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Multiple Gain Staging for Correct PA Output (Preventing Going Into Red)

Smallmouth_Bass

Smallmouth_Bass

Dec 29, 2005
8,005
6,027
Montreal, Quebec, Canada
#1
I find myself running the PA at most of my bar band's gigs. I have a SoundCraft Ui24R digital mixer and we're all on in-ears, but most of the locations we frequent have analogue mixing boards that go to a power amp and to house speakers. One of the difficulties I have is trying not to hit and inputs too hard (at each stage). It seems easy, right? But I often find am going into the red on the mains of the receiving mixer and have my levels maxed out with nowhere to go.

In general, I am setting the input gain (mics or whatever instrument) so that the general level is at O db on the meter (occasional peaks into the yellow band, but stays at the top of the green 98% of the time). I do the same on the mains of the digital mixer, the same on the input of the analogue mixer and mains. Is there a special trick or something I am missing?

A couple of venues, I can bypass their mixer and run straight to the powered speakers and it is much easier and straightforward. Unfortunately, other venues have restricted the access and I have no choice but to piggyback into their system.
 
#4
Smallmouth_Bass said:
The clipping is happening at the output of the mixer I am piggybacking on.
Click to expand...
If I understand correctly, the problem occurs because the gain is too low after the mixer.

I put bold where you indicate the clipping occurs:

Mic > digital mixer channel input > digital mixer mains out > venue analogue mixer channel input > analogue mains out > power amp > passive speakers

If the outputs are hooked up directly to the power amp, either the amp is not turned up enough, the amp is not powerful enough, or there is a mismatch between the output level of the analog mixer and the input sensitivity of the power amp. Some power amps have a switch that allows you to change the sensitivity.

Here's a possibility. The venue has the amps dialed back so it impossible to exceed the desired volume without clipping.

You need to work this out with the venue.

Meter indications can vary between digital and analog. With digital you usually get harsh clipping at the highest LED in the meter. 0 means 0dB of headroom remains.

From Yamaha LS9 OM

1767591669317.png


The meters on analog boards have a transition at 0dB. Where clipping occurs varies from model to model. It may be at +3dB, +6dB, or higher. The meter leds may turn from green to orange as the level goes above 0dB. There may also be a transition from orange to red leds.

Form A&H MixWizard 16 OM

1767591482344.png
 
#5
Wasnex said:
If I understand correctly, the problem occurs because the gain is too low after the mixer.

I put bold where you indicate the clipping occurs:

Mic > digital mixer channel input > digital mixer mains out > venue analogue mixer channel input > analogue mains out > power amp > passive speakers

If the outputs are hooked up directly to the power amp, either the amp is not turned up enough, the amp is not powerful enough, or there is a mismatch between the output level of the analog mixer and the input sensitivity of the power amp. Some power amps have a switch that allows you to change the sensitivity.

Here's a possibility. The venue has the amps dialed back so it impossible to exceed the desired volume without clipping.

You need to work this out with the venue.

Meter indications can vary between digital and analog. With digital you usually get harsh clipping at the highest LED in the meter. 0 means 0dB of headroom remains.

From Yamaha LS9 OM

View attachment 7402750

The meters on analog boards have a transition at 0dB. Where clipping occurs varies from model to model. It may be at +3dB, +6dB, or higher. The meter leds may turn from green to orange as the level goes above 0dB. There may also be a transition from orange to red leds.

Form A&H MixWizard 16 OM

View attachment 7402749
Click to expand...

One venue is like this, I think. The power amp is actually in a case that's locked that I cannot see or access the settings.

The one I played this past weekend, I had access to the power amp and the settings appeared to be good. Plus, a DJ came in after us and ran through the same system and it was way louder than we were.

Interesting enough, we were running into an Allen & Heath MixWizard WZ3 16:2. I think I will have to play with the input level/gain of the channel on the A&H. It's the only input where I do not see any metering. Is that what the PFL button does?
 
#6
Smallmouth_Bass said:
One venue is like this, I think. The power amp is actually in a case that's locked that I cannot see or access the settings.

The one I played this past weekend, I had access to the power amp and the settings appeared to be good. Plus, a DJ came in after us and ran through the same system and it was way louder than we were.

Interesting enough, we were running into an Allen & Heath MixWizard WZ3 16:2. I think I will have to play with the input level/gain of the channel on the A&H. It's the only input where I do not see any metering. Is that what the PFL button does?
Click to expand...


PFL stands for pre fader listen. Pressing the PFL on a given channel allows you to monitor the level on the meter and solo the channel in the monitor (headphone) bus. If you press the PFL on multiple channels, the levels are summed at the meter and mixed in the headphone bus.

You might want to read the MixWiz 3 manual: https://prosoundonline.com/wp-content/uploads/AllenHeath_WZ3162_Manual.pdf
 
#7
Wasnex said:
PFL stands for pre fader listen. Pressing the PFL on a given channel allows you to monitor the level on the meter and solo the channel in the monitor (headphone) bus. If you press the PFL on multiple channels, the levels are summed at the meter and mixed in the headphone bus.

You might want to read the MixWiz 3 manual: https://prosoundonline.com/wp-content/uploads/AllenHeath_WZ3162_Manual.pdf
Click to expand...

Yes, thanks! I already downloaded it and had a quick look.

Ideally, the venues (or the band) would have a dedicated soundman. Unfortunately, that is not in the budget and we have to make due with our (my) limited skills.
 
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#8
Sounds like you are clipping at the venue's mixer because you are plugging your Line level main outs from your mixer into the Mic level inputs on the venue's mixer. So you are sending a line level signal through a preamp giving it even more gain and that will cause it to clip. You need to connect your mixer to Line level inputs on the venue's mixer.
 
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#11
TommyGunz said:
Sounds like you are clipping at the venue's mixer because you are plugging your Line level main outs from your mixer into the Mic level inputs on the venue's mixer. So you are sending a line level signal through a preamp giving it even more gain and that will cause it to clip. You need to connect your mixer to Line level inputs on the venue's mixer.
Click to expand...

I am aware of this. I think it is a result of different venue systems, a condensed setup time and no real soundcheck. And, I am fully aware that you cannot really mix from the stage. Add to that, the individual band members asking for monitor adjustments - it can be somewhat stressful when things are not going properly (including troubleshooting venue's equipment when it's not working properly).

All it takes is a missed pressed chicklet button or a mute somewhere in the line...

On the positive side, I save all the venue's settings in the digital mixer, so provided my band members are not constantly changing their equipment and levels, we only usually have to tweak settings. It's just getting proper and balanced levels out front.

Drum bleed into the vocal mics, that's a whole other issue!
 
#12
Smallmouth_Bass said:
I am aware of this. I think it is a result of different venue systems, a condensed setup time and no real soundcheck. And, I am fully aware that you cannot really mix from the stage. Add to that, the individual band members asking for monitor adjustments - it can be somewhat stressful when things are not going properly (including troubleshooting venue's equipment when it's not working properly).

All it takes is a missed pressed chicklet button or a mute somewhere in the line...

On the positive side, I save all the venue's settings in the digital mixer, so provided my band members are not constantly changing their equipment and levels, we only usually have to tweak settings. It's just getting proper and balanced levels out front.

Drum bleed into the vocal mics, that's a whole other issue!
Click to expand...
In my neck of the woods, most bands have their own monitor rigs - to run IEM’s and/or wedges.
They also have splitter snakes when using the House PA. My sat gig will be using an X32 Rack with a 16-ch splitter snake, with the snakes stage box housed in the same rack as the X32. We all connect directly to the splitters stage box.
One side of the splitter goes to the bands mixer, the other to the House.
One of my other bands uses the UI24, but again with a splitter snake.

This configuration makes your issues instantly vanish as you only need to configure the Ui24 for your ears, not feeding FOH.
 
Last edited:
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#14
s0c9 said:
In my neck of the woods, most bands have their own monitor rigs - to run IEM’s and/or wedges.
They also have splitter snakes when using the House PA. My sat gig will be using an X32 Rack with a 16-ch splitter snake, with the snakes stage box housed in the same rack as the X32. We all connect directly to the splitters stage box.
One side of the splitter goes to the bands mixer, the other to the House.
One of my other bands uses the UI24, but again with a splitter snake.

This configuration makes your issues instantly vanish as you only need to configure the Ui24 for your ears, not feeding FOH.
Click to expand...

Forgive my ignorance: what is a splitter snake? You send all the input lines to an analogue board and have to remix for front of house?
 
#18
Smallmouth_Bass said:
And that happens before going to the monitor mixer? Or is it taking a feed out of the monitor mixer?
Click to expand...

The split is usually before the inputs of both mixers. I.E. both mixers get an unprocessed signal from each sound source.


There are different ways of doing it.

Crest used to make small analog monitor mixer (XR20M). The channels had split outs so you didn't need a separate splitter snake.
1767832019347.png


The split can also be done in the digital domain. With digital, one mixer may need to function as a master to set input gain levels. Both boards get exactly the same unprocessed signals.
 
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#19
Smallmouth_Bass said:
Forgive my ignorance: what is a splitter snake? You send all the input lines to an analogue board and have to remix for front of house?
Click to expand...

A splitter snake as just like a venues stage box.. the ones in the pic are analog, there are digital ones that work with specific vendors mixers tho.
Basically you plug into the stage box like the 32-ch one in this pic.
One of those sets (legs) of XLR cables goes to your IEM mixer, the other goes to the House - either directly to the back of their mixer, or into THEIR stage box up on the stage.
There are various configs, but thats' the simplest explanation.
Well worth the investment!

1767833200959.png
 

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