Does Native PCM exist or has existed ?

[Miska]

On 4/15/2021 at 10:50 AM, opus101 said:

 Therefore almost all PCM has indeed been through an S-D modulator (not very likely to be 1bit though) at some stage in its life.

 

Quite a lot of gear use TI's PCM1804, PCM4202 or PCM4204 chips which are all pure 1-bit converters. This includes number of RME ADC's and cards like HDSPe AIO.

 

[Miska]

9 hours ago, PeterSt said:

I recall from the 1792 that theoretically it should be able to work in native PCM mode, but it can't shut off its internal filtering (or whatever was "wrong" with it). This makes it again "worthless" for someone who wants the filtering outboard (in advance of it - in-software).

 

All these "Advanced Segment" TI chips can operate to max 6-bit in native PCM mode. Rest 19-bits (MSB + 18 LSBs) are through very rude simple 3rd order 5-level delta-sigma modulator. But they can operate in native DSD mode by reconfiguring the conversion section into analog filter for DSD with four different arrangements. Their modulator produces quite a set of spurious tones and noise floor modulation, so you certainly get best performance out of TI/BB chips by running them in DSD mode at DSD256.

 

See the "Theory of operation" section in the datasheet.

[Miska]

8 minutes ago, Jean Paul D said:

which Dacs allow to run TI/BB chips in DSD mode at DSD256 ?

 

For example iFi does. Maybe some others too, but don't remember right now top of my head.