I am a relative newbie to all of this so please forgive the basic questions:Let's say that I have one mic connected to a console and I set it's fader such that its level peaks at 0db (unity). If I also set my main faders to 0db, will the meters for the mains show a signal level of 0db? If, instead, I then have 10 inputs, all peaking at 0db, what will the main meters show? My understand is that the main meters will show a level that is the sum of all the inputs. But, I don't understand how the math works when the get summed. The question is related to advice I have seen to operate channel faders around 0db. If I manage to do this, don't I need to worry about getting two high a level on the main bus?
Thanks for all the replies. I'll respond here as opposed to each one individually.David: This was very helpful. You actually addressed one of the things I was confused about. I was worried about overdriving the main bus. I thought that if I operated my channel faders around 0, I'd end up needing a huge amount of headroom on the main bus (3db for every doubling of channels -> 12db for 16 channels). It sounds like maybe I don't need to worry about this if the console automatically attenuates the combined signal from the channels before sending it to the main. In case it helps, the console is the Roland M200i.One thing that puzzles me is that our previous console (Presonus 16.4.2) seems to behave differently wrt the main fader meter. I didn't spend enough time to correlate the numbers, but Roland's main level seemed to be quite a bit lower than the level for the single channel I was playing with. Meanwhile, the Presonus main level was very similar to the channel's level.Steve: Actually, this is precisely what started all this thinking. With our previous console, we've been operating channels on the low side and I wanted to change this. I do know that this is where I want to be running. With our new Roland, I want to re-balance things better.Tim: By unity gain, I guess I mean 0db...no amplification and no attenuation of the signal. I expected these terms to be interchangeable. Marketing BS aside, aren't they the same thing? Don't get me wrong, I'm not saying I like that term or need to use it .TJ: Could you clarify your first comment about 0db? What I think it means is that the amplitude of whatever signal comes into the fader section of the circuit is not modified. Of course, there can be all kinds of things before the fader in question (channel, subgroup, or main) that can modify signal amplitude. Was this your point or was it something else. And yes, I do know that none of this necessarily implies any specific "loudness".Also, your workflow example is very helpful. A few follow-up questions:-Once you have your channel faders running around -5db, do you care about what the main fader is set to? I assume you would ideally want it around -5db as well for the same reason you want the channel faders this way. If it ends up being too low (turning it up more would make the mix too loud), it seems like you'd want to to turn down the power amp, right?-As of right now, the way our church amp is set up, the main fader needs to be turned way down to get the right output volume (or the channel faders end up being low). The M200i has an attenuation setting on the mains. Would adding attenuation with this control be the same as turning down the power amp? Or, is there some downside to doing this?-For subgroups, I'm assuming I'd want these faders to be set around -5 or 0, right? If so, I'd be inclined to start with all my subgroup faders set to -5db and, more or less, forget about them while adjusting the mix with the channel faders. Then I would use the subgroup faders during mass to play with overall levels for the groups. Does this sound reasonable?Thanks,Dan
Steve: Actually, this is precisely what started all this thinking. With our previous console, we've been operating channels on the low side and I wanted to change this.
"Unity gain", if it means anything, is the desired optimum level of signal above noise floor THROUGHOUT A SYSTEM. As such, it proceeds from your pre-amp settings through your channel faders to the summing amps and so on out to the amplifiers and speakers. So there may or may not be a "unity gain" setting at each point in the chain, but it definitely has nothing to do with numbers, "o'clocks" or physical positioning of any knobs or sliders, simply denoting that the signal is not overly boosted or attenuated at any given stage. That's where the term "gain staging" enters in, a better and more comprehensive term which includes the concept of "unity gain".At least that's the way I think of it...
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