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Audio voltages in relation to audio

post #1 of 26
5/4/10 at 11:44am
Thread Starter 
I've hunted around for a definite answer but haven't got anywhere, hopefully someone nice will be able to help me. I may get flamed for this, but I just can't figure it out.

Basically I need to know how the current flows to/from a speaker. I know that if there is no current flowing to the speaker then it will produce nothing, fair enough. I know that the speaker has to vibrate back and forth past it's resting point 0v. Does that mean that the current is flowing backwards and forwards AKA AC?
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post #2 of 26
5/4/10 at 1:39pm
yup, and the current I = V / R
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post #3 of 26
5/4/10 at 2:09pm
Hi,

See the menu on the right hand side of this page: Basic Car Audio Electronics

Suggest you start with menu items 3, 5, 21, 23, and 31.

: )
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post #4 of 26
5/4/10 at 2:10pm
Thread Starter 
Hmm, thought so. That leads me to my next question.

How comes most amps that I've looked at only appear to amplify the signal in one direction only?
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post #5 of 26
5/4/10 at 7:08pm
An audio signal in one direction? No such thing. Dig into those tutorials Pageygeeza!
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post #6 of 26
5/4/10 at 8:04pm
Quote:
Originally Posted by Pageygeeza View Post
Hmm, thought so. That leads me to my next question.

How comes most amps that I've looked at only appear to amplify the signal in one direction only?
Analog audio signals are basically AC current/voltage. Why do you say the amplifiers appear to amplify in only one direction?
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post #7 of 26
5/5/10 at 2:55am
Maybe he's talking about something like that:


see wiki: amplifier
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post #8 of 26
5/6/10 at 12:18am
Thread Starter 

I think XNOR is closer to what I'm getting at.   :)

 

Basically the audio current itself is AC, but in every amp configuration that I'm aware of the amplifier orientation for each channel seems to point in one way only.  Maybe I do need to read up on it more, but the way the amp is set up, does that make it bi-directional?  So it both amplifies a positive and negative current?  

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post #9 of 26
5/6/10 at 2:49am

Yeah you should read those wiki page(s).

And the pic I linked is for one channel only, as you can see there's only one input and output and the output is the same as the input (only amplified): AC.


Edited by xnor - 5/6/10 at 7:50am
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post #10 of 26
5/6/10 at 9:21am
Thread Starter 

Thanks.  Does any of it make a difference in audio quality?

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post #11 of 26
5/6/10 at 12:04pm
Quote:
Originally Posted by Pageygeeza View Post

Basically I need to know how the current flows to/from a speaker.
 
How comes most amps that I've looked at only appear to amplify the signal in one direction only?

 

Let's say one connector of the speaker is connected to ground---0 volts.  For the speaker to move back and forth properly, the voltage on the wire has to go up and down around zero --- so it goes negative about half the time. 
 

You can have a power amplifier that drive the speaker, which only has a positive side and the signal is always positive, if you capacitively couple the output. The cap blocks the DC.

 

In the A/B amp xnor showed above, it has both positive and negative rails, so the signal is driven both positive and negative, and doesn't need a cap.

 

There's a few other ways to do it too.

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post #12 of 26
5/10/10 at 8:57am
Quote:
Originally Posted by xnor View Post

yup, and the current I = V / R


thus, when the voltage is negative, so is the current.  so, flipping your orientation, you can think of it as positive current flowing to the amp.  more accurately, the amp sucking current from ground through the speaker.

 

is this what you're asking?

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post #13 of 26
5/10/10 at 12:59pm
Quote:
Originally Posted by etiolate View Post

sucking current from ground through the speaker.


Doesn't that make your cheeks collapse?

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post #14 of 26
5/11/10 at 9:33am
Thread Starter 
Quote:
Originally Posted by etiolate View Post




thus, when the voltage is negative, so is the current.  so, flipping your orientation, you can think of it as positive current flowing to the amp.  more accurately, the amp sucking current from ground through the speaker.

 

is this what you're asking?

 

Yeah.  I can't get my head around the fact that once the current flows backwards through the opamp that there will be more resistance? So when the current flows from the opamp to ground there should be less resistance than when the current flows from ground to either channel?

 

Does that make any sense to you? 


 

Quote:
Originally Posted by Tyll Hertsens View Post




Doesn't that make your cheeks collapse?


Depends how hard you suck on it.  :P

 

Serious now.  I'm playing with the idea of a 4 channel headphone amp, but really need to know more about current flows and opposing audio waves through the ground.  :S

 

I can get pretty confusing at times.  XD

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post #15 of 26
5/11/10 at 9:55am
Quote:
Originally Posted by Pageygeeza View Post

I'm playing with the idea of a 4 channel headphone amp, but really need to know more about current flows and opposing audio waves through the ground.  :S

 

I can get pretty confusing at times.  XD

 

Um ... yeah. How much electronics have you studied?  It's not something that you can kinda guess at.


 

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