Sub problem?

dave shepard

In the past I had an issue with a slight audible humm comming through the speakers and had a post reguarding it (for those that remember) and ever since I have became use the it so it didn't really trouble me that much. Since then I bought a 7 chennel amp and now the humm has become more audible. I have traced it down to my sub. When I disconnect the sub cable from the Denon and power everything up there is no humm from the speakers but the sub has a humm (you have to put your ear to the back of it to hear it) when I reconnect the subs cable the humm comes back through the speakers the amp just makes it more audible. I have for the heck of it tried putting cheeter plugs on the amp and the surge protector everything else does not have a grounded plug and still the humm is there except when I disconnect the sub completely from the system. I have as of yesterday turned the room around and the sub is now in a differant outlet but the humm is still there. I have E-mailed SVS and they suggested that I have a ground loop problem and to get an isolator from RS but my question is if the grounds have been eliminated with a cheeter plug how can it be a ground loop? and if only when I connect and power up the sub the humm is present would it not be the sub causing it?

Dave

dave shepard

http://www.siber-sonic.com/broadcast/GLoopwhatis.html

I found this. Looks intirely too involved for any real explanation and will need to use the isolator I bought from RS until I can get an electric man in to see about adding a seperate breaker box for the system.

Dave

Tour2ma

Dave,
What happens to the hum if you:
- turn off the sub?
- unplug the sub's AC power cord?

dave shepard

Originally posted by Tour2ma
Dave,
What happens to the hum if you:
- turn off the sub?
- unplug the sub's AC power cord?

When I cut the power to the sub the humm stops. I have a electriction comming out he thought that with the simptoms that there is a ground problem also, but still don't know how if something doesn't have a ground prong how the ground can cause a problem and with the sub not connected to the reciever just plugged into the wall and on there is a slight humm comming from the sub. I will probably be putting in a dedicated breaker box for the HT to run especally since the amp requires it's own 15 amp breaker w/8ohm speakers or 2-15 amp breakers w/4ohm speakers as I'm sure so do all other high power amps. Also there have been other odd sounds happening when the amp plays that need to be addressed and the sure way is to put in a seperate power supply with it's own ground. The bad thing is that it will be another month before he can get out because he is backed-up with other jobs.

Dave

sowen010599

What happens if the sub is connected to the same outlet as the rest of your gear? Could it be on a different circuit?

Also, what happens if you unplug your cable (cable TV or SAT cable)?

Tour2ma

Originally posted by dave shepard
...but still don't know how if something doesn't have a ground prong how the ground can cause a problem and with the sub not connected to the reciever just plugged into the wall and on there is a slight humm comming from the sub.

In two-prong AC wiring one of the two "prongs" is the live power in, and the second is to ground. Both "grounds" end up in the same place in the breaker box.

Rereading your initial post made me wonder if there is an issue with the interconnect feeding your sub... Is there another you can try in it's place?

dave shepard

I admitly don't know much about home wireing except being able to wire-in a new outlet, switch or celing fan to an exsisting wired home short of that I don't know much not to mention problem solving and the one in my family that did is no-longer hear. As for the sub cable I can try a new one but will have to get one, I want to switch it out with a DH-lab one anyhow.

Thanks
Dave

Tour2ma

You're not alone, dave.

A year or so ago I basically made a statement along the line of your "still don't know" point. An electrician posting here at the time set me straight... straight to my breaker box, that is. Darned if he wasn't right...

dave shepard

The electricition came out the other day and went to the beaker box and the first thing he noticed was the new copper water lines we had installed was not grounded (local code requires the copper lines to be directly grounded) he also looked inside the box and noticed that the ground had oxidation on it and that the installer didn't properly clean the wires or use any contact grease to prevent that from happening I had assumed that since the original installer was certified and the service had to be inspected by the code officer that everything was done properly, guess I was wrong. I had the new electrition do his recomended repaires (clean the ground cable in the box, install 2-20amp breakers 1 for the amp 1 for the sub, install 2 outlets and install a direct ground for the copper piping). The end result is the humm has went away and the amp seems to be breathing better with it's own breaker. I'm sure you all feel the same way I do THANK GOD THAT'S FIXED .

Thanks for your patients and assistance

Dave

brody05

Glad your sorted, I may need to try something similar but I am running four subs and the only ones with the humm is the RT3000s, I have heard there is an upgrade on them as they had a common problem with humming, is this correct and if so does anyone know how involved it is, being in New Zealand makes it hard for me sometimes but hey, I met up with someone from this forum that was also a kiwi and into polk, how cool is that???