# Why do we need to have the gains bottomed out?



## MillburyAuditorium (Jan 11, 2010)

I am not a sound guru by any meens and I am kind of noobish at wireless and frequency's and what not, 
8 of our wireless mics are set for -30 on the beltpack and two newer ones, are at -60. These are the lowest they go on the belt packs. And on the board, a Mackie VLZ 24*4, the gains for the wireless channels are bottumed out and the new oens a tad above that. If we go any higher we get bad feedback and screeching until turned down. But the volume is still adiquit for the room.

We don't have any problems with it set this way, I am just wodnering why this happens.


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## themuzicman (Jan 11, 2010)

Not answering your question, just saying how I work it so you don't have everything bottomed out.

I set my faders to unity (0db), and my mic packs to 0db, and then adjust the channels gain to a usable level, just so you are at a nice medium. 

Having the gains bottomed out and the mic packs bottomed means you have no way to go in the event you have a problem. You can only go up, and that is not a good solution. 

Try to find a happy medium!


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## DuckJordan (Jan 11, 2010)

the question lies in the EQ of your venue, and also speaker placement and mic placement. We have had several issues over the years with new microphone systems that are a tad bit more sensitive than others we fix this problem with a tune up using a real time analyzer on our EQ, it has solved a lot of our problems. whats probably happened in your venue is (assuming its a school) the principal looking at two choices spend the $300 to bring some one in to do an EQ setup, or have the TD take all the gains down as far as they go. considering which was cheaper the Principal and possibly the school board decided lets just turn down the mics. we had that problem in our space until me and two other designers/directors brought it up and then they paid the money for the EQ setting.( Dang Automatic Feedback Exterminators, usesless they are.)


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## MillburyAuditorium (Jan 11, 2010)

Sorry I should of mentioned this before,

Well, let my just run through our entire sound setup.

We have a 130 Foot snake with many more channels then needed, and a small 6 channel snake. About 50F long. Our four floors mics are connected to the small snake then that snake is plugged into our larger snake starting backstage, then our six hanging mics connect to the snake as well. Then the snake runs up along the side wall of the house and over to the sound board, a Mackie VLZ 24*4, all the hanging and floor mics hooked up accordingly. Then the wireless receivers, which are in two stacks of five onto of each other with the antenna arranged apart as much as possible, and the frequencies spaced accordingly. Then since we are running mono, we use the Mono main out, into our 15 band EQ, which is in a 8 space rack onto of our CD mixer, the EQ is a dual 15 Band, but we only use Channel A since we are running Mono. So out of the EQ back through the snake and out of whatever channel we are using as the main out connect another XLR wire from that channel on the snake box, then up to a 10 space wall rack that swing open plus a locking door, so, Into a processor, out to our sad single 250 watt amp, then out to the speakers.

Not sure if maybe or EQ would have anything to do with it? Through my knowlege of EQing it seems fine.


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## DuckJordan (Jan 11, 2010)

the whole reason you would get a feedback noise is a loop is being created through your microphone out through your speakers then back to the microphone, the easiest way to fix a problem like this is to use the auto setup on the eq system assuming it has one, if its a lower end it probably doesn't we have a digital eq in our space so we hook up everything we need hit setup microphone and it automaticaly tunes down the freqs that cause feedback in our space. also speaker placement could be a huge issue.


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## Chris15 (Jan 12, 2010)

Whats the make and model of the wireless?

To me there's a mic / line selection not set right at the moment somewhere. Possibly on the back of the RF receivers and they are spitting out line level that's being fed into a mic input...


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## SHARYNF (Jan 12, 2010)

I agree with Chris your wireless mics probably have a mic out and a Line out, sometimes they are externally selectable sometimes it is based on the jack connection. It looks like you have a line out set and connecting to a mic in on your mixer. I would say someone has set these wireless mics to line out thinking that was what was needed based on the distance and the snake which is not correct. Don't know what model of wireless you have. The setting on the belt pack is so not to overload the receiver, and can be independent of the setting on the Receiver output to the mixer, so Suggest you look at the output of the receiver not the beltpack. 

BTW trying to use a 15 channel graphic eq for feedback control is typically not successful. The alteration of the eq is just too broad to not have a significant audible effect. An inexpensive DBX 231 dual channel 31 eq would make things much much easier (a 1231 is a better unit but a bit more money)
Really sounds like your system was sort of cobbled together by some inexperienced folks. Your setup seems to be designed by a DJ with stage sound added on to it. So every time you use the DJ cd mixer setup (probably a Numark??) you run the risk of completely altering the settings for the pa audio. Basically just from your description you should have an independant line mixer that takes the outputs of the PA feed from your Mackie, and the outputs of your DJ CD Mixer and combines these and is pretty much Set and Forget, that way, you can set up the mic system and the DJ system independantly and not have to worry about one changing the other. In setups like yours I have used a Whirlwind Matrix Mixer 44 which then allows for your to have maximum flexibility and allow you to add additional amps later on 

http://www.fullcompass.com/product/290893.html

Again just some thoughts, cannot really design a system this way 


Sharyn


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## David Ashton (Jan 12, 2010)

You have all got it horribly wrong.
There is only one correct answer.
SET YOUR GAIN STRUCTURE
All your fiddling around trying different things is a waste of time.
You must learn how to set your gain structure or you are just wasting your time.
Sorry to be blunt but there is no other way to say it.


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## gpforet (Jan 12, 2010)

My guess is that the wireless recievers are putting out line-level, and are patched into mic inputs on the console. I suspect all will be well if the receivers are plugged into the LINE input of the channel, rather than the MIC input.


MillburyAuditorium said:


> I am not a sound guru by any meens and I am kind of noobish at wireless and frequency's and what not,
> 8 of our wireless mics are set for -30 on the beltpack and two newer ones, are at -60. These are the lowest they go on the belt packs. And on the board, a Mackie VLZ 24*4, the gains for the wireless channels are bottumed out and the new oens a tad above that. If we go any higher we get bad feedback and screeching until turned down. But the volume is still adiquit for the room.
> 
> We don't have any problems with it set this way, I am just wodnering why this happens.


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## gpforet (Jan 12, 2010)

David, I've preached this until I've given up the fight. There's still people talking about setting the fader to 0db and then using trim to get volume up. In fact, some schools are now teaching this approach. I've challenged anyone to refer me to a console operation manual which promotes this approach. Of course, no one has stepped forward. I've checked out the Mackie manual for the console mentioned and guess what, a complete section on IMPORTANT SENSITIVITY ADJUSTMENT PROCEDURE, directing the user to solo the channel, set trim so meters indicate 0, etc, etc. As you and I both know, gain structure begins at the input, not at the fader. 


David Ashton said:


> You have all got it horribly wrong.
> There is only one correct answer.
> SET YOUR GAIN STRUCTURE
> All your fiddling around trying different things is a waste of time.
> ...


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## hsaunier (Jan 12, 2010)

I'm counting 10 area mics.... which if all are condensers and all are open, then introduce another slew of wireless mics into the mix...... let the ringing begin. The stage space is being amplified and reamplified so many times there WILL be problems. (Unless the stage is 100'X100')


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## SHARYNF (Jan 12, 2010)

gpforet said:


> David, I've preached this until I've given up the fight. There's still people talking about setting the fader to 0db and then using trim to get volume up. In fact, some schools are now teaching this approach. I've challenged anyone to refer me to a console operation manual which promotes this approach. Of course, no one has stepped forward. I've checked out the Mackie manual for the console mentioned and guess what, a complete section on IMPORTANT SENSITIVITY ADJUSTMENT PROCEDURE, directing the user to solo the channel, set trim so meters indicate 0, etc, etc. As you and I both know, gain structure begins at the input, not at the fader.




The reason some schools are teaching this method is that when the faders are set to unity, then the output meter is reading the input level since by definition unity gain means neither attenuating or boosting the signal level.

using a PFL (Pre Fader Level) signal sent to the meter does the same thing of course, BUT if you use the SOLO BUTTON your signal is POST FADER level (ON MANY MIXERS, Mackie combines SOLO AND PFL) so if the faders are not set to Unity, if THAT signal is sent to the meter the Fader setting is effecting the reading. Most Mixers Send the signal from the PFL button to the Monitor ONLY but Solo is sent to the Main outputs. 
Because Mackie SOLO/PFL is combined, the Left Meter reads the signal, and of course the level in your headphones if you were using them to monitor then may go up significantly if previous to this you were monitoring with the fader set below unity.

Sharyn 

Sharyn


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## gpforet (Jan 12, 2010)

The console referred to allows you select whether you want SOLO to be PFL or not...and yes, PFL is the way to set gain. Setting the fader to zero does not provide you with knowledge of the input gain hitting the aux busses unless all eq is trimmed to zero as well so it won't help you here. It will also capture any gain aquired thru channel inserted devices, so, again, it's a false reading. The goal is not to get zero out, the goal is to ensure that the gain is properly staged at every point in the path....PFL to meter is the only way to see what the first gain stage is doing to the input signal. This sets the condition of the signal for all subsequent points where the signal is split.

PFL the channel, trim to near zero, use the fader to mix. Still waiting for someone to show me an operation manual which says otherwise.

By the way, I haven't run across a console that sends the SOLO to the main outputs, everyone I've used sent SOLO to MONITOR and/or PHONES out.


SHARYNF said:


> The reason some schools are teaching this method is that when the faders are set to unity, then the output meter is reading the input level since by definition unity gain means neither attenuating or boosting the signal level.
> 
> using a PFL (Pre Fader Level) signal sent to the meter does the same thing of course, BUT if you use the SOLO BUTTON your signal is POST FADER level (ON MANY MIXERS, Mackie combines SOLO AND PFL) so if the faders are not set to Unity, if THAT signal is sent to the meter the Fader setting is effecting the reading. Most Mixers Send the signal from the PFL button to the Monitor ONLY but Solo is sent to the Main outputs.
> Because Mackie SOLO/PFL is combined, the Left Meter reads the signal, and of course the level in your headphones if you were using them to monitor then may go up significantly if previous to this you were monitoring with the fader set below unity.
> ...


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## SHARYNF (Jan 12, 2010)

I am not saying I agree with the zero the faders, just trying to offer some input on why the schools seem to be teaching this method

My error on the Solo comment to main out, still early in morning ;-) in a multi track recording setup sometimes what you are actually listening to is the Monitor output as your "main output" 

the other thing the schools are probably thinking about, )again don't agree with it but then schools are schools) is that most of the cheaper mixers use a Latching switch, (reason Mackie added the Rude solo light) and so it is easy for the inexperienced to forget that some of the solo buttons are still pushed/

But back to the original question. I agree getting the gain structure correct is essential BUT I still think the problem Might be that the wireless receivers are set to Line instead of mic level. 

Sharyn


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## museav (Jan 12, 2010)

Another thought, you noted two level settings, one on the bodypacks and one on the console. There are probably a lot more than that affecting gain before feedback. Start with that your wireless mic may have a gain level on the transmitter and then another on the receiver as well as different level outputs available on the receiver.

The first thing to do is probably to verify whether the receiver output is mic or line and that it is running into the appropriate input. Then step back from what the numbers are on the gain settings and look at what the levels are. If you PFL a wireless mic, what level do you see? What level do you get at the output with just that one wireless mic routed to it and that channel fader at 0?

I won't get into the console trim setting argument, I'll just say that with modern consoles there are electronic and functional pros and cons to both approaches as well as to variations on them (e.g. reducing trim level to account for expected summing on buses). And if you want to take it to another level, look at what many people are doing for remote preamps when they don't have control of the preamp gain at the console, since they can't grab the level easily if it clips they often set the nominal level an additional 10-20dB down to provide more headroom. So don't be afraid to try any of the approaches and find what works best for you in the application at hand.


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## MillburyAuditorium (Jan 12, 2010)

Well not going to answer everyone individually, so here goes,

Well I was looking at the board today trying to figure out why it is so quit but getting so much feedback, this has never happened in previous years. So I am looking at the back of the board, and again we use a mono output.
And I notice the Output Gain is up to 75  Kicked that down to 40 and I will bring the channel gains up a bit and test the mics tomorrow, It was after everyone left rehearsal today. Hope that works.
Whoever said 10 area mics, 
Well they are not all on at the same time. The three rear hangings are only used for full stage performances which the plays are not. So two or three hanging mics on, and four floors. Plus the biggest seen uses 5 wireless at the same time.

And so you guys suggest not using the Mic input? I never really thought of that, I assumed it would be the same, and XLR would be better. Right now the wireless receivers are connected to their channel on the board through the Mic In which is an XLR input.
I will try and get 10 5 feet quarter inches if you guys think it will make a difference?

And for whoever wanted the make and model,
They all all Sennheiser makes, and the two new ones we just bought, and they work really great, are ew122 G3's Sennheiser USA - ew 122 G3, lavalier wireless microphones systems, microphone, transmitter, receiver - Professional Audio
And we have 8 older ones, I do not know the model right now. But I cannot find them on the Sennheiser site. Must be to old. But they are the same family I believe.

Edit:

Also, I noticed, even the most cheap Sennheiser body packs are the smallish roundy body packs. Our 8 old body packs are rectangular with flat edges.


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## mbenonis (Jan 13, 2010)

MillburyAuditorium said:


> Also, I noticed, even the most cheap Sennheiser body packs are the smallish roundy body packs. Our 8 old body packs are rectangular with flat edges.



Sounds to me like Evolution G1 (the first evolution wireless).


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## museav (Jan 13, 2010)

MillburyAuditorium said:


> And so you guys suggest not using the Mic input? I never really thought of that, I assumed it would be the same, and XLR would be better. Right now the wireless receivers are connected to their channel on the board through the Mic In which is an XLR input.
> I will try and get 10 5 feet quarter inches if you guys think it will make a difference?
> 
> And for whoever wanted the make and model,
> ...


Remember that an XLR is simply a connector type, it is not limited to mic level signals. The EM 100 G3 receiver has both XLR and 1/4" TRS output connections but they are simply wired in parallel and both are balanced line level (+18dBu max) outputs, so they should run into a line level input on the mixer.


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## GreyWyvern (Jan 13, 2010)

museav said:


> Remember that an XLR is simply a connector type, it is not limited to mic level signals. The EM 100 G3 receiver has both XLR and 1/4" TRS output connections but they are simply wired in parallel and both are balanced line level (+18dBu max) outputs, so they should run into a line level input on the mixer.



A couple quick questions, to (hopefully) help clarify.

When hooking the receivers up with a 1/4" cable, should it be TS or TRS?

Some consoles have a mic/line input button, but both inputs will work regardless of the button position. What is that button for (does it simply select the input level) and what position should it be in for different setups? (Such as xlr out of receiver to xlr into console and 1/4" out of receiver to 1/4" into console.)

Dave


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## SHARYNF (Jan 13, 2010)

GreyWyvern said:


> A couple quick questions, to (hopefully) help clarify.
> 
> When hooking the receivers up with a 1/4" cable, should it be TS or TRS?
> 
> ...



TS or TRS depends on whether the output and input is TS or TRS, A lot of 1/4 inch devices are unbalanced

The line/mic button typically adds a pad to bring down the line level to mic level for the preamp. Some designs might bypass the mic preamp.

Sharyn


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## museav (Jan 13, 2010)

SHARYNF said:


> TS or TRS depends on whether the output and input is TS or TRS, A lot of 1/4 inch devices are unbalanced.


And specific to this application, there are even some wireless mic receivers with unbalanced outputs on XLR, certainly not normal but not actually wrong in any specific way. That's why you should always check the product specs to verify the level and format of the output(s) regardless of the connector type used.


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## SHARYNF (Jan 13, 2010)

I guess putting things a bit more bluntly, before changing ANYTHING you first need to research what you have and how it all interfaces. I have seen many posts about your school and there seems to be one problem after another, stolen speakers by contractor, destroyed main drape, improperly set up systems

I also see a tendency to take a ready fire aim sort of approach

Changing the levels on the wireless transmitter, or the output level on the mono on the Mackie etc, all should never have been done without first looking at what you have. Several of us all pointed out that the probably error was using line out into mic in on the mixer. It was only when it was guessed what wireless units you had that it was clear that these are line out only and that was the basic problem.

Since this is an educational orientated site, I think it is important to realize that it is RESEARCH FIRST before ACTING. the old RTFM (read the .... Manual) really is important especially now a days when a google search can typically find the missing manual or specs

Gain structure is important, but understanding what you have and the levels of the inputs and outputs that are expected is important FIRST It comes down to: is it line of mic, is it pro level or consumer, is it balanced or unbalanced in most cases, this information really is IMPORTANT to make decisions before action. Otherwise you wind up with a difficult situation trying to resolve problems some of which you may have introduced by changing things.


It is easy (relatively speaking) to operate when everything works, where this site, and the people on it are trying to help is teaching HOW to diagnose problems and resolve them. 

Sharyn


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## MillburyAuditorium (Jan 13, 2010)

Yeah, I was looking at the mics today. The old ones are EW 100 G1s and the new ones are EW 100 G3s
Now that we lowered the main gain and turned up the channel gains the older mics are able to be much louder without any squealing. I will have to take the new belt packs up to -30 though since they are now not as loud as the old ones at -30. SO that should solve this problem. I will also try the Line In suggestion as well.

I have read most of the manual.


Other questions-

I do not know if it is the age of the board or what, but I have two things. One, I was playing a recording of the orchestra for practice one day from the CD player, and it was pretty loud, so I put on the headset to listen to the actors to EQ them, so I am listening to them on solo. And the CD channel is not on solo, but I realized I was still getting some of the CD being played through the headset, I hit the solo button for that channel and it came in louder and clearer through the headset, turned it off, and it was still there just a little muffled and quit.
Also, I was recording clips of the rehearsal today for a commercial we do plus we need them to make something for the opening, So I was running out of one of headphone jacks to the mic in on my laptop, I played music through the 'Line' channel form my iPod, had the channel on solo, and my laptop was picking it up fine, but it was also coming out the speakers very faintly. I was confused, the slider was all the way down, yet still coming out a bit.

Why is this?


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## SHARYNF (Jan 13, 2010)

The gain on the belt pack is for control of the signal in the belt pack, so that you do not overload it and cause distortion. It is set so that you still have a hot enough signal so that you have good SNR ration but don't overload. it is important to get it correct since there are electronics in both the belt pack and the receiver that need to have the proper gain structure for them

Making sure that since you only have line out on your receivers you have the input pad and trim set properly on the Mackie is important so that you don't overload the input stage on the MIXER

The control on the mono output on the mixer is so that you don't overload the input stage on what is down stream from the MIXER... Your amps probably have a level control on them which adjusts the LEVEL OF THE INPUT since the amps them selves run at a fixed setting it is just the level of the input signal that is varied. 

You seem to keep attempting to correct the wrong end of the problem. 


Your fader will not be able to completely shut off a signal that is too hot coming in to and thru the preamp. So if you are putting a line level signal from a CD player into a mic input and don't have the pad and trim set correctly the fader will not completely cut off the signal. You can check this by simply muting the input, the low level you are hearing should go away.(assuming a reasonable level of channel isolation on the Mackie)

Taking headphone out and putting it in to MIC in is another Level mismatch. Typically you should use LINE out, and LINE in. Just because the jacks fit does not mean the signal will work properly. Are you going to get something, sure but is it the correct way to do it ??? At a minimum take the Headphone out and put it into a LINE level input.

As mentioned before Gain structure is important and should not be ignored

At each stage you are trying to get the best match of signal level above noise and before clipping.

If you run your belt packs too low, you will get too much noise, if they are too high you will get distorted overload. If you run line levels into mic level settings on a mixer you will get an overload input and as you have seen an inability to totally shut off the signal via the fader. 

As I said you need to take some time and think about all this, it is not just that the plug fits, but that you have the correct level to match the signal thru the system, There really is a reason for the adjustment controls that are placed on the ins and outs of most pro gear. It is not like consumer stuff where they are all designed to pretty much just plug in and the compromises are made by the manufacturer

Sharyn


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## Morpheus (Jan 13, 2010)

This is where your wireless mics should be coming in.


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## SHARYNF (Jan 15, 2010)

Morpheus is correct, on the Mackie you have there is NO input pad, and it is not possible to connect a line level signal to the xlr inputs without a real danger of overloading the pre's So you need to get some cable adaptors that convert from xlr to trs.

Sharyn


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## MillburyAuditorium (Jan 15, 2010)

Alright, Well it's been running like this for years. Good thing nothing has happened. I'll get those adapters soon.

And about the not being able to cut off the sound. It isn't really that, we can cut off all sound via the faders, so say I have the headphones on and nothing on solo. I hear nothing, good. I press solo on channel 11 (wireless 1), and I can faintly hear the CD track through the headset.

And I dont understand what you meen plug the headphones into a Line in? DO I not conect it to 0one of the two Headphone Outs?

And the CD player is using a line in, not mic.

It's fine that our floor and hanging mics are using MIC inputs right?


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## SHARYNF (Jan 15, 2010)

I am just responding to what you wrote

Also, I was recording clips of the rehearsal today for a commercial we do plus we need them to make something for the opening, So I was running out of one of headphone jacks to the mic in on my laptop


Connecting a headphone out jack to the mic in on a laptop is going to cause problems.


Sharyn


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## MillburyAuditorium (Jan 15, 2010)

Oh about the laptop one. Well it worked out alright. And I really wasn't sure where to connect it. I tried the Aux. Stereo Outs but that wasn't working and I didn't have much time to try things.


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## Morpheus (Jan 16, 2010)

stuff like line level out into mic level in (like your laptop thing, or even the hanging mics you mentioned vs the wireless) is all about matching the correct levels....

Basically, your "line level" signal is up here: ↱

while your "mic level" is down here: ↳

So, when you put the connector into the device, it's dumb and doesn't know what you want it to do, it only does what is expected, which is get the signal here: →
So.... that means it boosts what it thinks is "mic" level, and cuts what it thinks is "line level"...
And if it boosts too much, it clips and sounds bad.
If it cuts too much, you don't hear anything.


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## museav (Jan 16, 2010)

Morpheus said:


> stuff like line level out into mic level in (like your laptop thing, or even the hanging mics you mentioned vs the wireless) is all about matching the correct levels....
> 
> Basically, your "line level" signal is up here: ↱
> 
> ...


Good points but the last couple may be misunderstood. Mixers are not trying to get a signal level between mic and line level, they are essentially trying to get everything internally at a nominal line level. Being of much lower level, mic level signals coming in to a mixer typically need significant gain or boost their signal to get to that nominal level while line level signals may require either some lesser gain or some attenuation.

Clipping does not result from the gain (boost) or attenuation (cut) applied, it results from the signal level being greater than the electronics can handle. Every electronic circuit will have maximum signal levels it can properly handle and any signal level above that is 'clipped', which is undesired electronically and audibly. In general, a signal of higher or lower level than optimum can be undesired in terms of how it affects the signal, the resulting noise or the operating headroom (the room between the average signal level and the peak level when clipping occurs). That is where gain structure comes into play in optimizing the signal levels.


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## Morpheus (Jan 16, 2010)

museav said:


> Good points but the last couple may be misunderstood. Mixers are not trying to get a signal level between mic and line level, they are essentially trying to get everything internally at a nominal line level. Being of much lower level, mic level signals coming in to a mixer typically need significant gain or boost their signal to get to that nominal level while line level signals may require either some lesser gain or some attenuation.
> 
> Clipping does not result from the gain (boost) or attenuation (cut) applied, it results from the signal level being greater than the electronics can handle. Every electronic circuit will have maximum signal levels it can properly handle and any signal level above that is 'clipped', which is undesired electronically and audibly. In general, a signal of higher or lower level than optimum can be undesired in terms of how it affects the signal, the resulting noise or the operating headroom (the room between the average signal level and the peak level when clipping occurs). That is where gain structure comes into play in optimizing the signal levels.



Well, yea.
I was trying to make it simpler to understand... Sometimes i get really into the tech and make it way more complicated than it needs to be


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## MillburyAuditorium (Jan 16, 2010)

Well as I said, it sounds fine now, was just the Amp master was down and the EQ gain was up to much. I will see about those 1/4" converters.

Maybe this is why we keep the beltpack gains at -40?


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## SHARYNF (Jan 16, 2010)

Somehow I get the impression that you really have not read carefully the recommendations and the discussion on gain structure

Sharyn


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## MillburyAuditorium (Jan 16, 2010)

What makes you say that? If you are because I said the amp was down..Obviously if an 800 watt amp is turned down to only give out 50 watts, I was being forced to increase the gains and levels. But now that I turned the amp up to were it should be I can do things normally now.

And I people are saying using a Line out to Mic In is bad so either way I would want to get the Mic-Line converters.


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## museav (Jan 16, 2010)

MillburyAuditorium said:


> What makes you say that? If you are because I said the amp was down..Obviously if an 800 watt amp is turned down to only give out 50 watts, I was being forced to increase the gains and levels. But now that I turned the amp up to were it should be I can do things normally now.


An 800W amp is an 800W amp and a set signal level to the amplifier crcuit in the amp will generate that, all turning down the levels does is attenuate the signal level before the amplifier circuit itself, it does not reduce the potential amp output or prevent getting the full rated output.

The most common and recommended approach is to properly set gain structure then adjust the amp levels to get the desired output levels.


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## Morpheus (Jan 16, 2010)

SHARYNF said:


> Somehow I get the impression that you really have not read carefully the recommendations and the discussion on gain structure
> 
> Sharyn



Reading and comprehending are two different things....


MillburyAuditorium said:


> What makes you say that? If you are because I said the amp was down..Obviously if an 800 watt amp is turned down to only give out 50 watts, I was being forced to increase the gains and levels. But now that I turned the amp up to were it should be I can do things normally now.
> 
> And I people are saying using a Line out to Mic In is bad so either way I would want to get the Mic-Line converters.


wait, when did we start discussing amps and signal post-mixer? (while we're there, if you need to clamp your amp down that much, time to look at getting a different amp)
It's good that you're starting to think about the gain structure, but start from the right end - start at the top of the signal chain, not the bottom


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## Eboy87 (Jan 16, 2010)

MillburyAuditorium said:


> What makes you say that? If you are because I said the amp was down..Obviously if an 800 watt amp is turned down to only give out 50 watts, I was being forced to increase the gains and levels. But now that I turned the amp up to were it should be I can do things normally now.
> 
> And I people are saying using a Line out to Mic In is bad so either way I would want to get the Mic-Line converters.



The gain controls on amps don't work that way. They attenuate (turn down) the incoming signal. They don't control the output wattage. You still need to read the article on gain structure. There's more going on here than you're willing to admit, much of it probably over your head at this point. This isn't about getting the maximum output from everything, there are impedance mismatch issues as well as level mismatches in your system. Spend some time here. It's the study hall over at ProSoundWeb. Read some articles and understand the principles of what's going on with how the gain structure relates to each piece of gear. You need a foundation before you can accurately diagnose your problem, and the people in this thread have been trying to help.

Now, for your mic/line level situation. I look at it this way; I would rather have line level coming into my board (via the Line level jacks on the back of your Mackie) than mic level. I would find 1/4" balanced (TRS) to 1/4" balanced cables, and connect your mic receivers that way. Sending line level signals to an input expecting a mic level will overload the circuit, leaving you with garbage for a signal. The garbage in/garbage out ratio applies here. 

I also suggest you go back and re-read this thread carefully, paying attention to what is being suggested. It will actually benefit you in the long run. I would also suggest you bring in someone more knowledgeable in audio to help you with this, and also to tech you and any other techs at your school just what is going on with your system.

Good luck!


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## SHARYNF (Jan 16, 2010)

My Mistake, reading and comprehension are not one and the same

several of us tried to explain the difference with the setting on the belt pack and the line out on the receiver

The reason why you need to convert the line out on the receiver with an XLR connector to 1/4 TRS 

Why connecting a Speaker level signal to a Mic level input is not a good idea

Why Understanding gain structure is important, and the in and out levels on devices and how the input control on an amp works.


Sharyn


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## MillburyAuditorium (Jan 16, 2010)

Guys, I dont know why your yelling at me 0_0. I have said that I am going to be doing what you have suggested.

And you are not understanding what I am saying.

I DO NOT need to turn the amp down.

And my problem is resolved by the way. The reason why I couldn't get hardly any sound out without turning the gains up so much was because someone had turned the amp nearly all the way down. I have turned it back up and we are all good.

I do not know if our amps are different then others? Because our single 800 watt amp has a physical knob that read VOLUME. And if the VOLUME knob is all the way down, it doesnt mater if the gains are set perfectly on the board nothing is going to come out..


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## DuckJordan (Jan 16, 2010)

your misconception is you considering it volume after amplification, this is not the case its volume before amplification, its the incoming signal being adjusted not the signal leaving the amp.


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## MillburyAuditorium (Jan 16, 2010)

Alright, sorry maybe I did not understand that the volume on the amp controls the input not output. But either way. My only problem was because the amp volume was nearly off..and the amp treble was all the way up.. That's why it would squeal so quickly. 
Our amp is back stage, not near the control area. So I did not notice this until I went back there.


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## SHARYNF (Jan 17, 2010)

MillburyAuditorium said:


> .... But either way. My only problem was because the amp volume was nearly off..and the amp treble was all the way up.. That's why it would squeal so quickly.




OH well sad that after all this you come to this conclusion

Sharyn


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## MillburyAuditorium (Jan 17, 2010)

Ah highschool theatre ; )
Thinking of cutting some semi circle in the amp rack backstage to put the cables through and still lock the cabinet.

And painting Do Not Block signs on the floor in a rectangle around the breakers, dimmer rack and amp rack so I am not climbing over mountains of sets.. And maybe also under the ends of the light bars. Yesterday I am trying to lower a light bar and it isn't going down, Im like "wtf.." Only to see a big wall in the way of the bar on the other side of the stage.


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## derekleffew (Jan 17, 2010)

MillburyAuditorium said:


> ...And painting Do Not Block signs on the floor in a rectangle around the breakers, dimmer rack and amp rack so I am not climbing over mountains of sets. ...



I'm with you on this one! Perhaps some of these signs also?


Electrical Panel Signs ? Keep Operating Environment Safe with Danger Signs , SKU: S-0645
Of course, for it to have an effect and be enforced, the directive will have to originate from an administrator, not a student.

SIDENOTE: 
While googling, I found this site: La Mesa, CA - Official Website - Fire Safety Checklist for Schools
Without reading the URL carefully, I thought it said "www. City of Flames a .com"
Contains very useful guidelines pertaining to the California Fire Code (your state's may vary), including: 

> *30 inches of clearance shall be provided in front of electrical panels.* _Do not tape circuit breakers in the open position, cover electrical panels with any material or obstruct in any manner. (CFC 605.3)_


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## MillburyAuditorium (Jan 17, 2010)

Oh, nice. Haha, we have a storage closest that people like to go into, Maybe I will put a similar sign on the door 
And yeah those signs would be helpful too, The other day I was going to turn the amp off and I was walking on a mattress, boing, boing. 
I love intimidating signs


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## museav (Jan 17, 2010)

MillburyAuditorium said:


> Oh, nice. Haha, we have a storage closest that people like to go into, Maybe I will put a similar sign on the door
> And yeah those signs would be helpful too, The other day I was going to turn the amp off and I was walking on a mattress, boing, boing.
> I love intimidating signs


It's not an intimidating sign, it is simply stating a code requirement. I would be cautious about intentionally misapplying such signs, it could be a red flag to an inspector. It might be better to use more vague language in those situations.


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## MillburyAuditorium (Jan 19, 2010)

Yeah, I guess I just need to keep it locked up more often. 

So it is 32 inches in front of electrical boxes right? Dont want to put up a false sign.
All our breakers and the dimmer rack is in a corner.


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## cprted (Jan 19, 2010)

MillburyAuditorium said:


> So it is 32 inches in front of electrical boxes right? Dont want to put up a false sign.
> All our breakers and the dimmer rack is in a corner.


Check your local electrical and fire codes. Each jurisdiction will be a little different. For example, in British Columbia, it is 1 Meter of clear space (39 1/3 inches).


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## SHARYNF (Jan 19, 2010)

Typically there is a box drawn on the floor with a statement to keep clear.

Sharyn


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## MillburyAuditorium (Jan 19, 2010)

Sharyn, Yeah if I do anything I will be doing that. And I also mentioned probably making a somewhat small rectangle below the edges of the electrics. I was bringing one down the other day and it stopped, was like "Did the power tubing get caught?" so when I am at the other side of the stage Is ee a wall with the end of the electric resting on top. Five minutes of moving that thign and I was back to replacing lamps.
Going to have take a trip to the art room and borrow some paint and stencils


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## dafunkmonster (Jan 25, 2010)

I think what you've missed is this:

Every device in the chain from signal origin to the amplifier has the ability to boost or attenuate the signal. As has already been stated (somewhere in this thread), you want to keep your signal at a level so that it is well above the noise floor, but not so high that it clips. See picture...



This is what people were trying to convey to you.


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## gpforet (Jan 28, 2010)

I think what you are showing here is the result of compression.....increasing or reducing gain will not affect the dynamic signature and relationships of a complex waveform (compress) until you reach the limits of a systems headroom. When that occurs, the waveform is not compressed but clipped at the peaks, resulting in harmonic distortion (never to be confused with compression).

Your written description is correct, your diagram is misleading.


dafunkmonster said:


> I think what you've missed is this:
> 
> Every device in the chain from signal origin to the amplifier has the ability to boost or attenuate the signal. As has already been stated (somewhere in this thread), you want to keep your signal at a level so that it is well above the noise floor, but not so high that it clips. See picture...
> 
> ...


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## museav (Jan 28, 2010)

I'm not sure what the lower black line is but I took the upper black line to be the maximum signal level, or the clip level, and the idea being to show that you want your signal between that maximum and the noise floor. I think the difference may be that it appears the intent was for the diagram to reflect the path through the, you are not seeing the signal waveform but rather the signal level at different points in the system. Perhaps more like the signal level diagram at the bottom of http://www.yamahaproaudio.com/products/mixers/mg32_24/pdf/MG32_14FX_block_level_diagram.pdf.

In that case it makes the point but is very simplified compared to a real system where the you may have the equipment noise floor and maximum level varying at different points and multiple steps of gain and attenuation affecting both the noise floor and the signal level.


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## gpforet (Jan 28, 2010)

I see now. Man, that confused me big time. Since I was not seeing anything along the horizontal to signify gain stages or components, I thought I was looking at waveform.


museav said:


> I'm not sure what the lower black line is but I took the upper black line to be the maximum signal level, or the clip level, and the idea being to show that you want your signal between that maximum and the noise floor. I think the difference may be that it appears the intent was for the diagram to reflect the path through the, you are not seeing the signal waveform but rather the signal level at different points in the system. Perhaps more like the signal level diagram at the bottom of http://www.yamahaproaudio.com/products/mixers/mg32_24/pdf/MG32_14FX_block_level_diagram.pdf.
> 
> In that case it makes the point but is very simplified compared to a real system where the you may have the equipment noise floor and maximum level varying at different points and multiple steps of gain and attenuation affecting both the noise floor and the signal level.


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