Boulder 1160 - Input DC Offset Voltage Detection; Clip Detection; Thermal Protection

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Operation
Operation
Input DC Offset Voltage Detection
The Boulder 1160 is a direct-coupled power amplier with a servo for
zeroing out any DC voltage offset coming from the preamplier or other
sources connected to the amplier’s input.
If the DC at the inputs is sufcient to cause three volts or more at the
output terminals, a protection circuit will mute the amplier’s output by
electronically disconnecting the loudspeakers. The front panel LED
will also turn red. This condition will continue until the source of DC is
corrected or removed.
If the indicator remains red, it is recommended that the user correct the
DC offset of the source device before continuing.
Clip Detection
Clipping of the waveform results when any amplier is driven at too high a
level. A clip detection circuit is included in the 1160 Stereo Power Amplier.
The front panel LED will indicate clipping by momentarily turning from
white to red. Both voltage and current modes of clipping are detected,
although it is generally only voltage clipping that occurs.
Thermal Protection
A thermal protection circuit prevents high operating temperatures that are
unpleasant to the touch and potentially harmful to the amplier. A thermal
cutout circuit will mute the amplier when the transistor cases reach 85°C,
and the front panel LED will turn red. If this happens, the output level of
the system should be reduced and more ventilation should be provided for
the amplier.