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DiMarzio Patents Explained – Airbucker, Virtual Vintage, and Dual Resonance
In the world of aftermarket electric guitar pickups, Larry DiMarzio is among a small group of individuals who altered history. Though he wasn’t the first to produce aftermarket pickups, DiMarzio became incredibly popular throughout the 1970s with the introduction of the Super Distortion, which started a revolution in rock guitar. From the beginning, DiMarzio sought to create innovative designs that weren’t available, which likely was a key driver to the company’s success. The Super Distortion itself was an entirely new design from what was available, utilizing a large ceramic magnet and thicker pole pieces.
Throughout the past few decades, Dimarzio has filed patents around their innovations. While the most famously discussed patent is the double cream bobbin, we will be focusing on the patents that influence a pickup’s sound.
You’ve probably seen DiMarzio models that start with the word “Air” – the Air Classic, Air Norton, and Air Zone. Filed in 1993, the patent states its goal is “to provide an electromagnetic pickup for musical instruments in which the magnetic field strength is reduced by a predetermined desired amount to enable the instrument with which it is used to produce more pleasing tonal qualities.”
“In accordance with the present invention, the controlled reduction in magnetic field strength is achieved by providing a predetermined non-magnetic gap or spacing between the permanent magnet element, preferably made of Alnico 5, and the ferromagnetic pole pieces, thereby reducing field strength. In the embodiments described, the spacing is provided by a non-magnetic element, which may be made of any non-magnetizable material such as aluminum, brass, plastic, etc., inserted between the poles of the magnet and their respective pole pieces, or by an air gap, the reduction in intensity of the magnetic field being dependent upon the magnitude of the spacing. The spacer element is in the form of a bar which retains and supports the pole pieces and, when assembled with the magnet, maintains the pole pieces in the desired spaced relationship to the magnetic poles.”
So, why do this? By reading the patent, we can see their stated goal was to reduce magnet pull to increase sustain. However, there is another reason why this might be useful – Replicating an “aged” magnet. DiMarzio’s product description of the Air Classic provides this detail.
“We love the sound of late 1950s humbuckers, but we didn’t want to simply imitate them by using Alnico 2 or “aged” Alnico 5 magnets. Airbucker™ technology was created to capture all of the best sonic qualities of vintage humbuckers while avoiding the technical problems.”
In the world of vintage replica pickups, “aged” magnets are brought up consistently. An “aged” magnet refers to a magnet that has lost a portion of its magnetism, known as becoming degaussed. There’s a theory in the pickup world that vintage guitars sound great due to old pickups having lost magnetism over time. While it’s possible that there are pickups that have lost magnetism, in general, fully charged magnets are very stable. Quoting Bill Lawrence, “Since the 50’s, we use Alnico 5 magnets which lose, under normal conditions, less than half a percent per 100 years.”
However, that doesn’t mean a degaussed magnet shouldn’t be used in a pickup design to achieve a certain goal. Intentional degaussing is easy to achieve, simply by pushing two magnets’ common ends against each other. DiMarzio even makes a pickup that uses a degaussed Alnico 5 magnet, the PAF 59. The technical issue is that a degaussed magnet is less stable than a fully charged one, and is likely to continue degaussing. It’s also difficult to consistently produce magnets that have been degaussed equally. By creating a small gap between the magnet and pole pieces, you can decrease magnetism to the strings, all while using a magnet that is fully charged and stable.
In theory, creating this gap should only reduce the output of the pickup. In practice, it’s not so simple. To create this gap, the pickup’s keeper bar is generally removed, and replaced with a non-ferrous spacer. On the slug side, the bottoms of each slug are narrowed to create room for spacers. This removal of ferrous material decreases the inductance of the pickup, which changes the overall character of the pickup.
So how does DiMarzio account for this? For that, let’s look at the next patent, Virtual Vintage.
Like Airbucker, you’ve probably seen models over the years with Virtual in the name. Virtual P90, Virtual Vintage Blues, Virtual Solo, and more. It’s generally referenced in DiMarzio’s noiseless single coil pickups, but it’s also used for other models. In fact, it’s used in the Super Distortion, before it was even patented!
From the patent filled in 1997, it states that Virtual Vintage “[provides] additional ferromagnetic material in the gaps between the pole pieces of a pickup bobbin and/or beneath, around and/or in close proximity to the bobbin.”
“This arrangement has the advantage of increasing the inductance of the pickup without causing a corresponding increase in the pickup’s DC resistance and impedance. Thus, a sound with better tonality and less harshness results.”
So, why is increasing inductance important? For this situation, you can think of inductance as output, though it is much more complicated than that. It also has an impact on the resonant frequency of the pickup. Let’s take our Airbucker example. If we remove metal to create air gaps, we can add metal back by inserting it inside the bobbins. This allows DiMarzio to bring the inductance level back to the level they desire. Several of their models use both Virtual Vintage and Airbucker, but it’s not a requirement. Increasing the inductance is just another lever to pull in creating a pickup’s sound.
For DiMarzio’s noiseless single coils, it’s used similarly, but for a different purpose. Without going into too much detail, DiMarzio makes their noiseless single coils by stacking two coils on top of each other. Together, they work to cancel hum like a humbucker does. However, while one coil is producing the sound you hear, the other is used to cancel the hum. This hum cancelling coil is smaller, and doesn’t have as much output as the top coil. By adding in Virtual Vintage, the bottom coil can be boosted enough to counter the frequencies of the top coil, without needing a ton of wire.
Virtual Vintage does not look the same in all DiMarzio pickups. Many times it’s a metal slug in between pole pieces, other times it’s a metal plate connected to the magnet. As we analyze more pickups, we continue to discover different ways DiMarzio has implemented the design.
Now we go back in time to one of DiMarzio’s oldest patents, filed in 1983. I first came across Dual Resonance when learning about Steve Vai’s signature pickups, but it’s used in many other DiMarzio pickups. Dual Resonance is probably the simplest of DiMarzio’s patents to understand. It’s simply using a different wire gauge for each bobbin of a humbucker.
“The present invention avoids the shortcomings of prior two-coil hum-bucking pickups by winding the coils such that both coils of the pair have substantially the same number of turns but are wound with wire of different diameter or gauge. It has been found that by means of this construction, low frequency cancellation is emphasized, providing more effective elimination of 60 cycle hum without affecting the higher harmonics of the 60 cycle signal which may contribute to the desired tonal qualities. Moreover, because of the difference in impedance characteristics resulting from different diameter wire on the respective coils, overall frequency response can be selectively adjusted to provide improved tonal qualities.”
This claim is harder to analyze, as it’s hard to find a comparable model that’s only difference is wire gauge. DiMarzio’s patent claims that by using a dual wire gauge design, less hum cancellation of high frequencies is achieved, allowing for high harmonics to shine through. When playing my personal DiMarzio Utopia pickups which include Dual Resonance, I recall noticing that. However, it could just as easily be my brain interpreting that happening because I knew what the marketing material said. In any case, we will do more work to test this claim.
There are some things we can confirm about this design. First, changing the wire gauge changes the DC resistance. A narrower wire gauge has more resistance/ft, so an equal amount of wire will have a higher DC resistance. Secondly, in a standard series setting, a Dual Resonance humbucker will not actually have two resonant frequencies. This is because the resonance curve of one bobbin goes into the next (series), combining those curves. See this example of a DiMarzio Evolution.
| Evolution – Series | Evolution – North Coil | Evolution – South Coil | |
| DC Resistance | 14.2 K | 6.08 K | 8.25 K |
| Magnet | Ceramic (2.25″ x .5″ x .25″) | Ceramic (2.25″ x .5″ x .25″) | Ceramic (2.25″ x .5″ x .25″) |
| Inductance | 6.7 H | 2.9 H | 3.05 H |
| Capacitance | 123.6 pF | 103.8 pF | 195.2 pF |
| Resonant Frequency | 2.2 kHz | 3.5 kHz | 4.0 kHz |
Which DiMarzio models use each technology?
While many DiMarzio models list the technology they use, many do not. As we continue analyzing more pickups, we will update this list. So far, here’s what we know:
| Model | Dual Resonance | Virtual Vintage | Airbucker |
| 36th Anniversary Bridge | X | X | |
| Air Classic | X | ||
| Air Norton | X | ||
| Air Zone | X | ||
| Area 58 | X | ||
| Area 61 | X | ||
| Area 67 | X | ||
| Area Hot T | X | ||
| Area T | X | ||
| Area T 625 | X | ||
| AT-1 | X | X | |
| Evo 2 | X | X | |
| Evolution | X | ||
| FRED | X | ||
| Fusion Edge | X | ||
| Humbucker From Hell | X | ||
| Injector | X | ||
| Mo’ Joe | X | ||
| Norton | X | X | |
| PAF Joe | X | ||
| Steve’s Special | X | ||
| Super Distortion | X | ||
| Tone Zone | X | ||
| Tone Zone P90 | X | ||
| Tone Zone S | X | ||
| Tone Zone T | X | ||
| Utopia | X | X | X |
| Virtual P90 | X | ||
| Virtual Vintage 54 | X | ||
| Virtual Vintage Blues | X | ||
| Virtual Vintage Heavy Blues 2 | X | ||
| Virual Solo | X |
Conclusion
Of all the guitar pickups I’ve analyzed so far, DiMarzio pickups have been surprisingly non-traditional. I’ve heard remarks about DiMarzio pickups being forward thinking and modern, but I didn’t understand what that meant until I started investigating their models on a deeper level. There’s nothing wrong with a traditional design, but it’s fantastic to have companies out there that are trying something new. Whether you’re looking for something traditional or modern, DiMarzio has an option for you.
1 thought on “DiMarzio Patents Explained – Airbucker, Virtual Vintage, and Dual Resonance”
On the note of how series coils do not have separate resonant frequencies, that is not entirely true. While two ‘inductors’ affect each other as a reactive sum, two ‘tranducers’ react independently when going from magnetic to electrical . The magnetic disturbances in the field flux introduce frequencies as a matter of their position from the antinode, which is slightly different. But more importantly, the coils’ inherent reactive properties due to their windings, gauge and field distribution are still independent when transducing these magnetic distubances to the electrical circuit. The electrical conditions that the pickup imparts to the circuit are otherwise a static sum condition that the pickup signal is filtered through.
Let me know your thoughts on this.