Re: [LAU] RF noise suppression?

On Sat, 3 Apr 2010 17:48:43 -0400 (EDT)
Rick Green <rtg@email-addr-hidden> 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?

First question, is the laptop running from it's battery or the mains?

If battery, how good is it's charge retention?

If mains, is it a fully isolated PSU or is there a possible earth loop?

Note some PSUs are really nasty and have filtering caps that bridge
across L N & E

Do you get the same problem if you go via any route *other* than
firewire?

I don't know about laptops, but I've learned to avoid emachines
desktop machines like the plague. They are the crappiest build
imaginable :(

-- 
Will J Godfrey
http://www.musically.me.uk
Say you have a poem and I have a tune.
Exchange them and we can both have a poem, a tune, and a song.
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