ModWright Tube Buffer

No dig on ModWright.  They build good stuff.  I would look at one of their pres used.  

I own a ModWright Analog Bridge and absolutely love it! It’s probably one of my favorite pieces in my setup. It immediately added depth and smoothness (not color), and the tube rolling is awesome too. I bought a brand-new RCA version (because my Rega Aethos amp only has RCA inputs) directly from ModWright and got a great price. Dan is great to work with. Buy it — you definitely will not regret it.

I would not buy one to create “the sound of tubes” but I would consider one to optimize impedance matching and improve dynamics if I were using a DAC with an internal volume control, or a passive volume control.

dan’s unit is full featured

otoh deckert’s zstage is absolutely minimalist (in terms of very small case, ultra simple internal wiring/configuration, and the use of single dual triode 12au7, so its easy and fun to tube roll as well)

https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1288548883

correct, z-stage has no switch to allow in/out of circuit though (minimalist ethos here)

but each in their own way does what it does excellently

i enjoy my zstage, and use it sometimes with DACs that are clear and spacious but a touch lean in tone, or low in output voltage

Impedance matching is a common reason for using a buffer.  The Modwright unit, with its output impedance of <20 ohms, is likely to be more effective in that regard than the Zstage that is spec’ed at an output impedance of <1,000 ohms.