Voice effect

Discussion in 'General Electronics Chat' started by TheBellows, Nov 20, 2009.

  1. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Hey, i'm kinda noob at this, but i made this circuit and it sounds kinda cool except for the continous oscillation in the background.

    Are there any simple ways to filter or gate away the annoing tone?
    I've tried to filter it away with some caps and some resistors here and there, but with no acceptable results...

    Are there better ways to acheive this sort of voice effect?
     
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Indeed there is! You want to have a double balanced modulator (DBM) at the junction of your audio and the chopped wave.

    I use a similar effect using audio to modulate a NOISE source, using a DBM. Also very cool :)

    eric
     
  3. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Hi, thanks. :)

    Can you tell more about this DBM?
    If i use an unbalanced signal from my guitar to modulate through this circuit, do i then need an Unbalanced Modulator?

    I found some chips called "Double Balanced Modulator/Demodulator", is this what I need?
     
  4. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Now i made a simple J-FET based guitar preamp (with large cap gain boost)and connected my guitar through the preamp and then through the chopper.
    All powered from the same voltage regulated 9V source.
    I placed an extra 1uF cap from +9V to ground and that seemed to get rid of some of the annoying tone, but it's still there in the background.

    Here is a short recording of the effect. Notice the continous tone at the end: http://www.archive.org/details/CircuitTest
     
    Last edited: Nov 20, 2009
  5. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    I have searched around on the net to find some more info on DBM, but all i can find are these DBM chips and i'm not shure how to use them.

    Please, any help is appreciated. :)
     
  6. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Check with MINICIRCUITS.com for info on doubly balanced mixers.

    You can also build your own with Gilbert Cells, if you like.


    Eric
     
  7. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Thank you, this issue seems to be a lot more difficult than i thought...
    Do you have a suggestion to which IC i should try?
    As i said earlier i'm a noob at electronics and the information i read about DBM is too technical for me.
    Do you know any schematics for these kind of circuits? (all i can find are some radio frequency circuits)

    Do i need a balanced signal to get these chips to work? I would like to use only unbalanced signal from my guitar or similar...
     
  8. boriz

    New Member

    Jul 16, 2009
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    Idea: (Untested)

    Use the 555 to drive a bright LED. Fix the LED to two LDRs so that they are both equally illuminated. Wrap black insulating tape around it to isolate it from external light. Use the LDRs together as a divider. The impedance at the centre will change from high-to-low-to-high at the 555 frequency. This can modulate your signal without adding any DC problems like you’re getting with your circuit.
     
  9. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Wouldn't this work only with the 555 as a LFO?
    If the frequency of the 555 circuit is like 10khz wouldn't the LDR's just stay at a fixed resistance?

    If you listen to the sound sample i provided in a few posts up you can hear how i modulate the guitar with a higher freqency tone.
    I like this effect and i don't see how to produce such an effect with the LDR approach, but please tell me if i'm wrong.
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Why not ask Fenris.
    He made a voice modulator for the Dalek's.
    This uses a 4066 to chop the signal.

    Greetings,
    Bertus
     
  11. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Thanks, who exactly is Fenris?
     
  12. bertus

    Administrator

    Apr 5, 2008
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  13. TheBellows

    Thread Starter Active Member

    Jan 18, 2009
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    Ok, thanks, I'll ask him if i caan't figure something out.

    I just came up with a new approach to get the job done, but i'm still not exactly shure how to do it.
    The idea is to make a sound triggered switch in the way that when the line in signal is very low a switch turns off the modulation signal.
    I'll google some circuits to see if i can find what i need.
     
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