Re: [LAU] Recommended USB interface with 2 XLR inputs?

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To: Mark Knecht <markknecht@...>
Cc: <linux-audio-user@...>
Date: Monday, May 2, 2011 - 10:19 am

On 1 May 2011 18:51, Mark Knecht wrote:

According to the proper USB1/2 specs, you're only supposed to feed
0.5A at 5V (a measly 2.5W!) to an individual port. Now, most USB
chipsets don't have the necessary hardware to achieve this and will
provide up to 2A for a bus of four, letting any device draw as much
current as they require (10W!). Most hard disks, on the other hand,
will require more than 0.5A at 5V. Thus if you have a compliant
machine, they won't work. If you have a dodgy machine with no
isolation between the USB devices, it's more likely to work! Hubs
without their own power supply draw the power from the mother board,
making the power issue even more of an issue (4 devices served by a
0.5A current source).

All of this means that since none of your hard drives works, your
machine has a good, proper implementation of the spec with isolation
between individual ports plugged into the same internal bus. Also it
means any device that's completely broken in power requirement will
struggle.

Even different machines from the same manufacturer has issues. My Dell
laptop can't drive one of my disks but a Dell PC can.

USB3 has increased the individual current amount to 0.9A at 5V (4.5W).
Most likely the implementation will be broken and a whole pile of USB
powered devices will arrive soon, drawing massive amount of power
(18-20W?).
--
Hakan (m1fcj) - http://www.hititgunesi.org
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Messages in current thread:
[LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Fri Apr 29, 10:25 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Jaromír Mikeš, (Thu May 12, 7:03 am)
Re: [LAU] , Rafal Zawadzki, (Wed May 25, 1:55 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Emanuel Rumpf, (Wed May 25, 3:30 pm)
Re: [LAU] , Rafal Zawadzki, (Thu May 26, 4:57 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Thomas Vecchione, (Sat Apr 30, 9:56 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Thomas Vecchione, (Sun May 1, 6:46 am)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Bernardo Barros, (Tue Oct 11, 7:19 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Clemens Ladisch, (Tue Oct 11, 7:40 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Jeremy Jongepier, (Sat Apr 30, 6:55 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Sat Apr 30, 9:33 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Arnold Krille, (Sun May 1, 3:33 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Jeremy Jongepier, (Sun May 1, 8:57 am)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Hakan Koseoglu, (Mon May 2, 10:19 am)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Arnold Krille, (Mon May 2, 9:36 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Mon May 2, 10:10 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Thomas Vecchione, (Mon May 2, 10:30 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Thomas Vecchione, (Tue May 3, 10:09 am)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Dave Phillips, (Sat Apr 30, 10:05 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Sat Apr 30, 10:27 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Jeremy Jongepier, (Sun May 1, 8:51 am)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Fritz Meissner, (Sat Apr 30, 5:22 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Ronald Stewart, (Fri Apr 29, 11:22 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Sat Apr 30, 6:15 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Fons Adriaensen, (Sat Apr 30, 8:11 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Sat Apr 30, 9:27 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Fons Adriaensen, (Sat Apr 30, 10:19 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Arnold Krille, (Sun May 1, 3:29 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Fons Adriaensen, (Sun May 1, 7:42 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Mark Knecht, (Sat Apr 30, 10:32 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Gabriel M. Beddingfield, (Fri Apr 29, 10:34 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Fritz Meissner, (Sat Apr 30, 12:14 pm)
Re: [LAU] Recommended USB interface with 2 XLR inputs?, Jeremy Jongepier, (Sat Apr 30, 6:51 pm)