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Thread: amp probelms.... crappy sound

  
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    amp probelms.... crappy sound

    i finally got around to installing my amp....

    and at low volumes you can hear a "fuzzy crackle" in the best terms i can use to describe it.

    you can hear the music beneath this crackle, and when you crank up the volume the music is really clear (but you can still hear the crackle if you listen hard)

    i checked the earths on the amp, and i'm pretty sure it's fine...

    i thought it might be my computer, so plugged a minidisc player into the end of the rca connected to the amp and played music from that - same crackle.

    any ideas? basil - any similar problems you've heard of with computer installs? (thinking it could possibly be some mismatch on the voltage out?!?!)
    My car - Rusty Custom Creations Inc....

    The only natural pilots are born with feathers.... except me.

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    A5TRA 59ORT's Avatar
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    it could be your RCA picking up nioise on the way to the amp which is then amplified
    does your power lead run along side/next to your RCAs?

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    must be crossing a live of some description, sounds like alittle interferrance into the RCA's IMO

    Probably wrong though !

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    nope to the above....


    the noise is now gone - no idea how.

    even odder still, with the fuse removed, and subsequently the 12v cable removed from the amp, when removing the earth cable the screwdriver touched the case and BAM! sparks everywhere.... so somehow the case was positively charged even with no live connection.


    after that, noise seemed to have disappeared.....


    :roll: :roll: :roll:
    My car - Rusty Custom Creations Inc....

    The only natural pilots are born with feathers.... except me.

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    Generally noise of this type is caused by one of two things Ground loops or EMI interference.

    EMI interfrence is what has been described above with your RCA's picking up the noise via electromagnetic means. In you case it does not sound like this.

    This sounds like a ground loop problem to me. Was your amp making contact with the chassis of the vehicle, if it is or was, ensure that you isolate the amp housing with rubber grommits or a non-conducting board. Was you amp earthed properly(to bare metal) and is the grounding points metal of sufficient thickness? Are you using an earth wire of sufficient thickness and as short as possible(from my experience under 2 feet)?

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    the chassis was not in contact with the chassis... currently the amp is just on the carpet.

    the earth cable is short, and of a good thickness. grounded to bare metal (just polished bare it the other day with a dremel)

    also, tried plugging in my groundloop isolater and it actually made things slightly worse (got other noises)



    anyway - for now it seems to have gone, so unless it comes back i'm hapy for now
    My car - Rusty Custom Creations Inc....

    The only natural pilots are born with feathers.... except me.

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    it would be the PC my friend - not the amp.

    I get the same if i lower volumes in media engine instead of with the h/u.

    Seems the lower voltage output starts picking up crap and losing parts too.

    I think it's because the soundcard is putting out a seriously low voltage signal where-as the h/u will put out a signal about 3 times the voltage.

    Could be wrong though but thats why it is with me - hence the purchase of a terratec sound card soon as funds permit which has a 4v line out instead of the usual 2 or less of most sound cards.
    Skuzzle - Powered by Badgerbyte Web & IT Services

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    Your amp will still have power in it for a bit after disconnecting it.

    You should always use an insulated screwdriver anywhere near an amp !
    (Makes you crap yourself !)

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    Quote Originally Posted by M40COO
    Your amp will still have power in it for a bit after disconnecting it.

    You should always use an insulated screwdriver anywhere near an amp !
    (Makes you crap yourself !)
    If your disconneting the live power from the amp it is always advisable to remove the fuse near the battery first, before diconnecting the power wire. The ground wire is last thing to be disconnected. Yes, it will keep a charge for a small while but it should not be enough to make it spark, as that would imply that the amp casing is charged, hence a bit of chassis grounding. On some amps you cannot use a screwdriver only the supplied allen key which is not insulated but if you do it in the order above you should not have any problems.

    Anyways, Rusty sometimes finding the source of noise is not that clear cut, but from what you told me you tried the amp without the PC, so the noise is probably unrelated to the PC. But then again as Skuzzle says PC's are notorious for noise, especially soundcards in PC's. If I sound confused it is because finding the source of noise is not always that simple, worse as I am not sure what your ICE wiring looks like.

    If it does it again I would start testing each thing individually, check each run of cable, till you get to the source of the noise. It is not the easy way but sometimes it is the only way to do it.

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    I fitted some ICE in a MG yesterday and had exactly the same problem, it turns out the amp was faulty and had a problem with the eearth inside of it, Its very weird cos it was exactly the same noise as you said!

    swapped the amp over and it was fine, Hope its ok for you Rusty, its not the Crystal is it?
    :shock:

    Regards

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