Re: [LAU] My Tascam US-122

From: Martin Horn <martin.horn@email-addr-hidden>
Date: Thu Aug 14 2008 - 18:11:30 EEST

On Thu, Aug 14, 2008 at 5:29 PM, Jamie McLaughlin <
j.mclaughlin@email-addr-hidden> 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@email-addr-hidden <mailto:arnold@email-addr-hidden>
> > > <mailto:arnold@email-addr-hidden <mailto:arnold@email-addr-hidden>>>
> wrote:
> > >
> > > Am Mittwoch, 13. August 2008 schrieb Martin Horn:
> > > > On Wed, Aug 13, 2008 at 3:18 AM, Shawn Wallis
> > > <miesco251@email-addr-hidden <mailto:miesco251@email-addr-hidden>
> > <mailto:miesco251@email-addr-hidden <mailto:miesco251@email-addr-hidden>>> 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...
> > >
> > > _______________________________________________
> > > Linux-audio-user mailing list
> > > Linux-audio-user@email-addr-hidden
> > <mailto:Linux-audio-user@email-addr-hidden>
> > > <mailto:Linux-audio-user@email-addr-hidden
> > <mailto:Linux-audio-user@email-addr-hidden>>
> > > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
> > >
> > >
> > >
> > >
> >
> ------------------------------------------------------------------------
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> >
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Received on Thu Aug 14 20:15:02 2008

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