[sdiy] power woes

[dan snazelle]

Ok

I am sitting here with a pile of DC adapters. (trying to find one to bundle with my products)

half of them cause HUM, half of them cause a whine (switching)

Only 2 out of the pile don't cause ANY noise


One is a DUNLOP class 2, 60hz 7w, 9vdc 200ma adapter which is made in china and has a chinese model number of

ad-0920


i can find these online for $12-15 dollars a piece



the other is one of the new BOSS switching adapters.

(it costs 30 bucks!)


one of the odd things is that some of the switching adapters or class 2 adapters have 
seemingly the same SPECS but cause different problems or noise  


SO...my question is whether anyone has any advice on DC adapters


i might be able to get a bunch from dunlop but it still doesnt answer WHY some cause noise and some dont


thanks so much!