AW: [sdiy] what exacly is "audio" in electronics terms?

[Czech Martin]

let me see...

<SMARTASS_MODE_ON>
Information exchange happens via electro magnetic waves a la Maxwell/Hertz.
I.e. you have the electric force and the magnetic force.
For audio applications we can reduce this to voltage and current, both are
there at the same time, you can not have one without the other (well DC,
but then you can't transfer any information).
Even if you look at a device like a capacitor, between the plates there
is current if you start to charge it, even if you build a vacuum dielectric
capacitor. 

So , for wire bound communication we have electrons that wiggle for and back
(AC current), these particles "transfer" voltages and currents.
The capacitor example shows that voltage and current can distribute even
in vacuum, this is radio.
If you have DC electron current you can even see the material transport
if your wires are very thin. E.g. the aluminum in ICs suffers from
"migration",
i.e. the alu moves in the direction of the DC current via transfer of
momentum
from electrons to atoms, finally leaving a mushroom on one end and a
 void or open circuit somewhere else.
This is very illustrative if you see it in a microskope, and also very
frightening
for us engineers.

<SMARTASS_MODE_OFF>


> -----Ursprüngliche Nachricht-----
> Von: Scott Bernardi [mailto:sbernardi at home.net]
> Gesendet: Dienstag, 27. November 2001 06:07
> An: Synth-DIY list
> Betreff: Re: [sdiy] what exacly is "audio" in electronics terms?
> 
> 
> OK, Ian took me to task on a misleading statement I made 
> about it being
> voltages in the patch cords. He's right, voltage doesn't 
> flow, electrons do,
> and it is the flow of electrons that make up a current.
> In general we deal with voltages in synth module inputs and 
> outputs (ie,
> "voltage controlled"). Basically, you could run a current 
> source output into a
> direct short with no problem, but I wouldn't advise doing 
> that to your VCO
> output because it's a voltage source (low output impedence) 
> rather than a
> current source (high output impedence).  It would try to 
> supply a huge current.
> (Note: it's common practice to put a 1K resistor in series 
> with outputs of
> modules. As you plug your patch cords, you short the tip to 
> the jack ground for
> a short period of time, and the 1K resistor limits the current).
> Module inputs have a high input resistance (typically 100k), 
> and when you apply
> a voltage to an resistance (impedence is like ac resistance and can be
> frequency dependent), it draws a current according to Ohm's 
> law  I = V / R.
> You have this conversion from voltage to current and visa 
> versa all over the
> place in analog circuits.  For example, in a simple opamp 
> inverter,  you apply
> a voltage to the input resistor, and it is converted to a 
> current Iin =
> Vin/Rin.  This same current flows through the feedback 
> resistor Rf (negligible
> current flows into the opamp inverting input) which converts 
> it back to a
> voltage Vrf = In * Rf = Vin/Rin * Rf. Since the inverting 
> input is a virtual
> ground, the output is negative, Vout = -Vin * Rf/Rin.
> 
> 
> Ian Fritz wrote:
> 
> > You're saying that voltage "flows"? Electrons are what "flow"!
> > And signals usually include both voltage and current variation.
> >
> > ----- Original Message -----
> > From: "Scott Bernardi" <sbernardi at home.net>
> > Cc: "SDIY" <synth-diy at dropmix.xs4all.nl>
> > Sent: Monday, November 26, 2001 6:33 AM
> > Subject: Re: [sdiy] what exacly is "audio" in electronics terms?
> >
> > > It's voltage. "Audio" also designates that it is an ac 
> signal in the
> > > frequency range that is audible to human hearing, around 
> 20-20khz (for
> > > young pups, less high freq for some of us older guys). 
> This is opposed to
> > > control signals like gates, triggers, envelopes, keyboard v/octave
> > > voltages, etc. which are sub-audio.
> > >
> > > Glue Sniff wrote:
> > >
> > > > what exactly is flowing through those wires and patch
> > > > cords as, "audio" ? I have built many synths and
> > > > effects pedals through the years,  but I am still in
> > > > the dark about this most basic of questions. is it,
> > > > amperage, voltage, resistance?  in the case of a sine
> > > > wave what is it that is rising and falling?
> > > >
> > > > __________________________________________________
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> > >
> > > --
> > > Scott Bernardi
> > > sbernardi at home.net
> > >
> > >
> 
> --
> Scott Bernardi
> sbernardi at home.net
> 
>