Art SLA-4 User Manual page 15

PROTECTION
The SLA-4's output circuitry is fully protected from short circuits. An
ultrasonic network decouples RF from the output and helps keep the
amplifier stable with reactive loads.
The SLA-4's external heatsinks do most of the work in getting heat
away from the amplifier, in normal operation. A quiet, rear mounted
variable-speed fan provides extra cooling of the amplifiers internal
circuitry as needed. Normally, at low to moderate signal levels, the fan
runs at a low speed idle. If the internal temperature rises above a set
level then the fan switches to a higher speed to remove more heat
from the inside. If, in the unlikely event the heatsinks should reach 194
degrees Fahrenheit, the amplifier will mute, until it cools down enough
for safe operation. Make sure there is adequate ventilation around the
heatsinks if you plan on rack mounting the SLA-4 in an enclosed
space.
The SLA-4 is fully protected from shorts, opens, over-current, and
over-voltage. A relay disconnects the outputs under any of these fault
conditions and automatically returns to normal operation once the fault
is removed.
The amplifier is stable into loads as low as 2 ohms (stereo mode), and
4 ohms (bridged mode) when used in a fixed or permanent installation.
However, for continuous operation of all channels at mid to high signal
levels, the amplifier should be operated with a minimum load of 4 ohms
per channel in stereo mode and 8 ohms per channel in bridged mode,
otherwise the overload and thermal protection circuitry may cycle the
amplifier on and off as it protects itself.
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