How to choose a class D amplifier board?

Updated: 10-12-2017

Whether you want to buy a class D amplifier board to be used for a particular purpose or you just want to test a class D amplifier chip, the easiest and cheapest is often to buy an amplifier board with that chip and then modify the board as needed. Today almost all class D amplifier chips are supplied in packages for SMD mounting. SMD mounting is intended for robot assembly and then the production costs of the board are lowered considerably. But, SMD package outlines are often so small hat you need to make a PCB with good (rather professional) tools because the tolerances are very small. So, traditional breadboarding is very difficult.

Choosing an amplifier board is normally a matter of understanding the information you may find for the amplifier chip and the implementation on the board from the Internet.

First, decide what are the most important qualities you want: High quality sound (low THD)? Output power level? For DIY modification or use "as is"? Cooling possibilities? Price level? Find a realistic compromise and do not just want all to be the best.

Then understand that there are certain components the manufacturers try to save on:

Amplifier boards, in particular class D amplifier boards, are sold with the same amplifier chip but at different price levels. The differences in price normally relate to the quality of the remaining components used on the board. Which one you should choose depends largely on how much you are willing to do yourself in modifying the board for good operation and how much money you are ready to spend. Even if you are prepared to do modifications yourself there are situations where a well equipped board is available and not so much more expensive, compared to a cheap board, that the difference is obviously worth the higher cost. It also depends on your level of perfectionism.

You can get a lot of information about an amplifier board sold on the Internet from an else rather sparse description. In particular the photos are useful.
For a start find out what chip is used (normally specified for an amplifier board). Look for the data-sheet of that chip on the Internet and get an idea about its potential performance. In particular THD level, maximum supply voltage for operation, quiescent current, impedance of power switches and cooling features are important. Then you can get an idea about what performance level can be achieved by the chip and what quality of the other components in the circuit are needed.
Look at the photo(s) of the amplifier board and try to estimate:

With such an evaluation prepared you have a good idea about the effort the board is going to require. There are evidently issues you may only notice once you have the board for test.
Whenever receiving a board, always test it for a start and make sure it seems to work “as is”. The moment you start modifying anything your guarantee is normally lost. But, that risk is inherent for DIY activities.

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