ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: JonDunlap on March 20, 2017, 04:57:46 pm

Title: Setting System Gain
Post by: JonDunlap on March 20, 2017, 04:57:46 pm
My Equipment:
Yamaha MG 24/14fx Mixing Console
Yamaha PS7000 Amp (Running Yamaha SW118 Subs)
Yamaha PS3500 Amp (Running Yamaha SV115 Mains)

Today I attempted to set my system gain. Would just like some feedback as to wether I did it correctly, anything I might have missed, done wrong etc...

1. Turned amp sensitivity all the way down.
2. Unhooked Speaker.
3. Hooked Input device through Stereo Channel on mixer.
4. Turned fader all the way down on channel.
5. Set stereo bus fader to "0"
6. Ran Pink Noise through channel to set input level.
7. Adjusted gain on channel to set level just above "0" (+3...mixer goes to +5 then clip)
8. Maxed out fader on channel with Pink Noise. Level was just barely clipping so I backed off the
    gain a touch.
9. Rolled up the sensitivity on the amp channels until they clipped, then backed them off 1-2
    notches.

Does it sound like I did any of it right or am I even close?
Title: Re: Setting System Gain
Post by: Jean-Pierre Coetzee on March 20, 2017, 05:23:00 pm
My Equipment:
Yamaha MG 24/14fx Mixing Console
Yamaha PS7000 Amp (Running Yamaha SW118 Subs)
Yamaha PS3500 Amp (Running Yamaha SV115 Mains)

Today I attempted to set my system gain. Would just like some feedback as to wether I did it correctly, anything I might have missed, done wrong etc...

1. Turned amp sensitivity all the way down.
2. Unhooked Speaker.
3. Hooked Input device through Stereo Channel on mixer.
4. Turned fader all the way down on channel.
5. Set stereo bus fader to "0"
6. Ran Pink Noise through channel to set input level.
7. Adjusted gain on channel to set level just above "0" (+3...mixer goes to +5 then clip)
8. Maxed out fader on channel with Pink Noise. Level was just barely clipping so I backed off the
    gain a touch.
9. Rolled up the sensitivity on the amp channels until they clipped, then backed them off 1-2
    notches.

Does it sound like I did any of it right or am I even close?

Some questions:

I'm pretty sure that it would work better to have had a dummy load connected or to just look up to voltages in the manual and done some basic math and gotten to an approximate exact number.

From what is see in the manual the PS3500 will clip before the PS7000, you will probably have the attenuator on one set around 20 and the other just before the 25 mark on the amp if I look at it quickly.
Title: Re: Setting System Gain
Post by: JonDunlap on March 20, 2017, 06:05:14 pm
Some questions:
  • Were you at clip or just below clip on your master output when you set the amps to at/just below clip?
  • Did you have the filter engaged for the subs when you set the amps to at/just below clip
  • You are aware that you adjusted the input attenuators and not input sensitivity?

I'm pretty sure that it would work better to have had a dummy load connected or to just look up to voltages in the manual and done some basic math and gotten to an approximate exact number.

From what is see in the manual the PS3500 will clip before the PS7000, you will probably have the attenuator on one set around 20 and the other just before the 25 mark on the amp if I look at it quickly.

#1..I was just below clip when I set the amps. My meter goes to +5 then the next light is clip...I set it at +3.

#2..By filter are you talking the one on the back of the amp? If so, yes it was engaged.

#3..when you say attenuators vs. sensitivity are you talking about the dials on the amp?
Title: Re: Setting System Gain
Post by: Paul G. OBrien on March 20, 2017, 06:31:56 pm
Quote from: JonDunlap
5. Set stereo bus fader to "0"
Not correct IMO, it should go to whatever position produces roughly 0dB on the meters, and that position will be lower the more inputs are connected to the console.
Quote from: JonDunlap
8. Maxed out fader on channel 
I'd also chose unity(0dB) not max position here.

My experience with these Yamaha mixers is that they don't appear to have as much headroom as some of its direct competitors so you NEVER want the signal level to exceed unity or 0dB on the meters at any stage, that means the only control that will end up at or near unity are the channel faders.
Title: Re: Setting System Gain
Post by: Ivan Beaver on March 20, 2017, 07:22:14 pm
There are basically 3 ways to set "system gain".

1: For the most dynamic range.  This DOES NOT mean it will get any louder.  But if setup properly it will get quieter.

Not in max output, but rather by lowering the noise floor.

2: Have "0" on the console indicate where the amps are clipping.

3: Have "0" on the console indicate some predetermined SPL.  This is most common in Churches.

There are of course some variations, but those are the basic ones.

So FIRSTS you need to determine what you want to accomplish by "setting system gain".

Then use the method to suite that end.
Title: Re: Setting System Gain
Post by: Tim McCulloch on March 21, 2017, 12:15:08 am
Hi Jon-

You can use the search engine of your choice for "Piezo clipping test".  It's method #1 in Ivan's list.

In a nutshell, you use a sine wave instead of pink noise or program material and you listen for the harmonics of clipping in the piezo tweeter.  You started at the mixer and worked your way down system EQ & EFX to the system crossover or power amp inputs.  It results in a system where every item in the signal chain clips at the same time (more or less), so any actual clipping on the console outputs mean everything else downstream is just under or at clip.  You'll have a VERY hot signal.

In this method, if you're driving your amplifiers directly you will very often have their input level controls set considerably lower than you might have in the past.

You end up with a very quiet system - very low self noise - but you'll be running the console hotter.

Anyway, do a search and see what you think.  You seem to have space to work and the inclination to experiment so maybe try a couple of ways and post back with how they did and did not work for you.
Title: Re: Setting System Gain
Post by: Brian Jojade on March 21, 2017, 12:27:51 am
There are basically 3 ways to set "system gain".

1: For the most dynamic range.  This DOES NOT mean it will get any louder.  But if setup properly it will get quieter.

Not in max output, but rather by lowering the noise floor.

2: Have "0" on the console indicate where the amps are clipping.

3: Have "0" on the console indicate some predetermined SPL.  This is most common in Churches.

There are of course some variations, but those are the basic ones.

So FIRSTS you need to determine what you want to accomplish by "setting system gain".

Then use the method to suite that end.

#3 is typically where I try to set the system.  I generally want the loudest sound I plan to run the evening to be somewhere near 0db on the mixer.  Usually, if that's the case, that then means #1 is pretty close to true as well.  If that means #2 is also correct, then I need a bigger rig.
Title: Re: Setting System Gain
Post by: Tim Padrick on March 21, 2017, 12:37:08 am
The common wisdom is to set up the gain structure such that everything clips simultaneously.  Unless the system has a LOT of headroom over what you'll need, I disagree with this methodology.  Most "weekend warrior" systems will occasionally (if not often) be run hot enough that there will be a little amp clipping.  This can slip by relatively unnoticed if it's not too much too often.  However if something else in the system clips at the same time, it will sound BAD.  You want headroom in everything ahead of the amps so that there is no chance of clipping anyplace else.  If you are using system limiters, this this is especially important.

Most boards and processors can put out around +22 dBu.  I recommend that the gain structure be set up such that the amps clip with the board and processors no hotter than say +12 (consult your owners manual to figure out where on the meters that is - some have 0 = 0 dBu, some don't).  This will give you a 10dB margin between board/processor clipping and amp clipping.  Then of course don't forget to set the system limiters.   You'll be able to push the system with minimal sonic degradation.

Amp level controls: If you run the amps full, if they get messed with, things will get quieter - no biggie.

If you run the amps at less than full, the amps can be turned up by accident or by a saboteur.  If your system limiters are ahead of your amp level controls, your limiters just became useless.
Title: Re: Setting System Gain
Post by: Ivan Beaver on March 21, 2017, 07:26:56 am
The common wisdom is to set up the gain structure such that everything clips simultaneously.  Unless the system has a LOT of headroom over what you'll need, I disagree with this methodology.  Most "weekend warrior" systems will occasionally (if not often) be run hot enough that there will be a little amp clipping.  This can slip by relatively unnoticed if it's not too much too often.  However if something else in the system clips at the same time, it will sound BAD.  You want headroom in everything ahead of the amps so that there is no chance of clipping anyplace else.  If you are using system limiters, this this is especially important.



I agree with this.

I almost every case I am willing to give up a couple of dB of noise floor in order to keep the system from "totally crapping out" on the short peaks.

If only the amps (most amps anyway) are clipping, most people will not notice.

But if everything clips (especially digital gear) it can sound quite bad.

If you do blind testing, it will surprise people how much clipping is going on before they actually detect/hear it.
Title: Re: Setting System Gain
Post by: Mark Amber on March 24, 2017, 03:55:10 pm
In the world of 0dBFS being the absolute max... and somehow so easy to hit, this is something that interests me a lot.

Here's a situation I run in to a lot (and a way I fix it which I don't quite like):

My subs are on a matrix or aux. I want my subs to be "10 dB ish louder than my mains" (I don't mean literally 10 dB, I mean I want the customer to smile and that means running my subs as loud as possible with no regard for balance... that's not to say loud subs aren't fun)

I push my "subs" matrix up until the mixer output clips... but what's this?? The amp doesn't clip!  Oh it's because I have a LPF on there at around 80 Hz. Shoot well that stinks now I turn the output of the processor up... but now my clipping doesn't line up anymore! What to do?

I put a LPF on my console. Then I have a LPF on my processor and console. Not good. But at lease I can push my subs harder.

What am I battling against? What might be the best option?


Sent from my iPhone using Tapatalk
Title: Re: Setting System Gain
Post by: Geert Friedhof on March 24, 2017, 08:02:38 pm
Play music at 95-100dB, adjust low and/or high amplifier to taste where one of them is at max, and be done.
Title: Re: Setting System Gain
Post by: Luke Geis on March 25, 2017, 01:21:31 pm
In the world of 0dBFS being the absolute max... and somehow so easy to hit, this is something that interests me a lot.

Here's a situation I run in to a lot (and a way I fix it which I don't quite like):

My subs are on a matrix or aux. I want my subs to be "10 dB ish louder than my mains" (I don't mean literally 10 dB, I mean I want the customer to smile and that means running my subs as loud as possible with no regard for balance... that's not to say loud subs aren't fun)

I push my "subs" matrix up until the mixer output clips... but what's this?? The amp doesn't clip!  Oh it's because I have a LPF on there at around 80 Hz. Shoot well that stinks now I turn the output of the processor up... but now my clipping doesn't line up anymore! What to do?

I put a LPF on my console. Then I have a LPF on my processor and console. Not good. But at lease I can push my subs harder.

What am I battling against? What might be the best option?


I actually posted a video realted to this a couple weeks ago: https://www.youtube.com/watch?v=ycJfDYpkpMk

My approach would be to set the amps full up and adjust the needed gain via the DSP processing.

There are several ways to setup gain structure. The most common is to set for everything clipping at once. Not truly bad since if you see red, you know your at the end of the line. Not hard to tell if things are going bad either. The most proper way to set gain structure is probably to go for the most dynamic range by making it so that each piece of gear inline has outputs and inputs set to be more in sync with each other. You don't gain output, but you lower the noise floor and you get as much level as is needed. In theory, if done this way, the unit with the lowest output capability will be the determining factor for max level output. Most all units these days will output enough to clip just about any amp.

The good old where to set the amp gain knob at question. As mentioned, all the way up is pretty much standard practice these days. The beauty of the amplifiers gain knob is that it is not actually a gain knob at all; it's an attenuation knob. The amp is a fixed gain beast. What you put in will be output at some ratio higher than the input. While not ideal to clip the amplifier, the hope is that the system will get more than loud enough long before the amp clips anyway. If you need less output, it is best done by turning things down earlier in the chain. This is of course unless your amp has a lot of hiss and self noise when fully opened up. If you need a quieter system, you may need to attenuate the amps input a little to get the noise floor down. In most cases the hiss and self noise of the amps is negligible in comparison to other parts of the system. Just listen to the noise made when you have 16+ channels up in a quiet room. The mixer and channels self noise will outweigh the amps self noise considerably.
Title: Re: Setting System Gain
Post by: Jordan Wolf on March 26, 2017, 10:49:45 am
There's a RaneNote (http://www.rane.com/note135.html) for that!

Hi Jon-

You can use the search engine of your choice for "Piezo clipping test".  It's method #1 in Ivan's list.