Almost all of the noise floor is determined in the recording process and in the ambient playback room. Oh, and add the vinyl playback system.
As for modern digital and audio playback equipment, if they are correctly setup, they don't enter the listening noise floor picture.
So, some facts for the gang: it is possible to lower the noise in a "system", but is impossible to eliminate it completely. When something is powered, there will always be some level of noise.
Additionally, the noise from the power supplies of ampilfication components can and does go
back out of the power supplies of the components via the power cord to be re-distributed into
other components in the amplification chain.
Regarding modern digital and audio playback equipment: These devices are some of the most egregious and prolific sources of noise because the types and degree of the noise components they produce.
1) Computers of any type contribute signficant high-bandwidth RF and impulse noise from their CPUs and GPUs that audibly impact and degrade the sound quality of a stereo system. Additionally, this high-bandwidth noise can be picked up by many speaker cables (most which are unshielded for sound engineering reasons), and which literally function as antennas for these high-bandwidth noise components, and be fed
backwards into the power amplifier, only to be reproduced
again as amplified noise by the power amplifier. Any smart devices in the home, e.g. mobile phones, Wifi routers, tablets, non-audio computers, and smart devices also contribute the high-bandwidth RF and impulse noise in listening rooms. One of the best things you can do to improve your audio system is to move any computer-based music server, e.g., laptops, Mac Minis, Intel NUCs, etc. out of the audio rack and well away, distance-wise, from the main system as they are very "dirty".
2) The dreaded switch-mode power supply aka SMPS: this ubiquitous device powers almost everything these days, from computer's internal power supplies to streamers, network bridges, routers, NAS' and external hard drives, switches, fiber media convertors,
etc., etc.. They are very dirty and nasty sources of noise as they create both low-impedance and high-impedance AC leakage currents, which travels down the DC power buses and lines, USB or coaxial cables ultimately to our DACs. In particular, high-impedance leakage currents are particularly insidious as they cause increased jitter and most importantly,
clock phase noise.
3) Cheap clocks: The el cheapo clocks in consumer-grade cable modems, network routers, Ethernet switches and fiber media convertors also contribute notable
clock phase noise to the analog square wave voltages that are the actual embodiment of the digital music file bitstream, and the more of them in the configuration, the more the original signal is degraded.
4) Flip-flops on Ethernet Switches, etc.: The flip-flops in consumer-grade cable Ethernet switches, routers, and fiber media convertors are also really cheap, and also contribute notable clock phase noise, just as with the clocks referenced above.
5) Noise on copper Ethernet cables. Copper Ethernet cables are are susceptible to number of noise factors, including RF, EMI, the low- and high-impedance leakage currents described above, (lack of) galvanic isolation, and common-mode noise. A good mitigation strategy for this is to use a run of optical fiber between music server and network bridge/streamer/DAC.
6) The transformers and transformer cores on isolation transformers on Ethernet switch's RJ45 jacks are susceptible to the AC leakage currents described above "jumping" to adjacent jacks.
7) Noise on power cables for digital device power supplies: Even if high-quality linear power supplies are used to power the digital devices referenced above, the power cords for these power supplies are susceptible to impulse noise.
Bottom-line: there is noise virtually
everywhere with digital audio systems...
*– High-impedance leakage currents were only actually discovered 2 years ago, because existing test equipment did not exist to detect it. It was discovered and detected by John Swenson in Oct. 2017 after building bespoke test equipment to detect it. 
