JBL S800 - Manual (Page 10)

Quiet Cooling
The S800 utilizes a fan to cool the amplifier channels,
ensuring long-term reliability. To reduce fan noise to an
absolute minimum, a thermal sensing and control
circuit has been incorporated in the Synthesis S800
that senses increases in temperature within the amplifier
and powers a fan at a speed proportional to that
temperature increase. When the S800 is "loafing", the
fan turns very slowly – and quietly. At high listening
levels (and the higher operating temperatures this
creates within any amplifier), the sensing circuitry
causes the fan to turn faster, producing increased
cooling. As a result, the fan is never turning faster than
necessary, and most of the noise that is generated is
masked by the program being listened to.
Comprehensive and Isolated Circuit Protection
The S800 amplifier employs a sophisticated protective
circuit (one for each channel) that senses many
possible fault conditions, such as shorted loudspeaker
wires or excess power demand, and turns the affected
channel(s) and their blue front panel indicators off until
the fault condition is removed, at which time normal
operation is automatically restored. While protection of
this sort is not uncommon in today’s well-designed
amplifiers, a remarkable feature of the Synthesis S800’s
protective circuits is that they are optically-coupled to
the signal circuit; there is no direct electrical connection
between the signal path and the protective circuitry.
As a result, there can be no coloration of the
music, no interaction between protection and
amplification, until certain thresholds are
exceeded, at which point the channel(s) turn
off completely.
9
2.0
INTRODUCTION
AND FEATURES
2.0
INTRODUCTION
AND FEATURES