[linux-audio-user] Re: The famous "Jack Hum" (Can't record and desparate)

[Paul Winkler]

On Mon, Nov 13, 2006 at 03:01:48AM +0100, Karsten Wiese wrote:
> Am Montag, 13. November 2006 01:28 schrieb Lee Revell:
> > On Sun, 2006-11-12 at 21:29 +0100, Carlo Capocasa wrote:
> > > > But the most intriguing part of the whole story: Not only did the noise 
> > > > get louder at a lower latency, it also seemed to precisely double its 
> > > > frequency when running at halve the number of frames. I even tried to 
> > > > measure the frequency of the noise. As far as I remember, when running 
> > > > jack for instance at 44100Hz, periodsize 32, the noise was at exactly 
> > > > 44100/32 = 1378Hz!
> > > 
> > > That is absolutely fascinating. I WILL investigate this; if it
> > > coincides, we have a VERY strong case that this is the same problem. 
> > 
> > Really sounds like you have a singing capacitor.  IOW your problem is
> > cheap hardware.  If this is the case, you won't be able to fix it.
> > 
> Guess Lee is right.
> Does noise vanish when laptop is running on battery?

Oooh yeah, I didn't notice you guys were talking about a laptop.
Try unplugging the power supply.
I found with all three laptops I've had (all Dells) that
the power supply makes a lot of really horrible noise
that leaks into all my audio gear. Only solution I've found is
to use a 3-prong-to-2-prong power adapter and leave the grounding
tab unconnected to anything. Dunno how safe that is :-\

-- 

Paul Winkler
http://www.slinkp.com