USB Sound and Bus powered hub

**Suprapc** · 04-13-2003, 11:10 PM

All right guys I pulled most of my gear out of my main car (87 Supra) and dumped it (quite literally) into my 91 Celica due to the Supra's ongoing rebuild. Since the dump I've developed a new problem with my USB sound card, which is plugged into a bus-powered hub along with my wireless, mouse and char LCD. The problem is that whenever I use the mouse, or the LCD backlight changes to anything other than full on or full off I get noise through the speakers. In the Supra I had a dedicated USB extension cord for sound however I don't want to rip any wires out to get rid of a problem in a temporary setup. Has anyone used USB sound with a powered hub? If so how did it work? Any other ideas are welcome, this noise is getting aggravating.

Thanks in advance.

**Telek** · 04-18-2003, 10:13 PM

Can you just buy another USB extension cord? How much more length do you need? Those cords can be pretty cheap.

I'll bet that if you ran the power seperately from the USB hub itself (i.e. run just a pair of wires back to your computer and splice into a +5V lead, or the keyboard jack, or the other USB jack) it would get rid of the noise. The sound has to get to the USB soundcard via digital means anyway, so it can't be affecting the signal wires, so it must be coming in via the power wires.

Alternatively you could wire an inductor inline with the USB power wires (again though you'd have a splice a cable)... That might help get rid of the AC fluctuations in the power that's likely causing the noise.

**Suprapc** · 04-19-2003, 12:15 AM

Yeah, I think I'll just buy another extension chord. Does anybody know if Best Buy or Circuit City sells them? I was kind of hoping for a quick fix.

Sorry, I didn't make it clear but the hub is powered by USB no adapter.

Thanks

**Telek** · 04-19-2003, 02:00 AM

Here's an easier fix!

POWER YOUR HUB.

The reason that is probably happening is because you're stressing the USB bus beyond the 500ma/channel that it can provide. This is bad.

**Suprapc** · 04-19-2003, 09:46 AM

I believe your right.

**vikrampant** · 04-19-2003, 09:02 PM

Don't know if you have 2 (or more) USB ports on the mobo.

If you do, plug your sound straight into the 1 port and use the other for your other accessories.

Do check your power usage via Device Manager, and double click your USB hub and choose the power tab.

500mA is max per port and I have a GPS and it's 500mA itself.

-- Vikram

**Telek** · 04-19-2003, 09:49 PM

vikrampant: The point was that what you are suggesting is what he used to do, however he doesn't have an extension cable for use in the current car so it won't reach, which is why he needs to use the hub. In his original car he has a dedicated extension cable to do exactly what you said.

Good point about checking power consumption though. It's only a "rough" number based upon what the USB device tells the hub that it needs, not based on actual current being used, so treat it as a "max" number.

The USB sound card probably takes the full 500mA, my corded optical mouse takes 100mA and the LCD probably uses the full 500mA as well, which means very bad to put them all off the same port without supplimental power.