Picking up radio in the sub input cable

SithSolo1

Diamond Member
Mar 19, 2001
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So I've finally got my bedroom setup how I want it and now I'm picking up the local college radio station through the LFE cable. I've tried 3 cables so far including a "double-shielded" one from monoprice and put two ferrite core chokes on it. The chokes did reduce the problem but did not eliminate it. Should I add more ferrite? Should I try something else?
 

queequeg99

Senior member
Oct 17, 2001
571
5
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Based on posts of yours I've seen, I assume you've already done a bunch of troubleshooting, but here are a few questions:

1. Is this a new receiver or one you've used before with no problem?

2. Have you tried using a different receiver to see if the problem persists?

3. Assuming your AVR has a radio tuner, what station is it normally tuned to? This college radio station?

4. In a more general sense, what has changed? You say you've got your bedroom setup now and you've got this problem. Is this a completely new set up or did you add/replace stuff on an already-existing set up and now you have this problem?

5. Have you tried plugging your components (AVR and sub) into different outlets (or even taking them to a nearby neighbor's house to see if the problem persists)? You might have some weird grounding issue.
 

SithSolo1

Diamond Member
Mar 19, 2001
7,740
11
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I've been using the same receiver for a few years now. All I did was rotate my setup 90 degrees counter-clock wise within the room and added rear speakers. It was up against the outside wall, now its up against the wall to the left of the outside wall.

So far I've tried the following connection wise:

Everything fully connected and powered: Radio
Fully connected w/ Receiver off, Sub on: Radio
Sub on, LFE cable only plugged into sub and disconnected from receiver: Radio
Sub on, no LFE cable: Silence
Different outlet has no effect.

The outer wall has a set of windowed french doors in it. The way I had the sub previously was on the right of the doors, now its on the left. I'm in a condo practically on campus but I have no idea where the tower is located. However I wonder if before there was wall between the sub and tower and now its lined up through the doors. I guess the simplest thing is just to put it back where it was and see if it still picks it up. Then if it still picks it up start lugging it around the house and see whats going on.
 

SithSolo1

Diamond Member
Mar 19, 2001
7,740
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Well after some trial and error I've found another spot for the sub. The sub was picking the radio up in the old spot when I tried it again, it was just quieter. Now I've got it where its not audible from my chair and it no longer triggers the auto-power on.
 

JoeBleed

Golden Member
Jun 27, 2000
1,408
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This is probably stupid, but with the sub unplugged from the receiver, but still having the cable plugged in and picking up the radio with a shielded cable, are you sure the connection on the sub is grounded for shielding?

Tried wrapping aluminum foil around the speaker for crappy makeshift shielding? (my probable stupid idea)

Called the radio station to see if they've recently changed something?
 

SithSolo1

Diamond Member
Mar 19, 2001
7,740
11
81
This is probably stupid, but with the sub unplugged from the receiver, but still having the cable plugged in and picking up the radio with a shielded cable, are you sure the connection on the sub is grounded for shielding?

Not sure what this means, I'm an electrical idiot. The sub is an Energy S10.3. The RCA LFE connector on the back of the sub looks just like the one on the back of the receiver.

I also have a spare amp/input board that Energy sent me when I first got the sub because it wasn't turning off properly with the Auto-On feature and it would make a loud "burp" when the RCA cable was inserted even when powered off. Thinking back on it now I wonder if the amp ground is faulty and the signal was strong enough back then to keep the auto-on triggered. I never changed the amp out as one day it just started working normally.

Tried wrapping aluminum foil around the speaker for crappy makeshift shielding? (my probable stupid idea)

Haha, no I haven't tried that.

Called the radio station to see if they've recently changed something?

I'll try to contact them today.
 

SithSolo1

Diamond Member
Mar 19, 2001
7,740
11
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Well the station go back to me, no changes on their end and their engineer also said it sounds like a shielding issue. I guess I'll pop in the spare amp and see if that fixes it.
 

queequeg99

Senior member
Oct 17, 2001
571
5
81
This is probably stupid, but with the sub unplugged from the receiver, but still having the cable plugged in and picking up the radio with a shielded cable, are you sure the connection on the sub is grounded for shielding?

Tried wrapping aluminum foil around the speaker for crappy makeshift shielding? (my probable stupid idea)

Although I have never experienced this precise problem, I have had humming issues with subs in the past and have been intrigued by your issue so I did a bit of reading up. What follows is nothing more than some of what I've read so take it with a grain of salt (I'm definitely not an EE or anything).

I think what he means is that even the most heavily shielded cable can potentially still act like an antenna unless the shielding in the cable is connected to a ground. It sounds like your subwoofer interconnect cable shielding might not be working properly. This could be because the radio transmitter is really really close (in which case you might be SOL). But it also could be because the shielding in the cables you're using hasn't actually been connected to a ground. This can happen for a number of reasons.

1. The shielding connects to ground through connections at the cable plugs. Sometimes these connections fail. And in some cases, a device you're connecting to isn't designed to ground the shielding (sometimes the case with subs). You can test this out by using temporary replacements if you have access to a spare sub and receiver. You will want to switch out your sub for a replacement and then your receiver. If your sub isn't designed to ground the shielding, you need to rely on the receiver's ground. If the receiver isn't properly grounding the shielding (either because you've disconnected the sub cable or because of a fault with the receiver or because the receiver's electrical outlet isn't grounded), you might have an effectively unshielded cable.

2. Some subwoofer cables are made to be connected in a specific direction. This isn't because of some black magic audiophile stuff. This is because the shielding on some cables is connected to the plug at one end only (i.e. the cable is designed to reach ground through one end only). Cable companies sometimes make sub cables in this manner to try to reduce ground loop problems (humming). Typically, such cables will have an arrow at one of the cable. The arrows show the direction the signal should be travelling (i.e. from the receiver to the sub). The end of the cable to which the arrow is NOT pointing is where the shielding is connected to the plug (i.e. the shielding reaches ground through the AVR). If you've been using such cables and connecting them in the wrong direction, the cable shielding might not be grounded. I doubt this is the reason if only because I own three different monoprice sub cables and none of them are unidirectional. But I thought I would mention it if only because switching the direction of the cables is easy enough to do.

3. The tin foil idea might work if you can find a way to ground the foil. I suspect it would work better if you wrapped it around the cable (and grounded it).

Good luck. These problems suck.
 
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