Denon PMA480R amplifier
 

I have one of these and replaced the only two opamps inside it that I could replace easily. I used DIP sockets incase I wanted to try other IC's. I used OPA2134's in place of the JRC 45xx that was there. Sounds far better now. Especially after burn in for 5 days !!
That's at least about 75 hours 'On' .

Does anyone have a circuit diagram for it. I find that using the tone defeat button causes significant volume shift AND it does not sound the same ! So tone defeat button In / Out sounds different . I wanted to try and figure out why .
Thanks.
ashok.

I'm looking for the same
 

Hi there

Did you ever get a reply about the service manual or circuit diagram? I'm looking for the same thing as I want to do a few mods.
Cheers