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此時無聲勝有聲！8 N5 q9 _+ Z& ?
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* @1 ^6 T2 u+ UA typical high-impedance system is shown in Figure 1. A transformer at the power-amplifier output steps up the voltage to approximately 70 volts at full power. Each speaker has a step-down transformer that matches the 70V line to each speaker's impedance. The primaries of all the speaker transformers are paralleled across the transformer secondary on the power amplifier.- ^) U& M- E$ ]7 |
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ADVANTAGES OF 70V OPERATION6 e: m# d6 W* P9 }
As stated before, a 70V line reduces power loss due to cable heating. That's because the speaker cable carries the audio signal as a low current. Consequently you can use smaller-gauge speaker cable, or very long cable runs, without losing excessive power. Another advantage of 70V operation is that you can more easily provide the amplifier with a matching load. Suppose you're connecting hundred of speakers to a single 8-ohm amplifier output. It can be difficult to wire the speakers in a series-parallel combination having a total impedance of 8 ohms. Also it's bad practice to run speakers in series because if one speaker fails, all the speakers in series are lost. This changes the load: r" n3 f$ |6 R6 U
impedance seen by the power amplifier., ]$ _) |5 b1 g; X' c
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发表于 2016-8-28 17:05
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发表于 2016-8-30 23:17
