Another tube buffer well worth considering is a kit (K295) from Oatley Electronics here in Australia.
https://oatleyelectronics.com/files/k295notes.pdf
The K295 uses two Raytheon JAN6418 miniature pentodes wired as triodes.
I don't know about the buffer introducing "tube sound" but used to buffer the ProtoDAC (420hm I/V resistors) it works as intended to isolate the DAC from varying loads.
The 6418 is said to be microphonic but using the rubber grommets shown in the notes I could not detect any in practical use.
At US$24 the K295 is well worth an hour or so with the soldering iron
https://oatleyelectronics.com/files/k295notes.pdf
The K295 uses two Raytheon JAN6418 miniature pentodes wired as triodes.
I don't know about the buffer introducing "tube sound" but used to buffer the ProtoDAC (420hm I/V resistors) it works as intended to isolate the DAC from varying loads.
The 6418 is said to be microphonic but using the rubber grommets shown in the notes I could not detect any in practical use.
At US$24 the K295 is well worth an hour or so with the soldering iron
