[Nature Recordists] extension cables

[vickipowys <>]

All,

I have been happily using a Telinga 'LS-10' stereo mic with PIP (plug 
in power) connected to an Olympus LS-10 recorder, with a shielded 
extension cable measuring 7 metres.

What I would like to know is what is the potential maximum length of 
cable I could use with such a set up?  Fifty metres?  Or less than that?

I am well away from civilization and radio waves although I do have 
mains power connected to my house, and have found that I need to use 
shielded cable to prevent mains hum.

The sort of cable I mean will have 3.5mm plugs and sockets.  I have 
ordered some 2-core shielded cable, but while I await its delivery I 
am hoping someone might comment on cable length.

Any suggestions?

Vicki Powys
Australia