Gold/silver bimetallic nanoparticles still attract extensive interest due to their favorable properties e.g. in plasmonics or catalysis. We present here a facile and robust way for the production of clean Au/Ag binary nanoparticles (BNPs) with a total control over the composition via the spark discharge nanoparticle generation technique. With the application of pure Ag and Au electrodes, a tuning range of 55 to 90% Au content was achieved, but this can be further extended to the full 0 to 100% range by using a couple of alloyed electrodes. An added benefit of the approach is that either the concentration or the mean particle size can be kept constant at every composition by adjusting the generator parameters. Based on the systematic experimental data collected, a semi-empirical model for the prediction of the Au/Ag BNP composition was also developed. This model was used to calculate the theoretically achievable Au/Ag composition at a given spark parameter set in the parameter range most commonly used in the literature.