What is the Variable Attenuation Control System (VACS)?
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.