Tech Bench - Pickup: The Pieces
By ED FRIEDLAND
Thu, 25 Jul 2013
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Bartolini 8CBP
DiMarzio Aria J
ONE SIMPLE WAY TO PROFOUNDLY AFFECT THE basic character of your instrument is to swap out the pickups— a mod that can often be carried out with no alteration to the bass itself. But to attain your version of sonic nirvana, it helps to understand what factors determine a pickup’s tone, and how a pickup interacts with your instrument.

In specific, we’re talking about magnetic pickups, which can be made from a variety of materials and come in several different form factors. They consist of magnets (either a solid bar or individual magnetic pole pieces), a bobbin around which copper wire is coiled, and the wire itself. The type and size of the magnet, the thickness and length of the wire, and bobbin size all affect the pickup’s character, but the instrument itself and the pickup placement also significantly influence the overall result. In other words, changing pickups may—or may not— have the life-altering effect you are looking for, but if you can do it without cutting up your axe, it’s an easy experiment.

Pickups use one of three types of magnet: ceramic, alnico, or neodymium, each with their unique characteristics. Alnico was the first type of alloyed magnet used for pickups, and hence it has become associated with vintage tone. Alnico is a blend of aluminum, nickel, cobalt, and iron, and provides a sweet top end, smooth overall response, and moderate output. Ceramic is a term used for hard ferrite magnets, a material developed in the mid 1950s as a low-cost alternative to metallic magnets. They are characterized as having a brighter, edgier tone with strong attack. Neodymium or rare-earth magnets have become more common in bass pickups since the late ’90s, and their magnetic strength allows for smaller, lighter pickup designs. Neo is said to have a wide, uniform tonal response, and basses by Dingwall, as well as the Ernie Ball MusicMan Bongo, take advantage of that quality.

Wire thickness, and the amount of winds around the bobbin, have a significant effect on a pickup’s output and tone. Essentially, the more wraps around the coil, the more powerful the pickup. But with the higher output comes an increase in midrange frequency response, which tends to mask the high frequencies and in turn accentuate the low end. If you’re playing aggressive rock and don’t need a lot of crystalline high end, a “hot” pickup might be just the ticket. On the other end of the spectrum, EMG builds their pickups with relatively few winds, thus producing a low-output pickup with an even, full-range frequency response. The signal is then bumped up to normal levels with a preamp built into the pickup.

Single-coil pickups (like those found in a typical Fender Jazz Bass) are well loved for their airy, “open” quality, but one single-coil pickup on its own is an incomplete circuit that induces 60-cycle hum. This is why Jazz Basses use two reversewound, reverse-polarity (RWRP) single-coil pickups to complete the circuit. If you are replacing two J pickups with a set from a manufacturer, you should have no issues with hum and polarity. But if you replace just one pickup, make sure you get the correct one. Be aware that while Fender (among others) makes the bridge pickup a bit longer than the neck pickup, other builders use the same size for both positions. Even if the size matches, when replacing one pickup, make sure the new pickup has the same polarity as the old one. One simple compatibility check is to turn over the new pickup and bring it close to the old one. If the top of the pickup you want to replace repels the top of the new pickup, they are the same magnetic polarity, and most likely wound the same, too.

Nordstrand NJ5
Aguilar AG 5J-HC
Some J-style pickups are designed with two coils split in half to fit into a J-size casing, while others have two coils stacked on top of each other. These “split-coil” or “stacked” J pickups eliminate 60-cycle hum, making them great for use in a PJ configuration, or with humbuckers (see below). They tend to be louder and have a bit more upper midrange than a single coil, although some, like the DiMarzio DP149 Ultra Jazz and Nordstrand NJ4SV, come very close to single-coil tone without the hum.

A humbucker uses two RWRP coils in the same case to eliminate 60-cycle hum. The massive Gibson Sidewinder, the Music Man Stingray pickup, G&L’s MFD pickup, as well as many of the “soapbar-type” pickups made by Bartolini, Seymour Duncan, and EMG are all humbuckers despite their different sizes and design. (The term “soapbar” refers to the size of the case only; internally they can be humbuckers, split, or single coils.) Humbuckers tend toward a thicker, more complex tone, and higher output than single coils—but by altering their “recipe,” many different characteristics can be achieved.

When replacing your pickups, not only does the size of the case have to fit your existing slot (unless you want to rout the body), the width of the magnetic field is critical, especially with five or more strings. As mentioned earlier, some pickups have individual pole-pieces that sit under the strings, while others use a single blade. If the pole-pieces don’t line up properly with your string spacing, you will have uneven response. A blade-style pickup solves that issue, but make sure the magnetic field is wide enough to cover the total string width where the pickup sits.

In last month’s installment, the attempt to get a modern hi-fi slap tone from my Lull MV5 by changing the bridge proved futile, so my next move was a pickup swap. I kept the existing Bartolini NTMB preamp, as I’ve had great experiences with it in other basses. As my goal was more high end, I tried a set of Nordstrand NJ5s with the “70s” wind, which use less wire for a clearer tone. They definitely opened up the high end on the bass and gave it an aggressive, Geddy-ish growl that cut through the mix better. However, my sonic goal was scalpel-like high end, and at this point I was getting more in the range of “very sharp hunting knife.” One day, a student brought in his brand new Fodera with EMG pickups, and I immediately recognized the sound I was looking for. After some research on the EMG website, I chose a set of JAX pickups with a BQC preamp. The first step was getting the case size and string spacing correctly matched. Measuring the Lull’s pickups, I found both slots were the same length as a bridge-position 4-string Jazz pickup (3.70"), and luckily, EMG has a set of those. Assuming that they’d fit without routing, I next checked the string spacing. As this particular EMG uses a blade-style magnet, individual string spacing wasn’t an issue, but the overall string width at the pickup fit nicely into the 2.72” maximum EMG suggested. Special thanks to Bobby Vega at EMG for the help!

EMG J
Seymour Duncan Basslines Blackouts for Bass
For the install, I went to luthier Lauren Ellis, Austin’s go-to repair person. I figured if she can keep the highly sensitive Eric Johnson’s axes in shape, this would be a piece of cake. EMG uses a solder-less connection system that makes it considerably easier to install, but in spite of having a roomy control cavity, the way the EMG pots (each with its own circuit-board) fit on the J-style control plate meant some minor internal routing work had to be done. And it turned out the EMG case was ever so slightly different from the Nordy’s, and the pickup holes had to be opened up a smidge in the corners. I was glad the bass was in good hands; unless you are a skilled woodworker, or simply don’t mind potentially screwing up your bass—don’t try this at home!

Overall, it was not a tough install for a pro, but I probably would have had a few meltdowns if I tried it on my own. However, at this point in time, the result is rocking my world. The JAX set uses alnico magnets, and there is a noticeable sweetness to the top end. It’s not as in-your-face as ceramic versions of the same pickup, but combined with the 3-band BQC active EQ, it’s a powerful and versatile system. When I consider the pronounced midrange the Lull’s alder body delivers, it seems the perceived high-mid scoop of the EMGs are just what I needed to hit the mark. The extended high-frequency range gives me that scalpel-thing I was looking for, and as an added plus, the electronics are dead quiet. At this point, I feel I’ve accomplished my tone goal with this bass, and it’s great to have this sound available in a killer 5-string platform. That feeling should hold for a while, but let’s face it—no one knows when next the mod bug shall bite.

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