9
Operating Manual - nX, nXe, and nXp 150W/75W Power Amplifiers
2.7 Cooling
Air vents on the amplifier front and side panels must have access to free flowing room temperature air. Cool air is drawn in
through the side and blown out the front. It is not necessary to leave empty rack spaces above or below the amplifier. See the
BTU/hr chart in section 15 for specific thermal output characteristics. nXp models are used to illustrate worst case, nX and nXe
models will be slightly lower.
3 nX AMPLIFIER PROTECTION
Power-On Delay
-
All models have a fixed and non-defeatable warm-up delay of several seconds when first powered on or awak
-
ened from sleep. This is necessary to prevent excessive in-rush current during start-up. Additionally, nXe and nXp amplifiers have
programmable Power-On Delay ranging from zero to 25 seconds in 100ms increments
(see section 9.2)
.
Thermal Protection
- The c
ooling fan is continuously variable, increasing in speed as the amp heats up. The fan is at its maximum
speed when an amplifier channel reaches 80% of its safe operating temperature, and the Temp LED also turns on. At 90%, the
Protect LED turns on to indicate that countermeasures are being applied to attenuate the input signal to the overheating channel.
A Temp LED turns on dim at first, then increases in brightness as the amp channel approaches maximum safe temperature. 100%
critical temperature will shut down the amplifier but allow the fan to still run.
Power Limit Protection
-
To protect internal components from excessive output power conditions, a protection scheme in each
output stage reduces audio output power until the fault condition is no longer present.
Output DC Protection
-
If DC is detected on an output, this is a critical fault and the main power supply is shut off to avoid
damage to circuitry or speakers. Output DC protection is indicated on the amplifier front panel by the lighting of the protect
LED, sleep LED, plus the signal and clip LED on any channel that has output DC. A power cycle is required to clear an output
DC fault, using either the power switch or disconnecting the AC mains.
Power Supply Fault Protection
-
When the internal power supply voltage is outside its normal operating range, the protect
LED is lit and the amplifier channels are muted. If the power supply voltage reaches a critical level, the main power supply is
shut off and the protect, sleep, and mute LEDs are lit. To clear power supply voltage fault protection, a power cycle is required
using either the power switch or by disconnecting the AC mains.
Note:
Whenever protect and sleep LEDs are simultaneously lit, this indicates that the main power supply is disabled. The power
supply is disabled whenever there is a critical fault, or during initial power-up until the power supply has stabilized. For more
details of these protection schemes and indicators, see
Troubleshooting
in section 14.
