how much output does an amplifier furnish to the subwoofer output

[computernewby]

my amp has a subwoofer output of about 50 mv peak to peak as read on a scope. Is that enough to power a powered subwoofer or is my amp bad?

 

[Karadjgne]

If it's a pre-amp output (line out) then yes it should be fine. That's only a signal output. Power for the amplifier is separate

 

[americanaudiophile]

Normal line level output would be max of 2v.
What signal were you using to take your measurement? Frequency should be about 50hz.
What was the subwoofer level set to in the receiver speaker set up menu?