anyone had central station / buss comp problems?

[BusyBoxSt7]

[[i also posted this under DIY gear as I'm not sure which it should be in]]

I have a presonus central station. Here's the signal chain during mixing...

-aurora converters, 16 ch. out to ->
-roll music folcrom passive summing device, 2 ch out to ->
-mic preamp (can be API 3124, Chandler TG2, etc, doesn't matter), 2 ch out to ->
-klark teknik dn504 plus compressor, 2 ch out to ->
-presonus central station.

THE PROBLEM
When I run this, I show full meter activity on mic pre, compressor, and the central station, BUT ALMOST NOTHING COMES OUT THE SPEAKERS. It's almost inaudible until the last 5% of the volume knob, then it suddenly jumps a little louder (while sounding terribly grainy) AND the meters on the central station DROP about an inch as the volume picks up.

WHAT'S ALREADY BEEN TESTED
1) I've run the exact chain and sent the output from the compressor back into pro tools. It has healthy volume and doesn't sound all grainy/crunchy).
2) I've run the same setup without the comp (preamps straight to the compressor) and it runs fine
-in other words, all the cabling has been tested + the individual hardware pieces.

ANYONE HAVE A CLUE?
currently waiting on phone for presonus tech support, 30 minutes to get the guy on the phone, of no help. his supervisor says it's not designed to take signal from a compressor which would not be true line level signal (what?).

If you use a buss comp, please enlighten me as to where you put this in your chain. Thanks.