I received my speakers a few weeks back and didnt get a chance to hook anything up until yesterday. What a treat. However, the subwoofer (EP350) is causing a humm in all the other speakers. I have a Denon AVR-3805 amp, and the sub is connected via an RCA type cable to it. I know nothing of configuring the amp and sub (filters LFE whatever) so if anyone has any pointers for me...

As soon as I unplug the sub, complete silence (no more hum). Sounds like electrical interference almost... (tried different outlets...)

Thanks,

Marc

Hello,

This sounds like you are experiencing the dreaded ground loop. A quick way to try to eliminate the hum without any troubleshooting is simply by attaching a 3-2 prong adapter also known as a cheater plug to the end of subwoofer power cable. Just remember this is usually against electrical code and is not meant to be used as a permanent solution. The article below describes the steps needed in order to solve what component is causing the hum and how to get rid of the hum completely. The key to solving ground loops is being patient and methodical in the process.

http://www.axiomaudio.com/tips_eliminate_hum.html

Thanks for the link. Interesting read.

However, I had tried isolating the source (I unplugged the power from every component one by one and no luck.) I also unplugged the audio cable from the component to the amplifier, still no change. Only unplugging the sub got rid of it.

From reading this, the only thing I didnt try it unplugging the cable TV from the STB. Wouldnt unplugging the STB from the wall do the same thing though?

Try disconnecting the cable running to the STB and unplugged. This is a common source of ground loops. Also try a cheater plug with the subwoofer power cable. You can pick them up for around $1 at any hardware store.

Can you also try this for me? Does the subwoofer hum if it is plugged into the outlet, turned on, without any cables connected to it.

Good luck!

I forgot to mention, there might be a ground screw present on the back of the EP350 amp (ground screws seem to be common on Axiom subwoofers). In the past they have suggested people to unscrew them if they are experiencing hum. This might solve the issue as well.

I"m at work, but don't think my new 350's have a ground screw like the EP DSP series...

If you have cable TV then that is likely the cause. If so, you might need one of these:
http://www.axiomaudio.com/groundisolator.html

Worked great for me.

Ok. If I unplug the sub's coaxial, it's dead silent. Once plugged I get the hum.

I unplugged the sub from the wall outlet and plugged it in to my Monster Cable (I know...) power center and it has gone down significantly but it's still there. Unplugging the coax going to the STB helped a bit more. So I guess I would need one of those Ground Isolators, but that doesn't seem to fix everything...

There is a ground logo next to a regular screw behind the EP350. I'll try removing it...

The only fix for me was to buy the ground isolator. Problem fixed.

Does the screw look like this below. Otherwise I would not unscrew it. When looking at the EP350 guide just now it does not say anything about a ground screw being present.

http://www.axiomaudio.com/troubleshooting_ep500.html#

This is what the one on the EP500 looks like.
click on view chasis ground screw

Hi SUBnet,

As Hansang notes, the ground isolator WILL fix everything. But you might get lucky and not require it. Do try the ground screw if there is one on your EP350. We have made some upgrades and the manuals have not kept up.

With my own EP500, I solved the ground loop hum by connecting the EP500 to a different AC electrical circuit on the other side of my living room. I didn't have to use the ground isolator.

And to answer a previous question, yes, the cable-TV box can deliver ground loop hum even if it's turned off and disconnected from the AC power source. It's the ground (shield) side of the cable that is at a different electrical potential than the rest of your system and that causes the hum. Disconnecting the cable-TV feed from your wall outlet or at the cable box input is the only way to confirm if that's the source of the ground loop.

Regards,
Alan

I looked at the back and while I see the ground logo I can't figure out which screw it is, so I guess I'll just order the isolator...

Please let us know how this all works out for you.

also, you dont have to remove the ground screw completely.. just loosening it up a bit should do the trick.

With my ground loop problem loosening the screw on my ep500 helped a lot but didn't 100% fix the hum. When I got the ground isolator it was 100% gone. I think I have to have the ground screw tightened back down when using the Isolator... for some reason it seems like I still had a slight hum with the ground screw loose and the isolator connected... not sure why.

David, I'm glad you no longer have a screw loose.