Re: [Alsa-user] USB adapters known to work well?

[Sergei S. <ste...@li...>]

On Sat, 11 Feb 2006 21:47:39 +0000
John Haxby <jc...@th...> wrote:

> Sergei Steshenko wrote:
> 
> >On Thu, 9 Feb 2006 12:02:10 +0000
> >John Haxby <jc...@th...> wrote:
> >
> >  
> >
> >>I have a Griffin iMic which works perfectly.    I think it does 
> >>everything you want, it's also cheap: mine is the older silver model and 
> >>cost $35.  Haven't tried (or seen) the newer white one but I'd be very 
> >>surprised if it didn't just work.    The quality is pretty good 
> >>although, for some odd reason, I can hear hum from my laptop power 
> >>supply when I connect it to an amplifier instead of headphone.   I 
> >>suspect that's more a problem with the laptop rather than the iMic.
> >>
> >>    
> >>
> >Try a thick wire to connect your laptop's ground with your
> >amplifier's one.
> >
> >Outer connectors shields, like the ones of serial port or display
> >connector are good candidates to be used as ground.
> >  
> >
> That's a good idea.   An earth loop does seem to be the most likely 
> problem.   Mind you, neither the mixer nor the power amp have their own 
> earth so I suspect that it's the two computers that provide input to the 
> mixer having a bit of a fight.    The Dell laptop power supply does seem 
> to have an earth connection.   Alas, in the only case where it really 
> matters (in a theatre) adding an extra earth connection isn't 
> practical.   It's a Dell laptop and seems to have an earth connection 
> running through the external power supply: other laptops I've used in 
> the past don't have an earth connection for the external power supply 
> and are probably just fine.   I'm really not sure wh Dell think an earth 
> is important :-)   The battery lasts long enough though ...
> 
> I was somewhat surprised at the hum, but since there isn't electrical 
> isolation between the audio output and the rest of the computer I 
> shouldn't be that surprised I suppose.
> 
> jch
> 
> 
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Regarding "ind you, neither the mixer nor the power amp have their own 
earth" - well, my Denon AV receiver has a special plastic capped nut on
a threaded rod being marked as ground - the marks looks more or less like
this:

  |
-----
/////

.

It's on the back of the receiver.

If you do not have a dedicated ground connection, you probably have
a lot of screws on the back of your power amp, so you can use them
to connect the two grounds.