Members ckcondon Posted January 6, 2007 Members Share Posted January 6, 2007 Hi Gang, I tried searching for this, but I couldn't find the explanation or opinion I was looking for.We (I) run sound from the stage and it's basically "set & forget"When it comes to setting up a live mix, there are basically 2 techniques for gain structure I've seen over the years. The one I use is to set the gain first on each input to just below clippping, then channel faders to taste. I've also seen and tried setting all channel faders to unity and adjusting the mix via gain knob.I like the idea of unity settings, but then any gain tweaks during the show also affect the monitor mixes... I also usually get the monitor mix before bringing up FOH so the stage volume is accurate and feedback problems created by monitors can be eliminated before blasting the crowd. I guess it can be "whatever works for you", but I'm curious to see what others with more knowledge do. Thanks in advance! Link to comment Share on other sites More sharing options...
Members dboomer Posted January 6, 2007 Members Share Posted January 6, 2007 Originally posted by ckcondon I guess it can be "whatever works for you", but I'm curious to see what others with more knowledge do. I'm assuming you are talking about gain structure within the mixer and not overall system gain. Actually that IS the answer. Setting the gains is a compromise between the noise floor and the onset of distortion (actually some people prefer distorted signals). It also depends on mixing styles. If you set any channel to operate at "unity" and then you boost any channel EQ, your channel is now operating at above unity. You could be clipping a channel but not getting a clip light (unless your mixer samples from more than one channel point ... there are very few that do unless it's one of mine ) Link to comment Share on other sites More sharing options...
Members ckcondon Posted January 6, 2007 Author Members Share Posted January 6, 2007 Thanks Don, Funny you should mention it... I ordered my 16FX yesterday!Yes, I'm talking mixer gain not system. I get your point about EQ boost affecting unity. I usually don't mess with channel EQ as it's the same instruments, mics etc. at each show. I guess I'm looking for plusses and minuses of each technique or explanation of those mixing styles. CC Link to comment Share on other sites More sharing options...
Members where02190 Posted January 6, 2007 Members Share Posted January 6, 2007 Setup the system with all masters at 0, console, eq, crossover, and adjust amps as needed. EQ as needed for room acoustics. PFL input levels, setting to the nominal that the console sounds best at, typcially between 0- to +6dbu. Mix to taste, however avoid all the faders at 0, as this will overload the summing amps in the mix L/R buss. (0db+0db=+6db.) Link to comment Share on other sites More sharing options...
Members dboomer Posted January 6, 2007 Members Share Posted January 6, 2007 Originally posted by where02190 Mix to taste, however avoid all the faders at 0, as this will overload the summing amps in the mix L/R buss. (0db+0db=+6db.) Only if the signals are coherent ... which they rarely are. Of course you never know how the manufacturer of your mixer manages mix busses (well you do in ours because we actually monitor each gain stage ) Link to comment Share on other sites More sharing options...
Members Rbts Posted January 7, 2007 Members Share Posted January 7, 2007 Hmmm... it is my understnding that of the two approaches you mentioned, the best is to use the "gain" control to set each input to "just under clipping". this gives the most useable signal to the mixer, and maximizes signal to noise right? Link to comment Share on other sites More sharing options...
Members where02190 Posted January 7, 2007 Members Share Posted January 7, 2007 Originally posted by Rbts Hmmm... it is my understnding that of the two approaches you mentioned, the best is to use the "gain" control to set each input to "just under clipping". this gives the most useable signal to the mixer, and maximizes signal to noise right? NO, set the PFL (pre fader listen) so the nominal (average) level is somewhere between 0 to +6dbu, dependin on the console. Some consoles sound better driving the pres a bit harder, like Soundcraft, while others like Allen Heath sound better driving the pres a bit more coservatively. Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 8, 2007 Members Share Posted January 8, 2007 Originally posted by dboomer Only if the signals are coherent ... which they rarely are. Of course you never know how the manufacturer of your mixer manages mix busses (well you do in ours because we actually monitor each gain stage ) Don't forget about the magic mic pre sweetspot Don;) Neither Jim nor I could ever figure out if we had designed in a magical sweetspot in our respective products... so we must be stupid engineers that don't know anything about the circuits we design:D Link to comment Share on other sites More sharing options...
Members dboomer Posted January 8, 2007 Members Share Posted January 8, 2007 By all means ... avoid the sour spot Link to comment Share on other sites More sharing options...
Members ckcondon Posted January 8, 2007 Author Members Share Posted January 8, 2007 Thanks for the info guys. I never tried setting gain via the PFL before... Usually set it with all channels open - Makes sense! I'll give it a shot this weekend. Chris Link to comment Share on other sites More sharing options...
Members Rbts Posted January 8, 2007 Members Share Posted January 8, 2007 On my Allen heath, I set the gain, using the PFL button and the led lights so the the input signal from each channel (one at a time) is "leaving" the green, and "entering" the yellow. The red I tak it is "clipping"? In this way I imagine I am keeping the inputs I guess "somewhat under" rather than "just under" clipping. I have thought this would give "a healthy" if not "maximun" amount of signal, and tend to make the most of the signal to noise. "ratio". Forgive me... am I off base? Link to comment Share on other sites More sharing options...
Members where02190 Posted January 8, 2007 Members Share Posted January 8, 2007 Originally posted by Rbts On my Allen heath, I set the gain, using the PFL button and the led lights so the the input signal from each channel (one at a time) is "leaving" the green, and "entering" the yellow. The red I tak it is "clipping"?In this way I imagine I am keeping the inputs I guess "somewhat under" rather than "just under" clipping. I have thought this would give "a healthy" if not "maximun" amount of signal, and tend to make the most of the signal to noise. "ratio".Forgive me... am I off base? Nope you're right on target. Link to comment Share on other sites More sharing options...
Members Prog Posted January 8, 2007 Members Share Posted January 8, 2007 Originally posted by where02190 (0db+0db=+6db.) You make good points, where. But, You do need a reference level for that addition, don't you? As in, what is 1dB + 1dB? Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 8, 2007 Members Share Posted January 8, 2007 It's the new math;) Link to comment Share on other sites More sharing options...
Members sharnrock Posted January 9, 2007 Members Share Posted January 9, 2007 what happens when you go above unity? Unfortunately with my set up I have to go above unity quite a bit. The main meter never really goes above clipping though... Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 9, 2007 Members Share Posted January 9, 2007 Originally posted by sharnrock what happens when you go above unity? Unfortunately with my set up I have to go above unity quite a bit. The main meter never really goes above clipping though... What do you mean by unity. This term gets thrown around with a lack of definition. The engineering definition is with respect to gain and frequency response... unity gain is a gain of 1 (no gain, no loss) and unity frequency response is flat (no gain, no loss) through the defined passband. Link to comment Share on other sites More sharing options...
Members sharnrock Posted January 9, 2007 Members Share Posted January 9, 2007 Ok, let's say my fader goes from -60 to +10 if I stick my faders on +10db will it ruin my sound? Or I have to go above the "U" on the fader (I guess it's 1db or whatever unity is.) Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 9, 2007 Members Share Posted January 9, 2007 Do you have an input gain (or trim) control? When you go above the unity position (assuming it's really "unity", that means the signal to the mix bus is neither amplified or attenuated. If your input signal is weak, increasing to above unity will add necessary gain (at the expense of additional noise) but if the signal is very strong and your master fader is down low then you run the risk of distorting the mix bus summing amps. The input gain/trim control adjusts the channel's input gain to normalize the signal to a reasonable working level for the rest of the stages. I believe Peavey has a good primer on their website about gain structure. Link to comment Share on other sites More sharing options...
Members where02190 Posted January 9, 2007 Members Share Posted January 9, 2007 Originally posted by sharnrock what happens when you go above unity? Unfortunately with my set up I have to go above unity quite a bit. The main meter never really goes above clipping though... Does your console master fader have a pfl? Sadly this is often eliminated for cost savings, but is a very important feature. What you are not seeing is the input to the master section, which, if you have all your faders at or over 0, is getting hammered, and overloading the summing amps. If you've got the master fader at 0, then you obviously have your pres set very conservatively. I'd recommend opening up the pres more, and pulling the channel faders back, and see how that sounds. It may sound the same, it may sound better, I doubt it'll sound worse. I'd also recommend not paying attention to the clowns. Seems lately the little clique is more bored than usual. Link to comment Share on other sites More sharing options...
Members sharnrock Posted January 9, 2007 Members Share Posted January 9, 2007 I have a mackie 12-cfx mixer I solo each channel and get the leds to go up to about 0 or as close to. So, the little clip light kinda comes on whenever that channel makes a sound. I set subs 1 and 2 (which go to main stereo left and right) to unity. Then I have to put my master fader up past "U"(not all the way up, but maybe around +5 DB. I have a rat shack mic that doesn't put out much, so that is set all the way up on the channel fader. I just wanted to know if I'm hurting my mixer. The amp doesn't clip and the speakers don't distort. I don't hear a lot of noise coming out of the speakers, I just didn't know if I was hurting the mixer or the sound by putting it past "u". Link to comment Share on other sites More sharing options...
Members 6Imzadi Posted January 9, 2007 Members Share Posted January 9, 2007 Originally posted by sharnrock I have a mackie 12-cfx mixerI solo each channel and get the leds to go up to about 0 or as close to. So, the little clip light kinda comes on whenever that channel makes a sound.Are you sure the "clip" light is on? When the led's are at 0, you should not have a clip light on on the channel. The channel fader should start out at 0 or unity. I set subs 1 and 2 (which go to main stereo left and right) to unity. Then I have to put my master fader up past "U"(not all the way up, but maybe around +5 DB.Your sub faders and master fader should be at 0 or unity. I have a rat shack mic that doesn't put out much, so that is set all the way up on the channel fader. You really should get a better mic, even if for DJ'ing. I just wanted to know if I'm hurting my mixer. The amp doesn't clip and the speakers don't distort. I don't hear a lot of noise coming out of the speakers, I just didn't know if I was hurting the mixer or the sound by putting it past "u". The people here are trying to inform you on how to set it correctly. Please pay attention, and you will soon realize the sonic difference for yourself. Link to comment Share on other sites More sharing options...
Members Dogoth Posted January 9, 2007 Members Share Posted January 9, 2007 I asked basically the same question as the OP in a post called "Gain stageing and the real world" (I couldn't seen to find it using the search function (maybe it's too old)). The way I do it is use the PFL function to set the trim (gain) to peaks of somewhere between 6 and 20 Db below clipping (this depends on the instrument (some have a lot more hidden transients that are too fast for meter's response time) and also whether you trust the performer to not turn up what they're sending you once the performance begins:D ). Once I set my input gain I pretty much leave it (unless that crazy guy I mentioned earlier decides to turn up:D ) and mix with the faders (and aux knobs if I'm sending another feed such as monitors etc...). Hey I figure they made them faders to give you some graphical representation of you're mix. Someone sent a link to great article (I think it was a A&H board manual) which described the whole procedure quite well. Yes I've seen guys who set all of their faders at unity and then get a mix using the trims. The guy's I work with call them "full Sail Graduates" (not knocking the school - I think they do turn out some good people) because this is how you'd setup for tracking in a studio (provided your board was calibrated with your multitrack). But when it comes to mixing (either live or mixdown), that's what the faders are for. Link to comment Share on other sites More sharing options...
Members 6Imzadi Posted January 9, 2007 Members Share Posted January 9, 2007 Yep, I should have finished my sentence. Are you sure the "clip" light is on? When the led's are at 0, you should not have a clip light on on the channel. The channel fader should start out at 0 or unity. I said start out at unity. That does not mean that they have to stay there. Sometimes, while doing sound check on the drums, I will bring the faders up to the 0 mark. Then they come down after I get my "fix". Once the lead vocal comes in and we start the night, everything evens out with the faders, and they come down to where they belong. Link to comment Share on other sites More sharing options...
Members where02190 Posted January 9, 2007 Members Share Posted January 9, 2007 Originally posted by sharnrock I have a mackie 12-cfx mixerI solo each channel and get the leds to go up to about 0 or as close to. So, the little clip light kinda comes on whenever that channel makes a sound. I set subs 1 and 2 (which go to main stereo left and right) to unity. Then I have to put my master fader up past "U"(not all the way up, but maybe around +5 DB. I have a rat shack mic that doesn't put out much, so that is set all the way up on the channel fader. I just wanted to know if I'm hurting my mixer. The amp doesn't clip and the speakers don't distort. I don't hear a lot of noise coming out of the speakers, I just didn't know if I was hurting the mixer or the sound by putting it past "u". If you are setting FPL levels at 0, and the clip light comes on with any input, then your mixer has a problem. I'd recommend setting your pfl level to between +3 and +6, and keeping the master fader at 0. This will lower your s/n slightly, and instead of getting the gain from the mix buss, get it from the mic pre. You can run the Mackie pres fairly hot without trouble. You're not "hurting anything" but there is a better cleaner way to set your gain stages. Link to comment Share on other sites More sharing options...
Members The Real MC Posted January 9, 2007 Members Share Posted January 9, 2007 If there is one thing I have learned doing FOH sound, I set gain PFL levels to around -3 to -6dB, not 0dB. Players and singers tend to be subdued during soundcheck (especially drummers) and then the stage volume tends to creep up as the show goes on. If you set levels to 0dB during soundcheck then you risk clipping if you're not paying attention. Link to comment Share on other sites More sharing options...
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