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Macro-Tech
®
602/1202/2402 Power Amplifiers
subjected to a magnetic field from a power cord or
power transformer. One way to prevent inductive cou-
pling is to lace the input cables together along their
length and route them as far away as possible from
power transformers and power cords. The use of
shielded pair cable is another effective way to reduce
or eliminate hum resulting from inductive coupling.
Input and output grounds are sometimes tied together
for testing or metering. This can cause feedback oscil-
lation from load current in the test loop. In some sys-
tems, even the AC power line may provide this
feedback path. Proper grounding, input isolation and
isolation of common AC devices in the system is good
practice.
Use Good Output Connectors
1. To prevent possible shorts, do not expose
the loudspeaker cable connectors.
2. Do not use connectors that might acci-
dentally tie two channels together when mak-
ing or breaking connections (for example, a
standard three-wire stereo phone plug).
3. Connectors that can be plugged into AC
power receptacles should never be used.
4. Connectors with low current-carrying ca-
pacity should not be used.
5. Connectors with any tendency to short
should never be used.
3.3.5 Output Connection
Consider the power-handling capacity of your load be-
fore connecting it to the amplifier. Crown is not liable for
damage incurred at any time due to overpowering. Fus-
ing loudspeaker lines is highly recommended (see Sec-
tion 3.3.6). Also, please pay close attention to the
precautions provided in Section 4.1.
HOW TO DETERMINE
APPROPRIATE WIRE GAUGE
It is important to use loudspeaker cables with sufficient
Reference Manual
gauge (thickness) for the length being used. The resis-
tance introduced by inadequate loudspeaker cables
will reduce both the output power and the motion con-
R
L
R
S
DAMPING
FACTOR
20,000
10,000
5,000
2,000
R
L
1,000
40
LOAD
RESISTANCE
500
(ohms)
30
200
100
20
50
20
15
10
5
10
9
2
8
1
7
6
5
4
3
Example Shown:
R = 8 ohms; R
L
Cable Length = 10 ft.; answer: #8 wire
2
1.5
1
0.9
0.8
0.7
0.6
0.5
Fig. 3.13 Wire Size Nomograph
.0002
R
S
SOURCE
RESISTANCE
(ohms)
.0004
.0006
.001
.002
.004
.006
.01
.02
8000
COPPER
.04
WIRE
5000
(AWG)
.06
(ohms/1000 ft.)
.1
1000
2-COND.
CABLE
500
(feet)
.2
1
2
#28
100
5
#26
.4
10
50
#24
.6
#22
20
#20
50
1
#18
100
10
#16
200
#14
5
500
#12
2
1000
#10
2000
#8
1
#6
4
5000
#4
.5
#2
6
#0
#00
10
.1
#0000
.05
20
.01
40
= 0.016 ohms or D.F. = 500;
S
Page 17
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