SOS! Eliminating Humming noise from active subwoofer

[vivek.saikia]

Hi All,

I have recently purchased an active subwoofer from the Blindfold sale in eZone, Pune Central. It is a cheapo Sensei subwoofer which I got for a discounted price of 5590 bucks. Happy I was in getting an active subwoofer with 10 inch woofer, variable crossover control, speaker level as well as line level inputs and 175W RMS amp (I seriously doubt it) in such a low price.
I was planning to pair this sub to my stereo setup consisting of a NAD C350 and Wharfedale Diamond 8.2 speakers for movies (very rarely) and even rarer moments when I become a basshead. So, spending heavily on an expensive sub was out of question for me. So, buying this sub was an instant impulsive descision.

Now, A lesson learnt a harder way. Cheaper products ALWAYS loose out on quality control.
This subwoofer has an inherent humming noise (about 60Hz) whenever I switch it on, with no input signal. Please note that this is not an external ground loop problem as the humming persists even when the subwoofer is not connected to the amp and no RCA cable is connected to it. One observation is that when I touch on any conductive area of the plate amp, the humming noise reduces considerably (but still there).
This subwoofer has a 2 pin power cord.

So, I need help from all the DIY electronics gurus, on eliminating the hum from the subwoofer. Any easy solution on eliminating this annoying noise from the sub? One solution I can think of, is to use a three pin power cord and connecting the ground to the body of the plate amp. But I am not sure if it will resolve the problem and even doing a trial will involve lots of wiring to be done as all my equipments are connected to a two pin extension cord.

Please help!

Vivek

 

[subhash]

had a similar problem long back with sonodyne roarII sub , this too had a 2 pin and the hum was noticed on directly connecting it to power socket

the people at sonodyne advised to connect the sub via an xtension box/chord
on doing this hum was considerably less ,try it out

 

[vivek.saikia]

had a similar problem long back with sonodyne roarII sub , this too had a 2 pin and the hum was noticed on directly connecting it to power socket

the people at sonodyne advised to connect the sub via an xtension box/chord
on doing this hum was considerably less ,try it out

So, the power connection to the subwoofer needs to be isolated from the other equipment? Will have to try that out.
This noise is very annoying, My ears are fatigued due to this and now even while listening to music without the subwoofer connected, I am keeping the bass all the way down to 0 level. Such a bad effect is having on my ears.

 

[rallynut]

somehow,still sounds like a ground loop prob to me.here u have an active sub,2 prong plug,...:indifferent14:.do correct me if otherwise.cheers

 

[vivek.saikia]

somehow,still sounds like a ground loop prob to me.here u have an active sub,2 prong plug,...:indifferent14:.do correct me if otherwise.cheers

That's right Rallynut.
Ground looping might be due to some faulty circuit design, as the sub "hums" even without any other component connected to it. I still have to check try out connecting it to a separate power socket and isolating from the other equipments. Gounding the amp also seems to be a solution, but that will involve lots of wiring the ground from the socket to the sub. Anyone had this problem and tried this solution? I want to proceed with it only if it guarantees some result.

 

[Adhiraj]

Try this ,it worked for me
Take a wire and attach it to one of the screws on the plate amp section of the subwoofer and the other end to the ground pin only in a 3 pin socket.Plug that into the wall and use the 2 pin normally as you were before.Methinks this is an earthing issue,I had a similar problem with my Klipsch RW12 except it was actually giving me feedback current so much so that I was getting zapped touching my Ipod.However after implementing the above the problem was completely eliminated.

Good luck!

 

[vivek.saikia]

Try this ,it worked for me
Take a wire and attach it to one of the screws on the plate amp section of the subwoofer and the other end to the ground pin only in a 3 pin socket.Plug that into the wall and use the 2 pin normally as you were before.Methinks this is an earthing issue,I had a similar problem with my Klipsch RW12 except it was actually giving me feedback current so much so that I was getting zapped touching my Ipod.However after implementing the above the problem was completely eliminated.

Good luck!

Thanks Adhiraj, I will try out this tried and tested solution and ground the plate amp to the mains socket earth.

 

[rallynut]

do keep us posted vivek,as i have had similar issues which are solved for most part with adequate grounding.in fact what i still dont get is that while all my components are plugged into a belkin strip thru a stabilizer,my laptop on charging tends to introduce some hum into my speakers thru my dac's :sad:.minimal hum,but there.weird.unplug the charger,and no prob.every other component seems fine and noise free .need some enlightenment here too.apologise for the OT.cheers

 

[Adhiraj]

Rallynut ,

This is a problem I have experienced as well ,caused in most part by power supplies and SMPS's .I usually run my laptop charger on a completely different circuit.These ruddy little things really screw with cleanliness of power line.You can try one thing tho,use a ground loop isolator,or if your laptop has a 3 prong plug ,use a wire which has 2 prongs alternatively use one of them nifty multi plug thingys and remove the earth pin.If you experience any "funny vibes" from touching any metal parts of the laptop then this is a no go,back to the isolator/different circuit plan.

HTH.

 

[Adhiraj]

Oh! before I forget,make sure the ground in the house circuit is working fine.Test it using a 100 watt bulb attached to a holder.One wire to phase one to neutral ,bulb should illuminate as normal.Now remove the neutral wire and connect it to the earth.If the bulb is dim then you need to have the earthing checked.Full illumination =no worries .

Note:
The publisher of this note bears no responsibility for death caused by electrocution to the readers of such note.It is assumed proper and standard safety procedures will be followed during application of said test.In the event of any electrocution type event/equipment damage,please feel free to use expletives or have your wife do the test.

 

[vivek.saikia]

My lappy power supply is also connected to the same extension cord to which the sub is connected. So, that might be the culprit.
I will unplug it and see if it helps. If it does then it will be the easiest solution.

 

[rallynut]

@adhiraj,thanks.i keep thinking the same,laptop charging boards have always been a b****!!!!and ur most likely correct about the grounding(i suspect the same),looks to be that vivek and me seem to be having the same issues.to think that this is after adequate measures have been taken .darn electricians in small towns,always taking the easy way out!!am sure something is amiss,..somewhere .cheers

 

[Adhiraj]

try using the ground lift approach I had detailed earlier,disconnect the earth pin from the supply and see if that helps, it did in my case.

Cheers!

 

[vivek.saikia]

Update: My lappy power supply is not the culprit. Have tried unplugging everything from the extension cord but the hum remains.
When I touch the plate amp the hum goes off.
So, Now have to try out the 2nd option of connecting the amp body to earth. Lots of wiring has to be done as the extension cord is a two wire one

 

[Adhiraj]

@Vivek- no pain no gain my friend.

The more I read up on this the more it seems to be just a grounding issue,when you touch the plate amp it finds a ground but you aint that good a conductor hence only slight attenuation of the hum.Im guessing the level will vary based on whether you are wearing socks or not lol.But it seems the only way is for you to ground the plate amp ,you might have to scrape a bit of the paint or powder coating away to get a good contact with the metal.This should solve your issue once and for all ,hopefully.

Usually the Laptop charger generates a sound that is more like interference that a constant hum.It sounds at times like a radio channel.Sometimes like in my case ,operating a process on the computer changes the nature of the interference ,for example when I minimize a screen or insert a CD ,the hum goes away for a second and then comes back, when the mouse moves the buzzing also changes in pitch(strange musical instrument this I tell you).If you face a peculiar thing like this then you know its your lappy for sure but if its constant it might be something else.

Good luck ,do let us know if you have managed to nail the issue.

 

[vivek.saikia]

Guys what guys!! I have found the simplest solution to remove the humming noise from my active subwoofer.
The sub has speaker level inputs and it has clip type connectors for speaker wire. What I have done is, I attached a wire end to a screw of the plate amp body and have inserted the other end to the negative input terminal of the high level input. And voila!!! The noise is totally gone

:clapping::yahoo:

 

[anm]

????
pls post a pic.

Congrats on fixing the issue - enjoy the music!:yahoo:

 

[vivek.saikia]

????
pls post a pic.

Congrats on fixing the issue - enjoy the music!:yahoo:

Pics will follow soon, as soon as I will have a relaxed schedule.

 

[rallynut]

hope it has been resoved to ur satifisfaction vivek.as for me,the charger of the laptop is the prob and im facing the same issue that adhiraj mentioned.like a radio interference,high pitched which changes in intensity during a process execution,disappears on unplugging the charger unit.unfortunately dunno what else i can do to resolve it,as by cheating the ground,it will only leave the setup more vulnerable to spikes in our everfluctuant power supply .cheers

 

[gobble]

hope it has been resoved to ur satifisfaction vivek.as for me,the charger of the laptop is the prob and im facing the same issue that adhiraj mentioned.like a radio interference,high pitched which changes in intensity during a process execution,disappears on unplugging the charger unit.unfortunately dunno what else i can do to resolve it,as by cheating the ground,it will only leave the setup more vulnerable to spikes in our everfluctuant power supply .cheers

And give you a shock of your life ... hyeah: