ADCs can still be on board but might be designed in a different way vs regular Sony tech
Not only the ADC could be different. Take a look at the white paper pointed to by this link:http://www.aptina.com/products/technology/DR-Pix_WhitePaper.pdf
Unfortunately -- at least for my perspective -- it seems that it was written by a product manager, not an engineer, but it does offer two interesting -- again, at least for me -- insights.
The first is the separation of dynamic range into Intra-scene DR and Inter-scene DR. I've been working with ISO-less sensors almost exclusivly for the last couple of years, so the distinction is a little jarring to me, but those of you who work with Canons will be able to get your head around it more easily.
The second is the idea that the operation of the sensor ship could be configured with the ISO knob in ways other than changing the pre-ADC gain and the ADC resolution. This latter notion may explain some of the a7S performance, because it appears to me that the inter-scene DR can't be explained easily by read noise and the intra-scene DR.
I have an a7S on order and will test and report when it arrives.