I don't want to create a drone, I want to use the drone I have like a bagpipe's drone; a constant pitch with notes played over the top. Yes, I realise I need to turn up the Audio In on the mixer to hear anything.
Sorry, I misunderstood what you meant when you said "all the oscillators are at zero in the mixer".
The Minibrute only has one VCA – so you won't be able to have a constant drone PLUS notes that "stop and start" over the top. If you want that, then you'll have to mix your external drone oscillator with the Minibrute's output using an external mixer. In other words, the Minibrute's VCA is either held on (for the constant drone part), or it's turned on and off (for the "notes over the top" part), but it can't do both simultaneously.
I know a couple of people who own Minibrutes and their behaves the same. Neither of them are using their Audio In's due to the low level of the input without a preamp of some sort. I'm wonder what others are using to get a high enough gain so the Audio In is usable?
Ah – here, some of the confusion is revealed. This thread was originally about using the "Audio" setting of the "Gate Source" switch, i.e. triggering the Minibrute's envelopes using the audio input as the source. As I understand you, you are just trying to mix in an external oscillator through the "Audio In" fader – but you don't care about triggering the gate with it?
For external sound sources, being added to the Minibrute's mixer via the "Audio In" fader, I generally haven't had trouble getting enough level. One exception to that is there are a couple battery-powered drum machines I've input, and they are definitely on the quiet side. So in that case, some kind of boost is necessary. A preamp with a DI is one option. A guitar pedal (a boost or overdrive or anything with gain, clean or otherwise) would be another option.