how to increase this audio circuit

Discussion in 'The Projects Forum' started by paldep, Mar 16, 2016.

  1. paldep

    Thread Starter Member

    Mar 3, 2016
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    Hi, i want to use a 5 volt source and i want to increase the audio output of this circuit. How to do? C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_F3K2SVFFHWN77C8_MEDIUM.gif
     
  2. wayneh

    Expert

    Sep 9, 2010
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    How much change to the circuit can you accept? I'd replace it entirely.
     
  3. Veracohr

    Well-Known Member

    Jan 3, 2011
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    Do you want to increase the voltage, or current capability, or both?

    To begin with:

    - Remove R3, it does nothing useful
    - If you remove R2 and connect RV2 directly to the battery you can adjust the gain over a much larger range
    - Increase the capacitor sizes to about 47uF if you want the circuit to be useful over the whole audio range
    - Add a small resistor to the emitter of Q1. Or better yet, add a larger, partially bypassed resistor to the emitter of Q1 and increase R_ear

    What kind of output level do you want?
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
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    A chip is much easier - the TDA7052 works well down to 5V, but its a BTL so not much good for earphones if you need stereo.

    The A suffix part has DC volume control.
     
  5. paldep

    Thread Starter Member

    Mar 3, 2016
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    Thanks guys. I Will try the veracohr suggestions. This Circuit comes from a spy ear toy. I wanted to have much gain. I am working to a hearing empaired project :)
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    My TL431 electret capsule booster was published in Elektor a few years ago - someone here has a link to an online copy of the article.

    The device is based on a 2.5V reference, so 5V would be cutting it fine - but might work well enough with 32/64 Ohm earphones.

    With 12V supply it runs slightly warm loaded with an 80R speaker, its "comfortable" with a 140R telephone earpiece.

    The TL431 can be had in TO92, SMD, 8-DIL and SOIC-8. With a small handful of passives you can be up and running. You can use a logic level MOSFET for more output drive, but biasing is easier if you use an interstage coupling transformer.
     
  7. paldep

    Thread Starter Member

    Mar 3, 2016
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    Thanks but i am a beginner. I dont Know if i can!
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I know how, as a beginner, it seems easier to use discrete components. This is not true, and I encourage you to look at integrated circuits. Yes they are complex on the inside, but that is not your problem. They are designed by teams of experts to do exactly what you want, and you usually have to do little but power them and connect inputs and outputs as described by the data sheet. You will get so much farther, so much faster, once you accept that. Designing your own transistor amplifier is challenging, and you'll never match what the pros have already done for you.
     
  9. #12

    Expert

    Nov 30, 2010
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    MikeML is a wizard with the TL431 so he got me curious. There is a low level amplifier in the datasheet.
    I'm thinking about a 1000 ohm to 8 ohm audio transformer I bought at Radio Shack. Too bad most of them are closed now.:(
    Oh well. If you have to go to an internet vendor to buy an audio transformer you will be more likely to get one that is right for the job instead of making the job right for the transformer.
     
  10. paldep

    Thread Starter Member

    Mar 3, 2016
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    I have some problem to Connect this device with one single battery. I think the problem is on the connection of the max4466 electret. It has a common ground and it make me impossible the connection with the pam 8403 that have separate ground. Audio- and battery -. How can i Connect it properly? Maybe a diode? C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_circuit.jpg
     
  11. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Your pam chip uses a bridge output for each channel, it doesn't use a common ground.

    Try a Tda2822 chip
     
    Last edited: Mar 18, 2016
  12. paldep

    Thread Starter Member

    Mar 3, 2016
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    No no. The problem is not in the output, but in the input. If i use a battery For each single chip. It Works.. How to Connect properly the pam8403 and the electret max4466? It's seems so easy.
     
  13. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You cant use the supply ground and signal ground together, they have to be separated, so you need to use two separate batteries., or a different chip.

    datasheet
     
  14. paldep

    Thread Starter Member

    Mar 3, 2016
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    Maybe this can work. I need to find a dc to dc Converter 5volt to 3.3 C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_uY7IL(1).png
     
  15. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need an Isolated output Dc to Dc converter.
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    The TDA7052 I suggested in an earlier post uses the absolute minimum of external components.

    Literally; a supply, a decoupling capacitor, a speaker and a volume pot.

    The A suffix part I mentioned has DC volume control, so the pot varies the DC bias on the control pin instead of dividing the input signal voltage.

    Being a BTL amp, it also works well down to 5V.
     
  17. paldep

    Thread Starter Member

    Mar 3, 2016
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    Hey Ian field can you give me some suggestion to isolate the ground of power supply to the ground of audio?. I posted an image before.
     
  18. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You need an isolated dc to dc converter like one of these, choose one with your voltage range.
     
    paldep likes this.
  19. paldep

    Thread Starter Member

    Mar 3, 2016
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    One For each chip?
     
  20. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    No,just one it isolates the supply so you can use one battery or psu.
     
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