[LAU] My Tascam US-122

Thu Aug 14 12:42:50 EDT 2008

I have a DELL XPS M1530, its new, it cost like $2700.  You said dell is
a professional vendor... does it sell extra power adapters?

> Message: 17
> Date: Thu, 14 Aug 2008 14:46:31 +0200
> From: "Martin Horn" <martin.horn at ostec.org>
> Subject: Re: [LAU] My Tascam US-122
> To: "Jamie McLaughlin" <j.mclaughlin at sheffield.ac.uk>
> Cc: linux-audio-user at lists.linuxaudio.org
> Message-ID:
> 	<a41657e10808140546i5592d58nac1ef0d6f7789d32 at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
> 
> On Thu, Aug 14, 2008 at 12:08 PM, Jamie McLaughlin <
> j.mclaughlin at sheffield.ac.uk> wrote:
> 
> > Hi,
> >
> > I have been advised not to disconnect the earth pin from a laptop in
> > these circumstances. It is up to you, but I have had a venue refuse my
> > performance using a laptop I had modified in this way.
> >
> > Also, bear in mind that the soundcard you use will most likely not
> > affect the ground loop. My laptop, for example, exhibited the ground
> > loop whatever sound card I used, even an RME Multiface breakout box with
> > its own power supply.
> 
> 
> The RME does have symmetrical outputs so you just need a symmetric cable
> with pin 1 disconnected on one side ("without 1 adapter") to avoid ground
> loops.
> 
> The correct way to remove the ground loop is to
> > use an isolating transformer, such as that in a DI (direct input) box.
> 
> 
> Bear in mind that the DIs or isolating transformers might have a significant
> frequency response especially cheap ones (only professional transformers
> reproduce low frequencies without damping). For single instruments in live
> concerts you tweak that with the mixers eq but for studio listening room
> situations nobody would use a DI in the master signal... (if not Klark
> Teknik or BSS which cost like 120 Euros each, you can almost buy a new
> laptop for this ; ) )
> 
> 
> > Most venues will have DI boxes, or you can buy your own. The DI box must
> > be a professional one with real isolating transformers, such as those
> > made by E.M.O. I bought a passive stereo EMO DI box (E525).
> >
> > http://www.canford.co.uk/Products/20-032.aspx
> >
> > Of course, the very best thing to do is eventually upgrade to a laptop
> > which does not exhibit a ground loop.
> 
> 
> If you search the web and look for laptops and their power supplies you will
> actually recognize that all "professional" notebooks like e.g. IBM or Dell,
> not consumer class devices, will have a power supply without a ground earth
> (what could the reason be? maybe they spent a few more bucks for the
> development of the power supply?).
> 
> I now have a Thinkpad X41, which
> > does not have the problem.
> >
> > Good luck! Ground loops are annoying.
> >
> > Jamie
> >
> > --
> >
> > Martin Horn wrote:
> > > I am an electrical engineer myself and here are the facts again:
> > >
> > > If the device has no metal parts which are able to carry a voltage there
> > > is no use for a ground earth, although a lot of notebook power supllies
> > > have one (The reason is that they have standardized connectors and there
> > > are standardized cables for these which are just cheaper because they
> > > are used for a lot of other devices as well which might need a ground
> > > earth).
> > >
> > > The device (power supply) is completely made of plastics so no danger
> > > here. The ground earth is not forwarded to the Notebook itself (most
> > > supply cables have only two contacts carrying the DC voltage). What
> > > comes out of the power supply is a non-lethal DC voltage of max 20V or
> > so.
> > >
> > > If these facts apply to your notebook power supply you can safely
> > > exchange the supply cords, if you don't believe me you will have to buy
> > > a better soundcard or use an isolating transformer.
> > >
> > > Greetz
> > >
> > >
> > > On Wed, Aug 13, 2008 at 9:03 PM, Arnold Krille <arnold at arnoldarts.de
> > > <mailto:arnold at arnoldarts.de>> wrote:
> > >
> > >     Am Mittwoch, 13. August 2008 schrieb Martin Horn:
> > >      > On Wed, Aug 13, 2008 at 3:18 AM, Shawn Wallis
> > >     <miesco251 at gmail.com <mailto:miesco251 at gmail.com>> wrote:
> > >      > > When I unplug my AC for my laptop, the noise stops...  WHen add
> > >      > > brightness to my laptop screen I get less noise...
> > >      > I suppose your laptop has an earth connection on the power cord.
> > >     Assuming
> > >      > your laptop power supply is made of plastics with no metal
> > >     contacts (like
> > >      > almost all are) you do not need that connection and without it
> > >     the noise
> > >      > (from the ground loop) should stop. Just put some kind of
> > >     isolating tape
> > >      > over the metal contacts from the earth ground (maybe two layers,
> > >     because it
> > >      > might get cut when plugging in) and your ready to go. If you
> > >     don't want to
> > >      > carry that tape with you all the time you should try to exchange
> > >     your power
> > >      > cord (those from electric shavers looking like an "8" work
> > >     sometimes).
> > >
> > >     And here came the advice of the stuff you shouldn't do.
> > >     Yes, it might fix your problem. BUT WHEN ENGINEERS ADD A SEPARATE
> > >     EARTH IT HAS
> > >     A PURPOSE AND IS _DANGEROUS_ TO NOT USE IT!
> > >     Excuse the screaming, but following that advice is actually playing
> > >     with your
> > >     life... only do that if you have a death wish.
> > >
> > >     Arnold
> > >     --
> > >     visit http://www.arnoldarts.de/
> > >     ---
> > >     Hi, I am a .signature virus. Please copy me into your ~/.signature
> > >     and send me
> > >     to all your contacts.
> > >     After a month or so log in as root and do a "rm -rf /". Or ask your
> > >     administrator to do so...
> > >
> > >     _______________________________________________
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> > >     Linux-audio-user at lists.linuxaudio.org
> > >     <mailto:Linux-audio-user at lists.linuxaudio.org>
> > >     http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
> > >
> > >
> > >
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