David, what Alan points out relating to buying a separate DAC is certainly supported by hard evidence, rather than fanciful illusions. In addition to controlled blind listening tests, measurements of units taken(including their internal DACs)are pretty uniform in demonstrating audibly flat frequency response with inaudibly low noise and distortion.

Despite this, the urge to tweak the untweakable persists, and of course there are sellers only too happy to profit handsomely by satisfying the urge.

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Enjoy the music, not the equipment.