Love the C-60 pre-amp! I bought one a few years ago because I wanted to try different cartridge loading, and fell in love with that whole series of Yamaha products. Since then I have also bought two T-80 tuners and a TX-1000 tuner, to go along with my M-4 amp (another product I love).
OPAMP rolling is one of those areas like recapping. Is it necessary? Do you hear a difference? On paper, the newer parts are better. But does that translate to sounding better? The placebo effect is a big factor here, IMHO. You spent money on a new part, you were careful to install it, it MUST sound better! Or does it? With our audio memory being so short, without two identical units to blind test together, it could be hard to really say. A largely personal decision for the most part. You could introduce problems where there were none before.
For myself, I'm not into swapping chips, OPAMPS, whatever, just for the sake of it. I swap them when they have failed, that's it. Recapping is a different story for me. But again, a largely personal decision.
The C-60/65/80/85 pre's are near identical, share the same boards, with the 80/85's adding parametric tone controls and the inverted outputs. But other than those two differences, are all pretty much identical. They sound nice. The biggest pitfalls with these pre's is the input selector switches getting dirty, and the corrosive glue under the heat sinks corroding a couple of resistors. The larger sized1000uF/25V "For audio" caps in my C-60 (C-201/202/361/362) were seriously down on capacitance, well below their 20% tolerance. But they are easy to work on, and well worth the trouble. Go for it! I'd enjoy a write up on it with pictures, of course!
