My first mistake had been to assume what "flat" meant. I started over once I understood that the settings weren't flat unless I set pbass and treble at noon, dimed the mids, turned the presence freq knob to 0, and put the bass freq at 120Hz. It quickly became obvious just how much control I had over my tone. Adjusting treble and presence while choosing a frequency gave me precise control of the top end; I dialed in lows (tight, never flabby) with the help of bass and the 60Hz/120Hz bass freq button. The unit's mid-cut-only approach was more flexible than I expected, especially combined with the presence controls. The 201S-800D emphasizes clean, faithful reproduction: If you love the sound of your instruments, you'll love this preamp. Even set flat, other tube preamps automatically added a layer of warmth and girth to every bass I plugged in, but the Demeter was sterile-merciless, even-until I dialed in what I wanted.
Bradman, E. E. (2014) Demeter 201-800D Preamp/Power Amp. In: Bass Player, Vol. 25, No. 1, pp. 58-59. Available at https://openmusiclibrary.org/article/1028917/.