Your username sounds like it was from the song by Tears for Fears called "Shout" just read the lyrics.
Question - Why would you want to? This is a very OLD Sansui with a SNR that is very low.
Look for Sansui integrated amplifiers made in or after 1997, That’s where the real good headphone outs were implemented. Prior to that, they were "experimenting" and a lot of their older stuff would become defective for no good reason. The engineering really matured after 1997.
Examples:
AU-α607NRA
AU-α707NRA
AU-α907NRA
AU-α607NRAII
A-α7
A-α9
I have heard or owned practically all of them at some point in my journey. And guess what? Their headphone outs make a whole bunch of of modern headphone amps sound basic. Plenty of power on tap too, will drive your headphones with ease and clarity, with a speaker-like sound if open-backed.
And lastly (for now) here's the adapter you want: Planet Waves PW-P047E Headphone Adapter TRS 3.5mm to 6.3mm TRS– Badie Studio & Stores
Totally lossless, no micro-arching /vibrations like run of the mill super cheap adapters. Lasts forever. I have many.