Ashdown RPM1 octaver

[plankspanker]

I've recently bought an Ashdown RPM1 to drive my Peavey CS800S and I'm very pleased with it except the octaver doesn't seem to work. There's an in/out switch to enable the function and a level control to set how much of the note an octave below is added to the straight bass sound. Even with the level flat out it doesn't seem to make any difference. I've tried a standard guitar but no difference then either. I use a passive Carvin four-string and Peavey and Ashdown cabs. The sound is good and everything else works fine but no octave below - any ideas? Thanks in advance.