5protection features
CCTM owner’s manual
CCSeries amplifiers incorporate several circuits to protect both themselves and loudspeakers under virtually any situation. Crest Audio has attempted to make the amplifiers as foolproof as possible by making them immune to short and open circuits, mismatched loads, DC voltage, and overheating. If a channel goes into the Automatic Clip Limiting or ACL™ gain reduction mode, the speaker load remains connected, but clipping percentage or output power are instantly reduced. When a problem occurs that causes a channel to go into a protection mode, the Temp LED for that channel will glow. DC voltage on the output, excessive subsonic frequencies, or thermal overload will cause the channel’s output relay to disconnect the speaker load until the problem is corrected or the amplifier cools down.
automatic clip limiting (ACL)
Any time a channel is driven into hard, continuous clipping, the clip limiter circuit will automatically reduce the channel gain to a level just slightly into clipping, guarding the speakers against the damaging high power continuous square waves that may be produced. Situations that may activate the clip limiter include uncontrolled feedback, oscillation, or an improper equipment setting or malfunction upstream from the amplifier.Normal program transients will not trigger the clip limiter; only steady, excessive clipping will.The ACL LED will glow brightly and continuously when limiting occurs.
IGM™ impedance sensing
CCSeries amplifiers feature innovative circuitry that allows safe operation into any load. When an amplifier sees a load that overstresses the output stage, the Instantaneous Gain Modulation (IGM) circuit adjusts the channel gain to a safe level.This method of output stage protection is far superior to conventional, brute force type limiting found on other amplifiers. The IGM circuit is sonically transparent in normal use and unobtrusive when activated.
thermal protection
The internal fans will keep the amplifier operating well within its intended temperature range under all normal conditions. If a channel’s heat sink temperature reaches 75°C, which may indicate an obstructed air supply, that channel will protect itself independently by disconnect- ing its load and shutting down until it has cooled. During this time, the channel’s Temp LED will glow, the Active LED will go out, the ACL LEDs will stay lit and the cooling fans will run at high speed. The CC 1800 utilizes one common heat sink and single fan, but retains the separate circuitry.
short circuit
If an output is shorted,the IGM and thermal circuits will automatically 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 over current stress. If the short circuit remains, the channel will eventually thermally protect itself by disconnecting the load.
DC voltage protection
If an amplifier channel detects DC voltage or subsonic frequencies at its output terminals, its output relay will immediately open to prevent loudspeaker damage.
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