Thing is, when I turn on my system and no music is going through it, I can't hear anything, unless I put my ear right up to the speaker and the AC isn't running and the fan isn't on, etc. And with music on the only thing I hear is any recorded hiss that might be from the recording. So what I dont get is when they say a piece of equipment sounds quieter, do they mean somehow that the hiss on the recording is lower? I cant see how that would be possible...I agree that, on the face of it, this seems impossible. But Ive had a number of experiences that have led me to conclude otherwise.
For a long time I thought that my system was dead quiet, due to the fact that there was no audible noise floor when the system was on and no music was playing. As a result, whenever I heard hiss during playback, I believed that the hiss was in the recording.
Several months ago, I made an effort to reduce RFI/EMI in my system, which is discussed in this thread. One of the consequences of those changes was that hiss during playback was dramatically reduced. But the reduction of hiss was audible ONLY WHEN MUSIC WAS PLAYING.
From this I concluded that a significant fraction of the noise floor that I thought was IN THE RECORDING was actually IN THE SYSTEM. But the noise floor in the system was not perceptible when the system was "at idle."
I know that seems paradoxical, but that's what I experienced.
Bryon