Correcting Phase of STA311b System with speaker response?

[bernhard23]

Posted on November 24, 2014 at 12:52

Hello,

I built a system using a ad converter (PCM4202 from TI) and a sta311b DSP. I drive the power fets with the ffx pwm stage of the sta311b.

When I measure the phase response of the hole system (without any dsp settings) I get a very bad phase plot.

Is it possible to correct the phase with the speaker tune option? Can I measure the Phase and generate a speaker response file like I would do with a mems microphone?

Thanks in advance.

[Marco VENERI]

Posted on November 25, 2014 at 12:26

I'm unsure about the root cause of your bad phase plot but it will arguably depends on the overall system architecture (including ADC and power FETs). You could try to optimized the response by measuring it and compensating with STA311B embedded filtering stages but I would first try to understand what's the real culprit of your bad response. Also, STSpeakerTune technology is more to compensate the frequency response, not the phase - a new topic on this subject has just been posted highlighting how to quickly assess the feature.

Marco

[bernhard23]

Posted on November 26, 2014 at 10:04

Hello Marco,

thanks a lot for your fast reply. So I measured the phase just above the adc and sta311b. The adc (pcm4202 from ti) has a very low phase marging, nearly zero. I know it from other projects.

The phase response over the fet stage and lc filter is 8° max. So that's ok.

Now some screenshots form my rohde&schwarz upl system:

First: STA311b with dsp bypassed, Input driven with 96kHz 24bit I2S 256fs

http://www.mikrocontroller.net/attachment/238173/Phase_AnalogIn-AMP_out.jpg

Second: STA311b with dsp bypassed, Input driven with 192kHz 24bit I2S 128fs

http://www.mikrocontroller.net/attachment/238180/Phase_192khz.jpg

In 192kHz mode the phase over the sta311 looks much better but still not linear. Do you have any idea? Do you have a phase plot from your labor?

Thanks,

Bernhard

[bernhard23]

Posted on December 03, 2014 at 09:25

Hi Marco,

can you say anything about my Phase plots? Do you have a Phase plot over the sta311b from your lab?

Regards

Bernhard

[Nickname1623_O]

Posted on December 04, 2014 at 02:01

Hi Bernhard ,

the group delay of STA311B is around 0.53mS @ 48Khz FS , so if you increaed sample frequency , the delay will be reduced .

Thanks

[bernhard23]

Posted on December 05, 2014 at 20:46

Hi Zhao,

Group delay should have no influence to the phase delay... Have you looked at the screens I added in my previous post? You can see a high phase delay and yes the delay gets better with higher sampling rate but still not acceptable even with 192kHz.

Can you make a phase plot in your lab?

Thanks again

Bernhard

[Nickname1623_O]

Posted on December 10, 2014 at 04:38

hi bernhard,

plesae find phase shift plot in attachment.

if the x aixs had been divieded in linear, you can find the phase shift period was fixed , measns a constant delay timingcaused this shift.

Thanks

________________

Attachments :

phase_shift_linear_.emf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Ht1Z&d=%2Fa%2F0X0000000aIw%2FcoNdk5JoJO0ESnLXRlKODLsyURWytDKps4fXEcSM.Es&asPdf=false

phase_shift_log.emf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006Ht1e&d=%2Fa%2F0X0000000aIx%2FUBBsWAb24OdLdoW.0yIaenRY4_WJuEU_tfdoA._vfIE&asPdf=false