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Best way to run mixer and amp outputs?

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(@tshooter91)
New Member
Joined: 21 years ago
Posts: 2
Topic starter  

Hello all.  I'm in a situation with a church where they have two 600W speakers and a Mackie 1400 amp for their sanctuary which is only about 60ft. deep.  I'm told they bought this equipement thinking it would be useful at times for other venues.

The problem is if I set up the trim/gain on the mixer where it should be, then I either have to have the master sliders way down, or the amp gain has to be way down to keep from blowing everyone out.

Somewhere I got the idea that running the gain on an amp that low can actually hurt it over time, or maybe it was that if the speakers get a low power signal it hurts them. (?)

So what I'd like to know:  Is there any truth to that?  Is there OBJECTIVE (logical) reasons for running devices at certain output levels?

I work in computers and I understand electronics very well.  I read the article about running a mixing board.  The information about running the preamp on the board as high as you can to prevent electronic noise from the board makes logical sense to me.  Is the amp going to have the same problem?

I've talked to alot of people and everyone has their own way of wanting to run things, but these electronics have to be designed for a "best" way of operation.  So what is it?

I hope what I'm asking is clear, I guess I'm asking mostly about how an amp is designed to run.

I also know from electronics that I could attenuate the signal out of the board (using resistors and such) so that the signal sent to the amp would be weaker.  Would this be a better idea?


   
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(@danlasley)
Noble Member
Joined: 16 years ago
Posts: 2118
 

The input on the amplifier is just a potentiometer.  The amp itself is fixed gain (and fixed noise).  So yes, the best answer is to turn down the input level on the amplifier.

One alternative is if you have a system EQ between the mixer and amp, turn down the output level from the EQ.

-Laz


   
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(@wes-inman)
Illustrious Member
Joined: 21 years ago
Posts: 5582
 

Hi tshooter91

I own my own PA, but I'm not an expert by any means. However, I like to hang out at Scott's PA Tutorial board. There are some real experts on there including Bob Lee of QSC amplifiers. These guys will be able to answer any questions you have.

http://disc.server.com/Indices/22769.html

If you know something better than Rock and Roll, I'd like to hear it - Jerry Lee Lewis


   
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(@tshooter91)
New Member
Joined: 21 years ago
Posts: 2
Topic starter  

Thanks for the responses, guys.  From the responses here and on the PA System Tutorial Forum, I have decided that we should be setting the amp lower and running a stronger signal out of the mixing board.

It makes sense that sending a weak signal from the board is just asking for noise and hiss.

We also do have an eq that isn't installed yet, so I may use that to attenuate the signal to the amps a little, but I'll have to see if that causes any noise or hiss problems.


   
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(@forrok_star)
Noble Member
Joined: 21 years ago
Posts: 2337
 

By using the correct signal levels throughout the system will minimize the humming, noise and distortion. Gain controls in PA power amplifier be typically set between half-way and fully up. Amplifier gain controls set at a lower position require input signals to be set to a higher level to obtain suitable power levels. Particularly with unbalanced input lines, the hotter your signal is at the input of an amplifier, the more noise propogation you will have into your amplifiers.

If you have set the amplifier gain set too low your system may become such that you will reach the maximum gain travel of a fader, at your source device, before obtaining expected power within your amplifiers.  Use the mixer out faders to control the sound level not the power amps.

Joe


   
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