I'm working on a tube preamp project, and I'm using a LM7805 to provide a regulated source for two filaments - it's lower than standard voltage but it has to do with the transformer winding I have....in any case I noticed a lot of hum in the circuit and looking at the +5 volt line on a scope I saw a 5 Mhz 1V pk-pk signal on the supply! My question is how to go about attempting to fix this? Should I put more capacitance on the input, or on the output? Right now I have 2200uF on the input and just the 0.1uF the data sheet recommends on the output. The total current draw is 450 mA. Thanks in advance for any advice.