Has anyone thought of a way to compress the volume of the vocalizer? Whenever I turn it on I must lower the mic level (and vice versa). I use the separate mic output on the SD1. Is there some type of inexpensive device that I can interrupt the mic line with to keep the level uniform?

Try the Behringer DSP110 Shark (Sharc) !
It is small, inexpensive and has in it :
Compressor/limiter
Noise gate,
Equalizer
Feedback-eliminator(automatic !)
Delay-line (max of 2000ms)
Phantom power
Mic preamp
XLR in/out
6.3mm in/out

Have a look at http://www.behringer.com/DSP110/index.cfm?lang=ENG

Roel