I did a frequency response test (using miniDSP EARS & REW) on my SMSL SU-8 v2 DAC and found that the phase performance is strange. I used 2 headphones: Sennheiser HD650 & Hifiman HE-4XX, both single-ended. I also compared the SU8 to 2 other DACs: Grace SDACB & XiangSheng DA-05B. All DACs were...