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How do pickups work exactly? Old school stuff?

Discussion in 'Pickups & Electronics [BG]' started by CaptainWally, May 16, 2001.

  1. CaptainWally

    CaptainWally Supporting Member

    Oct 21, 2000
    Sandy Eggo, CA
    Hi bass gurus,

    I had a couple of questions I'm intersested in hearing
    you opinions on. Firstly, I've come to realize that I
    don't REALLY know how pickups work that well. I am
    familiar with Maxwell's Equations, and I understand that
    when the metal strings move, they affect the magnets
    in the pickups which causes electric signal to be directed
    through the output jack (often amplified through a preamp).
    What does active/passive mean exactly? Here is what
    is really weird...we pay so much attention to the kinds of
    wood, etc., but the wood is only affecting the way the
    string vibrates??? - and thus causes electrical signals
    to be created slightly differently?

    Don't get me wrong, I love this instrument, but what is
    the shelf life of this configuration? As we get more
    sophisticated electronics, we can depend on them to
    shape our tones more and less on the wood our instruments
    are made from...and thus make it sound like anything we
    want, right??? Has anyone messed w/ MIDI, etc.?

  2. jazzbo


    Aug 25, 2000
    San Francisco, CA
    I hope this helps:

    Selecting A Pickup
    By Scott Malandrone

    Strolling into a music store to buy a new pickup can be a harrowing experience. Passive, active, single-coil, humbucker, soapbar, alnico, ceramic ... the options seem endless. With a little pre-shopping homework, though, you can reduce the risk of disappointment. (Helpful hint: Many used-instrument dealers and pawnshops sell used pickups at rock-bottom prices and usually have an overflowing box of them. You might even stumble on a weird, funky $5 pickup that will become your sound.) Questioning music-store personnel and other players can help to steer you in the right direction; tell them what kind of sound you're after, what kind of bass you own, what type of music you play, and whether most of your gigs are live or in the studio. And while it might be useful to find out what your favorite pro uses, most likely the pickups in his or her bass have been custom-wound — so don't be fooled by the endorsement game. Besides, there's much more to good tone than the pickup — it's just one piece of the puzzle.

    When looking for a pickup, remember that it's the first step in your signal chain. Even if you spend thousands of dollars on high-end cables, preamps, power amps, and speakers, your bass will sound only as good as your pickup will allow it to. So, if the pickup in your bass is masking certain frequencies, you'll never get that elusive "dream tone," no matter how much money you spend elsewhere.

    How do you select the right pickup? In many ways, it's like picking the right tool for a particular job. Would you use a sledgehammer to hang a picture? (Okay — maybe there are a few of you who would!) It's unlikely that a bassist in a metal band would find a low-output vintage replacement pickup to his liking. Similarly, a jazz player probably wouldn't go for a kick-ass high-output model. It's important to understand both your options and your goals. To help you with the pickup-picking predicament, here's some basic information on pickups and electronics.

    Basically, there are four types of pickup configurations:

    Single coil. This design is the simplest and purest-sounding of the bunch. It's largely associated with the Fender Jazz Bass, which has two single-coil pickups, although early Fender Precision Basses (1951- 1957) have one single-coil pickup. Basically, the design involves four or more magnetic polepieces (or a long blade) that "view" the vibration of the strings. A single coil of wire is wrapped around the polepieces; the number of turns is an important factor in determining the pickup's output and frequency response. These pickups are hard to beat for their punchy midrange and crystal-clear highs. The downside is that they are susceptible to picking up 60-cycle hum from stage lights and amp transformers, which can cause a loud buzz to emanate from your speakers.

    Humbucker. This pickup basically consists of two single coils mounted side-by-side, with their coils wound in opposite directions and one of the two magnets reversed; this design cancels 60-cycle hum (thus the name). The bass humbucking design is most associated with the Fender P-Bass from 1957 on. Humbuckers have a powerful, dark sound with less highs than single-coil pickups — mainly due to the increased number of wire turns. (As you wind more turns of wire onto a pickup the output increases, but the upper-end response decreases.) Also, because they "see" more of the string's length due to the wider side-by-side design, more highs cancel each other out. Humbuckers can also have a "split" design, where the pickup is separated into two halves; this is the case with the "second-generation" P-Bass pickups.

    Stacked humbucker. This design looks like a narrow single-coil pickup, but it's actually one single coil lying on top of another to cancel hum. These pickups are a good choice for ridding a J-Bass of noise without having to rout a larger hole in the bass for a traditional humbucker. They're not as fat-sounding as a side-by-side humbucker, but they still sound big and retain many of the same humbucking qualities. Another variation of this design is the single-coil-size side-by-side humbucker; again, this looks like a single-coil pickup but has two thin single coils mounted next to each other underneath a J-style cover.

    Soapbar. The term "soapbar" refers to any rectangular-shaped pickup. Underneath its plastic housing could be a single coil, humbucker, or whatever else the designer had in mind. Using a soapbar housing gives you more room to put an active preamp or larger magnets — for a stronger sound — inside the casing. One way to find out what's lurking underneath the cover is by testing the pickup with "magic paper" made by EMG (see photo, next page); this is a thin plastic envelope that contains millions of tiny magnetic particles, suspended in oil, which align in the pattern of the pickup's magnetic field — revealing the size and shape of the magnet(s).

    There are two types of pickup electronics:

    Passive. A pickup that doesn't require a power source to transmit a signal is called passive or high-impedance. All early basses, like classic Fenders and Gibsons, use passive pickups and electronics. The passive design has a natural, uncluttered sound, and it's favored for its accuracy and "organic" tone. Passive electronics can only cut the output of a signal; that's why on a passive bass you can only turn down the treble with the tone control. With passive pickups and circuitry you lose high end when you use a long cord, because there's nothing supplying additional gain to the output signal of the bass.

    Active. This type of pickup has revolutionized the sound and cutting power of the bass. Active pickups and electronics were made popular by Alembic in the late '60s; they require a power source (usually a 9-volt battery) to preamplify the signal before it's sent to additional amplifiers. These pickups are low impedance because they use less wire around the magnets for a wider frequency response. The downside is they have a lower output — hence the need for onboard preamplification. (Some brands, like EMG, have a preamp built into the pickup itself, eliminating the need for an onboard preamp in the control cavity.) There are many advantages to going active: a quieter sound (no hum), a wider frequency response (more lows and highs), hotter output levels (to drive longer lengths of cord), and an onboard EQ system (for additional tone shaping). Due to the ability to cut and boost the signal and various EQ bands, this type of electronics is very versatile.

    Now here's a curveball: while most basses use either passive pickups with passive electronics or active pickups with active electronics, you can also use passive pickups with active electronics or active pickups (with built-in preamps) with passive electronics. A passive pickup can be connected to an active preamp with, say, a 3-band onboard EQ, for a totally different sound. This is a popular approach on many basses today, allowing both passive purity and active power.

    Aside from configuration and electronics type, there are several other factors that affect a pickup's sound. One is magnet material; alnico (a mixture of aluminum, nickel, and cobalt) is used for its soft, musical tones, while ceramic (a mixture of clay and metal) gives a more cutting, aggressive sound. The size and number of polepieces, type and gauge of wire used, the potting of the coils in wax or epoxy (to prevent microphonics), as well as many other variables, all contribute to the sound of a pickup. As Rick Turner once said, designing pickups is more of an art than a science.

    Unfortunately, the bottom line is this: you'll always sound different from the next guy who's using the same pickup, so you need to get out there and experiment. Who knows — with some patience and a good set of ears (and hands), maybe you'll be the next player with the tone everybody wants. So heat up those soldering irons and get to it!
  3. Suburban


    Jan 15, 2001
    lower mid Sweden
    Oh, captain, my captain.....

    You can make whatever sound electronically these days. Very few of us would hear the difference, if it is well done (i.e. including rythmic and tonal mistakes!).

    To us, "purists" or "reactionaries" or whatever, the *feel* of each instrument will never be matched. That is in making the music, as we rarely hear a difference in a recording. And some of us love to make music and refuse to listen to it :D (no, not me)

    Go peek in our MIDI guru forum - Dann Glenn!