Got a nice 1994 Sony Discman model-a D-131 several weeks ago

It has line-out and variable MEGA BASS (norm/mid/max).

Controls are on the front and are open, hold,LCD display, play mode, repeat/enter, stop, play/pause, track previous/next, MEGA BASS (norm/mid/max) and AVLS.

The sound quality is very good when using the bass boost.

Some technical information:
-uses KSM-331A optical pickup
This optical pickup is also used in Sony's D-121 and Aiwa XP-7 for instance
-very easy to dissassemble and has trim pots for various adjustments
-DC jack is intergrated on the main board (instead of being on a separate board-as seen in models like the D-121)
-main IC's used in the D-131 are:

Sony:
CXA1672Q
CXD2507AQ
CXP508L6

Motorola:
SC111281

Other:
BA3574AFS
TC 424 9293FN



Internal photo: