Hi Terry,
Terry said:
Thanks all, glad I asked, as I hadn't realised it needed such a heavy duty
supply. At worse, I'll get out to the shed and make one.
Again, it only needs that sort of supply if you have devices that
1) need lots of power (e.g., a laptop disk drive powered from
the USB port) and 2) don;t provide it themselves. Some devices
(e.g., the sort of laptop drive I mentioned) have options for
both. Mice, keyboards, etc. usually rely on the USB port for
their (typically modest) power requirements.
BTW, if you'll excuse a related question, is it usual for USB ports on the
front of a PC case to be less reliable than ports on the back? Perhaps
with lower current delivery? That's my motive for deploying this powered
hub. An operation that failed from the front worked OK from the back
(connecting an iPad to run an iTunes sync). That wasn't the only thing I
changed, so it's not conclusive. But from subsequent googling I've seen
several suggestions that this difference is a real one.
A lot of this depends on the vintage/manufacturer of the PC.
All bets are off when it comes to an "add in" USB card (which
would typically be USB2 or USB3 and most likely "powered" -- but,
could just as easily be an ancient USB1.1 card, etc.)
Some manufacturers put "good" (fast, powered) ports on the front
of the machine leaving slower ports on back for the keyboard/mouse
and giving the user more flexibility in what he can CONVENIENTLY
plug into the front of the machine. Other machines may be the
exact opposite with the philosophy that the fast devices you are
likely to use will be semi-permanently attached and you'll just
need the front ports for things like thumb drives (modest power
requirements).
The ports *in* keyboards are almost never capable of delivering
and sort of power (I've seen some that won't support a thumb drive).
And, of course, you are limited to the speed of the keyboard's
connection to the PC (in addition to the hub/controller within the
keyboard).
It is also not uncommon for connectors to be flakey -- the "pins"
*in* the USB connector as well as the pigtail that invariably connects
the "front connectors" to the motherboard (the rear panel connectors
are more often than not directly soldered to the motherboard).
And, of course, iPod cables are also notoriously flakey
(not to mention the &*^!@#*&$% "charge only" cables!)
HTH