Most of those ART TOOB bits (and other toob gear of that 1996-2010 era)are built to a low price point. Starved plate designs that basically use the tube as a distortion source, if that. A lot of them work with the tube removed.
I can promise you ART never did this. ARTs competition was the likes of behringer and Alesis. All made some usable gear from time to time(Alesis made some real gems)but all to low low price points.
All that gear has its place. A functional mic pre for ~$25, not a bad deal. But put it beside something design with a level of quality in mind and you'll immediately hear a difference. Then, occasionally, there are pieces that dona phenomenal job of both price point and quality. FMR Audios products are a great example of that. The RNP and RNC have amazing function in economical packaging at a good price point.
Crap, I'm ranting...
Edit, just checked the tube mo schematic. The anode is tied to 48v. LOL