Components on a Class D amp board

[rattlesnake]

I recently purchased two Douk A5 amps, based partly on Amir's positive review. I love them - they do exactly what I need. I understand the basics of how a class D amp works using a comparator, pulse width modulation, and a low-pass filter before sending the signal to the speakers. However I would like to understand the function of the components on the circuit board. I recognize the op amp chip and I assume that the large capacitor is either for the adjustable high-pass filter or the fixed low-pass filter. However I wonder where the switching transistors are, and what the other components are. I've attached a picture of the board (from the top) in case anyone has information.

Thanks,

-Tom

 

[MaxwellsEq]

I recently purchased two Douk A5 amps, based partly on Amir's positive review. I love them - they do exactly what I need. I understand the basics of how a class D amp works using a comparator, pulse width modulation, and a low-pass filter before sending the signal to the speakers. However I would like to understand the function of the components on the circuit board. I recognize the op amp chip and I assume that the large capacitor is either for the adjustable high-pass filter or the fixed low-pass filter. However I wonder where the switching transistors are, and what the other components are. I've attached a picture of the board (from the top) in case anyone has information.

Thanks,

-Tom

I believe this is a "chip-amp" based amplifier. Pretty much everything is inside the chip so you won't see switching transistors, 1st order filters, modulators etc. Designs by Purifi and Hypex are discrete and on these you can see the separate components more easily.

If you look at page 15 of the TI design doc for the TPA3255 you can see the inner workings...

 

[voodooless]

Yellow: input stage op-amps
Orange: DC-blocking caps
Green: The chip will be underneath, doing most of the heavy lifting
Magenta: Low-pass filter on the output
Blue: Power supply buffer cap

 

[rattlesnake]

Thank you @voodooless !

 

[rattlesnake]

@voodooless , on my Douk amp, the low-pass filter gets hot. Do you know of that heat is from the filter itself or of it’s conducted from the power amp chip?

 

[NTK]

@voodooless , on my Douk amp, the low-pass filter gets hot. Do you know of that heat is from the filter itself or of it’s conducted from the power amp chip?

Most likely from the inductor (core loss).

 

[rattlesnake]

Thank you! I love learning this stuff