Handcrafted basses

PICKUPS

The heart of guitar-electronics is a pickup. These come in five flavours:

1. Single-coil pickups. An awful lot of thin, isolated copper-wire wound around a magnet. When the magnetic field is disturbed (by a steel string for instance), a small electric current is generated with the frequency of the string. This small current can be amplified and...voila, the basics of an electric guitar!
Differences in sound can be obtained by varying the number of windings, thickness of the wire, material and shape of the magnet. If you want to make a pickup yourself: be prepared to wrap a hair-thin copperwire 4000 to 12000 times around a magnet. This type of pickup can be found on a.o. the Stratocaster, Telecaster, Jazz Bass. The single-coil has a clear, bright sound, with lots of precence in the higher frequency range. Well known "single-coil" players: Eric Clapton, Jimi Hendrix.

2. Humbuckers. A single-coil pickup is relatively sensitive for electro-smog, for instance nearby power-cables, transmitters, bad earth in amplifiers etc. This can cause irritating humming and hissing sounds when amplified. The solution for this is to place two single-coils next to each other, with the copperwire wound in opposite directions. The "humming" dissapears, and that's where the name "humbucker" comes from.
This is why humbuckers were invented, but the reason a guitarplayer wants a humbucker or not has nothing to do with this. The humbucker has a different sound from the single-coil pickup. It sounds warmer, fuller and usually a lot louder then a single-coil. The Les Paul, Gibson SG a.o. are fitted with these. You don't need a lot of overdrive to obtain the fat, distorted sound of Slash (Guns ‘n Roses), or Carlos Santana.
Maybe you've noticed I only mentioned Gibson and Fender Guitars here: well, they were the pioneers. The early models go back to the 40's and 50's, and there really wasn't much choice until the 70's. Japanese manufacturers started making cheap copies of Fenders and Gibsons and later presented improved models of new design. Today these guitars are among the best available, and companies like Ibanez, Kawai, Yamaha absolutly make fine instruments.
The pickups also got better over the years and the characteristics of single-coils and humbucker became less distinctive. Stronger magnets made the single-coils louder and hybrid models are now available, like a dual-coil pickup in a single-coil housing.

3. Active pickups. Another way of reducing unwanted noise is to lower the impendance of the coil. In other words: using less copperwire. This results in a low output signal. Before integrated circuits were available this was a major problem: the signal coming from the guitar was just too weak. It could be amplified of course, but this resulted in having the noise back again. With the availability of energy efficient, low noise preamps-chips it now is an option to build a preamp in the guitar. This is what active pickups are about. There is not much distinction to the sound of an active pickup. You can get almost any sound you want, due to the build-in electronics. Parametric equalizers and stuff like that are not unusual.


4. Piezo pickups. You can compare these with the old-fashion telephone-microphones. Though in use mostly for accoustic guitars, These are available for solid body guitars and basses as well (often incorporated in the bridge). It picks up vibrations in the air, or, when sticked on the guitar, from the wood. Very sensitive, goes easily in feedback mode. PEEEEEEEEEP!

5. The latest development concerning pickups is the optical pickup. It works with a small laserbeam and a light sensor, just like an elevator door. The strings vibrates in the lightbeam, and the sensor picks up the differences in brightness. This is converted into an audio signal. This pickup is part of the bridge. The advantages are obvious: no feedback, and no unwanted noises. This pickup is built by Lightwave Systems. Check out their site if you want to know more.

LightWave bass with optical pickup


Make a pickup yourself

Yes, that is also possible. There is a lot to be said about this subject, about what kind of magnets to use, about how thick the wire should be, and about the number of windings. And again this is for the biggest part a matter of taste. More windings of thinner wire mean more low frequencies. If you want to know more about this subject, go to the LINKS page, there is a link about winding pickups.

Anyway, When I built the MB1J, I had to solder a new wire to the pickup (an old JazzBass style pickup), and guess what: the winding broke at the inner side of the coil. So I wasn't able to reconnect the wire. Throw the pickup away and buy a new one? No. I decided to try the winding myself, it was worth to try it, since the thin, isolated copperwire is not very expensive (about 6 EURO's for 1500 metres of 0,05mm wire). I found out that a vintage '67 Jazzbass pickup had 10,000 windings. That's the one I was going to try. I cut the old copperwire off the pickup. The thing left is called a "bobbin", a bunch of magnets, held together with 2 pieces of some kind of cardboard (see picture).

I put some isolating tape around the magnets, and I made a little machine for winding the pickup (see picture below). Don't laugh, I made it from Lego, wich I borrowed from the kids. Works fine. After 2,5 hours of turning the machine, all the copperwire was on the bobbin.

When the magnetic field of a pickup is disturbed, a small electric current is generated (the sound), and is sent to the amplifier. Another way of generating current is to move the windings. This is what happens when a pickup is "microphonic". The windings are a bit loose, espacially on a hand-wound pickup, causing the pickup to act as a microphone. You can hear it clearly when you tap on the pickup with your finger. I even had a pickup once, you could shout "HELLO" in it, and hear it back from the guitaramp! The microphonic effect also causes feedback (PEEEEP!!, remember?).

To reduce or even cancel out this effect, the pickup has to be "potted". This is dipping the coil in hot wax. You melt a couple of waxine-candles till you have a clear fluid. Put the coil in, and wait untill no more bubbles come out of it. The hot wax penetrates the coil and solidifies when you get the coil out and let it dry. See picture below how the potting is done.

As you can see the bowl of wax is placed in water before it is heated. There are two reasons. 1: safety. Wax is flammable, you have to watch out with open fire. 2: The water functions as a buffer for high temperature. The wax shouldn't be too hot or else it might damage the isolation of the copperwire.

This is the one I, it sounds great. When I finished the potting, I put some tape around the coil, and some aluminumfoil for shielding. After that some more tape to keep everything in place. Use shielded wires to connect the pickup to the volume and tone controls. As said before, the single coil pickups pick up more interference then a humbucker, so you have to take the shielding seriously.


Next page: The next thing is to connect the pickup to the electronics. How? Look at the ELECTRONICS page.