I have made a radio that can pick up remote stations when I use a battery (that has 6V left in it). If I change the battery to a DC adapter rated at 6V, 300mA, then all I get is a 60Hz hum mixed in with the radio. How do I remove it? My design is similar to: http://www.tricountyi.net/~randerse/superrgn.htm but I swapped the emitter and collector of the transistor, and connected the inductor to ground, and connected the 0.01uF and 10K in parallel to +ve instead of ground, and omitted the .01uF capacitor between the second NPN and ground. I also converted this stage into a push-pull amplifier stage to gain more volume. I think that I need some sort of filter so that I can convert adapter DC voltage to battery DC voltage. Can someone help me? thanks.