When using a genuine CCxx LEF amplifier module (e.g. CC75 or CC80) a sound quality improvement and design simplification are easy to achieve. Due to the LEF current amplifier and a very low THD voltage amplifier stage a negative feedback loop is not necessary anymore.
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Fig. 2 shows such design.
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The current to voltage conversion is done passively without any dynamic sound quality degradation. 6 signal “copies” of the traditional design are replaced by just 2 signal “copies” - just one voltage amplifier stage and one LEF current driver.
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In addition the basic circuitry of the CCxx modules suites balanced designs much better than any OP-amplifier. Most high quality applications require balanced circuitry. A true balanced circuitry solution with operational amplifiers further increases the number of amplifier stages.
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Even though this circuit already improves the sound quality remarkably compared to traditional solutions, it is not perfect indeed. The passive current to voltage conversion causes a voltage swing at the DAC output. Thus some DAC increase the amount of harmonic distortions. The noise figures of a single ended class A amplifier without any negative feedback loop are limited to about 100 dB, which is quite good already.
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The voltage amplifier inside the CCxx module produces a higher distortion level than a traditional amplifier with negative feedback loop correction. The total distortion level is about 10 times higher than high quality OP-amplifier solutions. Regarding no use of any feedback loop this is an excellent result anyway. |
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