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CONTRACTOR PRECISION SERIES
Owner‘s Manual 9
For fixed amplifier installations in a device control room that incorporate a central air-cooling system or air conditioners,
calculating the maximum heat emission may be necessary. Please also take notice of the information on page 31.
2.6 Groundlift
The ground lift switch allows eliminating noise loops. When operating the power amplifier together with other
equipment in a rack case, setting the switch to the GROUNDED position is recommended. Set the switch to
UNGROUNDED, when the power amplifier is operated together with appliances with differing ground
potentials.
2.7 High Pass Filter (HPF)
The Hi-Pass filter (50 Hz, 18 dB/oct) allows effective attenuation of low frequency audio signals, which could
cause saturation problems with connected output transformers. Set the switch to the 50Hz position for
activating the High Pass Filter. Set the switch to the OFF position if no attenuation of low frequency audio
signals is required.
2.8 Power on delay
The ON DELAY switch at the amplifier rear panel allows selecting the power on delay time.
Following table shows possible switch settings and corresponding delay times.
CAUTION:
Blocking/closing the power amp’s ventilation louvers is not permissible. Without sufficient
cooling/ventilation, the power amplifier may automatically enter protect mode. Keep ventilati-
on louvers free from dust to ensure unhindered airflow.
Do not use the power amplifier near heat sources, like heater blowers, stoves or any other heat
radiating devices.
To ensure trouble-free operation, make certain that the maximum allowable ambient tempera-
ture of +40°C is not exceeded.
ON DELAY Delay time
(in s)
ON DELAY Delay time
(in s)
0 0.52 8 1.05
1 0.59 9 1.15
2 0.63 A 1.25
3 0.69 B 1.40
4 0.75 C 1.49
5 0.84 D 1.55
6 0.90 E 1.61
7 0.95 F 1.69