[LAU] RF noise suppression?

[Ken Restivo]

On Sat, Apr 03, 2010 at 05:48:43PM -0400, Rick Green wrote:
> I'm using a FOcusrite Saffire pro 26 I/O  with ffado, jack, and Ardour to 
> make  multitrack recordings of live concerts, to my emachines M6810 laptop 
> running ubuntustudio.  I'm plagued by noise that sounds to me like RF 
> interference from the laptop, getting into the audio portions of the 
> interface.  It's most obvious when I'm at home trying to mix down my 
> recordings, as its almost constant in my monitors and most noticable in 
> a quiet room, but it also manifests itself sometimes during shows, showing 
> up on the input lines to the interface, which are plugged 'half-way' into 
> the FOH mixer's channel inserts, so it invades the PA and the performers' 
> monitors.  WHen that happens, I've no other choice but to abandon the 
> recording and shut down the laptop.
> 
>    Has anyone else encountered this problem?  Got any suggestions how to 
> filter it?  I'm going to try some ferrite cores snapped around the 
> firewire cable first.  Anything else I might try?
> 

I had exactly the same problem, almost exactly 3 years ago when I first gigged with a laptop.

The solution was to lift the ground on the AC adapter, using one of those three-prong-to-two-prong adapters. Haven't had a problem since then, been gigging my ass off the whole time (although a year ago I mostly switched to using my EEE netbook, which only has a two-prong adapter anyway, and never had the problem with it).

-ken