Turtlerock Forum

Hi guys,

just a question....does anyone have a good link which explains the flow of electrons through wire?

I am trying to get a "complete" or...(as complete as my brain will allow) understanding of how a signal gets captured from a mic capsule, and travels down a microphone cable....

I get that electrons are travelling down the wire, but specifically want to understand how the different frequencies in an audio signal translate to electrons, and so on...

perhaps such a question is too difficult to understand as a beginner, but my mind has trouble understanding details in audio engineering when a fundamental question like this remains sort of cloudy.

Its all about waveform propagation... at least, that is what my feable understanding tells me.

Imagine a river with a boat running up and down it. Two things are happening to the water molecules. The first, is current - collectively the water molecules move in the one direction. The second is a wave that propagates out from the boat as it passes.

In an oversimplified way, a similar thing occurs within audio circuits. The actual flow of electrons is rather slow (centimeters per second), while the propagation of a waveform through electrons is much closer to the speed of light. Now that I think about it, In the case of phantom powered microphones there is a direct current running towards the microphone, while a waveform propagates down the same wire in the opposite direction!

I'd be keen for a deeper response! Rob?

i still dont understand what that means, or how the frequencies betwen 20-20khz are phsycially manifested through that wire. Voltage being proportional to amplitude makes sense to me, thats fine...no worries there, but the different frequencies....WTF!?

Maybe this is one of those..."listen to what we say, dont ask questions" kinda questions

more of an issue, i dont know how to word my question to Google....i've tried a few search strings, and the explanations always get vague.

http://van.physics.illinois.edu/qa/listing.php?id=3341


don't know if that helps any...

excellent, thats more like it...after reading it 400 times, i think i'll understand it. i'll read it at home...a bit busy at the moment

dunno if this helps?

http://www.electronics-tutorials.ws/acc ... eform.html

it might, my brain is starting to melt though

and from here http://lofi.forum.physorg.com/Electroma ... 21568.html (just being lazy here as I don't have a textbook to hand)

"Electromagnetic waves are a combination of electric and magnetic waves perpendicular to each other. Since a moving electric charge creates a magnetic field and a moving magnetic charge creates an electric field, an electro-magnetic wave sort of self propagates. The electromagnetic spectrum ranges from very long wavelengths (radio freqs [RF]) to very small wavelengths (gamma and x-rays) with the visible light part of the spectrum around 450 to 700 nanometers. All EM waves travel at the speed of light © in a vacuum.
Sinusoidal current (or voltage) in an electric circuit is just a moving electric charge. This 'ac' wave can originate as an EM wave picked up by a transducer (antenna) and stimulate an electric circuit.
…
A voltage source is just an electrical potential. I you were to connect a conductor between the higher (absolute value + or -) potential and a zero potential (ground), the electrons in the outer shell of the , say copper atoms, move from one copper atom to the next, like boxcars of a train. This is current. If the potential stays at a constant voltage, you get a constant current. This is DC. If you have a potential that moves from a higher than zero potential to a lower than zero potential, the electrons will move accordingly (according to their neg charge, that is). Hence it alternates ; AC. "

So, flow of electrons = current yeah?

First off it's important to differentiate between direct and alternating current.

Direct current - you get a flow of electrons in one direction

Alternating current - you get a flow of electrons in two directions, oscilating at a number of cycles per second.

A 'typical' audio signal is an alternating current whose frequency and amplitude vary in an analog of acoustic waveforms.

This might be the clearest link a short google produced (from an old TC electronics manual no less) http://g-force.info/electronics.htm

we're getting there, i'll have to read these tonight though, thanks Mr carter.

Also maybe have a read through this stuff

http://www.animations.physics.unsw.edu.au/waves-sound/

http://www.allaboutcircuits.com/

jkhuri44 wrote:i still dont understand what that means, or how the frequencies betwen 20-20khz are phsycially manifested through that wire. Voltage being proportional to amplitude makes sense to me, thats fine...no worries there, but the different frequencies....WTF!?

Maybe this is one of those..."listen to what we say, dont ask questions" kinda questions

Not at all! If you understand that voltage is proportional to amplitude you probably have more of a grasp on it than you think.

Excuse the question as an answer, but how does frequency manifest itself in a sound wave? there is a direction correlation between sound and the function of audio circuits because they both operate on the basic concepts of wave propagation. "Frequency" is manifested in an acoustic waveform like sound, and an electromagnetic waveform like those wires in an audio circuit in exactly the same way... One is just the oscillation of air molecules, while the other is the oscillation of electrons.

Text_Edifice wrote:dunno if this helps?

http://www.electronics-tutorials.ws/acc ... eform.html

thanks Dave, reading this now, starting from tutorial one...very good.

It's a pretty cool resource - the unsw physics ones are also great, written by a muso / really great educator too which I think helps immensely.

Text_Edifice wrote:It's a pretty cool resource - the unsw physics ones are also great, written by a muso / really great educator too which I think helps immensely.

nice, i was watching UNSW lectures for higher computing as well...really good stuff available for free...who needs uni