[maemo-users] Audio connection problem

From: Mark wolfmane at gmail.com
Date: Fri Mar 14 02:22:34 EET 2008
On Thu, Mar 13, 2008 at 4:58 PM, Larry Battraw <lbattraw at gmail.com> wrote:
>  We're obviously talking about different things.  Mine only occurs when
>  charging and is a pronounce alternating hum and buzz as the n800 draws
>  current and pauses (Easy to see on a charger w/a LED).  It stops the
>  second I remove the charger.  To demonstrate my point about the
>  coupling I've connected the n800 to a switch-mode charger connected to
>  batteries: it removes the noise completely.  I used the term
>  ground-loop because from the reference of the receiver your input has
>  a ground, particularly if it's hooked to a PC as mine is which has a
>  grounded output.  The charger is not grounded and so floats in
>  reference to the receiver except for the AC current induced by the
>  switching of the power supply and current to the n800, coupled via the
>  mains lines going to both the receiver and charger.  Hence the noise.
>  It doesn't necessarily fit the classic definition of a ground loop but
>  was the closest thing I could think of.
>  I'm puzzled by your description of low output levels.  If anything,
>  with both the "speaker volume" and the application volume up all the
>  way I have to turn it down a bit to avoid overdriving what I'm
>  connected to.  The only thing I can think of is that you're not
>  resetting the device volume to the maximum after plugging something
>  into the headphone jack since that drops the volume automatically a
>  fair bit.
>  I've hooked it to plain amplified speakers, a guitar effects box, a
>  cassette adapter, a Sony receiver, and myriad other devices with and
>  without inline volume controls.  I really don't think impedance has
>  anything to do with it; my receiver measures at around 100K ohms for
>  the inputs which is essentially infinite compared to the internal
>  speakers or headphones and works well outside the charger noise.  I
>  did have one thought: when you connect it to whatever amplifier you're
>  using have you tried using a 4-conductor audio plug?  I believe the
>  tip is powered (with a pull-up resistor) to support the headset
>  microphone and your plug might be partially contacting that, causing
>  noise.
>  Larry

Yes, this is definitely not a hum, buzz or whine like you get with a
ground problem. It's more of a variable hissing, like a really bad
tape recording and the tape has been crinkled (although the music
itself is fine).

I've turned the volume(s) all the way up, both the master volume and
in the media player app, which makes it a little better, but the noise
is still pronounced to the point of intolerability. The noise gets
worse during quiet or silent passages.

I'm using a regular 3-conductor plug patch cord, and it's identical to
the plug on the headphones I'm using that sound fine. I have several
of those cords, and they all have the same result. Also, my mp3
player, DVD player and everything else I've tried sounds just fine
using the same hookup and power points.


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