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# what exactly controls volume in a circuit? amperage, voltage, what? Answered

i see all these altoids amp circuits, and i want to build a small amp circuit into my backpack, but i just wanna know, what the hell is actually being raised? amperage going up? voltage going up? ohms going down? im confused!

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## 9 Replies

orksecurity (author)2009-08-28

Oversimplifying since I don't think you want to deal with integrating imaginary numbers: Two out of three answers are "yes".

V=IR, though in this case R is impedance rather than just resistance since we're dealing with a coil and a changing signal level.

Theoretically current is what you want to control since that's what's directly affecting the strength of the magnetic field and hence the motion of the speaker. But since the impedance is constant, changes in voltage and current will always be proportional to each other and to raise either you must also raise the other.

So: Yes, Yes, No, and I hope you're a bit less confused now.

orksecurity (author)2009-09-02

I should add: Human hearing is nonlinear. Loudspeaker response is nonlinear. Between the two, the same signal strength will be, or seem (or both) louder at some frequencies than at others. (Psychoacoustics is a whole field of specialization, if you really want to understand this in detail.)

seandogue (author)2009-08-29

Lolz...I had written a really long post explaining the V=IR relationship and included the complex portions presented by the speakers, and source but canned it on the realization that it might very well be an eye glazer to the author, resulting in less educational value rather than more, and so chose to replace it with a simplified version that is imo much easier to comprehend for someone who actually needs to ask this question in that way in the first place

I culled it because I didn't want to overcomplicate matters. If he/she wants or needs more info than what was presented, he/she is more than welcome to write back and ask for further qualification. Many of us can take him/her thru every portion and bore him/her to death, but really, I'm not in the mood to conduct a course in 200/300 level electronics for an instructables query of this kind... I'l stick with a simplification unless I recognize a certain base level of previous knowledge/experience on which I can build a deeper understanding for the question's author. (that's subject of course...I judged based on what I read).

It only makes sense to teach a first year engineering student that an object drops according to the equation

x1 = 1/2gt2 + vt + x0,

rather than telling them how it really works don't you think?

seandogue (author)2009-08-28

voltage.

we change the amplification value...that is, (simplified)

Vout = Vin x N. where the pot controls the value of N

frollard (author)2009-08-28

Also, the more voltage flows, the more current there is.

kelseymh (author)2009-08-28

Shame on you! :-) Voltage doesn't flow. Current flows. Voltage is the pressure that keeps the current flowing.

frollard (author)2009-08-28

slipped words - the more voltage, the more current will flow. (the more that electricity wants to get from a to b, the more of it will go from a to b at a fixed resistance) Thanks for catching that. It's late, and I'm distracted at work :S

kelseymh (author)2009-08-29

No worries! I was just rattling your cage :-)

megapix (author)2009-08-29

You are raising voltage. That is the direct effect of an amplifier. But the current through your speaker is proportional to the voltage, so more voltage will result in more current (amperage). The ohms don't change--that is a characteristic of your speaker (or earphones or headset).