A one-pot synthesis approach for a SiBNC precursor polymer is presented. With respect to composition and structure it is similar to the polymer as produced from the known single-source precursor DMTA (dichloroboryl methyl trichlorosilyl amine), as confirmed by FTIR spectroscopy. The new route results in a higher ceramic yield compared to the DMTA approach, and in a comparably high temperature resistance of the final ceramic against crystallization and decomposition. Chemical composition and the short range order of the amorphous ceramics appear to be identical, according to NMR and IR spectroscopy. The new procedure presented is the most economic way to produce preceramic polymers for SiBNC networks, known so far. The inexpensive, commercially available reactants methylamine, SiCl₄ and BCl₃ are used in a simple one step reaction.