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.

Thanks,
Matt
mab33

Showing 5 responses by nerspellsner

Did you test the power at the meter yet? Is the hum still present before the power enters your dwelling?
Call your power company and have them test the transformer and install a data recorder at your meter if the CATV and phone grounds are not the problem. CATV and phone must be connected to the same ground rod as the service grounding conductor. Most power companies are required to provide clean power to the service. If you have a well, the ground rod or rods are your ground and the water pipes are not. The pipes are bonded to the ground for saftey. Never ever disconnect the ground wire of the service with the main breaker on. Turn off the main breaker before disconnecting the service grounding conductor. You could get electricuted if you dont. Your lights will dim for 1-3 seconds no matter what the size of the transformer when you AC starts. What you are hearing is probably a 60Hz hum. The hum could be coming in through the neutral from the transformer. If you lift (remove) grounds on your equipment with metal housings, you have a small chance of getting killed. If the power company will not help you do this. Hire an electrician and ask him to connect an outlet directly to the line (street)side of the meter socket. Plug your subwoofer or you whole system into that outlet. If it still hums, complain to your power company about bad power and have them fix it.

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You dont have to (steal) power to do this test. I will describe the legal way to test your power. This has to be done by a licenced electrician. Open your meter socket.Leave the meter in the socket and disconnect the feeder wires at the load side of the meter socket.As long as the meter is in place, you are not stealing power. Connect a fused or circuit breaker protected outlet attached to an extension cord long enough to reach your equipment. You have to find out if the hum is from the street or is coming from your house somewhere before you try to fix it.
A few more questions. Do you have only one main electrical panel or do you also have a sub panel installed. Is your main circuit breaker in the panel or in the meter socket? On to another subject. There is a chance that somewhere in the house, a bare ground wire is touching the neutral terminal of an outlet. This problem would not be indicated with a plug in outlet tester. If the ground touches the neutral, current will be flowing through the ground wire and produce a hum. I hate to say this but the only way to find out is to remove every outlet in the house and visually inspect each one. Sometimes you can see the problem by just removing the cover plate. Turn off the circuit breakers before you do this. You can wrap the outlets with high grade electrical tape to cover the screw terminals to prevent the ground from touching the neutral screw. This problem could also happen in light fixtures or switches or even a screw or nail going through the cable but much less common than the outlets. Before spending time doing this, find out if the hum is originating from the street or your house by using the method described in my previous post. Good Luck.
This is a great product for surge protection and power enhancement that installs at your main panel. This is whats inside of the old Seakay Linerover line conditioners. It will not help with the hum problem. http://www.usesmfg.com/