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voice module help please

Discussion in 'General Electronics Discussion' started by Mandalorian, Jun 11, 2015.

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  1. Mandalorian

    Mandalorian

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    Jun 11, 2015
    Hi
    I was trying to put together a voice module for a costume and have run into a snag. I bought a module that I can save 5 different sound clips to which are played through an attached speaker by pushing individual buttons. The speaker was too quiet so I removed this and added a connector which then plugs into an amp. Both have their own power supply. the module runs off 3 x 1.5 volt button batteries and the amp has its own re chargeable power pack which states 5 volts. When I first connected it up it worked, but then 1 button worked and the other 4 produced only the initial first second of the sound clip. I tried switching the buttons round to see if it was the buttons or the connections but the same sound clip played ok with a different button and the others didn't. Do I have a power problem from the voice module and would upping this solve it or is there something else. Thanks. Dave
     

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  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Welcome to electronicspoint.

    Does the sound module work (albeit at low volume) when used without the amplifier?
    Your way of putting the assembliy into a piece of cloth without proper ESD protection may have resulted in an electrostatic discharge that may have destroyed components. If the module doesn't work standalone (+speaker -amplifier), chances are the module is defect and cannot be repaired. Sorry for the bad news in this case.

    If the sund module works without amplifier, reconnect them. Test the assembly on the workbench. Make sure no short circuits exist. If the assembly works, put it into an ESD-proof package (e.g. from the packages with which you received the module), ensure no short circuits can happen and place the pack back into the costume.
    If the assembly doesn't work, I'm out of my wits.

    Harald
     
  3. Mandalorian

    Mandalorian

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    Jun 11, 2015
    just tried putting back on the original speaker and it works fine but not with the amp attached
     
  4. Martaine2005

    Martaine2005

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    May 12, 2015
    Hi Mandalorian, and Harald Kapp. Do you mind if I ask a question?

    Mandalorian, you have connected an amplifier to an amplifier and to the original speaker.
    Do you know what Ω's the original speaker and amp is.?
    Secondly, amplifying an amplified signal will play havoc. You are basically using your added amp as a speaker and then amplifying again to the speaker.
     
  5. Mandalorian

    Mandalorian

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    Jun 11, 2015
    Er bit confused. The voice module sends a recorded sound clip to a speaker attached to it when a button is pushed. The speaker was too quiet so I removed the speaker and in its place attached a cable which plugs into the AUX port of a voice amplifier (which has a speaker in it) like tour guides use. It is not going through two amps unless the the voice module has an amp on it. I am sorry i have no idea what ohms the original speaker and amp is.
     
  6. BobK

    BobK

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    Jan 5, 2010
    If the sound module itself is very low volume, I don't think there would be any problem with putting it's speaker output to an AUX input of another amplifier. The signal is likely in the 1V range, which is perfectly OK for an AUX input.

    The problem might be that the sound module does not work properly without a load on the speaker output. The input of the other amp will not be nearly as high a load as the speaker was. Try connecting both the speaker and the other amplifier and see if it works better. If it does, a proper resistor could replace the speaker.

    Bob
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    A mismatch of impedances at the sound module's output is likely to produce distorted sound, but not the symptoms observed by the op. Anyway, it's worth a try to add a resistor (e.g. 33Ω or similar) in parallel to the amplifier's input to simulate a load to the sound module.
     
  8. Martaine2005

    Martaine2005

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    May 12, 2015
    Yes, I just read my post above and am confused too..o_O

    BobK and Harald Kapp explained it in English..

    Probably should have read 'using the added amp as a load' (speaker).
    All amplifiers should always have a load, invariably the speaker.
    If the speaker is removed the amp will easily be damaged.
    Hence the 'above' two comments about a load resistor.
    Phew...
    Martin.
     
  9. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Um I wonder why only one message works and the others cut short. Is the first message shorter in length than the time the other messages cut out after.
    Adam
     
  10. Martaine2005

    Martaine2005

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    May 12, 2015
    In post #3 he said it works fine with speaker back on the module.

    The speaker could be anything from 2ohms to 64ohms.
    Martin.
     
  11. Arouse1973

    Arouse1973 Adam

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    Yeah but also he said one message worked with the amp and the others cut short. Seems strange maybe something was getting hot?
    Adam
     
  12. Martaine2005

    Martaine2005

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    May 12, 2015
    Is it possible for the AUX in to try and pull more current than the module outputs to the speaker?
     
  13. Arouse1973

    Arouse1973 Adam

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    I doubt it, the input impedance is going to be around 10K. Something odd is happening for the first message to play and the others only for a short amount of time.
    Adam
     
  14. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    You can try a low pass filter (~5kHz) between the voice module and the amplifier.
    The voice module possibly has a kind of primitive class-D amplifier (or PWM) that relies on the inductance and mechanical inertia of the speaker to generate the sound. This may not work with an amplifier, some EMC issue?

    Another thought: are bot modules (sound and amplifier) powered by the same voltage source? In that case the current drawn by the amplifier may induce voltage variations on the power supply which in turn may cauese the voice module to behave erratic.This may not happen at the much lower volume of th evoice module alone. It will also depend on the content of the sound files.
    Easily to be tested using two separate power supplies and or swapping sound files.
     
  15. BobK

    BobK

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    Jan 5, 2010
    In the OP he states that the recorder module and amp have different batteries.

    Bob
     
  16. Harald Kapp

    Harald Kapp Moderator Moderator

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    Oops, that escaped me. Sorry.
     
  17. Mandalorian

    Mandalorian

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    Jun 11, 2015
    Thanks for all your replies guys, Sorry have not had a chance to get back on here, Harald whats a low pass filter? Sorry guys I am a complete beginner at this, I did wonder if the module needed more power but i am not sure now. I just need some way to increase the volume of the module, any ideas?
     
  18. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    A low pass filter is a circut that lets low frequencies pass and suppresses high frequencies. Before you build that, go back to the last part of my post #14 and find out what happens when you swap sound files.
     
  19. BobK

    BobK

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    Did you try what I suggested in post #6?

    Bob
     
    Arouse1973 likes this.
  20. Mandalorian

    Mandalorian

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    Jun 11, 2015
    Sorry Bobk i forgot about that and ur a genius it works perfect now with the speaker and amp attached. Thank you so much.
     
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