I have upgraded the caps in my previos phono preamp. I had already upgraded the op amps, resistors, coupling caps and regulators. So I can definitively speak to the effect of just changing power supply caps.
In my case the backround got blacker as in the very low level detail was not lost or masked in the backround noise.
Also, the high frequencies lost an annoying zingyness. It was like I had changed from an agressive metal dome tweeter to a smoother silk dome type.
In my case the existing caps were very cheap and I replaced them with Blackgates.
I will also conceed that I may not have heard much of a difference if I had not already upgraded virtually everything else in the circuit.
Ofcourse, YMMV
In my case the backround got blacker as in the very low level detail was not lost or masked in the backround noise.
Also, the high frequencies lost an annoying zingyness. It was like I had changed from an agressive metal dome tweeter to a smoother silk dome type.
In my case the existing caps were very cheap and I replaced them with Blackgates.
I will also conceed that I may not have heard much of a difference if I had not already upgraded virtually everything else in the circuit.
Ofcourse, YMMV