MACKIE HR824 - Manual (Page 13)

13
Thermal Protect
All amplifiers produce heat. The HR824 is
designed to be efficient both electrically and ther-
mally.
• If for some reason the heatsinks get too hot,
a thermal switch activates, placing the
HR824 into Standby mode (indicated when
the red
PWR LED turns off).
• Should this happen, make sure that airflow
to the rear of the cabinet is not restricted.
• When the heatsinks cool down to a safe
temperature, the switch resets and normal
operation resumes.
INTEGRATED MAGNETIC SHIELDING
The HR824 Studio Monitor contains drivers
with large magnet structures. The drivers’ mag-
nets are shielded to help prevent the magnetic
field from radiating out into the environment
and playing havoc with computer monitors or
TV screens. Unshielded speakers can cause
distortion in both the shape and color of the
picture if placed too close to a CRT (cathode
ray tube). If you have a particularly sensitive
computer monitor or TV screen, it may be nec-
essary to move the speakers a few inches away.
INPUT SIGNAL WIRING
You should use high-quality, shielded cable
to connect the signal source to the SIGNAL
INPUT jack on the HR824.
• 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 HR824s, if the receiver doesn’t have
preamp outputs or other line-level output
connections.
You can either make or purchase a speaker-
level to line-level attenuator to reduce the
signal from the receiver’s speaker output so
it can be connected to the HR824’s input.
The following illustrations show how to
make an attenuating pad for the balanced
XLR and TRS connectors. Use a 330 ohm
resistor (R2) for a 30 dB pad, and a 620
ohm resistor (R2) for a 25 dB pad. This
attenuator can be used safely with amplifi-
ers rated up to 500 watts into 8 ohms.
2 1
3
3-Conductor Cable
Male
XLR
Shield
+
From Speaker Output
of Receiver
R1
(10K
.5W)
–
R2
(330 Ω .25W for –30 dB)
or
(620 Ω .25W for –25 dB)
2
3 1
SHIELD
COLD
HOT
From Speaker Output
of Receiver R1
(10K
.5W)
R2
(330 Ω .25W for –30 dB)
or
(620 Ω .25W for –25 dB)
3-Conductor Cable
3-Conductor Cable
3-Conductor Cable
1/4"
TRS Plug
1/4"
TRS Plug
SHIELD
+
From Speaker Output
of Receiver
From Speaker Output
of Receiver
R1
(10K
.5W)
–
SLEEVE (SHIELD)
TIP (HOT)
RING (COLD)
TIP SLEEVE RING
TIP R1
(10K
.5W)
R2
(330 Ω .25W for –30 dB)
or
(620 Ω .25W for –25 dB)
R2
(330 Ω .25W for –30 dB)
or
(620 Ω .25W for –25 dB)
SLEEVE RING
Figure 3. Speaker-level to Line-level XLR Pad
Figure 4. Speaker-level to Line-level TRS Pad