Redbook played with the transport set to 176.4 and with NOS is definitely superior to just 44.1, and I can live with that as is, or even just Redbook without the upsampling. The Holo is a very good dac, but if I happen to stumble onto an intriguing mod I am bound like everyone else here to follow it down its hole.
Upsampling/Oversampling
I need some technical insight here. My Jay's Audio CTD3 Mk3 CD transport has the toggle switch for turning Redbook CD files into 4x upsampled (176.4kz) files. The dac being fed the files is a Holo May KTE. Holo Audio recommends keeping the dac in non-oversampled state all the time. The dac itself does no upsampling. The upsampling alone coming from the CD transport with dac in NOS mode makes for some very nice music, but I find I am liking the dac to be in oversampled (OS) mode when handling the 176.4 despite Holo recommending against it. In OS mode the detail, nuance, and air goes up a notch and voices gain more subtle inflection, and the music sounds a bit tubey and very pleasantly so. Problem is that after an hour or two of playing there will suddenly intrude pops and clicks that mandate stopping play.
I am assuming, perhaps wrongly, that the issue is that the dac's oversampling of already upsampled files is causing a mismatch of data processing that eventually catches up with and impedes proper data processing, and that the music feels more PRAT-y because there is some "euphonious distortion" that happens to sound "good."
After I have turned the CD transport off for awhile it can be re-started and all is well again when running the dac in OS mode - for awhile.
Any insights welcome.