....since we hold the Key to every former (analog) STUDER legacy/heritage product I can confirm there was never a Stereo version of the STUDER A or B30 Series!
Schematic / Manual are all present in our Archives....
Hope this helps
STUDER HERITAGE SERVICES
Seestrasse 41; CH-3700 Spiez ( Switzerland)
Tel/Fax: ++41 (0) 33 654 93 22