i haven’t seen or heard it tried either… however, i’m in the same boat as you and i’m about to pull the trigger on a cathedral to use specifically for vocals. i think the cathedral would be great for live vocals as it has a TONE knob and a PRE-DELAY function… which can help to keep the vocal signal clear and avoid feedback… not to mention the cathedral has awesome reverbs in its own right.

i can only tell you that you need to do one of 2 things:

1) either use run the microphone to a small format mixer and use the cathedral in the AUX SEND/RETURN of the mixer, or;

2) make sure you use an impedance matcher at the pedal end of your microphone cable to plug into the Cathedral… then make sure the outs run to either a passive (preferable) or active DI…

these two set-ups are the only way i’ve been able to incorporate vocal effects live and avoid either pissing of the soundperson or WALLS of feedback/weak signal.