[LAU] My Tascam US-122

Martin Horn martin.horn at ostec.org
Thu Aug 14 11:11:30 EDT 2008


On Thu, Aug 14, 2008 at 5:29 PM, Jamie McLaughlin <
j.mclaughlin at 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 at arnoldarts.de <mailto:arnold at arnoldarts.de>
> >      > <mailto: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>
> >     <mailto: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...
> >      >
> >      >     _______________________________________________
> >      >     Linux-audio-user mailing list
> >      >     Linux-audio-user at lists.linuxaudio.org
> >     <mailto:Linux-audio-user at lists.linuxaudio.org>
> >      >     <mailto: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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> >
> >
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