Setting Amplifier Gain

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Bassmaster84

New DJ
Jul 23, 2008
58
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57
www.hotspotsdj.com
Our system is pretty basic: CD players & PC - mixer - amp - (4) speakers (R & L in parallel). I've always been told to set mixer main output faders to 0. Then adjust the other faders to avoid clipping on the VU meter.

My question is where do I set the L & R gains on the amplifier? Turn them up until amp clips and then back off?
 
For all practical purposes, amp attenuators should be set to no attenuation (wide open). This gives the user the maximum headroom that the amp can offer.

If you've got your front end gain structure adjusted correctly, attenuating an amp shouldn't be necessary.

Thoughts?
 
All out ;)
 
Wide open on the amp.

If you start clipping the amp, you need a bigger one.

I was taught to run channels on mixer always higher than master output of the mixer. The master is just that, it controls the system volume. If the master is high enough to clip the amp you will need to bring it down.
 
I set the mixer level up until it reaches a "0" reading on the PFL meter. Then I adjust other components and amps accordingly. I find that if I have the amps wide open, I usually never get a reading on the PFL meter, and the little hums that come and go depending on my setup and the venue power are all amplified a little.
 
This has been debated to death. I set my system up this way. With the amp off, I set the gains on each piece of gear so that everything 'clips' at the same time. This includes mixer, eq, compresser/limiter, etc. I then turn the amp on and raise the levels up until I get the maximum amout of volume I think I will need for the night. I use the master fader on my mixer to then turn it down to the volume level needed for the start of the evening. If I need more volume later, I turn up the amp. This was mentioned on a previous thread from a QSC rep. as the way to do it. Others did not agree.
 
Back when I ran amps, I would usually set them at about 75-80%, if I ever needed more sound I got another amp and more speakers. Never remember ever seeing a clipping light, and never had a problem with any amp going thermal on me.
 
I really appreciate everyone's advice. I even recall reading (or hearing) about using some kind of 0 dB reference tone to set-up a system.

Anyone tried this?

Well typically white or pink noise is used. Pink noise is especially because it includes sound from each frequency. The best way to set up your system is to turn the amps off, set your mixer and other component gains till they reach "0 unity" with music playing. Then adjust your amps for volume.
 
Pink noise is also helpful for finding horn dispersion. You can audibly hear with pink noise when the SPL drops off from the horns when you move around a room.

Not a big deal with small systems usually, but bigger line array setups it becomes increasingly important.
 
I turn my amp up to 11!
most amps only go up to 10...
but look: 'dis one goes to 11
one more
 
Okay so how would one go about setting gain on an all in one system like the Yorkville EX-1. It has a volume setting on the back of the sub for the sub and each of the two tops. I would assume this is the same kind of set up on a Matrix 1000 system or for that matter JT's new Dynacords. I have always just run the gain settings on the back of the sub at 12:00 and the gains on my mixer at the same place. I run the master volume on the mixer at the 0 and then adjust each individual channel as needed. I can then max out each individual channel and it just gets into the yellow with the odd peak touching the red. I know to back it off when I get into the yellow and I try to keep it out of the red zone but some peaks get up there.

young...
 
I turn my amp up to 11!
most amps only go up to 10...
but look: 'dis one goes to 11
one more
DAMN, I was going to say that.


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Set them according to your speaker... if your running 1000W amp and only 300W speakers, your gunna kill the speakers...


This isn't always true.

You kill speakers more often with less, or Not Enough power
I run my sub cabs at 1.5-2x the rms power
 
Set them according to your speaker... if you're running 1000W amp and only 300W speakers, your gunna kill the speakers...
The question should be what speakers do you have and what amp are you running...
There is a measure of truth to this. While I do not advocate this much amp headroom, the attenuators can be backed off to avoid overpowering the 300 watt boxes.

Professional power amps don't have volume controls They have attenuators. There is a difference. Attenuators can limit how much power is permitted to be dissipated. Also, pro amps offer switchable limiting. Live sound typically uses no amp limiting but for our purposes, it's adviseable to have it switched on.

As to the powered or active cabinet scenario, I can't honestly say. I've never owned nor loaded an active PA system. I do know that active systems rarely offer any amp headroom. What you've got in that cabinet is all you've got.
 
You kill speakers more often with less, or Not Enough power
I run my sub cabs at 1.5-2x the rms power
Wow... Im going to pretend the first line does not exist... Sorry, but wow... NO...
As for the second line, thats why there is Peak Power... RMS is Constant... Peak is the high points you hit... Dont want to go too far past those...
You can run higher than your RMS, but your just going to distort the sound... over heat the coil, damage the insulation... story only goes down hill after this...