Hello fellow Axiom enthusiasts, I finally brought the Axiom Epic60/500 system about one week ago now. It's a fantastic system with a Denon AVC4310 A/V receiver (called AVR4310CI in north America). However I have the very irritating sub hum with nothing connected to it. Currently Brent from Axiom is trying to help me isolate the problem and he has been very helpful. So in the mean time I will try the forum to see what comments come back.
At first Brent thought maybe an internal AMP problem and sent me a new replacement AMP but with the same resulting problem. I have tried unplugging everything electrical in the apartment and tried the SUB in different AC outlets but still hum. My only guess is that it's coming directly from the AC outlet to the EP500. I live in a high rise apartment building in Japan on the 13 level. AC is 100v 50HZ. The new AMP Brent sent was modified to accept 100v 50/60Hz because we thought the difference in Hz might have been causing the problem. I'm thinking I have to put something between the AC outlet and the EP500 power cord to try and eliminate what is coming through the outlet? I appreciate any suggestions you can give me.

I assume you've tried the usual cheater plug fix? I doubt that would apply, since you mentioned that it hums without anything connected to it, but hey...

I would try a good quailty surge suppressor or something along the lines of the Belkin PF60 which a few of us on the forum have, unfortunately I can't say whether or not it would help as I bought it strictly for eye candy and ease of a central plugin for all the electronics.

Hi kcarlile, yes I've tried with and without a cheater plug. I even tried my Denon power cord as it fits the EP500 but got the same transformer like humming noise. Thanks for the suggestion though

Hi jakewash, the Belkin PF60 sure looks like eye candy alright hehehe. There is a local audio store near where I live that may let me take the sub in and try there AC outlet to see what happens and may have the gear you suggested. My experience in Japan is normally no one will help you unless you show them the money but it's worth a shot.
Thank for you suggestion.

Dragon, it still appears to be a problem with the internal sub amplifier, despite the fact that it's been replaced already. With nothing connected to the sub but the power cord it can't be a ground loop hum because there's nothing to form a loop. The rectifier and filter capacitors in the power supply section of the sub amp are supposed to supply clean DC, with inaudible hum, to the amplifying section.

Hi JohnK, so that means I would have to try yet another AMP? Axiom sent a letter with the replacement saying it had been tested in a enclosure and was working with no problems.
I've sent Brent an email, so I will see what he comes up with.
Thanks for your input.

I assume you tried loosening the ground screw at the back of your sub?

do the newer 500's even have a ground screw anymore? Unless the sub is picking up some type of interference from something nearby, although unlikely, it still sounds like the amp itself, if the power chord is the only thing plugged in to the sub when it makes the noise.

Hi EFalardeau, yes I tried loosening the ground screw with no change.
Thanks for your suggestion.

Wow! That's bad.

Sounds like the amp is faulty. I think the only way you are going to fix this is get Axiom to send you another replacement amp.

Do you have access to a UPS generating its current from a battery? That could isolate completely the sub from your electrical system if that proves to be the problem.

I know a few people in the movie industry who are using that type of solution to fix strange electrical problems on location.

I would not invest in anything at the moment. You should ask for another replacemnt amp that is quality control inspected and tested before it is shipped to you. If another replacment hums, then surely there is somethng more devious going on and time to look at other fixes.

I dunno. Perhaps lug it over to someone else's house or to your workplace and plug it in there. See if it does it elsewhere.

Many UPSes use "stepped sine" output, which can also cause transformer hum. It depends on how susceptible the transformer is, and how bad the power is in the house. Sometimes there is so much noise on the 60 Hz sine wave of the house, that a stepped sine from a UPS is actually cleaner.

He did and they did, now he is looking for other answers.

You mentioned you tried different outlets with no success. Have you tried any outlets outside your HT room? Maybe try plugging just the subwoofer into an outlet in your bedroom?

good thought, get a lonnnnnnnnnnnnnng extension chord and run it to another room in the house, or over to your neighbors.

Solar panel? On a serious note, how long is the shipping to Japan?

Hi Dr House, yes I tried every outlet in my apartment and even unplugged all other electrical equipment when I did.
I've tried two AMPs from Axiom with the same result.

Hi EFalardeau, unfortunately I would have to buy an UPS to try this option. Whats your though on an AC filter between the outlet and the EP500?

I read on the Polk audio forum about "transformer lamination noise" and is caused by the building and collapsing magnetic field that surrounds the core laminations of the AC power transformers. Does anyone have experience in this field?
Could the EP500 be picking this up from the AC outlet.
It was mentioned in an earlier post to try at work your the neighbors place. Both are not possible but there is a audio store near me that may let me try plugging in the Sub there. That will be a few days away though.

Dragon, to clarify a point, although you did say earlier that it was a "transformer like" humming noise, is this actually a humming electronic sound coming from the driver or a mechanical hum coming from the amplifier itself?

AC filter like a Belkin power conditioner? I am not a big fan of these things even if I do own one (it makes a nice unit-friendly power bar. I got it to try to help my own ground loop problem and it did not. In your case, you might want to try given your distance.

Hi JohnK, it's an electronic sound coming from the driver.

EFalardeau, so a AC filter is a power conditioner? I'm normally a plug it into the wall and everything just works kind of guy, but since still is my first hifi problem I've had to read more about conditioners and electronic stuff...it's like being back at school hahaha

That was a question, not an answer... You mentionned an AC filter and I asked if meant a power conditioner or something else that would be called an AC filter with which i'm unfamiliar (we ALL learn!).
Hopefully things will get resolved soon enough for you. This is the type of problems that can quickly build up into a lot frustration.

Oh sorry EFalardeau yes I see it was a question. AC filter is nothing I came across when I was searching the net for answer on the topic. From what I understand an AC filter is a small box (like an adapter plug) that is meant to block out magnetic interference coming through the AC outlet. It plugs directly into the AC outlet, then your component plugs into the filter.
Only thing is I've not seen anything like that in Japan.
Yeah it's frustrating but step by step I'll conquer this problem.
Everyone's input here is very helpful.

If there's a possibility that it's not the subwoofer and possibly an electrical problem, can you try it at a friends or family members house?

I could be way off base, I didn't read through the entire thread.

Yes, that's what I'd assumed that you meant. If instead it was the transformer vibrating to cause a hum(which all transformers do to some extent), it could be excessive because of the 50Hz AC or some DC polluting the supply and increasing the vibration. Again, if the power supply section of the sub amplifier is working correctly, electronic hum should be at an inaudible level.

Hi wheelz999, I have an hifi store near where I live. So if they are friendly enough I will see if they will let me plug in the sub in the store. I'll have to wait until Monday though because of my work hours.

Hi JohnK, yeah Brent from Axiom thought along the same line as you as well. He send a replacement AMP that was modified to accept 50 and 60Hz. I'm guessing it's what you send about power supply being polluted. Tonight I actually was able to bring home an UPS that has a warning light on the back which comes on if the AC power supply is bad or not ground correctly. I plugged it in to all the AC outlets and the light came on every time. I tried the sub plugged into the UPS too and got the same hum. So I could been stuck with this problem maybe.

If every outlets tests bad, it may be that your service is wired incorrectly into the building. Call an electrician, or your landlord to call an electrician. It probably isn't a hard fix, and isn't to code right now.