[Brian Huether]

This has confused me for a very long time... I am overwhelmed by how many
various volume controls there are in a signal chain: preamp gain, mixer
channel volume, mixer master volume, powered PA spkr volume. Where should
volume be predominantly controlled? I mean, I figure preamp gain should be
such that you get good dynamic range, and then mixer master should be around
unity and channel volumes some degree +/- unity. Used this method today for
an acoustic/classical guitar duo and could only turn up the PA spkr volume
(Mackie SRM450) up slightly before feedback.

BTW - I am first and foremost a musician and so that might explain why some
of my questions seem so ignorant. But I am trying to be as skilled a sound
person as well.

thanks,

brian

[Scott Dorsey]

Brian Huether wrote:
This has confused me for a very long time... I am overwhelmed by how many
various volume controls there are in a signal chain: preamp gain, mixer
channel volume, mixer master volume, powered PA spkr volume. Where should
volume be predominantly controlled? I mean, I figure preamp gain should be
such that you get good dynamic range, and then mixer master should be around
unity and channel volumes some degree +/- unity. Used this method today for
an acoustic/classical guitar duo and could only turn up the PA spkr volume
(Mackie SRM450) up slightly before feedback.

There is a discussion of gain structure in the FAQ, but what you really want
is the Yamaha Sound Reinforcement Handbook. Really, buy it. It is worth
every penny.

The point at which the system feeds back really has only to do with the
_total_ system gain, though. If you're having feedback issues, it's probably
not due to gain structure so much as mike and speaker placement.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Laurence Payne]

On Fri, 22 Dec 2006 21:12:45 -0500, "Brian Huether"
wrote:

This has confused me for a very long time... I am overwhelmed by how many
various volume controls there are in a signal chain: preamp gain, mixer
channel volume, mixer master volume, powered PA spkr volume. Where should
volume be predominantly controlled? I mean, I figure preamp gain should be
such that you get good dynamic range, and then mixer master should be around
unity and channel volumes some degree +/- unity. Used this method today for
an acoustic/classical guitar duo and could only turn up the PA spkr volume
(Mackie SRM450) up slightly before feedback.


Preamp gain must be set so there is a healthy level with NO chance of
input overload. This is commonly achieved on a mixer by setting
channel and output sliders to nominal zero, adjusting input trim to
approach a nominal level on the output meters. Then back off a bit -
performance levels always creep up louder than soundcheck levels :-)

You then have scope to pull individual channel faders down to achieve
balance. Always reduce the channel that is too loud, don't boost the
one that is too soft. (Though there's a bit of fader above the zero
mark for emergencies :-). Turn the main amplifier levels (or powered
speaker levels) to maximum. If this means the main output faders on
the mixer need to be quite low, fine. If the amplifiers have LOTS of
power available compared with what is required for the room, OK turn
their levels down a bit. But the rule is - amplifiers high, output
low.

Modern mixers are quiet. Even cheap ones sound pretty good until you
push levels too high. You don't have to be frightened of keeping
levels moderate through the mixer.

[Mike Rivers]

Brian Huether wrote:
This has confused me for a very long time... I am overwhelmed by how many
various volume controls there are in a signal chain: preamp gain, mixer
channel volume, mixer master volume, powered PA spkr volume. Where should
volume be predominantly controlled?

You should hear Bob Katz' latest rant. He doesn't believe in using the
term "volume control" since there's no precise definition of "volume"
in the context in which we're accustomed to using it in audio. (as
opposed to the volume of Crown Royal you need to buy in order to get a
bag that fits a particular mic).

I mean, I figure preamp gain should be
such that you get good dynamic range, and then mixer master should be around
unity and channel volumes some degree +/- unity. Used this method today for
an acoustic/classical guitar duo and could only turn up the PA spkr volume
(Mackie SRM450) up slightly before feedback.

You're doing it right. You should get all the low level signal gain you
need right at the front end (the mic preamp) and then run the rest of
the system close to unity gain, making balance adjustments around that
point. Assuming that everything needs to be amplified (not always the
case in a PA system, but always the case in recording) the balance
between channels isn't likely to deviate much more than about +/- 3 dB
from their unity gain position.

The final control, the input level of the power amplifier, can be set
wherever it needs to be in order to get the nominal level you need.
This shouldn't need to change more than about 6 dB during the show
unless the audience starts to get pretty rowdy. Set it so that the
speakers are a little louder than you expect to need in the worst case,
with the meters on the mixer well within their working range when the
master fader is at its unity gain position. It's acceptable to start
out quieter if you need to, with the mixer's master fader below the
unity gain position, but it's bad to need to push it up higher than its
maximum travel.

If feedback is what limits how far you can turn up the final (power
amplifier) gain control, you probably should work on getting rid of
that limitation if feedback occurs below or just barely at your
expected loudest listening level.