I have used a LP 5.3 for about 10 years now. I have never owned the power supply.
Even sans the power supply, the 5.3 is better than most turntables arms and cartridges that could be used with it.
One had better have every aspect of placement, isolation, level, spindle to pivot distance, arm height, overhang, azimuth, VTA, VTF, as close to perfect as one can attain. Then after doing that, if you have a big problem with what you are hearing you can justify suspecting a deficiency in the Moon phono stage. If everything is adjusted superbly, the Moon LP 5.3 or 310 should be perfectly satisfactory.
Even sans the power supply, the 5.3 is better than most turntables arms and cartridges that could be used with it.
One had better have every aspect of placement, isolation, level, spindle to pivot distance, arm height, overhang, azimuth, VTA, VTF, as close to perfect as one can attain. Then after doing that, if you have a big problem with what you are hearing you can justify suspecting a deficiency in the Moon phono stage. If everything is adjusted superbly, the Moon LP 5.3 or 310 should be perfectly satisfactory.