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PGA2311: PGA2311 channel leakage at high volume (80–100 dB SPL)

Falguni Sharma
Prodigy 190 points

Part Number: PGA2311
Other Parts Discussed in Thread: TLV320AIC3104, TPA6120A2

I am using the PGA2311 as an analog volume control in my audio setup. The audio codec used is TLV320AIC3104. I am facing a channel leakage / crosstalk issue between Left and Right channels at higher volume levels, especially when output SPL is in the range of 80–100 dB SPL.

Current Architecture

  • Audio source → TLV320AIC3104 DAC

  • Digital volume control applied inside TLV320AIC3104

  • Analog volume control using single PGA2311 (stereo)

  • Output goes to headphone/receiver driver stage

  • Application requires very high dynamic range

Observed Issue

  • At higher volume, some leakage between Left and Right channels is observed.

  • This becomes noticeable mainly above ~80 dB SPL.

My Questions

1) Stereo vs Separate PGA2311

Would using two separate PGA2311 ICs
(one dedicated for Left channel and one for Right channel)
help reduce inter-channel leakage / crosstalk at high volume levels?

  •  

2) Best Practice for Volume Control (Codec + PGA)

Currently, volume is controlled using both:

  • Digital volume inside TLV320AIC3104

  • Analog volume via PGA2311

From a noise, distortion, and leakage perspective:

  • Is it recommended to use both digital + analog volume control, or

  • Should the codec DAC be kept at fixed level (0 dB) and use only PGA2311 for volume control?

3) Only PGA2311 with Feedback / Looping Concept

If I control volume only using PGA2311, and:

  • Use separate PGA2311 for Left and Right

  • Implement volume control via MCU with feedback/looping logic

Would this be a more efficient and cleaner architecture for high-SPL, low-leakage applications?

4) Required Volume Range

My application requires volume control in the range of:

–10 dB HL to +120 dB HL

Best regards

Falguni

 

  • 0
    TI__Mastermind 28155 points

    Hi Falguni, 

    Are you able to share your schematic either here or over private E2E chat with me? 

    Have you isolated the PGA2311 by itself and injected an audio signal into it's inputs to see if the issue you are seeing/hearing is still present? It would be helpful to know if the issue is the codec or the PGA and for this reason isolating each can be helpful. 

    Falguni Sharma said:

    Observed Issue

    • At higher volume, some leakage between Left and Right channels is observed.

    When you mention leakage, are you referring to measured current leakage, or is this "leakage" you can hear? I am trying to understand what is meant by leakage so I have a better understanding of the issue. 

    Best Regards, 
    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Prodigy 190 points

    Leakage here is audible properly .

     Our application requires to have sound in only one channel when command is set to play tone in that respective channel only. (for ex left channel)
    There should be no  sound in the other channel.(Right channel)
    But the problem is that there is  small tone of around 2 to 20 mVrms. This becomes hearable when sound is above 95 db Spl.
    And it gets really audible around 35 db Spl to 45 db Spl at 120dB spl in other channel.

    We are currently using single PGA2311 IC to control volume of both left and right channel. In some PCB i have seen that PGA2311 IC is used separately for both the channels .Is this effective way to reduce this leakage problem.

    My path is MCU->TLV320AIC3104->OPA1622->PGA2311->TPA6120A2 . 

    Best regards 

    Falguni 

  • 0 in reply to Falguni Sharma
    TI__Mastermind 28155 points

    Hi Falguni, 

    Assuming that another IC in the signal chain is not mixing in the signal then yes, separating the left and right channels into their own PGA2311 would be a valid solution. 

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Prodigy 190 points

    On separating PGA2311 of both the channels is there any need to change the level shifters also ?As I'm controlling my PGA2311 with my MCU using SPI .

    Tell me in brief how i can connect PGA2311 separately for two channels:

     Using two level shifters from MCU having separate SPI lines for SCLK,CS,MOSI 

    Or by using one level shifter and two PGA2311 IC in the high side of level shifter .

    Also tell me if i have to make any feedback loop in PGA2311 side of channels if I will use two PGA IC .

    Best regards 

    Falguni

  • 0 in reply to Falguni Sharma
    TI__Mastermind 28155 points

    Hi Falguni, 

    I'll need about two business days to review and respond to your request. I'll get back to you as soon as possible after that.

    Best Regards, 

    Chris Featherstone