TAS2505-Q1: AP555 THD+N test set up on digital in and analog in

Imelda Zhang

Part Number: TAS2505-Q1
Other Parts Discussed in Thread: TAS2505

Hi Expert,

My customer Bosch is using TAS2505-q1 for quite a long time. We are setting bench to test the THD+N EVM on analog input mode and digital input mode.

Analog Input

I do the test on analog input mode. However, it seems the set up of AP is wrong. You can see the AP set up and Bench set up below.

It seems that there is no output. I am so confused. The i test the PWM on P+ and P-. There do have PWM.

Then I change the set up of AP. I change the AP output from balance to unbalanced( I change the wire on AP too, but i didn't take the photo) What's more, i just connect 1 line P- to AP input. The i get the THD+N, but it seems that the value is too large.

Then the 2 channel all have PWM wave form. But it seems that the waveform are all the same. Because when i connect the P+ and P- to AP analog input, there is no output.

Digital Bench test

My customer bosch test the digital input. The AP output is digital serial and AP input is AP unbalanced. Customer didn't use the GUI. They key in the register. You can see the attached.

TAS2505 Setting.xlsx

However the result is shown below:

Vout=1.4V

No load : THD+N 0.05%

4ohm：THD+N 1.2%

The I2S serial configuration is shown below.

All in all, would you mind sharing with me the AP THD+N test project for TAS2505-Q1 analog input and digital input? If the AP/ HW/ GUI set up are not correct, could you please point out any specific errors?

Thanks a lot!

Kind Regards

Imelda

11 months ago

0 Imelda Zhang 11 months ago

TI__Expert 4385 points

Hi expert,

I want to add that we has connected the AP GND to TAS2505 EVM GND. When i do the analog input test, the wire are twisted.

If you are not use the AP555 I am afraid i cannot open the project. You can send me the screenshot. Many thanks!

Kind Regards

Imelda

0 Ivan Salazar 11 months ago in reply to Imelda Zhang

TI__Guru** 102475 points

Hi Imelda,

At first glance, there's some errors in the device configuration for analog input, if using R and L as mono-differential, then the mixerP and mixerN configuration must be complementary, if all the mixer signal paths are enabled then the input signal will be cancelled.

I'll check in detail the information provided and come back with further comments and AP files within the next couple of days.

Best regards,
-Ivan Salazar
Applications Engineer

0 Imelda Zhang 11 months ago in reply to Ivan Salazar

TI__Expert 4385 points

Hi Ivan,

Thanks a lot for your kind help!

1. I change the set up of Analog input. I open the input of mixer P. The configuration is right?

2. On Digital input, Would you mind helping me to review the GUI configuration?

What's more the set up of AP is shown below

Kind Regards

Imelda

+1 Ivan Salazar 11 months ago in reply to Imelda Zhang

TI__Guru** 102475 points

Hi Imelda,

Attached is the test report with the details of each input type of test.
Let me know if you have any questions.

Best regards,
-Ivan Salazar
Applications Engineer

TAS2505 Test Setup.pdf

0 Imelda Zhang 11 months ago in reply to Ivan Salazar

TI__Expert 4385 points

Hi Ivan，

Many thanks for your strong help! I will try and feedback to you!

Kind Regards

Imelda

+1 Imelda Zhang 11 months ago in reply to Imelda Zhang

TI__Expert 4385 points

Hi Ivan,

We retest the THD+N. However, On Bosch we don't have the AUX-0025 filter.

Bosch TAS2505-Q1 THD+N.pdf

1. If customer don't use the standard AP wire, the test result will be influenced? We do the twisted wire. Is there any suggestions on HW set up?

2. Will the AUX-0025 filter affect the test result? I konw it's a little rediculous, would u mind provding me the test result without AUX Filter? In other words, will the Aux filter affect the test result? I do search the AUX information. It seems that it will cut off the frequency above 20KHz. AP do have AES17 filter. Different filter will have some influence on THD+N, right?

AUX-0025 / 0040 / 0100 Switching Amplifier Measurement Filters - Audio Precision (ap.com)

Kind Regards

Imelda

+1 Ivan Salazar 11 months ago in reply to Imelda Zhang

TI__Guru** 102475 points

Hi Imelda,

I tested without AUX filter and results are about the same, you should be OK to test by using AES17 filter only.
The test results you shared seem OK to me.

Best regards,
-Ivan Salazar
Applications Engineer

0 Imelda Zhang 11 months ago in reply to Ivan Salazar

TI__Expert 4385 points

Hi Ivan,

Would you mind sharing with me why external Filter is needed? There is 20K low pass filter in AP

+1 Ivan Salazar 11 months ago in reply to Imelda Zhang

TI__Guru** 102475 points

Hi Imelda,

External AUX filter becomes more important for higher power amplifiers, you can refer to the last paragraph from this AP article: Selecting appropriate AES-17 pre-analyzer filters for the 2700 Series analyzers - Audio Precision

Switching (Class D) power amplifiers present a special case. Because their speaker outputs often contain high frequency switching noise at much higher voltage levels than line level devices, slew-induced distortion can be caused on the audio analyzer’s input stages. This holds true for all audio analyzer models and brands. To eliminate this problem, passive filtering must be done before the signal enters the analyzer. AP makes the AUX-0025, AUX-0040 and AUX-0100 filters for this purpose. As the primary function of the external passive filter is to prevent input overload, the steeper brick-wall S-AES17 filter is still necessary to eliminate all out-of-band noise that might influence measurements.

For relatively low voltage amplifiers like TAS2505 the impact is not as large.

Best regards,
-Ivan Salazar
Applications Engineer

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TAS2505-Q1: AP555 THD+N test set up on digital in and analog in