Simple question about amping electical currents

  • #1
[Solved?] Simple question about amping electical currents

Homework Statement


I am attempting to build a pocket guitar amplifier. So far this is what I have.
http://img174.imageshack.us/img174/6724/dscf0004yf2.th.jpg [Broken]
What you can see in that picture WORKS! The tiny electrical current from the guitar goes through the battery powered "box wrapped in red duct tape" that is then sent to the head phones, where i can hear the sound of my bass guitar.

So after i got that much working, I added this.
http://img299.imageshack.us/img299/791/dscf0003lv8.th.jpg [Broken]
What you see there is the wire (as a whole) wrapped around a circular shaped permanent magnet.

My question is this. Is the wire being wrapped around the magnet helping, hurting, or doing nothing for, my goal?

(My goal is to make the existing amp louder and more "crisp".)

Homework Equations


I can hear sound clearly through the headphones both with and without the magnet however, I think (no proof) that its slightly louder with the magnet.

I asked around and looked on google only to wind up here. Therefore I have no other equations.


The Attempt at a Solution


I have tried both with and with out the magnet taking mental notes....
 
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Answers and Replies

  • #2
mgb_phys
Science Advisor
Homework Helper
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You are trying to invent the choke http://www.aikenamps.com/Chokes.html [Broken]
I wouldn't have thought one that size would have much effect at audio frequenices.
 
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  • #3
WOW! Fast reply! Thank you for that, I think this is solved already. However I'll see what others have to say first.


EDIT:

I do not know what possessed me to use this area of the forums but i got an answer so I am happy :D
 
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  • #4
454
0
There will be a singal and a ground wire (or shield) in that lead, and the current through
them will be equal and opposite. This means there will be no magnetic field produced, so
this gadget won't act as an inductance.

Even if you wrapped a single wire 5 times around a magnet or a piece of iron of the kind used in transformers, I don't think it would do much at audio frequencies.

Using a permanent magnet just produces a constant magnetic field wich will have no electrical effects.

If you used a really large inductance in the guitar leads, it would act as a low pass filter.
I don't think you want that.

The article about chokes is about chokes as a filter for the power supply.
 
  • #5
Okay so now I have 2 opinions. In my own opinion, kamerling makes more since. However I still want one more then I'll keep or discard the magnet.
 
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  • #6
mgb_phys
Science Advisor
Homework Helper
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Isn't a guitar output just like a RIAA stage, it isn't differential so there shouldn't be a current in the shield (ideally there should never be a current in a shield).

Using a magnet rather than a ferrite core doesn't have any extra effect, but the magnet material is probably soft iron anyway unless you used some expensive rare earth magnet it is effectively a ferrite-core.
The sheild will not have very much effect on the magnetic field creating the inductance - but as you say a few turns around a small core isn't going to have any great effect at audio frequencies, it might reduce very high frequency RF pickup but the audio amp is going to filter that out anyway.
I suspect the biggest effect is going to be it's weight on the cable pulling the plug slightly and making a poorer contact - especially if you go in for arm windmilling 'The Who' style guitar playing!
 

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