raysay could you prove it mate, have you a receipt ? could you evidence the d30pro sitting with the other gear ? or do you work actually for Schitt :-)
It happens every time I go from pre to hpa or hpa to pre. It doesn’t change with volume on the amp, usual listen level vs full attenuation it’s the same. With the dac powered off it behaves the exact same
Perhaps its a consequence of the irregular impedances? if this skews some frequencies it might explain why something isn't sounding "right/correct" in your mind
in an RCA only system is there any benefit to having the Pre90 over an L30. Remote control is an obvious one but in terms of sound quality as a pre-amp with RCA out connection to a power amp.