Peavey CS 1200 User Manual

FRONT PANEL
INPUT SENSITIVITY CONTROLS (1)
The CS-1200 employs a 31 detented, calibrated sensitivity control tor each channel. These controls are labeled in a more functional
manner, replacing the conventional Oto 10 segmented circle with the actual input sensitivity ratings of the amplifier for various settings uf this
control. In the past, this control has often confused even the most experienced audio technician as to its purpose and usage, especially when
it is simply called level (rather than sensitivity). This new labeling/calibrating technique will help to explain the need and function of these
controls and the significance of the sensitivity rating. We offer the following in way of explanation: The input sensitivity rating of a power
amplifier is the RMS voltage level required at the input to produce full rated power into the rated load at the output. This voltagethen becomes
the level at which the associated mixer must operate in order to drive the amplifier to full output. Operation at levels above this rating wil
causethepoweramplifiertoclip (produce distortion) unlessthe associated amplifier has acompressoror limiterto mimmizethisdistortion
Such a system, called DDT'" (U.S. Patent #4.318,053). Is included in CS-1200 power amplifiers, and the advantages should be obvious.
Without DDT, the sound engineer must "ride gain” on the mixer in order to prevent power amp clipping.
Traditionally, the input sensitivity rating of a power amplifier receives low billing on a typical specification sheet Often it gets lost among
other interesting specs, such as damping factor, slew rate, transient intermodulation distortion and others. This rating, however, must be
known to have performance visibility at the mixer. Further, the rated sensitivity on the spec sheet is only correct when the power amplifier
sensitivity control is set at full clockwise or maximum setting. Any other setting increases the value. With a numbered circle from Oto 10, this
new higher value is not indicated. Thus, the CS-1200 sensitivity control is calibrated in both RMS voltage levels (usually given in power amp
spec sheets) and the equivalent dBV values (usually listed in typical mixer specs). ThedBV values are more useful, since most contemporary
mixers employ LED arrays to indicate mixer output levels and are calibrated in dBV Knowing the power amplifier sensitivity rating in dBV will
allow the mixer operator to knowthestatus of the power amplifier (whether they areclipping/ccmpressmg or not) by noting which LED on the
mixer is peaking. Obviously, the LED labeled the sameor closest to thesensitivity rating of the power amplifier will indicate full power output
of the system. Operation below that level will indicate how much so called power amplifier headroom is left. Operation above that level will
cause clipping (or compression if the DDT system is operational). Perhaps an example will be helpful: Referring to the CS-120G face plate,
you will notice that at full clockwise setting of the sensitivity control, the sensitivity rating is 1.4V RMS or +3 dBV The critical LED on the
driving mixer then is the one labeled +3dBV. It will correlate with the CS-1200 DDT active LED in that whenever the +3 dBV LED on the mixer
flashes on peaks, the DDT active LED will also flash indicating full power output is achieved. If the CS-1200sensitivity control was adjusted to
a higher value, this new value would become the new correlation level on the associated mixer. There is a very simple rule regarding the
setting of the sensitivity (or level) control
“Unless there is a specific reason not to, the sensitivity control on any power amplifier should be set to full clockwise
position, resulting in the minimum sensitivity rating.’’
There are several valid exceptions to thefull clockwise rule The first one presented here Involves large systems where it is often necessary
to employ many power amplifiers to supply the same signal to multiple speaker systems to achieve the necessary sound pressure levels or
audionce coverage. If thevarious power amplifiers have different sensitivity ratings and/or the various loudspeaker enclosures have different
efficient ratings, then it might bonecessary to adjust certain sensitivity controls to achieve a balanced sound pressure level between The parts
of the system. In this case, the loudest amplifier/speaker combinations will require those amplifier sensitivity controls to be adjusted
counter-clockwise asnesessary. Often in such systems, both Peavey and non-Peavey power amplifiers might be employed. In this case, as a
starting point, it might be necessary to match thesensitivity rating of the Peavey power amplifier to that of the competitive power amplifier. As
an example, several competitive power amplifiers on the market have a sensitivity rating of 2 volts RMS (that’s +6 dBV as read from the
CS-i 200 sensitivity control clock). If such a competitive amplifier is used with the CS-1200, then the CS-1200 must beset to +6 dBV. A second
valid exception to the rule might occur whenever a biamp system is used. This exception will be discussed later in this manual when biamped
systems are presented. A third valid exception is involved in small club, church and studio applications, where the full power output capability
of the power amplifier is not needed or there is no requirement for large amounts of headroom capability. Simultaneously, these applications
usually require a very low noise system. In thiscafce, it is possible to reduce the overall system noise at the expense of headroom capability by
increasing the power amplifier sensitivity accordingly. As an example, if instead of a sensitivity rating of +3 dBV, we adjust the CS-1200 to a
rating of +10 dBV, overall system noise will improved by 7 dB with the resulting 7 dB decrease in system headroom Remember, once this is
done, the mixer operator cannot reestablish full headroom performance settings atthe mixer. If he wants this headroom back, he must doit by
resetting the power amplifier sensitivity

Peavey CS 1200 Specifications

General

Channels	2
Signal to Noise Ratio	> 100 dB
Input Impedance	20k ohms balanced, 10k ohms unbalanced
Weight	35 lbs
Dimensions	3.5" H x 19" W x 15.25" D