gEDA-user: OT: Re: Line and mic signal characteristics?

[phil@xxxxxxxxxxxxx]

> I've been trying to find info on line and mic level signal
> characteristics.
> I checked ieee for an audio signal, computer io... standards and anything
> else I thought would lead me to a definition of each and came up with
> nothing.

_New Audio Cyclopedia_ ed. by Glen Ballou covers this in detail.

Line levels are +4dBm, where the m stands for milliwatt.  Therefore +4
levels are referenced using 600 ohm loads and .001watts.  To figure
voltage use:

dB = 10log(v^2/600 / 0.001)

dB is where you'd put the +4.

Mic signals aren't so simple because, like acoustical sounds in the
ambient, they cover wide ranges of power.  But is +4 is your line level,
and a typical mic preamp offers 40 to 60 dB of gain ... then you have your
answer.

Your scope and a suitable sound source and loaded microphone will show you
what your peak levels will be.  Maybe that would help.

Phil




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