[Richard Crowley]

"Laurence Payne" wrote ...
"Richard Crowley" wrote:

It seems that the plug-in power on your Sony is noisy, when the AC
adaptor is connected. You can blame this on the power adapter, the
recorder or the microphone. Maybe even on your mains power. You
may
be able to solve it by building a simple battery power supply box to
go between mic and recorder. This would be, I think, cheap and
simple enough to be the thing you try first. Can someone point to
a
suitable circuit?

The circuit is trivial, but should not be necessary.
Something is broken here and should be repaired
or replaced.

Indeed. With hindsight, some part(s) of this system probably should
not have been purchased. But they have been, and there may be an
easy fix. Can you point us to a source of the trivial circuit,
please?

The circuit is a ~2.5K ohm resistor to a 3-5V supply of
clean DC, with a blocking capacitor of your choice. Google
returned 522,000 hits for: diy microphone battery box.

The problem here is that whatever AC hash is going
upstream through the microphone connection (assuming
that is the apparent problem) will NOT be solved by an
external power source. The AC coupling through the
blocking capacitor will faithfully carry the undesired
noise just as surely as it is flowing now.

And if the problem is that some kind of EMI is being
picked up by the microphone/cable, the battery box
won't help that, either. The microphone already
converted the EMI into audio before it got to the
battery box.

If the problem is in the MD player, no fooling around with
external battery boxes is going to solve the problem. If
the problem is in the OP's microphones, they appear to
be inexpensive ($5) throw-away things.