I recently purchased an used Pro-Ject Phono box phono pre-amplifier. I am extremely satisfied with the sound quality, definitely richer when compared to my Pyle PP999, but what annoys me is that the background humming noise is much louder and can be heard much sooner when I turn the volume knob compared to the Pyle. Even the integrated phono input on my amplifier produces a much quieter humming. I made sure everything was correctly connected and grounded, tried to use separate wall power plugs and disconnect everything connected to the same power outlet as well as all the other devices connected to my amplifier, leaving only my turntable, pre-amp and amplifier connected but nothing of the above seems to work right now. Is this loud humming normal? Is there anything I can do to fix this? My guess is that the Pro-ject phono box is not properly grounded but I have no idea how to fix this. Thank you.