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Audio mixer op amp selection

Icy
Intellectual 265 points
Other Parts Discussed in Thread: TPA2011D1, LME49726, LME49721

Is there an op amp that would be ideally suited for being used in a summing amplifier configuration for audio? I'm creating an audio mixer to mix two signals together. 

  • 0
    TI__Guru* 95385 points
    Hi Icy,

    There are several opamps that you could select from.
    Is there any special requirement in your application? Like split supply or single supply? Differential input? Supply voltage range?
    What is the application you're working on? There are also some low power (class-D) that could be configured in a summing configuration, like TPA2011D1.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Intellectual 265 points

    The application will use a single supply with +3.3V power. The application is an audio mixer to mix an audio signal (not to be amplified) with an amplified microphone signal (using headphone amplifier).

    Also I noticed an audio mixer circuit that was based on a transistor instead of an op amp...is there an advantage of using one method over the other?

  • 0 in reply to Icy
    TI__Guru* 95385 points
    Icy,

    I think this is similar to your previous post about pre-amplifier.
    You can choose a general purpose opamp and use it in a summing (voltage adder) configuration. This could be something like OPA3xx. These devices usually come on a single supply range of around 2-V to 5.5-V

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Intellectual 265 points

    Would there be an advantage to using an audio op amp like LME49721 instead of using a general purpose op amp? 

  • 0 in reply to Icy
    TI__Guru* 95385 points
    op amps like LME49721 have some higher performance specs, like THD+N, PSRR, Slew Rate. If your looking for a performance application regardless of the size/package you could choose from LME49721 or LME49726. OPA3xx comes in a wider variety of sizes/packages and number of op amps per IC.

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Intellectual 265 points

    I'm using the LME49726 audio op amp with a 3.3V supply and biasing the + input at VCC/2. I looked at the specs and found that the input common mode voltage range is from VSS+0.1 to VDD-1.6. With VCC/2 being 1.65V, this doesn't work well. The output of the op amp is connected to headphones (which can be as low as 10 ohms). Is there a better audio op amp solution for this? 

  • 0 in reply to Icy
    TI__Guru* 95385 points
    Hi Icy,

    You could take a look at LME49721, this devices comes with a common mode voltage range from VSS+0.1 to VDD-0.1

    Best regards,
    -Ivan Salazar
    Texas Instruments
  • 0 in reply to Ivan Salazar
    Intellectual 265 points

    Hi Ivan,

    I'm using the LME49721, and it' gives a loud "pop" sound when it powers on. Is there a solution to eliminate this pop sound, or do I need to use an op amp with pop suppression? Do you have a recommendation?