CSL Series Power Amplifiers
Page 9
3 Operation
3.1 Precautions
Although your amplifier is protected from external faults,
the following safety precautions are recommended:
1. There are important differences among the Stereo,
Bridge-Mono and Parallel-Mono operating modes.
Refer to Sections 2.1 and 2.2.
2. WARNING: Do not change the stereo/mono
switch unless the amplifier is first turned off.
3. CAUTION: In Parallel-Mono mode, a jumper is in-
stalled between the red output posts. Be sure to
remove this jumper for Bridge-Mono or Stereo
mode, otherwise inefficient operation, high dis-
tortion and excessive heating will occur.
Also,
check the stereo/mono switch for proper position.
4. Use care when making connections, selecting sig-
nal sources and controlling the output level.
5. Do not short the ground lead of an output cable to
the input signal ground. This may form a ground loop
and cause oscillations.
6. Operate the amplifier from AC mains of not more
than 10% variation above or below the selected line
voltage and only at the specified line frequency.
7. Never connect the output to a power supply output,
battery or power main.
8. Circuit tampering by unqualified personnel, or mak-
ing unauthorized circuit changes voids the warranty.
Remember: Crown is not liable for any damage that
results from overdriving other system components.
3.2 Indicators
When lit, the amber LED shows that the unit is turned
on, and the low voltage power supply is working. It does
not show the status of the high voltage supplies.
3.3 Protection Systems
CSL amplifiers have extensive protection systems, in-
cluding
ODEP, ultrasonic/RF protection, drive protec-
tion, transformer thermal protection and fuses or circuit
breakers that protect the power supplies.
3.3.1
ODEP
Crown invented
ODEP to prevent amplifier shutdown
during demanding operation and to increase the effi-
ciency of the output circuitry. To do this, Crown estab-
lished a rigorous program to measure the
safe
operating area (SOA) of each output transistor. Then,
Crown designed intelligent circuitry to simulate instan-
taneous transistor conditions. Its name describes what
it does: Output Device Emulation Protection, or
ODEP.
In essence,
ODEP compares transistor conditions to
their known SOA. If more power will be asked of them
than they can deliver with the present conditions,
ODEP
limits the drive until conditions fall within the SOA. Lim-
iting is proportional and kept to an absolute minimum—
only what is required to prevent output transistor
damage. Under normal conditions, no limiting is re-
quired and
ODEP is transparent to the audio signal.
ODEP makes possible a quantum leap in output effi-
ciency and reliability—with
ODEP, the show goes on.
3.3.2 Ultrasonic and Radio Frequency (RF) Protection
CSL amplifiers have a controlled slew rate. This means
that their design limits the frequencies that they can re-
produce. The limiting occurs far above audible frequen-
cies (20 Hz to 20 kHz), but it protects sensitive loads
like tweeters from ultrasonic and radio frequencies. An
amplifier’s slew rate only needs to be large enough to
deliver the maximum voltage at the highest required
frequency—higher slew rates actually allow undesir-
able frequencies to be reproduced.
3.3.3 Drive Protection
The drive protection system temporarily removes out-
put drive to protect the amplifier and its loads. Drive
protection can be activated in two situations. First, if
dangerous subsonic frequencies or direct current (DC)
is detected in the amplifier’s output, the unit will activate
its DC/low frequency protection circuitry which also
activates drive protection mode. This protects the loads
and prevents oscillations. The unit resumes normal op-
eration as soon as dangerous output is no longer de-
tected. Although it is extremely unlikely that you will ever
activate the DC/low frequency protection system, im-
proper source materials like subsonic square waves or
input overloads that excessively clip the input signal
can activate this system.
The amplifier’s fault protection system will activate drive
protection mode in rare situations where the output de-
vices see heavy common-mode current. The output
devices should never see heavy common-mode cur-
rent unless the circuitry is damaged. Activating drive
protection helps prevent further damage.
3.3.4 Transformer Thermal Protection
CSL amplifiers have transformer thermal protection.
