This pickup is an 'Under-saddle pickup' and runs on “piezo-electric” technology…which uses a strip of crystals placed under the bridge saddle of the guitar to sense pressure created by the vibrating strings. Magnetic soundhole pickups – ONLY hears the strings at the sound hole, and none of the body. The transducer or Piezo hears the whole vibrations caught at the end of the strings not just in the middle. Under-saddle pickups have a brighter, thinner sound, with a stronger attack. Compared to magnetic pickups, these “piezo-type” pickups generate a comparatively small voltage and have a weak signal so require a preamp to boost the original signal. Furthermore they need a pre-amp to get the signal to a PA system unless you use an acoustic amp.
There are two types of Piezo / transducers. The stick on the under side of the soundboard and the Under saddle (inside the bridge plate slot) like this one. The Piezo has an excessively large dynamic range.
The stick on the under side of the soundboard has 1/2 pressure = 1/4 volume – more prone to feedback
The Under the saddle has 2x pressure (because it gets sound from both sides of the transducer) = 4x volume – will feedback but is less affected
This transducer requires Professional installation. Both the floor of the saddle slot and the base of the saddle must be flat to give even and good sound.
Alun Ashworth-Jones known as Al Jones moved to Cornwall. He gradually built up his own business making pick-ups for acoustic instruments in the 1990's - those Ashworth transducers have been used by the stars, Terry Martin, Mark Knopfler, and Van Morrison. His pickups became really successful because they sounded so good. He told me that in the early days he moaned about how bad the amped sound was in a pub with friends. One