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TAS3251: Tas3251

Part Number: TAS3251
Other Parts Discussed in Thread: TEST

Hello, 
I use Tas3251 to do 1.1 amplifier, one channel for woofer , another for tweeter. I want to use 2 EQ  for treble and bass control. But I ever used EQ8 for bass shelf and EQ9 for Bass shelf, if I turn the Treble and bass up (+6dB), then turn down the bass slowly, I found the sound volume get down a lot suddenly, then I turn down the treble to middle (0dB) , the sound volume back to normal. I think is shoud be something wrong , the treble EQ and bass EQ afect each other when it be changed.
Then I set Bass EQ in crossover EQ5 (Woofer), didn't find same  problem, but I found a new problem: when I turn the master Volume to maximum , then turn treble to max also (+6dB), then I turn down the master volume slowly, when it be turned down 4 steps (like 6dB down), the sound output get down a lot suddenly. 
So please can you help me to solve the problem above. How can i use EQ for BASS and TREBLE setting?

Thanks!

  • Sorry,  EQ8 for bass EQ9 for treble

  • Hi Kenny

        If you set the frequency of Bass and Treble frequency very close to each other, they will affect each other. You can think all the EQ are cascaded. And about the output volume, it's not linear change between the total gain and output. The higher output volume, the decrease of gain setting will more striking. Also because you are using EQ, if you give a different frequency input signal, the output change will also be a lot different.

        If you still think there's any problem, you can use a resistor as the load, and test the system with AP. Check the connections between gain change and the output power, if there's anything wrong by calculation. By listening won't help you to get a right conclusion. 

  • Hi Shadow He
    Thanks for your reply.
    We set different EQ data at each volume step (EQ1,2,3,4), and the Treble EQ at EQ12,  when I change volume, the EQ1,2,3,4 data changed together. I turn the Treble to high levle (eg.+6db) and volume to Max first, then I turn the master volume down form Max, when i turn the volume from 3rd to 4th step, I found the amp power output get down 6dB more( measure form Ondoscop), acturely I set 1.5 db each step for volume change.
    If I  set the Treble EQ at EQ1, the other EQ at EQ2,3,4,5, when change volume, the EQ 2,3,4,5 will be change together, Do you think it will help to solve the problem?

    Kind regards!

  • Hi Kenny

        It's interesting that you said the volume would affect the EQ settings. Is it convenient for you to share your PPC3 setting file? I'll check it. Also please capture some screen shot, witch value change are you referring to.

  • Ok , I can't send the PPC3 file here,the attached  picture to show which EQ will be change when adjust volume.


  • Hi Kenny

        I can't reproduce this phenomenon at my side. If it is convenient, you can send your PPC3 settings through e-mail. shadow-he@ti.com

  • Hi Shadow
     I just send the ppc3 file to you via Email, and I send the other EQ file which I use to set Treble and Bass and different EQ setting for each Volume step. Maybe it is useful for you to find out the problem. Please help to check.

    Thank you!

  • Hi Kenny

       Sure, I'll check it today.