Does anyone know of a patch for the gnx4 that is as close as possible to a true bypass?

I have tried a fair few, and they all add unwanted characteristics to the sound.

I am trying to use an electronic drum machine through it, but want to enable the use of effects for the line in so i can keep the sound as clean as possible, but just use the whammy pedal effect.

Any advice would be great, thanks.
RG's & Mesa's
Your post isn't very clear. You can use direct instead of an amp model. It sounds like you want to use the whammy on the drum machine. Have you tried it? The whammy has to detect and track a single note. A drum machine is noise, which is a lot of random notes. I can't imagine what it would sound like with a whammy. But a convention of yakking R2D2's comes to mind.