What is a pickup Wire or Coil?

What is a pickup WIRE or COIL?

Almost all guitar pickups share the same basic ingredients, and one of the most important of these is the coil. Without the coil the electromagnetic pickup cannot function (for more on electromagnets and how they work, see our article: What is an electromagnet?) The following article will tell you everything you need to know about different types of coil, so that you can make an informed choice when purchasing a new pickup. There are many variables, but we’ll try to make things as clear and easy as we can.

The varieties:

Most pickups are wound with a copper wire, and although rare, one can find pickups wound even with a sliver coil.

Pickup coil specs mainly vary in two ways – Gauge and Insulation.
Gauge refers to the thickness of the wire. Guitar pickup coil gauges usually range between 41 and 44 AWG (American Wire Gauge), with the most commonly used gauge being 42 and 43. The higher the number – the thinner the coil.
Insulation is required in order to keep the coil from shorting out, but has a profound impact on capacitance – and therefore on the tone. There are many types of insulation but the most common are Plane Enamel, Heavy Formvar, Polyurethane and Poly-Nylon.

Gauges and Resistance:

As mentioned above most pickups are wound with 42 or 43 gauge wire.
The thickness of the wire changes some parameters in the tone and behaviour of the pickup.
Firstly – the thickness changes the resistance, which is described in “Ohm”s or the symbol “?” for short.  If you take a look at pickup’s specs, you will find a measurement that is called DC Resistance. A standard guitar pickup has a resistance of thousands of ohms, with each 1000 ohms (or ?) marked as 1 K?. For example 8.5K? actually means 8500?. By itself resistance tells us very little about the pickup’s final tone, but it can certainly help us if we combine this information with other aspects of the pickup – such as the magnets.

As a rule, a thicker wire has less resistance and therefore conducts more electricity. A thinner wire has more resistance, over the same length of wire, and thus conducts less electricity. For instance, 4000 turns of coil on a bobbin with a 42 AWG will have much less resistance than a 43 AWG with the same bobbin. The longer the coil the more resistance is produced. Through measuring the amount of resistance we can estimate the amount of turns around the bobbin, or the length of the wire.

Take a look at these equations to clarify the idea: 

X K? = (Y length of 42 AWG) and 

X K?  = (Z length of 43 AWG) then

(Y length of 42 AWG) > (Z length of 43 AWG).

The change in resistance changes the resonance peak of the pickup, the output and the general dynamic range  (with the same magnets and bobbins).

For example a read of 14K? with 43AWG should be less bright and higher in gain than a 10K? pickup with the same wire. 

The decision behind using one type of coil over another is not just a tonal one. In some cases a certain design will not allow for a lot of turns of the wire around the bobbin due to a lack of space. Too little resistance will result in low output and a thin sound. If space is an issue a thinner coil can be used, but there will always be a sacrifice in the overall dynamics of the pickup. A good example would be mini-humbuckers, which always lack some dynamic range.  

If we compare a thin wire to a thicker wire we can see some distinct differences.
This table is a comparison of two coils, but can be associated to other coils gauges such as 41 AWG and 44 AWG. 

Of course, it’s definitely ok to use 42 AWG and still play Metal, and perfectly fine to play Soft indie with a 43… It’s up to the player to decide which character of tone and feel is right for them…

Insulation:

As discussed earlier, there are some options regarding the insulation material of each coil. These materials have distinct characteristics, some are technical but more importantly tonal.

Plain Enamel (PE for short): A relatively tough wire that is hard to solder, brownish-purple in color, and is one of the first insulation materials ever invented and used. This inconsistent coil makes it unpredictable when winding a pickup and causes greater variations in DC resistance in the end result.
This doesn’t necessarily mean that it’s of poor quality and tone.. Sometimes those inconsistencies create a different character to the tone and make it totally unique. This wire tends to produce some harmonic dryness by allowing some of the overtones to bleed out.

Heavy Formvar (HF): This very tough insulation is called heavy because of its thickness – 0.0004” (compared to 0.0002” of other insulation materials). It is less consistent than Poly wires and helps to achieve a vintage, percussive, dry tone. The thickness also helps to reduce capacitance in the pickup, thus higher frequencies are easily projected through the amp.

Polyurethane and Poly-Nylon: These insulation materials are extremely similar in regards to pickups. Nylon is better at deflecting heat and is regarded as a better quality material – not really much of a factor for our application for usage in a guitar pickup. These materials are highly consistent and allow for a rich sound, full of overtones and feel. They are very easy to solder and their consistency helps to build highly accurate resistance levels.

Capacitance:

Capacitance (according to wikipedia) is the ratio of the change in electric charge of a system, to the corresponding change in its electrical potential.

Why does this matter to us? In order to make things easy, and not to veer off topic, let’s consider capacitance as the amount of filtration that the coil has. That is – high capacitance = lower frequencies and higher bleeding of hi frequencies. A change in the wire’s thickness will decrease the overall capacitance of the pickup by adding more gaps between each turn of the coil.

It’s worth noting that the material used for insulation is just one factor in the overall capacitance. Another key factor (even greater than the insulation) is the person or machine that wounds the coil.

Scatter Wound or Machine Wound?

Vintage pickups were all wound by hand. This is called “scatter winding” because the coil is wound inconsistently and small pockets are formed between each turn of the coil. Although this inconsistency is bad for accurate measurement of resistance, it creates a lower capacitance pickup. It decreases slightly the overall output but increases the EQ range produced by the pickup, especially in high frequencies, and gives a more dynamic, airy tone. 

Every pickup wound by hand is slightly different. Each person holds the coil with a different amount of tension and varies the spread speeds during the winding, which creates varied capacitance in every wind. Some players prefer a more dynamic and open tone and will sacrifice consistency in the product in order to get a truly unique tone.

As mass production evolved machines started doing the work. Several pickups could now be produced with the exact same speed and tension. Pickups became more consistent, but this process increases the capacitance of the product, making it a little louder but also darker in tone and less dynamic.

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