Axiom Home Page Forums General Discussion Technical Questions EP350 Humming After I Moved Homes

Denon 3808Ci Receiver
Axiom EP350 V3 Powered subwoofer
7.1 speaker setup

I recently moved and when I went to reconnect my AV setup, everything is working fine except for the ep350 sub. It continuously makes a humming noise no matter what volume I use on the sub. The sub is connected to receiver with just the preout RCA plug, same exact wire I had previously used that was working, now it makes the humming noise. I've replaced the sub with a KEF powered sub, using the same wire and it works fine, no humming. The sub does play sound and bass, so it works, but continues to hum no matter what output level.

I've tried playing with all the settings on the receiver, speaker setup, different wires, even using the preout from the KEF sub to the Axiom sub and still the humming? Any thoughts, did the sub just run its course, amp messed up on the sub? This is driving me nuts?!?!?!

Update:

Moved the sub to my other onkyo receiver in another room, where the KEF is normally plugged in and it still hums. Tried replacing the power strip, no changes. I'll try a ground loop isolator tomorrow?

Gog, welcome. The fact that the hum existed when plugged into outlets in different rooms raises at least a possibility that this isn't a ground loop hum. If you disconnect the sub cable(while it's humming)and just have the power cord as the only connection, does the hum still exist? If so, there's no connection to form a path for a ground loop, and the problem is in the sub amp. If not, the next thing to try would be removing the chassis ground screw on the back of the sub amp.

Yes I have tried having just the sub powered on and removing the coax plug from the receiver and the hum goes away.

Will try removing the ground screw on the back of the sub tonight.

Can you specify where this chassis ground screw is? I only see the back panel of the sub, here is a pic of the back:

http://imgur.com/npR5Q

Yours doesn't have a ground screw. Try a cheater plug and/or a ground loop isolator.

Just read about the Satellite TV might be causing it too, will try removing that from the receiver tonight.

Awesome thanks, I think that might be it. In my previous setup I didn't have Sat tv hooked up to this receiver/sub.

Aha. Well, then Axiom does have a ground loop isolator that's supposed to fix that sort of thing. Don't know if you can find it locally cheaper, but there we are.

Gog, apparently the Axiom site info is outdated or simply incorrect as to the recent EP350s. It continues to both illustrate and suggest the use of the "Chassis Ground" screw in cases of possible ground loop hum.

Using a "cheater plug" will certainly stop the hum, but the absence of the previous chassis ground screw raises a question as to whether there'd be an alternate ground through the sub cable or if there'd be none at all if the ground through the sub power cord is defeated. Axiom should clarify this.

Yes, disconnect the satellite cable to see if that's the link in the ground loop. The Axiom ground loop unit isn't suitable for satellite TV use since it would interfere with signals to the dish.

That's not a recent EP350, either, John. Unless I'm mistaken, that's an early v3, whereas from my experience, the current one could be considered a v5 or v6.


Not that the current one has a ground screw either.

The EP350 that I got a month or so ago had a ground screw. It hummed like crazy until I removed it. It was a B stock though. The new ones don't have them?

I couldn't see one on my 350 amp or in the picture on Axiom's site, but I'll let you know when I get my new amp.

The ground screw should be near where you plug the power cord into the back of the unit. That's probably below the lowest point on your picture.

Removed the Sat. receiver from the DENON, still a hum on the sub. Also tried unplugging and plugging in the rca plug from denon to ep350 and the hum goes away once unplugged? So I'm still at a loss for what is causing this, I had no issues at my old house.

Yes it is the EP350 V3 as in the title.

One funny thing I did notice is that when the AC in the house powered on, the "hum" on the receiver also changed. The hum changed audibly along with the AC powering on. As if the current from the house is causing the hum, this is indeed a much older house.

Did you try the cheater plug?

Not yet, heading to radio shack today.

my 350's don't have a ground screw either, the cheater plug worked for my 350's after they starting buzzing/humming once Direct TV was introduced to the system.

in this here house, i'm the only one humming (along with the music). ;-)

I checked with Steve to see if I should update the EP350 page, and all the current amps have a ground screw. There were some changes throughout the production runs but the current production all have it.

Where should I put this ground loop isolater?



Here is a pic of the back panel, is that screw next to the power plug the ground screw? sorry for the huge pic, camera phone having issues.

http://i.imgur.com/ZcKQT.jpg

Oh god that was it, unplugged the ground screw and the hum is gone. Been racking my brains on this for days lol. If only the first pic showed the entire back panel... Thanks for all the help guys, never would've figured that out with out you.

I'm mistaken--my EP350 amp DOES have a ground screw. It's just hard to spot.