I have DENON 3805, A 60VS810 Hitachi Rear LCD TV, 6 Axiom speakers and a EP-500 sub. Here's my issue. For SOME reason, I get a ground loop hum when the sub is connected. If I removethe ground loop screw from the sub, it reduces about 85% but it is still there. When I replace the ground loop screw AND add a 2 prog connector to the 3 prong AC sub plug, then the the hum goes away (but, this does not seem right since I should not have to add this. AND, the sound from the sub seems muddy. Also, just a background, all AV equipment is on a dedicated AC line with it's own circuit (no other appliances, lights etc on the circuit) AND I am using a Brick Wall Surge protector. Now here's where it gets even more bizzare -
I am without a doubt getting a magnetic field issue because I get nothing but an rumbling-type interference from the tuner when it is tuned to FM. AM is not really any better. The farther away I move the sub (it was never closer to RCVR than 5 ft), the slightly better the reception is but it is nowhere near of listening quality. The farthest I can move it it 13 ft and it was about 40% better but still, full of interference, runmbling etc.
Rearding other sources - The TV, CD etc. seem to work with sub but the sound is a bit muddy and unclear.
OK, part three - Axiom replaced the sub with a new one - SAME ISSUE! Today I am returning the Denon Receiver for a new one. (ABT electronics - also awesome guys to do business with)
All the equipment, cables etc are 3 weeks old.
I have done all the following troubleshooting -
1 - tried a different AC outlet
2- Tried a different RCA shielded sub cable
3 - Did NOT use the surrge protector
4- Tried a different AC outlet on a different circuit with combinations of items 2 and 3 above.
5 - Tried a GFI outlet - tried a non-GFI outlet.
6 - Tried bypass of crossover ; tried different ohm settings.
7) Disconnected all speakers except sub, tried various combinations.
I am calling Axiom today - is it possible I received two defective subs? That seems totally unlikely to me. Is the sub too bug for my room (16x20)? Is it normal to get such a strong magnetic force?
I am so lost and confused! I have spent over 8K and get tune in a radio station! I am also not convinced the muddiness I am getting from other components from the sub is how it should be responding.
What can I do next? The Axiom guys have been great but I don't want to have them keep paying for shipping this thing back and forth if there's something I'm doing wrong.
Please, PLEASE HELP!!!
Just checking -- does the interference with FM/AM go away when power is disconnected from the sub ?
Also, the room is about 16 x 18 or so.
Sorry... I got so tired of people asking "what kind of speakers should I get" without describing their room that I just added "how big is your room ?" to my signature
Do you have cable?
If so, have you tried disconnecting that from your system completely?
Check out
this thread and
this one and finally
this one.
Sounds like it might be a ground loop problem and a cheater plug usually solves that (pretty cheap solution). Take a look at
this thread and click on the cheater plug link that is provided.
Ok -
I am using a "cheater Plug" - 2 prong.
I have also disconnects all the cable TV as I know this is often the source of ground loop hum issues.
Still.. I'mm getting this, (what I am guessing is) magnetic interference. Also, with respect to the "cheater plug".. shoul I really have to do this? Aren't I defeating the ground if I use this?
kemrt23:
Boy! I am really interested in the outcome of this thread. I have almost the exact same situation occuring, except for the magnetic interference. But this I'll have to check on since I rarely listen to radio. At first I thought the cable tv was the culprit as when it was disconnected, the humming stopped. I purchased an isolator for it and everything seemed fine until a couple of days later the humming returned, though not as loud. When I removed the ground loop screw on the 500, the humming grew much louder. I disonnected all equipment except the 3805 and the 500, but it remained. I even went so far as to turn off all circuits. Did not help. The only thing I have not done is to remove all items from the back of the 3805. I'll do that today.
Let us know how the replacent 3805 does.
In reply to:
Also, with respect to the "cheater plug".. shoul I really have to do this? Aren't I defeating the ground if I use this?
I don't believe so. I could be wrong about this, my knowledge of this is pretty hazy, and those with more knowledge will correct me if I lead you astray.
The hum is caused by having TWO paths to ground, one through the third prong on your sub's cord, and one back through the wire connecting your sub to the receiver, which also has a ground connection. By using the cheater plug you merely lift one of those paths to ground. The other is still in effect, and grounding your sub. I hope I've got that right. All I know is I've been using cheater plugs for 40 years and have never had problems.
You can read more about ground loops
here, and
here, and other hum problems
here.
Nowhere in these tutorials will you find them recommending using a cheater plug. They can't do that because it's "cheating."
OK, I'm no expert on these issues, but I was getting the hum as well on my EP500. I had a mediocre shielded subwoofer interconnect, and that was the main culprit. By playing with the cable location (holding it away from the power cords of other equipment) I was able to greatly reduce the noise. However, real life didn't allow where I had it strung out to be a viable long term solution. What I did instead was go to blue jeans cable, and got the Canare LV-77S coax interconnect. This was a BIG improvement. Even though this cable has to run parallel to a couple power cords, it still almost eliminates the hum. I can only hear any hum at all now if I stick my head in the grill.
So to summarize, mediocre cable -- big hum. Good shielded cable -- no audible hum from beyond 2 feet.
Ok, just checked the fm reception. Here is what I did:
Turned on the 3805 and made sure the sub was powered up;
Tuned in an FM station - came in week
Turned disconnecte the rca cable from the sub, leaving the sub on; reception strengthened
Turned off sub - receptioned increased
At this point I removed the cheater plug from the sub, plugged in directly to a grounded outlet, and re-ran the test. The outcome remained the same - reception was best when the sub was not connected.
What's happening here?
HI -
Well, I spoke with Axiom this morning - turns out the "magnetic" issue I am having with the tuner is a result of the existing amp in the sub. Axiom is sending me a new amp that now has a coil or something to it to eliminate this problem (they are sending that out to me today). They also told me I am not "losing" any grounding by using the cheater plug. This was encouraging news.
So, to address the tuner interference problem, I will need to replace the amp in the sub with the new amp. (they said it's very easy to do) and send them back the other amp.
Hoepfully this will solve the tuner reception issue.
Although I have the Denoin 3805 in my trunk ready to exchange I think I will forego this - everyting works fine except for this sub issue which now seems to have a fix from Axiom - I will keep you all posted....
Hey, that's great! I was debating wether or not to begin replacing the 500 amp with the replacement they sent earlier this week. I don't think I will get to it today but in case I do, I'll post the results.
kemrt23:
I went ahead and swapped out the amps this afternoon, connected the sub, and re-ran the fm reception test. For me, nothing has changed. It would be interesting to see if the 3805 has an issue.
well if it comes down to it, send me the 500 and i'll mail you my 350 (which works just fine, no hums) and you won't have to worry about it anymore
Resolved!! Well, Cudos to the folks at Axiom. While it did take while to get to the bottom of things, turns out the interference with the tuner was not a result of the subwoofer. The small antenna supplied with the Denon 3805 (just a simple wire) was the culprit. I needed to hook up a shielded coax cable to an antenna - I did, and, viola!! there was no interference.. Through the course of all this, Axiom had sent me two replacement subs, call me frequently and was very vested in getting this resolved. They too will now benefit from this info - use a shielded cable when connecting (even a small, seemingly trivial, FM antenna). I can now, at long last, say everything works beautifully! The only disaappointment now is that, after only three months, my Hitachi 60VS810 TV has dropped $300. Ah well.... the train of technology never stops!
Thanks to all!
Mark
Glad you got everything worked out.
Sounds like Axiom treated you well as it seems they do evreyone.