Hi, My avs2000 fluctuates +/- 2 to 3 tenths of a volt on the output when the line voltage fluctuates -8 to +3 volts. The noises the unit makes are the servo switches changing taps on the transformer to stabilize the output voltage. The third display on mine is an amp-meter to show current draw of the connected load. I felt the avs200 made a noticeable difference in my system. Hope this helps.
Best Regards,
Greg.
Best Regards,
Greg.