I have fairly old DENON UTP-250 Pre-Amplifier and UPO-250 Power Amplifier. I have connected CD-Player to CD Input, iPod to TAPE in via Airport Express. system worked fine. I use mostly iPOD to play music. one day while try to play a song system stooped giving me loud noise. thereafter gives me annoying buzz at 0 volume also each time i try to play. Pre-Amplifier section has power inputs for other devices those i used to give power to CD-Player and Plate player. after that incidents Power sources did not work anymore.(this is not a problem because i can hook up other devices directly).system works as it was before but annoying noise still exists on when I switch to TAPE mode where i hooked up iPOD. can anyone suggest me what went wrong and why it gave me annoying buzz at 0 volume ?. I am still thinking of repairing the Pre-Amp. what cause sudden loud sound?