To ensure maximum playback quality while completely isolating the phono preamplifier from the power grid, the Power Box RS Phono has been designed with battery power. The quality of the power supply is particularly crucial when the signals to be amplified are very small. A low-output MC cartridge typically has an output voltage of 0.2 mV. Such signals are highly sensitive to interference from the power grid. When the Power Box RS Phono is connected to and powered on with the Phono Box RS, there is only a battery connection to the Phono Box RS. Since the power supply and charging unit are physically separated, interference from the power grid cannot adversely affect the sound quality. If the battery charge falls below a certain level, further playback could damage the batteries. Therefore, the charging electronics are automatically activated, with the charging status indicated by LEDs on the front of the device. Playback continues, but the advantage of complete isolation from the power grid is not available during the charging period. Although this means that the greatest benefit is temporarily lost, the battery still acts as a filter, and the sound quality remains significantly better than with a standard power supply. Once the batteries are fully charged, the charging electronics are automatically disconnected, and the Phono Box RS is powered solely by the batteries.