You've probably heard from various professional guitarists the notion that removing a pickup cover can make your electric guitar sound brighter. Some attest to this presumed fact, while others claim it's mostly a placebo effect.
Do guitar pickup covers affect tone? Though pickup covers do have some effect on the tone of a guitar, the impact on pickup performance is negligible. However, installing pickup covers to match the original height of the pickups will alter tone due to an increased distance between the strings and pickup magnets.
In this article, we'll discuss how pickup covers work with guitar pickups and whether they affect the overall tone of a guitar or not.
A Primer On How Pickups Work
As said above, the influence of pickup covers on a guitar's output is a highly disputed topic. In order to understand the concepts behind these discussions, it's useful to review how pickups work in the context of sound delivery.
The pickup is a device composed of a certain number of magnetic poles/bars that match the number of strings attached to the guitar. The magnets are inserted in a bobbin and are wound by thousands of turns of conductive copper wire underneath the housing.
Each of the pickup's magnetic poles pieces acts to magnetize their respective strings. As the strings vibrate, they disturb the magnetic field around the conductive coil of the pickup. Electromagnetic induction causes a coinciding electrical signal in the coil. As the strings oscillate back and forth, the electrical current in the coil alternates, causing an audio signal.
Those signals travel throughout the circuit until they finally arrive at an amplifier. The amplifier is the unit responsible for serving as the “soundbox” of the electric guitar, which projects adequate sound levels.
Pickups may consist of one or two coils. The number of magnet rows can visually determine the number of coils. The coils are, properly speaking, the circuits that operate under the bobbin.
Originally, pickups only contained one coil. These single-coil pickups are still common today.
By the 1950s, the first dual-coil pickups started to be implemented on electric guitars to address an issue common to single-coil pickups, namely electromagnetic noise from power mains (50 or 60-cyle hum, depending on your location in the world).
Dual-coil pickups are also nicknamed “humbuckers”, describing their ability to decrease or “buck” the 50 or 60 Hz humming prevalent with single-coil pickups. The noise cancellation is attained by winding each coil in opposite polarity.
The Purpose Of Pickup Covers
Earlier, we stated that coils could be identified by the magnet rows present in a pickup. However, many pickups are designed with covers that hide the magnets. These covers are most commonly made of nickel, chrome, or plastic.
Pickups are similar to antennae that capture any vibrations in their surroundings. In that sense, while covers serve multiple purposes. Perhaps the most important one is to ground the guitar's electronics and shield the pickup from a kind of noise pollution known as electromagnetic interference (EMI). These frequencies are emitted by most electronic devices that lie adjacent to the pickups (the most obvious example being the guitar amplifier itself) that eventually find their way into the magnetic field.
It should be stressed that dual-coil pickups were implemented in electric guitars principally to improve noise cancellation, as noise was the primary concern of its proponents. Modern covered humbuckers are a throwback to the original “horseshoe pickup” designed precisely to achieve this goal.
Since humbuckers are designed with two coils that cancel out electromagnetic interference, they don't really need a cover for that purpose.
Single-coil pickups, however, do see arguable EMI-rejection benefits from pickup covers.
Perhaps the main purpose of a pickup cover is to protect the pickups from environmental damage. Whether you're jamming in the garage or on stage every night, your pickups may be exposed to more harm than you think.
A pickup cover can protect the pickup from external forces, from physical contact with a pick to accidental spillage to the accumulation of dust, grime, and sweat.
While this may have been considered a great bonus, it was probably not the main preoccupation on the part of the designers. Nevertheless, it's an important reason to keep the covers, considering how demanding it is to fix a pickup and/or its coils.
Additionally, pickup covers add to the aesthetics of the guitar. Of course, this is subjective. However, it's worth mentioning.
How Covers May Or May Not Affect Tone
Further elaborating on the initial question. Some factors need to be considered:
Although there may be some semblance of consensus regarding the tonal shift induced by the cover, the most disputed claim is whether it has a significant effect on tone.
The material of the cover may also determine the degrees by which the tone is impacted. Plastic covers will hardly make any difference since plastic doesn't have any magnetic properties. Nickel and magnetic alloy covers, on the flip side, intervene in the magnetic field more meaningfully.
Moreover, there are differences between various types of metallic covers. Chrome and nickel-silver have diverse levels of capacitance that reduce the tone's brightness to a greater or lesser extent.
It's a scientific truth that a ferromagnetic cover will affect the magnetic field of a pickup and will have an effect on the overall performance of the pickup. However, the tonal changes may not be obvious.
One common phenomenon present in covered pickups is the feedback they may cause when using high-powered amplifiers. If the pickup or pickup cover vibrates due to resonant sound waves in the environment, there will be a risk of a positive feedback loop as the pickup and strings will be vibrating and causing electrical signals.
Humbuckers have more moving parts and are, therefore, more prone to feedback. Wax, epoxy, tape and even solder are commonly used to help keep pickups and their covers from vibrating and causing unwanted microphonic feedback.
Although not directly related to tone, I should reiterate that pickup covers may reduce 50/60-cycle hum and electromagnetic interference more generally, which will technically provide a cleaner tone.
However, practically speaking, pickup covers will do little in the real world to affect the tone of a guitar.
Installing Or Removing Pickup Covers
After reading the paragraphs above, you may be inspired to install covers over your pickups or remove the current covers from your setup. I wouldn't advise doing either for tone's sake, though I would never discourage experimentation. With that being said, let's consider the basics of installing and removing pickup covers.
Removing Guitar Pickup Covers
The first step to removing a guitar pickup cover is to remove the pickup. If the guitar has a pickguard, you'll likely have to remove it before loosening the pickups. Removing or at least loosening the strings will help as well. Note that you don't have to remove the lead wires from the pickup to remove the case, so you can leave the pickup electrically connected.
Humbucker pickup covers are often soldered in place over their pickups. To remove the cover, then, we should melt the solder with a soldering iron before separating the cover from the pickup. Forcing the cover off may result in damage to the pickup and cover.
Additionally, there is typically a wax (either paraffin or beeswax) that secures and dampens the cover and pickup together to avoid the aforementioned microphonic feedback. This wax can be gently heated and scraped or wiped away to clean up and separate the humbucker pickup and cover.
Single-coil pickup covers typically fit snuggly over their pickups and are not soldered in place. By removing these single-coil pickups, the cover should come off easily.
Installing Guitar Pickup Covers
To install guitar pickup covers, have the pickups out of their cavities. This, again, generally requires removing the pickguard and strings.
For single-coil pickups, ensure the covers fit snuggly over their respective pickups, place the pickups back into their cavities, and secure the pickups and pickguard (if applicable) into place before reattaching the strings.
For humbuckers, ensure there is a wax coating on the inside of the cover before fitting it on the pickup. Once fitted, solder it in place by adding new solder on to the inside edge of the humbucker cover and the baseplate. When the solder dries, apply gentle, low heat to allow the wax to settle properly.
Set the humbuckers into their respective cavities, secure the pickups and the pickguard, and restring the guitar.
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