[LAU] RF noise suppression?

[Rick Green]

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
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                                   -Benjamin Franklin

"As for our common defense, we reject as false the choice between our
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                                -President Barack Obama 20 Jan 2009