Background noise.

@ditusa  I think you missed my point. That everything gets put back onto the line as noise. Also, I'm surprised a rack company has a blanket statement opinion about power conditioning. That's the first haha. 

Great thread; thanks, ghdprentice! I’ve got several things to say here.

First, I completely agree that ambient noise is almost surely a far bigger problem for most high-end systems than any less-than-optimal component. It’s at least as important as room acoustics and proper speaker positioning. In my previous house, when I had to buy a new fridge, my first criterion: how quiet the damn thing was. This always amused salesmen. Now, I’m lucky; the house is big, the kitchen is two rooms (and walls) away, and my listening room is very quiet. So quiet, that the slight hum my old amplifier’s transformer has developed bugs me. I’ve tried many strategies to resolve this, some of them discussed, or learned about, on this forum (e.g., a varnish "dip-and-bake"; you don’t want to know). Like curiousjim, I also took my unit to a very competent tech, and he couldn’t hear the hum at all. Of course, his shop was on a busy street. But I’m fanatical, I’ll admit, about creating as quiet a space as possible for listening. I think it was ghdprentice who mentioned watching a fire while listening. I’ve got a fireplace in my listening room, too, but I never do any serious listening with a fire going. The fire makes too much noise!

I’ve got a John Cage story that’s relevant here. I met him once, through my wife. He told me about having spent an hour in an anechoic chamber. He claimed that, even in "complete silence," he heard two faint sounds, one very low, one very high. He concluded the low tone was the sound of his blood coursing through his body, and the high hiss-like tone was the sound of his neural activity. But I think he just suffered from tinnitus without realizing it; there’s no way one can "hear" one’s neurons firing as a constant high-pitched hiss! Of course, John Cage was all about the impossibility of "silence," about how "music" is more a matter of the attention of the listener than the intention of a composer, so his story had a Cagian moral.

As for SPL meters, on Apple products or whatever else—you know, I suppose, that they must be properly "weighted." Most inexpensive SPL meters are "A" weighted, and meant for testing ambient noise at worksites that may be dangerous. "A" weighting cuts out at 100 Hz, if I remember correctly; it’s somewhere below which there is A LOT of musical information. If you have a meter that can switch between "C" and "A" weighting, it’s startling to do so; music that reads, say, 80 db in "A" will jump to 90 db or more in "C." And, of course, Apple products don’t prioritize the noise metering they throw into their devices. Get a proper meter if you want an accurate reading.

Regarding panzewagn’s comment about architects using HVAC and other drone noises to "create some sense of privacy"—yes, of course this seems crazy, but it may not be not quite as pointless as it seems. My dad was a Caltech scientist, and a very finicky person. We lived at the end of a private road up against the San Gabriel mountains, where it was very quiet—but not quiet enough for him! In his study, he had an old heater with a fan; the heater didn’t work, but the fan did, and he ran it all the time when he was working. He claimed that the constant droning sound distracted him from being disturbed by the occasional dog bark or distant car horn or whatever. I think I get this.

One last thing. There’s a psychoacoustic phenomenon—I forget what it’s called, but there’s a Wikipedia page about it—according to which certain low-level kinds of noise actually focus the mind’s attention on the "meaningful" sounds those noises might otherwise seem to mask or distract from. There is a theory, which makes a lot of sense to me, that this phenomenon explains why some people prefer vinyl to digital: the surface noise and the occasional pop and click, far from distracting from the music, actually provide a background against which conscious attention isolates the musical information, highlights it as it were. This could explain my dad’s practice mentioned above, but would be diametrically opposite to the preponderance of views expressed here (including my own) that serious listening demands as quiet a "noise floor" as possible. It’s one of the reasons I don’t buy into the vinyl fetish; there’s just too much scientific evidence of its irrationality, and in any case, it certainly doesn’t correspond with my own listening preferences. Most of us live in perpetually noisy environments; it is possible that, for those who do, brain "circuitry" has accommodated itself to attention against a constant background of noise, and this may be why vinyl sounds better to them. I’m lucky in that regard to live almost all the time in environments that are very close to silent.

Thanks for your thoughtful comments @snilf. On your father and background noise. I struggled with ADHD through school until I was around 30. I did not know I had it… but I could not concentrate… nearly flunking out of college more than once. I noticed sometimes if I studied in the Student union cafeteria I could concentrate for a while… all the talking would become background noise and suddenly I could study. Many times it would not work. For much of my life I just thought I was stupid… that was my fathers belief.

I found that being in exceptional shape (massive amounts of daily exercise) also allowed my mind to concentrate. I figured this out in my early 30’s. Then I went to graduat school where I graduated near the top of my class. I figured out that I had ADHD while in my mid 40’s. Confirmed by my doctor when I was 60. Maybe your dad had a little AD.

Boxcarman: Absolutely brilliant. It's nice to know vaudeville is still alive!

Thinking further along the line of low levels of background noise, I dawns on me that different systems have different presentations of low level detail. I am thinking of the recording venue. Let’s assume a symphony hall for the moment.

I used to listen at the symphony to just the reflections of the sounds. So, if the violas would abruptly start playing I could hear the sound reflect off the sides of stage left, then the ceiling and then blend from the same sounds reflecting at the back of stage. These are pretty sublet and only a small number of db above background.

One my major realizations were that many systems overemphasize the venue of the recording. So say these reflections were 5db above the background… my current system would represent them as about 5db. But a lot of systems… my last generation included would represent them as 10db above the background. This is what I consider details forward. An overemphasis on quiet detail. Thirty years ago, I would have chosen this as “better sounding”.

My thought is that these two systems would sound very different in rooms with different background noise levels. Assuming the same character of sound in a noisier room, one would probably identify the 10db venue as better balanced because the details would not be drowned out. One more variable in evaluating systems.

Better and better equipment tends to get better at presenting all sounds proportionally (I think… assume.. in general). So if you don’t make sure your audio environment is up to the challenge, you could be losing a lot. Maybe by accident, I have worked at more and more aspects of sound as my system has improved… so I now have the best quietest audio room I have ever owned.

I am not adding, change volume… because that adds a bunch of additional variables.