Noisy cable box, I think

Posted by: labrat on 23 December 2005

I took the plunge yesterday and had NTL cable tv, phone and broadband installed.
I have an old pioneer amp (A400) that i take sound to from my DVD player. Since plugging in and connecting the digital reciever I now have a constant hum that can only be lost by removing the "digibox" from the set up. Has anyone any experience of this with ntl boxes?
Is this likely to be a configuration issue or is it likely I have a very noisy (and frankly downright ugly) reciever.

Any thoughts gratefully received

Posted on: 23 December 2005 by labrat

Stuart

Thanks for the prompt reply. I guess the easy solution will be the breaker option. I might try wiring the ntl box into the same block as the amp and DVD which currently share one block. The problem only started when ntl arrived.

Is this a sign of things to come I wonder?

Posted on: 23 December 2005 by Stuart M

Appologies, I was mistaken that the hum was caused by the DVD player. If it only occurs when the digibox is conected then that is probably the source of the earth loop so swap DVD for digibox in the previous post.

I'm not sure if phone lines need to be earthed or if a NTL digibox would connect -Ve on the output to earth, if so just by having the phone line connected you may get an earth loop so a breaker may be best. Best advice (try out various mains combinations for your power supplies to see if you can eliminate the loop).

From my own experience (with phone/LAN), after adding, then adding, then adding equpment I got a hum, but then disassembling and resassembling ( I guess something was changed) this solved the problem. On the other hand if there are any dodgy power supplies involved then a breaker may be the best option.

Posted on: 24 December 2005 by Steve2701

Stuart, if you do a search on 'earth loop' & 'hum' on here you will find loads of info on how to sort it & stop it. Most seem to end up with an earth loop isolator fitted and that seems to end the problem.

Posted on: 05 January 2006 by labrat

Thanks Stuart and Steve

Earth loop isolator ordered at Christmas slotted in to the system today and annoying hum removed.

Again many thanks and I wish you a happy new year

Posted on: 05 January 2006 by Stuart M

Great we could help.