PA Powered Amp Gain Settings Question

[email protected] wrote:
> So I've been trying to look around the Internet for information on how
> I should have my powered amplifier set for my PA which I'm using for
> singing in a rock band.

> I found this video
> Which suggests turning down the powered amp gain and settings all
> volume knobs to unity (0) and turning my mixer preamp gain up until
> clipping occurs while the mic is in use (someone singing loudly into
> it, basically).

You should probably leave a little more headroom than that (turn the
gain up until it clips and then turn it down about 6 dB) but that's not
a bad procedure when you don't know anything else about a system.

> After following this advice I only turn my powered amp up to about 25%
> before I start getting feedback.

Feedback is definitely a limiting point, but it has nothing to do with
gain structure, and everything to do with system gain which includes the
microphones, the speakers, the air between them, and the walls, floor,
and ceiling that reflect sound.

> Is this too low to have my powered amp gain set to?

It doesn't matter. I would be inclined to maybe lower the mixer output a
bit and raise the power amp gain to compensate, but you should be
shooting for a gain setting that gives you the sound as loud as you need
it, not the gain at which the system feeds back. If you can't get enough
volume before feedback, gain staging won't fix your problem. Moving mics
and speakers, and maybe improving mic technique and getting the proper
mics is the way to solve that, as well as some minor equlaization of the
system.

> According to this other video I found on youtube it is:
> He seems to be saying that having your amp gain turned down is
> 'shutting the door' on the sound.

I didn't watch the video, but from your summary it sounds like he's full
of horse manure. Dood, don't try to learn about sound system setup from
YouTube videos. Get yourself a copy of the Yamaha Sound Reinforcement
Handbook and hang out with some people who know how it all works.


--
If you e-mail me and it bounces, use your secret decoder ring and reach
me here:
double-m-eleven-double-zero at yahoo -- I'm really Mike Rivers
([email protected])

<[email protected]> wrote:
>So I've been trying to look around the Internet for information on how
>I should have my powered amplifier set for my PA which I'm using for
>singing in a rock band.

You want to read the discussion of gain structure in the FAQ for this
newsgroup, or in the Yamaha Sound Reinforcement Handbook.

>I found this video: http://www.youtube.com/watch?v=tornRFVtGxI
>
>Which suggests turning down the powered amp gain and settings all
>volume knobs to unity (0) and turning my mixer preamp gain up until
>clipping occurs while the mic is in use (someone singing loudly into
>it, basically).

This seems kind of silly... if you do this, your console will clip long
before the amp will.

>After following this advice I only turn my powered amp up to about 25%
>before I start getting feedback.

The feedback issue is totally different. Gain structure has nothing to
do with feedback... feedback is a function of the total gain of the system
and the placement of mikes and speakers, and the room. You can have all
the gain on the console or all the gain on the amp and it will still
feed back at the same point. It will clip at a different point and it
will change the noise floor, but it won't do anything about feedback.

>Is this too low to have my powered amp gain set to?
>
>According to this other video I found on youtube it is:
>http://www.youtube.com/watch?v=G0WrHpZxN3g
>
>He seems to be saying that having your amp gain turned down is
>'shutting the door' on the sound.

In a perfect world, you would set your gain structure up so that everything
in the signal path clipped at about the same time. This gives you the
lowest possible noise and the highest possible level.

However... that doesn't help you. You can already turn the level up to
the point where it feeds back, so being able to turn it up any farther
doesn't do you any good.

>Which of these people is correct? I'm inclined to believe the first
>guy since he seems to be a professional but I'm confused.

Neither one of them, but it's not relevant to your problem anyway.
Get the Yamaha Sound Reinforcement Handbook.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

On Jul 17, 7:15 pm, [email protected] wrote:
> So I've been trying to look around the Internet for information on how
> I should have my powered amplifier set for my PA which I'm using for
> singing in a rock band.
>
> I found this video:http://www.youtube.com/watch?v=tornRFVtGxI
>
> Which suggests turning down the powered amp gain and settings all
> volume knobs to unity (0) and turning my mixer preamp gain up until
> clipping occurs while the mic is in use (someone singing loudly into
> it, basically).

Anyone who tells you to intentionally clip a signal is defacto wrong.

> After following this advice I only turn my powered amp up to about 25%
> before I start getting feedback.
>
> Is this too low to have my powered amp gain set to?

Probably.
Look at the amp level control as a trim of sorts, an attenuator
really.
In most cases it should be at full or near full, unless it needs to be
lower to correct some other problem in the gain structure.

> According to this other video I found on youtube it is:http://www.youtube.com/watch?v=G0WrHpZxN3g
>
> He seems to be saying that having your amp gain turned down is
> 'shutting the door' on the sound.

Kinda goes along with what I said.
The overall volume should be controlled at the main faders on the
mixer.
Is there any gain reduction in the system ? Compressor, or clipping
protection on the amp ? This needs to be taken into account for
setting
overall system gain.

Basically, I'd set the amp on max, the channel trims so the channels
DON'T clip, the channel faders to set mix balance and the main faders
to control volume as needed.

> Which of these people is correct? I'm inclined to believe the first
> guy since he seems to be a professional but I'm confused.

Mike's advise to read the Yamaha "bible" is your best bet.

rd

On Thu, 17 Jul 2008 17:57:55 -0700 (PDT), RD Jones <[email protected]>
wrote:

>Anyone who tells you to intentionally clip a signal is defacto wrong.

Unless, of course, if it has an "11" setting. This is
the defacto setting for a band's last tour.

Much thanks, as always,
Chris Hornbeck

On 2008-07-18, RD Jones <[email protected]> wrote:
>
> Probably.
> Look at the amp level control as a trim of sorts, an attenuator
> really.
> In most cases it should be at full or near full, unless it needs to be
> lower to correct some other problem in the gain structure.

I like to have the metering on my desk giving an indication of how my
amp's doing, so the "set your system so it all clips at once", or at
least the red lights on the desk mean you're getting close.

On the other hand I've not had to take a system that loud in any room
I've worked - or rather my power amp has always had more than enough
power for what I need. I tend to set its gain lower then so I get the
kind of levels I need while working the desk nearer its 0dB point which
would seem better from a noise point of view. I still have headroom in
the desk (another 18dB or so on mine). Thinking of it, the Loft Theatre
where I learned used to be the same kind of setup.

In the theatre setup I've been known to tweak the power-amp settings
to compensate for the difference between empty house and full house of
sound absorbing audience - another probably better idea is to tweak the
masters on the desk - so that the queued effects levels are still OK
and I still say "Dog barking, up-stage-right, -20dB"

The church I help out likes to run its desk signals around -20dB or below
which seems low, but with so many auxes going in so many places changing
it in the half hour before a service is not going to happen. If the amps
and speakers can take it (maybe I'll find out one day but I expect they
can) it means we could deafen the congregation quite nicely. I wouldn't
be surprised if the installer calibrated it so that things start clipping
together.

- Richard