Creative MP3+ problem

**w8liftr** · **06-20-06, 11:59 AM**

I have a Dell Inspiron 8600 laptop and the Creative MP3+ external soundcard and I get an power error when I plug it in the USB port. Will a powered USB hub fix this problem? Any suggestions are appreciated. Thanks in advance.

Tommy

**JohnM** · **06-20-06, 04:59 PM**

Yes, sounds like a powered hub is probably your best shot.

Edit Could also try unplugging any other USB devices you can do without or try another USB port.

**w8liftr** · **06-20-06, 06:14 PM**

Quote:

JohnM wrote:

Yes, sounds like a powered hub is probably your best shot.

Edit Could also try unplugging any other USB devices you can do without or try another USB port.

Thanks, I've tried without any USB devices and all ports. I'll give the powered hub a shot.

**khellandros66** · **06-21-06, 09:57 PM**

Standard laptop USB ports aren't so powerful. Standard desktop USB can supply 5-12v over USB where as a laptop usually 2-3v. Its because of the smaller powersupply (laptops typically 70-90w some higher end ones are 120w) and this leaves a major lack in voltage rails etc.

You are much better off with a $40 Belkin 4-7 port hub with its own method of power.

~Bob

**JohnM** · **06-22-06, 04:17 AM**

The limiting factor is really the current the port can supply. If you look in the device manager at the USB hub entries there is a power tab in the properties which shows how much current the hub can supply and how much current the attached devices are consuming. Laptop ports are sometimes limited to 100mA per port, whereas USB soundcards can demand much more - for example, I think the SB Live! External card requires 380mA, from memory. A powered hub, or the hub in a desktop, will generally allow up to 500mA.

**w8liftr** · **06-22-06, 06:44 AM**

Thanks, I got a powered hub last night and it fixed the problem. Now I can start taking some measurements and get my subs dialed in.

**Otto** · **06-22-06, 11:13 AM**

Quote:

khellandros66 wrote:

Standlaptop USB ports aren't so powerful. Standard desktop USB can supply 5-12v over USB where as a laptop usually 2-3v. Its because of the smaller powersupply (laptops typically 70-90w some higher end ones are 120w) and this leaves a major lack in voltage rails etc.

Wow, and you stated that with such authority!

**khellandros66** · **06-22-06, 08:02 PM**

Quote:

Otto wrote:

Wow, and you stated that with such authority!

LOL Not sure how to interpret this comment, if you can PM me if there is an issue. Otherwise yes, mose laptops lack the strength in the voltage rails most cases 4-6 amps. This is enough to power a mobile CPU, Graphics, and smaller HDDs (2.5in uses less then half of a typical 3.5in one). Now some of the larger laptops come with a 120w Powersupply and some of the higher performers ($5000+) come with 150-175w powersupply. These of course can give non vital systems (USB, Sound, Wireless Ethernet, etc) more amperage.

~Bob

**RollsRoyce** · **06-26-06, 11:55 AM**

The built-in hub in my Toshiba laptop allows 500 mA. No worries when using just the soundcard, but now that I know it draws so close to the hub's max current, I'll have to find out what my USB-MIDI adapter draws, just out of curiosity.

**Otto** · **06-26-06, 01:08 PM**

Quote:

Standard laptop USB ports aren't so powerful. Standard desktop USB can supply 5-12v over USB where as a laptop usually 2-3v. Its because of the smaller powersupply (laptops typically 70-90w some higher end ones are 120w) and this leaves a major lack in voltage rails etc.

Well, it looks like my original post was lost the other night, as was John M's, but that's OK.

Anyway, I was just pointing out that it's a lack of current, and not voltage, that's causing the problem. Current is measured in amps. Also, not sure about your reference to "voltage rails". I would generally think of the rails as the absolute max voltage (either positive or negative) available to a circuit.

Also, USB is spec'd to have 5V on its power supply line, not 2, 3 or 12 V. This voltage should hold steady to operate USB driven devices. Then, if there's not enough current, the device may not work properly. It looks like, in general, USB is spec'd to support 500mA at 5V, and if a device requires more than that, it may be necessary for it to supply its own power. So, I guess there could be two failure modes -- 1) the USB circuit not supplying enough current to operate the device because of other current requirements in the system (there's just not enough current available in the system, and the USB takes a hit), or 2) the external device requiring more current (power, actually, but since V is held steady, this translates back to current) than the USB could ever source based on its spec.

Here's a link to Wikipedia's entry on USB, in the "power supply" section.

Quote:

You are much better off with a $40 Belkin 4-7 port hub with its own method of power.

Now that I can agree with.

Not trying to be difficult, just trying to keep the facts straight.

Best regards.

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