[Laurence Payne]

On 13 Jan 2007 11:08:45 -0800, wrote:

I have the SONY RH1 minidisc recorder, and recently got binaural
microphones from Sound Professionals ( MT350 ). When I run the
recorder on mains power, I get a real buzz on the recording. SP tells
me that I should record on battery power only, and this does indeed
solve the problem, but I really want to be able to use ac whenever
possible. The SONY 907 mic works fine with no buzz, even on AC power.
(The SP mics get their power through the recorder, the SONY has a
battery.) Any suggestions on what to do next? Get an ac line filter?
If so, where from? Get new mics? If so, any suggestions? I do want
to upgrade from the 907, and am thinking of spending up to about $150.
Thanks for any advice - I'm technically not very savvy, so please spell
it out!

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?