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Speaker Popping

Discussion in 'Electronic Repair' started by Don, Aug 4, 2003.

  1. Don

    Don Guest

    I was given this old Playmaster 40/40 amplifier to fix some hum problems
    which I have solved but there is another problem I have found, but could be
    a design fault, if another electrical device, ie a light on the same ac
    mains circuit is switched on it produces a loud pop in the speakers. I have
    also noticed that there is a loud pop when the amplifier is switched on as
    well. How can I fix this?
     
  2. Could be bad coupling capacitors in the outputs feeding the speakers.
    For both to have the same problem is unlikely, although it's possible
    for an old amplifier. May be just poor design.

    Tom
     
  3. Check it on an o'scope to see if the amplifiers are under biased or
    under compensated, making it very susceptible to spurious oscillation.
    There may also be remaining problems related to what was causing the hum.
     
  4. James Meyer

    James Meyer Guest

    Does the pop when external devices are turned on or off happen when
    there is absolutely nothing plugged into any of the amp's input jacks?

    The pop when the amp is turned on is something that happens "normally"
    to many older amps.

    Jim
     
  5. Jerry G.

    Jerry G. Guest

    Many of the older amplifiers, and some of the very high power amplifiers
    do not have a delayed muting relay on the output. Many of the consumer
    type amplifiers have this type of relay to not allow the speakers to be
    connected until the power supply and output stage are fully started up.
    The speakers are therefore not connected until the amp is properly
    started.

    What you can do is leave the speakers in the off position for about 10
    seconds after turning on the amplifier. If here are no speaker
    switches, you can wire some external switches and mount them in a box on
    the side.

    Or, you can do what I do, is to leave the amp on 24/7. I found that
    overall there were less problems with this type of practice.

    --

    Greetings,

    Jerry Greenberg GLG Technologies GLG
    ==============================================
    WebPage http://www.zoom-one.com
    Electronics http://www.zoom-one.com/electron.htm
    Instruments http://www.zoom-one.com/glgtech.htm
    ==============================================
    I was given this old Playmaster 40/40 amplifier to fix some hum problems
    which I have solved but there is another problem I have found, but
    could be
    a design fault, if another electrical device, ie a light on the same ac
    mains circuit is switched on it produces a loud pop in the speakers. I
    have
    also noticed that there is a loud pop when the amplifier is switched on
    as
    well. How can I fix this?
     
  6. N. Thornton

    N. Thornton Guest


    Exactly. It just indicates lack of PSU regulation and low PSU noise
    rejection. Simplest solution is a 0.22uF cap across the mains
    transformer secondary, and another one on the PSU rail near the
    amplifier. Usually that will de-pop it reasonably well.

    Regards, NT
     
  7. I'm having a similar problem, but for now, I don't care about the "power on" pop. My setup is at the church I
    go to and I'm not exactly sure if its the amp or the wireless microphones are at fault. The pops are very random
    and I'm not sure what the cause really is. I've narrowed it down to these odd possibilities:
    1) Some EMI noise source.
    2) Static electricity.
    3) A mechanical "noise" from the microphone holder.
    4) A poor connection at the battery holder or power switch in the microphone.
    5) Popcorn noise from the microphone.
     
  8. Don

    Don Guest

    I'll try the 0.22uF cap but would you place it directly across the secondary
    or after the bridge reg's?
     
  9. N. Thornton

    N. Thornton Guest


    Well Jim, you know its my job to disagree with you :) Seriously tho,
    these old amps will be vulnerable to numerous switches etc. You can't
    snub the source because there isn't one, there's a house full of them.
    The only practical solution is to give the amp some click-proofing
    filtering.

    Regards, NT
     
  10. N. Thornton

    N. Thornton Guest

    Maybe you'd best not take the cover off at all.

    Regards, NT
     
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