Thermal Protection - Peavey PV 3800 Operating Manual

Protection Features
The PV® 3800 amplifier incorporates several circuits to protect both themselves and loudspeakers under virtu-
ally any situation. Peavey has attempted to make the amplifiers as foolproof as possible by making them immune
to short and open circuits, mismatched loads, DC voltage, and overheating. If a channel goes into the Distortion
Detection Technique or DDT™ gain reduction mode, the speaker load remains connected, but clipping percent-
age or output power are instantly reduced. DC voltage on the output, excessive subsonic frequencies or thermal
overload will cause the channel's output relay to disconnect the speaker load until the problem is corrected or
the amplifier cools down.
Distortion Detection Technique™ (DDT)
Any time a channel is driven into hard, continuous clipping, the DDT circuit will automatically reduce the channel
gain to a level just slightly into clipping, guarding the speakers against the damaging high power continuous
square waves that may be produced. Situations that may activate the DDT circuit include uncontrolled feedback,
oscillation, an improper equipment setting or malfunction upstream from the amplifier. Normal program
transients will not trigger the DDT, only steady, excessive clipping will. The DDT LED will glow brightly and
continuously when limiting occurs.
LFC™ Impedance Sensing
The PV 3800 amplifier features innovative circuitry that allows safe operation into any load. When an amplifier
sees a load that overstresses the output stage, the Load Fault Correction (LFC) circuit adjusts the channel gain to
a safe level. This method of output-stage protection is far superior to conventional, brute force-type limiting found
on other amplifiers. The LFC circuit is sonically transparent in normal use and unobtrusive when activated.

Thermal Protection

Internal fans keep the amplifier operating well within its intended temperature range under all normal conditions.
If a channel's heat sink temperature reaches 75°C, which may indicate an obstructed air supply, that channel will
independently protect itself by disconnecting its load and shutting down until it has cooled. During this time, the
POWER LED will go out, the DDT LEDs will remain lit and the cooling fans will continue running at high speed.
Short Circuit
If an output is shorted, the LFC and thermal circuits will automatically protect the amplifier. The LFC circuit senses
the short circuit as an extremely stressful load condition and attenuates the signal, protecting the channel's
output transistors from over-current stress. If the short circuit remains, the channel will eventually thermally
protect itself by disconnecting the load.
DC Voltage Protection
If an amplifier channel detects DC voltage or subsonic frequencies at its output terminals, its output relay will
immediately open to prevent loudspeaker damage.
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