restorer-john
Grand Contributor
Why are they considered so special?
Discontinue anything with an avid following, legendary performance (for its time) and watch the demand (and price) skyrocket.
Simple economics.
The original Philips TDA-1541 S1 (and later the less desirable S2) is arguably the most valuable (if you can find an actual original) D/A in the world. Not the best, but the absolute best Philips could make in 1990. Then came Bitstream which was cheap crap. Then it was refined and displaced the 'king' of D/As.
The Burr Brown PCM-58P selection S (for Sony) is the best 18 bit converter they made. Until they made the PCM-63.