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TourClass® Protection Features
Every model in the CKd Power Processing line incorporates Crest Audio's
TourClass protection features. Derived from Crest's extensive experience with the
world's largest sound rental companies, the TourClass group of features sets new
standards in load and amplifier protection.
Automatic Clip Limiting (ACL)
Automatic Clip Limiting (ACL) circuitry protects both loudspeakers and audio fidelity
against damaging square-wave clipping. When the amplifier reaches its maximum
output power (the point at which the amplifier would begin to clip), the ACL circuitry
automatically reduces the amplifier's gain to keep the signal from being driven into
hard clipping. Situations that may activate ACL include: uncontrolled feedback,
oscillations, or an improper equipment setting or malfunctions upstream from the
amplifier. Normal program transients will not trigger ACL, only steady or excessive
clipping. ACL is virtually transparent in operation and full signal bandwidth is
maintained.
Instantaneous Gain Modulation (IGM)
Instantaneous Gain Modulation (IGM) is an innovative impedance sensing circuit
that allows the CKd amplifier to operate safely into any load. When the amplifier
sees a load that overstresses the output stage, the IGM circuit reduces the channel
gain to a safe level. Like ACL, the IGM circuit is sonically transparent in normal use.
Thermal Protection
If the temperature of the amplifier's output devices becomes abnormally high, the
CKd channel will protect itself by shutting down the amplifier's output stage. The
channel's 'Active' LED will turn off and the channel 'Fault' LED will light if this
occurs.
Once adequately cooled, the amplifier channel will resume operation
automatically.
A thermal limiter option is available to further protect channels from shutting down
due to thermal faults. The thermal limiter will activated when a channel approaches
its thermal limit. This is indicated by a dimly lit ACL/IGM LED. When the thermal
limiter is active, the channel will lower its IGM threshold until the temperature
stabilizes.
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.
DC Voltage Protection
If an amplifier channel detects DC voltage at its output terminals, amplifier channels
will shutdown to prevent loudspeaker damage. When a DC voltage is detected on
channels 1 through 4, Power Supply 1 will shut down, deactivating channels 1
through 4. When a DC voltage is detected on channels 5 through 8, Power Supply 2
will shut down, deactivating channels 5 through 8.
AutoRamp Protection
AutoRamp gradually increases the amplifier gain from -∞ to the attenuator setting
every time the amplifier is turned on or is reactivated after a protect condition. This
exclusive Crest feature avoids unnecessary stress on the loudspeakers by
CKd Series Owners Manual v1e
CKd Owner's Manual
Because of the
complexity of the design
and the risk of electrical
shock, all repairs must
be attempted only by
qualified technical
personnel. If the unit
needs to be shipped
back to the factory, it
must be sent in its
original carton. If
improperly packed, your
amplifier may be
damaged.
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