6 responses Add your response
My 4004's right channel recently went out but it wasn't preceded by any noises. It turned out to be leaking capacitors in the power supply. I decided to buy a new amp because my 4004 is about 23yrs old, who knows what else is about to go. I think replacing the caps should be done whether it's the problem or not just as a precaution.
If you have a good local repair shop/technician and you have the original 4004 (non MKII), you could have them do an upgrade to MKII status. I was considering doing this but didn't due to my amp's age. I have a website (www.hbassociates.us-004mkIIUpgrade.pdf) that has the instructions and parts list for the upgrade. I think the original MKII upgrade was initiated by Aragon due to some resistors being flammable. Hope this helps.