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Can a Humbucker Pickup Really Cancel Out Hum? Exploring the Science and Art of Noise Reduction in Electric Guitars
If you have ever played an electric guitar with single-coil pickups, you may have noticed that sometimes the sound can have a background hum or buzz, especially when you are near electrical devices, fluorescent lights, or other sources of electromagnetic interference. This so-called 60-cycle hum is caused by the pickup’s sensitive coil(s) picking up the alternating current (AC) from the surrounding environment, which interferes with the desired signal of the vibrating strings. While some guitarists may like the added warmth or grit of hum, others prefer a cleaner tone with less noise. That’s where humbucker pickups come in.
A humbucker pickup, also known as a double-coil pickup, uses two coils wound in opposite directions and connected in series or parallel to cancel out the hum while retaining the original signal. This design was invented by Seth Lover for Gibson in the 1950s, and it soon became popular among jazz and rock guitarists who wanted a more versatile and reliable sound. However, the question remains: can a humbucker pickup really cancel out hum completely? And if so, how does it work?
To answer these questions, we need to delve into some physics and electronics. But don’t worry, we will keep it simple and practical. Before we see how humbucker pickups can reduce hum, let’s first understand what causes hum in single-coil pickups.
What Causes Hum in Single-Coil Pickups?
As mentioned earlier, single-coil pickups can pick up unwanted humming or buzzing sounds from various sources of electromagnetic interference, such as power lines, transformers, motors, or even other nearby musical instruments. This interference is usually at a frequency of about 60 Hz (cycles per second) in North America or 50 Hz in Europe and other parts of the world, corresponding to the AC mains voltage. The exact frequency can vary depending on the location, the type of interference, and the distance between the source and the pickup.
The humming sound is generated by the pickup’s coil acting as an antenna that receives the AC interference and adds it to the audio signal from the strings. This is due to the physical and electrical properties of the coil, which is made of a thin wire wound around a magnet or magnets. The coil has a certain resistance, capacitance, and inductance, which together determine its overall impedance (the opposition to electric current). The impedance of a coil varies with the frequency of the signal, and it can magnify or attenuate certain frequencies more than others. In particular, the impedance of a coil can be lower or higher than the impedance of the surrounding environment, which leads to a transfer of energy between them. This transfer can create interference or noise if the environment has a different voltage or current than the pickup’s circuit.
The most common way to reduce the hum in single-coil pickups is to shield the pickup cavity and the wires with a grounded metal plate, usually made of copper or aluminum foil or paint. This shielding acts as a Faraday cage, blocking or diverting the electromagnetic waves away from the pickup’s coil, and grounding any residual noise that gets through. However, shielding alone may not be enough to eliminate all hum, especially if the interference is strong or pervasive. That’s where humbucker pickups come in.
How Do Humbucker Pickups Cancel Out Hum?
As mentioned earlier, humbucker pickups use two coils wound in opposite directions and connected in phase or reversed phase to eliminate or reduce the hum. The two coils are wired together in series or parallel, and they share a common ground wire or shield. When a string vibrates near the magnetic field of the pickup, it induces a current in both coils, but in opposite directions. This is because the vibrating string disturbs the magnetic field by changing its distance and velocity, and the coil responds by inducing a proportional voltage. However, since the two coils are wound in opposite directions, the voltages they generate cancel each other out, effectively producing a signal that is twice as strong as that of a single coil, but with no hum.
This cancellation occurs because the hum or interference that affects the two coils is usually in phase, meaning that it has the same polarity and frequency for both coils. Therefore, when the two signals are combined, the hum cancels out due to their opposite phases. The desired signal, however, adds up due to their same phase. This is illustrated in the following figure:
So, in theory, humbucker pickups should be able to cancel out hum completely, assuming that the coils are well-matched, the wiring is correct, and the shielding is effective. In reality, however, there are still some factors that can affect the cancellation or the tonal quality of humbucker pickups, such as:
– Coil imbalance: if the two coils have slightly different impedance or winding patterns, the cancellation may not be exact, and some hum may leak through. This can happen when the pickup is poorly made or damaged, or when the strings are not properly aligned with the poles.
– Phase inversion: if the wiring of the pickup is reversed or gets reversed unintentionally by other gear or cables, the humbucking effect may be lost or even worsened, as the two coils will add up their hum instead of cancelling it. This can happen when you use different guitars or amps, or when you swap pickups without checking the wiring diagram.
– Magnetic field strength: if the magnets used in the pickup are weak or uneven, the pickup may not be able to capture all the string vibrations or produce a balanced tone. This can happen when the pickup is old or poorly designed, or when the magnets get demagnetized or damaged by external forces or heat.
– Tone color: if the two coils have different frequency responses, due to their placement, size, or number of turns, the pickup may sound different from a single-coil or another humbucker pickup, even if it cancels out hum. This can happen when you choose pickups with different specs or brands, or when you customize the pickups by rewinding them or adjusting the height or screws.
Therefore, when you choose a humbucker pickup, it is important to consider not only its hum-cancelling capability but also its overall tonal character and compatibility with your guitar and playing style. There are many types of humbucker pickups available, each with its own sound signature and price range, from vintage-style PAF to modern high-gain ceramic. Some of the most popular brands and models are:
– Gibson Burstbucker series
– Seymour Duncan Antiquity series
– Fender Wide Range humbuckers
– DiMarzio Air Norton, Tone Zone, Super Distortion, and PAF 36th Anniversary
– EMG 81, 85, and 60
– Bare Knuckle pickups
You can also choose between open or covered pickups, depending on your preference for looks and tone. Open pickups expose the coils and the magnets, while covered pickups shield them from dust, sweat, and scratches, but may also affect the high-end frequencies or sustain.
Conclusion: Yes, Humbucker Pickups Can Really Cancel Out Hum, but…
In summary, a humbucker pickup can indeed cancel out hum by using two coils wound in opposite directions and connected in series or parallel to produce an equal and opposite signal that cancels the undesired hum but retains the desired signal. However, the cancellation may depend on various factors such as coil balance, phase inversion, magnetic field strength, and tone color, which can affect the overall performance and sound of the pickup. Therefore, when you choose a humbucker pickup, make sure to consider not only its hum-cancelling capability but also its tonal character, compatibility with your guitar and amp, and cost-effectiveness. Also, don’t forget to shield your guitar and the cables from electromagnetic interference, and to enjoy the music you make. Happy playing!
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