Amplifier AC Current Draw

Discussion in 'Archived Threads 2001-2004' started by John H, Jan 1, 2002.

  1. John H

    John H Second Unit

    Joined:
    Nov 27, 1998
    Messages:
    472
    Likes Received:
    0
    I use 2 stereo pro amps bridged mono in my system. High amplitude low frequencies cause the clip indicators to flash occasionally.
    During this low frequency clipping is the amplifier drawing it's maximum AC current and reaching it's limits?
    Is occasional low frequency clipping harmful to the amp?
    John
     
  2. ToddJoseph

    ToddJoseph Stunt Coordinator

    Joined:
    Sep 9, 2000
    Messages:
    66
    Likes Received:
    0
    Do you have a dedicated outlet, (20 amp) for your amplifier.If not your amps, could be trying to draw enough power from your outlet, not getting it for the bass scenes and cutting out.
     
  3. John H

    John H Second Unit

    Joined:
    Nov 27, 1998
    Messages:
    472
    Likes Received:
    0
    The pro amps are Crown K2's
    Each amp has it's own dedicated 20A circuit. I am not having any performance problems with them.
    I was just curious. When an amplifier clips a low frequency signal does this mean it is reaching it's AC power draw limits if it has adequate power to draw on?
    Also is occasional low frequency clipping harmful to an amp.
    John
     
  4. KevinYS

    KevinYS Extra

    Joined:
    Mar 18, 1999
    Messages:
    24
    Likes Received:
    0
    John,

    This is what I think:

    For an amp to clip, it is possible 1) the input singal clips already before coming into the amp. 2) input or driver stage of the amp being over driven to clipping. 3) output stage being over driven to clipping. I don't think its a problem of not enough incoming AC current, but one of the three possibilities listed above. When the amplifier clips, it puts some stress on the transistors and other devices, it is not a good thing to let it happen.

    My $0.02...

    Kevin
     
  5. James Mudler

    James Mudler Stunt Coordinator

    Joined:
    Feb 1, 2001
    Messages:
    207
    Likes Received:
    0
    2nd Kevin comments. AC power would not be my concern. A clipped input/output signal would. A very rare flicker would not rasie a eyebow but a constant would. Clipping is bad for both amplifier and speakers. High frequency drivers (tweeters) and be damaged quickly by clipped signals. Lower the "gain" (signal) from the preamp and see if it goes away. If not lower the amp gain next.
     
  6. John H

    John H Second Unit

    Joined:
    Nov 27, 1998
    Messages:
    472
    Likes Received:
    0
     
  7. Arthur S

    Arthur S Cinematographer

    Joined:
    Jul 2, 1999
    Messages:
    2,568
    Likes Received:
    0
    To answer the first part of your qeustion: the amp is drawing close to its maximum AC pull when low frequency demands flash the light.

    Speaker testers like to use the big Crown amp in parallel bridged mono mode to see how much juice a speaker can take. Over the years a few speakers were able to absorb the equivalent of 10,000 watts (for very short periods) without damage to the speaker or amp. Probably take a hell of a dedicated circuit to deliver the needed voltage without sag.

    Unfortunately, I am not aware of any current mass media speaker tester using the big Crown. Tom Nousaine who is the current king of subwoofer testing uses the big Crown to drive his basement loaded 8 driver sub to thunderous levels.

    One member of this forum has or had the big Crown. The current incarnation of it is available for about $3,500. Anyone need 1200 watts per channel into 4 ohms?
     
  8. John H

    John H Second Unit

    Joined:
    Nov 27, 1998
    Messages:
    472
    Likes Received:
    0
    I just finished talking to Crown Audio tech support.
    I was told it is not a problem for the amplifiers clip indicators to flash on demanding low frequency peak signals.
    You just don't want them to stay on continuously.
    I have been driving the amps set to occasional low frequency clip for a few days now.
    I can demo the Episode I "pod race" at reference looped for over 30 minutes and the amps are barly warm to the touch.
    Thanks for all the replies,
    John
     

Share This Page