Undergraduate Research - Joining Two Different Groups?

I'm currently a second-year undergraduate physics major, and I joined an experimental nuclear physics (astrophysics primarily) group a few months ago. I joined the group wanting to work extremely hard to learn new things, apply them (and my intuition and previous knowledge) to solve problems, and present my findings and progress on a weekly basis, reporting to the group head on a more frequent basis though. It started out like that at first - the head made me solve a problem, write a GUI/applet for it (just to show that I got , and then implement that into a particular framework that would be used for an actual experiment later on down the road. I noticed that the head also didn't like to be a mentor too much - that is, he only liked to tell me what I needed to know for my task and nothing else, leaving extra learning for myself.

The problem with this is I'm left mentally starved. I've been assisting this other person in my group (relatively new graduate) on preparations for that actual experiment that I mentioned earlier, and that feels good. I've learned more of what's going on behind the scenes (significance of the experiment, theoretical implications of the results obtained, detector and equipment [and setup]) through publications, other people within the university, and asking the group head, but all of this was essentially on my own. As a result, I feel that any average joe with minimal work-ethic and intuition could thrive in a group like this. I've learned a lot more about nuclear physics/astrophysics (hence, more about this universe we live in) through sources that I might have not come across had I not joined the group, so that's good.

Also, just quick side note, the experiment is coming up soon, and I'm sure I'll learn a whole bunch through that process, and sorting out and analyzing the data after the experiment will certainly put me to work.

I've been thinking about possibly trying to join another research group, just so I can quench my mental thirst. There is a nuclear theory group at my university, and even though I know nuclear theory is probably way over my head, but I'm willing to put a lot of time into working hard to learning. I guess if I want to start something I've got to start somewhere.

Here is my question: Is attempting to join another group a bad idea? Should I instead tell the group head how I feel, and see where to go from there, or would that be far too disrespectful?

Please excuse any ignorance of mine.