We generalized the Snoke's method of inversion of amplitude ratios and polarities (P, SH, SV) designed to determine double-couple earthquake focal mechanism (Snoke, 2003). We search for a general dipole source described by unconstrained seismic moment tensor, i.e. non-double-couple (non-DC) source components are allowed as well. Based on synthetic tests simulating various configurations of seismic stations from sparse to dense networks and from low to high number of stations, conditions for successful inversion were found. We specified minimum amount of data, i.e. number of stations used and amplitude ratios employed, for reliable retrieval of non-shear source components. We showed that processing of non-DC data by traditional DC-constrained algorithm could provide distorted fault-plane solution. The approach is demonstrated with local data (1st arrival amplitudes) from 1997 West Bohemia, Czechia earthquake swarm and from 2000 injection experiment in KTB, Germany.