Peavey CS 1200X manual DDT’lM Compression, Thermal System

turn really is maximum compression range), the input sensitivity control should be set at Ihe maximum clockwise setting. This is always the best setting to start with. If, however, the ampti- fier is used in a small club, church, or studio application where the full-output capability of the power amplifier is seldom needed, or there is no need for large amounts of headroom capability, the full-clockwise setting may not be the wisest choice. Then too, such applications often require low system noise. In this case, it is possible to reduce the overall system noise at the expense of headroom capability by increasing the power amplifier sensitivity as in the following example: if, instead of a sensitivity rating of +3 dB V, we adjust the CS 1200X to a rating of + t2dB V, overall system noise wilt be improved by 9 dB, and the system headroom will decrease 9 dB.

DDT’lM COMPRESSION

The CS 1200X is a compact and powerful amplifier that features a new type of dynamic com- pression. This compression system enables the user to maximize the performance of the ampti- fier/speaker combination. We have determined through much research that the compression circuitry should prevent the power amplifier from running out of headroom (clipping) and should be as simple to operate as possible to avoid undue complication for the user. This compression system is activated by our exclusive DDT compression circuitry, which senses conditions that might overload the amplifier and activates compression when clipping is imminent. In other words, compression takes place whenever signal conditions exist that prevent the amptil‘iers from faithfully reproducing the input signal. In this case, threshold is clipping itself, and no specific threshold control is provided. This technique effectively utilizes every precious watt available from the power amplifier. Techniques using external compressors/limiters are usually less effective, severely limit output power levels and require additional controls, and add complexity to an already complicated system. The DDT system is an automatic, hands-ofl‘approach to Ihe problem of amp clipping. Because of the dynamics of music and vocals, it is quite common lo activate the DDT compression circuitry almost constantly during a high-level performance, since this is what it was designed to do: i.e., to maximize the dynamics available from the amplifier within its power-output capabilities regardless of power supply/AC line voltage variations and load impedance selection. Defeating the DDT compression should be very carefully considered before one just “flips the switch.” Most loudspeaker systems simply cannot handle the square wave power of the CS 1200X, and defeating the D9T system opens up the door for sevcrc clipping! Often studio engineers feel the need to defeat the DDT compressor, for fear it might color the sound in studio listening. The DDT compressor is only activated when clipping is imminent. LJntit this occurs, it’s simply a passive friend. The only reason the dcfcat switch is there in the first place is to allow check-out technicians to evaluate the power amplifier at clip- ping. Valuable performance illformation, such as power- supply ripple and regulation, can only be assessed when an amplifier is allowed to clip.

THERMAL SYSTEM

The CS 1200X has a unique thermal system that employs a tunnel-type heat sink design to provide maximum cooling for the 32 power transistors (16 for each channel). A single 100 CF;M fan mounted on the back panel of the unit provides an almost unrestricted airflow through Ihe tunnel to provide the lowest possible operating temperature for the power devices. This approach is so efficient that even continuous operation into 2 ohms will not cause a thermal shutdown unless the ambient air temperature is considerably higher than normal (above 40” C). Under

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