Four-channel power amplifier with built in battery charger for emergency power supply of VARIODYN D1 Comprio. 4XD125B has 4 independent amplifier channels each with 125 W in class D direct drive technology. Due to the fact that all amplifier channels are completely independent from each other, it is possible to use one channel for back up. This could be for the other 3 channels or alternatively for other amplifier channels of other amplifiers with the same or lower output power (only 4XDxxxB models). The amplifier may be used with the VARIODYN D1 Comprio, as well as a DOM. It is also possible to use the amplifier with a separate PSU, in this case the internal battery charger must be disabled.