HELP!! Major hum coming from my subwoofer - AVS Forum
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post #1 of 12 Old 08-08-2000, 02:47 PM - Thread Starter
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I'm looking for some advice. I just picked up a used (4 months old) Lexicon DC-1 ver 4. I was hooking it all up last night and after I connected the sub and turned on the pre I was getting a major hum from my sub. At the moment I don't have an amp hooked to the lex so I went directly out from lex to sub pre in and still getting hum. I hook sub up to another receiver and it's fine. I checked the ground in the power and that's fine. I tried another ac outlet(diff. ckt) an same. Even when lex is off, but power is going to it same problem. Tried multiple cables, still bad hum. Is there something I'm missing.
My amp shows up in 2 days and I want my set up to work.
Ira
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post #2 of 12 Old 08-08-2000, 04:59 PM
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Have you unplugged all sources so it is just the Lex pre-amp and the sub ?

Does the lex expect or require directional cables ?

Might you have a ground-loop hum between the sub and pre because they are on separate circuits ?

Some amplifiers are really sensitive to ground loop and your other receiver may have been shielding the sub's amp from the differential where-as the Lex is not.

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[This message has been edited by dreamer (edited August 08, 2000).]

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post #3 of 12 Old 08-08-2000, 05:20 PM - Thread Starter
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Have you unplugged all sources so it is just the Lex pre-amp and the sub ?

Yes unplugged all sources so it's just lex and sub

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Might you have a ground-loop hum between the sub and pre because they are on separate circuits ?

Even on the same circuit I recieve the hum. Only when connected to the lex do I get the hum.
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Some amplifiers are really sensitive to ground loop and your other receiver may have been shielding the sub's amp from the differential where-as the Lex is not.

Ok it is probably a ground loop, and the lex is sensitive. so my problem is how to fix it. I tried a 2 prong adapter, no luck. I tried plugging lex into another outlet,no luck. I even unpluged ALL equipt. except lex and sub, no luck. But I do think that this is the problem(ground loop)
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post #4 of 12 Old 08-09-2000, 05:41 AM
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Isolo,

I am having similar problems with my setup. I have a Lex DC1 and a Sunfire True Subwoofer MKII.

What happens in my case is that the sub will run fine for a while, then all of a sudden start to make this loud buzzing sound. Sometimes turning the volume all the way down, disconnecting the input, waiting, plugging the input back in, and turning up the volume will clear the problem. Other times I need to do this multiple times, other times I have to power off the sub and wait.

Once the sub goes into buzzing mode I can turn off the Lexicon but the buzzing continues. I originally had everything on the same circuit but still had the problem. I then installed a dedicated circuit for the sub and played around with grounding options and orientations.

Things worked very well for a while (about 1 year). Last night I installed a new center channel and changed the center setting on the Lex to large for the center channel. I now get the buzzing issue every half hour or so.

I now need to focus onsolving the problem. Is it the Lex interaction with the sub or something more basic?

SS10MAN have any of the add on devices helped?


Steve
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post #5 of 12 Old 08-09-2000, 06:42 AM - Thread Starter
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Ok, here's the latest. I unplugged everything in the house. And I mean everything Fridge,microwave,etc. There was nothing plugged in the house at all. I shut off all ceiling fans. I plugged in the lex and the sub, no luck still hum. I used a cheater plug, no luck still hum. I plugged them in the same outlet, no luck still hum. I called lex tech support, got hung up on first time, called back got voice mail. I am running out of options. Would running dedicated circuit definitely fix the problem. What exactly does that entail(spelt right)? I have a electrician friend that I will probably call on this. All I want is clean sound. I'll even settle for just sound without a hum. The system works fine when I set up my reciever. AS soon as I hook up the lex I get the hum. Could it be a problem with the lex. It seems other people are having similar problems with their lex??
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post #6 of 12 Old 08-09-2000, 07:01 AM - Thread Starter
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ss10man you refer to these products:
Also Sonance makes a ground loop isomator circuit that you could add between your DC-1 and Sub, it is a active circuit.

Also I have bought a device called a MAGIC "Mondial Antenna Ground Isolation Circuit", it a passive device needs no external power.

Both these products seem to think that the cause of the hum is from a signal coming into the house, cable or whatever. If all my equiptment was disconnected and there was nothing plugged into the house except the lex and sub, would the hum still be coming from cable or similar device??
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post #7 of 12 Old 08-09-2000, 07:17 AM - Thread Starter
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Ok so now I spoke with Lexicon and they seem to think it's a problem with the unit itself and want me to send it in flat rate cost of $325. They seem to think there might be a problem with the connector in back. Any feedback would be appreciated.
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post #8 of 12 Old 08-10-2000, 07:47 AM - Thread Starter
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Well, The problem is solved! I do appreciate all who replyed. everyone had good advice and did help in the troubleshooting process. It is the lex unit that is defective. When I called lex and the service rep said it was the unit I was suspect. Thinking all he wanted was some cash. Well I moved the lex over to the other side of the room where the sub is. I pluged the lex and the sub into the same wall outlet, used a 3 ft rca cord and plugged them in. HUMMMMMMMMM. I jiggled the connector on the end of the lex and it went away. I tried multiple cables and the same results. SO I sent the lex to the manufacturer yesterday. When I get it back I'll let all know the results. Bummer though, because I'm getting my amp today(Parasound 1205a) so I'll have it all set up and ready to go when my baby comes back from the doctor. I am really looking to see if I am able to hear a difference from my old reciever(Pioneer 608) to the lex. Thanks again to all who replyed.
Ira

[This message has been edited by isolo (edited August 10, 2000).]
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post #9 of 12 Old 08-10-2000, 03:37 PM
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I had the same problem with the Lex Mc-1 and Levinson 336 amp. A cheater plug on the Levinson cured the problem. I think Lex is the problem. A different pre-amp hooked up eliminated the noise.

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post #10 of 12 Old 08-10-2000, 06:11 PM
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I tried the subwoofer with a different processor. Same issue. I spoke with Sunfire who said I should send the subwoofer in and they will check it out. They also send be a new box and packaging for free as I do not have the original packing materials.


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post #11 of 12 Old 08-10-2000, 07:17 PM - Thread Starter
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Gages,
Check out this site. http://smr-home-theatre.org/Forum_3/.../wwwboard.html
scroll down to the subject of rusidual HUMMMM. It talks about other lex and sunfire owners with the hum problem. Granted it is an old post 1998 but it did have some info.
Ira

[This message has been edited by isolo (edited August 11, 2000).]
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post #12 of 12 Old 08-11-2000, 04:32 PM
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I got a loaner sub from my dealer today. Hooked it up to the Meridian no issues. We will see what Sunfire has to say after they check out the unit.


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