According to my research the XM-M542 uses a TPA3116D2 audio chip which has differential inputs.

 

According to my research the XM-M542 uses a TPA3116D2 audio chip which has differential inputs.

True, XH-M542 use a bridgecoupled TPA3116D2 to produce 100W. But how can it have differential input when IN minus is connected to Vcc minus ?

 

True, XH-M542 use a bridgecoupled TPA3116D2 to produce 100W. But how can it have differential input when IN minus is connected to Vcc minus ?

Did you connect it that way are you saying it came that way?

 

Did you connect it that way are you saying it came that way?

I just measured that they were connected.

 

Then the chip is already configured for mono operation on the XH-M542 module which makes sense. Apparently has the required input capacitors as well.
In that case back to my original post.

 

I want to mount the boards close to each other. Is that a (noise) problem ? Is a voltage regulator noisy ?

 

Is a voltage regulator noisy ?

Not normally if configured correctly. The system design turns the audio amp ON by switching the negative side of the 24 volt supply.
That might be an issue if the analog ground and power ground are hardwired together.
When testing the BT with the amp module was it connected to the control module board you made?

 

Not normally if configured correctly. The system design turns the audio amp ON by switching the negative side of the 24 volt supply.
That might be an issue if the analog ground and power ground are hardwired together.
When testing the BT with the amp module was it connected the control module board you made?

Yes, the power regulator board was mounted on the bluetooth board 5V and AGND with an additional wire going to the amp board 24v. The bluetooth SPK_R was connected to the amp board IN+.

 

What is this power regulator board, did you make it. Any photos?

 

What is this power regulator board, did you make it. Any photos?

 

Looks OK. Does the regulator chip get warm? What are the values of the caps?

 

Looks OK. Does the regulator chip get warm? What are the values of the caps?

TP2202-5, 2x1uF caps
Tried 10uF out, but made no change noisewise.

 

What is supplying the 24 volts?

 

What is supplying the 24 volts?

A cheap 24V 6A AC adapter.

 

Try installing a resistor in series with the regulator. What is the current draw of the BT?

 

Try installing a resistor in series with the regulator. What is the current draw of the BT?

Appr. 100 mA. I put a 8.2v 1.5w zener diode in front of the voltage regulator to make it cooler.

 

Did that help with the noise?

 

Did that help with the noise?

No

 

No

Do you have an oscilloscope?

 

Do you have an oscilloscope?

No