I am using a NOS R2R DAC, Mojo Audio’s Mystique X SE with nano-crystalline chokes and AD1862-Z chips (2 of them), which are said to be just as good (or better) than the AD1865 chip. I have directly compared all the Metrum Acoustics DACs, the Tambaqui, the Merason DAC1 MkII, and others, and I have not yet found one I like better than the Mystic X SE NCZ.
I will soon have a chance to compare again as I have an Aries Cerat Helene on the way. I appreciate all the positive comments you Helene owners have made, and I would appreciate any further insights about how to achieve the best sound from the Helene, such as whether tube changes can make a significantly positive difference (I hope not), the benefits (or not) of changing the bias, and where to buy new tubes (especially since they suggest leaving it powered up all the time).