New QSC RMX 1450 = bad AC hum

Discussion in 'Home Theater Projects' started by David Giesbrecht, Aug 7, 2003.

  1. David Giesbrecht

    David Giesbrecht Second Unit

    Joined:
    May 28, 2001
    Messages:
    306
    Likes Received:
    0
    Trophy Points:
    0
    My new QSC amp finally arived today and holy crap is it heavy it probably weighs more than my receiver,cd player and dvd player put together and it sounds great to the only problem is there is a constant hum comming from my subs that I cannot get rid of for anything and its loud. I had a little bit of a buzz before comming from my subs with my old amp but it was nothing like this. 25 DB under reference and you can still hear it in the background. Is there any way to get rid of it?

    THX
     
  2. Patrick Sun

    Patrick Sun Studio Mogul

    Joined:
    Jun 30, 1999
    Messages:
    38,779
    Likes Received:
    493
    Trophy Points:
    9,110
    Usually it's a grounding problem. You can test to see if it is by getting a cheater plug from the hardware store. A cheater plug converts the normal 3-prong electrical plug into a 2-prong electrical plug. They usually cost
    $1 or so.

    There are pluses and minuses with using a cheater plug:

    Plus - possibly getting rid of the hum.

    Minus - proper grounding of the amp gets circumvented, could cause problem if a power surge were to find its way to your place.

    That's the cheap solution. Otherwise, you'll have to check your house's electrical grounding, and also see if perhaps the Cable TV feed isn't grounded properly as well.
     
  3. Arnold_R

    Arnold_R Stunt Coordinator

    Joined:
    Nov 12, 2002
    Messages:
    66
    Likes Received:
    0
    Trophy Points:
    0
    You may have some kind of ground loop. I have a QSC MX 700 for my sub amp and had a similar problem. I had a constant hum. I had my amp plugged into a dedicated 20 amp panel and the rest into another outlet. I started disconnecting RCA connectors til the hum disappeared. Apparently when the input was plugged into my MX 700 > hum. I ended up plugging every thing into the dedicated 20 amp outlet which cured the hum issue. Apparently one of the outlets is mis-wired which caused the hum.

    You may also have a bad RCA connection? May be you have your gains set too high on the 1450? I have my set at 12 o'clock.

    Good Luck.

    Arnold
     
  4. David Giesbrecht

    David Giesbrecht Second Unit

    Joined:
    May 28, 2001
    Messages:
    306
    Likes Received:
    0
    Trophy Points:
    0
    I think I'll try the cheater plug, my previous Technics amp wasn't grounded at all and it had a little buzz but you could hear it only with your ear right up against the sub.

    I've tried different RCA connections and it doesnt seem to make any difference at all. You can reduce the hum by turning the gain down but the subs also turn down by the same amount I have my gains set at about 2 o'clock.
     
  5. David Giesbrecht

    David Giesbrecht Second Unit

    Joined:
    May 28, 2001
    Messages:
    306
    Likes Received:
    0
    Trophy Points:
    0
    I fixed it, its all good now my dad had one of those bank mult plug deallies with the ground cut off and now I have less hum than my previous amp.

    Thanks Pat!
     

Share This Page