I've also recently delved into the wonderful world of wobblevision. it took ages for me to find a black and white telly to do it on!
i've placed the box of joy near the remote speakers which are in another room from the amp. i've stipped a tiny bit of the speaker cable and tapped into the signal for the wobble trigger. couple of croc clips on a jack lead, and it's wibbly joy. just another option which could be used if you want to tap into a single stereo speaker system...
i'm at a cestron 'wave vessel' stage. hmmm, i 'm getting an urge to see the four yoke circle setup....
god, this is addictive. hope i don't kill myself poking around. i had a sparking moment last time i went in there. from the board. erm, er..