Power supply for Purifi Eval board...

Hi all,

Just wondering about the requirement for the purifi Eval 1 PDR gate drive rail (15v) to be grounded to the main negative rail (nominally -65v). I have a large transformer with multiple secondaries, can I safely connect any nominally chosen wire to act as ground for this 15v line? More specifically I would have the linear stage, so the negative of the linear 15v would be connected to the -65v as ground.... Is that a safe thing to do?

Equally if I have two transformers and two separate supplies, so that one gives me +65/0/-65 and one 15v/0, is is save to connect the ground of the 15v to the -65v, and do I need to be aware of any risks?

In all cases I will be working with linear supplies and transformers, no smps intended.
 
I'm considering using a linear power supply to power a Purifi or Hypex NCore based amplifier's input buffer (opamps) instead of using the usual Hypex SMPS Vdr 15V 500mA aux, as Apollon audio does for their premium Purifi and NCore amps:
lps+buffer.jpg

It makes sense since you need the cleanest power to preamplify the line signal through the opamps, and a SMPS seems not optimal. The Power modules may not matter, but the line-stage does.
It employs a toroidal transformer from the mains and a linear power supply with regulators to feed the buffer.

I could use an integrated LPS like these if it fits within the box:

https://www.audiophonics.fr/en/diy-...ted-dc-lm317t-lm337-125v-18v-05a-p-11647.html
https://www.audiophonics.fr/en/line...c-power-suppy-module-lm317-lm337-p-16921.html

Both can be configured to output +-15V and 500mA. Do you think they could elevate the sound quality to be worth the Apollon 4.5k€ amplifiers?