Nexo NXAMP4x1mk2, Руководство пользователя

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NXAMPMK2 USER MANUAL PAGE 33 / 70
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External generator: The Load Monitoring uses an external HF pilot tone (sent to the NXAMPmk2 with
the audio program) and this signal is used to measure the impedance of the connected speakers.
FREQUENCY
Here can be adjusted the frequency at which the impedance measurement will be done for the speaker(s)
connected to the channel selected. The frequency is adjustable from 14500 to 21000 Hz in 1/12 octave
steps.
Most of the time, there is no need to change this frequency if you are using the Internal Generator.
If external pilot tone is used (from the audio program sent to the NXAMPmk2 on its analog or digital inputs),
be sure that the frequency selected here is close as possible to the pilot tone frequency.
LEVEL
The level of the internal HF burst generator can be adjusted here when using the Internal Generator mode.
The level is adjustable from 0 to 5 volts, with 0.5 volts steps. This voltage is intended to be given at the
output of the NXAMPmk2 speakON connectors for the channel selected.
NB: Setting the level to 1 volt is a good start, then adjust the output level to have a stable reading of the
impedance on the screen. Long speaker cable and high impedance speaker(s) connected might need a
higher output voltage. An output voltage too high can lead to sub-harmonic generation that can be audible
at the speaker output.
IMPEDANCE HIGH AND LOW LIMITS
Once the measured impedance is displayed on the screen, you can select low and high limits that will trigger
the
alerts “High” or “Low” impedance. These two alerts can be monitored directly through network or via the
GPIO port (see GPIO section, to route them to GPIO pins).
NB: These limits should be adjusted with care. External parameters such as cable type and length,
temperature, wind and output leve
l can slightly change the speaker’s impedance measurement. Be sure to
adjust these limits on site in real-life conditions to prevent false triggering of the impedance fault.
MEASURED IMPEDANCE
If the impedance of the connected load is between 0 and 100 Ohm at the measurement frequency, the actual
value of the impedance will be displayed, for example “ =1 . Ω”.
If the NXAMPmk2 is unable to measure the impedance of the speaker because there is no pilot tone (Internal
generator at 0V or external pilot tone not detected),
“Z=??Ω” will be displayed, and both “High” and “Low”
impedance alerts will be raised.