Subwoofer hum again

Doctor Smith

Well-known Member
I have a BK P12 300 connected to a denon amp via a single phono cable.
I was watching a quiet movie last night when I noticed a slight hum coming from my sub.
When there is no sound source going to the sub but power and phono cable are connected I can hear the hum. When I turn up gain volume the hum gets louder.

If I unplug phono cable but leave sub powered on the hum disappears. The phono cable is 5 metres long. Any ideas?
Cable was quite expensive so I want to be certain it's a faulty cable before I replace it. Thanks
 

Doctor Smith

Well-known Member
Update - I have plugged in a cheap 3ft RCA cable and it hums. If I hold the middle of the cable with one hand a and touch the other phono input with my finger the hum disappears.
 

gibbsy

Moderator
Update - I have plugged in a cheap 3ft RCA cable and it hums. If I hold the middle of the cable with one hand a and touch the other phono input with my finger the hum disappears.
That's because you are working as an earth for any current. That more than confirms that the hum is being caused by an earthing problem.
 

Doctor Smith

Well-known Member
That's because you are working as an earth for any current. That more than confirms that the hum is being caused by an earthing problem.
Thanks. Any idea how to troubleshoot and resolve?
 

gibbsy

Moderator
Check all bits of kit that are connected together. The earth problem may not be with the sub itself but can be anything in the chain from the TV to the AV amp. It's a case of elimination, unplugging individual pieces from the mains. It can be beneficial to have all your kit running off one socket with an extension lead.

Worse case scenario is that there is an earthing problem on another piece of electrical goods in the house and an electrician may be needed to help sort it out. Often a problem in older houses with an inadequate earth.
 

fatboy frank

Distinguished Member
Might seem a stupid suggestion ........... but it never does any harm to remove the cable and have a good clean of all the contact surfaces, including the Sub and AVR connectors too. Double check none of your cabling especially power cables have moved ..... and try again, it can be a bit hit and miss trying to get to the bottom of these things.
 

Doctor Smith

Well-known Member
Thanks everyone. Will start investing at the weekend.
 

fatboy frank

Distinguished Member
Thanks everyone. Will start investing at the weekend.
Could always try giving Tom a call at BK, sure he would probably have a few suggestions to try or at least confirm if it's the sub itself.
 

Gasp3621

Distinguished Member
While ago some member mentioned that Tom from BK sended him some "magical" power cable and the humm stopped. Not sure which thread it was.. Anyway @Doctor Smith give Tom a call before they go on summer vacation and shut down the company!

Tel ; 01702 527572
 

IWC Dopplel

Distinguished Member
I am not sure if the BK sub is earthed at the socket, you might make up a lead that is just an earth lead, I have a RCA to earth pin and RCA to RCA, only that I sometimes deploy (earth only)
 

Doctor Smith

Well-known Member
While ago some member mentioned that Tom from BK sended him some "magical" power cable and the humm stopped. Not sure which thread it was.. Anyway @Doctor Smith give Tom a call before they go on summer vacation and shut down the company!

Tel ; 01702 527572
Thanks will give him a call.
 

Doctor Smith

Well-known Member
I am not sure if the BK sub is earthed at the socket, you might make up a lead that is just an earth lead, I have a RCA to earth pin and RCA to RCA, only that I sometimes deploy (earth only)
Sorry for sounding dumb. How do you make and connect an earth lead?
 

MemX

Well-known Member
Am I correct in thinking that central heating radiator systems are earthed?

If so, touching something metal (like a cable core) from the casing to one of the (unpainted parts of) the system should earth it??



(This may be nonsense :D lol)
 

IWC Dopplel

Distinguished Member
Well sort of. The earth for you electrics are on the incoming electricity cable, this then should be your earth throughout and will also be used for grounding other items so they dont end up being at a different ground and therefore pass charge.

In your kit this earth is also sort of used as the ultimate earth as well its more about how it gets there and what the potential difference is on the way. In your electronics any voltage that you send will be in reference to another usually ground, hence an RCA has a ground on the outside and a voltage that is referenced to this ground called zero if you follow. Some talk about circuit ground and earth lifts but this is more about trying to get the ground to flow in one way.

The 'complexity' is that this simple and 'elegant' idea has problems when this isn't executed that well, earth or zero isn't earth or zero relative to another earth or zero, hence you now have a loop or small circuit with a potential difference etc.

Because of some complexity with how earthing is done (some components are designed to have an earth via the RCA and to another piece of equipment and NOT earth via their own plug and so on). Really good earthing affects sound quality so I have a cable made up that is RCA earth (nothing connected to the signal pin and the other end to the mains cable earth pin) and one that is RCA earth shield with a good connection - thick mains cable size wire from the RAC shield to the other RCA shield and I often try using these around equipment to better understand any hum.

I do have some of these cable in place permanently as it sounds bette, but I dont recommend unless you know what you are doing as you may be removing any short to earth system. People forget that signal is the difference between the positive signal and ground they are both as important everyone is most interested in the precious signal and less bothered about the other as important part.
 

Doctor Smith

Well-known Member
Hi, did you manage to resolve this?

I'm having the same problem with the same sub.
No didn't get it resolved. I moved the Sub further away from listening position. I can hear from a meter away. All BK subs I've owned eventually start humming. I'm going for another brand next time.
 

DavidT

Well-known Member
My XLS200 hums, it has been humming for the last 2 or 3 years but very faint so it doesn't bother me that much. My sub hums even when only connected to power.

Edit: Since moving the sub to the back of the room the hum has gone very quiet.
 
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Doctor Smith

Well-known Member
I seem to have the same issue. Did you solve it in the end?
Unfortunately not. Changed all leads and different plug sockets. I have moved it further away from seating area so can't hear it now. I have owned 3 BK subs and all have suffered from it. All have just been out of warranty when the hum started.
 

password1

Distinguished Member
Unfortunately not. Changed all leads and different plug sockets. I have moved it further away from seating area so can't hear it now. I have owned 3 BK subs and all have suffered from it. All have just been out of warranty when the hum started.
Im using a Rel, BK and Q Acoustics sub at the moment and they all hum from the same wall sockets. Every sub (new and used) Ive had all hum so I doubt it's isolated to certain makes of sub.

What sub(s) are you using now?
 

Doctor Smith

Well-known Member
Im using a Rel, BK and Q Acoustics sub at the moment and they all hum from the same wall sockets. Every sub (new and used) Ive had all hum so I doubt it's isolated to certain makes of sub.

What sub(s) are you using now?
Sounds like you have a ground loop issue.
In the past I've had kef, warfdale and Rel. No hum at all with them. Just strange it starts after a couple of years.
 

maxkolonko123

Well-known Member
I've recently noticed my ham is caused due to pc graphic card once I've disconnected hdmi to avr from pc hum was gone
 

Gasp3621

Distinguished Member
It´s amazing how they can`t get rid of the humming/buzzing issues. Seems like on going issue for many years. Maybe it`s time re-design the amps. I was lucky no humming with my BK sub during 4years.

Tom Pearce from BK (technical guy) sent something for one member as he`s new Monolith buzzed and it stopped. I would call to BK and talk with him if it bothers you. One thing is good with BK stuff the repairs are very cheap what i have seen so even 10year old product can be fixed under 100£ possibly.
 
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