3 Operation
3.1 Volume Control
In DUAL and PARALLEL mode, the level controls CH A and CH B on the power amp’s front panel are used to control the amplification of the corresponding channel. Turning the control to the right increases and turning it to the left decreases the volume. In BRIDGED mode operation, the output volume of the power amp is only controlled by the CH A level control. Any changes in the setting of the CH B level control are ignored.
3.2 Indications
PROTECT
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. In that case, the output relays separate the power amps from the load connected to prevent the connected loudspeaker systems and the power amplifiers as well from being damaged. Whatever caused the fault – e.g. a short-circuited speaker cable – needs to be removed. In case of thermal overload you have to wait until the power amplifier cools down and automatically regains normal operation.
-40dB...LIMIT
Level indication is realized via vertical LED chains on the power amp’s front panel that individually indicate the actual levels of each channel at -40dB, -30dB, -20dB and -10dB below full modulation and 0dB as soon as full modulation is reached. 0dB indication results from comparing the power amp‘s internal ratio of input to output voltage, which ensured precise indication of the full modulation limit, even before limiting becomes audible. The LIMIT LED lights as soon as the integrated dynamic audio limiter is activated and the power amplifier is driven at the clipping limit or generally at its maximum capacity. Short-term blinking is not a problem, because the internal limiter controls input levels of up to +21 dBu down to a THD of approximately 1 %. If, on the other hand, the LIMIT LED light constantly, reducing the volume is recommended to prevent the loudspeaker systems connected from being damaged by probable overload.
POWER
The POWER LED lights green when the power amplifier is on. If the POWER-LED does not light, despite the fact that the amplifier has been switched on, this indicates that the power amp is not connected to the mains or the primary fuse has blown.
3.3 FAN Cooling
The power amplifier has two fans. The fans are switched in three performance-optimized levels, i.e. they are not running permanently but the speed of the fans is controlled depending on the ambient temperature. That in return ensures very silent running during idle state. The temperatures of the power amps‘s channels are registered and monitored separately.
