Does your CT-120 provide speaker-level in/out connections? If your pre-amp or integrated amp is meant for stereo only (no processor) and/or lacks an output labeled "subwoofer" or similar (which are usually filtered) you may get a better result using the high-level (speaker-level) connections to the sub in your case. It sounds counter-intuitive, but connecting a powered sub this way can actually sound a lot better if your preamp or integrated is not fitted with a line-level sub output.
Also, the "line out" on many powered subs is often not meant to feed a signal back to the pre-amp, but may be used to "daisy-chain" another sub. That may explain why you are not getting any sound from your main speakers with it connected this way.
Try running speaker cable from your preamp to the sub's speaker level inputs, then another set to your monitors from the sub's speaker outputs (assuming it has this connection, of course), and the adjustable crossover in the Velodyne will filter out the low frequencies before they reach your monitors so they will play louder and cleaner than otherwise. Definately worth a try! JZ
Also, the "line out" on many powered subs is often not meant to feed a signal back to the pre-amp, but may be used to "daisy-chain" another sub. That may explain why you are not getting any sound from your main speakers with it connected this way.
Try running speaker cable from your preamp to the sub's speaker level inputs, then another set to your monitors from the sub's speaker outputs (assuming it has this connection, of course), and the adjustable crossover in the Velodyne will filter out the low frequencies before they reach your monitors so they will play louder and cleaner than otherwise. Definately worth a try! JZ