5 Advanced Features
and Options
NOTE: For detailed information about these Crown amplifier features, please consult the Crown Amplifier Application Guide, available on the Crown website at www.crownaudio.com.
5.1 Protection Systems
Your Crown amplifier provides extensive pro- tection and diagnostic capabilities, including ODEP, ultrasonic/RF protection, drive protec- tion, and power supply fuses or breakers.
controlled slew rate has no effect on audio per- formance because the
5.1.3 Drive Protection
A transformer can overheat during very severe conditions: higher than rated output levels, excessively
— from damage.
5.1.5 Fuses and Circuit Breakers
5.1.1 ODEP
Crown invented ODEP to prevent amplifier shutdown during demanding operation, and to increase the efficiency of the output circuitry.
To do this, Crown measured the safe operating area (SOA) of each output transistor before installing it in an amplifier. Next, Crown designed intelligent circuitry to simulate the instantaneous operating conditions of those output transistors. Its name describes what it does: Output Device Emulation Protection or ODEP. In addition to simulating output transis- tor operating conditions, it compares their operation to their known SOA. If ODEP sees that more power will be asked of the output devices than they can deliver, ODEP immedi- ately limits the drive level until it falls within the SOA. Limiting is proportional and kept to an absolute minimum
This level of protection enables Crown to increase output efficiency to
5.1.2Ultrasonic and Radio Fre- quency Protection
This system temporarily removes drive from the output stages to protect the amplifier and its loads, and prevents oscillation. Drive protec- tion can be activated in two situations. First, if dangerous subsonic frequencies or direct cur- rent (DC) is detected in the amplifier's output, drive protection will activate. The amplifier resumes normal operation when it no longer detects dangerous output. Activating this pro- tection is very unlikley, but improper source signals like subsonic square waves or a severely clipped signal can activate this sys- tem.
Second, the amplifier's fault protection system puts the affected channel into drive protection mode in rare situations where heavy common- mode current is detected in its output. The amplifier should never output heavy common- mode current unless its circuitry is damaged. Activating drive protection helps prevent further damage.
5.1.4Transformer Thermal Protection
This activates in the rare case where the unit's transformer temperature rises to unsafe levels. Then the amplifier will remove power from the affected channel's
120 VAC, 60 Hz models and all
With rated loads and output levels, the fuses (or circuit breakers) should shut down the amplfi- ier only in the rare instance of a catastrophic failure. ODEP protection keeps the amplifier operational under most other severe condi- tions. The fuses (or circuit breakers) can also shut down the amplifier if extremely low- impedance loads and high output levels result in current draw that exceeds their rating. Again, this should be possible only when operating outside rated conditions, as when the amplifier is used to drive a
Operation Manual | page 13 |