Documentation on Amplifiers

I need to provide someone with a document explaining why amplifiers are supposed to be run wide open.

I'm sure this is right up Steve's alley but if anyone else has the answer or link I greatly appreciate the info.

Man...I'm all ears for this one. I currently run a driverack with my high gain way down and my QSC still needs to only be turned up halfway....

I like halfway, but I know theoretically its wrong. I just don't logistically know why....

The main reason for running amps wide open is headroom headroom and headroom.

But there are also reasons for running at different levels as well

Noise, if you have a noisy system or dirty power at a venue you can reduce the gain on the amps to reduce some of this. Not that it eliminates the noise just that it is less noticeable.

Gain Balance,

Some boards may reach unity gain at 0 DB another may reach it at, +4 DB and so on. Amps may be set to reach unity at .75 volts or 1.0 volts or 1.75 volts even 2.25 volts. Using multipule amps with differing input voltage levels this can be leveled by adjusting the gain on the amps so that each go hot at the same time and in concert with the output level on the board. This also applies for other inline gear as well such as EQ's, Drive racks ect.

Man...I'm all ears for this one. I currently run a driverack with my high gain way down and my QSC still needs to only be turned up halfway....

I like halfway, but I know theoretically its wrong. I just don't logistically know why....


JT,

There may be a setting on your mixer to accomadte this, may be a switch that says 0 DB - -4DB or even -30 DB. My Rane mixers have an adjustable range output, you may want to look around on your mixer for such an adjustment or switch.

JT,

There is also a switch on the back of your driverack that adds 4db or takes away 10 db to the input signal.

I have mine set to the +4db.

I also have QSC amps with JBL speakers and depending on the room, the gains on the amps usually stick around 12 (don't know the db off the top of my head).

At least for me running the AMP gains wide open has never made a lot of sense, so I would like to know why too.

I have always been told that GAIN BALANCE/STRUCTURE is what you are looking for.

Balance between you mic/line level inputs, with your master volume, and you amp gains.

Seems to make sense to me ...

Jamie
Houserockers DJ

Jamie,

The why once again is headroom, less signal input for reasonable amount of gain.

By reducing the gain on the amps you will run out of headroom on your mixer much sooner for the same amount of DB level. Of course anytime you are running at or near max on any inline piece of gear you are introducing distortion to the output.

This may have been said, just in a different way, But I know if you turn the speaker amp (or amp for the passive guys) you can keep the mixer and the rest of the equipment much lower, This keeps the "Noise" Down and gets rid of a lot of noise... I know some mixer put out to much gain, and it creates noise, but thats what I have been told...

pure geniuses I tell ya....pure geniuses.

Thanks,

This is why I have always incorporated a separate Pre-Amplifier unit to my system. It processes the signal coming out of my mixer and gives me a pure signal to my EQ. One more piece of gear but then again, thats just me.

This is why I have always incorporated a separate Pre-Amplifier unit to my system. It processes the signal coming out of my mixer and gives me a pure signal to my EQ. One more piece of gear but then again, thats just me.

Your mixer is a pre-amp You are pre-amping a pre-amp signal!

Your mixer is a pre-amp You are pre-amping a pre-amp signal!

I know! But it still sounds so good not to mention the extra headroom!