Lexicon CX-7 Stereo Amplifier User Manual


 
Basic Operation
Lexicon
2-8
PROTECTION MODES
The CX amplifiers are equipped to protect against overheating and
miswiring, as well as electrical failures such as short circuits, device
failures, internal faults, and DC output to the speakers.
THERMAL PROTECTION
The amplifier includes thermal protection for each channel, the
main power transformer, and chassis. If a heatsink temperature
exceeds 95˚C, the channel will deactivate and the corresponding
channel status LED will flash blue. When the heatsink cools to
normal operating temperature, the channel will automatically reac-
tivate and the corresponding channel status LED will return to
constant blue.
If the amplifier chassis exceeds a temperature of 58˚C, the amplifi-
er will shut down all channels and all the channel status LEDs will
flash blue. When the chassis cools to normal operating tempera-
ture, all of the channels will automatically reactivate and the chan-
nel status LEDs will return to steady blue.
If the main power transformer temperature exceeds 100˚C, the
transformer will deactivate, all channel status LEDs will no longer
be lit, and the red standby LED will flash rapidly. Once the trans-
former has cooled, it will automatically be reset and the amplifier
will operate normally. The channel status LEDs will return to
constant blue, and the red standby LED will no longer be lit.
CURRENT PROTECTION
The CX amplifiers use a combination of voltage and current infor-
mation to protect the output transistors. The amount of current
capable of being delivered to the load is dependent on how much
voltage appears across the output transistors. Inversely, this means
that the more output voltage available, the more current capabili-
ty available, which translates into higher power output.
In addition to the voltage and current thermal protection, the CX
amplifiers have a time dependent instantaneous current limit. The
amplifier is capable of delivering 20 amps peak into a load for a
short duration of time.
DC PROTECTION
Each channel includes DC protection to prevent DC and frequen-
cies below 10Hz from reaching the speakers. If this protection
activates, the output relay will open and the corresponding front
panel channel status LED will flash blue. After approximately 4-sec-
onds, DC protection will be automatically deactivated. The relay
will close and the corresponding channel status LED will return to
constant blue. If DC or frequencies below 10Hz are still present, DC
protection will be automatically reactivated. The amplifier will
continue to engage this protection until the problem is no longer
present.