I have an old PSU that provides +12v 2A and +5v 2A. I'm trying power an amplifier TDA3116D2 that has a requirement of 12-20v. Can I combine the rails? If so, what is the resulting output?

Sidebar: I bought this amp board on Ebay for cheap. I'm confused as to why it does have a heat-sink. Anybody have any experience with this board?

 

No. The 5V and 12V will have a common 0V I reckon.
But, what is the power supply"? Is it an linear regulated one or a switch mode?
If a linear one, you may be able to use the pre 12V regulator supply.

 

Are the grounds common or isolated?
If they are common, then the answer is absolutely not. You'll let the magic smoke out.

 

No. The 5V and 12V will have a common 0V I reckon.
But, what is the power supply"? Is it an linear regulated one or a switch mode?
If a linear one, you may be able to use the pre 12V regulator supply.

 

If you mean put the 12V and the 5V in series, the answer is likely no. It is possible that the two supplies are isolated and you can, but that would be unusual. If you want to know if they sre isolated, disconnect it from power, then measure the resistance between the two negatives. If they are isolated, it will show high resistance, if not isolated, the two will be connected together and show less than 2 Ohm.

As far as the heat sink goes, I assume you mean “does not have a heat sink”. It should. Every other board I looked at does. You might get by with using at 12V without, but no guarantee.

 

Ah, you picture shows the grounds common, so do not try to put them in series.

 

Ah, you picture shows the grounds common, so do not try to put them in series.

Thank you!

 

Just run it on the 12V and see how it goes.
Or fine yourself an old laptop 19V supply.