The ST-85 from VTL belongs to the family of Tube stereophonic power amplifiers. The power amplifier is a device that accepts the signal from the respective source (cd/dvd player, turntable, radio, etc.), after it has passed through a pre-amplifier. It then amplifies it properly and transfers it to the speakers for playback. For this reason, power amplifiers usually only have the on/off button. In this case, it operates with tubes, so it has a warmer and more natural sound.