Boss VF-1 Effect Processor

Hello-
I've used to VF-1 pretty extensively for some time now. I am just 
getting around to trying out the Vocoder and it doesn't seem to make 
much sound. I am using a non-powered mic in the Left input and 
various constant synth waves in the Right input. Is this because the 
Mic isn't powered/pre-amped? The reason I thought thi would work is 
becuase the other Vocal patches work fine with an unpowered Mic. Any 
suggestions?

THanks,
Brooks