Crest Audio Stereo Amplifier - Manual (Page 17)

Crest Audio Pro Series Power Amplifiers Page 15
All loudspeakers have electrical, thermal, and physical limits which must be observed to prevent damage or failure. Too much power,
low frequencies applied to high frequency drivers, severely clipped waveforms, and DC voltage can all be fatal to cone and compres-
sion drivers. The Crest Audio Professional Series amplifiers automatically protect speakers from DC voltages and subsonic signals. For
more information, see the section on Protection Features. Mid- and high-frequency speakers, especially compression drivers, are high-
ly susceptible to damage from overpowering, clipped waveforms, or frequencies below their rated passband. Be extremely careful that
the low and mid bands of an electronic crossover are connected to the correct amplifiers and drivers and not accidentally connected to
those for a higher frequency band. The amplifier’s clipping point is its maximum peak output power, and some of the higher power
Crest Audio Professional Series amplifiers can deliver more power than many speakers can safely handle. Be sure the peak power capa-
bility of the amplifier is not excessive for your speaker system.
To ensure that the speakers never receive excessive power and that the amplifier never clips, use a properly adjusted external limiter (or
a compressor with a ratio of 10:1 or higher) to control power output; in systems with active electronic crossovers, use one for each fre-
quency band. The clip limiter will automatically limit the duration of squared-off, continuous waveforms applied to the speakers. The
amplifier will, however, allow normal musical transient bursts to pass. Of course, when the amplifier does clip, it is right at its maxi-
mum output power. Some speaker systems are packaged with processors that have power limiting circuits and should not require addi-
tional external limiting. Fuses may also be used to limit power to speaker drivers, although as current-limiting rather than voltage-lim-
iting devices, they are an imperfect solution, and as the weakest links, they only limit once before needing replacement. Some poor
quality fuses have a significant series resistance that could degrade the amplifier’s damping of the speaker’s motion and may even dete-
riorate the system’s sound quality. If you elect to use fuses, check with the speaker manufacturer to determine the proper current rat-
ing and time lag required.
Do not drive any low-frequency speaker enclosure with frequencies lower than its own tuned frequency; the reduced acoustical damp-
ing could cause a ported speaker to bottom out even at moderate power. Consult the speaker system specifications to determine its fre-
quency limits.
Amplifier Maintenance and User Responsibility
If you use the air filter supplied with your Professional Series amplifier, the filter element must be cleaned or replaced periodically to
maintain adequate airflow. How often you must do this depends on the environment in which you operate the amplifier. A very dusty
environment will necessitate a shorter service interval than a less dirty one. To clean the element, unsnap the filter element/guard assem-
bly from the fan housing, and remove the filter element. On two-piece guards, pry the two sides apart to remove the element. Wash and
rinse the element using soap and water, then squeeze it dry and reinstall. Instead of cleaning, you may also cut a replacement element
from a sheet of air conditioner foam filter material, using the old element as a pattern. Never operate an amplifier with a clogged fil-
ter; it will quickly overheat. Replacement filter elements and element/guard assemblies can also be ordered from Crest Audio. A
Professional Series amplifier requires no other routine maintenance and should never need any internal adjustment during its lifetime.
Your Professional Series amplifier is very powerful and can be potentially dangerous to loudspeakers and humans alike. It is your
responsibility to read the Important Precautions section and to make sure that the amplifier is installed, wired, and operated properly
as instructed in this manual. Many loudspeakers can be easily damaged or destroyed by overpowering, especially with the high power
available from a bridged amplifier. Read the Speaker Protection section and always be aware of the speaker’s continuous and peak
power capabilities.
Service / Warranty Information
In the unlikely event that your amplifier develops a problem, it must be returned to an authorized distributor, service center or shipped
directly to our factory. To obtain service, contact your nearest Crest Audio Service Center, Distributor, Dealer, or any of the worldwide
Crest Audio offices. For contact information, reach Crest Audio Inc. Customer Service directly at: T
EL 201.909.8700 (USA) F AX
201.909.8744 (USA). For technical inquiries only, the Crest Audio Technical Services department can be faxed at 201.587.0550 (USA).
Because of the complexity of the design and the risk of electrical shock, all repairs should be attempted only by qualified technical per-
sonnel. 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.
For those with Internet access, please visit the Crest Audio website at: http://www.crestaudio.com
Use common sense…
it’s the most important facet of any speaker protection scheme.