[MovingTarget]

This weekend when I turned on my 10 year old Sony receiver it started to smoke. I quickly had it completely unhooked and ready for the trash. When I unhooked everything my Energy S8 (I think that's the model, the sub that came with the Take 5 system) sub started a loud hum. I unplugged it figuring something was messed up with where the wires ended up.


Anyway, I picked up the cheap Onkyo 504 receiver from CC and hooked everything up yesterday. All sounds fantastic, only problem is when I turn off the receiver my sub starts that loud hum.


I checked the wires and can't see anything wrong. However let me describe how I've had this setup.


I have some in-wall speaker wire that goes from the back of my room to the front. I took a decent quality cable with RCA ends and cut it in half, stripped the wires and twisted them onto the ends of the in-wall wire and taped them up making sure none of the metal from the wires touched. There were some strands of wire in the cable that were not shielded that I figured were there to give some more structure and make the cable stronger that I did not connect to anything. There were 2 insulated wires in the RCA cable, one red and one black. So now I've effectively got a long cable with RCA ends so I can plug one into my sub and another into the receiver.


I've tried everything I can think of (verifying everything is plugged in tightly and verifying the twisted wires aren't touching and the electric tape is in good shape. But the only way I can make the sub stop humming loudly is to either turn on the receiver or unplug it, that's not a good solution.


Can anyone help give me some ideas?

 

[mailiang]

The entire cable has to be shielded 75ohm. You have a mismatched wire without the proper shielding. It is not surprising you are having problems. Get a good quality 75ohm shielded RCA cable for your sub to replace what you are using now.


Ian

 

[louthewiz]

To verify and see if the wire is faulty un hook the subwoofer and take it near the avr and try another cable and if there is no hum then the cable needs to be replaced.

 

[mailiang]



Quote:
Originally Posted by louthewiz /forum/post/0


To verify and see if the wire is faulty un hook the subwoofer and take it near the avr and try another cable and if there is no hum then the cable needs to be replaced.

How can it not be faulty? If I am reading it right, he claims he is splicing 75ohm shielded RCA cable with 300ohm non shielded speaker wire.

Quote:
There were some strands of wire in the cable that were not shielded that I figured were there to give some more structure and make the cable stronger that I did not connect to anything

Thats part of the ground!

Ian

 

[MovingTarget]

Well, it did work fine for 3 years with no issues. The wire running through the walls is designed to be run through a wall. If I had speaker jack plates with female RCA connectors on them, then plugged in some RCA wires to connect the jack to the receiver and another to the sub, then you're saying that wouldn't work because I've mixed wire?


Don't some people run RG6 for all their in wall speaker runs to plates and wouldn't they connect speaker wire to basically RG6 therefore mixing types of wires?


Good suggestion moving the sub close to the receiver and verify it's the wire before running something else (which won't be fun).

 

[mailiang]



Quote:
Originally Posted by MovingTarget /forum/post/0


Well, it did work fine for 3 years with no issues. The wire running through the walls is designed to be run through a wall. If I had speaker jack plates with female RCA connectors on them, then plugged in some RCA wires to connect the jack to the receiver and another to the sub, then you're saying that wouldn't work because I've mixed wire?


Don't some people run RG6 for all their in wall speaker runs to plates and wouldn't they connect speaker wire to basically RG6 therefore mixing types of wires?


Good suggestion moving the sub close to the receiver and verify it's the wire before running something else (which won't be fun).

I'm not sure what you mean by "speaker wire". Also even if you are using shielded 75ohm cable all the way through, you should use a barrel connecter (female on each end) and RCA's to connect the two. When using 75ohm coax with standard speaker wire you need to use a 300 ohm transformer to change the impedance when connecting them. Sometimes these are built into the wall plates. If not you need to get an external one. Some types of speaker wire is 75ohms, but I do not recommend it for your sub since it is not shielded and can create noise issues.


Ian

 

[MovingTarget]

So I was thinking that if I did need to run a new wire that I would get quad shield RG6 and put male RCA connectors on each end that go directly to the receiver and directly to the sub. Is this not a good idea then? I don't want to spend hundreds on a Monster subwoofer cable because that just feels like a waste of money to me. I also have heard advice from local specialty HT stores to use coax for subwoofer runs. (sort of wish I knew that when they were building my house and I ran all that inwall speaker wire).

 

[mailiang]

Any good quality RCA 75ohm shielded cable should work.


Ian