[LAU] Line noise

[Ken Restivo]

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On Mon, Oct 29, 2007 at 10:52:15PM +0100, Fons Adriaensen wrote:
> On Sun, Oct 28, 2007 at 06:45:54PM +0100, leslie.polzer at gmx.net wrote:
> 
> > > You cannot do that in a sane way - the output of a guitar pickup needs to be 
> > > modified (amplified and converted to high impedance) before, otherwise the 
> > > signal will suffer (treble loss).
> > 
> > I believe you, but I'd be grateful if someone could explain to me how
> > one would know that the treble will suffer? I mean, we were talking
> > about real impedancies, and to determine how the line will react with
> > respect to certain frequencies we would need the complex part...
> 
> The impedance of a guitar PU is mostly inductive, i.e. it rises
> with frequency. So if you load this with a low impedance the
> effect is that of a low-pass filter. That's the simplest case -
> in practice the inductance can resonate within the audio band
> when connected to a cable (which is capacitive) and this is why
> guitar cables can have a distinctive sound. 
> 
> Anyway, for a guitar you need a high-impedance input, not a 
> microphone input.
> 

My audio interface has a switch with two settings: "instrument" and "line" for its XLR/TRS jacks. No "mic" setting, surprisingly.

I'm guessing that would be "line". It also has a "pad" switch for dealing with hot inputs.

- -ken
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