Help me cure my slight hum problem

Discussion in 'Archived Threads 2001-2004' started by Philip Hamm, Nov 22, 2002.

  1. Philip Hamm

    Philip Hamm Lead Actor

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    I'm getting a little bit of hum from my main speakers. I'd like to get rid of it. Right now I am using the fairly good cables that came with my Sherwood Newcastle AVM9080 amplifier (preamp is the matching AVP9080). I was thinking of trying some BetterCables, I think the problem may be that my cables aren't shielded well enough. Am I on the right track? I get silence when I turn my preamp off and leave the amp on and I get hum with the pre on (on digital PCM sound with nothing playing - so the source is within the preamp). EDIT - that was incorrect - I got hum even with the pre off.
    Since I'm a vinyl fan I'm used to a little noise underneath really great sound so this is not very distracting. It would be nice to fix though.
     
  2. Chu Gai

    Chu Gai Lead Actor

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    Geez Phil, i once had an annoying squeak coming from the back of my car. the dealer examined it and said it was my mother-in-law. Ok enough of the Friday jokes.
    You know as well as anyone that hum can come from a variety of sources so its diagnosis can be terribly problematical.
    I'm assuming there's no CATV or satellite hooked up to the system in any way. Rather than suggest cables, can you tell me if you just got this system or if not, then have you always experienced this? Also, are there any halogens on the same ciruit...anything with dimmers?
     
  3. Philip Hamm

    Philip Hamm Lead Actor

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    By "main speakers" I mean all 5 of the 5.1 array that are aimplified by the (great sounding) AM-9080.
    I have a cheap sattelite receiver box. You can see my setup on my page - click the little green house. There is a lot of shit and I just got a SACD player that's not on that list.
    I have had problems with the AM-9080 cables being close to the wall wart that powers the Outlaw ICBM, that's why I'm thinking inadequate shielding in the cables between the pre and power amps may be at fault. When I had the wall wart near those cables the hum got worse.
    There is no dimmer on the circuit that I know of.
    I have a halogen torchier (sp?) lamp in the room temporarily but it's turned off. I don't really need it. When it is dimmed the hum is awful. I've had this hum as long as I've had the system together. I don't know that there's a solution. I'm using a Powermax RacMax surge protector, I don't know if it has any kind of regulator in it.
    ALSO - this may be important - I have many of my power cords routed into the legs of my rack, so they are running 120V house power in unshielded lamp cord right next to my audio cables.
     
  4. Chu Gai

    Chu Gai Lead Actor

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    I'd be initially looking at two things Phil.
    1) If that's just some el-cheapo wallwart, consider replacing it with something better. Want a cheapie suggestion that you can return with no hassles if you don't like it? Try the Belkin Isolators available at Staples.
    2) if you're of the mind to replace the interconnects, consider something with a star-quad geometry.
     
  5. Shion_ca

    Shion_ca Stunt Coordinator

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    The Accoustic Research Master Series are the best cheap (ish) well sheilded cables I've seen. Pick up a pair from futureshop, if they don't fix your problem you can always return them. Another important hint is to arrange your layout so that your power cables and interconnects run perpendicular to each other. Also try to keep your amp isolated from your signal producing and carrying lines. Futureshop sells a $100 Sattelite serge protector etc. bar with their FNT's in it. This will slightly condition the incoming AC signal. You can also take it back if it doesn't work. Let me know how these suggestions work out for you.
     
  6. RussKon

    RussKon Stunt Coordinator

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    you have a ground loop in your system...keep all of your audio/video components plugged into the same outlet...and put all other electricals...lights, etc. in a different circuit
     
  7. Philip Hamm

    Philip Hamm Lead Actor

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  8. Philip Hamm

    Philip Hamm Lead Actor

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    Chu, Look at my system. The sattelite receiver is directly on top of my preamp. Should I try moving it?
     
  9. Chu Gai

    Chu Gai Lead Actor

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    give it a shot Phil. you've read enough posts around here to also know cable/sat tv systems have given people headaches with hum also so you might also want to try disconnecting that part from your system and seeing what happens. don't know what kind of walwart you've got back there, but if it's an elcheapo power strip, give that Belkin unit a shot as I believe you can get them with as many as 6 or 8 outlets. Each pair of outlets is 'isolated' to a degree from the adjacent pair. Hence the pair furthest from the power inlet will have the greatest degree of noise attenuation. However that's only going to be effective with respect to line-born noise. My reasoning for suggesting interconnects that are in a 'star-quad' configuration primarily has to do with their rejection properties to EMI/RFI via the airwaves. If you've got a car stereo installation place, give them a call and see if they've got RCA's made like that. Phoenix I do believe makes them. As always I look for a very consumer friendly return policy.
     
  10. Philip Hamm

    Philip Hamm Lead Actor

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    I don't know if you understand what I mean by "Wall wart". The ICBM runs on DC power and uses an external adapter. That's a "wall wart", not a power strip. I am using a cheap power strip in addition to the RacMax (since everything won't plug into the PowerMax).
     
  11. Chu Gai

    Chu Gai Lead Actor

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    shows what i get for not reading properly!
    not familiar with the unit you've got phil, however if you feel comfortable opening it up, then check out this link for a possible solution that might not require cables. also you might want to head on over to your local Guitar Center and see what they've got that's better quality. Their return policy is quite good. They do have wallwarts with a grounding pin that's said to be much better.
     
  12. Philip Hamm

    Philip Hamm Lead Actor

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    Man, it's bad and it's driving me crazy.
    The whole room is one circuit and for all I know it may be running other bad stuff in the house. I tried plugging in nothing but the amp and even that directly into the wall - and it hums. There's something else on the circuit in the house, it could be a new refrigerator that I just got. [​IMG]
    The ICBM is now gone because I don't need it anymore.
    I've got to do some more investigating. I've rearranged things so the satellite box is at the top and replaced my preamp because the old one died.
    Has anyone ever called an electrician to have a dedicated circuit installed? I have my fusebox right in the corner of my room, with an outlet below it in the wall. It may be very easy to install a dedicated circuit.
     
  13. Bob McElfresh

    Bob McElfresh Producer

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    Try moving those audio cables so they hand down the middle of the rack away from the power cords. Try to move the speaker wires away from everything else as well.

    Did you disconnect your CATV feed to see if this is injecting 60 hz into your equipment?

    With the system making the sound, try touching some of the un-used inputs on your receiver or inputs on the VCR. Does the hum change sound? If so, there are some RCA caps you can buy that shield the un-used inputs from noise.

    There is a myth about shielding: the shield on all your cables is connected to the signal ground or 0.00 volt reference in your gear. Putting on a cable with a better shield is the same as putting on a better antenna to inject noise into your equipment. So I dont think other cables will solve the problem.
     
  14. Chu Gai

    Chu Gai Lead Actor

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    Me, I'm an enterprising bastard and if I want a separate circuit I just put it in. Myself, I've found the public library an invaluable resource with their DIY video tapes when it comes to that as well as my local electrical supply house. But for the faint of heart...well you know!
    Without knowing what's on your circuit Phil its really hard to say what the problem is or where its coming from. For starters, if I never had the problem before, I'd be looking at what I've done differently since then and then try disconnecting things in an attempt to isolate the offending culprit. I've got another thought also Phil, not necessarily guaranteed to cure your problem, which is to buy an outlet tester. They're about $10 and should be able to do the things this one can. At the very least you wind up having peace of mind knowing that all your outlets are wired correctly.
     
  15. Philip Hamm

    Philip Hamm Lead Actor

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  16. Chu Gai

    Chu Gai Lead Actor

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    Hey Phil, if i'm reading you correctly, you're saying you moved the satellite box but still haven't physically disconnected it. Just disconnect the feed going into your system and see what happens. If that's the problem, we can look at a couple of approaches to all this.
     
  17. Philip Hamm

    Philip Hamm Lead Actor

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    Well, I did some more testing tonight.

    Went down and listened to Steely Dan's excellent "Gaucho" DTS disc while doing some housework.

    Silence. Total silence. Not a bit of hum. A little hiss coming out of the main L/R speakers (curiously not coming from the center - got to check the cables). No hum - well maybe a little tiny tiny bit. I unplugged the satellite box from the wall and it may have made a barely perceptible difference if my ear was right next to the speaker.

    Went up and opened the new fridge for a minute or so. New fridge kicked on about 10 minutes later - here I am in humsville. Awful hum from every speaker. Bigtime.

    Most definitely my problem is my new refrigerator. It is more efficient and runs almost constantly as opposed to the old one which ran less often but used a lot more electricity.

    And I tripped the circuit breaker to my HT room hoping the Fridge was on the same circuit - no dice.

    What can I do about this? Any ideas?

    Can I get an electrician in here to make a dedicated circuit for my home theater? A better circuit breaker switch perhaps to isolate the one exising circuit from the rest of the house?
     
  18. Chu Gai

    Chu Gai Lead Actor

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    Phil, if you've no objections I'm going to post this question somewhere else to elicit some responses. Right now it seems that your HT is on a different circuit from the fridge. A line conditioner won't do squat as the frequencies it attenuates are way up there. Now it's possible that the fridge is emitting garbage via the air. How close is your fridge to your system?
     
  19. Philip Hamm

    Philip Hamm Lead Actor

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    The kitchen is directly above the HT room. The fridge is probably less than 20 feet from the system, maybe 15 feet. Thanks for asking elsewhere. Please post a link. I can't believe that no-one on HTF can help!

    I highly suspect that this was happening before, and it may even have been responsible for the on-off hiss problem with my old preamp (that's my doubt talking). I wouldn't have noticed the problem before because it didn't show up as often.

    I'm going to ask Kenmore tech support for help also.
     
  20. Chu Gai

    Chu Gai Lead Actor

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    Don't forget to go out and get thee an outlet tester. If anything Phil, its good for peace of mind.
     

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