Hello there. Can you take a look at this? Original op-amp on the KA-5500 was the in-line, TA7136P -- a long time ago "...when op-amps were still young." (Echowars) Far better op-amps are made today. So what I am wondering... Would an op-amp upgrade improve performance enough to justify? Which reasonably priced, readily available op-amp (ideally Mouser-stocked), would be a good choice? What other modifications would be needed? Some weeks ago Hopjohn (THANKS), suggested to me -- IF one were to switch out the op-amp -- possibly go with 595-OPA2132PA. He added caveats. One, 'op-amp rolling' is not his specialty. Two, there is give and take, from what he understands. Three, it would be advisable to seek counsel from others. In 2002 Echowars posted a thread on an op-amp upgrade he did on his KA-5500; said performance enhancement was significant. He noted that improved performance also was attributable in-part to electrolytic capacitor upgrades. In any event the op-amp Echowars selected was the now, no longer available / outdated (Burr-Brown - later Texax Instruments), OPA604AP with a .18uF stacked film cap soldered directly to the leg of an IC socket to deal with "supply voltage outrageous by opamp standards (+/- 19V)." The OPA604AP was an eight-pin DIP. To adapt he had fashioned a small PC board which he wired to the Kenwood PC board; incorporating a a gold DIP socket, in case someone came up with another op-amp that might be fun to try. Edit: I think I left out that he may also have adjusted resistors, as follows: "... the preamp supply voltage resistors are dropping the supply voltage from +/- 19V to about +/- 17.5V. I was prepared for this, and changed the resistors to get the supplies back up to 19V." Tin pin gold DIP socket 575-11043308?