Mixing desk into amp = extra volume?

[@war]

Hi all

I came across an interesting phenomenon the other evening on a gig and wondered if anyone could explain it to me.

I was sharing my amp (Hartke HM5210c) with a double bass player for the night, and because he mics his bass we put a small Mackie mixer into the 'active' input on my amp and both plugged into the mixer so when either of us wasn't playing we could just mute and save the effort of plugging in and out all the time.

Anyway, what I discovered was that before we plugged the mixer in I had the amp volume on around 6/10 to get the balance on stage right, but when we introduced the mixer we got the same volume at 3/10 (at unity gain and 0dB on the mixers controls and no eq boost).

Is this because even at unity the mixer's preamp has more gain than my bass going straight into the amp?

As I understand 'unity gain' that means that the gain of the bass should be unaffected by the mixer...

Thanks for reading! Hope someone can answer this!

[aledeville]

The line mixer works on line level. This is higher than the instrument level.

[billfitzmaurice]

Originally Posted by @war

Is this because even at unity the mixer's preamp has more gain than my bass going straight into the amp?

It's because it wasn't unity gain.

[dincz]

and your cable has unity gain