due to clipping. A less linear preamp (like a single-FET amplifier) might be preferable due to softer clipping characteristics. Such an amplifier starts to distort sooner, which makes the distortion less "buzzy" and less audible than a more linear, but less forgiving op-amp. However, at least one study indicates that most people cannot tell the difference between FET and op-amp circuits in blind listening comparisons of electric instrument preamps, which correlates with results of formal studies of other types of audio devices. Sometimes, piezoelectric pickups are used in conjunction with magnetic types to give a wider range of available sounds. For early pickup devices using the piezoelectric effect, see phonograph. Other transducers Some pickup products are installed and used similarly to piezoelectric pickups, but use different underlying technology, for instance electret or condenser microphone technology. Double systems pickups There are basically four principles used to convert sound into an alternating current, each with their pros and cons: A microphone registers the vibrations of the air caused by the instrument. In general this technique guarantees a good sound quality, but with two limitations: feedback and crosstalk. Contact pickups register the vibrations of the instrument itself. They have the advantage of producing little feedback and no crosstalk at all. In spite of their lesser sound quality and thanks to their low price, contact pickups (and especially the piezoelectric pickup) have become the most popular transducer. Magnetic pickups. Magnetic pickups, as applied in electric guitars, register the vibrations of nickel or steel strings in a magnetic field. They have the advantage that they can be connected directly to an (electric guitar) amplifier, but in combination with a steel-string acoustic guitar the sound tends to be electric. This is why acoustic guitarists typically choose a piezoelectric pickup, built in microphone, or both. Electrostatic pickups. Another way is to use the changing capacitance between the string and a pickup plate. These electronic pickups produce much higher dynamics than conventional pickups, so the difference between a soft and a loud pick strike is more pronounced than with other types of pickups. An amplification system with two transducers combines the qualities of both. A combination of a microphone and a piezoelectric pickup typically produces better sound quality and less sensitivity to feedback, as compared to single transducers. However, this is not always the case. A less frequently used combination is a piezoelectric and a magnetic pickup. This