Dynacord Power Amplifier DPA 4245 Owner's Manual page 24

T
CIRCUIT TO
CHASSIS SWITCH
GROUNDED
UNGROUNDED
POWER
POWER REMOTE
+
+24V ON
0V OFF
CH A CH B
LIMIT
SIGNAL
PROTECT
POWER
GROUND Lift Switch
The ground lift switch helps is a perfect means for eliminating possible
ground noise loops. In case the power amplifier is operated together with
other equipment inside of a rack shelf system, the switch should be set to its
GROUNDED position. When using the power amplifier together with other
equipment that operates on different ground potentials, the switch should be
set to UNGROUNDED.
Power On And Remote Control
When the power amplifier is operated via power remote start (standard ope-
ration) an external 24 V power source has to be connected to the POWER
REMOTE terminal strip and the mains switch has to be set to its OFF-positi-
on. When correctly connected and with a present supply voltage, the power
amplifier is operational. The fans run for approximately 2 seconds and the
POWER ON-LED on the front panel lights. The mains switch POWER on
the rear of the appliance bridges the mains relay. It is meant for service pur-
poses only. This allows to operate the power amplifier without the presence
of an external 24 V power source. The current consumption at the POWER
REMOTE input is approximately 25mA.
Limit Indicator
The indicator lights whenever the integrated limiter is activated. While short
blinking means no problem, the continuously lit LED indicates that the vo-
lume level needs to be reduced to prevent the connected loudspeaker sys-
tems from being damaged by overload.
The audio limiters are capable of controlling overdrive levels of up to 20
dB. Most other power amplifiers without integrated limiters begin to clip,
generating nasty distortion that not only attacks your ears but also lead to
damaging the connected loudspeaker systems by overload. The limiters are
activated only in case of the occurrence of non-linear conditions within the
power amplifier; e. g. signal clipping at the operation voltage limit. The limit-
ers do not affect the power amplifier's overall dynamic range.
Signal Indicator
This indicator is lit when the audio signal exceeds –30 dB. In case short-
circuits resulting from broken loudspeaker cables are detected or one of
the power amplifier's protection circuits is activated, the signal indicator is
dimmed.
PROTECT
The PROTECT-LED lights whenever one of the power amplifier's protection
circuits – thermal overload, RF, DC, Back-EMF – is activated. In PROTECT
mode all loudspeaker lines and output transformers are disconnected via
relays and the power amplifier's audio inputs are short-circuited to prevent
the connected loudspeaker systems from being damaged. When the power
amplifier enters the PROTECT mode please examine first whether the appli-
ance is overheated. If this is the case, the front and rear ventilation louvres
are possibly covered, the nominal load impedance has fallen below the spe-
cified minimum value, or a short-circuit occurred at the power output.
When switching the power amplifier on, the PROTECT-LED lights for appro-
ximately 2 seconds. This is normal. It signals that the protection circuitry is
in working order.
Power ON Indicator
This LED lights when the power amplifier is connected to the mains and
its power switch is set to the ON-position. If the indicator does not light alt-
hough the power amplifier is switched on, the appliance is not connected to
the mains or the primary fuse is blown.
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