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此時無聲勝有聲！
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A 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.& a! D- f$ O" B# K* D
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ADVANTAGES OF 70V OPERATION
+ B2 W2 f9 i9 I5 A) K$ i) v; S* FAs 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 load4 k2 p1 _, y5 X( R! h( g& U
impedance seen by the power amplifier.
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发表于 2016-8-28 17:05
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反对！
发表于 2016-8-30 23:17
