A booster, or even some dirt, like OD or even fuzz after the octaver. Provides a volume boost and some more midsy freqs for punch.
That pedal, from my experience gigging with it, did suffer from any one voice not being loud enough on its own. I found each voice, clean or sub, were roughly equal to my bypass volume when they were dimed. So with both voices up at 1/2, the volume of the unit is also roughly the bypass volume. If you run just the sub voice, while it is just as loud as your bypass, it is lower: so it cuts less, has less present mids, and needs more power to be "equal volume" in the band mix.
So when I used it as just a sub tone, I had the low octave voice dimed, and I still needed some OD after it to help it pop up in the mix and give enough punch to carry the bassline. The pedal itself is just really subby, without much cutting lower mids or square wave to the tone.
I use a BOD for this now, and it is louder on its own, especially the sub octave, than the EBS unit was. I traded my EBS to a guitarist friend for his OC-2. He uses it for bass in his looping project, and the EBS sounds great doing that. I use the OC-2 for a straight+octave tone.
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