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<< back to Kens column Trainwreck thinking by ken Fischer As we start chapter two, I would like to mention that, what you are about to read, is based on my experience gained in the United States. Since this article is on an internationally read website, your experience, in a different country may, or may not be the same as mine. I am always happy to learn from anyone who has information to contribute. Knowledge promotes understanding in all areas of life. Chapter two: In this chapter I am going to talk about pickups. When a string is made to vibrate, the pickup converts that vibration to an electrical signal that can then be amplified by an electronic circuit. Just as there are many types of microphones, such as dynamic, condenser, ribbon, and others so are there many types of pickups. The most common for electric guitar is the magnetic pickup. This type corresponds to the dynamic microphone, in that it generates its electric output by varying a magnetic field. The dynamic microphone has a diaphragm with a voice coil that move in the magnetic circuit. The magnetic guitar pickup uses the string vibration to vary the magnetic field from the pickup. Of course this means that musical instrument strings must be made of materials that will react to the field of the pickup, such as iron or steel. Before we go on, a little history of the first guitar pickups, that I know of, might be of interest, as they pre-date the magnetic type. When I was a young boy, the first electronic phonographs, were on the 78 RPM type. They used lacquer records as vinyl did not yet exist. To "pickup", the signal contained in the grooves, a cartridge, with a piezo crystal connected to a stylus, (commonly a phonograph needle), was used. When the needle vibrated the piezo crystal, a voltage was produced and amplified by the electronic circuits to drive a speaker. As an aside, Enrico Piezo was an Italian geologist, who discovered that his piezo crystals could be used to measure small movements of the earths crust. The 78 cartridge had a thumbscrew to make it easy to change the needle that wore out rather quickly. The 78 cartridge became a guitar pickup when someone got the idea to jab the needle into a guitar, and the affix the cartridge to the needle using the thumbscrew. A long wire was connected between the cartridge and the phonograph. The phonograph became the first, "guitar", amplifier. Back to the magnetic pickups. There are several forms of magnetic pickups. The most common ones we see to day have one or two coils of wire, with one or two magnetics beneath the coils, and polepieces carrying the magnetic field to the strings. A less common type, called a contact pickup, uses a diaphragm that is placed against the instrument. As the diaphragm vibrates, a coil with a magnetic polepieces generates signal voltage. A variation of this, used on the Ampeg Baby Bass, has the bridge resting on a diaphragm, with a coil and polepeice below. An early pickup design, used on the Rickenbacker guitars and basses, used a, "horseshoe", magnet. The coil was mounted to the body, and the magnet was brought up and over the strings. The strings were therefore between the magnet and the coil. The main disadvantage to this setup is that you can not pick the string over the coil because the magnet blocks your access. Common, modern pickups are the humbuckers, single coil, low impedance, and active electronics types. Let us start with high impedance, passive types, as these are by far the most widely used types. The single coil, as the name implies, uses a single coil of wire. This type offers excellent fidelity, fast pick attack, and tend to have the best clean tones. Typical single coil picups are used on Strats, Telecasters, and the Gibson P-90pickup. The main disadvantage is that they pickup hum from stray electrical fields. The Humbucker pickup uses two coils of wire in series. These coils are arranged so that they are, "in phase", to the string vibration, but, "out of phase", to stray electronic fields. When used in a stray electrical field, each coil generates an equal, but opposite voltage, and since the noise voltage are opposite polarity, the cancel out, and the pickup is quiet, but does sound different. Due to technical reasons that I will not get into here, the humbucker also weakens some string information due to cancellation in the coils. The side by side coil humbucker tends to, "read", a longer portion of the string than a single coil, again giving it a unique voice. Ther are common misconceptions about pickups. The most common one is that you can judge the output, or fidelity, of a pickup by taking, or looking at the published data on the pickups Ohm reading. This is totally incorrect. Pickups are complex devices. They have inductance, capacitance, and resistance. In other words they are tuned circuits all by themselves. Pickups use many types of magnets, which can be charged to different strengths. 5000 turns of 42 gauge wire wound will read less Ohms than 5000 turns of 43 gauge wire wound so that total footage is the same. Pickups, both old and new can come with or develop shorted turns. A few shorted turns will not be seen on the Ohm meter, but the eddy currents in shorted turns can have a drastic affect on output, and tone. The way the wire is wound on the bobbin will change the output, and tone of a pickup. The type of wire, and the wires insulation will effect output, and tone. The material in the non-magnet polepiece will have an affect. Blade versus individual polepeices performs on different ways. As you can see many factors affect pickup design. Active pickups are yet a whole other subject. As this is Ultimate Guitar Gear, I guess you might like some advice on pickup selections. First as I have said before, THRUST YOUR OWN EARS! Ask questions, talk to friends, if possible play guitars with pickups you have interest in. There are too many good, and bad, pickup makers for me to list. Also, there are many brands I have not heard. What I will do, is tell you the brands of pickups I have in my current guitars. It's only a starting point. My personal guitars are currently equipped with, Lindy Fralin, J.M. Rolph, Bill Lawrence, Duncan Custom Shop, (EVH), and Gibson P-90 pickups. I use both single coil and humbucker pickups. I almost forgot a brand! In the 1980's I was an ESP guitar dealer. I use both the LH200 and LH150 model humbuckers they made at the time. I don't know if these pickups still are being made. Multi-sound Humbucker wiring Below you can see a schematic on a very useful Multi-sound Humbucker wiring for a Studio situation. With this you can get over 100 different sound/combinations in you guitar with only two humbuckers.  (click here for bigger picture) Sound list for each pickup: 1. Humbucker in phase 2. Humbucker out of phase 3. Coil A off + in phase coil B 4. Coil A off + out of phase coil B 5. Coil B off + in phase coil A 6. Coil B off + out of phase coil A 7. Coil A bottom end only + coil B in phase 8. Coil A bottom end only + coil B out of phase 9. Coil B bottom end only + coil A in phase 10. Coil B bottom end only + coil A out of phase Until the next time, I wish you all the best, Ken Fischer. << back to Kens column |