Eela Audio S120 Technical manual.

Comes in 4 parts as pdf file, right click to save:

S120 text file, description, adjustments,

S120 diagrams part 1,  Input modules: S121, S122, S123.

S120 diagrams part 2, output modules, S124, S125, S126, S127, S128, general diagrams

EA902 power supply.

Please note: The S120 is manufactured over a long period, several versions do exist.