An apparatus and method for determining stimulation channels for a stimulating device is provided. This method and apparatus may involve computing a set of weights for the plurality of stimulation channels of the stimulating hearing prosthesis. These weights may be determined by determining a transimpedance matrix for the stimulating hearing prosthesis where a diagonal of the transimpedance matrix is determined by extrapolation. A transadmittance matrix may then be computed for this transimpedance matrix. An error may then be computed base on positive off-diagonal terms of the transadmittance matrix. The apparatus and method may determine the weights for the stimulation channels by determining an adjustment to the diagonal of the transimpedance matrix that results in a computed error that does not exceed a specified criterion level.
