[sdiy] Shielding

harry harrybissell at prodigy.net
Sun Dec 2 04:22:46 CET 2001


Sorry... I missed the statement about batteries. That would say ground loop.
Now how would you fix THAT ???

(I'd say cheater plug... but with an offline (non isolated) switching supply...
that
might be a bad thing)

I think I'd use a 120V isolation transformer... then separate the DC ground from
the
AC ground.

Printers and other AC powered peripherals might make the problem come back...

H^) harry


I see a lot

Theo wrote:

> Moho Disco said the noise was not there when the laptop ran of batteries.
> Think that rules out the sound card
> and points a heavy finger to wards a ground loop.
>
> Theo
>
> From: harry <harrybissell at prodigy.net>
>
> > Hi Ingo....
> >
> > I'd be more suspicious of the card itself. A lot of cheapie sound cards
> were
> > not designed for high quality audio use.  Maybe 50dB signal to noise is OK
> > for a video game, but not an album !
> >
> > It would be easy to cheat the ground on the computer (2 to 3 wire plug
> adapter)
> > and find out.  If it goes away, its ground loop and you can buy the
> isolation
> > transformer (I paid $50 new for a stereo unit from ebtech). I bet the
> noise remains.
> >
> > H^) harry
> >
> > Ingo Debus wrote:
> >
> > > Moho Disco wrote:
> > > > Currently I'm just using the laptop's crappy internal soundcard, which
> > > > is wired directly into my Mackie 1604vlz.  A laptop adapter for my
> > > > Layla24 sound card should be arriving Monday, and I'm *praying* that
> > > > it does not exhibit the same symptoms.
> > > >
> > > > >If you remove all the wires, does the noise stop ?  (the idea is if
> the noise
> > > > >stops... it is being conducted by some wiring, not through the
> air...)
> > > >
> > > > Yep, the noise stops when I disconnect the cables from the computer
> > > > to the mixer.  It is most definitely being conducted through a wire...
> > > > But it doesn't matter what wire I use, they all transmit it.
> > >
> > > Like Theo obviously suspects too, this is most likely a ground loop
> > > problem. A friend of mine had that prob too with a Mackie mixer. It's
> > > difficult to disconnect signal ground from protective earth in these
> > > mixers without affecting electrical safety. All jacks are connected
> > > directly to the case as well as the power transformer, power switch and
> > > so on. An option is re-building the mixer's power supply into an
> > > external case (larger DIY project). Another option is using DI boxes or
> > > isolation transformers in the audio pathes between mixer and computer.
> > > I don't know the Layla card, if it has assymetrical (unbalanced)
> > > ins/outs the problem most likely won't go away :-(
> > >
> > > Ingo
> >
> > --
> > Jihad Terrorism Conspiracy New World Order
> > Revolution Black Helicopters Freedom of
> > Speech First Amendment Rights: Carnivore Bait
> > go ahead and READ my e-mail I have nothing to
> > hide... how about YOU ???
> >
> >

--
Jihad Terrorism Conspiracy New World Order
Revolution Black Helicopters Freedom of
Speech First Amendment Rights: Carnivore Bait
go ahead and READ my e-mail I have nothing to
hide... how about YOU ???





More information about the Synth-diy mailing list