Did some real work on the Oppo 95 mod today.
The first step is to see what we can do with the existing unit, without adding our own PCB. There is SOME room, right above the drive, where a PCB of our own could be mounted. This is really the only place that I consider noise free enough, to locate a new analog stage - tube or SS.
For now however, I went over the existing power supply design, analog stage and DAC and digital supplies. The linear regulated supply is good and well done. The analog stage, although op-amp based, is also very good and there are no coupling caps in the signal path.
I have so far removed one op-amp stage from the circuit and implemented our own op-amp free revision. I then took the final op-amp gain/buffer stage and optimized its performance to work with our input stage. This made a big difference in clarity, resolution and overall soundstage. This could be done to all of the MCH and 2CH circuits.
I have a few more things that I want to experiment with and then I will likely wrap up the 'Level I' mod, which will be a high-value and affordable mod.
For those who want a tube mod, I need to see how we can fit a PCB in the space available and what would be required to do so.