^That^20×log(n), where n is the number of parallel rows of identical signal, gives the dB increase.
Combining two equal signals will give a 6 dB increase in level. Combining two uncorrelated signals of equal level will give a 3 dB increase.^That^
But as a quickie, combining 2 is ~6dB![]()
The formula above specifically calls out 'identical signals'.Yeah, it depends on the content of each parallel signal path, so there's not one formula that will work for all situations. It gets complicated quickly when you factor in the frequency, phase, and time aspects of each path's signal.