The AN-S3 is a step-up transformer designed to be used with a moving coil (MC) cartridge and a phono preamp that has a moving magnet (MM) input stage. The purpose of the AN-S3 is to provide the necessary gain and impedance matching to allow a low-output MC cartridge to be connected to a standard MM phono preamp. 

The AN-S3 uses internal transformers that are exclusively manufactured by Audio Note (UK) with the best core materials and winding technology available. The transformers are made with 0.1 mm laminated mumetal 250 and 99.99% pure Copper wire.

Matching the impedance of the MC Cartridge to the input impedance of the AN-S3 is important for achieving the best possible sound quality. For this reason the AN-S3 is available in six versions ranging from low impedance, to medium impedance, to high impedance.