How Do Hum-Cancelling Pickups Work?

Written by Kenny Prochazka

At Mojotone, we are proud of all of our pickup designs. From humbuckers to acoustic pickups, our dedicated team of builders gives their very best to everything that comes off of their workbenches. Of course, every pickup manufacturer says something similar - we hope!

Among our ever-expanding catalog of pickups, however, there is one glorious piece of engineering that has consistently captured our hearts, and the ears of guitar players around the world: our widely acclaimed Quiet Coil™ series.

It has been said before, but our approach was very simple: to make hum-cancelling single-coil pickups that look and sound like real single-coils, with minimal parts and adhering to actual vintage single-coil attributes. This involves matching resonant peak frequencies and the inductances of various single-coils, so they sit right in the frequency response and feel without having to compensate at all.

Sounds easy, but it certainly is not.

For those unaware, 60-cycle hum is a persistent low-pitched hum (right around 60Hz) that results from alternating current (AC) and the way it is processed through electrical transformers and the wiring of a particular room or building. 60-cycle hum can come from ballasts and transformers for fluorescent lights, neon signs or any number of household appliances, and even an unmagnetized single-coil guitar pickup is effectively a radio frequency antenna. This hum is most noticeable when you are not playing, but it can still show up in the mix if you are recording or using high gain, and it can cover up some of the softer dynamic range of delicate picking styles.

Now, there are a number of companies out there that make hum-cancelling or noiseless single-coil shaped pickups. The vast majority of them are made to look like single-coils, but abandon many things that made the original pickup sound the way it does. In this field, you will usually find one or more of the following:

• Stacked coils, which change the geometry of the pickup and its magnetic field. These can also often be significantly taller than actual single-coils, making it tough to fit into vintage pickup routes.

• Ceramic magnets, which can be stronger for smaller bobbins, but do not react like original AlNiCo magnets

• Batteries, which can again boost the signal for smaller magnets, but also contribute to extra compression, unlike actual single-coils

We at Mojotone have one simple rule for any of our Quiet Coil™ pickups: If it doesn't sound and react like one of the best single-coils that we have heard, we will not sell it. If it looks like a single-coil, but just sounds like a humbucker, we will not sell it. There is absolutely no reason for us to offer anything that doesn’t meet our exacting standards.

For this reason, our Quiet Coils™ use responsive AlNiCo magnets and keep to the same single-coil geometry, so that the magnetic field has the same footprint and sensitivity that one would expect from a true single-coil. The multiple magnets in our Quiet Coils™ can result in a darker sound, so they will usually perform best using 500K potentiometers, but you will not find a better single-coil sound from a noise-cancelling pickup. (And there is at least one video out there that uses 250K pots, so what do we know?)

That is just the beginning, though.

Just because we can build them doesn’t mean that they are always a rip-roaring success. The next step with any completed prototype is to install it in a guitar and let everyone in the company test it; from our CEO to our flatwork engineers, visiting artists, neighbors, friends, etc. With that many ears and hands, it does not take long to find any shortcomings. And if it does not pass muster, it goes back to the design phase.

Our perceptive readers will have caught the phrase “multiple magnets” in a previous paragraph, and will ask if these are actually humbuckers. In a semantic sense, yes, these do “buck” the 60-cyle hum, but there is a bit more to it. When you reverse the coils to remove the hum, and reverse the magnets to make sure that the string signal is in phase, you have to be very careful which frequencies you are “bucking” or you will lose much of what makes the single-coil signal so special. Every one of our Quiet Coil™ pickups is finely tuned to make sure that the resulting sound is as close to the original single-coil as possible.

This design phase can last for years in some cases, if we cannot get the pickups to sound exactly right. Does it need more or fewer winds? A different type of coil wire? A different winding pattern? A differently-cut bobbin? Some of you may bemoan our lack of a Quiet Coil™ version of a particular pickup, and we certainly hear you! We are probably working on it right now, and will only offer it for sale when we are completely happy with the result.

We approach everything with intention, including the heart and soul of your guitar. Our goal is to make you as happy with your guitar signal as possible, and to get all of the responsiveness and tone that you want from single-coil pickups, without modifying your guitar, and without any annoying 60-cycle hum.

Now that you understand some of the magic behind our celebrated Quiet Coil™ pickups, which ones are your favorites? And which ones do you wish we would make? The time has come to get out there, find your sound and love your tone!