Sub Amp Hum [long]

Discussion in 'Home Theater Projects' started by PaulT, May 19, 2003.

  1. PaulT

    PaulT Supporting Actor

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    Just received my Servo-15 a couple of days ago. On plugging it in (it has a 2 wire AC cord) with no other inputs I heard a 'hum' coming from the Amp module which I could hear from 3 - 4 feet away.

    I moved the Sub (90 pounds worth...) around the house to 3 separate circuits and the hum was evident in all of them.

    At that point I called the Dealer who immediately and with no questions asked sent their truck to come and get the unit. Brought another new unit home which we had opened in the store and plugged in (no hum). When I plugged it in at home, the hum is there - this is still without attaching the sub to anything other than AC. Damn, house problem.

    Borrowed a Monster 2500 Clean power from a neighbor (I know Chu, clean what?? but it was there) and it made absolutely no difference.

    Since then I have tried 2 other circuits, unplugged the refrigerator and any halogen or 'cheap' lights. I went as far as turning off everything in the house but the sub and the hum is there.

    My Main Panel is 40 years old but has good NMD 14-2 wiring with a 6 ga ground wire strapped (bonded) to both the water pipes (metal) and an 8 foot ground rod outside the house. I had previously checked all the plugs in the house for proper ground and wiring with a tester as I had to replace all the 2 wire receptacles with 3 wire when I moved in. All of the boxes (and plugs) are properly grounded and wired hot/neutral OK.

    Since the sub is 2 wire, this is not a ground loop problem but 'noise', either RF or EMI on the line IMO.

    What are some of the things I could check further, and what options do I have. I own the house, but will be selling it, so a whole house solution might be too cost prohibitive.

    Note that the hum does NOT come through the speaker, it is in the amp itself, so when it is in the corner of the room away from the listening area it cannot be heard. I just 'know' it is there so it annoys me.....

    I have emailed Paradigm for their opinion but it is the long weekend here and I would expect them to reply after Tuesday.
     
  2. Chu Gai

    Chu Gai Lead Actor

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    I understand what you mean about knowing it's there. Just gnaws at one. You may yet have AC issues but at least you borrowed it first Paul!

    Perhaps a very foolish question on my part, but what happens when you
    a) connect everything to it and or...
    b) run a ground wire (old speaker wire will do) from the sub to the wall ground( must be something metal on there that's got a screw.
    c) disconnect and unplug your cable box from the system (I know the sub's not connected to anything)

    90lbs is a bear to be lugging around. talk about a weekend workout.

    On a side note, I have heard that Paradigm has a noise
    isolation kit for consumers (free I believe) for situations such as yours.
     
  3. PaulT

    PaulT Supporting Actor

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    Makes one wonder what Monster Clean Power does [​IMG]
    maybe it's cleaning the 'negative waves' around the wall plug.

    Not foolish questions/answers:
    a) same thing, no hum from any speakers (thank *%$%)
    b) good idea, will try it later today - have a bunch of running around to do.
    c) no change

    Will await Paradigms response, perhaps they might suggest their isolation kit, that's very good info to have. One good thing is the area rep lives here in town.

    Will let you know about 'b', thanks very much.

    BTW if you wish to insult the Leader of a Sovereign Nation, then you should at least get his name right [​IMG] Our politicians did. [​IMG]
     
  4. Chu Gai

    Chu Gai Lead Actor

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    LOL...depends where you are in Canada...my experience was the more rural areas had issues with 'Jean' but that sort of thing runs true in most countries including the states. In retrospect I shouldn't have said it.

    Yes, it's my understanding that such a unit exists and is free for the consumer. As to it's efficacy, I really don't know, but the fact it exists certainly suggests the company is aware of an 'issue'. I'll grant you it's a puzzling thing and certainly not uniform. I'd be sorely pressed to open the unit up and confirm it's coming from the amp inside.
     
  5. Bob McElfresh

    Bob McElfresh Producer

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    Have you hooked it up to the LFE output with an audio cable so the amp has a zero-volt reference?

    Try touching the input jacks on the sub. Does the hum stop?

    Just having the connectors not-connected to anything leaves them floating. The hum could be simply noise awaiting a connection to give the inputs something to do.
     
  6. PaulT

    PaulT Supporting Actor

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    Thanks Bob but it does the same thing hooked up or not. Me 'grounding' the RCA plug with my finger also doesn't change anything. It's definately my AC as it works just fine at the Dealers with no input.

    Chu, we in the West have no love of things 'French-Canadian', I'll leave it at that [​IMG]

    Been out eating and drinking all afternoon for the long weekend so I think I'll leave the electricity until tomorrow.

    I know that the Servo-15 is a sealed unit, but am not sure if I would break the seal pulling the amp unit off the back. I'll wait for Paradigm's response before I get out the tools.
     
  7. Chu Gai

    Chu Gai Lead Actor

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    I sure wouldn't want you to void the warranty. post back on the response you get.
     

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