Resources - 70 Volt System Beginners - Parts Express Wattage is Easier. The wattage of any 70V power amplifier is always given by the manufacturer. Most are from 20W up to about 100W. The transformer on each of the speakers in the system will generally have four different wattage taps on the secondary, often ranging from ½ watt to as high at 30W or more.[PDF] SYSTEM DESIGN - Bogen Communications Inc 70V Paging Systems consist of: • A Centralized Amplifier which offers a variety of features to enhance voice and music reproduction as well as easy system expansion. • Speakers that connect with a simple 2-wire installation because the audio power is supplied from the central- ized amplifier.