@peng : Do you know if also the X6500H has the same bypass? This is what I've got in another forum
"Any analog signal presented to the Denon will be passed through a JRC NJM8080 opamp then to the AKM AK5358BET ADC, which is then steered by the TI PCM9211 DIX to the DSP which then presents the digital signal to the PCM1690 ΔΣ DAC. All of these components are tabletop radio quality at best. The ADC can only support up to 24/96kHz and the NJM8080’s performance leaves a lot to be desired.
If you pass signal via SPDIF or HDMI to the AVR, you will remove the ADC from the mix, that would be your first step at higher quality, however, it’s Achilles heel is it’s usage of the NJM8080 throughout."
I wasn't able to find the Service Manual for the x6500h. I've got this from the x6400h service manual.
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