When you send your pristine and clean signal to the amplification stage for playback over your studio monitors the amplifier adds noise. You can prove this by only routing the mixer to the amp with no signal. The noise floor from the mixer will be amplified and if you turn up the volume on the amplifier you will hear “air” or a slight bit of static. This is before you send any audio program signal to the amp for playback. So, as you can see, not everything is your fault. While a digital recording can be produced to almost perfection, for now, there will be noise in the signal that has been inherited from the other components.
Some audio reproduction systems are cost prohibitive for the home recording enthusiast but for exceptional audio program playback with the absolute least amount of equipment noise it is well worth the investment. As you can see there are always going to be extenuating circumstances and equipment issues so you should do the best with what you have and invest in better equipment when your budget allows. Allow for your specific field of audio production. If you produce electronic dance music you won’t need much hardware/equipment. On the other hand, if you are interested in recording the performance of an orchestra you will need microphones, cables, amps etc. This can be a cost prohibitive endeavor for someone that owns little recording equipment.
Even if your entire signal chain has been digitally recorded and is as absolutely clean as possible you will still encounter noise on certain playback systems such as home computer speakers, touch screen audio applications and MP3 players. These systems are mass produced using affordable off-the-shelf electronics and according to FCC regulations must accept interference without causing interference to other electronic devices such as pace makers etc. This is one of the main reasons airports ask their patrons to disable electronic devices when traveling by air.
There is also a considerable amount of atmospheric interference that naturally occurs on Earth and from space weather. These enormous electrostatic and magnetic storms effect all electronics that are not shielded from such events. A transient electromagnetic disturbance, if powerful enough, can disable all non-shielded electronic devices and power sources such as batteries. At the end of the day with all things considered, you are recording audio under the most severe and almost impossible conditions and yet here we are.