By its very functional principle, DSD has RFI of twice the maximum level of the audio signal and four times the nominal DSD “0dB” point between, 1.4MHz and 2.8MHz. DSD must be lowpass filtered to avoid these extremely high levels of RFI going out from the DAC chip and messing with the sound quality. Each filter is different. There is always a trade-off between impulse response, phase response, frequency response, and selectivity (how much-unwanted signals are suppressed). Which filter is preferred depends on many factors and it is hard to predict, simply try them all, pick the one that is preferred.
Did this article solve your problem?
If you’re still having problems, why not contact the iFi Support Centre. We’re available Monday to Friday.