Variable Attenuation Control System (VACS) provides automatic control of frequency and levels to minimize distortion.
Even if you turn the volume up to a high level, the VACS feature will cause you to hear minimal distortion. This is done automatically by a circuit that was exclusively designed by Sony to maintain bass and midrange audio signals in the best quality even in high volume listening.
NOTE: VACS is an automatic feature on the device to enhance the audio playback. The feature cannot be turned on or off.