Ok I have a Jebao DC 12000 used that I have running on my 120. I think it has 10 circles on the power setting or ten leds. So if I run it on 8 I hear nothing. On ten I hear a faint whine. Like if you heard a vacuum cleaner in an office building but could just barely hear it at all. On the 9th setting the whine is more faint. Seems to come and go. But on 10 I can hear it and on 8 I cannot. Is it normal to hear any whine on a Jebao? I had a hard time getting this to work I had to soak it in vinegar.