I connected the DigiOne to a Pro-Ject Pre-Box S2 Digital and went from there to the RCA inputs of the NAC252. But the sound was unsatisfactory.
The DigiOne Signature is now connected to the enclosed power supply on the RPI side and for the clean side I use an iFi Audio ipower 5V.
Since this (NDS / 555 PS DR) is a very expensive DAC , I will deal with the Chord Qutest or the Mytek Brooklyn DAC +.
Thanks! I am currently using an iFi Audio ipower 5V to power a DigiOne connected via DC1 BNC-BNC to a Naim DAC. The DigiOne sound quality improves if one grounds the iFi as explained in the "SMPS and grounding" thread in the UpTone Audio subforum of the CA forums. Allo do not recommend the iFi following their measurements. If you are after the best results withe the DigiOne Signature, you could perhaps power its clean side with a battery pack, see posts above, e.g., by RX8R3ROD. Enjoy the Signature!