Much of the information in this post was derived from this brilliant electrosmash article on pickups
My current dilemma
I am a particular person when it comes to guitar pickups. I like my pickups to have plenty of treble, medium-high output, and very little in the way of mids, or at least I think I do. I have plans to eventually pull out my favorite pickup (a Dimarzio super 2 in the bridge position for the curious) and measure it's frequency response. While I figure out the best way to do that I may as well explain why I think it's worth doing.
As mentioned above I like a very particular sound, and the specifics of this sound mean that I'm somewhat limited when it comes to pickups that aren't black, F spaced 6 string humbuckers. I recently replaced the pickup in a guitar that for aesthetic reasons needed to be white, and, while it was not impossible to find something that fit my needs, my options were very limited. Fast forward a few months to the present, where I am looking at buying a cheap 7 string and upgrading it. I have again run into the problem of not being able to find a pickup I like that fits my needs. This sure would be easier if I could just make my own pickups...
A brief tangent about physics
As a Chemist, Physics can suck my tone knob.
A less brief and somewhat relevant bit about physics
Coils of wire a re pretty cool. If you run a current through them they can generate a magnetic field. If you have control over the current and voltage, then you can control the field that is created. Put a magnet into the center of the coil and you've got a very basic motor. Congratulations you've done a physics.
If you do the opposite of the above and move a magnet through a loop of wire, a current is generated in the coil. in the most basic sense this is how guitar pickups work. The string forms a standing wave above a row of magnets (or a single blade in some cases), which are attracted to the string. These magnets in turn move through a coil of wire with many thousands of turns which, through the magic of physics, creates guitar tone
That's some interesting physics but how does it relate to tone?
As mentioned above, a traditional guitar pickup can have anywhere up to around 10,000 turns. The number of turns is related to output power (higher turns - higher output), so any reasonably loud pickup will therefore need to have a similar number of turns. Getting a coil of wire with this number of turns is impractical for the hobbyist, unless they are willing to put considerable effort into a coil winder. This has been done before but I personally am not interested in this at the current time. Thankfully another option exists, but it is not a simple solution.
Active pickups
Most guitarists will have heard of active pickups already. Many will tell you that they're lifeless and dull. Many people will tell you the opposite too, so don't put yourself into either camp just yet. Lets take a look at the properties of the pickup that give them their tonal properties first.
A guitar pickup can be pretty accurately measured using a resistance, a capacitance and an inductance in the following arrangement, where R and L are properties of the copper coil, and C is a property of the fact that the universe is a harsh and unloving mistress. A 500K resistor has been added in place of a volume pot to ensure the pickup is loaded as it would be in a normal guitar. These 3 properties combine to give a pickup resonance, which is responsible for the majority of its tonal properties.
(Once I have taken some measurements of my own there will be more graphs here, but for now have a look over at the electrosmash article linked above. Theirs are pretty cool)
Active pickups (for example the EMG81) use a coil with many fewer turns (fewer turns - lower output), and compensate for this with an active preamp circuit. The obvious problem with this is that it requires a 9V battery (more on that in a future post though). The less obvious (and more relevant) issue can be found by looking at an extreme example of Alumtone pickups, which while not active themselves feature a single loop of aluminium around a magnet. Changing the size and shape of the coil will change its tone. in other words a coil with fewer turns will have an overall shorter length of wire, which will affect both R and L, resulting in a much flatter sounding pickup. Some people like that, and if that's your thing then great but flat pickups are not for me.
There are ways to manipulate the resonance of a pickup, but they require tweaking the active circuitry, and are topics for another time.
To summarize
I am a fussy mf when it comes to picukps and it would be a lot easier to just make my own.
I am unwilling to invest the time and money into a proper coil winding setup so will need to use a few orders of magnitude less turns of wire. As for how I'm going to get around the effect this has on tone? You'll just have to read the next few posts to find out (no promises about when that will be though)
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