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12
PROTECTION CIRCUITS CONNECTIONS
There are several protection mechanisms
designed into the HRS120 to safeguard the
loudspeaker and amplifier from inadvertent
damage.
Peak Limiter
A peak limiter is located at the input to the
power amplifier section. It monitors both the
amplifier output signal and the power supply
voltages to guard against clipping and over-
loading the amplifier. This allows for loud and
punchy bass performance without distortion,
ensuring long-term reliability.
Thermal Protect
All amplifiers produce heat. The HRS120 is
designed to be efficient both electrically and
thermally.
• If for some reason the heatsink or power
transformer gets too hot, a thermal switch
activates, placing the HRS120 into Standby
mode.
• Should this happen, make sure that airflow
to the rear of the cabinet is not restricted.
• When the heatsink or power transformer
cools down to a safe temperature, the switch
resets and normal operation resumes.
Note: The
POWER
LED remains lit if the ther-
mal protection circuit is activated.
Input and Output Signal Wiring
You should use high-quality, shielded cable
to connect the signal source to the
LEFT
and
RIGHT IN
and
OUT
jacks on the HRS120.
• Foil shielded cables, such as Belden 8451,
8761, or 9501 are commonly used for studio
wiring.
• Microphone cables work well.
• The better the shield, the better the
immunity from externally induced noise
(like EMI and RFI). Route the cable away
from AC power cords and outlets. These are
common sources for hum in an audio
signal. Wall warts and line lumps are
especially insidious hum inducers!
You can purchase quality cables from your
Mackie dealer.
• In certain home theater applications, it
may be necessary to connect the speaker
outputs from a stereo receiver to the inputs
of the HRS120s, if the receiver doesn’t have
preamp outputs or other line-level output
connections.
CAUTION: Do not attempt
to connect a speaker output
directly to the input of the
HRS120! Speaker levels are
much higher than line
levels and can damage the input circuitry
in the HRS120.
You can, however, insert a speaker-level to
line-level signal attenuator between the
receiver’s speaker output and the HRS120’s
input. Your Mackie dealer may be able to
help you find one, or you can build your
own. Contact our tech support department
for more information.