In the world of 0dBFS being the absolute max... and somehow so easy to hit, this is something that interests me a lot.
Here's a situation I run in to a lot (and a way I fix it which I don't quite like):
My subs are on a matrix or aux. I want my subs to be "10 dB ish louder than my mains" (I don't mean literally 10 dB, I mean I want the customer to smile and that means running my subs as loud as possible with no regard for balance... that's not to say loud subs aren't fun)
I push my "subs" matrix up until the mixer output clips... but what's this?? The amp doesn't clip! Oh it's because I have a LPF on there at around 80 Hz. Shoot well that stinks now I turn the output of the processor up... but now my clipping doesn't line up anymore! What to do?
I put a LPF on my console. Then I have a LPF on my processor and console. Not good. But at lease I can push my subs harder.
What am I battling against? What might be the best option?
I actually posted a video realted to this a couple weeks ago:
https://www.youtube.com/watch?v=ycJfDYpkpMkMy approach would be to set the amps full up and adjust the needed gain via the DSP processing.
There are several ways to setup gain structure. The most common is to set for everything clipping at once. Not truly bad since if you see red, you know your at the end of the line. Not hard to tell if things are going bad either. The most proper way to set gain structure is probably to go for the most dynamic range by making it so that each piece of gear inline has outputs and inputs set to be more in sync with each other. You don't gain output, but you lower the noise floor and you get as much level as is needed. In theory, if done this way, the unit with the lowest output capability will be the determining factor for max level output. Most all units these days will output enough to clip just about any amp.
The good old where to set the amp gain knob at question. As mentioned, all the way up is pretty much standard practice these days. The beauty of the amplifiers gain knob is that it is not actually a gain knob at all; it's an attenuation knob. The amp is a fixed gain beast. What you put in will be output at some ratio higher than the input. While not ideal to clip the amplifier, the hope is that the system will get more than loud enough long before the amp clips anyway. If you need less output, it is best done by turning things down earlier in the chain. This is of course unless your amp has a lot of hiss and self noise when fully opened up. If you need a quieter system, you may need to attenuate the amps input a little to get the noise floor down. In most cases the hiss and self noise of the amps is negligible in comparison to other parts of the system. Just listen to the noise made when you have 16+ channels up in a quiet room. The mixer and channels self noise will outweigh the amps self noise considerably.
