USER MANUAL
i - S E R I E S
i - S E R I E S
a d v a n c E d a m p l I f I E R S
P.16
4 OPERA
TION
4.4 Power Amp Protection Systems
4.4.1 Clip Limiter / Underimpedance Limiter
The DSP section of the
iD4
offers various limiter and compressor settings,
both on the signal inputs and on the signal outputs. Those limiters and
compressors can be adjusted and even switched off completely if desired.
Disabling the limters is done by setting the thresholds to their highest
values.
But in case the amplifier is driven into hardware clip (i. e. when the Clip-
LED is glowing orange or red) for longer periods of time, the
threshold
setting of the
output limiter
will automatically be reduced temporarily.
Note that this is automatically done inside the amplifier and cannot be
seen in the DSP control application.
This automatic threshold reduction will especially take place at low output
impedances (smaller 4 Ω) and high output powers and shall prevent the
amplifier from being operated in continuous hard amplifier cliping.
4.4.2 SOA Protection
Whenever the power transistors leave their Safe Operation Area (SOA), the
SOA-protection switches back the rail of the respective channel.
4.4.3 DC Protection
Each output of the power amp is constantly monitored for persis-
tent DC voltage levels. If the 3 V thresholds are exceeded at any
of the outputs, the corresponding channel will be muted. If DC
was only detected for a short moment, the amplifier will release
mute and work as normal. If DC is detected for longer periods or
repeatedly, the amplifier will switch to standby mode and disable the
main power supply. If this happens the display will indicate “Error – amp
switched off”.
In this case, switch off the amplifier for at least 4 minutes and switch the
amplifier on again.
4.4.4 Over Current Protection
Over current is permanently controlled in the output stage. There are two
limit ing levels of over current depending on output voltage. These limits
will be set automatically. This improves reliability without degrading sound
quality when driving complex loads.
4.4.5 Thermal Protection
There are several sensors inside the amplifier 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.
4.5 Mains Protections
4.5.1 Inrush Current Limitation
Within 2 seconds of the amplifier being switched on, the inrush current
limiter will increase mains current from nearly zero to nominal value. This
value depends on program material, output level and speaker loads.
4.5.2 Mains Over Voltage Detection
Mains over voltage detection is always operative. When the mains voltage
exceeds approx. 263 V (220 / 230 V operation) or 134 V (110 / 120 V opera-
tion), the amplifier will be switched off. The system will try to restart in inter-
vals and will return with a soft start when the regular mains voltage returns.
4.5.3 Mains Surge Overvoltage Protection
The
iD4
is fitted with a varistor unit, protecting the SMPS from sporadic
surge overvoltages coming from the mains distribution.
4.5.4 Mains Failure Detection
Mains failure detection is always operative. When the mains supply is inter-
rupted for about 2 mains cycles, the amplifier will be switched off. When
the mains voltage returns to a normal value, a soft start occurs.