So after a little bodge on the power pins the PCM4202 lives. Using the ADAU1452 with sigma studio is nice, also my soundcard can toggle between SPDIF and Analogue out on the fly. This means I can compare direct digital into the DSP with the analogue sound into the PCM4202 and back out again through the ADAU1966. Whilst this seems pretty "pointless" it is quite useful if the intended use is as an active crossovers after existing audio equipment.
I didn't expect there to be such a big difference in sound, I'm not sure how much of an effect my sound card is having but this isn't anything subtle at all. Whatever is causing the difference both options sound fine and I could listen to either of them all day. .
An electronics engineer and a long term electronics hobbyist. I like tinkering with stuff and making things.