For achieving an even better solution than Fig. 2, preserving the original music signal and achieving measurement specs beyond any discussion, the traditional idea of thinking in separate functional units (DAC, voltage amplifier, current booster…) has to be replaced by integrative thinking. The result is Current Injection combined with LEF
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Fig 3 shows a simplified Current Injection solution.
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The DAC (digital analogue converter) is drawn inside of the CCxx module, which symbolizes the merging of these functional stages. The DAC is an internal part of the amplifier design and there is no more amplifier input. A voltage amplifier does not exist anymore. The output voltage is generated by the original DAC current and thus no “copy”. Current injection avoids the input noise and almost all distortions caused by a voltage amplifier.
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"Un-measurable" specs like dynamic performance are also unmatched when using Current injection.
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At last there is just the LEF current booster left providing the only “copy” of the original music signal. This LEF circuit provides an outstanding performance.
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There is also no voltage swing at the DAC output and thus the DAC provides it's optimum performance.
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Without any negative feedback, without a lot of amplifier stages, with single ended class A performance and with optimum balanced signal handling current injection achieves noise and distortion specs on the level of top operational amplifier solutions. However Current Injection / LEF surpasses the traditional circuitry in any musical aspect. Unlike the traditional design, the non-feedback Current Injection / LEF design has no difference of static (e.g. sine-wave measurement) and dynamic performance (music). |
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