Abstract : This paper deals with the simulation of a high gain triode stage of a guitar amplifier. Triode models taking into account various "secondary phenomena" are considered and their relevance on the stage is analyzed. More precisely, both static and dynamic models (including parasitic capacitances) are compared. For each case, the stage can be modeled by a nonlinear differential algebraic system. For static triode models, standard explicit numerical schemes yield efficient stable simulations of the stage. However, the effect due to the capacitances in dynamic models is audible (Miller effect) and must be considered. The problem becomes stiff and requires the use of implicit schemes. The results are compared for all the models and corresponding VST plug-ins have been implemented.