I have a Sound Devices USB Pre 2, very good preamps but its not a really field mixer, so if you really want a solid chassis i would prefer the Pre-D
As a little experiment today I tried hooking the Zoom H1's output to the GH2's microphone input through a cheap headphone volume control. Much to my surprise, it worked perfectly! There's virtually no difference between the sound of the H1's recording and the GH2's. This cheap headphone volume control even has two outputs, so I can connect headphones for monitoring.
$5 at Radio Shack: http://www.radioshack.com/product/index.jsp?productId=3268770
I set the GH2 input level to 1, the Zoom H1 output level to 30, and adjusted the volume wheel to about 1/3.
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