On Thu, Aug 14, 2008 at 5:29 PM, Jamie McLaughlin
<j.mclaughlin@sheffield.ac.uk> wrote:
Martin Horn wrote:
> 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.
Thanks, that's really useful to know. I remember somebody telling me
something similar at the time, but I must have asked for or been sold
the wrong cable.
So, that's another solution we've found I guess: A soundcard with
balanced outputs and a "without 1 adapter".
Unfortunately there are only few soundcards having balanced outs and of course none in the lower price range ...
The solution again is to use a DI to get symmetric outs. With the "without 1 adapter" you can also use a cheap active DI. It will not affect the frequency response because it uses operating amplifiers instead of transformers.
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@arnoldarts.de <mailto:arnold@arnoldarts.de>
> > <mailto:arnold@arnoldarts.de <mailto:arnold@arnoldarts.de>>> wrote:
> >
> > Am Mittwoch, 13. August 2008 schrieb Martin Horn:
> > > On Wed, Aug 13, 2008 at 3:18 AM, Shawn Wallis
> > <miesco251@gmail.com <mailto:miesco251@gmail.com>
> <mailto:miesco251@gmail.com <mailto:miesco251@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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> >
> >
> >
> >
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