The actual physics of wire gauge... why 42-43?

[MichaelScottPerkins]

Why are modern pickups usually made with 42 or 43 AWG wire? Why not as small as 50 AWG or as large as 40?

Maybe another important question is, are the number of wraps, i.e. the total length of the wire that increases a pickup’s strength, or is it the total mass of copper? For example, why not, simply cast a copper ingot with 6 holes through it for the magnets, and put that on the bobbin rather than wrapping wire? That would be a big increase in the total mass of copper. Since no one does it that way, it must have something to do with the overall length of the wire, i.e. # of wraps.

 

[Adieu]

Re: The actual physics of wire gauge... why 42-43?

Cuz the necessary quantity of turns fits on the bobbins

 

[Clint 55]

Re: The actual physics of wire gauge... why 42-43?

Maybe because it conducts mostly along the length of the wire and a little bit between strands making the wire pattern have an effect on the tone.

 

[Chistopher]

Re: The actual physics of wire gauge... why 42-43?

Here's the formula for resistance of a wire:



As you can see both changing the length of the wire and the area of the cross section of the wire will equally effect the resistance. A wire 2 feet long with an area of 4 square inches in the cross section will have the same resistance of a wire of equal material that is 4 feet long with 2 square inches of area. But since area equals pi multiplied by the radius squared, a change in diameter (and hence radius) will have a much greater effect on the resistance than changing the length of the wire.

 

[ItsaBass]

Re: The actual physics of wire gauge... why 42-43?

The wire gauge used is all about fitting the desired number of coil windings onto the chosen bobbin. It was found early on in the realm of stringed instrument pickups that wire gauges in the low 40's gave you about as many windings as you needed to make the pickups sound "right" for the music of the time.

Insulation thickness can play a role as well. When so many thousands of windings are used in a pickup coil, differences in insulation thickness can add up.

Some early guitar pickups were made with thicker wire, like 40 or 38 gauge, IIRC.

I once wound one coil of a humbucker with 40 gauge, and the other with 42 gauge, just to see what would happen (and just because I happened to have an old spool of 40 gauge sitting around, and no use for it).

Resistance per unit of length varies from wire gauge to wire gauge, so DC resistance is only a useful indicator of how heavily a pickup is wound when comparing two pickups wound with the same wire...and it's indication of such is always indirect. DCR is easy to measure using commonly owned tools and commonly understood concepts, and that's why everyone uses it. But it doesn't tell you a whole ton about a pickup, in and of itself.

 

[Jacew]

Re: The actual physics of wire gauge... why 42-43?

Used gauges are mostly chosen for the biggest wire that allows necessary amount of turns to fit on the bobbin. Thicker is easier to wind.

The effect of coil comes from the electric running through the coiled wire. That's same effect what may cause interference when you coil too long wires behind you tv for instance.

 

[GuitarDoc]

Re: The actual physics of wire gauge... why 42-43?

Cuz the necessary quantity of turns fits on the bobbins

Another brilliant, relevant reply.

 

[GuitarDoc]

Re: The actual physics of wire gauge... why 42-43?

The answer to your question is simple.

First of all, it is helpful to think of electricity as water. A larger diameter garden hose allows a greater volume of water to flow through it with little resistance. Conversely, a very small diameter hose allows very little volume of water to flow through it because of the increased resistance to its flow. Also, the longer the hose, the greater the resistance. If you have a 1/2" dia hose that is only 1 foot long the water will flow out with great speed and force. If you increase the length of the hose to 500' you get water that flows very little.

So, smaller gauge wire creates greater resistance when compared to larger gauge wire of the same length. Also, using a smaller gauge wire allows you to fit more winds on the coil (greater length) which increases resistance even more (if desired).

A pickup works because of the field created around it which is formed from electrical current flowing around a magnet. If you had a solid block of copper instead of a coil of wire, you would not have a current flowing around the magnet and essentially no resistance...it would go straight from the input to the output, and therefore there would be no output energy of the pup...it would be dead/shorted out.

Generally speaking, increasing the resistance of a pup (by reducing the diameter of the wire and/or increasing the length) increases the output and the midrange and reduces the highs of a pup.

Pickup winding is a science but it is also an art. By varying wire diameters and lengths/winds you can change tone and output of a pup to create many variations. That's why there are so many different pups on the market.

 

[Francois]

Re: The actual physics of wire gauge... why 42-43?

Thanks Guitar Doc ! It was a nice explanation.