Incorporate guitar amp in my bass rig?

Question

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).

Answer 1

When I've done things like using multiple amps for different sounds, I've done it by splitting the signal from the instrument so that each amp has its own dedicated input from the instrument (signal runs in parallel).

I'd recommend this approach especially when running a bass signal into a guitar amp. Guitar amps are not meant to reproduce low frequencies very well (and in fact the lows somewhat ruin the sound if overdriven). However, eq-ing out the low guitar tones will clean up the distorted sound being generated by the guitar amp.

Compression settings could differ between amps (quite common); and effects like reverb sound worse when pumped with a lot of low frequencies.

You can also individually adjust the loudness of each amp and mix the signals to taste. Overall, you end up with a sound that is far clearer than running the signal first into two amps in series.

Answer 2

I would go one further to the comments and suggest you use a crossover. A Rolls SX21 would do the job, and use up very little space. Basically you want to remove the low frequencies from the signal you are sending to your second amp. You will also probably want to buffer each circuit (treble and bass) separately, and you don't want the ground of one amp seeing the ground of another, else you get an unpleasant hum.

Answer 3

I want to piggyback on what's been said already. The Rolls SX21 is an awesome, small and wonderful tool to split your bass signal. I am doing things a little different though I am splitting the input between a GK 250w 1X12 and a TC Electronic 250w 2X10. But, the thing that I like to do different is use the 2X10 for the lows (under 200hz) and the 1X12 for the highs (above 200hz). The large 12" speaker doesn't sound tinny or harsh. Because the speaker is large in tends to have smooth pleasant sounding highs. I HIGHLY recommend the Rolls SX21 as a means to have a great, smooth and tight bass sound.