Just passing by in 2021 but what you could use is the Triatt from Intellijel. Versatile module which will send out a constant CV signal when there's no input. I use it specifically for this combined with the Mutable Links mix/sum tool.
The downside of 2hp DC is that you can only add, so you can't subtract, which you can do with Triatt.

https://www.modulargrid.net/e/intellijel-triatt
-- tboy

Very cool, thanks! That module could do several utilities.