Two sorts of ways of looking at this. The noise floor that is the noise you hear when the volume is turned up, this noise hardly even matters. In my system this noise level is so high you can hear it from the door. Its totally obvious from the sweet spot. When the needle drops the groove noise is even louder. When the music starts none of this matters.
Because when the music starts then there's the noise floor that is the silence between the notes. When this noise floor is low you can hear the subtle acoustic signature of the recording venue clearly, sometimes even between the notes in fairly loud passages. Its just there all the time.
Whether you even call this a noise floor, or consider it more micro-dynamics or detail, or say its the ability of the system to start and stop so fast and clean, there's different ways of looking at it. Whatever you call it this one matters a whole lot more than the other one.
Grounds and dedicated circuits mostly affect the second more meaningful form of noise. The kind of noise that tends to become interwoven into the signal and part of the music. The other white noise, and sometimes low level hum, these are more constant and so more easily heard when nothing is playing, but also more easily tuned out by the ear/brain once the music starts.
Because when the music starts then there's the noise floor that is the silence between the notes. When this noise floor is low you can hear the subtle acoustic signature of the recording venue clearly, sometimes even between the notes in fairly loud passages. Its just there all the time.
Whether you even call this a noise floor, or consider it more micro-dynamics or detail, or say its the ability of the system to start and stop so fast and clean, there's different ways of looking at it. Whatever you call it this one matters a whole lot more than the other one.
Grounds and dedicated circuits mostly affect the second more meaningful form of noise. The kind of noise that tends to become interwoven into the signal and part of the music. The other white noise, and sometimes low level hum, these are more constant and so more easily heard when nothing is playing, but also more easily tuned out by the ear/brain once the music starts.