I built a piccolo a few years ago and I've been running it on batteries ever since. I decided to order a wall wart and use that but the one I ordered didn't fit the jack I used

, the plug for the wall wart I got is 5.5x2.1mm so the jack I used on my piccolo is maybe 5.5x2.5mm ???
is there a wall wart with that size plug that would work for the piccolo?
second, I went to radio shack and bought a 5.5x2.1 jack and wired it in to the piccolo board where the battery supply wires in.
I ended up with a pretty nasty (60hz I think) hum.
Is this because I wired it into the board where the battery power is wired in and I bypassed some filtering or is the wall wart junk?
so after the wall wart was noisy, I wired up a 5.5x2.1 dc plug to a bugle power supply that I built years ago. Plugged it into the same plug that is wired to the battery traces on the board.
No 60hz hum from that but I was getting a high pitched squeal, it was pretty faint, wasn't sure I even heard it at first but it was slightly annoying.
The bugle PS isn't in a case or anything and I just twisted some hookup wire together and ran that to the piccolo (maybe 2 ft. worth), could that pickup high frequency noise and bleed it into the piccolo?
any ideas on this noise? my rechargable batteries are about done. only get a 10hrs or so out of each recharge now.
I'm tempted to just buy some more rechargable batteries but the bugle PS is just sitting around so...
thanks for any help.