Sonoma Wire Works made quite a splash when it released GuitarJack for the iPhone last September, but it had one problem — it wasn’t compatible with the iPhone 4. That’s going to change.

[ad#Google Adsense 300×250 in story]While I was at NAMM earlier this month, I snapped a few pics of GuitarJack 2, the newest piece of hardware from the company that will support iPhone 4. The company wouldn’t say when it would be available, but clearly they are making some units, at least for testing purposes.

GuitarJack uses the the iPhone’s dock connector instead of the headphone jack like its competitors. Sonoma believes this gives the user better audio quality than the headphone jack when connecting a guitar.

Like its predecessor, GuitarJack 2 is a rugged feeling piece of hardware. It’s also very nice looking and features a 1/4-inch instrument input with configurable pad, as well as Lo-Z and Hi-Z modes; an 1/8-inch stereo mic/line input with pad, and includes normal and boost modes; and an 1/8-inch stereo output with increased drive for headphones.