Thank you Calvin for the detailed explanation and the effort you put in it, much appreciated.
Another non directly related question...
I have 2 5V linear power supplies that I would like to use for powering the +\- OPA860, I know the virtual ground method of how to get + and - voltage from 2 power supplies but where do I need to connect the virtual ground point from the joined power supplies in the OPA860 circuit? do I need to connect it to the AGND from the AD1862?
Another non directly related question...
I have 2 5V linear power supplies that I would like to use for powering the +\- OPA860, I know the virtual ground method of how to get + and - voltage from 2 power supplies but where do I need to connect the virtual ground point from the joined power supplies in the OPA860 circuit? do I need to connect it to the AGND from the AD1862?
Who have compare by listening test this discrete version from Nelson Pass's D1 underHi,
instead of a stacked pair/triple of AD844s (a pair seems the minimum to cope with the +-1mA of DAC current) a single OPA860 or OPA861, which use the same topology as the AD844, may be used.
The OPA861 featuring a OTA only (Operational Transconductance Amplifier), the OPA860 also featuring a integrated Buffer, like the AD844.
If You want to design Your own Buffer something like a diamond made from bipolars is what is typically used in the integrated circuits.
If You want to use the bipolar I-V linked to in my last post You may even use the same bipolars in a diamond buffer.
jauu
Calvin
Here´s a fully dimensioned sim.
https://www.diyaudio.com/community/threads/diy-d1-i-v-stage.181449/
against the integrated versions AD844 resp. OPA860/OPA861 ?