The thickness of wire is rated in gauges. Use the chart below to determine the correct gauge of wire to use according to the distance between the speakers and the amplifier, and the impedance of the load the amplifier is driv- ing. This ensures that the power lost across the speaker wire is less than 0.5 dB.
| Load | Gauge of |
Wire Length | Impedance | Wire |
Up to 25 ft. | 2Ω | 14 gauge |
| 4Ω | 16 gauge |
| 8Ω | 18 gauge |
Up to 40 ft. | 2Ω | 12 gauge |
| 4Ω | 14 gauge |
| 8Ω | 18 gauge |
Up to 60 ft. | 2Ω | 10 gauge |
| 4Ω | 12 gauge |
| 8Ω | 16 gauge |
Up to 100 ft. | 2Ω | 8 gauge |
| 4Ω | 10 gauge |
| 8Ω | 14 gauge |
Up to 150 ft. | 2Ω | 6 gauge |
| 4Ω | 8 gauge |
| 8Ω | 12 gauge |
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Up to 250 ft. | 2Ω | 4 gauge |
| 4Ω | 6 gauge |
| 8Ω | 10 gauge |
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70V DISTRIBUTION SYSTEMS
A distributed sound system uses a constant- voltage,
tions when setting up a
Because of the high power capability of the M•1200/M•1400 amplifiers, they can be used to directly drive 70V
M•1200: K = 800W/625W = 1.28. Thus, a 2.5W tap becomes 3.2W, a 5W tap becomes 6.4W and a 10W tap becomes 12.8W.
M•1400: K = 850W/625W = 1.32. Thus, a 2.5W tap becomes 3.3W, a 5W tap becomes 6.6W and a 10 W tap becomes 13.2W.
CAUTION:A characteristic of tappedtransform- ers is that they saturate at very low frequencies, which causes their impedance to decrease, ap- proaching the DC resistance of the copper wire. This can result in overloading the amplifier if the signal contains lots of low frequencies. When using an FR Series amplifier in a 70V dis- tribution system, set the LOW CUT FILTER
FR SERIES
POWER AMPLIFIER IN BRIDGE MODE
+
CH 1
–
–
CH 2
+
RC NETWORK
+C1 C2+
R1
to 100Hz or higher. In addition, install an RC network at the SPEAKER OUTPUT of the amplifier, as shown in the figure below.
70V LINE
RC NETWORK VALUES
C1 = C2 = 660∝F @ 250VDC
R1 = 4Ω @ 100W
ALTERNATE RC NETWORK
Note: You can substitute |
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a single capacitor for C1/C2. |
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C3 = 330∝F @ 250VDC, |
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2.5W | 5W | 10W | 2.5W | 5W | 10W |
++
––
CONSTANT
VOLTAGE
TRANSFORMER
2.5W | 5W | 10W |
POWER TAP
SWITCH
+
–
70V Constant Voltage | 25 |
Distribution System |