Vandersteen Sub & Adcom Processor Debugging

I just bought a used Vandersteen V2W sub via Audiogon and am having trouble getting it working with an Adcom GTP-880 pre-processor.

Here's what I've tried:

* running the Sub Output to both of the phased inputs (one at a time)
* Plugging the sub directly into the wall & into a Monster 3600 Power Switch

When I plug the sub in, I get a pop so I know the amp is coming on. When I run a test signal, I barely get any noise out of the sub, even when I turn it's gain control all the way up to 15dB and the processor's up to 10dB (both max settings).

I don't seem to be able to get any noticeable sound out of the sub on CDs/DVDs or TV.

I'm using a Monster sub cable which doesn't have a seperate ground which Vandersteen suggests, but I find hard to believe that accounts for no sound. I did swap the sub cable in as an interconnect to one of my front channels and it works fine, so I think I can safely rule out a bad cable.

Any suggestions on how to narrow it down to either the sub or the processor? Is it safe to hook the sub input up to a front output, which I know works, to verify the sub functions?

The processor was a B-Stock purchase & this is the first sub I've attempted to hook up to it, so I have no guarantees the processor's "Sub" output is definitely good. I have turned the Sub ON in the Adcom setup and am running large Fronts (Vandy 2CEs). I currently don't have surrounds/center, but have turned them on to give non-stereo input choices to ensure the sub should be operational.

Thanks for any suggestions, as the lack of bass is quite a disappointment so far.
Yes, it is safe to hook the sub up to a front input. That's what I would do if I were you.
Can't you run a speaker level connection (instead of line level)to the sub? You may ultimately find you get better integration this way, by using the sub's crossover instead of the preamp...

The V2W is line-level input only.
I have two GTP-880's in my house and am an Adcom dealer, so I am a little familiar with them.

If you are running the fronts as large, then you are not crossing them over and as such, you will not send the bass to the sub.

Set your mains to "small" and set the crossover point wherever you want on the GTP-880. That should send bass below that point into your sub. The GTP-880 will not send your bass to the mains AND the LFE. You can set the crossover point lower than 80Hz if you want, so try a few settings and see which one you like best.
Thanks for the suggestions. Turns out it was a combo of setting things large & not having calibrated the fronts relative to the sub. After changing over to the fronts as small & a 40 Hz crossover, plus calibrating with a sound meter, I'm now getting good performance out of the sub.

Thanks for the tips.