I have an old Boss DD-3 (I think it's a first revision, with the huge Roland IC on the PCB), and it's great to play with, but it hums pretty loudly. Now as I see it, short of getting a new one(!), these are my options:
1. Would it be safe to assume the hum is coming from my power supply? None of my other pedals hum with this supply, but maybe they contain power smoothing circuitry? If so, could I put in some LC configuration in a box before the input jack?

9V in _())))____________ 9V out
               |
               |
             __|__
             _____
               |
               |
0V   __________|________

2. Failing that, since the DD-3 can be used with two outputs (one dry, one wet), how easy would it be to make a box that is effectively a FX loop with dry/wet control?

Thanks for any help in advance!
Joe