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Peabody
12-15-2013, 08:26 AM
This seems different from other hum-related posts, so I'm going to ask. Is it normal for the F15HP to make a faint constant hum? Is this just from the sub's amp? It can only be heard when the room is quiet, with no music or movies playing. (Why is there no music playing, you are probably asking? I sometimes, although rarely, just read in silence. :rolleyes:)

The hum occurs whenever the sub is plugged in. It occurs regardless of the power switch position - off/auto/on. It is also present regardless of which electrical outlet the sub is plugged into.

The hum is present whether the rca cable is connected or not.

The level of the hum is constant and doesn't change when the sub volume is adjusted. It also doesn't get louder when the AV receiver volume is turned up. It doesn't seem to be coming from the driver, and is not noticeable when listening to music or soundtracks.

So, is this just a normal sound of the sub's amp? I can certainly live with it, but would like to know so I can quit worrying. Thanks!

davef
12-16-2013, 11:22 PM
This seems different from other hum-related posts, so I'm going to ask. Is it normal for the F15HP to make a faint constant hum? Is this just from the sub's amp? It can only be heard when the room is quiet, with no music or movies playing. (Why is there no music playing, you are probably asking? I sometimes, although rarely, just read in silence. :rolleyes:)

The hum occurs whenever the sub is plugged in. It occurs regardless of the power switch position - off/auto/on. It is also present regardless of which electrical outlet the sub is plugged into.

The hum is present whether the rca cable is connected or not.

The level of the hum is constant and doesn't change when the sub volume is adjusted. It also doesn't get louder when the AV receiver volume is turned up. It doesn't seem to be coming from the driver, and is not noticeable when listening to music or soundtracks.

So, is this just a normal sound of the sub's amp? I can certainly live with it, but would like to know so I can quit worrying. Thanks!

Hi Peabody,

The Rythmik subs are typically dead quiet. What you are describing sounds like some form of ground loop issue and these can be hard to troubleshoot -- and in older homes, sometimes impossible to resolve without "lifting" the ground to the subwoofer. It is not going to cause any problems and ground loop isolators can often clear it up instantly.

FirstReflect
12-17-2013, 01:27 PM
Not to disagree with DaveF, since I completely agree that it could be a ground loop issue, but I have run across this similar (potentially) sort of low level, constant hum, which was not loud enough or at the same 60Hz frequency to be a ground loop. Instead, it was just an operational, electrical hum from a transformer, or some other part of the power section of a device.

Almost all high power devices with large transformers in them seem to produce SOME level of electrical hum. But it's usually completely inaudible unless you are extremely close with your ear to the device. For example, my older HSU VTF-3 MK2 subwoofer uses a BASH amplifier. If I physically press my ear against the amp or the cabinet of the subwoofer itself, I can faintly hear a soft hum that is just coming from the power supply of that amplifier. But if my ear is not in physical contact with some part of that subwoofer, I cannot hear any hum what-so-ever. So, effectively, it is dead silent.

If I get very, very close to the air vents of my older Onkyo TX-NR705 AV Receiver, I can hear a very faint hum from its power supply.

But, sometimes, that hum becomes fairly audible. Or there is even a sort of buzz to the sound. Any time that has happened to me, I've had the power section replaced. My Pioneer Kuro had a pretty loud buzz when I first got it. A good portion of that is just from the plasma panel itself, and there's no avoiding it. But this buzz was louder than normal. Turned out to be a known issue with the power supplies in my particular model, and it was repaired under warranty.

My Axiom EP500 subwoofer had an audible buzz. That amp was swapped out by Axiom, and now it's the same situation as my HSU VTF-3 MK2 where I have to physically press my ear against the sub to hear any sort of hum from it at all.

Even my ATI AT1805 amplifier had some noise floor issues when I first got it. One of the two, gigantic toroidal transformers was replaced, and now it is dead silent.

In all of these cases, I can't tell you exactly what was wrong, but there was something amiss in the power section of these devices, and all were repaired or replaced under warranty. A great thing to do with reputable companies -- and Rythmik is certainly counted among them -- is to make a short video and record the audio along with it of the problem you are having. It can be very difficult to describe what you're hearing in an email using only text. And it's easier to dismiss problems such as these as being user error, or a ground loop problem.

But, I've definitely had noisy power supplies, as I've mentioned in all the examples above! It's not uncommon. It happens with high power devices from time to time. And all of these manufacturers seemed to be aware of it, and came through with replacements or repairs under warranty. So, I definitely think it couldn't hurt to make a little video with audio that demonstrates what you're hearing. Send that off to Rythmik, and I'm confident they will take care of you. They want you to be a happy, satisfied customer. And there are certainly instances of slightly faulty power supplies and amps that produce an audible hum or buzz. So, I think it's worth the effort to at least ask :)

Hope that helps!

Peabody
12-17-2013, 03:16 PM
Thanks Dave and jonathan_teller for your replies. After researching ground loop issues, I am inclined to think that is not the case here, especially since the hum is present even if the rca cable is not connected, and when all other equipment is not connected to power outlets. I even checked using a three-prong to two-prong adapter to remove the sub's ground from the equation. I certainly am not going to operate the sub without a ground in place, but just tried that to see if it would eliminate the hum, which it didn't. I am not very technically savvy, so I suppose it could still be ground loop related. It might be the type of electrical hum that jonathan_teller described, but I don't think it is even loud enough to capture in a video. I will try.

At any rate, since it is faint enough to not be audible unless the room is very quiet, I think I will not worry about it anymore. It is actually about the same level as the slight buzz from my Panasonic plasma, although that's definitely a buzz whereas this is a hum.

So I'm just going to go back to enjoying music on my wonderful new Ascend speakers. They are fantastic!! Thanks!

FirstReflect
12-17-2013, 03:39 PM
You're welcome!

That is not a ground loop. Not if you tried a 2-prong power cord and it was still humming.

I know you said you could live with it, but it shouldn't be like that. As Dave said, it should be dead silent. As I said, MAYBE if you physically press your ear against the subwoofer, you should hear a faint hum. But, it shouldn't be audible from your seat. You shouldn't have to have a masking effect from other speakers before you no longer notice it.

You're correct that it can be difficult to capture a faint hum in a video. Something like the mic on a camcorder or a smartphone might not be able to pick it up well enough. If you have any other sort of microphone, though -- like, even a headset. I have a USB mic I use for podcasting. Something like that might work well. I have the benefit of owning a Behringer ECM8000 measurement mic, so I can pick it up easily with that. But, just any mic better than your smartphone might do.

I just don't think you should ignore it, because it isn't right. Heck, you probably don't even need the video -- not with Rythmik. If you tell them what you said here -- about using a 2-prong adapter and not having anything else connected or plugged in, and it's still humming -- that really should be enough!

Yeah...honestly, sorry about all the "make a video" talk :p It's not necessary. I just found it helpful in explaining my own situations when they happened. But, from what you've written here, that's all you should need.

Contact Rythmik. They are definitely a company that wants happy, satisfied customers. Like I say, this sort of low level hum from high powered devices is not at all uncommon. I'm positive Rythmik has dealt with it before. They're not immune to the occasional slightly faulty amplifier. It really sucks that you happened to be unlucky, and you got one of those rare, defective amps. But, you shouldn't just ignore it. Rythmik stands behind their products. And it SHOULD be dead quiet. Get in touch with them :)

RicardoJoa
12-17-2013, 04:18 PM
Mine makes a hum noise on the Off swicth. So i leave it at on all the time. Does the hum changes when you move the on,auto, off switch?

Peabody
12-17-2013, 09:00 PM
Mine makes a hum noise on the Off swicth. So i leave it at on all the time. Does the hum changes when you move the on,auto, off switch?

Good to know. On mine the hum is there whether in the off, auto, or on position. Makes no difference. Thanks.