Help, Sub Woofer picks up talk radio!

dedick · « **on:** 1 Jan 2005, 06:52 pm »

I recently decided to add a sub woofer in addition to my Athena F2 speakers to fill out the bottom octave. I picked up a Acoustic Energy Ageis powered sub on Ebay which was cheap and appeared adequate for the job.

Anyway, I've tried hooking it up two different ways with two different amps and ran into the same problem both times. The sub picks up a local AM talk radio station (KGO) faintly. It's just audible enough to be annoying during quiet passages. I am located about 5 miles away from KGO's transmitting tower, but I've never encountered this with anything else. I've tried it hooked up to a JVC RX-ES1SL AV receiver (see the digital amp circle if you're unfamiliar with it) hooked up to the subwoofer line out. I also tried it hooked up to a Norh SE-9 single ended tube amp using the speaker level inputs. Both times I get the talk radio in the background and the sub doesn't shut itself off after the amp is off. I can kill the talk radio by flipping the phase switch to 180 degrees. I have no idea why this would have any effect. But that isn't the optimum way to run the sub in my room. Adjusting the crossover frequency has no effect. The only other thing I can add is that the sub won't pick up the radio station on its own. It will only do it while connected to the amp and the amp is turned on. Even if the cables are left loose connected to the sub, it won't pick it up.

Soooo, is there something I can do to prevent this?

bubba966 · « **Reply #1 on:** 1 Jan 2005, 08:05 pm »

Are you using a shielded IC on the sub?

It sounds like the IC you're using is acting like an antenna. If so a well shielded IC should take care of that problem.

zachslc · « **Reply #2 on:** 1 Jan 2005, 08:35 pm »

It's all about the shielding.

lonewolfny42 · « **Reply #3 on:** 1 Jan 2005, 08:44 pm »

Welcome dedick.....What's so bad about having a second tuna....sort of like getting two item's for the price of one.....

Just kidding....switch cables , should do the trick as others have stated.[/list:u]

dedick · « **Reply #4 on:** 1 Jan 2005, 08:50 pm »

Yes, I am using a shielded IC with the JVC's sub output. I thought of that too. That's why I did the test with the Norh using the speaker inputs. I wasn't using shielded speaker cable with that, but I figured a high level input wouldn't be suspectable to picking up RF.

In fact, I just tried another shielded IC a minute ago. This one one was much longer, 12 feet vs 6. When I plugged it in to the sub, all I got was a hum. Then I plugged the other end into the receiver, and got KGO again. That's the only other IC I have laying around that'll reach. All my others are 3 footers or the crappy ones that come with equipment.

It also occured to me that I might have a ground loop problem. I previously had the amps and the sub plugged into different outlets. So I moved the sub to the outlet that I had the amps on. No change.

/Dave/

Carlman · « **Reply #5 on:** 1 Jan 2005, 11:15 pm »

I wonder if there's a loose solder joint in the sub's amp. I have fought RFI for some time... I live just down the road from a huge FM tower. Sometimes they play cool music, though... like 'Atomic Dog' was on yesterday...

I pick it up in my cheap computer speakers. However, I've eliminated it in the main system by resoldering everything, replacing clips with direct soldering, heavy use of ERS, proper grounding, and some luck.

I'd wager there's something loose or not perfectly soldered at the preamp/sub output. Does anything change when you wiggle the RCA cable at the preamp? If not, it'll be really tough to diagnose over the web... Chasing these kinds of problems is really hard without being there.

-C

electricbear · « **Reply #6 on:** 2 Jan 2005, 05:12 pm »

add a variable capacitor to your sub cable and see if you can get a station you like

dedick · « **Reply #7 on:** 2 Jan 2005, 07:53 pm »

Hey Electricbear,

I like that one. If I could move to a station that played some decent tunes, it wouldn't be so bad. I could just swipe the cap from an old radio. Anything but talk radio, please...

Hey Carlman,

I'm afraid you might be right. I've replaced everything external to the sub. I hate the idea of having to hunt for one lousy bad solder joint though. Frankly, the sub isn't worth that much to me.

/Dave/