One could ask themselves why
A: the TDA387 chips are dumped on the market and picked up by DIY and cheap Chinese DAC manufacturers.
B: These chips are/were not used in any serious DACs and CDP's.
C: Why these days paralleling is the rage.
D: Why the chip design is about 25 years old.
E: Why the specifications are mediocre at best and then are only valid at 192kHz (meaning they are worse at lower bitrates).
F: Why the datasheet specifically mentioned 2, 4 and 8 times oversampling.
G: Why this chip is designed for portable equipment and wasn't used in more expensive desktop equipment back in the days.
H: Why there are only testimonials and no measurements shown anywhere.
I: Why R2R DAC chips are normally fed via digital filters, yet cheap DAC manufacturers and DIY decided it is a good thing to leave them out.
A: Possibly recycled from Sound Blaster AWE cards, they were sold in millions - I don't mind.
B: Probably the same as with TDA1541/5. Expensive to stack many chips in parallel, Denon was the only one example I know. However these chips has created many DIY projects. TDA1387 was the last design in series, it didn't create DIY interest. It probably come late, as market was taken by inexpensive four-bit delta-sigma modulators (same design as all current). From my experience single-bit delta-sigma converters sounded totaly crap, so I settled for PCM63. The current design sounds better, but is fatiguing. The another factor is that LSB portion of the current source was self-calibrating. It didn't create audiophiles confidence for true 16-bit resolution, but no-one took an effort to prove allegations.
C: There is a technical reason for this (actually two). Now we've got flood of cheap DACs (see A), so why don't use more? Not a new concept, Denon is an example (16 chips), I don't remember model number. PCM63 was paralleling too, for a cost of $xxxx
D: Pass.
E: That is for TDA1543. TDA 1387 is improved to 256kHz I think. Why no more? See D:
F: The same as my PCM63 based DAC. It it does matter to you.
G: Denon?
H: Business? R2R DACs do not meassure well, but they sound better.
I: R2R DAC chips do not have built-in digital filter, so designers have an option. I don't comment whether it is good or wrong, it is a topic for another debate. Delta-sigma modulators come with built-in digital filters and free plug-in libraries.