I finally choose MUR115, but dunno if ultra fast diode...will introduce RF noise or not......
for my case, I compare my USB DAC against the DZ1855
although in Specification, DZ1855 should win...however, I feel that USB DAC 's sound is more dynamic, more bass and less noise at the background..... I dunno how to discribe......DZ1855, I was using 1N4004.....LM317/337 for LPF and LM1085-5 for AD1855, USB DAC using MUR115....LT317/337 for LPF and LM1085-5/LM1085-3.3 for PCM2702
Testing Condition:
2theMax(EPOX) 8RDA+ 's SPDIF out and USB2.0 onboard
Windows XP with Winamp 2.81 with MAD plugin and SRCC
For DZ1855---> MAD 24bit, SRCC 24bit, 96Khz
For USB DAC---> MAD 16bit , SRCC 24bit, 48Khz
Playback:
GIGI Leung and Kit Yee Chan legal CDs, Joey Yeung mp3 192Khz.
I do think LT317/337 used in LPF and Diode give these differences....or maybe layout of pcb, Chang has done a good job