Blackness - how quiet does it need to be?

This is not complicated. Your right on the mark, Last Lemming. The recording has nothing to do with it. We're talking about gear. However, noise floor is not the only factor influencing low level resolution. Typically, if you put your ear up to the speaker at 0-half volume and don't hear anything except the tweeter, the amp has a low noise floor. Especially on an efficient speaker like a Klipsh. If it's noisy, it stands to reason that resolution is going to suffer commensurate with the level of that noise since the amp is going to amplify whatever it's being fed. At "couch" distance it's irrelevant unless of course you can hear it there! Differences are apparent when A/B ing amps with the same recordings and other gear. So in answer to your question; yes, they mean the equipment is quieter. From your description it looks like you have a nice quiet amp.

Csontos - CDP is also an equipment and can be very noisy when playing but quiet when not. That way noise is undetectable without music (proportional to volume). In addition amplifier might create noise of its own by intermodulation etc. (speakers can also intermodulate).

Last_lemming, your amp might appear as quiet but in reality can be very noisy.

Sure, but I was referring exclusively to amps of considerable quality where differences are relatively small.

The OP's question, regarding how noise that is not audible beyond a very short distance from the speaker when no music is playing might have audible significance, is an excellent one, that I've pondered myself at times.

I think that Kijanki's answers are on the mark.

In the digital domain, the explanation is easy, namely jitter effects, as he indicated.

In the analog domain, it is not that clear, but the one explanation that occurs to me relates to intermodulation effects, as he also indicated. The ear is much more sensitive to some frequencies than to others, as can be seen in the figure in this Wikipedia writeup on the Fletcher-Munson Effect. Non-linearities in the speakers, and perhaps also in the electronic components that are in the analog signal path, will result to some degree in intermodulation effects, producing (at very low but conceivably significant levels) new frequencies corresponding to the sum and difference between all of the frequency components that are present. Hiss typically contains a mix of essentially all frequencies within some broad range, especially in the upper treble region (and beyond, at ultrasonic frequencies that are inaudible in themselves). Perhaps intermodulation of some of the frequency components of the music (and perhaps also frequency components of recorded noise, tape hiss, and/or LP surface noise) with those upper treble and ultrasonic system noise components results in difference frequencies in the lower treble or mid-range regions, where the ear is more sensitive.

That's my speculation, anyway, elaborating on what IMO were excellent answers by Kijanki.

Regards,
-- Al

I'm trying to understand the concept of the CDP contributing to noise while playing vs. when not. How would one hear this noise while the CDP is playing? In my case it's a transport to DAC. What I do know, is that on high quality hi'er res material like 96k/24 bit, on quiet passages, the hiss level hardly goes up, even on more than average listen levels. In other words I can only hear the hiss if Im very near the speakers, but certainly not when sitting. Now this only holds true for well recorded sources. Of couse I have hi res recordings that have hiss in the recording like my Miles Davis, Kind of Blue that I can hear from my couch, but this is not the same thing that Kijanki is speaking of.

I don't quite understand what IMD is, in layman terms. So Im off to look that up.