Mono block Preamp

I believe Nucleosis also made a mono, but it's nothing you'd want.

Mono pres were a forerunner to Differentially/true balanced preamps/amps, where both channels share nothing in come, aside from the power supply

I hate dual volume controls......  I will pass on true dual mono preamps

Mark Levinson made the first one back around 1980. It was the ML6 and sold for $6K the pair. Outrageous price then, now pocket change for today’s moneyphiles (who dominate the High End).

Lamm LL1 Signature is a true mono block preamp. completely separate left and right dual chassis. no remote volume control.

https://positive-feedback.com/reviews/hardware-reviews/lamm-ll1-1-signature-dual-mono-preamplifier/

Gryphon Commander likely comes next closest, as it even has two power cords....and a separate power supply connection for the control processes. 

https://gryphon-audio.dk/shop/preamplifiers/commander

when you consider the switching and gain functions there is a need for a common control chassis. the Lamm is a bit too ’hair shirt’ for many with no remote volume control. a non-starter for most people.