Subwoofer hum has just started - possible reasons outlined

xar

Well-known Member
Thanks both. Since you all seem to know a lot more than me, see the pics attached to see if they are the same/ similar to what you are suggesting.

The bottom pic is my main conditioner. When using it the hum does seem to reduce, but ONLY when I run an extenstion from the sub to it on the last plug point in the spur in my room. i.e. if I plug the sub into the conditioner, then the conditioner into the 'normal' plug point the sub usually goes in (the 1st point in the spur), I still get the hum (albeit slightly reduced)

The 1st pic is a transformer I borrowed. Adding it between the normal plug point and the sub made no difference, nor did putting it in between the amp and its its normal plug point.

Worth noting that the hum only occurs when I connect the XLR to the sub. i.e. sub plugged into its normal plug point with no XLR = NO HUM. Plug in the XLR (which is also plugged into the amp), lots of hum...

So that makes me think its the amp at fault, not the sub...?

IMG_0171.jpg
IMG_0173.jpg
 

xar

Well-known Member
Just to add (in case if signifies anything), this is what the Torus conditioner was showing when plugged in between the mains and amp. To be fair it sees to have lowered to circa 244 after a few days
40A64863-9C89-436F-B18E-35E2516DD6B7.JPG
 

ggwoodland

Well-known Member
No expert by any means - but I did go down this rabbit hole and it seems 2 things that cause hum 1. Ground loop 2. DC noise. With XLR which is how mine is connected ground loop issues are reduced. XLR doesn’t affect DC noise as that is through the power cable. If I was you I would take up Conrad’s offer and try the DC Blocker. For me the JL DC a blocker worked (and looks like for Conrad as well). If that doesn’t work then a few other options to try - george
 

xar

Well-known Member
Super - thanks all.

@Conrad. I would be delighted to take you up on your offer. I shall supply my details via PM and cover postage.

Just for my general awareness, hows does the DC blocker work? It is just an interim unit between the amp and plug point?
 

ggwoodland

Well-known Member
If it is your sub - plug DC a blocker into sub and sub cable into DC Blocker - I would try that first
 

xar

Well-known Member
Thanks - do you have a link to a comparable product? I have been googling it and there seems to be a smorgasbord of different things coming up, so not quite sure what I am looking at :confused:
 

Conrad

Moderator
Mine is a power based DC blocker: DC Blocker Trap Filter – Assembled in Case – v.3 | ATL Audio Ltd.

It sits inline on the power supply, one IEC in and one out. It's basically got massive capacitors in it to "soak up" all the DC. I'm no electrician so I don't really know why it works. My two power amps have huge torroidal transformers in. They hum without it, they don't with it. That's good enough for me.
 

ggwoodland

Well-known Member
I did chat to a vendor on this I must admit I got a bit lost in explanation. All you need to worry about is the DC Blocker can handle the power of the sub - which means you usually need the bigger DC blockers that are made. That’s why if Conrad’s unit works might be worth checking with REL as I checked with JL - george
 

Conrad

Moderator
I checked with the guy that made mine and he confirmed that it'd handle my power amp (5 x 300w into 8 ohm, 5 x 600w into 4 ohm). That's a 3kW load at 4 ohm. My house would give up before the device did I suspect!
 

barnitto

Active Member
My wife’s hair straighteners causes really bad DC and makes my 7 channels amp really hum..that is not a joke.

I might try one of those ATL dc blockers
 

Conrad

Moderator
@xar is having a think about whether that approach is right for him. If he doesn’t want it I’m happy to lend mine out as a test unit.

it’ll be one of the worlds most travelled dc blockers!
 

xar

Well-known Member
Please let @barnitto have first dibs. I have an interim workaround for now, albeit in 3-4 weeks I will probably have lost the rag with it (again!) and be looking for a lend of it!
 

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