Every system will have some noise inherent in the electronic circuits themselves. What your friend is hearing is the noise inherent in the circuit of his amp and preamp. Some are quieter than others (due to circuit design, layout of internal components and wiring, and the internal component parts themselves). Interconnects, speaker cables and power cords will also have an impact. So will the quality of the electrical power to the system.
The critical issue about this inherent noise (the noise floor of your system) is its volume relative to the music. Systems with materially high inherent noise will reduce the reproduction of the low volume details of the music, reduce the overall dynamic range of the system, and reduce the sense of "aliveness" that some systems are able to achieve.
To lower the noise floor: be aware of the contribution your cables are making and chose accordingly, supply good clean power to your system (dedicated isolated ground electrical lines, etc.), clean and apply a contact enhancer to your connections (like Pro Gold or Walker SST or Mapleshare Silclear), use fewer active devices in your system's signal path. Of course, component selection will play a big role.
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The critical issue about this inherent noise (the noise floor of your system) is its volume relative to the music. Systems with materially high inherent noise will reduce the reproduction of the low volume details of the music, reduce the overall dynamic range of the system, and reduce the sense of "aliveness" that some systems are able to achieve.
To lower the noise floor: be aware of the contribution your cables are making and chose accordingly, supply good clean power to your system (dedicated isolated ground electrical lines, etc.), clean and apply a contact enhancer to your connections (like Pro Gold or Walker SST or Mapleshare Silclear), use fewer active devices in your system's signal path. Of course, component selection will play a big role.
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