Subwoofer cable picking up noise

[Trdat]

I'm getting a massive hum from my subwoofer initiated from the RCA cables.

I can play around with the cables and can get them to potentially stop but it's a fight.

Any remedies?

 

[Rip City Dave]

Sounds like a ground loop problem.

 

[AnalogSteph]

I'm confused: Isn't the sub amp like a JSL D2400, which is a PA job with XLR combo inputs? And the SU-8 has balanced outputs? Hence I would expect XLR there. What do the RCA cables connect then? The C356 for the horn obviously, but that's nothing to do with the sub. Also, an NC222MP does not actually exist, just 122 and 252.

Also, please define "play around with the cables". You would expect a ground loop problem to vary in severity depending on loop area, but intermittency would rather be indicating bad soldering or cables.

 

[DVDdoug]

Or an intermittent ground... Usually, you can pull the RCA plug partly out, breaking the ground while still making the signal connection. If that duplicates the problem, there's the answer.

I can play around with the cables and can get them to potentially stop but it's a fight.

What does that mean? Wiggling the connections? Which end? I assume you've tried replacing the cables?

Since you said cables it's unlikely that both cables would have a broken ground. It might be a broken/intermittent connection inside the sub or receiver.

A ground loop is unlikely to make "massive" hum but an isolation transformer can isolate the signal ground from the AC power ground. Normally, I'd try to avoid transformers in the audio path but if it eliminates massive hum it would be a massive improvement.

As a temporary ground-loop test you can try a ground-lift adapter. But that removes the safety-ground and it's not the intended use of the adapter. The ground is supposed to be connected to the grounded screw attaching the cover plate.

 

[Trdat]

I'm confused: Isn't the sub amp like a JSL D2400, which is a PA job with XLR combo inputs? And the SU-8 has balanced outputs? Hence I would expect XLR there. What do the RCA cables connect then? The C356 for the horn obviously, but that's nothing to do with the sub. Also, an NC222MP does not actually exist, just 122 and 252.

Also, please define "play around with the cables". You would expect a ground loop problem to vary in severity depending on loop area, but intermittency would rather be indicating bad soldering or cables.

I have a second system, which is my AVR connected to passive crossover speakers which I use mainly for television but some music and have 2 SVS SB1000. I also have another 2 subs at the back which are DIY with the same SVS amp but for some reason they don't hum, just the front ones do.

Yes, all my equipment connected to my triamped system that is mentioned under my avatar are XLR but unfortunately my 4 subs with the SVS plate amps connected to my AVR are RCA.

When I say play around, I mean I touch them and it could go away. I place them in a different position and the hum dissapears but eventually it comes back.

 

[Trdat]

Or an intermittent ground... Usually, you can pull the RCA plug partly out, breaking the ground while still making the signal connection. If that duplicates the problem, there's the answer.

What does that mean? Wiggling the connections? Which end? I assume you've tried replacing the cables?

Since you said cables it's unlikely that both cables would have a broken ground. It might be a broken/intermittent connection inside the sub or receiver.

A ground loop is unlikely to make "massive" hum but an isolation transformer can isolate the signal ground from the AC power ground. Normally, I'd try to avoid transformers in the audio path but if it eliminates massive hum it would be a massive improvement.

As a temporary ground-loop test you can try a ground-lift adapter. But that removes the safety-ground and it's not the intended use of the adapter. The ground is supposed to be connected to the grounded screw attaching the cover plate.

Ive struggled hard to understand this ground loop concept, its just one of those things I have given up in understanding and just go straight into remedying and process of elimination.

I will try pulling the RCA partly out, like you mentioned and see what I get and report back. But when you say duplicated you mean if the hum is made worse by pulling the RCA partly out?

Pretty much yes, I lift it off the ground(floor) and it stops or if I hold a part of the cable in my hand or even the part that connects into the AVR, it stops and it could even stop for a while but it does come back.

I do have to mention though that I have two seperate RCA cables connected to each other to reach the subs with a connector in between could that play a role? Perhaps that is why the back subs dot hum cause its one new long cable...? I think I might have ansered my own queston lol but yeh any input will help. You did mention a broken or intermittent connection so that could be it, but you said in the sub but can it be the intermittent cable run?

I'll check out ground lift adapter might help.

 

[Godataloss]

Are the subs that are humming plugged into different power outlets than the main stereo system? If so, you can try cheater plugs on the subs to remove the ground or flip the phase- at your own risk of course, lol.

 

[LTig]

Are the subs that are humming plugged into different power outlets than the main stereo system? If so, you can try cheater plugs on the subs to remove the ground or flip the phase- at your own risk of course, lol.

Do this only to diagnose the problem, not to fix it.

 

[antcollinet]

Ive struggled hard to understand this ground loop concept, its just one of those things I have given up in understanding and just go straight into remedying and process of elimination.

I will try pulling the RCA partly out, like you mentioned and see what I get and report back. But when you say duplicated you mean if the hum is made worse by pulling the RCA partly out?

Pretty much yes, I lift it off the ground(floor) and it stops or if I hold a part of the cable in my hand or even the part that connects into the AVR, it stops and it could even stop for a while but it does come back.

I do have to mention though that I have two seperate RCA cables connected to each other to reach the subs with a connector in between could that play a role? Perhaps that is why the back subs dot hum cause its one new long cable...? I think I might have ansered my own queston lol but yeh any input will help. You did mention a broken or intermittent connection so that could be it, but you said in the sub but can it be the intermittent cable run?

I'll check out ground lift adapter might help.

For a start - try swapping the cables with one from the back subs. That will rule out (or in) contact problems in the cables.

 

[sonitus mirus]

Not sure if this info will be helpful or not, but maybe someone that stumbles across it can benefit. I have an RME ADI-2 DAC FS using balanced cables to a stereo amp to power floor speakers and I use the DAC's RCA outputs to an SVS powered subwoofer. I have the same issue with a setup in another room using a Topping D30 Pro in a similar configuration, with the balanced outputs used to powered satellite speakers and the RCA outputs going to a subwoofer. If the source is my laptop (Macbook Pro with M1) using USB, I have trouble with a ground loop when charging the laptop. If I disconnect the RCA cables to the subwoofers, the noise is removed, as the balanced connections adequately cancel the ground loop noise.

My solution was to use an Intona high speed USB isolator between the laptop and DACs. It is a simple solution (not exactly cheap) that should future-proof just about any similar laptop/PC source going forward.

 

[Trdat]

For a start - try swapping the cables with one from the back subs. That will rule out (or in) contact problems in the cables.

I'll try this soon and see. My gut feeling is that the issue is from the interconnectors or the extension of the RCA cable as the back doesn't have the same issue.

 

[Trdat]

Do this only to diagnose the problem, not to fix it.

Firstly I'm confused about what the cheater plug exactly will do. It's essentially a 3 plug connecting into a 2 plug socket? How come the advice against it? Something dangerous?
Not that I was eager to try it just trying to get my head around it.

 

[antcollinet]

Firstly I'm confused about what the cheater plug exactly will do. It's essentially a 3 plug connecting into a 2 plug socket? How come the advice against it? Something dangerous?
Not that I was eager to try it just trying to get my head around it.

It disconnects the earth. So the chassis of your kit is no longer earthed. That means you are no longer protected from faulty wiring or catastrophic failure in any of the connected equipment, and risk of anything up to and including lethal electric shock.

 

[Trdat]

It disconnects the earth. So the chassis of your kit is no longer earthed. That means you are no longer protected from faulty wiring or catastrophic failure in any of the connected equipment, and risk of anything up to and including lethal electric shock.

Well my building doesn't have an earth, not sure if that changes things?

Most of my equipment have the earth on the socket but it doesn't really go anywhere.

 

[Trdat]

And yes, both the front subwoofers are plugged into the same outlet. Switching them to a different outlet makes no difference.

I even switched up the front and back subs for aesthetic reasons and the back(now front subs) still doesn't hum. Even if I plug the front sub into one of the outlet of the back subs, that particular front sub hums horribly, I mean very loud continous hum.

I also have to mention that I get massive static electricity everytwhere in the apartment, is that something to do with the earth or just winter as some forums have it?

 

[antcollinet]

Static is nothing to do with your earthing.

However it definitely sounds like you have earth loop problems. Which is not a huge surprise since you have numerous interconnected devices plugged into the wall all around the room.

Start by disconnecting everything from the amp, except passive speakers, and ONE of the subs that is humming. If that still hums get an extension lead that allows you to plug it into the same socket as the amp. If the hum goes, connect each non humming device in turn. If the hum comes back, plug THAT device into the same socket as the amp. Where power leads go on the same path back to that socket, bundle them together. (Try to reduce the open area between grounds).

Your alternative might be to get some balanced line drivers/receivers for the audio to the front subs such as:

KMTech 2-Channel DRV134/INA Differential Balanced Line Driver and Receiver | eBay

Manufacturer: KMTech Design (UK). A high performance, stereo, low noise balanced line driver and receiver system by KMTech Design. By buying these together you will save 10GBP. However if your priority is sound quality and value for money, then look no further!

www.ebay.co.uk

Though I'm not aware of any low cost finished/boxed devices like this.

 

[Trdat]

Static is nothing to do with your earthing.

That's good news. Someone once mentioned build up of static could be because the apartemnt is not earthed.

However it definitely sounds like you have earth loop problems. Which is not a huge surprise since you have numerous interconnected devices plugged into the wall all around the room.

Yes, an understatement. Around 12 devices inbetween 2 sockets and 2 subs at the back.

Start by disconnecting everything from the amp, except passive speakers, and ONE of the subs that is humming. If that still hums get an extension lead that allows you to plug it into the same socket as the amp. If the hum goes, connect each non humming device in turn. If the hum comes back, plug THAT device into the same socket as the amp. Where power leads go on the same path back to that socket, bundle them together. (Try to reduce the open area between grounds).

Thanks for simple explanation.

When you say from the amp you mean from my main Marantz AVR Pre amp?

I tried all in the one socket and the humming is still there. To be honest its loud and intense. But I will try your advice part by part.

And when you say non humming devices you mean like my power amp connected to the pre amp?

Your alternative might be to get some balanced line drivers/receivers for the audio to the front subs such as:

KMTech 2-Channel DRV134/INA Differential Balanced Line Driver and Receiver | eBay

Manufacturer: KMTech Design (UK). A high performance, stereo, low noise balanced line driver and receiver system by KMTech Design. By buying these together you will save 10GBP. However if your priority is sound quality and value for money, then look no further!

www.ebay.co.uk

Though I'm not aware of any low cost finished/boxed devices like this.

Lastly, how effective is this device? I can buy a cheap aluminium case from China and DIY the holes. I am presuming it doesn't need a power supply so its just RCA holes and XLR holes. If it works then great, might be a worthwile investement. And I just did some googling it was measured here on ASR with very decent measureements.

 

[antcollinet]

That's good news. Someone once mentioned build up of static could be because the apartemnt is not earthed.

Yes, an understatement. Around 12 devices inbetween 2 sockets and 2 subs at the back.

Thanks for simple explanation.

When you say from the amp you mean from my main Marantz AVR Pre amp?

I tried all in the one socket and the humming is still there. To be honest its loud and intense. But I will try your advice part by part.

And when you say non humming devices you mean like my power amp connected to the pre amp?

Lastly, how effective is this device? I can buy a cheap aluminium case from China and DIY the holes. I am presuming it doesn't need a power supply so its just RCA holes and XLR holes. If it works then great, might be a worthwile investement. And I just did some googling it was measured here on ASR with very decent measureements.

Yes preamp - I'd forgotten about that. In fact disconnect the power amp from the pre- just the preamp powered, connected to one sub. Does it still hum?

I've been wondering if the lack of earth could make ground loops worse. How is the room wired? Is there an earth wire between sockets, but then no actual ground anywhere?

Re the line driver/reciever. They each need a +/- dc PSU.

 

[Trdat]

Yes preamp - I'd forgotten about that. In fact disconnect the power amp from the pre- just the preamp powered, connected to one sub. Does it still hum?

Yes both hum, regardless of what combination of sockets the subs are in even with amp disconnected it always hums. Even the back subs hum when I put my finger on the RCA ending but nothing when connected to the pre amp. The fronts, hum regardless, they might stop temporarily like i mentioned if touch the cable or move it but sooner or later it will start its loud hum.

I've been wondering if the lack of earth could make ground loops worse. How is the room wired? Is there an earth wire between sockets, but then no actual ground anywhere?

Yes, there is an earth wire between 80% of all the sockets on the devices but no actual ground, the main doesn't have the third pin. I actually had a thread about earthing the apartment but everyone went crazy and said get a profesional but they lacked the understanding of third world intricacies and that profesionals don't exist in my country, I mean at least few and far inbetween and that the goal was to understand what is going to be done before I get someone in to keep an eye on the whoever was taking on the job. The thread was closed down and I have no idea what to do for safe grounding or even if i need it. Some mentioned, that if i don't have a problem it wont really matter, others said that earthing is important, others mentioned that you can just put pole in the ground yourself and the thread was closed down. Kind of think closing the thread down was significantly more dangerous than allowing me to understand what needs to be done. But by all means perhaps grounding is not so important and that was the point.

The building is old and the whole building has no ground. I can call the electricity department but all they do is stick a pole in the ground as well and have no idea how they will hook up each apartment to the that pole. And then someone said that becuase I am on the bottom floor that if the whole apartement installs ground then the shock can build up to my apartement so its better to leave, well this was one advice. So without a conclusion, I have just left things as they are with the only issue this ground loop. If a simple device an fix it then great.

Re the line driver/reciever. They each need a +/- dc PSU.

Okay thats easy enough, is there a some instructions on how to connect it up?

And is it effective? I mean will it fix the problem 100% of the time or it could still be a hit and miss.

 

[antcollinet]

Whether it is effective depends on where the noise is coming from. If you still have loud hum with only the preamp and sub connected and both plugged into the same socket, then I'm not socket, then I'm not sure what you can do.