Going to be putting a Darkglass Tone Capsule in a new bass build and looking for suggestion from users whether to run as 9V or 18V. Bass will have a single Nordstrand MM4.2 pickup (Musicman Humbucker). Let me know your experience and pros/cons for each.
Start with 9V. If you notice any compression or distortion coming from the bass (and not from your amp/pedals/cabinet/etc.), move to 18V. You can temporarily try 18V for testing before making permanent changes to your bass.
Try 9v and record yourself with a DI. Play like you regularly do. See the recorded wave sound. If you see any signal clipping, go to 18v and check again.