We do not suggest to use another battery charge. Tthe Brown PCM2704 IC may be burnt if you use incorrect power supply. Kindly take note that Trends UD-10 used dual power regulation circuits design (normal implementations are just directly apply the 5V USB bus power). No matter the power is supplied from the USB bus or from external socket, it is regulated before supply to the related ICs. Dual regulated powers are supplied to digital circuits and analog circuits individually.
