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TAS5731 output mixer

John Crisco
Prodigy 180 points

We have a 2.0 audio system.  We are trying to use the bass channel 3 for low frequency bass boost in both channels so that we can use the separate DRC on this channel and not compress all audio when extra bass is used.  As suggested by Diego, we have tried to use the settings

X51 00 80 00 00 00 00 00 00 00 40 00 00 
X52 00 80 00 00 00 00 00 00 00 40 00 00

This appears to give us bass boost  in one channel but not the other channel.  The documentation is not clear on how signals are routed to the output mixer and it is easy to overload the amp and cause damage to the amplifier.

It appears from experimentation that the following will mix the bass into left and right channels equally.

X51 00 80 00 00 00 00 00 00 00 40 00 00 
X52 00 80 00 00 00 40 00 00 00 00 00 00

This would mean that on X51(Ch1/Left) that bass is remixed via Mixer 0 but on X52(Ch2/Right) that bass is remixed via Mixer 1.  Is this correct and will I risk any damage to amp with this configuration?

Thanks

John

  • 0
    TI__Guru 57800 points

    Hi, John,

    Thanks for your comments, you are right I thought you had a mono signal for the bass, but the configuration you mention is correct for the use of Stereo Bass added.

    The addition of the bass channel with your current settings may saturate the output of the amplifier, so you need to make sure that both bass and "normal" signals are properly limited to avoid this. Another solution would be to reduce the "normal" signal to have a factor of 0.5 (00 40 00 00) instead of 1 (00 80 00 00).

    Please let me know if you have further questions. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 180 points
    Thanks Diego,

    When I test this using the EVM kit, it does not appear to work. I do not see any change to the right channel when I change X52. Is this a limitation of the EVM? I ask because I did see it work on our production part but then I saturated the amp and damaged it. I have limited supply so I do not want to try this on another board and damage another amp.

    Also, is there any documentation that shows the signal path to each mixer setting?
  • 0 in reply to John Crisco
    TI__Guru 57800 points

    Hi, John,

    If you are loading the code directly to the amplifier via I²C Memory tool, the amplifier should work as in your board. If you are using the GUI to configure the amplifier, you may need to manually set bit D5 of register 0x46 as '0' to enable both DRCs. In order to avoid damaging your boards, you may want to set the mixing as I mentioned before, with a 0.5 factor (00 40 00 00).

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Prodigy 180 points

    Hi Diego,

    Still not working for me.  Here is what I get when using the evm:

    x46: 00 00 00 03

    x51: 00-40-00-00-00-00-00-00-00-40-00-00

    x52: 00-40-00-00-00-40-00-00-00-00-00-00

    Bass matched on left and right channels below 200 Hz

    Above 200 hz, Left channel is now 10 dB lower than right

    When I have the following:

    46: 00 00 00 03

    x51: 00-80-00-00-00-00-00-00-00-40-00-00

    x52: 00-80-00-00-00-40-00-00-00-00-00-00

    or 

    x52: 00-80-00-00-00-00-00-00-00-40-00-00

    Below 200 Hz - right channel is lower by 7-10 dB

    Above 200 Hz - about the same (within 2 dB)

    Does not seem to matter if I input values via I2C tool or GUI.

    Any ideas what is happening?

  • 0 in reply to John Crisco
    TI__Guru 57800 points

    Hi, John, 

    Sorry for the delay, I was performing some tests. I tested the application you are trying to accomplish in the EVM, and generated a .cfg file for the correct mixing. Please refer to the attached diagram of the path followed, please let me know if this is correct for your application. 

    One thing I noticed is that the Low pass filter for the Right Channel (BQ 0x5E) is not available in the GUI for configuration. So, You need to write the coefficient manually (included in the attached configuration file). I performed the following steps in the EVM to make the configuration work:

    • Connect the GUI and EVM. 
    • Exit Shutdown and unmute the device.
    • Configure the DRCs with the desired parameters.
    • Run the attached script using I²C Memory Tool.
    • Unmute the device.

    Please take a look and let me know the results.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

     2-DRC_Sub2.cfg

  • 0 in reply to Diego Melendez
    Prodigy 180 points

    Is it possible for this to work?

    In your above post, the result I get is that the Right channel ends up being 5dB louder left.

    Thanks,

    John