Subject: Re: [linux-audio-user] multichannel and spazialization
From: Jörn Nettingsmeier (nettings_AT_folkwang-hochschule.de)
Date: Thu Mar 28 2002 - 13:45:03 EET
francesco whalley wrote:
>
> hello to everyone in the list
> so, if i can ask some question:
> - i'm quite a newbie... what's the real difference between
> balanced (...servo balanced) and unbalanced outputs?
unbalanced: one wire carries the signal, one is ground (plus an
additional screening wire mesh probably).
balanced: one wire carries an in-phase signal, one carries the
out-of-phase signal, one is ground (plus screening)
to create a balanced signal, you need a diffential op-amp (is that
the correct term in english ?) or a transformer like this:
unbal. signal---//|//-------in-phase
//|//
//|//-------ground
//|//
ground----------//|//-------out-of-phase
the idea is this: when noise creeps into the cable, it will be the
same on both signal wires.
in a balanced input stage, the out-of-phase signal is inverted and
added to the in-phase signal.
so one component of the noise will be inverted, the other won't - it
cancels out, while the signal is amplified.
another important advantage is that balanced cables are ground-free:
there is no ground connection between different devices (or at least
it can be switched off with a ground-lift), so you won't get ac hum
loops as easily.
-- Computer Science is no more about computers than astronomy is about telescopes. - Edsger W. Dijkstra Sigh. - me
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