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
.
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
-
If the amplifier's internal power supply voltage ever exceeds or falls below its normal safe
operating range, the amplifier channels are muted and the protect LED is lit. If the power supply rails reach a critical level, the
main power supply is shut off and the protect, sleep, and mute LEDs become lit. This protection mode is latching, meaning it
will not automatically recover. The amplifier must be reset using either the power switch or by disconnecting the AC mains.
For full details of these protection schemes and indicators, see
in section 14.
