So as some of you know, I had a problem a while back with the 800 "vibrating" as soon as I plugged the cable in. Then I brought it back to Axiom to have it fixed and while I was there to pick it up the vibration was still there just not as evident. When I got home and plugged it in though, all was great - no vibration and the sub worked as expected (even better than expected).

Well, I moved recently and plugged in the sub connected the cable and... it's back! and then when I turned the power on to the Denon3808 it was REALLY back... a loud continuous hum from both woofers... and vibration from both (feel it when you touch it)...

Don't know what to do... tried different outlets, but I think there all connected on the same line anyway... but I really don't think that's it because at the last place I used the same outlet before and after and someway, somehow the problem went away.

Any suggestions?

Is it a ground loop humm?

It's a ground loop issue.

Temporarily...........plug the sub into an outlet without the ground plug being used (Usually, using a 3-to-2 prong adapter) and see if it goes away.

Give this a read.

http://www.audioholics.com/tweaks/connec...em-hum-and-buzz

Something of note... when I disconnect the sub cable from the back of the Denon... the vibration stops of course... BUT if I am still touching any metal part of the denon while I holding the plug in the other hand the problem vibration and humming are still present.

Could it be a setting in the denon?

Thanks Mark,

I checked the site out. I know it's not the cable because the cable is running in completely different room nowhere near the setup.

I really believe it's the denon... gonna try to hook it up to the onkyo and see if it'll make a difference

nope... it's there with the onkyo as well. Back to the drawing board... ARRRRGHHHHH! lol!

what to do? what to do?...

Don't you just hate when things don't "just work"! lol!

Are the subs plugged into the same outlet, or other outlets on the same circuit? I had a similar problem once, as soon as I used an outlet on the same circuit, no issue. Does the 800 have a ground screw like previous EP models?

yes it does, but I removed it and it's in one of my boxes. can't locate it...

The subs and the denon are plugged in different outlets but I'm pretty sure they are on the same circuit as the outlets are on the same wall (but I don't know much about electricity so...).

The thing that gets me is when I had this problem before I have no idea what changed that solved the problem.

eeesh... I did not want to have to deal with this issue now... cause I won't rest until I have it solved. Which means the unpacking is now put on hold! oh well...

Do you have a power strip, so you can plug everything into one wall outlet?

The fact that when you ground the plug with your body to the Denon causes the humming to return pretty much confirms Marks assertion that you have a ground loop issue. I would follow the guidance in the link provided by the doc to figure out what is causing it only then can you apply the best solution.

Have you tried removing the CHASSIS GROUND screw? Located between the Trigger out and Trigger in sockets.

Edit: Or putting it back in.

Hi majik,

I would agree with others here that you absolutely have a ground-loop hum. In almost all cases, it enters your system through the cable-TV or satellite system feed, so try disconnecting the cable at the input of the cable box. The hum should go away.

Here is an excerpt from my article on eliminating hum:
http://www.axiomaudio.com/tips_eliminate_hum.html

"Disconnect the incoming TV-cable or satellite feed to a set-top box or to your TV and the A/V receiver. If the hum disappears (and you don't use a satellite dish) complain to the cable-TV company. They may know what you need and supply you with a ground-isolating transformer. If they don't know what you are talking about you'll need to order a video ground isolator and install it in-line with the TV cable before it enters your set-top cable-TV box. Axiom has special wide-band isolation transformers that will not interfere with any digital TV or HDTV signal. (N.B. You CANNOT use one of these with a satellite decoder box.)"

Regards,
Alan

okay, so I unplugged the denon from the wall, and there is still vibration and hum from the woofers.. as long as the sub cable is connected to both the receiver and the sub, it doesn't seem to matter if there is current going to the denon or not.

Does this mean anything?

Hi Alan, thanks for the help, but it's not the satellite feed (I have bell expressvu). I disconnected the cable feed from the pvr and it still hums (the thing is the pvr is in one room and the receiver is in another. I don't know if it makes a difference, but the pvr is not even connected to the receiver.

I do have dsl internet though, and they came in to put a filter on my jack could that cause it?

On another note, I cannot find the ground chassis screw anywhere in all my boxes, would it be possible to get another one? Maybe I need to put it back in?

I don't think it's the cable because it was working fine in my last place (after the initial issues of course).

Other than the above mentioned steps I've also tried:

- having them plugged in different outlets
- same outlet
- same outlet using power strip
- even took the sub to another room to see if using an outlet there would make a difference.

none of these things worked.

Thanks for your input guys.

Maj, unless there's some detail that you haven't described, there was no path for a ground loop to form when you unplugged the receiver power cord. Is there something else connected to the receiver which is also plugged in, such as a player?

Majik,

Yes, the dsl connection could trigger a ground loop, so try disconnecting it to see if the hum goes away. If a sub is connected to AC power, but there is no subwoofer cable connected to your Denon and there is no hum, then there is no problem with the subwoofer.

I'm still fairly certain the hum can be traced to your PVR/DSL connections so remove those and see if the hum goes away.

Normally, the AV receiver is never the root cause of a ground loop. The loop results from other components connected to the AV receiver. And the loop can occur even when all the components are powered off, except for the subwoofer.

It takes patience and persistence to track down the source of a ground loop but it can always be corrected.

Alan

Hi John,

No, I have nothing hooked up to it yet. I did have my ipod connected via a 3.5mm jack to rca cable, but disconnected yesterday to see if maybe that was causing the problem but it's not... and I now know it's not the cable because I came across an axiom speaker cable (I guess the ppl that lived here before me had some axioms as well) and the the hum/buzz and vibration is still there.

I'm gonna look into getting another ground loop screw from Axiom and hopefully that will fix it.

any other suggestions in the mean time and in between time?

Alan,

I've disconnected the DSL and the satellite feeds - neither of which were connected to the receiver - and the hum/buzz/vibration is still there.

I don't have anything connected to the receiver and as previously mentioned, I connected the sub to my onkyo 605 receiver and that did not solve the problem; and I didn't have anything connected to the receiver then either.

How do I go about buying another ground chassis screw? Maybe that will help?

Hi majik,

Ground loops are pesky buggers. Just stay patient and be methodical.

Since you moved into a new house is there any dimmer lights, flourescent lights or computers being used that are on the same circuit as your HT gear?

How about turning everything off at the circuit breaker box except the circuit the Subwoofer is on. If the hum goes away, turn them on one at a time until the hum returns, then it has to be something on that last circuit turned back on.

Just to clear up what that screw actually does. It isn't a "ground loop screw", it's a point of connection between the chassis (safety) ground, and the signal ground.

A device that has a 3-prong electrical connection connects the chassis to the third prong, so any shorts are shunted to ground rather than finding the path there through a person touching it.

RCA cables need their external shield connected to the chassis ground for best noise rejection. But that shield is also used as the signal ground for the audio being carried on the cable.

If everything is working right, there should be no problem tying the two grounds together. But quite often things aren't right. So it worth trading the lesser noise rejection for separating the signal ground from the chassis ground to break a possible ground loop.

XLR cables solve this problem. They have an external shield which should always be connected to the chassis ground, and a separate ground pin for the signal ground. When using an XLR cable, the connected devices should never tie the two grounds together (thus why Axiom has the removable screw).

I'd also like to take a moment to rant about so called "double isolated" electronic equipment with only 2-prong connections. I hate this trend to suppose that what ever design the engineer has come up with will always fail safe, and thus not need a safety ground. It is also not able to provide a true chassis ground for shielding, making any XLR jacks less useful (like in Onkyo's pre-pro line).

EDIT: Of course none of this gets you any closer to solving your problem. I just like to hear myself type sometimes. (It is a nice sound on this Unicomp, buckling spring keyboard.)

I have unplugged everything that could be on the same circuit. still a low hum and vibrating subs.

no dimmers nor any fluorescent lights.

The fact that the problem did not go away when I moved the equipment to another room and again with trying a different receiver is (mis?)leading me to believe that it has something to do with the sub...

Just wish I could find my ground chassis screw so I could check that.

Did you try what I suggested, 3 messages back?

Catbrat - Only saw the message just after submitting my last post. I'm going to try that now and see what happens.

Do you get any humming or vibrations from the sub with it just plugged into the outlet (turned on) without the cable connected to the sub and AVR?

so I've turned everything off except the sub and receiver... and the hum is still there. so I tried changing outlets: plugged the receiver and sub to another outlet that had its own circuit (the fridge), and still there.

then I unplugged the receiver from that outlet and plugged it in another one and still there...

I'm about to throw in the towel!!

what about the vibrating subs? is that normal when power is on and connected to receiver?

okay, I just disconnected the cable from the sub and when I touch the cones there is still vibration felt(albeit quite a bit less, but it's still there.. the level of vibration seems to be related to crossover setting: 150 will vibrate more than at 100) but if I connect the sub cable it's much stronger with a louder hum... could that mean it's the sub then? because there is no power anywhere else in the house... The only thing receiving current is the sub.

I would have to wait for Axiom's response on that one.

You can't diagnose a ground loop just by shutting off the components. You have to physically disconnect each component, one at a time. As an example with my most recent ground loop, I diagnosed it/eliminated the hum by disconnecting the component video cable that was hooked up from the DVD player to the television.

Any type of audio/video player you should disconnect one by one as well.

Maj, you've gotten good info on ground loops, but as I indicated in my previous reply, from your description it appears that there can't be a ground loop. For a ground loop to be formed there has to be at least one power connection path to the sub besides the direct connection through its power cord. This could be be through a plugged-in receiver or something connected to the receiver which in turn is plugged in to the wall, such as a player. Neither this nor any other subwoofer connection to the power other than the subwoofer power cord is present, and one connection can't make a loop. There have to be grounds to two areas having different electrical potentials so that the difference in voltage between them causes a small current to flow, with a resulting hum.

No, when the sub is plugged in and turned on, but not connected to any signal source there should be no cone movement or sound audible. The rectifier and filter capacitors in the amplifier power supply section should remove any audible noise coming in through the power cord. Possibly the repair to the sub amp was ineffective, or it's been somehow damaged since then.

As to the sub cable itself(not connected to the receiver at the time?)causing the problem to worsen, this may be reaching, but possibly it's acting as an antenna picking up airborne electrical interference to add to that coming in through the power cord and not being adequately suppressed by the amp power supply section. Tough one!

when the cable causes increase in the hum/vibrations it is indeed connected to the receiver.. but this happens even if the receiver is not plugged in (no power)? I just find it weird.

So it looks like I'm going to have to live with it? That sucks. I didn't do anything to cause damage to the sub... I didn't even put the sub on the truck with the other speakers, I drove it here in the magnum myself to be on the safe side. Like I said, when I left Axiom with the sub there was still hum, I get home and the hum was gone... I get here and the hum is back... maybe I have to move again?? lol!

I'm going to send Alan a private message and see what can be done. Thanks for all the input guys, I really appreciate it. I'll let you know comes of it.

I'm curious: does the cable cause an increase in the hum if it's plugged in to the sub but not the receiver?

The fact the hum was still there when you left Axiom with it and then it was gone at the old house suggests to me a loose/faulty connection/component in the amp. Now that the sub/amp has been moved and bounced around a little the faulty internal connection/component is now causing the same problem. I think Axiom should/will look after you with another new amp/sub as it has a 5 year warranty.

BTW if you purchased the EP800 during one of the initial runs, there has been two or three amp revisions since then. If this is the case you would get the version 3 amp for replacement. It is supposedly a more robust design in terms of reliability and performance.

Theoretically, at least, Axiom was shipping new amps to every EP800 owner. Not sure if they finished that or not, but I'm pretty sure Ian said they wanted to finish that before they shipped the VP180, so maybe.

Yes, it does! and then even more when I plug it in the receiver. but it's definitely noticeable you can hear it and feel it!

Do you know what this could mean then?

I don't think I have the new amp... just spoke to Brent and he said that there were no new amps that were supposed to be shipped to ep800 owners.

I should be getting a return phone call today to see what can be done.

I think you may be right. I'm going to check with a ground chassis screw first, and if that's a no go... I'm going to have them send out a new amp (hopefully I'll get version 3??).

When did you get the sub, Majik?

Version 3 is the latest amp for the EP800. That is what you would get if you buy one brand new at this time or acting as a replacement to an initial run EP800.

Well great news! they are sending me a whole new sub!! Wow, these guys are great aren't they?!

It seems that since I have one of the first ep800s made, I have the old "boot?" and the new amp does not fit in the old sub...
Brent just called me back and they are going to ship a new one to me! He said I should have received a new sub when I brought my last one back... I guess something got mixed up somewhere, and the fact that I dropped it off AND picked it up outside regular hours of operation definitely could have helped cause the mix-up!

I'm telling you.. and I've said this on the forums before, but any money I spend on speakers and subs will be with Axiom... It's not about never encountering an issue (although in a perfect world that would be great), it's about how you're dealt with when you do! And there is no doubt in my mind that Axiom is Top Dog in that department!

Time for me to go ahead and get the epic grand master for my dedicated television room!

I'll keep you guys posted on everything... and thanks again for all the help.

I actually bought the sub before they were ready to ship out. I had to wait a couple of months for them to finalize everything and start shipping them out

Glad to hear the fine folks at Axiom are taking care of you majik, that's really good news!

Thanks Rick! I just took a look at your room! Nice! If you don't mind me asking, what did you put in the corners of the room behind the floor standing speakers? Was that for sound improvement?

The whole room looks wicked!

It's great to hear the news that you will be getting a new sub from Axiom Majik. You will not be disappointed!

Very good, maj; now you can turn all the power circuits back on and re-plug the 73 things which you unplugged! Seriously, it's again an illustration of fine Axiom customer service to replace a unit which clearly wasn't being merely affected by a ground loop.

When you get the new sub, the chassis screw should probably be left in, since as Chris correctly pointed out in his excellent description of its function, it can have some beneficial effect if hum isn't present with it in.

On the question about the sub cable alone(not even connected to the receiver)causing more hum, I was just curious if it did seem to be acting as an antenna for airborne electrical interference, as I'd speculated. Of course, the point is now moot. Enjoy.

Ok, I know Axiom is sending me a new sub and that this thread is "solved", but I just wanted to let everyone know that I finally found my chassis screw and as soon as I tighten it all the way, the humming and vibration stops! Yay right? nope... because know the old problem is back... when every there's a rumble (cars driving by in talladega nights) the sub starts rumbling and doesn't stop when the cars source of the rumble stops.. it just keeps on rumbling; of if it's a sudden thump the old helicopter sound of the propellers kicks in.... so needless to say, I'm VERY happy axiom is taking care of the situ.

I'll keep you guys posted

That does sound like the problem other people were having with the first series of amps.

Didn't one person's get really hot and melt something internal? I'm just bringing that up, because you may want to unplug the sub when it's not in use, just to be on the safe side.

Yes; that happened to Steve Roode.

Will do. thanks for the tip.

The "helicopter sound" was plagued with the first initial run of amps. The new version seems to have fixed that issue as well.

Mine was the one that melted a bit. But it was during use, not when sitting idle.

and you had that helicopter effect (subs thumping repeatedly) whenever there was a sudden "bang" or "thump"? what about the subs rumbling continuously?

********update********

I received the new sub! I've had it since monday but haven't taken it out of the box yet... I didn't have time and then I started to think it would be best to save it until I finish most of of my set up (carpet, acoustic panel, acoustic curtains... etc.).

I'll update when I've finally had a chance to try it out.

What a tease!

I think I would pull the sub out, try it to be sure the issue is not there and if not, rebox the sub till the set up is complete. This way if the issue or another from shipping is present you can have another sub on the way while finishing the remodel.

Good call Jason, I'll do that tonight.