I have a Hartke 30w bass amplifier with preamp-out and speaker-in jacks. It has a decent tone and plenty of bottom and head-room for the space (small theatre). But I also have a new Vox vt20x (20w) with a tube and lots of modeling and effects.
I want to use some of these sounds from the guitar amp with my bass (the flanger in particular is really nice). Now the vox doesn't have a speaker-out or a line-out, just a headphone-out which doesn't seem promising.
I've tried plugging the bass into the Hartke, then running the preamp-out into the Vox input and it does seem to give me more shape on the lows and more head-room. And I'm guessing that I'm not going to blow any circuits by doing this, but is there a better way to either beef-up the low-end from the Vox or get a signal out of it that I can feed to the bass speaker?
Edit: tried the same chaining setup again and there is still sound from the bass speaker. So I am getting some degree of splitting. There's also a line-out on the Hartke with similar result.
Update: I didn't try either of the suggestions, but went ahead to rehearsal with the preamp-out jury-rig. The result was too noisy for the space. So I reduced my gear to just the Hartke amp and an envelope-filter pedal. For future shows, I think the real solution is a smaller Bass Amp, like 15w, so I can drive the amp more into its sweet spot. With the 30w, I have my volume on 3, and any more would be too loud. More details in my facebook post.
I cannot judge between the 2 answers yet, but either would probably be less noisy than what I tried. But the real crux of the issue for this show, is that 30w + 20w is just too much amplification for the space.
Update (much later) I have bought a lot more pedals so I don't need the guitar amp's effects. Adding a JHS Little Black Box in the loop on the bass amp (new 75w 12") gives me much more control of the overall volume while keeping the preamp in the sweet spot. This setup worked really well in my last show (The Who's Tommy).