Thanks for the post!
Saw this:
For mastering purposes, Cello has developed the first new tape head playback circuitry in 30 years. Studios have been taking original analog tapes and making digital masters on very modern expensive equipment. Standard circuitry in tape decks between the playback head and the "real world" introduces audible sonic coloration, distortion, and noise which limit the quality of the final product. The Cello Audio Suite Mainframe can be equipped with P603/P301 modules which serve as state-of-the-art playback electronics for decks by Studer, Telefunken, Ampex, and other companies. Still this day, the musician/professional connection continues and many recording studios and engineers still use and acknowledge the sonic excellences of the Cello products in their work.
So I assume that Cello had converted their phono section into a tape head preamp back then?