Need help switching a dual power supply op-amp for a single one.

Discussion in 'The Projects Forum' started by Gear_Clinkz, Aug 17, 2016.

  1. Gear_Clinkz

    Thread Starter New Member

    May 25, 2013
    3
    0
    Hello and thank you in advance for your help.

    I'm trying to make desktop USB microphone using a dynamic cardioid type mic and a small sound card. (The mics resistance is 650Ω)
    I know that dynamic mics need a pre-amplifier and here comes my problem.
    I took apart an old Sony Sound system and i found a small mic pre-amp module. This module uses a 5218A op-amp that requires a dual power supply but the problem is that i want to use the 5V that the USB provides thus eliminating the need for an external power source. After some searching I found that the LM358 does not require a dual power supply and works at 5V. I tried switching the two op-amps but I got nothing... The mic only picks up sound when i softly blow on it and even that its heavily distorted.
    So I ask... Is there a way I can make this work? And if not, can somebody please post a circuit that will help me?

    NOTE: I don't have the schematic of the board :/ I hope the pictures will help.. 20160817_181204.jpg 20160817_181225.jpg

    This is the microphone I'm using 20160817_181444.jpeg
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,518
    1,247
    The 5218 is an improved version of the 358, and is pin compatible. A 358 should drop into a 5218 circuit and work, but with higher distortion. However, there is much more to converting a dual-power-supply circuit to a single-supply circuit than just changing the power supply. Since you have a single-sided pc board, you can trace all of the circuit connections and draw a schematic. With that, we can discuss what changes are necessary to convert it to single-supply operation.

    ak
     
  3. Gear_Clinkz

    Thread Starter New Member

    May 25, 2013
    3
    0
    Thank you for your answer.
    I'll try to make the schematic right now. Should I also try and find the values of each resistor?
     
  4. Gear_Clinkz

    Thread Starter New Member

    May 25, 2013
    3
    0
    I think it's right. Hope it helps
    ^71D5046E02226D927F0B6C636A622001C8A10FC74220E91E76^pimgpsh_fullsize_distr.jpg
     
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