Crown Audio STUDIO AMPLIFIER Protection Systems, 2 Studio Reference Indicator States, Page

Studio Reference I & II Professional Studio Amplifiers

The green signal presence indicators flash synchro- nously with the amplifier’s output signal. The signal de- tector is connected to the signal path after the input gain stages and level controls, so a flashing indicator tells you that there is audio in and out of the amplifier. Note: The signal presence indicators may not report signal presence if the output signal level is too low.

The dynamic range /level meters are five-segment output meters that can be set to monitor either the dy- namic range or the level of the output signal. They are factory-set to show dynamic range. A switch located behind the front panel is used to select the meter dis- play mode (see Section 4.4 for complete instructions).

As dynamic range meters they show each channel’s ratio of peak-to-average power in dB. The dynamic range may be low for sources like AM/FM radio or low- quality recordings. Other sources like live music or high-quality recordings may be much higher. As out- put level meters they show how high the output levels are in dB relative to full power. At 0 dB, the unit is deliv- ering full standard 1 kHz power (see Section 6).

4.3 Protection Systems

Studio Reference amplifiers provide extensive protec- tion and diagnostics capabilities. Protection systems include ODEP, standby mode, an AC circuit breaker

Indicator Status			Amplifier Condition
ODEP	IOC	SIGNAL	There is no power to the amplifier.	Possible reasons: (1) The amplifier’s enable switch is off. (2) The
			amplifier is not plugged into the power	receptacle. (3) The AC mains circuit breaker has been tripped.
			(4) The amplifier’s circuit breaker has	been tripped.
OFF	OFF	OFF
ODEP	IOC	SIGNAL	Normal operation for a channel with	NO output. Possible reasons: (1) There is no input signal.
			(2) The input signal level is very low.	(3) The channel’s level control is turned down.
ON	OFF	OFF
ODEP	IOC	SIGNAL	The amplifier is in standby mode.	Possible reasons: (1) The amplifier has just been turned on and
			is still in the four second turn-on delay.	(2) A P.I.P. module such as an IQ-P.I.P. has turned off the
			channel’s high-voltage supply. (3) The	DC/ low-frequency protection circuitry has been activated.
OFF	ON	OFF	(4) The fault protection circuitry has been activated. (5) The transformer thermal protection circuitry
			has been activated. (6) The overvoltage protection circuitry has been activated.
ODEP	IOC	SIGNAL	ODEP limiting is about to begin or has just ended. Possible reasons: (1) The amplifier’s air filter is
			blocked and needs to be cleaned. (2) There is insufficient cooling because of inadequate air flow or air
OFF	OFF	Active	that is too hot. (3) The load impedance for the channel is too low because the output is shorted or the
			amplifier is driving too many loudspeakers for the selected stereo/mono mode. (4) The amplifier
			channel is continuously being driven to very high output levels.
ODEP	IOC	SIGNAL	Channel 2 only: The amplifier is in Parallel-Mono mode with no output. The channel 2 IOC indi-
			cator always turns on when the amplifier’s stereo/mono switch is moved to the Parallel-Mono position.
ON	ON	OFF
ODEP	IOC	SIGNAL	Normal operation for a channel with audio output. The ODEP indicator will remain at full intensity
			to show that there is reserve thermal-dynamic energy and the signal presence indicator will flash to
			show that there is audio output.
ON	OFF	Active
ODEP	IOC	SIGNAL	ODEP limiting has been activated. Possible reasons: (1) The amplifier’s air filter is blocked and needs
			to be cleaned. (2) There is insufficient cooling because of inadequate air flow or air that is too hot.
			(3) The load impedance for the channel is too low because the output is shorted or the amplifier is
OFF	ON	Active	driving too many loudspeakers for the selected stereo/mono mode. (4) The amplifier channel is
			continuously being driven to very high output levels.
ODEP	IOC	SIGNAL	The channel’s output is exceeding 0.05% distortion. The input signal level is too high, and IOC is
			reporting either an input overload or output clipping.
ON	ON	Active		OR
			Channel 2 only: The amplifier is in Parallel-Mono mode and has output. The channel 2 IOC indi-
			cator always turns on when the amplifier’s stereo/mono switch is moved to the Parallel-Mono position.
			Fig. 4.2 Studio Reference Indicator States

Page 20