Hi all I´m the owner of two Casio keyboards, WK-3800 and WK-7500.Since the old WK-3800 has much better speaker quality (frecuency response, basses and trebles ) ,I was wondering about hearing WK-7500´s sounds through the 3800´s speakers.But.... WK-3800 hasn´t a "Line In" or "Audio In" jack .Is it possible to add this INPUT?Any suggestion..Thanks Daniel