Which good discrete R2R multibit DAC & why NOS ?

Some of the best very expensive Wadia dacs use PCM56 and PCM63 chips in them, with what they called the discrete "Sledgehammer" output boards.
They also had what I found to be the best way to link it to their transports with AT&T glass BNC optical link, using a dab of very expensive "optical indexing fluid" on both ends, so there was no air gaps to the AT&T receivers

And Accuphase used the AD1865 in great numbers their top line expensive dacs also.

Mark Levinson, Linn and Naim were a big user of the (best I felt PCM1704’s) in their top end players and dacs.

Naim got amazing sound from the CD555 and PS555 power supply combo. Even today you won’t get this pairing cheap anywhere. https://www.naimaudio.com/product/cd555

Cheers George

The Reimyo CDP 777 used 2 PCM1704 and Nippon SM5847AF filters and JVC K2 DSP which is why it was a good CD player it wasn’t NOS and made use of good filtering and up sampling which any decent R2R implementation needs to do.

Please enlighten:

@georgehifi 
"But I can’t find what the Reimyo uses for dac chips, my guess would be the R2R PCM1704K’s, I don’t think it’s discrete R2R"
What is the difference between a discrete R2R & non discete R2R DAC ?

@djones51
" it wasn’t NOS and made use of good filtering and up sampling which any decent R2R implementation needs to do."
Please explain further, I thought R2R implied NOS or upsampling.

Thanks

What is the difference between a discrete R2R & non discete R2R DAC ?

A discrete R2R uses individual (discrete) close tolerance resistors in the R2R ladder. The non-discrete uses an IC with those resistors on the die of the IC where they're trimmed by laser after fabrication.

@rost 
The R2R PCM1704 chip doesn't do the oversampling it's the K2 DSP and Nippon filters that pass the over/up sampled signal to them. R2R is the DAC architecture there is more going on in a good DAC or CD player. NOS is in some kind of nostalgia thing right now but as you can see with your Reimyo the best even 20 years ago didn't do NOS without proper filters, Why? It didn't sound very good.

While each of the corporations contributes to the overall sound of the Reimyo, it is the K2 processor that gives it its heart and soul. The K2 processor, operating with 24-bit resolution, takes the incoming digital signal and oversamples it to 176.4kHz. From there the digital signal is passed on to the digital filters, which upsamples the signal 4 times to 705.6kHz before being passed on to the twin PCM-1704 digital to analog converters. The DAC's are multi-bit in operation. As a result, every CD that is played through the CDP-777 is reproduced at an incredible 705.6kHz, which is among the fastest sampling rates available from any CD player on the market today.

http://www.enjoythemusic.com/superioraudio/equipment/0304/combakreimyocdp777.htm