noise pickup in stompbox

[Paul Perry]

I'm about to layout a PCB that suffers from noise
pickup by the input amplifier.
Do people think it would be worth having a fet 
right at the input (where the input jack mounts on the board)
to act as a preamp or just as an impedance lowerer so the trace
to the first amp is less susceptible to noise pickup?
Also, the power diodes I have are radiating right up into the RF.
Are some rectifiers better thaqn others?
Should I put a tiny cap straight across them? Or would thid be
bad luck?

looking foward to any & all answers,

paul perry Melbourne AUstralia