The incredible guitar virtuosity from the likes of Joe Satriani, Eric Johnson and Stanley Jordan all rely on their string-picking proficiency being registered by the instrument's pickups. These vibrations are then transformed into electrical signals and sent off to an amplifier for our listening pleasure. Using such a setup, string movement can only be read on one axis, the horizontal. The 3Dxy pickup system reads each string twice, on both the horizontal and the vertical and is said to result in a rich, surround sound effect called natural stereo.

The 3Dxy system has been developed by Spain's Just L Pauls. Although not a guitarist himself, he is a musician and plays both saxophone and flute. He told Gizmag that after studying electronic engineering at La Salle Bonanova in Barcelona, he began searching for a rich, natural tone and started experimenting with magnetic coils.

Four months ago, he came up with the idea of having a pickup read "the movement of the string not only up & down but also left and right. That gives two different signals, but complementary, because both coils read the same point of the string. The resulting signals, one to the left stereo channel and the other to the right, makes the surround sound or what we call natural stereo."

Before taking a look at Pauls' 3Dxy system, a little bit about passive pickups as we've come to know them today. Although the design has changed significantly over the years, a pickup is basically a magnet with very thin wire wound around it many thousands of times. Magnetic poles sit underneath each string and as the string vibrates, the magnetic field is disturbed and an alternating current is induced through the wire coil. The resulting signal is sent through the volume and tone potentiometers and off to be considerably amplified via the instrument's output jack. Of course, if you're anything like me, a lot of distortion or other effects get thrown into the mix too.

A bit basic perhaps, but the important point to note here is that being positioned underneath the strings, the pickup only registers string vibration on one axis. A 3Dxy pickup, on the other hand, detects string vibration on two axes. Each string on a guitar using this system has two mini-coil pickup poles pointing at it. These poles are set at a 90 degree angle to each other down the left and right of the pickup so that string movement on both the horizontal and vertical axes is registered.

All of the left mini-coils in a series produce a left channel signal and all those on the right, well you can probably work out the rest. The two resulting ground wires are combined and a standard stereo plug configuration results – one ground, one left and one right.

The 3Dxy pickup is said to be of a similar shape and size to standard mono pickups, so there should be no need for messy internal body reshaping during installation. That said, in order to enjoy the "natural surround sound sensation" that the system is said to offer, it will be necessary to turn mono output into stereo... and you'd then need a stereo amplifier, of course.

Realizing that many guitarists don't use such an amplifier, Pauls tweaked the design to produce natural 3Dxy mono. This is achieved by combining the left and right stereo channels – the stereo surround sound effect is sacrificed but he says that the modification still delivers a more natural and rich tone than that offered by other, traditionally-wired passive mono pickups.

Other benefits of the 3Dxy system are reported to include a low 300 ohm impedance and a longer note decay. Each 3Dxy pickup is made to order and prices start at EUR120 (about US$152) for an electric bass and EUR180 (about US$229) for an electric guitar. Pickups for double bass and violin are currently being developed.