As I wrote in my review
of the Bricasti M1 D/A processor in February 2012, it seemed a good idea in the late 1980s: upgrade the performance of your CD player by feeding its digital output to an outboard digital/analog processor. British manufacturer Arcam, one of the first companies to see the opportunities in this strategy, introduced their Black Box in 1988. When I reviewed the Black Box
in February 1989, I found that its low-level linearity was among the best I had measured at that time for a product featuring the 16-bit Philips TDA1541 DAC chip set. However, that linearity still wasn't very good in absolute terms. Back then, it required heroic and expensive engineering to obtain D/A performance that did justice to the 16-bit CD. These days, however, the semiconductor foundries produce a plethora of relatively inexpensive D/A processor chips that both handle 16-bit data with ease and wrest full resolution from 24-bit data.