In this study we report from our experiences designing and re-designing a lab where engineering students studied transient response in electric circuits. In the first version of the lab students had difficulties doing the mathematical modeling of the experimentally measured graphs as it required students' to link the time- and frequency domains as well as the object/event and theory/model worlds simultaneously. In the re-designed lab some computer simulations were included together with the original experiments on real circuits. The simulations opened up for learning and enabled students to establish links that are hard access directly with real experiments. Still doing real experiments is important to secure students ability to make links between models and theories and the physical reality. This study demonstrates that synergetic learning effects can be achieved by a careful design using an insightful combination of real experiments and computer simulations. Hence, we propose that the question of "real" experiments or "virtual" labs using computer simulations are best for students' learning is not an either or question. Rather, it is a question of finding the right blend to achieve synergetic effects.