[maemo-users] Audio connection problem

From: Mark wolfmane at gmail.com
Date: Thu Mar 13 19:42:48 EET 2008
I am very familiar with the ground loop problem, and this is not
related to that. Ground loop problems are a result of noise created by
other devices, whereas this noise is created by the Nokia itself. It's
also a completely different kind of noise - ground loops usually cause
a whine (that varies with rpm's in a running vehicle), but this is a
swishing white noise that seems to vary with the sound that the Nokia
is playing. Also, no other devices, including my standalone mp3
player, exhibit this noise when connected identically.

The reason the cassette adapter works is not because of isolation but
because of completely different power and impedance characteristics -
it's a lot closer to headphones than to a line input.


On 3/13/08, Larry Battraw <lbattraw at gmail.com> wrote:
> On Thu, Mar 13, 2008 at 7:21 AM, David Hagood <david.hagood at gmail.com> wrote:
>  > I have found that running the N800 through a ground loop isolator helps immensely - especially if you are charging the device as you use it.
>  >
>  >  The Radio Shack ground loop isolator (RS #270-054) works well for this.
> Yes, this is key.  The n800 will transmit noise via the headphone jack
>  if you are charging at the same time, particularly when charging from
>  something from something that can leak tiny amounts of AC current back
>  to the amplifier.  This is pretty much the case every time when
>  charging and connected to a AC-powered amplifier or even a DC amp
>  where you're using 120V inverter or 12V charger connected to the same
>  battery.  That's why it's minimized when using a tape adapter; there
>  is very little AC coupling between the tape read head and the tape
>  adapter.  Like the ground loop islolator, an audio transformer will do
>  the trick too (You'll need a 1:1 ratio on the windings).
>  Just my 2 cents-
> Larry

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