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FRONT PANEL
This indicator lights when the power amplier has been switched on. Causes for
the POWER-indicator not lighting are: the appliance is not connected to the mains
network or a defective primary fuse.
The PROTECT LED lights indicating that one of the internal protection circuits
against thermal overload, short-circuit, Back-EMF, HF-occurrence at the output,
etc., has been activated. The output relays interrupt the connected loads from
the power amps while input signals are interrupted as well, preventing the connected
loudspeaker systems and the power amplier itself from being damaged.
Whatever caused the fault – e.g. a short-circuited speaker cable – needs to be
remedied. In case of thermal overload you have to wait until the power amplier
automatically regains normal operation.
The SIGNAL LED lights as soon as an audio signal of approximately 30dB below full
modulation is present at the output. The LED is dimmed when speaker cables are
short-circuited or a protection circuit has been activated.
The 0dB LED lights whenever the power amplier is driven at its limits. Higher input
voltage does not result in higher peak output voltage. In addition, the 0dB indicator
comes in handy when adjusting external limiters.
This indicator lights as soon as the integrated dynamic audio signal limiter is
activated and the power amplier is driven at the clipping limit or generally
at its maximum capacity. Short-term blinking is not a problem, because the internal
limiter trims input levels of up to +21dBu down to an S/N-ratio of approximately 1%.
If, on the other hand, this LED lights constantly, reducing the volume is
recommended to prevent the loudspeaker systems connected from being damaged
by probable overload.
Detent potentiometers scaled in dB (steps of 1dB) for
adjusting the power amp’s overall amplication. To prevent
distortion in mixing consoles connected to the amp, setting
these controls to a value between 0dB and -6dB is generally
recommended. The dB-scale provides direct indication of the
control attenuation applied to the xed internal amplication.
Use the POWER switch located on the front panel to power-on the appliance. The soft-start function
protects against current inrush peaks on the mains, which in addition prevents the mains line protection
switch from activating during power-on. The loudspeaker outputs are activated via relay switching with
a delay of approximately 3 seconds to efciently attenuate eventual power-on noise. The PROTECT
LED lights during the delay time and the fans run at maximum speed. This is normal, conrming the
immaculate operation of the protection circuitry.