I have the speaker output wired to a jack, which I use to experiment with plugging into various size/shape cabinets. (Cardboard boxes!) If I use the Hacks! output to plug into some other amp, and leave the Stella's speaker jack unplugged, am I going to do any damage to anything on the Stella?
I remember trying to, quite naively, make a similar modification to an old Acoustic bass amp years ago - using it's line out with no speaker connected to the amp worked great for about 5 minutes, then a big resistor on the circuit board caught on fire. Needless to say, don't want to repeat the same failed experiment on my beautiful new Stella!