First question: Did you have it plugged into your dulcimer before plugging the cable into the amp? Second question: Does the hum also happen without the cable plugged in? Generally there are two reasons for a hum; a ground fault or RF interference. If the amp has a three prong plug and is plugged into a grounded outlet there shouldn't be a hum. If there is a hum, it could be the cable, a ground problem with amps wiring, or RF interference. If it is RF interference look for a florescent light nearby or something with a motor (refrigerator, fan, air conditioner, etc.) If that is the case try moving the amplifier away from that source of interference. This can also happen if one of those items is plugged into the same outlet or circuit as the amp.
Ken
"The dulcimer sings a new song."
