Your mystery is like "Mitos of Ariadnes" (from Greek Mythology) same psu, identical adapter but the noise is differente, but remaining the answer of Flash2light what is marking of U2 in ver. 3.3. Probably, there is a difference there...
Well that's not too bad, I'll be more scared to look around for the answer if it resembled the story of Medusa, it wouldn't be cool turning to stone.
There are a couple of things I've been thinking about. I took a real good look at my new PSU board and discovered that one of the new decoupling capacitors is probably missing. There is no capacitor where C23 is supposed to be. C23 is supposed to be at the end of the adapter board connector. I see glue residue, as if the component was there but fell off during the soldering process. However, I don't think this would cause such a big difference in noise by itself.
Flash2light, can you tell me if this capacitor is present on your PSU board?
The other thing I've been thinking about is that I don't have the battery option. With a battery installed you have additional filtering for the 8.4V supply. The battery itself can act as a super capacitor. I don't know for sure if the results from dgmoore78@yahoo.com and Flash2light were obtained with the optional battery installed.
dgmoore78@yahoo.com and Flash2light, can you clarify this, and if possible, if your test was done with the battery installed, can you do the test again without the battery?