[pjchappy]

I have a QSC RMX850 amp I use to power my sub.

It only has gain controls on the front.  As I increase the gain, what is the difference between that and increasing the volume. . .

I understand gain is active and volume is passive; however, since this thing only has gain controls on it, what is the difference in simple terms.  

When I use this in conjunction w/ a pre-amp, what are some tips on matching it so the amp basically would act as a separate amp w/o its own gain controls?--I will be doing this once I get my XR45.  Or, should I use this w/o a preamp and just use its gain controls w/ the amp being fed unamplified analog signals from a CD player.

p

[JohnR]

Gain is the ratio of the output voltage to the input voltage. If the gain is less than one, then it might also be referred to as attenuation, and that is exactly what a potentiometer or switched resistive attenuator does.

Volume is the amount of acoustic energy reaching your ear. The source voltage, times the gain, times the speaker sensitivity, plus room effects, gives you the volume. In this case though, "volume" is short for "volume control," which is the same as gain control.

For using the QSC with a preamp, turn the gain controls all the way up.

HTH

[nathanm]

The gain trims also can be used to affect the apparent resolution of your preamp volume control.  Turning the QSC's gain down will give you more room to move the volume knob up and down.  Depending on the sensitivity of your speakers you could have a lot of room to play with there.

As a sub amp you'll want to use the gains to match up the loudness of the mains with the sub.  Hopefully you'll have a bit of headroom, but it depends.