you do really need to get an extra volume control for SFL Line 3. In fact any preamp needs an external volume control. That's how they're designed pretty much...
Sonic Frontiers Line 3 unity gain
I'm searching to set unity gain on my Sonic Frontier Line 3 preamp to run the leedh volume control from a Lumin T2. HT setting is only for single ended connections and I use balanced. Is there a particular setting to achieve this?