I'm searching for a CLEAN signal, input
I write late at night external noise is not an option,
has anybody found a working CLEAN input
to this recorder?
Thanks.
http://www.larrythebassman.com

I think your best option is the Alesis ProTrack, even though it has hardware monitoring and doesn't support full duplex audio. You can still monitor with headphones on the output to the iPhone, or with a dock extender and an iPod. Another option is the macally iVoicePro, it has stereo line in, if you can find them. The macally builtin speaker and mic are pathetic, but the unit works if used as a line in connector.

You could try a Belkin TuneTalk stereo mic. It has a mini input that overrides the mic. I've used it with a Pocket POD and it works great. The output from the KORG should be similar.