I've got an old, 1991, Aiwa HS-T50 "Stereo Radio Cassette Player". All black plastic. 4.5 X 3.6 X 1.5 inches, 11. 1 onces with batteries, Alkalines, and tape.
It takes 2 AA Alkalines. Runs 4 or 5 hours playing tapes and 7 or 8 playing FM. 5 Presets AM&FM, Clock, 3 band EQ including adjustable "Super-Bass", Auto-reverse, Normal/Chrome switch.
Drives HD600's to ear shattering volume with a bit to much distortion. At 85db "C-Slow" it's clean with beautiful clear highs and deep tight bass. Barometer Soup as a test tape. At my normal listening levels, below 80db, it's at least as good as my big Kenwood 103CT home deck.
KSC35's and KSC50's were apparently designed, engineered for this unit. They sound better than from my Kenwood pcdp/TA combo. Really awesome.
But, as I stated earlier, it's 2 AA's and they don't last too long. No problem though because I've got 12 Panasonic 1600 mah NiMH's that I got at Costco for 6 for $12.95. Best price by a bunch anywhere.
I think what we're all seeing is the fact that the older portable units, all media, were actually built better, possibly cheaper materials, but better QC and design. Not designed for battery life, but more for better audio quality. Bigger, bulkier, better sounding. The new stuff is tiny, light and the batteries last. Sound quality is about 8th on design criteria, if that high. As long as it's still under a pound, I don't have a problem carrying it and the sound quality is definitely worth it.
BTW, this thing's been in a box in the attic for 4 years, and I got it down last week after some posts about cassettes on this forum. No specs or manuals. Oh well.