ODP: audio electrical info

[Roman Sowa]

1.
Impedance is a complex value determining current to
voltage relation, to tell the story short, and... too-tech.

Every input or output, if it will be amp input, or CV, or a speaker
has a impedance, which generally at audio frequencies
is real (no phase difference between current and voltage)
As for the speaker, it's not so simple any more, since its
coil is, well, a coil and has significant amount of inductance
(is my english right?) which leads to imaginary part of its
impedance, and phase difference between current and voltage
varying with frequency.

Basically output impedance is a resistor in series with theoretically
ideal (with unlimited current capability) voltage source.
Input impedance is a resistor from input to gound (or between
lo and hi lines in symetrical input).
They become important, when you connect things.
If the next device will have low input impedance, signal will split
on output and input impedancies, or in another words:
will attenuate. So if out imp. is much lower than in of next device
it's no problem. If out imp. is much higher than in of next dev.
you'll get almost no signal

2.
Standard line level is +4dBu or 3.5Vpp sinus
0dBu is signal which causes 600 ohm load to dissipate 1mW power
Line signal is from -20dBu to +20 dBu
Mic level is everything below -20dBu
Speaker level is above +30 dBu

3.
How to divide signal? Use resistor divider with the lowest
suitable resistor values. Then you need an amplifier.
I'm not sure exactly what do you expect to acheive

Hope it could help you

Roman

> -----Oryginalna wiadomość-----
> Od:	adam [SMTP:amr at gpu.srv.ualberta.ca]
> Wysłano:	25 września 1998 21:58
> Do:	synth-diy at mailhost.bpa.nl
> Temat:	audio electrical info
> 
> Hi.  How do audio signals work?
> I understand that voltage=volume, freq=freq...
> 
> But how does impedence fit?
> 
> i.e. what is the difference between a line level signal, a mic signal, and
> one that goes to your speaker?{be specific if possible - what is the
> nominal voltage PP(i am assuming the means peak to peak) for each.}
> 
> furthermore, how do i safely attenuate a say a line signal down to 360mv
> PP,
> then after running it through a chip get it back up to line level (with
> minimal noise)
> 
> thanks
> adam.
> 
>