Peavey PA 700S - Page 2

PA-7005
If any mixing unit is to be compatible with a
wide variety of input signals it must have the capa-
bility to control the sensitivity of each channel.
This requires an INPUT ATTENUATOR (1) some-
times referred to an an input pad. Some mics
and
signal
sources
can
be
at
such
a
level
as
to
overdrive or clip the input circuitry of a mixer.
An input attenuator allows the operator to reduce
the input gain when input clipping occurs. Some
manufacturers put attenuators in their snake
or stage box to be able to control the sensitivity
of
the
mic
or
signal
source.
This
is
not
the
best
approach if you are sending your signals through
cable runs of any length. Many times it would be
impossible to make an adjustment on one of the
attenuators if necessary during the performance.
You shouldn’t have to run up to the stage and
pick up the drummer's leg so you can adjust a
mic input!
In use, the operator must adjust the input
attenuator in such a manner that input clipping
is avoided. This can easily be done by setting up
the channel with the highest expected input sig-
nal level and adjusting the input attenuator so that
no clipping or distortion is heard from the speaker
system. After the mixer has been used several
times, the operator will have a very good idea of
the signal levels encountered and will be able to
set up the attenuators accordingly. The different
types -of microphones will have different output
levels and different performers will get widely
varying levels from mics depending on the strength
of their voices and/or their basic “mic techniques”.
The input attenuator should be operated in
the position yielding the least attenuation required
to avoid clipping. Operation in this mode allows
maximum gain to be utilitized in the input preamp
where it is most efficiently obtained. Excessive
input padding sometimes makes necessary higher
settings of the channel gain controls and/or master
control thus yielding a less than optimum signal-
to-noise ratio for any given situation.
It is important to realize that not all “break-
up” is caused by the mic signal overloading the
input stage of the mixer. If the performer's mic
technique includes very close and/or very loud
situations, the internal elements of the mic can
“bottom out” or distort just as a loudspeaker can
when it is overdriven. Quite a few of the mics
now used by performers lack the dynamic range
required to adequately handle the tremendous
sound pressure levels encountered in a very loud
rock and roll concert situation. It is vital for the
professional soundman and the musicians to be
aware of the limitations of the various links in
the audio system in order to correctly diagnose
and solve the various problems encountered in
a sound reinforcement situation.
Overall, the input attenuator is the first
control in the circuit and must be set up properly
in order for the remaining circuits to function
properly. “Common sense” and experience opera-
ting the PA 7005 on several jobs will allow the