ok use pendrive? If you use it you should use a button that has on the front that changes from usb to help that button always gets damaged and puts a good channel to sound and another bad check it another on the amplified card where the transistors are located locate the signal (r ) and (l) and exchange that two signals to see if the fault is in the audio input or in the bone amplified card if it had any damaged component in that channel it will sound the same if it did not sound good and the fault is before reaching the amplified card