Which good discrete R2R multibit DAC & why NOS ?


In another thread concerning upsampling and upconversion in servers, mention was made by georgehifi :
¨Should just have a good listen to Redbook 16/44 PCM converted through a "good" discrete R2R Multibit nos dac.¨
Which would these be and why NOS ? Are there no R2R multibit DACs being made today ?
My Reimyo CDP777 although quite old has the K2 conversion and being one-box and top-loading made sense  to me at the time of purchase.
Most importantly, would adding an external R2R bring a noticible improvement or just be sidestepping ?

Thanks in advance

rost
Thanks George for that informative list.

Thank you also Lalitk 
Your views echo my concerns as to how much of an improvement, if any, an external DAC plus the added cable expense would make.
As of yet, no immediate plans to get into streaming, too many lps & cds.

Just further on the K2 of the Reimyo, I had many moons ago the flagship JVC K2 player, it used the Bur Brown R2R PCM56P dac chips in it.

Also today the Zanden Model 5000 MkIV is a K2 player also, it uses the R2R Philips TDA1541 double crowns in it.
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

The Zanden didn’t get much love from JA on the Stereophile test bench. For one I can’t believe how much it was rolled off in the bass
https://www.stereophile.com/content/zanden-5000-mkivsignature-da-converter-2000-premium-cd-transport-measurements

Cheers George
US-based Mojo Audio makes R2R NOS dacs.  Their Mystique V3 has won a few awards.  It uses the 20-bit, AD1862 R2R chips.  They have dacs from $2500-7500.

I thought I had read somewhere that the Reimyo DAP 777 used PCM63's, but now can't find anything on it.   I sometimes look for old dacs that have that chip, and I remember the Reimyo being on my mental list.






Yes Mojo also do good R2R Multibit dacs now.
They wrote a great article a few years ago on DSD vs PCM and the d to a conversion to do each. R2R (multibit) vs Delta Sigma (single bit)  Here's what they said.
When a PCM file is played on a native DSD single-bit converter, the single-bit DAC chip has to convert the PCM to DSD in real-time. This is one of the major reasons people claim DSD sounds better than PCM, when in fact, it is just that the chip in most modern single-bit DACs do a poor job of decoding PCM.
https://www.mojo-audio.com/blog/dsd-vs-pcm-myth-vs-truth/

Cheers George
@veroguy  

https://www.ebay.com/itm/202167842535

I use this seller's AD1865 DAC and I really like it. I would like to know what the PCM63 DAC sounds like. 

The link below is for a PCM56P-K DAC that I'm also considering just for the sake of trying something different. 

https://www.ebay.com/itm/362843900577