The answer varies depending on what devices are connected.
CD players put out about 0dB and so should need no gain through the mixer.
On the other hand a none powered mic puts out a very small signal and needs plenty of gain through the mixer.
The less gain you use the less the noise will be amplified.
Thought i would reserect this thread,
Thanks for the replys folks, much appreciated, Been toying with the mixer over the few weeks and had it set with the master volume halfway and my amp at 50% and it sounds well, I always run my sliders at full and trim the gain to suit.
Anyway just thought i would post my outcome
You need to think about the gain stages in the signal path. There are often at least 4:-
pre-amp on mixer (trim)
channel strip on mixer
master volume on mixer
amp volume.
The thing to remember is that if you add gain to the signal you also add gain to the background noise, but if you reduce the gain to the signal within the mixer the background noise level stays the same. For this reason you should start with the trim as hot as possible without clipping. This way the pre-amp is delivering close to 0db (the point where the clip light comes on) and the noise floor of the equipment is prob down at say -70db. In an ideal world you want to keep the difference between the signal and the noise as great as possible, so have the channel strip higher than the master volume, and use the amp itself to regulate the main volume for the room.
Try it. adjust your rig to get the same volume in two different ways by first running the gains low to high, i.e. trim low, channel strip a bit higher - say -30db, master volume a bit higher - perhaps -15db and the amp pushed high to work from a weak signal. Then try it high to low, with the trim high - just not clipping, channel strip at say -3db and master volume at say -3db to -6db.The amp will be running lighter at the same volume as the first setup working from the hotter signal from the mixer. In both set-ups the overall volume will be the same, but the background noise should be much lower in the second set-up.
Its easy to demonstrate the impact of noise if you plug the mixer output into a PC line input and open it up as a record input in some recording software that has VU meters (e.g. reaper). Play with the faders and watch how the noise floor changes.
Gofer, Roadie, Techie for www.rotodisco.co.uk
I work through 2 mixers and this is how I set things up.
All equipment is initially turned on with all volume levels set to zero (amp turned ON last and turned OFF first so I don't get any pops through the speakers when I turn the rest on or off), I then turn the amp to full volume, then the master volume on the DJ mixer is set to the top thicker marker line which is ¾ of the volume.
The gains on the DJ mixer are set to about 10 too, because I know the setting on this now I then set the channels on the DJ mixer to about 2 bars up which is just under ¼ volume.
I know with these settings that as a rule the led lights are just below amber and only hit amber at peak, so that's the DJ mixer basically set.
Because I use a desk mixer as an addition (more control of the mic and sound independently), I also have to set that up, so I set the master again to the ¾ mark and the input faders (I have 2 as plugged in on mono channels) are again set to roughly 2 bars.
I find that when I initially play the first track the volume is under what I want so I then take up the desk mixer input slider volumes to the desired volume.
From there on I just alter the DJ mixers input volumes if a particular track is recorded with slightly less volume.
Last edited by One Vision; 20-08-2008 at 11:37 AM.
i tend to keep my amps at about half which leavesa bit more room if you need a little more volument and then tend to control it with the mixer and bass enhancer when i'm using subs other than that i try not to ever let the mixer of amp run on clipping for any amount of time, just asking for a real amount of trouble especially if the amp clips out and you have to wait for it to reset. asking for all the boo's etc etc.
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