4.2 Controls
4.2.1 Volume Control
A volume control with 41 notched settings controls the audio signal. These
settings have been selected to correspond to human hearing characteristics
(logarithmically) and therefore guarantee an optimal range of settings for
practical applications. Each channel can be set individually.
Set the volume to zero before turning on the amplifi er to prevent the occur-
rence of sudden high volume levels which may cause damage to your hearing
and/or the speakers.
4.2.2 Gain Selector
A switch on the rear of the Q-POWER amplifi ers allows the maximum amplifi ca-
tion attainable to be set directly in the input stage.
4.2.3 Limiter Switch
This switch is located at the rear of Q-POWER amplifi ers. It allows you to activate
the clip limiter function on the channels A/B and C/D respectively.
4.3 Power Amp Protection Systems
4.3.1 Clip Limiter
If the power amp is overdriven and the limiter is set to on (see section 4.2.3)
the clip detection triggers the Attack-Release-Circuit (ARC). The ARC delivers
the control voltage for the gain reduction.
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The Q-POWER amplifi ers have a 26 dB and 32 dB
voltage gain setting along with a 1,4 V sensitivity
setting.
4.3.2 SOA Protection
Whenever the power transistors leave their Safe Operation Area (SOA), the SOA-
protection will either switch back the current rail of the respective channel
(Q-POWER 6) or limit the maximum load current in the power transistors
(Q-POWER 10).
4.3.3 DC Protection
Each output of the power amp is constantly monitored for persistent DC voltage
levels. If the 3 V thresholds are exceeded at any of the outputs, the correspond-
ing channel will be muted. If DC was only applied for a short moment, the ampli-
fi er will release mute and work as normal. If DC is applied for longer periods or
several short times the amplifi er will switch to standby mode.
If this happens, switch off the amplifi er, wait until all indicator LEDs extinguish
and switch the amplifi er on again.
4.3.4 DC Servo
To prevent DC Offset at the speaker output the Q-POWER amplifi ers are fi tted
with a DC Servo.
4.3.5 Over Current Protection
Over current is permanently controlled in the output stage. In case of exessive
loading the maximum output current of the amplifi ers is automatically limited.
This improves reliability without degrading sound quality when driving com-
plex loads.
4.3.6 Thermal Protection
There are sensors in each amplifi er heatsink in order to ascertain tem perature
data. If a temperature of more than 85 °C is detected at the heat sinks, the input
signal on that channel is reduced proportionally to prevent further heating of
the amplifi er. If the temperature exceeds approximately 100 °C, the main SMPS
is switched off(safety shut-off ).
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S E R I E S