Understanding electronics in a guitar?

[Tim Mason]

You are viewing a re-constructed thread by the ANZLF recovery team. For more information click here.

"Originally Posted on:"Wed Aug 04, 2010 ""

I've been ripping into things and putting them back together, reading how/why, and this is basically where im up to. Starting from ur pickup, this is how I THINK it all works. If you see something you dont agree on, let me know

Guitar Pickup

Shifty at MLP
The strings moving in the magnetic field of the pickups induces AC, not DC. Technically, there is no "+/-". The polarity changes depending on the frequency of the string movement, 440 times per second in case of an A (440Hz) and so on.

img~

img~

And i think the current flows through a humbucker like this(seymour duncan colour code)

img~

But with a humbucker, the direction of signal confuses me, irrelevant if you can wire up so it works, maybe, but its bugging me. Before i move on to the wiring/pots and switch, ill leave my humbucker theory open for critisism. This topic caused a storm over at MPL

So how do you think this info I've posted looks? Ok so far?

[Nick]

Ok I'm having a slight problem with your links/pictures, They aren't showing up (just shows the broken link icon on my puter). Apparently you need to be a member of the Les Paul forum before they'll show up maybe that's why they aren't showing. Or maybe it's just me

[Tim Mason]

Really? I am a member at MLP and i posted these pics there, seems to work for me, i see them fine, hmmm. Is anyone else able to see them?

Can you upload pics from your PC to this forum? I could redo it that way if all else fails

[Nick]

It may be just me (or the settings I run on Mozilla) . You have enough posts up now that you should be able to upload pictures onto the forum (can't remember how many posts it is you have had to have made before the feature is available). There is a tutorial on how to do it somewhere here but essentially when you make a post in the box, where you enter your text, you should see a button on the upper right corner above the text box saying "upload picture" just hit that and it'll walk you through it.

[Kim]

I followed the link to the images and this is what displays on site:

My_Lespaul.com wrote:

You are not logged in or you do not have permission to access this page. This could be due to one of several reasons:

1. You are not logged in. Fill in the form at the bottom of this page and try again.
2. You may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
3. If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

Log in
User Name:
Password:
Forgotten Your Password? Remember Me?
The administrator may have required you to register before you can view this page.

Obviously that site requires login to view images. You can upload direct to this forum just have a look at the edit/images and follow your nose, if you get stuck, their is a tute in the tutorial section.

Cheers

Kim

[Nick]

Yeah I did the same thing Kim when they wouldn't display for me.
But going back to the original post,

Aexion wrote:

And i think the current flows through a humbucker like this(seymour duncan colour code)

The current will flow through a pickup which ever way you connect the 'hot' and earth around which in the following diagram
http://www.seymourduncan.com/support/wi ... olor_codes
for a Seymour Duncan would be the green & the black. if you made the green the hot this is essentially reversing the phase of the pickup, but there are numerous different ways to configure the pickup, each one giving you a different sound at the output.

[Tim Mason]

The pic i drew is using SD color coding, but you cant see it
I cant seem to upload pics yet, maybe not enough posts? Ill try again in a day or two.

Sorry for the mix up

[Bob Connor]

I've enabled pic upload for you so you can go for your life.

Regards

[Tim Mason]

Was nervius before well here goes

Guitar Pickup


The strings moving in the magnetic field of the pickups induces AC, not DC. Technically, there is no "+/-". The polarity changes depending on the frequency of the string movement, 440 times per second in case of an A (440Hz) and so on.

img~

img~


And i think the current flows through a humbucker wired in series(seymour duncan colour code)

img~

img~


But with a humbucker, the direction of signal confuses me, irrelevant if you can wire up so it works, maybe, but its bugging me. Before i move on to the wiring/pots and switch, ill leave my humbucker theory open for critisism.

So how do you think this info ive posted looks? Ok so far?

[matthew]

i'm a bit confused about what the question is here . There is no directionality in the signal.

As you know, a humbucker is essentially two identical coils out of phase with each other, and wiring them in series causes induced EM hum to be cancelled out. (If both coils were at exactly the same place on the string, they'd cancel out the string sound as well, but they're not, so they don't.)

AFAIK here is no difference between the hot and cold wire other than that cold may be connected to shielding.

[Tim Mason]

I understand the "no hot or cold", but as i understand it, the current induced by the coil travels only one way in a wire and this can be predicted, depending on the polarity of the magnet in relation to the grounding/hot lead placement of a coil.

That is why the out of phase mod can be done with a magnet rotation in one bucker or by reversing the ground/hot lead with a push pull. Im trying to figure out what direction the signal runs in a bucker when wired paralelle/in phase (regular), so i can follow the signal throuought components in a basic guitar circuit.

[Bob Connor]

Quote:
The strings moving in the magnetic field of the pickups induces AC, not DC. Technically, there is no "+/-".


I'm a bit confused by this.

If the pickups are producing alternating current there must be a positive and negative part of the resulting waveform. That's what the alternating bit is all about.

Direct current inverts the negative part of an AC waveform by sending the current through a bridge rectifier and then through a power regulator so that the DC voltage remains constant.(and in the positive)

As far as I know a DC current will have no +/-. Not an AC current.

[matthew]

the direction of current depends on the direction of the coils, the polarity of the magnet and the direction of movement of the inducer (the string)

simply, the current runs one way when the string is moving north, and runs the other way when the string is moving south.

faraday's law i think.

[Tim Mason]

Thanks bob, that part was getting to me aswell.

And nigel, i think u may be on to something the:hmm:

Also, is it correct to assume the magnetic field is not pushed by the strings as in the diagram above, but infact moves this field as the string vibrates by conductively pulling on the field?

[kiwigeo]

One must not confuse swings in voltage with swings in current direction (ie direction of electron flow).

DC moves in one direction. AC moves backwards and forwards....50 times a second for Australia 240 volt domestic supply.

A synthesizer can produce a DC signal that oscillates (ie voltage varies) but its not an AC signal because the direction of electron flow is constant.

A power station generator is set up so that the coils and permanent magnets change orientation with respect to each other as the generator spins around. It produces an AC current.

[Bob Connor]

Sounds like you need to do an intro course in electronics.

Maybe your local TAFE is offering short courses at night.
You will get access to someone who really knows his stuff and can give you far more comprehensive answers that a part time electronics hack like me.

I teach at a TAFE here in Geelong and one of our electronics teachers spent a lot of his working life modifying FA-18's for the Air Force. Access to someone like that is invaluable. Particularly if you want to get into something relatively simple like guitar pickups.

If you really want to get into this field you will need a sound knowledge of electronic theory, at least in AC and DC circuits.

[Nick]

The way I've always understood it is that the string isn't moving the magnetic field (as per your diagram), it is moving within the magnetic field. The field (or flux) senses these fluctuations or disturbances within it which generates a signal at the wire coil. As long as the two ends of the coil/s are kept at a different place in the signal path, a signal will be 'seen' at any termination of the wire and can be used.
Our resident guru Rick Turner hopefully will pop his head in to explain it better than I can.

[Tim Mason]

Yeah, your right nick, The magnetic fields is not circular like that in the picture. Nor are the changes in the field correct. I think the strings become a temporary magnet conductor. So, in essence, in an electric guitar, you are moving the magnetic fields flux rather than pushing it.

Thanks guys, you have already helped make things a little clearer, unfortunately no time for an electrinics course, maybe later in life.

I have to go plug in , thanks guys

[kiwigeo]

Aexion wrote:

T
Also, is it correct to assume the magnetic field is not pushed by the strings as in the diagram above, but infact moves this field as the string vibrates by conductively pulling on the field?

The vibrating metal strings interfere with the magnet field around the pickups.

It's how metal detectors work.

The same principle is used in the ranging tool theyre using in the Gulf of Mexico to check how close the relief well theyre drilling is to the blow out well. The metal casing in the target well interferes with the magnet field generated by the ranging tool in the relief well.

[liam_fnq]

It is indeed Faraday's Faw at work.

As a conductor cuts through a magnetic line of force AKA magnetic field AKA flux a voltage is induced into that conductor. the denser that magnetic field (more lines of force) the greater the voltage. The longer the conductor within the mag field the greater the voltage. The faster the conductor is moving relative to the mag field the greater the voltage . The angle at which the conductor cuts the lines of force dictates the direction the voltage acts in. the current is given by the voltage applied and the impedance/resistance in the circuit. Ohm's law.

Now to pick-ups. The coil is stationary. The magnets are stationary. how the hell are any conductors moving relative to any magnetic fields? Are the strings some how magnetised by the pick-up magnets?

[Localele]

Shit , Liam as I started to read that all my old Tech homework came flooding back and I thought you were going to set everyone straight . Your first paragraph was a cracker but when I hit the second one it all fell in a heap.

[kiwigeo]

Here's a simple anaolgy:

1. pebble dropped into a large borderless pond. Watch the ripples radiate from the pebble.
2. place a rock into the same pond. Now drop the pebble and see what happens as the ripples react with the rock.

Think of the magnetic field around the pick up coil as a field of ripples.

[liam_fnq]

It's my understanding that the magnetic field in a pick-up will neither ripple, bulge, flex nor move in any way.

The string is moving or rippling or whatever. This, via Faraday's Law causes a corresponding moving or rippling or whatever of the voltage in the coil. This voltage drives a corresponding current down the leads. The amplifier reads this and sends it to the speaker.

[kiwigeo]

"When you can grasp the magnet from my hand Grasshopper......"

[Tim Mason]

Love the pond/ripple rock analogy