Microphone system

Discussion in 'The Projects Forum' started by alonso1999, Jul 16, 2008.

  1. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Hello
    I have a mic system is a desktop conference system daisy chain not been able to use it for a while design problem when sombody open a door in the room or any small noise activates the protection gate I guess shot the mics for a few seconds but is to sensitive no variable component so there's no adjustment I need to find it and change it to a variable, also has a pop when the mic switch is turn on or off,
    I need some help I will provide details.it has 2 earphones jacks, channel selector for 3 ch 8 pin din conector electret mic 12 volt circuit
     
  2. theamber

    Active Member

    Jun 13, 2008
    318
    0
    You can use an attenuator T or II circuit to reduce level output.
     
  3. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Please explain I need more info than that,
    I need to find the culprit to replace the circuit or component how I do that.
    I know some but not as much, Thats why I need more help.and very Important to me to fix this problenm so I can travel with it.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    The first step is to post a schematic, baring that, the make/model of the offending equipment. Otherwise we're guessing, and most of the folks here don't like to guess without some information to back them up.
     
  5. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Well there's the problem with an schematic ,it will be easy to find,
    however i don't have the schematic I can give you the model # but I research that and is not on the internet, this was custom made very expensive in Japan for a friend of mine in NY long time ago, you wont find another system like this that easy.they never provided the schematic and can't find the company now.
    I can provide pictures, model # manufacture but I will think they were using a common circuit that You guys will have knowledge of how to change to a variable one,change it so is no so sentive or elimenate the closing gate

    Thanks.
     
  6. theamber

    Active Member

    Jun 13, 2008
    318
    0
    Did you try to change the Microphone?
    You can use a mic. with a different impeadance so the mismatch will reduce the sensitivity. You may go to an audio store and get some help there.
     
  7. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Sadly, without a schematic, we will be hard pressed to answer your questions.

    hgmjr
     
  8. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Yes I did same problem.
    This circuit is use in the whole system, cause there's another unit that also use a mic this one is a headset mic and have the same problem.

    I have a microphones system thats like 20 desktop microphones(call a delegate unit) on a daisy chain.each unit has 2 earphones jacks, volume control, 4 channel selector ,electret mic,switch on off, 8 pin din conector.
    This is very small unit Analog, it was custom made very expensive in Japan a while ago for a friend of mine in NY.
    I dont have the schematic, the company is no longer in Bussinees cant find it in the internet ,
    The problem is been since the begining the design has some kind of fixed gate that is to sensitive and every time somebody closes or open a door in a room or any small noise even a voice pop causes the mic to shut down for a few seconds and comeback again, so is not usuable and it hasn't been for many years, I like it is very portable small and everything but never been able to fix it, also has a pop on the PA when the on off switch is use.
    I just need help finding the componet or components that make this autogate circuit and change it to variable one or elimenated it
    Thanks
     
  9. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    I will think with someone experience and knowledge maybe here I will find that person to guide me to maybe some component or circuits to look for because this unit has I guess 3 parts power 12V amp for earphones and mic preamp and I need to identified the whole mic preamp and amp circuit.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    It is likely an overly sensitive AGC circuit (automatic gain control) that is causing the problem.

    But without schematics or access to the circuit, it will be just about impossible for us to help you.
     
  11. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Yes, Thats what I think it is,and I untherstand about the schematic thats why I haven't been able to trace the problem and need help , but I will provide any info need it pictures etc
     
  12. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Yes, Thats what I think it is,and I untherstand about the schematic thats why I haven't been able to trace the problem and need help , but I will provide any info need it pictures etc
     
  13. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Here;s the links for the pictures of the system

    The model # is ICMR-3
    Conference Unit Manufacture in Japan BY IVS (japan) LTD
    The IC's Are.
    DKI
    MSM4066RS
    3771
    14 pin

    Toshiba 4027BP
    16 pin

    TA7140P
    7 pin
    NEC UPC1170H
    8 pin

    http://i45.photobucket.com/albums/f58/alonso1999/turkey0708187.jpg
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    Last edited by a moderator: Jul 30, 2008
  14. tibbles

    Active Member

    Jun 27, 2008
    249
    3
    couldnt he just put a 10k preset in each mic line
     
  15. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    You can't use a volume control at the mic if it is an electret type because it still needs to be properly biased.
     
  16. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    What I need is a way to eliminate the over sensitive AGC, but first I have to find it,
    I don't know which one is the circuit making the AGC.
     
  17. alonso1999

    Thread Starter Member

    Jul 16, 2008
    11
    0
    Please any help with this will be appreciated.
    Thanks
     
  18. ICS

    New Member

    Aug 3, 2009
    1
    0
    I know this is a very late reply, but I have just found this forum.

    Your system was designed by Yoshihito (John) Sugita of IVS.

    There are no schematics, he keeps it all in his head.

    The email address for IVS is "ivsjapan@titan.ocn.ne.jp"

    I doubt if you will get any satisfaction, as he guards his designs stringently, but it may be worth a try.

    Good luck.

    Alan
     
  19. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    There were a few of that type of conference system made in the 80's. They had very poor performance but costed a fortune. My local city hall has one.

    Shure (the professional microphone manufacturer) made a gated mic mixer. Frequently when you talked, your mic turned off and the mic beside you and across from you turned on. Frequently nothing turned on. The first syllable was always chopped off.
     
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