I will consider the top mass dependence of top-antitop quark pairs produced at large energy in electron-positron annihilation. This process provides an extremely interesting warm-up to calculations of precision top observables at the LHC. The process considered is characterized by well separated scales: the center-of-mass energy, the top mass, the top width, and the confinement scale. I demonstrate how soft collinear effective theory and an interesting new formulation of heavy-quark effective theory can be used to disentangle physics from each of these scales. Furthermore the effective field theory (EFT) calculation makes evident a number of subtleties that arise in calculations of precision observables in an hadronic environment. Fortunately, nearly all of the issues can be address in a systematic fashion in an EFT framework. I will discuss each of the issues that arises and give a final result for the differential cross section. The conclusion is that the observable considered can provide a measurement of the top quark mass with precision better than 100 MeV.