I started looking at passive preamps from Goldpoint and Marchand. Digging deeper, I'm uncovering all kinds of details about input and output impedance, buffer stages, amplifier gain, DAC voltage out, etc. Most of what I find online distills down to "passive preamps are great in a well designed system", mostly about having a low source output impedance and a high amp input impedance. The Modius outputs 75 ohms and 4 volts, a passive preamp may have a 10k or 20k resistor, and the hypex has a 1.8k ohms with 26 db of gain.
If source to amp impedance needs to go low to high 75>10k>1.8k doesn't seem like a good idea (sans a buffer stage).
Whereas something like a Schitt Aegir at 22k makes more sense.
Please feel free to chime in or point me to some literature on the topic. A common dismissal of passive preamps is that they don't sound good with longer interconnects.