Blackness - how quiet does it need to be?

If I got this right, the equipment is the conduit and the music is the signal. That signal can sound cleaner depending on the equipment. One familiar enough with a recording can discern a lower noise floor using the same signal (music) while comparing different makes of equipment. And a really good piece of equipment can detect the noise floor limits of a so-so recording. It works both ways as it would be difficult to decide if you have a really good recording if your equipment is not up to par with the recording.

Familiarity with your equipment is necessary. Now if you hear a slight hiss with your ear at the speaker (really slight) and not at your listening spot, I wouldn't worry. If your system were to mask the hissing of a poor recording, I would worry. Sound to me like your system is okay.

On Diana Kralls Love Scenes CD I can hear when she comes in and out of the music. She is recorded separately as the noise floor on her voice is messier compared to the rest of the recording. Right before she comes in, the noise floor is comparatively low and when she does come in, you can hear the hiss levels rise along with her voice. When I first heard it, it was quite disconcerting. As she stops singing, the hissing goes away to reveal a quieter background as her backup musicians play on.

That's why I tend to go for better recordings which can really limit what I listen to. That is the price you pay for your endeavors.

All the best,
Nonoise

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