My 6 years old Audioengine 5 also developed problems like crackle, massive pops and "blow into microphone" sounds
These happens as soon as any song is played.
Unfortunately, we do not have audioengine service in India.
So, I got it repaired from other sources. Here are some details which may help other A5 users.
The below is my assumption - please correct if you see a mistake.
There are two circuit boards in the audioengine 5. The left one seems like the preamp. It has two voltage regulators, some 8-9 solid caps and other caps. The right one may be the power amp (caps like 475j 100v are present here).
I can see repair was carried on the left board only. The right board is untouched.
Looks like 4 capacitors are changed and a resistor also added.