01010101 color rowhammering the memory at 144Hz...

Coil whine?

Can't be, as the noise isn't coming from my computer.

I've been wondering if one of these would solve folks Ikea chair problems (where the piston causes emf sufficient to make some monitors loose signal)

Haha, my (I think damaged) MSI monitor gets that when I shift in my chair sometimes!

For those who missed the discussion: https://news.ycombinator.com/item?id=35742476

These seem to have become much less common. I'm guessing better filtering in devices themselves and possibly better cable construction?

From https://www.ti.com/sc/docs/apps/msp/intrface/usb/emitest.pdf :

> If a single ferrite bead is used it is not usually necessary to also have the separate beads as shown in Figure 8

Yup, it's probably cheaper to put a few small ferrite beads on the board than to put a big one on the cable.

Being a differential signal, I never understood why USB cables would _need_ them, but seeing it on a premium cable inspires the feeling that you bought a better product? I also think reduced 900MHz interference from cordless phones (remember those?) made homes quiet enough that the bead became more of a value-add for most applications. Just guessing...

Oops, just removed one of these from an old Logitech mouse because it made it hard to plug into my 1040ST..

Can anyone explain the noticable symptoms of interference or radiating, in situations where usb is not filtered?

Anecdotal, but back when I was playing with spark gaps, my housemate's USB game controller would disconnect from the host every time I shot a spark. It would refuse to reconnect until they unplugged and replugged the cable back in. They switched to a better cable (with a bead), and it stopped happening.

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