Amp at full strength

pdadda

pdadda

Captain Sea Boots
I guess this is more of a live sound question, but it applies to amps as a whole. A reputable local sound man told me at a recent gig that you should always turn your amp all the way up and simply turn the main fader down at the board if you want a lower overall volume. Is this correct, or is this bad for the amp?
 
Was he the soundman for spinal tap? :D

Tube amps can sound better with the output tubes being driven hard - that may have been what he meant.
 
It's a headroom issue. If the amps are opened up, you won't have to push your mixer into the red to get the rated output.
Think of it like a master volume on a guitar amp where the power amps are the master and the mixer is the preamp.
And it's not bad for the amps at all. It's the way they're designed to be run.
 
There are many methods of setting up a live sound system. It comes down to personal choice, convenience, and the needs of the situation. I prefer to have my master faders at unity, and adjust other places, but to each his own.
 
MadMax said:
It's a headroom issue. If the amps are opened up, you won't have to push your mixer into the red to get the rated output.

And it's not bad for the amps at all. It's the way they're designed to be run.
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exactly. At the same time, you don't want to swamp the stage is blaring guitar amp, and have to crank the monitor mixes to get over it..
 
MadMax said:
And it's not bad for the amps at all. It's the way they're designed to be run.
Click to expand...

I don't know if I'd say that. If they were designed to run that way, there wouldn't be any controls. :)
 
Just to clarify, he was talking about the amp that powered the mains, not my guitar amp.
 
I think the original poster is talking about PA power amps, not guitar amps.

OOPS! pasted at the same time. Well then, yeah, run the amps wide open and adjust levels at the board/crossover/comp, wherever else you have gain controls.
 
I would agree with that as long as the amp isn't so powerful that you can barely move the master fader before heads start popping.
 
pdadda said:
I guess this is more of a live sound question, but it applies to amps as a whole. A reputable local sound man told me at a recent gig that you should always turn your amp all the way up and simply turn the main fader down at the board if you want a lower overall volume. Is this correct, or is this bad for the amp?
Click to expand...
Yes, I've worked for a few pro sound companies and we always ran every power amp on 10. (100%) We always control the volume at the mixers, both FOH and monitor mixers. This is standard practice for most (if not all) large sound companies.

Even when set to 10, if the mixer sends signal at say, 30%, then the amps will amplify by a factor of 30%. So, what's the problem?

Go ask that question here. They will tell you the same thing.

RD
 
yup, keeps the overdrive out of it
you also have to peak the preamps first though, it's really not that simple, well it is once you "get it"
 
you wont do it that way if you understand gain staging....the idea is to get each piece in the chain operating in it's own optimum area.... remember that each peice has it's own noise floor... and it doesnt change it's always there... so lets say we have a console the output is at say 50db and the noise is for the sake of arguement 40db down at 10db.... with me so far??? now we want to amplify the signal to say 90dbso adding 40 db of gain to the signal also adds 40 db of gain to the noise!!! so the noise is now at 50db.... if on the otherhand we could have bossted the signal at the console say 20 db more... then when we amplified it 20 db the noise would now be at 30db not 50....

now the #'s i used were not typical... but pulled outta thin air for an example... so dont slam me for the #'s... the concept still holds true....

so in MOST cases your better off running the output of a stage hotter and then padding it down at the next... as opposed to running something wide open and padding down the previous stage.... :cool:
 
All of my amp racks run at wide open almost all the time. However, I also have a crossover in line that I can use to trim levels so that the mixer can still run around the unity area. It is a bad idea to just blindly keep the amps wide open if you get to -35 on your mixer and things are loud enough. What would happen if you had a live mix at a good volume using -35 on your master fader? All may be just fine until somone pushes the master fader up and then you will be out a bunch of speakers and probably a client.
 
Working soundmen learn early on that the noise floor is not that high on the list of concerns. Most soundmen learn their craft in noisy smoke filled barrooms with drunks talking and shouting, glasses and ashtrays clanking, air conditioners running, guitar amps buzzing, and heels on the dance floor shuffling. The last damn thing anyone will notice is a little background hiss. (True though, when you get into bigger systems that noise becomes more apparent.) They also learn about high dynamic spikes from unexpected things like hard snare rimshots or bass string popping routines. Those spikes can lead to blown speakers unless you have lots of clean amp overhead. We don't want to restrict it too much with compression either because those dynamic blasts help give live music its excitement.

I believe if you turn those amps down, you are restricting or eliminating that reserve power zone, (that vital buffer zone.)

RD
 
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