TourClass® Protection Features.
Every model in the CK Power Processing incorporates TourClass protection features. Derived from Crest’s extensive experience with the world’s largest sound rental companies, the TourClass group of circuits sets new standards in load and amplifier protection.
ACL (Active Clip Limiting).
At the amplifier’s full power, or clipping point, ACL will be activat- ed. This is indicated by illumination of the Clip/ACL LED. The channel gain will automatically be reduced, guarding the loudspeak- ers against damaging high power and continuous square waves that would otherwise be produced. Situations that may activate ACL include: uncontrolled feedback, oscillations, or an improper equip- ment setting or malfunctions upstream from the amplifier. Normal program transients will not trigger ACL; only steady or excessive clipping will. ACL is virtually transparent in operation and full sig- nal bandwidth is maintained. If NexSys control is installed, ACL operation is reported to NexSys.
IGM Impedance Sensing.
IGM (Instantaneous Gain Modulation) is an innovative circuit that allows the amplifier to operate safely into any load. When the ampli- fier sees a load that overstresses the output stage, the IGM circuit adjusts the channel gain to a safe level. Like ACL, the IGM circuit is inaudible in normal use. In addition, if extreme low impedance is encountered, the amplifier’s output relay will open. If NexSys con- trol is installed, IGM operation is reported to NexSys.
AutoRamp Protection.
AutoRamp operates every time the amplifier is turned on or is reacti- vated after a protect condition. This exclusive Crest feature gradually increases gain to the attenuator setting after the output relays close, avoiding unnecessary stress on the loudspeakers.
Thermal Protection.
If the heatsink temperature reaches an abnormally high temperature, the amplifier will protect itself by disconnecting speakers and shut- ting down until sufficiently cooled. During this time, the Protect LED will light. If the power transformer gets too hot, its thermal sensing circuit will disconnect both channel outputs. During this time, the Active LED will extinguish, the Protect LED will illumi- nate, and ACL LEDs will stay off, and the cooling fan will stay run- ning. Once cool enough, the amplifier will resume operation auto- matically. If NexSys control is installed, thermal protect operation is reported to NexSys.
Short Circuit.
If an output is shorted, the IGM and thermal circuits will automati- cally protect the amplifier. The IGM circuit senses the short circuit as an extremely stressful load condition and attenuates the signal, protecting the channel’s output transistors from overcurrent stress. If the short circuit remains, the load will be disconnected by the ther- mal protection circuitry.
DC Voltage Protection.
If an amplifier channel detects DC voltage at its output terminals, the output relay will immediately open to prevent loudspeaker damage. The Protect LEDs will light. If NexSys control is installed, a DC pro- tect condition is reported to NexSys.
Crest Audio CK Power Processing Amplifiers | Page 9 |