Question Hum from Wharfedale Powercube PC-10A

D-an-W

Active Member
Evening folks, after doing a bit of research I decided to try my sub with the earth lead disconnected in the plug and lo and behold it removes the hum I have lived with
for many years!

I am trying to find a service manual to see if the earth lead is used internally (I assume it is) but wanted to ask if this is considered safe and classed as a permanent fix or should I take another approach?


EDIT: Done more reading and won't be leaving this modified lead in place but I have also found if I unplug the TV from the mains the hum greatly reduces so I guess this is where at least one Ground Loop is?
 
Last edited:

D-an-W

Active Member
So, the Isolator arrived today and it does cure them hum but as expected it lowers the output (More than I thought though!).

I now have to have the sub turned to max for it to reach the same level as before without the Isolator.

The ground loop hum also stops if I unplug both HDMI cables from the TV which I assume is the path it is using to get to the sub via the AVR (AVR has no earth in cable).

Would it be worth trying another cable or is there perhaps a mod I can do to my existing cable to stop the hum without reducing the level so drastically?
 

John24ssj

Active Member
How far is the subwoofer from the receiver?
 

John24ssj

Active Member
You could run a single wire from the chassis of the sub to the chassis of the receiver. Can't say this will definitely work but it might help with a ground loop
 

D-an-W

Active Member
Thanks, is the theory behind that electricity is lazy and takes the easy path?

I think the 4500H has an earth point on the rear, will that be ok to use?
 

John24ssj

Active Member
This video here is doing a similar thing. But not an expect, so can't confirm if this will help
 

D-an-W

Active Member
Using the ground point on the receiver for a length of wire then touching that to the outer of the RCA connectors on the sub made no difference at all.

I did notice though that the hum actually comes from all speakers when the sub is connected normally, never actually knew that.
 

John24ssj

Active Member
Hmm that might mean you have noise in your mains 🤔
 

D-an-W

Active Member
Could it actually be the sub or the TV (Panasonic Plasma) creating it?

As I mentioned, if the earth terminal is removed from the mains lead to the sub there is no hum at all and obviously the Ground Loop Isolator does the trick but requires the sub to be on full volume!

I would buy a new sub if I could be sure it would fix it, do new ones come without an earth connection like the receiver?
 

The latest video from AVForums

Panasonic HZ2000 OLED TV Review: The best OLED for movie viewing in 2020
Top Bottom