Transformer hum!

alokgovil

I have just bought Polk AMR130 powered 5.1 speaker system. All's great.

Problem: Transformer makes a hum sound, that is audible at night. It's not too bad, but with my ears (which God shaped to detect noise) ... I cannot hear the hum when music is playing. Before going to sleep, I pulled the power plug out to get rid of it.

The system is under 30 day satisfaction guarantee, so I can get it replaced from the reseller, but I am not interested in that. Other option is to have transformer sent to Polk and have it repaired or replaced. (Third option is to live with it.)

Hum sound is not too bad, but I know that transformers which are OK do not make it. This transformer is certainly abormal. Question is should I get it replaced, or whole system replaced (not preferable), or live with it. Looking for advice at first.

Regards - Alok Govil

polkatese

Have you tried a cheater plug? the one without the ground plug? ratshack sells them for about $2. hope it helps...

danger boy

polkatese what would that do exactly? a cheater plug

polkatese

danger boy,
what it is a simple plug adapter that bypass the ground prong. Hum usually indicates ground loop problem. I have encountered these problem several times in the past, and the cheap solution that works for me was to use cheater plug. What I found was subwoofer tends to be the culprit/easily affected by ground loop problems (no scientific explanation, of course) and using the cheater plug has been a solution that work for me. Another solution with ground loop is to use power conditioner, such as the panamax, monster cable hts series, etc.

alokgovil

From what I am getting, a cheater plug takes in a three-prong plug and has a two-prong plug that goes into the wall without connecting to the ground. If that is the case, well, then the current plug hasn't got a gound prong in the first place!

Second thing to notice is that the transformer keeps on making the sound even when the main power switch of the system is turned off. So subwoofer cannot be the cause of the problem.

Also, though the transformer has this hum, I haven't noticed slightest supply hum in the subwoofer or any of the satellites.

Regards - Alok

polkatese

Alok,
if that is the case, then it must not be a ground loop problem. You could be right, it could be a defective transformer, and since it's still within 30 days of purchase, if I were you, I would exchange it and get a new one. A bit of inconvenience, nonetheless, rather have a different unit. btw, you can also hear hum from ground loop even when the system is off, as long as the plug is connected to the wall outlet.

alokgovil

Hi,

The reason why I am reluctant to not get it replaced by the reseller, is that I have already used that facility once! In the previous set, the subwoofer probably had its coil touching the magnets. The reseller has been maintaining these speakers in the stock since Nov 2001 (!), might have thrown the boxes around ...

Now that I have got the speakers which are just great, I don't wanna learn that in the next shipment, transformer is OK, speakers are not. (Not that I consider Polk to be bad, in fact speakers are so good, just that it was hard to find resellers selling AMR130 who also have a recent stock, and give 30 day satisfaction guarantee.)

If you still say that I should get those replaced again, I will certainly consider that.

Thanks - Regards - Alok

vissa

I have the same speakers (amr130) and am about to return them for the 3rd and final time. The adapter/transformer puts noise on the speakers if its too close to certain items (like my computer or the subwoofer). I don't think the power supply is shielded very well.

I also have a problem with the center channel making a "breaker" noise a few times a minute (sounds like someone pressing the cb breaker button).

-Victor

alokgovil

Just a comment:

Many people have complained (as I know) about short 'click' sounds coming from the speakers (and have considered static to be the cause). I have that problem too; but do not understand if the "breaker" noise you are talking about is the same thing. If possible, could you please explain more. (PS: I am not a technician, so please do not expect anything coming out of a discussion with me.)

vissa

alokgovil,

Its hard to describe this sound. It lasts for less than a second. Sounds like someone coming on the "line" and then leaving. It definately has a click/pop aspect to it (at the beginning and end). In the middle its a static sound. Sometimes it doesn't happen for 5 minutes, then in will happen 10 times in a minute.

And actually its not just the center. I unplugged the center and the front left/right still do it (haven't checked the rears).

alokgovil

If I have heard any such sounds, they came from some computer hardware activity (DVD drive in my case). I will suggest the following simple experiment described in detail below:

1. Double-click volume icon that shows in the system tray of your computer (bottom right where date shows up). If it does not shows up in the system tray, go to control panel-> sounds and multimedia. In the settings somewhere, you can check "Show volume control om the taskbar.

2. When you double-click the volume icon, a window will pop-up. By default, advanced controls do not show up. Click Options -> Properties and check all volume controls -- play control, SPDIF, CD Audio, TAD, etc. Close this dialog box.

3. Check Options -> Advanced controls.

4. Now you can separately adjust volume of all sound sources, and can mute some of those.

5. Mute all sound sources which you do not need. For example, you can start your music player and mute all the ones which do not mute the music.

6. If the above makes the bad sound disappear (while music sound comes right when you play it), then you know that it is not the speakers.

7. Keep in mind that you have muted most sound sources, if someday you discover that something is not making sound when the music still sounds (like your modem, cd drive...), enable those.

8. Though it is a digital world inside the computer, because of interference, circuits sometimes add noise to the sound. Why have all ten of those sources always on, when 99% of the time you do not need them.

9. If with this experiment, you have found that speakers (and/or sound card) is not the problem, then you can turn on and off various volume controls till you find out which exactly is the device causing the trouble.

10. In my case, a sound very much like what you described, used to come from my DVD drive. Muted. If you need the sound source you just muted, you can either turn that particular volume control on and off when you need it, or get that device replaced under guarantee (I will not go for that since the replaced one too will do the same thing, you know it well by this time!).

If this experiment does not help, let's see what can be done.