On my Allnic D5000 dac I have balanced cables and HF reference cables in place. Both hooked to the pre-amp. I can immediately go a-to-b, b-to-a. The pre to amps are HF reference cables.
The result: Much wider, deeper soundstage, better inner detail, 3-D imaging. 20% louder too--like the proverbial voice of GOD. I know the output voltages are spec the same.
If someone is to purchase one cable, I would say source to pre is most effective.