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Unwound: Fishman Rethinks the Electric Guitar Pickup


Fishman uses a “shuttle” system to swap pickups instantly.

Perfect Copies
The team had many variables to experiment with: the thickness of each trace, the number of windings, the number and thickness of the layers. But the variables were all controllable—and perfectly reproducible.

Here’s what they came up with after untold iterations: Stack 48 layers on top of each other, add a spacer to provide a gap, and stack another 48 layers below, but with reversed coil direction to cancel hum. Perfectly matched halves perfectly cancel hum. The gap prevents unwanted communication between the upper and lower stacks.

A critical but elusive consideration was the flux properties of the magnets. That’s where Fishman’s Ching-Yu Lin, Ph.D., came in. Lin knew little about guitars before joining Fishman several years ago, but much about acoustic engineering. He set about measuring and visually mapping the magnetic properties of the best-sounding pickups.

The magnetic fields of different pickups produce distinct magnetic maps, so Lin created 3-D visualizations of the fields in order to study each pickup’s unique magnetic fingerprint and create a tangible “magnet goal.”

Pickups, as you probably know, employ magnets of different materials (alnico 2, alnico 5, ceramic, etc.) and different shapes (bar magnets in humbuckers, magnetic pole pieces in most Fender pickups, and so forth). But the magnets themselves can vary from batch to batch, and sometimes the attractive qualities of a particular pickups result from environmental changes to the magnets after the pickups were manufactured.

Lin set about measuring and visually mapping the magnetic properties of the best-sounding pickups the team could find. The magnetic fields of different pickups produce distinct magnetic maps, so Lin created 3-D visualizations of the fields in order to study each pickup’s unique magnetic fingerprint and create a tangible “magnet goal.”

How to control the variations in the magnets’ properties? Supercharge the magnets, and then de-magnetize them in a controlled way.

From Notes to Voltage

A science class refresher on how a pickup turns guitar playing into voltage: The vibrating metal string excites the pickup’s magnetic field, which causes a matching vibrating current in the copper coil. To make this happen, of course, the string must be within the area of magnetic pull. But the fact that the string is within the magnetic field also affects the eddy currents causing the pull, as well as the vibration of the string itself. The interactions can become far more complex than you might suppose.

From Flat to Flavorful
The magnetic properties of a pickup aren’t simply matters of tone and frequency. The interaction between the vibrating string and the magnetic field greatly affects the physical dynamics. The Fluence team’s goal was to also replicate the physical string-and-magnet interaction, informed by Lin’s magnet maps.

Simply positioning magnets in the center of those printed circuit racetracks yields a perfectly flat-sounding pickup. That’s not a tone most players seek, but it’s a perfect platform for replicating the character of different pickups.

With traditional pickups, changing one parameter alters others. For example, adding additional winds increases output and lows, but sacrifices highs. Take Strat pickups: A vintage ’54 pickup has more sparkle than a modern, overwound “Texas”-style pickup with its fatter, more bottom-heavy sound. The new technology permits designers to address those variables with less hard-to-control interactivity.

By starting with a perfectly flat pickup, and then filtering some frequencies while boosting others, the team can “image” the sound of various pickups, tweaking as they see fit. For instance, they can match a hot output of the overwound Strat pickup without sacrificing the high end of the vintage model.

Selectively altering a pickup’s frequency response is old news at Fishman—they’ve done it countless times with their under-saddle piezo pickups. But an exciting new wrinkle of Fluence technology is the possibility of combining multiple profiles in a single pickup. Instead of having to choose between vintage and modern Strat pickups, for example, players could access a switch allowing them to change profiles on the fly. The switch can reside on a standard push/pull pot, so both pickup and pot can be added as a completely reversible modification to most guitars.

Once the printed coils are assembled and the magnets matched, the preamp filters and boosts the signal
to match the curves shown here.

Fluence Benefits
Perfectly consistent and reproducible “printed” coils. A way to replicate the pull of the magnets based on ideal pickups. Accurate and consistent ways to control frequency response. The ability to choose between multiple pickup profiles. It’s impressive—but there’s more.

As mentioned, hum has been eliminated, even from single-coil pickups. The usual method of creating hum-free single-coil pickups—“stacking” two coils—inevitably causes high-end loss. But Fluence can eliminate hum while retaining the original single-coil sound, thanks to filtering and boosting within the preamp.

There are other advantages: A guitar’s volume control and the instrument cable can attenuate high-end frequencies. (In fact, draw a schematic showing a pickup, a volume control, and an instrument cable, and you have a perfect diagram of a tone control.) The instrument cable carries a capacitance—the longer the cable, the higher the capacitance and the greater the high-end loss. That’s not a problem with Fluence, because the pickup connects to a preamp, which acts as a buffer. Tone-wise, what you hear with the volume set to 10 is the same as what you hear when it’s dialed down to 2, only louder. A 10-foot cable sounds identical to a 100-foot cable. Want to use a 100-foot cable with your guitar volume set at 2? No problem.

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