About the amplification of acoustic stringed instruments

About the amplification of acoustic stringed instruments.

If you want to amplify an acoustic stringed instrument you need an amplification system, consisting of a transducer, a pre-amp and a power supply. The  transducer converts the instrument’s sound into an electric signal, the pre-amp makes this signal suitable to for an acoustic amplifier or P.A, while the power supply provides for the necessary energy.

Transducers- finding the holy grail

Universal sensor, electro-static pick-up, electro-dynamic pick-up, contact microphone, contact pick-up, electret condenser etc. etc. Manufacturers keep on claiming revolutionary new techniques that will improve the sound reproduction of acoustic instruments. But in the end it all boils down to 3 principles used to convert sound into an alternating current, each with their pro’s and con’s.

1* Microphone 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.

2* Contact pick-up Contact pick-up’s 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 pick-up’s (and especially the piëzo pick-up) have become the most popular transducer.

3* Magnetic pick-up Magnetic pick-up’s, as applied in electric guitars, register the vibrations of nickel or steel strings in a magnetic field. They have in their favour that they can be directly connected to an (electric guitar) amplifier, but in combination with a steelstring acoustic guitar the sound tends to be electric. This is why most people choose for the piëzo in the end.

Double system

An amplification system with two transducers  has the purpose of combining the good qualities of both. In the case of a combination of a microphone and a piëzo pick-up one should expect a better sound quality and less sensitivity for feedback as compared to the single transducers. Unfortunately this is not always the case. Another, less frequently used combination, is a piëzo- and a magnetic pick-up. This combination can work well for a solid sound with dynamics and expression.

Pre-amp and power supply

At this moment the great majority of amplified acoustic guitars are elektro-acoustic guitars with a piëzo pick-up and a built in pre-amp, powered by a 9V battery. For the player it is handy to have control over his sound but for authentic, valuable instruments this does’nt seem a good idea. In this case people rather use “instrument-friendly” solutions. This means no changes of the guitar with the exception of an output which replaces the strap button. The battery and the pre-amp stay inside of the instrument. This means first releasing string tension before changing a battery. People who don’t like this solution can choose for some form of phantom power where the power supply stays outside of the instrument.

Volume and audibility

Depending on playing style and acoustic circumstances one player will need more amplification than another. But it is not just the volume that decides audability.  Sound colour can make a big difference and decide if an amplified acoustics will be heard among a noisy rockband or in a crowded café. Read more about choosing the appropriate amplification.