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[Bob Burke]

the setting on the volume knob on the amp has no affect on clipping. It is there to match the input of the amp with the output of whatever is driving the amp. The amp itself is at 100% at all times. If you turn the knob down on the amp, but turn the output up from the mixer, the music you hear remains the same. Just like if you were to turn your guitar amp down at the amp, but then turn the volume up on one of your pedals, the music is just as loud as before. A 1000 watt amps is a 1000 watt amp with the volume knob at 50% or at 100%. An amp can actually put out considerably more power than it's rating if you send it a hot enough signal(overdrive it), and that is where the danger is in tearing up speakers.

David, I think it's starting to get into my thick head! I know it must be tedious for you guys answering these stupid questions, but this info is solid gold to me.

  This is from the QSC manual - I didn't understand it before:

"The amplifier Gain control
should be in the upper half of its range to prevent input overload."

  So I should be running my amp at 3 or 4 O'clock instead of 12? Or should I run it wide open and just keep my mixer from clipping? Which would result in the best sound?

Thanks.

[David Parker]

David, I think it's starting to get into my thick head! I know it must be tedious for you guys answering these stupid questions, but this info is solid gold to me.

  This is from the QSC manual - I didn't understand it before:

"The amplifier Gain control
should be in the upper half of its range to prevent input overload."

  So I should be running my amp at 3 or 4 O'clock instead of 12? Or should I run it wide open and just keep my mixer from clipping? Which would result in the best sound?

Thanks.

it's all a balancing act. The volume knob on the amp is to help balance everything. It's kinda like the problem that can happen on a mixer. You keep turning up separate channels until the overall level is too high, so then you back down the master. Before long all the channels are all the way up, and the master is all the way down, and all you hear is distortion. If anything in your signal chain is way high or way low, you might need to do some leveling. There is no correct setting for the volume control on the amp. If there was a correct setting, it would come set that way and there would be no knob. At any stage of your signal chain there is the possibility to overdrive and cause distortion. There are articles on balancing gain structure, but it isn't rocket science. An old rule of thumb was to have no channel fader higher than the master fader. Not a hard fast rule, but something to consider if anything anywhere is way high or way low.

[Tim McCulloch]

Thanks Tim. So, if my QSC is set at 12 O'clock (-10) it is putting out 1/2 of the rated power, regardless of the mixer output?

No.  It takes 10dB MORE signal to reach the same output voltage than if you had it wide open.

The knob DOES NOT CHANGE the amount of gain the amp has available (output voltage potential).

[Bob Burke]

Roger that. Thanks.

[Art Welter]

Roger that. Thanks.

Post #13 may make more sense to you now, the input knobs attenuate by -10 dB (takes 10 times the input level to reach amp full power) at "noon", around 4 pm is -3 dB, where it takes double the input power to reach full output.

If you look at your console, you will see that it does not take much fader movement to equal those level changes. Start listening to the level changes as you move a fader or attenuator to get an idea of what is happening in terms of power.
Have Fun!

[Bob Burke]

Thanks Art and everyone who responded. I just had to unlearn some things I "knew".

 I'm getting much better sound now, and I owe it all to you guys.

[Rob Spence]

One feature of running the amp with the attenuators wide open is that someone cannot bump them up. Worse case is bumping down.


Sent from my iPad using Tapatalk HD

[Bob Burke]

One feature of running the amp with the attenuators wide open is that someone cannot bump them up. Worse case is bumping down.


Sent from my iPad using Tapatalk HD

Rob,

  I understand about bumping up, but I don't understand how bumping down is "worse".

[Steve M Smith]

Because things will get quieter!


Steve.

[Chris Hindle]

Rob,
  I understand about bumping up, but I don't understand how bumping down is "worse".

He ment that if it get's "bumped down", the worse that can happen is it get's quiet.
Getting "bumped up" usually costs drivers.

[ProSoundWeb Community]