TAS5825M: TAS5751M amplifier frequency response attenuation is too large

Hi Found.

What frequency of your sample rate?

It seems that you use a 8Ohm speaker, right? You can use 8Ohm resistance to test again.

And whether you open some tuning in PPC3, like EQ, AGL? 

If you open some tuning, please close them to test the frequency response again.

Thanks

My sample rate is 48kHz
The result of this test is the 8 ohm resistor
This amplifier is not an EVM board, we do not use the PPC3 and other EQ adjustment, including the software internal gain is 0.

OK, where is the input signal from? Are you using digital audio input through AP?

Input signal from the AP, due to the amplifier does not have a digital interface, the signal is generated by the AP analog signal, access to the audio processor, the processor and then through the network will be transmitted to the amplifier digital signals

Do you have a test frequency response curve for the EVM board?

Hi Found,

TAS5751 only supports digital input, I don't understand the meaning of you said.

FOUND HUANG said:

due to the amplifier does not have a digital interface

And it's possible that your audio processor results to this problem.

For example, the input filter of ADC in audio processor maybe cause this phenomenon.

Please input digital signal directly from AP.

I don't have the test frequency response curve for the EVM board, but your curve is extremely abnormal.

Hello, I mean we amplifier products digital signals can only be transmitted through the network cable to an interface board, the interface board and then digital signal transmission to the chip, yesterday I found that interface board is indeed a bit of a problem, replaced the audio signal has no effect on the full interface board test, get the frequency response normal point, the high-frequency part of the stabilization of the frequency attenuation of the frequency response are in the 3dB or so. Now can I see the curve you measured?

OK, I will measure frequency response curve for you in this week.

Okay. Thank you very much.

Hello, while waiting I would like to ask again why my amplifier can only reach a maximum power of about 42W, I see that the specification can reach 70W. the amplifier is supplied with a voltage of 24V,PBTL mode, room temperature of 25 degrees Celsius, a load of 4 ohms, the board is a 4-layer board. Amp power maxes out at 23.5W when loaded at 8 ohms.

Hi Found,

When you exceeded maximum power, it triggered OT or OC? Please describe the phenomenon.

And how you test the power, using AP? Did you set the load resistance in AP correctly?

1, the amplifier reached the maximum power did not trigger the protection, but increase the input, the power can not go up.
2, AP load set right, AP generates 1kHZ sine wave through the processor transmission to the amplifier, the amplifier connected to the load feedback to the AP input.

Hi Found,

Please give the waveform of OUTPUT when power exceeds 42W.

I want to observe whether it is clipped.

FOUND HUANG said:

why my amplifier can only reach a maximum power of about 42W,

Hi, this has been tested many times, I keep increasing the input and can't exceed 42W,but as the amp input increases the power stays the same and the sine wave gets clipped.

Hi please give the output waveform. We should make sure the value of clipped voltage. 

Hi,

You use 4Ohm load and 24VPVDD when you can't exceed 42W, right?

Please examine the power of PVDD.

And I measured frequency response curve.

The load is 8Ohm.

Hi, I've been researching with the software engineer for the past two days and found that the power can't exceed 42W because the previous employee limited it with the software, after I lifted the limitation the amplifier can now reach 57W then over-temperature protection. Then I looked at the frequency response you measured, it seems that my design is still a problem, I also want to achieve your kind of frequency response, please I need to focus on those aspects!

Hi Found,

I think your interface board maybe cause some influence.

Please directly connect the I2S from AP to TAS5751.

And close all DSP tuning function to test again.