The NAK - CA series preamps were not designed by NP, but as I stated earlier the circuitry in these pres are very NP like in form and function.
The PA & CA Naks were built when Nakamichi was at its zenith, so much so that they didn't mind paying to use some one else's stasis technology as opposed to the 'not invented here' approach of many corporations.
My tech tells me that the parts and assembly were superior to just about anything else on the market at the time regardless of cost.
BTW: he works on Thresholds also, and he states that they're no match quality wise to the NAKs.