Amplifier hum - normal?

Is it normal for amps to emit a slight humming noise from the transformer when turned on?

I never noticed it in my old integrated that I lived with for over 10 years, but that was lower power. Now I've gone from 50wpc to 120wpc... don't know if that makes a difference here though.

I mean, it's not nearly enough to bother me or even really be audible past 3 feet away... but I am curious if this is typical for amplifiers to do this.