[LAU] OT: Guitar level- Mic or Line?

[Fons Adriaensen]

On Tue, May 27, 2008 at 02:49:29PM -0500, Reuben Martin wrote:

> Back on Tuesday 27 May 2008, Simon Williams was like:
>
> > Are guitars mic or line or what?
> 
> Hi-Z Line level. (The output level can vary quite drastically depending on the 
> type of pickup though) 

Well, I'd say they are neither. Typical levels for a guitar are
well below standard line level, and on many pro equipment the
line input Z could well be as low as 10k so, which is too low
for a guitar. It can work, but the sound won't be the same.
This is because the impedance of a typical guitar is not only
high but also inductive, and in many cases (depending on the 
setting of the controls on the guitar) this can resonates in
the audio band with the capacitance of the cable. Connecting
it to a medium Z line input will kill that resonance. Guitars
expect at least a few hundred k.

Use an active DI-box, in particular if the guitar output has
to be split for a guitar amp as well.

The only reason why guitars are as they are is historical.
The first ones were built at at time there were only tube
amps. This can easiliy have an high imput impedance. Making
the pickup high-Z enabled it to produce an higher output
voltage, and require one tube less in the amplifier. For
the same reason you could buy high-Z mics 50 years ago.
These would be hard to find today. Guitars are unbalanced
also only because it's cheaper.

Today (and for the last 30 years) it would be perfectly
possible to make guitars low-Z, balanced, and compatible
with a normal mic input. It would save all of us a lot of
trouble, and would also allow for phantom-powered active
electronics in the guitar. So why didn't this happen ?
Because a guitar manufacturer would push himself out of
the market by doing it. People expect any guitar to work
with existing guitar amps.

Ciao,

-- 
FA

Laboratorio di Acustica ed Elettroacustica
Parma, Italia

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