On Sat, 3 Apr 2010, Folderol wrote:
> First question, is the laptop running from it's battery or the mains?
> If battery, how good is it's charge retention?
>
From the mains supply. The battery might not make the 3+ hours for
sound check and show.
>
> If mains, is it a fully isolated PSU or is there a possible earth loop?
Possible ground loop. There is low-resistance DC continuity from the
input earth pin to the output negative of the PSU.
That said, the noise doesn't sound like 60hz hum. It's a more raucus
whine, with a once-per-second staccato blip which I'm guessing correlates
with some regular interrupt routine in the CPU. If I take my fingers off
the keyboard, and I'm not recording or playing back, the noise goes away
after about ten seconds, and then immediately reappears as soon as I
disturb the system by moving the mouse. Movement of the mouse is
accompanied by a raucus buzz on the background whine, which goes away as
soon as I stop causing mouse interrupts.
>
>
> Do you get the same problem if you go via any route *other* than
> firewire?
No other route possible, as the interface is firewire only.
>
> I don't know about laptops, but I've learned to avoid emachines
> desktop machines like the plague. They are the crappiest build
> imaginable :(
I'm quite familiar with the reputation. I was not in a position to turn
up my nose to an outright gift of a brand-new AMD64 laptop which would
boot Linux without major issues, back when 64-bit laptops were few and far
between. And I'm not financially secure enough even now to be shopping
for a new one.
--
Rick Green
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-Benjamin Franklin
"As for our common defense, we reject as false the choice between our
safety and our ideals."
-President Barack Obama 20 Jan 2009
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