Help with buzz / hum that's making me insane r

Thanks everyone for your responses.

Sonofnorway: the only interaction between my video and audio setup is I have the audio of cable going through the integrated with a humbuster rca pair. I disconnected the that rca pair and unplugged all the power of the video setup (plasma screen, brain, cable and dvd) from the wall and the hiss was still there. I didn't unplug the cable from the cable box, but there was no power going to any of the video gear and they weren't linked to audio setup with any ICs.

Nick778: thanks for the clarifying question. It's definitely a hiss that also has a very slight fizz to it, like a digital hiss. It's only on the dome tweeters of the Dali's; the ribbon tweeter and other drivers are dead silent.

Apachef1: On the same circuit I have my NAS for my media server, a Cable modem, a printer, a phone and two lamps, both non-halogen. All kitchen appliances (fridge etc) are on a different line. (I can't install dedicated lines, FWIW).

Hififile: No dimmers, but kitchen apps are on a neighboring circuit. It's a condo in 50-unit building. I don't think my breaker box has any screws to tighten--it's all just breakers w/switches, but I'll check.

Herman: The only problem is that this is a new thing I'm experiencing. The hiss may have been there all along and I'm just now noticing it, but the way it manifests itself in listening is that vocalists with higher-pitched voices, or violins, etc have a very, very subtle distortion. So, vocals that seem to me like they should be crystal clear in production (annie lenox, etc) have a very slight throatiness to them. In most cases this just sounds like texture to me, but sometimes sounds like distortion. Again, it's very subtle and it could be that all the upgrades have made my system more revealing and I'm hearing things I wasn't before that sound like slight distortion but are just texture; however, I'm perplexed and do want to get to the bottom of this. I notice this more on voices in the middle of the soundstage. All other frequencies sound frigging amazing, and not all treble sounds this way, so it could be psychosomatic, but I would like to figure out if there's an issue or I need to adjust to my system. Sure I'm not the first!

There are few amps that don't produce the hiss you describe if you are talking about getting your ear within six inches or less. The more efficient your speakers the more noticeable the hiss.
There are two amps which come to mind that were dead quiet, the Acurus A-200 and Sony TA-F707es. A noisy amp that comes to mind was the Portal Panache. It hummed and hissed and also produced an annoying thump during power on/off. The odd thing is the Portal was one of the best sounding amps I've owned once the music started.

The amp is dead silent. I just disconnected everything, save the amp and threw the breakers on the rest of the house and the hiss was still there. Then plugged in sources one by one, then added video section--still hiss. Then powered up rest of house--still hiss.

The hiss is only audible with ear next to speaker (the same was the case when I connected different speakers, so it's not the speaker, and the hiss was there with different amp, so it's not the amp).

I'm realizing I may be a big huge idiot. My wife feels, and she has very good ears, that this is just a more revealing system then any I've had, so voices actually have texture, as opposed to always sounding pristine. I can't imagine it's a ground loop, since I've disconnected everything and the sound is still there. The sound of my system is amazing, so maybe I'm trying to hear something that isn't there, which may be true because I don't notice it on all recordings. Can this hobby drive you crazy or what! If others can chime in as having experience this, or it being normal (as has happened in this thread) then maybe I need to trust that advice.

The hiss with your ear next to the dome tweeters means they are working. Agree with Herman it's not a malfunction. Advise you not increase the volume above normal listening levels to listen only to the hiss.

You can lift ground by adding a two prong cheater to the end of a three prong plug. So long as one component is properly grounded all the others linked via interconnects will share that ground. That's why if you did have hum, which sounds like you do not, the hum will persist even if the offending units are turned off but remain connected.

Dissatisfaction with the system's sound indeed indicates distortion. Surely it has nothing to do with your operating dome tweeters.

Enjoy that pretty room you have but move the carpet over so it's centralized equally between your speakers.

Thanks Rockvirgo, I am moving the carpet tomorrow. Can't believe I never picked up on it. I have been, and am still VERY happy with my system; however, in thinking about my hiss issue, I've decided there are two separate things going on:

1) The tweeter hiss is perfectly normal and only audible if ear is at tweeter
2) I could have a sibilance issue do to recabling and adding new ICs

Assuming the sibilance is cable related, I guess I'm wondering what to do. I didn't notice it before installing the Nordost cables, so I will swap them out and see if that is the issue, although I'd be surprised (wouldn't be the first time). If that's not it, I'm wondering what my next step should be. My speaker cables are 3 meters, which is more than I need, so I've got the excess length coiled under my stand. I had them this way before the sibilance became an issue, although I did recently remove them and put them back in, and I know purist cables are thought to take a while to settle back in, so maybe it's just a waiting game.

If it's not the SCs and not the ICs, then what next? From reading other descriptions of this sibilance issue from other people on the net who've experienced it, I'm pretty sure that's what's going on.

Should I clean my connectors? cap off any unused inputs on my integrated?