Sliders. Tracktion Waveform, the DAW I also work on uses almost no knobs. (I think the only one is pan on the mixer). The problem with them is that they are big. When we don't have room we make them small and then a bigger one pops up when you click on it.
They use numeric text boxes which also pop a slider when given focus.
You can also let the users drag the textbox left and right directly (with some visual cue), thus achieving the same functionality as the current implementation, but still without getting in the way of someone who just prefers to use the textbox normally.
