Electrical issue

I have an electrical issue/s that I could use some help with. It's a hum issue, but after exhaustive research here and on AA I still cannot figure it out. I have 4 dedicated lines for my stereo run approximately 75 feet with 10/2 romex all connected to Porter Ports. I own Von Schweikert DB-99's, which have a powered sub built in. I have tried lifting the grounds on all the equipment except one(and every conceivable variation,I think), I've tried plugging everything into a power strip and then that into just one outlet, I've even tried using other outlets(not dedicated). In the end, if I disconnect everything and just plug the speaker into the wall with no other connections I will get a hum thru the woofer only. I have even put a PS Audio P500 between the speaker and the outlet to see if it made any difference to the hum, but no luck. If I leave the speaker wires connected and turn on the main amp then I will hear hum thru all the speakers(tweeter/mid/woofer).

I called VS and spoke with Kevin and he said that the signal is split in the speaker before the sub amp which would suggest that the hum is coming from my electrical system rather than my equipment. IOW, if I heard hum only thru the woofer and not the other drivers when the main amp is connected then there could be a problem with the sub amp, but this is not the case.

My house is new and the electrical and grounding system seem to be in good shape. I have checked every outlet I could find with a polarity/ground checker and did not find any problems. My panel is grounded both to the water line and a spiral rod buried next to the house. According to the builder these are acceptable to code here in Austin, Tx.

The only thing that seems odd is that when my A/C turns on, and sometimes my TV, the lights will dim for a second. I had the builder double check all the connections and made sure the proper gauge of wire etc. was used to hook up the A/C, but nothing seems to be wrong. Is it perhaps the Transformer on the pole outside? It's definitely old as it looks a bit rusty up there(new house - old neighborhood).

The hum is not particularily loud, but i can here from my listening position 10 feet away when no music is playing. I appreciate any help you may have to offer, and I'll answer as many questions as you have because I'd really like to solve this.

This may be totally off track, but I was a technician and was troubleshooting a problem at a customers home. I found no problem at the home, but with an RF meter, walked down the street and found a neighbor had installed an invisible fence for his dogs. He had the gain turned up to the max and this was affecting their TV, appliances and garage door opener. Their tv had lines and a hum. This may not be your issue, but worth a look. The man turned the gain down and the problem went away.
Good luck!
Do you have any halogen lites? I had a hum problem that none of my friends who are also into this hobby could solve. Turned out it was the halogen bulbs in my listening room's pot lites. Changed all of them and the hum was gone.Although we live in different places it seems as if the"power company" plays by it's own set of rules.In my case they lost when they read the weekends power read out and installed a new transformer on the outside pole.Of course I did mention that they would be liable if my AC and refridgerator motors burnt out.
I sypathize. I am having very similar issues. So far, the only thing that has helped is plugging my amp into the richard gray 4000pro and having that run into the pole pig. I am going to see if it helps with the second amp and external crossover. I have been suffering with my hum for close to a year now and since I live in the virgin islands, if you think your power company is bad.........

120hz would be the ripple component frequency of a rectified power supply. Trying to determine if it's an electrical or electronics problem. The PS unit should have isolated the equipment from AC, since it regenerates it's own. Did you try it with every thing hooked up to it, and all grounds floating? Also, does the Topaz offer 240/120 stepdown? You could try this and establish a good ground at the secondary, or float it. Doing this may determine if you have a problem with an unbalanced service transformer. Another thing, how about light dimmers? The triacs used in them have been known to cause problems. Floresence fixtures?

The topaz can step 240 down to 120 as far as I know. I believe we hooked it up that way at one point. We tried various connections, even wiring it for balanced output. What/How would grounding, or floating the ground, on the output side tell us about the service transformer?