Remember that the human component (you) of your system is the biggest variable you have. Both your physical and mental condition affect what you perceive and those factors are constantly changing.
That is not to say your power supply couldn't be an issue, but if it is, you should be able to measure noise on the line with the appropriate equipment. A related factor could also be EMI/RFI noise that your system is picking up through the air. I've got a shortwave radio fellow who lives half a block from me and I can always tell when he's busy with his hobby, particularly if I'm playing LPs.
However, over the years, I've found I'm more often the weak link in the system than any component.
That is not to say your power supply couldn't be an issue, but if it is, you should be able to measure noise on the line with the appropriate equipment. A related factor could also be EMI/RFI noise that your system is picking up through the air. I've got a shortwave radio fellow who lives half a block from me and I can always tell when he's busy with his hobby, particularly if I'm playing LPs.
However, over the years, I've found I'm more often the weak link in the system than any component.