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SIDEGIG-GUITAREVM: When used with TPA3220EVM-MICRO

Part Number: SIDEGIG-GUITAREVM
Other Parts Discussed in Thread: TPA3220EVM-MICRO, , TPA3220

Hello,

     I do not understand the purpose of R16 in this circuit. It creates a minimum gain that is much too high. Can this resistor be removed and replaced with a jumper?

     Also, please be advised that when this board is used with the TPA3220EVM-MICRO, the TPA3220EVM-MICRO will not supply the required 12V power needed for operation. The literature would lead you to believe that all modules with the AIB connector would supply this power. Unfortunately, there is no place provided on the SIDEGIG-GUITAREVM to accept an external source other than the AIB connector.

Thanks,

Tom

  • there is some comments explain how to use R16:

    VDD – This supply is used for the non-PVDD power of the device for blocks such as the front-end and
    control circuitry. The TPA3220 internal 5-V LDO is also powered by this pin. VDD can be powered by 5
    V directly if using the TPA3220 with the internal regulator OFF. In this case, tie the GVDD and AVDD
    pins directly to VDD through R18 and remove R16. When the internal regulator is used, VDD must be
    between 7 V and PVDD through R16. GVDD and AVDD are only 5-V tolerant, so R18 must be
    removed.

    Robert will give you more detailed explain and follow up.
  • Hi,

         Thank you for your reply, but you misunderstand. I was referring to R16 on the SIDEGIG-GUITAREVM. Not on the TPA3220EVM-MICRO. It relates to the gain of U2A.

         I have no issues with the power supplies for the TPA3220. I was just making sure that people knew that the TPA3220EVM-MICRO does not supply 12V to the AIB connector. If they want to use an extension module with this board, that requires a 12V supply, it will need to be provided externally. There is no 12V source on the module.

    Tom

  • Hi Thomas,

    The engineer who designed this set the gain that was optimal for the guitar he was testing on. It's possible your guitar outputs a higher Vrms than the one he was using?

    Ah yes the Sidegig-GuitarEVM came out before the TPA3220EVM-Micro came out. Sounds like we need to go back and edit the document.


    Best Regards,
    Robert Clifton
  • Hi Robert,

    Thank you, but I don't think the output of the guitar is the issue, as I have tried several. I would just like to know if you foresee any issues with removing R16 and installing a jumper. I know the maximum allowable gain will be reduced, but that is okay. I can already drive the TPA3220 into clipping.

    Tom
  • Hi Thomas,

    What gain setting are you using on the TPA3220? Depending on which gain setting your in will change the maximum allowable input Vrms.

    Also can you tell me what the output of the guitarEVM is when you start seeing clipping in the TPA3220?

    Thanks,
    Robert Clifton
  • Hi Robert,

    The gain of the TPA3220 is at the lowest setting, 18db. I have not measured the output of the GUITAREVM, but I suspect it can reach over 1.5v.

    Tom
  • Hi Thomas,

    Strange, I ran this test with the guitar we have in the lab and got half that Vrms voltage. Can you please confirm?

    Are you in drive or clean mode?

    Regards,
    Robert Clifton
  • Hi Robert,

    In clean mode. Are you saying that in your test the amplifier clipped with half the voltage? I won't be able to test the output until this evening. Can you confirm that the output with the volume at minimum is unusually high? I would still like to hear your opinion on the removal of R16.

    Thanks,
    Tom
  • Hi Thomas,

    I'm saying that when I ran the Sidgig at maximum volume with my guitar I only got the output of the sidgig to be about 750mVrms. That's why I'm so confused you are seeing this behavior at minimum volume and not even maximum volume.

    You can remove R16 and replace it with a different valued resistor (or just a shunt) to get the volume range you want out of the device.

    Best Regards,
    Robert Clifton
  • Hi Robert,

    To be clear, I am not getting clipping at minimum volume. The amp clips at about 3/4 volume in clean mode. I will test the output tonight.

    Thanks,
    Tom
  • Hi Thomas,

    Also what is the Vrms input signal you are putting into the device? Let me know when you get done with this testing.

    Regards,
    Robert Clifton
  • Hi Robert,

         I apologize for the delay. With a .72V 1kHz input to the GuitarEVM, I have a .69V output at minimum volume and a 3.2V output at maximum volume.

    Tom

  • Hi Thomas,

    That's completely fine! Now it's my turn to apologize for the delay.

    I'm assuming those voltages are in Vrms. As you were asking, I would recommend lowering the output max volume voltage by changing the resistors. It will likely take some experimenting to get the right values but you seem to have a good idea on what to do!

    Best Regards,
    Robert Clifton
  • Hi Robert,

         I have eliminated R16 and installed a shunt. I now get acceptable control with the volume knob, and there is still enough headroom. I had to create a separate power supply board to power the module, and it wasn't easy to deliver it to the board, but it is working. Thanks for your help. I am going to mark this thread as resolved.

    Tom